JPH07260263A - Device for two-stage compression refrigeration - Google Patents

Abstract

PURPOSE:To provide a device for two-stage compression refrigeration which enables the operation to be free of an unbalance in oil between the higher-stage compressor and the lower-stage one. CONSTITUTION:The refrigerant discharged from the lower-stage compressor 1 is compressed again by the higher-stage compressor 2 and discharged. There are provided an oil separator 6 and an oil-return circuit 21, the oil separator 6 for separating the oil from the refrigerant discharged from the higher-stage compressor 2 and the oil-return circuit 21 for returning the oil from the oil separator 6 to each of the higher-stage compressor 2 and the lower-stage compressor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage compression refrigerating apparatus for use in a prefabricated refrigerator, a case, etc., which has a low-stage compressor and a high-stage compressor.

[0002]

2. Description of the Related Art Conventionally, this type of two-stage compression refrigeration system is constructed so that the refrigerant discharged from the low-stage compressor is compressed again by the high-stage compressor and discharged. The oil in the refrigerant discharged from the side compressor is separated by the oil separator and returned to both compressors.

When returning the oil, conventionally, the oil is first returned from the oil separator to the crankcase chamber side of the high-stage compressor, while the low-stage compressor is crankcase chamber of the high-stage compressor. Therefore, oil is returned to the crankcase chamber side of the low-stage compressor by applying resistance with a capillary tube.

[0004]

However, in such a conventional oil-return system, the difference between the suction pressure of the high-stage compressor and the discharge pressure of the low-stage compressor is large or small, so that the difference between the high-stage compressor and the low-stage compressor is low. The oil balance of the stage compressor changes. In particular, when the pressure difference ΔP becomes small, it becomes difficult for the oil to return from the crankcase chamber of the high-stage compressor to the crankcase chamber side of the low-stage compressor, and the oil level of the low-stage compressor decreases to cause wear. -There was a problem that inconvenience such as seizure and deterioration of sealing property occurred.

The present invention has been made in order to solve the problems of the prior art, and is a two-stage compression refrigeration system capable of eliminating the oil imbalance between the high-stage compressor and the low-stage compressor. The purpose is to provide a device.

[0006]

A two-stage compression refrigerating apparatus according to the invention of claim 1 is one in which the refrigerant discharged from a low-stage compressor is re-compressed by a high-stage compressor and then discharged. , An oil separator for separating the oil in the refrigerant discharged from the high-stage compressor, and an oil return circuit for returning the oil from the oil separator to the high-stage compressor and the low-stage compressor, respectively. is there.

In the two-stage compression refrigeration system of the invention of claim 2, the refrigerant discharged from the low-stage compressor is compressed again by the high-stage compressor and discharged. An oil separator that separates the oil in the refrigerant discharged from the
A first oil return circuit that returns oil from the oil separator to the high-stage and low-stage compressors respectively, and a second oil return circuit that supplies oil from the high-stage compressor to the low-stage compressor It is equipped with and.

[0008]

According to the two-stage compression refrigeration system of the present invention, since the oil return circuits for returning the oil from the oil separator to the high-stage side compressor and the low-stage side compressor are respectively provided, the suction pressure of the high-stage side compressor is reduced. The oil can be returned directly from the oil separator to both compressors without being affected by the magnitude of the difference ΔP between the discharge pressure of the low-stage compressor and the discharge pressure of the low-stage compressor. Therefore, eliminating the oil level imbalance between the high-stage compressor and the low-stage compressor,
It is possible to prevent damage from occurring.

In particular, according to the second aspect of the present invention, since the oil return circuit for returning the oil from the conventional high-stage compressor to the low-stage compressor is also provided, the oil level of both compressors is canceled. The balance can be minimized.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a main part of a two-stage compression refrigerating apparatus of the present invention used in, for example, a prefabricated refrigerator or a showcase, where 1 is a low-stage compressor and 2 is a high-stage compressor. Both compressors 1 and 2 are connected in series via a pipe 3 so that the refrigerant discharged from the crankcase 1C side of the low-stage compressor 1 is sucked into the motor 2M side of the high-stage compressor 2. ing.

The discharge pipe 4 provided on the crankcase 2C side of the high-stage compressor 2 has an oil separator 6
The refrigerant outlet of the oil separator 6 is connected to the condenser 8 via the pipe 7. The pipe 9 on the outlet side of the condenser 8 is then connected to the subcooler 11, and the pipe 12 on the outlet side of the subcooler 11 passes through an expansion valve (not shown) and an evaporator (evaporator) also not shown.
It is connected to the. The outlet side of this evaporator is connected to a suction pipe 13 provided on the motor 1M side of the low-stage compressor 1.

Further, a connecting pipe 16 branches from the pipe 9, passes through the sub-cooler 11 via the solenoid valve 17 and the expansion valve 18, and then is connected to the pipe 3. Most of the refrigerant from the condenser 8 flows into the sub-cooler 11, but some of the refrigerant flows into the communication pipe 16 and
After the pressure is reduced by the expansion valve 18 provided in the sub-cooler 11, the vapor is evaporated while passing through the sub-cooler 11.

On the other hand, a first oil return circuit 21 is connected to the oil outlet of the oil separator 6. The oil return circuit 21 branches into two directions on the way, one branch pipe 22 is connected to the crankcase chamber 2C of the high-stage compressor 2 via a capillary tube 23, and the other branch pipe 24 is connected to a solenoid valve 26. Also, it is connected to the crankcase chamber 1C of the low-stage compressor 1 via the capillary tube 27.

A second oil return circuit 31 is connected to the crankcase chamber 2C of the high-stage compressor 2, and this oil-return circuit 31 passes through a solenoid valve 32 and a capillary tube 33 to compress the low-stage side. It is connected to the crankcase chamber 1C of the machine 1.

The operation of the refrigerating apparatus having the above structure will be described.
It is assumed that the solenoid valves 17, 26, 32 are open. In this embodiment, R-22 is used as the refrigerant, and the gas refrigerant sucked from the pipe 13 to the low-stage compressor 1 is discharged to the pipe 3 after being compressed by the low-stage compressor 1. From the pipe 3, the high-stage compressor 2 is sucked and further compressed. The high-temperature and high-pressure gas refrigerant discharged from the high-pressure stage compressor 2 flows into the oil separator 6, where the oil in the refrigerant is separated. Refrigerant from the oil separator 6 is pipe 7
Sent to the condenser 8. The condensed and liquefied refrigerant cooled by the condenser 4 flows out of the condenser 8 and then splits in two directions.

As described above, the liquid refrigerant is mostly subcooled.
After passing through the la 11 and being cooled, it reaches the expansion valve through the pipe 12, where it is decompressed and flows into the evaporator, where it is evaporated and heat is taken from the surroundings. At this time, the temperature of the evaporator is about -45 ° C., which cools the storage room such as a prefabricated refrigerator or a showcase. The refrigerant discharged from the evaporator is sucked into the low-pressure stage compressor 1 through the pipe 13, compressed again, and discharged into the pipe 3 as described above.

A part of the liquid refrigerant from the condenser 8 is divided into the communication pipe 16 and then decompressed by the expansion valve 18, and passes through the subcooler 11. The refrigerant flowing through the connecting pipe 16 evaporates in the process of passing through the subcooler 11, and supercools the liquid refrigerant that goes to the evaporator. And
The refrigerant itself flowing through the connecting pipe 16 absorbs heat, and then the pipe 3
And joins the refrigerant discharged from the low-stage compressor 1.

As a result, the temperature of the refrigerant sucked into the high-stage compressor 2 is lowered, and the rise in the discharge temperature of the high-stage compressor 2 is suppressed. The expansion valve 18 is controlled by the temperature sensing unit 18A provided in the refrigerant inflow side pipe 3 of the high-stage compressor 2.

On the other hand, the compressor oil separated from the refrigerant by the oil separator 6 flows into the oil return circuit 21. The oil that has flowed into the oil return circuit 21 is then branched into the branch pipes 22 and 24, and after being decompressed by the capillary tubes 23 and 27, respectively, the crankcase chamber 2C of the high-stage compressor 2 and the low-stage compressor 1 Are returned to the crankcase chambers 1C.

Therefore, since the oil is directly returned from the oil separator 6 to both compressors 1 and 2, both compressors 1 and 2 are
The amount of oil returned to the high-stage side compressor 2 and the low-stage side compressor 1 is not affected by the magnitude of the difference ΔP between the suction pressure of the high-stage side compressor 2 and the discharge pressure of the low-stage side compressor 1. It is possible to eliminate the imbalance of the oil level of the compressor 1 and prevent damage from occurring.

Further, a part of the oil returned to the crankcase chamber 2C of the high-stage compressor 2 is resisted by the capillary tube 33 from the oil return circuit 31, and then the crankcase of the low-stage compressor 1 Since it is also supplied to the chamber 1C, it is possible to minimize the unbalance of the oil levels of the compressors 1 and 2.

[0022]

As described in detail above, according to the present invention, since oil return circuits for returning oil from the oil separator to the high-stage side compressor and the low-stage side compressor are provided, respectively, the suction of the high-stage side compressor is reduced. Oil can be directly returned from the oil separator to both compressors without being affected by the magnitude of the difference ΔP between the pressure and the discharge pressure of the low-stage compressor. Therefore, it is possible to eliminate the imbalance between the oil levels of the high-stage side compressor and the low-stage side compressor and prevent damage from occurring.

In particular, according to the second aspect of the present invention, since the oil return circuit for returning the oil from the conventional high-stage compressor to the low-stage compressor is also provided, the oil level of both compressors is canceled. The balance can be minimized.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of a main part of a two-stage compression refrigeration system of the present invention.

[Explanation of symbols]

 1 Low-stage side compressor 2 High-stage side compressor 6 Oil separator 21, 31 Oil return circuit 22, 24 Branch pipe

Claims (2)

[Claims] 1. A two-stage compression refrigeration system in which a refrigerant discharged from a low-stage compressor is re-compressed by a high-stage compressor and then discharged, wherein oil in the refrigerant discharged from the high-stage compressor A two-stage compression refrigeration system comprising: an oil separator that separates the oil separator and an oil return circuit that returns oil from the oil separator to the high-stage compressor and the low-stage compressor, respectively. 2. In a two-stage compression refrigeration system in which a refrigerant discharged from a low-stage compressor is recompressed by a high-stage compressor and then discharged, the oil in the refrigerant discharged from the high-stage compressor A first oil return circuit for returning oil to the high-stage side compressor and the low-stage side compressor from the oil separator, and the high-stage side compressor to the low-stage side compressor. A two-stage compression refrigeration system comprising a second oil return circuit for supplying oil.