Inkjet printing apparatus and method for estimating deterioration state

Abstract

Regarding inkjet printing equipment, the aim is to make it easy to determine the deterioration status of the degassing filter without requiring expensive equipment. [Solution] In an inkjet printing apparatus equipped with a degassing filter, when an instruction to perform a test print is given, the depressurization setting (S20), printing of a test pattern (S30), and imaging of the printed test pattern (S40) are repeated multiple times. The control unit controls the operation of the depressurization pump drive unit and the ink ejection head so that multiple test pattern prints are performed while sequentially changing the depressurization in response to a single instruction to perform a test print.

Description

Technical Field

[0001] The present invention relates to an inkjet printing apparatus, and more particularly to a technology for estimating the deterioration state of a deaeration filter that constitutes a deaeration module provided in an inkjet printing apparatus for removing gas contained in ink.

Background Art

[0002] Conventionally, inkjet printing apparatuses that perform printing on a print medium by ejecting ink onto the print medium (such as printing paper) using heat or pressure have been known. An inkjet printing apparatus includes a head unit composed of a plurality of heads having a large number of nozzles that eject ink (hereinafter referred to as "ink ejection heads"). One head unit is constituted by, for example, five ink ejection heads. A typical inkjet printing apparatus for color printing is provided with at least a head unit for K color (black), a head unit for C color (cyan), a head unit for M color (magenta), and a head unit for Y color (yellow). As described above, typically, a head unit is provided for each color. Further, an ink supply mechanism for supplying ink to the plurality of ink ejection heads constituting the head unit is provided for each ink color.

[0003] In the inkjet printing apparatus as described above, ink ejection failure may occur due to intrusion of foreign matter (such as dust) into the interior of the ink ejection head, drying of ink caused by evaporation of solvent near the nozzles, generation of air bubbles in the ink, and the like. When ejection failure occurs, defects in a printed image such as white streaks and missing dots occur.

[0004] Regarding ejection failures caused by the generation of air bubbles, examples include phenomena such as air bubbles remaining in the ink flow path obstructing ink supply, and air bubbles in the pressure chamber of the ink ejection head in piezo inkjet systems absorbing and attenuating the pressure wave necessary for ink ejection. Incidentally, the volume of gas that can be dissolved in ink decreases as the ink temperature rises. Gas that can no longer dissolve in the ink due to the rising ink temperature precipitates in the ink as air bubbles. Thus, rising ink temperature is one of the causes of air bubble generation.

[0005] To prevent the occurrence of ejection failures caused by the generation of air bubbles as described above, inkjet printing apparatuses have recently been provided that incorporate a degassing module in the ink supply mechanism for removing air bubbles from the ink. The degassing module includes a degassing filter consisting of numerous gas permeable membranes (typically hollow fiber membranes) that are permeable to the gas contained in the ink. In such a degassing module, degassing of the ink is performed by reducing the pressure outside the gas permeable membrane while ink is flowing inside the gas permeable membrane, or by reducing the pressure inside the gas permeable membrane while ink is flowing outside the gas permeable membrane. By performing ink degassing in this way, the occurrence of ejection failures caused by the generation of air bubbles is prevented.

[0006] However, degassing filters become clogged with prolonged use. In other words, the performance of degassing filters deteriorates over time. If a degassing filter with significantly reduced performance is used, the ink will not be sufficiently degassed, resulting in poor discharge due to the generation of air bubbles. Therefore, Japanese Patent Publication No. 5701886 describes a configuration comprising a gas pressure adjustment tank for adjusting the gas pressure acting on the degassing filter and a gas pressure changing mechanism for adjusting the air pressure inside the gas pressure adjustment tank, in which it is determined whether the degassing filter has reached the time for replacement based on the gradient of the change in air pressure inside the gas pressure adjustment tank when the gas pressure changing mechanism reduces the pressure inside the gas pressure adjustment tank. Furthermore, Japanese Patent Application Publication No. 2019-130511 describes detecting clogging inside the hollow fiber based on the air pressure difference between one end and the other end of the hollow fiber when the hollow fiber is depressurized, and the time it takes for the air pressure inside the hollow fiber to reach a certain pressure when opened to the atmosphere. Furthermore, a method is known in which the dissolved oxygen concentration of the ink is measured for a predetermined period of time, and the replacement time of the degassing filter is determined based on the change in the dissolved oxygen concentration over time. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5701886 [Patent Document 2] Japanese Patent Publication No. 2019-130511 [Overview of the project] [Problems that the invention aims to solve]

[0008] According to the method disclosed in Japanese Patent Publication No. 5701886, it is necessary to set a threshold (a threshold for comparison with the gradient of the pressure change in the gas pressure adjustment tank) used to determine whether or not the degassing filter has reached its replacement time, but it is extremely difficult to set this threshold appropriately. Similarly, it is extremely difficult to set an appropriate threshold in the method disclosed in Japanese Patent Application Publication No. 2019-130511. Therefore, it is not possible to easily grasp the deterioration state of the degassing filter using these methods. In addition, methods for measuring the dissolved oxygen concentration of ink require expensive equipment.

[0009] Therefore, the present invention relates to an inkjet printing apparatus and aims to enable easy determination of the deterioration state of a degassing filter without requiring expensive equipment. [Means for solving the problem]

[0010] The first invention is an inkjet printing apparatus, An ink ejection head that ejects ink toward the printing medium, An ink pipe which is the flow path for the ink supplied to the ink ejection head, A degassing module inserted into the ink piping is configured to degas the ink by having the gas contained in the ink flowing through the ink pass through the degassing filter in accordance with the negative pressure (degassing pressure) applied to the degassing filter, and the degassing of the ink is performed as the gas contained in the ink flowing through the ink piping passes through the degassing filter. A pressure reducing pump drive unit that drives the aforementioned pressure reducing pump, A control unit controls the operation of the pressure reducing pump drive unit and the operation of the ink ejection head so that multiple test patterns are printed while sequentially changing the pressure in response to a single instruction to execute a test print. It is characterized by being equipped with [the following features].

[0011] The second invention is, in the first invention, The control unit is characterized by including an appropriate depressurization estimation unit that estimates the appropriate pressure for depressurization.

[0012] The third invention is, in the second invention, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit further includes a mathematical model generation unit that generates a mathematical model representing the relationship between the lifespan of the degassing filter and a defect index value indicating the degree of defects in the degassing and the captured image, based on captured images obtained by the test printing performed at multiple points in time during a period when the degassing is maintained at normal pressure, except when the test pattern is printed.

[0013] The fourth invention is, in the third invention, The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by applying the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

[0014] The fifth invention is, in the third invention, The inkjet printing apparatus further includes a storage device that stores a data table which holds the defect index values ​​corresponding to the combination of the number of years of use of the degassing filter and the degassing, and which is a data table created based on the mathematical model. The appropriate degassing estimation unit is characterized by estimating the appropriate pressure by referring to the data table based on the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

[0015] The sixth invention is, in the third invention, The control unit further comprises a deterioration state estimation unit configured to estimate a deterioration state of the degassing filter based on the mathematical model.

[0016] In a seventh invention according to the sixth invention, The deterioration state estimation unit estimates the service life of the degassing filter when use of the degassing filter is continued in a state where the degassing pressure is maintained at the normal pressure by substituting the normal pressure as the degassing pressure and a defect allowable value that is a limit value allowable as the defect index value into the mathematical model.

[0017] In an eighth invention according to the third invention, The mathematical model is represented by the following formula.

Mathematical Expression

[0018] In a ninth invention according to the second invention, The inkjet printing apparatus further comprises an imaging device configured to capture a printed image formed on the print medium by ejecting ink from the ink ejection head, The control unit further comprises a mathematical model generation unit configured to generate a mathematical model representing a relationship between cumulative ink usage, the degassing pressure, and a defect index value indicating a degree of defect in captured images, based on captured images obtained by the imaging device capturing printed images formed on the print medium by execution of printing of the test pattern, the captured images being obtained by the test printing executed at a plurality of time points during a period in which the degassing pressure is maintained at the normal pressure except when the printing of the test pattern is executed.

[0019] In a tenth invention according to the ninth invention, The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by applying the actual cumulative ink usage and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

[0020] The eleventh invention is, in the ninth invention, The inkjet printing apparatus further comprises a storage device that stores a data table which holds the defect index values ​​corresponding to the combination of the cumulative ink usage and the depressurization, and which is a data table created based on the mathematical model. The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by referring to the data table based on the actual cumulative ink usage and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

[0021] The twelfth invention is, in the ninth invention, The control unit further includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on the mathematical model.

[0022] The 13th invention is, in the 12th invention, The deterioration state estimation unit is characterized by estimating the total amount of ink that can be used from the present moment onward if the degassing filter is used while the degassing pressure is maintained at the normal pressure, based on the cumulative ink usage obtained by applying the normal pressure as the degassing pressure and the defect tolerance value, which is the limit value of the allowable value as the defect index value, to the mathematical model, and the actual cumulative ink usage at the present moment.

[0023] The 14th invention is, in the 9th invention, The aforementioned mathematical model is characterized by being expressed by the following formula.

number

[0024] The 15th invention is, in the first invention, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit is characterized by including a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on an image obtained by capturing the printed image formed on the printing medium by the execution of printing the test pattern with the imaging device.

[0025] The 16th invention is, in the 15th invention, The inkjet printing apparatus further includes a storage device that pre-stores a plurality of image images corresponding to each of a plurality of different years of use or a plurality of different cumulative ink usage amounts. The deterioration state estimation unit is characterized by estimating the deterioration state of the degassing filter by comparing the image obtained immediately before with a plurality of image images held in the storage device.

[0026] The 17th invention relates to any of the first to 16th inventions, The multiple depressurization processes, each corresponding to the printing of multiple test patterns performed in response to a single instruction to execute the test print, are characterized by including a normal pressure and a negative pressure with an absolute value smaller than the normal pressure.

[0027] The 18th invention relates to any of the first to 16th inventions, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit further controls the operation of the ink ejection head so that the test pattern is printed N times (where N is an integer of 2 or more) while the degassing pressure is maintained at a constant negative pressure, and includes a defect cause determination unit that determines whether or not a defect is caused by deterioration of the degassing filter based on the location of a defect in each of the N captured images obtained by capturing the N printed images formed on the printing medium by the execution of the N times the test pattern is printed using the imaging device.

[0028] The 19th invention relates to any of the first to 16th inventions, The inkjet printing apparatus comprises at least four ink ejection heads, each ejecting black ink, cyan ink, magenta ink, and yellow ink, The ink piping and the degassing module are provided for each ink color. The control unit is characterized by controlling the operation of the at least four ink ejection heads so that multiple test patterns are printed for each ink color in response to a single instruction to perform a test print.

[0029] The 20th invention is a method for estimating the deterioration state of a degassing filter in an inkjet printing apparatus comprising: an ink ejection head for ejecting ink toward a printing medium; an ink pipe which is a flow path for ink supplied to the ink ejection head; a degassing filter comprising a plurality of gas permeable membranes permeable to gas contained in the ink; a degassing module inserted in the ink pipe, configured such that degassing of the ink is performed when gas contained in the ink flowing through the ink pipe passes through the degassing filter in accordance with the degassing pressure, which is the negative pressure applied to the degassing filter; and a degassing pump drive unit for driving the degassing pump, wherein the apparatus is equipped with a degassing module and a degassing pump drive unit for driving the degassing pump, the method for estimating the deterioration state of the degassing filter, A test pattern printing step in which the operation of the pressure reducing pump drive unit and the operation of the ink ejection head are controlled to print multiple test patterns while sequentially changing the pressure reduction, An estimation step in which the deterioration state of the degassing filter is estimated based on the printed image formed on the printing medium in the test pattern printing step, It is characterized by including. [Effects of the Invention]

[0030] According to the inkjet printing apparatus of the present invention, in an inkjet printing apparatus equipped with a degassing filter for degassing ink, in response to a single instruction to execute a test print, multiple test patterns are printed while sequentially changing the degassing pressure. At that time, by deliberately reducing the degassing pressure (absolute value of degassing pressure) to cause defects (e.g., nozzle defects) in the printed image, it becomes possible to easily estimate the deterioration state of the degassing filter from the degree of defects. Furthermore, it is unnecessary to measure the dissolved oxygen concentration of the ink. As a result, with respect to the inkjet printing apparatus, it is possible to easily grasp the deterioration state of the degassing filter without requiring expensive equipment. This prevents printing using a degassing filter with significantly reduced performance, and for example, it prevents the wasteful consumption of ink and printing media caused by reprinting due to ejection failures.

[0031] According to the deterioration state estimation method of the present invention, the same effects as those of the above-mentioned inkjet printing apparatus can be obtained. [Brief explanation of the drawing]

[0032] [Figure 1] This is a schematic diagram showing one example configuration of an inkjet printing apparatus according to one embodiment of the present invention. [Figure 2] This is a plan view showing one example of the configuration of the recording unit in the above embodiment. [Figure 3] This is a block diagram showing the hardware configuration of the print control device in the above embodiment. [Figure 4] The above embodiment is a schematic diagram showing one example of the configuration of an ink supply mechanism corresponding to one head unit. [Figure 5] This is a schematic diagram showing one example of the configuration of the degassing module in the above embodiment. [Figure 6] In the above embodiment, this figure shows an example of the relationship between the number of years of use of the depressurization and deaeration filters and the number of nozzle chips. [Figure 7] The graph above shows an example of the "relationship between degassing and the number of nozzle defects" for different states of the degassing filter in the above embodiment. [Figure 8] This graph shows an example of the relationship between the number of years of use of the degassing filter and the number of nozzle chips when focusing on one degassing operation in the above embodiment. [Figure 9] This figure illustrates the results of calculating the number of nozzle defects using a mathematical model in the above embodiment. [Figure 10] This figure shows an example of a data table created based on the mathematical model in the above embodiment. [Figure 11] The above embodiment is shown in a schematic diagram illustrating the relationship between the service life of the degassing filter, degassing, and the number of nozzle defects. [Figure 12] This is a block diagram showing the functional configuration of the control unit realized by the execution of a print control program in the print control device in the above embodiment. [Figure 13] The flowchart above shows the detailed procedure for the deterioration state estimation process in the above embodiment. [Figure 14] This figure shows an example of a test pattern in the above embodiment. [Figure 15] This figure shows an example of an image captured from a printed test pattern when nozzle chipping occurs in the above embodiment. [Figure 16] This diagram illustrates the operation of the deterioration state estimation process in the above embodiment. [Figure 17] This figure illustrates the estimation of the degradation state using a mathematical model in the above embodiment. [Figure 18] This figure compares the print output stoppage period when the degassing filter becomes unusable between the conventional technology and the above embodiment. [Figure 19]The above embodiment is a flowchart illustrating a preferred operational example regarding the use and replacement of the degassing filter. [Figure 20] This figure illustrates the calculation of the number of nozzle defects by linear interpolation in the first modified example of the above embodiment. [Figure 21] This figure illustrates the calculation of the number of nozzle defects by linear interpolation in the first modified example described above. [Figure 22] This figure illustrates the calculation of the total amount of ink that can be used from this point forward, in a second modified example of the above embodiment. [Figure 23] This is a block diagram showing the functional configuration of the control unit realized by the execution of a print control program in the print control device in the third modified embodiment described above. [Figure 24] This figure illustrates that, in the third modified example described above, the captured image is held in the captured image holding unit beforehand. [Figure 25] This figure illustrates a fourth modified example of the above embodiment, illustrating the comparison of printed images by a skilled professional using visual inspection. [Figure 26] This is a block diagram showing the functional configuration of the control unit realized by the execution of a print control program in the print control device in the fifth modified example of the above embodiment. [Figure 27] This diagram illustrates the determination of the cause of the defect in the fifth modified example described above. [Figure 28] This diagram illustrates the determination of the cause of the defect in the fifth modified example described above. [Modes for carrying out the invention]

[0033] An embodiment of the present invention will be described below with reference to the attached drawings.

[0034] <1. Overall configuration of the printing system> Figure 1 is a schematic diagram showing one configuration example of an inkjet printing apparatus 10 according to one embodiment of the present invention. This inkjet printing apparatus 10 consists of a printing control device 100, which is a computer, and a printing press body 200. The printing press body 200 includes a paper delivery unit 21 that supplies printing paper (e.g., roll paper) PA, which is the printing medium, a printing mechanism 20 that performs printing on the printing paper PA, and a paper winding unit 28 that winds up the printed printing paper PA. The printing mechanism 20 includes a first drive roller 22 for transporting the printing paper PA into the mechanism, a plurality of support rollers 23 for transporting the printing paper PA inside the printing mechanism 20, a recording unit 24 for recording a printed image on the printing paper PA, a drying mechanism 25 for drying the printing paper PA on which the printed image has been recorded, an imaging device (e.g., an inline scanner) 26 for capturing an image of the printed image (printed printing paper PA), and a second drive roller 27 for outputting the printing paper PA from inside the printing mechanism 20. The captured image (image data) 31 obtained by capturing the print image with the imaging device 26 is sent to the print control device 100.

[0035] The print control device 100 controls the operation of the printing press body 200 configured as described above. When the print control device 100 is given a command to print output, the print control device 100 controls the operation of the printing press body 200 so that the printing paper PA is transported from the paper feeding unit 21 to the paper winding unit 28. First, the recording unit 24 prints on the printing paper PA, then the drying mechanism 25 dries the printing paper PA, and finally, if necessary, the imaging device 26 captures the printed image.

[0036] Figure 2 is a plan view showing one example configuration of the recording unit 24. As shown in Figure 2, the recording unit 24 consists of a K-color head unit 2K, a C-color head unit 2C, an M-color head unit 2M, and a Y-color head unit 2Y, which are arranged in a row in the transport direction (sub-scanning direction) of the printing paper PA. Each head unit 2 consists of a plurality of ink ejection heads (print heads) 240 arranged in a staggered pattern. Each ink ejection head 240 contains a number of nozzles (not shown in Figure 2) that eject ink. Each nozzle of the ink ejection head 240 included in the K-color head unit 2K ejects K-color ink, each nozzle of the ink ejection head 240 included in the C-color head unit 2C ejects C-color ink, each nozzle of the ink ejection head 240 included in the M-color head unit 2M ejects M-color ink, and each nozzle of the ink ejection head 240 included in the Y-color head unit 2Y ejects Y-color ink.

[0037] <2. Hardware configuration of the print control device> Figure 3 is a block diagram showing the hardware configuration of the print control device 100. As shown in Figure 3, the print control device 100 includes a main unit 110, an auxiliary storage device 121, an optical disc drive 122, a display unit 123, a keyboard 124, and a mouse 125. The main unit 110 includes a CPU 111, memory 112, a first disk interface unit 113, a second disk interface unit 114, a display control unit 115, an input interface unit 116, and a network interface unit 117. The CPU 111, memory 112, first disk interface unit 113, second disk interface unit 114, display control unit 115, input interface unit 116, and network interface unit 117 are connected to each other via a system bus. The auxiliary storage device 121 is connected to the first disk interface unit 113. The auxiliary storage device 121 is a magnetic disk drive or the like. The optical disc drive 122 is connected to the second disk interface unit 114. An optical disc 19, such as a CD-ROM or DVD-ROM, which is a computer-readable recording medium, is inserted into the optical disc drive 122. A display unit (display device) 123 is connected to the display control unit 115. The display unit 123 is a liquid crystal display or the like. The display unit 123 is used to display information desired by the operator. A keyboard 124 and a mouse 125 are connected to the input interface unit 116. The keyboard 124 and mouse 125 are used by the operator to input instructions to this print control device 100. The network interface unit 117 is connected to the network (communication line) 4.

[0038] The auxiliary storage device 121 stores a print control program (a program for controlling the execution of printing processes by the printing press 200) P. The CPU 111 reads the print control program P stored in the auxiliary storage device 121 into the memory 112 and executes it, thereby realizing various functions of the print control device 100. The memory 112 includes RAM and ROM. The memory 112 functions as a work area for the CPU 111 to execute the print control program P stored in the auxiliary storage device 121. The print control program P is provided stored on the above-mentioned computer-readable recording medium (non-transient recording medium). That is, for example, the user purchases an optical disc 19 as a recording medium for the print control program P, inserts it into the optical disc drive 122, reads the print control program P from the optical disc 19, and installs it in the auxiliary storage device 121. Alternatively, the print control program P transmitted via the network 4 can be received by the network interface unit 117 and installed in the auxiliary storage device 121.

[0039] In the example shown in Figure 3, the print control device 100 is equipped with only one CPU 111 as a processor, but this is not the only option. Configurations using multiple processors, such as a configuration using multiple CPUs, can also be adopted. In addition to the CPU 111, other processors such as an MPU (Micro Processing Unit), GPU (Graphics Processing Unit), and DSP (Digital Signal Processor) can also be used. Furthermore, a combination of multiple types of processors can be used. Moreover, a configuration including an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit) can also be adopted.

[0040] <3. Ink supply mechanism> Figure 4 is a schematic diagram showing one example configuration of an ink supply mechanism corresponding to one head unit 2. The ink supply mechanism shown in Figure 4 includes a supply tank 52 for storing ink to be supplied to five ink ejection heads 240(1) to 240(5), a recovery tank 51 for storing ink recovered from the five ink ejection heads 240(1) to 240(5), a first pressure adjustment mechanism 512 for adjusting the air pressure in the recovery tank 51, a second pressure adjustment mechanism 522 for adjusting the air pressure in the supply tank 52, a supply pipe (supply manifold) 53 that forms a flow path for ink supplied from the supply tank 52 to the five ink ejection heads 240(1) to 240(5), a recovery pipe (recovery manifold) 54 that forms a flow path for ink recovered from the five ink ejection heads 240(1) to 240(5) to the recovery tank 51, and a return pipe (one of the "ink pipes" of the present invention) for returning ink from the recovery tank 51 to the supply tank 52. Example) 55 includes five supply branch pipes 530(1) to 530(5) that form ink flow paths from supply pipe 53 to each of the five ink ejection heads 240(1) to 240(5), five recovery branch pipes 540(1) to 540(5) that form ink flow paths from each of the five ink ejection heads 240(1) to 240(5) to recovery pipe 54, five supply control valves 531(1) to 531(5) corresponding to each of the five ink ejection heads 240(1) to 240(5), five recovery control valves 541(1) to 541(5) corresponding to each of the five ink ejection heads 240(1) to 240(5), a pump 56 inserted into the return pipe 55, a return control valve 57 inserted into the return pipe 55, and a degassing module 58 inserted into the return pipe 55. Each supply control valve 531 controls the flow of ink in the corresponding supply branch pipe 530, each recovery control valve 541 controls the flow of ink in the corresponding recovery branch pipe 540, and the return control valve 57 controls the flow of ink in the return pipe 55. A pump 56 pumps ink from the recovery tank 51 to the supply tank 52. A degassing module 58 degasses the ink flowing through the return pipe 55.In the above configuration, a circulation path is formed in which ink circulates in the following order: "supply tank 52 ~ supply piping 53 ~ supply branch piping 530 ~ ink ejection head 240 ~ recovery branch piping 540 ~ recovery piping 54 ~ recovery tank 51 ~ return piping 55 ~ supply tank 52".

[0041] <4. Degassing Module> Figure 5 is a schematic diagram showing one example configuration of the degassing module 58. The degassing module 58 consists of a casing 580 having an ink inlet 581, an ink outlet 582, and an exhaust port 583, a pressure reducing pump 585, and a pressure reducing pipe 586, one end of which is connected to the exhaust port 583 and the other end of which is connected to the pressure reducing pump 585. Inside the casing 580 is a degassing filter 584 made up of multiple hollow fiber membranes, which are gas permeable membranes that can permeate gas. Note that materials other than hollow fiber membranes may be used as gas permeable membranes as long as they are gas permeable materials. The pressure reducing pump 585 applies negative pressure to the degassing filter 584. One end of the degassing filter 584 (one end of each hollow fiber membrane) is connected to the ink inlet 581, and the other end of the degassing filter 584 (the other end of each hollow fiber membrane) is connected to the ink outlet 582. The ink inlet 581 and the ink outlet 582 are connected to the return pipe 55. As described above, in this embodiment, the degassing module 58 is interposed in the recirculation pipe 55. However, the present invention is not limited thereto, and a configuration in which the degassing module 58 is interposed in ink piping other than the recirculation pipe 55 (the flow path for ink ultimately supplied to the ink ejection head 240) can also be adopted.

[0042] Ink flowing into the degassing module 58 from the ink inlet 581 passes through the hollow fiber membrane constituting the degassing filter 584 and flows out to the outside of the degassing module 58 from the ink outlet 582. When the pressure inside the casing 580 (but outside the degassing filter 584) decreases due to the operation of the depressurizing pump 585, gas (including bubbles) contained in the ink passing through the hollow fiber membrane permeates the membrane. In this way, the ink is degassed.

[0043] The operation of the depressurizing pump 585 is controlled by the depressurizing pump drive unit (depressurizing pump drive circuit) 29. The depressurizing pump drive unit 29 controls the operation of the depressurizing pump 585 according to the set pressure, which is the target negative pressure inside the casing 580. For example, if the set pressure for depressurization is -86 kPa (kilopascals), the depressurizing pump drive unit 29 drives the depressurizing pump 585 so that the actual depressurization is -86 kPa. Since depressurization is generally a negative pressure, in this specification, a large absolute value of depressurization is referred to as "large depressurization," and a small absolute value of depressurization is referred to as "small depressurization."

[0044] The inkjet printing apparatus 10 is equipped with a degassing module 58 as described above. In this embodiment, as will be described later, a process is performed to estimate the deterioration state of the degassing filter 584. Hereinafter, the series of processes for estimating the deterioration state of the degassing filter 584 will be referred to as the "deterioration state estimation process".

[0045] Incidentally, regarding the degassing module 58 described above, it is known that the greater the degassing pressure, the lower the dissolved oxygen concentration of the ink. Therefore, as long as the dissolved oxygen concentration of the ink remains within an appropriate range, increasing the degassing pressure is necessary to enhance the degassing effect of the ink. However, the greater the set pressure of the degassing pressure, the longer the time required from the start of depressurization by the depressurizing pump 585 to the generation of the desired degassing pressure. Furthermore, if the set pressure of the degassing pressure is set unnecessarily high, the depressurizing pump 585 will be subjected to a high load. If the depressurizing pump 585 remains under high load for a long period of time, it becomes difficult to generate and maintain the desired degassing pressure, and the depressurizing pump 585 will need to be replaced. Generally, the set pressure of the degassing pressure is determined taking the above factors into consideration.

[0046] <5. Mathematical Models> Generally, the degassing module 58 is used while maintaining a constant negative pressure (a negative pressure that allows for stable and effective degassing of ink and provides sufficient productivity in terms of print output). When nozzle defects (defects in the printed image caused by poor ink ejection from the nozzle) occur, cleaning or a correction process called "nozzle defect correction" (a process that corrects the density of the print data so that ink droplets that should be ejected by the defective nozzle are ejected from other nozzles) is performed. If the nozzle defects are not resolved by cleaning or the above correction process, the ink ejection head 240 or the degassing module 58 is replaced. For this reason, it is preferable to be able to estimate the deterioration state of the degassing filter 584 so that it is possible to predict when the degassing module 58 should be replaced. In this embodiment, the mathematical model described below is used to estimate the deterioration state of the degassing filter 584.

[0047] Regarding the degassing module 58, as described above, the greater the degassing pressure, the more effectively the ink is degassed. Therefore, the greater the degassing pressure, the less likely nozzle chipping is to occur, and the less the degassing pressure, the more likely nozzle chipping is to occur. Also, the greater the degree of deterioration of the degassing filter 584, the more likely nozzle chipping is to occur. In general, the degree of deterioration of the degassing filter 584 increases with the number of years of use, so the longer the degassing filter 584 has been used, the more likely nozzle chipping is to occur. Based on the above, the relationship between degassing pressure, the number of years of use of the degassing filter 584, and the number of chipped nozzles (the number of chipped nozzles that occur when printing a predetermined test pattern) is as shown in Figure 6, for example.

[0048] The example shown in Figure 6 is an example of an inkjet printing apparatus 10 in which the depressurization pressure is normally maintained at -86kPa. In this example, at 2.0 years of use, the number of nozzle defects is 0 when the depressurization pressure is maintained at -86kPa. When the depressurization pressure is changed to -71kPa, the number of nozzle defects becomes 2, and when the depressurization pressure is changed to -56kPa, the number of nozzle defects becomes 10. In this invention, in order to understand the deterioration state of the degassing filter 584, a method is adopted in which the depressurization pressure is deliberately made lower than normal to cause nozzle defects. Note that the constant negative pressure as the depressurization pressure under normal conditions is called the "normal pressure," and in this embodiment (including modified examples), it is assumed that the normal pressure is set to -86kPa.

[0049] Figure 7 is a graph showing an example of the relationship between degassing and the number of nozzle chips for different conditions of the degassing filter 584. The dotted line labeled 61 shows the above relationship for a new degassing filter 584, the solid line labeled 62 shows the above relationship for a degassing filter 584 in a state of prolonged use, and the thick dotted line labeled 63 shows the above relationship for a degassing filter 584 in a state of unusable condition. As the degassing filter 584 continues to be used, the relationship between degassing and the number of nozzle chips gradually changes from the relationship shown by the dotted line labeled 61 to the relationship shown by the solid line labeled 62, and then to the relationship shown by the thick dotted line labeled 63.

[0050] Furthermore, focusing on a single degassing process, the relationship between the service life of the degassing filter 584 and the number of nozzle chips can be represented, for example, by the curve labeled 65 in Figure 8. From Figure 8, it can be seen that the number of nozzle chips increases exponentially as the service life of the degassing filter 584 increases.

[0051] Based on the above, in this embodiment, the relationship between the service life of the degassing filter 584, depressurization, and the number of nozzle chips is represented by a mathematical model, and as will be described in detail later, the service life of the degassing filter 584 and the appropriate pressure for depressurization are estimated using this mathematical model. In this specification, the number of years from the start of use of the degassing filter 584 to the point in time when the degassing filter 584 becomes unusable when the depressurization is set to normal pressure is referred to as the "service life."

[0052] In this embodiment, the mathematical model is represented by the following equation (1).

number

[0053] The mathematical model is generated for each device (for each individual inkjet printing device 10). That is, the values ​​of the coefficients (a1, a2, b1, b2, c1, and c2) in equation (1) above differ for each device. The values ​​of the coefficients are determined for each device using data obtained from test prints performed at multiple points in time during the period when depressurization is maintained at normal pressure. For example, if test prints are performed using three different negative pressures as depressurization at each of three time points, nine data points are obtained that combine the years of use of the degassing filter 584, depressurization, and the number of nozzle defects. Then, the values ​​of each coefficient are calculated using these nine data points, for example, by the least squares method.

[0054] The following are specific examples of the values ​​of each coefficient obtained using data from test prints performed at multiple points in time. a1:0.00750878 a2:0.00369934 b1:0.03753298 b2:8.62371719 c1:-0.8330769 c2:-1.8135592

[0055] Figure 9 shows the results of calculating the number of nozzle failures corresponding to four types of negative pressure (-56kPa, -71kPa, -86kPa, -92kPa) at three time points (0.1 years, 2.0 years, and 4.6 years) using equation (1) above, where the values ​​of each coefficient are set to the values ​​of the specific example above. In this example, the degassing filter 584 has been used continuously since the start of use, with the degassing pressure maintained at the normal pressure (-86kPa), except during test printing. In Figure 9, the dotted line labeled 67 shows the number of nozzle failures in the original data (data obtained from test printing), the dotted line labeled 68 shows the number of nozzle failures calculated using the mathematical model, and the dotted line labeled 69 shows the error between the number of nozzle failures in the original data and the number of nozzle failures calculated using the mathematical model (the value obtained by subtracting the number of nozzle failures in the original data from the number of nozzle failures calculated using the mathematical model). From Figure 9, it can be seen that the number of nozzle failures is estimated with relatively good accuracy based on the mathematical model.

[0056] Once the mathematical model is generated, a data table like the one shown in Figure 10 can be created based on that mathematical model. This data table holds the number of nozzle failures corresponding to combinations of the degassing filter 584's service life in 0.5-year increments and depressurization in 5 kPa increments. For "number of nozzle failures corresponding to combinations of service life and depressurization" that are not held in the data table, they can be calculated, for example, by linear interpolation. In this way, the number of nozzle failures corresponding to any combination of service life and depressurization can be calculated from the data table rather than directly from the mathematical model.

[0057] Figure 11 is a schematic diagram showing the relationship between the service life of the degassing filter 584, depressurization, and the number of nozzle chips. From Figure 11, it can be seen that if nozzle chipping occurs after a certain number of service years, increasing the depressurization can at least temporarily prevent further nozzle chipping.

[0058] In this embodiment, the relationship between the service life of the degassing filter 584, depressurization, and the number of nozzle defects is represented by a mathematical model as described above, but the present invention is not limited thereto. For example, the relationship between the service life of the degassing filter 584, depressurization, and the size (area) of the largest nozzle defect may also be represented by a mathematical model. That is, it is preferable that the relationship between the service life of the degassing filter 584, depressurization, and a value indicating the degree of defects in the captured image (a captured image obtained by capturing a printed image formed on the printing paper PA by test printing with the imaging device 26) (hereinafter referred to as the "defect index value") be represented by a mathematical model.

[0059] <6. Degradation State Estimation Process (Degradation State Estimation Method)> Figure 12 is a block diagram showing the functional configuration of the control unit 150, which is realized when the print control program P is executed in the print control device 100. However, Figure 12 only shows the components related to the degradation state estimation process. As shown in Figure 12, the control unit 150 includes a continuous test print execution control unit 151, a mathematical model generation unit 152, a degradation state estimation unit 153, and an appropriate depressurization estimation unit 154. The mathematical model generation unit 152 includes an image analysis unit 1521. The detailed procedure of the degradation state estimation process will be described below with reference to the flowcharts shown in Figures 12 and 13.

[0060] First, the operator issues an instruction to perform a test print (step S10). For example, when various menus for controlling the operation of the printing press 200 are displayed on the display unit 123 of the print control device 100 (see Figure 3), the operator selects a menu that instructs the operator to perform a test print for the deterioration state estimation process.

[0061] When a test print execution command is issued, the processes described in steps S20 to S40 below are repeated multiple times. In step S20, the depressurization setting is performed. If the processes in steps S20 to S40 are repeated three times, the first, second, and third depressurizations will be set to different negative pressures. In this case, for example, the depressurization will be set to -56kPa in the first instance, -71kPa in the second instance, and -86kPa in the third instance. Thus, the multiple depressurizations set sequentially for a single test print execution command include normal pressure (-86kPa) and negative pressures with absolute values ​​smaller than normal pressure (-56kPa, -71kPa). In step S20, the continuous test print execution control unit 151 controls the operation of the pressure reducing pump drive unit 29 so that the depressurization settings are performed as described above.

[0062] After depressurization is set, the continuous test print execution control unit 151 controls the operation of the ink ejection head 240 that constitutes the recording unit 24, thereby printing a predetermined test pattern (step S30). In this embodiment, in step S30, a test pattern for detecting nozzle defects is printed for each ink color. Figure 14 shows an example of a test pattern 71 printed in step S30. As shown in Figure 14, the test pattern 71 is composed of a plurality of linear patterns 710. Each linear pattern 710 is a pattern formed by the ejection of ink from a corresponding nozzle. In reality, the test pattern 71 is composed of more linear patterns 710 than shown in Figure 14. For example, if one head unit 2 contains 24,000 nozzles, the test pattern 71 for one color is composed of 24,000 linear patterns 710.

[0063] After the test pattern 71 is printed, the imaging device 26 captures an image of the printed test pattern 71 based on the control of the continuous test print execution control unit 151 (step S40). The captured image (image data) 31 obtained by capturing the printed image of the test pattern 71 by the imaging device 26 is sent to the control unit 150.

[0064] Since the process described in steps S20 to S40 is repeated multiple times, multiple captured images 31 for each color are provided to the control unit 150 for each test print execution instruction. If the process described in steps S20 to S40 is repeated three times, then three captured images 31 for each color (in the above example, an captured image 31 corresponding to -56kPa, an captured image 31 corresponding to -71kPa, and an captured image 31 corresponding to -86kPa) are provided to the control unit 150 for each test print execution instruction.

[0065] Subsequently, the image analysis unit 1521 within the mathematical model generation unit 152 performs analysis of the captured images 31 (step S50). Specifically, in step S50, the number of nozzle defects is counted for each captured image 31. In this regard, an captured image 31 when no nozzle defects occur is as shown in Figure 14. In contrast, an captured image 31 when nozzle defects occur is as shown in Figure 15, for example. In the example shown in Figure 15, nozzle defects occur in the parts labeled 711 and 712 (the linear pattern 710 is not printed properly). Therefore, in this example, the number of nozzle defects is 2.

[0066] After the captured image 31 has been analyzed, the mathematical model generation unit 152 generates the mathematical model 32 described above (step S60). In order to generate the mathematical model 32, data from multiple time points in time is required. Therefore, the processes in steps S10 to S50 must be executed multiple times before the process in step S60 is executed. For example, in one example of operation, as shown in Figure 16, the processes in steps S10 to S50 are executed in year 0.1 and year 0.3, and then the processes in steps S10 to S80 are executed in year 0.5. As described above, the mathematical model 32 is a model that represents the relationship between the number of years used by the degassing filter 584, depressurization, and the number of nozzle defects. Therefore, in step S60, the mathematical model 32 is generated using multiple "data combining the number of years used by the degassing filter 584, depressurization, and the number of nozzle defects" obtained by printing test patterns using multiple types (for example, three types) of negative pressure as depressurization at each of multiple time points (three time points in the example shown in Figure 16) (the values ​​of each coefficient in equation (1) above are calculated). In the example shown in Figure 16, the degassing pressure is maintained at the normal pressure (-86kPa) from the time the degassing filter 584 is put into use until 0.5 years later, except when the test pattern is being printed.

[0067] As described above, the mathematical model generation unit 152 generates a mathematical model 32 that represents the relationship between the lifespan of the degassing filter 584, the degassing pressure, and the number of nozzle defects (defect index value) in the captured image 31, based on the captured image 31 obtained by capturing the printed image formed on the printing paper PA by the execution of printing the test pattern with the imaging device 26, and the captured image 31 obtained by test printing performed at multiple points in time during the period when degassing pressure is maintained at normal pressure, except when printing the test pattern. In this specification, the limit value (maximum value) that can be tolerated for the number of nozzle defects is defined as the "defect tolerance value". In this regard, although the number of nozzle defects will not actually be a negative value, the defect tolerance value may be a negative value.

[0068] After the mathematical model 32 is generated, the deterioration state estimation unit 153 estimates the deterioration state of the degassing filter 584 based on the mathematical model 32 (step S70). In this embodiment, specifically, the lifespan of the degassing filter 584 is estimated. Here, we assume that the values ​​of each coefficient in equation (1) above are the values ​​in the specific example above. In this case, if the above-mentioned defect tolerance value is set to -0.2, the lifespan of the degassing filter 584 when degassing is maintained at normal pressure is estimated to be 0.97 years by substituting -86 for x in equation (1) above and -0.2 for y in equation (1) above. In this regard, we assume that the "relationship between the service life of the degassing filter 584 and the number of nozzle chips" when degassing is maintained at normal pressure (-86kPa) is represented by the curve labeled 72 in Figure 17 based on the mathematical model 32 in equation (1) above. In this case, the value of the horizontal axis coordinate t1 at the position labeled 73 in Figure 17 is 0.97. In reality, the number of nozzle defects will never appear as a negative value, and the degassing filter 584 can be used continuously until nozzle defects actually occur. In this case, the defect tolerance value is set to -0.2 with the intention of providing a buffer, and in reality, even after 0.97 years have passed, it is considered that nozzle defects will not occur even if degassing is maintained at the normal pressure (-86kPa) for a short period of time.

[0069] As described above, the deterioration state estimation unit 153 estimates the lifespan of the degassing filter 584 if its use continues while the degassing pressure remains at the normal pressure, by applying the normal pressure as degassing pressure and the defect tolerance value to the mathematical model 32.

[0070] After the deterioration state of the degassing filter 584 is estimated, the appropriate degassing pressure estimation unit 154 estimates the appropriate pressure for degassing (the appropriate negative pressure to apply to the degassing filter 584) (step S80). In this embodiment, the appropriate pressure is defined as the negative pressure at which the number of nozzle defects equals the defect tolerance value at the present time. In other words, the appropriate pressure is defined as the negative pressure with the smallest absolute value that does not cause nozzle defects at the present time. Specifically, the appropriate pressure is calculated by substituting the actual number of years of use of the degassing filter 584 into t in equation (1) above, and substituting the defect tolerance value into y in equation (1) above. In this way, the appropriate degassing pressure estimation unit 154 estimates the appropriate pressure by applying the actual number of years of use of the degassing filter 584 and the defect tolerance value to the mathematical model 32.

[0071] In this embodiment, the test pattern printing step is performed in steps S20 and S30, and the estimation step is performed in step S80.

[0072] <7. What to do when the degassing filter becomes unusable> According to conventional methods (methods disclosed in Japanese Patent Publication No. 5701886 and Japanese Patent Publication No. 2019-130511), it is possible to determine whether or not a degassing filter has reached the time for replacement. However, when a degassing filter actually becomes unusable (a state in which discharge failure occurs due to a deterioration in the performance of the degassing filter), it is not always possible to immediately replace the degassing filter with a new one. This is because the user may not have a new degassing filter on hand, nor may they be able to immediately secure a worker to replace the degassing filter. This will be explained with reference to part A of Figure 18. For example, suppose the degassing filter becomes unusable at time t91. In this case, for the reasons mentioned above, it is not always possible to start the degassing filter replacement work from time t91, and the degassing filter replacement work may be carried out, for example, between time t92 and time t93. In this example, print output cannot be performed throughout the period from time t91 to time t93. Thus, with conventional methods, if the degassing filter becomes unusable, printing output is effectively impossible until the degassing filter is replaced, resulting in a significant decrease in printing productivity.

[0073] Therefore, in this embodiment, if the degassing filter 584 becomes unusable during the period when the degassing pressure is maintained at the normal pressure, the use of the degassing filter 584 is continued by changing the degassing pressure considering the appropriate pressure estimated in step S80 of Figure 13. In this regard, in the example shown in Figure 17, if time t1 is the present time, the appropriate pressure is estimated to be -86kPa. In such a case, if the use of the degassing filter 584 is continued by maintaining the degassing pressure at -86kPa, nozzle chipping will occur after a short period of time. Therefore, it is advisable to set the degassing pressure to a negative pressure greater than -86kPa until the replacement work of the degassing filter 584 is actually started. The curve labeled 74 in Figure 17 represents the "relationship between the number of years of use of the degassing filter 584 and the number of nozzle chips" obtained by substituting -92 for x in the mathematical model 32 of equation (1) above. In this embodiment, the mathematical model 32 is generated when the inkjet printing device 10 is in operation with the depressurization set to the normal pressure (-86kPa). Therefore, the curve labeled 74 does not represent the permanent relationship between the lifespan of the degassing filter 584 and the number of nozzle failures when the depressurization is changed from -86kPa to -92kPa. However, this curve allows us to grasp the short-term trend of the relationship between the lifespan of the degassing filter 584 and the number of nozzle failures after changing the depressurization from -86kPa to -92kPa. From the curve labeled 72 and the curve labeled 74 in Figure 17, it can be seen that changing the depressurization from -86kPa to -92kPa delays the point at which nozzle failures occur. In other words, the lifespan of the degassing filter 584 can be extended.

[0074] As described above, in this embodiment, even if the degassing filter 584 becomes unusable during the period when the degassing pressure is maintained at the normal pressure, it is possible to temporarily continue using the degassing filter 584 by changing the degassing pressure to a negative pressure greater than the appropriate pressure. As mentioned above, the larger the set pressure of the degassing pressure, the longer the time required from the start of depressurization by driving the depressurizing pump 585 to the generation of the desired degassing pressure. Therefore, changing the degassing pressure from -86kPa to -92kPa will reduce printing productivity compared to normal conditions. However, in the past, when the degassing filter 584 became unusable, printing output was practically impossible until the replacement of the degassing filter 584 was completed (see part A in Figure 18), whereas in this embodiment, even if the degassing filter 584 becomes unusable, printing output can be performed, albeit with reduced productivity, until the replacement work of the degassing filter 584 is started. This will be explained with reference to part B in Figure 18. For example, let's assume that the degassing filter 584 becomes unusable at time t11. At this time, by changing the degassing pressure setting as described above, print output can be performed even after time t11, until time t12 when the degassing filter 584 replacement work actually begins. Then, print output will be disabled only during the period when the degassing filter 584 replacement work is actually being performed (the period from time t12 to time t13).

[0075] Based on the above, a preferred operational example regarding the use and replacement of the degassing filter 584 will be described with reference to Figure 19. First, the inkjet printing device 10 is introduced (step S110). That is, the use of a new degassing filter 584 begins. Next, the degassing pressure is set to -86kPa (step S120). Then, with the degassing pressure set to -86kPa, printing output is performed as needed. Test printing is also performed at appropriate points in order to generate the mathematical model 32. Throughout the period during which the degassing filter 584 is used with the degassing pressure set to -86kPa, it is determined at any time whether the degassing filter 584 is unusable or not (step S130). As a result, if the degassing filter 584 is unusable, the degassing pressure is set to -92kPa (step S140). That is, the degassing pressure is changed from -86kPa (normal pressure) to -92kPa (negative pressure with a larger absolute value than the normal pressure). Then, with the degassing pressure set to -92kPa, printing is performed as needed. After the degassing pressure is set to -92kPa, it is determined as needed whether or not the degassing filter 584 is ready for replacement (step S150). If the degassing filter 584 is ready for replacement, it is actually replaced (step S160). After that, the degassing pressure is set to -86kPa (step S120). In other words, the degassing pressure is changed from -92kPa to -86kPa (normal pressure). In this way, it is possible to shorten the period during which printing output must be completely stopped when the degassing filter 584 needs to be replaced compared to conventional methods.

[0076] <8. Effects> According to this embodiment, in an inkjet printing apparatus 10 equipped with a degassing filter 584 for degassing ink, when the operator instructs the execution of a test print for deterioration state estimation processing, the test pattern is printed multiple times while sequentially changing the degassing pressure, and the number of nozzle defects is counted for each image captured of the printed test pattern 31. Based on the data obtained by performing such processing at multiple points in time, a mathematical model 32 is generated that represents the relationship between the service life of the degassing filter 584, the degassing pressure, and the number of nozzle defects (defect index value). In this regard, by appropriately including negative pressure that causes defects (nozzle defects) in the printed image in the multiple degassing pressures sequentially set when printing the test pattern, a mathematical model 32 is generated that can grasp the degree of increase in the number of nozzle defects over time. This makes it possible to easily estimate the deterioration state of the degassing filter 584. Furthermore, there is no need to measure the dissolved oxygen concentration of the ink. As described above, according to this embodiment, it is possible to easily grasp the deterioration state of the degassing filter 584 in the inkjet printing apparatus 10 without requiring expensive equipment. This prevents printing from being performed using a degassing filter 584 with significantly reduced performance, thus reducing wasted ink and PA paper consumption caused by reprinting due to, for example, ejection failures. In this way, it can contribute to achieving the SDGs (Sustainable Development Goals).

[0077] Furthermore, according to this embodiment, even if defects occur in the printed image due to deterioration of the degassing filter 584, it is possible to temporarily continue using the degassing filter 584 by increasing the set pressure of the degassing system. In other words, it is possible to shorten the period during which printing output must be completely stopped when the degassing filter 584 needs to be replaced compared to conventional methods. This prevents a significant decrease in printing productivity when the degassing filter 584 needs to be replaced.

[0078] <9. Variation> Modifications of the above embodiment will be described below.

[0079] <9.1 First variation> In the above embodiment, the lifespan of the degassing filter 584 and the appropriate pressure for degassing were determined directly from the mathematical model 32 (steps S70, S80 in Figure 13). However, the present invention is not limited thereto. In this modified example, the lifespan of the degassing filter 584 and the appropriate pressure for degassing are determined based on a data table as shown in Figure 10.

[0080] In this modified example, after the mathematical model 32 is generated (i.e., after the completion of step S60 in Figure 13), a data table is created based on the mathematical model 32. This data table is stored in the auxiliary storage device 121. Thus, the auxiliary storage device 121 stores a data table that holds the number of nozzle defects (defect index values) corresponding to the combination of the service life of the degassing filter 584 and degassing, and is created based on the mathematical model 32.

[0081] After the data table is created, the deterioration state estimation unit 153 estimates the deterioration state of the degassing filter 584 based on the data table (step S70 in Figure 13). In this modified example, specifically, the lifespan of the degassing filter 584 is estimated. By linear interpolation of the portion of the data table shown in Figure 20, the number of nozzle defects corresponding to the combination of the service life of the degassing filter 584 in 0.1-year increments and the depressurization in 1 kPa increments is calculated, and the values ​​shown in Figure 21 are obtained. Here, if the above-mentioned defect tolerance value is set to 0, the normal pressure for depressurization is -86 kPa, so from Figure 21, the lifespan is estimated to be approximately 1.2 years.

[0082] As described above, in this modified example, the deterioration state estimation unit 153 estimates the lifespan of the degassing filter 584 if its use is continued while the degassing pressure is maintained at the normal pressure, by referring to a data table based on the normal pressure as the degassing pressure and the defect tolerance value.

[0083] After the deterioration state of the degassing filter 584 is estimated, the appropriate degassing pressure estimation unit 154 estimates the appropriate pressure for degassing (step S80 in Figure 13). In this modified example as well, the appropriate pressure is defined as the negative pressure at which the number of nozzle defects equals the defect tolerance value at the present time. Here, if the actual service life of the degassing filter 584 is 1.1 years, and the above-mentioned defect tolerance value is set to 0, the appropriate pressure is estimated to be -85kPa from Figure 21.

[0084] As described above, in this modified example, the appropriate depressurization estimation unit 154 estimates the appropriate pressure by referring to a data table based on the actual service life and defect tolerance of the degassing filter 584.

[0085] <9.2 Second variation> In the above embodiment, the deterioration state of the degassing filter 584 was estimated by estimating the lifespan of the degassing filter 584. However, the present invention is not limited thereto. In this modified example, the deterioration state of the degassing filter 584 is estimated by estimating the total amount of ink that can be used from the present time onward.

[0086] In this modified example, the relationship between the cumulative ink usage for each ink color in this inkjet printer 10, depressurization, and the number of nozzle defects (defect index value) is represented by mathematical model 32. Mathematical model 32 in this modified example is represented by the following equation (2).

number

[0087] As can be seen from equation (2) above, in this modified example, the mathematical model 32 is generated using cumulative ink usage data instead of the usage year data in the above embodiment. That is, in this modified example, the mathematical model generation unit 152 generates a mathematical model 32 that represents the relationship between cumulative ink usage, depressurization pressure, and the number of nozzle defects (defect index value) in the captured image 31, based on the captured image 31 obtained by capturing the printed image formed on the printing paper PA by the execution of printing a test pattern with the imaging device 26, and the captured image 31 obtained by test printing performed at multiple points in time during a period when depressurization pressure is maintained at normal pressure except when printing a test pattern is performed.

[0088] In this modified example, in step S70 of Figure 13, the total amount of ink available from the present moment onward is estimated based on the mathematical model 32. More specifically, by substituting the normal pressure as depressurization for x in equation (2) above, and substituting the aforementioned defect tolerance value for y in equation (2) above, the cumulative ink usage up to the point in time when the degassing filter 584 becomes unusable if depressurization is maintained at the normal pressure is calculated. Then, by subtracting the calculated cumulative ink usage from the actual cumulative ink usage at the present moment, the total amount of ink available from the present moment onward, assuming depressurization is maintained at the normal pressure, is calculated. Thus, in this modified example, the deterioration state estimation unit 153 estimates the total amount of ink available from the present moment onward, assuming continued use of the degassing filter 584 while depressurization is maintained at the normal pressure, based on the cumulative ink usage obtained by applying the normal pressure as depressurization and the defect tolerance value to the mathematical model 32, and the actual cumulative ink usage at the present moment.

[0089] For example, based on the mathematical model 32 of equation (2) above, let's assume that the "relationship between cumulative ink usage and the number of nozzle defects" when depressurization is maintained at normal pressure (-86kPa) is represented by the curve labeled 81 in Figure 22. In this case, if the defect tolerance is set to -0.2, the value of the horizontal axis coordinate u2 at the position labeled 82 in Figure 22 is calculated as the cumulative ink usage up to the point in time when the degassing filter 584 becomes unusable when depressurization is maintained at normal pressure. Here, if the actual cumulative ink usage at the present time is u1, the amount of ink corresponding to the length of the arrow labeled 83 in Figure 22 is calculated as the total amount of ink that can be used from the present time onward if the use of the degassing filter 584 continues while depressurization is maintained at normal pressure.

[0090] In step S80 of Figure 13, the appropriate pressure for depressurization is estimated based on the mathematical model 32. More specifically, the appropriate pressure is calculated by substituting the actual cumulative ink usage at the present time into u in equation (2) above, and the defect tolerance value into y in equation (2) above. Thus, in this modified example, the appropriate depressurization estimation unit 154 estimates the appropriate pressure by applying the actual cumulative ink usage and the defect tolerance value to the mathematical model 32.

[0091] Furthermore, the estimation of the total amount of ink available for use from this point forward and the estimation of the appropriate pressure may be performed using a data table created based on mathematical model 32, in the same manner as the first modification described above. <9.3 Third Variation> In the above embodiment, a mathematical model 32 was used to estimate the deterioration state of the degassing filter 584. However, the present invention is not limited thereto. In this modified example and the fourth modified example described later, the deterioration state of the degassing filter 584 is estimated without using the mathematical model 32.

[0092] Figure 23 is a block diagram showing the functional configuration of the control unit 150, which is realized in this modified example when the print control program P is executed in the print control device 100 (similar to Figure 12, only the components related to the degradation state estimation process are shown). As shown in Figure 23, the control unit 150 includes a continuous test print execution control unit 151, a degradation state estimation unit 153, and an captured image holding unit 155. The captured image holding unit 155 is realized by an auxiliary storage device 121 as hardware (see Figure 3).

[0093] The image retention unit 155 pre-stores multiple captured images 31 obtained by printing test patterns using multiple types of negative pressure as depressurization at multiple time points in time using another device. For example, test patterns are printed annually using three types of negative pressure (-56kPa, -71kPa, -86kPa) in another device. In this case, as schematically shown in Figure 24, three captured images 31 corresponding to the three types of negative pressure for each year are pre-stored in the image retention unit 155. Information is also stored indicating which year's captured image 31, corresponding to the normal pressure (-86kPa), has a nozzle defect count equal to the defect tolerance value.

[0094] Under the above premise, the inkjet printing device 10 performs printing of multiple test patterns while sequentially changing the depressurization pressure. When the captured image 31 is held in the captured image holding unit 155 as shown in Figure 24, the test pattern is printed using three types of negative pressure (-56kPa, -71kPa, -86kPa). Then, the imaging device 26 captures three printed images corresponding to the three types of negative pressure, thereby obtaining three captured images 31. The deterioration state estimation unit 153 estimates the deterioration state of the degassing filter 584 by comparing these three captured images 31 with the multiple captured images 31 held in the captured image holding unit 155.

[0095] For example, if the number of nozzle defects in the captured image 31 held in the captured image holding unit 155 and corresponding to -86kPa is equal to the defect tolerance value, and the number of nozzle defects in the captured image 31 of the printed image obtained when a test pattern was printed with the depressurization set to -56kPa in this inkjet printing device 10 is equal to the number of nozzle defects in the captured image 31 held in the captured image holding unit 155 and corresponding to -56kPa in the second year, then it is estimated that if the degassing filter 584 is used continuously while the depressurization is maintained at the normal pressure (-86kPa), the degassing filter 584 will become unusable after three years.

[0096] As described above, in this modified example, multiple captured images 31 corresponding to multiple different years of use are stored in advance in the captured image holding unit 155 (auxiliary storage device 121), and the deterioration state estimation unit 153 estimates the deterioration state of the degassing filter 584 by comparing the captured image 31 obtained immediately beforehand (multiple captured images 31 obtained by printing test patterns using multiple types of negative pressure as degassing) with the multiple captured images 31 stored in the captured image holding unit 155.

[0097] Furthermore, by pre-holding multiple captured images 31 corresponding to each of several different cumulative ink usage amounts in the captured image holding unit 155, the deterioration state of the degassing filter 584 can also be estimated by comparing the most recently obtained captured image 31 with the multiple captured images 31 held in the captured image holding unit 155.

[0098] <9.4 Fourth variation> In this modified example, the deterioration state of the degassing filter 584 is estimated by visually comparing multiple printed images by an expert, without using mathematical model 32. The method is described below.

[0099] In this modified example, multiple printed images obtained by printing test patterns using multiple types of negative pressure as depressurization in another device are prepared in advance. For example, multiple printed images obtained by printing test patterns using three types of negative pressure (-56kPa, -71kPa, -86kPa) are prepared. In this regard, if the number of nozzle defects in the printed image obtained by printing a test pattern with the depressurization set to -86kPa in the third year in another device is equal to the defect tolerance value, then three printed images obtained by printing test patterns using those three types of negative pressure in the third year are prepared.

[0100] Under the above premise, the inkjet printer 10 performs printing of multiple test patterns while sequentially changing the depressurization pressure. In the above example, the test patterns are printed using three types of depressurization pressure (-56kPa, -71kPa, and -86kPa). Then, as shown in Figure 25, a skilled worker visually compares three pre-prepared printed images 35 with three printed images 36 obtained by printing the test patterns with the inkjet printer 10. This allows the skilled worker to estimate the deterioration state of the degassing filter 584.

[0101] <9.5 Fifth variation> As described above, if the degassing filter 584, whose performance has significantly deteriorated due to aging, is used as is, the ink will not be sufficiently degassed, resulting in ejection failures caused by the generation of air bubbles. However, ejection failures can also occur for reasons other than the deterioration of the degassing filter 584. Therefore, in this modified example, as shown in Figure 26, the control unit 150 is provided with a defect cause determination unit 156 that determines whether or not the ejection failure is caused by the deterioration of the degassing filter 584, in addition to the components in the above embodiment (see Figure 12).

[0102] When the operator selects a menu that instructs the execution of a process to determine the cause of the ejection failure, the defect cause determination unit 156 controls the operation of the ink ejection head 240, which constitutes the recording unit 24, so that multiple test patterns are printed while the depressurization pressure is set to a constant negative pressure (typically normal pressure). The defect cause determination unit 156 then determines whether or not the defect is caused by deterioration of the degassing filter 584, based on the location of the defect in each of the multiple captured images 31 obtained by capturing multiple printed images formed on the printing paper PA by the execution of multiple test patterns with the imaging device 26.

[0103] In the process of determining the cause of the ejection failure, for example, the printing of a test pattern 71 as shown in Figure 14 is repeated three times. This yields three captured images (first image, second image, and third image) 31. Now, let's assume that three captured images 31 as shown in Figure 27 have been obtained. In this case, the defect location 851 in the first image, the defect location 852 in the second image, and the defect location 853 in the third image are the same. When defects occur at specific locations in this way, the defect cause determination unit 156 determines that the defect (ejection failure) is due to a reason other than deterioration of the degassing filter 584. Next, let's assume that three captured images 31 as shown in Figure 28 have been obtained. In this case, the defect location 861 in the first image, the defect location 862 in the second image, and the defect location 863 in the third image are different from each other. When defects occur at random locations in this way, the defect cause determination unit 156 determines that the defect (ejection failure) is due to deterioration of the degassing filter 584.

[0104] According to this modified version, in addition to the same effects as the above embodiment, it is possible to determine whether or not a defect in the printed image is caused by deterioration of the degassing filter 584.

[0105] <10. Others> The present invention is not limited to the above embodiments (including modifications), and can be implemented with various modifications without departing from the spirit of the invention. For example, in the above embodiments (including modifications), an inkjet printing apparatus 10 that performs color printing was used. However, the present invention is not limited thereto, and an inkjet printing apparatus that performs monochrome printing may also be used. Also, in the above embodiments (including modifications), an inkjet printing apparatus 10 that uses water-based ink was used. However, the present invention is not limited thereto, and an inkjet printing apparatus that uses UV ink (ultraviolet-curing ink), such as an inkjet printing apparatus for label printing, may also be used. In this case, the printing mechanism 20 (see Figure 1) is provided with an ultraviolet irradiation mechanism that cures the UV ink on the printing paper PA by ultraviolet irradiation, instead of a drying mechanism 25.

[0106] <11. Addendum> Based on the above disclosures, an inkjet printing apparatus with the following configuration is also conceivable.

[0107] An ink ejection head that ejects ink toward the printing medium, An ink pipe which is the flow path for the ink supplied to the ink ejection head, A degassing module inserted into the ink piping is configured to degas the ink by having the gas contained in the ink flowing through the ink pass through the degassing filter in accordance with the negative pressure (degassing pressure) applied to the degassing filter, and the degassing of the ink is performed as the gas contained in the ink flowing through the ink piping passes through the degassing filter. A pressure reducing pump drive circuit that drives the aforementioned pressure reducing pump, Processor and The memory that stores the program and Equipped with, An inkjet printing apparatus in which the processor controls the operation of the pressure reducing pump drive circuit and the operation of the ink ejection head so that, in response to a single instruction to execute a test print, multiple test patterns are printed while sequentially changing the pressure reduction, based on the program stored in the memory.

[0108] <12. Summary of Embodiments> The first invention is an inkjet printing apparatus, An ink ejection head that ejects ink toward the printing medium, An ink pipe which is the flow path for the ink supplied to the ink ejection head, A degassing module inserted into the ink piping is configured to degas the ink by having the gas contained in the ink flowing through the ink pass through the degassing filter in accordance with the negative pressure (degassing pressure) applied to the degassing filter, and the degassing of the ink is performed as the gas contained in the ink flowing through the ink piping passes through the degassing filter. A pressure reducing pump drive unit that drives the aforementioned pressure reducing pump, A control unit controls the operation of the pressure reducing pump drive unit and the operation of the ink ejection head so that multiple test patterns are printed while sequentially changing the pressure in response to a single instruction to execute a test print. It is characterized by being equipped with [the following features].

[0109] The second invention is, in the first invention, The control unit is characterized by including an appropriate depressurization estimation unit that estimates the appropriate pressure for depressurization.

[0110] The third invention is, in the second invention, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit further includes a mathematical model generation unit that generates a mathematical model representing the relationship between the lifespan of the degassing filter and a defect index value indicating the degree of defects in the degassing and the captured image, based on captured images obtained by the test printing performed at multiple points in time during a period when the degassing is maintained at normal pressure, except when the test pattern is printed.

[0111] The fourth invention is, in the third invention, The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by applying the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

[0112] The fifth invention is, in the third invention, The inkjet printing apparatus further includes a storage device that stores a data table which holds the defect index values ​​corresponding to the combination of the number of years of use of the degassing filter and the degassing, and which is a data table created based on the mathematical model. The appropriate degassing estimation unit is characterized by estimating the appropriate pressure by referring to the data table based on the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

[0113] The sixth invention is, in the third invention, The control unit further includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on the mathematical model.

[0114] The seventh invention is, in the sixth invention, The deterioration state estimation unit is characterized by estimating the lifespan of the degassing filter in years if the degassing filter is used while the degassing pressure is maintained at the normal pressure, by applying the normal pressure as the degassing pressure and the defect tolerance value, which is the limit value of the allowable defect index value, to the mathematical model.

[0115] The eighth invention is, in the third invention, The aforementioned mathematical model is characterized by being expressed by the following formula.

number

[0116] The ninth invention is, in the second invention, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit further includes a mathematical model generation unit that generates a mathematical model representing the relationship between cumulative ink usage, the depressurization pressure, and a defect index value indicating the degree of defects in the captured image, based on captured images obtained by the test printing performed at multiple points in time during a period when the depressurization pressure is maintained at normal pressure, except when the test pattern is printed.

[0117] The tenth invention is, in the ninth invention, The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by applying the actual cumulative ink usage and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

[0118] The eleventh invention is, in the ninth invention, The inkjet printing apparatus further comprises a storage device that stores a data table which holds the defect index values ​​corresponding to the combination of the cumulative ink usage and the depressurization, and which is a data table created based on the mathematical model. The appropriate depressurization estimation unit is characterized by estimating the appropriate pressure by referring to the data table based on the actual cumulative ink usage and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

[0119] The twelfth invention is, in the ninth invention, The control unit further includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on the mathematical model.

[0120] The 13th invention is, in the 12th invention, The deterioration state estimation unit is characterized by estimating the total amount of ink that can be used from the present moment onward if the degassing filter is used while the degassing pressure is maintained at the normal pressure, based on the cumulative ink usage obtained by applying the normal pressure as the degassing pressure and the defect tolerance value, which is the limit value of the allowable value as the defect index value, to the mathematical model, and the actual cumulative ink usage at the present moment.

[0121] The 14th invention is, in the 9th invention, The aforementioned mathematical model is characterized by being expressed by the following formula.

number

[0122] The 15th invention is, in the first invention, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit is characterized by including a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on an image obtained by capturing the printed image formed on the printing medium by the execution of printing the test pattern with the imaging device.

[0123] The 16th invention is, in the 15th invention, The inkjet printing apparatus further includes a storage device that pre-stores a plurality of image images corresponding to each of a plurality of different years of use or a plurality of different cumulative ink usage amounts. The deterioration state estimation unit is characterized by estimating the deterioration state of the degassing filter by comparing the image obtained immediately before with a plurality of image images held in the storage device.

[0124] The 17th invention relates to any of the first to 16th inventions, The multiple depressurization processes, each corresponding to the printing of multiple test patterns performed in response to a single instruction to execute the test print, are characterized by including a normal pressure and a negative pressure with an absolute value smaller than the normal pressure.

[0125] The 18th invention relates to any of the first to 16th inventions, The inkjet printing apparatus further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head. The control unit further controls the operation of the ink ejection head so that the test pattern is printed N times (where N is an integer of 2 or more) while the degassing pressure is maintained at a constant negative pressure, and includes a defect cause determination unit that determines whether or not a defect is caused by deterioration of the degassing filter based on the location of a defect in each of the N captured images obtained by capturing the N printed images formed on the printing medium by the execution of the N times the test pattern is printed using the imaging device.

[0126] The 19th invention relates to any of the first to 16th inventions, The inkjet printing apparatus comprises at least four ink ejection heads, each ejecting black ink, cyan ink, magenta ink, and yellow ink, The ink piping and the degassing module are provided for each ink color. The control unit is characterized by controlling the operation of the at least four ink ejection heads so that multiple test patterns are printed for each ink color in response to a single instruction to perform a test print.

[0127] The 20th invention is a method for estimating the deterioration state of a degassing filter in an inkjet printing apparatus comprising: an ink ejection head for ejecting ink toward a printing medium; an ink pipe which is a flow path for ink supplied to the ink ejection head; a degassing filter comprising a plurality of gas permeable membranes permeable to gas contained in the ink; a degassing module inserted in the ink pipe, configured such that degassing of the ink is performed when gas contained in the ink flowing through the ink pipe passes through the degassing filter in accordance with the degassing pressure, which is the negative pressure applied to the degassing filter; and a degassing pump drive unit for driving the degassing pump, wherein the apparatus is equipped with a degassing module and a degassing pump drive unit for driving the degassing pump, the method for estimating the deterioration state of the degassing filter, A test pattern printing step in which the operation of the pressure reducing pump drive unit and the operation of the ink ejection head are controlled to print multiple test patterns while sequentially changing the pressure reduction, An estimation step in which the deterioration state of the degassing filter is estimated based on the printed image formed on the printing medium in the test pattern printing step, It is characterized by including.

[0128] According to the first invention described above, in an inkjet printing apparatus equipped with a degassing filter for degassing ink, multiple test patterns are printed while sequentially changing the degassing pressure in response to a single instruction to execute a test print. At that time, by deliberately reducing the degassing pressure (absolute value of degassing pressure) to cause defects (e.g., nozzle defects) in the printed image, it becomes possible to easily estimate the deterioration state of the degassing filter from the degree of defects. Furthermore, it is unnecessary to measure the dissolved oxygen concentration of the ink. As a result, with respect to the inkjet printing apparatus, it is possible to easily grasp the deterioration state of the degassing filter without requiring expensive equipment. This prevents printing using a degassing filter with significantly reduced performance, and reduces the wasteful consumption of ink and printing media due to reprinting caused by, for example, ejection failures. In this way, it can contribute to achieving the SDGs (Sustainable Development Goals).

[0129] According to the second invention described above, even if defects occur in the printed image due to deterioration of the degassing filter (i.e., even if the degassing filter becomes unusable), it is possible to temporarily continue using the degassing filter by changing the degassing pressure setting pressure, taking into account the estimated appropriate pressure. In this way, the lifespan of the degassing filter can be temporarily extended, and the period during which printing output must be completely stopped when the degassing filter needs to be replaced is shortened compared to conventional methods. This prevents a significant decrease in printing productivity when the need arises to replace the degassing filter.

[0130] According to the third invention described above, by appropriately including negative pressures that cause defects in the printed image in multiple degassing settings that are sequentially set when printing a test pattern, a mathematical model is generated that can grasp the change in the degree of defects over time. By using such a mathematical model, it becomes possible to more easily grasp the deterioration state of the degassing filter.

[0131] According to the fourth invention described above, the appropriate pressure for depressurization can be estimated with high accuracy.

[0132] According to the fifth invention described above, the same effects as those of the fourth invention described above can be obtained.

[0133] According to the sixth invention described above, the deterioration state of the degassing filter can be determined accurately and objectively.

[0134] According to the seventh invention described above, it becomes possible to accurately predict in advance when the degassing filter needs to be replaced.

[0135] According to the eighth invention described above, the same effects as those of the third invention described above can be obtained.

[0136] According to the ninth invention described above, by appropriately including negative pressures that cause defects in the printed image in multiple degassing settings that are sequentially set when printing a test pattern, a mathematical model is generated that can grasp the change in the degree of defects as the cumulative amount of ink used increases. By using such a mathematical model, it becomes possible to more easily grasp the deterioration state of the degassing filter.

[0137] According to the tenth invention described above, the appropriate pressure for depressurization can be estimated with high accuracy.

[0138] According to the 11th invention described above, the same effects as those of the 10th invention described above can be obtained.

[0139] According to the 12th invention described above, the deterioration state of the degassing filter can be determined accurately and objectively.

[0140] According to the 13th invention described above, it becomes possible to accurately predict in advance when the degassing filter needs to be replaced.

[0141] According to the 14th invention described above, the same effects as those of the 9th invention described above can be obtained.

[0142] According to the 15th invention described above, the estimation of the deterioration state of the degassing filter is performed not by a person, but by a control unit (typically a computer). Therefore, the deterioration state of the degassing filter can be determined accurately and objectively.

[0143] According to the 16th invention described above, the same effects as those of the 15th invention described above can be obtained.

[0144] According to the 17th invention described above, even if no defects occur in the printed image when the depressurization pressure is set to normal pressure, it is possible to induce defects in the printed image by setting the depressurization pressure to a negative pressure with an absolute value smaller than normal. Therefore, by performing test prints at multiple points in time, it is possible to understand how the degree of defects changes over time.

[0145] According to the 18th invention described above, in addition to the same effects as the first invention described above, it is possible to determine whether or not a defect in the printed image is caused by the deterioration of the degassing filter.

[0146] According to the 19th invention described above, the same effects as those of the first invention can be obtained in an inkjet printing apparatus that performs color printing.

[0147] According to the 20th invention described above, the same effects as the first invention described above can be obtained. [Explanation of symbols]

[0148] 10… Inkjet printing equipment 24…Records Department 26…Imaging device 29... Pressure reducing pump drive unit 32… Mathematical Models 51… Recovery Tank 52…Supply tank 55... Refrigeration piping 58… Degassing module 100…Printing control device 150... Control Unit 151...Continuous Test Print Execution Control Unit 152...Mathematical Model Generation Unit 153...Deterioration state estimation unit 154...Optimal depressurization estimation unit 155...Image retention unit 156...Defect Cause Determination Unit 200... Printing machine body 240... Ink ejection head 584... Degassing filter

Claims

1. An ink ejection head that ejects ink toward the printing medium, An ink pipe which is the flow path for the ink supplied to the ink ejection head, A degassing module inserted into the ink piping is configured to degas the ink by having the gas contained in the ink flowing through the ink pass through the degassing filter in accordance with the negative pressure (degassing pressure) applied to the degassing filter, and the degassing of the ink is performed as the gas contained in the ink flowing through the ink piping passes through the degassing filter. A pressure reducing pump drive unit that drives the aforementioned pressure reducing pump, A control unit controls the operation of the pressure reducing pump drive unit and the operation of the ink ejection head so that multiple test patterns are printed while sequentially changing the pressure in response to a single instruction to execute a test print. An inkjet printing apparatus characterized by comprising the following features.

2. The inkjet printing apparatus according to claim 1, characterized in that the control unit includes an appropriate depressurization estimation unit that estimates an appropriate pressure for depressurization.

3. The device further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head, The inkjet printing apparatus according to claim 2, further comprising a mathematical model generation unit that generates a mathematical model representing the relationship between the lifespan of the degassing filter and a defect index value indicating the degree of defects in the degassing and the captured image, based on captured images obtained by the test printing performed at multiple points in time during a period in which the degassing is maintained at normal pressure, except when the test pattern is printed, by capturing the printed image formed on the printing medium by the execution of printing the test pattern with the imaging device.

4. The inkjet printing apparatus according to claim 3, characterized in that the appropriate depressurization estimation unit estimates the appropriate pressure by applying the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

5. The storage device further comprises a data table that holds the defect index values ​​corresponding to the combination of the number of years of use of the degassing filter and the degassing, and the data table that is created based on the mathematical model, The inkjet printing apparatus according to claim 3, characterized in that the appropriate depressurization estimation unit estimates the appropriate pressure by referring to the data table based on the actual number of years of use of the degassing filter and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

6. The inkjet printing apparatus according to claim 3, wherein the control unit further includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on the mathematical model.

7. The inkjet printing apparatus according to claim 6, characterized in that the deterioration state estimation unit estimates the lifespan of the degassing filter if the degassing filter is used continuously while the degassing pressure is maintained at the normal pressure, by applying the normal pressure as the degassing pressure and the defect tolerance value, which is the limit value of the allowable defect index value, to the mathematical model.

8. The inkjet printing apparatus according to claim 3, characterized in that the mathematical model is expressed by the following formula: [Number 7] Here, y is the defect index value, t is the number of years the degassing filter has been in use, x is the depressurization, and a1, a2, b1, b2, c1, and c2 are coefficients.

9. The device further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head, The inkjet printing apparatus according to claim 2, further comprising a mathematical model generation unit that generates a mathematical model representing the relationship between cumulative ink usage, the depressurization, and a defect index value indicating the degree of defects in the captured image, based on captured images obtained by the test printing performed at multiple points in time during a period in which the depressurization is maintained at normal pressure, except when the test pattern is printed.

10. The inkjet printing apparatus according to claim 9, characterized in that the appropriate depressurization estimation unit estimates the appropriate pressure by applying the actual cumulative amount of ink used and the defect tolerance value, which is the limit value that can be allowed as the defect index value, to the mathematical model.

11. The storage device further comprises a data table that holds the defect index values ​​corresponding to the combination of the cumulative ink usage and the depressurization, and a data table created based on the mathematical model, The inkjet printing apparatus according to claim 9, characterized in that the appropriate depressurization estimation unit estimates the appropriate pressure by referring to the data table based on the actual cumulative amount of ink used and the defect tolerance value, which is the limit value that can be allowed as the defect index value.

12. The inkjet printing apparatus according to claim 9, wherein the control unit further includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on the mathematical model.

13. The inkjet printing apparatus according to claim 12, characterized in that the deterioration state estimation unit estimates the total amount of ink that can be used from the present time onward if the degassing filter is used while the degassing pressure is maintained at the normal pressure, based on the cumulative ink usage obtained by applying the normal pressure as the degassing pressure and the defect tolerance value, which is the limit value of the allowable value as the defect index value, to the mathematical model and the actual cumulative ink usage at the present time.

14. The inkjet printing apparatus according to claim 9, characterized in that the mathematical model is expressed by the following formula: [Number 8] Here, y is the defect index value, u is the cumulative ink usage, x is the depressurization, and a1, a2, b1, b2, c1, and c2 are coefficients.

15. The device further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head, The inkjet printing apparatus according to claim 1, characterized in that the control unit includes a deterioration state estimation unit that estimates the deterioration state of the degassing filter based on an image obtained by capturing the printed image formed on the printing medium by the execution of printing the test pattern with the imaging device.

16. The device further includes a storage device that pre-stores multiple image images corresponding to multiple different years of use or multiple different cumulative ink usage amounts, The inkjet printing apparatus according to claim 15, characterized in that the deterioration state estimation unit estimates the deterioration state of the degassing filter by comparing the image obtained immediately before with a plurality of image images held in the storage device.

17. The inkjet printing apparatus according to any one of claims 1 to 16, characterized in that the multiple depressurizations corresponding to the printing of multiple test patterns performed in response to a single instruction to execute the test print include a normal pressure and a negative pressure with an absolute value smaller than the normal pressure.

18. The device further comprises an imaging device for capturing a printed image formed on the printing medium by the ejection of ink from the ink ejection head, The inkjet printing apparatus according to any one of claims 1 to 16, further comprising: a control unit that controls the operation of the ink ejection head so that the test pattern is printed N times (where N is an integer of 2 or more) while the degassing pressure is maintained at a constant negative pressure; and a defect cause determination unit that determines whether or not a defect is caused by deterioration of the degassing filter based on the location of a defect in each of the N captured images obtained by capturing the N printed images formed on the printing medium by the execution of the N times printing of the test pattern with the imaging device.

19. It is equipped with at least four ink ejection heads that eject black ink, cyan ink, magenta ink, and yellow ink, respectively. The ink piping and the degassing module are provided for each ink color. The inkjet printing apparatus according to any one of claims 1 to 16, characterized in that the control unit controls the operation of the at least four ink ejection heads so that multiple test patterns are printed for each ink color in response to a single instruction to execute a test print.

20. A method for estimating the deterioration state of the degassing filter in an inkjet printing apparatus comprising: an ink ejection head for ejecting ink toward a printing medium; an ink pipe which is a flow path for ink supplied to the ink ejection head; a degassing module inserted in the ink pipe, which includes a degassing module and a pressure reducing pump that applies negative pressure to the degassing filter, wherein the degassing of the ink is performed when the gas contained in the ink flowing through the ink pipe passes through the degassing filter in accordance with the negative pressure applied to the degassing filter; and a pressure reducing pump drive unit that drives the pressure reducing pump, the method for estimating the deterioration state of the degassing filter. A test pattern printing step in which the operation of the pressure reducing pump drive unit and the operation of the ink ejection head are controlled to print multiple test patterns while sequentially changing the pressure reduction, An estimation step in which the deterioration state of the degassing filter is estimated based on the printed image formed on the printing medium in the test pattern printing step, A method for estimating a deterioration state, characterized by including the following:

Images