GB617901A - Improvements in or relating to hydromechanical transmissions - Google Patents

Abstract

617,901. Hydraulic power transmitters. BORG-WARNER CORPORATION. Feb. 26, 1946, No. 5958. Convention date, May 5, 1943. [Class 69 (ii)] [Also in Group XXIV] A hydro-mechanical variable-speed gear com. prises a hydraulic torque converter, the reaction member of which is rotated through gearing whilst taking reverse torque, but is allowed to rotate freely under forward torque by the automatic release of a coupling unit taking the gearing reaction. As shown applied to a motor vehicle transmission, the reaction member 55 of a hydraulic torque converter, the pump 52 and turbine 54 of which are connected to input and output shafts 50, 51 respectively, is rotated either forwardly or reversely from the shaft 51 whilst taking fluid torque reaction. Rigid with the shaft 51 are the interengaging planet carrier 63 and sun 72 of two epicyclic gears, the annuli 58, 71 of which are alternatively connectible by friction clutches 64, 78 to the hollow shaft 56 of the reaction member 55. The remaining sun 60 and single planet carrier 74 are unitary and are prevented from reverse rotation by a one-way roller detent 76 so that engagement of the clutches 64, 78 causes respectively forward and reverse rotation of the reaction member whilst the latter is taking fluid torque reaction. When such reaction ceases, the detent 76 allows free forward rotation of the reaction member, the engaged epicyclic gear idling. Engagement of the clutch 64 gives less torque magnification in the converter and fluid torque reaction on the reaction member up to higher output speeds than would be the case with a stationary reaction member, whilst engagement of the clutch 78 has the reverse effect. The clutches 64, 78 each comprise inner and outer clutch discs splined respectively to the annulus 58 or 71 and to a member 66 rigid with a flange 65 on the shaft 56, and are alternatively hydraulically operated by pistons 69, 82. Pressure fluid is supplied to one or other of the pistons from a conduit 92 and exhausted from the inoperative piston through a conduit 90 or 91, according to the axial position of a valve member 83 having lands controlling ports 88, 89 leading to the pistons. The valve member 83 is spring-loaded to engage the clutch 78, but is movable to engage the clutch 64 upon full depression of the vehicle engine accelerator pedal 94 acting on the valve through a Bowden cable 97. In Figs. 1 and 3 (not shown) giving respectively permanent forward and reverse rotation of the reaction member whilst. taking fluid torque reaction, one epicyclic train only, having its annulus rigid with the reaction member, is used in each case.