Patent GB-1350184-A (GB)
Title: Automatic transmission controls for an automative vehicle driveline
IPC: F16H61/02
Filed: 1972-01-17
Abstract: 1350184 Change-speed control FORD MOTOR WORKS Ltd 17 Jan 1972 [16 Feb 1971] 2097/72 Heading F2D In an automatic transmission on a motorvehicle, having three forward ratios and one reverse, selected by hydraulically engaged clutches and brakes, and wherein one, e.g. the second ratio, brake 150 is applied by supplying fluid pressure to the apply side of a servo piston 152, and released by simultaneous supply of release pressure to its larger opposite side 158, a restrictor 280 is arranged in the brake release line 160, to delay its exhaust and hence brake application during a 3-2 downshift, and is bypassed by two independent speed-responsive valves (a) a 3-2 coast valve 276 closed below 20 mph to delay brake engagement, and opened above that speed by governor pressure 270 to by-pass the restrictor for normal overlapped shifts, and (b) a 3-2 shift timer 278 shifted by governor pressure 270 at above 50 m.p.h. to re-introduce the restrictor 280 into the exhausting brake-release line 160 to delay brake engagement to allow time for engine acceleration. Independent calibration for both these conditions is therefore possible. Gear arrangement.-The gear, Figs. 1A and 1B, not shown, is the usual torque-converterdriven Simpson planetary gear set, with a forward clutch 76, Fig. 2A, engaged in all forward ratios; a direct-reverse clutch 68 engaged in third and reverse; the second ratio brake 150; and a manual low-reverse brake 14 in parallel with a one-way brake for automatic low. Fluid pressure supply and regulation.-A single input-driven pump 52 supplies a system main 96 under control of a main pressureregulating valve 202, loaded by a boost piston 214, itself loaded by throttle pressure 258, supplied by an engine-intake-regulator valve 230, through a governor-pressure loaded cut-back valve 226 and line 224, which exhausts the line 224 at higher speeds. The boost-piston 214 is also loaded by line pressure supplied through a manual PRND21 valve 94, in reverse setting R for pressure augmentation in reverse. A 2-low range coasting boost valve 264, operated by governor pressure 270, provides increased regulator valve loading at high speeds with relaxed throttle in 2-low and reverse ranges, for engine braking, by supplying line pressure from the manual valve 94 and lines 132 or 134, through a double check valve 184 and the coast boost valve 264, to the boost piston 214 of the main regulator valve 202. Shift valves, 1-2 and 2-3, 128 and 146, are loaded leftwards for upshift by pressure 270, 142 from a compound output driven governor 144, not described, and rightwards for downshift by throttle pressure 258, first processed in a throttle pressure boost valve 260 and then in a throttle pressure modulator valve 198, which last two permit calibration of shift points independently of throttle pressure loading on the main regulator valve. Kickdown valve 314, actuated by the throttle control, provides forced downshifts below predetermined speeds. Other features.-An accumulator 166, connected to the release side 158 of the second ratio brake 150, in parallel with a one-way check-valve 164, also controls exhaust of that side to modify the rate of brake application on 3-2 downshift. A 2-3 back-out valve 148, actuated by throttle pressure 258, connects the apply side 154 of the second ratio brake 150 to the direct clutch 68 during a 3-2 zero throttle downshift, whereby the brake servo acts as an accumulator to delay disengagement of the direct clutch 68 to cushion the downshift. Low-reverse servo piston 326 is of stepped construction. In D, 2, and 1 settings of the manual valve 94, line pressure is applied at 112 to a space above the piston 326. In manual low this pressure assists the springs in opposing the apply pressure applied to the larger face below the piston so that the brake engages with moderate pressure. In reverse setting R the line 112 is exhausted at the manual valve 94, thus effectively augmenting the brake-apply load.