The present invention relates to an image forming apparatus using an electro-photography process for forming and developing a static latent image on an image supporting member.
In a conventional image forming apparatus such as a printer, a facsimile, an electro-photography color recording apparatus, and the likes, a charging film or a charging roller charges a surface of a photosensitive drum. Then, an exposure light source irradiates the surface of the photosensitive drum according to image information, thereby forming a static latent image on the surface of the photosensitive drum. After, a developing roller attaches toner as developer to the static latent image, a transfer device transfers a toner image to a recording medium, and a fixing device fixes the toner image to the recording medium. Toner is supplied from a toner cartridge to the photosensitive drum through a toner supplying roller and the developing roller.
In the conventional image forming apparatus, after the toner supplying roller and the developing roller rotate one rotation, an amount of toner supplied from the toner supplying roller to the photosensitive drum through the developing roller decreases. More specifically, it is possible to develop an image with a proper density on the recording medium over a length corresponding to a sum of a rotational circumferential length of the photosensitive drum while the developing roller rotates one rotation and a rotational circumferential length of the photosensitive drum while the toner supplying roller rotates one rotation. The density of the image to be developed on the recording medium, however, decreases beyond the length.
To this end, Patent Reference has disclosed conventional technology to prevent the density from decreasing. In the conventional technology, after a photosensitive drum rotates over a length corresponding to a sum of a rotational circumferential length of the photosensitive drum while a developing roller rotates one rotation and a rotational circumferential length of the photosensitive drum while a toner supplying roller rotates one rotation, an amount of toner supplied from the toner supplying roller to the photosensitive drum through the developing roller increases. Accordingly, it is possible to prevent a density step from forming in an image to be printed on a recording medium.    Patent Reference: Japan Patent Publication No. 10-260573
In the conventional technology disclosed in Patent Reference, when an image with a high density is printed on the recording medium, even though an amount of toner supplied from the toner supplying roller to the photosensitive drum through the developing roller increases after the photosensitive drum rotates over the length corresponding to the sum of the rotational circumferential length of the photosensitive drum while the developing roller rotates one rotation and the rotational circumferential length of the photosensitive drum while the toner supplying roller rotates one rotation, it is difficult to sufficiently prevent the density step from forming in the image to be printed on the recording medium.
In view of the problems described above, an object of the present invention is to provide an image forming apparatus capable of solving the problems of the conventional image forming apparatus. In the image forming apparatus of the present invention, even when an image with a high density is printed on a recording medium, it is possible to sufficiently prevent a density step from forming in an image to be printed on a recording medium.
Further objects of the invention will be apparent from the following description of the invention.