Fluid-pressure and analogous brake systems – Speed-controlled – Odd condition or device detection
Reexamination Certificate
1999-06-24
2001-02-27
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Odd condition or device detection
C180S170000
Reexamination Certificate
active
06193333
ABSTRACT:
BACKGROUND TO THE INVENTION
The invention relates to control of a vehicle 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.
It is known from WO 96/11826 to provide a brake control system for a vehicle in which the brakes are automatically controlled so as to limit the vehicle speed to a predetermined value such that, with the help of an anti-lock brake function, the descent of a steep hill can be controlled without the need for skilled inputs from the driver.
SUMMARY OF THE INVENTION
The present invention provides a braking system for a vehicle having a transmission which can be shifted between a plurality of transmission ratios, the system comprising braking means, control means for controlling application of the braking means, and ratio detection means for detecting which ratio the transmission is operating in, wherein the control means is arranged to control the braking means so as to limit the speed of the vehicle to a target speed, the magnitude of which is dependent on which transmission ratio is selected.
This arrangement allows increased control for the driver and helps the vehicle to behave in a manner under control of the system which more closely resembles normal driving on flat ground.
If the vehicle includes a manual gear lever the ratio detection means may comprise a simple microswitch, or similar sensor, on the gear lever. Alternatively, it may form part of a control system on the vehicle, such as the engine management system or the anti-lock braking system or a combination of the two, which can determine the gear selected from the engine speed and vehicle road or wheel speed. This is obviously more likely to be used in vehicles without a traditional gear lever, for example those with upshift and downshift buttons on the steering wheel, or those with automatic transmissions. As a further alternative if the vehicle includes an electronic transmission controller which controls the transmission ratio, for example as in more sophisticated continuously variable transmissions, that controller can act as the ratio detection means.
Preferably the transmission ratios are spread over a range from a highest ratio to a lowest ratio and the target speed is higher for a higher one of said ratios than for a lower one. In this specification a higher gear ratio means one in which the transmission produces a higher vehicle speed for a given engine speed.
Preferably the control means is arranged, if the transmission ratio is changed while the system is activated, to change the target speed thereby to change the speed at which the vehicle will travel.
Preferably the control unit is arranged to change the target speed at a controlled rate thereby to limit the acceleration or deceleration rate of the vehicle as it changes between the target speeds.
Preferably, in at least one of said transmission ratios, the target speed can be increased by operation of an accelerator of the vehicle.
Preferably, for each of said transmission ratios, the control means defines a characteristic relating accelerator position to target speed so that, in each of said ratios, the speed of the vehicle can be controlled by operation of the accelerator.
An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings.
REFERENCES:
patent: 5003483 (1991-03-01), Hedstrom
patent: 5452946 (1995-09-01), Warner
patent: 5941614 (1999-08-01), Gallery et al.
patent: 5997108 (1999-12-01), Claussen et al.
patent: 96/11826 (1996-04-01), None
Davis and Bujold
Graham Matthew C.
Rodriguez Pamela J.
Rover Group Limited
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