JPS6240709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for properly maintaining electrophotographic images.

In general, the electrophotographic copying method consists of a step of forming an electrostatic latent image by charging a photoreceptor and exposing it to light, a developing step, a transfer step, a fixing step, a cleaning step, and a charge removal step. The copied image changes over time,
Due to environmental changes, etc., various optimum conditions may be deviated from, resulting in a copy image of poor quality. Among the conditions of each process that result in such poor quality copied images, the electrostatic latent image forming process is the most relevant.

The present invention has been made in view of these points, and provides a proper maintenance device for electrophotographic copied images that can always maintain an electrostatic latent image in the most appropriate state to obtain a high quality copied image. The purpose is to obtain.

An embodiment of the present invention will be described with reference to the drawings. First, a contact glass 1 having a predetermined width and a predetermined length is provided, and a reference original 2 is provided at the end of this contact glass 1. The reflective surface of the standard original 2 includes a black part 3 with low reflectance and a large area, a white part 4 with high reflectance and a large area, and a strip part 6 formed by black stripes 5 formed in this white background. Become. Further, various types of copy originals 7 are placed on the contact glass 1 .

At the bottom of the contact glass 1, a lamp 8 whose length is longer than the width of the contact glass 1 and a plurality of reflective mirrors 9, 10, 1 are provided.
1 and 12 and a lens 13, the optical path of this optical system 14 reaches the surface of a drum-shaped photoreceptor 15 to form an exposure section 16. A charger 17 is provided on the front-process side of the exposure section 16, and a surface potential detector 18 for detecting the potential of the electrostatic latent image formed on the surface of the photoreceptor 15 is provided on the post-process side. There is.
A measurement circuit 19, a comparison circuit 20, and a control circuit 21 are sequentially connected to the surface potential detector 18.

The photoreceptor 15 is exposed to light reflected from the reference original 2 to form an electrostatic latent image on its surface, but the appropriate conditions for the potential of this electrostatic latent image are determined by the second
It will look like the solid line in the figure. That is, a portion corresponding to the black portion 3 has a high potential, a portion corresponding to the white portion 4 has a low potential, and the strip portion 6 has a high potential although not as high as the black portion 3. Therefore, if the amount of exposure is insufficient, the overall potential will be high, as shown by the dotted line in Figure 2, and if the amount of charge is insufficient, the overall potential will be low, as shown by the dashed line. Become. Such a state is converted into a predetermined electrical signal by a measuring circuit 19, which is compared with a reference signal corresponding to the initial condition by a comparing circuit 20, and a necessary control signal is provided from a control circuit 21 based on the result. That is, if only the exposure amount has changed, a signal for changing the lamp voltage or the slit opening width is output, and these are automatically corrected or a correction display is performed.
That is, an exposure amount control means and an exposure amount display means are provided. Further, if only the amount of charge is insufficient, the voltage of the charger 17 is automatically increased or a display is made. That is, a charge amount control means and a charge amount display means are provided. Further, if both the exposure amount and the charge amount are fluctuating, it becomes somewhat complicated, but by correcting either one and copying several times, both can be corrected to appropriate values. That is, a cleaning means and a cleaning display means are provided.

Further, regarding the potential of the strip portion 6, there is a relationship as shown in FIG. That is, when the horizontal axis represents the density, specifically the Kodak gray scale density, and the vertical axis represents the photoreceptor surface potential, the optical system 14 for exposure slit opening angles of 0°, 5°, 10°, and 15°
There is a relationship as shown in the figure before and after cleaning. Of course, before the optical system 14 is cleaned, it means that 40,000 to 50,000 copies have been made, and toner and dust are attached to the optical system 14. Therefore, when the concentration is high, the dirt causes diffuse reflection of light, which becomes flare light, so that the potential before cleaning is low and the potential after cleaning is high. Furthermore, when the density is low, the amount of light decreases due to dirt, so the potential is high before cleaning and becomes low after cleaning. Therefore,
A reference potential is determined depending on whether black or white is used for the striped portion 6, and dirt on the optical system 14 is detected by fluctuations in the potential. Depending on the result, the optical system 14 is automatically cleaned or a message indicating that it should be cleaned is displayed.

In addition, when detecting the potential of each part using Standard Original 2, if the photoreceptor 15 material has a large residual potential change, such as zinc oxide or organic photoconductor (OPC),
It is desirable to perform automatic detection by performing detection every time each copy is made. In addition, if the photoreceptor 15 is made of a material such as Se, which has a small residual potential change, an electrostatic latent image due to the reference original 2 will not be formed under normal conditions, and a proper maintenance operation switch operated during regular maintenance by a service person can be used. In that case, the standard original 2
Detection may also be performed by In this case, the reference original 2 may be set in the main body or may be placed on the contact glass 1. Further, when the reference original 2 is provided in the main body, the lamp 8 may have a large overall length, and the reference original 2 may be set on the side of the contact glass 1 at all times.

In addition, when using a photoreceptor 15 made of Se or the like with less fatigue phenomenon, the main purpose is to correct the initially set charge amount and exposure amount as described above, and to correct changes over time. By detecting the potential of the electrostatic latent image based on the reference original 2 every time, the amount of light from the lamp 8 due to input voltage fluctuations is detected, and the amount of charge due to the charger 17 changes due to input voltage fluctuations. Furthermore, a function is added to correct fluctuations such as fluctuations in charge amount due to environmental changes. Furthermore, when using the photoreceptor 15 made of zinc oxide or an organic photoconductor that has a large fatigue phenomenon, or when performing high-speed copying even if the fatigue phenomenon is small, in addition to the above-mentioned functions, it is necessary to keep the brightness and dark charging potential constant. This has the function of eliminating the apparent fatigue phenomenon.

The present invention forms an electrostatic latent image on a photoreceptor using a reference original having a black portion, a white portion, and a striped portion as described above, and detects the surface potential of this electrostatic latent image using a surface potential detector. The charge amount control means is controlled by the surface potential corresponding to the black part, white part, and striped part.
The amount of charge and exposure can be maintained appropriately using the exposure amount control means and the cleaning means, and can be prevented from being affected by dirt on the optical system, and it is possible to know what needs to be adjusted using each display means. It is something.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. Fig. 1 is a side view, Fig. 2 is a characteristic diagram showing the relationship between the reference original and the latent image potential of the photoconductor, and Fig. 3 is a diagram showing the relationship between the reference original and the latent image potential of the photoreceptor, and Fig. 3 shows the optical system after cleaning. FIG. 3 is a characteristic diagram showing the relationship between density and photoreceptor surface potential. 2...Reference original, 3...Black part, 4...White part, 6...Striped part, 14...Optical system, 15...Photoreceptor,
18...Surface potential detector.

Claims (1)

[Claims] 1 A photoreceptor is provided which forms an electrostatic latent image by receiving a light image from a document after being charged, and has a large black area, a large white area, and a different black or white color within these black areas or white areas. A reference original consisting of a striped portion on which stripes are formed is provided, and a surface potential detector is provided for detecting the potential of an electrostatic latent image on the photoreceptor formed by this reference original, and a surface potential detector corresponding to the black portion is provided. A charge amount control means or a charge amount display means that automatically controls the amount of charge according to the detected value of the surface potential, and an exposure amount that automatically controls the amount of exposure according to the detected value of the surface potential corresponding to the white area. An electronic device comprising: a control means or an exposure amount display means; and a cleaning means for cleaning the optical system according to a detected value of the surface potential corresponding to the striped portion; or a cleaning display means for indicating that the optical system should be cleaned. Appropriate maintenance device for photocopied images.