JP4354372B2 - Refrigeration system and vehicle air conditioner - Google Patents

Description

The present invention relates to a refrigeration system, and more particularly to a refrigeration system using a CO ₂ refrigerant and a vehicle air conditioner employing the refrigeration system.

In recent years, a refrigeration system using a refrigerant having a small global warming potential has been developed in consideration of the global environment. An example of this type of refrigerant is natural CO ₂ (carbonic acid) gas.
However, this CO ₂ refrigerant has a relatively high evaporation pressure, and therefore easily leaks from the refrigerant circulation path. In addition, there is a concern about the durability of the compressor among the devices on the route. For this reason, the technique which improves the durability of this compressor is disclosed (for example, refer patent document 1).
JP 2002-225549 A

By the way, this kind of compressor compresses a refrigerant | coolant, but this refrigerant | coolant normally contains refrigeration oil (oil). This oil not only lubricates the sliding surfaces and bearings in the compressor, but also functions as a seal for the sliding surfaces. However, the circulation in the circulation path by the oil becomes a factor of reducing the cooling capacity of the refrigeration system.
More specifically, if the oil circulation rate (OCR) in the evaporator exceeds 0.5%, there is a problem that the amount of heat exchange is extremely reduced. That is, in the above-described conventional technology, no special consideration is given to the reduction in cooling capacity.

In this case, it may be possible to add a new passage or equipment for directly connecting the oil separator and the compressor, but considering the cost of the system, heat exchange in the evaporator with the existing configuration It is desirable to guarantee the amount.
This invention is made | formed in view of such a subject, and it aims at providing the refrigeration system and vehicle air conditioner which can prevent the fall of a cooling capability with the existing structure.

In order to achieve the above object, a refrigeration system according to claim 1 is a refrigeration system in which CO ₂ refrigerant circulates in a circulation path, and the circulation path has a compressor, a gas cooler, and an expansion in the flow direction of the refrigerant. A valve and an evaporator are sequentially inserted, and are provided between a gas cooler and an expansion valve. The oil separator includes an oil separator that separates oil for a compressor from a refrigerant. The oil separator includes a main body that stores oil. The suction pipe is disposed in the main body and connected to the circulation path, and the suction pipe includes a terminal portion opened toward the main body and a pore disposed in the middle of the suction pipe. When the amount of stored oil is equal to or less than the position where the pores are disposed, the end portion is blocked with oil and only the refrigerant passes through the pores and circulates in the circulation path. If the installation position is exceeded, In addition to the end, the pores are closed with oil, and the oil and refrigerant are circulated through the end part and circulated in the circulation path, so that the oil circulation rate in the evaporator is kept below a predetermined value. It is characterized by intermittent circulation.

In the invention of claim 2, the main body has a bottomed cylindrical shape, the suction pipe extends upward in a substantially vertical direction in the main body, and the uppermost end portion of the suction pipe is connected to the circulation path. The circulation path is connected to a tangential direction of the cylindrical portion of the main body at an upper portion of the main body .

Further, the invention according to claim 3 is characterized in that the oil separator is a device having a function as an accumulator.
Furthermore, a vehicle air conditioner according to a fourth aspect is characterized by including the above-described refrigeration system.

Therefore, according to the refrigeration system of the first aspect of the present invention, the CO ₂ refrigerant contains oil, which flows out of the compressor, is cooled by the gas cooler, and reaches the oil separator. In this oil separator, oil is separated from the refrigerant, but this oil circulates in the circulation path intermittently. That is, the oil is circulated in the circulation path while suppressing the oil circulation rate in the evaporator to a predetermined value (for example, 0.5%) or less. As a result, the amount of heat exchange in the evaporator is guaranteed only by using the energy of the existing compressor , and the cooling capacity is prevented from being lowered while the refrigeration system using the CO ₂ refrigerant is reduced in price .

Further, if the oil separator is provided not on the outlet side of the compressor but on the outlet side of the gas cooler, the oil cooled by the gas cooler has a high oil viscosity and is easily separated from the refrigerant. As a result, efficient oil separation is achieved.
Furthermore, it is possible to circulate within intermittently circulating path OIL, oil circulation rate in the evaporator is reliably prevented from exceeding 0.5%. Therefore, an extreme decrease in the amount of heat exchange is reliably avoided.
According to the second aspect of the present invention, the refrigerant that has flowed into the oil separator from the circulation path descends while turning around the outer periphery of the suction pipe in the main body, and in this process, the oil in the refrigerant is centrifuged. Based on the principle of separation, it is separated from the refrigerant and adheres to the inner peripheral surface of the cylindrical body, so oil separation with guaranteed heat exchange in the evaporator can be achieved simply by using the energy of the existing compressor. This makes it possible to reduce the cooling capacity while reducing the cost of the refrigeration system using the CO ₂ refrigerant.

  Furthermore, according to the invention described in claim 3, the oil separator has a function as an accumulator in addition to a function as an oil separator. And compared with the case where the oil separator is provided on the outlet side of the compressor, the refrigerant is temporarily stored in a higher density state, so even if the refrigerant is reduced, the system balance may be lost. Does not occur. Therefore, the reliability of the refrigeration system is improved.

Furthermore, according to the vehicle air conditioner of the fourth aspect, the energy of the existing compressor is used without adding a new passage or equipment for connecting the oil separator and the compressor. Thus, the amount of heat exchange in the evaporator can be guaranteed, and the refrigeration system can be made inexpensive. In addition, if CO ₂ refrigerant, which is a natural refrigerant, is used in the vehicle air conditioner, it greatly contributes to reducing the environmental load.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of a refrigeration system 2 of an embodiment constituting a vehicle air conditioner. The refrigeration system 2 cools the interior of a passenger compartment 4 at a desired set temperature.
The refrigeration system 2 includes a refrigeration circuit 6 that circulates a CO ₂ refrigerant (hereinafter simply referred to as a refrigerant) that is a natural refrigerant. The refrigeration circuit 6 extends from an engine room 8 having an engine 10 to a vehicle compartment 4. Installed.

  Specifically, the refrigeration circuit 6 has circulation paths 11 to 15 for the refrigerant, and most of the circulation paths 11 to 15 are arranged in the engine room 8 of the vehicle, but a part of the circulation paths 11 to 15 is a vehicle vehicle. It also extends into the chamber 4. A compressor (compressor) 18, a gas cooler 20, an oil separator 22, an expansion valve 24, and an evaporator (evaporator) 26 are sequentially inserted in the circulation paths 11 to 15 from the upstream side. The compressor 18, the gas cooler 20, the oil separator 22, and the expansion valve 24 are disposed in the engine room 8, and the evaporator 26 is disposed in the vehicle compartment 4.

In FIG. 1, reference numerals 11, 12, 13, and 14 form the forward path portion of the circulation path, and reference numeral 15 forms the return path portion of the circulation path.
The compressor 18 is operated by the driving force of the engine 10, sucks and compresses the refrigerant in the gas state, and discharges it to the circulation flow path 11 in a high temperature and high pressure gas state. That is, the compressor 18 generates a refrigerant flow while compressing the refrigerant.

  And the gas cooler 20 receives the wind from the fan and the vehicle front which are not shown in figure, and air-cools the refrigerant | coolant which flows through the inside. Further, the high-pressure refrigerant from the gas cooler 20 is supplied to the evaporator 26 through the expansion valve 24, and becomes a relatively low-temperature and low-pressure gas state in the evaporator 26. The downstream side of the evaporator 26 is connected to the compressor 18 via the circulation channel 15, and the refrigerant in the low temperature and low pressure gas state is sucked into the compressor 18.

  The oil separator 22 of this embodiment is disposed between the gas cooler 20 and the expansion valve 24, that is, between the circulation path 12 and the circulation path 13, and separates compressor oil from the refrigerant. The oil separated from the refrigerant is returned to the compressor 18 from the oil separator 22 via the circulation paths 13 to 15. More specifically, the oil separator 22 does not return the oil directly toward the compressor 18 side, but circulates the oil intermittently in the circulation paths 13 to 15. That is, the oil separated from the refrigerant by the oil separator 22 is stored in the oil separator 22 and from the oil separator 22 in order to suppress the oil circulation rate (OCR) in the evaporator 26 to 0.5% or less. It is divided into the case where it is sent out, and only in this case, it reaches the evaporator 26 through the circulation path 13, the expansion valve 24 and the circulation path 14, and is returned to the compressor 18 via the circulation path 15. Yes. The oil circulation rate in the evaporator 26 is indicated by a ratio between the oil amount in the evaporator 26 and the total amount of the oil amount and the refrigerant amount.

Details of the oil separator 22 are shown in FIG.
The oil separator 22 includes a bottomed cylindrical main body 30, and a suction pipe 32 extends upward in the main body 30 in a substantially vertical direction. Further, as shown in FIG. 5A, the circulation path 12 is connected to the tangential direction of the cylindrical portion 32 at an upper portion of the cylindrical portion 32. On the other hand, as shown in FIG. 2B, the suction pipe 32 is provided with a pore 34 at a predetermined appropriate position, and the suction pipe 32 is further provided with a terminal portion 36 opened at the lowermost end portion. It has been. The uppermost end portion of the suction pipe 32 is connected to the circulation path 13.

  And this oil separator 22 isolate | separates oil from the refrigerant | coolant flowed in from the circulation path 12 connected to the gas cooler 20, and stores these refrigerant | coolants and oil temporarily in the main body 30 in the separated state. In other words, the oil separator 22 of this embodiment also has a function as an accumulator. Next, at a predetermined timing, only the refrigerant or oil and refrigerant is sent from the suction pipe 32 to the circulation path 13.

Specifically, first, as shown in FIG. 3A, when the amount of oil stored in the oil separator 22 is at a level that does not reach the position where the pores 34 are disposed, only the CO ₂ refrigerant having a low viscosity is used. It is delivered to the circulation path 13 through the pores 34. On the other hand, as shown in FIG. 5B, when the amount of stored oil is at a level exceeding the arrangement position of the pores 34, the oil having a large viscosity blocks the pores 34. As a result, the oil in the oil separator 22 is sucked up from the end portion 36 of the suction pipe 32 upward and is sent out to the circulation path 13. Further, the refrigerant at this time is sent not from the pore 34 but from the end portion 36 to the circulation path 13 following the oil until the pore 34 is closed by the oil. Note that when the blockage of the pores 34 by the oil is released, only the refrigerant is again sent to the circulation path 13 through the pores 34, and the oil storage in the main body 30 is resumed.

According to the refrigeration system 2 described above, the refrigerant is compressed from the evaporator 26 with the operation of the compressor 18. That is, due to the adiabatic compression action of the compressor 18, the specific enthalpy and the pressure increase and change from point A to point B in FIG. 4. Then, a refrigerant in a high-temperature and high-pressure gas state is supplied to the gas cooler 20 through the circulation path 11.
This refrigerant is cooled in the gas cooler 20. That is, the specific enthalpy is reduced by the cooling action of the gas cooler 20, and the pressure is changed from the point B to the point C in FIG. Then, the oil separator 22 is supplied via the circulation path 12.

  The refrigerant that has flowed into the oil separator 22 from the circulation path 12 descends while turning around the outer periphery of the suction pipe 32 in the main body 30. In this process, the oil in the refrigerant is separated from the refrigerant based on the principle of centrifugal separation and adheres to the inner peripheral surface of the cylindrical main body 30. The refrigerant is temporarily stored in the oil separator 22 and then sent out toward the circulation path 13 through the pores 34 of the suction pipe 32.

Thereafter, the refrigerant in the high-pressure gas state is supplied to the expansion valve 24 via the circulation path 13. Then, the expansion is caused by the throttle action of the expansion valve 24, the pressure decreases while maintaining its specific enthalpy constant, changes from point C to point D in FIG. 4, and enters the evaporator 26 through the circulation path 14. Erupt.
Next, the air around the evaporator 26 is cooled by the heat of vaporization of the refrigerant. Then, the cool air is sent into the passenger compartment 4 and the passenger compartment 4 is cooled. The refrigerant in the evaporator 26 returns to the compressor 18 via the circulation path 15, and is then compressed again by the compressor 18, and circulates in the circulation paths 11 to 15 as described above.

  On the other hand, in the oil separator 22, the oil separated from the refrigerant flows down along the inner peripheral surface of the main body 30 and is stored. When the amount of stored oil exceeds the pore 34, the oil is sent toward the circulation path 13 through the end portion 36 of the suction pipe 32, and the circulation path 13, the expansion valve 24, the circulation path 14, and the evaporator. 26, and returned to the compressor 18 via the circulation path 15.

As described above, the present embodiment focuses on improving the oil circulation rate in the evaporator 26 with the existing configuration in the vehicle air conditioner using the CO ₂ refrigerant.
According to this embodiment, the refrigerant and oil flow out of the compressor 18, are cooled by the gas cooler 20, and reach the oil separator 22. In the oil separator 20, oil is separated from the refrigerant, and this oil circulates through the circulation paths 13 to 15 intermittently.

More specifically, as shown in FIG. 5, when the amount of stored oil does not reach the level of the pores 34, only the refrigerant is sent to the circulation path 13 and the oil is stored in the oil separator 22 ( Oil storage period H). At this time, the oil circulation rate in the evaporator 26 becomes very small. On the other hand, when the amount of stored oil exceeds the level of the pores 34, oil and refrigerant are sent to the circulation path 13 (oil circulation period R). Therefore, by using the intermittent oil delivery type oil separator as described above, the oil circulation rate in the evaporator 26 is 0.5% in the short period such as the oil circulation period R (2 points in the figure). In the oil storage period H that is longer than the oil circulation period R, the oil circulation rate is kept very small as described above. It can be seen that the amount of heat exchange in the evaporator 26 is guaranteed as compared to (indicated by a dotted line in the figure). As a result, a decrease in the cooling capacity of the vehicle air conditioner using the CO ₂ refrigerant is avoided.

Further, since the oil separator 22 is provided not on the outlet side of the compressor 18 (point B in FIG. 4) but on the outlet side of the gas cooler 20 (point C in FIG. 4), the oil separator 22 is cooled by the gas cooler 20. Only the oil viscosity becomes higher. This facilitates the separation of oil from the refrigerant. As a result, efficient oil separation is achieved.
Further, the configuration of the oil separator 22 allows the evaporator 26 to be used only by using the energy of the existing compressor 18 without adding a new passage or equipment for connecting the oil separator 22 and the compressor 18 separately. The amount of heat exchange in the system can be guaranteed, and the cost of the system can be reduced.

Furthermore, since the oil separator 22 has a function as an accumulator in addition to a function as an oil separator, the refrigerant is temporarily stored in a higher density state. In other words, even if there is a decrease in the refrigerant, the system balance can be avoided.
In addition, if CO ₂ refrigerant, which is a natural refrigerant, is used in the vehicle air conditioner, it greatly contributes to reducing the environmental load.

The description of one embodiment of the present invention is finished above, but the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the suction pipe 32 extending in a substantially vertical direction is shown, but the present invention is not necessarily limited to this form. For example, the lower portion of the suction pipe 32 may be curved and the end portion 36 may be opened in the horizontal direction. In this case as well, in the same way as described above, it is possible to prevent the cooling capacity from being lowered. it can.

1 is a schematic configuration diagram of a refrigeration system according to an embodiment of the present invention. It is a block diagram of the oil separator of FIG. It is explanatory drawing of the operation | movement by the oil separator of FIG. FIG. _{2 is} a schematic Mollier chart of a CO ₂ refrigerant in the refrigeration system of FIG. 1. It is explanatory drawing of the oil circulation rate in the evaporator of FIG.

Explanation of symbols

2 Refrigeration system 11, 12, 13, 14, 15 Circulation path 18 Compressor 20 Gas cooler 22 Oil separator 24 Expansion valve 26 Evaporator 30 Main body 32 Suction pipe 34 Pore 36 End

Claims (4)

A refrigeration system in which a CO ₂ refrigerant circulates in a circulation path,
In the circulation path, a compressor, a gas cooler, an expansion valve, and an evaporator are sequentially inserted in the flow direction of the refrigerant,
An oil separator that is disposed between the gas cooler and the expansion valve and separates oil for the compressor from the refrigerant;
The oil separator is composed of a main body for storing the oil, and a suction pipe disposed in the main body and connected to the circulation path,
The suction pipe has a terminal portion opened toward the inside of the main body and a pore disposed in the middle of the suction pipe,
When the oil storage amount is equal to or less than the position where the pores are disposed, the end portion is blocked with the oil, and only the refrigerant is circulated through the pores in the circulation path, When the amount of stored oil exceeds the arrangement position of the pores, in addition to the end portion, the pores are also closed with the oil, and the circulation path passes through the oil and the refrigerant through the end portion. The refrigeration system is characterized in that the oil is circulated intermittently in the circulation path so as to circulate in the interior and keep the oil circulation rate in the evaporator below a predetermined value. The main body has a bottomed cylindrical shape,
The suction pipe extends upward in a substantially vertical direction in the main body, and an uppermost end portion of the suction pipe is connected to the circulation path.
The refrigeration system according to claim 1, wherein the circulation path is connected to a tangential direction of a cylindrical portion of the main body at an upper portion of the main body .   The refrigeration system according to claim 1 or 2, wherein the oil separator is a device that also functions as an accumulator.   A vehicle air conditioner comprising the refrigeration system according to any one of claims 1 to 3.

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