| 摘要 |
PURPOSE:To prevent the disturbance of and density irregularity by providing plural developing devices along the outside circumferential face of a photosensitive drum and controlling the rotation of a permanent magnet constituting each developing roll or a sleeve. CONSTITUTION:When a permanent magnet 2b is rotated at a high speed in the direction of an arrow A and a sleeve 2a is rotated a low speed in the direction of an arrow B, a developer 6 is carried from an opening port 5 to a stopper 4 through a developing region. In this case, the developer in the upper layer is carried in the direction of an arrow C and is U-turned by the stopper 4 and is shifted to the lower layer and is carried in the direction of an arrow D, and a magnetic brush is stabilized. When the rotation of the permanent magnet 2b is stopped while rotating the sleeve 2a as it is, the developer from the opening port 5 to the stopper 4 is recovered into a storage tank 3, and development is not executed. Consequently, respective rotations of permanent magnets 2b of developing rolls 2 of developing devices 11-13 are controlled to perform the development of four colors without disturbance of images and density irregularity. |
