GB1212004A - Remote control apparatus for controlling shift operation of a forward/reverse gear - Google Patents

Abstract

1,212,004. Change-speed control. S.R.M. HYDROMEKANIK A.B. 17 Nov., 1967, No. 52510/67. Heading F2D. In a fluid pressure remote control of a Forward-Neutral-Reverse epicyclic gear following an electric motor or I.C. engine-driven hydrodynamic torque converter in a motor vehicle, positive clutch, brake or sliding gear ratioestablishment is facilitated by sequentially (i) braking the -F-N-R gear output, (ii) braking the -F-N-R gear input, (iii) permitting energization of a ratio-establishing pneumatic servomotor 23, and (iv) releasing the -F-N-R gear input to enable the ratio-establishing teeth to suitably align and engage. The epicyclic gear (Fig. 1, not shown) comprises an input sun (8) connected to a torque converter turbine (4), an output ring (11), and a carrier (9) axially slidable, from a Neutral position, rightwards, to engages a dog clutch (13), (14) between the carrier and ring, for solid 1/1 Forward, and leftwards, to engage a dog brake 15, 16 to station the carrier, for Reverse. The carrier is axially shifted by a fork 19 fast with a piston-rod 20 of the servomotor 23, the latter having two pistons 21, 22 displaceable between stop rings 24, 25, 26 on the rod so as to be movable before fork displacement. In operation, when the vehicle wheel brake pedal is fully depressed so as to station the -F-N-R gear output, a detent R<SP>1</SP> is actuated, by wheel braking system pressure, to release an -F-N-R Selector valve A. On movement of the latter from Neutral to Forward or Reverse, a Neutral line 29 is vented and a Forward line 30 or a Reverse line 31 pressurized, the latter being blocked, at this stage, by a rightwardly positioned Blocking valve 32. At the same time, pressure in the line 30 or 31 is directed through a 3-way shuttle valve 33 to a spring loaded Synchronizing valve 35. When the latter is moved rightwards by said pressure, the latter is directed through a Safety valve 28 (open in Neutral) to a servomotor 17 to apply a Synchronizing brake 18 to the sun 8 i.e. the -F-N-R gear input. At a predetermined pressure in the Synchronizing brake servomotor 17 sufficient to stall the turbine, a valve 41A allows pressure to be applied to leftwardly shift the Blocking valve 32 to connect the lines 30, 31 to lines 42, 43 for appropriate energization of the servomotor 23 and shifting of the fork 19. Whilst clutch or brake engagement may be thereby fully completed, more often the end faces of the clutch or brake dogs abut. Pressure directed to the servomotor 23 is therefore also directed through a 3-way shuttle valve 47 and a line 48 to the Synchronizing valve 35 and when pressure builds to a predetermined value the Synchronizing valve 35 is leftwardly returned and the Synchronizing brake servomotor 17 is vented so that the turbine may start to rotate and the clutch or brake engage. To maintain the Blocking valve 32 in its leftward position when the Synchronizing brake servomotor pressure falls, the line 48 is connected for pressure therein to act leftwardly on a piston 50 of the Blocking valve. Upon a subsequent shift, the Selector valve A passes through Neutral and pressure in the line 29 is directed to act on the other side of the piston 50 to return the Blocking valve to its blocking state. To ensure Synchronizing brake release on gear establishment, the Safety valve 28 is acted on by the piston-rod 20 at its end positions to vent the Synchronizing servomotor 17. In systems where the torque converter reactor is releasable, pressure may be directed from the servomotor 23 in its Neutral position to effect the reactor release. Further, pressure to the Synchronizing brake servomotor 17 may be used to release the reactor. The servomotor 17 may be arranged to act indirectly on the synchronizing brake via a further valve. The dog clutch and brake teeth may be suitably chamfered at one side (Fig. 3, not shown) to assist engagement.