EXPLOSION PROOF SEALING PLATE FOR SEALED BATTERY AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To provide a current shutting off function having high volume productivity, accurate braking strength, and high reliability by arranging a tongue piece part having a connection part surrounded by a C-shaped ventilation part surrounding the central part and an easily breakable part formed between both end hole edges of the ventilation port in a lower metal foil valve of upper and lower metal foil valves interposing an insulating gasket between the surrounding parts and having a connecting part welded to the central part. SOLUTION: An upper metal foil valve 17 having a PTC element 20 on the top surface has a C-shaped easily breakable thin part 24 in the surrounding of a recess 23 in the center. An easily breakable part 31 is formed between both end hole edges of a C-shaped ventilation port 29 surrounding a tongue piece part 25 having a connection part 28 in an projection part 27 in the center of a lower metal foil valve 18 welded to the C-shaped easily breakable thin part 24 in the connecting part 28 off the central point S. When the inner pressure of a battery reaches the specified value, the easily breakable part 31 is broken by the reverse turning of the recess 23, the tongue piece part 25 is integrally separated together with the upper metal foil valve 17 to shut off current, and the thin part 24 is cleaved in the next stage. The straight line distance L for setting the breaking strength of the easily breakable part 31 is short and the easily breakable part 31 is aslant cleaved smoothly.