Patent GB-927163-A (GB)
Title: Hydro-mechanical infinitely variable transmission
IPC: F16H41/26
Filed: 1960-02-01
Abstract: 927,163. Hydrodynamic torque-converters. BORG-WARNER CORPORATION. Feb. 1, 1960 [Feb. 4, 1959], No. 3549/60. Class 69 (2). [Also in Group XXIV] A variable - speed transmission for vehicles comprises a hydro - dynamic torque converter 15 followed by a torque-combining simple planetary gear 16. Gearing.-The torque converter comprises an impeller 23 fast with an input shaft 10, a turbine 24 having blades 31, 33 and splined to a planet carrier 46 of the gear 16, a floater member 25 having blades 35, 36, and a reactor 26 held unidirectionally by a oneway detent 21. The planetary gear 16 comprises the driving planet carrier 46 which has intermeshing planets 44, 45 meshing respectively a sun-gear 42 and an output ring-gear 43. The floater member 25 can be held unidirectionally by a one-way clutch 22 on applying a band brake 17, so that the member 25 acts as a reactor at low speed ratios of the converter and floats at high speed ratios. Due to its having two sets of blades the floater member serves to redirect the fluid even when it is floating. The floater can be coupled to the sun 42 of the gear 16 by engaging a multi-plate clutch 20 so that it acts as a turbine at high speed ratios. The floating member causes the coupling point of the converter to occur at a higher speed ratio (output speed; input speed) than would otherwise be the case, and after the coupling point has been reached it increases the torque transmissible by the converter and reduces slip, thus rendering a lock-up clutch unnecessary. The converter has a rising instead of a drooping k curve, k being defined as the input speed of the converter divided by the square root of the input torque, enabling the transmission as a whole to be better matched to the vehicle engine, thus causing the engine speed to be maintained in its high torque region for longer periods as the vehicle is accelerated than would be the case with a conventional three-element converter, and it also has greater efficiency. All the blade angles are specified. Function.-Two forward driving ranges and reverse and three degrees of engine braking are provided. A " drive " range is provided by applying the brake 17 and engaging clutch 20 so that the floater 25 and sun-gear 42 are held against reverse rotation at low speed ratios and the gear 42 is driven forwardly by the floater at high speed ratios of the converter. In order to obtain greater acceleration at certain vehicle speeds a " performance " range is provided by stationing the sun-gear 42 by a brake 18, releasing clutch 20 and holding the floater oneway by applying brake 17. The planetary gear 16 thus provides a reduction ratio throughout the entire range. Performance curves are given. For reverse drive a band brake 19 is applied to station the planet carrier 46 and the turbine 24. Clutch 20 is engaged so that the floater member 25 drives the sun-gear 42 in reverse. The greatest braking effect is obtained by engaging brake 19 and clutch 20 as for reverse. The turbine is stationed and the floater member is driven forwardly by the ring gear and causes toroidal flow of fluid in the converter in the opposite direction to that caused by the impeller. Opening the vehicle throttle causes the impeller to generate flow in opposition to the floater member flow thus reducing the torque absorption in the converter and so controlling the braking effect. A lesser braking effect is obtained by applying brakes 17, 18 with the clutch 20 engaged. The turbine is driven forwardly and causes flow of fluid through the converter opposite to that produced by the impeller. The floater is held stationary and absorbs most of the energy, the rest being transmitted from the impeller to the vehicle engine. The lightest braking is obtained with only the brake 18 applied so that the sun 42 is stationary. The ring gear 43 drives the turbine 25 at a step-up ratio, driving the fluid reversely through the torque converter and the energy is transmitted to the impeller and thence to the engine. The floater idles and does not aid in the braking. Modifications.-A modification shown in Fig. 15 is identical with the embodiment shown in Fig. 2 except for an additional one-way clutch 170 interposed between the one-way clutch 22 and the brake 17, and the sun-gear 42 is connected to the common race of the oneway clutches. A further modification is described in which the connections of brake 17 and sun 42 to the clutch 170 are interchanged.