Patent ID: 7348698

Claim:
An actuator for operating a transmission control valve of an automatic transmission apparatus, said actuator comprising: a stepping motor comprising: an exterior casing having a first end and a second end in a direction of a motor central axis; a motor main body composed of: a stator disposed inside said exterior casing; and a rotor rotatably disposed inside said stator around said motor central axis, said rotor being having magnets constituting magnetic poles mounted to an outer circumferential surface of a cylindrical bush, and an internal thread portion being formed on an inner peripheral wall surface of said bush; and a shaft having a first end and a second end, said shaft being disposed such that said second end thereof projects outward from said exterior casing at a position of said motor central axis by screwing an external thread portion formed on said first end of said shaft into said internal thread portion of said bush; a housing linked to said second end of said exterior casing in said direction of said motor central axis, said second end of said shaft projecting outward from said housing along said direction of said motor central axis; a power conversion mechanism for converting torque acting around said motor central axis of said rotor into a motive force in a direction along said motor central axis by regulating rotation of said shaft so as to move said shaft in said direction along said motor central axis; and an operating member mounted to a second end portion of said shaft projecting outward from said housing, said operating member being moved in said direction along said motor central axis to operate said transmission control valve, wherein a penetrating aperture is disposed through said first end of said exterior casing in said direction of said motor central axis so as to communicate between an interior portion of said bush and an exterior portion of said exterior casing, and a filter is disposed so as to cover said penetrating aperture from said second end of said exterior casing in said direction of said motor central axis.