PURPOSE: To restrain swelling-up of the bottom part of a battery can to the outside within a tolerence by fixing a reinforcing plate along the inner wall part of the bottom wall of the battery can, the plate being bent to protrude in the direction to be apart from the inner wall part before it is fixed.
CONSTITUTION: A battery can 10 is composed of a side wall 20 and a bottom wall 30. A reinforcing plate 40 is fixed by resistance welding along an inner wall part 30a of the bottom wall 30. A bent plate 40a is used and fixed as the plate 40. The curved plate 40a is provided with a plurality of projection parts for welding 40b..., a shape of disc of which center protrudes in one direction and a projection face 40a1 and recessed face 40a2 at its opposed faces. Resistance welding is carried out by pressing the projection face 40a1 by a pressing rod constituting a welding electrode to form a plurality of welded parts 50. Under such a condition, the reinforcing plate 40 is provided with residual stress to tend to return to the shape at the time before it is fixed. The mechanical strength against the swelling-up of the can bottom due to the internal pressure increase in a battery is increased and swell-out of the bottom can be restrained.
TORITSUKA TAKAHISA
SUZUKI MIKITO
