Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-04-26
2001-10-16
Olszewski, Robert P. (Department: 2167)
Land vehicles
Wheeled
Running gear
C280S093513, C701S042000, C180S446000
Reexamination Certificate
active
06302441
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a steering control apparatus for a vehicle provided with a transmission ratio varying mechanism capable of varying the transmission ratio between the rotation of the steering wheel and the turn angle of the wheels.
2. Description of Related Art
There are known steering control apparatus for vehicles provided with a transmission ratio varying mechanism capable of varying the transmission ratio between the rotation of the steering wheel and the turn angle of the wheels. For example, in Japanese Laid-open Patent Application No. 62-46771, the responsiveness of the transmission ratio is changed according to the acceleration/ deceleration of the vehicle.
Specifically, the responsiveness of the wheels to the steering wheel is improved by keeping the transmission ratio high during acceleration, while stability of steering is enhanced by keeping the transmission ratio low during deceleration so as to reduce the quick alteration of transmission ratio with a reduction in vehicle speed.
SUMMARY OF THE INVENTION
When rounding a curve, steering is conducted in such a way that the steering handle (steering wheel) is rotated (for example right steering) in the cornering direction when entering the curve and the steering handle is then slowly returned (for example left steering) when entering the exit of the curve. In Japanese Laid-open Patent Application No. Sho 62-46771 consideration is not given to the steering operation when rounding a curve and to the change in the speed of the vehicle on that occasion, and so during cornering of the vehicle the responsivity of the transmission ratio varies based only on the accelerated/decelerated state of the vehicle. Therefore, it fails to set the transmission ratio correctly during cornering.
The present invention has solves this problem and provides a steering control apparatus for a vehicle that can correctly set the transmission ratio for the steering operation during cornering with acceleration or deceleration.
The steering control apparatus for a vehicle is an apparatus having a transmission ratio varying mechanism. The transmission ratio varying mechanism varies a transmission ratio of the rotation of the steering handle to the turn angle of the wheel. The steering control apparatus for vehicle has an accelerated/decelerated state judging means for judging whether a vehicle is in an accelerated/decelerated state, a steering state judging means for judging a steering state, based on the steering angle of the steering handle, a base transmission ratio determining means for determining a base transmission ratio according to the running condition of the vehicle, a compensation amount determining means for, when the accelerated/decelerated state judging means judges that the vehicle is in acceleration/deceleration, determining a compensation amount for the base transmission ratio, based on the result of judgment of the steering state judging means and a transmission ratio setting means for setting a transmission ratio of the transmission ratio varying mechanism, based on values determined by the base transmission ratio determining means and the compensation amount determining means.
The accelerated/decelerated state judging means judges, for example, whether the vehicle is in acceleration or in deceleration, and the steering state judging means judges, for example, whether steering is feed steering or return steering. The compensation amount determining means determines the compensation amount for the base transmission ratio in view of the accelerated/decelerated state of the vehicle and the steering state thus judged.
The steering control apparatus for vehicle according to the above, wherein the compensation amount determining means determines the compensation amount so as to decrease the base transmission ratio state during acceleration/deceleration and feed steering or so as to increase the base transmission ratio where the steering state during acceleration/deceleration and return steering.
By determining the compensation amount in this way, the base transmission ratio is compensated so as to be quicker (or so as to make the rotation amount to the turn of the wheel amount larger) in the case of feed steering during acceleration/deceleration. In the case of return steering during acceleration/deceleration the base transmission ratio is compensated so as to be slower (or so as to make the rotation amount to turn of the wheel amount smaller), which acts to direct a turn angle of the wheels more toward the neutral position (straight driving position). This reduces the steering amount during return steering. Accordingly, the compensation amount by the compensation amount determining means allows running through the curve with less steering of the steering handle.
The steering control apparatus for a vehicle as noted above, further comprising slow change means for slowly changing the transmission ratio set by the transmission ratio setting means with a lapse of time at the start of compensation and at the end of compensation, for the base transmission ratio. At the start of compensation and at the end of compensation the transmission ratio set by the transmission ratio setting means may vary suddenly because of influence of the compensation amount. Intervention of the slow change means can suppress the sudden change of transmission ratio.
The steering control apparatus for vehicle according to the above, wherein the compensation amount determining means determines the compensation amount according to whether the steering state is feeding steering during acceleration, return steering during acceleration, feed steering during deceleration and return steering during deceleration. When the compensation amount is determined according to each steering state in this way, the transmission ratio can be set so as to be suited for each steering state during acceleration/deceleration.
The steering control apparatus for a vehicle according to the above, wherein the compensation amount determining means has inhibiting means for inhibiting alteration of the compensation amount where the steering angle change amount is smaller than a predetermined threshold. The addition of this inhibiting means permits a constant cornering state to be maintained without reacting to minute steering fluctuations during cornering.
The steering control apparatus for a vehicle according to the above, also having threshold setting means for setting the threshold in the inhibiting means according to a running condition of the vehicle.
The threshold in the inhibiting means is a threshold value for judging whether the steering handle is in a hold state. On the other hand, the transmission ratio, which specifies the relation between the steering angle of the steering handle and the turn angle of the wheels, varies according to the running condition of the vehicle. When the threshold in this inhibiting means is thus set according to the running condition of the vehicle, the judgment can be more accurate as to whether the steering is in the hold state, i.e., whether the compensation amount should be changed.
The steering control apparatus for vehicle is the steering control apparatus for vehicle according to the above, wherein the compensation amount determining means further comprises adjusting means for changing the compensation amount according to the magnitude of an acceleration or a deceleration. The provision of this adjusting means can change the transmission ratio more promptly or, conversely, to suppress a sudden change of transmission ratio, with increase in the acceleration/deceleration of the vehicle.
The steering control apparatus for a vehicle according to the above, wherein the compensation amount determining means also has adjusting means for changing the compensation amount according to the magnitude of the speed of the vehicle. The addition of this adjusting means can prevent the transmission ratio from changing too much in the high speed range.
The steering control apparatus for a vehicle accor
Kawamuro Junji
Kojo Takahiro
Matsuda Morihiro
Shindo Masahiko
Fischer Andrew J.
Oliff & Berridg,e PLC
Olszewski Robert P.
Toyota Jidosha & Kabushiki Kaisha
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