| 摘要 |
PROBLEM TO BE SOLVED: To retard the deterioration of an image carrier and eliminate a defective image by making the detection sampling frequency of a lifetime detection means different between a pre-multiple rotation mode before an image formation start and a post-rotation mode after the formation of the preset number of images. SOLUTION: A detection circuit 26 as a lifetime detection means formed out of a resistor R to measure direct current flowing from an electrification drum 228 to a photosensitive drum 240, and a capacitor C to bypass the direct current is provided across the electric conductor 240 of the photosensitive drum 240 and the ground. Also, voltage across the terminals of the resistor R is measured and the thickness of the photosensitive layer 240b of the photosensitive drum 240 is detected on the basis of the voltage across the terminals. thereby making judgement about the lifetime of the photosensitive drum 240. A lifetime for a pre-multiple rotation mode is detected before starting the formation of an image. Also, a lifetime for a post-rotation mode is detected, when a frequency for transfer paper sheets to travel through the photosensitive drum 240 reaches the preset value. In this case, the detection sampling frequency of the photosensitive drum 240 per rotation in the pre-multiple rotation mode is less than in the post-rotation mode. |
