Abstract: A first gear set includes an input member that serves as a first gear and an inner ring that serves as a second gear. A first end of the inner ring is inclined with respect to the input member and is in mesh with the input member. The input member has a plurality of retention grooves that are formed in an input member body and a plurality of pins that are retained in the respective retention grooves and that respectively constitute teeth of the input member. The first end has a plurality of tooth grooves that are engageable with the pins. A resultant force of forces applied to each pin from the retention groove and the tooth groove urges the pin toward the retention groove.

Abstract: An oscillating gear device includes an axially fixed gear piece rotatable around a first axis and an axially oscillating gear piece that oscillates while being inclined with respect to the first axis. A plurality of pins held by one of the gear pieces engage with a plurality of tooth grooves of the other gear piece in engagement regions at a predetermined length in longitudinal directions of the pins. A formula rC0/rF0=ZC/ZF is satisfied, where rC0 is a distance between an arbitrary point on the central axis of the pin in a corresponding section corresponding to the engagement regions of the pin as viewed in the radial direction of the pin and the first axis, rF0 is a distance between the arbitrary point and the second axis, ZC is the number of pins of the one gear piece, and ZF is the number of tooth grooves of the other gear piece.