JP2015212718A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that is configured compact and has prevented the occurrence of damage to and abnormal images on documents.SOLUTION: An image forming apparatus includes: loading means on which documents or sheets to which toner images are transferred are loaded; reading means that is arranged on the downstream in the conveyance direction of the loading means; and a conveyance path 20 through which the documents or the sheets are conveyed, the conveyance path 20 being formed to pass through the reading means, transfer means 41, and fixing means 50. At least any one of a transfer rotating body and one of a fixing rotating body pair is formed of a movable rotating body. When the documents are conveyed through the common conveyance path 20, the movable rotating bodies are controlled to be separated from nips 46 and 56 formed by the movable rotating bodies.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that stacks a document and a sheet onto which a toner image is transferred on the same stacking unit.

  In general, a flatbed reader that reads a document on the upper part of the apparatus main body is arranged, a multifunction machine having a copy function that conveys a recording sheet from a paper feed cassette and prints an image of the document read by the flatbed reader on the recording sheet. Such image forming apparatuses are known.

  However, such an image forming apparatus is increased in size by the provision of a flat bed type reader. Therefore, in order to reduce the size of the apparatus, a flatbed reader is not provided, and a reading sensor for reading an image of a document is arranged downstream in the conveyance direction of the sheet cassette, and a document or recording paper is stored in the sheet cassette. There are image forming apparatuses that share these transport paths.

  Conventionally, a document to be transported and a recording sheet are branched upstream in the transport direction of the transfer device and the fixing device, and when the document is read, the rotation driving of the fixing device is stopped and the preheating of the fixing device is performed. An image forming apparatus that does not perform the above has been proposed (see Patent Document 1). Also, when reading a document, the transfer unit is turned off, the setting temperature of the fixing roller is set lower than that at the time of printing, or the pressing force of the pressure roller that is in pressure contact with the fixing roller is set lower. It has been proposed (see Patent Document 2).

JP 05-199357 A JP 05-219299 A

  However, the image forming apparatus described in Patent Document 1 has a problem that it takes time to start up during printing because the fixing device is not preheated. Further, since the document and recording paper discharge trays are separately provided, there are problems that the cost is increased and the apparatus is enlarged.

  In the image forming apparatus described in Patent Document 2, the fixing roller and the pressure roller are in pressure contact with each other for conveying the document even if the pressure of the pressure roller is set to be small. For this reason, the fixing roller is worn out to convey a document that does not require image fixing, and the maintenance frequency of the fixing roller is increased, which increases the running cost of the apparatus. Further, there is a possibility that the original document may be damaged or an abnormal image may be caused by toner contamination on the transfer unit or heat of the fixing roller.

  Accordingly, the present invention solves the above-described problems by configuring at least one of the transfer roller and the fixing roller with a movable roller that can move, and preventing the movable roller from forming a nip when reading a document. The purpose is to do.

  The present invention relates to a stacking unit that stacks a document or a sheet onto which a toner image is transferred, a reading unit that is disposed downstream of the stacking unit in the conveyance direction, and that reads an image of the document, and an image that forms a toner image on an image carrier. The toner image is heated and fixed to the sheet by a fixing unit formed by a forming unit, a transfer rotator, a transfer unit that transfers the toner image of the image carrier to the sheet by a transfer nip, and a fixing nip formed by a pair of fixing rotators. A fixing unit, a conveyance path formed so that a sheet on which a conveyed document or toner image is transferred passes through the reading unit, the transfer unit, and the fixing unit; the transfer rotator; and the fixing rotator. At least one of the pair is a movable movable member that can move. The movable rotary member can be used as the transfer nip or the fixing nip and the transfer nip or the fixing two. And a movable rotating body moving means for moving the movable rotating body to a position away from the transfer nip, and the movable rotating body so as to be separated from the transfer nip or the fixing nip when it is determined that the document is conveyed to the conveyance path. And a control means for controlling the movable rotating body moving means.

  In the present invention, when the control means determines that the document is conveyed to the conveyance path, the movable rotator constituted by the transfer rotator or the fixing rotator is separated from the transfer nip or the fixing nip. Alternatively, it is possible to extend the life by suppressing the wear of the fixing rotator. In addition, since the document is transported away from the movable rotating body, it is possible to prevent the document from being damaged or having an abnormal image due to toner contamination on the transfer unit or heat of the fixing rotating body.

1 is an overall sectional view showing an image forming apparatus to which the present invention is applied. Sectional drawing which shows the reading means which reads an image. 1 is a front view showing an image forming apparatus. FIG. 4 is a front view showing a changeover switch for switching between a document conveyance mode and a sheet conveyance mode. The upper perspective view which shows a paper feed cassette. 4A and 4B are diagrams illustrating a configuration for moving the transfer roller, in which FIG. 5A is a state in which the transfer roller is in contact with the secondary transfer inner roller, and FIG. 5B is a state in which the transfer roller is separated from the secondary transfer inner roller. . The figure which shows the movement of a transfer roller and a pressure roller. The control block diagram to which this invention is applied. The flowchart figure which shows control of a control means. The figure which shows the warning message displayed on an operation part. The figure which shows the movement of the guide member which concerns on 2nd Embodiment. The figure which shows the movement of the assist conveyance roller pair which concerns on 3rd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. The color multifunction peripheral 1 as an image forming apparatus has functions such as printing, scanning, and copying, and has a plurality of paper feed cassettes 10a, 10b, and 10c at the bottom of the apparatus as shown in FIG. Yes. Above the paper feed cassette 10a, image forming means 90, 96, 97, 98 for forming toner images on the intermediate transfer belt 40 as an image carrier are disposed.

  Since the sheet cassettes 10a, 10b, and 10c have the same configuration, only the uppermost sheet cassette 10a will be described. A sheet (hereinafter referred to as a sheet) S as a recording material onto which a toner image is transferred is stored in the paper feed cassette 10a in a form of being stacked on a stacking plate 11 (stacking means). The sheets S stacked on the top of the stacking plate 11 are picked up one by one by the paper feed roller 12 and fed in accordance with the image forming timing of the image forming means 90, 96, 97, 98. When a plurality of sheets S are picked up at the same time, the separation and conveyance roller pair 14 separates and conveys the sheets one by one.

  The image forming unit 90 includes a charging unit 99, a photoconductor 91, an exposure device 93, a developing device 92, a primary transfer device 45, a photoconductor cleaner 95, and the like. The exposure device 93 emits light based on the image information signal sent to the photosensitive member 91 whose surface is uniformly charged in advance by the charging means 99 and rotates counterclockwise, and an electrostatic latent image is formed. The The electrostatic latent image formed on the photoconductor 91 in this way is subjected to toner development by the developing device 92, and a toner image is formed on the photoconductor 91. Thereafter, the toner image on the photoreceptor 91 is transferred onto the intermediate transfer belt 40 by being given a predetermined pressure and an electrostatic load bias by the primary transfer device 45. The toner remaining on the photoconductor 91 is collected by the photoconductor cleaner 95, and the photoconductor 91 prepares for the next image formation.

  The image forming means 90 described above corresponds to one color of yellow (Y), and in addition, image forming means 96 corresponding to three colors of magenta (M), cyan (C), and black (Bk), respectively. There are 97, 98. Note that the image forming unit is not limited to four colors, and the color arrangement order is not limited to this.

  The intermediate transfer belt 40 is stretched by rollers such as a drive roller 42 and a secondary transfer inner roller 43, and is conveyed and driven in the direction of arrow B in the figure. The four color toner images formed by the image forming units 90, 96, 97, and 98 are superimposed on the intermediate transfer belt 40, and a full color toner image is formed on the intermediate transfer belt 40. The full-color toner image formed on the intermediate transfer belt 40 is given a predetermined pressure and an electrostatic load bias at a transfer nip 46 formed by the secondary transfer inner roller 43 and the transfer roller 44 (transfer rotator). And transferred to the conveyed sheet S.

  The sheet S conveyed from the sheet feeding cassettes 10a, 10b, and 10c is conveyed to a pair of registration rollers 30 (first conveyance roller pair) through a common conveyance path 20 (conveyance path). The sheet S is subjected to skew correction and timing correction of the sheet S by the registration roller 30, and then the toner image formed on the intermediate transfer belt 40 is transferred at the transfer nip 46. Thereafter, the toner image is heated and fixed by the fixing nip 56 of the fixing unit 50, and the sheet S is discharged by the paper discharge roller 51 to the paper discharge tray 52 (placement unit) at the upper part of the apparatus. The fixing unit 50 includes a pair of fixing rollers (a pair of fixing rotators) including a pressure roller 53 (heating rotator) and a heating roller 54 (pressure rotator). The fixing nip 56 is formed.

  When forming an image on both sides of the sheet S, when the trailing edge of the sheet S passes through the reverse conveyance unit 70, the paper discharge roller 51 performs a reverse operation. The sheet S is conveyed to the duplex conveying device 80 with the leading and trailing ends thereof being switched by performing a switchback operation by the reverse operation of the paper discharge roller 51. Thereafter, the sheet S on which the image has already been fixed on the first surface is joined from the refeed path 85 to the common conveyance path 20, and an image is formed on the second surface by the transfer means 41 and the fixing means 50, and the discharge tray 52 is discharged.

  In this embodiment, as shown in FIGS. 1 and 2, image reading units 210U and 210D are provided in the lowermost sheet cassette 10c, and a document or sheet S is stored in the sheet cassette 10c. The image reading unit 210U includes a contact image sensor (hereinafter referred to as CIS) 230U (reading unit) capable of reading an image of a document through the contact glass 213, and a conveyance roller 211U facing the contact glass 213. doing. Further, the image reading unit 210U has a xenon lamp 212 that passes through the contact glass 213 and illuminates the document or sheet S. The level of reflected light of the document or sheet S illuminated by the xenon lamp 212 is determined by the CIS 230U. Is detected.

  The length of the CIS 230U in the direction orthogonal to the conveyance direction (hereinafter referred to as the width direction) is set to be longer than the length of the document or sheet S in the width direction, and image detection of the document or sheet S is performed once. The CIS 230U supports color image detection, and converts the density (luminance) level of each color separated into RGB into a digital value in the A / D conversion unit 240 (see FIG. 8), and the CPU 551 (see FIG. 8). ) Pass the density data of each color. The conveyance roller 211U is formed of a flexible member such as rubber and is driven by a driving source (not shown) to convey the document or the sheet S while applying pressure to the contact glass 213. As a result, the document or sheet S is brought into close contact with the contact glass 213 and can be detected with high accuracy by the CIS 230U.

  The image reading unit 210U performs image detection on the front side of the document or the sheet S, and the back side is performed by an image reading unit 210D arranged upside down with the same configuration as the image reading unit 210U. The image reading unit 210D includes a CIS 230D (reading unit), a conveyance roller 211D that faces the contact glass 213, and a xenon lamp 212, but the description thereof is omitted because it has the same configuration as the image reading unit 210U. . These image reading units 210U and 210D can detect double-sided images in one pass. In this embodiment, the CIS is used as a detection sensor, but other types of image detection means such as a CCD may be used.

  The original fed from the paper feed cassette 10c passes through the image reading units 210U and 210D and is transported on the common transport path 20 as in the case of the sheet S. Then, it passes through the transfer means 41 and the fixing means 50 and is discharged to the paper discharge tray 52. Since the common conveyance path 20 and the paper discharge tray 52 are shared by the original and the sheet S, the apparatus can be configured compactly. Alternatively, the paper discharge roller 51 may be moved in the thrust direction so that the original and the sheet S are shifted and discharged to the paper discharge tray 52 to prevent confusion between the original and the sheet S. In the common conveyance path 20, the document or sheet S conveyed on the common conveyance path 20 by a plurality of conveyance roller pairs passes at least the CIS 230U, 230D (reading means), the transfer means 41, and the fixing means 50. Is formed.

  As shown in FIG. 3, an operation unit 250 for performing various setting operations is provided in the upper part of the color multifunction peripheral 1, and a rotatable changeover switch 16 (on the front surface of the lowermost sheet cassette 10c is provided. Switching means) is provided. As shown in FIG. 4, the changeover switch 16 can switch between the document conveyance mode and the sheet conveyance mode by setting the guide 16 a to “white paper” or “document”. The document transport mode is a mode in which the user transports the document to the common transport path 20 because the user has stored the document in the paper feed cassette 10c. The sheet conveyance mode is a mode in which the user conveys the sheet S to the common conveyance path 20 because, for example, a blank sheet S is stored in the sheet feeding cassette 10c. Since the changeover switch 16 is provided on the front surface of the paper feed cassette 10c, it is difficult for the user to forget to set the document conveyance mode or the sheet conveyance mode. Note that the changeover switch 16 is not limited to the front face of the paper feed cassette 10c, and may be placed anywhere as long as it is located near the paper feed cassette 10c in order to prevent forgetting to set the changeover switch 16. For example, the changeover switch 16 may be disposed on the front surface of the paper feed cassette 10b or on the left and right side surfaces of the paper feed cassette 10c.

  Further, as shown in FIG. 5, the sheet feeding cassette 10c includes side regulating plates 18a and 18b that are provided so as to be movable in the sheet width direction, and a rear end regulating plate that is provided so as to be movable in the sheet feeding direction. 19. The user can move the side regulating plates 18a and 18b and the rear end regulating plate 19 in accordance with the size of the document or sheet S stacked on the stacking plate 11. The positions of the side regulating plates 18a and 18b and the rear end regulating plate 19 are detected by the size detecting unit 111 (see FIG. 8), and the size information of the document or sheet S is recognized by the CPU 551 (see FIG. 8). Similarly, the CPU 551 recognizes the size information of the sheets S stored in the other paper cassettes 10a and 10b.

  Next, a configuration for moving the transfer roller 44 of the transfer unit 41 and the pressure roller 53 of the fixing unit 50 will be described. Since the transfer roller 44 and the pressure roller 53 are movable rollers that can move, and the moving means has the same configuration, only the moving configuration of the transfer roller 44 will be described. In this embodiment, both the transfer roller 44 and the pressure roller 53 are configured as movable rollers, but only the transfer roller 44 or only the pressure roller 53 may be configured as a movable roller. Further, instead of the pressure roller 53, the heating roller 54 may be a movable roller.

  As shown in FIG. 6, the transfer roller 44 is fixed to a rotating shaft 44 a, and the rotating shaft 44 a is rotatably supported by a bearing 47. The transfer roller 44 pressurizes the secondary transfer inner roller 43 by a spring 48 that biases the bearing 47 to form a transfer nip 46. The rotating shaft 44a is in contact with a link 49 that rotates about a fulcrum 49a, and the link 49 resists the biasing force of the spring 48 by a cam 310 that is rotated by driving of the secondary transfer detaching motor 302. Rotate. The secondary transfer desorption motor 302 and the cam 310 constitute a movable rotating body moving means. The transfer roller 44 is provided so as to contact or be separated from the secondary transfer inner roller 43 in accordance with the rotation of the link 49. The pressure roller 53 of the fixing unit 50 is provided so as to be in contact with or separated from the heating roller 54 by a fixing / removing motor 303 (see FIG. 8) constituting the movable rotating body moving unit and a cam driven by the fixing / removing motor 303. ing. That is, the secondary transfer desorption motor 302 and the cam 310 move the transfer roller 44 to the transfer nip 46 and a position away from the transfer nip 46. A constant attachment / detachment motor 303 and a cam driven by the fixing / removal motor 303 move the pressure roller 53 to the fixing nip 56 and a position away from the fixing nip 56. The transfer roller 44 and the pressure roller 53 do not have to be moved by individual cams and motors, and may be configured to move by one cam and motor.

  As shown in FIG. 7, the transfer roller 44 and the pressure roller 53 form a transfer nip 46 and a fixing nip 56, respectively, when the sheet S is conveyed to the common conveyance path 20. The image is transferred and fixed by heating. A registration roller 30 is arranged upstream of the transfer unit 41 in the conveyance direction, and a post-fixing conveyance roller 55 (second conveyance roller pair) is arranged downstream of the fixing unit 50 in the conveyance direction. The transfer nip 46 and the fixing nip 56 are arranged on one side (right side) with respect to a connecting line L1 (straight line) connecting the nip of the registration roller 30 and the nip of the post-fixing conveyance roller 55. When the document is conveyed to the common conveyance path 20, the transfer roller 44 and the pressure roller 53 are separated from the transfer nip 46 and the fixing nip 56, respectively, and the transfer nip 46 and the fixing nip with respect to the line L1. It is configured to be located on the opposite side (left side) to 56. The connecting line L1 is set to be shorter than the length in the conveyance direction of the document or sheet S that can be conveyed by the color multifunction peripheral 1, and the transfer roller 44 and the pressure roller 53 are separated from the transfer nip 46 and the fixing nip 56, respectively. However, the document or sheet S can be conveyed.

  As a result, when the document is transported, the document is transported in a state of being separated from the transfer roller 44 and the pressure roller 53, and wear of the transfer roller 44 and the pressure roller 53 is suppressed during transport of the document. The life of the roller 53 can be extended. In addition, it is possible to prevent the original from being damaged or having an abnormal image due to toner contamination on the transfer unit or heat from the heating roller. Note that the heating roller 54 maintains the temperature-controlled state even when the pressure roller 53 is separated, as in the case where the sheet S is conveyed to the common conveyance path 20. That is, the surface temperature of the heating roller 54 is maintained at a predetermined temperature or higher. As a result, even when the document conveyance mode is shifted to the sheet conveyance mode, the printing operation can be performed immediately.

  FIG. 8 is a control block diagram of the present embodiment, and the color multifunction peripheral 1 has a CPU 551 (control means). A memory 511, a RAM 561, a ROM 571, an input / output device 581 and the like are connected to the CPU 551. The memory 511 stores information (for example, size, basis weight, thickness, etc.) of the sheets in the sheet cassettes 10a, 10b, and 10c. The ROM 571 stores a control program for each unit, and the RAM 561 is used as a work area for the CPU 551. The input / output device 581 can communicate with the CPU 551 and an external personal computer 501 and the like via the network 502, and can transfer image data and an operation command from the external personal computer 501.

  Further, the changeover switch 16, the size detecting unit 111, the secondary transfer detaching motor 302, the fixing detaching motor 303, the A / D converting unit 240, and the like are connected to the input side of the CPU 551. An operation unit 250, a conveyance motor 307, a drum drive motor 304, an ITB drive motor 305, a fixing drive motor 306, and the like are connected to the output side of the CPU 551. A transport motor 307, a drum drive motor 304, an ITB drive motor 305, and a fixing drive motor 306 rotate and drive the transport rollers, the photosensitive member 91, the drive roller 42, and the heating roller 54, respectively.

  Next, control of each unit in the document conveyance mode and the sheet conveyance mode will be described with reference to the flowchart shown in FIG. First, in the standby state, the transfer roller 44 and the pressure roller 53 are separated (released) from the transfer nip 46 and the fixing nip 56, respectively (steps S101 and S102). This is because the transfer roller 44 and the pressure roller 53 have a rubber layer and a PFA tube, so that the life of the transfer roller 44 and the pressure roller 53 can be extended by reducing the time during which pressure is applied as much as possible.

  Next, the CPU 551 determines whether the changeover switch 16 is set to the document conveyance mode or the sheet conveyance mode (step S103). The CPU 551 determines one of a document transport mode in which a document is transported to the common transport path 20 and a sheet transport mode in which, for example, a blank sheet S is transported, depending on the position of the guide 16 a of the changeover switch 16. If the document transport mode is set in step S103, the ITB drive motor 305, drum drive motor 304, and fixing drive motor 306 are stopped (steps S104, S105, S106). When these are stopped from the beginning, the stopped state is maintained. Thereby, the rotation of the driving roller 42, the photoconductor 91 and the heating roller 54 can be stopped to save energy, and the life of components can be extended.

  In this state, the original is fed from the paper feed cassette 10c according to the designation of the scan or copy operation. The fed original is read by the image reading units 210U and 210D, and the read image information is stored in the memory 511 and then discharged to the paper discharge tray 52. Even if there is a page with no image during reading of the document, the document reading is advanced without stopping the apparatus. Even when the sheet S to which the toner image is to be transferred is read due to a user's setting error, the sheet S can be reused.

  When the copy operation is designated, after all the originals are read and the originals are discharged to the paper discharge tray 52, the sheet S is fed from the other paper feed cassettes 10a and 10b, and the sheet S is supplied to the sheet S. Image formation is performed based on the read image. When an image is formed on the sheet S, the transfer roller 44 and the pressure roller 53 naturally form a transfer nip 46 and a fixing nip 56, respectively.

  In step S103, when the changeover switch 16 is set to the sheet conveyance mode, the process proceeds to step S108, and in this step S108, the image reading results of the CIS 230U and 230D are checked. When the image is not detected as a result of reading by the CIS 230U and 230D and it is determined that the sheet is blank, the secondary transfer desorption motor 302 is driven, and the transfer roller 44 contacts the secondary transfer inner roller 43 to form the transfer nip 46. (Step S110). Further, the ITB drive motor 305 and the drum drive motor 304 are started to be driven, and the intermediate transfer belt 40 and the photoreceptor 91 are driven (steps S111 and S112). Further, when the fixing / removing motor 303 is driven, the pressure roller 53 presses the heating roller 54 to form the fixing nip 56 (step S113). Thereafter, the fixing driving motor 306 is driven to rotate the heating roller 54 (step S114). In this state, the sheet S is conveyed to the common conveying path 20, and image transfer and image fixing are performed on the sheet S. S is discharged to the discharge tray 52.

  When the CIS 210U, 210D detects an image in step S108, the CPU 551 stops the operation of the entire apparatus such as the transport motor 307, the drum drive motor 304, the ITB drive motor 305, and the fixing drive motor 306 (step S115). . At that time, the operations of the image forming units 90, 96, 97, 98, the transfer unit 41, and the fixing unit 50 are also controlled to stop. Then, for example, as shown in FIG. 10, a warning message is displayed on the operation unit 250 including a touch panel (step S116). If “Yes” is selected, it is determined that the printing operation is to be continued, and the process proceeds to step S110 (step S117: OK). When “No” is selected, the sheet S is conveyed to the common conveyance path 20 while the drum drive motor 304, the ITB drive motor 305, the fixing drive motor 306, and the like are stopped. The sheet S is discharged to the discharge tray 52 without image transfer and image fixing on the sheet S (step S117: NG).

<Second Embodiment>
Next, a second embodiment of the present invention will be described. However, with respect to the same configuration as the first embodiment, the illustration is omitted, or the same reference numerals are given to the drawings and the description is omitted. As shown in FIG. 11, guide members 321 and 322 that are movable in the same direction as the transfer roller 44 and the pressure roller 53 are disposed upstream and downstream of the fixing unit 50 in the conveyance direction. These guide members 321 and 322 are movable between a position indicated by a solid line and a position indicated by a dotted line in FIG.

  The transfer nip 46 and the fixing nip 56 are disposed on a connecting line L1 connecting the registration roller 30 and the post-fixing conveyance roller 55. When the sheet S is transported to the common transport path 20, the guide members 321 and 322 are disposed on one side (right side) of the connecting line L <b> 1 so as not to interfere with the transported sheet S.

  When the document is transported to the common transport path 20, the guide members 321 and 322 are interlocked with the transfer roller 44 and the pressure roller 53 moving to positions away from the transfer nip 46 and the fixing nip 56, respectively. Then, it moves to the other side (left side) of the connecting line L1. At that time, the guide members 321 and 322 guide the document so that the document is conveyed between the secondary transfer inner roller 43 and the transfer roller 44 and between the heating roller 54 and the pressure roller 53.

  As a result, the document passes through the document conveyance path L2 that is separated from the transfer roller 44, the pressure roller 53, the transfer nip 46, and the fixing nip 56, so that it is possible to prevent the document from being damaged by dirt or heat.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. However, for the same configuration as the first and second embodiments, the illustration is omitted, or the same reference numerals are given to the drawings and the description is omitted. . As shown in FIG. 12, between the transfer unit 41 and the fixing unit 50, a pair of assist conveyance rollers including a moving roller 331 and a fixed roller 332 that can move in the same direction as the transfer roller 44 and the pressure roller 53. 330 is arranged.

  When the sheet S is conveyed through the common conveyance path 20, the moving roller 331 is disposed on one side (right side) of the connection line L1, and is fixed on the other side (left side) of the connection line L1. It is separated from the roller 332. Then, the conveyed sheet S passes through the fixing nip 56 on the connecting line L1, that is, between the transfer nip 46, the moving roller 331 and the fixed roller 332.

  When the document is transported to the common transport path 20, the moving roller 331 moves in conjunction with the transfer roller 44 and the pressure roller 53 moving to positions away from the transfer nip 46 and the fixing nip 56, respectively. It moves to the other side (left side) of the connecting line L1. At that time, the moving roller 331 and the fixed roller 332 contact each other to form a nip. The document transported to the common transport path 20 is transported by the registration roller 30, the assist transport roller pair 330, and the post-fixing transport roller 55, and passes through the document transport path L3.

  As a result, the document is conveyed while being separated from the transfer roller 44, the pressure roller 53, the transfer nip 46, and the fixing nip 56, so that it is possible to prevent the document from being damaged by dirt or heat. Further, the distance between the nip between the registration roller 30 and the assist conveyance roller pair 330 and the distance between the nip between the assist conveyance roller pair 330 and the post-fixing conveyance roller 55 are based on the length in the conveyance direction of the document that can be conveyed by the color multifunction peripheral 1. Is also set short. By arranging the assist conveyance roller pair 330 between the registration roller 30 and the post-fixing conveyance roller 55, it is possible to convey even a small-size document, and to deal with various document sizes. It should be noted that a plurality of assist conveyance roller pairs may be arranged to cope with various document sizes.

  Note that the first to third embodiments described above can be used in combination. Further, although the description has been made using the roller as the fixing unit (specifically, the heating roller and the pressure roller), a belt body may be used. Further, the heating source of the heating roller may use IH (induction heating) or a planar heating element, and the transfer means is not limited to the roller, and a belt body may be used.

1: color multifunction peripheral (image forming apparatus), 11: stacking plate (stacking means), 20: transport path (common transport path), 40: intermediate transfer belt (image carrier), 41: transfer means, 44: transfer roller (Transfer rotor, movable rotor), 46: transfer nip, 50: fixing means, 53: pressure roller (fixing rotor pair, movable rotor), 54: heating roller (fixing rotor pair, movable rotor) 56: fixing nip, 90, 96, 97, 98: image forming means, 230U, 230D: contact image sensor (CIS, reading means), 302: secondary transfer detaching motor (movable rotating body moving means), 303: fixing Desorption motor (movable rotating body moving means), 310: cam (movable rotating body moving means), 551: CPU (control means), S: seat

Claims (12)

Stacking means for stacking a sheet on which a document or toner image is transferred;
A reading unit that is arranged downstream of the stacking unit in the conveying direction and reads an image of a document;
An image forming means for forming a toner image on the image carrier;
A transfer means having a transfer rotating body and transferring the toner image of the image carrier to a sheet by a transfer nip;
Fixing means for heating and fixing a toner image on a sheet by a fixing nip formed by a pair of fixing rotating bodies;
A conveyance path formed so that a sheet on which a document to be conveyed or a toner image is transferred passes through the reading unit, the transfer unit, and the fixing unit;
At least one of the transfer rotator and the fixing rotator pair is a movable movable rotator, and the movable rotator is moved from the transfer nip or the fixing nip and from the transfer nip or the fixing nip. A movable rotating body moving means for moving to a distant position;
Control means for controlling the movable rotating body moving means so as to separate the movable rotating body from the transfer nip or the fixing nip when it is determined that the document is conveyed to the conveying path.
An image forming apparatus. The movable rotating body is one rotating body of the fixing rotating body pair.
The image forming apparatus according to claim 1. The movable rotating body is the transfer rotating body.
The image forming apparatus according to claim 1. The movable rotating body is one rotating body of the fixing rotating body pair and the transfer rotating body,
The image forming apparatus according to claim 1. A placement means for placing a discharged document or a sheet onto which a toner image is transferred downstream in the conveying direction of the fixing means;
The image forming apparatus according to claim 1. A first conveyance roller pair disposed upstream of the transfer unit and a second conveyance roller pair disposed downstream of the fixing unit in the conveyance direction in the conveyance path;
The transfer nip or the fixing nip formed by the movable rotating body is arranged on one side with respect to a straight line connecting the nip of the first conveying roller pair and the nip of the second conveying roller pair, and the movable rotation In a state where the body is separated from the transfer nip or the fixing nip, the movable rotating body is located on the opposite side of the transfer nip or the fixing nip with respect to the straight line.
The image forming apparatus according to claim 1. A guide member that moves in the same direction as the movable rotating body in conjunction with the movement of the movable rotating body to a position away from the transfer nip or the fixing nip;
The guide member guides an original so as to be separated from the movable rotating body, the transfer nip, or the fixing nip in a state where the movable rotating body is separated from the transfer nip or the fixing nip.
The image forming apparatus according to claim 1. In conjunction with the movement of the movable rotator to a position away from the transfer nip or the fixing nip, they abut each other, and in conjunction with the movable rotator forming the transfer nip or the fixing nip, Provided with an assist conveyance roller pair separated from each other,
The assist conveyance roller pair conveys the document while being separated from the movable rotator, the transfer nip, or the fixing nip in a state where the movable rotator is separated from the transfer nip or the fixing nip.
The image forming apparatus according to claim 1. The control unit stops the operations of the image forming unit, the transfer unit, and the fixing unit when it is determined that the document is conveyed to the conveyance path.
The image forming apparatus according to claim 1. The fixing rotator pair includes a heating rotator and a pressure rotator,
The pressure rotator is the movable rotator,
When the control unit determines that the document is transported to the transport path, the control unit controls the surface temperature of the heating rotator to be in the same state as when the sheet onto which the toner image is transferred is transported. To
The image forming apparatus according to claim 2 or 4. A switching unit capable of switching between a document transport mode for transporting a document from the stacking unit to the transport path and a sheet transport mode for transporting a sheet on which a toner image is transferred from the stacking unit to the transport path;
The control unit stops the operations of the image forming unit, the transfer unit, and the fixing unit when the reading unit detects an image in the sheet conveyance mode.
The image forming apparatus according to claim 1. The switching means is disposed in the vicinity of the loading means;
The image forming apparatus according to claim 11.

Images