Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/02—Lubrication
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
  • F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/0005—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00 adaptations of pistons
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/02—Lubrication
  • F04B39/0215—Lubrication characterised by the use of a special lubricant
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/02—Lubrication
  • F04B39/0223—Lubrication characterised by the compressor type
  • F04B39/023—Hermetic compressors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/02—Lubrication
  • F04B39/0223—Lubrication characterised by the compressor type
  • F04B39/023—Hermetic compressors
  • F04B39/0238—Hermetic compressors with oil distribution channels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/02—Lubrication
  • F04B39/0223—Lubrication characterised by the compressor type
  • F04B39/023—Hermetic compressors
  • F04B39/0238—Hermetic compressors with oil distribution channels
  • F04B39/0246—Hermetic compressors with oil distribution channels in the rotating shaft
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B39/00—Component parts, details, or accessories, of pumps or pumping systems specially adapted for elastic fluids, not otherwise provided for in, or of interest apart from, groups F04B25/00 - F04B37/00
  • F04B39/12—Casings; Cylinders; Cylinder heads; Fluid connections
  • F04B39/122—Cylinder block
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/06—Control using electricity
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B1/00—Compression machines, plants or systems with non-reversible cycle
  • F25B1/02—Compression machines, plants or systems with non-reversible cycle with compressor of reciprocating-piston type
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2203/00—Motor parameters
  • F04B2203/02—Motor parameters of rotating electric motors
  • F04B2203/0204—Frequency of the electric current

Definitions

• the present invention relates to: a hermetic refrigerant compressor for use in, for example, a refrigerator or an air conditioner; a method of operating the hermetic refrigerant compressor; and a refrigerator-freezer using the hermetic refrigerant compressor.
• COP coefficient of performance
• oil refrigerating machine oil, lubricating oil
• Patent Literature 1 discloses a refrigerant compressor with increased efficiency. The increased efficiency of the refrigerant compressor is achieved by setting the viscosity of oil stored inside a sealed container of the refrigerant compressor within the range of VG3 to VG8.
• An object of the present invention is to provide: a hermetic refrigerant compressor that makes it possible to achieve a more favorable coefficient of performance (COP) by using refrigerating machine oil having a further reduced viscosity; a method of operating the hermetic refrigerant compressor; and a refrigerator-freezer using the hermetic refrigerant compressor.
• COP coefficient of performance
• a hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s
• an average speed of the piston moving in the reciprocating manner may be set to greater than 0.31 m/s.
• the lower limit of the average speed of the piston moving in the reciprocating manner i.e., mean piston speed
• the operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• low-viscosity oil having a further reduced viscosity low-viscosity oil whose kinematic viscosity at 40°C is set within the range of 1.0 mm 2 /s to 2.5 mm 2 /s
• a favorable oil film can be formed between the piston and the compression chamber by the piston, which moves in the reciprocating manner at a high speed. This consequently makes it possible to favorably suppress the leakage of refrigerant gas from between the piston and the compression chamber. Therefore, when the low-viscosity oil is used as the refrigerating machine oil, the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• COP coefficient of performance
• a hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• a ratio S / D of a stroke amount (S) of the piston moving in the reciprocating manner to a piston diameter (D) of the piston may be within a range of 0.78 to 1.00.
• the ratio S / D is set within the predetermined range. Owing to this setting, the stroke amount (S) can be relatively increased. Accordingly, the mean piston speed can be relatively increased. For this reason, the amount of leakage of the refrigerant gas can be favorably suppressed.
• the piston diameter (D) can be relatively reduced. Consequently, the total area of a clearance between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder can be reduced, which makes it possible to favorably suppress the leakage of the refrigerant gas.
• the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• a hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• a ratio L1 / D of a piston overall length (L1) of the piston to a piston diameter (D) of the piston may be within a range of 0.8 to 1.0.
• a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner may be a sealing length (L2).
• a ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) may be within a range of 0.9 to 1.0.
• the ratio L1 / D and the ratio L2 / L1 are set within the respective predetermined ranges. Owing to these settings, the sealing length (L2) can be relatively increased without excessively increasing the piston overall length (L1) while suppressing an increase in sliding loss. Consequently, between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder, the viscous force of the oil film can be increased while suppressing an increase in sliding loss.
• the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• the hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• the method may include setting an average speed of the piston moving in the reciprocating manner to greater than 0.31 m/s when an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• a refrigerator-freezer may include a refrigerant circuit, the refrigerant circuit including: the hermetic refrigerant compressor configured as described above; a radiator; a decompressor; and a heat absorber.
• the hermetic refrigerant compressor, the radiator, the decompressor, and the heat absorber may be connected by piping in an annular manner.
• the present invention is configured as described above, and has an advantage of being able to provide: a hermetic refrigerant compressor that makes it possible to achieve a more favorable coefficient of performance (COP) by using refrigerating machine oil having a further reduced viscosity; a method of operating the hermetic refrigerant compressor; and a refrigerator-freezer using the hermetic refrigerant compressor.
• a hermetic refrigerant compressor that makes it possible to achieve a more favorable coefficient of performance (COP) by using refrigerating machine oil having a further reduced viscosity
• COP coefficient of performance
• a compression chamber is formed inside a cylinder included in a cylinder block, and a piston is inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• Refrigerating machine oil is present as an oil film between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder (i.e., the inner peripheral surface of the compression chamber), and lubricates the reciprocating motion (i.e., sliding motion) of the piston.
• the thickness of the oil film formed between the piston and the cylinder is reduced in accordance with a reduction in the kinematic viscosity of the refrigerating machine oil. Sliding loss due to the reciprocating motion (sliding motion) of the piston can be reduced by reducing the thickness of the oil film. In this case, however, a leakage of refrigerant gas from between the piston and the cylinder may occur.
• the inventors of the present invention experimentally verified and evaluated the amount of refrigerant gas leaking from between the piston and the cylinder by using refrigerating machine oils having different kinematic viscosities at 40°C under the condition of a low-speed operating frequency of, for example, 17 r/s (rps) in a hermetic refrigerant compressor having a conventional configuration.
• rps r/s
• the amount of leakage of the refrigerant gas tends to increase in accordance with a reduction in the kinematic viscosity at 40°C of the refrigerating machine oil in use.
• the viscosity of the refrigerating machine oil is reduced, if the kinematic viscosity at 40°C of the refrigerating machine oil is greater than 2.5 mm 2 /s, sliding loss in the hermetic refrigerant compressor can be effectively reduced, the positive influence of which is greater than the negative influence caused by the increase in the amount of leakage of the refrigerant gas, and consequently, the coefficient of performance (COP) can be improved.
• the amount of leakage of the refrigerant gas is excessive in a case where the kinematic viscosity at 40°C of the refrigerating machine oil is less than or equal to 2.5 mm 2 /s. Accordingly, in this case, it has been found that the refrigeration capacity of the refrigeration cycle of the hermetic refrigerant compressor deteriorates, and consequently, the coefficient of performance (COP) cannot be improved.
• the inventors of the present invention conducted further diligent studies, and as a result of the studies, they have found that the coefficient of performance (COP) can be improved by effectively suppressing the leakage of the refrigerant gas from between the piston and the cylinder. Consequently, they have arrived at the present invention.
• COP coefficient of performance
• a hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s
• an average speed of the piston moving in the reciprocating manner may be set to greater than 0.31 m/s.
• the lower limit of the average speed of the piston moving in the reciprocating manner i.e., mean piston speed
• the operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• low-viscosity oil having a further reduced viscosity low-viscosity oil whose kinematic viscosity at 40°C is set within the range of 1.0 mm 2 /s to 2.5 mm 2 /s
• a favorable oil film can be formed between the piston and the compression chamber by the piston, which moves in the reciprocating manner at a high speed. This consequently makes it possible to favorably suppress the leakage of refrigerant gas from between the piston and the compression chamber. Therefore, when the low-viscosity oil is used as the refrigerating machine oil, the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• COP coefficient of performance
• the hermetic refrigerant compressor with the above-described configuration may be configured such that a ratio S / D of a stroke amount (S) of the piston moving in the reciprocating manner to a piston diameter (D) of the piston is within a range of 0.78 to 1.00.
• the ratio S / D is set within the above range. Owing to such setting of the ratio S / D, as described below, the stroke amount (S) can be relatively increased, and the piston diameter (D) can be relatively reduced.
• the amount of leakage of the refrigerant gas can be favorably suppressed, and also, input power to cause the piston to move in the reciprocating manner can be reduced. Therefore, when the low-viscosity oil is used as the refrigerating machine oil, the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• COP coefficient of performance
• the hermetic refrigerant compressor with the above-described configuration may be configured such that: a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2); a ratio L1 / D of a piston overall length (L1) of the piston to the piston diameter (D) is within a range of 0.8 to 1.0; and a ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is within a range of 0.9 to 1.0.
• the ratio L1 / D and the ratio L2 / L1 are set within the respective predetermined ranges. Owing to the setting of these ratios, as described below, the sealing length (L2) can be relatively increased without excessively increasing the piston overall length (L1).
• the viscous force of the oil film can be increased while suppressing an increase in sliding loss, and also, the leakage of the refrigerant gas can be further suppressed.
• Another hermetic refrigerant compressor includes: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• a ratio S / D of a stroke amount (S) of the piston moving in the reciprocating manner to a piston diameter (D) of the piston is within a range of 0.78 to 1.00.
• the ratio S / D is set within the predetermined range. Owing to this setting, the stroke amount (S) can be relatively increased. Accordingly, the mean piston speed can be relatively increased. For this reason, the amount of leakage of the refrigerant gas can be favorably suppressed.
• the piston diameter (D) can be relatively reduced. Consequently, the total area of a clearance between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder can be reduced, which makes it possible to favorably suppress the leakage of the refrigerant gas.
• the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• the hermetic refrigerant compressor with the above-described configuration may be configured such that: a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2); and a ratio L2 / L1 of the sealing length (L2) to a piston overall length (L1) of the piston is within a range of 0.9 to 1.0.
• the ratio L1 / D and the ratio L2 / L1 are set within the respective predetermined ranges. Owing to the setting of these ratios, as described below, the sealing length (L2) can be relatively increased without excessively increasing the piston overall length (L1).
• the viscous force of the oil film can be increased while suppressing an increase in sliding loss, and also, the leakage of the refrigerant gas can be further suppressed.
• Yet another hermetic refrigerant compressor includes: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• a ratio L1 / D of a piston overall length (L1) of the piston to a piston diameter (D) of the piston is within a range of 0.8 to 1.0.
• a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2).
• a ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is within a range of 0.9 to 1.0.
• the ratio L1 / D and the ratio L2 / L1 are set within the respective predetermined ranges. Owing to these settings, the sealing length (L2) can be relatively increased without excessively increasing the piston overall length (L1) while suppressing an increase in sliding loss. Consequently, between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder, the viscous force of the oil film can be increased while suppressing an increase in sliding loss.
• the coefficient of performance (COP) of the hermetic refrigerant compressor can be further improved.
• the hermetic refrigerant compressor with any of the above-described configurations may be configured such that the compression element includes: a shaft part that is a crankshaft including a main shaft and an eccentric shaft; and a bearing part that pivotally supports the shaft part, the bearing part including a main bearing and an eccentric bearing, the main bearing pivotally supporting the main shaft, the eccentric bearing pivotally supporting the eccentric shaft, the main shaft includes a sliding surface that slides on the main bearing and that is divided into a plurality of sliding surfaces, a sum of lengths of the plurality of sliding surfaces in an axial direction is a total sliding length Tt, and a ratio Tt / K of the total sliding length Tt to an external diameter K of the main shaft is less than or equal to 1.26.
• a main shaft sliding portion that is formed by the main shaft and the main bearing can be favorably lubricated, and wear of the main shaft sliding portion can be favorably suppressed. Consequently, the reliability of the refrigerant compressor can be further improved. Even in a case where the refrigerant compressor is operated at a low rotation speed at which the operating frequency is greater than or equal to 16 r/s and less than or equal to 35 r/s, and the feeding amount of the refrigerating machine oil is reduced, favorable wear resistance can be achieved. This makes it possible to suppress an increase in sliding loss also at the main shaft sliding portion, and consequently, a favorable coefficient of performance (COP) can be achieved.
• COP coefficient of performance
• the hermetic refrigerant compressor with any of the above-described configurations may be configured such that the compression element includes: a shaft part that is a crankshaft including a main shaft and an eccentric shaft; and a bearing part that pivotally supports the shaft part, the bearing part including a main bearing and an eccentric bearing, the main bearing pivotally supporting the main shaft, the eccentric bearing pivotally supporting the eccentric shaft, the main shaft includes a sliding surface that slides on the main bearing, the sliding surface being either a single sliding surface or divided into a plurality of sliding surfaces, in a case where the sliding surface is the single sliding surface, a length the single sliding surface in an axial direction is a single sliding length T, whereas in a case where the sliding surface is divided into the plurality of sliding surfaces, a length of one sliding surface of the plurality of sliding surfaces in the axial direction, the one sliding surface having a shortest length in the axial direction in the plurality of sliding surfaces, is the single sliding length T, a ratio T / K of the single sliding length T to an external diameter K
• a main shaft sliding portion that is formed by the main shaft and the main bearing can be favorably lubricated, and wear of the main shaft sliding portion can be favorably suppressed. Consequently, the reliability of the refrigerant compressor can be further improved. Even in a case where the refrigerant compressor is operated at a low rotation speed at which the operating frequency is greater than or equal to 16 r/s and less than or equal to 35 r/s, and the feeding amount of the refrigerating machine oil is reduced, favorable wear resistance can be achieved. This makes it possible to suppress an increase in sliding loss also at the main shaft sliding portion, and consequently, a favorable coefficient of performance (COP) can be achieved.
• COP coefficient of performance
• the hermetic refrigerant compressor with any of the above-described configurations may be configured such that the compression element further includes: a crankshaft including a main shaft and an eccentric shaft; a main bearing that pivotally supports the main shaft; and a thrust bearing provided on a thrust surface of the main bearing, one end of a sliding surface of the main bearing is a first end, and an opposite end of the sliding surface of the main bearing is a second end, the first end being closer to the compression chamber than the second end is, a distance between a center axis of the compression chamber and the second end of the sliding surface of the main bearing is a distance P, a distance between the center axis of the compression chamber and the first end of the sliding surface of the main bearing is a distance Q, and the distance Q is less than or equal to 16 mm when the distance P is within a range of 38 mm to 51 mm.
• a main shaft load can be reduced.
• the distance Q in the refrigerant compressor is set to less than or equal to 16 mm. Therefore, increased efficiency and favorable reliability of the refrigerant compressor can be achieved not only at the sliding portion between the piston and the cylinder, but also at the main shaft sliding portion. Consequently, a more favorable coefficient of performance (COP) of the refrigerant compressor can be achieved.
• COP coefficient of performance
• the present disclosure also includes a method of operating a hermetic refrigerant compressor.
• the hermetic refrigerant compressor may include: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber.
• the method may include setting an average speed of the piston moving in the reciprocating manner to greater than 0.31 m/s when an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• the present disclosure also includes a refrigerator-freezer in which the hermetic refrigerant compressor configured as described above or the hermetic refrigerant compressor with which the above-described method is performed is used.
• the refrigerator-freezer according to the present disclosure may include a refrigerant circuit, the refrigerant circuit including: the hermetic refrigerant compressor configured as described above (or the hermetic refrigerant compressor with which the above-described method is performed); a radiator; a decompressor; and a heat absorber.
• the hermetic refrigerant compressor, the radiator, the decompressor, and the heat absorber may be connected by piping in an annular manner.
• FIG. 1 is a schematic sectional view showing one example of the configuration of a hermetic refrigerant compressor 100 according to Embodiment 1 of the present disclosure (hereinafter, in some cases, the hermetic refrigerant compressor 100 is simply referred to as "the refrigerant compressor 100").
• the refrigerant compressor 100 includes a sealed container 102 filled with refrigerant gas 181, which is, for example, R600a. Mineral oil is stored in the bottom of the sealed container 102 as refrigerating machine oil 180.
• a compressor body 108 is accommodated in the sealed container 102.
• the compressor body 108 is elastically supported by a suspension spring 190.
• the compressor body 108 includes an electric element 104 and a compression element 106.
• the electric element 104 includes at least a stator 150 and a rotor 152.
• the compression element 106 is a reciprocating element driven by the electric element 104.
• the compression element 106 includes, for example, a crankshaft 120, a cylinder block 130, a piston 140, and a coupler 142.
• the crankshaft 120 includes, at least, a main shaft 124 and an eccentric shaft 122.
• the rotor 152 is fixed to the main shaft 124 by shrinkage fitting.
• the eccentric shaft 122 is formed such that it is eccentric with the main shaft 124.
• the crankshaft 120 is formed from, for example, a ferrous material.
• a flange 128 is provided between the main shaft 124 and the eccentric shaft 122.
• the rotational axis of the crankshaft 120 corresponds to the center axis of the main shaft 124.
• the main shaft 124 and the eccentric shaft 122 are fixed via the flange 128, such that the center axis of the main shaft 124 and the center axis of the eccentric shaft 122 are shifted from each other. Therefore, the center axis of the eccentric shaft 122 is eccentric with the center axis of the main shaft 124 (i.e., eccentric with the rotational axis of the crankshaft 120).
• the eccentric shaft 122 of the crankshaft 120 is positioned in the upper side of the refrigerant compressor 100, whereas the main shaft 124 of the crankshaft 120 is positioned in the lower side of the refrigerant compressor 100. Therefore, this upper-lower positional relationship (direction) is utilized herein when describing positions on the crankshaft 120.
• the upper end of the eccentric shaft 122 faces the inner upper surface of the sealed container 102, and the lower end of the eccentric shaft 122 is connected to the main shaft 124.
• the upper end of the main shaft 124 is connected to the eccentric shaft 122, and the lower end of the main shaft 124 faces the inner lower surface of the sealed container 102.
• the lower end of the main shaft 124 is immersed in the refrigerating machine oil 180.
• the crankshaft 120 is provided with an oil feeding mechanism 125.
• the oil feeding mechanism 125 feeds the refrigerating machine oil 180 from the lower end of the main shaft 124, which is immersed in the refrigerating machine oil 180, to the upper end of the eccentric shaft 122.
• the refrigerating machine oil 180 lubricates sliding portions included in the refrigerant compressor 100, and serves to seal between a compression chamber 133 and the piston 140.
• the outer peripheral surface of the main shaft 124 of the crankshaft 120 includes sliding surfaces 126a and 126b and a non-sliding outer peripheral surface 127.
• the sliding surface 126a which is an upper sliding surface of the main shaft 124
• the sliding surface 126b which is a lower sliding surface of the main shaft 124
• the non-sliding outer peripheral surface 127 is positioned between the first sliding surface 126a and the second sliding surface 126b.
• sliding surface means the outer peripheral surface or the inner peripheral surface of each of a plurality of sliding members forming the sliding portions, the outer or inner peripheral surface slidably contacting the other inner or outer peripheral surface.
• non-sliding outer peripheral surface is the surface that does not come into contact with the other inner or outer peripheral surface.
• the non-sliding outer peripheral surface 127 is formed by reducing (narrowing) the external diameter of a part of the main shaft 124 from the external diameter of the sliding surfaces 126a and 126b (i.e., the non-sliding outer peripheral surface 127 is recessed from the sliding surfaces 126a and 126b, or the non-sliding outer peripheral surface 127 is formed by recessing the middle portion of the outer peripheral surface of the main shaft 124).
• the cylinder block 130 includes a cylinder 132 and a main bearing 134.
• the cylinder 132 includes the compression chamber 133 formed therein.
• the main bearing 134 pivotally supports the main shaft 124, such that the main shaft 124 is rotatable.
• the cylinder 132 and the main bearing 134 are integrally formed as a single cylinder block 130, for example, by iron casting.
• the direction in which the crankshaft 120 extends is referred to as a "longitudinal direction”.
• the cylinder block 130 includes a body that extends in a "transverse direction” (i.e., the direction orthogonal to the longitudinal direction) inside the refrigerant compressor 100.
• the main bearing 134 has a tubular (cylindrical) shape that extends in the "longitudinal direction" (vertical direction) relative to the body of the cylinder block 130.
• the inner peripheral surface of the main bearing 134 is slidably in contact with the outer peripheral surface of the main shaft 124, i.e., in contact with the sliding surfaces 126a and 126b. Therefore, the inner peripheral surface of the main bearing 134 is a sliding surface.
• the non-sliding outer peripheral surface 127 of the main shaft 124 is positioned between the upper end and the lower end of the main bearing 134. Therefore, in a state where the main shaft 124 is pivotally supported by the main bearing 134, the upper end of the main bearing 134 is in contact with the first sliding surface 126a of the main shaft 124, and the lower end of the main bearing 134 is in contact with the second sliding surface 126b of the main shaft 124.
• the non-sliding outer peripheral surface 127 whose external diameter is less than that of the sliding surfaces 126a and 126b is not in contact with the inner peripheral surface (sliding surface) of the main bearing 134, and is neither exposed from the upper end nor exposed from the lower end of the main bearing 134.
• the main bearing 134 includes a thrust surface 136 and a tubular extension 137.
• the thrust surface 136 of the main bearing 134 is a flat surface that spreads in a direction (horizontal direction) orthogonal (perpendicular) to the extending direction (vertical direction) of the center axis, i.e., the main shaft 124.
• the tubular extension 137 of the main bearing 134 is a tubular (cylindrical) portion that extends further upward from the thrust surface 136.
• the tubular extension 137 is a portion that extends upward from the body of the tubular main bearing 134.
• the tubular extension 137 together with the body of the main bearing 134, includes an inner peripheral surface (sliding surface) that faces the outer peripheral surface (sliding surface) of the main shaft 124.
• a thrust ball bearing 210 is provided on the thrust surface 136 of the main bearing 134.
• the cylinder 132 is included in the body of the cylinder block 130, and the interior of the cylinder 132 serves as the compression chamber 133.
• the compression chamber 133 is a bore that extends in the "transverse direction" inside the refrigerant compressor 100 and that has a cylindrical shape (columnar shape).
• the piston 140 is inserted in the compression chamber 133 such that the piston 140 is movable in a reciprocating manner in the compression chamber 133. Therefore, the compression chamber 133 is closed by the piston 140 inserted therein.
• the direction of the reciprocating motion of the piston 140 is the "transverse direction".
• the coupler 142 is, for example, an aluminum casting product.
• the coupler 142 pivotally supports the eccentric shaft 122, and is coupled to the piston 140.
• the eccentric shaft 122 and the piston 140 are coupled together by the coupler 142.
• the electric element 104 includes the rotor 152 and the stator 150.
• the stator 150 is disposed coaxially with the rotor 152 in a manner to surround the rotor 152.
• the stator 150 is disposed on the outer peripheral side of the rotor 152, such that substantially a constant gap is formed between the stator 150 and the rotor 152.
• the stator 150 is fixed to the leg of the cylinder block 130.
• the rotor 152 is fixed to the main shaft 124 of the crankshaft 120.
• the crankshaft 120 rotates.
• the center axis of the eccentric shaft 122 is eccentric with the center axis of the main shaft 124, and the eccentric shaft 122 is coupled to the piston 140 by the coupler 142.
• the piston 140 is inserted in the compression chamber 133 in the cylinder 132 such that the piston 140 is movable in a reciprocating manner in the compression chamber 133. Accordingly, when the crankshaft 120 rotates, the rotation of the eccentric shaft 122 causes the piston 140 to move in a reciprocating manner in the compression chamber 133.
• the oil feeding mechanism 125 feeds the refrigerating machine oil 180 to the sliding portions.
• the sliding portions are lubricated by the refrigerating machine oil 180.
• the present embodiment includes: a sliding portion formed by the main shaft 124 of the crankshaft 120 and the main bearing 134; a sliding portion formed by the piston 140 and the compression chamber 133 (the cylinder 132); a sliding portion formed by a coupling portion of the coupler 142 and a coupling portion of the piston 140; a sliding portion formed by the eccentric shaft 122 of the crankshaft 120 and a coupling portion of the coupler 142; etc. It should be noted that these sliding portions are formed by sliding members.
• the sliding portion formed by the piston 140 and the compression chamber 133 (the cylinder 132) is hereinafter referred to as a "cylinder sliding portion” for the sake of convenience of the description.
• the sliding portion formed by the main shaft 124 of the crankshaft 120 and the main bearing 134 is hereinafter referred to as a “main shaft sliding portion” for the sake of convenience of the description.
• the refrigerant compressor 100 according to the present disclosure may include the electric element 104 and the compression element 106, and the compression element 106 may include: the cylinder block 130 including the compression chamber 133; and the piston 140 inserted in the compression chamber 133 such that the piston 140 is movable in a reciprocating manner in the compression chamber 133.
• the electric element 104 is positioned in the lower side of the sealed container 102 and the compression element 106 is positioned in the upper side of the sealed container 102.
• the electric element 104 may be positioned in the upper side of the sealed container 102, and the compression element 106 may be positioned in the lower side of the sealed container 102.
• the electric element 104 is of an inner rotor type, and the rotor 152 is rotatably disposed on the inner peripheral side of the stator 150, such that the rotor 152 is coaxial with the stator 150.
• the electric element 104 is not limited to this configuration.
• the electric element 104 may be of an outer rotor type. That is, the rotor 152 may be rotatably disposed on the outer peripheral side of the stator 150, such that the rotor 152 is coaxial with the stator 150.
• the main shaft 124 of the crankshaft 120 includes the first sliding surface 126a, the non-sliding outer peripheral surface 127, and the second sliding surface 126b.
• the main shaft 124 is not limited to this a configuration.
• a sliding surface 126 of the main shaft 124 may constitute the entire outer peripheral surface of the main shaft 124, or the main shaft 124 may include three or more sliding surfaces 126.
• a specific configuration of the refrigerating machine oil 180 used in the present disclosure is not particularly limited.
• a specific configuration of the low-viscosity oil is not particularly limited.
• a mineral oil having a low viscosity is used.
• a different oil substance may be used instead of the mineral oil, or another oil substance may be used in combination with the mineral oil, or various additives and so forth may be added to the refrigerating machine oil 180.
• the kinematic viscosity at 40°C of the refrigerating machine oil 180 (low-viscosity oil) in the present disclosure is greater than 2.5 mm 2 /s, it results in excessively high viscous resistance of the refrigerating machine oil 180 in light of achieving a favorable coefficient of performance (COP).
• COP coefficient of performance
• the kinematic viscosity at 40°C of the refrigerating machine oil 180 is less than 1.0 mm 2 /s, it results in an excessively thin oil film being formed on each sliding portion in the refrigerant compressor 100. If the oil film on the sliding portion is too thin, there is a high possibility of breakage of the oil film, and consequently, a favorable lubricating function cannot be obtained at the sliding portion. This results in increased metal contacts between sliding surfaces at the sliding portion, and consequently, the reliability of the sliding portion may deteriorate.
• the upper limit value or the lower limit value of the kinematic viscosity at 40°C of the refrigerating machine oil 180 may be changed within the aforementioned range as necessary depending on various conditions.
• the upper limit value of the kinematic viscosity at 40°C of the refrigerating machine oil 180 may be 2.4 mm 2 /s.
• the lower limit value of the kinematic viscosity at 40°C of the refrigerating machine oil 180 ⁇ may be 1.5 mm 2 /s.
• the upper limit value or the lower limit value may include (i.e., may be less than or equal to, or may be greater than or equal to) the numerical value specified by the upper limit value or the lower limit value, or may not include (i.e., may be less than, or may be greater than) the numerical value specified by the upper limit value or the lower limit value.
• the upper limit value may be less than 2.5 mm 2 /s, or may be less than or equal to 2.4 mm 2 /s, or may be less than 2.4 mm 2 /s. The same applies to the lower limit value.
• the kinematic viscosity at 40°C of the refrigerating machine oil 180 may be set to less than or equal to 2.4 mm 2 /s, or to less than 2.4 mm 2 /s, or may be set to greater than or equal to 1.5 mm 2 /s, or to greater than 1.5 mm 2 /s, and with such setting of the kinematic viscosity at 40°C of the refrigerating machine oil 180, more suitable viscous resistance or a more suitable oil film thickness can be readily achieved.
• the "piston configuration" herein includes not only a specific configuration of the piston 140, but also, for example, conditions that are set when the piston 140 moves in a reciprocating manner in the compression chamber 133.
• the refrigerant compressor 100 first, electric power from a commercial power supply is supplied to the electric element 104, thereby causing the rotor 152 of the electric element 104 to rotate. Since the rotation of the rotor 152 causes the crankshaft 120 to rotate as described above, eccentric motion of the eccentric shaft 122 relative to the main shaft 124 is transmitted to the piston 140 via the coupler 142. As a result, the eccentric motion of the eccentric shaft 122 is converted into reciprocating motion of the piston 140, and the piston 140 is driven to move in a reciprocating manner in the cylinder 132, i.e., in the compression chamber 133. The refrigerant gas 181 is led into the sealed container 102, and due to the reciprocating motion of the piston 140, sucked into the compression chamber 133 and compressed therein.
• the refrigerant compressor 100 is inverter-driven at a plurality of operating frequencies. That is, the refrigerant compressor 100 according to the present disclosure may include, as a controller to control the operation of the refrigerant compressor 100, at least an inverter circuit to control the operating frequency.
• a specific configuration of the inverter circuit is not particularly limited, so long as the inverter circuit can drive the rotation of the electric element 104 at a plurality of operating rotation speeds.
• the inverter circuit may be configured as a chip, or may be a microprocessor or the like that operates in accordance with a program that drives the rotation of the electric element 104 at a plurality of operating rotation speeds.
• low-viscosity oil low-viscosity lubricating oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s is used.
• the lubricating function at the sliding portions tends to be reduced. Accordingly, in a case where the refrigerating machine oil 180 is low-viscosity oil, in order to avoid or suppress a reduction in the lubricating function, generally speaking, the sliding surfaces of the sliding portions are, for example, surface-treated.
• the amount of leakage of the refrigerant gas 181 from between the piston 140 and the cylinder 132 is excessive in a case where the kinematic viscosity at 40°C of the refrigerating machine oil 180 is less than or equal to 2.5 mm 2 /s (see also Examples described below).
• reducing a clearance between the surface of the piston 140 and the inner surface of the compression chamber 133 is generally selected as a way to reduce the amount of leakage of the refrigerant gas 181.
• low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s is used as the refrigerating machine oil 180 stored in the sealed container 102, and when the operating frequency is being controlled by the inverter circuit (or the controller) to be greater than or equal to 16 r/s and less than or equal to 35 r/s, the refrigerant compressor 100 is operated such that the average speed of the piston 140 moving in a reciprocating manner (i.e., mean piston speed) is greater than 0.31 m/s.
• FIG. 2 is a schematic side view (a schematic fragmentary sectional view) showing, in an enlarged manner, an essential part of the configuration of the cylinder sliding portion included in the refrigerant compressor 100 of FIG. 1 .
• FIG. 2 schematically shows: a part of the cylinder 132 included in the cylinder block 130; a part of the compression chamber 133 formed in the cylinder 132; and a part of the piston 140 slidably inserted in the compression chamber 133.
• the inside of the compression chamber 133 is filled with the refrigerant gas 181, and an oil film of the refrigerating machine oil 180 is formed between the outer peripheral surface of the piston 140 and the inner peripheral surface of the cylinder 132 (the inner peripheral surface of the compression chamber 133).
• the viscous force of the oil film of the refrigerating machine oil 180 present between the piston 140 and the cylinder 132 can be expressed by an equation (1) shown below, where: ( ⁇ ) is the viscosity of the refrigerating machine oil 180; (L2) is the sealing length of the piston 140; ( ⁇ ) is the clearance between the piston 140 and the cylinder 132; and (V) is the mean piston speed.
• F 1 ⁇ ⁇ L 2 ⁇ V / ⁇
• the sealing length (L2) is the length of a region in which the piston 140 seals the inside of the compression chamber 133 by moving in a reciprocating manner therein.
• the viscous force (F1) of the oil film is, as schematically indicated as a block arrow in FIG. 2 , force from the outer side toward the inner side of the compression chamber 133.
• the clearance ( ⁇ ) between the piston 140 and the cylinder 132 is schematically shown in FIG. 2 .
• the oil film of the refrigerating machine oil 180 fills the clearance ( ⁇ ) without oil breakage.
• the mean piston speed (V) is set high in order for the oil film to exert favorable viscous force between the piston 140 and the cylinder 132 when the refrigerating machine oil 180 is low-viscosity oil.
• the operating frequency (operating rotation speed) of the refrigerant compressor 100 is not particularly limited.
• a typical example of the lower limit of the operating frequency is 13 r/s (rps).
• the lower limit may be 16 r/s.
• the upper limit of the operating frequency may be 80 r/s.
• the upper limit may be 75 r/s.
• a typical range of the operating frequency is, for example, the range of 13 to 80 r/s, or the operating frequency may be within the range of 16 to 75 r/s.
• the operating frequency may be within the range of 16 to 80 r/s, or may be within the range of 13 to 75 r/s.
• the upper limit of the operating frequency may be set to higher than 80 r/s. In this case, however, the input power of the refrigerant compressor 100 is great.
• the operating frequency may be set to lower than 13 r/s.
• the operating frequency is set too low, there is a possibility that sufficient reliability cannot be obtained for both the coefficient of performance (COP) of the refrigerant compressor 100 and wear of the cylinder sliding portion.
• the lower limit of the operating frequency may be 16 r/s.
• the range of greater than or equal to 16 r/s and less than or equal to 35 r/s is defined as a "low-speed operating frequency" range.
• the mean piston speed is set to a high speed of greater than 0.31 m/s. Therefore, in the present disclosure, the lower limit of the mean piston speed may be greater than 0.31 m/s.
• the mean piston speed is less than or equal to 0.31 m/s, the oil film of the low-viscosity oil (the refrigerating machine oil 180) between the piston 140 and the cylinder 132 cannot exert sufficient viscous force. Consequently, when the refrigerant compressor 100 is operating within the low-speed operating frequency range, the refrigerant gas 181 tends to leak from between the piston 140 and the cylinder 132.
• the lower limit value of the mean piston speed may be greater than 0.31 m/s. However, in accordance with various conditions, the lower limit value of the mean piston speed may be set to greater than or equal to 0.32 m/s, or may be set to greater than or equal to 0.34 m/s. If the lower limit of the mean piston speed is greater than or equal to 0.32 m/s, although depending on various conditions, the oil film of the refrigerating machine oil 180 between the piston 140 and the cylinder 132 can readily exert more favorable viscous force. This makes it possible to more favorably suppress the leakage of the refrigerant gas 181 from between the piston 140 and the cylinder 132.
• a configuration in which a ratio S / D of a stroke amount (S) of the piston 140 moving in a reciprocating manner to a piston diameter (D) of the piston 140 is set within the range of 0.78 to 1.00 can be adopted (0.78 ⁇ S / D ⁇ 1.00).
• the stroke amount (S) of the piston 140 moving in a reciprocating manner is determined by a twice of the eccentric radius of the eccentric shaft 122.
• the ratio S / D is a condition that is set when the piston 140 moves in a reciprocating manner in the compression chamber 133. Accordingly, the ratio S / D can be considered as being included in the aforementioned piston configuration.
• the ratio S / D of the stroke amount (S) to the piston diameter (D) is set within the aforementioned range, and thereby the stroke amount of the piston 140 can be made relatively large (can be relatively increased), which makes it possible to increase the mean piston speed (V).
• V mean piston speed
• the viscous force (F1) of the oil film can be increased, and the oil film can be readily formed between the piston 140 and the cylinder 132. This makes it possible to suppress the leakage of the refrigerant gas 181.
• the stroke amount (S) being increased when the ratio S / D is within the aforementioned range means the piston diameter (D) being relatively reduced.
• the piston diameter (D) By reducing the piston diameter (D), the total area of the clearance ( ⁇ ) between the piston 140 and the cylinder 132 can be reduced.
• the total area of the clearance being reduced means an "opening region", through which the leakage of the refrigerant gas 181 may occur, being reduced. This makes it possible to suppress the leakage of the refrigerant gas 181 from between the piston 140 and the cylinder 132.
• a compressive load to compress the refrigerant gas 181 by the piston 140 can be reduced.
• a load applied from the refrigerant gas 181 in the compression chamber 133 to the distal end surface of the piston 140 when the piston 140 moves in a reciprocating manner in the compression chamber 133 is relatively reduced.
• input power to cause the piston 140 to make the reciprocating motion can be reduced. This makes it possible to improve the coefficient of performance (COP) of the refrigerant compressor 100.
• COP coefficient of performance
• the ratio S / D of the stroke amount (S) to the piston diameter (D) is desirably within the range of 0.4 to 0.8 as disclosed in "HERMETIC REFRIGERATOR" authored by Mutsuyoshi KAWAHIRA and published by Japanese Association of Refrigeration in July 1981.
• the ratio S / D is set within the range of 0.78 to 1.00. That is, the ratio S / D in the present disclosure is set such that it is substantially greater than the conventional range.
• the lower limit of the ratio S / D may be greater than or equal to 0.81 (0.81 ⁇ S / D), or may be greater than or equal to 0.84 (0.84 ⁇ S / D).
• the ratio S / D is less than 0.78, when low-viscosity oil (whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s) is used as the refrigerating machine oil 180, there is a possibility that the stroke amount (S) of the piston 140 cannot be relatively increased, and that the piston diameter (D) cannot be relatively reduced. If the lower limit of the ratio S / D is greater than or equal to 0.81, effects that the stroke amount (S) can be relatively increased and the piston diameter (D) can be relatively reduced can be exerted more assuredly. If the lower limit of the ratio S / D is greater than or equal to 0.84, these effects can be exerted even more assuredly.
• a specific stroke amount (S) of the piston 140 is not particularly limited.
• the lower limit of the stroke amount (S) may be, for example, greater than or equal to 19.5 mm.
• the lower limit of the stroke amount (S) may alternatively be greater than or equal to 20 mm.
• the upper limit of the stroke amount (S) is also not particularly limited. However, if the stroke amount (S) is increased excessively, there is a possibility that sliding loss between the piston 140 and the cylinder 132 is relatively increased. In light of this, the upper limit of the stroke amount (S) may be less than or equal to 30 mm.
• a specific value of the clearance ( ⁇ ) between the piston 140 and the cylinder 132 is also not particularly limited.
• the lower limit of the clearance ( ⁇ ) may be, for example, 3 ⁇ m
• the upper limit of the clearance ( ⁇ ) may be, for example, 10 ⁇ m. If the clearance ( ⁇ ) is greater than 10 ⁇ m, particularly when low-viscosity oil is used as the refrigerating machine oil 180, the viscous force (F1) is reduced (see the above equation (1)).
• the clearance ( ⁇ ) is less than 3 ⁇ m, particularly when low-viscosity oil is used as the refrigerating machine oil 180, there is a possibility that the piston 140, which makes the reciprocating motion, tends to come into contact with the inner peripheral surface of the cylinder 132 (the compression chamber 133).
• a configuration with the following ratio settings can be adopted: a ratio L1 / D within the range of 0.8 to 1.0 (0.8 ⁇ L1 / D ⁇ 1.0), which is the ratio of a piston overall length (L1) of the piston 140 to the piston diameter (D); and a ratio L2 / L1 within the range of 0.9 to 1.0 (0.9 ⁇ L2 / L1 ⁇ 1.0), which is the ratio of the sealing length (L2) to the piston overall length (L1).
• the ratio L1 / D is a part of the specific configuration of the piston 140 (i.e., is a condition for the piston 140), and the ratio L2 / L1 is a condition set when the piston 140 moves in a reciprocating manner in the compression chamber 133. Accordingly, these ratios can be considered as being included in the aforementioned piston configuration.
• FIG. 3A is a schematic side view showing one representative example of the piston 140 used in the refrigerant compressor 100 of FIG. 1
• FIG. 3B is a schematic side view showing one representative example of a conventional piston.
• the piston overall length (L1) which is the length of the piston 140 in the direction in which the piston 140 makes the reciprocating motion, is about equal to the piston diameter (D), which is the diameter of the piston 140.
• the piston overall length (L1) is about equal to the sealing length (L2), which is the length of the aforementioned region in which the piston 140 seals the inside of the compression chamber 133 by moving in a reciprocating manner therein.
• the viscous force (F1) of the oil film of the refrigerating machine oil 180 can be increased by increasing the sealing length (L2).
• an increase in the sealing length (L2) means an increase in the size of a region at the cylinder sliding portion, the region being sealed by the oil film. Accordingly, even with a relative increase in the sealing length (L2) alone, the leakage of the refrigerant gas 181 can be favorably suppressed.
• the piston overall length (L1) In order for the sealing length (L2) to be a sufficient length, it is necessary for the piston overall length (L1) to be a sufficient length. However, if the piston overall length (L1) is too large, it causes an increase in sliding loss at the cylinder sliding portion. Particularly in a case where the refrigerating machine oil 180 is low-viscosity oil (whose kinematic viscosity at 40°C is less than or equal to 2.5 mm 2 /s), it is more difficult to form a favorable oil film at the cylinder sliding portion than in a case where the refrigerating machine oil 180 has a higher viscosity.
• the inventors have conducted diligent studies on what should be used as a reference for setting a suitable piston overall length (L1). As a result of the studies, it has been found that particularly in a case where the refrigerating machine oil 180 is low-viscosity oil, the piston diameter (D) can be used as the reference.
• the ratio L1 / D is less than 0.8, when low-viscosity oil is used as the refrigerating machine oil 180, the piston overall length (L1) is relatively reduced. As a result, a sufficient sealing length (L2) cannot be secured, and consequently, not only is the size of the region sealed by the oil film insufficient, but also the viscous force (F1) of the oil film based on the above equation (1) cannot be increased.
• the ratio L1 / D is greater than 1.0, for example, as in the case of the conventional piston 240 shown in FIG. 3B , when low-viscosity oil is used as the refrigerating machine oil 180, the piston overall length (L1) is increased excessively. This may cause an increase in sliding loss at the cylinder sliding portion. The increased sliding loss hinders the achievement of a favorable coefficient of performance (COP).
• COP coefficient of performance
• the sealing length (L2) is made as large as possible.
• the piston overall length (L1) is too large, it causes an increase in sliding loss at the cylinder sliding portion.
• the ratio L2 / L1 is set within the range of 0.9 to 1.0.
• the sealing length (L2) can be relatively increased without excessively increasing the piston overall length (L1). Consequently, as is clear from the above equation (1), the viscous force (F1) of the oil film can be increased while suppressing an increase in sliding loss at the cylinder sliding portion.
• sealing length (L2) being increased relatively to the piston overall length (L1) means that the region sealed by the oil film of the refrigerating machine oil 180 is also relatively increased. For this reason, the leakage of the refrigerant gas 181 can be further suppressed. Moreover, as a result of the sealing length (L2) being increased, the orientation of the piston 140 moving in a reciprocating manner in the compression chamber 133 can be stabilized. Consequently, an increase in sliding loss can be further suppressed.
• the ratio L2 / L1 is less than 0.9, for example, as in the case of the conventional piston 240 shown in FIG. 3B , when low-viscosity oil is used as the refrigerating machine oil 180, a sufficient sealing length (L2) cannot be secured. As a result, the viscous force (F1) of the oil film cannot be increased, and also, the size of the region sealed by the oil film is relatively reduced. Consequently, there is a risk that the leakage of the refrigerant gas 181 cannot be sufficiently suppressed.
• the ratio L2 / L1 never exceeds 1.0 (because the sealing length (L2) is less than or equal to the piston overall length (L1)).
• the outer peripheral surface of the piston 140 may be a smooth surface with no irregularities intentionally formed thereon.
• an annular oil feeding groove may be formed on the outer peripheral surface of the piston 140.
• a specific configuration of the annular oil feeding groove is not particularly limited.
• the number of oil feeding grooves is not particularly limited. Typically, the number of oil feeding grooves may be one. Of course, two or more oil feeding grooves may be formed.
• the width of the oil feeding groove is also not particularly limited. For example, the width may be within the range of 0.1 to 0.5 mm.
• the width of the oil feeding groove is less than 0.1 mm, even if the refrigerating machine oil 180 is low-viscosity oil, it is difficult to feed a sufficient amount of refrigerating machine oil 180 to the sealed region.
• the width of the oil feeding groove is greater than 0.5 mm, if the refrigerating machine oil 180 is low-viscosity oil, the width of the oil feeding groove is too wide, and as a result, the refrigerating machine oil 180 flows out of the sealed region. Consequently, it is difficult to retain a suitable amount of refrigerating machine oil 180 in the sealed region.
• the above-described setting in which the average speed of the piston 140 moving in a reciprocating manner i.e., mean piston speed
• V mean piston speed
• the above-described setting in which the ratio S / D of the stroke amount (S) of the piston 140 moving in a reciprocating manner to the piston diameter (D) of the piston 140 is set within the range of 0.78 to 1.00 is simply referred to as "ratio S / D setting”
• the above-described setting in which the ratio L1 / D of the piston overall length (L1) of the piston 140 to the piston diameter (D) of the piston 140 is set within the range of 0.8 to 1.0 and the ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is set within the
• the refrigerant compressor 100 by applying at least one of the mean piston speed (V) high-speed setting, the ratio S / D setting, or the ratio L1 / D and ratio L2 / L1 setting to the refrigerant compressor 100 according to the present disclosure, even when low-viscosity oil is used as the refrigerating machine oil 180, the leakage of the refrigerant gas 181 can be favorably suppressed, and a more favorable coefficient of performance (COP) can be achieved.
• V mean piston speed
• the hermetic refrigerant compressor according to Embodiment 1 may be configured such that when low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s is used as the refrigerating machine oil 180, if the refrigerant compressor 100 includes, for example, the controller to control the operating frequency of the refrigerant compressor 100, when the controller is controlling the operating frequency to be greater than or equal to 16 r/s and less than or equal to 35 r/s, the average speed of the piston 140 moving in a reciprocating manner is set to greater than 0.31 m/s.
• the hermetic refrigerant compressor according to Embodiment 1 may be configured such that when the above low-viscosity oil is used as the refrigerating machine oil, the ratio S / D of the stroke amount (S) of the piston 140 moving in a reciprocating manner to the piston diameter (D) of the piston 140 is within the range of 0.78 to 1.00.
• the hermetic refrigerant compressor according to Embodiment 1 may be configured such that when the above low-viscosity oil is used as the refrigerating machine oil 180, in a case where the length of the region in which the piston 140 seals the inside of the compression chamber 133 by moving in a reciprocating manner therein is referred to as the sealing length (L2), the ratio L1 / D of the piston overall length (L1) to the piston diameter (D) is within the range of 0.8 to 1.0, and the ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is within the range of 0.9 to 1.0.
• the hermetic refrigerant compressor includes any of the above configurations, when low-viscosity oil is used as the refrigerating machine oil 180, the leakage of the refrigerant gas 181 from between the piston 140 and the compression chamber 133 can be further suppressed. This makes it possible to further improve the coefficient of performance (COP) of the hermetic refrigerant compressor.
• COP coefficient of performance
• the fundamental configuration of the hermetic refrigerant compressor according to Embodiment 2 is the same as the fundamental configuration of the hermetic refrigerant compressor according to Embodiment 1.
• the hermetic refrigerant compressor according to Embodiment 2 has additional characteristic features in relation to the main shaft sliding portion (the sliding portion formed by the main shaft 124 of the crankshaft 120 and the main bearing 134). It should be noted that since the fundamental configuration of the hermetic refrigerant compressor according to Embodiment 2 is the same as the configuration described in Embodiment 1 and shown in FIG. 1 , a detailed description thereof is omitted.
• FIG. 4A is a schematic diagram showing one configuration example in a case where, on the crankshaft 120 included in the refrigerant compressor 100 of FIG. 1 , a sliding surface is a single sliding surface.
• FIG. 4B and FIG. 4C are schematic diagrams each showing one configuration example in a case where, on the crankshaft 120, the sliding surface is divided into a plurality of sliding surfaces.
• the main shaft 124 of the crankshaft 120 is configured to include the first sliding surface 126a and the second sliding surface 126b. Accordingly, it can be considered that the sliding surface of the main shaft 124 is divided into a plurality of sliding surfaces.
• the configuration of the main shaft 124 shown in FIG. 1 i.e., the configuration in which the sliding surface is divided into two sliding surfaces, correspond to the schematic diagram shown in FIG. 4B .
• the shaft part according to the present disclosure is not limited to this configuration.
• the sliding surface of the main shaft 124 may be a single sliding surface.
• the outer peripheral surface of the main shaft 124 need not be divided into a plurality of sliding surfaces, but instead, the main shaft 124 may include only one sliding surface 126.
• a specific configuration in which the sliding surface is divided into a plurality of sliding surfaces is not particularly limited.
• a recess that is recessed (or receding) from the sliding surfaces toward the center axis may be formed.
• the recess serves as the non-sliding outer peripheral surface 127 as shown in FIG. 1 and FIG. 4B .
• a specific shape of the recess is also not particularly limited.
• the depth of the recess may be set to any depth, so long as the set depth does not affect, for example, the stiffness and strength of the main shaft 124.
• the width of the recess i.e., the distance between the plurality of sliding surfaces
• the width of the recess can be suitably set in accordance with how much the sliding surfaces are to be narrowed down (i.e., in accordance with an intended reduction or decrease in the sliding area).
• the sliding surface is divided into a plurality of sliding surfaces
• the plurality of sliding surfaces is not particularly limited to a specific number of sliding surfaces.
• the sliding surface may be divided into the first sliding surface 126a and the second sliding surface 126b, i.e., a total of two sliding surfaces.
• the sliding surface may be divided into a first sliding surface 126c, a second sliding surface 126d, and a third sliding surface 126e, i.e., a total of three sliding surfaces, or may be divided into four or more sliding surfaces.
• FIG. 1 and FIG. 4B the sliding surface may be divided into the first sliding surface 126a and the second sliding surface 126b, i.e., a total of two sliding surfaces.
• the sliding surface may be divided into a first sliding surface 126c, a second sliding surface 126d, and a third sliding surface 126e, i.e., a total of three sliding surfaces, or may be divided into four or more sliding surfaces.
• a first non-sliding outer peripheral surface 127a which is the same recess as the non-sliding outer peripheral surface 127, is positioned between the first sliding surface 126c and the second sliding surface 126d, and a second non-sliding outer peripheral surface 127b is positioned between the second sliding surface 126d and the third sliding surface 126e.
• the ratio of the length of the sliding surface of the main shaft sliding portion in the axial direction to the external diameter (the diameter) of a part of the main shaft sliding portion, the part serving as the sliding surface is set to less than or equal to a predetermined value, and thereby the sliding area can be reduced without substantially affecting the wear resistance.
• the length of the single sliding surface in the axial direction is a single sliding length T
• the sliding surface is divided into a plurality of sliding surfaces (e.g., FIG. 4B or FIG. 4C )
• the shaft part is designed such that a ratio T / K of the single sliding length T to the external diameter K of the shaft part is less than or equal to 0.51.
• FIG. 4A is illustrated such that the length T of the single sliding surface 126 (i.e., the single sliding length T) is greater than the external diameter K. If the length T of the single sliding surface 126 relative to the external diameter K is exactly as illustrated in FIG. 4A , the ratio T / K is greater than 0.51.
• the ratio T / K can be set to less than or equal to 0.51 (T / K ⁇ 0.51).
• the sliding surface is divided into the first sliding surface 126a and the second sliding surface 126b.
• a length Ta of the upper first sliding surface 126a in the axial direction is less than a length Tb of the lower second sliding surface 126b in the axial direction (Ta ⁇ Tb).
• the first sliding surface 126a is the "sliding surface having the shortest length".
• Ta / K may be less than or equal to 0.51 on the first sliding surface 126a.
• FIG. 4B is also illustrated in such a manner that the length Ta is greater than the external diameter K.
• the ratio T / K can be set to less than or equal to 0.51 by, for example, increasing the length of the non-sliding outer peripheral surface 127 in the axial direction or forming an unshown non-sliding outer peripheral surface (a recess) on the upper side of the first sliding surface 126a.
• the sliding surface is divided into the first sliding surface 126c, the second sliding surface 126d, and the third sliding surface 126e.
• a length Td of the middle second sliding surface 126d in the axial direction is less than a length Tc of the upper first sliding surface 126c in the axial direction, and the length Tc is less than a length Te of the lower third sliding surface 126e in the axial direction (Td ⁇ Tc ⁇ Te).
• the second sliding surface 126d is the "sliding surface having the shortest length”.
• Te / K may be less than or equal to 0.51 on the second sliding surface 126d.
• the lower limit value of the ratio T / K is not particularly limited. As one preferable example, the lower limit value may be greater than or equal to 0.15. Accordingly, as a preferable range of the ratio T / K in the present disclosure, the ratio T / K may be within the range of 0.15 to 0.51. As a more preferable example, the lower limit of the ratio T / K may be 0.30, and as an even more preferable example, the lower limit of the ratio T / K may be 0.42.
• the ratio T / K is greater than 0.51
• low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s
• a sulfur-based sliding modifier described below is added to the refrigerating machine oil 180
• the ratio T / K is less than 0.15, although depending on various conditions of the shaft part, there is a possibility of the sliding surface becoming too narrow.
• the ratio T / K is greater than or equal to 0.15, the sliding area is not reduced excessively. Therefore, even if low-viscosity oil is used as the refrigerating machine oil 180, suitable wear resistance of the main shaft sliding portion can be achieved by the sulfur-based sliding modifier.
• Embodiment 2 in a case where the sliding surface of the main shaft sliding portion is divided into a plurality of sliding surfaces, another length in the axial direction different from the above-described single sliding length T may be defined, and the ratio of this other length in the axial direction to the external diameter (the diameter) of the sliding surface may be set to less than or equal to a predetermined value. This makes it possible to reduce the sliding area without substantially affecting the wear resistance.
• the shaft part in a case where the sliding surface is divided into a plurality of sliding surfaces, when the total of the lengths of the plurality of sliding surfaces in the axial direction is a total sliding length Tt, the shaft part may be designed such that a ratio Tt / K of the total sliding length Tt to the external diameter K is less than or equal to 1.26 (Tt / K ⁇ 1.26).
• FIG. 4A is an example in which the first feature is applied to the main shaft sliding portion
• FIG. 4B and FIG. 4C shows an example in which both the first feature and the second feature are applied to the main shaft sliding portion. It is of course understood that the present disclosure is not limited to the configurations shown in FIG. 4A to FIG. 4C . As previously mentioned, only the second feature may be applied to the main shaft sliding portion.
• the sliding surface is divided into a plurality of sliding surfaces, if the ratio T / K is less than or equal to 0.51 and the ratio Tt / K is less than or equal to 1.26, then in a state where low-viscosity oil (whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s) is used as the refrigerating machine oil 180 and the sliding area is reduced, the wear resistance of the main shaft sliding portion derived from the below-described sulfur-based sliding modifier can be more improved.
• low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s
• the lower limit value of the ratio Tt / K is not particularly limited. As one preferable example, the lower limit value may be greater than or equal to 0.3. Accordingly, as a preferable range of the ratio Tt / K in the present disclosure, the ratio Tt / K may be within the range of 0.3 to 1.26. As a more preferable example, the lower limit of the ratio Tt / K may be 0.60, and as an even more preferable example, the lower limit of the ratio Tt / K may be 0.99. Generally speaking, if the ratio Tt / K is greater than or equal to 0.3, the sliding area is not reduced excessively even in a case where the sliding surface is divided into a plurality of sliding surfaces. For this reason, even if low-viscosity oil is used as the refrigerating machine oil 180, suitable wear resistance of the main shaft sliding portion can be achieved with the sulfur-based sliding modifier.
• the main shaft 124 of the crankshaft 120 is described as the shaft part, and the ratio T / K and the ratio Tt / K are described in relation to the main shaft 124.
• the present disclosure is not limited to this.
• the eccentric shaft 122 As described in Embodiment 1, the eccentric shaft 122 and the coupling portion of the coupler 142 form a sliding portion.
• a part of the coupler 142 slidably coupled to the eccentric shaft 122 serves as an "eccentric bearing".
• the sliding surface of the eccentric shaft 122 which slides on the "eccentric bearing" (the eccentric shaft 122 and the coupling portion of the coupler 142), is a single sliding surface
• the length of the single sliding surface in the axial direction is the single sliding length T
• the sliding surface of the eccentric shaft 122 is divided into a plurality of sliding surfaces
• the length of one sliding surface of the plurality of sliding surfaces in the axial direction, the one sliding surface having the shortest length in the axial direction in the plurality of sliding surfaces is the single sliding length T.
• the ratio T / K of the single sliding length T to the external diameter K of the eccentric shaft 122 may be less than or equal to 0.51.
• the ratio Tt / K of the total sliding length Tt to the external diameter K of the eccentric shaft 122 may be less than or equal to 1.26.
• At least one of the main and eccentric shafts 124 and 122, which are included in the shaft part, may satisfy the "first feature” that the ratio T / K is less than or equal to 0.51.
• at least one of the main and eccentric shafts 124 and 122 may satisfy the "second feature” that the ratio Tt / K is less than or equal to 1.26.
• at least one of the main and eccentric shafts 124 and 122 may satisfy both the first feature and the second feature.
• the refrigerating machine oil 180 used in Embodiment 2 may be, as described in Embodiment 1, low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s. More specific features of the refrigerating machine oil 180 in the present disclosure are described in the embodiment below.
• the low-viscosity oil serving as the refrigerating machine oil 180 contains a sulfur-based sliding modifier.
• the crankshaft 120 is formed from a ferrous material.
• the ferrous material is not particularly limited to a specific kind, but may be a metal material containing iron as its principal component, for example, one of the known various cast irons or a steel material.
• the sulfur-based sliding modifier may be any sulfur-based sliding modifier, so long as it allows the ferrous material and sulfur to react with each other.
• the sliding modifier in Embodiment 2 may be sulfur, or may be a sulfur compound that contains sulfur and that is reactive with the ferrous material.
• sulfur compounds usable as the sliding modifier include a sulfurized olefin, a sulfide-based compound (e.g., dibenzyl disulfide (DBDS)), a xanthate, a thiadiazole, a thiocarbonate, a sulfurized oil or fat, a sulfurized ester, a dithiocarbamate, and a sulfurized terpene.
• DBDS dibenzyl disulfide
• the sulfur-based sliding modifier content in the refrigerating machine oil 180 is not particularly limited.
• the sliding modifier may be added to the refrigerating machine oil 180, such that the sliding modifier content therein in terms of the atomic weight (mass) of sulfur is greater than or equal to 100 ppm.
• the lower limit value of the addition amount of the sliding modifier i.e., the lower limit value of the sliding modifier content
• being 100 ppm in terms of the atomic weight of sulfur is greater than the upper limit value of a general addition amount of a sulfur-based extreme-pressure additive that will be described below.
• the sliding modifier content (the addition amount of the sliding modifier) is less than 100 ppm in terms of the atomic weight of sulfur, although depending on various conditions, there is a possibility that in a state where low-viscosity oil is used as the refrigerating machine oil 180 and the sliding area of the main shaft sliding portion is reduced, suitable wear resistance of the main shaft sliding portion cannot be achieved.
• the lower limit of the sulfur-based sliding modifier content may be greater than or equal to 150 ppm in terms of the atomic weight of sulfur.
• the upper limit of the sulfur-based sliding modifier content may be less than or equal to 1000 ppm in terms of the atomic weight of sulfur, and as a more preferable example, the upper limit of the sulfur-based sliding modifier content may be less than or equal to 500 ppm in terms of the atomic weight of sulfur.
• a compound that is the same as a known sulfur-based extreme-pressure additive can be used as the sulfur-based sliding modifier in the present disclosure.
• a compound that is more reactive with the shaft part material than known extreme-pressure additives can be used as the sulfur-based sliding modifier in the present disclosure.
• a known extreme-pressure additive in an amount greater than a general addition amount i.e., greater than a general extreme-pressure additive content may be added to the refrigerating machine oil 180.
• an extreme-pressure additive is a compound containing an active element such as sulfur, halogen, or phosphorus, and chemically reacts with the surface of the material of a sliding portion (i.e., chemically reacts with a sliding surface) to form a film.
• an active element such as sulfur, halogen, or phosphorus
• chemically reacts with the surface of the material of a sliding portion i.e., chemically reacts with a sliding surface
• the presence of the film suppresses, for example, wear, seizing, or fusion of sliding members.
• sulfur-containing compounds easily react with copper.
• copper wire is used as the winding of the electric element 104.
• copper pipes are often used as refrigerant piping.
• copper tends to corrode by reacting with a sulfur-containing compound.
• sulfur-based extreme-pressure additive it is necessary to take measures to avoid or suppress the corrosion of a member made of copper (or a copper-containing member) included in the refrigerant compressor 100 or the refrigerator-freezer, thereby preventing lowering of the reliability thereof.
• the inventors of the present invention have conducted diligent studies including experimental verification. As a result of the studies, they have found that in the case of using low-viscosity oil as the refrigerating machine oil 180 and reducing the sliding area of the main shaft sliding portion such that the above-described ratio T / K is less than or equal to 0.51 (the first feature of the main shaft sliding portion) or such that the above-described ratio Tt / K is less than or equal to 1.26 (the second feature of the main shaft sliding portion), not only is favorable wear resistance achieved, but also the corrosion of a member made of copper (or a copper-containing member) can be substantially avoided, by using a sulfur-based compound having higher reactivity as the sliding modifier or by increasing the addition amount of the sliding modifier (i.e., by increasing the sliding modifier content).
• a surface layer e.g., an oxidized layer
• a sliding modifier forms a film (an anti-wear film) in place of the removed surface layer. This makes it possible to prevent the metal protrusions from fusing together. Consequently, wear of the sliding portion can be favorably suppressed.
• an extreme-pressure additive quickly forms a film (an extreme pressure film, EP film) in place of the removed surface layer.
• the EP film is more firmly formed on the sliding surface compared to the anti-wear film formed by the sliding modifier.
• the reason for this is that the extreme-pressure additive is intended for suppressing wear of the sliding portion that is in a lubrication state where the contact pressure between the sliding surfaces is relatively high and breakage of the oil film tends to occur, i.e., an "extreme pressure state".
• an additive to add to the refrigerating machine oil 180 for the purpose of suppressing wear of the sliding portions included in the refrigerant compressor 100 is, for example, an extreme-pressure additive.
• an extreme-pressure additive it is not common to add to the refrigerating machine oil 180 a sliding modifier whose film formation speed is slower than the film formation speed of an extreme-pressure additive.
• a film is formed on the main shaft sliding portion at a gradual speed, and consequently, it is expected that sulfur tends to be present locally (i.e., present unevenly) on the main shaft sliding portion.
• Embodiment 2 in the refrigerant compressor 100, in which low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s is used as the refrigerating machine oil 180, at least one of the mean piston speed (V) high-speed setting, the ratio S / D setting, or the ratio L1 / D and ratio L2 / L1 setting described above in Embodiment 1 is applied, and further, at least at the main shaft sliding portion, the first feature that the ratio T / K of the single sliding length T to the external diameter K of the shaft part is less than or equal to 0.51 or the second feature that the ratio Tt / K of the total sliding length Tt to the external diameter K of the shaft part is less than or equal to 1.26 (or both the first feature and the second feature) is applied together with the feature of using the sulfur-based sliding modifier.
• V mean piston speed
• the refrigerant compressor 100 in a case where the refrigerant compressor 100 is configured to be inverter-driven, there are two operation modes of the electric element 104, in one of which the electric element 104 is operated at a low rotation speed (low-speed operation), and in the other of which the electric element 104 is operated at a high rotation speed (high-speed operation). Particularly in the present disclosure, there is a case where the electric element 104 is operated at a low rotation speed at which the operating frequency is greater than or equal to 16 r/s and less than or equal to 35 r/s. Generally speaking, during the low-speed operation, the oil-feeding performance of the oil feeding mechanism 125 provided at the crankshaft 120 is lowered, and for this reason, the amount of refrigerating machine oil 180 fed to each sliding portion tends to be reduced.
• the mean piston speed can be set to a high speed and the viscous force of the oil film can be increased. Consequently, also at the cylinder sliding portion, an increase in sliding loss can be suppressed, and also, the leakage of the refrigerant gas 181 can be suppressed. This makes it possible to achieve a favorable coefficient of performance (COP).
• COP coefficient of performance
• the sliding area between the main shaft 124 and the main bearing 134 is relatively reduced, and even when the feeding amount of the refrigerating machine oil 180 is reduced, favorable wear resistance can be achieved.
• This makes it possible to also suppress an increase in sliding loss at the main shaft sliding portion, and consequently, a favorable coefficient of performance (COP) can be achieved.
• COP coefficient of performance
• the lubrication state of the main shaft sliding portion can be made more favorable. This makes it possible to achieve a more favorable coefficient of performance (COP).
• the fundamental configuration of a hermetic refrigerant compressor according to Embodiment 3 is the same as the fundamental configuration of the hermetic refrigerant compressor according to Embodiment 1.
• the hermetic refrigerant compressor according to Embodiment 3 has additional characteristic features in relation to its thrust bearing. It should be noted that since the fundamental configuration of the hermetic refrigerant compressor according to Embodiment 3 is the same as the configuration described in Embodiment 1 and shown in FIG. 1 , a detailed description thereof is omitted.
• FIG. 5 and FIG. 6 are schematic partial sectional view of the refrigerant compressor 100 of FIG. 1 .
• FIG. 5 schematically shows one example of distances P and Q that are set on the thrust bearing included in the refrigerant compressor 100, and also schematically shows a load applied to the main shaft sliding portion (i.e., a main shaft load).
• FIG. 6 schematically shows one example of the configuration of an essential part of the thrust bearing.
• the main bearing 134 has a circular tubular or circular cylindrical shape that extends in the vertical direction relative to the body of the cylinder block 130, which is wide in the "transverse direction" in the sealed container 102.
• the body of the main bearing 134 extends downward from the cylinder block 130.
• the tubular extension 137 extends above the cylinder block 130 as described in Embodiment 1. Accordingly, the body of the main bearing 134 and the tubular extension 137 form a single circular tubular or circular cylindrical structure.
• the inner peripheral surface of the main bearing 134 is a sliding surface. Accordingly, as shown in FIG. 5 , the upper edge of the inner peripheral surface of the main bearing 134 is a sliding surface upper end 138, and the lower edge of the main bearing 134 is a sliding surface lower end 139.
• the sliding surface upper end 138 corresponds to the upper edge of the inner peripheral surface of the tubular extension 137.
• the tubular extension 137 is an "extension portion" that is a result of extending the main bearing 134 upward.
• the main bearing 134 includes the tubular extension 137 thus configured, when defining the upper limit of the distance Q described below, the overall length of the main bearing 134 can be increased without increasing the overall height of the refrigerant compressor 100. This makes it possible to improve the orientation of the crankshaft 120 inserted in the main bearing 134 while the refrigerant compressor 100 is operating.
• the upper end inner surface of the tubular extension 137 may be machined, for example, chamfered.
• the inner edge of the chamfered portion of the inner surface of the tubular extension 137 is the sliding surface upper end 138 of the main bearing 134.
• the upper edge of the inner surface of the tubular extension 137 is the sliding surface upper end 138 of the main bearing 134.
• the distance between the center axis of the compression chamber 133 and the sliding surface lower end 139 of the main bearing 134 is defined as the "distance P”
• the distance between the center axis of the compression chamber 133 and the sliding surface upper end 138 of the main bearing 134 is defined as the "distance Q”
• the distance Q is less than or equal to 16 mm when the distance P is within the range of 38 mm to 51 mm.
• the thrust bearing is provided on the thrust surface 136 of the main bearing 134.
• a specific configuration of the thrust bearing is not particularly limited.
• Various rolling bearings are adoptable as the thrust bearing.
• the thrust ball bearing 210 is used as shown in FIG. 1 , FIG. 5 , or FIG. 6 .
• the thrust ball bearing 210 includes: a lower race 206 positioned on the thrust surface 136; an upper race 202 positioned facing the lower race 206; and balls 204 serving as a plurality of rolling elements that are arranged between the upper and lower races 202 and 206 and that are rollably in contact with the upper and lower races 202 and 206.
• a vibration-reducing member such as an elastic member, may be provided between the lower race 206 and the thrust surface 136 of the main bearing 134.
• the thrust ball bearing 210 is disposed on the outer peripheral side of the tubular extension 137, and the plurality of balls 204 are accommodated in a retainer 205.
• the upper race 202 and the lower race 206 are, for example, annular metal plates that are arranged parallel to each other. It should be noted that each of the upper race 202 and the lower race 206 may be provided with an arc-shaped groove.
• the lower race 206, the balls 204, and the upper race 202 are stacked in this order on the thrust surface 136 and are in contact with each other, and the flange 128 of the crankshaft 120 is seated on the upper surface of the upper race 202.
• the thrust ball bearing 210 is configured in this manner.
• the thrust ball bearing 210 is a rolling bearing in which the balls 204 roll while being in point contact with the upper race 202 and the lower race 206. Accordingly, the thrust ball bearing 210 allows the main shaft 124 to rotate with less friction while supporting a load in a perpendicular direction. It should be noted that the thrust ball bearing 210 is a "ball bearing” in which the balls 204 serve as rolling elements. Alternatively, the thrust ball bearing 210 may be a "roller bearing” in which rollers serve as rolling elements, or may be a different type of rolling bearing.
• the thrust ball bearing 210 which is a rolling bearing
• the bearing function is thus changed and thereby loss reduction is achieved, which makes it possible to effectively increase the efficiency of the refrigerant compressor 100.
• the installation of the thrust bearing, such as the thrust ball bearing 210 causes increase in the overall height of the refrigerant compressor 100.
• the distance P and the distance Q are set such that when the distance P is within the range of 38 mm to 51 mm, the distance Q is less than or equal to 16 mm.
• a simple conceivable way to reduce the distance Q is, for example, adopting a technique to reduce the wall thickness of a support portion of the cylinder block 130, or adopting a technique to reduce the thickness of the flange 128 to 4 mm or less. That is, it is conceivable to adopt a technique to reduce the wall thickness of a particular component (or a part of the particular component) (i.e., adopt a wall thickness reduction technique).
• the efficiency of the refrigerant compressor 100 can be increased. In this case, however, there is a risk that the reliability of the refrigerant compressor 100 may be reduced due to deformation of a particular component.
• Embodiment 3 As a result of experimental verification, the inventors of the present invention have found on their own that by setting the upper limit of the distance Q to a predetermined value, specifically to a value less than or equal to 16 mm, both increased efficiency and favorable reliability can be achieved without adopting a wall thickness reduction technique.
• the distance Q when the distance P is set within the range of 38 mm to 51 mm, the distance Q is set to less than or equal to 16 mm, or the distance Q may be set within the range of 12 mm to 16 mm (i.e., the lower limit value of the distance Q is, as one example, 12 mm). Therefore, it is not necessary to increase the overall height of the refrigerant compressor 100. This makes it possible not only to achieve increased efficiency of the refrigerant compressor 100 while maintaining favorable quality (in particular, favorable reliability) of the refrigerant compressor 100, but also to eliminate the necessity to increase the size of the engine room (machinery room) of the refrigerator-freezer. Consequently, a sufficient internal volume of the refrigerator-freezer can be secured.
• the upper limit of the distance Q between the center axis of the compression chamber 133 and the sliding surface upper end 138 of the main bearing 134 is specified to 16 mm.
• the efficiency of the refrigerant compressor 100 can be further increased without increasing the overall height of the refrigerant compressor 100.
• the flange 128 is not made excessively thin, not only increased efficiency but also favorable reliability of the refrigerant compressor 100 can be achieved.
• low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s, i.e., oil with a very low viscosity, is used as the refrigerating machine oil 180. Therefore, the frictional coefficient can be reduced only by using this low-viscosity oil as the refrigerating machine oil 180.
• the main shaft load F2 can be further reduced. This makes it possible to reduce sliding loss at the main shaft sliding portion.
• the diameter of the piston 140 i.e., the piston diameter (D), or the internal diameter of the compression chamber 133, in which the piston 140 is inserted, need not be particularly limited. So long as the distance Q is set to less than or equal to 16 mm when the distance P is within the range of 38 mm to 51 mm, it is unnecessary not only to make the flange 128 excessively thin, and also to substantially define the piston diameter (D) or the internal diameter of the compression chamber 133.
• Embodiment 1 by setting the ratio S / D of the stroke amount (S) to the piston diameter (D) within the range of 0.78 to 1.00, the viscous force (F1) of the oil film can be increased at the cylinder sliding portion (see the equation (1) above).
• This setting of the ratio S / D results in a reduction in the piston diameter (D).
• Embodiment 3 by setting the distance Q to less than or equal to 16 mm, the main shaft load F2 is reduced, and consequently, even though the low-viscosity oil is used as the refrigerating machine oil 180, a suitable oil film can be easily formed during low-speed operation.
• the operating frequency is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• Embodiment 3 are sufficiently applicable to the configuration described in Embodiment 1 also for when the low-speed operation is performed. This makes it possible to effectively suppress or avoid wear or seizing at the main shaft sliding portion. Thus, even in a case where the refrigerant compressor 100 performs the low-speed operation, the features described in Embodiment 3 are readily applicable to the configuration described in Embodiment 1.
• Embodiment 2 by combining the configuration described in Embodiment 1 and the configuration described in Embodiment 2, a more favorable coefficient of performance (COP) of the refrigerant compressor 100 can be achieved. Also by combining the configuration described in Embodiment 1 with the configuration described in Embodiment 3, a more favorable coefficient of performance (COP) can be achieved. Therefore, by combining the configuration described in Embodiment 1, the configuration described in Embodiment 2, and the configuration described in Embodiment 3, a favorable synergistic effect can be exerted in terms of achieving a favorable coefficient of performance (COP).
• COP coefficient of performance
• the eccentric shaft 122 is provided on the upper part (upper end) of the main shaft 124; the piston 140 is coupled to the eccentric shaft 122 via the coupler 142; and the piston 140 is inserted in the compression chamber 133, which is disposed horizontally, such that the piston 140 is movable in a reciprocating manner in the compression chamber 133. That is, in Embodiment 3, the piston 140 and the compression chamber 133 are positioned in the upper part of the refrigerant compressor 100.
• the configuration of the refrigerant compressor 100 according to the present disclosure is not limited to this.
• the piston 140 and the compression chamber 133 may be positioned in the lower part of the refrigerant compressor 100.
• the distance P is defined as a distance between the center axis of the compression chamber 133 and the sliding surface upper end
• the distance Q is defined as a distance between the center axis of the compression chamber 133 and the sliding surface lower end.
• the crankshaft 120 extends in the "longitudinal direction" (vertical direction) of the refrigerant compressor 100. Accordingly, the main shaft 124 and the eccentric shaft 122 also extend in the vertical direction.
• the refrigerant compressor 100 according to the present disclosure is not limited to this configuration.
• the crankshaft 120 may extend in the "transverse direction” (the direction perpendicular to the longitudinal direction), and the piston 140 and the compression chamber 133 may be positioned locally on one side not in the longitudinal direction but in the transverse direction in the refrigerant compressor 100.
• both of the sliding surface ends which serve as the references for the respective distances P and Q, are positioned not in the longitudinal direction, but in the transverse direction.
• one end of the sliding surface of the main bearing 134 is defined as a first end, and the opposite end of the sliding surface of the main bearing 134 is defined as a second end.
• the one end defined as the first end is closer to the compression chamber 133 (or the eccentric shaft 122) than the opposite end defined as the second end is. Therefore, the distance P can be defined as a distance between the center axis of the compression chamber 133 and the second end of the sliding surface of the main bearing 134, whereas the distance Q can be defined as a distance between the center axis of the compression chamber 133 and the first end of the sliding surface of the main bearing 134.
• the sliding surface upper end 138 is the first end
• the sliding surface lower end 139 is the second end.
• the refrigerating machine oil 180 used in Embodiment 3 may be the above-described low-viscosity oil
• the low-viscosity oil used as the refrigerating machine oil 180 may be one containing a high molecular weight component (which is referred to as suitable oil in the description below) as described in Embodiment 4 below. If the refrigerating machine oil 180 is the suitable oil described below, a more favorable oil film can be formed on the sliding portions. Consequently, the functional advantages obtained by the configuration described in Embodiment 3 can be further improved, and also, the functional advantages obtained by the configuration described in Embodiment 1 (in a case where the features described in Embodiment 2 are applied thereto, also the functional advantages obtained thereby) can be further improved.
• the fundamental configuration of a hermetic refrigerant compressor according to Embodiment 4 is the same as the fundamental configuration of at least one of the above-described hermetic refrigerant compressors according to Embodiments 1 to 3.
• the low-viscosity oil used as the refrigerating machine oil 180 has additional characteristic features. It should be noted that, in Embodiment 4, specific configuration examples of the refrigerating machine oil 180 are described, which are applicable to any of the refrigerant compressors 100 described in Embodiments 1 to 3. Therefore, a specific description of the refrigerant compressor 100 is omitted in Embodiment 4.
• the refrigerating machine oil 180 is not particularly limited, so long as it is low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s.
• at least one kind of oil substance selected from the group consisting of mineral oils, alkyl benzene oils, and ester oils can be suitably used as the refrigerating machine oil 180.
• a typical example of the oil substance is, as previously mentioned, a mineral oil.
• a combination of two or more kinds of oil substances herein includes not only a combination of, for example, two or more different kinds of oil substances that are both mineral oils, but also a combination of, for example, at least one kind of oil substance that is a mineral oil and at least one kind of oil substance that is an alkyl benzene oil (or at least one kind of oil substance that is an ester oil).
• the refrigerating machine oil 180 may contain various known additives in addition to the above oil substance(s). Those known in the field of the refrigerating machine oil 180 can be suitably used as the various additives to be added to the refrigerating machine oil 180. Typical examples of such additives include a sliding modifier, an extreme-pressure additive, an oily agent, an oxidation inhibitor, an acid scavenger, a metal deactivator, a defoaming agent, an anti-corrosive agent, and a dispersant.
• a sulfur-based sliding modifier is added to the low-viscosity oil used as the refrigerating machine oil 180.
• a known extreme-pressure additive may be added thereto.
• a specific extreme-pressure additive to be added to the refrigerating machine oil 180 is not particularly limited, and a known extreme-pressure additive can be suitably used.
• Examples of known extreme-pressure additives that can be suitably used include a phosphorus-based compound, such as a phosphate ester, and a halogenated compound, such as a chlorine-based hydrocarbon or a fluorine-based hydrocarbon.
• extreme-pressure additives only one kind of extreme-pressure additive may be added to the low-viscosity oil (oil substance), or a suitable combination of two or more kinds of extreme-pressure additives may be added to the low-viscosity oil (oil substance).
• a phosphorus-based compound can be used preferably.
• Typical examples of the phosphorus-based compound include tricresyl phosphate (TCP), tributyl phosphate (TBP), and triphenyl phosphate (TPP).
• TCP is particularly preferable.
• the phosphorus-based extreme-pressure additive is added to the refrigerating machine oil 180, and thereby, for example, wear of the main shaft sliding portion can be reduced favorably.
• the amount of the extreme-pressure additive to be added to the low-viscosity oil is not particularly limited.
• the refrigerating machine oil 180 oil substance
• the addition amount of the extreme-pressure additive may be, as one example, within the range of 0.5 to 8.0% by mass, or may be, as another example, within the range of 1 to 3% by mass.
• the sliding modifier, the extreme-pressure additive, or other additive(s) may be added to the refrigerating machine oil 180 used in the configuration described in Embodiment 1 or in the configuration described in Embodiment 3.
• These additives can be added to the refrigerating machine oil 180 according to the present disclosure within such an addition amount range that the functional advantages obtained by the configurations described in Embodiments 1 to 3 will not be hindered and the functional advantages derived from the additives can be obtained.
• the refrigerating machine oil 180 used in the refrigerant compressor 100 according to the present disclosure may be formed from an oil substance whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s.
• the kinematic viscosity at 40°C of the oil composition may be within the above range.
• the refrigerating machine oil 180 according to the present disclosure may be an "oil composition” that contains, in addition to at least one kind of oil substance, a sulfur-based sliding modifier (or a different sliding modifier), a phosphorus-based extreme-pressure additive (or a different extreme-pressure additive), or other additive(s).
• the oil composition used as the refrigerating machine oil 180 can be considered as "low-viscosity oil” whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s.
• the molecular weight of the oil substance used as the refrigerating machine oil 180 may be within a predetermined range.
• a number average molecular weight Mn of the oil substance used as the refrigerating machine oil 180 may be 150 to 400.
• a weight average molecular weight (or a mass average molecular weight) Mw of the oil substance may be 150 to 400, or may be 200 to 300.
• a polydiversity index (PDI) of the oil substance i.e., a ratio Mw / Mn of the weight average molecular weight Mw to the number average molecular weight Mn, may be within the range of 1.0 to 1.1.
• a method of measuring the oil substance and the below-described molecular weights is not particularly limited. In the present disclosure, for example, these weights can be measured and expressed in terms of standard polystyrene by GPC (Gel Permeation Chromatography) technique.
• the oil substance used as the refrigerating machine oil 180 has a low viscosity
• the oil substance has a low molecular weight.
• components (extractable components) contained in the resin material tend to be extracted. That is, there is a concern for "deterioration by extraction”.
• the polydiversity index Mw / Mn of the oil substance is at least within the range of 1.0 to 1.1, a variation in the molecular weight of the oil substance is reduced, and as a result, an excessive reduction in the molecular weight of the oil substance is suppressed.
• This consequently makes it possible to significantly reduce the possibility of the "deterioration by extraction" by the refrigerating machine oil 180, i.e., to significantly reduce the possibility that the refrigerating machine oil 180 extracts the extractable components from the resin material used in the refrigerant compressor 100.
• the extractable components extracted from the resin material are mixed into the low-viscosity oil used as the refrigerating machine oil 180. This may result in deterioration in the quality of the refrigerating machine oil 180. If the quality of the refrigerating machine oil 180 deteriorates, it is possible that favorable lubrication is not achieved at the cylinder sliding portion or the main shaft sliding portion, and in addition, it is possible that a favorable oil film is not formed at the cylinder sliding portion. In this case, it is possible that the leakage of the refrigerant gas 181 from between the piston 140 and the cylinder 132 cannot be suppressed effectively. Therefore, the molecular weights and the polydiversity index of the low-viscosity oil (specifically, its principal component, i.e., the oil substance) used as the refrigerating machine oil 180 may be set within the aforementioned ranges.
• the refrigerating machine oil 180 according to the present disclosure may contain, other than the oil substance, a component having a relatively large molecular weight, i.e., a high molecular weight component.
• the refrigerating machine oil 180 according to the present disclosure may be, for example, an "oil composition" that contains, as its principal component, an oil substance having a molecular weight within the aforementioned predetermined range and that further contains a high molecular weight component.
• the oil composition (low-viscosity oil) as the refrigerating machine oil 180 is not limited to a configuration containing a high molecular weight component. Therefore, hereinafter, the oil composition that contains a high molecular weight component is referred to as "suitable oil” for the sake of convenience of the description.
• the weight average molecular weight (the mass average molecular weight) Mw of the high molecular weight component contained in the suitable oil may be greater than or equal to 500. Also, when the total mass of the oil composition used as the refrigerating machine oil 180 is 100% by mass, the high molecular weight component content may be greater than or equal to 0.5% by mass.
• the suitable oil used as the refrigerating machine oil 180 in Embodiment 4 may originally contain the high molecular weight component.
• an oil substance serving as the high molecular weight component may be added to the suitable oil, such that the suitable oil contains 0.5% by mass or greater of the high molecular weight component.
• a mineral oil may be used as the refrigerating machine oil 180.
• a raw material mineral oil that is unrefined or that has been roughly refined may be refined to prepare (produce) the suitable oil.
• refining conditions or refining technique for refining the raw material oil may be adjusted such that 0.5% by mass or greater of the high molecular weight component remains after the refining.
• a mineral oil, an alkyl benzene oil, or a polyalkylene glycol oil may be contained in the suitable oil as its "principal component” and an oil substance serving as the high molecular weight component may be added as an "additive component" to the principal component.
• the molecular weights and the polydiversity index of the oil substance as the principal component of the suitable oil may be within the aforementioned ranges. If the molecular weights and the polydiversity index of the suitable oil are within these ranges, then in a case where the suitable oil contains 0.5% by mass or greater of the high molecular weight component, particularly when the distance Q is set to less than or equal to 16 mm in the configuration of the thrust bearing described in Embodiment 3, a suitable oil film can be formed at the main shaft sliding portion.
• the upper limit content of the high molecular weight component is not particularly limited, so long as it does not affect at least the function of the suitable oil or the functional advantages of the suitable oil.
• the upper limit content of the high molecular weight component may be 7.0% by mass or less.
• the upper limit content may be 6.0% by mass or less.
• the upper limit content may be 5.0% by mass.
• the high molecular weight component content is greater than 7.0% by mass, it may affect the viscosity of the oil (oil composition) used as the refrigerating machine oil 180.
• the kinematic viscosity at 40°C of the oil (oil composition) may exceed the range of 1.0 mm 2 /s to 2.5 mm 2 /s. Consequently, it is possible that a coefficient of performance (COP) improvement effect obtained in this case is unfavorably disproportionate to the high molecular weight component content.
• COP coefficient of performance
• the coefficient of performance (COP) of the refrigerant compressor 100 is improved by containing the high molecular weight component in the suitable oil is, as experimental verification results indicate, that even though the suitable oil has a low viscosity (the kinematic viscosity at 40°C being in the range of 1.0 mm 2 /s to 2.5 mm 2 /s), the suitable oil contributes to the formation of a favorable oil film at the sliding portions owing to the high molecular weight component. Therefore, in a case where the suitable oil containing the high molecular weight component is used as the refrigerating machine oil 180, it is considered that a more favorable oil film is formed not only at the main shaft sliding portion, but also at the cylinder sliding portion. Consequently, not only is favorable lubrication achieved at these sliding portions, but also further suppression of the leakage of the refrigerant gas 181 can be expected at the cylinder sliding portion.
• the suitable oil is prepared by adding a high molecular weight component to the principal component
• a specific material or specific kind of the high molecular weight component is not particularly limited.
• the high molecular weight component may be an oil substance whose weight average molecular weight Mw is greater than or equal to 500.
• the principal component is a mineral oil
• the high molecular weight component may also be a mineral oil, or the high molecular weight component may be an alkyl benzene oil, a polyalkylene glycol oil, or a different oil substance.
• the suitable oil is prepared by adding a high molecular weight component as an additive component to an oil substance serving as the principal component (i.e., the suitable oil is an oil composition)
• a high molecular weight component i.e., the suitable oil is an oil composition
• one kind of oil substance may be used as the principal component, and another oil substance that is a different kind of oil substance from the principal component may be used as the high molecular weight component.
• two or more kinds of oil substances may be used as the principal component, and one kind of oil substance may be used as the high molecular weight component.
• one kind of oil substance may be used as the principal component, and two or more kinds of oil substances may be used as the high molecular weight component.
• two or more kinds of oil substance mixtures, in each of which a high molecular weight component is added to the principal component may be mixed together to prepare the suitable oil.
• a sliding modifier e.g., sulfur or a sulfur-containing compound
• an extreme-pressure additive e.g., a phosphorus-containing compound
• other known additive(s) may be contained in at least one kind of oil substance that serves as the principal component of the refrigerating machine oil 180.
• an oily agent may be added as an additive.
• an oil film is more easily formed on the sliding surfaces of the sliding portions by the suitable oil. Consequently, friction at the sliding portions can be reduced more favorably, and also, the leakage of the refrigerant gas 181 can be suppressed at the cylinder sliding portion.
• the oily agent is not particularly limited to a specific kind of oily agent.
• Typical examples of the oily agent include higher fatty acids, higher alcohols, esters (ester-based compounds), ethers, amines, amides, and metal soaps.
• these oily agents only one kind of oily agent may be used, or two or more kinds of oily agents may be suitably used in combination.
• the addition amount of the oily agent(s) is not particularly limited. The addition amount of the oily agent(s) may be within the range of, for example, 0.01 to 1% by mass when the total mass of the suitable oil (oil composition) is 100% by mass.
• the ester-based compound may be a compound having an ester structure in which an alcohol and a carboxylic acid are reacted with each other.
• the alcohol may be a monohydric alcohol, or may be a polyhydric alcohol, which is at least bivalent.
• the carboxylic acid may be a monocarboxylic acid, a dicarboxylic acid, or a tricarboxylic acid (or may be a carboxylic acid containing four or more carboxyl groups).
• a commercially available ester-based oily agent can be suitably used.
• the suitable oil is an oil composition containing the oily agent
• the oil film formation performance can be further improved. Specifically, it is considered that since the suitable oil contains a high molecular weight component, the high molecular weight component is present on the sliding surfaces of the sliding portions (e.g., the main shaft sliding portion, the cylinder sliding portion, etc.), and consequently, a favorable oil film can be formed thereon. Further, it is considered that by containing the oily agent in the suitable oil, the oily agent adheres to the sliding surfaces, and thereby the formation of the oil film by the suitable oil (oil composition) is further facilitated.
• the oily agent is an ester-based compound
• the oily agent has an ester linkage. Accordingly, owing to the polarity derived from the ester linkage, the adhesion of the oil film formed by the suitable oil (oil composition) to the sliding portions can be further facilitated (i.e., the adhesiveness of the oil film can be further improved). This makes it possible to further improve the oil film formation performance of the suitable oil. Therefore, the frictional coefficient can be further reduced, and the friction at the sliding portions can be reduced more favorably. In addition, since a favorable oil film is formed more easily at the cylinder sliding portion between the piston 140 and the cylinder 132, the leakage of the refrigerant gas 181 can be suppressed more favorably.
• a sulfur-based sliding modifier or a phosphorus-based extreme-pressure additive may be contained in the suitable oil as additives as described above.
• a sulfur-based sliding modifier or a phosphorus-based extreme-pressure additive may be contained in the suitable oil as additives as described above.
• functional advantages achieved by these additives can be imparted to the suitable oil, and also, synergistic effects owing to these additives can be expected. This makes it possible not only to achieve more favorable slidability at the sliding portions, but also to favorably suppress the leakage of the refrigerant gas 181 at the cylinder sliding portion.
• the suitable oil need not contain at least one of the sulfur-based sliding modifier, the phosphorus-based extreme-pressure additive, or the ester-based oily agent, or need not contain any of these. In other words, it suffices if the suitable oil contains a suitable additive as necessary.
• a specific additive to be contained therein is not limited to the above-described sulfur-based sliding modifier, phosphorus-based extreme-pressure additive, ester-based oily agent, etc.
• Low-viscosity oil containing no high molecular weight component may be used as the refrigerating machine oil 180.
• Embodiment 5 one example of a refrigerator-freezer that includes the refrigerant compressor 100 described above in Embodiments 1 to 4 is specifically described with reference to FIG. 7 .
• the refrigerant compressor 100 according to the present disclosure can be widely and suitably used in various apparatuses (refrigerator-freezers) that include a refrigeration cycle or that include substantially the same components as those of a refrigeration cycle.
• apparatuses include refrigerators (household refrigerators, professional-use refrigerators), ice-making machines, showcases, dehumidifiers, heat-pump-type water heaters, heat-pump-type washing and drying machines, vending machines, air conditioners, and air compressors. These are non-limiting examples.
• Embodiment 2 a fundamental configuration of the refrigerator-freezer is described by taking a product storage apparatus shown in FIG. 7 as one application example of the refrigerant compressor 100 according to the present disclosure.
• the refrigerator-freezer includes, for example, a body 301, a dividing wall 304, and a refrigerant circuit 305.
• the body 301 includes a thermally insulated box, a door, and so forth.
• the box is configured to have one opening face, and the door is configured to open/close the opening of the box.
• the interior of the body 301 is divided by the dividing wall 304 into a product storage space 302 and a machinery room 303.
• An unshown air feeder is provided in the storage space 302. It should be noted that the interior of the body 301 may be divided into, for example, spaces that are different from the storage space 302 and the machinery room 303.
• the refrigerant circuit 305 is configured to cool the inside of the storage space 302.
• the refrigerant circuit 305 includes the refrigerant compressor 100 described in each of the above embodiments, a radiator 307, a decompressor 308, and a heat absorber 309, which are connected by piping in an annular manner. That is, the refrigerant circuit 305 is one example of a refrigeration cycle using the refrigerant compressor 100 according to the present disclosure.
• the inside of the refrigerant compressor 100 (i.e., the inside of the sealed container 102) is filled with the refrigerant gas 181, which is, for example, R600a.
• the refrigerant gas 181 filling the inside of the refrigerant compressor 100 is in a relatively low-temperature state such that the pressure of the refrigerant gas 181 is substantially equal to the pressure in the low-pressure side of the refrigerator-freezer.
• the refrigerant gas 181 is not particularly limited to a specific kind of refrigerant gas. Hydrocarbon-based refrigerant gas having a low global warming potential, such as R600a, can be suitably used as the refrigerant gas 181.
• the heat absorber 309 of the refrigerant circuit 305 is disposed in the storage space 302. Cooling heat of the heat absorber 309 is stirred by the unshown air feeder, such that it circulates inside the storage space 302 as indicated by dashed arrows in FIG. 7 . In this manner, the inside of the storage space 302 is cooled.
• the refrigerator-freezer according to Embodiment 5 includes the refrigerant compressor 100 according to the above-described Embodiments 1 to 4.
• the coefficient of performance (COP) of the refrigerant compressor 100 can be further improved by using low-viscosity oil whose kinematic viscosity at 40°C is within the range of 1.0 mm 2 /s to 2.5 mm 2 /s as the refrigerating machine oil 180 in the refrigerant compressor 100. Therefore, by including such a refrigerant compressor 100 in the refrigerator-freezer, the power consumption of the refrigerator-freezer can be reduced.
• a total of four kinds of mineral oils having different kinematic viscosities at 40°C from each other (1.8 mm 2 /s, 2.5 mm 2 /s, 3.3 mm 2 /s, and 5.0 mm 2 /s) were each used as the refrigerating machine oil 180 (i.e., the kinematic viscosity of the refrigerating machine oil 180 was varied).
• the operating frequency of the conventional refrigerant compressor was at 17 r/s
• the amount of leakage of the refrigerant gas 181 from between the piston 140 and the cylinder 132 i.e., refrigerant leakage amount
• the refrigerant leakage amount was measured (evaluated) in the following manner.
• the refrigerant compressor (see FIG. 1 ) to be subjected to the measurement (evaluation) was modified to seal up its suction port (not shown in FIG. 1 ), and a container in which the refrigerant gas 181 in a certain amount is encapsulated (a refrigerant container) was connected to the discharge port (not shown in FIG. 1 ) side of the refrigerant compressor.
• a refrigerant leakage amount measurement system was prepared.
• the refrigerant gas 181 is led from the refrigerant container into the hermetic refrigerant compressor through between the piston 140 and the cylinder 132. Therefore, in this measurement system, a reduction in the pressure in the refrigerant container can be regarded as a refrigerant leakage amount.
• the refrigerant compressor was operated at an arbitrary frequency, and the refrigerant leakage amount was evaluated in each case in which a corresponding one of the four different kinds of mineral oils having different kinematic viscosities from each other was used.
• the horizontal axis represents the kinematic viscosity at 40°C of the refrigerating machine oil 180 (in units of mm 2 /s), and the vertical axis represents the refrigerant leakage amount (in units of %).
• the refrigerant leakage amount in FIG. 8 the result obtained when the refrigerating machine oil 180 having a kinematic viscosity at 40°C of 5.0 mm 2 /s was used was defined as 100%.
• the coefficient of performance (COP) of the refrigerant compressor 100 of Example and the coefficient of performance (COP) of the conventional refrigerant compressor were each calculated as the ratio of refrigeration capacity to energy consumption (input) (refrigeration capacity / input).
• COP coefficient of performance
• the result obtained when the refrigerating machine oil 180 having a kinematic viscosity at 40°C of 5.0 mm 2 /s was used was defined as 100%.
• the refrigerant compressor 100 to which the settings shown in Table 1 (mean piston speed, ratio S / D, ratio L1 / D, and ratio L2 / L1) were applied, was used, in which a total of seven kinds of mineral oils having different kinematic viscosities at 40°C from each other (1.8 mm 2 /s, 2.2 mm 2 /s, 2.3 mm 2 /s, 2.5 mm 2 /s, 2.7 mm 2 /s, 3.3 mm 2 /s, and 5.0 mm 2 /s) were each used as the refrigerating machine oil 180 (i.e., the kinematic viscosity of the refrigerating machine oil 180 was varied), and the coefficient of performance (COP) in each case was evaluated.
• Table 1 mean piston speed, ratio S / D, ratio L1 / D, and ratio L2 / L1
• COP coefficient of performance
• FIG. 9 shows the results when the operating frequency was 27 r/s
• FIG. 10 shows the results when the operating frequency was 17 r/s.
• circular symbols represent the results in Example.
• the horizontal axis represents the kinematic viscosity at 40°C of the refrigerating machine oil 180 (in units of mm 2 /s)
• the vertical axis represents the coefficient of performance (COP).
• the conventional refrigerant compressor i.e., the refrigerant compressor having the same configuration as that of the refrigerant compressor of Example except that the settings shown in Table 1 were not applied, was used, in which a total of five kinds of mineral oils having different kinematic viscosities at 40°C from each other (1.8 mm 2 /s, 2.3 mm 2 /s, 2.7 mm 2 /s, 3.3 mm 2 /s, and 5.0 mm 2 /s) were each used as the refrigerating machine oil 180 (i.e., the kinematic viscosity of the refrigerating machine oil 180 was varied), and the coefficient of performance (COP) in each case was evaluated.
• FIG. 9 shows the results when the operating frequency was 27 r/s
• FIG. 10 shows the results when the operating frequency was 17 r/s. It should be noted that, in the graphs of FIG. 9 and FIG. 10 , x symbols represent the results in Conventional Example.
• the coefficient of performance (COP) is reduced if the kinematic viscosity (at 40°C) of the refrigerating machine oil 180 is less than or equal to 2.5 mm 2 /s.
• COP coefficient of performance
• Example exhibits an improvement in the coefficient of performance (COP) even when the kinematic viscosity (at 40°C) of the refrigerating machine oil 180 is less than or equal to 2.5 mm 2 /s.
• COP coefficient of performance
• the mean piston speed in Conventional Example is 0.31 m/s at 17 r/s, whereas the mean piston speed in Example is 0.34 m/s at 17 r/s.
• a favorable coefficient of performance (COP) can be achieved even when low-viscosity oil is used as the refrigerating machine oil 180.
• a favorable coefficient of performance (COP) cannot be achieved when low-viscosity oil is used as the refrigerating machine oil 180.
• a favorable coefficient of performance can be achieved if the mean piston speed is at least greater than 0.31 m/s when the operating frequency is within the range of 16 r/s to 35 r/s, which is defined as the operating frequency range for the low-speed operation in the present disclosure.
• a hermetic refrigerant compressor including: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber, wherein when an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s, an average speed of the piston moving in the reciprocating manner is set to greater than 0.31 m/s.
• a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2); a ratio L1 / D of a piston overall length (L1) of the piston to the piston diameter (D) is within a range of 0.8 to 1.0; and a ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is within a range of 0.9 to 1.0.
• a hermetic refrigerant compressor including: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber, wherein a ratio S / D of a stroke amount (S) of the piston moving in the reciprocating manner to a piston diameter (D) of the piston is within a range of 0.78 to 1.00.
• a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2); and a ratio L2 / L1 of the sealing length (L2) to a piston overall length (L1) of the piston is within a range of 0.9 to 1.0.
• a hermetic refrigerant compressor including: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber, wherein: a ratio L1 / D of a piston overall length (L1) of the piston to a piston diameter (D) of the piston is within a range of 0.8 to 1.0; a length of a region in which the piston seals an inside of the compression chamber by moving in the reciprocating manner is a sealing length (L2); and a ratio L2 / L1 of the sealing length (L2) to the piston overall length (L1) is within a range of 0.9 to 1.0.
• the compression element includes: a shaft part that is a crankshaft including a main shaft and an eccentric shaft; and a bearing part that pivotally supports the shaft part, the bearing part including a main bearing and an eccentric bearing, the main bearing pivotally supporting the main shaft, the eccentric bearing pivotally supporting the eccentric shaft, the main shaft includes a sliding surface that slides on the main bearing and that is divided into a plurality of sliding surfaces, a sum of lengths of the plurality of sliding surfaces in an axial direction is a total sliding length Tt, and a ratio Tt / K of the total sliding length Tt to an external diameter K of the main shaft is less than or equal to 1.26.
• the compression element includes: a shaft part that is a crankshaft including a main shaft and an eccentric shaft; and a bearing part that pivotally supports the shaft part, the bearing part including a main bearing and an eccentric bearing, the main bearing pivotally supporting the main shaft, the eccentric bearing pivotally supporting the eccentric shaft, the main shaft includes a sliding surface that slides on the main bearing, the sliding surface being either a single sliding surface or divided into a plurality of sliding surfaces, in a case where the sliding surface is the single sliding surface, a length the single sliding surface in an axial direction is a single sliding length T, whereas in a case where the sliding surface is divided into the plurality of sliding surfaces, a length of one sliding surface of the plurality of sliding surfaces in the axial direction, the one sliding surface having a shortest length in the axial direction in the plurality of sliding surfaces, is the single sliding length T, a ratio T / K of the single sliding length T to an external diameter K of the main shaft
• the compression element further includes: a crankshaft including a main shaft and an eccentric shaft; a main bearing that pivotally supports the main shaft; and a thrust bearing provided on a thrust surface of the main bearing, one end of a sliding surface of the main bearing is a first end, and an opposite end of the sliding surface of the main bearing is a second end, the first end being closer to the compression chamber than the second end is, a distance between a center axis of the compression chamber and the second end of the sliding surface of the main bearing is a distance P, a distance between the center axis of the compression chamber and the first end of the sliding surface of the main bearing is a distance Q, and the distance Q is less than or equal to 16 mm when the distance P is within a range of 38 mm to 51 mm.
• a method of operating a hermetic refrigerant compressor including: a sealed container; refrigerating machine oil that is stored in the sealed container and whose kinematic viscosity at 40°C is within a range of 1.0 mm 2 /s to 2.5 mm 2 /s; a cylinder block accommodated in the sealed container and forming a compression chamber; and a piston inserted in the compression chamber such that the piston is movable in a reciprocating manner in the compression chamber, the method including setting an average speed of the piston moving in the reciprocating manner to greater than 0.31 m/s when an operating frequency of the hermetic refrigerant compressor is greater than or equal to 16 r/s and less than or equal to 35 r/s.
• a refrigerator-freezer including a refrigerant circuit, the refrigerant circuit including: the hermetic refrigerant compressor according to any one of technique 1 to technique 9 or the hermetic refrigerant compressor on which the method according to technique 9 is performed; a radiator; a decompressor; and a heat absorber, wherein the hermetic refrigerant compressor, the radiator, the decompressor, and the heat absorber are connected by piping in an annular manner.
• the hermetic refrigerant compressor according to the present invention makes it possible to achieve a more favorable coefficient of performance (COP) by using refrigerating machine oil having a further reduced viscosity. Therefore, the present invention is widely applicable to various equipment that uses a refrigeration cycle.
• COP coefficient of performance

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