Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1994-01-12
1995-05-30
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 96, 303102, 303110, 180197, B60T 832, B60T 800, B60K 2816
Patent
active
054196221
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A drive-slip control system is known, for example, from WO 87/02948.
SUMMARY OF THE INVENTION
With the invention, the braking pressure supplied to the individual brakes, and hence the braking moment, is determined with close approximation in a simple and inexpensive manner. The present differential blocking effect is known from a comparison of the pulse differences of the two driven wheels. This information can be taken into consideration, for example, in a likewise existing engine moment controller, and this controller can thus be designed more adaptively. A correlation is possible between the driving moment and the braking moment.
The built-up locking moment between the driving wheels may be determined and influenced. The driving situation may be assessed from the known pressure level (locking moment).
In the invention, pressure buildup and reduction times are determined for the successive pulses leading to desired changes in pressure in the wheel cylinders, taking into consideration the pressure volume characteristic and other marginal conditions. These successively occurring changes in pressure may be selected (determined) arbitrarily, but they may also be selected to be of the same magnitude. Preferable a count of a forward-backward counter is set for each of the pressure stages and is allocated pulse times for pressure buildup and reduction. These times are preferably determined in tests.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention is described with reference to the drawing in which:
FIG. 1 illustrates a block circuit diagram of a drive slip control system according to the invention.
FIG. 2 is a table showing the times for pressure buildup and reduction pulses in relation to the position of the counter.
DESCRIPTION OF A PREFERRED EMBODIMENT
FIG. 1 shows a block circuit diagram of a drive slip control system having velocity sensors 1 to 4 associated with the driven wheels and the nondriven wheels. From the sensor signals, an electronic control device 5 obtains control signals in a known manner for the driven wheels that indicate whether a tendency to spin exists (standard deviation BRA>0). If this is the case, pulses are emitted from the control device by way of the upper lines 14; during the pulse time, these pulses set valves 6 and 7, respectively, in the position in which pressure from the pressure source line, pump 10 is applied to the brakes 8 and 9, respectively. If the control signal then disappears (BRA<0), then pressure reduction pulses are fed by way of the lower lines 15 to valves 6 and 7, which connect the brake cylinders to return lines 11 and 11, respectively, which are only partially indicated here.
The inputs of a forward-backward counter 12 are connected to the lines 14, 15 to valve 7 (the input lines for valve 6 are not shown). At the beginning of a regulating process, the counter is always in an initial position, for example position 15 (FIG. 2). A pulse time T.sub.1 for a pressure buildup pulse and a different time T.sub.1, for a pressure reduction pulse are allocated to this position in the control device. The occurrence of the control signal (BRA>0) activates the first pulse with time T.sub.1, thus building up pressure. The end of the pulse moves the counter 12 on by one position into position 14. This position is also allocated pulses with durations T.sub.2 and T.sub.2 '; the durations are determined in such a way that an identical change in pressure of, for example, 10 bar takes place with each pulse (whether buildup or reduction). The pressure buildup pulses are fed to valve 7 until the control signal disappears (BRA<0), for instance when counter position 10 is reached. Now a pressure reduction pulse is activated, with the pressure reduction pulse duration associated with position 10, the counter is brought into position 11, and further reduction pulses follow until the control signal (BRA>0) reappears, or the end of the regulation process is recognized.
FIG. 2 shows a table whose middle line gives the p
REFERENCES:
patent: 4950037 (1990-08-01), Kopper et al.
patent: 5058699 (1991-10-01), Fennel et al.
patent: 5131730 (1992-07-01), Kollers et al.
Burg Andreas
Isella Thomas
Schmitt Johannes
Butler Douglas C.
Robert & Bosch GmbH
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