Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Patent
1994-04-07
1995-10-24
Ballato, Josie A.
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
303 3, 303 15, B60T 832, B60T 800
Patent
active
054604346
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a means for obtaining improved braking distribution in vehicle braking systems, whether electronically controlled or mechanical.
The curve governing the relationship between axle braking for a two-axle vehicle is well known but does not take into account other sources of braking which would cause vehicles to come virtually to rest without friction brakes being employed. Such other sources of braking are primarily frictional losses in rotating parts and, more importantly, engine braking. Many heavy vehicles have means of increasing engine braking or have some form of retarder, in the form of an additional type of endurance brake which acts on the driving wheels. In such vehicles in particular, the use of combined braking seriously unbalances the braking distribution away from the ideal in which utilization of adhesion between axles is equal. In conventional vehicles, efforts are made to obtain good distribution of foundation (friction) braking but the additional braking sources generally represent an option or an afterthought and are in no way integrated into an overall braking system for the vehicle.
In a Brake-by-Wire or Electronic Braking System, electronic controls are provided in the combined braking scheme which, of course, uses electrical signalling, in order to make braking distribution near to the ideal so as to improve safety in braking. Such a system has therefore to include some level of integration of the sources of braking. This may be the full integration of a blended braking system or the lesser integration of an interlinked system in which the foundation brake controls make suitable allowance for other sources of vehicle braking--referred to hereinafter as background braking--in order to achieve a more ideal braking distribution in actuality. It is this latter type of braking system which is the subject of the present invention.
It is recognised as impossible to measure all the sources of background braking because the sources are distributed and often quite small and, as such, sensors are not available to measure the effects of what is often losses and subject to relatively significant disturbances during vehicle movement. However, it is possible to measure some of the sources of background braking directly, such as driveline torque. It is also possible to measure the combined effect of all the sources of background braking in the deceleration which is produced on the vehicle and from a study of typical vehicles to allocate this effect between axles.
SUMMARY OF THE INVENTION
Thus, in accordance with the present invention in its broadest aspect, there is provided a method and apparatus for achieving improvements to braking distribution in a multi-axle vehicle having a controlled braking system, wherein allowance is made for selected sources of background braking by assessing through measurement the corresponding background braking force and assigning this in a predetermined proportion between the vehicle axles.
In one embodiment, for example, the selected source can be the driveline torque which can be measured directly and the corresponding background braking force assessed.
However, it is presently preferred to assess the total background braking force by its resultant effect on the vehicle performance, namely its decelerating effect. This assessment can therefore be made by measurement of the deceleration of the vehicle at a time when the vehicle is not being driven forward and the foundation brakes are not being applied, that is, by measurement of the total vehicle rolling deceleration.
The deceleration effect is measured using a vehicle borne decelerometer, which is zeroed when level in order to obtain a figure which is compensated for gradient changes.
Of the background braking contribution which is thus allocated between axles, the majority is assigned to the drive axle (usually the rear axle in the case of trucks and heavy vehicles), and the equivalent braking pressure is calculated from the brake factors and the total
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Brearley Malcolm
Micke Sigmar
Ballato Josie A.
Lucas Industries Public Limited Company
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