Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1988-09-26
1990-05-29
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
188181C, 303 97, 303106, 36442602, B60T 858, B60T 860, B60T 832
Patent
active
049290347
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an anti-locking brake control system of the type having wheel velocity pickups, which provide signals to an evaluation circuit, which provides signals to brake pressure control valves. The evaluation circuit controls relief of pressure on the basis of wheel retardations and accelerations occurring in rapid succession.
When driving over rough roads a constant alternation takes place between the loading and unloading of the wheels. When the brakes are applied, therefore, a rapid succession of strong retardations and accelerations of the wheel circumference are produced. The electronic anti-locking brake control system therefore produces a frequent relieving of the brake pressure. This results in an underbraking of the vehicle.
To avoid this disadvantage it is known to suppress the relief of the brake pressure on a wheel for a period of time at the end of the reacceleration of this wheel.
It is furthermore known to trigger a rapid pressure increase in the event of great accelerations of the wheel circumference, which is intended to compensate for the previous pressure relief.
A sufficient increase in the brake pressure during the period when the wheel is reaccelerating is not possible in most cases, since, even on smooth roadways, strong accelerations occur which, in the event of rapid pressure rises such as would be necessary on rough road surfaces, can lead to unwanted disturbances caused by resonance.
Furthermore, it is known to determine the maximum wheel acceleration in the reacceleration phase of the wheel and increase the pressure relief threshold according to the magnitude of this acceleration, as disclosed in GB-A No. 2151732, to which U.S. Pat. No. 4,701,855 to Fennel corresponds.
SUMMARY OF THE INVENTION
The evaluation circuit of the present invention includes a summing circuit which provides a sum indicative of an instability threshold based on wheel retardation and/or slippage at which braking pressure is relieved. More particularly, the invention relates to increasing the instability threshold when the brakes are frequently applied. This is accomplished by reducing the sum in accordance with the given function, and increasing it by a numerical value whenever a wheel acceleration of a given magnitude occurs after an instability threshold is reached. The instability threshold at any time is determined by the magnitude of the sum at that time.
For example, after an instability is recognized, such as one caused by pressure retention or reduction, if a decided reacceleration of a wheel takes place, a down counter is increased by a certain amount. In particular, this counter can be common to several or all wheels of a vehicle and can be increased by all wheels which are affected by this counter. The counter continually counts down according to a given function. In the simplest case the countdown is linear. The countdown can also be blocked under certain conditions.
It is also possible to provide a separate counter for each wheel. However, then the complexity increases and effectiveness suffers.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1a is a plot of wheel velocities versus time during braking on a rough road (period 1) and a smooth road (period 2).
FIG. 1b is a plot of the counter value versus time for the conditions of FIGS. 1a.
FIG. 1c is a plot of brake pressure versus time for the conditions of FIG. 1a.
FIG. 2 is part of the evaluation circuit of an anti-locking control represented in FIG. 3.
FIG. 3 is an anti-locking control arrangement.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The count provided by the counter indicates the amount of the increase in the criteria controlling the detection of instability, i.e., by how much the detection thresholds are raised. FIGS. 1a to 1c show an embodiment in which two wheels, 1 and 2, increase the counter. In these figures the counter changes during braking on a rough road (period 1) and then during braking on a smooth road (period 2). By considering the state of the counter in determining in
REFERENCES:
patent: 4113322 (1978-09-01), Ruhnau et al.
patent: 4230376 (1980-10-01), Brearley et al.
patent: 4260200 (1981-04-01), Brearley et al.
patent: 4320459 (1982-03-01), Lindemann et al.
patent: 4485445 (1984-11-01), Braschel
patent: 4585280 (1986-04-01), Leiber
patent: 4660896 (1987-04-01), Matsuda
patent: 4666218 (1987-05-01), Masaki et al.
patent: 4672547 (1987-06-01), Masaki et al.
patent: 4701855 (1987-10-01), Fennel
patent: 4717209 (1988-01-01), Hagiya et al.
patent: 4739484 (1988-04-01), Fennel
patent: 4769758 (1988-09-01), Masaki et al.
patent: 4797825 (1989-01-01), Shimanuki et al.
patent: 4807133 (1989-02-01), Shimanuki et al.
Braschel Volker
Seitz Dieter
Butler Douglas C.
Robert & Bosch GmbH
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