Actuator, method of manufacturing actuator case thereof, and core for manufacturing

A method of manufacturing an actuator case, the actuator case comprising:

• an output hole formed so as to allow an output member to pass therethrough;
• and
• a fitting groove into which a mounting portion of a boot for covering an outer portion, which protrudes to an outside of the output hole, of the output member is to be mounted,
• the fitting groove being defined on an inner peripheral surface of the output hole by:
• a plurality of first protruding walls formed on an outer end portion of the output hole so as to protrude radially inward and alternate with first gaps in a circumferential direction of the output hole;
• and a plurality of second protruding walls formed on an inner end portion of the output hole so as to protrude radially inward and alternate with second gaps in the circumferential direction of the output hole,
• the first protruding walls and the second protruding walls being arranged so as to avoid overlapping with each other when the output hole is seen in plan view,
• the method comprising a step of molding the actuator case of a resin,
• wherein, in the molding step,
• a core for forming an inner peripheral surface of the output hole is provided, and the core is formed by fitting a first core half body positioned on an outer end side of the output hole and a second core half body positioned on an inner end side of the output hole together so that the first core half body and the second core half body are separable in an axial direction,
• first recessed portions and second recessed portions for forming the first protruding walls and the second protruding walls, respectively, are defined between the first core half body and the second core half body, and
• the resin is injected into a cavity including the first recessed portions and the second recessed portions, which is defined by the first core half body and the second core half body and an outer die for forming an outer surface of the actuator case.