JP2006056664A - Paper delivery device and image forming device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper delivery device capable of eliminating the possibility of causing damage or jamming at the edge of a paper sheet when the paper sheet is fed to a double carrying passage by reversely rotating a delivery roll and an image forming device using the paper delivery device. <P>SOLUTION: This paper delivery device comprises a delivery means switchable between a delivery operation for delivering a recording paper on which an image is formed to the outside and a switchback operation for carrying the recording paper during delivery to the double carrying passage in the device. The device also comprises a paper attitude restriction means for restricting the attitude of the recording paper in the switchback operation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper discharge device for discharging paper and an image forming device using the same in an image forming apparatus such as a printer or a copier that employs an electrophotographic method, and in particular, switches a paper having an image formed on one side BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper discharge device that discharges paper and an image forming device using the same in an image forming apparatus that forms an image on both sides of a paper sheet by backing it and conveying it to a double-sided conveyance path.

JP-A-5-43110

  Conventionally, image forming apparatuses such as printers and copiers that employ this type of electrophotographic method charge the surface of a photosensitive drum as an image carrier to a predetermined potential, and then perform image exposure according to image information. Forming an electrostatic latent image and developing the electrostatic latent image as a toner image, the toner image is directly transferred and fixed onto the recording paper, or transferred onto the recording paper via an intermediate transfer member. An image is formed by fixing.

  In such an image forming apparatus, when images are formed on both sides of a recording sheet, the recording sheet on which the image is formed on one side is not directly discharged onto the discharge tray by the discharge roll, but the recording sheet is formed by the discharge roll. There is a configuration in which the recording paper is switched back and conveyed to the double-sided conveyance path by reversing the discharge roll while the rear end is sandwiched to form an image on the back surface of the recording paper.

  In the image forming apparatus, as disclosed in JP-A-5-43110 and the like, when a sheet having an image formed on one side is discharged onto a discharge tray by a discharge roll, the discharge tray In order to discharge the paper smoothly upward, a plurality of ribs are provided between the plurality of discharge rolls so as to face the discharge roll along the axial direction of the discharge roll, and the paper is forcibly waved. By hitting the sheet, the sheet is discharged onto the discharge tray in a state where the rigidity of the sheet is improved.

  However, the above prior art has the following problems. That is, in the case of the image forming apparatus, in order to smoothly discharge the recording paper onto the discharge tray, the discharge rolls are arranged so as to face the discharge rolls along the axial direction of the discharge rolls. The recording paper is configured to forcibly wave the recording paper, so when forming images on both sides of the recording paper, the discharge roll is reversed to switch back the recording paper. When the paper is transported to the duplex transport path, the trailing edge of the undulated recording paper becomes the leading edge and enters the duplex transport path. Or had the problem of causing jams.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to reverse the discharge roll and transport the sheet to the double-sided conveyance path. An object of the present invention is to provide a paper discharge device and an image forming apparatus using the same, in which there is no possibility that the end portion is damaged or jammed.

In order to achieve the above object, the invention described in claim 1 includes a discharge operation for discharging the recording paper on which an image is formed to the outside, and a switchback for transporting the recording paper being discharged to a double-sided conveyance path inside the apparatus. In a paper discharge device having a discharge means that can be switched between operation,
The paper discharge device is characterized in that paper posture restriction means for restricting the posture of the recording paper during the switchback operation is provided.

  Further, the invention described in claim 2 is characterized in that the sheet posture regulating means causes the leading edge of the recording sheet to be biased toward the double-sided conveyance path during the switchback operation. It is a paper device.

  Furthermore, the invention described in claim 3 is such that the paper attitude regulating means is in contact with the recording paper discharged by the discharging means on the downstream side of the discharging direction of the discharging means, and conveys the recording paper on both sides. The paper discharge device according to claim 2, comprising a member that is biased toward a road side.

  According to a fourth aspect of the present invention, there is provided the paper discharge mechanism according to the third aspect, wherein at least a portion of the paper posture regulating means that contacts the recording paper is formed in a rib shape. Device.

  Furthermore, the invention described in claim 5 is the paper discharge device according to claim 3, wherein a roller is disposed at least in a portion of the paper attitude regulating means that contacts the recording paper.

  The invention described in claim 6 is characterized in that the distance between the paper contact portion of the paper posture regulating means and the nip portion of the discharge means is set to 10 to 20 mm. The paper discharge device described in the above.

  Furthermore, the invention described in claim 7 is characterized in that the offset angle of the recording paper by the paper attitude regulating means is set to 5 to 10 degrees with respect to the paper discharge direction of the discharge means. The paper discharge device according to claim 3.

  The invention described in claim 8 is the paper discharge device according to claim 3, wherein the paper attitude regulating means is provided at both side ends of the discharge means.

The invention described in claim 9 further includes a fixing unit that fixes the unfixed toner image transferred onto the recording paper while conveying the recording paper, and the recording paper on which the toner image is fixed. A paper discharge roller that can be switched between a paper discharge operation to be discharged and a switchback operation to return the recording paper that is being discharged to the inside; a switch that branches from the recording paper conveyance path from the fixing means to the paper discharge roller; In an image forming apparatus including a double-sided conveyance path for conveying a backed recording sheet,
An image forming apparatus comprising: a sheet posture regulating unit that regulates a posture of the recording sheet during the switchback operation.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the sheet posture regulating unit causes the recording sheet discharged by the discharge roller to be biased toward the double-sided conveyance path. It is.

  Furthermore, the invention described in claim 11 is the image forming apparatus according to claim 9, wherein an entrance of the double-sided conveyance path is provided above the fixing unit.

  According to a twelfth aspect of the present invention, the paper attitude regulating means includes a rib that comes into contact with the discharged recording paper, and the offset angle of the recording paper is in a paper discharge direction of the paper discharge roll. The image forming apparatus according to claim 9, wherein the distance between the sheet contact portion and the nip portion of the sheet discharge roll is 10 to 20 mm.

  Furthermore, the invention described in claim 13 is the image forming apparatus according to claim 9, wherein the sheet posture regulating means is provided on both side ends of the sheet discharge roller.

  According to the present invention, it is possible to provide an image forming apparatus in which the end of the paper is not damaged or jammed when the discharge roll is reversed and the paper is conveyed to the double-sided conveyance path. .

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

Embodiment 1
2 shows a tandem type full-color printer as an image forming apparatus to which the paper discharge device according to the first embodiment of the present invention is applied. FIG. 3 shows the paper discharge device according to the first embodiment of the present invention. 1 illustrates an image forming unit of a tandem type full-color printer as an applied image forming apparatus. In addition, the arrow in FIG. 3 has shown the rotation direction of each rotation member.

  As shown in FIGS. 2 and 3, the full-color printer 01 includes photosensitive drums (image carriers) 11, 12, yellow (Y), magenta (M), cyan (C), and black (K). Image forming units 1, 2, 3, 4 having 13, 14, and charging rolls (charging means) 21, 23, 24 for primary charging that are in contact with or close to these photosensitive drums 11, 12, 13, 14 The laser optical unit shown in FIG. 2 that writes an electrostatic latent image by irradiating laser beams 31, 32, 33, and 34 of yellow (Y), magenta (M), cyan (C), and black (K). (Latent image writing means) 03, developing device (developing means) 41, 42, 43, 44, and two of the four photosensitive drums 11, 12, 13, and 14 in contact with the photosensitive drums 11 and 12 The first primary intermediate transfer drum (intermediate transfer member) 51 and the second primary intermediate transfer drum (intermediate member) contacting the other two photosensitive drums 13 and 14 (Transfer body) 52, a secondary intermediate transfer drum (intermediate transfer body) 53 in contact with the first and second primary intermediate transfer drums 51, 52, and a transfer roll (transfer) in contact with the secondary intermediate transfer drum 53 The main part is composed of the member 60). In this embodiment, in order to improve maintainability, a process including the photosensitive drums 11, 12, 13, 14 and the intermediate transfer drums 51, 52, 53, etc., excluding the developing devices 41, 42, 43, 44. The cartridge 02 is configured to be replaceable with respect to the printer main body 100.

  As shown in FIG. 3, the photosensitive drums 11, 12, 13, and 14 are arranged in parallel to each other at a constant interval so as to have a common tangential plane M.sub.2. Further, the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52 are surfaces whose rotational axes are parallel to the photosensitive drums 11, 12, 13, and 14 and have predetermined symmetry planes as boundaries. They are arranged in a symmetrical relationship. Further, the secondary intermediate transfer drum 53 is arranged so that the rotation axis thereof is parallel to the photosensitive drums 11, 12, 13, and 14.

  Signals corresponding to the image information for each color are rasterized by an image processing unit (not shown) and input to the laser optical unit 03 shown in FIG. In the laser optical unit 03, yellow (Y), magenta (M), cyan (C), and black (K) laser beams 31, 32, 33, and 34 are modulated in accordance with image information, and the corresponding colors. The photosensitive drums 11, 12, 13, and 14 are irradiated to write an electrostatic latent image.

  Around each of the photosensitive drums 11, 12, 13, and 14, an image forming process for each color is executed by a well-known electrophotographic method. First, as the photoconductor drums 11, 12, 13, and 14, for example, photoconductor drums using an OPC photoconductor having a diameter of 24 mm are used. These photoconductor drums 11, 12, 13, and 14 are, for example, It is rotationally driven at a rotational speed of 161 mm / sec. As shown in FIG. 3, the surfaces of the photosensitive drums 11, 12, 13, and 14 are applied with a DC voltage of about -800 V to charging rolls 21, 22, 23, and 24 as contact-type charging means. For example, it is charged to about -300V. The contact type charging means includes a roll type, a film type, a brush type, etc., but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. Further, in order to charge the surfaces of the photosensitive drums 11, 12, 13, and 14, in this embodiment, a charging method in which only DC is applied is used, but a charging method in which AC + DC is applied may be used.

  Thereafter, the surfaces of the photosensitive drums 11, 12, 13, and 14 correspond to yellow (Y), magenta (M), cyan (C), and black (K) colors by a laser optical unit 03 as an exposure unit. The laser beams 31, 32, 33, and 34 are irradiated, and an electrostatic latent image corresponding to input image information for each color is formed. When the electrostatic latent image is written by the laser optical unit 03, the surface potential of the image exposure portion of the photosensitive drums 11, 12, 13, and 14 is discharged to about −60 V or less.

  Further, the electrostatic latent images corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the surfaces of the photosensitive drums 11, 12, 13, and 14 are compatible. Are developed by the developing devices 41, 42, 43, and 44, and yellow (Y), magenta (M), cyan (C), and black (K) are provided on the photosensitive drums 11, 12, 13, and 14, respectively. Visualized as a toner image.

  In this embodiment, a magnetic brush contact type two-component development method is adopted as the developing devices 41, 42, 43, 44. However, the present invention is not limited to this development method. Of course, the present invention can be sufficiently applied to other development systems such as a contact development system.

The developing devices 41, 42, 43, and 44 are filled with two-component developers including yellow (Y), magenta (M), cyan (C), and black (K) toners and carriers, each having a different color. Has been. When the toner is replenished from the toner cartridges 04Y, 04M, 04C, 04K shown in FIG. 2, these replenishing toners 41, 42, 43, 44 are supplied to the auger 404 as shown in FIG. Is sufficiently agitated with the carrier and triboelectrically charged. Inside the developing roll 401, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is fixed. By the paddle 403 that conveys the developer to the developing roll 401, the amount of the developer conveyed to the vicinity of the surface of the developing roll 401 is regulated by the developer amount regulating member 402. In this embodiment, the amount of the developer is 30 to 50 g / m ² , and the charge amount of the toner existing on the developing roll 401 at this time is about −20 to 35 μC / g.

The toner used in the developing devices 41, 42, 43, 44 has a shape factor MLS2 defined by the following equation of 100 to 140, for example, MLS2 = 130, and an average particle size of 3 μm to 10 μm. So-called “spherical toner” is used.
MLS2 = {(absolute maximum length of toner particles) ² )}
/ {(Projection area of toner particles) × π × 1/4 × 100}

  The toner supplied onto the developing roll 401 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 11, 12, 13, and 14. ing. A developing bias voltage of AC + DC is applied to the developing roll 401 to develop the toner on the developing roll 401 into an electrostatic latent image formed on the photosensitive drums 11, 12, 13, and 14. It is formed. In this embodiment, the development bias voltage is about 4 kHz for AC, 1.5 kVpp, and about −230 V for DC.

  Next, the yellow (Y), magenta (M), cyan (C), and black (K) toner images formed on the photosensitive drums 11, 12, 13, and 14 are first primary images. The secondary transfer is electrostatically performed on the intermediate transfer drum 51 and the second primary intermediate transfer drum 52. The yellow (Y) and magenta (M) color toner images formed on the photoconductive drums 11 and 12 are formed on the first primary intermediate transfer drum 51 and cyan (on the photoconductive drums 13 and 14). The toner images of C) and black (K) are transferred onto the second primary intermediate transfer drum 52, respectively. Therefore, on the first primary intermediate transfer drum 51, the single color image transferred from either the photosensitive drum 11 or 12 and the two color toner images transferred from both the photosensitive drums 11 and 12 are superimposed. A double color image is formed. In addition, similar single-color images and double-color images are also formed on the second primary intermediate transfer drum 52 from the photosensitive drums 13 and 14.

  The surface potential necessary for electrostatically transferring the toner image from the photosensitive drums 11, 12, 13, 14 onto the first and second primary intermediate transfer drums 51, 52 is about +250 to 500V. It is. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. As shown in FIG. 2, the ambient temperature and humidity are detected by an environmental sensor that detects the ambient temperature and humidity. As described above, when the charge amount of the toner is in the range of −20 to 35 μC / g and is in a normal temperature and humidity environment, the surface potential of the first and second primary intermediate transfer drums 51 and 52 is + 380V is desirable.

The first and second primary intermediate transfer drums 51 and 52 used in this embodiment have an outer diameter of 42 mm, for example, and a resistance value of about 10 ⁸ Ω. The first and second primary intermediate transfer drums 51 and 52 are cylindrical rotating bodies having a single layer or a plurality of layers whose surfaces are flexible or elastic, and are generally made of Fe, Al, or the like. A low resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is provided on a metal pipe as a metal core material having a thickness of about 0.1 to 10 mm. . Furthermore, the outermost surfaces of the first and second intermediate transfer drums 51 and 52 are typically high release layers (R = 10 ⁵ to 10 ⁹ Ω) and bonded with a silane coupling agent-based adhesive (primer). What is important here is the resistance value and the releasability of the surface, and the resistance value of the high release layer is about R = 10 ⁵ to 10 ⁹ Ω. It is not limited.

  The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 51 and 52 in this way are electrostatically secondary-transferred onto the secondary intermediate transfer drum 53. Accordingly, a final toner image from a single color image to a quadruple color image of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the secondary intermediate transfer drum 53. Will be.

  The surface potential necessary for electrostatically transferring the toner image from the first and second primary intermediate transfer drums 51 and 52 onto the secondary intermediate transfer drum 53 is about +600 to 1200V. This surface potential is the same as when the toner is transferred from the photosensitive drums 11, 12, 13, 14 to the first primary intermediate transfer drum 51 and the second primary intermediate transfer drum 52. Will be set to the optimum value. Further, since what is necessary for the transfer is a potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53, the first and second primary intermediate transfer drums 51 and 52 have different potentials. It is necessary to set the value according to the surface potential. As described above, the charge amount of the toner is in the range of −20 to 35 μC / g, and the surface potential of the first and second primary intermediate transfer drums 51 and 52 is +380 V in a normal temperature and humidity environment. The surface potential of the secondary intermediate transfer drum 53 is about +880 V, that is, the potential difference between the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53 is + It is desirable to set it to about 500V.

The secondary intermediate transfer drum 53 used in this embodiment is formed to have the same outer diameter as that of the first and second primary intermediate transfer drums 51 and 52, for example, 42 mm, and the resistance value is set to about 10 ¹¹ Ω. . Similarly to the first and second primary intermediate transfer drums 51 and 52, the secondary intermediate transfer drum 53 is a cylindrical rotating body having a single layer or a plurality of layers whose surface is flexible or elastic. In general, a low resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is formed on a metal pipe as a metal core made of Fe or Al. It is provided at about 0.1-10mm. Further, the outermost surface of the secondary intermediate transfer drum 53 is typically formed by forming a fluororubber in which fluororesin fine particles are dispersed as a high release layer having a thickness of 3 to 100 μm, and a silane coupling agent-based adhesive. (Primer). Here, the resistance value of the secondary intermediate transfer drum 53 needs to be set higher than that of the first and second primary intermediate transfer drums 51 and 52. Otherwise, the secondary intermediate transfer drum 53 will charge the first and second primary intermediate transfer drums 51, 52, making it difficult to control the surface potential of the first and second primary intermediate transfer drums 51, 52. Become. The material is not particularly limited as long as the material satisfies such conditions.

  Next, the final toner image from the single color image to the quadruple color image formed on the secondary intermediate transfer drum 53 is tertiary transferred onto the recording paper P passing through the paper conveyance path by the final transfer roll 60. Is done. As shown in FIG. 2, the recording paper P passes through a registration roller 90 through a paper feeding process from a paper feeding cassette 05 and is fed into a nip portion between the secondary intermediate transfer drum 53 and the transfer roll 60. After this final transfer process, the final toner image formed on the recording paper P is fixed by heat and pressure by a fixing device 70 as a heat fixing means, and is discharged by a discharge roll 111 through a paper conveyance path 110. The paper is discharged onto a discharge tray T provided at the upper part of the full-color printer main body 100, and a series of image forming processes is completed. The fixing device 70 has a heating roller 71 having a heating source such as a halogen lamp inside and a pressure belt 72 that are pressed against each other, and heats and presses the recording paper P on which the unfixed toner image is transferred, thereby unfixing. The toner image is fixed on the recording paper P.

The transfer roll 60 has an outer diameter of 20 mm, for example, and a resistance value of about 10 ⁸ Ω. The transfer roll 60 is a tube having a semi-conductive coating layer made of urethane rubber or the like on a metal shaft, and a surface microhardness equal to or higher than a value corresponding to a polyimide resin or a polyetherimide resin on the coating layer. It is comprised by covering. Specifically, a tube made of polyimide resin or polyetherimide resin is used. The optimum value of the voltage applied to the transfer roll 60 varies depending on the ambient temperature, humidity, paper type (resistance value, etc.), and is approximately +1200 to 5000V. In this embodiment, a constant current method is employed, and a current of about +10 μA is applied in a normal temperature and humidity environment to obtain a substantially appropriate transfer voltage (+1600 to 2000 V).

  When images are formed on both sides of the recording paper P, as shown in FIG. 2, the recording paper P having an image formed on one side is not directly discharged onto the discharge tray T by the discharge roll 111. While the discharge roll 111 holds the rear end of the recording paper P on which the image is formed on one side, the discharge roll 111 is reversed and the recording paper P is transported on both sides with the front and back sides reversed. The recording sheet P is conveyed again to the transfer section by the conveying roll 117 via the path 116, and an image is formed on the back surface of the recording sheet P.

  In FIG. 2, reference numeral 08 denotes a paper feed roll for transporting the recording paper P supplied from a manual feed tray MSI (not shown), 09 denotes a control circuit, and 10 denotes a power supply circuit.

  By the way, in this embodiment, there is a discharge means capable of switching between a discharge operation for discharging the recording paper on which the image is formed to the outside and a switchback operation for transporting the recording paper being discharged to the double-sided conveyance path inside the apparatus. The paper discharge device is provided with a paper posture regulating means for regulating the posture of the recording paper during the switchback operation.

  In this embodiment, the paper attitude regulating means is configured to bias the leading edge of the recording paper toward the double-sided conveyance path during the switchback operation.

  Further, in this embodiment, the paper attitude regulating means abuts on the recording paper discharged by the discharging means on the downstream side in the discharging direction of the discharging means, and biases the recording paper to the double-sided conveyance path side. It is comprised so that it may consist of the member to make.

  In this embodiment, at least a portion of the paper posture regulating means that contacts the recording paper is formed in a rib shape.

  Furthermore, in this embodiment, a roller is disposed at least in a portion of the paper attitude regulating means that contacts the recording paper.

  In this embodiment, the distance between the paper contact portion of the paper posture regulating means and the nip portion of the discharge means is set to 10 to 20 mm.

  Furthermore, in this embodiment, the deviation angle of the recording paper by the paper attitude regulating means is set to 5 to 10 degrees with respect to the paper discharge direction of the discharge means.

  Further, in this embodiment, the paper posture regulating means is configured to be provided on both side ends of the discharge means.

  That is, in this embodiment, as shown in FIG. 2, the recording paper P, on which the toner image is fixed on one side by the fixing device 70, is conveyed to a discharge roll 111 as discharge means via a paper conveyance path 110. The paper is discharged onto the discharge tray T by the discharge roll 111. As shown in FIG. 4, the discharge roll 111 includes a lower discharge roll 114 in which four rolls 113 are arranged at predetermined intervals along the axial direction of the rotating shaft 112, and the lower discharge roll 114. And two upper discharge rolls 115 disposed so as to abut each other.

  Further, as shown in FIG. 2, the discharge roll 111 is configured to discharge the recording paper P on which the image is formed by forward rotation and discharges the recording paper P which is being driven reversely and is being discharged inside the apparatus. It is possible to switch to a switchback operation for conveying to the double-sided conveyance path 116. The discharge roll 111 is reversely rotated after a predetermined time has passed after the rear end of the recording paper P having the toner image fixed on one side thereof by the fixing device 70, and the rear end of the recording paper P is moved to the front end. As described above, it is configured to be switched to a switchback operation for conveying to the double-sided conveyance path 116. As shown in FIG. 2, the double-sided conveyance path 116 is branched from the single-sided paper conveyance path 110 at the upper portion of the fixing unit 70, and is continuous with the single-sided paper conveyance path 110 in a straight line. It is provided in a state of being inclined obliquely downward toward the back side of the printer body. Further, as shown in FIG. 5, a plurality of ribs 118 that come into contact with the recording paper P are provided on the double-sided conveyance path 116 in a protruding manner. Further, in the middle of the double-sided conveyance path 116, a conveyance roll 117 for conveying the recording paper P is rotatably disposed as shown in FIGS.

  Further, as shown in FIG. 1, a rib 120 is provided on the downstream side of the discharge roll 111 as a paper posture regulating means for regulating the posture of the recording paper P during the switchback operation. As shown in FIG. 4 to FIG. 6, the regulating rib 120 has a side surface on the both end sides (both outer sides) of the discharge roll 113 located at both ends of the plurality of discharge rolls 114 below the discharge roll 111. As shown in FIG. 1, the lower end surface 121 of the regulation rib 120 that is arranged in a right triangle shape is slightly inclined obliquely upward from the horizontal direction on the downstream side of the discharge roll 111 as shown in FIG. In the state, it protrudes over a predetermined length. Then, after the recording paper P discharged by the discharge roll 111 passes through the discharge roll 111, the posture of the recording paper P is forcibly regulated downward by the regulating rib 120 at both ends in the width direction. The rear end is pressed toward the double-sided conveyance path 116 by a reaction force based on the rigidity of the recording paper P whose posture is regulated downward.

  Further, the distance L between the curved sheet contact portion 122 of the regulating rib 120 and the nip portion of the discharge roll 111 is preferably set to 10 to 20 mm as shown in FIG. The deviation angle θ of the recording paper P by the regulating rib 120 is preferably set to 5 to 10 degrees with respect to the paper discharge direction A of the discharge roll 111. It should be noted that rollers may be arranged on at least a portion of the restriction rib 120 that contacts the recording paper P, for example, the paper contact portion 122.

  In the above configuration, in the case of the full-color printer according to this embodiment, the edge of the paper is damaged when the discharge roll is reversed and the paper is conveyed to the double-sided conveyance path as follows. Or the possibility of jamming can be prevented.

  That is, in the case of the full-color printer according to this embodiment, as shown in FIG. 2, each image forming unit 1, 2, magenta (M), cyan (C), and black (K) is formed as shown in FIG. A toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) is formed on the photoconductor drums 11, 12, 13, and 14, and these photoconductor drums The toner images of the respective colors formed on 11, 12, 13, and 14 are transferred onto the recording paper P by the transfer roll 60 via the first and second primary intermediate transfer drums 51 and 52 and the secondary intermediate transfer drum 53. The final transfer.

  The recording paper P on which the toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K) are transferred is heated and pressed by a fixing device 60 as shown in FIG. After fixing, in the case of single-sided printing, the paper is discharged as it is onto the discharge tray T by the discharge roll 111 that is driven forward.

  Further, when images are printed on both sides of the recording paper P, the discharge roll 111 is temporarily stopped while the rear end of the recording paper P is held between the discharge rolls 111 as shown in FIG. Alternatively, the recording paper P is reversed immediately to guide the recording paper P to the double-sided conveyance path 116.

  At this time, as shown in FIG. 1, a regulating rib 120 is provided on the downstream side of the discharge roll 111 on the upper discharge roll 115 side, so that the leading edge of the recording paper P discharged by the discharge roll 111 is provided. The upper surface (back surface) of the side 130 is bent downward by the regulating rib 120. Therefore, when the trailing edge 131 of the recording paper P is pressed toward the double-sided conveyance path 116 by the reaction force F accompanying the rigidity of the tip bent downward, the recording paper 111 is driven in reverse. The rear end side 131 of P is reliably conveyed as it is to the double-sided conveyance path 116 while being pressed to the double-sided conveyance path 116 side.

  Therefore, in the full color printer 01 according to this embodiment, when the discharge roll 111 is reversed and the recording paper P is conveyed to the double-sided conveyance path 116 side, the rear end side 131 of the recording paper P is the double-sided conveyance path 116. Therefore, the end of the recording paper P can be prevented from being damaged or jammed.

Experimental Example Next, in order to confirm the effect of the present invention, the inventors made a prototype of a printer configured as shown in FIGS. 1 to 3 and bent the restriction rib 120 as shown in FIG. The effect of causing the recording paper P to be biased by variously changing the distance L between the paper contact portion 122 and the nip portion of the discharge roll 111 and the biasing angle θ of the recording paper P by the regulating rib 120; An experiment was conducted in which the recording paper P was bent to increase the rigidity, and the corrugation effect for reliably discharging the recording paper P was confirmed.

  FIGS. 10 and 11 show the results of the above experimental example. The experiment in which the offset angle θ is changed is based on the distance between the curved sheet contact portion 122 of the regulating rib 120 and the nip portion of the discharge roll 111. The experiment in which L was set to 15 mm and the distance L was changed was performed with the offset angle θ set to 10 °.

  As is clear from FIG. 10, when the deviation angle θ of the sheet is in the range of 0 to 4 °, the deviation effect of the sheet is hardly obtained at the time of switchback, and the corrugation effect at the time of discharging is insufficient. On the other hand, when the paper bias angle θ is in the range of 5 to 10 °, the paper has a bias effect at the time of switchback, and the corrugation effect at the time of paper discharge is also appropriate. Further, when the deviation angle θ of the paper is 10 ° or more, there is a deviation effect of the paper at the time of switchback, but the corrugation effect at the time of paper discharge becomes excessive and inappropriate.

  On the other hand, as is apparent from FIG. 11, when the distance L from the discharge roll 111 is in the range of 5 to 10 mm, there is an offset effect of the paper at the time of switchback, but the corrugation effect at the time of paper discharge is insufficient. On the other hand, when the distance L from the discharge roll 111 is in the range of 10 to 20 mm, there is an offset effect of the paper at the time of switchback, and the corrugation effect at the time of discharge is also appropriate. Further, when the distance L from the discharge roll 111 is 20 mm or more, the offset effect of the paper is weak at the time of switchback, and the corrugation effect at the time of discharge is also present or insufficient.

  As is clear from the above, it is desirable that the deviation angle θ of the recording paper P by the restriction rib 120 is set to 5 to 10 ° with respect to the paper discharge direction A of the discharge roll 111. It can be seen that the distance L between the curved sheet contact portion 122 and the nip portion of the discharge roll 111 is preferably set to 10 to 20 mm.

  As shown in FIG. 12, when the regulating rib 120 is provided inside the paper discharge roll 113, there is no difference in the offset effect of the paper, but the corrugation effect at the time of paper discharge is significantly deteriorated. Paper capacity deteriorated.

FIG. 1 is a block diagram showing a main part of a tandem type full color printer as an image forming apparatus to which a paper discharge device according to Embodiment 1 of the present invention is applied. FIG. 2 is a configuration diagram showing a tandem full-color printer as an image forming apparatus to which the paper discharge device according to Embodiment 1 of the present invention is applied. FIG. 3 is a block diagram showing an image forming unit of a tandem type full color printer as an image forming apparatus to which the paper discharge device according to Embodiment 1 of the present invention is applied. 4 is a block diagram showing a paper discharge device according to Embodiment 1 of the present invention. FIG. 5 is a front structural view showing a main part of a tandem type full color printer as an image forming apparatus to which the paper discharge device according to Embodiment 1 of the present invention is applied. FIG. 6 is a perspective configuration diagram showing a main part of a tandem type full-color printer as an image forming apparatus to which the paper discharge device according to Embodiment 1 of the present invention is applied. FIG. 7 is a configuration diagram showing the dimensional shape of the main part of the paper discharge device according to Embodiment 1 of the present invention. FIG. 8 is an explanatory view showing the operation of a tandem type full color printer as an image forming apparatus to which the paper discharge device according to Embodiment 1 of the present invention is applied. FIG. 9 is an explanatory diagram showing experimental conditions. FIG. 10 is a chart showing experimental results. FIG. 11 is a chart showing experimental results. FIG. 12 is an explanatory diagram showing other experimental conditions.

Explanation of symbols

  111: discharge roll, 116: double-sided conveyance path, 120: regulating rib, P: recording paper.

Claims (13)

In a paper discharge device having a discharge means capable of switching between a discharge operation for discharging the recording paper on which an image is formed to the outside and a switchback operation for transporting the recording paper being discharged to a double-sided conveyance path inside the device,
A paper discharge device provided with a paper posture regulating means for regulating the posture of the recording paper during the switchback operation. 2. The paper discharge device according to claim 1, wherein the paper attitude regulating means biases the leading edge of the recording paper toward the double-sided conveyance path during the switchback operation. The paper attitude regulating means is a member that contacts the recording paper discharged by the discharging means on the downstream side in the discharging direction of the discharging means and biases the recording paper to the double-sided conveyance path side. The paper discharge device according to claim 2. 4. The paper discharge device according to claim 3, wherein at least a portion of the paper attitude regulating means that contacts the recording paper is formed in a rib shape. The paper discharge device according to claim 3, wherein a roller is disposed at least in a portion of the paper attitude regulating unit that contacts the recording paper. The paper discharge device according to claim 3, wherein a distance between a paper contact portion of the paper posture regulating means and a nip portion of the discharge means is set to 10 to 20 mm. 4. The paper discharge apparatus according to claim 3, wherein a deviation angle of the recording paper by the paper attitude restriction unit is set to 5 to 10 degrees with respect to a paper discharge direction of the discharge unit. The paper discharge apparatus according to claim 3, wherein the paper posture restriction unit is provided at both side ends of the discharge unit. Fixing means for fixing an unfixed toner image transferred onto the recording paper while transporting the recording paper; a paper discharging operation for discharging the recording paper on which the toner image is fixed; A paper discharge roller that can be switched to a switchback operation for sending the recording paper back to the inside; a double-sided conveyance path that branches from the recording paper conveyance path from the fixing means to the paper discharge roller and conveys the switched back recording paper; In an image forming apparatus comprising:
An image forming apparatus, comprising: a paper posture regulating unit that regulates a posture of the recording paper during the switchback operation. The image forming apparatus according to claim 9, wherein the paper posture regulating unit causes the recording paper discharged by the discharge roller to be biased toward the double-sided conveyance path. The image forming apparatus according to claim 9, wherein an entrance of the double-sided conveyance path is provided above the fixing unit. The paper attitude regulating means is a rib that contacts the discharged recording paper, and the offset angle of the recording paper is 5 to 10 degrees with respect to the paper discharge direction of the paper discharge roll, and the paper contact The image forming apparatus according to claim 9, wherein a distance between the contact portion and a nip portion of the paper discharge roll is 10 to 20 mm. The image forming apparatus according to claim 9, wherein the sheet posture regulation unit is provided at both side ends of the sheet discharge roller.

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