Battery pack

Abstract

This suppresses the formation of weld marks at the corners between multiple beams that make up the frame that at least partially surrounds the battery cell. [Solution] The battery pack 1 comprises a battery cell 11 and a housing 20 that houses the battery cell 11. The housing 20 has a support frame 222 that at least partially surrounds the battery cell 11. The support frame 222 includes a center beam 222a and a light beam 222b that extend in different directions and are welded to each other. The light beam 222b defines a recess 223a into which at least partially a first weld mark 241 formed at the corner between the center beam 222a and the light beam 222b is inserted.

Description

Technical Field

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

Background Art

[0002] In recent years, various battery packs have been developed. A battery pack includes a battery cell and a housing that accommodates the battery cell.

[0003] Patent Document 1 describes welding of a base plate and a gusset plate. A notch is formed at a corner of the gusset plate on the base plate side. The base plate and the gusset plate are welded to each other in a state where a surface of the base plate and an end surface of the gusset plate having the notch face each other.

[0004] Patent Document 2 describes welding of a steel column and an H-shaped steel. A groove having a slope and a joining piece is formed at a tip end of a flange of the H-shaped steel. The groove at the tip end of the flange is filled with weld metal.

[0005] Patent Document 3 describes electroslag welding of a skin plate and a diaphragm. The diaphragm is sandwiched between a pair of backing strips. The pair of backing strips have notches facing each other.

Prior Art Literature

Patent Literature

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problem to be Solved by the Invention

[0007] The housing for the battery cells may have a frame that at least partially encloses the battery cells. The frame may include multiple beams that extend in different directions and are welded to one another. When multiple beams are welded to one another, weld marks are formed at the corners between the beams. However, if the weld marks are large and protruding, it may become difficult to secure space for housing the battery cells within the area enclosed by the frame.

[0008] One example of the object of the present invention is to suppress the bulging of weld marks that form at the corners between multiple beams constituting a frame that at least partially surrounds a battery cell. Other objects of the present invention will become apparent from the description herein. [Means for solving the problem]

[0009] One aspect of the present invention is as follows: 1. Battery cell and, A housing for the aforementioned battery cell, Equipped with, The housing has a frame that at least partially surrounds the battery cell, The frame includes a plurality of beams extending in different directions and welded to one another. A battery pack in which at least one beam defines a recess into which a weld mark formed at the corner between the plurality of beams is at least partially embedded. 2. The battery pack according to 1, wherein other weld marks are formed at boundaries different from the corners of the plurality of beams. 3. The battery pack according to 2., wherein the weld marks and the other weld marks are at least partially discontinuous between the weld marks and the other weld marks. 4. A battery pack according to any one of 1 to 3, wherein the ratio of the throat thickness of the weld to the width of the weld is 0.16 or more. 5. A battery pack according to any one of 1. to 4., wherein the throat thickness of the welded mark is 1.4 mm or more. 6. A battery pack according to any one of 1. to 5., wherein the width of the weld mark is 8.5 mm or less. [Effects of the Invention]

[0010] According to the above embodiment of the present invention, it is possible to suppress the protrusion of welding marks formed at the corners between a plurality of beams constituting a frame that at least partially surrounds a battery cell. [Brief explanation of the drawing]

[0011] [Figure 1] This is a top view of the battery pack according to the embodiment. [Figure 2] This is a top view of the battery pack according to an embodiment in which the upper case has been removed. [Figure 3] This is a perspective view of region α shown in Figure 2, with multiple battery modules removed. [Figure 4] This is a cross-sectional view along the virtual plane S in Figure 3. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. In all drawings, similar components are denoted by the same reference numerals, and their descriptions are omitted where appropriate.

[0013] Figure 1 is a top view of the battery pack 1 according to the embodiment. Figure 2 is a top view of the battery pack 1 according to the embodiment with the upper case 23 removed.

[0014] In this embodiment, the battery pack 1 is mounted in an automobile. Specifically, the battery pack 1 is mounted between the front and rear wheels of the automobile. Hereafter, unless otherwise specified, the battery pack 1 will be described as being mounted in an automobile. However, the battery pack 1 can also be applied to applications other than automobiles.

[0015] In FIGS. 1 and 2, for description purposes, X-axis, Y-axis and Z-axis indicating X direction, Y direction and Z direction respectively are shown. In FIGS. 1 and 2, a white circle with a black dot indicating the Z-axis indicates that the arrow of the Z-axis is directed toward the front of the drawing sheet. The X direction indicates the front-rear direction of the battery pack 1. The Y direction is one of the directions perpendicular to the X direction. The Y direction indicates the left-right direction of the battery pack 1. The Z direction is a direction perpendicular to both the X direction and the Y direction. The Z direction indicates the up-down direction of the battery pack 1. The direction indicated by the tip of the X-axis arrow, the direction indicated by the tip of the Y-axis arrow, and the direction indicated by the tip of the Z-axis arrow respectively indicate the rear direction, right direction, and upper direction of the battery pack 1. The relationship between the X direction, Y direction, and Z direction and the front-rear direction, left-right direction, and up-down direction of the battery pack 1 is not limited to this example.

[0016] In the embodiment, the front-rear direction, left-right direction, and up-down direction of the battery pack 1 are determined by the vehicle on which the battery pack 1 is mounted. The X direction, Y direction, and Z direction respectively indicate the front-rear direction, left-right direction, and up-down direction of the vehicle. The direction indicated by the tip of the X-axis arrow, the direction indicated by the tip of the Y-axis arrow, and the direction indicated by the tip of the Z-axis arrow respectively indicate the rear direction, right direction, and upper direction of the vehicle. However, the relationship between the front-rear direction, left-right direction, and up-down direction of the battery pack 1 and the front-rear direction, left-right direction, and up-down direction of the vehicle is not limited to this example.

[0017] Hereinafter, unless otherwise specified, the +X side or +X refers to the side indicated by the tip of the X-axis arrow, and the -X side or -X refers to the side opposite to the side indicated by the tip of the X-axis arrow. Hereinafter, unless otherwise specified, the +Y side or +Y refers to the side indicated by the tip of the Y-axis arrow, and the -Y side or -Y refers to the side opposite to the side indicated by the tip of the Y-axis arrow. Hereinafter, unless otherwise specified, the +Z side or +Z refers to the side indicated by the tip of the Z-axis arrow, and the -Z side or -Z refers to the side opposite to the side indicated by the tip of the Z-axis arrow.

[0018] As shown in Figures 1 and 2, the battery pack 1 according to this embodiment comprises a plurality of battery modules 10 and a housing 20.

[0019] In the example shown in Figure 2, the battery pack 1 comprises four battery modules 10 arranged in two rows and two columns in the X and Y directions, respectively, and one battery module 10 positioned on the +X side relative to the four battery modules 10. The number and arrangement of the battery modules 10 are not limited to the example shown in Figure 2. In the example shown in Figure 2, each of the four battery modules 10 has a plurality of battery cells 11 stacked in the Y direction. In the example shown in Figure 2, each of the battery cells 11 in the four battery modules 10 has a longitudinal direction in the X direction, a short direction in the Z direction, and a thickness direction in the Y direction. In the example shown in Figure 2, the single battery module 10 has a plurality of battery cells 11 stacked in the X direction. In the example shown in Figure 2, the battery cells 11 in the single battery module 10 have a longitudinal direction in the Y direction, a short direction in the Z direction, and a thickness direction in the X direction. In each battery module 10, the plurality of battery cells 11 are electrically connected in series, parallel, or a combination of series and parallel. The number and arrangement of the multiple battery cells 11 in each battery module 10 are not limited to the example shown in Figure 2.

[0020] Each battery module 10 may have a separate housing for housing multiple battery cells 11, in addition to the housing 20. Specifically, each battery module 10 may be housed in the housing 20 with the multiple battery cells 11 of each battery module 10 housed in a different housing from the housing 20. Alternatively, each battery module 10 may not have a separate housing for housing multiple battery cells 11. Specifically, the multiple battery cells 11 of each battery module 10 may be directly housed in the housing 20.

[0021] The housing 20 houses multiple battery modules 10. As shown in Figures 1 and 2, the housing 20 has a lower plate 21, a frame 22, and an upper case 23. The frame 22 includes a side frame 221 and a support frame 222.

[0022] As shown in Figure 2, the lower plate 21 is positioned substantially perpendicular to the Z direction. The multiple battery modules 10 are located on the +Z side of the lower plate 21. Therefore, the multiple battery modules 10 and the lower plate 21 overlap each other at least partially in the Z direction. In the example shown in Figure 2, viewed from the +Z side, the lower plate 21 has a substantially rectangular shape with a pair of long sides substantially parallel to the X direction and a pair of short sides substantially parallel to the Y direction, with its four corners cut off. In other words, viewed from the +Z side, the lower plate 21 has a substantially octagonal shape. The shape of the lower plate 21 is not limited to the example shown in Figure 2. A flow channel for fluid to regulate the temperature of the multiple battery modules 10 is provided inside the lower plate 21.

[0023] The side frame 221 is located on the +Z side relative to the +Z plane of the lower plate 21. Viewed from the +Z side, the side frame 221 extends along the outer circumference of the lower plate 21, except for the right front corner and the left front corner of the lower plate 21. The lower plate 21 and the side frame 221 are fastened to each other by fasteners such as bolts.

[0024] The support frame 222 is located on the +Z side with respect to the +Z plane of the lower plate 21. As shown in Figure 2, viewed from the +Z side, the support frame 222 is located within the area enclosed by the side frame 221 and at least partially encloses each of the multiple battery modules 10. The lower plate 21 and the support frame 222 are fastened to each other by fasteners such as bolts. Each battery module 10 and the support frame 222 are fastened to each other by fasteners such as bolts.

[0025] As shown in Figure 1, the upper case 23 is positioned approximately perpendicular to the Z direction. The upper case 23 is located on the +Z side relative to the multiple battery modules 10 and the frame 22. The portion of the side frame 221 and the upper case 23 that overlaps with the side frame 221 in the Z direction is fastened to each other by fasteners such as bolts, with a seal placed between the +Z plane of the side frame 221 and the -Z plane of the upper case 23. With the portions of the side frame 221 and the upper case 23 that overlap with the side frame 221 in the Z direction fastened to each other, the lower plate 21, frame 22, and upper case 23 define a housing space for accommodating the multiple battery modules 10.

[0026] Figure 3 is a perspective view of the region α shown in Figure 2 with multiple battery modules 10 removed. Figure 4 is a cross-sectional view along the virtual plane S in Figure 3. The virtual plane S is located approximately in the center of the first weld mark 241, which will be described later, in the Z direction.

[0027] The support frame 222 in the approximate central part of the housing 20 will be described with reference to Figures 3 and 4. Refer to Figure 2 as needed.

[0028] As shown in Figures 2 and 3, the support frame 222 includes a center beam 222a, a right beam 222b, and a left beam 222c.

[0029] As shown in Figures 2 and 3, when viewed from the +Z side, the center beam 222a extends in the X direction. When viewed from the +Z side, the center beam 222a extends from one side between the two battery modules 10 on the -X side and from one side between the two battery modules 10 on the +X side to the other.

[0030] As shown in Figures 2 and 3, when viewed from the +Z side, the light beam 222b extends in the Y direction. Therefore, when viewed from the +Z side, the center beam 222a and the light beam 222b extend in different directions. When viewed from the +Z side, the light beam 222b extends between the two battery modules 10 on the +Y side. As shown in Figure 3, the -Y side end face of the light beam 222b abuts against the +Y side of the center beam 222a.

[0031] As shown in Figures 2 and 3, when viewed from the +Z side, the left beam 222c extends in the Y direction. Therefore, when viewed from the +Z side, the center beam 222a and the left beam 222c extend in different directions. When viewed from the +Z side, the left beam 222c extends between the two battery modules 10 on the -Y side. As shown in Figure 3, the +Y side end face of the left beam 222c abuts against the -Y surface of the center beam 222a.

[0032] The center beam 222a and the light beam 222b are welded to each other by arc welding. Specifically, the center beam 222a and the light beam 222b are welded to each other at the corner between the +Y plane of the center beam 222a and the +X plane of the light beam 222b, at the corner between the +Y plane of the center beam 222a and the -X plane of the light beam 222b, and at the boundary between the +Z plane of the center beam 222a and the +Z plane of the light beam 222b. Therefore, as shown in Figure 3, a first weld mark 241 is formed at the corner between the +Y plane of the center beam 222a and the +X plane of the light beam 222b. In the example shown in Figure 3, the first weld mark 241 is formed over substantially the entire Z direction of the corner between the +Y plane of the center beam 222a and the +X plane of the light beam 222b. Furthermore, a second weld mark 242 is formed at the boundary between the +Z plane of the center beam 222a and the +Z plane of the light beam 222b. In the example shown in Figure 3, the second weld mark 242 is formed over substantially the entire X-direction of the boundary between the +Z plane of the center beam 222a and the +Z plane of the light beam 222b. Although not shown in the viewpoint of Figure 3, a weld mark is also formed at the corner between the +Y plane of the center beam 222a and the -X plane of the light beam 222b. The boundary between the -Z plane of the center beam 222a and the -Z plane of the light beam 222b may or may not be welded.

[0033] In this embodiment, no wrap-around welding is performed between the first weld mark 241 and the second weld mark 242 with respect to the center beam 222a and the right beam 222b. Therefore, the first weld mark 241 and the second weld mark 242 are at least partially discontinuous between the +Z side end of the first weld mark 241 and the +X side end of the second weld mark 242. Consequently, the joining of the center beam 222a and the right beam 222b can be facilitated compared to the case where wrap-around welding is performed. The same applies to the weld mark formed at the corner between the +Y plane of the center beam 222a and the -X plane of the right beam 222b, and the second weld mark 242.

[0034] As shown in Figure 4, the +X surface of the -Y end of the light beam 222b defines a recess 223a into which the first weld mark 241 is at least partially inserted. The recess 223a is defined by a notch formed on the +X surface of the -Y end of the light beam 222b. In order to obtain the desired joint strength of the weld at the corner between the +Y surface of the center beam 222a and the +X surface of the light beam 222b, it is necessary to ensure that the penetration depth D1 in the Y direction of the first weld mark 241 into the +Y surface of the center beam 222a, the penetration depth D2 in the X direction of the first weld mark 241 into the +X surface of the light beam 222b, and the throat thickness T of the first weld mark 241 are relatively large. In the absence of the recess 223a, in order to ensure a large penetration depth D1 in the Y direction, a large penetration depth D2 in the X direction, and a large throat thickness T of the first weld mark 241, it is necessary to raise the first weld mark 241 relatively large on the +X+Y side. However, if the first weld mark 241 is raised large on the +X+Y side, it may become difficult to secure space to accommodate the battery module 10 on the +X+Y side. In this embodiment, even without raising the first weld mark 241 large on the +X+Y side, the recess 223a makes it easier to ensure a large penetration depth D1 in the Y direction, a large penetration depth D2 in the X direction, and a large throat thickness T of the first weld mark 241. Therefore, compared to the case where the recess 223a is not provided, the raising of the first weld mark 241 towards the +X+Y side can be suppressed. Therefore, interference between the battery module 10 on the +X+Y side and the first weld mark 241 can be suppressed.

[0035] From the viewpoint of improving the joint strength of the first weld mark 241, the throat thickness T of the first weld mark 241 is relatively thick, for example, 1.4 mm or more. From the viewpoint of improving the joint strength of the first weld mark 241, there is no particular upper limit to the throat thickness T of the first weld mark 241. The throat thickness T of the first weld mark 241 is, for example, 7.0 mm or less, depending on factors such as the thickness in the Y direction of the portion of the center beam 222a where the first weld mark 241 is formed, or the thickness in the X direction of the portion of the light beam 222b where the first weld mark 241 is formed.

[0036] The first weld mark 241 is formed in a relatively narrow corner between the +Y plane of the center beam 222a and the +X plane of the light beam 222b. Therefore, the width W of the first weld mark 241 is relatively narrow, for example, greater than 0 and 8.5 mm or less. The width W of the first weld mark 241 is the maximum dimension of the first weld mark 241 in the direction perpendicular to the Z direction between the +Y plane of the center beam 222a and the +X plane of the light beam 222b, as viewed from the +Z side or the -Z side. In the example shown in Figure 3, the width W of the first weld mark 241 is the dimension of the first weld mark 241 in a direction inclined approximately 45° from the +X direction to the -Y direction, as viewed from the +Z side or the -Z side. By narrowing the width W of the first weld mark 241, it is possible to suppress the bulging of the first weld mark 241 toward the +X+Y side.

[0037] The length L of the first weld mark 241 in the Z direction is relatively long, for example, 70 mm or more. By increasing the length L of the first weld mark 241, the joint strength of the first weld mark 241 can be improved. From the viewpoint of improving the joint strength of the first weld mark 241, there is no particular upper limit to the length L of the first weld mark 241 in the Z direction.

[0038] From the viewpoint of suppressing the bulging of the first weld mark 241 toward the +X+Y side and improving the joint strength of the first weld mark 241, it is preferable that the throat thickness T of the first weld mark 241 is relatively thick and the width W of the first weld mark 241 is relatively narrow. Therefore, the ratio T / W of the throat thickness T of the first weld mark 241 to the width W of the first weld mark 241 may be 0.16 or more, for example, given the throat thickness T of 1.4 mm or more and the width W of 8.5 mm or less mentioned above.

[0039] In this embodiment, the recess 223a is formed continuously over substantially the entire Z-direction of the light beam 222b. The location of the recess 223a is not limited to this example. For example, the recess 223a may be provided intermittently in the Z-direction.

[0040] In the example shown in Figure 4, the angle between the +Y plane of the center beam 222a and the recess 223a of the light beam 222b, as viewed from the +Z side, is approximately 60°. This angle is not limited to approximately 60° as shown in Figure 4. This angle is determined, for example, by how far the first weld mark 241 is inserted into the recess 223a. In the example shown in Figure 4, the recess 223a is substantially linear as viewed from the +Z side. The shape of the recess 223a is not limited to the substantially linear shape shown in Figure 4; for example, it may be curved as viewed from the +Z side.

[0041] In the example shown in Figure 4, the light beam 222b defines the recess 223a. Therefore, compared to the case where the center beam 222a defines the recess 223a, it is easier to align the recess 223a to the position where the first weld mark 241 is formed. The recess 223a may be provided on the center beam 222a, or on both the center beam 222a and the light beam 222b.

[0042] The matters described with reference to Figure 4 can also be applied to other corners of the support frame 222, such as the corner between the +Y plane of the center beam 222a and the -X plane of the right beam 222b, the corner between the -Y plane of the center beam 222a and the +X plane of the left beam 222c, and the corner between the -Y plane of the center beam 222a and the -X plane of the left beam 222c.

[0043] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted. [Explanation of Symbols]

[0044] 1 Battery pack, 10 Battery module, 11 Battery cell, 20 Housing, 21 Lower plate, 22 Frame, 221 Side frame, 222 Support frame, 222a Center beam, 222b Right beam, 222c Left beam, 223a Recess, 23 Upper case, 241 First weld mark, 242 Second weld mark

Claims

1. Battery cell and A housing for the aforementioned battery cell, Equipped with, The housing has a frame that at least partially surrounds the battery cell, The frame includes a plurality of beams extending in different directions and welded to one another. A battery pack in which at least one beam defines a recess into which a weld mark formed at the corner between the plurality of beams is at least partially embedded.

2. The battery pack according to claim 1, wherein other weld marks are formed at boundaries different from the corners of the plurality of beams.

3. The battery pack according to claim 2, wherein the weld marks and the other weld marks are at least partially discontinuous between the weld marks and the other weld marks.

4. The battery pack according to any one of claims 1 to 3, wherein the ratio of the throat thickness of the weld to the width of the weld is 0.16 or more.

5. The battery pack according to any one of claims 1 to 3, wherein the throat thickness of the weld mark is 1.4 mm or more.

6. The battery pack according to any one of claims 1 to 3, wherein the width of the weld mark is 8.5 mm or less.

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