Movable body reciprocating mechanism, cleaning mechanism, optical scanning device, and image forming apparatus

A movable body reciprocating mechanism comprising:

• a rotation shaft that has:
• a circumferential surface;
• and a spiral ridge part protruded on the circumferential surface and extending spirally in an axial direction, and that is rotatable in a first rotation direction and a second rotation direction opposite to the first rotation direction;
• a drive source that causes the rotation shaft to rotate;
• and
• a moving body that includes:
• a cylinder part through which the rotation shaft is inserted;
• and an engaging part protruded on an inner circumferential surface of the cylinder part and engaging with the spiral ridge part, and that reciprocates along the axial direction in an engaged state in which the engaging part is engaged with the spiral ridge part as the rotation shaft rotates,
• wherein
• a state of the moving body changes among:
• a first state in which the moving body is in the engaged state and moves in a first movement direction as the rotation shaft rotates in the first rotation direction;
• a second state in which the moving body releases the engaged state after moving in the first movement direction;
• and a third state in which, as the rotation shaft rotates in the second rotation direction, the engaging part reengages with the spiral ridge part to form the engaged state and the moving body moves in a second movement direction opposite to the first movement direction,
• the rotation shaft has, successively disposed adjacent to an end part of the spiral ridge part at a side of the spiral ridge part in the first movement direction:
• a planar part composed of only the circumferential surface;
• and a cylindrical protrusion part that is protruded radially outward from the circumferential surface, and
• the cylinder part of the moving body has:
• a first end part that is located at a side of the cylinder part in the first movement direction and fits onto the cylindrical protrusion part in the second state;
• and a second end part that is located at a side of the cylinder part in the second movement direction and radially faces an outer circumferential surface of the spiral ridge part in the second state;
• the movable body reciprocating mechanism further comprising
• a biasing member that biases the moving body toward the second movement direction when the moving body is in the second state, and that places the moving body in the third state by causing the engaging part to reengage with the spiral ridge part when the rotation shaft rotates in the second rotation direction,
• wherein
• the engaging part of the cylinder part includes:
• an engagement leading end part at a side of the engaging part in the second movement direction;
• and a lateral wall that extends along the axial direction toward the first movement direction from the engagement leading end part,
• the reengagement is realized by the engagement leading end part and the lateral wall being invited in by a spiral starting end part at a side of the spiral ridge part in the first movement direction upon transition from the second state to the third state, and
• the lateral wall has, with respect to the axial direction, a predetermined inclination toward a spiral direction of the spiral ridge part.