Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Patent
1997-04-09
1999-08-24
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
180170, B60T 800
Patent
active
059416149
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a wheeled vehicle having a braking system, and in particular to the use of the braking system to control the descent of hills by the vehicle. It is particularly useful for off-road vehicles.
When a wheeled vehicle such as a car is going down a steep slope, it is usual to put the car into a low gear and use engine braking to slow the vehicle. The speed of the vehicle will depend upon the gear selected and the steepness of the slope. As a result, the brakes may still need to be used from time to time if the slope becomes particularly steep. On very steep slopes engine braking may not be sufficient to allow a controlled descent. In an off road environment slopes are frequently far steeper than usually encountered and traction can be poor, particularly in wet or muddy conditions.
It is known from DT 24 19 242 to provide a braking system wherein the brakes are controlled so that the position of the brake pedal defines exactly the retardation which will be produced. However, such a system would not be effective in controlling the descent of a hill under conditions of poor traction because, as soon as traction is lost, the speed of the vehicle will change and the system will not be able to return it to a speed suitable for the conditions.
According to the present invention there is provided a wheeled vehicle having a plurality of wheels, a plurality of braking means each for braking one of said wheels, wheel lock detection means for detecting locking of any of said wheels, and control means which has activated and de-activated states, characterized in that in its activated state the control means is arranged to apply each braking means to slow the vehicle when a detected vehicle speed is above a predetermined constant threshold speed and no wheel locking is detected, but to release any of the braking means if locking of its respective wheel is detected while the detected vehicle speed is above said threshold speed.
Preferably, the control means, in its activated state, is arranged so that operation of an accelerator of the vehicle by a driver can accelerate the vehicle above the threshold vehicle speed.
Preferably the control means in its activated state is arranged to respond to operation of an accelerator of the vehicle by a driver by controlling the braking means to control the speed of the vehicle.
Preferably the control means is arranged to set a target vehicle speed, the value of which is controlled by operation of the accelerator, and to control the braking means so as to maintain the vehicle speed at the target speed.
Preferably, over at least the first part of travel of the accelerator, the target vehicle speed is increased with increased travel of the accelerator. This means that, when the target speed rises above the actual vehicle speed brake pressure is released and the vehicle is free to accelerate under the engine power output or the effect of gravity. In this way, if acceleration is required, the control means need not be de-activated for the accelerator to be used. This may be important if a dangerous situation arises while the control means is activated and acceleration is required.
Preferably the control means is arranged to control the rate of change of speed of the vehicle towards the threshold speed if the vehicle speed is substantially different from the threshold speed.
Preferably the control means is arranged, on entering its activated state, to compare the vehicle speed with the threshold vehicle speed and to control the braking means to bring the vehicle speed towards the threshold speed.
Preferably the control means in its activated state is arranged to be over-ridden by the operation of a braking demand means of the vehicle by a driver to increase the amount of braking over that provided by the control means to slow the vehicle below the threshold vehicle speed if no wheel lock is detected. Thus, where braking is required while the control means is activated, the control means need not be de-activated in order for the braking to take full effect.
Preferably, t
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Patent Abstracts of Japan, vol. 10 No. 281 (M-250), Sep. 25, 1986 & JP,A,61 102336 (Mazda) May 21, 1986, with English Translation.
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Beever Paul Andrian
Gallery Michael John
Parsons Keith Reginald
Butler Douglas C.
Rover Group Limited
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