Importance

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Abstract

A hydraulic brake-power booster unit is provided for a vehicle having a dual-circuit brake system and an antilock system operating according to the drain principle. When the brake system is intact, the booster unit provides dynamic pressure to one of the two brake circuits and static pressure admission to the other. The pressure to the static brake circuit takes place by the separate-power-assisted shifting of an emergency piston. On one side, the emergency piston delimits an output pressure space to which the brake circuit that can be statically acted upon by pressure is connected. This brake circuit also remains operable in the case of a breakdown of the hydraulic power source only by the operation of the pedal and the resulting possible shifting of the emergency piston. A path transducer generates an electrical signal proportional to the position of the emergency piston. A pressure transducer generates an electrical signal proportional to the pressure in the output pressure space for the static brake circuit. Starting from a minimum position of the emergency piston, the brake circuit that initially could be acted upon statically by pressure is now acted upon dynamically. The reversing is caused by a mechanically path-controlled reversing valve. When the actual value of the output pressure of the brake-power booster unit is lower than a desired value, an electronic comparison arrangement generates a warning signal.

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First Claim