| 摘要 |
PURPOSE:To improve working efficiency by providing plural developing devices and controlling them so that another developing device is arranged in an operating position when the developing density of a developing device in developing operation is a prescribed value or below. CONSTITUTION:This device is provided with plural developing devices 1 and 2 for sticking developer to electrostatic latent images formed on an image carrier 3. When the developing density of, e.g., the developing device 1, which is arranged in the operating position opposed to the image carrier 3 and carries out the developing operation, is lowered to the prescribed value or below, the operating developing device 1 is controlled so as to be arranged in the operating position in place of another developing device 2. Therefore, without manually replacing the developer, image formation can be succeeded by the fresh developing device 2 with a high developing density, and thus, the work efficiency can be improved. |
