Patent Description:
Conventionally, an end plate is formed using a plate-shaped member, and a flange portion is provided at an end portion of the plate-shaped member.

Examples of the background art include <CIT> and <CIT>.

Further, patent document <CIT> discloses a power supply device, comprising: a battery laminate in which a plurality of square battery cells are laminated; a plan view rectangular end plate having a pressing surface which covers an end surface of the battery laminate; and a fastening member which fastens the battery laminate. The end plate forms, on the pressing surface, flat pressing regions respectively formed on the end edge sides in the up-down direction, and a bead region which is formed on the middle side in the up-down direction and curves to a shape projecting to the back surface side of the pressing surface. The foregoing allows the pressing regions for pressing the battery laminate to remain on the end plate, while making it possible to improve strength by changing the shape forming the bead region in the middle.

Patent document <CIT> discloses a power source apparatus which is provided with battery blocks made up of a plurality of battery cells connected in battery stacks, and an outer case that holds the battery blocks. A block circuit board to control the battery cells that make up each battery stack and electrical components connected to the block circuit board or the battery stack are disposed in the end-planes of each battery stack.

Patent document <CIT> discloses a battery pack device including a plurality of battery cells, a bind bar, and a regulation member. The plurality of battery cells has a rectangular box exterior shape. The bind bar couples the plurality of battery cells to each other with the battery cells being arranged side by side. When the battery pack is secured onto a horizontal surface, the regulation member regulates upward deviation of at least one of the battery cells, which is located in a central part of the battery pack in the side-by-side arrangement direction of the battery cells.

Patent document <CIT> relates to the technical field of batteries, and in particular, to a battery and an electrical device. The battery comprises: a plurality of battery cells arranged in a first direction; end plates disposed at end portions of the plurality of battery cells in the first direction; and an insulating component connected to the end plates and disposed on the top surfaces of the end plates in a second direction, wherein the second direction is perpendicular to the first direction; the maximum length of the insulating member in a third direction is A; the maximum length of the end plates in the third direction is B; A ≥ <NUM> B; the third direction is perpendicular to the first direction and the second direction.

In addition, patent document <CIT> discloses that to provide a power supply device including a battery stack in which battery cells are stacked, in order to prevent entering of water due to a capillary phenomenon and unintended conduction from occurring, the power supply device including, in a battery stack, a spacer interposed between adjacent battery cells, end plates that press end surfaces of the battery stack, a plurality of fastening members each formed into a plate shape extending in a stacking direction of the plurality of battery cells, the fastening members being disposed on opposite side surfaces of the battery stack and fastening end plates to each other, an output terminal that connects the plurality of battery cells in series or in parallel and outputs electric power, and a lower plate that is made of metal and covers a lower surface of the battery stack, wherein the output terminal is disposed near an upper surface side of the battery stack, and one or more wide regions expanded to be intervals at which a capillary phenomenon does not occur are formed in a path of a gap from the lower plate or the plurality of fastening members to the output terminal.

Even when the shape of the plate-shaped member is changed, it is required to avoid strength of the end plate from being decreased due to stress concentration. In another aspect, it is required to secure a region for a flat surface portion of the plate-shaped member and promote 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 above object is solved by the subject-matter of claim <NUM>. Further advantageous configurations of the invention can be drawn from the dependent claims.

A first explanatory aspect of the present disclosure provides a battery module comprising: 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 includes a flat surface portion, a flange portion, and a transition portion, the flange portion being provided at an end portion of the plate-shaped member in a third direction orthogonal to the first direction and the second direction, the flange portion protruding from the flat surface portion in the first direction, the transition portion continuously transitioning from the flat surface portion to the flange portion, and the flat surface portion, the transition portion, and the flange portion are provided to be arranged side by side in the second direction.

A second explanatory aspect of the present disclosure relates to the first explanatory aspect, wherein the end plate includes a fastening portion that is provided in the flat surface portion adjacent to the transition portion and that is fastened to the restraint member.

A third explanatory aspect of the present disclosure relates to the second explanatory aspect, wherein the fastening portion is provided to be located at each of both end portions of the end plate in the second direction.

A fourth explanatory aspect of the present disclosure relates to any one of the first to third explanatory aspects, further comprising 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.

A fifth explanatory aspect of the present disclosure relates to the fourth explanatory aspect, wherein the plate-shaped member has a protrusion and a recess each extending in the second direction and arranged side by side in the third direction, and the protrusion is in abutment with the case in the first direction.

A sixth explanatory aspect of the present disclosure relates to the fourth or fifth explanatory aspect, wherein the unit includes two or more battery cells, and each of the two or more battery cells has 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 binding 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 side view showing end plate 42Q. <FIG> is a front view showing end plate 42Q.

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. 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>.

As shown in <FIG>, each of a total length (L1) of flange portion <NUM> and transition portions <NUM> in the X axis direction and a total length (L2) of flange portion <NUM> and transition portions <NUM> in the X axis direction is smaller than a pitch (L) between fastening holes 44A in the X axis direction (L > L1, L2). Therefore, at the both end portions in the X axis direction, it is possible to secure regions for flat surface portions <NUM>, <NUM> to provide fastening holes 44A on the lower end side (-Z axis direction side).

As exemplary sizes shown in <FIG> and <FIG>, L is about <NUM>, L1 is about <NUM>, L2 is about <NUM>, and each of H1 and H2 is about <NUM> to <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>.

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>.

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>.

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 plurality of battery cells (<NUM>) arranged side by side in a first direction (Y), 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 (Y); and
a restraint member (<NUM>) that restrains the plurality of battery cells (<NUM>) and the end plate (<NUM>) along the first direction (Y), 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 (X) orthogonal to the first direction (Y), wherein
the end plate (<NUM>) includes a plate-shaped member (<NUM>, <NUM>),
the plate-shaped member (<NUM>, <NUM>) includes a flat surface portion (<NUM>, <NUM>) extending orthogonally to the first direction (Y), a flange portion (<NUM>, <NUM>), and a transition portion (<NUM>, <NUM>), the flange portion (<NUM>, <NUM>) being provided at an end portion of the plate-shaped member (<NUM>, <NUM>) in a third direction (Z) orthogonal to the first direction (Y) and the second direction (X), the flange portion (<NUM>, <NUM>) protruding from the flat surface portion (<NUM>, <NUM>) in the first direction (Y), the transition portion (<NUM>, <NUM>) continuously transitioning with a continuous curved surface that has no angular portion from the flat surface portion (<NUM>, <NUM>) to the flange portion (<NUM>, <NUM>),
the plate-shaped member (<NUM>, <NUM>) has a wave shape including a protrusion (<NUM>) and a recess (<NUM>) each extending in the second direction (X), the flat surface portion (<NUM>, <NUM>) is provided to be located at the recess (<NUM>),
the flange portion (<NUM>, <NUM>) is not provided at both end portions of the end plate (<NUM>) in the second direction (X), the flat surface portion (<NUM>, <NUM>) extends to a tip in the third direction (Z) of the plate-shaped member (<NUM>, <NUM>), and
the flat surface portion (<NUM>, <NUM>), the transition portion (<NUM>, <NUM>), and the flange portion (<NUM>, <NUM>) are provided to be arranged side by side in the second direction (X).