Patent GB-1195970-A (GB)
Title: Multi-Ratio Transmission.
IPC: F16H61/02
Filed: 1969-03-20
Abstract: 1,195,970. Change-speed gear. GENERAL MOTORS CORP. 20 March, 1969 [4 April, 1968], No. 14689/69. Heading F2D. Fluid pressure engaged ratio-establishing clutches and brakes 114 &c., in a multi-ratio planetary gear, are each energized by an individual shift-valve 246 &c., Fig. 2, having an upper upshift position activating the ratio and a lower downshift position de-activating it, each shift-valve having at its upper end a pressurechamber 256 &c., controlled by an exhaust valve 264 &c., which, when closed, provides a downshift bias on the valve, and when opened by a solenoid 262 &c. controlled by a manual selector cam-shaft 501, upshifts the valve, and, at the same time, provides a restricted exhaust on any previously upshifted valve to delay downshift movement of that valve until the upshifting valve has completed its upshift movement. In this Specification, the upshift position of a shift-valve means the ratio-established position of the ratio which that valve controls; and the downshift position is the ratio-released position of that same ratio. Gear arrangement.-The gear, which is driven through a torque-converter 11 with lock-up clutch 12, is used to provide four reduced ratios, direct drive and overdrive, and one reverse, and comprises four planetary sections as follows. A torque-splitting direct-overdrive section 16; a three-speed range section 18 having a low train 58 and an intermediate train 56; a torque multiplying and combining section 19 and a reverse section 21. Ratios are:- First (low-low), using combining train 19 alone, with ring gear 71 braked at 72, sun 64 driven at converter speed by the inner shaft 38, and carrier 63 permanently fast to output 69. In this ratio, as well as in neutral and reverse the torquesplit train 16 is locked in direct drive by a clutch 84 to control the rotation of elements of the section 18. All the remaining forward ratios are torque-split. Second (low). The splitter section clutch 84 remains engaged, locking the train 16, the ring gear of which drives through an outer shaft 89 the connected suns 91, 92 of the three-speed section 18. Applying a brake 102 to the ring gear of the low train 58 of section 18 causes its carrier 96 to drive the ring gear 71 of the combining train 19, the sun 64 of which is still driven at converter speed through the inner shaft 38, producing overall second speeds. Third (intermediate). In the section 18 the brake 102 is released and a brake 114 applied to the ring gear 111 of the intermediate train 56 which now compounds with the low-train 58 to drive the ring gear 71 of the combining train 19 at a higher speed than in second, but still reducing, the sun 64 being converter-driven as before. Fourth (high). The splitter 16 is upshifted by releasing its direct-drive clutch 84 and applying an overdrive brake 82 to its sun 78, so that its input carrier 62 overdrives the ring-gear 76 and with it the sun-shaft 89 of the section 18 which latter remains as for third, giving overall fourth. Fifth (direct-drive), is by engaging the lock-up clutches 84, 114, downshifting the splitter section 16 and upshifting the section 18. Sixth (overdrive), is by upshifting the splitter 16 with the overdrive brake 82, which then overdrives the ring-gear 71 of the combining section 19 through the still-locked section 18, whilst the sun 64 continues to be driven directly by the converter, giving overall overdrive. Reverse.-A rear brake 122 is applied to the ring 121 of the reverse train 21, which then compounds with the combining train 19 so that their connected carriers drive the output 69 reversely, the sun 64 of the combining train 19 being still driven directly by the converter. A powder take-off, directly driven by input 24, is provided at 48. Control; general.-The control system comprises individual solenoid shift-valves 281 &c., Fig. 2, for each ratio, manually switched by a selector cam-shaft 501, and associated with individual trimmer-valves 416 &c., for regulating shift sequence and servo pressure during shift. The shift-valves are such that even if a solenoid of an effective ratio fails, the ratio remains effective and some shifts can still be made. The torque-converter lock-up clutch 42 is engaged automatically under control of pitot pressure 184 responsive to the speed of the splitter output shaft 89, and engagement is blocked in reverse, neutral, first and second ratios, and also when the flow requirement of the shift-control system is high. Downshift movement of the selector cam-shaft 501 is positively prevented when the converter lock-up clutch 42 is engaged, by a switch 506 responsive to lock-up pressure 45, to energize a solenoid which thrusts a spring-retracted pawl 507 into engagement with ratchet teeth 511 on the cam-shaft 501. Fluid pressure supply and regulation.-An input driven three-element pump 151 has two delivery lines, one, 154, supplying the torqueconverter, the other, 153, supplying a main pressure-regulating valve 156 feeding a control line 158. Spill 166 from the main regulator 156 supplies a lubricating line 176 through a spring- loaded check-valve 177, which, when lubricating pressure exceeds converter feed pressure 154 by a predetermined differential, opens to the line 154 to assist converter feed. For servo pressure augmentation in reverse, neutral, first and second ratios, spring-loading of the main regulator valve 156 is boosted by fluid pressure 172 derived from the appropriate shift-valves. Also co-operating is a priority valve 230, Fig. 2, which ensures that when the pump 151 starts to produce pressure in neutral from the rest position in which all the shift-valves are sprihg-upshifted, this pressure is first directed to downshift all the shift-valves, and further ensures that the control main 202 is not connected to the shift-pressure supply-line 231 until control pressure rises above a value below which slip might occur. Control; shift. Torque-converter lock-up.- The torque-converter lock-up clutch 42 is engaged automatically by speed-responsive governor pressure 184, derived from a pitot can 182 driven by the splitter gear output shaft 89 and acting on a lock-up shift valve 186, Fig. 1, which at a predetermined speed, is moved left by governor pressure 184 to supply main pressure 158, to the lock-up clutch 42 through a cutoff valve 196 and line 45. Acting rightwards on the lock-up valve 186 is the line 172<SP>1</SP> fed by boost pressure 172 derived from the appropriate shift-valves, which, in reverse, neutral, first and second ratios, moves the lock-up valve 186 right to block the engaging line 45 of the lock-up clutch 42. Engagement is also blocked by the cut-off valve 196, which is normally maintained rightwards in the open position shown, by pressure fed to the main shift control feed line 202 through a restrictor 201 from the pressure main 158, this pressure reaching the left end of the cut-off valve through a one-way restrictor 204. If the shift-feed pressure 202 falls, due to a flow requirement, e.g. to fill a shiftmotor, rightward pressure is rapidly released around the restrictor 204, permitting main pressure 158 to shift the cut-off valve 196 left, blocking supply 45 to the lock-up clutch 42 and later by-passing the restrictor 201 in the shift-feed line 202. Ratio shift-valves.-Ratios are controlled by six individual shift valves 331, 302, 281, 246, 361, Fig. 2, and 381, Fig. 3, actuated by solenoids, e.g. 292 for 281, energized by switches closed by the manual selector cam-shaft 501. Operation of the valves, apart from a detail below and the valve 381 is similar, being, for the valve 281 as follows. A multi-landed spool is biased downwardly to a downshift (ratio disengaged) position by common main control pressure 202 applied continuously to an upper chamber 287 through a restrictor 291. At the lower end of the valve this downshift pressure is opposed by a spring 28A and an equal upshift pressure supplied to a lower chamber 286 through passages controlled by others of the shift-valves, as described below. With equalized fluid pressure at both ends, or an exhausted lower chamber 286, the spring 284 maintains upshift (ratio engaged) position, which is also the position assumed in the absence of any fluid pressure (e.g. with the supply pump 151 at rest). With the supply pump 151 rotating in neutral, control pressure 202 is supplied through the restrictors to the upper chambers of all the shift valves which are consequently downshifted to ratio-disengaged position, except shift-valve 381, which controls the splitter unit 16 and in its downshifted position engages the splitter low clutch 85 which remains engaged in neutral to control rotation of following gears. To engage a ratio, the particular valve of that ratio e.g. 281, is upshifted by energizing its solenoid 292 to open an exhaust valve 293 to the upper chamber 287, permitting the spring 284 to upshift the valve to ratio-engaged position in which it is subsequently held latched by fluid pressure supplied to its lower chamber 286 through passages opened by the other shift-valves in their downshift (neutral) positions (and exhausted in their upshift positions), this condition being maintained independently as to whether or not the solenoid 292 becomes de-energized through failure or otherwise. Since the shift-valves are held in their upshift position by latching pressure in their lower chambers (286), this ensures that, during a shift, a suspended shift valve remains in its upshift (ratio engaged) position until upshift of the newly selected shift-valve exhausts its latching lower chamber. The first and second shift-valves 331, 302 and the splitter shift-valve 381, have solenoids 339, 312 and 396 respectively for exhausting their upshift chambers and these are energized in neutral setting of the control switch. They ensure that a shift direct from second or first to neutral can be made and that the splitter down