Brakes – With condition indicator – Wear
Patent
1997-01-06
1998-12-15
Butler, Douglas C.
Brakes
With condition indicator
Wear
340453, 340454, F16D 6602
Patent
active
058486720
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wear sensing systems for the brake linings of vehicle brakes of the type in which friction linings are applied to a rotatable braking member such as a disc or drum.
2. Discussion of the Background
Lining wear-out sensors have been in operation on vehicles for many years and usually employ conductors which are embedded in the lining and which ground out on the disc or drum or form an electrical circuit which is cut as the wear-out condition is approached. Such sensors thus only provide a warning signal when a particular predetermined wear condition has been achieved.
It will be a requirement of diagnostic systems in the future to provide a sensor which indicates how much lining is left and it is unlikely, for several practical reasons, that such sensors will be incorporated within the brake lining in the traditional manner.
The presently favored approach is thus to position the wear sensor, not within the linings, but rather within the brake mechanism itself. An example of how this can be achieved is described and illustrated in detail in our copending UK Application No. 9320369.3 to which reference is hereby directed and in FIGS. 1 to 4 of drawings accompanying the present Application. If the wear sensors are mounted within the brake mechanism in this type of manner, then the disc thickness or drum inner diameter must be taken into account or the reading will be likely to become progressively greater as the life of the brake increases. Whilst the absolute measurements obtained will become increasingly pessimistic, the disc or drum will be protected but at an increased cost of unused lining.
From DE-A-3816949 there is known a process for monitoring the thickness of brake linings of a disc brake wherein sensors responsive to caliper/disc spacing are operated with simple software to (a) memorize the km. reading at start of first use, (b) take the km. reading when a prescribed test interval is reached, (e.g. when linings 75% worn); (c) establish the number of km, since new to reach 75% worn condition; and (d) establish how many more miles will be available to the prescribed worn-out condition by linear extrapolation. Regular recalibration is made after each mm of detected wear. The measurement signal is generated throughout the service life but, except when the test interval is reached, this is used only for system fault detection. The start of the prescribed interval is predetermined within the system to correspond to the (75%) worn condition. No possibility for changing the starting point for acceptable wear condition signals to be used in calculating "km to go" is accommodated within the system of DE-A-3816949 and the system is therefore unable to take account of wear to the disc itself.
SUMMARY OF THE INVENTION
A primary object of the present invention is thus to provide a means and method for predicting a wear-out point that takes account of wear on the disc or drum with operation life.
According to a first aspect of the present invention, there is provided a lining wear measurement system, operating from a displacement sensor coupled to a moving element within a vehicle brake, the system having a microprocessor controller, a system memory adapted to hold internally in system memory a starting point and a target wear-out point representing a minimum acceptable brake lining thickness based upon the characteristics of known linings; characterised by: the brake has been equipped with a new unused set of linings; means that the brake has been equipped with a set of new unused linings, to generate and automatically set into the memory a new reference datum for wear measurements; and wear-out point, representing a minimum acceptable brake lining thickness, obtained by subtracting from said new reference datum the known thickness of new unused linings, thereby enabling the target wear-out point to take into account the reducing disc or drum thickness as the life of the brake progresses.
According to a second aspect of the
REFERENCES:
patent: 4937554 (1990-06-01), Herman
patent: 5339069 (1994-08-01), Penner et al.
Brearley Malcolm
Fawkes Paul Antony
McCann Dennis John
Ward Andrew John
Butler Douglas C.
Lee Tyrone M.
Lucas Industries Public Limited Company
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