Method and apparatus for controlling wheel slip on differentially mounted wheels

An apparatus for controlling wheel slip on differentially driven wheels (8), (9) when one of the wheels (8/9) loses traction and rotates faster than the other, comprising:

• a pair of spring engaged, hydraulically released brakes (15), (15'), said brakes being connected to the wheels (8), (9);
• a source of hydraulic pressure (49);
• generating means (20), (21), (24) for generating a slip signal proportional to any difference in the rotational speeds of the wheels (8), (9);
• pressure reducing valve means (30) for reducing the hydraulic pressure to the brake (15) of the faster rotating wheel;
• a control valve means (29) for modulating the reducing valve means (30);
• selector valve means (28) for connecting the reducing valve means (30) to the brake of the faster rotating wheel, said selector valve means (28) being actuated by the signal generating means (20), (21), (24) and connected to the two brakes (15), (15');
• and
• a plurality of conduits (54), (79), (82) connecting the source of hydraulic pressure (49) to the selector valve means (28) and the modulating control valve means (29) and the pressure reducing valve means (30) to the selector valve means (28).

An apparatus for controlling wheel slip on differentially driven wheels (8), (9) when one of the wheels (8/9) loses traction and rotates faster than the other, comprising:

• a pair of spring engaged, hydraulically released brakes (15), (15'), said brakes being connected to the driving wheels (8), (9);
• a source of hydraulic pressure (49);
• generating means (20), (21), (24') for generating a slip signal proportional to any difference in the rotational speeds of the driving wheels;
• first valve means (85) for reducing the hydraulic pressure to the brakes (15') of one of the driving wheels (9);
• second valve means (85') for reducing the hydraulic pressure to the brake (15) of the other driving wheel (8);
• a modulating control valve means (29) actuated by the slip signal, said control valve means (29) being connectable to modulate the first and second valve means (85), (85');
• selector valve means (111) for connecting on command the modulating control valve means (29) to one of the first and second valve means (85), (85'), said selector valve means (111) being actuated by and connected to the signal generating means (20), (21), (24');
• and
• a plurality of conduits (50), (54), (17), (18), (116), (117), (115) connecting the source of hydraulic pressure (49) to the first and second valve means (85), (85') and connecting the first and second valve means to the brakes (15), (15') and to the modulating control valve means (29) via the selector valve means (111).

An apparatus for a motor vehicle for controlling wheel slip on differentially driven wheels (8), (9) when one of the wheels (8/9) loses traction and rotates faster than the other, said motor vehicle having both a service braking system (16) and a parking/emergency braking system (51), (53), comprising:

• a pair of spring engaged, hydraulically released brakes (15), (15'), said brakes being connected to the driving wheels (8), (9);
• means (20), (21), (24) for generating a slip signal proportional to any difference in the rotational speeds between the driving wheels;
• a source of hydraulic pressure (49);
• a plurality of conduits (50), (54), (17), (18);
• parking/emergency brake valve means (51) for actuating said brakes (15), (15') said brake valve means (51) being connected to the source of hydraulic pressure (49) and to the brakes (15) by the conduits (50), (54), (17), (18);
• pressure reducing valve means (30) for reducing the hydraulic pressure from the parking/emergency brake valve means (51) to the brake (15/15') of the faster rotating wheel to minimize any rotational speed difference between the driving wheels (8), (9), said reducing valve means (30) being connected to one of the conduits (54''') between the brake valve means (51) and the brakes (15), (15');
• and
• a modulating control valve means (29) actuated by the slip signal, said control valve being connected to modulate the reducing valve means (30) in response to the slip signal to proportionally vary the braking force applied to the faster rotating wheel by said reducing valve means (30).

A method for controlling wheel slip on driven wheels (8), (9) having fluid actuated brakes (15), (15') when one of the wheels (8/9) loses traction and rotates faster than the other, comprising the steps of:

• sensing any difference between the rotational speeds of the driven wheels (8), (9);
• developing a slip signal proportional to the speed difference between the wheels (8), (9);
• variably actuating the brake (15/15') of the faster rotating wheel (8/9) by varying the level of fluid pressure communicated thereto;
• and
• modulating the fluid pressure communicated to the faster rotating wheel (8/9) in response to the slip signal.