Patent GB-849293-A (GB)
Title: Improvements in or relating to automatic control systems
IPC: F16H47/08
Filed: 1958-05-27
Abstract: 849,293. Change-speed gear. FORD MOTOR CO. Ltd. May 27, 1958 [May 24, 1957], No. 16862/58. Class 80 (2). Relates to a two-speed and reverse planet gear on a vehicle, having ratioestablishing brakes 132, 134 and a clutch 88 engaged by fluid-pressure maintained at a steady level by a regulator-valve 156 subject to loading by a compensator pressure 260 such that servo pressure level decreases with increase in output speed, but only up to a predetermined limiting speed, and increases with accelerator depression (engine torque factor) but only up to a limiting engine throttle opening. According to this invention such compensator pressure is supplied by a single compensating valve 154 acting as described below. Function summary.-Control is by a manual selector valve 138 having settings Park, Reverse, Neutral, Drive and Low (PRNDL), L of which provides an invariable reduced drive, whilst D provides automatic shift between that same reduced drive and direct under control of a two-position automatic shift valve 142, loaded by opposing fluid pressures 232 responsive to vehicle speed and 206 responsive to accelerator pedal setting, the latter being further modulated by a modulator valve 144. A timer valve 140 provides a delay in brake application and release in shifts, and is subject to control by the speed and accelerator-responsive pressures. Servo pressure is regulated as above stated and is augmented in reverse. Gear arrangement.-The gear comprises intermeshed planets carried by a final output shaft 52 and meshing two suns, one 48 input driven through a hydrodynamic torque converter 20; the other 86 held by a band-brake 132 for reduced drive or clutched at 88 to the input sun for direct. A ring-gear meshing one of the planet sets is braked at 134 for reverse. Fluid-pressure supply and regulation.-Input and output driven pumps 62, 130 supply the system-main 158 through check-valves. The main regulator valve 156 first meters inputpump delivery 160, and later output-pump delivery 158 to suction 162 in opposition to downward spring-loading 172 and assisted by upward loading by compensator pressure 260 provided by the compensator valve 154. The latter comprises a central metering valve member 266 loaded leftwards by "-TV" (throttlevariable) pressure 206, 286, metered by the usual accelerator-loaded TV valve 146; and loaded rightwards by output speed-responsive governor pressure 232 metered by a tail-shaft mounted centrifugal governor-valve 152, whereby differential lands 266, 268 control communication between the compensator pressure line 260 and either line pressure 196 or exhaust x. This arrangement inverts both governor and TV pressure, whereby compensator pressure increases with output speed and decreases with throttle opening. The limit control, above referred to, is imposed as follows. At the right end of the compensator valve 154 is a differentially-landed plug 288 initially maintained in an ineffective extreme right position clear of the metering valve 266 by line pressure 196, 294. Governor pressure 232 acts leftward at 300 on the plug 288, and when it reaches a predetermined upper limit (equivalent to 20 m.p.h. at full throttle) the plug 288 contacts and provides a leftward load on the metering valve 266 which equalizes that of the rightward acting governor pressure whereby there is no further increase in compensator pressure 260 with speed. TV pressure 206, 284 also acts rightwards on a plug 274 at the left end of the compensator valve 154 and is ineffective there until it reaches a predetermined limit (at 60% throttle opening) whereupon the plug 274 acts through a tappet 280 and spring-loaded thimble 278 on the metering valve 266 with a rightward force which equalizes that of TV pressure acting leftward at 286, whereby compensator pressure 260 is not further reduced with increase in TV pressure. Compensator pressure 260 acts upwards on the main regulator valve 156 in opposition to downward pressure-increasing spring loading, so that line pressure 158 increases with throttle opening and reduces with speed increase up to the predetermined limits of both. In reverse R, the manual valve 138 pressurizes also a line 298 to act leftwards on the metering element 266 of the compensating valve 154, thus reducing compensator pressure, and through action on the regulator valve 156, increasing line pressure 158. Shift control.-In both D and L settings the manual valve 138 directs line pressure 158 through a line 176 to the apply side of the servo of the reduced-drive brake 132, and to the automatic shift-valve 142. The latter is subject to downward loading by governor pressure 232 and upward by TV pressure 206 after modulation by the TV modulator valve 144. In L setting full-line pressure 158 is supplied through the manual valve 138 and lines 224, 222, 214 to maintain the automatic shift-valve 142 in its upper, downshift, position, and through the line 176 to the apply side of the servo of the low brake 132. In D setting, shown, the line 224 is exhausted, permitting the automatic shift valve 142 to be moved down by a predominance of governor pressure 232 over modulated TV, to feed line pressure 176, 184 through the automatic shift-valve 142 to a line 188 engaging the direct-drive clutch 88, and passing through the timer valve 140 to the release side of the servo of the low brake 132. Timer valve action.-In its spring-biased lower position the timer valve 140 imposes a restrictor 252 in the low brake release line 188, acting in both directions, so that brake application on downshift and brake release on upshift are both delayed in comparison with clutch actuation. At high road speeds and/or wide throttle openings the timer valve 140 is raised (as shown) by governor and/or TV pressure 232, 206, respectively, whereby the restrictor 252 is freely by-passed.