Patent ID: 6747382
Filing Date: 2004-06-08
Classification: H02K

Abstract:
A small-sized stepping motor comprising:a substantially cylindrical shaped rotor including a rotor magnet portion; a rotary shaft inserted and fixed through said rotor magnet portion, said rotary shaft including a narrow portion provided on an output side of said rotary shaft so as to be separated from the rotor magnet portion; a stator opposed to said rotor, wherein the stator comprises two pairs of stator cores, each stator core comprising an inner yoke and an outer yoke, and the inner and outer yokes being integrated by a coil bobbin; an output side bearing provided on an output side face of one of the two pairs of stator cores of said stator, and supporting a portion near an output portion of said rotary shaft; an opposite side bearing holding portion provided on an opposite side face of the other of the two pairs of stator cores of said stator for holding an opposite side bearing movable in an axial direction and supporting an opposite side of said rotary shaft; an urging member held by the opposite side bearing holding portion for urging the opposite side bearing toward the output side so that the rotor and the rotary shaft are urged toward the output side; and a resin washer fitted on said narrow portion of said rotary shaft and pushed by the urging member via the narrow portion of said rotary shaft to be brought into contact with the output side bearing to thereby be positioned in the axial direction of the rotary shaft; wherein said stator cores are integrally formed with the coil bobbin by insert molding, and said output side bearing, the coil bobbin and the opposite side bearing holding portion are made of the same resin and integrally formed with each other, whereby the output side bearing and the opposite side bearing holding portion are integrated through the coil bobbin with the same resin; wherein a lead screw is formed at the output portion protruded from the output side bearing and a rotation of said lead screw directly moves an operated member.