| 摘要 |
PURPOSE:To perform smooth and quiet valve opening by providing a supporting member supported at a position where the second valve sheet abuts to the second valve seat at the initial stopping position of a power piston, at least, and when the power piston is returned to the initial position, the second valve sheet support at a position specified distance apart from the second valve seat. CONSTITUTION:Because even in treading a brake pedal a head section 8a (the second valve sheet) is left abutting a ring step section 7 (the second valve seat), smooth operation is performed without generating clapping sound. When treading force against the brake pedal is eliminated, an input rod 10 is moved toward the brake pedal to bring a ring projection section 7a (the first valve sheet) into contact with a ring step section 2b (the first valve seat) for stopping power liquid pressure. At the same time, the head section 8a is separated from the ring step section 7b to open a valve, and a boost chamber 2f is communicated with a reservoir 30 through a drain port 1d, and pressure is reduced. At this time the head section 8a is held at a position a specified distance apart from the ring step section 7b by a supporting member 5. |
