Patent GB-623688-A (GB)
Title: Improvements in variable speed power transmission mechanism
IPC: F16H47/08
Filed: 1947-05-13
Abstract: 623,688. Hydromechanical variable-speed gearing. FORD MOTOR CO., Ltd. May 13, 1947, No. 12912. Convention date, June 5, 1946. [Class 80 (ii)] A hydrodynamic torque converter preceding multiple planetary gearing is arranged within an input housing, which is clutched to the converter impeller to give a low speed gear range through the converter and gearing, but is disconnected from the impeller to cut out the converter, and is connected directly to a sun of the gearing, for intermediate and high speed ratios. As shown, applied to a motor vehicle transmission, low and intermediate speed multiplate clutches A, B, Fig. 3, are alternately operable to connect a member 15, driven from the engine flywheel 13 through a spring coupling 14, Fig. 7, either to the converter impeller 16 or to a clutch carrier 26 integral with a sun gear 41. The converter runner 17 is connected through an intermediate shaft 11 with a second sun 42, and a third sun 43 is rigid with the driven shaft 12. The suns 41, 43 mesh stepped planets the carrier 34 of which has a one-way clutch connection with the converter reactor 18 operable to allow the latter to overrun the former forwardly. During the low speed range the carrier 34 is prevented from backwards rotation by a brake 45 acting through a one-way clutch 44, vehicle free-wheeling being prevented by a one-way clutch 49 between the shafts 11, 12 which allows engine braking through the converter at an approximately 1 to 1 ratio. Bidirectional stationing of the carrier 34 by a brake 47 ensures engine braking in intermediate speed. To change from intermediate to high speed, which is direct drive, a third multiplate clutch C is additionally engaged to connect the clutch carrier 26 and planet carrier 34 and so lock up the planetary gearing. A reverse speed range is provided by stationing the clutch carrier 26 through a brake 46 and engaging the clutch A, giving a branched drive through the converter and planetary gearing. Both the clutches and brakes may be automatically controlled by speed responsive means such as a sleeve valve arranged concentrically with the transmission main shaft and moved axially by a centrifugal governor against spring action to monitor the supply of operating fluid to suitable oil or other fluid pressure brake and clutch operating means. As shown, the clutches A, B, C are hydraulically-actuated by expansible fluid chambers 22, 29, 36 supplied with oil or other pressure fluid from a pair of pumps (not shown) powered respectively from the driving member 15 and the driven shaft 12 through pinions 52, 53. The fluid pressure may be caused to vary automatically with engine torque, so that the torque capacity of the clutches is related thereto, by a pressure relief valve employed in connection with the fluid pump and modulated by an expansible vacuum chamber connected with the engine manifold. The modulated fluid pressure so obtained may be caused to act on the above mentioned sleeve valve in opposition to the centrifugal governor so as to give combined torque-speed control of the gearing. A brake 48 on the driven shaft 12 is automatically engageable when the engine is idling to prevent creeping of the transmission in neutral. Operative pressure fluid, supplied by a pump 57, Fig. 6, driven from the pinion 52, is admitted to the brake actuating cylinder when closing of the throttle plate 62 in the carburetter 61 raises the intake manifold engine suction sufficiently to open a vacuumoperated valve 58. The force of application of the brake 48 is also varied to suit the idling speed by means of a by-pass 65, in parallel with a main relief valve 63, and which is ineffective when the fluid is cold and the engine set to idle at high speed but passes enough fluid to lower the relief pressure and reduce the force of brake application when the fluid is warm and the engine therefore set for slow idling. A variable orifice 66 may be provided for initial adjustment