Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-07-23
2001-11-06
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C303S176000, C303S195000
Reexamination Certificate
active
06312066
ABSTRACT:
TECHNICAL FIELD
The present invention relates ABS control, and more particularly relates to improved ABS control in rough road conditions.
BACKGROUND OF THE INVENTION
Anti-lock control systems are part of the standard equipment in medium-class and upper-class vehicles. Lower-category and low-cost cars are increasingly included in this group. The advantages of anti-lock control are beyond doubt, although there are exceptional situations where the stopping distance may become longer caused by anti-lock control operations than in braking operations where the wheels lock.
Such exceptional driving situations are especially important for off-road travel conditions or off-road vehicles having a braking performance on gravel, broken stones and similar pavements. There is a relatively frequent braking control of a locked wheel on such road pavements, with the result that anti-lock control may cause an extended stopping distance. Therefore, it has been known in the art to provide a possibility of deactivating the anti-lock control system in off-road vehicles in order to ensure maximum possible deceleration during off-road travel.
Such a deactivation is of course critical because faulty operation is imminent. Also, when both front wheels lock, the vehicle cannot be steered. When the rear wheels lock, driving stability is known to be jeopardized.
Further, it is known in the art to activate a special control mode in off-road vehicles during off-road driving which allows anti-lock control operations for the second wheel of an axle only after the respective first wheel of the axle has locked.
Therefore, an object of the present invention is to develop a method of improving the control behavior of an anti-lock control system in off road travel situations which has favorable effects on the stopping distance in such a situation and on steerability and driving stability.
The special feature of the method of the present invention is that in the special control mode in the wheel brake of the wheel which is the first to exceed the predetermined normal control thresholds, different from the normal control mode, braking pressure reduction is prevented and the braking pressure on this wheel is maintained constant until reacceleration of this wheel commences. Upon reacceleration of the wheel, braking pressure increase is permitted, and the special control mode for this wheel is terminated when the normal control thresholds are reached. Further, it is ensured that the special control is principally allowed for only one wheel of an axle at a time, and the normal control mode applies to the other wheel of the axle.
In a preferred embodiment, the existence of brake slip and a rising or constant wheel deceleration are predetermined as necessary conditions for the activation of the special control after entry of a wheel into normal control or after the normal control thresholds have been exceeded. These two conditions must be satisfied for the commencement of the special control on the wheel at issue.
Maintaining driving stability and steerability has basically priority at high vehicle speeds. Therefore, in another embodiment of the present invention, the special control mode is admitted only at a vehicle speed or vehicle reference speed which is below a predetermined limit value. It is also possible to principally trigger the special control mode when the speed is below the limit value, however, to prevent it at higher speeds.
The existence of an off-road travel situation is automatically ‘identified’ in a favorable aspect of the present invention by evaluating chassis vibrations, wheel vibrations, etc., which are typical of off-road travel. On the other hand, it is also possible to provide a switch in the vehicle which can be operated manually in order to signal an off-road travel situation to the control system and thereby allow the special control mode.
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Buschmann Gunther
Gronau Ralph
Butler Douglas C.
ITT Manufacturing Enterprises Inc.
Rader & Fishman & Grauer, PLLC
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