Patent GB-622825-A (GB)
Title: Improvements in or relating to variable speed transmissions
IPC: F16H3/78
Filed: 1946-02-27
Abstract: 622,825. Hydrochemical variable-speed gearing; claw clutches. BORG-WARNER CORPORATION. Feb. 27, 1946, No. 6095. Convention date, March 8, 1943. [Class 80 (ii)] In a hydromechanical variable-speed gear comprising a direct-drive positive clutch bridging a series arrangement of hydraulic transmitter and torque-multiplying epicyclic gear, the epicyclic gear is rendered effective by a one-way brake which over-runs when the clutch is engaged, means such as repelling teeth being 'provided to prevent clutch engagement so long as there is a relative rotation between the input and output shafts. As shown applied to a motor vehicle transmission, an input shaft 10 carries rigidly both the converter impeller 12 and the driving member of a claw clutch 36'whose driven member 30 is slidably splined inside the tubular end of an output shaft 11 to which the driven annulus 24 of the epicyclic gear is secured. The converter runner 14 powers through a tubular shaft 15 the carrier 27 of interengaging planets 25, 26 meshing the annulus 24 and a reaction sun 22 respectively. An outer tubular shaft 17, which can be held against backwards rotation by a fluid-operated brake 21 acting through a one-way roller detent 19, is rigid with the sun 22 and, through a one-way roller clutch 18, prevents relative backwards rotation of the converter reaction element 16. Direct and reduced forward drives, with the brake 21 engaged, are therefore provided by engagement and disengagement respectively of the clutch 36. For reverse drive, the brake 21 and clutch 36 are released and a positive detent 64 is spring- projected into the path of teeth 65 on the carrier 27 to station the latter and the turbine 14. The impeller 12 then drives the element 16 and the annulus 24 reversely. The clutch 36 is engaged by fluid pressure acting on the rear of the member 30, and disengaged by a spring 32, only when the output shaft 11 overruns the input shaft 10 on vehicle coasting, bevelled clutch teeth 35a, 31a being provided to ensure this at engagement. Combined manual and automatic gear-controlling means are provided. A manual forward-reverse lever 41 actuates both a switch 74 controlling through a solenoid 66 the detent 64, and a valve 39 monitoring the flow of pressure fluid to the operating cylinder 44 of the brake, 21 and to a solenoid valve 47 controlling the clutch 36. A centrifugal governor 63 driven from the output shaft 11 closes a switch 59, to energise the solenoid 49 of the valve 47 and move the latter to the left against spring pressure, when the vehicle is travelling above a predetermined speed. With the lever 41 in its central position, as shown, the transmission is in neutral, the switch 74 being closed to energise the solenoid 66 and hold the detent 64 inoperative, the fluid supply conduit 37 being closed by the valve 39, and the brake 21 and clutch 36 being rendered inoperative by connection to exhaust conduits 42 and 50. Anticlockwise rotation of the lever 41 maintains the switch 74 closed but opens the supply conduit 37 to engage the brake 21. With the switch 59 open the clutch 39 remains disengaged to give reduced forward drive. When the vehicle exceeds the predetermined speed the switch 59 closes and the valve 47 is moved to supply fluid to the clutch 36. Accelerator release then brings in direct drive. Upon the vehicle speed falling sufficiently to re-open the switch 59, accelerator release again engages reduced forward drive. Clockwise rotation of the lever 41 from its central position maintains the supply conduit 37 closed but opens the switch 74 to allow the detent 64 to engage under spring pressure and bring in the reverse drive. Both the solenoids 49, 67 have operating and holding coils in parallel, the former being cut out by armatureactuated switches 57, 70 respectively.