Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
1998-08-07
2001-05-15
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
C303S115200
Reexamination Certificate
active
06231133
ABSTRACT:
The contents of Tokugan Hei 9-213661, with a filing date of Aug. 7, 1997 in Japan, are hereby incorporated by reference.
FIELD OF THE INVENTION
This invention relates to brake control in a vehicle, and in particular, brake control when a brake actuator becomes defective.
BACKGROUND OF THE INVENTION
In a vehicle brake system, a master cylinder generates oil pressure according to a brake pedal operation of a driver, and this oil pressure is distributed between wheel cylinders. U.S. Pat. No. 4,653,815 further provides a motor drive type actuator for every wheel cylinder to control a brake pressure supply to the respective wheel cylinders. The actuator is provided with a shutoff valve which cuts off the master cylinder and wheel cylinder, and a piston which increases the pressure of the wheel cylinder in response to an electric motor.
The actuator operates according to a signal from a control unit. The pressure of the master cylinder is detected by a pressure sensor. The control unit multiplies this pressure by a coefficient of one or more, so as to compute a target pressure, close the shutoff valve and drive the piston so that the wheel cylinders reach the target pressure.
This device can adapt to normal brake operation or to an antiskid brake function which prevents wheel spin merely by changing over the target value. When one of the actuators is found to be defective, braking is performed by opening all shutoff valves and supplying the pressure of the master cylinder directly to the wheel cylinders.
However, when a specific actuator is occurs. For example, if braking is performed while the left front wheel actuator is defective, brake Pressure is first supplied to the other three wheels by the corresponding pistons. As a result, due to difference force between the left and right front wheels, the vehicle starts to turn right. In particular, on the road surface with a low frictional coefficient, three of the wheels lock due to braking and only the left front wheel rotates.
When the shutoff valve is opened in this state, and the pressure of the master cylinder is supplied directly to all four wheels, the left wheel which was rotating also locks, and it may occur at all four wheels lose their grip in the horizontal direction.
In this case, the vehicle may behave differently from what the driver intends.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to increase the directional stability of a vehicle in braking when an actuator becomes defective.
In order to achieve the above object, this invention provides a brake pressure controller for use with a vehicle brake device. The device comprises a first actuator group comprising one or more actuators for generating a brake pressure for a predetermined combination of a left wheel and a right wheel corresponding to a depression degree of a brake pedal, and a second actuator group comprising one or more actuators for generating a brake pressure for another predetermined combination of a left wheel and a right wheel corresponding to a depression degree of the brake pedal.
The controller comprises a sensor for detecting a faulty actuator and a microprocessor programmed to prevent, when a faulty actuator is found, a faulty actuator group to which the faulty actuator belongs from generating a brake pressure, while controlling the other actuator group to continue generating a brake pressure.
It is preferable that the microprocessor is further programmed to control the other actuator group so as to generate a brake pressure greater than the brake pressure corresponding to the depression degree of the brake pedal.
It is also preferable that the microprocessor is further programmed to control the other actuator group to generate a brake pressure which is lower than the brake pressure corresponding to the depression degree of the brake pedal for a predetermined time, and then generate a brake pressure corresponding to the depression degree of the brake pedal.
When the brake device further comprises a master cylinder for generating a master cylinder pressure corresponding to the depression degree of the brake pedal and a valve for supplying the master cylinder pressure respectively to the wheels, it is preferable that the microprocessor is further programmed to control the faulty actuator group and the valve to apply the master cylinder pressure to the wheels corresponding to the faulty actuator group.
It is also preferable that the microprocessor is further programmed to control the faulty actuator group to decrease the brake pressure generated in the faulty actuator group to be equal to zero.
It is also preferable that the predetermined combination of a left wheel and a right wheel is a left front wheel and a right front wheel, the other predetermined combination of a left wheel and a right wheel is a left rear wheel and a right rear wheel, and the microprocessor is further programmed to control the second actuator group when the faulty actuator group is the second actuator group such that the brake pressure generated by the second actuator group is zero, and control the first actuator group to generate a brake pressure greater than the brake pressure corresponding to the depression degree of the brake pedal.
It is also preferable that the predetermined combination of a left wheel and a right wheel is a left front wheel and a right front wheel, the other predetermined combination of a left wheel and a right wheel is a left rear wheel and a right rear wheel, the brake device is provided with a master cylinder for generating a master cylinder pressure according to the depression degree of the brake pedal and a valve for supplying the master cylinder pressure respectively to the wheels, and the microprocessor is further programmed to control the first actuator group and the valve to apply the master cylinder pressure to the left front wheel and right front wheel, when the faulty actuator group is the first actuator group.
In this case, it is further preferable that the microprocessor is further programmed to control the second actuator group to generate a brake pressure which is lower than the brake pressure corresponding to the depression degree of the brake pedal for a predetermined time, and then generate the brake pressure corresponding to the depression degree of the brake pedal.
It is also preferable that the predetermined combination of a left wheel and a right wheel is a left front wheel and a right front wheel, the other predetermined combination of a left wheel and a right wheel is a left rear wheel and a right rear wheel, the brake device is provided with a master cylinder for generating a master cylinder pressure according to the depression degree of the brake pedal and a valve for supplying the master cylinder pressure respectively to the wheels, and the microprocessor is further programmed to control the second actuator group and the valve to apply the master cylinder pressure to the left rear wheel and right rear wheel, when the faulty actuator group is the second actuator group.
It is also preferable that the predetermined combination of a left wheel and a right wheel is a left front wheel and a right front wheel, the other predetermined combination of a left wheel and a right wheel is a left rear wheel and a right rear wheel, the brake device is provided with a master cylinder for generating a master cylinder pressure according to the depression degree of the brake pedal and a valve for supplying the master cylinder pressure respectively to the wheels, and the microprocessor is further programmed to control the first actuator group and the valve to apply the master cylinder pressure to the left front wheel and right front wheel when the faulty actuator group is the first actuator group, and control the second actuator group to generate a brake pressure greater than the brake pressure corresponding to the depression degree of the brake pedal.
It is also preferable that the predetermined combination of a left wheel and a right wheel is a right front wheel and a left rear wheel, the other predetermined combinatio
Foley & Lardner
Nissan Motor Co,. Ltd.
Schwartz Christopher P.
Williams Thomas J.
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