Anti-lock hydraulic brake system with plunger system and pump

Claim 1

An anti-lock hydraulic brake system for use with automotive vehicles comprising a pedal-actuated braking pressure generator (1) including a braking pressure modulator, comprising a plunger system (7, 8) which is inserted into the pressure fluid conduits leading from the braking pressure generator to the wheel brakes, an auxiliary-pressure supply system and electromagnetically actuatable multidirectional control valves for the control of the plunger systems, further comprising wheel sensors and electronic circuits which serve to generate electric signals by logical combining and signal processing for the purpose of control of the multidirectional control valves as a function of the wheel rotational behavior and additional criteria, wherein in each brake circuit (I, II) one said plunger system (7, 8) is provided which comprises a stepped plunger piston (43, 44) applied by the braking pressure, which plunger piston on braking operations without slip control is kept in its initial position by the force of a first resetting spring (45, 46) opposed to the braking pressure and wherein each plunger system (7, 8) includes a valve piston (48) slidably mounted within said stepped plunger piston (43, 44) and wherein one end of said valve piston (48) includes a valve member (56) which closes a channel (54) which extends from a valve seat surface facing said valve member (56), through said valve piston and into a chamber (52) which surrounds said resetting spring (45, 46), said valve member (56) closing a transverse passage through said stepped plunger piston (43, 44) and through an annular chamber (49, 50) in said plunger piston (43, 44), said passage being connected at one end thereof to said auxiliary-pressure supply system by way of a first conduit (11, 12) and being connected at the other end thereof to an unpressurized supply reservoir (18) by way of a second conduit (19, 20), said valve piston (48) terminating in a frontal chamber (41, 42) at its other end thereof, said frontal chamber (41, 42) communicating with the braking pressure generator (1) by way of a non-return valve (37, 38) that is kept open in the initial position of the plunger piston (43, 44) by an extension of said valve piston (48) which engages said non-return valve (37, 38) an electromagnetically actuated normally open valve (21, 22) connected in said second conduit (20) between said other end of said passage and said unpressurized reservoir (18), and wherein said plunger piston (43, 44) is displaceable in opposition to the force of the resetting spring (45, 46) by the introduction of auxiliary pressure which is applied in said annular chamber (49, 50) within the plunger system (7, 8) to an annular surface of the plunger piston (43, 44) caused by the step, while said non-return valve (37, 38) that is kept open in the initial position of the plunger piston (43, 44) closes, which thereby shuts off the pressure fluid conduit from the braking pressure generator (1) to the plunger piston (43, 44) and causes enlargement of the frontal chamber (41, 42) which is confined by the pressurized plunger piston surface and thereby brings about braking pressure reduction in at least one of the wheel brakes connected.