Patent ID: 6866608

Claim:
A planetary gear device comprising: a ring-shaped or columnar first member having a circular outer circumferential surface; a second ring-shaped member disposed concentrically so as to surround the circular outer circumferential surface of the first member; a third ring-shaped member disposed concentrically so as to surround a circular outer circumferential surface of the second ring-shaped member; an internal gear coaxially attached to one ring-shaped end surface of the third ring-shaped member; a sun gear coaxially attached to an end surface, which is circular or ring-shaped, of the first member; a plurality of planet gears that are attached to a ring-shaped end surface of the second ring-shaped member and engage with the internal gear and the sun gear; a first bearing formed between the circular outer circumferential surface of the first member and a circular inner circumferential surface of the second ring-shaped member; and a second bearing formed between a circular outer circumferential surface of the second ring-shaped member and a circular inner circumferential surface of the third ring-shaped member, wherein the first member and the sun gear are formed from a single member having a ring shape or columnar shape, and an inner ring-side raceway groove of the first bearing is formed in an outer circumferential surface part of a circular outer circumferential surface of the single member on one side in a device axial direction, and external teeth that compose the sun gear are formed in an outer circumferential surface part on the other side of the single member.