Method and apparatus for controlling manual downshifting in an automatic transmission

An apparatus for use in a vehicle having an engine driven transmission which includes a plurality of gear ratios, comprising:

• a sensor, wherein said sensor senses an operating parameter and responsively produces a parameter;
• a speed sensor, wherein said speed sensor senses a parameter indicative of transmission input speed and responsively produces a transmission input speed signal;
• a downshift switch, wherein said downshift switch controllably produces a downshift signal;
• an engine speed sensor, wherein said engine speed sensor senses engine speed and responsively produces an engine speed signal;
• a controller, wherein said controller receives the parameter, transmission input, engine speed, and downshift signals, processes the parameter signal to produce a transmission control signal, produces a down shift enable value as a function of the engine speed signal, and modifies the transmission control signal to correspond to a lower gear ratio in all but the lowest gear ratio when the downshift signal is received and the transmission input speed signal is less than the down shift enable value;
• and
• an actuator, wherein said actuator receives the transmission control signal and responsively controls the transmission gear ratio.

An apparatus for use in a vehicle having an engine driven transmission which includes a plurality of gear ratios, comprising:

• a sensor, wherein said sensor senses a parameter indicative of vehicle speed and responsively produces a vehicle speed signal;
• a downshift switch, wherein said downshift switch controllably produces a downshift signal;
• an engine speed sensor, wherein said engine speed sensor senses engine speed and responsively produces an engine speed signal;
• a controller, wherein said controller receives the vehicle speed, engine speed, and downshift signals, processes the vehicle speed signal to produce a transmission control signal, processes the vehicle speed signal to produce a transmission input speed signal, produces a down shift enable value which increases proportionally with the engine speed signal, and modifies the transmission control signal to correspond to a lower gear ratio in all but the lowest gear ratio when the downshift signal is received and the transmission input speed signal is less than the down shift enable value;
• and
• an actuator, wherein said actuator receives the transmission control signal and responsively controls the transmission gear ratio.

A method for use in a vehicle having an engine driven transmission which includes a plurality of gear ratios, a speed sensor, wherein said speed sensor senses a parameter indicative of vehicle speed and responsively produces a vehicle speed signal, and a downshift switch, wherein said downshift switch controllably produces a downshift signal, comprising the steps of:

• producing a transmission control signal in response to the vehicle speed signal;
• producing a down shift enable value as a function of engine speed;
• modifying the transmission control signal to correspond to a lower gear ratio in all but the lowest gear ratio when the downshift signal is received and a value responsive to the vehicle speed signal is less than the down shift enable value;
• and
• controlling the transmission gear ratio in response to the transmission control signal.