Patent ID: 8344561

Claim:
A stepping motor comprising: a rotor having a drive magnet; and a stator having a drive coil, the drive coil being wound in a tube shape and disposed on an outer peripheral side of the drive magnet; wherein the stator comprises: a first yoke provided with a first end plate part formed in an approximate ring shape, the first end plate part being disposed so as to cover one end face of the drive coil in an axial direction of the rotor; a second yoke provided with a second end plate part formed in an approximate ring shape, the second end plate part being disposed so as to cover an other end face of the drive coil in the axial direction; a plurality of first pole teeth provided in the first yoke, formed to stand up from an inner peripheral end of the first end plate part, and disposed so as to face an outer peripheral face of the drive magnet; and a plurality of second pole teeth provided in the second yoke, formed to stand up from an inner peripheral end of the second end plate part, and disposed so as to face the outer peripheral face of the drive magnet; wherein the plurality of first pole teeth and the plurality of the second pole teeth are alternately disposed in a circumferential direction of the rotor; wherein one end face in the axial direction of the drive magnet is disposed between a first base end part that is a base end part of the first pole tooth that is formed at a boundary part, and a second tip end part of the second pole tooth, wherein said boundary part is defined between the first end plate part and the first pole tooth in the axial direction; wherein the other end face in the axial direction of the drive magnet is disposed between a second base end part that is a base end part of the second pole tooth that is formed at a boundary part and a first tip end part of the first pole tooth, wherein said boundary part is defined between the second end plate part and the second pole tooth in the axial direction; wherein the first tip end part and the second tip end part are formed in a convex curved shape; and wherein a distance between the one end face of the drive magnet and the first base end part in the axial direction is shorter than a distance between the one end face of the drive magnet and the second tip end part in the axial direction, and a distance between the other end face of the drive magnet and the second base end part in the axial direction is shorter than a distance between the other end face of the drive magnet and the first tip end part in the axial direction.