Patent GB-726740-A (GB)
Title: Improved control system for variable-speed power transmission mechanism for vehicles
IPC: F16H61/02
Filed: 1953-05-22
Abstract: 726,740. Change-speed gear. GENERAL MOTORS CORPORATION. May 22, 1953 [June 4, 1952], No. 14415/53. Class 80 (2) [Also in Groups XXIX and XXXIV]. Shifts between a fluid-pressure operated directdrive clutch 49 and a reduced-drive reaction bandbrake 57 in a two-speed and reverse planet gear behind a torque-converter on a motor vehicle, are controlled by an automatic shift-valve 190, Fig. 6, subject to opposing fluid-pressures responsive respectively to vehicle speed (acting leftward, Fig. 6) and accelerator depression (rightward), together with an additional spring-pressed valve 197, which reduces and limits accelerator-metered pressure 305 and supplies it to a chamber 209, where, in reduced drive position only, it acts rightwards on a relatively large area, land 194, of the automatic shift-valve 190, which latter, when moved to its leftward direct-drive position, positively takes along the additional valve 197, which cuts off the reduced pressure from, and exhausts at 306, 185, the chamber 209, so that the rightward downshaft. fluid-pressure now acting on the shift-valve 190 is only accelerator-metered pressure 305 still acting on the relatively small left face of the additional valve 197. An accelerator kickdown valve 177 by-passes the said limiting valve 197 and applies full accelerator-metered pressure to the automatic shift-valve for kickdown shift. A manual selector valve 150 is controlled by means having the usual PNDLR positions, the first, P, closing a positive park lock on the output shaft; D giving drive with automatic shift between reduced and direct; L, enforced low and R reverse. A downshift inhibitor valve may be provided to enforce direct-drive in the D position. Servo system pressure is controlled by a main regulator valve 250 subject to modulation by engine-suction at 316 for torque response; by hydraulic means at 280 to provide pressure augmentation in manual low and reverse; and by the automatic shift valve to provide pressure reduction in direct drives. Speed responsive pressure is derived from an output driven governor valve, Fig. 8, the compound masses of which have a twostage action. Torque-converter. The single-stage two-phase converter has a main impeller 4 fast in a driving drum 2 on an input shaft 1; an auxiliary impeller 6 connected by a forward-overun one-way clutch 11 to the main impeller 4; two reactors 13, 14 on forward-overun one-way detents 19, 19'; a single turbine 5 fast on an output shaft 21; and, within the core space, supplementary blading 30, 32 on the turbine and impeller respectively, the former 30 being at a slightly greater radius than the latter to provide one-to-one engine-brake drive on torque-reversal. Oil is pumped, as described below, through a passage 313 to a space between the main and auxiliary impellers, 4, 6, and leaves between the turbine 5 and reactor 13 and a passage 315, which feeds a lubrication main of the gear through a pressure-regulating valve 430, Fig. 6. This valve comprises a stemmed piston 436, loaded by a spring into a position in which a coned portion thereon permits minimum flow passage in a restriction 434, being gradually lifted to increase the flow passage in response to converter exit pressure. A modification of this valve, Fig. 6a, not shown, has a permanent fixed restriction and a piston-controlled variable one, together with an excess-pressure relief to exhaust. Gear. The four-element, intermeshed-planet train comprises an input sun 46, fast on the output shaft 21 of the torque-converter, intermeshed planets carried by a final output shaft 65; a freelymounted ring 58, band-braked at 60 for reverse. and a freely-mounted reaction sun 47, bandbraked at 57 for reduced drive or disc-clutched at 49 to the input shaft 21 for direct-drive. The gear is lubricated by the line 315 fed from the converter-regulating valve 430, referred to above, and feeding into the interior 65a of the shafts and thence through radial drillings to the gear parts. Ratio brakes and clutch. The direct-drive clutch 49 is engaged, in opposition to a spring 52 by oil pressure, supplied through a passage 307 to a piston 55. The reduced drive brake-band 57 is contracted onto the rotating drum 49 by supplying oil-pressure through a passage 302, Fig. 3, to a piston 96, acting on the adjacent end of the band 57 through a strut 94, between which and the piston-rod clearance is maintained in the disengaged position by a spring 99a. An adjustably anchored strut 89 supports the other end of the band, and a spring 93 opens the band-ends on release, which, for neutral, is effected by simply exhausting the brake-apply line 302, whilst during an automatic upshift is effected by supplying equal brake-release pressure to the left of the piston, the apply-pressure remaining on, and release being performed by a spring 99 in both cases. The reverse brake-band 60, Fig. 2, is contracted by supplying oil-pressure through a passage 301, to act rightwards on a piston 80, the stem of which is slotted for a lever 83, the hooked end of which engages a strut 77 acting on the adjacent band end, whilst its intermediate fulcrum is a pin 73 fixed in the casing and also on an extension 72 of a strut 71 acting on the remote band end. An adjustable slotted anchor stud 78 supports the band-strut 77. An inner spring around the piston 80 provides an initial lost-motion between the piston and its rod, whilst the band ends are spread by a spring 75 on release, which is effected only by exhausting the apply-line 301. Positive park-lock. Rounded teeth 104 on the final output planet-carrier are engaged by similar teeth on a pawl 101, Fig. 5, pivoted on a fixed pin 102 into engagement by rocking an arm 107 having a roller 108 riding idly over notches 109 in the pawl as the shaft 106 of the arm 107 is turned between positions "R, L, D, N," by a control of a manual valve all described later, and moving on a cam surface 110 of the pawl as the manual control moves to "P position for parking, such final movement pushing and locking the pawl in engagement. If the vehicle is moving at this time, the teeth reject mesh and a torsion coil spring 111 between the shaft 106 and arm 107 yields until mesh can be effected. A torsion coil spring 105 lifts the pawl 101 out of engagement when freed. Pressure supply. The servo system, converter and lubricating line are supplied by input and output-driven gear oil-pumps P, Q, Figs. 1 and 6, feeding a common pressure-main 300 through a double check-valve 340 which closes the delivery of that pump producing the lower pressure. Servo system components are as follows: A manual selector valve 150 movable to Park, Neutral, Drive, Low and Reverse positions (PNDLR) in that order, the L position providing enforced reduced drive, whilst D gives automatic shifts between reduced and direct-drive. A main pressure-regulating valve 250 with hydraulic and engine-suction loading and providing pressure augmentation in low and reverse. A valve-group 164, which includes a " T V " valve 162 providing " T V " or throttle-valve responsive-pressure to be applied, after reduction in a TV limit valve 197, to one face of an automatic shift valve 190 where it is opposed by vehicle-speed responsive pressure supplied to the other face by an output-driven governor-valve 210. Included in the group 164 is an accelerator kickdown shift valve 177. A spring loaded accumulator 280 in the line of the hydraulic loading device of the main pressure regulating valve prevents surge effects, and the main pressure-feed line 300 has a relief-valve 297. Operation. Drive. In D position, shown, with the engine idling and the vehicle initially stationary, the input pump P delivery line 312 feeds the main supply line 300 through the regulator valve 250, now in its lowest position, and the check valve 340, in which latter it closes the delivery line 314 of the output pump Q. Pressure from the main 300 passes at 263 to the underface of the regulator 250 moving it upwards in opposition to its loading spring 264 to open with a metering action a feed to the converter-supply line 313 and a port 258 leading to the pump suction line 310. Pressure from the main 300 also passes through the manual valve 150 into the line 302 to apply the low brake 57, and a line 303 to the inlet of the automatic shift-valve 190 where it is blanked in the initial rightward position which that valve (190) assumes under spring load 199 in the absence of governor pressure. With reduced drive thus engaged, the vehicle can be started through the converter by simply accelerating the engine. With fully released accelerator, main pressure 300, passing through a restriction to the right face of the TV valve 162, moves the latter leftwards against a loading spring 168 sufficiently to exhaust TV delivery passage 305 at 169, but accelerator depression by turning anticlockwise through linkage (Fig. 15, not shown), a cam plate 240, increases the spring loading whereby the TV valve controls inlet and exhaust ports to feed the passage 305 with a pressure responsive to accelerator depression. This TV pressure in passage 305 acts on the left face of the TV-limit valve 197, moving it to the right, in opposition to a loading spring 198 to supply pressure, further reduced and metered through a port 201 to the shift-valve loading-chamber 209 in which it acts rightwards on the automatic shift valve 190, this further metering causing the pressure supplied to the chamber 209 by this path to be always limited to a value about 9.5 p.s.i. less than TV pressure 305. Under these initial conditions a feed-line 307, leading to the direct-drive clutch 49, is exhausted through the automatic shift-valve 190 at 206. Automatic upshift. At 15 m.p.h., the output pump Q takes over by changing over the check valve 340 to the position shown, so that its delivery pressure 314 feeds the main 300, this pressure increase also raising the regulator valve 250 to connect th