Gear unit

A gear unit for transmitting torque, at a predetermined reduction gear ratio, between a pair of partner members which are relatively and rotatably coupled to each other,

• the gear unit comprising:
• an outer cylinder which can be fixed to one of the partner members;
• a plurality of internal gear pins which are mounted on an inner peripheral face of the outer cylinder;
• a carrier which is housed inside the outer cylinder and can be fixed to the other one of the partner members;
• a crank shaft which includes a shaft part rotatably supported by the carrier and a plurality of eccentric parts which are decentered relative to the shaft part;
• a plurality of oscillating gears which include through-holes of a size, in which the eccentric parts of the crank shaft can be inserted therethrough, and external teeth capable of engaging with the internal gear pin, and which are supported by the carrier so as to oscillate in conjunction with a rotation of the crank shaft;
• a plurality of roller bearings which are respectively provided to the plurality of eccentric parts of the crank shaft, and support the oscillating gear so that it is relatively rotatable in relation to the eccentric parts of the crank shaft on an inner peripheral face of the through-holes of the oscillating gear, and has rolling elements and a retainer which rollably retains the rolling element between the oscillating gear and the eccentric parts;
• and
• a washer which is provided at a position where the washer is able to come into contact with the retainer of the roller bearing provided to each of the adjacent eccentric parts, and which regulates a movement of the roller bearing in an axial direction, wherein
• a housing recess which houses the washer is formed on at least one face among faces of the adjacent oscillating gears that face each other,
• the washer is housed in the housing recess, and
• the housing recess includes an axial direction regulating surface which comes into contact with the washer from the axial direction of the crank shaft and regulates movement of the washer in the axial direction, and a radial direction regulating surface which comes into contact with an outer peripheral surface of the washer and regulates movement of the washer in a radial direction.