Battery module

Abstract

The present invention relates to a battery module. An end plate (300) includes a recess (310) opening toward a restraining member (400). The restraining member (400) has a through-hole (410) communicating with the recess (310). A bolt (500) includes a first portion (510) passing through the through-hole (410) and the recess (310) and a second portion (520) located on a front end side of the first portion (510). A gap is formed between the first portion (510) of the bolt (500) and the through-hole (410) and the recess (310), and the second portion (520) of the bolt (500) is threadedly engaged with the end plate (300). The length of the first portion (510) of the bolt (500) is 40% or more of the nominal length of the bolt (500).

Description

Technical Field

[0001] This technology relates to battery modules. Background Technology

[0002] As described in Japanese Patent Application Publication No. 2020-047573, in the past, an end plate was provided at the end of the stack of single cells, and the constraint member that constrains the single cell in the stacking direction was fastened to the end plate by bolts.

[0003] Japanese Patent Application Publication No. 2005-315387 discloses the use of bolts for fixing parts of the driving-side rotating body and the driven-side rotating body. Summary of the Invention

[0004] When multiple components are fastened with bolts, due to factors such as differences in the coefficients of linear expansion between the components, a load in the deflection direction applied to the bolt may exert a force in the slack direction on the bolt seating surface. To suppress bolt slack, the fastening structure can be enlarged by lengthening the threaded joint. With an enlarged fastening structure, the thickness of the end plate increases, which also involves the enlargement of the battery module. The objective of this technology is to provide a miniaturized battery module.

[0005] The battery module involved in this technology comprises: a laminate including a plurality of individual cells arranged along a first direction; an end plate disposed at an end of the laminate in the first direction; a constraint member fastened to the end plate, constraining the laminate and the end plate in the first direction; and a bolt for fastening the end plate and the constraint member. The end plate includes a recess opening toward the constraint member. The constraint member has a through hole communicating with the recess. The bolt includes a first portion passing through the through hole and the recess, and a second portion located at the front end side of the first portion. A gap is formed between the first portion of the bolt and the through hole and the recess, and the second portion of the bolt is threadedly engaged with the end plate. The length of the first portion of the bolt is more than 40% of the nominal length of the bolt.

[0006] The above and other objects, features, aspects, and advantages of the invention will become clear from the following detailed description relating to the invention in conjunction with the accompanying drawings. Attached Figure Description

[0007] Figure 1 This is a 3D view of the battery module.

[0008] Figure 2 This is a 3D diagram showing the individual cells included in the battery module.

[0009] Figure 3 This is a diagram showing the constrained components included in the battery module.

[0010] Figure 4This diagram shows the state of the fastening structure between the end plate and the constraint component as viewed from the stacking direction (first direction) of a single cell.

[0011] Figure 5 This is a cross-sectional view of the fastening structure involved in the reference example.

[0012] Figure 6 This is a cross-sectional view of the fastening structure involved in one embodiment.

[0013] Figure 7 It means Figure 6 The cross-sectional view shown is of the deformed fastening structure.

[0014] Figure 8 It is a diagram used to illustrate the structure around the bolt.

[0015] Figure 9 This is a diagram showing a bolt in a deformed state.

[0016] Figure 10 It is a diagram showing the state of the fastener involved in the modified example after it has been deformed.

[0017] Figure 11 It is a diagram showing the relationship between the depth of the recess and the reaction force acting on the bolt support surface.

[0018] Figure 12 This is a diagram showing the relationship between the length of the non-fastening part and the nominal length of the bolt (underhead length). Detailed Implementation

[0019] The following describes the implementation of this technology. Wherein, the same or equivalent parts are labeled with the same reference numerals in the accompanying drawings, and sometimes their descriptions are not repeated.

[0020] In the embodiments described below, unless otherwise specified, the scope of this technology is not necessarily limited to the number, quantity, etc., when they are mentioned. Furthermore, in the embodiments described below, each constituent element is not necessarily essential to this technology unless otherwise specified. Additionally, this technology is not limited to necessarily achieving all the effects mentioned in this embodiment.

[0021] Furthermore, in this specification, the terms "comprise," "include," and "have" are open-ended. That is, when a structure is included, other structures besides that structure may be included, or other structures besides that structure may not be included.

[0022] Furthermore, when using geometric terms and terms indicating positional / directional relationships, such as "parallel," "orthogonal," "tilted at 45°," "coaxial," and "along," these terms allow for manufacturing errors or slight variations. When using terms indicating relative positional relationships, such as "upper side" and "lower side," these terms are used as terms indicating relative positional relationships in one state, and the relative positional relationships may be reversed or rotated to any angle depending on the setting direction of each mechanism (e.g., reversing the overall vertical orientation of the mechanism).

[0023] In this specification, "battery" is not limited to lithium-ion batteries, but may include other batteries such as nickel-metal hydride batteries.

[0024] In this manual, "single battery" can be used in hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs). However, the application of "single battery" is not limited to vehicle use.

[0025] Figure 1 This is a perspective view of battery module 1 (excluding the constraint component 400 described later). Figure 1 As shown, battery module 1 includes a single battery 100, a separator component 200, and an end plate 300.

[0026] Each cell 100 is a square cell, and multiple such cells are arranged along the Y-axis direction (first direction). A separator component 200 is disposed between the multiple cells 100. The separator component 200 prevents unwanted electrical conduction between adjacent cells 100. The separator component 200 ensures electrical insulation between adjacent cells 100. End plates 300 are disposed at both ends of the stack of cells 100 and separator components 200 along the Y-axis direction. The end plates 300 are fixed to a base such as a housing of the battery module 1.

[0027] Figure 2 This is a 3D diagram representing a single battery (100). For example... Figure 2 As shown, the single cell 100 has a square shape. The single cell 100 has electrode terminals 110, a frame 120, and a gas discharge valve 130.

[0028] Electrode terminals 110 are formed on the frame 120. Electrode terminals 110 have positive terminals 111 and negative terminals 112 arranged along an X-axis direction (second direction) orthogonal to the Y-axis direction (first direction). Positive terminals 111 and negative terminals 112 are separated from each other in the X-axis direction.

[0029] The frame 120 has a cuboid shape, forming the appearance of the single battery 100. The frame 120 includes a housing body 120A that houses electrodes (not shown) and electrolyte, and a sealing plate 120B that seals the opening of the housing body 120A. The sealing plate 120B is joined to the housing body 120A by welding.

[0030] The frame 120 has an upper surface 121, a lower surface 122, a first side 123, a second side 124, and two third side surfaces 125.

[0031] The upper surface 121 is a plane orthogonal to the Z-axis direction (the third direction), which is orthogonal to both the Y-axis and X-axis directions. Electrode terminals 110 are disposed on the upper surface 121. The lower surface 122 is opposite to the upper surface 121 along the Z-axis direction.

[0032] Each of the first side 123 and the second side 124 is composed of a plane orthogonal to the Y-axis. Each of the first side 123 and the second side 124 has the largest area among the multiple sides of the frame 120. Each of the first side 123 and the second side 124 has a rectangular shape when viewed along the Y-axis. Each of the first side 123 and the second side 124 has a rectangular shape with the X-axis as the longer side and the Z-axis as the shorter side when viewed along the Y-axis.

[0033] Multiple individual cells 100 are stacked such that adjacent individual cells 100, 100 in the Y-axis direction have their first side 123 facing each other and their second side 124 facing each other. Thus, in the Y-axis direction where the multiple individual cells 100 are stacked, the positive terminal 111 and the negative terminal 112 are arranged alternately.

[0034] A gas discharge valve 130 is provided on the upper surface 121. In the event of an abnormal temperature rise in the single cell 100 (thermal runaway) or the internal pressure of the frame 120 exceeding a specified value due to gas generated inside the frame 120, the gas discharge valve 130 discharges the gas to the outside of the frame 120.

[0035] Figure 3 This is a diagram representing constraint component 400. (For example...) Figure 3 As shown, the constraint member 400 connects the two end plates 300 to each other. The constraint member 400 is engaged with the end plates 300 under a Y-axis compressive force applied to the stack of multiple individual cells 100, separator member 200, and end plates 300. Then, the compressive force is released, thereby applying a tensile force to the constraint member 400 that connects the two end plates 300. In response, the constraint member 400 presses the two end plates 300 towards each other.

[0036] Figure 4This diagram shows the state of the fastening structure between the end plate 300 and the constraint member 400 as viewed from the Y-axis direction. Among them, in Figure 4 And the following Figures 5-10 In the illustration, the size of the 500 bolt is exaggerated and depicted as very large.

[0037] like Figure 4 As shown, the end plate 300 and the constraint member 400 are fastened together by bolts 500. Multiple bolts 500 are arranged in the Z-axis direction (two in this embodiment). The bolts 500 are arranged along the Y-axis direction to fasten the end plate 300 and the constraint member 400.

[0038] Thus, the battery module 1 includes: a stacked body including a plurality of single cells 100 arranged along the Y-axis direction; an end plate 300 disposed at the end of the stacked body in the Y-axis direction; a constraint member 400 fastened to the end plate 300 to constrain the single cells 100, the separator member 200 and the end plate 300 in the Y-axis direction; and bolts 500 to fasten the end plate 300 to the constraint member 400.

[0039] Figure 5 This is a cross-sectional view of the fastening structure involved in the reference example. For example... Figure 5 As shown, the constraint component 400 has a through hole 410, and the bolt 500 is threadedly engaged with the end plate 300 through the through hole 410.

[0040] For example, when the end plate 300 is made of aluminum and the constraint member 400 is made of iron, a Z-direction offset occurs at the interface between the end plate 300 and the constraint member 400 due to the difference in their coefficients of linear expansion. Since the bolt 500 is threadedly engaged with the end plate 300, simultaneously with the Z-direction offset at the interface between the end plate 300 and the constraint member 400, the support surface of the bolt 500 and the constraint member 400 displace together, generating a flexural force. Relative to this flexural force, friction (vertical resistance × friction force = axial force × interface friction coefficient) acts on the interface between the bolt 500 support surface and the constraint member 400, which can, to some extent, suppress the offset of the interface between the constraint member 400 and the bolt support surface. When this flexural force (offset force) exceeds the friction force and the interface between the bolt 500 support surface and the constraint member 400 offsets, a relaxed rotational force is generated relative to the bolt 500 support surface. To prevent bolt 500 from loosening, while increasing axial force can improve friction, it is also necessary to ensure the strength of the threaded joint of bolt 500 and end plate 300. That is, the fastening structure can be enlarged by increasing the nominal length (threaded joint length) of bolt 500.

[0041] Figure 6 This is a cross-sectional view of the fastening structure involved in this embodiment. Figure 7 It means Figure 6The cross-sectional view shown is of the deformed fastening structure.

[0042] like Figure 6 , Figure 7 As shown, in the fastening structure according to this embodiment, the end plate 300 includes a recess 310 opening toward the restraint member 400, and the bolt 500 includes a first portion 510 (non-fastening portion) passing through the through hole 410 and the recess 310, and a second portion 520 (fastening portion) located at the front end side of the first portion 510. A gap is formed between the first portion 510 of the bolt 500 and the through hole 410 and the recess 310. The second portion 520 of the bolt 500 is threadedly engaged with the end plate 300.

[0043] In one embodiment, the end plate 300 is made of a material having a first coefficient of linear expansion. The constraint member 400 is made of a material having a second coefficient of linear expansion, different from the first coefficient of linear expansion. As an example, the end plate 300 is made of aluminum, and the constraint member 400 is made of iron. In this case, the coefficient of linear expansion of the end plate 300 is greater than that of the constraint member 400. Specifically, the coefficient of linear expansion of aluminum is about 23 μ / ℃, and that of iron is about 11.7 μ / ℃. Therefore, the coefficient of linear expansion of the end plate 300 is approximately twice that of the constraint member 400.

[0044] Thus, when the end plate 300 and the constraint component 400 have different coefficients of linear expansion, the amount of deformation between the end plate 300 and the constraint component 400 will differ when temperature changes occur during the use of the battery module 1.

[0045] In the fastening structure described in this embodiment, by forming a recess 310 of appropriate depth in the end plate 300, even if there is an offset in the contact surface direction between the end plate 300 and the restraining member 400, it is possible to achieve the desired fastening. Figure 7 As shown, the flexural force (offset force) between the restraint member 400 and the support surface of the bolt 500 is reduced by the flexure of the bolt 500, thus suppressing the offset. As a result, the reduction in the axial force of the bolt 500 can be suppressed without excessively increasing the nominal length of the bolt 500.

[0046] Figure 8 This is a diagram used to illustrate the construction around bolt 500. Figure 9 This is a diagram showing bolt 500 in a deformed state.

[0047] like Figure 8 As shown, the opening of the recess 310 has a first diameter (D1). The first diameter (D1) is obtained by the following equation (1).

[0048] First diameter (D1) ≥ Bolt diameter + ([coefficient of linear expansion of end plate 300] - [coefficient of linear expansion of constraint component 400]) × [distance between fastening positions of bolt 500] × [target temperature difference when battery module 1 is in use] × 2 = Bolt diameter + linear expansion amount × 2 ···(1)

[0049] For example, if the end plate 300 is made of aluminum and the restraint component 400 is made of iron, assuming the distance between the fastening positions of the bolts 500 is approximately 70 mm and the target temperature difference is approximately 45°C, then the linear expansion is approximately 0.07 mm. The first diameter (D1) is determined to be the amount of deflection that can pass through the bolts 500. Figure 9 The D in the middle is used to absorb the above linear expansion.

[0050] The through hole 410 of the constraint member 400 has a second diameter (D2). Figure 8 In the example, the second diameter (D2) is greater than the first diameter (D1). The second diameter (D2) can also be approximately the same as the first diameter (D1).

[0051] The length (H) of the first part 510 and the length (L) of the second part 520 of bolt 500 are determined to ensure the tightening force of bolt 500 while minimizing the nominal length (H+L) of bolt 500.

[0052] Figure 10 This is a diagram showing the deformed state of the fastening structure involved in the modified example. For example... Figure 10 As shown, the recess 310 of the end plate 300 may have a tapered shape with a diameter that expands outward (toward the head side of the bolt 500).

[0053] The recess 310 of the end plate 300 and the through hole 410 of the constraint member 400 typically have a generally circular shape when viewed from the Y-axis direction (in the X-Z plane). However, the shape of the recess 310 and the through hole 410 is not limited to this, for example, they may also have a shape that is longer in the Z-axis direction than in the X-axis direction.

[0054] Figure 11 This diagram illustrates the relationship between the depth of the recess 310 in the end plate 300 and the reaction force acting on the support surface of the bolt 500 in the relaxation direction during deformation caused by temperature changes. The second part 520 (fastening part) of the bolt 500 is threaded into the end plate 300, and the support surface of the bolt 500 displaces along with the restraint member 400 due to linear expansion, resulting in a flexural force (offset force) in the bolt 500. This flexural force (offset force) becomes the reaction force between the restraint member 400 and the support surface of the bolt 500 in the relaxation direction. Figure 11As shown, when the depth of the recess 310 is approximately 10 mm, the short deflection portion of the bolt 500 (high stiffness) results in a large reaction force in the relaxation direction acting on the support surface of the bolt 500 during deformation caused by temperature changes. Conversely, when the depth of the recess 310 is approximately 20 mm or more, the long deflection portion of the bolt 500 (low stiffness) reduces the reaction force in the relaxation direction acting on the support surface of the bolt 500 during deformation caused by temperature changes. Consequently, excessive strength enhancement of the fastening portion of the bolt 500 is unnecessary, allowing for a shorter bolt length. Therefore, the nominal length (H+L) of the bolt 500 can be shortened to miniaturize the fastening structure.

[0055] Figure 12 This is a diagram showing the relationship between the length (H) of the non-fastening part and the nominal length (H+L) of the bolt 500. Figure 12 In the example, for the nominal length (H+L) of bolt 500, the length of the second part 520, which can ensure the minimum required tightening force of bolt 500, will be taken into account, considering the deformation caused by temperature changes.

[0056] like Figure 12 As shown, when the length (H) of the first part 510 of the bolt 500 is about 40% to 80% (preferably about 50% to 70%) of the nominal length (H+L) of the bolt 500, the nominal length (H+L) of the bolt 500 can be shortened as a whole.

[0057] As explained above, in the battery module 1 of this embodiment, by forming a recess 310 of appropriate depth, the bolt 500 can be allowed to flex. As a result, even if a misalignment occurs in the contact surface (X-Z plane) direction between the end plate 300 and the constraint member 400 due to reasons such as the difference in the coefficient of linear expansion between the end plate 300 and the constraint member 400, the misalignment between the bolt 500 support surface and the constraint member 400 can be prevented by the flexure of the bolt 500, and the loosening of the bolt 500 (reduction of axial force) can be suppressed.

[0058] Embodiments of the present invention have been described, but it should be considered that the embodiments disclosed herein are illustrative rather than restrictive in all respects. The scope of the present invention is shown by the technical solutions claimed in this application, and is intended to include all modifications of the same meaning and scope as the technical solutions claimed in this application.

Claims

1. A battery module, characterized in that, include: A stack comprising a plurality of individual cells arranged along a first direction; An end plate is disposed at the end of the laminate in the first direction; A constraint component, fastened to the end plate, constrains the laminate and the end plate in the first direction; as well as Bolts are used to fasten the end plate to the constraint component. The bolt is positioned along the first direction. The end plate includes a recess that opens toward the constraint member. The constraint component has a through hole communicating with the recess. The bolt includes a first portion passing through the through hole and the recess, and a second portion located at the front end of the first portion. A gap is formed between the first portion of the bolt, the through hole, and the recess; the second portion of the bolt is threadedly engaged with the end plate. The length of the first portion of the bolt is more than 40% of the nominal length of the bolt.

2. The battery module according to claim 1, characterized in that, The opening of the recess has a first diameter, and the through hole has a second diameter that is larger than the first diameter.

3. The battery module according to claim 1 or 2, characterized in that, The end plate is made of a material having a first coefficient of linear expansion, and the constraint component is made of a material having a second coefficient of linear expansion that is different from the first coefficient of linear expansion.

4. The battery module according to claim 3, characterized in that, The end plate is made of aluminum, and the constraint component is made of iron.

5. The battery module according to claim 1 or 2, characterized in that, The single cell is a square secondary single cell.

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