Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1993-01-14
1994-06-21
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031135, 36442602, B60T 862
Patent
active
053223560
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and a circuit configuration to augment or preserve the driving stability of a road vehicle by controlling the traction slip by means of a brake management system.
To improve the starting behavior and the traction of a road vehicle, it is known to install devices on the vehicle which prevent spinning of the drive wheels or excessive traction slip. Such spinning tendencies occur as soon as the traction torque of the vehicle engine exceeds the torque which is transmittable through the wheels onto the road.
With rising traction slip, it is not only the torque in the driving direction that is transmittable onto the road which decreases--after having exceeded a maximum--but also the lateral guide force of the wheels decreases to a relatively very small amount. Due to this, the steerability and the driving behavior during cornering is impaired in vehicles with front-wheel drive. In vehicles with rear-wheel drive, there is even the risk of skidding when the lateral guide force is too small.
To control the traction slip, it is known from German published patent application 36 24 722 A1, which herein is referred to as an example of a great number of publications relating to systems of this type, to stabilize the imminently spinning drive wheel by way of brake management. In consideration of the temperature and the loading capacity of the brake, the period of time in which the brake can compensate for the excess torque of the drive axle is very limited. For this reason, brake management is combined with engine management in other known traction slip control systems, for instance as described in German published patent application 38 09 101 A1. However, this entails considerably greater expenditures.
DE 38 01 267 A1 teaches a vehicle brake system wherein, for augmenting the driving stability during braking on a surface with a different coefficient of friction right/left, the braking pressure is reduced on that rear wheel running on the non-skid road surface once the brake slip on this wheel exceeds a predefined value. This way, the lateral guiding force which can be generated by this wheel is increased, and swerving of the vehicle is prevented. This brake system is used instead of an anti-lock brake system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of controlling traction slip which is exclusively based on brake management, the operation of which is not limited for a short period of time in consideration of the brake load. This method should contribute to enhancing the driving stability.
It has been shown that this object can be achieved by a method by which the rotational pattern of a wheel (HM-wheel) is monitored and stabilized by brake management as soon as the traction slip of this wheel exceeds a limit value and after commencement of brake management on the wheel (HM-wheel) having the higher coefficient of friction, the introduction of braking pressure into the wheel brake of the second wheel (LM-wheel) of the axle is prevented, and braking pressure existing in the wheel brake of this second wheel (LM-wheel) is kept constant or is decreased.
Previously, traction slip control served above all to stabilize by brake management that wheel of the drive axle which was relieved from load and exhibited the lower coefficient of friction. The present invention is based on the findings that it is sufficient and useful to ensure, in every situation and every driving condition, that the wheel driven on the higher coefficient of friction remains stable. Traction slip tendencies on this HM-wheel are compensated for by brake management, so that the lateral guide force of this wheel is preserved. The behavior of the wheel relieved from load (LM-wheel) is of secondary importance in this situation. By using a method in accordance with the invention, further pressure increase on this LM-wheel is prevented and, as the case may be, prevailing braking pressure is reduced.
What is important is to properly identify, at an
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Kolbe Alexander
Roesch Klemens
Alfred Teves GmbH
Lewis J. Gordon
Muratori Alfred
Oberleitner Robert J.
Seitter Robert P.
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