GB955691A - Power transmission - Google Patents

Abstract

955,691. Hydro-mechanical variable-speed gear. ROLLS-ROYCE Ltd. Oct. 26, 1961 [Oct. 21, 1960; Dec. 1, 1960], Nos. 36112/60 and 41272/60. Heading F2D. In a variable-speed gear for motor vehicles wherein in at least one gear the drive is split into two parallel paths which are combined to provide the gear output, a two-speed sun-ring train 19, 18, 17 giving overdrive and direct drive, is provided in one of the paths. As shown, in a combined torque converter, or fluid coupling, and variable-speed epicyclic gear, a first planet train comprises an engineconnected ring 3, a carrier 4 connected to the fluid-coupling impeller 6, and a sun 7 which may be clutched to the carrier at 9 or braked at 8 respectively for direct or reduced drive of the impeller, and a second planet train comprises an output carrier 13, a sun 12 connected to the fluid-coupling runner 10, and a ring 14 which for first and second gears is braked, the whole of the drive passing through the fluid coupling, and for third and fourth gears is clutched at 16 to the impeller 6, the drive being split into two paths between the first and second trains, one direct mechanical and one through the fluid coupling. A reversing train compounding with the second train is shown, but not described. For forward drive in first and second gears the ring 14 may be braked directly (Fig. 1, not shown) or, as shown, by a one-way detent 22 braked at 23 which latter need only be released for reverse. As shown, a direct brake 15 for the ring 14 provides for engine braking on overrun in second gear. The overdrive/direct train 19, 18, 17 is arranged in the mechanical path as an alternative to the clutch 16, the carrier 18 and the ring 17 being connected to the impeller 6 and the ring 14 respectively, and the sun 19 being braked at 20 for overdrive. Whilst the overdrive may be used on third and fourth gears it is used only on fourth gear to provide fifth gear. To prevent undesirable high-speed idle overdrive of the sun 19, an hydraulically engaged, spring disengaged, multiplate friction clutch may be provided between the carrier 18 and the impeller 6 and disengaged in first and second gear. The clutches may be, as shown, of the multiplate friction type, hydraulically actuated, or fluid couplings filled and emptied to be engaged and disengaged. The torque converter or fluid coupling 6, 10 may be replaced by an hydrodynamic device acting as a coupling in one range and as a torque converter in another range, or emptied and filled in different drive conditions. Control of the overdrive may be manual and/or automatic, e.g. manual-hydraulic overridden, to return to direct drive, by road speed responsive governor pressure.