Elective automatic shift transmission

Claim 1

For use in a vehicle of the type having an engine coupled with traction wheels through a driveline including a change-speed transmission, said transmission including drive direction reversing means, a drive direction selector for manual control of the reversing means and having a forward and reverse position, said transmission including ratio changing means, a manual gear selector for operation of the ratio changing means for shifting the transmission into a selected gear, and control means responsive to a control signal for upshifting and downshifting between first and second gears, the inprovement comprising: a speed signal generator adapted to be coupled with said driveline for producing a speed signal corresponding to the speed of the vehicle, a shift point signal means coupled with the speed signal generator and responsive to said speed signal for producing a second gear signal when the speed signal increases above a first predetermined value and a first gear signal when the speed signal decreases below a second predetermined value, a reversing signal generator connected with said drive direction selector and adapted to produce a reversing signal in response to movement of the selector means between forward and reverse positions, inhibit means responsive to the reversing signal for producing an inhibit signal having a predetermined time duration after the occurrence of said reversing signal, speed decision logic means including means coupled with the shift point signal means and responsive to the second gear and first gear signals for producing respective upshift and downshift signals and being responsive to an inhibit signal for delaying the change from an upshift signal to a downshift signal for a time interval corresponding to the duration of the inhibit signal, said time interval being at least as long as the time required for operation of said reversing means, whereby the transmission cannot be downshifted while the drive reversing means is being actuated, a manually actuable mode selector means for producing an on signal or an off signal, and gear decision logic means having a first input coupled with the speed decision logic means, a second input coupled with the mode selector means and an output coupled with said control means, said gear decision logic means being operative to develop a second gear or first gear control signal in response to the upshift or downshift signals respectively from the speed logic means when the mode selector produces an on signal and being operative to develop only a second gear when the mode selector produces an off signal.