JP2019156521A - Sheet processing apparatus and image forming apparatus - Google Patents

Abstract

To improve waviness caused by an end in a width direction of a sheet extending in a conveying direction more than the vicinity of a center.SOLUTION: A sheet processing apparatus includes a tension applying device for applying a tension in a conveying direction to a central region in a width direction perpendicular to the conveying direction of the sheet by nipping and conveying the sheet, in a state where the sheet is conveyed in a shortest conveying path by being guided with an endless guide member while the sheet is wound around multiple roller pairs that are provided at intervals in the conveying direction and downstream in a conveying direction of a fixing unit for heating and fixing a toner image on the sheet.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming system such as a copying machine, a printer, and a facsimile using a method of fixing an unfixed toner image by heating and pressing.

  Conventionally, an image forming apparatus using an electrophotographic method develops a latent image formed on a photosensitive drum as an image carrier to form a visible image, and uses this visible image (toner image) on a sheet using electrostatic force. To transcribe. Next, the toner image on the sheet is fixed by heat and pressure, whereby an image is recorded and formed on the sheet.

  As a fixing device of such an image forming apparatus, a fixing nip portion is formed by pressing a resilient pressure roller against a fixing roller having a heat source such as a heater and maintained at a predetermined temperature. A heat roller fixing system is employed in which the toner image is fixed on the sheet at the part.

  In recent years, in an image forming apparatus (especially a full-color image forming apparatus) in which this type of fixing device is used, the heating time can be extended and the fixing can be performed from the viewpoint of improving the color developability and image quality of the toner image. A fixing device that can increase the speed is known. For example, as shown in Japanese Patent Laid-Open No. 5-150679, a so-called belt nip type fixing device is known in which an endless fixing belt stretched around a plurality of rolls is pressed against a heating roll.

  In recent years, it has become necessary to increase the process speed in order to increase the output speed of the image forming apparatus. For this reason, a wider nip width is required in the width direction perpendicular to the sheet conveyance direction, and a belt fixing system that secures a wide nip width by replacing the fixing roller and pressure roller or both with an endless belt. Has been proposed and commercialized.

  In the heat fixing process of these fixing devices, since heat and pressure are applied to the sheet on which the toner image is transferred, moisture evaporates from the inside of the sheet after the pressure nip and the pressure nip. Due to the change in the amount of moisture due to the heat of the sheet and the stress caused by the pressure applied to the sheet, a phenomenon called a curl in which the sheet is curved and a phenomenon called a wave in which the sheet has a wavy shape occur.

  Here, a sheet-like paper that is most commonly used as a sheet is viewed at the fiber level. Paper is composed of short fibers entangled with each other, and moisture is contained inside or between the fibers. Furthermore, since the fiber and water are in an equilibrium state with hydrogen bonds formed, smoothness is maintained.

  When heat and pressure are applied to the paper in the fixing process, the fibers are displaced due to the pressure, and when heat is applied and moisture evaporates, further hydrogen bonds are formed between the fibers and deform. If this paper is left unattended, it absorbs moisture from the environment, and the hydrogen bonds between the fibers are cut off again to return to the original state. However, there is no moisture between some fibers of the paper, thereby maintaining the deformation of the paper. The deformation pattern includes the above-described curl and undulation, and the curl is generated due to a difference in expansion / contraction between the front and back of the paper, and the undulation is generated due to an expansion / contraction difference between the center and the edge of the paper.

  The first cause of undulations at the end of the sheet is in the process of passing the sheet through the nip portion of the fixing device. For example, in the case of a fixing device having a wide nip such as a belt fixing method, in order to prevent sheet wrinkling in the process of passing a sheet through the nip portion, an end portion from a central portion in the width direction perpendicular to the sheet conveyance direction in the nip Set the side transport speed higher. As a result, when the sheet has a squeezing action, the sheet end portion extends in the transport direction from the vicinity of the center after passing through the nip portion, and undulation is generated at the end portion of the sheet.

  The second cause of the occurrence of undulations at the end of the sheet is after the sheet passes through the nip portion of the fixing device. In the state of being stacked as a sheet bundle, each sheet is in contact with the atmosphere at the end portion, so that moisture enters and exits rapidly. When heat is applied to the sheet in the fixing process and moisture in the sheet evaporates, the moisture content is rapidly absorbed from the end of the sheet, causing unevenness in the moisture content distribution inside the sheet, and undulation is generated at the end of the sheet.

  In particular, in the belt fixing method in which the fixing roller and the pressure roller or both are replaced with an endless belt to ensure a wide nip width, the distance and time for the sheet to stay between the nips increase compared to the heat roller method. The problem of corrugation at the edge of the sheet tends to become prominent.

  Therefore, the sheet is humidified by the sheet humidifier, and the fiber and water are transitioned to an equilibrium state in which hydrogen bonds are generated to release the bonds in the fibers. Subsequently, by applying a straight tension to the center of the sheet in the conveyance direction, the bonds in the fibers in the center of the sheet were released, and the waviness at the sheet edge was reduced.

Japanese Patent Laid-Open No. 5-150679

  However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified. The mechanism relating to the occurrence of curling is shown in FIGS. Humidification is performed on a sheet immediately after fixing, in which the front surface is a paper fiber surface and the back surface is an image surface with a high toner density and there is a difference in image density between the front and back surfaces (FIG. 1a). Moisture absorption occurs from the paper fiber surface. On the other hand, on the image surface with a high toner concentration, the moisture permeability of the toner layer is low, so that it is difficult for the paper fiber surface to absorb moisture.

  As a result, the paper fiber surface side expands due to moisture absorption, and both ends become convex with respect to the image surface having a high toner density (FIG. 1b). Subsequently, the humidified sheet is left in the environment. The environment at this time is assumed to be air at a temperature of 23 ° C. and a humidity of 50% (hereinafter referred to as a normal temperature and low humidity environment). The sheet is dried by leaving the humidified sheet in a room temperature and low humidity environment. Drying moves moisture from the sheet to a room temperature and low humidity environment, and the sheet contracts (FIG. 1c). The amount of displacement corresponding to the amount of moisture in the paper is path-dependent, and the amount of expansion when absorbing only a minute amount of water and the amount of contraction when considering only the amount of minute water are not always equivalent. As a result, the amount of expansion due to moisture absorption of the sheet is different from the amount of shrinkage due to drying of the sheet, so that the curl remains after standing.

  In order to improve the curl (FIG. 1b) for improving the curl immediately after the paper discharge, the curl immediately after the paper discharge can be prevented by applying the decurling immediately after the humidification, but the curl after being left is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to propose a configuration that efficiently reduces waviness with respect to paper waviness caused by a difference in paper length at the center edge.

  Another object of the present invention is to propose a configuration that achieves both curling due to humidification and undulation in paper undulation correction using humidification.

  In order to achieve the above object, a typical configuration of the present invention is a detachable connection to an image forming apparatus having a fixing unit that heats and fixes a toner image on a sheet, and a sheet discharged from the image forming apparatus. In a sheet processing apparatus that performs processing on a sheet, a plurality of pairs of rollers provided at intervals in the sheet conveyance direction are provided while the sheet is wound around the plurality of roller pairs provided at intervals in the sheet conveyance direction. A tension applying device that applies tension in the transport direction to the sheet in a central region in the width direction orthogonal to the transport direction of the sheet by holding and transporting the sheet is provided.

  The image forming system according to the present invention has a configuration in which an endless guide member is disposed on one roller in a roller pair and one roller in another roller pair, and the guide is disposed on the roller. The outer diameter of the member is smaller than the outer diameter of the roller so that no conveying force is given to the sheet, and the sheet is conveyed with the shortest distance to the nip portion formed by a plurality of pairs of rollers. And

  In addition, the configuration of a typical image forming system of the present invention is detachably connected to an image forming apparatus having a fixing unit that heats and fixes a toner image on a sheet, and the sheet discharged from the image forming apparatus is connected to the image forming apparatus. In a sheet processing apparatus that performs processing, a plurality of pairs of rollers provided at intervals in the sheet conveyance direction are nipped while a sheet is wound around a plurality of pairs of rollers provided at intervals in the sheet conveyance direction. And a tension applying device that applies a tension in the conveyance direction to the central region in the width direction perpendicular to the conveyance direction of the sheet.

  According to the present invention, it is possible to apply a tension in the conveyance direction to the central region in the width direction of the sheet while winding the sheet while preventing the sheet from being looped by conveying the sheet through the shortest path. Thereby, the coupling | bonding in the fiber of a sheet | seat can be released, and the corrugation of a sheet | seat edge part can be improved.

1A, 1B, and 1C are schematic diagrams for explaining the problem. FIG. 2 is a cross-sectional view showing the electrophotographic printer according to the first embodiment. FIG. 3 is a block diagram illustrating the control of the printer and the sheet wavy correction device according to the first embodiment. FIG. 4 is a cross-sectional view showing the humidifying device of the first embodiment. FIG. 5 is a cross-sectional view illustrating the tensile conveyance device according to the first embodiment. FIG. 6 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the first embodiment. FIG. 7 is a perspective view illustrating the tensile conveyance device according to the first embodiment. FIG. 8 is a front view illustrating the tensile conveyance device according to the first embodiment. FIG. 9 is a cross-sectional view illustrating the curl correction apparatus according to the first embodiment. FIG. 10 is an external view showing the shape of the sheet. FIGS. 11A, 11B, and 11C are table diagrams showing the state of the sheet by experiment. FIG. 12 is a cross-sectional view illustrating the tensile conveyance device of the second embodiment. FIG. 13 is a cross-sectional view illustrating a transport path in the tensile transport device according to the second embodiment. FIG. 14 is a cross-sectional view illustrating a tensile conveyance device according to the third embodiment. FIG. 15 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the third embodiment. FIG. 16 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the fourth embodiment. FIG. 17 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the fifth embodiment. FIG. 18 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device according to the first embodiment. FIG. 19 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device according to the first embodiment. FIG. 20 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the first embodiment. FIG. 21 is a cross-sectional view illustrating a conveyance path in the tensile conveyance device of the first embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[Example 1]
The image forming apparatus including the sheet processing apparatus according to the first embodiment will be described with reference to FIGS. In the following description, the image forming apparatus will be described first, and then the sheet processing apparatus will be described. In this embodiment, an image forming system in which a sheet processing apparatus is connected to the outside of the image forming apparatus will be described. However, even in a configuration of an image forming system in which the sheet processing apparatus is integrated in the image forming apparatus. The present invention is effective.

  First, referring to FIG. 2, an image forming apparatus and a sheet processing apparatus detachably connected to the image forming apparatus will be described as an example of an image forming system. FIG. 2 is a cross-sectional view schematically showing a color electrophotographic printer 500 that is an example of an image forming apparatus, and a sheet wavy correction device 900 that includes a tension applying device and a moisture adding device that are examples of a sheet processing apparatus. It is sectional drawing along the conveyance direction of a sheet | seat. In the following description, the color electrophotographic printer is simply referred to as “printer”.

  The sheet is a sheet on which a toner image is formed. Specific examples of the sheet include plain paper, a resin sheet that is a substitute for plain paper, cardboard, and overhead projector.

  The printer 500 shown in FIG. 2 includes an image forming unit 510 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). Each color image forming unit 510 forms a toner image of each color on a sheet. An endless intermediate transfer belt 531 as an intermediate transfer member is disposed so as to face these image forming portions. In other words, the image forming apparatus adopts a tandem method in which processes up to visualization are processed in parallel for each color.

  Note that the arrangement order of the image forming units for each of the colors Y, M, C, and K is not limited to the arrangement order shown in FIG. In addition, the present invention is not limited to the full-color intermediate transfer type image forming apparatus shown in FIG.

  Each color image forming unit 510 shown in FIG. 2 includes the following process means. An electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 511 as an image carrier that carries an electrostatic latent image on the surface corresponding to each of Y, M, C, and K, a charging roller 512, a laser scanner 513, A developing unit 514 is provided. The photosensitive drum 511 is charged in advance by the charging roller 512. Thereafter, the photosensitive drum 511 is exposed by a laser scanner 513 to form a latent image. The latent image is developed by the developing device 514 to be visualized as a toner image.

  Each toner image formed and carried on the surface of the photosensitive drum 511 shown in FIG. 2 is sequentially superimposed on the intermediate transfer belt 531 by the primary transfer roller 515 in the primary transfer portion between the photosensitive drum 511 and the primary transfer roller 515. The primary transfer.

  On the other hand, the sheets P are fed one by one from the feeding cassette 520 shown in FIG. 2 and fed to the registration roller pair 523. The registration roller pair 523 temporarily receives the sheet P and corrects the skew when the sheet is skewed. The registration roller pair 523 sends the sheet P to the secondary transfer portion between the intermediate transfer belt 531 and the secondary transfer roller 535 in synchronization with the toner image on the intermediate transfer belt 531. The color toner image on the intermediate transfer belt 531 is secondarily transferred collectively onto the sheet P by a secondary transfer roller 535 which is a transfer portion.

  Thereafter, the sheet on which the image (toner image) is formed by the image forming unit as described above is conveyed to the fixing device 100 shown in FIG. The fixing device (fixing unit) 100 fixes the toner image on the sheet by sandwiching the sheet at the fixing nip and applying heat and pressure to the unfixed toner image. The sheet that has passed through the fixing device 100 is sent to a sheet waving correction device 900 as a sheet processing device that processes the sheet by the discharge roller pair 540, and after correcting the sheet waving by the sheet waving correction device 900, the discharge tray 565. To be discharged.

  Here, the fixing device will be described. The fixing device 100 shown in FIG. 2 includes a fixing roller 110 that is a heating rotator and a pressure roller 111 that is a pressure rotator. The fixing roller 110 applies heat generated by an internal halogen heater (not shown) to the toner on the sheet P and conveys the sheet P together with the pressure roller 111. The fixing roller 110 incorporates a halogen heater in a metallic core made of an aluminum cylindrical tube having an outer diameter of 56 mm and an inner diameter of 50 mm, for example. For example, an elastic layer made of silicone rubber having a thickness of 2 mm and a hardness (Asuka C) of 45 ° is coated on the surface of the metal core, and a PFA or PTFE heat release layer is coated on the surface of the elastic layer.

  The pressure roller 111 shown in FIG. 2 conveys the sheet P together with the fixing roller 110. The pressure roller 111 also has a metallic core made of an aluminum cylindrical tube having an outer diameter of 56 mm and an inner diameter of 50 mm, for example. For example, an elastic layer made of silicone rubber having a thickness of 2 mm and a hardness (Asuka C) of 45 ° is coated on the surface of the metal core, and a PFA or PTFE heat release layer is coated on the surface of the elastic layer.

  A fixing nip portion is formed by the fixing roller 110 and the pressure roller 111 shown in FIG. In the experiments of the present inventors, the sheet P is set under the conditions that the set temperature of the surface layer of the fixing roller 110 is 180 ° C., the set temperature of the surface layer of the pressure roller 111 is 100 ° C., the ambient temperature is 23 ° C. Is conveyed at a conveyance speed of about 300 to 500 mm / sec. Then, the sheet P heated and pressed in the fixing nip portion has an end portion as a result that the end portion in the width direction orthogonal to the transport direction of the sheet P is larger than the center side and the fibers extend in the transport direction. Waves (hereinafter referred to as waves) occur.

  Note that the paper type information of the sheet P in the feeding cassette 520 shown in FIG. 2 is input by the user using the operation panel 570 and sent to the control unit 500C having the CPU and memory in the printer 500 shown in FIG. . Further, the image density information of the toner image on the sheet P on which the image is formed by the image forming unit 510 is sent to the control unit 500C having the CPU and memory in the printer 500 shown in FIG. The temperature and humidity in the image forming apparatus 500 are detected by an environmental sensor 500D installed on the upper side of the feeding cassette 520 in the image forming apparatus 500, and the temperature and humidity information is sent to a control unit 500C having a CPU and a memory. Sent.

  The sheet P on which the toner image is fixed by the fixing device 100 shown in FIG. 2 is sent to the sheet wavy correction device 900 by the discharge roller pair 540. The sheet P is conveyed along the conveyance guide 902 by the inlet roller pair 901 of the sheet waviness correction apparatus 900, and after the conveyance direction is changed vertically downward (in the direction of arrow B in FIG. 1) by the conveyance guide 902, the moisture adding apparatus ( The sheet is fed to a sheet humidifier 400 as a moisture adding means. Here, the sheet P is humidified by the humidifying roller pair 401 and 402.

  The sheets P discharged from the sheet humidifying apparatus 400 shown in FIG. 2 are successively sent to the sheet pulling and conveying apparatuses 101 and 201 as tension applying apparatuses in succession. After the sheet humidifying device 400 has humidified more than a predetermined amount of water, the sheet pulling and conveying devices 101 and 201 are sequentially passed through, and the widthwise central portion perpendicular to the conveying direction of the sheet P is pulled in the conveying direction. The difference in the length in the conveying direction between the end portion and the central sheet P is reduced.

  In this way, the sheet P whose waviness at the end in the width direction of the sheet P is improved is then sent to the decurling apparatus 600, and the curl generated in the sheet pulling and conveying apparatuses 101 and 201 is corrected.

  The curled sheet P is conveyed by the conveying roller pair 904 while turning the conveying direction vertically upward (in the direction of arrow C in FIG. 2) by the conveying guides 903 and 905. Thereafter, the sheet P is conveyed by the conveyance roller pair 906 and 908 while being guided by the conveyance guides 907 and 909, discharged by the discharge roller pair 910 to the outside of the sheet wavy correction device 900, and stacked on the discharge tray 565.

  In FIG. 1, reference numeral 400A denotes a water storage tank in which a humidifying liquid L for humidifying the sheet P is accommodated. The humidifying liquid L accommodated in the water storage tank 400A is supplied with water through the water supply pipe (not shown) toward the water tank (not shown) provided in the sheet humidifier 400 by the pump 400B as needed. The humidifying liquid (also referred to as coating liquid) L is mainly composed of water.

  Here, the control relationship of the entire image forming system will be described with reference to FIG. FIG. 3 is a block diagram showing a control relationship between the printer 500 and the sheet wavy correction device 900 constituting the image forming system. The control unit 500C of the printer 500 and the control unit 901C of the sheet wavy correction device 900 are computer systems having a CPU, a memory, an arithmetic unit, an I / O port, a communication interface, a drive circuit, and the like.

  Control by the control units 500C and 901C shown in FIG. 3 is performed by each CPU executing a predetermined program stored in the memory. The control unit 901C of the sheet wavy correction device 900 controls operations of the sheet humidifying device 400, the sheet pulling and conveying devices 101 and 201, and the decurling device 600 that constitute the device. In addition, each of the control units 500C and 901C described above is connected via the communication unit COM and can exchange information.

  Here, the control unit (control unit) 901C included in the sheet wavy correction device 900 illustrated in FIG. 3 is controlled by the control unit (control unit) 500C included in the printer 500 to control the operation of the sheet wavy correction device 900. However, the present invention is not limited to this. For example, the sheet waviness correction apparatus may have no control means, and the control means of the printer may control the operation of the sheet waviness correction apparatus.

  Next, the sheet humidifier 400 will be described in detail with reference to FIG. FIG. 4 is a cross-sectional view showing the entire sheet humidifying device 400.

  The sheet P sent in the direction of arrow B in FIG. 4 which is the same as the direction of arrow B in FIG. 2 is guided by the entry guides 414 and 414 and sent to the nip portion of the first humidifying roller pair 401 and 402, and the humidifying liquid L Is humidified by being transferred to the surface. The sheet P that has passed through the nip portion of the humidifying rollers 401 and 402 is sent to the first sheet pulling and conveying apparatus 101 via the discharge guide 413.

  Humidifying rollers 401 and 402 shown in FIG. 4 are elastic rollers in which a solid rubber layer mainly composed of NBR, silicone or the like is formed on the surface of a shaft core made of a metal rigid body such as stainless steel.

  Water supply rollers 405, 406, 407 and 408 shown in FIG. 4 are water supply members for sequentially supplying the humidifying liquid L in the water supply tanks 412 and 413 to the humidifying roller pairs 402 and 403. The water supply rollers 405, 406, 407, and 408 are solid rubber layers mainly composed of a material having a hydrophilic surface capable of holding water on a shaft surface made of a rigid metal such as stainless steel, such as NBR. Is an elastic roller formed. The solid rubber layer may be made of metal or a hydrophilic resin.

  Water pumps 407 and 408 shown in FIG. 4 feed the humidifying liquid L to the water supply rollers 405 and 406 by pumping up the humidifying liquid L in the water tanks 412 and 413 and then contacting the water supply rollers 405 and 406. The water supply rollers 405 and 406 contact the humidification rollers 401 and 402 to supply the humidification liquid L to the humidification rollers 401 and 402.

  The first restriction rollers 409 and 410 are first restriction members for restricting the amount of water supplied to the water supply rollers 407 and 408. The first regulating rollers 409 and 410 are rollers in which a surface of an axial core made of a metal rigid body such as stainless steel is plated with nickel or chromium.

  The first regulating roller 409 and the first regulating roller 410 shown in FIG. 4 are in contact with the water supply roller 407 and the water supply roller 408, respectively, and suppress the amount of the humidifying liquid held on the surface of each solid rubber layer to an appropriate amount. The amount of moisture supplied to P is regulated. That is, the first regulating rollers 409 and 410 are pressed against the solid rubber layers of the water supply rollers 407 and 408, respectively, and deformed to squeeze the humidified liquid held on the surface.

  The second regulating rollers 403 and 404 shown in FIG. 4 are second regulating members for regulating the amount of water supplied to the humidifying rollers 401 and 402. The second regulating rollers 403 and 404 are rollers in which the surface of the shaft core made of a metal rigid body such as stainless steel is plated with nickel, chromium or the like.

  The second regulating roller 403 shown in FIG. 4 is in contact with the humidifying roller 401 and the second regulating roller 404 is in contact with the humidifying roller 402, respectively, and the amount of humidifying liquid held on the surface of each solid rubber layer is suppressed to an appropriate amount. The amount of moisture supplied to P is regulated. That is, the second regulating rollers 403 and 404 are pressed against and deformed by the solid rubber layers of the humidifying rollers 401 and 402, respectively, and squeeze the humidifying liquid held on the surface.

  As a result, the sheet P is humidified to an optimal amount of moisture, and the tension effect is promoted by the sheet pulling and conveying apparatuses 101 and 201 described above.

  A driving gear (not shown) is fixed to the shaft end portion side of the humidifying roller 402 shown in FIG. 4, and rotational driving is transmitted from a driving motor (not shown). The other rollers are driven to rotate by driving transmission from the surface of the humidifying roller 402.

  As described above, the amount of moisture given to the sheet P by the humidifying roller pair that humidifies the sheet P is cut off from the hydrogen bond between the fibers of the sheet P, and the tension to the center in the width direction of the sheet P by the sheet pulling and conveying devices 101 and 201 It is possible to increase the moisture content necessary to promote expansion and contraction due to load.

  Next, the configuration of each sheet pulling and conveying apparatus (101, 201) alone will be described with reference to FIG. 5, FIG. 6, FIG. 7, and FIG. In the present embodiment, the configurations of the first sheet pulling and conveying apparatus 101 and the second sheet pulling and conveying apparatus 201 are the same, and the tension for extending the central portion in the width direction of the sheet P in the conveying direction is applied to the sheet P. A plurality of roller pairs are provided. Therefore, the description of the configuration of the later-described sheet pulling and conveying apparatus will be made on behalf of the first sheet pulling and conveying apparatus 101, and the detailed description of the second sheet pulling and conveying apparatus 201 will be omitted.

FIG. 5 is a front sectional view for explaining the sheet pulling and conveying apparatuses 101 and 201 of the present embodiment. FIG. 7 is a perspective view illustrating the sheet pulling and conveying apparatuses 101 and 201 of the present embodiment, and FIG. 8 is a front view illustrating the sheet pulling and conveying apparatuses 101 and 201 of the present embodiment.
Here, as a plurality of roller pairs, a first roller pair described below and a second roller pair provided on the downstream side in the transport direction from the first roller pair are illustrated.

  The first roller pair shown in FIG. 5 is in contact with the first drive roller 104, which is a rotatable first roller, and the first drive roller 104, forms a nip portion N11, and sandwiches and conveys the sheet P. The first pressure roller 105 is a first pressure roller.

  The second roller pair is provided on the downstream side in the transport direction from the first roller pair. The second roller pair includes a second driving roller 106 that is a rotatable second roller, and a second addition roller that is pressed against the second driving roller 106 to form a nip portion N12 and sandwiches and conveys the sheet P. It consists of a second pressure roller 107 which is a pressure roller.

  The sheet pulling and conveying apparatus 101 shown in FIG. 5 includes a first driving roller 104, a first pressure roller 105, and a second driving roller that form a second roller pair 106, 107. 106 and the second pressure roller 107, the sheet P is conveyed while being nipped, and the endless first driven guide member 141 wound around the first driving roller 104 and the second pressure roller 107, or the first pressure roller The sheet P is guided by the endless second driven guide member 143 wound around the 105 and the second drive roller 106.

  The sheet pulling / conveying device 101 further conveys the sheet P, wraps the sheet P around the first driving roller 104 or the second driving roller 106, and applies tension to extend the central portion in the width direction of the sheet P in the conveying direction. To P.

  As shown in FIG. 5, the first driving roller 104, the first pressure roller 105, the second pressure roller 106, and the second pressure roller 107 are made of elastic rubber 104b, 105b, 106b, 107b such as silicone, NBR, EPDM. Have The elastic rubbers 104b, 105b, 106b, and 107b are respectively formed on the surface layers of the roller shafts 104a, 105a, 106a, and 107a using a highly rigid material such as stainless steel and steel. In this embodiment, the elastic rubbers 104b, 105b, 106b, 107b all have the same outer diameter φ (for example, 20 mm).

  Further, as shown in FIG. 5, the width of the sheet P is set so that the elastic rubbers 105b and 107b of the first pressure roller 105 and the second pressure roller 107 are uniform with respect to the sheet passing center (width direction center). It forms in the area | region of length L1 of the center part in a direction. Here, the sheet passing center is a position in the center in the width direction which is a reference when the sheet P is conveyed. The length L1 is shorter than the length in the width direction of the maximum sheet P in which undulation shown in FIG. 9 is a problem. In this embodiment, L1 = 100 mm. The length L1 may be shorter than the length in the width direction of the maximum sheet P to be conveyed.

  Further, as shown in FIG. 5, a groove is formed in the roller shafts 104a, 105a, 106a, 107a and the elastic rubbers 104b, 105b, 106b, 107b formed on the surface of the roller shaft. In the present embodiment, the thickness of the first driven guide member 141 and the second driven guide member 143 is 1.5 mm, the groove portion is provided in each of the rubber layer and the roller shaft, and the rubber thickness (for example, 1 mm) and the roller shaft are set. The roller shaft is set to a depth in the radial direction of the roller shaft (for example, 2 mm) and a width in the axial direction of the roller (for example, 2 mm).

  The depth of the groove between the first driving roller 104 and the second pressure roller 107 is larger than the thickness of the first driven guide member 141, and the groove between the first pressure roller 105 and the second driving roller 106. The depth may be larger than the thickness of the second driven guide member 143.

  The outer shape of the first driven guide member 141 and the second driven guide member 143 is smaller than the outer diameter of the rubber layer of the first drive roller 104, the second drive roller 106, the first pressure roller 105, and the second pressure roller 107. But you can. Thereby, the conveyance force to the sheet P by the driven guide is reduced, and wrinkles due to the conveyance speed difference are reduced.

  Further, in order to reduce the resistance to the sheet P by the driven guide, it is preferable to select a material with good sliding property as the first driven guide members 141 and 142 and the second driven guide members 143 and 144.

  Further, the inner length of the first driven guide member 141 is set to be equal to or shorter than the length in which the outer periphery of the first drive roller 104 and the outer periphery of the second drive roller 107 are continuously connected to each tangent line, The inner length of the second driven guide member 143 was set to be equal to or shorter than the length in which the first pressure roller 105, the second drive roller 106, and the respective tangent lines were continuously connected. That is, when the first driven guide member 141 is disposed on the outer periphery of the first drive roller 104 and the second pressure roller 107, the first driven guide member 141 is given an internal tension, and the first pressure roller When arranged on the outer periphery of the 105 and the second drive roller 106, an internal tension is applied to the second driven guide member 143.

  Due to the internal tension, the first driven guide member 141 and the second driven guide member 143 are accommodated in the groove portion and are not always in contact with the sheet P. Further, when the sheet P passes through the shortest conveyance path, the sheet P does not contact the first driven guide member 141 and the second driven guide member 143. On the other hand, when the sheet P does not follow the shortest conveyance path, the sheet P contacts either the first driven guide member 141 or the second driven guide member 143 and is guided to the shortest conveyance path.

  In the first drive roller 104 and the second drive roller 106 shown in FIG. 5, both end portions of the roller shafts 104a and 106a are supported by the upper plate 119 via bearings (not shown).

  In the first pressure roller 105 shown in FIG. 5, both end portions of the roller shaft 105a are supported by the pressure plate 112 via bearings (not shown). The first pressure roller 105 is biased by a first pressure spring 109 between the pressure plate 112 and a bearing (not shown). Thereby, the first pressure roller 105 is pressed against the first drive roller 104, thereby forming the first nip portion N11. In this embodiment, the biasing force of the first pressure spring 109 is set so that the total roller pressing force is about 98 N (10 kgf).

  In the second pressure roller 107 shown in FIG. 5, both end portions of the roller shaft 107a are supported by the pressure plate 112 via bearings (not shown). The second pressure roller 107 is biased by a second pressure spring 108 between the pressure plate 112 and a bearing (not shown). As a result, the second pressure roller 107 is pressed against the second drive roller 106, thereby forming the second nip portion N12. In this embodiment, the urging force of the second pressure spring 108 is set so that the applied pressure is about 98 N (10 kgf).

(Description of drive configuration)
7 and 8, the motor gear MG1 of the drive motor M1, which is a drive source (drive means), causes the first drive roller 104 to rotate by receiving rotational drive via the drive transmission gears 123, 124, 125, 126. Is done. The second drive roller 106 is rotated by receiving rotational driving via the drive transmission gears 123, 127, 128, and 129.

  The first pressure roller 105 and the second pressure roller 107 that are pressed against the first drive roller 104 and the second drive roller 106 shown in FIG. 7 are rotated by the first drive roller 104 and the second drive roller 106, respectively. Follow and rotate.

  The drive transmission gear 124 is provided with a one-way clutch (not shown). The one-way clutch is locked when the first drive roller 104 rotates in the conveyance direction of the sheet P, and transmits the drive of the drive motor M1 to the first drive roller 104.

  Further, the second drive roller 106 shown in FIG. 7 rotates at substantially the same conveying speed as the entrance roller pair 503. The first drive roller 104 is generated upstream of the first drive roller 104 when the conveyance speed is lower than that of the second drive roller 106 and a size parallel to the conveyance direction of the maximum sheet P that can be passed is passed. The conveyance speed is set so that the sheet P is not bent by the loop.

  In this embodiment, the conveyance speed of the first drive roller 104 is set to be about 2% smaller than the conveyance speed of the second drive roller 106.

  As shown in FIG. 8, the drive gear 104G2 is fixed to the other end of the first drive roller 104, and is connected to the torque limiter 131 via the drive transmission gear 130. Here, the torque limiter 131 only needs to apply a driving load to the first driving roller 104, and may be an electromagnetic brake, a brake pad, or the like.

  In the present embodiment, when the same sheet P exists in both the first nip portion N11 and the second nip portion N12 by the torque limiter 131, the torque limiter is adjusted so that the tension applied to the sheet P is about 68 N (7 kgf). Setting value is set. The set value of the torque limiter 131 is set in a range in which a sufficient tension is applied to the sheet P and no damage is applied to the sheet P.

  Next, the operation when the sheet P is conveyed to the sheet pulling and conveying apparatus will be described. The sheet P is guided by the inlet guides 102 and 121 in the sheet pulling and conveying apparatus 101 and nipped by the first nip portion N11 of the sheet pulling and conveying apparatus 101. The sheet P is conveyed at the conveyance speed set to the first nip portion N11 until it is nipped by the first nip portion N11 to the second nip portion N12. In this embodiment, the rotational speed of the drive motor M1 is set so that the conveyance speed is 294 mm / s in the first nip portion N11.

  Next, when the sheet P is nipped by the second nip portion N12 of the sheet pulling and conveying apparatus 101, the sheet P is conveyed by the second nip portion N12 at a higher conveyance speed than the first nip portion N11. In the present embodiment, when the first nip portion N11 is transported at a transport speed of 294 mm / s, the second nip portion N12 is set to have a transport speed of 300 mm / s. At this time, since the transport speed is faster in the second nip portion N12 on the downstream side in the transport direction than in the first nip portion N11 on the upstream side, the one-way clutch rotates idly.

  That is, since the drive is not transmitted to the first drive roller 104, the first roller pair 104 and 105 of the sheet pulling and conveying apparatus 101 rotates following the sheet P conveyed by the second roller pair 106 and 107.

  Since the first drive roller 104 is connected to the load means 131 via the drive gear 104G2 and the drive transmission gear 130, a torque load is generated to rotate the first drive roller 104. As a result, the sheet P is conveyed while tension is generated between the first roller pair 104 and 105 and the second roller pair 106 and 107.

  Tension is applied to the sheet P when the sheet P forms the shortest conveyance path between the first nip portion N11 and the second nip portion N12. Further, when the sheet P forms the shortest path, the sheet P is wound around the first driving roller 104 and the second driving roller 204. When the sheet P has a loop between the first nip portion N11 and the second nip portion N12 of the sheet pulling and conveying apparatus 101, the sheet P does not form the shortest conveyance path, and no tension is applied to the sheet P.

  Further, since the sheet P is conveyed by the second nip portion N12 at a faster conveyance speed than the first nip portion N11, the sheet P is nipped and conveyed by the first nip portion N11 and the second nip portion N12. The loop size gradually decreases. On the other hand, when the first nip portion N11 and the second nip portion N12 reach and there is a loop, no tension is applied to the leading end portion of the sheet P, so that the sheet P cannot be expected to be effectively stretched.

  That is, since the sheet P is conveyed by the shortest conveyance path, time for eliminating the loop of the sheet P is eliminated, tension can be applied over the entire sheet P, and effective elongation can be expected. it can. Further, when the sheet P is nipped by the first nip portion N11 and conveyed, the sheet P is guided by the first driven guide members 141A to 141G and the second driven guide members 143A to 143G and conveyed by the shortest conveyance path. The

(Wrinkle countermeasure and belt longitudinal arrangement)
However, there is a problem that wrinkles occur when the paper is transported by the arrangement of the roller pair and the transport belt shown in FIGS. The cause and countermeasure configuration will be described below.

  18 is a cross-sectional view of the sheet pulling and conveying apparatus 101 in FIG. 8 cut along a cross section A-A ′ in the present embodiment. The cross section of the sheet pulling / conveying apparatus 201 is the same as that of the sheet pulling / conveying apparatus 101, and therefore will be omitted.

(Occurrence of wrinkles)
As described above, the sheet P is conveyed while applying tension and winding force to the nip between the first roller pair 104, 105 and the second roller pair 106, 107. In order to convey the sheet P to the nip therebetween, the first driven guide members 141A to 141G and the second driven guide members 143A to 143G are guided. However, as shown in FIG. 18, when the sheet P is conveyed in a configuration in which the first driven guide member 143D and the second driven guide 141D are opposed to each other, the first roller pair 104, 105 and the first driven guide 143D, Wrinkles due to the speed difference occurred in the vicinity of the boundary line orthogonal to the sheet conveying direction of the second driven guide 141D.

  The cause of the speed difference will be described below. As the relationship of the conveyance speed applied to the sheet P, the conveyance speed of the sheet P conveyed at the nip of the first roller pair 104, 105 shown in the longitudinal view of FIG.

  A region A shown in FIG. 18 is a region where the first driven guide 143D is wound around the first roller 104, and the second driven guide 141D is wound around the outer shape of the first driven guide 143D. Here, it is set as the conveyance speed V2 by 1st driven guide 143D and 2nd driven guide 141D. The external speed of the first driven guide 143D in the range where the first driven guide 143D is wound around the first roller 104 is stably conveyed at a value equivalent to V1. Similarly, the outer speed of the second driven guide 141D in the range where the second driven guide 141D is wound around the first roller 105 is stably conveyed at a value equivalent to V1.

  However, in the region A shown in FIG. 18, the second driven guide 141D is in a state of being hooked on the outer shape of the first driven guide 143D, and the conveyance speed V2 becomes unstable with respect to V1. Factors that cause instability of the speed include the material thickness of the first driven guide member 142 and the second driven guide member 141, the tension between the two, and the like. Accordingly, in the region A, the conveyance speed applied to the sheet P becomes V1> V2 in the vicinity of the first rollers 104 and 105, the first driven guide 143D, and the second driven guide 141D, so that the sheet P is wrinkled. .

(Belt longitudinal arrangement as a measure against wrinkles)
A configuration for preventing wrinkles due to the speed difference applied to the sheet P will be described below. FIG. 19 is a perspective view of the sheet pulling and conveying apparatuses 101 and 201 of the present embodiment. FIG. 20 is a front view of the sheet pulling and conveying apparatus 101, 201 of this embodiment. 21 is a cross-sectional view of the sheet pulling and conveying apparatus 101 cut along cutting lines BB ′ and CC ′ in FIG.

  In this embodiment, in order to reduce the speed difference in the vicinity of the first rollers 104 and 105, the first driven guide 143D, and the second driven guide 141D, as shown in FIG. The first driven guides 143 </ b> A to 143 </ b> C and the second driven guides 141 </ b> A to 141 </ b> D are not opposed to each other and are arranged in a comb shape in a direction orthogonal to the sheet P conveyance direction. As shown in FIG. 19, the comb-like arrangement indicates that the first driven guides 143A to 143C and the second driven guides 141A to 141D are arranged at different positions in a direction orthogonal to the sheet conveying direction. .

  The first driven guides 143A to 143C and the second driven guides 141A to 141D arranged in a comb shape will be further described.

The first rollers 104 and 105 have grooves 104A to 104G and grooves 105A to 105G, respectively. The first driven guides 143A to 143C are rotatably arranged in grooves 105B, 105D, and 105F provided on the first roller 104, respectively. Similarly, the second driven guides 141 </ b> A to 141 </ b> C are rotatably disposed in grooves 104 </ b> B, 104 </ b> D, and 104 </ b> F provided on the first roller 104. Here, the first roller 104 has grooves 104B, 104D, and 104F at positions facing the first driven guides 143A to 143C, respectively. The first driven guides 143A to 143C that rotate are slid by the first roller 104. Avoid rubbing.

  As a result, the occurrence of wrinkles on the sheet P due to the difference in the conveyance speed as shown in FIG. 18 can be avoided. Similarly to the first rollers 104 and 105, the second rollers 106 and 107 have grooves 106A to 106G and 107A to 107G with respect to the first driven guides 143A to 143C and the second driven guides 141A to 141C, respectively. (Not shown).

  Further, as shown in FIG. 20, similarly, the sheet pulling and conveying apparatus 201 does not make the first driven guides 142 </ b> A to 142 </ b> C and the second driven guides 144 </ b> A to 144 </ b> D face each other, Arrange in a shape.

  Next, the cross-sectional arrangement of the first driven guide 143 and the second driven guide 141 will be described with reference to FIG.

  Regions B and C in FIG. 21 correspond to region A in FIG. Wrinkles occurred in the sheet P in the area A described with reference to FIG. On the other hand, as shown in FIG. 21, in the regions B and C, by eliminating the driven guides facing the first driven guide 143B and the second driven guide 141B, the occurrence of the conveyance speed difference V1> V2 is prevented. Thereby, the generation of wrinkles is reduced.

  By pulling the sheet P while bending, it is possible to expect a larger elongation of the sheet P than when the sheet P is pulled straight. The difference in elongation of the sheet P was compared and examined through experiments. An outline of the experiment and experimental data are shown in FIGS. First, a sheet having a certain thickness and having a certain width was wound around a driving roller at 0 °, 23 °, and 45 ° and pulled with a constant force (FIG. 9a). The sheet elongation at this time is shown in FIG. 9b. As a result, it was found that greater elongation can be expected by pulling the sheet P while bending the sheet P than when the sheet P is pulled straight in the conveyance direction (FIG. 9b).

  5 and 6 show a configuration in which the sheet P is pulled while being bent. A straight line connecting the center of the first drive roller 104 and the center of the first pressure roller 105 is defined as a roller center line R1. Subsequently, a straight line connecting the center of the second drive roller 106 and the center of the second pressure roller 107 is defined as a roller center line R2.

  5 and 6, the second roller pairs 106 and 107 are inclined with respect to the first roller pairs 104 and 105 arranged perpendicular to the transport path C2. The center line R1 and the transport path C1 may be perpendicular to each other, the center line R2 and the transport path C2 may be perpendicular to each other, and the center line R1 and the center line R2 may not be parallel to each other.

  5 and 6, a second winding angle Θ2 that is an angle at which the sheet P is wound around the second drive roller 106, and a first winding angle Θ1 that is an angle at which the sheet P is wound around the first drive roller 104, To do. In this embodiment, the first roller pair 104, 105 is perpendicular to the transport direction, so Θ1 = 0.

  At this time, the sheet P is wound around the second driving roller 106 with the second winding angle Θ2, so that bending stress is applied to the sheet P simultaneously with the tensile stress. When the tensile stress and the bending stress exceed the yield point of the sheet P, plastic elongation occurs with respect to the sheet P. The object is to obtain plastic elongation of the sheet P while reducing the amount of humidification. Further, the first winding angle Θ1 may be larger than the second winding angle Θ2, or the first wrapping angle Θ1 and the second wrapping angle Θ2 may be equivalent. Furthermore, although the conveyance path C2 is on the side facing the first drive roller 104, it may be on the first drive roller side.

  5, 6, 19, and 20, the sheet P, the first drive roller 104 and the second drive roller 204 around which the sheet P is wound, and the first nip portion N11 and the second nip portion N12 A first pressure roller 105 and a second pressure roller 107 that are in contact with the sheet P, and first driven guide members 141 to 141D and second driven guide members 143A to 143D that guide the sheet P to the shortest conveyance path; Describes the mechanical relationship in. First, a force acts between the surfaces of the first driven guide members 141 to 141D and the groove portions of the first drive roller 104 and the second pressure roller 107.

  When the first driven guide members 141A to 141D are arranged in the grooves provided in the first driving roller 104 and the second pressure roller 107 to generate a contact area, internal tension is applied to the first driven guide members 141 to 141D. The result is a mutual grip force G1 in the contact area. On the other hand, when the sheet P deviates from the shortest conveyance path and comes into contact with the first driven guide members 141A to 141D having the internal tension force, at the contact boundary between the sheet P and the first driven guide members 141A to 141D, each other. The grip force G2 is activated.

  At this time, the internal tension force of the first driven guide members 141A to 141D was adjusted so that the mutual grip G1 was larger than the mutual grip force G2 (G1 ≧ G2). By maintaining G1 ≧ G2, the first driven guide members 141A to 141D are not greatly deformed by the urging force of the sheet P, and the sheet P can be guided to the shortest conveyance path. Further, the relationship between the sheet P, the first driven guide members 141A to 141D, the first drive roller 104, and the second pressure roller 107 has been described. The sheet P, the second driven guide members 143A to 143D, and the first pressure roller The same applies to the relationship between the roller 105 and the second drive roller 106.

  In addition, assuming a case where a pair of a driving roller and a pressure roller that urges the driving roller to form a nip and a plurality of roller pairs are provided, the driving roller, one of the plurality of rollers, and the driving roller And a force acting on a driven guide member disposed on one of the plurality of rollers and a force acting on a driven guide member disposed on the sheet P, the driving roller, and one of the plurality of rollers. Gb satisfying Gd ≧ Gb, or the force acting on the pressure roller and the other roller of the plurality of rollers and the driven guide member disposed on the pressure roller and the other roller of the plurality of rollers A configuration that satisfies Gp ≧ Gq in Gp and the force Gq acting on the sheet P, the pressure roller, and the driven guide member disposed on one of the plurality of rollers may be used.

  Hereinafter, the relationship between the plurality of sheet pulling and conveying apparatuses (101, 201) will be described. In this embodiment, a configuration in which a plurality of sheet pulling and conveying apparatuses and two sheet pulling and conveying apparatuses 101 and 201 are provided is illustrated.

  The reason for providing a plurality of sheet pulling and conveying devices is to sufficiently obtain the pulling effect of the sheet P. The tensile effect of the sheet P can also be increased by increasing the tension between the first nip portion N11 and the second nip portion N12. However, if the tension is excessively increased and the sheet P is suddenly stressed, damage to the sheet P is increased and the quality of the product may be deteriorated. Further, since the load for the second drive roller 106 to be pulled out from the first nip portion N11 becomes large, slip occurs in the second nip portion N12, resulting in variations in the tensile effect of the sheet P and variations in the conveyance speed. There is a possibility that.

  Therefore, by providing a plurality of sheet pulling and conveying devices and pulling the sheet P stepwise, a tensile effect can be imparted to the sheet P without these problems. In the present embodiment, for example, if a tension of 98 N (10 kgf) or more is applied, the damage to the sheet P increases, and the quality of the product is deteriorated. Therefore, the tension setting values of the torque limiters 131, 231 and 331 are about 68N (7 kgf), and a plurality of sheet pulling and conveying apparatuses 101 and 201 are provided.

  Further, the curved shape Pwave generated at the upper or lower side of the sheet P shown in FIG. 11, that is, the end in the width direction orthogonal to the conveying direction is referred to as end undulation, and among these, the gap between the measurement platen 650 and the gap is measured. The maximum Xmax was used as the corrugation amount, and the maximum Ymax among the distances from the measurement surface plate 650 at the four corner ends of the sheet P was used as the object of evaluation.

  FIG. 10 shows the results of an experiment for confirming the effect of the tension applying device in the present example conducted by the present inventors.

  As an experimental condition, a sheet moisture amount of 7% or more immediately after passing through the sheet humidifying apparatus 400 is set with 70% toner image placed on the front side of the sheet P and no toner image placed on the back side.

  The sheet moisture content in this example was measured by the present inventors using the sheet P immediately after the sheet P passed through the sheet wavy correction device 900 and was discharged onto the discharge tray 565. In this example, a microwave paper moisture meter was used.

  FIG. 10A shows the amount of undulation in the sheet P when the sheet P immediately after passing through the fixing device 100 does not pass through the sheet humidifying device 400 and does not pass through the sheet pulling and conveying devices 101 and 201. In FIG. 10B, the sheet P immediately after passing through the fixing device 100 is passed through the sheet humidifying device 400 so that the moisture content of the sheet is largely adjusted, and then the sheet P is passed through the sheet pulling and conveying devices 101 and 201. The amount of undulation in the sheet P when it is pulled straight is shown.

  In FIG. 10C, the sheet P immediately after passing through the fixing device 100 is passed through the sheet humidifying device 400, so that the moisture content is adjusted to be small, and then the sheet P is passed through the sheet pulling and conveying devices 101 and 201. Shows the amount of undulation in the sheet P when the wire is pulled straight.

  In FIG. 10D, the sheet P immediately after passing through the fixing device 100 is passed through the sheet humidifying device 400 so that the moisture content of the sheet is reduced and then the first driven guide member 141 and the second driven guide shown in FIG. The amount of undulation in the sheet P when the sheet P is pulled while being bent by passing the sheet pulling and conveying apparatus 101, 201 having no member 143 and winding the sheet P around the second driving roller 106 and pulling the sheet P is shown. .

  In FIG. 10E, the sheet P immediately after passing through the fixing device 100 is passed through the sheet humidifying device 400, so that the moisture content of the sheet is reduced and the first driven guide member 141 and the second driven guide shown in FIG. When the sheet P is conveyed by the shortest conveyance path by passing through the sheet pulling and conveying apparatuses 101 and 201 having the member 143, and then wound around the second driving roller 106 and pulled, thereby pulling the sheet P while bending it. The amount of undulation in the sheet P is shown.

  FIG. 11 shows a state in which the sheet P immediately after passing through the fixing device 100 passes through the sheet humidifying device 400 and also passes through the sheet wavy correction device 900, the length Ledge [mm] of the end portion of each sheet P, and the central length Lcenter [ mm], the maximum waviness amount Xmax [mm], and the maximum curl amount Ymax [mm] are shown.

  As shown in FIG. 10A, immediately after passing through the fixing device, the extension amount of the center length Lcenter of the sheet P is 0.0 mm, whereas the extension amount of the end length Ledge is 0.6 mm. The end is longer than the center by 0.6 mm. As a result, the maximum waving amount Xmax was as large as 3.3 mm. The maximum curl amount Ymax was 5.0 mm.

  Next, as shown in FIG. 10B, in the state where the sheet P is greatly humidified and straightly pulled immediately after passing through the fixing device, the center length Lcenter of the sheet P is extended by 0.6 mm, and a sufficient tensile effect is obtained. As a result, the maximum corrugation amount Xmax was reduced to about 1/8, 0.5 mm. However, the maximum curl amount Ymax increased to 30 mm.

  Next, as shown in FIG. 10C, in the state where the sheet P is slightly humidified immediately after passing through the fixing device and pulled straight, the center length Lcenter of the sheet P is extended by 0.2 mm, and a sufficient tensile effect is obtained. The maximum waving amount Xmax remained relatively large at 3.0 mm. The maximum curl amount Ymax was 6.0 mm.

  Next, as shown in FIG. 10 (d), the sheet P is adjusted to be slightly humidified immediately after passing through the fixing device, and without having the first driven guide member 141 and the second driven guide member 143, the sheet P is moved to the roller pair. In a state where the sheet P is pulled while being bent by being wound around one side, the center length Lcenter of the sheet P is extended by 0.2 mm, a sufficient tensile effect cannot be obtained, and the maximum undulation amount Xmax is 3.0 mm. And remained relatively large. The maximum curl amount Ymax was 7.0 mm.

  Next, as shown in FIG. 10 (e), the sheet P is adjusted to be slightly humidified immediately after passing through the fixing device, and the first driven guide member 141 and the second driven guide member 143 are used to adjust the sheet P to one side of the roller pair. In a state where the sheet P is pulled while being bent without being wound around the loop, the center length Lcenter of the sheet P is extended by 0.4 mm, a sufficient tensile effect is obtained, and the maximum undulation amount Xmax is 1.0 mm. It decreased to about 1/3. The maximum curl amount Ymax was 6.0 mm.

  That is, according to the CPU in the image forming apparatus, the sheet information sent to the control unit having the memory, the image density information of the toner image on the image-formed sheet P, the temperature and humidity information by the environmental sensor 500D, and the humidification amount information. The curl can be adjusted for each sheet.

  In this way, the corrugation and curl of the sheet are corrected, so that the occurrence of a conveyance failure such as a jam is not likely to occur, and the sheet can be stably conveyed, and further, the sheet can be stacked on the discharge tray. it can.

  In this embodiment, the elastic rubbers 105b and 107b of the first pressure roller 105 and the second pressure roller 107 have a width of 100 mm. However, the present invention is not limited to this. The outer diameters of the elastic rubbers 105b and 107b of the first pressure roller 105 and the second pressure roller 107 change at least in part in the rotation axis direction, and the central portion in the rotation axis direction is more than the end in the rotation axis direction. You may enlarge it.

  In the present embodiment, the first driven guide member 141 and the second driven guide member 143 are endless guide members, but the present invention is not limited to this. Either the first driven guide member 141 or the second driven guide member 143 may be an endless guide member, and the other may be a linear, planar, or three-dimensional guide member that guides the sheet.

  As described above, a plurality of sheet pulling and conveying devices are provided, and the quality of the product is deteriorated by pulling the sheet P while eliminating the loop by conveying the sheet with the shortest conveying path using the conveying member. In addition, the tensile effect of the sheet can be sufficiently obtained, and the waviness of the sheet can be improved. In order to perform undulation correction, the sheet is conventionally humidified and tension is applied straight to the sheet. However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified.

  Therefore, by adding a configuration that bends the sheet to a configuration that pulls the sheet straight, the sheet is pulled while bending, and the amount of undulation is reduced while reducing the amount of humidification. Since the amount of undulation can be reduced while reducing the amount of humidification, the occurrence of curling due to humidification can be reduced.

  Also, the design of the transport path is easier than in other embodiments. Therefore, it is possible to obtain the effect of reducing the undulation by winding while reducing the distance between the pair of rollers on the upstream side in the transport direction and the pair of rollers on the downstream side in the transport direction. However, when a plurality of sheet pulling and conveying apparatuses are arranged in series and the roller pair on the upstream side in the conveying direction and the roller pair on the downstream side in the conveying direction are not parallel to each other, a conveyance path between the sheet pulling and conveying apparatuses is separately provided. It is necessary to provide it.

[Example 2]
A second embodiment will be described with reference to FIGS. In this embodiment, since the same configuration is adopted except that only the sheet pulling and conveying apparatus in the sheet processing apparatus mechanism of the first embodiment is changed, the description is omitted.

  12 and 13, when a tension is applied to the sheet P, the sheet forms a conveyance path between the nip portion N11 and the nip portion N12. The sheet P is wound around the first drive roller 104 and the second drive roller 204 while applying tension to the sheet P by the two pairs of rollers that form the nip portion N11 and the nip portion N12.

  12 and 13 show a configuration in which the sheet P is pulled while being bent. A straight line connecting the center of the first drive roller 104 and the center of the first pressure roller 105 is defined as a roller center line R1. Subsequently, a straight line connecting the center of the second drive roller 106 and the center of the second pressure roller 107 is defined as a roller center line R2. Further, by applying tension to the sheet P, the sheet P forms a tensile conveyance path C1 on the downstream side in the conveyance direction from the first nip portion N11. Further, tension is applied to the sheet on the upstream side in the conveyance direction from the second nip portion N12, thereby forming a tensile conveyance path C2 formed by the sheet.

  12 and 13, the second roller pair 106 and 107 are inclined with respect to the first roller pair 104 and 105 arranged perpendicular to the conveying direction, and the second nip portion N12 is the first The configuration has a right side with respect to the nip portion N11. The center line R1 and the transport path C1 may not be perpendicular to each other, the center line R2 and the transport path C2 may not be perpendicular to each other, and the center line R1 and the center line R2 may not be parallel to each other.

  12 and 13, a second winding angle Θ <b> 2 that is an angle at which the sheet P is wound around the second drive roller 106, and a first winding angle Θ <b> 1 that is an angle at which the sheet P is wound around the first drive roller 104, To do. In the present embodiment, the second winding angle Θ2 is larger than the first winding angle Θ1.

  At this time, the sheet P is wound around the second drive roller 106 with the second winding angle Θ2, so that a large bending stress is applied to the sheet P simultaneously with a large tensile stress. When the tensile stress and the bending stress exceed the yield point of the sheet P, plastic elongation occurs with respect to the sheet P. The object is to obtain plastic elongation of the sheet P while reducing the amount of humidification. Further, the first winding angle Θ1 may be larger than the second winding angle Θ2, or the first wrapping angle Θ1 and the second wrapping angle Θ2 may be equivalent.

  As described above, a plurality of sheet pulling and conveying devices are provided, and the quality of the product is deteriorated by pulling the sheet P while eliminating the loop by conveying the sheet with the shortest conveying path using the conveying member. In addition, the tensile effect of the sheet can be sufficiently obtained, and the waviness of the sheet can be improved. In order to perform undulation correction, the sheet is conventionally humidified and tension is applied straight to the sheet.

  However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified. Therefore, by adding a configuration that bends the sheet to a configuration that pulls the sheet straight, the sheet is pulled while bending, and the amount of undulation is reduced while reducing the amount of humidification. Since the amount of undulation can be reduced while reducing the amount of humidification, the occurrence of curling due to humidification can be reduced.

  Further, a larger winding angle can be obtained as compared with the first embodiment, and a larger paper elongation can be expected than the result. By providing a large winding angle, an effect equivalent to that of the first embodiment or more can be obtained.

Example 3
Example 3 will be described with reference to FIG. In this embodiment, since the same configuration is adopted except that only the sheet pulling and conveying apparatus in the sheet processing apparatus mechanism of the first embodiment is changed, the description is omitted.

  When tension is applied to the sheet P, the sheet forms a conveyance path between the nip portion N11 and the nip portion N12. The conveyance path approximates the shortest path connecting the nip portion N11 and the nip portion N12. The sheet P is wound around the first drive roller 104 and the second drive roller 204 while applying tension to the sheet P by the two pairs of rollers that form the nip portion N11 and the nip portion N12.

  FIG. 15 shows a configuration in which the sheet P is pulled while being bent. A straight line connecting the center of the first drive roller 104 and the center of the first pressure roller 105 is defined as a roller center line R1. Subsequently, a straight line connecting the center of the second drive roller 106 and the center of the second pressure roller 107 is defined as a roller center line R2.

  In FIG. 15, the first roller pair 104, 105 and the second roller pair 106, 107 are arranged perpendicular to the conveying direction, and the second nip portion N12 is on the right side with respect to the first nip portion N11. It has the composition to have. The center line R1 and the transport path C1 may not be perpendicular to each other, the center line R2 and the transport path C2 may not be perpendicular to each other, and the center line R1 and the center line R2 may be parallel to each other.

  In FIG. 15, a second winding angle Θ <b> 2 that is an angle at which the sheet P is wound around the second drive roller 106, and a first winding angle Θ <b> 1 that is an angle at which the sheet P is wound around the first drive roller 104. In this embodiment, the second winding angle Θ2 is equal to the first winding angle Θ1.

  At this time, when the sheet P is wound around the first driving roller 104 with the first winding angle Θ1, or when the sheet P is wound around the second driving roller 106 with the second winding angle Θ2, a large tensile stress is applied to the sheet P. At the same time, a large bending stress is applied. When the tensile stress and the bending stress exceed the yield point of the sheet P, plastic elongation occurs with respect to the sheet P. The object is to obtain plastic elongation of the sheet P while reducing the amount of humidification.

  As described above, a plurality of sheet pulling and conveying devices are provided, and the quality of the product is deteriorated by pulling the sheet P while eliminating the loop by conveying the sheet with the shortest conveying path using the conveying member. In addition, the tensile effect of the sheet can be sufficiently obtained, and the waviness of the sheet can be improved. In order to perform undulation correction, the sheet is conventionally humidified and tension is applied straight to the sheet.

  However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified. Therefore, by adding a configuration that bends the sheet to a configuration that pulls the sheet straight, the sheet is pulled while bending, and the amount of undulation is reduced while reducing the amount of humidification. Since the amount of undulation can be reduced while reducing the amount of humidification, the occurrence of curling due to humidification can be reduced.

  Moreover, the effect equivalent to Example 1, 2 can be acquired, although a compact structure can be implemented compared with Example 1,2.

Example 4
As illustrated in FIG. 16, a configuration in which the sheet P is wound around a roller 152 that is fixed to the roller support base 151 so as to be rotatable, and the sheet is stretched to obtain a sheet elongation will be described.

  The sheet P is conveyed to the sheet pulling and conveying apparatus shown in FIG. The sheet P passes through the first nip portion N11 formed by the first drive roller 104 and the first pressure roller 105. The sheet P passes through the surface of the roller 152 through a sheet guide (not shown). The sheet P passes through the second nip portion N12 formed by the second drive roller 106 and the second pressure roller 107. When the sheet P is simultaneously passing through the first nip portion N11 and the second nip portion N12, a tension force is applied to the sheet P. When a tension force is applied to the sheet P, the sheet P forms a conveyance path C1 between the first nip portion N11 and the roller 152.

  Further, the sheet P forms a transport path C2 between the roller 152 and the second nip portion N12. In the conveyance path C1, the sheet P is wound around the first driving roller 104 and the roller 152 at the first winding angle Θ1. In the conveyance path C2, the sheet P is wound around the roller 152 and the second drive roller 106 at the second winding angle Θ2. Therefore, in the roller 152, the sheet P is wound by the sum of the conveyance path C1 and the conveyance path C2. Therefore, the sheet P is wound at the roller 152 by Θ1 + Θ2 obtained by adding the first wrapping angle Θ1 and the second wrapping angle Θ2.

  At this time, the sheet P is wound around the roller 152 with an angle of Θ1 + Θ2 so that bending stress is applied to the sheet P simultaneously with the tensile stress. When the tensile stress and the bending stress exceed the yield point of the sheet P, plastic elongation occurs with respect to the sheet P. The object is to obtain plastic elongation of the sheet P while reducing the amount of humidification.

  Also, a configuration in which the first winding angle Θ1 is larger than the second winding angle Θ2 or a configuration in which the second winding angle Θ2 is larger than the first winding angle Θ1 or the first winding with respect to the roller 152. Any of the configurations having a large winding angle (not shown) with respect to any of the winding angle Θ1, the second winding angle Θ2, and the sum of the first winding angle Θ1 and the second winding angle Θ2. Such a configuration is also acceptable.

  FIG. 16 shows a configuration in which the sheet P is pulled while being bent. A straight line connecting the center of the first drive roller 104 and the center of the first pressure roller 105 is defined as a roller center line R1. Subsequently, a straight line connecting the center of the second drive roller 106 and the center of the second pressure roller 107 is defined as a roller center line R2.

  In FIG. 16, the first roller pair 104, 105 and the second roller pair 106, 107 are arranged perpendicular to the transport direction, and the first nip portion N11 and the second nip portion N12 are on the transport shaft. And the sheet P is wound around the rollers 152 disposed between the first nip portion N11 and the second nip portion N12. Further, the center line R1 and the transport path C1 are not perpendicular to each other, or the center line R2 and the transport path C2 are not perpendicular to each other, or the center line R1 and the center line R2 are parallel to each other, and the first nip portion N11 A winding member (not shown) including a roller 152 and a sheet guide (not shown) may be disposed between the second nip portion N12 and the second nip portion N12.

  As described above, the tension applying device of this embodiment is passed, and the sheet is conveyed in the shortest conveyance path by using the conveyance member, and the central portion in the sheet width direction is wound in the conveyance direction while eliminating the loop. By pulling, the difference in sheet length between the end portion and the central portion can be reduced and the waviness can be improved.

  As described above, by providing a plurality of sheet pulling and conveying devices and pulling the sheet P, the sheet pulling effect can be sufficiently obtained without deteriorating the quality of the product, and the sheet waviness can be improved. Can do. In order to perform undulation correction, the sheet is conventionally humidified and tension is applied straight to the sheet. However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified.

  Therefore, by adding a configuration that bends the sheet to a configuration that pulls the sheet straight, the sheet is pulled while bending, and the amount of undulation is reduced while reducing the amount of humidification. Since the amount of undulation can be reduced while reducing the amount of humidification, the occurrence of curling due to humidification can be reduced.

  Further, an elongation corresponding to Example 1 can be obtained. However, since the distance between the roller and the roller pair and the distance between the roller pairs are increased, the chance of applying tension to the sheet P is reduced. Therefore, it is necessary to ensure the transportability of the sheet P while reducing the distance between the rollers and making the sheet guide compact.

Example 5
As shown in FIG. 17, a configuration in which the sheet P is wound around the second drive belt 146 and pulled to obtain the sheet elongation will be described.

  The second drive endless belt 126, the second drive roller 106, the second drive side endless belt roller 116, and the second drive side pressure pad 136 constitute a second drive belt 146. The second pressure endless belt 127, the second drive roller 107, the second pressure side endless belt roller 117, and the second pressure side pressure pad 137 constitute a second pressure belt 147. In addition, since the upstream roller pair and the like correspond to the configuration of the first embodiment, detailed description thereof is omitted.

  The sheet P is conveyed to the sheet pulling and conveying apparatus shown in FIG. The sheet P passes through the first nip portion N11 formed by the first drive roller 104 and the first pressure roller 105. The sheet P passes through a sheet guide (not shown) and passes through a second nip portion N12 formed by the second drive belt 146 and the second pressure belt 147. When the sheet P is simultaneously passing through the first nip portion N11 and the second nip portion N12, a tension force is applied to the sheet P.

  When a tension force is applied to the sheet P, the sheet P forms a conveyance path C1 on the downstream side of the first nip portion N11. Further, on the upstream side of the second nip portion N12, the sheet P forms a conveyance path C2. In FIG. 17, the transport path C1 and the transport path C2 are on the same straight line. In the conveyance path C2, the sheet P is wound around the second drive belt 146 at the second winding angle Θ2.

At this time, when the sheet P is wound around the second drive belt 146 with the second winding angle Θ2, bending stress is applied to the sheet P simultaneously with the tensile stress. When the tensile stress and the bending stress exceed the yield point of the sheet P, plastic elongation occurs with respect to the sheet P. The object is to obtain plastic elongation of the sheet P while reducing the amount of humidification.
Further, the first winding angle Θ1 may be larger than the second winding angle Θ2, or the first wrapping angle Θ1 and the second wrapping angle Θ2 may be equivalent.

  FIG. 17 shows a configuration in which the sheet P is pulled while being bent. A straight line connecting the center of the first drive roller 104 and the center of the first pressure roller 105 is defined as a roller center line R1. Subsequently, a straight line connecting the center of the second drive roller 106 and the center of the second pressure roller 107 is defined as a roller center line R2.

  In FIG. 17, the second belt pairs 148 and 149 are inclined with respect to the first roller pairs 104 and 105 arranged perpendicular to the transport path C2. The first roller pair 104, 105 and the second belt pair 148, 149 may be replaced with each other. Further, the first roller pair 104, 105 may be a configuration equivalent to the second belt pair 148, 149.

  In addition, the center line R1 and the transport path C1 may be perpendicular to each other, the center line R2 and the transport path C2 may be perpendicular to each other, and the center line R1 and the center line R2 may not be parallel to each other. The center line R1 and the transport path C1 may not be perpendicular to each other, the center line R2 and the transport path C2 may not be perpendicular to each other, and the center line R1 and the center line R2 may be parallel to each other. The center line R1 and the transport path C1 may not be perpendicular to each other, the center line R2 and the transport path C2 may not be perpendicular to each other, and the center line R1 and the center line R2 may be parallel to each other.

  As described above, the tension applying device of this embodiment is passed, and the sheet is conveyed in the shortest conveyance path by using the conveyance member, and the central portion in the sheet width direction is wound in the conveyance direction while eliminating the loop. By pulling, the difference in sheet length between the end portion and the central portion can be reduced and the waviness can be improved. In order to perform undulation correction, the sheet is conventionally humidified and tension is applied straight to the sheet. However, there is a problem that curling occurs when a sheet having an image density difference between the front and back sides is humidified.

  Therefore, by adding a structure for bending the sheet to the structure for pulling the sheet straight, the sheet is pulled while bending, and the amount of undulation is reduced while reducing the amount of humidification. Since the amount of undulation can be reduced while reducing the amount of humidification, the occurrence of curling due to humidification can be reduced.

  In addition, since the roller pair configuration in the first to fourth embodiments is replaced with the belt pair configuration, the conveying force is improved, and the elongation corresponding to the first embodiment can be obtained.

CL ... Electromagnetic clutch L ... Humidifying liquid, coating liquid M, M1, M2, M3, M32, M52, M61, M62, M63 ... Motor N, N1, N2, N4, N5, N6 ... Nip part P ... Sheet S ... Liquid Holding space T... Toner Pwave... Edge waviness Xmax... Wave amount Lcenter... Transport direction length Ledge in the center of the sheet... Transport direction length 100 at the end of the sheet 100. Fixing devices 101 and 201. DESCRIPTION OF SYMBOLS 103 ... Sheet sensor 104 ... 1st drive roller 105 ... 1st pressure roller 106 ... 2nd drive roller 107 ... 2nd pressure roller 110 ... Fixing roller 111 ... Pressure roller 123, 124, 125, 126, 127, 128 129, 130 ... drive transmission gear 131 ... load means 134 ... pressure release cams 141A-141G, 142A-1 42G, ... 1st driven guide member 143A-143G, 144A-144G ... 2nd driven guide member 151 ... Roller support stand 152,153, 154 ... Roller 400 ... Sheet humidifier 400A ... Water storage tank 400B ... Pump 400C ... Water supply pipe 400C1 ... branching sections 401, 402 ... humidifying roller pairs 403, 404, 409, 410 ... regulating rollers 405, 406, 407, 408 ... water supply roller 412 ... water supply 411a, 412a ... water supply hole 420 ... pressure spring 450 ... sheet humidifying device 451 ... Shutter 452 ... Jet outlet 500 ... Printer 500C ... Control part 500D ... Environmental sensor 510 ... Image forming part 600 ... Decal device 601 ... Curl correction part 603 ... Sponge roller 604 ... Rigid roller 609 ... Backup roller 800 ... Moisture application device 801 ... Application roller 802 ... Click-up roller 803,822 ... regulating member 804 ... Water roller 810, 810 ... spray nozzle 850 ... liquid holding member 900 ... sheet waviness correction apparatus 901C ... control region A, region B, region C

Claims (11)

A driven guide member having an endless shape;
A pressure roller having a groove for suspending the driven guide member;
A driving roller having a groove portion for forming a nip by urging the pressure roller and suspending the driven guide member;
Comprising one or a plurality of roller pairs in which the pressure roller and the driving roller are paired;
The driven guide member is suspended by the pressure roller and one roller of one or a plurality of roller pairs along a path for conveying the sheet, and the driven guide member is disposed along the path for conveying the sheet. The sheet processing is characterized in that the sheet is suspended by a driving roller and the other roller in one or a plurality of roller pairs, the sheet is conveyed by a nip between the driving roller and the pressure roller, and the sheet is guided by the driven guide member. apparatus. The depth of the groove portion applied to the pressure roller is larger than the thickness of the driven guide member, the driven guide member does not protrude from the surface of the pressure roller, and the depth of the groove portion applied to the drive roller. The depth is larger than the thickness of the driven guide member, and the driven guide member does not protrude from the surface of the drive roller,
The sheet processing apparatus according to claim 1. The driven guide member has an internal tension by being suspended by the pressure roller and one roller of the single or plural roller pairs, so that one of the sheet, the pressure roller, and the single or plural roller pairs is suspended. F2 is F1 in the relationship between the force F1 acting at the boundary with the surface of the roller and the force F2 acting at the boundary between the driven guide member, the pressure roller, and the surface of one of the roller pairs. It is the above,
The sheet processing apparatus according to claim 1 or 2. The driven guide member is suspended by the driving roller and one roller of the single or plural roller pairs and has an internal tension, so that the sheet, the driving roller, and the one or plural roller pairs of one roller F3 is greater than or equal to F4 in relation to the force F3 that works at the boundary with the surface and the force F4 that works at the boundary between the driven guide member, the drive roller, and the surface of one of a pair of rollers. It is characterized by
The sheet processing apparatus according to any one of claims 1 to 3. A driven guide member having an endless shape;
A guide member for guiding paper;
A pressure roller having a groove for suspending the driven guide member;
A driving roller that forms a nip by urging the pressure roller;
Comprising one or a plurality of roller pairs in which the pressure roller and the driving roller are paired;
The driven guide member is suspended by the pressure roller and one roller of one or a plurality of roller pairs along a path for conveying the sheet, and the sheet is moved closer to the driving roller than the path for conveying the sheet. A sheet processing apparatus comprising: a guide member disposed along a conveying path; a sheet is conveyed by a nip formed by a driving roller and a pressure roller; and the sheet is guided by the driven guide member and the guide member.
The depth of the groove portion applied to the pressure roller is larger than the thickness of the driven guide member, and the driven guide member does not protrude from the surface of the pressure roller.
The sheet processing apparatus according to claim 5. The driven guide member has an internal tension by being suspended by the pressure roller and one roller of the single or plural roller pairs, so that one of the sheet, the pressure roller, and the single or plural roller pairs is suspended. F5 is F6 in relation to the force F5 that works at the boundary with the surface of the roller and the force F6 that works at the boundary between the driven guide member, the pressure roller, and the surface of one of the roller pairs. It is the above,
The sheet processing apparatus according to claim 5 or 6. The recording material bending means is
A first roller pair that includes a rotatable first drive roller, and a first pressure roller that is in pressure contact with the first drive roller to form the first nip portion N11 and sandwich and convey the sheet;
A second driving roller that is rotatable, and a second pressure roller that is pressed against the second driving roller to form the second nip portion N12 and sandwiches and conveys the sheet. A second pair of rollers in
Have
Each of the front and back surfaces of the sheet at least once, the first roller pair,
The sheet processing apparatus according to claim 1, wherein the sheet is wound around the second roller pair. In the direction orthogonal to the sheet conveying direction, the driven guide member is
The sheet processing apparatus according to any one of claims 1 to 8, wherein the sheet processing apparatus is comb-shaped. Equipped with moisture adding means for adding moisture to the sheet,
10. The sheet processing apparatus according to claim 1, wherein the moisture adding unit is arranged upstream of the plurality of roller pairs in a sheet conveying direction. 11. It has curl correction means to correct the curl of the sheet,
11. The sheet processing apparatus according to claim 1, wherein the curl correcting unit is arranged downstream of the plurality of roller pairs in a sheet conveying direction.