An armature of a rotary motor described in patent document 1, for example, is provided with a core of which individual magnetic teeth are wound by concentrated-winding type coils and a commutator. The concentrated-winding type coils on the individual magnetic teeth enable reductions in a dimension in an axial direction and in resistance of the windings, thus allowing a compact, low-amperage rotary motor to be configured as compared to an armature with distributed windings.
A method used for increasing conductor packing factor of concentrated-winding type coils is to split a core and wind conductors under conditions where interference between any adjacent magnetic teeth is avoided. A method used in document 1 mentioned above is to split a core having a plurality of magnetic teeth into a first core portion and a second core portion. Used in document 2 is a method in which a core unit is made up of separate members, that is, a plurality of coil cores and a center core, and the coil cores and the center core are joined with recesses and protrusions thereof fitted together after coils are wound on coil-winding portions of the coil cores. Additionally, referring to document 3, inventors invented a core shape in which each magnetic tooth can be pulled outward to such an extent that winding operation is possible without causing interference between adjacent magnetic teeth. The structure of document 3 has an advantage that split magnetic teeth can be united to form a single body by force-fitting a rotary shaft into a hole in a back yoke portion of each of the magnetic teeth which are alternately overlapped upon completion of conductor winding on all of the magnetic teeth.    Patent document 1: Japanese Patent Application Publication No. 2004-88902 (paragraph 0024)    Patent document 2: Japanese Patent Application Publication No. 2004-328987 (FIG. 4)    Patent document 3: Japanese Patent Application Publication No. 2004-208359 (FIGS. 1 to 8)