Rotary apparatus including a rotation shaft and sleeve having tapped portions, and laser beam printer having the same

A laser beam printer comprising:

• a rotary apparatus having:
• a sleeve;
• a rotation shaft which is inserted into the sleeve;
• a polygon mirror which is fixed to the rotation shaft;
• a yoke which is fixed to the rotation shaft;
• permanent magnets which are fixed to the yoke;
• and a stator which is fixed to the sleeve, and which is opposed to the permanent magnets;
• a laser oscillating apparatus;
• and
• a photosensitive drum, wherein:
• tapped portion is formed in a part of an outer circumference of the rotation shaft, and a part of an inner circumference of the sleeve, respectively;
• the tapped portions are temporarily engaged with each other in a process of inserting the rotation shaft into the sleeve by a rotating of the rotation shaft to a predetermined direction, and then the tapped portions are separated from each other by continuing the rotating;
• the rotation shaft that is inserted into the sleeve is retained by the separated condition;
• and
• a rotation direction of the rotation shaft in a driving process is identical with the predetermined direction.