Patent ID: 8146705

Claim:
An oscillating gear device comprising: an axially fixed gear piece that has a central axis on a first axis and is rotatable around the first axis; and an axially oscillating gear piece that has a central axis on a second axis that oscillates while being inclined with respect to the first axis, and is rotatable around the second axis, wherein one gear piece of the axially fixed gear piece and the axially oscillating gear piece has a plurality of holding grooves aligned radially around the central axis of the one gear piece on a side surface thereof, and pins that are held in the holding grooves and constitute teeth of the one gear piece, wherein the pins are arranged to engage with tooth grooves aligned radially around the central axis of the other gear piece of the axially fixed gear piece and the axially oscillating gear piece on a side surface of the other gear piece, wherein the pin and the tooth groove engage with each other in engagement regions at a predetermined length with respect to the longitudinal direction of the pin, and wherein the following formula (1): r C0 /r F0 =Z C /Z F (1) is satisfied, where r C0 is a distance between an arbitrary point on the central axis of the pin in the corresponding section corresponding to the engagement regions of the pin as viewed in the radial direction of the pin and the first axis, r F0 is a distance between the arbitrary point and the second axis, Z C is the number of pins of the one gear piece, and Z F is the number of tooth grooves of the other gear piece.