Patent ID: 7979007

Claim:
A developing device comprising: a developer container for accommodating 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 bears 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 multi helical blades formed on a periphery of the rotary shaft, the multi helical blades include one or more ring-shaped helical blades and one or more small-diametric helical blades, the small-diametric helical blade has a second outside diameter smaller than a first outside diameter of the ring-shaped helical blade, a helical pitch of the ring-shaped helical blade is the same as a helical pitch of the small-diametric helical blade, and the ring-shaped helical blade and the small-diametric helical blade have the same twist direction.