Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
2000-06-30
2002-05-21
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S113400, C303S140000
Reexamination Certificate
active
06390568
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a vehicle motion control system. More particularly, the present invention pertains to a vehicle motion control system which supplies hydraulic pressure generated by an automatic hydraulic pressure generator, capable of generating hydraulic pressure irrespective of a brake pedal operation, to a wheel brake cylinder via a control valve. This vehicle motion control system is applicable to a brake steering controller (a controller for preventing vehicle lateral skidding) and to a traction controller.
BACKGROUND OF THE INVENTION
A known type of vehicle motion control system is described in Japanese Patent No. 2790288 issued in 1998, and U.S. Pat. No. 4,966,248. In this vehicle motion control system, a switching solenoid valve is connected to a vacuum servo unit or vacuum booster. The switching solenoid valve is capable of being selectively switched between either a non-operative position in which a servo unit does not operates when a brake pedal is not depressed or an operative position in which a vacuum servo unit operates independently when the brake pedal is not depressed. During an acceleration slip of the driving wheels (i.e., during a traction control), the switching solenoid valve is switched to the operative position, the vacuum servo unit is operated, and a master cylinder generates a hydraulic pressure without any brake pedal operation. The master cylinder hydraulic pressure is controlled by a modulation unit (a hydraulic pressure control valve) and is supplied to a wheel brake cylinder of a driving wheel which is experiencing acceleration slipping.
The known system described above suffers from several drawbacks. Because the switching solenoid valve is maintained at the operative position during traction control, the hydraulic pressure generated in the master cylinder could exceed the hydraulic pressure that the traction control requires when a negative pressure supplied to a constant pressure chamber of the servo unit changes. An undesired switching noise is generated when a hydraulic brake pressure of a wheel brake cylinder is adjusted by the modulation unit in the above situation.
The switching noise is generated when the fluid communication between the master cylinder and the wheel brake cylinder is switched from the open to closed condition by the modulation unit while excessively high master cylinder hydraulic pressure exists. Also, when the fluid communication between the master cylinder and the wheel brake cylinder is switched from the closed to the open condition, a switching noise is generated by the differential pressure between the master cylinder and the wheel brake cylinder. Likewise, a switching noise is generated when the connection between the wheel cylinder and the reservoir is opened or closed by the modulation unit.
The phenomenon mentioned above occurs remarkably when the known vehicle motion control system is applied to a control for preventing vehicle lateral skidding because the hydraulic pressure necessary for the vehicle lateral skidding control is high.
In light of the foregoing, a need exists for a vehicle motion control system which generates less switching noise when the hydraulic pressure valve is switched while the motion control is under operation.
SUMMARY OF THE INVENTION
The present invention provides a vehicle motion control system that includes a wheel brake cylinder disposed on a wheel to supply a braking force to the wheel, an automatic hydraulic pressure generator which generates hydraulic pressure irrespective of brake pedal operation, a hydraulic pressure control valve disposed between the automatic hydraulic pressure generator and the wheel brake cylinder to adjust the hydraulic brake pressure of the wheel brake cylinder by controlling fluid communication between the automatic hydraulic pressure generator and the wheel brake cylinder, and a braking controller for performing the motion control by actuating the hydraulic pressure control valve in accordance with the motion condition of the vehicle. A hydraulic pressure detecting device detects the generated hydraulic pressure of the automatic hydraulic pressure generator, and a braking control mechanism includes a necessary hydraulic pressure setting device for setting a hydraulic pressure required for the motion control in accordance with the vehicle motion condition during the motion control, and a hydraulic pressure adjusting device for controlling the automatic hydraulic pressure generator and adjusting the generated hydraulic pressure thereof in accordance with the compared result of the actually generated hydraulic pressure of the automatic hydraulic pressure and the required pressure for the motion control.
The motion control system can also include a brake steering control, or control for preventing a vehicle lateral skidding, a traction control and an automatic brake control (a control of the distance between moving vehicles).
The system of the present invention is capable of reducing the switching noise generated when the hydraulic pressure control valve is switched. This is because the generated hydraulic pressure of the automatic hydraulic pressure generator is regulated to the level of the necessary hydraulic pressure for the motion control by adjusting the generated hydraulic pressure of the automatic hydraulic pressure generator in accordance with the comparison between the necessary hydraulic pressure for the motion control and the actually generated hydraulic pressure of the automatic hydraulic pressure generator.
Because the automatic hydraulic pressure generator is controlled in accordance with the result of the comparison between the necessary hydraulic pressure for control and the generated hydraulic pressure of the automatic hydraulic pressure generator, the operation frequency of the hydraulic pressure controller can be reduced. Thus the generation frequency of the switching noise can be reduced.
The necessary hydraulic pressure setting device sets the necessary hydraulic pressure of each wheel in accordance with the vehicle motion attitude during the motion control. Preferably, the hydraulic pressure adjusting device controls the automatic hydraulic pressure generator to adjust the generated hydraulic pressure in accordance with the comparison between the generated hydraulic pressure of the automatic hydraulic pressure generator and the maximum value of the necessary hydraulic pressure of a plurality of controlled wheels. The necessary hydraulic pressure is supplied to all of the controlled wheels securely because the generated hydraulic pressure of the automatic hydraulic pressure generator is adjusted in accordance with the result of the comparison between the generated hydraulic pressure of the automatic hydraulic pressure generator and the maximum value of the necessary hydraulic pressure of a plurality of the controlled wheels.
It is preferable that the hydraulic pressure adjusting mechanism is adapted to control the automatic hydraulic pressure generator to make the generated hydraulic pressure of the automatic hydraulic pressure generator correspond to the necessary hydraulic pressure of the controlled wheels. The switching noise generated when the hydraulic pressure control valve is switched and the frequency of generation of the switching noise can thus be reduced. Further, the necessary hydraulic pressure for the motion control can thus be supplied to the controlled wheels.
It is also preferable that the necessary hydraulic pressure setting device is adapted to set the necessary hydraulic pressure for the motion control for every motion control action, and to calculate the maximum value of a plurality of the necessary hydraulic pressures when a plurality of the motion controls are performed to the vehicle. Also, the hydraulic pressure adjusting device is adapted to adjust the generated hydraulic pressure of the automatic hydraulic pressure generator in accordance with the result of the comparison between the generated hydraulic pressure of the automatic hydraulic pressure generator and the
Nishio Akitaka
Tozu Kenji
Aisin Seiki Kabushiki Kaisha
Burns Doane , Swecker, Mathis LLP
Graham Matthew C.
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