SCREW MECHANISM AND LINEAR MOTION ACTUATOR HAVING THE SAME

To stably maintain operation accuracy required for a screw shaft for a long period while reducing costs of a screw mechanism.SOLUTION: A screw mechanism 3 comprises a nut 31 and a screw shaft 32, and the shaft screw 32 moves forward to one axial direction or backward to the other axial direction according to a rotation direction of the nut 31. A stopper 34 restraining a backward movement limit of the screw shaft 32, and a detent member 35 restraining the screw shaft from rotating around its axial line by being fitted with a guide groove 5e of a housing 5 are aligned and fixed in an area nearer one axial side than the nut 31 in an axial direction.SELECTED DRAWING: Figure 1 【課題】ねじ機構のコスト低減を図りつつ、ねじ軸に必要とされる動作精度を長期間に亘って安定的に維持可能とする。【解決手段】ナット３１とねじ軸３２とを備え、ナット３１の回転方向に応じてねじ軸３１が軸方向一方側に前進又は軸方向他方側に後退移動するねじ機構３において、ねじ軸３１の外周面のうち、ナット３２よりも軸方向一方側の領域に、ねじ軸３１の後退移動限を規定するストッパ３４と、ハウジング５の案内溝５ｅに嵌合されることによりねじ軸がその軸線回りに回転するのを規制する回り止め部材３５とを軸方向に並べて固定した。【選択図】図１