JP2011095632A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a guide section, capable of forming a satisfactory transfer image on a sheet by suppressing the sheet from fluttering. <P>SOLUTION: In the guide section 20 of the image forming apparatus 10, an area S1 and an area S2 are set to satisfy conditional expressions (1) and (2), where expression (1) is S1≤5 mm<SP>2</SP>and expression (2) is S2≥S1×2. Additionally, a tip edge section 31 of a first guide member 21 is defined as a point A; a tip edge section 32 of a second guide member 22 is defined as a point B; an intersection of a vertical L2 from the point B to a first tip edge section 26 of the first guide member 21, with the first tip edge section 26 being defined as a point C; the intersection of a tangent L3 of an image carrier 125, as viewed from the point A and a vertical L4 to the tangent L3 from the point B, is defined as a point D; the area of a triangle connecting the point A, the point B and the point C is defined as S1; and the area of a triangle connecting the point A, the point B and the point D is defined as S2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system.

  Conventionally, an image forming apparatus using an electrophotographic method has been widely used. The image forming apparatus forms a toner image on a sheet such as paper, and a nip portion is formed between an image carrier such as a photosensitive drum or a transfer belt on which the toner image is formed, and the image carrier. A transfer member that forms and transfers the toner image onto the sheet at the nip portion; and a guide member that conveys the sheet to the nip portion.

  The guide member is an important component for forming a good transfer image on the sheet. For example, in the image forming apparatus of Patent Document 1, a pair of pre-transfer upper guide and pre-transfer lower guide are used as guide members. The front end portion of the lower guide before transfer is set so as to be positioned on the image carrier side as viewed from the nip tangent at the nip portion. With this position setting, a good transfer image is formed on the sheet at the nip portion of the sheet.

JP 2001-117375 A

  The sheet on which the image is formed is conveyed from a registration roller provided on the upstream side of the transfer unit to a nip portion between the image carrier and the transfer member, and the toner image on the image carrier is transferred at the nip portion. Is done. A guide member for guiding the sheet is provided between the registration roller and the transfer nip portion.

  Generally, at least one of the registration rollers is made of a rubber material having elasticity. And it is mutually pressing-contacted by biasing means, such as a spring provided in the both ends of the axial direction of a roller. The sheet is nipped between the registration rollers and conveyed along the guide member. Since the registration roller and the guide member are provided so as to extend in the width direction of the sheet, some errors occur in the pressing contact state of the registration roller, the perpendicularity to the conveyance direction, the mounting position of the guide member, and the like. As a result, the sheet conveyance force and conveyance speed by the registration rollers, the conveyance resistance by the guide member, and the like may differ between one side and the other side in the width direction. Such a situation causes a slight deflection of the sheet at the nip portion and the registration roller pair. When the sheet is bent, the sheet may come into contact with the toner image on the surface of the image carrier upstream of the nip portion, and an image defect such as image bleeding may occur at the rear end portion of the sheet.

  Although the guide member of the above-described Patent Document 1 optimizes the angle of entry of the sheet into the nip portion, a slight amount is applied to the sheet between the nip portion and the registration roller due to variations in the registration roller and the guide member. No measures are taken for image defects caused by bending. Therefore, it is difficult to form a good transfer image on the sheet.

  Therefore, in view of the above circumstances, the present invention can form a good transfer image on a sheet even if the sheet is slightly bent between the nip portions due to factors of variation in registration rollers and guide members. An object of the present invention is to provide an image forming apparatus having a simple guide portion.

In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention forms a nip portion between an image carrier that carries a toner image and the image carrier, and the nip portion includes the nip portion. A transfer member for transferring the toner image onto the sheet, a first guide member having a first tip portion extending toward the nip portion, and a second guide member having a second tip portion extending along the first tip portion. And a guide portion that conveys the sheet to the nip portion while sandwiching the sheet between the first guide member and the second guide member. The first tip portion is located on the image carrier side as viewed from the nip tangent line of the nip portion, the tip edge portion of the first guide member is point A, and the tip edge of the second guide member And the intersection of the perpendicular to the first tip of the first guide member from the point B and the first tip is a point C, and the tangent of the image carrier viewed from the point A And the point of intersection of the perpendicular to the tangent line from the point B is the D point, the area of the triangle connecting the point A, the point B and the point C is S1, the point A, the point B and the point D Is an image forming apparatus in which the area S1 and the area S2 are set so as to satisfy the following conditional expressions (1) and (2).
S1 ≦ 5 mm ² (1)
S2 ≧ S1 × 2 (2)

  According to the image forming apparatus of the first aspect of the present invention, the first guide member and the second guide member are positioned with respect to the image carrier so that the conditional expressions (1) and (2) are satisfied. Yes. For this reason, the rear end portion of the sheet whose conveying posture is determined by the position of the first front end portion located on the image carrier side as viewed from the nip tangent and the position of the nip portion is after the separation of the first front end portion. It does n’t flutter. As a result, even if the sheet is slightly bent between the nip portions due to variations in the registration roller and the guide member, transfer image defects such as image bleeding are suppressed. As a result, a good transfer image can be formed.

  In the image forming apparatus according to a second aspect of the present invention, the front end edge of the first front end is positioned so that a gap between the first end and the image carrier is 0.2 mm to 1.0 mm. Yes.

  According to the image forming apparatus of the second aspect of the present invention, since the sheet is appropriately brought into contact with the image carrier and conveyed to the nip portion, a good transfer image can be formed.

  In the image forming apparatus according to claim 3 of the present invention, a gap between the tip edge portion of the second tip portion of the second guide member and the image carrier is set to 0.5 mm or more. .

  According to the image forming apparatus of the third aspect of the present invention, it is possible to prevent the toner image on the image carrier from being scattered on the second guide member and contaminating the second tip portion.

  In the image forming apparatus according to a fourth aspect of the present invention, the first tip portion of the first guide member is located on an imaginary line extending from the second tip portion of the second guide member.

  According to the image forming apparatus of the fourth aspect of the present invention, since the first tip portion of the first guide member is located on an imaginary line extending from the second tip portion of the second guide member, the second tip portion Can be prevented from colliding with the image carrier. Thereby, inconveniences such as transfer misalignment due to the collision are suppressed.

  According to the guide portion of the image forming apparatus according to the present invention, it is possible to suppress the flapping of the sheet and form a good transfer image on the sheet.

1 is a cross-sectional view schematically showing an internal structure of an image forming apparatus according to an embodiment. FIG. 2 is an enlarged view of a peripheral portion of a transfer nip portion in the image forming apparatus of FIG. 1 and shows a configuration of a guide portion. It is a further enlarged view of the peripheral part of a transfer nip part. It is explanatory drawing which shows the positional relationship with respect to the transfer belt of the 1st guide member of a guide part, and a 2nd guide member. It is explanatory drawing which shows the positional relationship of the 1st front-end | tip part of a 1st guide member, and the 2nd front-end | tip part of a 2nd guide member.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows an internal structure of the image forming apparatus according to the present embodiment. The image forming apparatus 10 is, for example, a tandem color printer, and includes an apparatus main body 11 having a box shape. The apparatus main body 11 includes an image forming unit 12 that forms an image based on image information transmitted from an external device such as a computer, and a fixing process performed on the image formed by the image forming unit 12 and transferred to the paper P. It includes a fixing unit 13 to be applied, and a paper storage unit 14 for storing the paper P for transfer. A paper discharge unit 15 for discharging the paper P after the fixing process is provided on the upper portion of the apparatus main body 11.

  The image forming unit 12 forms a toner image on a sheet (sheet) P fed from the sheet storage unit 14. In the present embodiment, the image forming unit 12 is downstream from the upstream side (the right side in FIG. 1). Magenta unit 12M using magenta toner (developer), cyan unit 12C using cyan toner, yellow unit 12Y using yellow toner, and black And a black unit 12K using a color toner.

  Each unit 12M, 12C, 12Y, 12K includes a photosensitive drum 121 and a developing device 122. The photosensitive drum 121 forms an electrostatic latent image and a toner image (visible image) along the electrostatic latent image on the peripheral surface, and corresponds to the development while rotating counterclockwise in FIG. Toner is supplied from the device 122. Each developing device 122 is supplied with toner from a toner cartridge (not shown) disposed at an appropriate position of the apparatus main body 11.

  A charging device 123 is provided immediately below each photosensitive drum 121, and an exposure device 124 is provided below each charging device 123. The circumferential surface of each photosensitive drum 121 is uniformly charged by a charging device 123, and laser light corresponding to each color based on image data input from a computer or the like is charged from the exposure device 124 to the circumference of the photosensitive drum 121 after charging. The surface is irradiated. Thereby, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 121. When toner is supplied to the electrostatic latent image from the developing device 122, a toner image is formed on the peripheral surface of the photosensitive drum 121.

  Above the photosensitive drum 121, a transfer belt 125 (image carrier) is disposed between the driving roller 125a and the driven roller 125b. The transfer belt 125 is pressed against the circumferential surface of the photosensitive drum 121 by a transfer roller 126 provided corresponding to each photosensitive drum 121, and is driven with a driving roller 125 a and a driven roller in synchronization with the photosensitive drum 121. Circulate between 125b.

  A tension roller 125c is provided between the driving roller 125a and the driven roller 125b and at a position close to the driven roller 125b. The tension roller 125c applies tension to the transfer belt 125 and is biased upward by a biasing force of a biasing member (not shown). Therefore, the transfer belt 125 is pushed upward by the tension roller 125c between the driving roller 125a and the driven roller 125b.

  Along with the rotation of the transfer belt 125, first, primary transfer of a magenta toner image is performed on the surface (image carrying surface) of the transfer belt 125 by the photosensitive drum 121 of the magenta unit 12M. Next, the cyan toner image is transferred to the transfer position of the magenta toner image on the transfer belt 125 by the photosensitive drum 121 of the cyan unit 12C in an overcoated state. Similarly, the transfer of the yellow toner image by the yellow unit 12Y and the transfer of the black toner image by the black unit 12K are performed in the overcoating state. As a result, a color toner image is formed on the surface of the transfer belt 125.

  A drum cleaning device 127 that removes and cleans residual toner on the peripheral surface of the photosensitive drum 121 is provided at the left position of each photosensitive drum 121 in FIG. The peripheral surface of the photosensitive drum 121 cleaned by the drum cleaning device 127 goes to the charging device 123 for a new charging process. Waste toner removed from the peripheral surface of the photosensitive drum 121 by the drum cleaning device 127 is collected in a toner collection bottle (not shown) through a predetermined path.

  At the left position of the image forming unit 12 in FIG. 1, a paper conveyance path 111 extending in the vertical direction is formed. A conveyance roller pair 110 is provided at an appropriate position on the sheet conveyance path 111, and the sheet P from the sheet storage unit 14 is conveyed toward the transfer belt 125 by driving the conveyance roller pair 110. In addition, a secondary transfer roller 113 (transfer member) that is in contact with the surface (image carrying surface) of the transfer belt 125 at a position facing the driving roller 125a is provided in the paper transport path 111. The secondary transfer roller 113 is urged toward the shaft center of the drive roller 125a by unillustrated pressing springs provided at both ends in the axial direction, and the transfer nip N between the transfer belt 125 and the image carrying surface. Form. The sheet P is pressed and nipped by the transfer belt 125 and the secondary transfer roller 113 at the transfer nip N, whereby the toner image on the transfer belt 125 is secondarily transferred to the sheet P.

  Further, a pair of registration rollers 112 are disposed below the transfer nip portion N in the paper conveyance path 111. The registration roller 112 conveys the paper P toward the transfer nip portion N at an appropriate timing and corrects the oblique feeding of the paper P. Between the transfer nip portion N and the registration roller pair 112, a guide portion 20 that conveys the paper P toward the transfer nip portion N is disposed. The registration rollers 112 are urged by urging means (not shown) at both end portions in the axial direction to be in a pressed state.

  The sheet storage unit 14 includes a manual feed tray 141 that can be freely opened and closed on the right side wall of the apparatus main body 11 in FIG. 1, and a paper tray 142 that is removably mounted in the apparatus main body 11 below the exposure device 124. including. In the paper tray 142, a paper bundle P1 formed by stacking a plurality of papers P is stored. The paper tray 142 is configured by a box that opens upward, and the paper bundle P1 can be stored. The uppermost sheet P of the sheet bundle P1 stored in the sheet tray 142 is fed out one by one toward the sheet conveyance path 111 by driving the pickup roller 143. The paper P fed out from the paper tray 142 is conveyed toward the transfer nip N through the paper conveyance path 111 by driving the conveyance roller pair 110.

  The fixing unit 13 performs a fixing process on the toner image on the sheet P that has been secondarily transferred. The fixing unit 13 includes a heating roller 131 having an energized heating element as a heating source therein, a fixing roller 132 disposed to face the heating roller 131, and a fixing belt 133 stretched between the fixing roller 132 and the heating roller 131. And a pressure roller 134 disposed opposite to the fixing roller 132 with the fixing belt 133 interposed therebetween. The sheet P supplied to the fixing unit 13 is subjected to a fixing process by obtaining heat from the fixing belt 133 while passing between the pressure roller 134 and the high-temperature fixing belt 133. The color-printed paper P for which the fixing process has been completed is discharged toward the paper discharge tray 151 of the paper discharge section 15 through the paper discharge conveyance path 114 extended from the upper part of the fixing section 13.

  Hereinafter, the guide unit 20 for conveying the paper P to the transfer nip N will be described with reference to FIG. FIG. 2 is an enlarged view of the peripheral portion of the transfer nip portion N and shows the configuration of the guide portion 20. The guide unit 20 includes a first guide member 21 extending upward from the position near the left registration roller 112 in FIG. 2 to the transfer nip N in the pair of registration rollers 112 and a position near the right registration roller 112. And a second guide member 22 extending upward along the first guide member 21.

  The first guide member 21 is a plate-like member extending along the longitudinal direction of the drive roller 125a and the secondary transfer roller 113, and is a first base fixed to a predetermined frame near the left registration roller 112. An end portion 23, a first inclined portion 24 inclined to the right in FIG. 2 from the first base end portion 23 to the right registration roller 112 side, and extending substantially perpendicularly from the first inclined portion 24 toward the driving roller 125a. 2 includes a first intermediate portion 25 and a first tip portion 26 that is inclined in the left direction in FIG. 2 from the first intermediate portion 25 toward the transfer nip portion N. The 1st guide member 21 has the 1st conveyance surface 41 which counters the 2nd guide member 22 mentioned below. In the present embodiment, the first guide member 21 is a member facing the back surface opposite to the transfer surface of the paper P.

  The second guide member 22 is a plate-like member extending along the longitudinal direction of the driving roller 125a and the secondary transfer roller 113, and is a second base fixed to a predetermined frame at a position near the right registration roller 112. An end portion 27, a second intermediate portion 28 extending substantially perpendicularly from the second base end portion 27 toward the drive roller 125a, and a curve from the second intermediate portion 28 toward the transfer nip portion N in the left direction in FIG. And a second tip portion 29. The second guide member 22 has a second transport surface 42 that faces the first transport surface 41 of the first guide member 21. In the present embodiment, the second guide member 22 is a member facing the transfer surface of the paper P. By the first guide member 21 and the second guide member 22 configured as described above, the sheet conveyance path 111 in the guide portion 20 extends while being slightly curved leftward from the pair of registration rollers 112 toward the transfer nip portion N. ing.

  The first leading end portion 26 of the first guide member 21 protrudes toward the transfer nip portion N from the second leading end portion 29 of the second guide member 22, and the transfer belt as viewed from the nip tangent line L 1 in the transfer nip portion N. 125 and the driving roller 125a side. Accordingly, when the paper P discharged from the pair of registration rollers 112 is conveyed to the transfer nip portion N, the paper P enters the transfer nip portion N depending on the position of the first leading end portion 26 and the position of the transfer nip portion N. A conveyance posture is determined.

  As shown in FIG. 3, the first front end portion 26 has a first front end edge portion 31 that is positioned so as to be separated from the image carrying surface 50 of the transfer belt 125 via a predetermined gap G1. Specifically, the gap G <b> 1 is an image of the transfer belt 125 and the first corner portion 34 between the first tip surface 33 and the first transport surface 41 facing the transfer nip portion N at the first tip edge 31. It is a gap set between the carrying surface 50. The first corner portion 34 is a portion of the first guide member 21 that is closest to the image carrying surface 50 of the transfer belt 125.

  The predetermined gap G1 is set to any length in the range of 0.2 to 1.0 mm. By setting the gap G1 to be 0.2 mm or more, the toner of the toner image on the transfer belt 125 is attracted to the first leading end portion 26 that is frictionally charged by contact friction with the paper P, and the toner is attracted to the first leading end portion 26. Is suppressed. On the other hand, by setting the gap G1 to be 1.0 mm or less, the paper P is transported toward the transfer nip portion N at an appropriate rush angle while maintaining the transport posture.

  As shown in FIG. 3, the first conveyance surface 41 of the first guide member 21 and the second conveyance surface 42 of the second guide member 22 are separated from each other via a predetermined gap G2. The gap G2 forms a part of the paper transport path 111. The gap G2 is set to a predetermined thickness that is greater than or equal to +0.1 mm with respect to the thickness of the thickest paper P (for example, a postcard) among the papers P conveyed to the transfer nip portion N by the guide unit 20. When the sheet P is conveyed toward the transfer nip portion N while being sandwiched between the first guide member 21 and the second guide member 22, the sheet P contacts the first guide member 21 and the second guide member 22. If G2 is set as described above, the load caused by the contact of the paper P with the first guide member 21 and the second guide member 22 is reduced, so that the paper P is transported well toward the transfer nip portion N. be able to.

  Further, as shown in FIG. 3, the second leading end portion 29 has a second leading end edge portion 32 that is positioned so as to be separated from the image carrying surface 50 of the transfer belt 125 via a predetermined gap G3. Yes. Specifically, the gap G <b> 3 is a gap set between the image bearing surface 50 and the facing surface 35 that faces the image bearing surface 50 of the transfer belt 125 at the second leading edge portion 32. The gap G3 is set to a predetermined length of 0.5 mm or more. By setting the gap G3 to 0.5 mm or more, the toner of the toner image on the transfer belt 125 is attracted to the second leading end portion 29 that is frictionally charged by contact friction with the paper P, and the toner is attracted to the second leading end portion 29. Is suppressed.

  In the guide unit 20 having the above-described configuration, the gaps G1 to G3 are set as described above, and further, the positional relationship among the first guide member 21, the second guide member 22, and the image carrying surface 50 of the transfer belt 125 is set. is doing.

Specifically, as shown in FIG. 4, the first corner portion 34 of the first guide member 21 is a point A, and the second tip portion 29 of the second tip portion 29 is opposed to the transfer nip portion N at the second tip edge portion 32. The second corner 37 between the tip surface 36 and the second transport surface 42 is a point B, and the intersection of the perpendicular L2 with respect to the first transport surface 41 of the first tip 26 from the point B and the first transport surface 41. Is the point C, the intersection of the tangent line L3 of the image bearing surface 50 of the transfer belt 125 viewed from the point A and the perpendicular line L4 to the tangent line L3 from the point B is the point D, and further the points A, B, and C are When the area of the connected triangle is S1, and the area of the triangle connecting the points A, B, and D is S2, the area S1 and the area S2 satisfy the following conditional expressions (1) and (2). Is set.
S1 ≦ 5.0 mm ² (1)
S2 ≧ S1 × 2 (2)

  Here, the above setting will be described. For example, when a slight difference occurs between both ends of the urging force of the urging means of the registration roller 112, the conveyance force of the registration roller 112 is different between the left and right in the width direction. Since the feeding of the sheet P is slightly increased on the side where the conveying force is strong, the sheet P on that side is bent between the transfer nip portion N and the registration roller 112 pair. When the bent portion of the paper P comes into contact with the surface of the transfer belt 125 near the transfer nip portion N, the toner image formed there is disturbed, resulting in an image defect such as a blurred image on the paper P.

Here, if the area S1 is set to 5.0 mm ² or less and the area S2 is set to be twice or more of S1, the bending of the paper P is restricted by the first guide member 21 and the second guide member 22. In addition, contact with the surface of the transfer belt 125 can be prevented. In order to restrict the bending of the paper P, the distance K in the transport direction of the second tip portion 29 of the second guide member 22 with respect to the first tip portion 26 of the first guide member 21 is preferably made as small as possible. Further, the gap G2 between the first conveyance surface 41 of the first guide member 21 and the second conveyance surface 42 of the second guide member 22 is preferably as narrow as possible within the range in which the paper P can pass. When the distance K and the gap G2 are set, if the relationship between them is set in a range in which the area S1 is 5.0 mm ² or less, it is possible to appropriately regulate the bending of the paper P.

  On the other hand, when the first guide member 21 and the second guide member 22 are close to the transfer belt 125, the sheet P comes into contact with the surface of the transfer belt 125 even if the paper P is slightly bent. Therefore, it is preferable to set a wide space between the first guide member 21 and the second guide member 22 and the transfer belt 125 within a range in consideration of the transportability and transferability of the paper P to the transfer nip portion N. The area S2 corresponds to the space, and when the area S1 is set, the angles of the first guide member 21 and the second guide member 22 with respect to the transfer belt 125 are appropriately set, and the area S1 It is better to set it to more than twice. With this setting, even if a minute deflection that cannot be regulated by the first guide member 21 and the second guide member 22 occurs in the paper P, the bent portion can be prevented from contacting the surface of the transfer belt 125. Is possible.

  Further, the first tip portion 26 of the first guide member 21 is set so as to be positioned on an imaginary line obtained by extending the second tip portion 29 of the second guide member 22. Specifically, as shown in FIG. 5, the first transport surface 41 at the first tip portion is set to be positioned on a virtual plane P <b> 1 that extends from the second transport surface 42 at the second tip portion 29. Yes.

  According to the guide portion 20 having the above-described configuration, the gap G1 between the first corner portion 34 of the first guide member 21 and the image carrying surface 50 of the transfer belt 125 is set to 0.2 to 1.0 mm, and the first A gap G2 between the transport surface 41 and the second transport surface 42 is set to +0.0 with respect to the thickness of the thickest paper P (for example, a postcard) among the papers P transported to the transfer nip portion N by the guide unit 20. After setting the gap G3 between the facing surface 35 of the second leading edge 32 and the image carrying surface 50 of the transfer belt 125 to 0.5 mm or more, the above conditional expression (1) and The first guide member 21 and the second guide member 22 are positioned with respect to the image carrying surface 50 of the transfer belt 125 so that (2) is satisfied.

  Therefore, the rear end portion of the sheet P (that is, the sheet P in the sheet P) whose conveying posture is determined by the position of the first leading end portion 26 located on the transfer belt 125 side when viewed from the nip tangent L1 and the position of the transfer nip portion N. The downstream portion as viewed from the paper transport direction does not flutter at the moment when the first tip portion 26 and the second tip portion 29 are separated. Thereby, deterioration of the transferred image such as image scattering due to flapping of the paper P is suppressed. As a result, a good transfer image can be formed.

  In addition, since the first transport surface 41 at the first tip portion 26 is set to be positioned on the virtual plane P <b> 1 that extends from the second transport surface 42 at the second tip portion 29, the first tip surface 26 extends along the second tip portion 29. The sheet P conveyed in this way can be prevented from colliding with the transfer belt 125. Thereby, inconveniences such as transfer misalignment due to the collision are suppressed.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Guide part 21 1st guide member 22 2nd guide member 26 1st front-end | tip part 29 2nd front-end | tip part 41 1st conveyance surface 42 2nd conveyance surface 112 Registration roller 113 Secondary transfer roller 125 Transfer belt 125a Drive Rollers G1 to G3 Gap K Distance L1 Nip tangent N Transfer nip

Claims (4)

An image carrier for carrying a toner image;
A transfer member that forms a nip portion with the image carrier and transfers the toner image onto a sheet at the nip portion;
A first guide member having a first tip portion extending toward the nip portion; and a second guide member having a second tip portion extending along the first tip portion, wherein the sheet is the first guide member. And a guide part that is conveyed between the second guide member and the nip part,
With
The first tip is located on the image carrier side as seen from the nip tangent of the nip,
The tip edge of the first guide member is point A, the tip edge of the second guide member is point B, the perpendicular from the point B to the first tip of the first guide member and the point The point of intersection with the first tip is C point, the point of intersection of the tangent of the image carrier viewed from point A and the perpendicular to the tangent from point B is D point, point A, point B and If the area of the triangle connecting the points C is S1, and the area of the triangle connecting the points A, B and D is S2,
The image forming apparatus in which the area S1 and the area S2 are set to satisfy the following conditional expressions (1) and (2).
S1 ≦ 5 mm ² (1)
S2 ≧ S1 × 2 (2)   2. The image forming apparatus according to claim 1, wherein a gap between the first edge portion of the first guide member and the image carrier is 0.2 mm to 1.0 mm. An image forming apparatus having a position set.   2. The image forming apparatus according to claim 1, wherein a clearance between the tip edge portion of the second tip portion of the second guide member and the image carrier is set to 0.5 mm or more. An image forming apparatus.   4. The image forming apparatus according to claim 1, wherein the first tip portion of the first guide member is positioned on an imaginary line extending from the second tip portion of the second guide member. 5. An image forming apparatus.

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