Hydraulic vehicle braking system with anti-lock arrangement

PCT No. PCT/DE96/01351 Sec. 371 Date May 21, 1997 Sec. 102(e) Date May 21, 1997 PCT Filed Jul. 18, 1996 PCT Pub. No. WO97/12791 PCT Pub. Date Apr. 10, 1997A hydraulic brake system for a vehicle with an anti-lock arrangement operable by wheel brake pressures are individually variable in front wheel brakes and rear wheel brakes, connected to diagonal brake circuits, of a four-wheeled vehicle, in order to reduce or eliminate a threat of wheel locking. The anti-lock arrangement has at least one return pump per brake circuit. The anti-lock arrangement is equipped with a total of four electrically controllable valves. In each of the brake circuits I, II there is one first valve between the master cylinder and a front wheel brake and one second valve between the master cylinder and the rear wheel brake. All the valves are embodied as normally open valves and are electrically closable. Inlets of each of the return pumps communicate directly with the respective front wheel brakes and indirectly with the rear wheel brakes through throttles. Check valves that open toward the inlets of the return pumps are provided in series with the throttles. The anti-lock arrangement creates the possibility that in the anti-lock mode, for instance in travel on an icy road, rear wheel brake pressures may be higher than front wheel brake pressures, to improve the braking action.