Cooling device for vehicle battery

Abstract

To prevent liquid refrigerant from flowing into a first compressor.SOLUTION: A cooling device for a vehicle battery includes a heat exchanger 2 that exchanges heat between a refrigerant and a battery cell 71, a first compressor 3 that pressurizes the refrigerant flowing out from the heat exchanger 2, a condenser 4 that cools and condenses the refrigerant pressurized by the first compressor 3, and a refrigerant pulsation device that is provided between the condenser 4 and the heat exchanger 2 in a refrigerant path 10 through which the refrigerant passes, and that pulsates the refrigerant.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed herein belongs to the technical field relating to cooling devices for vehicle-mounted batteries. [Background technology]

[0002] 2. Description of the Related Art Conventionally, cooling devices are known that cool a battery mounted on a vehicle by exchanging heat between the battery and a refrigerant.

[0003] For example, Patent Document 1 discloses a cooling device that includes a temperature control plate through which a temperature control fluid (refrigerant) flows to control the temperature of battery cells, a pump that pressurizes the temperature control fluid, and a pulsation generating mechanism that is disposed in a fluid circulation pipeline between the pump and the inlet of the temperature control plate and generates pulsations in the temperature control fluid; when air is contained in the temperature control fluid, the pulsation generating mechanism is operated to change the flow of the temperature control fluid. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-191203 A Summary of the Invention [Problem to be solved by the invention]

[0005] Some battery cooling devices cool the batteries by an endothermic reaction that occurs when a liquid refrigerant changes phase to gas. In such cooling devices, the refrigerant that has been vaporized through heat exchange with the batteries is pressurized by a compressor, and then cooled and condensed. If liquid refrigerant flows into the compressor at this time, it may accelerate deterioration of the compressor.

[0006] The technology disclosed herein has been made in consideration of these points, and its purpose is to prevent liquid refrigerant from flowing into a pressurizer in a cooling device that cools batteries by an endothermic reaction occurring when the liquid refrigerant changes phase to gas. [Means for solving the problem]

[0007] In order to solve the above problems, a first aspect of the technology disclosed herein is directed to a cooling device for an on-board battery that cools a battery by an endothermic reaction that occurs when a liquid refrigerant changes phase to a gaseous state, and is configured to include a heat exchanger that exchanges heat between the refrigerant and the battery, a pressurizer that pressurizes the refrigerant flowing out of the heat exchanger, a condenser that cools and condenses the refrigerant pressurized by the pressurizer, and a refrigerant pulsation device that is provided between the condenser and the heat exchanger in a refrigerant path through which the refrigerant passes and that pulsates the refrigerant.

[0008] According to this configuration, when the refrigerant is pulsated by the refrigerant pulsation device, the refrigerant is stirred, so that the entire refrigerant is evenly heat-exchanged with the batteries in the heat exchanger. As a result, the entire refrigerant is warmed in the heat exchanger, so that the entire refrigerant is more likely to vaporize. Therefore, it is possible to prevent the liquid refrigerant from flowing into the pressurizer.

[0009] In a second aspect of the technology disclosed herein, the first aspect is further provided with a controller that controls the refrigerant pulsation device, and when a portion of the refrigerant flowing into the pressurizer is liquid, the controller causes the refrigerant to pulsate using the refrigerant pulsation device.

[0010] With this configuration, the load on the refrigerant pulsation device can be reduced compared to when the refrigerant pulsation device is constantly operated, which allows the refrigerant to be pulsated appropriately and more appropriately prevents the liquid refrigerant from flowing into the pressurizer.

[0011] In a third aspect of the technology disclosed herein, in the second aspect, an expansion valve is provided between the condenser and the refrigerant pulsation device in the refrigerant path to reduce the pressure of the refrigerant condensed in the condenser, and the refrigerant pulsation device is configured as a pressure regulator that pulsates the refrigerant by adjusting the pressure of the refrigerant that has passed through the expansion valve.

[0012] With this configuration, the flow rate of the refrigerant flowing into the heat exchanger can be adjusted by adjusting the opening of the expansion valve. Even if the amount of refrigerant increases, the pressure regulator pulsates the refrigerant, allowing the refrigerant to exchange heat evenly with the batteries. This makes it possible to more appropriately prevent liquid refrigerant from flowing into the pressurizer.

[0013] In a fourth aspect of the technology disclosed herein, in the second aspect, the refrigerant pulsation device has an expansion valve that reduces the pressure of the refrigerant condensed in the condenser, and the controller pulsates the refrigerant by opening and closing the expansion valve.

[0014] With this configuration, it is possible to adjust the flow rate of the refrigerant flowing into the heat exchanger and to pulsate the refrigerant with a single device, which makes it possible to suppress the flow of liquid refrigerant into the pressurizer and to make the cooling device compact in configuration.

[0015] In a fifth aspect of the technology disclosed herein, the third or fourth aspect is provided with a refrigerant heat exchanger that exchanges heat between the refrigerant flowing out of the heat exchanger and before flowing into the compressor, and the refrigerant flowing out of the condenser and before passing through the expansion valve.

[0016] According to this configuration, the refrigerant flowing out of the condenser and before passing through the expansion valve is pressurized by the compressor, and therefore, even if it is cooled by the condenser, it is at a higher temperature than the refrigerant flowing out of the heat exchanger and before being pressurized by the compressor. Therefore, even if a part of the refrigerant flowing out of the heat exchanger is liquid, the liquid refrigerant can be vaporized by being warmed by the refrigerant heat exchanger. This makes it possible to more effectively prevent the liquid refrigerant from flowing into the compressor.

[0017] In a sixth aspect of the technology disclosed herein, in any one of the first to fourth aspects, the heat exchanger has a piping through which the refrigerant passes, and the piping has an area enlargement portion for increasing the contact area with the refrigerant.

[0018] This configuration promotes heat exchange between the refrigerant and the battery, allowing the entire refrigerant to vaporize properly. In addition, for example, when the area enlargement portion is formed by a protrusion protruding into the piping, the pulsating refrigerant interferes with the protrusion and becomes turbulent. This makes it easier for the refrigerant to be agitated, making it easier for the entire refrigerant to vaporize. Therefore, it is possible to more effectively prevent the liquid refrigerant from flowing into the pressurizer. Effect of the Invention

[0019] As described above, according to the technique disclosed herein, it is possible to prevent the refrigerant in a liquid state from flowing into the compressor. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a configuration diagram of a vehicle having a cooling device according to a first embodiment. [Diagram 2] FIG. 2 is a plan view showing the arrangement of the heat exchangers. [Diagram 3] FIG. 3 is a cross-sectional view showing the piping of the heat exchanger. [Figure 4] FIG. 4 is a schematic cross-sectional view of the second compressor. [Diagram 5] FIG. 5 is a block diagram showing a control system of the cooling device. [Figure 6] FIG. 6 is a graph showing the relationship between the position of the refrigerant path in the cooling device and the refrigerant temperature. [Figure 7] FIG. 7 is a flowchart showing the processing operation of the controller when controlling the second compressor. [Figure 8] FIG. 8 is a graph showing the relationship between the amplitude and frequency of the pulsation and the cooling capacity. [Figure 9] FIG. 9 is a time chart showing the relationship between the battery temperature, the degree of superheat of the refrigerant, and the flow of the refrigerant in the heat exchanger. [Figure 10] FIG. 10 is a cross-sectional view showing a first modified example of piping of a heat exchanger. [Figure 11]FIG. 11 is a cross-sectional view showing a second modified example of piping of a heat exchanger. [Figure 12] FIG. 12 is a configuration diagram of a vehicle having a cooling device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Exemplary embodiments will now be described in detail with reference to the drawings.

[0022] (Embodiment 1) Overall configuration of the cooling device 1 shows a vehicle 100 having a cooling device 1 according to the present embodiment 1. The vehicle 100 is an automobile capable of running on electric power, such as an electric vehicle or a hybrid vehicle.

[0023] The vehicle 100 has a battery module 70 in which power is stored. The battery module 70 is configured by stacking a plurality of rectangular box-shaped battery cells 71 (see FIG. 2). The battery module 70 is disposed under a floor panel of the vehicle 100. The vehicle 100 is equipped with an electric motor (not shown) as a drive source, and the electric motor is driven to rotate by the power stored in the battery module 70, thereby rotating the wheels 101 and running the vehicle. The battery cells 71 are configured by, for example, lithium ion batteries or nickel metal hydride batteries.

[0024] The cooling device 1 cools each of the battery cells 71 of the battery module 70 by an endothermic reaction that occurs when a liquid refrigerant changes phase to gas. The refrigerant is, for example, an HFO (hydrofluoroolefin) refrigerant, specifically, R1234yf.

[0025] The cooling device 1 has a heat exchanger 2 that exchanges heat between a refrigerant and battery cells 71, a first compressor 3 that pressurizes the refrigerant flowing out of the heat exchanger 2, a condenser 4 that cools and condenses the refrigerant pressurized by the first compressor 3, and a refrigerant path 10 that is formed in a ring shape by connecting the heat exchanger 2, the first compressor 3, and the condenser 4 to each other. The cooling device 1 also has an expansion valve 5 that reduces the pressure of the refrigerant condensed in the condenser 4, and a second compressor 6 that pulsates the refrigerant in the heat exchanger 2. The second compressor 6 corresponds to a refrigerant pulsation device.

[0026] 2 and 3, the heat exchanger 2 has a cooling plate 21 arranged on the underside of the battery module 70, and a thermally conductive sheet 22 arranged between the cooling plate 21 and the battery module 70. Although only one battery module 70 is shown in Fig. 2, in reality, a plurality of battery modules 70 are provided, and the cooling plates 21 and the thermally conductive sheets 22 are provided according to the number of battery modules 70. Furthermore, the number of battery cells 71 constituting the battery module 70 is 10 in Fig. 2, but it may be 11 or more, or may be less than 9.

[0027] The cooling plate 21 has a rectangular plate shape with its long sides extending in the stacking direction of the battery cells 71. The length of the short sides of the cooling plate 21 is smaller than the longitudinal width of the bottom surface of the battery cells 71. The cooling plate 21 is made of a metal with high thermal conductivity, such as aluminum.

[0028] As shown in FIG. 3, the cooling plate 21 has a plurality of pipes 23 extending in the long side direction. Each pipe 23 is a path through which the refrigerant flows. One end of each pipe 23 is an inlet for the refrigerant, and the other end of each pipe 23 is an outlet for the refrigerant. A plurality of protrusions 23a extending in the longitudinal direction of the pipe 23 are formed in each pipe 23. The protrusions 23a correspond to area enlargement portions for increasing the contact area with the refrigerant. Note that, although the protrusions 23a are formed only on the top and bottom surfaces of the pipe 23 in FIG. 3, they may also be formed on the side surfaces of the pipe 23.

[0029] The thermally conductive sheet 22 extends so as to cover all of the bottom surfaces of the multiple battery cells 71 that make up the battery module 70. The longitudinal length of the thermally conductive sheet 22 is equal to the longitudinal length of the battery module 70, and the transverse length of the thermally conductive sheet 22 is slightly greater than the width of the bottom surface of the battery module 70 in a direction perpendicular to the stacking direction. The presence of the thermally conductive sheet 22 makes it possible to conduct heat from the entirety of each battery cell 71 to the cooling plate 21, even if the length of the short side of the cooling plate 21 is smaller than the longitudinal width of the bottom surface of the battery cell 71.

[0030] The heat transferred to the cooling plate 21 via the thermal conduction sheet 22 spreads throughout the entire cooling plate 21 and exchanges heat with the refrigerant in each of the pipes 23. Therefore, even if the refrigerant in each of the pipes 23 has vaporized and is located in the upper part of the pipes 23, heat exchange can be performed between the battery cells 71 and the liquid refrigerant remaining in the pipes 23.

[0031] The first compressor 3 pressurizes the refrigerant after heat exchange with the battery cells 71. The first compressor 3 is, for example, a scroll compressor, and the pressure of the refrigerant flowing out can be adjusted by adjusting the rotation speed. When the refrigerant is pressurized by the first compressor 3, the temperature of the refrigerant increases. The refrigerant pressurized by the first compressor 3 flows out in gas form without being liquefied.

[0032] Condenser 4 is disposed in the front portion of vehicle 100. An electric fan 41 is provided on the vehicle rear side of condenser 4. Condenser 4 cools the refrigerant with air generated by the vehicle while vehicle 100 is traveling, and cools the refrigerant with air drawn in by the rotation of electric fan 41 while vehicle 100 is stopped. In condenser 4, the refrigerant condenses and liquefies as the temperature drops without a drop in pressure.

[0033] A receiver tank 42 is provided downstream of the condenser 4. The receiver tank 42 temporarily stores the refrigerant liquefied by the condenser 4. The receiver tank 42 is connected to the refrigerant path 10. When the refrigerant liquefied by the condenser 4 flows into the receiver tank 42, an amount of refrigerant equivalent to the amount of the inflowing refrigerant flows out from the receiver tank 42 to the refrigerant path 10.

[0034] The refrigerant path 10 has a liquid refrigerant path 11 through which mainly liquid refrigerant passes, and a gas refrigerant path 12 through which mainly gas refrigerant passes. The liquid refrigerant path 11 is a path from the condenser 4 to the inlet of the heat exchanger 2. The gas refrigerant path 12 is a path from the outlet of the heat exchanger 2 to the condenser 4. The above-mentioned first compressor 3 is provided midway through the gas refrigerant path 12.

[0035] The expansion valve 5 is provided midway through the liquid refrigerant path 11. The expansion valve 5 reduces the pressure of the refrigerant in the liquid refrigerant path 11. The refrigerant that passes through the expansion valve 5 is reduced in pressure, resulting in a decrease in temperature. In addition, as the pressure is reduced by the expansion valve 5, the saturation temperature (equivalent to the boiling point) is lowered, making it easier for the refrigerant to vaporize in the pipe 23 of the heat exchanger 2. In addition, as the pressure is reduced by the expansion valve 5, the flow of the refrigerant in the pipe 23 slows, so that the refrigerant in the pipe 23 exchanges heat evenly with the battery cells 71.

[0036] The expansion valve 5 is also used to adjust the flow rate of the refrigerant flowing into the heat exchanger 2. Specifically, the larger the opening of the expansion valve 5, the larger the flow rate of the refrigerant flowing into the heat exchanger 2, whereas the smaller the opening of the expansion valve 5, the smaller the flow rate of the refrigerant flowing into the heat exchanger 2.

[0037] The second compressor 6 adjusts the pressure of the refrigerant that has passed through the expansion valve 5 to pulsate the refrigerant. The second compressor 6 is configured as a scroll compressor as shown in FIG. 4. The second compressor 6 adjusts the pressure of the refrigerant by increasing or decreasing the flow rate of the refrigerant that flows out by adjusting the rotation speed. In detail, the second compressor 6 pulsates the refrigerant by alternately increasing the rotation speed to increase the flow rate of the refrigerant and decreasing the rotation speed to decrease the flow rate of the refrigerant. The refrigerant can pass through the second compressor 6 even when the second compressor 6 is not operating. For example, the second compressor 6 may have a bypass path that connects the upstream and downstream of the second compressor 6.

[0038] The cooling device 1 has a refrigerant heat exchanger 8 that exchanges heat between the refrigerant flowing through the gas refrigerant path 12 from the heat exchanger 2 to the first compressor 3 and the refrigerant flowing through the liquid refrigerant path 11 from the condenser 4 to the expansion valve 5. That is, the refrigerant heat exchanger 8 exchanges heat between the refrigerant that flows out of the heat exchanger 2 and before it flows into the first compressor 3 (hereinafter referred to as high-pressure refrigerant) and the refrigerant that flows out of the condenser 4 and before it passes through the expansion valve 5 (hereinafter referred to as low-pressure refrigerant). The high-pressure refrigerant has a high saturation temperature because it is pressurized by the first compressor 3. On the other hand, the low-pressure refrigerant has a low saturation temperature because its pressure is significantly reduced by the expansion valve 5. Therefore, even if the high-pressure refrigerant is condensed and liquefied by the condenser 4, it is still at a high temperature compared to the low-pressure refrigerant. Therefore, the refrigerant heat exchanger 8 heats the low-pressure refrigerant with the high-pressure refrigerant. Note that a known refrigerant heat exchanger 8 can be used, and therefore a detailed description of its configuration will be omitted.

[0039] <Cooling device control system> Next, the control system of the cooling device 1 will be described.

[0040] 5, the vehicle 100 has a BECM (Battery Energy Control Module) 81, which is a controller that mainly controls charging and discharging of the battery module 70 and the flow rate of the refrigerant in the heat exchanger 2. The BECM 81 includes one or more processors 81a having a CPU, and a memory 81b configured with a ROM and a RAM and storing various programs. The memory 81b is, for example, a non-volatile memory.

[0041] The BECM 81 receives detection results from a battery temperature sensor SW1 that detects the temperature of the battery cells 71, a refrigerant temperature sensor SW2 that detects the temperature of the refrigerant flowing into the first compressor 3, a first refrigerant pressure sensor SW3 that detects the pressure of the refrigerant pressurized by the first compressor 3 and before being depressurized by the expansion valve 5, and a second refrigerant pressure sensor SW4 that detects the pressure of the refrigerant depressurized by the expansion valve 5 and before being pressurized by the first compressor 3. The battery temperature sensor SW1 is disposed, for example, near the refrigerant outlet of the battery module 70. The refrigerant temperature sensor SW2 and the second refrigerant pressure sensor SW4 are disposed in positions downstream of the refrigerant heat exchanger 8 and upstream of the first compressor 3 in the gas refrigerant path 12. The first refrigerant pressure sensor SW3 is disposed in a position downstream of the first compressor 3 and upstream of the condenser 4 in the gas refrigerant path 12. A plurality of battery temperature sensors SW1 may be provided, and may be disposed, for example, in the vicinity of the coolant outlet of the battery module 70, as well as in the center of the battery module 70 in plan view.

[0042] The BECM 81 controls the expansion valve 5 based on signals from the sensors SW1 to SW4. Specifically, the BECM 81 controls the opening of the expansion valve 5. When increasing the flow rate of the refrigerant flowing into the heat exchanger 2, the BECM 81 increases the opening of the expansion valve 5 from the current opening, whereas when decreasing the flow rate of the refrigerant flowing into the heat exchanger 2, the BECM 81 decreases the opening of the expansion valve 5 from the current opening.

[0043] Furthermore, the BECM 81 controls the second compressor 6 based on signals from the sensors SW1 to SW4. The BECM 81 controls the rotation speed of the second compressor 6. The BECM 81 increases or decreases the rotation speed of the second compressor 6 to pulsate the refrigerant flowing into the heat exchanger 2. The BECM 81 controls the second compressor 6 so that the time average of the pressure (flow rate) of the refrigerant flowing into the heat exchanger 2 becomes the pressure (flow rate) of the refrigerant when it passes through the expansion valve 5. When increasing the amplitude of the pulsation, the BECM 81 increases the maximum and minimum values ​​of the rotation speed to be increased or decreased. When increasing the frequency of the pulsation, the BECM 81 increases or decreases the rotation speed to shorten the period.

[0044] The control performed by the BECM 81 is stored as a program in the memory 81b. The BECM 81 is an example of a controller.

[0045] The vehicle 100 has a PCM (Powertrain Control Module) 80, which is a controller that controls the entire power system of the vehicle 100. The PCM 80 includes one or more processors 80a having a CPU, and a memory 80b having a ROM and RAM and storing various programs. The memory 80b is, for example, a non-volatile memory.

[0046] The PCM 80 receives the detection result of the outside air temperature sensor SW5 that detects the outside air temperature. The outside air temperature sensor SW5 is located on the vehicle front side of the condenser 4. The detection result of the outside air temperature sensor SW5 corresponds to the temperature of the air drawn in by the electric fan 41. The PCM 80 also obtains the detection results of the sensors SW1 to SW4 via the BECM 81.

[0047] The PCM 80 controls the electric fan 41 and the first compressor 3 based on signals from the sensors SW1-SW4. The PCM 60 sets a target cooling capacity based on the detection result of the battery temperature sensor SW1, and sets the rotation speed of the first compressor 3 based on the set target cooling capacity. The PCM 60 sets the rotation speed of the electric fan 41 based on the detection results of the first refrigerant pressure sensor SW3 and the outside air temperature sensor SW5.

[0048] The control performed by the PCM 80 is stored as a program in the memory 80b.

[0049] <State of refrigerant at each position in the refrigerant path> Fig. 6 shows a schematic diagram of the refrigerant temperature at each position in the refrigerant path 10. Fig. 6 shows the change in refrigerant temperature from a position downstream of the receiver tank 42 and upstream of the refrigerant heat exchanger 8 in the liquid refrigerant path 11 to a position downstream of the refrigerant heat exchanger 8 and upstream of the first compressor 3 in the gas refrigerant path 12. Fig. 6 also shows the change in refrigerant temperature when the second compressor 6 is not operating.

[0050] First, let us look at the temperature change indicated by the solid line. The refrigerant is in the state of the high-pressure refrigerant upstream of the refrigerant heat exchanger 8 in the liquid refrigerant path 11, so even if it is liquefied, its temperature is relatively high. When the refrigerant passes through the refrigerant heat exchanger 8, it exchanges heat with the low-pressure refrigerant passing through the gas refrigerant path 12, and its temperature drops. Next, when the refrigerant passes through the expansion valve 5, the temperature of the refrigerant drops significantly due to adiabatic expansion. Then, when the refrigerant enters the pipe 23 of the heat exchanger 2, the temperature of the refrigerant rises slightly and it vaporizes. The refrigerant cools the battery cells 71 by an endothermic reaction when it vaporizes. Since the refrigerant continues to vaporize while flowing through the pipe 23 of the heat exchanger 2, the temperature is maintained at the saturation temperature. In this example, at the outlet of the heat exchanger 2, the refrigerant is not completely vaporized, and a part of it remains in a liquid state. Therefore, the temperature of the refrigerant that flows out of the heat exchanger 2 remains at the saturation temperature. After that, when the refrigerant flows into the refrigerant heat exchanger 8, the refrigerant exchanges heat with the high-pressure refrigerant passing through the liquid refrigerant path 11. This heat exchange causes the refrigerant to completely vaporize, which causes the refrigerant to reach a temperature higher than the saturation temperature.

[0051] In this way, some of the refrigerant remains in liquid form in the heat exchanger 2, and when it completely vaporizes in the refrigerant heat exchanger 8, the refrigerant is constantly undergoing an endothermic reaction while passing through the pipes 23 of the heat exchanger 2, making it possible to efficiently cool the battery cells 71. In addition, because almost no liquid refrigerant flows into the first compressor 3, deterioration of the first compressor 3 can be suppressed.

[0052] Here, if the flow rate of the refrigerant to the heat exchanger 2 is small, the refrigerant will completely vaporize partway through the heat exchanger 2, as shown by the dashed dotted line in Figure 6, and the refrigerant temperature will rise in the pipes 23 of the heat exchanger 2. If the refrigerant completely vaporizes partway through the heat exchanger 2, it will become particularly difficult to cool the battery cells 71 located near the outlet of the cooling plate 21, and the temperature of the battery cells 71 will rise.

[0053] When the BECM 81 receives information from the battery temperature sensor SW1 that the temperature of the battery cells 71 has risen and reached a predetermined temperature TC or higher, it controls the expansion valve 5 to increase the flow rate of the refrigerant. However, if the flow rate of the refrigerant becomes too high, there is a risk that liquid refrigerant will remain even after passing through the refrigerant heat exchanger 8, as shown by the two-dot chain line in Figure 6. If liquid refrigerant remains, it may flow into the first compressor 3, accelerating the deterioration of the first compressor 3.

[0054] Therefore, in this embodiment, when a portion of the refrigerant flowing into the first compressor 3 is liquid, the BECM 81 causes the second compressor 6 to pulsate the refrigerant flowing into the heat exchanger 2.

[0055] <Control of the second compressor> FIG. 7 shows a flowchart of the control of the second compressor 6 by the BECM 81.

[0056] First, in step S1, the BECM 81 reads the detection results of the sensors SW1 to SW4.

[0057] Next, in step S2, it is determined whether the battery temperature TB is equal to or higher than a predetermined temperature TC. If the battery temperature TB is equal to or higher than the predetermined temperature TC (YES), the BECM 81 proceeds to step S3. On the other hand, if the battery temperature TB is lower than the predetermined temperature TC (NO), the BECM 81 returns.

[0058] In step S3, the BECM 81 increases the flow rate of the refrigerant by increasing the opening degree of the expansion valve 5.

[0059] Next, in step S4, the BECM 81 determines whether or not a part of the refrigerant flowing into the first compressor 3 is liquid. When it is estimated that the refrigerant is entirely vaporized in the gas refrigerant path 12 between the refrigerant heat exchanger 8 and the first compressor 3, the BECM 81 determines that the refrigerant flowing into the first compressor 3 is entirely vaporized, whereas when it is estimated that liquid refrigerant remains in the gas refrigerant path 12, the BECM 81 determines that a part of the refrigerant flowing into the first compressor 3 is liquid. The BECM 81 estimates whether or not the refrigerant in the gas refrigerant path 12 is entirely vaporized based on the detection results of the refrigerant temperature sensor SW2 and the second refrigerant pressure sensor SW4. Specifically, the BECM 81 calculates the average pressure in the gas refrigerant path 12 from the detection result of the second refrigerant pressure sensor SW4. Next, the BECM 81 calculates the saturation temperature of the refrigerant at the average pressure. The BECM 81 stores a vapor pressure curve for the refrigerant (for example, a vapor pressure curve for R1234yf) in advance in the memory 81b, and reads the vapor pressure curve to calculate the saturation temperature. Next, the BECM 81 compares the detection result of the refrigerant temperature sensor SW2 with the saturation temperature. When the refrigerant temperature detected by the refrigerant temperature sensor SW2 is higher than the saturation temperature, the BECM 81 estimates that all of the refrigerant in the gas refrigerant path 12 has been vaporized, whereas when the refrigerant temperature is equal to or lower than the saturation temperature, the BECM 81 estimates that liquid refrigerant remains in the gas refrigerant path 12.

[0060] In step S4, the BECM 81 returns when the result is YES, that is, all of the refrigerant flowing into the first compressor 3 is gas. On the other hand, when the result is NO, that is, that is, part of the refrigerant flowing into the first compressor 3 is liquid, the BECM 81 proceeds to step S5.

[0061] In step S5, the BECM 81 strengthens the pulsation caused by the second compressor 6. The BECM 81 adjusts the rotation speed of the second compressor 6 to increase at least one of the amplitude and frequency of the pulsation. After step S5, the process returns to step S4. Note that "strengthening the pulsation" here also includes a case where the refrigerant is made to pulsate from a non-pulsating state.

[0062] FIG. 8 shows the relationship between the amplitude and frequency of the pulsation and the cooling capacity. The high frequency curve in FIG. 8 has the highest frequency among the three curves, and the low frequency curve has the lowest frequency among the three curves. The medium frequency curve is a curve with a frequency intermediate between the high frequency and the low frequency. As shown in FIG. 8, when the amplitude and frequency of the pulsation are increased, the cooling capacity is improved. This is because turbulence occurs in the pipe 23 of the heat exchanger 2, and the refrigerant is stirred, so that the refrigerant exchanges heat evenly. In particular, in this embodiment, as described above, the protruding portion 23a is formed in the pipe 23, so that the protruding portion 23a acts as an obstacle to easily form a turbulent flow, and further, the protruding portion 23a increases the surface area, so that the heat exchange is easily promoted. As a result, the vaporization of the refrigerant in the pipe 23 is promoted, and the amount of liquid refrigerant contained in the refrigerant flowing out from the heat exchanger 2 is reduced. As a result, it is possible to suppress the inflow of liquid refrigerant into the first compressor 3.

[0063] 9 shows the relationship between the battery temperature, the degree of superheat of the refrigerant in the gas refrigerant path 12 between the refrigerant heat exchanger 8 and the first compressor 3, and the flow rate of the refrigerant in the heat exchanger 2. The degree of superheat of the refrigerant is the difference between the temperature of the refrigerant and the saturation temperature. If the degree of superheat is greater than 0, it means that the refrigerant is entirely vaporized, and if the degree of superheat is 0, it means that part of the refrigerant is in a liquid state.

[0064] First, in the initial state, the battery cells 71 are sufficiently cooled, the refrigerant is all vaporized, and the degree of superheat is greater than 0. Also, in the initial state, the second compressor 6 is not operating.

[0065] Assume that the battery temperature rises from this initial state at time t1. At this time, the refrigerant is completely vaporized before flowing out of the heat exchanger 2 and is heated by the heat of the battery cells 71, so the degree of superheat of the refrigerant increases.

[0066] At time t2, the battery temperature reaches a predetermined temperature T C When this occurs, the refrigerant flow rate is increased, thereby preventing the battery temperature from increasing and reducing the degree of superheat.

[0067] Then, at time t3, when the degree of superheat becomes 0, the second compressor 6 is operated to pulsate the refrigerant in the heat exchanger 2. This causes the flow rate of the refrigerant in the heat exchanger 2 to increase or decrease.

[0068] Here, assume that the current amplitude and frequency do not provide sufficient cooling capacity, and part of the refrigerant remains liquid, i.e., the degree of superheat remains 0. In this case, the pulsation is strengthened at time t4. Here, the amplitude of the pulsation is increased. This improves the cooling capacity, lowers the battery temperature, and all of the refrigerant evaporates, increasing the degree of superheat of the refrigerant.

[0069] After time t5, the amplitude of the pulsation becomes constant, and the flow rate of the liquid refrigerant flowing out of the heat exchanger 2 also becomes almost constant, so that the degree of superheat of the refrigerant increases only in the refrigerant heat exchanger 8 and becomes almost constant.

[0070] Effects of the First Embodiment Therefore, in the first embodiment, the system includes a heat exchanger 2 that exchanges heat between the refrigerant and the battery cells 71, a first compressor 3 that pressurizes the refrigerant that flows out of the heat exchanger 2, a condenser 4 that cools and condenses the refrigerant pressurized by the first compressor 3, and a second compressor 6 that is provided between the condenser 4 and the heat exchanger 2 in the refrigerant path 10 through which the refrigerant passes and pulsates the refrigerant. When the second compressor 6 pulsates the refrigerant, the refrigerant is agitated, and the entire refrigerant is evenly heat-exchanged with the battery cells 71 in the heat exchanger 2. As a result, the entire refrigerant is warmed in the heat exchanger 2, making it easier for the entire refrigerant to vaporize. Therefore, it is possible to prevent the refrigerant in a liquid state from flowing into the first compressor 3.

[0071] In particular, in the first embodiment, a BECM 81 that controls the second compressor 6 is provided, and when a portion of the refrigerant flowing into the first compressor 3 is liquid, the BECM 81 causes the second compressor 6 to pulsate the refrigerant. This allows the second compressor 6 to operate only when necessary, and therefore the load on the second compressor 6 can be reduced compared to when the second compressor 6 is operated all the time. As a result, the refrigerant can be appropriately pulsated, and the flow of liquid refrigerant into the first compressor 3 can be more appropriately prevented.

[0072] In the first embodiment, even after the second compressor 6 is operated, the BECM 81 increases at least one of the amplitude and frequency of the pulsation when part of the refrigerant flowing into the first compressor 3 is liquid. This improves the cooling capacity and makes it easier for the entire refrigerant to vaporize. As a result, it is possible to more appropriately prevent the refrigerant in a liquid state from flowing into the first compressor 3.

[0073] Moreover, in the first embodiment, an expansion valve 5 is provided between the condenser 4 and the second compressor 6 in the refrigerant path 10 to reduce the pressure of the refrigerant condensed in the condenser 4, and the second compressor 6 adjusts the pressure of the refrigerant that has passed through the expansion valve 5 to pulsate the refrigerant. This makes it possible to adjust the amount of refrigerant flowing into the heat exchanger 2 by adjusting the opening degree of the expansion valve 5. Even if the amount of refrigerant increases, the second compressor 6 pulsates the refrigerant, allowing the refrigerant to exchange heat evenly with the battery cells 71. This makes it possible to more appropriately prevent the refrigerant in a liquid state from flowing into the first compressor 3.

[0074] Moreover, in the first embodiment, a refrigerant heat exchanger 8 is provided that exchanges heat between the refrigerant that flows out of the heat exchanger 2 and before flowing into the first compressor 3, and the refrigerant that flows out of the condenser 4 and before passing through the expansion valve 5. As a result, even if a part of the refrigerant that flows out of the heat exchanger 2 is liquid, the liquid refrigerant can be vaporized by being warmed by the refrigerant heat exchanger 8. As a result, the liquid refrigerant can be more effectively prevented from flowing into the first compressor 3.

[0075] Moreover, in the first embodiment, the heat exchanger 2 has a pipe 23 through which the refrigerant passes, and the pipe 23 has a protruding portion 23a for increasing the contact area with the refrigerant. This promotes heat exchange between the refrigerant and the battery cells 71, so that the entire refrigerant can be vaporized appropriately. In addition, the pulsating refrigerant comes into contact with the protruding portion 23a, resulting in a turbulent flow. As a result, the refrigerant is more easily agitated, so that the entire refrigerant is more easily vaporized. Therefore, it is possible to more effectively prevent the refrigerant in a liquid state from flowing into the first compressor 3.

[0076] In the first embodiment, the second compressor 6 is disposed downstream of the expansion valve 5 and upstream of the heat exchanger 2. This allows the second compressor 6 to apply pulsation to the low-pressure refrigerant, thereby reducing the load on the second compressor 6.

[0077] (Modification 1 of the first embodiment) 10 shows a first modification of the first embodiment, in which the structure of the pipes 223 of the cooling plate 21 is different. Specifically, in this first modification, instead of the protruding portions, a plurality of recesses 223a are formed, which are recessed toward the outside of the pipes 223 and extend in the longitudinal direction of the pipes 223. By forming these recesses 223a, the contact area between the wall surface of the pipes 223 and the refrigerant can be enlarged. For this reason, the recesses 223a correspond to area enlarging portions.

[0078] Even in this first modification, the formation of the recesses 223a promotes heat exchange between the refrigerant and the battery cells 71, so that the entire refrigerant can be vaporized appropriately. In addition, the pulsating refrigerant is disturbed by the recesses 223a and becomes in a turbulent state. As a result, the refrigerant is more easily agitated, so that the entire refrigerant is more easily vaporized. Therefore, it is possible to more effectively prevent the liquid refrigerant from flowing into the first compressor 3.

[0079] (Modification 2 of the first embodiment) 11 shows a second modification of the first embodiment, in which the structure of the pipes 323 of the cooling plate 21 is different. Specifically, in the second modification, instead of the protruding portions, a plurality of grooves 323a are formed over the entire longitudinal direction of the pipes 323, the grooves 323a being recessed toward the outside of the pipes 323 and extending in a direction perpendicular to the longitudinal direction of the pipes 323. By forming the grooves 323a, the contact area between the wall surface of the pipes 323 and the refrigerant can be enlarged. Thus, the grooves 323a correspond to area enlargement portions.

[0080] Even in this second modification, the formation of the grooves 323a promotes heat exchange between the refrigerant and the battery cells 71, so that the entire refrigerant can be vaporized appropriately. In addition, the pulsating refrigerant is disturbed by the grooves 323a and becomes in a turbulent state. As a result, the refrigerant is more easily agitated, so that the entire refrigerant is more easily vaporized. Therefore, it is possible to more effectively prevent the liquid refrigerant from flowing into the first compressor 3.

[0081] (Embodiment 2) Hereinafter, the second embodiment will be described in detail with reference to the drawings. In the following description, the same reference numerals will be used to designate the same parts as those in the first embodiment, and detailed description thereof will be omitted.

[0082] FIG. 12 shows a vehicle 100 equipped with a cooling device 201 according to the second embodiment. The second embodiment differs from the first embodiment in that the second compressor 6 is not provided. In the second embodiment, the refrigerant is pulsated by adjusting the opening of the expansion valve 5. That is, the BECM 81 pulsates the refrigerant by alternately repeating increasing the opening of the expansion valve 5 and decreasing the opening of the expansion valve 5. The BECM 81 controls the opening and closing of the expansion valve 5 so that the average pressure (average flow rate) of the refrigerant supplied to the heat exchanger 2 becomes a target pressure (flow rate).

[0083] In the configuration of the second embodiment, the refrigerant is also agitated, so that the entire refrigerant exchanges heat evenly with the battery cells 71 inside the heat exchanger 2. As a result, the entire refrigerant is warmed inside the heat exchanger 2, making it easier for the entire refrigerant to vaporize. This makes it possible to prevent liquid refrigerant from flowing into the first compressor 3.

[0084] Furthermore, in the second embodiment, since the adjustment of the flow rate of the refrigerant flowing into the heat exchanger 2 and the pulsation of the refrigerant can be achieved by a single device, the cooling device 201 can be made compact in configuration.

[0085] (Other embodiments) The technology disclosed herein is not limited to the above-described embodiment, and may be substituted without departing from the spirit and scope of the claims.

[0086] In the above-described first and second embodiments, the BECM 81 pulsates the refrigerant flowing into the heat exchanger 2 when a portion of the refrigerant flowing into the first compressor 3 is liquid. However, the present invention is not limited to this, and the BECM 81 may always pulsate the refrigerant flowing into the heat exchanger 2. In this case, the BECM 81 normally pulsates the refrigerant with a relatively small amplitude and a relatively low frequency, and increases at least one of the amplitude and frequency of the pulsation when it is determined that a portion of the refrigerant flowing into the first compressor 3 is liquid.

[0087] Furthermore, in the above-described first and second embodiments, the refrigerant heat exchanger 8 is provided, but the refrigerant heat exchanger 8 may be omitted.

[0088] In the above-described first and second embodiments, the protrusion 23a, the recess 223a, and the groove 323a are provided as the area enlarging portion. However, the area enlarging portion is not limited to this, and may be a structure in which something like a fin is provided inside the pipe, or a structure in which the wall surface of the pipe is roughened.

[0089] The above-described embodiments are merely illustrative and should not be construed as limiting the scope of the present disclosure. The scope of the present disclosure is defined by the claims, and all modifications and variations within the scope of the claims are within the scope of the present disclosure. [Industrial Applicability]

[0090] The technology disclosed herein is useful as an engine control device for an on-board battery cooling device, which cools the battery by an endothermic reaction that occurs when a liquid refrigerant changes phase to a gas. [Explanation of symbols]

[0091] 2 Heat exchanger 3. First Compressor 4 Capacitors 5 Expansion valve (refrigerant pulsation device) 6. Second compressor (refrigerant pulsation device) 8 Refrigerant heat exchanger 10 Refrigerant path 21 Cooling plate 22 Thermal Conductive Sheet 23 Piping 23a Protruding part (area enlarged part) 223 Piping 223a Concave portion (area enlarged portion) 323 Piping 323a Groove section (area expansion section)

Claims

1. A cooling device for an on-board battery that cools a battery by an endothermic reaction that occurs when a liquid refrigerant changes phase to a gas, a heat exchanger for exchanging heat between the refrigerant and the battery; a compressor that pressurizes the refrigerant flowing out from the heat exchanger; a condenser that cools and condenses the refrigerant pressurized by the pressurizer; a refrigerant pulsation device provided between the condenser and the heat exchanger in a refrigerant path through which the refrigerant passes, for pulsating the refrigerant.

2. The vehicle battery cooling device according to claim 1, A controller for controlling the refrigerant pulsation device is provided. The cooling device for an in-vehicle battery, wherein the controller pulsates the refrigerant using the refrigerant pulsation device when a portion of the refrigerant flowing into the pressurizer is liquid.

3. The vehicle battery cooling device according to claim 2, an expansion valve provided between the condenser and the refrigerant pulsation device in the refrigerant path to reduce the pressure of the refrigerant condensed in the condenser; The cooling device for an automotive battery, wherein the refrigerant pulsation device is composed of a pressure regulator that pulsates the refrigerant by adjusting the pressure of the refrigerant that has passed through the expansion valve.

4. The vehicle battery cooling device according to claim 2, The refrigerant pulsation device has an expansion valve that reduces the pressure of the refrigerant condensed in the condenser, The cooling device for an in-vehicle battery, wherein the controller pulsates the refrigerant by opening and closing the expansion valve.

5. The cooling device for an in-vehicle battery according to claim 3 or 4, a refrigerant heat exchanger that exchanges heat between the refrigerant that flows out of the heat exchanger and before it flows into the pressurizer, and the refrigerant that flows out of the condenser and before it passes through the expansion valve.

6. The cooling device for an on-board battery according to any one of claims 1 to 4, The heat exchanger has a pipe through which the refrigerant passes, The cooling device for an in-vehicle battery, wherein the piping has an area enlargement portion for increasing a contact area with the refrigerant.

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