Battery pack

Abstract

To provide a configuration of in which a case 4 and a cover 5 constituting the housing of a battery pack 1 are formed from a conductive material and structures 4a, 4b, and 6 are provided to electrically insulate them from a battery module including a battery cell 2 and electrical components contained therein, in which, in preparation for a short circuit between the case and cover and the battery module, the case and cover are electrically connected to each other to achieve equal potential and to suppress galvanic corrosion in the conductive parts between the case and cover.SOLUTION: In a battery pack in which a conductive case and a conductive cover are connected at their peripheral portions and a battery module is housed in a space defined therebetween with the case and cover insulated from each other, the case and cover are connected and electrically conductive via a conductive member 8, and the peripheral portions of the case and cover are sealed to each other around their entire periphery by an insulating sealing member 9 on the outer side of the connection point of the conductive member between the case and cover.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery pack accommodating a battery module including a plurality of battery cells, and more particularly, to a structure of a battery pack in which a conductive case and a conductive cover are connected at peripheral portions, and a space for accommodating the battery module is defined inside thereof.

Background Art

[0002] A battery pack mounted for driving an electric vehicle has a shape in which a battery module including a stack formed by stacking a plurality of battery cells is housed in a housing. For example, in Patent Document 1, a battery module including a plurality of battery cells is accommodated in a housing constituted by an upper casing and a lower casing respectively surrounding the upper side and the lower side thereof, wherein the upper casing and the lower casing are formed by arranging a plurality of molding materials, which may be sheet molding compounds formed by impregnating glass fibers with a resin and molding into a sheet shape, in a mold in a stacked manner and subjecting to heat and pressure molding, and a configuration is disclosed in which the peripheral edge portions thereof are fastened by fasteners such as bolts via a sealing member made of a rubber material or the like. Note that Patent Document 2 discloses a structure in which conductive pins are vertically inserted between overlapping portions of a plurality of carbon fiber reinforced plastic panels constituting an aircraft body to electrically connect the panels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0004] As described above, a battery pack has a configuration in which a battery module, which includes a stack composed of multiple battery cells and associated electrical components such as busbars, is housed within a casing. More specifically, typically, the casing consists of a member that supports the battery module (hereinafter referred to as the "case") and a member that covers the battery stack and electrical components (hereinafter referred to as the "cover"), and the edges of the case and cover are fastened together so that they abut. The case and cover are formed in a state that insulates them from the conductive parts of the battery module so that the battery voltage is not transmitted even if a person touches them. In this regard, when a battery pack is mounted on machinery such as a vehicle, it is preferable that the case, which is installed on the vehicle body or the frame of the machinery, has a coefficient of thermal expansion as close as possible to that of the vehicle body or frame. Therefore, it is preferable that the case be made of the same material as the vehicle body or frame. Accordingly, when the vehicle body or frame is made of aluminum or other metal, the case is also made of aluminum or other metal, and in that case, the case is conductive. Furthermore, while the cover can be formed from any material, it is preferable that it be as lightweight as possible. For example, a component made of carbon fiber reinforced plastic (CFRP) is advantageous, and in that case, the cover also becomes conductive. When the case and cover are formed from conductive materials in this way, a configuration (insulating structure) is provided in the case and cover to electrically insulate them from the battery module, such as by applying an insulating material layer to the inside, so that the battery voltage does not transmit to the case and cover.

[0005] In a configuration where an insulating structure is provided on a conductive case and cover as described above, if the battery pack housing is subjected to impact or deformation due to contact between the vehicle or machinery equipped with the battery pack and other obstacles, the insulating structure may be damaged, causing the case or cover to short-circuit with a conductive part of the battery module, allowing the battery voltage to be transmitted to the case or cover. In this case, if the case and cover are connected to the same battery terminals, no potential difference will occur between the case and cover. However, if the case and cover are short-circuited to different battery terminals, and the case and cover are not conductive, a potential difference will occur between them, raising concerns about electric shock from human contact. Therefore, when the case and cover are made of conductive materials, it is preferable that the case and cover are conductive to each other and always at the same potential (if the case and cover are conductive to different battery terminals, a large current will flow between the positive and negative electrical terminals at that moment, activating safety mechanisms such as fuses that break, thus interrupting the current between the battery terminals). However, if the case and cover are electrically conductive, and they are made of different materials, galvanic corrosion can occur when water or mud adheres to the parts that electrically contact them, potentially leading to deterioration and weakening of the appearance of the fastening joints between the case and cover.

[0006] In view of the above circumstances, the main object of the present invention is to provide a configuration in which the case and cover constituting the housing of a battery pack are made of a conductive material and a structure is provided to electrically insulate them from the battery module housed therein, in order to prepare for a short circuit between the case and cover and the battery module by electrically connecting the case and cover to achieve equipotential, and to suppress galvanic corrosion of the conductive portion between the case and cover. [Means for solving the problem]

[0007] According to the present invention, the above problem is solved by a battery pack in which a conductive case and a conductive cover are connected at their peripheral edges, and a battery module is housed in a space defined inside them in an insulated state from the case and the cover, wherein the case and the cover are connected and electrically connected via a conductive member, and the peripheral edges of the case and the cover are sealed together by an insulating sealing member around their entire circumference, on the outer side of the connection portion of the conductive member on the case and the cover.

[0008] In the above configuration, the "battery pack" is, as described above, a device that houses batteries inside a housing and is mounted on an electric vehicle or other machinery for driving or operating it. The "case" and "cover," as already mentioned, are components molded from a conductive material such as metal or CFRP, respectively, from the viewpoint of requirements, weight, or cost in the machinery on which they are mounted. The "battery module" includes electrical components such as a battery stack appropriately configured by stacking multiple battery cells, wires and busbars that electrically connect the battery cells and connect to terminals for outputting power to the battery pack, a control device that controls the operation of the battery, and safety mechanisms such as fuses. The battery module is held between the case and cover via an insulating member, and as a result, in normal conditions, it is kept insulated from the case and cover. Furthermore, in this invention, the conductive member connected between the case and cover and providing electrical conductivity between them may be made of any conductive material (solid). The "insulating sealing member" may be a member formed from any material capable of sealing between two connecting members, such as insulating rubber or resin. In the present invention, it is particularly applied to seal between the case and the cover over the entire circumference of the peripheral portion of the case and the cover.

[0009] In the above configuration, the case and cover that constitute the housing for the battery module are each made of a conductive material, and the case and cover are connected and electrically connected by a conductive member. As a result, even if the housing of the battery pack is subjected to an impact or the mechanism that maintains the insulating state between the case and cover and the battery module is damaged, and the case and cover come into contact with any part of the battery module, causing the case and cover to short-circuit with separate electrodes of the battery, the case and cover will remain at the same potential, so there is no concern that a person may be electrocuted by simultaneously touching the case and cover. In this regard, when the case and cover are electrically connected by a conductive member, and these members are made of different materials, galvanic corrosion may occur if the connection part of the conductive member and its surroundings are exposed to water or mud. Therefore, in the present invention, as described above, the peripheral portions of the case and cover are sealed together by an insulating sealing member around their entire circumference, on the outer circumference side of the connection part of the conductive member in the case and cover. This protects the connection points of the conductive components in the case and cover, as well as their surrounding areas, from water, mud, and other elements, thereby preventing the occurrence of galvanic corrosion as described above.

[0010] In the above-described configuration of the present invention, the conductive member that connects the case and the cover may be made of a flexible elastic material (such as conductive rubber). With this configuration, when the cover is attached to the case with the conductive member in between, the conductive member is slightly compressed and adheres closely to the surfaces of the case and the cover, and an electrical connection between the two is easily achieved. Furthermore, even if the case or cover is deformed by the action of an external force, or if a misalignment occurs in the connecting part between them, the conductive member will deform in accordance with the deformation or misalignment, thereby maintaining the electrical connection between the case and the cover.

[0011] In the above-described configuration of the present invention, the mechanism for holding the battery module in an insulated state from the case and cover may be formed in any manner. The battery cells and busbars in the battery module may be supported by a member made of an insulating material relative to the case so as not to come into direct contact with the conductive parts of the case. Furthermore, the inner surface of the region of the case or cover facing the battery module may be covered with an insulating layer, for example, a cloth-like member made of poly(p-phenylene terephthalamide) fibers, thereby preventing electrical contact with the battery module as much as possible.

[0012] In the above-described configuration of the present invention, the peripheral portions of the case and the cover are in contact with each other via an insulating layer and may be fastened together using bolts or the like. From the outside to the inside of the peripheral portions of the case and the cover, fastening portions such as bolts, sealing portions with sealing members, and conductive portions with conductive members are formed in that order. [Effects of the Invention]

[0013] Thus, according to the configuration of the present invention, in a battery pack in which a battery module is housed in a housing composed of a case and a cover made of a conductive material, the case and the cover are electrically connected by a conductive member and are at the same potential. Therefore, even if the voltage of the battery is transmitted to the case and the cover by a short circuit with the battery module, electric shock due to human contact is prevented. Furthermore, since the contact area between the case, the cover and the conductive member is sealed from the outside of the housing by a sealing member, moisture, mud, etc. cannot reach the contact area of ​​the conductive member. Consequently, the occurrence of galvanic corrosion near the contact area of ​​the conductive member can be prevented, and deterioration and weakening of the appearance near the contact area of ​​the conductive member can be avoided. The battery pack of the present invention may be used in various electric vehicles and other machinery and equipment that operate using the power of batteries.

[0014] Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention. [Brief explanation of the drawing]

[0015] [Figure 1] Figures 1(A) and 1(B) are schematic cross-sectional views of the vicinity of the peripheral edges of the case and cover of a battery pack to which this embodiment is applied. (A) shows the portion where bolts for fastening the case and cover are provided, and (B) shows the portion where bolts are not provided. [Figure 2] Figures 2(A) and 2(B) are schematic cross-sectional views of the vicinity of the peripheral edges of the case and cover of a battery pack to which this embodiment is not applied. (A) shows the case where the case and cover are not electrically connected, and (B) shows the case where the case and cover are electrically connected on the outside. [Explanation of Symbols]

[0016] 1...Battery pack, 2...Battery cell, 3...Bus bar, 3a...Bus bar and cell fastener, 4...Case, 4a...Bus bar support member, 4b...Cell support member, 5...Cover, 6...Insulating layer, 7...Bolt, 7a...Bolt holder (insulating), 8...Conductive member, 9...Sealing member, S...Short circuit area, X...Conductive area, w...Water droplets, etc. [Best Mode for Carrying Out the Invention]

[0017] The present invention will be described in detail below with reference to the attached figures, with reference to several preferred embodiments. In the figures, the same reference numerals indicate the same parts.

[0018] Basic configuration of the battery pack housing Referring to Figures 1(A) and (B), in the battery pack 1 mounted on a motor vehicle or other mechanical device for driving or operating purposes according to this embodiment, an electrical module is fixedly supported in a case 4 by support members 4a and 4b. This module consists of a stack of multiple battery cells 2 connected in series or parallel and stacked, a busbar 3 fixed to the cells 2 by a fixing device 3a, a busbar 3 connected to terminals (not shown) for connecting the cells 2 and outputting power from the cells 2 to the outside of the battery pack 1, other conductors, a control device (not shown) for controlling the operation of the battery, and safety mechanisms (not shown) such as fuses. A cover 5 is fixed to the case 4 so as to cover the electrical module in cooperation with the case 4, thereby forming an enclosure in which the case 4 and cover 5 house the electrical module.

[0019] In the configuration of the above-described housing, when the case 4 is installed on a frame (frame body) of a mechanical apparatus such as a vehicle, it is preferable that the linear thermal expansion coefficient of the case 4 matches that of the frame as much as possible. Therefore, typically, the case 4 is formed of the same material as the frame of the mechanical apparatus. Accordingly, when the frame of the mechanical apparatus is a metal material such as aluminum, the case 4 is generally formed of the same metal material, and in that case, the case 4 becomes electrically conductive. Therefore, to prevent the battery voltage from being transmitted to the case 4, the support members 4a and 4b that support the electrical module relative to the case 4 are formed of an insulating material. On the other hand, the cover 5 disposed relative to the case 4 so as to cover the electrical module may be formed of any material, but is formed of a CFRP material for reasons such as light weight and low cost, and in that case, the cover 5 also becomes electrically conductive. Therefore, to prevent the battery voltage from being transmitted to the cover 5, the insulating material layer 6 or the like is applied to the inner wall of the cover 5, particularly the wall surface facing the bus bars 3 and other conductive portions of the electrical module. The insulating material layer 6 may be, for example, a cloth-like member formed of polyparaphenylene terephthalamide fibers. As can be understood from the drawings, the peripheral edge portion of the cover 5 faces the peripheral edge portion of the case 4 over the entire circumference thereof, and fasteners such as bolts 7 are inserted from the cover 5 to the case 4 at appropriate intervals to be fastened. When the bolts 7 are formed of a conductive material, as illustrated, the bolts 7 may be fastened to the cover 5 and the case 4 with a holder 7a formed of an insulating material interposed therebetween so as not to directly contact the cover 5.

[0020] Countermeasures in case of a short circuit between the battery module and the housing In the above-described battery pack configuration, the cover 5 and case 4 are properly insulated from the battery module. However, if the vehicle or machinery on which the battery pack is mounted comes into contact with an obstacle, and the battery pack is subjected to an impact, the support members 4a and 4b may be damaged, the battery module may be displaced by piercing the insulating layer 6, or the cover 5 or case 4 may be deformed. In such cases, the conductive part of the battery module may come into contact with the conductive part of the cover 5 or case 4, causing a short circuit between the battery electrodes and the cover 5 or case 4. In that case, as shown in Figure 2(A), the cover 5 and case 4 are insulated from each other, and a route S is formed that shorts between the cover 5 and case 4 to separate electrodes of the battery, a potential difference ΔV is generated between the cover 5 and case 4. This raises concerns that an electric shock may occur if an operator touches both the cover 5 and case 4 simultaneously while working on the battery pack 1. Therefore, in order to keep the cover 5 and case 4 at the same potential at all times, it is conceivable to make the cover 5 and case 4 electrically connected, as indicated by the symbol X in Figure 2(B). However, if the conductive portion between the cover 5 and case 4 is exposed to the outside, when water or mud (w) reaches it, if the cover 5 and case 4 are made of different materials, 'galvanic corrosion' may occur in and around the conductive portion between the cover 5 and case 4, potentially causing deterioration of the appearance and weakening of the connection.

[0021] Accordingly, in the present embodiment, as depicted in FIGS. 1(A) and (B), the cover 5 and the case 4 are connected via the conductive member 8 and brought into mutual conduction on the inner side of their opposing peripheral edge portions, and the sealing member 9 is applied on the outer side thereof so as to seal the space between the cover 5 and the case 4. The sealing member 9 extends over the entire circumference between the cover 5 and the case 4 so as to block fluid communication between the inner side and the outer side thereof. The conductive member 8 may be disposed over the entire circumference between the cover 5 and the case 4, or may be disposed at appropriate intervals. According to such a configuration, the cover 5 and the case 4 are always maintained at the same potential through the conductive member 8, and water and mud do not reach the contact portion of the conductive member 8 between the cover 5 and the case 4 and the vicinity thereof, so that galvanic corrosion in the vicinity of the contact portion of the conductive member 8 can be suppressed.

[0022] In the configuration of the above-described present embodiment, the conductive member 8 may preferably be formed of an elastic material, and such an elastic material may specifically be an elastic body containing an inorganic filler (such as elastic silicone added with nickel / carbon, or elastic polyurethane wrapped with conductive fibers around the periphery), conductive rubber, or the like. According to such a configuration, when the peripheral edge portion of the cover 5 is fastened to the peripheral edge portion of the case 4, the conductive member 8 is compressed and held between the peripheral edge portions of the case 4 and the cover 5, whereby the conductive member 8 is brought into close contact with the case 4 and the cover 5, and conduction between the case 4 and the cover 5 is ensured. In addition, even if the case 4 or the cover 5 is deformed by an external force or a displacement occurs in the peripheral edge portion, the conductive member 8 deforms following the deformation or displacement, so that the conduction state between the case 4 and the cover 5 can be maintained.

[0023] Thus, in the configuration of this embodiment described above, in the battery pack, equipotentiality for ensuring the safety of the housing, which is composed of a cover formed from a conductive material such as CFRP and a case formed from a conductive material such as metal, and the deterioration and weakening of the housing's appearance due to galvanic corrosion can be avoided. The electric pack of this embodiment can be advantageously used as a drive unit for electric vehicles or for driving or operating other mechanical devices.

[0024] While the above description is made in relation to embodiments of the present invention, many modifications and changes are readily possible for those skilled in the art, and it will be clear that the present invention is not limited to the embodiments illustrated above, but can be applied to various devices without departing from the concept of the present invention.

Claims

1. A battery pack comprising a conductive case and a conductive cover connected at their peripheral edges, with a battery module housed in a space defined inside them, insulated from the case and the cover, wherein the case and the cover are connected and electrically conductive via a conductive member, and the peripheral edges of the case and the cover are sealed together around their entire circumference by an insulating sealing member on the outer side of the connection portion of the conductive member on the case and the cover, and the conductive member is an elastic material.

2. A battery pack according to claim 1, wherein the inner surface of the region of the cover facing the battery module is covered with an insulating layer.

Images