BATTERY PACK

A battery pack according to an aspect of the present disclosure includes a battery module and an external case accommodating the battery module therein. The external case includes: a case body having a tubular shape having an opening; and a lid part closing the opening of the case body. The lid part includes: an inner lid connected to the opening of the case body; and an outer lid fixed to the inner lid and closing the opening of the case body. The inner lid is connected to an inner surface of the case body at the opening of the case body. The outer lid is fixed to an outer surface of the inner lid.

TECHNICAL FIELD

The present disclosure relates to a battery pack including a battery module accommodated in an exterior case having a tubular shape.

BACKGROUND ART

FIG.5is an exploded perspective view of a conventional battery pack. An exterior case including a tubular case body is advantageously mass-produced while the case body has a sufficient strength. The battery module is accommodated in the case body, and a lid is fixed to an opening of the case body (PTL 1).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

The battery pack including a tubular case body closed at each of both end openings with a lid part is required, as shown inFIG.5, to include fixing protrusion ridges96having threaded holes97into which locking screws95penetrating lid parts94are screwed to fix lid parts94to case body93. Since case body93shown inFIG.5includes fixing protrusion ridges96protruded on its inner surface, fixing protrusion ridges96restrict the inner volume of the battery pack. Battery pack90having the inner volume restricted by fixing protrusion ridges96is required to increase the outer shape of case body93so as to allow battery module91having a specific outer shape to be accommodated in case body93. As a result, the volumetric energy density is reduced. The fixing protrusion ridges may protrude on the outer surface of the case body so as to prevent the fixing protrusion ridges from restricting the inner volume of the battery pack. In this configuration, however, the fixing protrusion ridges enlarge the outer shape of the battery pack, so that the volumetric energy density may be reduced.

A battery pack according to the present disclosure may solve the above-described disadvantage of the conventional battery pack. An object of the present disclosure is to provide a battery pack including a case body with a tubular shape so as to allow the case body to be efficiently mass-produced and to allow an opening of the case body to be closed without fixing protrusion ridges on an inner or outer surface of the case body so that a high volumetric energy density, which is an important characteristic required for the battery pack, is obtained.

A battery pack in accordance with an aspect of the present disclosure includes a battery module and an external case accommodating the battery module therein. The external case includes: a case body having a tubular shape having an opening; and a lid part closing the opening of the case body. The lid part includes: an inner lid connected to the opening of the case body; and an outer lid fixed to the inner lid and closing the opening of the case body. The inner lid is connected to an inner surface of the case body at the opening of the case body. The outer lid is fixed to an outer surface of the inner lid.

In the above-described battery pack, the lid part for closing the opening of the case body with a tubular shape includes the inner lid that connected to the inner surface of the case body and the outer lid fixed to the inner lid so that the opening of the case body may be closed by the outer lid. The battery pack does not require fixing protrusion ridges, which are required in the conventional battery pack to fix the lid part, on the inner surface or the outer peripheral surface at the opening of the case body. Therefore, while the case body has a tubular shape which may be efficiently mass-produced, it is possible to obtain a high volumetric energy density, which is an important characteristic for the battery pack.

A battery pack in accordance with another aspect of the present disclosure may further include a gasket sandwiched between the outer lid and the opening of the case body to provide the external case with a waterproof structure to seal the opening of the case body. The inner lid may be connected to the opening of the case body with a non-waterproof structure. The outer lid may have a shape closing the opening of the case body. The gasket may be pressed on the case body by the outer lid to provide the external case with the waterproof structure to seal the opening of the case body.

In the above-described battery pack, the inner lid is connected to the opening of the case body with a non-waterproof structure, the outer lid is fixed to the outer surface of the inner lid, and the outer lid presses the gasket on the case body to provide the waterproof structure with the gasket and outer lid to seal the opening of the case body. Accordingly, this battery pack does not require fixing ridges that are provided in the conventional battery pack for fixing the lid to the opening of the case body to constitute a watertight structure. Therefore, the external case has a waterproof structure to seal the opening of the case body with a compact external shape.

In a battery pack in accordance with still another aspect of the present disclosure, the gasket is sandwiched between respective surfaces of the outer lid and an opening edge of the case body which face each other.

In the above-described battery pack, the outer lid is fixed to the inner lid so that the gasket is pressed on the case body by the outer lid. Accordingly, the outer lid may not be necessarily connected to the case body through the gasket in a secure waterproof structure.

In a battery pack in accordance with still another aspect of the present disclosure, the inner lid may be connected to the case body with an engaging structure in which the inner lid is inserted into the inner surface of the case body to be engaged with the inner surface of the case body.

In the above-described battery pack, the inner lid is inserted into the inner surface of the case body and connected to the case body by an engaging structure. Accordingly, the inner lid may be connected to the case body by a simple structure. Further, the connection by the engaging structure allows the inner lid to be connected to a predetermined position on the case body accurately without any misalignment.

In a battery pack in accordance with still another aspect of the present disclosure, the case body may have a plurality of engaging recesses in the inner surface of the case body at the opening of the case body. The inner lid may include a plurality of engaging projections projecting from an outer periphery of the inner lid configured to be guided into the engaging recesses, respectively. The plurality of engaging projections may be guided into the plurality of engaging recesses to connect the inner lid to a predetermined position on the case body.

In the above-described battery pack, the engaging recesses are provided in the inner surface of the case body, the engaging projections configured to be guided to the engaging recesses are provided on the outer periphery of the outer lid, and the engaging projections are guided to the engaging recesses to connect the inner lid to a predetermined position on the case body. Accordingly, the inner lid may be connected to the predetermined position on the case body by a simple step of inserting the inner lid into the inside of the case body.

In a battery pack in accordance with still another aspect of the present disclosure, the inner lid may include a peripheral wall inserted into the inner surface of the case body from the opening. The plurality of engaging projections may be disposed on an outer surface of the peripheral wall. The plurality of engaging projections may be guided to the plurality engaging recesses, respectively, to connect the inner lid to the inner surface of the case body.

In the above-described battery pack, the inner lid includes the peripheral wall, and the engaging projections project from the outer surface of the peripheral wall. Accordingly, the peripheral wall may slide on the inner surface of the case body to move the inner lid from the opening to the inside of the case body while keeping the inner lid in a position parallel to the opening of the case body. Therefore, the engaging projections provided on the peripheral wall of the inner lid all together may be guided to the engaging recesses provided in the inner surface of the case body to easily connect the inner lid to the case body by an engaging structure.

In a battery pack in accordance with still another aspect of the present disclosure, the peripheral wall may be made of an elastically deformable plate. The peripheral wall may elastically deform to fit the engaging projections to the engaging recesses.

In the above-described battery pack, the peripheral wall on which the plurality of engaging projections are provided elastically deforms. Accordingly, the engaging projections may slide smoothly along the inner surface of the case body to guide the engaging projections to the engaging recesses, so that the inner lid can be connected to a predetermined position on the case body by an engaging structure.

In a battery pack in accordance with still another aspect of the present disclosure, the inner lid may be welded or adhered to the case body to be connected to the case body.

In the above-described battery pack, the inner lid is welded to the case body or adhered to the case body to connect the inner lid to the case body. Accordingly, the inner lid is securely connected to the case body in a wide area or in a long region.

In a battery pack in accordance with still another aspect of the present disclosure, the outer lid may be connected to the inner lid with a locking screw penetrating the outer lid with a waterproof structure and screwed into the inner lid.

In the above-described battery pack, the outer lid may be easily connected to the inner lid, and to press the gasket on the case body in the step of fixing the outer lid to the inner lid, so that the outer lid, the gasket and the inner lid can be securely connected to the case body to provide the external case with a waterproof structure.

In a battery pack in accordance with still another aspect of the present disclosure, the outer lid may have a recess provided in an outer surface of the outer lid. A head of the locking screw may be disposed in the recess.

In the above-described battery pack, the outer lid has the recess therein and the screw head of the locking screw is disposed in the recess. Accordingly, the outer lid is fixed to the inner lid while preventing the locking screw from projecting from the outer surface of the outer lid or while reducing a projecting amount of the locking screw from the outer surface of the outer lid.

In a battery pack in accordance with still another aspect of the present disclosure, the case body may be made of aluminum and have a tubular shape.

In the above-described battery pack, the case body may be efficiently mass-produced by a drawing process or an extrusion process.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present disclosure will be described in detail with reference to the drawings. Although, in the following description, terms indicating particular directions or positions (e.g., “top,” “bottom,” and other terms each containing either of these terms) will be used as needed, such terms will be used to help the disclosure with reference to the drawings to be easily understood. Accordingly, it should not be construed that the technical scope of the present invention is limited by the meanings of those terms. Also, the parts appearing in two or more drawings with like reference marks will indicate like or similar parts or members.

Further, the exemplary embodiments described hereinafter show concrete examples of the technical idea of the present invention, and are not intended to limit the present invention to the following embodiments. Also, dimensions, materials, shapes, and relative arrangements of the components described hereinafter are not intended to limit the scope of the present invention to those components, unless otherwise specifically described so, but intended to show as examples. Also, contents described in one exemplary embodiment or one working example are applicable to other exemplary embodiments or other working examples. Also, sizes or positional relations of the members shown in the drawings may be sometimes exaggerated to clarify the explanation.

Battery pack100shown inFIGS.1-4includes battery module1accommodated in external case2. Battery module1includes a battery block including battery cells connected in series or parallel or series-parallel to one another, and a circuit board connected to the battery block. In the battery block, in order to have a desired charge/discharge capacity, the battery cells are connected in series or parallel or series-parallel to one another, and each the battery cells are disposed at predetermined positions by a battery holder. A protective circuit is mounted on the circuit board. The protective circuit is connected to the battery block to control charging and discharging operations the battery block. Each battery cell may be a secondary battery, such as a lithium ion battery. Battery module1including the lithium ion secondary batteries as the battery cells provide a large charge/discharge capacity compared to its volume and weight. However, the battery cells of the battery block may not necessarily be the lithium ion secondary batteries, and may be any of the secondary batteries that are currently available or that would be developed in future such, for example, as the all-solid-state batteries.

External case2includes case body3with a tubular shape and lid parts4that close openings3A of case body3, respectively. Each lid part4includes inner lid5connected to opening3A of case body3, and outer lid6fixed to outer surface5A of inner lid5and closing opening3A of case body3. Inner lid5is connected to an inner surface of case body3at opening3A. Outer lid6is fixed to outer surface5A of inner lid5and closes opening3A of case body3. External case2shown inFIGS.1-4further includes gasket7sandwiched between outer lid6and case body3so that lid part4may be connected to opening3A of case body3so as to provide external case2with a waterproof structure. External case2having the waterproof structure prevents various harmful effects caused by water infiltrated into the inside of case body3such, for example, as the leakage current or the short-circuit current due to reduction of the insulating resistance, to thereby secure a higher safety.

Case body3may be produced by forming a plastic or preferably a metal into a tubular shape by a drawing process or an extrusion process. Case body3with a tubular shape may be efficiently mass-produced by forming a metal or a plastic into a long tube and cutting the long tube to pieces having predetermined lengths. Case body3formed by the drawing process or the extrusion process may have a uniform cross-sectional shape so as to be configured to smoothly slide and insert the later-described inner lid5into the inner surface of case body3at opening3A. Case body3made of a metal may be produced by processing preferably an aluminum or an aluminum alloy by a drawing process or an extrusion process. Case body3made of a metal has an excellent impact strength, as well as a desirable thermal conductivity to allow the heat generated by heat generating components disposed inside the battery pack to be efficiently radiated to the outside. However, the present disclosure is not intended to limit the metal of case body3to aluminum. Case body3may be made of a metal other than aluminum. For example, case body3may be made of a light-weight metal, such as magnesium, with a small weight so that a high gravimetric energy density may be obtained while having an excellent impact strength. Case body3may be made of a plastic. In this case, reinforcing fibers such as glass fibers or carbon fibers, may be buried to produce a tough case body3.

Case body3shown inFIGS.2-4has engaging recesses8formed in the inner surface at opening3A for connecting inner lid5at a predetermined position in case body3by an engaging structure. Engaging recesses8are configured to guide engaging projections9provided on the outer surface of inner lid5so that engaging projections9are fitted to engaging recesses8to connect inner lid5to case body3without a misalignment. The fitting structure of engaging recesses8and engaging projections9may be realized as a shape that allows engaging projections9to be guided to engaging recesses8without any gaps. The fitting structure for guiding engaging projections9to engaging recesses8may be realized by making a gap between each of engaging recesses8and a corresponding one of engaging projections9to be, for example, 0.2 mm or smaller, and preferably 0.1 mm or smaller.

To guide engaging projections9smoothly, each of engaging recesses8may be formed to have a chamfered opening edge or may be formed in such a tapered shape that the opening area increases as becoming closer to opening3A.

Engaging recesses8are formed in the inner surface at opening3A of case body3without passing through case body3. Engaging recesses8may be formed by, for example, pressing inner surface3C (inner surface3D) of case body3with a tubular shape. In this press-working method, a press mold having projections for forming engaging recesses8is inserted into the inside of case body3so that both ends of the press mold are projected from both openings3A of case body3, and the projected portions are pressed by a press mechanism to form engaging recess8. However, the present disclosure is not intended to limit the method for forming engaging recesses8in the inner surface of case body3. Any of all other methods that can form engaging recesses8on the inner surface of case body3may be used.

In case body3having a rectangular tubular shape, engaging recesses8are provided in respective inner surfaces of side walls forming the rectangular tubular shape to stably and securely connect inner lid5to case body3by an engaging structure. In case body3shown inFIGS.2-4, engaging recesses8are formed at respective opposite positions in the inner surfaces. Case body3has the rectangular tubular shape which has an inner surface including four inner surfaces perpendicular to adjacent two. Engaging recesses8are provided in four inner surfaces of the rectangular tubular shape of tubular case body3, so that inner lid5may be connected to case body3more accurately without any misalignment, while keeping inner lid5be perpendicular to an axial direction of case body3(a horizontal position in the drawings). Case body3shown inFIG.3has engaging recesses8therein such that the number of engaging recesses8on each wider surface3acorresponding to a longer side of the rectangular shape is larger than the number of engaging recesses8on each narrower surface3bcorresponding to a shorter side of the rectangular shape. Case body3having this structure allows inner lid5having a rectangular shape to be kept perpendicular to the axial direction of case body3(a horizontal position in the figure) and connected to a predetermined position in case body3. The number of engaging recesses8formed in each inner surface may be increased to allow inner lid5to be kept be perpendicular to the axial direction of case body3and firmly connected to a predetermined position in case body3. On the other hand, the number of engaging recesses8may be decreased to efficiently perform the step of connecting inner lid5and case body3. Accordingly, the number of engaging recesses8may be determined optimally considering the size and bending strength of inner lid5.

Although case body3shown inFIGS.1-3has the rectangular tubular shape, the tube shape of case body3may not be limited to be a rectangular in the lateral cross-sectional shape. The lateral cross-sectional shape of tubular case body3may be an ellipse, a circle or a polygon with rounded corners. Case body3having any of these shapes may have engaging recesses8therein arranged at predetermined intervals to allow inner lid5to be kept be perpendicular to the axial direction of case body3and connected to a predetermined position in case body3.

Inner lid5is connected to the inner surface of case body3at opening3A. Inner lid5shown inFIGS.2-4is connected to case body3by an engaging structure. Inner lid5connected to case body3by an engaging structure may be inserted into the inner surface of case body3at opening3A to be simply and easily connected to a predetermined position in case body3without any misalignment.

Inner lid5connected to case body3by an engaging structure includes engaging projections9projecting from the outer periphery of inner lid5to configured to be guided to engaging recesses8in the inner surface of case body3. Since engaging projections9are guided to engaging recesses8to connect inner lid5to a predetermined position in case body3, each engaging projection9may preferably have, as described before, an outer shape configured to be guided to engaging recesses8by the engaging structure.

In external case2having a waterproof structure, the waterproof structure is not realized by inner lid5and case body3, but is realized by gasket7between outer lid6and case body3. Since inner lid5may not necessarily be connected to case body3with a waterproof structure, inner lid5may not be configured to have a waterproof structure, and can be simply engaged to the inner surface of case body3with a non-waterproof structure. Inner lid5is configured to fix outer lid6to opening3A of case body3, and is not required to have a function of closing opening3A of case body3by itself. Accordingly, inner lid5may be easily connected to case body3by an engaging structure. However, the connecting structure may not be limited to the engaging structure. Any other structure that can connect inner lid5to case body3may be used. For example, inner lid5may be adhered to case body3. As another method, the outer periphery of inner lid5may be welded to the inner periphery of case body3.

Inner lid5shown inFIGS.3and4is produced by pressing a metal plate into a box shape having body plate10and peripheral walls11formed at a peripheral portion of body plate10so as to be inserted into the inner surface of case body3at opening3A. Engaging projections9are provided on outer surfaces of peripheral walls11. Inner lid5having this structure may be produced by press-working a flat metal plate to form engaging projections9, cutting the metal plate to pieces each having a predetermined outer shape, and bending the periphery of body plate10perpendicularly to form peripheral walls11. In this shape, inner lids5each having accurate dimensions and shape may be efficiently mass-produced by a pressing step, a cutting step and a bending-working step. Further, inner lid5allows peripheral walls11to slide on inner surfaces3C (inner surface3D) of case body3so that inner lid5may move from opening3A to the inside of case body3while keeping a position parallel to opening3A of case body3to guide engaging projections9to engaging recesses8. Accordingly, engaging projections9provided on peripheral walls11of inner lid5may be guided altogether to respective engaging recesses8provided in inner surface3D of case body3, so that inner lid5can be disposed at a predetermined position in case body3. Further, since the inside space surrounded by peripheral walls11becomes a part of a space for accommodating battery module1therein, the heights of peripheral walls11may be high (the vertical width in the figure may be increased) without narrowing the space for accommodating battery module1therein, so that inner lid5may move along inner surface3D, while keeping the horizontal position, to be connected to case body3.

Further, In the above-described inner lid5, each of the metal plates constituting peripheral walls11may have an elastically deformable width of 2 mm or thinner so that peripheral walls11with engaging projections9can smoothly slide along inner surface3D of case body3to guide engaging projections9to engaging recesses8. In addition, engaging projections9having been guided to engaging recesses8can be held to be prevented from being released from engaging recesses8by the elastic restoring force of peripheral walls11, so that inner lid5can be firmly connected to case body3. In inner lid5having such elastically deformable peripheral walls11, the pressure of engaging projections9pressing inner surface3D of case body3is decreased due to the elastic deformation of peripheral walls11. Engaging projections9decreased in the pressure of pressing inner surface3D reduce the frictional resistance between each of engaging projections9and inner surface3D of case body3since the frictional resistance increases in proportion to the pressing force. Engaging projections9reduced in the frictional resistance can smoothly slide along inner surface3D to be quickly guided to engaging recesses8. Further, since engaging projections9having been guided to engaging recesses8are held in engaging recesses8by the elastic restoring force, inner lid5can be disposed at a predetermined position in case body3. In other words, inner lid5having the above-described structure can realize such ideal properties that inner lid5is smoothly connected to a predetermined position in case body3and that inner lid5in the connected state is kept at the predetermined position in case body3without being released from the connected state. This feature is important in a case where external case2is required to guide a lot of engaging projections9to engaging recesses8to securely connect a large inner lid5to case body3. Since increase in the number of engaging projections9and engaging recesses8generally increase the total frictional resistance between engaging projections9and inner surface3D of case body3, which in turn causes difficulty in smooth connection of inner lid5to case body3.

Inner lid5has threaded holes12into which locking screws13for fixing outer lid6are screwed. In inner lid5shown inFIGS.3and4, threaded holes12are arranged in the periphery of body plate10so as to oppose to positions on outer lid6through which locking screws13penetrate outer lid6. Each of threaded holes12has been processed by the burring method so that locking screw13screwed into each threaded hole12can be firmly fixed.

Outer lid6is fixed to outer surface5A of inner lid5and closes opening3A of case body3. Outer lid6may be produced as a plate made of a plastic or a metal and having an outer shape that can closes opening3A of case body3. Outer lid6shown inFIGS.1-4has an outer periphery that is the same in shape as the outer periphery of case body3with the same shape, so that the outer periphery of outer lid6may be flush with the outer periphery of case body3. Outer lid6can be fixed to inner lid5with locking screws13that pass through outer lid6with a waterproof structure. Each locking screw13is provided on a center of its screw head with a driving recess having a non-circular shape, such as a hexagonal shape, a star shape or an elliptic shape, and can be screwed into inner lid5by inserting a driver into the driving recess and rotating the driver. Each locking screw13passes through outer lid6while seal14with a ring shape is sandwiched between the screw head and the surface of outer lid6, and is fixed to inner lid5by screwing the threaded portion of locking screw13into threaded hole12of inner lid5. Locking screw13that does not connect outer lid6with a waterproof structure passes through outer lid6without using seal14and is screwed into inner lid5.

Outer lid6shown inFIGS.1-4has recess15in outer surface6A as a space for the screw heads of locking screws13to be disposed. In the illustrated outer lid6, rectangular recess15is provided in an area excluding the outer peripheral portion. The depth of recess15is larger than the height of the screw head so that outer lid6can be fixed to inner lid5while the screw heads do not project from the outer surface of outer lid6. Recess15has through-holes16therein through which locking screws15are inserted. Through-holes16are arranged along the outer periphery of recess15so that the outer periphery of outer lid6can be fixed to inner lid5with locking screws13inserted through penetrating holes16to allow the outer peripheral portion of outer lid6to tightly contact opening3A of case body3. Outer lid6having recess15in the area excluding the outer periphery may be fixed to inner lid5while the screw head of each locking screw13does not project from the outer surface of outer lid6or the amount of projection of the screw head is small. Further, the outer periphery of outer lid6may be thick to increase the bending strength so that the outer periphery of outer lid6can securely and tightly contact and be fixed to opening3A of case body3. Further, recess15advantageously reduces the weight of outer lid6. Battery pack100including outer lid6with the reduced weight may have outer lid6made of a metal, such as aluminum. Outer lid6made of metal such as aluminum has an adequate strength, provides an excellent heat radiation property, and reduces the weight of external case2, so that a high gravimetric energy density can be obtained. Outer lid6may not be made of a metal, but may be made of a plastic. Outer lid6made of a plastic may have recess15therein to reduce its weight so that a high gravimetric energy density can be obtained.

Outer lid6shown inFIG.4has guide groove17therein for guiding gasket7, which is a member for outer lid6to be fixed to case body3with a waterproof structure, to a predetermined position. Guide groove17is provided in a surface of the outer lid facing opening end surface3B of case body3. The depth of guide groove17is smaller than the thickness or outer diameter of gasket7so that gasket7is compressed while outer lid6is fixed to inner lid5to tightly contact opening end surface3B of case body3.

Gasket7is made of a rubber-like elastic material, such as elastomer or rubber or a material with a ring shape that can be pressed to tightly contact outer lid6and opening end surface3B of case body3to realize a waterproof structure. Gasket7is disposed in guide groove17and pressed by outer lid6on case body3to elastically deform. Gasket7may be an O-ring made of elastomer or a rubber or may be a sheet that can be pressed to tightly contact the opposing surfaces to provide external case2with a waterproof structure. In a state in which outer lid6is fixed to inner lid5, gasket7tightly contact respective surfaces of outer lid6and case body3which face each other to provide external case2with the waterproof structure to seal external case2.

External case2shown inFIG.4includes gasket7that is sandwiched between outer lid6and the opening edge of case body3to provide external case2with a waterproof structure to seal opening3A of case body3. In battery pack100, inner lid5is connected to opening3A of case body3with a non-waterproof structure, outer lid6has an outer shape that can close opening3A of case body3or preferably has an outer shape nearly equal to the outer shape of case body3, and gasket7is pressed by outer lid6on the opening edge of case body3. Gasket7made of a rubber-like elastic material and pressed by outer lid6elastically deforms in the pressed direction to tightly contact the outer periphery of outer lid6and opening end surface3B of case body3, thereby providing external case2with the waterproof structure to seal opening3A of case body3.

INDUSTRIAL APPLICABILITY

The present disclosure is favorably applicable as a battery pack that includes a battery module encased in a tubular external case and can obtain a high volumetric energy density.