Actuator

An actuator configured to drive a boost pressure control valve of a supercharger, the actuator comprising:

• an electric motor;
• an output shaft that is coupled to the boost pressure control valve through a linkage mechanism;
• 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 output shaft is made of metal;
• the output gear is made of resin;
• the output shaft has a surface-processed portion that has a series of projections and recesses and is formed at a portion of an outer peripheral surface of the output shaft;
• the output gear includes:
• a fixing portion that is joined to the surface-processed portion;
• a connecting portion that connects between a toothed portion of the output gear and the fixing portion with the resin while the toothed portion includes a plurality of teeth;
• and
• a magnetic circuit device that is provided to sense a rotational position of the output gear;
• a length, which is measured from a center of a boundary surface between the connecting portion and the fixing portion in an axial direction of an axis of the output shaft to one end part of a joint between the surface-processed portion and the fixing portion on the linkage mechanism side along the joint, is indicated by L1;
• a length, which is measured along the joint from the center of the boundary surface to an opposite end part of the joint that is opposite to the linkage mechanism in the axial direction of the axis of the output shaft, is indicated by L2;
• and
• a relationship of L1>L2 is satisfied.