Patent ID: 8331828
Filing Date: 2012-12-11
Classification: G03G

Abstract:
1. A developing device comprising: a developer conveying passage through which a developer containing a toner and a magnetic carrier is conveyed; a developer conveying member disposed in the developer conveying passage to agitate and convey the developer in a predetermined direction; and, a toner supply passage for leading supplementary toner into the developer conveying passage, wherein one or more electromagnets for forming a magnetic field inside the toner supply passage are provided along the outer periphery of the toner supply passage; wherein a plurality of electromagnets are disposed apart across the toner supply passage so that the plurality of electromagnets form a magnetic field in which magnetic field lines are directed in the same direction as each other inside the toner supply passage; wherein the magnetic field formed by the one or more electromagnets is specified so that the magnetic flux density inside the toner supply passage falls within the range from 500 mT to 2,000 mT; wherein the one or more electromagnets are arranged at a position 5 to 30 mm away from the surface of the developer in the developer conveying passage below the toner supply passage; and wherein the distance between the one or more electromagnets arranged opposing each other across the toner supply passage is specified to be 5 to 25 mm.