Fluid-pressure and analogous brake systems – Speed-controlled – And traction control
Reexamination Certificate
1998-08-26
2001-10-23
Schwartz, Chris (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
And traction control
C303S113200
Reexamination Certificate
active
06305761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a traction control system for a vehicle capable of regulating driven wheel speeds by varying braking forces for driven wheels in accordance with excessive slipping of the driven wheels.
2. Description of the Related Art
Such a type of traction control system is conventionally known, for example, from Japanese Patent Application Laid-Open No. 3-109158. The traction control is basically utilized to converge the driven wheel speed into an optimal target wheel speed for preventing a reduction in accelerating efficiency due to excessive slipping of the driven wheels and a reduction in stability of the behavior of the vehicle body. Namely, the driven wheel speed is controlled by decreasing the engine output and by braking the driven wheels according to a difference between the target wheel speed and the driven wheel speed.
In the known traction control system, however, when the engine output is decreased by a driver's will, it cannot be definitely discriminated whether the reduction in slip rate of the driven wheels is caused by the traction control or by the driver's operation. Notwithstanding that the need for inhibiting the excessive slipping of the driven wheels has been eliminated, inappropriate traction control may be carried out, thereby providing an uncomfortable decelerating feeling to the driver.
For example, in a system designed to inhibit the excessive slipping of the driven wheels by controlling the braking pressure of a driven wheel brake, as shown in
FIG. 5A
, a target wheel speed is determined in consideration of a constant slip rate relative to the vehicle speed presumed based on at least the follower wheel speed, and a threshold value is determined slightly larger than such wheel speed. The braking pressure is increased as shown in
FIG. 5C
from the time point when the driven wheel speed exceeds the threshold value to start the traction control. However, when a throttle in an engine is brought to a fully-closed state, as shown in
FIG. 5B
, by the driver's will during carrying-out of the traction control, it cannot be definitely discriminated whether the reduction in slip rate due to a reduction in driven wheel speed is caused by the traction control or by the driver's operation, in spite of the fact that the reduction in driven wheel speed due to the reduction in engine output has been caused by the fully-closed value of the throttle opening degree. Therefore, the traction control based on the braking pressure is continued, whereby the braking pressure is gradually reduced after the driven wheel speed becomes less than the threshold value. For this reason, the driven wheel speed is excessively reduced relative to the follower wheel speed and hence, the deceleration of the vehicle may be increased more than necessary to provide an uncomfortable feeling to the driver.
The present invention has been accomplished with such circumstance in view, and it is an object of the present invention to provide a traction control system for a vehicle, wherein a deceleration greater than necessary is prevented from being produced, whenever a driver has acted so as to reduce the driven wheel speed during carrying-out of the traction control, thereby avoiding the uncomfortable feeling provided to the driver.
SUMMARY OF THE INVENTION
To achieve the above object, there is provided a traction control system for a vehicle including a driven wheel speed regulating means capable of regulating driven wheel speeds by varying braking forces for driven wheels in accordance with excessive slipping of the driven wheels, the traction control system comprising a detecting means for detecting that a driver has operated an engine output to reduce the driven wheel speed, and a control unit adapted to stop the traction control in response to the detecting means having detected the driver's operation to reduce the driven wheel speed during carrying-out of the traction control.
With such arrangement, when the driver has performed the operation for reducing the engine output during carrying-out of the traction control by increasing the braking liquid pressure of the driven wheel brake, the traction control is stopped. Therefore, a reduction in driven wheel speed by the traction control cannot be provided in addition to a reduction in driven wheel speed attendant on the driver's operation and hence, a deceleration providing an uncomfortable feeling to the driver can be avoided.
The control unit is arranged so that in a state in which the driver's operation to reduce the driven wheel speed is not detected by the detecting means, the traction control is started in accordance with the driven wheel speed exceeding a first threshold value set to be greater than a target wheel speed, but when the driver's operation to reduce the driven wheel speed has been detected by the detecting means, the traction control is started in accordance with the driven wheel speed exceeding a second threshold value set to be greater than the first threshold value.
In order to ensure that even if the driven wheel speed instantaneously exceeds the target wheel speed due to an unevenness of a road surface or the like, the control mode does not enter the traction control, the threshold value for determining the start of the traction control is conventionally determined to have a value greater than the target wheel speed. However, the threshold value (the second threshold value) when the driver's operation to reduce the driven wheel speed has been detected, is set to be greater than the threshold value (the first threshold value) when the driver's operation to reduce the driven wheel speed is not detected. Therefore, the start of the traction control, after being stopped in response to the detection of the driver's operation to reduce the driven wheel speed, is avoided in a state in which the driver's operation to reduce the driven wheel speed is being continued.
REFERENCES:
patent: 5025882 (1991-06-01), Ghoneim et al.
patent: 5224044 (1993-06-01), Tamura et al.
patent: 5315519 (1994-05-01), Chin et al.
patent: 5340204 (1994-08-01), Okazaki et al.
patent: 5407257 (1995-04-01), Iwata
patent: 6002979 (1999-12-01), Ishizu
patent: 3-109158 (1991-05-01), None
Armstrong, Westerman Hattori, McLeland & Naughton
Honda Giken Kogyo Kabushiki Kaisha
Schwartz Chris
LandOfFree
Traction control system for vehicle does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Traction control system for vehicle, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Traction control system for vehicle will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2603707