Single-Axis Actuator

Abstract

As compared to a single-axis actuator in which a ball returning passage of a ball screw mechanism is made of a circulating tube, the cross-sectional shape perpendicular to the longitudinal direction of a threaded shaft of a slider can be made small, when the diameter of the outer circumferential circle of the threaded shaft of the present invention is same as that of the circulating tube type, and the load capacity can be made large, when the size in the longitudinal direction of the threaded shaft of the slider of the present invention is same as that of the circulating tube type. The ball returning passage for returning the balls ( 4 ) of a ball screw mechanism from an end point to a start point of a raceway encompasses: a through hole ( 24 ) penetrating through a slider ( 2 ) in a longitudinal direction of a threaded shaft ( 3 ); and end deflectors ( 6 ). Each of the end deflector ( 6 ) has a direction changing passage to be connected with the through hole ( 24 ). A main body ( 61 ) of the end deflector ( 6 ) is fit into a notch part ( 26 ) arranged on each of both ends in the longitudinal direction of the threaded shaft ( 3 ) of a slider body ( 2 A).

1 . A single-axis actuator comprising:
 a guide rail having a letter U shaped cross section perpendicular to a longitudinal direction of the single-axis actuator;   a slider arranged in a depression of the guide rail having the letter U shaped cross section;   a plurality of rolling elements allocated between the guide rail and the slider;   a nut formed in the slider to be parallel to the guide rail;   a threaded shaft penetrating through the nut; and   a plurality of balls allocated in a raceway between a spiral groove of the nut and a spiral groove of the threaded shaft, wherein   the guide rail has a rolling face implementing a rolling passage for the plurality of rolling elements, on each of inner side faces opposing each of side faces of the slider,   the slider includes a rolling face for opposing the rolling face of the guide rail and implementing the rolling passage, a returning passage for the plurality of rolling elements, and a direction changing passage for communicating the returning passage and the rolling passage,   the plurality of rolling elements are allocated in a circulating passage implemented by the rolling passage, the returning passage, and the direction changing passage,   a ball returning passage for returning the plurality of balls from an end point of the raceway to a start point of the raceway is implemented by a through hole penetrating through the slider in a longitudinal direction of the threaded shaft, and circulating parts having direction changing passages connected with the through hole and allocated at both ends in the longitudinal direction of the threaded shaft of the slider, and   a rotational force of the threaded shaft is transmitted via the plurality of balls to the nut by rotation of the threaded shaft, the rolling elements circulate in the circulating passage while rolling in a loaded state, and the slider is movable along the guide rail.   
     
     
         2 . The single-axis actuator according to  claim 1 , wherein the plurality of the rolling elements are rollers, and a virtual intersection point of load effecting lines of rows of the rollers rolling in a double-row rolling passage formed in the each of side faces of the slider exists on an inner side of the rolling passage in a width direction of the guide rail. 
     
     
         3 . The single-axis actuator according to  claim 1 , wherein an area S 1  of an outer circumferential circle of the threaded shaft and an area S 2  of a cross section cut along a plane of the slider perpendicularly to the longitudinal direction of the threaded shaft satisfies S 1 >=0.2S 2 . 
     
     
         4 . The single-axis actuator according to  claim 1 , wherein
 the slider includes a slider body and an end cap secured on an outer side of the slider body in the longitudinal direction of the threaded shaft,   the spiral groove of the nut is formed in the slider body,   an end of the slider body in the longitudinal direction of the threaded shaft has a non-nut part in which the spiral groove is not formed,   a circulating part depression is formed for fitting the circulating part at a boundary with the non-nut part on an inner circumferential face of a nut part in which the spiral groove is formed,   the circulating part is fit in the circulating part depression,   a spacer is arranged in the non-nut part, and   the spacer is arranged between the circulating part and the end cap in a contact state.   
     
     
         5 . The single-axis actuator according to  claim 4 , wherein a spacer depression into which the spacer is fit is formed to be continuous with the circulating part depression in the longitudinal direction of the threaded shaft, and the spacer is fit in the spacer depression. 
     
     
         6 . The single-axis actuator according to  claim 1 , wherein the through hole implementing the ball returning passage is allocated within a range of a circle indicating a groove bottom of the spiral groove of the nut in a vertical direction of the slider body. 
     
     
         7 . The single-axis actuator according to  claim 1 , wherein
 the slider includes a slider body and an end cap secured on an outer side of the slider body in the longitudinal direction of the threaded shaft,   the spiral groove of the nut is formed in the slider body,   the slider body has a depression into which the circulating part is fit, and   a direction of the circulating part scooping the plurality of balls is parallel or perpendicular to a top face of the slider body.   
     
     
         8 . The single-axis actuator according to  claim 1 , wherein the slider includes a plurality of the sliders. 
     
     
         9 . The single-axis actuator according to  claim 2 , wherein an area S 1  of an outer circumferential circle of the threaded shaft and an area S 2  of a cross section cut along a plane of the slider perpendicularly to the longitudinal direction of the threaded shaft satisfies S 1 >=0.2S 2 .