JP7551769B2 - Refrigeration Cycle Equipment - Google Patents

Description

An embodiment of the present invention relates to a refrigeration cycle device.

The refrigeration cycle device is composed of a compressor, a condenser, an expansion valve, and an evaporator as its main components. For example, during heating or heating operation, the refrigeration cycle device absorbs heat from the outside air with the evaporator and supplies the heat to the indoor air or hot water with the condenser. At that time, the higher the outside air temperature, the greater the amount of heat absorbed by the evaporator, and the higher the temperature and pressure of the refrigerant drawn into the compressor. If this causes the compressor to overheat, the temperature of the refrigerant discharged from the compressor may rise excessively. Such an increase in the discharge refrigerant temperature may, for example, reduce the viscosity of the lubricating oil that lubricates the compression mechanism of the compressor, causing damage to the motor in the compressor. Therefore, various measures are taken to prevent such an increase in the discharge refrigerant temperature.

One example is adding an injection flow path to the refrigerant circulation path, which guides a portion of the liquid refrigerant to the compressor. The injection flow path is connected between the condenser and the expansion valve in the circulation path, and includes a check valve, a two-way valve, an expansion valve (injection flow path expansion valve), etc. By using the injection flow path, a portion of the liquid refrigerant that has passed through the condenser is injected into the cylinder chamber of the compressor, and the gas refrigerant sucked into the compressor is cooled by the liquid refrigerant. This prevents the compressor from overheating.

Such an injection flow path is controlled to open and close in response to, for example, the outside air temperature. When the injection flow path is opened and then closed, or during a power outage, the liquid phase refrigerant is sealed in the injection flow path (liquid-sealed state). When the outside air temperature (ambient temperature) rises in the liquid-sealed state, the liquid phase refrigerant expands in the injection flow path. For example, if the liquid phase refrigerant expands between the two-way valve and the check valve of the injection flow path, depending on the extent of the expansion, there is a risk of damage to the piping between these valves, which are in a liquid-sealed state. For this reason, when providing an injection flow path, it is necessary to use a piping configuration that does not cause such a liquid-sealed state.

Patent No. 6514964

The present invention has been made based on this, and its object is to provide a refrigeration cycle device equipped with an injection flow path that can avoid a liquid-sealed state with relatively simple piping without complicating the piping.

According to an embodiment, the refrigeration cycle device includes a refrigerant circuit including a single compressor that discharges a gas phase refrigerant, a heat source side heat exchanger, a first expansion valve, a utilization side heat exchanger, and an injection flow path that divides a part of the liquid phase refrigerant and injects only the divided liquid phase refrigerant into the compressor, and in which the refrigerant circulates. The injection flow path includes a solenoid valve, a check valve, and a second expansion valve arranged in this order from the upstream side in the flow direction of the liquid phase refrigerant in the injection flow path. The second expansion valve is not fully closed, but is in a stop state in which it is kept open by a stop opening degree that is larger than the fully closed state.

FIG. 1 is a circuit diagram that illustrates a refrigeration cycle of a refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to an embodiment. FIG. 2 is a control flow diagram during opening and closing control of an injection flow passage in a refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to the embodiment. FIG. 3 is a diagram illustrating a flow of a portion of the liquid-phase refrigerant in a state in which the injection flow path is opened in the cooling mode of the refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to the embodiment. FIG. 4 is a diagram that illustrates a flow of a portion of the liquid-phase refrigerant in a state in which the injection flow path is opened in the heating mode of the refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to the embodiment. FIG. 5 is a diagram illustrating a flow of a portion of the liquid-phase refrigerant in a state in which the injection flow path is closed in the refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to the embodiment. FIG. 6 is a circuit diagram that illustrates a refrigeration cycle of another embodiment of the refrigeration cycle apparatus (air-cooled heat pump chilling unit) according to the embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1 is a circuit diagram showing a refrigeration cycle of an air-cooled heat pump chilling unit (hereinafter simply referred to as a chilling unit) 1 according to an embodiment. The chilling unit 1 is an example of a refrigeration cycle device, and can operate in a cooling mode and a heating mode. The refrigeration cycle device is not limited to the chilling unit 1 having a refrigeration cycle as shown in Fig. 1, and may be, for example, an air conditioner or a water-cooled heat source device.

As shown in FIG. 1 , the chilling unit 1 includes a refrigeration cycle unit 2 , a water circuit unit 5 , a control unit 7 , and an operation unit 8 .
The refrigeration cycle unit 2 is composed of a refrigerant circuit R including, as main elements, a compressor 20, a four-way valve 21, an air heat exchanger section 22, a pair of expansion valves (first expansion valves) 23a, 23b, a receiver 24, a water heat exchanger (use side heat exchanger) 25, and a gas-liquid separator 26. These elements of the refrigerant circuit R are connected via a main pipe 27 through which the refrigerant circulates.

For example, the compressor 20 is a variable capacity type compressor that discharges a high-temperature, high-pressure gas-phase refrigerant from a discharge port. The discharge port of the compressor 20 is connected to the first port 21a of the four-way valve 21 via a discharge pipe 28. The discharge pipe 28 is provided with a first temperature sensor (detection unit) T1 that detects the temperature of the high-temperature, high-pressure gas-phase refrigerant and a first pressure sensor P1 that detects the pressure of the high-temperature, high-pressure gas-phase refrigerant discharged from the compressor 20.

The second port 21b of the four-way valve 21 is connected to the air heat exchanger section 22. In this embodiment, as an example, the air heat exchanger section 22 includes a pair of air heat exchangers 29a, 29b and a fan 30. The air heat exchangers 29a, 29b correspond to heat source side heat exchangers. In the air heat exchanger section 22, the air heat exchangers 29a, 29b form an exhaust passage extending in the vertical direction between the air heat exchangers 29a, 29b and the shielding plate. The fan 30 is supported on the upper end of the air heat exchangers 29a, 29b via a support member so as to be located at an exhaust port that opens at the upper end of the exhaust passage.

When the fan 30 is driven in the air heat exchanger section 22, outside air passes through the air heat exchangers 29a and 29b and is drawn into the exhaust passage. The outside air drawn into the exhaust passage is sucked up toward the exhaust port and discharged from the exhaust port above the air heat exchanger section 22.

The inlets of the air heat exchangers 29a and 29b are connected in parallel to the second port 21b of the four-way valve 21. A second temperature sensor T2 is provided near the inlets of the air heat exchangers 29a and 29b to detect the temperature of the gas-phase refrigerant flowing into the air heat exchangers 29a and 29b. The inlets are inlet ports through which the refrigerant flows into the air heat exchangers 29a and 29b in the cooling mode described below, and are outlet ports through which the refrigerant flows out (outlet ports of the air heat exchangers 29a and 29b) in the heating mode.

The outlets of the air heat exchangers 29a and 29b are connected to pipes 41a and 41b having expansion valves 23a and 23b. The pipes 41a and 41b merge downstream of the expansion valves 23a and 23b and are connected to a single collective pipe 42. The collective pipe 42 is connected to the third port 21c of the four-way valve 21 via the receiver 24 and the water heat exchanger 25. The outlet is an outlet through which the refrigerant flows out of the air heat exchangers 29a and 29b in the cooling mode described below, and an inlet through which the refrigerant flows in (the inlet of the air heat exchangers 29a and 29b) in the heating mode.

The fourth port 21d of the four-way valve 21 is connected to the suction side of the compressor 20 via the gas-liquid separator 26. A third temperature sensor T3 is provided in the pipe 43 connecting the fourth port 21d of the four-way valve 21 and the inlet of the gas-liquid separator 26 to detect the temperature of the two-phase gas-liquid refrigerant guided to the gas-liquid separator 26.

Furthermore, a second pressure sensor P2 is provided in the pipe 44 connecting the outlet of the gas-liquid separator 26 and the suction side of the compressor 20 to detect the pressure of the low-temperature, low-pressure gas-phase refrigerant sucked into the compressor 20.

A pipe 46 is provided between the gas-liquid separator 26 and the four-way valve 21. The pipe 46 connects the inlet of the gas-liquid separator 26 to the first port 21a of the four-way valve 21, and a normally closed solenoid valve 47 is provided midway along the pipe 46.

The water heat exchanger 25 has a refrigerant flow path 25a and a water flow path 25c. The refrigerant flow path 25a is connected to the collector pipe 42 downstream of the receiver 24 in the cooling mode described below, and upstream of the receiver 24 in the heating mode described below.

In addition to these configurations, the refrigerant circuit R is equipped with an injection flow path 6. The injection flow path 6 is configured to include three flow paths (hereinafter referred to as the first to third injection flow paths) 6a, 6b, and 6c. The first injection flow path 6a and the second injection flow path 6b are flow paths that branch off from the refrigerant circuit R. The third injection flow path 6c is a flow path where the first injection flow path 6a and the second injection flow path 6b join together.

The first injection flow path 6a is a flow path for high-pressure liquid-phase refrigerant condensed by heat exchange with outside air passing through the air heat exchangers 29a and 29b. One end of the first injection flow path 6a is connected between the air heat exchanger 29b and the expansion valve 23b. As a result, the first injection flow path 6a branches off from the pipe 41b between the air heat exchanger 29b and the expansion valve 23b, that is, downstream of the air heat exchanger 29b and upstream of the expansion valve 23b in the flow direction of the liquid-phase refrigerant.

The second injection flow path 6b is a flow path for high-pressure liquid-phase refrigerant that has exchanged heat with the water flowing through the water flow path 25c and passed through the water heat exchanger 25. One end of the second injection flow path 6b is connected between the water heat exchanger 25 and the receiver 24. As a result, the second injection flow path 6b branches off from the collecting pipe 42 between the water heat exchanger 25 and the receiver 24, that is, downstream of the water heat exchanger 25 and upstream of the receiver 24 (in other words, expansion valves 23a, 23b) in the flow direction of the liquid-phase refrigerant.

The third injection flow path 6c is a flow path where the first injection flow path 6a and the second injection flow path 6b join together and high-pressure liquid-phase refrigerant flows. That is, in the flow direction of the liquid-phase refrigerant, the first injection flow path 6a and the second injection flow path 6b are arranged upstream and the third injection flow path 6c is arranged downstream. One end of the third injection flow path 6c is connected to the other end of the first injection flow path 6a and the other end of the second injection flow path 6b, and the other end is connected to the injection port 20a of the compressor 20.

By providing these injection flow paths 6a, 6b, and 6c, a portion of the liquid-phase refrigerant is injected into a cylinder chamber (not shown) of the compressor 20, and the high-temperature gas-phase refrigerant sucked into the compressor 20 is cooled by this liquid-phase refrigerant, thereby preventing overheating of the compressor 20. In the injection flow path 6, solenoid valves 61a and 61b, check valves 62a and 62b, and an expansion valve (second expansion valve) 60c are arranged in this order from the upstream side in the flow direction of the liquid-phase refrigerant.
Here, the operation for injecting liquid-phase refrigerant into the cylinder chamber of the compressor 20 via the injection flow paths 6a, 6b, and 6c for cooling is referred to as liquid injection operation.

The first injection flow path 6a is provided with a solenoid valve (hereinafter referred to as the cooling solenoid valve) 61a and a check valve (hereinafter referred to as the cooling check valve) 62a. In the flow direction of the liquid-phase refrigerant in the first injection flow path 6a, the cooling solenoid valve 61a is disposed upstream of the cooling check valve 62a. When the chilling unit 1 is operated in the cooling mode (cooling operation), a portion of the liquid-phase refrigerant branches off from the pipe 41b and flows into the first injection flow path 6a as necessary.

The second injection flow path 6b is provided with a solenoid valve (hereinafter referred to as the heating solenoid valve) 61b and a check valve (hereinafter referred to as the heating check valve) 62b. In the flow direction of the liquid-phase refrigerant in the second injection flow path 6b, the heating solenoid valve 61b is disposed upstream of the heating check valve 62b. When the chilling unit 1 is operated in the heating mode (heating operation), a portion of the liquid-phase refrigerant branches off from the collecting pipe 42 and flows into the second injection flow path 6b as necessary.

The third injection flow path 6c is provided with an expansion valve (second expansion valve) 60c. The expansion valve 60c is an electronic valve and is a valve-less valve. The valve-less valve does not close completely, but has a valve structure that stops at an opening degree (hereinafter referred to as a stop opening degree) larger than the full closing state. In other words, even if the expansion valve 60c stops, it remains open only at the stop opening degree, and does not block the flow of the liquid-phase refrigerant. The high-pressure liquid-phase refrigerant that has passed through the first injection flow path 6a or the second injection flow path 6b flows into the third injection flow path 6c. The high-pressure liquid-phase refrigerant that has flowed into the third injection flow path 6c is decompressed in the process of passing through the expansion valve 60c, and is injected into the cylinder chamber from the injection port of the compressor 20.

The water circuit unit 5 is a water flow path that exchanges heat with the refrigerant in the water heat exchanger 25, and its main elements include a water circulation pump 50 and first to third water pipes 51a, 51b, and 51c.

The water circulation pump 50 is, for example, a variable capacity type, and the intake port is connected to one end of the first water pipe 51a and the discharge port is connected to one end of the second water pipe 51b. The other end of the first water pipe 51a is connected to the water outlet of the chilling unit 1 on the user equipment side. The other end of the second water pipe 51b is connected to the inlet of the water flow path 25c of the water heat exchanger 25. The second water pipe 51b is provided with a third pressure sensor P3 that detects water pressure and a fourth temperature sensor T4 that detects water temperature. The third water pipe 51c has one end connected to the outlet of the water flow path 25c and the other end connected to the water inlet of the chilling unit 1 on the user equipment side. The third water pipe 51c is provided with a fourth pressure sensor P4 that detects water pressure and a fifth temperature sensor T5 that detects water temperature.

The control unit 7 controls the operation of each element of the refrigeration cycle unit 2 and the water circuit unit 5, and controls the operation of the chilling unit 1. The control unit 7 includes a CPU, memory, a storage device (non-volatile memory), an input/output circuit, a timer, etc., and controls the operation of each element of the refrigeration cycle unit 2 and the water circuit unit 5, and controls the operation of the chilling unit 1. For example, the control unit 7 acquires various information (data) necessary for operation control of the chilling unit 1, such as starting and stopping the operation of the chilling unit 1, selecting the cooling operation and heating operation modes, the temperature and pressure of the refrigerant, the water temperature, and the water pressure. By executing a predetermined calculation process according to the acquired information, the control unit 7 controls the operation of each of the above elements, and starts and stops the operation of the chilling unit 1, switches between the cooling operation and the heating operation, opens and closes the injection flow path 6, etc. Specifically, the control unit 7 controls each operation, such as starting and stopping the compressor 20, switching the ports of the four-way valve 21, and opening and closing the expansion valves 23a and 23b, the expansion valve 60c, the cooling solenoid valve 61a, and the heating solenoid valve 61b.

The operation unit 8 includes, for example, an operation panel, switches, buttons, a display, etc., and is connected to the control unit 7 via a wired or wireless connection. The operation unit 8 is an interface through which a user performs predetermined operations, such as starting the operation of the chilling unit 1, selecting the cooling operation mode or the heating operation mode, and setting the water supply temperature, etc.

The operation of the chilling unit 1 in cooling mode and heating mode will be described below.

For example, when the chilling unit 1 operates in cooling mode, the four-way valve 21 switches so that the first port 21a is connected to the second port 21b and the third port 21c is connected to the fourth port 21d, as shown by solid lines in Figure 1.

Then, the compressor 20 operates, and high-temperature, high-pressure gas-phase refrigerant is discharged from the compressor 20 to the discharge pipe 28. The high-temperature, high-pressure gas-phase refrigerant discharged from the compressor 20 is guided via the four-way valve 21 to the air heat exchangers 29a and 29b.

The gas-phase refrigerant guided to the air heat exchangers 29a and 29b exchanges heat with the outside air passing through the air heat exchangers 29a and 29b by the operation of the fan 30, condenses, and changes into a high-pressure liquid-phase refrigerant. The high-pressure liquid-phase refrigerant is reduced in pressure as it passes through the expansion valves 23a and 23b, and changes into a two-phase gas-liquid refrigerant of intermediate pressure. The two-phase gas-liquid refrigerant is guided to the water heat exchanger 25 via the receiver 24. The two-phase gas-liquid refrigerant guided to the water heat exchanger 25 exchanges heat with the water flowing through the water flow path 25c. As a result, the water in the water flow path 25c loses its latent heat and becomes cold water. The cold water is supplied to the utilization device from the third water piping 51c.

The low-temperature, low-pressure two-phase gas-liquid refrigerant that has passed through the water heat exchanger 25 is guided via the four-way valve 21 to the gas-liquid separator 26, where it is separated into liquid-phase refrigerant and gas-phase refrigerant. The gas-phase refrigerant separated from the liquid-phase refrigerant is sucked into the compressor 20, where it becomes high-temperature, high-pressure gas-phase refrigerant again and is discharged from the compressor 20.

On the other hand, when the chilling unit 1 operates in heating mode, the four-way valve 21 switches so that the first port 21a is connected to the third port 21c and the second port 21b is connected to the fourth port 21d, as shown by the dashed lines in Figure 1.

When operation begins in heating mode, the high-temperature, high-pressure gas-phase refrigerant compressed by the compressor 20 is guided to the water heat exchanger 25 via the four-way valve 21. The gas-phase refrigerant guided to the water heat exchanger 25 and flowing through the refrigerant flow path 25a exchanges heat with the water flowing through the water flow path 25c. As a result, the water in the water flow path 25c is heated and becomes hot water. The hot water is supplied to the utilization device from the third water pipe 51c.

The high-pressure liquid-phase refrigerant that has passed through the water heat exchanger 25 changes to an intermediate-pressure gas-liquid two-phase refrigerant while passing through the receiver 24 and the expansion valves 23a and 23b, and is then guided to the air heat exchangers 29a and 29b. The gas-liquid two-phase refrigerant guided to the air heat exchangers 29a and 29b exchanges heat with the outside air passing through the air heat exchangers 29a and 29b by the operation of the fan 30, evaporates, and changes to a low-temperature, low-pressure gas-liquid two-phase refrigerant.

The low-temperature, low-pressure two-phase gas-liquid refrigerant that has passed through the air heat exchangers 29a and 29b is guided via the four-way valve 21 to the gas-liquid separator 26, where it is separated into liquid-phase refrigerant and gas-phase refrigerant. The gas-phase refrigerant separated from the liquid-phase refrigerant is sucked into the compressor 20, where it is discharged from the compressor 20 as a high-temperature, high-pressure gas-phase refrigerant again.

Here, as an example of operation control in the chilling unit 1, operation control focusing on the opening and closing control of the injection flow path 6 in the refrigerant circuit R will be described according to the control flow of the control unit 7. The injection of liquid phase refrigerant into the compressor 20 is controlled by opening and closing control of the injection flow path 6. Figure 2 shows the control flow of the control unit 7 when controlling the opening and closing of the injection flow path 6.

When the chilling unit 1 has started operating, the control unit 7 controls the opening and closing of the injection flow path 6 as follows. When controlling the opening and closing of the injection flow path 6, the control unit 7 determines the operation mode of the chilling unit 1. As an example of the control flow in FIG. 2, the control unit 7 determines whether the operation mode of the chilling unit 1 is the cooling mode (S101). At that time, the control unit 7 receives a signal indicating the operation mode from, for example, the operation unit 8, and if the received signal is a selection signal for the cooling mode, it determines that the operation mode is the cooling mode, and if the received signal is any other signal, it determines that the operation mode is not the cooling mode.

When the operation mode is the cooling mode, the control unit 7 operates the chilling unit 1 in the cooling mode (S102). In this case, the control unit 7 controls the operation of the four-way valve 21 to connect the first port 21a to the second port 21b and to connect the third port 21c to the fourth port 21d, and operates the compressor 20.

Next, the control unit 7 determines whether the injection flow path 6 can be opened (S103). The opening condition is a condition for determining whether the injection flow path 6 can be opened. Here, the opening condition is determined depending on whether the temperature (Td) of the refrigerant discharged from the compressor 20 is equal to or lower than a predetermined temperature (T0). The temperature of the refrigerant discharged from the compressor 20 (hereinafter referred to as the discharge refrigerant temperature Td) is the temperature of the refrigerant detected by the first temperature sensor T1. The predetermined temperature (hereinafter referred to as the reference temperature T0) is a threshold for determining whether the discharge refrigerant temperature Td has risen excessively, or in other words, whether the compressor 20 is in an overheated state. The value of the reference temperature T0 is predefined, for example, according to the performance of the compressor 20, and is stored in the storage device of the control unit 7, and is read into the memory as a parameter when the opening condition is determined. In this embodiment, as an example, the value of the reference temperature T0 is assumed to be about 100°C, but is not limited to such a value. Moreover, the reference temperature T0 may be a fixed value, or may be a variable value that varies depending on, for example, a set water supply temperature.

In determining whether the opening condition is satisfied, the control unit 7 acquires the detection value of the discharged refrigerant temperature Td from the first temperature sensor T1 and compares the acquired value with a reference temperature T0. If the discharged refrigerant temperature Td exceeds the reference temperature T0 (Td>T0), the control unit 7 determines that the opening condition is satisfied, and if the discharged refrigerant temperature Td is equal to or lower than the reference temperature T0 (Td≦T0), the control unit 7 determines that the opening condition is not satisfied.

If the opening condition is not satisfied (Td≦T0), the control unit 7 closes the injection flow path 6. In this case, the control unit 7 closes the cooling solenoid valve 61a of the first injection flow path 6a and closes the heating solenoid valve 61b of the second injection flow path 6b (S104). For example, if the cooling solenoid valve 61a or the heating solenoid valve 61b is open, the control unit 7 closes the valve. On the other hand, if the cooling solenoid valve 61a and the heating solenoid valve 61b are closed, the control unit 7 maintains this state. In addition, the control unit 7 stops the expansion valve 60c (S104). For example, if the expansion valve 60c is not stopped, the control unit 7 stops the expansion valve 60c. On the other hand, if the expansion valve 60c is stopped, the control unit 7 maintains this state.

On the other hand, when the opening condition is satisfied (Td>T0), the control unit 7 opens the injection flow path 6. In this case, the control unit 7 opens the cooling solenoid valve 61a of the first injection flow path 6a and closes the heating solenoid valve 61b of the second injection flow path 6b (S105). For example, when the cooling solenoid valve 61a is closed, the control unit 7 opens it. On the other hand, when the cooling solenoid valve 61a is open, the control unit 7 maintains this state. Also, when the heating solenoid valve 61b is closed, the control unit 7 maintains this state, and when it is open, the control unit 7 closes it. Then, the control unit 7 opens the expansion valve 60c (sets it to an open state) (S105). For example, when the expansion valve 60c is in a stopped state, the control unit 7 opens it. On the other hand, when the expansion valve 60c is open, the control unit 7 maintains this state. The control unit 7 appropriately adjusts the opening degree of the expansion valve 60c.

Figure 3 shows the state in which the injection flow path 6 is opened in the cooling mode. In this case, as shown by the white arrows in Figure 3, a portion of the liquid-phase refrigerant is diverted from the pipe 41b, passes through the first injection flow path 6a, and is injected into the cylinder chamber (not shown) of the compressor 20 through the third injection flow path 6c.

Furthermore, if it is determined in S101 that the operation mode is not the cooling mode, the control unit 7 determines whether the operation mode of the chilling unit 1 is the heating mode (S106). At that time, the control unit 7 receives a signal indicating the operation mode from, for example, the operation unit 8, and if the received signal is a selection signal for the heating mode, it determines that the operation mode is the heating mode, and if the received signal is any other signal, it determines that the operation mode is not the heating mode.

If the operation mode is the heating mode, the control unit 7 operates the chilling unit 1 in the heating mode (S107). In this case, the control unit 7 controls the operation of the four-way valve 21 to connect the first port 21a to the third port 21c and to connect the second port 21b to the fourth port 21d, and operates the compressor 20.

Next, the control unit 7 determines whether the opening condition is satisfied (S108). In determining whether the opening condition is satisfied, the control unit 7 obtains the detection value of the discharged refrigerant temperature Td from the first temperature sensor T1 and compares the obtained value with the reference temperature T0.

If the open condition is not satisfied (Td≦T0), the control unit 7 closes the injection flow path 6. In this case, the control unit 7 closes the cooling solenoid valve 61a of the first injection flow path 6a and closes the heating solenoid valve 61b of the second injection flow path 6b (S104). The control unit 7 also stops the expansion valve 60c (S104). The control by the control unit 7 in this case is the same as when the operation mode is the cooling mode.

On the other hand, when the opening condition is satisfied (Td>T0), the control unit 7 opens the injection flow path 6. In this case, the control unit 7 closes the cooling solenoid valve 61a of the first injection flow path 6a and opens the heating solenoid valve 61b of the second injection flow path 6b (S109). For example, when the heating solenoid valve 61b is closed, the control unit 7 opens it. On the other hand, when the heating solenoid valve 61b is open, the control unit 7 maintains this state. Also, when the cooling solenoid valve 61a is closed, the control unit 7 maintains this state, and when it is open, the control unit 7 closes it. Furthermore, the control unit 7 opens the expansion valve 60c (sets it to an open state) (S109). The control of the control unit 7 in this case is the same as when the operation mode is the cooling mode. Also in this case, the control unit 7 appropriately adjusts the opening degree of the expansion valve 60c.

Figure 4 shows the state in which the injection flow path 6 is opened in the heating mode. In this case, as shown by the white arrows in Figure 4, a portion of the liquid-phase refrigerant is diverted from the collecting pipe 42, passes through the second injection flow path 6b, and is injected into the cylinder chamber (not shown) of the compressor 20 through the third injection flow path 6c.

Then, when the injection flow path 6 is closed in S104, the control unit 7 determines the operation stop condition of the chilling unit 1 (S110). Also, when the injection flow path 6 is opened in S105 or S109, the control unit 7 determines the operation stop condition of the chilling unit 1 (S110). The operation stop condition is a condition for determining whether or not to stop the operation of the chilling unit 1, and is determined, for example, based on whether or not the control unit 7 has received a signal indicating that the operation of the chilling unit 1 is stopped. The signal indicating that operation is stopped is transmitted, for example, when operation stop is selected on the operation unit 8.

If the operation stop condition is not met, the control unit 7 determines whether or not the operation mode of the chilling unit 1 is the cooling mode (S101), and selectively repeats the subsequent processes (S102 to S109) depending on the determination result.
On the other hand, if the operation stop condition is met, the control unit 7 stops the operation of the chilling unit 1 (S111).

That is, while the chilling unit 1 is operating, a series of opening and closing controls of the injection flow path 6 is repeated. Then, when the chilling unit 1 is stopped, the series of opening and closing controls of the injection flow path 6 also ends.

Note that even if it is determined in S106 that the operating mode is not the heating mode, the control unit 7 stops the operation of the chilling unit 1. In this case, it is assumed that the chilling unit 1 is not operating in either the cooling mode or the heating mode (e.g., an error state), and the operation of the chilling unit 1 is stopped in preparation for an unforeseen event. In addition to or instead of stopping the operation, the control unit 7 may execute a specified abnormality process. For example, it is possible to thoroughly inform the user of the error state by turning on (flashing) a warning light, sounding a warning sound, displaying a warning message, etc.

In this way, according to this embodiment, it is possible to avoid a liquid-sealed state in the injection flow path 6. In other words, even if the injection flow path 6 is closed, the liquid-phase refrigerant in the injection flow path 6 can be caused to flow as follows.

Figure 5 shows the state in which the injection flow path 6 is closed in this manner. For example, when the injection flow path 6 is opened and then closed, the liquid phase refrigerant that has flowed into the injection flow path 6 remains in the target flow path X, as shown in Figure 5. The target flow path X is a flow path in the injection flow path 6 that is defined by the cooling check valve 62a of the first injection flow path 6a, the heating check valve 62b of the second injection flow path 6b, and the expansion valve 60c of the third injection flow path 6c.

Here, as described above, even when the expansion valve 60c is stopped, it remains open only to the stop opening. Therefore, the liquid phase refrigerant in the target flow path X is able to flow through the expansion valve 60c toward the cylinder chamber (not shown) of the compressor 20, as shown by the white arrow in FIG. 5. In other words, the liquid phase refrigerant only remains temporarily in the target flow path X and is not blocked within the target flow path X. Therefore, when the injection flow path 6 is opened and then closed, it is possible to prevent the liquid phase refrigerant that has flowed into the injection flow path 6 from becoming liquid-sealed.

The injection flow path 6 is branched into a first injection flow path 6a that injects a portion of the liquid-phase refrigerant into the compressor 20 when the chilling unit 1 is operating in the cooling mode, and a second injection flow path 6b that injects a portion of the liquid-phase refrigerant into the compressor 20 when the chilling unit 1 is operating in the heating mode. Therefore, regardless of whether the chilling unit 1 is operating in the cooling mode or the heating mode, a liquid-sealed state of the liquid-phase refrigerant in the target flow path X of the injection flow path 6 can be avoided.

In addition, such a liquid-sealed state is avoided in the same way even in a power outage. In a power outage, the power supply to each element of the chilling unit 1 is cut off. Therefore, in a power outage, the cooling solenoid valve 61a and the heating solenoid valve 61b are closed in the injection flow path 6, and the expansion valve 60c is stopped. Therefore, even in a power outage, the liquid-phase refrigerant that has flowed into the injection flow path 6 may remain in the target flow path X. However, even in this case, the expansion valve 60c remains open only to the stop opening degree, so that the liquid-phase refrigerant that has remained in the target flow path X can pass through the expansion valve 60c and flow toward the cylinder chamber (not shown) of the compressor 20 as shown in FIG. 5. Therefore, even in a power outage, the liquid-phase refrigerant that has flowed into the injection flow path 6 can be prevented from becoming liquid-sealed.

That is, according to this embodiment, it is possible to avoid liquid sealing of the liquid-phase refrigerant in the target flow path X by simply providing the injection flow path 6, without providing a bypass flow path in the injection flow path 6 to avoid a liquid-sealed state. Therefore, it is possible to avoid liquid sealing of the liquid-phase refrigerant in the target flow path X even with relatively simple piping without complicating the piping. Furthermore, by using relatively simple piping, it is possible to save space in the injection flow path 6. In addition, by using relatively simple piping, it is possible to reduce costs and the risk of refrigerant leakage due to vibration.

In addition, by providing a cooling check valve 62a in the first injection flow path 6a and a heating check valve 62b in the second injection flow path 6b, one of the solenoid valves 61a and 61b can be closed and the other opened to perform liquid injection operation. In this case, the check valves 62a and 62b prevent backflow of liquid-phase refrigerant in the injection flow paths 6a and 6b due to a malfunction of the solenoid valves 61a and 61b, allowing for stable liquid injection operation and stable refrigeration cycle operation.

In particular, solenoid valves 61a, 61b used as two-way valves may experience backflow when pressure is applied in the opposite direction to the default forward flow path depending on the shape and quality of the solenoid valve. However, by providing check valves 62a, 62b downstream of each solenoid valve 61a, 61b, it is possible to perform liquid injection operation in one of the injection flow paths 6a, 6b while preventing backflow caused by a pressure difference occurring in the other injection flow path connected in parallel to the one flow path, thereby enabling stable refrigeration cycle operation.

In other words, the flow can be controlled by the solenoid valves 61a and 61b against forward pressure and by the check valves 62a and 62b against reverse pressure, so that the liquid injection operation and the refrigeration cycle operation can be performed stably. Furthermore, even if the liquid injection operation is stopped and restarted, the operation can be performed relatively stably.

In the above-described embodiment, the refrigeration cycle unit 2 of the chilling unit 1 is configured to include a single refrigerant circuit R, but the refrigerant circuit may include multiple systems.
6 shows an example of the configuration of a chilling unit 10 (refrigeration cycle unit 2) equipped with four refrigerant circuits RA, RB, RC, and RD as another embodiment of the present invention. The first refrigerant circuit RA, the second refrigerant circuit RB, the third refrigerant circuit RC, and the fourth refrigerant circuit RD are each configured in the same manner as the above-mentioned refrigerant circuit R, and each includes elements common to the refrigerant circuit R.

In the example shown in FIG. 6, the water heat exchanger 25 has a first refrigerant flow path 25a, a second refrigerant flow path 25b, and a water flow path 25c. The first refrigerant flow path 25a of the water heat exchanger 25 is connected to the collector pipe 42 of the first refrigerant circuit RA downstream in the cooling mode and upstream in the heating mode with respect to the receiver 24. The second refrigerant flow path 25b of the water heat exchanger 25 is connected to the collector pipe 42 of the second refrigerant circuit RB. That is, the first refrigerant circuit RA and the second refrigerant circuit RB are connected in parallel to one water heat exchanger 25 and share the water heat exchanger 25. Similarly, the third refrigerant circuit RC and the fourth refrigerant circuit RD are connected in parallel to one water heat exchanger 25 and share the water heat exchanger 25. In this way, the refrigeration cycle unit 2 of the chilling unit 10 has two water heat exchangers 25.

The water circuit unit 5 includes, as main components, a water circulation pump 50, and first to fourth water pipes 51a, 51b, 51c, and 51d.
The first water pipe 51 a connects between a water outlet on the utilization device side of the chilling unit 10 and a suction port of the water circulation pump 50 .
The second water pipe 51b connects the discharge port of the water circulation pump 50 to the water flow paths 25c of the water heat exchangers 25 of the first refrigerant circuit RA and the second refrigerant circuit RB. The second water pipe 51b is provided with a third pressure sensor P3 for detecting the water pressure and a fourth temperature sensor T4 for detecting the water temperature.

The third water pipe 51c connects in series between the water flow paths 25c of the water heat exchangers 25 of the first refrigerant circuit RA and the second refrigerant circuit RB and the water flow paths 25c of the water heat exchangers 25 of the third refrigerant circuit RC and the fourth refrigerant circuit RD. The third water pipe 51c is provided with a fifth temperature sensor T5 that detects the water temperature.
The fourth water pipe 51d connects the water flow paths 25c of the water heat exchangers 25 of the third refrigerant circuit RC and the fourth refrigerant circuit RD to the water inlets of the utilization equipment side of the chilling unit 10. The fourth water pipe 51d is provided with a fourth pressure sensor P4 for detecting the water pressure and a sixth temperature sensor T6 for detecting the water temperature.

6, the control unit 7 controls the operation of each element of the refrigeration cycle unit 2 and the water circuit unit 5, and controls the operation of the chilling unit 10. The operation unit 8 is connected to the control unit 7 by wire or wirelessly, and is used to perform operations such as starting the operation of the chilling unit 10, selecting the cooling operation mode or the heating operation mode, and setting the water supply temperature.

When the chilling unit 10 operates in the cooling mode, the four-way valve 21 switches so that the first port 21a of the first to fourth refrigerant circuits RA, RB, RC, RD communicates with the second port 21b, and the third port 21c communicates with the fourth port 21d, as shown by solid lines in Fig. 6. Subsequent control is the same as when the chilling unit 1 operates in the cooling mode. In this case, in the cooling mode, the water chilled in the water heat exchanger 25 shared by the first refrigerant circuit RA and the second refrigerant circuit RB is cooled again by heat exchange with the gas-liquid two-phase refrigerant flowing in the first refrigerant flow path 25a and the second refrigerant flow path 25b of the other water heat exchanger 25 while passing through the water flow path 25c of the other water heat exchanger 25 shared by the third refrigerant circuit RC and the fourth refrigerant circuit RD. The cold water that has been cooled in two stages is supplied to the utilization device from the fourth water pipe 51d.

On the other hand, when the chilling unit 10 operates in the heating mode, the four-way valve 21 switches so that the first port 21a of the first to fourth refrigerant circuits RA, RB, RC, RD communicates with the third port 21c, and the second port 21b communicates with the fourth port 21d, as shown by the dashed lines in FIG. 6. The subsequent control is the same as when the chilling unit 1 operates in the heating mode. In the heating mode, the water heated in the water heat exchanger 25 shared by the first refrigerant circuit RA and the second refrigerant circuit RB is heated again by heat exchange with the gas-liquid two-phase refrigerant flowing in the first refrigerant flow path 25a and the second refrigerant flow path 25b of the other water heat exchanger 25 while passing through the water flow path 25c of the other water heat exchanger 25 shared by the third refrigerant circuit RC and the fourth refrigerant circuit RD. The hot water heated in two stages is supplied to the utilization device from the fourth water pipe 51d.

The first to fourth refrigerant circuits RA, RB, RC, and RD each have an injection flow path 6 (first injection flow path 6a, second injection flow path 6b, and third injection flow path 6c) equivalent to that of the chilling unit 1. As in the chilling unit 1, each injection flow path 6 is provided with a cooling solenoid valve 61a, a cooling check valve 62a, a heating solenoid valve 61b, a heating check valve 62b, and an expansion valve 60c.

Therefore, in the chilling unit 10, for example, without providing a bypass flow path in the injection flow path 6 to avoid a liquid-sealed state, the liquid-phase refrigerant can be avoided from being sealed in the target flow paths XA, XB, XC, and XD simply by providing the injection flow path 6.

Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims.

1, 10... refrigeration cycle device (air-cooled heat pump chilling unit), 2... refrigeration cycle unit, 5... water circuit unit, 6... bypass flow path (injection flow path), 6a... first injection flow path, 6b... second injection flow path, 6c... third injection flow path, 7... control unit, 8... operation unit, 20... compressor, 21... four-way valve, 22... air heat exchanger unit, 23a, 23b... expansion valve (first expansion valve), 24... receiver, 25... water heat exchanger, 25a, 25b... refrigerant flow path, 25c... water flow path, 26... gas-liquid separator, 27... main pipe, 28... discharge pipe, 29a, 29b... air heat exchanger, 30... fan, 41a, 41b... pipe, 42... Collecting piping, 43, 44, 46...piping, 47...solenoid valve, 60c...expansion valve (second expansion valve), 61a...solenoid valve (cooling solenoid valve), 61b...solenoid valve (heating solenoid valve), 62a...check valve (cooling check valve), 62b...check valve (heating check valve), R, RA, RB, RC, RD...refrigerant circuit, T1...first temperature sensor, X, XA, XB, XC, XD...target flow path.

Claims (4)

The refrigerant circuit includes a single compressor that discharges a gas-phase refrigerant, a heat source-side heat exchanger, a first expansion valve, a user-side heat exchanger, and an injection flow path that divides a portion of the liquid-phase refrigerant and injects only the divided liquid-phase refrigerant into the compressor, and the refrigerant circulates through the refrigerant.
a solenoid valve, a check valve, and a second expansion valve are disposed in the injection flow path in this order from an upstream side in a flow direction of the liquid-phase refrigerant in the injection flow path,
The refrigeration cycle device, wherein the second expansion valve is not fully closed, but is in a stopped state in which it is kept open by a stop opening degree that is larger than the fully closed state. the injection flow path includes a first injection flow path and a second injection flow path which respectively branch off the refrigerant circuit, and a third injection flow path where the first injection flow path and the second injection flow path join together;
the first injection flow path branches off from the refrigerant circuit between the heat source side heat exchanger and the first expansion valve, and during a cooling operation in which the heat source side heat exchanger functions as a condenser and the utilization side heat exchanger functions as an evaporator, diverts a portion of the liquid phase refrigerant that has passed through the heat source side heat exchanger,
2. The refrigeration cycle apparatus according to claim 1, wherein the second injection flow path branches off from the refrigerant circuit between the utilization side heat exchanger and the first expansion valve, and diverts a portion of the liquid phase refrigerant that has passed through the utilization side heat exchanger during a heating operation in which the heat source side heat exchanger functions as an evaporator and the utilization side heat exchanger functions as a condenser. a cooling solenoid valve and a cooling check valve are disposed in the first injection flow path in this order from an upstream side in a flow direction of the liquid-phase refrigerant in the first injection flow path,
a heating solenoid valve and a heating check valve are disposed in the second injection flow path in this order from an upstream side in a flow direction of the liquid-phase refrigerant in the second injection flow path,
The refrigeration cycle apparatus according to claim 2 , wherein the second expansion valve is disposed in the third injection passage. A detection unit that detects the temperature of the gas phase refrigerant discharged from the compressor;
A control unit that controls operations of the compressor, the first expansion valve, the solenoid valve, and the second expansion valve,
The control unit is
During the cooling operation, when the temperature of the gas-phase refrigerant detected by the detection unit exceeds a predetermined temperature, the cooling solenoid valve is opened, the heating solenoid valve is closed, and the second expansion valve is opened;
During the heating operation, when the temperature of the gas-phase refrigerant detected by the detection unit exceeds a predetermined temperature, the cooling solenoid valve is closed, the heating solenoid valve is opened, and the second expansion valve is opened;
4. The refrigeration cycle device according to claim 3, wherein, during the cooling operation and the heating operation, when the temperature of the gas phase refrigerant detected by the detection unit is equal to or lower than a predetermined temperature, the cooling solenoid valve is closed, the heating solenoid valve is closed, and the second expansion valve is brought into the stopped state.

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