| 摘要 |
A brake booster has a first booster cylinder and a booster piston disposed in it for displacing a master cylinder piston to pressurize a brake circuit. A tappet displaces the first booster piston directly if boost fluid pressure is inadequate. A second booster piston in a parallel booster cylinder drives a pump piston which also pressurizes the brake circuit. The second booster piston and the pump piston have hydraulically effective surface areas which are matched to one another so as to have a larger boosting ratio than the first booster piston and master cylinder piston. Forward displacement of the second booster piston causes a bent arm to contact and push the first booster piston forward. If the boost pressure supply apparatus fails, then only the first booster piston and the master cylinder piston are displaced by the brake pedal; brake pedal travel increases considerably. |
