GB676055A - Improvements relating to change-speed gearing - Google Patents

Abstract

676,055. Change-speed gearing; clutches. DAIMLER-BENZ AKT.-GES. July 20, 1950 [July 22, 1949], No. 18207/50. Class 80 (ii). Planetary change-speed gearing for motor vehicles comprises a planet carrier 2, 5 rigid with the driving shaft 1, an annulus 6 rigid with the driven shaft 8, and a sun wheel 7, 9 which is adapted to be arrested by a brake 10 to give overdrive but which is normally coupled to a polygonal sleeve 17 fast on the shaft 1 by doubleacting wedging rollers 18 so as to give bi-directional direct drive, the rollers being rendered inoperative in the forward direction (clockwise in Figs. 3, 5, 6) prior to and during overdrive while remaining operative in the reverse direc-. tion so that the gear jams in overdrive when the vehicle tends to move rearwardly and thus prevents such movement. The cage 21 for the rollers 18 has an arcuate recess 22 into which a ball 23 is adapted to be moved by a conical part of a spring-loaded piston valve 24 which is movable by pressure fluid admitted through a passage 26 to the space 27 behind the valve and which controls the passage of the pressure fluid through a passage 14 to a piston 13 applying the brake 10. So long as the brake 10 is disengaged, the valve 24 then occupying the position shown in Fig. 1, the rollers 18 act to couple the sun 7 to the carrier 2, so as to produce direct drive, whether the engine drives or the vehicle over-runs, the ball 23 being moved out of the recess 22 during such over-run, as shown in Fig. 5. To change to overdrive, pressure fluid is supplied to passage 26, tending to move valve 24 to the right. Such movement is, however, prevented by the ball 23 if the vehicle is over-running, and the change can accordingly take place only when the engine is speeded up to driving condition, whereupon the ball reengages the recess 22 and the valve 24 is free to move to the right, causing the brake 10 to be engaged to produce overdrive, whether the engine drives or the vehicle over-runs. The rollers 18 now occupy the position shown in Fig. 6, backward movement of the cage 21 being limited by engagement of the forward end of its recess 22 with the ball 23, which is now held in the recess by a cylindrical part of the valve 24. The valve 24 is held in its new position by the pin, 34 of a spring-loaded piston 33 in the sleeve 17 engaging a radial surface 36 of the valve. To release the valve, so as to allow it to return to direct gear position after supply to the passage 26 has been cut off, pressure fluid must be supplied to passages 31, 30 so as, firstly, to retract the piston 33 with its pin and, secondly, to engage a friction clutch 11 which is arranged between the sun 7 and the carrier 2 and which serves to synchronise the parts so as to prevent shock, particularly when the vehicle is overrunning. The supply of pressure fluid to passage 26 may be controlled manually or automatically by speed, while the. supply to passages 30, 31 can occur only when supply to passage 26 has been cut off. A main change-speed gear is arranged in front of or behind the planetary gear.