Patent Description:
As indicated in <CIT>, it has been conventionally practiced to form an end plate using a plate-shaped member and to fix the end plate by a bolt. <CIT>, <CIT>, and <CIT> disclose battery modules comprising a stack of prismatic battery cells. End plates and restraint members enclose the stack. Each of the end plates includes a plate-shaped member having an abutment portion and a recess. The recess has a flat bottom surface and a portion having an uneven shape. <CIT> and <CIT> further battery modules.

It is required to secure a region for a flat surface portion of a plate-shaped member to facilitate fastening thereof to a restraint member (binding bar) while satisfying a demand for size reduction of a battery module.

It is an object of the present technology to provide a battery module to maintain strength and attain a reduced size.

The present technology provides a battery module comprising: a stack including a plurality of battery cells arranged side by side in a first direction, each of the plurality of battery cells having a prismatic shape; an end plate provided to be arranged side by side with the plurality of battery cells in the first direction; and a restraint member that restrains the plurality of battery cells and the end plate along the first direction, the restraint member being provided to be arranged side by side with the plurality of battery cells and the end plate in a second direction orthogonal to the first direction, wherein the end plate includes a plate-shaped member, the plate-shaped member has an uneven shape including an abutment portion and a recess, the abutment portion being in abutment with the stack in the first direction, the recess being located in a direction away from the stack with respect to the abutment portion, the recess includes a first portion and a second portion, the first portion having a flat surface shape, the first portion constituting a bottom surface of the recess, the second portion having been through a process for forming the uneven shape, and a pressing process has been performed onto the plate-shaped member at a region overlapping with the second portion having been through the process for forming the uneven shape when viewed in the first direction so as to form a pressing-processed portion continuous to the first portion and expanding the first portion.

The end plate may include a fastening portion that is provided in the first portion and that is fastened to the restraint member.

The fastening portion may be provided to be located at each of both end portions of the end plate in the second direction.

The abutment portion and the recess may be formed to each extend in the second direction and to be adjacent to each other along a third direction orthogonal to the first direction and the second direction.

Each of widths of the abutment portion and the recess in the third direction may be changed along the second direction, and the pressing process may have been performed onto the abutment portion at a portion having a relatively narrow width in the third direction.

The battery module may further comprise a case that accommodates the plurality of battery cells, that supports the plurality of battery cells in at least the first direction, and that forms a unit including the plurality of battery cells.

The unit may include two or more battery cells, and each of the two or more battery cells may have an output density of <NUM> W/L or more.

Hereinafter, embodiments of the present technology will be described. It should be noted that the same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly.

It should be noted that in the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment.

It should be noted that in the present specification, the terms "comprise", "include", and "have" are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included.

Also, in the present specification, when geometric terms and terms representing positional/directional relations are used, for example, when terms such as "parallel", "orthogonal", "obliquely at <NUM>°", "coaxial", and "along" are used, these terms permit manufacturing errors or slight fluctuations. In the present specification, when terms representing relative positional relations such as "upper side" and "lower side" are used, each of these terms is used to indicate a relative positional relation in one state, and the relative positional relation may be reversed or turned at any angle in accordance with an installation direction of each mechanism (for example, the entire mechanism is reversed upside down).

In the present specification, the term "battery" is not limited to a lithium ion battery, and may include other batteries such as a nickel-metal hydride battery and a sodium ion battery. In the present specification, the term "electrode" may collectively represent a positive electrode and a negative electrode.

<FIG> is a perspective view showing a battery module according to an embodiment of the present invention. <FIG> is an exploded assembly diagram showing the battery module in <FIG>. <FIG> is a perspective view showing a battery cell unit included in the battery module in <FIG>. <FIG> is a perspective view showing a battery cell included in the battery cell unit in <FIG>.

Referring to <FIG>, a battery module <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 description of the structure of battery module <NUM>, the "Y axis" represents an axis extending in parallel with a stacking direction of a plurality of below-described battery cells <NUM>, the "X axis" represents an axis extending in a direction orthogonal to the Y axis, and the "Z axis" represents an axis extending in a direction orthogonal to the Y axis and the X axis. An obliquely rightward upward direction in the plane of sheet of <FIG> is "+Y axis direction", and an obliquely leftward downward direction in the plane of sheet of <FIG> is "-Y axis direction". An obliquely rightward downward direction in the plane of sheet of <FIG> is "+X axis direction" and an obliquely leftward upward direction in the plane of sheet of <FIG> is "-X axis direction". An upward direction in the plane of sheet of <FIG> is "+Z axis direction" and a downward direction in the plane of sheet of <FIG> is "-Z axis direction". Typically, battery module <NUM> is mounted on a vehicle in such a posture that the +Z axis direction corresponds to the upward direction and the -Z axis direction corresponds to the downward direction.

First, an overall structure of battery module <NUM> will be described. As shown in <FIG>, battery module <NUM> has a plurality of battery cell units <NUM> (21A, 21B, 21C, 21D, 21E, 21F).

The plurality of battery cell units <NUM> are arranged side by side in the Y axis direction. Battery cell unit 21A, battery cell unit 21B, battery cell unit 21C, battery cell unit 21D, battery cell unit 21E, and battery cell unit 21F are arranged side by side in this order from the negative side to the positive side in the Y axis direction. It should be noted that the number of battery cell units <NUM> included in battery module <NUM> is not particularly limited as long as two or more battery cell units <NUM> are included.

As shown in <FIG>, each of battery cell units <NUM>, i.e., each of battery cell units 21A to 21F includes a plurality of battery cells <NUM> and a case body <NUM>.

In each battery cell unit <NUM>, two battery cells <NUM> are arranged side by side continuously in the Y axis direction. It should be noted that the number of battery cells <NUM> included in each battery cell unit <NUM> is not particularly limited as long as a plurality of battery cells <NUM> are included.

Each of battery cells <NUM> is a lithium ion battery. As an example, battery cell <NUM> can have an output density of <NUM> W/L or more. Battery cell <NUM> has a prismatic shape. More specifically, battery cell <NUM> 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 the external appearance of battery cell <NUM>. An electrode assembly and an electrolyte solution are accommodated in exterior package <NUM>.

Exterior package <NUM> has a cell side surface <NUM>, a cell side surface <NUM>, and a cell top surface <NUM>. Each of cell side surface <NUM> and cell side surface <NUM> is constituted of a flat surface orthogonal to the Y axis direction. Cell side surface <NUM> and cell side surface <NUM> are oriented oppositely in the Y axis direction. Each of cell side surface <NUM> and cell side surface <NUM> has the largest area among the areas of the plurality of side surfaces of exterior package <NUM>. Cell top surface <NUM> is constituted of a flat surface orthogonal to the Z axis direction. Cell top surface <NUM> is oriented in the +Z axis direction.

Battery cell <NUM> further has a gas-discharge valve <NUM>. Gas-discharge valve <NUM> is provided in cell top surface <NUM>. Gas-discharge valve <NUM> is provided at the center portion of cell top surface <NUM> in the X axis direction. When internal pressure of exterior package <NUM> becomes more than or equal to a predetermined value due to gas generated inside exterior package <NUM>, gas-discharge valve <NUM> discharges the gas to the outside of exterior package <NUM>. The gas from gas-discharge valve <NUM> flows through a below-described duct <NUM> and is discharged to the outside of battery module <NUM>.

Battery cell <NUM> further has electrode terminals <NUM> including a pair of a positive electrode terminal 16P and a negative electrode terminal 16N. Electrode terminals <NUM> are provided on cell top surface <NUM>. Positive electrode terminal 16P and negative electrode terminal 16N are provided on both sides with gas-discharge valve <NUM> being interposed therebetween in the X axis direction.

Case body <NUM> has a rectangular parallelepiped appearance. Case body <NUM> is composed of a resin. In each battery cell unit <NUM>, case body <NUM> accommodates a plurality of battery cells <NUM>. Case body <NUM> has a case top portion <NUM>. Case top portion <NUM> has a wall shape having a thickness direction corresponding to the Z axis direction with case top portion <NUM> being disposed in parallel with the X-Y axes plane.

As shown in <FIG> and <FIG>, the plurality of battery cells <NUM> are stacked in the Y axis direction (first direction) across battery cell units 21A to 21F arranged side by side in the Y axis direction. The plurality of battery cells <NUM> are stacked such that cell side surfaces <NUM> of battery cells <NUM> adjacent to each other in the Y axis direction face each other and cell side surfaces <NUM> of battery cells <NUM> adjacent to each other in the Y axis direction face each other. Thus, positive electrode terminals 16P and negative electrode terminals 16N are alternately arranged in the Y axis direction in which the plurality of battery cells <NUM> are stacked. Positive electrode terminal 16P and negative electrode terminal 16N adjacent to each other in the Y axis direction are connected to each other by a bus bar (not shown). Thus, the plurality of battery cells <NUM> are electrically connected together in series.

As shown in <FIG> and <FIG>, battery module <NUM> further has a pair of end plates <NUM> (42P, 42Q) and a pair of binding bars <NUM> (restraint members). The pair of binding bars <NUM> and the pair of end plates <NUM> collectively hold the plurality of battery cell units <NUM> (the plurality of battery cells <NUM>) arranged side by side in the Y axis direction.

The pair of end plates <NUM> are disposed at both ends beside the plurality of battery cells <NUM> (the plurality of battery cell units <NUM>) in the Y axis direction. End plate 42P faces battery cell unit 21A in the Y axis direction, and end plate 42Q faces battery cell unit 21F in the Y axis direction.

The pair of binding bars <NUM> are disposed at both ends of the stack of battery cells <NUM> in the X axis direction (second direction). That is, the pair of bind bars <NUM> are provided to be arranged side by side with the plurality of battery cell units <NUM> and end plates <NUM> in the X axis direction. Each of binding bars <NUM> extends in the Y axis direction. An end portion of binding bar <NUM> in the -Y axis direction is connected to end plate 42P by a bolt <NUM>. An end portion of binding bar <NUM> in the +Y axis direction is connected to end plate 42Q by a bolt <NUM>. The pair of binding bars <NUM> and the pair of end plates <NUM> apply a restraint force in the Y axis direction onto the plurality of battery cells <NUM> (the plurality of battery cell units <NUM>). It should be noted that a retainer may be further provided which extends in the X axis direction with the retainer intersecting a below-described duct <NUM> and which is connected to the pair of binding bars <NUM> at both end portions thereof.

Stud bolts <NUM> are attached to end plates <NUM>. Battery module <NUM> is fixed to a supporting mechanism (such as a pack case) via stud bolts <NUM>.

Battery module <NUM> further has duct <NUM> and a cover body <NUM>.

Duct <NUM> is composed of a resin such as polybutylene terephthalate resin (PBT resin). Duct <NUM> extends in the Y axis direction with duct <NUM> facing the plurality of battery cells <NUM> (the plurality of battery cell units <NUM>) in the Z axis direction (third direction). Duct <NUM> is an elongated body extending in the Y axis direction. Duct <NUM> forms a path through which gas discharged from each of the plurality of battery cells <NUM> flows. Duct <NUM> is attached to an attachment-target member <NUM>. Attachment-target member <NUM> is a member held by battery cells <NUM>, and, in the present embodiment, is constituted of the plurality of case bodies <NUM> arranged side by side in the Y axis direction.

Cover body <NUM> is composed of a resin. Cover body <NUM> is provided to cover the plurality of battery cells <NUM> in the Z axis direction. Cover body <NUM> is provided to face case top portions <NUM> of case bodies <NUM> in the Z axis direction. Cover body <NUM> is provided to further cover duct <NUM>.

<FIG> is a side view showing surroundings around abutment portions between end plate 42Q and case body <NUM> of battery cell unit 21F. Each of <FIG> and <FIG> is a perspective view showing end plate 42Q. <FIG> is a perspective view showing a plate-shaped member <NUM> included in end plate 42Q. <FIG> is a front view showing plate-shaped member <NUM>.

It should be noted that one end plate 42Q is shown in <FIG>; however, the other end plate 42P has substantially the same structure as that of end plate 42Q.

Referring to <FIG>, end plate 42Q is constituted of two plate-shaped members <NUM>, <NUM>. Plate-shaped member <NUM> has a wave shape including protrusions <NUM> and recesses <NUM>. Protrusions <NUM> and recesses <NUM> are formed by a bending process to provide a continuous, curved surface with no angular portion. As shown in <FIG>, protrusions <NUM> constitute abutment portions 110A, 110B that are each in abutment with case body <NUM>.

Plate-shaped member <NUM> has flange portions <NUM>, <NUM> each protruding to the case body <NUM> side along the Y axis direction. A clearance is formed between each of the tips of flange portions <NUM>, <NUM> in the Y axis direction and case body <NUM> (A and B in <FIG>).

Plate-shaped member <NUM> has: a flange portion <NUM> protruding opposite to case body <NUM> along the Y axis direction; and a flange portion <NUM> protruding to the case body <NUM> side. A clearance is formed between the tip of flange portion <NUM> in the Y axis direction and case body <NUM> (B in <FIG>).

In plate-shaped member <NUM>, the plurality of protrusions <NUM> and the plurality of recesses <NUM> are alternately formed to be arranged side by side in the Z axis direction. That is, each of abutment portions 110A, 110B and each of recesses <NUM> are formed to adjacent to each other along the Z axis direction. Each of protrusions <NUM> and recesses <NUM> is formed to extend in the X axis direction. In each of the plurality of recesses <NUM> (three in the example of <FIG>), a flat surface portion <NUM> is formed. Fastening holes 44A (fastening portions) extending through plate-shaped members <NUM>, <NUM> are formed at flat surface portions <NUM> located at the both end portions of end plate 42Q in the X axis direction. Bolts <NUM> for fastening end plate 42Q to binding bar <NUM> are inserted into fastening holes 44A.

Respective flange portions <NUM>, <NUM> of plate-shaped members <NUM>, <NUM> are provided only at the center portion of end plate 42Q in the X axis direction, and are not provided at the both end portions of end plate 42Q in the X axis direction. Hence, at the both end portions of end plate 42Q in the X axis direction, flat surface portions <NUM>, <NUM> extend to the lower end portions (tips in the -Z axis direction) of plate-shaped members <NUM>, <NUM>.

Between flange portion <NUM> and flat surface portion <NUM> each located at the lower end portion of plate-shaped member <NUM>, a transition portion <NUM> is provided to continuously transition from flat surface portion <NUM> to flange portion <NUM>. Transition portion <NUM> is adjacent to flat surface portion <NUM> located at the lower end portion of plate-shaped member <NUM>. Transition portion <NUM> is formed by performing a twisting process (twist-bending process) onto plate-shaped member <NUM>. Therefore, the transition is made to provide plate-shaped member <NUM> with a curved surface that has no angular portion and that is continuous from each of flat surface portions <NUM> on the both end sides of end plate 42Q in the X axis direction to flange portion <NUM> on the center side of end plate 42Q in the X axis direction. Flat surface portion <NUM>, transition portion <NUM>, and flange portion <NUM> each located at the lower end portion of plate-shaped member <NUM> are arranged side by side in the X axis direction (second direction).

Similarly, between flange portion <NUM> and flat surface portion <NUM> each located at the lower end portion of plate-shaped member <NUM>, a transition portion <NUM> is provided to continuously transition from flat surface portion <NUM> to flange portion <NUM>. Transition portion <NUM> is adjacent to flat surface portion <NUM> located at the lower end portion of plate-shaped member <NUM>. Transition portion <NUM> is formed by performing a twisting process (twist-bending process) onto plate-shaped member <NUM>. Therefore, the transition is made to provide plate-shaped member <NUM> with a curved surface that has no angular portion and that is continuous from each of flat surface portions <NUM> on the both end sides of end plate 42Q in the X axis direction to flange portion <NUM> on the center side of end plate 42Q in the X axis direction. Flat surface portion <NUM>, transition portion <NUM>, and flange portion <NUM> each located at the lower end portion of plate-shaped member <NUM> are arranged side by side in the X axis direction (second direction).

Flange portion <NUM> of plate-shaped member <NUM> and flange portion <NUM> of plate-shaped member <NUM> are formed to be arranged side by side in the Z axis direction. Flange portion <NUM> is located on the +Z axis direction side with respect to flange portion <NUM>.

Each of the widths of abutment portions 110A, 110B extending in the X axis direction is changed along the X axis direction, and abutment portions 110A, 110B have portions wide in width (D1A, D1B) and portions narrow in width (D2A, D2B). As shown in <FIG>, each of the widths of abutment portions 110A, 110B is continuously and smoothly changed (in the form of a curve) between each portion wide in width and each portion narrow in width.

Stud bolts <NUM> are attached to end plate 42Q (plate-shaped member <NUM>) on sides opposite to the portions wide in width (D1A, D1B) shown in <FIG>. This leads to improved supporting strength for battery module <NUM>.

<FIG> is an enlarged view of surroundings around fastening hole 44A. As shown in <FIG>, fastening hole 44A is formed in flat surface portion <NUM> (first portion) constituting the bottom surface of recess <NUM>. Each of unevenness-processed portions <NUM> (second portion) having been through a process for forming the uneven shape of plate-shaped member <NUM> is located adjacent to flat surface portion <NUM>. A pressing process for forming a flat surface continuous to flat surface portion <NUM> has been performed in a range of a radius R1 (> a radius R2 of fastening hole 44A) from the center of fastening hole 44A. The pressing process has been performed to a region overlapping with unevenness-processed portion <NUM> when viewed in the Y axis direction. Thus, pressing-processed portions 150A are formed to expand flat surface portion <NUM>, thereby securing an installation space for a nut to be fastened to bolt <NUM> while attaining the size reduction of end plate 42Q.

In the example of <FIG>, a distance (L1, L2) from the center of fastening hole 44A to each of unevenness-processed portions <NUM> (interference region) is about <NUM> or more and <NUM> or less, whereas the pressing process is performed to the region in the range of the radius (R1) of about <NUM> or more and <NUM> or less. Thus, flat surface portion <NUM> is expanded, with the result that an M6 nut can be securely installed. It should be noted that in the present technology, the size of the region subjected to the pressing process is not limited to the above-described numerical range.

The shape of the region subjected to the pressing process is not limited to the substantially circular shape, and the pressing process may be performed to a region having a substantially elliptical shape or a substantially polygonal shape, for example.

Plate-shaped members <NUM>, <NUM> may be spot-welded together at a spot welding portion <NUM>. Pressing-processed portion 150A that expands flat surface portion <NUM> is not limited to being formed around fastening hole 44A, and may be formed around spot welding portion <NUM>, for example.

In battery module <NUM> according to the embodiment of the present technology, the strength of end plate 42Q can be improved by forming plate-shaped member <NUM> included in end plate 42Q into the wave shape including protrusions <NUM> and recesses <NUM>.

Here, as shown in <FIG>, since the pressing process has been performed to expand flat surface portion <NUM> of plate-shaped member <NUM> included in end plate 42Q, an installation space for a nut to be fastened to bolt <NUM> can be secured without sacrificing the strength of end plate 42Q, thereby attaining the size reduction of battery module <NUM> while avoiding the restriction in space.

Moreover, the strength of end plate 42Q can be further improved by providing flange portions <NUM>, <NUM>, <NUM>, <NUM> protruding along the Y axis direction from the upper and lower end portions (the upper and lower end portions in the Z axis direction) of plate-shaped members <NUM>, <NUM>.

Further, since flat surface portions <NUM>, <NUM> extend to the lower end portions of plate-shaped members <NUM>, <NUM> without providing flange portions <NUM>, <NUM> at the lower end portions in the both end portions of end plate 42Q in the X axis direction, the areas of flat surface portions <NUM>, <NUM> can be secured while suppressing increased heights of plate-shaped members <NUM>, <NUM> in the Z axis direction, with the result that the size reduction of end plate 42Q is avoided from being inhibited.

Thus, in battery module <NUM>, flange portions <NUM>, <NUM> (the center portion in the X axis direction) and flat surface portions <NUM>, <NUM> (the both end portions in the X axis direction) are provided at the lower end portions of plate-shaped members <NUM>, <NUM>. This causes formation of respective boundary portions between flange portions <NUM>, <NUM> and flat surface portions <NUM>, <NUM>. Since transition portions <NUM>, <NUM> are provided at these boundary portions to continuously transition from flat surface portions <NUM>, <NUM> to flange portions <NUM>, <NUM>, an angular portion that causes excessive stress concentration can be avoided from being formed in each of plate-shaped members <NUM>, <NUM>, with the result that flange portions <NUM>, <NUM> can be connected to flat surface portions <NUM>, <NUM> respectively without impairing the strength of end plate 42Q.

As a result, it is possible to attain the size reduction of battery module <NUM> (particularly, suppression of increased size in the Z axis direction) while maintaining the strength of end plate 42Q.

Further, in battery module <NUM>, by forming battery cell units <NUM> that each accommodate the plurality of battery cells <NUM> in case body <NUM> with the plurality of battery cells <NUM> being arranged side by side in the Y axis direction and by forming battery module <NUM> by arranging the plurality of battery cell units <NUM> side by side in the Y axis direction, a manufacturing process can be simplified as compared with a case where battery module <NUM> is manufactured based on each of the plurality of battery cells <NUM> as one unit.

In battery module <NUM>, by forming battery cell units <NUM> that each accommodate the plurality of battery cells <NUM> in case body <NUM>, battery module <NUM> can be readily disassembled or replaced based on each battery cell unit <NUM> as a unit.

In battery module <NUM>, by forming battery cell units <NUM> that each accommodate the plurality of battery cells <NUM> in case body <NUM>, battery module <NUM> can be divided based on each battery cell unit <NUM> as one unit in order to lower the voltage to be handled when discarding battery module <NUM>. Therefore, battery module <NUM> can be readily discarded.

Claim 1:
A battery module comprising:
a stack including a plurality of battery cells (<NUM>) arranged side by side in a first direction, each of the plurality of battery cells (<NUM>) having a prismatic shape;
an end plate (<NUM>) provided to be arranged side by side with the plurality of battery cells (<NUM>) in the first direction; and
a restraint member (<NUM>) that restrains the plurality of battery cells (<NUM>) and the end plate (<NUM>) along the first direction, the restraint member (<NUM>) being provided to be arranged side by side with the plurality of battery cells (<NUM>) and the end plate (<NUM>) in a second direction orthogonal to the first direction, wherein
the end plate (<NUM>) includes a plate-shaped member (<NUM>),
the plate-shaped member (<NUM>) has an uneven shape including an abutment portion (110A, 110B) and a recess (<NUM>), the abutment portion (110A, 110B) being in abutment with the stack in the first direction, the recess (<NUM>) being located in a direction away from the stack with respect to the abutment portion (110A, 110B), and
the recess (<NUM>) includes a first portion (<NUM>) and a second portion (<NUM>), the first portion (<NUM>) having a flat surface shape, the first portion (<NUM>) constituting a bottom surface of the recess (<NUM>), the second portion (<NUM>) having been through a process for forming the uneven shape, characterized in that
a pressing process has been performed onto the plate-shaped member (<NUM>) at a region overlapping with the second portion (<NUM>) having been through the process for forming the uneven shape when viewed in the first direction so as to form a pressing-processed portion (150A) continuous to the first portion (<NUM>) and expanding the first portion (<NUM>).