1. Field of the Technology
The technology relates to a developing unit and an image forming apparatus using this. The technology, in particular, directed to a developing unit including an agitating and conveying portion for agitating and conveying a developer in the developer storing portion for storing the developer containing an electrostatically chargeable toner and a magnetic carrier to visualize an electrostatic latent image formed on a photoreceptor drum with the toner, which is constructed to agitate the developer in the developer storing portion without unevenness as well as to an image forming apparatus using this developing unit.
2. Description of the Prior Art
In a conventional image forming apparatus such as a printer etc. using the electrophotography, a printout of an image is formed by electrifying a photoreceptor drum that is driven rotationally by a charger, forming an electrostatic latent image by illuminating the photoreceptor drum with light in accordance with image information, forming a toner image by applying the toner to the electrostatic latent image by a developing unit and transferring the toner image to a sheet material or other recording media.
As the developer used for the developing unit of the image forming apparatus, use has been made of, for example a dual-component developer which is prepared by mixing two components, or an electrostatically chargeable toner and a magnetic carrier.
In the thus constructed image forming apparatus, the developer is stored in the developer storing portion as a part of the developing unit and is agitated inside the developer storing portion and conveyed to the developing roller by an agitating and conveying means.
Conventionally, the means for agitating and conveying the developer in the above way has been usually realized with conveyor belts, conveying screws, paddles and the like.
As an example using a conveyor belt, there has been proposed a configuration for agitating and conveying the toner in the toner supply container, in which an circulating endless conveyor belt having conveying projections on its outer surface and agitating projections on its inner surface is arranged to agitate and convey the toner inside the toner supply container (see Patent document 1: Japanese Patent Application Laid-open Hei 9-138579).
Also three has been proposed a configuration for agitating and conveying the developer in the developing unit, in which a magnetic belt is adopted as a conveyor belt so that the magnetic belt carrying the developer on its surface by magnetic force is moved to convey the developer toward the developing roller while agitating the developer therearound (see Patent document 2: Japanese Patent Application Laid-open 2003-302837).
Further, there has been proposed another configuration, in which a screw is used to send back the collected toner into the developing unit while inside the developing unit the collected toner is conveyed by a conveyor belt (see Patent document 3: Japanese Patent Application Laid-open 2001-201930).
However, since in any of the above conventional technologies, the developer containing toner is agitated and conveyed by moving the belt surface or agitating and conveying projections of the conveying belt upwards or downwards, the agitating effect in the vertical direction is weak. Further, there is a problem that when the developer is conveyed toward the developing roller, the developer is unlikely to be agitated and dispersed uniformly with respect to the axial direction of the developing roller or across the main scan direction.