Motor vehicles – Power – Electric
Reexamination Certificate
1998-07-29
2001-04-17
Johnson, Brian L. (Department: 3618)
Motor vehicles
Power
Electric
C180S002100, C180S165000, C180S170000, C701S078000, C303S152000
Reexamination Certificate
active
06216808
ABSTRACT:
This application claims priority under 35 U.S.C. 119 to No. 9-220124 filed in Japan on Jul. 30, 1997 and No. 9-270530 filed in Japan on Sep. 17, 1997, the entire contents of which are herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brake control system for an electrically operated vehicle to perform a regenerative braking operation and a hydraulic braking operation, and more particularly to the brake control system which is adapted to reduce a regenerative braking torque and add a hydraulic braking force to compensate for lack of the regenerative braking torque, when voltage of a battery exceeds a predetermined upper limit, thereby to protect the battery.
2. Description of the Related Arts
In an electrically operated vehicle provided with an electric motor as a power source, the electric motor also functions as a generator for performing the regenerative braking operation to recover energy by charging a battery and use the energy for driving the motor. Since the braking force applied to the vehicle wheels through the regenerative braking operation is limited, it must be compensated by a hydraulic braking operation. Therefore, both of the regenerative braking operation and the hydraulic braking operation are performed, as disclosed in Japanese Patent Laid-open Publication No.5-161210. According to the prior brake control system for the electrically operated vehicle as disclosed in the Publication No.5-161210, when the voltage of the battery increases to exceed a predetermined threshold level, the regenerative braking torque is reduced so as to protect the battery, whereby the braking force through the regenerative braking operation is reduced. However, when the control for reducing the regenerative braking torque is initiated, if the regenerative braking torque is reduced rapidly, the compensation through the hydraulic braking operation will be delayed, so that deceleration of the vehicle may be reduced temporarily. As a result, feelings to a vehicle driver in his braking operation will be varied.
Also, according to the prior brake control system as disclosed in the Japanese Patent Laid-open Publication No. 5-161210, the regenerative braking torque is reduced temporarily, so that if the voltage of the battery decreases to enable the regenerative braking operation, it will be restarted. In this case, there remains the braking force such as the hydraulic braking force which compensated for the lack of the braking force when the regenerative braking torque was reduced. Therefore, the deceleration of the vehicle will be increased by the restarted regenerative braking operation. In other words, additional braking force will be applied against the vehicle driver's intention. As a result, feelings to the vehicle driver in his braking operation will be deteriorated.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a brake control system for an electrically operated vehicle which is adapted to provide a rapid compensation by a hydraulic braking control when a control for reducing a regenerative braking torque is initiated, to ensure a proper brake feeling.
And, it is another object of the present invention to provide a brake control system for an electrically operated vehicle which is adapted to provide a smooth braking operation until the vehicle stops, even if voltage of a battery exceeds a predetermined upper limit, to ensure a proper brake feeling.
In accomplishing the above and other objects, a brake control system is provided for controlling a braking force applied to a wheel of an electrically operated vehicle. The brake control system includes an electric motor which is operatively connected to a wheel for rotating the wheel. A battery is mounted on the vehicle and electrically connected to the electric motor for driving the electric motor. A motor control unit is provided for controlling the electric motor to apply a rotating force to the wheel and apply a regenerative braking torque to the wheel. A wheel brake cylinder is operatively mounted on the wheel for applying a hydraulic braking force to the wheel. A pressure control device is provided for supplying pressurized brake fluid to the wheel brake cylinder in response to operation of a manually operated braking member to apply a hydraulic braking force to the wheel, and controlling the pressure in the wheel brake cylinder. A voltage detector is provided for detecting voltage of the battery. A reducing device is provided for reducing the regenerative braking torque when the voltage of the battery detected by the detector exceeds a predetermined upper limit. And, a compensation device is provided for actuating the pressure control device to supply the pressurized brake fluid to the wheel brake cylinder when the regenerative braking torque reduced by the reducing device exceeds a predetermined level.
In the brake control system as described above, the compensation device may be adapted to actuate the pressure control device to supply the pressurized brake fluid to the wheel brake cylinder, when a rate for reducing the regenerative braking torque by the reducing device exceeds a predetermined rate. Or, the compensation device may be adapted to actuate the pressure control device to supply the pressurized brake fluid to the wheel brake cylinder, when an amount of the regenerative braking torque reduced by the reducing device exceeds a predetermined amount.
The brake control system may further comprise a holding device for holding the reducing device in a condition for reducing the regenerative braking torque, when the amount reduced by the reducing device in a predetermined period is in transition from an increase to a decrease, and the pressure control device may continue to apply the hydraulic braking force to the wheel after the transition of the increase to the decrease of the reduced amount, until the vehicle stops.
Preferably, the pressure control device comprises a static pressure generator for pressurizing the brake fluid stored in a reservoir in response to operation of the manually operated braking member to generate a static hydraulic pressure, an auxiliary power source for pressurizing the brake fluid stored in the reservoir irrespective of operation of the manually operated braking member to generate a power pressure, and a dynamic pressure generator for regulating the power pressure in response to operation of the manually operated braking member to generate a dynamic hydraulic pressure.
REFERENCES:
patent: 3972380 (1976-08-01), Hudson et al.
patent: 4181366 (1980-01-01), Dobner
patent: 5318355 (1994-06-01), Asanuma et al.
patent: 5399000 (1995-03-01), Aoki et al.
patent: 5433512 (1995-07-01), Aoki et al.
patent: 5714856 (1998-02-01), Young
patent: 5839533 (1998-11-01), Mikami et al.
patent: 5839800 (2000-11-01), Koga et al.
patent: 5941328 (1999-08-01), Lyons et al.
patent: 6021365 (2000-02-01), Ishii et al.
patent: 6142586 (2000-11-01), Sakai
patent: 43 27 206 (1995-02-01), None
patent: 44 35 953 (1995-05-01), None
patent: 2 282 651 (1995-04-01), None
patent: 5-161210 (1993-06-01), None
patent: 7-336806 (1996-12-01), None
patent: 95/05299 (1995-02-01), None
Asano Kenji
Kuno Tetsuya
Ohori Harumi
Terazawa Tadashi
Urababa Shingo
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Johnson Brian L.
Luby Matthew
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