Fluid-pressure and analogous brake systems – Speed-controlled – Regenerative brakes
Reexamination Certificate
1998-09-16
2001-06-12
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Regenerative brakes
C180S165000, C303S003000
Reexamination Certificate
active
06244674
ABSTRACT:
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 a lack of regenerative braking torque, smoothly.
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, a lack of braking force must be compensated by the hydraulic braking operation for example. 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, the regenerative braking torque is set in accordance with a predetermined torque map or hydraulic pressure coefficient, and a lack of regenerative braking torque, which is caused in a relatively low speed range for example, is compensated by the hydraulic braking operation or the like. However, since the hydraulic braking force to be compensated is varied, the amount of regenerative braking torque to be compensated may be excessive occasionally. In this case, feelings to a vehicle driver in his braking operation will be varied.
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 provides effective countermeasures to a variation of hydraulic braking force to be compensated for a lack of regenerative braking force, thereby 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 the 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 force to the wheel. A wheel brake cylinder is operatively mounted on the wheel for applying a hydraulic braking force to the wheel. A pressure generator is provided for pressurizing brake fluid to generate a hydraulic braking pressure in response to operation of a manually operated braking member. A pressure control device is provided for controlling the hydraulic braking pressure generated by the pressure generator and supplied to the wheel brake cylinder to apply the hydraulic braking force to the wheel. A monitor is provided for monitoring a braking condition of the vehicle. A braking torque reducing device is provided for reducing the regenerative braking torque in response to the braking condition monitored by the monitor. A pressure difference detector is provided for detecting a pressure difference between the hydraulic braking pressure of the brake fluid discharged from the pressure generator and the hydraulic braking pressure in the wheel brake cylinder. And, a modifying device is provided for modifying a characteristic of the regenerative braking torque reduced by the braking torque reducing device, in response to the pressure difference detected by the pressure difference detector.
In the brake control system as described above, the pressure generator may include a master cylinder for pressurizing the brake fluid stored in a reservoir in response to operation of the manually operated braking member to generate a static hydraulic braking pressure, and the pressure difference detector may be adapted to detect the pressure difference between the hydraulic braking pressure of the brake fluid discharged from the master cylinder and the hydraulic braking pressure in the wheel brake cylinder.
Preferably, the pressure control device includes a master cylinder for pressurizing the brake fluid stored in a reservoir in response to operation of the manually operated braking member to generate a static hydraulic braking pressure, and 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 hydraulic pressure. And, the pressure control device may be adapted to supply the power hydraulic pressure to the wheel brake cylinder to apply the hydraulic braking force to the wheel, and the pressure difference detector may be adapted to detect the pressure difference between the hydraulic braking pressure of the brake fluid discharged from the master cylinder and the hydraulic braking pressure in the wheel brake cylinder.
REFERENCES:
patent: 5326158 (1994-07-01), Ohori et al.
patent: 5450324 (1995-09-01), Cikanek
patent: 5492192 (1996-02-01), Brooks et al.
patent: 5511859 (1996-04-01), Kade et al.
patent: 5707115 (1998-01-01), Bodie et al.
patent: 5895100 (1999-04-01), Ito et al.
patent: 5-161210 (1993-06-01), None
patent: 7-336806 (1995-12-01), None
Kuno Tetsuya
Ohori Harumi
Suzuki Yoshinori
Terazawa Tadashi
Urababa Shingo
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Graham Matthew C.
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