Transmission

863,815. Change-speed control. GENERAL MOTORS CORPORATION. April 3, 1959 [April 25, 1958], No. 11377/59. Class 80 (2). The hydraulic circuit controlling a changespeed gear described in Specification 809,761 is modified by a ratio-establishing pressure-control valve 640, Fig. 7, replacing an hydraulic accumulator and operating to vent a pipe 425, the pressure in which is the same as that in a pipe leading to the ratio-establishing servomotors, to a restricted exhaust 648 during establishment of a newly selected ratio so as to obtain cushioned engagement, the working of the valve being modulated by the pressure in a pipe 90 connected to a torque converter by-pass clutch disengaged during ratio shifts and the valve itself comprising two pistons 641, 644 biased apart by a spring 647. Gearing.-A shaft 1, Fig. 2, drives the impeller of a torque converter 10 having its turbine driving through a shaft 8 to the ring gear 26 of a simple planetary train having planet pinions 31 meshing a sun-gear 34 and mounted by a carrier 32 upon an intermediate shaft 33. The torque converter 10 has two stators 9 carried upon the gear case by one-way detents, and may be filled by supplying oil under pressure through a pipe 100 and emptied by allowing the oil to flow out through a pipe 101. By supplying oil under pressure through a pipe 90, a servomotor 21 is energized to engage a disc clutch 16 which connects the input shaft 1 to the turbine and the shaft 8 of the torque converter, which is accordingly by-passed. A hydrodynamic brake 25 is filled by supplying oil through a pipe 180 to retard rotation of the shaft 8 and is emptied via a pipe 181. By supplying oil under pressure through a pipe 170, a servomotor 39 is energized to engage a clutch 38 which connects the sungear 34 and the planet carrier 32, so that the planetary gear is locked solid for direct drive. If, however, oil under pressure is supplied through a pipe 150 to engage a brake 35, the sun gear 34 is stationed, and a step-down drive from the shaft 8 is'obtained to the intermediate shaft 33. Sun gears 58, 71 of two parallel planetary trains 20, 46 are mounted upon the intermediate shaft 33. By supplying oil under pressure through a pipe 270, a servomotor is energized to apply a brake 72 which stations the ring gear 66 of the train 46, so that a step-down low ratio is obtained from the shaft 33, through planet pinions 67 mounted upon a carrier 68 and meshing the sun-gear 71 and the ring-gear 68, to an output shaft 69. B