LINEAR MOTION ACTUATOR

To provide a linear motion actuator in which occurrence of biting between a rotary part constituting a screw mechanism and a screw section of a linear motion part and a failure in an electric motor are prevented in advance.SOLUTION: In a linear motion actuator 1, a linear motion part 33 moving back and forth in an axial direction in accordance with rotation of a screw shaft 31 has: a first linear motion member 34 that is screwed with the screw shaft 31; a second linear motion member 35 that is disposed so as to be movable in the axis direction relatively to the first linear motion member 34; and a coil spring 36 that is interposed between the linear motion members 34, 35, and is deformed so as to be expanded/contracted in the axial direction in accordance with the axial relative movement of the linear motion members 34, 35. The linear motion actuator has a first magnetic sensor 7A as a position detection sensor 7 for detecting the advancing limit of the first linear motion member 34, wherein when the first magnetic sensor 7A detects the advancing limit of the first linear motion member 34, rotational motion of an electric motor 2 that positively rotates the screw shaft 31 while contraction deformation of the coil spring 36 is allowed, is electrically restricted.SELECTED DRAWING: Figure 1 【課題】直動アクチュエータにおいて、ねじ機構を構成する回転部と直動部の螺合部での噛み込みの発生と、電動モータの故障とを未然に防止する。【解決手段】ねじ軸３１の回転に伴って軸方向に進退移動する直動部３３が、ねじ軸３１と螺合した第１直動部材３４と、第１直動部材３４に対して軸方向に相対移動可能に設けられた第２直動部材３５と、両直動部材３４，３５間に介在し、両直動部材３４，３５の軸方向の相対移動に伴って軸方向に伸縮変形するコイルばね３６とを有する直動アクチュエータ１である。第１直動部材３４の前進限を検出する位置検出センサ７としての第１磁気センサ７Ａを有し、このセンサ７Ａが第１直動部材３４の前進限を検出したとき、コイルばね３６の圧縮変形が許容された状態でねじ軸３１を正回転させる電動モータ２の回転運動が電気的に規制される。【選択図】図１