| 摘要 |
A parking brake system is provided in which, a lock mechanism ( 25 ) is provided within a casing ( 23 ) to the rear of a parking piston ( 24 ) that can give a parking brake state by forward movement in response to the action of a parking control fluid pressure, the lock mechanism ( 25 ) operating in response to forward movement of the parking piston ( 24 ) in order to mechanically lock the parking piston ( 24 ) at a forward position and unlocking in response to the action of a parking release control fluid pressure. The lock mechanism ( 25 ) includes a lock piston ( 30 ) that is disposed to the rear of the parking piston ( 24 ) while having an axis orthogonal to the axis of the parking piston ( 24 ) and that makes a forward urging force act on the parking piston ( 24 ) at least when the parking piston ( 24 ) moves forward, and opposite end parts of the lock piston ( 30 ) are slidably fitted into and supported on the casing ( 23 ). This enables an automatic parking brake state to be obtained by a simple structure without consuming power.
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