JP2006089180A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely cope with both of upward curl and downward curl in response to condition of paper sheets. <P>SOLUTION: A paper sheet carrying destination selector member 40 provided with a selector plate 42 capable of changing posture between a downward curl position S1 and an upward curl position S2 is provided just downstream of a nip part 24 between a fixing roller 22 and pressurizing roller 23. A carrying roller 51, an upper nip roller 52 and a lower nip roller 53 are provided downstream of the paper sheet carrying destination selector member 40, and the carrying roller 51 is structured possible to select rotating direction thereof for discharging paper sheets P in response to setting position of the selector plate 42. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile apparatus, and a printer, which includes a fixing device that performs a fixing process on a transfer image on a sheet.

  Conventionally, an image forming apparatus including a fixing device as described in Patent Document 1 is known. This fixing device performs a fixing process by heating a transfer image on a sheet onto which a toner image on the peripheral surface of a photosensitive drum is transferred in an image forming unit. The fixing roller includes an energizing heating element, and the fixing roller. A pressure roller having a peripheral surface directly in contact with the roller, and a sheet from the image forming unit is passed between the rollers so that the fixing process of the transferred image is performed. It has become.

  By the way, when the sheet is, for example, a sheet for an overhead projector (OHP sheet), the conveyance speed is set slower than that for a normal sheet, so that the time for which the sheet contacts the fixing roller is longer than usual. As a result, the melted state of the toner on the OHP sheet becomes remarkable, and a hot offset state occurs due to the welding of the toner to the fixing roller, thereby deteriorating the image state. In order to avoid this, when the OHP sheet after fixing is separated from the fixing roller earlier by another roller pair, the curl of the added roller is increased due to the curvature of the added roller.

In order to eliminate such inconvenience, in the fixing device described in Patent Document 1, a pair of conveyance rollers configured to be able to change the vertical position is provided at a position immediately downstream of the nip portion between both rollers, particularly for an OHP sheet. As described above, the conveying roller pair is moved slightly above the sheet carrying-out direction from the nip portion (in a direction away from the fixing roller earlier). In this way, hot offset caused by the toner on the sheet being welded to the fixing roller can be prevented. On the other sheet, the conveyance roller pair is not moved, and the lower curl of the sheet is eliminated.
JP 2003-162167 A

  However, the paper does not always bend downward at the nip portion depending on the type and transfer situation, and a concave so-called upper curl may be formed on the upper side. Addressing the upper curl is not listed as a solution.

  Moreover, although the thing of patent document 1 needs to move the conveyance roller pair which needs drive rotation, the structure for doing this becomes very complicated, and only the number of parts increases and apparatus cost increases. However, it is difficult to install the transport roller pair moving structure in a narrow space in the image forming apparatus, and there is a disadvantage that it is impossible to meet the demand for downsizing of the image forming apparatus.

  The present invention has been made in view of such a situation, and provides an image forming apparatus including a fixing device that can reliably cope with both an upper curl and a lower curl according to the state of a sheet. It is aimed.

  According to a first aspect of the present invention, there is provided a fixing roller that applies a fixing process by heating to a transfer image transferred to a sheet by an image forming unit, and a pressure roller that is disposed to face the fixing roller. In an image forming apparatus having a fixing device in which a nip portion for nipping a sheet is formed at a contact position between the surface and the peripheral surface of the pressure roller, the image is discharged from the nip portion immediately downstream of the nip portion. A paper transport destination switching member is provided that is changeable between a first guiding attitude for guiding the transported paper sheet to the fixing roller side and a second guiding attitude for guiding the pressure roller side, On the downstream side of the destination switching member, a conveyance roller that is rotatable about an axis extending in the sheet width direction orthogonal to the sheet conveyance direction and that has a circumferential surface facing the sheet conveyance destination switching member. And the peripheral surface of the conveying roller First, the sheet guided by the sheet transport destination switching member arranged in parallel so as to come into contact with the fixing roller side of the surface and set in the first guide attitude is nipped by the transport roller and discharged. The nip roller and the paper guided by the paper transport destination switching member arranged in parallel so that the peripheral surface is in contact with the pressure roller side of the peripheral surface of the transport roller and set in the second guide posture, A second nip roller that nips and discharges with the transport roller is provided, and the transport roller is configured to be able to switch the rotation direction so as to discharge the paper according to the set posture of the paper transport destination switching member. It is characterized by this.

  In the present invention, there is no particular limitation on the positional relationship between the fixing roller and the pressure roller, and either may be provided on the upper side or any may be provided on the right side. In the following description of the operation, the case where the fixing roller is provided on the upper side of the pressure roller is described in order to simplify the description.

  According to the first aspect of the present invention, the sheet transport destination switching member is set in the first posture for the sheet that has been subjected to the fixing process and discharged from the nip portion formed between the fixing roller and the pressure roller. In this state, the paper is transported toward the first nip roller guided by the paper transport destination switching member, and is discharged between the first nip roller and the transport roller while rotating between them. In a state where the switching member is set to the second attitude, the sheet is conveyed toward the second nip roller guided by the sheet conveyance destination switching member, and the both are rotated while being sandwiched between the second nip roller and the conveying roller. Is discharged outside the system.

  If the paper is normal copy paper, the fixing-treated paper discharged from the nip portion of the fixing device has a higher temperature on the front side of the paper because the fixing roller is hotter than the pressure roller. Although the expansion amount is larger than the thermal expansion amount on the back surface side, the so-called lower curl where the front and rear ends of the sheet are concave downward is likely to occur, but the sheet transport destination switching member is set to the first posture. Accordingly, the sheet discharged from the nip portion of the fixing device is discharged to the first nip roller side, which is a direction around the fixing roller, so that the lower curl is corrected by the winding operation of the sheet.

  On the other hand, if the paper is thin, or if it is ordinary copy paper and printed on both sides, the amount of heat supplied from the fixing roller to the paper will be excessive, and The toner is excessively melted, and the excessively melted toner adheres to the peripheral surface of the fixing roller and wraps around the fixing roller, so that an upper curl is likely to be formed on the paper. By setting the paper transport destination switching member to the second posture, the paper discharged from the nip portion of the fixing device is discharged to the second nip roller side, which is a direction around the pressure roller. This curling action corrects the top curl.

  In this way, by changing the posture of the paper transport destination switching member in accordance with the type of paper and the transfer status, fixing is performed by switching the paper transport destination after the fixing process between the first nip roller side and the second nip roller side. Curling of the paper discharged from the apparatus is suppressed.

  According to a second aspect of the present invention, in the first aspect of the present invention, there is provided control means for outputting a control signal for changing the posture to the paper transport destination switching member in accordance with the status of the paper on which the fixing process is performed. It is characterized by that.

  According to such a configuration, the type of paper (for example, whether the paper is a normal copy paper or a paper thinner than usual) subjected to a transfer process in advance on the control unit, and the transfer status (for example, In this case, it is possible to input or detect whether the paper is one-sided or double-sided printed, so that the control means according to the type of the paper and the transfer situation. It is possible to output a control signal for changing the posture of the paper transport destination switching member from the paper transport destination switching member to the paper transport destination switching member. Curling is automatically corrected.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the rotation speed of the conveyance roller is set according to a set posture of the sheet conveyance destination switching member. It is.

  According to such a configuration, by appropriately setting the rotation speed of the conveyance roller according to the set posture of the sheet conveyance destination switching member, while slipping the sheet with the conveyance roller according to the type of sheet and the transfer situation It can be pulled from the nip portion of the fixing device, and this adjusts the degree of adhesion of the paper to the fixing roller or pressure roller (that is, the pressing force of the paper to the fixing roller or pressure roller). Thus, the paper is subjected to an appropriate curl correction treatment according to the type and transfer status.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the conveying roller is a driving roller to which a driving force of a driving motor is transmitted via a gear mechanism. The second nip roller is a driven roller that is driven by the rotation of the conveying roller.

  According to this configuration, the first and second nip rollers are driven by the driving rotation of the conveying roller via the gear mechanism driven by the driving motor, thereby fixing the fixing device regardless of the set posture of the sheet conveying destination switching member. The paper discharged from the nip portion of the paper can be discharged while being sandwiched between the transport roller and the first or second roller, and when driving the nip roller side (in this case, for the first nip roller and the second nip roller) And two drive motors are required), the number of parts is reduced.

  According to the first aspect of the present invention, the sheet transport destination after the fixing process is changed between the first nip roller side and the second nip roller side by changing the posture of the sheet transport destination switching member according to the type of sheet and the transfer situation. By switching at, occurrence of curling of the paper discharged from the fixing device can be effectively suppressed.

  According to the second aspect of the present invention, the control unit can input and detect the type of paper to be subjected to the transfer process and the transfer status in advance, so that the type of the paper and the transfer status can be detected. Thus, it is possible to output a control signal for changing the posture of the paper transport destination switching member from the control means to the paper transport destination switching member. Curling in the fixing device can be automatically corrected.

  According to the invention of claim 3, by appropriately setting the rotation speed of the conveyance roller in accordance with the set posture of the sheet conveyance destination switching member, the sheet is referred to as the conveyance roller according to the type of sheet and the transfer situation. It can be pulled from the nip part of the fixing device while slipping, and by adjusting the degree of adhesion of the paper to the fixing roller or the pressure roller, this can be done according to the type of paper and the transfer situation. It is possible to properly correct the curling of the paper.

  According to the fourth aspect of the present invention, the first and second nip rollers are driven by the driving rotation of the conveying roller via the gear mechanism driven by the driving motor, and thereby the sheet conveying destination switching member is set in a set posture. The paper discharged from the nip part of the fixing device can be discharged while being sandwiched between the transport roller and the first or second roller, and the number of parts can be reduced compared to driving the nip roller side. And it can contribute to the reduction of manufacturing cost.

  First, an outline of the internal structure of a copying machine (image forming apparatus) 10 to which a paper transport destination switching mechanism according to the present invention is applied will be described with reference to FIG. FIG. 1 is a schematic explanatory view in cross-section showing an embodiment of the internal structure of a copying machine 10 according to the present invention. As shown in this figure, the copying machine 10 is provided with a document reading section 12 for reading a document image on the upper part of a box-shaped copying machine main body 11, and from the document reading section 12 in the copying machine main body 11. An image forming unit 13 that forms an image based on image information of a document read by the document reading unit 12 at a lower position, and a fixing unit that performs a fixing process on the image formed by the image forming unit 13 and transferred to a sheet. 14 and a paper storage unit 15 for storing a transfer paper.

  The document reading unit 12 includes a document presser 121 provided on the upper surface of the copier body 11 so as to be openable and closable, and an optical system unit 122 disposed in the copier body 11 so as to face the document presser 121 via a contact glass 123. It is configured with. The contact glass 123 includes a placed document contact glass 123a having a slightly smaller planar shape than the document presser 121 for reading the document surface of the placed document, and a front-rear direction for reading the document surface of the automatically fed document. Is provided with a long and thin contact glass 123b for automatic paper feeding.

  On the upper surface of the copying machine main body 11 on the front side (front side of the paper surface of FIG. 1) of the document reading unit 12, an operation panel 124 is provided for inputting processing conditions relating to document reading and copying processing. The operation panel 124 is disposed on the upper surface of the front portion of the processing copier main body 11, and is provided with a display panel, a numeric keypad, a start button, a mode switching key, and the like (not shown). The display panel displays various types of input information and output information on a liquid crystal display, or inputs information selected from the displayed processing conditions by a touch-in operation. The numeric keypad is mainly for setting quantity information such as the number of copies. The mode switching key is for switching the mode of the copying machine 10, and the copying machine 10 can be used as a facsimile machine or a printer by pressing the mode switching key. Yes.

  The document presser 121 is attached to the copying machine main body 11 so as to be opened and closed by rotating forward and backward about a predetermined axis provided on one side of the upper surface of the apparatus main body. The document presser 121 has a two-stage structure, and includes a document tray 125 for placing a document provided at the upper level, and a document discharge tray 126 for discharging a scanned image document provided at the lower level. And have. A document feeding portion 127 interposed between the document tray 125 and the document discharge tray 126 is formed on the left side of the document retainer 121, and an unillustrated document feeding mechanism provided in the document feeding portion 127 is used. One document at a time is picked up from a bundle of sheets placed on the document tray 125 and supplied to the automatic feeding contact glass 123b. The picked-up document is read by the optical system unit 122 through the automatic paper feeding contact glass 123b while being moved. The original after the original image is read is discharged to the original discharge tray 126.

  The optical system unit 122 includes a light source (not shown), a plurality of mirrors, a lens unit, and a CCD (charge coupled device). Then, light from the light source is reflected on the surface of the original, and this reflected light is input to the CCD as an upper part of the original via these mirror and lens unit. The document information as an analog amount input to the CCD is converted into a digital signal and stored in a predetermined storage device as digital document information.

  The image forming unit 13 forms a toner image on the paper fed from the paper storage unit 15. In this embodiment, the image forming unit 13 sequentially arranges the image from the upstream side (the right side of the paper surface in FIG. 1) to the downstream side. A yellow unit 13Y, a magenta unit 13M, a cyan unit 13C, and a black unit 13K are provided.

  Each unit 13Y, 13M, 13C, 13K is provided with a photosensitive drum 131 and a developing device 132, respectively. Each photoconductive drum 131 is supplied with toner from a corresponding developing device 132 while rotating clockwise in FIG.

  A charging unit 133 is provided at a position on the upper left side in FIG. 1 of each photoconductor drum 131, and an exposure unit 134 is provided at a position on the upper right side in FIG. Each photosensitive drum 131 is uniformly charged at its peripheral surface by the charging unit 133, and a laser beam based on image data input from the document reading unit 12 is charged from each exposure unit 134. By irradiating the peripheral surface of 131, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 131. By supplying toner from the developing device 132 to the electrostatic latent image, a toner image is formed on the peripheral surface of the photosensitive drum 131.

  Further, a cleaning device 135 for removing and cleaning residual toner on the peripheral surface of the photosensitive drum 131 is provided at the lower left position in FIG. 1 of each photosensitive drum 131. The peripheral surface of the photosensitive drum 131 cleaned by the cleaning device 135 goes to the charging unit 133 for a new charging process.

  Below each photoconductor drum 131, a transport belt 136 is provided so that the transport surface faces each photoconductor drum 131. The conveyor belt 136 is wound around a driving roller provided slightly downstream of the black unit 13K and a driven roller provided slightly upstream of the yellow unit 13Y, and circulates by driving rotation of the driving roller. It is supposed to be. The paper supplied from the paper storage unit 15 is guided by the circumference of the transport belt 136 and moves while abutting on the peripheral surface of the photosensitive drum 131 to be subjected to a transfer process.

  The fixing unit 14 performs fixing processing on the toner image on the paper transferred by the image forming unit 13 and discharges the toner image. The fixing device 20 performs fixing processing on the toner image, and the toner image fixing processing. And a paper transport destination switching mechanism 30 for discharging the paper subjected to the above.

  The fixing device 20 includes a fixing roller 22 provided with an energizing heating element serving as a heating source in a fixing device main body 21 disposed vertically opposite thereto, and a pressure roller 23 disposed below the fixing roller 22 facing the fixing roller 22. Is formed by interior decoration. Then, the transfer-processed paper derived from the image forming unit 13 by the rotation of the conveying belt 136 is pressed and nipped while being heated by the fixing roller 22 at the nip portion 24 between the fixing roller 22 and the pressure roller 23. The toner image is fixed by the heat treatment according to the above, and a stable color image after the fixing process is formed on the paper. The sheet with the color image that has been subjected to the fixing process passes through a sheet discharge conveyance path 102 formed on the downstream side of the sheet conveyance destination switching mechanism 30 and is discharged from the left side wall in FIG. It is discharged toward the tray 101.

  The paper transport destination switching mechanism 30 includes a later-described paper transport destination switching member 40 provided on the downstream side of the fixing device 20 and a curl correction roller mechanism provided further on the downstream side of the paper transport destination switching member 40. 50. The paper transport destination switching member 40 determines the type of the paper P (whether it is a normal copy paper or a thin paper) and the status of the transfer process for the paper P (whether it is single-sided printing or double-sided printing). According to the other, the conveyance direction can be switched between the diagonally upper side and the diagonally lower side toward the downstream side.

  The curl correction roller mechanism 50 corrects curl formed during the fixing process on the paper P discharged in the direction set by the paper transport destination switching member 40. The paper P can correct the curl by a pulling action when it passes through the curl correction roller mechanism 50.

  The paper storage unit 15 has a plurality of paper trays 151 that are detachably attached to the copying machine main body 11. Each sheet tray 151 stores a sheet bundle. Then, the paper P is fed out from the paper bundle of the selected paper tray 151 one by one by driving the pickup roller 152, and introduced into the image forming unit 13 through the paper feeding / conveying path 153.

  In the copying machine 10 of the present embodiment, a sheet reversing unit 16 for performing double-sided printing on the sheet P is provided in the copying machine main body 11. The sheet reversing unit 16 is provided between the image forming unit 13 and the sheet storage unit 15 and supports a sheet P having a fixed image on one side and a curling correction roller mechanism 50. A switching guide 162 that is provided at a position immediately downstream and distributes the paper P to one of the paper discharge conveyance path 102 and the return conveyance path 103 with respect to the paper P after the fixing process, and the paper P supported by the support plate 161. On the other hand, a reversing roller pair 163 that continues the clamping state is provided.

  The paper P supported by the support plate 161 while being held between the return conveyance path 103 and the reverse roller pair 163 by the switching operation of the switching guide 162 is discharged from the rear end side by the reverse rotation of the reverse roller pair 163. The sheet is directed to the paper feed conveyance path 153 through the reverse conveyance path 104. The paper P that has been turned upside down and supplied to the paper feed conveyance path 153 is supplied again to the image forming unit 13, whereby the back side is subjected to a transfer process.

  2 and 3 are perspective views showing an embodiment of the paper transport destination switching mechanism 30. FIG. 2 is a view in which the switching plate 42 of the paper transport destination switching member 40 is in the first lowered posture (first guide posture). FIG. 3 shows the state in which the switching plate 42 has been set to the forward-facing posture (second guiding posture). As shown in FIGS. 2 and 3, the paper transport destination switching mechanism 30 applies the fixing-processed paper P discharged from the nip portion 24 that is a contact position between the fixing roller 22 and the pressure roller 23 of the fixing device 20. A curl correction process is performed on the paper P. The paper transport destination switching member 40 that switches the transport destination according to the type and situation of the paper P, and the paper P for which the transport destination is set by the paper transport destination switching member 40. And a curl correction roller mechanism 50 that performs a curl correction treatment.

  The sheet transport destination switching member 40 is disposed between the nip portion 24 of the fixing device 20 and the curl correction roller mechanism 50 and is disposed on the upstream side of the curl correction roller mechanism 50 and is long in the sheet width direction. And a switching plate 42 rotatably provided at the upstream end of the support plate 41. The support plate 41 is fixed to a predetermined frame in the copying machine main body 11, whereby the relative positional relationship between the nip portion 24 of the fixing device 20 and the curl correction roller mechanism 50 is determined.

  The support plate 41 has an isosceles triangle shape when viewed from the front, the bottom portion of the support plate 41 is opposed to the curl correction roller mechanism 50, and an upper inclined surface 411 inclined upward toward the downstream side on the upper surface side. A lower inclined surface 412 that is inclined downward toward the downstream side is formed on the lower surface side. In addition, a pair of bracket portions 413 projecting toward the upstream side are provided at both ends between the upstream sides of the support plate 41, and are long in the paper width direction for mounting the switching plate 42 between the bracket portions 413. A long mounting recess 414 is formed.

  The switching plate 42 is dimensioned so that its length is slightly shorter than the inner dimension between the pair of bracket portions 413 of the support plate 41, whereby the longitudinal direction is oriented in the paper width direction perpendicular to the paper transport direction. Thus, it can be fitted into the mounting recess 414 between the pair of bracket portions 413. Then, the switching plate 42 is fixed to the cylindrical shaft 43 that penetrates the bracket portion 413 so as to be rotatable around the axis center in a state where the downstream end portion of the switching plate 42 is fitted in the mounting recess 414. By rotating integrally around the cylindrical shaft 43, the tip end has a tip-down posture (first guide posture) S1 and the tip has a tip-up posture (second guide). Posture) The posture can be changed with S2.

  Therefore, the sheet P discharged from the pressure roller 23 of the fixing device 20 is guided to the upper surface of the switching plate 42 in a state where the switching plate 42 is set to the first descending posture S1, and the upper inclined surface of the support plate 41. On the other hand, the switching plate 42 heads toward the lower inclined surface 412 of the support plate 41 in a state in which the switching plate 42 is set in the forwardly rising posture S2.

  In the present embodiment, an upper guide plate 44 facing the upper inclined surface 411 is disposed above the support plate 41, and a lower guide facing the lower inclined surface 412 below the support plate 41. A sheet P is provided, and the sheet P discharged from the nip portion 24 of the fixing device 20 is guided to the guide plates 44 and 45 so as to be surely directed to the transport roller 51.

  The curl correction roller mechanism 50 includes a transport roller 51 provided on the downstream side of the support plate 41, an upper nip roller (first nip roller) 52 disposed above the transport roller 51 and opposed to the transport roller 51, and transport. A lower nip roller (second nip roller) 53 disposed opposite to the conveying roller 51 is provided below the roller 51.

  The conveying roller 51 is set to have a diameter substantially larger than the thickness dimension of the support plate 41 (approximately 3 to 5 times in the present embodiment), and the peripheral surface thereof faces the downstream surface of the support plate 41. It is arranged in parallel with the support plate 41 and is supported so as to be concentrically and integrally rotatable around a conveyance roller shaft 511 installed between frames (not shown) of the copying machine main body 11.

  The upper nip roller 52 is disposed at a position slightly upstream from the position immediately above the transport roller 51 so that the peripheral surface thereof is in contact with the peripheral surface of the transport roller 51. It is supported so that it can rotate integrally and concentrically around the installed upper roller shaft 521. The lower nip roller 53 is disposed at a position slightly upstream of the position immediately below the transport roller 51 so that the peripheral surface thereof is in contact with the peripheral surface of the transport roller 51. The lower roller shaft 531 laid between them is supported so as to be concentric and integrally rotatable.

  Accordingly, the paper P discharged from the fixing device 20 is guided to the upper surface of the switching plate 42 in a state where the switching plate 42 is set to the first lowering posture S1, and is conveyed through the upper inclined surface 411 of the support plate 41. After the paper is fed between the upper nip roller 52 and the upper nip roller 52, the discharge is continued while being driven by the driving rotation of the transport roller 51 and the driven rotation of the upper nip roller 52, while the switching plate 42 is set to the forward posture S 2. In this state, the sheet is guided to the lower surface of the switching plate 42 and fed between the conveying roller 51 and the lower nip roller 53 via the lower inclined surface 412 of the support plate 41, and then the driving rotation of the conveying roller 51 and the lower nip roller The discharge is continued by being guided by the driven rotation of 53.

  In the present embodiment, the transport roller 51 is made of heat-resistant CR rubber (chloroprene rubber), EPDM (ethylene propylene diene methylene link), or silicon rubber. Further, as the upper and lower nip rollers 52 and 53, those made of POM (polyoxyethylene), PET (polyethylene terephthalate) or PBT (polybutylene phthalate) are employed.

  The reason why such a substance is used as the material of the conveying roller 51 and the upper nip roller 52 is that, as a result of various tests, the substance has a property that it can perform an appropriate compression elastic deformation, This is because it has been found that the material has an appropriate slip property.

  Hereinafter, the gear mechanism 70 that transmits the driving force of the driving motor 60 to the curl correction roller mechanism 50 will be described with reference to FIGS. 4 and 5. 4 and 5 are partially enlarged perspective views of FIG. 2 for explaining an embodiment of the gear mechanism 70, and FIG. 4 corresponds to the fact that the switching plate 42 is set to the first lowered posture S1. FIG. 5 shows a state in which the transport roller 51 is rotating in the clockwise direction when the switching plate 42 is switched to the forward-up posture S2. . 6 is a front view of the gear mechanism 70 shown in FIGS. 4 and 5. FIG. 6A is a diagram corresponding to FIG. 4, and FIG. 6B is a diagram corresponding to FIG. 5.

  As shown in these drawings, the gear mechanism 70 includes a drive gear 71 concentrically and integrally fixed to the drive shaft 61 of the drive motor 60, and a planet that revolves around the drive gear 71 while meshing with the drive gear 71. A gear 72, a transport roller gear 73 concentrically and integrally fixed to the transport roller shaft 511 of the transport roller 51, an upper idle gear group 74 that meshes with the planetary gear 72 at the top, and a mesh with the transport roller gear 73 at the bottom. The lower idle gear group 75 and the driving force transmission path of the drive motor 60 to the transport roller gear 73 between the path passing through the upper idle gear group 74 and the path passing through the lower idle gear group 75 via the planetary gear 72. And a sheet transport destination switching member 76 that is switched at the same time.

  The drive motor 60 is disposed horizontally so that the drive shaft 61 penetrates the tube shaft 43, so that the tube shaft 43 can be rotated concentrically with the tube shaft 43. The drive gear 71 is provided at a position where the center position is on a horizontal line including the center of the transport roller gear 73 and is spaced a considerable distance from the transport roller gear 73 toward the upstream side (right side in FIG. 5).

  The upper idle gear group 74 is provided at a position above a straight line connecting the axis of the transport roller shaft 511 and the axis of the drive shaft 61, and the first upper idle gear 741 and the first upper idle gear from the upstream side. A second upper idle gear 742 that meshes with 741, and a third upper idle gear 743 that meshes with both the second upper idle gear 742 and the transport roller gear 73.

  The lower idle gear group 75 is provided at a position below a straight line connecting the axis of the transport roller shaft 511 and the axis of the drive shaft 61, and the first lower idle gear 751 and the first lower idle gear from the upstream side. 751 and a second upper idle gear 752 that meshes with both the transport roller gear 73.

  The planetary gear 72 meshes with the first upper idle gear 741 in a state where the planetary gear 72 is positioned at the upper position by the switching operation of the paper transport destination switching member 76, while the lower position is lowered by the switching operation of the paper transport destination switching member 76. The installation position is set so as to mesh with the first lower idle gear 751 in the state where the position is set.

  The sheet transport destination switching member 76 is integrally rotated around the cylinder axis 43 by the actuator 761 having a solenoid, the operation rod 762 projecting upward and downward from the actuator 761, and the operation rod 762 being moved up and down. And an operation plate 763 to be configured. The upper end of the operation rod 762 is provided with a columnar connecting piece 764 protruding toward the operating plate 763, while the operating plate 763 is penetrated by the connecting piece 764. A long hole 765 extending in the longitudinal direction of the plate 763 is formed.

  Therefore, when the connecting piece 764 is fitted in the elongated hole 765, the operation rod 762 is lowered by driving the actuator 761 (specifically, the solenoid 76 in the actuator 761 is cut off from being energized). When the operation rod 762 is lowered by the urging force of the urging means), the operation plate 763 rotates integrally around the cylinder shaft 43 in the clockwise direction, whereby the switching plate 42 integrated with the cylinder shaft 43 is As shown in FIG. 4 and FIG. 6A, the posture is set to the first descending posture S1, while the operation rod 762 is lifted by driving the actuator 761 (specifically, the solenoid in the actuator 761 is energized). As a result, the operating rod 762 rises against the urging force of the urging means), and the operation plate 763 is moved around the cylinder shaft 43. As a result, the switching plate 42 that is integral with the cylinder shaft 43 is set in the forward-up posture S2 as shown in FIGS. 5 and 6B. Yes.

  In the state in which the switching plate 42 is set to the first descending posture S1, the upper surface of the switching plate 42, the upper inclined surface 411 of the support plate 41, the conveying roller 51, and the upper portion as shown in FIG. While the upper discharge path R1 is formed by the nip portion with the nip roller 52, the switching plate 42 is in the state where the switching plate 42 is set to the forwardly rising posture S2, as shown in FIG. The lower discharge path R <b> 2 is formed by the lower surface, the lower inclined surface 412 of the support plate 41, and the nip portion between the conveying roller 51 and the lower nip roller 53.

  Accordingly, the sheet P discharged from the nip portion 24 by driving the fixing roller 22 and the pressure roller 23 in a state where the switching plate 42 is set to the first descending posture S1 is shown in FIG. 4 and FIG. As shown in FIG. 3, the sheet is discharged through the upper discharge path R1 to the downstream discharge conveyance path 102 (FIG. 1), while the switching plate 42 is discharged from the nip portion 24 in a state of being set in the forwardly rising position S2. The paper P thus discharged is discharged to the paper discharge conveyance path 102 through the lower discharge path R2 as shown in FIGS.

  In the present invention, in the state where the switching plate 42 is set to the first descending posture S1 (that is, the state where the entrance-side transport path R1 is selected), the peripheral speed of the transport roller 51 is the peripheral speed of the fixing roller 22. It is set to be 2.0% to 4.0% (3% in the present embodiment) faster. Incidentally, the nip force between the conveying roller 51 and the upper nip roller 52 is set slightly weaker than the nip force between the fixing roller 22 and the pressure roller 23.

  Therefore, after the paper P reaches the nip portion between the transport roller 51 and the upper nip roller 52, the transport roller 51 and the upper nip roller 52 are pulled with respect to the paper P while the paper P is pulled upstream. Therefore, the sheet P is wound around the peripheral surface of the fixing roller 22 with a predetermined pressing force as compared with the case where the sheet P advances straight from the nip portion 24 of the fixing device 20. The upper curl state will be corrected.

  Incidentally, the difference in peripheral speed between the upper nip roller 52 and the lower nip roller 53 is realized by making the gear ratio of each gear of the upper idle gear group 74 different from the gear ratio of each gear of the lower idle gear group 75. be able to.

  FIG. 7 shows a mechanism for correcting the curl of the paper P. FIG. 7 is an enlarged explanatory view showing a state in which the paper P passes through the nip portion 24 between the fixing roller 22 and the pressure roller 23. Normally, the nip portion 24 between the fixing roller 22 and the pressure roller 23 is formed by compressing and elastically deforming the peripheral surface of the pressure roller 23 so that the peripheral surfaces of the fixing roller 22 and the pressure roller 23 have points N1 and N2. There is a surface contact between them. Therefore, as shown by a one-dot chain line in FIG. 7, when the paper P is directed downstream in the same conveyance direction as the upstream side (right side in FIG. 7) of the nip portion 24 (comparative example), the paper P Is limited to a very narrow range between point N1 and point N2, whereas in the present invention, the switching plate 42 is set in the first descending posture S1 (ie, the upper discharge path R1 is selected). (FIG. 4)), the sheet P is wound from the point N1 over the point N2 to the point N3, so that the lower curl of the sheet P is corrected.

  Incidentally, the switching plate 42 is set to the first descending posture S1 when a normal copy paper that tends to cause a lower curl is adopted as the paper P.

  On the other hand, the paper P is a thin paper or a normal copy paper, but the paper P discharged from the fixing device 20 after the fixing process is performed on the back side of the double-sided copy immediately after the transfer process is performed. In this case, the switching plate 42 is set in the forward posture S2 (that is, the lower discharge path R2 is selected (FIG. 5)). At this time, the peripheral speed of the conveying roller 51 is set to the fixing roller 22. The peripheral speed is set to be 0.5% to 2.0% (1% in the present embodiment) faster than the peripheral speed of the sheet. The route R1 is made smaller than when the route R1 is selected.

  The reason for this is that when a thin paper or the like that is likely to cause an upper curl is adopted as the paper P, the upper curl is not as significant as the lower curl, and the paper P is placed in the lower discharge path R2. This is because it is only necessary to recognize the degree to which the bending formed before reaching the conveyance roller 51 is removed, and therefore it is not necessary to increase the slip amount.

  In the copying machine 10 according to the present invention having the sheet transport destination switching member 40, the curl correction roller mechanism 50, and the gear mechanism 70 configured as described above, a control device (control means) for controlling the change in the posture of the switching plate 42. ) 80 is provided. FIG. 8 is a block diagram illustrating an embodiment of the control device 80. As shown in this figure, the control device 80 includes a posture setting determining unit 81 that determines the posture setting of the switching plate 42, and a control signal that outputs a control signal to the actuator 761 based on the determination result to the posture setting determining unit 81. And an output unit 82.

  On the other hand, on the operation panel 124 (FIG. 1), a duplex printing button 83 that is pressed when duplex printing is performed, and a thin paper use button 84 that is pressed when thin paper P is used (these duplex printing are performed). The button 83 and the thin paper use button 84 are provided with a concept including a touch switch on a display screen using, for example, an LCD (liquid crystal display).

  The orientation setting determination unit 81 determines that the paper P to be used is a normal copy paper unless the double-sided printing button 83 and the thin paper use button 84 are pressed, and a control signal output unit 82 receives a command signal indicating that. It is designed to output towards the. Upon receiving this command signal, the control signal output unit 82 outputs a control signal that causes the actuator 761 to perform an operation such that the switching plate 42 is in the first lowering posture S1, and when the operation rod 762 is lowered by this, the switching plate 42 is moved. 42 is in a state in which the forward-falling posture S1 is maintained ((A) in FIGS. 4 and 6).

  On the other hand, when the double-sided printing button 83 is pressed, the posture setting determination unit 81 moves up the switching plate 42 with respect to the actuator 761 in anticipation of the timing at which the back side transfer process is performed on the paper P. A control signal for changing the posture to the posture S2 is output. Then, the actuator 761 to which this control signal is inputted drives the operation plate 763 to be raised, so that the switching plate 42 changes its posture from the first lowered posture S1 to the first raised posture S2 (FIGS. 5 and 5). 6 (B)), the sheet P discharged from the nip portion 24 of the fixing device 20 is discharged to the discharge conveyance path 102 through the lower discharge path R2.

  When the thin paper use button 84 is pressed, the posture setting determination unit 81 determines whether the paper used for the control signal output unit 82 is thin regardless of single-sided printing or double-sided printing. A command signal indicating that it is a signal is output. Upon receiving this command signal, the control signal output unit 82 immediately outputs a control signal for raising the operating rod 762 toward the actuator 761, so that the switching plate 42 changes its posture to the forwardly raised posture S 2 by the raising of the operating rod 762. As a result, the thin paper P is discharged to the paper discharge transport path 102 through the lower discharge path R2.

  Next, another embodiment of a copying machine to which a paper reversing part structure suitable for correcting the curl of the paper P is applied will be described with reference to FIG. FIG. 9 is an explanatory diagram for explaining a copying machine 10 ′ to which another embodiment of the paper reversing structure is applied. In this embodiment, a so-called in-body discharge type in which the sheet P is discharged to an in-body discharge tray 105 provided immediately below the document reading section 12 of the copier body 11 is adopted as the copying machine 10 '. Has been.

  On the other hand, the paper transport destination switching mechanism 30 including the paper transport destination switching member 40 provided with the switching plate 42 and the curling correction roller mechanism 50 provided with the transport roller 51 and the upper and lower nip rollers 52 and 53 is described above. The thing similar to the thing of embodiment is employ | adopted.

  As for the sheet reversing unit 16 ′, the previous one (the sheet reversing unit 16 shown in FIG. 1) is provided immediately below the image forming unit 13. It is provided between the inner discharge tray 105. A switchback conveyance path 103 ′ corresponding to the previous return conveyance path 103 is disposed from the nip portion between the conveyance roller 51 and the upper nip roller 52 toward the reverse roller pair 163.

  The paper discharge conveyance path 102 ′ extends from the nip portion between the conveyance roller 51 and the lower nip roller 53 toward the paper discharge tray 101. The return conveyance path 103 ″ for feeding the paper P to the reverse conveyance path 104 by reverse driving of the reverse roller pair 163 extends from the reverse roller pair 163 toward the reverse conveyance path 104 while intersecting the paper discharge conveyance path 102 ′. It is installed.

  Further, an in-cylinder sheet discharge conveyance path 106 that leads the sheet P being conveyed through the switchback conveyance path 103 ′ to the in-cylinder sheet discharge tray 105 is provided to be branched from the return conveyance path 103 ″ and the upper nip roller 52. A switching guide 162 is provided at a position corresponding to the in-body discharge conveyance path 106 at a position where the switchback conveyance path 103 ′ and the return conveyance path 103 ″ are in the upper position. Then, the sheet P led out from the nip portion of the transport roller 51 and the upper nip roller 52 to the switchback transport path 103 ′ by changing the posture of the switching guide 162 is discharged in the cylinder so that the transport destination is directed to the sheet reversing unit 16 ′. Switching between the in-body discharge tray 105 via the conveyance path 106 is possible.

  According to the copying machine 10 ′ configured as described above, when the paper P is for ordinary copying and duplex printing is performed, the paper P is discharged toward the paper transport destination switching mechanism 30 after the fixing processing by the fixing device 20. In the state where the switching plate 42 is set in the first descending posture S1 (FIG. 2) as shown by a solid line, the paper P that has been fed is transported 51 and the upper nip roller 52 as shown by a solid line arrow (a). The paper is fed toward the nip. When the switching guide 162 opens the switchback conveyance path 103 ′ side as shown by a solid line (that is, when the paper P is directed toward the support plate 161 for double-sided printing), the paper P As shown by the solid line arrow (b), it passes through the switchback conveying path 103 ′ and is supported by the support plate 161 while being sandwiched between the pair of reverse rollers 163 (solid line arrow (c)).

  The paper P supported by the support plate 161 is reversely driven by the reverse roller pair 163, passes through the return conveyance path 103 ″, and passes through the reverse conveyance path 104 to the image forming unit 13 as indicated by a solid arrow (d). It is retransmitted (solid arrow (e)) and used for the back side transfer process.

  Then, the double-side printed paper P that has been subjected to the transfer process on the back side and has been subjected to the fixing process again by the fixing device 20 is brought into contact with the transport roller 51 by the switching plate 42 set in the forwardly rising position S2 (FIG. 3). The sheet is fed toward the nip portion with the lower nip roller 53, and is discharged onto the discharge tray 101 via the discharge conveyance path 102 'as indicated by a dotted arrow (f).

  In this way, when the paper P is a normal copy paper, the paper P that has been subjected to the transfer process on the front side is subjected to the fixing plate S1 when the fixing plate 20 is subjected to the fixing process at the upstream position S1. The posture is set and a sufficient amount of heat is supplied by being conveyed so as to be wound around the fixing roller 22. Then, as shown in FIG. 7, the sheet is once discharged to the sheet reversing portion 16 'with the lower curl corrected (solid arrow (c)).

  Subsequently, when the transfer process is performed on the back side of the paper P by the image forming unit 13, the paper P has already been warmed up. If the switching plate 42 is passed through the fixing device 20 in the forwardly lowered posture S1, the amount of heat is increased. Excessive curling or hot offset may occur. For this reason, the sheet P on which the transfer processing on the back side has been completed to avoid this is guided through the switching plate 42 set in the forwardly rising position S2 and is discharged via the sheet discharge conveyance path 102 'so as to be separated from the fixing roller 22. The paper is discharged to the paper tray 101 (dotted arrow (f)). By doing so, excessive heat supply can be avoided, and upper curling and hot offset are prevented.

  On the other hand, when the sheet P is a normal copy sheet and only one-side printing is performed, the switching plate 42 is set to the first descending posture S1 as described above with reference to FIG. Since the sheet is conveyed so as to be wound around the fixing roller 22, just a sufficient amount of heat is supplied, so that the switchback conveyance path 103 ′ is closed and the in-body discharge conveyance path 106 side is opened. As indicated by a solid line arrow (g), the paper is discharged to the in-cylinder discharge tray 105 through the in-cylinder discharge conveyance path 106 through the switching guide 162 indicated by the dotted line.

  Further, in double-sided copying, the amount of heat supplied to the paper P by the fixing roller 22 during the fixing process is less than in the case of single-sided copying, and the toner on the transfer surface of the paper P melts and sticks to the peripheral surface of the fixing roller 22. So-called hot offset and upper curl may be made less likely to occur.

  Next, when the paper P is thin and single-sided printing is performed, the amount of heat supplied from the fixing roller 22 in the fixing device 20 becomes excessive due to the thin paper P, and hot offset is likely to occur. For this reason, the switching plate 42 is set to the forward rising posture S2 and passes through the lower nip roller 53 as shown by the dotted arrow (f), and is discharged to the discharge tray 101 via the discharge conveyance path 102 '. . Thereby, hot offset and upper curl can be prevented.

  As described in detail above, the copying machine 10 according to the present invention includes a fixing roller 22 that performs a fixing process by heating the transfer image transferred to the paper P by the image forming unit 13, and a fixing roller 22 that is disposed opposite to the fixing roller 22. The fixing device 20 includes a pressure roller 23 that nips the paper P with the roller 22, and the nip that nips the paper P formed between the fixing roller 22 and the pressure roller 23. Between a forwardly lowered posture S1 that guides the conveyance destination of the paper P discharged from the nip portion 24 to the fixing roller 22 side and a forwardly raised posture S2 that guides it to the pressure roller 23 side immediately downstream of the portion 24. A paper transport destination switching member 40 having a changeable switching plate 42 is provided, and can be rotated about an axis extending in the paper width direction orthogonal to the paper transport direction on the downstream side of the paper transport destination switching member 40. And also around Is arranged in parallel so that the circumferential surface of the conveyance roller 51 is in contact with the fixing roller 22 side of the circumferential surface of the conveyance roller 51, and the first descending posture S1. The upper nip roller 52 that nips and discharges the paper P guided by the paper transport destination switching member 40 with the transport roller 51, and the pressure roller 23 side of the peripheral surface of the transport roller 51. A lower nip roller 53 that nips and discharges the paper P guided by the paper transport destination switching member 40 that is arranged in parallel so as to come into contact with each other and that is set in the forward posture S2 with the transport roller 51 is provided. The transport roller 51 is configured such that the rotation direction can be switched in order to discharge the paper P in accordance with the setting posture of the switching plate 42.

  By configuring the copying machine 10 in this way, the sheet transport destination switching member 40 is used for the first sheet P that has been subjected to the fixing process and is discharged from the nip portion 24 formed between the fixing roller 22 and the pressure roller 23. In the state where the posture is set, the paper is transported toward the upper nip roller 52 guided by the paper transport destination switching member 40, and is sandwiched between the upper nip roller 52 and the transport roller 51 and rotated outside of the system. While the sheet conveyance destination switching member 40 is set to the second posture, the sheet is conveyed toward the lower nip roller 53 guided by the sheet conveyance destination switching member 40, and the lower nip roller 53 And the conveyance roller 51, and are discharged out of the system by both rotations.

  When the paper P is a normal copy paper, the fixing-processed paper P discharged from the nip portion 24 of the fixing device 20 is higher in the fixing roller 22 than the pressure roller 23. Although the front side of the paper P has a larger thermal expansion amount than the back side, the front and rear ends of the paper P are likely to have a so-called lower curl. By setting the posture 40 to the first posture, the paper P discharged from the nip portion 24 of the fixing device 20 is discharged to the upper nip roller 52 side, which is a direction around the fixing roller 22, and thus the paper P The lower curl is corrected by this winding operation.

  On the other hand, when the paper P is thin, or even when a normal copy paper is printed on both sides, the amount of heat supplied from the fixing roller 22 to the paper P becomes excessive. As a result, the toner on the paper P becomes excessively melted, and the excessively melted toner adheres to the peripheral surface of the fixing roller 22 and is wound around the fixing roller 22, so that an upper curl is formed on the paper P. However, by setting the paper transport destination switching member 40 to the second posture, the paper P discharged from the nip portion 24 of the fixing device 20 is wound around the pressure roller 23. Since the sheet P is discharged to the lower nip roller 53 side, the upper curl is corrected by the winding operation of the sheet P.

  As described above, the conveyance destination of the paper P after the fixing process is switched between the upper nip roller 52 side and the lower nip roller 53 side by changing the posture of the paper conveyance destination switching member 40 according to the type of the paper P and the transfer situation. As a result, the curling of the paper P discharged from the fixing device 20 is suppressed.

  Further, depending on the situation of the sheet P to which the fixing process is performed (that is, whether the sheet P is a normal copy sheet, whether it is a normal copy sheet but duplex printing is performed, or the sheet P is Since the control device 80 for outputting the control signal for changing the posture is provided on the switching plate 42 (depending on whether the paper is thin), the paper P on which the transfer processing is performed on the control device 80 in advance. Type (for example, whether the paper P is a normal copy paper or a paper thinner than normal), transfer status (for example, whether the paper P is printed on one side, double-sided printing) In other words, the sheet conveyance is performed from the control device 80 toward the sheet conveyance destination switching member 40 in accordance with the type of the sheet P and the transfer situation. Position of the tip switching member 40 A further control signal is output, which due to the curling of the sheet P in the fixing device 20 of the sheet P in the posture change of the switching plate 42 automatically, and can be effectively corrected.

  Further, since the rotation speed of the transport roller 51 is set according to the set posture of the paper transport destination switching member 40, the transport roller 51 slips the paper P with the transport roller 51 according to the type of the paper P and the transfer situation. However, the sheet P can be pulled from the nip portion 24 of the fixing device 20, and the degree of adhesion of the sheet P to the fixing roller 22 or the pressure roller 23 (that is, the fixing roller 22 or the pressure roller 23 of the sheet P). By adjusting the pressing force on the paper P, it is possible to perform an appropriate curl correction treatment according to the type and transfer state of the paper P.

  Further, the transport roller 51 functions as a drive roller to which the driving force of the drive motor 60 is transmitted via the gear mechanism 70, and the upper and lower nip rollers 52 and 53 function as driven rollers that are driven by the drive rotation of the transport roller 51. Therefore, the upper and lower nip rollers 52 and 53 are driven by the driving rotation of the conveying roller 51 via the gear mechanism 70 driven by the driving motor 60, and thereby the switching plate 42 is set in a set posture. The sheet P discharged from the nip portion 24 of the fixing device 20 can be discharged while being sandwiched between the transport roller 51 and the upper nip roller 52 or the lower nip roller 53, and the nip roller side is driven (in this case, the upper portion Compared with two drive motors 60 for nip roller 52 and lower nip roller 53) Can be reduced, it is possible to contribute to a reduction of the apparatus cost.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, the transport roller 51 is a driving roller to which the driving force of the driving motor 60 is transmitted via the gear mechanism 70, while the upper nip roller 52 and the lower nip roller 53 are in contact with each other on the circumferential surface. However, the present invention is not limited to the conveyance roller 51 and the nip rollers 51 and 52 as the driving roller and the driven roller, respectively. The nip rollers 51 and 52 are not limited to the driven rollers. In addition to the driving roller, the conveyance roller 51 may be a driven roller that is driven by the nip rollers 51 and 52.

  (2) In the above embodiment, the transport roller 51 is made of heat-resistant CR rubber, EPDM, or silicon rubber, and the upper and lower nip rollers 52, 53 are made of POM, PET, or PBT. However, instead of this, both the conveying roller 51 and the upper and lower nip rollers 52 and 53 may be made of ordinary natural rubber or synthetic rubber.

  (3) In the above embodiment, both the transport roller 51 and the upper and lower nip rollers 52 and 53 are entirely made of a synthetic resin material having an elastic force. Instead of this, a roller made of a metallic material is used. You may employ | adopt what performed the coating process which apply | coats or bakes a synthetic resin material to the surrounding surface.

  (4) In the above embodiment, for the pressing contact between the upper and lower nip rollers 52 and 53 with respect to the transport roller 51, the distance between the shaft centers of the transport roller shaft 511 and the upper and lower roller shafts 521 and 531 is set as follows: It is set to be slightly smaller than the value obtained by adding the radius of the transport roller 51 and the radii of the upper and lower nip rollers 52 and 53, and this is performed by compressive elastic deformation of the transport roller 51 and the upper and lower nip rollers 52 and 53. However, instead of this, the roller shafts 521 and 531 of the upper and lower nip rollers 52 and 53 are urged against the conveying roller 51 by an urging means such as a compression spring, whereby the upper and lower nip rollers 52 and 53 are urged. You may make it press-contact to 51.

  (5) In the above embodiment, three idle gears (first to third upper idle gears 741, 742, 743) are employed as the upper idle gear group 74, and two lower idle gear groups 75 are employed. Although idle gears (first to second lower idle gears 751 and 752) are employed, the present invention is limited to that the upper and lower idle gear groups 74 and 75 are each composed of three and two idle gears. The upper idle gear group 74 may be an odd number of idle gears, and the lower idle gear group 75 may be an even number of idle gears.

1 is a schematic explanatory view in cross section showing an embodiment of an internal structure of a copying machine according to the present invention. FIG. 9 is a perspective view showing an embodiment of a paper transport destination switching mechanism, and shows a state in which the switching plate of the paper transport destination switching member is set to a first lowering posture (first guide posture). FIG. 6 is a perspective view showing an embodiment of a paper transport destination switching mechanism, and shows a state in which the switching plate is set in a forward-up posture (second guide posture). FIG. 3 is a partially enlarged perspective view of FIG. 2 for explaining an embodiment of the gear mechanism, and shows a state in which the transport roller is rotated counterclockwise in response to the switching plate being set to the first lowered posture. Show. FIG. 3 is a partially enlarged perspective view of FIG. 2 for explaining an embodiment of the gear mechanism, and shows a state in which the transport roller is rotating in the clockwise direction when the switching plate is switched to the upwardly rising posture. FIG. 6 is a front view of the gear mechanism shown in FIGS. 4 and 5, in which (a) is a diagram corresponding to FIG. 4, and (b) is a diagram corresponding to FIG. 5. FIG. 5 is an enlarged explanatory view showing a state in which a sheet P passes through a nip portion between a fixing roller and a pressure roller. It is a block diagram which shows one Embodiment of a control apparatus. It is explanatory drawing for demonstrating the copying machine to which other embodiment of the paper inversion structure was applied.

Explanation of symbols

10, 10 'Copying machine (image forming device)
101 discharge tray 102, 102 'discharge conveyance path 103, 103 "return conveyance path 103' switchback conveyance path 104 reverse conveyance path 105 in-cylinder discharge tray 106 in-cylinder discharge conveyance path 11 copier body 12 original reading section 121 Document Presser 122 Optical System Unit 123 Contact Glass 123a Placed Document Contact Glass 123b Automatic Feeding Contact Glass 124 Operation Panel 125 Document Tray 126 Document Discharge Tray 127 Document Feed Section 13 Image Forming Section 13Y Yellow Unit 13M For Magenta Unit 13C Cyan unit 13K Black unit 131 Photosensitive drum 132 Developing device 133 Charging unit 134 Exposure unit 135 Cleaning device 136 Conveying belt 14 Fixing unit 15 Paper storage unit 151 Paper tray 152 Pickup roller La 153 Paper feed transport path 16, 16 'Paper reversing portion 161 Support plate 162 Switching guide 163 Reversing roller pair 20 Fixing device 21 Fixing device main body 22 Fixing roller 23 Pressure roller 24 Nip portion 30 Paper transport destination switching mechanism 40 Paper transport destination Switching member 41 Support plate 411 Upper inclined surface 412 Lower inclined surface 413 Bracket portion 414 Mounting recess 42 Switching plate 43 Tube shaft 44 Upper guide plate 45 Lower guide plate 50 Curl correction roller mechanism 51 Transport roller 511 Transport roller shaft 52 Upper nip roller (first nip roller) 1 nip roller)
521 Upper roller shaft 53 Lower nip roller (second nip roller)
531 Lower roller shaft 60 Drive motor 61 Drive shaft 70 Gear mechanism 71 Drive gear 72 Planetary gear 73 Transport roller gear 74 Upper idle gear groups 741 to 743 First to third upper idle gears 75 Lower idle gear groups 751 to 752 First to first 2 Lower idle gear 76 Paper transport destination switching member 761 Actuator 762 Operation rod 763 Operation plate 764 Connection piece 765 Long hole 80 Control device (control means) 81 Posture setting determination unit 82 Control signal output unit 83 Duplex printing button 84 Thin paper use button P Paper R1 Upper discharge path R2 Lower discharge path S1 First descending posture (first guiding posture)
S2 Climbing posture (second guiding posture)

Claims (4)

A fixing roller for performing a fixing process by heating the transfer image transferred to the paper in the image forming unit; and a pressure roller disposed to face the fixing roller, and a peripheral surface of the fixing roller and a periphery of the pressure roller. In an image forming apparatus equipped with a fixing device in which a nip portion that nips a sheet is formed at a contact position with a surface,
The posture can be changed between a first guide posture for guiding the conveyance destination of the paper discharged from the nip portion to the fixing roller side and a second guide posture for guiding the pressure roller side to the downstream side of the nip portion. A paper transport destination switching member is provided,
On the downstream side of the paper transport destination switching member, it is arranged so as to be rotatable about an axis extending in the paper width direction orthogonal to the paper transport direction and so that the peripheral surface faces the paper transport destination switching member. Transport rollers,
The paper guided by the paper transport destination switching member, which is arranged in parallel so that the peripheral surface is in contact with the fixing roller side of the peripheral surface of the transport roller and is set to the first guide posture, A first nip roller that nips and discharges,
The paper guided by the paper transport destination switching member, which is arranged in parallel so that the peripheral surface is in contact with the pressure roller side of the peripheral surface of the transport roller and is set in the second guide posture, is transferred to the transport roller. And a second nip roller that nips and discharges,
The image forming apparatus according to claim 1, wherein the transport roller is configured to be capable of switching a rotation direction so as to discharge a sheet in accordance with a change in posture of the sheet transport destination switching member.   2. The image forming apparatus according to claim 1, further comprising a control unit configured to output a control signal for changing a posture to the sheet transport destination switching member in accordance with a condition of a sheet on which the fixing process is performed.   The image forming apparatus according to claim 1, wherein a rotation speed of the transport roller is set according to a set posture of the paper transport destination switching member.   The conveying roller is a driving roller to which driving force of a driving motor is transmitted through a gear mechanism, and the first and second nip rollers are driven rollers that are driven by driving rotation of the conveying roller. The image forming apparatus according to claim 1.

Images