| 摘要 |
PURPOSE:To increase the degree of freedom of a plan of a reduction gear ratio by a method wherein a lowmost part is positioned on a radial axis passing approximately the center of arbitrary one tooth part of an internal gear and a part of the shaft part of a bolt is engaged with an axially extending recessed groove formed in the outer peripheral surface of the internal gear. CONSTITUTION:When an internal gear 20 is formed independently from a cutting part machine frame 13, a lowermost part is positioned on a radial axis (a) passing approximately the center of an arbitrary one tooth part 20a of the gear 20, and axially extending recessed grooves 20b are formed in number, conforming to that of bolts 14, in the outer peripheral surface of the gear 20. When the gear 20 is mounted, it is positioned so that a part of the shaft part of the bolt 14 is engaged with the recessed groove 20b formed in the outer peripheral surface thereof. This constitution enables the substantial increase of the outer size of the gear 20, resulting in enlargement of a range in which the size of a tooth root and a pitch circle can be increased. |
