Battery case

Abstract

A battery case (1) according to the present invention is provided with a battery case lower part (3) and a battery case upper part (5), the battery case lower part (3) having: a case bottom part (15); a housing front-rear vertical wall part (17) and a housing left-right vertical wall part (19) which are vertically arranged on the periphery of the housing bottom part (15); and a case flange section (21) formed on the upper ends of the case front-rear vertical wall section (17) and the case left-right vertical wall section (19) toward the outside and joined to the battery case upper section (5), the case flange section (21) being bonded or coated with a resin (25) on at least the inner surface and / or the outer surface of any one of the case front-rear vertical wall section (17), the case left-right vertical wall section (19), and the case bottom section (15), and the case flange section (21) being bonded or coated with a resin (25) on the outer surface and / or the inner surface of any one of the case front-rear vertical wall section (17) and the case left-right vertical wall section (19). A reinforcing plate (27) disposed so as to cover the resin (25) is adhered to the resin (25).

Description

Technical Field

[0001] The invention relates to a battery casing of an electric vehicle. Background Art

[0002] The battery case of an electric vehicle needs to have a very strong structure to prevent damage to the internal battery pack during a vehicle collision. Therefore, a large number of battery case cross members are provided inside or outside the battery case body to increase the stiffness of the battery case. In addition, since a floor cross member is generally provided on the floor (floor panel) of a car, if the floor cross member is made high-strength and the load during a side collision is transferred to the floor cross member as much as possible, the input load to the battery case can be reduced.

[0003] The above-mentioned floor cross beam and battery case cross beam are components composed of a hat-shaped section part based on a high-strength high-tensile steel sheet, an aluminum extruded material, etc., and are arranged in multiple numbers in the vehicle width direction and length direction. If these components are increased for the purpose of protecting the battery case, the space for configuring the battery will be reduced, and the battery mounting capacity will be reduced. In addition, due to the increase in the number of components, the weight of the vehicle increases, which becomes the reason for the reduction in cruising distance. Therefore, the optimal structure for protecting the battery case has been studied for a long time.

[0004] As a conventional document related to a battery case, for example, there is a "battery case for electric motor car" disclosed in Patent Document 1. In the "battery case for electric motor car", a tray in the shape of a bathtub with a bottom frame and a top cover are used to seal the storage part of the battery, thereby ensuring high sealing performance. In addition, a frame is arranged so as to surround the entire circumference of the tray, which can ensure high collision strength.

[0005] In addition, Patent Document 2 discloses a "lower tray for a battery case" having a plurality of reinforcements and a plurality of stiffeners connecting adjacent reinforcements. In the "lower tray for a battery case", when a pressing force is applied to a region between adjacent reinforcements, the pressing force is dispersed and transmitted to a plurality of reinforcements via the stiffeners, thereby reducing the stress transmitted to one reinforcement. As a result, the reinforcements are less likely to buckle, thereby preventing deformation of the tray body.

[0006] Furthermore, Patent Document 3 discloses a "battery case" having an outer peripheral wall, a reinforcement member for reinforcing the outer peripheral wall, and a bottom plate. In this "battery case", in order to improve durability against loads from the road surface, the bottom plate is set as a sandwich panel formed by sandwiching an intermediate member made of foamed resin (foam material) between an upper plate and a lower plate of a metal plate. Furthermore, in the relationship with the surrounding wall of the battery module composed of the outer peripheral wall and the reinforcement member, by changing the expansion ratio of the intermediate member, it is possible to achieve weight reduction while ensuring the rigidity of the bottom plate.

[0007] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2021-041783 Patent Document 2: Japanese Patent Application Publication No. 2020-053132 Patent Document 3: Japanese Patent Application Publication No. 2019-091633 Summary of the invention

[0008] Problems to be solved by the invention

[0009] The "battery case for electric vehicle" of Patent Document 1 can ensure sufficient strength and sealing, but a large number of frames connected to the tray are required to maintain the required strength, so the area that can accommodate the battery is significantly limited relative to the surface area of ​​the tray. In addition, since the frame is made of metal, the weight increases, resulting in reduced electricity consumption.

[0010] According to the "lower tray for battery case" of Patent Document 2, if it is made of metal, there is no problem in strength and deformation of the tray body can be prevented, but if it is made of iron, the weight increases significantly, and if lightweight metal is used for lightness, it costs money. In addition, if it is made of resin, lightness can be achieved, but on the other hand, strength becomes weak, so in order to prevent deformation of the tray body, it is necessary to increase the thickness of the resin or reinforce the tray body, which has the problem of increased weight and increased cost.

[0011] The "battery case" of patent document 3 sets the bottom plate of the battery case as a sandwich plate to ensure durability against loads from the road surface. However, since there is a foam body with built-in foaming gas in the foamed resin of the sandwich plate, the effective cross-sectional area of ​​the resin itself in the foamed resin is small, and the shear strength of cohesive failure of the foamed resin is low. Therefore, when a large bending deformation occurs in the sandwich plate and a shear force is applied to the foamed resin layer, cohesive failure (cohesive failure) that is destroyed inside the foamed resin layer is easily generated. Therefore, when a large load of a degree of bending deformation is applied to the bottom plate of the battery case from the road surface, durability cannot be ensured. In particular, the side pole impact (side impact) from the side of the vehicle that causes a large bending deformation of the bottom plate of the battery case is relatively fragile, and it is almost impossible to expect the effect of improving the rigidity of the battery case. Therefore, in order to ensure the rigidity of the battery case with respect to the side collision of the vehicle, a large amount of metal peripheral walls and metal reinforcements for strengthening the peripheral walls are required, and there is a problem of lightweighting the battery case as a whole. Although there is a method of reducing the foaming ratio to solve these problems, there is still the problem of a significant increase in weight. In addition, due to the presence of voids with built-in foaming gas, the thermal conductivity of the foamed resin is low, and there are problems with the heat dissipation of the battery case. Moreover, in the manufacture of sandwich panels composed of foamed resins with locally different foaming ratios, it is necessary to repeatedly inject the foamed resin and bake it for foaming, which also poses a problem in terms of productivity.

[0012] As described above, although many technologies for preventing deformation of a battery case during a side collision of a vehicle have been disclosed, there are problems that these technologies are accompanied by a significant increase in weight, an increase in manufacturing cost, and an impact on vehicle design.

[0013] The present invention has been made in view of the above problems, and an object thereof is to provide a battery case having higher rigidity and strength than conventional ones and excellent vibration-damping properties without requiring a significant increase in weight, an increase in manufacturing cost, or a change in the automotive structure.

[0014] Technical solutions to solve problems

[0015] A battery case according to a first aspect of the present invention comprises: a battery case lower portion (battery case lower) having a rectangular shape, which is mounted under a floor of a vehicle body and stores a battery; and a battery case upper portion (battery case upper) which is arranged to cover an upper surface of the battery case lower portion, wherein the battery case lower portion comprises: a case bottom portion; a case front and rear longitudinal wall portion (side wall portion) and a case left and right longitudinal wall portion, which are erected at a peripheral edge of the case bottom portion; and a case flange portion (case flange portion) which is formed outward at upper ends of the case front and rear longitudinal wall portion and the case left and right longitudinal wall portion and is joined to the battery case upper portion, a resin is pasted or applied to an inner surface and / or an outer surface of at least one of the case front and rear longitudinal wall portion, the case left and right longitudinal wall portion and the case bottom portion, and a reinforcing plate (reinforcing plate) which is arranged so as to cover the resin is bonded to the resin.

[0016] A resin may be pasted or applied to at least the surface of the case flange formed at the upper ends of the left and right vertical walls of the case opposite to the upper portion of the battery case, and a reinforcing plate arranged so as to cover the resin may be bonded to the resin.

[0017] The battery case involved in the second embodiment of the present invention comprises: a rectangular battery case lower part, which is mounted under the floor of the vehicle body and stores the battery; and a battery case upper part, which is configured to cover the upper surface of the battery case lower part, and is characterized in that the battery case lower part has: a case bottom; front and rear longitudinal walls of the case and left and right longitudinal walls of the case, which are upright and arranged on the periphery of the case bottom; and a case flange part, which is formed on the upper ends of the front and rear longitudinal walls of the case and the left and right longitudinal walls of the case toward the outside and is joined to the battery case upper part, and resin is pasted or coated on at least the surface of the case flange part formed on the upper ends of the left and right longitudinal walls of the case opposite to the battery case upper part, and a reinforcing plate configured to cover the resin is bonded to the resin.

[0018] The thickness of the resin may be 0.1 mm to 5 mm, the thickness of the reinforcing plate may be 0.15 mm to 1.0 mm, and the adhesive strength between the resin and the lower portion of the battery case and the reinforcing plate may be 5 MPa or more.

[0019] Effects of the Invention

[0020] In the battery case of the present invention, the rigidity of the battery case is improved by setting resin and reinforcing plates on the inner and / or outer surfaces of at least one of the front and rear longitudinal walls of the case, the left and right longitudinal walls of the case, and the bottom of the case. In addition, by setting resin and reinforcing plates on at least the surface of the case flange formed at the upper end of the left and right longitudinal walls of the case opposite to the upper part of the battery case, the collision energy absorption property of the case flange is improved, and the load input to the longitudinal wall and the bottom of the case can be reduced. As described above, by improving the rigidity / strength of the battery case body or reducing the load input to the battery case body, the deformation of the battery case during a side impact can be prevented. In addition, the thinning of the battery case cross beam and the reduction in the number of roots can be achieved, which helps to reduce weight and is also excellent in vibration reduction. Moreover, since the present invention hardly changes the appearance of the battery case, it will neither reduce the battery carrying volume nor affect the vehicle design. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a diagram for explaining the battery case according to the first embodiment of the present invention. Figure 1 (a) is a three-dimensional view of the lower part of the battery housing. Figure 1 (b)~ Figure 1 (e) Yes Figure 1 (a) is a cross-sectional view taken along the A plane, showing an example of arrangement of the resin and the reinforcing plate. Figure 2 It is a diagram for explaining the overall structure of the battery case. Figure 3 This is a cross-sectional view of the battery housing and surrounding components in the vehicle width direction. Figure 1 FIG. 5 is a diagram showing examples of resin and applicable positions of reinforcing plates. Figure 4 The present invention describes a model for evaluating the plane stiffness of the front and rear longitudinal walls of the lower part of the battery case in the prior art (prior art model) and a model for evaluating the plane stiffness of the lower part of the battery case in the prior art (prior art model). Figure 1 FIG. 1 is a diagram of a model (invention model) of the surface rigidity of the front and rear longitudinal walls of the lower part of the battery case. Figure 5 Yes Figure 4 A graph showing the results of evaluating the surface rigidity of the prior art model and the inventive model. Figure 6 It is a diagram for explaining the deformation state of the lower portion of the battery case during a side collision. Figure 7 It is a diagram for explaining another form 1 of the battery case according to the first embodiment. Figure 7 (a) is a three-dimensional view of the lower part of the battery housing. Figure 7 (b)~ Figure 7 (e) Yes Figure 7 (a) is a cross-sectional view taken along the plane B, showing an example of arrangement of the resin and the reinforcing plate. Figure 8 This is a cross-sectional view of the battery housing and surrounding components in the vehicle width direction. Figure 7 FIG. 5 is a diagram showing examples of resin and applicable positions of reinforcing plates. Fig. 9 It is a diagram for explaining another form 2 of the battery case according to the first embodiment. Fig. 9 (a) is a three-dimensional view of the lower part of the battery housing. Fig. 9 (b) Fig. 9 (c) Yes Fig. 9 (a) is a cross-sectional view taken along the C plane, showing an example of arrangement of the resin and the reinforcing plate. Fig.10 This is a cross-sectional view of the battery housing and surrounding components in the vehicle width direction. Fig. 9 FIG. 5 is a diagram showing examples of resin and applicable positions of reinforcing plates. Fig.11 It is a diagram for explaining a battery case according to a second embodiment of the present invention. Fig.11 (a) is a three-dimensional view of the lower part of the battery housing. Fig.11 (b) Yes Fig.11 (a) is a cross-sectional view taken along the D plane, showing an example of arrangement of the resin and the reinforcing plate. Fig.12 This is a cross-sectional view of the battery housing and surrounding components in the vehicle width direction. Fig.11 FIG. 5 is a diagram showing examples of resin and applicable positions of reinforcing plates. Fig.13 This is a graph showing the results of Example 3. DETAILED DESCRIPTION

[0022] [Implementation Method 1]

[0023] First, the overall structure of the battery case 1 according to the present embodiment and the arrangement of the battery case 1 when mounted on a vehicle body are shown. Figure 2 , Figure 3 .exist Figure 2In the drawings described below, the direction of arrow FR indicates the front of the vehicle body, and the direction of arrow UP indicates the upper side of the vehicle body.

[0024] like Figure 2 , Figure 3 As shown, the battery case 1 according to the present embodiment includes a battery case lower portion 3 and a battery case upper portion 5, and is mounted under a vehicle body floor 7. A pair of side sills 9 arranged so as to extend in the vehicle body front-rear direction are joined to both ends of the vehicle body width direction of the floor 7. The battery case 1 is fixed to the side sills 9 via a fixing member 11 having an L-shaped cross section.

[0025] A floor cross member 13 is provided on the upper surface of the floor 7 so as to cross the pair of side members 9. The floor cross member 13 is provided so as to cross the top of the battery case 1 in the vehicle width direction, and both ends are joined to the side members 9. Figure 3 As shown, the floor cross member 13 is provided above the battery case 1 and protrudes to both sides in the vehicle width direction from the battery case 1. As a result, the load during a side collision is input to the floor cross member 13 before being input to the battery case 1, and the load input to the battery case 1 is reduced. The various structures of the battery case 1 are described in detail below.

[0026] <Battery Case Lower Part>

[0027] The battery case lower part 3 is a bottomed frame made of metal (e.g., steel plate) and composed of a rectangular case bottom 15 and side walls erected on the periphery of the case bottom 15, and stores the battery of the electric vehicle. Among the side walls, a pair of side walls opposite to each other in the vehicle front-rear direction are set as case front-rear longitudinal wall parts 17, and a pair of side walls opposite to each other in the vehicle width direction are set as case left-right longitudinal wall parts 19. At the upper ends of the case front-rear longitudinal wall parts 17 and the case left-right longitudinal wall parts 19, a case flange part 21 for joining the battery case lower part 3 to the battery case upper part 5 is formed toward the outside.

[0028] Inside the battery case lower portion 3 , a battery case cross beam 23 as a reinforcing member is provided across the case left and right vertical walls 19 , thereby increasing the rigidity of the battery case lower portion 3 .

[0029] Furthermore, the case front and rear vertical walls 17 ( Figure 3 The area shown in gray is patched or coated with resin at a predetermined strength, and a reinforcing plate is arranged to cover the resin. Figure 1 This point will be explained in detail.

[0030] Figure 1 (a) is a perspective view of the lower portion 3 of the battery case, with the front and rear longitudinal walls 17 of the case shown in gray. Figure 1 (b)~ Figure 1 (e) shows an example of the arrangement of the resin 25 and the reinforcing plate 27 provided on the front and rear vertical walls 17 of the housing. The resin 25 may be Figure 1 (b) Figure 1 (c) is provided on the outer surface of the front and rear vertical walls 17 of the housing, or Figure 1 (d) Figure 1 (e) The resin 25 may be formed by pasting a preformed component (injection molding resin component) on the case front and rear vertical walls 17 or by applying the preformed resin 25 to the case front and rear vertical walls 17 and baking it.

[0031] The lower limit of the thickness of the resin 25 is about 0.1 mm, which can be evenly applied, when the resin 25 is formed by coating, and about 20 μm when the resin 25 is pasted in a film form. In addition, from the perspective of cost, the upper limit of the thickness of the resin 25 is preferably about 5 mm. The method of determining the thickness of the resin based on the perspective of reducing the weight and improving the rigidity of the battery case will be described later.

[0032] The reinforcing plate 27 provided in a manner covering the resin 25 is bonded to the resin 25 with a predetermined strength to prevent the resin 25 from peeling off from the front and rear longitudinal walls 17 of the case, and cooperates with the resin 25 to improve the surface rigidity of the front and rear longitudinal walls 17 of the case as described later. By improving the surface rigidity of the front and rear longitudinal walls 17 of the case, the rigidity of the lower part 3 of the battery case is improved. The surface rigidity will be described later. The reinforcing plate 27 may be as follows: Figure 1 (b) Figure 1 (d) by spot welding the upper and lower ends to the front and rear longitudinal walls 17 of the housing. Figure 1 (c) Figure 1 (e) The lower end side is fixed to the case bottom 15. When the lower end is fixed to the case bottom 15, the range where the resin can be bonded can be expanded.

[0033] The effect of improving the surface rigidity produced by the resin 25 and the reinforcing plate 27 does not greatly depend on the tensile strength of the raw material of the reinforcing plate 27, so the tensile strength of the reinforcing plate 27 can be lower than the raw material of the battery case lower part 3. From the perspective of reducing manufacturing costs, the tensile strength can be 270MPa-class to 590MPa-class. In addition, the reinforcing plate 27 only needs to prevent the resin 25 from peeling off from the front and rear longitudinal walls 17 of the battery case lower part 3, so the thickness of the reinforcing plate 27 can be thinner than the thickness of the raw material of the battery case lower part 3. For example, from the perspective of weight reduction and manufacturing cost reduction, the plate thickness can be a steel plate of 0.15 to 1 mm.

[0034] The reason why the tensile strength is set to 270MPa to 590MPa is that the 270MPa grade has the lowest tensile strength among commonly used steel plates, and if it exceeds 590MPa, the cost will increase significantly. In this range, from the perspective of cost, the 270MPa grade (so-called mild steel) of the cheap general cold-rolled steel sheet and plated steel sheet, which are called common carbon steel according to the JIS standard SPCC, is particularly preferred. In addition, the reason why the plate thickness is set to 0.15 to 1mm is that when it is less than 0.15mm, the manufacturing cost increases, and if it exceeds 1mm, the lightweight effect decreases.

[0035] A general battery case in the prior art is made of only a metal plate, so in order to improve strength and rigidity, the thickness of the metal plate needs to be increased, which increases weight. In this regard, the battery case 1 of the present embodiment is thickened by providing a resin 25 and a reinforcing plate 27 on the front and rear longitudinal walls 17 of the case, but since the resin 25 having a lower density than metal is used, it is less likely to increase weight compared to the case of increasing the thickness of the metal plate as in the prior art.

[0036] Furthermore, by adopting a sandwich structure (three-layer laminate structure) in which the resin 25 is sandwiched between the front and rear longitudinal walls 17 of the metal battery case lower part 3 and the reinforcing plate 27, the surface rigidity of the front and rear longitudinal walls 17 of the case is improved. The so-called surface rigidity is the resistance (yield strength) to the bending deformation of the front and rear longitudinal walls 17 of the case, that is, the maximum load that can be borne without buckling deformation against the load input from the end of the front and rear longitudinal walls 17 of the case in the plane direction. In this regard, based on Figure 4 , Figure 5 Provide explanation.

[0037] exist Figure 4 The prior art model for evaluating the surface rigidity of the front and rear longitudinal walls 17 of the lower part of the battery case of the prior art and the invention model for evaluating the surface rigidity of the front and rear longitudinal walls 17 of the lower part 3 of the battery case of the present embodiment are shown in the figure. The prior art model is a model composed only of steel plates, and the invention model is a model of a sandwich structure formed by sandwiching the resin 25 between the front and rear longitudinal walls 17 of the case and the reinforcing plate 27. Figure 4 In, with Figure 1 Corresponding parts are marked with the same reference numerals.

[0038] When the surface rigidity is only composed of steel plates as in the conventional model, it is generally given by the product EI of the material's Young's modulus E and the geometrical moment of inertia I. On the other hand, when the surface rigidity is a sandwich structure as in the invention model, it can be obtained using the following formula (1).

[0039] [Formula 1]

[0040] In the above formula (1), L is the width of the laminated body, i is the material, n is the number of layers, and E i is the Young's modulus of material i, h i is the thickness of the layer from material i=1 to material i, and λ is the distance from the surface of material i=1 to the neutral plane of the stack.

[0041] To the general Figure 4 The difference in surface rigidity EI when the prior art model and the invention model are set to be approximately the same weight is compared, and the results are shown in Figure 5 .exist Figure 5 In the above, the thickness of the front and rear longitudinal walls of the shell of the prior art model is set to 1.2t (total thickness 1.2t), the thickness of the front and rear longitudinal walls of the shell of the present invention model is set to 0.6t, the thickness of the resin is set to 1.5t, and the thickness of the reinforcing plate is set to 0.3t (total thickness 2.4t), and the respective surface rigidities EI are calculated using formula (1). Figure 5 The weight ratio of the two models in FIG. 1 is 0.97 for the inventive model when the weight of the prior art model is taken as a reference (1.00).

[0042] like Figure 5 As shown, the surface rigidity of the invented model (1.65×10 -7 GPa·m 4 ) is improved to the existing technology model (0.31×10 -7GPa·m 4 ). Thus, by making the plate thickness of the front and rear longitudinal walls 17 of the housing thinner than that of the prior art model, and providing a resin and a reinforcing plate 27 having a lower density and a lower Young's modulus than that of metal, the total thickness of this part is made thicker than that of the prior art model, thereby significantly improving the surface rigidity even with the same weight as that of the prior art model. When the index representing the endurance is set to the buckling load obtained by, for example, the formula (2) described later, the buckling load is proportional to the surface rigidity (E×I), and therefore the endurance to bending deformation also increases in proportion to the surface rigidity.

[0043] Next, use Figure 6 The point that the rigidity of the battery case 1 is improved by increasing the surface rigidity of the case front and rear vertical wall portions 17 of the battery case lower portion 3 will be described. Figure 6 2 is a diagram for explaining the deformation state of the battery case lower portion 3 when the side surface of the vehicle body collides with the pillar 29. Figure 6 (a) is a top view of the state before the collision with the column 29. Figure 6 (b) is a top view of the state after the collision of the column 29. In an actual vehicle body, there are other components such as the battery case upper part 5, the floor 7, and the floor cross member 13 on the upper side of the battery case lower part 3, but Figure 6 Illustration of these parts is omitted.

[0044] like Figure 6 As shown in (b), when the left side of the vehicle body collides with the column 29, as shown by the curved arrows in the figure, a bending moment acts on the front and rear longitudinal walls 17 of the battery case lower part 3, the left and right longitudinal walls 19 of the case, and the bottom 15 of the case. For example, the bending moment acting on the front and rear longitudinal walls 17 of the case generates bending deformation such as compression on the inner surface side and stretching on the outer surface side of the front and rear longitudinal walls 17 of the case as shown by the black arrows in the figure. Therefore, by providing the resin 25 and the reinforcing plate 27 on the front and rear longitudinal walls 17 of the case, the surface rigidity of the front and rear longitudinal walls 17 of the case is improved, thereby improving the resistance to the above-mentioned bending deformation, and the front and rear longitudinal walls 17 of the case will not be buckled and deformed even in a side collision and can maintain their shape. As a result, the rigidity and strength of the battery case 1 itself are improved, and deformation can be prevented.

[0045] The case front and rear vertical walls 17, the resin 25 and the reinforcing plate 27 are integrated to bear the load, thereby effectively improving the surface rigidity. Therefore, the case front and rear vertical walls 17 and the resin 25, and the resin 25 and the reinforcing plate 27 need to be bonded with a predetermined strength. This point will be described with reference to a specific example.

[0046] When the thickness of the front and rear longitudinal walls 17 of the housing is set to 1.0 mm, the thickness of the resin 25 is set to 1.0 mm, and the thickness of the reinforcing plate 27 is set to 0.6 mm, if the front and rear longitudinal walls 17 of the housing are bonded to the resin 25, and the resin 25 is bonded to the reinforcing plate 27, the surface rigidity EI is 2.72×10 -7 GPa·m 4 The above surface rigidity is calculated by setting the Young's modulus of iron to 206 GPa and the Young's modulus of the resin 25 to 2 GPa. When the resin 25 and the reinforcing plate 27 are not bonded, the surface rigidity EI of the bonded housing front and rear vertical walls 17 and the resin 25 is 0.19×10 -7 GPa·m 4 The surface rigidity EI of the reinforcing plate 27 alone is 0.04×10 -7 GPa·m 4 Therefore, although the overall surface rigidity is 0.23×10 -7 GPa·m 4 , but it is significantly lower than the case where the resin 25 and the reinforcing plate 27 are bonded. Therefore, in order for the front and rear longitudinal walls 17 of the housing, the resin 25 and the reinforcing plate 27 to bear the load integrally, it is important that the front and rear longitudinal walls 17 of the housing and the resin 25 are bonded with sufficient strength, and the resin 25 and the reinforcing plate 27 are bonded with sufficient strength.

[0047] As the bonding strength, for example, it is preferably 5MPa or more. If the bonding strength is 5MPa or more, even if the front and rear longitudinal wall portions 17 of the housing are bent and deformed, as long as the bending deformation is about 90°, the resin 25 will not peel off from the front and rear longitudinal wall portions 17 of the housing. The above-mentioned bonding strength is measured based on the "Adhesive-Rigid Adhesive Tensile Shear Bonding Strength Test Method" of JIS K 6850, and the maximum shear stress (maximum shear stress) or average shear stress (average shear stress) acting on the interface (interface) of the metal plate and the resin parallel to the bonding surface can be used as the bonding strength. The bonding strength (tensile shear bonding strength) measured according to JIS K 6850 does not distinguish between the failure modes of interface peeling (destruction at the bonding interface between the resin and the adhered material) and cohesive failure (destruction inside the resin). Therefore, no matter which of the interface peeling and cohesive failure occurs, the stress at this time is evaluated as the bonding strength. Therefore, in the case of a resin that undergoes cohesive failure under a relatively small load, such as a foamed resin, it is not possible to ensure a bonding strength of 5 MPa. Therefore, the resin in the present invention is preferably any one of epoxy, modified epoxy, polyurethane, modified polyurethane, acrylic acid, and modified acrylic acid that is difficult to undergo cohesive failure.

[0048] <How to determine the resin thickness>

[0049] The present invention does not limit the thickness of the resin 25 of the battery case 1, but when the resin 25 is too thin, the effect of improving the surface rigidity of the front and rear longitudinal walls 17 of the case is reduced, and when it is too thick, the effect of lightweighting is reduced. Therefore, it is preferable to consider the balance between the two to determine the resin thickness. An example of a method for determining the resin thickness is described below.

[0050] First, prepare a metal battery case lower part 3 that will serve as the basis for the study, and find the weight and the surface rigidity of the front and rear vertical walls 17 of the case. Hereinafter, the battery case lower part 3 will be referred to as "base". Next, prepare two metal battery case lower parts 3 that are thinner than the above-mentioned "base". Hereinafter, the battery case lower parts 3 will be referred to as "sample A" and "sample B". It is assumed that the plate thickness of "sample A" and "sample B" is the same.

[0051] First, for Sample A, for example Figure 1 As shown in (b), resin 25 and reinforcing plate 27 are provided on the front and rear longitudinal walls 17 of the housing. At this time, the thickness of the resin is adjusted so that the surface rigidity of the front and rear longitudinal walls 17 of the housing is the same as that of the "Base". Thus, "Sample A" ensures the same degree of surface rigidity as "Base" and maximizes the lightweight effect produced by using resin 25 with a lower density than metal.

[0052] In addition, for Sample B, resin 25 and reinforcing plate 27 are arranged in the same configuration as Sample A on the front and rear longitudinal walls 17 of the housing. At this time, the resin thickness is adjusted so that the weight of Sample B including the resin 25 and reinforcing plate 27 is about the same as the weight of the Foundation. Sample B maximizes the effect of improving the surface rigidity by increasing the thickness of the low-density resin 25 to the same weight as the Foundation.

[0053] The resin thickness can be determined by setting the resin thickness of "Sample A" which does not reduce the surface rigidity and can be maximally lightened compared to "Base" as the lower limit, and setting the resin thickness of "Sample B" which does not increase the weight and can maximally improve the surface rigidity as the upper limit. By setting the resin thickness within the above range, both the effects of lightening and improving the surface rigidity can be achieved, so it is preferred.

[0054] The above description uses the example of providing the resin 25 and the reinforcing plate 27 on the front and rear vertical walls 17 of the battery case lower portion 3, but the present invention is not limited thereto. Figure 6As described in the above, the left and right vertical walls 19 and the bottom 15 of the housing also experience bending moments, which cause bending deformation. Therefore, the surface rigidity of the left and right vertical walls 19 and the bottom 15 of the housing can be increased to improve the resistance to bending deformation. Other aspects of this embodiment are described below.

[0055] exist Figure 7 (a) and Figure 8 In the figure, the gray color indicates the applicable position when the resin 25 and the reinforcing plate 27 are provided on the left and right vertical walls 19 of the housing. In addition, the configuration example of the resin 25 and the reinforcing plate 27 in this case is shown in FIG. Figure 7 (b)~ Figure 7 (e). In this case, Figure 1 Similarly to the example, by pasting or applying the resin 25 on the inner surface or outer surface of the left and right vertical wall portions 19 of the case and arranging the reinforcing plate 27 to cover the resin 25, the surface rigidity of the left and right vertical wall portions 19 of the case can be improved.

[0056] In addition, Fig. 9 (a) and Fig.10 In FIG. 1 , the applicable position when the resin 25 and the reinforcing plate 27 are provided on the housing bottom 15 is indicated by gray. In addition, the configuration example of the resin 25 and the reinforcing plate 27 in this case is shown in FIG. Fig. 9 (b) Fig. 9 (c). In this case, as in the other examples, the surface rigidity of the housing bottom 15 can be improved by pasting or coating the resin 25 on the inner surface or the outer surface of the housing bottom 15 and arranging the reinforcing plate 27 so as to cover the resin 25. In these other embodiments, the preferred thickness of the resin 25, the plate thickness of the reinforcing plate 27, the tensile strength, the bonding strength, etc. are also the same as those in the above-mentioned embodiments.

[0057] As described above, according to the present embodiment, the rigidity of the lower portion 3 of the battery case is improved, the deformation of the battery case 1 during a side collision is suppressed compared to the prior art, and the battery case 1 can be made lighter. In addition, by improving the rigidity of the battery case 1 itself, the battery case cross beam 23, which is a reinforcing member of the battery case 1, is made thinner or the number of the battery case cross beams 23 is reduced, thereby further lightweighting can be expected. In addition, since the appearance of the battery case 1 is hardly changed in the present embodiment, neither the degree of freedom of vehicle design nor the battery loading volume is reduced. The present embodiment can also improve vibration damping. This point will be described in detail in Example 1 described later.

[0058] In the above-mentioned embodiment, the example in which the resin 25 and the reinforcing plate 27 are provided on any one of the inner and outer surfaces of the case front and rear longitudinal walls 17, the case left and right longitudinal walls 19, and the case bottom 15 of the battery case lower part 3 is shown, but the present invention is not limited thereto. The resin 25 and the reinforcing plate 27 may be provided on the inner and outer surfaces of the case front and rear longitudinal walls 17, the case left and right longitudinal walls 19, and the case bottom 15, respectively. In addition, although the resin 25 and the reinforcing plate 27 may be provided on at least any one of the case front and rear longitudinal walls 17, the case left and right longitudinal walls 19, and the case bottom 15, the resin 25 and the reinforcing plate 27 may be provided on any two or all of them.

[0059] [Implementation Method 2]

[0060] In the first embodiment, resin 25 and reinforcing plate 27 are provided on the case front and rear vertical wall portions 17, the case left and right vertical wall portions 19, and the case bottom 15 of the battery case lower portion 3, thereby increasing the surface rigidity of the portions and increasing the rigidity of the battery case 1 to prevent deformation. In the present embodiment, an example is described in which the collision energy absorption performance (EA) of the case flange portion 21 is increased by providing resin 25 and reinforcing plate 27 on the case flange portion 21 of the battery case lower portion 3, thereby preventing deformation of the battery case 1.

[0061] The battery case 31 of this embodiment is composed of the same components as those described in the first embodiment, and only the positions of the resin 25 and the reinforcing plate 27 are different. Therefore, the same reference numerals as those in the first embodiment are given to each component and the description thereof is omitted. Fig.11 , Fig.12 The positions where the resin 25 and the reinforcing plate 27 are provided will be described.

[0062] The battery case 31 of this embodiment is provided at the case flange portion 21 ( Fig.11 (a) and Fig.12 The gray portion is provided with a resin 25 and a reinforcing plate 27. Specifically, Fig.11 As shown in (b) , a resin 25 is pasted or applied to the lower surface of the case flange portion 21 (the surface opposite to the upper portion of the battery case), and a reinforcing plate 27 arranged to cover the resin 25 is bonded to the resin 25 .

[0063] The upper surface of the case flange portion 21 is a portion joined to the flange portion of the battery case upper portion 5 (see Fig.12), therefore, if the resin 25 and the reinforcing plate 27 are provided on the upper surface of the housing flange portion 21, the airtightness (sealing performance) of the battery housing 1 may be reduced. Therefore, when the resin 25 and the reinforcing plate 27 are provided on the housing flange portion 21, they are provided only on the lower surface of the housing flange portion 21. In addition, even when the resin 25 is provided on the lower surface of the housing flange portion 21, if the end of the reinforcing plate 27 covering the resin 25 is wound from the lower surface of the housing flange portion 21 to the upper surface and spot-welded on the upper surface, it is not preferred from the viewpoint of the airtightness mentioned above. Therefore, it is possible to Fig.11 As shown in (b), the end portions of the reinforcing plate 27 are fixed to the lower surface of the case flange portion 21 and the case left and right vertical walls 19 .

[0064] By providing the resin 25 and the reinforcing plate 27 on the shell flange portion 21 as described above, the collision energy absorption performance of the shell flange portion 21 during a side collision can be improved. This point will be described in detail below.

[0065] The housing flange 21 is a portion for joining the battery housing upper portion 5 to the battery housing lower portion 3, and is Figure 6 As shown in (b), it also has the function of generating axial crush when a collision occurs on the side of the vehicle, and absorbing the collision energy through the axial crush. Specifically, when a collision load is input, the shell flange portion 21 is repeatedly buckled in a bellows-shaped manner to generate axial crush, thereby absorbing the collision energy. If a fracture occurs in the bent portion that has undergone the buckling deformation during the axial crushing process, the collision energy absorption effect is significantly reduced. Therefore, by preventing the shell flange portion 21 from breaking when the axial crushing occurs, the collision energy absorption performance of the shell flange portion 21 can be improved.

[0066] In this regard, since the battery case 31 of this embodiment has resin bonded to the lower surface of the case flange 21, when the case flange 21 is buckled and deformed in a wrinkled shape, the resin is sandwiched between the metal plates at the curved portion of the wrinkled shape. As a result, the bending radius of the curved portion becomes larger, making it difficult to cause cracks.

[0067] The housing flange 21 is formed around the entire periphery of the battery housing lower portion 3, but the portion formed at the upper ends of the housing left and right vertical walls 19 is likely to be axially crushed during a side collision (see Figure 6 (b)) Therefore, if the resin 25 and the reinforcing plate 27 are provided at least on the lower surface of the case flange portion 21 formed at the upper end of the case left and right vertical wall portions 19, the collision energy absorption performance during a side collision can be improved.

[0068] In the first embodiment, it is explained that by setting the bonding strength of the resin 25 to 5 MPa or more, the resin is difficult to peel off until the bending radius is about 90°, but in the present embodiment, since the resin is provided at the portion that is axially crushed, it is preferable to set the bonding strength to be higher. For example, if the bonding strength between the resin 25 and the housing flange 21 and between the resin 25 and the reinforcing plate 27 is 10 MPa or more, the resin 25 is difficult to peel off even when the housing flange 21 is axially crushed, which is effective.

[0069] As described above, according to the present embodiment, by providing the resin 25 and the reinforcing plate 27 on the lower surface of the housing flange portion 21, the collision energy absorption performance of the housing flange portion 21 can be improved. By improving the collision energy absorption performance of the housing flange portion 21, the load input to other parts of the battery housing lower portion 3 is reduced, and deformation of the battery housing 31 can be prevented. Thus, as in the first embodiment, the battery housing 31 and the battery housing cross beam 23 can be thinned, and lightweighting can also be expected. In addition, since the appearance of the battery housing 31 is hardly changed in the present embodiment, neither the degree of freedom of vehicle design nor the battery loading volume is reduced. Moreover, the present embodiment can also improve vibration damping. This point will be specifically described in Example 2 described later.

[0070] The resin 25 and the reinforcing plate 27 may be provided at both the position described in the first embodiment and the position described in the second embodiment. That is, the resin 25 and the reinforcing plate 27 may be provided at least at any one of the inner and outer surfaces of the case front and rear vertical walls 17, the case left and right vertical walls 19, and the case bottom 15 of the battery case lower portion 3, and the resin 25 and the reinforcing plate 27 may also be provided on the lower surface of the case flange portion 21. Thus, the load input to the front and rear vertical walls of the battery case lower portion 3 and the like can be reduced, and the rigidity of the battery case lower portion 3 can also be increased, so that deformation of the battery case can be further prevented.

[0071] Example 1

[0072] A specific study was conducted to evaluate the effects of the battery case 1 described in the first embodiment, and the results are described. In this embodiment, as an index for evaluating rigidity (endurance until deformation begins), the surface rigidity when a resin and a reinforcing plate are applied to the case front and rear vertical walls 17, the case left and right vertical walls 19, or the case bottom 15 is calculated (inventive examples 1 to 5). In addition, in order to compare the rigidity of the battery case with that of the prior art, the surface rigidity of the battery case composed only of a steel plate is also calculated and compared (comparative example 1).

[0073] In addition, in order to evaluate the vibration characteristics of the above-mentioned invention examples and comparative examples, a test body of 100×300mm (wherein the resin range in the case of the invention example is 100×250mm) was prepared, and an impact vibration test (impact vibration test) using an impact hammer was carried out. In the impact vibration test, an acceleration sensor (acceleration sensor) is installed near the edge of the side where the resin is not set in the suspended thick plate (equivalent to the component of the battery case) as the test body, and an impact vibration is performed near the edge of the opposite side (the side where the resin is set) using an impact hammer. Then, the exciting force (impact force) obtained from the impact hammer and the acceleration (acceleration) measured by the acceleration sensor are input into an FFT (Fast Fourier Transform) analyzer to calculate the acceleration (Accelerance) (m / s 2 The frequency response function is obtained by averaging the results of five impact tests.

[0074] Table 1 shows the details of the inventive examples and comparative examples, as well as the calculated surface rigidity and the results of the impact vibration test.

[0075] [Table 1]

[0076] The "weight" in Table 1 is the weight of the entire battery case lower portion 3 when the resin and the reinforcing plate are arranged in the position shown in the "reinforcement position" in the configuration shown in the "resin / reinforcing plate configuration". The "surface rigidity" is calculated based on the calculation formula shown in the above formula (1). In addition, the "vibration reduction" is the value of acceleration (Accelerance) at a frequency of 200 Hz obtained by the impact vibration test.

[0077] Comparative Example 1 is a structure composed of steel plates only, and the battery case lower part 3 is composed of a steel plate with a tensile strength of 440 MPa and a plate thickness of 1.4 mm. As shown in Table 1, in Comparative Example 1, the weight is 31.7 kg, and the surface rigidity of each part is 0.5×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 300m / s 2 / N.

[0078] Inventive Example 1 A steel plate having a tensile strength of 440 MPa and a thickness of 1.0 mm is used to form the lower portion 3 of the battery housing. Figure 1As shown in (b), the front and rear vertical walls 17 of the housing are provided with a 2 mm thick resin 25 and a reinforcing plate 27 which is a steel plate with a tensile strength of 270 MPa and a thickness of 0.4 mm. In this case, the weight is 24.0 kg, and the surface rigidity of the front and rear vertical walls 17 of the housing is 4.6×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 3m / s 2 / N. Compared with Comparative Example 1, this example is 7.7 kg lighter (24.3% lighter), and the surface rigidity of the housing front and rear vertical walls 17 is increased by 9.2 times, and the vibration can be suppressed to 1 / 100.

[0079] Invention Example 2 Figure 1 The resin 25 and the reinforcing plate 27 are provided as shown in (e), and the other conditions are the same as those of the invention example 1. In this case, the weight is 24.2 kg, and the surface rigidity of the front and rear vertical walls 17 of the housing is 4.6×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 3m / s 2 / N. Compared with Comparative Example 1, this example is 7.5 kg lighter (23.7% lighter), and the surface rigidity of the housing front and rear vertical walls 17 is increased by 9.2 times, and the vibration can be suppressed to 1 / 100.

[0080] Inventive Example 3 A steel plate with a tensile strength of 440 MPa and a thickness of 1.0 mm is used to form the lower portion 3 of the battery housing. Figure 7 As shown in (c), the left and right vertical walls 19 of the housing are provided with a resin 25 with a thickness of 1 mm and a steel plate 27 with a tensile strength of 270 MPa and a thickness of 0.4 mm. In this case, the weight is 24.2 kg, and the surface rigidity of the left and right vertical walls 19 of the housing is 1.9×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 5m / s 2 / N. Compared with Comparative Example 1, this example is 7.5 kg lighter (23.7% lighter), and the surface rigidity of the left and right vertical walls 19 of the housing is increased by 3.9 times, and the vibration can be suppressed to 1 / 60.

[0081] Invention Example 4 Figure 7 The resin 25 and the reinforcing plate 27 are provided as shown in (d), and the other conditions are the same as those of the invention example 3. In this case, the weight is 24.5 kg, and the surface rigidity of the left and right vertical walls 19 of the housing is 1.9×10 -7 GPa·m 4The acceleration (Accelerance) at 200Hz obtained by the impact test is 5m / s 2 / N. Compared with Comparative Example 1, this example is 7.2 kg lighter (22.7% lighter), and the surface rigidity of the left and right vertical walls 19 of the housing is increased by 3.9 times, and the vibration can be suppressed to 1 / 60.

[0082] Inventive Example 5 A steel plate having a tensile strength of 440 MPa and a thickness of 0.8 mm is used to form the lower portion 3 of the battery housing. Fig. 9 As shown in (d), the housing bottom 15 is provided with a 2 mm thick resin 25 and a reinforcing plate 27 which is a steel plate with a tensile strength of 270 MPa and a thickness of 0.2 mm. In this case, the weight is 28.2 kg, and the surface rigidity of the housing bottom 15 is 2.2×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 7m / s 2 / N. Compared with Comparative Example 1, this example is 3.5 kg lighter (11.0% lighter), and the surface rigidity of the housing bottom is increased by 4.5 times, and the vibration can be suppressed to 1 / 43.

[0083] As described above, the inventive examples 1 to 5 are lighter than the comparative example 1, and the surface rigidity and vibration damping performance of the portion provided with the resin 25 and the reinforcing plate 27 are greatly improved. Since the rigidity of the battery case lower part 3 itself is improved as long as the surface rigidity of at least one of the case front and rear vertical wall portions 17, the case left and right vertical wall portions 19, and the case bottom 15 of the battery case lower part 3 is improved, the deformation of the battery case 1 can be suppressed.

[0084] Example 2

[0085] A specific study was conducted to evaluate the effect of the battery case 31 described in Embodiment 2, and the results are described. In this embodiment, as an indicator for evaluating the collision energy absorption performance (EA), the buckling load when the resin 25 and the reinforcing plate 27 are applied to the case flange portion 21 is calculated (Invention Examples 6 and 7). In addition, in order to compare the collision energy absorption performance of the battery case of the prior art, the buckling load of the battery case composed only of a steel plate was also calculated and compared (Comparative Example 2). In this embodiment, the surface rigidity was calculated in the same manner as in Example 1, and an impact vibration test was performed.

[0086] Table 2 shows the details of the inventive examples and comparative examples, as well as the above-calculated buckling load, surface rigidity, and impact vibration test results.

[0087] [Table 2]

[0088] The calculation methods of “weight”, “surface rigidity” and “vibration reduction” in Table 2 are the same as those in Example 1. “Buckling load” is calculated based on the following formula (2).

[0089] Pcr=C×π 2 ×E×I / l 2 …… (2) Pcr: Buckling load [N] C: coefficient of fixity E: Young's modulus [GPa] I: Sectional moment of inertia [m 4 ] l: effective length of column [m] Assume C=0.25, E×I=the value of “surface rigidity”, and l=0.02.

[0090] Comparative Example 2 is an example of a structure consisting only of a steel plate, and is an example of the same conditions as Comparative Example 1 in Table 1. Comparative Example 2 is the same as Comparative Example 1, with a weight of 31.7 kg and a surface rigidity of 0.5×10 -7 GPa·m 4 The acceleration (Accelerance) at 200Hz obtained by the impact test is 300m / s 2 / N, the buckling load is 0.3×10 -10 N.

[0091] Inventive Example 6 A steel plate having a tensile strength of 440 MPa and a thickness of 1.0 mm is used to form the lower portion 3 of the battery housing. Fig.11 As shown in (b), a 2 mm thick resin 25 and a 0.4 mm thick steel plate, i.e., a reinforcing plate 27, are provided around the entire lower surface of the housing flange 21. In this case, the weight is 24.1 kg, and the surface rigidity of the housing flange 21 is 4.6×10 -7 GPa·m 4 , the buckling load is 2.81×10 -10 N, the acceleration (Accelerance) at 200Hz obtained by impact test is 3m / s 2 / N. The buckling load of the housing flange 21 is increased in this example compared with Comparative Example 2. In addition, the weight is reduced by 7.6 kg (24.0% reduction rate) compared with Comparative Example 2, and the surface rigidity of the housing flange 21 is increased by 9.2 times, and the vibration can be suppressed to 1 / 100.

[0092] Inventive Example 7 A steel plate having a tensile strength of 440 MPa and a thickness of 0.8 mm is used to form the lower portion 3 of the battery housing. Fig.11 As shown in (b), a 1 mm thick resin 25 and a 0.4 mm thick steel plate, i.e., a reinforcing plate 27, are provided around the entire lower surface of the housing flange portion 21. Figure 1 (b) Figure 7 As shown in (b), resin 25 and reinforcing plate 27 are also provided on the housing front and rear vertical walls 17 and the housing left and right vertical walls 19. In this case, the weight is 22.5 kg, and the surface rigidity of the part provided with resin 25 and reinforcing plate 27 is 1.5×10 -7 GPa·m 4 , the buckling load is 0.94×10 -10 N, the acceleration (Accelerance) at 200Hz obtained by impact test is 10m / s 2 / N. Compared with Comparative Example 2, the buckling load of the part where the resin 25 is provided is increased, and the surface rigidity is increased by 3 times. Therefore, in this example, the collision energy absorption performance of the housing flange portion 21 is improved, and the rigidity of the battery housing lower portion 3 is also improved, so it is effective when the deformation prevention effect of the battery housing is to be further improved. In this case, the weight is also reduced by 9.2 kg (lightening rate 29.0%) compared with Comparative Example 2, and the vibration can be suppressed to 1 / 30.

[0093] As described above, the inventive examples 6 and 7 are lighter than the comparative example 2, and the surface rigidity, buckling load and vibration damping performance of the part where the resin 25 and the reinforcing plate 27 are provided are greatly improved. Since the energy absorption performance of the housing flange 21 is improved as long as the buckling load of the housing flange 21 of the battery housing lower part 3 is improved, the load input to other parts of the battery housing lower part 3 can be reduced, and the deformation of the battery housing can be suppressed. In addition, by providing the resin 25 and the reinforcing plate 27 on at least one of the housing front and rear longitudinal walls 17, the housing left and right longitudinal walls 19, and the housing bottom 15 in addition to the housing flange 21, the rigidity of the battery housing lower part 3 itself is also improved, so the deformation of the battery housing can be further suppressed.

[0094] Example 3

[0095] As shown in Examples 1 and 2, by applying the present invention, the rigidity of the battery case lower portion 3 and the energy absorption performance of the case flange portion 21 are improved, and the deformation of the battery case can be suppressed. In addition, in order to maximize the above-mentioned effects, it is preferred that the resin 25 does not peel off from the battery case lower portion 3 and the reinforcing plate 27 during the deformation process as described in the embodiment. Therefore, in the present invention, the preferred bonding strength of the resin 25 is set to 5 MPa or more.

[0096] Therefore, in this example, the effect of setting the adhesive strength of the resin 25 to 5 MPa or more was confirmed, and the result will be described.

[0097] In this embodiment, a collision analysis based on the finite element method is performed to analyze the collision between the side of the vehicle body and the pillar (see Figure 6 ) was evaluated for the amount of intrusion (offset amount) of the column into the lower part of the battery case (column intrusion amount, deformation amount of the left and right longitudinal walls 19 of the case in the lower part of the battery case). The column collided with the side of the vehicle body at a collision speed of 32 km / h in a direction perpendicular to the front-rear direction of the vehicle. The lower part 3 of the battery case is composed of a steel plate with a tensile strength of 440 MPa and a plate thickness of 1.0 mm, the resin 25 is 2 mm thick, and the reinforcing plate 27 is a steel plate with a tensile strength of 270 MPa and a plate thickness of 0.4 mm. The results of the reinforcement position and bonding strength based on the resin 25 of the invention example and the comparative example, and the amount of intrusion of the column into the lower part of the battery case are shown in Table 3.

[0098] [Table 3]

[0099] Comparative Example 3 is an example in which the lower portion 3 of the battery case is formed only of a steel plate. As shown in Table 3, the column intrusion amount of Comparative Example 3 is 30.0 mm. Figure 1 As shown in (c), the resin 25 and the reinforcing plate 27 are provided on the case front and rear vertical walls 17. Furthermore, the bonding strength between the resin 25 and the battery case lower part 3 and the reinforcing plate 27 is 3.6 MPa, which is outside the preferred range (<5 MPa). In this case, the column intrusion amount is 28.5 mm, which is an improvement of 1.5 mm (5.0%) compared with Comparative Example 3.

[0100] In contrast, in Example 8, the resin 25 and the reinforcing plate 27 are provided at the same position as in Comparative Example 4, and the bonding strength is set to 7.9 MPa, which is within the preferred range (≥5 MPa). In this case, the column intrusion amount is 12.4 mm, and the improvement over Comparative Example 3 is 17.6 mm (58.8%). By setting the bonding strength to 5 MPa or more, the improvement over Comparative Example 3 is about 12 times that of Comparative Example 4, and the column intrusion amount can be significantly reduced.

[0101] Comparative Example 5 Figure 7As shown in (c), resin 25 and reinforcing plate 27 are provided on the left and right vertical walls 19 of the case. Furthermore, the bonding strength between resin 25, battery case lower portion 3 and reinforcing plate 27 is 4.9 MPa, which is outside the preferred range (<5 MPa). In this case, the column intrusion amount is 28.8 mm, which is an improvement of 1.2 mm (4.0%) compared to Comparative Example 3.

[0102] In contrast, in Example 9, the resin 25 and the reinforcing plate 27 are provided at the same position as in Comparative Example 5, and the bonding strength is set to 6.5 MPa, which is within the preferred range (≥5 MPa). In this case, the column intrusion amount is 15.9 mm, and the improvement over Comparative Example 3 is 14.1 mm (47.1%). By setting the bonding strength to 5 MPa or more, the column intrusion amount can be significantly reduced compared to Comparative Example 5 in which the reinforcement position is the same.

[0103] Comparative Example 6 Fig. 9 As shown in (c), the resin 25 and the reinforcing plate 27 are provided on the case bottom 15. The bonding strength between the resin 25 and the battery case lower portion 3 and the reinforcing plate 27 is 3.0 MPa, which is outside the preferred range (<5 MPa). In this case, the column intrusion amount is 29.3 mm, which is an improvement of 0.7 mm (2.5%) compared to Comparative Example 3.

[0104] In contrast, in Example 10 of the invention, the resin 25 and the reinforcing plate 27 are provided at the same position as in Comparative Example 6, and the bonding strength is set to 5.4 MPa, which is within the preferred range (≥5 MPa). In this case, the column intrusion amount is 21.2 mm, and the improvement over Comparative Example 3 is 8.8 mm (29.4%). By setting the bonding strength to 5 MPa or more, the column intrusion amount can be significantly reduced compared with Comparative Example 6 in which the reinforcement position is the same.

[0105] Comparative Example 7 Fig.11 As shown in (b), resin 25 and reinforcing plate 27 are provided around the entire lower surface of the housing flange 21. Furthermore, the bonding strength between the resin 25 and the battery housing lower portion 3 and the reinforcing plate 27 is 4.9 MPa, which is outside the preferred range (<5 MPa). In this case, the column intrusion amount is 29.4 mm, which is an improvement of 0.6 mm (2.0%) compared to Comparative Example 3.

[0106] In contrast, in Inventive Example 11, resin 25 and reinforcing plate 27 are provided at the same position as Comparative Example 7, and the bonding strength is set to 11.4 MPa, which is within the preferred range (≥5 MPa). In this case, the column intrusion amount is 22.9 mm, which is an improvement of 7.1 mm (23.5%) over Comparative Example 3. By setting the bonding strength to 5 MPa or more, the column intrusion amount can be significantly reduced compared with Comparative Example 7 in which the reinforcement position is the same.

[0107] In Comparative Example 8, the housing front and rear vertical walls 17 ( Figure 1 (c)), the left and right vertical walls 19 of the housing ( Figure 7 (c)), shell bottom 15 ( Fig. 9 (c)) and the entire circumference of the lower surface of the housing flange portion 21 ( Fig.11 (b) The resin 25 and the reinforcing plate 27 were provided at 4.6 MPa, which is outside the preferred range (<5 MPa). In this case, the column intrusion amount was 26.0 mm, and the improvement over Comparative Example 3 was 4.0 mm (13.4%).

[0108] In contrast, in Inventive Example 12, the resin 25 and the reinforcing plate 27 were provided at the same position as in Comparative Example 8 with an adhesive strength of 11.6 MPa. In this case, the column intrusion amount was 0.0 mm, and the improvement amount relative to Comparative Example 3 was 30.0 mm (100.0%). By setting the adhesive strength to 5 MPa or more, the column intrusion amount can be significantly reduced compared with Comparative Example 12 with the same reinforcement position.

[0109] exist Fig.13 , the intrusion amount of the column into the lower part of the battery case in the above-mentioned Inventive Examples 8 to 12 and Comparative Examples 3 to 8 is shown in a graph. Thus, it can be confirmed that by setting the bonding strength to 5 MPa or more, the resin 25 will not be peeled off from the various reinforcement positions and the reinforcement plate 27 of the lower part of the battery case even when bending deformation occurs, and a large surface rigidity or energy absorption performance can be maintained, thereby reducing the deformation of the battery case.

[0110] Industrial Applicability

[0111] According to the present invention, it is possible to provide a battery case which has higher rigidity and strength than conventional ones and is excellent in vibration damping properties without requiring a significant increase in weight, an increase in manufacturing cost, or a change in vehicle structure.

[0112] Description of symbols 1 Battery Case (Implementation 1) 3 Lower part of battery housing 5 Upper part of battery housing 7 Floor 9 Side beam 11. Fixing parts 13 Floor beams 15 Shell bottom 17 Shell front and rear longitudinal walls 19 Shell left and right vertical walls 21 Shell flange 23 Battery housing crossbeam 25 Resin 27 Reinforcement plate 29 columns 31 Battery case (Embodiment 2).

Claims

1. A battery case, comprising: a battery case lower portion having a rectangular shape, mounted under a floor of a vehicle body and storing a battery; and a battery case upper portion, arranged to cover an upper surface of the battery case lower portion, wherein: The lower part of the battery case comprises: a case bottom; a case front and rear longitudinal wall part and a case left and right longitudinal wall part, which are erected on the periphery of the case bottom; and a case flange part, which is formed on the upper ends of the case front and rear longitudinal wall part and the case left and right longitudinal wall part toward the outside and is joined to the upper part of the battery case. Resin is pasted or applied to the inner surface and / or outer surface of at least one of the front and rear longitudinal walls of the housing, the left and right longitudinal walls of the housing, and the bottom of the housing, and a reinforcing plate arranged to cover the resin is bonded to the resin.

2. The battery casing according to claim 1, wherein: A resin is pasted or applied to at least the surface of the case flange portion formed at the upper ends of the left and right vertical walls of the case opposite to the upper portion of the battery case, and a reinforcing plate arranged so as to cover the resin is bonded to the resin.

3. A battery case, comprising: a battery case lower portion having a rectangular shape, mounted under the floor of a vehicle body and storing a battery; and a battery case upper portion, arranged to cover an upper surface of the battery case lower portion, wherein: The lower part of the battery case comprises: a case bottom; a case front and rear longitudinal wall part and a case left and right longitudinal wall part, which are erected on the periphery of the case bottom; and a case flange part, which is formed on the upper ends of the case front and rear longitudinal wall part and the case left and right longitudinal wall part toward the outside and is joined to the upper part of the battery case. A resin is pasted or applied to at least the surface of the case flange portion formed at the upper ends of the left and right vertical walls of the case opposite to the upper portion of the battery case, and a reinforcing plate arranged so as to cover the resin is bonded to the resin.

4. The battery housing according to any one of claims 1 to 3, wherein: The thickness of the resin is 0.1 to 5 mm, the thickness of the reinforcing plate is 0.15 to 1.0 mm, and the bonding strength between the resin and the lower portion of the battery housing and the reinforcing plate is greater than 5 MPa.

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