| 摘要 |
PROBLEM TO BE SOLVED: To save machining cost for a ventilation hole by improving the assembly property, reducing the manufacturing cost and dispensing with the ventilation hole communicating to the atmosphere for coping with the volume increase/ decrease by an over adjust preventing operation in the space between the end seal ring and cup shape seal ring of a second piston, in a disk brake device. SOLUTION: A second piston (limit piston) is inserted unrotatably in a first piston (brake piston) but slidably in the rotor axis direction and arranged so as to move to an over-adjustment preventing position against a second spring and an annular groove provided on the inner periphery of a backup ring 41 against the cup shape seal ring 40 of the second piston is used as an air sump chamber 41a. The annular groove, communicated with the space 43 between an end seal ring 42 and cup seal ring 40 provided on the inner periphery of the first piston, is used as the air sump chamber 45.
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