Boots – shoes – and leggings
Patent
1989-03-30
1991-01-15
Chin, Gary
Boots, shoes, and leggings
303103, B60T 832
Patent
active
049858394
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an antilock braking system for a motor vehicle brake system having a wheel speed sensor and an electronic evaluation circuit which generates brake pressure control signals. The evaluation circuit includes a timing device that produces an increase of the brake pressure, for a time duration, with a large gradient, relative to the gradient over the entire time duration, and then with a smaller gradient. The time duration is a function of the length of the directly preceding pressure reduction.
An antilock braking system of this type is known from published German patent application OS No. 23 07 368, to which U.S. Pat. No. 3,888,550 corresponds. In this known system a deceleration signal which reduces the brake pressure is supplied to a timing element. When this deceleration signal is of greater length than the time constant of the timing element, a timing element with a long time constant is made effective in fixing the duration of the first pressure-buildup pulse, which then determines the length of the pressure buildup. If the pressure reduction was shorter than the first-mentioned time constant, a timing element with a shorter time constant becomes controlling in fixing the duration of the pressure-buildup pulse. Thus the duration of the pressure-buildup pulse is made a function of the duration of the preceding pressure reduction.
From published German patent application OS No. 24 60 904 to which U.S. Pat. No. 4,054,328 corresponds, it is further known to make the determination of the duration of the first pressure-buildup pulse, which produces a pressure buildup with a large gradient, a function of the duration of the pressure rise in the preceding control cycle rather than of the preceding pressure reduction. For example, when the pressure buildup with the small gradient is produced through several pulses, the sum of the pulses required is determined and allowance is made for that sum in fixing the duration of the first pressure buildup in the next control cycle.
SUMMARY OF THE INVENTION
The determination of the duration of the first pressure-buildup pulse, i.e., the duration of the pressure buildup with a large gradient according to the invention, makes better allowance for the different characteristic curves for pressure buildup and pressure reduction and thus arrives at a more nearly optimal duration for the pressure buildup which brings the brake pressure instantly into the vicinity of the lockup pressure.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention and to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the electronic control portion of an antilock braking system according to the preferred embodiment of the present invention.
FIG. 2 is a block diagram of an evaluation circuit which may be used in the control system of FIG. 1.
FIG. 3a is a typical brake pressure curve obtainable with an antilock braking system known in the art.
FIG. 3b is a typical brake pressure curve which is obtainable with the antilock braking system according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1, sensors 1 and 2 are associated with two wheels of the vehicle and deliver signals corresponding to the wheel speed to an evaluation circuit 3. The latter generates therefrom brake-pressure signals for actuation of a pressure inlet valve 4 and an outlet valve 5 to control the hydraulic brake pressure for one wheel. For the sake of simplicity, the corresponding valves for the other wheel are not shown in FIG. 1.
The evaluation circuit 3 includes two integrators 3a and 3b, two memories 3c and 3d, and a computing circuit 3e. Corresponding components (not shown) are provided for the second valve combination, which is also not shown. The integrator 3a connected to the actuating line for the pressure inlet valve 4 determines, during the pressure-buildup phase, the sum of the pr
REFERENCES:
patent: 4320460 (1982-03-01), Brearley et al.
patent: 4485445 (1984-11-01), Braschel
patent: 4788644 (1988-11-01), Inagaki
patent: 4859002 (1989-08-01), Yoshino
Chin Gary
Robert & Bosch GmbH
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