Automatic transmission with add-on overdrive

摘要

An add-on overdrive unit for location on an extended output shaft of an automatic transmission. The unit includes a planetary gear set connected by means of its annulus gear to an outer face of a one-way clutch. The one-way clutch inner face is concentrically interconnected to the transmission output shaft. An hydraulic piston operates a first direct-drive clutch pack and a second overdrive clutch pack. The piston is normally biased to its non-pressurized failsafe direct drive position by a compression coil spring. As a result the direct drive clutch pack is engaged causing the planetary sun gear to be locked to the annulus gear providing a one-to-one direct drive speed ratio to the overdrive output shaft via the engaged one-way clutch outer race. Upon the piston being pressurized the overdrive clutch pack is engaged and the direct drive clutch pack is released grounding the sun gear to the overdrive case. In its overdrive mode torque is transferred from the transmission output shaft via a planet carrier ring, the planet gears and the annulus gears to the outer face of the disengaged one-way clutch. Thus, drive torque is transferred through the direct-drive clutch pack only in the reverse mode of the transmission.