JP2004277100A - Sheet carrier guide and image forming apparatus equipped with sheet carrier guide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet carrier guide capable of preventing production of an abnormal picture image due to electric discharge and occurrence of fixing failure due to insufficient discharging of a sheet and an image forming apparatus with such a sheet carrier guide high in reliability. <P>SOLUTION: The sheet carrier guide 6 is arranged immediately downstream of a transfer belt 31. Volume resistivity of the sheet carrier guide 6 is specified within a range of 1×10<SP>-5</SP>times to 1×10<SP>5</SP>times of volume resistivity of the transfer belt 31, preferably 1×10<SP>-3</SP>times to 1×10<SP>3</SP>times. A discharging member 8 is provided in parallel with a sheet carrier surface 31a of the transfer belt 31 on a downstream side part 6b of the sheet carrier guide 6. The discharging member 8 has a shape forming a plurality of discharging needles 8a on one end of a flat plate. The discharging needle 8a is directed downstream in the sheet carrying direction and projected from an end surface 66 on the downstream side of the sheet carrier guide 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is used in an image forming apparatus such as a copying machine or a printer, and is provided downstream of a transfer belt that transports a sheet on which a toner image is transferred by an image carrier of an image forming apparatus by electrostatically attracting the sheet. The present invention also relates to a sheet transport guide in which the leading end of the sheet separated from the transfer belt is directed to the fixing device. The present invention also relates to an image forming apparatus equipped with the sheet transport guide.
[0002]
[Prior art]
An image forming apparatus such as a copying machine or a printer includes an image forming apparatus that forms a toner image on the surface of an image carrier, a transfer device that transfers the toner image to a sheet, and a sheet that melts the toner image by heat to form a sheet. And a fixing device for fixing the image on the sheet. Some transfer devices include a transfer belt that electrostatically attracts a sheet on which a toner image on an image carrier of an image forming device is transferred and conveys the sheet to a fixing device.
[0003]
Here, after the conveyed sheet is separated from the transfer belt, a large potential difference may occur between the charged sheet and a member that contacts the sheet. At this time, a discharge occurs due to a sudden change in potential, and unfixed toner on the paper scatters. This causes a problem that the toner image is disturbed and an abnormal image is generated.
[0004]
The paper separated from the transfer belt is charged to the same polarity as the toner. If the sheet enters the fixing device without removing the charge accumulated on the sheet as it is, repulsion occurs between the sheet and the toner, so that the toner is not fixed normally and the toner adheres to the fixing roller. As a result, a problem of a fixing offset in which an image is printed twice at the pitch of the fixing roller occurs.
[0005]
As a means for removing the charges causing the image disturbance, a configuration has been proposed in which a paper transport guide provided with a charge removing member is disposed downstream of the transfer belt in the paper transport direction (see Patent Document 1). .
[0006]
[Patent Document 1]
JP-A-6-317990
[Problems to be solved by the invention]
In the configuration described in Patent Literature 1, the transfer belt is formed of a material having a medium electrical resistance, and the guide surface of the paper transport guide is formed of a conductive material. However, in such a configuration, when the conveyed sheet separates from the transfer belt and moves onto the sheet conveyance guide, a large potential difference generated between the charged sheet and the sheet conveyance guide is sufficiently improved. I can't say that.
[0008]
Further, in the configuration described in Patent Literature 1, a static elimination member is provided at an end portion where the downstream height of the paper guide surface is the lowest, protruding above the paper guide surface. As a result, the sheet is caught on the protruding charge removing member, and a sheet jam occurs.
[0009]
The present invention has been made in view of the above points, and suppresses the occurrence of an abnormal image due to discharge and the occurrence of a fixing failure due to insufficient charge removal of a sheet in a sheet transport guide disposed downstream of the transfer belt in the sheet transport direction. It is an object of the present invention to provide a paper transport guide capable of performing the following. It is another object of the present invention to provide a highly reliable image forming apparatus equipped with such a sheet transport guide.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a method of separating a transfer belt on which a toner image of an image carrier of an image forming apparatus is transferred from a transfer belt downstream of the transfer belt in a sheet transfer direction for electrostatically attracting and transferring the transfer sheet. In the sheet transport guide in which the leading end of the sheet is directed to the fixing device, the volume resistivity is set in a range of 1 × 10 ⁻⁵ to 1 × 10 ⁵ times the volume resistivity of the transfer belt. At the same time, a static elimination member is provided on the downstream side.
[0011]
Here, “the volume resistivity of the paper transport guide is in the range of 1 × 10 ⁻⁵ times to 1 × 10 ⁵ times the volume resistivity of the transfer belt” means, for example, that the volume resistivity of the transfer belt is 10 times. ^{If it is 11} Ω · cm (1 × 10 ¹¹ Ω · cm), the volume resistivity of the paper transport guide is in the range of 10 ⁶ to 10 ¹⁶ Ω · cm (1 × 10 ⁶ to 1 × 10 ¹⁶ Ω · cm). It means there is.
[0012]
According to the above configuration, a large potential difference does not occur between the sheet separated from the transfer belt and the sheet conveyance guide. As a result, when the conveyed paper separates from the transfer belt and moves onto the paper conveyance guide, it is possible to suppress discharge due to a sudden change in potential, and to prevent scattering of unfixed toner on the paper. It is. Further, the charge accumulated on the sheet can be efficiently removed by the charge eliminating member provided on the downstream side of the sheet transport guide. As a result, the scattering of the unfixed toner can be efficiently prevented, and the occurrence of the phenomenon that the toner adheres to the fixing roller can be suppressed. Therefore, it is possible to prevent problems such as an abnormal image and a fixing offset. Thus, stable image forming performance can be obtained.
[0013]
Further, the volume resistivity of the paper transport guide is in the range of 1 × 10 ⁻³ to 1 × 10 ³ times the volume resistivity of the transfer belt.
[0014]
Thus, by limiting the volume resistivity of the paper transport guide, the stability of image formation can be further improved. As a result, it is possible to obtain more reliable image forming performance.
[0015]
The static elimination member has a shape in which a plurality of static elimination needles are formed at one end of a flat plate, and an upper surface of the static elimination member is substantially parallel to a sheet conveyance surface of the transfer belt, and the static elimination needle is positioned downstream in a sheet conveyance direction. I decided to be oriented.
[0016]
According to this configuration, the charge eliminating member does not protrude above the paper guide surface of the paper transport guide. This prevents the paper from being caught on the charge removing member, thereby preventing the occurrence of paper jam.
[0017]
Further, the static elimination needle protrudes from an end face on the downstream side of the paper transport guide.
[0018]
According to this configuration, the shape of the paper transport guide does not adversely affect the static elimination action of the paper by the static elimination member, and the entire static elimination member can eliminate the static electricity of the paper. As a result, the static elimination of the paper can be effectively performed, and more stable image forming performance can be obtained.
[0019]
The static elimination member is provided so that the distance from the tip of the static elimination needle to the paper transport path is in a range of 1 ≦ D ≦ 4 mm.
[0020]
In this way, by limiting the disposition position of the charge removing member, it is possible to prevent the charged paper from being in a state of insufficient charge removal or excessive charge removal. As a result, it is possible to effectively suppress the scattering of unfixed toner, the occurrence of fixing offset, or the occurrence of abnormal discharge in a portion where excessive static elimination is performed, thereby improving the stability of image formation.
[0021]
In the present invention, the paper transport guide is mounted on an image forming apparatus.
[0022]
According to this configuration, it is possible to obtain a more reliable image forming apparatus in which scattering of unfixed toner and occurrence of fixing offset are suppressed.
[0023]
Further, a fixing approach guide is provided downstream of the sheet transport guide in the sheet transport direction so that the leading end of the sheet is directed to the nip portion of the fixing device, and the fixing approach guide is made of a conductive material.
[0024]
According to this configuration, even after the sheet has passed the sheet transport guide, the sheet can be discharged. As a result, the effect of suppressing the fixing offset generated in the fixing device can be further enhanced, and the image forming performance can be improved.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
A paper transport guide according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side view showing a sheet transport guide. FIG. 2 is a partially enlarged perspective view of the paper transport guide shown in FIG. FIG. 3 is a top view of the paper transport guide shown in FIG. FIG. 4 is an enlarged top view of a cross section of a main part of the paper transport guide shown in FIG. FIG. 5 is a schematic partial cross-sectional view of an image forming apparatus equipped with the paper transport guide shown in FIG. Note that FIG. 3 is drawn with the intermediate portion omitted.
[0027]
First, the structure of the image forming apparatus 1 will be described with reference to FIG. The image forming apparatus 1 includes an image forming device 20, a transfer device 30, and a fixing device 40. PL indicates a paper transport path.
[0028]
In the image forming apparatus 20, a photosensitive drum 21 which is an image carrier on which a toner image is formed is disposed. The transfer device 30 transfers the toner image formed by the image forming device 20 onto a sheet, and includes a transfer belt 31, a transfer roller 32, and rollers 33 to 36. The transfer roller 32 is provided so as to face the photosensitive drum 21 via the transfer belt 31. The fixing device 40 melts an unfixed toner image on a sheet by heat and fixes the unfixed toner image on the sheet, and includes a fixing roller 41 and a pressure roller 42. The sheet is inserted into a nip formed by the fixing roller 41 and the pressure roller 42 being in contact with each other.
[0029]
The sheet separation claw 2 is disposed immediately downstream of the nip formed by the photosensitive drum 21 and the transfer belt 31 in the sheet conveyance direction. The sheet separating claw 2 is for forcibly separating the sheet adhered to the photosensitive drum 21. Downstream of the sheet separation claw 2, rotators 3 and 4 for preventing the sheet from being transported upward and an upper guide 5 are provided. In addition, a cleaning device 50 that collects toner remaining on the surface of the photosensitive drum 21 is provided near the photosensitive drum 21.
[0030]
The paper transport guide 6 is for preventing the paper from falling down, and is disposed immediately downstream of the transfer belt 31. The fixing entry guide 7 is for causing the sheet to enter a nip formed by the abutment of the fixing roller 41 and the pressure roller 42, and the sheet transport guide is arranged so that its downstream end is located near the nip. 6 is located immediately downstream. The fixing approach guide 7 is made of a conductive material.
[0031]
Next, details of the sheet transport guide 6 will be described with reference to FIGS. As described above, FIG. 3 is drawn with the intermediate portion omitted. 1 to 4 indicate the paper transport direction.
[0032]
The paper transport guide 6 is a rod-like member that is long in the paper width direction (the vertical direction in FIG. 3). The paper is transported above the paper transport guide 6, and the upper surface of the paper transport guide 6 is the paper guide surface. The paper transport guide 6 is made of a phenol resin or a noryl resin, and has a volume resistivity of 10 ¹⁰ Ω · cm (1 × 10 ¹⁰ Ω · cm). Since the volume resistivity of the transfer belt 31 is 10 ^11.5 Ω · cm (1 × 10 ^11.5 Ω · cm), the volume resistivity of the paper transport guide 6 is 1 × the volume resistivity of the transfer belt 31. ^10-1.5 times.
[0033]
As shown in FIGS. 1 and 2, the upstream end 61 of the paper guide surface of the paper transport guide 6 is located below the extension 31L of the paper transport surface 31 a of the transfer belt 31. The transfer belt 31 includes an upstream portion 6a that becomes higher as it moves downstream from the unit 61 in the sheet transport direction, and a downstream portion 6b that is parallel to the sheet transport surface 31a of the transfer belt 31.
[0034]
A flat surface 62 is formed on the upper surface of the upstream portion 6 a of the paper transport guide 6. Further, the downstream portion 6 b is configured by a flat portion 63 and a rib portion 64. The rib portion 64 is provided with a plurality of ribs 65 (see FIG. 2). The rib 65 is provided so as to be parallel to the paper transport direction. The upper surface of the rib 65 is flat, and is flush with the flat portion 63.
[0035]
Further, a static elimination member 8 is provided on the downstream side portion 6 b of the paper transport guide 6. The static elimination member 8 is made of SUS304 (a stainless steel type according to Japanese Industrial Standards) and has a shape in which a plurality of static elimination needles 8a are formed at one end of a flat plate. The pitch of the static elimination needle 8a is 1 mm, and the length of the needle is 2.5 mm. The discharging member 8 is provided such that the upper surface thereof is parallel to the sheet conveying surface 31a of the transfer belt 31, and the discharging needle 8a is directed downstream in the sheet conveying direction (see FIG. 1). Further, the static elimination needle 8 a protrudes from an end surface 66 on the downstream side of the paper transport guide 6. The protrusion amount is 1 mm. The charge removing member 8 is provided so that the distance D from the tip of the charge removing needle 8a to the paper transport path, that is, the height from the upper surface of the charge removing member 8 to the upper surface of the paper transport guide 6 is 2.5 mm.
[0036]
At both ends of the paper transport guide 6 in the paper width direction, mounting portions 67 for fixing to the image forming apparatus 1 are provided.
[0037]
Next, the operation of the paper transport guide 6 will be described with reference to FIGS. FIG. 6 is a side view illustrating a state in which the paper is transported on the paper transport guide. FIG. 7 is a side view illustrating a state of sheet conveyance on the sheet conveyance guide and the fixing approach guide. The white arrow in the drawing indicates the paper transport direction, and the thick solid line indicates the paper P.
[0038]
As shown in FIG. 6A, after the sheet P is separated from the transfer belt 31, the leading end of the sheet P contacts the plane 62 of the upstream portion 6 a of the sheet transport guide 6. The flat surface 62 gradually becomes higher from the upstream end portion 61 toward the downstream in the sheet conveying direction, so that the separation of the sheet P from the transfer belt 31 can be promoted. Further, since this portion where the sheet P comes into contact with the front end is flat, the sheet P comes into contact with the sheet transport guide 6 almost simultaneously in the entire area in the sheet width direction.
[0039]
In addition to the paper being transported in this manner, the volume resistivity of the paper transport guide 6 is 1 × 10 ^−1.5 times the volume resistivity of the transfer belt 31, so that the ^space between the paper and the paper transport guide Therefore, a large potential difference does not occur. Therefore, since it is expected that the paper P is sufficiently neutralized, scattering of unfixed toner can be prevented, and the occurrence of the phenomenon that toner adheres to the fixing roller 41 can be suppressed. The effect of the relationship between the volume resistivity of the paper transport guide 6 and the volume resistivity of the transfer belt 31 on the occurrence of scattering of unfixed toner will be described later (see FIG. 8).
[0040]
Thereafter, as shown in FIG. 6B, the paper P is conveyed while being in contact with the paper guide surface. The rib portion 64 is formed on the downstream side portion 6b of the paper transport guide 6, and the plurality of ribs 65 are provided. Therefore, the contact area between the paper P and the paper guide surface can be reduced. The sheet P can be prevented from sticking to the sheet transport guide 6. Thereby, the transportability of the paper P is improved.
[0041]
Then, a static elimination member 8 is provided on the downstream side portion 6b. By providing the static elimination member 8 as described above, the static elimination member 8 does not protrude above the paper guide surface. Therefore, since the paper P is not caught on the charge removing member 8, it is possible to prevent the occurrence of paper jam. Further, the electric charges accumulated on the paper P can be efficiently removed. As a result, it is possible to enhance the effect of suppressing the occurrence of the abnormal image due to the discharge and the occurrence of the fixing failure due to the insufficient charge elimination of the sheet P. Thereby, more stable image forming performance can be obtained.
[0042]
Next, as shown in FIG. 7, the sheet P is conveyed while being in contact with the fixing approach guide 7, and the leading end of the sheet P enters the nip portion of the fixing device 40. Since the fixing approach guide 7 is made of a conductive material, the electricity of the sheet P can be removed even after the sheet P has passed the sheet transport guide 6. As a result, the effect of suppressing the fixing offset generated in the fixing device 40 can be further increased, and the image forming performance can be improved.
[0043]
FIG. 8 is a graph showing the effect of the relationship between the volume resistivity of the paper transport guide and the volume resistivity of the transfer belt on the occurrence of scattering of unfixed toner. This figure shows the unfixed state when the magnification of the volume resistivity of the paper transport guide 6 based on the volume resistivity of the transfer belt 31 is changed in the range of 1 × 10 ⁻⁹ to 1 × 10 ^6. The results of evaluation of toner scattering are shown. Note that, for example, “10 ⁻³ ” on the horizontal axis in the drawing means “1 × 10 ⁻³ ”.
[0044]
Here, the occurrence of scattering of the unfixed toner is evaluated based on the following test. First, two types of originals are prepared: an A4-size original of a full-scale gray image, and an original in which several black solid portions (30 mm × 30 mm) are drawn. These are successively printed on both sides of a new sheet three times in a row. For this double-sided printing paper, the state of occurrence of scattering of unfixed toner is evaluated. The evaluation method was “5 points” if no image was generated, “4 points” if there was a slight trace of the occurrence of scattering on the front end of the back surface of the entire gray image printing paper, "3 points" when there is a trace of the occurrence of scattering around the black solid portion, and "2 points" when there is a trace of the occurrence of scattering on the entire surface of the entire gray image printing paper. The surface having traces of the occurrence of scattering is designated as "one point". The higher the evaluation point, the better the performance.
[0045]
As a result of the evaluation as described above, the following was found. In other words, the magnification of the volume resistivity of the paper transport guide 6 based on the volume resistivity of the transfer belt 31 is high in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁵ , and particularly 1 × 10 ^−5. In the range of 10 ⁻³ times to 1 × 10 ³ times, even better results are obtained.
[0046]
Therefore, the volume resistivity of the paper transport guide 6 is preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁵ times the volume resistivity of the transfer belt 31, and more preferably 1 × 10 ⁻³ to 1 × 10 ^5. 10 ³ times the range is good. Based on this result, the paper transport guide 6 of the above-described embodiment has a volume resistivity of 1 × 10 ^−1.5 times the volume resistivity of the transfer belt 31.
[0047]
As described above, by limiting the volume resistivity of the paper transport guide 6, a large potential difference does not occur between the paper separated from the transfer belt 31 and the paper transport guide 6. As a result, when the transported paper separates from the transfer belt 31 and moves onto the paper transport guide 6, discharge due to a sudden change in potential can be suppressed, and scattering of unfixed toner on the paper can be prevented. Is possible.
[0048]
FIG. 9 is a table showing the effect of the distance from the leading end of the static elimination needle to the paper transport path on scattering of unfixed toner and occurrence of fixing offset. This figure shows the evaluation results of the scattering of the unfixed toner and the occurrence of the fixing offset when the distance D from the tip of the static elimination needle 8a to the paper transport path is changed in the range of 0.5 mm to 4.5 mm.
[0049]
The occurrence of scattering of the unfixed toner is evaluated based on the same test as the above-described test. However, the evaluation method used here was "◎" if no image was generated, "○" indicates that there was a slight mark of scattering on the front end of the back surface of the entire gray image printing paper, and scattering was generated around the solid black area Is marked "x".
[0050]
The occurrence of the fixing offset is evaluated based on the following test. First, a manuscript is prepared in which a text, a design, and the like are drawn in a range of 150 mm from the leading end on the A3 size, and nothing is drawn on the downstream side from there. This is continuously printed on 10 sheets. With respect to this printing paper, it is evaluated whether a fixing offset occurs in a pure white portion on the downstream side. The evaluation method is “◎” if no occurrence occurs, “○” if the eye can be checked closely, and “×” if a clear offset image is printed.
[0051]
As a result of the evaluation as described above, the following was found. That is, the scattering of the unfixed toner is almost suitable when the distance D is in the range of 1 mm to 4.5 mm, and preferably in the range of 2 mm to 4.5 mm. As for the fixing offset, it is almost preferable that the distance D is in the range of 0.5 mm to 4 mm, and more desirably, it is in the range of 0.5 mm to 3 mm.
[0052]
Therefore, in consideration of both of these evaluation results, the distance D from the tip of the static elimination needle 8a to the paper transport path is preferably in a range of 1 ≦ D ≦ 4 mm, and more preferably in a range of 2 ≦ D ≦ 3 mm. . Based on this result, the static elimination member 8 of the above embodiment has a distance D from the tip of the static elimination needle 8a to the paper transport path, that is, a height from the upper surface of the static elimination member 8 to the upper surface of the paper transport guide 6 of 2.5 mm. It is provided so that
[0053]
In this way, by limiting the arrangement position of the charge removing member 8, it is possible to prevent the charged paper from being in a state of insufficient charge removal or excessive charge removal. As a result, scattering of unfixed toner and occurrence of fixing offset can be effectively suppressed, and the stability of image formation can be improved.
[0054]
By mounting the above-described paper transport guide 6 on the image forming apparatus 1, it is possible to obtain a more reliable image forming apparatus 1 in which scattering of unfixed toner and occurrence of fixing offset are suppressed. It becomes.
[0055]
Although the embodiment of the present invention has been described above, other various modifications can be made without departing from the gist of the present invention.
[0056]
【The invention's effect】
According to the configuration of the present invention, a large potential difference does not occur between the sheet separated from the transfer belt and the sheet conveyance guide. As a result, when the conveyed paper separates from the transfer belt and moves onto the paper conveyance guide, it is possible to suppress discharge due to a sudden change in potential, and to prevent scattering of unfixed toner on the paper. It is.
[0057]
The charge accumulated on the sheet can be efficiently removed by the charge eliminating member provided on the downstream side of the sheet transport guide. As a result, the scattering of the unfixed toner can be efficiently prevented, and the occurrence of the phenomenon that the toner adheres to the fixing roller can be suppressed. Therefore, it is possible to prevent problems such as an abnormal image and a fixing offset. Thus, stable image forming performance can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view showing a paper transport guide according to an embodiment of the present invention. FIG. 2 is a partially enlarged perspective view of the paper transport guide shown in FIG. 1. FIG. 3 is a top view of the paper transport guide shown in FIG. 4 is an enlarged top view of a main part of the paper transport guide shown in FIG. 1; FIG. 5 is a schematic partial cross-sectional view of an image forming apparatus equipped with the paper transport guide shown in FIG. 1; FIG. 7 is a side view showing a paper conveyance state on a paper conveyance guide and a fixing approach guide. FIG. 8 A relationship between the volume resistivity of the paper conveyance guide and the volume resistivity of the transfer belt is undecided. FIG. 9 is a graph showing the effect of the toner on the occurrence of scattering. FIG. 9 is a table showing the effect of the distance from the tip of the static elimination needle to the paper transport path on the scattering of unfixed toner and the occurrence of a fixing offset.
DESCRIPTION OF SYMBOLS 1 Image forming apparatus 6 Paper conveyance guide 6a Upstream part (of paper conveyance guide) 6b Downstream part (of paper conveyance guide) 7 Fixing approach guide 8 Static elimination member 8a Static elimination needle 20 Imaging device 30 Transfer device 40 Fixing device 61 Upstream end 62 (of the paper conveyance guide) Flat surface 63 Flat surface 64 Rib portion 65 Rib 66 Downstream end surface (of the paper conveyance guide)

Claims (7)

The transfer belt, which electrostatically attracts and transports the paper on which the toner image of the image carrier of the image forming apparatus has been transferred, is located downstream in the paper transport direction, and the leading end of the paper separated from the transfer belt faces the fixing device. In the paper transport guide arranged as described above, the volume resistivity is set in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁵ times the volume resistivity of the transfer belt, and a discharging member is provided on the downstream side. A paper transport guide, characterized in that: 2. The paper transport guide according to claim 1, wherein the volume resistivity of the paper transport guide is in a range of 1 × 10 ⁻³ to 1 × 10 ³ times the volume resistivity of the transfer belt. ³ . The static elimination member has a shape in which a plurality of static elimination needles are formed at one end of a flat plate, and an upper surface of the static elimination member is substantially parallel to a sheet conveying surface of the transfer belt, and the static elimination needle points downstream in the sheet conveying direction. The paper transport guide according to claim 1 or 2, wherein 4. The paper transport guide according to claim 3, wherein the static elimination needle protrudes from an end surface on the downstream side of the paper transport guide. The paper according to claim 3 or 4, wherein the static elimination member is provided so that a distance from a tip of the static elimination needle to a paper transport path is in a range of 1 ≦ D ≦ 4 mm. Transport guide. An image forming apparatus comprising the paper transport guide according to any one of claims 1 to 5. A fixing approach guide is provided downstream of the sheet transport guide in the sheet transport direction so that the leading end of the sheet is directed to a nip portion of the fixing device, and the fixing approach guide is formed of a conductive material. Item 7. An image forming apparatus according to Item 6.

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