Abstract: A method for assembling a rotor and a sliding structure of a rotor and an oscillator which allow easy assembly with an improvement in productivity. The method is one for assembling a rotor of a power transmission device having an oscillator and a rotor rotatably assembled into said oscillator, said rotor making rotations and oscillations of said oscillator, comprising the steps of: loading a plurality of rolling elements to be arranged between the eccentric body and the oscillator via a retainer for positioning the rolling elements from inside the retainer; and assembling the eccentric body into inside the loaded rolling elements.

Abstract: There is provided a method for manufacturing an external gear with a maintained high quality at low cost, which maintains a lubricated state of tooth flanks of the external gear with smaller manufacturing steps than the conventional method. The method for manufacturing an external gear internally in mesh with an internal gear inside the internal gear includes: a cold forging step of setting a material 80 in a lower cold forging die 100 having a tooth profile forming part 102 on an inner periphery of a circular recess 101 thereof, and pressing the material 80 so as to extend outward in the radial direction in order to form the material into a disc 81 and simultaneously, form an external tooth profile on the outer periphery of the disc 81; and a punching step of punching the disc 81 to form holes 11, 15, 17 required for constituting a power transmission mechanism. The surface roughness of the tooth flanks due to the cold forging is maintained on the completed product.