JP2013086425A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can control a landing positional shift in a sheet end section by the horizontal air current of a suction fan.SOLUTION: In the image forming apparatus 100 which has a recording head 50 ejecting ink toward a sheet P to record an image on the sheet P and a conveyer belt 43 conveying the sheet P to make the sheet P pass through an ink ejection area with the recording head 50 and makes the sheet P be sucked to the conveyer belt 43 by generating negative pressure by the suction fan 44, a driving electric current detection means 71 detecting an electric current flowing to the suction fan 44 and a driving voltage switching means 72 which switches driving voltage applied to the suction fan 44 in accordance with a change in the driving current detected by the driving current detection means 71 are provided.

Description

  The present invention relates to an image forming apparatus that adsorbs and conveys a recording medium by a conveying belt in which a negative pressure is formed by a suction fan, and forms an image by ejecting ink onto the conveyed recording medium.

  Conventionally, in this type of image forming apparatus, a suction fan is used so that the differential pressure between the pressure around the image recording unit and the pressure around the conveyance belt necessary to reliably adsorb the recording medium to the conveyance belt is minimized. In addition to controlling the air volume of the recording medium and suppressing the pressure with an air damper provided in the image recording unit and the conveyance belt, the ink landing position accuracy is deteriorated due to the air flow at the leading end of the recording medium and the image quality is deteriorated. A technique for suppressing this is known (for example, see Patent Document 1).

  However, in the technique described in Patent Document 1, in order to suppress the deviation of the ink landing position, in addition to the negative pressure forming unit that fixes the recording medium by suction, an air flow generating unit provided in the image recording unit, the image recording unit And a cover that covers the medium fixing portion, and further, an air damper is provided in the image recording portion and the medium fixing portion. Therefore, there is a problem that a very complicated configuration and control are required.

  The present invention has been made to solve such a problem, and provides an image forming apparatus capable of suppressing landing position deviation at the end of a sheet due to a horizontal airflow of a suction fan.

  An image forming apparatus according to the present invention includes: an ink discharge unit that discharges ink toward a recording medium to record an image on the recording medium; and the recording medium so that the recording medium passes through an ink discharge region of the ink discharge unit. In an image forming apparatus, comprising: a conveyance belt that conveys a recording medium; and an adsorption unit that generates a negative pressure by a suction fan to adsorb the recording medium to the conveyance belt, and detects a drive current flowing through the suction fan. Drive current detection means; and drive voltage switching means for switching a drive voltage applied to the suction fan in accordance with a change in drive current detected by the drive current detection means.

  According to the present invention, it is possible to provide an image forming apparatus capable of suppressing the landing position deviation at the end of the sheet due to the horizontal airflow of the suction fan.

1 is a side view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a plan view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating drive voltage control based on detection of a drive current of a suction fan in a transport unit of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a side view illustrating a state of the conveyance unit of the image forming apparatus according to the embodiment of the present invention when waiting for paper conveyance. FIG. 5 is a diagram illustrating a driving voltage and a driving current of a suction fan when the conveyance unit of the image forming apparatus according to an embodiment of the present invention is in a paper conveyance standby state. FIG. 6 is a side view illustrating a state at the start of sheet conveyance of the conveyance unit of the image forming apparatus according to the embodiment of the present disclosure. FIG. 6 is a diagram illustrating a driving voltage and a driving current of a suction fan when a sheet conveyance of a conveyance unit of an image forming apparatus according to an embodiment of the present invention is started. FIG. 4 is a side view illustrating a state in which the conveyance unit of the image forming apparatus according to the embodiment of the present invention is conveying a sheet. FIG. 5 is a diagram illustrating a driving voltage and a driving current of a suction fan during conveyance of a sheet in a conveyance unit of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a side view illustrating a state at the end of sheet conveyance of the conveyance unit of the image forming apparatus according to the embodiment of the present disclosure. FIG. 6 is a diagram illustrating a driving voltage and a driving current of a suction fan when the conveyance of the conveyance unit of the image forming apparatus according to the embodiment of the present invention is completed. It is a side view which shows the modification of the conveyance part of the image forming apparatus which concerns on one embodiment of this invention. It is a top view which shows the other modification of the conveyance part of the image forming apparatus which concerns on one embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the image forming apparatus 100 is configured as a line type image forming apparatus, and includes an apparatus main body 1, a paper feed tray 2 on which paper P is stacked and fed, and printed paper. A paper discharge tray 3 that discharges and stacks P, a transport unit 4 that transports paper P from the paper feed tray 2 to the paper discharge tray 3, and a recording that discharges and prints droplets on the paper P transported by the transport unit 4 A head unit 5 having a head 50, a maintenance device 6 as a maintenance / recovery mechanism that performs maintenance / recovery of each recording head 50 of the head unit 5 after completion of printing or at a predetermined timing, and a cap member and a wiper (not shown) of the maintenance device 6 A cleaner device 7 is provided as a wiper cleaning means for cleaning the member (blade means).

  The apparatus main body 1 includes front and rear side plates and stays (not shown), and the paper P stacked on the paper feed tray 2 is fed to the transport unit 4 one by one by the separation roller 21 and the paper feed roller 22. It has come to be.

  The transport unit 4 includes a transport drive roller 41A, a transport driven roller 41B, and an endless transport belt 43 wound between the transport drive roller 41A and the transport driven roller 41B. A plurality of suction holes (not shown) are formed on the surface of the conveyor belt 43, and a suction fan 44 that generates negative pressure and attracts the paper P to the conveyor belt 43 is disposed below the conveyor belt 43. Yes. Further, on the upper part of the transport driving roller 41A and the transport driven roller 41B, a transport guide roller 42A and a transport guide roller 42B are held by guides (not shown) and are in contact with the transport belt 43 by their own weight.

  The conveyance belt 43 rotates around when the conveyance drive roller 41A is rotated by a motor (not shown), and the paper P is sucked onto the conveyance belt 43 by the suction fan 44. It is conveyed so as to pass through the ink discharge area. The transport driven roller 41B and the transport guide rollers 42A and 42B are driven to rotate by the transport belt 43. In the present embodiment, the endless transport belt 43 is configured such that the surface thereof moves endlessly. However, the present invention is not limited to this, and for example, the transport belt 43 is unwound by one of two rollers. It may be configured to be wound by the other roller, and the surface thereof may be moved by the rotation of these two rollers.

  A head unit 5 having a plurality of heads 101 for ejecting droplets to be printed on the paper P is disposed above the transport unit 4 so as to be movable (in the present embodiment, it can be moved up and down). During the maintenance and recovery operation (maintenance), the head unit 5 is raised to a position where the maintenance device 6 secures a space for entering the lower part of the head unit 5.

  The head unit 5 includes four head rows 51A to 51D (hereinafter, also simply referred to as the head row 51) composed of a plurality of (in this example, five) heads 101 arranged in a row on a base member 52 that is a head holding member. The recording head 50 is provided. In the head 101, a plurality of nozzles for discharging droplets are arranged in two rows on the nozzle surface.

  Then, one of the two nozzle rows of each head 101 of the head rows 51A and 51B discharges yellow (Y) droplets and the other ejects magenta (M) droplets. One nozzle row ejects cyan (C) droplets and the other ejects black (K) droplets. That is, in the head unit 5, two head arrays 51 that discharge droplets of the same color are arranged side by side in the sheet transport direction, and the two head arrays 51 constitute a nozzle array corresponding to one sheet width. . In the present embodiment, one line of 150 dpi image is used.

  The line configuration of each color is not limited to the above, and the arrangement of each color is not particularly limited. Further, the configuration of the head unit 5 is not limited to this example. For example, a configuration in which two head units 5 are arranged, one color is assigned to one head row, and the image resolution is doubled as described above. Good.

  In the head unit 5, branch members (not shown) that supply ink to the heads 101 of the recording head 50 are arranged for each color, and a sub tank (not shown) is disposed on the upstream side of the branch member. Due to the water head difference from 101, a negative pressure appropriate to hold the meniscus of the nozzle of the head 101 is formed. Furthermore, a replaceable main tank (not shown) for storing ink is disposed upstream of the sub tank.

  On the downstream side of the transport unit 4, a transport guide 45 that discharges the paper P to the paper discharge tray 3 is disposed. The paper P transported by the transport guide 45 is discharged to the paper discharge tray 3. The paper discharge tray 3 includes a pair of side fences 31 that regulate the width direction of the paper P and an end fence 32 that regulates the leading edge of the paper P.

  A maintenance device 6 for maintaining the nozzle surface of the head 101 is disposed on the side of the head unit 5 above the transport unit 4. The maintenance device 6 includes a cap 61 for capping the nozzle surface corresponding to each head 101 of the head arrays 51A to 51D, and a blade-like wiper member (wiper blade) not shown for wiping the nozzle surface corresponding to each head 101. And suction means (not shown) for sucking the inside of the caps 61 for one row.

  The maintenance device 6 is adapted to recover the ejection performance of the head 101 by discharging the ink thickened from the nozzle by sucking with a cap 61 while the nozzle surface of the head 101 is sealed. .

  The suction means 63 of the maintenance device 6, the flow path connecting the cap 61 and the suction means, and other pressure chambers are disposed outside the rear plate of the apparatus body 1 and may be connected using a route such as a tube. it can. Further, the inside of the head 101 may be pressurized by a pressurizing unit from the upstream side of the head 101 instead of or at the time of suction during maintenance recovery.

  The maintenance device 6 is disposed above the transport unit 4 so as to be slidable along the paper transport direction. After the head unit 5 is lifted during head maintenance, it moves to the lower part of the head unit 5, and during printing, FIG. Retreat to the position shown in.

  A cleaner device 7 for cleaning droplets (waste liquid) adhering to the cap 61 and a wiper blade (not shown) is disposed on the maintenance device 6. The cleaner device 7 is arranged so as to be vertically movable with respect to the sheet conveying surface by a cleaner moving means (not shown).

  When the maintenance device 6 that has completed the maintenance of the head 101 is retracted to the side of the head unit 5, the cleaner device 7 moves downward to clean the cap 61 and the wiper blade.

  Further, in the present embodiment, the image forming apparatus 100 includes a drive current detection unit 71 that detects a drive current flowing through the suction fan 44, and a suction fan according to a change in the drive current detected by the drive current detection unit 71. Drive voltage switching means 72 for switching the drive voltage applied to the drive circuit 44.

  Here, the drive voltage control (switching) based on the detection of the drive current of the suction fan 44 will be described with reference to the flowchart of FIG.

  First, when printing is started, the drive voltage of the suction fan 44 is set to a low voltage V1 (step S1). In step S1, when the paper P is not transported, the suction force by the transport belt 43 is not necessary, so that the horizontal airflow immediately below the recording head 50 has a low suction force that does not affect the ejection position deviation. The low voltage V1 is set.

  Note that the horizontal airflow immediately below the recording head 50 is generated when air sucked by the suction fan 44 flows from the outside through a narrow space between the recording head 50 and the conveyance belt 43.

  Next, it is determined whether or not the designated number of printed sheets has been reached (step S2). If the designated number of printed sheets has been exceeded, printing is terminated, and if the number of designated printed sheets has been reached, the process proceeds to step S3.

  In step S3, it is determined whether the change in the drive current detected by the drive current detection means 71 is equal to or greater than the threshold value.

  In step S3, when the paper P is not fed and when the entire surface of the paper P is on the transport belt 43, the driving load of the suction fan 44 is constant, and the driving current of the suction fan 44 hardly changes. Therefore, the process returns to step S2 and the drive voltage is not switched.

  Here, when feeding other than the above is started and the suction port of the transport belt 43 is started to be closed, and when printing is almost finished and the paper P starts to be discharged and the suction hole of the transport belt 43 is started to open. In this case, the opening area of the suction port of the conveyor belt 43 changes, the drive load of the suction fan 44 changes, and the drive current of the suction fan 44 changes. In step S3, it is determined whether or not the amount of change in the drive current of the suction fan 44 is equal to or greater than a preset threshold value.

  In step S4, it is determined whether the change in the drive current of the suction fan 44 is increased or decreased. If it is increased, the process proceeds to step S6. If it is decreased, the process proceeds to step S5.

  In this step S4, when the change in the drive current of the suction fan 44 is a decrease, the printing is almost finished and the discharge of the paper P is started. Therefore, in order to reduce the suction force of the suction fan 44, The process proceeds to step S5 so as to lower the drive voltage.

  Further, in this step S4, if the drive current change of the suction fan 44 is an increase change, the sheet P is newly fed, so the drive voltage is set to increase the suction force of the suction fan 44. The process proceeds to step S6 so as to increase.

  In step S5, the drive voltage of the suction fan 44 is set to a low voltage V1 (that is, the voltage V1 set in step S1 is maintained), and the process returns to step S2, and in step S6, the drive voltage of the suction fan 44 is set to the high voltage V2. And return to step S2. In this flowchart, the processing of step S3 to step S6 is executed by the drive voltage switching means 72.

  As shown in FIGS. 4 and 5, the suction fan 44 is driven at a low voltage V <b> 1 during the paper conveyance standby. In other words, when there is no paper P on the conveyance belt 43 during the paper conveyance standby, all the suction ports of the conveyance belt 43 are opened and the suction fan 44 is hardly subjected to a suction load. It is driven with V1.

  Since the voltage V1 is a voltage that can perform the minimum suction for attracting the paper P to the transport belt 43, the horizontal airflow immediately below the recording head 50 generated by the suction of the suction fan 44 hardly occurs.

  As shown in FIGS. 6 and 7, when the sheet conveyance is started, the load of the suction fan 44 is increased as the suction port of the conveyance belt 43 is covered with the conveyed sheet P, and the drive current of the suction fan 44 is increased. To increase. When the drive current detection unit 71 detects an increase in current value equal to or greater than a predetermined threshold value Δi, the drive voltage switching unit 72 switches the drive voltage of the suction fan 44 to a high voltage V2.

  Since the voltage V2 is set to a voltage at which a sheet suction force required for transporting the paper P can be obtained, a reliable paper transport that does not cause a positional shift or lift of the paper P is started by the suction force of the suction fan 44. The In addition, since the area of the suction port covered with the paper P increases at the start of paper conveyance, the horizontal airflow generated immediately below the recording head 50 is suppressed.

  As shown in FIGS. 8 and 9, during conveyance of the sheet, the sheet P being conveyed covers the suction port immediately below the recording head 50, and the suction load of the suction fan 44 does not change greatly, and sheet conveyance starts. Since the suction fan 44 is driven with the voltage V2 set at that time, the suction fan 44 sucks, so that reliable suction conveyance without positional displacement or floating occurs. During the conveyance of the paper, the suction port directly below the recording head 50 is covered with the paper P, so that no horizontal airflow is generated immediately below the recording head 50 due to the suction of the suction fan 44.

  As shown in FIGS. 10 and 11, at the end of paper conveyance, the area covered by the suction port of the conveyance belt 43 decreases with the conveyance of the paper P, and the driving load of the suction fan 44 decreases in the same manner. The drive current of 44 decreases.

  When the drive current detection unit 71 detects a decrease in current value that is equal to or greater than a predetermined threshold value Δi, the drive voltage switching unit 72 switches the drive voltage of the suction fan 44 to a low voltage V1. Since this voltage V1 is set to a minimum driving voltage for adsorbing the paper P, the next paper P is transported in a state in which the horizontal airflow caused by the suction of the suction fan 44 directly below the recording head 50 is suppressed. Will be prepared.

  As shown in FIG. 12, by providing a plurality of independent negative pressure forming chambers 74 that respectively accommodate the suction fans 44 in the paper transport direction, the negative pressure forming chamber of the portion covered with the paper P as the paper P is transported. Since only the driving voltage of the suction fan 44 of 74 is driven by the high voltage V2, and the suction fan 44 of the negative pressure forming chamber 74 of the other part is driven by the low voltage V1, the horizontal airflow generated immediately below the head is further increased. Can be suppressed.

  In FIG. 12, six negative pressure forming chambers 74 that respectively accommodate the suction fans 44 are provided in the paper transport direction, and the suction fans 44 of these six negative pressure forming chambers 74 are independently driven and controlled. It is like that.

  As shown in FIG. 13, the sheet P is conveyed by providing a plurality of independent negative pressure forming chambers 74 that respectively accommodate the suction fans 44 in the sheet conveying direction and the direction (width direction) perpendicular to the sheet conveying direction. Corresponding to the position and paper size (width, length), the suction fan 44 of the negative pressure forming chamber 74 in the portion not covered by the paper P is driven with a low voltage V1, so that the position and size of the paper P are adjusted. Without being affected, the horizontal airflow immediately below the recording head 50 can be further reduced.

  In FIG. 13, a total of 42 negative pressure forming chambers 74 that respectively accommodate the suction fans 44 are provided in 6 rows in the paper transport direction and 7 rows in the direction perpendicular to the paper transport direction (width direction). The suction fans 44 of these six negative pressure forming chambers are independently driven and controlled.

  As described above, the image forming apparatus 100 according to the present embodiment includes the drive current detection unit 71 that detects the drive current flowing through the suction fan 44 and the change in the drive current detected by the drive current detection unit 71. Drive voltage switching means 72 for switching the drive voltage applied to the suction fan 44.

  With this configuration, when the load and drive current of the suction fan 44 change as the paper P is carried in and out, the drive voltage switching unit 72 switches the drive voltage of the suction fan 44 so as to suppress the horizontal airflow. Can do. Therefore, it is possible to suppress landing position deviation at the end of the sheet due to the horizontal airflow of the suction fan 44. In addition, since the configuration is simple, the cost can be reduced. Further, current consumption of the suction fan 44 other than when suction operation is necessary can be reduced.

  The image forming apparatus 100 according to the present embodiment is characterized in that the drive voltage switching unit 72 switches the drive voltage to a higher voltage when the drive current detected by the drive current detection unit 71 increases.

  With this configuration, reliable paper conveyance that does not cause positional deviation or lifting of the paper P due to the suction force of the suction fan 44 is started. In addition, since the area of the suction port covered with the paper P increases at the start of paper conveyance, the horizontal airflow generated immediately below the recording head 50 due to the suction of the suction fan 44 is suppressed.

  Further, the image forming apparatus 100 according to the present embodiment is characterized in that the drive voltage switching unit 72 switches the drive voltage to a lower voltage when the drive current detected by the drive current detection unit 71 decreases.

  With this configuration, it is possible to prepare for the conveyance of the next sheet P in a state where the horizontal airflow generated immediately below the recording head 50 by the suction of the suction fan 44 is suppressed.

  Further, the image forming apparatus 100 according to the present embodiment is characterized in that the suction means is configured by arranging a plurality of negative pressure forming chambers 74 each accommodating the suction fan 44 in the paper transport direction.

  With this configuration, as the sheet P is transported, only the driving voltage of the suction fan 44 in the portion of the negative pressure forming chamber 74 covered with the sheet P is switched to the high voltage V2, and the other portion of the negative pressure forming chamber 74 is switched. Since the suction fan 44 is driven at a low voltage V1, horizontal airflow generated directly below the recording head 50 can be further suppressed.

  Further, in the image forming apparatus 100 according to the present embodiment, the suction unit has a plurality of negative pressure forming chambers 74 each accommodating the suction fan 44 arranged in a matrix in the paper transport direction and the direction orthogonal to the paper transport direction. It is characterized by comprising.

  With this configuration, the suction fan 44 is sucked by the low voltage V1 in the portion not covered by the paper P corresponding to the transport position and the paper size (width and length) of the paper P. The horizontal airflow immediately below the recording head 50 can be further reduced without being affected by the size.

DESCRIPTION OF SYMBOLS 1 Apparatus main body 4 Conveyance unit 5 Head part 43 Conveyor belt 44 Suction fan (adsorption means)
45 Conveyance guide 50 Recording head (ink ejection means)
51 Head array 52 Base member 63 Suction means 71 Drive current detection means 72 Drive voltage switching means 74 Negative pressure forming chamber 100 Image forming apparatus 101 Head

JP 2006-240185 A

Claims (5)

Ink ejection means for ejecting ink toward a recording medium to record an image on the recording medium;
A transport belt for transporting the recording medium such that the recording medium passes through an ink discharge area of the ink discharge means;
An image forming apparatus comprising: suction means for generating a negative pressure by a suction fan and sucking the recording medium to the transport belt;
Drive current detection means for detecting the drive current flowing through the suction fan;
An image forming apparatus comprising: a drive voltage switching unit that switches a drive voltage applied to the suction fan in accordance with a change in the drive current detected by the drive current detection unit.   The image forming apparatus according to claim 1, wherein the drive voltage switching unit switches the drive voltage to a higher voltage when the drive current detected by the drive current detection unit increases.   3. The image forming apparatus according to claim 1, wherein the drive voltage switching unit switches the drive voltage to a low voltage when the drive current detected by the drive current detection unit decreases.   The image according to claim 1, wherein the suction unit includes a plurality of negative pressure forming chambers each housing the suction fan in a recording medium conveyance direction. Forming equipment.   The suction unit includes a plurality of negative pressure forming chambers each accommodating the suction fan arranged in a matrix in a recording medium conveyance direction and a direction orthogonal to the recording medium conveyance direction. The image forming apparatus according to claim 1.

Images