Patent ID: 6721526
Filing Date: 2004-04-13
Classification: G03G

Abstract:
An image forming apparatus comprising an image forming body, and a developing device for developing a latent image formed on the image forming body with a two-component developer consisting of a toner and a carrier,the developing device including a rotary sleeve positioned facing the image forming body, for delivering the two-component developer and, a magnet system positioned inside the rotary sleeve, for forming a plurality of magnetic poles to form a magnetic brush made of the two-component developer on the surface of the rotary sleeve, and a developer layer regulating member positioned facing the surface of the rotary sleeve, for regulating the amount of the two-component developer delivered by the rotary sleeve, wherein where dt (&mgr;m) represents volume mean particle diameter of the toner in the two-component developer, &rgr;t (g/cm3) represents density of the toner, dc (&mgr;m) represents volume mean particle diameter of the carrier, &rgr;c (g/cm3) represents density of the carrier, and Rw represents weight ratio of the toner and the carrier (the ratio of the weight of the toner to the weight of the carrier), Conditions 1, 2 and 3 are satisfied, Condition 1: the volume mean particle diameter dt of the toner falls within the range of 3Ëœ5 &mgr;m, Condition 2: the volume mean particle diameter dc falls within the range of 5 dtËœ10 dt, and Condition 3: the weight ratio Rw of the toner and the carrier falls within the range of 1.6 (dt/dc)Ã—(&rgr;t/&rgr;c)Ëœ2.4 (dt/dc)Ã—(&rgr;t/&rgr;c) and wherein among a plurality of the magnetic poles included in the magnet system, a main magnetic pole, forming the strongest magnetic field on the surface of the rotary sleeve, is positioned in proximity to the position where the rotary sleeve and the image forming body come closest to each other, and wherein where H (mm) represents the free tip height of the magnetic brush formed at the position of the main magnetic pole, and D (mm) represents the closest distance between the rotary sleeve and the image forming body, Condition 4 is satisfied, Condition 4: the closest distance D falls within the range of 0.5 HËœ0.8 H.