Fluid-pressure and analogous brake systems – Speed-controlled – Left or right speed comparison
Patent
1997-12-29
2000-07-04
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Left or right speed comparison
303112, 303186, 303DIG6, B60T 866
Patent
active
060828358
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is concerned with electronic braking systems in road vehicles and in particular with an electronic braking system which can recognise and respond to differential braking across an axle.
DISCUSSION OF THE BACKGROUND
In conventional vehicle braking systems, braking force imbalance across an axle of the vehicle can occur from a number of sources of which the primary cause is the differential friction coefficient between the fixed lining and the rotary parts of the brakes resulting from material and working condition variations. Brake actuation components are subject to tolerance and friction variations which affect braking input forces. Physical differences between one brake adjuster and another cause modification of input displacements which have a similar effect. Actuating pressures are generally equal on most pneumatic systems in which the same circuit communicates with both brakes. However, with electronic braking systems, axle wheel pressures can be different to some extent due to component tolerances, because the brakes have actuating pressures which are individually controlled. Our European Patent No. 0386953 describes a system in which the two brakes are linked together by a specially provided pipe which restores the pressure equality in the event of primary imbalance. Such a means provides pressure balance in the two braking circuits but does not seek to address the possible brake force imbalance which may be present nevertheless.
U.S. Pat. No. 4,685,745 (EP-A- 0 189 076) discloses an electronic braking system wherein signals representative of the braking force values at different vehicle wheels across an axle are compared in an electronic controller to generate a regulation control signal which is used to control pressure regulating valves to reduce braking imbalance across the axle. The electronic controller can be arranged to update the braking value correction on the basis of braking values fed to it during or after the application of the vehicle brakes.
SUMMARY OF THE INVENTION
An object of the present invention is to provide means in an electronic braking system (EBS) for correcting brake force imbalance which may result from any of the possible causes mentioned above.
In accordance with a first aspect of the present invention, there is provided an electronic braking system having means for recognising differential braking across an axle and providing an adaptive capability whereby a braking controller is able to determine a value of the braking imbalance using a learning process and correct on the basis of this by introducing differential pressure adjustments such as to increase braking at the wheel with the lower brake output and/or reduce braking at the wheel with the higher brake output, the learning process being completed over selected parts of several vehicle stops and being repeated continuously, the means of assessment of the level of differential braking is provided by measurement of the differential distance travelled during braking, by the respective wheels on an axle per pre-set unit of distance so travelled.
Advantageously, the system has means for averaging the recorded braking imbalance over said several vehicle stops and storing same for use as a diagnostic output.
Advantageously, differences in rolling radii are assessed during the periods of running between vehicle stops to arrive at a background distance difference signal by accumulation over a pre-set unit of distance travelled under specially selected non-braking conditions, stored for use as a correction figure and subtracted from the braking differentials obtained.
In some situations where the detected background differential is high, this causes the differential braking control learning process to be suspended and provides a driver warning since the condition is most likely to result from serious tire pressure error.
In some embodiments, wheel speed differences can be accumulated from measurements made at regular intervals and there is accompanying simultaneous ac
REFERENCES:
patent: 3706351 (1972-12-01), Neisch
patent: 3744854 (1973-07-01), Ooya et al.
patent: 3771840 (1973-11-01), Hubbard
patent: 3804999 (1974-04-01), Hubbard
patent: 4566737 (1986-01-01), Masaki et al.
patent: 4685745 (1987-08-01), Reinecke
patent: 4712839 (1987-12-01), Brearley et al.
patent: 5004299 (1991-04-01), Brearley et al.
patent: 5004300 (1991-04-01), Brearley et al.
patent: 5011236 (1991-04-01), Toepfer et al.
patent: 5042883 (1991-08-01), McCann et al.
patent: 5080445 (1992-01-01), Brearley et al.
patent: 5088042 (1992-02-01), Brearley et al.
patent: 5328251 (1994-07-01), Brearley
patent: 5333940 (1994-08-01), Topfer
patent: 5362139 (1994-11-01), Watanabe
patent: 5404302 (1995-04-01), Matsuda et al.
patent: 5407258 (1995-04-01), Giers et al.
patent: 5407259 (1995-04-01), Itabashi et al.
patent: 5575543 (1996-11-01), Pheonix
patent: 5992579 (1999-11-01), Kyrtsos
Lucas Industries Public Limited Company
Oberleitner Robert J.
Williams Thomas J.
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