JPH11249521A - Photoreceptor drum protecting device for image forming device, and method for protecting photoreceptor drum for same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a photoreceptor drum from being damaged by a foreign matter. SOLUTION: This image forming device is provided with a blanking lamp for forming a belt-like latent image 64 over the width of the photoreceptor drum, outside of a latent image area 60 on the photoreceptor drum, developing means arranged opposite to the photoreceptor drum, for forming a toner layer on the latent image and on the belt-like latent image, controlling means adjusting the time interval for forming the belt-like latent image 64 and the length L of the belt-like latent image, corresponding to the toner cumulative consumption of the image forming device, and cleaning means disposed in slidably contact with the photoreceptor drum, for removing the residual toner on the photoreceptor drum. In such a case, for instance, the belt-like latent image 64 is formed for every time copying one sheet up to first 100 sheets after the operation of the image forming device, then subsequently the belt-like latent image 64 is formed for every time copying 50 sheets. Therefore, the foreign matter is smoothly removed by the toner between the cleaning blade and the photoreceptor drum, without damaging the photoreceptor drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a photosensitive drum protection device and a photosensitive drum protection method for an image forming apparatus. More specifically, the present invention relates to an apparatus for protecting a photosensitive drum of an image forming apparatus and a method for protecting a photosensitive drum in an image forming apparatus having a cleaning device for removing foreign matter on the photosensitive drum.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine usually has
A cleaning device is provided for removing toner remaining on the photosensitive drum from the photosensitive drum. The cleaning device has a blade that comes into sliding contact with the photoconductor drum, and the blade scrapes and removes residual toner on the photoconductor drum. In the early stage of the operation of the image forming apparatus, the blade of the cleaning device and the photosensitive drum are hardly adapted to each other, and the blade may be turned up due to friction between the two. For this reason, there is a method in which a toner layer is formed with a fixed length over the width of the photosensitive drum, and the toner layer is adjusted so as to be scraped off by a blade.
This is because, when an appropriate amount of toner is intentionally attached to the blade, the blade and the photosensitive drum are blended and smoothly in contact with each other, so that the blade can be prevented from turning over.

[0003]

However, by simply preventing the blade from turning up as in the prior art described above, foreign matter such as dust adhering to the photosensitive drum at the time of storage before operation may cause the blade and the photosensitive member to be moved in the early stage of operation. In some cases, the photosensitive drum is caught between the drum and the photosensitive drum. It is difficult to remove such foreign matter only by applying a large amount of toner at a time as in the related art. In addition, when the image forming apparatus is operated for a long time, a large amount of paper dust and the like generated in the image forming apparatus easily accumulates between the blade and the photosensitive drum. May cause scratches.

SUMMARY OF THE INVENTION An object of the present invention is to prevent a photosensitive drum from being damaged by foreign matters such as dust and paper dust and to protect a photosensitive drum of an image forming apparatus for forming a high-quality image for a long period of time. Is to provide.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus for applying toner to a latent image area formed on a photosensitive drum and removing residual toner. A protection device for an image forming apparatus, comprising a belt-shaped latent image forming unit, a developing unit, a control unit, and a cleaning unit.

The belt-like latent image forming means forms a belt-like latent image outside the latent image area on the photosensitive drum over the width of the photosensitive drum. The developing means is arranged to face the photosensitive drum,
A toner layer is formed on the latent image and the belt-like latent image. The controller adjusts the time interval for forming the belt-shaped latent image and the length of the belt-shaped latent image according to the accumulated amount of toner used in the image forming apparatus. The cleaning means is provided in sliding contact with the photosensitive drum, and removes residual toner on the photosensitive drum.

A toner layer is formed on the formed belt-like latent image. However, since this toner layer is out of the range of the sheet, the toner layer remains as it is and is removed by cleaning means such as a blade. Foreign matter such as dust is trapped between the blade and the photosensitive drum. The residual toner on the belt-like latent image enters between the blade and the photosensitive drum so as to wrap up the foreign matter between the blade and the photosensitive drum, and the foreign matter is also removed. Since the residual toner prevents direct contact between the foreign matter and the photosensitive drum, the foreign matter does not damage the photosensitive drum, and a high-quality image can be formed.

When the cumulative amount of toner used is small, it is considered that the amount of residual toner between the blade and the photosensitive drum is small. Should be adjusted so that a sufficient amount of residual toner is present. As the cumulative amount of toner used increases, the frequency of forming the belt-like latent image may be reduced. Since the toner consumption increases if the belt-shaped latent image is formed too long, the length of the belt-shaped latent image is appropriately adjusted according to the accumulated amount of toner used and the time interval for forming the belt-shaped latent image.

According to a second aspect of the present invention, in the photosensitive drum protection device of the image forming apparatus, the time interval for forming the belt-like latent image is adjusted by the control means. The adjustment is performed such that a band-shaped latent image is formed at a first time interval in an early stage of operation of the image forming apparatus, and a band-shaped latent image is formed at a second time interval after a predetermined time. This is performed so that the second time interval is longer than the interval.

For example, up to 100 copies at the start of operation,
A band-shaped latent image area is formed for each sheet, and thereafter, a band-shaped latent image is formed at an appropriate periodic interval, for example, for every 50 sheets, in the same manner as described above. It is possible to prevent the photoconductor drum from being damaged by dust that tends to adhere to the photoconductor drum during storage before use of the image forming apparatus or paper dust that adheres to the photoconductor drum by a copying operation.

According to a third aspect of the present invention, in the photosensitive drum protection device of the image forming apparatus, the image forming apparatus further includes a toner replenishing device for supplying the developing device with toner. The control means adjusts the time interval for forming the belt-like latent image and the length of the belt-like latent image based on the cumulative driving time of the toner supply device. If the band-shaped latent image is formed too frequently or its area is too large, expensive toner is wasted. Therefore, the accumulated usage amount of the toner is estimated based on the accumulated driving time of the toner replenishing device. If the accumulated driving time of the toner replenishing device is long, it is considered that the toner is being used more. Assume less. If the amount of toner used is large, it is considered that the amount of residual toner between the blade and the photosensitive drum is relatively large, so the frequency and length of the formation of the belt-like latent image are adjusted to be small. If toner usage is low,
Conversely, the frequency and length of the formation of the belt-like latent image are adjusted to be relatively large.

According to a fourth aspect of the present invention, there is provided the photosensitive drum protection device for an image forming apparatus according to the third aspect, wherein the control unit sets the time for forming the belt-like latent image as the cumulative driving time of the toner replenishing device becomes longer. Adjust so that the interval is longer. If the accumulated driving time of the toner replenishing device is long, the accumulated amount of toner used is large. Therefore, it is considered that a relatively large amount of residual toner exists between the cleaning device and the photosensitive drum. Therefore, the time interval for forming the belt-like latent image is adjusted to be longer as the accumulated toner usage increases, thereby preventing wasteful consumption of toner.

According to a fifth aspect of the present invention, there is provided a method for protecting a photosensitive drum of an image forming apparatus for applying toner to a latent image area formed on the photosensitive drum, comprising:
Provided is a method for protecting a photosensitive drum of an image forming apparatus, comprising a developing step, a control step, and a cleaning step. The band-shaped latent image forming step forms a band-shaped latent image over the width of the photosensitive drum outside the latent image area on the photosensitive drum. The development process is
A toner layer is formed on the latent image and the belt-shaped latent image so as to face the photosensitive drum. The control step adjusts the time interval for forming the band-shaped latent image and the length of the band-shaped latent image according to the accumulated amount of toner used in the image forming apparatus. In the cleaning step, residual toner on the photosensitive drum and foreign matters other than toner are removed.

A belt-like toner layer is formed on the belt-like latent image formed outside the latent image area corresponding to the paper, and the toner layer is removed by a cleaning means such as a blade. An appropriate amount of residual toner is present. It is considered that the residual toner wraps foreign matters such as paper dust and dust attached to the photosensitive drum, and is removed together with the foreign matters while protecting the photosensitive drum from the foreign matters. Therefore, it is possible to prevent damage to the photosensitive drum due to foreign matter that has caught between the blade and the photosensitive drum, and to form a high-quality image for a long period of time.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Overall Configuration> An image forming apparatus to which an embodiment of a photosensitive drum protection device of the present invention is applied will be described with reference to FIG. The copying machine has a main body 10 and a document holder 11 mounted on the upper part of the main body 10 so as to be openable and closable.

Inside the main body 10, a document table 15 on which a document is placed is provided at an upper portion, and an image forming section 16 is provided at the left end when viewed from the front and substantially at the center in the vertical direction. In the lower part, a paper feed cassette 1 for storing paper is provided.
7 is provided detachably. A feed roller 37 for feeding out the sheets in the cassette is provided above the end of the sheet cassette 17 on the sheet exit side. Paper cassette 1
A bypass paper feed unit 18 is provided on the left side of 7 so that paper can be manually fed from the lower left side of the apparatus. An optical system 19 for reading image information of a document placed on the document table 15 is provided below the document table 15. A fixing device 20 for fixing an image on a sheet is provided diagonally above the left side of the image forming unit 16, and a discharge roller 21 is further provided diagonally above the left side thereof. The discharge roller 21 is connected to a number detection sensor (not shown) to detect the number of copies. In addition, the discharge roller 2
A discharge tray (not shown) is provided on the outside of the main body 1.

Paper feed cassette 17 and bypass paper feed section 18
A vertical transport path 25 that transports the supplied paper vertically toward the image forming unit 16 is provided between the image forming unit 16 and the image forming unit 16. Further, between the image forming section 16 and the discharge roller 21, there is provided an oblique conveyance path 26 for conveying the image-formed paper obliquely upward and discharging the sheet. Image forming unit 16
Has a photosensitive drum 30 on the surface of which an electrostatic latent image is formed, and further includes a main charging device 31, a blank lamp 32, a developing housing 33,
It has a transfer device 34 and a cleaning blade 35. A drive motor and a rotation detection sensor (not shown) are connected to the photoconductor drum 30 to detect the number of rotations of the photoconductor drum 30. The cleaning blade 35 is provided in sliding contact with the photosensitive drum 30 and removes residual toner and the like from the surface of the photosensitive drum 30.

Above the developing housing 33, there is provided a toner cartridge 36 for storing replenishing toner. The toner cartridge 36 includes a developing housing 33.
And a paddle 42 for stirring the toner in the cartridge. The spiral 41 is driven to rotate by a motor (not shown), and conveys the toner in one direction or stops the conveyance, thereby supplying the toner into the developing housing. In addition, a rotation detection sensor (not shown) is connected to a drive motor that drives the spiral 41, and detects the rotation speed of the spiral 41. <Control System> The photosensitive drum protection device used in the image forming apparatus having the above-described configuration includes a control unit 50 shown in FIG.

The control unit 50 includes an exposure device 19, a main charging device 31, a blank lamp 32, and a photosensitive drum counter 5.
1, a spiral counter 52, a number counter 53, an input key 54, and a ROM 55 are connected. The photoconductor drum counter 51 is connected to a rotation detection sensor of the photoconductor drum 30 and counts the number of rotations of the photoconductor drum 30. The spiral counter 52 is connected to the rotation detection sensor of the spiral 41, and counts the cumulative driving time of the spiral 41. The number of sheets counter 53 is
It is connected to a copy number detection sensor for detecting the number of copies discharged from the printer, and counts the cumulative number of copies. Input key 5
From 4, setting of copy conditions and a copy start command are performed by the operation of the operator. The ROM 55 stores data necessary for the operation of the image forming apparatus.

FIGS. 3 and 4 show an example of the relationship between the on / off timing of the main charging device 31 and the blank lamp 32 stored in the ROM 55 and the latent image area of the photosensitive drum. FIG. 3 shows a case where a band-shaped latent image is formed, and FIG. 4 shows a case where it is not formed. As shown in FIGS. 3 and 4,
The main charging device 31 has a charging area 6 wider than the latent image area 60.
It is turned on and off to form a one. After a lapse of a predetermined time T1 when the main charging device 31 is turned on, the blank lamp 32
Is turned off to allow the toner to adhere to the latent image area 60. The sheet 62 is sent to the fixing unit 34 at such a timing that a slight margin 62a is formed at the leading end thereof.

After the exposure of the latent image area 60 by the exposure device 19, that is, after the lapse of a predetermined time T2, the blank lamp 3
2 is turned on again to discharge the toner from adhering to the outside of the latent image area 60. An area 61 c where the blank lamp 32 discharges the toner is slightly outside the latent image area 60.
The predetermined time interval T4 has been adjusted. Next, in the case shown in FIG. 3, after a predetermined time T5 has elapsed, the blank lamp 32 is turned off for a predetermined time interval T6, and the charging area 6 is turned off.
A belt-like latent image 64 is formed on the image 1. After the belt-shaped latent image 64 is formed, the blank lamp 32 is turned on and the main charging device 31 is simultaneously turned off, and the toner is prevented from adhering to the photosensitive drum 30 to wait for the formation of the next latent image.

In the case shown in FIG. 4, since the belt-shaped latent image 64 is not formed, the main charging device 31 is turned off after a lapse of a predetermined time T3 when the blank lamp 32 is turned on after exposure, and the charging is performed outside the latent image area 60. The region 61b is formed. <Operation of Image Forming Apparatus> Next, the operation of the image forming apparatus having the photosensitive drum protection device of the present invention will be described with reference to the flowchart shown in FIG.

When a main switch (not shown) is turned on, initial settings such as setting the number of copies to one and putting the current cumulative number of copies into the count value C0 for detecting the number of cumulative copies are performed in step S1. . In step S2, the process waits for completion of the copy preparation operation. When the preparation is completed, the process moves to step S3.

In step S3, it is determined whether or not the print key has been pressed, and if the print key has been pressed, the flow proceeds to step S6. If the print key has not been pressed, the process proceeds to step S4. In step S4, it is determined whether or not another key has been pressed, and if it has been pressed, the process proceeds to step S5 to execute a process corresponding to the pressed key. If another key is not pressed or another process ends in step S5, the process returns to step S3 and repeats steps S3 to S5 again. That is, in steps S3 to S5,
Wait for operator input.

In step S6, it is determined whether or not the counter value C0 indicating the cumulative number of copies is 100 or less.
If it is determined that the number is equal to or less than the number, the process proceeds to step S7. If it is determined that the cumulative number of copies exceeds 100, the process proceeds to step S10. That is, up to 100 sheets at the beginning of the operation of the image forming apparatus, a band-shaped latent image is formed for each copy.

In step S7, a band-shaped latent image subroutine described later is executed, and when the process is completed, the process proceeds to step S8.
In step S8, a counter C0 indicating the cumulative number of copies is set.
Is incremented, and the routine goes to Step S9. In step S9, it is determined whether or not to end copying, and if it is determined to end, the process returns to step S3. If it is determined that the processing is not to be terminated, the process returns to step S6 to perform processing distribution based on the cumulative number of copies.

In step S10, it is determined whether or not the counter value C0 indicating the cumulative number of copies is a multiple of 50. If C0 is a multiple of 50, the process proceeds to step S7 to execute a band latent image subroutine described later. Upon completion, the flow shifts to step S8 to repeat the same processing as described above. Conversely, C0 is 50
If it is not a multiple of, go to step 11. That is, after the image forming apparatus is operated and 100 copies are made, the adjustment is performed so that a belt-like latent image is formed every 50 copies.

In step S11, a latent image forming subroutine to be described later is executed. When the subroutine is completed, the process proceeds to step S8, and the same processing as described above is performed. <Latent Image Forming Operation> Next, the latent image forming subroutine shown in FIG. 6 will be described with reference to FIG. If the cumulative number of copies exceeds 100 and is not a multiple of 50, the program proceeds to step S10 of the main routine shown in FIG.
Then, the process proceeds to a latent image forming subroutine shown in FIG.

Referring to FIG. 6, in step S20, initial setting for turning on the blank lamp 32 and setting zero to the counter value C1 for detecting the blank lamp on / off timing and the counter value C3 for detecting the main high voltage on / off timing are performed. Do. In step S21, the main charging device 31 is turned on, and the process proceeds to step S22.

In step S22, it is determined whether or not the counter value C1 is equal to or greater than a predetermined value NT1, and if it is determined that the value does not exceed NT1, the process proceeds to step S23. If it is determined that it is NT1 or more, the process proceeds to step S24. Step S2
At 3, the counter value C1 is incremented, and the process returns to step S22.

In step S24, the blank lamp 32
Turn off. That is, after a predetermined time T1 after the main charging device 31 is turned on, the blank lamp 32 is turned off to allow the formation of a latent image. The time T1 from when the main charging device 31 is turned on to when the blank lamp 32 is turned off is
This corresponds to the charging area 61a shown in FIG. Step S25
Then, the optical system 19 (see FIG. 1) is driven, and the predetermined time T
A latent image is formed in the latent image area 60 corresponding to No. 2. Also,
Although not shown, other processes required for the image forming operation are simultaneously performed.

In step S26, the blank lamp 32 is turned on again after the lapse of the predetermined time T2, and the adhesion of toner in the charged area outside the latent image area 60 is prohibited.
Move to 27. In step S27, the count value C3
Is greater than or equal to a predetermined value NT3, and count value C3
Does not exceed NT3, the process proceeds to step S28. If the count value C3 exceeds NT3, step S
Move to 29.

In step S28, the count value C3 is incremented, and the flow returns to step S27. Step S
In 29, since the predetermined time T3 has elapsed since the blank lamp 32 was turned on in step S26, the main charging device 31 is turned off to stop the formation of the charging area 61, and the process returns to the main routine. The time T1 + T2 + T3 during which the main charging device 31 is on corresponds to the charging area 61 shown in FIG. <Photoconductor Drum Protection Control> Next, the operation of the photoconductor drum protection device will be described with reference to FIG. 3 based on the band latent image subroutine shown in FIG. The cumulative number of copies is 100
The program shifts from step S6 or S10 of the main routine shown in FIG. 5 to a latent image forming subroutine shown in FIG. 7 every time the number of sheets does not exceed or exceeds 100.

In step S40, the blank lamp 32
Is turned on, and initial values are set such that the counter values C1 and C5 for detecting blank lamp on / off timing and the counter value C6 for detecting main high pressure on / off timing are set to zero. Steps S41 to S46 are the same as the processing of steps S21 to S25 in FIG. That is, in step S41, the main charging device 31 is turned on, and the process proceeds to step S42.

In step S42, it is determined whether or not the counter value C1 is equal to or greater than a predetermined value NT1. If it is determined that the counter value C1 does not exceed NT1, the process proceeds to step S43. If it is determined that the counter value C1 is equal to or greater than NT1, the process proceeds to step S44. In step S43, the counter value C1 is incremented, and the process returns to step S42.

In step S44, the blank lamp 32
Turn off. That is, after a predetermined time T1 (see FIG. 3) has elapsed after the main charging device 31 is turned on, the blank lamp 32 is turned off, and the formation of a latent image on the photosensitive drum 30 is permitted. As described above, the time T1 from when the main charging device 31 is turned on to when the blank lamp 32 is turned off corresponds to the charging area 61a shown in FIG.

In step S45, the optical system 19 (see FIG. 1) is driven, and the latent image area 60 corresponding to the predetermined time T2
A latent image is formed thereon. Although not shown, other processes necessary for the image forming operation are simultaneously performed. In step S46, the blank lamp 32 is turned on again immediately after the latent image area 60 to inhibit the toner from adhering to the charged area outside the latent image area 60, and the process proceeds to step S47. Strictly, the timing when the blank lamp 32 is turned on is after a lapse of a predetermined time T4 since the rear end of the latent image area 60 has passed through the blank lamp 32.

In step S47, it is determined whether or not the counter value C5 is equal to or greater than a predetermined value NT5. If the counter value C2 is not equal to or more than NT5, the process proceeds to step S48,
If so, the process moves to step S49. Step S4
At 8, the counter value C5 is incremented, and the process returns to step S47.

In step S49, the blank lamp 32
Since the predetermined time T5 has elapsed since the switch was turned on, the blank lamp 32 is turned off, and the process proceeds to step S50. The time T5 during which the blank lamp 32 is turned on after the latent image is formed is the latent image area 60 and the band-shaped latent image 64 shown in FIG.
Corresponds to the charged area 61c. Step S50
Then, it is determined whether or not the counter value C6 is equal to or greater than a predetermined value NT6. If the counter value C6 is not equal to or greater than NT6, the process proceeds to step S51.
Move to.

In step S51, the counter value C6 is incremented, and the flow returns to step S50. Step S5
In step 2, the blank lamp 32 is turned on. That is,
The time T6 during which the blank lamp 32 is turned off after the formation of the charged area 61c corresponds to the length L of the strip-shaped latent image 64 shown in FIG.

In step S53, the main charging device 31 is turned off, and the process returns to the main routine. The sum of the predetermined times T5 and T6 is set to be the same as the time T3 until the main charging device 31 is turned off after the latent image is formed.
Is formed at the end of the charged area 61. <Other Embodiments> (a) In FIG. 5, the process of forming a belt-like latent image is divided depending on whether the cumulative number of copies is 100 or less, but this is an example showing the initial operation period of the image forming apparatus. However, the present invention is not necessarily limited to this example. In addition, 5 when 100 sheets are exceeded
Although a belt-like latent image is formed every 0 sheets, this is also an example. For example, optimal time, such as forming a belt-shaped latent image every 20 sheets after 100 sheets and up to 10,000 sheets every 50 sheets, every 10,000 sheets after 10,000 sheets and up to 20,000 sheets, and thereafter every 20 sheets because paper dust increases. The interval and the length of the band-shaped latent image are appropriately adjusted depending on the use environment and the characteristics of each image forming apparatus.

(B) In the above example, the time interval and the length of forming the belt-like latent image are adjusted based on the cumulative number of copies, but there are cases where high density is often used and cases where it is not. The adjustment can be made in consideration of the above. In this case, for example, the spiral 4 in the toner cartridge 36
1 is counted by a spiral counter 52 (see FIG. 2), and a time interval and a length L for forming a band-shaped latent image are adjusted for each range by dividing the range of the cumulative rotation speed of the spiral 41. Can be considered. (C) In the above example, the length L of the band-shaped latent image to be formed when the cumulative number of copies is up to 100 and thereafter.
Are the same, but they can be different.

[0043]

According to the present invention, there is provided a photosensitive drum protecting device and a photosensitive drum protecting method for an image forming apparatus, wherein an appropriate amount of residual toner is supplied between a photosensitive drum and a cleaning device to protect the photosensitive drum. It is possible to prevent the photosensitive drum from being damaged by foreign matter that has caught between the cleaning device and the photosensitive drum.

[Brief description of the drawings]

FIG. 1 is an overall view of an image forming apparatus employing a photosensitive drum control device of the present invention.

FIG. 2 is a block diagram illustrating an example of a control system of the photosensitive drum control device.

FIG. 3 is a diagram showing an example of a correspondence relationship between a strip-shaped latent image and ON / OFF timing of a blank lamp.

FIG. 4 is a diagram showing an example of a correspondence relationship between a latent image and ON / OFF timing of a blank lamp.

FIG. 5 is a flowchart illustrating an operation of the image forming apparatus.

FIG. 6 is a flowchart illustrating a latent image forming operation.

FIG. 7 is a flowchart showing a belt-shaped latent image forming operation.

[Explanation of symbols]

 30; photoconductor drum 32; blank lamp 33; developing housing 35; blade 60; latent image area 61; charged area 64; strip latent image L;

Claims (5)

[Claims] 1. A photosensitive drum protection device of an image forming apparatus for applying toner to a latent image region formed on a photosensitive drum, wherein the photosensitive drum is provided outside the latent image region on the photosensitive drum. A belt-like latent image forming unit that forms a belt-like latent image over a width; a developing unit that is arranged to face the photoconductor drum and forms a toner layer on the latent image and the belt-like latent image; Control means for adjusting a time interval for forming a latent image and a length of the band-shaped latent image in accordance with an accumulated amount of toner used in the image forming apparatus; and a photosensitive drum provided in sliding contact with the photosensitive drum. A photosensitive drum protecting device for an image forming apparatus, comprising: a cleaning unit that removes the residual toner on the photosensitive drum. 2. The image forming apparatus according to claim 1, wherein the control unit forms the band-shaped latent image at a first time interval in an early stage of the operation of the image forming apparatus, and forms the band-shaped latent image at a second time interval after a predetermined time. The time interval for forming the band-shaped latent image is adjusted such that the second time interval is longer than the first time interval.
3. A photosensitive drum protection device for an image forming apparatus according to claim 1. 3. The image forming apparatus further includes a toner replenishing device for supplying toner to the developing device, wherein the control device regenerates the belt-shaped latent image based on an accumulated driving time of the toner replenishing device. 2. The photosensitive drum protection device for an image forming apparatus according to claim 1, wherein a time interval to be formed and a length of the band-shaped latent image are adjusted. 4. The photosensitive drum of the image forming apparatus according to claim 3, wherein said control means adjusts a time interval for forming said band-shaped latent image to be longer as an accumulated driving time of said toner supply device becomes longer. Protective equipment. 5. A method for protecting a photosensitive drum of an image forming apparatus, wherein toner is applied to a latent image area formed on the photosensitive drum, wherein the photosensitive drum is provided outside the latent image area on the photosensitive drum. A band-shaped latent image forming step of forming a band-shaped latent image over a width, a developing step arranged to face the photosensitive drum, and forming a toner layer on the latent image and the band-shaped latent image; A control step of adjusting a time interval for forming an image and a length of the band-shaped latent image in accordance with a cumulative amount of toner used in the image forming apparatus; and removing residual toner and foreign matters other than toner on the photosensitive drum. A method for protecting a photosensitive drum of an image forming apparatus, comprising: a cleaning step.