Battery and method of manufacturing same

Abstract

A battery case includes a case-penetrating hole. An external terminal includes a member-engaging hole and is stacked on an outside of the battery case so that the member-engaging hole and the case-penetrating hole align with each other. An internal terminal includes a shaft portion and a fastening portion. The shaft portion is inserted through the case-penetrating hole and the member-engaging hole from an interior of the battery. The fastening portion is fastened to a circumferential periphery of the member-engaging hole by crushing a tip end of the shaft portion. The internal terminal is stacked on an inside of the battery case. The fastening portion and the external terminal include a welded portion welded along a weld line set across a periphery of the fastening portion. The welded portion has a length K1 along the weld line and a width K2 along a direction perpendicular to the weld line, and the length K1 is at least 1.5 times longer than the width K2.

What is claimed is: 
     
         1 . A battery comprising:
 a battery case;   an external terminal; and   an internal terminal, wherein:   the battery case includes a case-penetrating hole;   the external terminal includes a member-engaging hole and is stacked on an outside of the battery case so that the member-engaging hole and the case-penetrating hole align with each other;   the internal terminal is stacked on an inside of the battery case; and
 the internal terminal includes: a shaft portion inserted through the case-penetrating hole and the member-engaging hole from an interior of the battery; and 
 a fastening portion fastened to a circumferential periphery of the member-engaging hole at a tip end of the shaft portion; 
   the fastening portion and the external terminal include a welded portion welded along a weld line set across a periphery of the fastening portion; and   the welded portion has a length K1 along the weld line and a width K2 along a direction perpendicular to the weld line, and the length K1 is at least 1.5 times longer than the width K2.   
     
     
         2 . The battery according to  claim 1 , wherein a portion of the welded portion that is provided external to the fastening portion has a length along the weld line at least 2.5 times longer than a portion of the welded portion that is provided internal to the fastening portion. 
     
     
         3 . The battery according to  claim 1 , wherein:
 the at least one welded portion includes at least two or more of the welded portions; and   adjacent ones of the welded portions are circumferentially spaced from each other.   
     
     
         4 . The battery according to  claim 1 , wherein the welded portion includes an inner edge of the fastening portion, the inner edge being located radially outward of the member-engaging hole when viewed axially along the shaft portion. 
     
     
         5 . A method of manufacturing a battery, comprising the steps of;
 preparing a battery case including a case-penetrating hole;   preparing an external terminal including a member-engaging hole;   preparing an internal terminal including a shaft portion;   assembling the battery case, the external terminal, and the internal terminal together so that the external terminal is stacked on an outside of the battery case, the internal terminal is stacked on an inside of the battery case, and the shaft portion is inserted through the case-penetrating hole and the member-engaging hole;   forming a fastening portion by crushing a tip end of the shaft portion and fastening the tip end of the shaft portion to a circumferential periphery of the member-engaging hole on an outside of the external terminal; and   laser welding the fastening portion and the external terminal seamlessly along at least one weld line that is set so as to extend across a periphery of the fastening portion along an outer surface of the fastening portion.   
     
     
         6 . The method according to  claim 5 , wherein, in the step of laser welding, a region that is to be laser welded is set to be at least 2.5 times longer in a region external to the fastening portion than in a region internal to the fastening portion. 
     
     
         7 . The method according to  claim 5 , wherein, in the step of laser welding, the at least one weld line is set at two or more locations of the fastening portion that are circumferentially spaced from each other, the fastening portion and the external terminal are laser welded together along a plurality of the weld lines, and a plurality of welded portions that are circumferentially spaced from each other are formed by the laser welding. 
     
     
         8 . The method according to  claim 5 , wherein, in the step of laser welding, the welded portion does not extend into an inside of the member-engaging hole when viewed axially along the shaft portion.