To solve the problem, in which a molten lead runs down along a taper of a tubular lead bushing and a columnar lead pole due to a usage of a tubular lead bushing whose internal diameter increases from the upper end to the lower end, then a distorted terminal is formed, and molten lead reaches a polar plate that is positioned at a lower part of a pole to possibly cause an internal short circuit, during a terminal welding.

In a terminal welding, a terminal is formed by filling molten lead in a tapered gap 26 whose internal diameter increases in an upward direction between a tubular lead bushing 20 and a pole 24, by using the pole 24 and the tubular bushing 20 whose inner wall 21 has a taper, of which internal diameter increases from the lower end to the upper end.