Hydraulic brake system for motor vehicles

Claim 1

A hydraulic brake system (10) having an anti-skid and traction control apparatus for motor vehicles, a brake line (13) that extends between a master brake cylinder (11) and a wheel brake (14) for carrying pressure fluid to said wheel brake, a shutoff valve (15) disposed in the brake line (13), said shutoff valve includes a valve housing (33), a bore (34) in said valve housing, a sleeve (35), and a tappet (38) in said bore (34), a valve seat (36) on an upper end of said sleeve (35), a closing member (39) on a lower end of said tappet, said tappet engages an armature (59) which forces the closing member (39) onto the valve seat (36) by action of a magnetic force, a restoring spring (40) is supported firmly by a lower end on an upper end of said sleeve (35) and has an upper end that engages said tappet (38), the armature (59) has a blind bore (60), defined by a press-fit bolt (61), a prestressed compression spring (64) is received in said blind bore (60) and is supported on one end of the armature (59) via the press-fit bolt (61) and on the other end exerts a force upon an intermediate element (63) which is supported on a bore step (62) of the armature (59) and connected to the tappet (38), the prestressing force of the compression spring (64) received in the armature (59) is greater than a force of the restoring spring (40), in a closing process of the shutoff valve (15) the armature (59) is moved solely by an action of a magnetic force to overcome the restoring spring (40) until an engagement of the closing member (39) with the valve seat (36), and subsequently overcomes only the prestressed compression spring (64) until a full stroke of the armature (59) has been executed, a high-pressure pump (30) connected between the shut-off valve (15) and the wheel brake that feeds a pressure fluid into the brake line (13), and a pressure limiting valve (21) connected to the shutoff valve (15), in which the pressure fluid is diverted to the master brake cylinder (11) by said pressure limiting valve if a response pressure from said pump is exceeded, said compression spring (64) is disposed within said blind bore in the armature between a bottom of the blind bore in the armature (59) and the closing member (39) of the shutoff valve (15) which in a valve closing position said compression spring (64) exerts a force, according to a response pressure, upon the closing member (39).