| 摘要 |
A brake booster has a first booster cylinder and a booster piston disposed in it for displacing a rod-like master cylinder piston of a master cylinder which supplies at least one brake circuit (I, II), having a tappet for mechanically displacing the first booster piston as needed if the brake boosting is inadequate, and having a brake valve coupled to the tappet and the first booster piston for direction boosting pressure into the first booster cylinder. A second, annular booster piston surrounds the rod-like master cylinder piston and likewise has a booster cylinder. Thsi second booster piston is joined to a pump piston which is likewise annular and sealingly surrounds the rod-like master cylinder piston. When the pressure supply apparatus is in operation, actuation of the brake pedal simultaneously displaces both booster pistons and generates braking pressures in the brake circuits (I, II). If the pressure supply apparatus fails, then only the rod-like master cylinder piston is displaced by the brake pedal so that the brake pedal travel becomes considerably longer.
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