To improve the rotation force transmission efficiency between a high speed shaft and a low speed shaft.
A change gear mechanism incorporated in a casing 8 is constituted of a sun roller 4 co-rotatably provided on a high speed shaft 2, a plurality of planetary rollers 5 or the same diameter whose outer circumferential faces abut on the outer circumferential face of the sun roller 4 and which are rotatably journalled about a roller shaft 53, an armor ring 7 whose internal circumferential face abuts on the outer circumferential face of the respective planetary rollers 5, and a carrier 6 which journals the respective roller shafts 53. The planetary rollers 5 are constituted of a large-diameter roller 51 which abuts on the sun roller 4, and a pair of same-size small-diameter rollers 52 which are concentrically projected to the front/rear of the large-diameter roller; the armor ring 7 whose internal circumferential face abuts on the small-diameter rollers 52 is formed by providing an annular recess part 74 which is recessed from the internal circumferential face in the radial direction so as to loosely fit around the large-diameter roller 51; and the armor ring 7 and the small- diameter rollers 52 are so set that respective abutment faces 72a, 52a become parallel to the axial center.
SAITO MASAAKI
OKAMURA KIKUO
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