JP2009120329A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device and its control method preventing abnormality of conveying (jamming) from being generated when paper is conveyed on a guide having a curved part and preventing reduction of productivity concerning abnormality of conveying (jamming). <P>SOLUTION: The image forming device has the curved guide for guiding the paper; a conveying roller arranged at an entrance part and an exit part of the guide and conveying the paper; and an input means for inputting direction information of a fiber constituting the paper. The conveying roller at at least entrance part of the conveying rollers has a nip pressure variation means for varying a nip pressure for nipping the paper, and the image forming device has a control means for controlling the nip pressure variation means so as to vary the nip pressure according to the direction information of the fiber input by the input means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly, to a paper conveying method.

  2. Description of the Related Art Conventionally, there has been known an image forming apparatus that includes a detecting unit that detects line information of a sheet on which a line is recorded as an attribute of a recording sheet, and changes a pickup pressure at the time of feeding according to the line information (for example, , See Patent Document 1).

There is also known an image forming apparatus that separates a sheet conveyed on a conveying belt using a separation claw and a spur that prevents the sheet from being lifted during separation on a conveying belt that conveys the sheet (for example, Patent Documents). 2).
JP 2000-356861 A JP 2005-247476 A

However, the image forming apparatus described in Japanese Patent Laid-Open No. 2005-228561 conveys paper at the time of paper feeding by changing the pickup pressure at the time of paper feeding based on detection information of a detection unit that detects attribute information (basis weight, streak) of transfer paper. Even though we can prevent abnormalities,
There is a problem that it is necessary to describe the attribute information such as basis weight, streak, etc. in advance on the transfer paper by barcode etc.
Also, when transfer paper in the longitudinal fiber direction is supplied, particularly when the longitudinal transfer paper is transported through a guide having a curved portion, the rigidity of the transport roller is caused by the rigidity in the transport direction derived from the longitudinal transfer paper. There is a problem that the conveyance resistance becomes larger than the conveyance force, the conveyance becomes impossible, and a conveyance abnormality (jamming) may occur.

Further, the image forming apparatus described in Patent Document 2 can separate and supply the horizontal paper,
When transfer paper in the longitudinal fiber direction is supplied, especially when the vertical transfer paper is transported through a guide having a curved portion, the transport roller transports due to the rigidity in the transport direction derived from the vertical transfer paper. There is a problem that conveyance resistance becomes larger than force, conveyance becomes impossible, and conveyance abnormality (jamming) may occur.

  The present invention has been made in view of the above problems, and prevents a conveyance abnormality (jamming) from occurring when a sheet is conveyed through a guide having a curved portion, and prevents a decrease in productivity related to the conveyance abnormality (jamming). It is an object of the present invention to provide an image forming apparatus and a control method thereof.

  The above object can be achieved by the following means.

(1) a curved guide for guiding paper;
A transport roller disposed at the entrance and exit of the guide for transporting paper;
An image forming apparatus having input means for inputting direction information of fibers constituting the paper,
Of the transport rollers, at least the transport roller at the entrance has nip pressure changing means for changing the nip pressure for nipping the paper,
An image forming apparatus comprising: control means for controlling the nip pressure changing means so as to change the nip pressure in accordance with the fiber orientation information input by the input means.

  (2) The control means is orthogonal to the paper transport direction when the fiber orientation information input by the input means is a vertical eye indicating the fiber orientation parallel to the paper transport direction. 2. The image forming apparatus according to item 1, wherein the nip pressure changing means is controlled so as to have a higher nip pressure than in the case of a horizontal eye indicating the direction of fibers in a direction.

The nip pressure changing means for changing the nip pressure of the conveying roller arranged with the curved guide for guiding the paper is changed to a higher nip pressure when the fiber orientation information is vertical, than when it is horizontal. By increasing the conveying force,
Provided are an image forming apparatus that prevents a conveyance abnormality (jamming) from occurring when a sheet having a curved portion is conveyed, and prevents a decrease in productivity related to the conveyance abnormality (jamming), and a control method thereof.

  Embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  In addition, the same part numbers are assigned to members having similar forms and functions in the respective drawings.

  First, in order to facilitate the understanding of the invention, the concept of paper conveyance in the curved portion will be described.

  Here, the curved portion refers to a portion where the sheet is guided with a certain curvature along the guide.

  FIG. 1 is an explanatory diagram for explaining the behavior of a sheet conveyed through a curved portion.

  For easy understanding, the gap of the guide G1 is widely illustrated.

  The sheet S is conveyed by the curved guide G1 by the conveyance roller R1 and the conveyance roller R2 which nip and convey the sheet S.

  The sheet S is nipped by a conveyance roller R1 that rotates in the direction of the arrow and is conveyed to the leading end G11 of the guide G1.

  Then, the paper S is further transported and transported inside the guide G1 along the alternate long and short dash line A, and advances straight due to the rigidity of the paper S and hits the B point.

  The leading edge of the sheet S that has hit the point B moves toward the conveying roller R2 while rubbing the curved portion C along the outer guide plate G12 by the conveying force f by the conveying roller R1, and the leading edge of the sheet S is conveyed to the conveying roller. Nipped into R2.

  Then, the sheet S is conveyed in a state of being pulled by the conveying roller R2, and is conveyed downstream from the conveying roller R2.

  However, when the sheet S advances straight and hits point B, and the leading edge of the sheet S moves toward the conveying roller R2 while rubbing the curved portion C along the outer guide plate G12 by the conveying force f by the conveying roller R1. A frictional force is generated between the sheet S and the outer guide plate G12 (curved portion C).

  When the component force f 'of the frictional force toward the transport roller R1 is larger than the transport force f, the transport of the sheet S by the transport roller R1 becomes impossible.

  Here, the transport force f is expressed as follows: transport force f = friction coefficient μ1 × pressing force f1 where the friction coefficient between the transport roller R1 and the sheet S is μ1, and the pressing force for nipping the sheet S of the transport roller R1 is f1. Indicated.

  Accordingly, even if the component force f 'directed to the transport roller R1 is large, the transport force R that overcomes the force (adding the pressing force f1) can be applied to transport the paper S by the transport roller R1.

  In the drawing, since the gap of the guide G1 is shown large, it seems that the leading edge of the paper S easily moves toward the transport roller R2 while rubbing the curved portion C.

However, in reality, the gap of the guide G1 is as narrow as 1 to several mm, and when the paper is thick (when the basis weight is large) or when the paper is vertical, the rigidity in the transport direction of the paper S increases.
As described above, the component force f ′ of the frictional force toward the conveyance roller R1 tends to be so large that it cannot be ignored with respect to the conveyance force f.

Note that the vertical eye (longitudinal paper) refers to the case where the arrangement direction of the fibers constituting the paper is oriented in the vertical direction (parallel direction) with respect to the paper transport direction,
A horizontal eye (horizontal paper) refers to a case where the arrangement direction of the fibers constituting the paper is in the horizontal direction (orthogonal direction) with respect to the paper conveyance direction.

  FIG. 2 is a cross-sectional view illustrating the overall configuration of the image forming apparatus.

  An overall outline of the image forming apparatus 1 will be described with reference to FIG.

  The image forming apparatus 1 has an automatic document feeder 2 at the top of the image forming apparatus main body, an image reading unit 3 for reading a document image, an electrophotographic image forming unit (hereinafter also simply referred to as an image forming unit) 4, a sheet The storage unit 5, the paper feed unit 6, the refeed paper path 7, the reverse path 8, the reverse transport path 9, and the paper discharge tray 10 are provided.

  The automatic document feeder 2 is a device that feeds a document one by one, conveys the document to an image reading position, and discharges the document after the document image has been read to a predetermined location.

  Here, a plurality of documents (not shown) placed on the document placing table 11 are separated one by one by the document separating means 12 and conveyed toward the slit 21 which is an image reading position by the document conveying means 13. Is done.

  Then, the image of the original is read through the slit 21, and the original on which the image has been read is discharged onto the original discharge table 15 by the original conveying means 13.

  The image reading unit 3 is a unit for reading an image of a document and obtaining image data.

  Here, the lamp 231 that illuminates the original through the slit 21 illuminates the original, the first mirror unit 23 and the second mirror unit 24 reflect the reflected light from the original, and the reflected light from the second mirror unit 24. The imaging lens 25 forms an image on the line-shaped CCD 26.

  The optical image formed by the linear CCD 26 is photoelectrically converted to obtain analog image information.

  The image processing means (not shown) performs various image processing including A / D conversion processing on the analog image information of the original read by the image reading means 3.

  Then, the image-processed digital image data of the document is compressed and temporarily stored in the memory M1.

  The paper storage unit 5 that stores the paper S includes storage containers 64, 65, and 66 that store the paper S in a stacked state, and paper feeding units 67, 68, and 69.

  The paper feeding units 67, 68, and 69 have paper feeding rollers 511, 512, and 513 and separation rollers 521, 522, and 523 for preventing multi-layering, and separates the paper S from the storage container and feeds the paper one by one. To do.

  In addition, the sheet feeding unit 6 serves as a conveying roller pair (hereinafter also simply referred to as a conveying roller) 531, 532, and 533 as a unit for conveying the sheet S from the storage containers 64, 65, and 66 to the image forming unit 4. 534, 535, and 536.

  A conveyance roller 501 is a conveyance roller provided downstream of the conveyance roller 534, and a conveyance path merging section between the sheet S sent out via the reverse conveyance path 9 and the sheet S fed from each of the storage containers 64 to 66, for example. Is provided.

  A conveyance roller 502 is a conveyance roller that conveys the paper S.

  The registration roller 503 corrects the bending of the sheet S and conveys the sheet S toward the photosensitive drum 32 in synchronization with the image formation by the image forming unit 4.

  The image forming unit 4 is a part where an image is formed using an electrophotographic process.

  The image forming unit 4 includes a photoconductor drum 32 having a photoconductive photosensitive layer as an image carrier on its surface, a charger 33 for uniformly charging the surface of the photoconductor drum 32, and photosensitivity based on the digital image data. A laser writing system 34, which is an exposure means for exposing the surface of the photosensitive drum 32 to form an electrostatic charge latent image, and development for developing the electrostatic charge latent image formed on the photosensitive drum 32 into a toner image. A unit 35, a transfer pole 36 for transferring the toner image onto the paper S, a static eliminator 37 for promoting separation of the paper S from the photosensitive drum 32 by AC corona discharge, and a toner remaining on the photosensitive drum 32 are cleaned. And a cleaning means 38 for the purpose.

  Here, after the photosensitive drum 32 is sequentially charged by a charger 33, an electrostatic latent image corresponding to the digital image data is formed by dot exposure by a laser writing system 34, and the electrostatic latent image is developed by a developing unit 35. Is a toner image.

  Next, a toner image is transferred onto the sheet S fed by the rotation start of the registration roller 503 through the action of the transfer pole 36.

  Next, the sheet S on which the toner image is transferred is separated from the photosensitive drum 32 by the separating unit 49.

  The fixing device 39 includes a heating source H, and includes a heating roller 390 that rotates independently around the heat source H, and a pressure roller 393 that rotates while being in pressure contact with the heating roller 390, and fixes the toner image on the paper S.

  Downstream of the fixing device 39, a reverse discharge roller 506, a switching unit 507 for switching the conveyance path of the paper S, and a paper discharge roller 508 for discharging the paper S to the outside of the apparatus are provided.

Then, by the non-operation of the switching unit 507, the sheets S conveyed by the reverse discharge roller 506 are accumulated as they are in the discharge tray 10 through the discharge roller 508,
Further, in order to form an image on the back surface (second surface) of the sheet S by the operation of the switching unit 507, the sheet is directed to the registration roller 503 via the refeed path 7, the reversing path 8, and the reversing conveyance path 9. Refeed.

  Hereinafter, the refeed path 7, the reverse path 8, and the reverse conveyance path 9 will be described.

  The paper refeeding path 7 conveys the sheet S conveyed obliquely downward in the figure by the switching unit 507 toward the reversing path 8 by the conveying rollers 541, 542, and 543.

  The reversing path 8 reverses the front and back of the sheet S conveyed from the refeed path 7 by a conveying roller 551 capable of forward and reverse rotation.

  In the reverse conveyance path 9, the paper S conveyed from the reverse path 8 is conveyed toward the conveyance roller 501 by conveyance rollers 552, 553, 554, 555, and 556.

  As described above, the refeeding path 7, the reversing path 8, and the reversing transporting path 9 are the circulation transporting path (registration roller 503 to the refeeding path 7 to the reversing path 8 to the reversing path) of the sheet S that reverses the sheet S. A part of the conveyance path 9 to the circulation path from the registration roller 503 is formed to enable double-sided printing.

The operation panel 90 includes various switches and a touch panel (not shown) described in detail later.
On the touch panel, for example, a printing method selection key for selecting a printing method (single-sided, double-sided, etc.), a basis weight selection key for selecting the basis weight of the paper S, and a fiber of the paper S to be fed as fiber orientation information And a fiber orientation selection key for selecting the orientation (longitudinal, lateral).

The basis weight selection key is provided with two keys of a predetermined basis weight or more, for example, 200 g / mm ² or more, and less than a predetermined basis weight, for example, less than 200 g / mm ² , and one of them is selected.

It should be noted that the basis weight of the paper may be input with a numeric key. In this case, it is determined whether the control means is 200 g / mm ² or more, for example, less than 200 g / mm ² .

  Then, the selection information of these keys is input to the control means 80.

  In this way, image formation is performed on the sheet S. Hereinafter, the conveyance of the sheet S in the guide having the curved portion will be described in detail with reference to FIGS.

In FIG. 2, the guide having a curved portion includes, for example, between the conveyance roller 541 and the conveyance roller 542, between the conveyance roller 551 and the conveyance roller 552, and between the conveyance roller 556 and the conveyance roller 501.
Hereinafter, a curved portion between the transport roller 541 and the transport roller 542 will be described as an example.

  FIG. 3 is an explanatory diagram relating to the conveyance of the paper in the curved portion.

  A curved guide G <b> 2 is disposed between the conveyance roller 541 and the conveyance roller 542, and the curved guide G <b> 2 guides the sheet S pushed out from the conveyance roller 541 toward the conveyance roller 542.

  The conveying roller 541 on the upstream side of the guide G2 includes a driving roller 541a that is rotated in the direction of an arrow by a rotation driving unit (not shown), a biasing roller 541b that presses and biases the sheet S toward the driving roller 541a, and a biasing force. And an upstream biasing means 544 for biasing the roller 541b toward the driving roller 541a.

  Then, the urging roller 541b presses the sheet S toward the drive roller 541a by the upstream urging means 544.

  The conveyance roller 542 on the downstream side of the guide G2 includes a driving roller 542a that is rotated in the direction of the arrow by a rotation driving unit (not shown), a biasing roller 542b that biases the sheet S toward the driving roller 542a, and a biasing roller 542b. Urging means 545 downstream of the drive roller 542a.

  Then, the biasing roller 542b presses the sheet S toward the driving roller 542a by the downstream biasing means 545.

  The sheet S pushed out and conveyed by the conveying roller 541 goes straight and hits the guide plate G22 outside the guide G2.

  As described with reference to FIG. 1, the leading edge of the sheet S moves toward the conveyance roller 542 while rubbing the curved portion C1 along the outer guide plate G22 by the conveyance force f by the conveyance roller 541. The leading end of the sheet S is nipped by the conveyance roller 542.

  Then, the sheet S is conveyed in a state of being pulled by the conveying roller R2, and is conveyed downstream from the conveying roller 542.

Here, the sheet S goes straight and hits the outer guide plate G22,
When the sheet S moves toward the conveying roller 542 while rubbing the curved portion C1 along the outer guide plate G22 by the conveying force fa by the conveying roller 541, the sheet S and the outer guide plate G22 (curved portion C) are moved. A frictional force is generated between them.

  When the component force f ′ (that is, the conveyance resistance) of the friction force toward the conveyance roller 541 is smaller than the conveyance force fa, the sheet S is conveyed by the conveyance roller 541.

  However, since the frictional force changes depending on the rigidity of the paper S and the curl direction, the component force f ′ directed toward the conveying roller 541 also changes.

  Therefore, in order to enable conveyance, even if the component force f ′ (conveyance resistance) of the frictional force toward the conveyance roller R1 changes, the component force f ′ changed by the upstream biasing means 544 is overcome. The pressing force f1 is changed.

  The sheet S is pushed out to the guide G2 by the conveying roller 541 and is conveyed while meandering between the two while contacting the outer guide plate G22 and the inner guide plate G23 (one-dot chain line).

  Further, when the sheet S is meandered between the outer guide plate G22 and the inner guide plate G23 while being conveyed, a conveyance resistance fh (not shown) is generated by friction.

  The conveyance roller 541 needs to have a conveyance force fa larger than the above-described component force f ′ when the sheet S comes into contact with the guide G2 and larger than the conveyance resistance fh after the contact.

  For this reason, the upstream urging means 544 directs the urging roller 541b toward the drive roller 541a with a pressing force f1a that generates a conveyance force larger than the above-described component force f ′ (conveyance resistance) and greater than the conveyance resistance fh. And press.

  Further, the conveyance roller 542 assists the conveyance of the sheet S by the conveyance roller 541 and pulls out the sheet S from the guide G2, so that the sheet S meanders between the outer guide plate G22 and the inner guide plate G23. Therefore, a transport force fb larger than the transport resistance generated when transported is required.

  For this reason, the downstream urging means 545 presses the urging roller 542b toward the driving roller 542a with the pressing force f1b that generates the conveying force fb.

  Hereinafter, a change in pressure by the urging means 544 upstream of the conveying roller 541 disposed on the upstream side with the curved guide G2 interposed therebetween and the urging means 545 downstream of the conveying roller 542 disposed on the downstream side. Means will be described.

  Since the upstream urging means 544 and the downstream urging means 545 have the same configuration, operation, and effect, the upstream urging means 544 will be described below as a representative of the urging means.

  FIG. 4 is a first explanatory diagram of the urging means.

  FIG. 4A is an explanatory diagram of the first embodiment of the upstream biasing means 544.

  Hereinafter, the first urging means 544a of the conveying roller 541 disposed on the upstream side of the curved guide G2 will be described with reference to FIG.

  The urging roller 541b is urged toward the driving roller 541a by the first urging means 544a.

  The urging roller 541b has a shaft 541c, and the shaft 541c is movably fitted in the elongated hole 5443 of the urging roller holding member 5442.

  Both ends of the first elastic member 5444 that urges the shaft 541c toward the drive roller 541a are fixed to the fixed shaft 5445 so as to have a circular arc shape protruding to the side opposite to the drive roller 541a.

  The substantially central portion of the first elastic member 5444 is in contact with the shaft 541c and urges the urging roller 541b in the direction of pushing up the shaft 541c, that is, in the direction of pressing the urging roller 541b toward the drive roller 541a.

  Further, the second elastic member 5446 abuts on the opposite side to the first elastic member 5444 with respect to the shaft 541c, and can be urged in a direction in which the shaft 541c is pushed down, that is, a direction in which the urging force toward the drive roller 541a is suppressed. It is said.

The second elastic member 5446 is an elastic member whose rigidity is smaller than that of the first elastic member 5444, and the side that contacts the shaft 541c is a free end,
The opposite side is connected to the urging force changing means 5447, and the urging force changing means 5447 changes the urging force of the first elastic member 5444 toward the drive roller 541a.

  Further, for example, a rotary solenoid is used as the biasing force changing means, and the biasing force changing means is hereinafter referred to as a rotary solenoid 5447.

  The rotary solenoid 5447 rotates the second elastic member 5446 in the n direction when turned on (energized).

  The rotation in the n direction is the rotation direction in the case of the longitudinal paper S in which the conveyance resistance increases.

  In this case, since the second elastic member 5446 does not urge the first elastic member 5444 in the reverse direction (the lower side in the drawing), a larger urging force, that is, a larger nip force is applied to the rotation in the m direction. As a result, a large conveying force can be obtained.

  Further, the rotary solenoid 5447 rotates the second elastic member 5446 in the m direction when it is OFF (not energized).

  The rotation in the m direction is the rotation direction in the case of the horizontal sheet S or the sheet S of less than a predetermined basis weight.

  In this case, since the second elastic member 5446 urges the first elastic member 5444 in the reverse direction (the lower side in the figure), a smaller urging force (normal urging force) with respect to rotation in the n direction, that is, The same normal nip force as in the case of the horizontal eye is applied, and as a result, a normal conveying force can be obtained.

  As described above, the first urging means 544a can be changed so that the urging force (nip pressure) of the urging roller 541b with respect to the drive roller 541a is increased with respect to the horizontal eye in the case of the vertical eye. Yes.

  FIG. 4B is a diagram of a second embodiment in which a linear solenoid is used as the biasing force changing means instead of the rotary solenoid 5447.

  The second elastic member 5446 of the second urging means 544b is an elastic member having rigidity smaller than that of the first elastic member 5444. The side that contacts the shaft 541c is a free end, and the opposite side is rotatable about the shaft 5448. It is connected to the.

  A linear solenoid 5449 is connected to the second elastic member 5446, and the second elastic member 5446 is rotated in the arrow direction m or the arrow direction n about the shaft 5448.

  The direct acting solenoid 5449 rotates the second elastic member 5446 in the n direction when ON (energized).

  The rotation in the n direction is the rotation direction in the case of the longitudinal paper S.

  In this case, since the second elastic member 5446 does not urge the first elastic member 5444 in the reverse direction (the lower side in the drawing), a larger urging force, that is, a higher nip pressure is applied to the rotation in the m direction. It becomes possible.

  Further, the direct acting solenoid 5449 rotates the second elastic member 5446 in the m direction when OFF (non-energized).

  The rotation in the m direction is the rotation direction in the case of the horizontal sheet S or the sheet S of less than a predetermined basis weight.

  In this case, since the second elastic member 5446 urges the first elastic member 5444 in the reverse direction (the lower side in the figure), a smaller urging force (normal urging force) with respect to rotation in the n direction, that is, It becomes possible to apply a normal nip force.

  As described above, the second urging means 544b can be changed so that the urging force (nip pressure) of the urging roller 541b with respect to the drive roller 541a is increased with respect to the horizontal eye in the case of the vertical eye.

  Others are the same as those of the first urging means 544a, and the description thereof is omitted.

  The urging force (nip pressure) of the urging roller 541b with respect to the driving roller 541a can be changed in two steps by the urging force changing means according to the type of paper or the direction of the fibers described with reference to FIGS. With this configuration, it is possible to reliably convey the sheet even in the curved portion.

  FIG. 5 is a second explanatory view of the urging means.

  In the following, a third embodiment of the upstream biasing means 544 using an eccentric cam as the biasing force changing means instead of the rotary solenoid 5447 will be described.

  The second elastic member 5446 of the third urging means 544c is an elastic member having a rigidity smaller than that of the first elastic member 5444. The side that contacts the shaft 541c is a free end, and the opposite side is rotatable about the shaft 5448. It is connected to the.

  The second elastic member 5446 is rotated in the arrow direction m or the arrow direction n about the shaft 5448 by the motor 5451 that rotates the eccentric cam 5450 through the eccentric cam 5450, the cam roller 5452, and the shaft 5453. It is possible to stop at any position.

  When the convex portion 5455 of the eccentric cam 5450 stops at a position facing upward in the drawing, the second elastic member 5446 stops at a position rotated in the n direction.

  The position where the convex portion 5455 faces in the drawing is a stop position of the eccentric cam 5450 in the case of the longitudinal paper S.

  In this case, since the second elastic member 5446 does not urge the first elastic member 5444 in the reverse direction (the lower side in the drawing), a larger urging force with respect to the stop position on the side opposite to the convex portion 5454, that is, more A high nip pressure can be applied.

  When the convex portion 5455 of the eccentric cam 5450 stops at a position facing downward in the drawing, the second elastic member 5446 stops at a position rotated in the m direction.

  The position where the convex portion 5455 faces downward in the drawing is the rotation direction in the case of the horizontal sheet S or the sheet S having a weight less than a predetermined basis weight.

  In this case, since the second elastic member 5446 urges the first elastic member 5444 in the reverse direction (the lower side in the drawing), a smaller urging force (normal urging force) with respect to the stop position on the convex portion 5455 side. That is, a normal nip force can be applied.

  As described above, the third urging means 544c4 can be changed so that the urging force (nip pressure) of the urging roller 541b against the driving roller 541a is increased with respect to the horizontal eye in the case of the vertical eye.

  The urging force (nip pressure) of the urging roller 541b with respect to the driving roller 541a can be changed in two steps by the urging force changing means according to the type of the paper S or the direction of the fibers described with reference to FIGS. With this configuration, the sheet S can be reliably conveyed even in the curved portion.

  As described above, in order to facilitate understanding, the case where the second elastic member 5446 stops at two upper and lower positions has been described. However, for example, the second elastic member 5446 may stop at an arbitrary position depending on the basis weight. .

  By doing so, it is possible to change the nip force with high accuracy according to papers of various basis weights, and it is possible to transport the paper S more reliably even at curved portions.

  Others are the same as those of the first urging means 544a, and the description thereof is omitted.

  FIG. 6 is a block diagram of the image forming apparatus.

  The image forming apparatus includes a control unit 80, an operation panel 90, an image reading unit 3, an automatic document feeder 2, an image forming unit 4, a paper feeding unit 6, a fixing device 39, an upstream biasing unit 544, and a downstream biasing unit. 545 and communication means 81.

  The control unit 80 includes a CPU (Central Processing Unit) 802, a RAM 803, a ROM 804, an I / O controller 806, and a bus 801 that interconnects them.

  The I / O controller 806 includes an image reading unit 3, an automatic document feeder 2, an image forming unit 4, a sheet feeding unit 6, a fixing device 39, an operation panel 90, an upstream biasing unit 544 and a downstream biasing unit 545, The communication means 81 and the like are controlled under the control of the CPU 802.

  The ROM 804 stores in advance a program for controlling the entire image forming apparatus, screen display information for a screen for inputting various information, and the like.

  Examples of the screen display information include screen display information for inputting information related to the paper S (basis weight, vertical eye, horizontal eye, etc.).

  The program, screen display information, and the like stored in the ROM 804 are stored in the RAM 803 by the CPU 802, read out as necessary, and control described later is performed.

  The operation panel 90 serving as information input means includes various switches (such as an activation key 900) and a touch panel (not shown).

On the touch panel, a paper feed cassette selection key 901 for selecting a paper feed cassette to be fed, a printing method selection key 902 for selecting a printing method (single-sided printing, double-sided printing, etc.),
A paper basis weight selection key 903 for selecting the basis weight of the paper S, which is information relating to the paper S, and a fiber orientation selection key for selecting the fiber orientation (longitudinal, lateral eye) with respect to the transport direction of the paper S to be fed 904, etc. are displayed.

  The paper basis weight selection key 903 may be a paper thickness selection key for selecting the paper thickness (thick paper, plain paper, etc.).

In this case, 200 g / m ² or more of the paper basis weight selection key 903 in the flow described later corresponds to the thick paper.

  Then, the key operation information is input to the control means 80.

  When the ON information of the activation key 900 is input from the operation panel 90 via the I / O controller 806 under the control of the control unit 80, the image reading unit 3 reads the original image and sends the original image information to the control unit 80. input.

  Then, the control unit 80 processes the document image information read by the image reading unit 3 into digital image data, and stores the digital image data in, for example, an HDD (hard disk drive) not shown.

  The communication unit 81 is connected to an external PC (personal computer), an image forming apparatus, a server 812 or the like via a network 811, and these and digital image data are transmitted via the I / O controller 806 under the control of the control unit 80. And so on.

  The control unit 80 stores the digital image data received by the communication unit 81 in the HDD or the like.

  The image forming unit 4 forms a toner image on the photoconductor based on the digital image data read from the HDD via the I / O controller 806 under the control of the control unit 80.

  Then, based on the operation information of the paper feed cassette selection key 901 input from the operation panel 90, the toner image is transferred onto the paper fed from the paper feed cassette.

  The paper feeding unit 6 feeds the paper S from a predetermined paper feeding cassette via the I / O controller 806 under the control of the control means 80.

  The fixing device 39 includes a heating source H such as a halogen lamp, and a drive motor 391 that rotationally drives the heating roller 390.

  Then, via the I / O controller 806 under the control of the control means 80, the temperature adjustment of the heating roller 390 is performed by turning on / off the heating source H, and the rotation driving of the heating roller 51 is performed by turning on / off the drive motor 391. Is done.

As described above, the biasing means includes the upstream biasing means 544 and the downstream biasing means 545,
The upstream biasing means 544 and the downstream biasing means 545 have the same form.

  As described above, the upstream urging means 544 and the downstream urging means 545 have three forms (first urging means 544a and 545a, second urging means 544b and 545b, and third urging means 544c. And three forms of 545c).

  The first urging means 544a and 545a have a rotary solenoid 5447, and the rotary solenoid 5447 is turned ON / OFF via the I / O controller 806 under the control of the control means 80. Accordingly, the second elastic member 5446 is rotated in the m direction or the n direction.

  In the case of the second urging means 544b and 545b, a direct acting solenoid 5449 is provided, and the direct acting solenoid 5449 is turned ON / OFF via the I / O controller 806 under the control of the control means 80. Accordingly, the second elastic member 5446 is rotated in the m direction or the n direction.

  In the case of the third urging means 544c and 545c, the motor 5451 is provided, the stop position of the motor 5451 is controlled via the I / O controller 806 under the control of the control means 80, and the eccentric cam 5450 The second elastic member 5446 is positioned at an arbitrary position.

  Hereinafter, the biasing means and the image forming apparatus control method will be described by taking the upstream biasing means 544 as an example because the downstream biasing means 545 is the same as the upstream biasing means 544.

  Unless otherwise specified, the following control is performed by the control means 80.

  FIG. 7 is a flowchart relating to control of the image forming apparatus.

1. Reading of printing form (single-sided, double-sided printing, etc.) and information on paper S (basis weight, fiber orientation, paper feed cassette, etc.) (step S101)
Information related to the printing mode, for example, a selection screen (not shown) such as single-sided printing or double-sided printing, and
Information relating to the paper S, for example, a selection screen for a cassette to be fed, a selection screen for paper basis weight (not shown), and a selection screen (not shown) for the direction of the fibers of the paper S (longitudinal, horizontal, etc.) The image display information is read from the ROM 804,
A selection screen (not shown) for selecting the print format (single-sided, double-sided printing, etc.)
A selection screen for a cassette to be fed, a basis weight selection screen for the paper S, and a selection screen for the fiber orientation of the paper S (longitudinal paper, horizontal paper, etc.) are displayed on the operation panel 90.

  When the information selected on these selection screens is input, the input information is stored in the RAM 803, and the process proceeds to the next step.

2. Subroutine for setting the conveyance roller nip pressure by the urging means (step S102)
This step is a subroutine for setting the conveyance roller nip pressure by the urging means, and the flow shown in FIGS. 7 and 8 is executed.

  That is, setting of the urging force (conveying roller nip pressure) by the upstream urging means 544 and the downstream urging means 545 according to the basis weight selection information and the fiber orientation selection information selected and stored in step S101. To proceed to the next step.

  For the setting of the urging force (conveying roller nip pressure), see the flow of FIG.

3. Startup monitoring (step S103)
The activation key 900 on the operation panel 90 is monitored, and if the activation key is detected ON (Yes), the process proceeds to the next step, and step S103 is repeated until the activation key is turned ON (No).

4). Document reading (step S105)
The automatic document feeder 2 transports the document and causes the image reading unit 3 to read the document image. Then, A / D conversion or the like is performed to obtain digital image information of the document, and the process proceeds to the next step.

5). Image formation (step S105)
The toner image is formed on the image forming unit 4 based on the digital image information of the document, and the process proceeds to the next step.

6). Paper feeding (step S106)
The paper feeding unit 6 feeds the paper S from the paper feeding cassette selected and stored in step S101, transfers the toner image onto the paper S, and proceeds to the next step.

7). Fixing (Step S107)
Fixing is performed by the fixing device 39, and the process proceeds to the next step.

8. Determination of print mode (step S108)
The printing mode selected / stored in step S101 (single-sided printing, double-sided printing, etc.) is read, and if it is single-sided printing (Yes), it proceeds to the next step. Proceed to step S110.

9. Paper discharge (step S109)
The fixed paper S is accumulated on the paper discharge tray 10.

  Then, step S105 to step S108 are repeated until a predetermined number of images are formed and fixed under preset job conditions.

10. Back side printing (step S110)
When the duplex printing is performed, the switching unit 507 is operated to transport the sheet S to the refeed path 7 in order to print on the back surface.
Next, the front and back sides are reversed by the reversing path 8, transported to the reversing transport path 9, and after image formation is performed on the back surface, fixing is performed, and the process proceeds to step S109.

  At this time, the conveyance roller 541 and the conveyance roller 542 sandwiching the guide having the curved portion, the conveyance roller 551 and the conveyance roller 552 sandwiching the guide having the curved portion, and the conveyance roller 556 sandwiching the guide having the curved portion and the conveyance roller 556 are conveyed. The rollers 501 and the like convey the paper S with a nip pressure based on the setting of the urging force described in the flow of FIG.

  Even if it is other than the above, it goes without saying that the conveying roller sandwiching the guide having the curved portion conveys the sheet S by the nip pressure based on the setting of the urging force described in the flow of FIG.

  FIG. 8 is a first flowchart relating to the setting of the conveyance roller nip pressure by the urging means.

  The “feed roller nip pressure setting subroutine by the urging means” shown in step S102 has the following flow.

1. Reading of information (fiber orientation) relating to the paper S stored in S101 (step S201)
In step S101, the fiber orientation information (longitudinal, lateral, etc.) stored in the RAM 803 is read, and the process proceeds to the next step.

2. Determination of fiber orientation (longitudinal paper, horizontal paper, etc.) (step S202)
If the read information is “vertical eye” (Yes), the process proceeds to the next step. If the read information is not “vertical eye” (No), it is determined to be a horizontal eye and the process proceeds to step S204.

3. Set nip pressure “high” (step S203)
In FIG. 4, the rotary solenoid 5447 is turned on to rotate the second elastic member 5446 in the n direction (the second elastic member 5446 biases the first elastic member 5444 in the reverse direction (the lower side in the drawing)). The first urging member 5444 applies a larger urging force than usual, that is, a higher nip pressure, by the first elastic member 5444, and the process returns to step S102.

4). Nip pressure “normal” setting (step S204)
In FIG. 4, the rotary solenoid 5447 is turned OFF and the second elastic member 5446 is rotated in the m direction (the first elastic member 5444 is biased in the reverse direction (the lower side in the drawing) by the second elastic member 5446. The normal urging force, that is, the normal (lateral) nip pressure is applied by the urging roller 541b by the first elastic member 5444, and the process returns to step S102.

In the second urging means 544b, the same control is performed on the linear solenoid 5449 in step S203 and step S204,
In the third urging means 544c, it goes without saying that the same control is performed via the eccentric cam 5450 by the motor 5451 in step S203 and step S204.

  FIG. 9 is a second flowchart relating to the setting of the conveyance roller nip pressure by the urging means.

  The “feed roller nip pressure setting subroutine by the urging means” shown in step S102 has the following flow.

1. Reading of information (basis weight, fiber orientation) relating to the paper S stored in S101 (step S301)
In step S101, information related to the paper S stored in the RAM 803 (paper basis weight, vertical eyes, horizontal eyes) is read, and the process proceeds to the next step.

2. Paper basis weight determination “predetermined value or more” (step S302)
If the basis weight read in step S301 is a predetermined value or more, for example, 200 g / m ² or more (Yes), it is determined that the rigidity of the sheet is large and there is a high possibility of causing a conveyance abnormality, and the process proceeds to the next step.
If it is less than the predetermined value, for example, less than 200 g / m ² (No), it is determined that the rigidity of the sheet is small and the possibility of causing a conveyance error is low, and the process proceeds to step S306.

3. Instruction for setting the direction of the horizontal direction of the sheet (step S303)
In order to have the operator set the fiber orientation of the paper stored in the paper cassette to a horizontal direction with low rigidity in the conveyance direction, for example, instruct the operation panel 90 to “Set the paper in the horizontal direction”. And go to the next step.

4). Judging the direction of paper fibers (longitudinal, transverse, etc.) (step S304)
If the orientation of the fiber read in step S301 is “longitudinal” (Yes), it is determined that the rigidity of the paper is large and there is a high possibility of causing a conveyance abnormality, and the process proceeds to the next step.
If it is not “longitudinal” (No), it is determined that it is a horizontal eye and the sheet has low rigidity and is less likely to cause a conveyance error, and the process proceeds to step S306.

5). Set nip pressure “high” (step S305)
In FIG. 4, the rotary solenoid 5447 is turned on to rotate the second elastic member 5446 in the n direction, and the second elastic member 5446 urges the first elastic member 5444 in the reverse direction (the lower side in the drawing). Instead, the first elastic member 5444 applies an urging force larger than usual, that is, a higher nip pressure by the urging roller 541b, and the process returns to step S102.

6). Nip pressure “normal” setting (step S306)
In FIG. 4, the rotary solenoid 5447 is turned OFF and the second elastic member 5446 is rotated in the m direction (the first elastic member 5444 is biased in the reverse direction (the lower side in the drawing) by the second elastic member 5446. The normal urging force, that is, the normal (lateral) nip pressure is applied by the urging roller 541b by the first elastic member 5444, and the process returns to step S102.

In the second urging means 544b, the same control is performed on the linear solenoid 5449 in step S305 and step S306,
In the third urging means 544c, it goes without saying that the same control is performed via the eccentric cam 5450 by the motor 5451 in steps S305 and S306.

The paper transport mode and method have been described above by taking the transport roller 541 and the transport roller 542 sandwiching the guide having a curved portion as an example.
Needless to say, any upstream and downstream conveying rollers sandwiching a guide having a curved portion can be suitably used in an image forming apparatus and a post-processing apparatus.

Further, it is preferable that the urging means is provided on both the upstream conveying roller 541 and the downstream conveying roller 542.
The urging unit may be provided only on the upstream conveying roller 541.

  Further, the monochrome image forming apparatus has been described as an example, but may be used for a color image forming apparatus.

  Hereinafter, the conveyance state when the nip force (conveyance force) is changed in accordance with the basis weight of the sheet in the conveyance at the curved portion of the longitudinal sheet, which is a feature of the present invention, is shown in the third appendix of FIG. A result of comparison using the biasing means 544c will be described.

First, as comparison data,
As a representative example of the conventional configuration, the eccentric cam 5450 is placed in the m direction so that the conveying force is less than 8N, for example, 4N, regardless of whether it is vertical or horizontal as in the past. A case where the motor 5451 is rotated and fixed will be described.

The horizontal paper was free of abnormal transport regardless of whether it was a thick paper as a representative having a basis weight of 200 g / m ² or more and a thin paper as a representative having a basis weight of less than 200 g / m ² .

  However, in the case of the long paper, the conveyance abnormality frequently occurred in the case of the thick paper, and the conveyance abnormality did not occur in the case of the thin paper.

  As described above, in the conventional configuration, it has been confirmed that there is a possibility that the conveyance abnormality may occur when the basis weight is large in the longitudinal direction.

Next, in the present embodiment, attention is paid to the conveyance of vertical paper in the curved portion.
In the case of the horizontal eye, the eccentric cam 5450 is rotated so that the second elastic member 5446 is in the m direction so that the conveying force is less than 8N, for example, 4N (normal), regardless of the basis weight,
When the longitudinal dimension is less than 200 g / m ² , the motor 5451 is rotated so that the eccentric cam 5450 comes in the m direction so that the conveying force is less than 8N, for example, 4N. ,
When the longitudinal dimension is 200 g / m ² or more and the basis weight is 200 g / m ² or more, the eccentric cam 5450 is arranged so that the second elastic member 5446 is in the n direction so that the conveying force is 8 N or more, for example, 12 N (large). A case where 5451 is rotated will be described.

  The horizontal paper did not cause any abnormal transport regardless of the basis weight.

Longitudinal sheets had a basis weight of less than 200 g / m ² and no abnormality in conveyance by rotating the motor 5451 so that the second elastic member 5446 was in the m direction with the eccentric cam 5450.

Further, in the vertical paper, when the eccentric cam 5450 is rotated so that the second elastic member 5446 is in the n direction, the conveyance abnormality does not occur even when the basis weight is 200 g / m ² or more.

As described above, in the case of the vertical eye, the nip force, that is, the conveying force is changed to be larger than the horizontal eye,
In addition, even in the case of the longitudinal eye, it has been found that the occurrence of a conveyance abnormality can be suppressed by changing the nip force, that is, the conveyance force, to increase as the basis weight increases.

It is explanatory drawing explaining the behavior of the paper conveyed by a curved part. 1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus. FIG. 10 is an explanatory diagram relating to conveyance of a sheet in a curved portion. It is the 1st explanatory view of a biasing means. It is the 2nd explanatory view of a biasing means. 1 is a block diagram of an image forming apparatus. 3 is a flowchart relating to control of the image forming apparatus. FIG. FIG. 6 is a first flowchart relating to setting of a conveyance roller nip pressure by an urging unit. FIG. 10 is a second flowchart relating to setting of a conveyance roller nip pressure by an urging unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 7 Refeeding path 8 Reversing path 9 Reverse conveying path 80 Control means 90 Operation panel 501 Conveying roller 541 Conveying roller 541a Driving roller 541b Energizing roller 542 Conveying roller 544 First energizing means 545 Second applying Energizing means 551 Conveying roller 552 Conveying roller 556 Conveying roller 5444 First elastic member 5446 Second elastic member 5447 Rotary solenoid 5449 Linear solenoid 5450 Eccentric cam 5451 Motor f 'Component force fa Conveying force f1 Pressing force G2 Guide

Claims (2)

A curved guide that guides the paper;
A transport roller disposed at the entrance and exit of the guide for transporting paper;
An image forming apparatus having input means for inputting direction information of fibers constituting the paper,
Of the transport rollers, at least the transport roller at the entrance has nip pressure changing means for changing the nip pressure for nipping the paper,
An image forming apparatus comprising: control means for controlling the nip pressure changing means so as to change the nip pressure in accordance with the fiber orientation information input by the input means. In the case where the direction information of the fibers input by the input unit indicates a longitudinal eye indicating the direction of the fibers in a direction parallel to the paper transport direction, the control unit is configured to output fibers in a direction orthogonal to the paper transport direction. 2. The image forming apparatus according to claim 1, wherein the nip pressure changing unit is controlled so as to have a higher nip pressure than in the case of a horizontal eye that indicates the direction of the image.

Images