An image forming apparatus comprises a photosensitive drum, a pivot
inserted through the center of the photosensitive drum for rotatably
supporting the photosensitive drum, and a mass body disposed at the pivot
in the photosensitive drum for changing a frequency of the pivot by
changing the center of gravity and the shape of the pivot. The mass body
is cylindrical in shape. Accordingly, noise and vibration of a developing
device, generated due to friction between rollers and the photosensitive
drum, are absorbed by the mass body. The natural frequency of the pivot is
changed so that amplification of noise and vibration, due to resonance of
a vibration frequency and the natural frequency, can be prevented.
Therefore, exacerbation of the noise and the vibration can be prevented.
