Ink jet printing machine and ink jet printing method

Abstract

To determine failure of a filter which is provided between an air tank and an ink tank and removes foreign matters from air.SOLUTION: Failure of a filter 673 is determined on the basis of a frequency of execution of an operation such that an atmospheric pressure opening electromagnetic valve 668 opens an air chamber 662 to atmosphere (length of an OFF period Toff). Thus, failure of the filter 673, which is provided between an air tank 661 and a sub-tank 62 and removes foreign matters from air, can be determined.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a technique for adjusting the pressure in an air chamber of an air tank that communicates with an ink tank that supplies ink to a recording head that ejects ink, and more particularly to a technique for determining defects in a filter provided between the air tank and the ink tank. [Background technology]

[0002] Inkjet printers are commonly used that print images on a recording medium by ejecting ink from a recording head onto the recording medium using an inkjet method. In such inkjet printers, various filters are used to maintain good operation. For example, in Patent Document 1, a hollow fiber filter is provided in an ink flow path, and a gas pressure adjustment tank connected to the hollow fiber filter is depressurized to a negative pressure to remove dissolved gas from the ink passing through the hollow fiber filter. Furthermore, Patent Document 1 proposes a technology that determines a filter defect (clogging) and notifies the user when it is time to replace the filter. Specifically, if it takes a long time to depressurize the gas pressure adjustment tank, it is determined that a filter defect has occurred. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5701886 Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to the above-mentioned hollow fiber filter that removes dissolved gas from the ink, an inkjet printer may also use a filter that removes foreign matter from the ink from the air. In other words, the shape of the ink meniscus is important for proper ink ejection from the recording head. Therefore, a technology can be used to control the shape of the ink meniscus by providing an ink tank having a storage chamber that stores the ink to be supplied to the recording head, and an air tank having an air chamber that communicates with the storage chamber, and adjusting the air chamber to a predetermined air pressure (negative pressure).

[0005] In this case, in order to prevent foreign matter from entering the ink tank, it is appropriate to provide a filter between the air tank and the ink tank to remove foreign matter from the air. However, this filter can become defective (clogged) due to the adhesion of ink mist. Therefore, a technology for determining whether the filter is defective is required. However, it is difficult to adapt the technology for determining whether a filter that removes dissolved gas from ink is defective, as in Patent Document 1, to determine whether a filter that removes foreign matter from gas is defective.

[0006] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a technique for determining whether a filter that is provided between an air tank and an ink tank and removes foreign matter from the air is defective. [Means for solving the problem]

[0007] The inkjet printing machine according to the present invention comprises a recording head which applies ink to a recording medium by ejecting ink, an ink tank having a storage chamber for storing ink and supplying ink from the storage chamber to the recording head in response to the recording head ejecting ink, an air tank having an air chamber, a communicating tube which connects the storage chamber of the ink tank with the air chamber of the air tank, a filter provided in the communicating tube between the ink tank and the air tank for removing foreign matter from the air in the communicating tube, an air release valve connected to the air chamber of the air tank and selectively performing one of an operation of opening the air chamber to the atmosphere and an operation of blocking the air chamber from the atmosphere, a sensor which detects the pressure of the air chamber of the air tank, a pressure control unit which adjusts the pressure of the air chamber of the air tank by controlling the operation of the air release valve based on the pressure of the air chamber detected by the sensor, and a filter defect determination unit which determines whether the filter is defective based on the frequency with which the air release valve performs the operation of opening the air chamber to the atmosphere under the control of the pressure control unit.

[0008] The inkjet printing method according to the present invention includes the steps of: applying ink to a recording medium by ejecting ink from a recording head; supplying ink to the recording head from a storage chamber of an ink tank that stores ink in response to the recording head ejecting ink; detecting, by a sensor, the pressure of an air chamber of an air tank that communicates with the storage chamber via a communicating tube; adjusting the pressure of the air chamber of the air tank by controlling, based on the pressure of the air chamber detected by the sensor, the operation of an atmosphere release valve that is connected to the air chamber of the air tank and selectively performs one of an operation of opening the air chamber to the atmosphere and an operation of closing the air chamber from the atmosphere; and determining whether a filter is defective, which is provided in the communicating tube between the ink tank and the air tank and removes foreign matter from the air in the communicating tube, and whether the filter is defective is determined based on the frequency at which the atmosphere release valve performs the operation of opening the air chamber to the atmosphere.

[0009] In the present invention (inkjet printer and inkjet printing method) configured as described above, ink is supplied from the storage chamber of the ink tank to the recording head in response to the recording head ejecting ink. Therefore, when the recording head ejects ink with the air release valve blocking the air tank from the atmosphere, the air-liquid interface in the storage chamber of the ink tank drops, and the pressure (atmospheric pressure) of the air layer above the air-liquid interface drops. In response to this, the pressure (atmospheric pressure) of the air chamber of the air tank communicating with the storage chamber of the ink tank is detected by a sensor, and the pressure of the air chamber of the air tank is adjusted by controlling the operation of the air release valve based on the pressure detected by the sensor. Therefore, when the pressure of the storage chamber of the ink tank drops excessively as the recording head ejects ink, the air tank is opened to atmospheric pressure, and the pressure of the storage chamber of the ink tank rises to an appropriate pressure range. In this way, the shape of the meniscus of the ink formed in the recording head can be appropriately maintained.

[0010] In this case, if there is a defect in the filter, it takes time for the pressure in the air tank's air chamber to follow the drop in pressure in the ink tank's storage chamber. This reduces the frequency with which the air release valve opens the air tank's air chamber to the atmosphere. In other words, there is a correlation between the frequency of the air release operation and filter defects. Based on this knowledge, in the present invention, a filter defect is determined based on the frequency with which the air release valve opens the air chamber to the atmosphere. In this way, it becomes possible to determine a defect in the filter that is provided between the air tank and the ink tank and removes foreign matter from the air.

[0011] The inkjet printer may be configured to further include a memory unit that stores a reference period that is a standard for determining whether a filter is defective based on frequency, and the filter defect determination unit determines whether a filter is defective based on a comparison between a blocking period, during which the air release valve blocks the air chamber from the atmosphere under control of the pressure control unit, and the reference period. In this configuration, a filter defect can be determined by simple control such as comparing the blocking period with the reference period.

[0012] The inkjet printer may be configured to further include a test discharge control unit that causes the recording head to perform a test discharge that discharges a predetermined amount of ink per unit time. In this configuration, a filter defect can be accurately determined based on the frequency of the air release operation during the execution of the test discharge.

[0013] The inkjet printer may be configured so that, during the period in which the test discharge control unit causes the recording head to perform test discharge, the filter defect determination unit measures the blocking period to obtain a measured blocking period and determines whether the filter is defective based on a comparison between the measured blocking period and a reference period. With this configuration, it is possible to accurately determine whether the filter is defective based on the result of measuring the frequency of the air release operation during the execution of test discharge.

[0014] The inkjet printer may be configured such that the filter defect determination unit determines that a filter defect has occurred when the measured cutoff period is longer than the reference period. In this configuration, a filter defect can be determined by a simple control such as confirming that the measured cutoff period is longer than the reference period.

[0015] The inkjet printer may be configured such that, during the period in which the test discharge control unit causes the recording head to perform test discharge, the filter defect determination unit acquires a plurality of measured blocking periods, and determines that a defect has occurred in the filter if the average value of the plurality of measured blocking periods is longer than a reference period. In this configuration, a filter defect can be determined by simple control such as confirming that the average value of the plurality of measured blocking periods is longer than the reference period.

[0016] The inkjet printer may be configured such that the test discharge control unit causes the recording head to perform test discharge by causing the recording head to discharge ink so as to print a predetermined image on the recording medium. In this configuration, it is possible to accurately determine whether the filter is defective based on the frequency of the air release operation during the execution of the test discharge.

[0017] The inkjet printer may further include a pressure reducing pump connected to an air chamber of the air tank and venting the air chamber based on the control of the pressure control unit, and a main tank for storing ink to be supplied to the ink tank, and the filter defect determination unit further includes a machine learning model that learns the relationship between environmental conditions, including at least one of the cumulative amount of ink supplied from the main tank to the ink tank, the cumulative amount of ink ejected by the recording head, the cumulative operating time of the pressure reducing pump, and the temperature of the environment in which the inkjet printer is installed, and the frequency of the filter being normal, and the relationship between the environmental conditions and the frequency of the filter being defective, and the inkjet printer may be configured to determine whether the filter is defective based on the machine learning model and the frequency. With this configuration, it is possible to accurately determine whether the filter is defective based on the learning result of the machine learning model. Effect of the Invention

[0018] As described above, according to the present invention, it is possible to determine whether a filter that is provided between the air tank and the ink tank and removes foreign matter from the air is defective. [Brief description of the drawings]

[0019] [Figure 1] 1 is a front view showing a schematic diagram of an example of an inkjet printer according to the present invention; [Diagram 2] FIG. 2 is a bottom view illustrating a schematic configuration of the head unit. [Diagram 3] FIG. 2 is a diagram illustrating an example of an ink supply mechanism that supplies ink to an ejection head of a head unit. [Figure 4] 4 is a block diagram showing a first example of a controller that controls the ink supply mechanism of FIG. 3. [Diagram 5] 13 is a diagram showing an example of pressure control of an air chamber based on pressure in the air chamber detected by a pressure sensor; FIG. [Figure 6A] FIG. 13 is a schematic diagram showing an example of comparison of the subtank pressure tracking ability to the air tank pressure when the filter is normal and when the filter is abnormal. [Figure 6B]FIG. 13 is a schematic diagram showing an example of comparison of the subtank pressure tracking ability to the air tank pressure when the filter is normal and when the filter is abnormal. [Figure 6C] FIG. 13 is a schematic diagram showing an example of comparison of the subtank pressure tracking ability to the air tank pressure when the filter is normal and when the filter is abnormal. [Figure 7] FIG. 13 is a schematic diagram showing an example of comparison of the subtank pressure tracking ability to the air tank pressure when the filter is normal and when the filter is abnormal. [Figure 8] 11 is a diagram showing a schematic diagram of a difference in frequency of opening the air chamber to the atmosphere between when the filter is normal and when the filter is abnormal. FIG. [Figure 9] 6 is a flowchart showing a first example of a filter defect determination process. [Figure 10] 10 is a flowchart showing a second example of a filter defect determination process. [Figure 11] 4 is a block diagram showing a second example of a controller that controls the ink supply mechanism in FIG. 3. [Figure 12] 10 is a flowchart showing a third example of a filter defect determination process. [Figure 13] FIG. 2 is a diagram illustrating a configuration and operation of a maintenance unit provided in the inkjet printing machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Fig. 1 is a front view showing a schematic diagram of an example of an inkjet printer according to the present invention. In this specification, the horizontal X direction, the horizontal Y direction perpendicular to the X direction, and the vertical Z direction are indicated as appropriate. The inkjet printer 1 prints an image on a long strip-shaped web W by ejecting ink onto the web W by an inkjet method while transporting the web W in a roll-to-roll manner. The material of the web W is paper or film, and the web W is flexible.

[0021] The inkjet printer 1 includes a transport section 2 that transports the web W in the web transport direction Dw. The transport section 2 includes a feed roller 21 and a take-up roller 22, and transports the web W in a roll-to-roll manner by winding the web W fed by the feed roller 21 with the take-up roller 22. The transport section 2 includes a take-up section 23 that takes in the web W fed from the feed roller 21, between the feed roller 21 and the take-up roller 22. The take-up section 23 includes two drive rollers 231, two nip rollers 232, and an edge position adjustment section 234 provided between the two drive rollers 231. Each drive roller 231 rotates by the driving force of a motor while winding the web W around it, thereby driving the web W. The two nip rollers 232 are provided corresponding to the two drive rollers 231, respectively, and each nip roller 232 sandwiches the web W between the corresponding drive roller 231. The edge position adjustment unit 234 adjusts the position of the edge of the web W in the X direction, which is the width direction of the web W.

[0022] The transport section 2 also has a plurality of support rollers 24 that support the web W between the take-in section 23 and the winding roller 22. The support rollers 24 transport the web W in the Y direction while supporting the web W from below, on which ink is discharged by the inkjet method. In particular, the support rollers 24 are arranged at an incline so that the support rollers 24 on the downstream side of the transport direction (Y direction) of the web W are positioned at a higher position. Therefore, the web W transported by the support rollers 24 is transported at an incline so as to rise toward the Y direction. The transport section 2 also has a plurality of support rollers 25 that support the web W between the support rollers 24 and the winding roller 22, and a drive roller 281 and a nip roller 282 that are arranged between the support rollers 25 and the winding roller 22. The drive roller 281 drives the web W by rotating by the driving force of a motor while winding the web W around it. The nip roller 282 sandwiches the web W between the drive roller 281 and the nip roller 282.

[0023] The inkjet printer 1 has a plurality of (five) head units 3 (FIG. 2) facing from above the web W supported by a plurality of support rollers 24. FIG. 2 is a bottom view showing a schematic configuration of the head unit. Each head unit 3 has a plurality of (five) ejection heads 31. The ejection heads 31 are arranged at different positions in the X direction, and are arranged in two rows in a staggered manner in the X direction. In other words, a head row C31 consisting of three ejection heads 31 arranged parallel to the X direction and a head row C31 consisting of two ejection heads 31 arranged parallel to the X direction are provided in the Y direction. The bottom surface of each ejection head 31 is a nozzle opening plane 310 facing the web W, and the nozzle opening plane 310 has a rectangular shape in a bottom view. A plurality of nozzles 311 are opened in the nozzle opening plane 310. The plurality of nozzles 311 are arranged in a staggered manner in the X direction and face the web W from above, and each nozzle 311 ejects ink to the web W by an inkjet method. The head unit 3 has a head holding member 32 that holds each ejection head 31. The bottom surface of the head holding member 32 is a web-facing plane 320 that faces the web W, and the web-facing plane 320 has a rectangular shape when viewed from the bottom. A plurality of head insertion holes 321 corresponding to the plurality of ejection heads 31 are opened in the web-facing plane 320. The plurality of ejection heads 31 are fixed to the head holding member 32 in a state where they are inserted into the corresponding head insertion holes 321. The head holding member 32 can be made of a non-elastic member such as metal or resin.

[0024] 1, the posture of each of the multiple head units 3 is set according to the inclination of the web W supported by the multiple support rollers 24. In other words, the multiple head units 3 are arranged such that the more upstream the head unit 3 is in the transport direction of the web W, the greater the inclination with respect to the Z direction. However, the most downstream head unit 3 in the transport direction (Y direction) of the web W is arranged horizontally and is not inclined with respect to the Z direction, and the head units 3 other than the most downstream head unit 3 are inclined so as to become higher toward the transport direction of the web W. The inclination of the head unit 3 can be evaluated by the angle that the nozzle opening plane 310 of the ejection head 31 in which the nozzles 311 are formed makes with respect to the Z direction.

[0025] Of the five head units 3, one head unit 3 located at the most upstream in the web transport direction Dw ejects white ink onto the web W. Among the five head units 3, four head units 3 located downstream of the one head unit 3 in the web transport direction Dw eject different color inks, specifically yellow, magenta, cyan, and black inks onto the web W. The ink ejected by the head unit 3 is UV (ultraviolet) ink that is cured by irradiation with ultraviolet light. In contrast, the inkjet printer 1 includes two UV irradiators 4 that irradiate ultraviolet light onto the UV ink ejected onto the web W. Of the two UV irradiators 4, one UV irradiator 4 irradiates ultraviolet light onto the web W between the head unit 3 ejecting white ink and the head unit 3 ejecting color inks, and the other UV irradiator 4 irradiates ultraviolet light onto the web W downstream in the web transport direction Dw of the head unit 3 ejecting color inks.

[0026] The number of head units 3 and the color of ink are not limited to the above example. In addition, the ink ejected by the head unit 3 is not limited to UV ink, and may be water-based ink. When the head unit 3 ejects water-based ink, a heater for drying the water-based ink may be provided instead of the UV irradiator 4.

[0027] The inkjet printer 1 also includes a plurality of lifting drive units 5 respectively provided corresponding to the plurality of head units 3. Each lifting drive unit 5 can raise and lower the corresponding head unit 3, thereby positioning the head unit 3 at one of a plurality of positions at different heights. In FIG. 1, each head unit 3 is positioned at a printing height h0 that is closest to the web W. Such lifting drive unit 5 can be realized by a known specific configuration, and can be configured to raise and lower the head unit 3 by, for example, driving a ball screw or an eccentric cam with a motor.

[0028] Fig. 3 is a diagram showing a schematic example of an ink supply mechanism that supplies ink to the ejection heads of the head units, and Fig. 4 is a block diagram showing a first example of a controller that controls the ink supply mechanism of Fig. 3. The ink supply mechanism 6 of Fig. 3 and the controller 7 of Fig. 4 are provided for each of the multiple head units 3. Fig. 4 also shows a display 8 that the inkjet printing machine 1 is equipped with, in addition to the ink supply mechanism 6. This display 8 displays various information to the user according to the control of a display control unit 719.

[0029] As shown in Fig. 4, the controller 7 has a calculation unit 71 and a storage unit 72. The calculation unit 71 is a processor such as a CPU (Central Processing Unit), and constitutes a main control unit 711, a filter defect determination unit 712, a pressure control unit 713, a switching control unit 714, a maintenance control unit 715, a discharge control unit 717, a liquid delivery control unit 718, and a display control unit 719, by executing a predetermined program stored in the storage unit 72, for example. The storage unit 72 is a storage device such as an SSD (Solid State Drive). This storage unit 72 stores a reference period Trf to be used in subsequent filter defect determination.

[0030] 3, the ink supply mechanism 6 has a main tank 61 and a sub tank 62, each of which stores ink. The main tank 61 has an ink storage chamber 611, and ink is stored in the ink storage chamber 611. The sub tank 62 has an ink storage chamber 621 that is smaller in capacity than the ink storage chamber 611 of the main tank 61, and ink is stored in the ink storage chamber 621.

[0031] The ink supply mechanism 6 also has an ink supply unit 63 that supplies ink to the sub tank 62 by sending ink from the main tank 61 to the sub tank 62. The ink supply unit 63 has a pipe 631 that connects the ink storage chamber 611 of the main tank 61 and the ink storage chamber 621 of the sub tank 62 to each other. Therefore, the ink coming out of the ink storage chamber 611 of the main tank 61 flows through the pipe 631 and enters the ink storage chamber 621 of the sub tank 62. The ink supply unit 63 also has a supply pump 632 attached to the pipe 631. The supply pump 632 is controlled by the liquid sending control unit 718. That is, the supply pump 632 drives the ink in the pipe 631 from the ink storage chamber 611 of the main tank 61 to the ink storage chamber 621 of the sub tank 62 in response to a liquid sending command from the liquid sending control unit 718. As a result, ink is sent from the ink storage chamber 611 to the ink storage chamber 621 .

[0032] The ink supply unit 63 has a filter 633 attached to the pipe 631 between the main tank 61 and the supply pump 632. This filter 633 removes foreign matter from the ink flowing through the pipe 631. The ink supply unit 63 also has a degassing filter 634 attached to the pipe 631 between the supply pump 632 and the sub tank 62. This degassing filter 634 removes gas from the ink flowing through the pipe 631. The ink supply unit 63 also has a supply solenoid valve 635 attached to the pipe 631 between the filter 633 and the supply pump 632. This supply solenoid valve 635 is controlled by the liquid sending control unit 718. That is, the supply solenoid valve 635 allows the ink to be sent from the main tank 61 to the sub tank 62 by opening (by turning ON) in response to an open command from the liquid sending control unit 718, while it prohibits the ink from being sent from the main tank 61 to the sub tank 62 by closing (by turning OFF) in response to a close command from the liquid sending control unit 718.

[0033] The ink supply mechanism 6 has an ink supply unit 64 that supplies ink from the ink storage chamber 621 of the subtank 62 to the ejection head 31. The ink supply unit 64 has a pipe 641 that extends from the ink storage chamber 621 of the subtank 62, and a plurality of pipes 642 that branch off from the pipe 641 to the plurality of ejection heads 31. That is, the ejection head 31 communicates with the ink storage chamber 621 of the subtank 62 through the pipe 642 and the pipe 641 that are connected to the ejection head 31. Therefore, ink can be supplied from the ink storage chamber 621 of the subtank 62 to the ejection head 31 through the pipe 641 and the pipe 642. Specifically, as the ejection head 31 ejects ink from the nozzle 311, ink is sucked out of the ink storage chamber 621 of the subtank 62 and supplied to the ejection head 31. The ink supply unit 64 also has a plurality of head solenoid valves 643 that are attached to the plurality of pipes 642, respectively. This head solenoid valve 643 is controlled by the discharge control unit 717. In other words, the head solenoid valve 643 allows the transfer of ink from the subtank 62 to the discharge head 31 by opening (turning ON) in response to an open command from the discharge control unit 717, and prohibits the transfer of ink from the subtank 62 to the discharge head 31 by closing (turning OFF) in response to a close command from the liquid transfer control unit 718.

[0034] Furthermore, the discharge control unit 717 controls the discharge of ink from the nozzles 311 by the discharge head 31. That is, the discharge head 31 discharges ink from the nozzles 311 by an inkjet system in response to a drive signal from the discharge control unit 717. Specifically, a piezoelectric element is provided in a pressure chamber communicating with each nozzle 311 of the discharge head 31, and the ink is discharged from the nozzles 311 by the piezoelectric element being displaced in response to the drive signal to push the ink in the pressure chamber out of the nozzles 311. Note that the ink discharge system is not limited to the piezoelectric system, and may be a thermal system.

[0035] Furthermore, the ink supply mechanism 6 has a maintenance execution unit 65, a meniscus formation unit 66, and a switching unit 67. The switching unit 67 switches between the maintenance execution unit 65 and the meniscus formation unit 66 to communicate with the ink storage chamber 621 of the subtank 62. This switching unit 67 has a switching solenoid valve 671. The switching solenoid valve 671 has a first input port Ii1, a second input port Ii2, and an output port Io, and selectively performs either a first connection operation that connects the first input port Ii1 to the output port Io, or a second connection operation that connects the second input port Ii2 to the output port Io. This switching solenoid valve 671 is controlled by the switching control unit 714. In other words, the switching solenoid valve 671 allows air to flow from the first input port Ii1 to the output port Io while prohibiting air to flow from the second input port Ii2 to the output port Io by performing a first connection operation in response to a first connection command from the switching control unit 714. Also, the switching solenoid valve 671 allows air to flow from the second input port Ii2 to the output port Io while prohibiting air to flow from the first input port Ii1 to the output port Io by performing a second connection operation in response to a second connection command from the switching control unit 714.

[0036] The switching unit 67 also has a pipe 672 that connects the output port Io of the switching solenoid valve 671 and the ink storage chamber 621 of the subtank 62. In particular, the pipe 672 opens to an air layer B formed above the gas-liquid interface A of the ink in the ink storage chamber 621 of the subtank 62, and the output port Io of the switching solenoid valve 671 connects to this air layer B. Furthermore, the switching unit 67 has a filter 673 attached to the pipe 672 between the output port Io and the ink storage chamber 621 of the subtank 62. This filter 673 removes foreign matter from the gas (air) flowing through the pipe 672.

[0037] The maintenance execution unit 65 has a pipe 651 that connects the first input port Ii1 of the switching solenoid valve 671 and the purge pressure supply source Pp, and a purge solenoid valve 652 that is attached to the pipe 651 between the first input port Ii1 of the switching solenoid valve 671 and the purge pressure supply source Pp. This purge solenoid valve 652 is controlled by the maintenance control unit 715. In other words, the purge solenoid valve 652 communicates the purge pressure supply source Pp and the first input port Ii1 by opening (turning ON) in response to an open command from the maintenance control unit 715, and blocks the purge pressure supply source Pp and the first input port Ii1 by closing (turning OFF) in response to a close command from the maintenance control unit 715. The maintenance execution unit 65 also has a pipe 654 that connects a branch point 653 between the first input port Ii1 of the switching solenoid valve 671 and the purge solenoid valve 652 in the pipe 651 to the atmosphere Pa, and an atmosphere release solenoid valve 655 that is attached to the pipe 654 between the branch point 653 and the atmosphere Pa. This atmosphere release solenoid valve 655 is controlled by the maintenance control unit 715. That is, the atmosphere release solenoid valve 655 communicates between the atmosphere Pa and the first input port Ii1 by opening (by turning ON) in response to an open command from the maintenance control unit 715, and closes (by turning OFF) in response to a close command from the maintenance control unit 715 to block the atmosphere Pa from the first input port Ii1.

[0038] In particular, when the maintenance control unit 715 closes the atmosphere release solenoid valve 655 and opens the purge solenoid valve 652 while closing the atmosphere release solenoid valve 655 in a state in which the switching control unit 714 causes the switching solenoid valve 671 to perform the first connecting operation, the purge pressure generated by the purge pressure supply source Pp is supplied to the ink storage chamber 621 of the subtank 62 via the pipes 651 and 672. This purge pressure pushes down the gas-liquid interface A of the ink storage chamber 621, pushing ink from the ink storage chamber 621 to the ejection head 31, causing the ink to flow out of the nozzles 311 of the ejection head 31 (purging). Also, when the maintenance control unit 715 closes the purge solenoid valve 652 while opening the atmosphere release solenoid valve 655 in a state in which the switching control unit 714 causes the switching solenoid valve 671 to perform the first connecting operation, the atmospheric pressure of the atmosphere Pa is supplied to the ink storage chamber 621 of the subtank 62 via the pipes 654, 651, and 672. In this way, the air layer B of the ink storage chamber 621 is opened to the atmosphere Pa.

[0039] The meniscus forming portion 66 has an air tank 661, a pipe 663 that communicates between an air chamber 662 provided in the air tank 661 and a second input port Ii2 of the switching solenoid valve 671, and a pipe 664 extended from the air chamber 662 of the air tank 661. Of one end 664A and the other end 664B of this pipe 664, the one end 664A opens to the air chamber 662 of the air tank 661.

[0040] Further, the meniscus forming unit 66 has a decompression pump 665 and a pipe 666 that communicates the decompression pump 665 with the other end 664B of the pipe 664. Therefore, the decompression pump 665 communicates with the air chamber 662 of the air tank 661 via the pipe 666 and the pipe 664. The decompression pump 665 is controlled by the pressure control unit 713. That is, the decompression pump 665 starts in response to a start command from the pressure control unit 713, thereby evacuating the air chamber 662 of the air tank 661. This reduces the pressure in the air chamber 662. On the other hand, the decompression pump 665 stops in response to a stop command from the pressure control unit 713, thereby stopping the evacuation of the air chamber 662 of the air tank 661. This stops the decompression of the air chamber 662.

[0041] Furthermore, the meniscus formation unit 66 has a pipe 667 that communicates the atmosphere Pa with the other end 664B of the pipe 664, and an atmospheric pressure release solenoid valve 668 attached to the pipe 667 between the atmosphere Pa and the other end 664B of the pipe 664. This atmospheric pressure release solenoid valve 668 is controlled by the pressure control unit 713. That is, the atmospheric pressure release solenoid valve 668 communicates the atmosphere Pa with the air chamber 662 of the air tank 661 by opening (by turning ON) in response to an open command from the pressure control unit 713, and on the other hand, it blocks the atmosphere Pa from the air chamber 662 of the air tank 661 by closing (by turning OFF) in response to a close command from the pressure control unit 713.

[0042] Furthermore, the meniscus forming portion 66 has a pressure sensor 669 that detects the pressure (atmospheric pressure) of the air chamber 662 of the air tank 661. Then, the pressure control portion 713 controls the decompression pump 665 and the atmospheric pressure release solenoid valve 668 based on the pressure detected by the pressure sensor 669, thereby adjusting the pressure of the air chamber 662 to a negative pressure within a predetermined range.

[0043] FIG. 5 is a diagram showing an example of pressure control of the air chamber based on the pressure of the air chamber detected by the pressure sensor. In the graph of FIG. 5, the horizontal axis is time, and the vertical axis is the pressure of the air chamber 662 detected by the pressure sensor 669 (detected pressure Pd). The pressure control of FIG. 5 is performed in a state in which the switching solenoid valve 671 performs the second connecting operation and the second input port Ii2 and the output port Io are in communication with each other, in other words, in a state in which the air chamber 662 of the air tank 661 and the air layer B of the ink storage chamber 621 of the subtank 62 are in communication with each other. Note that, as described above, the filter 673 is provided in the air flow path (i.e., the piping 672) between the air chamber 662 and the air layer B, and foreign matter (dust, ink mist, etc.) is removed by the filter 673 from the air passing through the filter 673 between the air chamber 662 and the air layer B.

[0044] The purpose of this pressure control is to appropriately maintain the shape of the meniscus of the ink formed in the nozzle 311 of the ejection head 31. That is, during printing, in which ink is ejected from the nozzle 311 of the ejection head 31 to print an image on the web W, it is necessary to maintain the pressure of the air layer B of the subtank 62 within a predetermined negative pressure range to appropriately maintain the shape of the meniscus of the ink. However, when ink is supplied from the ink storage chamber 621 of the subtank 62 to the ejection head 31 as ink is ejected from the ejection head 31, the air-liquid interface A in the subtank 62 drops. As a result, the volume of the air layer B increases and the pressure of the air layer B drops. Therefore, by executing pressure control based on the detected pressure Pd of the air chamber 662 communicating with the air layer B, the drop in the pressure of the air layer B is suppressed and the pressure of the air layer B is maintained at a negative pressure for forming a meniscus of an appropriate shape. In this pressure control, four types of pressures Pu(n), Pu(f), Pl(f), and Pl(n) are used. The magnitude relationship between these pressures is pressure Pu(n)>pressure Pu(f)>pressure Pl(f)>pressure Pl(n).

[0045] The pressure Pu(n) provides the timing for starting the decompression pump 665. In other words, when the detected pressure Pd rises from a value lower than the pressure Pu(n) to the pressure Pu(n) while the decompression pump 665 is stopped, the pressure control unit 713 starts the decompression pump 665 to start decompressing the air chamber 662 by the decompression pump 665.

[0046] The pressure Pu(f) provides the timing for stopping the decompression pump 665. In other words, when the detected pressure Pd drops from a value higher than the pressure Pu(f) to the pressure Pu(f) while the decompression pump 665 is operating, the pressure control unit 713 stops the decompression pump 665, thereby stopping the decompression of the air chamber 662 by the decompression pump 665.

[0047] The pressure Pl(n) provides the timing for opening the atmospheric pressure release solenoid valve 668. In other words, when the detected pressure Pd drops from a value higher than the pressure Pl(n) to the pressure Pl(n) while the atmospheric pressure release solenoid valve 668 is closed, the pressure control unit 713 opens the atmospheric pressure release solenoid valve 668 to release the air chamber 662 to the atmosphere Pa.

[0048] The pressure Pl(f) provides the timing for closing the atmospheric pressure release solenoid valve 668. In other words, when the detected pressure Pd rises from a value lower than the pressure Pl(f) to the pressure Pl(f) while the atmospheric pressure release solenoid valve 668 is open, the pressure control unit 713 closes the atmospheric pressure release solenoid valve 668 to isolate the air chamber 662 from the atmosphere Pa.

[0049] 5, at time t1 when the detected pressure Pd rises to pressure Pu(n), the decompression pump 665 starts and starts decompressing the air chamber 662. At time t2 when the detected pressure Pd drops to pressure Pu(f) due to the decompression by the decompression pump 665, the decompression pump 665 stops and the decompression of the air chamber 662 by the decompression pump 665 stops. At time t3 when the detected pressure Pd drops to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens and releases the air chamber 662 to the atmosphere Pa. At time t4 when the detected pressure Pd rises to pressure Pl(f) due to the release to the atmosphere Pa by the atmospheric pressure release solenoid valve 668, the atmospheric pressure release solenoid valve 668 closes and the air chamber 662 is cut off from the atmosphere Pa. Then, at time t5 when the detected pressure Pd rises to pressure Pu(n), the decompression pump 665 starts and starts decompressing the air chamber 662. By repeating these operations, the pressure in the air chamber 662 is adjusted to a negative pressure within a predetermined range.

[0050] Incidentally, the above pressure control is premised on the pressure of the air layer B of the subtank 62 accurately following the pressure of the air chamber 662. However, if the filter 673 provided between the air chamber 662 and the air layer B becomes defective, such as clogged due to the adhesion of foreign matter, the pressure of the air layer B will not follow the pressure of the air tank 661, and the meniscus pressure will not be able to be maintained appropriately.

[0051] 6A, 6B, 6C, and 7 are schematic diagrams showing an example of comparing the follow-up of the pressure of the sub tank to the pressure of the air tank when the filter is normal (i.e., when no defect occurs) and when the filter is abnormal (i.e., when a defect occurs). In particular, FIG. 6A shows specific values ​​of each parameter that are the premise of this example. In the example of FIG. 6A, the capacity of the ink storage chamber 621 of the sub tank 62 is L ml, and the capacity of the air chamber 662 of the air tank 661 is 100 L ml. That is, the capacity of the air chamber 662 is 100 times the capacity of the ink storage chamber 621. In addition, the initial pressure of the air chamber 662 and the air layer B before starting printing is -M1 kPa. Furthermore, the pressure Pu(n) that turns on the decompression pump 665 is -M2 kPa, and the pressure Pl(n) that turns on the atmospheric pressure release solenoid valve 668 is -M3 kPa. However, the magnitude relationship between these pressures is (-M2)>(-M1)>(-M3). Furthermore, the amount of ink ejected per unit time by the multiple ejection heads 31 included in the head unit 3, i.e., the amount of ink supplied from the subtank 62 per unit time, is Nml / s.

[0052] When the filter 673 is not defective (when the filter is normal), the amount of air (Nml / s) flowing from the air tank 661 to the sub tank 62 per unit time through the filter 673 is approximately equal to the amount of ink (Nml / s) flowing from the sub tank 62 per unit time. On the other hand, when the filter 673 is defective (when the filter is abnormal), the amount of air (0.6 Nml / s) flowing from the air tank 661 to the sub tank 62 per unit time through the filter 673 is less than the amount of ink (Nml / s) flowing from the sub tank 62 per unit time. Therefore, as shown in FIG. 7, the time T1 required for the pressure Pd detected by the pressure sensor 669 to decrease to the pressure Pl(n) after printing starts at time 0 when the filter is abnormal is longer than the time T2 required for the pressure Pd detected by the pressure sensor 669 to decrease to the pressure Pl(n) after printing starts at time 0 when the filter is normal. In other words, as the degree of failure of the filter 673 progresses, the frequency with which the pressure control unit 713 opens (i.e., turns on) the atmospheric pressure release solenoid valve 668 to open the air chamber 662 of the air tank 661 to the atmosphere decreases.

[0053] Fig. 8 is a diagram showing a schematic diagram of the difference in the frequency of opening the air chamber to the atmosphere between when the filter is normal and when the filter is abnormal. The first graph from the top of Fig. 8 shows the change over time in the detected pressure Pd of the air chamber 662 when the filter is normal and when the filter is abnormal. The second graph from the top of Fig. 8 shows the change over time in the operation of the atmospheric pressure release solenoid valve 668 when the filter is normal. The third graph from the top of Fig. 8 shows the change over time in the operation of the atmospheric pressure release solenoid valve 668 when the filter is abnormal.

[0054] First, the filter normal state will be described. At time t21 when the detected pressure Pd drops to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens and releases the air chamber 662 to the atmosphere Pa. As the atmospheric pressure release solenoid valve 668 releases the air to the atmosphere Pa, at time t22 when the detected pressure Pd rises to pressure Pl(f), the atmospheric pressure release solenoid valve 668 closes and the air chamber 662 is isolated from the atmosphere Pa.

[0055] At time t23 when the detected pressure Pd has dropped to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens, opening the air chamber 662 to the atmosphere Pa. As the atmospheric pressure release solenoid valve 668 releases the air to the atmosphere Pa, at time t24 when the detected pressure Pd has risen to pressure Pl(f), the atmospheric pressure release solenoid valve 668 closes, and the air chamber 662 is isolated from the atmosphere Pa.

[0056] At time t25 when the detected pressure Pd has dropped to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens, opening the air chamber 662 to the atmosphere Pa. As the atmospheric pressure release solenoid valve 668 releases the air to the atmosphere Pa, at time t26 when the detected pressure Pd has risen to pressure Pl(f), the atmospheric pressure release solenoid valve 668 closes, blocking the air chamber 662 from the atmosphere Pa.

[0057] Next, a description will be given of the condition when the filter is abnormal. At time t31 when the detected pressure Pd drops to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens and releases the air chamber 662 to the atmosphere Pa. As the atmospheric pressure release solenoid valve 668 releases the detected pressure Pd to the atmosphere Pa, at time t32 when the atmospheric pressure release solenoid valve 668 rises to pressure Pl(f), the atmospheric pressure release solenoid valve 668 closes and the air chamber 662 is isolated from the atmosphere Pa.

[0058] At time t33 when the detected pressure Pd has dropped to pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens, opening the air chamber 662 to the atmosphere Pa. As the atmospheric pressure release solenoid valve 668 releases the air to the atmosphere Pa, at time t34 when the detected pressure Pd has risen to pressure Pl(f), the atmospheric pressure release solenoid valve 668 closes, blocking the air chamber 662 from the atmosphere Pa.

[0059] At time t35 when the detected pressure Pd drops to the pressure Pl(n), the atmospheric pressure release solenoid valve 668 opens to open the air chamber 662 to the atmosphere Pa.

[0060] When the filter is normal, the pressure in the air chamber 662 of the air tank 661, i.e., the pressure Pd detected by the pressure sensor 669, quickly responds to pressure changes in the air layer B of the ink storage chamber 621 of the subtank 62. Therefore, the frequency of the operation in which the atmospheric pressure release solenoid valve 668 opens the air chamber 662 to the atmosphere (opening to the atmosphere operation) is relatively high. In contrast, when the filter is abnormal, the pressure in the air chamber 662 of the air tank 661, i.e., the pressure Pd detected by the pressure sensor 669, responds slowly to pressure changes in the air layer B of the ink storage chamber 621 of the subtank 62. Therefore, the frequency of the opening to the atmosphere operation when the filter is abnormal is lower than the frequency of the opening to the atmosphere operation when the filter is normal.

[0061] Various indexes are assumed to represent the frequency of the air release operation. For example, the intervals Ta1 and Ta2 at which the air release operation is performed can be used as an index of frequency. In this case, the interval Ta2 at which the air release operation is performed when the filter is abnormal is longer than the interval Ta1 at which the air release operation is performed when the filter is normal. Alternatively, the time interval at which the atmospheric pressure release solenoid valve 668 is closed (turned off) can be used as an index of frequency. In other words, the speed at which the pressure of the air chamber 662 increases after the air chamber 662 is released to the atmosphere does not change significantly between when the filter is normal and when the filter is abnormal. Therefore, the period during which the atmospheric pressure release solenoid valve 668 is open (turned on) does not change significantly between when the filter is normal and when the filter is abnormal. Therefore, the period during which the atmospheric pressure release solenoid valve 668 is turned off can be an index of frequency of the air release operation. In this case, the period Tb2 at which the atmospheric pressure release solenoid valve 668 is turned off when the filter is abnormal is longer than the period Tb1 at which the atmospheric pressure release solenoid valve 668 is turned off when the filter is normal.

[0062] In other words, the frequency (time interval) of the operation of opening the air chamber 662 to the atmosphere reflects the degree of failure (clogging) of the filter 673. Based on this knowledge, in this embodiment, the following filter failure judgment is performed.

[0063] FIG. 9 is a flow chart showing a first example of filter defect judgment. In this filter defect judgment, when a defect occurs in the ejection of ink from the nozzles 311 of the ejection head 31 (step S101), steps S102 to S106 are executed. The occurrence of this ejection defect may be confirmed, for example, by an operator visually checking a defect in an image printed on the web W, or by the main control unit 711 recognizing the defect based on the result of capturing the image by a camera mounted on the inkjet printing machine 1. In the former case, for example, an operator commands the main control unit 711 to execute steps S102 to S106 via a user interface. In the latter case, the main control unit 711, having confirmed the defect, executes steps S102 to S106. During the execution of steps S102 to S106, the switching control unit 714 causes the switching solenoid valve 671 to execute the second connection operation, so that the air chamber 662 of the air tank 661 and the air layer B of the ink storage chamber 621 of the subtank 62 communicate with each other.

[0064] In step S102, the main control unit 711 outputs a test chart printing command to the discharge control unit 717. The discharge control unit 717 receives the test chart printing command and controls the discharge head 31 so that a predetermined test chart is printed. As a result, the discharge head 31 discharges ink from the nozzles 311 to print the test chart. This test chart is, for example, a uniform image having a predetermined gradation (50% or 100%). By causing the discharge head 31 to print the test chart, the discharge head 31 discharges a predetermined amount of ink per unit time.

[0065] As the ejection head 31 ejects ink by printing such a test chart, the pressure of the air layer B decreases. Therefore, control is executed in parallel to open the air chamber 662 communicating with the air layer B to the atmosphere, as shown in Fig. 8. In response to this, in step S103, the filter defect determination unit 712 measures the off period Toff (corresponding to the period Tb1 or Tb2 in Fig. 8) during which the atmospheric pressure release solenoid valve 668 is closed.

[0066] In step S104, the filter defect determination unit 712 reads out the reference period Trf from the storage unit 72 and compares the off period Toff measured in step S103 with the reference period Trf. This reference period Trf is a standard for determining whether a defect has occurred in the filter 673, and the reference period Trf is set in advance so that when a defect has occurred in the filter 673, the off period Toff is longer than the reference period Trf, and when no defect has occurred in the filter 673, the off period Toff is equal to or shorter than the reference period Trf.

[0067] Therefore, if the off period Toff measured in step S103 is longer than the reference period Trf (if "YES" in step S104), it is assumed that the cause of the ejection failure that occurred in step S101 is a defect in the filter 673. Therefore, the display control unit 719 causes the display 8 to display a notification to replace the filter 673 (step S105).

[0068] On the other hand, if the off period Toff measured in step S103 is equal to or shorter than the reference period Trf (if "NO" in step S104), it is assumed that the cause of the ejection failure that occurred in step S101 is something other than a defect in the filter 673. Therefore, the display control unit 719 causes the display 8 to display a notice that the cause of the ejection failure is something other than a defect in the filter 673 (step S106).

[0069] In the embodiment described above, ink is supplied from the ink storage chamber 621 (storage chamber) of the subtank 62 (ink tank) to the ejection head 31 in response to the ejection head 31 (recording head) ejecting ink. Therefore, when the ejection head 31 ejects ink in a state in which the atmospheric pressure release solenoid valve 668 (atmospheric pressure release valve) blocks the air tank 661 from the atmosphere, the air-liquid interface A in the ink storage chamber 621 of the subtank 62 drops, and the pressure (atmospheric pressure) of the air layer B above the air-liquid interface A drops. In response to this, the pressure (atmospheric pressure) of the air chamber 662 of the air tank 661 communicating with the ink storage chamber 621 of the subtank 62 is detected by the pressure sensor 669, and the operation of the atmospheric pressure release solenoid valve 668 is controlled based on the pressure detected by the pressure sensor 669, thereby adjusting the pressure of the air chamber 662 of the air tank 661. Therefore, when the pressure in the ink storage chamber 621 of the subtank 62 drops excessively due to the ejection of ink from the ejection head 31, the air tank 661 is opened to atmospheric pressure, and the pressure in the ink storage chamber of the ink tank rises to an appropriate pressure range. In this way, the shape of the ink meniscus formed in the ejection head 31 can be maintained appropriate.

[0070] At this time, if the filter 673 is defective, it takes time for the pressure in the air chamber 662 of the air tank 661 to follow the drop in pressure in the ink storage chamber 621 of the subtank 62. Therefore, the frequency with which the atmospheric pressure release solenoid valve 668 executes the operation of opening the air chamber 662 of the air tank 661 to the atmosphere decreases. In other words, there is a correlation between the frequency of the atmosphere release operation and a defect in the filter 673. Based on this knowledge, in this embodiment, a defect in the filter 673 is determined based on the frequency with which the atmospheric pressure release solenoid valve 668 executes the operation of opening the air chamber 662 to the atmosphere (the length of the off period Toff). In this way, it is possible to determine a defect in the filter 673 that is provided between the air tank 661 and the subtank 62 and removes foreign matter from the air.

[0071] Also provided is a storage unit 72 that holds a reference period Trf that is a standard for determining whether the filter 673 is defective based on the frequency of the atmosphere release operation (the length of the off period Toff). The filter defect determination unit 712 determines whether the filter 673 is defective based on a comparison between the reference period Trf and an off period Toff (blocking period) during which the atmospheric pressure release solenoid valve 668 blocks the air chamber 662 from the atmosphere Pa under the control of the pressure control unit 713. With this configuration, it is possible to determine whether the filter 673 is defective by simple control such as comparing the off period Toff with the reference period Trf.

[0072] Also provided is a discharge control unit 717 (test discharge control unit) that causes the discharge head 31 to execute test discharge (step S102) that discharges a predetermined amount of ink per unit time. With this configuration, it is possible to accurately determine whether the filter 673 is defective based on the frequency of the air release operation during the printing of the test chart (test discharge) in step S102.

[0073] During the period in which the discharge control unit 717 causes the discharge head 31 to perform test discharge (step S102), the filter defect determination unit 712 measures the off period Toff (step S103) and determines whether the filter 673 is defective based on a comparison between the off period Toff (measured cut-off period) and the reference period Trf (steps S104 to S106). With this configuration, it is possible to accurately determine whether the filter 673 is defective based on the result of measuring the frequency of the air release operation (length of the off period Toff) during the execution of the test discharge (step S102).

[0074] Furthermore, if the measured off period Toff is longer than the reference period Trf, the filter defect determination unit 712 determines that a defect has occurred in the filter 673 (steps S104 to S105). In this configuration, it is possible to determine whether the filter 673 is defective by a simple control such as confirming that the measured off period Toff is longer than the reference period Trf.

[0075] Furthermore, the discharge control unit 717 causes the discharge head 31 to perform test discharge (step S102) by causing the discharge head 31 to discharge ink so that a test chart (predetermined image) is printed on the web W. In this configuration, a defect in the filter 673 can be accurately determined based on the frequency of the air release operation during the execution of the test discharge (step S102).

[0076] 10 is a flowchart showing a second example of filter defect determination. In step S201, in the same manner as described above, the ejection head 31 ejects ink from the nozzles 311 to print a test chart. Then, in step S202, the filter defect determination unit 712 measures the off period Toff during which the atmospheric pressure release solenoid valve 668 is closed, and records the measured value in the memory unit 72.

[0077] In step S203, the filter defect determination unit 712 determines whether the measurement and recording of the off period Toff have been performed a predetermined number of times, which is equal to or greater than two. If the number of times the off period Toff has been measured and recorded is less than the predetermined number of times ("NO" in step S203), the process returns to step S202 and the measurement and recording of the off period Toff is continued.

[0078] When the number of measurements and recordings of the off period Toff reaches a predetermined number and recording of the predetermined number of off periods Toff is completed ("YES" in step S203), the filter defect determination unit 712 calculates the average value of the predetermined number of off periods Toff as the average off period Tav (step S204).

[0079] In step S205, the filter defect determination unit 712 compares the average off period Tav calculated in step S204 with the reference period Trf. If the average off period Tav is longer than the reference period Trf (if "YES" in step S205), the display control unit 719 causes the display 8 to display a notice to replace the filter 673 (step S206). On the other hand, if the average off period Tav calculated in step S204 is equal to or shorter than the reference period Trf (if "NO" in step S205), the display control unit 719 causes the display 8 to display a notice that the cause of the discharge defect is something other than a defect in the filter 673 (step S206).

[0080] Then, when the filter defect determination unit 712 resets the OFF period Toff recorded in the storage unit 72 (step S207), the process returns to step S201.

[0081] In this embodiment, during a period in which the discharge control unit 717 causes the discharge head 31 to perform test discharge (step S201), the filter defect determination unit 712 measures a number of off periods Toff (steps S202 to S203). Then, if the average off period Tav, which is the average value of the measured off periods Toff (measured cut-off period), is longer than the reference period Trf ("YES" in step S205), it is determined that a defect has occurred in the filter 673 ("YES" in step S205). In this configuration, a defect in the filter 673 can be determined by simple control such as confirming that the average value of the measured off periods Toff is longer than the reference period Trf.

[0082] Fig. 11 is a block diagram showing a second example of a controller that controls the ink supply mechanism of Fig. 3, and Fig. 12 is a flowchart showing a third example of a filter defect determination. The filter defect determination of Fig. 12 is executed by the controller of Fig. 11. The controller in the second example of Fig. 11 differs from the controller in the first example of Fig. 4 in that it does not use the reference period Trf and that the filter defect determination unit 712 has a machine learning model M.

[0083] In steps S301 and S302 of this filter defect judgment, the following parameters are Accumulative amount of ink supplied from the main tank 61 to the sub tank 62 The cumulative amount of ink ejected by the ejection head 31 Accumulated operating time of the pressure reducing pump 665 Temperature of the environment where the inkjet printer 1 is installed The machine learning model M is made to learn the relationship between the environmental conditions, including the above, and the frequency of the operation of releasing the air chamber 662 to the atmosphere by the atmospheric pressure release solenoid valve 668.

[0084] That is, in step S301, the machine learning model M learns training data (normal training data) indicating the environmental conditions and the frequency of the venting operation when a normal filter 673 is used. In addition, in step S302, the machine learning model M learns training data (abnormal training data) indicating the environmental conditions and the frequency of the venting operation when an abnormal filter 673 is used.

[0085] In step S303, the machine learning model M creates a classifier based on the learning results in steps S301 and S302. This classifier classifies the filter 673 into either normal or abnormal based on the values ​​of each parameter included in the environmental conditions.

[0086] In step S304, the filter defect determination unit 712 acquires the current values ​​of each parameter and inputs them to the machine learning model M. Then, the machine learning model M classifies the filter 673 as normal or abnormal based on the input values.

[0087] When the filter defect determination unit 712 determines that the filter 673 is abnormal based on the machine learning model M classifying the filter 673 as abnormal ("YES" in step S305), the display control unit 719 causes the display 8 to display a notification to replace the filter 673 (step S306). On the other hand, when the filter defect determination unit 712 determines that the filter 673 is normal based on the machine learning model M classifying the filter 673 as normal ("NO" in step S305), the process returns to step S304.

[0088] 11 and 12, it is possible to accurately determine whether the filter 673 is defective based on the learning results of the machine learning model M.

[0089] As described above, in this embodiment, the web W corresponds to an example of the "recording medium" of the present invention, the ejection head 31 corresponds to an example of the "recording head" of the present invention, the ink storage chamber 621 corresponds to an example of the "storage chamber" of the present invention, the sub-tank 62 corresponds to an example of the "ink tank" of the present invention, the air chamber 662 corresponds to an example of the "air chamber" of the present invention, the air tank 661 corresponds to an example of the "air tank" of the present invention, the pipes 672 and 663 correspond to an example of the "communicating pipe" of the present invention, the filter 673 corresponds to an example of the "filter" of the present invention, the atmospheric pressure release solenoid valve 668 corresponds to an example of the "atmospheric release valve" of the present invention, the pressure sensor 669 corresponds to an example of the "sensor" of the present invention, and the pressure control unit 713 corresponds to an example of a "pressure control unit" of the present invention, the filter defect judgment unit 712 corresponds to an example of a "filter defect judgment unit" of the present invention, the inkjet printing machine 1 corresponds to an example of an "inkjet printing machine" of the present invention, the reference period Trf corresponds to an example of a "reference period" of the present invention, the memory unit 72 corresponds to an example of a "memory unit" of the present invention, the off period Toff corresponds to an example of a "blocking period" of the present invention, the ejection control unit 717 corresponds to an example of a "test ejection control unit" of the present invention, the pressure reduction pump 665 corresponds to an example of a "pressure reduction pump" of the present invention, the main tank 61 corresponds to an example of a "main tank" of the present invention, and the machine learning model M corresponds to an example of a "machine learning model" of the present invention.

[0090] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the specific method for performing test ejection is not limited to printing the above-described test chart, and may be, for example, a method using a maintenance unit (FIG. 13).

[0091] Fig. 13 is a diagram showing a schematic configuration and operation of a maintenance unit provided in an inkjet printer. As shown in Fig. 13, the head unit 3 can be raised and lowered between a printing height h0, a retracted height h1 higher than the printing height h0, and a capping height h2 higher than the printing height h0 and lower than the retracted height h1. Meanwhile, the maintenance unit 9 can move in the X direction between a maintenance position La facing the head unit 3 from below, and a retracted position Lb retracted in the X direction relative to the head unit 3.

[0092] 13 shows a process from when the head unit 3 finishes printing until maintenance is performed on the head unit 3. In step S401, when printing is finished, the head unit 3 is located at the printing height h0, and the maintenance unit 9 is located at the retracted position Lb and retracts in the X direction from the head unit 3. Next, in step S402, when the head unit 3 rises to the retracted height h1, the maintenance unit 9 moves in the X direction from the retracted position Lb to the maintenance position La and faces the head unit 3 from below with a gap therebetween. In step S404, when the head unit 3 descends to the capping height H2, each ejection head 31 of the head unit 3 is covered (capped) by the maintenance unit 9, and the ejection heads 31 are moisturized.

[0093] In the inkjet printer 1 equipped with such a maintenance unit 9, a test ejection may be performed between steps S403 and S404, in which the ejection head 31 executes a test ejection in which a predetermined amount of ink is ejected per unit time. During the execution period of this test ejection, a defect in the filter 673 can be determined based on the result of measuring the frequency of the atmospheric pressure release solenoid valve 668 opening the air chamber 662 to the atmosphere.

[0094] Furthermore, the parameters that the machine learning model M learns do not need to be all of the above parameters, but may be just a part of them. [Industrial Applicability]

[0095] The present invention can be applied to all techniques for determining whether a filter provided between an air tank and an ink tank is defective. [Explanation of symbols]

[0096] 1. Inkjet printer 31...Discharge head 61…Main tank 62…Subtank 621…Ink storage chamber 661…Air tank 662…Air chamber 663…Plumbing 665…Reducing pump 668...Atmospheric pressure release solenoid valve 669...Pressure sensor 672…Plumbing 673…Filter 712...Filter defect determination unit 713... Pressure control section 717...Discharge control unit 72...Storage section M: Machine learning model Toff…Off period Trf…Reference period W…Web

Claims

1. a recording head that applies ink to a recording medium by ejecting ink; an ink tank having a storage chamber for storing ink, and supplying ink from the storage chamber to the recording head in response to the recording head ejecting ink; an air tank having an air chamber; a communication pipe that communicates the storage chamber of the ink tank with the air chamber of the air tank; a filter provided in the communication pipe between the ink tank and the air tank for removing foreign matter from the air in the communication pipe; an atmosphere release valve connected to the air chamber of the air tank and selectively performing one of an operation of opening the air chamber to the atmosphere and an operation of closing off the air chamber from the atmosphere; a sensor for detecting a pressure in the air chamber of the air tank; a pressure control unit that adjusts the pressure of the air chamber of the air tank by controlling an operation of the atmosphere release valve based on the pressure of the air chamber detected by the sensor; a filter defect determination unit that determines a defect of the filter based on a frequency with which the atmosphere release valve executes an operation of opening the air chamber to the atmosphere under the control of the pressure control unit; An inkjet printer equipped with

2. a storage unit that stores a reference period that is a criterion for determining whether the filter is defective based on the frequency, The inkjet printing machine according to claim 1 , wherein the filter defect determination unit determines whether the filter is defective based on a comparison between a blocking period, which is a period during which the atmospheric release valve blocks the air chamber from the atmosphere under the control of the pressure control unit, and the reference period.

3. 3. The inkjet printer according to claim 2, further comprising a test discharge control unit that causes the recording head to execute a test discharge in which a predetermined amount of ink is discharged per unit time.

4. 4. The inkjet printer according to claim 3, wherein, during a period in which the test ejection control unit causes the recording head to execute the test ejection, the filter defect determination unit measures the blocking period to obtain a measured blocking period, and determines whether the filter is defective based on a comparison between the measured blocking period and the reference period.

5. The inkjet printer according to claim 4 , wherein the filter defect determination unit determines that a defect has occurred in the filter when the measured blocking period is longer than the reference period.

6. 5. The inkjet printer according to claim 4, wherein during a period in which the test ejection control unit causes the recording head to execute the test ejection, the filter defect determination unit acquires a plurality of measured blocking periods, and if an average value of the plurality of measured blocking periods is longer than the reference period, determines that a defect has occurred in the filter.

7. 7. The inkjet printer according to claim 3, wherein the test ejection control unit causes the recording head to execute the test ejection by ejecting ink from the recording head so that a predetermined image is printed on the recording medium.

8. a pressure reducing pump connected to the air chamber of the air tank and configured to exhaust the air chamber under the control of the pressure control unit; a main tank for storing ink to be supplied to the ink tank; Further equipped with The inkjet printing machine according to claim 1, wherein the filter defect determination unit further comprises a machine learning model that learns the relationship between environmental conditions, including at least one of a cumulative amount of ink supplied from the main tank to the ink tank, a cumulative amount of ink ejected by the recording head, a cumulative operating time of the pressure reduction pump, and a temperature of the environment in which the inkjet printing machine is installed, and the frequency when the filter is normal, and the relationship between the environmental conditions and the frequency when the filter is defective, and determines whether the filter is defective based on the machine learning model and the frequency.

9. A step of applying ink to a recording medium by ejecting ink from a recording head; supplying ink to the recording head from a storage chamber of an ink tank that stores ink in response to the recording head ejecting ink; Detecting the pressure of an air chamber of an air tank, which communicates with the storage chamber via a communication pipe, by a sensor; a step of adjusting the pressure of the air chamber of the air tank by controlling the operation of an atmosphere release valve, which is connected to the air chamber of the air tank and selectively performs one of an operation of opening the air chamber to the atmosphere and an operation of closing off the air chamber from the atmosphere, based on the pressure of the air chamber detected by the sensor; determining whether a filter provided in the communication pipe between the ink tank and the air tank for removing foreign matter from the air in the communication pipe is defective; Equipped with The inkjet printing method, wherein a defect in the filter is determined based on a frequency with which the atmosphere release valve performs an operation of opening the air chamber to the atmosphere.

Images