Patent GB-918342-A (GB)
Title: Improvements in change-speed transmissions
IPC: F16H47/08
Filed: 1961-05-17
Abstract: 918,342. Hydromechanical variable-speed gear; securing gear wheels on shafts. GENERAL MOTORS CORPORATION. May 17, 1961 [Sept. 16, 1960], No. 17955/61. Class 80 (2). [Also in Groups XXIX and XXXIV] Hydromechanical variable-speed planetary gearing for motor cars gives a first ratio through an hydrodynamic torque converter and a change-speed planetary gearing, a second ratio which is all mechanical through the changespeed gearing, and a third, or direct drive, ratio with torque splitting through the torque converter and the mechanical gearing. An engine flywheel 1 drives through a vibration damper 2 to a shaft 3 fast with which is the impeller 31 of a torque converter which can be emptied and filled, as required. For the first ratio, the torque converter is filled and a first turbine 35 drives through a shaft 42 to the sun gear 50 of a first planetary train 13, the ring gear of the train being stationed by a band brake 64 so that a carrier 51 mounting planet pinions 52 and fast with an output shaft 87 is driven at a reduced ratio. A second turbine 46 fast with a sleeve 54 secured to the planet carrier 51 at the same time rotates forwardly with the output shaft 87, and functions as a forwardly rotating reaction member to re-direct liquid delivered by the first turbine 35 to the impeller 31, so that the re-directed liquid entering the impeller tends to rotate the latter forwardly. Accordingly, in first ratio, the hydrodynamic torque converter acts as a ratio converting device, so that the output shaft 87 is driven partially by mechanical torque multiplication of the planetary gearing 13 and partially by the torque multiplication of the torque converter. To establish the second ratio, the torque converter is emptied, and a fluid pressure operated multi-disc clutch 59 is engaged to couple the impeller 31 to the ring gear 56 of a second planetary train 14, the band brake 64 being maintained engaged. Planet pinions 58 mounted upon a carrier 57 fast with the sleeve 54 mesh the ring gear 56 and also mesh a sun gear 65 which is fast with a sleeve 62 connected to the ring gear of the first planetary train 13. Since this ring gear is now stationed by the band brake 64, the second planetary train 14 gives a reduced ratio drive to the shaft 54, which is fast with the planet carrier 51 of the first planetary train, in turn secured to the output shaft 87. Accordingly an all-mechanical drive is established. For direct drive, the brake 64 is disengaged, the clutch 59 is maintained engaged, and the torque converter is filled. The second turbine 46 now prevents the sun gear 50 of the first planetary train 13 from rotating substantially above the speed of the impeller 31, a split-torque drive being obtained. For reverse, the torque converter is filled, the clutch 59 is disengaged, the brake 64 is disengaged and an hydraulically controlled friction cone brake 70 is engaged to station the ring gear 56 of the second gear train 14. Drive is transmitted through the torque converter to the sun gear 50 of the first planetary train 13, and through the planet pinions 53 and the ring gear thereof to the sun gear 55 of the second planetary train 14, so that the planet carriers 51, 57 of the two trains, which are fast together, rotate in the reverse direction to drive the output shaft 87 backwards. Securing gear-wheels on shafts.-The sunwheel 50 of the first planetary train 13 is formed with widely spaced splines 115, Fig. 8, which engage loosely in splines 117, Fig. 12, on the shaft 42, so that the gear can turn a limited amount relatively to the shaft. A casing 121, Fig. 10, is mounted within a space 127 in the sun gear and has an ear 125 engaging a notch 116 in the gear, so that it is rotationally fast therewith. A resilient annulus is bonded within the casing 121 and has inwardly directed splines 126 engaging closely in the splines 117 at the end of the shaft 42. When the torque converter is empty and the sun-gear 50 transmits no torque, the resilient splines centre the sun-gear upon the shaft 42 and prevent it from rattling. When the sun-gear 50 transmits torque, the resilient splines 126 yield until the splines 115 in the hub of the sun gear engage the splines 117 on the shaft.