Patent GB-1321522-A (GB)
Title: Variable speed transmissions
IPC: F16H3/12
Filed: 1971-01-06
Abstract: 1321522 Change-speed gear; friction clutches DANA CORP 6 Jan 1971 [27 Jan 1970] 705/71 Headings F2C and F2D Ten reduced ratios, direct-drive and one reverse are provided by selectively clutching freely-mounted wheels 52 ... 60 and 62 ... 70, driven by wheels 32 . . . 40 fast on an input shaft 14, to two countershafts 16, 18, which drive respectively through wheels 84, 88 and 92, 94, a sun 90 and ring gear 96 of a planet train, the planet-carrier 98 of which is fast on a final output shaft 15. In all the reduced ratios the input shaft 14 is driven through a friction clutch 138, direct drive being provided by a second friction clutch 136 driving through an inner shaft 13. During shift both these clutches are in temporary slipping engagement for synchronizing. For the first two ratios the countershaft 16 is driven alone through wheel 52 or 54 and clutch 72, to drive the sun 90 whilst the ring 96 reacts on plunger-controlled detents 110. For the remaining reduced ratios both countershafts 16, 18 are driven simultaneously through appropriate selector clutches 72 ... 76, 78 ... 82, to drive the sun 90 and ring 96 at successively increasing speeds, the detents 110 being released. For the one reverse the ring detents 110 are again locked by their plungers, all the countershaft clutches are released, and a clutch 104 is engaged to drive a reverse idler shaft 100 from wheels 32, 52, 102, providing a reversed drive to the sun 90 through meshing wheels 106, 84. For each forward shift it is necessary to engage only one dog clutch and disengage another. Thus in fourth ratio clutch 78 engages gear 64 and clutch 72 gear 54. To shift to fifth ratio, clutch 72 is disengaged, and clutch 74 engaged with wheel 56. The clutch 78 remains engaged with wheel 64, and hence only one dog clutch engagement is required. All other shifts to ten have this same feature. Friction clutches.-The direct and gear clutches 136, 138, Fig. 3A (detailed in Fig. 2, not shown) are engaged by supplying liquid pressure 826, 804 selectively to their presser plates 1110, 1120 respectively, the arrangement being such, that during a gear shift, both presser plates receive the full clutch-engaging pressure (60 p.s.i.), but the provision of slidable distance pins 1130 between the presser plates permits only a limited slipping engagement of both clutches. Under this condition the gear clutch 138 is caused to preponderate by the provision of small inner pistons 1150 sliding in the presser plate 1120, and exposed to clutch engaging pressure. The distance pins 1130 also produce positive release of one clutch when the other is fully engaged by its presser plate. Cooling is described below. Selection system pneumatic.-The six dog clutches 72 ... 82, Fig. 1, are actuated by six individual double-acting piston motors 528 ... 538, of which four provide two active positions and neutral, whilst 532 and 538 provide one active position and neutral. The actuator for reverse is not shown. Exhaust of pressure air from one or other side of each motor to produce a shift is controlled by a pair of rotary valves 454, Fig. 7, turned by a selectively-toothed rack 197, moved axially by a thirteen-position piston 350, controlled by a thirteen-position manual selector-valve 194, all as detailed below. Shift servos.-The shift servos 528 ... 538 are basically all similar and each comprises a pair of inner pistons 582, Fig. 10, fast on a piston-rod 594 actuating its dog clutch through a bellcrank 614. The inner pistons 582 slide in outer pistons 584 which abut a central snap-ring 592 in the neutral position shown, to which they are moved by supplying equal air pressure to both ends of the cylinder 530. Exhausting the air pressure from either end causes both inner and outer pistons to move to that end and engage the dog clutch. For a two-position motor 532 operative movement from neutral is upwards only, downward movement therefrom being prevented by a stop sleeve 532a. Interlock.-The shift cylinders are arranged in groups of three, one 528, 530, 532 operating the three clutches of the lower countershaft 18, the other 534, 536, 538 those of the upper countershaft 16. The piston-rods of each group are interlocked by large and small drift pins 634, 638, the latter passing through the pistonrods, the former having bevel-ended lock surfaces. The end pins actuate interlock valves 650a, 650 to provide a liquid pressure neutral signal in a line 682d for a purpose described below. In first and second speeds and reverse all the clutches of the countershaft 18 remain in neutral, and to prevent the interlock valve 650 from issuing a false neutral signal under these conditions, a lock piston 630 at the opposite ended drift pin prevents the pins from opening the valve 650, and also prevents the pistons of any of these three motors moving from neutral. In all ratios other than first, second, neutral, and reverse the ring-gear detent plungers 110 are retracted, and this action directs liquid pressure through a line 649 to retract the piston 630, which frees the interlock pins 634 for operating the valve 650 to produce a neutral signal, when appropriate, in the line 682d, and for operation of the motors. The upper interlock valve 650 produces a similar neutral signal in the same line, but its action is not restricted. Selector valve complex.-Pressure air is normally supplied to both ends of the shift cylinders 528 &c. through passages 542, 546 &c. Fig. 9, leading from two circular series 482, 484 of ports in a constantly pressurized valve chamber 449, Fig. 9, one series 482 for the cylinders 528, 532, the other 484 for the cylinders 534, 538. Centred one on each circular series 482, 484 is a control valve 454, which is selectively turned to overlie individual ports 486 &c. of its series, cutting it off from pressure 449 and exhausting it through a valve passage 458 to actuate the appropriate shift cylinder 528 &c. These two control valves 454 carry pinions 420, 422 meshing opposite sides of a rack 197 having selectively positioned teeth 432 to turn the valves in a required shift sequence as the rack is stepped axially by a thirteen-position piston 350, the pinions being held whilst not being operated by spring-loaded detents 436. The position of the rack-piston 197 is determined by a thirteen-position manual selector valve 194, Fig. 5, comprising a radial valve plate 292 which is turned by a manual shift-lever 238, guided in a slotted gate 246, to position exhaust outlets 234 over a selected one of two arcuate series of ports connected by pipes 327 &c. with selectively positioned ports 356 &c. in the wall of the rack-piston cylinder 196, to which pressure air is constantly supplied at both ends. When a selected port 356 &c. is exhausted by the manual valve 194 the rack-piston 350 travels axially until it covers the exhausting port and then holds that position. Control hydraulic.-Liquid pressure for engaging the gear and direct clutches 138, 136 is supplied to lines 682, 684, Figs. 3A, 3B, by a pump 672. Clutch pressure is controlled manually by a clutch valve 686, the regulator loading of which is controlled by a spring-loaded clutch pedal P, depression of which releases clutch pressure, causing clutch disengagement. The clutch pedal is used for starting only, and not during gear shift. The pressure line 684 feeds also a screwadjustable primary pressure regulating valve 706 which regulates supply pressure to 60 p.s.i. for clutch engagement, and its by-pass feeds a by-pass regulator valve 730 regulating to 30 p.s.i. for feed to a gear lubricating line 737 and a clutch cooling line 746, the latter being exhausted during clutch disengagement, to avoid clutch drag, by release of clutch pressure 766, 762 normally acting on the left face of a spring- loaded valve 740. Selection between the gear and direct clutches 138, 136 is performed by an alternator valve 748, in conjunction with two lag valves 750, 752. During a shift the alternator valve 748 is shifted leftwards to use both clutches for torque unloading and synchronizing, by air pressure exhausted by the selector valves 200, 202 from the dog clutch actuating cylinders 528 &c., Fig. 3B, and passing through a ball check 516 and line 806 to act on an end piston 810, Fig. 3B, of the alternator valve 748, this pressure being exhausted at 834 in full leftward movement, but the leftward position being maintained until gear establishment by a liquid pressure neutral signal 682d, provided by valves 650, 650a operated by the interlocks of the two shift cylinder groups 528, 532 and 534, 538, pressure being fed to the interlock valves through a neutral valve 395 actuated by the linear rack piston 197 in settings above second ratio. Operation neutral-1.-Depression of the clutch pedal P, Fig. 3B, zeroises the delivery pressure 766, 804 from the clutch valve 686, releasing the clutches 136, 138 and allowing the cool valve 740 to move left to exhaust the clutch cool line 746. The manual shift lever 328 is now turned to first ratio setting, which exhausts the port 396 of the linear actuator 196, Fig. 7, causing its rack-piston 197 to make one upshift step left. This turns only the upper selector valve 200 Figs. 7, 8, one step clockwise to vent the port (498, Fig. 9, not shown) leading to the top of the cylinder 534, which loads the dog clutch 72, Fig. 1, right to clutch the wheel 52. The lower selector valve 202, Fig. 3B, remains unmoved, venting at 486 a line 542 which permits air pressure 902 (received from the left end of the linear actuator 196) to thrust inwards detents 110 holding the ring gear 96 establishing first ratio. In engaging the first ratio clutch 72 the cylinder 534, Fig. 3B, closes the interlock valve 650a, whilst 650 is kept closed by an interlock piston 630 spring loaded to an upper position shown, when inward movement of the detents 110 blocks a pressure release line 649. With first ratio established, rele