JP2012185257A - Image deletion detection device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which is capable of operating for a long period without decreasing durability of a photoreceptor.SOLUTION: An image forming apparatus is characterized in comprising: a charging part; a light exposure part; a potential measuring part for measuring a potential of a latent image formed by the light exposure part; a time measuring part for measuring a time during which a photoreceptor is stopped; a detection part for detecting, when detecting at the time measuring part that the photoreceptor is stopped for a prescribed time, a charging counter position on the photoreceptor, opposed to the photoreceptor; a potential measuring control part for measuring at the potential measuring part, a reference potential which is a measured potential of a latent image formed in a reference position out of the charging counter position on the photoreceptor, and a charging counter position potential which is a measured potential of a latent image formed in the charging counter position on the photoreceptor; a determination part for determining that when the difference between the reference potential and an abnormal part measurement potential is equal to or more than a first prescribed value, an image deletion has been generated; and a photoreceptor surface repair part for polishing a surface of the photoreceptor when the determination part determines that the image deletion has been generated.

Description

  The present invention relates to an image flow detection device and an image forming apparatus.

  In a high-temperature and high-humidity environment, when the image forming device has been left for a long time and the photoconductor has been stopped for a long time, moisture remaining in the air is decomposed by the ozone remaining in the vicinity of the charger, causing nitrogen oxidation. It is generally known that an ion product such as a product or an ammonium salt is generated, and the ion product adheres to the photoconductor, so that the resistance of the surface of the photoconductor is easily reduced.

  When the ion product adheres to the photoconductor, a lateral flow of potential occurs due to a decrease in resistance on the surface of the photoconductor, thereby causing an image flow of an electrostatic latent image formed on the surface of the photoconductor, resulting in output. It is generally known that image flow occurs.

  Image formation that cleans the surface of a photoconductor by rubbing the surface of the photoconductor with a rubbing polishing roller when the output of a temperature and humidity sensor provided in the apparatus exceeds a predetermined value as means for preventing the occurrence of image flow An apparatus is known (for example, refer to Patent Document 1).

JP 2002-14589 A

  However, even when the photosensitive member has been stopped for a long time, image flow does not always occur when the temperature and humidity are high, and the image forming apparatus described in Patent Document 1 has temperature and humidity. Since the surface of the photoconductor is rubbed when the output of the sensor exceeds a predetermined value, there is a possibility that the surface of the photoconductor is rubbed even if no image flow occurs.

  In such a case, there has been a problem that the surface of the photoreceptor is rubbed and polished more than necessary, and the surface of the photoreceptor is worn to shorten the life of the photoreceptor more than necessary.

  SUMMARY OF THE INVENTION In view of the above-described problems, an object of the present invention is to provide an image flow detection device that can operate for a long period of time without shortening the life of the photosensitive member, and an image forming apparatus using the image flow detection device.

  The above object is achieved by the following configuration.

1. A charging unit that uniformly charges the photoconductor;
An exposure unit for forming a latent image on the photoreceptor;
An electric potential measuring unit for measuring the electric potential of the latent image formed by the exposure unit provided facing the photoconductor;
A time measuring unit for measuring the time during which the photosensitive member is stopped;
A detection unit that detects a charging facing position that is a position of the photosensitive member facing the charging unit when the timing unit detects that the photosensitive member has been stopped for a predetermined time; and
A reference potential obtained by measuring the potential of the latent image formed by the exposure unit at a reference position off the charging counter position on the photoconductor, and a potential of the latent image formed by the exposure unit at the charging counter position. A potential measurement control unit that measures the measured charge-facing position potential and the potential measurement unit;
A determination unit that determines that an image flow has occurred when a difference between the reference potential and the charging counter position potential is equal to or greater than a first predetermined value;
An image flow detection device comprising:

2. The reference potential is a potential of a latent image formed at the reference position measured by the potential measurement unit when the reference position reaches a position facing the potential measurement unit by rotation of the photoconductor,
The charging counter position potential is determined based on the latent image formed at the charging counter position measured by the potential measuring unit when the charging counter position reaches a position facing the potential measuring unit by rotation of the photoconductor. Is a potential,
2. The image flow detection device according to 1 above, wherein

3. The exposure unit forms a first latent image forming a first patch with a first exposure amount at the charging facing position, and forms a second latent image forming a second patch on the first latent image. A third latent image is formed with a second exposure amount larger than the exposure amount, and a third latent image for forming a third patch is formed with the first exposure amount at the reference position, thereby forming a fourth patch. 4 latent images are formed with the second exposure amount,
The determination unit has a first potential difference that is a difference between a third latent image potential that is a potential of the third latent image and a first latent image potential that is a potential of the first latent image, It is determined that image flow has occurred when the first predetermined value is exceeded.
3. The image flow detection device according to 2 above, wherein

  4). The determination unit is one of the reference potential and the fourth latent image potential that is the potential of the fourth latent image, and one of the charging opposing position potentials, which is measured by the potential measurement unit. It is determined that image flow has occurred when a second potential difference, which is a difference between the second latent image potential and the second latent image potential, is equal to or greater than the first predetermined value. 4. The image flow detection device as described in 3 above.

5. A developing unit for developing the latent image formed on the photoreceptor;
A density measuring unit that measures the density of the first patch, the second patch, the third patch, and the fourth patch formed by the developing unit;
The determination unit includes a reference density which is a density measured by the density measuring unit with respect to the density of the first patch, and a charged counter position density which is a density measured with the density measuring unit. 5. The image flow detection device according to 3 or 4, wherein it is determined that image flow has occurred when the difference between the two values becomes equal to or greater than a second predetermined value.

6). The reference density is a density of a patch formed at the reference position measured by the density measurement unit when the reference position reaches a position facing the density measurement unit by rotation of the photoconductor,
The density of the charging counter position is a density of the patch formed at the charging counter position measured by the density measuring unit when the charging counter position reaches a position facing the density measuring unit by rotation of the photoconductor. is there,
6. The image flow detection device as described in 5 above.

7). The developing unit forms the first patch and the second patch at the charging facing position, and forms the third latent image and the fourth patch at the reference position,
The determination unit determines that a first density difference, which is a difference between a third patch density that is the density of the third patch and a first patch density that is the density of the first patch, is the second density. It is determined that image drift has occurred when the value exceeds a predetermined value.
7. The image flow detection device according to 5 or 6 above, wherein

  8). The determination unit measures the fourth patch density, which is one of the reference densities, and the second patch density, which is one of the charging opposing position densities, measured by the density measurement unit. 8. The image processing apparatus according to item 7, wherein the image density is determined to occur when a second density difference, which is a difference between the second patch density and the second patch density, is equal to or greater than the second predetermined value. Image flow detection device.

9. An image forming apparatus having the image flow detection device according to any one of 1 to 8,
The determination unit has a photoconductor surface repair unit that polishes the surface of the photoconductor when it is determined that image flow has occurred,
The photoconductor surface repair unit includes a rotatable cleaning brush, a flicker roller that collects toner scraped by the cleaning brush, and a brush moving unit that can move the cleaning brush toward the photoconductor. And
The brush tip of the cleaning brush is in contact with the photoconductor, and the brush tip is rubbed against the photoconductor by the rotation of the cleaning brush. Polishing the surface,
An image forming apparatus.

  10. When the determination unit determines that an image flow has occurred, the rotational speed of the cleaning brush is changed to increase the relative speed between the cleaning brush and the surface of the photoconductor, and the toner adhering to the cleaning brush 10. The image forming apparatus as described in 9 above, which improves the polishing ability of the surface of the photoreceptor.

  11. When the determination unit determines that image flow has occurred, the amount of toner adhering to the cleaning brush is increased, thereby improving the ability of the surface of the photoreceptor to be polished by the toner adhering to the cleaning brush. 10. The image forming apparatus as described in 9 above.

12.1 Increase the toner amount per unit area of the toner band formed between the toner images for one page,
12. The image forming apparatus as described in 11 above, wherein the toner amount adhering to the cleaning brush is increased by conveying the toner band having an increased toner amount to the photoconductor surface repair section.

  13. When the determination unit determines that image flow has occurred, the relative distance of the flicker roller to the cleaning brush is increased, thereby reducing the amount of overlap of the flicker roller with respect to the cleaning brush, thereby reducing the amount of the cleaning brush. 10. The image forming apparatus as described in 9 above, wherein the amount of toner adhering is increased to improve the polishing ability of the surface of the photoreceptor by the toner adhering to the cleaning brush.

14 The photoconductor surface repair portion has a cleaning blade for removing toner remaining on the photoconductor,
The cleaning blade has a front end in contact with the photoconductor, and the surface of the photoconductor is polished with toner adhering to the front end by rubbing the photoconductor rotating the front end. 14. The image forming apparatus according to any one of 9 to 13, characterized in that

  15. When the determination unit determines that image flow has occurred, the amount of toner adhering to the cleaning blade is increased, thereby improving the polishing ability of the surface of the photoreceptor by the toner adhering to the cleaning blade. 15. The image forming apparatus as described in 14 above.

16. Increase the toner amount of the toner band formed between the toner images for one page,
16. The image forming apparatus according to item 15, wherein the toner amount attached to the cleaning blade is increased by transporting the toner band having an increased toner amount to the photoconductor surface repair unit.

  According to the above invention, the image flow can be detected correctly, so that the life of the photoconductor is not shortened and the image forming apparatus can be operated for a long time.

FIG. 2 is an explanatory diagram of an image forming apparatus. FIG. 4 is an explanatory diagram relating to the potential of the toner image and the density of the toner image when normal and when image flow occurs. FIG. 5 is an explanatory diagram of a γ curve of a toner image when the image flow is not normal and when the image flow is abnormal. Explanatory drawing of the sensor which detects the patch formed on a photoreceptor, and a patch. The flowchart which concerns on image flow generation | occurrence | production detection mode. Explanatory drawing (side view) of a photoreceptor surface restoration part. FIG. 3 is an explanatory diagram of a color image forming apparatus.

  FIG. 1 is an explanatory diagram of an image forming apparatus.

  Hereinafter, a monochrome image forming apparatus A will be described as an example of the image forming apparatus.

  The image forming apparatus A displays an original image reading unit 1, an image forming unit 2, a paper feeding unit 3, a fixing device 4, and various types of information and an operation for a user to input various types of information according to display contents. It has a panel SP and a control unit C that controls them, and an automatic document feeder B is placed on the upper part of the image forming apparatus A.

  The automatic document feeder B picks up the documents G placed on the paper feed tray B1 one by one, conveys them to the document reading area r, and discharges the document G in which image information is read in the document reading area r. Discharge to tray B2.

  The document image reading unit 1 includes a light source 11, a movable scanning unit 12, and an optical system 14 that forms an image of the document on a line image sensor 13. For example, in the case of a stationary optical system type reading operation, scanning is performed. The unit 12 is fixed to the original reading area r, and the image of the original G conveyed by the automatic original conveying apparatus B is read by the line image sensor 13.

  The analog signal of the original image photoelectrically converted by the line image sensor 13 is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like by the control unit C, and becomes digital image data.

  The control unit C has an image formation stop timer TM that measures the stop time of the photoconductor 21.

  And it has the function which concerns on the control in the below-mentioned electric potential measurement control part, the judgment part, and an image flow detection apparatus.

  The image formation stop timer TM measures the time from when the photosensitive member 21 stops to when it starts rotating. When the machine is turned on or returned from the sleeping mode, the machine is left for a long time. When it is determined that the measurement time is equal to or longer than the predetermined time when returning from the state, the fact that the photosensitive member 21 has been stopped for the predetermined time is output.

  Further, the image formation stop timer TM can operate even with standby power, and does not stop when the power switch for turning on / off the image forming apparatus A on a daily basis is turned off. The stop time can be kept timed.

  This makes it possible to know whether or not the photosensitive member 21 has been stopped for a predetermined time or more when the power switch of the image forming apparatus A is turned on.

  Around the photosensitive member 21, an exposure unit 22 that forms a latent image on the photosensitive member 21, a developing unit 23 that develops the latent image formed on the photosensitive member 21, and a charging unit that uniformly charges the photosensitive member 21. 24, a transfer unit 27 for transferring the toner image carried on the photoconductor 21 to the paper P, a separation claw 26 for separating the paper P from the photoconductor 21, and a photoconductor surface repair unit 5 described later are provided. Has been.

  Based on the digital image data, the exposure unit 22 forms a latent image on the photoreceptor 21 having a curable surface layer made of a filler and a monomer.

  The latent image formed on the photoconductor 21 is developed with toner by the developing unit 23, and the toner images formed on the photoconductor 21 are sequentially transferred onto the paper P by the transfer unit 27, and the toner image is formed on the paper P. It is formed.

  In the rotation direction of the photoconductor 21 (the direction of the arrow b), the photoconductor surface repair unit 5 disposed on the downstream side of the transfer unit 27 and the upstream side of the charging unit 24 polishes the surface of the photoconductor 21 by polishing the surface. Ion products such as nitrogen oxides and ammonium salts adhering to the body 21 are polished and removed, and at the same time, toner remaining on the surface of the photoreceptor 21 without being transferred to the paper P is removed.

  The paper feed unit 3 includes a plurality of paper feed cassettes 31 that are paper storage members, and the paper P is accommodated inside the paper feed cassette 31.

  The stored paper P is picked up one by one by a paper feed roller 32, transported by a plurality of transport rollers 33, and transported to a transfer region 35 in synchronization with a toner image formed on the photosensitive member 21 by a registration roller 34. .

  The sheet P on which the toner image is transferred by the transfer unit 27 in the transfer area 35 is separated from the photoreceptor 21 by the separation claw 26 and is heated and pressed by the heating unit 41 and the pressurizing unit 42 of the fixing device 4. Is fixed to the paper P.

  The paper P on which the toner image is fixed is sandwiched between the paper discharge rollers 37 and discharged from the discharge port 38 to the outside of the apparatus.

  Note that the reference position Z0, the charging facing position Z1, the exposure facing position Z2, the potential measuring position Z3, the developing facing position Z4, and the density measuring position Z5 indicate the positions in the circumferential direction of the photoconductor 21, respectively. This will be described in detail with reference to FIG.

  Hereinafter, in order to facilitate understanding of the invention, the potential of the toner image and the density of the toner image when the image flow does not occur normally and when the image flow occurs abnormally will be described.

  FIG. 2 is an explanatory diagram relating to the potential of the toner image and the density of the toner image when the image is normal and when the image flow occurs.

  FIG. 2A shows the potential distribution on the surface of the photoconductor when predetermined exposure is performed in each of a normal time when no image flow occurs in the output image and an abnormal time when image flow occurs. The horizontal axis indicates the axial position of the photoconductor 21, and the vertical axis indicates the potential.

  When the image flow is not normal (solid line), the potential of the exposed portion is the target value x. When the image flow is abnormal (dashed line), the charge on the surface of the photoreceptor is low because of the low resistance. As a result, the electric potential does not become the target value x, and an inverted mountain shape in which the electric potential flows around the exposed portion is formed.

  One of the features of the present invention is that, as described above, the potential becomes the target potential when the image flow does not occur normally, but the potential does not become the target value when the image flow occurs abnormally. This is used to detect the occurrence of image flow.

  FIG. 2B shows a photoconductor when a predetermined exposure is performed to form a latent image and the latent image is developed in each of a normal time when no image flow occurs and an abnormal time when image flow occurs. The density distribution of the toner image formed on the surface is shown, the horizontal axis shows the axial position of the photoreceptor 21, and the vertical axis shows the density.

  When the image flow is not normal (solid line), the density of the exposed portion is the target value y, but when the image flow is abnormal (dashed line), the density is the target value y. Not only does this occur, it becomes a mountain shape in which the density flows out around the exposed area.

  Hereinafter, the difference in density between normal and abnormal will be described.

  FIG. 3 is an explanatory diagram of a γ curve of the toner image when the image flow does not occur normally and when the image flow occurs abnormally.

  In the figure, the horizontal axis indicates the input (exposure amount of the latent image), the vertical axis indicates the output (toner image density), the solid line indicates the normal density without image flow, and the broken line indicates the image. It shows the concentration at the time of abnormal flow.

  The relationship between input and output in a normal state is generally an arc (solid line) slightly lower than a line (dot-dash line) in which input and output are directly proportional.

  However, the relationship between input and output at the time of anomaly that causes image flow is a curve (broken line) like a hysteresis curve. For example, when the input is 20% and 70%, the output value (solid line) at the normal time is used. As a result, the output value (broken line) at the time of abnormality is greatly shifted.

  In normal operation, individual dots are clearly formed, whereas in abnormal conditions, individual dots become thinner due to image flow when the input is low, and individual dots due to image flow when the input is high. This is due to the crushing and becoming solid and dark.

  One of the features of the present invention is that, as described above, the density at the time of low input and at the time of high input is greatly deviated from the density at the time of normal when the image flow is abnormal. Is used to detect the occurrence of image flow.

  FIG. 4 is an explanatory diagram of a patch formed on the photoconductor and a sensor for detecting the patch.

  4A is a view of the photoconductor 21 as viewed from the side, and FIG. 4B is a view (perspective view) of the photoconductor 21 as viewed obliquely. In FIG. 4B, the exposure unit 22, the developing unit 23, and the charging unit 24 are omitted for easy understanding of the drawing.

  4A and 4B, a charging unit 24 that uniformly charges the photoconductor in the rotation direction of the photoconductor 21 is provided around the photoconductor 21 that rotates in the direction of arrow b, and the photoconductor. 21, an exposure unit 22 that forms a latent image, a potential sensor 211 that is a potential measurement unit that measures the potential of the latent image formed by the exposure unit 22, a developing unit 23 that visualizes the latent image with toner, A density sensor 212 which is a density measuring unit for measuring the density of the toner image is provided.

  When the time measuring unit for measuring the time when the photosensitive member 21 is stopped (hereinafter, the time measuring unit is referred to as an image formation stop timer TM) detects that the photosensitive member 21 has been stopped for a predetermined time, the charging unit 24 is charged. A photoconductor phase sensor 213, which is a detection unit that detects the charging counter position Z <b> 1 that is the position of the photoconductor 21 facing the photoconductor 21, is connected to the photoconductor 21.

  Here, the potential sensor 211 is disposed downstream of the exposure unit 22 and upstream of the developing unit 23, and the density sensor 212 is disposed downstream of the developing unit 23 and upstream of the transfer region 35 (not shown). It is installed.

  The potential sensor 211 includes a first potential sensor 211a and a second potential sensor 211b that are provided apart from each other in the axial direction of the photoconductor 21.

Then, the first potential sensor 211a measures the potential of a _first latent image S ₁ (not shown) and a third latent image S ₃ (not shown) which will be described later, and the second potential sensor 211b is a second potential sensor which will be described later. The potentials of the latent image S ₂ (not shown) and the fourth latent image S ₄ (not shown) are measured.

  The density sensor 212 includes a first density sensor 212 a and a second density sensor 212 b that are provided apart from each other in the axial direction of the photoconductor 21.

Then, a first patch P ₁ below the first density sensor 212a is developing a latent image S ₁ of the first _(not shown), the third of the third patch later developing the latent image S ₃ The density of P ₃ (not shown) is measured. The fourth patch _{P 4} of the second density sensor 212b is developed and the development and second patch _{P 2} below were (not shown), a latent image _{S 4} of the fourth to the second latent image _{S 2} (Not shown) is measured.

  Outputs of the potential sensor 211, the density sensor 212, and the photoconductor phase sensor 213 are input to the control unit C, respectively.

  When it is detected by the image formation stop timer TM that measures the time that the photosensitive member 21 is stopped, that the photosensitive member 21 has stopped for a predetermined time, the position on the photosensitive member 21 that faces the charging unit 24 is set as the charging opposing position Z1. Called.

  The charging opposing region S1 is a region on the photosensitive member 21 where the photosensitive member 21 and the charging unit 24 face each other at the charging opposing position Z1 [FIG. 4 (b) one-dot chain line]. Therefore, the charging counter area S1 moves in the direction of arrow b as the photosensitive member 21 rotates.

  As described above, when the image formation is not performed for a long time (the photoconductor does not rotate) and the same position of the photoconductor 21 is opposed to the charging unit 24 for a long time as described above, Ion products are generated by the ozone remaining in the facing region where the body 21 and the charging unit 24 face each other, and the ion products adhere to the photoreceptor 21 to reduce the resistance of the surface of the photoreceptor (generation of image flow). It is also an area.

  Further, the reference position Z0 deviates from the position where the photosensitive member 21 and the charging unit 24 face each other when the image formation stop timer TM that measures the stop time of the photosensitive member 21 detects that the photosensitive member 21 has stopped for a predetermined time. Further, it is the circumferential position of the photoreceptor where no image flow occurs.

  The reference region S0 is a region of the photosensitive member 21 (a broken line in FIG. 4B) where the photosensitive member 21 and the charging unit 24 do not face the charging unit 24 at the reference position Z0. Accordingly, the reference position Z0 moves in the direction of arrow b as the photoconductor 21 rotates.

  Further, the reference region S0 is a region where the ion product does not adhere to the photoconductor 21 even if the photoconductor 21 is stopped for a long time.

  The exposure facing position Z <b> 2 is a circumferential position of the photoconductor 21 that faces the exposure position of the exposure unit 22. Therefore, the reference position Z2 does not move even if the photoconductor 21 rotates.

When the charged area S1 and the reference area S0 by the rotation of the photosensitive member 21 reaches the respective exposure facing position Z2, the exposure unit 22 and the first latent image S ₁ of the aforementioned second and the latent image S ₂ third latent An image S ₃ and a fourth latent image S ₄ are formed on the photoconductor 21.

  The potential measurement position Z3 is a circumferential position of the photoreceptor facing the potential sensor 211. Therefore, the reference position Z3 does not move even if the photoconductor 21 rotates.

When the rotation of the photosensitive member 21 and the charging region S1 and the reference area S0, respectively reaches the potential measurement position Z3, the aforementioned formed by exposure facing position Z2 of the first latent image S _{1 ~} fourth latent image S ₄ The potential sensor 211 measures the potential.

  The development facing position Z4 is a circumferential position of the photoconductor facing the development position of the developing unit 23. Therefore, the reference position Z4 does not move even if the photoconductor 21 rotates.

When the rotation of the photosensitive member 21 and the charging region S1 and the reference area S0 reaches the developing position facing Z4 respectively, the first latent image S _{1 ~} fourth latent described above the developing unit 23 is formed at the exposure position opposite Z2 developing the image _{S 4.}

  The density measurement position Z5 is a circumferential position of the photoconductor 21 facing the density sensor 212. Therefore, the reference position Z5 does not move even when the photosensitive member 21 rotates.

When the charged area S1 and the reference area S0 by the rotation of the photosensitive member 21 reaches the density measurement position Z5, respectively, the first patch P ₁ described above the concentration sensor 212 is formed in the developing position facing Z4 and second patch P ₂ and the third patch _{P 3} the concentration of the fourth patch _{P 4} is measured.

  FIG. 5 is a flowchart according to the image flow occurrence detection mode.

  Hereinafter, a method for detecting the occurrence of image flow will be described with reference to FIGS. The program relating to the flow shown in FIG. 5 is stored in the storage unit of the control unit C, and is read and executed by the CPU of the control unit C.

  The image flow occurrence detection mode shown in FIG. 5 is a mode for detecting the occurrence of image flow. When the machine is turned on or returned from the sleeping mode, an image is formed when the machine is returned from a state where it is left for a long time. This is executed when it is detected by the stop timer TM that the photoconductor 21 has stopped for a predetermined time.

1. Detection of whether or not the photoreceptor has stopped for a predetermined time (step S1)
When the above-described image formation stop timer TM that measures the stop time of the photoconductor 21 detects the stop of the photoconductor 21 over a predetermined time (Yes), the control unit C determines that there is a possibility of image flow. Proceed to the next step.

  When the time of the image formation stop timer TM is less than the predetermined time (No), the photosensitive member 21 is not stopped for a predetermined time or more and it is determined that there is no possibility of image flow, so that image formation can be performed. move on.

  Here, the predetermined time of the image formation stop timer TM is the longest stop time of the photoconductor 21 that is assumed to cause no image flow, and is a value determined in advance by experiments or the like.

2. Storage of photoconductor position (step S2)
When the image formation stop timer TM detects the stop of the photoconductor 21 for a predetermined time or longer, the output of the photoconductor phase sensor 213 is read and the position of the photoconductor facing the charging unit 24 (the charging counter of FIG. 4). The position Z1) is stored. That is, a portion where there is a possibility of image flow is stored.

  At the same time, the photosensitive member position (reference position Z0 in FIG. 4) not facing the charging unit 24 is stored. That is, a portion where there is no possibility of image flow is stored, and the process proceeds to the next step.

3. Formation of patch latent image (step S3)
The current position where the charging facing position Z1 and the reference position Z0 are moved by the rotation of the photosensitive member 21 is acquired.

  When the charging counter position Z1 and the reference position Z0 reach the exposure counter position Z2 of the exposure unit 22, the exposure unit 22 forms latent images corresponding to the following patches at the charging counter position Z1 and the reference position Z0, respectively. .

Specifically, when the charge opposite position Z1 of the photosensitive member reaches the exposure position facing Z2 of the exposure section 22, the exposure unit 22, a first latent image S ₁ for forming a first patch P ₁ first the formed with an exposure amount L _1, to form a second latent image S ₂ to form the second patch P ₂ in the first exposure amount L ₁ larger second exposure amount L _2.

Further, when the reference position Z0 of the photosensitive member reaches the exposure position facing Z2 of the exposure section 22, the exposure unit 22, a third latent image S ₃ of forming a third patch P ₃ the first exposure amount L formed by _1, the fourth latent image S ₄ to form a fourth patch P ₄ is formed by the second exposure amount L _2, the process proceeds to the next step.

The first exposure amount L ₁ is an exposure amount at which the density becomes approximately 20% when the first patch P ₁ and the third patch P ₃ are formed without causing image flow. The exposure amount L ₂ of ₂ is an exposure amount at which the density becomes approximately 70% when the second patch P ₂ and the fourth patch P ₄ are formed without causing image flow.

  The reason why the density is about 20% and about 70% is as described with reference to FIG. 2 and FIG. 3, as compared with the potential and density when the image flow is caused, and the potential and density when the flow is not caused. However, it is significantly different and easy to detect.

4). Measurement of the potential of the patch latent image (step S4)
The current position where the charging facing position Z1 and the reference position Z0 are moved by the rotation of the photosensitive member 21 is acquired.

  When the charging facing position Z1 and the reference position Z0 reach the potential measurement position Z3, the non-contact potential sensor 211 measures the potential of the latent image.

  For this reason, the potential measurement control unit (control unit C) detects the potential of the latent image formed by the exposure unit 22 at the reference position Z0 off the charging facing position Z1 on the photoconductor 21 by the potential measurement unit (potential sensor 211). And the potential of the latent image formed by the exposure unit 22 at the charging facing position Z1 is measured by the potential measurement unit (potential sensor 211).

Specifically, when the charge opposite position Z1 of the photosensitive member reaches the potential measurement position Z3 of the potential sensor 211, the first latent image _{S 1} potential at the first potential sensor 211a (first latent image potential _E 1) It was measured, measuring a second potential sensor 211b in the second latent image _{S 2} potential (second latent image potential _{E 2).}

Further, when the reference position Z0 of the photosensitive member reaches the potential measurement position Z3 of the potential sensor 211, a third potential of the latent image _{S 3} (third latent image potential _{E 3)} measured by the first electric potential sensor 211a, fourth potential of the latent image _{S 4} (fourth image potential _{E 4)} is measured at the second potential sensor 211b.

  Then, each measured value is stored and the process proceeds to the next step.

5. Development of patch latent image (step S5)
The current position where the charging facing position Z1 and the reference position Z0 are moved by the rotation of the photosensitive member 21 is acquired.

  When the charging facing position Z1 and the reference position Z0 reach the developing facing position Z4, the developing unit 23 develops the latent image formed in step S3.

Specifically, when the charge opposite position Z1 of the photoreceptor reaches the development position opposite Z4, the developing unit 23, the first to form a patch P ₁ is developed first a latent image S _1, second a latent image S ₂ to form the second patch P ₂ and developed.

Further, when the reference position Z0 of the photoreceptor reaches the development position opposite Z4, the developing unit 23, a third latent image S ₃ form a third patch P ₃ is developed, the fourth latent image S ₄ by developing the form the fourth patch P _4, the process proceeds to the next step.

6). Patch density measurement (step S6)
The current position where the charging facing position Z1 and the reference position Z0 are moved by the rotation of the photosensitive member 21 is acquired.

  When the charging facing position Z1 and the reference position Z0 reach the density measurement position Z5, the density sensor 212 measures the density of the patch.

Specifically, when the charge opposite position Z1 of the photosensitive member reaches the density measurement position Z5 of the density sensor 212, the first density of the patch P ₁ at a first concentration sensor 212a measures (first patch density D ₁ ), the second concentration of the patch _{P 2} measured by the second density sensor 212b (second patch density _D 2).

Further, when the reference position Z0 of the photosensitive member reaches the density measurement position Z5 of the density sensor 212, at a first concentration sensor 212a measures the third density of the patch _{P 3} (third patch density _D 3), the second measuring the concentration of the fourth patch _{P 4} at a concentration sensor 212b (fourth patch density _D 4).

  Then, each measured value is stored and the process proceeds to the next step.

7). Calculation of difference between reference potential and measurement potential (step S7)
A potential tendency corresponding to the γ curve with respect to the potential of the latent image at the reference position Z0 where no image flow occurs, and a potential tendency corresponding to the γ curve with respect to the potential of the latent image at the charging facing position Z1 where image flow may occur. And analogy with the difference.

  For this reason, the potential sensor 211 measures the measured potential of the latent image formed at the reference position Z0, that is, when the reference position Z0 reaches the position facing the potential measurement unit (potential sensor 211) by the rotation of the photosensitive member 21. The reference potential which is the potential of the latent image formed at the reference position Z0 and the measured potential of the latent image formed at the charging facing position Z1, that is, the charging facing position Z1, When the position opposite to the potential sensor 211) is reached, a difference between the charge facing position potential, which is the potential of the latent image formed at the charging facing position Z1 measured by the potential sensor 211, is calculated.

Specifically, measured in the step S4, the first latent image S ₁ potential is one of the charging position opposed potential (a first latent image potential E _1), the third is one of the reference potential A first potential difference Df _E1 , which is the difference between the potential of the latent image S ₃ (third latent image potential E ₃ ), is calculated.

Further, the potential of the second latent image S ₂ (second latent image potential E ₂ ), which is one of the charging opposing position potentials, and the potential of the fourth latent image S ₄ (fourth latent potential), which is one of the reference potentials. A second potential difference Df _E2 which is the difference between the image potential E ₄ ) and the image potential E ₄ ) is calculated, and the process proceeds to the next step.

Incidentally, when calculating the first potential difference Df _E1 is previously found through experiment or the like in advance a potential corresponding to the third latent image potential E ₃ that does not cause image flow, instead of the third latent image potential E ₃ It may be calculated using this. Also, when calculating the second potential difference Df _E2 is previously found through experiment or the like in advance a potential corresponding to the fourth latent image potential E ₄ which does not cause image flow, instead of the fourth latent image potential E ₄ It may be calculated using this.

8). Determination of occurrence of image flow (step S8)
When the difference calculated in step S7 exceeds the first predetermined value, it is determined that image flow has occurred.

Specifically, if one of the first potential difference Df _E1 and the second potential difference Df _E2 calculated in step S7 is greater than or equal to the first predetermined value (No), it is determined that image flow has occurred and step S11 is performed. If both the first potential difference Df _E1 and the second potential difference Df _E2 are less than the first predetermined value (Yes), it is determined that the potential is normal (no image flow is likely to occur) and the process proceeds to the next step.

In order to ensure the determination of the occurrence of image flow, if both the first potential difference Df _E1 and the second potential difference Df _E2 are equal to or greater than the first predetermined value (No), image flow occurs. You may make it determine that it carried out and to make it progress to step S11.

9. Calculation of difference between reference concentration and measured concentration (step S9)
The difference between the γ curve of the density of the toner image at the reference position Z0 where no image flow occurs in the output image and the γ curve of the density of the toner image at the charging facing position Z1 where image flow may occur in the output image is calculated. Analogy.

  For this reason, the density of the patch that does not cause image flow in the output image is measured by the density measurement unit (density sensor 212), and the density of the patch that generates image flow in the output image is determined. The difference between the abnormal part measurement density which is the density of the abnormal part measured by the sensor 212 is calculated.

Specifically, the density of the first patch P ₁ (first patch density D ₁ ), which is one of the abnormal part measured densities, and the third patch P, which is one of the reference densities, measured in step S6. _A first density difference Df _D1 that is a difference from the density of 3 (third patch density D ₃ ) is calculated.

Also, the density of the second patch P ₂ (second patch density D ₂ ), which is one of the charging opposing position potentials, and the density (fourth patch density D) of the fourth patch P ₄ , which is one of the reference potentials. ₄ ) A second density difference Df _D2 that is a difference from the above is calculated, and the process proceeds to the next step.

Incidentally, when calculating the first concentration difference Df _D1 is previously found through experiment or the like in advance the concentration corresponding to the third patch density D ₃ which does not cause image blurring, instead of the third patch density D ₃ You may calculate using this. Also, when calculating the second concentration difference Df _D2 is previously found through experiment or the like in advance the concentration corresponding to the fourth patch density D ₄ which does not cause image blurring, instead of the fourth patch density D ₄ You may calculate using this.

10. Determination of occurrence of image flow (step S10)
When the difference calculated in step S9 is greater than or equal to the second predetermined value, it is determined that image flow has occurred.

Specifically, if one of the first density difference Df _D1 and the second density difference Df _D2 calculated in step S9 is equal to or greater than a predetermined value (No), it is determined that image flow has occurred, and the process proceeds to step S11. If both the first density difference Df _D1 and the second density difference Df _D2 are less than a predetermined value (Yes), it is determined that the γ characteristic curve is normal, that is, there is no possibility of image flow, and the process proceeds to step S12. .

In order to ensure the determination of the occurrence of the image flow, if both the first density difference Df _D1 and the second density difference Df _D2 are equal to or greater than the second predetermined value (No), the image flow is determined. It may be determined that the error has occurred and the process may proceed to step S11.

11. Execution of recovery mode (step S11)
A recovery mode, which will be described later, for polishing the surface of the photoreceptor 21 is executed, and when the recovery mode ends, the process proceeds to the next step.

12 Execution of image formation (step S12)
Start or restart image formation according to the job, and proceed to the end.

  In the case of image formation in step S12 after executing the recovery mode in step S11, it is confirmed that there is no possibility of image flow by executing steps S2 to S11, and then image formation corresponding to the job is performed. May be started or resumed.

Further, in the determination of the occurrence of image flow in step S8, if the first potential difference Df _E1 and the second potential difference Df _E2 calculated in step S7 are each less than a predetermined value (Yes), the potential abnormality that is a cause of density abnormality Therefore, it may be determined that there is no possibility of image flow and step S9 and step S10 are not executed (the determination based on the density is not performed), and the process may proceed to step S12.

  In this case, step S5 and step S6 relating to density measurement may not be executed, and the process may proceed from step S4 to step S7.

Further, step S8 and step S9 are not performed, and in the determination of image flow occurrence in step S10, at least one of the first density difference Df _D1 and the second density difference Df _D2 calculated in step S9 is a second predetermined value. If it is equal to or greater than the value (No), it is determined that image flow has occurred, and the process proceeds to step S11. If the first density difference Df _D1 and the second density difference Df _D2 are each less than a predetermined value (Yes), the image is displayed. It may be determined that no flow has occurred and the process may proceed to step S12.

  In this case, step S4 relating to the potential measurement may not be performed and the process may proceed from step S3 to step S5.

  As described above, by measuring the potential of the latent image formed on the photoconductor and / or the density of the toner image carried on the photoconductor, it is possible to reliably detect the occurrence of image flow and It is possible to prevent erroneous detection of image flow despite no occurrence.

  Note that the charging unit 24, the exposure unit 22, the potential measuring unit 211, the time measuring unit (image formation stop timer TM), the detecting unit (photoconductor phase sensor 213), the potential measuring control unit, and the determining unit (described above). (One function of the control unit) also functions as an image flow detection device that detects image flow.

  FIG. 6 is an explanatory diagram (side view) of the photosensitive member surface repair portion.

  The photoconductor surface repair unit 5 that polishes the surface of the photoconductor 21 has at least a cleaning unit 52. When the difference between the reference potential and the charged counter position potential becomes equal to or greater than a first predetermined value, image flow is improved. When the determination unit (control unit C) that determines that the image has occurred, determines that the image flow has occurred, the photoconductor surface repair unit 5 polishes the surface of the photoconductor 21.

  Hereinafter, the case where the photoconductor surface repair unit 5 includes the cleaning unit 52 and the cleaning blade 51 will be described.

  The cleaning blade 51 has a tip 511 that is in contact with the photosensitive member 21, and when the toner attached to the tip 511 is polished by rubbing the photosensitive member 21 rotating by the tip 511, the surface of the photosensitive member 21 is polished. At the same time, the toner remaining on the photoreceptor 21 is removed.

  The cleaning unit 52 includes a cleaning brush unit 53 and a flicker roller unit 54.

  The cleaning brush unit 53 includes a rotation shaft 531, a brush 532 radially planted on the surface of the rotation shaft 531, and a rotation driving unit 533 that rotates the brush 532 in the direction of arrow c.

  The tip 534 of the loop-shaped brush 532 made of a polyester material is in contact with the photoconductor 21, and the tip 534 rubs against the photoconductor 21 by the rotation of the brush 532, so that it adheres to the brush 532. The toner thus polished polishes the surface of the photoreceptor 21.

  In addition, by making the shape of the brush 532 into a loop shape, it is easy to hold the toner on the brush 532 and the polishing property of the photosensitive member 21 is improved.

  The flicker roller unit 54 includes a flicker roller 541 that is in sliding contact with the brush 532 of the cleaning brush unit 53 and is grounded, and a roller moving unit 543 that can move the flicker roller 541 toward the photosensitive member 21. .

  The roller moving unit 543 can adjust the position of the flicker roller 541 with respect to the brush 532.

  Here, when the overlap between the flicker roller 541 and the brush 532 increases, the force with which the flicker roller 541 slides on the brush 532 increases (the force to eject the toner adhering to the brush 532 increases), and the toner adhering to the brush 532 increases. As a result, the surface of the photoconductor 21 is less polished by the brush 532.

  Further, when the overlap between the flicker roller 541 and the brush 532 is reduced, the force with which the flicker roller 541 slides on the brush 532 is reduced (the force for ejecting the toner adhering to the brush 532 is reduced), and the toner adhering to the brush 532 is reduced. As the amount increases, polishing of the surface of the photoreceptor 21 by the brush 532 increases.

  In the above description, when the cleaning blade 51 is not provided in the photoconductor surface repair unit 5, the cleaning blade 51 for removing the toner remaining on the photoconductor 21 is provided on the downstream side of the photoconductor surface repair unit 5.

  Hereinafter, a method for repairing the surface of the photoreceptor will be described with reference to FIG.

  Note that the photoconductor surface repair described below corresponds to the execution of the recovery mode in step S11 in the flowchart relating to the above-described image flow occurrence detection mode.

  In addition, any one of a plurality of recovery modes described below may be executed, but a plurality of recovery modes may be executed simultaneously.

  The recovery mode of the first form will be described.

  When the control unit C, which is the determination unit, determines that image flow has occurred, the rotation number of the brush 532 is changed by the rotation driving unit 533 with respect to the current rotation number of the brush 532 of the cleaning brush unit 53. The relative speed between the brush 532 and the surface of the photoconductor 21 is increased, and the polishing ability of the surface of the photoconductor 21 by the toner attached to the brush 532 is improved.

  For example, the rotational speed of the tip of the brush 532 is preferably lowered to 330 mm / S, for example, compared to 570 mm / S at normal times.

  Then, image formation is performed for a predetermined time in a state where the polishing ability is improved, and the rotational speed of the brush 532 is returned to the original after the predetermined time has elapsed.

  The cleaning blade 51 rubs the photoconductor 21 rotating at the tip 511 so that the toner attached to the tip 511 polishes the surface of the photoconductor 21 and at the same time removes the toner remaining on the photoconductor 21. .

  As described above, by changing the number of rotations of the brush 532, the relative speed between the brush 532 and the surface of the photoconductor 21 is increased, and the polishing ability of the surface of the photoconductor 21 by the toner adhering to the brush 532 is improved. Can do.

  The recovery mode of the second form will be described.

  When the determination unit (control unit C) determines that image flow has occurred, the amount of toner attached to the cleaning blade 51 and the brush 532 is increased.

  Specifically, the toner amount of the toner band formed between the toner images for one page is increased, and the toner band with the increased toner amount is not transferred to the paper P and is conveyed as it is to the photoreceptor surface repair unit 5. Let

  The increase in the toner amount of the toner band is a value obtained in advance by experiments or the like, and the width of the toner band in the sub-scanning direction is increased to, for example, 5 mm when the amount of adhered toner is increased, while the normal width is, for example, 1 mm. It is preferable.

  Then, the toner in the toner band having an increased width is attached to the brush 532 of the photoconductor surface repair unit 5, and the polishing ability of the surface of the photoconductor 21 is improved by the increased adhering toner.

  Then, image formation is performed for a predetermined time with the polishing ability improved, and the toner amount per unit area of the toner band is restored after the predetermined time has elapsed.

  The cleaning blade 51 rubs the photoconductor 21 rotating at the front end portion 511 so that more toner attached to the front end portion 511 is polished on the surface of the photoconductor 21 and remains on the photoconductor 21 at the same time. Remove toner.

  As described above, the toner amount attached to the brush 532 and the cleaning blade 51 is increased by increasing the width of the toner band, so that the surface of the photoreceptor 21 can be polished by the toner attached to the brush 532 and the cleaning blade 51. Can be further improved.

  A third mode of recovery mode will be described.

  When the determination unit (control unit C) determines that image flow has occurred, the relative distance of the flicker roller 541 to the brush 532 is increased with respect to the current position of the flicker roller 541 with respect to the brush 532.

  Thereby, the amount of overlap of the flicker roller 541 with the brush 532 is reduced, and the force for ejecting the toner attached to the brush 532 is reduced. As a result, the amount of toner attached to the brush 532 increases, and the polishing ability of the surface of the photoreceptor 21 by the toner attached to the brush 532 can be improved.

  Note that the overlap amount of the flicker roller 541 with respect to the brush 532 is a value obtained in advance by experiments or the like, and is preferably set to, for example, 0 mm when increasing the amount of adhered toner, compared to 0.6 mm for normal time.

  Then, image formation is performed for a predetermined time with the polishing ability improved, and the distance of the flicker roller 541 to the brush 532 is restored after the predetermined time has elapsed.

  The cleaning blade 51 rubs the photoconductor 21 rotating at the tip 511 so that the toner attached to the tip 511 polishes the surface of the photoconductor 21 and at the same time removes the toner remaining on the photoconductor 21. .

  As described above, the amount of toner adhering to the brush 532 is increased by increasing the relative distance of the flicker roller 541 with respect to the brush 532, and the polishing ability of the surface of the photoconductor 21 by the toner adhering to the brush 532 is improved. be able to.

  The recovery mode of the first mode, the recovery mode of the second mode, and the recovery mode of the third mode have been described as performing image formation for a predetermined time in a state where the polishing capability is improved. In this state, a predetermined number of images may be formed.

  The recovery mode according to the configuration in which the cleaning surface 51 and the cleaning brush portion 53 are provided in the photoconductor surface repair portion 5 has been described above. However, the cleaning brush portion 53 is provided by providing only the cleaning brush portion 53 in the photoconductor surface repair portion 5. The surface of the photosensitive member 21 may be polished.

  In this case, the photosensitive member surface repairing part 5 has only the action related to the cleaning brush part 53 without the action related to the cleaning blade 51 described above.

  The cleaning blade 51 disposed on the downstream side of the photosensitive member surface repairing part 5 mainly functions to remove the toner remaining on the photosensitive member 21, and particularly in the recovery mode of the second embodiment, the photosensitive member surface repairing part. Since the amount of toner conveyed to 5 increases, it has the effect of polishing the surface of the photoreceptor 21 as a secondary function.

  As described above, it is possible to detect the occurrence of image flow, and when it is detected, the surface of the photoconductor can be efficiently polished, and the occurrence of image flow can be prevented.

  The monochrome image forming apparatus has been described above as an example. Needless to say, the color image forming apparatus A ′ can be applied to the above-described image flow detection and the photoreceptor surface repair unit 5. A configuration in the case where the photoreceptor surface repair unit 5 is applied to the image forming apparatus A ′ is shown.

  FIG. 7 is an explanatory diagram of a color image forming apparatus.

  Members having the same functions as those of the monochrome image forming apparatus described above are given the same part numbers. For this reason, description of similar members is omitted.

  The endless belt-shaped intermediate transfer member 28 is rotatably stretched by rollers 281, 282, 283, and 284, and is driven in the direction of arrow a ′ via the roller 283 by a driving device (not shown).

  The intermediate transfer member 28 is provided with the photosensitive members 21 (21Y, 21M, 21C, and 21K) for the respective colors facing each other. 24, the exposure unit 22, the potential sensor 211, the developing unit 23, the density sensor 212, and the photoconductor surface repair unit 5 are disposed. For each photoconductor, detection of image flow and polishing of the surface of the photoconductor are performed when the occurrence of image flow is detected.

  Then, the color toner images carried on the intermediate transfer body 28 are collectively transferred onto the paper P by the pressing of the secondary transfer roller 36. Further, the toner remaining on the intermediate transfer body 28 without being transferred to the paper P is removed by the cleaning unit 29.

  Needless to say, the cleaning unit 29 may not be provided, and the remaining toner may be removed by the cleaning blade 51 of the photoreceptor surface restoration unit 5.

  In this case, it is possible to detect the image flow on each photoconductor and to polish the photoconductor when detecting the image flow, and to prevent the output image from being degraded due to the image flow.

  As another form, the potential sensor 211 and the density sensor 212 are not arranged on each photoconductor, the photoconductor surface repairing part 5 is arranged facing each photoconductor 21, and the density sensor 212 (not shown) is intermediately transferred. You may arrange | position facing the body 28. FIG.

  In this case, a density sensor 212 is provided on the intermediate transfer body 28 on the downstream side of the secondary transfer unit 37 and on the upstream side of the cleaning unit 29. In the photosensitive member 21, the downstream side of the transfer unit 27 and the upstream side of the charging unit 24. Is provided with a photoconductor surface repair unit 5, and the image sensor detects the image flow by measuring the density of the color toner patch by the density sensor 212 arranged on the intermediate transfer member 28, and the photoconductor arranged on the photoconductor 21 when the occurrence of the image flow is detected. The photoconductor 21 is polished by the body surface repair unit 5.

  In this case, the photosensitive member surface repairing part 5 may be provided so as to face the intermediate transfer member 28, and the surface of the intermediate transfer member 28 soiled by the photosensitive member surface repairing part 5 can be polished.

  As described above, even in a color image forming apparatus, it is possible to detect the occurrence of image flow, and if detected, the surface of the photoconductor can be polished efficiently, and the occurrence of image flow can be prevented. It becomes.

DESCRIPTION OF SYMBOLS 5 Photoconductor surface restoration part 21 Photoconductor 22 Exposure part 23 Developing part 24 Charging part 28 Cleaning part 51 Cleaning blade 52 Cleaning part 53 Cleaning brush part 54 Flicker roller part 211 Potential sensor 212 Density sensor 213 Photoreceptor phase sensor 532 Brush A Image Forming device C control unit

Claims (16)

A charging unit that uniformly charges the photoconductor;
An exposure unit for forming a latent image on the photoreceptor;
An electric potential measuring unit for measuring the electric potential of the latent image formed by the exposure unit provided facing the photoconductor;
A time measuring unit for measuring the time during which the photosensitive member is stopped;
A detection unit that detects a charging facing position that is a position of the photosensitive member facing the charging unit when the timing unit detects that the photosensitive member has been stopped for a predetermined time; and
A reference potential obtained by measuring the potential of the latent image formed by the exposure unit at a reference position off the charging counter position on the photoconductor, and a potential of the latent image formed by the exposure unit at the charging counter position. A potential measurement control unit that measures the measured charge-facing position potential and the potential measurement unit;
A determination unit that determines that an image flow has occurred when a difference between the reference potential and the charging counter position potential is equal to or greater than a first predetermined value;
An image flow detection device comprising: The reference potential is a potential of a latent image formed at the reference position measured by the potential measurement unit when the reference position reaches a position facing the potential measurement unit by rotation of the photoconductor,
The charging counter position potential is determined based on the latent image formed at the charging counter position measured by the potential measuring unit when the charging counter position reaches a position facing the potential measuring unit by rotation of the photoconductor. Is a potential,
The image flow detection apparatus according to claim 1, wherein The exposure unit forms a first latent image forming a first patch with a first exposure amount at the charging facing position, and forms a second latent image forming a second patch on the first latent image. A third latent image is formed with a second exposure amount larger than the exposure amount, and a third latent image for forming a third patch is formed with the first exposure amount at the reference position, thereby forming a fourth patch. 4 latent images are formed with the second exposure amount,
The determination unit has a first potential difference that is a difference between a third latent image potential that is a potential of the third latent image and a first latent image potential that is a potential of the first latent image, It is determined that image flow has occurred when the first predetermined value is exceeded.
The image flow detection device according to claim 2, wherein   The determination unit is one of the reference potential and the fourth latent image potential that is the potential of the fourth latent image, and one of the charging opposing position potentials, which is measured by the potential measurement unit. It is determined that image flow has occurred when a second potential difference, which is a difference between the second latent image potential and the second latent image potential, is equal to or greater than the first predetermined value. The image flow detection device according to claim 3. A developing unit for developing the latent image formed on the photoreceptor;
A density measuring unit that measures the density of the first patch, the second patch, the third patch, and the fourth patch formed by the developing unit;
The determination unit includes a reference density which is a density measured by the density measuring unit with respect to the density of the first patch, and a charged counter position density which is a density measured with the density measuring unit. 5. The image flow detection device according to claim 3, wherein an image flow is determined to occur when the difference between the first and second values exceeds a second predetermined value. 6. The reference density is a density of a patch formed at the reference position measured by the density measurement unit when the reference position reaches a position facing the density measurement unit by rotation of the photoconductor,
The density of the charging counter position is a density of the patch formed at the charging counter position measured by the density measuring unit when the charging counter position reaches a position facing the density measuring unit by rotation of the photoconductor. is there,
The image flow detection device according to claim 5. The developing unit forms the first patch and the second patch at the charging facing position, and forms the third latent image and the fourth patch at the reference position,
The determination unit determines that a first density difference, which is a difference between a third patch density that is the density of the third patch and a first patch density that is the density of the first patch, is the second density. It is determined that image drift has occurred when the value exceeds a predetermined value.
The image flow detection device according to claim 5 or 6, wherein   The determination unit measures the fourth patch density, which is one of the reference densities, and the second patch density, which is one of the charging opposing position densities, measured by the density measurement unit. 8. The method according to claim 7, wherein when the second density difference, which is a difference between the second patch density and the second patch density, becomes equal to or greater than the second predetermined value, it is determined that image flow occurs. The image flow detection device described. An image forming apparatus comprising the image flow detection device according to claim 1,
The determination unit has a photoconductor surface repair unit that polishes the surface of the photoconductor when it is determined that image flow has occurred,
The photoconductor surface repair unit includes a rotatable cleaning brush, a flicker roller that collects toner scraped by the cleaning brush, and a brush moving unit that can move the cleaning brush toward the photoconductor. And
The brush tip of the cleaning brush is in contact with the photoconductor, and the brush tip is rubbed against the photoconductor by the rotation of the cleaning brush. Polishing the surface,
An image forming apparatus.   When the determination unit determines that an image flow has occurred, the rotational speed of the cleaning brush is changed to increase the relative speed between the cleaning brush and the surface of the photoconductor, and the toner adhering to the cleaning brush The image forming apparatus according to claim 9, wherein a polishing ability of a surface of the photosensitive member is improved.   When the determination unit determines that image flow has occurred, the amount of toner adhering to the cleaning brush is increased, thereby improving the ability of the surface of the photoreceptor to be polished by the toner adhering to the cleaning brush. The image forming apparatus according to claim 9. Increasing the amount of toner per unit area of the toner band formed between toner images for one page,
The image forming apparatus according to claim 11, wherein the toner amount attached to the cleaning brush is increased by transporting the toner band having an increased toner amount to the photoconductor surface repair unit.   When the determination unit determines that image flow has occurred, the relative distance of the flicker roller to the cleaning brush is increased, thereby reducing the amount of overlap of the flicker roller with respect to the cleaning brush, thereby reducing the amount of the cleaning brush. The image forming apparatus according to claim 9, wherein the amount of toner adhering is increased to improve the polishing ability of the surface of the photoreceptor by the toner adhering to the cleaning brush. The photoconductor surface repair portion has a cleaning blade for removing toner remaining on the photoconductor,
The cleaning blade has a front end in contact with the photoconductor, and the surface of the photoconductor is polished with toner adhering to the front end by rubbing the photoconductor rotating the front end. The image forming apparatus according to claim 9, wherein the image forming apparatus is an image forming apparatus.   When the determination unit determines that image flow has occurred, the amount of toner adhering to the cleaning blade is increased, thereby improving the polishing ability of the surface of the photoreceptor by the toner adhering to the cleaning blade. The image forming apparatus according to claim 14. Increase the amount of toner in the toner band formed between the toner images for one page,
The image forming apparatus according to claim 15, wherein the toner amount attached to the cleaning blade is increased by transporting the toner band having an increased toner amount to the photoconductor surface repair unit.

Images