Battery Cooling System

Abstract

To easily maintain refrigerants in a plurality of branched flow passages in liquid states, in a battery cooling system having a refrigeration cycle in which decompression devices and evaporators are arranged in the plurality of branched flow passages.SOLUTION: A battery cooling system comprises a refrigeration cycle and a control circuit. The refrigeration cycle comprises a compressor, a condenser, a plurality of evaporators arranged in response to a plurality of batteries, a plurality of branched flow passages, and a plurality of decompression devices arranged in the plurality of branched flow passages, respectively. The condenser exchanges heat between a refrigerant supplied from the compressor and atmospheric air existing around the condenser. The control circuit stores data which stipulate a correspondence between and among an atmospheric air temperature, a battery temperature and a target rotational speed of the compressor which can maintain the refrigerants in the plurality of branched flow passages in liquid states in advance. The control circuit determines the target rotational speed corresponding to detection results of the atmospheric air temperature and the battery temperature by referring to the data, and controls the rotational speed of the compressor to the target rotational speed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a battery cooling system for cooling multiple batteries. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2020-184427 (Patent Document 1) discloses a battery cooling system that cools multiple battery modules. The refrigeration cycle installed in this battery cooling system is configured to branch refrigerant supplied from a condenser into multiple branch flow paths to cool each of the multiple battery modules, with an expansion valve and an evaporator disposed in each of the multiple branch flow paths, and each evaporator cooling each current module. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-184427 Summary of the Invention [Problem to be solved by the invention]

[0004] In a refrigeration cycle configuration in which an expansion valve and an evaporator are disposed in each of multiple branch flow paths, such as the battery cooling system disclosed in JP 2020-184427 A, it is desirable to distribute the same amount of refrigerant to each of the multiple branch flow paths in order to evenly cool the multiple battery modules. To achieve this, it is desirable to maintain the refrigerant in the multiple branch flow paths in a liquid state (subcooled state). However, due to the influence of the temperature of each battery module and the outside air temperature around the condenser, the refrigerant in the multiple branch flow paths may not necessarily be in a liquid state.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to make it easier to maintain the refrigerant in a liquid state in multiple branch flow paths in a battery cooling system equipped with a refrigeration cycle in which a pressure reducing device such as an expansion valve and an evaporator are arranged in each of multiple branch flow paths. [Means for solving the problem]

[0006] (Item 1) A battery cooling system according to the present disclosure cools batteries. The battery cooling system includes a refrigeration cycle forming a circuit through which a refrigerant circulates, and a control circuit. The refrigeration cycle includes a compressor, a condenser, multiple evaporators arranged corresponding to multiple batteries, a first flow path connected to the compressor's discharge port and one end of the condenser, a second flow path connected to the other end of the condenser, multiple branch flow paths connecting the second flow path to one ends of the multiple evaporators, multiple pressure reduction devices arranged in the multiple branch flow paths, and a third flow path connecting the other ends of the multiple evaporators to the compressor's intake port. The condenser exchanges heat between the refrigerant supplied from the compressor and a cooling fluid present around the condenser. The battery cooling system further includes a first temperature detector that detects the temperature of the cooling fluid and a second temperature detector that detects the temperature of the batteries. The control circuit determines a target rotation speed of the compressor that maintains the refrigerant in the multiple branch flow paths in a liquid state based on the temperature of the cooling fluid and the temperature of the batteries, and controls the compressor rotation speed to the target rotation speed.

[0007] According to the configuration (1) above, the rotational speed of the compressor is controlled to a rotational speed that can maintain the refrigerant in the branch flow paths in a liquid state based on the temperature of the cooling fluid and the temperatures of the plurality of batteries, making it easier to maintain the refrigerant in the branch flow paths in a liquid state.

[0008] (Item 2) In the battery cooling system described in item 1, the control circuit pre-stores data that defines the correspondence between the temperature of the cooling fluid, the temperature of the battery, and the target rotation speed of the compressor that can maintain the refrigerant in the multiple branch flow paths in a liquid state, and determines the target rotation speed that corresponds to the detection results of the first and second temperature detection units by referring to the data, and controls the rotation speed of the compressor to the target rotation speed.

[0009] (Item 3) In the battery cooling system described in item 2, the target rotation speed in the data is specified so as to reduce the power consumption of the compressor within a range that allows the refrigerant in the multiple branch flow paths to be maintained in a liquid state.

[0010] (Item 4) In the battery cooling system described in item 3, the target rotation speed in the data is defined to be lower as the temperature of the cooling fluid is lower.

[0011] (Item 5) In the battery cooling system described in item 3, the target rotation speed in the data is defined to be lower as the temperature of the plurality of batteries increases.

[0012] (Item 6) In the battery cooling system described in any one of Items 2 to 5, the data defines a correspondence relationship between the temperature of the cooling fluid, the temperatures of the plurality of batteries, the flow rate of the cooling fluid, and the target rotation speed. The control circuit refers to the data to determine the target rotation speed corresponding to the detection results of the first and second temperature detection units and the flow rate of the cooling fluid, and controls the rotation speed of the compressor to the target rotation speed. [Effects of the Invention]

[0013] According to the present disclosure, in a battery cooling system having a refrigeration cycle in which a pressure reducing device and an evaporator are arranged in each of a plurality of branch flow paths, it is possible to make it easier to maintain the refrigerant in the plurality of branch flow paths in a liquid state. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing the overall configuration of a battery cooling system. [Figure 2] 10A and 10B are diagrams illustrating an example of the arrangement of a plurality of branch flow paths and a plurality of pressure reducing devices. [Figure 3] 4 is a diagram showing a schematic relationship between the outside air temperature Tout and the compressor rotation speed Ncomp at which the refrigerant in the branch flow passage becomes liquid. FIG. [Figure 4]10 is a diagram showing a schematic relationship between the battery temperature Tbat and the compressor rotation speed Ncomp at which the refrigerant in the branch flow path becomes liquid. FIG. [Figure 5] 4 is a diagram schematically showing map data indicating the correspondence between the battery temperature Tbat and the outside air temperature Tout and the target rotation speed Ntag. FIG. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure of a control circuit. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0016] (Overall configuration of battery cooling system 1) 1 is a diagram showing the overall configuration of a battery cooling system 1 according to the present embodiment. The battery cooling system 1 is mounted on, for example, a vehicle.

[0017] The battery cooling system 1 includes a plurality of battery modules 2, a refrigeration cycle 10, temperature sensors 50 and 60, and a control circuit 100. The battery cooling system 1 cools the plurality of battery modules 2 using the refrigeration cycle 10.

[0018] Each battery module 2 is configured by connecting a plurality of battery cells (not shown). The plurality of battery modules 2 are packaged as a single battery pack, for example, by being housed in a housing (not shown).

[0019] (Configuration of refrigeration cycle 10) The refrigeration cycle 10 forms a circuit through which a refrigerant circulates. The refrigeration cycle 10 includes a compressor 11, a condenser 12, a plurality of pressure reducing devices 14, a plurality of evaporators 15, flow paths 31, 32, and 35, a plurality of branch flow paths 33, and a plurality of branch flow paths 34.

[0020] The compressor 11 compresses the refrigerant gas drawn from the flow path 35 and discharges the compressed gas into the flow path 31. The operating amount (rotation speed, etc.) of the compressor 11 is controlled in accordance with a command signal from the control circuit 100.

[0021] The flow path 31 connects the discharge port of the compressor 11 and the inlet of the condenser 12 .

[0022] The condenser 12 exchanges heat between the refrigerant supplied from the compressor 11 and flowing inside the condenser 12 (hereinafter also referred to as the "internal refrigerant") and the cooling fluid present around the condenser 12 (hereinafter also referred to as the "external fluid").

[0023] The flow path 32 connects the outlet of the condenser 12 to the connection point N1. The flow path 32 branches at the connection point N1 into a plurality of branch flow paths 33. The plurality of branch flow paths 33 connect the connection point N1 to the inlets of the plurality of evaporators 15, respectively.

[0024] The pressure reducing devices 14 are expansion valves (throttle valves) respectively provided on the branch flow paths 33. The pressure reducing devices 14 are configured by, for example, inexpensive fixed orifices.

[0025] 2 is a diagram showing an example of the arrangement of a plurality of branch flow paths 33 and a plurality of pressure reducing devices 14. As shown in Fig. 2, a main pipe 33m that connects the connection point N1 to each branch flow path 33 is arranged between the connection point N1 and each branch flow path 33. The refrigerant from the flow path 32 is supplied to the main pipe 33m at the connection point N1 and distributed to each branch flow path 33 from the main pipe 33m.

[0026] Returning to Fig. 1, the multiple evaporators 15 are arranged corresponding to the multiple battery modules 2, respectively, and perform heat exchange between the refrigerant flowing therethrough and each of the multiple battery modules 2. The multiple evaporators 15 have the same shape. Therefore, the flow path cross-sectional areas of the multiple evaporators 15 are the same.

[0027] The branch flow paths 34 respectively connect the outlets of the evaporators 15 to the connection point N2. The branch flow paths 34 merge into a flow path 35 at the connection point N2. The flow path 35 connects the connection point N2 to the intake port of the compressor 11.

[0028] The temperature sensor 50 detects the temperature of the external fluid that exchanges heat with the internal refrigerant in the condenser 12. In the following description, it is assumed that the external fluid of the condenser 12 is the outside air present around the condenser 12, and the temperature sensor 50 detects the outside air temperature Tout around the condenser 12. The external fluid of the condenser 12 is not limited to the outside air (gas), and may be a liquid refrigerant separate from the internal refrigerant.

[0029] The temperature sensor 60 detects the temperatures of the plurality of battery modules 2. The temperature sensor 60 may be configured to detect the temperatures of each of the plurality of battery modules 2, or may be configured to detect the temperature of some of the plurality of battery modules 2 (for example, modules arranged in positions where the temperature is likely to become high). In the following description, it is assumed that the temperature sensor 60 detects a representative temperature (for example, the highest temperature) of the plurality of battery modules 2 as the battery temperature Tbat.

[0030] The control circuit 100 includes a CPU (Central Processing Unit), memory (storage device), input / output buffers, etc. (none of which are shown), and controls the operation of the compressor 11 in the refrigeration cycle 10 in accordance with the detection results of the temperature sensors 50 and 60. This control is not limited to software processing, and can also be processed by dedicated hardware (electronic circuitry).

[0031] (Cooling operation) When the compressor 11 is operated, the high-temperature, high-pressure gas refrigerant compressed by the compressor 11 is sent to the condenser 12 and condensed by the condenser 12. The high-temperature, high-pressure liquid refrigerant condensed by the condenser 12 is supplied to the flow path 32 and distributed from the flow path 32 to each of the plurality of branch flow paths 33.

[0032] The refrigerant distributed to each of the branch flow paths 33 is decompressed by the multiple pressure reducing devices 14 and then sent to the multiple evaporators 15. The low-pressure refrigerant sent to the multiple evaporators 15 exchanges heat with the multiple battery modules 2 in the multiple evaporators 15 and evaporates to become low-pressure gas refrigerant. This cools the multiple battery modules 2. The low-pressure gas refrigerant evaporated in the multiple evaporators 15 is merged with the flow path 35 at the connection point N2, passes through the flow path 35, and is sucked into the compressor 11 again.

[0033] During the cooling operation described above, in order to uniformly cool the plurality of battery modules 2, it is desirable to distribute the same amount of refrigerant to each of the plurality of branch flow paths 34. To achieve this, it is desirable to maintain the refrigerant in the plurality of branch flow paths 33 in a liquid state (subcooled state).

[0034] However, due to the influence of the battery temperature Tbat and the outside air temperature Tout, the refrigerant in the multiple branch flow paths 33 may not necessarily be in a liquid state (subcooled state). If the rotation speed of the compressor 11 (hereinafter also referred to as "compressor rotation speed Ncomp") is set to an excessively high value as a countermeasure, there is a concern that the power consumption of the compressor 11 will become unnecessarily large.

[0035] Therefore, in this embodiment, data defining the correspondence between the outside air temperature Tout and battery temperature Tbat and the compressor rotation speed Ncomp that can maintain the refrigerant in the plurality of branch flow paths 33 in a liquid state is obtained in advance by experiment or the like and is stored in advance in the memory of the control circuit 100. Then, using the detection results (outside air temperature Tout and battery temperature Tbat) of the temperature sensors 50, 60 and the above data stored in the memory, the control circuit 100 controls the rotation speed of the compressor 11 (compressor rotation speed Ncomp) so as to minimize the power consumption of the compressor 11 while maintaining the refrigerant in the branch flow paths 33 in a liquid state.

[0036] 3 is a diagram schematically showing the correspondence relationship between the outside air temperature Tout and the compressor rotation speed Ncomp at which the refrigerant in the branch flow path 33 becomes liquid. In FIG. 3, the region where the compressor rotation speed Ncomp is higher than the boundary indicated by the solid line is the region where the refrigerant in the branch flow path 33 can be maintained in a liquid state. The control circuit 100 controls the compressor rotation speed Ncomp so that it is in the region higher than the boundary indicated in FIG. 3 and is as small as possible. This makes it possible to maintain the refrigerant in the branch flow path 33 in a liquid state while minimizing the power consumption of the compressor 11.

[0037] 4 is a diagram schematically showing the correspondence relationship between the battery temperature Tbat and the compressor rotation speed Ncomp at which the refrigerant in the branch flow path 33 becomes liquid. In FIG. 4, the region where the compressor rotation speed Ncomp is higher than the boundary indicated by the solid line is the region where the refrigerant in the branch flow path 33 can be maintained in a liquid state. The control circuit 100 controls the compressor rotation speed Ncomp so that it is in the region higher than the boundary indicated in FIG. 4 and is as small as possible. This makes it possible to maintain the refrigerant in the branch flow path 33 in a liquid state while minimizing the power consumption of the compressor 11.

[0038] In view of the characteristics shown in Figures 3 and 4, data defining the correspondence between the battery temperature Tbat and the outside air temperature Tout and the minimum value of the compressor rotation speed Ncomp (hereinafter also referred to as the "target rotation speed Ntag") at which the refrigerant in the branch flow path 33 can be maintained in a liquid state is stored in the memory of the control circuit 100 as a map.

[0039] 5 is a diagram showing a map data diagrammatically illustrating the correspondence relationship between the target rotation speed Ntag and the battery temperature Tbat and the outside air temperature Tout. In this map data, the target rotation speed Ntag is preset using the battery temperature Tbat and the outside air temperature Tout as parameters, as shown in FIG.

[0040] In consideration of the characteristics shown in Fig. 3, the target rotation speed Ntag in this map data is defined to decrease as the outside air temperature Tout decreases. In consideration of the characteristics shown in Fig. 4, the target rotation speed Ntag in this map data is defined to decrease as the battery temperature Tbat increases.

[0041] The control circuit 100 refers to the map data shown in FIG. 5 to determine the target rotation speed Ntag corresponding to the detection results of the temperature sensors 50, 60 (outside air temperature Tout and battery temperature Tbat), and controls the rotation speed of the compressor 11 to the target rotation speed Ntag.

[0042] (flowchart) 6 is a flowchart showing an example of a processing procedure of the control circuit 100. This flowchart is repeatedly executed at a predetermined interval.

[0043] The control circuit 100 acquires the outside air temperature Tout and the battery temperature Tbat detected by the temperature sensors 50, 60 (step S10).

[0044] Next, the control circuit 100 refers to the map data shown in FIG. 5, which is stored in advance in the memory, and determines the target rotation speed Ntag corresponding to the outside air temperature Tout and the battery temperature Tbat acquired in step S10 (step S20).

[0045] Next, the control circuit 100 controls the compressor 11 so that the compressor rotation speed Ncomp becomes the target rotation speed Ntag determined in step S20 (step S30).

[0046] As described above, the control circuit 100 according to this embodiment stores in advance map data that defines the correspondence between the outside air temperature Tout and battery temperature Tbat and the target rotation speed Ntag of the compressor 11 that can maintain the refrigerant in a liquid state in the plurality of branch flow paths 33, and determines the target rotation speed Ntag that corresponds to the detection results (outside air temperature Tout and battery temperature Tbat) of the temperature sensors 50, 60 by referring to this map data, and controls the rotation speed of the compressor 11 to the target rotation speed Ntag. This makes it possible to maintain the refrigerant in the plurality of branch flow paths 33 in a liquid state, thereby making it possible to distribute the refrigerant in the plurality of branch flow paths 33 in equal amounts.

[0047] Furthermore, the target rotation speed Ntag in the map data is defined so that the rotation speed of the compressor 11 is reduced within a range that allows the refrigerant in the multiple branch flow paths 33 to be maintained in a liquid state. More specifically, the target rotation speed Ntag in the map data is defined so that it is reduced as the outside air temperature Tout is reduced. Furthermore, the target rotation speed Ntag in the map data is defined so that it is reduced as the battery temperature Tbat is increased. Therefore, it is possible to minimize the power consumption of the compressor 11 while maintaining the refrigerant in the multiple branch flow paths 33 in a liquid state.

[0048] [Variations] When a blower fan for increasing the heat exchange efficiency of the condenser 12 is provided near the condenser 12, the state of the refrigerant in the multiple branch flow paths 33 is affected not only by the outside air temperature Tout and the battery temperature Tbat, but also by the operating amount of the blower fan (the flow rate of the external fluid contacting the condenser 12).

[0049] Therefore, map data may be configured to prescribe the correspondence relationships among the outside air temperature Tout, battery temperature Tbat, the flow rate of the external fluid, and the target rotation speed Ntag. Then, the control circuit 100 may refer to the map data to determine the target rotation speed Ntag corresponding to the outside air temperature Tout, battery temperature Tbat, and the flow rate of the external fluid (for example, the operation amount of the blower fan), and control the rotation speed of the compressor 11 to the target rotation speed Ntag. This makes it possible to more appropriately maintain the refrigerant in the multiple branch flow paths 33 in a liquid state while minimizing the power consumption of the compressor 11. The flow rate of the external fluid can be derived by taking into account the vehicle speed and the opening state of the grille shutter in addition to the operation amount of the blower fan.

[0050] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0051] 1 Battery cooling system, 2 Battery module, 10 Refrigeration cycle, 11 Compressor, 12 Condenser, 14 Pressure reducing device, 15 Evaporator, 31, 32, 35 Flow path, 33, 34 Branch flow path, 33m Main pipe, 50, 60 Temperature sensor, 100 Control circuit, N1, N2 Connection point.

Claims

1. A battery cooling system for cooling a battery, a refrigeration cycle that forms a circuit through which a refrigerant circulates; a control circuit; The refrigeration cycle includes: A compressor; A condenser; a plurality of evaporators arranged corresponding to the plurality of batteries, respectively; a first flow path connected to a discharge port of the compressor and one end of the condenser; a second flow path connected to the other end of the condenser; a plurality of branch flow paths connecting the second flow path to one ends of the plurality of evaporators, respectively; a plurality of pressure reducing devices respectively disposed in the plurality of branch flow paths; a third flow path connecting the other ends of the plurality of evaporators and a suction port of the compressor; The condenser performs heat exchange between the refrigerant supplied from the compressor and a cooling fluid present around the condenser, a flow path from the compressor to each of the plurality of pressure reducing devices in the refrigeration cycle is a flow path in which no pressure reducing device is present, The battery cooling system includes: a first temperature detector for detecting a temperature of the cooling fluid; a second temperature detection unit that detects the temperature of the battery; The control circuit A battery cooling system that determines a target rotation speed of the compressor that can maintain the refrigerant in the multiple branch flow paths in a liquid state based on the temperature of the cooling fluid and the temperature of the battery, and controls the rotation speed of the compressor to the target rotation speed.

2. The control circuit storing in advance data defining a correspondence relationship between the temperature of the cooling fluid, the temperature of the battery, and a target rotation speed of the compressor that can maintain the refrigerant in the plurality of branch flow paths in a liquid state; The battery cooling system according to claim 1 , wherein the data is referenced to determine a target rotation speed corresponding to the detection results of the first and second temperature detection units, and the rotation speed of the compressor is controlled to the target rotation speed.

3. The battery cooling system of claim 2 , wherein the target rotation speed in the data is defined so as to reduce the power consumption of the compressor within a range that allows the refrigerant in the plurality of branch flow paths to be maintained in a liquid state.

4. The battery cooling system according to claim 3 , wherein the target rotation speed in the data is defined to be lower as the temperature of the cooling fluid is lower.

5. The battery cooling system according to claim 3 , wherein the target rotation speed in the data is defined to be lower as the temperature of the battery increases.

6. the data defines a correspondence relationship between the temperature of the cooling fluid, the temperature of the battery, the flow rate of the cooling fluid, and the target rotational speed; A battery cooling system as described in any one of claims 2 to 5, wherein the control circuit refers to the data to determine a target rotational speed corresponding to the detection results of the first and second temperature detection units and the flow rate of the cooling fluid, and controls the rotational speed of the compressor to the target rotational speed.

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