JPH02275079A - Refrigerating plant - Google Patents

Abstract

PURPOSE:To improve the extent of operation efficiency by using at least one unit of plural units of compressors as a variable displacement compressor which varies its displacement automatically in a stepless manner according to refrigeration load, while discriminating a load state with this compressor operated at full load and thereby determining the operating mode. CONSTITUTION:In such one that assembles two compressors 30A, 30B parallelly in a refrigerant circuit and operates them separately or simultaneously by a command out of a controller 40, the compressor 30A on one side is set down to a variable displacement compressor and the compressor 30B on the other to a fixed displacement compressor, respectively. When both these compressors 30A, 30B are simultaneously operated in a state of refrigeration load unknown, opening of a control valve 36 is set to zero of the specified time by an opening decision means 43 through a command out of a time setting means 46, and thereby the variable displacement compressors 30 are operated at full load. Whether it is in a low load operating state or not is judged from output of a low-tension switch 38a at that time, and according to the discriminated result, an operating mode of the compressor is determined.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to refrigeration devices such as refrigerators, air conditioners, and dehumidifiers.

(Prior art and its problems) In a refrigeration system in which a plurality of constant capacity expansion compressors with different capacities are installed in parallel in a refrigerant circuit, the number of operating compressors is increased or decreased depending on the refrigeration load. However, since the compression capacity changes in stages according to the number of compressors in operation, the compression capacity often does not match the refrigeration load, and if it does not match, not only will the efficiency of the refrigeration equipment deteriorate,
Problems such as frost forming on the evaporator and the evaporation pressure of the refrigerant becoming too low occur. Furthermore, when the refrigeration load falls below the compression capacity of the compressor with the minimum capacity, it is necessary to repeatedly start and stop the compressor.

In order to deal with this, an inverter is used to determine the frequency μ of the current, which is the driving weight of the compressor, i.e. It was proposed to increase or decrease steplessly, but this would not only increase the cost of the inverter as the capacity of the compressor increases, but also require the compressor to continue operating at an extremely low load. , as the efficiency decreases and the amount of lubricating oil discharged from the compressor together with the refrigerant decreases.
This may cause problems such as lack of lubrication of the compressor or seizures due to this.

(Means for Solving the Problems) The present invention 1i was invented to solve the above-mentioned firlfg, and its gist is that a plurality of compressors are used to distribute refrigerant in parallel in a path. In the refrigeration equipment, at least one of the plurality of compressors mentioned above is made into a variable capacity compressor whose capacity automatically changes steplessly according to the refrigeration load, and this variable capacity compressor is Fully load the aircraft for a specified period of time; military change!” Low load by
A control device is provided which has a determination -f'- stage for determining whether or not the compressor is in a 1Jli rotation, and an operation a-susceptibility determining means for determining the operating mode of the plurality of compressors according to the determination result of the determination stage f.
The refrigeration equipment is characterized by the following: .

The determination means may be configured to determine that the operation is at low load when the pressure of the refrigerant flowing through the suction pipe drops below a predetermined value during full load operation of the variable capacity expansion and compression rock. In addition, the mode determining means may be configured to eliminate the number of operating compressors or change the operation of the large capacity compressor to the operation of the small capacity compressor when the discrimination means determines that the operation is in the low negative direction. can.

(Function) In the present invention, since the above configuration is provided, 7f1
The capacity of the positive displacement compressor changes automatically according to the refrigeration load, and the refrigeration system is operated in a state where the total compression capacity of the plurality of compressors matches the refrigeration zero load.

Part 1. Then, by operating the variable capacity compressor at full load for a predetermined period of time, it is determined whether or not it is operating under low load, and based on the result of this determination, the operating mode of the multiple compressors is determined, and the The entire compression capacity is lost to the refrigeration load.

During full load operation of the variable capacity pressure tank Azusa, the pressure of the refrigerant flowing through the suction pipe is detected, and when this falls below a predetermined value, low load i! In addition, when it is determined that low load operation is occurring, the number of compressors in operation can be reduced or the number of large capacity compressors i! By switching the operation of the compressor to the operation of a small capacity compressor, the total compression capacity of multiple compressors can be increased to 7? f Freezing load C2 match (can be predicted).

Embodiment An embodiment of the present invention is shown in FIGS. 1 and 2 at 41 degrees.

FIG. 1 shows a system diagram of the refrigeration system.

This refrigeration system has a plurality of compressors 30A and 30B (two in the figure), and these compressors 30^ and 308 are connected in parallel in the refrigerant circuit U, and these are connected to the controller 40. Operates independently or simultaneously upon receiving commands.

At least one of the plurality of compressors, i.e. compression@30
A is a variable capacity compressor having a variable capacity mechanism which will be described later, and the other compressor 30B is a fixed rate compressor.

The high-temperature, high-pressure refrigerant gas discharged from the compressed*3OA or 30B flows as shown by the arrow and enters the condenser 31, where it is condensed and liquefied to become a high-pressure liquid refrigerant. This liquid refrigerant enters the restrictor W32, such as an expansion valve, where it expands adiabatically and becomes a two-phase gas-liquid.Next, this refrigerant enters the aeration generator 33, where it evaporates and becomes low temperature. - It becomes a low-pressure gas refrigerant and circulates to the compressor 30^ or 30R.

A control valve 3G is interposed in a bypass pipe 35 that connects a working chamber of an unloader cylinder built in the compressor 30A, which will be described later, and a refrigerant pipe 34 at the outlet of the evaporator 33. Its opening degree is controlled by the command. This refrigerant pipe 34 has a sensor 3 that detects the pressure of the refrigerant flowing therein or 41 degrees, that is, the refrigeration load.
7 and a low pressure switch 38a are attached, and the outputs of the sensor 37 and the low pressure switch 18a are input to the controller 40. In addition, the suction pipe 34a of the compressor 30A
A low pressure switch 381J is attached to detect the pressure of the refrigerant flowing inside the :, and the output of this low pressure switch 38b is also manually input to the controller 40.

FIG. 2 shows a variable capacity mechanism of the compressor 30A.

In Fig. 2, 1 is a cylinder, 2 is a piston, 3 is a valve plate, 4 is a cylinder head, 5 is a suction cavity, 6 is a suction valve, 7 is a discharge valve, 8 is a discharge chamber, 9 is an unloader cylinder, 10 is a The unloader piston is shown.

The lower end of the unloader cylinder 9 is fixed to the valve plate 3, and the upper end is covered by a cover 20.

An unloader piston 10 is placed inside this unloader cylinder 9.
By sealingly and slidably fitting the unloader piston 10, an operating chamber 16 is defined above the unloader piston 10, and a chamber 19 is defined below the unloader piston 10. And this chamber 19 has an opening 18
The working chamber 16 communicates with the gas compression chamber 12 through the gas compression chamber 12, and the working chamber 16 communicates with the discharge chamber 8 through a throttle hole 24 formed in the cover 20.
is connected to. Further, the working chamber 16 communicates with a bypass pipe 35 via a pressure guiding pipe 15 and a passage 21 bored in the valve plate 3 . In FIG. 2, 23 is a seal ring wound around the upper end of the unloader piston 10, 25 is a piston ring wound around the piston 2, and 26 is a washer fixed to the lower end of the unloader cylinder 9.

When the piston 2 moves back, the refrigerant gas passes through the suction passage 11 formed in the valve plate 3 from the suction cavity 5, pushes open the suction valve 6, and is sucked into the gas compression chamber 12.

When the piston 2 moves forward, the refrigerant gas in the gas compression chamber 12 is compressed, pushes the discharge valve 7 open, enters the discharge chamber 8 through the passage 13, and is discharged from there through a discharge pipe (not shown).

The refrigerant gas in the gas compression chamber 12 flows into the chamber 19 through the opening 18 . On the other hand, the discharge gas in the discharge chamber 8 flows into the working chamber 16 through the throttle hole 24, and the gas in the chamber 19 flows through the minute gap between the inner peripheral surface of the unloader cylinder 9 and the outer peripheral surface of the unloader piston 10. will flow in. Then, the gas in the working chamber 16 is transferred to the pressure conduit 15 and the passage 21.
, the control valve 36 , and the bypass pipe 35 to flow out into the refrigerant pipe 34 . By controlling the flow rate of gas passing through the bypass pipe 35 using the control valve 36, the pressure in the working chamber 16 can be set to an arbitrary pressure.

Thus, the unloader piston 10 moves up and down depending on the difference between the pressure acting on the working chamber 16 and the average pressure in the gas compression chamber 12 acting on the chamber 19, and depending on this up and down position, the unloader piston 10 moves up and down by the chamber 19 and the opening 18. The configured top clearance volume changes, and accordingly, the capacity of the compressor 30^ changes steplessly.

As shown in FIG. 1, the output of the sensor 37 is input to the comparison means 41 of the controller 40, where it is compared with the set value input from the setting means 42, thereby calculating the deviation between the two. . This deviation is determined by the opening degree determining means 43.
The opening degree of the control valve 36 is determined according to the control rule input from the storage means 44. Note that the storage means 44 stores information about the control valve 3 corresponding to the deviation and its rate of change.
A control rule that determines the opening degree of 6 (for example, PI[l 1
11wj, table comparison control, fuzzy control, etc.) are stored. The determined opening degree is outputted to the control valve 36 via the output means 45, and the control valve 36 assumes the determined opening degree.

As a result, the flow rate of gas passing through the control valve 36 is determined, and accordingly, the capacity of the compressor 30A is determined.

In this way, while the variable capacity maximum compressor 30^ and the constant volume pot compressor 30B are operating simultaneously, the capacity of the variable capacity maximum compressor 30A is automatically and continuously adjusted steplessly according to fluctuations in the refrigeration load. Change. Therefore, the total compression capacity, which is the sum of the compression capacities of the variable capacity maximum compressor 30^ and the constant capacity pot compressor 30B, matches the refrigeration load, and the refrigerant pressure at the outlet of the evaporator 33, that is, the low pressure is maintained constant. Ru.

When the simultaneous operation of the variable capacity maximum compressor 30A and the constant volume pot compressor 30B continues for a certain period of time without knowing the refrigerating load, the opening degree determining means 4 receives a command from the time setting means 46.
3 determines that the opening degree of the control valve 36 will be zero for a predetermined time,
This command is output to the control valve 36 via the output means 45,
The opening degree of the control valve 36 becomes zero.

Then, the variable displacement maximum compressor 30A is operated at full load for a predetermined period of time, and during this period, the total compression capacity, which is the sum of the compression capacities of the variable displacement compressor 30^ and the constant volume pot compressor 30B, is greater than the refrigeration load. Accordingly, the pressure of the refrigerant flowing inside the refrigerant pipe 34 decreases. This pressure is low pressure pressure switch 3
If it is higher than the cutout value of 8a, the determining means 47 receives the output of the low pressure switch 38a that detects this and determines that the load of the variable capacity expansion compressor 30^ immediately before the full load operation is equal to or higher than a predetermined value. . This determination result is input to the operation mode a determining means 48, where the variable capacity expansion compressor 3
The capacity control operation of 0A and the simultaneous operation of the constant volume pot compressor 30B are determined. This determination result is outputted to the variable capacity expansion compressor 30^ and the constant volume pot type compressor 30B via the output means 50, and is outputted to the variable capacity expansion compressor 30^ and the constant volume pot type compressor 30B.
Simultaneous operation will continue.

However, if the pressure of the refrigerant flowing in the refrigerant pipe 34 is lower than the cutout value of the low pressure switch 38a, the determining means 47 determines whether the variable capacity expansion-compressor 3 immediately before full load operation
It is determined that the load of 0^ is less than a predetermined value. In response to this determination result, the operation a birch determining means 48 selects the constant volume pot type compressor 30.
The decision result is output to the constant volume bottle compressor 30B via the output means 50.
will stop operating.

Thereafter, only the variable capacity expansion/compressor 30A is operated and continues to operate while automatically changing its capacity to correspond to the refrigeration load.

When this state continues for a certain period of time, the opening determining means 43 receives a command from the time setting means 46 and outputs a command to set the opening of the control valve 36 to zero for a predetermined period of time, so that the variable capacity expansion compressor 30A is operated at full load, and the pressure of the refrigerant flowing in the suction pipe 34a decreases accordingly. If this pressure is higher than the cant-out value of the low-pressure pressure switch 38b, the determining means 47 determines that the load on the variable capacity expansion and compressor 3OA immediately before full load operation is equal to or higher than a predetermined value, and the variable capacity expansion and compressor 30^ Capacity control operation will continue.

However, if the pressure of the refrigerant flowing in the suction pipe 34a is lower than the cantout value of the low pressure switch 38b,
The determining means 47 determines that the load on the variable capacity expansion compressor 30A immediately before full load operation is less than a predetermined value. In response to this judgment result, the operation mode determining means 48 decides to stop the variable capacity expansion compressor 30A, and thereafter, the variable capacity expansion compressor 30^
stops.

When only the variable capacity expansion compressor 30A is in operation, if the refrigeration load increases beyond the capacity adjustment range of the variable capacity expansion compressor 30A, the output from the sensor 37 that detects this increases via the comparison means 41. The operation mode determining means 48 then enters the opening degree determining means 43 and determines the operation of the constant volume pot compressor 30B based on the command from now on. In this way, the variable capacity expansion and compressor 30A and the constant volume pot compressor 30B are operated simultaneously, thereby lowering the low pressure, and from then on, the capacity of the variable capacity expansion and compressor 30^ is controlled, and this compression capacity and constant volume are controlled. The operation is continued in a state where the total compression capacity of the pot-shaped compressor 30B matches the refrigeration load.

Note that the cutout value of the low pressure switch 38a is set larger than that of the low pressure sludge punch 38b.

When the pressure is detected by the sensor 37, this output may be input to the determining means 47 instead of the output of the low pressure switch 38a.

A second embodiment of the invention is shown in FIG.

Suction pipe 34a and working chamber 16 of variable capacity expansion compressor 3OA
A constant pressure valve 60 and a solenoid valve 61 are interposed in the bypass pipe 35 connecting the two, and the solenoid valve 61 is opened and closed by commands from the controller 40^.

When the suction pressure of the variable capacity expansion compressor 30^ decreases, such as when the capacity of the variable capacity expansion compressor 30^ is large compared to the load, the opening degree of the constant pressure valve 60 increases in order to keep the pressure at its outlet constant. and,
When the opening degree becomes large, the gas in the working chamber 16 flows into the constant pressure valve 60.
Since a large amount of the air flows into the suction port of the variable capacity expansion and compressor 30A, the pressure inside the working chamber 16 decreases. As a result, the pressure inside the working chamber 16 becomes lower than the average cylinder pressure introduced into the chamber 19, so the unloader piston 10 rises, the top clearance polyneum increases, and the capacity of the variable displacement expansion compressor 30A increases. decreases. When the capacity of the variable capacity expansion compressor 30^ decreases, its suction pressure increases, and henceforth the suction pressure is kept constant.

Conversely, when the suction pressure of the variable displacement expander-compressor 30A increases, such as when the capacity of the variable displacement expander-compressor 30A is small compared to the load, the opening degree of the constant pressure valve 60 becomes smaller and the pressure within the working chamber 10 increases. As a result, the unloader piston 10 descends and the tosofurireliance volume decreases, so the variable displacement expansion compressor 3
The capacity of 0A increases, and the suction pressure of the variable capacity expansion compressor 30A is kept constant thereafter.

When the simultaneous operation of the variable capacity expansion compressor 30^ and the constant capacity expansion compressor 30B continues for a certain period of time without knowing the refrigeration load, the opening degree determining means 4 receives a command from the time setting means 46.
3^ decides to keep the solenoid valve 61 open for a predetermined time, and this command is output to the solenoid valve 61 via the output means 45, and the solenoid valve 61 is closed. Thus, variable capacity expansion compressor 3
0A is operated at full load for a predetermined period of time. If the low pressure during full load operation is higher than the cutout value of the low pressure switch 38a, the determining means 47 receives the output of the low pressure switch 38a that detects this and determines whether the variable capacity expansion compressor 30A is in the position immediately before the full load operation. It is determined that the load is equal to or higher than a predetermined value, and the capacity control operation of the variable capacity expansion compressor 30A and the simultaneous operation of the constant capacity expansion compressor 30B are continued.

However, if the pressure of the refrigerant flowing inside the refrigerant pipe 34 is lower than the cutout value of the low pressure switch 38a,
The determining means 47 determines that the load on the variable capacity expansion and compressor 30^ immediately before the full load operation is below a predetermined value, and thereafter only the variable capacity expansion and compressor 30A is operated and its capacity is adjusted to correspond to the refrigeration load. Continues operation while automatically changing the

When this state continues for a certain period of time, in response to a command from the time setting means 46, the opening determining means 43 outputs a command to open the solenoid valve 61 for a predetermined period of time, and the variable capacity expansion compressor 30
^ is operated at full load for a predetermined period of time. If the low pressure during this full load operation is higher than the cutout value of the low pressure switch 38b, the capacity control operation of the variable capacity expansion compressor 3OA is continued.

However, if the low pressure is lower than the cutout value of the low pressure switch 38b, then the variable capacity expansion compressor 30
Operation of A is stopped.

FIG. 4 shows a third embodiment of the present invention, in which the maximum capacity of a variable capacity expansion and compressor 30A is larger than the capacity of a constant capacity expansion and compressor 30B.

Therefore, when only the variable capacity expansion compressor 30A is in operation, when it is operated at full load to detect its load,
When the low pressure is lower than the cutout value of the low pressure switch 38a, the operation mode determining means 48B stops the operation of the variable capacity expansion compressor 30A, and instead determines the operation of the constant capacity expansion compressor 30B, Hereinafter, the constant capacity expansion compressor 30
Only B is operated.

During operation of only the constant displacement compression type 1130B, when the refrigeration load exceeds the capacity of the constant displacement expansion compressor 30B, the operation mode determining means 48B stops the operation of the variable displacement expansion compressor 30B,
Instead, it is decided to operate the variable capacity expansion compressor 30A,
Thereafter, only the variable capacity expansion compressor 30A continues its operation while changing its capacity.

Further, while only the constant capacity expansion and compressor 30B is in operation, if the refrigeration load becomes less than the compression capacity of the constant capacity expansion and compressor 30B, this is detected by the pressure switch 62, and the constant capacity expansion and compression is performed based on the future output. Operation of machine 30B is stopped.

The other configurations and operations are the same as those of the first embodiment shown in FIG. 1, and corresponding members are given the same reference numerals and explanations will be omitted.

In each of the above embodiments, two compressors are installed in parallel in the refrigerant circuit, but three or more compressors can be installed. In this case, the number of variable capacity expansion and compression machines can be two or more.

(Effects of the Invention) In the present invention, in a refrigeration system in which a plurality of compressors are installed in parallel in a refrigerant circuit, the capacity of at least one of the plurality of compressors is automatically adjusted according to the refrigeration load. A variable capacity expansion and compressor that changes steplessly, and a determining means for determining whether or not the variable capacity expansion and compressor is operating at a low load by operating the variable capacity expansion and compressor at full load for a predetermined period of time;
Since a control device is provided that has an operation mode determining means that determines operation mode a of a plurality of compressors in accordance with the discrimination result of the discrimination means, the capacity of the variable capacity compressor is automatically changed to 2 in accordance with the refrigeration load. Station! The refrigeration equipment is operated in a state where the total compression capacity of the plurality of rJX compressors matches the refrigeration load. Then, the variable capacity expansion compressor is operated at full load for a predetermined period of time, and it is determined whether or not it is in low load operation, and the operating mode of the plurality of compressors is determined according to the result of this determination. ,-Lera? The operation of the refrigeration system can be continued while the total compression capacity is lost to the refrigeration load. Therefore, even when the refrigeration load is low, the compressor can continue operating without being placed in an extremely low load state, and
Since the compressor is operated under extremely low load conditions, its efficiency is not significantly reduced, and damage to the compressor due to wasted fishing power or lack of oil return fleas is avoided. Avoidable 8

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show a first embodiment of the present invention.
The figure is a system diagram, and FIG. 2 is a partial vertical sectional view of the variable capacity mechanism of the variable capacity expansion compressor. State 31 is a system diagram showing the second embodiment of the present invention, and FIG. 4 is a system diagram showing the third embodiment of the invention. Variable capacity turgor pressure fine root・30A, constant capacity type EtE compressor-30
11. Controller 40.408, 40B, Discrimination means...47. 48; Driving style determining means Fig. 4

Claims (3)

[Claims] (1) In a refrigeration system in which multiple compressors are installed in parallel in a refrigerant circuit, at least one of the multiple compressors has variable capacity that automatically changes steplessly according to the refrigeration load. In addition to being a displacement type compressor, there is also a determination means for determining whether or not the variable displacement compressor is operated at low load by operating the variable displacement compressor at full load for a predetermined period of time, and a plurality of compressors are operated according to the determination result of this determination means. A refrigeration system characterized by comprising a control device having an operating mode determining means for determining an operating mode of the refrigeration system. (2) The variable displacement compressor according to claim (1) is characterized in that the variable displacement compressor has a determining means for determining low load operation when the pressure of the refrigerant flowing through the suction pipe decreases to a predetermined value or less during full load operation of the variable displacement compressor. Refrigeration equipment. (3) It is characterized by having an operation mode determining means for reducing the number of operating compressors or changing the operation of a large capacity compressor to the operation of a small capacity compressor when the discrimination means discriminates that the operation is a low load operation. The refrigeration apparatus according to claim (1) or (2).