Patent GB-1324720-A (GB)
Title: Automatic change speed transmission
IPC: F16H41/00
Filed: 1970-11-30
Abstract: 1324720 Change-speed control FORD MOTOR CO Ltd 30 Nov 1970 [8 Dec 1969] 56817/70 Heading F2D In a motor-vehicle automatic transmission, wherein intermediate (second) ratio is established by supplying fluid pressure 310 to an apply chamber of a planetary reaction brake 66; and high (third) ratio by supplying fluid pressure 258 to a high (and reverse) clutch 34 and to a release chamber of the intermediate brake 66, the rate of exhaust from the said intermediate brake release chamber during a shift involving brake application (e.g. 1-2 and 3-2), is subject to delay by two restrictors 80, 294, which act independently in high and low speed ranges. During a shift involving pressurizing of the release chamber these restrictors are by-passed by one-way valves 180, 296 for unrestricted brake release. The restrictors for exhaust, for brake application, comprise a fixed restrictor 294, operative alone at high speeds, and a variable restrictor provided by a land 170 of an intermediate servo accumulator 80, itself controlled by a cut-back control valve 268, subject to governor (202) and TV pressure (358, 280) control, these items coacting as follows:- Firstly at low speeds, the cut-back valve 268 is in its upper position, shown, and provides a bypass around the fixed restrictor 294, through a path 290, 292, to exhaust at the appropriate shift valve through the intermediate servo accumulator 80, which provides a restriction at the land 170 determined by the upward loading on that differential land 170 by TV pressure 358, supplied through the cut-back valve 268 through a path 358, 280, 284, 164. The lowspeed exhaust rate is thus determined by the restriction offered by the intermediate servo accumulator 270 above. Secondly, at high speeds, governor pressure 202, opposed by TV 358, 280, acting on a differential land 274 of the cut-back valve 268, depresses the latter, blocking the by-pass 290, 292, thus inserting the fixed restrictor 294 in the release-chamber exhaust path, and at the same time cutting off TV pressure 358, 280 from the line 284, 164, which unloads the intermediate servo accumulator 80, eliminating its flow resistance, so that the rate of exhaust from the brake-release chamber is now determined solely by the fixed restrictor 294, which can be calibrated independently of the intermediate servo accumulator 80 for a delay of brake application suitable for the high speed shift. During all the shifts the direct clutch exhausts without delay. Gear arrangement.-The gear, Fig. 1, not shown, is the usual torque-converter-driven Simpson planet set, with a forward clutch 32 engaged in all forward ratios; a one-way brake for automatic low, bridged by a band brake 64 for two-way manual low and reverse; an intermediate brake 66; and a direct and reverse clutch 34. Fluid pressure supply and regulation.-A single input-driven pump 28 feeds a system main 102 and a main pressure-regulator valve 76, a first low-pressure spill 124 from which feeds the torque-converter 12. The regulator valve 76 is loaded by a constant spring 119 and an inner spring 120 abutting a pressure-boost piston 86, which is acted on by TV pressure 358, 158, responsive to engine intake depression from a primary TV valve 346; additional primary TV pressure supplied to a line 160, 162 from TV line 358 through the cut-back valve 268, which is depressed by governor pressure 202 to exhaust this TV loading 160, 162 at higher speeds; an alternative line pressure feed to line 162 through a two-way check-valve 150 from a linepressure coating boost-valve 78, which, at low speeds and throttle-openings, modulates line pressure 144, under spring loading, into a line 146, but which, at high speeds on accelerator release, is permitted by the absence of TV pressure 358, 148, and the exhausting of a line 140, 164, 284, by the cut-back control valve 268, to rise (position shown), to supply full line pressure 102, 218, 234, 144 to the line 162, to act on the main regulator booster 86 for coast boost; and line pressure fed to a line 155 pressurized in reverse setting R of a manual valve 74 for reverse pressure augmentation. In the cut-back valve 268, primary TV pressure 358 acts upwardly on a differential land, before that land is exhausted by the downward movement of the valve caused by governor pressure 202. Boosted TV pressure 314 (see below), also acts upwards on a top differential land of the cut-back valve 268 to delay its downward movement during acceleration thus maintaining servo pressure at that time. A throttle pressure limit valve 380 limits the maximum TV pressure 358, to prevent excessive line pressure 102 being produced by the main regulator valve 76. Control pressures. (1) Governor.-Outputdriven primary and secondary valves 384, 382, receive line pressure 386 at the latter in forward settings only of the manual selector valve 74. The secondary valve 382 modulates a governor pressure to output 202, except when, at low speeds, the primary valve 384 blocks a crossover passage 388 through which the secondary exhausts for modulation. (2) TV.-Primary TV pressure 358 is delivered by the throttle valve 346, loaded at 352 by engine intake pressure. Primary TV 358 is indicative of actual engine torque, and as such is used to modulate servo pressure by the abovedescribed regulator valve loading. At high throttle openings, although still indicating actual torque, it does not indicate torque demand, as determined by accelerator setting, and for this purpose primary TV pressure 358 loads a TV boost valve 366 to modulate line pressure 102, 376 into a boosted TV line 314. After reduction in a throttle modulator valve 250 (below the 2-3 shift valve) this modulated TV boost pressure 206 is used to load the shift valves for ratio shift control. Shift-valves. (1) Manual.-The manual selector valve 74 receives line pressure 102, 104 and feeds the shift valves to provide three automatic ratios in D, a fixed second and first in 2 and 1, reverse R and neutral N. In all forward settings it feeds the forward clutch line 208, the 1-2 shift valve 182 at 210, and the governor at 386. (2) Automatic.-Differentially landed 1-2 and 2-3 shift-valves 182, 230 are loaded downwards for upshift by governor pressure 202, in opposition to springs, modulated TV 206, and line pressure 210, 260 blocked by the downward upshift movement of the shift-valves to provide snap action and operational hysteresis. Initially, with both shift-valves 182, 230 in the upper downshifted position shown, the vehicle starts in one-way low. At predetermined speed and throttle conditions, the 1-2 shift valve 182 is upshifted downwards to supply line pressure 104, 228, 210 to a line 214 and thence through a 1-2 transition valve 298 (described below), and line 310 to the apply side of the intermediate brake 66 for 1-2 upshift. At a higher speed the 2-3 shift-valve 230 also upshifts downwards to supply the direct clutch 34 through a line 258 from a line 256 fed from the line 214, receiving line pressure 210 through the now upshifted 1-2 shift-valve 182. Direct clutch pressure 258 passes through one-way check-valves 180, 296 to the release chamber of the second brake 66 to complete 2-3 upshift. Accumulator and restrictor actions are described below. Manual 2 setting pressurizes a line 238, directly upshifting the 1-2 shift-valve 182, and supplies line pressure through 238, 236, check-valve 234 and line 235, to downshift the 2-3 shift-valve 230. Manual 1 setting pressurizes a line 218 which downshifts the 1-2 valve 182, and supplies pressure through it and a line 222 to act upwards on the bottom end of the valve to lock it in its downshifted position, the 2-3 shift-valve 230 remaining downshifted by line 235. Pressure 222 also passes through a line 224, a low servo modulator 332 (described below), and line 318 to the low-reverse brake 64, establishing manual low. Reverse setting R is the same as manual 1, except that now the forward clutch line 208 is exhausted at 228, and line pressure 104 fed through lines 234, 155, the 2-3 shift-valve 230, and line 258 to the direct-reverse clutch 34. Detent (kickdown) shift.-Full throttle pedal depression acts on a throttle downshift valve 332 to supply boosted TV pressure 314, at this time approximately line pressure, to a line 340 to downshift both shift-valves 182, 230. 1-2 transition valve 316 acts as a fluid interlock between the low and second brakes 64, 66 by blocking pressure supply to the intermediate servo apply line 310 from 214 whenever pressure 318 is supplied to the low-reverse servo 64, such pressure depressing the 1-2 transition valve for this purpose. Low servo modulator valve 320 modulates pressure supplied at 318 to the low-reverse servo 64 under spring loading in low; but in reverse, passage 328 receives line pressure 234 from the manual valve 74 to override the modulating action and supply line pressure to the lowreverse servo 64. Intermediate servo accumulator 80 provides a governor and TV responsive exhaust to the release side of the intermediate servo 66 under control of the cut-back valve 268 during 1-2 and 3-2 shifts. For each such shift the release side must exhaust from the line 174 to 176 through a restricted path determined by the land 170 of the accummulator 80, the resistance of which is rendered operative by cut-back pressure 164, 284 supplied from primary TV line 358 through the cut-back valve 268 in its upper, low-speed, position shown, to act upwardly on the differential land 170 of the accumulator 80. For the 3-2 downshift, the direct clutch 34 exhausts without delay, but the rate of exhaust of the release side of the intermediate brake 66 is thus delayed by the accumulator resistance to permit a free engine acceleration period. At higher speeds the governor-operated cut-back valve 268 is depressed and exhausts the cutback line 284, 164 eliminating accumulator resistance, but inserting the fixed restrictor 294 into