Patent ID: 7848665

Claim:
An image forming apparatus, including a development unit having (i) a developer bearing member, internally having a magnetic field generation means, which is provided with a rotatable non-magnetic and conductive sleeve and which carries on its surface a developer containing carrier and toner; and (ii) a developer regulation member for regulating an amount of the developer supplied from the developer bearing member to an image bearing member, said image forming apparatus visualizing an electrostatic latent image formed on a surface of the image bearing member with the developer supplied from the development unit to the image bearing member, said image forming apparatus comprising: a resistance detection means for measuring a volume resistivity of the developer on the surface of the developer bearing member; a resistance memory section for storing therein a preset volume resistivity; a resistance comparison means for comparing the volume resistivity of the developer which has been measured by the resistance detection means with the preset volume resistivity stored in the resistance memory section; and a control means for carrying out a process for replacing the developer or the carrier if the volume resistivity of the developer is lower than the preset volume resistivity.