| 摘要 |
PROBLEM TO BE SOLVED: To realize excellent image formation without irregular pitch, etc., even when operation is shifted to normal image forming operation immediately after detecting the density of a patch image by eliminating influence by a discharge product adhering to the sleeve surface of a developing means at the time of patch image forming operation. SOLUTION: At the time of forming the patch image, a developing device 4k on the most downstream side in the rotating direction of a photo-receptor drum 1 is moved to a developing position so as to develop a patch latent image on the drum 1, and the density of the patch image is measured by a sensor 13 and recorded as an initial value. While restoring the device 4k to a home position, developing bias is made off, and a sleeve is stopped, then the image forming operation of a developing device 4m on more upstream side than the device 4k by one is performed in the same procedure. Thus, ozone, etc., from an electrifier 2 carried on the flow of air caused by the rotation of the drum 1 is dammed by the rotating sleeve 44 of the device 4m and prevented from adhering to the surface of the sleeve of the device 4k. The image forming operation of developing devices 4c and 4y on the upstream side is performed in the same manner successively, and the rotation of the drum 1 is stopped. |
