Commutator

Abstract

A commutator includes a cylindrical insulator and commutator pieces, which are formed on the outer circumferential surface of the insulator and arranged side by side in the circumferential direction of the insulator. The commutator pieces are each composed of a conductive plate material, and each includes a connection claw and an engagement claw. The connection claw extends outward in the radial direction of the insulator while being configured to electrically being connected to an armature coil. The engagement claw extends inward in the radial direction of the insulator and engages with the insulator. The commutator pieces each include a recess portion with an undercut formed in a surface facing inward in the radial direction of the insulator.

1 . A commutator comprising:
 a cylindrical insulator, and   a plurality of commutator pieces formed on an outer circumferential surface of the insulator, the commutator pieces being arranged side by side in a circumferential direction of the insulator, wherein   the commutator pieces are each composed of a conductive plate material,   the commutator pieces each include   a connection claw, which extends outward in a radial direction of the insulator and is configured to be electrically connected to an armature coil, and   an engagement claw extending inward in the radial direction of the insulator, the engagement claw engaging with the insulator, and   the commutator pieces each include a recess portion with an undercut formed in a surface facing inward in the radial direction of the insulator.   
     
     
         2 . The commutator according to  claim 1 , wherein
 each commutator piece includes opposite ends with respect to an axial direction of the insulator, with engagement claws arranged at the opposite ends, and   each recess portion is provided between two of the engagement claws with respect to the axial direction of the insulator.   
     
     
         3 . The commutator according to  claim 1 , wherein
 the recess portions are first recess portions   the undercuts are first undercuts each having a first tilt direction,   each commutator piece further includes a second recess portion, and   the second groove portion has a second undercut having a second tilt direction different from the first tilt direction.   
     
     
         4 . The commutator according to  claim 1 , wherein
 each commutator piece has two or more of the recess portions, and   the depth of each of the recess portions that are formed in an area facing one of the connection claws is deeper than that of the recess portions formed in other areas.   
     
     
         5 . The commutator according to  claim 1 , wherein
 each engagement claw is formed by forming a cut in the surface of the corresponding commutator piece facing inward in the radial direction of the insulator and raising the cut, and   the recess portions each include a resultant groove resulting from formation of one of the engagement claws.   
     
     
         6 . The commutator according to  claim 5 , wherein
 each commutator piece has two or more of the engagement claws that are spaced in the circumferential direction of the insulator, and   the engagement claws are each formed by forming a cut and raising the cut, wherein the cut is formed in an area of the commutator piece different from an edge of the commutator piece with respect to the circumferential direction of the insulator.