| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To highly accurately set the position of the main magnetic pole of a magnet roll provided to a developing device with respect to an image holding body, in the developing device or an image forming apparatus, forming a toner image at high speed. <P>SOLUTION: A plurality of developing rolls 44, 46 and 48 arranged so as to face the circumferential surface of a photoreceptor drum 22 include the magnet roll fixedly supported and a sleeve rotatably supported around the magnet roll. The first magnet roll 44a of the first developing roll 44 arranged at the most downstream in the rotational direction of the photoreceptor drum is magnetized as the main magnetic pole facing the photoreceptor drum, so that a series of areas where magnetic flux density in a vertical direction is 90% or more of a peak value is 40% or more of the total width. The magnetic flux density of the main magnetic pole in the peripheral direction, that is, in the tangential direction is measured and the position with respect to the photoreceptor drum is set with a point where the magnetic flux density is zero as a reference. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
