Fluid-pressure and analogous brake systems – Speed-controlled – With yaw control
Reexamination Certificate
1998-03-27
2001-02-06
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With yaw control
C303S140000
Reexamination Certificate
active
06183052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus and method for properly controlling the braking forces applied to the wheels of a motor vehicle when the vehicle is turning, to stabilize turning behavior of the vehicle.
2. Description of the Related Art
A control apparatus for a motor vehicle disclosed in Unexamined Japanese Patent Publication (KOKAI) No. 8-310360, for example, controls the braking forces applied to a pair of diagonally located wheels when the vehicle is turning, to produce a difference of braking force between these wheels. Such a difference in braking force acts upon the vehicle as a turning moment or a returning moment. The turning moment serves to cancel out understeer of the vehicle, while the returning moment serves to cancel out oversteer of the vehicle, whereby the turning behavior of the vehicle is stabilized.
The difference of braking force to be produced between the pair of controlled wheels is determined in accordance with the turning state, that is, required yaw moment, of the vehicle. If, however, the driver further depresses the brake pedal after the difference between the braking forces to be applied to the controlled wheels is determined, the braking forces applied to all wheels of the vehicle increase, with the result that a desired difference cannot be produced between the braking forces applied to the controlled wheels. In the above control apparatus, therefore, if the brake pedal is further depressed while the vehicle is turning, the turning behavior control is canceled at this point of time.
SUMMARY OF THE INVENTION
An object of this invention is to provide a control apparatus and a control method which permit both turning behavior control of a motor vehicle and braking force control based on driver's operation of the brake pedal to be performed in a compatible manner.
An apparatus for carrying out a control method according to this invention comprises wheel brakes provided for the respective wheels, each of the wheel brakes being supplied with a braking pressure and applying a braking force to a corresponding one of the wheels; an adjusting device connected to the wheel brakes, the adjusting device being capable of adjusting the braking pressures of two, right and left wheels, among the wheels, independently of driver's braking operation; a detection device for the vehicle, the detection device including a plurality of sensors arranged in the vehicle and detecting a traveling state of the vehicle based on outputs from the sensors when the vehicle is turning; brake controllers connected to brake circuits for supplying the braking pressures to the wheel brakes, respectively, and detecting fluid pressures in the brake circuits which are indicative of actual braking pressures in the wheel brakes, respectively; and a control device connected to the detection device and the brake controllers. The control device receives outputs of the detection device and the brake controllers and performs the following operations:
The control device sets a target braking force difference to be produced between right and left wheels, selects one of the right and left wheels as a controlled wheel, determines a target braking pressure for the controlled wheel based on the target braking force difference and the actual braking pressure of a non-selected one of the right and left wheels, and controls the actual braking pressure of the controlled wheel by means of the adjusting device in accordance with the target braking pressure, thereby producing the target braking force difference between the right and left wheels and applying yaw moment to the vehicle.
With the above control apparatus, even if the braking operation by the driver changes after the target braking force difference for the controlled wheel is determined, the actual braking pressure of the controlled wheel is controlled taking account of the actual braking pressure of the non-selected wheel. Consequently, the target braking force difference can be produced with accuracy between the controlled wheel and the non-selected wheel, whereby a desired yaw moment is applied to the vehicle and thus the turning behavior of the vehicle is stabilized.
The control device preferably performs feedback control such that the actual braking pressure of the controlled wheel becomes equal to the target braking pressure.
Still preferably, the controlled wheel and the non-selected wheel are an outer front wheel and an inner rear wheel as viewed in a turning direction of the vehicle, respectively.
The detection device may include, as the aforementioned sensors, a yaw rate sensor for detecting a yaw rate of the vehicle, wheel speed sensors for detecting speeds of the wheels, a longitudinal acceleration sensor for detecting a longitudinal acceleration of the vehicle, a lateral acceleration sensor for detecting a lateral acceleration of the vehicle, and an angle sensor for detecting a rotational angle of a steering wheel of the vehicle. In this case, the detection device may further include a state-of-motion calculation circuit for calculating a state of motion of the vehicle based on outputs supplied thereto from the yaw rate sensor, the wheel speed sensors, the longitudinal acceleration sensor and the lateral acceleration sensor, and outputting a result of calculation, and a driving operation calculation circuit for calculating a state of driver's driving operation based on an output of the angle sensor supplied thereto, and outputting a result of calculation. This detection device can accurately detect the traveling state of the vehicle.
The adjusting device may include automatic brake circuits connecting an air tank containing compressed air to the wheel brakes, and may further include a supply valve, a pressure control valve and an air over hydraulic booster arranged in each of the automatic brake circuits in series from an air tank side. Specifically, the supply valve comprises a normally-open, solenoid-operated on-off valve and supplies compressed air from the air tank to the corresponding automatic brake circuit when opened. The pressure control valve adjusts pressure of the compressed air supplied from the corresponding supply valve and supplies the adjusted air pressure to the corresponding air over hydraulic booster. The air over hydraulic booster converts the air pressure supplied from the corresponding pressure control valve to hydraulic pressure, to thereby generate a braking pressure in a corresponding one of the wheel brakes. A brake system including such automatic brake circuits is suited for use in a heavy-duty vehicle such as a truck or bus.
Preferably, the detectors each detect an air pressure in the corresponding automatic brake circuit at a location more upstream than the corresponding air over hydraulic booster.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific example, while indicating preferred embodiment of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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Harada Masaharu
Matsuda Katsushi
Sakata Kunio
Graham Matthew C.
Mitsubishi Jidosha Kabushiki Kaisha
Williams Thomas J.
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