Image-forming machine equipped with an exchangeable developing unit

摘要

The image-forming machine has an electrostatic latent image-bearing member on which an electrostatic latent image will be formed and an exchangeable developing unit. The developing unit includes a developing housing, a developing agent contained in the developing unit and a developing agent applicator for applying the developing agent onto the surface of the electrostatic latent image-bearing member. A counter is provided that counts the number of times the developing unit has been used and that can be reset. In the developing unit is disposed a developing agent depletion detector that detects the depletion of the developing agent. The developing unit further has a reset that resets the counter when the use of the developing unit is started. When the developing agent depletion detector has detected the depletion of the developing agent, a developing unit exchange signal is formed to indicate that the developing unit be renewed. The developing unit exchange signal is formed even when the counter has counted a predetermined number that corresponds to the life of the developing unit.