PURPOSE: To enable rapid origin returning processing without useless action even when a reference position is at any point in an action range by arranging a dog whose rotation angle area detected as a reference position overlaps the rotation angle area detected as an action range border zone.
CONSTITUTION: A dog 51 whose rotation range that a reference is detected from a reference position detection light shield detection part 53 partially overlaps the rotation range that a range limit is detected from an upper limit or a lower limit detection light shield detection part 52 or 54 works so that each set of output of the upper limit detection light shield detection part 52, the lower limit detection light shield detection part 54 and the reference position detection light shield detection part 53 do not overlap each other during all rotation ranges. Thus, there will be no such a state that the direction of the reference position is not known, and origin returning processing can be executed rapidly and without useless action.
KAKINUMA BUICHI
HARADA TADANORI
