Battery pack

Abstract

A battery pack (P) is provided with a battery module (M) in which a plurality of battery cells (C) are arranged between a pair of end plates (1), and a case (2) in which the battery module (M) is housed, and has a structure in which the end plates (1) are fixed to a bottom wall (3) of the case (2), and is configured such that at least a fixing portion (4) of the bottom wall (3) and the end plates (1) within the case (2) is covered by water-proof and electrically insulating insulators (5, 6). When water is immersed in the housing (2), the formation of a short circuit caused by ion conduction in the water is prevented.

Description

TECHNICAL FIELD

[0001] The present application relates to a battery pack in which a battery module in which a plurality of battery cells are arranged is housed in a case, and particularly relates to a battery pack having a function of suppressing short-circuit current at the time of water immersion. BACKGROUND

[0002] In the past, as the battery pack as described above, for example, there has been the battery pack described in Patent Literature 1. The battery pack described in Patent Literature 1 is a structure in which a plurality of battery modules are arranged and held between a pair of metal mounting members (end plates) in the up-and-down direction and each of the mounting members is fixed to the bottom wall of the case by a bolt. An annular insulating portion is inserted between the mounting member and the bolt, and the annular insulating portion has an upper tubular portion that houses the head portion of the bolt and a lower tubular portion through which the threaded portion of the bolt penetrates. Thus, in the battery pack, in addition to the direct conduction insulation between the mounting member and the bolt, in the case where condensation water adheres to the gap therebetween, the annular insulating portion is used to prevent short-circuiting between the mounting member and the bolt via the condensation water.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: WO2014 / 155995 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the conventional battery pack as described above, there is a problem point that, in the case where water immersion occurs in the case, the mounting member (end plate) and the head portion of the bolt are short-circuited due to ion conduction in the water, and a short-circuit circuit can be formed in the entire body including the battery modules, and it has been a subject to solve such a problem point.

[0008] The present application is made in view of the above-described conventional problem, and an object thereof is to provide a battery pack that has a configuration in which a plurality of battery modules in which a plurality of battery cells are arranged are arranged between a pair of end plates and a case that houses the battery modules, and in which, in the case where water immersion occurs in the case, formation of a short-circuit circuit due to ion conduction in the water is prevented.

[0009] MEANS FOR SOLVING THE PROBLEM

[0010] The battery pack of the present application has a configuration in which a plurality of battery modules in which a plurality of battery cells are arranged are arranged between a pair of end plates and a case that houses the battery modules, and in which the end plates are fixed to the bottom wall of the case. Also, the battery pack is characterized in that at least the fixing portions of the end plates and the bottom wall in the case are covered with an insulating body having water resistance and electrical insulation.

[0011] EFFECT OF THE INVENTION

[0012] The battery pack of the present invention adopts the above-mentioned structure. In a battery pack having a battery module in which a plurality of battery cells are arranged between a pair of end plates and a shell for accommodating the battery module and having a structure for fixing the end plates to the bottom wall of the shell, when water intrusion occurs in the shell, the insulator can be used to make the resistance of water between the bottom wall in the shell and the fixed part of the end plates and the end plates infinite, thereby preventing the formation of a short circuit caused by ion conduction in the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram illustrating a first embodiment of a battery pack, with an enlarged view of the main part. Figure 1 A side cross-sectional view of a battery module will be described below.

[0014] Figure 2 It is a plan view illustrating the arrangement of battery modules in a battery pack.

[0015] Figure 3 The upper portion is a cross-sectional view showing a short circuit generated between modules. Figure 3 The lower portion is a plan view showing a short circuit generated in the entire battery pack.

[0016] Figure 4 It is a side cross-sectional view showing a second embodiment of the battery pack.

[0017] Figure 5 It is a side cross-sectional view of a main part showing a third embodiment of a battery pack. DETAILED DESCRIPTION

[0018] <First embodiment>

[0019] Figure 1 The illustrated battery pack P includes a battery module M having a plurality of battery cells C arranged between a pair of end plates 1, 1, and a housing 2 for housing the battery module M. The end plates 1, 1 are secured to a bottom wall 3 of the housing 2. Furthermore, in the battery pack P, at least the portion of the housing 2 where the bottom wall 3 and the end plates 1, 1 are secured is covered with an insulating socket 5, which is a waterproof and electrically insulating insulator, and an insulating resin potting material 6.

[0020] The battery cell C is a structure in which a positive electrode foil and a negative electrode foil are wound or stacked with a separator interposed therebetween, and the wound or stacked body is housed in a metal flat outer casing 11 ( Figure 1 In the battery module M, there are no restrictions on the number or connection method of the battery cells C. However, in the illustrated example, eight battery cells C are provided, and the external terminals provided on the top of each battery cell C are connected in series using bus bars B.

[0021] Each end plate 1 is made of metal and has a vertical wall 1A facing the battery cells C and a horizontal fixed wall 1B extending from the lower end of the vertical wall 1A toward the outside of the battery module M. Although not shown in its entirety, the housing 2 is constructed, for example, with a flat, box-shaped lower housing that opens upward and an upper housing that closes the upper portion of the lower housing. The bottom wall 3 of the housing 2 is a two-layer structure consisting of an insulating resin layer 3A on the inside and a metal layer 3B on the outside.

[0022] The fixing portion between bottom wall 3 and end plates 1, 1 includes bolts 4 that penetrate fixing walls 1B and insulating resin layers 3A of end plates 1, 1 and are threadedly engaged with metal layers 3B. The insulator covering this fixing portion includes insulating sockets 5 that cover the outer periphery of the heads of bolts 4 and are inserted between bolts 4 and end plates 1, and insulating resin potting material 6 that seals the upper end of insulating sockets 5 and covers the upper surface of the heads of bolts 4.

[0023] The insulating socket 5 has a large-diameter portion 5A that accommodates the head of the bolt 4 and a small-diameter portion 5B through which the threaded portion of the bolt 4 passes. The lower end of the insulating socket 5 reaches the insulating resin layer 3A of the bottom wall 3. The insulating socket 5 secures the end plate 1 to the bottom wall 3 by applying the tightening force of the bolt 4 to the end plate 1. Simultaneously, the lower end of the small-diameter portion 5B secures the end plate 1 to the bottom wall 3, ensuring watertightness between the two. An insulating resin potting member 6 fits seamlessly inside the upper portion of the large-diameter portion 5A of the insulating socket 5, with its outer periphery in close contact with the large-diameter portion 5A, ensuring watertightness between the two.

[0024] The material of the insulating resin potting material 6 is not limited as long as it has waterproof properties and electrical insulation properties, but more preferably, one of a polyurethane resin potting material, a silicone resin potting material, and an epoxy resin potting material can be used.

[0025] like Figure 2 As shown, the battery pack P can be configured to include multiple battery modules M. In the illustrated example, four battery modules M are arranged vertically and horizontally. The battery cells C and C at the ends of the upper and lower battery modules M on the left side of the figure are connected to each other using a first bus bar B1. The battery cells C and C of the upper and left battery modules M and M are connected to each other using a second bus bar B2. The battery cells C and C of the upper and left battery modules M and M are connected to each other using a third bus bar B3.

[0026] Thus, the battery modules M are connected in series in a clockwise direction from the lower left battery module M in the figure to the lower right battery module M. Furthermore, the battery cells C, C located near the center of the battery pack P in the lower left and right battery modules M, M in the figure are connected to external extraction connectors via bus bars and wiring harnesses (not shown).

[0027] In the battery module M of the battery pack P having the above structure, Figure 1 When water is flooded in the housing 2 as shown in the water surface F, if the insulating resin potting member 6 is not present and the heads of the bolts 4 are exposed, a short circuit may occur due to ion conduction of water (including salt water) W between the end plate 1 and the bolts 4 .

[0028] Furthermore, the battery module M also generates a short circuit due to ion conduction of water W between the end plate 1 and the adjacent battery cell C, resulting in a short circuit. Figure 1 A bolt 4 on the right side of the middle portion passes through the water W, an end plate 1, the water W, a battery cell C at one end, a bus bar B and battery cells C and C connected by the bus bar B, a battery cell C at the other end, the water W, another end plate 1, the water W, another bolt 4 and the metal layer 3B of the bottom wall 3 to form a short circuit to a bolt 4 ( Figure 1 At this time, a short circuit occurs in the battery cells C and C at both ends via their respective metal exterior bodies 11. However, this is not directly related to the present invention, and therefore a detailed description thereof will be omitted.

[0029] In addition, the battery pack P of this embodiment is as follows Figure 2 As shown in FIG, the four battery modules M are arranged vertically and horizontally. Figure 3 As shown in the lower part of , a short circuit (dashed line) is generated through all modules M. At this time, as Figure 3 As shown in the upper part of the drawing, a short-circuit path (dashed line) is generated between the modules M and M on the lower left and right sides of the drawing, from one bolt 4 to the other bolt 4 via the metal layer 3B of the bottom wall 3 .

[0030] In contrast, in the battery module M of the above-mentioned embodiment, the bolts 4 serving as the fixing parts between at least the bottom wall 3 in the shell 2 and the end plate 1 are covered by the insulating hole seat 5 and the insulating resin potting member 6 serving as an insulator, thereby blocking the short circuit caused by ion conduction in water between each end plate 1 and each bolt 4.

[0031] Specifically, the battery module M utilizes the insulators (insulating sockets 5 and insulating resin potting 6) covering the fixing portions to ensure that the ion conduction resistance R in water between the end plate 1 and the bolts 4 is infinite. This prevents short circuits caused by ion conduction in water throughout the battery pack P.

[0032] Thus, in the above-described battery pack P, in the configuration in which the battery module M in which a plurality of battery cells C are arranged between a pair of end plates 1, 1 and the housing 2 that houses the battery module M and fixes the end plate 1 to the bottom wall 3 of the housing 2 are provided, when water immersion occurs in the housing 2, the formation of a short circuit caused by ion conduction in water can be prevented. Thus, the battery pack P can of course prevent a short circuit caused by condensed water, and can improve the function of suppressing a short circuit current at the time of water immersion.

[0033] Further, in the above-described battery pack P, the fixing portion is provided with the bolt 4 that penetrates the end plate 1 and the insulating resin layer 3A and is screwed to the metal layer 3B, and the insulating bushing 5 and the insulating resin potting 6 are used, whereby the ion conduction in water between the end plate 1 and the bolt 4 can be completely blocked with a relatively simple structure, and the formation of a short circuit can be reliably prevented.

[0034] Further, in the above-described battery pack P, the lower end portion of the insulating bushing 5 reaches the insulating resin layer 3A, and thus, at the time of water immersion, the water tightness between the end plate 1 and the bolt 4 and between the end plate 1 and the bottom wall 3 can be ensured, and the bolt 4, which is generally made of metal, can be protected from water.

[0035] Further, in the above-described battery pack P, the insulating resin potting 6 as an insulator is one of a polyurethane resin potting, a silicone resin potting, and an epoxy resin potting, and thus further improvement in water tightness and electrical insulation can be sought, and the insulating resin potting 6 is in close contact with the insulating bushing 5 without a gap, and sufficient water tightness between the two can be ensured.

[0036] <2nd Embodiment>

[0037] Figure 4 is a drawing that illustrates a 2nd embodiment of a battery pack of the present application. Further, in the following embodiments, the same reference numerals are assigned to the same constituent portions as those of the 1st embodiment, and detailed description is omitted.

[0038] The illustrated battery pack P is a structure that has the same basic structure as the 1st embodiment and has an insulating ring 7 that is disposed centered on the bolt 4 and is compressed between the lower end portion of the end plate 1 and the bottom wall 3. The material of the insulating ring 7 is not limited, but for example, the same material as the insulating bushing 5 can be used.

[0039] The battery pack P having the above-described structure, as with the previous embodiments, is able to prevent the formation of a short circuit caused by ion conduction in water when water is introduced into the case 2. Also, in the battery pack P, in particular, by adopting the insulating ring 7, the fixing of the end plate 1 to the bottom wall 3 and the watertight configuration between the insulating bush 5 and the end plate 1, between the end plate 1 and the insulating ring 7, and between the insulating ring 7 and the bottom wall 3 are arranged coaxially as the bolt 4 is tightened to the metal layer 3B of the bottom wall 3, so these fixing and watertightness can be achieved simultaneously.

[0040] Also, in the above-described embodiments, the lower end of the small diameter portion 5B of the insulating bush 5 is made lower than the lower surface of the fixing wall 1B of the end plate 1, whereby the insulation and watertightness between the fixing wall 1B and the bolt 4 is ensured. Also, in the above-described embodiments, the inner diameter of the insulating ring 7 is made larger than the outer diameter of the small diameter portion 5B, whereby the insulating ring 7 is made to be crushed between the fixing wall 1B and the bottom wall 3 and is made to be pressed against both, so the watertightness between the fixing wall 1B and the bottom wall 3 is improved. In this way, according to the configuration in which the insulating ring 7 is crushed, it is possible to prevent the dimensional tolerance of the insulating bush 5 and the like from becoming excessively small.

[0041] <3rd Embodiment>

[0042] Figure 5 is a view that explains a 3rd embodiment of the battery pack of the present application. In Figure 5 a battery pack P is shown that has the structure of the insulating ring 7 explained in the 2nd embodiment and the lower end of the small diameter portion 5B of the insulating bush 5 reaches the insulating resin layer 3A of the bottom wall 3.

[0043] According to the above-described structure, it is possible to make the insulating ring 7 to be crushed between the fixing wall 1B of the end plate 1 and the bottom wall 3 and at the same time to make the small diameter portion 5B of the insulating bush 5 to be crushed in the axial direction, and it is possible to obtain a double-sealing configuration using the small diameter portion 5B and the insulating ring 7, so it is possible to further improve both the insulation and the watertightness between the fixing wall 1B, the bolt 4, and the bottom wall 3.

[0044] The structure of the battery pack of the present application is not limited to the above-described embodiments and can be changed as appropriate within the scope of the gist of the present application, and for example, it is also possible to further improve the function of preventing a short circuit caused by ion conduction in water by making the end plate of an insulating resin.

[0045] Explanation of Reference Signs

[0046] C, battery cell, M, battery module, 1, end plate, 2, case, 3, bottom wall of case, 3A, insulating resin layer, 3B, metal layer, 4, bolt (fixing site), 5, insulating bush (insulator), 6, insulating resin potting (insulator), 7, insulating ring, 11, metal outer body.

Claims

1. A battery pack comprising a battery module in which a plurality of battery cells are arranged between a pair of end plates and a housing for accommodating the battery module, wherein the end plates are fixed to a bottom wall of the housing, wherein: At least the fixing portion of the bottom wall and the end plate in the housing is covered with an insulator having waterproof and electrical insulating properties.

2. The battery pack according to claim 1, wherein: The bottom wall includes an insulating resin layer inside the shell and a metal layer outside the shell. The fixing portion includes a bolt that penetrates the end plate and the insulating resin layer and is threadedly engaged with the metal layer. The insulator includes an insulating hole seat and an insulating resin potting member. The insulating hole seat covers the outer periphery of the head of the bolt and is inserted between the bolt and the end plate. The insulating resin potting member seals the upper end of the insulating hole seat and covers the upper surface of the head of the bolt.

3. The battery pack according to claim 2, wherein: An insulating ring is provided between the end plate and the bottom wall. The insulating ring is arranged around the bolt and compressed between the end plate and the bottom wall.

4. The battery pack according to claim 2 or 3, characterized in that: The lower end portion of the insulating hole seat reaches the insulating resin layer.

5. The battery pack according to claim 1, wherein: The insulating resin potting member is one of a polyurethane resin potting member, a silicone resin potting member, and an epoxy resin potting member.

Images