Fluid-pressure and analogous brake systems – Speed-controlled – Wheel generated pulse signal control
Reexamination Certificate
1998-11-25
2001-03-27
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Wheel generated pulse signal control
C303S011000, C303S009620, C303S113500
Reexamination Certificate
active
06206490
ABSTRACT:
This application claims priority under 35 U.S.C. Sec. 119 to No.9-342069 filed in Japan on Nov. 26, 1997, the entire content of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake control system for a vehicle with a dual hydraulic pressure circuit system, wherein the braking force is applied appropriately to wheels in each hydraulic pressure circuit, when a brake pedal is depressed.
2. Description of the Related Arts
Recently, instead of a proportioning valve, it is proposed to employ electromagnetic valves for a braking force distribution control. For example, a Japanese Patent Laid-open Publication No.6-144179 discloses that a rear standard wheel speed is adjusted to be equal to or greater than a front standard wheel speed by actuating pressure control valves (inlet valve and outlet valve) connected to rear wheel brake cylinders to control the braking force applied to the rear wheels, so that a front and rear braking force distribution is approximated to an ideal front and rear braking force distribution. According to the publication, the braking force applied to the rear wheels is controlled such that the rear standard wheel speed is adjusted to be equal to or greater than the front standard wheel speed. In other words, the rear standard wheel speed is controlled not to be smaller than the front standard wheel speed. Therefore, if the braking force applied to the front wheels were reduced due to fade or the like in the front braking system, a decreasing rate of the front wheel speed would be reduced, so that the braking force to the rear wheels might be reduced excessively. As a result, the vehicle speed may not be decreased appropriately.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a brake control system for a vehicle with a dual hydraulic pressure circuit system, wherein the wheel speed is reduced appropriately even in the case where a slip rate of at least one of the front wheels of the vehicle is smaller than the slip rate of a wheel belonging to a different hydraulic pressure circuit from the hydraulic pressure circuit to which the one of the front wheels belongs.
In accomplish the above and other objects, a brake control system for a vehicle includes wheel brake cylinders operatively mounted on front and rear wheels of the vehicle, respectively, a master cylinder for pressurizing brake fluid to supply braking pressure to the wheel brake cylinders in response to depression of a brake pedal, a pair of main passages for communicating the master cylinder with the wheel brake cylinders to provide a dual hydraulic pressure circuit system. An auxiliary pressure source is provided for pressurizing the brake fluid to supply the hydraulic braking pressure to the main passages. Wheel speed sensors are provided for detecting wheel speeds of the wheels, and a slip rate calculation device is provided for calculating slip rates of the wheels on the basis of the wheel speeds detected by the wheel speed sensors. And, a controller is adapted to apply the hydraulic braking pressure discharged from the auxiliary pressure source to one of the wheel brake cylinders operatively mounted on at least one of the front wheels, in the case where the slip rate of the at least one of the front wheels is smaller than the slip rate of at least one of the wheels belonging to a different hydraulic pressure circuit from the hydraulic pressure circuit to which the at least one of the front wheels belongs, at least when the brake pedal is being operated.
Therefore, in the case where a difference is caused between the slip rates of the front wheels in a diagonal hydraulic pressure circuit system for example, the hydraulic braking pressure discharged from a master cylinder in response to depression of a brake pedal is supplied to the wheel brake cylinder operatively mounted on one of the front wheels having the larger slip rate, whereas the hydraulic braking pressure discharged from the auxiliary pressure source is added to the master cylinder pressure, with respect to the front wheel having the smaller slip rate.
Preferably, the controller is adapted to equalize the hydraulic braking pressure in the wheel brake cylinders operatively mounted on the rear wheels, on the basis of one of the rear wheels having a larger slip rate than the other one of the rear wheels.
In order to equalize the hydraulic braking pressure in the wheel brake cylinders operatively mounted on the rear wheels, on the basis of one of the rear wheels having a larger slip rate than the other wheel, the brake control system may further include a modulator which is disposed between the master cylinder and the wheel brake cylinders in each of the hydraulic pressure circuits for modulating the hydraulic braking pressure in each of the wheel brake cylinders in accordance with a pressure mode selected from at least a pressure increase mode and a pressure decrease mode.
REFERENCES:
patent: 5893896 (1999-04-01), Imamura et al.
patent: 5988774 (1999-11-01), Jonner et al.
patent: 6056372 (2000-05-01), Kamei et al.
patent: 4128087 (1993-02-01), None
patent: 19853651 (1999-06-01), None
patent: 6-144179 (1994-05-01), None
patent: 8-230634 (1996-09-01), None
Fukami Masanobu
Itoh Takayuki
Tozu Kenji
Yokoyama Satoshi
Aisin Shiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Kramer Devon
Oberleitner Robert J.
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