Patent ID: 8285180

Claim:
An image forming apparatus, comprising: an image carrier; a development apparatus configured to develop with toner an electrostatic latent image formed on the image carrier, the development apparatus including: a first toner carrier and a second toner carrier which are provided to face the image carrier, and each of which is configured to support the toner on a surface thereof and to convey the toner to develop the electrostatic latent image formed on the image carrier; a developer carrier, the developer carrier having: a magnet roller having a rotary shaft and a plurality of magnetic poles around the rotary shaft, the magnetic roller being capable of rotation about the rotary shaft to adjust positions of the magnetic poles; and a sleeve roller which is provided to face the first toner carrier and the second toner carrier and is configured to contain therein the magnet roller and to be rotatable, independently of the magnet roller, about the rotary shaft, and configured to support thereon developer containing toner and carrier and to convey the developer to supply the toner in the developer to the first toner carrier and the second toner carrier; a first adjustment member which is mounted on the rotary shaft so as to rotate the magnet roller and is configured to adjust and then to fix the magnet roller so that a facing portion between the developer carrier and the first toner carrier is located at a predetermined position with respect to the magnetic poles; a holding member which is provided to be connected with the rotary shaft of the magnet roller and to be rotatable about the rotary shaft, and configured to rotatably hold the second toner carrier at a position thereof which is a predetermined distance away from a position at which the holding member is connected with the rotary shaft; a second adjustment member which is provided in contact with the holding member and is configured to rotate the holding member about the rotary shaft of the magnet roller and then to fix the holding member such that a facing portion between the image carrier and the second toner carrier is located at a predetermined position with respect to the magnet poles; a pair of first gap members each of which is provided, on each of both end portions of the first toner carrier, coaxially with the first toner carrier, and has an outer diameter larger than a diameter of the first toner carrier; a pair of second gap members each of which is provided, on each of both end portions of the second toner carrier, coaxially with the second toner carrier, and has an outer diameter larger than a diameter of the second toner carrier; a guide member configured to guide the development apparatus in such a direction that all of the first gap members and the second gap members approach the image carrier; and a bias member configured to bias the development apparatus in such a direction that all of the first gap members and the second gap members are in contact with the image carrier.