Patent ID: 7847467
Filing Date: 2010-12-07
Classification: F02N,H01R,H02K

Abstract:
1. An electric rotary machine comprising: an armature working to produce torque; a commutator disposed on said armature, said commutator having a commutator surface; brushes riding on the commutator surface in electrical contact therewith, said brushes sliding on the commutator surface during rotation of said armature; a plurality of protrusions extending on the commutator surface in a circumferential direction of the commutator surface in which said brushes slide on the commutator surface, said protrusions being arrayed substantially in a widthwise direction of the commutator surface perpendicular to the circumferential direction; urging mechanisms each of which works to urge a surface of one of said brushes into constant engagement with said protrusions to establish the electrical contacts between the brushes and the commutator surface; and flat areas formed on end portions of the commutator surface which are opposed to each other in the widthwise direction, the flat areas being unoccupied by said protrusions, wherein a surface of each of the brushes, which rides on the commutator surface, has flat areas which slide on the flat areas of the commutator, respectively wherein each of said brushes has a bending strength of 16 MPa or more, as determined based on a bending strength of a test piece calculated according to an equation of 8×P×L/(2×A×B