Patent GB-1239179-A (GB)
IPC: F16H47/08
Filed: 1970-04-23
Abstract: 1,239,179. Change-speed gear. GENERAL MOTORS CORP. 23 April, 1970 [26 May, 1969], No. 19478/70. Heading F2D. In a control for fluid-pressure-engaged ratioselecting brakes 34, 46, 60 and a clutch 51 of an automatic transmission on a motor-vehicle, wherein 1-2 and 2-3 shift valves 212, 192 are responsive to TV pressure 166, sensitive to torque demand, provided by a modulator valve 158 loaded as by engine inlet manifold depression 159, the TV modulator valve 158 has additionally a loading chamber 168 fed with main pressure 78 through a restrictor 167, and exhausted by energizing a solenoid valve 169 at full throttle depression of the usual accelerator pedal 175 to raise TV pressure 166 to full line value 78, to produce a " through detent "  downshift. Function summary.-Two reduced ratios, direct drive and one reverse are controlled by a manual selector valve 114, which, in D setting, provides automatic shift between all three forward ratios responsive to output governor pressure 191 and TV pressure 166, the effect of which latter is cancelled on upshift but substituted by additional pressure 184 (" T " pressure, see below) at the higher torque demands above half throttle. Intermediate setting I suppresses the third ratio, but if third is in action at the time of shift to I, the downshift to second will be automatic only, by governor and TV pressure. L setting enforces first ratio, but as in I, only after this ratio has been reached by one or two automatic downshifts. First and second ratios only have cushioned entry by a TV-loaded trimmer valve 236, and servo pressure is augmented in first and reverse. A power take-off clutch 68 can be engaged at any time by a solenoid-valve 131, which also acts as a pressure regulator, maintaining a constant lower pressure in the power take-off clutch 68. Gear arrangement.-The torque-converterdriven gear, arranged between input and output shafts 14, 16, comprises front, middle and rear sun-ring-planet trains 38, 26, 54, interconnected as shown to provide two reduced ratios, directdrive and one reverse, each requiring engagement of only one brake or clutch. First ratio uses the middle train 26 alone, its sun 28 being driven by the converter turbine T, carrier secured to output 16 and ring 29 held by a brake 34, which also provides reaction for the torqueconverter reactor S. In split-torque second, the ring 44 of the front train 38 is held by a brake 46, whilst its sun 39 is directly and mechanically driven by input 14, and its carrier drives the ring 29 of the middle train 26 which combines the converter torque applied from the turbine T to its sun 28, drive issuing from its planetcarrier to output 16. In third, the front train 38 is locked up by a clutch 51 so that, in the middle train 26, the ring 29 is mechanically driven at input speed and the sun 28 driven through the converter giving a split-torque direct-drive. For reverse the middle and rear trains compound, the rear ring 59 being braked at 60. Drive enters at the converter-driven middle sun 28 and issues at 16 from the connected carriers. The power take-off shaft 67 is input driven through meshing gears 64, 66 and clutch 68. Fluid system. Pressure supply and regulation.- A single input-driven pump 72 supplies a system main 78, the pressure in which is controlled by a main regulator valve 80 loaded by a spring 104, and in low and reverse, for pressure augmentation, by pressure supplied to a loading chamber 102 from the corresponding brake line 224 or 124, through an underlap valve 260, which closes to that one of the lines which is without pressure. The regulator 80 first supplies a torque-converter feed line 108, and later spills to exhaust 109. Delivery pressure 78 reaches the top loading chamber through a bore 95 in the valve spool. Control pressures. Governor pressure 191 is provided by a pitot can 189 on the output shaft 16, maintained full from the gear lubrication line. TV pressure 166 is provided by the TV modulator valve 158, loaded by engine-manifold depression 159. An opposing load from the TV line 166 through a restrictor 167 is provided in a chamber 168 at the top of the valve, this chamber being exhausted to cause TV pressure 166 to rise to full line pressure 78 by energizing a solenoid valve 169 by full depression of the accelerator pedal 175 for " through detent " (kickdown) shift. T pressure,-At high torque-demand, exceeding half throttle, a secondary modulator valve 178 begins to regulate TV pressure 166 into a T pressure line 184 where it provides an additional bias on the shift valves for raising downshift speeds (see below). Shift valves. Automatic.-Each of the 1-2, 2-3 shift valves has three spool sections. Taking the 2-3 shift-valve 192, a centre spool 193 directs line pressure 126 from the manual valve 114 through a line 202 to the 1-2 shift valve 212 and exhausts the direct-drive clutch line 203 in its lower, downshifted position shown; and in its upper, upshifted position, pressurises the clutch line 203 from 126 and exhausts the 1-2 feed line 202 to an exhaust line 210, leading to a relief-valve 129 at the end of the manual valve-body, the purpose being to maintain a low filling pressure in disengaged brakes. Below the centre spool section 193 is a governor plug 196 loaded upwards by governor pressure 191, and above the section 193 is a TV plug 198, loaded downwards by a spring and in the downshifted position, shown, by TV pressure 166. In the upshifted position TV pressure 166 is blanked off by the TV plug 198 so that downshift bias is due to the spring alone until, at the higher torques above half throttle, or for " through-detent " downshift, T pressure 184 is supplied to the upper valve-chamber to assist the spring, thus raising downshift speed points. The 1-2 valve 212, fed from the 2-3 valve 192 through the line 202, exerts similar control over the low and intermediate brake lines 224, 226. Shift valve, manual 114, in its D setting, feeds main pressure 78 through the line 126 to the 2-3 shift valve 192. In its I (Intermediate) setting it feeds also a line 127 to the 2-3 shift valve 192. If the latter is already upshifted, this is without effect, until governor pressure 191 is overcome by the spring, aided or not by T pressure 184, to produce automatic 3-2 downshift, whereupon full line pressure 127 acts between the TV plug 198 and the centre spool section 193 to prevent a return 2-3 upshift. In L setting a line 128 is pressurized in addition to 126, 127 to act similarly after automatic 2-1 downshift to maintain a fixed first ratio. Trimmer valve 236 controls the rate of engaging pressure increase during shifts into first and second ratios only, the rate being subject to TV pressure control. The trimmer has two steady state conditions, neutral and shifted. In the steady state neutral position shown, when pressure is first applied to the 1-2 valve 212 through the line 202 to engage first ratio, or on 3-2 downshift, it passes downstream of a restrictor 211 to thrust downwards an upper valve element 237 and contacting spring-loaded lower plug 241, exhausting the pressure 202 at 258. At the same time the pressure passes slowly through a restrictor 254 in a spring- loaded orifice plate 252 to thrust downwards the lower plug 241 against a spring 244 until it contacts a lower stop 257, at which time the upward load of the spring 243, assisted by TV pressure 166 acting on a differential land, causes a gradual upward movement of the valve element 237, closing the exhaust 258 and regulating the increase in pressure in the line 202 to full line value. The trimmer 236 is now in its steady state shifted position, with the plug 241 at the bottom, and if a shift is to be made between first and second ratios, the consequent initial loss of pressure in the 1-2 feed-line 202, due to change of shift servos, permits the orifice plate 251 to open and expel pressure rapidly into the line 202 as the spring 244 pushes the plug 241 to its upper position shown, ready to cushion the subsequent shift as above described.