JP2019200288A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of effectively suppressing fluttering of a recording medium on the upstream side of a transfer nip, and reducing a conveyance load when conveying a recording medium having a strong elasticity. An image forming apparatus includes an image carrier, a transfer member, a registration roller pair, and a conveyance guide. The transport guide is composed of a first transport guide and a second transport guide that face the surfaces of the recording medium transported from the pair of registration rollers to the transfer nip on the image carrier side and the transfer member side. The second conveyance guide has a convex portion that protrudes closest to the first conveyance guide side in the recording medium conveyance path from the registration roller pair to the transfer nip, and a step portion that is formed adjacent to the downstream side of the convex portion. The main body, an elastic member protruding toward the first transport guide side from a plane passing through the downstream end of the convex portion and the downstream end of the stepped portion, and an elastic surface facing the first transport guide of the main body are elastic members. And a film member covering the same. [Selection diagram] Fig. 3

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly to a method for stabilizing the conveyance state of a recording medium on the upstream side of an image carrier and a transfer member.

  In an image forming apparatus using an electrophotographic system, a toner image is formed by attaching toner to an electrostatic latent image formed on an image carrier such as a photosensitive drum, and the toner image is formed into a sheet-like recording medium such as paper. Then, the toner image on the paper is fixed by a fixing device (fixing unit).

  In such an image forming apparatus, units such as a photosensitive drum and a developing unit are densely packed from the viewpoint of space saving, so that the airtightness around the photosensitive drum is high. In the above configuration, for example, the timing when the leading edge of the paper enters the nip (transfer nip) between the photosensitive drum and the transfer roller from the registration roller pair, or the trailing edge of the paper is separated from the nip or intermediate roller of the registration roller pair. At the timing or the like, a change in the volume of the conveyance space occurs due to a change in the conveyance state of the sheet (paper fluttering or a sudden change in posture), and an air flow is generated due to a change in atmospheric pressure caused by the change.

  When this air flow passes through the gap (development nip) between the photosensitive drum and the developing roller, toner particles flying from the developing roller to the photosensitive drum are scattered by the developing electric field. As a result, a horizontal streak may occur in a halftone image or a solid image due to attachment at a position shifted from the original attachment position on the photosensitive drum.

  On the other hand, if the gap between the upper and lower pre-transfer guides arranged on the upstream side of the transfer nip with respect to the paper transport direction is reduced to suppress paper flapping, the transport load when transporting stiff paper such as thick paper is increased. Therefore, there is a possibility that transfer defects such as a decrease in transfer magnification and transfer deviation may occur.

  Therefore, a method has been proposed for suppressing transfer defects by smoothly guiding a sheet to a transfer nip regardless of whether plain paper or thick paper is used. For example, Patent Document 1 discloses a flexible film. Disclosed is a process cartridge and an image forming apparatus that reduce the load of cardboard while maintaining the state in which plain paper enters the photoconductor by providing the first guide member and the second guide member that are members upstream of the transfer position. Has been.

  In Patent Document 2, a flexible guide plate that supports a sheet conveyed by a paper feed roller or the like on one side and guides the sheet toward the photosensitive drum, and the other side of the guide plate are provided. A sponge that is softer than the guide plate, and the sponge protrudes from the edge of the guide plate on the photosensitive drum side to the photosensitive drum side, thereby vibrating the guide plate and flapping the trailing edge of the paper. The structure which suppresses the repelling sound of a guide plate while suppressing this is disclosed.

JP 2006-208840 A JP 2008-26810 A

  In the configuration of Patent Document 1, since the gap between the sheet and the upper guide changes due to the elastic deformation of the first guide member that is a film member, it is not possible to prevent the generation of airflow due to the change in the attitude of the sheet, and the toner in the developing nip due to the airflow It was not possible to suppress the scattering. Further, in the configuration of Patent Document 2, when there is an upper conveyance guide that faces the guide plate, the guide plate is pressed downward by a heavy paper conveyance load, the sponge is compressed, and the gap between the guide plate and the upper conveyance guide is increased. It spreads. For this reason, there has been a problem that flapping at the rear end when the thick paper is conveyed cannot be sufficiently suppressed.

  In view of the above problems, the present invention provides an image forming apparatus capable of effectively suppressing the fluttering of the recording medium on the upstream side of the transfer nip and reducing the transport load when transporting a strong recording medium. The purpose is to provide.

  In order to achieve the above object, a first configuration of the present invention is an image forming apparatus including an image carrier, a transfer member, a registration roller pair, and a conveyance guide. The transfer member transfers the toner image formed on the image carrier to a recording medium. The registration roller pair conveys the recording medium to the transfer nip between the transfer member and the image carrier at a predetermined timing. The conveyance guide includes a first conveyance guide that faces the surface on the image carrier side of the recording medium conveyed from the registration roller pair to the transfer nip, and a second conveyance guide that faces the surface on the transfer member side of the recording medium. Is done. The 2nd conveyance guide has a main-body part, an elastic member, and a film member. The main body includes a convex portion that protrudes most toward the first conveyance guide side in the recording medium conveyance path from the registration roller pair to the transfer nip, and a step portion that is formed adjacent to the downstream side of the convex portion in the recording medium conveyance direction. And having. The elastic member protrudes toward the first transport guide from the plane passing through the downstream end of the convex portion and the downstream end of the stepped portion. The film member covers the opposing surface of the main body portion to the first conveyance guide along with the elastic member over the entire region in the width direction orthogonal to the recording medium conveyance direction.

  According to the first configuration of the present invention, the elastic member is protruded to the first conveyance guide side from the plane passing through the downstream end portion of the convex portion of the second conveyance guide and the downstream end portion of the stepped portion. By disposing the recording medium, the recording medium can be transported along the first transport guide when transporting the weak recording medium, and fluttering of the recording medium can be suppressed. On the other hand, when a strong recording medium is conveyed, the elastic member is elastically deformed to reduce the conveyance load. In addition, since the distance between the second conveyance guide and the first conveyance guide is kept constant, the fluttering of the recording medium can be suppressed as much as possible. Therefore, the fluttering of the recording medium can be suppressed regardless of the stiffness of the recording medium being conveyed, so that the scattering of toner at the developing nip due to the generation of an air current can be suppressed. Further, it is possible to suppress a decrease in transfer magnification and occurrence of transfer deviation due to an increase in the conveyance load of the recording medium.

1 is a side sectional view showing an internal structure of an image forming apparatus 100 according to a first embodiment of the present invention. FIG. 1 is a partially enlarged view showing a sheet conveyance path from the registration roller pair 13 to the fixing device 15 in FIG. Side surface sectional drawing which cut | disconnected the lower conveyance guide 32 which comprises the conveyance guide 30 used for the image forming apparatus 100 of 1st Embodiment along the conveyance direction. FIG. 4 is a side cross-sectional view illustrating a conveyance state of a sheet S from a registration roller pair 13 to a transfer nip N, and illustrates a case where the sheet S is a plain sheet S1. The enlarged view of the lower conveyance guide 32 in FIG. FIG. 9 is a side cross-sectional view illustrating a conveyance state of a sheet S from a registration roller pair 13 to a transfer nip N, and illustrates a case where the sheet S is a thick sheet S2. Enlarged view of the lower conveyance guide 32 in FIG. Side surface sectional drawing which cut | disconnected the lower conveyance guide 32 used for the image forming apparatus 100 which concerns on 2nd Embodiment of this invention along the conveyance direction. Side surface sectional drawing which cut | disconnected the lower conveyance guide 32 along which the cardboard S2 was conveyed and the elastic sheet 41 bent

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing the internal structure of an image forming apparatus 100 according to an embodiment of the present invention. FIG. 2 is a partially enlarged view showing a sheet conveyance path from the registration roller pair 13 to the fixing device 15 in FIG. As shown in FIG. 1, in an image forming apparatus (for example, a monochrome printer) 100, an image forming portion P that forms a monochrome image by each process of charging, exposure, development, and transfer is disposed. In the image forming portion P, along the rotation direction of the photosensitive drum 5 (counterclockwise direction in FIG. 1), the charging device 4, the exposure device (laser scanning unit, etc.) 7, the developing device 8, the transfer roller 14, and the cleaning A device 19 and a static eliminator (not shown) are provided.

  The charging device 4 includes a charging roller 4a that contacts the photosensitive drum 5 and applies a charging bias to the drum surface. The charging roller 4 a is made of conductive rubber and is disposed so as to contact the photosensitive drum 5. When the photosensitive drum 5 rotates in the counterclockwise direction in FIG. 2, the charging roller 4a that contacts the surface of the photosensitive drum 5 is driven to rotate in the clockwise direction in FIG. At this time, the surface of the photosensitive drum 5 is uniformly charged by applying a predetermined voltage to the charging roller 4a.

  The developing device 8 includes a developing roller 8a, and develops the electrostatic latent image formed on the photosensitive drum 5 into a toner image by the developing roller 8a. The developing roller 8a is disposed with a predetermined gap (development nip) with respect to the photosensitive drum 5, and rotates in the clockwise direction in FIG. The developing device 8 contains a one-component developer (hereinafter also simply referred to as toner) composed only of magnetic toner components. Toner is supplied to the developing device 8 from the toner container 9.

  The transfer roller 14 forms a transfer nip N by coming into contact with the photosensitive drum 5, and transfers the toner image formed on the surface of the photosensitive drum 5 onto a sheet S passing through the transfer nip N. The transfer roller 14 is connected to a transfer bias power source and a bias control circuit (both not shown) for applying a transfer bias having a polarity opposite to that of the toner. A neutralizing needle 21 is disposed in the immediate vicinity of the downstream side of the transfer roller 14 with respect to the paper transport direction. The neutralizing needle 21 applies a bias (transfer reverse bias) having the same polarity (positive polarity) as that of the toner to remove the residual charge (negative charge) of the paper S that has passed through the transfer nip N, and removes it from the photosensitive drum 5. Separation of the paper S is facilitated.

  The transfer roller 14 is installed offset to the upstream side (left side in FIG. 2) from the lower end of the photosensitive drum 5 with respect to the paper transport direction. As a result, the transport direction of the paper S that has passed through the transfer nip is directed downward, so that the paper S is difficult to roll up. For this reason, it is possible to satisfactorily neutralize the sheet S by the neutralization needle 21 after passing through the transfer nip N. Further, it is possible to suppress winding of the paper S around the photosensitive drum 5 when the curvature separation of the paper S from the photosensitive drum 5 is performed.

  The cleaning device 19 includes a rubbing roller 19 a and a cleaning blade 19 b, removes residual toner on the surface of the photosensitive drum 5 and polishes the surface of the photosensitive drum 5. Further, a static elimination device (not shown) for removing residual charges on the surface of the photosensitive drum 5 is provided on the downstream side of the cleaning device 19.

  A conveyance guide 30 is disposed in the first sheet conveyance path 16 a between the registration roller pair 13 and the transfer roller 14. The conveyance guide 30 extends along the sheet width direction (direction perpendicular to the sheet surface of FIG. 2), and includes an upper conveyance guide 31 that faces the upper surface of the sheet S, and a lower conveyance guide 32 that faces the lower surface of the sheet S. It consists of

  The registration roller pair 13 is disposed below the tangential direction of the photosensitive drum 5 on the entry side of the transfer nip N. As a result, the registration roller pair 13 is removed from the attachment / detachment path of the drum unit including the developing device 8, the toner container 9, and the photosensitive drum 5, so that the maintainability of the developing device 8, the toner container 9, and the photosensitive drum 5 is improved.

  Further, the sheet S entering the transfer nip N is conveyed along the photosensitive drum 5 in advance before coming into contact with the transfer roller 14 in order to suppress the scattering of toner on the upstream side of the transfer nip N. preferable. Therefore, the first paper transport path (pre-transfer transport path) 16a from the registration roller pair 13 to the transfer nip N is once inclined upward from the registration roller pair 13 by the upper transport guide 31 and the lower transport guide 32. An inverted V-shape is formed so as to incline downward toward the transfer nip N.

  When the image forming operation is performed, the photosensitive drum 5 rotating counterclockwise by the charging device 4 is uniformly charged. Next, an electrostatic latent image is formed on the photosensitive drum 5 by a laser beam from the exposure device 7 based on image data transmitted from a personal computer (not shown) or the like, and the developing device 8 develops the electrostatic latent image. An agent (hereinafter referred to as toner) is attached to form a toner image.

  The sheet S is conveyed from the sheet feeding cassette 10 via the pair of registration rollers 13 and the first sheet conveying path 16a toward the photosensitive drum 5 on which the toner image is formed as described above. The toner image formed on the surface of the drum 5 is transferred to the paper S. The sheet S on which the toner image has been transferred is separated from the photosensitive drum 5 and is conveyed to the fixing device 15 via the second sheet conveyance path 16b to fix the toner image.

  The sheet S that has passed through the fixing device 15 is conveyed to the upper part of the image forming apparatus 100 via the third sheet conveying path 16c, and when an image is formed on only one side of the sheet S (during single-sided printing), the discharge roller It is discharged to the discharge tray 18 via the pair 17.

  On the other hand, when images are formed on both sides of the paper S (during double-sided printing), after the trailing edge of the paper S passes through the branching portion 20 of the paper conveyance path 16, the discharge roller pair 17 is reversely rotated to reverse the conveyance direction. Let me. As a result, the sheet S is distributed from the branching section 20 to the reversal conveyance path 21 and re-conveyed to the registration roller pair 13 with the image surface reversed. Then, the next toner image formed on the photosensitive drum 5 is transferred to the surface of the sheet S on which the image is not formed by the transfer roller 14. The sheet S on which the toner image has been transferred is conveyed to the fixing device 15 where the toner image is fixed, and then discharged to the discharge tray 18 via the discharge roller pair 17.

  FIG. 3 is a side sectional view of the lower conveyance guide 32 constituting the conveyance guide 30 cut along the conveyance direction. The lower conveyance guide 32 includes a main body portion 35, an elastic member 37, and a film member 40. The main body portion 35 is formed of a conductive resin material. The main body 35 is formed adjacent to the convex portion 35a that protrudes upward in the first paper conveyance path 16a from the registration roller pair 13 to the transfer nip N, and on the downstream side of the convex portion 35a with respect to the paper conveyance direction. It has a step 35b and a tip 35c that extends downstream from the step 35b and is close to the transfer nip N (see FIG. 2).

  The elastic member 37 is fixed to the step portion 35b of the main body 35 over the entire region in the paper width direction (direction perpendicular to the paper surface of FIG. 3, hereinafter, also simply referred to as the width direction). In the present embodiment, a sponge is used as the elastic member 37. The elastic member 37 has a rectangular parallelepiped shape (a rectangular cross section), and the upper corner portion (upper right portion in FIG. 3) on the downstream side with respect to the sheet conveying direction is the downstream side of the edge portion E1 and the step portion 35b on the downstream side of the convex portion 35a. It is arranged so as to protrude to the upper conveyance guide 31 side from the plane L passing through the edge portion E2.

  The lower conveyance guide 32 covers the surface facing the upper conveyance guide 31 from the convex portion 35a of the main body portion 35 through the elastic member 37 to the front end portion 35c over the entire area in the paper width direction. It is wrapped around and fixed. The film member 40 is fixed with a tension that does not allow the elastic member 37 to be elastically deformed. As a material of the film member 40, a resin film having high wear resistance and good sliding properties is preferable. In order to prevent the toner from adhering to the sheet S due to friction with the sheet S, the film member 40 is preferably conductive. In the present embodiment, a conductive ultra high molecular polyethylene sheet is used as the film member 40.

  In addition, in order to release the charge accumulated in the film member 40 due to friction with the paper S, the film member 40 is preferably grounded (grounded). The film member 40 may be directly connected to the frame (not shown) of the image forming apparatus 100 and grounded. If the main body portion 35 is conductive, the film member 40 is grounded via the main body portion 35. Also good. When the resistance of the sheet S is low due to water content or the like, the transfer bias leaks to the ground through the sheet S and the lower conveyance guide 32. Therefore, when the film member 40 is grounded, a resistor having a resistance value in mega ohms ( It is preferable to ground via a Hi-Meg resistor).

  Next, the conveyance of the sheet S from the registration roller pair 13 to the transfer nip N in the image forming apparatus 100 of the present embodiment will be described. 4 is a side sectional view showing a state in which the plain paper S1 is conveyed from the registration roller pair 13 to the transfer nip N, and FIG. 5 is an enlarged view of the vicinity of the lower conveyance guide 32 in FIG. Since the plain paper S1 is weak, the amount of deformation of the elastic member 37 when the plain paper S1 is conveyed is small.

  As a result, since the film member 40 is supported in a convex shape by the ridge line 37a of the elastic member 37 formed in a straight line, as shown in FIG. 5, the transport path of the plain paper S1 (indicated by a broken line in FIGS. 4 and 5). ) Is a track close to the upper transport guide 31 over the entire width direction, and the gap between the plain paper S1 and the upper transport guide 31 does not widen, and the flapping of the plain paper S1 is suppressed. Therefore, toner scattering at the development nip due to the generation of airflow is suppressed.

  6 is a side sectional view showing a state in which the thick paper S2 is conveyed from the registration roller pair 13 to the transfer nip N, and FIG. 7 is an enlarged view of the vicinity of the lower conveyance guide 32 in FIG. Since the thick paper S2 is strong, the thick paper S2 is conveyed to the transfer nip N while being elastically deformed by pressing the convex portion (ridge line 37a) of the elastic member 37. Thereby, the friction between the thick paper S2 and the lower transport guide 32 is reduced, and the transport load during transport of the thick paper S2 is reduced.

  Further, as shown in FIG. 7, the transport path of the thick paper S2 (indicated by a broken line in FIGS. 6 and 7) is a path close to the lower transport guide 32 over the entire width direction. Since the convex portion 35a is provided, the gap between the convex portion 35a and the upper conveyance guide 31 is maintained at a constant width even if the elastic member 37 is elastically deformed. Therefore, even when the thick paper S2 is transported, it is possible to reduce the transport load while minimizing the flapping width of the thick paper S2.

  According to the configuration of the present embodiment, it protrudes above the plane L passing through the edge portion E1 on the downstream side of the convex portion 35a of the lower conveyance guide 32 and the edge portion E2 on the downstream side of the step portion 35b with respect to the paper conveyance direction. By disposing the elastic member 37 in such a manner, the paper S can be transported along a track close to the upper transport guide 31 when the plain paper S1 having weak stiffness is transported, and flapping of the trailing edge of the paper S can be suppressed. On the other hand, the elastic member 37 is elastically deformed during the conveyance of the thick thick paper S2, and the conveyance load is reduced. In addition, since the interval between the lower conveyance guide 32 and the upper conveyance guide 31 is maintained constant by the convex portion 35a, it is possible to suppress the flapping of the rear end during conveyance of the thick paper S2 as much as possible.

  Therefore, fluttering of the trailing edge of the sheet S can be suppressed regardless of the strength of the sheet S being conveyed, and toner scattering at the developing nip due to the generation of airflow can be suppressed. Furthermore, it is possible to suppress a decrease in transfer magnification and occurrence of transfer deviation due to an increase in the conveyance load of the paper S.

  Further, in the image forming apparatus 100 of the present embodiment, the first sheet conveyance path 16a from the registration roller pair 13 to the transfer nip N is once inclined upward from the registration roller pair 13 and then lowered toward the transfer nip N. It is configured in an inverted V shape so as to incline in the direction. In this case, it is particularly preferable to use the lower conveyance guide 32 of the present embodiment because the conveyance load tends to increase when the strong paper S such as the thick paper S2 is conveyed.

  FIG. 8 is a side sectional view of the lower conveyance guide 32 used in the image forming apparatus 100 according to the second embodiment of the present invention cut along the conveyance direction. In the lower conveyance guide 32 shown in FIG. 8, an elastic sheet 41 is provided instead of the elastic member 37. The structure of the other part of the lower conveyance guide 32 is the same as that of the first embodiment.

  One end portion of the elastic sheet 41 is fixed to the convex portion 35a, and the other end portion protrudes above the step portion 35b from the convex portion 35a toward the downstream side in the paper transport direction. The elastic sheet 41 has a ridge line 41a on the downstream side (right end in FIG. 6) with respect to the paper transport direction from a plane L passing through the downstream edge portion E1 of the convex portion 35a and the downstream edge portion E2 of the step portion 35b. Is also arranged so as to protrude toward the upper conveyance guide 31 side. As a material of the elastic sheet 41, a polyethylene terephthalate (PET) sheet is used.

  When the plain paper S1 is conveyed using the lower conveyance guide 32 of the configuration of the present embodiment, the amount of deformation of the elastic sheet 41 is small because the plain paper S1 is weak. As a result, as shown in FIG. 8, the elastic sheet 41 maintains a protruding state, and the film member 40 is supported in a convex shape by the ridge line 41a of the elastic sheet 41 formed in a straight line. The track along the film member 40 supported by the elastic sheet 41 is the same as the above. Accordingly, the gap between the plain paper S1 and the upper conveyance guide 31 is not widened, and the fluttering of the rear end of the plain paper S1 is suppressed, so that the scattering of toner at the developing nip due to the generation of the air current is suppressed.

  FIG. 9 is a side sectional view of the lower conveyance guide 32 showing a state in which the thick paper S2 is conveyed and the elastic sheet 41 is bent. As shown in FIG. 9, when the thick paper S <b> 2 having strong stiffness is conveyed, the thick sheet S <b> 2 is conveyed to the transfer nip N while being elastically deformed by pressing the convex portion (ridge line 41 a) of the elastic sheet 41. Thereby, the conveyance load at the time of conveyance of the thick paper S2 is reduced. Further, the paper transport track is a track along the elastic sheet 41 that is elastically deformed as in FIG. 6, but the lower transport guide 32 is provided with the convex portion 35a, so that even if the elastic sheet 41 is elastically deformed. The gap between the convex portion 35a and the upper conveyance guide 31 is maintained at a constant width. Accordingly, even when the thick paper S2 is transported, it is possible to reduce the transport load while minimizing the flapping of the rear end.

  Accordingly, as in the first embodiment, fluttering of the trailing edge of the sheet S can be suppressed regardless of the stiffness of the sheet S being conveyed, and thus toner scattering at the developing nip due to the generation of airflow can be suppressed. it can. Furthermore, it is possible to suppress a decrease in transfer magnification and occurrence of transfer deviation due to an increase in the conveyance load of the paper S.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the distance between the convex portion 35a and the upper conveyance guide 31, the elastic member 37, the protruding amount of the elastic sheet 41, the thickness of the elastic sheet 41, and the like can be appropriately set according to the type of the sheet S to be conveyed. .

  The present invention is not limited to the monochrome printer as shown in FIG. 1, but is connected to other types of image forming apparatuses such as color printers, monochrome and color copiers, digital multifunction peripherals, facsimiles, and the like, and image forming apparatuses. Of course, the present invention can also be applied to a paper post-processing apparatus.

  The present invention can be used in an image forming apparatus such as a copying machine, a printer, and a facsimile machine that includes a conveyance guide on the upstream side of a transfer nip. By using the present invention, it is possible to provide an image forming apparatus capable of effectively suppressing the fluttering of the recording medium on the upstream side of the transfer nip and reducing the conveyance load when conveying a strong recording medium. it can.

5 Photosensitive drum 13 Registration roller pair 14 Transfer roller 16a First paper conveyance path (recording medium conveyance path)
30 transport guide 31 upper transport guide (first transport guide)
32 Lower transport guide (second transport guide)
35 body part 35a convex part 35b step part 35c tip part 37 elastic member 37a, 37b ridgeline 40 film member 41 elastic sheet (elastic member)
41a Ridge line 100 Image forming apparatus N Transfer nip S Paper (recording medium)
S1 plain paper S2 cardboard

Claims (8)

An image carrier;
A transfer member for transferring a toner image formed on the image carrier to a recording medium;
A pair of registration rollers for conveying a recording medium at a predetermined timing to a transfer nip between the transfer member and the image carrier;
A first conveyance guide that opposes the surface on the image carrier side of the recording medium conveyed from the pair of registration rollers to the transfer nip, and a second conveyance guide that opposes the surface on the transfer member side of the recording medium. A transport guide configured;
In an image forming apparatus comprising:
The second transport guide is
A convex portion that protrudes most toward the first conveyance guide in the recording medium conveyance path from the pair of registration rollers to the transfer nip, and a step portion that is formed adjacent to the downstream side of the convex portion in the recording medium conveyance direction. A main body having
An elastic member protruding toward the first conveyance guide from a plane passing through the downstream end of the convex portion and the downstream end of the stepped portion with respect to the recording medium conveyance direction;
A film member that covers the opposing surface of the main body portion to the first transport guide together with the elastic member over the entire region in the width direction orthogonal to the recording medium transport direction;
An image forming apparatus comprising:   The elastic member is a rectangular parallelepiped sponge, and is fixed to the step portion along the width direction, and a corner portion on the downstream side of the elastic member with respect to the recording medium transport direction is the first than the plane. The image forming apparatus according to claim 1, wherein the image forming apparatus protrudes toward the conveyance guide side.   The elastic member is an elastic sheet, and one end portion is fixed to the convex portion along the width direction, and the other end portion protrudes so as to overlap the stepped portion. The image forming apparatus described in 1.   The image forming apparatus according to claim 1, wherein the film member has conductivity.   The image forming apparatus according to claim 4, wherein the film member is grounded through the main body.   The image forming apparatus according to claim 4, wherein the film member is grounded via a resistor having a resistance value in megaohms.   The image forming apparatus according to claim 1, wherein the film member is an ultra high molecular weight polyethylene sheet.   8. The recording medium conveyance path according to claim 1, wherein the recording medium conveyance path has an inverted V-shape that is once inclined upward from the pair of registration rollers and then inclined downward toward the transfer nip. The image forming apparatus according to any one of the above.

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