JP2018066922A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can reduce the occurrence of image defects and conveyance failure by inhibiting charging of a recording medium and a guide member.SOLUTION: An image forming apparatus comprises: a transfer part 21; a fixing device 10; an insulative first guide member 30 that is arranged between the transfer part 21 and fixing device 10 and defines an undersurface of a sheet conveyance path 4; and a conductive cover member 50 that covers a top face of the first guide member 30 and is electrically grounded. The top face of the first guide member 30 is provided with a plurality of ribs 31 that extend in a sheet conveyance direction and project from the top face of the cover member 50 through slits of the cover member 50; the amount of projection of the ribs 31 with respect to the cover member 50 becomes smaller from the downstream side toward the upstream side in the sheet conveyance direction; the ribs 31 are applied with an antistatic agent.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus including a guide member that is disposed between a transfer unit and a fixing unit and guides a recording medium.

  Conventionally, an electrophotographic image forming apparatus such as a copying machine or a printer has a toner image carried on the surface of an image carrier such as a photosensitive drum or an intermediate transfer belt, and the toner image carried on the surface of the image carrier. Is transferred to the recording medium by the transfer unit, and then the recording medium is sent to the fixing unit. After the toner image is fixed to the recording medium by the fixing unit, the recording medium is conveyed to a discharge tray or the like.

  As such an image forming apparatus, for example, Patent Document 1 discloses an image forming apparatus in which a guide member for guiding a lower surface of a recording medium is provided between a transfer unit and a fixing unit. A plurality of ribs extending in the recording medium conveyance direction and projecting into the recording medium conveyance path are provided on the upper surface of the guide member.

JP 2007-17888 A

  By the way, for example, when a fixing process is performed on a recording medium with a high printing rate or a recording medium on which a color image is formed in a wide range, the recording medium conveyance speed of the fixing unit may be lowered in order to ensure good fixing properties. In the image forming apparatus of Patent Document 1, when the recording medium conveyance speed of the fixing unit is lower than the recording medium conveyance speed of the transfer unit, the recording medium is bent, and the recording medium rubs strongly against the ribs of the guide member. As a result, static electricity is generated, the recording medium and the guide member are charged, unfixed toner on the recording medium is disturbed, and the recording medium sticks to the guide member. For this reason, there is a problem that an image defect occurs or a conveyance defect occurs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress the occurrence of image defects and conveyance defects by suppressing charging of the recording medium and the guide member. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a transfer unit that transfers a toner image carried on an image carrier to a recording medium, and a fixing that fixes the toner image to the recording medium. An insulating guide member that is disposed between the transfer portion and the transfer portion and the fixing portion and demarcates the lower surface of the recording medium conveyance path through which the recording medium is conveyed, covers the upper surface of the guide member, and is electrically grounded A conductive cover member. A plurality of ribs extending in the recording medium conveyance direction are formed on the upper surface of the guide member in a direction perpendicular to the recording medium conveyance direction, and a plurality of slits are formed on the cover member so as to face the plurality of ribs. The plurality of ribs protrude from the upper surface of the cover member through the plurality of slits to form the lower surface of the recording medium conveyance path, and the protruding amount of the ribs with respect to the cover member is from the downstream side to the upstream side in the recording medium conveyance direction. The rib is coated with an antistatic agent.

  According to the image forming apparatus of the first aspect of the present invention, a plurality of ribs extending in the recording medium conveyance direction are formed on the upper surface of the guide member in a direction orthogonal to the recording medium conveyance direction. The rib protrudes from the upper surface of the cover member, and an antistatic agent is applied to the rib. As a result, the recording medium conveyance speed of the fixing unit becomes lower than the recording medium conveyance speed of the transfer unit, and even when the recording medium is bent, the recording medium is prevented from being strongly rubbed against the rib of the guide member. It is possible to suppress static electricity from being generated between the recording medium and the guide member. Therefore, charging of the recording medium and the guide member can be suppressed, so that unfixed toner on the recording medium can be prevented from being disturbed and the recording medium from sticking to the guide member. As a result, it is possible to suppress the occurrence of image defects and conveyance defects.

  In addition, by reducing the protruding amount of the rib with respect to the cover member from the downstream side toward the upstream side in the recording medium transport direction, the leading end of the recording medium (the downstream end in the recording medium transport direction) can be moved faster along the guide member. Therefore, the conveyance of the recording medium can be further stabilized. Further, since the protruding amount of the rib with respect to the cover member can be relatively large on the downstream side in the recording medium conveyance direction, it is possible to suppress the recording medium from contacting the cover member on the downstream side in the recording medium conveyance direction. As a result, scattering of unfixed toner on the recording medium can be suppressed, and the occurrence of image defects can be further suppressed.

1 is a cross-sectional view illustrating a structure of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a structure around a transfer unit and a fixing device of an image forming apparatus according to an exemplary embodiment of the present invention. FIG. 3 is a perspective view illustrating a structure around a first guide member of the image forming apparatus according to the embodiment of the present disclosure. FIG. 3 is an exploded perspective view illustrating a structure around a first guide member of the image forming apparatus according to the embodiment of the present disclosure. 1 is a perspective view showing a structure of a cover member of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view illustrating a structure around a first guide member of the image forming apparatus according to the embodiment of the present disclosure. FIG. 3 is a cross-sectional view illustrating a structure around a first guide member of the image forming apparatus according to the embodiment of the present disclosure. FIG. 5 is a cross-sectional view illustrating a structure around an end portion of the first guide member on the downstream side in the sheet conveyance direction of the image forming apparatus according to the embodiment of the present disclosure. FIG. 4 is a cross-sectional view illustrating a structure around an end portion of the first guide member on the downstream side in the sheet conveyance direction of the image forming apparatus according to the embodiment of the present invention, and is a diagram illustrating a state in which the sheet is bent. FIG. 2 is a perspective view illustrating a structure around a cover member and a main body frame of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a perspective view illustrating a structure of a cover member and a ground metal plate of the image forming apparatus according to the embodiment of the present invention. It is the perspective view which showed the state which attached the earth metal plate of the image forming apparatus of one Embodiment of this invention to the main body frame.

  Embodiments of the present invention will be described below with reference to the drawings.

  An image forming apparatus 100 according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, an image forming apparatus 100 (here, a monochrome printer) includes a paper feed cassette 2 that accommodates sheets (recording media) stacked on the lower part of an apparatus main body (image forming apparatus main body) 1. Yes. In FIG. 1, the right side is illustrated as the front side of the image forming apparatus 100. Formed above the paper feed cassette 2 is a paper conveyance path 4 that extends substantially horizontally from the front to the rear of the apparatus main body 1 and further extends upward to reach the paper discharge unit 3 formed on the upper surface of the apparatus main body 1. A pickup roller 5, a feed roller 6, an image forming unit 9, a fixing device (fixing unit) 10, and a discharge roller pair 11 are arranged in this order along the sheet conveyance path 4 from the upstream side.

  The image forming unit 9 forms a predetermined toner image on a sheet by an electrophotographic process. The image forming unit 9 is a photosensitive drum 14 that is an image carrier that is rotatably supported in the clockwise direction in FIG. A charging device 15, a developing device 16, a cleaning device 17, a transfer roller 18 disposed so as to face the photosensitive drum 14 across the paper conveyance path 4, and the photosensitive drum 14. It is comprised from the exposure apparatus (LSU) 19 arrange | positioned in this, and the static elimination apparatus.

  When image data is input from a host device such as a personal computer, first, the charging device 15 uniformly charges the surface of the photosensitive drum 14. Next, an electrostatic latent image based on the image data input on the photosensitive drum 14 is formed by the laser beam from the exposure device 19. Further, the developing device 16 attaches toner to the electrostatic latent image and forms a toner image on the surface of the photosensitive drum 14.

  The toner image formed on the surface of the photosensitive drum 14 is transferred to a sheet supplied to the nip portion (transfer nip portion) between the photosensitive drum 14 and the transfer roller 18 by the transfer roller 18. The sheet onto which the toner image has been transferred is separated from the photosensitive drum 14 and conveyed toward the fixing device 10. The fixing device 10 is disposed on the downstream side of the image forming unit 9 with respect to the paper transport direction, and the paper on which the toner image has been transferred in the image forming unit 9 includes a heating roller 22 provided in the fixing device 10, and The toner image which is heated and pressed by the pressure roller 23 pressed against the heating roller 22 and transferred to the paper is fixed. The paper on which the image is formed in the image forming unit 9 and the fixing device 10 is discharged to the paper discharge unit 3 by the discharge roller pair 11.

  Next, the structure around the transfer roller 18 and the fixing device 10 will be described. As shown in FIG. 2, the transfer roller 18 is in pressure contact with the photosensitive drum 14, and forms a transfer portion 21 that transfers a toner image carried on the photosensitive drum 14 to a sheet. Between the transfer unit 21 and the fixing device 10, a first guide member (guide member) 30 made of insulating resin that guides the lower surface of the paper by defining the lower surface of the paper transport path (recording medium transport path) 4 and the second guide member 30. A guide member 40 is provided.

  The second guide member 40 is disposed downstream of the first guide member 30 in the sheet conveyance direction, and guides the sheet toward the fixing nip portion. On the upper surface of the second guide member 40, a plurality of ribs 41 extending in the paper transport direction and projecting inside the paper transport path 4 are formed in the paper width direction (direction perpendicular to the paper transport direction). The plurality of ribs 41 constitute the lower surface of the sheet conveying path 4 of the second guide member 40. The upstream end of the second guide member 40 in the paper transport direction (the right end in FIG. 2) is different from the downstream end of the first guide member 30 in the paper transport direction (the left end in FIG. 2) with the paper transport path 4. It is arranged on the opposite side (lower side). That is, a step portion is formed at the boundary portion between the first guide member 30 and the second guide member 40. For this reason, when the sheet conveyance speed of the fixing device 10 is lower than the sheet conveyance speed of the transfer unit 21, the sheet is bent so as to enter the stepped portion.

  As shown in FIGS. 3 and 4, a plurality of ribs 31 extending in the paper transport direction and projecting inside the paper transport path 4 are formed on the upper surface of the first guide member 30 in the paper width direction. The plurality of ribs 31 constitute the lower surface of the paper transport path 4 of the first guide member 30.

  The rib 31 suppresses friction between the paper and the first guide member 30 and suppresses static electricity from being generated between the paper and the first guide member 30, thereby preventing the paper and the first guide member 30. Is applied with an antistatic agent that suppresses the charging. Examples of the antistatic agent include betaine-type amphoteric surfactants (for example, Amphital 20HD (manufactured by Kao Corporation)), and the type (material) of the antistatic agent is not particularly limited.

  A cover member 50 made of a metal plate such as SUS (stainless steel) that is electrically grounded is disposed on the upper surface of the first guide member 30. As shown in FIG. 5, the cover member 50 is provided with a plurality of slits 51 that are disposed to face the ribs 31 and through which the ribs 31 penetrate.

  As shown in FIG. 6, the cover member 50 is provided with three engagement portions 52 formed with engagement holes at the end on the upstream side in the paper conveyance direction. As shown in FIG. 5, five engaging portions 52 in which engaging holes are formed are provided. As shown in FIG. 6, three engagement protrusions 32 that are engaged with the engaging portion 52 are provided at the upstream end of the first guide member 30 in the paper conveyance direction, and the downstream side in the paper conveyance direction. As shown in FIG. 4, five engaging projections 32 that are engaged with the engaging portion 52 are provided at the end portion of the first end portion. The cover member 50 is fixed to the first guide member 30 by engaging the engaging portion 52 with the engaging protrusion 32.

  With the cover member 50 attached to the first guide member 30, the ribs 31 of the first guide member 30 protrude from the slits 51 of the cover member 50 to the inside (upper side) of the paper conveyance path 4. As shown in FIG. 7, the protruding amount of the rib 31 with respect to the slit 51 of the cover member 50 gradually decreases from the downstream side to the upstream side in the paper transport direction. Specifically, the protrusion amount H1 of the portion of the rib 31 on the upstream side in the sheet conveyance direction with respect to the cover member 50 is set to 0.5 mm or more and 1.0 mm or less. The protrusion amount H2 with respect to the cover member 50 is set to 1.5 mm or more and 2.0 mm or less.

  As a method of gradually decreasing the protrusion amount of the rib 31 with respect to the slit 51 from the downstream side to the upstream side in the sheet conveyance direction, various methods can be mentioned. For example, the protrusion amount of the rib 31 with respect to the upper surface of the first guide member 30 may be changed, or the thickness of the cover member 50 may be changed. In the present embodiment, the protruding amount of the rib 31 with respect to the upper surface of the first guide member 30 and the thickness of the cover member 50 are substantially constant, but the downstream portion of the cover member 50 contacts the upper surface of the first guide member 30. The protrusion H1 is made smaller than the protrusion H2 by floating the portion on the upstream side of the cover member 50 from the upper surface of the first guide member 30 (with a gap). The protrusion amounts H1 and H2 can be set by the distance from the upper surface of the first guide member 30 to the engagement protrusion 32, or the like.

  The upper end of the rib 31 (the inner end of the paper transport path 4) includes a transport section 31a that forms the lower surface of the paper transport path 4, and an inclined section 31c that is disposed downstream of the transport section 31a in the paper transport direction. And a curved surface portion 31b connecting the conveying portion 31a and the inclined portion 31c.

  As shown in FIG. 8, the curved surface portion 31b is formed in an arc shape (curved shape) when viewed from the paper width direction.

  The inclined portion 31c is formed in a straight line when viewed from the paper width direction. Further, the inclined portion 31c is inclined downward toward the downstream side in the paper transport direction. The inclined portion 31c is inclined at an angle of 45 degrees or less (for example, about 15 degrees or more and about 25 degrees or less) with respect to the end portion 31d on the downstream side in the sheet conveyance direction of the conveyance section 31a. Therefore, when the sheet conveyance speed of the fixing device 10 is lower than the sheet conveyance speed of the transfer unit 21 and the sheet is bent, the sheet P follows the curved surface portion 31b and the inclined portion 31c as shown in FIG. Bend. When the inclined part 31c is inclined at an angle larger than 45 degrees with respect to the end part 31d, or when the transport part 31a and the inclined part 31c are connected by an inclined surface instead of the curved surface part 31b, A gap is generated between the paper P and the inclined portion 31c, or between the paper P and the inclined surface.

  Further, as shown in FIG. 8, the end of the cover member 50 on the downstream side in the sheet conveyance direction is arranged so as not to protrude to the inside (upper side) of the sheet conveyance path 4 with respect to the extension line L31c of the inclined portion 31c. Yes.

  As shown in FIG. 10, the transfer unit 21 (see FIG. 2), the first guide member 30, the second guide member 40, and the fixing device 10 (see FIG. 2) are held on one side in the paper width direction. A sheet metal main body frame 1a is provided. The main body frame 1a is at ground potential. As shown in FIG. 11, a ground metal plate 60 is in contact with the cover member 50. The ground metal plate 60 is formed with a contact piece 61 that is elastically deformable and contacts the engaging portion 52 of the cover member 50 by a restoring force, and a screw hole 62a that is fixed to the main body frame 1a using a screw 65 (see FIG. 12). And a fixing piece 63 formed with a screw hole 63a that is fixed to a main body frame (not shown) arranged below the transfer roller 18 by using a screw (not shown). . The cover member 50 is grounded to the main body frame 1a and a main body frame (not shown) via the ground metal plate 60.

  In the present embodiment, as described above, the upper surface of the first guide member 30 is provided with a plurality of ribs 31 that extend in the paper transport direction and protrude from the upper surface of the cover member 50. An inhibitor is applied. As a result, the sheet conveyance speed of the fixing device 10 becomes lower than the sheet conveyance speed of the transfer unit 21, and even when the sheet P is bent, the sheet P is strongly against the ribs 31 of the first guide member 30. While being able to suppress rubbing, it is possible to suppress static electricity from being generated between the paper P and the first guide member 30. Therefore, charging of the paper P and the first guide member 30 can be suppressed, so that unfixed toner on the paper P is disturbed and the paper P is prevented from sticking to the first guide member 30. can do. As a result, it is possible to suppress the occurrence of image defects and conveyance defects.

  Further, by providing a cover member 50 that is electrically grounded on the upper surface of the first guide member 30, a mirror image force with respect to the sheet P that is slightly charged with the same polarity as the toner is generated in the cover member 50. The sheet P is attracted to the cover member 50 by the mirror image force. For this reason, the paper P can be transported along the first guide member 30, and the transport of the paper P can be stabilized.

  Further, by reducing the protruding amount of the rib 31 with respect to the cover member 50 from the downstream side in the paper transport direction toward the upstream side, the leading end of the paper P (the downstream end in the paper transport direction) can be moved to the first guide member 30 earlier. Therefore, the conveyance of the paper P can be further stabilized. Further, since the protrusion amount H2 of the rib 31 with respect to the cover member 50 can be relatively increased on the downstream side in the paper transport direction, it is possible to suppress the paper P from contacting the cover member 50 on the downstream side in the paper transport direction. . As a result, scattering of unfixed toner on the paper P can be suppressed, and the occurrence of image defects can be further suppressed. Note that, on the upstream side in the sheet conveyance direction, the sheet P is nipped by the transfer unit 21 and the sheet P is in a state of being waisted. Therefore, the protrusion amount H1 of the rib 31 with respect to the cover member 50 is made relatively small. However, it is possible to suppress the sheet P from coming into contact with the cover member 50.

  In addition, as described above, the rib 31 includes the conveyance unit 31a that forms the lower surface of the sheet conveyance path 4, the inclined unit 31c that is inclined downward toward the downstream side in the sheet conveyance direction, and the conveyance unit 31a and the inclined unit 31c. And a curved surface portion 31b to be connected. As a result, the sheet conveyance speed of the fixing device 10 becomes lower than the sheet conveyance speed of the transfer unit 21, and when the sheet P is bent, the sheet P bends along the curved surface portion 31b and the inclined portion 31c. It is possible to suppress the contact area between the paper P and the rib 31 from being reduced. For this reason, since it can suppress that the paper P contacts locally with respect to the rib 31, it can suppress further that the paper P rubs against the rib 31 strongly. For this reason, since it can suppress more that static electricity generate | occur | produces between the paper P and the 1st guide member 30, it can suppress more that the paper P and the 1st guide member 30 are charged.

  In addition, as described above, the inclined portion 31c is inclined at an angle of 45 degrees or less with respect to the end portion 31d on the downstream side in the sheet conveying direction of the conveying portion 31a. Thereby, it is possible to make the paper P more easily along the inclined portion 31c.

  Further, as described above, the cover member 50 is disposed so as not to protrude inward of the sheet conveyance path 4 with respect to the extension line L31c of the inclined portion 31c. Thereby, it is possible to further suppress the sheet P from coming into contact with the cover member 50.

  Moreover, as described above, the cover member 50 is formed of SUS. Thus, even when, for example, a betaine type amphoteric surfactant is used as the antistatic agent, the cover member 50 reacts with the antistatic agent, unlike the case where the cover member 50 is formed of a galvanized steel plate. As a result, it is possible to prevent the reaction product from being generated in the paper conveyance path 4, so that it is possible to prevent a conveyance failure from occurring due to the reaction product.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, although an example in which the present invention is applied to a monochrome printer has been shown, the present invention is not limited to this. Needless to say, other image forming apparatuses such as a color printer, a monochrome copying machine, a color copying machine, a digital multifunction peripheral, and a facsimile may be used.

  In the above-described embodiment, an example in which the photosensitive drum 14 is used as the image carrier has been described. However, an intermediate transfer belt (intermediate transfer member) may be used as the image carrier. That is, the present invention may be applied to a guide member and a cover member disposed between a transfer portion that transfers a toner image carried on an intermediate transfer belt to a recording medium and a fixing portion.

4 Paper transport path (recording medium transport path)
10 Fixing device (fixing part)
14 Photosensitive drum (image carrier)
21 Transfer section 30 First guide member (guide member)
31 Rib 31a Conveying part 31b Curved part 31c Inclined part 31d End part (End part on the downstream side in the recording medium conveying direction of the conveying part)
50 Cover member 100 Image forming apparatus H1, H2 Projection amount L31c Extension line P Paper (recording medium)

Claims (5)

A transfer unit for transferring the toner image carried on the image carrier to a recording medium;
A fixing unit for fixing the toner image to the recording medium;
An insulating guide member disposed between the transfer unit and the fixing unit and defining a lower surface of a recording medium conveyance path through which the recording medium is conveyed;
A conductive cover member that covers the upper surface of the guide member and is electrically grounded;
With
A plurality of ribs extending in the recording medium conveyance direction are formed on the upper surface of the guide member in a direction orthogonal to the recording medium conveyance direction,
The cover member is formed with a plurality of slits arranged to face the plurality of ribs,
The plurality of ribs protrude from the upper surface of the cover member through the plurality of slits, and constitute the lower surface of the recording medium conveyance path,
The protruding amount of the rib with respect to the cover member decreases from the downstream side in the recording medium conveyance direction toward the upstream side,
An image forming apparatus, wherein an antistatic agent is applied to the rib.   The rib includes a transport portion that forms a lower surface of the recording medium transport path, and an inclined portion that is disposed on the downstream side in the recording medium transport direction with respect to the transport portion and is inclined downward toward the downstream side in the recording medium transport direction. The image forming apparatus according to claim 1, further comprising: a curved surface portion that connects the conveying portion and the inclined portion.   The image forming apparatus according to claim 2, wherein the inclined portion is inclined at an angle of 45 degrees or less with respect to an end portion of the conveying portion on the downstream side in the recording medium conveying direction.   The image forming apparatus according to claim 2, wherein the cover member is disposed so as not to protrude inward of the recording medium conveyance path with respect to an extension line of the inclined portion.   The image forming apparatus according to claim 1, wherein the cover member is made of stainless steel.

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