Inkjet printing apparatus

Abstract

To provide an inkjet printer capable of suppressing diffusion of ink mist.SOLUTION: The media sensors 4A to 4C detect the printing media 7 being conveyed. A space on the side of the inkjet head 26 through which the printing medium 7 passes is an open space in which nothing other than the passing printing medium 7 is disposed within a predetermined distance from the inkjet head 26. The controller performs control to eject ink from the inkjet head 26 with detection of the printing media 7 by the media sensor 4B for ejection control as a trigger, and also performs control of the mist collector. The controller determines whether or not there is a possibility that the ink ejection from the inkjet head 26 to the open space has been performed based on the operation status of the media sensors 4A to 4C, and controls the mist collection unit to perform the mist collection operation for the time of occurrence of the ink ejection to the open space when it is determined that there is a possibility that the ink ejection to the open space has been performed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to inkjet printing devices. [Background technology]

[0002] Inkjet printing devices generate ink mist, which are tiny mist-like ink droplets, when ink is ejected. The ink mist can adhere to the nozzle surface of the inkjet head, causing ink ejection problems, or can adhere to printed materials or the inside of the device, causing stains. For this reason, ink mist is collected in inkjet printing devices (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-138329 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, some inkjet printing devices have an inkjet head arranged with the nozzle surface in a vertical plane so that ink can be ejected horizontally, and are capable of printing on the vertical surface of a printing medium that is a three-dimensional object such as a cardboard box.

[0005] In this type of inkjet printing device, the transport mechanism that transports the print medium is not positioned opposite the nozzle face of the inkjet head, so the nozzle face side of the inkjet head (the side through which the print medium passes) is an open space with nothing located nearby.

[0006] In this type of inkjet printing device, ink may be ejected without the print medium being positioned opposite the inkjet head due to a problem with the print medium transport, etc. In this case, ink may be ejected into an open space, causing ink mist to spread over a wide area.

[0007] The present invention has been made in view of the above, and has an object to provide an inkjet printing apparatus that can suppress the diffusion of ink mist. [Means for solving the problem]

[0008] In order to achieve the above object, an inkjet printing device of the present invention comprises an inkjet head that ejects ink onto a print medium being transported, a mist collection unit that collects ink mist, at least one medium detection unit that detects the print medium, including a medium detection unit for ejection control arranged upstream of the inkjet head in the print medium transport direction, and a control unit that controls the mist collection unit and controls the ink ejection from the inkjet head in response to the detection of the print medium by the medium detection unit for ejection control, wherein the space on the side of the inkjet head through which the print medium passes is an open space with nothing placed within a predetermined distance from the inkjet head except for the passing print medium, and the control unit determines whether or not there is a possibility that ink has been ejected from the inkjet head into the open space based on the operating status of the at least one medium detection unit, and if it determines that there is a possibility that ink has been ejected into the open space, controls the mist collection unit to perform a mist collection operation for when ink is ejected into the open space. [Effects of the Invention]

[0009] According to the inkjet printing apparatus of the present invention, the diffusion of ink mist can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a block diagram showing a configuration of an inkjet printing apparatus according to an embodiment; [Figure 2] FIG. 2 is a perspective view showing a schematic configuration of a main part of the inkjet printing apparatus shown in FIG. [Figure 3] 2 is a plan view showing a schematic configuration of a main part of the inkjet printing apparatus shown in FIG. 1. FIG. [Figure 4] 2 is a partially enlarged view of a mist collection unit of the inkjet printing apparatus shown in FIG. 1. FIG. [Figure 5] 10A and 10B are diagrams illustrating the operating status of each medium sensor during normal printing operation. [Figure 6] 10A and 10B are diagrams illustrating an example of the operating status of each medium sensor when there is a possibility that ink has been ejected from the inkjet head into an open space. [Figure 7] 10A and 10B are diagrams illustrating another example of the operating status of each medium sensor when there is a possibility that ink has been ejected from the inkjet head into an open space. [Figure 8] 10A and 10B are diagrams illustrating an example of the operating status of each medium sensor when erroneous detection of the print medium occurs before ink ejection from the inkjet head onto the print medium begins. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] The following embodiments are examples of devices that embody the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the materials, shapes, structures, arrangements, etc. of each component to those described below. The technical idea of ​​the present invention can be modified in various ways within the scope of the claims.

[0013] Fig. 1 is a block diagram showing the configuration of an inkjet printing apparatus according to an embodiment of the present invention. Fig. 2 is a perspective view showing a schematic configuration of a main part of the inkjet printing apparatus shown in Fig. 1. Fig. 3 is a plan view showing a schematic configuration of a main part of the inkjet printing apparatus shown in Fig. 1. Fig. 4 is a partially enlarged view of a mist collection section of the inkjet printing apparatus shown in Fig. 1. In the following description, the up / down, left / right, front / rear directions indicated by arrows in Fig. 1 are referred to as up / down, left / right, front / rear directions. The up / down direction is the vertical direction, and the left / right and front / rear directions are perpendicular to each other and are all perpendicular to the up / down direction and parallel to the horizontal direction.

[0014] As shown in FIG. 1, the inkjet printing apparatus 1 according to this embodiment includes a transport unit 2, a printing unit 3, medium sensors (corresponding to medium detection units) 4A to 4C, a mist collection unit 5, and a control unit 6.

[0015] The transport unit 2 transports the printing medium 7 supplied from a medium supply unit (not shown). The printing medium 7 has a printing surface 7a on which printing is performed by the printing unit 3. The printing surface 7a is a surface (vertical surface) perpendicular to the horizontal direction when the printing medium 7 is placed on the transport unit 2 and transported. The printing medium 7 is, for example, a cardboard box.

[0016] As shown in FIGS. 1 and 2, the conveying unit 2 includes a conveying belt 11, a driving roller 12, a driven roller 13, a conveying motor 14, and an encoder 15.

[0017] The conveyor belt 11 is a circular belt stretched over a drive roller 12 and a driven roller 13. The conveyor belt 11 is driven to circulate counterclockwise when viewed from the right, thereby conveying the print medium 7 placed on the conveyor surface 11a in a conveyance direction from the rear to the front. The conveyor surface 11a is the upper surface of the conveyor belt 11 that is horizontal between the drive roller 12 and the driven roller 13.

[0018] The drive roller 12 rotates the conveyor belt 11 counterclockwise when viewed from the right side.

[0019] The driven roller 13 supports the conveyor belt 11 together with the drive roller 12. The driven roller 13 is disposed horizontally spaced apart from the drive roller 12. The driven roller 13 rotates in response to the rotation of the conveyor belt 11.

[0020] The conveying motor 14 drives the driving roller 12 to rotate.

[0021] The encoder 15 outputs a pulse signal in accordance with the rotation angle of the driven roller 13 .

[0022] The printing unit 3 performs printing on the printing surface 7a of the print medium 7. The printing unit 3 includes a plurality of head units 21 and a head holder 22.

[0023] The head units 21 perform printing by ejecting ink onto the print surface 7a of the print medium 7. In this embodiment, four head units 21 are provided. The four head units 21 eject ink of different colors (for example, black, cyan, magenta, and yellow). The four head units 21 have the same configuration except for the colors of ink they eject.

[0024] 2, the head unit 21 includes a plurality of inkjet heads 26. In this embodiment, the head unit 21 includes six inkjet heads 26. In the head unit 21, the inkjet heads 26 are arranged in a staggered pattern in the up-down direction. That is, in the head unit 21, the six inkjet heads 26 arranged in the up-down direction are arranged with their positions shifted alternately in the front-to-rear direction.

[0025] The inkjet head 26 has a nozzle surface 26a (see FIG. 4) in which a plurality of nozzles (not shown) are opened, and ink is ejected from the plurality of nozzles. The nozzle surface 26a is the left side surface of the inkjet head 26 and is a vertical surface.

[0026] During printing, the print medium 7 transported by the transport unit 2 passes to the left of the inkjet head 26. The inkjet head 26 prints an image on the print surface 7a by ejecting ink from nozzles to the left onto the print medium 7.

[0027] The transport surface 11a of the transport section 2 does not face the nozzle surfaces 26a of the multiple inkjet heads 26, and the space on the left side, which is the nozzle surface 26a side of the inkjet head 26 (the side through which the printing medium 7 passes), is an open space in which nothing is placed within a predetermined distance from the inkjet head 26 other than the passing printing medium 7.

[0028] Here, the above-mentioned specified distance is the minimum distance that, when there is a component arranged opposite the nozzle surface 26a, can sufficiently form an air flow path for collecting ink mist between the nozzle surface 26a and the above-mentioned component by driving the mist collection unit 5 described later.

[0029] The head holder 22 holds each inkjet head 26 of each head unit 21. The head holder 22 also holds an air supply path 33 and a suction path 34 of a mist collection unit 5 (described later) that is provided corresponding to each inkjet head 26. Note that the mist collection unit 5 is not shown in Figures 2 and 3.

[0030] The media sensors 4A to 4C detect the print medium 7 being transported by the transport unit 2. The media sensors 4A to 4C perform an on / off operation so that they turn on when they detect the print medium 7 and turn off when they do not detect the print medium 7.

[0031] The medium sensor 4A is disposed at the upstream end of the transport unit 2, upstream of the printing unit 3 in the transport direction of the print medium .

[0032] The medium sensor 4B is located downstream of the medium sensor 4A and near the upstream side of the printing unit 3. The medium sensor 4B is a discharge control sensor used to control the timing of ink discharge from each head unit 21.

[0033] The medium sensor 4C is disposed downstream of the printing unit 3 at the downstream end of the transport unit 2.

[0034] The mist collecting unit 5 collects the ink mist generated by the ink ejection from the inkjet head .

[0035] 1 and 4, the mist collection unit 5 includes a blower fan 31, a suction fan 32, a plurality of blower paths 33, a plurality of suction paths 34, and a plurality of filters 35. Here, the blower paths 33, the suction paths 34, and the filters 35 are provided for each inkjet head 26, and the number of the provided filters is the same as the number of the inkjet heads 26.

[0036] The blower fan 31 blows air to each air passage 33 and blows the air out from each air outlet 33a described later. The blower fan 31 is connected to each air passage 33 via a common air passage (not shown) and is capable of blowing air to each air passage 33.

[0037] The suction fan 32 draws in air through each suction port 34a of each suction path 34, which will be described later. The suction fan 32 is connected to each suction path 34 via a common suction path (not shown), and is capable of drawing in air through each suction port 34a.

[0038] The air blowing path 33 forms a flow path for air to be blown out toward the side (left side) where the printing medium 7 passes in order to collect the ink mist. The air blowing path 33 is located upstream (rear side) of the inkjet head 26. The left end of the air blowing path 33 opens toward the side (left side) where the printing medium 7 passes, forming an air blowing port 33a for blowing out air.

[0039] The suction path 34 forms a flow path for air to be sucked from the side (left side) where the printing medium 7 passes in order to collect the ink mist. The suction path 34 is located downstream (front side) of the inkjet head 26. The left end of the suction path 34 opens to the side (left side) where the printing medium 7 passes, forming a suction port 34a that sucks in air.

[0040] The filter 35 liquefies and holds the ink mist. The filter 35 is disposed in the suction path 34. The filter 35 is made of, for example, a sponge.

[0041] The control unit 6 controls the operation of each unit of the inkjet printing device 1. The control unit 6 is configured with a CPU, RAM, ROM, a hard disk, and the like.

[0042] Specifically, the control unit 6 controls the inkjet head 26 to eject ink onto the print medium 7 being transported by the transport unit 2, thereby printing. The control unit 6 controls the ink ejection from the inkjet head 26 when the detection of the print medium 7 by the ejection control medium sensor 4B is used as a trigger. The control unit 6 also controls the mist collection unit 5 to collect the ink mist.

[0043] Furthermore, the control unit 6 determines whether or not there is a possibility that ink has been ejected from the inkjet head 26 into an open space, based on the operating status of the medium sensors 4A to 4C. If it determines that there is a possibility that ink has been ejected into an open space, the control unit 6 controls the mist collection unit 5 to perform a mist collection operation for when ink is ejected into an open space. Here, the mist collection operation for when ink is ejected into an open space is a mist collection operation in which the airflow rates of the blower fan 31 and the suction fan 32 are set to predetermined airflow rates that are greater than the airflow rates in the mist collection operation under normal conditions. The mist collection operation under normal conditions is a mist collection operation in which the blower fan 31 and the suction fan 32 are driven at their standard airflow rates.

[0044] Furthermore, the control unit 6 determines whether or not erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 has started, based on the operating status of the medium sensors 4A to 4C. If it is determined that erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 has started, the control unit 6 stops ink ejection from the inkjet head 26 to the print medium 7.

[0045] Next, the operation of the inkjet printing apparatus 1 will be described.

[0046] When a print job transmitted from an external personal computer or the like is received, the control unit 6 controls the printing unit 3 to print on the print medium 7 being transported by the transport unit 2.

[0047] Specifically, the control unit 6 uses the detection of the print medium 7 by the ejection control medium sensor 4B as a trigger to eject ink from each inkjet head 26 onto the print medium 7. More specifically, the control unit 6 starts ejecting ink from each inkjet head 26 based on the print job, based on the number of output pulses from the encoder 15 after the medium sensor 4B detects the leading edge of the print medium 7. The control unit 6 then controls each inkjet head 26 to eject ink at a timing based on the output pulse signal from the encoder 15.

[0048] Furthermore, when at least one of the inkjet heads 26 faces the print medium 7, the control unit 6 controls the mist collection unit 5 to perform the mist collection operation for normal times.

[0049] Specifically, when the printing medium 7 reaches the most upstream (rear) head unit 21, the control unit 6 starts driving the blower fan 31 and the suction fan 32, and drives the blower fan 31 and the suction fan 32 at their respective standard airflow rates. Then, the control unit 6 stops the blower fan 31 and the suction fan 32 when the printing medium 7 passes the most downstream (front) head unit 21. Here, the control unit 6 can determine the timing when the printing medium 7 reaches the most upstream head unit 21 and the timing when it passes the most downstream head unit 21 based on the number of output pulses from the encoder 15 after the media sensor 4B detects the leading edge of the printing medium 7.

[0050] During normal mist collection operation, near the inkjet head 26 facing the print medium 7, as shown in Figure 4, an airflow Fa caused by air blown out from the air outlet 33a, an airflow Fb caused by air sucked into the suction port 34a, and a transport airflow generate an airflow Fc flowing from the air outlet 33a toward the suction port 34a. At this time, the space 41 between the inkjet head 26 and the print medium 7 is formed as an air flow path for collecting the ink mist, and the airflow Fc flows through this flow path. As a result, air containing ink mist near the nozzle surface 26a of the inkjet head 26 is sucked into the suction port 34a, and the ink mist is collected.

[0051] During the printing operation described above, the control unit 6 determines, based on the operating status of the medium sensors 4A to 4C, whether or not there is a possibility that ink has been ejected from the inkjet head 26 into the open space. The control unit 6 also determines, based on the operating status of the medium sensors 4A to 4C, whether or not erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 begins.

[0052] FIG. 5 shows the operating conditions of the medium sensors 4A to 4C during normal printing operation in which the transport unit 2 transports the print medium 7 and ink is ejected onto the print medium 7 normally.

[0053] As shown in Fig. 5, when printing is performed normally, the print medium 7 is detected sequentially by the medium sensors 4A to 4C. The times Ta to Tc, Tab, and Tbc in Fig. 5 fall within the estimated ranges, which are the ranges of estimated times.

[0054] The above times Ta to Tc are the durations for which media sensors 4A to 4C remain on (the times during which they detect the print medium 7). Time Tab is the time from time ta when media sensor 4A turns on to time tb when media sensor 4B turns on (the time from when media sensor 4A detects the leading edge of the print medium 7 until media sensor 4B detects the leading edge of the print medium 7). Time Tbc is the time from time tb when media sensor 4B turns on to time tc when media sensor 4C turns on (the time from when media sensor 4B detects the leading edge of the print medium 7 until media sensor 4C detects the leading edge of the print medium 7).

[0055] The estimated ranges of times Ta to Tc, Tab, and Tbc are found from the length of the print medium 7 in the transport direction and the transport speed of the print medium 7 by the transport unit 2.

[0056] In normal printing operation, as described above, the control unit 6 is triggered by the detection of the print medium 7 by the ejection control medium sensor 4B, which causes each inkjet head 26 to eject ink onto the print medium 7. Furthermore, when at least one of the inkjet heads 26 is facing the print medium 7, the control unit 6 executes normal mist collection operation, driving the blower fan 31 and suction fan 32 of the mist collection unit 5 at their respective standard airflow rates.

[0057] In contrast to this, for example, when the operating conditions of the medium sensors 4A to 4C are as shown in FIGS. 6 and 7, the control unit 6 determines that there is a possibility that ink has been ejected from the inkjet head 26 into the open space.

[0058] In the example of Figure 6, the operating conditions of media sensors 4A and 4B until media sensor 4B turns on are the same as those in Figure 5, but media sensor 4B has not turned off and media sensor 4C has not turned on.

[0059] In the example of FIG. 7, the operating conditions of the medium sensors 4A and 4B until the medium sensor 4B turns off are the same as those in FIG. 5, but the medium sensor 4C is not turned on.

[0060] In the examples of Figures 6 and 7, media sensor 4A is operating on and off, and media sensor 4B is on, which means that the print medium 7 is being transported and ink ejection by the inkjet head 26 has begun. Furthermore, if media sensor 4B does not turn off as in the example of Figure 6, or if media sensor 4C does not turn on as in the example of Figure 7, there is a possibility that a problem has occurred with the transport of the print medium 7 near the printing unit 3. For this reason, in the examples of Figures 6 and 7, there is a possibility that ink ejection into an open space was caused by ink ejection being performed while there was a problem with the transport of the print medium 7.

[0061] Here, if medium sensor 4B turns on after medium sensor 4A turns on and off as shown in Figures 5 to 7, and this on state continues for a predetermined time longer than the upper limit of the estimated range of time Tb, the control unit 6 determines that medium sensor 4B does not turn off as in the example of Figure 6. Then, the control unit 6 determines that there is a possibility that ink has been ejected into the open space.

[0062] 5 and 7, if the media sensor 4C remains in the off state for a predetermined time longer than the upper limit of the estimated range of (Tbc-Tb) after the media sensors 4A and 4B have been turned on and off as shown in Figures 5 and 7, the control unit 6 determines that the media sensor 4C will not turn on, as in the example of Figure 7. The control unit 6 then determines that ink may have been ejected into the open space.

[0063] If it is determined that ink may have been ejected into an open space, the control unit 6 controls the mist collection unit 5 to perform mist collection operations for when ink is ejected into an open space. Specifically, the control unit 6 drives the blower fan 31 and the suction fan 32 at predetermined air volumes that are greater than their respective standard air volumes. This increases the mist collection capacity of the mist collection unit 5 and suppresses the diffusion of ink mist. The mist collection operations for when ink is ejected into an open space are performed regardless of whether the print medium 7 faces the inkjet head 26.

[0064] Furthermore, for example, when the operating conditions of the medium sensors 4A to 4C are as shown in FIG. 8, the control unit 6 determines that erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 begins.

[0065] In the example of Figure 8, media sensor 4B is on without media sensor 4A being on. In this case, since media sensor 4A is not on, it can be determined that print medium 7 is not being fed to transport unit 2 and that media sensor 4B has detected something other than print medium 7.

[0066] Here, if the duration that media sensor 4A remains off until media sensor 4B turns on is equal to or longer than a predetermined time that is longer than the upper limit of the estimated range of (Tab - Ta), as in the example of Figure 8, the control unit 6 determines that media sensor 4B has turned on without media sensor 4A turning on.The control unit 6 then determines that erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 begins. This erroneous detection can occur, for example, when media sensor 4B detects part of the worker's body.

[0067] If it is determined that erroneous detection of the print medium 7 has occurred before ink ejection begins, the control unit 6 stops ink ejection from the inkjet head 26 onto the print medium 7. In other words, even if the medium sensor 4B is turned on, the control unit 6 does not cause the inkjet head 26 to eject ink. This prevents ink from being ejected into an open space, and suppresses the diffusion of ink mist.

[0068] In addition to the examples shown in Figures 6 to 8, the control unit 6 can determine from the operating status of the media sensors 4A to 4C whether ink may have been ejected into an open space and whether erroneous detection of the printing medium 7 occurred before ink ejection began, based on whether the times Ta to Tc, Tab, and Tbc fall within their respective estimated ranges.

[0069] As described above, in the inkjet printing device 1, the control unit 6 determines whether or not there is a possibility that ink has been ejected from the inkjet head 26 into an open space, based on the operating status of the medium sensors 4A to 4C. If it is determined that there is a possibility that ink has been ejected into an open space, the control unit 6 controls the mist collection unit 5 to perform a mist collection operation for when ink is ejected into an open space. As a result, even if ink has been ejected into an open space, the mist collection unit 5 performs a mist collection operation appropriate for that case, thereby suppressing the diffusion of ink mist.

[0070] Furthermore, in the inkjet printing device 1, the control unit 6 determines whether or not erroneous detection of the print medium 7 has occurred before ink ejection from the inkjet head 26 to the print medium 7 begins, based on the operating status of the medium sensors 4A to 4C. If it is determined that erroneous detection of the print medium 7 has occurred before ink ejection begins, the control unit 6 stops ink ejection from the inkjet head 26 to the print medium 7. This reduces ink ejection into open spaces and suppresses the diffusion of ink mist.

[0071] Furthermore, in the inkjet printing device 1, if the on state of the ejection control medium sensor 4B (a state in which the print medium 7 is being detected) continues for a predetermined time or longer, the control unit 6 determines that there is a possibility that ink has been ejected into an open space. This makes it possible to determine the possibility that ink has been ejected into an open space.

[0072] Furthermore, in the inkjet printing device 1, if the off state of the medium sensor 4C continues for a predetermined time or longer after the medium sensor 4B turns off (if the print medium 7 is not detected by the medium sensor 4C for a predetermined time or longer), the control unit 6 determines that there is a possibility that ink has been ejected into an open space. In this way, it is also possible to determine the possibility that ink has been ejected into an open space.

[0073] In addition, it is possible to determine whether or not a false detection of the printing medium 7 has occurred before the start of ink ejection onto the printing medium 7 based on the operating status of the media sensors 4A to 4C, and omit the process of stopping ink ejection from the inkjet head 26 if it is determined that such a false detection has occurred.

[0074] In the above-described embodiment, the inkjet printing device 1 is described as having three media sensors 4A to 4C. However, the number of media sensors is not limited to this, and it is sufficient that the inkjet printing device 1 includes at least one media sensor, including the media sensor 4B for ejection control.

[0075] For example, it is also possible to omit media sensor 4A and determine that ink may have been ejected into an open space if media sensor 4B does not turn off, as in the example of Figure 6, or if media sensor 4C does not turn on, as in the example of Figure 7. In addition to these cases, even in a configuration where media sensor 4A is omitted, it is possible to determine whether ink may have been ejected into an open space based on the operating status of media sensors 4B and 4C. It is also possible to determine whether erroneous detection of print medium 7 occurred before ink ejection began based on the operating status of media sensors 4B and 4C.

[0076] Also, for example, it is possible to omit medium sensor 4C and determine that ink may have been ejected into the open space if medium sensor 4B does not turn off, as in the example of Figure 6. In addition to this case, in a configuration in which medium sensor 4C is omitted, it is possible to determine whether ink may have been ejected into the open space based on the operating status of medium sensors 4A and 4B.

[0077] Furthermore, in a configuration in which media sensor 4C is omitted, it may be possible to determine whether or not erroneous detection of the print medium 7 has occurred before ink ejection begins when, for example, media sensor 4B turns on without media sensor 4A turning on, as in the example of Figure 8. In addition to this case, in a configuration in which media sensor 4C is omitted, it is also possible to determine whether or not erroneous detection of the print medium 7 has occurred before ink ejection begins based on the operating status of media sensors 4A and 4B.

[0078] Alternatively, for example, media sensors 4A and 4C may be omitted, and if media sensor 4B does not turn off as in the example of Fig. 6, it may be determined that ink may have been ejected into the open space. Furthermore, in a configuration in which media sensors 4A and 4C are omitted, it may be determined that erroneous detection of print medium 7 occurred before ink ejection began, based on the time from when the media supply unit starts supplying print medium 7 to transport unit 2 to when media sensor 4B turns on.

[0079] In the above-described embodiment, a case has been described in which the ejection control medium sensor 4B erroneously detects the print medium 7 before ink ejection begins. However, the medium sensor that may erroneously detect the print medium 7 before ink ejection begins is not limited to the ejection control medium sensor.

[0080] In the above-described embodiment, the mist collection unit 5 has been described as having a plurality of air outlets 33a and a plurality of suction ports 34a provided corresponding to each inkjet head 26. However, the configuration of the mist collection unit is not limited to this. For example, the mist collection unit may be configured such that, for each head unit 21, there is one air outlet located upstream of the head unit 21 and one suction port located downstream of the head unit 21. Alternatively, for example, the mist collection unit may be configured such that, for four head units 21, there is one air outlet located upstream of the most upstream head unit 21 and one suction port located downstream of the most downstream head unit 21.

[0081] In the above-described embodiment, the mist collection operation when ink is ejected into an open space is performed by driving the blower fan 31 and the suction fan 32 at predetermined airflow rates that are greater than their respective standard airflow rates. However, the mist collection operation when ink is ejected into an open space is not limited to this. For example, the mist collection unit may be provided with a dedicated mist collection mechanism for collecting ink mist caused by ink ejection into an open space, and this dedicated mist collection mechanism may be activated when it is determined that ink may have been ejected into an open space.

[0082] In the above-described embodiment, the inkjet printing device 1 has been described in which the nozzle surface 26a of the inkjet head 26 is a vertical surface, and the inkjet head 26 ejects ink in a horizontal direction. However, the orientation of the inkjet head 26 (nozzle surface 26a) is not limited to this. It is sufficient that the space on the nozzle surface side of the inkjet head (the side through which the print medium passes) is an open space in which nothing is placed within a predetermined distance from the inkjet head except for the passing print medium.

[0083] For example, even in an inkjet printing device in which the inkjet head is installed so that ink is ejected vertically downward with the nozzle surface as a horizontal plane and which prints on the top surface of a three-dimensional printing medium, it is sufficient if the distance between the printing medium transport mechanism and the nozzle surface is greater than a predetermined distance and the space below the inkjet head (the side through which the printing medium passes) is an open space.

[0084] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments.

[0085] [Note] The present application discloses the following inventions.

[0086] (Appendix 1) an inkjet head that ejects ink onto the transported print medium; a mist collection unit that collects ink mist; at least one medium detection unit that detects the print medium, the medium detection unit including a medium detection unit for ejection control that is arranged upstream of the inkjet head in the print medium transport direction; a control unit that controls the ejection of ink from the inkjet head in response to the detection of a print medium by the ejection control medium detection unit, and also controls the mist collection unit, a space on the side of the inkjet head where the printing medium passes is an open space in which nothing is placed within a predetermined distance from the inkjet head except for the passing printing medium; The control unit determines whether or not ink may have been ejected from the inkjet head into the open space based on the operating status of the at least one medium detection unit, and if it determines that ink may have been ejected into the open space, controls the mist recovery unit to perform a mist recovery operation in case ink is ejected into the open space.

[0087] (Appendix 2) The inkjet printing device described in Appendix 1 is characterized in that the control unit determines whether or not a false detection of the printing medium has occurred before ink ejection from the inkjet head to the printing medium begins, based on the operating status of the at least one medium detection unit, and if it determines that a false detection of the printing medium has occurred before ink ejection begins, it stops ejecting ink from the inkjet head to the printing medium.

[0088] (Appendix 3) The inkjet printing device described in Appendix 1 or 2 is characterized in that the control unit determines that ink may have been ejected into the open space if the state in which the medium detection unit for ejection control detects the printing medium continues for a predetermined period of time or more.

[0089] (Appendix 4) the at least one medium detection unit includes a medium detection unit that is arranged downstream of the inkjet head in the transport direction, The inkjet printing device described in Appendix 1 or 2, characterized in that the control unit determines that ink may have been ejected into the open space if the printing medium is not detected by a medium detection unit located downstream of the inkjet head for a predetermined period of time after the medium detection unit for ejection control detects the rear end of the printing medium. [Explanation of symbols]

[0090] 1. Inkjet printing device 2. Conveyor section 3 Printing Department 4A~4C Media Sensor 5. Mist collection section 6 Control Unit 7 Print media 21 Head Unit 26 Inkjet head 26a Nozzle surface 31 Blower fan 32 Suction fan 33 Air flow path 33a Air outlet 34 Suction path 34a Suction port

Claims

1. an inkjet head that ejects ink onto the transported print medium; a mist collection unit that collects ink mist; at least one medium detection unit that detects the print medium, the medium detection unit including a medium detection unit for ejection control that is arranged upstream of the inkjet head in the print medium transport direction; a control unit that controls the ejection of ink from the inkjet head in response to the detection of a print medium by the ejection control medium detection unit, and also controls the mist collection unit, a space on the side of the inkjet head where the printing medium passes is an open space in which nothing is placed within a predetermined distance from the inkjet head except for the passing printing medium; The control unit determines whether or not ink may have been ejected from the inkjet head into the open space based on the operating status of the at least one medium detection unit, and if it determines that ink may have been ejected into the open space, controls the mist recovery unit to perform a mist recovery operation in case ink is ejected into the open space.

2. The inkjet printing device described in claim 1, characterized in that the control unit determines whether or not a false detection of the printing medium has occurred before ink ejection from the inkjet head to the printing medium begins based on the operating status of the at least one medium detection unit, and if it determines that a false detection of the printing medium has occurred before ink ejection begins, it stops ink ejection from the inkjet head to the printing medium.

3. The inkjet printing device according to claim 1 or 2, characterized in that the control unit determines that ink may have been ejected into the open space if the state in which the ejection control medium detection unit detects the printing medium continues for a predetermined period of time or more.

4. the at least one medium detection unit includes a medium detection unit that is arranged downstream of the inkjet head in the transport direction, The inkjet printing device according to claim 1 or 2, characterized in that, if the medium detection unit for ejection control detects the rear end of the printing medium and then the printing medium is not detected by a medium detection unit arranged downstream of the inkjet head for a predetermined period of time or more, the control unit determines that ink may have been ejected into the open space.

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