Boots – shoes – and leggings
Patent
1990-09-05
1992-09-22
Lall, Parshotam S.
Boots, shoes, and leggings
303103, 303110, B60T 858
Patent
active
051502992
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
This invention relates to a wheel speed control device in an antilock brake system for preventing the wheels of a vehicle such as an automobile from locking while braking.
BACKGROUND ART
In a prior art antilock brake system, any excessive slip of wheels is detected by comparing the slip speed of each wheel, or a control variable calculated from its differentiated value, with a predetermined threshold value, the wheel speeds are controlled by increasing or reducing the brake pressure based on the result of the comparison, and the brake pressure on any wheel which has recovered from the locking state is increased at a fixed rate irrespective of the behavior of the wheel.
In order to detect a locking tendency of a wheel, it is an effective measure to carry out antilock control by comparing the slip speed, of each wheel or a control variable based on its differentiated value, with a predetermined threshold value as with the aforementioned prior art antilock brake system. But it is difficult to detect an excessively low slip speed resulting from an insufficient braking force when the wheels have recovered from the locking state and the wheel speeds have become substantially equal to the vehicle speed. Namely, during antilock control while the vehicle is moving, the vehicle deceleration is liable to drop below a predetermined value. This not only causes vibrations and pitching of the vehicle body but also leads to an extension of the braking distance.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, there is provided a wheel speed control device comprising a wheel speed calculating means for calculating the speed Vw of each wheel based on the output Vi (i =1 .... 4) of a wheel speed sensor of each wheel, a vehicle speed calculating means for calculating the vehicle speed Vv, a wheel speed differentiating means for producing a differentiated output Vd of the output Vw of the wheel speed calculating means, a slip speed calculating means for calculating the slip speed Si of each wheel from the output Vw of the wheel speed calculating means and the output Vv of the vehicle speed calculating means, and a brake pressure controller for calculating a control variable from the output Vd of the wheel speed differentiating means and the output Si of the slip speed calculating means and outputting, based on the results of the calculation, a pressure increase, pressure hold or pressure reduction command to a brake pressure control actuator to control the brake pressure on each wheel. The improvement of the invention includes a second brake pressure controller for integrally calculating any excess or shortage of the slip speed after recovering from locking state, based on the output Si of the wheel slip speed calculating means while the control variable calculated by the brake pressure controller satisfies predetermined conditions, and outputting a command to carry out a minor pressure increase having a small rate of pressure increase to the brake pressure control actuator.
With the wheel speed control device of this invention having the above-described structure, by the provision of an integration type brake pressure controller in addition to a conventional main brake pressure controller actuated based mainly on differentiation type judgements, it becomes possible to detect any excessively low slip speed resulting from an insufficient braking force while the wheels are recovering from a locking state during braking, which could not be detected with a differentiation type main brake pressure controller, and to carry out minor pressure increases in which the brake pressure is increased at a low rate. This permits more precise and more effective control of the wheel speeds.
Namely, the integration type brake pressure controller used in the wheel speed control device according to this invention functions as a timer and a counter. It checks at every control cycle .DELTA.t over a predetermined period .DELTA.T whether or not the wheel brake pressure is lower than a suitable level by comparin
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Auchteronie Thomas S.
Lall Parshotam S.
Sumitomo Electric Industries Ltd.
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