JP2008189393A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of stably conveying paper sheets without damaging the surface of the paper sheets in conveyance. <P>SOLUTION: This image forming device comprises a paper sheet conveying device having a conveyance path for conveying paper sheets, an imaging section for forming an image on the paper sheet on the way of the conveyance path, and a plurality of guide ribs 23 extended in the conveying direction in the guide surface formed with the conveyance path in parallel with each other in the cross direction of conveyance. An auxiliary rib 24 having a contact range larger than that of the guide rib 23 in relation to the paper sheets in the cross direction of conveyance is arranged on the guide surface near the guide rib 23. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a device having a composite function of these.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, generally, paper stored in a paper cassette is sent out to a paper transporting device side by a paper feeding unit, and then inside the paper transporting device. An image is formed on the paper transported through the transport path by the image forming unit, and the paper on which the image is formed is sent out to a paper discharge tray.

  A guide member for guiding the paper is provided in a part of the paper transport path in the paper transport device. For example, a plastic plate-like member is used as the guide member. If the guide surface of the guide member is flat, the contact resistance between the paper and the guide surface increases, and the paper is stably conveyed. However, there is a drawback that the frequency of occurrence of paper jam increases. Further, when a guide member having a flat guide surface is above the fixing device, condensation is likely to occur on the guide surface due to water vapor generated when the fixing device heat-fixes the toner image on the paper. In addition, there is a problem that the sheet to be conveyed gets wet when it contacts the guide surface.

For this reason, by providing a plurality of guide ribs extending in the transport direction on the guide surface in the transport width direction, the contact area with the paper is reduced, the transport resistance is reduced, and further, wetting of the paper due to condensation is prevented ( For example, see Patent Document 1 or Patent Document 2).
JP 2006-30274 A JP 2005-138969 A

  In recent years, there has been a demand for further downsizing of the image forming apparatus. When the downsizing of the image forming apparatus is attempted, a part of the sheet conveyance path provided in the image forming apparatus has to be largely bent. come. In such a bent conveyance path, the sheet is conveyed while being in strong contact with the guide rib. In particular, when transporting public postcards using thick and strong paper, the contact surface pressure with the guide rib is large, so when the paper comes into contact with the guide rib, the surface of the paper becomes streaky and the appearance becomes worse. . In addition, when double-sided printing is performed using the double-sided image forming apparatus as shown in Patent Document 2, there is a problem in that the print quality is deteriorated because printing is also performed on the scratched surface.

  SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide an image forming apparatus that does not damage the surface of a sheet when the sheet is conveyed with a simple configuration and has stable conveyance performance. is there.

  According to a first aspect of the present invention, a sheet conveying apparatus having a conveying path for conveying a sheet and an image forming unit that forms an image on the sheet in the middle of the conveying path are provided in a conveying direction on a guide surface on which the conveying path is formed. In the image forming apparatus in which a plurality of extending guide ribs are arranged side by side in the conveyance width direction, auxiliary ribs having a larger contact range in the conveyance width direction than the guide ribs are disposed on the guide surface in the vicinity of the guide ribs. is there.

  By making the paper come into wide contact with the auxiliary rib in the conveyance width direction, the paper is conveyed while reducing the contact pressure, and the paper is prevented from being strongly pressed against the guide rib.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the guide rib in the vicinity of the auxiliary rib is in non-contact with the paper in a state where the auxiliary rib is in contact with the paper. It is.

  By bringing the sheet into contact with the auxiliary rib, it is possible to reliably avoid the sheet from being strongly pressed against the guide rib.

  A third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the auxiliary rib is provided adjacent to the guide rib.

  It is possible to reliably prevent the paper from being strongly pressed against the guide rib. Further, the auxiliary rib can be efficiently arranged in a narrow range in the conveyance width direction.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the paper conveying device is capable of conveying a plurality of types of paper, and each of them regardless of the paper size. In this configuration, the bisectors in the width direction of the paper are conveyed so as to coincide with each other.

  In order to prevent paper skew, it is desirable to arrange the auxiliary ribs symmetrically with respect to the paper width direction bisector, but the width direction bisectors of each paper should be matched regardless of the paper size. If it is a center reference to convey the auxiliary ribs, the auxiliary ribs can be easily disposed at a position for preventing skew. In other words, in the case of the center reference, if the auxiliary ribs are arranged symmetrically with respect to the width direction bisector of the paper of a specific size, they are also arranged symmetrically with respect to the width direction bisector of other sizes of paper Will be. On the other hand, in the case of the end reference that conveys the left end or the right end of each size of paper, the auxiliary ribs may be arranged symmetrically with respect to the bisector of the paper of a specific size, It is not necessarily arranged symmetrically with respect to the bisector in the width direction of other sizes of paper. Thus, the center reference is advantageous in that it is easy to adjust the position of the auxiliary ribs and to prevent the skew of the paper.

  According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the guide rib and the auxiliary rib are respectively divided into a center line that bisects the conveyance width direction of the guide surface. They are arranged symmetrically.

  As a result, it is possible to prevent paper skew.

  A sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, wherein the guide ribs and the auxiliary ribs are disposed on both sides of the center line of the guide surface.

  In other words, by not providing guide ribs and auxiliary ribs on the center line, the paper transportability is stabilized.

  According to a seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, among the interval dimensions of the adjacent guide ribs, the interval dimension located at the center in the conveyance width direction is set to be larger than the other interval dimensions. It is a large setting.

  With this setting, the sheet can be stably conveyed.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the guide surface on which the auxiliary rib is disposed is disposed at a bent portion of the conveyance path.

  In particular, the sheet conveyed at the bent portion is often pressed strongly against the guide surface. If the auxiliary rib is provided at the location where the paper is strongly pressed in this way, the paper can be conveyed while reducing the contact pressure.

  According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the auxiliary rib is disposed in a conveyance width direction region of a public postcard.

  In general, public postcards made of thick and strong paper tend to be strongly pressed against the guide ribs during transportation and easily have streak-like scratches on the surface. In the present invention, an auxiliary rib is provided in the transport width direction region of the government postcard so that the government postcard is brought into wide contact with the auxiliary rib in the transport width direction to reduce the contact pressure, and the government postcard is strongly pressed against the guide rib. To prevent it.

  According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the auxiliary rib is 50 mm from the center line that bisects the conveyance width direction of the guide surface to both sides in the width direction. It is arranged within.

  In other words, an auxiliary rib is disposed in the conveyance width direction region of the government postcard having a width dimension of 100 mm to reduce the contact pressure by bringing the government postcard into contact with the auxiliary rib, and the government postcard strongly presses the guide rib. To prevent that.

  According to an eleventh aspect of the present invention, a concave guide surface having a paper conveyance device having a conveyance path for conveying a paper and an image forming section for forming an image on the paper in the middle of the conveyance path, and forming a bent portion of the conveyance path. In addition, an inlet of the reverse path for double-sided printing is formed, and a plurality of guide ribs extending in the transport direction are arranged in parallel in the transport width direction on the guide surface immediately before branching from the upstream side of the transport path to the entrance of the reverse path. In the image forming apparatus, auxiliary ribs having a larger contact range in the transport width direction than the guide ribs are disposed on the guide surface in the vicinity of the guide ribs.

  By making the paper come into wide contact with the auxiliary rib in the conveyance width direction, the paper is conveyed while reducing the contact pressure, and the paper is prevented from being strongly pressed against the guide rib. Further, by providing the auxiliary rib in the vicinity of the bent portion where the sheet is strongly pressed against the guide surface, the effect of reducing the contact pressure is sufficiently exhibited.

  According to a twelfth aspect of the present invention, in the image forming apparatus according to the eleventh aspect, the guide rib and the auxiliary rib close to the center in the conveyance width direction of the guide surface among the most downstream contact ends where the guide rib contacts the paper. The image forming apparatus according to claim 10, wherein the contact end portion is disposed on the upstream side of the contact end portion at a position away from the center in the transport width direction to both sides in the width direction.

  Immediately before the sheet passes through the contact edge away from the center, the sheet has slipped out of the contact edge closer to the center, so that the vicinity of the center in the width direction of the rear edge of the sheet swells and bends. Then, when the trailing edge of the sheet passes through the contact end portion away from the center, the sheet is in a bent state, and the trailing edge quickly returns while being bent and comes into contact with the opposing guide surface. At this time, the bent trailing edge of the sheet softly contacts the opposing guide surface in order from the center in the width direction to the left and right ends, so that the collision noise between the trailing edge of the sheet and the guide surface can be reduced. it can.

  According to a thirteenth aspect of the present invention, there is provided a paper transport device having a transport path for transporting paper, an image forming section for transferring a toner image onto the paper in the middle of the transport path, and a toner on the paper formed by the image forming section. An image forming apparatus comprising a fixing device that heat-fixes an image, wherein a plurality of guide ribs extending in the transport direction are arranged in parallel in a transport width direction on a guide surface that forms the transport path above the fixing device. On the guide surface, an auxiliary rib having a contact range larger than that of the guide rib in the conveyance width direction with respect to the sheet is disposed, and the auxiliary rib and the sheet are in line contact with the conveyance width direction, or in the conveyance width direction. It comprised so that a point contact might be carried out in multiple places.

  By making the paper come into wide contact with the auxiliary rib in the conveyance width direction, the paper is conveyed while reducing the contact pressure, and the paper is prevented from being strongly pressed against the guide rib. In addition, the water vapor generated when the toner image is heated and fixed on the paper may cause condensation on the guide surface above the fixing device. However, when the paper is brought into line contact or point contact with the auxiliary rib, There is no risk of getting wet with water droplets adhering to the guide surface.

  According to the image forming apparatus of the present invention, by providing the auxiliary rib, it is possible to reduce the contact pressure with the sheet and to prevent the sheet from being strongly pressed against the guide rib. It is possible to prevent the occurrence of streak-like scratches on the surface. Thereby, the appearance of the surface of the paper can be improved and the quality of the formed image can be improved. The configuration of the present invention is particularly effective when an image is formed on stiff paper or when duplex printing is performed.

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

    FIG. 1 is a cross-sectional view showing an outline of a color image forming apparatus. The main part of the image forming apparatus will be described below with reference to FIG. The image forming apparatus includes a sheet conveying apparatus 1 including a conveyance path 1a for conveying a sheet as a sheet-like recording medium, and an image forming unit 2 that forms an image on the sheet conveyed by the sheet conveying apparatus 1. . The image forming unit 2 forms an image with toner as developer of each color of yellow, magenta, cyan, and black corresponding to the color separation component of the color image, and is in the middle of the conveyance path 1 a of the sheet conveyance device 1. Includes a fixing device 3 for heating and fixing the toner image formed on the paper in the image forming unit 2.

  The image forming unit 2 includes an image carrier 4 (photosensitive drum), a charging member 5 that charges the surface of the image carrier 4, an exposure device 6 that exposes the surface of the image carrier 4, and an image carrier 4. A main component is a developing device 7 that forms a toner image on the surface and a transfer device 8 that transfers the toner image onto a sheet. Then, the process cartridge A (first process cartridge A1 to fourth process cartridge A4) integrally including the image carrier 4, the charging member 5, the developing device 7 and the like as an image forming unit is used for each color of the color image. Correspondingly, four process cartridges A are detachably attached to the main body of the image forming apparatus. Further, in each process cartridge A, a cleaning blade 10 that removes toner remaining on the surface of the image carrier 4 and a toner conveying means 12 that conveys the removed waste toner to the collecting unit 11 in the process cartridge A are provided. Provided.

  The transfer device 8 is hung on four primary transfer rollers 93 a, 93 b, 93 c, 93 d facing each image carrier 4, each primary transfer roller 93 a, 93 b, 93 c, 93 d, a driving roller 91 and a driven roller 92. It has an intermediate transfer belt 9 that is passed and circulated, and a secondary transfer roller 94 that is disposed to face the drive roller 91.

  At the bottom of the image forming apparatus, a paper feed cassette 13 that can store a large number of sheets and a paper feed roller 14 that feeds the sheets from the paper feed cassette 13 are provided. A pair of registration rollers 15a and 15b for temporarily stopping the paper are disposed in the transport path 1a slightly downstream of the paper feed roller. The paper discharge port 16 formed in the upper part of the image forming apparatus main body is provided with a pair of paper discharge rollers 17a and 17b as means for discharging the paper. A discharge tray 18 in which a part of the upper cover of the image forming apparatus is recessed inward is provided below the discharge port 16.

  The image forming apparatus shown in FIG. 1 has a double-sided printing mechanism, and a reverse path 1b for double-sided printing is provided by branching from a transport path 1a near the discharge port 16. In FIG. 1, the inlet 27 of the inversion path 1b is opened in the concave guide surface in which the bending part of the conveyance path 1a was formed. The reversing path 1b merges with the conveying path 1a below the pair of registration rollers 15a and 15b at the lower part of the image forming apparatus, and a pair of conveying rollers 19a and 19b are disposed in the middle of the reversing path 1b. .

  A basic image forming operation in this image forming apparatus will be described. First, the surface of the image carrier 4 is charged to a uniform high potential by the charging member 5. Next, the surface of the image carrier 4 is irradiated with a laser beam (L1 to L4) from the exposure device 6 based on the image data, and the potential of the irradiated portion is lowered to form an electrostatic latent image. Toner is transferred from the developing device 7 to the surface portion of each image carrier 4 on which the electrostatic latent image is formed, and a toner image of each color is formed (developed). Then, the toner images of the respective colors on the image carriers 4 are transferred to the intermediate transfer belt 9 so as to overlap, and the superimposed toner images are transferred by the secondary transfer roller 94 to the paper fed from the paper feed cassette 13. To do. Thereafter, the sheet onto which the toner image has been transferred is conveyed to the fixing device 3 where the toner image on the sheet is heated and fixed, and is discharged from the sheet discharge port 16 at the top of the image forming apparatus main body to the sheet discharge tray 18.

  On the other hand, the toner remaining on the surface of each image carrier 4 after the transfer is scraped off by the cleaning blade 10, and the scraped waste toner is sent to the collecting unit 11 by the toner conveying means 12 and stored.

  The case of duplex printing will be described with reference to FIG. 1 and FIGS. 2, 3, and 4 showing the main part thereof. First, an image is formed on one side of a sheet in the same manner as the image forming operation described above. The sheet that has passed through the fixing device 3 is guided by the guide member 20 above the fixing device 3, that is, on the downstream side in the transport direction, and is sent to the paper discharge port 16 as shown by an arrow (a) in FIG. Since the transport path 1a is bent near the paper discharge port 16, the sheet P is bent along the bent portion of the transport path 1a as shown in FIG. ), And a part thereof is sent out by the paper discharge roller pair 17a, 17b so that a part of the paper comes out from the paper discharge port 16. Then, as shown in FIG. 4, when the rear end of the paper P passes through the guide member 20, the rear end of the paper P jumps up as shown by the two-dot chain line due to the restoring action of the paper P in the bent state, and the reversing path 1b. Head to the entrance. In this state, the paper discharge rollers 17a and 17b rotate reversely, the paper P is switched back and pulled back into the interior. That is, the portion of the paper that has been the rear end side so far is moved backward in the direction of the arrow (A) in FIG. 2 and guided by the guide member 20 into the reversing path 1b.

  Then, the sheet conveyed in the reversing path 1b passes through the conveying roller pair 19a and 19b, reaches the registration roller pair 15a and 15b, and is sent out in time with the image for the back surface formed on the intermediate transfer belt 9. Then, the image is transferred to the back surface of the sheet when passing through the secondary transfer roller 94. As described above, the paper on which the images are formed on both sides passes through the fixing device 3 to fix the image on the back surface, and is discharged from the paper discharge port 16 to the paper discharge tray 18 by the paper discharge roller pair 17a and 17b. The

  As described above, the image forming apparatus of the present invention is provided with the guide member 20 that guides both when the paper is discharged and when it is reversed. Hereinafter, the configuration of the guide member 20 will be described. This will be described in detail.

  2, the guide member 20 is disposed on the front side of the image forming apparatus main body, in other words, on the outer side of the apparatus main body, and on the rear side of the outer guide surface 21, that is, on the inner side of the apparatus main body. The inner guide surface 22 is provided. The guide member 20 faces the inner guide surface 22 to form a conveyance path 1a (hereinafter referred to as a paper discharge guide surface) and the outer guide surface 21 faces to form a reversing path 1b. It has a surface 20b (hereinafter referred to as a reversing guide surface).

  FIG. 5 is a perspective view of the guide member 20 as viewed from the paper discharge guide surface 20a. As shown in FIG. 5, a plurality of guide ribs 23 extending in the transport direction are arranged on the paper discharge guide surface 20a in the transport width direction. It is installed. In FIG. 5, the upper side is the downstream side in the paper transport direction. The downstream edge of the paper discharge guide surface 20a corresponds to the portion 30 immediately before branching from the upstream side of the conveyance path 1a of the paper discharge guide surface 20a to the inlet 27 of the reverse path 1b shown in FIG. Four auxiliary ribs 24 that are thicker in the transport width direction than the guide ribs 23 and shorter in the transport direction than the guide ribs 23 are arranged in parallel in the transport width direction at the immediately preceding branch 30 or downstream edge.

  FIG. 6A is a cross-sectional view of the guide rib 23 cut in the conveyance width direction. As shown in the figure, the tip end of the guide rib 23 is formed in an arc shape or an arc shape, and comes into contact with the paper at the apex portion 25. FIG. 6B is a cross-sectional view of the auxiliary rib 24 cut in the conveyance width direction. In the cross-sectional view, the auxiliary rib 24 is attached to the sheet by a linear portion 26 extending in the conveyance width direction at the tip. Contact. As can be seen from FIGS. 6A and 6B, the auxiliary ribs 24 are formed so that the contact range with respect to the sheet is larger in the conveyance width direction than the guide ribs 23.

  This paper transport device is capable of transporting a plurality of types of paper, and transports the paper in the width direction bisector so as to coincide with the one-dot chain line C in FIG. 5 regardless of the paper size. It is a thing. That is, the alternate long and short dash line C is a center line that bisects the conveyance width direction of the paper discharge guide surface 20a. The guide ribs 23 and the auxiliary ribs 24 are arranged symmetrically (line symmetry) on both sides with respect to the center line C in order to prevent skewing of each size of paper. In this case, all the four auxiliary ribs 24 are provided adjacent to the guide ribs 23, and each auxiliary rib 24 is arranged closer to the center line C side from each adjacent guide rib 23.

  FIG. 7 is a rear view of the guide rib 20, that is, a view as seen from the paper discharge guide surface 20 a, and an area in the conveyance width direction indicated by a symbol H is an area in the conveyance width direction of a public postcard. All four auxiliary ribs 24 are disposed in the conveyance width direction region H of this government-made postcard. Specifically, since the postcard has a lateral width of 100 mm, the auxiliary ribs 24 are disposed within 50 mm from the center line C to both sides in the conveyance width direction. Three pairs of guide ribs 23 are disposed in the conveyance width direction region H of the government postcard, and the auxiliary ribs 24 are adjacent to the first and third pairs of guide ribs 23 on both sides from the center line C.

  Of the spacing dimensions W1, W2, and W3 of the adjacent guide ribs 23 in the transport width direction region H of the government-made postcard, the spacing dimension W1 that is located at the center in the transport width direction is greater than the other spacing dimensions W2 and W3. It is desirable to set a larger value. Furthermore, it is desirable to set the central interval dimension W1 to be larger than the other interval dimensions W5 and W6 in the entire conveyance width direction of the sheet discharge guide surface 20a. In FIG. 7, since the guide ribs 23 are arranged symmetrically with respect to the center line C, the spacing dimensions W2 to W6 are shown only on one side (left side).

  As shown in FIG. 7, the guide rib 23 a located at a position away from the center line C on both sides in the conveyance width direction extends more downstream than the guide rib 23 b and the auxiliary rib 24 near the center line C. Or, it is provided protruding. That is, among all the ribs including the guide rib 23 and the auxiliary rib 24, the downstream end portion of the rib near the center line C is arranged upstream (lower) than the downstream end portion of the rib far from the center line C. .

  Specifically, as shown in FIG. 2, the most downstream contact end T of the auxiliary rib 24 that contacts the paper (particularly the rear end) is formed on the guide rib 23a that is separated from the center line C that contacts the paper (particularly the rear end). It is arranged upstream from the most downstream contact end S. Further, the most downstream contact end portion of the guide rib 23b near the center line C that contacts the paper (particularly the rear end) is also at the same position as the contact end portion T of the auxiliary rib 24 (not shown). It arrange | positions upstream from the contact end part S of the most downstream of the separated guide rib 23b.

  The operation of the guide member 20 configured as described above will be described. As shown in FIG. 3, when the paper P is transported to the paper discharge port 16, the paper P bends along the bent portion of the transport path 1 a and reaches the auxiliary rib 24 provided at the downstream end of the guide member 20. While sliding, a part of the paper is conveyed out from the paper discharge port 16. The contact pressure is reduced by bringing the paper P being conveyed and the auxiliary rib 24 into line contact in the conveyance width direction. In a state where the paper P is in contact with the auxiliary rib 24, the paper P is not in contact with the guide rib 23 near the auxiliary rib 24, and there is a slight gap 28 between the paper P and the guide rib 23. . Further, in the state where the auxiliary rib 24 is in contact with the paper P, even if the guide rib 23 near the auxiliary rib 24 is in contact with the paper P, the contact pressure between the guide rib 23 and the paper P is reduced. The contact pressure should be the same as or smaller than that.

  If the contact range (contact area) between the auxiliary rib and the paper is too large, the sheet conveyance resistance tends to increase or water droplets due to condensation tend to adhere to the auxiliary rib. Conversely, if the contact range between the auxiliary rib and the paper is too small, the effect of reducing the contact pressure cannot be sufficiently exhibited. For this reason, it is desirable to set the contact range between the auxiliary rib and the paper within a range that does not cause these problems. The auxiliary rib and the paper may be in surface contact instead of line contact.

  When the paper P is further fed in the paper discharge direction, the rear end of the paper P first passes the most downstream contact end T of the auxiliary rib 24 and the most downstream contact end of the center (center line C) side guide rib 23b. Then, it passes through the most downstream contact end S of the guide rib 23a away from the center (center line C). Immediately before passing through the contact end S, as shown in FIG. 8 when the guide member 20 is viewed from the reverse guide surface 20b side (front side), the auxiliary rib 24 has already been provided near the center in the width direction of the rear end of the paper P. And the center guide rib 23b is passed, and the presser foot due to these is eliminated. On the other hand, since the left and right ends of the rear end of the paper P are pressed by the guide ribs 23a that are separated from the center, as a result, the rear end edge of the paper P bulges near the center in the width direction and bends.

  When the rear end of the paper P passes through the guide rib 23a away from the center of the guide member 20, the rear end of the paper P jumps up and collides with the opposing outer guide surface 21 by the restoring action of the paper P in the bent state. (See FIG. 4). At this time, since the rear edge of the paper P faces the guide surface 21 as described above and bends in a convex shape, when the paper P jumps, the paper P first contacts the outer guide surface 21 from the center in the width direction, Then, it comes into soft contact with the left and right sides in the width direction.

  Also in the conventional image forming apparatus, a plurality of guide ribs are disposed on the discharge guide surface 20a of the guide member 20, but the most downstream contact end portion that contacts the sheet of all the guide ribs is the same in the transport direction. Was placed in position. Accordingly, the trailing edge of the sheet when passing through the guide rib is straight without bending, and a large amount of noise is generated when the straight trailing edge collides with the opposing outer guide surface 21. On the other hand, in the present invention, the trailing edge of the paper that has passed through the guide member 20 is bent and is softly brought into contact with the outer guide surface 21 from the center of the paper, thereby reducing the occurrence of collision noise and the conventional sound. The problem is solved.

  Further, by arranging the contact end S (see FIG. 2) of the guide rib 23a away from the center extending downstream, the rear end of the sheet passes through the contact end S of the guide rib 23a. The path to contact with the outer guide surface 21 is shortened, leading to a reduction in collision noise with the outer guide surface 21.

  Further, the leading edge of the sheet conveyed through the conveyance path 1a is guided by the guide rib 23a away from the center, and is conveyed along the path (c) shown in FIG. The presence of the guide rib 23a extending downstream prevents the paper from being sent along the path (d) and colliding with the outer guide surface 21 to be jammed.

  In order to prevent jamming, it is necessary to provide at least one pair of guide ribs 23a extending downstream in the conveyance width direction region H of the government-made postcard which is the minimum size sheet conveyed by the sheet conveying apparatus (see FIG. 7). . In addition, it is important for a strong paper such as a government-made postcard to bend the rear edge of the paper sufficiently in order to reduce the impact sound on the outer guide surface 21. The guide rib 23a extending downstream is It is preferable to provide at a position as far as possible from the center in the transport width direction. Therefore, in this embodiment, as shown in FIG. 7, a pair of guide ribs 23 a extending downstream in the transport width direction region H of the government postcard is provided near the left and right boundaries of the region H of the government postcard. It is arranged at a position of 47 mm from the center line C to both sides in the conveyance width direction.

  Further, in order to sufficiently bend the trailing edge of the sheet when the sheet passes through the guide member 20, the guide rib 23 is placed on the center line C of the sheet discharge guide surface 20a of the guide member 20 (see FIG. 7). It is preferable that the auxiliary ribs 24 are not disposed. However, even when the guide rib 23 and the auxiliary rib 24 are provided on the center line C, the most downstream contact end of the rib contacting the paper is the most downstream contact end of the guide rib 23a away from the center. It suffices to be upstream from the section.

  The auxiliary rib 24 is not limited to the above-described form as long as the contact range is larger in the conveyance width direction than the guide rib 23 with respect to the sheet. For example, as shown in the cross-sectional view of FIG. 10, a plurality of small convex portions 29 extending in the transport direction are formed at the tip of the auxiliary rib 24 in the transport width direction, and the arc-shaped or arc-shaped tip of each small convex portion 29 is formed. You may comprise so that a point contact may be carried out in multiple places in the conveyance width direction. Furthermore, as shown in FIG. 11, the small convex portions 29 may be formed independently, and an assembly in which the small convex portions 29 are closely arranged may be used as one auxiliary rib 24.

  The auxiliary rib 24 is provided in the conveyance path 1a and the reversing path 1b, particularly at a location where the paper is strongly pressed, so that the effect of reducing the contact pressure with the paper is remarkably exhibited. In other words, the auxiliary ribs 24 may be disposed in the bent portion in the paper conveyance path or in the length region of the paper extending from the bent portion to the upstream side and the downstream side of the conveyance path. This is because when a part of the sheet comes into contact with the bent part, the other part of the sheet also has a bending action.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, the auxiliary ribs 24 may be disposed on the guide surface of the conveyance path or the guide surface of the reversing path other than those shown in the drawings. Further, the structure of the present invention may be applied to an ink jet type image forming apparatus that forms an image by ejecting ink from an ink ejection port of a print head onto a sheet-like recording medium.

1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view of a main part of the image forming apparatus. It is principal part sectional drawing which showed a mode that a paper sheet was conveyed. It is principal part sectional drawing which showed a mode that a paper sheet was conveyed. It is a back perspective view of a guide member. It is a principal part cross-sectional view of a guide member, Comprising: (a) is a cross-sectional view of a guide rib, (b) is a cross-sectional view of an auxiliary rib. It is a rear view of the guide member. FIG. 3 is a perspective view of a main part showing a state where a part of the outer cover of the image forming apparatus is removed. It is principal part sectional drawing which showed a mode that a paper sheet was conveyed. It is a transverse cross section showing other embodiments of an auxiliary rib. It is a cross-sectional view showing still another embodiment of the auxiliary rib.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper conveying apparatus 1a Conveying path 1b Reversing path 2 Image forming part 3 Fixing apparatus 4 Image carrier 5 Charged body 6 Exposure device 7 Developing apparatus 8 Transfer apparatus 20 Guide member 23 Guide rib 24 Auxiliary rib 27 Entrance C Center line H Transport width direction area S Contact end T Contact end

Claims (13)

A sheet conveying apparatus having a conveying path for conveying a sheet, and an image forming unit that forms an image on the sheet in the middle of the conveying path, and a guide rib extending in the conveying direction on a guide surface that forms the conveying path in the conveying width direction In a plurality of image forming apparatuses arranged side by side,
An image forming apparatus, wherein an auxiliary rib having a larger contact range in the conveyance width direction than the guide rib is disposed on the guide surface in the vicinity of the guide rib.   The image forming apparatus according to claim 1, wherein the guide rib in the vicinity of the auxiliary rib is not in contact with the paper in a state where the auxiliary rib is in contact with the paper.   The image forming apparatus according to claim 1, wherein the auxiliary rib is provided adjacent to the guide rib.   The paper conveyance device is configured to convey a plurality of types of paper, and to convey the paper in the width direction bisectors regardless of the paper size. The image forming apparatus according to any one of 1 to 3.   5. The image formation according to claim 1, wherein the guide ribs and the auxiliary ribs are arranged symmetrically with respect to a center line that bisects the conveyance width direction of the guide surface. 6. apparatus.   The image forming apparatus according to claim 5, wherein the guide rib and the auxiliary rib are respectively disposed on both sides of the center line of the guide surface.   7. The image forming apparatus according to claim 6, wherein among the interval dimensions of the adjacent guide ribs, the interval dimension located at the center in the conveyance width direction of the guide surface is set larger than the other interval dimensions.   The image forming apparatus according to claim 1, wherein the guide surface on which the auxiliary rib is disposed is disposed at a bent portion of the conveyance path.   9. The image forming apparatus according to claim 1, wherein the auxiliary rib is disposed in a conveyance width direction region of a public postcard.   10. The image formation according to claim 1, wherein the auxiliary rib is disposed within 50 mm on both sides in the width direction from a center line that bisects the conveyance width direction of the guide surface. apparatus. A sheet conveying apparatus having a conveying path for conveying a sheet, and an image forming unit for forming an image on the sheet in the middle of the conveying path, and a concave guide surface formed with a bent portion of the conveying path, a reversal for duplex printing In the image forming apparatus in which a plurality of guide ribs extending in the transport direction are arranged in parallel in the transport width direction on the guide surface immediately before branching from the upstream side of the transport path to the entrance of the reversing path.
An image forming apparatus, wherein an auxiliary rib having a larger contact range in a conveyance width direction than the guide rib is disposed on a guide surface in the vicinity of the guide rib.   Out of the most downstream contact ends where the guide rib and the auxiliary rib come into contact with the sheet, the contact end portions closer to the center in the transport width direction of the guide surface are arranged on both sides in the width direction from the center in the transport width direction. The image forming apparatus according to claim 11, wherein the image forming apparatus is disposed on an upstream side of the contact end located at a position apart from the center. A sheet conveying device having a conveying path for conveying a sheet, an image forming unit that transfers a toner image onto the sheet in the middle of the conveying path, and a fixing device that heats and fixes a toner image on the sheet formed by the image forming unit An image forming apparatus in which a plurality of guide ribs extending in the transport width direction are arranged side by side on a guide surface that forms the transport path above the fixing device.
An auxiliary rib having a larger contact range in the conveyance width direction than the guide rib is disposed on the guide surface in the vicinity of the guide rib so that the auxiliary rib and the sheet are in line contact in the conveyance width direction, or An image forming apparatus configured to make point contact at a plurality of locations in the conveyance width direction.

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