Control system for automatic vehicle transmissions

A system for controlling an automatic transmission of a vehicle having an input shaft connected to an internal combustion engine mounted on the vehicle and an output shaft connected to driven wheels of the vehicle, the transmission transmitting output torque generated by the engine and inputted through the input shaft to the driven wheels through the output shaft, including:

• operating condition detecting means for detecting operating conditions of the engine and the vehicle including at least a vehicle speed and a throttle opening:
• grade parameter determining means for determining a grade parameter indicative of upgrade or downgrade of a road on which the vehicle runs;
• shift program selecting means for selecting one from among a plurality of shift programs based on the determined grade parameter;
• and
• gear ratio determining means for determining a gear ratio based on the selected shift program;
• wherein the system includes:
• vehicle speed change calculating means for calculating a vehicle speed change in the detected vehicle speeds;
• road kind discriminating means for discriminating a kind of the road on which the vehicle runs;
• vehicle-stopping-time calculating means for calculating a vehicle-stopping-time during which the vehicle stops;
• vehicle running condition deducing means for deducing whether the vehicle is under a specific running condition based on at least the calculated vehicle speed change and the calculated vehicle-stopping-time;
• and
• shift program characteristic changing means for changing characteristics of the selected shift program based on the deduced running condition and the discriminated kind of the road such that the gear ratio determining means determines the gear ratio based on the shift program whose characteristics are changed.