Method and apparatus for controlling wheel slip on differentially mounted wheels

• US 4,349,233 A
• Filed: 05/07/1980
• Issued: 09/14/1982
• Est. Priority Date: 05/07/1980
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Tractor Co (Caterpillar Incorporated)
• Inventors: Bullard, David E., Myers, Allen D.
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US06/245,231
• Time in Patent Office: 860 Days
• Field of Search: 180/196, 180/197, 74/711, 188/106 F, 188/170, 188/181 A, 188/354, 303/2-4, 303/6 M, 303/6 R, 303/6 A, 303/9, 303/13-17, 303/91, 303/93-109, 303/113-119, 303/71, 303/89, 244/111
• US Class Current: 303/145
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/4809 Traction control, stability control, using both the wheel brakes and other automatic braking systems
• CPC Class Codes: Y10S 303/06 Axle differential control

Abstract

A standard motor vehicle having a pair of driving wheels (8), (9) powered by a drive shaft (10) through a differential (11) can experience difficulties when one of the two differentially driven wheels (8/9) loses traction. The differential (11) directs all of the power to the wheel that is slipping and the wheel with traction remains stationary. Various anti-spin devices have been developed but these often produce an abrupt transfer of all of the driving power to the wheel having traction. The anti-spin apparatus of this invention overcomes this problem and includes an electrical control circuit (24) and sensors (20), (21) for generating a slip signal representing the speed difference between the wheels (8), (9). The apparatus further includes a modulated hydraulic reducing valve (30), (110) for actuating the brake (15/15'"'"') on the faster rotating wheel (8/9) and a hydraulic modulating control valve (29) connected to the reducing valve (30), (110) and actuated by the slip signal. The reducing valve (30 ), (110) is modulated to proportionally vary the braking force applied to the faster rotating wheel in accordance with the difference in rotational speeds between the wheels (8), (9).

Claims

1. In an anti-slip apparatus for balancing the power transfer between a pair of driven wheels (8), (9) when one of the wheels loses traction and rotates faster than the other, said apparatus having braking means (15) for braking the wheels (8), (9) and generating means (20), (21), (24) for generating a slip signal corresponding to any difference in the rotational speeds between the wheels (8), (9), wherein the improvement comprises:

hydraulic actuating valve means (28), (30) for individually actuating said braking means (15) to minimize any rotational speed difference between the wheels (8), (9), said actuating valve means (28), (30) being connected to a source of hydraulic pressure (49) and to said braking means (15); and

,

hydraulic modulating valve means (29) for modulating said actuating valve means (28), (30) in response to the slip signal to proportionally vary the braking force individually applied to the wheels (8), (9) by the actuating valve means (28), (30).

2. An apparatus as in claim 1 wherein said braking means (15) includes a pair of spring engaged, hydraulically released brakes (15), (15'"'"') and wherein the valve means (28), (29), (30) includes means (29), (30) for reducing the hydraulic pressure to the brake (15/15'"'"') on the faster rotating wheel (8/9) in a manner proportional to the difference in the rotational speed between the wheels (8), (9).

3. 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).

4. An apparatus as in claim 3 wherein the plurality of conduits includes:

a first conduit (54'"'"') connecting the source (49) of hydraulic pressure to the selector valve means (28), said first conduit (54'"'"') carrying hydraulic fluid at system pressure;

a second conduit (54'"'"''"'"''"'"') connecting the source (49) of hydraulic pressure to the pressure reducing valve means (30), said second conduit (54'"'"''"'"''"'"') carrying hydraulic fluid at system pressure;

a modulating conduit (82) connecting the pressure reducing valve means (30) to the selector valve means (28), said modulating conduit (82) carrying hydraulic fluid at reduced pressure; and

wherein the selector valve means (28) includes means (38) for connecting the modulating conduit (82) to the brake (15) of the faster rotating wheel.

5. An apparatus as in claim 3 wherein the modulating control valve means (29) is a solenoid (37) actuated variable orifice valve, said orifice valve being connected to the pressure reducing valve means (30).

6. 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).

7. An apparatus as in claim 6 wherein the selector valve means (111) includes a solenoid (113), (38) operated, three position valve (111) actuated by the generating means (20), (21), (24'"'"'), in the first position said three position valve (111) connects the modulating control valve means (29) to the first valve means (85), in the second position it blocks communication of the modulating control valve (29) to both the first and second valve means (85), (85'"'"'), and in the third position it connects the modulating control valve means (29) to the second valve means (85'"'"').

8. An apparatus as in claim 6 wherein the modulating control valve means (29) is a solenoid (37) actuated variable orifice valve, said orifice valve being connected to the first and the second valve means (85), (85'"'"') via the selector valve means (111).

9. An apparatus as in claim 6 wherein the first and second valve means (110) each includes a spool valve (85), (85'"'"') the position of which is controlled by the modulating control valve means (29) via the hydraulic selector valve (111), said spool valves (85), (85'"'"') actuating the brake (15), (15'"'"') on the faster rotating wheel (8), (9) in proportion to the difference in rotational speeds between the wheels (8), (9).

10. 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).

11. 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.

12. A method as in claim 11 including the step of:

selectively communicating the varied level of fluid pressure to the brake (15/15) of the faster rotating wheel (8/9) and simultaneously communicating a higher level of fluid pressure to the other wheel (8/9) through a common selector valve (28).