| 摘要 |
PROBLEM TO BE SOLVED: To quickly release the pressure inside a case by promoting the cleavage of an arc-shaped groove.SOLUTION: An arc part is possessed in part of the fringe of a pressure release valve, the pressure release valve having an intersection groove, the intersection groove including a plurality of arc-shaped grooves connecting to an end part on a side of the intersection groove opposite its center position side and following along the arc part. When a virtual line extending along the intersection groove and intersecting the fringe of the pressure release valve is assumed, a first region enclosed by the virtual line and the fringe of the pressure release valve and having many portions in contact with the arc part and a second region enclosed by the virtual line and the fringe of the pressure release valve and having a few portions in contact with the arc part may be assumed, the area of the first region being larger than the area of the second region. |
