GB808339A - Improvements relating to variable speed driving systems - Google Patents

Abstract

808,339. Change-speed gear. VOITH G.m.b.H., J. M. Sept. 10, 1957 [Sept. 27, 1956], No. 28559/57. Class 80 (2). [Also in Group XXIX] In a vehicle or similar drive system having a gas turbine 101 driving through an hydrodynamic gear including a turbo torque con. verter W in a low-speed range and one, two, three or more high-speed ranges introduced by fluid couplings, electro-magnetic or friction clutches or brakes, the characteristic of the torque converter is such that the gear can accept torques only below those which would result in thermal overloading of the gas turbine. Thus, in Fig. 2, the curve 30 is the torque-speed characteristic of the gas turbine. The input torque-speed characteristic of the torque converter is chosen as that curve 32 lying outside the shaded area 31 which is the operating range where thermal overloading of the gas turbine occurs. A torque converter characteristic, such as 34 passing through the area 31 is unsatisfactory. The intersection 33 of the curves 30, 32 represents the shift point from torque converter to the high-speed fixed-ratio range which then follows the curve 30. Three different gear arrangements for a gas-turbine locomotive are shown. In one, Fig. 4, the gas turbine 101 drives jointed axle-drive shafts 115 through a reduction gear 102, the hydrodynamic gear, and a reverse gear 114. The torque converter W has a reactor with a one-way detent 117, and its turbine 105 drives a low-speed stage 106 through a one-way clutch 109, which overruns when a friction clutch K, which may be inside the converter, is engaged to introduce a wholly mechanical high-speed stage 108. The driven wheels of the two stages 106, 108 also form input wheels of the reverse gear which includes an idler 111 and forward-reverse clutch 114. Fig. 1, not shown, has two high-speed stages introduced by filling separate fluid couplings and emptying the torque converter through two valves. Control may be automatic in response to output speed, torque or fuel supply setting. A combined converter and coupling may be used. In Fig. 5 the low-speed drive is torque-split by a planet gear having an input sun 202 driven by the gas turbine 201, a sun 206 on a final output shaft 211, and a planet carrier 205 attached to the impeller 208 of the torque converter W, the turbine 209 of which is connected to output 211 through a one-way clutch 210. The last-named overruns when a band brake 214 is applied to the planet carrier for wholly mechanical overdrive. The brake 214 is applied automatically in response to output speed by supplying fluid pressure to a brake-apply piston 224 from an output-driven pump 215 through a spring-loaded valve 221, which opens when the speed-responsive pump pressure reaches a predetermined value. Multiple converters and couplings in parallel may be used. Converters may be cut out by displacement of their turbines.