Actuator, manufacturing method of actuator, light scanner and image forming apparatus

An actuator comprising:

• a movable part rotatable around a rotation center axis, the movable part having movable top and movable bottom surfaces opposite to each other, the movable top surface extending in a first direction;
• a pair of connection parts connected to the movable part, the pair of connection parts having connection top and connection bottom surfaces;
• and
• a support part that supports the pair of connection parts, wherein
• the movable part is in a cross shape in a plan view,
• the movable bottom surface has a recess, a recess bottom surface of the recess is located between the movable top surface and the movable bottom surface, and a permanent magnet is located on the recess bottom surface,
• each of the connection parts includes a pair of beam members,
• a beam distance between the pair of beam members gradually increases from the connection bottom surface toward the connection top surface when seen from a direction in parallel to the rotation center axis of the movable part,
• each of the beam members has inner and outer side surfaces between the connection top surface and the connection bottom surface, and one of the inner and outer surfaces having two inclined surfaces that incline with respect to the first direction, the two inclined surfaces extending in the same direction, and
• given that a first distance between ends at the connection bottom surface of the pair of beam members is W1 and a thickness of the pair of beam members in the thickness direction of the movable part is t, the following expression (1) is satisfied
• w
• 1
• <
• t
• tan
• ⁢
• ⁢
• 54.73
• ⁢
• °
• .
• (
• 1
• )