JP2005300615A - Image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which prevents troubles, resulting from uneven charging and uneveness in exposure sensitivity which are caused by uneven film thickness of a photoreceptor drum in the axial direction or resulting from fluctuations in transferability, by effectively prevents filming caused by paper powder which tends to occur at both ends of a recording paper that produces frequent occurrence of paper powder or paper powder sticking to the recording paper in the positions of both ends of a small-diameter resist roller. <P>SOLUTION: When the width of recording paper to be used is inside the areas at both ends of the resist roller with a slightly smaller diameter, end areas extending to both ends of recording paper to be used from one of both end areas of maximum recording paper which is closer to the middle, or the recording paper with the maximum width, the implanted bristles of a cleaning rotor, corresponding to the areas of both the ends of recording paper narrower than the maximum width nearer to the middle than to the end area is made harder or/and denser than those composing the other area of the cleaning rotor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used in a copying machine, a printer, a facsimile, and a complex machine using an electrophotographic method, and more particularly, a photosensitive drum by a cleaning mechanism using a cleaning rotating body such as a fur brush. The present invention relates to an image forming apparatus that removes residual toner.

  In an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine using an electrophotographic system, a toner image formed on a photosensitive drum is transferred onto a recording sheet and then remains on the photosensitive drum. The toner is cleaned by a cleaning device using a cleaning rotary member such as a rubber blade, a cleaning roll, or a fur brush.

  On the other hand, recently, various types of recording paper such as recycled paper and foreign paper have been used as the recording paper for such image forming apparatuses, and many of these recording papers contain paper dust. When such a recording sheet is used, there is a problem that filming occurs due to talc or the like contained in the paper dust due to paper dust adhering to the photosensitive drum. This fulling is particularly likely to occur near the edge of the recording paper. When such filming occurs, the filming cannot be effectively removed by a cleaning device using a cleaning blade or the like.

  However, in such a portion where filming is not removed and remains on the surface of the photoconductive drum, the original function of the photoconductive drum is impaired, and the charged potential and exposure potential as set can not be obtained, and desired image characteristics are obtained. When the film is not obtained or the filmed material is hygroscopic, there arises a problem that image flow occurs.

  The occurrence of this filming is not only the use of the above-mentioned recording paper that generates a lot of paper dust, but also corrects the posture of the recording paper sent from the paper feed cassette etc. and transfers it in accordance with the timing of the toner image formability. It tends to occur even at locations corresponding to positions where the diameter is slightly reduced, for example, in order to improve transportability of the recording paper, at both ends of the registration roller for feeding to the position. This is because the amount of paper dust adhering to the recording paper is larger than that of the rubbing portion because the rubbing with the recording paper is less in the portion where the diameter is reduced. Filming also occurs at locations corresponding to positions where the amount of generated paper dust increases, such as both ends of the paper. Note that even if paper dust is generated on the recording surface of the recording paper due to the conveyance process up to the registration roller, most of the paper dust is removed from the recording paper by the registration roller at the portion of the recording paper that the registration roller contacts. Therefore, there is little possibility of filming on the photosensitive drum corresponding to the portion of the registration roller where the recording surface of the recording paper abuts.

  As a countermeasure against such filming, a cleaning rotating body such as a cleaning roller or a fur brush is effective. However, a brush rubbing pressure sufficient to remove the filming portions at both ends of the sheet is applied to the entire area of the photosensitive drum. On the other hand, the drum wear other than the filming portion is promoted to shorten the life of the photosensitive drum. Moreover, if the characteristics of the fur brush are set while paying attention to wear other than the filming portion, there is a disadvantage that filming in both end regions of the sheet cannot be eliminated.

  As prior arts regarding the characteristics of the cleaning brush in such a cleaning apparatus using a cleaning brush such as a fur brush, there are, for example, Patent Documents 1 and 2.

  First, Patent Document 1 is a cleaning device using a cleaning blade and a brush roll. In such a conventional cleaning device, the cleaning brush is placed on the photosensitive drum in order to reduce friction between the cleaning blade and the photosensitive drum. The brush flock density is set sparse so as not to completely wipe out the toner, but the width of the cleaning blade should be in direct contact with the blade and the photosensitive drum at the portion where residual toner is not carried. In order to prevent this, the developing width (maximum print area width) is narrower, and thus the carried toner adheres to the photosensitive drum at both ends of the cleaning blade, causing a printing failure such as fogging. If the brush flock density is increased to eliminate this problem, less toner is carried to the cleaning blade, friction with the photosensitive drum increases, and the contact portion is swollen. In some cases, printing problems such as

  For this reason, the cleaning device disclosed in Patent Document 1 has a configuration in which the flocking density of the central portion of the brush roll is the same as that of the cleaning blade and the both ends thereof are dense. No mention is made of the relationship.

  In addition, the image forming apparatus disclosed in Patent Document 2 uses a rubber blade, a fur brush, or the like to clean the untransferred residual toner adhering to the photosensitive drum after transfer, and further, an exposure unit or a developing unit. In order to create a gap between the photosensitive drum and the other process section such as the photosensitive section, a gap roller is used, and conventionally, on the peripheral surface of the end of the photosensitive drum with which the gap roller contacts, Since the filming sticky toner adheres to the floating toner during printing, this part was cleaned with a fur brush, cleaning fleece, blade, etc., but the filming sticky toner adheres to improve the cleaning effect. The cleaning fleece part corresponding to both ends of the photosensitive drum is made rougher than usual, or the blade pressing pressure is changed when using a blade. I was walking.

However, in this method, the peripheral surface of the photosensitive drum is scratched and worn, the paper is turned over, slipped through, etc., and the toner on the blade is exposed to a large amount of solid toner such as a gap roller contact portion. Since much adhesion occurs, the cleaning effect is reduced. For this reason, there is a problem in that the original gap cannot be secured, and when a large amount of toner is fixed, the toner is peeled off at the contact portion with the gap roller to stain the periphery and affect printing. Therefore, in this patent document 2, the cleaning characteristics of the fur brush at the position where the gap-exposing roller on the outside of the printing area of the photosensitive drum is in contact with the photosensitive drum,
A. The outer portion including the position where the gap roller contacts the photosensitive drum is made harder by 10% or more than the inner portion. As a method of hardening, there are hair using high hardness, thick hair, short hair, and the like.
B. Similarly, the hair density of the hair is increased by 10% or more than the density of the hair in the inner part.
C. Similarly, some hairs are made harder by 10% or more than the inner part, and the hair density of the remaining hairs in the outer part is made 10% or more darker than the inner part.
For example, the cleaning characteristics in the print area (inner side) were made larger.

Japanese Patent Laid-Open No. 5-80682 Japanese Patent No. 3275219

  However, in the technique disclosed in Patent Document 1, the developing width (maximum print area width) is used to prevent the cleaning blade width from dripping in the portion where the residual toner is not conveyed and coming into direct contact with the photosensitive drum. For this reason, the flocking density of the same width as the cleaning blade in the central portion of the brush roll is sparse and the both ends thereof are dense. As described above, filming is a resist that conveys recording paper. It is likely to occur at the position of the photosensitive drum corresponding to the position where the diameter of both ends of the roller is reduced or the position where the amount of paper dust generation increases, such as both ends of the recording paper. If the width exceeds the part of the roller with a reduced diameter at both ends, filming of this part cannot be prevented. That.

  Patent Document 2 is an image forming apparatus having a complicated structure in which a gap roller for gap gap between another process and the peripheral surface of the photosensitive drum is provided outside the printing area of the photosensitive drum. For the part corresponding to the roller, the characteristics of the fur brush are hardened or the flocking density is increased, but in such a configuration, for example, if the end of the recording paper is inside the gaping roller installation position, recording is performed. Filming that occurs in the vicinity of the edge of the sheet cannot be prevented, and there is still a problem. Similarly to Patent Document 1, nothing is mentioned about the relationship with the registration roller.

  Therefore, paper dust that tends to occur at both ends of the recording paper when using recording paper that generates a lot of paper dust, and paper dust that adheres to the recording paper at a position where the diameter of both ends of the registration roller is reduced, etc. This effectively prevents the occurrence of filming due to the film, thereby impairing the original function of the photosensitive drum, failing to obtain the charging potential and exposure potential as set, and failing to obtain the desired image characteristics. The provision of an image forming apparatus capable of preventing the problem of image flow when the substance is hygroscopic is an unsolved problem in any of the above patent documents, and the relationship between the fur brush and the registration roller is clarified. Therefore, it is an object of the present invention to solve the above problems.

In order to solve the above problems, the present invention
A pair of registration rollers for feeding the recording medium to a transfer position in accordance with the transfer timing of the toner image carried on the photosensitive drum, and a cleaning rotating body for rubbing the photosensitive drum after the toner image transfer is provided. In the image forming apparatus,
The recording medium contact width between both ends of the registration upper roller located on the recording medium transfer surface side of the registration roller pair is set smaller than the maximum printing area of the photosensitive drum, while the photosensitive drum contact area of the cleaning rotating body Is set larger than the maximum print area,
The rubbing pressure of the cleaning rotator toward the photosensitive drum is varied in the axial direction, and at least one of the high rubbing pressure portions corresponds to both ends of the upper roller of the resist in the cleaning rotator. It is characterized in that it is set in an area extending from the inside to the outside of the maximum printing area.
And the rubbing pressure to the drum side of the fur brush refers to the drum rubbing pressure obtained by the hardness or flocking density of fur in each fur brush, and further the fur brush rotation speed, specifically, By increasing the rotational speed of the fur brush, it is possible to reduce the rubbing pressure toward the drum side of the fur brush in the axial direction. It can be different between the central part and the outer part.

Next, the process leading to the present invention will be described in order.
The registration roller pair is generally located on the recording medium transfer surface side. The registration upper roller is formed of hard urethane rubber, and the lower roller is formed of a metal roller such as iron or aluminum so as to increase the nip force of the paper and obtain a reliable conveying force. I have to.
In the first specific example of the present invention adopting such a basic configuration, as shown in FIG. 2, the resist upper roller, the recording medium contact width (L ₃ ) between both ends of the upper roller is set to the maximum printing area of the photosensitive drum. (L ₁₎ from the set to a small (and lower registration rollers recording medium contact width (L ₅₎ of the maximum printing area (L ₁₎ from the set larger of the photosensitive drum) maximum paper printing width (A3 vertical by (Alternatively, when A4 side) is inserted, fluctuations in the nip force in the axial direction are suppressed, skewing is prevented, and variations in the nip force in the axial direction are suppressed and paper dust is often generated. Even when paper is used, the recording medium in the center of the paper is positively pressed with a resist upper roller to suppress the generation of paper dust, and it is preliminary that the paper dust adheres to the photosensitive drum and causes filming. Prevent it.
If such an effect can be obtained, there is an opinion that it is preferable to make the recording medium contact width between both ends of the upper roller larger than the maximum printing area of the photosensitive drum. The above configuration is preferable in order to cause a problem that the outer portion always comes into direct contact with the metal portion of the lower roller and wear in the portion increases, and the skew and the nip pressure are liable to occur.
On the other hand, with such a configuration, a sheet in which a large amount of paper dust is generated before the toner image transfer of the photosensitive drum in the “(L ₁ −L ₃ ) + alpha (full width of recording medium−L ₁ )” portion of the recording medium. Is not pressed by the nip pressure, and the photosensitive drum and the paper come into contact with each other in a state where generation of paper dust is not suppressed.
Therefore, the present invention sets the drum contact area of a cleaning rotating body such as a fur brush or a cleaning roll to be larger than the maximum print area,
The rubbing pressure of the cleaning rotator toward the photosensitive drum is varied in the axial direction, and at least one of the high rubbing pressure portions corresponds to both ends of the upper roller of the resist in the cleaning rotator. It is characterized in that it is set in an area extending from the inside to the outside of the maximum print area.
More specifically, a pair of registration rollers for feeding the recording medium to a transfer position in accordance with the transfer timing of the toner image carried on the photosensitive drum according to claim 3, and the photosensitive after the toner image transfer. An image forming method comprising: a cleaning rotator for rubbing the body drum; and removing paper dust adhered to the photosensitive drum after the toner image is transferred by the cleaning rotator.
When the recording paper to be transferred includes an A3 or A4 horizontal size (hereinafter referred to as the maximum paper size), the rubbing pressure on the photosensitive drum side of the cleaning rotating member is different between the central portion and the end portion of the maximum paper size. The end portion is set to a rubbing pressure larger than the central portion, and the central portion of the maximum paper size is pressed against the sheet by a resist upper roller, and then the cleaning rotator is relatively weak in rubbing pressure. On the other hand, the end side portion of the maximum paper size is not subjected to pressure contact by the resist upper roller, and is cleaned with a cleaning rotating body having a relatively strong rubbing pressure. .

  Further, in the second specific example of the present invention adopting such a basic configuration, it is preferable that the portion having a high rubbing pressure is located outside the maximum printing region from the inside corresponding to the both ends of the resist upper roller in the cleaning rotating body. It is characterized in that it is set in accordance with the size of the paper to be used in a region other than the region leading to.

According to this invention, when the recording paper to be transferred includes an A4 vertical size (hereinafter referred to as a standard paper size), the rubbing pressure on the drum side of the cleaning rotating body is set to the standard paper size central portion and the end portion. The central portion of the standard paper size is rubbed and cleaned with a fur brush having a relatively low rubbing pressure, while the end side portion is set to a rubbing pressure larger than the central portion. The end portion of the size can be rubbed and cleaned with a fur brush having a relatively strong rubbing pressure.
As a result, the following paper dust removal configuration can be taken for the maximum paper size and standard size paper.
Maximum end side of the paper size (around _{L 1} in Figure 2):
Without being pressed by the resist upper roller, it is rubbed at the first outer portion (12) of the fur brush.
End side of the standard paper size (around _{L 4} in FIG. 3):
It is pressed by the resist upper roller and rubbed at the second outer portion (15) of the fur brush.
Central side from the end side of the maximum paper size (inner L ₃ of Figure 2):
It is pressed by the upper resist roller and rubbed at a portion (11 or 11b) where the rubbing pressure of the fur brush is weak.
Inside the end side of the standard paper size (inner L ₄ in FIG. 3):
It is rubbed at a portion (11 or 11b) that is pressed by the resist upper roller and has a weak rubbing pressure of the fur brush.
As a result, the edge of the A4 vertical size, which is used most frequently, is preliminarily suppressed by the pressing force of the resist upper roller, and more actively removes the paper dust at the second outer portion (15) of the fur brush. Can be planned.

  As described above, the present invention relates to paper dust that tends to occur at both ends of recording paper when recording paper that generates a lot of paper dust is used, and paper dust at the end of the recording paper at the end of the maximum paper size or standard paper size. Therefore, the original function of the photosensitive drum is impaired, and the charging potential and exposure potential as set can not be obtained, and the desired image characteristics cannot be obtained or filming has occurred. When the substance is hygroscopic, it is possible to prevent the problem of image flow and obtain a stable image.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is a side view of an essential part of an image forming apparatus provided with a cleaning device in an image forming apparatus according to the present invention, and FIG. 2 is a main component in the image forming apparatus for explaining the cleaning device in the image forming apparatus according to the present invention. FIG. 3 is a diagram for explaining a second embodiment of the cleaning device in the image forming apparatus according to the present invention.

Figure 1 is a photosensitive drum, 2 a charger, a developing roller 3, 4 the registration rollers 4 at the registration roller, the upper registration roller 4 ₁ is configured on a shaft such as a urethane rubber and iron and aluminum, etc. a lower registration roller 4 ₂ metallic are paired, upper registration roller 4 ₁ made of a urethane rubber, both end portions is not shown, just the diameter in order to improve the recording sheet conveyance property It is made smaller. 4 ₂ lower registration roller, the recording sheet 5, the transfer roller 6, 7 (hereinafter abbreviated as cleaning rotor) rotating body cleaning, such as a fur brush or a cleaning roller cleaning device having a 8 and a cleaning blade 10, 9 Is a developing device having the developing roller 3, 11 is a first region where the contact pressure of the central portion of the cleaning rotator 8 is relatively low, and 12 is a relative region of contact pressure as an end side region of the cleaning rotator 8. higher second region, 13 in the recording sheet of the maximum width for an image forming apparatus, for example, A4 lateral or A3 recording paper that vertically is inserted, L ₁ ~L ₆ width size of the members related each are shown, L ₁ is the maximum width for an image forming apparatus, i.e., A3 portrait or A4 landscape recording paper size width, L ₂ is the width of the transfer roller 6, L ₃ Les Strike on roller 4 ₁ of lower registration roller 4 ₂ in contact with portions of the width, L ₅ the relationship of lower registration roller 4 ₂ width and registration on roller 4 _first width the width of the lower registration roller 4 _2,
L ₅ > L ₃ and
Then, as shown in FIG. 2, when only the second region (first outer portion) (12) is formed on the cleaning rotator,
Relationship between _{L 8} of the second region (the first outer section) in end width _{L 7} and the outer end width is in the relation of _{L 8> L 1 ≧ L 3} > L 7.
Maximum paper (A3 vertical, A4 horizontal) by such a positional relationship first outer section of the end side (near L ₁ in FIG. 2), the cleaning rotary member without pressing the resist on roller size central side from the end side of the rubbing is and the maximum paper size (12) sliding weak sites pressure pressed and cleaning rotating body upper registration roller in (inner L ₃ in FIG. 2) (11 or 11b) Can be rubbed.
In addition, when the standard sheet size (A4 portrait, A5 landscape) is high, the relationship between the maximum paper (A3 portrait, A4 landscape) and the standard sheet size (A4 portrait, A5 landscape) is shown in FIG. More concretely,
Reference numeral 15 denotes a third region having a relatively high contact pressure inside a second region having a relatively high contact pressure in the cleaning rotator 8 via a fourth region 11b having a relatively low contact pressure. 15 is provided.
In this case, the relationship between the inner end width L ₆ of the third region 15 (second outer portion) and the outer end width L ₉ is set to a relationship of L ₉ > L ₄ > L ₆ .
Incidentally, in the case 16 is for example an image forming apparatus according to A3 portrait or A4 horizontal size of the maximum printing area, the recording sheet of A4 vertical as the standard paper size (A5 landscape): standard _{L 4} are A4 portrait (A5 horizontal) This is the width of the recording paper size.
Thus it is rubbed with in addition to the operation of FIG end side of the standard paper size second outer section (15) of the pressed and cleaning rotating body in registration on rollers (L ₄ near the 3) and the standard inside from the end side of the paper size rubbing weak sites pressure and cleaning rotary member is pressed by the upper registration roller (inner L ₅ in FIG. 3) (the first region 11 or the fourth region 11b) Rubbed.

  Next, the operation of the image forming apparatus including the cleaning device in the image forming apparatus according to the present invention will be briefly described with reference to the side view of the main part of FIG. When an image formation instruction is received, the photosensitive drum 1 is uniformly charged by the charger 2 and is exposed by an exposure device (not shown) to form a latent image. The latent image is developed with toner carried by the developing roller 3 in the developing device 9 to form a toner image.

  On the other hand, the recording paper 5 is sent to a registration roller 4 from a paper feeding cassette or a manual paper feeding device (not shown), the posture is corrected, and the toner image formed on the photosensitive drum 1 is positioned at the position of the transfer roller 6. It is sent out at the timing of reaching. The toner image is transferred from the photosensitive drum 1 to the recording paper 5 by the transfer bias applied to the transfer roller 6, and the recording paper 5 is sent to a fixing device (not shown) to fix the toner image and discharge it. Is done.

  After the toner image is transferred to the recording paper 5, the residual toner remaining on the photosensitive drum 1 is agitated by the cleaning rotator 8 in the cleaning device 7, cleaned by the cleaning blade 10, and the next image formation. Is done.

Such an image forming apparatus having a cleaning apparatus according to the present invention to operate, as shown in FIG. 2, if the width of the recording paper of the maximum width used was L _1, the transfer roller 6 is a width L It is a narrow width L ₂ than _1, the resist on the rollers 4 ₁ in the resist roller pair 4, although not shown, the diameter for both ends to improve the recording sheet conveyance properties are slightly smaller, lower registration roller 4 the width of ₂ in contact with portions has a narrower _{L 3} from the lower registration roller _{4 2.}

  The cleaning rotator 8 is configured to be able to clean almost the entire surface of the photosensitive drum 1 as shown in FIGS. 2 and 3, and the region 12 and the region 15 described above are the first region 11 and the fourth region 11b. The hair hardness is increased or the flocking density is increased, or the flocking density is increased at the same time as the hardness of the hair is increased.

Therefore, the end region 12 in the cleaning rotator 8 and the third region 15 shown in FIG. 3 are attached to the photosensitive drum 1 more than the first region 11 and the fourth region 11b in the center. can be removed filming due toner or paper dust more strongly prone to both end portions of the recording sheet 5 in the case of using the recording sheet 5 as larger occurrence of paper dust paper powder, the resist roller 4 ₁ Filming due to paper dust or the like generated at a position where the diameters at both ends of the sheet are reduced can be effectively prevented.

In the above description, the end portion side region 12 in the cleaning rotary member 8, the resist roller 4 ₁ is configured by a rubber, a slight diameter in order to improve the recording sheet conveyance of the two end portions including small portions, and up to both end portions of the cleaning rotary member 8 itself, but if the maximum width L ₁ of the recording sheet 5 is smaller than the width L ₃ of the resist roller 4 _1, opposite to the recording sheet 5 It is good also from the both-ends area | region including a little inner side from both ends to the both ends of cleaning rotary body 8 itself.

Further, not only the recording sheet 5 of the maximum width for an image forming apparatus as a recording sheet 5, as shown in FIG. 3, when using the recording paper 16 having a width L ₄ of the width L _1, the Since filming occurs in the portion, in this case, the bristles in both end regions 15 of the standard size recording paper 16 having a width L ₄ narrower than the maximum width L ₁ closer to the center than the end side region 12 are also hardened. You may make it harden or increase the flocking density, or increase the flocking density at the same time as increasing the hardness of the hair.

  Examples will be described below. The photosensitive drum 1 has a diameter of 300 mm and a rotational speed of 100 m / s. The cleaning rotary body 8 has a diameter of 12.5 mm and the hair of the cleaning rotary body 8 with respect to the photosensitive drum 1. Was set so that 110% of the portion touched, and 25,000 sheets were printed.

  As a result, when the hair flocking density in the 12 portions shown in FIG. 2 was the same as that in the 11 portion, filming was observed in about 10,000 pieces. Was increased by 10% or 20% from the 11 part, and no filming was observed even after printing 25,000 sheets.

  As described above, according to the present invention, the cleaning rotator 8 is formed in a region having a slightly small diameter at both ends of the registration roller 4 or a region of both ends of the maximum width recording paper in the recording paper 5 to be used. When using the end side region 12 from the region closer to the center to both ends and the recording paper 16 having a width narrower than the maximum width recording paper 5, the end side region 12 is closer to the center. Generation of paper dust by making the bristle hardness and the flocking density in both end regions 15 of the recording paper 16 narrower than the maximum width harder than the bristles constituting the other region and / or increasing the flocking density. This effectively prevents filming caused by paper dust generated from the edge of the recording paper, such as a large amount of paper, or paper dust adhering to the recording paper at a position where the diameters of both ends of the registration roller 4 are reduced. As a result, the original function of the photosensitive drum is impaired, the set charging potential and exposure potential cannot be obtained, the desired image characteristics cannot be obtained, and the image flow is caused when the filmed material is hygroscopic. Thus, it is possible to provide a cleaning device in an image forming apparatus that can always obtain a stable image by preventing the problem of occurrence of the image and an image forming apparatus using the cleaning device.

  According to the present invention, it is possible to effectively prevent the occurrence of filming due to paper dust generated from the edge of the recording paper or paper dust adhered to the recording paper at a position where the diameters of both ends of the registration roller are reduced. It is possible to provide an image forming apparatus capable of obtaining a processed image.

FIG. 3 is a side view of a main part of an image forming apparatus including a cleaning device in the image forming apparatus according to the present invention. FIG. 3 is a diagram illustrating a relationship among main components in the image forming apparatus in order to describe a cleaning device in the image forming apparatus according to the present invention. It is a figure for demonstrating 2nd Example of the cleaning apparatus in the image forming apparatus which becomes this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Developing roller 4 Registration roller 4 ₁ Upper resist roller composed of ₁ rubber roller 4 ₂ Lower resist roller made of metal 5 Recording paper 6 Transfer roller 7 Cleaning device 8 Cleaning rotator 9 Developing device 11 First region 12 in cleaning rotator Second region 13 as end-side region in cleaning rotator 13 Maximum width recording paper 15 Third region 16 in cleaning rotator Recording paper having width narrower than maximum width L ₁ Maximum width of recording paper L ₂ Width of transfer roller L ₃ Registration roller 4 ₁ Width L ₄ Width of recording paper narrower than maximum width

Claims (4)

A pair of registration rollers for feeding the recording medium to a transfer position in accordance with the transfer timing of the toner image carried on the photosensitive drum, and a cleaning rotating body for rubbing the photosensitive drum after the toner image transfer is provided. In the image forming apparatus,
The recording medium contact width between both ends of the registration upper roller located on the recording medium transfer surface side of the registration roller pair is set smaller than the maximum printing area of the photosensitive drum, while the photosensitive drum contact area of the cleaning rotating body Is set larger than the maximum print area,
The rubbing pressure of the cleaning rotator toward the photosensitive drum is varied in the axial direction, and at least one of the high rubbing pressure portions corresponds to both ends of the upper resist roller of the cleaning rotator. An image forming apparatus, wherein the image forming apparatus is set in an area extending from the inside of the position to the outside of the maximum printing area.   The portion having a high rubbing pressure is set in accordance with the size of the paper to be used other than the region extending from the inside corresponding to the both ends of the resist upper roller to the outside of the maximum printing region in the cleaning rotating body. The image forming apparatus according to claim 1, wherein: A pair of registration rollers for feeding a recording medium to a transfer position in accordance with the transfer timing of the toner image carried on the photosensitive drum, and a cleaning rotating body for rubbing the photosensitive drum after the toner image is transferred. In the image forming method in which the paper dust adhered to the photosensitive drum after the toner image transfer is removed by the cleaning rotator,
When the recording paper to be transferred includes an A3 or A4 horizontal size (hereinafter referred to as the maximum paper size), the rubbing pressure on the photosensitive drum side of the cleaning rotating member is different between the central portion and the end portion of the maximum paper size. The end portion is set to a rubbing pressure larger than the central portion, and the central portion of the maximum paper size is pressed against the sheet by a resist upper roller, and then the cleaning rotator is relatively weak in rubbing pressure. On the other hand, the end side portion of the maximum paper size is not subjected to pressure contact by the resist upper roller, and is cleaned with a cleaning rotating body having a relatively strong rubbing pressure. Image forming method.   When the recording paper to be transferred includes an A4 vertical size (hereinafter referred to as a standard paper size), the rubbing pressure on the photosensitive drum side of the cleaning rotator is made different between the central part and the end part of the standard paper size, The end portion is set to a rubbing pressure larger than the central portion, and the central portion of the standard paper size is rubbed and cleaned with a cleaning rotating body having a relatively weak rubbing pressure, while the standard paper size 4. The image forming method according to claim 3, wherein the end portion is rubbed and cleaned with a cleaning rotator having a relatively strong rubbing pressure.

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