Image forming apparatus provided with developing device using magnetic brush developing method

摘要

In an image forming apparatus including a developing device, an inequality of 1 ≤ ( alpha /100) x Vr x Hr<1/3> < 3.5 is satisfied, wherein Vr denotes the peripheral speed ratio of an outer circumferential surface of a developer carrying member to the outer circumferential surface of an image carrying member, Hd denotes a spacing of the outer circumferential surface of the developer carrying member to the outer circumferential surface of the image carrying member, Hh denotes an average value of a height of a magnetic brush layer, Hr denotes a ratio of an average value of the height Hh to the spacing Hd, and alpha (%) denotes a coverage ratio of an area of the magnetic brush layer to cover the outer circumferential surface of the developer carrying member to the outer circumferential surface of the developer carrying member. <IMAGE>