Recesses and projections that extend in an axial direction are formed on an outer-circumferential surface of a molded resin body. The recesses are provided on portions where are extended outward from the winding and are on the outer circumferential surface. In addition, further recesses and projections that extend in a radial direction are formed on an axial-direction end surface of the molded resin body. The further recesses are provided on portions of the axial-direction end surface that are aligned in the axial direction with the winding.