Patent GB-1163972-A (GB)
Title: Improvements in Serve-Controlled Change-Speed Transmissions of Vehicles
IPC: F16H63/44
Filed: 1966-12-20
Abstract: 1,163,972. Controlling change-speed gears; friction clutches. SOC. ANON. ANDRE CITROEN. 20 Dec., 1966 [23 Dec., 1965; 29 March, 1966], No. 57056/66. Headings F2C, F2D and F2L. In a vehicle change-speed gear having at least one ratio establishing selector clutch actuated by a servo-operated selector fork, a friction clutch 10 being automatically disengaged during ratio shifts by a control relay 111 tripped by members operatively connected to the fork, a lost motion connection between the selector clutch and the fork ensures that during a ratio shift the initial stroke of the fork, corresponding to the lost motion, trips the relay 111 to disengage the clutch 10 prior to the shift, the relay 111 being actuated for clutch 10 engagement at the end of the fork movement corresponding to establishment of a new ratio. Gearing.-An engine output shaft 14 drives the input shaft 1 of the change-speed gear via a hydrodynamic torque converter 11 and an hydraulically actuated friction clutch 10. Parallel input and output shafts 1, 2 carry constantly meshed gear pairs 4<SP>1</SP>-4, 5-5<SP>1</SP>, 6-6<SP>1</SP>, for Low, Intermediate, and High forward ratios and gears 3-3<SP>1</SP> connected by an idler (not shown) for Reverse. Gears 3, 4, 5, 6 are loose on their shafts and are selectively clutched thereto by double dog clutches 7, 8 actuated by forks 50, 51 respectively secured to shift rods 52, 53 actuated by opposed pistons 55, 56 and 61, 62 and urged to central neutral positions by springs 58, 59, 63, 64. Each fork engages its clutch with an axial play of 2j. Gear control.-Each ratio is established by admitting hydraulic fluid from a pressure line 82 to a respective one of pistons 56 (Reverse), 55 (Low), 62 (Intermediate), 61 (High), by energizing respective solenoid valves ER, EI, EII, EIII, from a manually or automatically controlled selector switch 97. When not energized, the valves connect their pistons to an exhaust line 78 leading to a reservoir G. A line 95, 96 returns leakage fluid from the valves. Interlocks.-A bar 110 engageable with grooves 106, 108 in shift rods 53, 52 prevents both rods from being out of neutral simultaneously. A bar 105 engageable with the groove 106 of rod 53 is displaced to open contacts 100 in the circuits of solenoids ER, EI when Intermediate or High are engaged, and a bar 107 engageable with the groove 108 of rod 52 is displaced to open contacts 103 in the circuits of solenoid valves EII, EIII when Reverse or Low are engaged. The Friction Clutch 10, in the torque converter housing 12, comprises a driven disc 19, secured to the shaft 1, between an input member 17, secured to the torque converter turbine 16, and a pressure plate 18. Plate 18 and member 17 form a fluid-tight chamber 21 connected by lines 22-24 to a clutch control valve 25. The housing 12 forms a second chamber 26 surrounding the clutch 10 and connected to the valve 25 by lines 27-29. Valve 25 connects the chamber 21 to a pressure line 35, supplied by a pump 36 from a reservoir 42, and chamber 26 to a return line 44 including a cooler 45 for clutch disengagement. For clutch engagement, chamber 26 is connected to pressure line 35 and chamber 21 to return line 44, a relief valve 46 opening in this case to allow flow from the torque converter to the cooler 45. Main clutch control.-With the gear in neutral, a spring 116 holds the spool 112 of relay valve 111 in a position connecting pressure line 82 to a chamber 115 of the valve 25, causing a piston 32 to hold the spool 30 of valve 25 in its clutch-disengaged position, against the action of a spring 31. When one of the shift rods 52, 53 is moved to a gear establishing position, one of shoulders 122-125 thereon acts via levers 120, 121 to move the relay valve spool to connect chamber 115 with exhaust line 78, allowing spring 31 to move the spool 30 to its clutch engaged position. Operation.-With the vehicle at rest, gear in Neutral, and main clutch disengaged, switch 97 is moved to contact CI to energize valve EI, admitting pressure fluid to piston 55 to move selector clutch 7 to engage the gear 4 for low. As the shift rod 52 reaches the end of its travel, shoulder 122 moves lever 120 to trip relay valve 111 causing clutch 10 engagement. (Reverse is engaged in similar manner, using contact CR). For shift to Intermediate, switch 97 is moved to contact CII, de-energizing valve EI so that spring 59 returns shift rod 52 to neutral, initial movement to take up the lost motion 2j causing shoulder 122 to release lever 120 for clutch 10 disengagement prior to selector clutch 7 disengagement. Holding contacts (133) (Fig. 2, not shown) prevent energization of valve EII, or any other of the valves, until the clutch 10 is fully disengaged. Then valve EII is energized causing piston 62 to move selector clutch 8 to engage the gear 5 for Intermediate. As shift rod 53 reaches the end of its travel, shoulder 125 acts on a lever to trip relay valve 111 for clutch 10 engagement. Other shifts are similar. Modifications.-An automatic clutch, e.g. centrifugal or electromagnetic, may replace the torque converter, and the clutch 10 may be electromagnetically actuated, with suitable modification of the control circuits. Ratio selection need not be sequential.