| 摘要 |
Disclosed is- a speed reducer which comprises a crankshaft adapted to be rotated in conjunction with a drive unit, a first eccentric portion provided on the crankshaft, a second eccentric portion provided on the crankshaft, a third eccentric portion provided on the crankshaft, a first externally-toothed gear adapted to be moved in conjunction with the first eccentric portion, a second externally-toothed gear adapted to be moved in conjunction with the second eccentric portion, a third externally-toothed gear adapted to be moved in conjunction with the third eccentric portion, a plurality of pin teeth disposed along an inner periphery of a case to allow each of the first, second and third externally-toothed gears to be in meshing engagement therewith, and an output shaft unit adapted to be rotated in conjunction with the first, second and third externally-toothed gears. The first, second and third eccentric portions are arranged with a given phase difference in a rotation direction of the crankshaft with respect to each other. In the speed reducer, each of the first, second and third externally-toothed gears is in meshing engagement with less than half of the plurality of pin teeth.
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