| 摘要 |
PROBLEM TO BE SOLVED: To perform a brake assist at a low cost with a simple structure by use of a hydraulic brake power assist having a hysteresis. SOLUTION: In the forward advance of an input shaft 21, the pressure of the reaction chamber 30 is held at the atmospheric pressure since a hydraulic fluid is introduced for a reservoir 9 to a reaction chamber 30 through a twelfth check valve. In the backward advance of the input shaft 21, the reaction chamber 30 is held at the wheel cylinder pressure since the hydraulic fluid of the reaction chamber 30 is discharged to wheel cylinder side through a thirteenth check valve 75 and a passage 74. Since the pressure of the reaction chamber 340 acts on the rear end of a reaction piston 23 making contact with the stepped part of the input shaft 21, a hydraulic brake power assist 2 has a hysteresis. The hydraulic pressure is introduced to a power chamber 25 through a pressure inlet port 69 when a brake assist is required, whereby the brake force is increased. In this case, the hydraulic pressure of the power chamber 24 is variously controlled within the hysteresis range of the hydraulic brake power assist 2. |
