Actuator

An actuator comprising:

• an electric motor;
• an output shaft;
• and
• a speed reducer that is configured to transmit rotation, which is outputted from the electric motor, to the output shaft after reducing a speed of the rotation outputted from the electric motor, wherein:
• the speed reducer has a plurality of gears that include an output gear joined to the output shaft;
• the plurality of gears further includes a compound gear, wherein the compound gear includes a large diameter gear, which has a plurality of large gear teeth, and a small diameter gear, which has a plurality of small gear teeth;
• one of the large diameter gear and the small diameter gear is a metal gear, which is made of a metal member, while another one of the large diameter gear and the small diameter gear is a resin gear, which is made of a resin member, and the resin gear is integrally molded together with the metal gear in one piece;
• the resin member, which forms the resin gear, holds a projection of the metal member, which projects in a radial direction of the compound gear;
• the projection has first and second action surfaces which are opposite to each other in a circumferential direction of the compound gear and respectively contacts the resin member, and the first and second action surfaces are respectively configured to apply a force, which is other than a frictional force, to the resin gear in a rotational direction of the compound gear or receives a force, which is other than the frictional force, from the resin gear in the rotational direction;
• the first and second action surfaces respectively have a constricted shape where a root side of the action surface, at which a root of the projection is located, is constricted relative to a distal side of the action surface, at which a distal end part of the projection is located;
• and
• first and second end surfaces of the projection, which are opposite to each other in an axial direction of the compound gear, respectively contact the resin member at a circumferential location between the first and second action surfaces of the projection.

An actuator comprising:

• an electric motor;
• an output shaft;
• and
• a speed reducer that is configured to transmit rotation, which is outputted from the electric motor, to the output shaft after reducing a speed of the rotation outputted from the electric motor, wherein:
• the speed reducer has a plurality of gears that include an output gear joined to the output shaft;
• the plurality of gears further includes a compound gear, wherein the compound gear includes a large diameter gear, which has a plurality of large gear teeth, and a small diameter gear, which has a plurality of small gear teeth;
• one of the large diameter gear and the small diameter gear is a metal gear, which is made of a metal member, while another one of the large diameter gear and the small diameter gear is a resin gear, which is made of a resin member, and the resin gear is integrally molded together with the metal gear in one piece;
• the resin gear includes a plurality of gate traces, each of which is a trace of injection of resin;
• and
• a perpendicular bisector of a line segment joining between adjacent two of the plurality of gate traces passes a location that is between adjacent two of a plurality of bottom lands of the resin gear on a radially outer side of an axis of the compound gear where the adjacent two of the plurality of gate traces are located.