Heat pump device and hot water supply device

Abstract

A heat pump device according to the present disclosure comprises: a principal refrigerant circuit that circulates a refrigerant through an injection-port-equipped compressor, a condenser, a principal

Description

Heat pump device and hot water heater

[0001] This technology relates to a heat pump device and a hot water supply device, and in particular to operation of the device when the temperature around the heat exchanger serving as an evaporator is low.

[0002] Conventionally, there are heat pump devices that utilize a heat pump cycle to provide hot water supply, air conditioning, etc. Heat pump devices basically have a refrigerant circuit that circulates refrigerant by connecting devices such as a compressor, a condenser, a throttling device (pressure reducing device), and an evaporator with refrigerant piping. Here, heat pump devices are often installed as separate devices, with an outdoor unit installed outdoors and an indoor unit.

[0003] Heat pump devices are installed in a variety of environments for use in hot water supply, air conditioning, and other applications. In recent years, in order to protect the global environment, heat pump devices that use air as a heat source are increasingly being introduced in cold regions, replacing boiler-type devices that use fossil fuels for heating. For this reason, heat pump devices are also installed in low-temperature environments where the outdoor air temperature is low. Here, a low-temperature environment refers to an outdoor air temperature of approximately -20°C or lower.

[0004] When a heat pump device heats a load such as water or air, the heat exchanger installed outdoors generally serves as the evaporator. In low outdoor temperature environments, refrigerant stagnation is likely to occur in the heat exchanger and piping installed outdoors in the refrigerant circuit.

[0005] Therefore, when an outdoor heat exchanger serves as an evaporator and exchanges heat between the refrigerant and the outside air, the low-pressure side of the refrigerant circuit, where the refrigerant is at a low pressure, becomes negative pressure. This also causes liquid refrigerant to be drawn into the compressor, resulting in liquid backflow. To prevent this, heat pump devices have an accumulator between the evaporator and the compressor in the refrigerant circuit, preventing liquid refrigerant from flowing from the evaporator to the compressor (see, for example, Patent Document 1).

[0006] Japanese Patent Application Laid-Open No. 2018-155451

[0007] However, conventional heat pump devices have an accumulator with a large volume, which hinders downsizing of the unit.

[0008] Therefore, an object of the present invention is to provide a smaller heat pump device and a water heater that can operate even in a low outdoor air temperature environment.

[0009] In order to solve the above problems, the heat pump device disclosed herein comprises a main refrigerant circuit which circulates the refrigerant by connecting a compressor having an injection port and compressing and discharging the refrigerant, a condenser which exchanges heat between the refrigerant and a load, a main circuit throttling device section which decompresses the refrigerant, and an evaporator which exchanges heat between the refrigerant and outside air through piping; an injection pipe which is connected at one end to the pipe between the condenser and the throttling device and at the other end to the injection port; an injection throttling device which adjusts the opening to adjust the amount of refrigerant flowing through the injection pipe; an outside air temperature detection device which detects the temperature of the outside air; an suction pressure detection device which detects the suction pressure of the refrigerant sucked into the compressor; and a control device, wherein the main circuit throttling device section has a plurality of main circuit throttling devices with different capacities connected in parallel, and when the control device determines during operation based on the temperature of the outside air that the temperature of the outside air is below a predetermined operating temperature, the control device opens the injection throttling device to control the opening, selects a main circuit throttling device from the plurality of main circuit throttling devices in the main circuit throttling device section based on the suction pressure, and controls the opening of the selected main circuit throttling device.

[0010] A hot water supply device according to the present disclosure includes the heat pump device described above and supplies hot water.

[0011] In the disclosed heat pump system, the control device opens the injection throttle device based on the outside air temperature during operation and injects refrigerant into the compressor via the injection pipe. This reduces the amount of refrigerant passing through the evaporator without reducing the amount of refrigerant used to supply heat to the load, allowing the refrigerant that passes through to evaporate while increasing the pressure on the low-pressure side of the main refrigerant circuit. Furthermore, a main circuit throttle device can be selected from multiple main circuit throttle devices connected in parallel based on the suction pressure, allowing for control suited to the environment. Therefore, even when the heat pump water heater is installed in a location with a low outside temperature, an accumulator is not required, allowing for a more compact system.

[0012] Fig. 1 is a diagram showing an example of the equipment configuration of a heat pump device according to embodiment 1. Fig. 2 is a diagram showing a process flow relating to the operation of heat pump water heater 100 according to embodiment 1. Fig. 3 is a diagram showing a process flow for heat pump water heater 100 according to embodiment 2. Fig. 4 is a diagram showing a process flow for heat pump water heater 100 according to embodiment 3. Fig. 5 is a diagram showing an example of the relationship between outside air temperature, heat medium outflow temperature, and the upper limit of the drive frequency of compressor 110 in heat pump water heater 100 according to embodiment 4.

[0013] Hereinafter, heat pump devices and the like according to embodiments will be described with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The dimensional relationships between components in the drawings may differ from those in reality. The configurations of components shown throughout the specification are merely illustrative and are not limited to the configurations described in the specification. Not all of the devices described in the specification may be included. In particular, the combinations of components are not limited to the combinations in each embodiment; components described in other embodiments may be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state, operation, etc. of the device. Furthermore, when multiple similar devices are distinguished by subscripts, the reference numerals, subscripts, etc. may be omitted if there is no need to distinguish or identify them.

[0014] Embodiment 1. FIG. 1 is a diagram illustrating an example of the equipment configuration of a heat pump apparatus according to Embodiment 1. The heat pump apparatus according to Embodiment 1 will be described as a heat pump water heater 100 that heats water and supplies hot water. The heat pump water heater 100 according to Embodiment 1 has a main refrigerant circuit in which a compressor 110, a flow switching device 120, a load-side heat exchanger 130, a refrigerant tank 140, an auxiliary heat exchanger 150, a main circuit throttle device unit 160, and a heat source-side heat exchanger 170 are connected in a circular configuration by refrigerant piping. Refrigerant circulates through the main refrigerant circuit. Here, the heat pump water heater 100 of FIG. 1 has two flow switching devices 120, two main circuit throttle devices 161 that constitute the main circuit throttle device unit 160, and two heat source-side heat exchangers 170. The flow path switching devices 120A and 120B, the main circuit expansion devices 161A and 161B, and the heat source side heat exchangers 170A and 170B are each installed in a parallel connection relationship with respect to the main refrigerant circuit. By providing two flow path switching devices 120 and two heat source side heat exchangers 170, one heat source side heat exchanger 170 can be used as an evaporator and the other heat source side heat exchanger 170 can be used for defrosting. However, the flow path switching devices 120 and the heat source side heat exchangers 170 in the heat pump water heater 100 of embodiment 1 do not have to be configured in this way.

[0015] The heat pump water heater 100 also has an injection flow path that branches off from the refrigerant piping of the main refrigerant circuit located between the heat source side heat exchanger 170 and the auxiliary heat exchanger 150 and through which the refrigerant flows into the compressor 110. The heat pump water heater 100 also has a water circuit that connects the load side heat exchanger 130, the hot water tank 180, and the hot water pump 190 and through which the water to be heated passes.

[0016] The compressor 110 draws in and compresses low-temperature and low-pressure gas refrigerant, then discharges it in a high-temperature and high-pressure state. The compressor 110 is, for example, an inverter compressor whose capacity can be controlled by changing the drive frequency. The compressor 110 has, for example, a low-pressure shell structure. A compressor with a low-pressure shell structure has a compression chamber within a sealed container, and the sealed container is filled with a low-pressure refrigerant pressure atmosphere, drawing in and compressing the low-pressure refrigerant within the sealed container. The compressor 110 of the first embodiment also has a structure including an injection port 111 that allows refrigerant to flow into the compression chamber from the outside. Therefore, the compressor 110 of the first embodiment can perform intermediate injection, in which refrigerant is introduced from the outside through the injection port 111 and injected into the refrigerant being compressed.

[0017] In the first embodiment, the load-side heat exchanger 130 functions as a condenser. The load-side heat exchanger 130 exchanges heat between the refrigerant and water passing through the water circuit, dissipating heat to the refrigerant and heating the water. Therefore, the water acts as a load in the main refrigerant circuit. The refrigerant tank 140, which serves as a receiver, temporarily stores liquid refrigerant. The main circuit throttle device unit 160 reduces the pressure of the high-pressure refrigerant and adjusts the refrigerant pressure and flow rate. In the heat pump water heater 100 of the first embodiment, the main circuit throttle device unit 160 includes multiple main circuit throttle devices 161 with different capacities. The main circuit throttle devices 161 are devices such as electronic expansion valves whose opening degree (opening area) can be controlled continuously or in multiple stages under the control of the control device 200 (described later). As described above, the heat pump water heater 100 of FIG. 1 includes two main circuit throttle devices 161A and 161B connected in parallel to the main refrigerant circuit. Here, the main circuit throttle device 161A has a smaller maximum opening area than the main circuit throttle device 161B, but is a device that can finely adjust its capacity. On the other hand, the main circuit throttle device 161B has a larger maximum opening area than the main circuit throttle device 161A, and is a device used for normal operation.

[0018] The auxiliary heat exchanger 150 exchanges heat between the refrigerant passing through the main refrigerant circuit and the refrigerant passing through the injection passage. The auxiliary heat exchanger 150 supercools the refrigerant passing through the main refrigerant circuit through heat exchange between the refrigerants, thereby increasing the dryness of the refrigerant passing through the injection passage. The heat source side heat exchanger 170 exchanges heat between the refrigerant passing through the heat source side heat exchanger 170 and outside air, such as outdoor air, to evaporate the refrigerant. The fan 171 sends outside air into the heat source side heat exchanger 170 to promote heat exchange in the heat source side heat exchanger 170.

[0019] The injection pipe 151 is a pipe that constitutes an injection flow path. One end of the injection pipe 151 is connected to a refrigerant pipe between the heat source side heat exchanger 170 and the auxiliary heat exchanger 150, and the other end is connected to the injection port 111 of the compressor 110. The refrigerant that has passed through the injection pipe 151 flows into the compression chamber of the compressor 110. At this time, the pressure of the inflowing refrigerant is high or medium pressure. The medium pressure is a pressure that is lower than the high-pressure side pressure in the main refrigerant circuit (for example, the refrigerant pressure in the condenser or the discharge pressure on the discharge side of the compressor 110) and higher than the low-pressure side pressure (for example, the refrigerant pressure in the evaporator or the suction pressure on the suction side of the compressor 110).

[0020] The injection throttle device 152 is installed in the injection pipe 151. The injection throttle device 152 adjusts the amount and pressure of the refrigerant that passes through the injection pipe 151 and flows into the injection port 111 of the compressor 110. The injection throttle device 152 is a device such as an electronic expansion valve whose opening degree can be controlled continuously or in multiple stages based on the control of the control device 200, which will be described later.

[0021] The water circuit in the heat pump water heater 100 of the first embodiment connects the load-side heat exchanger 130, the hot water tank 180, and the hot water pump 190 in a circular arrangement with piping. Hot water circulates through the water circuit. The hot water tank 180 stores the hot water. The hot water pump 190 pressurizes the hot water and circulates it through the water circuit.

[0022] The heat pump water heater 100 also includes a control device 200. The control device 200 controls the overall operation of the heat pump water heater 100 based on detection signals sent from the various sensors described above and instructions from a remote controller (not shown). For example, the control device 200 controls the drive frequency of the compressor 110. The control device 200 also controls the opening degree of the injection throttle device 152 and the main circuit throttle device 161 in the main circuit throttle device section 160 based on the suction pressure of the compressor 110. The control device 200 also controls the drive of the hot water pump 190. The control device 200 performs these controls to operate the heat pump water heater 100.

[0023] Here, the control device 200 includes a microcomputer. The microcomputer includes, for example, a control processing device such as a CPU (Central Processing Unit). The control device 200 also includes an I / O port for managing the input and output of various signals. The microcomputer also includes, as storage device 210, a volatile storage device (not shown) such as a random access memory (RAM) that can temporarily store data, and a non-volatile auxiliary storage device (not shown) such as a hard disk or flash memory. The storage device 210 stores program data that describes the processing procedures to be performed by the control processing device. The control processing device then executes processing based on the program data to realize the processing of each part. However, this is not limited to this, and each device may be configured as dedicated equipment (hardware). The control device 200 also includes a timing device 211, such as a timer, for timing. Here, the heat pump water heater 100 of FIG. 1 has the control device 200 installed inside. However, the installation location of the control device 200 is not particularly limited.

[0024] The heat pump water heater 100 has an intake pressure sensor 220, an outdoor air temperature sensor 230, and an outlet water temperature sensor 240. The intake pressure sensor 220, which serves as an intake pressure detection device, detects the pressure of the refrigerant drawn into the compressor 110 and outputs an intake pressure detection signal. The outdoor air temperature sensor 230, which serves as an outdoor air temperature detection device, is installed at the air inlet portion of the heat source heat exchanger 170. The outdoor air temperature sensor 230 detects, for example, the outdoor air temperature, which is the temperature around the installation location of the heat pump water heater 100, and outputs an outdoor air temperature detection signal. The outlet water temperature sensor 240, which serves as a load temperature detection device, detects the temperature of water flowing out of the load heat exchanger 130 in the water circuit as the load temperature and outputs a load temperature detection signal.

[0025] Fig. 2 is a diagram showing a process flow related to the operation of heat pump water heater 100 in embodiment 1. The process shown in Fig. 2 is performed by control device 200. Based on Fig. 2, the control process performed during operation of heat pump water heater 100 in embodiment 1 will be described.

[0026] During normal operation, the control device 200 acquires outside air temperature data contained in an outside air temperature detection signal from the outside air temperature sensor 230 (step S1). The control device 200 then determines whether the outside air temperature is equal to or lower than a preset operation temperature (step S2). The operation temperature is not particularly limited, but is assumed to be -20°C here, for example.

[0027] When the control device 200 determines that the outside air temperature is below the operating temperature setting of −20°C, it sends an instruction signal to the injection throttle device 152 to open the valve by a preset opening amount (step S3). Here, although not particularly limited, the preset opening amount is assumed to be the initial opening amount when the valve is opened from a closed state. The opening amounts after the initial opening amount are increased, for example, by 10% from the initial opening amount. On the other hand, when the control device 200 determines that the outside air temperature is higher than −20°C, it sends an instruction signal to the injection throttle device 152 to close the valve and block the flow of refrigerant through the injection flow path (step S4). Closing the injection throttle device 152 here includes leaving the valve closed if it is already closed (the same applies below).

[0028] The control device 200 also acquires suction pressure data contained in the suction pressure detection signal from the suction pressure sensor 220 (step S5). The control device 200 then determines whether the suction pressure is equal to or less than a preset pressure (step S6). The preset pressure is not particularly limited, but is assumed to be 0.10 MPa, for example. If the control device 200 determines that the suction pressure is equal to or less than the preset pressure of 0.10 MPa, it closes the main circuit throttle device 161B and controls the aperture of the main circuit throttle device 161A (step S7). On the other hand, if the control device 200 determines that the suction pressure is higher than the preset pressure of 0.10 MPa, it closes the main circuit throttle device 161A and controls the aperture of the main circuit throttle device 161B (step S8). Here, in step S8, the main circuit throttle device 161A is closed. However, the control device 200 may open the main circuit throttle device 161A and the main circuit throttle device 161B and control the opening degree thereof.

[0029] When the control device 200 determines that the set time has elapsed based on the timekeeping of the timer 211 (step S9), the control device 200 returns to step S1 and continues the process. Here, although not particularly limited, the set time is assumed to be 1 minute or more.

[0030] As described above, according to the heat pump water heater 100 of the first embodiment, the control device 200 opens the injection throttle device 152 during operation based on the outside air temperature. Opening the injection throttle device 152 allows the refrigerant to flow through the injection pipe 151, and performs intermediate injection, in which the refrigerant is directly injected into the compressor 110 through the injection port 111 of the compressor 110. This reduces the amount of refrigerant passing through the heat source heat exchanger 170 (which serves as an evaporator) and evaporates it, while maintaining the heating of the water load without reducing the amount of refrigerant required for condensation in the load heat exchanger 130. This increases the pressure on the low-pressure side of the main refrigerant circuit. Therefore, the heat pump water heater 100 of the first embodiment does not require an accumulator, allowing for compactness.

[0031] In the heat pump water heater 100 of the first embodiment, the main circuit throttle device section 160 includes multiple main circuit throttle devices 161 with different capacities connected in parallel to the main refrigerant circuit. Therefore, when the control device 200 determines that the outside air temperature is low and the low-pressure side of the main refrigerant circuit is at or below the set pressure of 0.1 MPa, it opens and controls the main circuit throttle device 161A, which can precisely control the opening area. This prevents a sudden drop in pressure on the low-pressure side of the main refrigerant circuit and suppresses the generation of liquid refrigerant. Furthermore, when the low-pressure side of the main refrigerant circuit is above the set pressure of 0.1 MPa, the control device 200 performs normal operation using the main circuit throttle device 161B.

[0032] The heat pump water heater 100 of the first embodiment also includes an auxiliary heat exchanger 150. The auxiliary heat exchanger 150 can supercool the refrigerant passing through the main refrigerant circuit and increase the dryness of the refrigerant passing through the injection flow path, thereby preventing intermediate injection of liquid refrigerant.

[0033] Second Embodiment Fig. 3 is a diagram showing a processing flow for heat pump water heater 100 in a second embodiment. The configuration of heat pump water heater 100 in the second embodiment is the same as the configuration in Fig. 1 described in the first embodiment. The processing shown in Fig. 3 is also performed by control device 200, as in the first embodiment. The processing described as being performed by control device 200 in the first embodiment relates to processing performed during normal operation. In the second embodiment, processing performed when compressor 110 is started, such as at the start of operation, is described.

[0034] When a switch or the like is turned on to instruct the control device 200 to start operation, the control device 200 acquires outside air temperature data contained in an outside air temperature detection signal from the outside air temperature sensor 230 (step S11). The control device 200 then determines whether the outside air temperature is equal to or lower than a preset startup temperature (step S12). The startup temperature is not particularly limited, but here it is set to, for example, −20° C., similar to the operation temperature in the first embodiment.

[0035] When the control device 200 determines that the outside air temperature is equal to or lower than the startup setting temperature of -20°C, it sends a command signal to the injection throttle device 152 to open the valve by a preset initial opening amount (step S13). The control device 200 then starts the compressor 110 and performs normal operation (step S14). The size of the initial opening amount is not particularly limited. On the other hand, when the control device 200 determines that the outside air temperature is higher than -20°C, it starts the compressor 110 and performs normal operation while keeping the injection throttle device 152 closed (step S15).

[0036] As described above, according to the heat pump water heater 100 of the second embodiment, the control device 200 opens the injection throttle device 152 based on the outside air temperature when starting the compressor 110, and controls the compressor 110 to perform intermediate injection, thereby starting the compressor 110. This makes it possible to prevent a sudden drop in pressure on the low-pressure side of the refrigerant circuit.

[0037] Third Embodiment. Figure 4 is a diagram showing a processing flow for the heat pump water heater 100 in the third embodiment. The configuration of the heat pump water heater 100 in the third embodiment is the same as the configuration in Figure 1 described in the first embodiment. The processing shown in Figure 4 is performed by the control device 200. In the main refrigerant circuit, generally, when the drive frequency of the compressor 110 is higher than expected, the refrigerant pressure on the low-pressure side of the main refrigerant circuit decreases. Therefore, in the heat pump water heater 100 in the third embodiment, when the control device 200 determines that the refrigerant pressure on the low-pressure side of the main refrigerant circuit is low, the control device 200 forcibly reduces the drive frequency of the compressor 110. By reducing the drive frequency of the compressor 110, the suction pressure of the compressor 110 can be increased and the discharge pressure can be decreased.

[0038] The processing of steps S21 to S29 performed by the control device 200 shown in Fig. 4 is similar to the processing of steps S1 to S9 described in embodiment 1. In embodiment 3, when the pressure on the low-pressure side of the main refrigerant circuit is adjusted by the main circuit throttle device 161B in step S27, the control device 200 determines whether the injection throttle device 152 is open (step S30). If the control device 200 determines that the injection throttle device 152 is open and is performing opening control, the control device 200 further determines whether the compressor 110 is operating at the minimum drive frequency (step S31).

[0039] If the control device 200 determines that the compressor 110 is not being driven at the minimum drive frequency, it reduces the drive frequency of the compressor 110 (step S32). Here, the drive frequency of the compressor 110 is reduced by a preset frequency. Although not particularly limited, for example, the control device 200 drives the compressor 110 at a drive frequency reduced by 10% of the drive frequency of the compressor 110. Then, if the control device 200 determines, based on the timing of the timer 211, that the set time has elapsed (step S29), it returns to step S21 and continues processing.

[0040] On the other hand, if the control device 200 determines in step S30 that the injection throttle device 152 is closed or that the compressor 110 is operating at the minimum operating frequency in step S31, it determines whether the set time has elapsed (step S29). If the control device 200 determines that the set time has elapsed, it returns to step S21 and continues the process.

[0041] As described above, according to the heat pump water heater 100 of the third embodiment, when the control device 200 determines that the injection throttle device 152 is open and the suction pressure is lower than the set pressure, the control device 200 drives the compressor 110 at a reduced drive frequency. This makes it possible to more reliably increase the pressure of the refrigerant on the low-pressure side of the main refrigerant circuit.

[0042] Fourth Embodiment. FIG. 5 illustrates an example of the relationship between the outdoor air temperature, the heat medium outlet temperature, and the upper limit of the drive frequency of the compressor 110 in a heat pump water heater 100 according to a fourth embodiment. The configuration of the heat pump water heater 100 according to the fourth embodiment is the same as that shown in FIG. 1 described in the first embodiment. FIG. 5 shows the relationship in a table format. Here, the outdoor air temperature (°C), the outlet water temperature (°C), and the upper limit of the drive frequency (Hz) of the compressor 110 are shown. The outlet water temperature is the temperature detected by the outlet water temperature sensor 240 and serves as data indicating the load status. Here, the outlet water temperature is used as the data indicating the load status, but this is not limiting. For example, the inlet water temperature of the water flowing into the load-side heat exchanger 130 may also serve as data indicating the load status.

[0043] In the third embodiment, the control device 200 reduces the drive frequency of the compressor 110 to increase the pressure on the low-pressure side of the main refrigerant circuit. However, the pressure on the low-pressure side of the main refrigerant circuit suddenly decreases over a short period of time. This means that the control device 200 may not be able to process the compressor 110 in time. Therefore, in the heat pump water heater 100 of the fourth embodiment, the upper limit of the drive frequency of the compressor 110 is determined in advance as drive frequency upper limit data based on the outside air temperature and the load state.

[0044] For this reason, the storage device 210 stores data relating to the determined upper limit of the drive frequency, as shown in Fig. 5. Then, the control device 200 controls the drive of the compressor 110 at a drive frequency equal to or lower than the determined upper limit.

[0045] As described above, according to the heat pump water heater 100 of the fourth embodiment, the storage device 210 stores data relating to the relationship between the outside air temperature, the heat medium outflow temperature indicating the load state, and the upper limit of the drive frequency of the compressor 110. The control device 200 controls the drive of the compressor 110 at a drive frequency equal to or lower than the upper limit based on the outside air temperature and the load state. This makes it possible to respond to a sudden drop in pressure on the low-pressure side of the main refrigerant circuit.

[0046] In the first embodiment described above, the heat pump water heater 100 has been described as an example of a heat pump device, but the present invention is not limited to this. For example, the present invention can be applied to other heat pump devices having a refrigerant circuit, such as air conditioners and heating devices.

[0047] 100 Heat pump water heater, 110 Compressor, 111 Injection port, 120, 120A, 120B Flow path switching device, 130 Load side heat exchanger, 140 Refrigerant tank, 150 Auxiliary heat exchanger, 151 Injection piping, 152 Injection throttling device, 160 Main circuit throttling device section, 161, 161A, 161B Main circuit throttling device, 170, 170A, 170B Heat source side heat exchanger, 171 Fan, 180 Hot water tank, 190 Hot water pump, 200 Control device, 210 Storage device, 211 Timing device, 220 Intake pressure sensor, 230 Outdoor air temperature sensor, 240 Outlet side water temperature sensor.

Claims

1. A main refrigerant circuit having a compressor with an injection port that compresses and discharges a refrigerant, a condenser that exchanges heat between the refrigerant and a load, a main circuit throttle device unit that decompresses the refrigerant, and an evaporator that exchanges heat between the refrigerant and external air, and circulating the refrigerant; an injection pipe having one end connected to the pipe between the condenser and the main circuit throttle device unit and the other end connected to the injection port; an injection throttle device that adjusts the amount of refrigerant flowing through the injection pipe by adjusting its opening; an outside air temperature detection device that detects the temperature of the external air; a suction pressure detection device that detects the suction pressure of the refrigerant sucked into the compressor; and a control device, wherein the main circuit throttle device unit has a plurality of main circuit throttle devices with different capacities that are connected in parallel, When the control device determines during operation based on the temperature of the external air that the temperature of the external air is below a predetermined operating set temperature, it opens the injection throttling device to control the opening degree, selects a main circuit throttling device from the multiple main circuit throttling devices in the main circuit throttling device section based on the suction pressure, and controls the opening degree of the selected main circuit throttling device.

2. The heat pump device of claim 1, wherein when the control device starts the compressor, if it determines based on the temperature of the outside air that the temperature of the outside air is below a preset start-up temperature, it opens the injection throttle device and starts the compressor.

3. A heat pump device as described in claim 1 or claim 2, wherein when the control device determines that the injection throttle device is open and the suction pressure is equal to or lower than a predetermined set pressure, the control device controls the compressor to operate at a reduced drive frequency.

4. A heat pump device as claimed in any one of claims 1 to 3, comprising: a load temperature detection device that detects the temperature related to the load that exchanges heat in the condenser as a load temperature; and a storage device that stores drive frequency upper limit data that associates the temperature of the external air, the load temperature, and an upper limit on the drive frequency of the compressor, wherein the control device controls the drive of the compressor within the range of the drive frequency upper limit data that is determined based on the temperature of the external air and the state of the load.

5. A heat pump device as described in any one of claims 1 to 4, comprising an auxiliary heat exchanger that exchanges heat between the refrigerant flowing from the condenser to the main circuit throttling device and the refrigerant that passes through the injection throttling device and flows through the injection piping.

6. A hot water supply device that has the heat pump device according to any one of claims 1 to 5 and supplies hot water.

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