Patent GB-1223947-A (GB)
Title: Shifting mechanism for multi-speed transmission
IPC: F16H63/44
Filed: 1969-06-23
Abstract: 1,223,947. Change-speed control. DR. ING. h.c.F. PORSCHE K.G. 23 June, 1969 [9 July, 1968], No. 31582/69. Heading F2D. A manually-operated shift-mechanism for a motor-vehicle C.S.G. providing four forward speeds and reverse comprises a disc-shaped shift plate 22, having the usual cam slots 20, 21 controlling striker forks 16, 17, rotated by a rack and pinion 25, 24 via a follow-up type hydraulic servomotor 26 controlled by a stepby-step selector valve 32 manually moved via a lever and ratchet 42, 41, the striker forks 16, 17 controlling positive dog-type clutch sleeves 16<SP>1</SP>, 17<SP>1</SP> for selective engagement of one or other output gears 3, on an output shaft 10<SP>1</SP>, in one or other pair of two separate two-speed constantmesh gear units, in parallel, the input gears 3 of which are mounted on separate coaxial shafts 4, 5 selectively drivingly connected via one or other of a pair of hydraulically operated main clutches 6, 7 to an engine crank-shaft 8, the shift-plate 22 having externally profiled control surfaces 45, 62 engaged by a shifting phase valve 39 and a clutch valve 60, respectively controlling both the rotational speed of the plate 22, i.e. speed of shift &c., and the selective engagement and disengagement of the pair of main clutches 6, 7 during each shift. Forward or backward movement of the step-by-step manual selector valve 32 via the lever 42, for an upshift or downshift, connects one or other side 35, 36 of the follow-up servomotor 26 to a pump pressure fluid source 46 via the shift phase valve 39 and ducts 47, 48 to rotate the shift plate 22 and rapidly move one or other clutch sleeve 16<SP>1</SP>, 17<SP>1</SP> for selection of the next gear, whilst still maintaining engagement of the existing gear, after which the shift phase valve 39 is moved by the shift plate control surface 45 to close duct 48 and open a duct 49 having a restrictor 50 to slow down the movement of the servomotor 26 and hence the rotational speed of the shift plate. Shifting from first to second gear, for example, and simultaneously with the displacement of the shift phase valve 39, the clutch valve 60 is moved by the shift plate control surface 62 to sever the connection between the pressure duct 47 and a clutch duct and accumulator 69, 58 and vent duct 59 to a tank 51 whereby the pressure in the annular chambers 55 and 57 of clutches 6 and 7, respectively, drops and the clutch 6 associated with first gear is disengaged whilst clutch 7, associated with second gear, is engaged for drive in second gear. By means of the shift plate 22, which continues to slowly rotate, the shift phase valve is again returned to its illustrated starting position, by the control surface 45, and re-connects the ducts 40 and 47 via the duct 48 to again rapidly rotate the plate 22 to disengage the first gear dog clutch 16<SP>1</SP> via the shift-plate slot 20, after which, i.e. the shift operation from first to second is accomplished, the follow-up servo is again in the illustrated starting position with respect to the selector valve slide 32 whereby the fluid pressure supply is interrupted and the shift plate accordingly stopped, ready for the next manual shift. A pedal-operated valve 73, in the pressure duct 47, effects fluid pressure regulation for starting the vehicle in first or reverse gear.