Patent ID: 7885581

Claim:
A developer transferring device comprising: a rotatably supported rotary shaft member; a developer transferring portion for transferring a developer containing a toner and a carrier in a rotary axis direction while agitating said developer as a screw member having a screw vane that protrudes in spiral form from a peripheral surface of said rotary shaft member rotates; and toner concentration detecting means for detecting a toner concentration of said developer transferred within said developer transferring portion, wherein, of an entire rotary axis direction region of said screw member, a reverse transfer vane for transferring said developer in an opposite direction to said screw vane as said rotary shaft member rotates protrudes from said rotary shaft member in a region where a gravitational direction lower side faces a bottom wall of said developer transferring portion and two lateral sides that are orthogonal to the rotary axis direction face respective side walls of said developer transferring portion, and said toner concentration detecting means are disposed to detect said toner concentration of said developer as said developer is transferred between said reverse transfer vane and a location of said screw vane adjacent to said reverse transfer vane.