Cooling circuit device for vehicle

Abstract

To provide a cooling circuit device for a vehicle capable of suppressing deterioration of cooling performance and improving a service life of an apparatus to be cooled.SOLUTION: A cooling circuit device for a vehicle includes: a pump 10 that sucks and discharges a refrigerant; a discharge passage 21 connected to a discharge side of the pump 10; a suction passage 22 connected to a suction side of the pump 10; a first passage 24 having one end connected to the discharge passage 21 and the other end connected to the suction passage 22; a second passage 25 having one end connected to the pump 10 side of a connection portion of the discharge passage 21 to the first passage 24 and the other end connected to a side away from the pump 10 of a connection portion of the suction passage 22 to the first passage 24; a first valve 24a provided at the other end of the first passage 24 and enabling switching of a flow passage between the suction passage 22 and the first passage 24; a second valve 25a provided at one end of the second passage 25 and enabling switching of a flow passage between the discharge passage 21 and the second passage 25; and a control section 30 that controls the first valve 24a and the second valve 25a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a cooling circuit device for a vehicle. [Background technology]

[0002] In recent years, from the viewpoint of reducing the environmental load, electric vehicles that are driven by electric power from on-board batteries have been developed. Such electric vehicles are equipped with devices that generate heat (devices to be cooled), and it is necessary to actively cool the devices to prevent a decrease in performance.

[0003] Therefore, as a method for efficiently cooling the equipment to be cooled, a liquid-cooling type cooling device that cools the equipment using a cooling circuit that circulates a refrigerant such as oil or cooling water is installed (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-67735 A Summary of the Invention [Problem to be solved by the invention]

[0005] In such a liquid-cooled cooling device, air may accumulate in the cooling circuit. Therefore, in Patent Document 1, the internal flow path of the cooling circuit and the reservoir tank (surge tank) are connected via a discharge flow path (vent line), so that even if air flows into the cooling circuit, the air is discharged to the reservoir tank together with the cooling liquid via the discharge flow path without being retained at the top of the internal flow path, and the cooling liquid and the air can be separated in the reservoir tank.

[0006] However, there are some cooling circuit structures in which the air inside the circuit cannot be exhausted even if a vent line is provided due to layout restrictions, etc. In the case of such cooling circuits, air cannot be completely removed, and the pump may run idly (so-called air entrapment), resulting in a decrease in cooling efficiency and a shortened lifespan of the pump and the equipment to be cooled.

[0007] Therefore, an object of the present disclosure is to provide a vehicle cooling circuit device that can suppress deterioration of cooling performance and improve the life of the pump and the equipment to be cooled. [Means for solving the problem]

[0008] The present disclosure has been made to solve at least some of the problems described above, and can be realized in the following aspects or application examples.

[0009] (1) A cooling circuit device for a vehicle according to this application example includes a pump that draws in and discharges a refrigerant, a discharge passage connected to a discharge side of the pump, a suction passage connected to a suction side of the pump, a first passage having one end connected to the discharge passage and the other end connected to the suction passage, a second passage having one end connected to the pump side of a connection portion of the discharge passage with the first passage and the other end connected to a side of the suction passage away from the pump of a connection portion of the suction passage with the first passage, a first valve provided at the other end of the first passage and capable of switching a flow path between the suction passage and the first passage, a second valve provided at one end of the second passage and capable of switching a flow path between the discharge passage and the second passage, and a control unit that controls the first valve and the second valve, wherein when the control unit detects an idle rotation of the pump, the first valve switches the refrigerant to flow from the first passage to the suction passage, and the second valve switches the refrigerant to flow from the discharge passage to the second passage.

[0010] In this way, when the vehicle cooling circuit device according to this application example detects the pump running idle, it controls the switching of the first valve and the second valve and drives the pump to change the flow direction of the refrigerant from the forward flow direction to the reverse flow direction. This allows the air trapped in the forward flow direction to be discharged and prevents malfunctions caused by the pump running idle. In other words, with this configuration, air trapped in the cooling passage can be efficiently discharged regardless of the vertical positional relationship in the cooling passage, preventing a decrease in cooling efficiency due to air mixing and damage to the pump and the equipment to be cooled, and improving the life of the equipment to be cooled.

[0011] (2) A cooling circuit device for a vehicle according to this application example includes a pump that draws in and discharges a refrigerant, a discharge passage connected to a discharge side of the pump, a suction passage connected to a suction side of the pump, a first passage having one end connected to the discharge passage and the other end connected to the suction passage, a second passage having one end connected to the pump side of a connection portion of the discharge passage with the first passage and the other end connected to a side of the suction passage away from the pump of a connection portion of the suction passage with the first passage, a first valve provided at one end of the first passage and capable of switching a flow path between the discharge passage and the first passage, a second valve provided at the other end of the second passage and capable of switching a flow path between the suction passage and the second passage, and a control unit that controls the first valve and the second valve, wherein when the control unit detects that the pump is running idly, the first valve switches the flow of refrigerant from the discharge passage to the first passage, and the second valve switches the flow of refrigerant from the second passage to the suction passage.

[0012] In this way, when the vehicle cooling circuit device according to this application example detects the pump running idle, it controls the switching of the first valve and the second valve and drives the pump to change the flow direction of the refrigerant from the forward flow direction to the reverse flow direction. This allows the air trapped in the forward flow direction to be discharged and prevents malfunctions caused by the pump running idle. In other words, with this configuration, air trapped in the cooling passage can be efficiently discharged regardless of the vertical positional relationship in the cooling passage, preventing a decrease in cooling efficiency due to air mixing and damage to the pump and the equipment to be cooled, and improving the life of the equipment to be cooled. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram showing a cooling circuit device of a first embodiment. [Diagram 2] 4 is a flowchart showing an air bleeding control routine of the VCU when the pump is running idly. [Diagram 3] 4 is an enlarged view showing the flow of refrigerant before and after the pump in the first embodiment during normal flow. FIG. [Figure 4] 5 is an enlarged view showing the flow of refrigerant before and after the pump during backflow in the first embodiment. FIG. [Diagram 5] 13 is an enlarged view showing the flow of refrigerant before and after the pump during backflow in the second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the "up-down direction" refers to the height direction (vertical direction) of the vehicle. The present invention is not limited to the contents described below, and can be modified as desired without departing from the gist of the present invention. Furthermore, the drawings used to explain the embodiments are all schematic representations of components, and may be partially emphasized, enlarged, reduced, or omitted to facilitate understanding, and may not accurately represent the scale, shape, etc. of the components.

[0015] Fig. 1 is a schematic diagram showing a vehicle cooling circuit device 1 in a first embodiment of the present invention. The vehicle on which the vehicle cooling circuit device 1 of the present embodiment is mounted is an electric truck. As shown in Fig. 1, the cooling circuit device 1 has a pump 10, a motor 11, an inverter 12, a radiator 13, and a surge tank 15 provided in a cooling passage 20.

[0016] The pump 10 is a so-called water pump, and is, for example, an electric pump that has a function of pumping the refrigerant circulating through the cooling circuit device 1. The pump 10 is also capable of controlling the flow rate and flow speed of the refrigerant. The pump 10 is also equipped with a torque sensor (not shown) that detects the driving torque of the pump 10. This torque sensor can detect a temporary decrease in the driving torque, thereby detecting idling of the pump 10 (also called air entrapment or dry run) caused by air being mixed in the refrigerant, for example.

[0017] The motor 11 is a rotary electric motor that serves as a power source for propulsion in the vehicle. The inverter 12 is a power converter that converts DC power supplied from a battery (not shown) mounted on the vehicle into AC power and supplies it to the motor 11. The motor 11 and the inverter 12 in this embodiment are integrated with each other, with the inverter 12 mounted on the top of the motor 11, as shown in Fig. 1. The cooling passage 20 passes through the insides of these objects to be cooled, thereby performing cooling.

[0018] The radiator 13 is a heat exchanger through which a refrigerant flows and cools the refrigerant by exchanging heat with outside air. The radiator 13 has a function of cooling the refrigerant whose temperature has risen and circulating it again to the cooling passage 20. An electric fan 14 is disposed near the radiator 13, and the introduction of outside air into the radiator 13 can be promoted by driving the electric fan 14.

[0019] The surge tank 15 is a tank that stores the refrigerant. The surge tank 15 allows an increase or decrease in the amount of refrigerant in the cooling passage 20, and is capable of gas-liquid separation so as to remove air from within the refrigerant.

[0020] The cooling passage 20 runs through the insides of each device, such as the pump 10, the motor 11, the inverter 12, the radiator 13, the surge tank 15, etc., and also connects each device together. The cooling passage 20 connecting each device together is formed of a tubular member made of metal or resin.

[0021] Specifically, the cooling passage 20 has a discharge passage 21 connected from the pump 10 to the inverter 12, a suction passage 22 connected from the motor 11 to the pump 10 via the radiator 13, and a surge tank passage 23 branched off from the suction passage 22 between the radiator 13 and the pump 10 and connected to the surge tank 15. Furthermore, between the discharge passage 21 and the suction passage 22, there are a first passage 24 and a second passage 25, each having one end connected to the discharge passage 21 and the other end connected to the suction passage 22, so as to bypass (detouring) the pump 10.

[0022] Specifically, one end of the first passage 24 is connected to the discharge passage 21, and the other end is connected to the suction passage 22. A first valve 24a is provided at the other end of the first passage 24. The first valve 24a is a three-way valve that can be switched between a flow path in which the valve on the first flow path 24 side is closed to allow the refrigerant to flow from the radiator 13 through the suction passage 22 to the pump 10, and a flow path in which the valve on the radiator 13 side is closed to connect the suction passage 22 and the discharge passage 21 via the first passage 24.

[0023] One end of the second passage 25 is connected to the pump 10 side of the connection portion of the discharge passage 21 with the first passage 24, and the other end is connected to the side of the suction passage 22 away from the pump 10 with respect to the connection portion of the first passage 24. A second valve 25a is provided at one end of the second passage 25. The second valve 25a is a three-way valve that can be switched between a flow path in which the refrigerant flows from the pump 10 through the discharge passage 21 to the inverter 12 by closing the valve on the second passage 25 side, and a flow path in which the suction passage 22 and the discharge passage 21 are connected via the second passage 25 by closing the valve on the inverter 12 side.

[0024] In the following description, the direction in which the refrigerant circulates from the suction passage 22 to the discharge passage 21 is referred to as the "forward flow direction," and the direction opposite to the forward flow direction, i.e., the direction in which the refrigerant flows from the discharge passage 21 to the suction passage 22, is referred to as the "reverse flow direction." In the cooling device 1 of this embodiment, the refrigerant flowing in the forward flow direction flows from the pump 10 through the discharge passage 21 into the inverter 12, flows from the inverter 12 into the motor 11, and flows from the motor 11 to the suction passage 22. As shown in FIG. 1, the discharge passage 21 is connected to the bottom of the inverter 12 from the upper side in the vertical direction. In such a connection relationship between the cooling passage 20 and the inverter 12, there is a possibility that air will accumulate in the inverter 12 or in the discharge passage 21 before the inverter 12. In this embodiment, the connection relationship between other devices and the cooling passage is not limited to the arrangement shown in the figure.

[0025] The vehicle is also equipped with a VCU 30 (Vehicle Control Unit, control section). The VCU 30 is a computer equipped with a central processing unit (CPU), a main memory device (ROM, RAM, etc.) for storing control programs, control maps, etc., an input / output device, a timer counter, etc. The VCU 30 is communicatively connected to various devices and other control units mounted on the vehicle via a control area network (CAN) that is an in-vehicle communication network. The VCU 30 of the first embodiment is communicatively connected to the pump 10, the first valve 24a, and the second valve 25a.

[0026] The VCU 30 can control ON / OFF of the drive of the pump 10, control the flow rate, and switch the flow paths of the first valve 24a and the second valve 25a. The VCU 30 executes air bleeding control, which controls the pump 10, the first valve 24a, and the second valve 25a, based on various information related to the vehicle and the pump 10, such as information about the pump 10 running idle.

[0027] Specifically, the air bleeding control executed by the VCU 30 will be described with reference to Fig. 2. Fig. 2 is a flowchart showing an air bleeding control routine. At the start of the flowchart, the first valve 24a and the second valve 25a on the first flow path 24 side and the second flow path 25 side are closed, and the refrigerant flows in the forward flow direction.

[0028] First, in step S1, the VCU 30 determines whether or not idling of the pump 10 has been detected. Idling of the pump 10 is detected by a torque sensor mounted on the pump 10. When the torque sensor detects torque loss of the pump 10, the VCU 30 determines that air has mixed into the refrigerant and the pump 10 has idled. In this case, the determination result in step S1 is true (Yes), and the VCU 30 proceeds to the next step S2. On the other hand, if the determination result in step S1 is false (No), that is, if idling of the pump 10 has not been detected, the VCU 30 returns from this routine.

[0029] In step S2, the VCU 30 issues a stop command to the pump 10, causing the pump 10 to stop.

[0030] In the next step S3, the VCU 30 controls to switch the first valve 24a and the second valve 25a. Specifically, the VCU 30 closes the valve on the radiator 13 and surge tank 15 side for the first valve 24a, and switches the flow path to connect the exhaust passage 21 and the intake passage 22 via the first passage 24. In addition, the VCU 30 closes the valve on the inverter 12 side for the second valve 25a, and switches the flow path to connect the exhaust passage 21 and the intake passage 22 via the second passage 25.

[0031] In step S4, after switching the first valve 24a and the second valve 25a, the VCU 30 issues a rotation command to the pump 10 to rotate the pump 10. As a result, the refrigerant flowing through the cooling passage 20 circulates in the reverse flow direction.

[0032] In step S5, after the refrigerant is caused to flow in the reverse flow direction for a predetermined time, the VCU 30 again issues a stop command to the pump 10 to stop the pump 10. Here, the predetermined time, i.e., the time for which the refrigerant is caused to flow in the reverse flow direction, is preset to the time it takes for the refrigerant to make one circuit through the cooling passage 20, and is set to, for example, about one minute. Note that the predetermined time differs depending on the cooling passage installed in the vehicle, and may be a time that allows the refrigerant to make one to several circuits through the cooling passage 20.

[0033] In step S6, the VCU 30 again controls the switching of the first valve 24a and the second valve 25a. Specifically, the VCU 30 closes the valve on the first passage 24 side of the first valve 24a to switch the passage to allow the refrigerant to flow from the radiator 13 through the suction passage 22 to the pump 10. The VCU 30 also closes the valve on the second passage 25 side of the second valve 25a to switch the passage to allow the refrigerant to flow from the pump 10 through the discharge passage 21 to the inverter 12.

[0034] In step S7, after switching the first valve 24a and the second valve 25a again, the VCU 30 issues a rotation command to the pump 10, controls the pump 10 to rotate, and returns the routine. As a result, the refrigerant flowing through the cooling passage 20 circulates in the forward flow direction.

[0035] In this way, when the VCU 30 detects that the pump 10 is running idly, the VCU 30 executes the control of steps S2 to S7 to temporarily circulate the refrigerant in the reverse flow direction.

[0036] Next, the flow direction of the refrigerant by switching the first valve 24a and the second valve 25a will be described in detail with reference to Figures 3 and 4. Figure 3 is an enlarged view of a part of the cooling passage 20, showing the state of each valve when the refrigerant flows in the forward flow direction, and Figure 4 is an enlarged view of the part of the cooling passage 20, showing the state of each valve when the refrigerant flows in the reverse flow direction. Note that the outlined arrows in the figures indicate the direction in which the refrigerant flows. Also, for ease of explanation, the direction in which the first valve 24a and the second valve 25a are closed and the flow path is blocked is indicated by a filled-in triangle.

[0037] First, the state of each valve when the refrigerant flows in the forward flow direction (start point in FIG. 2) will be described (see FIG. 3). When the refrigerant flows in the forward flow direction, the first valve 24a opens the suction passage 22 through which the refrigerant flows toward the pump 10, while blocking the flow path to the first passage 24. The second valve 25a opens the discharge passage 21 through which the refrigerant flows toward the inverter 12, while blocking the flow path to the second passage 25.

[0038] 3, the refrigerant (arrow A1) flowing through the suction passage 22 from the radiator 13 side is directly sucked into the pump 10 (arrow A2). The refrigerant (arrow A3) discharged from the pump 10 by the pumping of the radiator 13 flows through the discharge passage 21 (arrow A4) and enters the inverter 12.

[0039] Next, the state of each valve when the refrigerant flows in the reverse direction will be described (see FIG. 4). When the refrigerant flows in the reverse direction, the first valve 24a opens the suction passage 22 through which the refrigerant flows from the first passage 24 to the pump 10 side, and blocks the suction passage 22 through which the refrigerant flows from the first passage 24 to the side away from the pump 10 (the radiator 13 and surge tank 15 side). The second valve 25a opens the flow path through which the refrigerant discharged from the pump 10 flows from the discharge passage 21 on the pump 10 side to the second passage 25, and blocks the discharge passage 21 through which the refrigerant discharged from the pump 10 flows from the discharge passage 21 on the pump 10 side to the side away from the pump 10 (the inverter 12 side).

[0040] When the pump 10 is driven in this state, as shown in Fig. 4, the refrigerant flows from the inverter 12 side through the discharge passage 21 (arrow B1), through the first passage 24 (arrow B2), into the suction passage 22 flowing toward the pump 10 side (arrow B3), and is sucked into the pump 10. The refrigerant discharged by the pump 10 flows from the discharge passage 21 on the pump 10 side (arrow B4) through the second passage 25 (arrow B5), merges with the suction passage 22 on the side away from the pump 10, and flows toward the radiator 13 and the surge tank 15 (arrow B6). In this way, by circulating the refrigerant in the reverse flow direction, it becomes possible to send the air pocket generated in the forward flow direction to the surge tank 15. For example, air that has accumulated in the inverter 12 or in the discharge passage 21 upstream of the inverter 12 can be separated into gas and liquid by circulating the refrigerant in the reverse direction, and the air can travel from the discharge passage 21 through the first passage 24, the pump 10, the second passage 25, the suction passage 22, and the surge tank passage 23 to the surge tank 15.

[0041] As described above, when the vehicle cooling circuit device 1 in this embodiment detects the pump 10 running idle, it controls the first valve 24a and the second valve 25a to switch and drive the pump 10, thereby changing the flow direction of the refrigerant from the forward flow direction to the reverse flow direction. This allows air trapped in the forward flow direction to be discharged, and prevents malfunctions caused by the pump 10 running idle. In other words, with this configuration, air trapped in the cooling passage 20 can be efficiently discharged regardless of the vertical positional relationship in the cooling passage 20, preventing a decrease in cooling efficiency due to air mixing and damage to the pump and the equipment to be cooled, and improving the life of the equipment to be cooled.

[0042] Next, a second embodiment of the present invention will be described.

[0043] 5 is an enlarged view showing the flow of refrigerant before and after the pump during backflow in a cooling circuit device according to a second embodiment of the present invention. The following description will be given based on this figure. In the second embodiment, the same components as those in the first embodiment are given the same reference numerals and will not be described.

[0044] The cooling circuit device 2 according to the second embodiment is different from the cooling circuit device 1 according to the first embodiment in the positions of the first valve and the second valve.

[0045] Specifically, the first valve 24b according to the second embodiment is provided at one end of the first passage 24. The first valve 24b according to the present embodiment is a three-way valve that can be switched between a passage in which the refrigerant flows from the pump 10 through the discharge passage 21 to the inverter 11 by closing the valve on the first passage 24 side, and a passage in which the suction passage 22 and the discharge passage 21 are connected via the first passage 24 by closing the valve on the pump 10 side.

[0046] Further, the second valve 25b of the second embodiment is provided at the other end of the second passage 25. The second valve 25b of the present embodiment is a three-way valve that can be switched between a flow path in which the valve on the second passage 25 side is closed to allow the refrigerant to flow from the radiator 13 through the suction passage 22 to the pump 10, and a flow path in which the valve on the pump 10 side is closed to connect the discharge passage 21 and the suction passage 22 via the second passage 25.

[0047] The first valve 24b and the second valve 25b of the second embodiment are also connected to the VCU 30 so as to be able to communicate with each other, and the VCU 30 executes the air bleeding control. The procedure of the air bleeding control is the same as that of the first embodiment.

[0048] Next, the switching of each valve when circulating the refrigerant in the reverse flow direction in the second embodiment will be described. Note that the outlined arrows in Fig. 5 indicate the direction in which the refrigerant flows. For ease of explanation, the directions in which the first valve 24b and the second valve 25b are closed and the flow path is blocked are indicated by filled triangles in the figure.

[0049] 5, when the refrigerant flows in the reverse direction, the first valve 24b opens the flow path from the discharge passage 21 to the first passage 24, while blocking the discharge passage 21 through which refrigerant flows toward the pump 10. The second valve 25b opens the suction passage 22 through which refrigerant flows from the second passage 25 to the side away from the pump 10 (the radiator 13 and surge tank 15 side), while blocking the suction passage 22 through which refrigerant flows toward the pump 10.

[0050] When the pump 10 is driven in this state, the refrigerant flows from the inverter 12 side through the discharge passage 21 (arrow B1), and due to switching of the first valve 24b, the refrigerant cannot flow to the pump 10 side and flows into the first passage 24. The refrigerant that flows into the first passage 24 flows through the first passage 24 (arrow B2), merges with the suction passage 22, and is sucked into the pump 10 (arrow B3). Then, the refrigerant discharged by the pump 10 flows from the discharge passage 21 on the pump 10 side (arrow B4) through the second passage 25 (arrow B5), merges with the suction passage 22 on the side away from the pump 10, and flows toward the radiator 13 and surge tank 15 (arrow B6).

[0051] As described above, the vehicle cooling circuit apparatus 2 according to the second embodiment can achieve the same effects as the cooling circuit apparatus 1 according to the first embodiment.

[0052] That is, when the vehicle cooling circuit device 2 according to the second embodiment detects the pump 10 running idle, it controls the first valve 24b and the second valve 25b to switch and drive the pump 10, thereby changing the flow direction of the refrigerant from the forward flow direction to the reverse flow direction. This allows air trapped in the forward flow direction to be discharged, and prevents malfunctions caused by the pump 10 running idle. That is, with this configuration, air trapped in the cooling passage 20 can be efficiently discharged regardless of the vertical positional relationship in the cooling passage 20, and a decrease in cooling efficiency and damage to the pump and the equipment to be cooled due to air mixing can be prevented, thereby improving the life of the equipment to be cooled.

[0053] This concludes the description of the embodiment of the present invention, but the aspects of the present invention are not limited to this embodiment.

[0054] In each of the above embodiments, the idling of the pump 10 is detected by a torque sensor mounted on the pump 10, but the means for detecting the idling of the pump is not limited to this. For example, the flow rate of the refrigerant discharged from the pump may be detected, and it may be determined that the pump is idling when the flow rate temporarily decreases.

[0055] In addition, in each of the above embodiments, the pump 10, the first valves 24a, 24b, and the second valves 25a and 25b are controlled by the VCU 30, but they may be controlled by another control unit or via an electrical control circuit.

[0056] Although the vehicle 1 in each of the above embodiments is an electric truck, the present invention can be applied to other electric vehicles, such as passenger electric vehicles and hybrid electric vehicles.

[0057] In the above embodiment, the pump stop time corresponding to the time for which the refrigerant is allowed to flow in the reverse direction in step S5 is a preset predetermined time, but the time for which the refrigerant is allowed to flow in the reverse direction is not limited to this. For example, the refrigerant may be allowed to flow in the reverse direction until the value of the torque sensor of the pump becomes stable for a certain period of time. [Explanation of symbols]

[0058] 1, 2 Cooling circuit device 10. Pump 11 Motor 12 Inverter 13 Radiator 14 Air cooling section 15 Surge Tank 20 Cooling passage 21 Discharge passage 22 Suction passage 23 Surge tank passage 24 1st aisle 24a, 24b First valve 25 2nd aisle 25a, 25b Second valve 30 VCU

Claims

1. A pump that draws in and discharges a refrigerant; a discharge passage connected to a discharge side of the pump; a suction passage connected to a suction side of the pump; a first passage having one end connected to the exhaust passage and the other end connected to the suction passage; a second passage having one end connected to the discharge passage on a side closer to the pump than a connection portion between the discharge passage and the first passage, and having the other end connected to the suction passage on a side farther from the pump than a connection portion between the discharge passage and the first passage; a first valve provided at the other end of the first passage and capable of switching a flow path between the suction passage and the first passage; a second valve provided at one end of the second passage and capable of switching a flow path between the discharge passage and the second passage; A control unit that controls the first valve and the second valve, when the control unit detects that the pump is running idle, the control unit switches the first valve so that refrigerant flows from the first passage to the suction passage, and switches the second valve so that refrigerant flows from the discharge passage to the second passage.

2. A pump that draws in and discharges a refrigerant; a discharge passage connected to a discharge side of the pump; a suction passage connected to a suction side of the pump; a first passage having one end connected to the exhaust passage and the other end connected to the suction passage; a second passage having one end connected to the discharge passage on a side closer to the pump than a connection portion between the discharge passage and the first passage, and having the other end connected to the suction passage on a side farther from the pump than a connection portion between the discharge passage and the first passage; a first valve provided at one end of the first passage and capable of switching a flow path between the discharge passage and the first passage; a second valve provided at the other end of the second passage and capable of switching a flow path between the suction passage and the second passage; A control unit that controls the first valve and the second valve, when the control unit detects that the pump is running idle, the control unit switches the first valve so that the refrigerant flows from the discharge passage to the first passage, and switches the second valve so that the refrigerant flows from the second passage to the suction passage.

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