JPH09329926A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of always forming a stable image, without being affected by the unevenness of an image carrier, an environmental change, etc. SOLUTION: An electrifying charger 11 for applying a surface potential to an arsenic selenium photoreceptor drum 12, a developing unit 13, a transfer charger 14 for transferring a toner image to a transfer material and a surface potential sensor 67 for detecting the surface potential of the photoreceptor drum 12 are provided therearound. Then, a memory 93 is stored with the surface potential data of the photoreceptor drum corresponding to a dead time and an operating time and control data for controlling the electrifying current of the electrifying charger, in accordance with the surface potential data. A CPU 62 compares the surface potential detected by the surface potential sensor with the surface potential data stored in the memory, to correct the control data in accordance with the result of the comparison.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by an electrophotographic method, such as a copying machine and a printer.

[0002]

2. Description of the Related Art Electrophotographic copying machines, printers, and the like are widely known as image forming apparatuses. 2. Description of the Related Art In an electrophotographic copying machine or the like, a photosensitive drum is uniformly charged by a charging charger, and then an original on a platen is exposed, and reflected light is imaged on the photosensitive drum to form a photosensitive drum. An electrostatic latent image is formed thereon. Toner particles are supplied to the electrostatic latent image on the photosensitive drum by a developing device to perform electrostatic development, and the formed toner image is transferred onto a transfer paper charged by a transfer charger to form an image. .

In the electrophotographic copying machine of this kind, the copying speed has been increased in recent years, but with the increase in speed, the intrinsic sensitivity of the photosensitive drum is required to be higher. There is. However, the current organic photoreceptor (OP
In C), many of them lack intrinsic sensitivity, and the arsenic selenium photoconductor having the highest sensitivity at present is adopted in many copying machines.

This arsenic selenium photoconductor has the characteristics that it has a high intrinsic sensitivity as described above, and that it has a higher hardness and excellent printing durability than OPC. This is the reason why arsenic selenium photoconductors are applied to copying machines.

On the other hand, however, the arsenic selenium photoconductor has many inherent drawbacks such as poor temperature dependence and fast dark decay. One of them is the charging ability, that is, the arsenic selenium photoconductor drum. The upper surface potential is unstable. Further, a cold cathode tube is often used as a charge eliminating light source for an arsenic selenium photosensitive member, and the rising characteristic of the light quantity of this cold cathode tube also influences how the surface potential is glued.

This is because the arsenic selenium photoconductor has a characteristic that the initial charging ability increases depending on the dwell time of the photoconductor drum, and the cold cathode tube has an initial light amount when left for a long time. It tends to become low and gradually increase due to continuous lighting. Therefore, this is a cause of the tendency that the initial charging ability of the arsenic selenium photosensitive drum is increased. In particular, when the quiescent time of the photosensitive drum becomes long, the initial charging ability tends to increase.

As described above, the arsenic selenium photoconductor tends to have a high initial charging ability and a high initial surface potential depending on the dwell time of the photoconductor drum. When the body drum is continuously fatigued, the surface potential of the photosensitive drum drops rapidly at first and then gradually stabilizes at a constant potential.

In order to correct the instability of the surface potential of such a photosensitive drum, usually, the surface potential is kept constant by means for controlling the total charging current or the like according to the rest time and the operating time of the photosensitive drum. It keeps control. This control is performed so as to cancel the fluctuation of the surface potential depending on the dwell time and the operation time, that is, when the surface potential becomes high when the dwell time is long, the charging total current is lowered, and
When the surface potential gradually decreases depending on the operating time, the total charging current is gradually increased, and as a result, the surface potential is kept constant.

According to the copying machine disclosed in Japanese Patent Laid-Open No. 60-191162, for example, a pause time and an operating time are counted by using a timer of the copying machine main body as a structure for performing such control. The control is performed according to the count. Further, Japanese Patent Laid-Open No. 60-281258 discloses a method of controlling the dark decay of the photosensitive drum using a surface potential sensor.

[0010]

As described above, when the arsenic selenium photoconductor is used as the photoconductor drum,
Due to the characteristics of the photoconductor drum and the system of the copying machine, the stability of the surface potential deteriorates, that is, the surface potential of the photoconductor drum changes depending on the downtime and the operating time of the photoconductor drum and the system. The general control is to control the total charging current so as to cancel. However, conventionally, these controls have been performed uniformly by using a control table for controlling the copying machine main body and using the timer of the copying machine main body accordingly.

When such a control method is used, it is not possible to take into consideration variations in the photosensitive drums, variations in efficiency such as static elimination and static elimination before transfer, and variations in the environment, variations in life of the photosensitive drums, etc. There is a deviation in the control of the electric potential. As a result, the image density of the image formed by the copying operation changes after the copying operation is performed after the copying machine or the photoconductor drum is left for a long time, and when the copying operation is performed by continuous copying. Problems such as changes occur.

The present invention has been made in view of the above points, and an object thereof is to provide an image forming apparatus capable of always forming a stable image without being influenced by variations in an image carrier and environmental changes. To provide.

[0013]

In order to achieve the above object, the image forming apparatus of the present invention according to claim 1 is an image carrier in which the surface potential changes according to a dwell time, and the image carrier is charged. Image forming means for forming a developer image on the surface of the image carrier, transfer means for transferring the developer image formed on the image carrier to a transfer material, and the image carrier. Of the charging means based on a predetermined control data, a time detecting means for detecting a rest time, a surface potential detecting means for detecting a surface potential of the image carrier, a rest time detected by the time detecting means. According to the control means for controlling the charging current and the surface potential detected by the surface potential detecting means, the control data is set so that the surface potential of the image carrier charged by the charging means becomes a predetermined value. To correct It is characterized by comprising a positive means.

According to a second aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier whose surface potential changes according to a dwell time.
Image forming means for forming a developer image on the surface of the image carrier, and transfer means for transferring the developer image formed on the image carrier to a transfer material, which has a charging means for charging the image carrier. A storage means for storing control data for controlling the charging current of the charging means according to the surface potential data of the image carrier and the surface potential data corresponding to the rest time, and the surface potential of the image carrier. The surface potential detecting means for detecting is compared with the surface potential detected by the surface potential detecting means and the surface potential data stored in the storing means, and the image charged by the charging means according to the comparison result. And a control unit that corrects the control data so that the surface potential of the carrier becomes a predetermined value.

According to a third aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier whose surface potential changes according to a dwell time.
Image forming means for forming a developer image on the surface of the image carrier, and transfer means for transferring the developer image formed on the image carrier to a transfer material, which has a charging means for charging the image carrier. A storage means for storing control data for controlling the charging current of the charging means according to the surface potential data of the image carrier and the surface potential data corresponding to the rest time, and the surface potential of the image carrier. The surface potential detection means for detecting and the surface potential of the image carrier detected by the surface potential detection means for each elapse of a predetermined rest time are compared with the surface potential data stored in the storage means, and the comparison result is obtained. Accordingly, the control means corrects the control data so that the surface potential of the image carrier charged by the charging means becomes a predetermined value.

An image forming apparatus according to a fourth aspect of the present invention includes an image carrier whose surface potential changes according to operating time.
Image forming means for forming a developer image on the surface of the image carrier, and transfer means for transferring the developer image formed on the image carrier to a transfer material, which has a charging means for charging the image carrier. A time detecting means for detecting an operating time of the image carrier, a surface potential detecting means for detecting a surface potential of the image carrier, and an operating time detected by the time detecting means,
And a control means for controlling the charging current of the charging means based on predetermined control data, and the surface potential of the image carrier charged by the charging means in accordance with the surface potential detected by the surface potential detecting means. And a correction unit that corrects the control data so that becomes a predetermined value.

According to a fifth aspect of the present invention, in the image forming apparatus, an image carrier whose surface potential changes according to the operating time,
Image forming means for forming a developer image on the surface of the image carrier, and transfer means for transferring the developer image formed on the image carrier to a transfer material, which has a charging means for charging the image carrier. And storage means for storing the surface potential data of the image carrier corresponding to the operation time and the control data for controlling the charging current of the charging means in accordance with the surface potential data, and the surface potential of the image carrier. The surface potential detecting means for detecting is compared with the surface potential detected by the surface potential detecting means and the surface potential data stored in the storing means, and the image charged by the charging means according to the comparison result. And a control unit that corrects the control data so that the surface potential of the carrier becomes a predetermined value.

An image forming apparatus of the present invention according to claim 6 is an image carrier in which a surface potential changes according to an operating time,
Image forming means for forming a developer image on the surface of the image carrier, and transfer means for transferring the developer image formed on the image carrier to a transfer material, which has a charging means for charging the image carrier. And storage means for storing the surface potential data of the image carrier corresponding to the operation time and the control data for controlling the charging current of the charging means in accordance with the surface potential data, and the surface potential of the image carrier. The surface potential detection means for detecting and the surface potential of the image carrier detected by the surface potential detection means at each elapse of a predetermined operation time are compared with the surface potential data stored in the storage means, and the comparison result is obtained. Accordingly, the control means corrects the control data so that the surface potential of the image carrier charged by the charging means becomes a predetermined value.

According to the image forming apparatus having the above structure, the surface potential is applied to the image carrier by the charging means, and the surface potential is applied to the image carrier.
A developer image is formed by the image forming means. This developer image is transferred onto the transfer material by the transfer means. The charging current of the charging means is controlled by the control means according to the rest time or operation time of the image carrier. At this time, the surface potential detection means measures the transition of the surface potential due to the operating time of the surface potential of the image carrier when it is resting for a long time,
By calibrating the operation time control of the image carrier, and by measuring the surface potential corresponding to the dwell time of the image carrier,
Calibrate controls based on downtime. As a result, it is possible to minimize the deviation of the surface potential due to the variation of the image carrier and other mechanical parts, the environmental change, etc., and to always form a stable image.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic copying machine will be described below in detail with reference to the drawings. First, the overall configuration of the copying machine will be schematically described. As shown in FIG.
And an image carrier at almost the center of the housing.
For example, a photosensitive drum 12 made of arsenic selenium is rotatably provided. Around the photosensitive drum 12, a charging charger 11 and a developing device 1 functioning as a developing unit
3. The transfer charger 14, the peeling charger 15, the peeling claw 16, the cleaning device 17, and the static elimination lamp 18 functioning as a transferring means are arranged in this order to constitute the image forming unit 20.

A document placing table 32 made of transparent glass is provided on the upper surface of the housing 10, and an automatic document feeder (hereinafter referred to as ADF) 8 for automatically feeding the document D onto the document placing table 32.
0 is provided.

The ADF 80 is configured also as a document holder for opening and closing the document placing table 32, and is provided so as to face the document tray 82 on which the document D is placed and almost the entire surface of the document placing table, and conveys the document. And a belt 85. Then, the document placed on the document tray 82 is guided onto the document placing table 32 via the transport path 84, and is transported and positioned at a predetermined position by the transport belt 85. Then, the document read by the scanner described later is discharged to a document discharge unit 88 on the upper surface of the ADF 80 through the conveyance path 86 by the conveyance belt 85.

A scanner 22 for reading an image of the original document D placed on the original document table 32 is arranged below the original document table 32 in the housing 10. This scanner 2
2 includes an exposure lamp 24 whose back is surrounded by a reflector 23, and a first reflection mirror 25 mounted on a first carriage 33 together with the exposure lamp. The scanner 22 is mounted on the second carriage 34 and can move integrally with the second and third reflection mirrors 2.
6, 27, a lens 28, and fixed fourth, fifth and sixth
And the reflection mirrors 29, 30, and 31 of FIG.

First and second carriages 33, 34
Is moved at a predetermined speed along the document table 32, and scans the document D by the irradiation light from the exposure lamp 24. Then, the reflected light from the document D is guided to the photosensitive drum 12 by the first to sixth reflecting mirrors and the lens 28 to expose the surface of the photosensitive drum.

As a result, an electrostatic latent image corresponding to the image of the original is formed on the surface of the photosensitive drum 12 that is uniformly charged by the charging charger 11 as described later. The formed electrostatic latent image is developed by the developing device 13 using toner as a developer to form a toner image. As described above, the charger 11 and the scanner 22 constitute a latent image forming unit in the present invention.

An automatic exposure sensor 21 for measuring the amount of exposure light is provided between the third reflecting mirror 27 and the lens 28. Then, part of the light reflected by the third mirror 27 is incident on the automatic exposure sensor 21 and is
Outputs an output voltage corresponding to the image density to the CPU 92 described later as a document density signal.

First and second paper feed cassettes 35 and 36, each containing a large number of papers P as transfer materials, are detachably attached to the lower portion of the side surface of the housing 10. The first and second sheet cassettes 3 are provided in the housing 10.
The paper P taken out of the photosensitive drum 12
A transfer path 38 for transferring the sheet through a transfer portion located between the transfer path and the transfer charger 14 is formed, and a fixing device 40 is provided at the end of the transfer path. A discharge port 42 is formed on a side wall of the housing 10 facing the fixing device 40, and a discharge tray 43 is mounted on the discharge port 42.

The fixing device 40 includes a heat roller 40a having a built-in heater and a pressure roller 40 rollingly contacted with the heat roller.
b, a thermistor 4 for detecting the temperature of the heat roller 40a
0c and the like.

First and second paper feed cassettes 35, 36
Are provided with pickup rollers 44 for taking out the paper P from the paper feed cassettes, respectively.
A registration roller 46 for aligning the paper P is provided upstream of the photosensitive drum 12 in the transport path 38. A sensor 48 for detecting the arrival of the sheet P is provided near the registration roller 46.

The paper P picked up one by one from the first or second paper feed cassette 35, 36 by the pickup roller 44 is aligned by the registration roller 46 and then sent to the transfer section. Then, in the transfer section, the toner image on the photosensitive drum 12 is transferred onto the sheet P by the transfer charger 14.

The paper P on which the toner image has been transferred is peeled from the photosensitive drum 12 by the AC corona discharge from the peeling charger 15 and the peeling claw 16, and is conveyed to the fixing device 40 via the conveyance belt 50 forming the conveyance path 38. Be transported.
Then, the sheet P on which the toner image has been fused and fixed by the fixing device 40 is discharged onto a sheet discharge tray 43 by a sheet discharge roller 51.

Below the conveying path 38, the fixing device 4 is provided.
There is provided an automatic double-sided device 51 which reverses the paper P that has passed 0 and guides it again to the transfer portion via the registration roller 40. The automatic double-sided device 51 includes a reversing path 52 for branching off the transport path 38 and reversing the sheet P, a temporary accumulating section 53 for temporarily accumulating the inverted sheet P, and a sheet from the temporary accumulating section to the registration roller 46. Re-transport path 5 for transporting P
4 is provided.

A distribution gate 55 for guiding the sheet P to the reversing path 52 is provided between the fixing device 40 and the paper discharging roller 51, and a plurality of feed rollers 56 are arranged in the reversing path 52 and the re-conveying path 54. It is set up. In addition, the temporary accumulating unit 53
Inside, a pickup roller 57 for taking out the stacked sheets P one by one and sending it to the re-transport path 54 is provided.

When performing double-sided copying, the paper P that has passed through the fixing device 40 is fed to the reverse path 5 by the sorting gate 55.
2 and is accumulated in the temporary accumulation unit 53 after being inverted. After the accumulated paper P is taken out of the temporary accumulation section 53 by the pickup roller 57, the paper P is re-conveyed.
The toner image is then transferred to the registration roller 46, where the toner image is rearranged, and then the toner image is transferred again to the rear surface of the sheet P at the transfer unit. After that, the paper P is transferred to the conveyance path 38 and the fixing device 4.
The paper is discharged to the paper discharge tray 43 via the paper discharge roller 51 and the paper discharge roller 51.

Next, the structures of the photosensitive drum 12 and the image forming section 20 will be described in detail. As shown in FIG. 2, the charger 11 for uniformly charging the surface of the photosensitive drum 12 to a predetermined potential has a corona wire 11a and a grid 11b, and a voltage is applied to the corona wire to perform corona discharge. A power source (not shown) to be generated is connected. Further, the grid 11b is connected to a high voltage transformer 60 which functions as a power supply means for applying a grid voltage. These power supplies and high-voltage transformer 60
Is connected to the CPU 62 as a control means and a correction means.

With respect to the rotation direction of the photoconductor drum 12, an exposure position 12a on the surface of the photoconductor drum 12 which is exposed by the reflected light from the scanner 22 is located on the downstream side of the charger 11. At this exposure position, the photoconductor is exposed. An electrostatic latent image is formed on the drum surface.

An LED 65 for partial erasing is arranged between the exposure position 12a and the charger 11. The developing device 13 has a developing roller 13a for supplying toner particles to the electrostatic latent image on the surface of the photosensitive drum 12 to develop the electrostatic latent image. The developing roller 13a is controlled by a high-voltage transformer 76 under the control of the CPU 62. A development bias is applied.

A thermistor 66 which functions as a temperature detecting means for detecting the temperature of the surface of the photosensitive drum 12 is provided between the developing device 13 and the LED 65. The thermistor 66 is provided.
Is in contact with the drum surface at the end of the photosensitive drum. Then, the thermistor 66 outputs a detection signal to the CPU 62.

Further, between the developing device 13 and the LED 65,
A surface potential sensor 67 that functions as a potential detection unit that detects the surface potential of the photosensitive drum 12 is provided, and the surface potential sensor 67 is connected to the CPU 62.

The transfer charger 14 for transferring the toner image formed on the photoconductor drum 12 to the paper P and the peeling charger 15 for separating the paper P from the photoconductor drum are related to the rotation direction A of the photoconductor drum 12. Developer 13
Is provided on the downstream side. And the transfer charger 1
4 and the peeling charger 15 are integrally formed, and the CP via the high voltage transformers 68 and 70, respectively.
Connected to U62.

A cold cathode tube 100 which functions as a pre-transfer charge eliminator is provided between the developing device 13 and the transfer charger 14. The cold cathode tube 100 is provided on the photosensitive drum 12
The toner image formed on the surface and on the photoconductor drum is irradiated with the charge-eliminating light to eliminate the charge, and the electrostatic adhesion of the toner image to the surface of the photoconductor drum is reduced. Then, the cold cathode tube 100
Is arranged along the axial direction of the photoconductor drum 12, faces the photoconductor drum 12, and is connected to the CPU 62 via the power supply 106.

The peeling claw 1 is provided on the downstream side of the peeling charger 15.
6 is provided, and further, a cleaning device 17 having a cleaning blade 78 is provided on the downstream side of the peeling claw.
The toner that is provided in contact with the surface of No. 2 and that remains on the drum surface without being transferred is scraped off from the drum surface.

Between the peeling claw 16 and the cleaning device 17, a charger 77 having a corona wire for applying AC to the photosensitive drum 12 is provided as an auxiliary cleaning mechanism.
Is provided.

A static elimination lamp 18 is arranged between the cleaning device 17 and the charger 11.
The discharging lamp 18 is connected to the CPU 62 via a light source driver 94.
, And the light amount of the neutralization lamp 18 can be changed by changing the voltage applied to the light source driver 94 under the control of the CPU.

The CPU 62 has a timer 96 for measuring the down time of the copying machine, that is, the time from the end of one copying operation until the disclosure of the next copying operation, and the heat roller 40a of the fixing device 40. The thermistor 40c for detecting the temperature of the above and a memory 93 storing various control data are connected.

The timer 96 functions as the time detecting means in the present invention for detecting the down time and the operating time of the copying machine or the photosensitive drum 12, and the thermistor 40c also detects the down time based on the temperature of the heat roller 40a. Function as time detection means. Further, the thermistor 66 functions as a temperature detecting means for detecting the environmental temperature according to the temperature of the photosensitive drum 12.

FIG. 3 shows the relationship between the output of the surface potential sensor 66 and the surface potential of the photosensitive drum 12. Here, as a copying machine, a Toshiba electronic copying machine Leo Dry 655 is used.
The one in which the surface potential sensor 66 was attached to 0 was used.
A surface potential sensor manufactured by Murata Manufacturing Co., Ltd. was used as the surface potential sensor 66, and a Model 360SX manufactured by Trek was used to measure the actual surface potential output. The measurement environment was fixed at room temperature and normal humidity.

Here, the horizontal axis represents the Trek model 36.
The actual surface potential using 0SX is shown, and the vertical axis shows the output of the surface potential measured by the surface potential sensor manufactured by Murata Manufacturing.

As shown in FIG. 3, the output of the surface potential sensor is proportional to the surface potential of the photosensitive drum 12, and the surface potential of the photosensitive drum 12 can be converted into the output of the surface potential sensor. Recognize.

FIG. 4 shows an example of variations in the efficiency of the photoconductor drum, static eliminator, pre-transfer static eliminator, etc. in the copying machine, variations in the environment, and variations in the life of the photoconductor drum. With respect to the three photoconductor drums, variations in the surface potential of the first photoconductor drum 12 of the copy corresponding to the dwell time due to variations in products of the photoconductor drums are shown.

Here, the abscissa represents the dwell time of the photosensitive drum 12, and the ordinate represents the surface potential of the copy-1 sheet measured by the Trek Model 360SX. FIG.
As you can see, each photosensitive drum 12 of selenium arsenide
Indicates that the initial surface potential tends to increase as the rest time increases, and the rise in surface potential is almost stable when the photosensitive drum is stopped for 60 minutes. Then, it can be seen that the surface potentials of these photosensitive drums vary even during the same rest time.

FIG. 5 shows an example of variations in efficiency of the photoconductor drum, static eliminator, pre-transfer static eliminator, etc. in the copying machine, and variations in environment, life of the photoconductor drum, etc. For three photoconductor drums, variations in the surface potential according to the operating time of the photoconductor drum after a pause of 60 minutes due to product variations are shown.

Here, the abscissa represents the operating time of the photosensitive drum or the system, and the ordinate represents the variation in the transition of the surface potential during continuous copying measured by Trek Model 360SX. There is. From this figure,
Although the surface potential of the photosensitive drum tends to be high in the initial stage of operation after a pause of 60 minutes, continuous copying is performed, that is, by continuously fatigue the photosensitive drum, the surface potential of the photosensitive drum starts. Falls sharply, then gradually becomes gentle, and finally tends to stabilize at a constant surface potential. Then, in the same manner as the above-mentioned variation of the surface potential due to the rest time, in the three photosensitive drums,
It can be seen that there is a variation in the surface potential corresponding to the operating time.

As described above, when the variation of the surface potential according to the rest time or the variation of the surface potential according to the operating time is uniformly controlled based on the constant reference data, the surface potential deviates from the desired value. Occurs, which causes a problem such as a change in image density on the formed image or a change in exposure.

Therefore, according to the present embodiment, by using the surface potential sensor 67, by measuring the transition of the surface potential corresponding to the operating time of the surface potential of the photosensitive drum 12 in the case of a long rest, The operation time control of the photoconductor drum is calibrated, the surface potential of the photoconductor drum 12 is measured according to the rest time, and the rest time control is calibrated. Thereby, the deviation of the surface potential due to various variations as described above is minimized, and a stable image is always acquired.

More specifically, according to this embodiment, the operation of the copying machine is controlled by the following configuration and operation.
First, the copier, that is, the displacement of the surface potential of the photosensitive drum according to the operating time of the photosensitive drum 12 is actually measured,
The operation time control correction is performed to correct the control data according to the measurement result. This operation time control correction is performed, for example, every morning when the copying machine is warmed up.

As shown in FIG. 6, first, when the power of the copying machine is turned on, the temperature of the fixing device 40 is set to the thermistor 40c.
Of the fixing device 40 and the rest time of the photoconductor drum 12 (or the rest time of the system) is estimated from the detected temperature of the fixing device 40. Then, when the detected temperature is higher than the predetermined temperature and the pause time of the photosensitive drum 12 is short, the correction control is not performed and the control operation is ended.

When the detected temperature of the fixing device 12 is sufficiently low, that is, when the photosensitive drum 12 has been idle for a sufficiently long time, the correction control is started. First, at the time of start-up operation (pre-run) of the copying machine, the photosensitive drum 12
Simultaneously with the rotation of, the total charging current is output at a constant value. Then, normally, when the erasing LED 65 is all turned on and the surface of the photosensitive drum is neutralized, the surface potential sensor 66
Of the surface potential sensor 6 installed on the downstream side of the charger 11 and the erasing LED 65 by removing the electricity with the radiation of the portion corresponding to the detecting section 66a of the erasing LED 65 being turned off.
6, the current surface potential of the photosensitive drum 12 is measured. After that, all the erasing LEDs 65 are turned on again.

Then, 5 seconds after the rotation of the photosensitive drum 12 is started, the same measurement as above is performed again, and the surface potential of the photosensitive drum 12 is measured by the surface potential sensor 66. From the start of rotation of the photoconductor drum 12,
5 seconds, 10 seconds, 30 seconds, 60 seconds, 120 seconds, 200 seconds,
After 400 seconds, repeated measurement is performed and each measured value is stored in the memory 93.

Then, the measured values of the respective surface potentials,
The data of the transition of the surface potential that has been measured previously (or predetermined reference data), which is already stored in the memory 93, is compared, and the deviation of the surface potential corresponding to each operation time is calculated. Then, based on the calculated surface potential deviation data, the control table for controlling the total charging current is corrected according to the operation time of the photoconductor drum 12 so as to cancel each deviation, and the control ends.

Based on the control data thus corrected, the charging current is controlled according to the operation time of the photosensitive drum 12, that is, the charging charger 11
By controlling the applied voltage to the photosensitive drum 12
The surface potential can be always maintained at a desired value, and an image having a desired image density can be stably formed.

The measurement cycle of the surface potential of the photosensitive drum 12 is not limited to the above-mentioned cycle, and can be freely changed. For this, the number of times of measurement may be increased or decreased depending on the system configuration of the copying machine main body or the variation of the surface potential of the arsenic selenium photosensitive drum mounted on the copying machine being used. Further, the operation time correction control is not limited to the warm-up of the copying machine every morning, but the same effect can be obtained even if the control is automatically performed when the photoconductor drum or the copying machine pauses for + minutes. Is obtained.

Further, when the control is performed both during warm-up every morning and when the photosensitive drum is sufficiently rested (for example, when resting for 60 minutes or more), it is possible to further suppress the variation in control. It will be possible. Further, when setting up the copying machine or replacing the photosensitive drum, the above correction control is performed to set the control data for the operation time control regarding the installed photosensitive drum so that the surface potential does not shift. can do.

On the other hand, the rest time control is corrected by the control operation shown in FIG. Here, the pause time control correction is automatically entered when the copying machine is paused for an arbitrary time. If the copying machine enters the copying operation before the copying operation is stopped for an arbitrary time, the counting of the stopping time is canceled, and when the copying operation is completed, the stopping time is counted again. Further, when the photosensitive drum 12 is rested for a long time (for example, 60 minutes), the surface potential measurement data of the copy-1 sheet after the long rest in the control of the operation time control correction described above is used for the long rest. It was decided to use it as the data for the rest time control correction.

In the pause time control correction, as shown in FIG. 7, first, immediately after the control is started, immediately after the copying operation, or when the photosensitive drum 12 is idle for a certain period of time. To judge. When the photoconductor drum 12 has been idle for a certain period of time, the elapsed time from the end of the previous copying operation, that is, the pause time is calculated using the timer 96 of the copying machine. For example, the rest time is 30 seconds, 60 seconds, 180 seconds, 300 seconds, 600
If any one of seconds, 1800 seconds, and 3600 seconds, control correction is performed.

If the copying operation has just been completed, the time until the copying operation is completed and the photosensitive drum is stopped,
The total charging current is output at a constant output value, and the photosensitive drum 12
Apply surface potential to the surface and erase the surface potential
A part of 65 is turned off, and the surface potential sensor 67 measures the surface potential. Further, regarding the correction of the control by the rest time other than that, after calculating the rest time by the timer 96,
Control automatically.

In the control correction operation, the photosensitive drum 1
2 is rotated, and at the same time, the total charging current is output at a constant value, the surface potential is applied to the photosensitive drum 12, and the erase L
With a part of the ED 65 turned off, the surface potential sensor 67 detects the surface potential of the surface part of the photosensitive drum corresponding to the turned-off part.
Measured by Then, the measured surface potential is stored in the memory 93.

Then, the previous surface potential data stored in the memory 93 is compared with the measured surface potential value at each measured pause time to calculate the surface potential deviation. Then, the control table for controlling the charging current is corrected according to the pause time of the photoconductor drum or the copying machine system so as to cancel the calculated deviation.

The result of the above-described correction of the total charging current control, for example, the result of the correction of the charging control by the rest time among the above-mentioned control corrections will be described below. First, in the above-described control, the result of comparing the measured surface potential (the output of the surface potential sensor 67 converted to the actual surface potential) with the previous surface potential data stored in the memory 93 is shown. 8 shows.

Here, when the previous surface potential data stored in the memory 93 is compared with the surface potential data obtained by the correction control, the rest time is 30 seconds, 60 seconds,
It can be seen that the surface potential data detected by the correction is higher in each of 180 seconds, 300 seconds, 600 seconds, and 1800 seconds.

That is, when the total charging current is controlled based on the previous surface potential data to acquire an image, the surface potential obtained by charging becomes higher than a desired value, that is, the exposure becomes dark. I understand.

Therefore, the total charging current control is corrected based on the new surface potential data detected by the correction control. FIG. 9 shows an actual correction state of the total charging current control due to the pause time of the photosensitive drum and the above total charging current control due to the surface potential deviation.

Here, the horizontal axis represents the rest time of the photosensitive drum 12, and the vertical axis represents the control ratio of the surface potential represented by the output ratio of the total charging current. As can be seen from FIG. 9, as compared with the control before correction, since the surface potential is deviated, the control data is corrected so as to drop the control of the output ratio of the total charging current from the place where the down time is short, Correct the surface potential deviation. As a result, it becomes possible to control the charging current so as to prevent the occurrence of image defects due to the deviation of the surface potential, the change in exposure, and the like.

FIG. 10 shows how the exposure changes during continuous copying after a 10-minute pause before and after the actual correction. Here, the vertical axis represents the reflectance when a document having a reflectance of 51% was copied, and the horizontal axis represents the exposure change during continuous copying. Also from this figure, it can be seen that the correction of the charging current control makes the exposure change smaller than the case where the correction is not made.

As the data measurement cycle for the pause time control correction, immediately after, 30 seconds, 60 seconds, 180 seconds, 300 seconds,
Although the case is 600 seconds, 1800 seconds, or 3600 seconds, the present invention is not limited to this and can be changed as necessary. This is because the number of measurements may be reduced or it may be necessary to increase the number of measurements depending on the system configuration of the main body of the copier or the variation in the surface potential of the arsenic selenium photosensitive drum being used. is there.

Besides, the present invention is not limited to the above-described embodiments, but can be variously modified within the scope of the present invention. For example, the present invention is not limited to analog copying machines, but may be applied to other image forming apparatuses such as digital copying machines and laser printers. Further, the photoconductor drum is not limited to the one composed of an arsenic selenium photoconductor, but can be applied to a photoconductor drum using a photoconductor whose surface potential changes according to a rest time or an operation time.

[0077]

As described above in detail, according to the present invention, variations in the image carrier and other components of the image forming apparatus,
Minimize the deviation of the surface potential of the image carrier even if there is a deviation in the control of the surface potential according to the pause time or the operating time of the image carrier due to changes in the environment or variations in the life of the image carrier. It is possible to provide an image forming apparatus which can suppress and always obtain a stable image.

[Brief description of drawings]

FIG. 1 is a sectional view showing an entire copying machine according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an image forming unit and a control system of the copying machine.

FIG. 3 is a graph showing the relationship between the output of the surface potential sensor and the actual surface potential.

FIG. 4 is a graph showing changes in the surface potential of the photosensitive drum according to the rest time.

FIG. 5 is a graph showing changes in the surface potential of the photosensitive drum according to the operating time.

FIG. 6 is a flowchart showing the operation of the charging current control correction according to the operation time.

FIG. 7 is a flowchart showing the operation of the charging current control correction according to the pause time.

FIG. 8 is a diagram showing surface potential data stored in advance and surface potential data detected by a correction operation.

FIG. 9 is a graph showing charging current control data before and after correction corresponding to the pause time.

FIG. 10 is a graph showing a change state of exposure before and after correction corresponding to a pause time.

[Explanation of symbols]

 12 ... Photosensitive drum 13 ... Developing device 20 ... Image forming part 22 ... Scanner 40 ... Fixing device 40c ... Thermistor 62 ... CPU 66 ... Thermistor 67 ... Surface potential sensor 93 ... Memory 96 ... Timer 100 ... Cold cathode tube

Claims (6)

[Claims] 1. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to a dwell time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image bearing member to a transfer material, time detecting means for detecting the rest time of the image bearing member, and surface potential detection for detecting the surface potential of the image bearing member. Means, a pause time detected by the time detection means, and control means for controlling the charging current of the charging means based on predetermined control data, and according to the surface potential detected by the surface potential detection means, An image forming apparatus comprising: a correction unit that corrects the control data so that the surface potential of the image carrier charged by the charging unit has a predetermined value. 2. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to a dwell time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image carrier to a transfer material, surface potential data of the image carrier corresponding to the dwell time, and charging current of the charging means according to the surface potential data. Storage means for controlling control data, surface potential detecting means for detecting the surface potential of the image carrier, surface potential detected by the surface potential detecting means and surface potential data stored in the storing means. And a control unit that corrects the control data so that the surface potential of the image carrier charged by the charging unit has a predetermined value according to the comparison result. Image Forming apparatus. 3. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to a dwell time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image carrier to a transfer material, surface potential data of the image carrier corresponding to the dwell time, and charging current of the charging means according to the surface potential data. Storage means for storing control data for controlling the surface potential of the image carrier, surface potential detecting means for detecting the surface potential of the image carrier, and surface potential of the image carrier detected by the surface potential detecting means at each elapse of a predetermined rest time. Is compared with the surface potential data stored in the storage means, and according to the comparison result,
An image forming apparatus comprising: a control unit that corrects the control data so that a surface potential of the image carrier charged by the charging unit has a predetermined value. 4. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to operating time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image carrier to a transfer material, time detection means for detecting the operating time of the image carrier, and surface potential detection for detecting the surface potential of the image carrier. Means, an operating time detected by the time detecting means, and a control means for controlling a charging current of the charging means based on predetermined control data, and a surface potential detected by the surface potential detecting means, An image forming apparatus comprising: a correction unit that corrects the control data so that the surface potential of the image carrier charged by the charging unit has a predetermined value. 5. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to operating time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image carrier to a transfer material; surface potential data of the image carrier corresponding to the operating time; and charging current of the charging means according to the surface potential data. Storage means for controlling control data, surface potential detecting means for detecting the surface potential of the image carrier, surface potential detected by the surface potential detecting means and surface potential data stored in the storing means. And a control unit that corrects the control data so that the surface potential of the image carrier charged by the charging unit has a predetermined value according to the comparison result. Image Forming apparatus. 6. An image forming means for forming a developer image on the surface of the image bearing body, comprising an image bearing body whose surface potential changes according to operating time, and a charging means for charging the image bearing body. Transfer means for transferring the developer image formed on the image carrier to a transfer material; surface potential data of the image carrier corresponding to the operating time; and charging current of the charging means according to the surface potential data. Storage means for storing control data for controlling the surface potential of the image carrier, surface potential detecting means for detecting the surface potential of the image carrier, and surface potential of the image carrier detected by the surface potential detecting means each time a predetermined operation time elapses. Is compared with the surface potential data stored in the storage means, and according to the comparison result,
An image forming apparatus comprising: a control unit that corrects the control data so that a surface potential of the image carrier charged by the charging unit has a predetermined value.