Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1991-07-30
1993-11-30
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303DIG4, B60T 800
Patent
active
052659470
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a circuit configuration for a brake system having an anti-locking control for controlling the pressure build-up upon commencement of the control by generating pulse-type control signals capable to control multi-way valves that are inserted into pressure-fluid conduits leading to the wheel brakes, with the pressure, by dimensioning the pulse and pulse break times, being applicable first at a steep and then at a flatter gradient, and with the pressure build-up, in the first cycle after commencement of the control, being dependent on the preceding pressure drop and, in the other cycles, on the pressure increase in the preceding cycles.
A circuit configuration of the afore-described type has already been taught by DE-Patent 24 60 904 according to which the brake pressure, basically, during anti-locking control, first, is reincreased at a steep and, subsequently, at a flatter gradient. The steep pressure increase, preferably, is attained by an extended pulse while the flatter increase is attained by a short pulse which two pulses succeed one another at a relatively large interval, with the duration of the steep-gradient pressure rise being varied in response to the pressure build-up in the preceding control cycle(s). For dimensioning the steep phase of the first control cycle in respect of which there is no precedingly controlled pressure build-up, the level and duration, respectively, of the preceding brake pressure decrease will be taken into account.
According to European Patent Application No. 177 817, equally concerned with the pressure reincrease first at a steep and subsequently at a flatter gradient, it is known to render dependent the pressure level of the first pressure build-up pulse determining the phase of the steep pressure rise, in addition, on a quotient resulting from the maximum wheel acceleration divided by the sum of the amounts of maximum wheel acceleration and maximum wheel deceleration. In one example, the pressure level of the first pressure build-up pulse corresponds to the preceding pressure decrease multiplied by the above-mentioned quotient and a factor approximately "1".
SUMMARY OF THE INVENTION
A brake pressure control according to the foregoing will not, in all cases, bring about satisfactory results. It is, therefore, an object of the present invention to adjust, for attaining an improved control, the brake pressure rebuild-up even more precisely to the respective situation and the respective conditions to insure, on the one hand, a continued driving stability and, on the other hand, a short stopping distance through attaining, at an early stage, the anti-locking pressure level during the individual control cycles.
It has been found that this problem can be solved by a circuit configuration of the type described above, the special feature of which resides in that circuits are provided rendering dependent the pulse and pulse break times determining the pressure build-up, in the cycles following the first cycle, on the duration of the pressure build-up or the number of the pressure build-up pulses during the steep-gradient pressure build-up in the preceding cycle, on the duration of the entire pressure build-up phase of the preceding cycle and on the duration of the preceding pressure decrease, with the pulse times and especially the duration of the pressure increase in the steep-gradient phase being so dimensioned that at an approximately constant friction value and friction coefficient, respectively, and at an approximately constant static pressure, the locking limit of the wheel is rereached after a predetermined period of time and a predetermined number of pulses.
Static pressure in this context means the brake pressure in the master cylinder dependent on the level of force applied by the driver to the brake pedal.
If the constant frictional coefficient requirement is not complied with, the locking limit is rereached sooner or only after a major number of "fixed" pulses, i.e. short pulses succeeding one another at
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patent: 4923255 (1990-05-01), Braschel et al.
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patent: 4938544 (1990-07-01), Braschel et al.
patent: 4985839 (1991-01-01), Dominke
patent: 5033799 (1991-07-01), Braschel
Batistic Ivica
Buschmann Gunther
Ehmer Norbert
Fennel Helmut
Schmidt Robert
Ballato Josie A.
Lewis J. Gordon
Oberleitner Robert J.
Seitter Robert P.
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