JP2021070177A - Inkjet printing device - Google Patents

Abstract

To provide an inkjet printing device, which can be prevented from deteriorating in printing quality due to influence of cooling air.SOLUTION: An inkjet printing device comprises: a conveying part (2) that conveys a printing medium (P) while holding the medium on a conveying surface (10a); an inkjet head (20) that performs printing on the printing medium held on the conveying surface by ejecting ink; and a head holder (30) that holds the inkjet head on a head holding plate (31) opposing to the conveying surface, which further comprises: a communication part (39), formed in the head holding plate with an interval from a holding position (31a) of the inkjet head, which communicates a first space (S1) in the head holder with a second space (S2) between the holder and the conveying surface; cooling means (41 and 42) which feed cooling air to the inkjet head in the head holder; and shielding parts (50 and 60), provided in the first space, which shield at least portions between passages (S4 and S6) through which the cooling air passes and the communication part.SELECTED DRAWING: Figure 4

Description

The present invention relates to an inkjet printing device.

A line-type inkjet printing apparatus is known that prints by ejecting ink from an inkjet head fixed to a head holder. When ejecting ink from the inkjet head, mist-like ink mist is generated in addition to the main droplets of ink used for image formation.

At this time, a suction transport mechanism for transporting the generated ink mist while sucking and holding the print medium on the transport surface so as not to land on the print medium such as paper is widely used. By sucking the ink mist and adsorbing the print medium on the transport surface, the distance between the inkjet head and the print medium is kept constant while reducing the stains caused by the ink mist, and high-quality printing can be realized.

The suction transfer mechanism includes a transfer belt provided with a large number of suction holes and a suction fan arranged below the transfer surface of the transfer belt, and sucks air by the rotation of the fan to negatively affect the suction holes of the transfer belt. A pressure is generated to suck and hold the print medium on the transport surface. The transfer belt is driven in this suction-holding state to convey the print medium.

On the portion of the transport surface of the transport belt on which the print medium is placed, the suction holes are covered with the print medium, so that air flow through the suction holes is unlikely to occur. On the other hand, in the portion of the transport surface of the transport belt on which the print medium is not placed, when the suction fan is driven, the air above the transport surface flows through the suction holes into the space below the transport surface.

The suction air near the ink ejection surface of the inkjet head affects the behavior of the ink ejected from the inkjet head. In addition to the ejected ink, the ink mist is also easily affected by the suction wind, and the ink mist scattered by the suction wind adheres to the print medium at a position different from the main droplet, causing image distortion and stains on the print medium. become.

In an inkjet printing apparatus, there is known a technique of providing a communication path for communicating a space between a head holding plate for holding an inkjet head and a transport surface with a space of atmospheric pressure (see, for example, Patent Document 1). In the inkjet printing apparatus of Patent Document 1, the positive pressure in the space under the head holder is maintained by the communication path, the pressure difference between the upper side and the lower side of the transport belt is secured, and the suction force in the suction hole is reduced. , The accompanying transfer failure in the suction transfer mechanism is prevented.

Japanese Unexamined Patent Publication No. 2016-168679

If the head holding plate is provided with a communication path as in Patent Document 1, when the suction fan is driven, suction air of the flow from the communication path to the suction hole of the transport belt is likely to be generated, and directly under the inkjet head. Suction wind is less likely to occur. Therefore, the influence of the suction wind on the ink mist can be reduced.

In order to cool the inkjet head that generates heat during printing, a cooling means for sending cooling air around the inkjet head may be provided. The cooling air from the cooling means passes through the space above the head holding plate. However, when the above-mentioned communication path is provided, the cooling air may flow into the space below the head holding plate through the communication path and unnecessarily diffuse the ink mist to contaminate the print medium and peripheral members.

As described above, in the conventional inkjet printing apparatus, the suction air by the suction transfer mechanism and the cooling air by the cooling means may affect the ink mist in different situations. In particular, it has been desired to reliably reduce the influence of cooling air.

An object of the present invention is to prevent deterioration of print quality due to the influence of cooling air in an inkjet printing apparatus.

The present invention includes a transport unit that holds and transports a print medium on a transport surface, an inkjet head that ejects ink to print on the print medium held on the transport surface, and a head holding plate that faces the transport surface. In an inkjet printing apparatus including a head holder for holding the inkjet head, the head holder is formed on the head holding plate at a distance from the holding position of the inkjet head, and the first space in the head holder and the transport are formed. A communication portion that communicates with a second space between the surfaces, a cooling means for sending cooling air to the inkjet head in the head holder, a passage provided in the first space through which the cooling air passes, and the said. It is characterized by being provided with a shielding portion that blocks at least a part of the communication portion.

According to the inkjet printing apparatus of the present invention, the cooling air for cooling the inkjet head is less likely to affect the vicinity of the ink ejection portion of the inkjet head, and deterioration of print quality due to the influence of the cooling air can be prevented.

It is a side view which shows the printing part of the inkjet printing apparatus. It is a top view of the head unit which constitutes a printing part. It is sectional drawing which shows the inside of a head unit partially. It is sectional drawing which follows IV-IV of FIG. It is sectional drawing which shows the different form of a shielding part. It is sectional drawing which shows the comparative example which does not provide the communication part in the head holding plate. It is sectional drawing which shows the comparative example which provided the communication part in the head holding plate, and does not provide a shielding part.

Hereinafter, the inkjet printing apparatus according to the embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a printing unit 1 which is a part of an inkjet printing apparatus. The printing unit 1 has a platen unit 2 and a head unit 3. The paper P, which is a printing medium, is conveyed by the platen unit 2 which is a conveying unit at a predetermined speed, and ink is ejected from the head unit 3 to the paper P. And print. The inkjet printing apparatus includes a paper feeding unit and a paper ejection unit (not shown), and the paper P before printing is carried into the printing unit 1 from the paper feeding unit, and the paper P after printing is ejected by the paper ejection unit. The transport direction of the paper P conveyed by the platen unit 2 is the sub-scanning direction F2, and the width direction of the paper P orthogonal to the sub-scanning direction F2 is the main scanning direction F1.

As shown in FIG. 1, the platen unit 2 includes a transport belt 10, a drive roller 11, and a plurality of driven rollers 12, 13, 14. The transport belt 10 is an endless (loop-shaped) strip that is hung between the drive roller 11 and the plurality of driven rollers 12, 13, and 14. The transfer belt 10 in the suspended state forms a substantially horizontal transfer surface 10a between the drive roller 11 and the driven roller 12, and the paper P is placed on the transfer surface 10a. The drive roller 11 is rotationally driven by a belt motor (not shown). When the drive roller 11 rotates, the driving force is transmitted to the transfer belt 10, and the transfer belt 10 orbits while being guided by the driven rollers 12, 13 and 14, and the paper P supported on the transfer surface 10a is supported in the sub-scanning direction. Move to F2. The left side in each drawing is the upstream side of the paper transport, and the right side is the downstream side of the paper transport. The driven rollers 12, 13 and 14 rotate in a driven manner of the drive roller 11 via the transport belt 10.

The transport belt 10 is formed with a plurality of suction holes 10b (see FIGS. 3 and 4) penetrating the front and back surfaces. The platen unit 2 includes a suction fan 15 below the transport surface 10a between the drive roller 11 and the driven roller 12. The suction fan 15 is rotationally driven by a fan drive motor (not shown), and the rotation of the suction fan 15 produces an air flow from upward to downward. Therefore, when the suction fan 15 is rotated, a force (negative pressure) for sucking air from above the transport surface 10a is generated through the plurality of suction holes 10b, and the negative pressure acting on the suction holes 10b causes the paper P to move to the transport surface 10a. It is attracted and held. The drive roller 11 is rotated while driving the suction fan 15, and the paper P is conveyed while being attracted and held on the transfer surface 10a. As a result, the flatness of the paper P can be ensured and high-quality printing can be performed.

As shown in FIG. 1, the head unit 3 is arranged above the platen unit 2. The head unit 3 includes a plurality of inkjet heads 20 and a head holder 30 that holds the plurality of inkjet heads 20. The printing unit 1 of the present embodiment constitutes a line-type inkjet printing apparatus, and as shown in FIG. 2, includes a plurality of (three) inkjet heads 20 arranged at predetermined intervals in the main scanning direction F1. A plurality of rows (4 rows) of head rows L1, L2, L3, and L4 are arranged in the sub-scanning direction F2. In the two head rows adjacent to the sub-scanning direction F2, the inkjet heads 20 are arranged so as to be displaced from each other in the main scanning direction F1, and a plurality of inkjet heads 20 are arranged in a staggered pattern as a whole.

As shown in FIG. 4, each inkjet head 20 connects an ink ejection surface 21 facing the lower transport surface 10a, an upper surface 22 located above the ink ejection surface 21, and an ink ejection surface 21 and an upper surface 22. It has a rectangular parallelepiped-shaped housing having a side surface 23.

The ink ejection surface 21 facing downward is provided with a nozzle row composed of a plurality of nozzles (not shown) arranged in the main scanning direction F1. When printing on the paper P, the ink supplied to each inkjet head 20 from the ink supply path (not shown) is ejected downward from each nozzle in the nozzle row.

The head holder 30 includes a rectangular parallelepiped housing having a hollow inside, and a substantially horizontal bottom plate facing the transport surface 10a constitutes the head holding plate 31 (see FIG. 4). There is. The head holder 30 further includes a top plate 32 (see FIG. 4) located above the head holding plate 31 and four side plates 33, 34, 35, 36 (see FIG. 2) connecting the head holding plate 31 and the top plate 32. ) And. Note that FIG. 2 shows the inside of the head holder 30 so as to be seen through the top plate 32 of the head holder 30.

The internal space of the head holder 30 above the head holding plate 31 is the upper space S1 (first space), and the space between the head holding plate 31 and the transport surface 10a is the intermediate space S2 (second space). The internal space of the platen unit 2 below the transport surface 10a is defined as the lower space S3.

As shown in FIG. 4, the head holding plate 31 is formed with a head holding opening 31a penetrating in the vertical direction. The same number of head holding openings 31a as the plurality of inkjet heads 20 are provided. Each inkjet head 20 is inserted into the head holding opening 31a and fixed to the head holding plate 31, and in this fixed state, the ink ejection surface 21 is located below the head holding plate 31 (on the transport surface 10a side). .. Each inkjet head 20 is arranged so as to straddle the upper space S1 and the intermediate space S2, and the lower half portion including the ink ejection surface 21 projects downward from the head holding plate 31 and is located in the intermediate space S2. The upper half portion including 22 is located in the upper space S1 above the head holding plate 31.

Among the side plates of the head holder 30, a plurality of ventilation holes are formed in each of the side plate 33 and the side plate 34 facing the main scanning direction F1. The plurality of ventilation holes are formed at positions corresponding to the head rows L1, L2, L3, and L4 of the inkjet head 20. As shown in FIGS. 2 and 3, a duct 37 is connected to each ventilation hole of the side plate 33, and a duct 38 is connected to each ventilation hole of the side plate 34. The duct 37 and the duct 38 are ventilation passages protruding inward of the head holder 30, and have a conical shape in which the cross-sectional area (opening diameter) increases toward the tip. Ducts 37 and 38 are provided on both sides of each head row L1, L2, L3, and L4 in the main scanning direction F1 so as to face each other. That is, four ducts 37 and four ducts 38 are provided corresponding to the head rows L1, L2, L3, and L4.

The head unit 3 further has cooling means. The cooling means sends cooling air to the upper space S1 in the head holder 30 to cool each inkjet head 20 that generates heat during printing. As shown in FIG. 2, the head holder 30 is cooled in the main scanning direction F1. It is provided with blower portions 41 and suction portions 42 located on both sides.

The blower portion 41 includes a blower fan 44 in a housing 43 attached to the side plate 33 of the head holder 30. When the blower fan 44 is rotationally driven by a fan drive motor (not shown), cooling air is sent from the housing 43 side toward the inside of the head holder 30 through the ventilation holes of the side plate 33 and each duct 37.

The suction unit 42 includes a suction fan 46 in a housing 45 attached to the side plate 34 of the head holder 30. When the suction fan 46 is rotationally driven by a fan drive motor (not shown), the cooling air that has passed through the head holder 30 is sucked toward the housing 45 through the ventilation holes of each duct 38 and the side plate 34.

With the above cooling means, an air-cooled cooling system is configured in which the cooling air sent from the blower unit 41 into the head holder 30 takes heat from the periphery of each inkjet head 20 and is exhausted to the suction unit 42 side. To.

By the way, when printing is performed while sucking and holding the paper P on the transport surface 10a of the transport belt 10 and transporting the paper P, it is necessary to consider the influence of the air flow generated by the negative pressure for adsorption on the printing. More specifically, when the suction fan 15 is rotationally driven to bring the lower space S3 into a negative pressure state with respect to the intermediate space S2, the suction holes 10b formed in the transport belt 10 are not covered with the paper P. Air flows toward the exposed suction holes 10b, and a suction wind is generated from the intermediate space S2 toward the lower space S3. It is required that the suction air does not affect the ejection of ink from the inkjet head 20 and does not cause deterioration of print quality.

FIG. 6 shows a comparative example different from that of the present embodiment. In the comparative example of FIG. 6, the head holding plate 31 is blocked around the inkjet head 20, and air does not flow between the upper space S1 and the intermediate space S2. In this case, when the lower space S3 side is set to a negative pressure, the air near the ink ejection surface 21 in the intermediate space S2 is attracted to the suction hole 10b side not covered with the paper P, and the direction is different from the ink ejection direction. A suction wind T1 flowing to is generated. Then, of the ink ejected from the ink ejection surface 21 of the inkjet head 20, the mist-like ink mist IB, which is finer than the main droplet IA for image formation, is scattered by the suction wind T1. Then, the ink mist IB may adhere to the paper P at a position different from that of the main drop IA, disturbing the printed image, or the ink mist IB may adhere to the ink ejection surface 21 and stain the paper P. ..

FIG. 6 shows a state in which the vicinity of the tip of the conveyed paper P is located below the inkjet head 20. In this way, when printing the portion close to the edge of the paper P, the distance between the suction hole 10b not covered with the paper P and the ink ejection surface 21 of the inkjet head 20 becomes close, and the distance is directly below the inkjet head 20. Suction wind is likely to occur. Contrary to the state of FIG. 6, when the vicinity of the rear end portion of the conveyed paper P is located below the inkjet head 20, the suction air (suction air shown in FIG. 6) is similarly directly below the inkjet head 20. Suction air in the opposite direction to T1) is likely to occur.

In the present embodiment, the head holding plate 31 is located near the inkjet head 20. A communication portion 39 for communicating the upper space S1 and the intermediate space S2 is formed. As shown in FIGS. 2 and 3, the communication portion 39 is an elongated hole extending in the main scanning direction F1 along each head row L1, L2, L3, L4 of the inkjet head 20, and is positioned in the sub-scanning direction F2. Five communication portions 39 are formed differently. More specifically, there is one communication unit 39 between each of the four head rows L1, L2, L3, and L4, and one communication unit 39 on the upstream side (left side in each drawing) of the paper transport with respect to the head row L1. , One is provided on the downstream side (right side in each drawing) of the paper transport with respect to the head row L4. Therefore, the communication portions 39 are arranged in pairs on both sides of the sub-scanning direction F2 of each inkjet head 20. As shown in FIG. 4, on the head holding plate 31, the head holding opening 31a (holding position of the inkjet head 20) and the communicating portion 39 are formed at a predetermined interval in the sub-scanning direction F2 to hold the head. Between the opening 31a and the communication portion 39, there is a bridging portion 31b (see FIGS. 3 and 4) that is a part of the head holding plate 31.

By forming the communication portion 39 in the head holding plate 31, when the suction fan 15 is rotationally driven to make the lower space S3 a negative pressure, only the intermediate space S2 communicating with the lower space S3 through the suction hole 10b is used. However, air is also sucked from the upper space S1 that communicates with the intermediate space S2 via the communication portion 39. The upper space S1 is in a state close to atmospheric pressure, and the flow of suction air from the upper space S1 to the suction hole 10b via the communication portion 39 becomes dominant. As a result, the suction air from directly below the inkjet head 20 toward the suction hole 10b in the intermediate space S2 is reduced, and the ink mist IB is less likely to scatter to the surroundings.

As shown in FIG. 4, when the vicinity of the tip end portion of the conveyed paper P is located below the inkjet head 20, the communication portion located on the downstream side (right side of FIG. 4) of the paper conveying with respect to the inkjet head 20. From 39, a suction wind is generated toward the lower space S3 through the suction hole 10b located immediately below the suction hole 10b. On the other hand, when the vicinity of the rear end portion of the paper P to be transported is located below the inkjet head 20, the communication portion 39 located on the upstream side (left side in FIG. 4) of the paper transport with respect to the inkjet head 20 is used. A suction wind is generated toward the lower space S3 through the suction hole 10b located directly below. In this way, by providing the communication portions 39 in pairs on both sides of each inkjet head 20 in the sub-scanning direction F2, either the vicinity of the front end portion or the vicinity of the rear end portion of the paper P is positioned below the inkjet head 20. Even in this case, it is possible to reduce the influence of the suction wind in the vicinity of the ink ejection surface 21.

However, when the upper space S1 and the intermediate space S2 are communicated with each other by the communication portion 39, it is necessary to consider the influence of the state of the air flow in the upper space S1 on the ink mist IB. As described above, the cooling air by the cooling means is flowing in the upper space S1 in the head holder 30. This cooling air generally travels in the main scanning direction F1 from the blower unit 41 toward the suction unit 42, and is an air flow in a direction different from the ink ejection direction from the ink ejection surface 21 of the inkjet head 20 toward the paper P. is there. Further, the direction of the cooling air may change when it hits the internal structure of the head holder 30 or the inkjet head 20, and a more complicated air flow may be generated in the upper space S1.

FIG. 7 shows a comparative example in which no countermeasure is taken for the influence of the air flow from the upper space S1 to the intermediate space S2. When the cooling air in the upper space S1 (or the turbulent flow generated by the influence of the cooling air) enters the intermediate space S2 through the communication portion 39, the ink mist IB scatters due to the influence and is mainly applied to the paper P. The ink mist IB may adhere to the ink mist IB at a position different from the drop IA to deteriorate the print quality, or the ink mist IB may adhere to the ink ejection surface 21 to stain the ink. That is, if the communication portion 39 is formed on the head holding plate 31 in order to prevent the print quality from being deteriorated by the suction air to the platen unit 2, the cooling air from the cooling means may affect the print quality, and countermeasures are required. Be done.

In the inkjet printing apparatus of this embodiment, the shielding member 50 is provided in the upper space S1 inside the head holder 30. As shown in FIG. 4, the shielding member 50 is a box-shaped member provided on the head holding plate 31 and surrounding the inkjet head 20 (the upper half portion of the inkjet head 20 located in the upper space S1), and is a head. It has a pair of side walls 51 protruding upward from the holding plate 31, and an upper wall 52 connecting the upper ends of the pair of side walls 51. There is a gap between the upper wall 52 of the shielding member 50 and the top plate 32 of the head holder 30. As shown in FIG. 2, four shielding members 50 corresponding to the head rows L1, L2, L3, and L4 of the inkjet head 20 are provided, and each shielding member 50 extends long in the main scanning direction F1 and is individual. The three inkjet heads 20 included in the head row are continuously enclosed.

As shown in FIGS. 3 and 4, the pair of side walls 51 of the shielding member 50 are located between the head holding opening 31a and the communication portions 39 located on both sides thereof in the sub-scanning direction F2, and each side wall is located. The lower end of 51 is connected to the bridge connection portion 31b of the head holding plate 31. In other words, each shielding member 50 is provided at a position that does not overlap with the communication portion 39 in top view (FIGS. 2 and 3). As a result, with the inkjet head 20 held in the head holding opening 31a, a closed cross-sectional structure surrounded by the head holding plate 31 and a pair of side walls 51 and an upper wall 52 of the shielding member 50 in the upper space S1. Cylindrical space S4 (see FIG. 4) is formed. Then, the upper half of each inkjet head 20 is housed in the tubular space S4. The side surface 23 of the inkjet head 20 and the head holding opening 31a are sealed so that air does not flow between the tubular space S4 and the intermediate space S2. Each shielding member 50 has both ends open in the main scanning direction F1, a duct 37 is inserted at one end thereof, and a duct 38 is inserted at the other end (see FIGS. 2 and 3).

The cooling air from the blower portion 41 to the suction portion 42 cools the inkjet heads 20 of the head rows L1, L2, L3, and L4 through the tubular space S4 formed by the shielding member 50 and the head holding plate 31. To do. Since the tubular space S4 that serves as a passage for the cooling air and the communication portion 39 that communicates the upper space S1 and the intermediate space S2 are blocked by the side wall 51 and the upper wall 52 of the shielding member 50, the cooling air can be generated. It is possible to prevent the intermediate space S2 from being headed through the communication portion 39 and the turbulence of the air flow due to the cooling air from affecting the intermediate space S2. As a result, even when ink mist is generated, it is possible to prevent the ink mist from flowing downstream in the transport direction with an appropriate air flow and contaminating the print medium and peripheral members.

Since the shielding member 50 completely covers the upper surface 22 and the side surface 23 of the inkjet head 20 above the head holding plate 31 to form the tubular space S4 in a closed cross-sectional structure, the cooling air is directed to the outside of the tubular space S4. It is highly effective in preventing flow. Further, since the cooling air can be concentratedly supplied in the vicinity of the inkjet head 20 without leaking to the outside, it contributes to the improvement of the cooling efficiency.

Further, the shielding member 50 continuously surrounds the three inkjet heads 20 included in the individual head rows L1, L2, L3, and L4, and does not have an opening portion in the middle of the main scanning direction F1. Therefore, the cooling air can be reliably supplied to all the inkjet heads 20 of the head rows L1, L2, L3, and L4. Further, since the long tunnel-shaped tubular space S4 is formed in the main scanning direction F1, the cooling air can be smoothly guided from the blower portion 41 to the suction portion 42, and the turbulence of the airflow in the upper space S1 can be suppressed. ..

As described above, the communication portion 39 that communicates the upper space S1 and the intermediate space S2 is provided so that the suction wind toward the lower space S3 is less likely to affect the ink mist IB in the intermediate space S2, and the shielding member 50 is further provided. Is provided so that the cooling air in the upper space S1 is less likely to affect the ink mist IB in the intermediate space S2. As a result, printing that eliminates the effects of suction air and cooling air can be realized, and deterioration of print quality can be prevented.

Further, since the cooling air is passed through the tubular space S4 shielded by the shielding member 50 in the upper space S1, the cooling air can be efficiently sent to each inkjet head 20, and the cooling efficiency is improved. By improving the cooling efficiency, effects such as downsizing of the cooling means and reduction of power consumption can be obtained.

As shown in FIGS. 2 and 3, there is a gap between both ends of each shielding member 50 in the main scanning direction F1 and the side plates 33 and 34 of the head holder 30. The duct 37 connected to the blower portion 41 is inserted inside each shielding member 50 across a gap between the side plate 33 and one end of each shielding member 50. The duct 38 connected to the suction portion 42 is inserted inside each shielding member 50 across a gap between the side plate 34 and the other end of each shielding member 50. Therefore, it is possible to reduce the air leakage at both end portions of each shielding member 50 and allow the cooling air to surely pass from the blower portion 41 to the suction portion 42.

FIG. 5 shows different forms of the shielding portion that separates the passage through which the cooling air passes and the communication portion 39. In the configuration of FIG. 5, the shielding member 60 is provided not on the upper part of each inkjet head 20 (head row) but on the upper part of the communication portion 39. The shielding member 60 is provided with a partition wall 61 at a position corresponding to the pair of side walls 51 of the shielding member 50 described above. Further, the shielding member 60 is provided with a partition wall 62 at a position facing the partition wall 61 with the communication portion 39 in between. The lower end of the partition wall 61 is connected to the bridging portion 31b of the head holding plate 31 of the head holder 30. The lower end of the partition wall 62 is also connected to the head holding plate 31. The upper wall 63 connects the upper ends of the partition wall 61 and the partition wall 62, and the upper wall 63 is in contact with the top plate 32 of the head holder 30 from below. The partition wall 62 is formed with a through hole 64 penetrating in the sub-scanning direction F2.

A plurality of shielding members 60 are provided in the head holder 30, and the inside of the upper space S1 is partitioned by these shielding members 60. More specifically, a communication space S5 surrounded by the partition wall 61, the partition wall 62, and the upper wall 63 of each shielding member 60 is formed. Further, a tubular space S6 having a closed cross-sectional structure is formed which is surrounded by the partition wall 61 of two adjacent shielding members 60 and the head holding plate 31 and the top plate 32 of the head holder 30. The upper half of each inkjet head 20 is located in the tubular space S6.

The tubular space S6 serves as a cooling air passage for cooling the inkjet head 20 in the same manner as the tubular space S4 described above. Since the tubular space S6 is separated from the communication portion 39 by the partition wall 61 of each shielding member 60, it is possible to prevent the cooling air from affecting the air flow in the intermediate space S2 (the ink mist IB is scattered around). it can. Further, efficient cooling of the inkjet head 20 can be realized in the tubular space S6.

The communication space S5 is connected to the upper space S1 by a through hole 64 formed in the partition wall 62 of the shielding member 60. Therefore, in the head holder 30, an air passage from the upper space S1 to the communication portion 39 via the communication space S5 is formed, and it is possible to prevent a decrease in the suction force on the transport surface 10a of the platen unit 2.

In this way, the same applies not only to the configuration in which the shielding member 50 is provided at the position covering the inkjet head 20 (FIGS. 1 to 4) but also in the configuration in which the shielding member 60 is provided above the communication portion 39 (FIG. 5). It is possible to obtain an effect.

As described above, communication portions 39 are provided on both sides of the inkjet head 20 in the sub-scanning direction F2 so as to correspond to the case where either the front end portion or the rear end portion of the paper P is located below the inkjet head 20. There is. Correspondingly, it is desirable that at least the shielding portion includes a pair of wall portions that shield between the communication portions 39 on both sides and the inkjet head 20 (side surface 23). As a portion corresponding to the pair of wall portions, the shielding member 50 has a pair of side walls 51, and two shielding members 60 adjacent to each other in the sub-scanning direction F2 have a pair of partition walls 61. Therefore, in the configuration in which the communication portions 39 are provided on both sides of the inkjet head 20, it is possible to reliably prevent the cooling air from flowing through each communication portion 39.

As a modification of the shielding portion, the shielding member 60 may be configured to include only a portion corresponding to the partition wall 61 (the partition wall 62 and the upper wall 63 are omitted). Even with this configuration, it is possible to form the tubular space S6 shown in FIG.

As a modification of the shielding portion, the shielding member 50 may be configured to include only a portion corresponding to a pair of side walls 51 (the upper wall 52 is omitted). In this configuration, the upper end of each side wall 51 does not reach the top plate 32 of the head holder 30 (there is a gap), so that the cooling air passage surrounding the inkjet head 20 is like a tubular space S4 or a tubular space S6. It does not have a closed cross-sectional structure. However, even with such a configuration, a required effect can be obtained as a shielding portion in that it makes it difficult for the cooling air that cools the inkjet head 20 to proceed directly toward the communicating portion 39.

As can be seen from each of the above modifications, the shielding portion blocks the progress of the cooling air from the cooling air passage to the communicating portion 39 (blocks at least a part between the cooling air passage and the communicating portion 39). ), Anything that prevents the influence of the cooling air from affecting the ink ejection in the intermediate space S2 (prevents the influence on the print quality) is sufficient, and is not limited to a specific form.

Further, the shielding member 50 and the shielding member 60 described above block the cooling air by a flat plate-shaped side wall 51 or a partition wall 61 standing on the side of the communication portion 39, and the shape of the shielding portion is such a flat plate. It is not limited to the shape. For example, if a maze structure that reduces the speed of the airflow is applied to the shielding portion, and even if the cooling air reaches the communicating portion 39, the airflow in the intermediate space S2 is decelerated to such an extent that the airflow is not significantly disturbed. It is possible to prevent deterioration of quality. Therefore, a shielding portion having such a maze structure may be adopted.

Further, in the upper space S1 in the head holder 30, it is possible to adjust the velocity of the air flow traveling from the upper space S1 to the intermediate space S2 by providing the above-mentioned maze structure or the like for the portion other than the cooling air passage. It is possible. For example, in the configuration of FIG. 5, not only the through hole 64 may be simply opened, but also the path from the through hole 64 to the communication portion 39 may be complicated.

The platen unit 2 of the above embodiment is a type of transport unit that transports the paper P while adsorbing and holding the paper P on the transport surface 10a by a negative pressure. In the present invention, the printing medium (paper P) is sucked onto the transport surface. It is also possible to apply an electrostatic transfer type transfer unit without means. Since the phenomenon that the ink mist stains the print medium and peripheral members due to the turbulence of the air flow near the ink ejection surface of the inkjet head can occur even when the transfer unit is not provided with the suction means, printing with an electrostatic transfer type transfer unit is provided. The present invention is also useful for devices.

Although the present invention has been described above with reference to embodiments and modifications based on the accompanying drawings, the present invention is not limited to the above-described embodiments and modifications, and various modifications and applications are made without departing from the gist. It is possible. In the above-described embodiment, the configuration, control, and the like shown in the accompanying drawings are not limited to this, and can be appropriately changed within the range in which the effects of the present invention are exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the gist of the present invention. The inventions described in the claims at the time of filing the application of the present application are described below.
[Appendix 1]
A transport unit that holds the print medium on the transport surface and transports it,
An inkjet head that ejects ink to the printing medium held on the transport surface to print.
A head holder that holds the inkjet head on the head holding plate facing the transport surface, and
In an inkjet printing device equipped with
A communication portion formed on the head holding plate at a distance from the holding position of the inkjet head and communicating the first space in the head holder and the second space between the transport surfaces.
A cooling means that sends cooling air to the inkjet head in the head holder,
A shielding portion provided in the first space and blocking at least a part between the passage through which the cooling air passes and the communicating portion.
An inkjet printing device characterized by being equipped with.
[Appendix 2]
The communication portions are provided on both sides of the inkjet head in the sub-scanning direction in which the printing medium is conveyed by the conveying portion.
The inkjet printing apparatus according to Appendix 1, wherein the shielding portion has at least a pair of wall portions located between the communicating portions on both sides and the inkjet head in the sub-scanning direction.
[Appendix 3]
The shielding portion has an upper wall connecting the upper ends of the pair of wall portions.
The inkjet printing apparatus according to Appendix 2, wherein the passage through which the cooling air passes has a closed cross section surrounded by the shielding portion and the head holding plate.

1: Printing unit 2: Platen unit (conveying unit)
3: Head unit 10: Conveying belt 10a: Conveying surface 10b: Suction hole 20: Inkjet head 21: Ink ejection surface 30: Head holder 31: Head holding plate 39: Communication unit 41: Blower (cooling means)
42: Suction part (cooling means)
50: Shielding member (shielding part)
51: Side wall (pair of wall parts)
52: Upper wall 60: Shielding member (shielding part)
61: Partition wall (pair of wall parts)
62: Partition 63: Upper wall P: Paper S1: Upper space (first space)
S2: Intermediate space (second space)
S3: Lower space S4: Cylindrical space (passage through which cooling air passes)
S5: Communication space S6: Cylindrical space (passage through which cooling air passes)

Claims (3)

A transport unit that holds the print medium on the transport surface and transports it,
An inkjet head that ejects ink to the printing medium held on the transport surface to print.
A head holder that holds the inkjet head on the head holding plate facing the transport surface, and
In an inkjet printing device equipped with
A communication portion formed on the head holding plate at a distance from the holding position of the inkjet head and communicating the first space in the head holder and the second space between the transport surfaces.
A cooling means that sends cooling air to the inkjet head in the head holder,
A shielding portion provided in the first space and blocking at least a part between the passage through which the cooling air passes and the communicating portion.
An inkjet printing device characterized by being equipped with. The communication portions are provided on both sides of the inkjet head in the sub-scanning direction in which the printing medium is conveyed by the conveying portion.
The inkjet printing apparatus according to claim 1, wherein the shielding portion has at least a pair of wall portions located between the communicating portions on both sides and the inkjet head in the sub-scanning direction. The shielding portion has an upper wall connecting the upper ends of the pair of wall portions.
The inkjet printing apparatus according to claim 2, wherein the passage through which the cooling air passes has a closed cross section surrounded by the shielding portion and the head holding plate.

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