Assembled battery

A battery unit, a bottomed case, a plate-shaped cooling plate, and first heat transfer material are included. The cooling plate is fastened to a bottom part of the case from the outside of the case, and can cool the battery unit via the bottom part of the case. The first heat transfer material have a plastic property and are held between the bottom part of the case and the cooling plate. The bottom part of the case has heat transfer material housings that house excess first heat transfer material therein when the cooling plate has been fastened to the case.

TECHNICAL FIELD

The present invention relates to an assembled battery including a plurality of battery cells housed in a casing.

BACKGROUND ART

An assembled battery made by assembling a plurality of single batteries (battery cells) is known. Each battery cell generates heat through charge and discharge. In order to maintain the charge-discharge characteristics, it is necessary to appropriately control the temperature of the battery cells.

JP 2010-192207A and JP 2011-49139A disclose such an assembled battery including a plate-shaped support member that supports the supported surfaces of a plurality of single batteries, and cooling devices composed of a Peltier element and the like for cooling the support member.

JP 2011-23296A discloses provision of a heat conductive material between single batteries and an assembled battery mount on which an assembled battery is mounted. The heat conductive material is a sheet, elastic rubber, a paste, or a gel.

SUMMARY OF INVENTION

Configurations of the conventional techniques described in the aforementioned patent documents are such that the heat of single batteries is transferred to the outside via a support member, such as a case, provided at a bottom side of the single batteries. According to such configurations, this heat is cooled from the outside of the case.

A heat conductive material having an elastic or plastic property is interposed between the single batteries and the case for the purpose of increasing the efficiency of heat conduction, as with the conventional technique described in JP 2011-23296A.

In this configuration, if a battery unit made by stacking the single batteries is fastened to the case, the battery unit is pressed against the case, and thus the heat conductive material is pressed. As the heat conductive material is pressed by the battery unit, the heat conductive material deforms.

Deformation of the heat conductive material between the battery unit and the case may result in uneven distribution of the heat conductive material between the battery unit and the case. Uneven distribution of the heat conductive material gives rise to the possibility that an excessive force is applied to a part of the case due to uneven pressing forces between the battery unit and the case. This could possibly create a problem with the strength and durability of the case.

Uneven pressing forces between the battery unit and the case gives rise to the possibility that the heat conductive material cannot achieve a desired compression rate. This could possibly reduce the efficiency of heat conduction between the battery unit and the case, and lead to the failure to achieve a desired cooling performance.

The present invention has been designed in consideration of the problems described above, and an object thereof is to provided an assembled battery that can ensure not only the strength and durability of a case, but also the efficiency of heat conduction.

According to one aspect of the present invention, a battery unit including stacked battery modules, each battery module including a plurality of battery cells, a case for housing the battery unit therein, the case having a bottom part, a plate-shaped cooling plate, and first heat transfer material are included, the cooling plate is fastened to the bottom part of the case from the outside of the case, and cools the battery unit via the bottom part of the case. The first heat transfer material have a plastic property and are held between the bottom part of the case and the cooling plate. The bottom part of the case has heat transfer material housings that house excess first heat transfer material therein when the cooling plate is fastened to the case.

DESCRIPTION OF EMBODIMENTS

FIG. 1is a perspective view of an assembled battery10according to the embodiment of the present invention.

The assembled battery10is composed of a battery unit20accommodated in a case30. The case30has a bottom part31and a side part32that stands so as to enclose a peripheral portion of the bottom part31. Although not illustrated, a cover part that covers the case from above is provided over the case30.

The battery unit20is composed of a plurality of stacked battery modules21. As will be described later with reference toFIG. 3, each battery module21is composed of a plurality of battery cells22, and is surrounded by a battery case23.

Each battery cell22is composed of, for example, a secondary battery that can be charged and discharged, such as a lithium-ion battery and a nickel-hydrogen battery. Each battery module21is composed of a plurality of battery cells22. The battery unit20is composed of a large number of battery modules21stacked in series. The battery modules21are fastened together by bolts and the like along a stacking direction.

FIG. 2is an disassembled perspective view of the assembled battery10according to the embodiment of the present invention.

The assembled battery10is made by placing the battery unit20into the case30without a lid as shown inFIG. 2. A cooling plate40for cooling the battery unit20is provided to an outer side of the bottom part31of the case30.

The cooling plate40is structured such that a medium flows thereinside. As the medium conducts heat away from the battery unit20, the cooling plate40cools the battery unit20such that the temperature of the battery unit20does not rise beyond necessity. Also, as the medium applies heat to the battery unit20, the cooling plate40heats the battery unit20such that the temperature of the battery unit20does not drop beyond necessity. For example, two metallic plates that have been bent to form a flow passage for the medium on an inner side thereof are used as the cooling plate40. The cooling plate40is formed by brazing outer peripherals of the two metallic plates. The cooling plate40has a medium inlet41and a medium outlet42.

The cooling plate40controls the heat of the battery unit20via an outer side of the case30. First heat transfer material51, second heat transfer material52, third heat transfer material53, and a heat conductive plate50are provided so as to increase the efficiency of heat conduction without leaving any gap between the battery unit20and the case30, and between the case30and the cooling plate40.

Specifically, the heat conductive plate50is made of a metallic material having a high heat conductive property (e.g., aluminum), and is interposed between the battery unit20and the case30. The second heat transfer material52are interposed between the heat conductive plate50and the battery unit20. The third heat transfer material53are interposed between the heat conductive plate50and the bottom part31of the case30. The first heat transfer material51are interposed between the outer side of the bottom part31of the case30and the cooling plate40.

The first heat transfer material51, the second heat transfer material52, and the third heat transfer material53increase heat conductivity by filling gaps between the outer side of the bottom part31of the case30and the cooling plate40, between the battery unit20and the heat conductive plate50, and between the heat conductive plate50and the case30.

The first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are composed of, for example, elastic resin (e.g., silicone) and a filler of a metallic or similar material that increases heat conduction. They eliminate an air layer by coming in tight contact with a target object, and increase a heat conductive property with the help of high heat conductivity of the materials thereof.

The assembled battery10is made by placing the battery unit20and the heat conductive plate50into the case30, fastening them together with bolts and the like, and further fastening the cooling plate40to the outer side of the bottom part31of the case30with bolts and the like. The second heat transfer material52are interposed between the battery unit20and the heat conductive plate50. The third heat transfer material53are interposed between the heat conductive plate50and the bottom part31of the case30. The first heat transfer material51are interposed between the bottom part31of the case30and the cooling plate40. Such a configuration improves the efficiency of heat conduction between the battery unit20and the cooling plate40, and allows for appropriate control of the temperature of the battery unit20with the aid of the medium flowing inside the cooling plate40.

In a case where the assembled battery10is configured in the above-described manner, the following problems arise.

The first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are compressed when fastening together the battery unit20, the heat conductive plate50, the bottom part31of the case30, and the cooling plate40. Between the battery unit20and the heat conductive plate50, there is room for the pressed second heat transfer material52to enter gaps between the battery modules21.

Meanwhile, the third heat transfer material53between the heat conductive plate50and the case30, as well as the first heat transfer material51between the case30and the cooling plate40, are pressed when fastening the battery unit20. At this time, if excess third heat transfer material53and excess first heat transfer material51become uneven, uneven forces are applied especially to the case30that is interposed between the third heat transfer material53and the first heat transfer material51. Such uneven forces have a possibility of causing deformation of the case30, and the deformation of the case30has a possibility of reducing the strength and durability of the case30. Uneven forces between the battery unit20and the case30could possibly prevent the third heat transfer material53and the first heat transfer material51from achieving a desired compression rate, and hence could possibly reduce the efficiency of heat conduction between the battery unit20and the cooling plate40.

In view of this, the embodiment of the present invention incorporates the following configuration to prevent unevenness in the second heat transfer material52and the first heat transfer material51, a reduction in the strength and durability of the case30, and a reduction in the efficiency of heat conduction.

FIG. 3is a cross-sectional view of major components of the assembled battery10according to the embodiment of the present invention. The cross-sectional view ofFIG. 3illustrates a portion in which the battery unit20, the heat conductive plate50, the bottom part31of the case, and the cooling plate40are in contact with one another. InFIG. 3, white arrows with an outline indicate the movement of heat, and black arrows indicate the movement of the heat transfer material51,52,53.

The battery unit20is composed of a plurality of stacked battery modules21. Each battery module21is composed of a plurality of battery cells22and a battery case23accommodating the plurality of battery cells22. The battery cases23have a function of transferring the heat of the battery cells22to the outside.

Each battery cell22is connected to two, positive and negative electrode terminals24of the corresponding battery module21via electric connection to non-illustrated electrode tabs.

In the present embodiment, in order to prevent the above-described deformation of the case30, the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are arranged only in the vicinity of portions where the battery cases23for the battery modules21are in contact with the heat conductive plate50. That is to say, as the heat of each battery module21of the battery unit20is transferred via the corresponding battery case23, the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are arranged in the vicinity of portions where the battery cases23are in contact with the heat conductive plate50, i.e., boundaries between the stacked battery modules21.

Compared to a case in which a first heat transfer material51, a second heat transfer material52, and a third heat transfer material53are each arranged as a unified material, the above-described configuration provides room for the heat transfer material to move. Therefore, the above-described configuration suppresses unevenness in the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53, and prevents application of uneven forces to the case30.

In the embodiment of the present invention, slits50aare formed in the heat conductive plate50so as to make the second heat transfer material52and the third heat transfer material53movable. The slits50apermit the second heat transfer material52and the third heat transfer material53, which are respectively provided on a front side and a back side of the heat conductive plate50, to move between the front side and the back side of the heat conductive plate50.

The above-described configuration provides room for the second heat transfer material52and the third heat transfer material53to move to the front side or the back side of the heat conductive plate50. Consequently, unevenness in the second heat transfer material52and the third heat transfer material53is suppressed, and application of uneven forces to the case30is prevented. Especially, as many voids exist between the front side of the heat conductive plate50and the battery unit20due to the structure of the battery unit20, the third heat transfer material53located in areas where the back side of the heat conductive plate50is in planar contact with the case30can move to the front side.

For example, in a case where the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are arranged in the vicinity of boundaries between the battery modules21as stated earlier, it is favorable to arrange the slits50aof the heat conductive plate50in portions where the second heat transfer material52and the third heat transfer material53are not arranged, such that the slits50aextend along a direction perpendicular to the stacking direction of the battery modules21of the battery unit20.

In the embodiment of the present invention, the bottom part31of the case30is embossed so as to make the first heat transfer material51movable. That is to say, depressions are formed in the bottom part31so as to permit movement of the first heat transfer material51.

Specifically, depressions that are recessed toward a direction away from the cooling plate40are formed in the bottom part31of the case30, such that the depressions have a predetermined height and are arranged at a predetermined interval. The depressions function as heat transfer material housings35that house therein excess first heat transfer material51when the first heat transfer material51have deformed or flowed by being pressed.

The above-described configuration provides room for excess first heat transfer material51to move into the depressions, i.e., the heat transfer material housings35, especially between the bottom part31of the case30and the cooling plate40. Consequently, unevenness in the first heat transfer material51is suppressed, and application of uneven forces to the case30is alleviated.

In a case where the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are arranged in the vicinity of boundaries between contacting battery modules21as stated earlier, it is desirable that the embosses formed in the bottom part31of the case30be upward projections arranged in portions where the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53are not arranged, such that the upward projections extend along a direction perpendicular to the stacking direction of the battery modules21of the battery unit20.

The above-described configuration prevents unevenness in the first heat transfer material51, the second heat transfer material52, and the third heat transfer material53of the assembled battery10, thereby preventing deformation of the case30caused by application of uneven forces to the case30.

As described above, the embodiment of the present invention is applied to the assembled battery including the battery unit20, the bottomed case30, the plate-shaped cooling plate40, and the first heat transfer material51. The battery unit20is composed of the stacked battery modules21, each of which includes a plurality of battery cells22. The battery unit20is housed in the case30. The cooling plate40is fastened to the bottom part31of the case30from the outside of the case30, and can cool the battery unit20via the bottom part31. The first heat transfer material51have a plastic property and are held between the bottom part31of the case30and the cooling plate40.

The bottom part31of the case30has the heat transfer material housings35that house therein excess first heat transfer material51when the cooling plate40has been fastened to the case30.

In the embodiment of the present invention with the above-described configuration, the heat transfer material housings35are interposed between the bottom part31of the case30and the cooling plate40so as to provide room for excess first heat transfer material51to move into the heat transfer material housings35. Consequently, unevenness in the first heat transfer material51is suppressed, and application of uneven forces to the case30is prevented. This suppresses application of uneven forces to the case30, thereby preventing a reduction in the strength and durability of the case30.

The heat transfer material housings35are depressions that are recessed toward a direction away from the cooling plate40. As the first heat transfer material51move into the depressions, unevenness in the first heat transfer material51is suppressed, and application of uneven forces to the case30is prevented.

As the first heat transfer material51are dispersedly arranged in a plurality of areas between the bottom part31of the case30and the cooling plate40, areas where the first heat transfer material51are not arranged have room for excess first heat transfer material51to move. Consequently, unevenness in the first heat transfer material51is suppressed, and application of uneven forces to the case30is prevented.

The first heat transfer material51are dispersedly arranged in relation to positions of contact between the battery modules21of the battery unit20, more specifically, areas where the battery cases23for the battery modules21are in opposing contact with each other, such that the first heat transfer material51extend along a direction perpendicular to the stacking direction of the battery modules21. As the first heat transfer material51are thus arranged only in areas where they are necessary for transferring the heat of the battery unit20, areas where the first heat transfer material51are not arranged have room for excess first heat transfer material51to move. Consequently, unevenness in the first heat transfer material51is suppressed, and application of uneven forces to the case30is prevented.

The plate-shaped heat conductive plate50that conducts heat is interposed between the battery unit20and the case30. The second heat transfer material52are held between the battery unit20and the heat conductive plate50. The third heat transfer material53are held between the heat conductive plate50and the case30. The heat conductive plate50has the slits50aserving as movement openings that make the second heat transfer material52and the third heat transfer material53movable between the front side and the back side of the heat conductive plate50.

The above-described configuration provides room for the second heat transfer material52and the third heat transfer material53to move to the front side or the back side of the heat conductive plate50. Consequently, unevenness in the second heat transfer material52and the third heat transfer material53is suppressed, and application of uneven forces to the case30is alleviated.

As the slits50aof the heat conductive plate50are dispersedly arranged in correspondence with positions where the second heat transfer material52and the third heat transfer material53are not arranged (in relation to positions of contact between the battery modules21), areas where the second heat transfer material52and the third heat transfer material53are not arranged have room for excess third heat transfer material53and excess second heat transfer material52to move. Consequently, unevenness in the second heat transfer material52and the third heat transfer material53is suppressed, and application of uneven forces to the case30is prevented.

The above-described embodiment of the present invention merely illustrates one of example applications of the present invention, and the specific configuration of the above-described embodiment is not intended to limit a technical scope of the present invention.

Although the battery unit20composed of a large number of battery cells22is accommodated in the case30according to the configuration of the above-described embodiment, no limitation is intended in this regard. The above-described embodiment is similarly applicable to a battery unit that is composed of a single battery accommodated in a case and that is provided with the cooling plate40.

Furthermore, instead of forming the slits50ain the heat conductive plate50and embossing the bottom part31of the case30, slits may be formed in the bottom part of the case30and the heat conductive plate50may be embossed so as to provide room for the first heat transfer material51, the second heat transfer material52, or the third heat transfer material53to move.

Embodiments of the present invention were described above, but the above embodiments are merely examples of applications of this invention, and the technical scope of this invention is not limited to the specific constitutions of the above embodiments.

This application claims priority based on Japanese Patent Application No. 2013-148414 filed with the Japan Patent Office on Jul. 17, 2013, the entire contents of which are incorporated into this specification.