GB924185A - Continuously variable speed - Google Patents

Abstract

924,185. Hydro-mechanical variable-speed gear. FORD MOTOR CO. Ltd. Aug. 29, 1960 [Aug. 29, 1959], No. 29749/60. Class 80 (2). In a combined hydrostatic transmission and planet gear for motor vehicles, planets 40 on an input carrier 36 mesh an output ring 22 and a sun 23 which latter acts as a reaction member or drives an adjustable swash-plate pump 24 in closed circuit with an adjustable swash-plate motor 26 which is drivingly connectible to output through a friction or positive dog clutch 28. In the arrangement shown, which is suitable for front wheel drive or rear engine arrangements, the ring 22 is mounted on a hollow shaft 29 carrying a bevel pinion 30 meshing an output differential crown wheel 31. An input driven gear type pump 33 supplying transmission and control oil is arranged behind or, as shown, before a separating clutch 37. The sun 23 drives the hydrostatic pump 24 directly or through epicyclic or, as shown, conventional reduction gearing. Servomotors 38, 39 control motor and pump swash-plates 27, 25 respectively. The sun 23 may be braked by hydraulic locking of the pump or by a friction or a positive dog brake 34 which may be a one-way brake when the pump reaches maximum piston displacement. The clutch 28 and the brake 34 may be engaged by mechanically, hydraulically or electrically actuated engaging means. In operation, with the pump swash-plate 25 not tilted, the sun 23 idly overruns. By tilting the pump swash-plate the then driven motor 26 which has its swash-plate tilted to a high angle for low speed, high torque, drives the output shaft 29 through the engaged clutch 28. The output shaft is accelerated by swash-plate control until the speed of the output ring 22 exceeds that of the input carrier. The sun will first slow down, come to rest, and then, as it is urged to rotate backwards, the brake 34 and clutch 28 are simultaneously respectively engaged and disengaged, and the ring is overdriven for wholly mechanical transmission through the planet gear. For engine braking and towed starting, the output ring 25 drives the input carrier 36, the sun 23 being braked; alternatively, for a higher carrier speed, the clutch 28 may be engaged and the swash-plates appropriately controlled so that the motor drives the pump and hence rotates the sun. For reverse, the swash-plates are appropriately controlled to reversely rotate the motor 26 and the clutch 28 is engaged. In Fig. 2 (not shown) the pump and motor are coaxially close-coupled and offset parallel to the input and output shaft. In a conventional vehicle arrangement (Fig. 3, not shown), the input and output shafts extend from opposite sides of the gearing. In transversely mounted engine arrangements (Figs. 4 and 5, not shown) the output ring is geared to the differential cage on the driving axle. The gearing may be controlled manually or automatically depending on speed and load by means not described.