JPH02197860A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a detection means for correcting a change in sensitivity of a photoreceptor over time.

[Conventional technology]

As the sensitivity of the photoreceptor changes over time, the potential of the photoreceptor drum increases, causing problems such as scumming.

Therefore, in order to solve this problem, conventionally, an image is formed under certain image forming conditions using a pattern with a constant density of the initial potential of the photoreceptor, and this image is read using a reading sensor and used as the sensor output. The reference value was obtained by conversion. and,
By comparing the sensor output (comparison value) obtained by reading an image obtained through a process equivalent to the above-mentioned image forming conditions with the sensor output (reference value) obtained initially, it is possible to determine the presence or absence of an increase in drum potential or its level. can be made clear.

Therefore, the reference value and the comparison value of the pattern output are compared and fed to the image control means, and the developing bias is corrected to form an image.

[Problem to be solved by the invention]

By the way, in the above-mentioned conventional technology, even if the pattern has a constant density, if the position of the pattern and the document surface differs and the optical path length differs, the relationship between the document illuminance and the constant-density pattern portion illuminance changes depending on the filament position of the exposure halogen lamp. It changes as shown in Figure 36. In other words, for a pattern located at a position other than the original surface, the amount of reflected light will vary even if the pattern reflectance (original density OD) is constant. Further, since the sensor output and the drum potential have characteristics as shown in FIG. 32, as the drum potential increases as described above, the low output side of the sensor is used. This increases the influence of the offset level included in the sensor and variations in the sensor, resulting in a sensor output with a low S/N ratio. Furthermore, if the drum potential is too low, a linear relationship cannot be maintained and the accuracy of correction control decreases.

The present invention has been made in view of and to solve the problems of the prior art, and improves the accuracy of correction control, prevents infinite looping of image control processing, and enables image formation in which abnormal conditions can be diagnosed. The goal is to provide equipment.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a pattern for controlling image forming conditions, a means for forming an image of the pattern on a photoreceptor, a sensor for reading the image, and an initial output value read by the sensor. and determining means for determining whether or not the initial output value is within a preset range, and when reading the initial output value according to the pattern with the sensor after forming an image on the photoreceptor, the initial output value is within a preset range. The method is characterized in that the previous image forming conditions are changed so that the output value is included in a preset range, and further, the initial output value is included in the preset range. The image forming apparatus is characterized by comprising a warning means for issuing a warning when the initial output value does not fall within the range even after performing the process of changing the image forming conditions a predetermined number of times.

[For production]

Since the above means sets the sensor output within a preset range, it is possible to use a sensor output in which the sensor output and the drum potential have a linear relationship.

Therefore, the accuracy of the correction control is improved, and the influence of the offset level included in the sensor and variations in the sensor can be reduced, and a sensor output with a high S/N ratio can be obtained. Furthermore, it is possible to prevent an infinite loop and diagnose abnormal conditions.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a front view showing an overview of the overall configuration of a copying machine to which an image forming apparatus according to the present invention is applied, FIG. 2 is a cross-sectional view of main parts, FIG. The figure is a front view showing the relationship between the photosensor and the photoreceptor, FIG. 5 is a graph showing the data read by the photosensor, FIG.
The figures show the measurement results in Fig. 6, Fig. 8 is a block diagram of the control system, Fig. 9 is a timing chart of each signal, Fig. 10 is a flowchart showing the entire background stain check, and Figs. 28 is a flowchart showing details of the flowchart in FIG. 10, FIG. 29 is a diagram showing each data in the flowchart in FIG. 18, and FIGS. 30 to 34 are characteristic diagrams of the embodiment of the present invention. The figure is a characteristic diagram of the relationship between the drum potential v0 and the drum white part potential vL,
Fig. 31 is a characteristic diagram of the relationship between the exposure amount and the drum white part potential ■, Fig. 32 is a characteristic diagram of the relation between the drum white part potential vL and the photosensor output, and Fig. 33 is a drum potential v0 with density as a parameter. , the drum white part potential (■), and the output of the photosensor. Figures 34 (A) to (C) are the relationship between the amount of light and the density depending on the filament position. Figure 35 is the setting of the photosensor. The block diagram and FIG. 36 are graphs showing the light amount ratio depending on the lamp position when the light amount on the document surface is 1.0.

In these figures, 1 is a dustproof glass for preventing toner stains on optical systems such as lenses and mirrors (not shown), 2 is an eraser, 3 is a charger, and 4 is a photoreceptor using a selenium photoconductor. Drum, 5 is pcc (pre-cleaning charger), 6 is cleaning unit, 7 is separation claw, 8 is PQC (post-cleaning charger)
, 9 is a potential detection element (
1o is a registration roller, 11 is a transfer charger, 12 is a separation charger, 13 is a conveyor belt,
14 is a paddle wheel that pumps up the developer mixed with toner, and 15 is a developing sleeve to which the pumped up developer is sent.

In FIG. 1, the photosensitive drum 4 rotates in the direction of arrow A in response to a copy command or the like. At the same time as the rotation of the photoreceptor drum 4, the static eliminating charger 5° is installed so that the toner adhering to the photoreceptor drum 4 and uneven potential do not reach the charging charger 3 and the developing unit (consisting of the developing sleeve 15, etc.). 8, eraser 2, transfer charger 11
．． The separation charger 12, cleaning unit 6, etc. are driven.

As a result, after passing through a static elimination lamp (not shown), the surface potential of the photosensitive drum 4 becomes zero even after a jam or the like. In this case, the leading edge of the image is controlled by the cleaning unit 6.
This is the part after the position where it passed through. Here, the photoreceptor drum 4 is charged by the charger 3, and then an unnecessary portion is irradiated with light by the eraser 2, and an image frame suitable for the transfer paper or the projected image is created. When it reaches this point, the exposure image from the optical system is formed, and a latent image is formed within the image frame. The latent image on the photosensitive drum 4 is visualized as a toner image by a developing unit, and then static electricity is eliminated by a pre-transfer static elimination lamp and a pre-transfer static elimination charger (not shown). On the other hand, the transfer paper fed by the paper feed section (not shown) is stopped at 10 registration rollers in advance. 10. Furthermore, the transfer paper is conveyed again and the toner image is transferred by the transfer charger 11. At this time, since the surface of the photoreceptor drum 4 is very smooth, the adhesion between the photoreceptor drum 4 and the transfer paper is strong. Decreases adhesion to paper.

Next, the transfer paper is separated from the photosensitive drum 4 by the separating claw 7. The transfer paper separated in this manner is then sent to a fixing section (not shown) by a conveyor bell (13).

The developing bias V□ (see FIG. 2) is determined by applying a potential to the developing unit when the latent image on the photosensitive drum 4 is visualized as a toner image in the developing unit.
Dark or light images can be obtained.

Next, an example of the control system will be described with reference to the block circuit diagram of FIG.

In FIG. 8, 16 is a control unit, 17 is an operation unit,
18 is AC! ! 19 is a key power section, 20 is a display section, 21 is a fixing thermistor, 22 is a drum thermistor, 2
3 is a heater, 24 is a main motor, 25 is a lamp, 26
27 is a sensor, 28 is a developing bias, 29 is a charging unit, 3o is an optical control unit, 31 is a variable magnification motor, 32 is a position sensor, and the control unit 16 is a photo sensor. Sensor 9 is connected.

Next, an example of an imaging system will be described with reference to FIG.

When the photoreceptor drum 4 rotates to a fixed position in response to a copy command or the like, the original placed on the contact glass 33 is transferred to the first mirror 34, the illumination unit (lamp) 35, etc. The zero reflected light image scanned by the scanner 36 is the first mirror 34, the second mirror 37, and the third mirror 3.
8, a lens 39, a fourth mirror 40, and the like, the image is formed on the photosensitive drum 4. 41 is a pattern, 42 is a white reference pattern, and l is a moving distance from the hole position (the position of the first mirror 34 indicated by a broken line).

Next, the determination of the reference exposure amount will be explained.

As shown in Figure 3, the white reference pattern (original density: 0
0-0.1) 42 is provided on the bracket 43 between about 10w from the lead edges L and E sides.

This bracket 43 also has a black pattern (OD) for determining toner density and replenishment during normal copying operation.
-1,8) 41 is provided. This pattern 41
etc., the document surface and optical path length are different, so there will be large variations from machine to machine.

28(A) to (C) show the relationship between the density of the white reference pattern image and the amount of light depending on the filament position, using the potential vL of the white reference pattern image as a parameter,
From the experimental results, the white reference pattern image of ODo, 1 is 00
It changed from OD 0.18 to OD 0.35 (value converted to original surface).

FIG. 36 shows the light amount ratio depending on the lamp position when the light amount on the document surface is 1.0, and the scene ratio changes greatly depending on the position of the lamp filament as the position differs from the document surface.

In this way, even with a combination of constant light intensity (constant lamp 35 voltage) and white reference pattern 42, the exposure amount on the drum 4 surface changes greatly, so setting the reference value for each machine (setting the initial reference data) is difficult. The difference in exposure amount between machines can be solved by correcting the developing bias 28, which differs depending on the machine.

That is, since the amount of reflected light is not constant as described above, the potential of the pattern portion of the photoreceptor drum 4 is also not constant.
Since the amount of toner adhesion (pattern toner image density) determined by (pattern potential) - (development bias potential) is not constant, the development bias, which is an image forming condition, must be increased or decreased in response to the value of the sensor output. After doing,
Toner image formation corresponding to the constant density pattern is performed again. After performing this process, the level set in advance,
In this example, (Vsst (output) 13.0VfaVss
When t≦V16, the setting is completed. FIG. 35 is a block diagram for performing this processing.

The reason why this sensor output (:Vsst) is set to the setting level as shown in the above equation is that the increase in potential of the photosensitive drum 4 (over time) and the accompanying sensor output always have a linear relationship as shown in FIG. It is a condition for being. By maintaining a linear relationship, the accuracy of correction control can be improved.
．． The use of the low output side of the sensor can be prohibited due to constraints greater than or equal to Ov. As a result, the influence of the offset level included in the sensor 9 and the variation in the sensor 9 can be reduced, and the S/N
It is possible to achieve high sensor output.

In addition, if the sensor output still does not fall within the set level even after performing the process of varying the developing bias three times in total as described above, it will be assumed that there is an abnormality in the drum or sensor system, the process will be interrupted, and a warning will be displayed on the display unit 20. do.

Since the filament position of the exposure lamp is different for each machine, the developing bias (only the developing bias when forming the sensor pattern) will be different for each machine.

Note that although there are differences between machines, -machines show a constant OD value. In addition, 18 is the first scanner 36
This is the run-up distance.

Next, Section 5 describes an example of a potential detection and concentration detection system.
This will be explained with reference to the figures and FIG.

An exposure image is formed by the imaging system on the photosensitive drum 4 charged by the charging charger 3, and a latent image is formed.Next, the photosensor 9 composed of a light receiving element and a light emitting element emits light. A light-receiving element picks up the reflected light from the back surface of the photoreceptor drums 1 and 4, photoelectrically converts the light, and the signal is input to the control unit 16. Furthermore, when image density is detected, the latent image on the photoreceptor drum 4 is visualized by the developing unit.The density of the first visualized image pattern is detected by the photosensor 9, and corresponds to the detected potential. A signal is input to control unit 6. The control unit 16 performs toner concentration control, toner end detection, etc. based on the input value.

That is, the reading timing of the photosensor 9 is at the position A,,A! of the end of the pattern formed on the photoreceptor drum 4. It is also arranged to read the front and back of the gap (A+', At' in FIG. 5), thereby reading the output of the background of the photosensitive drum 4, and further reading the output of the background of the photosensitive drum 4.

The output of the AZ pattern will also be read. The data read in this way is shown in FIG. 5. The toner density is detected by the output ratio of the photoreceptor drum background output VSa and pattern output vsp, and when the output of VSF is large, the toner density is low (the toner is If it is black, it can be said that it reflects almost no light. Then, toner replenishment control and toner end detection processing are performed based on these *, . . . +VIP.

Further, in the embodiment, a drum thermistor 22 and a fixing thermistor 21 shown in FIG. Configured to read from the boat.

Generally, when the fuser roller is warmed up and the t-source switch is turned off, the temperature of the fuser roller decreases and approaches room temperature. In this case, the temperature drop curve is A,
It is given by the following equation, where B is a constant for each model and t is time.

The temperature detected by the fixing thermistor 21 is TF, the temperature detected by the drum thermistor 22 is T, and the difference T is expressed by the formula (2).

In the formula, if the pause time is long, T becomes approximately equal to room temperature. Therefore, the downtime of the device can be predicted based on the level of at least one of ΔT (as room temperature) and TF, that is, the downtime of the photoreceptor.As mentioned above, the downtime of the photoreceptor can be predicted depending on the downtime. Since the sensitivities are different, if the rest time is determined based on ΔT or T in this manner and the reference developing bias voltage is corrected, the correction can be performed efficiently and accurately.

In this case, if a backed-up timer is used instead of ΔT or Tr, the pause time can be detected with higher accuracy.

In this way, the embodiment is configured such that the idle state of the apparatus is detected before performing the background stain detection operation, and the background stain detection operation is not performed in a state where ΔT and Tr do not satisfy the above conditions (detection Do not set the start flag (1″).

Regarding an embodiment of such a configuration, the background stain checking operation will next be explained with reference to FIGS. 2 to 7.

(1) First, the standards (IVscm, Vssv (
7) Settings are made. This V□, (reference background output) is the reflection output (Vs
. ) is the average value read while rotating the photoreceptor drum 4, Vssv (i quasi-white pattern output) is the reflected output of the white reference pattern 42 read while rotating the photoreceptor drum 4, and the other reference values are: There is a developing bias output Vll, and this vl! is the white reference pattern 42
etc., on the photoreceptor drum 4, even if the lamp voltage is constant, the amount of exposure on the four surfaces of the photoreceptor drum varies from machine to machine, so the amount of toner attached corresponding to the white reference pattern 42 is variably controlled by the developing bias output V13. Then, the reference white pattern output V5. ! is 3.0≦v! st≦■,. It is stored in memory as follows.

This setting is done at a factory, for example, and
After the image adjustment of the m machine or after the forming is completed, the background of the photoreceptor drum 4 and the white reference pattern 4 are
2 is exposed as shown in FIG.
The reference ravs is the photo sensor 9 output of the pattern density when developed with a developing bias output VSS of 300V. ,
■, □ and ζ are stored in non-volatile memory (RAM). When setting this standard value, the following restrictions are attached, namely, ■□
is set to 4.0±0.2■, but due to the influence of eccentricity of the photoreceptor drum 4, generally vseg≠V3G (Vsat l 3.6 V ≦Vsas)
and * taV s 5T (If the D value is small, the area of formula
ssy 3.0≦Vli! ? ■□ is made to vary until it becomes (≦Vsss). In other words, vsst
Read, VsGs < 3.6V, 3, Ov≦vo,
≦V8GM ■8. , and this vo is also stored in memory. However, the constraints on vsst differ depending on the bias output step. In addition, in order to maintain the above-mentioned conditions, data on various conditions such as optical path length (magnification) and lamp voltage are also stored in the same way. Note that the output value of the developing bias vms is the value obtained by adding the repeat correction of the drum pause time, but the value of Vo is the value excluding the repeat correction.

Next, the output processing by the photosensor 9 will be explained.

A photo sensor 9 reads reflected light from the surface of the photoreceptor drum 4 . The details are explained in the section of the potential detection and concentration system above. In this embodiment, in order to be less susceptible to the effects of eccentricity of the photoreceptor drum 4, differences in reflectance, etc., such readings are performed at locations that equally divide the circumference of the photoreceptor drum 40, and the average value is used as the output value. Post-processing is performed as follows. FIG. 6 is an explanatory diagram when the photosensitive drum 4 is read in six divisions of 60° each. As shown in FIG. 6, the photosensor 9 is divided into six parts (photosensitive drum 4
At the same time as reading at the positions ■～■), each position
The photo sensor 9 reads eight times in synchronization with the drum pulse every time (3), and the average value is outputted as a read value. Further, the average of the reading values at each position (1) to (2) is taken as the output value data for one rotation, and the same reading is performed a total of six times, and the average value is taken as the average value. FIG. 7 shows data read by the above-mentioned method. As shown in FIG. 7, the first data, that is, 3.70 to 4 There is a variation up to .23, but by averaging these ① to ②, output value data of 3.90 is obtained. This output value data is, as shown in FIG.
has been calculated, and this Y is ■. It will be stored in memory. In this way, V when the drum rotates! , (adjusted to ■3°-4, OV when the machine is stopped) allows the reference white pattern output by the photosensor 9 when detecting background stains to be described later.■88. Also, the reference background output v36. It becomes possible to calculate a correction (output ratio with respect to V sat) according to the output voltage, and it is possible to improve the detection accuracy. Note that the reading start timings for the first to sixth readings are performed at random. In this way, the setting of the reference value is completed.

(2) Next, a comparison value reading is performed. For example, when the user detects the idle state of the apparatus as described above when the power is turned on, and the idle condition is satisfied, the comparison value is read. If it is determined that the power has remained off, the same reading as that of the photosensor 9 in the reference value setting (1) is performed.

By this reading, comparison background output (Vss): Vs
sc, and comparative white pattern output V,. is detected.

These VSGCs VICk are also calculated as average values in the same manner as described above. Based on the data obtained from this comparison 41i reading, the development bias output V□ previously set based on the formula described later is corrected by the background stain detection correction value +△vm, but +△■1 in the first comparison value reading is Set to zero.

(3) Next, correction value setting is performed. This correction value setting is performed after the second time of reading the comparison value, and the output obtained by adding this correction value +ΔV becomes the developing bias output. This correction value +ΔV is set as follows.

That is, the correction value Δ■ is determined by the following equation by constraining the output of the photosensor 9 within a certain level using the bias output v1 or the exposure amount.

Here, the conditions for the occurrence of background smear are considered to be an increase in drum potential V0 and a decrease in exposure amount (staining of the optical system).
As a result, the drum white part potential VL increases as well. Then, the pattern output of the photosensor 9 (Vss
t, Vs. ) and drum white part potential vL is V
sa-4,OV (setting value) is the photo sensor pattern output change (△■8.A).

Moreover, the formula for correcting the output ratio of 8, 3 and v sec to v scx is as follows.

Substituting this formula (■) into 2〇, it becomes ΔvL ΔvL ・・−−−−・−・−■, and in this example, the bias output step is 3
0V, and assuming that △VL = 30V in formula (■), vsst V,. ' l -0,526Vo, 5
26 ÷ (5, OV/, 255 bits) - 27 bits Therefore, if (Vssy Vsci '') is corrected by (△Vs =) 30V for every 27 bits for control purposes, the background stain correction value: ∆■.

becomes.

In addition, the bias output when reading the comparison value is vms+△■
, if the bias output of the comparison value is constant vms, the area that follows △vL is (1,0-3,7)
VX (-57) = 154V, which is only 2.5 notches (the development bias change is 1 notch -60V), but if the bias output is v, △v11, then ∆
(2) is added every time background stain is detected, so that the pattern section output can always be included in the range of 1.0V to 3.7V, and the formula (2) can always be satisfied.

In this way, in the example, 3,0■≦vsst≦vs
Correction is performed by varying the developing bias voltage V□ until it reaches a's. However, if the abnormality flag and the comparison value abnormality flag are set (i''), the correction data will not be added during the normal copy operation.

Further, the first scanner 36 normally has an H
P, that is, it is located below the black pattern 41, and during a normal copying operation, a black pattern for toner density control, which is a pattern for controlling image forming conditions, is formed on the photosensitive drum 4. On the other hand, when performing a background stain detection check, the first scanner 36 is moved below the white reference pattern 42, and the white reference pattern 42 is scanned onto the photoreceptor drum 4.
A latent image is formed in a circular pattern which is a pattern for controlling image forming conditions, and the latent image is read at equal intervals by the photosensor 9 as described above. This latent image does not have to be a circular pattern, but may be formed in segments at equal intervals, for example. Further, in reading by the photosensor 9, first the background output of the photosensitive drum 4 is read, then the above-mentioned -circumference pattern is formed, and this white pattern is read at the same location.

Both patterns are formed during the reciprocating movement of the first scanner 36. That is, the first scanner 36
is designed to reciprocate between the HP position shown in FIG. 2 and a position below the white reference pattern 42, which is a preset position. The black pattern for toner density control is formed on the photoreceptor drum 4 by executing various conditions (processes) necessary for pattern formation during the forward movement of the first scanner 36.
formed on top. On the other hand, the first scanner 36 is moved and stopped at the position farthest from the scanner home position, and a white pattern is formed on the photoreceptor drum 4 as described above. This image forming condition control pattern is -first scanner 3
6 is arranged parallel to the moving direction (reciprocating direction).

In this way, in the above embodiment, two patterns for controlling image forming conditions are used, but these are performed in one reciprocating operation (including stopping) of the first scanner 36, and depending on the density of the patterns, a black pattern is formed. The white pattern is read while the scanner is moving, and the white pattern is read while the scanner is stopped, and images are formed on the photosensitive drum 4, respectively. For this reason, black
When reading a white pattern, the reading error becomes smaller. In addition, multiple patterns for controlling image forming conditions can be generated with one scanner. For example, white patterns are usually affected by eccentricity of the photoreceptor drum 4, but small patterns can be read by stopping the scanner and reading multiple patterns. By doing so, the influence of eccentricity can be reduced. Therefore, large errors can be prevented from occurring in the detected values read by the photosensor 9, and the toner density (black pattern) and background output (white pattern) can be accurately corrected based on the detected values.

FIG. 9 is a time chart showing an example of the operation of the embodiment, and in each clock pulse range, main motor ON operation, charging, transfer 1 separation, PCC, PQC/
BR, QL, PTL, exposure lamp ON, scanner operation, erase operation, application of developing bias voltage, photo sensor illumination and detection are performed, VmGS and V9GC detection operation, vsst and V SCK detection operation, 3 ．． O
V≦v1! .

The development bias voltage is corrected so that ≦v sas.

By the way, the conditions for the occurrence of background smudge are thought to be an increase in the surface potential (drum potential) of the photoreceptor and a decrease in the exposure amount due to dirt in the optical system, but the decrease in the exposure amount is due to the potential of the white reference pattern image L. bring rise.

Figure 30 shows the drum potential v0 and the drum white potential ■.

This is a characteristic diagram showing the relationship between the two, and the variation in measured values is shown in a rectangular numerical range.

Fig. 31 is a characteristic diagram showing the relationship between exposure amount and drum white part potential vL, where the drum potential v0 at the time of measurement was 760 V, the thermistor temperature was 32 to 33°C, and the drum temperature was 25 to 27°C.
Met.

FIG. 32 shows the relationship between the drum white part potential ■1 and the photosensor output based on the drum potential V. It is a characteristic diagram showing as a parameter.

Figure 33 shows the drum potential ■ using density as a parameter. ,
FIG. 3 is a characteristic diagram showing the relationship between the drum white part potential (2) and the output of the photosensor.

Next, the entire development bias voltage correction operation in the embodiment will be explained using a flowchart.

Figure 10 is a flowchart showing an outline of the background stain check.
This is shown in the flowcharts in FIGS.

In step (10-1) of FIG. 10, the hibernation state of the device is detected based on the above-mentioned formula 0, and if the hibernation condition is satisfied, the process proceeds to P WOOI, and if the hibernation condition is not satisfied, the process proceeds to P WOOI. , copying is performed in normal copy mode.

Processing in P Wool is performed according to the flowchart shown in FIG. 11, and if it is determined in step (11-1) that the bias up/down flag is not 1 (set), the loop counter is set in step (11-2). In step (11-3), it is determined whether or not the detection start flag is 1. If it is 1, step (11-3) is performed.
Proceed to step 4), otherwise step (11-17)
The normal copy standby processing routine is entered via , and background stain detection is not performed.

In step (11-4), determine whether the VsaC background output) read flag is 1, and if it is 1, set the detection start flag to 0 (reset) 1.1-8)
, set the background stain check end flag to 0 (1l-9), set the background stain check operation flag to 1 (1l-10),
Set the correction end flag to 0 (11-11). Step (
11-1> is YES, the process proceeds to step (11-5), increments the loop counter by +1, and determines whether the loop counter is 3 or more (step 1l).
-6), if No in step (11-6), proceed to step c11-s>; on the other hand, if YES, the sensor output is set even if the process of varying the developing bias is performed three times as described above. Since it is not included in the level, it is assumed that there is an abnormality in the drum or sensor system, the process is interrupted, and an abnormality is displayed on the display (step 1l-7).

In step (11-12), it is determined whether the reference value setting flag is 1 (1l-8), and if it is 1, the reference value reading flag is set to 0 (1l-9), and the comparison value reading flag is set to 0. Then, as shown in FIG. 2, the first scanner 36 is moved 10 positions to standby (11-11), and each counter used in the background stain check is cleared (11-11). -12). In this way, it is determined whether or not to execute the background stain check.

Next, P WOIO in FIG. 10 is executed. In Fig. 12, turn on the power relay 12-1), turn on the blade solenoid 12-2), execute the operation key manual prohibition 12-3>, then turn on the blade 200m sec.
Start the timer (12-4).

Next, PWO20 in FIG. 10 is executed. In Fig. 13, if the plate 200m5ec timer is counting up (13-1), the main motor 24 is driven (13-2), the eraser lighting is set to standby (13-3), and Vsc It is determined whether the read flag is 1 (13-4), and if it is 1, the post-cleaning charger (PQC) 8 is activated (13-5).

In this way, in the P WOIO of FIG. 10, the process of moving the scanner to the white reference pattern position is performed.

Next, PWO24 and PWO25 in FIG. 10 are executed.

In Figure 14, the background output VSa read flag is 1 (14-1), and the drum clock pulse counter is 2.
If it exceeds 0 (14-2) and the drum clock pulse counter is less than 421 (14-3), transfer, separation,
Activate pre-cleaning charge (FCC) 5 14-
4) Turn on the exposure lamp 35 (14-5). Also,
If the drum clock pulse counter is 421 or more (
14-3), further judge whether it is more than or less than 57014
-6), if it is less than 570, stop the transfer and separation operations 14-7), and if it is more than 570, turn off the FCC5 (14-8). Next, in FIG. 15, if the background output vse lead flag is 1 (15-1) and the drum clock pulse counter is 100 or more and less than 380 (15
-2), (15-3), Turn on the charging (15-
4), and if the drum clock pulse counter is 380 or more (15-3), the charging operation is stopped (15-3).
-5) The on/off check of the high voltage power supply is performed according to the flowcharts shown in FIGS. 14 and 15.

Next, PWO30 in FIG. 10 is executed. In Figure 16,
If the Vaa read flag is 1 (16-1), if the drum clock pulse counter is 20 or more but less than 380 (16-2), (16-3), erase processing is performed on parts other than the reading part by the photosensor 9. -4),・
- If the VSa read flag is not set to 1, or the drum clock pulse counter is less than 20 or 38
If it is 0 or more, (16-1), (16-2).

<16-3) Erase the entire surface (16-5).

In this way, the eraser timing check is performed.

Next, p woso in FIG. 10 is executed. In FIG. 17, if the drum clock pulse counter is 200 or more (17-1), the photo sensor 9 is lead-on (17
-2). If it is less than 200, return (17-1).

Next, PWO51 to PWO056 in FIG. 10 are executed. 1st
In FIG. 8, output data reading timing processing is performed. This process is performed six times at each angular position, and the numerical values *1 to 5 are different each time, and these numerical values are shown in FIG. To explain the case of the first processing, if the drum clock pulse counter exceeds 219 and is less than 232 (
18-1), (18-2), save only the lower 3 bits of FPSNCK (byte data) 18-3
), if the lower 3 bits are φφH (18-4)
, execute READPS (subroutine) (1B-
5). And if the output read end flag is 1 (
1B-6), average value data to DPSTLI (address of each output data) to memory L (1B-7), output read end flag to 0 1B-8), next read flag FPSNCK (lower 3 bits) ) to φ
Change to IH (1B-9).

In FIG. 19, READPS (subroutine) has a photosensor read start flag of 1 (19-1).
, if the photosensor read flag is 1 (19-2)
, input the data addition buffer and photosensor output to the data addition buffer 19-3), set the photosensor read flag to 0 19-4), and set the data addition counter to +1
Count up (19-5), and when the data addition counter reaches 8 or more (19-6), set the photosensor read end flag to 1 (19-7), and set the photosensor read start flag to O (19-6). -8), input the value of (data addition buffer) + (data addition counter) to the average value data. 19-9), clear the data addition buffer and data addition counter (19-10), this average value data ( 19-9) is (1B-7) in Figure 18.
is input as average value data. - On the other hand, if the photosensor read start flag is not 1 (19-1), set the photosensor read start flag to 1.19-11
), step (19-10) is performed. Also, if the photosensor read flag is not 1 (19-2),
It is set to 1 at the evening and timing of the rise and fall of the drum clock pulse.

In this manner, in the processing shown in FIGS. 18 and 19, the photosensor 9 reads six locations on the photosensitive drum 4 at equal intervals of 60 @, and this is performed six times in total.

Next, PW610 in FIG. 10 is executed. In Figure 20,
The developing bias up/down flag is 1 (201
), if the developing bias up/down flag is 1 (2
0-2), perform bias up correction (20-3),
If the bias up/down flag is 1 (20-4)
, perform bias down correction (20-5), store the correction level (up, down) in memory 2O-6), set 1 to the bias change end flag (20-7), and perform correction processing corresponding to the drum rest time. (20-8). In this way, the bias processing at the time of creating the reference pattern is performed.

Note that the process in step (20-8) is equivalent to the correction during normal copying operation, in which the fatigue recovery degree of the photoreceptor drum 4 is predicted in advance, and the corresponding value is corrected using bias and other methods. This is done by output.

Next, PW611 in FIG. 10 is executed. In FIG. 21, if the total correction data is less than 7 (21-1),
Set the total correction data to 7 and set it to 21-), add the correction data to the correction level and set it to 2l-3), and (20-8) above.
Performs the same correction process for the drum pause time as (
21-4) In this way, bias processing is performed when creating a comparison pattern.

Next, PWO70 in FIG. 10 is executed. In FIG. 22, if the drum clock pulse counter is 650 or more (22-1), the first scanner 36 is moved to the home position (22-2), and each output around the drum is stopped.
2-3), the main motor 24 is stopped 22-4), and the background contamination check operation flag is set to O (22-5). In this way, the check operation is completed.

Next, PWloo in FIG. 1O is executed. In Figure 23,
If the background smearing flag is set to 1 (23-1),
It reaches LOOPI (23-9) and continues the detection operation.

On the other hand, if the background smearing flag is not set to 1 (2
3-1) Execute PWO80 to average the output. In FIG. 24, p woso first detects that if the background dirt check flag is not set to 1 (24-1),
Clear the data total counter (24-2), and set the photo sensor output data (0@~30) to the data total counter.
0°) 24-3), divide the data total counter by 6 to calculate the average value 24-4), and determine whether or not the background output VSa read flag is set to 1. (24-5). If 1 is set, it is further determined whether the reference value setting flag is set to 1 (24-
6).

Here, if 1 is set, the average value is stored in the reference white pattern output vssr.24-7>, P WO3
1 to check the reference output.

In Figure 25, ■8. (Skin output) Set the abnormality flag to O 25-1>, Standard background output v, 6. ≧3.6■ (25-2), and the reference white pattern output vast≧3.0
(253), and if Vsst≧vsss (25-4), the bias flag and bias down flag are set to 0 (25-5), (25-6).

On the other hand, if Vsst ≧Vs*s 1” (25-4)
Set 1 on the high 7s down flag (25-10),
Set the bias change end flag to 0 (25-11),
Also, if vsaa≧3.6v (25-2), the background output VSa abnormality flag is set to 1 (25-7), and if vssi≧3. If not (25-3), set the bias up flag to 1 (25-8), and set the bias change end flag to O (25-9). When the flowchart in FIG. 25 is completed, the process in FIG. Step (24-
In step 8), it is determined whether the bias up/down flag is set to 1. If 1 is not set, the reference value setting flag is set to 0 (24-9), and the reference value reading flag is set to 1. (24-10).

If the VSa lead flag is not set to 1 (24-5
), determine whether the reference value setting flag is set to 1 (24-11), and if it is set to 1, store the average value in the reference background output (Vtc): Vsas (24-1).
2) If 1 is not set, compare the average value and the background output (
Vse): Vs. (24-13)
. Also, if the reference value setting flag is not set to 1 (2
4-6) Compare average value White pattern output; VSell
24-14) and sets the comparison value read flag to 1 (24-15). When the flowchart of FIG. 24 is completed, PWO90 of FIG. 26 is executed.

This PWO90 is shown in FIG. 26 when the correction end flag is set to 1.
is not set (26-1) and the correction value reading flag is set to 1 (26-2), Vscg X V3GC
/ v sac - v tc *'26-3)
, Vsac≧2.5V teVscg' 2: 5.
If it is not OV (26-4).

(26-5) , PWO91 correction value ΔVm (7) Determination is performed, PWO91 first determines v
sst -Vscx' (7) Let the value be A27-1)
, determine whether Vsp/Vsa≧6/40 (
27-2), this V5P+ vsc is the output of the photosensor 9 for toner density control, and in addition to the background stain detection operation, the V5P+ vsc of the normal photosensor 9 is also output. P+V$. is detected and the correction data level is changed based on that value. If step (27-2) is No”ii?, VI
Determine whether P/v is ≧3/4027-3)
, If YES, compare the above values and if it is 0.53V or less, go to ■ (27-4), (27-5), 0
．． If 53V<As2.06Vte, jump to 2
7-6"), 1.06V<As2.59V, jump to ■27-7), 1.59V<A:
i; 2. If it's OV then jump to ■ 27-8)
,A>2. If it is OV, enter 4 in the correction data.
7-9), add this correction data to the correction data memory (27-10), while step (27-2) is Y
In the case of ES, the toner concentration is low, and As2.4
If it is 6V, go to ■ (27-15,113), 0.46V
< A so, if it is 93V, go to ■ (27-17) 0
．． If 93V < A ≦1.40V, go to ■ (27-
18) 1.40V < A ≦ 1'7!5v If TE, jump to ■ (27-19) respectively, A > 1.75
If V, proceed to step <27-9), and if step (27-3) is No, the toner concentration is low, and if As2.61V, proceed to (27-10, 11).
), if 0.61V<As2.21V, go to ■(27
-12>, 1.21V < A ≦1.82V Tearepo■ (27-13), 1.82V<As2.3■
If so, jump to ■ (27-14) and A>
If it is 2.3V, proceed to step (27-9).

In the above ■, enter 0 in the correction data 27-20), ■
Then enter 1 in the correction data 27-21), Input 2 into the correction data manually 27-22) In Q, enter 3 in the correction data 27-23), Then, these correction data are processed in step ( 27-10) for processing. 0 to 4 input to this correction data represent bias output steps, and each correction data output stage (+1
5-30v). In addition, PWO91 in Figure 27
28 is a flowchart for the case in which the toner density pattern output is taken into account, and the flowchart in the case in which the toner density pattern output is not taken into consideration. In FIG. 28, it is determined in step (2B-1) that Vssv Vscx'>Q, and if YES, Vsst -Vscx'>0.
53V is determined (28-2), and if YES, Vs
A determination is made that st -Vscg'>1.06V (2B-3).

If step (2B-3) is YES, v 5st-
V. '>1.59V was determined (28-4),
If YES, Vsst -Vsc+t'> 2. O
A determination of V is made (2B-5).

If step (28-5) is YES, 4 is input to the correction data (2B-6).

Also, steps (2B-1) and (28-2) are N
If the answer is O, enter 0 in the correction data 2B-7); if step (28-3) is NO, enter 1 in the correction data 2B-8); if step (28-4) is NO. If so, input 2 into the correction data (2B-9), and if step (2B-5) is NO, manually input 3 into the correction data (2B-10).

In step (2B-11), the correction data obtained as described above is added to the developing bias voltage during the normal copying operation.

When the flowchart of FIG. 27 or 28 is completed, the process proceeds to step (26-6) of FIG. 26, and 1 is set in the correction end flag. On the other hand, vscc≧2.5
If not v (26-4), or V! .

If ≧5.0■ (26-5), the comparison value abnormality flag is set to 1 (26-7), and in this way, the comparison background output vsec is corrected. When the flowchart in FIG. 26 is completed, the step in FIG. 23 (
Proceed to 23-2), determine whether 1 is set in the VS (i read flag, and if 1 is not set, V. Set 1 in the read flag (23-3), and set 1 in the bias upper limit flag. If it is not set (23-4), the bias correction counter is counted up by 1 (23-5), and if the bias correction counter is 15 (23-6), the bias correction upper limit flag is set to 1 (23-7), and step (23-8)
, that is, proceed to LOOP2 in FIG.

In the above embodiment, stable image control is achieved for each machine because the developing bias is increased or decreased to maintain the sensor output at a set level in response to variations in the amount of reflected light due to the position and layout of the reference pattern for image control. It becomes possible,
Improves accuracy. Also, a certain level (3 in the above example)
By providing a warning means for the image control process, it is possible to prevent the image control process from becoming an infinite loop (the process is repeated many times without completing it), and it is possible to diagnose sensor abnormalities, process condition abnormalities, etc. Further, by using a sensor that detects the initial output value together with a toner concentration sensor, parts around the drum can be simplified and costs can be reduced.

〔Effect of the invention〕

As explained above, according to the present invention, since the sensor output can be set within a predetermined range, the accuracy of correction control of image forming conditions can be improved, and the sensor output can have a high S/N ratio. Can be done. Further, according to the present invention, it is possible to prohibit an infinite loop of image control processing, and it is possible to diagnose an abnormal state.

[Brief explanation of the drawing]

All drawings are for detailed explanation of the present invention.
The figure is a front view showing an overview of the overall configuration of a copying machine to which an image forming apparatus according to the present invention is applied, FIG. 2 is a cross-sectional view of the main parts, FIG. A front view showing the relationship between the photosensor and the photoreceptor, FIG. 5 is a graph showing data read by the photosensor, FIG. 6 is a diagram showing the detection position in one rotation of the photoreceptor drum, and FIG. 8 is a block diagram of the control system, FIG. 9 is a timing chart of each signal, FIG. 1θ is a flowchart showing the entire background stain check, and FIGS. FIG. 29 is a diagram showing each data in the flowchart of FIG. 18, FIGS. 30 to 34 are characteristic diagrams of the embodiment of the present invention, and FIG. Figure 31 is a diagram showing the relationship between the exposure amount and the drum white potential ■, and Figure 31 is a diagram showing the relationship between the exposure amount and drum white potential ■.
FIG. 32 is a characteristic diagram of the relationship between drum white area potential vL and photosensor output, FIG. 33 is a relationship characteristic diagram between drum potential vo, drum white area potential vL, and photosensor output with density as a parameter, and FIG. Figures (A) to (C) are characteristic diagrams of the relationship between light intensity and density depending on the filament position, Figure 35 is a block diagram of the sensor output level setting system, and Figure 36 is when the light intensity on the document surface is set to 1.0. 3 is a graph showing the light amount ratio depending on the lamp position. 4... Photosensitive drum, 9... Photo sensor, 16.
...Control unit, 20...Display section, 28...Developing bias, 36...First scanner, 41...Pattern. Figure 4 Figure 5 Figure 2 Figure 3 Figure 18 Figure 20 Figure 19 Figure 2I Figure 22 Figure 23 Figure 26 Figure 30 Figure 31 Figure 33 Figure VL (V) Figure 32 Figure 34 Figure (A) mw/m2 O (0,193 α5 0.0 mw/m2 Figure 34 (B) 0.0 Figure 34 (C) mW/m2 Todoroki 01O (0,18~2/J 0. 5 Sugor dark* o, te

Claims (2)

[Claims] (1) A control pattern for image forming conditions, means for forming an image of the pattern on a photoreceptor, a sensor for reading the image, and an initial output value read by the sensor are set in advance. and judgment means for determining whether or not it is within the specified range,
When reading an initial output value according to the pattern by the sensor after forming an image on the photoreceptor, the previous image forming conditions are set so that the initial output value falls within a preset range. An image forming apparatus characterized by changing. (2) A warning is issued if the initial output value does not fall within the range even after performing the process of changing the image forming conditions a predetermined number of times so that the initial output value falls within the preset range. The image forming apparatus according to claim 1, further comprising warning means for issuing a warning.