JP5535010B2 - Inkjet printing device - Google Patents

Description

  The present invention relates to an inkjet printing apparatus that performs printing by ejecting ink onto a recording medium such as paper.

  In an inkjet printing apparatus, in order to correct the posture of paper that has been curled or undulated (hereinafter referred to as cockling), a large number of through-holes that generate suction force are formed on the surface of the platen, and the platen is porous. It is known that a sheet plate is sucked and conveyed by sliding an elastic platen belt and generating a suction force in a belt hole.

  Of the belt holes of the platen belt, when the belt hole not blocked by the paper passes over the through hole of the platen, the air above the platen belt is passed through the belt hole and the through hole not blocked by the paper. It flows downward and airflow is generated on the platen belt.

  When the edge of the paper is printed, if a disturbance in the airflow occurs near the nozzles of the ink jet head, minute ink droplets (hereinafter referred to as ink mist) at the time of ink ejection scatter and adhere to the paper. There is a risk of contamination by mist.

  On the other hand, Patent Document 1 proposes a technique for reducing the turbulence of the air current in the vicinity of the inkjet head by determining the arrangement mode of the through holes on the platen in consideration of the positional relationship with the head. .

JP 2004-216653 A

  By the way, many platens are molded integrally with resin, and due to uneven processing of pouring resin and cooling processing performed in the molding process, external stress acting in the process of incorporating the molded platen into the printer, etc. In some cases, a concave-shaped portion in which both the upper surface and the lower surface protrude downward is generated.

  FIG. 7 is a diagram illustrating the air flow when the platen 221 is flat, and FIG. 8 is a diagram illustrating the air flow when the concave portion C is generated in the platen 221. When such a concave portion C is generated, a gap S is generated between the platen 221 and the platen belt 222 in the concave portion C, and the platen hole 221a should not be communicated through the gap S. The belt hole 222a communicates with the platen hole 221a, and an unexpected air flow W1 may occur.

  Further, when the space between the platen 221 and the platen belt 222 is widened due to the generation of the concave portion C, the flow path resistance with respect to the air flow W2 from the belt hole 222a communicating with the platen hole 221a is reduced, and the air In some cases, the flow of the flow becomes large. When such an air flow different from the original design is generated, the air flow may be disturbed on the platen belt due to the air flow.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an ink jet printing apparatus that can reduce airflow turbulence on a platen belt caused by a concave portion existing in a platen.

  The ink jet printing apparatus of the present invention is an ink jet printing apparatus that performs printing by discharging ink onto a recording medium, and has a plurality of belt holes, and adsorbs and conveys the recording medium by negative pressure acting on the belt holes. A conveying belt, a platen having a plurality of through holes, a pressure reducing means for generating a negative pressure on the opposite side of the platen to the conveying belt, and a platen facing the platen. The direction in which the inkjet head that discharges ink from the nozzles onto the recording medium conveyed by the conveyance belt, the surface (upper surface) on the inkjet head side of the platen, and the surface opposite to the inkjet head (lower surface) move away from the inkjet head ( Negative pressure adjustment mechanism to reduce negative pressure in the space between the concave-shaped part projecting downward) and the conveyor belt The is characterized in that it comprises.

  In the above apparatus, the negative pressure adjusting mechanism is a groove formed on the surface of the platen on the side of the platen belt, and this groove communicates the space between the concave portion and the platen belt with the atmosphere. Also good.

  The groove may be formed in a region other than the region facing the ink jet head on the surface of the platen on the platen belt side.

  According to the inkjet printing apparatus of the present invention, an inkjet printing apparatus that performs printing by discharging ink onto a recording medium, has a plurality of belt holes, and adsorbs the recording medium by a negative pressure acting on the belt holes. A conveying belt that conveys the belt, a platen having a plurality of through holes, a decompression unit that generates a negative pressure on the opposite side of the platen from the conveying belt, and a platen facing the platen. The negative pressure in the space between the conveyance belt and the inkjet head that is provided and discharges ink from the nozzles onto the recording medium conveyed by the conveyance belt, and the concave shape part in which the upper and lower surfaces of the platen both protrude downward is reduced. A negative pressure adjusting mechanism that reduces the negative pressure in the space between the concave portion and the conveyor belt. Accordingly, it is possible to reduce the occurrence of different airflow from the original design due to its negative pressure. Thereby, the turbulence of the airflow on the platen belt due to the concave portion can be reduced.

  In the above apparatus, when the negative pressure adjusting mechanism is a groove formed on the surface of the platen on the side of the platen belt, and the groove communicates the space between the concave portion and the platen belt with the atmosphere. Can reduce the turbulence of the airflow on the platen belt due to the concave portion by a simple configuration in which grooves are formed on the platen surface.

  Further, when the groove is formed in a region other than the region facing the inkjet head on the surface of the platen on the side of the platen belt, the sheet can be prevented from floating near the inkjet head. .

Schematic configuration diagram of inkjet printing apparatus Top view of the head holder Perspective view of head holder Platen top view The figure which shows the state by which the edge part of the groove | channel was obstruct | occluded The figure which shows the state which connected the edge part of the groove | channel to air | atmosphere The figure which shows the flow of air in case a platen is flat The figure which shows the flow of air when a concave shape part generate | occur | produces in a platen

  Hereinafter, an embodiment of an ink jet printing apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus 1 according to the present embodiment. The inkjet printing apparatus 1 includes a paper feeding unit 10, a printing unit 20, a paper discharge unit 30, a reversing unit 40, and a control unit 50.

  The paper supply unit 10 supplies the paper P to the printing unit 20. The paper supply unit 11 stacks unprinted paper P provided below the side surface of the inkjet printing apparatus 1. The paper feeding path 12 leads to the printing unit 20, the paper feeding roller pair 13 that takes out the paper P one by one from the paper feeding tray 11, and the timing roller pair 14 that feeds the paper P to the printing unit 20 at a predetermined timing.

  The printing unit 20 carries in the paper P from the paper feeding unit 10, discharges and prints ink on the paper P, and carries out the paper P to the paper discharge unit 30. The head unit 21 that discharges ink, the head unit The platen unit 22 is configured to convey the paper P below 21. Details of the head unit 21 and the platen unit 22 will be described later.

  The paper discharge unit 30 conveys the printed paper P and discharges it. The paper discharge unit 31 stacks the printed paper P provided on the upper side surface of the inkjet printing apparatus 1 and the printed paper P. With a printing surface facing downward, a paper discharge path 32 that leads from the printing unit 20 to the paper discharge tray 31, and a plurality of paper discharge roller pairs 33 that feed the paper P on the paper discharge path 32 one by one. .

  The reversing unit 40 reverses the single-side printed paper P, and sends the paper P again to the printing unit 20 with the unprinted surface facing upward. A buffer space 41 provided on the back side of the paper discharge tray 31. A branch path 42 that branches from the middle of the paper discharge path 32 and leads the paper P to the buffer space 41, a refeed path 43 that leads the paper P from the buffer space 41 to the timing roller pair 14, a branch path 42, and a refeed path A plurality of reversing roller pairs 44 for feeding the paper P on the sheet 43 one by one are provided.

  The control unit 50 processes the operation of each unit and processes instructions from the user through an operation panel (not shown).

  Next, the overall operation of the inkjet printing apparatus 1 will be described. Unprinted paper P is taken out from the paper feed tray 11 onto the paper feed path 12 by the paper feed roller pair 13. The paper P on the paper feed path 12 is sent to the printing unit 20 at a predetermined timing by the timing roller pair 14.

  In the printing unit 20, the platen unit 22 transports the paper P at a predetermined speed, and the head unit 21 performs printing by ejecting ink onto the paper P. The printed sheets are fed one by one onto the sheet discharge path 32 by the pair of sheet discharge rollers 33, and are guided to the sheet discharge table 31 and discharged with the printing surface facing downward.

  When duplex printing is performed, the paper P on the paper discharge path 32 is sent to the branch path 42 by a path switching mechanism (not shown) provided in the middle of the paper discharge path 32 and guided to the buffer space 41. The paper P is sent out from the buffer space 41 to the paper re-feeding path 43, guided again to the timing roller pair 14, and re-fed to the printing unit 20. In the following description, the direction orthogonal to the transport direction of the paper P is described as the main scanning direction, and the transport direction of the paper P is described as the sub-scanning direction.

  The head unit 21 of the printing unit 20 will be described. The head unit 21 includes a plurality of inkjet heads 211 and a head holder 212 that holds the inkjet heads 211.

  FIG. 2 is a plan view of the head holder 212, and FIG. 3 is a perspective view of the head holder 212. The head holder 212 is formed with a total of 24 mounting holes 213 in a staggered manner at a predetermined interval in the transport direction and a direction orthogonal to the direction (hereinafter referred to as a scanning direction), as shown in the upper diagram. The head holder 212 is configured to insert each inkjet head 211 into each mounting hole 213 and hold the inkjet head 211 in a state where the inkjet head 211 is inserted with a flange or the like (not shown).

  A description will be given with reference to FIG. 1 again. The inkjet head 211 includes an inkjet nozzle that ejects ink toward the paper P. The ink jet nozzle vibrates the element by applying a voltage to the piezoelectric element attached to the nozzle 214, and discharges uniform droplets from the nozzle 214. The ink jet nozzle is linear in the scanning direction on the lower surface of the ink jet head 211. A line nozzle 215 is formed. That is, each inkjet head 211 ejects ink in line units.

  In the present embodiment, the inkjet heads 211 that eject the same color ink are classified in units of six, and eject any one of black K, magenta color M, cyan color C, and yellow color Y.

  Next, the platen unit 22 will be described. The platen unit 22 drives a platen 221 disposed at a position facing each nozzle 214 below the head unit 21, an endless platen belt 222 spanned so as to slide on the platen 221, and the platen belt 222. The driving roller 223, the driven roller 224, and a fan 225 that makes negative pressure in the space below the platen 221 are configured.

  FIG. 4 is a plan view of the platen 221. In FIG. 4, the projection position of each inkjet head 211 is indicated by a broken line. The platen 221 is a plate member, and a plurality of elongated through holes 221a are formed in a staggered manner in a range through which the platen belt 222 passes. Further, a concave portion 221b communicating with the through hole 221a is formed on the surface of the platen 221.

  In addition, a plurality of grooves 228 are formed on the upper surface of the platen 221 to communicate the space between the concave portion and the platen belt 222 with the atmosphere. These grooves 228 constitute a negative pressure adjusting mechanism in the present invention.

  As shown in FIG. 4, in the present embodiment, a total of ten grooves 228 are distributed and arranged in a balanced manner over the entire area other than the area directly below the inkjet head 211 on the upper surface of the platen 221. One end of each groove 228 extends to the vicinity of the outer periphery of the upper surface of the platen 221, and a closing wall 228b for closing the groove is formed at the end. Due to the presence of the blocking wall 228b, communication between the grooves 228 and the atmosphere in the outer peripheral region of the upper surface of the platen 221 is blocked, and by removing the blocking wall 228b, the space in the groove 228 can be communicated with the atmosphere. . FIG. 5 shows a state where the end of the groove 228 is closed by the blocking wall 228b, and FIG. 6 shows a state where the blocking wall 228b is removed and the groove 228 is communicated with the atmosphere.

  When a concave portion is detected on the platen 221, the groove 228 existing closest to the position of the detected concave portion is specified, and a blocking wall formed at the end of the specified groove 228 By removing 228b, the space in the groove 228 is communicated with the atmosphere. Then, the space between the concave portion and the platen belt 222 communicates with the atmosphere via the groove 228, and the negative pressure in the space is reduced.

  Here, the detection of the concave portion is performed by measuring the height of the upper surface of the platen 221 at points sampled at a predetermined interval, and the measured value at that point is compared with the measured value at the surrounding measurement points to a predetermined threshold value. This is done by detecting a lower point. For example, a point where a difference between a value obtained by averaging the measurement values at two adjacent measurement points across the point and the measurement value at that point is equal to or greater than a predetermined threshold is detected.

  Refer to FIG. 1 again. A plurality of belt holes 222a are formed in the platen belt 222 in a staggered manner. The fan 225 creates a negative pressure in the space below the platen 221 to generate a suction force in each through hole 221a. The space below the platen 221 is sealed with a frame (not shown).

  As the platen belt 222 slides on the platen 221, a suction force is also generated in the belt hole 222a that has passed over the recess 221b. The suction force generated in the belt hole 222a is maximized when passing over the through hole 221a. Further, the distance between the surface of the platen belt 222 and each nozzle 214 is adjusted by the thickness of the paper P, but is in the range of about 1 to 3 mm.

  The sheet P sent out by the timing roller pair 14 is detected at its leading end in the sub-scanning direction by a sensor (not shown), and is sucked and held on the platen belt 222 by each belt hole 222a. As the paper P passes through the position UP just below the nozzle 214 at a predetermined speed, ink is ejected from each inkjet head 211 in units of lines, and an image is formed on the paper P. The timing of ink ejection by the head unit 21 and conveyance of the paper P by the platen unit 22 is controlled by the control unit 50.

  As described above, according to the ink jet printing apparatus 1 according to the embodiment of the present invention, the negative pressure in the space between the platen belt 222 and the concave portion where both the upper surface and the lower surface of the platen 221 protrude downward is applied. Since the groove 228 to be reduced is provided, by using the groove 228 to reduce the negative pressure in the space between the concave portion and the platen belt 222, the air flow is different from the original design due to the negative pressure. Can be reduced. And since it is a simple structure of forming a groove | channel in the platen 221 surface, the manufacture is also easy.

  In addition, since the groove 228 is formed in a region other than the region facing the inkjet head 211 on the surface of the platen 221 on the side of the platen belt 222, it is possible to prevent the sheet from floating near the inkjet head 211.

  Moreover, in the said embodiment, although the negative pressure adjustment mechanism has illustrated about the case where the space between a concave shape part and the platen belt 222 is connected with air | atmosphere by the groove | channel 228 formed in the platen 221 upper surface, The specific configuration of the negative pressure adjusting mechanism 228 is not limited to that shown in the above-described embodiment, and the space between the concave portion existing in the platen 221 and the platen belt 222 can communicate with the atmosphere. If so, other configurations are possible.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 211 Inkjet head 214 Nozzle 221 Platen 221a Through hole 222 Platen belt 222a Belt hole 225 Fan 228 Groove (negative pressure adjusting mechanism)
228a Blocking wall C Recessed part

Claims (3)

An inkjet printing apparatus that performs printing by discharging ink to a recording medium,
A conveying belt that has a plurality of belt holes and sucks and conveys the recording medium by a negative pressure acting on the belt holes;
A platen that slidably supports the conveyor belt and has a plurality of through holes;
Pressure reducing means for generating the negative pressure on the opposite side of the platen from the conveyor belt;
An ink jet head that is provided to face the platen and that ejects the ink from nozzles onto the recording medium that is transported by the transport belt;
A negative pressure adjusting mechanism for reducing the negative pressure in the space between the concave belt and the conveyor belt, the surface of the platen on the ink jet head side and the surface opposite to the ink jet head projecting away from the ink jet head. An ink jet printing apparatus comprising:   The negative pressure adjusting mechanism is a groove formed on the surface of the platen on the conveyance belt side, and the groove communicates the space between the concave portion and the conveyance belt and the atmosphere. The inkjet printing apparatus according to claim 1.   3. The ink jet recording apparatus according to claim 2, wherein the groove is formed in a region of the surface other than a region facing the ink jet head.

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