JP2009015143A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely peel the paper from a transfer belt by arranging a means peeling paper to the transfer belt on the downstream side of a transfer nip area. <P>SOLUTION: In this image forming apparatus conveying the paper between a photoreceptor drum 3 and the transfer belt 103 to transfer a toner image formed on the surface of the photoreceptor drum 3 to the paper, a peeling roller 111 is arranged on the downstream side of a transfer roller 105 pressing the transfer belt 103 to the photoreceptor drum 3, and an angle difference between the conveying direction of the transfer belt 103 from the contact part 104 between the photoreceptor drum 3 and the transfer belt 3 to the peeling roller 111 and the conveying direction from the peeling roller 111 to the transfer belt 103 on the downstream side is set to be ≤19 degrees. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transfer belt type image forming apparatus that transfers a toner image formed on a surface of a photosensitive drum onto a sheet by conveying the sheet between the photosensitive drum and a transfer belt.

  Recently, a transfer belt type image forming apparatus for transferring a charged toner image (developer image) formed on the surface of the photosensitive drum onto the sheet by conveying the sheet between the photosensitive drum and the transfer belt. Is widely used (see, for example, Patent Document 1).

In this image forming apparatus, a plurality of transfer rollers that are pressed against the photosensitive drum are disposed below the transfer belt, and a voltage is applied by the plurality of transfer rollers to adjust the potential balance between the front and back surfaces of the transfer belt. It has been adopted.
JP-A-2005-70256

  In the above-described conventional image forming apparatus, after the sheet is brought into contact with the photosensitive drum in the transfer nip region, which is the pressure contact portion between the photosensitive drum and the transfer belt, before the next fixing process, the photosensitive drum and the transfer drum are transferred. It is necessary to securely peel the paper from the belt.

  In this case, with respect to the peeling from the photosensitive drum, a sheet peeling claw has been conventionally arranged on the downstream side of the transfer nip region of the photosensitive drum, and the paper stuck to the surface of the photosensitive drum is peeled off by this peeling claw. Is possible.

  On the other hand, the present situation is that no particular consideration has been given to the device for peeling the paper from the transfer belt. However, in recent years, a new problem has arisen that the peelability of the sheet from the transfer belt has deteriorated as the speed of the image forming apparatus has increased.

  The present invention has been devised to solve such problems, and its purpose is to reliably peel the paper from the transfer belt by arranging a means for peeling the paper on the transfer belt downstream of the transfer nip region. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to solve the above problems, the image forming apparatus of the present invention transfers a toner image formed on the surface of the photosensitive drum onto the sheet by conveying the sheet between the photosensitive drum and the transfer belt. In the image forming apparatus, a plurality of peeling members are provided on the downstream side of the transfer member that presses the transfer belt against the photosensitive drum. Specifically, the peeling member is constituted by a peeling roller that contacts the transfer belt, and the transfer member is constituted by a transfer roller, a blade, or the like.

  That is, the transfer belt is lifted slightly upward by the peeling roller, and the transfer belt is gently curved to facilitate the peeling of the sheet from the transfer belt. In addition, by smoothing the sheet conveyance path along the transfer belt, it is possible to prevent the leading edge of the sheet from floating from the transfer belt after peeling.

  Here, in the present invention, when one peeling roller is arranged, the transfer belt conveyance direction from the pressure contact portion between the photosensitive drum and the transfer belt to the peeling roller, and the transfer belt downstream from the peeling roller. Is set to 19 degrees or less. As a result, it is possible to ensure sufficient peelability of the paper. However, if the angle difference is set to be close to 19 degrees, there is a possibility that a slight lift will occur at the leading edge of the paper after peeling.

  Therefore, in the present invention, a plurality of (for example, three) separation rollers are arranged along the conveyance direction, and the conveyance direction of the transfer belt between the pressure contact portion between the photosensitive drum and the transfer belt and the first separation roller. And the angle difference with the transfer belt conveyance direction from the first peeling roller to the second peeling roller is set to 12 degrees or less. Further, the angle difference between the conveying direction of the transfer belt between the first peeling roller and the second peeling roller and the conveying direction between the second peeling roller and the third peeling row is 8 to 8. Set to 9 degrees or less. In this way, by curving the transfer belt little by little by a plurality of peeling rollers, it is possible to further suppress the slight lifting of the leading edge of the paper after peeling while ensuring sufficient paper peeling properties.

  According to the image forming apparatus of the present invention, it is possible to improve the releasability of the sheet from the transfer belt by gently curving the transfer belt by lifting the transfer belt slightly upward by the peeling member. In addition, by smoothing the sheet conveyance path along the transfer belt, it is possible to prevent the leading edge of the sheet from floating from the transfer belt after peeling.

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

<Description of Overall Configuration of Image Forming Apparatus>
FIG. 1 is an explanatory diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a partial detail view showing the configuration of the apparatus main body of the image forming apparatus.

  As shown in FIGS. 1 and 2, the image forming apparatus 1A according to the present embodiment has a cylindrical shape in which image data read by a scanner or image data transmitted from the outside is rotated by electrophotography. After an electrostatic latent image is formed on the photosensitive drum 3, the electrostatic latent image is visualized as a toner image with a charged developer by mixing two components of a chargeable toner and a magnetic carrier. The image forming apparatus 1A for transferring to a sheet and outputting it as a monochrome (single color) image, the image forming unit 14 having the photosensitive drum 3, and the toner image formed on the photosensitive drum 3 directly on the sheet Alternatively, the image forming apparatus includes a transfer mechanism 10 for indirectly transferring and a fixing unit 6 for fixing the toner image transferred onto the paper to the paper.

  In addition, the image forming apparatus 1A includes a paper feed tray 8 on which a plurality of sheets P can be stacked, a paper transport unit 59 that transports the paper P supplied from the paper feed tray 8 to the image forming unit 14, and an image forming unit. And a sheet conveying device 7 that conveys the unfixed toner on the sheet P printed on the sheet P to a fixing unit 6 that melts and fixes the sheet P, and conveys the sheet P corresponding to a plurality of preset discharge processing modes. Based on the speed, the conveyance speed of the paper P is selectively controlled according to the print request, so that the paper P can be automatically supplied from the paper feed tray 8 to the paper discharge tray 9.

  First, the overall configuration of the image forming apparatus 1A will be described.

  As shown in FIG. 1, the image forming apparatus 1A mainly includes an exposure unit 1, a developing device 2, a toner supply device 30, a photosensitive drum 3, a charger 4, a static elimination device 41, a photosensitive drum cleaning unit 160, and a fixing unit. The apparatus main body 1A1 includes a unit 6, a paper transport device 7, a paper transport path 7a, a paper feed tray 8, a paper discharge tray 9, a transfer mechanism 10, and the like, and an automatic document processing device 1A2.

  A document placing table 21 made of transparent glass on which a document is placed is provided on the upper surface of the apparatus main body 1A1. Above the document placing table 21, the automatic document processing device 1A2 is swingably opened upward. On the other hand, a scanner unit 22 serving as a document reading unit that reads image information of a document is disposed below the document placing table 21.

  Below the scanner unit 22, an exposure unit 1, a developing device 2, a photosensitive drum 3, a charger 4, a static eliminator 41, a photosensitive drum cleaning unit 160, a fixing unit 6, a paper transport device 7, and a paper transport path 7a. A paper discharge tray 9 and a transfer mechanism 10 are disposed, and a paper feed tray 8 storing paper P is disposed below the paper discharge tray 9 and the transfer mechanism 10.

  The exposure unit 1 irradiates and exposes the surface of the photosensitive drum 3 uniformly charged by the charger 4 according to the image data output from the image processing unit (not shown). It has a function of writing and forming an electrostatic latent image corresponding to image data on the surface of the body drum 3. The exposure unit 1 is disposed directly below the scanner unit 22 and above the photosensitive drum 3, and employs laser scanning units (LSU) 13 a and 13 b including laser irradiation units 11 and 11 and a reflection mirror 12.

  In the present embodiment, in order to perform high-speed printing processing, it is assumed that a two-beam technique using a technique that uses a plurality of laser beams and reduces the increase in irradiation timing is adopted.

  In the present embodiment, the laser scanning units (LSU) 13a and 13b are used for the exposure unit 1, but the light emitting elements arranged in an array, for example, an EL or LED writing head may be used. good.

  The photosensitive drum 3 has a substantially cylindrical shape, is disposed below the exposure unit 1, and is controlled to rotate in a predetermined direction (the direction of arrow A in the drawing) by a driving unit and a control unit (not shown). As shown in FIG. 2, along the outer peripheral surface of the photosensitive drum 3, the sheet peeling claw 31, the photosensitive drum cleaning unit 160, The charger 4 as the electric field generating unit, the developing device 2, and the charge eliminating device 41 are arranged in this order.

  The sheet peeling claw 31 is disposed so as to be able to contact and separate from the outer peripheral surface of the photosensitive drum 3 by a solenoid 32. The sheet peeling claw 31 is stuck to the surface of the photosensitive drum 3 when the unfixed toner image on the photosensitive drum 3 is transferred to the sheet P in a state of being in contact with the outer peripheral surface of the photosensitive drum 3. The sheet P is peeled off.

  Note that a driving motor or the like may be employed as the driving means for the sheet peeling claw 31 instead of the solenoid 32, and other driving means may be selected.

  The developing device 2 visualizes the electrostatic latent image formed on the photosensitive drum 3 with black toner, and is downstream of the charger 4 in the rotating direction of the photosensitive drum (the direction of arrow A in the figure). On the side, it is disposed substantially horizontally (right side in the figure) to the side of the photosensitive drum 3. A registration roller 15 is disposed below the developing device 2 on the upstream side in the recording medium conveyance direction. Details of the developing device 2 will be described later.

  The toner supply device 300 temporarily stores the toner discharged from the toner container 300 filled with toner in the intermediate hopper section 33 and then supplies the toner to the developing device 2, so that the toner supplying device 300 is adjacent to the developing device 2. Are arranged.

  The registration roller 15 aligns the front end of the paper P supplied from the paper feed tray 8 and the toner image on the photoconductive drum 3 and conveys it between the photoconductive drum 3 and the transfer belt 103 (not shown). The operation is controlled by the driving means and the control means.

  The charger 4 is a charging means for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential, and is disposed above the photosensitive drum 3 and in the vicinity of the outer peripheral surface thereof.

  In this embodiment, the charger type charger 4 is used. However, a contact type roller type or a brush type may be used instead.

  The static eliminator 41 is a pre-transfer static eliminator for reducing the surface potential of the photosensitive drum 3 in order to facilitate the transfer of the toner image formed on the surface of the photosensitive drum 3 to the paper P. It is disposed downstream of the developing device 2 in the rotating direction of the photosensitive drum and close to the outer peripheral surface below the photosensitive drum 3.

  In the present embodiment, the static eliminator 41 is configured using a static elimination electrode. However, a static elimination lamp may be used instead of the static elimination electrode, or static elimination may be performed by other methods. .

  The photosensitive drum cleaning unit 160 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer. The photosensitive drum cleaning unit 160 is positioned substantially opposite to the developing device 2 with the photosensitive drum 3 interposed therebetween. Thus, it is arranged substantially horizontally (left side in the figure) on the side of the photosensitive drum 3.

  As described above, the electrostatic image visualized on the photosensitive drum 3 is applied from the transfer mechanism 10 onto the paper P on which the electric field having the opposite polarity to the charge of the electrostatic image is conveyed. Transferred onto P. For example, when the electrostatic image has a charge of (−) polarity, the applied polarity of the transfer mechanism 10 is (+) polarity.

The transfer mechanism 10 is bridged by a driving roller 101, a driven roller 102, and another roller 108 (see FIG. 3), and has a predetermined resistance value (1 × 10 ⁹ to 1 × 10 ¹³ Ω · in this embodiment). a transfer belt unit having a transfer belt 103 having a range of cm), and the surface of the transfer belt 103 contacts a part of the cylindrical outer periphery of the photosensitive drum 3 below the photosensitive drum 3. Are arranged as follows. The transfer belt 103 conveys the paper P while pressing it against the photosensitive drum 3.

  At the contact portion 104 between the photosensitive drum 3 and the transfer belt 103, a transfer roller 105 made of an elastic conductive roller that is different from the driving roller 101 and the driven roller 102 and can apply a transfer electric field is disposed.

  The transfer roller 105 is made of a soft material such as elastic rubber or foamable resin. Since the transfer roller 105 has elasticity, the photosensitive drum 3 and the transfer belt 103 are not in line contact but in surface contact having a predetermined width called a transfer nip, and therefore, transfer efficiency to the conveyed paper P is improved. Improvements can be made.

  Further, on the downstream side of the transfer area of the transfer belt 103 in the paper conveyance direction, a static elimination roller 106 is transferred to neutralize the electric field applied to the conveyed paper P in the transfer area and smoothly carry it to the next process. It is arranged on the back side of the belt 103.

  As shown in FIG. 2, the transfer mechanism 10 is provided with a transfer belt cleaning unit 260 that removes dirt from residual toner on the transfer belt 103, and a plurality of charge removal mechanisms 108 that discharge the transfer belt 103. As a technique for performing static elimination used in the static elimination mechanism 108, there is a technique of grounding via an apparatus or a technique of positively applying a polarity opposite to the polarity of the transfer electric field.

  The electrostatic image (unfixed toner) transferred onto the paper by the transfer mechanism 10 is transported to the fixing unit 6 and pressurized and heated to melt the unfixed toner and fix it on the paper P.

  As shown in FIG. 2, the fixing unit 6 includes a heating roller 6a and a pressure roller 6b constituting a fixing roller, and the heating roller 6a is sandwiched between the heating roller 6a and the pressure roller 6b. And the toner image transferred onto the paper P is melted and fixed by passing between the heating roller 6a and the pressure roller 6b. A conveyance roller 16 that conveys the paper P is provided downstream of the fixing unit 6 in the paper conveyance direction.

  A paper discharge roller 17 for discharging the paper to the paper discharge tray 9 is provided on the downstream side of the transport roller 16 in the paper transport direction.

  The heating roller 6a includes a sheet peeling claw 611, a thermistor 612 that is a roller surface temperature detection member, and a fixing roller cleaning unit 360 that cleans the outer periphery of the heating roller 6a. A heat source 614 is provided for setting the roller surface to a predetermined temperature (fixing set temperature: approximately 160 to 200 ° C.).

  In the pressure roller 6b, pressure members 621 for pressing the pressure roller 6b with a predetermined amount of pressure against the heating roller 6a are arranged at both ends of the roller. Further, a paper peeling claw 622 and a roller surface cleaning member 623 are disposed on the outer periphery of the pressure roller 6b, similarly to the outer periphery of the heating roller 6a.

  As shown in FIG. 2, the fixing unit 6 heats the unfixed toner on the conveyed paper P by a heating roller 6a at a pressure contact portion 600 between a heating roller 6a and a pressure roller 6b called a so-called fixing nip portion. The unfixed toner is fixed on the sheet by a throwing action on the sheet by the pressure contact force between the heating roller 6a and the pressure roller 6b.

  The paper feed tray 8 is used to store a plurality of sheets of paper on which image information is output. The exposure unit 1, the developing device 2, the photosensitive drum 3, the charger 4, the charge eliminating device 41, and the photosensitive drum. The image forming unit 14 is disposed below the image forming unit 14 including the cleaning unit 160 and the fixing unit 6. A paper pickup roller 8 a is disposed on the upper side of the paper discharge side of the paper feed tray 8.

  The paper pick-up roller 8a picks up the sheets stacked and accommodated in the paper feed tray 8 one by one from the uppermost layer and moves toward the downstream side (for convenience, the flow side of the paper P, in other words, the cassette side is upstream, The paper side is the downstream side.) The paper is conveyed to the registration roller (also referred to as “idle roller”) 15 side on the paper conveyance path 7a.

  In the image forming apparatus 1A according to the present embodiment, in order to perform high-speed printing processing, a plurality of paper supply units that can store 500 to 1500 sheets of standard size sheets P in each tray are provided below the image forming unit 14. A paper tray 8 is disposed, and on the other hand, a large-capacity paper feed cassette 81 capable of storing a large amount of a plurality of paper types is disposed on the side surface of the apparatus. A manual feed tray 82 corresponding to size printing or the like is provided.

  The paper discharge tray 9 is disposed on the side of the apparatus opposite to the manual feed tray 82. Further, in place of the paper discharge tray 9, a post-processing device that performs stapling and punching processing of paper discharge, a multi-stage paper discharge tray, and the like can be arranged as options.

  The paper transport device 7 is disposed between the photosensitive drum 3 and the paper feed tray 8 described above, and receives the paper P supplied from the paper feed tray 8 via the paper transport path 7 a provided in the paper transport device 7. Each sheet is conveyed one by one to the transfer mechanism 10, in which the sheet on which the toner image is transferred from the photosensitive drum 3 is conveyed to the fixing unit 6, and after the unfixed toner image is fixed on the sheet in the fixing unit 6. The paper is transported by a paper transport path or a branching claw formed in accordance with the designated paper discharge processing mode.

  In the image forming apparatus 1A according to the present embodiment, a single-sided printing mode and a double-sided printing mode are set as preset discharge processing modes. In the single-sided printing mode, face-up discharge for discharging the print surface upward and face-down discharge for discharging the print surface downward are set as discharge processing.

  In the image forming apparatus 1 </ b> A according to the present embodiment, as shown in FIG. 2, the photosensitive drum cleaning unit 160, the transfer belt cleaning unit, and the image forming unit 14, the transfer mechanism 10, and the fixing unit 6, respectively. 260 and a fixing roller cleaning unit 360 are arranged to remove residual toner generated at each location as waste toner.

<Description of Peripheral Configuration of Photosensitive Drum 3>
Next, details of the peripheral configuration of the photosensitive drum 3, particularly the details of the transfer mechanism 10, will be described with reference to FIG.

  Around the photosensitive drum 3, a charger 4, an exposure unit 1, a developing device 2, a transfer mechanism 10, and a photosensitive drum cleaning unit 160 are arranged in this order.

  As described above, the transfer mechanism 10 is bridged by the driving roller 101, the driven roller 102, and the other roller 107, and the photosensitive drum 3 and the transfer belt 103 are brought into contact with each other in the transfer nip region by the transfer roller 105. Then, by conveying the sheet between the photosensitive drum 3 and the transfer belt 103, the charged toner image (developer image) formed on the surface of the photosensitive drum 3 is transferred onto the sheet.

  A transport mechanism for transporting the paper to the transfer nip region is disposed around the transfer nip region. Specifically, as shown in FIG. 3, a pair of upper and lower paper guides 89, a pair of registration rollers (paper feed rollers) 90, and a pair of upper and lower paper guides 88 on the upstream side in the sheet conveyance direction as viewed from the transfer nip region. Are arranged in this order. That is, when the leading edge of the paper conveyed between the paper guides 88 by another registration roller (not shown) enters the registration roller 90, the registration roller 90 is driven to rotate by a paper conveyance system drive motor (not shown). Is conveyed between the paper guides 89 and reaches the transfer nip region. A Pin sensor 87 is disposed on the lower paper guide 88. The Pin sensor 87 detects the presence or absence of paper.

  In the present embodiment, the Pin sensor 87 has a paper detection lever and a photo interrupter that protrude in the conveyance path between the paper guides 88. The paper detection lever is pivotally supported so as to rotate when it comes into contact with the paper. When the paper detection lever rotates, the end (other end) of the paper detection lever on the side not in contact with the paper is also displaced. The photo interrupter detects the displacement of the other end of the paper detection lever. When the photo interrupter detects that the other end is in the position when the paper detection lever is in contact with the paper, the photo interrupter outputs an ON signal indicating that the paper exists. On the other hand, if the photo interrupter detects that the other end is at a position when the paper detection lever is not in contact with the paper, the photo interrupter outputs an OFF signal indicating that no paper is present. For this reason, the timing at which the output from the Pin sensor 87 changes from the OFF signal to the ON signal indicates the timing at which the leading edge of the sheet is positioned at the Pin sensor 87. Conversely, the timing at which the output from the Pin sensor 87 changes from the ON signal to the OFF signal indicates the timing at which the trailing edge of the sheet is positioned at the Pin sensor 87.

  In the present embodiment, a sensor having a paper detection lever and a photo interrupter is used as the Pin sensor 87, but other sensors may be used. As another sensor, a reflective optical sensor or the like can be used.

  In this embodiment, in order to apply a voltage to the transfer roller 105 of the transfer mechanism 10, two high-voltage power sources, a constant voltage power source 83 and a constant current power source 84, a transfer output switching unit 85, and a control unit 86 are provided. Have.

  The constant current power source 84 outputs a voltage for attracting (adsorbing) the toner on the surface of the photosensitive drum 3 to the sheet to the transfer roller 105. Here, since the toner on the surface of the photosensitive drum 3 is negatively charged, the constant current power supply 84 outputs a current so as to give a positive charge amount to the transfer roller 105. That is, the constant current power supply 84 outputs a voltage having a polarity different from the polarity of the surface of the photosensitive drum 3.

  On the other hand, the constant voltage power supply 83 outputs a voltage for returning the toner on the transfer belt 103 to the photosensitive drum 3 side to the transfer roller 105. Here, since the toner is negatively charged, the constant voltage power supply 83 outputs a negative voltage to the transfer roller 105. That is, the constant voltage power supply 83 outputs a voltage having the same polarity as the polarity of the surface of the photosensitive drum 3. As a result, the negatively charged toner is returned to the photosensitive drum 3 side by the repulsive force, and the toner on the transfer belt 105 can be removed.

  The transfer output switching unit 85 connects either the constant voltage power source 83 or the constant current power source 84 to the transfer roller 105 based on a switching signal from the control unit 86. When the transfer output switching unit 85 receives the switching signal “A” from the control unit 86, the transfer output switching unit 85 connects the transfer roller 74 and the constant voltage power supply 83. When the transfer output switching unit 85 receives the switching signal “B” from the control unit 86, 74 and the constant current power supply 84 are connected. In addition, the control unit 86 controls the operation of each block in order to form an image at an appropriate position on the sheet and to suppress separation failure between the sheet and the photosensitive drum 3.

<Description of Arrangement Configuration of Peeling Roller According to the Present Invention>
In the above configuration, in this embodiment, a peeling roller for peeling the paper stuck to the transfer belt 103 is provided on the downstream side of the transfer roller 105 that presses the transfer belt 103 against the photosensitive drum 3. As an electrical method for peeling the paper from the transfer belt 103, the paper may be peeled from the transfer belt 103 by applying a voltage having a polarity opposite to the polarity of the transfer electric field to the peeling roller. This may be done by grounding the roller to the ground. In this case, the peeling roller can also be used as the charge eliminating roller 106.

  Hereinafter, an example of the arrangement configuration of the peeling roller will be described with reference to FIGS. 4 and 5.

Example 1
FIG. 4 shows an embodiment in which one peeling roller 111 is arranged on the downstream side of the transfer roller 105 that presses the transfer belt 103 against the photosensitive drum 3.

  That is, the transfer belt 103 is lifted slightly upward by the peeling roller 111, and the transfer belt 103 is gently curved, thereby prompting the release of the sheet from the transfer belt. In addition, by smoothing the sheet conveyance path along the transfer belt 103, it is possible to prevent the leading edge of the sheet from floating from the transfer belt 103 after peeling.

  The peeling roller 111 has a structure that can move up and down, and the bending angle of the transfer belt 103 can be adjusted by finely adjusting the position of the peeling roller 111 up and down. Further, the peeling roller 111 is a driven roller that is driven to rotate as the transfer belt 103 moves. However, the peeling roller 111 may be configured to be driven to rotate by providing a driving unit.

  Here, as in the first embodiment, when one peeling roller 111 is arranged, the transfer belt 103 is conveyed between the contact portion 104 between the photosensitive drum 3 and the transfer belt 103 and the peeling roller 111, and The angle difference (peeling angle) θ1 with respect to the conveyance direction of the transfer belt 103 downstream from the peeling roller 111 is preferably set to 19 degrees or less. If it is 19 degrees or more, the releasability is improved. However, when high-speed printing is performed, the lift of the leading edge of the paper peeled off from the transfer belt 103 may cause a slight problem, and the paper may not be smoothly conveyed to the next fixing process. Because it comes out. By setting in this way, it is possible to smoothly carry the paper to the next process while ensuring sufficient peelability of the paper.

(Example 2)
FIG. 5 shows an embodiment in which a plurality of (three in this embodiment) peeling rollers 112, 113, and 114 are arranged on the downstream side of the transfer roller 105 that presses the transfer belt 103 against the photosensitive drum 3. Yes.

  In other words, the transfer belt 103 is lifted slightly upward by these peeling rollers 112, 113, and 114, and the transfer belt 103 is gently curved, thereby urging the sheet from peeling from the transfer belt. In addition, by smoothing the sheet conveyance path along the transfer belt 103, it is possible to prevent the leading edge of the sheet from floating from the transfer belt 103 after peeling.

  These peeling rollers 112, 113, 114 have a structure that can be individually moved up and down, and the bending angle of the transfer belt 103 can be adjusted by finely adjusting the positions of these peeling rollers 112, 113, 114 individually. Can be adjusted. The peeling rollers 112, 113, and 114 are driven rollers that are driven to rotate as the transfer belt 103 moves. However, the peeling rollers 112, 113, and 114 may be configured to be rotationally driven individually or in conjunction with a driving unit. .

  Here, when the three peeling rollers 112, 113, 114 are arranged as in the second embodiment, the transfer from the contact portion 104 between the photosensitive drum 3 and the transfer belt 103 to the first peeling roller 112 is performed. The angle difference (peeling angle) θ2 between the belt conveying direction and the transfer belt conveying direction from the first peeling roller 112 to the second peeling roller 113 is preferably set to 12 degrees or less. Further, the angle between the conveying direction of the transfer belt between the first peeling roller 112 and the second peeling roller 113 and the conveying direction between the second peeling roller 113 and the third peeling row 114. The difference (peeling angle) θ3 is preferably set to 7 to 8 degrees or less. As described above, when the plurality of peeling rollers 112, 113, 114 are arranged, the transfer belt 103 can be gradually curved at each of the peeling rollers 112, 113, 114. It is not necessary to bend to nearly 19 degrees at a time, and for example, it is possible to bend to a desired angle (nearly 19 degrees) in two steps. Here, when the angle of curvature of the transfer belt 103 at the first peeling roller 112 is set to a smaller angle of 12 degrees or less, when the high-speed printing process is performed, the lifting of the leading edge of the sheet peeled off from the transfer belt 103 is further suppressed. This makes it possible to transport the paper more smoothly to the next fixing step.

  In this way, by curving the transfer belt 103 little by little by the plurality of peeling rollers 112, 113, 114, it is possible to more reliably suppress the lifting of the leading edge of the paper after peeling while ensuring sufficient paper peeling properties. It becomes possible.

1 is an explanatory diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a partial detail view showing a configuration of a main body of the image forming apparatus. FIG. It is a detailed explanatory view of the peripheral configuration of the photosensitive drum. It is explanatory drawing which shows Example 1 at the time of arrange | positioning one peeling roller in the downstream of a transfer roller. It is explanatory drawing which shows Example 2 at the time of arrange | positioning three peeling rollers in the downstream of a transfer roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A Image forming apparatus 1A1 Apparatus main body 1A2 Automatic document processing apparatus 2 Developing apparatus 3 Photosensitive drum 4 Charger 5 Photosensitive drum cleaning unit 6 Fixing unit 7 Paper conveying apparatus 7a Paper conveying path 8 Paper feed tray 9 Paper discharge tray 10 Transfer mechanism DESCRIPTION OF SYMBOLS 11 Laser irradiation part 12 Reflection mirror 13a, 13b Laser scanning unit 14 Image formation part 15 Registration roller 21 Original mounting stand 22 Scanner part 30 Toner supply apparatus 31 Paper peeling claw 32 Solenoid 33 Intermediate hopper 41 Static elimination apparatus 59 Paper conveyance part 83 Constant voltage Power supply 84 Constant current power supply 85 Transfer output switching section 86 Control section 87 Pin sensor 88, 89 Paper guide 90 Registration roller (paper feed roller)
DESCRIPTION OF SYMBOLS 101 Drive roller 102 Driven roller 103 Transfer belt 105 Transfer roller 106 Static elimination roller 107 Other roller 108 Static elimination mechanism 111-114 Peeling roller

Claims (5)

In an image forming apparatus for transferring a toner image formed on the surface of the photosensitive drum onto a sheet by conveying the sheet between the photosensitive drum and a transfer belt,
An image forming apparatus comprising: a plurality of peeling members provided downstream of a transfer member that presses the transfer belt against a photosensitive drum.   The image forming apparatus according to claim 1, wherein the peeling member is a peeling roller that contacts the transfer belt.   The image forming apparatus according to claim 2, wherein the transfer member is a transfer roller.   One transfer roller is disposed, the transfer belt conveyance direction from the pressure contact portion between the photosensitive drum and the transfer belt to the release roller, and the transfer belt conveyance direction downstream from the release roller The image forming apparatus according to claim 2, wherein the angle difference between and is set to 19 degrees or less.   A plurality of the peeling rollers are arranged, the transfer belt conveying direction from the pressure contact portion between the photosensitive drum and the transfer belt to the first peeling roller, and the second peeling from the first peeling roller The image forming apparatus according to claim 2, wherein an angle difference from a transfer belt conveyance direction to the roller is set to 12 degrees or less.

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