JPH0417827Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to, for example, a two-stage compression refrigerant compressor, and particularly to a reduction in the amount of oil circulated therein, that is, an improvement in oil return.

[Prior Art] Fig. 2 is a schematic diagram showing the configuration of a conventional two-stage compression refrigerant compressor equipped with two cylinders on the low stage side and one cylinder on the high stage side, and Fig. 3 shows the structure of the piston section. These are partial cross-sectional views, and in these figures, 1a is a low-stage intake port;
1b is a low stage suction chamber, 1c is a low stage discharge chamber, 1d is a high stage suction chamber, 1e is a high stage discharge chamber, 1f is a high stage discharge port, 1 is a cylinder cover provided with 1a to 1f, 2
3 is a valve plate, 3 is a suction valve, 4 is a discharge valve, 5a is a cast iron low-stage cylinder, 5b is a cast high-stage cylinder, and 6 is a casing that includes the cylinders 5a and 5b and accommodates a compression element. , 6a is the crank chamber,
6b is a motor chamber, 6c is a pressure equalizing hole, and 6d is an oil return hole, and these 6a to 6d constitute the casing 6. 7 is lubricating oil put in the bottom of the casing 6; 8 is a drive motor;
is housed in the motor chamber 6b. 9 is a piston, 9a is a ring groove, 10 is a piston ring, 1
0a is a piston ring joint, 11 is a piston pin, 12 is an oil oyster, 13 is a connecting rod, and 14 is a crankshaft, which constitute a compression element. The oil oyster 12 is attached to a connecting rod 13, and the crankshaft 14 is housed in a crank chamber. 15 is a connecting pipe; the connecting pipe 15
connects the low-stage discharge chamber 1c and the motor chamber 6b. In addition, the motor chamber 6b communicates with the high-stage suction chamber 1e.

Next, the operation will be explained. By rotating the drive motor 8 directly connected to the crankshaft 14,
The crankshaft 14 rotates, thereby driving the connecting rod 13. Thus, the piston 9 with the piston ring 10 inserted into the ring groove 9a is caused to reciprocate within the cylinders 5a, 5b via the piston pin 11. The piston ring 10 is installed between the cylinders 5a, 5b and the piston 9 to maintain airtightness, but each sliding part is lubricated by scraping up the lubricating oil 7 with an oil oyster 12 attached to the connecting rod 13. It is done by The flow of refrigerant gas enters the low-stage suction chamber 1b from the low-stage suction port 1a, pushes down the suction valve 3, and enters the cylinder 5a (two cylinders). Here, the compressed refrigerant gas discharge valve 4 is pushed up and enters the low-stage discharge chamber 1c, passes through the connecting pipe 15, and enters the high-stage suction chamber 1d via the motor chamber 6b. The refrigerant gas in the high-stage suction chamber 1d pushes down the suction valve 3 and the cylinder 5b (1
cylinder), where it is compressed again and pushes up the discharge valve 4, enters the high stage discharge chamber 1e, and enters the high stage discharge port 1.
Exhaled from f.

In the above configuration, an intermediate pressure is maintained from the low stage discharge chamber 1c to the connecting pipe 15, the motor chamber 6b, and the high stage suction chamber 1d, and the pressure is maintained through the gap between the abutment 10a of the piston ring 10 in the low stage cylinder 5a. The lubricating oil mixed in the refrigerant gas enters the motor chamber 6b from the connecting pipe 15 together with the refrigerant gas, and is separated from the refrigerant gas there. The lubricating oil separated and accumulated in the motor chamber 6b passes through the oil return hole 6d to the crank chamber 6.
returned to a. A pressure equalizing hole 6c is provided to allow return of lubricating oil, and a motor chamber 6b
and the crank chamber 6a are kept at approximately equal pressure.

Because of the pressure equalization hole 6c, the crank chamber 6a is also at intermediate pressure, so during the suction stroke of the low-stage cylinder, the refrigerant gas in the crank chamber 6a passes through the gap at the abutment 10a of the piston ring 10 and flows into the cylinder 5a. be sucked into. Also, during the compression stroke of the high-stage cylinder, high-pressure gas flows into the crank chamber 6a from the gap between the joints 10a of the piston rings 10.
leak inside.

The operating conditions are, for example, using refrigerant R22, high pressure = 17.6Kg/cm ² ads. (condensing temperature = +45°C), low pressure = 0.66Kg/cm ² ads. (evaporation temperature = -50°C), intermediate pressure = 2.6Kg/cm ² ads.The pressure difference is large in the high-stage cylinders, and even if there are many cylinders in the low-stage cylinders, normally (leakage amount in the high-stage cylinders)>
(Leakage amount in the low stage cylinder). Therefore, the internal pressure of the crank chamber 6a is maintained slightly higher than the internal pressure of the motor chamber 6b.

[Problem that the invention attempts to solve]

In this way, the pressure in the crank chamber 6a is slightly higher than the pressure in the motor chamber 6b, so the lubricating oil 7 in the motor chamber 6b tends to be maintained higher than the oil level of the lubricating oil 7 in the crank chamber 6a. (second
(See the dash-dotted line in the figure). Therefore, the lubricating oil 7 is scraped up by the rotor of the motor 8 rotating in the motor chamber 6b and enters the higher stage cylinder together with the refrigerant gas from the higher stage suction chamber 1d. In this way, valve cracking occurs in the high-stage cylinder due to oil (liquid) compression. There were also other problems, such as a lack of oil in the crank chamber, which caused seizures on the sliding parts.

[Means for solving problems]

This idea uses a piston ring made of synthetic resin or other material that has a coefficient of thermal expansion equal to that of the cylinder for the low-stage piston, and a piston ring made of synthetic resin or the like that has a higher coefficient of thermal expansion than the cylinder for the higher-stage piston. This setting is made so that there is no gap between the high-stage piston rings. It is also possible to increase the gap between the lower-stage piston rings, but this would reduce performance. In addition, if we try to use a piston ring on the high stage side that has the same coefficient of thermal expansion as the cylinder, it would be extremely uneconomical as it would require selecting and combining parts to reduce the gap at the joint. .

[Effect]

The two-stage compression refrigerant compressor of this invention uses a piston ring made of synthetic resin, etc., which has a higher coefficient of thermal expansion than the cylinder, for the high-stage piston, and eliminates the gap between the piston rings during operation. The amount of refrigerant gas leaking to the crank chamber is minimized, and on the other hand, since the low-stage piston ring has the same coefficient of thermal expansion as the cylinder, the gap between the piston rings is maintained, and the refrigerant gas in the crank chamber flows to the low-stage side. Since it is sucked into the cylinder, the pressure in the crank chamber is slightly lower than the pressure in the motor chamber.

[Embodiment] An embodiment of this invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a two-stage compression refrigerant compressor of the present invention. 16 is a low-stage piston ring having the same coefficient of thermal expansion as the cylinder 5a;
7 is a high-stage piston ring having a larger coefficient of thermal expansion than the cylinder 5b. All symbols other than those mentioned above are the same as those of a conventional two-stage refrigerant compressor.

The high-stage piston ring was made of a Teflon-based synthetic resin with additives added.

In the two-stage compression refrigerant compressor configured as described above, a piston ring made of synthetic resin or other material having a higher coefficient of thermal expansion than the cylinder is used for the higher-stage piston, so that there is no gap between the piston rings during operation. This prevents high-pressure refrigerant gas from leaking into the crank chamber (blow-by), and the low-stage piston ring joint maintains a gap as before, allowing refrigerant gas in the crank chamber to be sucked into the low-stage cylinder. As a result, the pressure inside the crank chamber is lower than the pressure inside the motor chamber. Thus, as shown in the figure, the oil level of the lubricating oil 7 in the crank chamber is maintained higher than the oil level of the lubricating oil 7 in the motor chamber. Therefore, the motor rotor no longer scrapes up lubricating oil.

[Effect of idea]

As explained above, this idea is designed so that the pressure in the crank chamber is normally slightly lower than the pressure in the motor chamber during operation, which creates a differential pressure that is the opposite of the conventional one. More of the separated lubricating oil moves toward the crank chamber. Therefore, lubricating oil is no longer scraped up by the rotor of the motor, and valve cracking due to oil (liquid) compression in the high-pressure cylinder is eliminated. Furthermore, since the amount of lubricating oil returned to the crank chamber is maintained in a large amount, there is no shortage of lubricating oil in the crank chamber, which has the effect of preventing seizure of sliding parts and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a two-stage compression refrigerant compressor showing an embodiment of this invention, FIG. 2 is a schematic diagram showing the configuration of a conventional two-stage compression refrigerant compressor, and FIG.
The figure is a partial sectional view of the piston part. In the figure, 5a is a low-stage cylinder, 5b is a high-stage cylinder, 6 is a casing, 9 is a piston,
16 and 17 indicate piston rings. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims for Utility Model Registration] (1) A low-stage cylinder and a high-stage cylinder are provided in the same casing, and below these cylinders, the casing accommodates the crankshaft of the compression element and has an oil reservoir at its bottom. The crank chamber has an intermediate pressure and a motor chamber adjacent to the crank chamber, and the crank chamber and the motor chamber are separated by a partition wall equipped with a pressure equalization hole and an oil return hole, and the motor chamber is connected to the lower cylinder. In a two-stage compression refrigerant compressor, in which the motor chamber is connected to the low-stage discharge port of the high-stage cylinder and the high-stage suction chamber of the high-stage cylinder, the low-stage piston has the same thermal expansion as the cylinder. Equipped with a piston ring having a rate of
A two-stage compression refrigerant compressor, characterized in that the high-stage piston is equipped with a piston ring having a coefficient of thermal expansion larger than that of the cylinder. (2) The two-stage compression refrigerant compressor according to claim 1, wherein the piston ring on the higher stage side is made of synthetic resin.