Patent GB-631768-A (GB)
Title: Change-speed gear
IPC: F16H47/08
Filed: 1947-07-14
Abstract: 631,768. Fluid-pressure servomotor-control systems. PACKARD MOTOR CAR CO. July 14, 1947, No. 18710. Convention date, Aug. 14, 1946. [Class 135] [Also in Groups XXIV and XXXIV] A fluid-pressure automatic ratio - shift and starting, control for a planetary gear on a vehicle comprises a .first valve 124, operated by accelerator - controlled engine-manifold depres, sion, for controlling a reduced - drive planetcarrier brake 20 to act as an automatic starting control, and a second valve 123 jointly controlling the reduced-drive brake 50 and a directdrive disc-clutch 64, and itself operated by a third valve 208 controlled jointly by engine-manifold depression and vehicle speed - responsive governor-masses 221 which automatically control ratio-shift. Stepped input suns 34, 35 of the planetary gear are driven by two separate runners 22, 24 respectively of a three-element fluid-coupling, and this, together with the valve-combination, an inter-connected accelerator-pedal control, and an interconnected antidrag control for a final series planetary reverse gear 72, results in the following enumerated functions described in detail below. Function summary.-(1) Release of the accelerator opens a suction-valve 154 to the brake-valve 124 thus releasing the carrierbrake 50 to interrupt geared drive ; (2) automatic transition from first to second geared ratios, is obtained by action of the fluid-coupling changing over from the sun 34 to that 35, the former over-running by means of a one-way clutch. 26 in its drive ; (3) the governor-valve 208 effects a pressurecontrol of a shift-valve 123 which, above a, predetermined vehicle-speed (15 m.p.h.), when vehicle-speed and engine-suction conditions permit, releases the geared-drive brake 50 and applies the direct-drive clutch 64 for upshift to direct-drive ; ;. (4) accelerator overtravel kickdown closes a switch 256 operating the shiftvalve 123 through a solenoid 252 to produce a return downshift to geared drive, such action being prevented above a predetermined vehiclespeed by a wind-switch 259 in the slipstream of the engine-fan, which breaks the solenoid kickdown circuit ; (5) manual downshift at any direct-drive speed is effected by a switch 261, short-circuiting the wind and accelerator kickdown switches 259, 257 ; (6) a steering-column. mounted shift-lever operates only the reversegear and actuates its shift-rail 86 through a lost-motion connection 88, which causes prior movement of a surrounding sleeve-valve 99 which, in neutral, applies an anti-drag friction disc-brake 79 to the input shaft 43 of the reversegear to facilitate mesh of its forward and reverse dogs 46, 75 ; (7) the reverse shift-rail 86 carries a valve 100 which in neutral, Fig. 8, cuts-off the pressure supply to the control valves 123, 124, thus ensuring that they are only effective in forward or reverse ; (8) one pressure-supply pump 106, driven by the vehicle actuates a lock-piston 272 engaging a, notch 276 on the reverse shift-rail sleeve 99 to prevent movement of the reverse control from the forward position whilst the vehicle is in motion ; (9) to prevent operation of the engine-starting motor in gear positions, the reverse' shift-rail 86 when in neutral position closes a switch 280 in the circuit to the starterswitch 283a, which is thus only effective in neutral ; (10) suitable restrictor-passages provide for engagement of the direct-drive clutch 64 before the gradual disengagement of the geared drive brake 50 to maintain drive-torque during upshift together with rapid release of the brake by the accelerator-release during manoeuvring in geared drive. Change-ratio gear system.-The planet-gear comprises the driving suns 34, 35 driven through concentric shafts by the fluid-coupling runners 22, 24 respectively, the former including a one-way clutch 26 permitting over-run as the latter picks up the second-speed drive. The driving-impeller 20 of the fluid-coupling is also connected through a yielding spring-coupling 32 and outer concentric shaft with the inner member of the direct drive friction disc-clutch 64, the outer member of which is the carrier 42 for three stepped planets meshing the driving suns 34, 35 and a driven sun 36, the latter integral with the input shaft 43 of the reversegear. During geared drive, the planet-carrier 42 is held by the contracting band-brake 50 actuated by a compound piston 54 described below, whilst for direct-drive the brake is released and the clutch 64 engaged by oilpressure on a group of pistons 69 acting against release springs. Direct - drive is therefore branched through two paths, one a mechanical path to the carrier, the other a fluid-coupling path to the second speed sun 35, so that the fluid-coupling is effective in all ratios forward and reverse. Reverse-gear.-In the simple three-element planetary reverse-gear, the sun and planetcarrier 72 slide together on the splined input shaft 43, for the sun to dog-clutch the final output shaft 44 at 46 for solid forward drive, or for the carrier 72 to dog-clutch the fixed casing at 75 for reverse. Oil-pressure supply system.-The main pressure-oil supply-lines 113, 114 are fed by two gear pumps, one 104, engine-driven, the other 106, vehicle-driven, the latter feeding through a spring-loaded, non-return valve 112 which is only opened by pressure of the vehicle-driven pump 106 when vehicle-speed is sufficient for the latter to supply the system. The main supply-line 122 of the clutch-brake -controlvalve system is open to the pressure-line 114 only when the valve 100 is opened by movement of the reverse shift-rail 86 to the forward or reverse driveposition. Clutch-brake valve system.-The valve 124 controlling the geared drive carrier-brake 50 comprises a grooved piston 138 secured to a spring- loaded diaphragm 141 subject to engine suction when the valve 154 is opened by release of the accelerator-pedal, whereupon the valve-piston 138 moves to the right, Fig. 8 position, (left Fig. 6), exhausting the pressure-supply line 122 through passages 130 and 152, the latter opening to the gear-casing. The brake-piston chamber 168 also exhausts through passages 171, 172 and the same outlet 152, and oilpressure is supplied through a port 174 to a chamber 169 to act on the rear face of a flange 167 on an outer sleeve 166 of the brake-piston, whereby the carrier-brake 50 is disengaged and geared drive is interrupted. Depression of the accelerator-pedal initiates a geared drive by closing the suction-valve 154 to vent the diaphragm 141, whereupon a spring 139 moves the valve-piston 138 to the left, Fig. 8, (right Fig. 6), its end covering the exhaust outlet 152 and opening the brake-piston supply-port 172 to the oil pressure-line 122, so that the brakeengaging chamber 168 is pressurised but the outer disengaging chamber 169, although cut-off from the pressure-supply by the valve 138, is not opened to exhaust, the oil remaining trapped therein to oppose the leftward (Fig. 8) brake-engaging movement of the piston assembly. Initially therefore the outer sleeve 166 of the piston assembly remains behind whilst an inner valve-member 175 of the piston. moves to the left, Fig. 8 (right Fig. 6) compressing a spring 180 acting on a second inner valve-member 176 secured. to the brakeactuating rod 55. Leftward movement of the inner valve members 175, 176 in the outer sleeve 166 is arrested by stops in a position in which the disengaging-chamber 169 is exhausted through registering ports 182, 181, 183, in the members, whereupon the pistonassembly 166, 175, 176 moves rapidly to the spring 180 to be compressed, permitting the outer valve-member 166 to move to the left, Fig. 8, closing the exhaust-port 181 so that the oil is again trapped in the disengaging chamber 169 to resist further engagement, and the piston members 175, 166, 176 come into positive abutment. Initial movement of the pistonassembly to the brake-applying position is thus rapid, with light pressure applied through the spring 180, but final engagement is slower under full oil-pressure applied positively through the now abutting members 175, 166 and 176 of the piston-assembly, which results in a gradual pick-up of geared drive under acceleratorcontrol. Governor-suction valve.-The valve 123 controlling the direct-drive clutch 64 is operated by the governor-suction valve, which latter comprises a rotating cylindrical valve-sleeve 211, driven by helical gears 214, 213 by the output shaft 44 of the gear and having within it two co-operating piston-valves, one 224 operated by spring-loaded centrifugal masses 221 pivoted on the outer valve-sleeve 211, the other 225 bearing against a spring-loaded diaphragm 236 subject to engine-suction. Ports 228, 229 in the piston-valves 224, 225 and 218 in the outer sleeve 211, are brought into registry above a predetermined speed (15 m.p.h.) only, and when speed and suction conditions are suitable, to close communication with an exhaust port and open a pressuresupply duct 220, leading from the vehicle-driven oil-pump 106 alone, to a delivery duct 207 feeding the direct-drive clutch-valve 123. In the latter oil-pressure passes through a groove in a small piston-valve 199 to act on the right (Fig. 8) face of a spring-loaded piston-valve 196 which moves to the left, cutting out an exhaust connection to a duct 133 through an outlet 200 and communicating ports 129, 134 to direct oil-pressure from the main supply 122 through the duct 133 to the direct-drive clutch-engaging pistons 69 and also to the left, Fig. 8 (right, Fig. 6), face of a supplementary piston 146 which has a spring-loaded stem slidable in a bore in the piston-valve 138 of the brakecontrol valve 124. In the geared-drive, brakeapplied position, Fig. 6, the pistons 146, 138 are directly abutting, so that oil-pressure, applied to the right face of the piston 146, moves the pistons to the left, Fig. 6 (right, Fig. 8), against t