Patent GB-1310070-A (GB)
Title: Variable-ratio power transmission mechanisms
IPC: F16H61/02
Filed: 1971-12-09
Abstract: 1310070 Change-speed control GENERAL MOTORS CORP 9 Dec 1971 [8 Jan 1971] 57252/71 Heading F2D A four forward and one reverse speed planetary gear on a motor-vehicle driven by a gas turbine, the power turbine of which is not driven continuously during operation, so that it may be stalled whilst the vehicle is stationary and conditioned for a forward or reverse ratio, is driven through a fluid coupling 12 or other fluid drive, which permits the power turbine to rotate under the above conditions with first speed established, but is rendered ineffective in all other forward ratios by a lock-up clutch 51 engaged automatically above a predetermined output speed, the coupling being also rendered ineffective at all times in reverse, which requires the engagement of a fourth-and-reverse clutch 63, connected directly to the main input 10, and a low-reverse brake 89, resulting in a wholly mechanical drive, with the coupling impeller and turbine rotating in opposite directions. All the clutches and brakes are fluid pressure operated and the control is wholly hydraulic apart from solenoid-valve detent. The fluid coupling may also be lock-up in a firstratio hold setting. Function summary.-A manual selector valve 191 selects RN and four forward ranges as follows. DR4 gives all four forward ratios automatically responsive to output speed and gas turbine compressor pressure (representing engine torque); DR3, the first three ratios similarly automatic at the same shift speeds; DR2, the first two, and DR1, first, the top ratio in the last three being subject to safety upshifts above predetermined speeds. Solenoid detent (kickdown) is provided at speeds lower than the hold speeds of the manual selector. Shifts are effected by shift-relay valves actuated by shift signal valves receiving the speed and load commands. Individual trimmer valves, with load-responsive loading by a common trimmer pressure regulator 441, control the rate of engagement and release of the clutches or brakes during shift. Servo pressure is augmented to a constant value (250 p.s.i.) in reverse, and is maintained at a constant lower value (150 p.s.i.) for all other settings. A priority valve 392 delays supply of servo pressure to the shift relay valves if pressure falls below a predetermined level, e.g. during shift.  Gear arrangement.-Three sun-ring trains 34, arranged as shown in Fig. 2, are connected between input and output shafts 10, 11. To the input 10 is secured the impeller P of the fluid coupling and the combined inputs of the lock-up clutch 51 and direct-reverse clutch 63, by which the input can be selectively clutched either to the sun 38 of the first train and coupled turbine T of the fluid coupling, or to coupled suns 43. 48 of the second and third trains. Ratios are: first, by a brake 89 alone for the first ring 39, the first sun 38 being driven through the fluid coupling; second, a brake 82 for the third carrier 47; third, a brake 76 for the suns 43, 48; and direct-drive fourth by the directreverse clutch 63, the lock-up clutch 51 being also engaged in all ratios except first. For the allmechanical reverse, the direct-reverse clutch 63 directly drives the sun 43 of the second train, and the ring 39 of the first is held by the lowreverse brake 89, the two trains compounding, the stun 38 and the fluid coupling turbine T also being driven together reversely. Fluid pressure supply and regulation.-A single pump 112 supplies a system main 117, in which line pressure is controlled by a main pressure regulator 119 loaded by a spring 123, which, in all forward ratios, is opposed by line pressure supplied through a manual selector valve 191 at 135, this pressure being exhausted by the manual valve in reverse to augment line pressure from 150 to 250 p.s.i. Spill 146 from the regulator 119 feeds the fluid coupling 12, the exit line 156 from which passes through a cooler 160 and relief valve 139 set at 40 p.s.i. to feed the lube system. A bypass relief 150 connects feed and exit lines. Control pressures. Governor.-An output driven governor valve 236, Fig. 5 (not further described), with primary and secondary masses 229, 231, produces stepped governor pressure in a line 236. The governor feeds its line through a fast forward, slow return restrictor 239 to prevent sharp pressure drop.  Torque.-Pressure from the compressor of the gas turbine set acts at 255 to apply inverse loading to a spring-loaded modulator valve 241 to produce modulated pressure 248 which varies inversely with compressor pressure and hence engine load. Detent regulated pressure 174 is produced by accelerator kickdown, to energize a solenoid valve 179, to exhaust a loading chamber 171 connected through a restrictor 169 to line pressure 117, permitting the detent valve 182 to regulate line pressure 117, 182 to the detent pressure line 174 at 38 p.s.i. Hold regulated pressure 204 provides downshift pressure for acting on the shift signal valves in the hold settings DR3, DR2 and DR1, and is produced by a hold regulator valve 209, receiving line pressure 117, 204 through the manual valve 191 in these settings, and supplying regulated hold pressure 204, at 45 p.s.i., which is higher than detent pressure 174, successively into DR3, DR2 and DR1 hold lines 201, 199, 198 as the manual valve is moved into these settings. Exhaust pressure regulator maintains a predetermined low pressure in a common exhaust line 306 from all the relay shift valves. Trimmer pressure regulator 441, inversely loaded by modulator pressure 248 regulates line pressure 117, 451 into a common line 452 providing load-responsive loading for the individual trimmer valves controlling pressure change rate in the clutches and brakes during shift (see below). Shift valves.-A lock-up valve 271 supplies line pressure 117, 283, 281 thereto when shifted left at a predetermined speed by governor pressure 236. Optionally, pressure from the DR1 hold line 198 may act at 185 on a differential land to produce lock-up. In addition to 1-2, 2-3 and 3-4 shift relay valves 378, 406, 424 there is a N-1 relay valve 298, each of these relay valves being actuated by a single signal from individual signal valves 316, 341, 358 and 286, themselves actuated by governor and modulator pressures 236, 248, acting in the same direction. Except for the N-1, all the signal valves have differentially landed valve elements and separate control pistons, as described below. Each shift relay valve receives its servo feed sequentially from the preceding shift relay valve only after that valve has upshifted, so that upshift beyond a disabled valve is not possible. The servo feed 393 to the first relay valve, the 1-2 relay 378, is derived from a line 203 receiving line pressure 117 from the manual valve 191 in all forward settings, the feed 393 being derived through the priority valve 392 which delays full servo feed until pressure is sufficient to open a valve 394 by-passing a restrictor 391, thereby delaying shift valve action during temporary pressure reduction on shift. Upshift sequence is as follows. Initially in N, line pressure 117 passes through the downshifted 1-2 relay valve 378, line 307, N-1 signal valve 286 and line 292 to shift left the N-1 relay valve 298, exhausting the low brake line 309 through the common exhaust line 306. All the clutches and brakes are also exhausted since the servo feed 398 is exhausted at the 1-2 relay valve 378. Selection of DR4 at the manual valve 191 pressurizes a line 203, which shifts left the valve element 287 of the N-1 signal valve 286, exhausting the line 292 and permitting the N-1 relay valve 298 to return right (shown), so that line pressure in 307, 308 feeds the lowreverse brake line 309 establishing first ratio for drive through the fluid coupling. At a predetermined speed, governor pressure 236 operates the lock-up valve 271 to engage the lock-up clutch 51 for all-mechanical drive. 1-2 Upshift.-In the 1-2 signal valve 316, when governor pressure 236, acting leftwards on the end land a of the valve element 317, and modulator (inverse torque) pressure 248, acting in the same direction on a large end land c of a control piston 319, overcome spring pressure, the valve element and piston move together left, and supply line pressure 117 to a 1-2 signal pressure line 322, which, acting rightwards on the end of the 1-2 relay valve 378, upshifts that valve right, which exhausts at 306 the feed line 307, 308, 309 to the low-reverse brake 89, and provides a servo feed 398, from 393, to the 2-3 relay valve 406 and thence, through that valve in its downshifted position (shown) to the apply line 419 of the second ratio brake 82. 2-3 Upshift is similar, the 2-3 signal valve 341 sending 2-3 signal pressure 354 to upshift the 2-3 relay valve 406 which then exhausts the second brake line 419 at 306 and feeds servo pressure 398, 415, through the downshifted 3-4 relay valve 424 to the third brake apply line 436. 3-4 Upshift is by a similar 3-4 signal 371 from the 3-4 signal valve 358, to upshift the 3-4 relay valve 424, which then directly exhausts the third brake line 436 at 306 and directly pressurizes the direct-reverse clutch line 432. Hysteresis in the signal valves is provided as follows, taking the 1-2 signal valve 316 as an example. On leftward upshift, the line pressure 117, supplied to the 1-2 signal line 322, also acts leftward in the space between differential lands a, b of the valve element 317, and modulator pressure 248 now acts with increased force on the differential area between lands c and a of the piston element 319 instead of on the smaller differential area between lands c and b at downshift, the land b, larger than a, but smaller than c, having moved out of its bore on upshift. This increased modulator force, plus the line pressure force, also not present on downshift, provide the hysteresis. Normal downshifts simply reverse the above sequence. Hold and detent downsh