Fluid-pressure and analogous brake systems – Pipeless valves
Patent
1980-05-07
1982-09-14
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Pipeless valves
303 71, 303 98, 180197, B60T 802
Patent
active
043492339
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to vehicle drive systems having wheels which are driven through a differential and, more particularly, to a method and apparatus for controlling wheel slip between differentially driven wheels due to a loss of traction by one of the wheels.
2. Background Art
A standard vehicle having a pair of driving wheels powered by a drive shaft through a differential can experience difficulties when one of the two differentially driven wheels loses traction. This can occur, for example, when a truck gets one of its drive wheels stuck in the mud. The other wheel may be on solid ground and have good traction, but the vehicle is often unable to move. The differential directs all of the power to the wheel in the mud and the wheel with traction remains stationary. The conditions which give rise to such a loss of traction commonly exist around construction sites, off-road locations, and during wet, snowy or icy weather conditions.
To alleviate this loss of traction condition, various mechanical anti-spin devices have been developed and put into commercial use. These devices, however, often produce an abrupt transfer of all of the driving power to the wheel or wheels having traction. This abrupt and full transfer of power can create such large mechanical stresses on the drive train that its useful life is shortened.
An alternative approach to the problem of slip involves the use of separately actuable wheel brakes. An operator using such a system can selectively apply a braking force to the spinning wheel and thus can balance the power from the drive shaft between the slipping and non-slipping wheels. The application of such a braking force simulates traction and results in a more even distribution of power between the wheels. These systems, however, are easily abused and can cause unacceptable wear on the drive train.
Automatic slip control systems using selectively actuable wheel brake systems are also well known. These systems include speed sensors located on or near each of the driven wheels for generating wheel speed signals, means for comparing the signals, and solenoid operated valves which actuate the wheel brake of the slipping wheel whenever a slip condition is detected.
One such automatic system is disclosed in U.S. Pat. No. 4,066,300 to Devlin, issued Jan. 3, 1978. Other similar systems are disclosed in U.S. Pat. No. 3,025,722 to Eger, Jr., issued Mar. 20, 1962 and in U.S. Pat. No. 3,981,545 to Eddy, issued Sept. 21, 1976. The Eddy system utilizes speed sensors for generating a velocity signal for each driven wheel, comparison means for determining when the rotational velocity of one wheel exceeds that of the other, and hydraulic valves to apply a braking force to the faster driven wheel.
All of the automatic systems involve an abrupt application and release of brake forces to the slipping wheel. These approaches, unless utilized with very light braking forces and at low speeds, can lead to abrupt or jerky motion of the vehicle.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention, an apparatus is provided for automatically balancing the power transfer between two driven vehicle wheels when one of the wheels loses traction and rotates faster than the other. The apparatus applies a varying braking force to the wheel which lacks traction. The apparatus includes a pair of wheels, means for braking the wheels and means for generating a slip signal corresponding to any difference in the rotational speeds between the wheels. The apparatus further includes an improvement comprising means for actuating the brake on the faster rotating wheel in a manner proportional to the difference in rotational speeds between the wheels.
In a second aspect of the invention a method is provided for controlling wheel slip on driven wheels when one of the wheels loses traction and rotates faster than the other. The method involves the steps of sensing any difference in rotational s
REFERENCES:
patent: 3025722 (1962-03-01), Eger, Jr. et al.
patent: 3779331 (1973-12-01), Burkhardt et al.
patent: 3901556 (1975-08-01), Prillinger et al.
patent: 3927737 (1975-12-01), Prillinger et al.
patent: 3944295 (1976-03-01), Lloyd et al.
patent: 3981545 (1976-09-01), Eddy
patent: 4006939 (1977-02-01), Schexhayder
patent: 4066300 (1978-01-01), Devlin
patent: 4156547 (1979-05-01), Marsh
patent: 4180223 (1979-12-01), Amberg
"Traction Control Prevents Spin-Out", Automotive Engineering, Sep. 1975, pp. 8, 10.
Bullard David E.
Myers Allen D.
Butler Douglas C.
Caterpillar Tractor Co.
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