Multi-stage planetary roller power transmission device

A multi-stage planetary roller power transmission device comprising:

• a high-speed power transmission mechanism including a first sun shaft rotatable about an axis thereof, a first fixed ring disposed radially outward of the first sun shaft so as to be concentric with the first sun shaft, a plurality of first planetary rollers disposed between the first sun shaft and the first fixed ring with a first negative clearance, a plurality of first support shafts configured to respectively support the first planetary rollers such that the first planetary rollers are rotatable, and a first carrier into which the first support shafts are press-fitted, the first carrier being configured to rotate in conjunction with revolution of the first planetary rollers, and the first carrier having an annular shape;
• and
• a low-speed power transmission mechanism including a second sun shaft rotatable about an axis thereof at a lower speed than a speed at which the first sun shaft rotates, a second fixed ring disposed radially outward of the second sun shaft so as to be concentric with the second sun shaft, a plurality of second planetary rollers disposed between the second sun shaft and the second fixed ring with a second negative clearance, a plurality of second support shafts configured to respectively support the second planetary rollers such that the second planetary rollers are rotatable, and a second carrier into which the second support shafts are press-fitted, the second carrier being configured to rotate in conjunction with revolution of the second planetary rollers, and the second carrier having an annular shape, wherein a clearance amount of the first negative clearance and a clearance amount of the second negative clearance are equal to each other, and the number of the first planetary rollers is smaller than the number of the second planetary rollers.