JP2003207219A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To skirt a problem in a refrigerating cycle device posed by the unbalance in optimum refrigerant amount among operation modes. <P>SOLUTION: A refrigerating cycle circuit is formed by circularly connecting a compressor, a plurality of heat exchangers, a decompressor and the like by a connection pipe, a switching means is mounted to switch the pressure of the refrigerant flowing in at least one heat exchanger A of the plurality of heat exchangers, between low pressure and high pressure, and carbon dioxide is used as the refrigerant. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle apparatus having a function of switching the inside of at least one heat exchanger between high pressure and low pressure.

[0002]

2. Description of the Related Art Conventionally, the refrigerant pressure in at least one heat exchanger of a plurality of heat exchangers constituting a refrigeration cycle is switched between high pressure and low pressure to act as a radiator or as a heat absorber. There is a refrigeration cycle device that operates or suppresses heat exchange.

For example, as shown in FIG. 7, a compressor 51,
An outdoor heat exchanger 52, a decompressor 53, and an indoor heat exchanger 54 are annularly connected by pipes, a four-way valve 55 is provided as a switching unit, and a refrigeration cycle apparatus in which an HCFC 22 is enclosed as a refrigerant is used for a refrigeration cycle such as a room air conditioner. It is well known that it has a basic configuration.

The operation of such a refrigeration cycle apparatus will be described.

First, when the four-way valve 55 is set as shown by the solid line in FIG. 7, the refrigerant (HCFC22) that has been compressed by the compressor 51 into a high-temperature and high-pressure gas passes through the four-way valve 55 and the outdoor heat exchanger. At 52, it is cooled by the outside air to become a liquid, and at the decompressor 53 it is decompressed to become a low-temperature low-pressure gas-liquid two-phase state and introduced into the indoor heat exchanger 54. In the indoor heat exchanger 54, heat is absorbed from the indoor air to be vaporized into gas, which is compressed again by the compressor 51 via the four-way valve 55. The above-described operation makes it possible to cool the room.

On the other hand, when the four-way valve 55 is set as shown by the broken line in FIG. 7, the refrigerant (HCFC22) compressed into high temperature and high pressure gas by the compressor 51 passes through the four-way valve 55 and the indoor heat exchanger. At 54, heat is radiated to the indoor air to become a liquid, which is decompressed at the decompressor 53 to be in a low-temperature low-pressure gas-liquid two-phase state and introduced into the outdoor heat exchanger 52. This outdoor heat exchanger 52
Then, it is evaporated by heat absorption from the outside air to become gas, and is compressed again by the compressor 51 via the four-way valve 55. The room can be heated by the above operation.

Further, as shown in FIG. 8, Japanese Patent Application Laid-Open No. 9-66722 proposes to apply a refrigeration cycle device as an auxiliary heating means of an air conditioner for an electric vehicle.

In FIG. 8, an engine 61 and a pump 6
2, the radiator 63, the water-refrigerant heat exchanger 64, and the heater core 65 constitute an engine cooling circuit 66. Further, the compressor 67, the water-refrigerant heat exchanger 64, the pressure reducer 68, the solenoid valve 69, the outdoor heat exchanger 70, the solenoid valve 71, the pressure reducer 7
2. The indoor heat exchanger 73 and the like constitute a refrigeration cycle device.

The operation of such a refrigeration cycle apparatus will be described.

First, in order to cool the passenger compartment, the solenoid valve 69 is set to open and the solenoid valve 71 is set to close as switching means. The refrigerant (HFC134a) that has been compressed by the compressor 67 into high-temperature and high-pressure gas is cooled by the cooling medium flowing through the engine cooling circuit 66 in the water-refrigerant heat exchanger 64,
After passing through the electromagnetic valve 69, it is further cooled by the outside air in the outdoor heat exchanger 70 to become a liquid, and is decompressed in the decompressor 72 to be in a low-temperature low-pressure gas-liquid two-phase state and introduced into the indoor heat exchanger 73. In the indoor heat exchanger 73, heat is absorbed from the air in the passenger compartment to evaporate into gas, which is compressed by the compressor 67 again. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 64 is further heated by the engine exhaust heat in the engine 61 via the heater core 65, and is cooled by the outside air in the radiator 63. At this time, the damper 74 can cool the vehicle interior by operating so that the air in the vehicle interior cooled by the indoor heat exchanger 73 does not pass through the heater core 65.

On the other hand, in order to heat the passenger compartment, the solenoid valve 69 is closed and the solenoid valve 71 is set to open as switching means. The refrigerant (HFC134a) that has been compressed by the compressor 67 into a high-temperature and high-pressure gas is cooled by the cooling medium flowing through the engine cooling circuit 66 in the water-refrigerant heat exchanger 64 to become a liquid, which is decompressed by the decompressor 68 and cooled to a low temperature. Low pressure gas-liquid 2
The phase state is introduced into the outdoor heat exchanger 70. In the outdoor heat exchanger 70, heat is absorbed from the outside air to evaporate into a gas, which is compressed by the compressor 67 again via the electromagnetic valve 71. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 64 is further heated by the engine exhaust heat in the engine 61 via the heater core 65. At this time, the damper 74
The air in the vehicle interior that has passed through the indoor heat exchanger 73 is heated by the heater core 65.
The vehicle interior can be heated by operating so as to pass through and be heated.

[0012]

However, in the refrigeration cycle apparatus as shown in FIG. 7, the indoor heat exchanger 54 is used.
The indoor heat exchanger 52 is required to be compact because it is installed indoors. On the other hand, the outdoor heat exchanger 52 is an indoor heat exchanger for energy saving during cooling by improving the condensing capacity and high capacity during heating by improving the heat absorption capacity. It is larger than the 54. Therefore, the amount of refrigerant required to realize efficient operation during cooling operation in which the large outdoor heat exchanger 52 is on the high pressure side and the refrigerant is condensed (optimum refrigerant amount during cooling)
Is greater than the amount of refrigerant (the optimal amount of refrigerant during heating) required for realizing efficient operation during heating operation in which the downsized indoor heat exchanger 54 is on the high pressure side and refrigerant is condensed. .

For this reason, when the heating operation is performed with the optimum amount of refrigerant during cooling, overfilling occurs, which causes the efficiency of the refrigeration cycle apparatus to decrease, the discharge pressure of the compressor to increase excessively, and the reliability of the compressor to decrease due to liquid compression. Was there. In addition, if the cooling operation is performed with the optimum amount of refrigerant during heating, in addition to the efficiency reduction of the refrigeration cycle device,
Due to the excessive rise in the discharge temperature of the compressor, the reliability of the compressor was reduced. Alternatively, the efficiency of the refrigeration cycle apparatus is reduced due to the eclectic refrigerant amount of the optimum cooling medium amount and the optimum heating medium amount.

Further, in the refrigeration cycle apparatus as shown in FIG. 8, the indoor heat exchanger 73 is generally installed in a very narrow space in the rear of the engine room, and therefore, miniaturization is strongly demanded, while outdoor heat exchange is performed. The device 70 is generally arranged in the front of the engine room, and is made larger than the indoor heat exchanger 54 in order to save energy during cooling by improving the condensing capacity and enhance capacity during heating by improving the heat absorption capability. Furthermore, the amount of refrigerant (the optimal amount of refrigerant during cooling) required to realize efficient operation during cooling operation in which the outdoor heat exchanger 70 is on the high pressure side and the refrigerant is condensed is the outdoor heat exchanger 7
0 becomes a low pressure side, and is larger than the amount of refrigerant (the optimal amount of refrigerant during heating) necessary for realizing efficient operation during heating operation in which the refrigerant is evaporated.

For this reason, when the heating operation is performed with the optimum amount of refrigerant during cooling, overfilling occurs, and in addition to the efficiency of the refrigeration cycle apparatus, the discharge pressure of the compressor rises excessively and the reliability of the compressor decreases due to liquid compression. Was there. In addition, if the cooling operation is performed with the optimum amount of refrigerant during heating, in addition to the efficiency reduction of the refrigeration cycle device,
Due to the excessive rise in the discharge temperature of the compressor, the reliability of the compressor was reduced. Alternatively, the efficiency of the refrigeration cycle apparatus is reduced due to the eclectic refrigerant amount of the optimum cooling medium amount and the optimum heating medium amount.

[0016]

In order to solve the above-mentioned problems, the first invention (corresponding to the invention described in claim 1).
Is a refrigerant that flows in the heat exchanger A of at least one of the plurality of heat exchangers by forming a refrigeration cycle circuit by annularly connecting a compressor, a plurality of heat exchangers, a pressure reducer and the like with connection pipes. It is characterized in that it is provided with a switching means for switching the pressure of 1 to a low pressure and a high pressure and uses carbon dioxide as a refrigerant.

A second aspect of the present invention (corresponding to the present invention according to claim 2) is characterized in that the switching means reverses the flow of the refrigerant in at least a part of the refrigeration cycle circuit.

According to a third aspect of the present invention (corresponding to the present invention according to claim 3), the switching means controls the amount of decompression on the refrigerant upstream side and the refrigerant downstream side of the heat exchanger A and opens / closes the valve. It is characterized by

The fourth aspect of the invention (corresponding to the invention of claim 4) is characterized in that a circuit for bypassing the heat exchanger A is provided.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Embodiment 1) FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to an embodiment of the present invention.

In FIG. 1, a compressor 1, an outdoor heat exchanger 2, a decompressor 3 and an indoor heat exchanger 4 are connected in an annular pipe, a four-way valve 5 is provided as a switching means, and carbon dioxide (CO2) as a refrigerant. Is a refrigeration cycle device in which is enclosed.

The operation of such a refrigeration cycle apparatus will be described.

First, when the four-way valve 5 is set as shown by the solid line in FIG. 1, the refrigerant (CO2) that has been compressed by the compressor 1 into a high-temperature and high-pressure gas passes through the four-way valve 5 and the outdoor heat exchanger. It is cooled by the outside air at 2 and is decompressed by the decompressor 3 to be a low temperature low pressure gas-liquid two-phase state and introduced into the indoor heat exchanger 4. In the indoor heat exchanger 4, heat is absorbed from the indoor air to be vaporized into gas, which is compressed by the compressor 1 again via the four-way valve 5. The above-described operation makes it possible to cool the room.

On the other hand, when the four-way valve 5 is set as shown by the broken line in FIG. 1, the refrigerant (CO2) compressed by the compressor 1 into a high temperature and high pressure gas passes through the four-way valve 5 and the indoor heat exchanger. The heat is radiated to the indoor air at 4, and the pressure is reduced by the pressure reducer 3 to form a low-temperature low-pressure gas-liquid two-phase state, which is introduced into the outdoor heat exchanger 2. In the outdoor heat exchanger 2, the heat is absorbed from the outside air to evaporate into a gas, which is compressed by the compressor 1 again via the four-way valve 5. The room can be heated by the above operation.

Since the indoor heat exchanger 4 is relatively smaller than the outdoor heat exchanger 2 as described above, the compressor 1 to the four-way valve 5 to the relatively small indoor heat exchanger during heating operation. 4 to the pressure reducer 3 on the high pressure side, the pressure reducer 3 to the relatively large outdoor heat exchanger 2 to the four-way valve 5 to the compressor 1 to the low pressure side, and the heating high pressure side internal volume <heating low pressure side internal volume Become.

During the cooling operation, the compressor 1, the four-way valve 5, the relatively large outdoor heat exchanger 2 and the decompressor 3 are on the high pressure side, and the decompressor 3 -the relatively small indoor heat exchanger 4 -four-way. The valve 5 to the compressor 1 are on the low pressure side, and the internal volume of the high pressure side during cooling> the internal volume of the low pressure side during cooling.

Therefore, a solution to the problem that the optimum amount of refrigerant during cooling and the optimum amount of refrigerant during heating are unbalanced was examined. At this time, the low-pressure side and the high-pressure side of the refrigerant such as R410A and R407C, which are HCFC22 and alternative refrigerants to the HCFC22, operate at a temperature below the critical point, whereas when CO2 is used as the refrigerant, it becomes supercritical on the high-pressure side. Focused on working in the state. Refrigerant physical property program "REFPROP
VER. 6.0 "HCFC22, R4140
The densities of A and CO2 are shown in comparison with (Table 1). Since CO2 becomes a supercritical state at 40 ° C, 40 ° C, 10 MPa
The density of was used.

[0029]

[Table 1]

From Table 1, CO2 has a smaller value of a / b than other refrigerants, that is, the change in density between the high pressure side and the low pressure side of the refrigeration cycle apparatus is small, and therefore CO2 is optimal for cooling. There is a possibility that the imbalance between the amount of refrigerant and the optimum amount of refrigerant during heating can be relaxed.

Therefore, in the refrigeration cycle apparatus as shown in FIG. 1, the size of the outdoor heat exchanger 2 and the size of the indoor heat exchanger 4 were changed to examine the optimum amount of refrigerant. The results are shown in FIG. When the heating low-pressure side internal volume is about 30% larger than the heating high-pressure side internal volume, when the refrigerant is HCFC22, the optimum cooling medium refrigerant amount is about 2 less than the heating optimal refrigerant amount.
Although it increased by 0%, when the refrigerant was CO2, it increased by about 13%, and the imbalance of the refrigerant amount was eased to about 2/3. A similar tendency was confirmed by comparing R410A, R407C and CO2. Therefore, by using CO2 as the refrigerant, the efficiency of the refrigeration cycle is reduced, the compressor discharge pressure is excessively increased, the liquid is compressed, and the compressor discharge temperature is excessively increased due to the imbalance of the refrigerant amount depending on the operation mode. It is possible to suppress deterioration of machine reliability.

(Second Embodiment) FIG. 3 shows another embodiment of the present invention.
It is a block diagram of the refrigerating-cycle apparatus which is embodiment.

In FIG. 3, engine 11 and pump 1
2, the radiator 13, the water-refrigerant heat exchanger 14, and the heater core 15 constitute an engine cooling circuit 16. Further, the compressor 17, the water-refrigerant heat exchanger 14, the pressure reducer 18, the solenoid valve 19, the outdoor heat exchanger 20, the solenoid valve 21, the pressure reducer 2
2. A refrigeration cycle apparatus is configured by enclosing carbon dioxide (CO2) as a refrigerant in a circuit including the indoor heat exchanger 23 and the like.

The operation of such a refrigeration cycle apparatus will be described.

First, in order to cool the passenger compartment, the solenoid valve 19 is set to open and the solenoid valve 21 is set to close as switching means. The refrigerant (CO2) that has been compressed by the compressor 17 into a high temperature and high pressure gas is cooled by the cooling medium flowing in the engine cooling circuit 16 in the water refrigerant heat exchanger 14, and the solenoid valve 1
After passing through 9, the air is further cooled in the outdoor heat exchanger 20 by the outside air, and is decompressed in the decompressor 22 into a low-temperature low-pressure gas-liquid two-phase state and introduced into the indoor heat exchanger 23. In this indoor heat exchanger 23, heat is absorbed from the air in the vehicle compartment to evaporate into gas, which is compressed by the compressor 17 again. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 14 is further heated by the engine exhaust heat in the engine 11 via the heater core 15, and is cooled by the outside air in the radiator 13. At this time, the damper 24 can cool the vehicle interior by operating so that the air in the vehicle interior cooled by the indoor heat exchanger 23 does not pass through the heater core 15.

On the other hand, in order to heat the passenger compartment, the solenoid valve 19 is closed and the solenoid valve 21 is set to open as switching means. The refrigerant (CO2) that has been compressed by the compressor 17 into a high-temperature and high-pressure gas is cooled by the cooling medium flowing through the engine cooling circuit 16 in the water-refrigerant heat exchanger 14, and is decompressed by the decompressor 18 to have a low temperature and low pressure. The gas-liquid two-phase state is introduced into the outdoor heat exchanger 20. In the outdoor heat exchanger 20, heat is absorbed from the outside air to evaporate into gas, which is compressed by the compressor 17 again via the electromagnetic valve 21. Further, the cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 14 is the heater core 1
After passing 5, the engine 11 is further heated by the engine exhaust heat. At this time, the damper 24 can heat the vehicle interior by operating so that the air in the vehicle compartment that has passed through the indoor heat exchanger 23 passes through the heater core 15 and is heated.

Further, in order to heat the vehicle compartment while dehumidifying it, the solenoid valve 19 is closed and the solenoid valve 21 is closed.
The refrigerant (CO2) that has been compressed by the compressor 17 into a high-temperature and high-pressure gas is cooled by the cooling medium flowing through the engine cooling circuit 16 in the water-refrigerant heat exchanger 14, and the decompressor 18
It is decompressed in a low-temperature low-pressure gas-liquid two-phase state and introduced into the outdoor heat exchanger 20. After the outdoor heat exchanger 20 absorbs heat from the outside air, the indoor heat exchanger 23 passes through the pressure reducer 22 to further absorb the heat from the air in the vehicle interior to evaporate and gasify, and at this time, the air in the vehicle interior is cooled and dehumidified. Then, the compressor 17 again
Compressed with. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 14 is further heated by the engine exhaust heat in the engine 11 via the heater core 15. At this time, the damper 24 operates so that the air in the vehicle compartment cooled and dehumidified by the indoor heat exchanger 23 passes through the heater core 15 and is heated, thereby heating the vehicle compartment while dehumidifying.

Here, as described above, during the heating operation or the dehumidifying and heating, the outdoor heat exchanger 20 which is relatively larger than the indoor heat exchanger 23 becomes the low pressure side, and the compressor 17 to the water-refrigerant heat exchanger 14 to the decompressor. 18 is the high pressure side, the pressure reducer 18 is a relatively large outdoor heat exchanger 20, the pressure reducer 22 is a relatively small indoor heat exchanger 23, the compressor 1 is the low pressure side, and the heating high pressure side internal volume <heating At that time, the internal volume on the low pressure side is reached.

During the cooling operation, the indoor heat exchanger 23
The relatively larger outdoor heat exchanger 20 is on the high pressure side,
Compressor 1-water refrigerant heat exchanger 14-solenoid valve 19-relatively large outdoor heat exchanger 20-pressure reducer 22 are on the high pressure side,
The pressure reducer 22 to the relatively small indoor heat exchanger 23 to the compressor 17 are on the low pressure side, and the cooling high pressure side internal volume> the cooling low pressure side internal volume.

Here, similarly to (Embodiment 1), the densities of HFC134a and CO2 obtained by the refrigerant physical property program "REFPROPVER.6.0" are shown in comparison with (Table 2). Since CO2 is in a supercritical state at 40 ° C, 4
A density of 0 ° C. and 10 MPa was used.

[0041]

[Table 2]

From Table 2, CO2 has a smaller value of a / b as compared with HFC134a, that is, the density change between the high pressure side and the low pressure side of the refrigeration cycle apparatus is small, so that the optimum refrigerant amount during cooling is There is a possibility that the imbalance between the optimum amount of refrigerant during heating and the optimum amount can be alleviated.

Therefore, in the refrigeration cycle apparatus as shown in FIG. 3, the size of the outdoor heat exchanger 20 and the size of the indoor heat exchanger 23 were changed to examine the optimum amount of refrigerant. The results are shown in FIG. When the internal volume of the low pressure side during heating is about 50% larger than the internal volume of the high pressure side during heating, the refrigerant becomes HFC13.
In the case of 4a, the optimum amount of refrigerant during cooling is about 35% higher than the optimum amount of refrigerant during heating, but when the refrigerant is CO2, it is about 2%.
It was 0% increase, and the imbalance of the refrigerant amount was eased to about 3/5. Therefore, by changing the refrigerant to CO2,
Due to the imbalance of the refrigerant amount due to the operation mode, the efficiency of the refrigeration cycle device is reduced, the compressor discharge pressure is excessively increased,
It is possible to suppress deterioration of compressor reliability due to liquid compression, excessive rise in compressor discharge temperature, and the like.

Further, when the solenoid valve 19 is closed and the solenoid valve 21 is closed, the CO2 refrigerant is slightly decompressed by the decompressor 18, further decompressed by the decompressor 22 via the outdoor heat exchanger 20, and the indoor heat exchanger. It is evaporated at 23 and is sucked into the compressor 17. That is, the inside of the outdoor heat exchanger 20 is in an intermediate pressure state,
By operating the decompression amount of the decompressors 18 and 19, the pressure inside the outdoor heat exchanger 20 is changed, and the amount of heat radiated from the outdoor heat exchanger 20 to the outside air or from the outside air to the outdoor heat exchanger 20 is changed.
The amount of heat absorbed by the water refrigerant heat exchanger 14 can be adjusted.
It is possible to adjust the heat radiation amount in the vehicle and the heat absorption amount in the indoor heat exchanger 23, and it is also possible to finely set the thermal environment of the vehicle interior air.

Although the pressure reducer 18 and the solenoid valve 19 are arranged in parallel in FIG. 3, the pressure reducer 18 can be reduced in pressure, including fully closed, by using an electronic expansion valve or the like. If the amount can be adjusted widely, the circuit of the solenoid valve 19 can be omitted. Further, the decompressor 22, the indoor heat exchanger 23, and the electromagnetic valve 21 are arranged in parallel, but by using an electronic expansion valve or the like for the decompressor 22, the decompression amount including the fully closed state of the decompressor 22 can be reduced. The circuit including the solenoid valve 21 can be omitted if the air can be widely adjusted and the vehicle interior air can be directly supplied from the vehicle interior between the indoor heat exchanger 23 and the heater core 15.

(Embodiment 3) FIG. 5 is a block diagram showing a further improvement of the refrigeration cycle apparatus as shown in FIG. 3 described in the second embodiment.

The difference between FIG. 5 and FIG. 3 is that the solenoid valve 19
Is configured to bypass the decompressor 18 and the outdoor heat exchanger 20. When configured in this way, the pressure reducer 18 is fully closed using an electronic expansion valve or the like,
When the solenoid valve 19 is set to open, the refrigerant (CO2) that has been compressed by the compressor 17 into a high temperature and high pressure gas is cooled by the cooling medium flowing through the engine cooling circuit 16 in the water refrigerant heat exchanger 14, and the electromagnetic After bypassing the outdoor heat exchanger 20 via the valve 19, the pressure is reduced by the pressure reducer 22 to become a low-temperature low-pressure gas-liquid two-phase state, and the indoor heat exchanger 23 absorbs heat from the air in the vehicle interior to evaporate gas, At this time, the air in the vehicle compartment is cooled and dehumidified. Then, it is compressed again by the compressor 17. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 14 is further heated by the engine exhaust heat in the engine 11 via the heater core 15. At this time, the damper 24
By operating so that the air in the passenger compartment cooled and dehumidified by the indoor heat exchanger 23 passes through the heater core 15 and is heated, the passenger compartment can be heated while being dehumidified.
Since the refrigerant (CO2) flows by bypassing the outdoor heat exchanger 20, it is possible to prevent heat exchange with the outside air, and thus it is possible to prevent the refrigerant state at the inlet of the decompressor 22 from changing due to the influence from the outside air. The cooling and dehumidifying ability of the indoor heat exchanger 23 can be stabilized.

(Embodiment 4) FIG. 6 is a block diagram showing a further improvement of the refrigeration cycle apparatus as shown in FIG. 3 described in the second embodiment.

The difference between FIG. 6 and FIGS. 3 and 5 is that
The electromagnetic valve 19 is configured to bypass the electromagnetic valve 25 and the outdoor heat exchanger 20. When configured in this way, the solenoid valve 19 is opened as switching means,
When the electromagnetic valve 25 is set to be closed, the refrigerant (CO2) compressed into the high temperature and high pressure gas by the compressor 17 is cooled by the cooling medium flowing through the engine cooling circuit 16 in the water / refrigerant heat exchanger 14, and the pressure is reduced. The pressure is reduced in the device 18, and the electromagnetic valve 25 and the outdoor heat exchanger 20 are bypassed via the electromagnetic valve 19.
It is further decompressed by the decompressor 22 to become a low-temperature low-pressure gas-liquid two-phase state, and the indoor heat exchanger 23 absorbs heat from the air in the vehicle interior to evaporate and gasify, and at this time, the air in the vehicle interior is cooled and dehumidified. Then, it is compressed again by the compressor 17. The cooling medium heated by the refrigerant in the water-refrigerant heat exchanger 14 is further heated by the engine exhaust heat in the engine 11 via the heater core 15. At this time, in the damper 24, the air in the passenger compartment cooled and dehumidified by the indoor heat exchanger 23 is supplied to the heater core 1.
By operating so as to pass through 5 and be heated, the vehicle interior can be heated while dehumidifying, but the inside of the outdoor heat exchanger 20 is in an intermediate pressure state and the refrigerant (CO2)
Since the air flows by bypassing the outdoor heat exchanger 20, even if the amount of outside air introduced into the outdoor heat exchanger 20 changes abruptly, it is possible to suppress a rapid change in the refrigerant state at the inlet of the decompressor 22 and to reduce the indoor heat. The cooling / dehumidifying ability of the exchanger 23 can be stabilized.

In the above embodiment, the engine cooling circuit provided with the engine is taken up and described.
The present invention is not limited to the engine as a heat source, and can be applied to a cooling circuit that processes exhaust heat of a fuel cell, a cooling circuit that processes heat generated by a motor or an inverter, and the like.

Although the air conditioner for a room air conditioner or an electric vehicle has been described as an example, the invention is not limited to this, and the pressure of the refrigerant in at least one heat exchanger is switched between high pressure and low pressure to achieve heat radiation. It can be applied to a refrigeration cycle device that switches to endothermic action.

[0052]

As described above, by using CO2 as the refrigerant, the efficiency of the refrigeration cycle apparatus is reduced, the compressor discharge pressure is excessively increased, the liquid compression and the compression are caused by the imbalance of the refrigerant amount depending on the operation mode. It is possible to suppress deterioration of the reliability of the compressor due to excessive rise of the discharge temperature of the machine.

Further, by providing a circuit for bypassing the outdoor heat exchanger, even if the amount of outside air introduced into the outdoor heat exchanger 20 changes abruptly, a sudden change in the refrigerant state at the inlet of the pressure reducer 22 can be prevented. Therefore, the cooling and dehumidifying ability of the indoor heat exchanger 23 can be stabilized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a refrigeration cycle apparatus that is an embodiment of the present invention.

FIG. 2 is a diagram showing a comparison between the optimum refrigerant amount during cooling and the optimum refrigerant amount during heating.

FIG. 3 is a configuration diagram of a refrigeration cycle apparatus which is another embodiment of the present invention.

FIG. 4 is a diagram showing a comparison between the optimum refrigerant amount during cooling and the optimum refrigerant amount during heating.

FIG. 5 is a configuration diagram of a refrigeration cycle apparatus which is another embodiment of the present invention.

FIG. 6 is a configuration diagram of a refrigeration cycle apparatus which is another embodiment of the present invention.

FIG. 7 is a configuration diagram of a conventional refrigeration cycle device.

FIG. 8 is a configuration diagram of another conventional refrigeration cycle apparatus.

[Explanation of symbols]

1,17 Compressor 2,20 outdoor heat exchanger 3,18,22 Decompressor 4,23 Indoor heat exchanger 5 four-way valve 11 engine 12 pumps 13 radiator 14 Water Refrigerant Heat Exchanger 15 heater core 16 Engine cooling circuit 19,21 Solenoid valve 24 damper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Fumitoshi Nishiwaki             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Noriho Okaza             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd.

Claims (4)

[Claims] 1. A refrigeration cycle circuit is constituted by connecting a compressor, a plurality of heat exchangers, a pressure reducer, etc. in an annular shape by connecting pipes,
A refrigeration cycle apparatus comprising switching means for switching the pressure of a refrigerant flowing in at least one heat exchanger A of the plurality of heat exchangers between a low pressure and a high pressure, and using carbon dioxide as the refrigerant. 2. The refrigeration cycle apparatus according to claim 1, wherein the switching means reverses the flow of the refrigerant in at least a part of the refrigeration cycle circuit. 3. The refrigeration cycle apparatus according to claim 1, wherein the switching means is operated by operating a pressure reduction amount and opening / closing a valve on the refrigerant upstream side and the refrigerant downstream side of the heat exchanger A. 4. The refrigeration cycle apparatus according to claim 3, wherein a circuit that bypasses the heat exchanger A is provided.