| 摘要 |
PURPOSE:To reduce ineffective stroke with a simple constitution by providing a second path affording communication between two pressure chambers of a hydraulic servo brake and opening the path in the backward movement of a piston and closing the path in the forward movement of the piston with a valve mechanism. CONSTITUTION:A power piston 5 is formed with a second path 20 affording communication between a negative pressure chamber 13 and a transformation chamber 14. The path 20 is provided with a second valve mechanism 26 which is constituted from first and second lever members 26a, 26b. When a valve plunger 23 advances in braking, the valve mechanism is changed over in the same manner as prior one to introduce the atmospheric pressure into the chamber 14 and advance a power piston 5. Since then the force of the valve plunger 23 does not act on the second lever member 26b through the first lever member 26a, the member 26b closes the path 20 by a spring 43 and the atmospheric pressure. When the braking is released and the valve plunger 23 retreats, the valve mechanism 28 is changed over while the lever member 26b opens the path 26 by the force of the valve plunger 23 to afford communication between both chambers 13, 14. |
