VORRICHTUNG ZUR BESTIMMUNG DER NUTZUNGSDAUER EINER PROZESSEINHEIT ZUR BILDERZEUGUNG, DER SCHLIESSUNG EINER ABZIEHBAREN ABDECKUNG DER EINHEIT UND DER ANWESENHEIT DER EINHEIT IN EINEM BILDERZEUGUNGSGERAET.

摘要

A device is provided for detecting the life expiry of a process unit detachably attached to an image forming apparatus for detecting the initial opening of a seal of the unit and for detecting attachment of the unit to the image forming apparatus. The device judges when the process unit has reached its life expiry by comparing the output of a sensor (65) for detecting the density of toner contained in the developing device with a predetermined value and detecting when the output of the sensor is above the predetermined value. When the process unit has a developer storage section defined by a seal member (63) for containing developer in the developing device, the seal member is normally opened whens the developing device is installed, so that developer is supplied into a developer chamber having a developing roller. The detecting device judges that the seal (63) is unopened when the output of the sensor (65) is not the output level of the normal use state. Thirdly, when attaching the process unit to the apparatus, the output terminal of the sensor (65) on the developing device and the input terminal of control means provided in the apparatus are connected with each other, so that the control means can judge that the process unit is not attached when the voltage of the input terminal of the control means is not the voltage level of the normal use state.