Developing device, method of producing developing device, and image forming apparatus

A method of producing a developing device comprising:

• providing a plurality of magnetic pole including a main magnetic pole on a peripheral face of a magnet roll in a cylindrical shape so as to be arranged in a tangential direction;
• measuring magnetic flux density of the main magnetic pole in a tangential direction at a position along the peripheral face of the magnet roll, and detecting a point where the magnetic flux density is zero;
• and
• supporting the magnet roll by fixing it to a supporting frame of a developing device which transposes a toner to a latent image by a difference in electrostatic potential thereby to form a visual image, and at the same time, supporting a sleeve in a cylindrical shape around the magnet roll so as to rotate in a tangential direction,
• wherein, when the magnet roll is fixed to the supporting frame of the developing device, the magnetic roll is adjusted and fixed in such a manner that when the magnet roll is supported so as to be opposed to an image holding body on a surface of which the latent image is formed, by setting a reference point at a position on the peripheral face where the magnetic flux density of the main magnetic pole in the tangential direction is zero, the reference point is the position which has been predetermined with respect to a position where the image holding body comes most closely to the magnet roll.