Patent GB-689352-A (GB)
Title: Improvements in or relating to variable-speed transmission mechanism
IPC: F16H61/00
Filed: 1951-02-28
Abstract: 689,352. Variable speed gear. BORGWARNER CORPORATION. Feb. 28, 1951 [Oct. 9, 1950], No. 4850/51. Class 80 (ii). [Also in Group XXXIV] An oil-pressure system for supplying servopressure for the operation of three reaction brakes 17, 18, 19 and two clutches 20, 21 (the former an all-mechanical direct drive clutch) of a three-speed and reverse compound planet-gear on a vehicle and driven through a hydrodynamic torque-converter 14 which receives a lower pressure supply from the same source, comprises input- and output-driven oil-pumps 80, 81 with individual pressure relief-valves 85, 86, the latter 86 of which exhausts the input pump 80 when output pump pressure rises sufficiently to take over, and there is an additional connection, through a restricted line 238 and non-return valve 240 through which the delivery 99 of the output pump 81 can feed directly the converter 14 at the required reduced pressure before the valve 86 cuts out the input pump 80. The output pump 81 is thereby gradually introduced into the system and shuttling between the two pumps 80 and 81 which occurs on its otherwise sudden introduction is avoided. The gear is controlled by the usual " PNDLR " manual selector-lever 257, the " L " position of which gives emergency low whilst the " D " position provides starting in intermediate ratio with subsequent shift to direct-mechanical high, and back, under the automatic control of an accelerator-pedal loaded output driven centrifugal governor 82. Converter idle-drag is prevented by an electromagnetic valve 287, which automatically retains a predetermined actuating pressure in the line 286 of the rear. servicebrakes 278 of the vehicle below a predetermined minimum vehicle-speed with the engine throttle 179 closed and the ignition switch 305 on. Gear system.-Emergency low speed is provided by applying brakes 18 and 17 to hold the suns of front and rear simple trains 15, 16, the former bi-directionally, the latter through a one-way brake 39. Drive proceeds from the input shaft 10 through the torque-converter 14, which is of the type having a reactor 24 on a forward-overrun detent 25, directly to the ring of the front train 15, the planet-carrier of which passes a reduced drive to the connected ring of the rear train 16, the planet-carrier of which passes a further reduced drive to the final output shaft 11. Braking of the front sun additional to that provided by the bi-directional brake 18, is obtained also from the brake 17 of the rear sun acting through a second one-way brake 40 in series with the first one-way brake 39 and arranged to act in the opposite direction. For intermediate speed the brake 18, which acts only in emergency low, is released, the rear brake 17 remains on and the front train is locked by a disc clutch 21 between its planetcarrier and sun. Drive is then at the reduced ratio of the rear train alone. Direct-drive topspeed is by engaging the converter lock-up discclutch 20, without necessarily releasing either the intermediate speed clutch 21 or rear brake 17, to transmit a mechanical drive directly from input to output shafts 10, 11. Reverse is by applying a band-brake 19 to the connected front planet-carrier and rear ring-gear. The front sun drives reversely the rear sun through the one-way brake 40, now acting as a clutch, so that the rear train drives at reduced ratio in the same (i.e. reversed) direction. Oil pressure engages the two clutches 20, 21 by acting on pistons 57, 53 and the band-brakes 17, 18. 19, by acting on pistons, 63, 64, 67. Pressure augmentation is provided for the low-speed brake 18 by an additional simultaneously supplied piston 65, and for the reverse brake 19 by an additional piston 66 with a delayed pressure supply as described below. Fluid system.-A regulated pressure line 112, supplying all major services, is fed by. the input and output driven oil pumps 80, 81 through individual delivery lines 95, 99 and relief-valves 85, 86 respectively, both pumps drawing from a sump 94. A six-position piston selector-valve 83, operated by the manual PNDLR lever 257 has outlets leading to the clutches and brakes, and in the regulated pressure line 112 feeding the selector-valve are a restrictor 131, and air accumulator 132 to ensure rapid filling and gradual pressure application. The regulated pressure line 112 supplies a torque-converter feed-line 211 through a converter-valve 87 which regulates converter-pressure to a lower value than regulated line-pressure. From the converter oil passes out through a pressure-maintaining spring-loaded valve 212, into the gearing and thence to the sump 94, a continuous cooling flow being provided. Initially the input pump 80 supplies all the pressure, but when increased vehicle speed raises output pump pressure in line 99 to a predetermined take-over value, such pressure depresses the piston of the outputpump regulator-valve 86, to exhaust the delivery 95 of the front pump at 107, and thereafter supply a regulated pressure from the rear pump only, through a non-return valve 128 to the regulated pressure line 112. At some predetermined lower pressure before this take-over occurs, output pump pressure 99 opens a spring- loaded valve 240 leading through a restricted branch-line 238 directly to the converter feedline 211 so that the output pump 81 is already feeding the torque-converter before taking over the servo system, at which latter point its takeover is rendered less abrupt. Forward speeds. - Pressure feed from the manual selector-valve 83 to the low speed brakes 17, 18 is direct when the selector lever is placed in the L position. In the D (Drive) position, which is that for normal starting, the selector valve 83, in addition to feeding the brake 17, feeds a line 155 leading to an output-driven centrifugal governor 82 which selectively feeds either the intermediate speed clutch 21, below a predetermined speed, or the high-speed clutch above that speed, giving automatic shift between intermediate and high-speeds up and down. Hunting is prevented by a supplementary piston 178 subject to clutch-pressure in the highspeed position and opposing the governor returnspring 176. The loading of the governor spring is also varied by the engine accelerator-pedal 170 acting on the upper governor-sleeve and serving to raise shift-speeds in accordance with accelerator depression, as well as permitting kickdown shift. Also linked to the acceleratorpedal 170 is a waisted plunger 190 controlling a lever 189 bearing on a latch 187, which, when released by the lever for leftward movement, snaps under an arm 170 fast with the lower governor-sleeve and prevents downward movement of the latter from the high to the intermediate speed position, the latch being only released, to permit downshift, when the accelerator-pedal is in or near positions corresponding to either closed throttle or overtravel fullthrottle kickdown. The governor 82 is lubricated from the delivery 99 of the output pump 81 through a ball valve 246 and restricted line 244. Reverse.-Movement of the manual selectorvalve 83 to position R, connects the regulated pressure line 112 with two lines, one, 153, leading directly to one piston 67 of the reverse brake 19; another, 154, to the underside of the piston of the input-pump regulator-valve 85, to augment the regulated pressure for reverse, and also through a line 210 to increase the rightward loading of the converter-regulator valve 87 whereby the augmented pressure is counterbalanced and no pressure increase is felt on the converter. When pressure has built up in the reverse brake line 153 to the first piston 67, it depresses a spring-loaded valve 89 and then passes into a previously exhausted line 236 to act on the second piston 66 of the reverse brake 19 and increase the brake-loading. This arrangement provides rapid initial brakeapplication followed by gradual final loading. The output pump 81 is always inoperative in reverse. To prevent engagement of reverse during forward movement of .the vehicle, pressure 99 from the output pump 81 in such circumstance, actuates a reverse interlock valve 88 which exhausts the entire reverse circuit through the lines 154, 210, and an exhaust port 223. Park lock.-In position P, the manual shift lever 257 mechanically applies a lock-pawl 251 to a toothed wheel 250 on the output shaft 11, to lock the vehicle against all movement, paw] engagement being prevented unless the vehicle is substantially stationary by a piston 254, which is moved into a pawl-obstructing position whenever pressure exists in the output-pump delivery line 99. Creep prevention.-To prevent the vehicle from creeping when stationary in gear due to idle drag of the torque-converter, braking pressure is retained in the fluid actuating line 286 of the service rear brakes 278 only, after depression and release of the actuating pedal 284, by an electromagnetic valve 287, which always permits free forward flow of fluid in the brakeapplying direction through holes 294 and a spring-loaded disc-valve 295, and, when deenergised, also in the reverse, brake-release, direction through a central opening 292. When the solenoid winding is energised, by simultaneous closure of three switches, one 272, of which closes whenever the output-pump pressure 99 falls to zero (i.e. with the vehicle stationary); a second, 307, which closes when the engine throttle lever 179 closes back against the idle stop 313; and a third, 305, the engine ignition switch, a valve armature 302 is pressed leftwards to apply a predetermined sealing pressure to the central opening 292. Under these conditions therefore, if the service brake pedal 284 has been previously depressed, a predetermined braking pressure is retained on the rear brakes without necessity for the operator to continue applying pedal pressure, and this is sufficient to prevent the idle drag of the converter from moving the vehic