US Patent 7514196 Developing method and developing unit

The present invention provides a developing method and a developing unit which can obtain a favorable image quality and the like even when a surface roughness Rz of a developing sleeve is changed or when an amorphous-silicon photoconductor is used by allowing the magnetic monocomponent toner to effectively jump to a photoconductor from a developing sleeve. To attain such an object, the present invention provides a magnetic monocomponent jumping developing system and a developing unit which uses the method, wherein as the magnetic monocomponent toner, a toner having a volume center particle size which is calculated from the particle size distribution based on volume and falls within a range from 6.0 to 7.8 μm, having the sphericity which falls within a range from 0.92 to 0.98, and setting a toner quantity having a volume particle size of 5.04 μm or less to a value which falls within a range from 2.5 to 10.0 volume % is used and, at the same time, assuming a toner quantity per unit area of the toner image as A, a following relationship formula (1) is satisfied.0.6 mg/cm2≦A≦0.9 mg/cm2  (1)