Battery case for electric vehicles and manufacturing method

1 . A battery case for an electric vehicle comprising:

a frame that has a polygonal frame shape in plan view, defines a space inside, and has an R shape provided to an inner side of a corner part of the polygonal frame shape; and

a tray of a bathtub shape that includes a bottom wall that is located in the space, a surrounding wall that is provided around the bottom wall and defines an opening part on a side opposite to the bottom wall, and a flange that is provided at a distal end of the surrounding wall, and is pressure-welded to and integrated with the frame,

wherein the tray includes a negative angle part that has a negative angle directed at least partially inward from the bottom wall toward the opening part of the tray.

2 . The battery case for the electric vehicle according to claim 1 , wherein the frame includes a main body that forms the polygonal frame shape, and a corner member that has the R shape disposed on the inner side of the corner part of the main body.

3 . The battery case for the electric vehicle according to claim 1 , wherein

the polygonal frame shape of the frame is formed by welding a linear extruded material, and

an end part of the extruded material is subjected to press work so as to have the R shape.

4 . The battery case for the electric vehicle according to claim 1 , wherein

the frame is composed of an extruded material made of an aluminum alloy, and

the tray is composed of a plate material made of an aluminum alloy.

5 . The battery case for the electric vehicle according to claim 1 , wherein

the frame is composed of a steel plate roll forming material, and

the tray is composed of a plate material made of steel.

6 . The battery case for the electric vehicle according to claim 1 , wherein

the frame is composed of a steel plate roll forming material that is subjected to an anti-corrosive coating, and

the tray is composed of a plate material made of an aluminum alloy.

7 . The battery case for the electric vehicle according to claim 1 , wherein

the frame is composed of an extruded material made of an aluminum alloy, and

the tray is composed of a coated steel plate or a laminated steel plate.

8 . The battery case for the electric vehicle according to claim 1 , wherein the frame includes a cross member.

9 . The battery case for the electric vehicle according to claim 1 , wherein a flow path of a coolant is molded in the bottom wall of the tray.

10 . A method for manufacturing a battery case for an electric vehicle, the method comprising:

preparing a frame and a molding target member having a flat plate shape, the frame including a main body that has a polygonal frame shape in plan view and defines a space inside, and a corner member that is disposed on an inner side of a corner part of the main body, and has an R shape;

overlaying and disposing the molding target member on the frame;

pressurizing the molding target member from a side opposite to the frame, pressing the molding target member against the frame, and bulging the molding target member in the space, thus deforming the molding target member into a tray of a bathtub shape, and integrating the molding target member with the frame, the tray including a bottom wall, and a surrounding wall that is provided at a circumferential edge of the bottom wall and defines an opening part; and

detaching the corner member from the frame after the molding target member and the frame are integrated.

11 . The method for manufacturing the battery case for the electric vehicle according to claim 10 , wherein the molding target member is pressurized by a rubber bulge method.

12 . The method for manufacturing the battery case for the electric vehicle according to claim 11 , wherein the molding target member is pressurized by the rubber bulge method in a state where the molding target member is heated and softened.

13 . The method for manufacturing the battery case for the electric vehicle according to claim 10 , the method further comprising:

further preparing a restraining die having a height dimension equal to or larger than a height dimension of the frame and that restrains movement of the frame;

fixing and disposing the restraining die on an outer side of the frame;

supporting a first outer edge part of the molding target member by the frame, supporting a second outer edge part on an outer side of the first outer edge part by the restraining die, and thus deflecting and disposing the molding target member such that a height of the molding target member becomes lower from an outer side to an inner side in plan view; and

pressurizing the molding target member in a state where the molding target member is deflected.

14 . The method for manufacturing the battery case for the electric vehicle according to claim 10 , wherein

the molding target member is pressurized at two stages,

the molding target member is molded into a bathtub shape at a first stage, and

the frame and the molding target member are pressure-welded and integrated at a second stage.

15 . The battery case for the electric vehicle according to claim 1 , wherein a flow path of a coolant is molded in the bottom wall of the tray.

16 . The method for manufacturing the battery case for the electric vehicle according to claim 11 , the method further comprising:

further preparing a restraining die having a height dimension equal to or larger than a height dimension of the frame and that restrains movement of the frame;

fixing and disposing the restraining die on an outer side of the frame;

supporting a first outer edge part of the molding target member by the frame, supporting a second outer edge part on an outer side of the first outer edge part by the restraining die, and thus deflecting and disposing the molding target member such that a height of the molding target member becomes lower from an outer side to an inner side in plan view; and

pressurizing the molding target member in a state where the molding target member is deflected.

17 . The method for manufacturing the battery case for the electric vehicle according to claim 13 , wherein

the molding target member is pressurized at two stages,

the molding target member is molded into a bathtub shape at a first stage, and

the frame and the molding target member are pressure-welded and integrated at a second stage.