JP2008179442A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of forming images of high quality by restricting upward bend of a paper sheet on an upstream side end thereof upstream a transferring section so as to prevent impact force to be applied to the transferring section. <P>SOLUTION: The image forming device 1 comprises a photoreceptor drum 41, a transferring section 50, a resist roller 31 as a conveying roller, and a paper sheet conveyance path 32 formed with a curve along the paper sheet conveying direction between the resist roller 31 and the transferring section 50. A guide roller 33 is provided to be projected into a conveyance space of the paper sheet conveyance path 32 from a side provided with the photoreceptor drum 41 so as to support the paper sheet P with a touch with the upstream side end of the paper sheet P released from a conveying nip of the resist roller 31. With this structure, the guide roller 33 can prevent upward bend of the paper sheet P when the upstream side end of the paper sheet P is released form the conveying nip of the resist roller 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus represented by a copying machine or a printer.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, an image forming unit (image forming unit) that forms a toner image on the surface of an image carrier, a transfer unit that transfers the toner image to a sheet, Components such as a fixing unit for fixing the toner image are provided. The sheet is conveyed along the sheet conveyance path between the components including these. In the sheet conveyance path, a guide plate constituting the path, a conveyance roller for feeding the sheet, a conveyance roller, a movable guide for switching the conveyance direction, and the like are arranged.

  Here, the transfer unit may transfer the toner image onto the sheet by electrostatic force after the sheet is brought into contact with the surface of the image carrier. In order to perform a suitable transfer of the toner image, the sheet must be brought into close contact with the surface of the image carrier. For the close contact of the sheet with the surface of the image carrier, the elastic force of the sheet itself may be used. In such an image forming apparatus, the sheet conveyance path disposed upstream of the transfer unit in the sheet conveyance direction is curved along the sheet conveyance direction. Therefore, the paper arriving at the transfer section is curved along the paper conveyance path, and the paper is brought into close contact with the surface of the image carrier by the elastic force acting on the paper due to this curvature.

  However, in the case of particularly stiff paper, when the upstream end of the paper is released from the conveyance nip of the conveyance roller immediately upstream of the transfer section, the paper is greatly splashed by the elastic force acting on the curve, and the impact force is transferred. May join the department. This impact force may cause image defects such as transfer deviation and conveyance defects such as oblique feeding. For this reason, a special guide member may be disposed on the upstream side of the transfer unit in the sheet conveyance direction. An example of an image forming apparatus in which a guide member is arranged on the upstream side of the transfer portion in that way can be seen in Japanese Patent Application Laid-Open No. 2003-122826.

In the image forming apparatus described in Patent Document 1, a transfer guide member made of a film-like elastic member is provided on the conveyance guide plate on the image carrier side immediately upstream of the transfer unit, and passes through the position of the conveyance guide plate. The upstream end of the sheet is brought into contact with the transfer guide member.
JP-A-8-76607 (page 4-5, FIG. 2)

  In the image forming apparatus described in Patent Document 1, the transfer guide member provided immediately upstream of the transfer unit receives the upstream end of the sheet that has passed through the position of the conveyance guide plate. This suppresses the occurrence of impacts that adversely affect the transfer portion. However, in this configuration, since the transfer guide member is in the form of a film, when using a wide variety of paper, there is a possibility that it may not be able to cope with various changes in the paper surface condition such as curling and waviness and waist strength. is there. Further, in this configuration, since the film-shaped transfer guide member comes into contact with the paper, the tip of the transfer guide member may be worn and deformed. In addition, there is a risk that the paper will be scratched, soiled, and noisy due to friction.

  The present invention has been made in view of the above points, and in an image forming apparatus provided with a sheet conveyance path curved in the sheet conveyance direction immediately upstream of a transfer unit, the image forming apparatus can cope with a wide variety of sheets. While avoiding the wear of the paper and its guide member, it is possible to suppress the splashing of the upstream edge of the paper upstream of the transfer section to prevent the transfer section from being applied with impact and to form a high quality image An object of the present invention is to provide a simple image forming apparatus.

  In order to solve the above-described problems, the present invention provides an image carrier that forms a toner image, a transfer unit that transfers the toner image to a sheet, and a conveyance roller that is provided upstream of the transfer unit in the sheet conveyance direction. In the image forming apparatus including a sheet conveyance path provided in a curved shape along the sheet conveyance direction between the conveyance roller and the transfer unit, the sheet is provided from the side on which the image carrier is provided. A guide roller is provided that supports the sheet by protruding into the conveyance space of the conveyance path and contacting the upstream end of the sheet released from the conveyance nip of the conveyance roller.

  In the image forming apparatus configured as described above, the guide roller is displaced toward the outside of the sheet conveyance path as the sheet comes into contact.

  In the image forming apparatus configured as described above, the guide roller includes an elastic member that biases the guide roller in a direction in which the guide roller protrudes into the conveyance space of the sheet conveyance path.

  In the image forming apparatus having the above-described configuration, the guide roller is positioned outside the sheet conveyance path between the conveyance roller and the transfer unit.

  In the image forming apparatus having the above-described configuration, the guide roller is supported by a support member that is rotatably provided around a position on the downstream side of the guide roller in the sheet conveyance direction, and the support member is formed on the sheet conveyance path. The upstream end of the sheet that protrudes into the conveyance space and is released from the conveyance nip of the conveyance roller comes into contact.

  In the image forming apparatus having the above-described configuration, a plurality of the guide rollers are arranged in the sheet width direction perpendicular to the sheet conveyance direction.

  According to the configuration of the present invention, an image carrier that forms a toner image, a transfer unit that transfers the toner image to a sheet, a conveyance roller that is provided upstream of the transfer unit in the sheet conveyance direction, and these conveyance rollers In the image forming apparatus comprising a sheet conveyance path provided in a curved shape along the sheet conveyance direction between the transfer unit and the transfer unit, the conveyance of the sheet conveyance path from the side on which the image carrier is provided The guide roller is provided with a guide roller that protrudes into the space and supports the paper when the upstream end of the paper released from the transport nip of the transport roller comes into contact with the upstream end of the paper from the transport nip of the transport roller. It is possible to prevent sheet splashing that occurs when the edge is released. Since the guide roller is heavier than a film-like member and rolls in contact with the paper, it can be used for a wide variety of papers having different surface conditions and stiffness. Further, the guide roller is not easily worn, and there is no fear of the paper being damaged. In this way, it can be applied to a wide variety of papers, and while preventing the paper and its guide rollers from being worn, it prevents the paper upstream end from splashing upstream of the transfer part, and impact force is applied to the transfer part. It is possible to provide an image forming apparatus capable of preventing the addition and forming a high-quality image.

  Further, since the guide roller is displaced toward the outside of the paper transport path as the paper comes into contact, the position of the guide roller can be changed according to the strength of the elastic force acting on the paper. Therefore, it is possible to cope with various types of paper having different waist strengths, and it is possible to suppress the splash at the upstream end of the paper upstream of the transfer portion regardless of the strength of the paper.

  In addition, since the guide roller is provided with an elastic member at its support portion that urges the guide roller in a direction in which the guide roller protrudes into the conveyance space of the sheet conveyance path, The contact pressure of the guide roller with respect to the paper can be adjusted in response to the increase or decrease of the pressure. Accordingly, for example, the guide roller can be brought into contact with the sheet with a strong force with respect to a thick sheet having a strong waist. Therefore, it is possible to further improve the performance that can cope with various types of paper having different waist strengths.

  In addition, since the guide roller is positioned outside the sheet conveyance path between the conveyance roller and the transfer unit, it is possible to prevent the guide roller from being always in contact with the sheet. Then, only when the upstream end of the sheet is bounced, the sheet can be brought into contact with the guide roller and the action of the guide roller can be obtained. Thereby, it is possible to prevent the guide rollers from interfering with normal sheet conveyance, and it is possible to prevent a decrease in sheet conveyance performance due to the addition of the guide rollers.

  The guide roller is supported by a support member that is rotatably provided around a downstream side of the guide roller in the sheet conveyance direction. The support member protrudes into the conveyance space of the sheet conveyance path, and the conveyance roller Since the upstream end of the sheet released from the conveyance nip comes into contact, the upstream end of the sheet can be supported by the support member even after the upstream end of the sheet has passed the location of the guide roller. Thus, the paper can be transported while gradually reducing the elastic force acting on the paper. Accordingly, it is possible to further improve the action of suppressing the splash at the upstream end of the sheet upstream of the transfer section, and to perform an image forming operation for obtaining a higher quality image.

  In addition, since a plurality of the guide rollers are arranged in the paper width direction perpendicular to the paper conveyance direction, one or a plurality of guide rollers can be brought into contact with the paper according to the size of the paper. It is. Therefore, with respect to the suppression of the splash at the upstream end of the sheet in the upstream of the transfer unit, the performance to cope with various types of sheets having different sizes is improved.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, the image output operation of the image forming apparatus according to the first embodiment of the present invention will be described while explaining the outline of the structure with reference to FIG. FIG. 1 is a schematic vertical sectional front view of an image forming apparatus. A solid line arrow in the drawing indicates a sheet conveyance path and a conveyance direction.

  As shown in FIG. 1, a cassette type paper feeding unit 20 is disposed at the lower part of the main body 2 of the image forming apparatus 1. The cassette type paper supply unit 20 is provided with a general general-purpose paper supply cassette 21 and a large capacity paper supply cassette 22. Two large-capacity paper feed cassettes 22 having the same capacity are arranged in the horizontal direction at the same height, and are configured as an upstream large-capacity paper feed cassette 22A and a downstream large-capacity paper feed cassette 22B. In these paper feed cassettes, paper P such as cut paper before printing is stacked and stored, and the paper P is separated and sent out one by one.

  A manual paper feed unit 3 is provided outside the upper right side of the main body 2. The manual paper feed unit 3 is loaded with paper that is not contained in the cassette type paper feed unit 20, thick paper such as postcards, or OHP sheets that are to be fed one by one.

  The image forming apparatus 1 includes a vertical conveyance unit 30 therein. The vertical conveyance unit 30 is located on the right side that is the paper feeding direction in terms of the cassette type paper feeding unit 20, and is located on the left side in terms of the manual paper feeding unit 3. The paper P delivered from the cassette type paper feeder 20 is conveyed vertically upward along the side surface of the main body 2 by the vertical conveyance unit 30, and the paper P delivered from the manual paper feeder 3 is conveyed substantially horizontally to the left. Of the two large-capacity paper feed cassettes 22, the paper P sent out from the left upstream large-capacity paper feed cassette 22A is positioned almost horizontally rightward immediately above the right downstream large-capacity paper feed cassette 22B. After being sent, it is conveyed vertically upward along the side surface of the main body 2.

  A registration roller 31, which is a kind of transport roller, is provided at the downstream end in the paper transport direction of the vertical transport unit 30 and immediately upstream of the transfer unit 50. The registration roller 31 feeds the paper P toward the transfer unit 50 in synchronization with the toner image formed by the image forming unit 40 while correcting the oblique feeding of the paper P.

  On the other hand, a document feeding unit 4 is provided on the upper surface of the main body 2 of the image forming apparatus 1, and an optical unit 5 is provided below the document feeding unit 4. An operation panel 6 is provided in front of the document feeding unit 4 at a position where the user can check the display from the outside or perform operations by pressing a button. When a user copies an original, an original on which images such as characters, graphics, and patterns are drawn is stacked on the original feeding unit 4, and printing conditions are input to the operation panel 6 to start printing. The document feeder 4 separates the documents one by one and feeds them, and the optical unit 5 reads the image data.

  An image forming unit 40 and a transfer unit 50 are provided on the downstream side of the registration roller 31 in the sheet conveyance direction and below the optical unit 5. The image forming unit 40 forms an electrostatic latent image of the document image based on the image data read by the optical unit 5. A toner image is developed from the electrostatic latent image, and the toner image is transferred by the transfer unit 50 to the pre-printing paper P sent in synchronization by the registration roller 31.

  A fixing unit 7 is provided on the downstream side of the transfer unit 50. The sheet P carrying the unfixed toner image in the transfer unit 50 is sent to the fixing unit 7 where the toner image is heated and pressed by a heat roller and a pressure roller to be fixed.

  A branching portion 8 is provided on the downstream side of the fixing portion 7 and in the vicinity of the left side surface of the main body 2. The paper P discharged from the fixing unit 7 is discharged from the branching unit 8 to a paper discharge tray 9 which is a paper discharge unit outside the apparatus when double-sided printing is not performed.

  A double-sided printing unit 10 that is a double-sided printing device is provided below the portion from the image forming unit 40 to the branching unit 8 and above the cassette type paper feeding unit 20. When performing double-sided printing, the paper P that has been printed on the first side and discharged from the fixing unit 7 is sent to the double-sided printing unit 10 through the branching unit 8. The transport direction of the paper P sent to the duplex printing unit 10 is subsequently switched for printing on the second side, and is sent again to the image forming unit 40 via the vertical transport unit 30 and the registration roller 31.

  Next, a detailed configuration of the area around the upstream side of the image forming unit 40 of the image forming apparatus 1 will be described with reference to FIGS. 2 and 3 in addition to FIG. 2 is a vertical sectional front view showing the periphery of the upstream side of the image forming unit, and FIG. 3 is a top view showing the periphery of the guide roller in FIG.

  As shown in FIGS. 1 and 2, the image forming unit 40 is provided with a photosensitive drum 41 as an image carrier at the center thereof. A developing device 42 is provided upstream of the transfer unit 50 in the rotation direction of the photosensitive drum 41.

  The photoconductive drum 41 extends in the paper width direction perpendicular to the paper conveyance direction in the image forming apparatus 1, that is, the paper surface depth direction in FIGS. 1 and 2, and is arranged with its axial direction horizontal. The photosensitive drum 41 is an inorganic photosensitive drum in which an amorphous silicon photosensitive layer, which is an inorganic photoconductive material, is provided by vacuum deposition or the like outside a conductive roller-shaped substrate made of aluminum or the like. The photosensitive drum 41 is rotated by a driving device (not shown) so that the peripheral speed thereof is the same as the paper conveyance speed.

  The transfer unit 50 is provided with a transfer conveyance belt 51 which is a transfer member constituted by an endless belt. The transfer / conveying belt 51 is wound around and supported by a plurality of rollers, and is rotated in a counterclockwise direction in FIG. 2 by a driving device (not shown) so that the peripheral speed thereof is the same as the peripheral speed of the photosensitive drum 41. ing. The transfer conveyance belt 51 is pressed against the photosensitive drum 41 from below and forms a transfer nip through which the paper P is inserted.

  As shown in FIGS. 1 and 2, a registration roller 31 is provided on the upstream side of the image forming unit 40 and the transfer unit 50 in the sheet conveyance direction and below the developing device 42.

  As shown in FIG. 2, the registration roller 31 is provided at the downstream end of the paper transport path 32 of the vertical transport unit 30. The registration roller 31 is constituted by a pair of a roller and a roller that are in pressure contact with each other, and the roller is rotated by a driving unit (not shown). The registration roller 31 is a kind of conveyance roller, and is synchronized with the toner image formed by the image forming unit 40 while correcting the oblique feeding of the sheet P conveyed on the sheet conveyance path 32 as described above. Then, the paper P is sent out toward the transfer unit 50.

  As shown in FIG. 2, the sheet conveyance path 32 is configured to transfer the sheet P conveyed from the cassette type sheet feeding unit 20 below between the registration roller 31 which is a kind of conveyance roller and the transfer unit 50. In order to guide to 50, it is provided in a curved shape so as to protrude upward along the transport direction. In addition, the paper transport path 32 includes a plurality of guide plates including upper guide plates 32a and 32b and lower guide plates 32c and 32d. These upper and lower guide plates are arranged at appropriate positions so as to form a paper transport space between them, and guide the paper P transported on the paper transport path 32 to the transfer nip of the transfer unit 50. .

  A guide roller 33 is provided immediately downstream of the registration roller 31. The guide roller 33 is supported by a support member 34 provided on the upper guide plate 32b so as to be rotatable in a vertical plane with a downstream side of the guide roller 33 as a center.

  A torsion coil spring 35, which is an elastic member, is provided at a location where the support member 34 is attached to the upper guide plate 32b. The torsion coil spring 35 biases the guide roller 33 in a direction in which the guide roller 33 protrudes into the conveyance space of the paper conveyance path 32. As a result, the guide roller 33 protrudes downward from the location of the upper guide plate 32b on the side where the photosensitive drum 41 is provided, in the conveyance space of the paper conveyance path 32. Note that the guide roller 33 is located outside the paper conveyance path between the registration roller 31 and the transfer unit 50, that is, on the upper side in FIG. There is no further downward displacement.

  As shown in FIG. 3, a plurality of guide rollers 33 are arranged side by side in the paper width direction perpendicular to the paper transport direction.

  Next, the details of the conveyance operation of the paper P will be described with reference to FIGS. 4 and 5 in addition to FIG. 2 at a location immediately upstream of the image forming unit 40 having the above configuration. FIG. 4 is a vertical sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. 2 and shows a conveyance state in which the sheet is held in the conveyance nip of the registration roller, and FIG. 5 is an image similar to FIG. FIG. 5 is a front view of a vertical section showing the periphery of the upstream side of the forming unit, and shows a conveyance state immediately after the sheet passes through the conveyance nip of the registration roller.

  The paper P delivered from the cassette type paper feeding unit 20 is transported on the paper transport path 32 of the vertical transport unit 30, and the paper transport indicated by the two-dot chain line in FIG. It is conveyed along the route as shown in FIG. At this location, the paper transport path 32 has a curved shape that is convex upward along the transport direction, and the paper P is similarly curved to be convex upward. Further, as described above, the paper P is in contact with the guide roller 33 located immediately downstream of the registration roller 31 while being held in the transfer nip of the transfer unit 50 and the conveyance nip of the registration roller 31. There is no.

  Subsequently, when the conveyance of the paper P proceeds and the upstream end of the paper P is released from the conveyance nip of the registration roller 31, the paper P is in the state shown in FIG. That is, the upstream end of the sheet P is displaced upward from the conveyance path when held at the conveyance nip of the registration roller 31 by the elastic force of the curved sheet P, contacts the guide roller 33, and is supported by this. The

  Then, the guide roller 33 is displaced toward the outside of the paper conveyance path 32, that is, upward in FIG. The guide roller 33 is displaced so as to rotate in a vertical plane around the attachment position of the support member 34 to the upper guide plate 32b.

  Here, the guide roller 33 is displaced toward the outside of the paper conveyance path 32 according to the elastic force of the paper P by the action of the torsion coil spring 35 provided at the attachment location of the support member 34. The amount of displacement of the guide roller 33 is large when the elastic force is strong such as cardboard, and is small when the elastic force is weak such as trace paper. Further, the torsion coil spring 35 increases its repulsive force as the displacement amount of the guide roller 33 increases.

  As described above, the photosensitive drum 41, which is an image carrier that forms a toner image, the transfer unit 50 that transfers the toner image onto the paper P, and the upstream side of the transfer unit 50 in the paper conveyance direction are provided. In the image forming apparatus 1, the image forming apparatus 1 includes a registration roller 31 that is a conveyance roller, and a sheet conveyance path 32 that is provided between the registration roller 31 and the transfer unit 50 in a curved shape along the sheet conveyance direction. A guide roller 33 that supports the paper P by projecting into the transport space of the paper transport path 32 from the side where the body drum 41 is provided and contacting the upstream end of the paper P released from the transport nip of the registration roller 31 is provided. Therefore, the guide roller 33 can prevent the sheet P from splashing when the upstream end of the sheet P is released from the conveyance nip of the registration roller 31. The guide roller 33 is heavier than a film-like member and rolls in contact with the paper P. Therefore, the guide roller 33 can handle various types of paper P having different surface conditions and waist strength. . Further, the guide rollers 33 are not easily worn, and the paper P is not damaged. In this way, it is possible to deal with a wide variety of sheets P, and while avoiding the wear of the sheet P and its guide rollers 33, it is possible to suppress the splash at the upstream end of the sheet upstream of the transfer unit 50 and to transfer the transfer unit 50. Thus, it is possible to provide the image forming apparatus 1 that can prevent an impact force from being applied to the cover 50 and can form a high-quality image.

  Further, since the guide roller 33 is displaced toward the outside of the paper transport path 32 as the paper P comes into contact, the position of the guide roller 33 can be changed according to the strength of the elastic force acting on the paper P. . Accordingly, it is possible to deal with various types of paper P having different waist strength, and it is possible to suppress the splash of the upstream edge of the paper upstream of the transfer unit 50 regardless of the waist strength of the paper P.

  The guide roller 33 is provided with a torsion coil spring 35, which is an elastic member that urges the guide roller 33 in a direction in which the guide roller 33 protrudes into the conveyance space of the paper conveyance path 32, at the support portion. Accordingly, the contact pressure of the guide roller 33 with respect to the paper can be adjusted in response to the paper becoming stiff or weak. Accordingly, for example, the guide roller 33 can be brought into contact with the sheet with a strong force with respect to a thick sheet having strong stiffness. Therefore, it is possible to further improve the performance that can cope with various types of paper having different waist strengths.

  Furthermore, since the guide roller 33 is located outside the sheet conveyance path between the registration roller 31 and the transfer unit 50, it is possible to prevent the guide roller 33 from always contacting the sheet P. Then, only when the upstream end of the paper P is bounced, the paper P comes into contact with the guide roller 33 so that the action of the guide roller 33 can be obtained. Thereby, it is possible to prevent the guide roller 33 from interfering with normal sheet conveyance, and it is possible to prevent a decrease in sheet conveyance performance due to the addition of the guide roller 33.

  Further, since a plurality of guide rollers 33 are arranged in the paper width direction perpendicular to the paper transport direction, one or a plurality of guide rollers 33 can be brought into contact with the paper P according to the size of the paper P. It is. Therefore, with respect to the suppression of the splash at the upstream end of the sheet upstream of the transfer unit 50, the performance of dealing with various types of sheets P having different sizes is improved.

  Next, the detailed configuration of the image forming apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a vertical cross-sectional front view showing the periphery of the upstream side of the image forming unit. The basic configuration of this embodiment is the same as that of the first embodiment described with reference to FIGS. 1 to 5, and therefore, the configuration common to the first embodiment is described in the drawings, and The description will be omitted.

  In the image forming apparatus 1 according to the second embodiment, the guide roller 33 is supported by a support member 36 as shown in FIG. The support member 36 is formed such that a portion between the attachment position to the upper guide plate 32b and the guide roller 33 is convex toward the lower side where the conveyance space of the paper conveyance path 32 is located and protrudes into the conveyance space. It is bent.

  Next, details of the operation of transporting the paper P will be described with reference to FIGS. 7 and 8 at a location immediately upstream of the image forming unit 40 where the support member 36 is provided. 7 is a vertical cross-sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. 6, and shows the conveyance state immediately after the sheet passes through the conveyance nip of the registration roller, and FIG. 8 is an image similar to FIG. FIG. 5 is a front view of a vertical section showing the periphery of the upstream side of the forming unit, and shows a conveyance state immediately after the sheet passes through the guide roller.

  When the conveyance of the paper P proceeds at the registration roller 31 and the transfer unit 50 in the configuration according to the second embodiment, and the upstream end of the paper P is released from the conveyance nip of the registration roller 31, the paper P is shown in FIG. The state shown in FIG. That is, the upstream end of the sheet P is displaced upward from the conveyance path when held at the conveyance nip of the registration roller 31 by the elastic force of the curved sheet P, and comes into contact with and supported by the guide roller 33. Is done.

  Further, when the conveyance of the paper P advances and the upstream end of the paper P passes the location of the guide roller 33, the paper P is in the state shown in FIG. That is, the upstream end of the sheet P is further displaced upward by the elastic force of the curved sheet P, and contacts the support member 36 that is bent so as to protrude into the conveyance space of the sheet conveyance path 32.

  In this manner, the guide roller 33 is supported by the support member 36 that is rotatably provided around the downstream side of the guide roller 33 in the sheet conveyance direction, and the support member 36 is conveyed in the conveyance space of the sheet conveyance path 32. Since the upstream end of the sheet P released from the conveyance nip of the registration roller 31 contacts, the upstream end of the sheet P is supported by the support member 36 even after the upstream end of the sheet P passes through the location of the guide roller 33. It is possible to support. Thereby, the paper P can be transported while gradually reducing the elastic force acting on the paper P. Therefore, it is possible to further improve the action of suppressing the splash at the upstream end of the sheet upstream of the transfer unit 50, and to perform an image forming operation for obtaining a higher quality image.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, in the embodiment of the present invention, a plurality of guide rollers 33 are arranged in the paper width direction, but a single guide roller 33 may be provided. In this case, it is desirable to arrange at the center in the paper width direction.

  The present invention can be used in general image forming apparatuses.

1 is a schematic vertical sectional front view of an image forming apparatus according to a first embodiment of the present invention. FIG. 2 is a vertical sectional front view showing the periphery of the upstream side of the image forming unit in FIG. 1. It is a top view which shows the guide roller periphery of FIG. FIG. 3 is a vertical cross-sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. FIG. 5 is a vertical cross-sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. FIG. 5 is a vertical sectional front view showing the periphery of an upstream side of an image forming unit of an image forming apparatus according to a second embodiment of the present invention. FIG. 7 is a vertical sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. 6, and shows a conveyance state immediately after the sheet passes through the conveyance nip of the registration roller. FIG. 8 is a vertical cross-sectional front view showing the periphery of the upstream side of the image forming unit similar to FIG. 7, and shows a conveyance state immediately after the sheet passes through the guide roller portion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 30 Vertical conveyance part 31 Registration roller 32 Paper conveyance path 33 Guide roller 34,36 Support member 35 Torsion coil spring (elastic member)
40 Image forming section 41 Photosensitive drum (image carrier)
50 Transfer section

Claims (6)

An image carrier that forms a toner image, a transfer unit that transfers the toner image to a sheet, a conveyance roller provided upstream of the transfer unit in the sheet conveyance direction, and a sheet between the conveyance roller and the transfer unit In an image forming apparatus provided with a paper conveyance path provided in a curved shape along the conveyance direction,
A guide roller that supports the sheet by projecting into the conveyance space of the sheet conveyance path from the side on which the image carrier is provided and contacting the upstream end of the sheet released from the conveyance nip of the conveyance roller; A featured image forming apparatus.   The image forming apparatus according to claim 1, wherein the guide roller is displaced toward the outside of the sheet conveyance path as the sheet contacts.   The image forming apparatus according to claim 1, wherein the guide roller includes an elastic member that urges the guide roller in a direction in which the guide roller protrudes into a conveyance space of the sheet conveyance path. .   4. The image forming apparatus according to claim 1, wherein the guide roller is located outside a sheet conveyance path between the conveyance roller and the transfer unit. 5.   The guide roller is supported by a support member that is rotatably provided around a position downstream of the guide roller in the sheet conveyance direction. The support member protrudes into the conveyance space of the sheet conveyance path and is conveyed by the conveyance roller. The image forming apparatus according to claim 1, wherein the upstream end of the sheet released from the nip contacts.   6. The image forming apparatus according to claim 1, wherein a plurality of the guide rollers are arranged in a sheet width direction perpendicular to the sheet conveyance direction.

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