JP5561243B2 - Refrigeration cycle - Google Patents

Description

  The present invention relates to a refrigeration cycle that includes a plurality of compression mechanisms and is configured to be able to switch between an operation in a cooling operation mode that cools a heat exchange target fluid and an operation in a heating operation mode that heats the heat exchange target fluid.

  Conventionally, Patent Document 1 discloses a vapor compression refrigeration cycle applied to an air conditioner, which includes a low-stage compression mechanism and a high-stage compression mechanism connected in series, and is a fluid subject to heat exchange. What is configured to be switchable between an operation in a cooling operation mode (cooling operation mode) for cooling indoor blown air and an operation in a heating operation mode (heating operation mode) for heating indoor blown air is disclosed. .

  In the refrigeration cycle of Patent Document 1, the cooling stage is switched to a normal refrigeration cycle in which refrigerant is compressed and discharged only by the low stage compression mechanism, and in the heating operation mode, the low stage compression mechanism and the high stage compression are switched. The so-called economizer type, in which the refrigerant is boosted in multiple stages by two compression mechanisms and the intermediate pressure refrigerant of the cycle is combined with the refrigerant discharged from the low-stage compression mechanism and sucked into the high-stage compression mechanism Switch to refrigeration cycle.

  Patent Document 2 discloses a vapor compression refrigeration cycle applied to an air conditioner, in which two compression mechanisms, a first compression mechanism and a second compression mechanism, are housed in a single housing, and the same electric motor is used. There is disclosed a compressor that includes a compressor to be driven and is configured to be able to switch between an operation in a cooling operation mode and an operation in a heating operation mode.

  In the refrigeration cycle of Patent Document 2, the two compression mechanisms are connected in series in the cooling operation mode to switch to the economizer refrigeration cycle similar to Patent Document 1, and in the heating operation mode, the two compression mechanisms are switched on. Switching to the normal refrigeration cycle by connecting in parallel.

  In the economizer-type refrigeration cycle, the compression ratio of both the low-stage and high-stage compression mechanisms is lowered to improve the compression efficiency of both compression mechanisms and to improve the cycle efficiency (COP). Can do.

JP 2001-235246 A Japanese Patent Laid-Open No. 9-145188

  However, in the refrigeration cycle of Patent Document 1, the high-stage compression mechanism is not operated in the cooling operation mode, so that the refrigeration cycle exhibits a high cooling capacity as compared with the case where the refrigerant discharge capacity is exhibited by the two compression mechanisms. I can't. In other words, the blown air cannot be efficiently cooled using the two compression mechanisms in the cooling operation mode.

  On the other hand, in the refrigeration cycle of Patent Document 2, although two compression mechanisms are operated in any operation mode, the cooling operation in which the compression ratio in both compression mechanisms tends to be lower than in the heating operation mode. Since the mode is switched to the economizer refrigeration cycle in the mode, the cycle efficiency improvement effect by switching to the economizer refrigeration cycle cannot be sufficiently obtained.

  In view of the above points, the present invention includes a plurality of compression mechanisms, and is configured to be able to switch between an operation in a cooling operation mode for cooling a heat exchange target fluid and an operation in a heating operation mode for heating the heat exchange target fluid. Another object of the present invention is to sufficiently improve the cycle efficiency in both operation modes in the refrigeration cycle.

In order to achieve the above object, according to the first aspect of the present invention, the first and second compression mechanisms (11a, 12a) for compressing and discharging the refrigerant and the use side for exchanging heat between the refrigerant and the heat exchange target fluid. Heat exchanger (15), decompression means (17, 20) for decompressing the refrigerant, outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air, and a refrigerant in a cooling operation mode for cooling the heat exchange target fluid Refrigerant circuit switching means (13, 14, 27, 31) for switching between the circuit and the refrigerant circuit in the heating operation mode for heating the heat exchange target fluid, and the refrigerant flowing out from the use side heat exchanger (15) in the heating operation mode A branch part (16) for branching the flow of
The decompression means (17, 20) decompresses the first refrigerant (17) for depressurizing one of the refrigerants branched at the branching part (16) and the other refrigerant branched at the branching part (16). Comprising a second pressure reducing means (20),
The refrigerant circuit switching means (13... 31)
In the heating operation mode, the refrigerant decompressed by the first decompression means (17) is merged with the refrigerant discharged from the first compression mechanism (11a) and sucked into the second compression mechanism (12a), and the second compression mechanism The refrigerant discharged from (12a) is radiated by the use side heat exchanger (15), and the other refrigerant that has flowed out of the use side heat exchanger (15) and branched at the branching section (16) is discharged. allowed to flow into the second pressure reducing means (20), the refrigerant reduced in pressure by the second pressure reducing means (20) and evaporated at the outdoor heat exchanger (21), the refrigerant flowing out from the outdoor heat exchanger (21) first By allowing the first compression mechanism (11a) to suck , the first compression mechanism (11a) and the second compression mechanism (12a) are switched to a refrigerant circuit that is always connected in series ,
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21), The refrigerant that has flowed out of the outdoor heat exchanger (21) flows into the second decompression means ( 20), and the refrigerant decompressed by the second decompression means ( 20) is evaporated by the use side heat exchanger (15), It is characterized by a refrigeration cycle that switches to a refrigerant circuit that draws refrigerant flowing out from the use side heat exchanger (15) into both the first and second compression mechanisms (11a, 12a).

  According to this, in the heating operation mode, the first and second compression mechanisms (11a, 12a) are connected in series. In the cooling operation mode, the first and second compression mechanisms (11a, 12a) are used. In any operation mode, the heat exchange target fluid is cooled or heated using the two compression mechanisms of the first and second compression mechanisms (11a, 12a). Can do.

  Furthermore, the cycle in which the compression ratio is compressed in multiple stages by connecting the first and second compression mechanisms (11a, 12a) in series in the heating operation mode in which the compression ratio of the entire cycle is likely to be higher than in the cooling operation mode. Since it switches to a structure, the cycle efficiency (COP) improvement effect by reducing the compression ratio of both compression mechanisms (11a, 12a) can be acquired effectively.

  Therefore, in a refrigeration cycle that includes a plurality of compression mechanisms and can be switched between the operation in the cooling operation mode and the operation in the heating operation mode, the cycle efficiency in both operation modes can be sufficiently improved.

In the first aspect of the present invention, in the heating operation mode, the intermediate pressure refrigerant decompressed by the first decompression means (17) is joined with the refrigerant discharged from the first compression mechanism (11a). Since the two-compression mechanism (12a) is inhaled , the economizer refrigeration cycle can be configured in the heating operation mode, and the effect of improving the cycle efficiency can be further obtained.

Further, as in the invention according to claim 2 , in the refrigeration cycle according to claim 1 , in the heating operation mode, the refrigerant is depressurized by the first depressurization means (17) and is branched by the branch portion (16). You may provide the internal heat exchanger (18) which heat-exchanges with the other made refrigerant | coolant.

  As a result, during the heating operation mode, the refrigerant decompressed by the first decompression means (17) and sucked into the first compression mechanism (11a) can be heated and vaporized, and the liquid compression of the first compression mechanism (11a) is achieved. Can be prevented. Furthermore, during the heating operation mode, the enthalpy of the refrigerant flowing into the outdoor heat exchanger (21) can be reduced, and the heat absorption amount of the refrigerant in the outdoor heat exchanger (21) can be increased.

In invention of Claim 3 , the 1st, 2nd compression mechanism (11a, 12a) which compresses and discharges a refrigerant | coolant, The utilization side heat exchanger (15) which heat-exchanges a refrigerant | coolant and the heat exchange object fluid, The decompression means (17, 20) for decompressing the refrigerant, the outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air, the refrigerant circuit in the cooling operation mode for cooling the fluid for heat exchange, and the fluid for heat exchange Refrigerant circuit switching means (13, 14, 27, 31) for switching the refrigerant circuit in the heating operation mode to be heated,
The decompression means includes a first decompression means (17) for decompressing the refrigerant flowing out from the use side heat exchanger (15) and a second decompression means for decompressing the refrigerant flowing into the outdoor heat exchanger (21) in the heating operation mode. (20), and further includes a gas-liquid separation means (29) for separating the gas-liquid of the refrigerant decompressed by the first decompression means (17) during the heating operation mode,
The refrigerant circuit switching means (13... 31) joins the gas-phase refrigerant separated by the gas-liquid separation means (29) with the refrigerant discharged from the first compression mechanism (11a) during the heating operation mode. The refrigerant sucked into the compression mechanism (12a), the refrigerant discharged from the second compression mechanism (12a) is radiated by the use side heat exchanger (15), and the refrigerant flowing out from the use side heat exchanger (15) is further discharged. The liquid phase flowed into the first pressure reducing means (17) and the refrigerant depressurized by the first pressure reducing means (17) is flowed into the gas-liquid separation means (29) and separated by the gas-liquid separation means (29). Refrigerant flows into the second decompression means (20), the refrigerant decompressed by the second decompression means (20) evaporates in the outdoor heat exchanger (21), and flows out of the outdoor heat exchanger (21) the first compression mechanism that is drawn into (11a), the first compression mechanism (11a) Switching the refrigerant circuit in a state in which the second compression mechanism and (12a) is always serially connected,
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21), The refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the gas-liquid separation means (29) through the second decompression means (20), and the liquid-phase refrigerant separated by the gas-liquid separation means (29) is supplied to the first refrigerant. Refrigerant that has been depressurized by the first depressurizing means (17), the refrigerant depressurized by the first depressurizing means (17) is evaporated by the use side heat exchanger (15), and flows out from the use side heat exchanger (15) It is characterized by a refrigeration cycle that switches to a refrigerant circuit that sucks the refrigerant into both the first and second compression mechanisms (11a, 12a) .

According to this, the effect similar to the above-mentioned effect by the invention of Claim 1 can be show | played.
In the invention according to claim 3, in the heating operation mode, the gas-liquid of the refrigerant depressurized by the first depressurization means (17) is separated by the gas-liquid separation means (29), and the separated gas phase is separated. An economizer refrigeration cycle in which the refrigerant is combined with the refrigerant discharged from the first compression mechanism (11a) and sucked into the second compression mechanism (12a) can be configured, and a further improvement in cycle efficiency can be obtained. it can.

In invention of Claim 4 , the 1st, 2nd compression mechanism (11a, 12a) which compresses and discharges a refrigerant | coolant, The utilization side heat exchanger (15) which heat-exchanges a refrigerant | coolant and the heat exchange object fluid, The decompression means (17, 20) for decompressing the refrigerant, the outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air, the refrigerant circuit in the cooling operation mode for cooling the fluid for heat exchange, and the fluid for heat exchange Refrigerant circuit switching means (13, 14, 27, 31) for switching the refrigerant circuit in the heating operation mode to be heated,
The refrigerant circuit switching means (13... 31)
In the heating operation mode, the refrigerant discharged from the first compression mechanism (11a) is sucked into the second compression mechanism (12a), and the refrigerant discharged from the second compression mechanism (12a) is used on the use side heat exchanger (15). Then, the refrigerant flowing out from the use side heat exchanger (15) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is supplied to the outdoor heat exchanger ( 21) is switched to a refrigerant circuit that evaporates and flows out of the outdoor heat exchanger (21) into the first compression mechanism (11a) ,
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21), The refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is evaporated by the use side heat exchanger (15), The refrigerant flowing out from the use side heat exchanger (15) is switched to a refrigerant circuit that sucks into both the first and second compression mechanisms (11a, 12a),
The refrigerant circuit switching means (13 ... 31) further includes a bypass passage (26) for allowing the refrigerant flowing out of the outdoor heat exchanger (21) to flow around the use side heat exchanger (15). While having the function to switch to the refrigerant circuit of the defrost operation mode which removes the frost which arrived at (21), from the refrigerant | coolant discharged from the 1st compression mechanism (11a) and the 2nd compression mechanism (12a) at the time of a defrost operation mode Both the discharged refrigerant and the refrigerant are dissipated by the outdoor heat exchanger (21), and the refrigerant flowing out of the outdoor heat exchanger (21) is discharged through the bypass passage (26) through the first and second compression mechanisms ( 11a, wherein the refrigeration cycle for switching the refrigerant circuit to the suction into both 12a).

  Here, in the heating operation mode, if the refrigerant evaporation temperature in the outdoor heat exchanger (21) becomes equal to or lower than the frosting temperature (specifically, 0 ° C.), frosting occurs in the outdoor heat exchanger (21). There is a fear. When such frost formation occurs, it becomes difficult for outside air to circulate through the outdoor heat exchanger (21), and the heat exchange capacity of the outdoor heat exchanger (21) is significantly reduced.

On the other hand, according to the invention described in claim 4 , during the defrosting operation mode, the refrigerant discharged from the first and second compression mechanisms (11a, 12a) is transferred to the outdoor heat exchanger (21) → bypass passage. (26) → A so-called hot gas bypass cycle that circulates in the order of the first and second compression mechanisms (11a, 12a) can be configured to defrost the outdoor heat exchanger (21).

In invention of Claim 5 , the 1st, 2nd compression mechanism (11a, 12a) which compresses and discharges a refrigerant | coolant, The utilization side heat exchanger (15) which heat-exchanges a refrigerant | coolant and the heat exchange object fluid, The decompression means (17, 20) for decompressing the refrigerant, the outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air, the refrigerant circuit in the cooling operation mode for cooling the fluid for heat exchange, and the fluid for heat exchange Refrigerant circuit switching means (13, 14, 27, 31) for switching the refrigerant circuit in the heating operation mode to be heated,
The refrigerant circuit switching means (13... 31)
In the heating operation mode, the refrigerant discharged from the first compression mechanism (11a) is sucked into the second compression mechanism (12a), and the refrigerant discharged from the second compression mechanism (12a) is used on the use side heat exchanger (15). Then, the refrigerant flowing out from the use side heat exchanger (15) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is supplied to the outdoor heat exchanger ( 21) is switched to a refrigerant circuit that evaporates and flows out of the outdoor heat exchanger (21) into the first compression mechanism (11a) ,
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21), The refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is evaporated by the use side heat exchanger (15), The refrigerant flowing out from the use side heat exchanger (15) is switched to a refrigerant circuit that sucks into both the first and second compression mechanisms (11a, 12a),
Furthermore , the auxiliary use side heat exchanger (28) for exchanging heat between the refrigerant discharged from the first compression mechanism (11a) and the heat exchange target fluid, and the refrigerant discharged from the second compression mechanism (12a) on the use side and a bypass passage (26) passing the heat exchanger (15) to bypass,
The refrigerant circuit switching means (13... 31) has a function of switching to the refrigerant circuit in the defrosting operation mode for removing frost attached to the outdoor heat exchanger (21), and at the time of the defrosting operation mode, the first compression mechanism (11a). ) Is sucked into the second compression mechanism (12a) through the auxiliary use side heat exchanger (28), and the refrigerant discharged from the second compression mechanism (12a) is passed through the bypass passage (26). The refrigeration cycle is switched to a refrigerant circuit that flows into the outdoor heat exchanger (21) and dissipates heat .

According to this, in the defrosting operation mode, the first compression mechanism (11a) → the auxiliary use side heat exchanger (28) → the second compression mechanism (12a) → the bypass passage (26) → the outdoor heat exchanger (21). The outdoor heat exchanger (21) can be defrosted by configuring a hot gas bypass cycle that circulates in this order. Further, since the auxiliary use side heat exchanger (28) is provided, the heat exchange target fluid is heated by the heat of the refrigerant discharged from the first compression mechanism (11a) even in the defrosting operation mode. can do.
In the inventions according to claims 4 and 5, the main configuration of the refrigerant circuit in the heating operation mode and the cooling operation mode is the same as that of the inventions described in claims 1 and 3 described above. Therefore, the same effects as those of the first and third aspects of the invention can be achieved during the heating operation mode and the cooling operation mode.

In the refrigeration cycle according to any one of claims 1 to 5 , as in the invention described in claim 6 , the refrigerant discharge capacities of the first and second compression mechanisms (11a, 12a) are independent of each other. Thus, it may be configured to be controllable. Thereby, at the time of heating operation mode, the compression ratio in the 1st compression mechanism (11a) and the compression ratio in the 2nd compression mechanism (12a) can be adjusted appropriately, and improvement in cycle efficiency can be aimed at further.

Further, as in the invention described in claim 7 , in the refrigeration cycle according to any one of claims 1 to 6 , the refrigerant circuit switching means includes at least the first and second four-way valves (13, 14). The first four-way valve (13) connects at least the first compression mechanism (11a) outlet side and the outdoor heat exchanger (21) in the cooling operation mode, and in the heating operation mode. The at least first compression mechanism (11a) discharge port side and the second compression mechanism (12a) suction port side are connected, and the second four-way valve (14) is at least the second compression mechanism (12a) in the cooling operation mode. The discharge port side and the outdoor heat exchanger (21) may be connected, and at least the second compression mechanism (12a) discharge port side and the use side heat exchanger may be connected in the heating operation mode.

  Thereby, in the cooling operation mode, the cycle is switched to a cycle in which the first and second compression mechanisms (11a, 12a) are connected in parallel, and in the heating operation mode, the first and second compression mechanisms (11a, 12a) are connected in series. The configuration for switching to the cycle can be realized specifically and easily.

  In addition, the four-way valve in this claim is not limited to the one configured by a rotary valve or the like, and has the same function as a four-way valve by combining a plurality of on-off valves (electromagnetic valves) or three-way valves. It is the meaning including what was comprised so that it might exhibit.

Further, as in the invention according to claim 8 , in the refrigeration cycle according to claim 7 , the refrigerant passage connecting the first four-way valve (13) and the outdoor heat exchanger (21) has a first four-way. Valve means (25) that only allows the refrigerant to flow from the valve (13) side to the outdoor heat exchanger (21) side may be arranged.

  Further, the reference numerals in parentheses of each means described in this column and in the claims are an example showing the correspondence with the specific means described in the embodiments described later.

It is a whole block diagram which shows the refrigerant circuit at the time of the heating operation mode of the refrigerating cycle of 1st Embodiment. It is a whole block diagram which shows the refrigerant circuit at the time of the cooling operation mode of the refrigerating cycle of 1st Embodiment. It is a Mollier diagram which shows the state of the refrigerant | coolant at the time of the heating operation mode of the refrigerating cycle of 1st Embodiment. It is a Mollier diagram which shows the state of the refrigerant | coolant at the time of the cooling operation mode of the refrigerating cycle of 1st Embodiment. It is a whole block diagram which shows the refrigerant circuit at the time of the defrost operation mode of the refrigerating cycle of 2nd Embodiment. It is a whole block diagram which shows the refrigerant circuit at the time of the defrost operation mode of the refrigerating cycle of 3rd Embodiment. It is a whole block diagram which shows the refrigerant circuit at the time of the heating operation mode of the refrigerating cycle of 4th Embodiment. It is a whole block diagram which shows the refrigerant circuit at the time of the cooling operation mode of the refrigerating cycle of 4th Embodiment.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. 1 and 2 are overall configuration diagrams of a vapor compression refrigeration cycle 10 of the present embodiment. This refrigeration cycle 10 is applied to a vehicle air conditioner for buses, and operates in a heating operation mode (heating operation mode) that heats blown air that is blown into a cabin (guest room) that is a space to be air-conditioned. And the operation in the cooling operation mode (cooling operation mode) for cooling the blown air can be switched.

  1 shows the refrigerant circuit in the heating operation mode of the refrigeration cycle 10, FIG. 2 shows the refrigerant circuit in the cooling operation mode, and FIGS. 1 and 2 show the flow of the refrigerant in each operation mode. This is indicated by a solid arrow.

  In the refrigeration cycle 10 of the present embodiment, a normal chlorofluorocarbon refrigerant (for example, R134a, R407c) is adopted as the refrigerant, and the pressure of the high-pressure side refrigerant in the cycle exceeds the critical pressure of the refrigerant in any operation mode. There is no subcritical refrigeration cycle. Further, the refrigerant is mixed with refrigerating machine oil (oil) for lubricating the sliding parts in the first and second compressors 11 and 12, and a part of the refrigerating machine oil circulates in the cycle together with the refrigerant. Yes.

  As shown in FIGS. 1 and 2, the refrigeration cycle 10 includes a first compressor 11 and a second compressor 12 as compressors that compress and discharge the refrigerant. The basic configurations of the compressors 11 and 12 are the same. Specifically, the first compressor 11 is an electric compression that drives a fixed capacity type first compression mechanism 11a by a first electric motor 11b. The second compressor 12 is an electric compressor that drives a fixed capacity type second compression mechanism 12a by a second electric motor 12b.

  As the first and second compression mechanisms 11a and 12a, various compression mechanisms such as a scroll compression mechanism, a vane compression mechanism, and a rolling piston compression mechanism can be employed. The first and second electric motors 11b and 12b are AC motors whose operation (number of rotations) is controlled by an AC current output from a dedicated inverter (not shown). The operation of these inverters is controlled by a control signal output from an air conditioning control device (not shown).

  And these inverters control the rotation speed of the 1st, 2nd electric motor 11b, 12b, and, thereby, the 1st, 2nd compressor 11, 12 (specifically, 1st, 2nd compression mechanism 11a, The refrigerant discharge capacity of 12a) is changed. That is, in this embodiment, the 1st, 2nd electric motors 11b and 12b comprise the discharge capability change means of the 1st, 2nd compression mechanisms 11a and 12a, respectively. Of course, DC motors may be employed as the first and second electric motors 11b and 12b.

  Further, a first four-way valve 13 as a refrigerant circuit switching means for switching between a refrigerant circuit in the cooling operation mode and a refrigerant circuit in the heating operation mode is connected to the refrigerant discharge port of the first compressor 11. The refrigerant discharge port is connected with a second four-way valve 14 as a similar refrigerant circuit switching means.

  The first four-way valve 13 is provided between a refrigerant discharge port side of the first compressor 11 and a refrigerant suction port side of the second compressor 12, and a gas phase refrigerant outlet side of an accumulator 23 described later and a check valve 25 described later. A refrigerant circuit for heating operation mode (circuit shown by a solid line in FIG. 1) that connects the upstream side at the same time, the refrigerant outlet side of the first compressor 11 and the upstream side of the check valve 25, and an accumulator The refrigerant circuit for the cooling operation mode (circuit shown by a solid line in FIG. 2) that simultaneously connects the gas phase refrigerant outlet side of 23 and the refrigerant inlet side of the second compressor 12 is achieved.

  The second four-way valve 14 is a heating unit that simultaneously connects between the refrigerant outlet side of the second compressor 12 and the use side heat exchanger 15 and between an outdoor heat exchanger 21 described later and the refrigerant inlet side of the accumulator 23. A refrigerant circuit for operation mode (a circuit indicated by a solid line in FIG. 1), a refrigerant outlet side of the second compressor 12 and the outdoor heat exchanger 21, and a refrigerant inlet side of the use side heat exchanger 15 and the accumulator 23. The refrigerant circuit for the cooling operation mode (circuit shown by the solid line in FIG. 2) that connects the two at the same time is switched.

  The operations of the first and second four-way valves 13 and 14 are controlled by a control signal output from the air conditioning control device.

  The use-side heat exchanger 15 is arranged in a casing (not shown) that forms an air passage for the blown air blown toward the vehicle interior by the blower fan 15a, and exchanges heat between the refrigerant circulating in the inside and the blown air. It is something to be made.

  Specifically, the use-side heat exchanger 15 functions as a radiator that causes the refrigerant discharged from the second compressor 12 to exchange heat with the blown air in the heating operation mode to dissipate heat, and in the cooling operation mode, the first heat exchanger 15 functions as a radiator. 1 and 2 function as an evaporator that evaporates the refrigerant sucked into the second compressors 11 and 12 by exchanging heat with the blown air. The blower fan 15a is an electric blower whose operation is controlled by a control voltage output from the air conditioning control device.

  One refrigerant inlet / outlet of the first branch portion 16 that branches the flow of the refrigerant flowing out of the use side heat exchanger 15 is connected to the outlet side of the use side heat exchanger 15 in the heating operation mode. The first branch portion 16 has a three-way joint structure having three refrigerant outlets. Such a 1st branch part 16 may connect and comprise piping, and may provide and provide a some refrigerant path in a metal block or a resin block.

  An intermediate pressure refrigerant flow path 18a of the internal heat exchanger 18 is connected to another refrigerant inlet / outlet of the first branch portion 16 via an intermediate pressure expansion valve 17, and a high pressure of the internal heat exchanger 18 is connected to another refrigerant inlet / outlet. A refrigerant flow path 18b is connected.

  The intermediate pressure expansion valve 17 is a decompression means (first decompression means) that decompresses the high-pressure refrigerant that has flowed out of the use-side heat exchanger 15 in the heating operation mode until it becomes intermediate-pressure refrigerant. Specifically, the intermediate pressure expansion valve 17 has a valve body configured to be able to change the throttle opening, and an electric actuator including a stepping motor that changes the throttle opening of the valve body. It is an electric expansion valve, and its operation is controlled by a control signal output from the air conditioning control device.

  Further, the intermediate pressure expansion valve 17 fully closes the throttle opening, thereby blocking the refrigerant flow in the refrigerant passage from the first branching portion 16 to the inlet side of the intermediate pressure refrigerant flow path 18a. The circuit can be switched. Therefore, the intermediate pressure expansion valve 17 of the present embodiment functions as a decompression unit and also functions as a refrigerant circuit switching unit. In the present embodiment, the throttle opening of the intermediate pressure expansion valve 17 is fully closed during the cooling operation mode.

  The internal heat exchanger 18 includes an intermediate pressure refrigerant decompressed by the intermediate pressure expansion valve 17 that circulates in the intermediate pressure refrigerant flow path 18a in the heating operation mode, and a first branch portion 16 that circulates in the high pressure refrigerant flow path 18b. Heat exchange is performed with the branched high-pressure refrigerant. Since the temperature of the high-pressure refrigerant is reduced by reducing the pressure, in the internal heat exchanger 18, the intermediate-pressure refrigerant flowing through the intermediate-pressure refrigerant flow path 18a is heated, and the high-pressure refrigerant flowing through the high-pressure refrigerant flow path 18b is cooled. Is done.

  As a specific configuration of the internal heat exchanger 18, a plurality of plate-like heat transfer plate members are stacked and intermediate pressure refrigerant flow paths 18a and high pressure refrigerant flow paths 18b are alternately formed between the heat transfer plate members. In addition, a plate type heat exchanger that exchanges heat between the high-pressure refrigerant and the intermediate-pressure refrigerant through the heat transfer plate is employed.

  Moreover, you may employ | adopt the double-tube-type heat exchanger structure which arrange | positions the inner side pipe | tube which forms the intermediate pressure refrigerant flow path 18a inside the outer side pipe | tube which forms the high pressure refrigerant flow path 18b. Of course, the high-pressure refrigerant flow path 18b may be an inner pipe and the intermediate-pressure refrigerant flow path 18a may be an outer pipe. Furthermore, the structure etc. which join the refrigerant | coolant piping which forms the high pressure refrigerant flow path 18b and the intermediate pressure refrigerant flow path 18a, and heat-exchange may be employ | adopted.

  One refrigerant inlet / outlet of the first junction 19 is connected to the outlet side of the intermediate pressure refrigerant flow path 18a of the internal heat exchanger 18 in the heating operation mode. The basic configuration of the first merging portion 19 is the same as that of the first branching portion 16, and one refrigerant inlet / outlet of the first four-way valve 13 is connected to another refrigerant inlet / outlet of the first merging portion 19. The inlet / outlet side of the second compressor 12 is connected to the refrigerant inlet / outlet.

  Thereby, during the heating operation mode, the intermediate pressure refrigerant flowing out from the intermediate pressure refrigerant flow path 18a flows into the first merging portion 19 and the intermediate pressure refrigerant discharged from the first compressor 11 is transferred to the first merging portion 19. It flows in and flows out to the suction port side of the second compressor 12. In the cooling operation mode, the low-pressure refrigerant that has flowed out of the accumulator 23 flows into the first merging portion 19 via the first four-way valve 13 and flows out to the suction port side of the second compressor 12.

  On the other hand, the inlet side of the low-pressure expansion valve 20 is connected to the outlet side of the high-pressure refrigerant flow path 18b of the internal heat exchanger 18 in the heating operation mode. The low pressure expansion valve 20 depressurizes the high pressure refrigerant flowing out from the high pressure refrigerant flow path 18b in the heating operation mode until it becomes a low pressure refrigerant, and in the cooling operation mode until the high pressure refrigerant flowing out from the outdoor heat exchanger 21 becomes the low pressure refrigerant. A decompression means (second decompression means) for decompressing.

  The basic configuration of the low pressure expansion valve 20 is the same as that of the intermediate pressure expansion valve 17. Therefore, the low-pressure expansion valve 20 is configured to include a valve body that can change the throttle opening degree and an electric actuator that changes the throttle opening degree of the valve body, and is a control that is output from the air conditioning control device. The operation is controlled by the signal.

  An outdoor heat exchanger 21 is connected to the outlet side of the low pressure expansion valve 20 in the heating operation mode. The outdoor heat exchanger 21 is arranged in the vehicle ceiling or the like, and exchanges heat between the refrigerant circulating inside the outdoor air (outside air) blown by the blower fan 21a.

  Specifically, the outdoor heat exchanger 21 functions as an evaporator that evaporates the refrigerant sucked into the first compressor 11 by exchanging heat with the outside air in the heating operation mode, and in the cooling operation mode, the first, The refrigerant discharged from both the second compressors 11 and 12 functions as a radiator that radiates heat by exchanging heat with the outside air. The blower fan 21a is an electric blower whose operation is controlled by a control voltage output from the air conditioning control device.

  Further, one refrigerant inlet / outlet of the second junction 22 is connected to the outlet side of the outdoor heat exchanger 21 in the heating operation mode. The basic configuration of the second merging portion 22 is the same as that of the first branching portion 16, and one refrigerant inlet / outlet of the second four-way valve 14 is connected to another refrigerant inlet / outlet of the second merging portion 22. One refrigerant inlet / outlet of the first four-way valve 13 is connected to the refrigerant inlet / outlet via a check valve 22.

  Thereby, in the heating operation mode, the low-pressure refrigerant flowing out of the outdoor heat exchanger 21 flows into the second junction 22 and flows out to the accumulator 23 side via the second four-way valve 14, and in the cooling operation mode, The high-pressure refrigerant discharged from the first compressor 11 flows into the second junction 22 through the first four-way valve 13, and the high-pressure refrigerant discharged from the second compressor 12 passes through the second four-way valve 14 to the second 2 flows into the junction 22 and flows out to the outdoor heat exchanger 21 side.

  The accumulator 23 is a gas-liquid separation unit that separates the gas-liquid of the refrigerant that has flowed into the accumulator 23. One refrigerant outlet / inlet of the second branch portion 24 is connected to the gas phase refrigerant outlet side of the accumulator 23. The basic structure of the second branch portion 24 is the same as that of the first branch portion 16, and the refrigerant inlet side of the first compressor 11 is connected to another refrigerant inlet / outlet of the second branch portion 24. The upstream side of the check valve 25 is connected to the entrance / exit.

  The check valve 25 is a valve that only allows the refrigerant to flow from one refrigerant outlet side (upstream side) of the first four-way valve 13 to the refrigerant inlet side of the accumulator 23 and the outdoor heat exchanger 21 side (downstream side). Means. This prevents the refrigerant that has flowed out of the outdoor heat exchanger 21 during the heating operation mode from flowing into the gas phase refrigerant outlet side of the accumulator 23 via the first four-way valve 13, and during the cooling operation mode, The refrigerant discharged from the first compressor 11 is allowed to flow out to the outdoor heat exchanger 21 side via the first four-way valve 13.

  Next, the electric control unit of this embodiment will be described. The air conditioning control device is a CPU that performs control processing and arithmetic processing, a well-known microcomputer including a storage circuit such as ROM and RAM that stores programs and data, and outputs that output control signals or control voltages to various control target devices. The circuit includes an input circuit to which detection signals from various sensors are input, a power supply circuit, and the like.

  On the output side of the air-conditioning control device, the inverters for the first and second compressors 11 and 12 (specifically, for the first and second electric motors 11b and 12b) as control target devices, the first The second four-way valves 13, 14, the blower fan 15 a, the intermediate pressure expansion valve 17, the low pressure expansion valve 20, the blower fan 21 a, etc. are connected, and the air conditioning control device controls the operation of these control target devices.

  In the air conditioning control device, the control means for controlling the operation of these control target devices is integrally configured. Among the air conditioning control devices, the configuration for controlling the operation of each control target device (hardware) Hardware and software) constitutes the control means of each control target device.

  For example, in this embodiment, the configuration hardware and software for controlling the refrigerant discharge capacity of the first compression mechanism 11a by controlling the operation of the inverter for the first electric motor 11b constitutes the first discharge capacity control means, The configuration for controlling the refrigerant discharge capacity of the second compression mechanism 12a by controlling the operation of the inverter for the second electric motor 12b constitutes the second discharge capacity control means.

  Therefore, the rotation speeds of the first and second electric motors 11b and 12b, that is, the refrigerant discharge capacities of the first and second compression mechanisms 11a and 12a are mutually controlled by the first discharge capacity control unit and the second discharge capacity control unit, respectively. It can be controlled independently.

  Further, the refrigerant circuit switching control is configured to control the operation of the first and second four-way valves 13 and 14 and the intermediate pressure expansion valve 17 to switch between the refrigerant circuit in the heating operation mode and the refrigerant circuit in the cooling operation mode. Means. Of course, the first and second discharge capacity control means and the refrigerant circuit switching control means may be configured as separate control devices for the air conditioning control device.

  On the other hand, on the input side of the air conditioning control device, an internal air temperature sensor as an internal air temperature detection means for detecting the internal air temperature Tr in the vehicle interior, an external air temperature sensor as an external air temperature detection means for detecting the external air temperature Tam outside the vehicle interior, use Various air-conditioning control sensors such as a blow-out temperature sensor as a blow-off air temperature detecting means for detecting the blow-out air temperature Te blown out from the side heat exchanger 15 are connected, and detection signals from these sensor groups are input to the air-conditioning control device. Is done.

  In addition, in this embodiment, although the heat exchange fin temperature of the utilization side heat exchanger 15 is specifically detected as a blowing temperature sensor, it distribute | circulates inside the utilization side heat exchanger 15 as a blowing temperature sensor. You may employ | adopt the temperature sensor etc. which detect the temperature of the temperature sensor which detects the temperature of a refrigerant | coolant, the temperature of the ventilation air which blows off toward the vehicle interior from the utilization side heat exchanger 15.

  Further, an operation panel provided in the driver's seat is connected to the input side of the air conditioning control device. The operation panel is provided with an operation / stop switch for outputting an operation request signal or a stop request signal for a vehicle air conditioner, a target temperature setting switch for setting a target temperature Tset in the vehicle interior, and the operation signals of these switches. Is input to the air conditioning controller.

  Next, the operation of this embodiment in the above configuration will be described. The refrigeration cycle 10 of the present embodiment operates when an operation panel stop / start switch is turned on (ON) in a vehicle start-up state. Specifically, when the operation / stop switch is turned on, the air conditioning control device executes the air conditioning control program stored in the storage circuit in advance.

  In this air conditioning control program, the detection signals of the various air conditioning control sensors described above and the operation signals output from the operation panel are read, and the control states of various control target devices are determined based on the read detection signals and operation signals. Further, a control signal or a control voltage is output to various devices to be controlled so that the determined control state is obtained.

  Then, until the operation stop of the vehicle air conditioner is requested by releasing (OFF) the operation panel stop / operation switch, etc., reading of the detection signal and operation signal described above → determining the control state of various control target devices → various A control routine such as output of a control signal or control voltage for the control target device is repeated.

  Further, as described above, the refrigeration cycle 10 of the present embodiment can be switched between the operation in the heating operation mode and the operation in the cooling operation mode. First, in the operation in the heating operation mode, when the air conditioning controller reads the detection signal and the operation signal, the target temperature Tset set by the target temperature setting switch is higher than the outside air temperature Tam detected by the outside air temperature sensor. It is executed when

  Specifically, in the heating operation mode, the air-conditioning control device is opposite to the refrigerant outlet side of the first compressor 11 and the refrigerant inlet side of the second compressor 12 and the gas phase refrigerant outlet side of the accumulator 23. The operation of the first four-way valve 13 is controlled so that the upstream side of the stop valve 25 is connected simultaneously, and the outdoor heat exchange between the refrigerant discharge port side of the second compressor 12 and the use side heat exchanger 15 is performed. The operation of the second four-way valve 14 is controlled so that the vessel 21 and the refrigerant inlet side of the accumulator 23 are connected simultaneously.

  Further, the air conditioning control device controls the operations of the intermediate pressure expansion valve 17 and the low pressure expansion valve 20 so that the respective throttle openings become predetermined predetermined openings. Thereby, it changes to the refrigerant circuit through which a refrigerant flows, as shown by the solid line arrow of FIG. Therefore, in the refrigeration cycle 10 in the heating operation mode, as shown in the schematic Mollier diagram of FIG. 3, the state of the refrigerant circulating in the cycle changes.

  In addition, the Mollier diagram of FIG. 3 shows the change of the state of the refrigerant when the condensation temperature of the refrigerant in the use side heat exchanger 15 is 20 ° C. and the evaporation temperature of the refrigerant in the outdoor heat exchanger 21 is −20 ° C. The change of the state of the refrigerant | coolant at the time of making it operate | move with the cycle structure at the time of the air_conditionaing | cooling operation mode on the same conditions is shown with the thin broken line.

First, the intermediate pressure refrigerant (a1 _H point in FIG. 3) compressed to the intermediate pressure in the first compressor 11 flows into the first merging portion 19 via the first four-way valve 13, and the first merging It merges with the intermediate pressure refrigerant that has flowed out of the intermediate pressure expansion valve 17 at the portion 19 (point a1 _H → a2 _H, point d1 _H → a2 _{H in} FIG. 3). The intermediate-pressure refrigerant flowing from the first confluence unit 19, is sucked into the second compressor 12, it is compressed to a high pressure refrigerant (a2 _H point in Fig. 3 → a3 _H point).

The high-pressure refrigerant discharged from the second compressor 12 flows into the use-side heat exchanger 15 and dissipates heat by exchanging heat with the blown air blown from the blower fan 15a (a3 _H point → b1 _H point in FIG. 3). ). Thereby, blowing air is heated and heating of a vehicle interior is implement | achieved. The flow of the high-pressure refrigerant that has flowed out of the use side heat exchanger 15 is branched at the first branching section 16.

One of the high-pressure refrigerants branched at the first branching portion 16 is decompressed by the intermediate-pressure expansion valve 17 until it becomes intermediate-pressure refrigerant, and flows into the intermediate-pressure refrigerant flow path 18a of the internal heat exchanger 18 (FIG. 3). B1 _H point → c1 _H point). On the other hand, the other high-pressure refrigerant branched by the first branch part 16 flows into the high-pressure refrigerant flow path 18 b of the internal heat exchanger 18.

In the internal heat exchanger 18, the intermediate pressure refrigerant flowing through the intermediate pressure refrigerant flow path 18a and the high pressure refrigerant flowing through the high pressure refrigerant flow path 18b exchange heat. Thereby, the refrigerant | coolant which distribute | circulates the intermediate pressure refrigerant | coolant flow path 18a is heated, an enthalpy is increased, it becomes a gaseous-phase refrigerant | coolant, and flows in into the 1st confluence | merging part 19 (c1 _H point-> d1 _H point of FIG. 3). On the other hand, the refrigerant flowing through the high-pressure refrigerant flow path 18b is cooled to lower the enthalpy (b1 _H point → b2 _H point in FIG. 3).

The high-pressure refrigerant that has flowed out of the high-pressure refrigerant flow path 18b of the internal heat exchanger 18 is reduced in pressure until it becomes low-pressure refrigerant in the low-pressure expansion valve 20, and flows into the outdoor heat exchanger 21 (b2 _H point → c2 _{H in} FIG. 3). point). In the outdoor heat exchanger 21, the low-pressure refrigerant is evaporated by absorbing heat from outside air blown by the blower fan 21a (c2 _H point in Fig. 3 → d2 _H point).

The low-pressure refrigerant that has flowed out of the outdoor heat exchanger 21 flows into the accumulator 23 via the second junction 22 and the second four-way valve 14 and is separated into gas and liquid. At this time, the action of the check valve 25 prevents the low pressure refrigerant from flowing backward from the second junction 22 to the gas phase refrigerant outlet side of the accumulator 23. Low-pressure gas-phase refrigerant flowing from the gas-phase refrigerant outlet of the accumulator 23 (e _H point in Fig. 3) is compressed again is sucked into the first compressor 11 (e _H point in Fig. 3 → a1 _H point).

  As described above, according to the refrigeration cycle 10 of the present embodiment, in the heating operation mode, the first compressor 11 (specifically, the first compression mechanism 11a) and the second compressor 12 (specifically, the first compressor 11). 2 compression mechanisms 12a) are connected in series to increase the pressure of the refrigerant in multiple stages, and the intermediate pressure refrigerant decompressed by the intermediate pressure expansion valve 17 is joined with the refrigerant discharged from the first compressor 11. A so-called economizer refrigeration cycle that is sucked into the two compressors 12 is configured, and heating of the passenger compartment is realized.

  Next, in the cooling operation mode, when the air conditioning controller reads the detection signal and the operation signal, the target temperature Tset set by the target temperature setting switch is less than or equal to the outside air temperature Tam detected by the outside air temperature sensor. It is executed when

  Specifically, in the cooling operation mode, the air-conditioning control device operates between the refrigerant discharge port side of the first compressor 11 and the upstream side of the check valve 25 and the gas phase refrigerant outlet side of the accumulator 23 and the second compressor. 12, the operation of the first four-way valve 13 is controlled so as to be simultaneously connected to the refrigerant suction port side, and between the refrigerant discharge port side of the second compressor 12 and the outdoor heat exchanger 21, and use side heat exchange. The operation of the second four-way valve 14 is controlled so that the container 15 and the refrigerant inlet side of the accumulator 23 are connected simultaneously.

  Further, the air conditioning controller controls the operation of the low pressure expansion valve 20 so that the intermediate pressure expansion valve 17 is fully closed and the throttle opening of the low pressure expansion valve 20 becomes a predetermined opening degree. Thereby, it changes to the refrigerant circuit through which a refrigerant flows, as shown by the solid line arrow of FIG.

  Therefore, in the refrigeration cycle 10 in the cooling operation mode, the state of the refrigerant circulating in the cycle changes as shown in the Mollier diagram of FIG. The Mollier diagram of FIG. 4 shows the change in the state of the refrigerant when the refrigerant evaporation temperature in the use side heat exchanger 15 is 20 ° C. and the refrigerant condensation temperature in the outdoor heat exchanger 21 is 50 ° C. The change of the state of the refrigerant | coolant at the time of making it operate | move by the cycle structure at the time of heating operation mode on the same conditions is shown with the thin line with the thin line.

First, the refrigerant compressed until it becomes a high-pressure refrigerant in the first compressor 11 flows into the second junction 22 through the first four-way valve 13 and the check valve 25, and the high-pressure refrigerant in the second compressor 12. The refrigerant that has been compressed until reaches the second merging portion 22 through the second four-way valve 14, and the refrigerant discharged from both compressors 11 and 12 merges at the second merging portion 22 (FIG. 4). A _C point).

The high-pressure refrigerant merged at the second merger 22 flows into the outdoor heat exchanger 21 and dissipates heat by exchanging heat with the outside air blown by the blower fan 21a (a _C point → b _C point in FIG. 4). The high-pressure refrigerant that has flowed out of the outdoor heat exchanger 21 is depressurized by the low-pressure expansion valve 20 until it becomes low-pressure refrigerant, and flows into the high-pressure refrigerant flow path 18b of the internal heat exchanger 18 (b _C point → c _{C in} FIG. 4). point).

  Here, in the cooling operation mode, the intermediate pressure expansion valve 17 is in a fully closed state, so that the refrigerant does not flow into the intermediate pressure refrigerant flow path 18a of the internal heat exchanger 18. Therefore, the internal heat exchanger 18 in the cooling operation mode does not exchange heat between the refrigerants, and the high-pressure refrigerant flow path 18b functions as a simple refrigerant passage.

Further, the flow of the low-pressure refrigerant flowing out from the high-pressure refrigerant flow path 18 b of the internal heat exchanger 18 flows into the use side heat exchanger 15 without being branched at the first branching portion 16. The low-pressure refrigerant flowing into the use side heat exchanger 15 absorbs heat from the blown air blown from the blower fan 15a and evaporates (c _C point → d _C point in FIG. 4). Thereby, blowing air is cooled and cooling of a vehicle interior is implement | achieved.

The low-pressure refrigerant that has flowed out of the use-side heat exchanger 15 flows into the accumulator 23 through the second four-way valve 14 and is separated into gas and liquid. The flow of the low-pressure refrigerant (point e _{C in} FIG. 4) that has flowed out of the gas-phase refrigerant outlet of the accumulator 23 is branched by the second branch section 24, and one of the branched low-pressure refrigerant is sucked into the first compressor 11. The other low-pressure refrigerant that has been compressed and branched is drawn into the second compressor 12 via the first four-way valve 13 and compressed again (point e _C → point a _{C in} FIG. 4).

  As described above, according to the refrigeration cycle 10 of the present embodiment, in the cooling operation mode, the first compressor 11 (specifically, the first compression mechanism 11a) and the second compressor 12 (specifically, the first compressor 11). A normal refrigeration cycle in which two compression mechanisms 12a) are connected in parallel is configured, and cooling of the passenger compartment is realized.

  Therefore, in the refrigeration cycle 10 of the present embodiment, the refrigerant discharge capacity can be exerted on the two compressors of the first and second compressors 11 and 12 in any operation mode, and only one compressor is used. In contrast to the case where the refrigerant discharge capacity is exhibited, the blown air blown into the vehicle interior, which is the heat exchange target fluid, can be efficiently heated or cooled.

  Furthermore, since the economizer refrigeration cycle using the internal heat exchanger 18 is configured in the heating operation mode, the refrigeration cycle 10 can exhibit high cycle efficiency (COP), and the intermediate pressure expansion valve 17 can The decompressed intermediate pressure refrigerant can be heated and vaporized, and liquid compression of the second compressor 12 can be prevented.

  By the way, in the heating operation mode, since the two compressors 11 and 12 are connected in series, the flow rate of the circulating refrigerant circulating in the cycle is reduced as compared to the case where they are connected in parallel. For this reason, we are anxious about the fall of the heating capability in the utilization side heat exchanger 15 which functions as a heat radiator at the time of heating operation mode.

The heating capacity in the use side heat exchanger 15 in the heating operation mode is the enthalpy and outlet side of the inlet side refrigerant of the use side heat exchanger 15 with respect to the refrigerant flow rate Gr flowing through the use side heat exchanger 15. It is defined as a value obtained by integrating the difference from the enthalpy of the refrigerant (enthalpy difference on the radiator side), that is, the enthalpy difference between the a3 _H point and the b1 _H point in FIG.

On the other hand, in this embodiment, since the internal heat exchanger 18 is provided, the difference between the enthalpy of the outlet side refrigerant and the enthalpy of the inlet side refrigerant of the outdoor heat exchanger 21 functioning as an evaporator (on the evaporator side) 3), that is, the enthalpy difference between the d2 _H point and the c2 _H point in FIG. 3 can be enlarged by ΔH1 in FIG. 3 with respect to the normal refrigeration cycle indicated by the thin broken line.

  Therefore, the heat absorption capacity of the refrigerant in the outdoor heat exchanger 21 defined by the product of the refrigerant flow rate Ge flowing through the outdoor heat exchanger 21 and the enthalpy difference on the evaporator side is increased, and the air blowing in the use side heat exchanger 15 is increased. It is possible to suppress a decrease in air heating capability.

On the other hand, in the cooling operation mode, since a normal refrigeration cycle is configured, the difference in enthalpy on the evaporator side in the use side heat exchanger 15 functioning as an evaporator, that is, between the points d _C and c _{C in} FIG. The enthalpy difference is reduced by ΔH2 in FIG. 4 with respect to the economizer refrigeration cycle indicated by the thin broken line. For this reason, there is a concern that the refrigerant heat absorption capacity (cooling capacity of the blown air) in the use-side heat exchanger 15 is reduced.

  In contrast, in the cooling operation mode, the difference between the refrigerant condensing pressure in the heat exchanger functioning as a radiator and the refrigerant evaporating pressure in the heat exchanger functioning as an evaporator (difference between high and low pressures of the cycle) is larger than that in the heating operation mode. Therefore, ΔH2 in FIG. 4 is also smaller than ΔH1 in FIG. Therefore, there is little decrease in the endothermic ability due to the enthalpy difference on the evaporator side being reduced by ΔH2.

  Furthermore, since the two compressors 11 and 12 are connected in parallel in the cooling operation mode, the use side heat exchanger 15 is connected to the case where the two compressors 11 and 12 are connected in series. The refrigerant flow rate Gr that is circulated can be increased to suppress a decrease in the refrigerant heat absorption capacity (cooling capacity of the blown air) in the use-side heat exchanger 15.

  Further, in the refrigeration cycle 10 of the present embodiment, the difference between the high and low pressures of the cycle becomes high, and the compression ratio in the first and second compressors 11 and 12 is higher in the heating operation mode than in the cooling operation mode. Since the second compressors 11 and 12 are connected in series to switch to an economizer refrigeration cycle that compresses refrigerant in multiple stages, cycle efficiency by reducing the compression ratio of the first and second compressors 11 and 12 The improvement effect can be obtained efficiently.

  At this time, since the refrigerant discharge capacities of the first compressor 11 and the second compressor 12 are configured to be controllable independently of each other, the pressure in the first compressor 11 can be adjusted by adjusting the pressure of the intermediate pressure refrigerant. The compression ratio and the compression ratio in the second compressor 12a can be adjusted appropriately. As a result, the cycle efficiency can be further improved.

  The compression ratio of the present embodiment is defined by the ratio of the discharge side refrigerant pressure to the suction side refrigerant pressure of the compressor. Therefore, the compression ratio of the entire cycle can be defined by the ratio of the refrigerant condensing pressure in the heat exchanger functioning as a radiator to the refrigerant evaporation pressure in the heat exchanger functioning as an evaporator.

Specifically, in the case of adopting the R134a as the refrigerant, the compression ratio of the entire cycle in the heating operation mode of the conditions described in FIG. 3 (e.g., the ratio of the pressure of b2 _H point relative c2 _H point in Fig. 3) Is 4.3, and the compression ratio (for example, the ratio of the pressure at the point b _{C to the} point c _C in FIG. 4 ) in the cooling operation mode under the conditions described in FIG. 4 is 2.3. It becomes.

  When R407c is employed as the refrigerant, the compression ratio of the entire cycle in the heating operation mode under the conditions described in FIG. 3 is 4.1, and the cooling operation mode under the conditions described in FIG. The compression ratio as a whole cycle at the time is 2.3.

(Second Embodiment)
In the present embodiment, as shown in the overall configuration diagram of FIG. 5, an outdoor heat exchanger 21 that functions as an evaporator in the heating operation mode by adding a bypass passage 26 and an on-off valve 27 to the first embodiment. The operation in the defrosting operation mode that removes the frost that has arrived at is possible.

  The bypass passage 26 of the present embodiment is a refrigerant passage that causes the refrigerant that has flowed out of the outdoor heat exchanger 21 to bypass the use-side heat exchanger 15 and flow to the refrigerant inlet side of the accumulator 23. A refrigerant passage between the exchanger 21 and the low-pressure expansion valve 20 and a refrigerant passage between the second four-way valve 14 and the accumulator 23 are connected. The on-off valve 27 is an electromagnetic valve that opens and closes the bypass passage 26, and its opening / closing operation is controlled by a control voltage output from the air conditioning control device.

  In addition, FIG. 5 has shown the refrigerant circuit at the time of the defrost operation mode of the refrigerating cycle 10 of this embodiment, and has shown the flow of the refrigerant at the time of a defrost operation mode by the solid line arrow. In FIG. 5, the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals. The same applies to the following drawings.

  Here, as described in the first embodiment, the refrigerant evaporating temperature in the outdoor heat exchanger 21 in the heating operation mode may be equal to or lower than the frosting temperature (0 ° C.). Frost may occur. When such frost formation occurs, the outdoor air passage of the outdoor heat exchanger 21 is blocked by frost, so that the heat exchange capability of the outdoor heat exchanger 21 is significantly reduced.

  Therefore, in the heat pump cycle 10 of the present embodiment, the state in which the blown air temperature Te detected by the blown temperature sensor is equal to or lower than the frosting temperature (0 ° C.) in the heating operation mode is a predetermined first reference time. When the operation continues (for example, 10 minutes), the operation is switched to the operation in the defrosting operation mode. Further, when the operation in the defrosting operation mode continues for a predetermined second reference time (for example, 30 seconds), the operation is switched again to the operation in the heating operation mode.

  Specifically, in the defrosting operation mode, the air conditioning control device controls the operation of the first and second four-way valves 13 and 14 as in the cooling operation mode of the first embodiment, and the intermediate pressure expansion valve 17 and The low pressure expansion valve 20 is fully closed, and the on-off valve 27 is opened. Thereby, as shown to the solid line arrow of FIG. 5, it switches to the refrigerant circuit into which a refrigerant | coolant flows.

  The pressure loss that occurs when the refrigerant passes through the on-off valve 27 is smaller than the pressure loss that occurs when the refrigerant passes through the low-pressure expansion valve 20 that is in the throttle state. For this reason, even if the low-pressure expansion valve 20 is in the throttle state, most of the refrigerant that has flowed out of the outdoor heat exchanger 21 flows into the bypass passage 26 when the on-off valve 27 is open.

  Furthermore, in the defrosting operation mode of the present embodiment, the on-off valve 27 is opened and the low-pressure expansion valve 20 is fully closed, so that the total flow rate of the refrigerant flowing out of the outdoor heat exchanger 21 is caused to flow into the bypass passage 26. be able to. That is, the on-off valve 27 and the low-pressure expansion valve 20 of this embodiment have a function as refrigerant circuit switching means.

  Accordingly, in the refrigeration cycle 10 during the defrosting operation mode, the high-temperature and high-pressure refrigerant compressed by the first compressor 11 and the high-temperature and high-pressure refrigerant compressed by the second compressor 12 are combined in the second merging manner, as in the cooling operation mode. They merge at the section 22 and flow into the outdoor heat exchanger 21. As a result, the outdoor heat exchanger 21 is defrosted by the heat of the high-temperature and high-pressure refrigerant that has flowed into the outdoor heat exchanger 21.

  Since the on-off valve 27 is open, the refrigerant flowing out of the outdoor heat exchanger 21 flows into the bypass passage 26 and drops in pressure when passing through the on-off valve 27 and into the accumulator 23. The flow of the low-pressure refrigerant that has flowed out of the gas-phase refrigerant outlet of the accumulator 23 is branched by the second branching section 24, and is sucked into the first compressor 11 and the second compressor 12 and compressed again in the same manner as in the cooling operation mode. Is done.

  Other configurations and operations are the same as those in the first embodiment. Therefore, according to the refrigeration cycle 10 of the present embodiment, the same effect as in the first embodiment can be obtained, and even if the outdoor heat exchanger 21 is frosted in the heating operation mode, the defrosting operation mode By switching to the operation, a so-called hot gas bypass cycle in which the refrigerant discharged from the first and second compressors 11 and 12 is supplied to the outdoor heat exchanger 21 can be configured to defrost the outdoor heat exchanger 21. it can.

(Third embodiment)
In the present embodiment, as shown in the overall configuration diagram of FIG. 6, a bypass passage 26, an on-off valve 27, and an auxiliary use side heat exchanger 28 are added to the first embodiment, and the same as in the second embodiment. In addition, the operation in the defrosting operation mode can be realized.

  The bypass passage 26 of the present embodiment is a refrigerant passage that causes the refrigerant discharged from the second compressor 12 to bypass the use-side heat exchanger 15 and flow to the outdoor heat exchanger 21 side. A refrigerant passage between the two-way valve 14 and the use side heat exchanger 15 and a refrigerant passage between the low pressure expansion valve 20 and the outdoor heat exchanger 21 are provided so as to connect the refrigerant passage.

  The auxiliary use side heat exchanger 28 heats the blown air by exchanging heat between the refrigerant flowing through the inside and the blown air blown from the blower fan 15 a, and in the same manner as the use side heat exchanger 15, in the casing. Has been placed.

  More specifically, the auxiliary use side heat exchanger 28 is disposed upstream of the use side heat exchanger 15 in the flow direction of the blown air. The refrigerant inlet / outlet of the auxiliary use side heat exchanger 28 is connected to one refrigerant inlet / outlet of the first four-way valve 13 and one refrigerant inlet / outlet of the first junction 19, respectively. Other configurations are the same as those of the second embodiment.

  Next, the operation of the present embodiment having the above configuration will be described. First, in the heating operation mode, the air conditioning control device controls the operations of the first and second four-way valves 13 and 14, the intermediate pressure expansion valve 17 and the low pressure expansion valve 20 as in the heating operation mode of the first embodiment. Further, the on-off valve 27 is closed.

  Therefore, the intermediate pressure refrigerant discharged from the first compressor 11 flows into the auxiliary use side heat exchanger 28, and exchanges heat with the blown air blown from the blower fan 15a to dissipate heat. Thereby, blowing air is heated. The refrigerant that has flowed out of the auxiliary use side heat exchanger 28 flows into the first merging portion 19 and merges with the intermediate pressure refrigerant that has flowed out of the intermediate pressure expansion valve 17 in the first merging portion 19.

  The intermediate pressure refrigerant that has flowed out of the first junction 19 is sucked into the second compressor 12, compressed until it becomes a high-pressure refrigerant, flows into the use-side heat exchanger 15, and blown air blown from the blower fan 15 a. Heat exchange with heat. Thereby, blowing air is further heated and heating of a vehicle interior is implement | achieved. Subsequent operations are the same as those in the first embodiment.

  As described above, in the heating operation mode of the present embodiment, the auxiliary use side heat exchanger 28 is disposed upstream of the use side heat exchanger 15 in the flow direction of the blown air. In 28, the blown air can be heated using the intermediate-pressure refrigerant as a heat source, and in the use-side heat exchanger 15, the blown air can be further heated using a high-pressure refrigerant having a higher temperature than the intermediate-pressure refrigerant as a heat source. That is, the temperature difference between the refrigerant and the blown air in the auxiliary use side heat exchanger 28 and the use side heat exchanger 15 can be secured and the blown air can be efficiently heated.

  Next, in the defrosting operation mode of the present embodiment, the air conditioning control device maintains the operating state of the first and second four-way valves 13 and 14 in the same manner as in the heating operation mode, and the intermediate pressure expansion valve 17 and the low pressure expansion valve 20 is fully closed, and the on-off valve 27 is opened. Thereby, it changes to the refrigerant circuit through which a refrigerant flows, as shown by the solid line arrow of FIG.

  Therefore, in the defrosting operation mode, as in the heating operation mode, the intermediate pressure refrigerant discharged from the first compressor 11 flows into the auxiliary use side heat exchanger 28 and the blown air blown from the blower fan 15a. Heat exchange to dissipate heat. Thereby, blowing air is heated. Further, the refrigerant flowing out from the auxiliary use side heat exchanger 28 is sucked into the second compressor 12 through the first junction 19.

  Since the on-off valve 27 is open, the refrigerant discharged from the second compressor 12 flows into the bypass passage 26 and drops in pressure when passing through the on-off valve 27 and flows into the outdoor heat exchanger 21. As a result, the outdoor heat exchanger 21 is defrosted by the heat of the high-temperature and high-pressure refrigerant that has flowed into the outdoor heat exchanger 21.

  The refrigerant flowing out of the outdoor heat exchanger 21 flows into the accumulator 23 through the second four-way valve 14 and is separated into gas and liquid. The flow of the low-pressure refrigerant that has flowed out from the gas-phase refrigerant outlet of the accumulator 23 is branched at the second branch section 24, and is sucked into the first compressor 11 and compressed again, as in the heating operation mode.

  The cooling operation mode and other operations are the same as in the first embodiment. Therefore, according to the refrigeration cycle 10 of the present embodiment, the same effect as in the first embodiment can be obtained, and even if the outdoor heat exchanger 21 is frosted in the heating operation mode, the defrosting operation mode By switching to operation, defrosting of the external heat exchanger 21 can be performed.

  Furthermore, according to the refrigeration cycle 10 of the present embodiment, since the auxiliary use side heat exchanger 28 is provided, the temperature of the blown air is lower in the defrosting operation mode than in the heating operation mode. It is possible to perform auxiliary heating in the room.

(Fourth embodiment)
In the present embodiment, as shown in FIGS. 7 and 8, the first branch portion 16 and the internal heat exchanger 18 are abolished with respect to the refrigeration cycle 10 of the first embodiment, and a gas-liquid separator 29, an intermediate The refrigeration cycle 50 provided with the pressure refrigerant passage 30 and the intermediate pressure on-off valve 31 will be described. 7 shows the refrigerant circuit in the heating operation mode of the refrigeration cycle 50, FIG. 8 shows the refrigerant circuit in the cooling operation mode, and FIGS. 7 and 8 show the flow of the refrigerant in each operation mode. This is indicated by a solid arrow.

Specifically, the gas-liquid separator 29 separates the gas-liquid refrigerant flowing out from the intermediate pressure expansion valve 17 in the heating operation mode, and separates the gas-liquid refrigerant flowing out from the low-pressure expansion valve 20 in the cooling operation mode. Gas-liquid separation means. The intermediate pressure refrigerant passage 30 is a refrigerant passage connecting the gas-phase refrigerant outlet of the gas-liquid separator 29 and one refrigerant inlet / outlet of the first merging portion 19. The intermediate pressure on / off valve 31 is an electromagnetic valve that opens and closes the intermediate pressure refrigerant passage 30 , and its opening / closing operation is controlled by a control voltage output from the air conditioning control device. Other configurations are the same as those of the first embodiment.

  Next, the operation of this embodiment in the above configuration will be described. First, in the heating operation mode, the air conditioning control device controls the operations of the first and second four-way valves 13, 14, the intermediate pressure expansion valve 17 and the low pressure expansion valve 20, as in the heating operation mode of the first embodiment. At the same time, the intermediate pressure on-off valve 31 is opened.

Therefore, as in the first embodiment, the intermediate pressure refrigerant discharged from the first compressor 11 flows into the first junction 19. At this time, since the intermediate pressure on-off valve 31 is open, the intermediate pressure refrigerant passage 30 is separated from the intermediate pressure refrigerant discharged from the first compressor 11 by the gas-liquid separator 29 in the first junction 19. The intermediate pressure refrigerant in the gas phase that flows into the first merging portion 19 through the merging portion.

  The intermediate-pressure refrigerant that has flowed out of the first junction 19 is sucked into the second compressor 12, compressed until it becomes a high-pressure refrigerant, and flows into the use-side heat exchanger 15. The high-pressure refrigerant that has flowed into the use-side heat exchanger 15 exchanges heat with the blown air blown from the blower fan 15a to radiate heat. Thereby, blowing air is heated and heating of a vehicle interior is implement | achieved.

The high-pressure refrigerant that has flowed out of the use-side heat exchanger 15 is decompressed by the intermediate-pressure expansion valve 17 until it becomes intermediate-pressure refrigerant, and flows into the gas-liquid separator 29. The gas-phase refrigerant separated by the gas-liquid separator 29 flows into the intermediate-pressure refrigerant passage 30 , and the separated liquid-phase refrigerant is decompressed by the low-pressure expansion valve 20 until it becomes a low-pressure refrigerant. Subsequent operations are the same as those in the first embodiment.

  As described above, according to the refrigeration cycle 50 of the present embodiment, in the heating operation mode, an economizer refrigeration cycle that separates the intermediate pressure refrigerant by the gas-liquid separator 29 is configured, and the refrigeration cycle 50 exhibits high cycle efficiency. However, heating of the passenger compartment can be realized.

  Next, in the cooling operation mode, the air conditioning control device controls the operation of the first and second four-way valves 13 and 14 as in the cooling operation mode of the first embodiment. Further, the air conditioning control device controls the operation of the intermediate pressure expansion valve 17 so that the throttle opening degree of the intermediate pressure expansion valve 17 becomes a predetermined opening degree, and opens the low pressure expansion valve 20 to the fully open state. The on-off valve 31 is closed. Thereby, it switches to the refrigerant circuit through which a refrigerant | coolant flows as shown by the solid line arrow of FIG.

  Therefore, as in the first embodiment, the high-pressure refrigerant discharged from the first and second compressors 11 and 12 merges at the second junction 22 and flows into the outdoor heat exchanger 21, and is blown by the blower fan 21a. Heat exchange with the blown outside air to dissipate heat. The refrigerant that has flowed out of the outdoor heat exchanger 21 flows into the gas-liquid separator 29 through the low-pressure expansion valve 20.

  At this time, since the low-pressure expansion valve 20 is fully opened, the high-pressure refrigerant that has flowed into the low-pressure expansion valve 20 flows into the gas-liquid separator 29 with almost no pressure reduction. The liquid phase refrigerant separated by the gas-liquid separator 29 flows into the intermediate pressure expansion valve 17, is decompressed until it becomes a low pressure refrigerant, and flows into the use side heat exchanger 15. On the other hand, the gas-phase refrigerant separated by the gas-liquid separator 29 does not flow into the intermediate pressure refrigerant passage 30 because the intermediate pressure on-off valve 31 is closed.

  The refrigerant flowing into the use side heat exchanger 15 absorbs heat from the blown air blown from the blower fan 15a and evaporates. Thereby, blowing air is cooled and cooling of a vehicle interior is implement | achieved. Subsequent operations are the same as those in the first embodiment.

  As described above, according to the refrigeration cycle 50 of the present embodiment, in the cooling operation mode, a normal refrigeration cycle in which the first compressor 11 and the second compressor 12 are connected in parallel is configured, and cooling of the vehicle interior is performed. Realized. Therefore, also in the refrigerating cycle 50 of this embodiment, the same effect as the refrigerating cycle 10 of 1st Embodiment can be acquired.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention.

  (1) Although the specific configuration of the first and second four-way valves 13 and 14 is not mentioned in the above-described embodiment, as the first and second four-way valves 13 and 14, for example, a rotary valve is rotated. A single valve configured to switch the refrigerant circuit may be employed, or the above-described refrigerant circuit switching function may be exhibited by combining a plurality of on-off valves (electromagnetic valves) or three-way valves. You may employ | adopt what was comprised by.

  (2) In the above embodiment, the example in which the heating operation mode and the cooling operation mode are switched based on the target temperature Tset and the outside air temperature Tam has been described. However, the switching between the heating operation mode and the cooling operation mode is performed. It is not limited to this. For example, a heating / cooling switching switch for switching between the heating operation mode and the cooling operation mode may be provided on the operation panel, and the heating operation mode and the cooling operation mode may be switched based on an operation signal of the switch.

  (3) Although the defrosting operation is not mentioned in the fourth embodiment described above, of course, the bypass passage 26 and the on-off valve 27 similar to those of the second embodiment are provided for the refrigeration cycle 50 of the fourth embodiment. In addition, the operation in the defrosting operation mode may be realized. Furthermore, the same bypass passage 26, on-off valve 27, and auxiliary use side heat exchanger 28 as those in the third embodiment may be added so that the operation in the defrosting operation mode can be realized.

  (4) In the above-described embodiment, the example in which the refrigeration cycle 10 of the present invention is applied to a vehicle air conditioner for buses has been described. However, the application of the present invention is not limited to this. For example, the present invention may be applied to a cold storage container such as a stationary air conditioner, a cold storage container, and a moving body (vehicle, ship). Furthermore, the present invention is effective when applied to a refrigeration cycle apparatus in which the compression ratio of the entire cycle in the heating operation mode is higher than the compression ratio of the entire cycle in the cooling operation mode.

  (5) In the above-described embodiment, the example in which the check valve 25 is employed as the valve means that only allows the refrigerant to flow from the first four-way valve 13 side to the outdoor heat exchanger 21 side has been described. Is not limited to this.

  For example, instead of the check valve 25, an on-off valve constituted by an electromagnetic valve is adopted, and the refrigerant that connects the first four-way valve 13 and the outdoor heat exchanger 21 when the air conditioning control device is in the heating operation mode. In the cooling operation mode, the operation of the on-off valve may be controlled so that the refrigerant passage connecting the first four-way valve 13 and the outdoor heat exchanger 21 is opened in the cooling operation mode.

11a, 12a 1st, 2nd compression mechanism 13, 14 1st, 2nd four-way valve 15 Use side heat exchanger 16 1st branch part 17 Intermediate pressure expansion valve 18 Internal heat exchanger 20 Low pressure expansion valve 21 Outdoor heat exchanger 25 Check valve 26 Bypass passage 27 Open / close valve 28 Auxiliary use side heat exchanger 29 Gas-liquid separator 31 Intermediate pressure open / close valve

Claims (8)

First and second compression mechanisms (11a, 12a) for compressing and discharging the refrigerant;
A use side heat exchanger (15) for exchanging heat between the refrigerant and the fluid to be heat exchanged;
Decompression means (17, 20) for decompressing the refrigerant;
An outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air;
Refrigerant circuit switching means (13, 14, 27, 31) for switching between a refrigerant circuit in a cooling operation mode for cooling the fluid for heat exchange and a refrigerant circuit in a heating operation mode for heating the fluid for heat exchange ;
A branching section (16) for branching the flow of the refrigerant flowing out of the use side heat exchanger (15) during the heating operation mode ;
The decompression means (17, 20) includes a first decompression means (17) for decompressing one refrigerant branched at the branch section (16) and a second refrigerant branched at the branch section (16). A second pressure reducing means (20) for reducing the pressure;
The refrigerant circuit switching means (13... 31)
During the heating operation mode, the refrigerant decompressed by the first decompression means (17) is merged with the refrigerant discharged from the first compression mechanism (11a) and sucked into the second compression mechanism (12a), The refrigerant discharged from the second compression mechanism (12a) dissipates heat in the use side heat exchanger (15), and further flows out of the use side heat exchanger (15) to the branch portion (16). the other refrigerant branched Te flowed into the second pressure reducing means (20), the refrigerant reduced in pressure by the second pressure reducing means (20) is evaporated in the outdoor heat exchanger (21), the outdoor The refrigerant flowing out of the heat exchanger (21) is sucked into the first compression mechanism (11a), so that the first compression mechanism (11a) and the second compression mechanism (12a) are always connected in series. Switch to the refrigerant circuit
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21). is further the outdoor heat exchanger the refrigerant flowing out of (21) to flow into the second pressure reducing means (20), said use side heat exchanger refrigerant reduced in pressure by the second pressure reducing means (20) Refrigeration characterized by switching to a refrigerant circuit that evaporates in (15) and flows out of the usage-side heat exchanger (15) into both the first and second compression mechanisms (11a, 12a). cycle. An internal heat exchanger (18) for exchanging heat between the refrigerant depressurized by the first depressurization means (17) and the other refrigerant branched by the branching section (16) in the heating operation mode; The refrigeration cycle according to claim 1 . First and second compression mechanisms (11a, 12a) for compressing and discharging the refrigerant;
A use side heat exchanger (15) for exchanging heat between the refrigerant and the fluid to be heat exchanged;
Decompression means (17, 20) for decompressing the refrigerant;
An outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air;
Refrigerant circuit switching means (13, 14, 27, 31) for switching between a refrigerant circuit in a cooling operation mode for cooling the fluid for heat exchange and a refrigerant circuit in a heating operation mode for heating the fluid for heat exchange;
The depressurizing means depressurizes the refrigerant flowing into the first heat depressing means (17) and the outdoor heat exchanger (21) for depressurizing the refrigerant flowing out from the use side heat exchanger (15) in the heating operation mode. Comprising a second pressure reducing means (20),
Furthermore, a gas-liquid separation means (29) for separating the gas-liquid of the refrigerant decompressed by the first decompression means (17) during the heating operation mode,
The refrigerant circuit switching means (13... 31)
During the heating operation mode, the gas-phase refrigerant separated by the gas-liquid separation means (29) is merged with the refrigerant discharged from the first compression mechanism (11a) and sucked into the second compression mechanism (12a). The refrigerant discharged from the second compression mechanism (12a) is radiated by the use side heat exchanger (15), and the refrigerant flowing out of the use side heat exchanger (15) is further reduced to the first pressure reduction. The refrigerant that has flowed into the means (17 ) and has been decompressed by the first decompression means (17) flows into the gas-liquid separation means (29), and has been separated by the gas-liquid separation means (29). The refrigerant flows into the second decompression means (20), the refrigerant decompressed by the second decompression means ( 20) is evaporated by the outdoor heat exchanger (21), and the outdoor heat exchanger (21). The refrigerant flowing out of the first compression mechanism (11a) It is, switching the refrigerant circuit in a state in which the first compression mechanism (11a) and the second compression mechanism and (12a) is always serially connected,
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21). Furthermore, the refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the gas-liquid separation means (29) through the second decompression means (20), and in the gas-liquid separation means (29) The separated liquid phase refrigerant is depressurized by the first depressurizing means (17 ), the refrigerant depressurized by the first depressurizing means (17 ) is evaporated by the use side heat exchanger (15), A refrigeration cycle, wherein the refrigerant circuit that switches the refrigerant flowing out of the use side heat exchanger (15) to the both first and second compression mechanisms (11a, 12a) is switched to a refrigerant circuit. First and second compression mechanisms (11a, 12a) for compressing and discharging the refrigerant;
A use side heat exchanger (15) for exchanging heat between the refrigerant and the fluid to be heat exchanged;
Decompression means (17, 20) for decompressing the refrigerant;
An outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air;
Refrigerant circuit switching means (13, 14, 27, 31) for switching between a refrigerant circuit in a cooling operation mode for cooling the fluid for heat exchange and a refrigerant circuit in a heating operation mode for heating the fluid for heat exchange;
The refrigerant circuit switching means (13... 31)
During the heating operation mode, the refrigerant discharged from the first compression mechanism (11a) is sucked into the second compression mechanism (12a), and the refrigerant discharged from the second compression mechanism (12a) is used as the use side heat. The heat is radiated by the exchanger (15), and the refrigerant flowing out from the use side heat exchanger (15) is caused to flow into the pressure reducing means (17, 20), and the pressure is reduced by the pressure reducing means (17, 20). The refrigerant is evaporated in the outdoor heat exchanger (21), and the refrigerant flowing out of the outdoor heat exchanger (21) is switched to a refrigerant circuit for sucking into the first compression mechanism (11a),
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21). Furthermore, the refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is used as the utilization side heat exchanger. (15) is switched to a refrigerant circuit that evaporates the refrigerant and flows out of the use side heat exchanger (15) into both the first and second compression mechanisms (11a, 12a) ,
And a bypass passage (26) for allowing the refrigerant flowing out of the outdoor heat exchanger (21) to flow around the use side heat exchanger (15).
The refrigerant circuit switching means (13... 31) has a function of switching to a refrigerant circuit in a defrosting operation mode for removing frost attached to the outdoor heat exchanger (21), and in the defrosting operation mode, Both the refrigerant discharged from the compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21), and the outdoor heat exchanger (21 ) Is switched to a refrigerant circuit for sucking the refrigerant flowing out from the first and second compression mechanisms (11a, 12a) through the bypass passage (26) . First and second compression mechanisms (11a, 12a) for compressing and discharging the refrigerant;
A use side heat exchanger (15) for exchanging heat between the refrigerant and the fluid to be heat exchanged;
Decompression means (17, 20) for decompressing the refrigerant;
An outdoor heat exchanger (21) for exchanging heat between the refrigerant and the outside air;
Refrigerant circuit switching means (13, 14, 27, 31) for switching between a refrigerant circuit in a cooling operation mode for cooling the fluid for heat exchange and a refrigerant circuit in a heating operation mode for heating the fluid for heat exchange;
The refrigerant circuit switching means (13... 31)
During the heating operation mode, the refrigerant discharged from the first compression mechanism (11a) is sucked into the second compression mechanism (12a), and the refrigerant discharged from the second compression mechanism (12a) is used as the use side heat. The heat is radiated by the exchanger (15), and the refrigerant flowing out from the use side heat exchanger (15) is caused to flow into the pressure reducing means (17, 20), and the pressure is reduced by the pressure reducing means (17, 20). The refrigerant is evaporated in the outdoor heat exchanger (21), and the refrigerant flowing out of the outdoor heat exchanger (21) is switched to a refrigerant circuit for sucking into the first compression mechanism (11a),
In the cooling operation mode, both the refrigerant discharged from the first compression mechanism (11a) and the refrigerant discharged from the second compression mechanism (12a) are radiated by the outdoor heat exchanger (21). Furthermore, the refrigerant that has flowed out of the outdoor heat exchanger (21) is caused to flow into the decompression means (17, 20), and the refrigerant decompressed by the decompression means (17, 20) is used as the utilization side heat exchanger. (15) is switched to a refrigerant circuit that evaporates the refrigerant and flows out of the use side heat exchanger (15) into both the first and second compression mechanisms (11a, 12a) ,
Furthermore, an auxiliary use side heat exchanger (28) for exchanging heat between the refrigerant discharged from the first compression mechanism (11a) and the heat exchange target fluid;
A bypass passage (26) for flowing the refrigerant discharged from the second compression mechanism (12a) by bypassing the use side heat exchanger (15),
The refrigerant circuit switching means (13... 31) has a function of switching to a refrigerant circuit in a defrosting operation mode for removing frost attached to the outdoor heat exchanger (21), and in the defrosting operation mode, The refrigerant discharged from the compression mechanism (11a) is sucked into the second compression mechanism (12a) via the auxiliary use side heat exchanger (28), and the refrigerant discharged from the second compression mechanism (12a) is discharged. A refrigeration cycle, wherein the refrigerant circuit is switched to a refrigerant circuit that releases heat by flowing into the outdoor heat exchanger (21) through the bypass passage (26) . The refrigeration cycle according to any one of claims 1 to 5 , wherein the refrigerant discharge capacities of the first and second compression mechanisms (11a, 12a) are configured to be controllable independently of each other. . The refrigerant circuit switching means is configured to have at least first and second four-way valves (13, 14),
The first four-way valve (13) connects at least the first compression mechanism (11a) outlet side and the outdoor heat exchanger (21) during the cooling operation mode, and at least during the heating operation mode, Connecting the discharge port side of the first compression mechanism (11a) and the suction port side of the second compression mechanism (12a);
The second four-way valve (14) connects at least the discharge side of the second compression mechanism (12a) and the outdoor heat exchanger (21) in the cooling operation mode, and at least in the heating operation mode. The refrigeration cycle according to any one of claims 1 to 6 , wherein a discharge port side of the second compression mechanism (12a) and the use side heat exchanger are connected. Further, in the refrigerant path connecting the first four-way valve (13) and the outdoor heat exchanger (21), the refrigerant flows from the first four-way valve (13) side to the outdoor heat exchanger (21) side. 8. A refrigeration cycle according to claim 7 , characterized in that valve means (25) allowing only flow is arranged.

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