Battery pack

Abstract

The utility model provides a battery pack which can reduce the temperature difference of each battery unit of a plurality of battery stacks arranged and accommodated in a shell so as to 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

[0002] In a battery pack including a battery stack in which a plurality of battery cells are stacked, a cooler can 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 as to reduce the temperature difference between the battery cells by the flow of refrigerant inside the cooler.

[0003] Patent Literature 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 in a thermal coupling state with each battery cell, and a cooling mechanism that forcibly cools the cooling plate. The battery system for a vehicle sets a first thermal insulation layer that restricts heat conduction from the battery cell to the cooling plate between the battery cell and the cooling plate. Further, the battery system for a vehicle makes the area of the first thermal insulation layer provided between each battery cell and the cooling plate different depending on the battery cell arranged in the stacking direction, and controls the heat energy that is heat-conducted from the battery cell to the cooling plate by the difference in the area of the first thermal insulation layer, thereby reducing the temperature difference of each battery cell.

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

[0005] A battery pack used as a power source for a vehicle such as an electric vehicle houses battery stacks each including a plurality of battery cells in parallel in a case. Such a battery pack is large in size and heavy in weight, and is mounted under the vehicle body of the vehicle in many cases. In the battery pack mounted under the vehicle body of the vehicle, a cooler (cooling plate) can be installed on the bottom surface of the plurality of battery stacks through the case.

[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 stack opposite to the side wall portion of the case is easily affected by external air. Therefore, in the technology described in Patent Literature 1, the temperature difference between the battery cell included in the battery stack opposite to the side wall portion of the case and the battery cell included in the battery stack arranged on the inner side of the battery stack in the arrangement direction of the plurality of battery stacks becomes large, which leads to a reduction in the service life of the battery pack. SUMMARY

[0007] The present utility model is completed in order to solve the above-mentioned problems, and aims at providing a battery pack capable of reducing the temperature difference of each battery cell of a plurality of battery stacks arranged and housed in a case and extending the service life.

[0008] In the present specification, the battery pack disclosed as the first aspect has: a plurality of battery stacks each of which is formed by stacking a plurality of battery cells in a first direction; a case that houses the plurality of battery stacks in a second direction orthogonal to the first direction; and a cooler that is installed to a bottom surface of the plurality of battery stacks with the case interposed therebetween and has a refrigerant flowing inside thereof, the case has a side wall portion that opposes the battery stack arranged at an end portion of the plurality of battery stacks with a prescribed gap interposed therebetween in the second direction, and the cooler has a plurality of first cooling portions and a second cooling portion each of which is formed so as to extend in the first direction, the plurality of first cooling portions oppose the respective bottom surfaces of the plurality of battery stacks, and the second cooling portion opposes the gap.

[0009] The second aspect is that, in the battery pack of the above-described first aspect, the cooler has a refrigerant introduction portion that introduces the refrigerant to an end portion on an opposite side to the second cooling portion in the second direction.

[0010] According to the present disclosure, it is possible to provide a battery pack that can reduce a temperature difference of each battery cell of a plurality of battery stacks housed in a case in a row and extend a life. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

[0014] Embodiments of the present disclosure will be described below 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 drawings is a part of the whole, and actually includes many other structures that are not shown. In addition, in the following description, the same or equivalent elements are given the same reference signs, and repeated description is omitted.

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

[0016] As shown in Figure 1 , the battery pack 1 has a plurality of battery stacks 10, that is, battery stacks 10a to 10d, a case 20, a cooler 30, andFigure 1 A heat conducting member 40 not shown.

[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. In a mounted state in which 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-hydrogen battery or a lithium-ion battery. The battery cell 11 has, for example, a square shape. The battery cell 11 can use a liquid electrolyte or a solid electrolyte. In addition, the battery cell 11 can be a unit capacitor configured to be capable of electric power storage.

[0018] The battery stacks 10a to 10d each can include an end plate sandwiching a stack of the plurality of battery cells 11 from both ends in the first direction, a fastening member fastening between the respective end plates, and a partition plate provided to a side surface of one of the second directions.

[0019] The battery stacks 10a to 10d are arranged in a second direction (DR2 direction) orthogonal to the up-down direction and the first direction. In the mounted state in which 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 houses the battery stacks 10a to 10d. The housing 20 has an upper housing 21 and a lower housing 22. The upper housing 21 has a substantially box shape that is open toward the lower side. The upper housing 21 can be composed of a metal material. In addition, in order to reduce the weight, the upper housing 21 can be composed of a resin material. The lower housing 22 has a substantially box shape that is open toward the upper side. The lower housing 22 is composed of a metal material. The lower housing 22 preferably has good thermal conductivity.

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

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

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

[0024] Further, the side wall portion 22d opposes the battery stack 10a arranged at one end of the battery stacks 10a to 10d in the second direction with a prescribed gap S (see FIG. 2) interposed therebetween. In addition, the side wall portion 22e opposes the battery stack 10d arranged at the other end of the battery stacks 10a to 10d in the second direction. The gap S interposed between the side wall portion 22d and the battery stack 10a is preferably as large as possible, because this reduces the temperature drop of the battery stack 10a due to the influence of external air from the side surface of each battery cell 11 opposing the side wall portion 22d. Figure 2

[0025] The cooler 30 is arranged below the bottom wall portion 22a of the lower housing 22. The cooler 30 is a device for cooling or heating the battery stacks 10a to 10d. The cooler 30 is composed of a metal material such as aluminum. A refrigerant flow path through which a refrigerant flows is provided inside the cooler 30. One end of the refrigerant flow path is connected to a refrigerant introduction portion 30a that introduces the refrigerant, and the other end is connected to a refrigerant discharge portion 30b that discharges the refrigerant. As the refrigerant, a liquid such as water or long life coolant (LLC) can be used. The cooler 30 is fixed to the lower housing 22 via a heat transfer member 40.

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

[0027] Further, the battery pack 1 can have 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 composed of a metal material and is arranged so as to cover the cooler 30 from the lower side.

[0028] Here, the cooler 30 will be described in detail. The cooler 30 includes a pair of holding portions 31, a plurality of cooling portions 32, and a front portion 33. The refrigerant flow path described above is provided inside these pair of holding portions 31, the plurality of cooling portions 32, and the front portion 33.

[0029] ​A pair of holding portions 31 is formed so as to extend in the second direction. The pair of holding portions 31 is arranged so as to be separated from each other in the first direction. The pair of holding portions 31 holds a plurality of cooling portions 32. The plurality of cooling portions 32 is formed so as to extend in the first direction, respectively. The plurality of cooling portions 32 is arranged so as to be arranged at intervals in the second direction. The plurality of cooling portions 32 is connected to the pair of holding portions 31, respectively.

[0030] The plurality of cooling portions 32 includes a plurality of first cooling portions 32a and a second cooling portion 32b. The first cooling portions 32a are provided in accordance with the number of the battery stacks 10a to 10d in a manner opposed to the bottom surfaces of the battery stacks 10a to 10d, respectively. The second cooling portion 32b is provided so as to be opposed to the gap S provided between the side wall portion 22d and the battery stack 10a.

[0031] The cooler 30 has a front portion 33 at an end portion thereof on the side opposite to the second cooling portion 32b in the second direction. The front portion 33 is provided so as to protrude from the end portion of the pair of holding portions 31 to the other side in the second direction. The front portion 33 has a substantially C-shaped shape. A refrigerant introduction portion 30a and a refrigerant discharge portion 30b are provided on the front portion 33.

[0032] Figure 1 The black arrows shown indicate the flow of the refrigerant. The refrigerant introduced from the refrigerant introduction portion 30a into the refrigerant flow path is cooled or heated by flowing through the first cooling portions 32a and the second cooling portion 32b to cool or heat the air layers of the battery stacks 10a to 10d and the gap S, and is discharged from the refrigerant discharge portion 30b.

[0033] A battery system including the above-described battery pack 1 has, for example, an ECU (Electronic Control Unit) that performs control relating to the battery pack 1, a battery temperature sensor 50, and the like. The ECU is constituted by a CPU (Central Processing Unit), a memory such as a RAM (Random Access Memory), a nonvolatile auxiliary storage device such as a ROM (Read Only Memory), and a computer including an interface for various input and output, and the like. The battery temperature sensor 50 is a battery temperature detection portion that detects the temperature of the plurality of battery cells 11. Each battery temperature sensor 50 inputs a detection result of the temperature of the mounted battery cell 11 to the ECU. The ECU limits the current flowing through the battery cell 11 on the basis of the input information input to the battery temperature sensor 50.

[0034] Here, Figure 3 A cross-sectional view of a portion of a battery pack of a comparative example is shown. In Figure 3The diagram shows a partial cross-sectional view of one end of the battery pack 1 in the second direction, viewed from one side in the first direction, wherein the sidewall portion 22d is not provided with the prescribed gap S between it and the battery stack 10a. (Refer to...) Figure 3 Explain the problems with the comparative example battery pack 100.

[0035] Figure 3 The battery pack 100 shown has a cooler 300 including a plurality of first cooling sections 32a but not including second cooling sections 32b. The plurality of first cooling sections 32a are respectively opposite to the bottom surfaces of the battery stacks 10a-10d and extend in a first direction. The battery stacks 10a-10d of the battery pack 100 are mounted in vehicles operating in low-temperature environments with low external temperatures. Due to the influence of external air from their bottom surfaces, their temperature can easily drop. Under low-temperature conditions, the input / output characteristics of the battery cells 11 deteriorate. Therefore, when the vehicle is operating in a low-temperature environment, it is preferable to raise the temperature of the battery cells 11 to ensure the input characteristics of the battery cells 11.

[0036] Therefore, by circulating a refrigerant heated such as warm water in the first cooling section 32a, the temperature drop of the battery stacks 10a to 10d caused by the influence of external air on the bottom side can be suppressed, and the temperature difference between each battery cell 11 can be reduced.

[0037] However, as Figure 3 As shown, when the battery stack 10a is positioned close to the side wall portion 22d, the temperature of the battery cells 11 contained in the battery stack 10a is easily lowered due to the influence of external air from the side of each battery cell 11 opposite to the side wall portion 22d. Therefore, the temperature difference between the battery cells 11 contained in the battery stack 10a and the battery cells 11 contained in the battery stacks 10b to 10d, which are positioned inside the battery stack 10a in the second direction, will increase.

[0038] Furthermore, among the multiple first cooling sections 32a provided in the cooler 300, the first cooling section 32a opposite to the battery stack 10a is located at the downstream end of the refrigerant flow path. Therefore, in a low-temperature environment, compared to the refrigerant flowing inside each of the first cooling sections 32a opposite to the battery stacks 10b to 10d, the refrigerant flowing inside the first cooling section 32a opposite to the battery stack 10a is more susceptible to temperature drop due to the influence of external air. Therefore, even if the refrigerant flows inside the first cooling section 32a opposite to the battery stack 10a, it is not sufficient to suppress the temperature drop of the battery cells 11 included in the battery stack 10a, 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 is limited by the battery cell 11 of the lowest temperature, and the battery pack 100 cannot achieve the required output performance. In addition, the temperature difference between the battery cells 11 causes the electrical characteristics of the battery cells 11 to be unbalanced, the remaining capacity to be uneven, and the life of a particular battery cell 11 to be shortened. Therefore, if the temperature difference between the battery cells 11 becomes large, the life of the entire battery pack 100 is shortened.

[0040] To address the above problem, the battery pack 1 according to the present embodiment has a cooler 30 including a plurality of first cooling portions 32a each opposing a bottom surface of the battery stack 10a to 10d in a first direction and a second cooling portion 32b opposing a gap S between the side wall portion 22d and the battery stack 10a disposed at an end portion of the battery stacks 10a to 10d in a second direction.

[0041] Here, Figure 2 is a cross-sectional view showing a part of the battery pack 1 according to the present embodiment. In Figure 2 is shown a partial cross-sectional view of the battery pack 1 as viewed from the first direction side toward the second direction end side, that is, a cross-sectional view corresponding to Figure 3 .

[0042] As shown in Figure 2 , in the battery pack 1 according to the present embodiment, the second cooling portion 32b is disposed at the most downstream side of the refrigerant flow path, and the plurality of first cooling portions 32a of the cooler 30 are disposed at the upstream side of the refrigerant flow path than the second cooling portion 32b. In the battery pack 1, as compared with the case of the battery pack 100, the temperature reduction of the refrigerant flowing in the first cooling portion 32a can be suppressed. This makes it possible to effectively suppress the temperature reduction of the battery stacks 10a to 10d due to the influence of the external air on the bottom surface side of the battery stacks 10a to 10d, and to reduce the temperature difference between the battery cells 11.

[0043] Further, in the battery pack 1 according to the present embodiment, the refrigerant flowing in the second cooling portion 32b causes the temperature of the gap S provided between the side wall portion 22d and the battery stack 10a to rise. This makes it possible to effectively suppress the temperature reduction of the battery stack 10a due to the influence of the external air on the side surface side of each battery cell 11 opposing the side wall portion 22d, and to reduce the temperature difference between the battery cells 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 a plurality of battery stacks 10 housed in a case 20 and extending the life.

[0045] In addition, the present disclosure is not limited to the above-described embodiments, and appropriate changes can be made within the scope of the gist.

Claims

1. A battery pack characterized by comprising: Having: a plurality of cell stacks each of which is stacked in a first direction by a plurality of cell units; a housing which houses the plurality of cell stacks in a second direction orthogonal to the first direction; and a cooler which is installed to a bottom surface of the plurality of cell stacks through the housing and in which a refrigerant flows, the housing has a side wall portion which opposes the cell stack arranged at an end portion of the plurality of cell stacks through a prescribed gap in the second direction, the cooler has a plurality of first cooling portions and a second cooling portion each of which extends in the first direction, the plurality of first cooling portions each opposing a respective bottom surface of the plurality of cell stacks, and the second cooling portion opposing the gap. the cooler has a refrigerant introduction portion which introduces the refrigerant at an end portion opposite the second cooling portion side in the second direction.

2. The battery pack of claim 1, wherein, ​

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