1. Field of the Invention
The present invention relates to a developing device that develops a latent image formed on an image bearing member, a process cartridge that attaches to and detaches from an apparatus main body of an image forming apparatus, and an image forming apparatus that forms an image on a recording medium.
The image forming apparatus includes an electrophotographic copying machine and an electrophotographic printer (for example, a laser beam printer, a light emitting diode (LED) printer, and the like), a facsimile machine, a word processor, and the like that employ an electrophotographic image forming process.
2. Description of the Related Art
Conventionally, a developing device is used for developing a latent image, formed on a photosensitive drum by a developer, in an image forming apparatus employing an electrophotographic image forming process.
In such a developing device, a developing blade is disposed on a developing roller as a developer bearing member. Furthermore, a seal member is disposed on an end portion of the developing roller in a longitudinal direction. The developing blade serves as a developer regulating member that regulates a thickness of a layer of the developer. The seal member prevents the developer from leaking in the longitudinal direction.
In the developing device, a gap between the developing blade and the seal member in the longitudinal direction might include an area where the thickness of the layer is not regulated by the developing blade. Thus, the developer in this area might be accidentally transferred onto the photosensitive drum. When this happens, an image defect (end portion fogging), in the form of a black streak, might occur in an end portion of a paper sheet (recording medium) in a direction orthogonal to a feed direction. The fogging basically means that the developer is attached to an unintended portion. The end portion fogging is the fogging occurring in the end portion of the recording medium.
A technique for preventing the end portion fogging have been discussed in Japanese Patent Application Laid-Open No. 2003-255702 and Japanese Patent No. 3403094. Specifically, for example, the developer not passing through the developing blade is scraped by a scraper and is prevented from being developed on a drum.