Actuator

An actuator, comprising:

• a body including a base portion, and a first side wall portion and a second side wall portion provided on the base portion and facing toward each other, an internal space being defined by the base portion, the first side wall portion, and the second side wall portion;
• a slider having a portion that moves inside the internal space;
• and
• a table provided on the slider and configured to be exposed from the internal space,
• wherein each of the first side wall portion and the second side wall portion includes a body side rail groove provided on a surface thereof, the surfaces facing toward the internal space,
• slider side rail grooves are formed respectively on surfaces of the slider that face toward the body side rail grooves,
• body side guide rails are disposed in the body side rail grooves, and slider side guide rails are disposed in the slider side rail grooves,
• the body side guide rails include body side rail accommodated portions accommodated in the body side rail grooves, and body side ball receiving portions configured to be exposed from the body side rail grooves and curved in an arc shape,
• the slider side guide rails include slider side rail accommodated portions accommodated in the slider side rail grooves, and slider side ball receiving portions configured to be exposed from the slider side rail grooves, and forming circular arc grooves together with the body side ball receiving portions,
• balls are retained in the circular arc grooves, and the slider is provided with circulation passages configured to allow the balls to be circulated therein, and
• a dimension of the slider side guide rails in a vertical direction perpendicular to a direction of movement of the slider is greater than a dimension of the body side guide rails in the vertical direction perpendicular to the direction of movement of the slider,
• wherein the body side guide rails include first ball receiving portions and second ball receiving portions serving as the body side ball receiving portions, and also include protruding end portions interposed between the first ball receiving portions and the second ball receiving portions and configured to project toward the slider side guide rails,
• the slider side guide rails include third ball receiving portions and fourth ball receiving portions serving as the slider side ball receiving portions, and also include flat portions interposed between the third ball receiving portions and the fourth ball receiving portions, and
• as the circular arc grooves, first circular arc grooves are formed between the first ball receiving portions and the third ball receiving portions arranged at positions lower than the first ball receiving portions, and second circular arc grooves are formed between the second ball receiving portions and the fourth ball receiving portion arranged at positions higher than the second ball receiving portions.