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Brake system for automotive vehicles

  • US 4,676,558 A
  • Filed: 01/17/1985
  • Issued: 06/30/1987
  • Est. Priority Date: 01/31/1984
  • Status: Expired due to Fees
First Claim
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1. A brake system for automotive vehicles comprising a dual-circuit hydraulic, pedal-actuated braking pressure generator further comprising a power brake booster and a master cylinder and which is connected to an auxiliary energy source and the two brake circuits each of which communicate with a front wheel and a rear wheel, the brake system comprising braking pressure modulators contained in pressure fluid lines leading to the rear wheels, and comprising pressure fluid lines leading from the rear-wheel brakes to a pressure supply reservoir and containing separating valves adapted to switch to the open position comprising switchable valves for reducing the boosting effect by decreasing the auxiliary energy transmitted onto the braking pressure generator, further comprising sensors and electric circuit configurations for the determination and evaluation of the wheel rotational behavior as well as for the generation of control signals for controlling on the distribution of braking pressure onto the front wheels and the rear wheels and on the braking pressure variation upon the occurrence of tendencies to lock wherein the two hydraulically isolated brake circuits (1, 2) are interconnected between the braking pressure generator (3) and the front-wheel brakes (12, 13) by a hydraulically actuated control element (20, 34) which compensates for braking pressure differences at the two front-wheel brake (12, 13), including a valve (19) wherein actuation of said valve (19) to thereby reduce the boosting effect permits reduction of the braking pressure in one of the two brake circuits (1,2) connected to the braking pressure generator (3), while reduction of braking pressure in the other brake circuit only occurs upon attainment of a residual pressure that is dependent upon the brake pedal force (F), wherein the braking pressure generator (3) is provided as a power brake booster combined with a single-type master cylinder and to which one of the two brake circuits (2) is in direct connection, and wherein a pressure fluid pump (8) is provided as an auxiliary energy source, the pressure side of which is connectable with the supply reservoir (11) by way of a valve (10) which is adapted to switch to the open position, wherein the control element (20, 34) is provided as a piston (23, 36) slidably arranged in a cylinder (22), the two end faces of said piston confining each one chamber (24, 25) communicating with one of the two brake circuits (1, 2), respectively, wherein the piston (23, 36) of the control element (20, 34) is mechanically coupled to a separating valve (21) which is inserted in terms of function into the pressure fluid line of one of the two brake circuits (1) between the braking pressure generator (3) and the control element (20, 34) the separating valve being opened in the pressure of like pressures at the two front-wheel brakes (12, 13) and in the event of higher pressure prevailing in the other brake circuit (2), the one leading directly from the braking pressure generator (3) to the front-wheel brake (13), wherein the separating valve (21) is inserted into the front-wheel brake circuit (1) connected to the single-type master cylinder (5), and wherein the front-wheel brake circuit (2) communicating with the power brake booster (4) is connected to the control element (20) by way of a hydraulically actuated valve (29) which is closed in the inactive position and which is adapted to assume its open position by a control pressure (p, p'"'"') applied thereto and delivered from the auxiliary energy circuit, and wherein a check valve (30) opening towards the control element (20) is connected in parallel to the hydraulically actuated valve (29).

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