Linear actuator having mechanism for stopping linear movement of output shaft without touching rotor

A linear actuator, comprising:

• a stator assembly shaped into a cylinder defining a hollow, the stator assembly including
• a plurality of windings, and
• a plurality of stator yokes each having an array of pole teeth which constitute an inner circumference of the stator assembly, and which are excited by the windings;
• a rotor assembly shaped into a hollow-cylinder, and rotatably housed in the hollow of the stator assembly, the rotor assembly including
• a ring-shaped magnet having a plurality of magnetic poles, constituting an outer circumference of the rotor assembly, and opposing the pole teeth of the stator assembly with a predetermined distance therebetween, and
• a female screw disposed at an inner circumference of the rotor assembly;
• an output shaft having a male screw formed at a rearward portion thereof and threadedly engaging with the female screw of the rotor assembly, the output shaft being inserted through the rotor assembly;
• a stopper pin fixedly disposed at a frontward portion of the output shaft, and axially controlling mode and amount of movement of the output shaft initiated by rotation of the rotor assembly;
• and
• a stopper member disposed fixedly with respect to the stator assembly, the stopper member stopping axial movement of the output shaft without making it happen that the stopper pin which moves together with the output shaft touches the rotor assembly.