Method for manufacturing motor yoke, motor yoke, and motor

A method for manufacturing a motor yoke, which has a cylindrical portion in which a stator core is accommodated, wherein the cylindrical portion has a securing portion at an axial section except the axial ends of the cylindrical portion, the securing portion abuts against the stator core to secure the stator core, and the securing portion projects radially inward with respect to the axial ends of the cylindrical portion, the method comprising:

• preparing a work that corresponds to the yoke before the securing portion is formed;
• inserting a mandrel, which includes a forming portion to form the securing portion, into the work, wherein the forming portion either includes a portion that has a radial dimension smaller than the inner diameters of the axial ends of the cylindrical portion or has an outer diameter smaller than the inner diameters of the axial ends of the cylindrical portion;
• and
• pressing the axial section of the cylindrical portion on which the securing portion is to be formed with a die from radially outside of the cylindrical portion toward the forming portion of the mandrel, thereby displacing the pressed section of the cylindrical portion radially inward and forming the securing portion on the work.