1. Field of the Invention
This invention relates to an image forming apparatus which forms an image on a transfer material by use of an electrophotographic process, and a charger installed in this image forming apparatus.
2. Description of the Related Art
A corona discharge type fixing device installed in an image forming apparatus using an electrophotographic process is classified broadly into a wire electric discharge type (Corotron, Scorotron, etc.) or pin discharge type (pin electrode, sawtooth electrode, etc.).
In a method generally known, a cleaning member such as felt provided to wrap around a wire electrode is moved in a longitudinal direction (axial direction of a photoconductor drum) of a charger, as a means to clean the wire electric discharge type wire electrode.
Another method is known in which a cylindrical cleaning member provided movably along the sawtooth electrode is moved while being pressed against the edge of the sawtooth electrode, as a means to clean the pin discharge type sawtooth electrode (Jpn. Pat. Appln. KOKAI Publication No. 9-211940).
Still another method is known in which the sawtooth electrode is rotatably provided, and electric discharge products deposited on the edge of the sawtooth electrode are scraped against the cleaning member (Jpn. Pat. Appln. KOKAI Publication No. 11-327265).
Furthermore, apparatuses or methods are known in which a driving force generator such as a motor is used to automatically clean the electrode of the charger (Jpn. Pat. Appln. KOKAI Publication No. 6-194934, Jpn. Pat. Appln. KOKAI Publication No. 7-49606, U.S. Pat. No. 3,842,273).
However, the abovementioned method using the cylindrical cleaning member in which cleaning is achieved by the rolling and contacting of a roller has the disadvantage that the electric discharge products, toner, dust and the like deposited on the edge of the sawtooth electrode are not adequately removed because of insufficient cleaning power.
Moreover, the problem of the above-described method of cleaning the rotatably provided sawtooth electrode is that the edge of the sawtooth electrode warps and deforms when it contacts the cleaning member, and the cleaning power decreases as the cleaning is performed time and time again. Further, the warping and deforming of the sawtooth edge cause improper corona discharge and insufficient electric discharge to an image carrier.