Patent GB-753436-A (GB)
Title: Improved variable-speed power transmission mechanism and control system therefor
IPC: F16H47/08
Filed: 1954-11-10
Abstract: 753,436. Change-speed gear. GENERAL MOTORS CORPORATION. Nov. 10, 1954 [Dec. 4, 1953], No. 32546/54. Class 80(2) [Also in Groups XXIX and XXXIV] A planet gear having fluid pressure engaged clutch and brakes, and driven through a fluid torque-converter 3 with a lock-up disc clutch 29 engaged by fluid-pressure under control of an automatic lockup shift-valve 280 responsive to speed and torque-demand. has also a lock-up cut-off valve 233 which momentarily disengages the lock-up clutch 29 during a shift in the planet gear to cushion said shift. Function summary. The gear provides one reverse and six forward ratios subdivided by a manual selector valve 246 into Neutral, N, Reverse, R, and three forward ranges High' Intermediate and Low (H, I, L) in each of which ranges a further automatic shift valve 270, also responsive to speed and torquedemand, provides automatic shift between two ratios, such shift occurring in a directoverdrive planet train 45 ahead of a three-speed and reverse triple-train planet gear controlled by the manual selector valve 246. Accelerator kickdownshift is provided below predetermined speeds in all ranges, such kickdown being also 'effective to release the lockup clutch 29 providing the speed is low enough. Servo pressure is regulated in accordance with speed and torque-demand, and is reduced in the High range. Pressure responsive to torque-demand is obtained by a metering valve 215 loaded by a vehicle accelerator pedal acting at 217, and to speed by a governor-valve 260 loaded by pitot pressure acting in a stationary tube 67, Figs. 1 and 4, responding to the speed of an intermediate shaft 63 of the gear. Gear arrangement. The gear provides four reduced ratios, direct drive, one overdrive and one reverse controlled by four disc brakes, a disc clutch and a one-way clutch. A two-phase torque-converter 3, Fig. 1 (maximum stall ratio 3.6), with lockup disc clutch 29, drives the gear input shaft 9 on which is the planet-carrier 40 of the first train, which provides direct-drive to an output ring gear 47 on an intermediate shaft 63, by a one-way clutch 49 between the carrier 40 and a reaction sun 45, and overdrive when the sun 45 is held by a disc brake 50. Suns 97, 120 of the second and third trains are both fast on the intermediate shaft 63. A lowest ratio is by braking at 128 the ring-gear 125 of the third train which then acts alone to drive the final output shaft 73 through its planet carrier 123. A compounded intermediate ratio is by braking at 101 the ring gear 100 of the second train, which drives the ring gear 125 of the third train forwards at reduced speed, thus increasing the speed of the third planet-carrier 123 to drive the output shaft 73 at an intermediate, still reduced speed. Direct drive is by a disc clutch 83 connecting the suns to the second planet-carrier 89. Reverse is by braking at 158 the ring gear 156 of a fourth train having its planet-carrier 153 on the output shaft 73, and acting compounded with the third train through a sleeve connecting the third ring gear 125 with the fourth sun 151. Individual overall ratios are obtained as described below. Brakes and clutches-are all of the disc type engaged by fluid pressure through annular pistons. Brakes 101, 128, 158 are actuated through diaphragm springs 111 &c., which have intermediate fulcrum ring engagement 115 with the respective presser plates to provide mechanical advantage between the piston and presser-plate. Fluid supply system. Input and output driven pumps 35, 175 supply the system, a ball non-return valve 304 retaining input pump pressure whilst the output pump is at rest or inoperative in reverse. The torque-converter exhaust line 321 includes an oil-cooler 322 feeding a gear-lubricating line 323 under control of a pressure-relief valve 324. Fluid system components-include the manual ranging valve 246; the "TV" valve 215, Figs. 5 and 7, metering acceleratorresponsive pressure which is thus throttlevariable and is hereafter referred to as "TV" pressure; the governor valve 260, Figs. 5 and 9, responsive to pitot pressure 67 to provide speed-responsive pressure; a main regulator valve 200, loaded by the TV and speed-responsive pressures; overdrive and lock-up shift valves 270, 280, Figs. 5, 10 and 11, each loaded by opposing TV and speed-responsive pressures to produce respectively upshift in the front gear unit- 45 and converter lock-up; and the lock-up cut-off valve 233, Figs. 5 and 7, for releasing the lock-up clutch 29 during gear shift. Operation. Neutral setting of the manual valve 246 exhausts the supply lines 340 ... 343, Fig. 5, of the clutch and brakes of the rear gear-unit. The overdrive brake line 333 of the front gear-unit exhausts through its shift-valve 270 at 276; the lockup clutch line 330 exhausts through the lock-up cut-off valve 233, Fig. 7, line 33a, lock-up shift valve 280, Fig. 11, and exhaust 286, all valves 270, 233, 280 being initially in their rightward positions (leftward positions are shown). The main regulator valve 200 meters to exhaust 203 input pump pressure line 300 supplying a torque-converter feed line 320, and the TV and lockup cut-off valves 215, 233. The TV valve 215, Fig. 7, meters TV pressure to a line 360 which acts leftwards on the main regulator valve 200 increasing regulated pressure 300, and in the rightwards, downshift direction, on the overdrive and lock-up shift-valves 270, 280, Figs. 10, 11. Low range. In this setting the space between lands 250, 251 of the manual valve 246 registers with the supply line 342 of the brake 128, Fig. 1, providing low speed in the rear unit, the other lines 340, 343 still exhausting. The low brake line 342 communicates through holes 254, bore 252 and holes 253 in the manual valve 246, with a line 308 receiving regulated pump-pressure 300 through an orifice 236 in the centre of the lock-up cut-off valve 233. Fig. 7. On accelerating the engine, drive ensues through the torque-converter, the front unit 45 in direct drive by its one way clutch 49 and the rear unit in low, giving one-way first speed, overall direct-low (mechanical ratio 3.56). With the output shaft rotating, the output pump 175 now supplies the governor valve 260, Figs. 5 and 9, through a line 315 including a restrictor 316, this pressure being metered as governor pressure to a line 350 under the opposing influences of outlet governer pressure 350 acting rightwards at 351 and speed responsive pressure acting leftwards at 335 and developed by the pitot tube 67, Figs. 1 and 4, the open end of which faces tangentially against the direction of rotation of an annulus of oil in a channel 66 carried by the intermediate shaft 63. Governor pressure 350 now acts leftwards on the overdrive and lock-up shift valves 270, 280 and rightwards on the main regulator valve 200, in all cases opposed by TV pressure 360. First upshift; converter lock-up. When governor pressure 350 predominates over TV pressure in the lock-up shift valve 280, Fig. 11, the latter moves left (position shown), passing pump pressure 300, 301 through a line 330a and lock-up cut-off valve 233, Fig. 7, now spring-pressed to its rightward position, to the lock-up clutch engaging line 330. Drive now becomes all mechanical, still in direct-low. The valveland 282 is larger than 280 to ensure clutch release at lower speed than engagement thus preventing hunting. First gear upshift. At a higher predetermined speed the overdrive shift valve 270 is similarly moved left (position shown) to supply pressure from the lock-up cut-off valve line 308, 309 to the overdrive brake line 333. Filling the actuating cylinder of the overdrive brake involves flow to the line 308 from the pump line 300 through the orifice 236 of the lock-up cut-off valve 233, such flow creating pressure difference across the orifice which moves the valve leftwards (position shown), exhausting the lock-up clutch line 330 at 239. Completion of engagement of the overdrive brake stops this flow and hence the orifice pressuredifference, permitting the cut-off valve 233 to return rightwards to pressurize again the lock-up clutch line 330. The shift is thus cushioned by momentary disengagement and re-engagement of the lock-up clutch 29. Two-way drive ensues in second speed, overdrive-low (ratio 2.56). The overdrive shift valve 270 has differential lands 270, 272 to prevent hunting as for the valve 280 above. Intermediate range-is by moving the manual valve 246 to I position in which its holes 254 register with the line 341 supplying only the intermediate speed brake 101 of the rear unit. As this involves flow from the supply line 308, the lock-up cutoff valve 233 is again momentarily operated as above described for release and reengagement of the converter lock-up clutch 29. At the same time the reduction in speed of the intermediate shaft 63 consequent on upshift in the rear gear unit causes the overdrive shift-valve 270 to downshift to brake release position, so that one-way drive ensues in third speed, directintermediate (ratio 1.89). At a higher output speed automatic upshift to overdrive in the front unit takes place automatically as above described giving twoway fourth speed, overdrive-intermediate (ratio 1.36). High range. In H position the holes 254 of the manual valve 246 pressurize the line 340 of the direct-drive clutch 83 of the rear unit the consequent upshift of which causes downshift in the front unit, the sequence being as above described, and the two automatic ratios being one-way fifth speed, direct-direct (ratio 100) and twoway sixth, overdrive-direct (ratio 0.72). The direct drive clutch line 340 pressurizes the left face of a plug 208, Fig. 5, which then acts rightwards on the main regulator valve 200, reducing the regulated servo pressure in the line 300. Kickdownshift, which is made felt to the operator by a collar 220, Fig. 7 on the TV valve 215 entering a recess 218 on acc