Battery Can and Method of Manufacturing the Same
To provide a battery can into which an electrode assembly can be housed smoothly without causing damage to the electrode assembly while ensuring the strength of the opening portion. In the battery can including a cylindrical side portion, a bottom, and an opening portion, the cylindrical side portion includes a first side portion formed at the bottom side, and a second side portion formed at the opening portion side. The thickness T 1 of the first side portion and the thickness T 2 of the second side portion are adjusted to satisfy a relational expression: T 1 <T 2 , and the inner diameter of the cylindrical side portion is constant from the opening portion side to the bottom side.
1 . A battery can comprising a cylindrical side portion, a bottom and an opening portion,
wherein said cylindrical side portion comprises a first side portion formed toward the side of said bottom and a second side portion formed toward the side of said opening portion,
the thickness T 1 of said first side portion and the thickness T 2 of said second side portion satisfy a relational expression (1): T 1 <T 2 , and
the inner diameter of said cylindrical side portion is constant from the side of said opening portion to the side of said bottom.
2 . The battery can in accordance with claim 1 ,
wherein said cylindrical side portion further comprises a junction provided between said first side portion and said second side portion and having a thickness that increases gradually from the side of said first side portion to the side of said second side portion, and
the length L 1 of said junction that extends from said first side portion side to said second side portion side, the thickness T 1 of said first side portion, and the thickness T 2 of said second side portion satisfy a relational expression (2):
50 ≦{L 1 /(T 2 −T 1 )} ≦100.
3 . A method for manufacturing a battery can comprising the steps of:
(1) subjecting a base can comprising a bottomed cylindrical body to a drawing and ironing process in which said base can is passed successively through a plurality of molding dies with a pressure applied by a molding punch,
so as to obtain an intermediate product comprising a cylindrical side portion, a bottom and an opening portion,
wherein said cylindrical side portion comprises a first side portion formed toward the side of said bottom and a second side portion formed toward the side of said opening portion,
the thickness T 1 of said first side portion and the thickness T 2 of said second side portion satisfy a relational expression (1): T 1 <T 2 , and
the outer diameter of said cylindrical side portion is constant from the side of said opening portion to the side of said bottom; and
(2) after said step (1), inserting an expanding punch, which comprises an inserting portion having a diameter equal to the inner diameter of said second side portion, and a convex portion formed at the rear of said inserting portion and having a diameter equal to the inner diameter of said first side portion, into the opening portion of said intermediate product from the side of said inserting portion,
in order that said second side portion is pressed from the inside toward the outside by said convex portion so as to obtain a battery can processed such that the inner diameter of said cylindrical side portion is constant from the side of said opening portion to the side of said bottom.
4 . The method for manufacturing a battery can in accordance with claim 3 ,
wherein the length L 2 of said convex portion in the length direction of said base can and the length L 3 of said second side portion in the length direction of said base can satisfy a relational expression (3):
0.05 ≦{L 3 /L 2 }≦0.4.