Patent ID: 8045896

Claim:
A developing device comprising: a developer container for storing a developer comprising a toner and a magnetic carrier; a developer conveying passage through which the developer is conveyed in the developer container; a developer conveying member disposed inside the developer conveying passage for agitating and conveying the developer in a predetermined direction; and, a developing roller which supports the developer in the developer conveying passage and supplies the toner contained in the developer to a photoreceptor drum, characterized in that the developer conveying member includes: a rotary shaft; and a multi-helically structured blade with helical blades formed on the periphery of the rotary shaft, the multi-helically structured blade includes: an inner helical blade arranged on the periphery of the rotary shaft; and, an outer helical blade having a ring-shaped form when viewed from the axial direction that inscribes the outer periphery of the inner helical blade, the inner helical blade is formed such that the radius of the helical blade varies cyclically, the second helical pitch of the outer helical blade is smaller than the first helical pitch of the inner helical blade, and, the outer helical blade inscribes the outer periphery at the minimum radius portions of the inner helical blade.