JP2018031949A - Paper ejection device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a difference in dryness between a printing surface and a non-printing surface of a print sheet having an image formed on the printing surface without using a configuration that heats the print sheet, and thereby making the print sheet flat.SOLUTION: A paper ejection tray 25 swings swinging pieces 25b of a tray body 25a at the start of printing, so as to hold the tray body 25a of the paper ejection tray along a print sheet P to which a convex curl or a concave curl has occurred due to an image M printed on a printing surface P1. The paper ejection tray 25 returns the swinging pieces 25b of the tray body 25a to the original flat state at the timing at which the convex curl or concave curl is automatically eliminated and the print sheet P returns to a flat state.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a paper discharge device that discharges printing paper on which an image is formed, and an image forming device that forms an image on the printing paper.

  It has been widely known that printing paper on which an image is formed (printed) is curled. When the curled print paper is discharged to the paper discharge tray, the print paper is not suitably stacked on the paper discharge tray, which may cause a discharge failure (jam) of the print paper in the paper discharge tray. Therefore, proposals for suppressing curling of printing paper have been made conventionally.

  Specifically, for example, there is a proposal for suppressing the curling of the printing paper by removing the moisture in the ink that has penetrated the printing surface from the non-printing surface side by heating the printing paper (for example, Patent Document 1). There is also a proposal for correcting the curl by causing the printing paper whose printing surface is heated by the pressure contact of the fixing roller to bend in the direction opposite to the direction curled on the paper discharge tray (for example, Patent Document 2).

Japanese Patent Laid-Open No. 9-30710 JP-A-9-208110

  By the way, curling of printing paper on which an image is formed can be said to be a phenomenon that is caused by a difference in dryness between the printing surface and the non-printing surface due to ink penetration or heating by a fixing roller. it can.

  From this point of view, the proposal in Patent Document 1 can be said to force the printing surface to dry and bring the dryness close to the non-printing surface. Will increase.

  On the other hand, since the proposal of Patent Document 2 corrects the curled printing paper according to the shape of the paper discharge tray, a configuration for heating the printing paper that causes an increase in power consumption is unnecessary. Instead, the output tray corrects the difference in dryness between the printed and non-printed surfaces of flattened printing paper by cooling the heated printing surface or drying the printing surface that has penetrated the ink. Curling in the direction opposite to the curl direction before the curling is promoted.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a configuration in which the printing paper is heated to determine the difference in dryness between the printing surface and the non-printing surface of the printing paper on which an image is formed on the printing surface. It is an object of the present invention to provide a paper discharge device and an image forming apparatus that can be reduced without being used and can flatten printing paper.

In order to achieve the above object, a paper discharge device according to the first aspect of the present invention comprises:
In a paper discharge device that discharges print paper on which an image is formed on the print surface by executing a print job to a paper discharge tray,
When the discharge of the printing paper on which the curling has occurred due to the image formation on the printing surface to the discharge tray, the discharge tray in the width direction of the printing paper intersects the discharge direction of the printing paper. A moving means for displacing the central portion relative to both ends to the convex side of the curl of the printing paper;
A return means for canceling the relative displacement of the central portion with respect to the both end portions after a lapse of a predetermined period from the end of the discharge of the printing paper after the image formation by the print job to the discharge tray;
Is provided.

  The paper discharge device according to the second aspect of the present invention is the paper discharge device according to the first aspect of the present invention, wherein the print discharged to the paper discharge tray at the end of the print job is performed during the predetermined period. This is a period in which the timing at which the difference in dryness generated in the image forming process between the printing surface and the non-printing surface of the paper starts to decrease is the end timing.

  Furthermore, in the paper discharge device according to the third aspect of the present invention, in the paper discharge device according to the first or second aspect of the present invention, the predetermined period is set based on the print setting information of the print job.

  According to a fourth aspect of the present invention, there is provided a paper discharge device according to the first, second, or third aspect of the present invention, wherein an image is formed on the printing surface using an ink jet method using liquid ink. To do.

In order to achieve the above object, an image forming apparatus according to a fifth aspect of the present invention provides:
In an image forming apparatus in which a print sheet on which an image is formed on a printing surface by executing a print job is discharged to a discharge tray by a discharge apparatus.
The paper discharge device includes a paper discharge device according to the first, second, third, or fourth aspect of the present invention.

  According to the present invention, the difference in dryness between the printing surface and the non-printing surface of the printing paper on which the image is formed on the printing surface is reduced without using the configuration for heating the printing paper, and the printing paper is flattened. be able to.

  That is, when an image is formed on the printing surface by executing a print job, a difference in dryness occurs between the printing surface and the non-printing surface. This difference is caused by, for example, the water of the liquid ink used for image formation penetrating the printing surface unevenly or heating the printing surface to fix the toner used for image formation.

  When such a difference in dryness occurs between the printing surface and the non-printing surface, a difference occurs in the stretch state of the fibers of the printing paper between the printing surface side and the non-printing surface side, and the fibers are relatively Curling occurs on the printing paper, with the extended surface side being the outside and the surface side where the fibers are relatively contracted being the inside.

  In addition, when the predetermined period has elapsed since the last print sheet was discharged to the discharge tray, there was a difference in dryness that occurred between the print side and the non-print side of the print sheet in the discharge tray. Decrease. Therefore, at that time, the stretched state of the fiber on the printing surface side of the printing paper and the stretched state of the fiber on the non-printing surface side approach each other, and the curling of the printing paper is resolved.

  Therefore, in the paper discharge device according to the first aspect of the present invention, the central portion of the paper discharge tray in the paper discharge direction is displaced relative to both ends to the convex side of the curl along the curled printing paper. . This displacement is continued for a predetermined period, and during that period, the curled printing paper is kept in a state in which it is difficult for an external force such as correcting the curl to be applied from the paper discharge tray.

  Further, when a predetermined period has elapsed since the last print sheet was discharged to the discharge tray, the relative displacement with respect to both ends of the central portion of the discharge tray is eliminated. As a result, an external force that deforms the print paper from the paper discharge tray to the print paper when the curl is eliminated is kept from being applied from the paper discharge tray.

  Therefore, the state of the discharge tray is changed at the timing when a predetermined period elapses after the last print sheet of the print job is discharged to the discharge tray, and the curl of the curled print sheet is eliminated. It is possible to prevent external force from being applied to the printing paper from the paper discharge tray. Therefore, the difference in the dryness between the printing surface and the non-printing surface of the printing paper curled by image formation can be eliminated naturally, and the printing paper can be returned to a non-curled state.

  As a result, it is possible to reduce the difference in dryness between the printing surface and the non-printing surface of the printing paper on which the image is formed on the printing surface without using a configuration for heating the printing paper, thereby achieving flattening of the printing paper. .

  When the difference in the dryness generated between the printing surface and the non-printing surface of the printing paper in the image forming process is reduced, the displacement of the central portion with respect to both ends of the discharge tray is eliminated. As in the paper discharge device according to the second aspect of the present invention, the timing at which the difference in dryness between the printed surface and the non-printed surface starts to decrease can be set as the timing at which the predetermined period ends.

  This reduces the difference in dryness between the printing surface and non-printing surface of the printing paper so that no correction force is applied to the printing paper from the output tray. It can be restored naturally to the state where it does not curl.

  In addition, the time required for the curl of the discharged printing paper to be resolved naturally depends on the printing setting conditions such as the type of printing paper, the printing conditions, the type of ink used for printing, and the printing method of the image forming apparatus. In the case of change, like the paper discharge device according to the third aspect of the present invention, the print setting condition is specified from the print setting information of the print job, and the predetermined period is set to an appropriate period according to the specified print setting condition. can do.

  Furthermore, when an image is formed on the printing surface by an ink jet method using liquid ink, the moisture of the liquid ink penetrates the printing surface and the fibers are elongated, resulting in a difference in dryness from the non-printing surface. Then, the printing paper is curled so that the printing surface is located on the outer side, and is discharged to the paper discharge tray.

  In the paper discharge device according to the fourth aspect of the present invention, the curling can be suppressed by reducing the difference in dryness between the printing surface and the non-printing surface of the printing paper without using the heating configuration.

  In the image forming apparatus according to the fifth aspect of the present invention, the effects obtained by the paper discharge apparatus according to the first, second, third, or fourth aspect of the present invention can be obtained.

It is explanatory drawing which shows schematic structure of the printing apparatus which concerns on one Embodiment of this invention. (A)-(c) is explanatory drawing which shows the state for every elapsed time from discharge | emission of the curl produced on the printing paper which printed the image with the printing apparatus of FIG. 1 according to the printing rate of an image. FIG. 2 is an explanatory diagram illustrating a composition example of ink used for printing an image by the printing apparatus of FIG. 1. FIG. 3 is an external perspective view illustrating an example of a paper discharge tray provided in a general printing apparatus. (A), (b) is explanatory drawing which shows the state of the printing paper at the time of leaving the printing paper curled by the printing of an image on the discharge surface of a discharge tray for a predetermined period. (A)-(c) is explanatory drawing which shows the shape of the paper width direction of the paper discharge tray used for verifying the curl state of the printing paper left after paper discharge. FIG. 6 is an explanatory diagram illustrating a curled state of a printing sheet when a printing sheet on which an image is formed on a printing surface using ink A is left on a discharge tray. FIG. 6 is an explanatory diagram showing a curled state of a printing paper when a printing paper on which an image is formed on a printing surface using ink B is left on a paper discharge tray. FIG. 4 is an explanatory diagram of a paper discharge tray in which a protrusion that curves upward the discharged print paper is provided on the tray surface. FIG. 2 is an explanatory diagram illustrating a schematic configuration of a paper discharge tray of the printing apparatus of FIG. 1. FIG. 2 is an explanatory diagram showing stepwise the occurrence mechanism of curl in printing paper printed by the printing apparatus of FIG. 1. 11 is a flowchart showing a procedure of processing relating to swinging of the swinging piece of the paper discharge tray of FIG. 10 performed by the control unit of the printing apparatus of FIG. 1. It is explanatory drawing which shows schematic structure of the printing apparatus which concerns on the reference example of this invention. It is explanatory drawing which shows schematic structure of the printing system which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a printing apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, a printing system 1 according to the present embodiment includes a computer 10 and a printing apparatus 20 connected to the computer 10 via a network such as a wired or wireless LAN (corresponding to the image forming apparatus in the claims). And.

  The computer 10 is configured to be able to edit image data to be printed on the printing paper P, generates print job data for creating a sealed letter including the image data, and outputs the print job data to the printing apparatus 20. To do.

  The print job data includes print setting information in addition to the image data described above. The print setting information includes information on the printing device 20 used for printing, information on the paper type of the printing paper P, information on ink used for printing in the printing device 20, information indicating double-sided printing or single-sided printing, and the like. include.

  The printing apparatus 20 includes an ink head unit 21 that ejects ink onto the printing paper P. The ink head unit 21 performs printing processing by ejecting ink onto the printing paper P based on the image data included in the print job data output from the computer 10. The ink head unit 21 of the present embodiment includes a plurality of line-type ink heads that eject ink of each color of black K, cyan C, magenta M, and yellow Y.

  Further, the printing apparatus 20 includes a paper feed tray 22 and a straight paper feed base 23 on which the print paper P is set. The paper feed tray 22 includes a first paper feed tray 22a, a second paper feed tray 22b, and a third paper feed tray 22c. Printing paper P having various paper types and paper sizes is placed in these paper feed trays. Set. Further, the printing paper P is also set on the straight paper feed tray 23.

  When printing is performed, the printing paper P designated by the print job is selected from the straight paper feed tray 23 or the paper feed tray 22 and picked up by a paper feed roller (not shown) or the like and fed.

  Further, the printing apparatus 20 includes a circulation conveyance path 24 that conveys the printing paper P. The circulation conveyance path 24 conveys the printing paper P fed from the paper feed tray 22 or the straight paper feed stand 23 from the upstream side to the downstream side of the ink head unit 21.

  The circulation conveyance path 24 is for discharging the printing paper P that has been subjected to the printing process in the ink head unit 21 as it is to the paper discharge tray 25 (corresponding to the paper discharge tray in the claims) during single-sided printing. is there. Further, in the case of double-sided printing, the circulation conveyance path 24 conveys the printing paper P that has undergone one-side printing processing to the reversing unit 26 formed on the lower surface of the paper discharge tray 25, and the reversing unit 26 reverses the front and back. The single-side printed printing paper P is conveyed again from the upstream side to the downstream side of the ink head unit 21. Thereafter, the circulation conveyance path 24 discharges the double-side printed printing paper P, which has been subjected to the printing process again in the ink head unit 21, to the paper discharge tray 25 as it is.

  Note that the circulation conveyance path 24 delivers the printing paper P for single-sided printing and double-sided printing to the communication conveyance path 27 after the printing process. The communication conveyance path 27 is connected to a paper receiving port of a post-processing apparatus (not shown) connected to the printing apparatus 20.

  The printing apparatus 20 includes a control unit 28 that controls the entire printing apparatus 20. The control unit 28 can be configured by, for example, a computer having a CPU, a ROM, and a RAM (all not shown). A display 29 is connected to the control unit 28. The display 29 is disposed on the upper part of the printing apparatus 20. The display 29 can be used as an input device and an information output device related to various operations of the printing apparatus 20.

  The control unit 28 receives print job data from the computer 10. Upon receiving the print job data from the computer 10, the control unit 28 prints an image based on the image data of the received print job data on the printing paper P by the printing process of the ink head unit 21 under the conditions specified in the print setting information. Let

  The control unit 28 determines the paper type and printing conditions of the printing paper P, the type of ink used for printing, the printing method of the printing apparatus 20, the presence / absence of post-processing, and the contents of the print job data received from the computer 10. It can be specified from the print setting information.

  By the way, when an image is printed on the printing paper P by the printing apparatus 20 due to execution of a print job from the computer 10, the printing paper P immediately after printing is curled so that the printing surface side is located outside.

  That is, when an image is formed on the printing surface by an ink jet method using liquid ink as in the printing apparatus 20, moisture of the liquid ink penetrates into the printing surface of the printing paper P, and the fibers are elongated. Since there is a difference in dryness between the printing surface and the printing surface, the printing paper P is curled and discharged onto the paper discharge tray 25 so that the printing surface is positioned on the outside.

  Here, the curl generated on the printing paper P is 3 seconds later than immediately after paper discharge when the image M having a high borderless printing rate shown in the explanatory diagram of FIG. 2A is printed on the entire surface of the printing surface P1. It becomes stronger after 5 seconds. Further, as shown in the explanatory diagrams of FIGS. 2B and 2C, the curl generated on the printing paper P decreases as the printing rate of the image M printed on the printing surface P1 decreases. Furthermore, when the printing rate of the image printed on the printing surface P1 is low, the curling of the printing paper P does not become strong as shown in FIG.

  Such a tendency is basically the same regardless of the type of ink used for printing. For example, regardless of which of the ink A and the ink B shown in the explanatory diagram of FIG. 3 is used for printing the image M, the curling of the printing paper P is stronger as the printing rate is higher. The curl was stronger after 5 seconds of paper discharge than immediately after.

  Next, a case where the curled printing paper P is discharged to a discharge tray of a general printing apparatus will be described. FIG. 4 is an external perspective view showing an example of a paper discharge tray provided in a general printing apparatus. A general paper discharge tray 150 shown in FIG. 4 is for stacking printed printing paper P discharged from a paper discharge port 140 of the printing apparatus.

  The paper discharge tray 150 includes a tray main body 151 having an inclined surface 151 a, a pair of side fences 152, 152, an abutting cover 153, and a protruding member 155.

  The paper discharge tray 150 is provided at a drop position of the print paper P discharged from the paper discharge port 140, and has a slope 151a having a predetermined angle that rises in the paper discharge direction (Y direction in the figure) of the print paper P. A main body 151 is provided. The tray main body 151 is a receiving base for stacking the printing paper P on the inclined surface 151a. On the inclined surface 151a, the printing paper P sequentially discharged from the paper discharge port 140 is placed in a stacked state.

  The pair of side fences 152, 152 are disposed on both outer sides in the width direction X of the printing paper P discharged on the inclined surface 151 a of the tray body 151, and are movable relative to the tray body 151 in the width direction X. Is provided.

  The distance between the side fences 152 and 152 can be set in accordance with the size of the printing paper P, and is usually slightly wider than the width of the printing paper P to be discharged. The pair of side fences 152 and 152 regulate the width direction X of the printing paper P and align the paper when the printing paper P discharged between them enters.

  In addition, an abutting cover 153 is provided at the lowermost part of the pair of side fences 152, 152. The abutting cover 153 returns to the rear of the paper ejection direction Y while the printing paper P ejected from the paper ejection port 140 slides on the inclined surface 151a of the tray body 151, and the paper ejection direction of the printing paper P to the abutting cover 153. The paper discharge direction Y of the printing paper P is aligned as the rear end of Y abuts.

  The protruding member 155 is provided on the inclined surface 151 a of the tray main body 151. The projecting member 155 has a triangular prism shape having triangular side surfaces when viewed in the width direction X, and slides along the paper discharge direction Y in a concave groove 151b formed in the center of the inclined surface 151a in the width direction X. Supported as possible. The protruding member 155 has a guide surface 155a having a larger inclination than the inclined surface 151a on the paper discharge outlet 140 side.

  The protruding member 155 described above prevents the printing paper P discharged from the paper discharge outlet 140 from slipping out of the tray body 151 from the tip of the inclined surface 151a due to the momentum of paper discharge.

  On the inclined surface 151a of the tray main body 151 of the paper discharge tray 150, for example, the printing paper P curled with the printing surface P1 as shown in FIGS. 2A to 2C outward is printed on the printing surface P1. Assume that the paper is discharged with face up (face-up). In this case, the printing paper P discharged onto the inclined surface 151a receives an external force from the flat inclined surface 151a to correct the curl and flatten the printing paper P.

  By the way, curling of the printing paper P is naturally resolved even if it is left as it is, when the moisture of the ink that has permeated the printing surface P1 evaporates and there is no difference in dryness between the printing surface P1 and the non-printing surface P2. The However, when the curled printing paper P is discharged onto the flat inclined surface 151a of the paper discharge tray 150 in FIG. 4, printing is performed in a state where the force for correcting the printing paper P to be flat is applied from the inclined surface 151a. The paper P is left unattended.

  When the moisture of the ink that has permeated the printing surface P1 of the printing paper P evaporates in a state where the printing paper P is flattened, the fibers on the printing surface P1 side of the printing paper P contract, and the explanatory diagram of FIG. As shown in FIG. 4, the printing paper P is curled with the printing surface P1 on which the image M is formed facing inside and the non-printing surface P2 facing outside.

  Therefore, the printing paper P is discharged onto a paper discharge tray (not shown) having an inclined surface with the central portion in the width direction X raised from both ends, as shown in FIGS. 2 (a) to 2 (c). An attempt was made to place the tray surface of the paper discharge tray along the curled print paper P immediately after paper discharge and leave it for a while. As a result, as shown in the explanatory view of FIG. 5B, the printing surface is placed on the inner side of the state of FIG. 5A where the printing paper P is discharged and left on the flat inclined surface on the discharge tray. The curling of the printed paper P made weak.

  In response to this result, the curling of the printing paper P left after being discharged using the discharge tray 250 having a different shape of the tray surface 251a of the tray body 252 shown in the explanatory diagrams of FIGS. I decided to verify the trend. 6A to 6C, the horizontal direction in the figure in which the pair of side fences 252 are arranged at intervals is the width direction X of the printing paper P, and the paper front and back direction in the figure is the figure. The paper discharge direction Y is not shown in the middle.

  In the tray body 251 of the paper discharge tray 250 in FIG. 6A, the central portion of the tray surface 251a in the width direction X is the same as the curled convex direction of the printing paper P immediately after paper discharge with respect to both ends. Curved upward.

  In addition, the tray body 251 of the paper discharge tray 250 in FIG. 6B has a flat tray surface 251a, and the central portion and both ends of the tray surface 251a in the width direction X have the same height. Further, in the tray main body 251 of the paper discharge tray 250 in FIG. 6C, the curl convex direction of the printing paper P immediately after paper discharge is the center of the tray surface 251a in the width direction X with respect to both ends. The opposite is curved downward.

  First, the printing paper P on which the image M is printed on the printing surface P1 using the ink A shown in FIG. 3 is flat with the paper discharge tray 250 of FIG. 6A having a convex tray surface 251a curved upward. The tendency of the printing paper P when the paper is discharged with the printing surface P1 facing upward to the paper discharge tray 250 of FIG.

  The verification using the paper discharge tray 250 of FIG. 6C having the concave tray surface 251a curved downward was not performed on the printing paper P on which the image was printed on the printing surface using the ink A. .

  Then, as a result of the verification, the printing surface P1 of the printing paper P when the tray surface 251a shown in the upper part of FIG. 7A is discharged and left on the discharging tray 250 of FIG. The curl on the inside was relatively small as shown in the lower part of FIG.

  On the other hand, the printing surface P1 of the printing paper P shown in the upper part of FIG. 7B when discharged and left on the discharge tray 250 of FIG. As shown in the lower part of FIG. 7B, the curled sheet is printed after being left as compared with the case where it is discharged and left on the upper discharge tray 250 having a convex tray surface 251a in FIG. 7A. The curl with the surface P1 inside was strong.

  Therefore, as the paper discharge tray 250 on which the print paper P on which the image M is printed on the print surface P1 using the ink A is discharged and collected, at least the tray surface 251a is flat as shown in FIG. It was found that the paper discharge tray 250 of FIG. 6A having a convex tray surface 251a is more suitable than the paper discharge tray 250 of FIG.

  Subsequently, the printing paper P on which the image M is printed on the printing surface P1 using the ink B shown in FIG. 3 is used, and the discharge tray 250 of FIG. 6A having a convex tray surface 251a and the tray surface 251a are flat. 6 (b) and the paper discharge tray 250 of FIG. 6 (c) having a concave tray surface 251a, the paper is discharged with the printing surface P1 facing upward, and left as it is. The tendency of the printing paper P was verified.

  As a result of the verification, the printing surface P1 of the printing paper P when the tray surface 251a shown in the upper part of FIG. 8A is discharged and left on the discharging tray 250 of FIG. As shown in the lower part of FIG. 8 (a), the curl with the inside was relatively small.

  On the other hand, the printing surface P1 of the printing paper P shown in the upper part of FIG. 8B when discharged and left on the discharge tray 250 of FIG. As shown in the lower part of FIG. 8B, the curled sheet is printed after being left as compared with the case where it is discharged and left as it is in the upper discharge tray 250 having a convex tray surface 251a in FIG. 8A. The curl with the surface P1 inside was strong.

  Further, the print surface P1 of the printing paper P when the tray surface 251a shown in the upper part of FIG. 8C is discharged and left on the discharge tray 250 of FIG. As shown in the lower part of FIG. 8C, the curl has an upper discharge tray 250 in FIG. 8A in which the tray surface 251a is convex, and an upper part in FIG. 8B in which the tray surface 251a is flat. The curl with the printing surface P1 after being left inside is stronger than when the paper is discharged to the paper discharge tray 250 and left as it is.

  Therefore, as the paper discharge tray 250 on which the printing paper P on which the image M is printed on the printing surface P1 using the ink B is discharged and stacked until collection, the tray surface 251a has a concave shape as shown in FIG. It was found that the paper discharge tray 250 of FIG. 6B having a flat tray surface 251a is more preferable than the paper discharge tray 250 of FIG. In addition, it was found that the paper discharge tray 250 in FIG. 6A having a convex tray surface 251a is more preferable than the paper discharge tray 250 in FIG. 6B having a flat tray surface 251a.

  From the above verification results, the curled state with the printing surface P1 of the printing paper P inside when discharged and left on the discharge tray 250 indicates the type of ink (ink A, ink B) used for printing. Regardless, it has been found that it is most preferable that the tray surface 251a is discharged and left on the discharge tray 250 of FIG.

  The tray main body 251 of the paper discharge tray 250 has a flat tray surface 251a as shown in the explanatory view of FIG. 9 in addition to the shape of FIG. 6A in which the tray surface 251a is curved in a convex shape. The rib 251b may be erected at the center of the paper sheet, and the central part in the width direction X of the printing paper P discharged to the tray body 251 may be lifted upward from the non-printing surface P2 side.

  As described above, when the paper discharge tray 250 shown in FIG. 6A is used as the paper discharge tray 250 on which the printing paper P having the image M printed on the print surface P1 is discharged, the curling is performed with the print surface P1 facing outward. Even if the printing paper P is discharged to the paper discharge tray 250 in this state, the curled printing paper P can be suitably stacked on the paper discharge tray 250 by the convex tray surface 251a of the tray body 251.

  However, even if the printing paper P is discharged to the paper discharge tray 250 in FIG. 6A, if the printing paper P is left as it is on the tray surface 251a, the printing paper P has the lower part of FIG. As shown in the lower part of FIG. 8 (a), the curl with the printing surface P1 on the inside remains.

  That is, the printing paper P on the paper discharge tray 250 in FIG. 6A has a stronger force to straighten the printing paper P than the paper discharge tray 250 in FIG. 6B where the tray surface 251a is flat. Works. Therefore, in this state, when the moisture of the ink that has permeated the printing surface P1 of the printing paper P evaporates and the fibers on the printing surface P1 side of the printing paper P contract, it is left on the paper discharge tray 250 in FIG. Although it is weaker than the case, the curl with the printing surface P1 on the inside remains.

  Therefore, in the printing apparatus 20 of the present embodiment shown in FIG. 1, the tray body 25a of the paper discharge tray 25 is divided into two parts divided at the center in the width direction X of the printing paper P as shown in the explanatory view of FIG. The swinging pieces 25b, 25b are configured so that each swinging piece 25b can be swung by the power of the motor 25d around the hinge portions 25c at both ends of the tray body 25a in the width direction X.

  Therefore, when each swing piece 25b is swung upward by the motor 25d, the position of the tip of the swing piece 25b located at the center in the width direction X of the tray body 25a is moved to the hinge portions 25c at both ends in the width direction. On the other hand, it is displaced relatively upward. On the contrary, when each swinging piece 25b is swung downward by the motor 25d, the position of the tip of the swinging piece 25b located at the center in the width direction X of the tray body 25a is the hinge part 25c at both ends in the width direction. It is displaced downward relative to

  Here, a basic mechanism relating to the occurrence of deformation (curl) of the printing paper P accompanying printing on the printing surface P1 will be described with reference to FIG. First, ink adheres to the printing surface P1 (front surface) of the printing paper P to form (print) an image (step 1).

  Then, in about 5 seconds after printing, the fibers on the printing surface P1 (printed material surface) of the printing paper P extend due to the adhesion of ink. At this time, the fibers on the non-printing surface P2 to which no ink is attached do not stretch. As a result, the printing paper P (printed material) is convexly curled with the printing surface P1 (front surface) facing upward for about 10 minutes (step 2).

  Thereafter, the water content of the ink gradually evaporates from the printing surface P1 (printed material surface) of the printing paper P, the fibers on the printing surface P1 gradually shrink, and by the time one hour has passed after printing, the printing surface P1 (front surface). The printing paper P which is convexly curled with the face up gradually returns to a flat surface (step 3).

  If the evaporation of the moisture on the printing surface P1 (front surface) continues thereafter, the printing surface P1 of the printing paper P is further dried, the fibers on the printing surface P1 are further shrunk, and the printing paper P faces the printing surface P1 inside. And concavely curls (step 4).

  Since the printing paper P after printing is deformed through the processes of steps 1 to 4 described above, the paper discharge tray 25 is used during the period of steps 1 and 2 in which the printing paper P is convexly curled with the printing surface P1 (front surface) facing up. As shown in FIG. 10, it is desirable to hold the printing paper P curled in a convex shape as it is on the tray body 25a.

  At this time, when the image M is printed on the printing surface P1 of the printing paper P using the ink A and the ink B in FIG. 3 described above, the width direction X of the tray main body 25a according to the convex curl amount of the printing paper P. It is desirable to make the central part of this part 30 mm or more higher than both ends.

  Further, during the period of step 3 in which the convex curled printing paper P returns to the flat state due to the drying of the printing surface P1, the swinging pieces 25b of the paper discharge tray 25 are swung downward to return to the flat state. It is preferable to hold the printing paper P, which has been returned to the flat surface by drying the surface P1, in the shape as it is on the tray body 25a.

  Note that the convex curl of the printing paper P when the image M is printed on the printing surface P1 lasts longer because the moisture content of the ink and the moisturizing agent content are less likely to evaporate. Even when the printing apparatus 20 is used in an environment with high humidity, the convex curl of the printing paper P lasts for a long time because the moisture of the ink hardly evaporates.

  Further, the convex curl of the printing paper P becomes stronger as the amount of ink adhering per unit area of the printing surface P1 increases. Specifically, any of the printing paper P that has one of the ink amount per droplet, the printing resolution of the image M, or the printing rate with respect to the printing surface P1 is larger than the printing paper P after the other printing, the remaining printing In the same case as the paper P, the convex curl becomes stronger than the other printing paper P.

  Furthermore, the smaller the content of filler (filler), the higher the percentage of fibers in the printing paper P, the greater the degree of expansion / contraction due to ink adhesion, and the less reinforcement due to the filler, so the stiffness is weak. The convex curl of the printing paper P becomes strong.

  Further, if the basis weight of the printing paper P is too high, the stiffness is strong and difficult to deform. On the other hand, if the basis weight is too low, the stiffness is weak and it is difficult to maintain the deformed shape, and the convex curl of the printing paper becomes weak. In other words, the convex curl becomes stronger as the printing paper P has a medium basis weight.

  Further, the printing paper P with a small amount of moisture also has a high degree of fiber curl when the ink on the printing surface P1 adheres to the non-printing surface P2, so that the convex curl of the printing paper P becomes strong. Even when the printing apparatus 20 is used in an environment with low humidity, the degree of elongation of the fibers on the printing surface P1 on which the ink adheres and the fibers extend with respect to the non-printing surface P2 on which the ink does not adhere and the fibers do not stretch is the humidity. Since it becomes larger than a high environment, the convex curl of the printing paper P becomes strong.

  Therefore, when the swinging pieces 25b of the paper discharge tray 25 are swung upward as shown in FIG. 10 in accordance with the convex curled printing paper P, the center portion in the width direction X of the tray body 25a is set at both end portions. It is preferable to appropriately adjust the dimension to be higher in consideration of the contents of the elements that influence the strength of the convex curl described above.

  In addition, the timing for returning the swinging pieces 25b of the paper discharge tray 25 swinged upward to the original flat position is also adjusted as appropriate in consideration of the contents of the factors that influence the duration of the convex curl. It is desirable.

  When the printing paper P is discharged to the paper discharge tray 25 with the printing surface P1 down (with the non-printing surface P2 up) (face-down paper discharge), as described above, the paper discharge tray 25 is discharged. In contrast to the case where the printing paper P is discharged with the printing surface P1 facing upward (face-up discharging), the printed printing paper P is positioned so that both ends of the printing paper P are located higher than the center in the width direction X. Concave curl as you do.

  Therefore, in this case, the swinging piece 25b of the paper discharge tray 25 shown in FIG. 10 is reverse to the direction shown in FIG. The concavely curled printing paper P is preferably held in the shape as it is on the tray body 25a.

  Further, during the period of step 3 in which the concavely curled printing paper P returns to the flat state by drying of the printing surface P1, the swinging pieces 25b of the paper discharge tray 25 are swung upward to return to the flat state, and printing is performed. It is preferable to hold the printing paper P, which has been returned to the flat surface by drying the surface P1, in the shape as it is on the tray body 25a.

  Next, when the printing apparatus 20 according to the present embodiment prints the image M on the printing surface P1 of the printing paper P based on a print job from the computer 10 and discharges it to the paper discharge tray 25, the control unit 28 performs discharge. A processing procedure related to the swinging of the swinging piece 25b of the tray body 25a of the paper tray 25 will be described with reference to the flowchart shown in FIG.

  First, the control unit 28 waits for input of print job data from the computer 10 (step S1). When the print job data is input (YES in step S1), the control unit 28 acquires print setting information in the input print job data (step S3).

  Then, the control unit 28 determines the discharge tray 25 based on the type of ink and printing paper P used for printing specified from the acquired print setting information and the discharge method (face-up discharge, face-down discharge). The operation pattern (swing direction, swing angle, return timing of the swing piece 25b, etc.) of each swing piece 25b of the tray body 25a is determined (step S5).

  Subsequently, the control unit 28 displaces (swings) the discharge tray 25 (each swinging piece 25b of the tray body 25a) according to the determined operation pattern, and starts printing on the printing paper P (step S9). ).

  Next, the control unit 28 checks whether or not all printing of the print job has been completed (step S11). If the printing is completed (YES in step S11), the discharge tray 25 (each tray body 25a) It is confirmed whether or not the timing for returning the swing piece 25b) to the original flat position has arrived (step S13).

  When the return timing arrives (YES in step S13), the control unit 28 returns the discharge tray 25 (the swing pieces 25b of the tray body 25a) to the original flat position (step S15). A series of processing ends.

  As is apparent from the above description, in this embodiment, step S7 in the flowchart of FIG. 12 is processing corresponding to the moving means in the claims. Further, in the present embodiment, step S15 in FIG. 12 is processing corresponding to the return means in the claims.

  Furthermore, in this embodiment, the return timing of step S13 in the flowchart of FIG. 12 corresponds to the end timing of the predetermined period in the claims. This return timing can be set during the period of step 3 in FIG.

  In the printing apparatus 20 of the present embodiment, the paper discharge tray 25 and the control unit 28 constitute the paper discharge apparatus in the claims.

  According to the printing apparatus 20 of the present embodiment described above, the convex curl or concave curl is generated by swinging the swinging piece 25b of the tray body 25a at the start of printing and printing the image M on the printing surface P1. The tray main body 25a of the paper discharge tray 25 is arranged along the printing paper P. Further, the swinging piece 25b of the tray main body 25a of the paper discharge tray 25 is returned to the original flat state in accordance with the timing at which the convex curl and the concave curl naturally resolve and the printing paper P returns to flat. did.

  For this reason, a force that straightens the printing paper P from the tray main body 25a of the paper discharge tray 25 is applied to the printing paper P before returning to the flat state from the convex curled or concave curled state, so that the printing paper P dries out moisture. It is possible to suppress curling in the direction opposite to the convex curl or concave curl when the convex curl or concave curl is resolved by itself.

  Therefore, the printing paper P can be flattened without providing the printing apparatus 20 with a configuration for heating and drying the printing paper P after printing.

  In the inkjet printing apparatus 20 described above, a difference in dryness occurs between the printing surface P1 and the non-printing surface P2 due to ink adhesion to the printing surface P1, and the printed printing paper P is deformed (curled). The case was described as an example.

  However, the present invention is also applicable to a printing apparatus that performs printing by a method other than inkjet.

  For example, in the electrophotographic printing apparatus 20a (corresponding to the image forming apparatus in the claims) according to the reference example of the present invention shown in the explanatory diagram of FIG. 13, the photosensitive member charged by the charging roller 212 in the printing unit 21a. A latent image is formed on the body drum 211 by the laser beam of the writing unit 213, and toner is attracted to the latent image by the developing roller 214 to be visualized, and the visualized toner image is transferred to the printing paper P by the transfer roller 215. The process of transferring onto the printing surface P1 is performed for each color of CKMY.

  Since only the printing surface P1 of the printing paper P is heated during the transfer of the toner image, the printing paper P after printing is dried by overheating of the fibers on the printing surface P1 side and the fibers on the non-printing surface P2 side. It is in a state of being further curled and concavely curled with the printing surface P1 being inward. This state is resolved naturally when the heated printing surface P1 returns to the original temperature. However, if the printing paper P in the concave curled state is discharged onto the flat tray body 25a of the paper discharge tray 25 and left to stand, it is the same as the printing paper P on which the image is printed on the printing surface P1 by the ink jet printing apparatus 20. Such a thing occurs.

  For this reason, even in the electrophotographic printing apparatus 20a, processing similar to that of the printing apparatus 20 is performed by executing the processing of the procedure shown in the flowchart of FIG. 12 in accordance with the curl state generated on the printing paper P after printing. The effect of can be obtained.

  Further, even in a stencil printing apparatus that transfers the image M from the stencil to the printing surface P1 of the printing paper P, the ink M containing the ink adhering to the printing surface P1 causes the image M to be transferred to the printing surface P1. Curling similar to that in printing occurs on the printing paper P.

  For this reason, the stencil printing apparatus 20a also performs the process of the procedure shown in the flowchart of FIG. 12 in accordance with the curl state generated on the printing paper P after printing, so that it is the same as the printing apparatus 20 The effect of can be obtained.

  Further, for example, as in the printing system 1 shown in the explanatory diagram of FIG. 14, post-processing (for example, punch hole drilling or the like) is performed on the printing paper on which the image M is printed on the printing surface P1 by the printing apparatus 20 using the various methods described above. 10 is applied to the discharge tray 31 (corresponding to the discharge tray in the claims), and the structure of the discharge tray 25 in FIG. It may be applied to the paper tray 31 so that the control unit 32 of the post-processing device 30 performs processing according to the procedure in accordance with the flowchart of FIG.

  In that case, the control unit 32 of the post-processing device 30 and the paper discharge tray 31 constitute the paper discharge device in the claims.

  That is, the present invention can be widely applied to a discharge tray of a printing apparatus using various methods such as an inkjet method and a stencil printing method, and a discharge tray of a post-processing device used in combination with a printing device of various methods.

1 Printing System 10 Computer 20, 20a Printing Device (Image Forming Device)
DESCRIPTION OF SYMBOLS 21 Ink head part 21a Printing part 22 Paper feed tray 22a 1st paper feed tray 22b 2nd paper feed tray 22c 3rd paper feed tray 23 Straight paper feed stand 24 Circulation conveyance path 25, 31 Paper discharge tray (paper discharge device, billing) (Output tray in the section)
25a Tray body 25b Oscillating piece 25c Hinge part 25d Motor 26 Reversing part 27 Communication conveyance path 28, 32 Control part (paper discharge device)
29 Display 30 Post-processing device 140 Paper discharge port 150,250 Paper discharge tray 151,251 Tray body 151a Inclined surface 151b Concave groove 152,252 Side fence 153 Cover 155 Protruding member 155a Guide surface 211 Photosensitive drum 212 Charging roller 213 Writing unit 214 Developing roller 215 Transfer roller 251a Tray surface 251b Rib M Image P Printing paper P1 Printing surface P2 Non-printing surface X Width direction Y Discharge direction

Claims (5)

In a paper discharge device that discharges print paper on which an image is formed on the print surface by executing a print job to a paper discharge tray,
When the discharge of the printing paper on which the curling has occurred due to the image formation on the printing surface to the discharge tray, the discharge tray in the width direction of the printing paper intersects the discharge direction of the printing paper. A moving means for displacing the central portion relative to both ends to the convex side of the curl of the printing paper;
A return means for canceling the relative displacement of the central portion with respect to the both end portions after a lapse of a predetermined period from the end of the discharge of the printing paper after the image formation by the print job to the discharge tray;
A paper discharge device.   The predetermined period is a timing at which a difference in dryness generated in an image forming process between the printing surface and the non-printing surface of the printing paper discharged to the discharge tray at the end of the print job starts to decrease. The paper discharge device according to claim 1, wherein the paper discharge period is a period with the end timing.   The paper discharge device according to claim 1, wherein the predetermined period is set based on print setting information of the print job.   The paper discharge device according to claim 1, wherein image formation on the printing surface is performed by an ink jet method using liquid ink. In an image forming apparatus in which a print sheet on which an image is formed on a printing surface by executing a print job is discharged to a discharge tray by a discharge apparatus.
As the paper discharge device, the paper discharge device according to claim 1, 2, 3 or 4,
Image forming apparatus.

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