| 摘要 |
1,239,794. Change-speed gear. SHIMANO KOGYO K.K. 7 Aug., 1968 [12 Aug., 1967], No. 37675/68. Heading F2D. A three ratio cycle hub planet gear has its ratio shifted automatically by input and output driven centrifugal governors 33, 44. The gear has planet pinions 17 on a carrier 20 meshing a fixed sun gear 16 and a ring gear 12 on a carrier 15. The planet carrier 20 and ring gear carrier 15 are selectively connected to a block 8 fast with a driving sprocket 11 by ratchet clutches 25, 22 and to a driven hub 2 by ratchet clutches 28, 31. The ratchet clutches 25, 31 are held disengaged by the centrifugal governors 33, 44 when the input and output speeds are below predetermined values. For low ratio, with the ratchet clutches 25, 31 disengaged, the block 8 drives the hub 2 through the ratchet clutch 22, ring gear carrier 15, planet gear 12, 17, planet carrier 20 and ratchet clutch 28. When the speed of driving block 8 exceeds a predetermined value the governor weights 33a, 33b pivot outwardly against the bias of a spring 43 to release the pawl of the ratchet clutch 25, whereupon the gear upshifts to direct-drive with the block 8 driving the hub 2 through the ratchet clutch 25, planet carrier 20 and ratchet clutch 28. The ratchet clutch 22 overrunning. When the speed of the hub 2 exceeds a predetermined value the governor weights 44a, 44b pivot outwardly against the bias of a spring 54 to release the pawl of the ratchet clutch 31, whereupon the gear upshifts to overdrive with the block 8 driving the hub 2 through the ratchet clutch 25, planet carrier 20, planet gears 17, 12, ring gear carrier 15 and rachet clutch 31. The ratchet clutches 22, 28 overrunning. The speeds at which ratio shift occur may be varied by adjusting the strength of the springs 43, 54. When the input and output speeds fall below the predetermined values downshifts are prevented until a torque reversal occurs (i.e. back-pedalling) to bring the pawls of the ratchet clutches 25, 31 into a position in which they are held disengaged by the governor weights. The governors 33, 44 may be adjusted so that the ratchet clutch 31 is engaged before the ratchet clutch 25 in which case the block 8 drives the hub 2 through the ratchet clutch 22, ring gear carrier 15 and ratchet clutch 31 for direct-drive. The other ratios being as specified above. |
