JPH05323742A - Image forming device - Google Patents

Abstract

PURPOSE:To improve a copying speed and to stabilize an image by providing a reference decision means and a correction means. CONSTITUTION:The surface potential of a photosensitive body 41 is detected by a potential sensor. However, the detected value is irregular in the circumferential direction of the body 41. The irregularity is caused by deflection by the eccentricity of the body 41 or the like. In order to optimally adjust the formation of the image such a condition as the potential V0 of a dark part and the potential Vi of a bright part when a reference toner image is formed should be fixed. Then, the best condition of electrostatic charge quantity and light quantity is previously decided before the image is formed. A latent image pattern equivalent to one round of the body 41 is formed and the potential is detected before the image is formed. Then, the average potential is calculated. Based on the calculated result, the image forming condition is decided. On the other hand, the image forming condition is easily corrected in order to increase the copying speed by forming the latent image at one part of the body 41 based on the condition and detecting the potential when the image is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image reproduction in an image forming apparatus by an electrophotographic process.

[0002]

2. Description of the Related Art Generally, a photosensitive member used in an electrophotographic process has variations in electrostatic characteristics due to environment, printing durability, and variations in electrostatic characteristics among individual photosensitive members. Further, the potential of the photoconductor is uneven in the circumferential direction. Particularly in a color copying machine, these variations in electrostatic characteristics have a great influence on color reproducibility, balance, and reproducibility in low-density areas. Therefore, in order to stabilize the image, the electrostatic characteristic of the photoconductor is detected to control the potential, and the image is stably maintained in a good state.

[0003]

The surface potential of the photoconductor is detected by the potential sensor, but the detected value is uneven in the circumferential direction of the photoconductor. This unevenness is caused by the eccentricity of the photosensitive member, such as a shake. Therefore, a large error occurs in the detection of the surface potential. So image stabilization
This must be done in consideration of the uneven potential. On the other hand, especially in continuous copying, it is required to improve the copying speed. In the image forming apparatus described in Japanese Patent Laid-Open No. 62-251763, in order to reduce the influence of potential unevenness on the circumference of the photoconductor, the dark potential and the light potential are detected at a certain position (detection) of the photoconductor. It is carried out at the positions corresponding to the average value, maximum value and minimum value of the electric potential).

An object of the present invention is to provide an image forming apparatus capable of improving the copying speed and stabilizing the image.

[0005]

An image forming apparatus according to the present invention comprises a charging means for charging a photoconductor, an exposing means for exposing the photoconductor, and a developing means for developing a latent image formed on the photoconductor. In an image forming apparatus equipped with, before image formation,
The first latent image pattern for one round of the photosensitive member is formed, and the potential of 1
A reference value determining unit that determines an average value for the circumference and determines a reference value for image formation based on the average value, and a photosensitive member on the photoreceptor under the condition based on the reference value by the reference value determining unit at the time of image formation. The potential of the second latent image pattern formed on one portion is detected by the potential detecting means, and the correcting means is provided for adjusting the image forming condition based on the detected value. Preferably, the charging means cleans the charge wire before charging. The second image forming apparatus according to the present invention is
In an image forming apparatus including a charging unit that charges a photosensitive member, an exposure unit that exposes the photosensitive member, and a developing unit that develops a latent image formed on the photosensitive member, before the image formation, Reference value determining means for forming a first latent image pattern for one cycle, obtaining an average value for one cycle of the potential, and determining the reference values of the charge amount and the light amount for image formation based on this average value; At the time of image formation, the electric potential of the second latent image pattern formed on one portion on the photoconductor is detected by the electric potential detecting means based on the reference value determined by the reference value determining means, and the light amount is adjusted based on the detected value. And a correction means for performing the correction. Preferably, the correction means is operated for each image formation when the image formation is continuously performed.

[0006]

In order to optimally adjust the image formation, it is necessary to make the dark portion potential Vo and the light portion potential Vi constant when forming the reference toner image under any condition. Therefore, the optimum conditions of the charge amount and the light amount are determined in advance before the image formation. Therefore, before forming an image, a latent image pattern for one rotation of the photoconductor is formed, the potential is detected, and the average potential is calculated.
The image forming conditions are determined based on this result. On the other hand, at the time of image formation, in order to speed up copying, a latent image is formed on a part of the photoconductor based on this condition, the potential is detected, and the image forming condition is easily corrected. Further, in another image forming apparatus according to the present invention, the standard of the charge amount and the light amount is determined before the image formation, and thereafter (for example, during continuous copying), in order to increase the copying speed, the photoconductor is Since the latent image pattern is formed only in one part of the above and the change in the charge amount is small, the adjustment time is shortened by adjusting only the light amount.

[0007]

Embodiments of the present invention will now be described in the following order with reference to the accompanying drawings. (A) Configuration of digital color copying machine (b) Image signal processing (c) Gradation correction (d) Automatic image density control (AIDC) (e) Improvement in accuracy of automatic density control (dark area potential Vo and bright before AIDC operation) (Detection of partial potential Vi and correction of grid potential V _G and maximum light amount) (f) Potential sensor distance characteristic and its correction (g) Correction of maximum density change and gradation change during continuous copying (g-1) ViC detection and Correction of maximum light amount (g-2) Light amount correction table during continuous copying (g-3) Modified example (h) Limitation of correction amount during continuous copying (i) Prevention of overcorrection at abnormal times (j) Light emission control mode Switching (k) Printer control flow (k-1) Description of main flow (k-2) Main switch closing process (k-3) V _G correction process (k-4) ViA detection process (k-5) AIDC operation Process (k-6) ViB detection process Process (k-7) Time control process (k-8) Environmental control process (k-9) Light emission control process (k-10) Copy process (k-11) Process after trouble such as jam (k-12) Continuous copy V _G correction process in (k-13) over-correction prevention process The present invention is particularly relevant to the sections (e), (g), and (k).
-1) section, (k-4) section, (k-6) section, (k-10)
It is a section.

(A) Configuration of Digital Color Copying Machine FIG. 1 is a sectional view showing the overall configuration of a digital color copying machine according to an embodiment of the present invention. The digital color copying machine includes an image reader unit 100 for reading a document image and a copying unit 20 for reproducing an image read by the image reader unit.
It is roughly divided into 0. In the image reader unit 100, the scanner 10 includes an exposure lamp 12 that illuminates a document.
And a rod lens array 1 that collects the reflected light from the original
3, and a contact-type C that converts the condensed light into an electric signal
A CD color image sensor 14 is provided. The scanner 10 is driven by a motor 11 when reading a document,
It moves in the direction of the arrow (sub-scanning direction), and scans the document placed on the platen 15. The image on the document surface illuminated by the exposure lamp 12 is photoelectrically converted by the image sensor 14. The R, G, and B multi-valued electrical signals obtained by the image sensor 14 are processed by the read signal processing unit 20 to be any of yellow (Y), magenta (M), cyan (C), and black (K). The converted 8-bit gradation data is stored in the synchronization buffer memory 30.

Next, in the copying section 200, the print head section 31 performs gradation correction (γ correction) on the input gradation data according to the gradation characteristics of the photoconductor, and then the corrected image. Data is D / A converted to generate a laser diode drive signal, and the semiconductor laser is caused to emit light by this drive signal (see FIG. 8). A laser beam generated from the print head unit 31 corresponding to the gradation data exposes the photosensitive drum 41 which is rotationally driven through the reflecting mirror 37. Photoconductor drum 41
The eraser lamp 42 before receiving the exposure for each copy.
And is uniformly charged by the charging charger 43. When exposed in this state, the photosensitive drum 41
An electrostatic latent image of the original is formed on top. Cyan, magenta,
Only one of the yellow and black toner developing devices 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. The developed toner image is transferred by the transfer charger 46 onto the copy paper wound around the transfer drum 51.

As shown in FIG. 2, a detector (light-shielding plate) 501 is attached to the transfer drum 51, and when the detector 501 passes a detection sensor (photo sensor) 502, the detection sensor 501 is detected. Reference numeral 502 detects the rotational position of the photosensitive drum 41, and controls the copying operation starting from this detection time point. Further, the photosensitive drum 41 and the transfer drum 51
Is configured such that the drum diameter is an integer ratio (2: 1) and is connected and driven, and the photosensitive drum 41 and the transfer drum 51 are always in contact with each other at the same position. This eliminates the deviation when the toner is polymerized. Further, it becomes possible to detect the adhesion amount by the AIDC sensor 210 and the potential detection by the potential sensor 44 at a fixed position on the photoconductor drum 41, and it is possible to ignore the influence of the eccentricity of the photoconductor drum 41 at the time of detection. ..

The above printing process is repeated for four colors of yellow (Y), magenta (M), cyan (C) and black (K). At this time, the photosensitive drum 41
The scanner 10 repeats the scanning operation in synchronization with the operation of the transfer drum 51. Thereafter, the copy paper is separated from the transfer drum 51 by operating the separation claw 47,
The image is fixed through the fixing device 48, and is discharged to the paper discharge tray 49. The copy paper is fed from the paper cassette 50, and the tip of the copy paper is chucked by the chucking mechanism 52 on the transfer drum 51 so that the positional deviation does not occur during transfer.

FIG. 3 shows a charge wire cleaning device. Charge wire 30 of charging charger 43
1 is cleaning members 302 and 3 attached to the mover 306.
03 and the charge wire 30
It is cleaned by moving it in the longitudinal direction of 1. The mover 306 is connected to the rope 304, and moves by winding the rope 304 by the motor 305. As a result, the deposits on the charge wire 301 are always removed to prevent uneven discharge. This cleaning operation is always performed before the detection of the electric potential and the adhered amount (AIDC operation), thereby suppressing the disturbance of the electric potential caused by the charge contamination and enabling the accurate electric potential correction.
In order to detect the electric potential and the adhered amount over the entire length in the longitudinal direction of the photoconductor drum 41, it is conceivable to arrange several sensors in the longitudinal direction or scan in the longitudinal direction, but in terms of configuration and cost. Be at a disadvantage. Therefore, if the cleaning is always performed by the charge wire 301 before the detection to eliminate the potential unevenness in the longitudinal direction due to the charge stain, the control by the single fixed potential sensor 44 becomes possible.

FIG. 4 shows the structure around the photosensitive drum 41. The potential sensor 44 is positioned at the laser exposure position as shown in the figure.
It is provided between (A) and the developing position (B). Potential sensor 44
The distance between the photosensitive drum 41 and the photosensitive drum 41 is set to about 3 mm. Further, the AIDC sensor 210 has a position after development.
In (C), the distance to the photosensitive drum 41 is set to about 3 mm. AIDC sensor 210 and potential sensor 44
By making the positions in the longitudinal direction of the photoconductor drum substantially the same, the influence of potential unevenness in the longitudinal direction of the photoconductor drum (which may be caused by partial mesh contamination) is reduced, and the AIDC sensor 210 The accuracy is maintained when the amount of adhesion is detected. Further, at the time of detecting the adhesion amount, the pre-transfer eraser 55 is turned off in order to prevent the light of the pre-transfer eraser 55 from entering the light receiving portion of the AIDC sensor 210. Similarly, at the time of detecting the potential, the developing device 45 is not pressed against the photoconductor drum 41, so that the light of the pre-transfer eraser 55 goes around to the potential sensor 44. Therefore, the pre-transfer eraser 55 is also erased at this time. Other, photosensitive drum 4
In the vicinity of 1, a temperature sensor 212 is attached in addition to the above-mentioned sensors (44, 210), whereby the temperature characteristic of the potential sensor 44 is corrected and the in-machine temperature is also monitored.

5 and 6 are overall block diagrams of the control system of the digital color copying machine according to the embodiment. The image reader unit 100 is controlled by the image reader control unit 101. The image reader control unit 101 uses the platen 15
The exposure lamp 12 is controlled via the drive I / O 103 and the scan motor driver 105 is controlled via the drive I / O 103 and the parallel I / O 104 by the position signal from the position detection switch 102 indicating the position of the upper original. Control. The scan motor 11 is driven by the scan motor driver 105. On the other hand, the image reader control unit 101 is connected to the image control unit 106 by a bus. The image control unit 106 is connected to each of the CCD color image sensor 14 and the image signal processing unit 20 by a bus. The image signal from the image sensor 14 is input to the image signal processing unit 20 and processed. The copying unit 200 includes a printer control unit 201 that controls general copying operations. A printer control unit 201 including a CPU is connected to a control ROM 202 storing a control program and a data ROM 203 storing various data (γ correction data and the like). The printer control unit 201 controls the print operation based on the data in these ROMs. The printer control unit 201 includes a V _O sensor 44 that detects the surface potential V _O of the photoconductor drum 41, an AIDC sensor 210 that optically detects the toner adhesion amount of the reference toner image that adheres to the surface of the photoconductor drum 41, and a developing unit. ATD for detecting toner concentration in the containers 45a to 45d
C sensor 211, temperature sensor 212 and humidity sensor 2
Analog signals from various sensors of 13 are input.

The printer control unit 201 includes the sensors 44,
210 to 213, operation panel 221 and data ROM
In order to control the copy controller 231 and the display panel 232 according to the contents of the control ROM 202 by the data from 203, and to perform the automatic density control by the AIDC sensor 210 or the manual density control by the input to the operation panel 221. Via the parallel I / O 241 and the drive I / O 242, a V _G generating high voltage unit 243 for generating the grid potential V _G of the charging charger 43 and a V _B generating high voltage for generating the developing bias potential V _B of the developing devices 45a to 45d. Control the unit 244. The printer control unit 201 has an internal RAM. The printer control unit 201 is also connected to the image signal processing unit 20 of the image reader unit 100 by an image data bus, and based on the image density signal coming through the image data bus, a γ (gradation correction) table. Stored data R
The semiconductor laser driver 263 is controlled via the drive I / O 261 and the parallel I / O 262 with reference to the contents of the OM 203. Light emission of the semiconductor laser 264 is driven by the semiconductor laser driver 263.
The gradation expression is performed by modulating the emission intensity of the semiconductor laser 264.

(B) Image Signal Processing FIG. 7 is a diagram for explaining the flow of image signal processing from the CCD color image sensor 14 to the printer control unit 201 via the image signal processing unit 20. With reference to this, the read signal processing for processing the output signal from the CCD color image sensor 14 and outputting the gradation data will be described. In the image signal processing unit 20, the image signal photoelectrically converted by the CCD color image sensor 14 is converted by the A / D converter 21 into multivalued digital image data of R, G, B. The converted image data is shading corrected by the shading correction circuit 22. Since this shading-corrected image data is the reflected light data of the document, the log conversion circuit 23 performs log conversion to convert the density data of an actual image. Furthermore, with the undercolor removal / blackening circuit 24,
Excessive black coloring is removed, and true black data K is generated from R, G, B data. Then, in the masking processing circuit 25, the data of the three colors of R, G, B are Y, M, C.
Are converted into data of three colors. Y thus converted,
The density correction circuit 26 performs density correction processing for multiplying the M and C data by a predetermined coefficient, the spatial frequency correction processing is performed by the spatial frequency correction circuit 27, and then outputs to the printer control unit 201.

FIG. 8 is a block diagram of image data processing in the printer control unit 201. Here, the image data (8 bits) from the image signal processing unit 20 is input to the first-in / first-out memory (hereinafter referred to as a FIFO memory) 252 via the interface unit 251. The FIFO memory 252 is a line buffer memory capable of storing gradation data of an image for a predetermined number of rows in the main scanning direction, and absorbs a difference in operating clock frequency between the image reader unit 100 and the copying unit 200. It is provided to do. The data in the FIFO memory 252 is
Next, it is input to the γ correction unit 253. As will be described later, the γ correction data in the data ROM 203 is sent to the γ correction unit 253 by the printer control unit 201, and the γ correction unit 25
3 corrects the input data (ID) and outputs the output level D /
It is sent to the A conversion unit 254. The analog voltage converted from the output level (digital value) in the D / A conversion unit 254 is then supplied to the printer control unit 20 in the gain switching unit 255.
In accordance with the gain set value from 1, the switches SW ₁ to SW ₈ (corresponding to different powers P _{1 to} P ₈ ) are switched and amplified by the gain switching signal generation circuit unit 256, and then, via the drive I / O 261. Is sent to the semiconductor laser driver 263 to cause the semiconductor laser 264 to emit light with the intensity of that value.

On the other hand, the printer control unit 201 sends a switching signal corresponding to a duty ratio described later to the light emission signal generation circuit 265. The light emission signal generation circuit 265 is a parallel I /
A light emission signal based on the clock switched by the switching signal is sent to the semiconductor laser drive unit 263 via the O circuit. The light emission signal generated by the light emission signal generation circuit 265 is generated based on a clock having a duty ratio corresponding to the clock switching signal. Semiconductor laser drive unit 263
Generates a drive current for the semiconductor laser 264 only when a light emission signal is input. Therefore, the duty ratio is switched by this light emission signal (clock). The semiconductor laser drive unit 263 outputs the image signal input from the drive I / O circuit 261 and drives the semiconductor laser 264 when the light emission signal is output.

(C) Gradation Characteristic Incidentally, in copying a halftone image, the gradation characteristic must be taken into consideration. Generally, various factors such as the photosensitivity of the photoconductor, the properties of the toner, and the usage environment are entangled, and the reading density level (hereinafter also referred to as the input level) (OD) of the original to be reproduced and the emission intensity level of the laser light (hence the reproduction). The image density level (ID)) is not exactly proportional to
As schematically shown in the upper right part of FIG. 9, a characteristic B deviated from the proportional characteristic A that should be originally obtained is shown. Such a characteristic is generally called a γ characteristic (gradation characteristic), which is a major factor that reduces the fidelity of a reproduced image printed on a halftone original. Therefore, with respect to the output power (also referred to as laser power) P of the semiconductor laser 264, the output characteristic is previously controlled by the γ correction unit 253 like the exposure correction characteristic in the lower right part of FIG. 9 to realize the proportional characteristic A. This is called gradation correction (so-called γ correction). That is, the output power is increased at low gradation and the output power is decreased at high gradation to make the density of the reproduced image proportional to the gradation. It should be noted that, as shown in the photoreceptor characteristics at the lower left of FIG. 9, the attenuation potential Vi of the photoreceptor changes non-linearly according to the output power of the semiconductor laser. Also, the toner adheres when Vi <V _B , as shown in FIG.
As shown in the development characteristic at the upper left, the toner adhesion amount also changes non-linearly.

(D) Automatic image density control (AIDC) FIG. 10 shows the charger 4 around the photosensitive drum 41.
3 and the arrangement of the developing device (for example, 45r) are schematically shown. Here, a charging charger 43 having a discharge potential V _C is installed opposite to the photoconductor drum 41. Charging charger 43
A negative grid potential V _G is applied to the grid of the above by the grid potential generation unit 243. The relationship between the grid potential V _G and the surface potential V _O of the photosensitive drum is approximately V _O =
Since it can be regarded as V _G , the potential V _{O on the} surface of the photosensitive drum 41 can be controlled by the grid potential V _G. The surface potential V _O
Is detected by a potential sensor 44 which is a surface electrometer.

First, before the laser exposure, a negative surface potential V is applied to the photosensitive drum 41 by the charging charger 43.
_O , and the developing bias generating unit 244 applies a low negative developing bias potential V _B (| V _B | <| V _O |) to the roller of the developing device 45r. That is, the developing sleeve surface potential is V _B. The laser exposure lowers the potential of the irradiation position on the photosensitive drum 41, and the surface potential V _O changes to the attenuation potential Vi of the electrostatic latent image. When the decay potential Vi becomes lower than the developing bias potential V _B, the toner (having a negative charge) carried to the sleeve surface of the developing device 45r adheres to the photosensitive drum 41. V _O and V _B
The difference between is not too large or too small. The toner adhesion amount increases as the developing voltage ΔV = | V _B −Vi | increases. On the other hand, the attenuation potential Vi changes as the surface potential V _O changes even with the same exposure amount. Therefore, if the surface potential V _O and the developing bias potential V _B are changed while maintaining the difference between V _O and V _B within a certain range, for example, while keeping the difference substantially constant, the difference between V _B and Vi is reduced. Since it changes, the toner adhesion amount can be changed and the density can be controlled.

Further, the toner adhesion amount of the reference toner image developed by exposing a predetermined area on the photoconductor with a predetermined light amount is
It is optically detected by the AIDC sensor 210. That is, a reference toner image serving as a reference for density control of the photosensitive drum 41 is formed, and light is obliquely incident on the reference toner image,
AIDC sensor 21 provided near photosensitive drum 41
By 0, the specular reflection light and the scattered reflection light of the reference toner image are detected. The respective detection signals are sent to the printer control unit 201.
The toner adhesion amount is obtained from the difference between the two detection signals.

Therefore, if V _O and V _B are changed in accordance with the detection value of the AIDC sensor 210, automatic image density control (AID
C) can be performed (see the AIDC operation process in FIG. 36). For example, the photoconductor sensitivity, but the damping characteristics of the toner charge quantity due to changes in environment such as relative humidity is changed, V _O, V
_The maximum concentration can be automatically kept constant by changing _B. Therefore, in this embodiment, one developing bias potential V
Made to correspond to one grid potential V _G to _B, and the set value of (V _B, V _G), corresponding to the detected value of the AIDC sensors 210 0
It is changed corresponding to the 15 density detection levels (LBA). Table 1 shows an example of the data of the set of (V _B , V _G ) set in this way. Tables 2 and 3 show the V _B output table and the V _G output table, and the grid potential V _G and the developing bias potential V _B are changed in steps of 20 V. The detection value of the AIDC sensor 210 is made to correspond to the levels of 0 to 15 shown in the leftmost column based on the size thereof, and V _B changes from 220 V to 20 V in increments of 20 V corresponding to each level, and becomes a maximum of 820 V. V _G is kept at a value 180 V greater than V _B and therefore varies from 400V to 1000V. It may be determined in response to a change amount control accuracy (V _G, V _B).

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

The AIDC operation is basically the best in terms of control reliability and accuracy before it is copied, but if this operation is always performed before the copy, the first copy time becomes long. In addition, the life of the photoconductor or the like is shortened due to the increase in the number of operations. Therefore, in this embodiment, AI
The DC operation timing is controlled as follows. When the power is turned on, the wire of the charger is cleaned immediately after the power is turned on (see FIG. 3), and then the AIDC operation is performed. Since this operation is performed during the fixing warming up, the first copy after the power is turned on can be shortened.
In cases other than the above, in consideration of time and environmental changes since the last AIDC operation, the operation is performed as follows. However, at the last AIDC operation, the timer is reset and the environment (temperature, humidity) at that time is stored. Time from the previous AIDC operation to the next copy operation (see the time control processing in FIGS. 39 and 40) When the time is less than 10 minutes, the AIDC operation is not performed. When the time is 10 minutes or more and less than 60 minutes, the AIDC operation is performed after the copying is completed. When the time is 60 minutes or more, the AIDC operation is performed before copying. Environmental changes between the last AIDC operation and the next copy operation (see environmental control process in FIG. 41) When temperature change is 5 ° C. or more or humidity change is 10% RH or more,
The AIDC operation is performed before copying. As mentioned above, AI
The DC operation timing is controlled to reduce the number of pre-copy operations and to extend the life of consumables (photoconductor, dye, toner). In addition, the set value of the above timer and the amount of environmental change is
Not limited to this, the setting can be changed depending on the characteristics of the consumable item.

(E) Improvement of accuracy of automatic density control (AIDC
(Detection of dark part potential Vo, bright part potential Vi and correction of grid potential V _G , maximum light amount before operation) As described above, the density detection and control by the AIDC operation is performed using the reference grid potential V _G and the development bias. The toner adhesion amount of the reference toner image formed on the photoconductor is detected by the potential V _B and the exposure amount, and (V _G , V _B ) is changed corresponding to the detected value to control the adhesion amount. At this time, the value of the surface potential Vo with respect to the reference V _G changes due to the sensitivity change due to the environment of the photoconductor or the dirt on the charging charger. Therefore, even if the same V _G , V _B and exposure amount are given, ΔV = | V _B −Vi | is different, and therefore the adhesion amount is changed (see FIG. 11). Further, Vi also changes due to the sensitivity change of the photoconductor due to the influence of environment, durability, and the like. Therefore, even if the same V _G , V _B and the exposure amount are given, | V _B −Vi | becomes different, and the adhesion amount changes (see FIG. 12). Of course, when both the dark portion potential Vo and the light portion potential Vi change, | V _B −V
i | and the attached amount change (see FIG. 13). Due to these phenomena, it is impossible to detect the adhering amount at a constant | V _B −Vi | which is a prerequisite for detecting the toner adhering amount by AIDC. As a result, the accuracy of the automatic density control of the maximum density level becomes low.

For these reasons, the AIDC sensor 21
In order to accurately perform the automatic density control by 0, it is necessary to make Vo and Vi constant when forming the reference toner image under any condition. Therefore, prior to the AIDC operation, by performing the detection and correction of grid potential V _G and the maximum amount of the dark portion potential Vo and the light portion potential Vi, AIDC
The accuracy of automatic density control by the sensor 210 is improved. A specific example is shown below. First, before the AIDC sensor 210 detects the density of the reference toner image (see FIG.
C shows an example of the situation before the operation), the predetermined grid potential -8
Surface potential Vo when applying 00V (No. 21 in Table 3)
The (dark area potential) is measured by the potential sensor 44. The reference V _G level during potential detection is the same as the V _G level used when forming a halftone during AIDC detection. Then, the detected surface potential Vo is determined whether the offset much from V _G -Vo the target characteristic, to determine a correction amount [Delta] V _G of V _G based on V _G correction table of Table 4 (FIG. 32 And Fig. 3
See V _G correction processing in 3). Setting range of V _{G in} this embodiment (4
In 00V~1000V), V _G -Vo characteristics as in the example of FIG. 14, the deviation occurs in like-almost inclination. Therefore, the V _G correction amount described in the V _G correction table in Table 4 is
It is designed based on this characteristic change. FIG. 16 shows the characteristics when V _G is corrected in this way to match the target dark part potential V ₀ .

[0030]

[Table 4]

After correcting V _G as described above and adjusting it to the target Vo, the maximum light amount is corrected. In this example, Table 5
As shown in the laser power table, the laser power is set at 0.05 mW / cm ² increments in the range of ^{0.70mW / cm 2 ~2.25mW / cm 2} . Then, the light amount is switched in 256 steps (levels 0 to 255) for each maximum light amount. Here, the potential pattern for maximum light amount correction is shown in Table 5 to have a predetermined maximum light amount of 1.15 mW / cm ² (Table 5
No. 9), select the light intensity level 100 at that maximum intensity.
With the intermediate light amount at, the photosensitive drum 41 having the corrected dark portion potential V ₀ on it is irradiated, and the potential Vi (light portion potential) of that portion is detected by the potential sensor 44 (see FIG. 16). ). Next, the maximum light amount is corrected from this detected value (ViA) based on the ViA correction tables for light amount correction shown in Tables 6 and 7 (see ViA detection processing in FIGS. 34 and 35). here,
The relationship between the detected value (ViA) and the light amount to be set is as shown in FIG. 17, and the ViA correction tables in Tables 6 and 7 are designed based on this relationship. By sequentially performing the above V _G correction and maximum light amount correction, the exposure characteristic can be made substantially the same as the target curve, as shown in FIG.
In addition, during continuous copying, if the light amount is significantly corrected,
The image change before and after the correction becomes noticeable. Therefore,
In the present embodiment, as shown in Table 5, the light amount change amount for each stage
(0.05 mW / cm ² ) is set so that the image change is not noticeable. Further, the potential detection interval is set in consideration of the potential fluctuation of the photoconductor so that the light amount is not corrected by one or more steps.

[0032]

[Table 5]

[0033]

[Table 6]

[0034]

[Table 7]

Since the potential sensor 44 cannot be placed at the developing position, it is placed before the developing position to measure the potential, as shown in FIG. Therefore, the ViA correction tables in Tables 6 and 7 are created in consideration of the potential attenuation from the potential sensor position to the developing position. However, this potential decay changes with the environment and is especially affected by temperature (Fig. 1).
(Refer to the temperature characteristic of 9). Therefore, in this embodiment, two ViA correction tables, one for high temperature and one for low temperature, are prepared and
The temperature sensor 212 shown in FIG.
The temperature in the vicinity is detected, and the ViA correction table is switched according to the detected value. In this embodiment, this switching is performed at 20 ° C.
It is done in.

(F) Potential sensor distance characteristic and correction thereof FIG. 20 shows the distance characteristic of the potential sensor 44 of this embodiment. This distance characteristic is because the capacitance C changes as the distance d between the potential sensor 44 and the measured surface of the photoconductor changes in the measurement situation shown in FIG. (The capacitance C is proportional to the reciprocal of the distance d.) The change in the distance d is also caused by the shake due to the eccentricity when the photosensitive drum 41 rotates, which causes a large error in the detection of the surface potential. Therefore, in this embodiment, when the potential before the AIDC operation is detected, the potential of one rotation of the photosensitive drum is detected and the detected values are averaged to eliminate the influence of the shake of the photosensitive drum 41 (see FIG. 37). (See ViA detection processing in FIG. 38). However, during continuous copying, if one rotation is detected for each copy, the copy speed decreases. Therefore, as will be described later in detail in section (h), detection is performed at a partial position.

FIG. 22 shows the temperature characteristics of the potential sensor 44 of this embodiment. This temperature characteristic is due to the temperature characteristic of the tuning fork and the piezoelectric element inside the potential sensor 44. In order to correct the output change due to this temperature characteristic, the temperature sensor 2
12 is used to detect the temperature in the vicinity of the potential sensor 44 before the potential is detected, and thereby the output of the potential sensor 44 is corrected. The potential sensor output temperature characteristic correction table in Table 8 is
This is an example, and in this example, the correction amount for each temperature is changed depending on the level of the detected potential.

[0038]

[Table 8]

In this system, the dark potential Vo correction and the bright potential Vi correction are compared with the reference value,
It is possible to correct changes up to ± 100 V for Vo and ± 75 V for Vi. Normally, if the environment is within the allowable range of use and the printing durability is within the life of the photoconductor, it is unlikely that the correction range of this system will be exceeded. However, this range may be exceeded due to, for example, the grid mesh of the charger, dirt on the charge wire, or abnormal wear of the photoconductor. In other words, when the detected value of the potential sensor 44 is out of the correction range, it is considered that a trouble or abnormality has occurred somewhere in the device. Therefore, in such a case, the operation of the apparatus is stopped and a warning is displayed (see S185 in FIG. 33).

(G) Correction of maximum density change and gradation change during continuous copying During the continuous copying, the dark area potential Vo and the light area potential Vi of the photoconductor are
Gradually changes with repeated charging and development. It is considered that the main cause is that the residual potential (V _R ) after erasing rises or falls. This change also depends on the environment and the degree of printing durability of the photoconductor. Therefore, when continuous copying is performed, the image gradually becomes darker or lighter. In order to eliminate this phenomenon, in this embodiment, the bright portion potential Vi (ViC) is detected between copy images during continuous copying, and the maximum light amount is corrected. The correction is performed every time or every plural sheets. The reason why ViC is detected and corrected for each copy is that in a full-color image, even a slight potential change has a great influence. Further, the change in potential during continuous copying is relatively small in the change in Vo as compared with the change in Vi. Vi also has a larger effect on the image. Therefore, in consideration of the short time between copies, in the present embodiment, only Vi is detected and the maximum light amount is corrected. Next, a detailed correction method will be described.

(G-1) ViC detection and correction of maximum light amount At the time of potential detection before the AIDC operation, the photosensitive drum 41 is detected.
Due to the eccentricity and the like, the photosensitive drum 41 is measured for one rotation and the average value thereof is obtained and used as the detected value (see section (K-6)). However, at the time of continuous copying, if the measurement for one rotation of the photosensitive drum is performed for each copy, the copy speed will be reduced. Therefore, during continuous copying, a latent image pattern (around 50 × 50 mm) is formed at the same position between the images in the circumferential direction of the photosensitive drum, and the fluctuation of the potential detection value (ViC) at that portion becomes the initial value (ViB). The maximum amount of light was corrected by judging how much it was compared. Here, the initial value (ViB) means the correction V _G obtained by the potential detection before the AIDC operation and the AIDC operation based on the maximum light amount, and then the predetermined V _G after the correction is applied to correct the value. Predetermined maximum light amount after (from Table 7, 1.15 W /
Level 100 when selecting cm ² ) as level 255
It is the detection value of the bright portion potential Vi when the light is irradiated at (see ViB detection processing in FIGS. 37 and 38). In this case, V
A pattern similar to the iC detection inter-image pattern ViC (mouth 50 × 50 mm) is created at the same position on the circumference of the photosensitive drum.
In addition, this inter-image pattern has the same conditions as when the initial value was created.
(V _G , maximum amount of light), and Vi is detected. With this method, even if there is unevenness in the potential of the photosensitive member in the circumferential direction or there is shaking of the photosensitive drum, it is not necessary to perform measurement for one rotation, and it is possible to detect the potential while maintaining the copy speed. As described in the overall configuration, the diameters of the photoconductor drum 41 and the transfer drum 51 are configured with an integer ratio (1: 2), and the photoconductor drum 41 and the transfer drum 51 are always the same in the circumferential direction. The positions are in contact with each other, and the rotational position of the photosensitive drum can be similarly detected by detecting the rotational position of the transfer drum 51. This enables the measurement at the same position as described above. (G-2) Light amount correction table for continuous copying Table 9 shows a light amount correction table for continuous copying. This table 9 may be created based on the relationship between the detected value ViA and the set light amount shown in the light amount correction before the AIDC operation. However, in this relationship, as shown in FIG. 23, the rate of change is not uniform, so in the case of correction during continuous copying, the initial value (ViB)
Even if the potential change amount between the inter-image detection value (ViC) and ViB is the same, the ratio of the amount of light to be corrected changes depending on the level of. Originally, the inter-image detection value corresponding to the initial value (ViB)
It is necessary to calculate the set light amount for the potential change amount of (ViC) or prepare all the tables, but this increases the memory capacity to be prepared. Therefore, in this embodiment, the correction table is created based on the average change amount ΔP / ΔVi of the relationship shown in FIG. In the case of this method, an error occurs at a distance from the center value, but this is not a problematic level. In addition, the memory capacity can be greatly reduced.

[0042]

[Table 9]

(G-3) Modified Example The case where the light amount correction is performed during continuous copying has been described above, but in the modified example described below, the dark portion potential on the photoconductor charged at a predetermined output during continuous copying. Vo is detected, and the grid voltage V _G is corrected so that Vo becomes constant (see the processing of FIGS. 52 and 53). Here, after the potential control and the AIDC operation described above, the corrected V _G is applied based on the V _G correction amount obtained during the potential control operation, and the potential is detected by the potential sensor 44. In this case, it is created at the same position as between the images during continuous copying. This detected value is the initial value VoB. Initial value Vo between images during continuous copying
The photoreceptor is charged with V _{G under} the same condition as B, and its potential (V
oC) is detected. Then, by the difference (change amount) between the initial value VoB and the detected value VoC every time, V _G at the time of continuous copying in Table 10 is
Obtain a correction amount of V _G by the correction table to correct the V _G of the next copy. Here, when the difference between the V _G correction amount based on the detection value at a certain copy and the V _G correction amount based on the detection value at the previous copying is ± 2 stages or more in the correction table of Table 10, immediately after the correction. Abrupt density change of the image. Therefore, the correction for each copy is limited to ± 1 step,
It suppresses sudden changes in concentration. Furthermore, in another embodiment, the developing bias voltage V _B is corrected by detecting the light portion potential instead of the dark portion potential (VoB). When the correction amount of the developing bias voltage V _B becomes a predetermined amount or more, the same limiter control is performed.

[0044]

[Table 10]

(H) Limitation of Correction Amount During Continuous Copying If the light amount correction is significantly performed during continuous copying, the image change before and after the correction becomes conspicuous. Therefore, as described above, in the laser power table of Table 5, the light amount change amount for each stage is set so that the image change is not noticeable (here, 0.05 mW / cm ² ). In continuous copying, the difference between the value detected by the potential sensor at a certain number of sheets and the previous detected value is the |
When ± 2 steps | or more, the amount of light amount correction increases, and the difference in density between the image immediately before correction and the image immediately after correction becomes large. become. Such rapid changes in copy density are not desirable when copying continuously. Therefore, even if the difference in the detected value from the previous time is | ± 2 steps | or more, the light amount is not corrected in two steps or more to prevent a rapid change in the image. The potential detection interval is set at an interval such that the light amount is not corrected by one step or more in consideration of the potential fluctuation of the photoconductor. On the contrary, when a value that requires correction by two or more stages in the correction table is detected as compared with the previous time, it is considered that there is some abnormality or the detected value contains noise. It is possible that the detected value will change significantly compared to the previous detected value, such as when noise is included in the detection. Conceivable. From this point of view, it is effective to make one correction at a time during continuous copying. The correction during continuous copying should not be performed more than a certain number of steps, and after that, the copying should be continued in the last corrected state (light intensity) to avoid overcorrection. When a detection value that requires multiple steps of light amount correction after the operation is performed, the copy operation may be stopped and a warning may be displayed. The same limitation may be applied when correcting the grid voltage V _G.

(I) Prevention of overcorrection at the time of abnormality The light amount correction at the time of continuous copying is performed according to Table 9. Normally, in continuous copying of about 1 to 100 sheets, the change of Vi of the photosensitive member from the first sheet is changed. Is at most 5 to 6 stages in Table 9, that is, about 20 to 25 V in terms of potential. If the sensor output value is detected such that the correction must be performed in more steps, it is considered that the potential is abnormally changed or the detected value includes noise. If correction is performed in 8 and 9 steps in such a state, overcorrection or adverse effects of other elements may occur (the amount of adhesion increases excessively, and the amount of dust and smoke increases).

It is considered that not only Vi but also Vo is largely changed when correction is performed for a certain number of stages or more during continuous copying. As described above, when there is no deviation of Vo during light amount correction, as shown in FIG. 24, the difference (ΔVi) between the reference value (ViB) and the detected value (ViC) is small, and Vi is corrected by the light amount. In that case, the LDC curve is corrected to an almost aimed curve. However, when Vo is shifted during continuous copying, as shown in FIG. 25, the reference value (V
The difference (ΔVi) between iB) and the detected value (ViC) becomes large, and the corrected curve is shifted from the target curve. Further, an example of the case deviation of Vo is small is shown in FIG. 26, LD by the correction of the grid potential V _G
The C curve is almost corrected to the target curve. However, as shown in FIG. 27, when the deviation of Vo is large, V _G
It is not possible to correct the target curve with just the correction. Therefore, when an abnormality is detected, copying is temporarily stopped at that point,
Return to the charge amount setting and redo the correction. Specifically, in this embodiment, the AIDC operation and the correction of Vo and Vi are performed prior to the AIDC operation, and then the copy operation is performed again (see the processing in FIG. 54).

In the process of FIG. 54, when the V _G correction amount exceeds a predetermined amount, the charging and the laser light amount setting including the AIDC operation are performed again. By performing such an operation, it is possible to reduce the shift amount of the bright portion potential portion due to the change of the dark portion potential. Similarly, in the modified example, instead of the dark part potential, the bright part potential is detected and the developing bias potential is corrected from the data. However, when the developing bias correction amount becomes equal to or more than a predetermined amount, V _b and V _{G are} again detected. Then, repeat from the correction of the light amount.

(J) Light emission control mode switching In this embodiment, the image reproduction can be changed by switching the light emission control mode of laser light emission. Specifically, a first light emission control mode of 1 dot per 1 pixel,
A second light emission control mode is provided in which the semiconductor laser 264 is operated / stopped periodically at a constant duty ratio for each pixel or a plurality of pixels. 28 and FIG. 29 respectively show a first light emission control mode and a second light emission control mode (in this example, light is emitted at a duty ratio of 70% for each pixel).
The middle part shows the attenuation of the surface potential of the photoconductor when the photoconductor is irradiated with a laser beam at the same light emission level continuously with three dots in the main scanning direction as in the upper part. Here, the continuation of small peaks indicates that the light intensity distribution of the laser beam changes temporally with the scanning in the main scanning direction. In the second light emission control mode (FIG. 29), the light intensity distribution changes at a cycle corresponding to one dot because the duty ratio is not 100%. On the other hand, in the first light emission control mode (FIG. 28), the light intensity distribution does not change during the light emission time of 3 dots. Correspondingly, the attenuation potential of the surface of the photoconductor also has a cycle for each dot in the second light emission control mode, while there is no change between dots in the first light emission control mode. Therefore, the toner adhesion state developed on the photosensitive drum also has a peak for each dot in the second light emission control mode as shown in the lower stage, and the toner adhesion amount is the same as that in the first light emission control mode as a whole. However, there are thin spots between the dots. As a result, in the second light emission control mode, the saturation of the density at the high light emission level is delayed. The light emission period is changed by the light emission signal generation circuit 265 according to the signal from the printer control unit 210 (see FIG. 8).

Compared to the first light emission control mode, in the second light emission control mode, gradation reproduction is smoothed, and the periodic start / stop of light emission makes it more resistant to noise. On the other hand, the resolution is reduced. Therefore, this mode switching can be selected by the user depending on the document to be reproduced. In such a case, it is considered necessary to perform potential detection and adhesion amount detection for image reproduction stabilization for each light emission control and make corrections. At this time, a control program for each light emission control and a gradation correction table (exposure amount) A correction table) is required. However, these lead to an increase in memory capacity. Therefore, in this embodiment, the gradation correction table for one light emission control mode (first light emission control mode) is stored, while for other light emission control modes,
Only the amount of deviation from the above gradation correction table is stored. When another light emission control mode is selected, the first
The light emission data is determined by adding the above deviation amount to the value of the gradation correction table in the light emission control mode.

Further, in this embodiment, the potential detection and the adhesion amount detection for stabilizing the image reproduction are performed in one emission control mode.
(In the present embodiment, the first light emission control mode) is performed, only the gradation correction table in that light emission control mode is stored, and the correction is performed accordingly (FIG. 42 S604). After that, the light emission control mode is switched at the start of copying (FIG. 42 S60).
5 to S607). This makes it possible to simplify the control program and significantly reduce the memory capacity.

In the second light emission control mode, 1
Since the laser emission is stopped in the pixel, the amount of light is insufficient for the first emission control mode. Therefore, the toner adhesion amount is reduced. Therefore, in order to supplement the light amount, the maximum light amount is increased as compared with the first light emission control mode. Table 11
The laser power emission control switching table of No. 3 shows the relationship, and the maximum light amount is changed from Table 11 simultaneously with the emission control switching. This has only a slight effect on the memory capacity.

[0053]

[Table 11] (K) Printer Control Flow (k-1) Description of Main Flow FIG. 30 is a main flowchart relating to the operation of the copying machine. First, when the power is turned on, the internal registers and various timers are initialized as initial states (S1), and the internal timer that defines the time of the main routine is started (S1).
2). Then, various processes S3 to S12 described later are performed. First, in S3, the main switch (SW) closing process (see FIG. 3).
1) is performed. In S4, the V _G correction process (see FIGS. 32 and 3) is performed.
3) is performed, and the dark portion potential V _{0 is obtained by} one rotation of the photosensitive drum.
Is detected and the temperature correction amount ΔV _G is determined. In S5,
The ViA detection process (FIGS. 34 and 35) is performed, the light potential (ViA) is detected by one rotation of the photosensitive drum, and the light amount is determined by the sensitivity determination. In S6, the AIDC operation process (FIG. 36) is performed, and A is set by using the conditions set above.
The IDC operation is performed with higher accuracy. In S7, the ViB detection processing (FIGS. 37 and 38) is performed, and the reference potential (ViB) at the time of copying is determined. In S8, the time control process (FIGS. 39 and 40) is performed. In S9, the environment measurement process (FIG. 41) is performed. In S10, the light emission control process (FIG. 42)
Is done. Copy processing in S11 (FIGS. 43 to 50)
Is done. In S12, the jam and trouble processing (Fig. 5)
1) is performed. Next, after performing other input processing (S13) and output processing (S14), the end of the internal timer is awaited (S15), and the process returns to S2.

Next, the outline of the image stabilization control in this flow will be described. To improve the accuracy of automatic image density control (AIDC) performed for image stabilization,
It is necessary to make the dark portion potential V ₀ and the light portion potential Vi constant when forming the reference toner image under any condition. Therefore, before the AIDC operation (S6), the V _G correction process (S
4) and ViA detection processing (S5) are performed. In the V _G correction process (S4), in order to eliminate the influence of the fluctuation of the potential in the circumferential direction of the photoconductor, the dark part potential is detected by one rotation of the photoconductor drum, the average value thereof is obtained, and the surface potential V ₀ is determined. To be done.
Next, in the ViA detection process (S5), a latent image is formed in the circumferential direction of the photoconductor with the above surface potential V ₀ and a predetermined light amount,
The dark area potential is detected for one rotation of the photoconductor drum, and the average value thereof is obtained and set as ViA. Further, maximum (MAX) light amount data is determined. The AIDC operation (S6) is performed based on the V _G and the maximum light amount data thus determined, and V _G , V _B and the gradation correction table are selected according to the detected value of the toner adhesion amount. It Next, copying is performed. In the potential control performed to correct the potential fluctuation at the time of copying, the latent image pattern is created only in one part (inter-image part) of the photoconductor in order to shorten the copying time. To detect the potential. First, in the ViB detection process (S7), A
A latent image is formed in the inter-image portion with V _G and the light amount in the best state obtained up to the IDC operation, and the bright portion potential is measured and set as the reference value (ViB). In the copy process (S11), before copying, a latent image pattern is created at the same position under the same conditions as in the ViB detection process (S7), the bright portion potential is measured, and the detected value ViC is set. Then, the maximum light amount is corrected according to the difference between the detected value ViC and the reference value ViB. In the case of continuous copying, ViC is detected for each copy and the maximum light amount is corrected. This is because in a full-color image, even a slight potential change has a great influence.

(K-2) Main switch closing process FIG. 31 shows the flow of the main switch closing process (FIG. 30S3) for performing the initial setting around the photosensitive drum 41.
In S101, it is checked whether the main switch (SW) of the operation panel 221 for instructing the start of copying has been turned on. If it is turned on, in S102 and S103, the photosensitive drum 4
1. Operate the main motor, the eraser lamp 42, and the pre-transfer eraser lamp 55. Next, in S104, since a predetermined grid voltage V _G is applied, V _G data (No. 2) is applied.
1, V _G = −800V) is set. Then, in S105, a voltage is applied to the grid of the charger 43.
Steps S106 to S109 are operations for detecting and storing the temperature and humidity around the photoconductor, and the detected data is used for the temperature characteristic correction of the potential sensor and the ViA detection process (maximum (MA
X) light intensity determination) and AIDC operation determination.
First, in S106, the humidity is detected and this value is set as RH1. This detected humidity RH1 is stored in the data 1 of the internal RAM (S107). Then, the temperature is detected in S108, and this temperature is set to TH1. The detected temperature TH1 is stored in the data 2 of the internal RAM (S109). And S
At 110, the potential control flag is set and the process returns.

(K-3) V _G Correction Processing FIGS. 32 and 33 show the flow of the V _G correction processing (FIG. 30S4). Here, the dark portion potential V ₀ is detected by one rotation of the photosensitive drum 41, and the temperature correction amount ΔV _G is determined. First, in S151, the state is checked. Here, the flow branches into 0 and 1 depending on the state. This state is set to 0 when the power is turned on. (The state is set to 0 when the power is turned on in all the state processes described later). In the state 0, the potential control flag (S152), the pre-copy potential control flag (S161),
After the copying, the potential control flag (S163) is checked. If any one of the flags is set, it means that the potential is in the controlled state, the charge wire cleaning of the charger 43 is started in S153, and the cleaning end is waited in S154.
In S155, S156, S177, all the flags are reset. Then, the pre-transfer eraser lamp 55 is stopped in S158, the detection permission timer T1 is set in S159, the state is set to "1" in S160, and the process of this state is finished. It should be noted that if none of the flags has been set, the process directly returns. However, if the print switch is not pressed even if the pre-copy potential control flag is set (NO in S162), the process directly returns. Further, even if the post-copy potential control flag is set, if the final copy is completed, the process directly returns. The reason why the pre-transfer eraser lamp 55 is stopped in S158 is as follows. During the AIDC operation described later, the pre-transfer eraser lamp 5 is transferred to the AIDC sensor 210.
When the light of No. 5 circulates through the developing unit and enters, the potential drops a little and accurate measurement cannot be performed. In this state, if the below-described potential control is performed, feedback is made to each element, and the AIDC operation is executed, the aimed image forming condition cannot be obtained. Therefore, the pre-transfer eraser lamp 55 is stopped at the time of potential detection so as to meet the operating conditions of the AIDC.

In state 1, the T1 timer is updated (S
171), when the T1 timer ends (when the potential of the photoconductor stabilizes), the T1 timer is reset (S172,
S173). This T1 timer is the time required for the potential on the photoconductor to stabilize after the activation of the charger and the activation of the photoconductor drum motor. Then, the potential is detected by the potential sensor 44 (S174), and when the number of detections reaches 100 (S175), the potential data of 100 times is averaged and this data is set to V1 (S176). The data measurement of 100 times corresponds to the time for one rotation of the photosensitive drum 41, and the averaging is 1
The average potential during rotation is calculated. This is because the potential sensor has an output dependency on the distance from the photoconductor (see FIG. 20). Therefore, if the diameter of the photoconductor drum 41 is eccentric, the distance changes due to the rotation of the photoconductor drum, This is because the output also changes. As a countermeasure against this, the output fluctuation due to this eccentricity is corrected by reading and averaging the potential for one rotation of the photosensitive drum.

Next, from the sensor temperature correction table (Table 8), V1 (average potential amount for one rotation of the photosensitive member) and data 2 (temperature T
H1, temperature correction potential amount ΔV corresponding to FIG. 31S108)
1 is calculated (S177). Then, V1 + ΔV1 is set to the potential Vo of the photoconductor (S178). Next, the corrected V _G amount ΔV _G corresponding to Vo is calculated from Table 4 (S179). Table 4
Then, the corrected V _G amount corresponds to a step, and one step is 20
It is V. This corrected V _G is stored in the data 3 of the internal RAM as ΔV _G (S182). Next, this correction amount ΔV _G
The absolute value of is not less than 100V (N in S181
O), it is determined that a trouble has occurred, and the trouble is dealt with (S)
185). If no trouble has occurred, then the correction amount ΔV _G is stored in the data 3 (S182), the ViA permission flag is set (S183), the state is set to “0” (S184), and the process returns.

(K-4) ViA Detection Processing FIG. 34 shows the flow of the ViA detection processing (FIG. 30S5). The ViA detection process determines the maximum (MAX) light amount of the semiconductor laser that matches the photoconductor sensitivity. First, the state is checked in S201. In the state "0", the ViA permission flag set in the V _G correction process (FIG. 33, S18).
The presence or absence of 3) is checked, and if this flag is not set, the process directly returns. If the ViA permission flag is set, the predetermined V _G data No. 21 (-800V) + △ V
Set _G (Data 3, FIG. 33 S182) to the grid voltage. Then, the MAX light amount data of a predetermined semiconductor laser
(No. 9, 1.15 mW / cm ² , Table 7) is set (S
204), the predetermined light quantity level "100" is set, and the semiconductor laser is operated (S205, S206). The ViA detection permission timer T2 is set (S207), and the state is set to "1" (S208). The timer T2 is a time period corresponding to a time margin until the latent image on the photosensitive drum 41 irradiated with the semiconductor laser passes through the potential sensor section.

In the state "1", the T2 timer is updated (S211), and when the T2 timer ends, the T2 timer is reset (S212, S213). Next, the potential (ViA) of the portion irradiated with the predetermined V _G and the predetermined light amount corrected by the V _G correction process (FIG. 30S4) is detected (S214).
When this potential is detected 100 times (YES in S215),
The semiconductor laser is stopped (S216), the detected potential is averaged, and the value is set to V2 (S217). The reason for detecting 100 times is to take the average for one rotation, as in the V _G correction process (FIG. 30S4). Then, from the sensor temperature characteristic correction table Table 8, V2 and TH1 (data 2)
Calculate the potential data correction amount corresponding to
2 (S218). Then, V2 (average value of 100 times data) + ΔV2 (correction amount) is set to ViA (S219). Next, it is checked whether the data 2 (temperature data TH1) is 20 ° C. or higher or lower (S220). Then, depending on the temperature of the data 2, the low temperature ViA correction table (Table 6) or the high temperature ViA correction table
The MAX light amount data is calculated from the A correction table (Table 7) (S221, S222), and the light amount data is stored in the internal RAM.
The data is stored in the data 4 (S223). Then, the ViA permission flag is set (S224), the AIDC permission flag is set (S225), the state is set to "0" (S226), and the process returns.

(K-5) AIDC operation processing FIG. 36 shows a flow of the AIDC operation processing (FIG. 30S6). This AIDC operation process is the V _G correction process (see FIG. 30).
The AIDC operation is executed with the V _G and MAX light amounts determined in S4) and the ViA detection process (FIG. 30, S5). First,
In S251, the presence or absence of the AIDC permission flag is checked. This flag is a ViA detection process (FIG. 31S225).
Can be set up in. If this flag is not set, it returns immediately. If the AIDC permission flag is set, halftone density detection processing for cyan (C), magenta (M), yellow (Y), and black (K) is performed in S252 to 255. Here, a predetermined V _G obtained by correcting the ΔV _G obtained by the above-described potential detection and a predetermined light amount level of the MAX light amount obtained by the potential detection are applied to the photosensitive drum 41 that has been charged and exposed to a predetermined V _G.
The level of the halftone density for each color, which is caused by using _B, is detected by the AIDC sensor 210, and the above correction is performed. In S256, V _G according to the detection value for each color,
A set of V _B and gradation correction table is selected from the AIDC table of Table 1. After that, the AIDC permission flag is reset in S257, the ViB detection flag is set in S258, and the process returns.

(K-6) ViB Detection Processing FIGS. 37 and 38 show the flow of ViB detection processing (FIG. 30S7). In this process, a potential pattern is created with a predetermined V _G and light amount for the purpose of correcting the potential fluctuation during copying. The potential during copying is corrected with reference to the potential (ViB) of this pattern. First, the state is checked in S300. In the state "0", first, in S301, the presence or absence of the ViB detection flag is checked. This flag is set in the AIDC operation process (S258 in FIG. 36). If this flag is not set, it returns immediately. Next, in S302, the pre-transfer eraser lamp 55 is operated. The reason for this is as follows. Vi
B needs to be created under the same conditions as a ViC pattern (a pattern created to correct the MAX MAX light amount at the time of copying) described later. However, the pre-transfer eraser lamp 5
If it is created under the condition that 5 is stopped, the condition is different from that at the time of measuring the ViC, and an appropriate MAX light amount cannot be selected. Therefore, the pre-transfer eraser 55 is operated. S303 and S3
In 04, T base (rotational position detection of transfer drum) is ON
Then, the detection timer T3 is set and started. The timer T3 is the time until the corrected V _G is applied and becomes stable. Then, in S305, V _G correction processing (see FIG.
The predetermined V _G data 21 (800 V) + data 3 (ΔV _G ) determined in 3) are set, and the state is set to “2” (S
306), the processing of the state “0” is completed.

In the state "2", the T3 timer is first updated (S311), and when the T3 timer expires (S312).
YES), the T3 timer is reset (S313).
Then, the corrected MAX light amount data stored in the data 4 is set (S314), and the predetermined light amount level "1" is set.
00 "is set (S315) and the semiconductor laser is activated (S316). Then, the ViB detection permission timer T5 is set (S317) and the state is set to" 3 "(S31).
8), the process of state "2" is completed. Timer T5
Is the time required for the latent image on the photoconductor that operates the semiconductor laser to reach the potential sensor plus the margin.

In state 3, the timer T5 is first updated (S321), and when it is finished, the T5 timer is reset.
(S322, S323). Then, the ViB pattern is detected (S324). When it is detected 10 times (YE in S325)
S) The potential data of 10 times is averaged to obtain V3 (S
326). The reason for detecting 10 times in S326 is as follows. The ViC pattern described below needs to be created in the inter-image portion, and in this inter-image portion, there is no time to detect for one rotation of the photosensitive drum. Therefore, it is necessary to create a latent image for a short time (a part on the photosensitive drum) and detect only that part. At that time, the potential pattern ViB that is the reference of the ViC pattern is the same as the photosensitive drum 41 as the ViC pattern.
If it is not made at the fixed point above, the eccentricity of the photosensitive drum 41,
Also, due to the influence of the potential unevenness on the outer circumference of the photosensitive drum, correct correction cannot be performed. Therefore, it becomes necessary to detect the ViC pattern and the ViB pattern at the fixed point position on the photosensitive drum for the same time. Next, the correction amount is calculated from the potential sensor temperature correction table (Table 8) from the V3 data and the temperature data 2 (TH1), and the data is set to ΔV3 (S327). ViB is calculated from V3 + ΔV3 (S32
8) Then, this is stored in the data 5 (S329). The ViB detection flag is reset (S330), and the time control flag and the environment control flag are set (S331, S33).
2) Then, the state is set to "0" (S333), and this processing ends.

(K-7) Time Control Processing FIGS. 39 and 40 show the flow of the time control processing (FIG. 30S8) for managing the time from the end of the ViB detection processing. In this embodiment, V _G correction processing (FIG. 30S4), ViA
Detection processing (FIG. 30S5), AIDC processing (FIG. 30S6),
The ViB detection process (FIG. 30S7) operates continuously, and the AIDC process is always included before the ViB detection process. Since this AIDC controls the toner adhesion amount on the photoconductor drum 41, if the charge amount of the developer, the electrostatic characteristics of the photoconductor, etc. change depending on the rest time, the image
(Image quality) changes. In order to obtain a good image all the time, the AIDC control may be always performed to perform the optimum toner adhesion amount control, but in that case, the AIDC process requires a long time and the copy speed decreases. Therefore, in this time control process,
The pause time that affects the charging characteristics before development and the electrostatic characteristics of the photoconductor is experimentally obtained, and the AIDC control is determined based on the pause time so that the AIDC control is executed only when necessary. First, the state is checked in S351. In the state "0", in S352, the presence or absence of the time control flag set in the ViB detection process (S331 in FIG. 38) is checked. If the time control flag is set,
After resetting the time control flag (S353), time counting is started (S354). Then, the state is set to "1" (S355), and this state is ended.

In the state "1", first, the time count is updated (S356). If less than 10 minutes have passed since the creation of ViB (YES in S357), the process directly returns. If it is determined that 10 minutes or more and less than 1 hour have passed since the creation of ViB (NO in S357, YES in S358), it is then determined whether the print switch is pressed (S359). If it is not pushed, the process returns as it is, but if it is pushed, the potential control flag is set after completion of copying (S
360). Next, the time count is reset (S36
2), the state is set to "0" (S363). Since copying is performed at this time, the AIDC operation is executed after the copying is completed. If one hour or more has passed since the creation of ViB (NO in S358), the pre-copy potential control flag is set (S361). Next, the time count is reset (S362) and the state is set to "0" (S36).
3). At this time, the AIDC operation is executed before copying.

(K-8) Environmental control processing FIG. 41 shows a flow of the environmental control processing (FIG. 30S9). Even if the time after AIDC is managed by time control (FIG. 30S8), if the environment (temperature, humidity) changes suddenly,
An appropriate image cannot be obtained because the charge amount of the developer and the electrostatic characteristics of the photoreceptor change. Therefore, the environment change when the print switch is pressed is detected from the environment at the time of the previous AIDC operation, and only when there is a large environment change, the AIDC operation is forcibly executed before copying to obtain a good image. I'm trying to get it. The environment at the time of the last AIDC operation in this embodiment is
It is based on the environmental data in the main switch closing process (FIG. 30S3).

First, in S401, the environment control flag set in the ViB detection process (S332 in FIG. 38) is checked. If the environment control flag is set, then S4
If the print switch is pressed at 02, the temperature is detected at S403, and this data is set to T
H2. If the difference between the temperature data 2 (TH1) and TH2 in the main SW input process is 5 ° C. or more (S404), the pre-copy potential control flag is set (S405) and the TH2 data is stored in the internal RAM. Stored in data 2 of (replace the data of TH1 and TH2). When it is determined in S404 that the temperature is lower than 5 ° C. or after S406 ends, the humidity is detected and this data is set as RH2 (S407). If the difference between the humidity data data 1 (RH1) and RH2 is 10% RH or more (YES in S408), the pre-copy potential control flag is set (S409), and the data of RH2 is set to the internal RAM data 1 To (replace the data of RH1 and RH2) (S410) and return. If the environment control flag is not set (NO in S401) or the print switch is not pressed (NO in S402), the process immediately returns.

(K-9) Light Emission Control Process FIG. 42 shows a flow of the light emission control process (FIG. 30S10). This processing is performed by the semiconductor laser 26 at the time of potential detection and at the time of image formation.
The light emission control mode of No. 4 is changed. The light emission of the semiconductor laser during the potential control is the first light emission control mode (L / L).
D control 1) is performed. Therefore, even if the second light emission control mode (L / D control 2) is selected during image formation, the laser light emission control during potential control is set to the first light emission control mode. as a result,
Various correction tables can be simplified. First, S601 to S6
At 03, the presence or absence of the ViA permission flag, the ViB permission flag, and the ViC permission flag is sequentially checked. If any one of them is in the potential control state, the semiconductor laser 264
The light emission of is set to the first light emission control mode (S605), and the process returns. If all the flags are absent, it is an image forming step, so in S604, the selected light emission control mode is determined, and the second light emission control mode (S606) or the first light emission control mode (S607) is selected. To return. The second
In the light emission control mode, since the difference from the value of the second light emission control mode is stored by using the gradation correction table of the first light emission control mode, the difference is read and added, and the added value is used as the light emission data. .. Further, the maximum light amount is switched in the gain switching unit 255 (FIG. 8) according to the laser power emission control switching table in Table 11.

(K-10) Copy Process FIGS. 43 to 50 show the flow of the copy process (S11 in FIG. 30). The copy processing is performed for the purpose of correcting the potential fluctuation during copying and the electrostatic characteristic change after the AIDC operation. First, in S451, a state check is performed. In the state "0", it is checked in S452 whether the print SW has been pressed. If the print switch is pressed, the presence or absence of the pre-copy potential control flag is checked in S453, and the absence of this flag is waited (until the AIDC operation is completed). If it is determined that there is no pre-copy potential control flag, then it is determined whether the mode is full color mode or mono color mode (S454). If the full color mode is determined, the state is set to "1" (S455). Then, in S456, the ViC detection flag is set, and in S4
At 57, a predetermined V _G (−800 V) + data 3 (ΔV _G ) is set. On the other hand, if the color mode is determined in S454, the state is set to "4" (S458), and the C development permission flag is set (S459). And S460,
At 461, the photosensitive drum 41, the main motor, and
Turn on the main eraser lamp and the pre-transfer eraser lamp to end this state.

In the state "1", it is checked whether or not the reference T-base signal of the transfer drum 51 is turned on (S471). When the T base signal is turned on, the detection permission timer T6 is set (S472) and the state is set to "
2 "(S473), and this state is ended. Since this timer T6 needs to make the ViC pattern and the ViB pattern at the same position on the photoconductor, the timer T6 is set to the same as the timer T3 for the ViB detection process (S304 in FIG. 37). I am doing it.

In the state "2", the T6 timer is updated (S481) and waits for the end of the T6 timer (S481).
(YES in 482), reset the T6 timer (S48
3). Next, the data 4 is set as the power data of the semiconductor laser (S484), the printing light amount data is set (S485), and the semiconductor laser 264 is turned on by the obtained MAX light amount data (S486), and the ViC detection permission is given. The timer (T8) is set (S487), the state is set to "3" (S488), and this state is ended. Like the timer T6, the timer T8 is set to be the same as the timer T5 (S317 in FIG. 37) for the ViB detection processing.

In the state "3", the T8 timer is updated (S491), the T8 timer is awaited (YES in S492), and the T8 timer is reset (S493). Then, the ViC of the latent image pattern formed on the photoconductor under the same condition as the ViB is detected (S494), and the process returns. When the number of ViC detections reaches 10, (S495
YES), the data is averaged to obtain V4 data (S496). (10 times detection is the same as the ViB detection process.) Then, the correction amount corresponding to V4 data and V2 and data 2 (TH1) is calculated from the V4 data and the potential sensor temperature correction table (Table 8), and The correction amount is set to ΔV4 (S497). Next, the data of V4 + ΔV4 is used as the ViC data (data after the temperature characteristic correction of the potential sensor) (S49
8), ViB (data stored in data 5) -ViC
Is set to ΔVi (S499). Next, from the light quantity correction table (Table 9), the semiconductor laser 2 corresponding to the difference ΔVi
The maximum (MAX) light quantity correction step number (STEP number) of 64 is calculated (S500), and the corrected MAX light quantity data is stored in "data 6" (S501). Then, the C development permission flag is set (S502), the ViC detection flag is reset (S503), and the state is set to "4" (S50).
4), this state ends.

In the state "4", first, the presence or absence of the C development permission flag is checked (S510). If the C development permission flag is present, the developing device is pressed against the photoconductor to form the C image. As can be seen from the above description, ViA, ViB, Vi
In each processing (creation) at the time of C and V _G correction, the developing device is not pressed against the photoconductor. This is to prevent waste toner from adhering to the photoconductor. Therefore, the C development permission flag causes the developing device to come into pressure contact after the creation and detection of the ViC pattern are completed and the pattern passes through the developing portion. Then, in S511 to S514, C, M, Y,
The K developing process is sequentially performed. Next, in S515, it is checked whether there is a next copy request. If there is no copy, it is determined that the copy is finished, the copy finish flag is set (S516), the state is set to "8" (S517), and this state is finished. If there is a next copy request (N in S515)
O), in S518, it is determined again whether it is the full color mode or the mono color mode. If it is the full color mode, the state is set to "5" (S519), and this state is ended.
In the mono-color mode, only the state 4 is looped, and the development permission / non-permission processing is entered during the development processing of each color. According to this processing, the designated color is copied.

State 5 and state 6 are the same processes as state 1 and state 2 and therefore will not be described. However, the detection permission timer T9 (S524) and the ViC permission timer T10 (S5 used in states 5 and 6 are used.
In 37), the timers T6 and T8 in states 1 and 2 are set to the same time.

In state 7, the T10 timer is updated (S
541) and the end (YES in S542), T10
The timer is reset (S543). Then, the latent image pattern ViC on the photoconductor formed under the same condition as ViB is detected again (S544), and the process returns. When the number of detections of ViC has reached 10 (YES in S545), the data is averaged to obtain V5 data (S546). Then, a correction amount for correcting the temperature of the potential sensor is calculated from the temperature characteristic table and set to ΔV5 (S547). next,
ViC is calculated by V5 + ΔV5 (S548), and ViB-
ΔVi is calculated from ViC (S549). And ΔV
From i, the MAX light amount correction step number is calculated from the light amount correction table (Table 9) (S550), and the corrected MAX light amount data is stored in the data 7 (S551). Then, in S552, the data 6 (MAX light amount by ViC for the first time) -data 7 is calculated to obtain the MAX light amount data difference. as a result,
If the difference is -1 stage or more, the MAX 6 light amount is decreased from the data 6 by 1 stage (S554).
Increase the MAX light intensity (S553). And S555
Then, the corrected MAX light amount data is stored in the data 6 (replaced with the previous light amount data). MAX light quantity correction step number during copying (S553, S554)
Is set to a maximum of 1, so that if an irregular value is detected during ViC detection, the previous copy and MA
It is prevented that the X light amount data is largely deviated from being selected (the image density difference from the previous copy is not made large).

Then, in S556, data 5 (ViB)-
If it is determined that the difference in the data 6 (ViC) is 5 steps or more in the MAX light amount step, the potential control flag is set (S557) and the state is set to "0" (S55).
8) Return. Here, setting the potential control flag in S557 means executing the AIDC operation again. Here, MAX being copied to ViB
The AIDC process is executed again when the deviation of the amount of light exceeds 5 steps. The reason is ViB and ViC
When the deviation of the pattern potential of is large, the initial surface potential
This is because the V _G correction for correcting the (dark area potential) may also be deviated, and in order to correct these, the AIDC operation is executed again to obtain a stable image. S556
When it is determined that the difference is less than 5 steps, the state is set to "8" and S559), and this state is ended. By this control processing, the correction of the image density change due to the sensitivity change of the photoconductor during copying is performed by the MAX of the semiconductor laser 264.
A stable image can be obtained by performing the correction of the light amount.

In the state "8", it is first determined whether or not the copy end flag is set (S561). If the copy is completed, then it is determined whether or not the potential control flag is present after the copy is completed (S562). After the copy is completed, the state is set to "0" (S563) after the potential control flag disappears, and this state is completed. If it is determined in S561 that copying will be continued, the state is set to "4" (S564), the C development permission flag is set (S565), and the ViC detection flag is reset (S5).
66), and this processing ends.

(K-11) Processing after trouble such as jam When there is a jam or trouble, paper may remain on the transfer drum 51. In order to remove it, the transfer drum 51 is released from pressure contact with the photosensitive drum 41. Therefore, the positional relationship between the photoconductor drum 41 and the transfer drum 51 before the release may be displaced. In this state, after returning to the machine, start image formation and perform correction during continuous copying.
Jam and trouble will be detected at a position where the electric potential is different from the circumferential position of the photoconductor drum 41 detected before,
When there is potential unevenness in the circumferential direction of the photoconductor drum 41, the difference due to the unevenness is detected in addition to the potential change.
The corrected potential does not reach an appropriate value. From the above,
After the jam and trouble processing, before the copying, the potential detection and the adhesion amount detection which operate before the normal copying are performed again, and a new initial value ViB for continuous copying is newly created. FIG. 51 shows jam and trouble handling (FIG. 30S1.
The flow of 2) is shown. If a paper jam remains on the transfer drum 51 after the ViB pattern is detected (after reading the reference pattern), and the paper remains on the transfer drum 51, the photoconductor drum 41 and the transfer drum 51 must be released to remove the paper. I have to. Thereby, the photosensitive drum 41
Then, the contact position of the transfer drum 51 may be displaced. If copying is performed in a state where the positional relationship between the photoconductor drum 41 and the transfer drum 51 is deviated, the ViB pattern and the ViC pattern cannot be created in the same portion of the photoconductor, and accurate potential correction becomes difficult. In order to correct this, in this processing,
When copying after the above trouble occurs, AIDC
The operation (potential control) is performed. First, in S651, it is determined whether a jam or trouble has occurred, and if not, the process immediately returns. When it occurs, the machine operation is stopped (S652), and the ViA permission flag, the ViB permission flag, and the ViC permission flag are reset (S653 to S655). Then, when the jam processing, the trouble processing, and the like are completed (YES in S656) and the print switch is pressed (YES in S657), the potential control flag is set (S658), the AIDC operation is updated, and the process returns.

(K-12) V _G Correction During Continuous Copy In the flow shown in FIGS. 52 and 53, instead of correcting the light amount during continuous copy, a dark portion on the photoconductor charged at a predetermined output during continuous copy. detects the potential Vo, Vo is corrected grid voltage V _G to be constant, equal to or less than a predetermined amount a correction amount of V _G when the copy is made continuously. S200
1 and S2002, a predetermined V _G is applied to apply the dark part potential (Vo
A) is detected and V _G correction is performed, and the corrected VoA
The laser light amount is corrected by irradiating a predetermined amount of laser light at to detect ViA. S200
In 3, AIDC is executed with the corrected V _G and the laser light amount. Then, the V _G , V _B , γ table of each color is selected. Next, in S2004, using the corrected data, Vo
B (dark area potential) is detected. This VoB is the same as the target potential at VoA, so the corrected potential of VoA is Vo.
It becomes B. However, VoA and ViA are the photosensitive drums 41.
In contrast to the average value of the electric potential for one rotation of
B and ViB detect the electric potential at a part of a predetermined position of the photosensitive drum 41. VoB detected in S2004
Is used as a reference potential for correcting the potential (V _G ) used during copying. Therefore, this data is stored in S2005 (D1). Next, in S2005, VoB
Dark part potential V of the pattern created under the same conditions as the pattern
oC is detected, and this data is designated as D2. And S2
In 006, it calculates the D1-D2 (VoB-VoC) = △ V G, from V _G correction table of the table 10 (the multi-copy),
The corrected V _G step number is obtained from ΔV _G.

Next, in S2007, the V _G level obtained by correcting the V _G correction step number determined in S2006 is calculated in the V _G table of each color selected in the AIDC operation, and S2 is calculated.
At 008, this V _G correction step number is stored as D3. Then, in S2009, C by the corrected V _G,
Images of M, Y, and K are sequentially formed, and in S2010, it is determined whether copying is further continued. If continued, S2011
, The VoC pattern is created again, the VoC is detected, and this level is set to D4. In S2012, D1-D
4 (VoB−VoC) = ΔV _G is calculated, and the number of V _G correction steps is calculated as data D5. Then, in step S2013, D5-D3 (difference between the number of correction V _G steps in the next copy and the number of previous correction steps) is calculated. , D3-1 stage correction processing is performed (S2014, S2015), and the data is updated as D3 in S2016. Then, returning to S2009, C, M, Y, K
Image formation is repeated. By performing such a series of processing, the V _G correction amount during continuous copying can be up to 10 (1
Therefore, the Vo correction is limited.

(K-13) Modified Example of Preventing Overcorrection FIG. 54 shows a process of performing the charging and the laser light amount setting including the AIDC operation again when the V _G correction amount becomes a predetermined amount or more. First, in S1001, a predetermined V _G is applied to detect the dark part potential (VoA), and V is adjusted so as to become the target Vo.
Obtain the _G correction amount from the table. In S1002, it detects the light portion potential (ViA) in the corrected V _G, to determine the amount of laser light, at S1003, by executing the AIDC operation at the corrected V _G and the laser light intensity, V _B, Each color is selected from the V _G and γ tables. In S1004, the dark area potential is detected under the corrected V _G condition, and this data is stored. S1
After 005, the potential correction at the time of copying is shown. First, S
At 1005, prior to copying, VoC (dark area potential) is detected under the same conditions as VoB. Then, in S1006, the amount of grid potential to be corrected at the time of image formation is calculated from VoB-VoC (ΔV _G ). If this ΔV _G is less than 50 V (YES in S1007), this ΔV _G is
Corrected to the V _G data selected by C (S100
8) The image forming operation starts (S1009). Then, this operation is continued until the copy is completed (S1010). If S10
At 07, if ΔV _G is 50 V or more, S100 is performed again.
Returning to step 1, the charging and exposure including the AIDC operation are adjusted and the copy operation is continued. Thus, when the correction amount becomes equal to or larger than the predetermined amount, the AIDC operation is performed again, so that the shift amount of the bright portion potential portion due to the change of the dark portion potential can be reduced (see FIG. 26).

[0083]

EFFECTS OF THE INVENTION Before the image formation, the potential of the latent image pattern for one revolution of the photosensitive member is used to determine the standard of charging for image formation. Since the adjustment of image formation is performed using the potential of the latent image pattern formed in
The adjustment time can be shortened, the detection accuracy can be improved in a short time, and the speed of copying in continuous copying can be increased while suppressing errors in detection due to uneven charging of the photosensitive member in the circumferential direction and eccentricity of the photosensitive member. Further, before the image formation, the standard of the charge amount and the light amount is determined, but during continuous copying, the adjustment time can be shortened and the copy speed can be increased by adjusting only the light amount.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall configuration of a digital color copying machine.

FIG. 2 is a diagram showing detection of a rotational position of a photosensitive drum.

FIG. 3 is a diagram of a charge wire cleaning device.

FIG. 4 is a diagram showing a configuration around a photosensitive drum.

FIG. 5 is an overall block diagram of a part of a control system of the copying machine.

FIG. 6 is an overall block diagram of a part of a control system of the copying machine.

FIG. 7 is a diagram for explaining the processing flow of an image signal.

FIG. 8 is a block diagram of image data processing in the printer control unit.

FIG. 9 is a diagram schematically showing an arrangement of a charging charger and a developing device around a photosensitive drum.

FIG. 10 is a diagram showing characteristics of an electrophotographic process.

FIG. 11 is a diagram showing the influence of the surface potential on the developing voltage.

FIG. 12 is a diagram showing an influence of a latent image potential on a developing voltage.

FIG. 13 is a diagram showing the influence of the surface potential and the latent image potential on the developing voltage.

FIG. 14 is a diagram showing V _G -Vo characteristics.

FIG. 15 is a diagram showing characteristics before V _G correction.

FIG. 16 is a diagram showing characteristics after V _G correction.

FIG. 17 is a diagram showing a relationship between a detected value (ViA) and a light amount to be set.

FIG. 18 is a diagram showing characteristics after correction of V _G and light amount.

FIG. 19 is a diagram showing attenuation of the potential from the potential sensor position to the developing position.

FIG. 20 is a diagram of distance characteristics of the potential sensor.

FIG. 21 is a diagram showing a situation of potential measurement by a potential sensor.

FIG. 22 is a diagram showing temperature characteristics of the potential sensor.

FIG. 23 is a diagram showing a relationship between a detected value ViA and a set light amount.

FIG. 24 is a diagram showing a correction curve when there is no deviation of V ₀ during light amount correction.

FIG. 25 is a diagram showing a correction curve when there is a deviation of V ₀ during light amount correction.

FIG. 26 is a diagram showing a correction curve when a deviation of V ₀ during V _G correction is small.

FIG. 27 is a diagram showing a correction curve when the deviation of V ₀ during V _G correction is large.

FIG. 28 is a diagram showing an example of changes in a light emission control mode and toner density.

FIG. 29 is a diagram showing an example of changes in a light emission control mode and toner density.

FIG. 30 is a main flowchart of copy control.

FIG. 31 is a flowchart of a main switch closing process.

FIG. 32 is a flowchart of a part of V _G correction processing.

FIG. 33 is a flowchart of a part of V _G correction processing.

FIG. 34 is a flowchart of part of the ViA detection process.

FIG. 35 is a flowchart of part of the ViA detection process.

FIG. 36 is a flowchart of AIDC operation processing.

FIG. 37 is a flowchart of a part of ViB detection processing.

FIG. 38 is a flowchart of a part of ViB detection processing.

FIG. 39 is a flowchart of part of the time control process.

FIG. 40 is a flowchart of part of the time control process.

FIG. 41 is a flowchart of environmental control processing.

FIG. 42 is a flowchart of a light emission control process.

FIG. 43 is a flowchart of a part of copy processing.

FIG. 44 is a flowchart of a part of copy processing.

FIG. 45 is a flowchart of a part of copy processing.

FIG. 46 is a flowchart of a part of copy processing.

FIG. 47 is a flowchart of a part of copy processing.

FIG. 48 is a flowchart of a part of copy processing.

FIG. 49 is a flowchart of a part of copy processing.

FIG. 50 is a flowchart of a part of copy processing.

FIG. 51 is a flowchart of a jam / trouble process.

FIG. 52 is a flowchart of a part of a process for performing V _G correction during continuous copying.

FIG. 53 is a flowchart of a part of a process for performing V _G correction during continuous copying.

FIG. 54 is a flowchart of overcorrection prevention processing.

[Explanation of symbols]

31 ... Print head, 41 ... Photosensitive drum, 42 ...
Eraser lamp, 43 ... Charging charger, 44 ... Potential sensor, 45a to 45d ... Toner developing device, 55 ... Pre-transfer eraser lamp, 201 ... Printer control unit, 20
3 ... Data ROM, 210 ... AIDC sensor, 212
... Temperature sensor, 243 ... High-voltage unit for generating V _B , 2
44 ... High voltage unit for generating V _G , 253 ... γ correction unit,
264 ... Semiconductor laser, 265 ... Emission signal generation circuit,
302, 303 ... Cleaning member.

Claims (4)

[Claims] 1. An image forming apparatus comprising: a charging unit for charging a photosensitive member; an exposing unit for exposing the photosensitive member; and a developing unit for developing a latent image formed on the photosensitive member. A reference determining means for forming a first latent image pattern for one revolution of the photosensitive member, obtaining an average value of the potential for one revolution, and determining a reference value for image formation based on the average value; A correction for detecting the potential of the second latent image pattern formed on one portion of the photoconductor by the potential detecting means based on the reference value obtained by the reference determining means, and adjusting the image forming condition based on the detected value. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the charging unit cleans the charge wire before charging. 3. An image forming apparatus comprising: a charging unit for charging a photosensitive member; an exposing unit for exposing the photosensitive member; and a developing unit for developing a latent image formed on the photosensitive member, before forming an image. , A standard for forming a first latent image pattern for one rotation of the photosensitive member, obtaining an average value for one rotation of the potential, and determining the reference values of the charge amount and the light amount for image formation based on this average value. At the time of image formation, the surface potential of the second latent image pattern formed on one portion of the photoconductor is detected by the potential detecting means based on the reference value obtained by the reference value determining means. An image forming apparatus comprising: a correction unit that adjusts a light amount based on the image forming apparatus. 4. The image forming apparatus according to claim 2, wherein the correction unit makes an adjustment for each image formation when the image formation is continuously performed.