Battery case

Abstract

To provide a battery case which can improve an allowable limit value of a binding load on a battery.SOLUTION: A battery case comprises: a frame 20 which presses ends in a battery lamination direction; a cross member 200 disposed toward the battery lamination direction; and a cross bracket 100 coupling the frame 20 to the cross member 200. The cross bracket 100 has: a base part 110 bonded to the frame 20; and a pair of corner bracket parts 120, 120 which extends from the base part 110 so as to sandwich a wall part 210 of the cross member 200 from both sides, and which is bonded to the wall part 210. A cutout 130 is formed at a portion where a surface 122 on the wall part 210 side of each of the pair of corner bracket parts 120, 120 intersects a surface 112 on the wall part 210 side of the base part 110.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a battery case for housing a battery, and more particularly to a battery case configured to restrain the battery in the stacking direction.

Background Art

[0002] A vehicle battery is mounted on a vehicle in a state where it is pressurized in the stacking direction of the battery, and a high compressive force is applied to shorten its length. Since the battery mounted on the vehicle tends to elongate in its stacking direction, it is necessary to restrain the battery in the stacking direction so as to prevent the elongation. Patent Document 1 discloses a technique of housing a battery stacked in the longitudinal direction of a vehicle between a pair of cross members spanned between a rocker panel and a floor panel, and restraining the battery by the pair of cross members.

[0003] In the technique described in Patent Document 1, the restraint load received by the cross member from the battery is input to the connection portion between the cross member and the rocker panel and the connection portion between the cross member and the floor panel. Stress is generated in each connection portion due to the input of the restraint load, but stress concentration may occur depending on the structure of the connection portion. However, Patent Document 1 does not disclose any measures for dispersing the stress. If the stress generated by the restraint load of the battery cannot be properly dispersed, it is difficult to improve the allowable limit of the restraint load of the battery.

[0004] In addition to Patent Document 1, Patent Document 2 below can be exemplified as a document showing the technical level of the technical field related to the present disclosure.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present disclosure has been made in view of the above problems, and an object thereof is to provide a battery case capable of improving the allowable limit value of the restraint load of a battery.

Means for Solving the Problems

[0007] The battery case of the present disclosure includes a frame that presses an end portion in the stacking direction of the battery, a cross member disposed in the stacking direction of the battery, and a cross bracket that connects the frame and the cross member. The cross bracket includes a base portion joined to the frame, and a pair of corner bracket portions that extend from the base portion and sandwich the wall portion of the cross member from both sides and are joined to the wall portion of the cross member. Notches are provided at portions where the surfaces on the side of the wall portion of each of the pair of corner bracket portions and the surface on the side of the wall portion of the cross member of the base portion intersect. The stress applied to the cross bracket by the restraint load of the battery is dispersed by the notches.

[0008] In the battery case of the present disclosure, the end portion of the wall portion of the cross member may contact the base portion. By having no gap between the end portion of the wall portion and the base portion, the run - on distance during a collision can be reduced.

[0009] In the battery case of the present disclosure, the base portion may have a rectangular shape with rounded upper ends on both sides or a semi - elliptical shape when viewed laterally from the stacking direction of the battery. Further, the base portion may be welded to the frame by a single welding line connecting one lower end to the other lower end. According to this, the number of start and end points of welding when arc - welding the cross bracket and the frame can be minimized, and arc - welding by a robot becomes possible.

[0010] In the battery case of the present disclosure, each of the pair of corner bracket portions may have a rectangular shape or an oval shape with the upper end of the tip rounded in a side view from a direction perpendicular to the stacking direction of the batteries. Further, each of the pair of corner bracket portions may be welded to the wall portion of the cross member by a single welding line connecting from near the upper notch to the lower end of the tip portion. According to this, the number of start and end points of welding when arc welding the cross bracket and the cross member can be minimized, and arc welding by a robot becomes possible.

Advantages of the Invention

[0011] According to the battery case of the present disclosure, the stress applied to the cross bracket due to the restraint load of the battery is dispersed by the notch provided at the portion where the side surface of the wall portion of the cross member of each of the pair of corner bracket portions intersects with the side surface of the wall portion of the cross member of the base portion. Thereby, the stress concentration generated in the cross bracket is alleviated, and the allowable limit value of the restraint load of the battery can be improved.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

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Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, when referring to the number of each element, quantity, amount, range, etc. in the following embodiments, the present invention is not limited to the mentioned number, except when specifically stated or clearly specified by the principle. Also, the structures described in the following embodiments are not necessarily essential to the present invention, except when specifically stated or clearly specified by the principle.

[0014] 1. Structure of the battery case FIG. 1 is a perspective view showing the configuration of a battery case 10 according to an embodiment of the present disclosure. However, the upper cover of the battery case 10 shown in FIG. 1 has been removed. When mounted on a vehicle, the upper cover is attached with the battery housed inside the battery case 10. The battery to be housed is a battery stack formed by stacking a large number of battery cells. The battery cell is a rechargeable secondary battery, for example, a lithium-ion secondary battery.

[0015] The battery case 10 includes a front frame 30 positioned at the front side of the vehicle, a rear frame 40 positioned at the rear side of the vehicle, and a pair of side frames 20 positioned at the lateral sides of the vehicle when mounted on the vehicle. Inside the frame composed of these four frames, a plurality of inner cross members (cross members) 200 are installed. The inner cross members 200 are arranged in parallel and at equal intervals with the front frame 30 and the rear frame 40. The frames and the inner cross members are die-cast products made of light metal, specifically aluminum. A base plate 50 is joined to the lower surface of the rectangular frame made of the frame.

[0016] In the battery case 10 having the above-described configuration, the battery is mounted with its stacking direction facing the vehicle width direction. The spaces surrounded by two inner cross members 200 adjacent to the side frames 20 on both sides, and the spaces surrounded by the side frames 20 on both sides, the rear frame 40, and the innermost row of inner cross members 200 are the mounting locations of the battery.

[0017] The battery is pressurized in its stacking direction, and is accommodated in the battery case 10 in a state where a high compressive force is applied to shorten its length. When mounted in the battery case 10, the battery attempts to elongate in its stacking direction, but the elongation of the battery in the stacking direction is blocked by the side frames 20 connected by a plurality of inner cross members 200. At this time, the restraint load of the battery received by the side frames 20 is borne by the inner cross members 200 that connect the side frames 20 on both sides together with the front frame 30 and the rear frame 40.

[0018] The restraint load acts on the joint portion between the side frame 20 and the inner cross member 200. Since the battery expands in the stacking direction due to heat, the restraint load acting on the joint portion increases during operation. Therefore, if the joint strength of the joint portion is weak, the joint portion may not be able to withstand the restraint load of the battery. Therefore, the side frame 20 and the inner cross member 200 are connected via a cross bracket 100. In the next chapter, the connection structure between the side frame 20 and the inner cross member 200 by the cross bracket 100 will be described.

[0019] 2. Connection Structure between Side Frame and Inner Cross by Cross Bracket Figure 2 is a perspective view showing the connection structure between side frame 20 and inner cross 200 by cross bracket 100. Cross bracket 100 includes a base portion 110 joined to side frame 20, and a pair of corner bracket portions 120 extending from base portion 110 and sandwiching wall portion 210 of inner cross 200 from both sides. Each of corner bracket portions 120 is joined to wall portion 210 of cross member 200.

[0020] Figure 3 is a plan view showing the above connection structure in more detail. Wall portion 210 of cross member 200 is pressed against base portion 110 of cross bracket 100. That is, end face 212 of wall portion 210 and side face 112 (the face on the side of wall portion 210) of base portion 110 are in contact without a gap. Under such a positional relationship, side face 214 of wall portion 210 and side face 122 (the face on the side of wall portion 210) of corner bracket portion 120 are joined.

[0021] When the restraint load of the battery acts, a tensile force acts between base portion 110 and corner bracket portion 120. The stress generated by the tensile force is likely to occur at the corner portion where the angle at which the surfaces intersect is small. Stress concentration causes damage and reduces the allowable limit of the battery's restraint load. For this reason, cross bracket 100 has a shape design to make stress concentration less likely to occur.

[0022] As a shape design of cross bracket 100, a notch 130 is provided at the portion where side face 122 of corner bracket portion 120 and side face 112 of base portion 110 intersect, that is, at the corner portion. By providing notch 130 at the corner portion, the stress generated by the tensile force is dispersed and the stress concentration is alleviated.

[0023] As a general method for relaxing stress concentration, a method of applying R processing to the corner portion is known. However, compared with the case of providing the notch 130, the effect of relaxing stress concentration by applying R processing is limited. Fig. 4(A) is a stress analysis diagram showing the stress distribution when the notch 130 is provided in the corner portion, and Fig. 4(B) is a stress analysis diagram showing the stress distribution when the R processing 132 is applied to the corner portion. As can be seen from the comparison between the two, stress concentration occurs when the R processing 132 is applied, whereas the stress can be dispersed when the notch 130 is provided. It was confirmed that even at the maximum value of the stress, it can be suppressed to approximately half of the case where the R processing 132 is applied when the notch 130 is provided.

[0024] In addition, if the purpose is simply to relax stress concentration, the R processing can also achieve that purpose. As shown by the dotted line in Fig. 5, by applying the R processing 134 with a reduced curvature to the corner portion, a stress concentration relaxation effect equivalent to that in the case of providing the notch 130 is expected. However, if such processing is performed on the corner portion, a large gap will occur between the end face 212 of the wall portion 210 of the cross member 200 and the side face 112 of the base portion 110. This gap will increase the run-on distance during a side impact of the vehicle. Therefore, in order to obtain a stress concentration relaxation effect while minimizing the run-on distance during a side impact, it can be said that providing the notch 130 is the most suitable method.

[0025] 3. Welding Structure of Cross Bracket, Side Frame, and Inner Cross Welding is used for joining the cross bracket 100 and the side frame 20. Also, welding is used for joining the cross bracket 100 and the inner cross 200. The welding method used is arc welding by a robot.

[0026] FIG. 6 is a plan view showing the welding structure of the cross bracket 100, the side frame 20, and the inner cross 200. The base portion 110 of the cross bracket 100 and the side frame 20 are welded by a welding line L1 connecting point P11 and point P12. Either one of point P11 and point P12 is the start end of the welding line L1 and the other is the end end. Also, one corner bracket portion 120 of the cross bracket 100 and the wall portion 210 are welded by a welding line L2 connecting point P21 and point P22. Either one of point P21 and point P22 is the start end of the welding line L2 and the other is the end end. The other corner bracket portion 120 of the cross bracket 100 and the wall portion 210 are welded by a welding line L3 connecting point P31 and point P32. Either one of point P31 and point P32 is the start end of the welding line L3 and the other is the end end.

[0027] In arc welding, the start end and the end end of the welding line are likely to be the starting points of fracture because the arc is unstable and the welding strength is relatively low. Therefore, it is desirable to minimize the number of start ends and end ends of the welding line. In the example shown in FIG. 6, the total number of start ends and end ends of the welding lines required to connect the side frame 20 and the inner cross 200 via the cross bracket 100 is suppressed to 6 in total. However, even if the number of start ends and end ends of the welding line is reduced, sufficient welding strength cannot be obtained when the total length of the welding line is short.

[0028] As a method of increasing the length of the welding line, it is conceivable to perform welding along the contour of the welding object. However, a robot performing arc welding can accurately draw a welding line only with a linear movement or a movement drawing a gentle curve. That is, it is difficult to adopt a long welding path depending on the outer shape of the welding object. Therefore, the cross bracket 100 is contrived in shape for taking a long welding line in arc welding by a robot.

[0029] FIG. 7 is a perspective view showing the welding structure of the cross bracket 100, the side frame 20, and the inner cross 200. The base portion 110 of the cross bracket 100 has a rectangular shape with rounded upper ends 116 on both sides, so-called a wasabi shape, in a side view from the stacking direction of the battery. The radius of curvature of the upper end 116 is, for example, 15 mm or more. By forming the base portion 110 in such a shape, a long, gently curved welding line L1 connecting point P11 and point P21 can be taken by taking point P11 at one lower end of the base portion 110 and point P12 at the other lower end. According to this, the number of start and end points of welding when arc-welding the cross bracket 100 and the side frame 20 can be minimized, and efficient arc welding by a robot becomes possible. Note that the shape of the base portion 110 may be a semi-elliptical shape in a side view from the stacking direction of the battery.

[0030] Each of the pair of corner bracket portions 120 has a rectangular shape with rounded upper ends 126 at the tip portions, so-called a semi-wasabi shape, in a side view from a direction perpendicular to the stacking direction of the battery. The radius of curvature of the upper end 126 is, for example, 15 mm or more. According to such a shape, a long, gently curved welding line L2 connecting both points P21 and P22 can be taken by taking point P21 near the upper notch 130 of one corner bracket portion 120 and point P22 at the lower end of the tip portion. Also, a long, gently curved welding line L3 connecting both points P31 and P32 can be taken by taking point P31 near the upper notch 130 of the other corner bracket portion 120 and point P32 at the lower end of the tip portion. According to this, the number of start and end points of welding when arc-welding the cross bracket 100 and the inner cross 200 can be minimized, and efficient arc welding by a robot becomes possible. Note that the shape of the corner bracket portion 120 may be a quarter-elliptical shape in a side view from a direction perpendicular to the stacking direction of the battery.

[0031] As described above, due to the shape improvement made to the cross bracket 100, the merit that high-quality and high-efficiency arc welding by a robot can be realized is obtained. This merit can be made clearer by comparison with two comparative examples described below.

[0032] In the first comparative example shown in FIG. 8, the inner cross 200 is butted against the side frame 20, and the side frame 20 and the inner cross 200 are directly welded. In this case, both sides of the end of the wall portion 210 of the inner cross 200 are welded to the side frame 20 by the welding lines L11 and L12. Also, the bottom portions 220 on both sides of the inner cross 200 and the side frame 20 are welded by the welding lines L13 and L14.

[0033] In the first comparative example, the total number of the start and end points of the welding lines is suppressed to 8. However, since each welding line is short, the strength is insufficient. That is, the first comparative example is inferior in strength compared to the case of using the cross bracket 100, and the purpose of improving the allowable limit value of the restraint load of the battery cannot be achieved.

[0034] In the second comparative example shown in FIG. 9, the side frame 20 and the inner cross 200 are connected via the cross bracket 300. Different from the cross bracket 100, the cross bracket 300 has a simple shape with each part processed at a right angle. The base portion 310 of the cross bracket 300 has a simple rectangular shape in a side view from the stacking direction of the battery. The corner bracket portion 320 has a simple rectangular shape in a side view from a direction perpendicular to the stacking direction of the battery.

[0035] Even if an attempt is made to set a welding line along a shape that bends at a right angle as in the second comparative example, the robot cannot follow it. Therefore, welding lines have to be set for each side and welded. For the welding of the side frame 20 and the base portion 310, a total of three welding lines are required: the horizontal welding line L21 and the two vertical welding lines L22 and L23. For the welding of the wall portion 210 of the inner cross 200 and the corner bracket portion 320, a total of four welding lines are required: the two horizontal welding lines L24 and L26 and the two vertical welding lines L25 and L27.

[0036] As a result, when using the cross bracket 300, a total of seven welding lines are required, and the number of start and end points of the welding lines increases to a total of 14. Since the start and end points are likely to be the starting points of fracture, it can be said that the second comparative example is inferior in terms of quality compared to the case of using the cross bracket 100. Also, since the number of welding lines increases, the number of processes increases, so it can be said that the second comparative example is also inferior in terms of efficiency compared to the case of using the cross bracket 100.

[0037] As is clear from the comparison results with the above two comparative examples, according to the cross bracket 100, while minimizing the number of welding lines and suppressing the number of start and end points that are likely to be the starting points of fracture to the minimum, the length of each welding line can be increased. Thereby, while ensuring high welding strength, high-quality and high-efficiency arc welding by the robot can be realized.

Explanation of Signs

[0038] 10 Battery case 20 Side frame (frame) 30 Front frame 40 Rear frame 50 Base plate 100 Cross bracket 110 Base portion 120 Corner bracket portion 130 Notch 200 Inner cross (cross member) 210 wall part L1, L2, L3 welding lines P11, P12, P21, P22, P31, P31 points (starting or ending points)

Claims

1. A plurality of battery stacks each including a plurality of battery cells stacked in a vehicle width direction; a pair of side frames disposed on both ends of each of the plurality of battery stacks in a vehicle width direction and extending in a front-rear direction of the vehicle; a cross member disposed between the battery stacks in a vehicle front-rear direction and extending in a vehicle width direction between the pair of side frames; A battery mounting structure comprising: One of the pair of side frames abuts against one end of the battery stack in a vehicle width direction, The cross member is A first portion; and a second portion that is disposed between the first portion and the one of the side frames, and has an end portion on the vehicle upper side that is disposed further toward the vehicle lower side than both an end portion on the vehicle upper side of the first portion and an end portion on the vehicle upper side of the one of the side frames, The cross member is welded to the one side frame in a linear manner at least from an end portion on an upper side of the vehicle toward a lower side of the vehicle in the second portion. Battery mounting structure for vehicle.

2. The cross member is linearly welded at least from an end portion on an upper side of the vehicle to a portion spaced upward from an end portion on a lower side of the vehicle in the second portion. A vehicle mounting structure for a battery according to claim 1.

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