Patent Description:
For example, <CIT> discloses a power supply device including: a battery block formed by stacking a plurality of prismatic batteries; a cooling plate fixed to a bottom surface of the battery block and coupled to each of the prismatic batteries in a thermal coupling state; and a cooling mechanism that cools the cooling plate.

Further, <CIT> discloses a power storage device including: a plurality of cells; a heat conduction sheet disposed in at least one cell of the plurality of cells so as not to be in contact with a whole or part of the bottom surface of the cell;
and a heat conduction paste interposed in a clearance between the heat conduction sheet and the bottom surface of the cell in which the heat conduction sheet is not in contact with the whole or part of the bottom surface of the cell.

A battery pack according to the preamble of claim <NUM> is known from <CIT>. Further battery packs are subject-matter of <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

In the power supply device disclosed in <CIT>, the cooling plate is fixed to the bottom surface of the battery block. However, since the cooling plate is provided with a coolant path through which coolant (including cooling water) circulates, the cooling plate needs to have a certain thickness or more. In this case, an overall height (overall length in the upward/downward direction) of the power supply device becomes large.

Thus, it is an object of the present invention to solve the above-described problem and to provide a battery pack having a small overall height.

A battery pack according to the present invention includes: a plurality of stacked battery cells; and a case body that has a first bottom portion and a first side portion and that accommodates the plurality of battery cells, the first bottom portion being a portion on which the plurality of battery cells are placed, the first side portion rising from the first bottom portion. A coolant path through which coolant flows is provided inside the first side portion.

According to the battery pack thus configured, since the coolant path is provided in the first side portion, the thickness of the first bottom portion in the upward/downward direction can be small. Thus, an overall height of the battery pack can be small.

The battery pack further includes a heat conduction member interposed between each of the battery cells and the case body. The heat conduction member has a second side portion disposed between each of the battery cells and the first side portion.

According to the battery pack thus configured, heat from each of the battery cells can be efficiently conducted, via the second side portion, to the first side portion provided with the coolant path. Thus, performance of cooling the battery cells can be improved.

An upper end portion of the second side portion is disposed above the coolant path. A lower end portion of the second side portion is disposed below the coolant path.

According to the battery pack thus configured, since the second side portion is more securely disposed between each of the battery cells and the coolant path, heat from each of the battery cells can be more efficiently conducted to the first side portion via the second side portion.

The heat conduction member is composed of an adhesive agent that joins each of the battery cells to the case body. According to the battery pack thus configured, since the heat conduction member serves to conduct heat generated in each of the battery cells and join each of the battery cells to the case body, the battery pack can have a simple configuration.

Preferably, the heat conduction member further has a second bottom portion contiguous to the lower end portion of the second side portion and disposed between each of the battery cells and the first bottom portion.

According to the battery pack thus configured, heat from each of the battery cells can be efficiently conducted, via the second bottom portion and the first bottom portion, to the first side portion provided with the coolant path. Thus, the performance of cooling the battery cells can be further improved.

Preferably, the battery pack further includes a protrusion that is disposed at a corner portion of the first bottom portion and the first side portion and that protrudes toward each of the battery cells.

According to the battery pack thus configured, a clearance in which the heat conduction member is not disposed can be prevented from being formed at the corner portion of the first bottom portion and the first side portion.

Preferably, the first bottom portion is composed of a solid plate material. According to the battery pack thus configured, the thickness of the first bottom portion in the upward/downward direction can be smaller.

Preferably, the first side portion is composed of a frame material that extends in a stacking direction of the battery cells and that defines and forms a hollow portion. The hollow portion forms the coolant path.

According to the battery pack thus configured, since the coolant flows directly through the hollow portion defined and formed by the first side portion, the battery pack can have a simple configuration.

Preferably, the battery pack includes a plurality of cell stacks. Each of the cell stacks is constituted of the plurality of battery cells stacked in one direction. The plurality of cell stacks are arranged side by side at intervals in a direction orthogonal to the stacking direction of the battery cells. The first side portion rises from the first bottom portion toward a space between adjacent cell stacks of the plurality of cell stacks and extends in the stacking direction of the battery cells.

According to the battery pack thus configured, the battery cells can be efficiently cooled in the plurality of cell stacks while attaining a small overall height of the battery pack.

Embodiments of the present invention will be described with reference to figures. It should be noted that in the figures referred to below, the same or corresponding members are denoted by the same reference characters.

<FIG> is a cross sectional view showing a battery pack according to an embodiment of the present invention. <FIG> is a perspective view showing a battery cell included in the battery pack in <FIG>. <FIG> is an exploded assembly diagram showing battery cells and a case body included in the battery pack in <FIG>.

Referring to <FIG>, a battery pack <NUM> is used as a power supply for driving a vehicle such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a battery electric vehicle (BEV).

In the present specification, for convenience of explanation of a structure of a battery pack <NUM>, a "Y axis" represents an axis extending in a stacking direction of a plurality of below-described battery cells <NUM> and in a horizontal direction, an "X axis" represents an axis extending in a direction orthogonal to the Y axis and in the horizontal direction, and a "Z axis" represents an axis extending in an upward/downward direction.

Battery pack <NUM> has a plurality of battery cells <NUM> and a case body <NUM>. The plurality of battery cells <NUM> are stacked in the Y axis direction. Case body <NUM> accommodates the plurality of battery cells <NUM>.

As shown in <FIG>, battery cell <NUM> is a lithium ion battery. Battery cell <NUM> has a prismatic shape and has a thin plate shape in the form of a rectangular parallelepiped. The plurality of battery cells <NUM> are stacked such that the Y axis direction corresponds to the thickness direction of each battery cell <NUM>.

Each of battery cells <NUM> has an exterior package <NUM>. Exterior package <NUM> is constituted of a housing having a rectangular parallelepiped shape, and forms an external appearance of battery cell <NUM>. An electrode assembly and an electrolyte solution are accommodated in exterior package <NUM>.

Exterior package <NUM> has a first side surface <NUM>, a second side surface <NUM>, a top surface <NUM>, and a bottom surface <NUM>. Each of first side surface <NUM> and second side surface <NUM> is constituted of a flat surface orthogonal to the Y axis. First side surface <NUM> and second side surface <NUM> are oriented oppositely in the Y axis direction. Each of first side surface <NUM> and second side surface <NUM> has the largest area among the areas of the plurality of side surfaces of exterior package <NUM>. Each of first side surface <NUM> and second side surface <NUM> has a rectangular shape. Each of first side surface <NUM> and second side surface <NUM> has a rectangular shape in which the X axis direction corresponds to the long side direction and the Z axis direction corresponds to the short side direction.

Each of top surface <NUM> and bottom surface <NUM> is constituted of a flat surface orthogonal to the Z axis. Top surface <NUM> is oriented upward. Bottom surface <NUM> is oriented downward. Top surface <NUM> is provided with a gas-discharge valve <NUM> for discharging gas generated in exterior package <NUM> to outside of exterior package <NUM> when internal pressure of exterior package <NUM> becomes equal to or more than a predetermined value due to the gas.

Battery cell <NUM> further has electrode terminals <NUM> including a pair of a positive electrode terminal 18P and a negative electrode terminal 18N. Electrode terminal <NUM> is provided on top surface <NUM>. Positive electrode terminal 18P and negative electrode terminal 18N are provided to be separated from each other in the X axis direction. Positive electrode terminal 18P and negative electrode terminal 18N are provided on both sides beside gas-discharge valve <NUM> in the X axis direction.

The plurality of battery cells <NUM> are stacked such that first side surfaces <NUM> of battery cells <NUM>, <NUM> adjacent to each other in the Y axis direction face each other and second side surfaces <NUM> of battery cells <NUM>, <NUM> adjacent to each other in the Y axis direction face each other. Thus, positive electrode terminals 18P and negative electrode terminals 18N are alternately arranged in the Y axis direction in which the plurality of battery cells <NUM> are stacked.

Between battery cells <NUM>, <NUM> adjacent to each other in the Y axis direction, positive electrode terminal 18P and negative electrode terminal 18N arranged side by side in the Y axis direction are connected to each other by a bus bar (not shown). The plurality of battery cells <NUM> are electrically connected to one another in series. The plurality of battery cells <NUM> may be electrically connected to one another in parallel or in parallel and series in combination.

The plurality of stacked battery cells <NUM> form a cell stack <NUM>. Cell stack <NUM> has a rectangular parallelepiped shape. The length of cell stack <NUM> in the Y axis direction is larger than the length of cell stack <NUM> in the Z axis direction and is larger than the length of cell stack <NUM> in the X axis direction.

Case body <NUM> is constituted of a box body having an external appearance with a rectangular parallelepiped shape. The length of case body <NUM> in the Y axis direction is larger than the length of case body <NUM> in the Z axis direction and is larger than the length of case body <NUM> in the X axis direction. Case body <NUM> has a case bottom portion <NUM>, first case side portions <NUM> (23A, 23B), second case side portions <NUM> (25C, 25D), and a case top portion <NUM>. In the present embodiment, case bottom portion <NUM> corresponds to a "first bottom portion" in the present invention, and each of first case side portions <NUM> corresponds to a "first side portion" in the present invention.

Case bottom portion <NUM> is disposed at the bottom of case body <NUM>. Case bottom portion <NUM> is composed of a plate material that has a thickness direction corresponding to the Z axis direction and that extends in the horizontal direction. Case bottom portion <NUM> is composed of a solid plate material. Case bottom portion <NUM> is not provided with a hollow portion. The plurality of battery cells <NUM> are placed on case bottom portion <NUM>. The plurality of battery cells <NUM> are placed on case bottom portion <NUM> with a below-described heat conduction member <NUM> (bottom portion <NUM>) being interposed therebetween.

Each of first case side portions <NUM> rises from case bottom portion <NUM> and extends upward. First case side portion <NUM> has a certain width in the X axis direction and extends in the Y axis direction. First case side portion <NUM> is provided along a peripheral edge of case bottom portion <NUM> extending in the Y axis direction. First case side portion 23A and first case side portion 23B are provided to be separated from each other in the X axis direction.

Each of first case side portions <NUM> (23A, 23B) is composed of a frame material that defines and forms hollow portions <NUM>. Each of hollow portions <NUM> extends in the Y axis direction, which is the stacking direction of the plurality of battery cells <NUM>. When cut along an X-Z axes plane, first case side portion <NUM> has such a cross sectional shape that is unchanged among all the cutting positions in the Y axis direction.

More specifically, first case side portion <NUM> has a frame portion <NUM> and partition wall portions <NUM>. When cut along the X-Z axes plane, frame portion <NUM> has such a cross section that frame portion <NUM> extends along four sides of a rectangular shape. Frame portion <NUM> forms an external appearance of first case side portion <NUM>. Partition wall portions <NUM> are provided inside frame portion <NUM>. Partition wall portions <NUM> define a space inside frame portion <NUM> into the plurality of hollow portions <NUM>. Each of hollow portions <NUM> has an opening having a rectangular shape when viewed in the Y axis direction. The plurality of hollow portions <NUM> are provided side by side in the X axis direction and the Z axis direction. As an example, first case side portion <NUM> is composed of an aluminum extrusion material.

It should be noted that first case side portion <NUM> may be provided with a single hollow portion <NUM>, or may be provided with a hollow portion <NUM> having a circular shape or a polygonal shape other than the rectangular shape.

Each of second case side portions <NUM> rises from case bottom portion <NUM> and extends upward. Second case side portion <NUM> has a certain width in the Y axis direction and extends in the X axis direction. Second case side portion <NUM> is provided along a peripheral edge of case bottom portion <NUM> extending in the X axis direction. Second case side portion 25C and second case side portion 25D are provided to be separated from each other in the Y axis direction. Second case side portion 25C and second case side portion 25D are provided on both sides beside the plurality of battery cells <NUM> stacked in the Y axis direction. The plurality of battery cells <NUM> are restrained by second case side portion 25C and second case side portion 25D in the Y axis direction.

First case side portions <NUM> and second case side portions <NUM> extend along the peripheral edges of case bottom portion <NUM>. Space <NUM> is defined at a position located above case bottom portion <NUM> and surrounded by first case side portions <NUM> and second case side portions <NUM> so as to be open upward and accommodate the plurality of battery cells <NUM> (cell stack <NUM>).

Case top portion <NUM> is disposed to face case bottom portion <NUM> in the Z axis direction. Case top portion <NUM> is detachably attached to upper end portions of first case side portions <NUM> and second case side portions <NUM> and serves as a cover body to close the opening of space <NUM>.

Case bottom portion <NUM>, first case side portions <NUM>, second case side portions <NUM> and case top portion <NUM> are constituted of separate members, and are combined together to form case body <NUM>. The case body of the present invention is not limited to such a configuration, and for example, the first case bottom portion and the first case side portions may be constituted of one member.

A coolant path <NUM> is provided inside first case side portion <NUM> (23A, 23B). Coolant path <NUM> is provided inside frame portion <NUM> that forms the external appearance of first case side portion <NUM>. Coolant path <NUM> allows coolant (for example, cooling water) to flow therethrough. Coolant path <NUM> allows the coolant to flow in the Y axis direction.

Coolant path <NUM> is provided adjacent to the plurality of battery cells <NUM> (cell stack <NUM>) in the X axis direction. Coolant path <NUM> extends between one end and the other end of the plurality of battery cells <NUM> in the Y axis direction.

Battery pack <NUM> further has a tube member <NUM>. Tube member <NUM> is disposed in a hollow portion <NUM>. Tube member <NUM> is disposed in a hollow portion <NUM> positioned adjacent to battery cells <NUM> in the X axis direction and just above case bottom portion <NUM> in the Z axis direction among the plurality of hollow portions <NUM>. Tube member <NUM> extends in the Y axis direction. Tube member <NUM> is provided in contact with the inner wall of first case side portion <NUM> that defines hollow portion <NUM>. Coolant path <NUM> is constituted of tube member <NUM>.

<FIG> is a cross sectional view showing a battery pack according to a comparative example. Referring to <FIG>, in the comparative example, a coolant path <NUM> is provided instead of coolant path <NUM> (tube member <NUM>) in <FIG>. Coolant path <NUM> is provided inside case bottom portion <NUM>. In such a configuration, since coolant path <NUM> extends in case bottom portion <NUM>, thickness t of case bottom portion <NUM> becomes large. This leads to a large overall height h of the battery pack, with the result that energy density with respect to the volume of the battery pack may be decreased and mountability of the battery pack onto a vehicle may be decreased.

Referring to <FIG>, in contrast, in battery pack <NUM> according to the present embodiment, coolant path <NUM> (tube member <NUM>) is provided inside first case side portion <NUM>. With such a configuration, since thickness T of case bottom portion <NUM> can be small, overall height H of battery pack <NUM> can be small.

The following continuously describes the structure of battery pack <NUM>. Battery pack <NUM> further has heat conduction member <NUM>.

Heat conduction member <NUM> is interposed between each of battery cells <NUM> and case body <NUM>. Heat conduction member <NUM> is interposed between each of the plurality of battery cells <NUM> (cell stack <NUM>) and case body <NUM>. Heat conduction member <NUM> is provided to extend between one end and the other end of the plurality of battery cells <NUM> (cell stack <NUM>) in the Y axis direction.

Heat conduction member <NUM> has a bottom portion <NUM> and side portions <NUM>. In the present embodiment, bottom portion <NUM> corresponds to a "second bottom portion" in the present invention, and each of side portions <NUM> corresponds to a "second side portion" in the present invention. Bottom portion <NUM> is disposed between each of battery cells <NUM> (bottom surface <NUM>) and case bottom portion <NUM>. Each of side portions <NUM> is disposed between each of battery cells <NUM> and first case side portion <NUM> (23A, 23B). Bottom portion <NUM> is contiguous to a lower end portion 43q of side portion <NUM>.

An upper end portion 43p of side portion <NUM> is disposed above coolant path <NUM> (tube member <NUM>). Upper end portion 43p of side portion <NUM> is disposed above a contact position of tube member <NUM> with first case side portion <NUM>. Lower end portion 43q of side portion <NUM> is disposed below coolant path <NUM> (tube member <NUM>).

Heat conduction member <NUM> is composed of a material having a heat conductivity higher than that of air. Heat conduction member <NUM> is composed of, for example, a gap filler. Heat conduction member <NUM> has fluidity during assembling of battery pack <NUM>, and is hardened when left at room temperature or when heated. Heat conduction member <NUM> is composed of a resin such as acrylic, urethane, or silicone. Heat conduction member <NUM> may be an adhesive agent that joins battery cells <NUM> to case body <NUM>.

According to such a configuration, since side portion <NUM> of heat conduction member <NUM> is disposed between battery cell <NUM> and first case side portion <NUM>, heat from battery cell <NUM>, which emits heat, can be efficiently conducted through side portion <NUM> to first case side portion <NUM> including coolant path <NUM> (tube member <NUM>). Thus, performance of cooling battery cells <NUM> can be improved. In this case, since upper end portion 43p of side portion <NUM> is disposed above coolant path <NUM> and lower end portion 43q of side portion <NUM> is disposed below coolant path <NUM>, side portion <NUM> can be disposed more securely on a path of conduction of heat from battery cell <NUM> to coolant path <NUM>. Further, since heat conduction member <NUM> has bottom portion <NUM> disposed between battery cell <NUM> and case bottom portion <NUM>, heat from battery cell <NUM> can be conducted to first case side portion <NUM> through bottom portion <NUM> and case bottom portion <NUM>. Thus, the performance of cooling battery cells <NUM> can be further improved.

When heat conduction member <NUM> is an adhesive agent, battery cell <NUM> can be fixed to case body <NUM> by using heat conduction member <NUM> for improving heat conduction from battery cell <NUM>.

Battery pack <NUM> further has protrusions <NUM>. Protrusions <NUM> are disposed at corner portions of case bottom portion <NUM> and first case side portions <NUM> (23A, 23B). Protrusions <NUM> protrude toward battery cells <NUM>. Each of protrusions <NUM> extends in the Y axis direction. Protrusion <NUM> has a rectangular shape when viewed in the Y axis direction. An upper end portion 51p of protrusion <NUM> is disposed above bottom surface <NUM> of battery cell <NUM>. Upper end portion 51p of protrusion <NUM> is disposed below the contact position of tube member <NUM> with first case side portion <NUM>. A lower end portion 51q of protrusion <NUM> is disposed below bottom surface <NUM> of battery cell <NUM>.

Each of <FIG> and <FIG> is a cross sectional view showing a step during assembling of the battery pack in <FIG>. Referring to <FIG>, a heat conduction material <NUM> having flowablility is disposed in space <NUM>. Heat conduction material <NUM> is disposed to have a certain height from case bottom portion <NUM>. Referring to <FIG>, next, the plurality of battery cells <NUM> (cell stack <NUM>) are disposed in space <NUM>. By soaking the bottom portion of cell stack <NUM> in heat conduction material <NUM>, heat conduction material <NUM> on case bottom portion <NUM> flows out to a space beside cell stack <NUM>. On this occasion, heat conduction material <NUM> can be smoothly guided to the space beside cell stack <NUM> by protrusions <NUM> disposed at the corner portions of case bottom portion <NUM> and first case side portions <NUM>. Further, since a clearance between each protrusion <NUM> and cell stack <NUM> in the X axis direction is small, an amount of flow of heat conduction material <NUM> toward the space beside cell stack <NUM> can be increased.

Then, heat conduction material <NUM> is hardened to form heat conduction member <NUM> having bottom portion <NUM> and side portions <NUM>. It should be noted that with protrusions <NUM>, a sealing characteristic between case bottom portion <NUM> and each of first case side portions <NUM> can be improved and the plurality of battery cells <NUM> can be more precisely aligned in the Y axis direction while ensuring a distance between each of first case side portions <NUM> and each of battery cells <NUM>.

Next, various modifications of battery pack <NUM> will be described. <FIG> is a cross sectional view showing a first modification of the battery pack (coolant path) in <FIG>. Referring to <FIG>, in the present modification, tube member <NUM> in <FIG> is not provided in hollow portion <NUM>, and hollow portion <NUM> constitutes coolant path <NUM> through which coolant flows. According to such a configuration, the number of components of the battery pack can be reduced.

<FIG> are cross sectional views showing second to fourth modifications of the battery pack (protrusion) in <FIG>. Each of <FIG> shows a cross section of the battery pack corresponding to a range surrounded by a chain double-dashed line VIII in <FIG>.

Referring to <FIG>, in the present modification, a side portion 51r of protrusion <NUM> facing battery cell <NUM> in the X axis direction is constituted of a tapered surface inclined with respect to the Z axis direction (upward/downward direction). The width of protrusion <NUM> in the X axis direction is smaller in a direction from lower end portion 51q toward upper end portion 51p. Referring to <FIG>, in the present modification, a chamfered portion <NUM> constituted of a flat surface is provided at a corner portion of side portion 51r and upper end portion 51p. Referring to <FIG>, in the present modification, a chamfered portion <NUM> constituted of a curved surface is provided at a corner portion of side portion 51r and upper end portion 51p.

According to these modifications, during the step of disposing the plurality of battery cells <NUM> (cell stack <NUM>) in space <NUM>, cell stack <NUM> is smoothly guided by protrusions <NUM> to a position just above case bottom portion <NUM>. Therefore, the step of disposing the plurality of battery cells <NUM> in space <NUM> can be performed readily. Further, by providing each of chamfered portions <NUM>, <NUM> shown in <FIG> and <FIG> in protrusion <NUM>, each of battery cells <NUM> (particularly, an insulating sheet material that covers exterior package <NUM> of battery cell <NUM>) can be suppressed from being broken due to contact with protrusion <NUM>.

<FIG> is a cross sectional view showing a fifth modification of the battery pack in <FIG>. Referring to <FIG>, in the present modification, a plurality of cell stacks <NUM> (10A, 10B, 10C) are arranged side by side at intervals in the X axis direction orthogonal to the Y axis direction. Case body <NUM> further has first frames <NUM> (29A, 29B) and second frames <NUM> (61A, 61B, 61C, 61D, 61E, 61F). In the present modification, each of second frames <NUM> corresponds to the "first side portion" in the present invention.

Each of first frames <NUM> has the same frame structure as that of first case side portion <NUM>, and is provided on case bottom portion <NUM> to extend upward. First frame 29A extends in the Y axis direction in a space between cell stack 10A and cell stack 10B. First frame 29B extends in the Y axis direction in a space between cell stack 10B and cell stack 10C.

Each of second frames <NUM> is composed of a frame material that rises from case bottom portion <NUM> and that extends in the Y axis direction. Second frame 61A is interposed between first case side portion 23A and cell stack 10A. Second frame 61B and second frame 61C rise from case bottom portion <NUM> toward the space between cell stack 10A and cell stack 10B. Second frame 61B is interposed between cell stack 10A and first frame 29A, and second frame 61C is interposed between first frame 29A and cell stack 10B. Second frame 61D and second frame 61E rise from case bottom portion <NUM> toward the space between cell stack 10B and cell stack 10C. Second frame 61D is interposed between cell stack 10B and first frame 29B, and second frame 61E is interposed between first frame 29B and cell stack 10C. Second frame 61F is interposed between cell stack 10C and first case side portion 23B.

A coolant path <NUM> is provided inside each of second frames <NUM> (61A, 61B, 61C, 61D, 61E, 61F). Coolant path <NUM> extends in the Y axis direction. With such a configuration, battery cells <NUM> can be efficiently cooled in the plurality of cell stacks <NUM> while attaining a small overall height of the battery pack.

Claim 1:
A battery pack, comprising:
a plurality of stacked battery cells (<NUM>); and
a case body (<NUM>) that has a first bottom portion (<NUM>) and a first side portion (<NUM>) and that accommodates the plurality of battery cells (<NUM>), the first bottom portion (<NUM>) being a portion on which the plurality of battery cells (<NUM>) are placed, the first side portion (<NUM>) rising from the first bottom portion (<NUM>), wherein
a coolant path (<NUM>) through which coolant flows is provided inside the first side portion (<NUM>),
the battery pack further comprising:
a heat conduction member (<NUM>) interposed between each of the battery cells (<NUM>) and the case body (<NUM>), wherein
the heat conduction member (<NUM>) has a second side portion (<NUM>) disposed between each of the battery cells (<NUM>) and the first side portion (<NUM>)
an upper end portion (43p) of the second side portion (<NUM>) is disposed above the coolant path (<NUM>), and
a lower end portion (43q) of the second side portion (<NUM>) is disposed below the coolant path (<NUM>)
characterized in that
the heat conduction member (<NUM>) is composed of an adhesive agent that joins each of the battery cells (<NUM>) to the case body (<NUM>).