Electric power steering device

摘要

An electric power steering device includes a worm which is swingably connected to the rotation shaft of an electric motor through a joint. A first end portion and second end portion of the worm are supported by a first bearing and a second bearing, respectively. A pair of elastic members elastically urge the worm to an axial neutral position. An annular leaf spring which is held by a housing urges the second end portion toward a worm wheel through the second bearing. A synthetic resin member having a sliding contact surface which is in contact with the leaf spring is integrally disposed on the second bearing.

主权项

1. An electric power steering device comprising:
a worm having a first end portion which is connected swingably and torque-transmittably to a rotation shaft of an electric motor through a joint, and having a second end portion which is on a side opposite to the first end portion; a worm wheel which meshes with the worm; a housing which houses the worm and the worm wheel; a first bearing which is held by the housing, the first bearing rotatably supporting the first end portion of the worm; a second bearing which rotatably supports the second end portion of the worm; a pair of elastic members which are placed on both sides of the first bearing with respect to an axial direction of the worm, respectively, the pair of elastic members elastically urging the worm to an axial neutral position; an annular leaf spring having an inner circumferential surface, the annular leaf spring held by the housing through frictional engagement to surround a periphery of the second bearing, the annular leaf spring elastically urging the second end portion of the worm toward the worm wheel through the second bearing; and a synthetic resin member having: (i) a first contact surface that is in sliding contact with the leaf spring, the synthetic resin member sliding along the inner circumferential surface of the leaf spring in the axial direction of the worm, a frictional force between the leaf spring and the sliding contact surface of the synthetic resin member being smaller than a frictional force between the leaf spring and the housing; and (ii) a second contact surface that is in contact with an outer periphery of the second bearing through fitting the synthetic resin member adjacent to the outer periphery of the second bearing.