Screw member tightening and loosening apparatus, and screw member tightening and loosening method

A screw member tightening and loosening method for tightening and loosening a screw member using a rotating body comprising a fitting part configured to fit to a fitted part of the screw member, and is supported so as to be rotatable about an axis of the fitting part, the fitting part shaped such that it repeatedly forms a predetermined shape about a rotational direction, and wherein one rotational direction is defined as a first rotation direction, and an opposite rotational direction is defined as a second rotation direction, the method comprising:

• a first step of moving the rotating body so that the fitted part and the fitting part are axially aligned with each other;
• a second step of, while maintaining a state in which the fitted part and the fitting part are axially aligned with each other, moving the rotating body to press the fitting part against the fitted part;
• a third step of, while maintaining a state in which the fitting part is pressed against the fitted part, rotating the rotating body to the first rotation direction by a first predetermined angle, wherein the first predetermined angle corresponds to a predetermined angle;
• and
• a fourth step of, while maintaining the state in which the fitting part is pressed against the fitted part, rotating the rotating body to the second rotation direction by a second predetermined angle, which is smaller than the first predetermined angle, the fourth step performed after the third step, wherein
• the fitting part is configured to fit to the fitted part when an angular position of the predetermined shape of the fitting part repeatedly appearing at every predetermined angle matches an angular position of a corresponding shape of the fitted part,
• the third step includes a first detection step of detecting a state of the rotating body, and
• in the third step, if it is determined based on the state of the rotating body detected in the first detection step that a shift in angular position between the fitted part and the fitting part is not greater than an angle threshold set to a value equal to or smaller than the second predetermined angle, the method advances to the fourth step, wherein
• a direction along the axis of the fitting part is an axial direction, and the axial direction to which the fitting part approaches the fitted part is a first axial direction,
• in the first detection step, at least one of a rotation torque of the rotating body, and a moving amount of the rotating body in the axial direction is detected, and
• in the third step, it is determined that a shift in angular position between the fitted part and the fitting part is not greater than the angle threshold if the rotation torque of the rotating body is greater than a first threshold, or if a moving amount of the rotating body to the first axial direction is greater than a second threshold.