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 that houses a battery module including a plurality of battery cells. More specifically, the present invention relates to a structure of a battery pack in which a conductive case and a conductive cover are connected at a peripheral portion, and a space for housing the battery module is defined inside them.

Background Art

[0002] A battery pack mounted for driving an electric vehicle has a shape in which a battery module including a stack or the like 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 housed in a housing composed of an upper casing and a lower casing that respectively surround the upper and lower sides thereof. Here, the upper casing and the lower casing are formed by laminating a plurality of sheet molding compounds obtained by impregnating glass fibers with resin and molding them into a sheet shape in a mold, heating, and pressure molding. A structure is disclosed in which the peripheral portion is fastened by a fastening tool such as a bolt via a sealing member made of a rubber material or the like. In Patent Document 2, a structure is disclosed in which conductive pins are vertically inserted between overlapping portions of a plurality of carbon fiber reinforced plastic panels constituting an aircraft fuselage to electrically connect the panels.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, the battery pack has a configuration in which a battery module including a stack composed of a plurality of battery cells and electrical components such as bus bars associated therewith is housed in a housing. More specifically, typically, the housing is composed of a member that supports the battery module (hereinafter referred to as a "case") and a member that covers the battery stack and electrical components (hereinafter referred to as a "cover"), and is fastened so that the edges of the case and the cover abut. And the case and the cover are formed in a state of being insulated from the conductive parts of the battery module so that the voltage of the battery does not conduct even when a person touches them. In this regard, when the battery pack is mounted on a mechanical device such as a vehicle, it is preferable that the case installed on the vehicle body or the frame of the mechanical device has a linear expansion coefficient as close as possible to that of the vehicle body or the frame. Therefore, when the vehicle body or the frame is made of aluminum or other metals, the case is preferably also made of aluminum or other metals, and in that case, the case becomes conductive. Also, the cover may be formed of any material, and it is preferably as lightweight as possible. For example, a member made of carbon fiber reinforced plastic (CFRP) is advantageously used. In that case, the cover also becomes conductive. Thus, when the case and the cover are formed of conductive materials, a configuration (insulation structure) is provided to electrically insulate the case and the cover from the battery module, such as applying an insulating material layer to the inside of the case and the cover so that the voltage of the battery does not conduct to the case and the cover.

[0005] In the configuration where the conductive case and cover are provided with an insulating structure as described above, when an impact is applied to the housing of the battery pack or deformation occurs due to contact between a vehicle or machine equipped with the battery pack and other obstacles, if the above insulating structure is damaged and the case or cover shorts to the conductive part of the battery module, the voltage of the battery can be transmitted to the case or cover. At this time, if the poles of the battery for which the case and cover are conductive are the same, no potential difference will occur between the case and the cover. However, when the case and cover short-circuit to different poles of the battery and are not electrically connected, a potential difference will occur between them, raising concerns about electric shock due to human contact. Therefore, when the case and cover are each formed of a conductive material, it is preferable to ensure that the case and cover are electrically connected to each other and always at the same potential. (If the case and cover are connected to different poles of the battery, a large current will flow between the positive and negative electrodes of the electricity at that moment, activating a safety mechanism such as a fuse blowing and interrupting the current between the poles of the battery.) However, when the case and cover are electrically connected and are formed of different materials, if water or mud adheres to the part where they are in electrical contact, galvanic corrosion may occur, potentially causing deterioration and weakening of the appearance of the fastening part between the case and the cover.)

[0006] In view of the above circumstances, the main problem of the present invention is that in a configuration where the case and cover constituting the housing of the battery pack are formed of a conductive material and are provided with a structure for electrically insulating them from the battery module housed therein, in preparation for a short circuit between the case, cover, and battery module, the case and cover are electrically connected to equalize the potential, and galvanic corrosion of the conductive part between the case and cover can be suppressed.

Means for Solving the Problem

[0007] According to the present invention, the above problems are solved by 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 inside them with the case and the cover being insulated from each other, wherein the case and the cover are connected and electrically conducted through a conductive member, and at an outer peripheral side of the connection portion of the conductive member on the case and the cover, the peripheral portions of the case and the cover are sealed from each other by an insulating seal member over their entire circumferences.

[0008] In the above configuration, the "battery pack" is, as described above, a device in which a battery is housed inside a housing and is mounted on an electric vehicle or other mechanical device for driving or operating it. The "case" and "cover" are members formed from a conductive material such as a metal material or a CFRP material, respectively, from the viewpoints of requirements, weight, cost, etc. in the mechanical device to be mounted. The "battery module" includes an electric component such as a battery stack appropriately configured by stacking a plurality of battery cells, a conductive wire or bus bar that electrically connects between the battery cells and is connected to a terminal for outputting power to the battery pack, a control device that controls the operation of the battery, and a safety mechanism such as a fuse. The battery module is held with respect to the case and the cover via an insulating member, and thus, in a normal state, is placed in a state insulated from the case and the cover. Further, in the present invention, the conductive member connected between the case and the cover to electrically conduct them may be formed of any conductive material (solid). The "insulating seal member" may be a member formed from any material capable of sealing between two connected members such as insulating rubber or resin, and in the present invention, is particularly applied to seal between the case and the cover over the entire circumference of the peripheral portions of the case and the cover.

[0009] In the above configuration, since the case and the cover that constitute the housing for accommodating the battery module are each formed of a conductive material, the case and the cover are connected by a conductive member to be electrically conductive. As a result, even if the housing of the battery pack is subjected to an impact or the like and the mechanism for maintaining the insulating state between the case and the cover and the battery module is damaged, and the case and the cover come into contact with any part of the battery module, and the case and the cover are short-circuited with separate electrodes of the battery, the case and the cover are kept at the same potential, so there is no concern that a person will be electrocuted by simultaneously contacting the case and the cover. In this regard, when the case and the cover are electrically connected by a conductive member and those members are formed of different materials, galvanic corrosion may occur when the connection part of the conductive member and its surroundings are exposed to water, mud, or the like. Therefore, in the present invention, as described above, the peripheral portions of the case and the cover are sealed from each other by an insulating seal member over their entire circumferences on the outer peripheral side rather than the connection part of the conductive member in the case and the cover. Thereby, the connection part of the conductive member in the case and the cover and its periphery are protected from water, mud, or the like, and the occurrence of galvanic corrosion as described above can be avoided.

[0010] In the configuration of the present invention described above, the conductive member that electrically connects the case and the cover may be formed of a flexible elastic body material (such as a conductive rubber material). According to such a configuration, when the cover is attached with the conductive member sandwiched between the case, the conductive member is slightly compressed and adheres to the surfaces of the case and the cover, and the electrical connection state between the two is easily achieved. Further, even if the case or the cover is deformed by the action of an external force or a displacement occurs in their connecting portion, the conductive member deforms following the deformation and the displacement, so that the electrical connection state between the case and the cover is maintained.

[0011] In the configuration of the present invention described above, the mechanism for holding the battery module in an insulated state with respect to the case and the cover may be formed in any manner. The battery cells and bus bars in the battery module may be supported using members made of an insulating material so as not to directly contact the conductive portions of the case. Further, the inner surface of the region of the case or the cover facing the battery module may be covered with an insulating layer, for example, a cloth-like member formed of polyparaphenylene terephthalamide fiber, etc., and thereby may be configured to prevent conduction with the battery module as much as possible.

[0012] In the configuration of the present invention described above, the peripheral portions of the case and the cover may be brought into contact via an insulating layer and fastened to each other using bolts or the like. From the outside to the inside of the peripheral portions of the case and the cover, a fastening portion for bolts or the like, a sealing portion by a sealing member, and a conduction portion by a conductive member will be formed in this order.

Advantages 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, since the case and the cover are electrically connected by a conductive member and are at the same electric potential, even if the voltage of the battery is transmitted to the case and the cover due to a short circuit with the battery module, electric shock due to human contact is prevented. Also, since the contact portions of the case, the cover, and the conductive member are sealed from the outside of the housing by a sealing member, moisture, mud, etc. cannot reach the contact portions of the conductive member. Therefore, the occurrence of galvanic corrosion in the vicinity of the contact portions of the conductive member can be prevented, and deterioration and weakening of the appearance in the vicinity of the contact portions of the conductive member can be avoided. The battery pack of the present invention may be used in various electric vehicles and other mechanical devices operated using the power of batteries.

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

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Explanation of Reference Numerals

[0016] 1... Battery pack, 2... Battery cell, 3... Bus bar, 3a... Fixture for fixing the bus bar and cell, 4... Case, 4a... Support member for the bus bar, 4b... Support member for the cell, 5... Cover, 6... Insulating material layer, 7... Bolt, 7a... Bolt holder (insulating), 8... Conductive member, 9... Sealing member, S... Short-circuit site, X... Conductive portion, w... Water droplets, etc.

Best Mode for Carrying Out the Invention

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

[0018] Basic configuration of the housing of the battery pack Referring to FIGS. 1(A) and 1(B), in a battery pack 1 mounted for driving or operating a mechanical device such as an electric vehicle according to the present embodiment, a stack formed by connecting and laminating a plurality of battery cells 2 in series or in parallel, a bus bar 3 fixed to the cell 2 by a fixture 3a, connecting between the cells 2 and connected to a terminal (not shown) for outputting power from the cell 2 to the outside of the battery pack 1, other conducting wires, a control device (not shown) for controlling the operation of the battery, a safety mechanism (not shown) such as a fuse, etc., an electric module composed of electrical components is fixedly supported by support members 4a and 4b in a case 4. Then, a cover 5 is fixed to the case 4 so as to cover such an electric module in cooperation with the case 4, whereby the case 4 and the cover 5 constitute a housing for accommodating the electric module.

[0019] In the configuration of the above-described housing, when the case 4 is installed on the frame (framework) of a mechanical device such as a vehicle, it is preferable that the linear thermal expansion coefficient is as close as possible to that of the frame. Therefore, typically, it is formed of the same material as the frame of the mechanical device. Accordingly, when the frame of the mechanical device is a metal material such as aluminum, it is generally formed of the same metal material, and in that case, the case 4 becomes conductive. Therefore, support members 4a and 4b that support the electric module with respect to the case 4 are formed of an insulating material so that the voltage of the battery does not reach the case 4. On the other hand, the cover 5 disposed with respect to the case 4 so as to cover the electric module may be formed of any material. For reasons such as being lightweight and inexpensive, it is formed of a CFRP material. In that case, the cover 5 also becomes conductive. Therefore, so that the voltage of the battery does not reach the cover 5, an insulating material layer 6 or the like is applied to the inner wall of the cover 5, particularly, the wall surface facing the bus bar 3 and other conductive parts of the electric module. Note that the insulating material layer 6 may be, for example, a cloth-like member formed of polyparaphenylene terephthalamide fiber. As can be understood from the figure, the peripheral portion of the cover 5 faces the peripheral portion of the case 4 over its entire circumference, and fasteners such as bolts 7 may be inserted through the cover 5 into the case 4 at an appropriate interval and fastened. When the bolt 7 is formed of a conductive material, as shown in the figure, the bolt 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] Measures in case of short circuit between the battery module and the housing In the configuration of the above-described battery pack, the cover 5 and the case 4 are properly insulated from the battery module. However, when the vehicle or machinery equipped with the battery pack contacts an obstacle, an impact acts on the battery pack, causing the support members 4a and 4b to break, piercing the insulating material layer 6 and displacing the battery module, or deforming the cover 5 or the case 4. In such cases, the conductive part of the battery module may come into contact with the conductive part of the cover 5 or the case 4, resulting in a short circuit between the battery electrodes and the cover 5 or the case 4. In that case, as shown in Fig. 2(A), when the cover 5 and the case 4 are insulated from each other and a short-circuit route S is formed between the cover 5 and the case 4 to different poles of the battery, a potential difference ΔV occurs between the cover 5 and the case 4. During the operation of the battery pack 1, there is a risk of electric shock if an operator touches the cover 5 and the case 4 simultaneously. Therefore, in order to always keep the cover 5 and the case 4 at the same electric potential, as shown by the reference X in Fig. 2(B), it is conceivable to connect the cover 5 and the case 4. However, if the conductive part between the cover 5 and the case 4 is exposed to the outside and water, mud, etc. (w) reaches there, when the cover 5 and the case 4 are made of different materials, "galvanic corrosion" may occur at the conductive part between the cover 5 and the case 4 and in its vicinity, possibly causing deterioration of the appearance and weakening of the connection part.

[0021] Therefore, in the present embodiment, as depicted in FIGS. 1(A) and 1(B), the cover 5 and the case 4 are connected to each other and electrically conducted through the conductive member 8 inside the inner peripheral portions facing each other, and a seal member 9 is applied to seal between the cover 5 and the case 4 on the outside. Note that the seal member 9 extends over the entire circumference between the cover 5 and the case 4 so as to block the fluid flow between the inside and the outside. The conductive member 8 may be arranged over the entire circumference between the cover 5 and the case 4, or may be arranged at appropriate intervals. According to such a configuration, the cover 5 and the case 4 are always maintained at the same electric potential through the conductive member 8, and water and mud do not reach the contact portion between the cover 5 and the case 4 of the conductive member 8 and the vicinity thereof, so 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 is preferably formed of an elastomeric material. Specifically, such an elastomeric material may be an elastomer containing an inorganic filler (such as an elastomer silicon added with nickel / carbon, or an elastomer polyurethane wound with conductive fibers), a conductive rubber, or the like. According to such a configuration, when fastening the peripheral portion of the cover 5 to the peripheral portion of the case 4, the conductive member 8 is sandwiched between the peripheral portions of the case 4 and the cover 5 while being compressed, whereby the conductive member 8 is in close contact with the case 4 and the cover 5, and the electrical conduction between the case 4 and the cover 5 is ensured. Further, even if the case 4 or the cover 5 is deformed by an external force or a displacement occurs in the peripheral 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 the above-described present embodiment, in the battery pack, equal potentialization for ensuring the safety of the housing composed of a cover formed of a conductive material such as CFRP and a case formed of a conductive material such as metals, and avoidance of deterioration and weakening of the appearance of the housing due to galvanic corrosion can be achieved. The electric pack of the present embodiment is advantageously used for driving a driving device of an electric vehicle or other mechanical appliances or for operation.

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

Claims

**Claim 1** 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 inside them with the case and the cover insulated from each other, wherein the case and the cover are connected and electrically conducted through a conductive member, and the peripheral portions of the case and the cover are sealed from each other by an insulating seal member over their entire circumference on the outer peripheral side of the connection portion of the conductive member in the case and the cover. **Claim 2** The battery pack according to claim 1, wherein the conductive member is an elastic body. **Claim 3** The battery pack according to claim 1, wherein an inner surface of a region of the cover facing the battery module is covered with an insulating layer.

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