Patent ID: 7893593

Claim:
An electric rotary machine comprising: a casing including an end frame; an armature equipped with an armature shaft to produce torque, the armature shaft being retained at an end thereof by the end frame to be rotatable through a bearing; a commutator disposed on said armature, said commutator having a cylindrical commutator surface over the armature shaft at a side of the end retained by said end frame; brushes riding on the commutator surface in electrical contact therewith, said brushes sliding on the commutator surface during rotation of the commutator; a holder plate secured to said casing; brush holders each of which retains one of said brushes, said brushes being secured to said holder plate; 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 an axial 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 a stopper mechanism provided at the side of the end of the armature shaft retained by said end frame, said stopper mechanism working to stop said armature from moving relative to the end frame in an axial direction of said armature, wherein said holder plate has surfaces which are opposed to each other in a thickness-wise direction thereof and which extend perpendicular to the armature shaft, said holder plate being in abutment of one of the surfaces with an end wall of the end frame oriented in the axial direction of said armature, and each of said brush holders has a holder wall facing one of opposed surfaces of a corresponding one of said brushes in the axial direction of said armature, the one of the opposed surfaces being farther from the end frame in the axial direction of said armature than the other, and the holder wall being so located as to be kept away from said brush through a gap when said armature is at a position farthest from the end frame within a range where said armature is allowed to move by said stopper mechanism.