| 主权项 |
1. A power steering system comprising:
a wheel turning shaft configured to move in an axial direction along with rotation of a steering wheel to turn a steered wheel; a housing configured to include a wheel turning shaft containing portion in which the wheel turning shaft is contained to be movable in the axial direction, and a decelerator containing portion which is disposed in an axially middle portion of the wheel turning shaft containing portion and formed to surround the wheel turning shaft; a wheel turning shaft-side ball screw groove configured to be disposed in an outer periphery of the wheel turning shaft and formed into a spiral groove; a nut configured to be disposed inside the decelerator containing portion, the nut including a main body formed into a ring to surround the wheel turning shaft; a bearing configured to be disposed between an inner wall of the decelerator containing portion and the nut in a radial direction, where a rotation axis of the nut is a central axis, and the radial direction is a radiation direction relative to the central axis, the bearing being formed to surround the nut and rotatably supporting the nut relative to the housing; a nut-side ball screw groove configured to be formed in an inner periphery of the nut, the nut-side ball screw groove being formed into a spiral groove, the nut-side ball screw groove forming a ball circulation groove together with the wheel turning shaft-side ball screw groove; a plurality of balls configured to be disposed in the ball circulation groove; an output pulley configured to be disposed in the nut and formed into a cylinder; an input pulley configured to be so disposed that a second reference axis which is a rotation axis is radially offset relative to a first reference axis which is the rotation axis of the nut, the input pulley being formed into a cylinder; a transmission member configured to extend over the output and input pulleys and transmit rotation of the input pulley to the output pulley; an electric motor configured to rotationally drive the input pulley to rotationally drive the nut through the transmission member and the output pulley, and to impart a steering force to the wheel turning shaft by the rotation of the nut being converted into axial motion of the wheel turning shaft; a circulation member configured to connect first and second ends of the ball circulation groove so that the plurality of balls circulate from the first end of the ball circulation groove to the second end or from the second to the first end; and a communicating hole configured to be disposed in a portion of the nut, avoiding a region in which the plurality of balls circulate in the nut-side screw groove, or in a member disposed radially outside than the nut and radially inside than the inner wall of the decelerator containing portion, the communicating hole allowing communication between a first chamber and a second chamber, in a case where space between the housing and the wheel turning shaft is divided into the first chamber and the second chamber, the first chamber being a space located on one side of the bearing and the plurality of balls on the first reference axis, the second chamber being a space located on the other side. |
