Fluid-pressure and analogous brake systems – Speed-controlled – Wheel speed sensor and braking pressure sensor
Reexamination Certificate
1998-12-28
2001-03-06
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Wheel speed sensor and braking pressure sensor
C303S116200, C303S155000
Reexamination Certificate
active
06196643
ABSTRACT:
This application corresponds to and claims priority under 35 U.S.C. §119 with respect to Japanese Application No. 09(1997)-356974 filed on Dec. 25, 1997, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to a brake control apparatus. More particularly, the present invention pertains to a brake control apparatus that increases or boosts the braking force when the driver applies a rapid or deep depressing force to the brake pedal.
BACKGROUND OF THE INVENTION
Under emergency situations, a driver may rapidly depress a brake pedal. However, the driver may not depress the brake pedal sufficiently or the driver may not maintain a sufficient force for a necessary period of time. Thus, to improve vehicle safety, some automatic brake assisting systems have been introduced in the market. Such known brake assisting systems employ a vacuum booster to automatically boost the braking force when the driver depresses the brake pedal rapidly.
Japanese Laid-Open Patent Publication No. H08-230634 published on Sep. 10, 1996, which corresponds to U.S. Pat. No. 5,727,852, discloses a brake assisting system. In the brake system described in this publication, a pump for anti-skid control or traction control is also used for boosting braking force in order to reduce the role of the vacuum booster. The system includes a wheel cylinder, a master cylinder, a main line connecting the master cylinder to the wheel cylinder, a modulator disposed in the main line to control pressure in the wheel cylinder, a reservoir connected to the wheel cylinder through the modulator, a first valve that opens and closes the main line between the master cylinder and the modulator, a pump connected between the reservoir and the wheel cylinder to supply pressurized brake fluid from the reservoir to the wheel cylinder, an auxiliary line connecting the inlet side of the pump to the master cylinder, and a second valve that opens and closes the auxiliary line.
Further, this known system also includes a pressure sensor to detect the output pressure from the master cylinder. The pump, the first valve and the second valve perform brake assistance under a proper control while the output pressure and/or the pressure increase ratio exceeds the predetermined value. To increase the pressure, the first valve is opened and the second valve is closed. Then, the pressure increase rate is controlled by turning the pressure pump on and off.
However, this system may suffer from disadvantages and drawbacks related to the performance of anti-skid control because the second valve is opened to increase the brake pressure.
During the brake assist control, the output pressure from the master cylinder is larger than the pressure stored in the reservoir because the driver has strongly depressed the brake pedal. Accordingly, the pump may discharge a lesser amount of brake fluid from the reservoir while the second valve is closed. Therefore, the reservoir may become full during a pressure decreasing period of the anti-skid control because the pump may not discharge all the brake fluid flowing into the reservoir.
In light of the foregoing, a need exists for a brake control apparatus that is not susceptible to the same disadvantages and drawbacks as those discussed above.
It would thus be desirable to provide a brake control apparatus that is able to simultaneously perform brake assist control and anti-skid control.
It would also be desirable to provide a brake control apparatus that is able to discharge brake fluid from a reservoir during anti-skid control.
SUMMARY OF THE INVENTION
The present invention provides a brake control apparatus that includes a wheel cylinder to apply brake for a wheel a master cylinder to generate pressurized brake fluid in accordance with the operation of a brake pedal, a main line connecting the master cylinder to the wheel cylinder, a modulator disposed in the main line to control pressure in the wheel cylinder, a reservoir connected to the wheel cylinder through the modulator, a first valve to open and close the main line between the master cylinder and the modulator, a pump connected between the reservoir and the wheel cylinder to supply pressurized brake fluid from the reservoir to the wheel cylinder, and an auxiliary line connecting the inlet side of the pump to the master cylinder. A second valve opens and closes the auxiliary line, and a pressure sensor detects the output pressure of the master cylinder. A controller controls the first valve, the second valve and the pump based upon the pressure detected by the pressure sensor so that the wheel cylinder receives a higher pressure than that of the master cylinder. Further, the controller closes the second valve when the pressure sensor detects the pressure over a certain pressure determined by the road surface condition.
The pressure sensor may be replaced by a deceleration sensor to detect the deceleration of the vehicle body, a brake force sensor or a slip rate sensor to detect the slip rate between the wheel and the road surface. Further, the certain pressure may be assumed from the deceleration of the vehicle body, the brake force or the slip rate.
According to the present invention, the controller closes the second valve while the pressure sensor detects the pressure over a certain pressure determined by the road surface condition. Therefore, brake fluid can be discharged from the reservoir while the brake assistance control and the anti-skid control are simultaneously performed.
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Fukami Masanobu
Itoh Takayuki
Tozu Kenji
Yokoyama Satoshi
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Graham Matthew C.
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