Image forming apparatus and image forming system

An image forming system for forming an image on a recording medium by using a cartridge detachably attachable to an image forming apparatus, said image forming system comprising:

• (a) a cartridge having:
• a developing apparatus equipped with a developer containing portion containing a developer;
• a residual developer amount detecting means for detecting a residual developer amount in said developer containing portion;
• and storage means for storing latest residual developer amount information;
• and
• (b) an image forming apparatus main body equipped with a continuous rest time counter configured to count a continuous rest time of a driving system of the image forming apparatus, and control means for prohibiting updating of the residual developer amount information stored in said storage means for a predetermined interval when said continuous rest time counter indicates a time not shorter than a predetermined time.

An image forming apparatus including a developing apparatus equipped with a developer containing portion containing a developer, a residual developer amount detector configured to detect a residual developer amount in the developer containing portion, and storage means for storing information, wherein said image forming apparatus comprises:

• a time measuring unit which is configured to measure a non-operating time of the developing apparatus;
• and
• a controller which is configured to write residual developer amount information in the storage means on the basis of an output of the residual developer amount detector during an operating time of the developing apparatus,
• wherein said controller controls a predetermined period during which is said controller does not write in the storage means residual developer amount information based on an output of the residual developer amount detector after the non-operating time of the developing apparatus on the basis of the non-operating time measured by said time measuring unit.