Developing device and image forming apparatus

摘要

A developing device having a developer bearing member for carrying thereon a developer having toner and carrier and conveying the developer to a developing area, an agitating member for agitating the developer, a rotation radius R (m) of the agitating member being 5.0x10-3 (m)<R<8.0x10-3 (m), and a density sensor for detecting a density of the toner in the developer, the density sensor detecting any change in the density of the toner as a change in a magnetic permeability of the developer, wherein when a shortest distance between an outermost surface of the agitating member and a detecting surface of the sensor is defined as Dmin (m) and a half length of the detecting surface of the sensor in a plane perpendicular to a rotary axis of the agitating member is defined as r, 0 (m)<Dmin<1.0x1031 3 (m) and 0.4<r/R<0.75.