Rail assembly applied to optical actuator, manufacturing method thereof and insert rail structure applied to optical actuator

1. A manufacturing method of a rail assembly which is applied to an optical actuator comprising a base and a carrier provided to be movable in an optical axis direction with respect to the base through a ball, comprising:

producing a metal insert member by press forming, the metal insert comprising an insert rail, a jig, and a connection bridge configured to connect the insert rail and the jig;

positioning the metal insert member in the injection mold using the jig;

performing injection molding by supplying a synthetic resin to the injection mold to form a guide groove structure into which the insert rail is inserted, wherein the guide groove structure is integrally formed with either a base or a carrier of the optical actuator; and

separating the connection bridge from the insert rail by cutting connection parts between the connection bridge and the insert rail, wherein, before the cutting, the connection parts are formed in the jig,

wherein the guide groove structure and the insert rail form the rail assembly,

the guide groove structure provided on at least one of the base and the carrier, formed of a synthetic resin, and configured to define a guide groove configured to extend long in the optical axis direction, and

the insert rail formed of a metal and installed in the guide groove to guide movement of the ball, the insert rail comprising:

a rail main body configured to extend long in the optical axis direction along the guide groove, insert molded into the guide groove structure, and having at least one contact surface configured to come into contact with the ball; and

at least one protrusion configured to protrude from a side surface of the rail main body and embedded in the guide groove structure,

wherein the rail main body comprises:

a first contact surface part and a second contact surface part formed by bending the rail main body with respect to a predetermined reference line configured to extend in the optical axis direction, and configured to come into contact with the ball on both sides of the reference line; and

at least one opening formed in the rail main body along the reference line.

2. The manufacturing method of claim 1 , wherein the guide groove structure comprises an insert fixing part configured to connect the first contact surface part and the second contact surface part within the guide groove.

3. The manufacturing method of claim 1 , wherein the guide groove structure comprises:

a bottom surface configured to form a bottom of the guide groove; and

a first side surface part and a second side surface part configured to extend from both sides of the bottom surface so as to define the guide groove together with the bottom surface,

wherein the insert rail is embedded in the bottom surface so that the at least one contact surface of the insert rail is exposed to come into contact with the ball.

4. The manufacturing method of claim 1 , wherein a pair of the main bodies and a pair of connection bridges are further included in the rail assembly, each main body connected to the jig by the connection bridge, respectively.