| 摘要 |
An object of the present invention is to perform motion conversion between a rotary motion and a linear motion accurately, stably, and efficiently with a relatively simple structure through combination of a planetary gear mechanism of helical gears and a planetary gear mechanism of screw gears. A sun shaft 14, planetary shafts 20, and a ring shaft 16 having respective axes of rotation in parallel with one another are provided. A helical sun gear 22, helical planetary gears 28, and a helical ring gear 42 are provided on the sun shaft 14, the planetary shafts 20, and the ring shaft 16, respectively, and cooperatively constitute a first planetary gear mechanism. A screw sun gear 26, screw planetary gears 30, and a screw ring gear 44 are provided on the sun shaft 14, the planetary shafts 20, and the ring shaft 16, respectively, and cooperatively constitute a second planetary gear mechanism. Either of the gear ratio of the screw sun gear 26 to the screw planetary gears 30 and the gear ratio of the screw ring gear 44 to the screw planetary gears 30 differs from the gear ratio of the helical sun gear 22 to the helical planetary gears 28 and from the gear ratio of the helical ring gear 44 to the helical planetary gears 28. |
