Control system for automatic vehicle transmission

摘要

A control system for an automatic vehicle transmission which has auto-shifting means or auto-shift mode for determining a gear to be shifted to in accordance with predetermined gearshift scheduling characteristics in response to the detected vehicle speed and the engine load, and manual-shifting means or manual-shift mode for determining a gear to be shifted to in response to a manual-shift command generated by the vehicle driver. The system further includes auto-downshifting means or sub-auto-shift mode for determining a gear to be downshifted to if the detected vehicle speed is less than a threshold value when the manual-shifting means is in operation. In the system it is estimated whether the vehicle is hill climbing or hill descending, and the threshold value is increasing when the vehicle is hill climbing or descending. With the arrangement, it becomes possible to downshift before the drivability or driver's comfort is degraded during the hill climbing or descending.