JPH0348508B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an image forming apparatus. Conventionally, values of parameters related to image quality are detected and a plurality of process means are automatically controlled based on the detected values. however,
For some reason, there were cases in which a desired image could not be obtained in the automatic control mode. In this case, in order to find out where the cause was, it was necessary to prepare a special measuring instrument and examine each part of the device. Further, in this case, there is a disadvantage that image formation cannot be performed until the abnormal location is repaired. The present invention has been made in view of the above points, namely, a plurality of process means 51, 62, 69 for forming an image on a recording medium, and detecting parameters related to the image quality of the image formed by the process means. means 67; an automatic control program for automatically controlling the operating conditions of the plurality of process means individually based on the detected values of the parameters in order to stabilize image quality; and the plurality of process means regardless of the detected values. and a non-automatic control program for individually controlling the operating conditions of each based on specific values, and outputs digital signals for individually controlling the plurality of process means according to each of the programs. control means CT7;
Means for converting the above digital signal into an analog signal
CT8, and selection command means SW2-A and SW2-B for individually selecting whether or not to execute the automatic control for each of the plurality of process means, and the control means is one of the plurality of process means. The automatic control program for the first process means is selected according to the first selection command signal of the selection command means for the first process means, and the automatic control program for the first process means is selected according to the first selection command signal of the selection command means for the first process means. selecting the non-automatic control program for the first process means in accordance with a selection command signal;
Selecting the automatic control program regarding the second process means in accordance with a third selection command signal of the selection command means regarding a second process means different from the first process means among the plurality of process means. Another object of the present invention is to provide an image forming apparatus that selects the non-automatic control program regarding the second process means in accordance with a fourth selection command signal of the selection command means regarding the second process means. As a result, by forming images in automatic control mode and non-automatic control mode for each of multiple process means and comparing the state of the resulting images,
It is possible to know whether the abnormality in the equipment is in the parameter detector, the D/A converter, or the process means, and the abnormality in the equipment can be easily found without using special measuring instruments. You can do it. Further, if the parameter detector is abnormal, by selecting the non-automatic control mode, image formation can be enabled for the time being, and the time when the apparatus is not in operation can be shortened. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1a is a sectional view of a copying apparatus to which the present invention can be applied. The surface of the drum 47 is made of a three-layer seamless photoconductor using a CdS photoconductor, is rotatably supported on a shaft, and is rotated in the direction of the arrow by a main motor 71 activated when the copy key is turned on. Start. When the drum 47 rotates by a predetermined angle, the original placed on the original platen glass 54 is moved to the first scanning mirror 44.
illuminated by an illumination lamp 46 integrally configured with
The reflected light is scanned by the first scanning mirror 44 and the second scanning mirror 53. By moving the first scanning mirror 44 and the second scanning mirror 53 at a speed ratio of 1:1/2, the original is scanned while the optical path length in front of the lens 52 is always kept constant. The above reflected light image shows the lens 52 and the third mirror 55.
After passing through, an image is formed on a drum 47 at an exposure section. The drum 47 is simultaneously neutralized by the pre-exposure lamp 50 and the pre-AC charger 51a, and then corona-charged (for example, +) by the primary charger 51b. Thereafter, the drum 47 is used as the exposure section, and the illumination lamp 46
The irradiated image is slit exposed. At the same time, AC or corona charge removal with a polarity opposite to the primary one (for example -) is performed by a charge remover 69, and then a high-contrast electrostatic latent image is formed on the drum 47 by uniform surface exposure using a full-surface exposure lamp 68. The electrostatic latent image on the photosensitive drum 47 is then developed with liquid by the developing roller 65 of the developing device 62 and visualized as a toner image, and the toner image is made easy to transfer by the pre-transfer charger 61. Upper cassette 10 or lower cassette 11
The transfer paper inside is fed into the machine by a paper feed roller 59, and is sent toward the photosensitive drum 47 with accurate timing by a register roller 60, so that the leading edge of the latent image and the leading edge of the paper are aligned at the transfer section. I can do it. Next, while the transfer paper passes between the transfer charger 42 and the drum 47, the toner image on the drum 47 is transferred onto the transfer paper. After the transfer is completed, the transfer paper is separated from the drum 47 by the separation roller 43, sent to the conveyance roller 41, guided between the hot plate 38 and press rollers 40, 41, and fixed by pressure and heat. The paper is discharged to the tray 34 by the discharge roller 37 via the paper detection roller 36 . After the transfer, the drum 47 continues to rotate and its surface is cleaned by a cleaning device comprising a cleaning roller 48 and an elastic blade 49, and the process proceeds to the next cycle. Here, a surface electrometer 67 for measuring the surface potential is connected to the drum 47 between the entire surface exposure lamp 68 and the developing device 62.
mounted in close proximity to the surface of the As a cycle executed prior to the above copy cycle, there is a step of pouring a developer into the cleaning blade 49 while the drum 47 is stopped after the power switch is turned on. Hereinafter, this will be referred to as pre-wet. This is to flush out the toner accumulated near the cleaning blade 49 and to provide lubrication to the contact surface between the blade 49 and the drum 47. After the prewetting time (4 seconds), the drum 47
Rotate the pre-exposure lamp 50 and pre-AC static eliminator 51
There is a step in which residual charges and memory on the drum 47 are erased by means such as a, and the drum surface is cleaned by a cleaning roller 48 and a cleaning blade 49. Hereinafter, this will be referred to as pre-rotation INTR.
This is to make the sensitivity of the drum 47 appropriate and to form an image on a clean surface. The pre-wet time and pre-rotation time (number) are automatically changed depending on various conditions (described later). Also, as a cycle after the set number of copy cycles are completed, the drum 47 is rotated several times.
There is a step in which residual charges on the drum are removed from the memory using an AC charger 69 or the like, and the drum surface is cleaned. Hereinafter, this will be referred to as post-rotation LSTR.
This is to leave the drum 47 electrostatically and physically clean. FIG. 1b is a plan view of the vicinity of the blank exposure lamp 70 in FIG. Blank exposure lamp 70-1
70-5 are turned on when the drum is rotating and not during exposure to erase the drum surface charge and prevent excess toner from adhering to the drum. However, since the blank exposure lamp 70-1 illuminates the drum surface corresponding to the surface electrometer 67, it is turned off momentarily when the dark area potential is measured with the surface electrometer 67. Also, for B size copies, the image area is A4
The blank exposure lamp 70-5 is turned on for the non-image area even when the optical system is moving forward. The lamp 70-0 is called a sharp cut lamp, and the separation guide plate 43
- Irradiate the drum part that is in contact with 1 with light,
The electric charge in that area is completely erased to prevent toner from adhering to the area and to prevent contamination of the width of the separation gap.
This sharp cutlet lamp has a rotating drum and is always lit. At each processing position in the copying process of such an electrophotographic copying device, how does the surface potential of the photosensitive drum correspond to the bright areas (areas that reflect more light) and dark areas (areas that reflect less light) of the document? Figure 2 shows how it changes. What is required for the final electrostatic latent image is the surface potential at the center point in the figure, and the surface potentials ○a and ○b in the dark and bright areas there are at the photosensitive drum 47.
When the ambient temperature of and contrast in bright areas cannot be obtained. A method for compensating for changes in surface potential due to temperature changes or aging will be described in detail below. First, a surface electrometer as a detection means for detecting surface potential will be explained. Figure 5 is a side sectional view of the surface electrometer, and Figure 6 is a side sectional view of the surface electrometer.
A cross-sectional view taken along the line X-X' in the figure.
FIG. 8 is a cross-sectional view taken along line Y--Y' in the figure, and a perspective view of a chopper as an intermittent interrupting means to be described later. In FIGS. 5, 6, 7, and 8, reference numeral 81 denotes an outer cylinder made of brass, and the outer cylinder has a surface charge detection window 88. 82 is a motor serving as a driving means for rotating the chopper 83; 83 is a cylindrical chopper having a light emitting diode light passage window 90 and a potential measurement window 89; 84 is a light emitting diode, 85 is a surface charge measuring electrode, 86 is a preamplifier printed board on which a detection circuit for detecting the output of the electrode 55 is formed;
87 is a phototransistor. The surface electrometer 67 is installed at a position 2 mm away from the drum surface, which is the surface to be measured, so that the surface charge detection window 88 faces the drum surface, and the voltage detected by the electrode 85 is stored in the surface electrometer. A preamplifier printed board 86 for amplifying the signal is built-in and integrally formed. When a sensor motor drive signal SMD is output from a control circuit (not shown), the sensor motor 82 is driven, the cylindrical chopper 83 rotates, and the charge on the drum surface is induced in the electrode 85 via the potential measurement window 89. Ru. The potential measurement windows 89 are provided at four locations on the chopper 83 at equal intervals, and the light emitting diode light passing windows 90 are provided at four locations at equal intervals exactly in the middle of each potential measurement window 89. The voltage induced at the electrode 85 becomes an alternating current voltage because the chopper 83 rotates and interrupts the drum surface and the electrode 85 at equal intervals. The light from the light emitting diode 84 is received by the phototransistor 87 when the chopper 83 intercepts the drum surface and the electrode 85, and the output of the phototransistor 87 is used as a synchronizing signal. Reference numeral 91 denotes a shielding member for preventing light from entering the phototransistor 87 from the outside, and prevents dust, toner, etc. from entering the surface electrometer and adversely affecting measurement. A variable resistor 92 that adjusts the gain of the surface potential detection output by changing the amplification factor of an amplifier mounted on the blind plate 86 can be adjusted through an opening 93 with a driver or the like. The surface electrometer 67 is slightly longer than the drum 47, and is attached to side plates 96, 97 that support the drum etc. by means of a circular vertical tip 94 for positioning and a rear end 95. The side plate 97 is removable. Next, an overview of the surface potential control method will be explained. In this embodiment, in order to detect the drum surface potential in bright and dark areas, the document illumination lamp 4 shown in FIG.
A blank exposure lamp 70 is used instead of a lamp 6. The surface potential of the portion of the drum surface that is irradiated with light from the blank exposure lamp 70 is measured as the bright surface potential, and the surface potential of the portion of the drum surface that is not irradiated with the light of the blank exposure lamp is measured as the dark surface potential. First, the values of the bright and dark potentials that allow obtaining an appropriate image contrast are set as target values. In this example, the target bright area potential V _LO is −
The target dark potential V _DO was set to 100V and +475V.
In this embodiment, the surface potential is controlled by controlling the current flowing through the primary charger and the AC charger, so that the bright area potential and the dark area potential are equal to the target potentials V _LO and V _{DO ,} respectively.
It is assumed that the positive charger reference current I _P1 and the AC charger reference current I _AC1 are as follows. In this embodiment, I _P1 = 350 μA I _AC1 = 160 μA. Explain the control procedure. First, the surface potentials detected at the first time are defined as a bright area potential V _L1 and a dark area potential V _D1 , respectively, and it is determined how much difference there is from the target bright area potential V _LO and the target dark area potential V _DO , respectively. If the difference voltages are △V _L1 and △V _D1 , respectively, △V _L1 = V _LO −V _L1 (1) △V _D1 = V _DO −V _D1 (2) The difference in bright area potential can be corrected using an AC charger. Although correction of the difference in dark area potential is performed by the primary charger, in reality, when an AC charger is controlled, not only the bright area potential but also the dark area potential is affected. Similarly, when controlling the primary charger, not only the dark potential but also the light potential is affected, so a modification method was adopted that takes both the AC charger and the primary charger into consideration. The corrected current value △I _P1 of the primary charger is △I _P1 = α ₁ △V _D1 + α ₂ △V _L1 (3). Here, the setting coefficients α ₁ and α ₂ are changes in the current value of the primary charger when the surface potentials V _D and V _L are changed, respectively, and can be expressed as follows. α ₁ = △I _P (Change in primary charger current) / △V _D (Change in dark potential) (4) α ₂ = △I _P (Change in primary charger current) / V _L (Light potential (5) On the other hand, the corrected current value △I _AC1 of the AC charger is: △I _AC1 = β ₁・△V _D1 +β ₂・△V _L1 (6) Here, the setting coefficients β ₁ and β ₂ are as follows. It can be expressed as β ₁ = △I _AC (Change in AC charger current) / △V _D (Change in dark potential) (7) β ₂ = △L _AC (Change in AC charger current) / △V _L (Change in light potential) change) (8) Therefore, the positive charger current I _P2 after the first correction
and AC charger current I _AC2 is expressed as follows. From equations (4), (5), and (1), similarly, I _P2 = α ₁・△V _D1 + α ₂・△V _L1 + I _P1 (9) I _AO2 = β ₁・△V _D1 +β ₂・△V _L1 +I _AC1 (10) Here, the setting coefficients α ₁ , α ₂ , β ₁ , and β ₂ are determined based on predetermined charging conditions, such as the temperature, humidity, and state of the corona charger, so they are dependent on the atmosphere. Because it is not known whether the surface potential will reach the target value with one control due to changes in the charger, deterioration of the charger, etc., the surface potential is measured multiple times when the device is in a specified state, and the output of the corona discharge device is controlled the same number of times as measurements. It's going around. Since the second and subsequent corrections use the same method as the first correction described above, the current values of the positive charger and AC charger after the nth correction
I _Po+1 and I _ACo+1 can be expressed as follows. I _Po+1 = α ₁・△V _Do +α ₂・△V _Lo +U _Po I _ACo+1 = β ₁・△ _Do +β・△X _Lo +I _ACo Figure 9 a and b show the primary charger control current I It shows the change in dark potential when _P is corrected three times. 9th
Figure a shows the case where the set calibration coefficient is smaller than the actual coefficient, and Figure 9b shows the case where the set calibration coefficient is larger than the actual coefficient. In this embodiment, the number of corrections was set as shown in the table below.

[Table] By setting in this way, it is possible to further stabilize the surface potential on the photoreceptor and at the same time to minimize the decrease in copy speed. Also, in state 1, the previous control output current values of the primary charger and AC charger are memorized, and based on those values,
The primary charger AC charger is controlled, and in state 2, the previous control output current is passed through the photoreceptor to detect and control the surface potential. In state 3, the previous control output current is similarly applied to the photoreceptor, the surface potential is detected, and the control is performed twice in consideration of the time elapsed since the previous control. In state 4, since a considerable amount of time has passed since the last control, the reference currents I _P1 and I _AC1 are applied during the first correction, and the control is performed four times. In this embodiment, the developing bias voltage is further controlled. FIG. 10 shows a schematic cross-sectional view for explanation. This is done in the following way. A standard white plate 8 attached to the side of the document table glass 54 just before exposing the document
0 with a halogen lamp 46 for exposing the original,
The scattered reflected light is irradiated onto the drum 47 via the mirrors 44, 53, 55, the lens 52, and the like. This irradiation light amount is a standard light amount, and then the exposure amount when the lamp 81 moves and the original is actually exposed is changed to the exposure amount arbitrarily set by the operator. The surface electrometer 67 measures the surface potential V _L of the portion of the drum 47 irradiated with the scattered reflected light, and sets the voltage obtained by adding +100 V to the measured value V _L as the developing bias voltage V _H. Due to the developing bias voltage V _H , the potential of the toner becomes almost the same as the bias voltage. For example, when the standard bright area potential, that is, the measured value V _L is -100V, the potential of the toner becomes VO, and the toner does not adhere to the drum, so the original background It is possible to always perform stable development by preventing capri in the portion, and as a result, stable images can be obtained. In addition, in this embodiment, a standard white plate 80 corresponding to the white part of a general original is irradiated with a standard amount of light, and when the original is actually exposed, the exposure amount is changed to the amount set arbitrarily by the operator, so that the background of the original is changed. Even when the drum is colored rather than white, a stable image can be obtained by changing the bright area surface potential of the drum depending on the exposure amount. As described above, since the developing bias voltage _VH is determined by shining light onto the standard white plate 80 using the document exposure lamp actually used for exposure, the precision of the control of the developing bias voltage is improved, and the control is performed immediately before exposing the document. There is no reduction in copy speed due to the high speed. Furthermore, since the exposure amount is changed to an amount arbitrarily set by the operator when exposing the original, a stable image can be obtained without fogging even when the background of the original is not white but colored. FIG. 11 shows a time chart for performing the image formation and surface potential control described above. In Figure 11, INTR is the last time to erase the residual charge on the drum and adjust the sensitivity of the drum.
Always executed before a copy operation. CONTR-N is the drum rotation to bring the drum to a steady state depending on the standing time, and at the same time, the bright area potential of each rotation of the drum is measured using a surface electrometer.
V _L and dark area potential V _D are alternately measured, and a surface potential control circuit (described later) works to bring the potential of the drum surface closer to the target value. Although the surface potentials V _D and V _L are detected once per rotation, it is of course possible to detect them multiple times. CR1 is the bright area potential V _L and the dark area potential at 06 rotations of the drum.
This is the drum rotation that detects _VD and controls the corona charger. CR2 is the rotation of the drum immediately before the start of copying, and is used to measure the bright area potential with a standard amount of light from the document illumination lamp and to determine the bias value for the developing roller. Always executed when copying starts.
SCFW indicates that the optical system is moving forward. In other words, it shows the actual copy operation rotation. A circuit for realizing the surface potential control described above will be described below. FIG. 12 shows a surface potential detection processing circuit that detects and processes the surface potential of the photosensitive drum 47, and FIG. 13 shows a primary charger,
FIG. 14 shows a charger control circuit that controls the AC static eliminator, and a bias voltage control circuit that controls the developing bias voltage using the control signal from FIG. 12. 13 and 14 are explained in detail in, for example, Japanese Patent Application No. 103037/1983, which was previously filed by the applicant of the present invention, so a detailed explanation thereof will be omitted here. In FIG. 12, CT1 is a motor control circuit that controls the rotation of the motor 82 in response to the sensor motor drive signal SMD, CT2 is a synchronization signal generation circuit that generates a synchronization signal by a combination of a light emitting diode 84 and a phototransistor 87, and CT3 is the AC detection signal from the preamplifier circuit PA to the circuit CT
CT4 and CT5 are smoothing circuits that DC-smooth the signals from circuits CT2 and CT3, respectively. CT6 is for receiving signals from a DC controller (not shown) that controls the main body of the copying machine. buffer circuit, buffer circuit
The output of CT6 is input to an 8-bit digital microcomputer CT7 with a built-in A/D converter. CT8 is a D/A converter that converts the output signal from the microcomputer CT7 into an analog quantity. The output signal of the D/A converter CT8 is level-converted by a level conversion circuit CT9. The output signal DCC of the circuit CT9 is inputted as a primary charger control signal, and the signal ACC is inputted as an AC static elimination control signal to the circuit shown in FIG. Further, the signal RBC is inputted to the circuit shown in FIG. 14 as a developing roller bias control signal. CT10 uses light emitting diodes LED1 to LED6 and LED to D according to the signal from computer CT7.
This is a display circuit that lights up 0~LED~D7. or,
SW1 and SW2 are switches for inputting control information to the computer CT7. The microcomputer CT7 has a built-in program for carrying out the above-described surface potential control method, and the program flowchart is shown in FIGS. 15A, B, and C. In FIGS. 15A, B, and C, DC is an 8-bit digital value for controlling the primary charger, and similarly, AC and RB are control digital values for the AC static eliminator developing bias. Also, DCSA, ACSA,
RBSA indicates a storage area of RAM in the microcomputer CT7 in which the digital values DC, AC, and RB are saved. Step PS1 is a step for setting initial values of the charger output and developing bias when the power is turned on. When the copy button is pressed and the main motor drive signal DRMD becomes 1, the process advances to step SP3 (step SP2). At step SP3, as is clear from the time chart in Figure 11, the signal DR-
At the same time as MD becomes 1, signal HVT1 also becomes 1, so light emitting diode LED1 indicating that signal DRMD is 1 and light emitting diode LED2 indicating that signal HVT1 is 1 are turned on, and the contents of storage areas ACSA and DCSA are turned on. Output. In step SP4, each of the timing signals
DRMD, HVT1, V _L CTP, V _D CTP, V _L CTP,
It monitors the RBTP input, and when each signal is input, it advances to the step that performs the corresponding processing. When DRMD becomes 0, in this case
Since HVT1 is also 0, the light emitting diodes LED1 and LED2 are turned off in step SP7. Also, with DRMD=1
When HVT ₁ = 0, the back rotation (LSTR) is in progress, so the light emitting diode and LED2 are turned off in step SP5, and the signals HVT1 and DRMD are checked in step SP6, and if HVT1 becomes 1 before DRMD becomes 0, the process returns to the previous step. . When DRMD becomes 0, step SP7
Turns off LED1 and LED2. Further, when V _L CTP is 1 in step SP4, processing is performed in step SP9, and the light emitting diode LED3 is turned on during the processing. Similarly each signal V _D
When CTP, V _L CTP, and RBTP are 1, respectively,
Processing is performed in steps SP12, SP13, and SP10, and LED4, LED5, and LED6 are lit during the processing, respectively. Light emitting diode LED1~
The relationship between LED 6 and each program step is shown in the table below.

[Table] That is, by checking which light emitting diode among the light emitting diodes LED1 to LED6 is lit, it is possible to know which part of the program in the computer CT7 is being executed.
In addition, the light emitting diodes LED1 to LED6 light up after the computer CT7 confirms the input of each signal using the software, so it can be confirmed that the signal is actually being input into the computer and that the computer is operating. . Furthermore, if an indicator is provided to confirm the generation of signals before the input terminal to the computer, by comparing the indicators corresponding to each signal, it is possible to determine whether the computer is defective or the input control signal is out of order. It is possible to judge whether In addition, as shown in step SP12, the light emitting diode LED-D1 is set to the primary charger control digital value.
Lights up when DC exceeds a controllable value. or,
The light emitting diode LED-D2 lights up when the digital value DC falls below a controllable value. Similarly AC
When the static eliminator control digital value AC is greater than or equal to a controllable value, LED-D3 lights up, and when it is less than the controllable value, LED-D4 lights up. Light emitting diode LED-D5 is at step SP1
As shown by 5, it lights up when there is no synchronizing signal from the electrometer 67, indicating that the sensor motor is not rotating. The light emitting diodes LED-D6 and LED-D7 have contrast as shown in step SP14.
CONT (difference voltage between light potential V _L and dark potential V _D )
Lights up when the voltage drops below 498V and 396V, respectively. Note that LED-D0 is a spare display light emitting diode. In this way, in this embodiment, the light emitting diode is used to display the abnormal state and the control state. SW1-A and SW1-B in Fig. 12 are the values of V _L , V _D , and V _L measured last.
Light emitting diodes from each save area in CT7
This is a switch for displaying 8 bits on LED-D0 to LED-D7. switch SW1
When both SW1-A and SW1-B are off, the above-mentioned status display is performed using the light emitting diodes LED-D1 to LED-D7. Also, when switch SW1-A is off and SW1-B is on, the digital value stored in the save area in computer CT7 of bright area potential _VL is read out as shown in step SP15, and the light emitting diode LED- Displayed in 8 bits on D0 to LED-DS. Similarly, switch SW1-A is on and SW
When switch 1-B is off, the dark potential V _D is displayed, and when both switches SW1-A and SW1-B are on, the standard light potential V _L is displayed. This display is performed by the subroutine EDSP in Fig. 15, and the subroutine EDSP is executed at steps SP4,
It is provided at SP6, SP8, and SP10, and is displayed using the signal duration. As described above, in this embodiment, the output of the electrometer is converted into a digital value by the A/D converter built in the digital computer CT7, and the output values of the A/D converter at different timings are respectively stored in the digital computer. The output values are stored and designated by a changeover switch, and the output values are digitally displayed using light emitting diodes based on the designations. With this configuration, the measured potential can be easily checked by simply switching a switch as a specifying means, without using an external measuring device such as a voltmeter.
Furthermore, since the potentials generated at different timings can be easily checked, it is also possible to diagnose the failure of a device equipped with a potential detection device. For example, if the primary charger is defective and the output is not sufficient and other circuits are normal, V _L , V _P , V _L will all be close to OV, so V _L , V _D , V _L ，
If both detected values are near OV, it can be determined that the primary charger is defective. Also, AC static eliminator, full exposure lamp,
When the original exposure lamp, flank exposure lamp, etc. is defective, V _L , V _D , and V _L exhibit unique values for each case, making it easy to find the location of the failure. In addition, switch SW2-A is the primary charger and AC
This switch is used to select whether the output of the static eliminator is controlled by the detected surface potential or by a predetermined value regardless of the detected potential.When it is off, the potential is controlled, and when it is on, the predetermined value is controlled. Similarly, when the switch SW2-B is off, the developing bias voltage is controlled by the detected potential, and when it is on, it is controlled to a predetermined value. However, when both W2-A and SW2-B are on, as shown in step SP15, the value obtained by A/D converting the measured value from the surface electrometer is used as the potential measurement display mode, and the value is directly displayed on the light emitting diode LED-D0 to LED.
-D-D7. This potential measurement display mode is, for example, a surface electrometer 6.
Used when adjusting the gain of the output of 7. To adjust the gain, a pseudo drum biased to a predetermined voltage is attached to the copying machine instead of the photosensitive drum, and the predetermined voltage and light emitting diodes LED-D0 to LED-D7 are adjusted.
This is done by adjusting the variable resistor 92 so that the displayed value coincides with the displayed value. At this time, Shin D-RMD
is 0, so on the flowchart step SP2,
Since the process of SP8 continues to be repeated, the mode is always in potential measurement display mode. In this way, the measured potential can be easily checked without using an external measuring device, making adjustment of the electrometer easier. Furthermore, since the display for displaying the status and the display for the measured potential are used together, and the measured potential is displayed only in a specific state, the cost increase can be kept to a minimum.

[Brief explanation of drawings]

FIG. 1a is a sectional view of a copying apparatus to which the present invention can be applied, FIG. 1b is a plan view of the vicinity of the blank exposure lamp 70, FIG. 2 is a characteristic diagram showing the surface potential of each part of the photosensitive drum, and FIG. , Fig. 4 is a characteristic diagram showing changes in surface potential, Fig. 5 is a side sectional view of the surface potential meter, Fig. 6 is a sectional view taken along the line X-X' in Fig. 5,
Figure 7 is a sectional view taken along the Y-Y' line in Figure 5;
9 is a perspective view of a cylindrical chipper, FIGS. 9a and 9b are diagrams showing changes in dark area surface potential, FIG.
Figure b is a lighting control circuit diagram of the original exposure lamp, No. 11.
The figure shows a time chart for image formation and surface potential control, Figure 12 is a surface charge detection processing circuit diagram, Figure 13 is a charger control circuit diagram, Figure 14 is a bias voltage control circuit diagram, and Figure 15A. ~FIG. 15C is a diagram showing a control flowchart of the computer CT7. In the figure, 47 is a photosensitive drum, 67 is a surface electrometer, LED1 to LED6, LED-D0 to LED-D
7 each indicate a light emitting diode.

Claims (1)

[Scope of Claims] 1. A plurality of process means for forming an image on a recording medium; A means for detecting a parameter related to the image quality of the image formed by the process means; and a method for detecting the parameter in order to stabilize the image quality. an automatic control program for individually and automatically controlling the operating conditions of the plurality of process means based on the values; and an automatic control program for individually controlling the operating conditions of the plurality of process means individually based on the specific values, regardless of the detected values. a control means having a memory storing a non-automatic control program and outputting a digital signal for individually controlling the plurality of process means according to each of the programs; and means for converting the digital signal into an analog signal. and selection command means for individually selecting whether or not to execute the automatic control for each of the plurality of process means, and the control means includes the above-mentioned control means for selecting the first process means among the plurality of process means. selecting the automatic control program related to the first process means in accordance with a first selection command signal of the selection command means;
selecting the non-automatic control program for the first process means in accordance with a second selection command signal of the selection command means for the first process means; selecting the automatic control program for the second process means in accordance with a third selection command signal of the selection command means for the second process means different from the second process means; An image forming apparatus characterized in that the non-automatic control program regarding the second process means is selected in accordance with a fourth selection command signal.