Fujitsu Corporation

Akebono Brake Industry Co., Ltd.

Akira Hoashi

Hideo Akima

Isao Yamaki

Katsuya Miyake

Haruki Shimanuki

Yuji Matsubara

Naoyuki Hagiya

Takao Maki

Toshifumi Maehara

Hiroshi Ikegami

An anti-skid brake control system for a motor vehicle comprising: a wheel speed sensor which is disposed for each wheel of a vehicle and generates a pulse signal having a pulse cycle which corresponds to a revolution speed of each wheel; a pulse cycle measuring circuit for detecting the cycle of the pulses of the pulse signal from the wheel speed sensor; and, condition setting means for setting anti-skid brake control condition factors in accordance with the wheel speed. The anti-skid brake system is controlled in accordance with the condition factors set by the condition setting means.

Anti-skid brake control system

An anti-skid brake control system for a motor vehicle comprises: a wheel speed sensor which is provided for each wheel of the vehicle and generates a pulse signal having a pulse cycle which corresponds to a revolutional speed of each wheel; a pulse cycle measuring circuit for detecting the cycle of the pulses of the pulse signal from each wheel speed sensor; and, a discriminator for discriminating an actual acceleration or deceleration state. The actual acceleration or deceleration state is discriminated in accordance with whether or not the period of the acceleration or deceleration state is longer than a predetermined time. The acceleration or deceleration state is calculated from the wheel speed data detected by the pulse cycle measuring circuit, and the system is controlled on the basis of the result of the discrimination by the discriminator.

An anti-skid control system for a motor vehicle, includes a brake fluid pressure buildup-control mode and a brake fluid pressure reduction mode, each of which occur cyclically. In each buildup-control mode, a control valve is repetitively opened and closed so that brake fluid pressure buildup and holding operations are performed alternately. The time period of each buildup-control mode is from a high peak of a wheel speed signal until a point of intersection between a reference velocity V.sub.W0 and the wheel speed V.sub.W. The reference velocity V.sub.W0 has an initial point Q positioned under the high peak V.sub.HP of the wheel speed V.sub.W by a velocity value .DELTA.V and extending straight at a gradient .theta.. The speed value .DELTA.V, the gradient .theta., and an initial pressure buildup time T.sub.P, in each building-control mode, are determined in accordance with the wheel acceleration in the preceding wheel acceleration, i.e., coefficient of friction of the road surface.

Anti-skid control system for motor vehicle

An apparatus for measuring the wheel speed for an anti-skid control system of a motor vehicle, comprising a sensor for generating a pulse signal, the cycle of which corresponds to the rotational speed of the wheel. The wheel speed signal is provided in every control cycle having a constant time. If the wheel speed is not provided because the rotational speed of the wheel is low, the anti-skid control is performed in accordance with a compensated wheel speed calculated on the basis of the wheel speed measured immediately beforehand.

Apparatus for measuring wheel speed for anti-skid control system

In an anti-skid control system for motor vehicle, there is provided means adapted, when the motor vehicle is running on a rough road, to detect that the road on which the motor vehicle is now running is a rough one, thereby preventing reduction of brake hydraulic pressure from being started early.

Anti-skid control system for motor vehicles

An anti-skid control system for motor vehicles is provided wherein when the time period from when the wheel velocity being decreased reaches a second reference velocity to a low peak of the wheel velocity at which the reduction of the brake pressure is to be stopped, is longer than a predetermined time period, the reduction of the brake pressure is continued until the wheel velocity is increased up to a first reference velocity which is higher than the second reference velocity. In this way, even if the wheel velocity drops sharply because the coefficient of friction of the road surface suddenly changes from high to low, the wheel velocity recovers so that the wheels of the motor vehicle are prevented from locking early.

An anti-skid control system for motor vehicles is provided wherein a computed wheel speed Vv is set up on the basis of the highest one of the wheel speeds of the motor vehicle; a first reference speed VT1 and a second reference speed VT2 are set up which are lower than and follow the computed vehicle speed Vv either with a first and second predetermined speed difference respectively or with a first and a second predetermined ratio respectively, the first reference speed VT1 being higher than the second reference speed VT2 (VT1&gt;VT2); in the case where the wheel speed continues decreasing with a deceleration lower than a predetermined threshold level of deceleration, reduction of brake pressure is started at a point of time when a predetermined time period T1 elapsed from a point of time when the wheel speed reached the level of the second reference speed VT2; and the reduction of the brake pressure is stopped at a point of time when the wheel speed was increased up to the level of the first reference speed VT1 as a result of the reduction of the brake pressure.

An anti-skid control system for motor vehicles is provided wherein a computed vehicle speed is set up on the basis of respective wheel speeds of the motor vehicle; a reference speed which is lower than the computed vehicle speed by a predetermined amout and follows the computed vehicle speed with such a speed difference, is calculated on the basis of the computed vehicle speed; a high peak of the wheel speed is compared with the reference speed; when the high peak of the wheel speed is equal to or higher than the reference speed, the brake pressure is increased; and when the high peak of the wheel speed is lower than the reference speed, the brake pressure is reduced again.

An anti-skid control system for motor vehicles is disclosed wherein in case the wheel speed is equal to or lower than a minimum speed which is detectable by a microcomputer, the wheel speed is set at a predetermined threshold speed level between the minimum speed and zero, thereby preventing reduction of brake pressure from being started when the wheel is lower than the threshold speed. The anti-skid control system may also be designed such that a computed vehicle speed is set up which is approximate to the real vehicle speed; a reference speed is also set up on the basis of the computed vehicle speed in such a manner that it is lower by a predetermined amount than and follows the computed vehicle speed with such a speed difference; when the wheel speed becomes equal to or lower than a minimum speed which is detectable by a microcomputer, the wheel speed is set at a predetermined threshold speed level between the minimum speed and zero; and if a brake pressure reducing condition is prevailing at a point of time when the reference speed becomes equal to the threshold speed, then such a condition is released.

An anti-skid control system for a motor vehicle in which, when a wheel speed to be controlled and being decreased through buildup of brake pressure becomes equal to a reference speed, this equality is judged as a fulfillment of a brake pressure reduction starting condition, and thus reduction of the brake pressure is started. The highest wheel speed is detected and a computed vehicle speed is set up based on the highest wheel speed by having the increase and decrease of the highest wheel speed limited to a predetermined range. The computed vehicle speed and the wheel speed to be controlled are compared; and when the comparison indicates that the wheel speed to be controlled is equal to or higher than the computed vehicle speed, no reduction of the brake pressure is started irrespective of whether the brake pressure reduction starting condition is fulfilled.

In an anti-skid control system for a motor vehicle, brake fluid pressure reduction-control mode and brake fluid pressure buildup-control mode occurs cyclically; in the reduction-control mode, reduction of the brake fluid pressure is started on the basis of detection of an abrupt drop in wheel speed which occurs when the wheel is braked; and in buildup-control mode, a valve is repetitively opened and closed so that brake fluid pressure buildup and holding operations are performed alternatley and repetitively, whereby the brake fluid pressure is caused to build up gradually. The length of time period for the first buildup operation in the buildup-control mode is determined on the basis of variation in the wheel speed occurring between a low peak point and a high peak point; and the length of time period for at least one of each pressure holding operation and each of the second and succeeding pressure buildup operations in the abovementioned buildup-control mode, is determined on the basis of variation in the wheel speed occurring immediately before the pressure holding or buildup operation is started.

An anti-skid control system for motor vehicles is provided wherein the higher one of the lefthand and righthand rear wheels is selected as a first computed speed; the lower one of the above two wheel speeds is selected as a second computed speed; the lower one of the first computed speed and lefthand front wheel speed is selected as a third computed speed; the lower one of the first computed speed and righthand front wheel speed is selected as a fourth computed speed; and a reference speed is set up on the basis of the first computed speed in such a manner that it is lower than the first computed speed by a predetermined amount and follows the first computed speed with such a speed difference. Reduction of brake pressure which has been increased, is started on the basis of the third or fourth computed speed; and in the case where the second computed speed being decelerated, goes below the reference speed, the reduction of the brake hydraulic pressure is stopped at time when the second computed speed which is now being increased as the result of the brake pressure reduction goes above the reference speed, and thereupon buildup of the brake pressure is started.

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Kawasaki, Japan

Akira Hoashi