GB621762A - Improvements in or relating to variable speed power transmission mechanism - Google Patents

Abstract

621,762. Hydromechanical variable-speed gearing. FORD MOTOR CO., Ltd. Oct. 16, 1946, No. 30778. Convention date, Nov. 14, 1945. [Class 80 (ii)] In a change-speed gear for motor vehicles having in combination a hydraulic. coupling used only in first speed and a multiple planetary gearing used in first and second speeds and locked in third speed for a direct drive, the speedchanges normally being controlled by speed-responsive hydraulicallyoperated clutches, manual control means are provided which, for engine braking purposes, simultaneously force a downshift from third to second speed and change the latter from a unidirectional to a bidirectional drive. As shown, applied to a gear of the kind described in Specification 615,175, stepped planets 25-27, Fig. 2, mesh respectively a sun 28 connected to a clutch carrier 21, a sun 29 on an intermediate shaft 14, and a driven sun 31. In first speed, the sun 29 is driven through a hydraulic coupling 17, 18 and a one-way clutch 19. In second speed, a hydraulicallyoperated clutch 22 is engaged to by-pass the coupling and drive the sun 28, the clutch 19 overrunning. A one-way brake 32 prevents reverse rotation of the planet carrier 23 in both these speeds. For third speed, which is direct drive, a hydraulically-operated clutch 24 between the members 21, 23 is additionally engaged to lock up the gearing. Pressure fluid for the clutches 22, 24 is supplied by a pump 38 through conduits 39, 41 and is controlled by a valve 42 regulated by a centrifugal governor 43 on the member 21. A brake drum 62, Figs. 1 and 3, is bolted to the planet carrier 23. When positioned, the inner rim of the drum engages arcuate flanges 68 on the planet axles 66 to prevent their rotation, spaced cut-aways on the rim being provided for initial assembly. A brake' band 71 is constricted on the drum 62 when pressure fluid from the pump 38 is supplied to an operating piston 76, Fig. 3, via a conduit 85 and a rotary valve 82 which may be turned to connect the conduit 85 either to the pump or to exhaust.. A second rotary valve 47, Fig. 6, controls the supply of pressure fluid from the pressure chamber 46 of the pump 38 to the conduit 41. The valve 47 may be turned by a quadrant arid pinion 60, 61 to bring a bore 40 in the valve body, connected with the conduit 41 through bores 51, 52 out of register with the discharge outlet 48 of the chamber 46 so as to cut off the fluid supply to the third speed clutch 24. The quadrant 60 is actuated against a spring 56a by one or other of two arms, 53, 54 independently pivoted on a collar 56 on the quadrant axle and acting on the collar through abutments 58. The arm 53 is linked to the accelerator pedal (not shown) to give a forced downshift from third to second speed upon kickdown thereof. The arm 54 is linked to a control knob (not shown) on the vehicle dashboard, and is connected by links 91, 94, Fig. 1, to the control arm 97 of the valve 82, so that operation of the control knob not only forces a downshift from third to second speed, but engages the brake 61 to provide a bidirectional drive through the gearing and allow engine braking, on downgrades.