JP2020157581A - Inkjet printer - Google Patents

Abstract

To reduce mist contamination of a printed matter.SOLUTION: An inkjet printer 1 comprises: a conveyance part 2 for conveying paper P; an inkjet head 36 for discharging ink on the paper P conveyed by the conveyance part 2; a paper suction fan 17 for adjusting strength of an air current in a head lower space 57 that is a space between the inkjet head 36 and the conveyance part 2; and a control part 5 for controlling the paper suction fan 17 so that the air current in the head lower space 57 gets stronger as surface tension of the ink discharged by the inkjet head 36 reduces.SELECTED DRAWING: Figure 1

Description

The present invention relates to an inkjet printing apparatus that ejects ink from an inkjet head to perform printing.

An inkjet printing device is known in which a droplet of ink is ejected from a nozzle of an inkjet head and landed on a printing medium to form an image.

In an inkjet printing device, satellites (also referred to as ink mist), which are minute droplets, are generated when ink is ejected. Ink mist causes stains on printed matter (mist stains).

On the other hand, Patent Document 1 discloses a technique of sucking and recovering ink mist floating in the air by a mist suction fan.

JP-A-2007-136847

However, even if the ink mist is collected by the mechanism for collecting the ink mist as in Patent Document 1, a part of the ink mist before the ink mist may adhere to the printed matter and cause mist stains.

The present invention has been made in view of the above, and an object of the present invention is to provide an inkjet printing apparatus capable of reducing mist stains on printed matter.

In order to achieve the above object, the inkjet printing apparatus of the present invention includes a transport unit that conveys a print medium, an inkjet head that ejects ink to the print medium conveyed by the transport unit, and the inkjet head and the transport unit. The adjustment unit that adjusts the strength of the airflow in the space under the head, which is the space between the heads, and the adjustment unit that adjusts the airflow in the space under the head as the surface tension of the ink ejected by the inkjet head becomes smaller. It is characterized in that it is provided with a control unit.

According to the inkjet printing apparatus of the present invention, mist stains on printed matter can be reduced.

It is a schematic block diagram of the inkjet printing apparatus which concerns on 1st Embodiment. It is a top view of the printing part of the inkjet printing apparatus shown in FIG. It is a top view of the vicinity of the head module of the printing part in 1st Embodiment. It is sectional drawing which follows the AA line of FIG. It is a control block diagram of the inkjet printing apparatus shown in FIG. It is a figure which shows the paper suction fan drive table. It is explanatory drawing of a satellite. It is a figure which shows an example of the distribution of the size of a satellite for each surface tension of an ink. It is explanatory drawing of the air flow of the space under a head in 1st Embodiment. It is a figure which shows the mist stain of the printed matter in 1st Embodiment. It is a figure which shows the mist stain of the printed matter in the comparative example. It is a top view of the vicinity of the head module of the printing part in 2nd Embodiment. It is sectional drawing along the line BB of FIG. It is explanatory drawing of the air flow of the space under a head in 2nd Embodiment. It is sectional drawing of the vicinity of the head module of the printing part in 3rd Embodiment. It is explanatory drawing of the air flow of the space under a head in 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

The embodiments shown below exemplify an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, arrangement, etc. of each component. Is not specified as the following. The technical idea of the present invention can be modified in various ways within the scope of claims.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of the printing unit of the inkjet printing apparatus shown in FIG. FIG. 3 is a plan view of the vicinity of the head module of the printing unit. FIG. 4 is a cross-sectional view taken along the line AA of FIG. FIG. 5 is a control block diagram of the inkjet printing apparatus shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is the front-back direction, and the front direction of the paper surface is the front. Further, the vertical and horizontal directions of the paper surface in FIG. 1 are defined as the vertical and horizontal directions. In FIG. 1, the direction from left to right is the transport direction of the paper P, which is the printing medium. In the following description, upstream and downstream mean upstream and downstream in the transport direction of the paper P.

As shown in FIGS. 1 and 5, the inkjet printing apparatus 1 according to the first embodiment includes a transport unit 2, a guide unit 3, a printing unit 4, and a control unit 5.

The transport unit 2 transports the paper P fed from the paper feed unit (not shown) by air suction. The transport unit 2 includes a transport belt 11, a drive roller 12, driven rollers 13 to 15, a belt motor 16, and a paper suction fan 17.

The transport belt 11 attracts and holds the paper P for transport. The transport belt 11 is an annular belt hung on the drive roller 12 and the driven rollers 13 to 15. A large number of belt holes 11a (see FIG. 9) are formed in the transport belt 11. The transport belt 11 sucks and holds the paper P on the transport surface 11b by the suction force generated in the belt hole 11a by driving the paper suction fan 17. The transport surface 11b is the upper surface of the horizontal portion of the transport belt 11 between the drive roller 12 and the driven roller 13. The transport belt 11 rotates in the clockwise direction in FIG. 1 to transport the suction-held paper P to the right.

The drive roller 12 rotates the transport belt 11 in the clockwise direction in FIG.

The driven rollers 13 to 15 support the transport belt 11 together with the driving rollers 12. The driven rollers 13 to 15 drive the driven rollers 12 via the transport belt 11. The driven roller 13 is arranged on the left side of the driving roller 12 at the same height as the driving roller 12. The driven rollers 14 and 15 are arranged below the drive roller 12 and the driven roller 13 at the same height so as to be separated from each other in the left-right direction.

The belt motor 16 rotationally drives the drive roller 12.

The paper suction fan 17 creates a downward air flow. As a result, the paper suction fan 17 sucks air through the belt hole 11a of the transport belt 11 to generate a negative pressure in the belt hole 11a, and sucks the paper P onto the transport belt 11. The paper suction fan 17 is arranged in a region surrounded by the annular transport belt 11.

The guide unit 3 guides the paper P transported to the downstream side of the transport unit 2. The guide portion 3 includes a pair of guide plates 21 and 22, and a mist suction member 23.

The guide plates 21 and 22 are members that guide the paper P to be conveyed from the conveying unit 2 to the conveying mechanism (not shown) on the downstream side thereof.

The mist adsorption member 23 is a member that adsorbs and collects ink mist (satellite) generated by ink ejection from the inkjet head 36 described later. The mist adsorption member 23 is installed on the guide plate 21.

The printing unit 4 prints on the paper P conveyed by the conveying unit 2. The printing unit 4 is arranged above the transport unit 2. The printing unit 4 includes a head unit 31 and a head cooling unit 32.

The head unit 31 ejects ink onto the paper P to print an image. The head unit 31 includes a plurality of inkjet heads 36 and a head holder 37. In this embodiment, the head unit 31 includes four inkjet heads 36.

The inkjet head 36 ejects ink onto the paper P. The four inkjet heads 36 eject inks of different colors (for example, black, cyan, magenta, and yellow). The four inkjet heads 36 are arranged in parallel along the transport direction (left-right direction) of the paper P. Each inkjet head 36 has a plurality of head modules 38. In this embodiment, each inkjet head 36 has six head modules 38, respectively.

The head module 38 has an ink chamber (not shown) for storing ink and a plurality of nozzles (not shown) for ejecting ink. A piezo element (not shown) is arranged in the ink chamber. Ink is ejected from the nozzle by driving the piezo element. The nozzle of the head module 38 is open to the discharge surface 38a, which is the lower surface of the transfer belt 11 facing the transfer surface 11b. The nozzles are arranged along the front-rear direction (main scanning direction).

In the inkjet head 36, the head modules 38 are arranged in a staggered manner along the front-rear direction. That is, in each of the inkjet heads 36, the six head modules 38 arranged along the front-rear direction are arranged so as to be alternately displaced in the left-right direction.

The head module 38 ejects ink supplied by an ink circulation mechanism (not shown) provided for each inkjet head 36 from a nozzle. The ink circulation mechanism is a mechanism for supplying ink to each head module 38 of the inkjet head 36 while circulating the ink. Ink is supplied to the ink circulation mechanism from an ink cartridge (not shown).

The head holder 37 holds the inkjet head 36. The head holder 37 is formed of a hollow box body. The head holder 37 is arranged above the transport unit 2. As shown in FIGS. 3 and 4, the bottom plate 37a of the head holder 37 is formed with a mounting opening 37b to which the head module 38 of each inkjet head 36 is mounted. The same number of mounting openings 37b as the head module 38 are formed on the bottom plate 37a of the head holder 37. The head holder 37 holds the head module 38 by projecting the lower end portion of the head module 38 downward from the mounting opening 37b.

The mounting opening 37b consists of a through hole larger than the cross section along the horizontal plane of the head module 38. As a result, the mounting position and angle of the head module 38 can be adjusted. Since the mounting opening 37b has such a size, the head module 38 is mounted on the mounting opening 37b via the gap 40.

The head holder 37 is provided with a sealing member 41. The sealing member 41 is a member that closes the gap 40 between the head module 38 and the mounting opening 37b.

The head cooling unit 32 generates cooling air in the head holder 37, and the cooling air cools the inkjet head 36. The head cooling unit 32 includes a spraying unit 46 and a suction unit 47.

The spraying portion 46 blows air into the head holder 37 from the outside. The spraying portion 46 is arranged on the front side of the head holder 37. The spraying portion 46 includes a spraying chamber 51 and a spraying fan 52.

The spray chamber 51 forms an air flow path between the spray fan 52 and the head holder 37. The spray chamber 51 has an elongated shape in the left-right direction and is formed in a hollow shape. The spray chamber 51 is arranged on the side plate on the front side of the head holder 37.

A plurality of spray holes (not shown) are formed on the surface of the spray chamber 51 in contact with the head holder 37. The spray hole of the spray chamber 51 is an air outlet from the spray chamber 51 when air is blown into the head holder 37. The spray hole of the spray chamber 51 is arranged at a position corresponding to a ventilation hole (not shown) formed in the side plate on the front side of the head holder 37. As a result, air can be blown into the head holder 37 from the spraying portion 46.

The blowing fan 52 blows air into the blowing chamber 51 from one end of the blowing chamber 51. As a result, air is blown into the head holder 37 through the spray chamber 51.

The suction unit 47 sucks air from the head holder 37. The suction portion 47 is arranged on the rear side of the head holder 37. The suction unit 47 includes a suction chamber 53 and a suction fan 54.

The suction chamber 53 forms an air flow path between the head holder 37 and the suction fan 54. The suction chamber 53 has an elongated shape in the left-right direction and is formed in a hollow shape. The suction chamber 53 is arranged on the side plate on the rear side of the head holder 37.

A plurality of suction holes (not shown) are formed on the surface of the suction chamber 53 in contact with the head holder 37. The suction hole of the suction chamber 53 is an air inlet to the suction chamber 53 when sucking air from the head holder 37. The suction hole of the suction chamber 53 is arranged at a position corresponding to a ventilation hole (not shown) formed in the side plate on the rear side of the head holder 37. As a result, the suction unit 47 can suck air from the head holder 37.

The suction fan 54 sucks air from one end of the suction chamber 53. As a result, air is sucked from the head holder 37 through the suction chamber 53.

The control unit 5 controls the operation of each unit of the inkjet printing device 1. The control unit 5 includes a CPU, RAM, ROM, a hard disk, and the like.

The control unit 5 stores the paper suction fan drive table 56 shown in FIG. The paper suction fan drive table 56 is a table in which the surface tension of the ink ejected by the inkjet head 36 is associated with the duty ratio (drive rate) of the drive signal of the paper suction fan 17. In the paper suction fan drive table 56 of FIG. 6, the duty ratios D1, D2, ... Are D1> D2> ...

Here, the larger the duty ratio of the drive signal of the paper suction fan 17, the higher the rotation speed of the paper suction fan 17. Further, as will be described later, the higher the rotation speed of the paper suction fan 17, the stronger the air flow in the space under the head 57, which is the space between the transport surface 11b and the inkjet head 36. In the first embodiment, the paper suction fan 17 has a function as an adjusting unit for adjusting the strength of the air flow in the space under the head.

When performing the printing operation, the control unit 5 sets the duty ratio of the drive signal of the paper suction fan 17 based on the surface tension of the ink ejected by the inkjet head 36 with reference to the paper suction fan drive table 56. That is, the control unit 5 controls the paper suction fan 17 so that the smaller the surface tension of the ink ejected by the inkjet head 36 during the printing operation, the stronger the air flow in the space 57 under the head.

Next, the operation of the inkjet printing apparatus 1 will be described.

When the print job is input, the control unit 5 starts driving the transport unit 2. Specifically, the control unit 5 starts driving the drive roller 12 by the belt motor 16. As a result, the circumferential drive of the transport belt 11 is started.

Further, the control unit 5 starts driving the paper suction fan 17. Here, the control unit 5 drives the paper suction fan 17 at a duty ratio corresponding to the surface tension of the ink ejected by the inkjet head 36.

Specifically, the control unit 5 acquires the surface tension of the ink of each inkjet head 36 from, for example, a storage tag provided in the ink cartridge. The surface tension of the ink in each of the inkjet heads 36 may change due to changes in the type of ink corresponding to each of the inkjet heads 36.

When the surface tension of the ink of each of the inkjet heads 36 is acquired, the control unit 5 calculates the average value of the surface tensions of the inks of all the inkjet heads 36. The control unit 5 takes this average value as the surface tension of the ink ejected by the inkjet head 36, and acquires a duty ratio corresponding to the surface tension from the suction fan drive table 56. Then, the control unit 5 drives the paper suction fan 17 with the duty ratio acquired from the suction fan drive table 56. As a result, the smaller the surface tension of the ink ejected by the inkjet head 36, the higher the rotation speed of the paper suction fan 17.

By driving the paper suction fan 17, air is sucked through the belt hole 11a of the conveyor belt 11, a negative pressure is generated in the belt hole 11a, and a suction force is generated.

Further, the control unit 5 starts driving the spray fan 52 and the suction fan 54 of the head cooling unit 32. By driving the spray fan 52, air is blown into the head holder 37 through the spray chamber 51. Further, by driving the suction fan 54, air is sucked from the head holder 37 through the suction chamber 53. As a result, cooling air flowing from the front side to the rear side is generated in the head holder 37.

When the transfer unit 2 and the head cooling unit 32 are started to be driven, the number of sheets of paper P printed in the print job is sequentially fed to the transfer unit 2. The paper P that has been fed is conveyed while being attracted and held by the transfer belt 11 of the transfer unit 2. In the transport unit 2, each paper P is transported between predetermined papers. The control unit 5 ejects ink from the head module 38 of the inkjet head 36 to print an image on the paper P conveyed by the conveying belt 11.

When ink is ejected from the nozzle of the head module 38, the ejected ink flies in a trailing manner, and a time difference or a speed difference occurs between the head portion and the tail portion of the flying ink. Therefore, as shown in FIG. 7, satellite 59, which is an unnecessary fine droplet, is generated along with the main droplet 58, which is the preceding main droplet. When the satellite 59 adheres to the paper P, it causes stains on the printed matter.

The size of the satellite is affected by the surface tension of the ink. FIG. 8 shows an example of the distribution of satellite sizes for each surface tension of the ink. FIG. 8 is a histogram obtained by acquiring the number and size of satellites at the time of ink ejection by image analysis. The size of the satellite is based on the size of the main drop 58, which is not affected by the surface tension of the ink. As shown in FIG. 8, the smaller the surface tension of the ink, the finer the satellite tends to be.

The smaller the satellite, the easier it is for the airflow to flow. Therefore, in the inkjet printing apparatus 1, the smaller the surface tension of the ink during the printing operation, the stronger the airflow in the space 57 under the head, and the finer satellites are blown off so as not to adhere to the paper P.

Specifically, as described above, the control unit 5 has a duty ratio of the drive signal of the paper suction fan 17 so that the smaller the surface tension of the ink ejected by the inkjet head 36, the higher the rotation speed of the paper suction fan 17. Is set.

Here, during the printing operation, as shown in FIG. 9, the conveyed airflow Fh is generated in the space 57 under the head. The transport airflow Fh is an airflow generated by the movement of the transport belt 11 and the paper P. The transport airflow Fh flows along the transport direction of the paper P.

Further, in the inter-paper region between the conveyed paper P and the paper P, there is no paper P on the belt hole 11a, and the belt hole 11a is exposed. Therefore, a suction airflow Fk is generated. The suction airflow Fk is an airflow that flows from the space above the transport surface 11b to the inside of the transport portion 2 through the belt hole 11a by driving the paper suction fan 17.

The larger the duty ratio of the drive signal of the paper suction fan 17, the higher the rotation speed of the paper suction fan 17, and the stronger the suction airflow Fk. When the suction airflow Fk becomes stronger, the airflow in which the transport airflow Fh and the suction airflow Fk are combined becomes stronger, so that the airflow in the space 57 under the head becomes stronger.

Therefore, the smaller the surface tension of the ink ejected by the inkjet head 36, the stronger the airflow in the space 57 under the head by increasing the rotation speed of the paper suction fan 17.

As a result, when the surface tension of the ink is relatively small, the finely divided satellites are blown off by the air flow so as not to adhere to the paper P, so that mist stains on the printed matter are reduced.

The satellite blown off by the air flow floats as an ink mist and is recovered by being sucked by the suction air flow Fk to the transport unit 2 or sucked by the mist suction member 23.

Here, since a large satellite is not easily affected by the air flow, it is not sufficiently blown off even if the air flow is strengthened, and it is flown halfway and lands at a position deviated from the landing position of the main drop on the paper P. There is. As a result, the satellite may land on the margin portion (non-printed portion) of the paper P, causing mist stains. If the airflow is sufficiently weak relative to the size of the satellite, the satellite will land on the dots due to the landed main droplet, and mist stains on the printed matter will be suppressed.

By setting the duty ratio of the drive signal of the paper suction fan 17 as described above, the larger the surface tension of the ink, the weaker the airflow in the space 57 under the head, so that a relatively large satellite is placed in the margin portion of the paper P. Mist stains caused by landing are also reduced.

FIG. 10 shows an example of mist stain on the printed matter when the paper suction fan 17 is driven as described above. Further, as a comparative example, FIG. 11 shows an example of mist stain on a printed matter when the paper suction fan 17 is driven at a predetermined duty ratio regardless of the surface tension of the ink. The example of FIG. 10 according to the present embodiment has less mist stains than the comparative example of FIG.

The paper P printed by the printing unit 4 is conveyed by a conveying mechanism (not shown) on the downstream side of the conveying unit 2 while being guided by the guide plates 21 and 22, and is discharged. When the last paper P is discharged, the control unit 5 stops the drive roller 12 and the paper suction fan 17. Further, the control unit 5 stops the spray fan 52 and the suction fan 54. As a result, a series of operations is completed.

As described above, in the inkjet printing apparatus 1, the control unit 5 controls the paper suction fan 17 so that the smaller the surface tension of the ink ejected by the inkjet head 36, the stronger the airflow in the space 57 under the head. As a result, when the surface tension of the ink is relatively large, the relatively large satellite is prevented from landing on the margin portion of the paper P, and when the surface tension of the ink is relatively small, the miniaturized satellite is formed. , It can be blown off by an air flow so as not to adhere to the paper P. As a result, mist stains on the printed matter can be reduced.

[Second Embodiment]
Next, a second embodiment in which a part of the first embodiment described above is modified will be described.

FIG. 12 is a plan view of the vicinity of the head module of the printing unit in the second embodiment. FIG. 13 is a cross-sectional view taken along the line BB of FIG.

In the second embodiment, as shown in FIGS. 12 and 13, the printing unit 4 has a configuration in which the sealing member 41 of the first embodiment is replaced with the sealing member 41A and a shutter 61 is added.

The shutter 61 opens and closes a part of the gap 40. In the present embodiment, the shutter 61 opens and closes a portion of the gap 40 along the left side surface of the head module 38. When the shutter 61 is opened, the cooling air in the head holder 37 leaks through the gap 40 and flows into the space 57 under the head, so that the airflow in the space 57 under the head becomes stronger. The shutter 61 has a function as an adjusting unit capable of individually adjusting the strength of the air flow in the space 57 under the head of each of the inkjet heads 36.

The sealing member 41A is a member that closes a portion of the gap 40 other than the portion opened and closed by the shutter 61.

In the second embodiment, in the printing operation, the smaller the surface tension of the ink ejected by the inkjet head 36 is, the stronger the airflow in the space 57 under the head of the inkjet head 36 is. Therefore, each shutter 61 corresponding to each head module 38 of the inkjet head 36 is controlled.

Here, when the shutter 61 is open during the printing operation, the cooling leak airflow Fc flows into the space 57 under the head as shown in FIG. The cooling leak airflow Fc is one in which the cooling air in the head holder 37 leaks from the gap 40. Since the cooling leak airflow Fc flows into the space 57 under the head, the airflow in the space 57 under the head becomes stronger than when the shutter 61 is closed. Further, the strength of the air flow in the space 57 under the head can be adjusted by intermittently opening and closing the shutter 61 and adjusting the opening / closing cycle and the opening time per cycle of the opening / closing operation.

Therefore, the control unit 5 opens or closes each shutter 61 so that the smaller the surface tension of the ink is, the stronger the airflow in the space 57 under the head of the inkjet head 36 is. It controls whether to perform intermittent opening / closing operation. Further, when the control unit 5 performs the intermittent opening / closing operation of the shutter 61, the opening / closing cycle and the opening time per cycle are increased so that the smaller the surface tension of the ink, the stronger the air flow in the space 57 under the head. To control. The opening / closing control content of the shutter 61 according to the surface tension of the ink is preset so that the air flow in the space 57 under the head has a strength corresponding to the surface tension of the ink.

As described above, in the second embodiment, in the second embodiment, the smaller the surface tension of the ink ejected by the inkjet head 36 is, the smaller the surface tension of the ink ejected by the inkjet head 36 is, the more the airflow in the space 57 under the head of the inkjet head 36 is generated. Each shutter 61 corresponding to each head module 38 of the inkjet head 36 is controlled so as to be strong. As a result, the strength of the air flow in the space 57 under the head of the inkjet head 36 can be adjusted according to the surface tension of the ink for each of the inkjet heads 36, so that mist stains on the printed matter can be further reduced.

[Third Embodiment]
Next, a third embodiment in which a part of the above-mentioned first embodiment is modified will be described.

FIG. 15 is a cross-sectional view of the vicinity of the head module of the printing unit according to the third embodiment.

In the third embodiment, as shown in FIG. 15, the printing unit 4 has a configuration in which the airflow adjusting fan 66 is added to the printing unit 4 of the first embodiment.

The airflow adjusting fan 66 is provided in the vicinity of the head module 38, one for each head module 38. The airflow adjusting fan 66 generates a downward airflow. The stronger the airflow generated by the airflow adjusting fan 66, the stronger the airflow in the space 57 under the head. The airflow adjusting fan 66 has a function as an adjusting unit capable of individually adjusting the strength of the airflow in the space 57 under the head of each of the inkjet heads 36.

In the third embodiment, the control unit 5 has a smaller surface tension of the ink ejected by the inkjet head 36 for each inkjet head 36 during the printing operation, the stronger the air flow in the space 57 under the head of the inkjet head 36. The airflow adjusting fan 66 corresponding to each head module 38 of the inkjet head 36 is controlled so as to be.

Here, when the airflow adjusting fan 66 is driven during the printing operation, as shown in FIG. 16, the adjusting airflow Fs generated by the airflow adjusting fan 66 flows into the space 57 under the head. Since the adjusted airflow Fs flows into the space 57 under the head, the airflow in the space 57 under the head becomes stronger than when the airflow adjusting fan 66 is stopped. Further, the stronger the adjusted airflow Fs, the stronger the airflow in the space 57 under the head.

Therefore, as the surface tension of the ink is smaller, the duty ratio of the drive signal of the airflow adjusting fan 66 is increased to increase the adjusted airflow Fs, so that the airflow in the space 57 under the head can be increased. The duty ratio of the drive signal of the airflow adjusting fan 66 according to the surface tension of the ink is preset so that the airflow in the space 57 under the head becomes the strength corresponding to the surface tension of the ink.

As described above, in the third embodiment, in the control unit 5, the smaller the surface tension of the ink ejected by the inkjet head 36, the smaller the surface tension of the ink ejected by the inkjet head 36, the more the air flow in the space 57 under the head of the inkjet head 36 becomes. Each airflow adjusting fan 66 corresponding to each head module 38 of the inkjet head 36 is controlled so as to be strong. As a result, as in the second embodiment, the strength of the air flow in the space 57 under the head of the inkjet head 36 can be adjusted for each of the inkjet heads 36 according to the surface tension of the ink, so that mist stains on the printed matter are further reduced. it can.

[Other Embodiments]
As mentioned above, the present invention has been described by the first to third embodiments, but the discourses and drawings that form part of this disclosure should not be understood to limit the invention. Various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art from this disclosure.

In the second embodiment described above, each shutter 61 is controlled for each of the inkjet heads 36 so that the smaller the surface tension of the ink, the stronger the airflow in the space 57 under the head of the inkjet head 36. However, as in the first embodiment, each shutter 61 may be controlled so as to adjust the strength of the air flow in the space 57 under the head based on the average value of the surface tensions of the inks of all the inkjet heads 36. .. Further, also in the third embodiment, as in the first embodiment, each airflow adjusting fan adjusts the strength of the airflow in the space 57 under the head based on the average value of the surface tensions of the inks of all the inkjet heads 36. 66 may be controlled.

Further, the control of the shutter 61 of the second embodiment and the control of the airflow adjusting fan 66 of the third embodiment may be combined to adjust the strength of the airflow in the space 57 under the head. Further, by combining at least one of the control of the paper suction fan 17 of the first embodiment, the control of the shutter 61 of the second embodiment, and the control of the airflow adjustment fan 66 of the third embodiment, the airflow in the space under the head 57 You may try to adjust the strength of.

Further, in the second embodiment, the head holder 37 may be divided into each of the inkjet heads 36, and each of the inkjet heads 36 may have a head cooling unit that generates cooling air. Further, in this configuration, the strength of the airflow in the space 57 under the head of the inkjet head 36 is combined with the adjustment of the cooling air strength corresponding to the inkjet head 36 and the control of each shutter 61 for each of the inkjet heads 36. You may try to adjust the size. Further, the airflow adjusting fan 66 of the third embodiment is added to this configuration, and for each of the inkjet heads 36, the strength of the cooling air corresponding to the inkjet head 36 is adjusted, the shutters 61 are controlled, and the shutters are controlled. The control of the airflow adjusting fan 66 may be combined to adjust the strength of the airflow in the space 57 under the head of the inkjet head 36.

Further, in the second embodiment described above, the shutter 61 has a configuration in which the open area of the gap 40 can be adjusted, and the strength of the air flow in the space 57 under the head is adjusted by adjusting the open area of the gap 40. It may be.

Further, in the third embodiment described above, the configuration is shown in which the strength of the airflow in the space 57 under the head is adjusted by the airflow adjusting fan 66 that generates the downward airflow, but the space under the head is adjusted by the fan that generates the upward airflow. It may adjust the strength of the airflow in 57.

Further, in the second and third embodiments described above, the transport unit 2 is not limited to the air suction type, and may be another type such as an electrostatic suction type.

Further, in the first to third embodiments described above, the configuration having a plurality of inkjet heads 36 has been described, but the configuration may have only one inkjet head 36.

As described above, it goes without saying that the present invention includes various embodiments not described here. Therefore, the technical scope of the present invention is defined only by the matters specifying the invention relating to the reasonable claims from the above description.

[Additional Notes]
This application discloses the following inventions.

(Appendix 1)
A transport unit that transports print media and
An inkjet head that ejects ink to a print medium conveyed by the transfer unit, and
An adjusting unit that adjusts the strength of the airflow in the space under the head, which is the space between the inkjet head and the conveying unit.
An inkjet printing apparatus including a control unit that controls the adjustment unit so that the smaller the surface tension of the ink ejected by the inkjet head, the stronger the airflow in the space under the head.

(Appendix 2)
A plurality of the above-mentioned inkjet heads are provided.
The adjusting unit can individually adjust the strength of the airflow in the space under the head of each of the inkjet heads.
The control unit controls the adjustment unit so that the smaller the surface tension of the ink ejected by the inkjet head, the stronger the airflow in the space under the head of the inkjet head. The inkjet printing apparatus according to Appendix 1.

1 Inkjet printing device 2 Transport unit 3 Guide unit 4 Printing unit 5 Control unit 11 Transport belt 11a Belt hole 11b Transport surface 17 Paper suction fan 31 Head unit 32 Head cooling unit 36 Inkjet head 37 Head holder 38 Head module 38a Discharge surface 41, 41A Sealing member 46 Spraying part 47 Suction part 56 Paper suction fan Drive table 57 Space under the head 61 Shutter 66 Air flow adjustment fan Fh Transport airflow Fk Suction airflow Fc Cooling leak airflow Fs Adjustment airflow

Claims (2)

A transport unit that transports print media and
An inkjet head that ejects ink to a print medium conveyed by the transfer unit, and
An adjusting unit that adjusts the strength of the airflow in the space under the head, which is the space between the inkjet head and the conveying unit.
An inkjet printing apparatus including a control unit that controls the adjustment unit so that the smaller the surface tension of the ink ejected by the inkjet head, the stronger the airflow in the space under the head. A plurality of the above-mentioned inkjet heads are provided.
The adjusting unit can individually adjust the strength of the airflow in the space under the head of each of the inkjet heads.
The control unit controls the adjustment unit so that the smaller the surface tension of the ink ejected by the inkjet head, the stronger the airflow in the space under the head of the inkjet head. The inkjet printing apparatus according to claim 1.