JP2008128493A - Refrigerating circuit, and air conditioner for vehicle using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating circuit stably operated by preventing decomposition of C-I binding even when a refrigerant including the C-I binding is used, and to provide an air conditioner for a vehicle using the refrigerating circuit. <P>SOLUTION: This refrigerating circuit 12 comprises a compressor 22, a condenser 24, an expander 26, an evaporator 28 and a refrigerant protecting means for keeping a temperature of the refrigerant to be lower than an upper limit temperature determined so that the C-I binding is not decomposed, successively disposed in a circulation passage 14 where the refrigerant including the C-I binding is circulated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigeration circuit and a vehicle air conditioner using the refrigeration circuit, and more particularly to a refrigeration circuit using a refrigerant including a C-I bond and a vehicle air conditioner using the refrigeration circuit.

Conventionally, the refrigerant used for the refrigeration circuit of the air conditioner is thermally sufficiently stable, and it has not been particularly necessary to provide a means for preventing decomposition of the refrigerant in the refrigeration circuit.
However, in recent years, the use of a refrigerant having a low thermal stability has been considered for the preservation of the global environment (for example, Patent Document 1). Patent Document 1 discloses mixing CF ₃ I (R13I1) with other refrigerants, but CF ₃ I is structurally vulnerable to heat. Specifically, the binding energy of the CI bond in CF ₃ I is 213 kJ / mol at 25 ° C., which is even lower than 485 kJ / mol of the CF bond and 339 kJ / mol of the C-Cl bond, which is considered to be relatively low. CF ₃ I is easily decomposed by heat or the like.
JP-T 8-507524

  The protection means provided in the refrigeration circuit of the conventional air conditioner abnormally increases the discharge gas temperature of the compressor and the temperature of the compressor body for the purpose of preventing the burn-in of the compressor and the damage of the air conditioner. To prevent that. However, the conventional protection means is not intended to prevent the decomposition of the refrigerant, and the temperature of the refrigerant sometimes exceeds 150 ° C. during the operation of the air conditioner. There is a possibility that the function of the refrigeration circuit is deteriorated due to the decomposition of the bonds.

  The present invention has been made based on the above circumstances, and the object of the present invention is to provide a refrigeration circuit that stably operates by preventing the decomposition of the CI bond even when a refrigerant including the CI bond is used, and the refrigeration circuit. It is in providing the used vehicle air conditioner.

In order to achieve the above object, according to the present invention, a compressor, a condenser, an expander and an evaporator sequentially inserted in a circulation path through which a refrigerant including CI coupling circulates, and the temperature of the refrigerant is set to the CI. There is provided a refrigeration circuit comprising a refrigerant protection means that keeps the temperature below an upper limit temperature set so as not to decompose the bond (Claim 1).
Preferably, the refrigerant protection means keeps the temperature of the refrigerant below the upper limit temperature by suppressing the degree of superheat of the refrigerant sucked into the compressor (Claim 2).

Preferably, the refrigerant protection means keeps the temperature of the refrigerant below the upper limit temperature by reducing a discharge capacity of the compressor (Claim 3).
Preferably, the expander expands the refrigerant so that a superheat degree of the refrigerant at an outlet of the evaporator is 5K or less as a part of the refrigerant protection means, and the refrigerant protection means includes the refrigerant And an accumulator inserted in a part of the circulation path from the evaporator to the compressor.

Preferably, the refrigerant protection means reduces the discharge capacity of the compressor when one of the temperature of the compressor and the temperature of the refrigerant discharged from the compressor exceeds a threshold value (Claim 5).
Preferably, the refrigerant protection means reduces the discharge capacity of the compressor when the degree of superheat of the refrigerant sucked into the compressor exceeds a threshold value (Claim 6).

Preferably, the refrigerant protection means continuously or intermittently circulates the circulation path through the refrigerant while power is supplied to the compressor.
Preferably, the refrigerant protection means calculates a discharge temperature of the refrigerant discharged from the compressor based on a rotation speed of the compressor and a pressure of the refrigerant discharged from the compressor, and the discharge temperature is When the threshold value is exceeded, the discharge capacity of the compressor is decreased (Claim 8).

  Preferably, the compressor compresses the refrigerant at least twice as part of the refrigerant protection means, and the expander expands the refrigerant at least twice as part of the refrigerant protection means, The refrigerant protection means returns the vapor phase component of the refrigerant expanded at least once by the expander to the compressor and uses it for the next compression together with the refrigerant compressed at least once by the compressor. ).

Preferably, the refrigerant protection means sets the maximum temperature of the compressor to 130 ° C. or less as an average value for 10 seconds (claim 10).
According to the present invention, there is provided a vehicle air conditioner comprising the refrigeration circuit according to any one of claims 1 to 10 (claim 11).

The refrigeration circuit according to claim 1 of the present invention is friendly to the global environment because the global warming potential of the refrigerant is smaller than that including CI coupling.
Further, in this refrigeration circuit, the refrigerant temperature is kept below the upper limit temperature by the refrigerant protection means, so that the CI bond in the refrigerant does not decompose. For this reason, this refrigeration circuit operates stably over a long period of time.

Furthermore, the refrigerant including the CI bond used in the refrigeration circuit is applicable not only with a small global warming coefficient but also with a significant design change to the conventional refrigeration circuit. For this reason, if the existing refrigerant is replaced while effectively utilizing the existing refrigeration circuit, the global environment can be preserved in terms of resource saving.
In the refrigeration circuit according to the second aspect, by suppressing the degree of superheat of the refrigerant sucked into the compressor, the temperature of the refrigerant in the compressor is kept low, and the temperature of the refrigerant is reliably kept below the upper limit temperature.

In the refrigeration circuit according to the third aspect, by reducing the capacity of the compressor, the temperature of the refrigerant discharged from the compressor is kept low, and the temperature of the refrigerant is reliably kept below the upper limit temperature.
In the refrigeration circuit according to the fourth aspect, the refrigerant superheat degree at the outlet of the evaporator is kept at 5K or less, so that the temperature of the refrigerant sucked into the compressor is kept low, and the refrigerant temperature is kept below the upper limit temperature. Securely kept. On the other hand, in this refrigeration circuit, even if the superheat degree of the refrigerant at the outlet of the evaporator is 5K or less, the refrigerant is separated into a liquid phase component and a gas phase component by the accumulator, and only the gas phase component is supplied to the compressor. Is done. For this reason, this refrigeration circuit is stably operated while preventing liquid compression in the compressor.

The refrigeration circuit according to claim 5 is configured such that when one of the compressor temperature and the refrigerant temperature discharged from the compressor exceeds a threshold, the capacity of the compressor is reduced, so that the refrigerant temperature is lower than the upper limit temperature. Securely kept.
In the refrigeration circuit according to the sixth aspect, when the temperature of the refrigerant sucked into the compressor exceeds the threshold value, the capacity of the compressor is reduced, so that the temperature of the refrigerant is surely kept below the upper limit temperature.

In the refrigeration circuit according to claim 7, while the power is transmitted to the compressor, the refrigerant circulates continuously or intermittently in the circulation path, whereby the compressor is cooled by the radiated refrigerant, and the temperature of the refrigerant is the upper limit. It is reliably kept below the temperature.
In the refrigeration circuit according to claim 8, the temperature of the refrigerant discharged from the compressor is obtained by calculation, and the refrigerant temperature is reduced by reducing the capacity of the compressor when the discharge refrigerant temperature obtained by calculation exceeds a threshold value. It is reliably kept below the upper limit temperature.

In the refrigeration circuit according to claim 9, the compressor compresses the refrigerant expanded once together with the refrigerant compressed once, so that the temperature of the refrigerant discharged from the compressor is compressed to the same pressure in one stage. It becomes lower than the case. Thereby, the temperature of a refrigerant | coolant is maintained below an upper limit temperature.
In the refrigeration circuit of claim 10, since the maximum temperature of the compressor is 130 ° C. or lower on average for 10 seconds, the temperature of the refrigerant is surely kept below the upper limit temperature.

  The vehicle air conditioner according to claim 11 uses the refrigeration circuit according to claims 1 to 10 so that the temperature of the refrigerant is kept below the upper limit temperature, and thus operates stably over a long period of time.

FIG. 1 shows an outline of a vehicle air conditioner according to the first embodiment. According to this vehicle air conditioner, the interior of the passenger compartment 10 can be cooled at a desired set temperature.
The vehicle air conditioner includes a refrigeration circuit 12, and the refrigeration circuit 12 includes a circulation path 14 for circulating a refrigerant including CI coupling. A preferred refrigerant is a mixed refrigerant of CF ₃ I (R13I1) and R152a.
The circulation path 14 is installed from the engine room 16 to the device space 18 beyond the partition wall 17, and the device space 18 is partitioned by an instrument panel 20 at a front portion of the vehicle compartment 10. A compressor 22 and a condenser 24 are sequentially inserted in the circulation path 14 extending in the engine room 16, and an expander 26 and an evaporator 28 are sequentially inserted in the circulation path 14 extending in the equipment space 18. It is inserted. The compressor 22 is operated by the power supplied from the engine 29. A fan 30 is disposed in the vicinity of the condenser 24, and a blower 31 is disposed in the vicinity of the evaporator 28.

  The expander 26 is an automatic temperature expansion valve, for example, and has a throttle portion 32 for expanding the refrigerant. The flow path cross-sectional area of the throttle portion 32 is variable, and is automatically increased or decreased based on the degree of superheat of the refrigerant at the outlet of the evaporator 28. The expander 26 is configured so that the degree of superheat of the refrigerant at the outlet of the evaporator 28 is 5K or less. In order to detect the degree of superheat of the refrigerant, the expander 26 has a temperature sensing cylinder 33, and the temperature sensing cylinder 33 is attached to a portion of the circulation path 14 near the outlet of the evaporator 28.

An accumulator 34 is inserted in the circulation path 14, and the accumulator 34 is located downstream of the evaporator 28 and upstream of the compressor 22.
Hereinafter, the operation of the above-described vehicle air conditioner will be described with reference to the Moliere diagram of FIG.
The gas-phase refrigerant compressed by the compressor 22 is indicated by a point A in FIG. 2 and is cooled by the wind from the front of the vehicle or the wind generated by the fan 30 when passing through the condenser 24. It becomes the liquid phase refrigerant | coolant shown by. The liquid-phase refrigerant expands when passing through the throttle portion 32 of the expander 26 and becomes a refrigerant in a gas-liquid mixed state indicated by a point C. The liquid-phase refrigerant contained in the refrigerant in the gas-liquid mixed state is vaporized when passing through the evaporator 28 and takes heat from the outside of the evaporator 28. At this time, if the blower 31 generates wind that flows outside the evaporator 28, the wind is deprived of heat and becomes cold. The cold air blows into the passenger compartment 10 to cool the passenger compartment 10.

  The refrigerant in the gas-liquid mixed state passes through the evaporator 28 to become a gas phase or substantially gas phase refrigerant having a superheat degree SH of 5K or less indicated by a point D. The refrigerant that has passed through the evaporator 28 flows into the accumulator 34, and the accumulator 34 allows only the gas-phase refrigerant having a superheat degree SH of substantially zero or more to pass even when the liquid-phase refrigerant has entered. That is, the accumulator 34 prevents the liquid phase refrigerant from being sucked into the compressor 22. The refrigerant that has passed through the accumulator 34 is sucked into the compressor 22 and compressed to return to the point A, and the above-described cycle is repeated thereafter.

The vehicle air conditioner described above is friendly to the global environment because it contains a CI bond and thus has a low global warming potential of the refrigerant.
When the refrigerant is a mixed refrigerant of CF ₃ I and a combustible refrigerant such as R152a, the combustibility of R152a is canceled by the fire extinguishing property of CF ₃ I, and the safety of the vehicle air conditioner is ensured. .
On the other hand, in the refrigeration circuit 12, the refrigerant protection means keeps the temperature of the refrigerant below the upper limit temperature set so that the CI bonds are not decomposed, so the CI bonds in the refrigerant are not decomposed. For this reason, the refrigeration circuit 12 operates stably over a long period of time.

More specifically, the refrigerant protection means suppresses the temperature (point D) of the refrigerant sucked into the compressor 22 by suppressing the degree of superheat of the refrigerant sucked into the compressor 22. As a result, the temperature (point A) of the refrigerant discharged from the compressor 22 via compression is suppressed, and the refrigerant temperature is reliably kept below the upper limit temperature.
Specifically, the refrigerant protection means includes an expander 26 and an accumulator 34. That is, the flow passage cross-sectional area or flow passage length of the expander 26 is set so that the superheat degree SH of the refrigerant at the outlet of the evaporator 28 is maintained at 5K or less, so that it is sucked into the compressor 22. The temperature of the refrigerant is kept low, and the temperature of the refrigerant is reliably kept below the upper limit temperature. On the other hand, even if the superheat degree of the refrigerant at the outlet of the evaporator 28 is 5K or less and the liquid phase refrigerant is easily contained, the refrigerant is separated into the liquid phase component and the gas phase component by the accumulator 34. Only the components are supplied to the compressor 22. For this reason, the refrigeration circuit 12 operates stably with the liquid compression in the compressor 22 prevented.

  Furthermore, the refrigerant including the CI bond used in the refrigeration circuit 12 not only has a small global warming coefficient, but also has a pressure / temperature characteristic that can approximate R134a. Applicable without design changes. For this reason, if the existing refrigerant is replaced with a refrigerant containing a C-I bond while effectively utilizing the existing refrigeration circuit, the global environment can be preserved from the viewpoint of resource saving.

The present invention is not limited to the first embodiment described above, and various modifications are possible. For example, the expander 26 is preferably configured such that the degree of superheat of the refrigerant at the outlet of the evaporator 28 is 5K or less, but the temperature of the refrigerant in the refrigeration circuit 12 is kept below the upper limit temperature. It is only necessary to be configured to suppress the degree of superheating of the refrigerant at the outlet of the evaporator 28.
The expander 26 may be a fixed throttle such as an orifice or a capillary. In this case, it is preferable that the flow path cross-sectional area or flow path length of the fixed throttle be configured so that the superheat degree SH of the refrigerant at the outlet of the evaporator 28 is 5K or less.

The compressor 22 may be any type of compressor such as a reciprocating compressor such as a swash plate type or a oscillating plate type, a scroll compressor or a vane compressor, and may be a fixed capacity type or a variable capacity type. It may be.
FIG. 3 shows a schematic configuration of the vehicle air conditioner of the second embodiment. The same components as those of the vehicle air conditioner of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  The refrigeration circuit 40 of this air conditioner has a variable capacity compressor 42. The compressor 42 is, for example, a swash plate compressor, and changes the pressure in the crank chamber and the refrigerant compression unit 44 having a cylinder block, a cylinder bore, a piston, a swash plate, a crank chamber, a cylinder head, a suction chamber, and a discharge chamber. And a capacity control valve 46 for changing the stroke (discharge capacity) of the piston. The capacity control valve 46 is, for example, an external control type, and is electrically connected to and driven by the control device 48 installed in the equipment space 18.

In the second embodiment, the discharge temperature sensor 50 is attached to a portion of the circulation path 14 near the discharge port of the compressor 42 and detects the temperature (discharge temperature) of the refrigerant discharged from the compressor 42. The discharge temperature sensor 50 is electrically connected to the control device 48, and the detected discharge temperature is input to the control device 48.
Although not shown, an evaporator temperature sensor, a room temperature sensor, a solar radiation amount sensor and the like are also electrically connected to the control device 48. Usually, the evaporator temperature, the indoor temperature, the solar radiation amount and the occupant detected by these sensors are connected. Based on the set temperature and the like, the control device 48 operates the vehicle air conditioner. That is, the control device 48 opens and closes the capacity control valve 46 so that the temperature in the passenger compartment 10 approaches the set temperature, and changes the discharge capacity of the compressor 42.

  However, when the detected discharge temperature exceeds a threshold value (discharge temperature threshold value), the control device 48 decreases the discharge capacity of the compressor 42 regardless of normal control. The discharge temperature threshold value is a threshold value set so that the C—I bond in the refrigerant does not decompose. By reducing the discharge capacity, the compression ratio becomes smaller. As a result, the temperature of the refrigerant discharged from the compressor 42 is kept below the upper limit temperature set so that the C—I bond is not decomposed.

The means for detecting the discharge temperature is not limited to the discharge temperature sensor 50. For example, the discharge temperature may be obtained by calculation based on the rotation speed sensor 52 and the discharge pressure sensor 54.
Specifically, the rotation speed sensor 52 is attached to the engine 29, for example, and detects the rotation speed of the engine 29. The rotational speed sensor 52 is electrically connected to the control device 48, and the detected rotational speed of the engine 29 is input to the control device 48. The control device 48 obtains the rotational speed of the compressor 42 by calculation, for example, by multiplying the detected rotational speed of the engine 29 by the drive ratio.

On the other hand, the discharge pressure sensor 54 is attached to a portion of the circulation path 14 near the discharge port of the compressor 42 and detects the pressure (discharge pressure) of the refrigerant discharged from the compressor 42. The discharge pressure sensor 54 is electrically connected to the control device 48, and the detected discharge temperature is input to the control device 48.
The control device 48 calculates the temperature (discharge temperature) of the refrigerant discharged from the compressor 42 based on the rotation speed of the compressor 42 calculated by the calculation and the detected discharge pressure. The rotation speed sensor 52 may be attached to the compressor 42 and directly detect the rotation speed of the compressor 42, or may detect a frequency component proportional to the rotation speed of the compressor 42.

In the second embodiment described above, a means for detecting the temperature of the compressor 42 (compressor temperature detecting means) and a suction to the compressor 42 in place of the means for detecting the discharge temperature or instead of the means for detecting the discharge temperature. One or both of the means for detecting the degree of superheat of the refrigerant (superheat degree detection means) may be provided.
As a compressor temperature detecting means, a temperature sensor (compressor temperature sensor) 56 is attached to the outer surface of the cylinder head of the compressor 42, and the compressor temperature sensor 56 detects the temperature of the discharge chamber of the compressor 42. The compressor temperature sensor 56 is electrically connected to the control device 48, and the temperature of the discharge chamber is input to the control device 48.

  When the temperature of the discharge chamber detected by the compressor temperature sensor 56 exceeds a threshold value (compressor temperature threshold value), the control device 48 controls the compressor 42 via the capacity control valve 46 regardless of normal control. Reduce discharge capacity. The compressor temperature threshold is a threshold set so that the C—I bond in the refrigerant does not decompose. By reducing the discharge capacity, the compression ratio becomes smaller. As a result, the temperature of the refrigerant compressed by the compressor 42 is kept below the upper limit temperature set so that the C—I bond is not decomposed.

The compressor temperature sensor 56 detects the temperature of the discharge chamber of the compressor 42, but may detect the temperature of other parts of the compressor 42 such as a lip seal or a mechanical seal. The compressor temperature sensor 56 preferably detects the temperature of the portion of the compressor 42 that is the hottest during the operation of the compressor 42.
As a superheat degree detection means, a superheat degree sensor 58 is attached to a part of the circulation path 14 from the outlet of the evaporator 28 to the suction port of the compressor 42, and detects the superheat degree of the refrigerant sucked into the compressor 42. . The superheat degree sensor 58 is electrically connected to the control device 48, and the detected superheat degree is input to the control device 48.

  When the detected superheat degree exceeds a threshold value (superheat degree threshold value), the control device 48 decreases the discharge capacity of the compressor 42 regardless of normal control. The superheat degree threshold is a threshold set so that the C—I bond in the refrigerant does not decompose. By reducing the discharge capacity, the compression ratio becomes smaller. As a result, the temperature of the refrigerant in the compressor 42 is kept below the upper limit temperature set so that the C—I bond is not decomposed.

  In the second embodiment described above, the compressor 42 is a variable displacement type. However, when the compressor 42 is a clutchless type and power is constantly transmitted from the engine 29, the circulation path 14 is continuously or It is preferable to circulate at least intermittently. In other words, it is preferable not to set the minimum discharge capacity of the compressor 42 to zero, but to set it to a value slightly larger than zero.

Specifically, when the compressor 42 operates at the minimum discharge capacity, the shutoff valve is not completely closed if the discharge port of the compressor 42 is provided with a shutoff valve that blocks the flow of the refrigerant. In the case where the discharge capacity changes depending on the angle of the swash plate of the compressor 42, it is preferable that the swash plate is slightly inclined with respect to the rotation axis.
Since the minimum discharge capacity is not zero, the refrigerant circulates in the circulation path 14, and the refrigerant that has radiated heat during the circulation is sucked into the compressor 22. Thereby, the temperature of the refrigerant in the compressor 22 is kept below the upper limit temperature set so that the CI bond is not decomposed. Note that the fact that the minimum discharge capacity is not zero includes not only a state in which the refrigerant is continuously discharged from the compressor but also a state in which the refrigerant is intermittently discharged by control or the like.

In the second embodiment described above, the expander 60 may not expand the refrigerant so that the degree of superheat of the refrigerant at the outlet of the evaporator 28 is 5K or less, but the expander according to the first embodiment. 26 and accumulator 34 may be used.
FIG. 3 shows a schematic configuration of the vehicle air conditioner of the third embodiment. The same components as those of the vehicle air conditioner of the first and second embodiments are denoted by the same reference numerals and description thereof is omitted.

  The refrigeration circuit 70 of the air conditioner is a multi-effect cycle. Specifically, the compressor 72, the condenser 24, the first expander 74, the gas-liquid separator 76, the second expander 78, and the evaporation are provided in the circulation path 14. The devices 28 are inserted sequentially. The compressor 72 includes a first compression unit 80 and a second compression unit 82 connected in series with each other, and the liquid phase component discharge port of the gas-liquid separator 76 is connected to the first compression unit 80 through the bypass channel 84. And the second compression unit 82 are connected to an intermediate flow path.

Hereinafter, the operation of the refrigeration circuit 70 will be described with reference to the Mollier chart shown in FIG.
The gas-phase refrigerant compressed by the second compression unit 82 of the compressor 72 is indicated by a point a in FIG. 5 and is passed by the wind from the front of the vehicle or the wind generated by the fan 30 when passing through the condenser 24. It is cooled to become a liquid-phase refrigerant indicated by point b. The liquid-phase refrigerant expands when passing through the first expander 74 and becomes a refrigerant in a gas-liquid mixed state indicated by a point c. The gas-liquid mixed refrigerant is separated into a liquid-phase refrigerant indicated by a point d and a gas-phase refrigerant indicated by a point e by a gas-liquid separator 76.

Among these, the liquid phase refrigerant indicated by the point d expands when passing through the second expander 78 and becomes a gas phase refrigerant having the degree of superheat indicated by the point g. Thereafter, the gas-phase refrigerant is sucked into the first compression unit 80 of the compressor 72 and compressed to become a gas-phase refrigerant indicated by a point h.
On the other hand, the gas-phase refrigerant indicated by the point e flows into the intermediate flow path through the bypass flow path 84 and is mixed with the gas-phase refrigerant indicated by the point h in the intermediate flow path. It becomes a refrigerant. The second compression unit 82 sucks and compresses the refrigerant indicated by point i in the intermediate flow path, and discharges the gas-phase refrigerant indicated by point a. Thereafter, the above-described cycle is repeated.

In the refrigeration circuit 70 described above, the compressor 72 compresses the refrigerant once expanded together with the refrigerant compressed once, so that the temperature of the refrigerant discharged from the compressor 72 is the same pressure as the point a in one stage. It becomes low compared with the case where the refrigerant is compressed. Thereby, the temperature of a refrigerant | coolant is maintained below an upper limit temperature.
In the third embodiment, although the refrigerant is compressed twice by one compressor 72, it may be compressed three times or more, and two or more compressors are connected in series instead of the compressor 72. May be. In the third embodiment, the refrigerant is expanded twice by the two expanders 74 and 78, but may be expanded three or more times by three or more expanders.

Moreover, you may combine suitably the component of the refrigerating circuit 12,40,70 of 1st Embodiment mentioned above, 2nd Embodiment, and 3rd Embodiment.
Furthermore, in the refrigeration circuits 12, 40, 70 of the first to third embodiments described above, the temperature (maximum temperature) of the portion where the temperature is highest in the compressors 22, 42, 72 is 130 ° C. or less on average for 10 seconds. Is preferred. This is because the temperature of the refrigerant is reliably maintained below the upper limit temperature.

  Finally, it goes without saying that the refrigeration circuit of the present invention is applicable to a refrigerator-freezer, an indoor air conditioner, and the like.

It is a figure which shows schematic structure of the vehicle air conditioner of 1st Embodiment. It is a Moliere diagram explaining operation | movement of the freezing circuit in the vehicle air conditioner of FIG. It is a figure which shows schematic structure of the vehicle air conditioner of 2nd Embodiment. It is a figure which shows schematic structure of the vehicle air conditioner of 3rd Embodiment. FIG. 5 is a Moliere diagram illustrating the operation of the refrigeration circuit in the vehicle air conditioner of FIG. 4.

Explanation of symbols

12,40,70 Refrigeration circuit
14 Circuit
22 Compressor
24 condenser
26 Inflator
28 Evaporator

Claims (11)

A compressor, a condenser, an expander, and an evaporator, which are sequentially inserted in a circulation path through which a refrigerant including a CI bond circulates;
And a refrigerant protection means for keeping the temperature of the refrigerant below an upper limit temperature set so that the CI coupling does not decompose.   The refrigeration circuit according to claim 1, wherein the refrigerant protection means keeps the temperature of the refrigerant below the upper limit temperature by suppressing a degree of superheat of the refrigerant sucked into the compressor.   The refrigeration circuit according to claim 1, wherein the refrigerant protection means maintains the temperature of the refrigerant at the upper limit temperature or less by reducing a discharge capacity of the compressor. The expander, as a part of the refrigerant protection means, expands the refrigerant so that the superheat degree of the refrigerant at the outlet of the evaporator is 5K or less,
3. The refrigeration circuit according to claim 2, wherein the refrigerant protection means includes an accumulator inserted in a portion of the circulation path from the evaporator to the compressor as viewed in a circulation direction of the refrigerant.   The said refrigerant | coolant protection means reduces the discharge capacity | capacitance of the said compressor, when one of the temperature of the said compressor and the temperature of the refrigerant | coolant discharged from the said compressor exceeds a threshold value. The refrigeration circuit described.   The refrigeration circuit according to claim 3, wherein the refrigerant protection means reduces the discharge capacity of the compressor when the superheat degree of the refrigerant sucked into the compressor exceeds a threshold value.   The refrigeration circuit according to claim 1, wherein the refrigerant protection means circulates the circulation path continuously or intermittently through the refrigerant while power is supplied to the compressor.   The refrigerant protection means calculates a discharge temperature of the refrigerant discharged from the compressor based on a rotation speed of the compressor and a pressure of the refrigerant discharged from the compressor, and the discharge temperature exceeds a threshold value. 2. The refrigeration circuit according to claim 1, wherein a discharge capacity of the compressor is reduced. The compressor compresses the refrigerant at least twice as part of the refrigerant protection means,
The expander expands the refrigerant at least twice as part of the refrigerant protection means,
The refrigerant protection means returns the gas phase component of the refrigerant expanded at least once by the expander to the compressor and uses it for the next compression together with the refrigerant compressed at least once by the compressor. The refrigeration circuit according to any one of claims 1 to 8.   The refrigeration circuit according to any one of claims 1 to 9, wherein the refrigerant protection means sets the maximum temperature of the compressor to 130 ° C or less in an average value for 10 seconds.   A vehicle air conditioner comprising the refrigeration circuit according to any one of claims 1 to 10.

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