Image forming device

Abstract

To provide an image formation apparatus capable of achieving stable conveyance of a recording medium by reducing toner pollution of a conveyance guide arranged on a recording medium conveyance path reaching a fixing part from a transfer part.SOLUTION: An image formation apparatus includes an image carrier body, a transfer part, a fixing part, a recording medium carrier path and a conveyance guide. The conveyance guide is arranged on the recording medium carrier path through which a recording medium conveyed from the transfer part to the fixing part passes, and faces a surface to which a toner image is not transferred. The conveyance guide includes a resin guide frame and a metallic guide plate. The guide frame has a plurality of guide ribs arranged at a prescribed interval in a width direction orthogonal to the conveyance direction of the recording medium, and a plurality of first opening parts partitioned by the guide ribs. The guide plate has a guide face in contact with the rear face of the guide frame and exposed on the inside of the recording medium conveyance path from the first opening part, and is formed with a second opening part on both ends in the width direction of the guide face.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine thereof that uses an electrophotographic system, and relates to an image forming apparatus that is equipped with a transport guide that transports a recording medium such as paper onto which a toner image has been transferred from an image carrier in a transfer section to a fixing section. [Background technology]

[0002] In electrophotographic image forming devices such as copiers, printers, and facsimiles, powder developer (toner) is mainly used, and the photosensitive layer on the surface of the photosensitive drum (image carrier) is charged to a predetermined surface potential (the same polarity as the toner's charging polarity) by a charging device, and then an electrostatic latent image is formed on the photosensitive drum by an exposure device.Then, the formed electrostatic latent image is visualized by toner in the developing device, and the toner image is transferred onto paper (recording medium) that passes through a transfer section facing the photosensitive drum, and then fixed in a fixing section.

[0003] Also, a configuration is known in which a metal transport guide is arranged in the paper transport path from the transfer unit to the fixing unit, and the behavior of the paper is stabilized by transporting the paper while pulling it toward the transport guide. For example, Patent Document 1 discloses an image forming apparatus equipped with a transport guide having a metal guide plate and a resin guide rib arranged to protrude from the surface of the guide plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-113679 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a considerable amount of floating toner in the paper transport path from the transfer unit to the fixing unit. The metal transport guide is electrically grounded, and the potential difference between the transport guide and the paper is used to attract the paper to the guide, stabilizing the paper's behavior. However, because the floating toner is also electrically charged, it is attracted to the transport guide in the area outside the edge of the paper.

[0006] As printing continues, the toner attracted to the transport guide adheres to the surface of the transport guide in layers, contaminating the guide. As a result, the grounding effect of the transport guide decreases, reducing the potential difference between the transport guide and the paper, thereby reducing the paper's adhesive force. Furthermore, because the adhered toner itself is electrically charged, repulsion from the charged paper at the transfer section further worsens the behavior of the paper, ultimately resulting in the problem of wrinkles on the paper.

[0007] In view of the above problems, the present invention aims to provide an image forming apparatus that reduces toner contamination of the transport guides arranged in the recording medium transport path from the transfer unit to the fixing unit, and that can transport the recording medium stably. [Means for solving the problem]

[0008] In order to achieve the above object, a first aspect of the present invention is an image forming apparatus including an image carrier, a transfer unit, a fixing unit, a recording medium transport path, and a transport guide. The image carrier carries a toner image. The transfer unit transfers the toner image formed on the image carrier onto a recording medium. The fixing unit fixes the toner image transferred by the transfer unit onto the recording medium. The recording medium transport path passes through the recording medium transported from the transfer unit to the fixing unit. The transport guide is disposed in the recording medium transport path and faces the side of the recording medium to which the toner image is not transferred. The transport guide includes a guide frame and a guide plate. The guide frame is made of resin and has multiple guide ribs arranged at predetermined intervals in a width direction perpendicular to the recording medium transport direction, and multiple first openings partitioned by the guide ribs. The guide plate is made of metal and has a guide surface that contacts the back surface of the guide frame and is exposed to the inside of the recording medium transport path through the first opening, and second openings are formed at both widthwise ends of the guide surface. [Effects of the Invention]

[0009] According to the first aspect of the present invention, by forming second openings at both widthwise ends of the guide plate, the phenomenon in which unfixed toner on the recording medium wraps around the widthwise edge of the recording medium and is attracted to the guide plate is suppressed. This makes it possible to suppress adhesion of toner to the guide surface, and to suppress the problem of toner adhering to the guide plate and the charged recording medium electrically repelling each other, which deteriorates the conveyance behavior and causes wrinkles on the recording medium. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus 100 according to a first embodiment of the present invention; [Figure 2] 1 is a partial cross-sectional view of the vicinity of a paper transport path 19 and a reverse transport path 20 in an image forming apparatus 100 according to a first embodiment; [Figure 3] 1 is a perspective view of the periphery of a conveying guide 30 of a conveying unit 23 mounted in the image forming apparatus 100 according to the first embodiment, as viewed from inside the image forming apparatus 100. [Figure 4]4 is an enlarged view of one end of the conveying guide 30 in FIG. [Figure 5] 1 is a perspective view of a guide plate 30b constituting the conveying guide 30, seen from the conveying surface side. [Figure 6] 1 is an enlarged plan view of the vicinity of the second opening 50 of the guide plate 30b. [Figure 7] A side cross-sectional view of the vicinity of the second opening 50 of the guide plate 30b. [Figure 8] FIG. 10 is an exploded perspective view of a transport unit 23 mounted in an image forming apparatus 100 according to a second embodiment of the present invention. [Figure 9] 10 is a partial cross-sectional view of the image forming apparatus 100 according to the second embodiment, from the secondary transfer nip portion N to the fixing unit 14. [Figure 10] 10 is an enlarged plan view of the vicinity of the second opening 50, showing a modified example of the guide plate 30b that constitutes the conveying guide 30. [Figure 11] 10 is a side cross-sectional view of the vicinity of the second opening 50, showing a modified example of the guide plate 30b that constitutes the conveying guide 30. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing the internal structure of an image forming apparatus 100 according to one embodiment of the present invention. Within the main body of the image forming apparatus 100 (here, a color printer), four image forming units Pa, Pb, Pc, and Pd are arranged in this order from the upstream side in the transport direction (left side in Fig. 1). These image forming units Pa to Pd are provided corresponding to images of four different colors (yellow, cyan, magenta, and black), and sequentially form images of yellow, cyan, magenta, and black through the processes of charging, exposure, development, and transfer, respectively.

[0012] Each of the image forming stations Pa through Pd is provided with photosensitive drums (image carriers) 1a, 1b, 1c, and 1d, which carry visible images (toner images) of each color. An intermediate transfer belt (intermediate transfer member) 8, which rotates counterclockwise in FIG. 1 by a belt drive motor (not shown), is provided adjacent to each of the image forming stations Pa through Pd. The toner images formed on the photosensitive drums 1a through 1d are sequentially transferred (primary transfer) onto the intermediate transfer belt 8, which moves while contacting the photosensitive drums 1a through 1d, and then superimposed on each other. The toner images primarily transferred onto the intermediate transfer belt 8 are then secondarily transferred onto a transfer sheet P (an example of a recording medium) by a secondary transfer roller 9. The transfer sheet P onto which the toner images have been secondarily transferred is then fixed in a fixing unit 13, and then ejected from the image forming apparatus 100. While the photosensitive drums 1a through 1d are rotating clockwise in FIG. 1, an image formation process is performed on each of the photosensitive drums 1a through 1d.

[0013] The transfer paper P onto which the toner image is secondarily transferred is stored in a paper cassette 16 located at the bottom of the main body of the image forming apparatus 100, and is transported via a paper feed roller 12 and a pair of registration rollers 13 along a paper transport path 19 to the nip between the secondary transfer roller 9 and a drive roller 11 of the intermediate transfer belt 8. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a seamless belt is usually used. In addition, a blade-shaped belt cleaner 19 is located downstream of the secondary transfer roller 9 to remove toner and other particles remaining on the surface of the intermediate transfer belt 8.

[0014] Next, the image forming units Pa to Pd will be described. Around and below the rotatably arranged photosensitive drums 1a to 1d, there are provided charging devices 2a, 2b, 2c, and 2d that charge the photosensitive drums 1a to 1d, an exposure device 5 that exposes image information onto each of the photosensitive drums 1a to 1d, developing devices 3a, 3b, 3c, and 3d that form toner images on the photosensitive drums 1a to 1d, and cleaning devices 7a, 7b, 7c, and 7d that remove developer (toner) and the like remaining on the photosensitive drums 1a to 1d.

[0015] When image data is input from a host device such as a personal computer, the charging devices 2a-2d first uniformly charge the surfaces of the photosensitive drums 1a-1d. Next, the exposure device 5 irradiates light according to the image data, forming electrostatic latent images on each of the photosensitive drums 1a-1d. The developing devices 3a-3d are filled with a predetermined amount of two-component developer containing yellow, cyan, magenta, and black toner, respectively. If the toner content in the two-component developer in each of the developing devices 3a-3d falls below a specified value due to the formation of a toner image (described below), toner is replenished from toner containers 4a-4d to each of the developing devices 3a-3d. The toner in the developer is supplied to the photosensitive drums 1a-1d by the developing devices 3a-3d and electrostatically adheres to them. This results in the formation of a toner image corresponding to the electrostatic latent image formed by exposure from the exposure device 5.

[0016] Then, primary transfer rollers 6a-6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a-6d and the photosensitive drums 1a-1d, and the yellow, magenta, cyan, and black toner images on the photosensitive drums 1a-1d are primarily transferred onto the intermediate transfer belt 8. These images are formed with a predetermined positional relationship. After that, in preparation for the subsequent formation of a new electrostatic latent image, toner and the like remaining on the surfaces of the photosensitive drums 1a-1d after the primary transfer are removed by cleaning devices 7a-7d.

[0017] The intermediate transfer belt 8 is stretched over a driven roller 10 on the upstream side and a drive roller 11 on the downstream side. When the intermediate transfer belt 8 starts to rotate counterclockwise in accordance with the rotation of the drive roller 11 by a belt drive motor (not shown), the transfer paper P is transported at a predetermined timing from the registration roller pair 13 to a secondary transfer nip N (see FIG. 2) between the drive roller 11 and the secondary transfer roller 9 provided adjacent to it. The toner image on the intermediate transfer belt 8 is then secondarily transferred onto the transfer paper P passing through the secondary transfer nip N.

[0018] The transfer paper P onto which the toner image has been secondarily transferred is transported to the fixing unit 14. The fixing unit 14 has a fixing belt 14a and a pressure roller 14b (see FIG. 2 for both). The fixing belt 14a is heated by a heating device (not shown) such as a heater or an induction heating unit. The pressure roller 14b is pressed against the fixing belt 14a to form a fixing nip and apply a rotational driving force to the fixing belt 14a.

[0019] The transfer paper P conveyed to the fixing unit 14 is heated and pressurized by the fixing belt 14a and pressure roller 14b, and the toner image is fixed to the surface of the transfer paper P, forming a predetermined full-color image. The transfer paper P on which the full-color image has been formed is then directed to a branching unit 15, which branches into multiple directions, and is then discharged directly (or after being sent to the double-sided conveying path 20 and having images formed on both sides) onto a discharge tray 18 by a pair of discharge rollers 17.

[0020] 2 is a partial cross-sectional view of the vicinity of the paper transport path 19 and the reverse transport path 20 in the image forming apparatus 100 of the first embodiment. The side cover 21 constitutes the side 102 of the image forming apparatus 100 and is rotatably supported on a cover support shaft 21a provided below the main body of the image forming apparatus 100. Hooks 22 are provided on the side edges of the side cover 21. The hooks 22 hold the side cover 21 in a closed state by engaging with engagement pins (not shown) provided on the front frame and rear frame of the main body of the image forming apparatus 100. The inner surface of the side cover 21 constitutes one transport surface of the reverse transport path 20.

[0021] A transport unit 23 is disposed inside the side cover 20. The transport unit 23 is rotatably supported on the main body of the image forming apparatus 100 around a unit support shaft 23a, and constitutes part of the transport surfaces of the reverse transport path 20 and the paper transport path 19. The reverse transport path 20 extends in the vertical direction along the side surface 102 of the image forming apparatus 100 between the inner surface of the side cover 21 and the outer surface of the transport unit 23, and is configured to curve in a substantially C-shape before merging with the paper transport path 19. On the inner surface of the transport unit 23, in this order from the upstream side in the paper transport direction (the lower side in FIG. 2), one roller 13b of the registration roller pair 13 and the secondary transfer roller 9 are attached.

[0022] By rotating only the side cover 21 in the open direction relative to the image forming apparatus 100, a wide area of ​​the reverse transport path 20 is exposed. Furthermore, by rotating the side cover 21 together with the transport unit 23 in the open direction, the transport unit 23 moves away from the main body of the image forming apparatus 100, exposing a wide area of ​​the paper transport path 19. On the other hand, by rotating the side cover 21 together with the transport unit 23 in the closed direction, the transport unit 23 comes into contact with the main body of the image forming apparatus 100, and the secondary transfer roller 9 is pressed against the drive roller 11 via the intermediate transfer belt 8.

[0023] Fig. 3 is a perspective view of the periphery of a transport guide 30 arranged in the transport unit 23 of the image forming apparatus 100 of the first embodiment, as seen from the inside of the image forming apparatus 100 (the left side of Fig. 2). Fig. 4 is an enlarged view of one end side (the front right side of Fig. 3) of the transport guide 30 in Fig. 3. As shown in Figs. 3 and 4, the transport guide 30 is arranged in the transport unit 23. The transport guide 30 guides the transfer paper P that has passed through the secondary transfer nip portion N in the paper transport path 19 downstream of the secondary transfer roller 9 to the fixing unit 14.

[0024] The conveying guide 30 has a guide frame 30a and a guide plate 30b. The guide frame 30a is made of resin and has a plurality of guide ribs 31 arranged at predetermined intervals in the paper width direction (left and right direction in FIG. 3) perpendicular to the paper conveying direction, and a plurality of first openings 33 partitioned by the guide ribs 31.

[0025] The guide plate 30b is formed by bending a metal plate into a predetermined shape. 6 The guide plate 30b is grounded (earthed) via a resistor (not shown) having a resistance in the unit of Ω. Second openings 50 are formed at both ends of the guide plate 30b in the paper width direction. Step portions 51 are provided inside the second openings 50. The detailed configuration of the guide plate 30b will be described later.

[0026] A charge-eliminating needle protective cover 34 is disposed between the secondary transfer roller 9 and the conveying guide 30. The charge-eliminating needle protective cover 34 is made of resin and protects the tip of the charge-eliminating needle (not shown). The charge-eliminating needle applies a voltage (transfer reverse voltage) of the same polarity (positive polarity) as the toner to remove residual charge from the transfer paper P passing through the secondary transfer nip N, improving the separation of the transfer paper P from the secondary transfer roller 9.

[0027] Fig. 5 is a perspective view of guide plate 30b constituting conveying guide 30, seen from the conveying surface side. Fig. 6 is an enlarged plan view of the vicinity of second opening 50 of guide plate 30b. Fig. 7 is a side cross-sectional view (cross-sectional view taken along arrow AA' in Fig. 6) of the vicinity of second opening 50 of guide plate 30b.

[0028] Guide plate 30b is formed by bending a metal plate into a roughly U-shape when viewed from the side, and has a guide surface 35, a support surface 37, and an upper surface 39. Guide surface 35 contacts the back surface of guide frame 30a and is exposed to the inside of paper transport path 19 through first opening 33, facing the non-printing surface of transfer paper P transported along paper transport path 19. A sensor placement window 35a is formed in the center of the longitudinal direction of guide surface 35. The detection surface of a paper detection sensor (not shown) is positioned in sensor placement window 35a, and detects transfer paper P transported along paper transport path 19.

[0029] The support surface 37 is connected to the lower end of the guide surface 35 via a folding line. A pair of support portions 40 are formed at both longitudinal ends of the support surface 37. The support portions 40 have a positioning hole 40a and a screw hole 40b. The positioning hole 40a fits into a positioning boss (not shown) formed on the transport unit 23, thereby positioning the guide plate 30b relative to the transport unit 23. A screw (not shown) is fastened into the screw hole 40b to secure the guide plate 30b to the transport unit 23.

[0030] The upper surface 39 is connected to the upper end of the guide surface 35 via a folding line and extends approximately parallel to the support surface 37. A pair of second openings 50 is formed at both longitudinal ends of the guide plate 30b, spanning from the upper surface 39 to the guide surface 35. A step portion 51 is formed on the inside of the second opening 50. As shown in FIGS. 6 and 7, the step portion 51 is formed by bending a protruding piece extending from the upper surface 39 to the inside of the second opening 50 parallel to the guide surface 35. At this time, a ridge line (folding line) between the upper surface 39 and the step portion 51 is bent and shifted relative to the guide surface 35 in a direction away from the conveying surface of the conveying guide 30 (the surface of the guide frame 30a), thereby forming a predetermined step (distance) d between the guide surface 35 and the step portion 51.

[0031] An anti-static sheet 41 is attached to the upstream end of the guide surface 35 in the paper transport direction (the lower end in Figures 5 to 7). The anti-static sheet 41 is attached with conductive double-sided adhesive tape across the entire width of the guide surface 35 (the left-right direction in Figure 5). The anti-static sheet 41 protrudes from the first opening 33 of the guide frame 30a and comes into contact with the transfer paper P transported along the transport guide 30, removing any residual charge on the transfer paper P that was not completely removed by the static elimination needles. This stabilizes the transport behavior of the transfer paper P. The anti-static sheet 41 is made of a material such as a conductive non-woven fabric.

[0032] As described above, unfixed toner on the charged transfer paper P tends to float on the paper transport path 19 from the secondary transfer nip N to the fixing unit 14. If this toner adheres to the surface of the guide plate 30b of the transport guide 30, the grounding effect of the guide plate 30b decreases, reducing the potential difference between the guide plate 30b and the transfer paper P and reducing the adhesive force on the transfer paper P. Furthermore, the toner adhering to the guide plate 30b and the charged transfer paper P electrically repel each other, worsening the transport behavior and potentially causing wrinkles in the transfer paper P. In particular, in areas outside the widthwise edges of the transfer paper P, unfixed toner on the transfer paper P tends to wrap around the widthwise edges and adhere to the guide plate 30b.

[0033] Therefore, in this embodiment, a second opening 50 is formed in the portion of guide plate 30b facing the widthwise edge of transfer sheet P, and a step 51 is provided inside second opening 50. Step 51 is located at a greater distance from the conveying surface of conveying guide 30 (the surface of guide frame 30a) than guide surface 35. This reduces the force attracting unfixed toner on transfer sheet P, thereby preventing toner from adhering to step 51. Note that providing second opening 50 and step 51 also reduces the attraction force of transfer sheet P at both widthwise ends of guide plate 30b, but because transfer sheet P is attracted by portions of guide plate 30b other than step 51 (guide surface 35), transfer sheet P can be stably conveyed along conveying guide 30.

[0034] In this embodiment, the second opening 50 and the step portion 51 are formed at a position that overlaps with the widthwise edge position (dashed line L1 in Figure 4) of the A3 size (420 x 297 mm), which is the maximum size of transfer paper P passing through the paper transport path 19, and the widthwise edge position (dotted line L2 in Figure 4) of the LEDGER size (431.8 x 279.4 mm).

[0035] If the step d between the guide surface 35 and the step portion 51 is too small, the effect of suppressing toner adhesion will be reduced, and the effect of stabilizing the transport of the transfer paper P will also be reduced. Therefore, it is preferable that the step d be 2 mm or more.

[0036] Furthermore, if the static elimination sheets 41 are not placed at both widthwise ends of the guide plate 30b due to the formation of the second opening 50 and the step portion 51, the charge imparted to the transfer sheet P when it passes through the secondary transfer nip N cannot be completely removed, and the transport behavior of the overcharged transfer sheet P becomes unstable. Therefore, in this embodiment, the static elimination sheet 41 is placed over the entire upstream end (lower end) of the guide plate 30b in the paper transport direction, and the second opening 50 and step portion 51 are formed downstream of the static elimination sheet 41. This makes it possible to achieve both the effect of removing charge from the transfer sheet P by the static elimination sheet 41 and the effect of suppressing toner adhesion to the guide plate 30b by the second opening 50 and step portion 51, thereby further improving the transport stability of the transfer sheet P.

[0037] Furthermore, the static elimination sheet 41 not only removes residual charge from the transfer paper P, but also has the function of dissipating charge accumulated in the non-conductive resin guide frame 30a by self-discharge, thereby eliminating the disturbance of the toner image and the unevenness of the transfer paper P transport state caused by excessive charging of the resin guide frame 30a.

[0038] 8 is an exploded perspective view of a transport unit 23 mounted on an image forming apparatus 100 according to a second embodiment of the present invention. In this embodiment, an intake fan 60 and a filter 61 are disposed at positions facing the second opening 50 and the step portion 51 on the rear side of the transport guide 30. The structures of the guide frame 30a and guide plate 30b that constitute the transport guide 30 are the same as those in the first embodiment shown in FIGS. 3 to 7.

[0039] The intake fan 60 sucks air through the second opening 50 (step d between the guide surface 35 and the step portion 51). In this embodiment, an axial flow fan is used as the intake fan 60. The filter 61 is disposed downstream of the intake fan 60 and collects foreign matter such as toner contained in the airflow sucked by the intake fan 60.

[0040] 9 is a partial cross-sectional view from the secondary transfer nip N to the fixing unit 14 in the image forming apparatus 100 of the second embodiment. As indicated by the white arrow in Fig. 9, the airflow sucked in by the intake fan 60 passes through a duct 63 in the transport unit 23, is exhausted to the width direction end of the fixing unit 14, and is blown against the axial direction end of the fixing belt 14a and the pressure roller 14b.

[0041] According to this embodiment, by using the intake fan 60 to draw air through the second opening 50 of the guide plate 30b, it is possible to compensate for the reduction in the attraction effect of the transfer paper P caused by the provision of the second opening 50 and the step portion 51, and the transport behavior of the transfer paper P can be further stabilized.

[0042] Furthermore, when small-sized transfer sheets P are continuously fed, the temperature drops in the axial center (sheet-feeding area) of the fixing belt 14a and pressure roller 14b as heat is absorbed by the transfer sheet P, whereas the axial ends (non-sheet-feeding areas) of the fixing belt 14a and pressure roller 14b are prone to becoming hot because heat is not absorbed by the transfer sheet P. In particular, if the temperature of the sheet-feeding area is maintained at the fixing temperature (target temperature) during continuous printing, the non-sheet-feeding areas may overheat, causing problems such as the fixing belt 14a, pressure roller 14b, etc. exceeding their heat-resistant limit and being damaged.

[0043] Therefore, by blowing the airflow generated by the intake fan 60 onto both axial ends of the fixing unit 14, it is possible to prevent excessive temperature rise at both axial ends of the fixing belt 14a and the pressure roller 14b.

[0044]

[0083] The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. For example, in the above-described embodiments, second openings 50 are formed at both widthwise ends of guide plate 30b constituting conveying guide 30, and step portions 51 are provided inside second openings 50. However, as shown in the modified examples in Figures 10 and 11, only second openings 50 may be formed at both widthwise ends of guide plate 30b, and step portions 51 may not be provided.

[0045] 10 and 11, as with the first and second embodiments, it is possible to prevent toner from adhering to the guide plate 30b, and therefore toner adhering to the guide plate 30b and the charged transfer paper P electrically repel each other, which deteriorates the transport behavior and prevents wrinkles from forming in the transfer paper P. However, the force attracting both widthwise ends of the transfer paper P is weaker than in the first and second embodiments in which the step portions 51 are provided. For this reason, the configurations of the first and second embodiments in which the step portions 51 are provided within the second opening 50 are more preferable.

[0046] Furthermore, the image forming apparatus of the present invention is not limited to an intermediate transfer type color printer as shown in FIG. 1, but may also be other image forming apparatuses equipped with a transport guide for paper transported from the transfer unit to the fixing unit, such as monochrome and color copiers, digital multifunction machines, monochrome printers, and facsimiles. [Industrial Applicability]

[0047] The present invention can be used in an image forming apparatus equipped with a transport guide that transports a recording medium, such as paper, onto which a toner image has been transferred from an image carrier to a fixing unit. By utilizing the present invention, it is possible to provide an image forming apparatus that can reduce toner contamination of the transport guide arranged in the recording medium transport path from the transfer unit to the fixing unit and can transport the recording medium stably. [Explanation of symbols]

[0048] Pa~Pd Image forming section 1a to 1d Photosensitive drum 7a~7d Cleaning device 8 Intermediate transfer belt (image carrier) 9 Secondary transfer roller 14 Fixing section 19 Paper transport path (recording medium transport path) 23 Transport unit 30 Transport guide 30a guide frame 30b Guide plate 31 Guide rib 33 First Opening 35 Guide surface 37 Support surface 39 Top side 40 Support part 41 Antistatic sheet (antistatic material) 50 Second opening 51 Step 60 Intake fan 61 filters 63 Duct 100 Image forming device N Secondary transfer nip (transfer area) P Transfer paper (recording medium)

Claims

1. an image carrier that carries a toner image; a transfer unit that transfers the toner image formed on the image carrier onto a recording medium; a fixing unit that fixes the toner image transferred by the transfer unit onto the recording medium; a recording medium transport path through which the recording medium passes when transported from the transfer unit to the fixing unit; a conveyance guide disposed on the recording medium conveyance path and facing a surface of the recording medium on which the toner image is not transferred; In an image forming apparatus comprising: The conveying guide is a resin guide frame having a plurality of guide ribs arranged at predetermined intervals in a width direction perpendicular to the conveyance direction of the recording medium and a plurality of first openings partitioned by the guide ribs; a metal guide plate that contacts the rear surface of the guide frame and has a guide surface that is exposed to the inside of the recording medium transport path through the first opening; and The guide plate is a second opening is formed at each end of the guide surface in the width direction; an image forming apparatus, characterized in that a step portion, which is a plane parallel to the guide surface and has a predetermined step with respect to the guide surface in a direction away from the guide frame, is provided inside the second opening;

2. 2. The image forming apparatus according to claim 1, wherein the second opening is formed so as to overlap an edge portion in the width direction of the recording medium of a maximum size that passes through the recording medium transport path.

3. An image forming apparatus as described in claim 1 or claim 2, characterized in that the step portion has a step of 2 mm or more relative to the guide surface.

4. The guide plate has a neutralizing member disposed across the entire width of the guide plate at an upstream end of the guide surface with respect to the conveying direction of the recording medium, 4. The image forming apparatus according to claim 1, wherein the second opening is formed downstream of the charge removing member.

5. An image forming apparatus as described in any one of claims 1 to 4, characterized in that an intake fan is arranged at a position opposite the second opening on the back of the transport guide to suck in air from the recording medium transport path through the second opening.

6. A duct that exhausts the air flow sucked by the intake fan to both ends of the fixing unit in the width direction; a filter that collects toner contained in the air flow passing through the duct; 6. The image forming apparatus according to claim 5, further comprising:

Images