Fluid-pressure and analogous brake systems – Speed-controlled – And traction control
Patent
1996-01-12
1997-11-18
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
And traction control
303148, 364426028, B60T 872
Patent
active
056880294
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the so-called anti-slip control (ASC), i.e. to a method for preventing the driven wheels of a vehicle from spinning.
Such ASC systems are also referred to as TC (traction control) systems.
The driven wheels of a vehicle always have a tendency to spin when the vehicle engine generated driving torque at the wheel is higher than the torque based on the momentary friction coefficient that can be transmitted via the wheels to the road.
Similar to block-protected braking (ABS), not only the driving torque that can be transmitted from the wheel to the road surface in the driving direction decreases with increasing traction slip after exceeding a maximum value, but also the cornering force of the wheels decreases to very low values after exceeding a maximum.
From the state of the art traction slip controllers are known, where on the one hand spinning of the driven wheels is prevented by reducing the drive power of the engine in the case of a spinning tendency of a wheel. On the other hand, traction slip controllers are known, where in the case of a spinning tendency of a driven wheel, the brake of that wheel is automatically actuated in order to improve the traction of that wheel. The state of the art generally provides for controlling both driven wheels of one axle on the basis of their individual rotation behaviour with respect to traction.
If, for example, one wheel of the axle shows a spinning tendency significantly before the other wheel (because the one wheel runs on a smoother road surface), the brake of the wheel that is the first to show a spinning tendency is supplied with brake pressure. When using a differential gear, the consequence for the respective axle is that the other driven wheel (not yet showing a spinning tendency) transmits a higher driving torque to the road surface.
With this known traction control system, the wheel which has first become instable (i.e. the wheel which is the first to show a spinning tendency) is being braked as long as is required by the rotational speed of the wheel. In other words: as long as the rotational speed of the wheel is exceeding a given threshold value, it is braked in order to prevent spinning.
If the other wheel which at first was stable also shows a spinning tendency, then this wheel is also braked accordingly.
DE 40 22 471 A1 discloses a traction control system for increasing the driving stability, where the driven wheel which momentarily shows a higher friction coefficient is determined, and the rotational speed of this wheel is monitored and stabilized by a braking effect. A brake pressure prevailing in the wheel brake of the second driven wheel of the same vehicle axle will be relieved. The control is therefore completely based on the rotational behaviour of the stable wheel, the brake pressure of which is controlled as a function of its rotational speed.
The present invention is based on the objective to provide a (convenient) anti-slip control system which annoys the driver as little as possible, which can function with a simple control algorithm, and which imposes only minimum load on the vehicle components.
First, the invention is based on the following finding:
With a conventional traction control system, in particular with rapidly changing friction coefficients between the wheel and the road surface, large variations of the braking torques prevailing at both wheels of one axle occur, and this leads to an extreme load acting on the gears, bearings and transmissions, particularly in the case of a vehicle axle with a so-called differential. This highly impairs the durability and the life of the drive train of the vehicle.
With conventional traction control systems, such loading of the components occurred particularly whenever both wheels of a drive axle are coupled via a differential. In the case of one wheel of the axle coming into the instable range, i.e. showing a spinning tendency, it will be braked down by the actuation of its wheel brake to a lower rotational speed. Because of the differential, this again results in the
REFERENCES:
patent: 3535004 (1970-10-01), Howard et al.
patent: 4484280 (1984-11-01), Brugger et al.
patent: 4950037 (1990-08-01), Kopper et al.
Bach Thomas
Helbing Stefan
Knechtges Josef
Schmitt Hubert
Lipka Pamela J.
Lucas Industries Public Limited Company
Oberleitner Robert J.
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