Patent ID: 7859159

Claim:
An electric motor comprising: a cylindrical stator having excitation coils of three phases; and a mover that is movable relative to the stator, wherein, when electric currents are supplied to the excitation coils, the mover moves relative to the stator, wherein the mover has an opposed surface facing the excitation coils, the opposed surface being provided with a field pole or a protrusion that helically extends about an axis of the mover, wherein each excitation coil extends helically in the same direction as the field pole or the protrusion about the axis of the mover so as to face the field pole or the protrusion, wherein each excitation coil is formed by a continuous single wire and includes a first coil portion, a second coil portion, and a folded-back portion, the first coil portion helically extending from a first end to a second end of the mover in the axial direction, the second coil portion helically extending from the second end to the first end in the same direction as that of the first coil portion, the folded-back portion being connected between the first coil portion and the second coil portion, and wherein the field pole has a north pole and a south pole, and is configured such that, when the first coil portion corresponds to the north pole, the second coil portion corresponds to the south pole.