Patent GB-844516-A (GB)
Title: Improved control system for variable-ratio power transmission mechanism
IPC: F16H61/02
Filed: 1958-05-21
Abstract: 844,516. Change-speed gear. GENERAL MOTORS CORPORATION. May 21, 1958 [June 6, 1957], No. 16309/58. Class 80 (2). In a regulator valve 64, controlling the level of oil pressure for engaging ratio-establishing friction brakes 38, 46, 49 and a clutch 42 in a two-speed and reverse planet gear following an hydrodynamic torque converter on a motor vehicle, and subject in one ratio to fluid pressure loading in a chamber 102 which increases with reduction in engine manifold depression to increase the regulated pressure 60 with input torque, the depression-modulation of the pressure 102 is disabled in a different ratio, whereby the regulator valve 64 maintains substantially constant pressure in that ratio. Function summary.-A manual selector valve 107 has settings Park, Reverse, Neutral, Drive and Low (P, R, N, D, L). L provides an invariable two-way low; D provides automatic shift between a one-way low and direct-drive under control of an automatic shift-valve 124 subject to opposing fluid-pressures 136, 155 responsive respectively to vehicle speed and accelerator-pedal setting; R provides an invariable two-way reverse; all brakes and the clutch are released in N and P. Accelerator kickdown shift is provided in D setting below a maximum vehicle speed. Servo pressure is subject to manifold-depression modulation in D and R and is augmented in R. Gear arrangement.-The gear comprises intermeshed planets carried by an output shaft 32, one meshing a sun 16 driven through the torque converter 12, the other meshing a ring gear 28 which can be held by a brake 46 for reverse, and a sun 26 which can be held for two-way low by a brake 38, or for one-way low by a brake 49 acting through a one-way clutch 47. A clutch 42 connects the sun 26 to input 16 for direct drive. The capacity of the two-way brake 38, although adequate for all over-run torques, is not adequate for maximum drive torque, and in two-way low both brakes 49, 38 are engaged together. Fluid-system components.-In addition to the manual selector valve 107, automatic shiftvalve 124, and pressure-regulator valve 64, these comprise the following. A depressionmodulated valve 88 is fed by pump pressure 60 to produce depression-modulated pressure in the regulator-valve chamber 102. A valve 144 is loaded through a spring by an acceleratoroperated member 158 to meter TV (throttlevariable) pressure through a line 155 to the automatic shift-valve 124. A kick-down valve 160 is operated by accelerator'over-travel at 158 for force downshift. A regulator 134 (not described) supplies output-speed responsive pressure 136 to oppose TV pressure 155 in the automatic shift valve 124. An air-release valve 87a permits rapid purge of air from the line on starting. Pressure supply and regulation.-Input and output-driven pumps 50, 52 supply, through check-valves, a system main 60 feeding a chamber 62 of the regulator valve 64 in which the pressure branches to act leftwards on a differential land in opposition to a spring 70. Pressure modulated by engine-manifold depression is metered by the depression valve 88 to the rightward loading-chamber 102 of the regulator valve 64 whereby regulated pressure in the line .60 increases with reduction in depression (increase in torque). In L setting of the manual selector-valve 107 this depressionmodulation is disabled by the valve 107 closing the exhaust of, and pressurizing a line 119, feeding the two-way low brake 38, through which the depression-valve 88 had been previously metering to exhaust, whereby the pressure in the regulator loading-chamber 102 rises to a constant full line pressure, and is neutralized wholly or partly by equal line pressure supplied to a chamber 106 at the opposite end of the regulator 64 through the manual valve 107 in all settings except R. This produces the following selector control of regulated pressure. In D, depression-modulated pressure 102 is effective to increase regulated pressure, line pressure 106 is effective to reduce it and pressure level varies from 55 p.s.i. at closed throttle to 140 p.s.i. at full throttle. In L, depression modulation is disabled, line pressure acts at 102, 106, leaving the spring 70 alone to give a constant regulated pressure of 140 p.s.i., or with differential end-lands in the regulator a pressure of 150 p.s.i. In R the pressmereducing chamber 106 is exhausted, depression modulation is effective at 102, and the pressure level varies from 140 p.s.i. to 250 p.s.i., from closed to open throttle. The torque converter is fed by a port 74 of the regulator 64 through a restrictor 76, which coacts with an outlet pressure relief valve 80 to maintain a converter pressure of 30 p.s.i. When the output pump 52 takes over the supply, the regulator 64 moves a little further left to exhaust the input pump 50 at 84 and maintain a slightly higher pressure level (140 p.s.i.) than that (130 p.s.i.) previously maintained by the input pump. Shift control.-In D setting the manual valve 107 supplies main pressure 60 to the reduced drive one-way acting brake 49, and through a line 122 to the automatic shift valve 124, for a start in low. When output-speed responsive pressure 136 predominates over TV pressure 155 the spool 126 of the automatic shift valve 124 moves left to pressurize the direct-drive clutch 42 for upshift, the reduced drive brake 49 remaining on, but being over-run. On accelerator over-travel, the kickdown valve 160 supplies TV pressure 155 to a chamber 166 of the automatic shift valve 124, producing forced downshift below a predetermined maximum vehicle speed. In L setting, the two-way and one-way low brakes 38, 49 are both engaged and the supply line 122 of the automatic shift valve 124 is exhausted. In R setting the reverse brake 46 is engaged alone, the line 122 remaining exhausted.