Heat pump device and its control method

Abstract

The present invention provides a heat pump device that can ensure a high-low pressure difference of the refrigerant circulating in the refrigerant circuit is greater than or equal to a predetermined value. [Solution] In a heating mode in which the water heat exchanger 7 operates as a condenser and the outdoor heat exchanger 15 operates as an evaporator, and when the outside air temperature is set to a first threshold or higher, the second expansion valve 13 controls the degree of superheating of the low-pressure refrigerant drawn into the compressor to a predetermined value, and the first expansion valve 9 controls the high-pressure refrigerant flowing through the water heat exchanger 7 to be set to a predetermined value or higher.

Description

Technical Field

[0001] The present disclosure relates to a heat pump device and a control method thereof.

Background Art

[0002] A heat pump type hot water supply and air conditioning device having a configuration in which an expansion valve for cooling and an expansion valve for heating are arranged in series with a receiver interposed therebetween is known (see Patent Document 1).

[0003] The document discloses controlling the expansion valve for cooling and the expansion valve for heating so that heating operation is possible even under extremely low temperature conditions.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, unlike extremely low temperature conditions, there may be cases where hot water supply operation is required under conditions where the outside air temperature is high, such as in summer. In such cases, the low pressure in the refrigerant circuit rises, the pressure difference between the high pressure and the low pressure becomes small, and there is a risk of hindering the operation, such as not satisfying the operating conditions of the compressor.

[0006] Furthermore, during cooling operation, the water heat exchanger acts as the evaporator and the outdoor heat exchanger acts as the condenser. The outdoor heat exchanger, which exchanges heat with the outside air, uses a fin-and-tube type heat exchanger or similar, and has a larger capacity than the water heat exchanger, which uses a plate type heat exchanger or similar. In this case, if the suction superheat of the compressor is controlled by the cooling electronic expansion valve downstream of the receiver, the receiver becomes high pressure, and a large amount of liquid refrigerant condensed in the outdoor heat exchanger is stored in the receiver. In contrast, during heating, the smaller capacity water heat exchanger is used as the condenser, so the amount of liquid refrigerant stored in the receiver is less than during cooling. For this reason, the amount of refrigerant to be sealed in the refrigerant circuit must be determined based on the amount used during cooling, which is a bottleneck in reducing the amount of refrigerant. Such a reduction in the amount of refrigerant to be sealed is particularly important when using flammable refrigerants such as R290.

[0007] This disclosure has been made in view of these circumstances and aims to provide a heat pump device and a control method thereof that can ensure a high-low pressure difference of the refrigerant circulating in the refrigerant circuit is greater than or equal to a predetermined value.

[0008] Furthermore, the objective is to provide a heat pump device and a control method thereof that can minimize the amount of refrigerant used. [Means for solving the problem]

[0009] A heat pump system according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; a switching valve for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger; and the heat exchanger A heat pump device comprising a heat transfer medium circuit that sends the heat transfer medium, which has undergone heat exchange in the exchanger, to a heat utilization destination, and a control unit that controls the outdoor heat exchanger side expansion valve and / or the heat transfer medium heat exchanger side expansion valve, wherein the control unit is set to a heating mode in which the heat transfer medium heat exchanger operates as a condenser and the outdoor heat exchanger operates as an evaporator, and when the outside air temperature is set to a first threshold or higher, the control unit controls the outdoor heat exchanger side expansion valve so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is set to a predetermined value, and the control unit controls the heat transfer medium heat exchanger side expansion valve so that the high-pressure refrigerant flowing through the heat transfer medium heat exchanger is set to a predetermined value or higher.

[0010] A heat pump device according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger for storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a switch for directing the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger. A heat pump device comprising a switching valve, a heat transfer medium circuit for sending the heat transfer medium, which has undergone heat exchange in the heat transfer medium heat exchanger, to a heat utilization destination, and a control unit for controlling the outdoor heat exchanger side expansion valve and / or the heat transfer medium heat exchanger side expansion valve, wherein the control unit controls the state of the refrigerant drawn into or discharged from the compressor by the heat transfer medium heat exchanger side expansion valve when the heat transfer medium heat exchanger is operating as an evaporator and the outdoor heat exchanger is operating as a condenser, and controls the high-pressure refrigerant flowing through the outdoor heat exchanger by the outdoor heat exchanger side expansion valve so that it is above a predetermined value.

[0011] A heat pump system according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; a switching valve for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger; and the heat transfer medium that has been heat exchanged in the heat exchanger. A heat pump device comprising a heat transfer medium circuit that sends the body to a heat utilization destination, and a control unit that controls the outdoor heat exchanger side expansion valve and / or the heat transfer medium heat exchanger side expansion valve, wherein in a cooling mode in which the heat transfer medium heat exchanger operates as an evaporator and the outdoor heat exchanger operates as a condenser, the control unit controls the heat transfer medium heat exchanger side expansion valve so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value, and when the opening degree of the heat transfer medium heat exchanger side expansion valve exceeds a predetermined value, the control unit fixes the opening degree of the heat transfer medium heat exchanger side expansion valve and controls the outdoor heat exchanger side expansion valve so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value.

[0012] A control method for a heat pump system according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger for storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a control method for flowing the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger. A control method for a heat pump device comprising a switching valve that switches between modes and a heat transfer circuit that sends the heat transfer medium, which has been heat-exchanged in the heat transfer medium heat exchanger, to a heat utilization destination, wherein the device is set to a heating mode in which the heat transfer medium heat exchanger operates as a condenser and the outdoor heat exchanger operates as an evaporator, and when the outside air temperature is set to a first threshold or higher, the outdoor heat exchanger side expansion valve controls the degree of superheating of the low-pressure refrigerant drawn into the compressor to a predetermined value, and the heat transfer medium heat exchanger side expansion valve controls the high-pressure refrigerant flowing through the heat transfer medium heat exchanger to a predetermined value or higher.

[0013] A control method for a heat pump system according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a control method for the refrigerant discharged from the compressor through the outdoor heat exchanger. Alternatively, a control method for a heat pump device comprising a switching valve that switches the flow of a heat transfer medium to a heat exchanger, and a heat transfer medium circuit that sends the heat transfer medium, which has undergone heat exchange in the heat exchanger, to a heat utilization destination, wherein in a cooling mode in which the heat transfer medium heat exchanger is operated as an evaporator and the outdoor heat exchanger is operated as a condenser, the state of the refrigerant drawn into or discharged from the compressor is controlled by the heat transfer medium heat exchanger side expansion valve, and the high-pressure refrigerant flowing through the outdoor heat exchanger is controlled by the outdoor heat exchanger side expansion valve to be above a predetermined value.

[0014] A control method for a heat pump system according to one aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger. A control method for a heat pump device comprising: a heat transfer circuit that sends the heat transfer medium, which has been heat-exchanged in the heat transfer heat exchanger, to a heat utilization destination, wherein in a cooling mode in which the heat transfer heat exchanger is operated as an evaporator and the outdoor heat exchanger is operated as a condenser, the heat transfer heat exchanger side expansion valve controls the superheating degree of the low-pressure refrigerant drawn into the compressor to a predetermined value, and when the opening degree of the heat transfer heat exchanger side expansion valve exceeds a predetermined value, the opening degree of the heat transfer heat exchanger side expansion valve is fixed, and the outdoor heat exchanger side expansion valve controls the superheating degree of the low-pressure refrigerant drawn into the compressor to a predetermined value. [Effects of the Invention]

[0015] The high-low pressure difference of the refrigerant circulating in the refrigerant circuit can be maintained at or above a predetermined value. Furthermore, the amount of refrigerant to be sealed in can be kept as small as possible. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of a heat pump device according to one embodiment of the present disclosure. [Figure 2] This is a flowchart showing how to control the heating mode (high outside temperature). [Figure 3] This is a flowchart showing how to control the cooling mode (low outside temperature). [Figure 4] This is a flowchart illustrating the control method for the cooling mode (circulating refrigerant amount control). [Modes for carrying out the invention]

[0017] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings.

[0018] Fig. 1 shows a schematic configuration of the heat pump device 1. The heat pump device 1 includes a refrigerant circuit C that constitutes a refrigeration cycle, and a water circuit (heat medium circuit) W that supplies water (heat medium, coolant) heated or cooled by the refrigerant circuit C to a heat utilization destination such as an indoor unit.

[0019] The refrigerant circuit C includes a compressor 3, a four-way valve (switching valve) 5, a water heat exchanger (heat medium heat exchanger) 7, a first expansion valve (heat medium heat exchange side expansion valve) 9, a receiver 11, a second expansion valve (outdoor heat exchange side expansion valve) 13, and an outdoor heat exchanger 15.

[0020] The compressor 3 is, for example, a rotary compressor, and compresses a flammable refrigerant such as R290. The rotational speed of the compressor 3 is transmitted to the control unit.

[0021] A high-pressure switch 17 and a discharge temperature sensor 19 are provided in a discharge pipe 16 connected to the discharge port of the compressor 3. The high-pressure switch 17 monitors the high-pressure value of the high-pressure refrigerant discharged from the compressor 3. The discharge temperature sensor 19 measures the discharge temperature of the high-pressure refrigerant discharged from the compressor 3. The outputs of the high-pressure switch 17 and the discharge temperature sensor 19 are transmitted to a control unit (not shown).

[0022] An accumulator 21 is provided upstream of the suction port of the compressor 3. A low-pressure sensor 23 and a suction temperature sensor 25 are provided upstream of the accumulator 21. The low-pressure sensor 23 measures the pressure value of the low-pressure refrigerant circulating in the refrigerant circuit C. The suction temperature sensor 25 measures the temperature of the low-pressure refrigerant sucked into the compressor 3. The outputs of the low-pressure sensor 23 and the suction temperature sensor 25 are transmitted to the control unit.

[0023] A high-pressure sensor 29 and a high-pressure temperature sensor 31 are installed in the refrigerant piping 27 between the heat exchanger 7 and the first expansion valve 9, directly adjacent to the heat exchanger 7. The high-pressure sensor 29 measures the pressure of the high-pressure refrigerant when the heat exchanger 7 is used as a condenser. The high-pressure temperature sensor 31 measures the temperature of the high-pressure refrigerant when the heat exchanger 7 is used as a condenser. The outputs of the high-pressure sensor 29 and the high-pressure temperature sensor 31 are transmitted to the control unit.

[0024] A water circuit W is connected to the water heat exchanger 7 in a way that allows for heat exchange. The water circuit W includes an indoor unit and a water pump (not shown). Heat exchange occurs in the water heat exchanger 7 between the refrigerant circulating in the refrigerant circuit C and the water circulating in the water circuit W. For example, a plate heat exchanger may be used for the water heat exchanger 7.

[0025] The opening degrees of the first expansion valve 9 and the second expansion valve 13 are controlled by the control unit according to each operating mode.

[0026] The outdoor heat exchanger 15 exchanges heat between the refrigerant and the outside air. For example, a fin-and-tube type heat exchanger is used as the outdoor heat exchanger 15. The outdoor heat exchanger 15 is used with a larger capacity than the water heat exchanger 7.

[0027] An outdoor fan 33 is provided opposite the outdoor heat exchanger 15. The outdoor fan 33's start / stop function and rotation speed are controlled by a control unit. Heat exchange takes place between the outside air guided by the outdoor fan 33 and the refrigerant flowing through the outdoor heat exchanger 15.

[0028] The control unit consists of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions are stored in the storage medium in the form of a program, for example. The CPU reads this program into the RAM and performs information processing and calculations to realize the various functions. The program may be pre-installed in ROM or other storage media, provided stored in a computer-readable storage medium, or distributed via wired or wireless communication. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memory.

[0029] The heat pump system shown in Figure 1 operates as follows, depending on the operating mode. <Cooling mode (normal)> In the cooling mode used during normal operation, such as in summer, the control unit switches the four-way valve 5 according to its command, operating as shown by the solid arrow. The high-pressure refrigerant discharged from the compressor 3 passes through the four-way valve 5 and is sent to the outdoor heat exchanger 15. In the outdoor heat exchanger 15, the refrigerant condenses as it releases heat to the outside air. The condensed and liquefied refrigerant passes through the second expansion valve 13 and is sent to the receiver 11. The second expansion valve 13 is set to fully open. The liquid refrigerant stored in the receiver 11 is guided to the first expansion valve 9 and reduced to a predetermined pressure. The opening of the first expansion valve 9 is controlled by the control unit so that the superheating degree of the refrigerant drawn into the compressor 3 is within a predetermined range. The superheating degree is calculated by the control unit from the measured values ​​of the low-pressure sensor 23 and the intake temperature sensor 25.

[0030] The refrigerant, depressurized by the first expansion valve 9, is sent to the water heat exchanger 7, where it absorbs heat from the water flowing through the water heat exchanger 7 and is evaporated. The refrigerant evaporated in the water heat exchanger 7 is then guided through the four-way valve 5 and the accumulator 21 to the suction side of the compressor 3.

[0031] The chilled water generated in the water heat exchanger 7 by the latent heat of vaporization of the refrigerant flows to the indoor unit by a water pump (not shown), and after the indoor unit has finished cooling, it is guided back to the water heat exchanger 7.

[0032] <Heating mode (normal)> In the heating mode, which is used under normal conditions such as during winter, the control unit switches the four-way valve 5 according to its command, and operates as shown by the dashed arrow. The high-pressure refrigerant discharged from the compressor 3 passes through the four-way valve 5 and is sent to the water heat exchanger 7. In the water heat exchanger 7, heat is released to the water introduced from the water circuit W, heating the water and turning it into hot water.

[0033] The refrigerant, condensed and liquefied in the water heat exchanger 7, passes through the first expansion valve 9 and is sent to the receiver 11. The first expansion valve 9 is set to fully open. The liquid refrigerant stored in the receiver 11 is guided to the second expansion valve 13 and reduced to a predetermined pressure. The opening of the second expansion valve 13 is controlled by the control unit so that the degree of superheating of the refrigerant drawn into the compressor 3 is within a predetermined range.

[0034] The refrigerant, depressurized by the second expansion valve 13, is sent to the outdoor heat exchanger 15, where it absorbs heat from the outside air and evaporates. The refrigerant evaporated in the outdoor heat exchanger 15 is then guided through the four-way valve 5 and the accumulator 21 to the suction side of the compressor 3.

[0035] The hot water generated in the water heat exchanger 7, heated by the latent heat of condensation of the refrigerant, flows to the indoor unit via a water pump. After heating is completed in the indoor unit, the hot water is returned to the water heat exchanger 7.

[0036] <Heating mode (high outside temperature)>

[0037] As shown in Figure 2, when the outside temperature is relatively high, such as in summer, the heating mode is controlled as follows.

[0038] When the temperature exceeds the first threshold (e.g., 0°C), the control shown in Figure 2 is initiated. The control unit obtains the low-pressure value of the refrigerant from the low-pressure sensor 23 and obtains the rotational speed of the compressor 3 (step S11). Alternatively, instead of the value from the low-pressure sensor 23, the saturation pressure calculated from the value of a refrigerant temperature sensor (not shown) installed on the outdoor heat exchanger 15 may be used.

[0039] Next, in step S12, the control unit calculates the target value of the refrigerant's high-pressure pressure (target high pressure) based on the following equation (1). HP = LP + α + β × A ... (1) Here, HP is the target high pressure, LP is the pressure value obtained from the low-pressure sensor 23, and A is the rotational speed of the compressor 3. α and β are constants determined from pre-tested tests.

[0040] The target high pressure (HP) is set by equation (1). The target high pressure (HP) is defined as the value that ensures the necessary differential pressure for the refrigerant circulating in the refrigerant circuit C.

[0041] Then, in step S13, the control unit compares the target high pressure HP with the actual high pressure. The actual high pressure is the current pressure value of the high-pressure refrigerant, specifically the value measured by the high-pressure sensor 29. Alternatively, instead of the high-pressure sensor 29, the saturation pressure calculated from the value of the refrigerant temperature sensor (not shown) of the water heat exchanger 7 may be used.

[0042] If the actual high pressure is less than the target high pressure HP, the control unit proceeds to step S14 and throttles the first expansion valve 9. By throttling the first expansion valve 9, the pressure upstream of the first expansion valve 9, i.e., on the high-pressure side, increases.

[0043] If the actual high pressure is greater than the target high pressure HP, the control unit proceeds to step S15 and opens the first expansion valve 9. By opening the first expansion valve 9, the pressure upstream of the first expansion valve 9, i.e., the high-pressure side, decreases.

[0044] The second expansion valve 13 is controlled by the control unit so that the superheating degree of the low-pressure refrigerant drawn into the compressor 3 reaches a predetermined value. This control of the second expansion valve 13 is the same as that for the heating mode (normal) described above.

[0045] By repeating the above steps S11 to S15, the actual high pressure is brought closer to the target high pressure HP, and the system is controlled to ensure a high pressure of a predetermined value or higher.

[0046] <Cooling mode (low outside temperature)>

[0047] When the outside air temperature is relatively low during cooling mode, the system is controlled as shown in Figure 3 to maintain the high-low pressure difference of the refrigerant, similar to the heating mode (high outside temperature) shown in Figure 2.

[0048] When the temperature falls below the second threshold (for example, 30°C), the control shown in Figure 3 is initiated. The control unit obtains the low-pressure value of the refrigerant from the low-pressure sensor 23 and obtains the rotational speed of the compressor 3 (step S21). Alternatively, instead of the value from the low-pressure sensor 23, the saturation pressure calculated from the value of the refrigerant temperature sensor (not shown) of the water heat exchanger 7 may be used.

[0049] Next, in step S22, the control unit calculates the target high pressure HP of the refrigerant based on equation (1) above.

[0050] Then, in step S23, the control unit compares the target high pressure HP with the actual high pressure. The actual high pressure is the current pressure value of the high-pressure refrigerant, specifically the value measured by a high-pressure sensor (not shown) installed between the outdoor heat exchanger and the second expansion valve. Alternatively, the saturation pressure calculated from the value of the refrigerant temperature sensor (not shown) of the outdoor heat exchanger 15 may be used instead of this high-pressure sensor.

[0051] If the actual high pressure is less than the target high pressure HP, the control unit proceeds to step S24 and throttles the second expansion valve 13. By throttling the second expansion valve 13, the pressure upstream of the second expansion valve 13, i.e., on the high-pressure side, increases.

[0052] If the actual high pressure is greater than the target high pressure HP, the control unit proceeds to step S25 and opens the second expansion valve 13. By opening the second expansion valve 13, the pressure upstream of the second expansion valve 13, i.e., the high-pressure side, decreases.

[0053] The first expansion valve 9 is controlled by the control unit so that the degree of superheating of the low-pressure refrigerant drawn into the compressor 3 reaches a predetermined value. This control of the first expansion valve 9 is the same as in the cooling mode (normal) described above.

[0054] By repeating steps S21 to S25 described above, the actual high pressure is brought closer to the target high pressure HP, and control is performed to ensure a high pressure of a predetermined value or higher.

[0055] <Cooling mode (refrigerant circulation control)>

[0056] If the amount of refrigerant circulating in refrigerant circuit C decreases during cooling mode, resulting in a decrease in cooling capacity, the system will be controlled as follows.

[0057] As shown in Figure 4, the first expansion valve 9 is controlled by the control unit so that the degree of superheating of the low-pressure refrigerant drawn into the compressor 3 reaches a predetermined value (step S31). This control of the first expansion valve 9 is the same as that for the cooling mode (normal) described above.

[0058] When the cooling mode is maintained, the amount of refrigerant condensed in the outdoor heat exchanger 15 and stored in the receiver 11 gradually increases, and accordingly the amount of refrigerant circulating in the refrigerant circuit C decreases. As the amount of circulating refrigerant decreases, the cooling capacity of the water heat exchanger 7 decreases, so the opening of the first expansion valve 9 is controlled to open.

[0059] Then, when the opening of the first expansion valve 9 exceeds a predetermined value, the control unit determines that the amount of circulating refrigerant is insufficient (step S32). However, the pressure value of the low-pressure refrigerant at this time is controlled to be above a certain value so that freezing does not occur in the water heat exchanger 7.

[0060] Then, the process proceeds to step S33, where the opening of the first expansion valve 9 is fixed at the opening determined in step S32 to indicate insufficient circulating refrigerant, and the second expansion valve 13 controls the superheating of the low-pressure refrigerant drawn into the compressor 3 to a predetermined value. At this time, to prevent freezing in the water heat exchanger 7, the pressure of the low-pressure refrigerant is controlled to be above a certain value, taking into account the pressure drop at the first expansion valve 9. Note that when the opening of the first expansion valve 9 is fixed in step S33, minute changes in the opening of the first expansion valve 9 (minor changes such as a few pulses of operation in 10 minutes) are permitted.

[0061] As a result, the refrigerant guided to the receiver 11, which is downstream of the second expansion valve 13 that controls the degree of superheating, becomes a two-phase flow, increasing the amount of circulating refrigerant and thus increasing the cooling capacity. Since the cooling capacity can be increased by controlling the degree of superheating with the second expansion valve 13 in this way, the amount of refrigerant required to match the increase in cooling capacity can be reduced.

[0062] The effects and advantages of this embodiment, as described above, are as follows. In heating mode (high ambient temperature), the second expansion valve 13 controls the superheating degree of the refrigerant intake from the compressor 3, and the first expansion valve 9 controls the high-pressure refrigerant flowing through the water heat exchanger 7 to reach the target high pressure HP. As a result, even when the ambient temperature is high in heating mode, the high and low pressure difference of the refrigerant can be kept above a predetermined value.

[0063] If compressor 3 is, for example, a rotary compressor, the rotary compressor is configured to use the high-pressure difference of the refrigerant to energize the vanes that separate the high-pressure and low-pressure compression chambers. The biasing force required for the vanes increases according to the rotational speed of the rotary compressor. For compressors that require a high-pressure difference of the refrigerant necessary for operation according to the rotational speed, it is effective to determine equation (1) so that it becomes the target value of the high-pressure refrigerant according to the rotational speed of the compressor, and to control the first expansion valve 9 accordingly.

[0064] In cooling mode (low outside temperature), the first expansion valve 9 controls the superheating of the refrigerant intake of the compressor 3, and the second expansion valve 13 controls the high-pressure refrigerant flowing through the outdoor heat exchanger 15 to reach the target high pressure HP. As a result, even when the outside temperature is low in cooling mode, the high and low pressure difference of the refrigerant can be kept above a predetermined value.

[0065] In cooling mode, when the opening of the first expansion valve 9 exceeds a predetermined value, it is determined that the amount of circulating refrigerant has decreased. The opening of the first expansion valve 9 is then fixed, and the superheating degree is controlled by the second expansion valve 13. As a result, compared to when the superheating degree is controlled by the first expansion valve 9, the pressure in the receiver 11 decreases, causing a two-phase flow to occur in the receiver, increasing the amount of circulating refrigerant and improving the cooling capacity. Therefore, it becomes unnecessary to set a large amount of refrigerant to be charged during cooling, and the amount of refrigerant to be charged can be kept as small as possible.

[0066] Since the outdoor heat exchanger 15 has a larger capacity than the water heat exchanger 7, when used as a condenser, the outdoor heat exchanger 15 condenses and liquefies more refrigerant. Therefore, more refrigerant tends to be required in cooling mode than in heating mode. In this embodiment, however, the cooling capacity can be improved by controlling the degree of superheating with the second expansion valve 13, eliminating the need to increase the amount of refrigerant charged in order to match the cooling mode.

[0067] In the above-described embodiment, the intake superheat degree was controlled, but this disclosure is not limited thereto. For example, the discharge superheat degree may be controlled, or the discharge temperature may be controlled.

[0068] The heat pump devices and their control methods described in each of the embodiments described above can be understood, for example, as follows.

[0069] A heat pump device (1) according to a first aspect of the present disclosure includes a compressor (3) for compressing a refrigerant, an outdoor heat exchanger (15) for exchanging heat between the refrigerant and outside air, a heat exchanger (7) for exchanging heat between the refrigerant and a heat transfer medium, a receiver (11) provided between the outdoor heat exchanger and the heat exchanger and capable of storing liquid refrigerant, an outdoor heat exchanger side expansion valve (13) provided between the outdoor heat exchanger and the receiver for expanding the refrigerant, a heat exchanger side expansion valve (9) provided between the heat exchanger and the receiver for expanding the refrigerant, and a device that discharges the refrigerant from the compressor to the outdoor heat exchanger or the heat exchanger. A heat pump device comprising a switching valve (5) that switches to flow smoothly, a heat medium circuit (W) that sends the heat medium that has been heat-exchanged in the heat medium heat exchanger to a heat utilization destination, and a control unit that controls the outdoor heat exchanger side expansion valve and / or the heat medium heat exchanger side expansion valve, wherein in heating mode, when the heat medium heat exchanger is operated as a condenser and the outdoor heat exchanger is operated as an evaporator, the control unit controls the state of the refrigerant drawn in or discharged to the compressor by the outdoor heat exchanger side expansion valve, and controls the high-pressure refrigerant flowing through the heat medium heat exchanger by the heat medium heat exchanger side expansion valve so that it is above a predetermined value.

[0070] The outdoor heat exchanger side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor (for example, intake superheat control, discharge superheat control, discharge temperature control), and the heat transfer medium heat exchanger side expansion valve controls the high-pressure refrigerant flowing through the heat transfer medium heat exchanger to be above a predetermined value. As a result, even when the outside air temperature is high in heating mode, the high and low pressure difference of the refrigerant can be kept above a predetermined value. Furthermore, this control may be implemented when the outside air temperature is higher than the first threshold, which is higher than the temperature during normal heating conditions such as winter (for example, in summer).

[0071] In the heat pump device according to a second aspect of the present disclosure, in the first aspect, the control unit controls the heat exchanger side expansion valve of the heat medium based on the rotational speed of the compressor so that the high-pressure refrigerant reaches a target value.

[0072] For example, a rotary compressor uses the high-pressure difference between the refrigerant to energize the vanes that separate the high-pressure and low-pressure compression chambers. The required energizing force for the vanes increases with the compressor's rotational speed. For compressors that require a high-pressure difference between the refrigerant necessary for operation depending on the rotational speed, it is effective to control the heat exchanger-side expansion valve to achieve a target value for the high-pressure refrigerant according to the compressor's rotational speed.

[0073] In the heat pump device according to the third aspect of the present disclosure, in the first or second aspect, the control unit controls the state of the refrigerant drawn into or discharged from the compressor by the heat exchanger side expansion valve when the heat transfer medium heat exchanger is operating as an evaporator and the outdoor heat exchanger is operating as a condenser, and controls the high-pressure refrigerant flowing through the outdoor heat exchanger by the outdoor heat exchanger side expansion valve so that it is above a predetermined value.

[0074] The heat exchanger-side expansion valve controls the state of the refrigerant being drawn in or discharged from the compressor (e.g., intake superheat control, discharge superheat control, discharge temperature control), while the outdoor heat exchanger-side expansion valve controls the high-pressure refrigerant flowing through the outdoor heat exchanger to be above a predetermined value. As a result, even when the outside air temperature is low in cooling mode, the high-low pressure difference of the refrigerant can be kept above a predetermined value. Furthermore, this control may be implemented when the outside air temperature is below the second threshold, which is lower than the temperature during normal cooling conditions such as summer (for example, in winter).

[0075] In the heat pump device according to the fourth aspect of the present disclosure, in any of the first to third aspects, the control unit controls the state of the refrigerant drawn in or discharged to the compressor by the heat exchanger side expansion valve when operating the heat transfer medium heat exchanger as an evaporator and the outdoor heat exchanger as a condenser in a cooling mode, and controls the state of the refrigerant drawn in or discharged to the compressor by the outdoor heat exchanger side expansion valve when the opening of the heat transfer medium heat exchanger side expansion valve exceeds a predetermined value.

[0076] In cooling mode, when the opening of the heat exchanger-side expansion valve exceeds a predetermined value, it is determined that the amount of circulating refrigerant has decreased, and the state of the refrigerant drawn into or discharged from the compressor is controlled by the outdoor heat exchanger-side expansion valve (e.g., intake superheat control, discharge superheat control, discharge temperature control). As a result, compared to when the state of the refrigerant drawn into or discharged from the compressor is controlled by the heat exchanger-side expansion valve, the pressure in the receiver decreases, a two-phase flow occurs in the receiver, the amount of circulating refrigerant increases, and the cooling capacity improves. Therefore, it is no longer necessary to set a large amount of refrigerant to be charged during cooling, and the amount of refrigerant to be charged can be kept as small as possible. Furthermore, when performing the above control, the opening degree of the heat exchanger-side expansion valve may be fixed (including slight changes in the opening degree).

[0077] In the fifth aspect of the present disclosure, the heat pump device has a larger capacity for the outdoor heat exchanger than for the heat transfer medium heat exchanger, in any of the first to fourth aspects.

[0078] Since the outdoor heat exchanger has a larger capacity than the heat transfer fluid heat exchanger, when used as a condenser, the outdoor heat exchanger condenses and liquefies more refrigerant. Therefore, in cooling mode, more refrigerant tends to be liquefied and stored in the receiver than in heating mode. As mentioned above, the cooling capacity can be improved by controlling the degree of superheating with the expansion valve on the outdoor heat exchanger side, eliminating the need to increase the amount of refrigerant charged to match the cooling mode.

[0079] In the heat pump device according to the sixth aspect of this disclosure, in any of the first to fifth aspects, the control unit controls the outdoor heat exchanger side expansion valve, or controls the outdoor heat exchanger side expansion valve and the heat exchanger side expansion valve, so that the heat transfer medium does not freeze in the heat transfer medium heat exchanger.

[0080] While the degree of superheating is being controlled by the outdoor heat exchanger expansion valve, the low pressure of the refrigerant may drop, potentially causing the heat transfer medium (water) to freeze in the heat transfer medium heat exchanger. Therefore, the outdoor heat exchanger expansion valve is controlled to prevent freezing in the heat transfer medium heat exchanger.

[0081] A heat pump system according to a seventh aspect of this disclosure includes a compressor for compressing a refrigerant, an outdoor heat exchanger for exchanging heat between the refrigerant and outside air, a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium, a receiver provided between the outdoor heat exchanger and the heat exchanger and capable of storing liquid refrigerant, an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant, a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant, and a switch for directing the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger. A heat pump device comprising a switching valve, a heat transfer medium circuit for sending the heat transfer medium, which has undergone heat exchange in the heat transfer medium heat exchanger, to a heat utilization destination, and a control unit for controlling the outdoor heat exchanger side expansion valve and / or the heat transfer medium heat exchanger side expansion valve, wherein the control unit controls the state of the refrigerant drawn into or discharged from the compressor by the heat transfer medium heat exchanger side expansion valve when the heat transfer medium heat exchanger is operating as an evaporator and the outdoor heat exchanger is operating as a condenser, and controls the high-pressure refrigerant flowing through the outdoor heat exchanger by the outdoor heat exchanger side expansion valve so that it is above a predetermined value.

[0082] A heat pump system according to the eighth aspect of this disclosure includes a compressor for compressing a refrigerant, an outdoor heat exchanger for exchanging heat between the refrigerant and outside air, a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium, a receiver provided between the outdoor heat exchanger and the heat exchanger and capable of storing liquid refrigerant, an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant, a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant, a switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger, and the heat exchanger A heat pump device comprising a heat transfer medium circuit that sends the heat transfer medium, which has undergone heat exchange in the exchanger, to a heat utilization destination, and a control unit that controls the outdoor heat exchanger side expansion valve and / or the heat transfer medium heat exchanger side expansion valve, wherein in a cooling mode in which the heat transfer medium heat exchanger operates as an evaporator and the outdoor heat exchanger operates as a condenser, the control unit controls the heat transfer medium heat exchanger side expansion valve so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value, and when the opening of the heat transfer medium heat exchanger side expansion valve exceeds a predetermined value, the control unit controls the outdoor heat exchanger side expansion valve so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value.

[0083] A control method for a heat pump system according to a first aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a control method for flowing the refrigerant discharged from the compressor to the outdoor heat exchanger or the heat exchanger. A control method for a heat pump device comprising a switching valve that switches to a certain setting, and a heat transfer circuit that sends the heat transfer medium, which has been heat-exchanged in the heat transfer medium heat exchanger, to a heat utilization destination, wherein the device is set to a heating mode in which the heat transfer medium heat exchanger operates as a condenser and the outdoor heat exchanger operates as an evaporator, and when the outside air temperature is set to a first threshold or higher, the outdoor heat exchanger side expansion valve controls the degree of superheating of the low-pressure refrigerant drawn into the compressor to a predetermined value, and the heat transfer medium heat exchanger side expansion valve controls the high-pressure refrigerant flowing through the heat transfer medium heat exchanger to a predetermined value or higher.

[0084] A control method for a heat pump system according to a second aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger, capable of storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a control method for the refrigerant discharged from the compressor, provided by the outdoor heat exchanger A control method for a heat pump device comprising a switching valve that switches the flow of a heat transfer medium to a device or the heat transfer medium heat exchanger, and a heat transfer medium circuit that sends the heat transfer medium, which has undergone heat exchange in the heat transfer medium heat exchanger, to a heat utilization destination, wherein in a cooling mode in which the heat transfer medium heat exchanger is operated as an evaporator and the outdoor heat exchanger is operated as a condenser, the state of the refrigerant drawn in or discharged to the compressor is controlled by the heat transfer medium heat exchanger side expansion valve, and the high-pressure refrigerant flowing through the outdoor heat exchanger is controlled by the outdoor heat exchanger side expansion valve to be above a predetermined value.

[0085] A control method for a heat pump system according to a third aspect of the present disclosure includes: a compressor for compressing a refrigerant; an outdoor heat exchanger for exchanging heat between the refrigerant and outside air; a heat exchanger for exchanging heat between the refrigerant and a heat transfer medium; a receiver provided between the outdoor heat exchanger and the heat exchanger for storing liquid refrigerant; an outdoor heat exchanger side expansion valve provided between the outdoor heat exchanger and the receiver for expanding the refrigerant; a heat exchanger side expansion valve provided between the heat exchanger and the receiver for expanding the refrigerant; and a switch for switching the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat exchanger. A control method for a heat pump device comprising a valve and a heat transfer circuit for sending the heat transfer medium, which has been heat-exchanged in the heat transfer medium heat exchanger, to a heat utilization destination, wherein in a cooling mode in which the heat transfer medium heat exchanger is operated as an evaporator and the outdoor heat exchanger is operated as a condenser, the heat transfer medium heat exchanger side expansion valve is controlled so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value, and when the opening degree of the heat transfer medium heat exchanger side expansion valve exceeds a predetermined value, the opening degree of the heat transfer medium heat exchanger side expansion valve is fixed, and the outdoor heat exchanger side expansion valve is controlled so that the degree of superheating of the low-pressure refrigerant drawn into the compressor is a predetermined value. [Explanation of Symbols]

[0086] 1. Heat pump system 3. Compressor 5. Four-way valve (switching valve) 7 Water heat exchanger (heat medium heat exchanger) 9. First expansion valve (heat exchanger side expansion valve) 11 Receiver 13. Second expansion valve (outdoor heat exchanger side expansion valve) 15 Outdoor heat exchanger 16 Discharge pipe 17 High-voltage switch 19 Discharge temperature sensor 21 Accumulator 23 Low-voltage sensor 25 Intake temperature sensor 27 Refrigerant Piping 29 High-voltage sensor 31 High-pressure temperature sensor 33 Outdoor fan C Refrigerant Circuit W Water circuit (heat transfer circuit)

Claims

1. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control unit that controls the outdoor heat exchange side expansion valve and / or the heat transfer medium heat exchange side expansion valve, A heat pump device equipped with, When the control unit operates the heat transfer fluid heat exchanger as a condenser and the outdoor heat exchanger as an evaporator in heating mode, The outdoor heat exchanger side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, A heat pump device that uses the heat exchanger-side expansion valve of the heat transfer medium to control the high-pressure refrigerant flowing through the heat exchanger of the heat transfer medium so that it is above a predetermined value.

2. The heat pump device according to claim 1, wherein the control unit controls the heat exchanger side expansion valve of the heat transfer medium based on the rotational speed of the compressor so that the high-pressure refrigerant reaches a target value.

3. When the control unit operates the heat transfer fluid heat exchanger as an evaporator and the outdoor heat exchanger as a condenser in a cooling mode, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, The heat pump device according to claim 1 or 2, wherein the outdoor heat exchanger side expansion valve controls the high-pressure refrigerant flowing through the outdoor heat exchanger to be above a predetermined value.

4. The control unit operates the heat transfer fluid heat exchanger as an evaporator and the outdoor heat exchanger as a condenser in a cooling mode, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, and when the opening degree of the heat exchanger-side expansion valve exceeds a predetermined value, The heat pump device according to claim 1 or 2, wherein the outdoor heat exchanger side expansion valve controls the state of the refrigerant drawn into or discharged from the compressor.

5. The heat pump device according to claim 4, wherein the capacity of the outdoor heat exchanger is larger than that of the heat transfer medium heat exchanger.

6. The control unit controls the outdoor heat exchange side expansion valve so that the heat transfer medium does not freeze in the heat transfer medium heat exchanger, or controls the outdoor heat exchange side expansion valve and the heat transfer medium heat exchange side expansion valve, according to claim 4.

7. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control unit that controls the outdoor heat exchange side expansion valve and / or the heat transfer medium heat exchange side expansion valve, A heat pump device equipped with, When the control unit operates the heat transfer fluid heat exchanger as an evaporator and the outdoor heat exchanger as a condenser in a cooling mode, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, A heat pump device that uses the outdoor heat exchanger side expansion valve to control the amount of high-pressure refrigerant flowing through the outdoor heat exchanger to be above a predetermined value.

8. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control unit that controls the outdoor heat exchange side expansion valve and / or the heat transfer medium heat exchange side expansion valve, A heat pump device equipped with, The control unit operates the heat transfer fluid heat exchanger as an evaporator and the outdoor heat exchanger as a condenser in a cooling mode, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, and when the opening degree of the heat exchanger-side expansion valve exceeds a predetermined value, A heat pump device that controls the state of the refrigerant drawn into or discharged from the compressor by the outdoor heat exchanger side expansion valve.

9. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control method for a heat pump device comprising: In a heating mode in which the heat transfer medium heat exchanger operates as a condenser and the outdoor heat exchanger operates as an evaporator, The outdoor heat exchanger side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, A control method for a heat pump device, wherein the heat exchanger-side expansion valve controls the high-pressure refrigerant flowing through the heat exchanger to be above a predetermined value.

10. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control method for a heat pump device comprising: In a cooling mode in which the heat transfer fluid heat exchanger operates as an evaporator and the outdoor heat exchanger operates as a condenser, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, A control method for a heat pump system, which uses the outdoor heat exchanger side expansion valve to control the amount of high-pressure refrigerant flowing through the outdoor heat exchanger to be above a predetermined value.

11. A compressor that compresses the refrigerant, An outdoor heat exchanger that exchanges heat between the refrigerant and the outside air, A heat exchanger that exchanges heat between a refrigerant and a heat transfer medium, A receiver is provided between the outdoor heat exchanger and the heat transfer fluid heat exchanger, and is capable of storing liquid refrigerant. An outdoor heat exchanger side expansion valve is provided between the outdoor heat exchanger and the receiver to expand the refrigerant, A heat exchanger side expansion valve is provided between the heat exchanger and the receiver, which expands the refrigerant. A switching valve that switches the refrigerant discharged from the compressor to flow to the outdoor heat exchanger or the heat transfer medium heat exchanger, A heat transfer circuit that sends the heat transfer medium, which has undergone heat exchange in the aforementioned heat transfer heat exchanger, to a heat utilization destination. A control method for a heat pump device comprising: In a cooling mode in which the heat transfer fluid heat exchanger operates as an evaporator and the outdoor heat exchanger operates as a condenser, The heat exchanger-side expansion valve controls the state of the refrigerant being drawn into or discharged from the compressor, and when the opening degree of the heat exchanger-side expansion valve exceeds a predetermined value, A control method for a heat pump system that controls the state of the refrigerant drawn into or discharged from the compressor by the outdoor heat exchanger side expansion valve.

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