JPH0526526A - Two-stage compression type freezing device - Google Patents

Abstract

PURPOSE:To provide oil control for preventing a compressor from the occurrence of deficiency in oil, in a two-stage compression type freezing device wherein different compressors being individually operable are used, the one forms a compressor on the low stage side and the other forms a compressor on the high stage. CONSTITUTION:In a two-stage compression type freezing device 1 formed such that a compressor 4 on the low stage side, an internal low pressure type compressor 7 on the high stage side, an oil separator 8, a condenser 9, an expansion valve 13, and a vaporizer 14 are interconnected, an oil piping 22 branched from the middle to the compressors 4 and 7 is connected to the oil separator 8 through an oil tank 23. Oil level regulators 24A and 24B are located in branched oil pipings 22A and 22B, respectively, and an intermediate pressure is applied in the oil tank 23 through a piping 27.

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 type refrigerating apparatus used for showcases, refrigerators and the like.

[0002]

2. Description of the Related Art Generally, many two-stage compression type refrigerating apparatuses are provided with a low-stage compression mechanism and a high-stage compression mechanism in one casing as disclosed in Japanese Patent Publication No. 60-51617. That is, a two-stage compression refrigeration system is constructed by connecting a compressor having a low-stage compression mechanism and a high-stage compression mechanism in one casing, an oil separator, a condenser, a decompression device, and an evaporator. Are configured. For this reason, the compressor did not run out of oil by returning the oil separated by the oil separator to the compressor.

Further, in such a two-stage compression refrigeration system, in order to obtain a lower evaporation temperature, the outlet pipe of the condenser is branched and one of them is connected to the evaporator through a supercooler, The other side was connected to the supercooler via the solenoid valve and the expansion valve for the supercooler, and was further connected to the connecting pipe between the low-stage compressor and the high-stage compressor.

[0004]

However, according to the above construction, when the two-stage compressor is composed of separate compressors, that is, one of the compressors is the low-stage compressor and the other compressor is the high compressor. When a two-stage compression type refrigerating device is configured as the stage compressor, it is naturally impossible to return the oil by the conventional method, and some measure must be taken.

The present invention has been made in view of the above point, and separate compressors that can be operated independently are used, one of which is a low-stage compressor and the other is a high-stage compressor. Even in a two-stage compression refrigeration system, it is an object of the present invention to realize oil control in which each compressor does not run out of oil.

[0006]

SUMMARY OF THE INVENTION The present invention is a two-stage compression system in which a low-stage compressor, an internal low-pressure high-stage compressor, an oil separator, a condenser, a pressure reducing device, and an evaporator are connected. In a refrigeration system, the oil separator is connected to an oil pipe branched from the middle through an oil tank to each compressor, an oil level controller is provided in each branched oil pipe, and the oil tank is provided in the oil tank. An intermediate pressure is applied.

Further, in a two-stage compression refrigerating apparatus in which a low-stage compressor, a high-stage compressor, an oil separator, a condenser, a pressure reducing device, and an evaporator are connected, the oil separator separates The oil pipe that returns the collected oil to the low-stage compressor via the high-stage compressor is provided, and the oil level controller is provided on the oil pipe that connects the low-stage compressor and the high-stage compressor. It is a thing.

[0008]

The two-stage compression refrigerating apparatus of the present invention has the above-mentioned former configuration, and during operation, after the oil separated by the oil separator is stored in the oil tank due to the pressure difference, the pressure from this tank is reduced. A predetermined amount of oil can be supplied to each compressor by a difference or a head difference, and when stopped, the oil regulator can prevent the reverse flow of oil from the oil tank to the low-stage compressor or the high-stage compressor. As a result, the low-stage side compressor and the high-stage side compressor are constituted by separate compressors, and even if there is a pressure difference between the compressors, one oil separator and one oil tank Thus, the amount of oil in each compressor can be maintained at a predetermined amount, and the compressor can be prevented from locking due to insufficient oil.

According to the latter construction, during operation, the oil separated by the oil separator is first returned to the high-stage compressor to secure a predetermined amount of oil in the high-stage compressor. After that, the oil that has exceeded a predetermined amount in this high-stage compressor, that is, the overflowed oil, can be returned to the low-stage compressor by the oil level controller, and at the time of stoppage, it can be reduced by the oil level controller. It is possible to prevent backflow of oil from the stage compressor to the high stage compressor. As a result, the low-stage side compressor and the high-stage side compressor are composed of separate compressors, and even if there is a pressure difference between the compressors, only one oil level is provided for the high-stage side compressor. With the simple configuration of providing the regulator, the amount of oil in each compressor can be maintained at a predetermined amount, and the compressor can be prevented from locking due to insufficient oil.

In addition, since the oil is returned directly from the oil separator to the high-stage compressor, the crank chamber of the high-stage compressor can be made to function as an oil tank, making the oil tank unnecessary and reducing the number of parts. Can be reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

Reference numeral 1 is a two-stage compression type refrigerating apparatus. This refrigeration system has a compression mechanism and an electric motor for driving the compression mechanism housed in a crank chamber 2 and a motor chamber 3 in one casing. A mechanism and an electric motor for driving the mechanism are housed in a crank chamber 5 and a motor chamber 6 in one casing, and a high-stage compressor 7 acting as a high-stage side, an oil separator 8, a condenser 9, and Double pipe type subcooler 12 connected to both pipes 10 and 11 branched from the outlet pipe of the condenser 9.
Expansion valve 13, evaporator 14, and accumulator 15
And are connected by piping as shown in FIG.

Reference numeral 16 is a pipe for sending the gas discharged from the low-stage compressor 4 to the high-stage compressor 7, and a muffler 17 for preventing discharge pressure pulsation is provided in the middle of the pipe 16. The mixer 18 is connected.

A solenoid valve 19 and a subcooler expansion valve 20 are connected to one of the pipes 10 branched from the condenser 9. The pipe 10 passes through the inner pipe of the subcooler 12, and then the muffler 17 is connected. Is connected to the pipe 16 between the mixer 18 and the mixer 18.

The other pipe 11 branched from the condenser 9 passes through the outer pipe of the subcooler 12 and is connected to the evaporator 14 via a solenoid valve 21 and an expansion valve 13.

Reference numeral 22 is an oil pipe branched from the middle of the oil separator 8 via the oil tank 23 to reach the compressors 4 and 7. The oil pipe 22 is divided into branched oil pipes 22A,
22B is provided with oil level adjusters 24A and 24B.

The oil tank 23 is connected to the mixer 18 by a pipe 27 so that the inside of the oil tank 23 is at an intermediate pressure (the discharge pressure of the low-stage compressor 4 or the suction of the high-stage compressor 7). Pressure).

Here, the oil level adjusters 24A and 24B are constructed as shown in FIG.
9, an arm 30 connected to one end of the float and having a fulcrum at the center, and a valve 31 formed downward at the other end of the arm, the oil level in the container 28 rises. When it comes, the float 29 rises, the valve 31 closes the openings 32 of the pipes on the compressors 4 and 7 side to stop the supply of oil to the compressors 4 and 7, and the oil level descends. The float 29 descends to open the opening 32 and supply oil to the compressors 4, 7.

Reference numeral 25 is a signal from a low pressure detector 26 provided in the suction pipe of the low-pressure stage compressor 4, and the low-pressure stage compressor 4 receives a signal.
And a control device that controls the operation stop of the high-stage compressor 7 and the opening and closing of the solenoid valves 19 and 21.

In the two-stage compression refrigerating apparatus having the above-mentioned structure, the gas vaporized by exchanging heat with the fluid to be cooled in the evaporator 14 is sucked into the low-stage compressor 4 through the suction pipe. The low pressure side compressor 4 pressurizes it to an intermediate pressure and then pipes 1
The refrigerant gas discharged to 6 is mixed with the low-temperature liquid refrigerant sent from the subcooler 12 at the place where it exits the muffler 17, cooled to a predetermined temperature, and then sucked into the high-stage compressor 7. To be done.

The high-temperature, high-pressure refrigerant gas pressurized to the discharge pressure by the high-stage compressor 7 separates the oil in the gas by the oil separator 8 and then enters the condenser 9 to be condensed.

The condensed liquid refrigerant is branched into the pipes 10 and 11, and the liquid refrigerant flowing into one of the pipes 10 is depressurized to an intermediate pressure by the expansion valve 20 for the subcooler through the solenoid valve 19. Then, the liquid refrigerant supplied to the outer pipe for the heat source refrigerant of the subcooler 12 and flowing into the other pipe 11 directly passes through the inner pipe of the subcooler 12 for the refrigerant to be cooled as described above. It flows into the pipe 16.

That is, both liquid refrigerants branched by the pipes 10 and 11 exchange heat with the subcooler 12, and the subcooler 1
The liquid refrigerant passing through the inner pipe of No. 2 is sufficiently cooled and the expansion valve 13
Flow into.

The liquid refrigerant flowing into the expansion valve 13 is decompressed here and then enters the evaporator 14 to be evaporated.

Thus, during operation of the two-stage compression refrigeration system 1,
That is, when both the low-stage compressor 4 and the high-stage compressor 7 are operating, the oil separated by the oil separator 8 has a pressure difference (the oil separator 8 has a high pressure, the oil tank 23 has a high pressure). Is the intermediate pressure)
After being stored in the oil tank 23, the oil is returned to the oil level controller 24A by a pressure difference (the oil tank 23 has an intermediate pressure and the low-stage compressor 4 has a low pressure) from this tank, and at the same time, the tank 23 It is possible to return the oil to the oil level adjuster 24B by a head drop and to supply a predetermined amount of oil from the oil level adjusters 24A and 24B to the compressors 4 and 7.
On the other hand, when stopped, the oil level adjusters 24A and 24B can prevent the reverse flow of oil to the low-stage compressor 4 and the high-stage compressor 7.

Here, the oil level adjusters 24A and 24A
B is designed so that the valve 31 does not open due to the above pressure and so-called blow-open even when the valve 31 closes the opening 32 when the float 29 rises. For example, reducing the buoyancy of the float 29,
Alternatively, it is conceivable to reduce the diameters of the branched oil pipes 22A and 22B.

As a result, the low-stage compressor 4 and the high-stage compressor 7 are composed of separate compressors, and even if the compressors 4 and 7 have a pressure difference, one oil is used. With the separator 8, the one oil tank 23, and the two oil level adjusters 24A and 24B, the oil amount of each compressor can be reliably maintained at a predetermined amount,
The lock of the compressor due to lack of oil can be prevented.

Further, the control device 25 controls the low-stage side compressor 4 and the high-stage side compressor 7 synchronously so that if either one of them stops, the other also stops. The solenoid valve 19 is controlled to close when the compressors 4 and 7 are stopped. Therefore, the normal operation as the two-stage compression type refrigeration system can be maintained at all times, and for example, when the compressors 4 and 7 are stopped, the liquid refrigerant remaining in the condenser 9 flows into the high-stage side compressor 7 and restarts. It is possible to prevent the simultaneous liquid compression from being caused, and further, it is possible to prevent the pressure rise of the low-stage side compressor 4 and prevent the short cycle at the same time as the restart.

It is also possible to stop the compressors 4, 7 by a so-called pump down system by the control device 25. In this case, a temperature sensor or the like for detecting a decrease in the ambient temperature of the evaporator 14 is used. Solenoid valve 1 by the signal of
9, 21 are closed.

Therefore, the refrigerant supply from the condenser 9 to the subcooler 12 and the evaporator 14 is stopped, but the compressor 4,
Since the operation of 7 continues, the suction side pressure decreases, and the compressors 4 and 7 are stopped by the signal of the low pressure detector 26 to bring the refrigerant into the condenser 9.

As a result, the stagnation of the refrigerant in the compressors 4 and 7 can be prevented, the liquid backing can be prevented at the same time when the two-stage compression refrigerating apparatus 1 is restarted, and the startability can be improved.

Further, when the two-stage compression type refrigeration system 1 is started up, the control device 25 controls the low-stage side compressor 4 to turn on after a fixed period of time after the high-stage side compressor 7 has been turned on. To prevent abnormal rise of the high-stage compressor 7
Can be operated under almost no load, and operating efficiency can be improved.

FIG. 3 shows another embodiment in which the low-stage compressor 4, the high-stage compressor 7, the oil separator 8, the condenser 9, the expansion valve 13 and the evaporator 14 are connected. In addition to providing oil pipes 40 and 41 for returning the oil separated by the oil separator 8 to the low-stage compressor 4 via the high-stage compressor 7,
Oil pipe 41 connecting the low-stage compressor 4 and the high-stage compressor 7
The oil level controller 42 is provided in the.

The oil level adjuster 42 is constructed as shown in FIG. 4, and has a float 44 in a container 43 and an arm 45 having one end connected to the float and a fulcrum at the center.
And a valve 46 formed downward at the other end of the arm, the float 44 rises when the oil level in the container 43 rises, and the valve 31 causes the low-stage compressor. The opening 47 of the fourth side pipe is opened to supply oil to the low-stage compressor 4, and when the oil level is lowered, the float 44 is lowered to close the opening 47 and close the low-stage compressor. The oil supply to 4 is stopped.

In this case as well, the oil level adjuster 42 is in a state where the valve 46 closes the opening 47 when the float 44 descends, but the valve 31 opens due to pressure, so-called blow open. Designed to never happen.

According to this structure, during operation, the oil separated by the oil separator 8 is first fed to the high-stage compressor 7
After securing a predetermined amount of oil in the compressor 7, the oil which has become a predetermined amount or more in this high-stage compressor, that is, overflowed oil, is adjusted by the oil level controller 42 to the low-stage compressor. The oil level adjuster 42 can prevent the reverse flow of oil from the low-stage compressor 4 to the high-stage compressor 7 when stopped. As a result, the low-stage side compressor 4 and the high-stage side compressor 7 are composed of separate compressors, and even if there is a pressure difference between the compressors, only one is provided for the high-stage side compressor 7. With the simple configuration of providing the oil level adjuster 42, the amount of oil in each of the compressors 4 and 7 can be maintained at a predetermined amount, and the lock of the compressors due to insufficient oil can be prevented.

In addition, since the oil is directly returned from the oil separator 8 to the high-stage compressor 7, the crank chamber of the high-stage compressor 7 can function as an oil tank, and the oil tank is unnecessary. The number of parts can be reduced.

[0038]

As described above, according to the structure of claim 1 of the present invention, during operation, the oil separated by the oil separator is stored in the oil tank due to the pressure difference, and then the oil is removed from this tank. A certain amount of oil can be supplied to each compressor due to the pressure difference or head difference, and at the time of stoppage, the oil level controller prevents backflow of oil from the oil tank to the low-stage compressor or high-stage compressor. it can. As a result, the low-stage side compressor and the high-stage side compressor are constituted by separate compressors, and even if there is a pressure difference between the compressors, one oil separator and one oil tank Thus, the amount of oil in each compressor can be maintained at a predetermined amount, and the compressor can be prevented from locking due to insufficient oil.

According to the second aspect of the present invention, during operation, the oil separated by the oil separator is first returned to the high-stage compressor to supply a predetermined amount of oil to the high-stage compressor. After securing the oil, the oil that has exceeded the specified amount in this high-stage compressor, that is, the overflowed oil, can be returned to the low-stage compressor by the oil level adjuster, and when stopped, the oil level adjuster The backflow of oil from the low-stage compressor to the high-stage compressor can be prevented. As a result, the low-stage side compressor and the high-stage side compressor are composed of separate compressors, and even if there is a pressure difference between the compressors, only one oil level is provided for the high-stage side compressor. With the simple configuration of providing the regulator, the amount of oil in each compressor can be maintained at a predetermined amount, and the compressor can be prevented from locking due to insufficient oil.

In addition, since the oil is returned from the oil separator directly to the high-stage compressor, the crank chamber of the high-stage compressor can be made to function as an oil tank, and the oil tank becomes unnecessary and the number of parts is reduced. Can be reduced.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of a two-stage compression refrigeration system.

FIG. 2 is an explanatory diagram of an oil level adjuster.

FIG. 3 is a refrigerant circuit diagram of a two-stage compression type refrigeration system showing another embodiment.

FIG. 4 is an explanatory view of an oil level adjuster showing another embodiment.

[Explanation of symbols]

1 Two-stage compression refrigeration system 4 Low-stage compressor 7 High-stage compressor 8 oil separator 9 condenser 13 Expansion valve 14 Evaporator 22 Oil piping 22A, 22B Branch oil pipe 23 oil tank 24A, 24B Oil level controller 27 piping

Claims (2)

[Claims] 1. A two-stage compression refrigeration system in which a low-stage compressor, an internal low-pressure high-stage compressor, an oil separator, a condenser, a pressure reducing device, and an evaporator are connected to each other, wherein the oil separation is performed. An oil pipe having an oil tank is connected to the container, and a branch oil pipe branched from this oil pipe is connected to each compressor, an oil tank is provided in the oil pipe, and an oil level controller is provided in the branch oil pipe. A two-stage compression refrigeration system characterized in that an intermediate pressure is applied in the tank. 2. A two-stage compression refrigeration system comprising a low-stage compressor, a high-stage compressor, an oil separator, a condenser, a pressure reducing device, and an evaporator, which are separated by the oil separator. The oil pipe that returns the collected oil to the low-stage compressor via the high-stage compressor is provided, and the oil level controller is provided on the oil pipe that connects the low-stage compressor and the high-stage compressor. A two-stage compression refrigeration system characterized by the above.