Patent ID: 7906884

Claim:
An electric motor comprising: a columnar or cylindrical rotor rotatable in a first direction about an axis of a rotating shaft, the rotor including at least one permanent magnet; a first stator core including a first set of teeth, each tooth of the first set of teeth including a first end portion positioned so as to oppose the rotor and a second end portion positioned at an opposite end from the first end portion, a winding wound around a circumferential side surface of each tooth of the first set of teeth; and a second stator core including a second set of teeth, the second set of teeth including first end portions positioned to oppose the second end portions of the first set of teeth, the second set of teeth also including second end portions retained by a retainer; wherein the second stator core is movable in at least the first direction or in a reverse rotational direction opposite to the first direction; when the second set of teeth are positioned directly opposite to the first set of teeth, a magnetic resistance between the second end portion of the one tooth of the first set of teeth and the first end portion of one tooth of the second set of teeth is smaller than a magnetic resistance between the first end portions of adjacent teeth of the first set of teeth to cause a magnetic flux of the permanent magnet to flow through the first stator core and the second stator core; and when the second set of teeth are moved so that the one tooth of the second set of teeth is placed at a position between the adjacent teeth of the first set of teeth, a magnetic resistance between the one tooth of the second set of teeth and the second end portion of the one tooth of the first set of teeth is larger than a magnetic resistance between the first end portions of the adjacent teeth of the first set of teeth to cause the magnetic flux of the permanent magnet to flow through the first end portions of the adjacent teeth of the first set of teeth.