Patent GB-759526-A (GB)
Title: Variable-speed transmission
IPC: F16H47/08
Filed: 1953-12-31
Abstract: 759,526. Change-speed gear; friction clutches. WINDFIELDS (1946), Ltd. Dec. 31, 1953 [Jan. 14, 1953], No. 36365/53. Class 80(2) [Also in Groups XXXIV and XXXVII] The selective connections of front and rear stepped-planet or sun-ring trains 36, 46, driven through a preceding fluid transmitter 17. are such that in low both trains reduce in series, their reaction planetcarriers being stationary; in second, the ratio of the rear train is increased by driving its carrier 30 directly forwards by, and at the same speed as, the main input shaft 1, and allowing its previous input member, sun 42, to rotate forwards at reduced speed to act as reaction member through the front train, still with reducing connection to input; and in third, direct-drive, torque-splitting occurs in both trains, as described below. An additional reduced ratio between low and second, with the rear train reducing alone, is provided under certain downshift conditions as described later. Automatic control of all shifts, one dependent on accelerator release, and one overriding manual downshift are provided. Hydromechanical torque-splitting occurs in second speed and direct drive, the torque-share of the fluid transmitter decreasing successively with each upshift. Gear arrangement. The main input shaft 1 drives the impeller 17 of a torque-converter, the reactor 19 of which has a oneway connection 25 with a sleeve-extension 28 of the front-train planet-carrier 37 which reacts to the casing through a oneway detent 40, which latter thus takes reaction from both the front train and the torque-converter. The input sun 32 of the front train is directly connected to the turbine 18 of the torque-converter through a sleeve-shaft 23, and pivoted on the planetcarrier 37 are the centrifugal shoes 61 of a torque-speed responsive friction clutch (described below), the complementary drum 21 of which is fast with the input impeller 17. The output sun 33 of the front train is fast, through a sleeve-shaft, with the input sun 42 of the rear train, the planet-carrier 30 of which reacts to the casing on a one-way detent 54, whilst its output sun 43 drives a final output shaft 91 through a bevel reverse gear controlled by a dog clutch-detent 99, the complementary clutch-detent elements 100, 101 of which have a yielding tangential spring mountings 111. The planet-carrier 30 of the rear train can be connected directly to the main input 1 through a disc clutch 12 engaged by liquid pressure applied in a space 7 to a piston 8 under the electrical control of an output driven enginethrottle-loaded centrifugal governor 158, Fig. 8. The gear provides five phases of operation, one of which is the converter to coupling change, and another of which is the intermediate 1-2 reduced ratio used on downshift. The phases are as follows:- Phase 1.-Lowest speed, ratio 4.33 overall; both planet carriers and the converterreactor stationary; all reducing in series. Phase 2.-ratio 2.06 overall; convertercoupling change; reactor 19 overrunning; no gear shift. Phase 3.-Automatic upshift to second gear, overall ratio 1.42, by the governor clutching the rear carrier 30 directly to input at 12; rear train input sun 42 acting as slow forward reaction member through the unchanged front train, reaction being finally taken by the front planet carrier 37; both trains acting compounded and torque is split into hydraulic and mechanical paths. Phase 4.-Direct drive; rear carrier 30 clutched at 12 to input, as before, front carrier 37 also clutched to input through the centrifugal clutch 61, rendered effective only on torque-reversal by acceleratorrelease. Torque is split in the rear train to half via the planet carrier and sun respectively, that half driving the sun 42 being also split into a mechanical half driving the front planet-carrier 37 and a fluid half driving the front input sun 32. Overall torque-share of the fluid path is thus onequarter of the overall torque. Phase 5.-Special downshift as described later; overall ratio 1.29; rear carrier driving clutch 12 released for reduced drive in rear unit only; split torque drive to rear unit input sun 42 through front train as for phase 4. Reverse.-To facilitate shift of the reverse clutch-dog 99, a band-brake 73 is provided on the input sun 42 of the rear train, this brake being of the back-turn type (described below) for relieving tooth pressure on the deverse shift-dog 99. Centrifugal clutch. - Three friction shoes 61 are pivoted on pins 60, Fig. 3, on the front planet-carrier 37 and engage centrifugally the surrounding input-connected drum 21, the shoes being tied together for simultaneous movement by cranks 65 engaging a common ring 63 which turns against springs 63A to resist outward movement of the shoes. The pivot pins 60 have flattened sides engaged by segmental bushings 60A, and having radial clearance in the shoe-holes. By turning the pins 60 to different radial positions on their mounting, a torque component may be caused to act on the shoes 61 to assist or resist outward movement. Back-turn brake. The brake-band 73 of the rear train input sun 42, used to facilitate shift of the forward-neutral-reverse dog 99, has both ends pivoted to an actuating lever 73A, Fig. 7, one end 75 being held against an adjustable stop 79 by a yielding spring 80. Application of negative-pressure to a piston 82, Fig. 10, rocks a lever 85 about a fixed end-fulcrum 86, to act through a pin 87 to slide a block 88 along a fixed guide 89, leftwards of Fig. 7, which block 88, through a link 90, rocks the bandlever 73A anti-clockwise, to apply the brake and subsequently rock the band and drum in the same direction against the normal direction of rotation, arrow 80C, and against the anchor spring 80, thus torque-relieving the reverse-dog 99. Fluid system.-Fluid for engaging the rear-carrier drive clutch 12 and for lubricating is supplied by a pump 114, secured to the intermediate sleeve-shaft connecting the output front sun 33 with the input rear sun 42, and drawing oil from a sump 116 and inlet port 118, Fig. 5, to feed a delivery port 119. A short-circuit pressure relief valve (not shown) is provided and pressure from the port 119 passes through a balanced piston valve 123 to a passage 122 leading to the pressure-space 7 of the clutch 12 through a central tube 128, Fig. 2, in the hollow centre shaft. A spring- loaded piston accumulator 140A, Fig. 5, cushions pressure-rise on the clutch 12. Low pressure oil for lubricating is supplied through a restrictor 138, Fig. 5, to a space 135, Fig. 2, provided with its own pressurerelief valve (Fig. 6, not shown), and thence forwards to a cylindrical passage 130 around the clutch-supply tube 128, and rearwards through external grooves in an end-collar 127 of the tube 128 to a passage 132, from which passages 130,132 radial drillings lead to the gear parts. Electrical circuit and governor switch.- The clutch control valve 123 is opened to engage the clutch 12 by energizing a solenoid 141, Fig. 5, in a circuit 145 which includes in series a governor switch 158, Fig. 8, and a manual switch 168, a lamp 170 being provided in a branch circuit from the manual switch to indicate closure of the manual switch. The governor switch comprises centrifugal masses 158, pivoted on a carrier on a shaft 152 driven by the usual speedometer drive gear 148, Figs. 2 and 8, on the final output shaft 91. Outward centrifugal movement of the masses 158 operates a contact-button 167 to close a circuit 145, 167a, and is opposed, through a lever 162 by a spring variably loaded by a screw-threaded arm 166 linked to the engine-throttle-controlling accelerator pedal, whereby the closing speed of the switch is raised with increased throttle opening. Operation of the manual switchbutton 168 opens the circuit for downshift when required. Fig. 11 shows a modified governor switch, wherein centrifugal expansion of the masses 184 closes the switch by depressing a pin 188, which actuates a snap switch 191 to shift a contact bar 192 to bridge terminals 195, 196. The pin 188 is carried on shaft 180, loaded by a spring 181, the compression of which is varied by a cam 174, linked by a rock-arm 175 with the accelerator-pedal and acting axially on the spring through the gear 172 which drives the mass-carrier shaft 183. Operation.-Upshift. Starts are made in condition of phase 1 above, increased speed producing in sequence the convertercoupling shift to phase 2; the first gear upshift to phase 3 by the governor-switch controlling engagement of the rear-carrier clutch 12; and finally the second gear upshift to direct-drive; phase 4, caused by the operator momentarily releasing the accelerator-pedal to cause, through torque reversal, forward drive of the centrifugal clutch-shoes 61 on the previously stationary front planet-carrier 37, thus engaging the centrifugal clutch if torque and speed conditions permit. Automatic downshift sequence depends on throttle opening as follows:- Light throttle.-Increased torque reaction on, and reduced speed of the front carrier 37 disengages the centrifugal clutch 61, permitting the front carrier 37 to be arrested by its detent 40 to introduce third phase (ratio 1.42). Further speed reduction causes the governor switch to disengage the rear-carrier clutch 12, introducing second phase (ratio 2.06), followed by the coupling-converter shift to first phase (ratio 4.33). Wide open throttle. - The governor switch causes the first downshift by releasing the rear-carrier clutch 12 to give rear train reduction only, phase 5 (ratio 1.29); followed by disengagement of the centrifugal clutch 61 to give phase 2 (ratio 2.06), and finally the coupling-converter shift to phase 1 (ratio 4.33). Manual downshift. - From phase 4, direct-drive, is by operating the switchbutton 168, Fig. 8, to open the solenoidvalve circuit 145, giving the same effect as full-thr