Stepped transmission with hydraulic actuator for motor vehicle - has electronic safety feature which inhibits actuation before completion of engagement of manually selected reverse gear

摘要

A hydraulically actuated sliding piston (36) enables a gear-shifting sleeve (9) to be positioned in two directions before a reverse gear engagement wheel (10) is moved by a mechanical positioner (43) coupled to the gear selector (44). The selection is sensed by an electric control unit (48) which operates a slide valve (27) in the hydraulic lines (37,38) to both ends (S1,S2) of the double-acting cylinder. When reverse gear is selected the system passes through neutral with the hydraulic actuator inhibited. ADVANTAGE - Erroneous ratio changes, forward movements and stresses on drive train in reverse gear are excluded.