JPS60119580A - Image forming device - Google Patents

Abstract

PURPOSE:To perform control corresponding to an image original by detecting the quantity of exposure and discriminating whether the density contrast of the original image is high or not, switching a preset control command according to the discrimination result, and controlling the density contrast. CONSTITUTION:An original density cintrast discriminating means 2 discriminates on whether the density contrast of the original is high or low from the quantity of exposure detected by an image exposure among detector 1. A determining means 3 for the standard potential of potential control decides the standard potential used for the potential control on the basis of the discrimination result. An arithmetic means 5 for correcting data on the amount of electrostatic charging calculates the amount of correction of the amount of charging from the standard potential and a model potential detected on a photosensitive body by a surface potential detector 4. A control means 6 for the amount of charging controls the adjustment amount of an adjusting means 7 for the amount of charging on the basis of the correction amount of the amount of charging. Consequently, the density contrast of a recording image is controlled. Thus, the density contrast of the recording image is controlled corresponding to the original image and even character patterns on a low-contrast original are copied sharply, thereby reducing the deterioration of the photosensitive body.

Description

[Detailed Description of the Invention] [Technical Field] The present invention provides a method for controlling the density contrast of a recorded image according to the density contrast of a document moving source.
Heat 1 is applied to the image forming device.

[Prior art]

In general, in image forming apparatuses, such as copying machines, that record images by forming an electrostatic latent image of a document image to be recorded, the electrostatic latent image formed by the electrophotographic method is It becomes unstable due to deterioration of the body and due to the photoreceptor being stopped for a long time. Therefore, as a means to deal with these problems, it is possible to form a model of the original image on the photoreceptor in the copy mJ7, and to control the latent image formation conditions f+, such as the amount of charge and the amount of exposure, as follows. It is being done.

That is, the model potential f of ^11 formed on the photoreceptor
The potential is detected by a % detector and compared with a predetermined standard potential, and the latent image forming conditions are set so that the model potential becomes equal to the standard potential.

? When determining the b image forming conditions, there is a sergeant who takes into consideration image density contrast, charging deterioration of the photoreceptor, etc., and the image source 1 of the background of the original and the character I/ is a low contrast original ( It is necessary to be able to copy character patterns clearly even with low-contrast originals, and to reduce deterioration due to charging of the photoreceptor.

Low-contrast originals include thin originals, new paperbacks, color printed originals, and the like.

In a device in which an electrostatic latent image is formed on a photoreceptor consisting of an insulating layer, a photosensitive layer, and a conductive layer by simultaneous image exposure and full-surface exposure with secondary charging and secondary charging, the potential of a completely unexposed area (dark area potential) )
If the model potential is set using the potential of the fully exposed area (light area potential), in order to clearly copy the entire character pattern of the low contrast original 6M, it is necessary to have a large potential difference between the dark area potential and the bright area potential. There is.

However, since it is L7, when the potential difference between the dark area potential and the light area potential is increased, the number of single charge zones and secondary charge ridges increases [7, which promotes the masculinization of the Δ-four light body. It had the disadvantage of being tampered with.

〔the purpose〕

This invention addresses the above-mentioned drawbacks of the conventional technology.

It is designed to detect the brightness of an image on the photoreceptor and determine the contrast level of the original image. By switching the iL1 scale value and controlling the density contrast of the recorded image, it is possible to clearly copy character patterns of low-contrast originals, and to prevent deterioration of the photoreceptor. The overall purpose of the present invention is to provide an image forming apparatus that makes it possible to reduce the amount of noise.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows each Yuzuhara No. 1. FIG. 2 is a diagram showing the relationship between the image exposure amount and the average image exposure amount obtained by averaging the image exposure values.

From this figure, the following can be seen by calculating the average image exposure (ABXP). CH is the ABXP value that is the boundary between high contrast and low contrast.

If CL (CI-1>C1,), then AEXP is Agx
p) If it is in the range of CH- or lxI・(Cb, it corresponds to a low-contrast original beat, and if it is in the range of Ct, ≦, it corresponds to a high-contrast original if it is in the range of Fi It can be seen that it is possible to distinguish between low-contrast originals, such as thin-print originals, newspapers, and color printing, and high-contrast originals, such as black-and-white printing and nine-color paper printing.

FIG. 2 is an overall configuration diagram illustrating the present invention in detail.

Il! Based on the image exposure amount detected by the il image exposure amount detector 1, the document density contrast determining means 2 determines whether the density contrast of the document is high or low. Based on the results of the determination,
The potential side slant standard potential determination means 3 determines the standard potential used for potential control. This standard potential and surface potential detector 4,4
The charge amount correction data calculating means 5 calculates a charge amount correction piece based on the model potential on the photoreceptor detected by. Based on this charging amount correction piece, the charging vibration suppressing means 6 controls the Wt4 adjustment of the charging and abrasive amount adjusting means 7, thereby controlling the density contrast of the recorded image.

FIG. 3 is a schematic diagram showing a copying apparatus according to the present invention.

In Figure VC, 8 is a primary charger, 9 is a secondary @electrosimultaneous imager, 10 is a full-surface lamp, 11 is a photosensitive drum (a photosensitive member formed in a drum shape), and 12 is an electrostatic latent. A developing device that converts the image into a visible image (toner image) using toner; 13 is transfer paper; 1
4 is a transfer charger that transfers the toner image on the photosensitive drum 11 onto the transfer paper 13; 15 is a paper feed roller that feeds the transfer paper 13 to the transfer charger 14; 16 is a heating roller and a pressure roller; A fixing device deposits the toner image on the transfer #t13 on the transfer paper 13, 17 a cleaning device that removes the toner remaining on the photosensitive drum 11, 18 a document table on which the document is placed, and 19 the document. Document illumination lamp for illumination,
20 is a power source for the original illumination lamp 19; 21 is a standard original density plate disposed in the non-original portion of the original platen 18 and used to adjust the light intensity of the original illumination lamp; This is an image exposure amount detector that detects the image exposure amount, and is arranged at a position where part or all of the image exposure 23 is blocked. 24 is an image measuring circuit for measuring the image exposure amount detected by the image exposure amount detector 22; 25 is a blank exposure lamp; and 26 is the photosensitive drum 11.
A surface potential detector placed nearby detects the entire surface potential of the photosensitive drum; 27 is a surface potential measuring circuit that measures the surface potential detected by the surface potential detector 26; and 28 is a surface potential measuring circuit that measures the density contrast of the original image. an arithmetic/control/memory circuit as a means for determining and switching a control target value set in advance in accordance with the determined result; 29 a high-voltage power source as a means for controlling the density contrast of the recorded image;
30 is a sequence control circuit that controls the entire copying apparatus.

FIG. 4 shows an example of formation 1- of the photosensitive drum 11,
11a is an insulating layer, 11b is a photosensitive layer, and 11c is a conductive layer.

FIG. 5 is a diagram showing the configuration of the calculation/control/storage circuit 28, in which 28a and 28b are Al1) converters, 28c is a calculation/control/storage unit, and 28dFiD/
It is an A converter.

The entire operation will be explained based on the above configuration.

The document on the document table 18 is illuminated by the document illumination lamp 19 connected to the power source 20, and then the document is placed on the document table 8. Secondary charging simultaneous image exposure device9. An electrostatic latent image corresponding to the original image is formed on the entire photosensitive drum 11 by the full exposure lamp 10. It is developed with toner in the electrostatic latent image device 12 to become a toner image. The transfer charger 14 transfers this toner image to a paper feed row 2.
15, the image is transferred onto the transferred transfer paper 13. Fuser 1
6 fixes the toner image on the transfer paper, the transfer paper with the toner fixed thereon is discharged, and the photosensitive drum 13 having the untransferred toner on its surface is cleaned by a cleaning device 19 to remove the remaining toner. / and the copy process ends.

Next, control of the temperature contrast of the recorded image in step 2 of the above copy process will be explained.

First, before making a copy, the blank exposure/pump is turned on at 25 gold to irradiate the photosensitive drum 11 with an amount of light equivalent to that of a normal blank sheet. The surface potential (write potential) at this time is detected by the surface potential detectors 4 and 26, and the potential is measured by the surface potential measuring circuit 27. L2 exposure lamp 2
5 is turned off [2, similarly, the surface potential (dark potential) 'k 6111 on the photosensitive drum 11 is determined. Measurement (IJ A/D conversion of the light potential and dark potential respectively by the A/D converter 28a in FIG. 5, and Al1 in the calculation/control/storage unit 28c) and a standard potential assuming a high-contrast original (a predetermined control target value for a high-contrast original). Then, a correction value is calculated so that the set light potential and dark potential match the standard potential. After that, D/A conversion is performed using the correction value fD7A converter 28d to fully control the high voltage power source 29, and the current values of the -next bender 8 and the secondary charging simultaneous image exposure device 9 are set to appropriate values, and charging is performed. quantity k tffl
I control J.

When the above-described pre-copy process is completed, the original is then illuminated, the image exposure detector 1.22 detects the amount of image light from the original, and the image exposure measurement circuit 24 measures the exposure. . Then, the output signal of the image exposure measuring circuit 24 is A/D converted by the iA/D converter 28b, and the converted signal is calculated, controlled, and stored in the calculation/control/storage unit 28c.
Enter. The calculation/control/storage unit 28c calculates an average image exposure amount by averaging the measured image exposure amounts. If the value is within a predetermined range for a high-contrast original, copying is performed with the same amount of charge. Further, if it is within the range assuming a predetermined low contrast original, control similar to the process before copying described above is performed using a standard potential 7 assuming a predetermined low contrast original. In other words, the preset control target value is switched to a standard potential assumed for all low-contrast originals, and this standard potential is
The primary charger 8
, set the current value of the secondary Teitun doshi image controller 9 to an appropriate value 7
to control band-M.

Hereinafter, the control of the density contrast of i+i+s: will be explained in detail based on the flowchart of FIG. 6 [al, tbl].

When a copy start key (not shown) is pressed and a predetermined co-enable condition is satisfied, a copy operation is started.

That is, when the copy start key is pressed, -next bending device 8
, secondary charging simultaneous image exposure device 9, and other chargers start charging, the entire surface exposure lamp 1o is turned on, and the photosensitive drum 11 rotates (step 1). When the pre-rotation of the photosensitive drum 11 is completed, the blank exposure rung 25 is turned on (step 2), and the photosensitive drum 11 is irradiated with an amount of light corresponding to a normal blank sheet. This irradiation forms a potential on the photosensitive drum 11, and the surface potential at this time (light potential (Vl))
is detected by the surface potential detector 4.26, and the potential is completely measured by the surface potential measuring circuit 27 (step 3). Next, the plastic exposure lamp 25 is completely turned off (step 4), and the surface potential (dark potential (Vd) of the photosensitive drum 11 is similarly
)) (Step 5). The arithmetic/control/storage circuit 28 generates a standard potential V1.7 assuming the defined Vl, Vd and all high-contrast originals. o, Vn. 1 (step 6.7). VLo is a light potential of a standard potential assuming all high contrast originals, and vDol is a dark potential of a standard potential assuming all high contrast originals.

As a result of the comparison, if the measured potential and the standard potential do not match, the calculation/control/storage circuit 28 calculates the difference between the measured potential and the standard potential, x = VDol-Vd, y = VL6Vl
Calculating Step 8) - Wide charging current correction value △P=
f(x, y), correction amount of secondary charging current t・S=g(x,
y) Perform all calculations (step 9).

Based on this calculated value, the high-voltage power supply 29f controls the following electric appliance 8. 7. Control the current value of the secondary charging simultaneous image exposure device 9 to an appropriate value; -Change the amount of next curve and second curve, and repeat steps 2 to 11 until the standard potential and the measured potential match.

If the measured potential and the standard potential match in step 7, the operation shown in FIG. 6 (bl) below is performed (moves from A in FIG. 6 fat to A in FIG. 6 (bl). In other words, document illumination Illuminate the entire document with the lamp 19 (step 1)
2) The image exposure amount (Exp) is detected by the image exposure amount detector 1.2.
Detection at step 2 (7, measurement is performed a predetermined number of times (Ns) by the image exposure measurement circuit 24 (steps 13 to 17).
The measured image exposure amount is calculated by the calculation/control/storage circuit 28V (average image exposure amount (AEXP)) (Step 1)
8).

Here, as mentioned above, if the average image exposure (ABXP) is within a predetermined range, that is, CL≦AEXP≦CH, it corresponds to a high contrast original, and AEXP (CI
4 (Agxp) CH corresponds to a low-contrast original, so by measuring AEXP i as described above, the calculation, control, and storage circuit 28 determines whether the density contrast of the original is high or low (step 19). .20).

In the case of high contrast originals, that is, CL≦AEXP≦
If it is OH, start copying as is, and if it is a low contrast original, i.e. AEXP<CL or AEXP
>CI (in case of 25 times, turn on the plastic exposure lamp 25 and measure the light potential (vgt), then turn on the blank exposure lamp 25
7 and measure the dark potential (Vd) (steps 21 to 24). The measured potentials Vl, Vd and standard potentials VL, VDo2 assuming a low contrast original are compared by the calculation/control/storage circuit 28Yc (step 2).
5.26). VL is a standard potential of a light potential assuming a low contrast original, and VDo2 is a standard potential of a dark potential assuming a low contrast original.

As a result of the comparison, if the measured potential and the standard potential do not match, the calculation/control/memory circuit 28 calculates the difference between each measured potential and the standard potential, X: VD02-V d +
y = vLo ” l lc it calculation 1. (,1,f
Whelk 27).

- Wide charging current correction amount ΔP = h (x ty)
- Correction of the secondary charging current calculates Δ5=i(x,y) (step 28). The high-voltage power supply 29 is controlled based on the calculated value, and the next bending electric appliance 8. Secondary charging simultaneous image exposure device 90″
The ridge value is controlled to an appropriate value, and the -order bending charge amount and secondary charge amount are changed. The operations of steps 21 and 30 are repeated until the standard potential and the measured potential match. If the measured potential and the standard potential match, copying is started.

Copies recorded by controlling the charged pupil as described above are copied with appropriate density contrast even if the original has low contrast, and the photosensitive drum 11 is not deteriorated. It can be kept to a minimum.

The following describes the results of experiments in which low-contrast originals were cohesed using a copying apparatus according to the present invention and a conventional copying apparatus.

The standard potentials of the light potential and dark potential of a conventional copying machine are assumed to be OV and 450V, respectively. The standard light potential of the copying apparatus according to the present invention is 20V, the standard dark potential is 350V assuming a high contrast original.
Standard dark potential for low-contrast originals'
Set to 600V. In addition, the average image exposure amount (AEX
P) ranges from 1 to 21ux for high contrast originals,
It is assumed that a document having a length of 0.95 Jux or less or 2.051 uxsec or more is a low contrast original.

The result of copying with the above settings is as follows (B)
, (b) will be described.

(b) The reflection density of the background part of the original is 0.07. When the reflection density of the text part is 3.

(b) When the reflection density of the background part of the original is 0.31, and the reflection density of the character part is 0.8, and the exposure amount is adjusted so that the background does not overlap on the copy.

In case (a), the reflection density of the text portion of the copy image was 0.5 in the conventional device, whereas the reflection density of the text portion of the copy image was 0.85 in the device according to the present invention (1). The image was copied with a high reflection density, and the copy was clear with no background overlapping.

In case (b), the conventional device had a reflection density of 0.4 in the text portion of the copy image, whereas the device according to the present invention had a reflection density of 0.4 in the text portion of the copy image.
．． 9 and was similarly copied with a large reflection density.

Next, we will discuss experimental results regarding charging deterioration of the photoreceptor.

When 50,000 sheets were copied using a conventional copying device and when 40,000 high-contrast originals and 10,000 low-contrast originals were copied using the copying device according to the present invention, the charged and deteriorated photosensitive drums were left in the copying device. It will be suspended for 141 hours. Thereafter, 100 sheets were continuously copied, and the dark potentials of the 1st and 100th sheets were measured.

As a result, the dark potential difference between the 1st and 100th sheets is.

In the conventional copying machine, the voltage was 70V, whereas in the copying machine according to the present invention, it was 40V, and it can be seen that the photoconductor has less charge deterioration in the copying machine according to the present invention.

Note that the charge amount of each of the high-contrast and low-contrast originals is controlled in advance using standard potentials, the controlled charge amounts are temporarily stored, and the average imageless amount of the original is measured L7. It is also possible to determine whether the density contrast is high or low, and to switch the charging IL'r according to the determined result.Compared to the previous embodiment, it is possible to start copying faster because calculations and controls are not performed after determining the contrast of the original. The time from when a key is pressed until the original image is copied onto the first sheet of transfer paper and the paper is ejected can be shortened.

Further, a standard original density plate 21 is provided in the non-original part of the original platen 18 shown in FIG. ,
Complete scanning exposure is performed by the original illumination lamp 19, and the exposure 2
It is also possible to form a model potential using 3 and perform control in the same manner. Furthermore, the average image exposure amount of the document is measured, and according to a predetermined calculation formula, the document illumination lamp 1
Calculate the lamp power supply voltage to obtain the proper exposure of 9.
By controlling the backup power supply 20, automatic exposure can also be performed.

〔effect〕

As explained above, the present invention includes a means for detecting the amount of fog light and determining whether the density contrast of the original image is high or low, and controlling the entire density contrast of the recorded image by switching a control target value set in advance according to the determined result. By providing a means for This has the effect of reducing the amount of

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between various originals and the average image no-light amount, FIG. 2 is an overall configuration diagram for explaining the invention in detail, and FIG. 3 is a schematic diagram showing an embodiment of the invention. , FIG. 4 is a diagram showing an example of the formation layer of the photosensitive drum, FIG. 5 is a diagram showing the configuration of the calculation/control/storage circuit shown in FIG. 3, and FIG.
al, (bl is a flowchart for explaining the density conotrast control. 10...
...Full exposure lamp 11...Photosensitive drum 19...Original illumination lamp 20...
... Lamp power supply 22 ... Image exposure amount detector 24 ...
...Image exposure measurement circuit 25...
Blank exposure lamp 26...Surface potential detector 27...Surface potential measurement circuit 28...
...... Arithmetic/control/memory circuit 29...
...High voltage power supply Figure 1 Figure 2 Figure 6 Figure 3 1 Figure 4 Figure 5 February (a)

Claims (1)

[Claims] An image forming apparatus configured to control the density contrast of a recorded image, the image forming apparatus comprising: means for detecting the amount of image exposure to a photoreceptor (7) and determining whether the density contrast of the original image is high or low;
The first set of suppressed eyes that has been set in advance according to the determined results
and means for controlling the density contrast of the recorded image.
Forming device.