Method of generating brake actuating pressure

摘要

A vehicle brake booster and master cylinder assembly has a vacuum suspended booster section which is controlled by movement of the vehicle brake pedal. A hydraulic booster section is in series with the vacuum suspended booster section, and a master cyclinder unit is in series with the hydraulic booster section. The assembly is so arranged that in normal operation the vehicle operator obtains boosted brake actuating pressures by operation of the vacuum suspended booster which acts through the hydraulic booster mechanism without operating the hydraulic booster. When greater brake actuating pressures are required, as indicated by increased brake pedal force exerted by the operator, the vacuum booster reaches its limit or runout condition and the hydraulic booster is operated so as to continue the increase in master cylinder output pressure. If still further master cylinder output pressure is required when the hydraulic booster has reached its runout condition, the master cylinder is actuated manually through mechanical force transmitting elements which are parts of the booster sections. In one embodiment the assembly utilizes a single hydraulic fluid for the hydraulic booster section and for the master cylinder and brake apply circuitry. In another embodiment the hydraulic booster section is operated by a separate fluid circuit which is fluidly independent of the master cylinder and brake apply pressure circuitry.