JP2007191057A - Refrigeration system, and air conditioner for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigeration system and an air conditioner for a vehicle using CO<SB>2</SB>refrigerant, which quickly respond to a heating requirement. <P>SOLUTION: The refrigeration system (2) makes the CO<SB>2</SB>refrigerant circulate in a circulation passage. In a heating mode, a compressor (18), an internal heat exchanger (22), an evaporator (26), and an expansion valve (42) are arranged in the circulation passage in the flowing direction of the refrigerant, and further a return passage (36) is provided so as to connect the down-stream side of the internal heat exchanger with the inside of the compressor by bypassing the evaporator and the expansion valve. The refrigerant in the internal heat exchanger flowing from the compressor toward the internal heat exchanger is cooled by the decompression of the refrigerant in the return passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 that employs 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.
Here, at the time of cooling of the refrigeration system using the CO ₂ refrigerant, the refrigerant discharged from the compressor reaches the four-way valve through one indoor heat exchanger, and the outdoor heat exchanger, the expansion valve, and the other indoor heat exchanger After that, it reaches the four-way valve again and returns to the compressor. On the other hand, at the time of heating, the refrigerant discharged from the compressor reaches the four-way valve through one indoor heat exchanger, and reaches the four-way valve again through the other indoor heat exchanger, the expansion valve, and the outdoor heat exchanger. A technique for returning to the compressor is disclosed (for example, see Patent Document 1).
JP 2004-218858 A

By the way, in the vehicle air conditioner adopting the refrigeration system, the heat source is obtained by exhaust heat of the engine, that is, cooling water of the radiator.
However, in view of the recent increase in engine efficiency, there is a concern as to whether this cooling water can be used as a heat source. This is because the temperature rise of the cooling water is suppressed so as to be moderate. As described above, the above-described conventional technology still has a problem with respect to promptly responding to a heating request.

In addition, in the above-described conventional technology, it should be noted that the flow directions of the cooling cycle and the heating cycle are reversed via the four-way valve. If the flow direction is reversed, there is a problem that it is difficult to simplify the refrigeration system.
The present invention has such has been made in view of the problems, and an object thereof is to provide a refrigeration system and a vehicle air-conditioning apparatus using CO ₂ refrigerant can be quickly respond to heating demand.

To achieve the above object, a refrigeration system according to claim 1, wherein is the refrigeration system CO ₂ refrigerant circulates through the circulation path, the circulation path of the heating, the compressor as viewed in the flow direction of the refrigerant, An internal heat exchanger, an evaporator, and an expansion valve are sequentially inserted, and a return path that bypasses the evaporator and the expansion valve and connects the downstream side of the internal heat exchanger and the inside of the compressor is provided. The refrigerant is depressurized, and the refrigerant in the internal heat exchanger from the compressor to the internal heat exchanger is cooled.

In the invention according to claim 2, a compressor, a gas cooler, an expansion valve, and an evaporator are sequentially inserted in the circulation path during cooling in view of the refrigerant flow direction. The path connecting the compressor and the internal heat exchanger bypasses the gas cooler.
Furthermore, the invention according to claim 3 is characterized in that a vehicle air conditioner includes the above-described refrigeration system.

The present invention focuses on the fact that the refrigerant temperature discharged from the compressor is high in the refrigeration system using the CO ₂ refrigerant.
And according to the refrigerating system of this invention of Claim 1, the self-cooling type internal heat exchanger is arrange | positioned in the upstream of an evaporator, and this internal heat exchanger adjusts heating capability. In other words, a heating cycle is formed by the compressor, the internal heat exchanger, the evaporator, the expansion valve, and the return path. Therefore, heating in the refrigeration system using the CO ₂ refrigerant is performed more quickly than in the past.

In addition, the refrigerant in the return path is used for cooling the refrigerant in the internal heat exchanger, and is returned to the compressor via the return path, so that the amount of refrigerant discharged from the compressor can be changed, and heating is performed. Contributes to capacity adjustment.
According to the invention described in claim 2, in the refrigeration system using the CO ₂ refrigerant, the discharge side of the compressor is branched into two, the gas cooler side and the internal heat exchanger side, and the cooling cycle and the heating Are formed in the same flow direction. Therefore, simplification of the refrigeration system can be achieved.

Furthermore, according to the third aspect of the present invention, it is possible to promptly respond to a passenger's heating request, improve the reliability of the air conditioner, and use CO ₂ refrigerant, which is a natural refrigerant, for the vehicle air conditioner. This will greatly contribute to the reduction of environmental impact.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an outline of a refrigeration system according to an embodiment constituting an air conditioner for a vehicle. The refrigeration system 2 cools and heats 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), which is a natural refrigerant, and the refrigeration circuit 6 extends from an engine room 8 including an engine 10 to a vehicle compartment 4. Installed.

  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 in the vehicle compartment 4 of the vehicle. It also extends. Specifically, in the circulation paths 11 to 15, the compressor (compressor) 18, the gas cooler 20, the internal heat exchanger 22, the cooling pressure reducing valve (expansion valve) 24, the evaporator (evaporator) 26, and the heating path are connected from the upstream side. A first pressure reducing valve (expansion valve) 42 is sequentially inserted. The compressor 18, the gas cooler 20, the internal heat exchanger 22, the cooling pressure reducing valve 24 and the first pressure reducing valve 42 are disposed in the engine room 8, and the evaporator 26 is disposed in the vehicle compartment 4. In the figure, 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.

Here, in the refrigeration system 2 of the present embodiment, both the cooling cycle and the heating cycle are formed in the same flow direction.
Specifically, the former cooling cycle includes a compressor 18, a gas cooler 20, a cooling pressure reducing valve 24, and an evaporator 26. The cooling pressure reducing valve 24 is adjusted to a small opening during cooling. In contrast, the refrigerant is depressurized, while the heating is adjusted to full open. In addition, a first on-off valve 34 for cooling is provided on the inlet side of the gas cooler 20 in the circulation path 11, and a second on-off valve 40 for cooling is provided on the inlet side of the compressor 18 in the circulation path 15. ing. These on-off valves 34 and 40 are adjusted to be fully open during cooling, while being fully closed during heating. The opening degree of the above-described cooling pressure reducing valve 24 and on-off valves 34 and 40 is adjusted by a signal from a controller (ECU) 50 disposed in the passenger compartment 4.

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 path 11 in a high-temperature and high-pressure gas state. That is, the compressor 18 generates a refrigerant flow while compressing the refrigerant.
Further, the gas cooler 20 receives a wind fan (not shown) and wind from the front of the vehicle, and air-cools the refrigerant flowing through the gas cooler 20. Further, the high-pressure refrigerant from the gas cooler 20 is supplied to the evaporator 26 through the cooling pressure reducing valve 24, and enters a 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 path 15, and the refrigerant in a low-temperature and low-pressure gas state is sucked into the compressor 18.

On the other hand, the latter heating cycle is composed of the compressor 18, the internal heat exchanger 22, the evaporator 26, and the first pressure reducing valve 42 at the time of heating. It is fixed.
More specifically, the outlet side of the compressor 18 in the circulation path 11 is branched, and the circulation path 11 and the circulation path 12 are connected via a bypass path (path) 30, and the bypass path 30 is connected to the gas cooler. The compressor 18 and the internal heat exchanger 22 are connected by bypassing 20. The bypass path 30 is provided with an opening / closing valve 32 for heating. The opening / closing valve 32 is adjusted to be fully open during heating by a signal from the ECU 50, while being adjusted to fully closed during cooling.

The internal heat exchanger 22 described above functions only during heating, and is configured as a self-cooling internal heat exchanger. That is, the internal heat exchanger 22 is disposed between the circulation path 12 and the circulation path 13, and the outlet side of the internal heat exchanger 22 of the circulation path 13 is branched and connected to the return path 36. .
More specifically, the return path 36 is provided with a second pressure reducing valve 38 during heating. The second pressure reducing valve 38 is adjusted to a small opening degree during heating by a signal from the ECU 50 to reduce the pressure of the refrigerant. In contrast, it is fully closed during cooling. The refrigerant decompressed during heating returns into the internal heat exchanger 22 and cools the refrigerant from the circulation path 12 in opposition to the refrigerant flow from the compressor 18 toward the internal heat exchanger 22. The return path 36 bypasses the evaporator 26 and the first pressure reducing valve 42 during heating, connects the internal heat exchanger 22 and the compressor 18, and the return used for cooling in the internal heat exchanger 22. The refrigerant in the path 36 reaches the intermediate pressure chamber of the compressor 18.

  The first pressure reducing valve 42 during heating bypasses the second opening / closing valve 40 during cooling and connects the outlet side of the evaporator 26 and the inlet side of the compressor 18. As a result, the high-pressure refrigerant from the internal heat exchanger 22 is supplied to the evaporator 26, becomes a relatively high-temperature and high-pressure gas state in the evaporator 26, and passes through the first pressure-reducing valve 42 during heating of the circulation path 15. The refrigerant in the low-temperature and low-pressure gas state is supplied to the compressor 18 and sucked into the compressor 18.

According to the refrigeration system 2 described above, the refrigerant from the evaporator 26 is compressed along with the operation of the compressor 18 during cooling. That is, due to the adiabatic compression action of the compressor 18, the specific enthalpy and the pressure each increase and change from a point A to a point D as indicated by a one-dot chain line in FIG. 2. 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, the specific enthalpy is reduced, the pressure is changed from point D to point E in FIG. 2, and is supplied to the cooling pressure reducing valve 24 via the circulation paths 12 and 13. Then, the expansion is caused by the throttling action of the pressure reducing valve 24 at the time of cooling, and the pressure decreases while maintaining the specific enthalpy constant, and changes from the point E to the point F in FIG. Erupt inside. 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, at the time of heating, the refrigerant having a flow rate that combines the refrigerant from the return path 36 and the refrigerant from the circulation path 15 is compressed by the compressor 18, and the specific enthalpy and pressure are further increased by the adiabatic compression action. It changes from point A to point B as shown by the solid line in FIG. Then, the high-temperature and high-pressure gas state refrigerant is supplied to the internal heat exchanger 22 through the circulation path 11 and the bypass path 30.

  This refrigerant is cooled in the internal heat exchanger 22. That is, heat is exchanged with the refrigerant in the return path 36, and the specific enthalpy is reduced. Specifically, as shown in FIG. 3, the heating capacity of the heating decreases as the operating ratio of the internal heat exchanger 22 increases, so that the second pressure reducing valve 38 during heating to obtain a desired heating capacity. The internal heat exchanger 22 is operated by adjusting the opening degree.

  Next, when the refrigerant from the internal heat exchanger 22 is supplied to the evaporator 26 and warm air is sent into the passenger compartment 4 to heat the passenger compartment 4, the specific enthalpy is further reduced and the point of FIG. The isobaric change from B to point C. Then, the pressure is supplied to the first pressure reducing valve 42 via the circulation path 15, receives expansion due to the throttling action of the first pressure reducing valve 42, and the pressure decreases while maintaining its specific enthalpy constant, from point C in FIG. 2. It changes to point A, is compressed again by the compressor 18, and circulates in the circulation paths 11-15 as mentioned above.

As described above, the present invention focuses on the fact that the refrigerant temperature discharged from the compressor 18 is high in the refrigeration system 2 using the CO ₂ refrigerant.
And according to the refrigerating system 2 of this embodiment, the self-cooling type internal heat exchanger 22 is arrange | positioned in the upstream of the evaporator 26, and this internal heat exchanger 22 adjusts the heating capability of heating. . In other words, a hot gas cycle is formed by the return path 36 having the compressor 18, the internal heat exchanger 22, the evaporator 26, the first pressure reducing valve 42 during heating, and the second pressure reducing valve 38 during heating. Yes. Therefore, without providing one or the other indoor heat exchanger or outdoor heat exchanger as described above, and without obtaining a heat source by the cooling water of the radiator, the Mollier chart has a small triangular shape as indicated by a point ABC in FIG. A cycle is formed, and heating in the refrigeration system using the CO ₂ refrigerant is performed more quickly than in the past. As a result, it is possible to quickly respond to the passenger's heating request and to improve the reliability of the air conditioner.

  The refrigerant in the return path 36 is used for cooling the refrigerant in the internal heat exchanger 22 and is returned to the compressor 18 through the return path 36, so that the amount of refrigerant introduced into the cycle is the same. Even if it exists, the amount of refrigerant | coolants discharged from the compressor 18 can be increased like the point A to the point B of FIG. 2, and it contributes to adjustment of a heating capability. As in this embodiment, connecting the return path 36 to the intermediate pressure chamber of the compressor 18 contributes to improving the efficiency of the cycle, but the return path 36 is connected to the inlet side of the compressor 18, that is, to the circulation path 15. You may connect.

Furthermore, as shown in FIG. 3, based on the relationship between the operating ratio of the internal heat exchanger 22 and the heating capacity, the internal heat exchanger 22 adjusts the heating capacity to the optimum value within the cycle. Overheating is prevented.
Furthermore, in the refrigeration system 2 using the CO ₂ refrigerant, the discharge side of the compressor 18 is branched into two parts, a gas cooler 20 side and an internal heat exchanger 22 side, so that the cooling direction and the heating are not reversed without reversing the flow direction. Each cycle is formed in the same flow direction. Therefore, a four-way valve is not necessary, and simplification of the refrigeration system can be achieved.

Further, by using the CO ₂ refrigerant is a natural refrigerant in an air conditioning system for vehicles, greatly contributes to reducing environmental impact.
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, although the above embodiment shows an example embodied in a vehicle air conditioner, the refrigeration system of the present invention is a CO ₂ like a commercial air conditioner, a household heat pipe, a water heater, a heater, etc. Applicable to all refrigeration and air conditioning cycles using refrigerants.

1 is a schematic configuration diagram of a refrigeration system according to an embodiment of the present invention. FIG. _{2 is} a schematic Mollier diagram of a CO ₂ refrigerant in the refrigeration system of FIG. 1. It is a figure explaining adjustment of the heating capability by the internal heat exchanger of FIG.

Explanation of symbols

2 Refrigeration system 11, 12, 13, 14, 15 Circulation path 18 Compressor 20 Gas cooler 22 Internal heat exchanger 24 Cooling pressure reducing valve (expansion valve)
26 Evaporator 30 Bypass route (route)
36 Return path 38 Second pressure reducing valve during heating 42 First pressure reducing valve (expansion valve) during heating

Claims (3)

CO ₂ refrigerant is a refrigeration system that circulates through the circulation path,
In the circulation path during heating, a compressor, an internal heat exchanger, an evaporator and an expansion valve are sequentially inserted in the flow direction of the refrigerant,
A return path that bypasses the evaporator and the expansion valve and connects the downstream side of the internal heat exchanger and the inside of the compressor, and the refrigerant in the return path is depressurized to exchange the internal heat from the compressor A refrigeration system that cools the refrigerant in the internal heat exchanger toward the refrigerator. The compressor, a gas cooler, an expansion valve, and the evaporator are sequentially inserted in the circulation path during cooling in the flow direction of the refrigerant,
2. The refrigeration system according to claim 1, wherein a path connecting the compressor and the internal heat exchanger out of the circulation path during the heating bypasses the gas cooler.   A vehicle air conditioner comprising the refrigeration system according to claim 1.

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