Battery pack

Abstract

To provide a battery pack capable of extending the life by reducing the temperature difference among battery cells of a plurality of battery stacks that are accommodated to be arranged side by side in a case.SOLUTION: A battery pack includes a battery stack in which a plurality of battery cells are stacked in a first direction, a case in which the plurality of battery stacks are accommodated to be arranged side by side in a second direction perpendicular to the first direction, and coolers that are attached to the bottom surfaces of the plurality of battery stacks through the case and through which a refrigerant flows. The case has a side wall portion that faces the battery stacks arranged at the ends of the plurality of battery stacks in the second direction with a predetermined gap therebetween. The coolers are each formed to extend in the first direction and include a first cooling section that faces the bottom surface of each of the plurality of battery stacks and a second cooling section that faces the gap.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] In a battery pack including a battery stack in which a plurality of battery cells are stacked, a cooler may be provided to cool or heat the battery stack. In order to extend the life of the battery pack, it is required to cool or heat the battery stack by flowing a refrigerant inside the cooler so that the temperature difference between each battery cell is reduced.

[0003] Patent Document 1 discloses a vehicle battery system including a battery block in which a plurality of battery cells are arranged in a stacked state, a cooling plate arranged in a thermally coupled state with each battery cell, and a cooling mechanism for forcibly cooling the cooling plate. This vehicle battery system is provided with a first heat insulating layer that restricts heat conduction from the battery cell to the cooling plate between the battery cell and the cooling plate. Further, the vehicle battery system 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 cell to the cooling plate by the difference in the area of the first heat insulating layer to reduce the temperature difference between each battery cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A battery pack used as a power source for a vehicle such as an electric vehicle accommodates battery stacks each including a large number of battery cells side by side in a case. Such a large-sized and heavy battery pack is mainly mounted under the vehicle body. In a battery pack mounted under the vehicle body, a cooler (cooling plate) may be attached to the bottom surfaces of a plurality of battery stacks with the case interposed therebetween.

[0006] However, in such a battery pack, not only the bottom surfaces of the plurality of battery stacks but also the side surfaces of the battery stacks facing the side wall portions of the case are easily affected by the outside air. Therefore, in the technique described in Patent Document 1, there is a problem that the temperature difference between the battery cells included in the battery stack facing the side wall portion of the case and the battery cells included in the battery stack disposed inside the plurality of battery stacks in the arrangement direction of the plurality of battery stacks becomes large, and the life of the battery pack is shortened.

[0007] The present disclosure has been made to solve such problems, and an object thereof is to provide a battery pack capable of reducing the temperature difference between the respective battery cells of a plurality of battery stacks accommodated side by side in a case and extending the life.

Means for Solving the Problems

[0008] A battery pack according to an embodiment includes a battery stack in which a plurality of battery cells are stacked in a first direction, a case that accommodates a plurality of battery stacks side by side in a second direction orthogonal to the first direction, and a cooler that is attached to the bottom surfaces of the plurality of battery stacks with the case interposed therebetween and through which a refrigerant flows inside. The case has side wall portions facing a battery stack disposed at an end of the plurality of battery stacks in the second direction with a predetermined gap therebetween. The cooler is formed to extend in the first direction and includes a first cooling portion facing the bottom surface of each of the plurality of battery stacks and a second cooling portion facing the gap.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a battery pack that can reduce the temperature difference between each battery cell of a plurality of battery stacks housed side by side in a case and can extend the life.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] Embodiment 1 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are appropriately simplified. What is shown in the drawings is a part of the whole, and many other configurations not shown are actually included. In the following description, the same or equivalent elements are denoted by the same reference numerals, and overlapping descriptions are omitted.

[0012] FIG. 1 is an exploded perspective view showing an example of the battery pack according to Embodiment 1. The battery pack 1 according to the present embodiment is mounted on, for example, a hybrid vehicle capable of traveling using the power of at least one of a motor and an engine, or an electric vehicle such as an electric automobile that travels with a driving force obtained from electric energy. The battery pack 1 is mounted, for example, below the floor panel of the vehicle.

[0013] As shown in FIG. 1, the battery pack 1 includes battery stacks 10a to 10d which are a plurality of battery stacks 10, a case 20, a cooler 30, and a heat conduction member 40 (not shown in FIG. 1).

[0014] Each of the battery stacks 10a to 10d has a plurality of battery cells 11 stacked in a first direction (DR1 direction) orthogonal to the vertical direction. The first direction is parallel to the width direction of the vehicle in the mounted state where the battery pack 1 is mounted on 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 rectangular shape. The battery cell 11 may use a liquid electrolyte or a solid electrolyte. Further, the battery cell 11 may be a unit capacitor configured to be capable of storing electricity.

[0015] Each of the battery stacks 10a to 10d may include end plates that sandwich the stacked body of the plurality of battery cells 11 from both ends in the first direction, fastening members that fasten between the respective end plates, and a partition plate provided on one side surface in the second direction.

[0016] The battery stacks 10a to 10d are arranged side by side in the vertical direction and a second direction (DR2 direction) orthogonal to the first direction. The second direction is parallel to the front-rear direction of the vehicle in the mounted state where the battery pack 1 is mounted on the vehicle.

[0017] The case 20 houses the battery stacks 10a to 10d. The case 20 has an upper case 21 and a lower case 22. The upper case 21 has a substantially box-shaped shape that is open downward. The upper case 21 may be made of a metal material. Further, for weight reduction, the upper case 21 may be made of a resin material. The lower case 22 has a substantially box-shaped shape that is open upward. The lower case 22 is made of a metal material. The lower case 22 preferably has good thermal conductivity.

[0018] The lower case 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 erected vertically in the vertical direction from the outer edge of the bottom wall portion 22a. The flange portion provided along the outer periphery of the lower case 22 is fastened to the flange portion provided along the outer periphery of the upper case 21 by fastening means such as bolts.

[0019] A heat conduction layer 23 is disposed 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 conduction layer 23 also functions as an adhesive layer, and adhesively fixes 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 by the heat conduction layer 23. The heat conduction layer 23 is, for example, an adhesive containing a silicone-based resin, an acrylic-based resin, a urethane resin, or an epoxy resin. The heat conduction layer 23 is formed in two rows so as to extend in the first direction for each of the battery stacks 10a to 10d.

[0020] The case 20 houses the battery stacks 10a to 10d arranged side by side in the second direction in the accommodation space surrounded by the side wall portions 22b to 22e. The side wall portions 22b and 22c face each other in the first direction with the battery stacks 10a to 10d interposed therebetween. The side wall portions 22d and 22e face each other in the second direction with the battery stacks 10a to 10d interposed therebetween.

[0021] And the side wall portion 22d faces the battery stack 10a disposed at one end of the battery stacks 10a to 10d in the second direction with a predetermined gap S (see FIG. 2) therebetween. Also, the side wall portion 22e faces the battery stack 10d disposed at the other end of the battery stacks 10a to 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 from the viewpoint of suppressing a temperature drop of the battery stack 10a due to the influence of outside air received from the side surface side of each battery cell 11 facing the side wall portion 22d.

[0022] The cooler 30 is disposed below the bottom wall portion 22a of the lower case 22. The cooler 30 is a device for cooling or heating the battery stacks 10a to 10d. The cooler 30 is made of a metal material such as aluminum. Inside the cooler 30, a refrigerant flow path through which a refrigerant flows is provided. One end of the refrigerant flow path is connected to a refrigerant introduction 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, for example, a liquid such as water or LLC (Long Life Coolant) can be employed. The cooler 30 is fixed to the lower case 22 via a heat conductive member 40.

[0023] The heat conductive member 40 is disposed 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 conductive member 40, the bottom wall portion 22a, and the heat conductive layer 23. The heat conductive member 40 also functions as an adhesive layer for bonding the bottom wall portion 22a and the cooler 30. As the heat conductive member 40, for example, an adhesive containing a silicone-based resin, an acrylic-based resin, a urethane resin, or an epoxy resin can be employed.

[0024] Furthermore, the battery pack 1 may have a shared panel or the like that protects the cooler 30 and suppresses water ingress into the cooler 30. Such a shared panel is made of a metal material and is disposed so as to cover the cooler 30 from the lower side.

[0025] Here, details of the cooler 30 will be described. The cooler 30 includes a pair of holding portions 31, a plurality of cooling portions 32, and a front portion 33. Inside these, the pair of holding portions 31, the plurality of cooling portions 32, and the front portion 33, the above-described refrigerant flow path is routed.

[0026] The pair of holding parts 31 are formed to extend 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 hold a plurality of cooling parts 32. The plurality of cooling parts 32 are each formed to extend in the first direction. The plurality of cooling parts 32 are arranged side by side at intervals in the second direction. The plurality of cooling parts 32 each connect the pair of holding parts 31.

[0027] The plurality of cooling parts 32 include a plurality of first cooling parts 32a and second cooling parts 32b. The first cooling parts 32a are provided according to the number of the battery stacks 10a to 10d so as to face the bottom surfaces of the battery stacks 10a to 10d respectively. The second cooling parts 32b are provided so as to face the gap S provided between the side wall part 22d and the battery stack 10a.

[0028] The cooler 30 has a front part 33 at an end on the side opposite to the second cooling part 32b side in the second direction. The front part 33 is provided to protrude from the ends of the pair of holding parts 31 to the other side in the second direction. The front part 33 has a substantially C-shaped configuration. The refrigerant introduction part 30a and the refrigerant discharge part 30b are provided on the front part 33.

[0029] The black arrows shown in FIG. 1 indicate the flow of the refrigerant. The refrigerant introduced into the refrigerant flow path from the refrigerant introduction part 30a flows through the first cooling parts 32a and the second cooling parts 32b to cool or heat the air layers of the battery stacks 10a to 10d and the gap S, and then is discharged from the refrigerant discharge part 30b.

[0030] A battery system including such a battery pack 1 has, for example, an ECU that controls the battery pack 1, a battery temperature sensor 50, etc. The ECU is composed of a computer including a CPU (Central Processing Unit), a memory such as a RAM (Random Access Memory), a non-volatile auxiliary storage device such as a ROM (Read Only Memory), and various input / output interfaces, etc. The battery temperature sensor 50 is a battery temperature detection unit that detects the temperatures of a plurality of battery cells 11. Each battery temperature sensor 50 inputs the detection result of the temperature of the attached battery cell 11 to the ECU. The ECU restricts the current flowing through the battery cell 11 based on the input information input to the battery temperature sensor 50.

[0031] Here, FIG. 3 is a cross-sectional view showing a part of a battery pack of a comparative example. FIG. 3 shows a partial cross-sectional view of one end side in the second direction of a battery pack 100 in which a predetermined gap S is not provided between a side wall portion 22d and a battery stack 10a, as viewed from one side in the first direction. Referring to FIG. 3, the problems of the battery pack 100 of the comparative example will be described.

[0032] The battery pack 100 shown in FIG. 3 includes a plurality of first cooling portions 32a that extend in the first direction while facing the bottom surfaces of the battery stacks 10a to 10d, but has a cooler 300 that does not include a second cooling portion 32b. The battery stacks 10a to 10d of the battery pack 100 mounted on a vehicle traveling in a low-temperature environment where the outside air temperature is low are likely to have their temperatures reduced due to the influence of the outside air from the bottom surface side. When the battery cell 11 becomes low in temperature, its input / output characteristics deteriorate. Therefore, when the vehicle travels in a low-temperature environment, it is preferable to raise the temperature of the battery cell 11 in order to ensure the input characteristics of the battery cell 11.

[0033] Therefore, by flowing a heated refrigerant such as warm water through the first cooling portion 32a, it is intended to suppress the temperature drop of the battery stacks 10a to 10d due to the influence of the outside air received from the bottom surface side and reduce the temperature difference between the battery cells 11.

[0034] However, as shown in FIG. 3, when the battery stack 10a is disposed close to the side wall portion 22d, the temperature of the battery cells 11 included in the battery stack 10a is likely to decrease due to the influence of the outside air from the side surface side of each battery cell 11 facing 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 disposed inward in the second direction from the battery stack 10a becomes large.

[0035] Furthermore, among the plurality of first cooling portions 32a provided in the cooler 300, the first cooling portion 32a facing the battery stack 10a is disposed at the most downstream of the refrigerant flow path. Therefore, in a low temperature environment, the refrigerant flowing inside the first cooling portion 32a facing the battery stack 10a is more likely to be affected by the outside air and its temperature is likely to decrease compared to the refrigerant flowing inside each of the first cooling portions 32a facing the battery stacks 10b to 10d. Therefore, even if the refrigerant is circulated inside the first cooling portion 32a facing the battery stack 10a, the temperature drop of the battery cells 11 included in the battery stack 10a cannot be sufficiently 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 becomes large.

[0036] When such a temperature difference occurs in each battery cell 11, the current that can flow through the battery cell 11 is limited by the coldest battery cell 11, so there is a problem that the battery pack 100 cannot exhibit the expected output performance. In addition, the temperature difference between the battery cells 11 leaves the electrical characteristics of the battery cells 11 unbalanced and the remaining capacity uneven, shortening the life of a specific battery cell 11. Therefore, when the temperature difference between the battery cells 11 becomes large, there is a problem that the life of the entire battery pack 100 decreases.

[0037] In response to such problems, the battery pack 1 according to this embodiment is formed to extend in the first direction, and includes a first cooling portion 32a facing the bottom surface of each of the battery stacks 10a to 10d, and a second cooling portion 32b facing a gap S provided between the side wall portion 22d and the battery stack 10a disposed at the end of the battery stacks 10a to 10d in the second direction. The battery pack 1 has a cooler 30.

[0038] Here, FIG. 2 is a cross-sectional view showing a part of the battery pack according to Embodiment 1. FIG. 2 is 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, and shows a cross-sectional view corresponding to FIG. 3.

[0039] As shown in FIG. 2, in the battery pack 1 according to this embodiment, a plurality of first cooling portions 32a provided in the cooler 30 are disposed upstream of the second cooling portion 32b disposed at the most downstream of the refrigerant flow path. In the battery pack 1, compared with the case of the battery pack 100, a decrease in the temperature of the refrigerant flowing through the first cooling portion 32a is suppressed. Thereby, a decrease in the temperature of the battery stacks 10a to 10d due to the influence of outside air received from the bottom surface side of the battery stacks 10a to 10d can be effectively suppressed, and the temperature difference between the respective battery cells 11 can be reduced.

[0040] Furthermore, in the battery pack 1 according to this embodiment, the refrigerant flowing through the second cooling portion 32b raises the temperature of the gap S provided between the side wall portion 22d and the battery stack 10a. Thereby, a decrease in the temperature of the battery stack 10a due to the influence of outside air received from the side surface side of each battery cell 11 facing the side wall portion 22d can be effectively suppressed, and the temperature difference between the respective battery cells 11 can be reduced.

[0041] As described above, according to this embodiment, it is possible to provide a battery pack 1 that can reduce the temperature difference between the respective battery cells 11 of the plurality of battery stacks 10 arranged and housed in the case 20 and can extend the life.

[0042] Note that the present disclosure is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist.

Description of Symbols

[0043] 1, 100 Battery Pack 10, 10a - 10d Battery Stack 11 Battery Cell 20 Case 21 Upper Case 22 Lower Case 22a Bottom Wall Portion 22b - 22e Side Wall Portions 23 Heat Conductive Layer 30, 300 Cooler 30a Refrigerant Introduction Port 30b Refrigerant Discharge Port 31 Holding Portion 32 Cooling Portion 32a First Cooling Portion 32b Second Cooling Portion 33 Front Portion 40 Heat Conductive Member 50 Battery Temperature Sensor S Gap

Claims

1. A battery stack in which a plurality of battery cells are stacked in a first direction, A case that houses a plurality of the battery stacks arranged side by side in a second direction orthogonal to the first direction, A cooler that is attached to the bottom surface of the plurality of battery stacks with the case interposed therebetween and through which a refrigerant flows inside, The case has, Side wall portions that face the battery stacks arranged at the ends of the plurality of battery stacks in the second direction with a predetermined gap therebetween, The cooler has, Each is formed to extend in the first direction, A first cooling portion that faces the bottom surface of each of the plurality of battery stacks, A second cooling portion that faces the gap, A battery pack including the above.

2. The cooler has, A refrigerant introduction portion for introducing the refrigerant at an end portion on the side opposite to the second cooling portion side in the second direction. The battery pack according to claim 1.

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