Electrophotography – Image formation – Development
Patent
1993-07-08
1996-11-05
Grimley, Arthur T.
Electrophotography
Image formation
Development
399259, G03G 1506
Patent
active
055722997
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
The present invention relates to a developing device used in an image formation apparatus such as a copying machine, a laser printer, a facsimile or the like, wherein an electrostatic latent image is electrostatically developed with a two-component developer.
PRIOR ART
Generally, in an image formation apparatus such as an electrophotographic recording apparatus, the following processes are typically carried out: an electrostatic latent image carrying body; surface by an optical writing means such as a laser beam scanner, an LED (light emitting diode) array, a liquid crystal shutter array or the like; toner, which is electrically charged to be electrostatically adhered to the latent image zone; from the body to a recording medium such as a cut sheet paper; and by a toner image fixing means such as a heat roller.
Typically, the electrostatic latent image carrying body may be an electrophotographic photoreceptor, usually formed as a drum, called a photosensitive drum, having a cylindrical conductive substrate formed of a metal such as aluminum, and a photoconductive insulating film bonded to a cylindrical surface thereof and formed of an organic photoconductor (OPC), a selenium photoconductor or the like.
As one type of developer, a two-component developer is well known, which is composed of a toner component (colored fine synthetic resin particles) and a magnetic component (fine magnetic carriers). Usually, a developing device using this type of developer includes a vessel for holding the two-component developer, wherein the developer is agitated by an agitator provided therein. This agitation causes the toner particles and the magnetic carriers to be subjected to triboelectrification, whereby the toner particles are electrostatically adhered to each of the magnetic carriers. The developing device also includes a magnetic roller provided in the vessel as a developing roller in such a manner that a portion of the magnetic roller is exposed therefrom and faces the surface of the photosensitive drum. The magnetic carriers with the toner particles are magnetically adhered to the surface of the magnetic roller to form a magnetic brush therearound, and by rotating the magnetic roller carrying the magnetic brush, the toner particles are brought to a nip zone or developing zone between the magnetic roller and the drum for development of an electrostatic latent image formed thereon. In the developing process, a developing bias voltage is applied to the magnetic roller so that the toner particles carried to the developing zone are electrostatically attracted only to the latent image, whereby the toner development of the latent image is carried out. The magnetic brush, from which the toner component is consumed for the development of the latent image, is removed from the magnetic roller and is then returned to the developer held in the vessel. For this reason, in the developer held in the vessel, the toner component cannot be uniformly distributed in the magnetic component. Of course, the non-uniform distribution of the toner component in the magnetic component causes an uneven development of a latent image.
One type of developing device using the two-component developer, a developer circulation type, which is known, is provided with an agitator including a pair of screw members provided in the developer vessel and disposed in parallel with each other, and a partition member disposed between the screw members. The screw members are arranged and rotated in such a manner that a part of the developer held in the vessel is circulated between the screw members for the purpose of a uniform distribution of the toner component in the magnetic component. Nevertheless, the conventional developer-circulation type developing device is not satisfactory because an even development of a latent image cannot be sufficiently ensured, and that the developer can be prematurely deteriorated, as discussed in detail hereinafter.
DISCLOSURE OF THE INVENTION
Therefore, an object of the present invention is to provid
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Araki Shin
Fujimoto Naoyuki
Kato Makoto
Sasaki Sachio
Sato Kunihiko
Fujitsu Limited
Grimley Arthur T.
Lee Shuk Yin
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