JP2012056097A - Inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce disturbance of air flow in the vicinity of the nozzles of line heads provided in the most upstream and most downstream in an ink jet printer where multiple inkjet heads are provided side by side in the carrying direction of a recording medium.SOLUTION: On a platen 221, the size of a through hole 221a which opens in an upstream region UR on the upstream side, in the carrying direction, of a position UP facing the nozzle in an ink jet head array A provided in the most upstream in the carrying direction, and in a downstream region LR on the downstream side, in the carrying direction, of a position LP facing the nozzle in an ink jet head array B provided in the most downstream in the carrying direction is set larger than size of a through hole 221a which is provided on the downstream side of the position UP in the carrying direction and opens in a middle stream region MR on the upstream side of the position LP in the carrying direction.

Description

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

  2. Description of the Related Art Conventionally, there has been known a line head type ink jet printing apparatus capable of recording an image for one line at a time by using a plurality of short heads arranged over a recording medium width or a single long head. ing. For example, a line head is assigned to each of black K, magenta color M, cyan color C, and yellow color Y, and four color line heads are arranged side by side in the paper transport direction (see Patent Document 1).

  In addition, in an inkjet printing apparatus, in order to correct the posture of a paper that has been deformed into a curled or wavy shape, a plurality of through holes that generate suction force are formed on the surface of the platen, and a porous platen belt is formed on the platen. It is known that the paper is sucked and conveyed by generating a suction force in the belt hole by sliding the belt. In this ink jet printing apparatus, when a belt hole not blocked by paper passes over the through hole of the platen, the air above the platen belt is sucked into the platen belt through the belt hole and the through hole, and the platen belt Airflow is generated above.

JP 2007-31007 A

  By the way, in the above-described line head type ink jet printing apparatus, a plurality of line heads are arranged densely in order to ensure ink landing accuracy, and the line head provided on the uppermost stream in the transport direction on the platen belt. In the space on the downstream side of the transport and the space on the upstream side of the line head provided on the most downstream side, the flow of air is suppressed by the presence of the line head surrounding the space.

  On the other hand, on the platen belt, there is no shielding for suppressing the air flow in the space upstream from the line head provided upstream and the space downstream from the line head provided downstream. Therefore, the airflow generated by the suction force of the belt hole increases, and there is a risk that the airflow may be disturbed in the vicinity of the nozzles of the line head provided on the most upstream side and the most downstream side. When airflow disturbance occurs near the nozzles, minute ink droplets (hereinafter referred to as ink mist) when ink is ejected scatters and adheres to the inside of the paper or the apparatus, causing deterioration in printing quality or contamination in the apparatus. .

  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 the turbulence of airflow in the vicinity of nozzles of line heads provided at the most upstream and the most downstream.

  A first ink jet printing apparatus according to 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 the recording medium is adsorbed by negative pressure acting on the belt holes. A conveying belt, a slidable support for the conveying belt, a platen having a plurality of through holes, a decompression means for generating a negative pressure on the opposite side of the conveying belt of the platen, and a conveying belt A plurality of inkjet heads that discharge ink from nozzles onto a recording medium to be printed, and arranged in the direction in which the recording medium is conveyed, and are arranged on the platen, and are the most in the conveying direction among the plurality of inkjet heads on the platen. The suction force in the upstream area from the position facing the nozzle of the inkjet head provided upstream is It is characterized in that less than the suction force in the region of the transport downstream from the.

  Here, the conveyance upstream side means the side on which the recording medium is carried in, and the conveyance downstream side means the side on which the recording medium is carried out. same as below.

  The suction force in the region means an amount obtained by multiplying the total area of the through holes existing in the unit region of a predetermined size in the region and the negative pressure acting on those through holes. same as below.

  In the above apparatus, the shortest distance between the nozzle of the inkjet head provided at the uppermost stream in the transport direction and the nozzle of the inkjet head adjacent to the inkjet head in the direction in which the recording medium is transported is D1, The suction force in the region within the range of the length D1 from the position facing the nozzle of the inkjet head provided at the most upstream in the transport direction is within the range of the length D1 from the facing position to the downstream side of the transport. It may be smaller than the suction force in the region.

  Further, the shortest distance between the nozzle of the ink jet head provided at the uppermost stream in the transport direction and the ink jet head adjacent to the ink jet head in the direction in which the recording medium is transported is D2, and the shortest distance in the transport direction on the platen. The suction force in the region within the range of the length D2 from the position facing the nozzle of the inkjet head provided upstream to the upstream side of the conveyance, and the suction in the region within the range of the length D2 from the opposite position to the downstream side of the conveyance It may be smaller than the force.

  Here, that the inkjet heads are adjacent in the transport direction means that at least a part thereof is adjacent in the transport direction. same as below.

  Further, the shortest distance between adjacent inkjet heads (or nozzles thereof) is the shortest distance among the shortest distances between adjacent inkjet heads (or nozzles thereof) when there are two or more adjacent inkjet heads. Means. same as below.

  Further, the suction force in the region within the range of 3 cm from the position facing the nozzle of the inkjet head provided on the uppermost stream in the transport direction on the platen to the upstream side of the transport is 3 cm from the facing position to the downstream side of the transport. It may be smaller than the suction force in the region within the range.

  Further, the suction force in a region within a range of 2 cm from the position facing the nozzle of the inkjet head provided on the uppermost stream in the transport direction on the platen to the transport upstream side is 2 cm from the facing position to the transport downstream side. It may be smaller than the suction force in the region within the range.

  Further, in a plan view, the average of the distance between each position on the nozzle of the inkjet head provided at the most upstream in the transport direction and the through hole located closest to the upstream side of the transport from that position is the other It may be smaller than the average of the distance between each position on the nozzle of the inkjet head and the through hole located closest to the upstream side of conveyance from that position.

  Here, the position of the through-hole is closest to a specific position on the nozzle in a plan view when the platen is viewed from the inkjet head side, the edge of the opening close to the nozzle and the specific position It means that the distance between is the smallest. same as below.

  A second ink jet printing apparatus according to 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 the recording medium by a negative pressure acting on the belt holes. A conveying belt, a slidable support for the conveying belt, a platen having a plurality of through holes, a decompression means for generating a negative pressure on the opposite side of the conveying belt of the platen, and a conveying belt A plurality of inkjet heads that discharge ink from nozzles onto a recording medium to be printed, and arranged in the direction in which the recording medium is conveyed, and are arranged on the platen, and are the most in the conveying direction among the plurality of inkjet heads on the platen. The suction force in the area on the downstream side of the conveyance from the position facing the nozzle of the inkjet head provided downstream is the position where It is characterized in that less than the suction force in the region of the transport upstream side from.

  In the above apparatus, the shortest distance between the nozzle of the inkjet head provided at the most upstream in the transport direction and the nozzle of the inkjet head adjacent to the inkjet head in the direction in which the recording medium is transported is D3, The suction force in the region within the range of the length D3 from the position facing the nozzle of the inkjet head provided at the most downstream in the transport direction is within the range of the length D3 from the facing position to the upstream side of the transport. It may be smaller than the suction force in the region.

  Further, the shortest distance between the nozzle of the ink jet head provided at the uppermost stream in the transport direction and the ink jet head adjacent to the ink jet head in the direction in which the recording medium is transported is D4. The suction force in the region within the range of the length D4 from the position facing the nozzle of the inkjet head provided downstream from the downstream side of the conveyance is the suction force in the region within the range of the length D4 from the opposite position upstream of the conveyance. It may be smaller than the force.

  Further, the suction force in the region within the range of 3 cm from the position facing the nozzle of the inkjet head provided on the most downstream side in the transport direction on the platen to the transport downstream side is 3 cm from the facing position to the transport upstream side. It may be smaller than the suction force in the region within the range.

  Further, the suction force in the region within a range of 2 cm from the position facing the nozzle of the inkjet head provided on the most downstream side in the transport direction on the platen to the transport downstream side is 2 cm from the facing position to the transport upstream side. It may be smaller than the suction force in the region within the range.

  Also, in plan view, the average distance between each position on the nozzle of the inkjet head provided on the most downstream side in the transport direction and the through hole located closest to the transport downstream side from each position is It may be smaller than the average of the distances between each position on the nozzle of the inkjet head and the through hole located closest to the downstream side of the conveyance from that position.

  According to the first ink jet printing apparatus of the present invention, there are a plurality of belt holes, a conveyance belt that adsorbs and conveys a recording medium by negative pressure acting on the belt holes, and a slidably supported conveyance belt. In addition, there are a platen having a plurality of through holes, a decompression unit that generates a negative pressure on the opposite side of the platen conveyance belt, and a plurality of inkjet heads that eject ink from nozzles onto a recording medium conveyed by the conveyance belt. And a printing unit arranged side by side in the direction in which the recording medium is conveyed, and upstream of the plurality of inkjet heads on the platen from the position facing the nozzle of the inkjet head provided in the uppermost stream in the conveyance direction. So that the suction force in the region on the side is smaller than the suction force in the region on the downstream side of the conveyance from the opposite position. Runode, it is possible to reduce the turbulence in the vicinity of the nozzle ink jet head provided at the most upstream, it is possible dirt reduces due to the ink mist caused by the turbulence of the air flow.

  Further, in the above apparatus, in a plan view, the distance between the nozzle of the inkjet head provided in the uppermost stream in the transport direction and the through hole located closest to the upstream side of transport from each position on the nozzle. If the average is smaller than the average of the distances between the nozzles of other inkjet heads and the through holes located closest to the upstream side of transport from each position on the nozzle, the suction force With this control, it is possible to reduce a decrease in the sheet suction force in the vicinity of the nozzles of the ink jet head provided in the uppermost stream in the transport direction, and it is possible to stably transport the sheet with a sufficient suction force.

  According to the second ink jet printing apparatus of the present invention, there are a plurality of belt holes, a conveyance belt that adsorbs and conveys the recording medium by the negative pressure acting on the belt holes, and a slidably supported conveyance belt. In addition, there are a platen having a plurality of through holes, a decompression unit that generates a negative pressure on the opposite side of the platen conveyance belt, and a plurality of inkjet heads that eject ink from nozzles onto a recording medium conveyed by the conveyance belt. And a printing unit arranged side by side in the direction in which the recording medium is conveyed, and is transported downstream from a position on the platen facing a nozzle of the inkjet head provided on the most downstream side in the conveyance direction among the plurality of inkjet heads. So that the suction force in the region on the side is smaller than the suction force in the region on the upstream side of conveyance from the opposite position. Runode, it is possible to reduce the air flow disturbance in the vicinity of the nozzle of the inkjet head provided at the most downstream can dirt reduced due to the ink mist caused by the turbulence of the air flow.

  In the above apparatus, in plan view, the average distance between the nozzle of the inkjet head provided on the most downstream side in the transport direction and the through hole located closest to the transport downstream side from each position on the nozzle is If the distance between the nozzles of other inkjet heads and the through-holes closest to the downstream side of conveyance from each position on the nozzles is smaller than the average, the suction force control is performed. Therefore, it is possible to reduce a decrease in the sheet suction force in the vicinity of the nozzles of the inkjet head provided at the most downstream in the transport direction, and it is possible to stably transport the sheet with a sufficient suction force.

Schematic configuration diagram of inkjet printing apparatus Top view showing head placement relative to platen Platen top view The figure which shows arrangement | positioning of the through-hole in the inkjet head row A vicinity. The figure which shows arrangement | positioning of the through-hole in another inkjet head row | line | column. The figure which shows arrangement | positioning of the through-hole in the inkjet head row B vicinity. The figure which shows the 2nd arrangement | positioning aspect of a through-hole The figure which shows the 3rd arrangement | positioning aspect of a through-hole

  Hereinafter, an embodiment of a first inkjet printing apparatus 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 43 includes a plurality of roller pairs 44 for feeding the paper P.

  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.

  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 top view showing the arrangement of the head with respect to the platen. In the present embodiment, a total of 24 inkjet heads 211 are formed in a staggered pattern at predetermined intervals in the transport direction and the scanning direction, and the scanning direction for each color of black K, magenta color M, cyan color C, and yellow color Y. Six inkjet heads 211 arranged in two rows are assigned.

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

  Next, the platen unit 22 will be described. The platen unit 22 drives a platen 221 disposed below the head unit 21 so as to face each ink jet nozzle 214, an endless platen belt 222 that is slid over the platen 221, and a platen belt 222. The drive roller 223, the driven roller 224, and the fan 225 (pressure reduction means) that make the space below the platen 221 negative pressure.

  FIG. 3 is a plan view of the platen 221. In FIG. 3, the projection positions of the respective inkjet heads 211 are indicated by broken lines. 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, the arrangement | positioning aspect on the platen 221 of the through-hole 221a is demonstrated in detail later.

  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 applies a substantially uniform negative pressure to the entire lower surface of the platen 221 by applying a negative pressure to the space below the platen 221 sealed by a frame (not shown). Thereby, a suction force is generated in each through hole 221a on the platen 221.

  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 inkjet 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 by a sensor (not shown) at the leading end upstream in the transport direction, and is sucked and held on the platen belt 222 by each belt hole 222a. As the paper P passes through a position directly below the inkjet 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.

  Next, referring to FIG. 3 again, the first embodiment in the arrangement mode of the through holes 221a will be described. As shown in FIG. 3, on the platen, the upstream area UR on the upstream side from the position UP facing the line nozzle 215 of the inkjet head row A provided on the uppermost stream in the transport direction and the most downstream side in the transport direction. In the downstream region LR on the downstream side of the conveyance from the position LP facing the line nozzle 215 of the inkjet head row B, the intermediate region MR is located on the downstream side of the conveyance from the position UP and on the upstream side of the conveyance from the position LP. A through hole 221a having a smaller size than the provided through hole 221a is provided. Here, the size of the through hole means the cross-sectional area of the through hole. If the cross-sectional area varies from place to place, it means the minimum cross-sectional area.

  Thereby, the total area of the through holes existing in the unit region (for example, the region SR1) having a predetermined size in the upstream region UR and the through holes existing in the unit region of the predetermined size (for example, the region SR2) in the downstream region LR. The total area is smaller than the total area of the through-holes existing in the unit region (for example, the region SR3) having a predetermined size in the midstream region MR. Here, the position and size of the unit area may be arbitrarily determined. However, it is necessary that the area is sufficiently large so that the size of the total area of the through holes can be compared between the areas to be compared. For example, it may be a region having a size that includes four or more through holes.

  Next, the arrangement of the through holes 221a in the vicinity of each inkjet head row will be described with reference to FIGS. 4 is a view showing the arrangement of the through holes 221a in the vicinity of the ink jet head row A, FIG. 5 is a view showing the arrangement of the through holes 221a in the vicinity of the ink jet head rows other than the ink jet head rows A and B, and FIG. It is a figure which shows arrangement | positioning of the through-hole 221a in the row | line | column B vicinity. 4 to 6, one inkjet head 211 is illustrated by a broken line.

  In the vicinity of the inkjet head row A, the through-hole 221a has a distance d1 from the position UP of the through-hole group C1 including a part of the through-holes existing on the upstream side of the conveyance from the position UP facing the line nozzle 215. In the vicinity of the inkjet head row, the through hole group C2 corresponding to the through hole group C1 is provided to be smaller than the distance d2 from the position MP facing the line nozzle 215.

  Thereby, in plan view, the average distance between each position on the line nozzle 215 of the inkjet head row A and the through hole located closest to the upstream side of conveyance from each position is the other inkjet head. This is smaller than the average of the distance between each position on the line nozzle 215 and the through hole located closest to the upstream side of conveyance from that position.

  Further, in the vicinity of the inkjet head row B, the through hole 221a has a distance d4 from the position LP of the through hole group C4 including a part of the through holes existing on the downstream side of the conveyance from the position LP facing the line nozzle 215. In the vicinity of the other inkjet head row, the through hole group C3 corresponding to the through hole group C4 is provided to be smaller than the shortest distance d3 from the position MP facing the line nozzle 215.

  Thereby, in a plan view, the average distance between each position on the line nozzle 215 of the inkjet head row B and the through hole located closest to the downstream side of conveyance from each position is the other inkjet head. This is smaller than the average of the distance between each position on the line nozzle 215 and the through-hole located closest to the downstream side of conveyance from that position.

  Next, a second embodiment of the arrangement mode of the through holes 221a will be described with reference to FIG. The second embodiment differs from the first embodiment in that the number per unit region (hereinafter referred to as density) is reduced without changing the size of the through hole. FIG. 7 is a plan view of the platen 221 as in FIG. 7 and 3 differ only in the arrangement of the through holes 221a on the platen 221. The same members are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

  In the second embodiment, as shown in FIG. 7, the density of the through holes 221 a opened in the upstream region UR and the downstream region LR on the platen is smaller than the density of the through holes 221 a opened in the midstream region MR. Are arranged as follows. As a result, the total area of the through holes existing in the unit area SR1 having the predetermined size in the upstream area UR and the total area of the through holes existing in the unit area SR2 having the predetermined size in the downstream area LR are respectively determined as the midstream area MR. Is smaller than the total area of the through holes existing in the unit region SR3 having a predetermined size.

  As described above, according to the ink jet printing apparatus 1 according to the arrangement mode of the respective through holes, the total area of the through holes existing in the unit region SR3 having a predetermined size in the upstream region UR and the downstream region LR is determined as the midstream region. By making the total area of the through holes existing in the unit region SR4 of a predetermined size in the MR, the suction force in the upstream region UR and the downstream region LR is made smaller than the suction force in the midstream region MR. Therefore, it is possible to limit the air flow flowing from the upstream region UR and the downstream region LR to the lower part of the platen, and to reduce the turbulence of the air current in the vicinity of the nozzles of the ink jet head provided at the most upstream and the most downstream.

  In the above embodiment, the suction force in the upstream region UR, the downstream region LR, and the midstream region MR of the platen 221 is adjusted by changing the size or number (density) of the through holes in the region. As described above, the present invention is not limited to this, and for example, a fan is provided in each of the upstream region UR, the downstream region LR, and the midstream region MR so that the space below the region has a negative pressure, and the suction force is adjusted by controlling the output of each fan. You may make it do. Specifically, the output of the fan that makes negative pressure in the space below the upstream region UR and downstream region LR may be smaller than the output of the fan that makes negative pressure in the space below the midstream region MR.

  In the above embodiment, the case where both the suction force in the upstream region UR and the suction force in the downstream region LR are made smaller than the suction force in the midstream region MR has been described. However, the suction force in the upstream region UR and the downstream region LR are described. Only one of the suction forces in the above may be made smaller than the suction force in the midstream region MR.

  Further, in the above embodiment, the suction force in the entire region upstream of the position UP facing the nozzle of the inkjet head A (upstream region UR) and the position LP facing the nozzle of the inkjet head B are moved downstream of the conveyance. When the suction force in the entire region (downstream region LR) is smaller than the suction force in the entire region (middle flow region MR) located downstream from the position UP and downstream from the position LP. However, the present invention is not limited to this, and the suction force on the platen in the region at least within the range of the length D1 from the position UP facing the nozzle of the ink jet head A to the upstream side of the platen is opposed to it. The suction force should be smaller than at least the area within the range of the length D1 from the position UP to the downstream side of conveyance. The suction force in the region within the range of at least the length D3 from the position LP facing the nozzle of the inkjet head B to the downstream side of the conveyance is at least in the region within the range of the length D3 from the opposed position LP to the upstream side of the conveyance. It may be made smaller than the suction force.

  For example, as shown in FIG. 8, the region UR1 within the range of the length D1 from the position UP facing the nozzle of the ink jet head A to the upstream side of the conveyance, and the region LR1 within the range of the length D1 from the position UP to the downstream side of the conveyance. A through hole having a smaller size than the through hole provided in the ink jet head B is provided, and the position LP facing the nozzle of the ink-jet head B is moved downstream from the position LP to the region LR2 within the range of the length D3. A through hole having a smaller size than the through hole provided in the region UR2 within the range of the length D3 may be provided on the side.

  Here, the length D1 is the shortest distance between the nozzle of the inkjet head A and the nozzle of the inkjet head adjacent to the inkjet head A in the direction in which the recording medium is conveyed, and the length D3 is the nozzle of the inkjet head B. And the inkjet head B in the direction in which the recording medium is conveyed is the shortest distance between the adjacent inkjet head nozzles.

  Here, the suction force in the region within the shortest distance D1 between the nozzle of the inkjet head A and the nozzle of the inkjet head adjacent to the nozzle located on the upstream side of the conveyance from the position UP is conveyed from the position UP. Although the case where it is defined to be smaller than the suction force in the region within the same length existing on the downstream side has been described, the nozzle of the inkjet head A existing on the upstream side of the conveyance from the position UP and the inkjet adjacent thereto The suction force in the region within the length range of the shortest distance D2 from the head may be smaller than the suction force in the region within the same length range existing on the downstream side of the conveyance from the position UP.

  Here, the suction force in the region within the shortest distance D3 between the nozzle of the inkjet head B and the nozzle of the inkjet head adjacent to the nozzle located on the downstream side of the conveyance from the position LP is conveyed from the position LP. Although the case where it is defined to be smaller than the suction force in the region within the same length existing on the upstream side has been described, the nozzle of the inkjet head B and the inkjet adjacent to the nozzle located on the downstream side of the conveyance from the position LP The suction force in the region within the length range of the shortest distance D4 from the head may be smaller than the suction force in the region within the same length range existing upstream from the position LP.

  Further, the suction force in the region within the range of at least 3 cm from the position UP facing the nozzle of the inkjet head A on the platen to the upstream side of the conveyance is the region within the range of at least 3 cm from the facing position UP to the downstream side of the conveyance. The suction force in the region within a range of at least 3 cm from the position LP facing the nozzle of the inkjet head B to the downstream side of the conveyance is at least from the opposite position LP to the upstream side of the conveyance. You may make it become smaller than the attraction | suction force in the area | region in the range of 3 cm.

  Further, the suction force in the region within the range of at least 2 cm upstream from the position UP facing the nozzle of the inkjet head A on the platen is the region within the range of at least 2 cm downstream from the facing position UP. The suction force in the region within a range of at least 2 cm from the position LP facing the nozzle of the inkjet head B to the downstream side of the conveyance is at least from the opposite position LP to the upstream side of the conveyance. You may make it become smaller than the attraction | suction force in the area | region in the range of 2 cm.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 211 Inkjet head 215 Line nozzle 221 Platen 221a Through hole 222 Platen belt 222a Belt hole 225 Suction means UR Upstream region MR Midstream region LR Downstream region P Paper

Claims (8)

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;
A plurality of inkjet heads that discharge the ink from nozzles onto the recording medium conveyed by the conveyance belt, and a printing unit that is arranged in a direction in which the recording medium is conveyed,
On the platen, the suction force in the region upstream of the position from the position facing the nozzle of the inkjet head provided in the uppermost stream in the transport direction among the plurality of ink jet heads from the position facing the downstream of the transport An ink jet printing apparatus characterized by being smaller than a suction force in a certain region. The shortest distance between the nozzle of the inkjet head provided in the uppermost stream in the transport direction and the nozzle of the inkjet head adjacent in the direction in which the recording medium is transported to the inkjet head is D1;
On the platen, the suction force in the region within the range of the length D1 from the position facing the nozzle of the inkjet head provided at the most upstream in the transport direction from the position facing the downstream of the transport 2. The ink jet printing apparatus according to claim 1, wherein the suction force is smaller than a suction force in a region within the range of the length D1. The shortest distance between the nozzle of the inkjet head provided on the uppermost stream in the transport direction on the platen and the inkjet head adjacent in the direction in which the recording medium is transported to the inkjet head is D2.
On the platen, the suction force in the region within the range of the length D2 from the position facing the nozzle of the inkjet head provided in the uppermost stream in the transport direction from the position facing the downstream of the transport The inkjet printing apparatus according to claim 1, wherein the suction force is smaller than a suction force in a region within the range of the length D <b> 2.   In plan view, the average distance between each position on the nozzle of the inkjet head provided at the most upstream in the transport direction and the through hole located closest to the upstream side of transport from each position is 2. The inkjet printing apparatus according to claim 1, wherein an average distance between each position on the nozzle of the inkjet head and a through hole located closest to the upstream side of conveyance from each position is smaller than an average. . 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;
A plurality of inkjet heads that discharge the ink from nozzles onto the recording medium conveyed by the conveyance belt, and a printing unit that is arranged in a direction in which the recording medium is conveyed,
A suction force in a region on the downstream side of the transport from the position facing the nozzle of the inkjet head provided on the most downstream side in the transport direction among the plurality of ink jet heads on the platen from the facing position to the upstream side of the transport An ink jet printing apparatus characterized by being smaller than a suction force in a certain region. The shortest distance between the nozzle of the inkjet head provided in the uppermost stream in the transport direction and the nozzle of the inkjet head adjacent to the inkjet head in the direction in which the recording medium is transported is D3,
On the platen, the suction force in the region within the range of the length D3 from the position facing the nozzle of the inkjet head provided on the most downstream side in the transport direction to the downstream side of the transport from the facing position to the upstream side of the transport 6. The ink jet printing apparatus according to claim 5, wherein the suction force is smaller than a suction force in a region within the range of the length D3. The shortest distance between the nozzle of the inkjet head provided on the uppermost stream in the transport direction on the platen and the inkjet head adjacent to the inkjet head in the direction in which the recording medium is transported is D4,
The suction force in the region within the range of the length D4 from the position facing the nozzle of the inkjet head provided on the most downstream side in the transport direction on the platen is the transport upstream side from the facing position. The inkjet printing apparatus according to claim 5, wherein the suction force is smaller than a suction force in a region within the range of the length D4.   In plan view, the average distance between each position on the nozzle of the inkjet head provided on the most downstream side in the transport direction and the through hole located closest to the transport downstream side from each position is the other. 6. The ink jet printing apparatus according to claim 5, wherein the distance is smaller than the average of the distance between each position on the nozzle of the ink jet head and the through hole located closest to the transport downstream side from each position. .