Battery pack

Abstract

The invention provides a battery pack which can reduce the temperature difference of each battery cell of a plurality of battery stacks accommodated in a shell and prolong the service life. The battery pack includes: a plurality of battery stacks each formed by stacking a plurality of battery cells in a first direction; a case in which the plurality of cell stacks are arranged and accommodated in a second direction orthogonal to the first direction; and a cooler which is attached to the bottom surfaces of the plurality of cell stacks across a case having a side wall portion facing the cell stacks disposed at the ends of the plurality of cell stacks across a predetermined gap in the second direction, and in which a refrigerant flows. The cooler has a plurality of first cooling portions and a second cooling portion formed extending in the first direction, the plurality of first cooling portions facing the respective bottom surfaces of the plurality of cell stacks, and the second cooling portion facing the gap.

Description

Technical Field

[0001] The present disclosure relates to a battery pack. Background Art

[0002] In a battery pack including a battery stack of a plurality of stacked battery cells, a cooler may be provided to cool or heat the battery stack. In order to extend the service life of the battery pack, the battery stack must be cooled or heated so that the temperature difference between the battery cells can be reduced by the flow of refrigerant inside the cooler.

[0003] Patent document 1 discloses a battery system for a vehicle, which includes a battery block in which a plurality of battery cells are arranged in a stacked state, a cooling plate arranged on each battery cell in a thermally coupled state, and a cooling mechanism for forcibly cooling the cooling plate. The battery system for a vehicle is provided with a first heat insulating layer between the battery cells and the cooling plate for limiting heat conduction from the battery cells to the cooling plate. In addition, the battery system for a vehicle makes the area of ​​the first heat insulating layer provided between each battery cell and the cooling plate different depending on the battery cells arranged in the stacking direction, and controls the heat energy conducted from the battery cells to the cooling plate by utilizing the difference in the area of ​​the first heat insulating layer, thereby reducing the temperature difference between each battery cell.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2010-277863.

[0005] The battery pack used as a power source for vehicles such as electric vehicles contains a battery stack containing multiple battery cells in parallel in a housing. This type of battery pack is large in size and heavy in weight, and is mostly mounted under the vehicle body. In the battery pack mounted under the vehicle body, a cooler (cooling plate) can be installed on the bottom surface of the multiple battery stacks through the housing.

[0006] However, in such a battery pack, not only the bottom surface of the plurality of battery stacks but also the side surface of the battery stacks facing the side wall of the housing are easily affected by the outside air. Therefore, the technology described in Patent Document 1 has the following problem: the temperature difference between the battery cells included in the battery stack facing the side wall of the housing and the battery cells included in the battery stack arranged inside the arrangement direction of the plurality of battery stacks becomes large, resulting in a shortened life of the battery pack. Summary of the invention

[0007] The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a battery pack capable of reducing the temperature difference among battery cells of a plurality of battery stacks arranged and accommodated in a casing, thereby extending the life of the battery pack.

[0008] In the present specification, a battery pack disclosed as a first embodiment comprises: a plurality of battery stacks, each formed by stacking a plurality of battery cells in a first direction; a shell, arranging and accommodating the plurality of battery stacks in a second direction perpendicular to the first direction; and a cooler, which is mounted on the bottom surfaces of the plurality of battery stacks via the shell and has a refrigerant flowing therein, the shell having a side wall portion opposite to the battery stacks arranged at the ends of the plurality of battery stacks via a predetermined gap in the second direction, and the cooler having a plurality of first cooling portions and a second cooling portion respectively extending in the first direction, the plurality of first cooling portions being opposite to the respective bottom surfaces of the plurality of battery stacks, and the second cooling portions being opposite to the gaps.

[0009] According to a second aspect, in the battery pack of the first aspect, the cooler includes a coolant introduction portion for introducing the coolant at an end portion on the opposite side to the second cooling portion side in the second direction.

[0010] According to the present disclosure, it is possible to provide a battery pack capable of reducing the temperature difference between the battery cells of a plurality of battery stacks arranged and accommodated in a casing, thereby extending the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is an exploded perspective view showing an example of a battery pack according to an embodiment.

[0012] Figure 2 It is a cross-sectional view showing a part of the battery pack according to the embodiment.

[0013] Figure 3 It is a cross-sectional view showing a part of a battery pack of a comparative example. DETAILED DESCRIPTION

[0014] The following describes the embodiments of the present disclosure with reference to the accompanying drawings. However, the present disclosure is not limited to the following embodiments. In addition, in order to make the description clear, the following description and drawings are appropriately simplified. What is shown in the figure is a part of the whole, and actually includes many other structures that are not shown. In addition, in the following description, the same symbols are given to the same or equivalent elements, and repeated descriptions are omitted.

[0015] Figure 1 1 is an exploded perspective view showing an example of a battery pack according to an embodiment. The battery pack 1 according to the embodiment is mounted in an electric vehicle such as a hybrid vehicle that can run using power from at least one of a motor and an engine, or an electric vehicle that runs using a driving force obtained from electric energy. The battery pack 1 is mounted, for example, below a floor panel of the vehicle.

[0016] like Figure 1 As shown, the battery pack 1 includes a plurality of battery stacks 10, namely, battery stacks 10a to 10d, a housing 20, a cooler 30, and Figure 1 The heat conducting member 40 is not shown in the figure.

[0017] The battery stacks 10a to 10d each have a plurality of battery cells 11 stacked in a first direction (DR1 direction) orthogonal to the up-down direction. When the battery pack 1 is mounted on a vehicle, the first direction is parallel to the width direction of the vehicle. The battery cell 11 is, for example, a secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The battery cell 11 has, for example, a square shape. The battery cell 11 may use a liquid electrolyte or a solid electrolyte. In addition, the battery cell 11 may also be a unit capacitor configured to store electricity.

[0018] Each of the battery stacks 10a to 10d may include end plates for sandwiching a stack of a plurality of battery cells 11 from both ends in the first direction, a fastening member for fastening the end plates together, and a partition provided on one side surface in the second direction.

[0019] The battery stacks 10a to 10d are arranged side by side in a second direction (DR2 direction) perpendicular to the up-down direction and the first direction. When the battery pack 1 is mounted on the vehicle, the second direction is parallel to the front-rear direction of the vehicle.

[0020] The housing 20 accommodates the battery stacks 10a to 10d. The housing 20 includes an upper housing 21 and a lower housing 22. The upper housing 21 has a generally box-shaped shape that is open downward. The upper housing 21 may be made of a metal material. In addition, in order to reduce weight, the upper housing 21 may also be made of a resin material. The lower housing 22 has a generally box-shaped shape that is open upward. The lower housing 22 is made of a metal material. The lower housing 22 preferably has good thermal conductivity.

[0021] The lower housing 22 has a bottom wall 22a and side walls 22b to 22e. The battery stacks 10a to 10d are placed on the bottom wall 22a. The side walls 22b to 22e are peripheral walls respectively erected in the up and down directions from the outer edge of the bottom wall 22a. The flange provided along the outer periphery of the lower housing 22 is fastened to the flange provided along the outer periphery of the upper housing 21 by a fastening mechanism such as bolts.

[0022] A heat-conducting layer 23 is arranged between the surface of the bottom wall 22a on the battery stack 10a to 10d side and the battery stack 10a to 10d. The heat-conducting layer 23 also functions as an adhesive layer to bond and fix the battery stack 10a to 10d to the bottom wall 22a. The battery stack 10a to 10d is in thermal contact with the surface of the bottom wall 22a on the battery stack 10a to 10d side through the heat-conducting layer 23. The heat-conducting layer 23 is, for example, an adhesive containing a silicone resin, an acrylic resin, a polyurethane resin, or an epoxy resin. The heat-conducting layer 23 is formed in two rows so that each battery stack 10a to 10d extends in the first direction.

[0023] The housing 20 houses the battery stacks 10a to 10d arranged in the second direction in a housing space surrounded by the side walls 22b to 22e. The side walls 22b and 22c face each other in the first direction with the battery stacks 10a to 10d interposed therebetween. The side walls 22d and 22e face each other in the second direction with the battery stacks 10a to 10d interposed therebetween.

[0024] Furthermore, the side wall portion 22d is separated from the side wall portion 22d by a predetermined gap S in the second direction (see Figure 2 ) is opposite to the battery stack 10a arranged at the end of one side of the battery stack 10a~10d. In addition, the side wall portion 22e is opposite to the battery stack 10d arranged at the end of the other side of the battery stack 10a~10d in the second direction. The gap S provided between the side wall portion 22d and the battery stack 10a is preferably as large as possible, because this can reduce the temperature drop of the battery stack 10a caused by the influence of the external air from the side of each battery unit 11 opposite to the side wall portion 22d.

[0025] The cooler 30 is arranged below the bottom wall portion 22a of the lower shell 22. The cooler 30 is a device for cooling or heating the battery stack 10a~10d. The cooler 30 is made of a metal material such as aluminum. A refrigerant flow path for refrigerant flow is provided inside the cooler 30. One end of the refrigerant flow path is connected to a refrigerant inlet portion 30a for introducing the refrigerant, and the other end is connected to a refrigerant discharge portion 30b for discharging the refrigerant. As the refrigerant, liquids such as water and long life coolant (Long Life Coolant, LLC) can be used. The cooler 30 is fixed to the lower shell 22 via a heat conductive component 40.

[0026] The heat-conductive member 40 is disposed between the bottom wall 22a and the cooler 30. The battery stacks 10a to 10d are cooled or heated by the cooler 30 via the heat-conductive member 40, the bottom wall 22a, and the heat-conductive layer 23. The heat-conductive member 40 also functions as an adhesive layer for bonding the bottom wall 22a to the cooler 30. As the heat-conductive member 40, an adhesive containing silicone resin, acrylic resin, polyurethane resin, epoxy resin, or the like can be used.

[0027] Furthermore, the battery pack 1 may include a common panel or the like that protects the cooler 30 and prevents the cooler 30 from coming into contact with water. Such a common panel is made of a metal material and is arranged so as to cover the cooler 30 from below.

[0028] Here, the details of the cooler 30 will be described. The cooler 30 includes a pair of holding parts 31, a plurality of cooling parts 32, and a front part 33. The above-mentioned refrigerant flow path is disposed inside the pair of holding parts 31, the plurality of cooling parts 32, and the front part 33.

[0029] The pair of holding parts 31 are formed in a manner extending along the second direction. The pair of holding parts 31 are arranged to be separated from each other in the first direction. The pair of holding parts 31 holds a plurality of cooling parts 32. The plurality of cooling parts 32 are respectively formed in a manner extending in the first direction. The plurality of cooling parts 32 are arranged at intervals in the second direction. The plurality of cooling parts 32 are respectively connected to the pair of holding parts 31.

[0030] The plurality of cooling units 32 include a plurality of first cooling units 32a and second cooling units 32b. The first cooling units 32a are provided in accordance with the number of battery stacks 10a to 10d so as to face the bottom surfaces of the battery stacks 10a to 10d. The second cooling units 32b are provided so as to face the gap S provided between the side wall 22d and the battery stack 10a.

[0031] The cooler 30 has a front portion 33 at the end portion opposite to the second cooling portion 32b in the second direction. The front portion 33 is provided to protrude from the end portions of the pair of retaining portions 31 to the other side in the second direction. The front portion 33 has a substantially C-shaped shape. The front portion 33 is provided with a refrigerant inlet portion 30a and a refrigerant discharge portion 30b.

[0032] Figure 1 The black arrows indicate the flow of the coolant. The coolant introduced into the coolant flow path from the coolant inlet 30a flows through the first cooling section 32a and the second cooling section 32b to cool or heat the battery stacks 10a to 10d and the air layer in the gap S, and then is discharged from the coolant discharge section 30b.

[0033] The battery system including the above-mentioned battery pack 1 has, for example, an ECU (Electronic Control Unit) that performs control related to the battery pack 1, a battery temperature sensor 50, etc. The ECU is composed of a CPU (Central Processing Unit), a memory such as RAM (Random Access Memory), a non-volatile auxiliary storage device such as ROM (Read Only Memory), and a computer including various input and output interfaces. The battery temperature sensor 50 is a battery temperature detection unit that detects the temperature of a plurality of battery cells 11. Each battery temperature sensor 50 inputs the detection result of the temperature of the installed battery cell 11 to the ECU. The ECU limits the current flowing through the battery cell 11 based on the input information input to the battery temperature sensor 50.

[0034] Here, Figure 3 : is a cross-sectional view showing a part of a battery pack of a comparative example. Figure 32 shows a partial cross-sectional view of one end side of the battery pack 1 in the second direction as viewed from the first direction side, wherein no predetermined gap S is provided between the side wall portion 22d and the battery stack 10a. Figure 3 Problems of the battery pack 100 of the comparative example will be described.

[0035] Figure 3 The battery pack 100 shown has a cooler 300 including a plurality of first cooling parts 32a but not a second cooling part 32b, wherein the plurality of first cooling parts 32a are respectively opposite to the bottom surfaces of the battery stacks 10a to 10d and extend in the first direction. The battery stacks 10a to 10d of the battery pack 100 are mounted in a vehicle traveling in a low-temperature environment with a low outside temperature, and the temperature is easily reduced due to the influence of the outside air from the bottom side thereof. Under low temperature conditions, the input and output characteristics of the battery cell 11 deteriorate. Therefore, when the vehicle is traveling in a low-temperature environment, it is preferred to increase the temperature of the battery cell 11 to ensure the input characteristics of the battery cell 11.

[0036] Therefore, by circulating heated coolant such as warm water in the first cooling unit 32 a , a drop in temperature of the battery stacks 10 a to 10 d due to the influence of outside air on the bottom surface side can be suppressed, and the temperature difference between the battery cells 11 can be reduced.

[0037] However, if Figure 3 As shown, when the battery stack 10a is arranged close to the side wall portion 22d, the temperature of the battery cells 11 included in the battery stack 10a is easily reduced by the influence of the external air from the side side of each battery cell 11 opposite to the side wall portion 22d. Therefore, the temperature difference between the battery cells 11 included in the battery stack 10a and the battery cells 11 included in the battery stacks 10b to 10d arranged on the inner side of the battery stack 10a in the second direction becomes larger.

[0038] In addition, among the plurality of first cooling units 32a provided in the cooler 300, the first cooling unit 32a opposite to the battery stack 10a is arranged at the most downstream of the refrigerant flow path. Therefore, in a low temperature environment, the refrigerant flowing inside the first cooling unit 32a opposite to the battery stack 10a is affected by the outside air and its temperature is easily reduced compared to the refrigerant flowing inside each first cooling unit 32a opposite to the battery stack 10b to 10d. Therefore, even if the refrigerant is circulated inside the first cooling unit 32a opposite to the battery stack 10a, the temperature reduction of the battery cells 11 included in the battery stack 10a cannot be fully suppressed, and the temperature difference between the battery cells 11 included in the battery stack 10a and the battery cells 11 included in the battery stacks 10b to 10d will increase.

[0039] If the temperature difference between the battery cells 11 occurs in this way, the current flowing through the battery cells 11 will be limited by the battery cell 11 with the lowest temperature, and the battery pack 100 will not be able to achieve the required output performance. In addition, the temperature difference between the battery cells 11 makes the electrical characteristics of the battery cells 11 unbalanced, making the remaining capacity uneven and shortening the life of a specific battery cell 11. Therefore, if the temperature difference between the battery cells 11 becomes large, the life of the entire battery pack 100 will be shortened.

[0040] In response to the above problem, the battery pack 1 involved in the present embodiment has a cooler 30, which includes a plurality of first cooling parts 32a and a second cooling part 32b extending along a first direction, and the plurality of first cooling parts 32a are respectively opposite to the bottom surfaces of the battery stacks 10a~10d, and the second cooling parts 32b are opposite to the gap S between the side wall part 22d and the battery stack 10a arranged at the end of the battery stack 10a~10d in the second direction.

[0041] Here, Figure 2 FIG. 1 is a cross-sectional view showing a portion of a battery pack according to an embodiment of the present invention. Figure 2 FIG. 2 shows a partial cross-sectional view of one end side of the battery pack 1 in the second direction as viewed from one side in the first direction, that is, Figure 3 The corresponding cross-sectional view.

[0042] like Figure 2 As shown, in the battery pack 1 involved in this embodiment, the second cooling unit 32b is arranged at the most downstream of the refrigerant flow path, and the plurality of first cooling units 32a of the cooler 30 are arranged on the upstream side of the refrigerant flow path than the second cooling unit 32b. In the battery pack 1, the temperature drop of the refrigerant flowing in the first cooling unit 32a can be suppressed compared with the case of the battery pack 100. This can effectively suppress the temperature drop of the battery stacks 10a to 10d caused by the influence of the outside air on the bottom side of the battery stacks 10a to 10d, and can reduce the temperature difference of each battery cell 11.

[0043] Furthermore, in the battery pack 1 according to the present embodiment, the refrigerant flowing in the second cooling portion 32b increases the temperature of the gap S provided between the side wall portion 22d and the battery stack 10a. This can effectively suppress the temperature drop of the battery stack 10a caused by the influence of the outside air on the side surface of each battery cell 11 opposite to the side wall portion 22d, and can reduce the temperature difference of each battery cell 11.

[0044] As described above, according to the present embodiment, it is possible to provide a battery pack 1 capable of reducing the temperature difference between the battery cells 11 of the plurality of battery stacks 10 arranged and accommodated in the case 20 and extending the battery life.

[0045] In addition, the present disclosure is not limited to the above-described embodiments, and appropriate changes can be made without departing from the scope of the present disclosure.

Claims

1. A battery pack, characterized in that: have: A plurality of battery stacks, each formed by stacking a plurality of battery cells in a first direction; a housing for arranging and accommodating the plurality of battery stacks in a second direction orthogonal to the first direction; and a cooler, which is installed on the bottom surface of the plurality of battery stacks via the housing and has a refrigerant flowing therein, The housing has a side wall portion that faces the battery stacks disposed at ends of the plurality of battery stacks with a predetermined gap therebetween in the second direction. The cooler includes a plurality of first cooling portions and a second cooling portion respectively extending in the first direction, the plurality of first cooling portions respectively facing the bottom surfaces of the plurality of battery stacks, and the second cooling portions facing the gap.

2. The battery pack according to claim 1, characterized in that: The cooler includes a refrigerant introduction portion for introducing the refrigerant at an end portion on the opposite side to the second cooling portion side in the second direction.

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