Patent GB-938779-A (GB)
Title: Improvements relating to variable-speed power transmissions for powered vehicles
IPC: F16H47/08
Filed: 1961-11-27
Abstract: 938,779. Hydro-mechanical variable-speed gear. C. SCHULER-VOITH, M. VOITH, H. W. SCHWEPPENHAUSER, and C. KNAPP, [trading as VOITH - GETRIEBE KOMM.-GES.]. Nov. 27, 1961 [Dec. 2, 1960], No. 42359/61. Class 80 (2). [Also in Group XXIX] A motor vehicle variable-speed gear comprises a torque-splitting planet gear in which a first main part is connected to an input (engine) shaft, a second main part is connected to a first, purely mechanical, transmission path, and a third main part is connected to a second, fluid, transmission path which is arranged in parallel with the first path and includes an hydrodynamic torque converter and a fluid coupling or mechanical clutch in parallel, the second and third main gear parts being selectively brakable, and an output shaft connected to the ends of the two transmission paths being connected to the first path through a one-way clutch. A further, multi-stage, planetary change-speed gear or reverse gear may be arranged to follow. As shown, the planet gear comprises an input sun 2, a sun 5 on a shaft 18 brakable at B 2  and connected to an intermediate output shaft 10 through a one-way clutch F, and stepped planets 3, 3<SP>1</SP> on a carrier 4 brakable at B 1  are connected to impellers 6, 7 respectively of an emptiable torque converter W having a fixed reactor and an emptiable fluid coupling K the turbines 8, 9 of which are fast on the shaft 10. A following reverse gear comprises wheels 11, 12 on the shaft 10 respectively meshing a wheel 13 and, through an idler 14, a wheel 15, a forward and reverse clutch 17 selectively connecting the sheels 13, 15 to a final output shaft 16. During idling, the converter W and the fluid coupling K are empty and the brakes B 1 , B 2  released. For first gear, the converter W is filled providing fluid/ mechanical split-torque drive with the oneway clutch F engaged. For second gear the converter W is emptied and the fluid coupling K filled providing fluid/mechanical split-torque drive with the one-way clutch F engaged. For third gear the fluid coupling remains filled and the brake B 2  is applied providing allfluid overdrive, the one-way clutch F releasing. For fourth gear the fluid coupling is emptied and the brake B 1  is applied for all-mechanical overdrive through the one-way clutch F. A possible further pure converter stage is not included. In Fig. 1a (not shown), the steppedplanet gear is replaced by a sun-ring train comprising an input carrier and a sun and ring respectively connected to the shaft 18 and the impellers 6, 7. In Fig. lb (not shown), the Fig. 1 train is modified by the addition of brakable rings respectively meshing the planet steps 3, 3<SP>1</SP>. In Fig. 3 (not shown), the separate fluid coupling is dispensed with, the torque converter having a releasable reactor so that the converter may function as a fluid coupling. The reactor may react on a one-way detent or be selectively held by a brake which may act directly on the reactor or be arranged in series or in parallel with the one-way detent. The turbine is connected to the intermediate output shaft through a further one-way clutch to reduce converter windage loss or in order that the converter need not be emptied. In Fig. 5 (not shown), in which a sun-ring planet gear comprises an input carrier geardriven from a parallel shaft, a brakable ring connected to output through a one-way clutch, and a brakable sun connected to the impeller of a torque converter having a turbine connected to output through a further one-way clutch, the torque converter is bridged by a mechanical clutch, is continuously filled, and its reactor both reacts on a one-way detent and may be directly selectively braked. The oneway clutches may be locked. For first gear the brakes are released for fluid-mechanical split-torque drive; for second gear the mechanical clutch is engaged for all-mechanical split torque 1/1 drive; for third gear the sun is braked for all-mechanical overdrive; and for fourth gear the ring is braked and the clutch engaged for all-mechanical overdrive. Seven engine braking stages may be obtained, four of which additionally provide hydrodynamic braking in the converter. The mechanical clutch may be arranged in the converter core or between discs carrying the impeller and turbine blades. In Fig. 5a (not shown), the sunring gear of Fig. 5 is replaced by one in which interengaging planets on a brakable carrier connected to output through a one-way clutch engage an input ring and a brakable sun connected to the converter impeller and the clutch. Reduction planetary gearing (not described) may replace the overdrive planetary gearing. Depending on the type of converter selected (designed turbine/impeller speed ratio and relative rotational direction) and the gear design (relative rotational direction and speed ratio of the second and third main parts) a further reversing and/or speed-reducing gear may be provided either before or behind the converter, the clutch and/or the purely mechanical path. The Specification includes details of gear stage gradation, and of the relation between converter maximum efficiency and the speed ratio of the second and third main parts of the gearing.