Electrophotography – Control of electrophotography process – Control of developing
Patent
1999-08-12
2000-11-14
Grainger, Quana M.
Electrophotography
Control of electrophotography process
Control of developing
399 58, G03G 1508
Patent
active
061481602
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a developer unit for an electrographic printer or copier with a toner acceptance surface accepting a layer containing toner particles, referred to in brief as toner layer.
2. Description of the Related Art
The structure of such a developer unit with a developer drum as toner acceptance surface is set forth in U.S. Pat. No. 4,777,106. For this developer unit, containing a toner reservoir where a toner-air mixture is located, and where toner particles are electrically charged and are subsequently deposited on the toner acceptance surface. This surface is either grounded or provided with a potential, and the charged toner particles are deposited thereon as a toner layer under the influence of an electrical force field. Due to the rotation of a developer drum whose generated surface forms the toner acceptance surface, the deposited toner particles are conducted past a development gap between the developer drum and a toner image carrier. The toner image carrier carries a latent charge image onto which toner particles are selectively applied at the development gap, creating a toner image. The toner image is then applied onto an ultimate image carrier, for example onto paper, from the toner image carrier with or without employing an intermediate image carrier.
A developer belt can also be used in place of the developer drum. A developer unit having more than one toner acceptance surface is explained in European Patent EP 0 494 454. The second toner acceptance surface is formed by the generated surface of a transfer drum on which the toner particles are applied directly from the reservoir. The toner particles are then deposited onto the surface of the developer drum at a transfer gap between the transfer drum and the developer drum.
The known developer units do not allow monitoring of the developing process and, in particular, of the amount of toner output by the developer unit. When the toner amount per surface on the toner acceptance surface or the charge amount per surface in the toner layer during developing lies outside of a predetermined range the error is not recognized until the finished print image is produced, resulting in a delayed corrective response. The disturbances in the print image are particularly noticeable for large-area picture elements.
Both dry and liquid toners can be used. The toners that are employed can also be divided into single-component and multi-component toners. Electrographic printers encompass electrophotographic printers, ionographic printers and magnetographic printers.
U.S. Pat. No. 5,006,897 or, respectively, U.S. Pat. No. 4,026,643 disclose developer units wherein the properties of a toner particle developer layer forming a magnetic brush are acquired with the assistance of a potential sensor and a capacitative circuit or, alternately an optical sensor.
SUMMARY OF THE INVENTION
An object of the invention is to specify a simply constructed developer unit that enables developing with high quality.
This object is achieved by an apparatus comprising a developer unit having a toner acceptance surface that accepts a layer of toner particles wherein a capacitive sensor acquires toner mass from a toner layer thickness on the toner acceptance surface (or alternately, a radiation source and sensor, particularly where the toner layer is thin), a potential sensor acquires an electrical potential over the toner layer on the toner acceptance surface, and an evaluation unit that calculates the mass-referred toner charge from the identified toner mass and the potential. This objective may further be achieved by utilizing controllers which control the average toner mass and average toner charge, and a system that is able to store various characteristic curves.
The invention is based on the principle that characteristic quantities that critically define the quality of the developing process and, thus, critically define the quality of the print image as well must be acquired in the developer unit prior to th
REFERENCES:
patent: 4026643 (1977-05-01), Bergman
patent: 4777106 (1988-10-01), Fotland et al.
patent: 5006897 (1991-04-01), Rimai et al.
patent: 5235385 (1993-08-01), Rushing
patent: 5285243 (1994-02-01), Rimai et al.
Apel Reinhard
Maess Vokhard
Schleusener Martin
Grainger Quana M.
Oce Printing Systems GmbH
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