Electrophotography – Control of electrophotography process – Having temperature or humidity detection
Reexamination Certificate
1999-05-12
2001-04-24
Royer, William J. (Department: 2852)
Electrophotography
Control of electrophotography process
Having temperature or humidity detection
C399S045000, C399S055000, C399S066000
Reexamination Certificate
active
06223004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine using an electrophotographic process.
2. Description of Prior Art
For an image forming apparatus such as a copying machine using an electrophotographic process, it is desirable to reproduce an image of the same density for the same image data. In order to reproduce an image of stabilized density on a paper, it is known to form a standard toner image. When a copy operation is started or when a predetermined mode is set, a standard toner image is formed on a photoconductor, and the transfer efficiency of the toner image onto the paper is detected. Then, development or transfer conditions are controlled according to the detected results.
However, the above-mentioned stabilization is not controlled appropriately in cases, for example, when toners are deteriorated or when the resistance of a paper on which a toner image is transferred becomes lower than expected by absorbing water content from the humidity of ambient environment. Even if toners have been charged normally, they are charged with the reverse polarity at a transfer section in a copying machine, and the amount of toners remaining on the photoconductor increases after passing the transfer section in the copying machine, so that the transfer efficiency becomes worse. Further, if toners are deteriorated, the amount of charges of toners after development and before transfer becomes lower. Toners are also charged with the reverse polarity at the transfer section in this case, so that the transfer efficiency becomes worse.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image forming apparatus which performs stable transfer irrespective of the state of a paper and toners.
In a first aspect of the invention, an image forming apparatus using an electrophotographic process comprises a photoconductor for forming a latent image, a development device for developing the latent image to form a toner image, and a transfer device for transferring the toner image onto a paper passing between the photoconductor and the transfer device. A measuring device measures an electrostatic capacitance between said photoconductor and said transfer device in predetermined conditions while a standard toner image is formed, and a controller controls image forming conditions, such as a development condition or a transfer condition, according to the measured electrostatic capacitance. Preferably, humidity of ambient environment is measured and the image forming conditions are controlled according to the electrostatic capacitance and the humidity.
In a second aspect of the invention, in an image forming apparatus using an electrophotographic process, a resistance of the paper is measured, and a controller controls image forming conditions according to the measured resistance.
In a third aspect of the invention, in an image forming apparatus using an electrophotographic process, a measuring device measures an amount of toner charges of a standard toner image, and a controller controls image forming conditions according to the measured amount of toner charges.
An advantage of the present invention is that transfer conditions can be controlled appropriately.
Another advantage of the present invention is that development conditions can be controlled appropriately.
A further advantage of the present invention is that reverse charging of toners at the transfer can be prevented.
REFERENCES:
patent: 5608506 (1997-03-01), Omoto
patent: 5761568 (1998-06-01), Haragakiuchi et al.
patent: 5799226 (1998-08-01), Shigeta et al.
patent: 5983044 (1999-11-01), Kodama et al.
patent: 4-149464 (1992-05-01), None
Minolta Co. , Ltd.
Royer William J.
Sidley & Austin
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