Abstract: A coupling apparatus is provided with a first coupling member, a second coupling member and a damper member. The damper member is arranged between the first coupling member and the second coupling member. At least one of the first coupling member and the second coupling member has a tubular circumferential wall surrounding the outer circumference of the damper member. Accordingly, it is easy to control the diameter of an accommodating hole accommodating the coupling apparatus.

Abstract: An armature includes an armature core, a rotary shaft inserted into a shaft fixing hole of the armature core, and coils each wound about one of teeth of the armature core. The teeth extend radially. The armature core includes an inner core having the shaft fixing hole, and an outer core that is provided about and is integrated with the inner core. The inner core is formed by laminating a plurality of magnetic steel plates. The outer core is formed by compression molding magnetic powder, and includes the teeth. Accordingly, the armature core has a high mechanical strength and is capable of obtaining a high magnetic flux density. Also, the armature core is easy to manufacture.

Abstract: A stator for a motor includes a stator core, an insulator, and coils. The stator core includes an annular portion and teeth, which extend radially from the annular portion. The stator core is divided into core segments in the circumferential direction. Each core segment has an arcuate portion and one of the teeth, which extends from the arcuate portion. The insulator insulates each coil wound around one of the teeth from the stator core. The insulator includes coupling portions at positions corresponding to the circumferential ends of the arcuate portions. Each coupling portion couples the adjacent core segments to be rotatable relative to each other. The insulator facilitates manufacture of the stator.

Abstract: A coupling apparatus is provided with a first coupling member, a second coupling member and a damper member. The damper member is arranged between the first coupling member and the second coupling member. At least one of the first coupling member and the second coupling member has a tubular circumferential wall surrounding the outer circumference of the damper member. Accordingly, it is easy to control the diameter of an accommodating hole accommodating the coupling apparatus.

Abstract: A rotor of a motor includes a cylindrical rotor shaft that is formed through plastic working. The shaft includes a positioning portion that is formed in an inner peripheral surface of the cylindrical shaft by the plastic working of the shaft. The positioning portion is detachably engageable with a securing member, which is insertable into the shaft in an axial direction of the shaft to position the shaft in a circumferential direction. When the positioning portion is engaged with the securing member, relative rotation between the shaft and the securing member is limited.

Abstract: An armature includes an armature core, a rotary shaft inserted into a shaft fixing hole of the armature core, and coils each wound about one of teeth of the armature core. The teeth extend radially. The armature core includes an inner core having the shaft fixing hole, and an outer core that is provided about and is integrated with the inner core. The inner core is formed by laminating a plurality of magnetic steel plates. The outer core is formed by compression molding magnetic powder, and includes the teeth. Accordingly, the armature core has a high mechanical strength and is capable of obtaining a high magnetic flux density. Also, the armature core is easy to manufacture.

Abstract: A cylindrical portion of a motor yoke has a securing portion to secure a stator core at an axial section except the axial ends of the cylindrical portion. When manufacturing the yoke, at first, a work is prepared that corresponds to the yoke before the securing portion is formed. A mandrel, which includes a forming portion, is then inserted into the work. The forming portion has an outer diameter smaller than the inner diameters of the axial ends of the cylindrical portion. Subsequently, the axial section of the cylindrical portion on which the securing portion is to be formed is pressed with dies from radially outside of the cylindrical portion toward the forming portion, thereby displacing the pressed section of the cylindrical portion radially inward and forming the securing portion on the work. As a result, the motor yoke with high accuracy is manufactured while reducing a waste of machining.

Abstract: A stator for a motor includes a stator core, an insulator, and coils. The stator core includes an annular portion and teeth, which extend radially from the annular portion. The stator core is divided into core segments in the circumferential direction. Each core segment has an arcuate portion and one of the teeth, which extends from the arcuate portion. The insulator insulates each coil wound around one of the teeth from the stator core. The insulator includes coupling portions at positions corresponding to the circumferential ends of the arcuate portions. Each coupling portion couples the adjacent core segments to be rotatable relative to each other. The insulator facilitates manufacture of the stator.

Abstract: A stator for a motor includes a stator core, an insulator, and coils. The stator core includes an annular portion and teeth, which extend radially from the annular portion. The stator core is divided into core segments in the circumferential direction. Each core segment has an arcuate portion and one of the teeth, which extends from the arcuate portion. The insulator insulates each coil wound around one of the teeth from the stator core. The insulator includes coupling portions at positions corresponding to the circumferential ends of the arcuate portions. Each coupling portion couples the adjacent core segments to be rotatable relative to each other. The insulator facilitates manufacture of the stator.

Abstract: A cylindrical portion of a motor yoke has a securing portion to secure a stator core at an axial section except the axial ends of the cylindrical portion. When manufacturing the yoke, at first, a work is prepared that corresponds to the yoke before the securing portion is formed. A mandrel, which includes a forming portion, is then inserted into the work. The forming portion has an outer diameter smaller than the inner diameters of the axial ends of the cylindrical portion. Subsequently, the axial section of the cylindrical portion on which the securing portion is to be formed is pressed with dies from radially outside of the cylindrical portion toward the forming portion, thereby displacing the pressed section of the cylindrical portion radially inward and forming the securing portion on the work. As a result, the motor yoke with high accuracy is manufactured while reducing a waste of machining.

Abstract: A rotor of a motor includes a cylindrical rotor shaft that is formed through plastic working. The shaft includes a positioning portion that is formed in an inner peripheral surface of the cylindrical shaft by the plastic working of the shaft. The positioning portion is detachably engageable with a securing member, which is insertable into the shaft in an axial direction of the shaft to position the shaft in a circumferential direction. When the positioning portion is engaged with the securing member, relative rotation between the shaft and the securing member is limited.

Abstract: Commutator segments are divided into a plurality of groups, each of which includes two or more of the commutator segments. Generally planar short-circuiting parts are respectively provided to the groups of the commutator segments and are located radially inward of the commutator segments in such a manner that the short-circuiting parts are spaced one after the other in an axial direction of the commutator. Each short-circuiting part is seamlessly and integrally formed with and is electrically connected to a corresponding sub-element of each commutator segment of a corresponding one of the groups of the commutator segments, and at least one of the short-circuiting parts is located within an axial extent of at least one of power supply brushes measured in the axial direction of the commutator. A dielectric body securely holds each commutator segment and each short-circuiting part.

Abstract: A stator for a motor includes a stator core, an insulator, and coils. The stator core includes an annular portion and teeth, which extend radially from the annular portion. The stator core is divided into core segments in the circumferential direction. Each core segment has an arcuate portion and one of the teeth, which extends from the arcuate portion. The insulator insulates each coil wound around one of the teeth from the stator core. The insulator includes coupling portions at positions corresponding to the circumferential ends of the arcuate portions. Each coupling portion couples the adjacent core segments to be rotatable relative to each other. The insulator facilitates manufacture of the stator.

Abstract: Commutator segments are divided into a plurality of groups, each of which includes two or more of the commutator segments. Generally planar short-circuiting parts are respectively provided to the groups of the commutator segments and are located radially inward of the commutator segments in such a manner that the short-circuiting parts are spaced one after the other in an axial direction of the commutator. Each short-circuiting part is seamlessly and integrally formed with and is electrically connected to a corresponding sub-element of each commutator segment of a corresponding one of the groups of the commutator segments, and at least one of the short-circuiting parts is located within an axial extent of at least one of power supply brushes measured in the axial direction of the commutator. A dielectric body securely holds each commutator segment and each short-circuiting part.

Abstract: A method of manufacturing a commutator includes the steps of punching a commutator forming plate out of a plate member having a plurality of projections formed at predetermined intervals in such a way that the projections extend in parallel to one another, forming the commutator forming plate cylindrical and arranging the projections on an inner surface of the cylindrical commutator forming plate, filling an interior of the cylindrical commutator forming plate with a molten resin, segmenting the cylindrical commutator forming plate at predetermined angular distances after curing of the resin to thereby form commutator pieces, and positioning the plate member in a mold. The step of punching the commutator forming plate is carried out using a first punch having a plurality of recesses corresponding to the projections. Formed at those portions of each recess which correspond to both corner portions of each projection narrow portions that become narrower in a depth direction of that recess.

Abstract: A cup shaped yoke made of sheet material has an opening portion provided in a side wall on an axial end side, a shoulder portion provided in the sidewall on another axial end side, a magnet installation portion for installing a magnet, which is provided in the side wall between the opening and shoulder portions and whose wall thickness is substantially equal to thickness of the sheet material, and a bottom portion, which is provided in a bottom wall, having a boss shaped bearing accommodating portion in a center thereof. Each wall thickness of the opening, shoulder and bottom portions including the boss shaped bearing accommodating portion is equal to or smaller than a half of wall thickness of the magnet installation portion.

Abstract: A rotor core includes a plurality of first core sheets and a plurality of second core sheets. The first core sheets and the second core sheets are laminated in the axial direction of the rotor core. Each first core sheet includes a plurality of first teeth laid out in a ring form on a same plane. Each second core sheet includes a plurality of second teeth laid out in a ring form on a same plane. Each first tooth is placed over the associated second tooth in the axial direction of the rotor core. Each tooth has a winding portion extending in the radial direction of the rotor core and an arm portion integrally provided at an outer end of the winding portion in the radial direction of the rotor core and extending in the peripheral direction of the rotor core. Each arm portion has a coupling portion at one end. Each first tooth is coupled to that one of the second teeth which is stacked on another first tooth adjoining in the peripheral direction of the rotor core by coupling of their coupling portions.

Abstract: A plate material is drawn to form a first-drawing product in the shape of an elliptically cylindrical container having an elliptical cross section. Then, the first-drawing product is drawn to form a re-drawing product in the shape of a generally circular cylindrical container. Next, the re-drawing product is drawn to form a late-drawing product in the shape of an elliptically cylindrical container having an elliptical cross section in which a major axis and a minor axis of the elliptical cross section are reversed with respect to a major axis and a minor axis of the elliptical cross section of the first-drawing product. Thereafter, the late-drawing product is drawn to form a final product as a yoke.

Abstract: A rotor core includes a plurality of first core sheets and a plurality of second core sheets. The first core sheets and the second core sheets are laminated in the axial direction of the rotor core. Each first core sheet includes a plurality of first teeth laid out in a ring form on a same plane. Each second core sheet includes a plurality of second teeth laid out in a ring form on a same plane. Each first tooth is placed over the associated second tooth in the axial direction of the rotor core. Each tooth has a winding portion extending in the radial direction of the rotor core and an arm portion integrally provided at an outer end of the winding portion in the radial direction of the rotor core and extending in the peripheral direction of the rotor core. Each arm portion has a coupling portion at one end. Each first tooth is coupled to that one of the second teeth which is stacked on another first tooth adjoining in the peripheral direction of the rotor core by coupling of their coupling portions.

Abstract: In a method of manufacturing a partly flat yoke having curved circumferential walls to which magnets are to be attached and having parallel flat circumferential walls which constitute main magnetic paths and whose each radial thickness is larger than that of the curved circumferential walls, by drawing a sheet of metal plate, the metal plate is held down between a die and projections of a wrinkle preventing plate provided at given angular positions around an outer circumference of a cavity of the die so as to correspond to the curved circumferential walls. Then, a punch presses down the metal plate into the cavity so that material of the metal plate extends axially into the cavity, while the material of the metal plate flows circumferentially from each side of the curved circumferential walls to sides of the parallel flat circumferential walls.