| 摘要 |
PROBLEM TO BE SOLVED: To prevent the degradation in the image quality of reading images by preventing the resonance of the vibration generated by the rotation of a fan and the vibration generated by the meshing of driving transmission means. SOLUTION: In the case of a meshing frequency fm0≈a vibration frequency ff0, a CPU 601 selectively switches the voltage of the control line of a regulator 602 with a voltage variable function by a switching circuit 603. The CPU switches the driving voltage of the fan motor 201 by making judgment from the meshing frequency fm0 determined from magnification in such a manner that the vibration frequency ff0 of the fan motor 201 is parted from the meshing frequency fm0 and attains the value of a frequency not matching an integral multiple of fm0, namely, (2fm0, 3fm0...).
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