Fluid-pressure and analogous brake systems – Speed-controlled – Braking pressure demand or braking force desire
Reexamination Certificate
1998-12-28
2001-01-30
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Braking pressure demand or braking force desire
C303S113400
Reexamination Certificate
active
06179396
ABSTRACT:
This application corresponds to and claims priority under 35 U.S.C. §119 with respect to Japanese Application No. 09(1997)-356973 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 which a pump for anti-skid control or traction control is also used for boosting the braking force to reduce the role of the vacuum booster. This system includes a wheel cylinder, a master cylinder, a main line connecting the master cylinder to the wheel cylinder, a first valve to open and close the main line, a pump having an inlet port and an outlet port to supply pressurized brake fluid to a point between the first line and the wheel cylinder, an auxiliary line connecting the inlet port of the pump to the master cylinder, and a second valve to open and close the auxiliary line.
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 proper control when the output pressure and 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 on and off the pressure pump. However, in this known system, the proper pressure increase rate may not be obtained in accordance with the driver's brake pedal operation when the electric motor keeps turning on.
It may be possible to obtain the proper pressure increase rate by turning on and off the electric motor. However, the pump may not discharge a sufficient amount of brake fluid from the reservoir because the pressure in the reservoir is less than the pressure in the master cylinder under anti-skid control. Accordingly, due to less discharge by the pump, the reservoir may be full so that anti-skid control may not be properly performed.
In light of the foregoing, a need exists for a brake control apparatus that is not susceptible to the foregoing drawbacks and disadvantages.
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 increase the brake pressure in a wheel cylinder immediately after initiation of brake assist control.
It would be further desirable to provide a brake control apparatus that is able to control the brake pressure in a wheel cylinder according to a driver's brake operation.
SUMMARY OF THE INVENTION
The present invention provides a brake control apparatus that includes a wheel cylinder for applying a brake force to a wheel, a master cylinder which generates pressurized brake fluid according to the operation of a brake pedal, a main hydraulic line to connect the master cylinder to the wheel cylinder, a first valve that opens and closes the main line, and a pump having an inlet port and an outlet port for supplying pressurized brake fluid to a point between the main line and the wheel cylinder. An auxiliary line connects the inlet port of the pump to the master cylinder, and a second valve opens and closes the auxiliary line. A brake operation sensor detects the operation of the brake pedal and an initiation judging device determines the necessity of a brake assist control based on the detection by the brake operation sensor. A controller controls the first valve, the second valve and the pump to perform brake assist control after the determination by the initiation judging device. The controller includes a duty control device which controls the second valve with a determined duty ratio based on the detection by the brake operation sensor.
According to the present invention, the duty ratio is determined based on the detection by the brake operation sensor when the brake assist control is judged to be necessary. The controller immediately drives the second valve with the determined duty ratio so that the pressure is promptly increased in the wheel cylinder in accordance with the driver's operation of the brake pedal.
REFERENCES:
patent: 5188437 (1993-02-01), Willmann
patent: 5570935 (1996-11-01), Monzaki
patent: 5607209 (1997-03-01), Narita et al.
patent: 5727852 (1998-03-01), Pueschel et al.
patent: 6019438 (2000-02-01), Sawada et al.
patent: 195 01 760 (1996-07-01), None
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patent: 2 297 134 (1996-07-01), None
patent: 2 326 452 (1998-12-01), None
patent: 5-116609 (1993-05-01), None
patent: 7-329766 (1995-12-01), None
patent: 8-230634 (1996-09-01), None
patent: 9-254773 (1997-09-01), None
Fukami Masanobu
Itoh Takayuki
Tozu Kenji
Yokoyama Satoshi
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Graham Matthew C.
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