Battery warm-up system

Abstract

To improve a warming-up performance of a battery in a battery warming-up system.SOLUTION: A battery warming-up system 10 comprises: a pressure sensor 32 that detects a discharge pressure of a coolant discharged from a compressor 12; a temperature sensor 33 that detects a temperature of a battery 20; and a switch valve 30 that is provided in a first pipe 21, can block a supply of the coolant discharged from the compressor 12 to a battery thermal exchange device 13, and can switch a first switch state that permits a flow to a bypass passage 28 of the coolant discharged from the compressor 12 and a second switch state that permits a supply to the battery thermal exchange device 13 of the coolant discharged from the compressor 12. The switch valve 30 switches the first switch state to the second switch state when a difference of a saturation steam temperature conducted from a pressure detected by the pressure sensor 32 and a temperature detected by the temperature sensor 33 exceeds a threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery warm-up system. [Background technology]

[0002] A battery warm-up system for warming up a battery is disclosed in, for example, Patent Document 1. Such a battery warm-up system includes a refrigeration cycle having a compressor, a battery heat exchanger, an expansion valve, and an accumulator. The compressor compresses and discharges a refrigerant. The refrigerant discharged from the compressor flows into the battery heat exchanger. The battery heat exchanger exchanges heat between the battery and the refrigerant. The expansion valve reduces the pressure of the refrigerant flowing out of the battery heat exchanger. The refrigerant reduced in pressure by the expansion valve flows into the accumulator. The accumulator allows gas refrigerant to flow into the compressor. In such a battery warm-up system, heat is exchanged between the battery and the refrigerant via the battery heat exchanger, and the battery is warmed up by the latent heat of condensation required when the gas refrigerant flowing through the battery heat exchanger changes to liquid refrigerant.

[0003] Furthermore, in order to efficiently warm up the battery, as in Patent Document 2, for example, it has been considered to introduce a portion of the refrigerant discharged from the compressor into the passage from the expansion valve to the accumulator or into the accumulator. In such a case, the battery warm-up system includes a bypass passage. The bypass passage bypasses the battery heat exchanger. The bypass passage branches off from a first passage connecting the compressor and the battery heat exchanger. The bypass passage is connected to the accumulator or to a second passage connecting the expansion valve and the accumulator. A throttle is provided in the bypass passage. A portion of the refrigerant flowing through the first passage is decompressed by the throttle and introduced into the second passage or the accumulator via the bypass passage. This heats the refrigerant in the accumulator, increasing the saturated vapor pressure of the gas refrigerant flowing out of the accumulator and being drawn into the compressor. This increases the saturated vapor temperature of the gas refrigerant discharged from the compressor due to the thermodynamic properties of the refrigerant. The increase in saturated vapor temperature increases the isotherm of the refrigerant in the two-phase region. The temperature of the refrigerant flowing through the battery heat exchanger is on an isothermal line, so the refrigerant temperature remains constant. Furthermore, compared to when the refrigerant in the accumulator is not heated, the isothermal line in the two-phase region of the refrigerant is elevated, making it easier to maintain the difference between the temperature of the refrigerant flowing through the battery heat exchanger and the temperature of the battery. As a result, the battery warm-up performance of the battery warm-up system is improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-60066 [Patent Document 2] Japanese Patent Publication No. 2022-34162 Summary of the Invention [Problem to be solved by the invention]

[0005] As heat exchange between the battery and the refrigerant proceeds through the battery heat exchanger, the temperature of the refrigerant passing through the battery heat exchanger decreases. As the refrigerant temperature decreases, the amount of liquid refrigerant condensed and liquefied in the battery heat exchanger increases. Consider a case where the outside air temperature is lower than the temperature of the liquid refrigerant decompressed by the expansion valve. In this case, the heat of the refrigerant introduced from the first passage through the bypass passage to the second passage or the accumulator may be used as the latent heat of evaporation required for the liquid refrigerant decompressed by the expansion valve to evaporate into saturated vapor. This makes it difficult for the refrigerant in the accumulator to heat up, making it difficult for the saturated vapor pressure of the gas refrigerant flowing from the accumulator and being drawn into the compressor to increase. This makes it difficult for the saturated vapor temperature of the gas refrigerant discharged from the compressor to increase, making it difficult to maintain the difference between the temperature of the refrigerant flowing through the battery heat exchanger and the temperature of the battery. As a result, the battery warm-up performance of the battery warm-up system decreases. [Means for solving the problem]

[0006] The battery warm-up system that solves the above-mentioned problems includes a refrigeration cycle having a compressor that compresses and discharges refrigerant, a battery heat exchanger through which the refrigerant discharged from the compressor flows and exchanges heat between the refrigerant and a battery, an expansion valve that decompresses the refrigerant flowing out of the battery heat exchanger, and an accumulator into which the refrigerant decompressed by the expansion valve flows and which allows gas refrigerant to flow to the compressor, and a bypass passage that bypasses the battery heat exchanger, the bypass passage branching off from a first passage connecting the compressor and the battery heat exchanger, and connected to a second passage connecting the expansion valve and the accumulator or to the accumulator, and the bypass passage has a throttle a pressure sensor that detects the discharge pressure of the refrigerant discharged from the compressor; a temperature sensor that detects the temperature of the battery; and a switching valve that is provided in the first passage and is switchable between a first switching state that blocks the supply of the refrigerant discharged from the compressor to the battery heat exchanger and allows the refrigerant discharged from the compressor to flow to the bypass passage and a second switching state that allows the refrigerant discharged from the compressor to be supplied to the battery heat exchanger, and when a difference between a saturated vapor temperature derived from the pressure detected by the pressure sensor and the temperature detected by the temperature sensor exceeds a threshold value, the switching valve switches from the first switching state to the second switching state.

[0007] According to this system, the switching valve remains in the first switching state until the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor and the temperature detected by the temperature sensor exceeds a threshold value. Therefore, until the difference between the saturated vapor temperature and the battery temperature exceeds the threshold value, the refrigerant discharged from the compressor is not supplied to the battery heat exchanger via the first passage but is instead introduced from the first passage through the bypass passage to the second passage or the accumulator. As a result, the refrigerant in the accumulator is heated, increasing the saturated vapor pressure of the gas refrigerant flowing out of the accumulator and being drawn into the compressor. This increases the saturated vapor temperature of the gas refrigerant discharged from the compressor due to the thermodynamic properties of the refrigerant. The increase in saturated vapor temperature increases the isotherm of the refrigerant in the two-phase region. When the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor and the temperature detected by the temperature sensor exceeds the threshold value, the switching valve switches from the first switching state to the second switching state. As a result, the refrigerant discharged from the compressor is supplied to the battery heat exchanger via the first passage. At this time, the temperature of the refrigerant flowing through the battery heat exchanger is on an isotherm, so the refrigerant temperature remains constant. Furthermore, since the isotherm in the two-phase region of the refrigerant is elevated compared to when the refrigerant in the accumulator is not heated, the difference between the temperature of the refrigerant flowing through the battery heat exchanger and the temperature of the battery is more easily maintained. Therefore, it is possible to avoid the situation where it becomes difficult to maintain the difference between the temperature of the refrigerant flowing through the battery heat exchanger and the temperature of the battery. As a result, the battery warm-up performance of the battery warm-up system can be improved.

[0008] In the battery warm-up system, when the switching valve is in the second switching state, the refrigerant discharged from the compressor is preferably allowed to flow into the bypass passage. According to this configuration, even when the switching valve is in the second switching state, the refrigerant discharged from the compressor is introduced from the first passage through the bypass passage to the second passage or the accumulator. Therefore, even when the switching valve is in the second switching state, the saturated vapor pressure of the gas refrigerant flowing out of the accumulator and being drawn into the compressor can be increased. This increases the saturated vapor temperature of the gas refrigerant discharged from the compressor due to the thermodynamic characteristics of the refrigerant. Therefore, even when the switching valve is in the second switching state, the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor and the temperature detected by the temperature sensor is unlikely to fall below the threshold. As a result, even when the switching valve is in the second switching state, the difference between the temperature of the refrigerant flowing through the battery heat exchanger and the temperature of the battery can be easily maintained.

[0009] In the above-described battery warm-up system, when in the second switching state, the switching valve may allow the refrigerant discharged from the compressor to be supplied to the battery heat exchanger, and may block the flow of the refrigerant discharged from the compressor to the bypass passage.

[0010] The battery warm-up system may further include a bypass switching valve that blocks the flow of refrigerant discharged from the compressor to the bypass passage when the switching valve is in the second switching state.

[0011] According to these, when the switching valve is in the second switching state, the refrigerant discharged from the compressor does not flow from the first passage to the bypass passage, and all of the refrigerant discharged from the compressor is supplied to the battery heat exchanger, thereby allowing the battery to be warmed up efficiently.

[0012] In the above-described battery warm-up system, the refrigeration cycle has an external fluid heat exchanger through which the refrigerant decompressed by the expansion valve flows and exchanges heat between the refrigerant and an external fluid, and the bypass passage may introduce the refrigerant discharged from the compressor into a passage extending from the outlet of the external fluid heat exchanger to the inlet of the accumulator.

[0013] The passage extending from the outlet of the external fluid heat exchanger to the inlet of the accumulator is suitable as a bypass passage connection in the refrigeration cycle. For example, unlike when the bypass passage is connected to the accumulator, there is no need to modify the accumulator from its existing configuration to connect the bypass passage to the accumulator. Therefore, the configuration of the battery warm-up system can be simplified. [Effects of the Invention]

[0014] According to the present invention, the battery warm-up performance of the battery warm-up system can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram illustrating a battery warm-up system according to an embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating a battery warm-up system. [Figure 3] FIG. 2 is a Mollier diagram showing the relationship between enthalpy and pressure of a refrigerant. [Figure 4] FIG. 10 is a Mollier diagram showing the relationship between enthalpy and pressure of a refrigerant in a comparative example. [Figure 5] FIG. 10 is a schematic diagram showing a battery warm-up system according to another embodiment. [Figure 6] FIG. 10 is a schematic diagram showing a battery warm-up system according to another embodiment. [Figure 7] FIG. 10 is a schematic diagram showing a battery warm-up system according to another embodiment. [Figure 8] FIG. 10 is a schematic diagram showing a battery warm-up system according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of a battery warm-up system will now be described with reference to Figures 1 to 4. The battery warm-up system of this embodiment is mounted on, for example, an electric vehicle. <Overall configuration of battery warm-up system 10> As shown in Figures 1 and 2, the battery warm-up system 10 includes a refrigeration cycle 11. The battery warm-up system 10 uses the refrigeration cycle 11 to warm up a battery 20. The battery 20 is configured by arranging a plurality of battery cells (not shown) in parallel. The battery cells are, for example, lithium-ion batteries or nickel-metal hydride batteries. The battery 20 is packaged as a single battery pack by accommodating the plurality of battery cells in, for example, a housing (not shown).

[0017] The refrigeration cycle 11 has a compressor 12, a battery heat exchanger 13, an expansion valve 14, an external fluid heat exchanger 15, and an accumulator 16. The compressor 12 compresses and discharges a refrigerant. The refrigerant discharged from the compressor 12 flows through the battery heat exchanger 13. The battery heat exchanger 13 is thermally coupled to the battery 20. The battery heat exchanger 13 exchanges heat between the battery 20 and the refrigerant. The expansion valve 14 reduces the pressure of the refrigerant flowing out from the battery heat exchanger 13. The expansion valve 14 is a fixed throttle that reduces the pressure of the refrigerant flowing out from the battery heat exchanger 13. The refrigerant reduced in pressure by the expansion valve 14 flows through the external fluid heat exchanger 15. The external fluid heat exchanger 15 exchanges heat between the refrigerant and outside air, which is an external fluid. The refrigerant flowing out from the external fluid heat exchanger 15 flows into the accumulator 16. Therefore, the refrigerant decompressed by the expansion valve 14 flows into the accumulator 16. The accumulator 16 allows the gas refrigerant to flow out to the compressor 12.

[0018] The compressor 12 and the battery heat exchanger 13 are connected by a first pipe 21. A first end of the first pipe 21 is connected to the discharge port 12a of the compressor 12. A second end of the first pipe 21 is connected to the inlet 13a of the battery heat exchanger 13. Therefore, the first pipe 21 forms a passage that extends from the discharge port 12a of the compressor 12 to the inlet 13a of the battery heat exchanger 13. The first pipe 21 forms a first passage that connects the compressor 12 and the battery heat exchanger 13.

[0019] The battery heat exchanger 13 and the expansion valve 14 are connected by a second pipe 22. A first end of the second pipe 22 is connected to the outlet 13b of the battery heat exchanger 13. A second end of the second pipe 22 is connected to the inlet 14a of the expansion valve 14.

[0020] The expansion valve 14 and the external fluid heat exchanger 15 are connected by a third pipe 23. A first end of the third pipe 23 is connected to the outlet 14b of the expansion valve 14. A second end of the third pipe 23 is connected to the inlet 15a of the external fluid heat exchanger 15.

[0021] The external fluid heat exchanger 15 and the accumulator 16 are connected by a fourth pipe 24. A first end of the fourth pipe 24 is connected to the outlet 15b of the external fluid heat exchanger 15. A second end of the fourth pipe 24 is connected to the inlet 16a of the accumulator 16. Therefore, the fourth pipe 24 forms a passage extending from the outlet 15b of the external fluid heat exchanger 15 to the inlet 16a of the accumulator 16. The third pipe 23 and the fourth pipe 24 form a passage extending from the expansion valve 14 to the accumulator 16. The third pipe 23 and the fourth pipe 24 form a second passage 40 connecting the expansion valve 14 and the accumulator 16.

[0022] The accumulator 16 and the compressor 12 are connected by a fifth pipe 25. A first end of the fifth pipe 25 is connected to the outlet 16b of the accumulator 16. A second end of the fifth pipe 25 is connected to the suction port 12b of the compressor 12.

[0023] The battery warm-up system 10 includes a branch passage 26. The branch passage 26 branches off midway through the third pipe 23. The branch passage 26 is, for example, a pipe. A first end of the branch passage 26 is connected midway through the third pipe 23. A second end of the branch passage 26 is connected to the fourth pipe 24. The branch passage 26 causes the refrigerant flowing through the third pipe 23 to bypass the external fluid heat exchanger 15 and flow into the fourth pipe 24.

[0024] The battery warm-up system 10 includes a valve device 27. The valve device 27 is provided in the fourth pipe 24. The valve device 27 is provided at a connection point of the fourth pipe 24 with the branch passage 26. The valve device 27 is configured to be switchable between a first switching state and a second switching state. The valve device 27 is, for example, a solenoid valve. In the first switching state, the valve device 27 allows the flow of refrigerant to the external fluid heat exchanger 15 and blocks the flow of refrigerant to the branch passage 26. In the second switching state, the valve device 27 blocks the flow of refrigerant to the external fluid heat exchanger 15 and allows the flow of refrigerant to the branch passage 26. The valve device 27 is, for example, a three-way valve.

[0025] The battery warm-up system 10 includes a bypass passage 28. The bypass passage 28 branches off from the first pipe 21. Therefore, the bypass passage 28 branches off from the passage extending from the discharge port 12a of the compressor 12 to the inlet 13a of the battery heat exchanger 13. The bypass passage 28 is, for example, a pipe. A first end of the bypass passage 28 is connected to the first pipe 21. A second end of the bypass passage 28 is connected to the fourth pipe 24. Therefore, the bypass passage 28 is connected to the passage extending from the outlet 15b of the external fluid heat exchanger 15 to the inlet 16a of the accumulator 16. Specifically, the second end of the bypass passage 28 is connected to a portion of the fourth pipe 24 closer to the accumulator 16 than the valve device 27. The bypass passage 28 introduces the refrigerant discharged from the compressor 12 into the fourth pipe 24 that constitutes a passage extending from the outlet 15b of the external fluid heat exchanger 15 to the inlet 16a of the accumulator 16. The bypass passage 28 branches off from the first pipe 21 that constitutes the first passage, and is connected to the second passage 40.

[0026] The battery warm-up system 10 includes a throttle 29. The throttle 29 is provided in the bypass passage 28. Therefore, the throttle 29 is provided in the bypass passage 28. The throttle 29 reduces the flow path cross-sectional area of ​​a portion of the bypass passage 28. The throttle 29 is a fixed throttle. The refrigerant discharged from the compressor 12 is decompressed by the throttle 29 and then introduced into the fourth pipe 24 via the bypass passage 28. Therefore, the refrigerant discharged from the compressor 12 is decompressed by the throttle 29 and then introduced into the passage from the expansion valve 14 to the accumulator 16 via the bypass passage 28.

[0027] The battery warm-up system 10 includes a switching valve 30. The switching valve 30 is provided in the first pipe 21. The switching valve 30 is provided in a portion of the first pipe 21 closer to the battery heat exchanger 13 than the connection point with the bypass passage 28. The switching valve 30 is, for example, a solenoid valve. The switching valve 30 is configured to be switchable to a first switching state that blocks the supply of refrigerant discharged from the compressor 12 to the battery heat exchanger 13 and allows the refrigerant discharged from the compressor 12 to flow into the bypass passage 28. The switching valve 30 is configured to be switchable to a second switching state that allows the refrigerant discharged from the compressor 12 to be supplied to the battery heat exchanger 13. In the first switching state, the switching valve 30 is in a closed state. In the second switching state, the switching valve 30 is in an open state. The switching valve 30 is, for example, an on / off valve.

[0028] <Electrical configuration of battery warm-up system 10> The battery warm-up system 10 includes a control device 31. The control device 31 includes a central processing unit (CPU). The control device 31 includes a memory configured from a read-only memory (ROM) that stores various programs, maps, etc. in advance, and a random access memory (RAM) that temporarily stores the results of CPU calculations, etc. The control device 31 includes a timer counter, an input interface, an output interface, etc.

[0029] The battery warm-up system 10 includes a pressure sensor 32. The pressure sensor 32 is configured to detect the discharge pressure of the refrigerant discharged from the compressor 12. The pressure sensor 32 is electrically connected to the control device 31. A detection signal related to the discharge pressure of the refrigerant detected by the pressure sensor 32 is output to the control device 31.

[0030] The battery warm-up system 10 includes a temperature sensor 33. The temperature sensor 33 is configured to detect the temperature of the battery 20. The temperature sensor 33 is electrically connected to the control device 31. A detection signal relating to the temperature of the battery 20 detected by the temperature sensor 33 is output to the control device 31.

[0031] The battery warm-up system 10 includes an outside air temperature sensor 34. The outside air temperature sensor 34 is configured to detect the temperature of the outside air. The outside air temperature sensor 34 is electrically connected to the control device 31. A detection signal relating to the temperature of the outside air detected by the outside air temperature sensor 34 is output to the control device 31.

[0032] The control device 31 is electrically connected to the valve device 27. The control device 31 controls the operation of the valve device 27. A program for switching the valve device 27 between a first switching state and a second switching state based on the outside air temperature detected by the outside air temperature sensor 34 is stored in advance in the control device 31. The control device 31 switches the valve device 27 to the first switching state when the outside air temperature detected by the outside air temperature sensor 34 is higher than a predetermined temperature. On the other hand, the control device 31 switches the valve device 27 to the second switching state when the outside air temperature detected by the outside air temperature sensor 34 is equal to or lower than the predetermined temperature. The "predetermined temperature" is a temperature higher than the temperature of the liquid refrigerant decompressed by the expansion valve 14.

[0033] The control device 31 stores in advance a map that associates the pressure detected by the pressure sensor 32 with the saturated vapor temperature of the gas refrigerant discharged from the compressor 12. The saturated vapor temperature is derived from the pressure detected by the pressure sensor 32. The control device 31 stores in advance a derivation program that derives the saturated vapor temperature from the pressure detected by the pressure sensor 32.

[0034] The control device 31 is electrically connected to the switching valve 30. The control device 31 controls the operation of the switching valve 30. The control device 31 pre-stores a program for switching the switching valve 30 between a first switching state and a second switching state based on the saturated steam temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33. The control device 31 switches the switching valve 30 to the first switching state when the difference between the saturated steam temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 does not exceed a threshold value. On the other hand, the control device 31 switches the switching valve 30 from the first switching state to the second switching state when the difference between the saturated steam temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds the threshold value. Therefore, when the difference between the saturated steam temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds a threshold value, the switching valve 30 switches from the first switching state to the second switching state.

[0035] [Operation of the embodiment] Next, the operation of this embodiment will be described. When the temperature of the outside air detected by the outside air temperature sensor 34 is higher than a predetermined temperature, the control device 31 switches the valve device 27 to the first switching state. Then, the valve device 27 allows the refrigerant to flow to the external fluid heat exchanger 15 and blocks the refrigerant from flowing to the branch passage 26. This causes heat exchange between the outside air and the refrigerant in the external fluid heat exchanger 15. As a result, the refrigerant is warmed by the outside air in the external fluid heat exchanger 15.

[0036] On the other hand, when the temperature of the outside air detected by the outside air temperature sensor 34 is equal to or lower than a predetermined temperature, the control device 31 switches the valve device 27 to the second switching state. Then, the valve device 27 blocks the flow of refrigerant to the external fluid heat exchanger 15 and allows the flow of refrigerant to the branch passage 26. As a result, heat exchange between the outside air and the refrigerant does not occur in the external fluid heat exchanger 15. Then, the liquid refrigerant decompressed by the expansion valve 14 flows from the third pipe 23 through the branch passage 26 into the fourth pipe 24. As a result, the refrigerant is prevented from being cooled by the outside air in the external fluid heat exchanger 15.

[0037] 3 and 4 show Mollier diagrams illustrating the relationship between refrigerant enthalpy and pressure when the valve device 27 is in the second switching state. In FIGS. 3 and 4, the horizontal axis represents refrigerant enthalpy, and the vertical axis represents refrigerant pressure. As shown in FIGS. 3 and 4, the curve extending upwardly bulging, the curve drawn to the left of the critical point CP, which is the apex of the curve, is the saturated liquid line L1, and the curve drawn to the right of the critical point CP is the saturated vapor line L2. The region enclosed by the saturated liquid line L1 and the saturated vapor line L2 is a two-phase region A1 in which the refrigerant is in a gas-liquid two-phase state. The region to the left of the saturated liquid line L1 is a supercooled liquid region A2 in which the refrigerant is in a supercooled liquid state. The region to the right of the saturated vapor line L2 is a superheated gas region A3 in which the refrigerant is in a superheated gas state.

[0038] The solid line L10 in FIG. 3 shows the relationship between the enthalpy and pressure of the refrigerant when the valve device 27 is in the second switching state and the refrigerant discharged from the compressor 12 is introduced from the first pipe 21 to the fourth pipe 24 via the bypass passage 28. The solid line L20 in FIG. 4 shows the relationship between the enthalpy and pressure of the refrigerant when the valve device 27 is in the second switching state and the refrigerant discharged from the compressor 12 is supplied to the battery heat exchanger 13 even if the difference between the saturated vapor temperature and the temperature of the battery 20 does not exceed the threshold value. The Mollier diagram in FIG. 4 is a comparative example of this embodiment. As heat exchange between the battery 20 and the refrigerant via the battery heat exchanger 13 progresses, the temperature of the refrigerant passing through the battery heat exchanger 13 decreases. As the refrigerant temperature decreases, the amount of liquid refrigerant condensed and liquefied in the battery heat exchanger 13 increases.

[0039] As shown by the solid line L20 in Fig. 4, the heat of the refrigerant introduced from the first pipe 21 to the fourth pipe 24 via the bypass passage 28 may be used as the latent heat of evaporation required when the liquid refrigerant decompressed by the expansion valve 14 evaporates and turns into saturated vapor. In this case, the temperature of the refrigerant in the accumulator 16 is less likely to be heated, and therefore the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and sucked into the compressor 12 is less likely to increase. Therefore, the saturated vapor temperature of the gas refrigerant discharged from the compressor 12 is less likely to increase, and therefore it is more difficult to maintain the difference between the temperature of the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20.

[0040] Therefore, in this embodiment, the switching valve 30 is in the first switching state until the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds the threshold value. Therefore, until the difference between the saturated vapor temperature and the temperature of the battery 20 exceeds the threshold value, the refrigerant discharged from the compressor 12 is introduced into the fourth pipe 24 via the bypass passage 28 without being supplied to the battery heat exchanger 13.

[0041] The dashed line L11 shown in Fig. 3 shows, as a comparative example, the relationship between the enthalpy and pressure of the refrigerant when the valve device 27 is in the second switching state and the refrigerant discharged from the compressor 12 is not introduced from the first pipe 21 to the fourth pipe 24 via the bypass passage 28. As can be seen by comparing the solid line L10 and the dashed line L11 in Fig. 3, the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and sucked into the compressor 12 is higher in the solid line L10 than in the dashed line L11.

[0042] When the refrigerant discharged from the compressor 12 is introduced into the fourth pipe 24 via the first pipe 21 and the bypass passage 28, the refrigerant in the accumulator 16 is heated. As a result, the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and being drawn into the compressor 12 increases. This increases the saturated vapor temperature due to the thermodynamic properties of the refrigerant. The increase in saturated vapor temperature raises the isotherm of the refrigerant in the two-phase region A1. When the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds a threshold, the switching valve 30 switches from the first switching state to the second switching state. As a result, the refrigerant discharged from the compressor 12 is supplied to the battery heat exchanger 13 via the first pipe 21. At this time, the temperature of the refrigerant flowing through the battery heat exchanger 13 is on the isotherm, and therefore the refrigerant temperature remains constant. Furthermore, compared to when the refrigerant in the accumulator 16 is not heated, the isotherm of the refrigerant in the two-phase region A1 is elevated, making it easier to maintain the difference in temperature between the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20. Therefore, it is possible to avoid the difference in temperature between the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20 becoming difficult to maintain.

[0043] As shown in FIG. 2, when the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 is allowed to flow into the bypass passage 28. Therefore, even when the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 is introduced from the first pipe 21 to the fourth pipe 24 via the bypass passage 28. Therefore, even when the switching valve 30 is in the second switching state, the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and being drawn into the compressor 12 increases. This increases the saturated vapor temperature due to the thermodynamic properties of the refrigerant. Therefore, even when the switching valve 30 is in the second switching state, the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 is unlikely to fall below the threshold value.

[0044] [Effects of the embodiment] The above embodiment can provide the following effects. (1) The switching valve 30 switches from the first switching state to the second switching state when the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds the threshold value. Accordingly, the switching valve 30 remains in the first switching state until the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds the threshold value. Therefore, until the difference between the saturated vapor temperature and the temperature of the battery 20 exceeds the threshold value, the refrigerant discharged from the compressor 12 is not supplied to the battery heat exchanger 13 via the first piping 21, but is instead introduced from the first piping 21 to the fourth piping 24 via the bypass passage 28. This heats the refrigerant in the accumulator 16, increasing the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and being drawn into the compressor 12. This increases the saturated vapor temperature of the gas refrigerant discharged from the compressor 12 due to the thermodynamic properties of the refrigerant. As the saturated vapor temperature rises, the isotherm of the refrigerant in the two-phase region A1 rises. When the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 exceeds a threshold, the switching valve 30 switches from the first switching state to the second switching state. As a result, the refrigerant discharged from the compressor 12 is supplied to the battery heat exchanger 13 via the first pipe 21. At this time, the temperature of the refrigerant flowing through the battery heat exchanger 13 is on the isotherm, and therefore the temperature of the refrigerant remains constant. Compared to when the refrigerant in the accumulator 16 is not heated, the isotherm of the refrigerant in the two-phase region A1 rises, making it easier to maintain the difference between the temperature of the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20. This avoids the difficulty of maintaining the difference between the temperature of the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20. As a result, the warm-up performance of the battery 20 in the battery warm-up system 10 can be improved.

[0045] (2) When the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 is permitted to flow into the bypass passage 28. Accordingly, even when the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 is introduced from the first pipe 21 to the fourth pipe 24 via the bypass passage 28. Therefore, even when the switching valve 30 is in the second switching state, the saturated vapor pressure of the gas refrigerant flowing out of the accumulator 16 and being drawn into the compressor 12 can be increased. This increases the saturated vapor temperature of the gas refrigerant discharged from the compressor 12 due to the thermodynamic properties of the refrigerant. Therefore, even when the switching valve 30 is in the second switching state, the difference between the saturated vapor temperature derived from the pressure detected by the pressure sensor 32 and the temperature detected by the temperature sensor 33 is unlikely to fall below the threshold. As a result, even when the switching valve 30 is in the second switching state, the difference between the temperature of the refrigerant flowing through the battery heat exchanger 13 and the temperature of the battery 20 can be easily maintained.

[0046] (3) The bypass passage 28 introduces the refrigerant discharged from the compressor 12 into the passage extending from the outlet 15b of the external fluid heat exchanger 15 to the inlet 16a of the accumulator 16. The passage extending from the outlet 15b of the external fluid heat exchanger 15 to the inlet 16a of the accumulator 16 is suitable as a connecting portion of the bypass passage 28 in the refrigeration cycle 11. For example, unlike when the bypass passage 28 is connected to the accumulator 16, there is no need to change the existing configuration of the accumulator 16 in order to connect the bypass passage 28 to the accumulator 16. Therefore, the configuration of the battery warm-up system 10 can be simplified.

[0047] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0048] As shown in FIG. 5 , a switching valve 30 may be provided at a connection point between the first pipe 21 and the bypass passage 28. In this case, the switching valve 30 is configured to, in a first switching state, block the supply of refrigerant discharged from the compressor 12 to the battery heat exchanger 13 and allow the refrigerant discharged from the compressor 12 to flow into the bypass passage 28. Furthermore, in a second switching state, the switching valve 30 is configured to allow the refrigerant discharged from the compressor 12 to be supplied to the battery heat exchanger 13 and block the flow of refrigerant discharged from the compressor 12 to the bypass passage 28. The switching valve 30 is a three-way valve. According to this, when the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 does not flow from the first pipe 21 to the bypass passage 28, and all of the refrigerant discharged from the compressor 12 is supplied to the battery heat exchanger 13, thereby efficiently warming up the battery 20.

[0049] As shown in FIG. 6 , the battery warm-up system 10 may further include a bypass switching valve 35. The bypass switching valve 35 is provided in a portion of the bypass passage 28 closer to the first pipe 21 than the throttle 29. The bypass switching valve 35 is, for example, a solenoid valve. The bypass switching valve 35 is, for example, an on-off valve. The bypass switching valve 35 is electrically connected to a control device 31. The control device 31 controls the operation of the bypass switching valve 35. The bypass switching valve 35 is configured to allow the refrigerant discharged from the compressor 12 to flow into the bypass passage 28 when the switching valve 30 is in the first switching state. The bypass switching valve 35 is configured to block the flow of the refrigerant discharged from the compressor 12 into the bypass passage 28 when the switching valve 30 is in the second switching state. According to this, when the switching valve 30 is in the second switching state, the refrigerant discharged from the compressor 12 does not flow from the first piping 21 to the bypass passage 28, and all of the refrigerant discharged from the compressor 12 is supplied to the battery heat exchanger 13, thereby allowing the battery 20 to be warmed up efficiently.

[0050] As shown in Fig. 7 , a second end of the bypass passage 28 may be connected to the accumulator 16. In this case, the refrigerant discharged from the compressor 12 is introduced into the accumulator 16 after being decompressed by a throttle 29.

[0051] 8 , the second end of the bypass passage 28 may be connected to the third pipe 23. In short, it is sufficient that the refrigerant discharged from the compressor 12 is decompressed by the throttle 29 and introduced into the passage from the expansion valve 14 to the accumulator 16 or into the accumulator 16 via the bypass passage 28. Therefore, it is sufficient that the bypass passage 28 branches off from the first pipe 21 and is connected to the second passage 40 or the accumulator 16.

[0052] In an embodiment, the expansion valve 14 may be a variable throttle valve. In the embodiment, the aperture 29 may be a variable aperture. In the above embodiment, the valve device 27 may be provided at a connection point of the third pipe 23 with the branch passage 26, for example.

[0053] In the above-described embodiment, the external fluid heat exchanger 15 may be configured to perform heat exchange between the refrigerant and the cooling water, which is the external fluid. In the above-described embodiment, the battery warm-up system 10 may not include the external fluid heat exchanger 15.

[0054] In the embodiment, the battery warm-up system 10 is not limited to being installed in an electric vehicle. Furthermore, the battery warm-up system 10 is not limited to being installed in a vehicle. In other words, the battery warm-up system 10 is not limited to being applied to a particular device. [Explanation of symbols]

[0055] 10...battery warm-up system, 11...refrigeration cycle, 12...compressor, 13...battery heat exchanger, 14...expansion valve, 15...external fluid heat exchanger, 15b...outlet, 16...accumulator, 16a...inlet, 20...battery, 21...first piping constituting first passage, 28...bypass passage, 29...throttle, 30...switching valve, 32...pressure sensor, 33...temperature sensor, 35...bypass switching valve, 40...second passage.

Claims

1. a compressor that compresses and discharges a refrigerant; a battery heat exchanger through which the refrigerant discharged from the compressor flows and which exchanges heat between the battery and the refrigerant; an expansion valve that reduces the pressure of the refrigerant flowing out from the battery heat exchanger; an accumulator into which the refrigerant decompressed by the expansion valve flows and which allows the gas refrigerant to flow out to the compressor, a bypass passage that bypasses the battery heat exchanger, the bypass passage branching off from a first passage that connects the compressor and the battery heat exchanger, and connected to a second passage that connects the expansion valve and the accumulator, or to the accumulator; The bypass passage is provided with a throttle, a pressure sensor for detecting a discharge pressure of the refrigerant discharged from the compressor; a temperature sensor for detecting the temperature of the battery; a switching valve that is provided in the first passage and is switchable between a first switching state that blocks the supply of the refrigerant discharged from the compressor to the battery heat exchanger and allows the refrigerant discharged from the compressor to flow to the bypass passage, and a second switching state that allows the refrigerant discharged from the compressor to be supplied to the battery heat exchanger; A battery warm-up system in which the switching valve switches from the first switching state to the second switching state when the difference between the saturated steam temperature derived from the pressure detected by the pressure sensor and the temperature detected by the temperature sensor exceeds a threshold value.

2. 2. The battery warm-up system according to claim 1, wherein when the switching valve is in the second switching state, refrigerant discharged from the compressor is allowed to flow into the bypass passage.

3. 2. The battery warm-up system according to claim 1, wherein the switching valve, when in the second switching state, allows the refrigerant discharged from the compressor to be supplied to the battery heat exchanger and blocks the flow of the refrigerant discharged from the compressor to the bypass passage.

4. 2. The battery warm-up system according to claim 1, further comprising a bypass switching valve that blocks the flow of refrigerant discharged from the compressor to the bypass passage when the switching valve is in the second switching state.

5. the refrigeration cycle includes an external fluid heat exchanger through which the refrigerant decompressed by the expansion valve flows and which exchanges heat between the refrigerant and an external fluid; The battery warm-up system according to any one of claims 1 to 4, wherein the bypass passage introduces the refrigerant discharged from the compressor into a passage extending from the outlet of the external fluid heat exchanger to the inlet of the accumulator.

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