| 摘要 |
PROBLEM TO BE SOLVED: To provide double servo characteristics capable of reducing a servo ratio during a servo-control with a simple structure. SOLUTION: Because a fluid pressure inside a power chamber does not rise to an operating pressure of a pressure selector valve 46 until an input becomes a specified value, the pressure selector valve 46 is kept set at a first position I and a reaction chamber 41 is kept connected to a reservoir 33. By this, a brake fluid pressure booster drive 1 is servo-controlled at a large servo ratio. Also, when the input reaches a specified amount and the fluid pressure inside the power camber reaches a working pressure of the pressure selector valve 46, the pressure selector valve 46 is switched over to set to a second position II so as to introduce the fluid pressure inside the power chamber as a servo ratio control pressure into the reaction chamber 41. Then the fluid pressure acts on a step part 18a of an input shaft 18. As a result, the brake fluid pressure booster 1 performs a servo-control at a small servo ratio. Thus the brake fluid pressure booster 1 provides double servo characteristics. |
