863,735. Variable-speed gear. GENERAL MOTORS CORPORATION. July 20, 1959 [Aug. 8, 1958], No. 24821/59. Class 80 (2). A variable-speed gear for motor vehicles includes an emptiable fluid coupling 44 connecting an input shaft 10 to an input sun 32 of one of two planetary trains 18, 16 having connected reaction elements 18, 22 and planet carriers, the last named also connected to an intermediate output shaft 29, and the input shaft 10 can also be connected by a fluid-operated friction clutch 50 to the input ring 16 of the other train 16. As shown, the intermediate output shaft 29 drives a final output bevel wheel 14 through a direct-overdrive auxiliary planet gear 52. Function summary.-The gear shown provides six forward speeds and one reverse. Two forward ratios may be eliminated and, where the overdrive unit is not present, three forward ratios and one reverse remain. A manual range selector valve 140 has settings P, N, D, I, L, R (park, neutral, drive, intermediate, low and reverse). P setting applies a positive lock to the output shaft. In P and N the fluid coupling is filled and the direct clutch 64 of the overdrive unit engaged. D setting provides automatic shift between all six forward ratios under control of opposing fluid pressures responsive respectively to output speed and barometric-corrected manifold depression. I setting cuts out both highest and next highest ratios, although above 70 m.p.h. an automatic upshift to the next highest occurs, and at all times a brake is applied to obtain two-way drive in one ratio. In L setting the lowest ratio is held until at 32 m.p.h. an upshift to the next higher ratio occurs automatically. In D and I settings various accelerator kickdown shifts can be obtained by an electrically operated kickdown valve 160, and in D setting only the overdrive unit can also be controlled by a manual electric switch 598. Three ranges of governor pressure control the automatic shifts. The rate of engagement of certain of the ratio establishing clutches and brakes is controlled by accumulators loaded by the manifold-depression modulated pressure, and of other clutches by suitable restrictors. Engagement of reverse is positively blocked above 7 m.p.h. by a governor pressure loaded reverse blocker 844. Gear arrangement.-The gear comprises a main unit consisting of two sun-ring trains 16, 18 operating above and compounded to give three forward ratios and one reverse; with or without an auxiliary direct-overdrive sun-ring output train 52, a final output bevel 14 being arranged between the main and auxiliary units. The auxiliary train provides three additional forward ratios V12, intermediate first (between first and second of the main unit); intermediate second (between second and third); and fourth (overdrive). An input fluid coupling 44 is filled in first ratio of the main unit; emptied and by-passed in second; and re-filled for split-torque third. Ratios are as follows. In the front unit a neutral brake 38 (released only for neutral) is applied to take, through a oneway detent 36, reaction of the connected rear ring 18 and front sun 22. The rear train 18 acts alone, with its input sun 32 connected to the input shaft 10 through the filled fluid coupling 44 and its output carrier 28 connected to the final output bevel 14 through the rear unit 52, now in direct drive with its direct clutch 64 engaged to connect its input carrier 54 to its reaction sun 60, its ring gear 52 being fast to the final output bevel 14. In parallel with the direct clutch 64 of the rear unit is a one-way clutch 66 which takes up the drive momentarily while the direct clutch 64 is engaging. For intermediate first, the front unit remains as for first, and the rear unit is upshifted to overdrive by releasing the direct clutch 64 and applying an overdrive brake 62 to the reaction sun 60. For second, the rear unit 52 is downshifted to direct by engaging the direct clutch 64 and releasing the overdrive brake 62. In the front unit the fluid coupling 44 is emptied and a second-speed clutch 50 engaged to connect the input 10 directly to the ring 16 of the front train, the sun of which reacts through the one-way detent 36 on the neutral brake 38, whilst its carrier 26 drives direct to the rear unit through the connected carrier 28 of the rear train 18. The front train 16 now acts alone. For intermediate second, the front unit remains as for second, and the rear unit 52 is upshifted to overdrive. For third, the rear unit 52 is downshifted to direct drive, whilst in the front unit the second speed clutch 50 remains engaged, but the fluid coupling 44 is again filled to drive the rear sun 32. With the rear sun 32 and front ring 16 driven at substantially input speed, the front unit is locked in split-torque drive, giving overall direct drive. For fourth, the rear unit is upshifted to overdrive. For reverse, the rear unit 52 is locked in direct drive by the direct clutch 64, and a cone, band or disc brake 67 is applied to the ring 16 of the front unit, all other clutches and brakes being released. The sun 32 of the rear train of the front unit is driven through the fluid coupling 44, and the two front unit trains act compounded for reverse. Under certain manually selected conditions described below, an overrun brake 42 is applied to by-pass the one-way detent 36 and neutral brake 38 to prevent overrun in a reduced ratio. The brakes and clutches are all applied by fluid pressure. Servo preasure supply and regulation.-The volume of fluid supplied by a single input-driven pump 100 is varied in accordance with the radial position of a slide 102 which is biased towards an upper, maximum supply position by a spring 104 assisted by supply pressure 108 supplied to a lower chamber of the pump through a passage 128 by a main regulator valve 110 in its upper position, shown. With increase in delivery pressure, the regulator valve 110 is moved downwards in opposition to a spring 122, to exhaust the lower pump chamber and supply pressure through a passage 130 to the upper pump chamber, which forces the pump slide 102 downwards, reducing pump output and maintaining a constant output pressure of 100 p.s.i. Control pressures. Automatic ratio shift is controlled by governor and throttle-variable or " TV " pressure supplied as follows. Governor pressure is supplied in three individual lines, each having a characteristic of different steepness. Gland G2 pressures are provided in lines 254, 256 by an output-driven governor valve 250 (not described) supplied with main line pressure 108. G3 pressure is regulated into a line 496 by a G3 valve 480 fed with line pressure 108, 490, 489, and loaded by G1 pressure 254, 488, G3 pressure being higher than G 1 pressure. TV pressure is regulated between zero and full line pressure to a line 236 by a TV valve 220, fed with line pressure 108, 218 through the manual selector valve 140, and loaded by a bellows 232 communicating with engine-manifold depression, together with an atmospheric pressure correcting screw-adjustable evacuated bellows 230. A reduced or modulated TV pressure 646 is provided by a trimmer valve 620 and is used to load an accumulator 660 in the second speed clutch line 658. Fluid system components.-In addition to those already referred to above, the components are as follows:- a neutral brake valve 300 controls the rate of engagement of the neutral brake 38 in accordance with TV pressure. An overrun modulator valve 320 controls the overrun-preventing brake 42 to provide two-way second ratio in the intermediate range. Filling and emptying the fluid coupling for ratio shift is initiated by a coupling signal valve 390 and takes place through a coupling fill valve 440 and a 2-1 coupling valve 350. The overdrive gear is controlled automatically by an overdrive gear unit valve 510 and manually by an overdrive gear unit manual control valve 578. TV loaded accumulators 530, 660 in the overdrive brake and second speed clutch lines 538, 658 respectively, regulate the rate of engagement of those members, whilst a direct clutch timing valve 550, TV loaded through a restrictor 560, similarly regulates the direct clutch 64 of the overdrive unit. Shift valves.-The shift valves are as follows. First to Intermediate First (referred to hereafter as 1-Inter. 1) shift valve 680; 1-2 shift valve 710; 2-3 shift valve 750; 3-4 shift valve 780; 2-1 downshift valve 370 and a 1-2 shuttle valve 460. The last named ensures precedence for shift in the front gear unit during shifts involving shifts in both gear units. The shift valves 710, 750 and 780 are all loaded to their leftward, downshift position, shown, by TV pressure 236, modulated to a somewhat lower value by spring-loaded regulator plugs 732, 764 and 790 respectively before being fed to the right end-faces of the shift valves where it acts in opposition to rightward governor pressure applied in some instances through separate governor plugs such as 718 for the valve 710 and 762 for 750. In the case of the 3-4 valve 780 the TV pressure 236, 910 acts permanently, but for the 1-Inter 1, 1-2 and 2-3 valves 680, 710, 750, TV pressure is cut out in the upshift position by the valves themselves, and remains cut out until return downshift except in the case of the 2-3 valve 750, where an alternative supply of TV pressure is provided in the upshift position by a partthrottle 3-2 TV valve 410, which, when TV pressure 236 on its larger left land overcomes opposing line pressure 108 on a smaller land, opens to direct TV pressure 236 through lines 420, 902 to provide leftward TV loading for the upshifted 2-3 valve 750. The part-throttle 3-2 TV valve operates at a TV pressure of 70 p.s.i. to provide a part-throttle 3-2 downshift as described later. The shift valves are differentially landed for downshift at a lower speed than upshift. Fluid coupling filling and emptying.-In its initial leftward position, shown, the coupling si