A Fundamental Consideration on Shift Mechanism of Automatic Transmission

A new shift mechanism for automatic transmissions was designed by considering a compact design and a better shift quality, which used exclusively plate clutches as the engaging elements of the planetary reaction members. The new shift mechanism is useful for three- or four-speed automatic transmissions. In this design, a shift control method for the new mechanism and the effect of the vibration system of vehicle on the shift quality were investigated both theoretically and experimentally.

As results of the study, it was clarified that the new shift mechanism shows a better shift quality, and that the shift characteristics are remarkably affected by the vibration system of vehicle, especially the torsional vibration of rear axles, the axle wind-up and the fore-and-aft vibration of engine.

The new shift mechanism has been successfully applied to a Toyota four-speed automatic transmission with overdrive.