JPWO2013005424A1 - Refrigeration cycle equipment - Google Patents

Abstract

  The refrigeration cycle apparatus (100) includes an upstream throttle device (14, 18), a gas-liquid separator (16), a refrigerant circuit (1) including a downstream throttle device (18, 14), an injection path (22), And a control device (30). A heater (24) is provided in the injection path (22). The control device (30) causes the temperature difference between the gas-liquid separation temperature detected by the intermediate pressure temperature sensor (26) and the injection temperature detected by the superheat degree temperature sensor (28) to be smaller than a predetermined value. After adjusting the opening of at least one of the upstream throttling device and the downstream throttling device, the intermediate pressure control for increasing the opening of the downstream throttling device until the gas-liquid separation temperature decreases by a predetermined temperature from the temperature at that time Do the driving.

Description

  The present invention relates to a refrigeration cycle apparatus used in a water heater, a hot water heater, an air conditioner, or the like.

  Conventionally, there has been known a refrigeration cycle apparatus having a compressor, a four-way valve, an indoor heat exchanger, an indoor expansion device, a gas-liquid separator, an outdoor expansion device, and an outdoor heat exchanger capable of switching between cooling and heating. ing. For example, Patent Document 1 discloses a refrigeration cycle apparatus 500 as shown in FIG.

  In the refrigeration cycle apparatus 500, the compressor 501 is connected to the indoor heat exchanger 512 and the outdoor heat exchanger 520 via a four-way valve 532, and the indoor heat exchanger 512 and the outdoor heat exchanger 520 are connected to the indoor side throttle. The device 514, the gas-liquid separator 516, and the outdoor expansion device 518 are connected. In addition, an injection path 522 is provided between the gas-liquid separator 516 and the compressor 510 to supply the intermediate-pressure gas refrigerant separated by the gas-liquid separator 516 to the compressor 510. Furthermore, the refrigeration cycle apparatus 500 includes heat exchange temperature sensors 544 and 546 that detect the condensation temperature and evaporation temperature of the refrigerant, and refrigerant in the gas-liquid separator 516 in order to control the intermediate pressure to be a target value. An intermediate pressure temperature sensor 526 for detecting an intermediate pressure temperature that is the temperature of

  The operation of the refrigeration cycle apparatus 500 configured as described above will be described below. When heating is performed, the refrigerant discharged from the compressor 510 passes through the four-way valve 532 and then exchanges heat in the indoor heat exchanger 512 and is reduced from high pressure to intermediate pressure by the indoor expansion device 514. The intermediate pressure refrigerant is separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 516, and the intermediate pressure gas refrigerant is supplied to the compressor 510 through the injection path 522. On the other hand, the intermediate-pressure liquid refrigerant is further depressurized by the outdoor expansion device 518, and the depressurized low-pressure refrigerant exchanges heat in the outdoor heat exchanger 520, passes through the four-way valve 532, and is sucked into the compressor 510. The When performing cooling, the refrigerant discharged from the compressor 510 passes through the four-way valve 532, and then performs heat exchange in the outdoor heat exchanger 520, and is reduced from high pressure to intermediate pressure by the outdoor expansion device 518. The intermediate pressure refrigerant is separated into a gas refrigerant and a liquid refrigerant by the gas-liquid separator 516, and the intermediate pressure gas refrigerant is supplied to the compressor 510 through the injection path 522. On the other hand, the intermediate-pressure liquid refrigerant is further depressurized by the indoor expansion device 514, and the depressurized low-pressure refrigerant performs heat exchange in the indoor heat exchanger 512, passes through the four-way valve 532, and is then sucked into the compressor 510. The

  Further, in refrigeration cycle apparatus 500, control device 530 determines a target intermediate pressure temperature based on the condensation temperature and evaporation temperature detected by heat exchange temperature sensors 544 and 546, and is detected by intermediate pressure temperature sensor 526. The opening degree of the expansion device (outdoor expansion device 516 during heating and indoor expansion device 514 during cooling) positioned downstream of the gas-liquid separator 516 is adjusted so that the intermediate pressure temperature becomes the target intermediate pressure temperature. Is done.

Japanese Patent No. 3317170

  Incidentally, the refrigeration cycle apparatus 500 shown in FIG. 9 leaves room for further efficiency improvement. In view of such circumstances, the present disclosure aims to improve the efficiency of the refrigeration cycle apparatus.

  In the present disclosure, a refrigerant is circulated through a compressor, a condenser, an upstream throttle device, a gas-liquid separator, a downstream throttle device, and an evaporator in this order, and the gas-liquid separator separates the refrigerant. An intermediate pressure for detecting a gas-liquid separation temperature which is a temperature of a refrigerant flowing from the refrigerant circuit into the injection path, an injection path for supplying the gas refrigerant to the compressor, a heater provided in the injection path The temperature difference between the temperature sensor, the superheat degree temperature sensor that detects the injection temperature that is the temperature of the refrigerant heated by the heater in the injection path, and the temperature difference between the gas-liquid separation temperature and the injection temperature is greater than a predetermined value. After adjusting the opening degree of at least one of the upstream throttle device and the downstream throttle device so that the Temperature and a control unit for performing intermediate pressure control operation to increase the opening of the downstream-side throttle device from temperature to be smaller by a predetermined temperature at that time, to provide a refrigeration cycle device.

  According to the above configuration, the reference temperature of the gas-liquid separation temperature is determined using the heater and the superheat degree temperature sensor, and a temperature lower than the reference temperature by a predetermined temperature is set as the target temperature of the gas-liquid separation temperature. The measurement error of the pressure temperature sensor can be canceled. Thereby, the intermediate pressure can be controlled to a target value with higher accuracy, and the efficiency of the refrigeration cycle apparatus can be improved.

The block diagram of the refrigerating-cycle apparatus which concerns on 1st Embodiment of this invention. The flowchart which shows the control method of the intermediate pressure control driving | operation in 1st Embodiment. The graph which shows the change of the opening degree of an upstream throttle device and a downstream throttle device in 1st Embodiment, and the change of discharge temperature, injection temperature, and gas-liquid separation temperature. The figure which shows the heater which concerns on one modification Configuration diagram of refrigeration cycle apparatus according to another modification Furthermore, the block diagram of the refrigerating-cycle apparatus which concerns on another modification The block diagram of the refrigerating-cycle apparatus which concerns on 2nd Embodiment of this invention. The flowchart which shows the control method of the intermediate pressure control driving | operation in 2nd Embodiment. Configuration diagram of conventional refrigeration cycle equipment

  In the refrigeration cycle apparatus 500 shown in FIG. 9, the intermediate pressure of the refrigerant supplied from the gas-liquid separator 516 to the compressor 510 through the injection path 522 is based on the temperature detected by the three temperature sensors 544, 546, 526. Therefore, the accuracy variation of the temperature sensor becomes a problem. A commonly used temperature sensor has a measurement error of at least ± 1.5 ° C. When control is performed using a plurality of temperature sensors as in the refrigeration cycle apparatus 500 shown in FIG. 9, measurement errors are accumulated as many as the number of temperature sensors (when one is ± 1.5 ° C., three are used. In case of ± 4.5 ° C). For this reason, the actually controlled intermediate pressure deviates from the target value, which may reduce the efficiency of the refrigeration cycle apparatus.

  A first aspect of the present disclosure includes a refrigerant circuit that circulates refrigerant so as to pass through a compressor, a condenser, an upstream throttle device, a gas-liquid separator, a downstream throttle device, and an evaporator in this order, and the gas-liquid An injection path for supplying the gas refrigerant separated by the separator to the compressor, a heater provided in the injection path, and a gas-liquid separation temperature which is a temperature of the refrigerant flowing from the refrigerant circuit into the injection path. An intermediate pressure temperature sensor to detect, a superheat temperature sensor to detect an injection temperature, which is a temperature of the refrigerant heated by the heater in the injection path, and a temperature difference between the gas-liquid separation temperature and the injection temperature After adjusting the opening of at least one of the upstream throttle device and the downstream throttle device so that is smaller than a predetermined value, Kiki liquid separation temperature and a control unit for performing intermediate pressure control operation to increase the opening of the downstream-side throttle device from temperature to be smaller by a predetermined temperature at that time, to provide a refrigeration cycle device.

  In addition to the first aspect, the second aspect of the present disclosure further includes a post-condensation temperature sensor that detects a condensation side outlet temperature that is a temperature of the refrigerant flowing out of the condenser, and the control device includes the intermediate pressure control. During operation, the gas-liquid separation temperature and the condensation side outlet temperature when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value are used in steady operation. Provided is a refrigeration cycle apparatus that corrects a calculation formula for a gas-liquid separation temperature.

  According to the second aspect, during the intermediate pressure control operation, the gas-liquid separation temperature and the condensation side outlet temperature when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value are used. Thus, the calculation formula for the gas-liquid separation temperature used in steady operation can be corrected.

  The third aspect of the present disclosure further includes, in addition to the second aspect, a pre-evaporation temperature sensor that detects an evaporation side inlet temperature that is a temperature of the refrigerant flowing into the evaporator, and the control device is used in a steady operation. When correcting the calculation formula of the gas-liquid separation temperature to be used, the refrigeration also uses the evaporation side inlet temperature when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value. A cycle device is provided.

  According to the third aspect, the gas-liquid separation temperature, the condensation side outlet temperature, and the evaporation side when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value during the intermediate pressure control operation. Using the inlet temperature, the calculation formula for the gas-liquid separation temperature used in steady operation can be corrected.

  In a fourth aspect of the present disclosure, in addition to the second aspect or the third aspect, the control device performs a steady operation using a calculation formula of a gas-liquid separation temperature corrected during the intermediate pressure control operation. A cycle device is provided.

  According to the fourth aspect, it is possible to perform the intermediate pressure control with higher accuracy in consideration of the measurement error of the temperature sensor in the steady operation.

  According to a fifth aspect of the present disclosure, in addition to any one of the first to fourth aspects, the control device provides a refrigeration cycle device that performs the intermediate pressure control operation during a start-up operation.

  According to the fifth aspect, the refrigeration cycle apparatus can shift from the startup operation to the steady operation in an optimum state.

  According to a sixth aspect of the present disclosure, in addition to any one of the first to fifth aspects, the control device provides a refrigeration cycle apparatus that performs the intermediate pressure control operation during a steady operation.

  According to the sixth aspect, the intermediate pressure control operation is performed even during the steady operation, and the intermediate pressure is controlled to the target value with higher accuracy.

  In addition to the fifth aspect, the seventh aspect of the present disclosure further includes a discharge temperature sensor that detects a discharge temperature that is a temperature of the refrigerant discharged from the compressor, and the control device is configured so that the discharge temperature is a target. The downstream throttle device is adjusted until the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value while adjusting the opening of the upstream throttle device so as to be maintained near the discharge temperature. A refrigerating cycle device is provided in which the opening degree of the downstream side throttle device is reduced and then the opening degree of the downstream side throttle device is increased.

  According to the seventh aspect, simple control can be realized by controlling the discharge temperature by the upstream throttle device and controlling the gas-liquid separation temperature by the downstream throttle device.

  In an eighth aspect of the present disclosure, in addition to any one of the first to seventh aspects, the refrigerant circuit includes an indoor heat exchanger and an outdoor heat exchanger that function as the condenser and the evaporator. A refrigeration cycle including an indoor throttle device and an outdoor throttle device functioning as the upstream throttle device and the downstream throttle device, and the refrigerant circuit is provided with a four-way valve that switches a flow direction of the refrigerant. Providing equipment.

  According to the eighth aspect, a refrigeration cycle apparatus capable of switching between cooling and heating is realized.

  A ninth aspect of the present disclosure provides the refrigeration cycle apparatus, in addition to any one of the first to eighth aspects, the heater is an electric heater.

  According to the ninth aspect, since the on-off control of the electric heater is easy, the refrigerant flowing through the injection path can be heated only when the refrigerant flowing through the injection path needs to be heated.

  In a tenth aspect of the present disclosure, in addition to any one of the first to eighth aspects, the heater accumulates heat discharged from the compressor, and uses the accumulated heat. Provided is a refrigeration cycle apparatus which is a heat storage unit for heating a refrigerant.

  According to the tenth aspect, the refrigerant flowing through the injection path is heated using the exhaust heat of the compressor.

  In an eleventh aspect of the present disclosure, in addition to any one of the first to eighth aspects, the heater flows through the refrigerant circuit and a first heat exchange unit to which a refrigerant flowing through the injection path is guided. A heat exchanger including a second heat exchanging part to which a refrigerant having a temperature higher than the gas-liquid separation temperature is guided, wherein the second heat exchanging part heats the first heat exchanging part in the heat exchanger. A refrigeration cycle apparatus is provided.

  According to the 11th aspect, the refrigerant | coolant which flows through an injection path | route is heated using the heat | fever which the refrigerant | coolant which flows through a refrigerant circuit has.

  According to a twelfth aspect of the present disclosure, in addition to the eleventh aspect, a refrigeration cycle apparatus is provided in which a refrigerant flowing between the compressor and the condenser is guided to the second heat exchange unit.

  According to the 12th aspect, the refrigerant | coolant which flows through an injection path | route is heated using the heat which the comparatively high-temperature refrigerant | coolant which flows through a refrigerant circuit has.

  According to a thirteenth aspect of the present disclosure, in addition to the eleventh aspect, a refrigeration cycle apparatus is provided in which a refrigerant flowing between the condenser and the upstream expansion device is guided to the second heat exchange unit.

  According to the thirteenth aspect, the refrigerant flowing through the injection path 22 is heated using the heat of the refrigerant flowing through the refrigerant circuit. Moreover, since the supercooling degree of the refrigerant | coolant of the condenser exit side of a refrigerant circuit increases, the capability of a refrigerating-cycle apparatus improves.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description relates to an example of the present invention, and the present invention is not limited to these.

(First embodiment)
FIG. 1 illustrates a refrigeration cycle apparatus 100 according to the first embodiment of the present disclosure. The refrigeration cycle apparatus 100 includes a refrigerant circuit 1 that circulates refrigerant and a control device 30.

  The refrigerant circuit 1 includes a compressor 10, a four-way valve 32, an indoor heat exchanger 12, an indoor expansion device 14, a gas-liquid separator 16, an outdoor expansion device 18, and an outdoor heat exchanger 20. The four ports of the four-way valve 32 are connected to the inlet and outlet of the compressor 10, the indoor heat exchanger 12, and the outdoor heat exchanger 20 by refrigerant piping. Moreover, the indoor heat exchanger 12, the indoor side expansion device 14, the gas-liquid separator 16, the outdoor expansion device 18, and the outdoor heat exchanger 20 are connected in series by refrigerant piping.

  The four-way valve 32 switches the flow direction of the refrigerant to the first direction indicated by the solid line arrow during heating, and switches to the second direction indicated by the broken line arrow during cooling. In the first direction, the discharge port of the compressor 10 is connected to the indoor heat exchanger 12, and the suction port of the compressor 10 is connected to the outdoor heat exchanger 20. In the second direction, the discharge port of the compressor 10 is connected to the outdoor heat exchanger 20, and the suction port of the compressor 10 is connected to the outdoor heat exchanger 12. That is, the refrigerant circulating in the refrigerant circuit 1 passes through the compressor 10, the indoor heat exchanger 12, the indoor expansion device 14, the gas-liquid separator 16, the outdoor expansion device 18 and the outdoor heat exchanger 20 in this order during heating. During cooling, the compressor 10, the outdoor heat exchanger 20, the outdoor expansion device 18, the gas-liquid separator 16, the indoor expansion device 14, and the indoor heat exchanger 12 are passed in this order.

  The indoor heat exchanger 12 functions as a condenser during heating and functions as an evaporator during cooling. On the other hand, the outdoor heat exchanger 20 functions as an evaporator during heating, and functions as a condenser during heating.

  As the indoor side expansion device 14 and the outdoor side expansion device 18, for example, an electric expansion valve capable of adjusting the opening degree is used. The control device 30 sends control signals to the indoor expansion device 14 and the outdoor expansion device 18 to adjust their opening degrees.

  An injection path 22 is provided between the gas-liquid separator 16 and the compressor 10 to supply the intermediate-pressure gas refrigerant separated by the gas-liquid separator 16 to the compressor 10. The injection path 22 is constituted by, for example, a refrigerant pipe having one end connected to the gas layer side of the gas-liquid separator 16 and the other end connected to an intermediate pressure inlet opening in the compression chamber of the compressor 10 during the compression process. . A heater 24 is provided in the middle of the injection path 22, and the intermediate-pressure gas refrigerant flowing through the injection path 22 is heated and then injected into the compressor 10.

  As the heater 24, for example, a heater, that is, an electric heater can be used. Examples of the electric heater include a resistance heater and an induction heater. The heater 24 does not necessarily need to constantly heat the refrigerant flowing through the injection path 22. For example, the heater 24 heats the refrigerant flowing through the injection path 22 only during an intermediate pressure control operation described later by on / off control of the electric heater. Also good.

Further, the refrigeration cycle apparatus 100 includes a discharge temperature sensor 34 that detects a discharge temperature Td that is a temperature of refrigerant discharged from the compressor 10, an outdoor temperature sensor 36 that detects an outdoor temperature To, and an indoor temperature Ti. An indoor temperature sensor 38 that detects the gas-liquid separation temperature Tm that is the temperature of the refrigerant flowing into the injection path 22 from the refrigerant circuit 1, and the refrigerant heated by the heater 24 in the injection path 22 A superheat temperature sensor 28 that detects an injection temperature Tinj, which is a temperature, is provided. The control device 30 mainly controls the opening degree of the indoor expansion device 14 and the outdoor expansion device 18 and the rotation speed of the compressor 10 based on the temperatures detected by various temperature sensors.

  The intermediate pressure temperature sensor 26 may be provided in the gas-liquid separator 16 or may be provided upstream of the heater 24 of the refrigerant pipe that constitutes the injection path 22. Alternatively, the intermediate pressure temperature sensor 26 may be provided in a refrigerant pipe connecting the gas-liquid separator 16 and the indoor expansion device 14 or a refrigerant pipe connecting the gas-liquid separator 16 and the outdoor expansion device 18. Good. The superheat degree temperature sensor 28 is provided on the downstream side of the heater 24 of the refrigerant pipe constituting the injection path 22.

  Next, the operation of the refrigeration cycle apparatus 100 will be described.

  During heating, the four-way valve 32 switches the refrigerant flow direction to the first direction indicated by the solid line arrow. In this state, the refrigerant compressed by the compressor 10 is guided from the compressor 10 to the indoor heat exchanger 12 after being discharged from the compressor 10. The refrigerant guided to the indoor heat exchanger 12 is guided to the indoor expansion device 14 after radiating heat to the indoor air. The refrigerant guided to the indoor expansion device 14 is depressurized by the indoor expansion device 14, becomes an intermediate pressure refrigerant having an intermediate pressure between the condensation pressure and the evaporation pressure, and is guided to the gas-liquid separator 16. The intermediate-pressure refrigerant guided to the gas-liquid separator 16 is separated by the gas-liquid separator 16, the liquid refrigerant of the intermediate-pressure refrigerant is guided to the outdoor expansion device 18, and the gas refrigerant flows into the injection path 22. The intermediate-pressure liquid refrigerant guided to the outdoor expansion device 18 is depressurized by the outdoor expansion device 18, guided to the outdoor heat exchanger 20, absorbs heat from outdoor air, and then returns to the compressor 10. The intermediate-pressure gas refrigerant that has flowed into the injection path 22 is heated by the heater 24 and then injected into the compressor 10.

  During cooling, the four-way valve 32 switches the refrigerant flow direction to the second direction indicated by the dashed arrow. In this state, the refrigerant compressed by the compressor 10 is discharged from the compressor 10 and then guided to the outdoor heat exchanger 20. The refrigerant guided to the outdoor heat exchanger 20 is guided to the outdoor expansion device 18 after radiating heat to the outdoor air. The refrigerant guided to the outdoor expansion device 18 is depressurized by the outdoor expansion device 18, becomes an intermediate pressure refrigerant having a pressure intermediate between the condensation pressure and the evaporation pressure, and is guided to the gas-liquid separator 16. The intermediate-pressure refrigerant guided to the gas-liquid separator 16 is separated by the gas-liquid separator 16, the liquid refrigerant of the intermediate-pressure refrigerant is guided to the indoor expansion device 14, and the gas refrigerant flows into the injection path 22. The intermediate-pressure liquid refrigerant guided to the indoor expansion device 14 is decompressed by the indoor expansion device 14, guided to the indoor heat exchanger 12, absorbs heat from the indoor air, and then returns to the compressor 10. The intermediate-pressure gas refrigerant that has flowed into the injection path 22 is heated by the heater 24 and then injected into the compressor 10.

  Although the flow direction of the refrigerant in the refrigerant circuit 1 is different between the heating time and the cooling time, the refrigerant flows in the same direction in the injection path 22, and therefore, the same method is used for controlling the intermediate pressure between the heating time and the cooling time. Can be used. Below, the indoor heat exchanger 12 during heating and the outdoor heat exchanger 20 during cooling are condensers, the outdoor heat exchanger 20 during heating and the indoor heat exchanger 12 during cooling are evaporators, and the indoor side during heating The expansion device 14 and the outdoor expansion device 18 at the time of cooling are referred to as an upstream expansion device, the outdoor expansion device 18 at the time of heating and the indoor expansion device 14 at the time of cooling are referred to as a downstream expansion device. Explain without distinction.

  In the present embodiment, the control device 30 performs the intermediate pressure control operation during the startup operation. The intermediate pressure control operation is such that the temperature difference between the gas-liquid separation temperature Tm detected by the intermediate pressure temperature sensor 26 and the injection temperature Tinj detected by the superheat temperature sensor 28 is smaller than a predetermined value ΔTi. After adjusting the opening degree of at least one of the upstream side throttle device and the downstream side throttle device, the opening degree of the downstream side throttle device is increased until the gas-liquid separation temperature Tm decreases from the temperature at that time by a predetermined temperature ΔTm. is there. Hereinafter, the intermediate pressure control operation performed by the control device 30 will be described in detail with reference to the flowchart of FIG.

  First, the control device 30 adjusts the opening of the upstream throttle device so that the discharge temperature Td detected by the discharge temperature sensor 34 is kept close to the target discharge temperature TD, and the gas-liquid separation temperature Tm and the injection are adjusted. The opening degree of the downstream side expansion device is reduced until the temperature difference from the temperature Tinj becomes smaller than the predetermined value ΔTi.

  Specifically, the control device 30 detects the outdoor temperature To by the outdoor temperature sensor 36, and detects the indoor temperature Ti by the indoor temperature sensor 38 (step S1). Next, the control device 30 determines a target discharge temperature TD based on the detected outdoor temperature To and indoor temperature Ti (step S2). Thereafter, the control device 30 detects the discharge temperature Td by the discharge temperature sensor 34 (step S3), and sets the difference between this and the target discharge temperature Td to a predetermined allowable value ΔTd (for example, 1.5 ° C.). Compare (step S4).

  If the difference between the detected discharge temperature Td and the target discharge temperature TD is equal to or greater than the allowable value ΔTd (NO in step S4), the control device 30 adjusts the opening degree of the upstream throttle device (step S5). Specifically, when the detected discharge temperature Td is lower than the target discharge temperature TD, the control device 30 reduces the opening degree of the upstream throttle device, and the detected discharge temperature Td is the target discharge temperature. When it is higher than TD, the opening degree of the upstream throttle device is increased. After step S5, the process returns to step S1. By repeating Steps S1 to S5, the actual discharge temperature Td approaches the predetermined temperature of the target discharge temperature TD. As a result, if the difference between the detected discharge temperature Td and the target discharge temperature TD is less than the allowable value ΔTd (YES in step S4), the process proceeds to step S6.

  In step S6, the control device 30 detects the gas-liquid separation temperature Tm of the intermediate pressure refrigerant with the intermediate pressure temperature sensor 26, and detects the injection temperature Tinj of the refrigerant after passing through the heater 24 with the superheat temperature sensor 28. (Step S6). Next, the control device 30 determines whether or not the temperature difference between the gas-liquid separation temperature Tm and the injection temperature Tinj is smaller than a predetermined value ΔTi (for example, 3 ° C.) (step S7).

  The temperature difference between the gas-liquid separation temperature Tm and the injection temperature Tinj is the degree of superheat of the gas refrigerant to be injected. Conventionally, since the heater 24 is not provided in the injection path 22, the superheat degree is not taken for the intermediate-pressure gas refrigerant to be injected. On the other hand, in this embodiment, by providing the heater 24 in the injection path 22, as long as only the gas refrigerant flows through the injection path 22, the intermediate-pressure gas refrigerant after passing through the heater 24 has a superheat degree. Will be taken.

  If NO in step S7, that is, if the degree of superheat is equal to or higher than a certain temperature, the control device 30 decreases the opening of the downstream side expansion device (step S8) and increases the gas-liquid separation temperature Tm. After step S8, the process returns to step S1. Control device 30 repeats steps S1 to S8 until YES is obtained in step S7.

  As the opening degree of the downstream throttle device is reduced, the pressure difference between the front and rear of the downstream throttle device increases, and the intermediate pressure increases accordingly. In addition, the ratio of the flow rate of the injected refrigerant increases. As the intermediate pressure increases, the dryness of the intermediate pressure refrigerant in the gas-liquid separator 16 decreases. If the opening degree of the downstream side throttle device is kept small as described above, the dryness will continue to decrease and the flow rate of the injected refrigerant will continue to increase, so that the liquid refrigerant flows into the injection path 22 at a certain stage.

  When the liquid refrigerant flows into the injection path 22, the liquid refrigerant is evaporated by being heated by the heater 24, and hence the injection temperature Tinj of the refrigerant after passing through the heater 24 is rapidly lowered by the latent heat at that time. Step S7 is a step for detecting that the injection temperature Tinj has rapidly decreased.

  In the case of YES in step S7, that is, when the injection temperature Tinj is suddenly lowered and the superheat degree of the gas refrigerant after passing through the heater 24 can no longer be higher than a certain temperature, the control device 30 The liquid separation temperature Tm is recorded as Tm0 (step S9).

  By increasing the intermediate pressure, the amount of work to be compressed again by the compressor 10 can be reduced, so that the power consumption of the compressor 10 can be reduced. However, when liquid refrigerant begins to flow into the injection path 22, the amount of liquid refrigerant flowing through the evaporator also decreases, evaporating capacity decreases, and the performance of the refrigeration cycle also decreases. Therefore, in order to obtain high performance in the refrigeration cycle apparatus 100 that performs injection, it is necessary to make the injection path 22 flow only through the gas refrigerant. Therefore, the control device 30 determines a target gas-liquid separation temperature Tm1 (step S10). Specifically, the control device 30 ensures that the superheat degree of the gas refrigerant after passing through the heater 24 cannot be kept above a certain temperature so as to reliably prevent the liquid refrigerant from flowing into the injection path 22. A target gas-liquid separation temperature Tm1 is calculated by subtracting a predetermined temperature (for example, 1 ° C.) determined in advance from the liquid separation temperature Tm0.

  After Step S10, the opening degree of the downstream side throttle device is adjusted again to lower the intermediate pressure and the gas-liquid separation temperature Tm so that only the gas refrigerant flows through the injection path 22. Specifically, the control device 30 detects the intermediate-pressure gas-liquid separation temperature Tm by the intermediate-pressure temperature sensor 26 (step S11), and compares it with the target gas-liquid separation temperature Tm1 determined in step S10 ( Step S12). If the detected gas-liquid separation temperature Tm is equal to or higher than the target gas-liquid separation temperature Tm1 (NO in step S12), the opening degree of the downstream throttle device is increased (step S13), and the intermediate pressure is lowered. When the degree of opening of the downstream throttle device is increased and the target gas-liquid separation temperature Tm1 falls below the target gas-liquid separation temperature Tm1 (YES in step S12), control is performed to maintain the target discharge temperature and target gas-liquid separation temperature. The operation proceeds to steady operation (step S14).

  Even after shifting to the steady operation, the control device 30 detects the gas-liquid separation temperature Tm and the discharge temperature Td by the intermediate pressure temperature sensor 26 and the discharge temperature sensor 34, and the upstream throttle device so that they are not far from the target values. And adjusting the opening of the downstream throttle device.

  The gas-liquid separation temperature Tm is controlled by adjusting the opening degree of the downstream side throttle device. Specifically, the opening degree of the downstream side throttle device is adjusted so that the detected gas-liquid separation temperature Tm is within a certain temperature ΔTms from the target gas-liquid separation temperature Tm1. When the gas-liquid separation temperature Tm becomes lower than Tm1-ΔTms, the opening degree of the downstream side throttle device is decreased, the gas-liquid separation temperature Tm is increased, and Tm is brought close to Tm1. Conversely, when the gas-liquid separation temperature Tm becomes higher than Tm1 + ΔTms, the opening degree of the downstream throttle device is increased, the gas-liquid separation temperature Tm is lowered, and Tm is brought close to Tm1. The adjustment amount of the opening degree of the downstream side throttle device during this adjustment may be constant, or the adjustment amount of the opening degree may be made smaller as it is closer to the target value.

  The discharge temperature Td is controlled by adjusting the opening degree of the upstream throttle device. Specifically, the opening degree of the upstream throttle device is adjusted so that the detected discharge temperature Td is within a certain temperature ΔTds from the target discharge temperature TD. When the discharge temperature Td becomes lower than TD−ΔTds, the opening degree of the upstream throttle device is decreased, the discharge temperature Td is increased, and Td is brought close to TD. On the contrary, when the discharge temperature Td becomes higher than Td + ΔTds, the opening degree of the upstream throttle device is increased, the discharge temperature Td is lowered, and Td is brought close to TD. The amount of adjustment of the opening degree of the upstream throttle device during this adjustment may be constant, or the degree of adjustment of the opening degree may be decreased as it approaches the target value.

  As shown in FIG. 1, since the gas-liquid separator 16 is disposed between the upstream throttle device and the downstream throttle device, the gas-liquid separation temperature Tm is greatly influenced by the adjustment of the opening degree of the upstream throttle device. receive. Specifically, if the opening degree of the upstream throttle device is reduced, the differential pressure before and after the upstream throttle device increases, and accordingly, the intermediate pressure decreases and the gas-liquid separation temperature Tm decreases. On the contrary, when the opening degree of the upstream throttle device is increased, the differential pressure before and after the upstream throttle device is reduced, and accordingly, the intermediate pressure is increased and the gas-liquid separation temperature Tm is increased. Thus, adjustment of the opening degree of the upstream throttle device affects not only the discharge temperature Td but also the gas-liquid separation temperature Tm. This is not limited to the upstream throttling device. When the opening degree of the downstream throttling device is adjusted, the amount of refrigerant flowing to the evaporator changes and the suction state of the compressor 10 changes. The adjustment of the opening degree affects not only the gas-liquid separation temperature Tm but also the discharge temperature Td.

  In this way, the respective opening adjustments of the upstream throttle device and the downstream throttle device affect the discharge temperature Td and the gas-liquid separation temperature Tm, respectively, but the discharge temperature Td is controlled by the upstream throttle device, If control is performed with each throttle device having a role such as controlling the gas-liquid separation temperature Tm by the downstream throttle device, simpler control can be realized.

  FIG. 3 shows how the opening degree of the upstream side throttle device and the downstream side throttle device, the discharge temperature Td, the injection temperature Tinj, and the gas-liquid separation temperature Tm change in the above-described intermediate pressure control operation. As shown in FIG. 3, in the present embodiment, first, the opening degree of the upstream throttle device is gradually reduced, and the discharge temperature Td gradually rises. Next, the degree of opening of the downstream side expansion device is reduced until the injection temperature Tinj rapidly decreases, and thereafter the degree of opening of the downstream side expansion device is increased.

  In the intermediate pressure control operation described above, the reference temperature Tm0 of the gas-liquid separation temperature Tm is determined using the heater 24 and the superheat degree temperature sensor 28, and the temperature lower than the reference temperature Tm0 by a predetermined temperature ΔTm is set to the gas-liquid separation temperature. By setting the target temperature Tm1, the measurement error of the intermediate pressure temperature sensor 26 can be canceled. Thereby, the intermediate pressure can be controlled to the target value with higher accuracy, and the efficiency of the refrigeration cycle apparatus 100 can be improved.

  In the present embodiment, since the intermediate pressure control operation is performed during the start-up operation, it is possible to shift from the start-up operation to the steady operation in an optimal state.

<Modification>
In the embodiment, the intermediate pressure control operation is performed during the start-up operation. For this reason, the opening degree of both the upstream throttle device and the downstream throttle device is adjusted so that the temperature difference between the gas-liquid separation temperature Tm and the injection temperature Tinj is smaller than a predetermined value. However, the control device 30 may perform the intermediate pressure control operation during the steady operation. In this case, the opening degree of either the upstream throttle device or the downstream throttle device may be adjusted so that the temperature difference between the gas-liquid separation temperature Tm and the injection temperature Tinj is smaller than a predetermined value. obtain.

  The flowchart in the case of performing the intermediate pressure control operation during the steady operation is exactly the same as FIG. That is, when some determination condition is satisfied during steady operation, the process may proceed to step S1. For example, the process may proceed to step S1 when the outside air temperature has changed and the cycle conditions have changed significantly, or may proceed to step S1 in response to a change in user's request. Or you may advance to step S1 by the elapsed time from the driving | operation start.

  In the embodiment, an electric heater is used as the heater 24. However, the heater 24 is not limited to means for applying heat to the refrigerant from the outside of the refrigerant circuit 1 such as an electric heater. For example, a part of the refrigerant pipe constituting the injection path 22 is brought into direct or indirect contact with the hermetic container or discharge pipe of the compressor 10 that is higher in temperature than the intermediate pressure refrigerant (gas-liquid separation temperature). Accordingly, a part of the refrigerant circuit 1 may constitute the heater 24. Below, the modification of the heater 24 is demonstrated in detail. In addition, the modification shown below is comprised similarly to the said embodiment except the case where it demonstrates especially.

  FIG. 4 shows a heater 24 </ b> A that is a modification of the heater 24. The heater 24A is a heat storage unit that accumulates heat discharged from the compressor 10 and heats the refrigerant flowing through the injection path 22 using the accumulated heat. Specifically, the heater 24 </ b> A includes a heat storage material 50 disposed so as to wrap the compressor 10, and a meandering pipe 52 that passes through the inside of the heat storage material 50 while meandering. The meandering pipe 52 constitutes a part of the injection path 22. Accordingly, the refrigerant flowing into the injection path 22 from the gas-liquid separator 16 is heated by flowing through the meandering pipe 52. Further, the refrigerant that has passed through the meandering pipe 52 is injected into the compressor 10. Thereby, the refrigerant flowing through the injection path 22 can be heated using the exhaust heat of the compressor 10. Since it is not necessary to provide an independent electric heater to heat the refrigerant flowing through the injection path 22, it is possible to realize power saving of the refrigeration cycle apparatus.

  FIG. 5 shows a refrigeration cycle apparatus 100 </ b> A that includes a heater 24 </ b> B that is another modification of the heater 24. The heater 24B is a heat exchanger having a first heat exchanging unit 60 to which the refrigerant flowing through the injection path 22 is guided and a second heat exchanging unit 62 to which the refrigerant flowing from the refrigerant circuit 1 is guided by being branched from the refrigerant circuit 1. . The first heat exchange unit 60 is also a part of the injection path 22. The temperature of the refrigerant guided to the second heat exchange unit 62 is higher than the gas-liquid separation temperature. The second heat exchange unit 62 is connected to the refrigerant circuit 1 between the condenser 12 and the upstream expansion device 14. Specifically, the second heat exchanging unit 62 includes one end connected to the refrigerant circuit 1 between the condenser 12 and the upstream expansion device 14, and the condenser 12 and the upstream expansion device downstream from the one end. 14 and the other end connected to the refrigerant circuit 1. Accordingly, the refrigerant flowing between the condenser 12 and the upstream side expansion device 14 is guided to the second heat exchange unit 62. Further, the second heat exchange unit 62 is arranged to heat the first heat exchange unit 60. Thereby, the refrigerant | coolant which flows through the injection path | route 22 is heated. Therefore, the refrigerant flowing through the injection path 22 can be heated using the heat of the refrigerant flowing through the refrigerant circuit 1. Since it is not necessary to provide an independent electric heater to heat the refrigerant flowing through the injection path 22, it is possible to realize power saving of the refrigeration cycle apparatus. In addition, since the degree of supercooling of the refrigerant on the outlet side of the condenser 12 of the refrigerant circuit 1 can be increased, the refrigeration cycle apparatus 100A with improved cooling capacity can be realized.

  The heater 24B is, for example, a double tube heat exchanger including an inner tube and an inner tube and a concentric outer tube. In this case, the inside of the inner tube corresponds to one of the first heat exchange unit 60 and the second heat exchange unit 62. Further, a space formed between the inner peripheral surface of the outer tube and the outer peripheral surface of the inner tube corresponds to one of the first heat exchange unit 60 and the second heat exchange unit 62. Further, for example, the heater 24 </ b> B may be configured by arranging the pipe that is the first heat exchange unit 60 and the pipe that is the second heat exchange unit 62 to be in contact with each other. In addition, as long as the 2nd heat exchange part 62 can heat the 1st heat exchange part 60, the structure of the heater 24B is not specifically limited.

  The valve 64 is provided on the upstream side of the second heat exchange unit 62. In the refrigerant circuit 1, a valve 66 is provided between a position where one end of the second heat exchange unit 62 is connected and a position where the other end of the second heat exchange unit 62 is connected. The valves 64 and 66 are electric valves whose opening degrees can be adjusted, for example. By controlling the opening and closing of the valves 64 and 66, heating of the refrigerant flowing through the injection path 22 can be controlled. For example, the opening and closing of the valves 64 and 66 may be controlled so as to heat the refrigerant flowing through the injection path 22 only during the intermediate pressure control operation. The valves 64 and 66 may be omitted. Further, the second heat exchanging unit 62 may not be branched from the refrigerant circuit 1. In other words, the second heat exchange unit 62 may be configured by a part of the refrigerant circuit 1 between the condenser 12 and the upstream expansion device 14.

  FIG. 6 shows a refrigeration cycle apparatus 100 </ b> B including a heater 24 </ b> C that is another modification of the heater 24. The heater 24 </ b> C is a heat exchanger having a first heat exchanging unit 70 to which the refrigerant flowing through the injection path 22 is guided and a second heat exchanging unit 72 to which the refrigerant flowing from the refrigerant circuit 1 is guided by being branched from the refrigerant circuit 1. . The first heat exchange unit 70 is also a part of the injection path 22. The second heat exchange unit 72 is connected to the refrigerant circuit 1 between the compressor 10 and the condenser 12. Specifically, the second heat exchanging unit 72 is connected to the refrigerant circuit 1 between the compressor 10 and the condenser 12 and between the compressor 10 and the condenser 12 on the downstream side of the one end. And the other end connected to the refrigerant circuit 1. Thereby, the refrigerant | coolant which flows between the compressor 10 and the condenser 12 which is comparatively high in the refrigerant | coolant which flows through the refrigerant circuit 1 is guide | induced to the 2nd heat exchange part 72. The temperature of the refrigerant guided to the second heat exchange unit 72 is higher than the gas-liquid separation temperature. The second heat exchanging unit 72 is arranged to heat the first heat exchanging unit 70. Thereby, the refrigerant | coolant which flows through the injection path | route 22 is heated. Therefore, the refrigerant flowing through the injection path 22 can be heated using the heat of the refrigerant flowing in the refrigerant circuit 1 having a relatively high temperature. Since it is not necessary to provide an independent electric heater to heat the refrigerant flowing through the injection path 22, it is possible to realize power saving of the refrigeration cycle apparatus.

  The 1st heat exchange part 70 and the 2nd heat exchange part 72 may be comprised by the structure similar to the 1st heat exchange part 60 and the 2nd heat exchange part 62 of the heater 24B. In addition, for example, the motor-operated valve whose opening degree can be adjusted includes the upstream side of the second heat exchange unit 72, the position where one end of the second heat exchange unit 72 is connected, and the other end of the second heat exchange unit 72. You may provide in the refrigerant circuit 1 between the connected positions. The second heat exchange unit 72 may not be branched from the refrigerant circuit 1. In other words, the second heat exchange unit 72 may be configured by a part of the refrigerant circuit 1 between the compressor 10 and the condenser 12.

(Second Embodiment)
FIG. 7 shows a refrigeration cycle apparatus 200 according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, an indoor heat exchanger-side temperature sensor 40 is provided between the indoor heat exchanger 12 and the indoor expansion device 14 in the refrigerant circuit 1, and the outdoor space between the outdoor expansion device 18 and the outdoor heat exchanger 20 is provided. A heat exchanger side temperature sensor 42 is provided. In addition, operation | movement of the refrigerating-cycle apparatus 200 of this embodiment is the same as operation | movement of the refrigerating-cycle apparatus 100 of 1st Embodiment.

  During heating, the indoor heat exchanger-side temperature sensor 40 detects the condensation-side outlet temperature Tc, which is the temperature of the refrigerant flowing out of the indoor heat exchanger (condenser) 12, and the outdoor heat exchanger-side temperature sensor 42 performs outdoor heat exchange. The evaporation side inlet temperature Te which is the temperature of the refrigerant flowing into the evaporator (evaporator) 20 is detected. During cooling, the outdoor heat exchanger side temperature sensor 42 detects the condensation side outlet temperature Tc, which is the temperature of the refrigerant flowing out of the outdoor heat exchanger (condenser) 20, and the indoor heat exchanger side temperature sensor 40 performs indoor heat exchange. The evaporation side inlet temperature Te which is the temperature of the refrigerant flowing into the evaporator (evaporator) 12 is detected. Hereinafter, the indoor heat exchanger side temperature sensor 40 at the time of heating and the outdoor heat exchanger side temperature sensor 42 at the time of cooling are post-condensing temperature sensors, the outdoor heat exchanger side temperature sensor 42 at the time of heating, and the indoor heat exchanger at the time of cooling. The side temperature sensor 40 is referred to as a pre-evaporation temperature sensor, and will be described without distinguishing between heating and cooling as in the first embodiment.

  The control device 30 performs an intermediate pressure control operation substantially similar to that of the first embodiment, but at that time, when the temperature difference between the gas-liquid separation temperature Tm and the injection temperature Tinj becomes smaller than a predetermined value ΔTi. The gas-liquid separation temperature used in steady operation is corrected using the gas-liquid separation temperature Tm, the condensation side outlet temperature Tc, and the evaporation side inlet temperature Te. Hereinafter, the intermediate pressure control operation performed by the control device 30 will be described in detail with reference to the flowchart of FIG.

  The flowchart shown in FIG. 8 is obtained by changing step S9 of the flowchart shown in FIG. 2 to steps S21 to S23, and other steps S1 to S8 and S10 to S14 are the same as those in the first embodiment. For this reason, below, it demonstrates centering on step S21-S23 original with this embodiment.

  In step S7, the control device 30 determines that the temperature difference between the gas-liquid separation temperature Tm detected by the intermediate pressure temperature sensor 26 and the injection temperature Tinj detected by the superheat degree temperature sensor 28 is a predetermined value ΔTi. When it is determined that the temperature is smaller, the condensation side outlet temperature Tc is detected by the post-condensation temperature sensor, and the evaporation side inlet temperature Te is detected by the pre-evaporation temperature sensor (step S21). Next, the control device 30 records the gas-liquid separation temperature Tm when YES in step S7 as Tm0, and sets the condensation side outlet temperature Tc and the evaporation side inlet temperature Te detected in step S21 as Tc0 and Te0, respectively. Store (step S22). Thereafter, the control device 30 uses the stored Tm0, Tc0, Te0 to correct the calculation formula for the gas-liquid separation temperature used in the steady operation (step S23).

Here, the calculation formula of the gas-liquid separation temperature used in the steady operation is a calculation formula for estimating the gas-liquid separation temperature only from the condensation side outlet temperature Tc and the evaporation side inlet temperature Te or the condensation side outlet temperature Tc. For example, it is expressed by the following formula (1).
Tm2 = αTc + β (1)

  When equation (1) is used, in other words, when the gas-liquid separation temperature is estimated only from the condensation side outlet temperature, it is not necessary to detect the evaporation side inlet temperature Te by the pre-evaporation temperature sensor in step S21. That is, the calculation formula of the gas-liquid separation temperature can be corrected using only Tm0 and Tc0. Hereinafter, in order to make the explanation easy to understand, it is assumed that the expression (1) is used.

  In step S23, control device 30 substitutes Tc0 stored in step S22 into equation (1) to calculate estimated temperature Tm2. The control device 30 compares the calculated estimated temperature Tm2 with the Tm0 stored in step S22 and calculates the gas-liquid separation temperature so that the difference is canceled as a measurement error between the intermediate pressure temperature sensor 26 and the temperature sensor after condensation. Rewrite. For example, when Tm0 is larger than Tm2, only the difference (Tm0−Tm2) is added as a correction value to the calculation formula, and when Tm0 is smaller than Tm2, the difference (Tm2−Tm0) Only subtract as a correction value in the formula. Alternatively, the coefficients α and β in the above equation (1) are changed.

  Thereafter, the control device 30 proceeds to steady operation through steps S10 to S13 (step S14). In the steady operation, the control device 30 performs the steady operation using the calculation formula of the gas-liquid separation temperature corrected during the intermediate pressure control operation. Specifically, the control device 30 sets the gas-liquid separation temperature Tm, the discharge temperature Td, the condensation side outlet temperature Tc, and the evaporation side inlet temperature Te to the intermediate pressure temperature sensor 26, the discharge temperature sensor 34, the post-condensation temperature sensor, and before evaporation. It detects with a temperature sensor, and adjusts the opening degree of an upstream side expansion device and a downstream side expansion device so that they may not leave | separate from target value.

  In the first embodiment, the target gas-liquid separation temperature Tm1 is constant, but in this embodiment, the estimated temperature Tm2 calculated using the calculation formula of the gas-liquid separation temperature corrected in step S23 is used as the target gas-liquid separation. Set with temperature. The discharge temperature Td and the gas-liquid separation temperature Tm are controlled by adjusting the opening degrees of the upstream side throttle device and the downstream side throttle device, as in the first embodiment.

  In this way, by correcting the calculation formula for estimating the gas-liquid separation temperature Tm from other temperature measurement points in the intermediate pressure control operation and using the corrected calculation formula in the steady operation, the temperature sensor can be used even in the steady operation. This makes it possible to control the intermediate pressure with higher accuracy in consideration of the measurement error.

<Modification>
In the flowchart shown in FIG. 8, step S21 for detecting the condensation side outlet temperature Tc and the evaporation side inlet temperature Te is arranged after step S7. However, step S21 is arranged between step S6 and step S7. Then, a step of determining a target gas-liquid separation temperature Tm3 based on the condensation side outlet temperature Tc and the evaporation side inlet temperature Te is arranged. In step S8, the detected gas-liquid separation temperature Tm and the target gas-liquid separation are arranged. When the difference from the temperature Tm3 is large, the opening adjustment amount may be increased, and when the difference is small, the opening adjustment amount may be decreased.

  Further, in step S10, when determining the target gas-liquid separation temperature Tm1, instead of using Tm0, the estimated temperature Tm2 obtained by the calculation formula corrected in step S23 may be used.

  Moreover, the heater 24 of 2nd Embodiment can be changed similarly to the modification of 1st Embodiment.

(Other embodiments)
In the above embodiment, the four-way valve 32 is provided in the refrigerant circuit 1 and switching between cooling and heating is possible. However, the refrigeration cycle apparatus of the present invention may be dedicated to cooling or heating only. .

  The refrigeration cycle apparatus of the present invention can be used as a heat pump apparatus for hot water heaters, hot water heaters, refrigeration or air conditioning equipment.

Claims (13)

A refrigerant circuit for circulating the refrigerant so as to pass through the compressor, the condenser, the upstream throttle device, the gas-liquid separator, the downstream throttle device, and the evaporator in this order;
An injection path for supplying the gas refrigerant separated by the gas-liquid separator to the compressor;
A heater provided in the injection path;
An intermediate pressure temperature sensor that detects a gas-liquid separation temperature that is a temperature of the refrigerant flowing into the injection path from the refrigerant circuit;
A superheat degree temperature sensor for detecting an injection temperature which is a temperature of a refrigerant heated by the heater in the injection path;
After adjusting the opening degree of at least one of the upstream throttle device and the downstream throttle device so that the temperature difference between the gas-liquid separation temperature and the injection temperature is smaller than a predetermined value, the gas-liquid separation A control device that performs an intermediate pressure control operation to increase the degree of opening of the downstream throttle device until the temperature decreases by a predetermined temperature from the temperature at that time;
A refrigeration cycle apparatus comprising: A post-condensation temperature sensor that detects a condensation side outlet temperature that is a temperature of the refrigerant flowing out of the condenser;
The control device determines the gas-liquid separation temperature and the condensation side outlet temperature when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value during the intermediate pressure control operation. The refrigeration cycle apparatus according to claim 1, wherein the refrigeration cycle apparatus is used to correct a calculation formula of a gas-liquid separation temperature used in steady operation. A pre-evaporation temperature sensor that detects an evaporation side inlet temperature that is a temperature of the refrigerant flowing into the evaporator;
The control device corrects the calculation formula of the gas-liquid separation temperature used in steady operation, and the evaporation when the temperature difference between the gas-liquid separation temperature and the injection temperature becomes smaller than a predetermined value. The refrigeration cycle apparatus according to claim 2, wherein the side inlet temperature is also used.   The refrigeration cycle apparatus according to claim 2, wherein the control device performs a steady operation using a calculation formula of a gas-liquid separation temperature corrected during the intermediate pressure control operation.   The said control apparatus is a refrigerating-cycle apparatus of Claim 1 which performs the said intermediate pressure control driving | operation in the case of starting operation.   The refrigeration cycle apparatus according to claim 1, wherein the control device performs the intermediate pressure control operation during a steady operation. A discharge temperature sensor that detects a discharge temperature that is a temperature of the refrigerant discharged from the compressor;
The control device adjusts the opening degree of the upstream throttle device so that the discharge temperature is kept close to the target discharge temperature, and a temperature difference between the gas-liquid separation temperature and the injection temperature is predetermined. The refrigeration cycle apparatus according to claim 5, wherein the opening degree of the downstream side throttle device is reduced until the value becomes smaller than the value, and then the opening degree of the downstream side throttle device is increased. The refrigerant circuit includes an indoor heat exchanger and an outdoor heat exchanger that function as the condenser and the evaporator, and an indoor throttle device and an outdoor throttle that function as the upstream throttle device and the downstream throttle device. Including equipment,
The refrigeration cycle apparatus according to claim 1, wherein the refrigerant circuit is provided with a four-way valve that switches a flow direction of the refrigerant.   The refrigeration cycle apparatus according to claim 1, wherein the heater is an electric heater.   The refrigeration cycle apparatus according to claim 1, wherein the heater is a heat storage unit that accumulates heat discharged from the compressor and heats the refrigerant using the accumulated heat. The heater includes a heat including a first heat exchange unit through which a refrigerant flowing through the injection path is guided and a second heat exchange unit through which the refrigerant flowing through the refrigerant circuit and having a temperature higher than the gas-liquid separation temperature is guided. An exchange,
The refrigeration cycle apparatus according to claim 1, wherein in the heat exchanger, the second heat exchange unit heats the first heat exchange unit.   The refrigeration cycle apparatus according to claim 11, wherein a refrigerant flowing between the compressor and the condenser is guided to the second heat exchange unit.   The refrigeration cycle apparatus according to claim 11, wherein a refrigerant flowing between the condenser and the upstream expansion device is guided to the second heat exchange unit.

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