Patent ID: 8301351

Claim:
A gear shift system for a vehicle comprising: an automatic transmission; and a control unit, said control unit being adapted in such a manner as to detect a vehicle speed, a first information representing a driver's operation of an accelerator pedal or a brake pedal, and a second information representing a running environment of said vehicle, characterized in that said control unit sets a parameter having one of the detected vehicle speed, an accelerator pedal position and a throttle position as well as a drive force as components, wherein each of the accelerator pedal position, the throttle position and the drive force is set according to said first information and said second information, said control unit sets a gear ratio according to said parameter and a map determining the gear ratio based on one of the accelerator pedal position and the throttle position as well as the vehicle speed and the drive force, and has down shift lines at which shifting is carried out in dependence on the vehicle speed and the drive force, wherein the shift-down lines change in accordance with changes of the accelerator pedal position or the throttle position such that the drive force decreases with an increase of the accelerator pedal position or the throttle position, and controls said automatic transmission to shift the gear according to said set gear ratio.