JPH01187576A - Copying machine - Google Patents

Abstract

PURPOSE:To easily perform maintenance and to always obtain a proper copied image by giving warning when the stain of an optical system and the variation of the characteristic of a photosensitive body are large. CONSTITUTION:Signals from a means 21 for detecting the density of a developed image on a drum and a means 22 for detecting original density are inputted in an exposure operation means 20, which outputs control signals to an exposing lamp control means 23 and a warning display means 24. And warning is given by detecting the variation of the characteristic caused by the stain of the optical system and the variation of the characteristic of the photosensitive body, etc., from the density of the developed image of a test pattern and the change of the voltage of the exposing lamp at that time. Thus, the proper copied image can be always formed with a precise countermeasure, such as cleaning of the stain of the optical system, etc., and maintenance can be easily performed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to electrostatographic copying machines.

(Prior art) A thin photocopying machine illuminates an original with an exposure lamp, exposes a photoreceptor to the image light to form an electrostatic latent image, develops it to make it visible, and transfers it to a transfer material. It is grooved so that it can be transferred onto the surface.

As a control for obtaining proper images with this type of copying machine, for example, Japanese Patent Application Laid-Open No. 119580 discloses a method that detects the density of the original, determines the contrast, and controls the contrast by the amount of exposure. However, if the optical system is dirty or the characteristics of the photoreceptor change, the y F
There is a problem in that a proper image cannot be obtained due to W9.

Also, JP-A-58-23043, JP-A-60-1
33475, JP-A-60-146256, and JP-A-6O-2GO072, etc., the density of the developed image formed on the photoreceptor is detected and developed so that it becomes appropriate. A method is disclosed in which the conditions and exposure conditions are controlled, and the control reference level is further corrected in consideration of changes in temperature and humidity, developer usage time, photoreceptor sensitivity, and the like.

However, with the method of detecting and controlling the image density, it is not affected by changes in the sensitivity of the optical system or photoreceptor, but the image density is determined regardless of differences in the density and contrast of the original. There are problems in that fine lines tend to fade or skip, and blurring tends to occur in the case of a crowded image.

Therefore, in Japanese Patent Application No. 62-59181, the present applicant previously measured the developed density of a test pattern on a photoreceptor in a method that detects and controls the original density, and based on the result, the exposure amount can be adjusted. By changing the control characteristics, we are proposing a method that eliminates the influence of changes over time in the sensitivity of the optical system and photoreceptor, etc., so that appropriate images can always be obtained.

(Problem to be solved by the invention, α) However, in any of the above conventional examples, the contamination of the optical system and the changes in the characteristics of the photoreceptor become large, and it becomes impossible to deal with them through control, making it impossible to form a proper copy image. The problem is that it is not possible to know the status until then.

In view of the above-mentioned conventional problems, the present invention provides a copying machine that is easy to maintain and can always obtain proper copied images by issuing a warning when the optical system becomes dirty or the characteristics of the photoreceptor become significantly changed. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present invention illuminates an original with an exposure lamp, exposes a photoreceptor to the image light to form an electrostatic latent image, and In an electrostatographic copying machine that develops a developed image and transfers it onto a transfer material, a developed density detection means detects the density of the developed image on a photoreceptor, a warning means, and a developed density of a test pattern. The apparatus is characterized by comprising means for activating the warning means based on a change in exposure lamp voltage during the developed image density measurement.

(Function) Since the present invention has the above configuration, it is possible to detect changes in characteristics due to dirt in the optical system, changes in characteristics of the photoreceptor, etc. from changes in the developed density of the test pattern and the exposure lamp voltage at that time, and issue a warning. By responding appropriately to this warning, such as cleaning dirt on the optical system, it is possible to always form a proper copy image, and maintenance becomes easier.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 2, the document table glass 2 on the top surface of the copying machine main body l
The original placed above is illuminated by an exposure lamp 3, and the image light is transmitted to a slit 4, a first mirror 5, a second mirror 5, a second mirror 6, and a third mirror 6.
7. Slit exposure is performed via the projection lens 8 and the fourth mirror 9 onto the photosensitive drum 10 disposed approximately in the middle heat section of the main body 1 of the copying machine. The exposure lamp 3, the sulin 14, and the first mirror 5 are held on a first moving table for scanning (not shown), and the second and third mirrors 6.
7 is a second moving table (
(not shown) to keep the projection optical path length constant.

Surrounding the photoreceptor drum 10 are a charger 11 that charges the photoreceptor drum 10 so as to form an electrostatic latent image through the slit exposure, a developer 12 that develops the electrostatic latent image with toner, and a photoreceptor drum. A transfer chart 13 that transfers the developed image on 10 onto a fed transfer paper.
, a separation charger 14 that separates the transfer paper from the photoreceptor drum 10, a cleaning device 15 that removes toner remaining on the surface of the photoreceptor drum 10 after transfer, and the like are provided.

In the copying machine configured as described above, in this embodiment, as shown in FIG. A signal is input and a control signal is output to the exposure lamp control means 23 and the warning display means 24.

The developed image density detection means 21 is composed of a seven-dimensional sensor 25 arranged around the photoreceptor drum 10 so as to receive reflected light from the developed image on the photoreceptor drum 10, and the original density detection means 22 includes: The projection optical system is comprised of seven optical sensors 26 arranged near the projection lens 8 to receive reflected light from the original. Further, each of the seven optical sensors 2526 is inputted to the exposure amount calculation means 20, which is a microcomputer, through amplifiers 27 and 28. Further, this exposure amount calculation means 20 includes a ROM.
29 is already connected.

A white pattern 30 as a test pattern is disposed at the vertical position of the moving end of the first moving table on one side of the platen glass 2, and as will be described in detail next, the photoreceptor of this own pattern 30 is placed vertically. It is configured to detect contamination of the optical system and changes in the characteristics of the photosensitive drum 10 by detecting the developed image density on the drum 10.

That is, when the own pattern 30 is exposed at a certain exposure lamp voltage VL and actually copied, the relationship between the exposure lamp voltage VL and the copied image density ID is as shown in FIG. 3.

The relationship between the output VS of the developed image density detecting means 21 which detects the developed image density on the photosensitive drum 10 and the copied image density ID obtained by copying the developed image is as shown in FIG. The relationship is known in advance and stored in the ROM 29. Here, if VS is proportional to the amount of reflected light,\
7S is expressed as an exponential function of ID, but at low concentrations where ID is 0.2 or less, it is affected by the background surface of the photoreceptor drum 10, so it deviates from the value shown by the broken line expressed as an exponential function. , the accuracy of ID measurement by \7S deteriorates.

Therefore, when exposing the white pattern 30, the ID when the developed image density on the photoreceptor drum 10 is measured is approximately 0.
It is exposed and developed at an exposure lamp voltage VL that provides a halftone density of 2 to 0.7. By doing so, it is possible to accurately measure IDT from the output VST of the developed image density detection means.

Here, the optical system, the photoreceptor drum 10, the charger 1
1. If the characteristics of the developing device 12 etc. change and the relationship between the exposure lamp voltage VL and the copied image density ID changes from the characteristic shown by the solid line in FIG. 5 to the characteristic shown by the dashed-dotted line, the developed density detection means The exposure lamp voltage when the output VS of No. 21 reaches a value corresponding to ID=0.1 (that is, the limit density that does not cause fogging on the background of the copied image) changes from \7LO to \1.

To explain how to calculate \7L1, it is thought that in the range of halftone density, even if the above characteristics change, the ID characteristics with respect to VL will move almost in parallel, so the initial characteristics are set as VL=
If expressed as g(ID), I when it changes as shown by the -dotted chain line
The exposure lamp voltage VLI for D=0.1 is \7L1=VLT++\7 LO-g(I D T)1
It can be found as

Here, VLO and g(ID) are known in advance, and therefore, the white pattern 30 is exposed and developed at an appropriate exposure lamp voltage VLT that provides a halftone density, and the developed density detection means 21
VLI can be known by detecting ST at , and calculating IDT as shown in FIG.

In this way, when the white pattern 30 is exposed and developed, I
Rather than directly adding the exposure lamp voltage VLI where D=0.1, the intermediate tone density IDT and the exposure lamp voltage VLT at that time
It is possible to obtain <VLI with better accuracy by calculating from .

Next, the optimum exposure lamp voltage VL for the original density OD
As shown by the solid line in FIG. 6, the value increases as the original density OD increases in order to prevent fog from occurring on the background of the copied image. Further, when the exposure lamp voltage limit that does not cause Jζ distortion in the copied image when exposing and developing the own pattern 30 as described above changes from VLO to VLI,
The optimum exposure lamp voltage for the original density is the exposure lamp voltage for the own pattern density changed from VLO to \7L1, as shown by the dashed line in FIG.

Therefore, the output Vs of the developed image density detection means 21 shown in FIG.
The relationship between and the copy image density ID is expressed as ID=I+(V
s) If the relationship between the original density OD and the exposure lamp voltage \/L in Figure 6 is expressed as ■L=f(OD), then the optimum exposure lamp voltage V for the original density ○D is
L is \7L = f (OD) + (\I Ll - V LO) =
r(OD)+\7LT-g(IDT)=f(OD)+
\I LT gll+(V 5T)1.

When the copy switch (not shown) is pressed, pre-scanning is performed, the density OD of the original placed on the original platen 2 is read by the original density detection means 22, and the optimum lamp voltage is set. The calculations are made according to the above equation, and the results are input to the exposure lamp control means 23 so that the exposure lamp 3 performs optimal exposure.

On the other hand, the main causes of fogging in the copied image are dirt on the optical system such as the document table 2, PS1 to third mirrors 5 to 7, projection lens 8, fourth mirror 9, etc. There is some dirt on the imaging system. If fogging occurs in the copied image due to such a cause, if VLI exceeds a certain value with respect to the limit exposure lamp voltage VLO that does not cause fogging in the copied image of a white original, the specific details vary somewhat depending on the system. exceeds approximately 6 V. In such a case, it is determined that the contamination of the optical system and image forming system exceeds the allowable range, and the user is notified by activating the warning display device 24 and cleaning etc. We request that appropriate measures be taken.

Then issue this warning! The u# operation will be explained with reference to FIG.

When the power is turned on, the program starts and steps #
Initialization is performed in step 1, and the exposure lamp voltage VL is set to the initial test lamp voltage VLTO. When the main switch is turned on, the photosensitive drum 1o rotates and the charger operates (step #2.3).

Next, the white pattern 30 is exposed and developed using the exposure lamp voltage VL set as described above, and the developed image density on the photoreceptor drum 10 is determined. tll and its output as \IST (step #4.5). The relationship between Vs and ID shown in Figure 4 is RO
Since it is stored in M29, IDT is calculated from VST (step #6), and IDT is 0.2<IDT<0.
If it does not fall within the range of halftone density 7, VL is increased or decreased by ΔV and the exposure and development of the white pattern 30 is repeated. ID
When T falls within the above range, VLT=VL (steps #7 to #11). Next, from IDT and VLT, VL
Find I-VLO=VLT-g(IDT) (Step #12).

Next, it is determined whether this VLI-VLO>6 or not (step #13), and if VLI-VLO exceeds 6, the warning indicator Pi24 is activated, and if not, the process continues to the next step. Move to well 15. Thereafter, the process waits until the copy switch is turned on, and when the copy switch is turned on, in step #16, exposure is performed using the exposure lamp 3 controlled to the above-mentioned optimum exposure lamp voltage to make a copy with an appropriate image density. Repeat the action. Also,
When a warning is displayed, you should take appropriate measures such as cleaning the optical system based on the warning, so that you can always obtain proper copied images.

(Effects of the Invention) As described above, according to the copying machine of the present invention, changes in characteristics due to dirt in the optical system, changes in sensitivity of the photoreceptor, etc. can be detected from changes in the developed density of the test pattern and the exposure lamp voltage at that time. The warning can be ignored, and by taking appropriate actions such as cleaning the optical system to remove dirt, it is possible to always form a proper copy Flfl&, which has the effect of making maintenance easier.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of the main parts of an embodiment of the present invention, Fig. 2 is a side view of the exposure and image forming section of the copying machine, and Fig. 3 shows the relationship between the lamp voltage and the density of the copied image. Graph shown, 4th
The figure shows developed density detection output and copy ii! ii A graph showing the relationship between image density, Figure 5 a graph showing the relationship between lamp voltage and copied image density, t5G graph showing the relationship between original density and optimum exposure lamp voltage, and Figure 7 a 70-chart for control. It is. 3...Exposure lamp 10...Photosensitive drum 20...Exposure amount calculation means 21...
...Visual density detection means 24... Warning display means 30 ... White pattern agent Patent attorney Katsutaka Katsushiro Ishihara (VVC-VII! Change of clothes

Claims (1)

[Claims] (1) Electrostatic photocopying in which an original is illuminated with an exposure lamp and a photoreceptor is exposed to the image light to form an electrostatic latent image, which is developed to become visible and transferred onto a transfer material. a developed density detection means for detecting the density of the developed image on the photoreceptor; a warning means; and a warning means based on the developed density of the test pattern and the change in the exposure lamp voltage at the time of measuring the developed density. A copying machine characterized by comprising: means for operating the copying machine.