Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-05-26
2001-07-31
Gamby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S083000, C701S084000, C180S197000
Reexamination Certificate
active
06269297
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a traction control apparatus and method for vehicles, which restrains an acceleration slip at wheels.
2. Related Background Art
There are practical traction control systems intended for efficiently yielding traction by restraining the acceleration slip at the wheels mounted on vehicles. An example of such known traction control systems is one as described in Japanese Patent Application Laid-Open No. 5-58264. The traction control system is constructed to detect slip states (for example, slip rates or the like) of the wheels and exert braking force according to the slip states on the wheels, so as to restrain the acceleration slip and maintain frictional force between wheels and road surface, thereby efficiently yielding the traction.
There are also cases wherein the traction control apparatus is designed to control the driving force generated by an engine and transmitted to driven wheels instead of the braking force. In some of these cases, the traction control apparatus is constructed to detect the slip states of the wheels and decrease the driving force transmitted to the wheels in accordance with the slip states, so as to restrain the acceleration slip and maintain the frictional force between wheels and road surface, thereby efficiently producing the traction. In certain cases both the acceleration-slip prevention by the braking force control and the acceleration-slip prevention by the driving force reduction as described above are used in combination. In such traction control, increase amounts of the braking force and/or decrease amounts of the driving force described above become larger as the slip states of the wheels become more prominent (for example, as the slip rates increase).
SUMMARY OF THE INVENTION
The traction control is normally started after predetermined control permission conditions are met. For example, in order to permit the traction control only when a driver has the will to run, the condition that the stroke of the accelerator pedal is not less than a predetermined value is set as one of the control permission conditions. In some cases the traction control is actively inhibited in order to prevent a breakdown of the brake actuator, for example, during hot periods of the brake actuator, and the condition that the traction control is not in such an inhibited state is set as one of the control permission conditions.
For this reason, if the slip rates of the wheels are already large at the start of the traction control after the control permission conditions are met, great braking force will be exerted on the wheels or reduction of the driving force will be large in the initial stage of the traction control. For example, the slip rates are already large in cases wherein from such a state that one wheel is spinning in a ditch or in a stuck state the driver steps the accelerator pedal down over the predetermined pedal stroke described above; then the control amounts are large in the initial stage of control in these cases. When the inhibited state of the traction control as described above is released during acceleration, the slip rates of the wheels are also already large and thus the control amounts are great in the initial stage of control.
When the traction control is activated to exert large braking force on the wheel demonstrating the large slip rate, the driver must feel great jerky motion of the vehicle and thus feel uncomfortable. If the traction control with large decrease of the driving force is effected at the wheel demonstrating the large slip rate, a stall feeling, an engine shake due to a sudden drop of engine power output, or the like will arise, so as to cause the driver to feel uncomfortable.
Further, if large braking force is exerted on the spinning wheel immediately after the start of the traction control, the wheel will suddenly stop spinning and thus a large torque will be exerted on the power train, so as to increase the load on the power train.
Yet further, in cases wherein the slip rate of only one wheel is large because of the stuck state thereof, when large braking force is produced at the wheel of the large slip rate, the driving force causing the wheel of the large slip rate to spin is suddenly delivered to the other wheel by the differential gear mechanism, so as to cause the vehicle to rush out, thereby making the driver feel uncomfortable.
There were thus demands for further improvement.
An object of the present invention is, therefore, to provide a traction control apparatus and method for vehicles that can restrain the uncomfortableness during the traction control and that can restrain large input into the power train.
A traction control apparatus for vehicles according to the present invention comprises: slip state detecting means for detecting a slip state of a wheel mounted on a vehicle; parameter determining means for determining a control parameter for generating braking force according to the slip state detected by the slip state detecting means; control permitting means for permitting traction control; parameter changing means for changing the control parameter so as to decrease the braking force generated at the wheel when the control parameter determined from the slip state of the wheel at the time of permission of the traction control by the control permitting means is one to generate the braking force at the wheel over permissible braking force which is permissible at a start of the control; and traction control means for executing the traction control by controlling the braking force at the wheel, based on the control parameter.
In the traction control apparatus for vehicles according to the present invention, when the control parameter determined from the slip state of the wheel at the time of permission of the traction control given by the control permitting means is one to generate the braking force at the wheel over the permissible braking force, the parameter changing means changes the control parameter so as to decrease the braking force by the traction control. This can prevent a large braking force from being exerted on the wheel at the control start of the traction control, whereby the driver can be prevented from feeling uncomfortable because of the jerky motion and the rushing motion of the vehicle. Since the large braking force can be prevented from being exerted suddenly on the wheel at the control start of the traction control, no large torque is exerted on the power train of the vehicle, so that the load is little on the power train.
In a preferred example, the traction control means comprises braking force adjusting means for effecting braking at the wheel by increasing hydraulic pressure in a wheel cylinder to urge a frictional material against the wheel or against a rotary member coupled thereto, the control parameter is a pressure increase rate of the hydraulic pressure, and the parameter changing means changes the pressure increase rate determined by the parameter determining means, to a lower rate. This makes a rise of the braking force gentler in the traction control, thereby decreasing the braking force by the traction control.
In another preferred example, the traction control means comprises braking force adjusting means for effecting braking at wheel by increasing hydraulic pressure in a wheel cylinder to urge a frictional material against the wheel or against a rotary member coupled thereto, the control parameter is a target pressure of the hydraulic pressure, and the parameter changing means changes the target pressure determined by the parameter determining means, to a lower pressure value. This decreases the maximum of the braking force in the traction control, thereby decreasing the braking force by the traction control.
Another traction control apparatus for vehicles according to the present invention comprises: slip state detecting means for detecting a slip state of a wheel mounted on a vehicle; parameter determining means for determining a control parameter for decreasing driving force transmit
Hosomi Kazushi
Saito Yasuhiro
Takagi Masashi
Yokokawa Mitsuyoshi
Gamby Richard M.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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