Turning device

1. A turning device comprising:

a hollow housing;

a turning shaft housed inside the housing, having a first male screw groove formed by one threading manner of a left screw and a right screw and a second male screw groove formed by the other threading manner of the left screw and the right screw, and turning left and right wheels to be turned by moving in an axial direction;

a first nut screwed to the first male screw groove and rotatably supported inside the housing;

a second nut screwed to the second male screw groove and rotatably supported inside the housing;

a first driving source generating a first driving force;

a second driving source operating independently of the first driving source and generating a second driving force;

a first power transmission part transmitting the first driving force generated by the first driving source to the first nut and giving an axial force to the turning shaft by rotating the first nut;

a second power transmission part transmitting the second driving force generated by the second driving source to the second nut and giving the axial force to the turning shaft by rotating the second nut;

a rotation regulating part provided over the housing and the turning shaft, allowing relative movement of the turning shaft with respect to the housing in the axial direction as well as regulating relative rotation of the turning shaft around its central axis with respect to the housing, wherein:

the rotation regulating part includes a turning shaft side engaging part provided in the turning shaft, and a housing side engaging part provided in the housing and engaged with the turning shaft side engaging part to allow relative movement of the housing and the turning shaft in the axial direction and to regulate relative rotation of the turning shaft around the axis with respect to the housing,

the rotation regulating part includes a protrusion that is the turning shaft side engaging part and extends to an outer side of the turning shaft in a radial direction or to an inner side of the housing in the radial direction, and a groove that is the housing side engaging part and is formed on an inner peripheral surface of the housing itself to extend in the axial direction of the turning shaft,

the protrusion and the groove are provided only at one place in an arbitrary part in a circumferential direction on an outer peripheral surface of the turning shaft, and

the protrusion is provided to protrude on an outer peripheral surface of an annular member, and an inner peripheral surface of the annular member is fitted to an outer peripheral surface of the turning shaft to be fixed to the turning shaft.

2. The turning device according to claim 1 ,

wherein the first driving source and the second driving source are configured, in cooperation with each other, to transmit the first driving force and the second driving force to the turning shaft through the first power transmission part and the second power transmission part so as to move the turning shaft.

3. The turning device according to claim 1 ,

an absolute value of a first torque applied to the turning shaft from the first nut by the first driving force transmitted by the first power transmission part and an absolute value of a second torque applied to the turning shaft from the second nut by the second driving force transmitted to the second power transmission part are equal.

4. The turning device according to claim 3 ,

wherein the first driving source and the second driving source generate the first driving force and the second driving force so that the absolute value of the first torque and the absolute value of the second torque become equal.

5. The turning device according to claim 3 ,

wherein an absolute value of the first driving force and an absolute value of the second driving force are equal, as well as a first reduction ratio at which the first power transmission part performs transmission to the first nut while reducing a rotation speed and a second reduction ratio at which the second power transmission part performs transmission to the second nut while reducing the rotation speed are equal.

6. The turning device according to claim 1 ,

wherein the first male screw groove and the second male screw groove respectively correspond to any one of a male screw groove of a ball screw having a rolling passage for rolling spherical rolling elements, a roller screw having a rolling passage for rolling roller-type rolling elements, and a sliding screw, and

the first nut and the second nut respectively correspond to any one of a ball screw nut housing the spherical rolling elements, a roller screw nut housing the roller-type rolling elements, and a sliding screw nut screwed to the sliding screw so as to correspond to the first male screw groove and the second male screw groove.

7. The turning device according to claim 6 ,

wherein the first driving source and the second driving source are arranged coaxially with the turning shaft and configured to directly transmit the first driving force and the second driving force to the first nut and the second nut, or arranged in parallel to the turning shaft and configured to transmit the first driving force and the second driving force to the first nut and the second nut through an endless member.

8. The turning device according to claim 1 ,

wherein an outer diameter of the outer peripheral surface of a fitting part of the turning shaft to which the annular member is fitted is larger than an outer diameter of the outer peripheral surface of the turning shaft other than the fitting part.

9. The turning device according to claim 1 ,

wherein a lubricating part is interposed between the housing side engaging part and the turning shaft side engaging part.