BATTERY FRAME, BATTERY MODULE AND MOVING OBJECT WITH BATTERY MODULE

The moving object includes a battery module. A battery frame of the battery module has retaining plates and connecting members. The retaining plate has a central portion, a plurality of arms, and a plurality of attachment portions. A coupling member is attached to each of the plurality of attachment portions, so that a tightening load is applied to the cell stack body by an elastic deformation of the plurality of arms. A first dimension which is the thickness of the attachment portions in the stacking direction is smaller than a second dimension which is the thickness of the central portion in the stacking direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2023-038210 filed on Mar. 13, 2023, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a battery frame, a battery module and a moving object with the battery module.

Description of the Related Art

JP 5393365 B2 discloses a battery module including a cell stack body formed by stacking a plurality of plate-like battery cells. For example, a tightening load is applied to such a cell stack body by the battery frame in the direction in which the battery cells are stacked.

SUMMARY OF THE INVENTION

To provide a lightweight battery frame capable of efficiently applying a tightening load to a cell stack body.

The present invention has the object of solving the aforementioned problem.

A first aspect of the present invention is a battery frame for holding a cell stack body formed of a plurality of battery cells stacked one another, the battery frame including a pair of retaining plates made of metal, which are disposed on both sides of the cell stack body in a stacking direction of the plurality of battery cells, and a plurality of coupling members connecting the pair of retaining plates to each other to apply a tightening load from the pair of retaining plates to the cell stack body, wherein the pair of retaining plates each include a central portion positioned at a central part of each of the retaining plates, a plurality of arms extending radially outward from the central portion, and a plurality of attachment portions formed at extended ends of the plurality of arms, the plurality of coupling members are respectively attached to the plurality of attachment portions, an elastic deformation of the plurality of arms causes the tightening load to act on the cell stack body, and a first dimension as a thickness of the attachment portions in the stacking direction is smaller than a second dimension as a thickness of the central portion in the stacking direction.

A second aspect of the present invention is a battery module including the battery frame described above and the cell stack body.

A third aspect of the present invention is a moving object including the battery module described above.

According to the present invention, it is possible to efficiently apply a tightening load to the cell stack body while making the battery frame light in weight.

DETAILED DESCRIPTION OF THE INVENTION

A battery frame10, a battery module12, and a moving object13with the battery module12according to an embodiment of the present invention will be described below with reference to the drawings. As shown inFIG.1, the battery module12according to the present embodiment is mounted on, for example, an aircraft15as the moving object13depicted inFIG.6. The aircraft15is, for example, an electric vertical take-off and landing (eVTOL) aircraft. The aircraft15includes a fuselage17, a plurality of (for example, four) VTOL rotors21, and a plurality of (for example, two) cruise rotors23. The VTOL rotors21generate an upward thrust on the aircraft15. The cruise rotors23generate a horizontal thrust on the aircraft15. The battery module12is disposed inside the fuselage17. The battery module12supplies electric power to an electric motor (not shown) that drives each of the VTOL rotors21and the cruise rotors23. The moving object13may be, for example, a vehicle, a ship, or the like. The battery module12is not necessarily mounted on the moving object13.

As shown inFIG.1, the battery module12includes four cell stack bodies14and four battery frames10. The four cell stack bodies14are arranged in the arrow Y direction. As shown inFIG.2, the cell stack body14includes a plurality of battery cells16, a plurality of first heat exchangers18, and a plurality of second heat exchangers20. The plurality of battery cells16are arranged in the arrow X direction.

The battery cell16is a laminated battery. The battery cell16is formed in a quadrangular plate shape. A plurality of terminal portions22protrude from one side of the battery cell16in the arrow Z direction. The plurality of battery cells16are connected in series to each other via the terminal portions22. The terminal portions22are schematically illustrated.

An electrical connection member (not shown) is joined to the plurality of terminal portions22by a bonding device100(seeFIG.4). The bonding device100is, for example, an ultrasonic bonding device. The bonding device100is not limited to the ultrasonic bonding device.

As shown inFIG.2, the first heat exchanger18includes a plate-shaped water jacket24and a water supply and discharge header26. The water jacket24extends in the arrow Y direction. Cooling water flows through a flow path formed inside the water jacket24. The water supply and drainage header26is provided at one longitudinal end of the water jacket24(the arrow Y direction). The cooling water is supplied to and discharged from the water jacket24through the water supply and discharge header26.

The second heat exchanger20is a similar in configuration to the first heat exchanger18. The first heat exchangers18are arranged such that the water supply and discharge headers26are positioned at one end in the arrow Y direction. The second heat exchangers20are arranged such that the water supply and discharge headers26are positioned at the other end in the arrow Y direction. The first heat exchanger18and the second heat exchanger20are alternately arranged in the arrow X direction.

Two buttery cells16are stacked in the arrow X direction between the first heat exchanger18and the second heat exchanger20adjacent to each other (seeFIG.3). Four battery cells16are arranged in the arrow Y direction between the first heat exchanger18and the second heat exchanger20adjacent to each other.

As shown inFIGS.1and3, the battery frame10holds the cell stack body14. The battery frame10includes a pair of retaining plates28, a pair of pressure receiving plates30, and four coupling members32. The pair of retaining plates28are respectively positioned at both ends of the battery module12in the arrow X direction. The pressure receiving plates30are disposed between the retaining plates28and the cell stack body14. The coupling members32connect the pair of retaining plates28to each other so that the pair of retaining plates28apply a tightening load (compressive load) to the cell stack body14. Thus, the expansion of the battery cells16are suppressed.

The pair of retaining plates28are positioned outward of the battery cells16in the stacking direction. The retaining plates28are made of, for example, a titanium alloy. The retaining plates28may be made of a metal material other than the titanium alloy.

As shown inFIG.4, the retaining plate28is formed in an X shape when viewed from the thickness direction (the arrow X direction) of the retaining plate28. The retaining plate28has a point-symmetrical shape. The retaining plate28includes a central portion34, four arms36, and four attachment portions38.

The central portion34is located at the center part of the retaining plate28. A circular through hole40is formed in the central portion34. The through hole40reduces the weight of the retaining plate28.

The four arms36extend radially outward from the central portion34. The four arms36are provided at equal intervals in the circumferential direction of the central portion34. The arm36has a width W that gradually decreases radially outward. The width direction of the arm36intersects the extending direction of the arm36and the stacking direction of the battery cells16(the arrow X direction). The arm36functions as a plate spring that is elastically deformed when a tightening load is applied to the cell stack body14.

A cut-away portion42is formed between the arms36adjacent to each other. The cut-away portion42is formed in a triangular shape when the retaining plate28is viewed from the thickness direction. The central portion34is formed by arc-shaped surfaces44of the cut-away portions42. The radius of curvature of the arc-shaped surface44is larger than the radius of the through hole40.

The attachment portion38is provided at an extended end of the arm36. The attachment portion38protrudes from the extended end of the arm36along the arrow Z direction (the direction in which the terminal portions22protrude). The coupling member32is connected to the attachment portion38. An insertion hole46through which a bolt58of the coupling member32is inserted is formed in the attachment portion38(seeFIG.3).

The attachment portion38is positioned outwardly of the cell stack body14when viewed in the stacking direction of the battery cells16(the arrow X direction). In other words, the attachment portions38do not overlap the terminal portions22when viewed from the arrow X direction. This makes it possible to avoid interference between the bonding device100and the attachment portions38when the terminal portions22are joined to the electrical connection member (not shown).

As shown inFIG.3, a first dimension D1, which is the thickness of the attachment portion38in the stacking direction of the battery cells16, is smaller than a second dimension D2, which is the thickness of the central portion34in the stacking direction of the battery cells16. In other words, the attachment portion38is thinner than the central portion34. Therefore, the weight of the retaining plate28can be reduced as compared with the case where both the attachment portion38and the central portion34have the same thickness. The first dimension D1is set to be, for example, 70% or less of the second dimension D2. The ratio of the first dimension D1to the second dimension D2is determined as necessary.

A third dimension D3, which is the thickness of the arm36in the stacking direction of the battery cells16, is larger than the first dimension D1and smaller than the second dimension D2. To be specific, the third dimension D3gradually decreases from the central portion34toward the attachment portion38. The third dimension D3decreases linearly from the central portion34toward the attachment portion38. The third dimension D3may decrease quadratically from the central portion34toward the attachment portion38.

As shown inFIGS.3and4, the pressure receiving plates30are provided for pressing the cell stack body14uniformly by the tightening load applied from the retaining plates28. The pressure receiving plate30is formed in a quadrangular shape. As shown inFIG.3, a first surface48of the pressure receiving plate30is in surface contact with an end surface of the cell stack body14. The central portion34of the retaining plate28is in surface contact with a second surface50of the pressure receiving plate30opposite to the first surface48.

The planar dimension of the pressure receiving plate30is substantially the same as the planar dimension of the battery cell16. The planar dimension of the pressure receiving plate30may be larger or smaller than the planar dimension of the battery cell16. The pressure receiving plate30is made of, for example, lightweight metal such as aluminum. The material for the pressure receiving plate30is not limited to metal and may be resin or a composite material.

As shown inFIG.4, the pressure receiving plate30is provided with a center projection52and a positioning projection54. The center projection52projects outward in the stacking direction of the battery cells16from the central part of the pressure receiving plate30. The center projection52is formed in a columnar shape. The center projection52is inserted into the through hole40of the central portion34of the retaining plate28. Thus, the central portion34of the retaining plate28can be easily positioned in alignment with the central portion of the pressure receiving plate30when the battery frame10is assembled.

The positioning projection54projects outward in the stacking direction of the battery cells16from a position shifted from the center of the pressure receiving plate30. The positioning projection54engages with the cut-away portion42of the retaining plate28. In other words, the positioning projection54is in contact with the arc-shaped surface44of the central portion34. Thus, the retaining plate28can be positioned with respect to the pressure receiving plate30in the circumferential direction of the center projection52when the battery frame10is assembled. The positioning projection54also functions as a rotation stopper that prevents the retaining plate28from rotating in the circumferential direction of the center projection52.

In a state where the retaining plate28is attached to the pressure receiving plate30, the four arms36extend so as to overlap with the four corners of the pressure receiving plate30, respectively, when viewed from the arrow X direction. In a state where the retaining plate28is attached to the pressure receiving plate30, there is a gap between the arms36and the corners of the pressure receiving plate30in the stacking direction. In a state where the retaining plate28is attached to the pressure receiving plate30, the four attachment portions38are positioned outwardly of the pressure receiving plate30when viewed from the arrow X direction.

As shown inFIG.3, the coupling member32includes a coupling shaft56, two bolts58, and two nuts60. The coupling shaft56extends along the stacking direction of the battery cells16. The coupling shaft56is made of metal such as stainless steel. The bolts58protrude from end surfaces of the coupling shaft56in the axial direction. The bolts58are inserted into the insertion holes46of the attachment portions38of the retaining plate28. The nuts60are screwed onto the bolts58. The attachment portion38is positioned between the nut60and the coupling shaft56.

When the nuts60are fastened to the bolts58, the retaining plate28is pressed toward the pressure receiving plate30. At this time, the four arms36are elastically deformed. The elastic force (spring force) of the four arms36acts on the cell stack body14as a tightening load via the pressure receiving plate30.

FIG.5shows experimental results indicating changes in the tightening load when the nuts60are fastened to the bolts58. The horizontal axis of the graph ofFIG.5represents the amount of deflection of the retaining plate28after the tightening load is applied. The vertical axis of the graph ofFIG.5represents the tightening load. The line segment L1represents an experimental result of the battery frame10according to the present embodiment. The line segment L2represents an experimental result of the battery frame10according to a comparative example. The battery frame10according to the comparative example is configured similarly to the battery frame10according to the present embodiment, except that each of the first dimension D1and the second dimension D2of the retaining plate28is set to the same thickness as the third dimension D3.

InFIG.5, a first tightening load P1is a lower limit value of the tightening load required for the battery cells16. The second tightening load P2is an upper limit value of the tightening load allowable for the battery cells16. The first amount of deflection81is the maximum amount of deflection of the retaining plate28when the manufacturing tolerance of the cell stack body14in the stacking direction of the battery cells16is minimum. The second amount of deflection82is the maximum amount of deflection of the retaining plate28when the manufacturing tolerance of the cell stack body14in the stacking direction of the battery cells16is maximum and the battery cells16are bulged maximally while in use.

As shown inFIG.5, in the battery frame10(line segment L1) according to the present embodiment, the tightening load increased quadratically as the amount of deflection of the retaining plate28increased. The line segment L1according to the present embodiment shows that a tightening load in the range between the first tightening load P1and the second tightening load P2was obtained in the range from the first amount of deflection81to the second amount of deflection82.

On the other hand, in the battery frame10(line segment L2) according to the comparative example, the tightening load increased linearly as the amount of deflection of the retaining plate28increased. The line segment L2according to the comparative example shows that the tightening load in the range between the first tightening load P1and the second tightening load P2was obtained in the range from the first amount of deflection81to the second amount of deflection82.

The tightening load of the line segment L1was smaller than the tightening load of the line segment L2in a range where the amount of deflection was smaller than the second amount of deflection82. That is, according to the experimental results ofFIG.5, the tightening load applied to the cell stack body14effectively suppressed as compared with the comparative example was obtained. In other words, the present embodiment exhibited an effect that the tightening load can be efficiently applied to the cell stack body14. In this case, the rigidity of the retaining plate28and the pressure receiving plate30does not have to be increased more than necessary, and thus the retaining plate28and the pressure receiving plate30can be made thin. Therefore, the battery frame10can be made lightweight.

The present embodiment is not limited to the above-described configuration. The width W of the arm36may be constant from the central portion34toward the attachment portion38. The third dimension D3of the arm36may be reduced in a stepwise manner from the central portion34toward the attachment portion38. The third dimension D3may be a constant value from the central portion34to the attachment portion38. The third dimension D3may be the same as one of the first dimension D1and the second dimension D2. The number of the arms36is not limited to four, and may be three, five, or more. The number of each of the cell stack bodies14and the battery frames10forming the battery module12is not limited to four, and may be any integer other than zero. The cell stack body14may not include the first heat exchanger18and the second heat exchanger20. The battery frame10may not include the pressure receiving plate30.

In addition to the above disclosure, the following appendices are further disclosed.

The battery frame (10) for holding a cell stack body (14) formed of a plurality of battery cells (16) stacked one another, the battery frame including: the pair of retaining plates (28) made of metal, which is disposed on both sides of the cell stack body in a stacking direction of the plurality of battery cells: and the plurality of coupling members (32) connecting the pair of retaining plates to each other to apply a tightening load from the pair of retaining plates to the cell stack body, wherein the pair of retaining plates each include: a central portion (34) positioned at a central part of each of the retaining plates, the plurality of arms (36) extending radially outward from the central portion, and the plurality of attachment portions (38) formed at the extended ends of the plurality of arms, the plurality of coupling members are respectively attached to the plurality of attachment portions, the elastic deformation of the plurality of arms causes the tightening load to act on the cell stack body, and the first dimension (D1) as the thickness of the attachment portions in the stacking direction is smaller than the second dimension (D2) as the thickness of the central portion in the stacking direction.

According to such a configuration, the weight of the retaining plates (battery frame) can be reduced as compared with a case where the first dimension of the attachment portion is set to be the same as the second dimension of the central portion. Further, the elastic deformation of the arm realizes efficient application of the tightening load to the cell stack body.

In the battery frame according to Appendix 1, the third dimension (D3) as the thickness of the arm in the stacking direction may be larger than the first dimension and smaller than the second dimension.

According to such a configuration, the battery frame can be further reduced in weight.

In the battery frame according to Appendix 2, the third dimension may gradually decrease from the central portion toward the attachment portion.

According to such a configuration, the battery frame can be further reduced in weight. Further, since the tightening load acting on the cell stack body can be changed quadratically, the tightening load can be applied to the cell stack body more efficiently.

In the battery frame according to any one of Appendixes 1 to 3, the cut-away portion (42) may be formed between the arms adjacent to each other.

According to such a configuration, the weight of the retaining plate can be reduced by the cut-away portion.

The battery frame according to any one of the Appendixes 1 to 4 may include the pressure receiving plate (30) configured to be brought into surface contact with an end surface of the cell stack body, between the retaining plate and the cell stack body. According to such a configuration, the tightening load can be uniformly applied to the cell stack body by the pressure receiving plate.

In the battery frame according to Appendix 5, the pressure receiving plate may be provided with the positioning projection (54) in engagement with the cut-away portion to position the retaining plate.

According to such a configuration, the retaining plate can be easily and accurately assembled to the pressure receiving plate.

In the battery frame according to any one of Appendixes 1 to 6, in a state where the pair of retaining plates hold the cell stack body of the battery cells having terminal portions (22) protruding from the battery cells in a direction intersecting the stacking direction, the attachment portions may protrude from the arms along a direction the same as the direction in which the terminal portions protrude, but so as not to overlap with the terminal portion when viewed from the stacking direction.

According to such a configuration, it is possible to avoid the bonding device and the terminal portion from interfering with each other when the terminal portion is joined to the electrical connection member.

In the battery frame according to any one of Appendixes 1 to 7, the width (W) of the arms in a direction intersecting both the extending direction of the arms and the stacking direction may be gradually reduced toward the attachment portions.

According to such a configuration, the battery frame can be further reduced in weight.

The battery module (12) includes the battery frame according to any one of Appendixes 1 to 8, and the cell stack body.

The moving object (13) includes the battery module according to Appendix 9.

Moreover, it should be noted that the present invention is not limited to the disclosure described above, and various configurations may be adopted therein without departing from the essence and gist of the present invention.