| 主权项 |
1. A power steering apparatus comprising:
a wheel turning shaft configured to turn a wheel to be steered by being moved in the axial direction of the shaft according to a rotation of a steering wheel; a ball screw mechanism configured to cause the wheel turning shaft to move in the axial direction of the wheel turning shaft; and an electric motor configured to provide a rotational force to the wheel turning shaft via the ball screw mechanism, wherein the ball screw mechanism includes a wheel turning shaft-side ball screw groove formed on an outer circumferential side of the wheel turning shaft and shaped into a spiral groove, a nut disposed to surround the wheel turning shaft and to be rotatable relative to the wheel turning shaft, the nut having a rotational axis, the nut including one end side and an opposite end side along the rotational axis, a nut-side ball screw groove formed on an inner circumferential side of the nut and shaped into a spiral groove, the nut-side ball screw groove being configured to define a ball circulation groove together with the wheel turning shaft-side ball screw groove, a plurality of balls disposed in the ball circulation groove, a circulation member disposed on an outer side of the nut in a radial direction relative to the rotational axis, the circulation member being configured to connect one end side and an opposite end side of the ball circulation groove so that the plurality of balls can circulate from the one end side to the opposite end side of the ball circulation groove, a housing formed to contain at least the one end side of the nut relative to the circulation member in the direction along the rotational axis, a bearing disposed on the one end side relative to the circulation member in the direction along the rotational axis between the nut and the housing and formed to surround the nut, the bearing being configured to rotatably support the nut in the housing, and a circular fixation member formed to surround the wheel turning shaft and provided with an abutment surface in abutment with an end surface of the bearing on one side in the direction along the rotational axis, the fixation member being configured to fix the bearing to the housing by being fixed in the housing with the abutment surface in abutment with the end surface of the bearing on the one side in the direction along the rotational axis, the fixation member being provided around the nut by being moved from the opposite end side to the one end side of the nut in the direction along the rotational axis at the time of assembling, wherein the plurality of balls moves in the ball circulation groove according to a rotation of the nut relative to the wheel turning shaft, thereby causing the wheel turning shaft to move relative to the nut in the longitudinal direction of the wheel turning shaft, wherein the electric motor is arranged to provide a rotational force to the nut so that the nut rotates relative to the wheel turning shaft, wherein the abutment surface of the fixation member is formed on at least an inner side of the fixation member in the radial direction, wherein the fixation member includes a cutout portion provided on the inner side of the fixation member in the radial direction, and formed to prevent the fixation member from interfering with the circulation member when the fixation member is inserted in the housing, and wherein the cutout portion is formed in such a manner that a distance from the rotational axis of the nut to an inner end of the cutout portion in the radial direction is longer than a distance from the rotational axis of the nut to an inner end of the abutment surface in the radial direction. |
