Patent GB-1270890-A (GB)
Title: Variable-ratio power transmission mechanisms
Inventor: SCHAEFER ROBERT HERMAN
IPC: F16H61/02
Filed: 1970-05-21
Abstract: 1,270,890. Change-speed gear; torquelimited hydrodynamic brakes; cooling. GENERAL MOTORS CORP. 21 May, 1970 [25 Aug., 1969], No. 24588/70. Headings F2D and F2E. Relates to a sequential arrangement of shift valves in a multi-ratio transmission for a wheeled or tracked vehicle having four fluidpressure-operated brakes and two clutches for establishing by manual selection only an emergency LOW and one Reverse, and by automatic selection four higher forward ratios. In automatic setting, 1-2, 2-3; and 3-4 shift valves 378, 406, 424 receive pressure sequentially, whilst LOW and Reverse are obtained only manually through a LO-1 shift valve 298, which also receives pressure through the downshifted 1-2 valve 378. Reverse requires also a clutch 63 used for direct drive and this, in reverse setting; receives its pressure through the downshifted 3-4 valve 424. Thus neither LOW nor Reverse can be established unless all the automatic shift valves are in their downshifted position. The arrangement includes one forward clutch 51 which is engaged through a manual ranging valve 191 and line 203 for all forward ratios and comprises a first automatic shift valve, 1-2 relay valve 378, having first and second supply ports 117, 393, and first and second outlet ports 307, 398, and arranged, in a downshifted rest position (shown), to connect the first supply port 117 to the first outlet port 307 and thence to feed one brake 89 for first automatic and reverse; and in an automatic range setting of the manual valve 191 is upshifted (right) by a signal 322 indicative of output speed, whereupon the second supply port 393 is connected to the second outlet port 398 and thence to feed a sequential arrangement of succeeding 2-3 and 3-4 shift valves 406, 424 for successive automatic upshifts. The manual valve 191 selects low and reverse in two other positions with the 1-2 relay valve 378 only in its downshifted rest position as follows. In manual LOW the valve 191 supplies pressure through a line 197, 292 to shift left a further valve, L0-1 shift valve 298, to supply pressure from the said first outlet port 307 to a low brake 103 through a line 294 to establish manual low; whilst in R setting the manual valve exhausts the line 197 to return the L0-1 shift valve 298 to its previous rightward setting (shown), again pressurizing the line 309 of the first ratio brake 89, the manual valve 191 also pressurizing a line 195 engaging, through the downshifted 3-4 relay valve 424, the second clutch 63, used also for direct-drive, to establish reverse. Thus both LOW and Reverse can only be established in the downshifted rest position of the 1-2 relay valve 378, since the first outlet port 307 is exhausted when the relay valve 378 is upshifted by the speed signal 322. Function summary.-Four reduced ratios, direct-drive and one reverse are provided. The first ratio is obtained only by setting a manual ranging valve 191 to LOW, and this ratio is rendered effective only below a predetermined output speed, above which the next higher ratio will be established. The remaining four ratios, numbered 1 to 4, are effective in automatic ranges, all four being effective in DR4 setting of the manual valve 191, whilst in settings DR3, DR2 and DR1, a fixed regulated hold pressure 204 cuts out fourth, fourth and third, and fourth third and second respectively, but in all the restricted ranges an automatic upshift occurs above predetermined output speeds. Automatic shift in all ranges is produced by fluid actuation of shift relay valves 378 &c., supplied with actuating pressure by shift signal valves 316 &c., operated by fluid pressure responsive to output speed, by a centrifugal governor valve 223, and torque demand, by engine intake-manifold depression loading a modulator valve 241. Detent (kickdown) shifts are possible in each automatic range by accelerator-controlled detent pressure 174, regulated to a fixed value, which is lower than hold pressure controlled by the manual valve 191, so that the latter can make a downshift at a higher speed than can detent. Screw pressure during shift is graduated by individual trimmer valves 461 &c., as well as by' restrictors in shift-valve feed and exhaust lines. The level of steady servo pressure is augmented in reverse, but is otherwise constant. A torque converter lock-up clutch 23 is engaged automatically above a predetermined input speed by an input-driven pitot governor 267, and is released momentarily during shift.  An hydrodynamic service brake 30 on the gear input shaft, shares a cooler 160 with the torque converter, and its control valve 541 includes a torque-limiting relief valve. Gear arrangement.-The gear comprises four sun - ring planet trains, interconnected, as shown in Fig. 2, between a torque-converterdriven input shaft 22 and an aligned output shaft 99. Selective clutches 51, 63 connect input 22 respectively to the connected third sun 38 and second ring 44, or to the connected first and second suns 48, 43. Brakes 76, 82, 89, 103 hold respectively the connected first and second suns 48, 43; the first carrier 47; the connected third and fourth rings 39, 101; and the fourth carrier 97. The clutch 51 (forward clutch) is engaged in all forward ratios. Four reduced ratios and direct-drive are obtained by also applying respectively brakes 103, 89, 82, 76 and clutch 63. The clutch 63 (direct clutch) also provides, with brake 89, the one reverse ratio, and that brake 89 is also applied alone in neutral. The driving torque-converter has a lock-up clutch 23. Hydrodynamic brake.-The turbine-driven gear input shaft 22 carries vanes 31, Fig. 2, coacting with fixed vanes 32 in a casing to form an hydrodynamic brake 30, when the casing is filled, as described below, with circulating liquid. Fluid pressure supply, pressure regulator and cooling.-Two pumps are provided, one, 112, supplying the system main 117, the other, 114, supplying a torque-converter feedline 146, with the assistance of spill from a tube pressure regulator 139 which supplies the gear lubricating system 136 at 80 p.s.i. A main pressure regulator 119 regulates system main pressure 117 by spill to the lubrication line 136 under the combined rightward (pressure-increasing) loading of a spring 123, acting through a plug e, and opposing leftward loading by delivery pressure 117 reaching its right end through a central bore 129, and by system pressure acting leftwards on the differential area of the plug e through a line 135 supplied in all forward ratios, but exhausted through the manual valve 191 in reverse setting, so that regulated pressure in reverse is augmented from its normal forward value of 180 p.s.i. to 300 p.s.i. The central valve bore 129 has an additional port leading to the space between equal end lands a, b of the regulator valve. Any leakage past the land b is exhausted at 134, and this provides a positive seal for the end chamber at the land a. A converter by-pass valve 150 regulates converter feed pressure 146 to 62À5 p.s.i., and the converter outlet 156 passes through a cooler 160 and line 154 to a converter pressure regulator 157, set for 25 p.s.i. The same cooler 160 is used by switching (described below) to cool flow from the hydrodynamic brake 30. The various shift valves exhaust the ratio servos which they control through a common exhaust line 306 and exhaust pressure regulator 313, which maintains a predetermined low pressure in the exhaust line 306. Control pressures. Output governor pressure 236, for ratio shift, is provided by an outputdriven governor valve 223, loaded by primary and secondary centrifugal masses 229, 231, not further described. Governor pressure 236 is supplied to the shift signal valves through a one-way ball check valve 238, for rapid pressure increase, but slow decrease through a parallel restrictor 239, to reduce drive line shock due to sudden reduction of governor pressure. Input governor pressure 270, for controlling torque-converter lock-up, is provided by a pitot tube 269 in an annular can 267 rotating with the turbine-driven gear-input shaft 22, and filled with liquid from the lubrication system. Modulator pressure 248, for assisting output governor pressure 236 for ratio shift, is provided by a modulator pressure regulator 241, loaded by engine inlet-manifold depression 256, to produce a modulator pressure 248 which varies inversely with torque demand (i.e. modulator pressure 248 is inverse TV pressure). Detent pressure 174, for detent downshifts, is provided by a through-detent valve 162, which normally exhausts the detent line 174 by line pressure 117 supplied to its left end chamber 171. Just before, or after, the engine throttle pedal 176 reaches full throttle position, it energizes a solenoid valve 179 to exhaust the chamber 171 and permit the detent valve 162 to regulate line pressure 117 into the detent line 174 at 38 p.s.i. Hold pressure 204, regulated to 45 p.s.i., is provided by a hold regulator valve 209, and is supplied by the manual selector valve 191 to the appropriate shift valves to prevent upshift beyond a particular ratio in a selected setting of the manual valve. Shift valves.-Each shift valve controls one ratio shift and comprises a relay valve which directs main pressure to the appropriate servo, and a signal valve which, in response to governor and modulator pressure, supplies a signal pressure to operate the relay valve. The valves for all shifts 1 to 4 act similarly and a specimen 1-2 shift is as follows. In its spring-biased left position shown, for downshift, the 1-2 relay valve 378 exhausts the second ratio brake line 419 through the downshifted 2-3 relay valve 406, line 398 and common exhaust line 306; and pressurizes the first ratio brake line 309 from the main 117 through a line 307 and the L0-1 shift valve 298. On receipt of 1-2 signal pressure in a line 322 from the 1-2 shift signal valve 316, the 1-2 relay valve 378 upshifts to the right, exha