| 摘要 |
PURPOSE:To reduce impact moise made on the rear wheel side when a parking brake is released by forming a small groove onto the inner surface of a cylinder main body so that air flows to a first air chamber from a second air chamber in a condition where a distance between a first piston and one end of the cylinder main body is a given distance or less. CONSTITUTION:When a first seal cup 18 slides to a small groove A, the first seal cup 18 can not seal the small groove A, and air flows into a first air chamber 15 from a third air chamber 19 via the small groove A. Thereupon, the third air chamber 19 vanishes, and a prutruded part 23a and a recessed part 12b are engaged again to concurrently slide. Consequently, the internal pressure in the third air chamber 19 vanishes, and a second seal cup 20 also can recede from the inner surface of the cylinder main body 11 to smoothly return first and second pistons 12 and 13 to their initial positions. This can relax the reaction force of an operation pedal before the first piston 12 returns to its initial position. |
