WO2015087862A1

WO2015087862A1 - Inkjet printing apparatus

Info

Publication number: WO2015087862A1
Application number: PCT/JP2014/082517
Authority: WO
Inventors: 大嗣清水; 石橋　大輔
Original assignee: コニカミノルタ株式会社
Priority date: 2013-12-11
Filing date: 2014-12-09
Publication date: 2015-06-18
Also published as: CN105793049A; JPWO2015087862A1

Abstract

The inkjet printing apparatus is provided with: a conveyor unit (3) for conveying the print medium (P); and multiple ink-discharging units (1) disposed in a row along the print medium conveyance direction (X). Each of the multiple ink-discharging units is provided with a suction mechanism (5) adjacent to said ink-discharging unit on the downstream side in the conveyance direction. The suction opening (511) of the suction mechanism is disposed so as to be closer to the ink-discharging unit adjacent to said suction mechanism on the upstream side in the conveyance direction than the ink-discharging unit adjacent to said suction mechanism on the downstream side in the conveyance direction.

Description

Inkjet recording device

The present invention relates to an ink jet recording apparatus.

There is an ink jet printer as an ink jet recording apparatus capable of forming an image on various recording media such as plain paper and plastic thin plate. Ink jet printers sometimes discharge minute satellite droplets together with main droplets that form dots from the nozzles of the head. Satellite droplets are finer than main droplets and are therefore susceptible to air resistance. As soon as they are ejected, the flying speed is reduced, and the mist floats in the air and adheres to the nozzle surface of the head. To do. This has caused unstable nozzle discharge and contamination around the head.

For this reason, in a conventional inkjet recording apparatus, a satellite droplet suction mechanism is provided on the downstream side of a plurality of head units arranged in the transport direction, and satellite droplets are sucked by an internal fan (for example, Patent Document 1). reference).

JP 2011-62982 A

In the conventional ink jet recording apparatus, satellite droplets are sucked by a single suction mechanism disposed on the downstream side in the transport direction with respect to a plurality of head units arranged in the transport direction of the recording medium.
For this reason, in the head unit close to the suction mechanism, a stable airflow is generated between the nozzle surface and the recording medium, and the satellite droplets can be sucked effectively. However, in the head unit away from the suction mechanism, a stable air current cannot be formed between the nozzle surface and the recording medium, and the satellite droplets floated and could not be sufficiently suppressed from adhering to the head or the like. . In addition, an unstable air flow is easily generated between the nozzle surface and the recording medium, and there is a problem that the image quality of the image formed by the head unit is deteriorated.
When the recording medium is a material that easily warps or has irregularities on the surface, the head unit is arranged at a distance from the nozzle surface to the recording medium. The longer the distance, the more unstable the airflow between them, and the deposition of satellite droplets and the instability of the airflow became more prominent.

An object of the present invention is to improve the image quality by reducing the influence of satellite droplets on a plurality of ink ejection portions.

The present invention includes a conveyance unit that conveys a recording medium, and a plurality of ink ejection units that are arranged side by side along the conveyance direction of the recording medium, and each of the plurality of ink ejection units includes the ink ejection unit. A suction mechanism adjacent to the downstream side in the transport direction of the suction mechanism, and the suction port of the suction mechanism in the transport direction of the suction mechanism is closer to the ink discharge unit adjacent to the downstream side of the suction mechanism in the transport direction. It is characterized in that it is arranged close to the ink discharge section adjacent on the upstream side.

In the inkjet recording apparatus, the ink ejection unit may be a head unit that holds a plurality of inkjet heads arranged in the width direction of the recording medium being conveyed.

In the inkjet recording apparatus, the ink discharge unit may be a single inkjet head having a plurality of nozzles arranged in the width direction of the recording medium being conveyed.

In the ink jet recording apparatus, the ink discharge unit and the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit may be integrated.

In the ink jet recording apparatus, the ink discharge unit and the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit may be separately disposed.

In the ink jet recording apparatus, a width of the suction port of the suction mechanism in a direction orthogonal to the transport direction is a direction orthogonal to the transport direction of a discharge region where the ink discharge unit can discharge ink. It may be wider than the maximum width.

In the inkjet recording apparatus, the ink ejection unit may have a plurality of nozzle rows arranged in the transport direction.

In the ink jet recording apparatus, the nozzle surface of the ink discharge unit and the suction port of the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit may be arranged on the same plane. good.

In the ink jet recording apparatus, a suction mechanism other than the suction mechanism adjacent to the downstream side may be added to all or a part of the plurality of ink ejection units.

Further, in the ink jet recording apparatus, at least one or more of the ink discharge units may discharge ink having a pigment density higher than that of the main solvent.

In the ink jet recording apparatus, at least one or more of the ink discharge units may discharge ink having a density of 1.2 to 1.5 [kg / l].

In the ink jet recording apparatus, the ink having a density of 1.2 to 1.5 [kg / l] may be white ink.

Further, in the ink jet recording apparatus, the recording medium may be a ceramic tile.

In the present invention, since a plurality of ink ejection units provided side by side in the transport direction are individually provided with a suction mechanism adjacent to the downstream side in the transport direction, satellite droplets generated in each ink ejection unit are effectively prevented. Therefore, it is possible to reduce individual differences in the suction amount of satellite droplets to each ink discharge portion. As a result, the occurrence of fouling due to satellite droplets in all ink ejection portions is reduced.
In addition, each suction mechanism is disposed closer to the ink discharge unit adjacent to the upstream side in the transport direction than the ink discharge unit adjacent to the downstream side in the transport direction. For this reason, it is possible to perform suction while suppressing the influence of other suction mechanisms on the ink discharge portion closest to the suction mechanism, and to prevent the airflow generated by suction between each ink discharge portion and the recording medium from being disturbed stably. Therefore, it is possible to improve the image quality of the image formed by each ink discharge unit.
Further, since suction is performed with respect to the ink discharge portion closest to the suction mechanism, even when the ink discharge portion is arranged away from the recording medium according to the thickness or surface shape of the recording medium, airflow stabilization can be realized. It becomes possible.

1 is a schematic diagram illustrating an outline of an ink jet recording apparatus as a first embodiment. FIG. 4 is a side view illustrating the head unit in a cross section taken along line WW in FIG. 3. FIG. 5 is a plan view illustrating the head unit in a cross section taken along line VV in FIG. 2. 2 is a bottom view of a single head unit 1. FIG. It is explanatory drawing which shows the positional relationship of a head unit and a suction mechanism. FIG. 9 is an example in which the head unit and the suction mechanism are separated, and is a side view illustrating the head unit in a cross section taken along line TT in FIG. 7. FIG. 7 is an example in which the head unit and the suction mechanism are separated, and is a side view illustrating the head unit in a cross section along the line SS in FIG. 6. It is explanatory drawing which shows the positional relationship at the time of arrange | positioning a head unit and a suction mechanism separately. FIG. 6 is an example in which a suction mechanism is added to the head unit located on the most upstream side in the transport direction, and is a side view illustrating the head unit in cross section. It is a bottom view of an inkjet head and a suction mechanism. It is a schematic diagram which shows the outline of the inkjet recording device as 2nd embodiment. It is a schematic diagram which shows the outline of the inkjet recording device as 3rd embodiment. It is a graph which shows the result of a comparative test. The example of the image in which the grain pattern produced in the comparative test is shown. An example in which a good image is formed in a comparative test is shown. It is explanatory drawing which shows the generation | occurrence | production state of the airflow when arrangement | positioning of a suction opening is improper. It is explanatory drawing which shows the generation | occurrence | production state of the airflow when arrangement | positioning of a suction opening is appropriate.

[First embodiment]
Hereinafter, an inkjet recording apparatus 100 according to the first embodiment will be described with reference to the drawings.
As shown in FIG. 1, the ink jet recording apparatus 100 is a line-type ink jet printer, and ejects ink onto a recording medium P from an ink jet head 12 serving as an ink ejection unit, thereby forming an image on the recording medium P. . The line-type inkjet printer includes a nozzle that has a plurality of inkjet heads over the same range as the maximum width in which image formation is possible in the medium width direction orthogonal to the transport direction. The image forming is performed on the conveyed recording medium without being moved along.
In addition, the inkjet recording apparatus 100 exemplified below forms an image on the plane of a sheet-like cut paper or a film substrate as the recording medium P.
In the following description, it is assumed that the recording medium P is transported horizontally at the image forming position by the transport unit 3 described later, and the transport direction is defined as X. Similarly, a direction that is horizontal and orthogonal to the conveyance direction X is defined as a medium width direction Y.

The ink jet recording apparatus 100 includes a head unit 1 as a discharge unit, a support frame 2, a transport unit 3, a suction mechanism 5, a supply unit 6, and a discharge unit 7.

[Transport section]
As shown in FIG. 1, the transport unit 3 transports the recording medium P so as to pass below each head unit 1.
The transport unit 3 includes a drive roller 30, a driven roller 31, an endless transport belt 33 laid over the drive roller 30 and the driven roller 31, and a motor (not shown) that rotates the drive roller 30.
The driving roller 30 and the driven roller 31 are such that at least a portion facing the nozzle surface (the surface on which ink is ejected) of the head unit 1 of the transport belt 33 stretched between the

rollers

30 and 31 forms a flat surface. They are arranged at the necessary intervals.
The conveyance belt 33 has a width wider than that of the recording medium P, and a plurality of suction holes (not shown) are formed on the belt surface. An adsorption chamber 34 is provided inside the conveyance belt 33, and the recording medium P is adsorbed and held on the conveyance belt 33 by applying a negative pressure to the inside by a fan.
When the driving roller 30 is rotated by driving a motor, the conveying belt 33 circulates between the driving roller 30 and the driven roller 31 in the clockwise direction in FIG. 1 and conveys the recording medium P placed on the upper surface thereof in the conveying direction X. Convey along.

[Supply section]
As shown in FIG. 1, the supply unit 6 is provided upstream of the transport unit 3 in the transport direction X of the recording medium P, and supplies the recording medium P to the transport unit 3.
The supply unit 6 stacks and stores the recording media P, a drawer roller 62 that pulls out the recording medium P from the cassette 61, and a feed that feeds the recording medium P pulled out by the drawer roller 62 toward the transport unit 3. And a roller 63.
In the cassette 61, recording media P cut to a certain size are stacked and stored.
The drawing roller 62 is pressed against the upper surface of the stored recording medium P. The drawing roller 62 pulls out the recording medium P from the cassette 61 by a frictional force with the recording medium P by its own rotation.
The feed roller 63 is provided at a position facing the recording medium P with the transport path therebetween. The feed roller 63 includes a pair of rollers, and rotates in opposite directions. The feed roller 63 can sandwich the recording medium P pulled out from the pull-out roller 62 and feed it toward the transport unit 3.

Note that the recording medium P is not limited to a sheet cut into a predetermined size such as a cut sheet, and may be, for example, a belt-like long sheet fed from a roll. In that case, it is desirable that the supply unit be configured to support the roll rotatably and to feed the roll downstream in the transport direction X by a roller similar to the feed roller 63.

[Discharge part]
As shown in FIG. 1, the discharge unit 7 is provided on the downstream side in the conveyance direction X of the recording medium P with respect to the conveyance unit 3, and discharges the recording medium P on which image formation has been completed to the outside. is there.
The discharge unit 7 includes a discharge roller 71 that takes out the recording medium P on which image formation has been completed from the conveyance belt 33 and discharges it, and a sorter 72 on which the recording medium P on which image formation has been completed is placed.

When the recording medium P is a long sheet fed from the roll described above, the discharge unit 7 is configured to wind the recording medium P after image formation with a motor, or the long sheet has a predetermined length. It is desirable to have a configuration having a cutting part cut at と and a stocker for the cut sheet.

[Head unit]
2 is a side view of the periphery of the head unit 1, FIG. 3 is a plan view thereof, FIG. 4 is a bottom view of the single head unit 1, and in FIG. 2, the head unit 1 is taken along the line WW in FIG. FIG. 3 shows the head unit 1 in a section taken along the line VV in FIG.
As shown in FIGS. 2 and 3, the five head units 1 have white (W), yellow (Y), magenta (M), cyan (C), and black (K) in order from the upstream side to the downstream side. These process color inks are incorporated, and these droplets are ejected vertically downward toward the recording medium P being conveyed.

As the ink of each color incorporated in each head unit 1, one having a pigment density greater than the density of the main solvent of the ink is used. The ink density is generally about 1.1 [kg / l], but the ink density of each color built in each head unit 1 is about 1.2 to 1.5 [kg / l]. In particular, since the white (W) ink contains a metal in the pigment, the density of the pigment tends to be higher than the density of the main solvent, and the density of the ink itself tends to increase.
In this way, in the case of an ink having a density higher than usual, particularly in the case where the density of the pigment is higher than that of the main solvent, the dispersion of the pigment in the main solvent tends to be non-uniform at the time of ejection. There is a tendency for satellites to occur easily.

The head unit 1 and the suction mechanism 5 are integrated. That is, the configuration of the head unit 1 and the suction mechanism 5 is arranged in one housing 11. The casing 11 has a substantially rectangular parallelepiped shape, and is attached to the support frame 2 with its longitudinal direction extending along the medium width direction Y. Further, the bottom surface of the housing 11 is maintained in a horizontal state, and is opposed to the upper surface of the conveyance belt 33 positioned below the housing 11 while maintaining a predetermined distance. In consideration of the occurrence of warping or unevenness of the recording medium P to be conveyed, the bottom surface of the housing 11 is close to the upper surface of the conveying belt 33 within a range that does not hinder the passage of the recording medium P. So that the height is adjusted.
And the upstream part in the conveyance direction X of the housing | casing 11 becomes the storage part 13 of the inkjet head 12, and the downstream part becomes the duct 51 of the suction mechanism 5 (refer FIG. 5).

The storage portion 13 of the inkjet head 12 has a wide opening at the bottom, and when viewed from below, seven inkjet heads 12 are staggered along the medium width direction Y inside the opening as shown in FIG. Is arranged.
The overall shape of the inkjet head 12 is a substantially rectangular parallelepiped shape, and a nozzle substrate 121 is provided at the bottom. In addition, flanges 122 for fixing to the storage unit 13 are provided at both ends of the inkjet head 12.
Further, the ink jet head 12 includes an ink path that guides ink supplied from an ink storage unit (not shown) provided in the head unit 1 to a plurality of nozzles formed on the nozzle substrate 121, and an internal partway along the ink path. A drive mechanism that discharges ink droplets by applying a discharge pressure to the ink is incorporated. This drive mechanism uses a piezoelectric element as a drive source, and the head unit 1 is provided with a drive circuit (not shown) for driving the piezoelectric element of each inkjet head 12 to control the drive of each inkjet head 12.

The inkjet head 12 is mounted in the storage unit 13 so that the nozzle surface (lower surface) of the nozzle substrate 121 is maintained in a horizontal state and the nozzle surface is at the same height as the bottom surface of the housing 11.
In addition, a plurality of nozzle rows composed of nozzles formed side by side along the medium width direction Y are arranged in the transport direction X on the nozzle surface of the nozzle substrate 121. The nozzle pitch of each nozzle row is uniform, and the arrangement of the nozzles in adjacent nozzle rows is offset in dot pitch units in the medium width direction Y. The dot pitch refers to the minimum dot interval that can be formed in the medium width direction Y by the inkjet head 12.
Since the inkjet head 12 has the nozzles arranged as described above, it is possible to form dot rows at the dot pitch by discharging from all the nozzles.

Further, the seven inkjet heads 12 arranged in a staggered manner in the storage unit 13 of the housing 11 are overlapped at the ends so that the dot formation region does not cause a dot formation gap in the medium width direction Y. Has been placed.
As a result, the head unit 1 can perform dot formation in the medium width direction Y in the range of the maximum width w in which image formation is possible as shown in FIG.

[Suction mechanism]
FIG. 5 shows the head unit 1 and the suction mechanism 5 in the same cross section as FIG. As shown in FIG. 5, the suction mechanism 5 includes a duct 51 formed on the downstream side in the transport direction X of the housing 11, a fan 52 provided in the duct 51, and satellite droplets sucked into the duct 51. And a filter 53 to be collected.
The duct 51 has a hollow inside, and includes a suction port 511 penetrating into the duct 51 from the bottom surface of the housing 11 and an exhaust port 512 provided on the upper surface of the duct 51.
The fan 52 blows air in a direction in which gas flows from the suction port 511 to the exhaust port 512 through the inside of the duct 51. The filter 53 is attached to the inner wall of the duct 51 so that all the gas passing through the duct 51 passes. The filter 53 may be attached so as to cover the entire opening of the suction port 511 or the exhaust port 512. The filter 53 may be detachable and replaceable.

The suction port 511 is formed in a slit shape along the medium width direction Y. The suction port 511 is formed at the same height as the nozzle surface (lower surface) of the nozzle substrate 121 of each inkjet head 12 of the head unit 1.
Further, as described above, the five head units 1 and the suction mechanisms 5 are arranged along the transport direction X, but the suction ports 511 of the suction mechanisms 5 are heads integrated by the housing 11. The arrangement is set so as to be closest to the unit 1 (the head unit 1 adjacent on the upstream side in the transport direction X).
That is, as shown in the drawing, the distance in the transport direction X from the suction port 511 to the adjacent head unit 1 on the upstream side in the transport direction X (strictly speaking, from the center position of the suction port 511 in the transport direction X to the transport direction X). Let b be the distance in the conveyance direction X to the intermediate position between the heads 12 arranged in a staggered manner in the head units 1 adjacent on the upstream side and the heads 12.
Further, the distance in the transport direction X from the suction port 511 to the adjacent head unit 1 on the downstream side in the transport direction X (strictly speaking, it is adjacent on the downstream side in the transport direction X from the center position in the transport direction X of the suction port 511. A distance in the transport direction X) between the heads 12 arranged in a staggered manner in the head unit 1 and the intermediate position between the heads 12 is defined as a.
In these cases, the interval between the suction mechanisms 5 (and the head units 1) adjacent to each other is set so that the distance b is shorter than the distance a.

With the above arrangement, the suction port 511 exclusively sucks satellite droplets generated from the head unit 1 adjacent to the suction port 511 on the upstream side in the transport direction X.
Further, the suction force generated from the suction port 511 acts exclusively on the head unit 1 adjacent on the upstream side in the transport direction X, and the influence of the suction force on the other head units 1 is reduced. For this reason, each head unit 1 can stably form an airflow toward the downstream side in the transport direction X between the nozzle surface of each inkjet head 12 and the recording medium P, and is discharged from each head unit 1. The main droplet reaches the recording medium P with a stable trajectory.
Thereby, the phenomenon which disturbs the locus | trajectory of the main droplet of each head unit 1 by disturbance of airflow is suppressed.

Further, as shown in FIG. 4, the opening width k in the medium width direction Y of the suction port 511 of each suction mechanism 5 is the maximum width w (of the discharge area where ink can be discharged in the head unit 1 described above. It is wider than the distribution range in the medium width direction Y of all the nozzles of all the ink jet heads 12 of the head unit 1. Then, both end portions of the suction port 511 in the medium width direction Y are spread outward from both end portions of the distribution range in the medium width direction Y of all the nozzles of all the ink jet heads 12 of the head unit 1.
If the opening width of the suction port 511 in the medium width direction Y is not sufficiently wide, the nozzles at both ends of the head unit 1 in the medium width direction Y are more influenced by the airflow by the suction mechanism 5 than at the center. There is little, and the disorder at the time of discharge tends to occur.
However, by expanding the suction ports 511 outside the distribution range in the medium width direction Y of all the nozzles as described above, the turbulence of the airflow at both ends in the medium width direction Y can be reduced.

[Image formation by inkjet recording apparatus]
In the inkjet recording apparatus 100 described above, the recording medium P is supplied from the supply unit 6 to the transport unit 3 through the drawing roller 62 and the feed roller 63.
The transport unit 3 transports the recording medium P toward the head units 1 while adsorbing the recording medium P onto the transport belt 33.
In each head unit 1, ink is selectively ejected from the nozzles of each inkjet head 12 to the recording medium P transported below the head unit 1 according to the formed image. At this time, when main droplets are ejected from each head unit 1, satellite droplets are generated accordingly, but are sucked by the suction mechanism 5 provided on the downstream side of each head unit 1.
A constant air flow is generated between the nozzle surface of the nozzle substrate 121 of the ink jet head 12 of each head unit 1 and the recording medium P toward the downstream side in the transport direction X by the suction of the suction mechanism 5.
Then, the recording medium P on which image formation has been performed by each head unit 1 passes from the transport unit 3 to the discharge unit 7 and is discharged to the sorter 72 by the discharge roller 71 to complete the operation.

[Technical effects of inkjet recording apparatus]
In the inkjet recording apparatus 100, since the suction mechanism 5 is individually provided in each head unit 1, satellite droplets are effectively sucked in each head unit 1, and adhesion to the periphery of the nozzle is reduced. In all of the head units 1, ink can be discharged from the nozzles satisfactorily.
In particular, inks with a pigment density greater than that of the main solvent, and inks with a density of about 1.2 to 1.5 [kg / l], are prone to satellite droplets, and are effective even when ejecting such inks. As a result, it is possible to suck out the satellite droplets and avoid the contamination around the nozzles and perform good ink ejection.

Further, a suction mechanism 5 is provided on the downstream side in the transport direction X of all the head units 1, and each suction mechanism 5 is closer to the head unit 1 adjacent to the upstream side than the head unit 1 on the downstream side of the suction mechanism 5. (Distance a> Distance b in FIG. 5), the suction force by the suction mechanism 5 can be applied exclusively to the head unit 1 on the upstream side. For this reason, for all the head units 1, the air droplets can be stably generated toward the downstream side in the transport direction X with respect to the recording medium P, and the main droplets due to the turbulent and unstable air currents. It is possible to reduce the influence of the flying state on the image and improve the image quality of the formed image.

Further, the opening width k in the medium width direction Y of the suction port 511 of each suction mechanism 5 is wider than the maximum width w of the discharge region where ink can be discharged in the head unit 1, and both end portions of the suction port 511 are Since it spreads outside the both ends of the distribution range in the medium width direction Y of the nozzle, it is possible to reduce the turbulence of the air flow at the nozzles at both ends and maintain high image quality over the entire width of the imageable area. It is.

In addition, since the head unit 1 and the suction mechanism 5 are provided in one housing 11, a gap generated between them can be eliminated, and space can be saved by close arrangement.
Further, since they are integrated, it is not necessary to adjust the positions of the head unit 1 and the suction mechanism 5 when they are attached, and the attaching operation can be performed easily and quickly.
Further, even when the nozzle surface of the head unit 1 and the suction port 511 of the suction mechanism 5 are arranged on the same plane, if they are integrated in advance, mutual positioning work is unnecessary, and attachment work is performed. This can be performed more simply.

In addition, the suction port 511 of the suction mechanism 5 and the nozzle surface of the nozzle substrate 121 of each inkjet head 12 of the head unit 1 adjacent on the upstream side in the transport direction of the suction mechanism 5 are arranged along the same plane. As a result, an air flow can be generated along the same plane during suction by the suction mechanism 5, and a more stable air flow can be generated.

Further, since each inkjet head 12 of each head unit 1 is formed with a plurality of nozzle rows along the medium width direction Y aligned in the transport direction X, the nozzles are not formed at a high density pitch equal to the dot pitch. It is possible to realize a minute dot pitch.
Further, when a plurality of nozzle rows are arranged, satellite droplets are likely to be generated when ink is ejected. However, since each head unit 1 is provided with a suction mechanism 5, these satellite droplets can be sucked effectively.

In addition, since the head unit 1 that discharges white ink among the head units 1 is disposed on the most upstream side in the transport direction X, the background of the formed image can be coated white.
Further, as described above, the white ink contains a metal in the pigment, and increases the density of the pigment and further increases the density of the ink itself. Such ink has the property of easily generating satellite droplets during ejection. However, since each head unit 1 is provided with a suction mechanism 5, these satellite droplets can be effectively sucked.

[Other arrangement examples of head unit and suction mechanism]
The present invention is not limited to the above-described embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.
For example, as shown in FIGS. 6 and 7, each head unit 1 and each suction mechanism 5 may be individually stored in

separate housings

14 and 15 and separated from each other. Also in this case, as shown in FIG. 8, for each suction mechanism 5, the distance from the suction port 511 to the transport direction X is smaller than the distance a in the transport direction X from the suction port 511 to the adjacent head unit 1 on the downstream side in the transport direction X. It is desirable that the distance b in the transport direction X to the adjacent head unit 1 on the upstream side is short.
Even when the suction mechanism 5 is separately arranged, the satellite droplets are satisfactorily sucked during ink ejection, the airflow between each head unit 1 and the recording medium P is stabilized, and the image quality of the formed image is improved. Is possible.
Further, since a gap is formed between the housing 14 of the head unit 1 and the housing 15 of the suction mechanism 5, the airflow from this gap accelerates the airflow from the head unit 1 during suction, and the satellite droplets are discharged. It becomes possible to suck more favorably.
Further, at the time of maintenance, only one of the housing 14 of the head unit 1 and the housing 15 of the suction mechanism 5 that is necessary can be removed, and work efficiency can be improved. Similarly, when the head unit 1 or the suction mechanism 5 is defective or malfunctions, only the head unit 1 or the suction mechanism 5 can be replaced, and there is an advantage that cost is good.

[Example of additional suction mechanism for the head unit]
In the inkjet recording apparatus 100 of FIG. 1, the case where one suction mechanism 5 is provided on the downstream side in the transport direction X with respect to each head unit 1 is illustrated, but the present invention is not limited to this.
For example, as shown in FIG. 9, a new suction mechanism 5 D may be newly provided adjacent to the upstream head unit 1 in the transport direction X adjacent to the upstream side.

Each head unit 1 has a suction mechanism 5 adjacent to the downstream side to generate an air flow toward the downstream side in the transport direction X below the head unit 1, and most satellite droplets are captured by the suction mechanism 5 toward the downstream side. Although collected, some of the satellite droplets also fly upstream in the transport direction X. In that case, in each head unit 1, satellite droplets are sucked by the suction mechanism 5 of the other head unit 1 arranged on the upstream side of the head unit 1, so that adhesion to the inkjet head 12 is avoided. However, since only the head unit 1 on the most upstream side in the transport direction X does not have the suction mechanism 5 on the upstream side, satellite droplets scattered on the upstream side of the head unit 1 are not sucked into any of the machines. There is a risk of adhesion.
Therefore, a new suction mechanism 5D is added to the most upstream head unit 1.

The suction mechanism 5D includes a duct 51D formed on the upstream side in the transport direction X of the housing 11, a fan 52D provided in the duct 51D, and a filter 53D that collects satellite droplets sucked into the duct 51D. It has.
As with the duct 51, the duct 51D includes a suction port 511D on the bottom surface and an exhaust port 512D on the top surface.
The suction port 511D has a slit shape along the medium width direction Y, and is formed with the same height as the suction port 511 and the same width in the medium width direction Y.
9, the distance in the transport direction X from the suction port 511D to the adjacent head unit 1 on the downstream side in the transport direction X (from the center position in the transport direction X of the suction port 511D on the downstream side in the transport direction X) The distance between the adjacent head units 1 in the staggered arrangement between the head units 1 and the intermediate position of the heads in the transport direction X) is longer than both the distance a and the distance b described above, and is sufficiently separated from the head unit 1. Are arranged as follows.
That is, the influence on the other head unit 1 is reduced by sufficiently separating the suction port 511D. As a result, suction of satellite droplets scattered in the upstream side in the transport direction X is also achieved while achieving uniformization and stabilization of the airflow generated below all the head units 1.

It should be noted that a new suction mechanism may be added to other head units 1 as well as the most upstream head unit 1 in the transport direction X. In that case, it is desirable to arrange the newly added suction mechanism so that the influence on the air flow generated below the other head unit 1 is reduced.

[Another example of ink ejection unit]
The head unit 1 as the ink discharge unit described above includes a plurality of inkjet heads 12 in the storage unit 13, but is not limited thereto, and the ink discharge unit is configured by a single inkjet head 12A shown in FIG. May be.
The inkjet head 12A has a substantially rectangular parallelepiped shape whose overall shape is longer than the inkjet head 12 in the medium width direction Y. In addition, the inkjet head 12A is provided with a nozzle substrate 121A at the bottom, and flanges 122A for fixing to the storage unit 13 at both ends.
On the nozzle substrate 121A, a plurality of nozzle rows along the medium width direction Y are formed side by side in the transport direction X, and dots are formed in the range of the maximum width w in which an image can be formed by the nozzle substrate 121A alone. The ink jet head 12A includes an ink path that guides ink to each nozzle of the nozzle substrate 121A and a drive mechanism that ejects ink droplets.
10 illustrates the case where the inkjet head 12A is stored in the storage unit 13 of the casing 11, the inkjet head 12A may not be stored in the casing. Further, the suction mechanism 5 can be stored in the above-described separation type casing 15 (see FIGS. 6 to 8).

[Second Embodiment]
An ink jet recording apparatus 100B according to the second embodiment will be described. Regarding the configuration of the ink jet recording apparatus 100B, the same reference numerals are given to the same configurations as those of the ink jet recording apparatus 100 described above, and redundant description is omitted.

The ink jet recording apparatus is not limited to a configuration in which the recording medium P is conveyed by a belt, and can be applied to a drum type line ink jet printer as shown in FIG. 11, for example.
In this case, the inkjet recording apparatus 100B includes five head units 1 that perform ink ejection of white (W), yellow (Y), magenta (M), cyan (C), and black (K), a support frame 2B, A transport unit 3B, five suction mechanisms 5 provided on the downstream side in the transport direction of each head unit 1, a supply unit 6, and a discharge unit 7 are provided. Note that the configurations and functions of the head unit 1, the suction mechanism 5, the supply unit 6, and the discharge unit 7 are the same as those of the inkjet recording apparatus 100 described above, and thus the description thereof is omitted.

The transport unit 3B rotates in the clockwise direction in FIG. 11 (referred to as the transport direction X) by driving a motor (not shown), and transports the recording medium P to each head unit 1 in close contact with the outer peripheral surface thereof. 31B, a first relay unit 32B that transports the recording medium P from the supply unit 6 to the transport drum 31B, and a second relay unit 33B that transports the recording medium P from the transport drum 31B to the discharge unit 7. .
In the second embodiment, the transport direction X is not horizontal, but is a circumferential direction along the outer peripheral surface of the transport drum 31B. The medium width direction Y is a direction along the rotation center line of the transport drum 31B.
The transport drum 31B has a large number of small holes perforated in a region that matches the size of the recording medium P over the entire surface, and the recording medium P is brought into close contact with the surface of the transport drum 31B by suction from the inside of the transport drum 31B. Transport.
Further, the front end portion of the recording medium P may be sandwiched and conveyed by a member (not shown) such as a claw.

The first relay unit 32B includes a guide 321B that guides the recording medium P fed from the feed roller 63 of the supply unit 6 to the outer peripheral surface of the transport drum 31B, and a pressure contact that causes the recording medium P to closely contact the outer peripheral surface of the transport drum 31B. And a roller 322B.

The second relay unit 33B includes a peeling roller 331B, a relay belt 332B, a guide 333B that guides the recording medium P from the relay belt 332B to the discharge unit 7, and a roller pair 334B provided in each part of the guide 333B. It has.
The peeling roller 331B can be rotationally driven by a motor (not shown). Further, the peeling roller 331B is provided on the outer peripheral surface of the transport drum 31B on the downstream side in the transport direction X of each head unit 1 and on the upstream side in the transport direction X with respect to the pressure roller 322B of the first relay unit 32B. ing. The peeling roller 331B is depressurized inside, adsorbs the recording medium P through small holes provided on the outer peripheral surface thereof, and peels the recording medium P from the transport drum 31B. In addition, the peeling roller 331B can release the attracted state at a contact position with the relay belt 332B located at the lower portion of the outer peripheral surface and can deliver the recording medium P to the relay belt 332B side.
The relay belt 332B is stretched between a pair of rollers each having a drive source at both ends, and can be conveyed to the guide 333B with the recording medium P placed on the relay belt 332B.
Each of the roller pairs 334B provided at various positions of the guide 333B is driven by a motor (not shown), and the recording medium P can be conveyed to the discharge unit 7 along the guide 333B.

Each head unit 1 is arranged so that the nozzle surface of the inkjet head 12 faces the outer peripheral surface of the transport drum 31B, and in order from the upstream side in the transport direction X, white (W), yellow (Y), magenta (M), cyan (C), and black (K) process color inks are incorporated. In addition, a suction mechanism 5 is integrally provided on the downstream side in the transport direction X of each head unit 1.

The ink jet recording apparatus 100B supplies the recording medium P from the supply unit 6 to the conveyance drum 31B via the first relay unit 32B, and the conveyance drum 31B conveys the recording medium P toward each head unit 1 while adsorbing the recording medium P. .
In each head unit 1, ink is selectively ejected from the nozzles of each inkjet head 12 to the recording medium P transported below the head unit 1 according to the formed image. At this time, the generated satellite droplets are sucked by the suction mechanism 5 provided on the downstream side of each head unit 1. In addition, a constant air flow is generated between each head unit 1 and the recording medium P toward the downstream side in the transport direction X by the suction of the suction mechanism 5.
Then, after the image formation is performed on the recording medium P, the recording medium P passes through the second relay section 33B and then is discharged to the discharge section 7, and is discharged to the sorter 72 by the discharge roller 71, thereby completing the operation.

Thus, the same technical effect as that of the inkjet recording apparatus 100 can be obtained also in the case of the drum conveyance type inkjet recording apparatus 100B.
That is, in the ink jet recording apparatus 100B, satellite droplets from each head unit 1 are effectively sucked by the suction mechanism 5 to prevent the ink droplets from adhering to the respective ink jet heads 12, thereby realizing good ink ejection.
Further, it is possible to maintain a stable air flow between each head unit 1 and the recording medium P, and to improve the image quality of the formed image.

[Third embodiment]
An ink jet recording apparatus 100C according to the third embodiment will be described with reference to FIG. About the structure of this inkjet recording device 100C, about the same structure as the inkjet recording device 100 mentioned above, the same code | symbol is attached | subjected and the overlapping description shall be abbreviate | omitted.
The ink jet recording apparatuses 100 and 100B described above both target paper or a sheet as a recording medium, but the ink jet recording apparatus 100C forms an image on a recording medium Q made of ceramic tiles.
This ink jet recording apparatus 100 C has the same configuration as the ink jet recording apparatus 100 with respect to each head unit 1, support frame 2, transport unit 3, and each suction mechanism 5.
However, since the recording medium Q of the ceramic tile is thicker than paper or sheet, each head unit 1 and the suction mechanism 5 are separated from the upper surface of the transport belt 33 by the thickness of the recording medium Q. It is arranged.

The ink jet recording apparatus 100C includes a supply unit 6C that supplies the recording medium Q to the transport unit 3 and a discharge unit 7C that discharges the recording medium Q from the transport unit 3 to the outside of the apparatus. Is different.
That is, since the ceramic tile is thick and hard, the supply unit 6 C transports the recording medium Q set on the tray 61 C to the transport unit 3 by the rollers 62 C and 63 C that are in contact with the lower surface of the recording medium Q.
Similarly, the discharge unit 7C discharges the tray 72C by a roller 71C in contact with the lower surface of the recording medium Q on which the image is formed.

Since the recording medium Q, which is a ceramic tile, has been baked after image formation, the ink ejected by each head unit 1 is suitable for firing. As the firing ink, a pigment having a density of the pigment larger than that of the main solvent and a density of the ink itself is used (for example, 1.2 to 1.5 [kg / l]).
Ink having a high pigment density and the density of the ink itself as described above tends to cause non-uniform dispersion of the pigment in the main solvent when ink is ejected. Although it is likely to occur, since the suction mechanism 5 is provided adjacent to the downstream side in the transport direction X of each head unit 1, the satellite droplets are effectively sucked, and the occurrence of the discharge failure due to the stain and the stain is effectively prevented. It is possible to suppress.
Also in the case of the ink jet recording apparatus 100C, it is possible to stabilize the airflow on the lower side of each head unit 1 and improve the image quality.

[Comparison test]
Next, FIG. 13 shows the results of comparative tests using various patterns in which the arrangement of the suction mechanism 5 with respect to the head unit 1 is changed using the configuration of the inkjet recording apparatus 100.
In this comparative test, the head unit 1 and the suction mechanism 5 are integrally stored in one casing 11 (example in FIG. 5), and the head unit 1 and the suction mechanism 5 are stored in

separate casings

14 and 15. In the case of separation (examples of FIGS. 6 to 8), the distance a in the transport direction X from the suction port 511 to the adjacent head unit 1 on the downstream side in the transport direction X and the transport direction X from the suction port 511 Comparison was made by changing the magnitude relationship with the distance b in the transport direction X to the head unit 1 adjacent on the upstream side.
That is, a configuration in which the casing of the head unit 1 and the suction mechanism 5 are integrated (hereinafter referred to as a series structure) and a configuration in which the casing of the head unit 1 and the suction mechanism 5 are separated (hereinafter referred to as independent structures) are respectively provided. Three patterns of distance a> distance b, distance a = distance b, distance a <distance b were prepared, and these were compared.
In the above test, the dot pitch of each inkjet head 12 of the head unit 1 is 360 [dpi] × 360 [dpi], the conveyance speed of the recording medium P is 24 [m / s], and the printing rate is 10%. Image formation was performed continuously for minutes, and it was determined whether or not a state (so-called wood grain pattern) in which image quality was disturbed due to airflow disturbance was generated. For reference, FIG. 14A shows a woodgrain image, and FIG. 14B shows a good image.

As shown in FIG. 13, when the distance is a <b in a series structure, a good formed image cannot be obtained, and in addition, the image formation for 10 minutes can be continued due to the ejection failure of the inkjet head 12. could not.
In addition, when the distance is a = b in the series structure, a wood grain pattern is generated in the formed image and the image is not formed correctly, and only when a> b is satisfied, good image formation is performed.

Further, even when the distance is a <b in the independent structure, image formation for 10 minutes cannot be continued due to ejection failure, and when a = b, a grain pattern is generated in the formed image and the image is correctly displayed. No image formation was performed, and good image formation was performed throughout only when a> b.

From these results, it became clear that the distance in the transport direction X of the suction port 511 of the suction mechanism 5 with respect to the head unit 1 is important. That is, as shown in FIG. 15A, when the suction port 511 of the suction mechanism 5 is not disposed closest to the adjacent head unit 1 on the upstream side in the transport direction X, the head unit 1 moves in the transport direction X. A bidirectional airflow is generated by receiving suction force from the upstream side and the downstream side, resulting in turbulence, and the droplets ejected from the inkjet head 12 fly in a state where the airflow is distorted, resulting in a grain pattern To do.
On the other hand, as shown in FIG. 15B, when the suction port 511 of the suction mechanism 5 is disposed closest to the adjacent head unit 1 on the upstream side in the transport direction X, the transport is exclusively performed with respect to the head unit 1. In order to stably generate an air flow toward the downstream side by receiving a suction force from the downstream side in the direction X, the liquid droplets ejected from the inkjet head 12 fly in the stable air flow toward the downstream side. It is possible to obtain a good image quality without occurrence of.

[Others]
The arrangement order of the head units 1 can be changed as appropriate. Further, the color and the number of colors of the ink used are not limited to this, and other colors such as light yellow (LY), light magenta (LM), and light cyan (LC) which are light inks may be used. Is possible.
In addition, in the case where white (W) undercoating is not necessary, the white (W) head unit 1 may be omitted.

Moreover, it is good also as a structure which discharges the ink whose density is less than 1.2 [kg / l] about a part or all the head units 1, and the density of a pigment is the density of a main solvent about a part or all the head units 1. The following ink may be ejected. Since these inks can also generate satellite droplets, they can be effectively sucked even in that case. Further, it is possible to stabilize the airflow below each head unit 1 and improve the image quality.

As described above, the present invention is suitable for providing an ink jet recording apparatus capable of reducing the influence of satellite droplets on a plurality of ink ejection units and improving the image quality.

1 Head unit (ink ejection part)
3,

3B Conveyance unit

5,

5D Suction mechanism

6,

6C Supply unit

7, 7C Discharge unit 11 Housing 12 Inkjet head 12A Inkjet head (ink ejection unit)
13

Storage portion

14, 15

Housing

51,

51D Duct

52,

52D Fan

53, 53D Filter 511 Suction port 512

Exhaust port

100, 100B, 100C

Inkjet recording device

121, 121A Nozzle substrate a Distance b Distance k Aperture width P, Q Recording Medium w Maximum width X Transport direction Y Medium width direction (width direction of the recording medium)

Claims

A transport unit for transporting the recording medium;
A plurality of ink ejection units arranged side by side along the conveyance direction of the recording medium,
Each of the plurality of ink ejection units is provided with a suction mechanism adjacent to the downstream side in the transport direction of the ink ejection unit,
The suction port of the suction mechanism is disposed closer to the ink discharge unit adjacent to the upstream side of the suction mechanism in the transport direction than the ink discharge unit adjacent to the downstream side of the suction mechanism in the transport direction. An ink jet recording apparatus.
2. The ink jet recording apparatus according to claim 1, wherein the ink discharge unit is a head unit that holds a plurality of ink jet heads arranged along a width direction of the recording medium to be conveyed.
2. The ink jet recording apparatus according to claim 1, wherein the ink discharge unit is a single ink jet head having a plurality of nozzles arranged in a width direction of the recording medium to be conveyed.
4. The ink jet recording apparatus according to claim 1, wherein the ink discharge unit and the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit are integrated.
The inkjet according to any one of claims 1 to 3, wherein the ink discharge unit and the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit are separately disposed. Recording device.
The width of the suction port of the suction mechanism in the direction orthogonal to the transport direction is wider than the maximum width in the direction orthogonal to the transport direction of the discharge region where the ink discharge unit can discharge ink. The ink jet recording apparatus according to claim 1, wherein:
The ink jet recording apparatus according to any one of claims 1 to 6, wherein the ink discharge unit includes a plurality of nozzle rows arranged in the transport direction.
The nozzle surface of the ink discharge unit and the suction port of the suction mechanism adjacent to the downstream side in the transport direction of the ink discharge unit are arranged so as to be aligned along the same plane. The inkjet recording apparatus as described in any one of 7 to 7.
The ink jet recording according to any one of claims 1 to 8, wherein a suction mechanism other than a suction mechanism adjacent to the downstream side is added to all or a part of the plurality of ink discharge portions. apparatus.
10. The ink jet recording apparatus according to claim 1, wherein at least one or more of the ink ejecting sections eject ink having a pigment density higher than a main solvent density.
11. The ink jet recording apparatus according to claim 1, wherein at least one or more of the ink ejecting units eject ink having a density of 1.2 to 1.5 [kg / l].
12. The ink jet recording apparatus according to claim 11, wherein the ink having a density of 1.2 to 1.5 [kg / l] is a white ink.
The inkjet recording apparatus according to any one of claims 1 to 12, wherein the recording medium is a ceramic tile.