Printing system, head-state estimation method, and printing device

Abstract

The present invention accurately estimates the state of a printing head.　An application server (30) that functions as a head-state estimation device is provided with: a first log acquisition unit (31) that acquires, as an extraction log (61a), a log (log including information pertaining to cleaning of printing head) outputted during an extraction period that is a predetermined period; a first cleaning frequency counting unit (32) that counts the number (62) of instances of cleaning for each unit period (for example, one day) in the extraction period on the basis of the extraction log (61a); and a health score calculation unit (36) that calculates a health score (S) which represents the state of the printing head on the basis of results obtained by comparing the number (62) of instances of cleaning for each unit period in the extraction period with a cleaning target determination threshold value (TH (1)) obtained by performing statistical processing on the number (63) of instances of cleaning for each unit period during a previous period before the extraction period.

Description

Printing system, head condition estimation method, and printing device

[0001] The present invention relates to a printing system including a printing device that prints by ejecting ink onto a printing medium, and more particularly to a method for estimating the state of a print head that constitutes the printing device.

[0002] Inkjet printing devices are known that print by ejecting ink onto a printing medium such as printing paper or film using heat or pressure. Inkjet printing devices typically include a head unit consisting of multiple print heads, one for each color of ink. Each print head includes multiple nozzles that eject ink. The gradation of a printed image is achieved by controlling the on / off state of ink ejection from each of the multiple nozzles, or by controlling the drop size of the ink ejected from each of the multiple nozzles in multiple stages.

[0003] Inkjet printing devices such as those described above can experience ink ejection problems due to factors such as ink solidification (drying) caused by prolonged disuse. If printing is performed while ink ejection problems are occurring, high-quality printouts cannot be obtained. Therefore, print head cleaning is performed as a countermeasure to ink ejection problems. However, even after cleaning, ink ejection problems may not be fully resolved. In such cases, the print head experiencing ink ejection problems is replaced.

[0004] Meanwhile, businesses (e.g., printing companies) that use inkjet printing devices are experiencing downtime due to sudden print head failures, including ink ejection problems (hereinafter referred to as "head failures"). Downtime reduces business productivity and customer satisfaction. Therefore, to prevent downtime due to head failures, it is common to continually estimate the condition of the print head and determine when it is time to replace the print head.

[0005] A known method for estimating the condition of a print head is to estimate the condition of the print head based on the values ​​of parameters that represent the usage status of the print head (hereinafter referred to as the "conventional method"). Details of the conventional method are disclosed in the following three prior art documents:

[0006] According to an image forming apparatus disclosed in Japanese Patent Application Publication No. 2023-084297, the presence or absence of image defects due to poor ink ejection is determined based on a captured image of a printed pattern image. If no image defects due to poor ink ejection are found, the lifespan of the print head is determined based on numerical values ​​related to the print head's usage history (the print head's usage period and number of ink ejections). According to an inkjet printer disclosed in Japanese Patent Application Publication No. 2005-254708, whether or not to issue a print head replacement warning is determined based on the results of comparing the number of cleanings since installation, the elapsed time, and the total ink ejection volume with respective thresholds. According to a print head condition determination method disclosed in U.S. Patent Application Publication No. 2015 / 0273923, the condition of the print head of a current printer is determined based on the cleaning operation data and cumulative print volume at the time of head failure of a reference printer and the cleaning operation data and print volume of a current printer (the printer being evaluated), taking into account an empirical rule, for example, that the higher the cleaning frequency, the higher the likelihood of print head failure.

[0007] Japanese Patent Publication No. 2023-084297 Japanese Patent Publication No. 2005-254708 US Patent Application Publication No. 2015 / 0273923

[0008] However, conventional methods such as those disclosed in Japanese Patent Application Publication Nos. 2023-084297 and 2005-254708 do not take into account the possibility that the print head condition may be restored by cleaning, and are therefore thought to be unable to estimate the print head condition with sufficient accuracy. Furthermore, the method disclosed in U.S. Patent Application Publication No. 2015 / 0273923 requires a reference printer (a printer that has previously experienced print head failure) separate from the printer being evaluated.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to make it possible to estimate the state of a print head with high accuracy.

[0010] A first aspect of the present invention is a printing system including a printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, and a head condition estimation device that estimates the condition of the print head, wherein the printing device and the head condition estimation device are connected via a communication line, and the printing device outputs a log that includes information regarding the cleaning of the print head, and the head condition estimation device comprises: a processor; and a memory that stores a program, and based on the program stored in the memory, the processor acquires, as extracted logs, logs that were output during an extraction period, which is a predetermined period, from the logs output from the printing device, counts the number of cleanings per unit period during the extraction period based on the extracted log, and calculates a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0011] A second aspect of the present invention is the first aspect of the present invention, wherein the processor, based on the program stored in the memory, further acquires, as preliminary logs, logs output from the printing device that were output during a preliminary period that is a period that precedes the extraction period and is longer than the extraction period; counts the number of cleanings per unit period during the preliminary period based on the preliminary logs; and determines the first threshold value by statistically processing the number of cleanings per unit period during the preliminary period.

[0012] A third aspect of the present invention is related to the second aspect of the present invention, wherein the printing device has a plurality of print heads, each of which ejects a different color of ink onto the print medium, and the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes, and the log includes information about the cleaning mode used when cleaning was performed, and the processor calculates a usage rate for each cleaning mode, where P is a constant of 10 or less, and sets the first threshold to 0 for cleaning modes whose usage rate is less than P percent, and calculates the first threshold for each ink color for cleaning modes whose usage rate is P percent or more using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

[0013] A fourth aspect of the present invention is related to the second aspect of the present invention, wherein the printing device has a plurality of print heads that each eject a different color of ink onto the printing medium, the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes, the log includes information about the cleaning mode used when cleaning was performed, and the processor calculates the first threshold for each cleaning mode for each ink color using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average value of the number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

[0014] A fifth aspect of the present invention is the first aspect of the present invention, wherein the processor counts the number of unit periods in which the number of cleanings exceeds the first threshold value in the extraction period as the number of times the threshold value is exceeded, based on the number of times cleanings is exceeded per unit period in the extraction period, and calculates the condition score based on the number of times the threshold value is exceeded.

[0015] A sixth aspect of the present invention is the fifth aspect of the present invention, wherein the cleaning mechanism is configured to be able to perform cleaning of the print head in a plurality of cleaning modes, the log includes information on the cleaning mode used when cleaning was performed, and the processor counts the number of times the threshold is exceeded for each cleaning mode and calculates the condition score based on a value obtained by weighting the number of times the threshold is exceeded according to the cleaning mode.

[0016] A seventh aspect of the present invention is the sixth aspect of the present invention, wherein the printing device has a plurality of print heads that each eject a different color of ink onto the printing medium, and n cleaning modes, numbered 1 to n, are prepared as the plurality of cleaning modes, and the processor calculates the condition score for each ink color using the following formula: where S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents the weighting factor for the i-th cleaning mode.

[0017] In an eighth aspect of the present invention, based on the fifth aspect of the present invention, the processor determines a regression line indicating a trend of increase or decrease in the number of cleanings during the extraction period based on the number of cleanings per unit period during the extraction period, and calculates the condition score taking into consideration a slope of the regression line.

[0018] A ninth aspect of the present invention is related to the first aspect of the present invention, wherein the printing device has a plurality of print heads, each of which ejects a different color of ink onto the printing medium; and the cleaning mechanism is configured to be able to clean the plurality of print heads in n cleaning modes numbered first to nth, and the log includes information on the cleaning mode used when cleaning was performed; and the processor, based on the program stored in the memory, further: acquires, as prior logs, logs output from the printing device that were output during a prior period that is a period before the extraction period and longer than the extraction period; counts the number of cleanings per unit period in the prior period based on the prior logs; and determines the first threshold by statistically processing the number of cleanings per unit period in the prior period; where P is a constant not greater than 10, the processor: calculates a usage rate for each cleaning mode; for cleaning modes whose usage rate is less than P percent, sets the first threshold to 0; and for cleaning modes whose usage rate is P percent or more, calculates the first threshold for each ink color using the following formula: TH(1) = AV(1) + CO(1) × σ(1) The processor, for each cleaning mode, counts the number of unit periods in which the number of cleanings exceeds the first threshold value during the extraction period as the number of times the threshold value is exceeded, based on the number of cleanings per unit period during the extraction period, and calculates the condition score for each ink color using the following formula. Here, TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient greater than or equal to 1, σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period, S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents a weighting coefficient for the i-th cleaning mode.

[0019] A tenth aspect of the present invention is the ninth aspect of the present invention, wherein the printing device includes a double-sided printing device having a print head that ejects ink onto a front side of the printing medium and a print head that ejects ink onto a back side of the printing medium, and the processor calculates the first threshold value for each cleaning mode for each side that ejects ink and for each color of ink for the double-sided printing device, and the processor calculates the condition score for each side that ejects ink and for each color of ink for the double-sided printing device.

[0020] An eleventh aspect of the present invention is based on the first aspect of the present invention, wherein the processor acquires the extracted log for each specified period that is set to a period shorter than the extraction period, counts the number of cleanings for each unit period in the extraction period, and calculates the condition score for each specified period.

[0021] A twelfth aspect of the present invention is based on the first aspect of the present invention, wherein the printing system further includes a management device having a display unit and connected to the head condition estimation device via the communication line, and the processor further generates a result display image based on the condition score based on the program stored in the memory, and the result display image is displayed on the display unit.

[0022] A thirteenth aspect of the present invention is the twelfth aspect of the present invention, wherein the processor, based on the program stored in the memory, further determines a second threshold value by statistically processing the condition scores calculated over a predetermined period of time in the past, and the result display image includes an image that graphically represents the relationship between the condition scores over the predetermined period of time and the second threshold value.

[0023] In a fourteenth aspect of the present invention, in the thirteenth aspect of the present invention, the processor calculates the second threshold value by the following formula: TH(2) = AV(2) + CO(2) × σ(2), where TH(2) represents the second threshold value, AV(2) represents the average value of the condition score in the predetermined period, CO(2) represents a coefficient of 1 or more, and σ(2) represents the standard deviation of the condition score in the predetermined period.

[0024] In a fifteenth aspect of the present invention, based on the twelfth aspect of the present invention, the result display image includes an image of a mark that is color-coded according to the condition score.

[0025] In a sixteenth aspect of the present invention, in the twelfth aspect of the present invention, when two consecutive extraction periods are defined as a preceding extraction period and a subsequent extraction period, the result display image based on the condition score in the subsequent extraction period includes an image showing an increase / decrease trend of the condition score from the preceding extraction period.

[0026] In a seventeenth aspect of the present invention, based on the first aspect of the present invention, when the printing device is started, the printing device outputs information about the serial number of the print head as the log.

[0027] An 18th aspect of the present invention is any one of the first to seventeenth aspects of the present invention, wherein the head condition estimation device is connected to each of a plurality of users' printing devices via the communication line, and the processor calculates the condition score for each user based on logs output only from the printing device of that user.

[0028] A nineteenth aspect of the present invention is a head condition estimation method for estimating the condition of a print head of a printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, wherein the printing device outputs a log including information regarding cleaning of the print head, and the head condition estimation method includes: a first log acquisition step of acquiring, as an extracted log, a log output during an extraction period that is a predetermined period from the logs output from the printing device; a first cleaning number count step of counting the number of cleanings per unit period during the extraction period based on the extracted log; and a condition score calculation step of calculating a condition score that represents the condition of the print head based on a result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0029] A twentieth aspect of the present invention is a printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, comprising: a storage device that holds a log including information about cleaning of the print head; a processor; and a memory that stores a program, wherein the processor, based on the program stored in the memory, obtains, as an extracted log, a log based on cleaning performed during an extraction period, which is a predetermined period, from the logs held in the storage device; counts the number of cleanings per unit period during the extraction period based on the extracted log; and calculates a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0030] According to a first aspect of the present invention, the number of cleanings per unit period during the extraction period is determined based on a log containing information about print head cleaning and output during a predetermined extraction period. Then, a condition score representing the condition of the print head is calculated based on the comparison of the number of cleanings per unit period during the extraction period with a threshold value (first threshold value). Generally, when color unevenness occurs in a printed image, the number of cleanings increases to prevent further deterioration in print quality, and as the degree of color unevenness worsens, the number of cleanings increases further. Therefore, by comparing the number of cleanings with an appropriately set threshold value (first threshold value), significant deterioration of the print head condition can be detected early. Furthermore, if a log containing information about cleaning is available, the condition score can be calculated. Furthermore, since print heads can be replaced at appropriate times, wasteful consumption of resources (such as ink and printing media) is reduced. In this way, it is possible to contribute to the achievement of the SDGs (Sustainable Development Goals).

[0031] According to the second aspect of the present invention, the threshold value (first threshold value) is calculated based on the results of past cleaning, making it possible to estimate the state of the print head with greater accuracy.

[0032] According to the third aspect of the present invention, in cases where print head cleaning can be performed in a plurality of cleaning modes, a threshold value (first threshold value) is preferably calculated for each cleaning mode.

[0033] According to the fourth aspect of the present invention, the same effects as those of the third aspect of the present invention can be obtained.

[0034] According to the fifth aspect of the present invention, the fact that cleaning has been performed a significantly large number of times in a unit period is reflected in the value of the condition score, making it possible to estimate the condition of the print head with greater accuracy.

[0035] According to the sixth aspect of the present invention, in cases where print head cleaning can be performed in a plurality of cleaning modes, the condition score is calculated appropriately even if cleaning is performed in various cleaning modes.

[0036] According to the seventh aspect of the present invention, the same effects as those of the sixth aspect of the present invention can be obtained.

[0037] According to the eighth aspect of the present invention, the tendency of the number of cleanings to increase or decrease during the extraction period is reflected in the condition score, so it is possible to present to the user a numerical value indicating the need for print head replacement.

[0038] According to a ninth aspect of the present invention, in cases where print head cleaning can be performed in multiple cleaning modes, even if cleaning is performed in various cleaning modes, a threshold (first threshold) is suitably calculated for each cleaning mode, and a condition score is suitably calculated. Furthermore, because the fact that cleaning has been performed a significantly large number of times in a unit period is reflected in the value of the condition score, it is possible to estimate the condition of the print head with greater accuracy.

[0039] According to the tenth aspect of the present invention, when a double-sided printing device is used, it is possible to accurately estimate the state of the print head that ejects ink onto the front side of the printing medium and the state of the print head that ejects ink onto the back side of the printing medium.

[0040] According to the eleventh aspect of the present invention, fluctuations in the health score are smoothed, and it is possible to present to the user transitions in the state of the print head that are closer to reality.

[0041] According to the twelfth aspect of the present invention, the user can visually grasp the state of the print head.

[0042] According to the thirteenth aspect of the present invention, the degree of deterioration of the print head can be visually grasped, so that the user can quickly determine whether or not the print head needs to be replaced, for example.

[0043] According to the fourteenth aspect of the present invention, the same effects as those of the thirteenth aspect of the present invention can be obtained.

[0044] According to the fifteenth aspect of the present invention, the user can visually grasp the approaching need to replace the print head.

[0045] According to the sixteenth aspect of the present invention, whether the condition of the print head is getting worse or better is visually displayed, making it possible to, for example, prevent the print head from being replaced more than necessary.

[0046] According to the seventeenth aspect of the present invention, it is possible to present information regarding print head replacement to the user.

[0047] According to the eighteenth aspect of the present invention, when calculating a condition score for a printing device of any user, the user's own policy regarding print head cleaning is taken into account, making it possible to estimate the condition of the print head of each user's printing device with significantly greater accuracy.

[0048] According to the nineteenth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained.

[0049] According to the twentieth aspect of the present invention, the same effects as those of the first aspect of the present invention can be obtained.

[0050] 1 is a diagram illustrating the overall configuration of a printing system according to one embodiment of the present invention. FIG. 2 is a schematic diagram illustrating an example configuration of an inkjet printing device in the embodiment. FIG. 3 is a schematic diagram illustrating another example configuration of an inkjet printing device in the embodiment. FIG. 4 is a plan view illustrating an example configuration of a recording unit in the embodiment. FIG. 5 is a plan view illustrating a detailed configuration of a print head in the embodiment. FIG. 6 is a block diagram illustrating an example hardware configuration of an application server in the embodiment. FIG. 7 is a diagram illustrating an example of a cleaning log in the embodiment. FIG. 8 is a diagram illustrating an example of a startup information log in the embodiment. FIG. 9 is a diagram for explaining a log sent from an inkjet printing device to a database server in the embodiment. FIG. 10 is a diagram illustrating an example of data associating an apparatus number with a user name in the embodiment. FIG. 11 is a state transition diagram showing the transition of the state of the print head. FIG. 12 is a diagram schematically illustrating the relationship between the state of the print head, print quality, and the number of cleanings. FIG. 13 is a flowchart illustrating the procedure for head state estimation processing in the embodiment. FIG. 14 is a flowchart illustrating a detailed procedure for calculating a cleaning purpose determination threshold in the embodiment. FIG. 15 is a diagram for explaining the cleaning purpose determination threshold in the embodiment. FIG. 16 is a diagram illustrating an example of the ratio of the number of times three cleaning modes are used in the embodiment. FIG. 17 is a diagram illustrating an example of cleaning purpose determination thresholds for the front and back sides and for each ink color for each of the three cleaning modes in the embodiment. FIG. 18 is a diagram for explaining counting the number of times the threshold is exceeded in the embodiment. FIG. 1 is a diagram showing an example of an image representing the relationship between the health scores of each of four colors (black, cyan, magenta, and yellow) and the deterioration threshold value in the embodiment. FIG. 2 is a block diagram showing a functional configuration for realizing a head condition estimation process in the embodiment. FIG. 3 is a diagram showing an example of a result display image including an image of a mark colored according to the health score in the embodiment. FIG. 4 is a diagram showing an example of a result display image including an image showing the increase / decrease trend of the health score in the embodiment. FIG. 5 is a diagram for explaining, in a first modified example of the embodiment, obtaining a regression line showing the increase / decrease trend of the number of cleanings during an extraction period.10 is a diagram showing an example of a result display image including an image showing an increase / decrease trend of the health score in a second modified example of the embodiment. FIG. 11 is a block diagram showing a functional configuration for realizing a head condition estimation process in a fourth modified example of the embodiment.

[0051] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0052] 1. Overall Configuration of the Printing System FIG. 1 is a diagram illustrating the overall configuration of a printing system according to an embodiment of the present invention. This printing system includes multiple inkjet printing devices 10, a database server 20, an application server 30, and an administrator computer (management device) 40. The multiple inkjet printing devices 10, the database server 20, the application server 30, and the administrator computer 40 are connected to one another via a communication line 5, such as the Internet or a dedicated line. The inkjet printing devices 10 are installed, for example, at a printing company. A printing company may have multiple inkjet printing devices 10. In other words, one user may own multiple inkjet printing devices 10. Although FIG. 1 illustrates only one administrator computer 40, multiple administrator computers 40 may exist. For example, a separate administrator computer 40 may be provided for each user. Furthermore, although FIG. 1 illustrates the database server 20 and the application server 30 as separate devices, the database server 20 and the application server 30 may be implemented as a single device.

[0053] The inkjet printing device 10 is composed of a printing machine main body 100 and a print control device 110 that controls the operation of the printing machine main body 100. The inkjet printing device 10 outputs a print image (i.e., performs printing) by ejecting ink onto printing paper as a printing medium without using printing plates, based on print data generated by RIP processing. The RIP processing is performed, for example, by a personal computer connected to the inkjet printing device 10 via a LAN. The inkjet printing device 10 also outputs a log indicating the execution details when printing is performed or when print head cleaning is performed. The log output from the inkjet printing device 10 is sent to the database server 20 via a communication line 5.

[0054] The database server 20 stores logs sent from multiple inkjet printing devices 10. The application server 30 functions as a head condition estimation device that estimates the condition of the print head included in each inkjet printing device 10 based on the logs stored in the database server 20. In this embodiment, the condition of the print head is quantified and visualized so that the degree of deterioration can be easily grasped. The application server 30 generates a display image as a result of quantifying and visualizing the print head condition, and this result display image is displayed on the display unit 400 of the administrator's computer 40. Note that, hereinafter, the process of estimating the condition of the print head included in each inkjet printing device 10 is referred to as the "head condition estimation process."

[0055] 2. Configuration of the Inkjet Printing Apparatus Main Body> Figure 2 is a schematic diagram showing an example configuration of an inkjet printing apparatus 10. As described above, this inkjet printing apparatus 10 is composed of a printing press main body 100 and a print control device 110. The printing press main body 100 is composed of a paper feed section 101 that supplies printing paper (in this example, rolled printing paper) 6 that is elongated in the transport direction, a printing mechanism (front side) 11a for printing on the front side, a reversing unit 109 that reverses the front and back sides of the printing paper 6, a printing mechanism (reverse side) 11b for printing on the back side, and a paper winding section 108 that winds up the printing paper 6 into a roll after printing. In this way, the inkjet printing apparatus 10 according to this embodiment is a so-called double-sided printing apparatus.

[0056] The printing mechanism 11a for front-side printing includes a first drive roller 102a for transporting the printing paper 6 inside the printing mechanism 11a, a plurality of support rollers 103a for transporting the printing paper 6 inside the printing mechanism 11a, a recording unit 104a for recording a print image on the printing paper 6, a cleaning mechanism 105a for cleaning the print head that constitutes the recording unit 104a, a drying mechanism 106a for drying the printing paper 6 on which the print image has been recorded, and a second drive roller 107a for outputting the printing paper 6 from inside the printing mechanism 11a. The printing mechanism 11b for rear-side printing has a configuration similar to that of the printing mechanism 11a for front-side printing. Note that the components of the printing mechanism 11a for front-side printing are designated with the suffix "a" and the components of the printing mechanism 11b for rear-side printing are designated with the suffix "b." However, hereinafter, when there is no need to distinguish between the printing mechanism 11a for front-side printing and the printing mechanism 11b for rear-side printing, the components will be designated with reference numerals only. For example, the recording unit is designated by the reference numeral 104 .

[0057] Although the present embodiment employs an inkjet printing device 10 capable of double-sided printing, the present invention is not limited to this. The present invention can also be applied to an inkjet printing device 10 having a configuration such as that shown in FIG. 3, which does not have a printing mechanism 11b for back-side printing.

[0058] FIG. 4 is a plan view showing an example configuration of the recording unit 104. As shown in FIG. 4, the recording unit 104 is composed of a K (black) head unit 13K, a C (cyan) head unit 13C, an M (magenta) head unit 13M, and a Y (yellow) head unit 13Y, which are arranged in a row in the transport direction of the printing paper 6. Hereinafter, when there is no need to distinguish between the K, C, M, and Y head units 13K, 13C, 13M, and 13Y, the head units will be referred to as "13." Each head unit 13 is composed of ten print heads 130 arranged in a staggered pattern. However, the number of print heads 130 included in each head unit 13 is not limited to ten. Each print head 130 includes a number of nozzles (not shown in FIG. 4) that eject ink. Each nozzle of the print head 130 included in the K color head unit 13K ejects black ink, each nozzle of the print head 130 included in the C color head unit 13C ejects cyan ink, each nozzle of the print head 130 included in the M color head unit 13M ejects magenta ink, and each nozzle of the print head 130 included in the Y color head unit 13Y ejects yellow ink.

[0059] FIG. 5 is a plan view showing the detailed configuration of the print head 130 in this embodiment. The print head 130 includes two sub-heads arranged side by side in the transport direction of the print paper 6. More specifically, the print head 130 includes a first sub-head 130a arranged upstream in the transport direction of the print paper 6 and a second sub-head 130b arranged downstream in the transport direction of the print paper 6. In this manner, the print head 130 is configured with two heads incorporated into a single housing. The first sub-head 130a and the second sub-head 130b each include a large number of nozzles 14. As can be seen from the portion designated by the reference numeral 51 in FIG. 5, the first sub-head 130a and the second sub-head 130b are configured so that the landing positions of ink ejected from the nozzles 14 included in the first sub-head 130a and the landing positions of ink ejected from the nozzles 14 included in the second sub-head 130b are alternately arranged on the print paper 6. For example, both the first sub-head 130a and the second sub-head 130b are capable of printing at 600 dpi, and together they can print at 1200 dpi. Note that the configuration shown in Figure 5 is just one example, and the present invention can also be applied to cases where a print head 130 is used that has only one head incorporated into one housing.

[0060] 3. Hardware Configuration of Application Server> FIG. 6 is a block diagram showing an example of the hardware configuration of the application server 30. As shown in FIG. 6, the application server 30 includes a main body 310, an auxiliary storage device 321, an optical disk drive 322, a display unit 323, a keyboard 324, and a mouse 325. The main body 310 includes a CPU (processor) 311, a memory 312, a first disk interface unit 313, a second disk interface unit 314, a display control unit 315, an input interface unit 316, and a network interface unit 317. The CPU 311, the memory 312, the first disk interface unit 313, the second disk interface unit 314, the display control unit 315, the input interface unit 316, and the network interface unit 317 are connected to one another via a system bus. The auxiliary storage device 321 is connected to the first disk interface unit 313. The auxiliary storage device 321 is a magnetic disk device or the like. The optical disk drive 322 is connected to the second disk interface unit 314. An optical disk 330, which is a computer-readable recording medium such as a CD-ROM or DVD-ROM, is inserted into the optical disk drive 322. A display unit (display device) 323 is connected to the display control unit 315. The display unit 323 is an LCD display or the like. The display unit 323 is used to display information desired by the operator. A keyboard 324 and a mouse 325 are connected to the input interface unit 316. The network interface unit 317 is an interface circuit for communications. The database server 20, the administrator's personal computer 40, and the print control device 110 also have the same hardware configuration as the application server 30. However, the database server 20 may be configured with only the main unit 310 and the auxiliary storage device 321, for example, from the components shown in FIG. 6.

[0061] The auxiliary storage device 321 stores programs and various data to be executed by the application server 30. In this embodiment, a head condition estimation program that estimates the condition of the print head 130 included in each inkjet printing device 10 is stored in the auxiliary storage device 321. The CPU 311 realizes various functions by reading the head condition estimation program stored in the auxiliary storage device 321 into the memory 312 and executing it. The memory 312 includes RAM (Random Access Memory) and ROM (Read Only Memory). The memory 312 functions as a work area for the CPU 311 to execute the head condition estimation program stored in the auxiliary storage device 321. The head condition estimation program is provided by being stored in, for example, the computer-readable recording medium (non-transitory recording medium).

[0062] In the example shown in FIG. 6 , the application server 30 is provided with only one CPU 311 as a processor, but this is not limited to this. A configuration using multiple processors, such as a configuration using multiple CPUs, can also be adopted. In addition to the CPU 311, other processors such as an MPU (Micro Processing Unit), a GPU (Graphics Processing Unit), or a DSP (Digital Signal Processor) can also be adopted. A combination of multiple types of processors can also be used. For example, with regard to the functional components within the application server 30 (see FIG. 20 ), some components and the remaining components can be implemented by different processors. Furthermore, a configuration including a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC) can also be adopted.

[0063] 4. Logs used in head condition estimation processing When the head condition estimation processing is performed by the application server 30, logs that are output from each inkjet printing device 10 and stored in the database server 20 are used. The logs used include a log that is output when cleaning is performed on the inkjet printing device 10 (hereinafter referred to as a "cleaning log") and a log that is output when the inkjet printing device 10 is started up (hereinafter referred to as a "startup information log").

[0064] FIG. 7 shows an example of a cleaning log. The cleaning log consists of six items: "Device Number," "Date and Time," "Front and Back," "Event," "Mode," and "Head to be Cleaned." The device number is a number that uniquely identifies the inkjet printing device 10 on which cleaning was performed. The date and time are the dates and times when cleaning was performed (e.g., the start or end time of cleaning). The "Front and Back" field indicates whether cleaning was performed on the printing mechanism 11a for front-side printing or the printing mechanism 11b for back-side printing. In the example shown in FIG. 7, "P1" indicates that cleaning was performed on the printing mechanism 11a for front-side printing, and "P2" indicates that cleaning was performed on the printing mechanism 11b for back-side printing. The "Event" field is information used to identify the type of log. The "Mode" field indicates the cleaning mode used when cleaning was performed. Cleaning modes will be described later. The "Head to be Cleaned" field is a number that identifies the print head 130 on which cleaning was performed. In this regard, for example, the dotted line portion labeled 52 in FIG. 7 indicates that cleaning has been performed on ten print heads 130 labeled Y1, Y2, Y3, Y4, Y5, K1, K2, K3, K4, and K5 in FIG. 4.

[0065] FIG. 8 shows an example of a startup information log. The startup information log is composed of five items: "Device Number," "Date and Time," "Front and Back," "Event," and "Serial Number." The device number is a number for uniquely identifying the started inkjet printing device 10. The date and time are the date and time when the inkjet printing device 10 was started. The "Front and Back" is information for identifying whether the serial number information (described later) is information about the print head 130 included in the printing mechanism 11a for front printing or the printing mechanism 11b for back printing. This information is provided because, when an inkjet printing device 10 is started, a log related to the printing mechanism 11a for front printing and a log related to the printing mechanism 11b for back printing are output as the startup information log. The "Event" is information for identifying the type of log. The serial number is a number for uniquely identifying each print head 130 included in the started inkjet printing device 10. A startup information log including serial number information is output each time the inkjet printing device 10 is started, so it is possible to determine whether the print head 130 needs to be replaced by comparing the serial number at a certain startup timing with the serial number at the previous startup timing.

[0066] Incidentally, each inkjet printing apparatus 10 transmits to the database server 20 at predetermined intervals a file containing a mixture of cleaning logs and startup information logs (for example, a CSV file as shown in FIG. 9 ). The database server 20 then identifies the type of each log in the transmitted file based on the event data. In this embodiment, a log whose event data is "Head Cleaning" is determined to be a cleaning log, and a log whose event data is "Head Info" is determined to be a startup information log. In the database server 20, for example, the cleaning log and the startup information log are stored in separate tables. In this case, event data is not required in each table. Alternatively, a configuration may be adopted in which each inkjet printing apparatus 10 transmits the cleaning log and the startup information log to the database server 20 in separate files.

[0067] In this embodiment, the head condition estimation process is performed for each user. More specifically, the head condition estimation process for each user is performed based on the logs output only from that user's inkjet printing apparatus 10. To achieve this, the user of the inkjet printing apparatus 10 that output each log must be identified from the apparatus number information included in each log. Therefore, for example, data such as that shown schematically in FIG. 10 that associates apparatus numbers with user names is stored in advance in the database server 20 or the application server 30.

[0068] 5. Cleaning Modes In the inkjet printing apparatus 10 according to this embodiment, one of three cleaning modes (Normal mode, Strong mode, Extreme mode) is selected when cleaning the print head 130. In other words, the cleaning mechanism 105 provided in the inkjet printing apparatus 10 according to this embodiment is configured to be able to clean the print head 130 in the three cleaning modes (Normal mode, Strong mode, Extreme mode).

[0069] Normal mode is a mode that should be selected under normal circumstances. Normal mode involves a flushing process that forcibly ejects ink from the print head 130 regardless of the print content, and a wiping process that uses a dedicated mechanism (wiper) to wipe away dirt from the nozzle surface of the print head 130. Strong mode is a mode that should be selected when cleaning in Normal mode is not sufficiently effective. Strong mode involves wiping and flushing more frequently than Normal mode. Extreme mode is a mode that should be selected when ejection defects known as "horizontal skipping" or "diagonal skipping" are occurring. Extreme mode involves wiping and flushing more frequently than Strong mode, with a larger ink ejection volume than Strong mode. Note that poor ejection, which causes the ink to land at a position that is shifted in the main scanning direction (a direction perpendicular to the transport direction of the printing paper 6) from the position where it should actually land, is called "sideways jumping," and poor ejection, which causes the ink to land at a position that is shifted in both the main scanning direction and the transport direction of the printing paper 6 from the position where it should actually land, is called "diagonal jumping."

[0070] For each log in the cleaning log (see FIG. 7), the cleaning mode used to perform cleaning can be identified based on the mode data in the cleaning log.

[0071] In this embodiment, three cleaning modes are provided as described above, but the number of cleaning modes that should be provided is not particularly limited. Furthermore, logs for only some of the cleaning modes provided may be used in the head condition estimation process. For example, in a case where six cleaning modes are provided, logs for three of the cleaning modes may be used in the head condition estimation process.

[0072] 6. Head Condition Estimation Process (Head Condition Estimation Method) The head condition estimation process in this embodiment will be described below. It is extremely difficult for a user of the inkjet printing device 10 to determine the appropriate time to replace the print head 130. Therefore, in this embodiment, the condition of the print head 130 is expressed numerically so that the user can objectively judge the condition of the print head 130 and replace the print head 130 at the appropriate time. Hereinafter, the numerical value representing the condition of the print head 130 will be referred to as the "health score." Note that in this embodiment, the better the condition of the print head 130, the smaller the health score value, and the worse the condition of the print head 130, the higher the health score value.

[0073] 6.1 Concept In companies and other organizations that have introduced the inkjet printing device 10, the print head 130 is generally cleaned periodically, and also when a missing nozzle (a defect in a printed image caused by poor ink ejection from a nozzle) occurs. Here, the state transitions of the print head 130 will be described with reference to the state transition diagram shown in FIG. 11 . When the print head 130 is in a normal state, periodic cleaning (hereinafter referred to as "regular cleaning") is performed. The state transitions of the print head 130 when regular cleaning is performed are indicated by the arrows labeled 53. When the print head 130 is in a normal state, a missing nozzle occurs, for example, due to long-term disuse. The state transitions of the print head 130 at this time are indicated by the arrows labeled 54. When a missing nozzle occurs, cleaning is performed separately from the regular cleaning. In this case, the cleaning intensity is increased or the number of cleanings is increased compared to regular cleaning. Hereinafter, cleaning performed separately from regular cleaning is referred to as "unregular cleaning." The transition in state of the print head 130 when the missing nozzle is not resolved even after non-regular cleaning is performed is represented by an arrow labeled 55, and the transition in state of the print head 130 when the missing nozzle is resolved by performing non-regular cleaning is represented by an arrow labeled 56. If the missing nozzle is unlikely to be resolved even after non-regular cleaning is performed, the print head 130 is replaced. The transition in state of the print head 130 at this time is represented by an arrow labeled 57. As shown in FIG. 11 , the state of the print head 130 may worsen or improve.

[0074] A state in which a missing nozzle occurs is the worst possible state for the print head 130. Missing nozzles do not suddenly occur when the print head 130 is in a normal state. Before missing nozzles occur, signs of a worsening condition, such as horizontal or diagonal skipping, appear. Furthermore, while print quality is good when the print head 130 is in a normal state, horizontal or diagonal skipping causes color unevenness in the printed image, and missing nozzles cause white streaks in the printed image. For these reasons, when color unevenness is confirmed through a sensory test in which a printed image such as a test pattern is visually inspected, the number of cleanings is likely to increase to prevent further deterioration in print quality. In other words, the relationship between the print head 130 condition, print quality, and number of cleanings is likely to be as shown in FIG. 12 . Therefore, in this embodiment, the condition of the print head 130 is estimated based on the number of cleanings. Estimating the condition of the print head 130 based on the number of cleanings in this manner is likely to enable early detection of significant deterioration in the print head 130 condition.

[0075] When cleaning is performed in the inkjet printing device 10, a cleaning log (see FIG. 7 ) indicating the details of the cleaning is conventionally output. As shown in FIG. 11 , the condition of the print head 130 can deteriorate or improve. However, the cleaning log does not include information indicating the occurrence of a missing nozzle (the state transition indicated by reference numeral 54 in FIG. 11 ) or the resolution of the missing nozzle (the state transition indicated by reference numeral 56 in FIG. 11 ). Therefore, it is not possible to distinguish between regular and irregular cleaning for each log. Therefore, in this embodiment, a threshold is set by statistically processing the number of cleanings per past unit period (e.g., per day). The number of cleanings per unit period is compared with this threshold to distinguish between regular and irregular cleaning for cleanings performed in each unit period. Specifically, cleanings performed in a unit period where the number of cleanings is equal to or less than the threshold are determined to be regular cleanings, and cleanings performed in a unit period where the number of cleanings is greater than the threshold are determined to be irregular cleanings. Note that, hereinafter, this threshold for distinguishing between regular and irregular cleanings is referred to as the "cleaning purpose determination threshold." Details of the cleaning purpose determination threshold will be described later.

[0076] 6.2 Processing Procedure The procedure for the head condition estimation process will be described with reference to the flowchart shown in Fig. 13. Here, we focus on the case where the condition of the print head 130 included in the recording unit 104 of a certain inkjet printing device 10 is estimated. Note that, for example, the process of step S100 is performed every three months, and the processes of steps S200 to S250 are performed once a week.

[0077] In the head condition estimation process, the cleaning purpose determination threshold value is calculated first (step S100). Details of the procedure for calculating the cleaning purpose determination threshold value will be described with reference to the flowchart shown in FIG.

[0078] First, logs for the inkjet printing device 10 to be estimated for a predetermined period in the past (hereinafter referred to as the "preliminary period") are acquired from the logs stored in the database server 20 (step S110). The preliminary period may be, for example, three months or six months. The time interval at which the process of step S100 is performed does not have to match the length of the preliminary period.

[0079] Next, based on the log (pre-log) acquired in step S110, the number of cleanings per unit period for each cleaning mode is counted (step S120). More specifically, for each cleaning mode, the number of cleanings per unit period in the pre-period is counted for each ink color and for each front and back side (i.e., for each head unit 13). Regarding the count of the number of cleanings, for example, if we focus on the portion marked with reference numeral 52 in FIG. 7, Y1 to Y5 and K1 to K5 are the heads to be cleaned. In this case, the number of cleanings for color Y is counted as "5," and the number of cleanings for color K is also counted as "5."

[0080] Next, the proportion of the number of times each cleaning mode has been used (usage proportion) is calculated (step S130). In step S130, first, based on the count values ​​obtained in step S120 (the number of cleanings per unit period in the preliminary period), the sum of the count values ​​for all combinations of the four ink colors and the front and back sides is calculated for each cleaning mode. This gives the cumulative number of cleanings in the preliminary period for each cleaning mode. Then, the cumulative number of cleanings for all cleaning modes in the preliminary period is obtained by summing the cumulative number of cleanings for each of the three cleaning modes. The cumulative number of cleanings for each cleaning mode in the preliminary period is then divided by the cumulative number of cleanings for all cleaning modes in the preliminary period to calculate the proportion of the number of times each cleaning mode has been used.

[0081] After the percentage of use counts for each cleaning mode is calculated, a cleaning purpose determination threshold is calculated for each cleaning mode according to the percentage of use counts (step S140). In this embodiment, for cleaning modes with a usage count percentage of less than 5%, the cleaning purpose determination threshold is set to 0. For cleaning modes with a usage count percentage of 5% or more, the cleaning purpose determination threshold is calculated by statistically processing the number of cleanings per unit period in the preliminary period for each ink color and for both sides. Specifically, the cleaning purpose determination threshold is calculated for each ink color and for both sides using the following formula (1). This cleaning purpose determination threshold realizes the first threshold: TH(1) = AV(1) + CO(1) × σ(1) (1) where TH(1) represents the cleaning purpose determination threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient greater than or equal to 1, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

[0082] In the above equation (1), the coefficient CO(1) is set to, for example, 1.5. In this case, if the distribution (frequency distribution) of the number of cleanings per unit period in the preliminary period is as shown in Fig. 15 and the average number of cleanings per unit period is the value indicated by the dotted line indicated by reference numeral 58 in Fig. 15, the cleaning purpose determination threshold value TH(1) will be the value indicated by the dashed-dotted line indicated by reference numeral 59 in Fig. 15 (this value is "19"). In this example, cleanings performed in a unit period in which the number of cleanings is 19 or less are determined to be regular cleanings, and cleanings performed in a unit period in which the number of cleanings is 20 or more are determined to be non-regular cleanings.

[0083] 16, the percentages of the number of times that the Normal mode and the Strong mode are used are 5% or more, so the cleaning purpose determination threshold TH(1) for each of the Normal mode and the Strong mode is calculated using the above formula (1), and the percentage of the number of times that the Extreme mode is used is less than 5%, so the cleaning purpose determination threshold TH(1) for the Extreme mode is set to 0. Examples of cleaning purpose determination thresholds TH(1) for the front and back sides and for each ink color for each of the three cleaning modes are shown in FIG.

[0084] In this embodiment, the cleaning purpose determination threshold TH(1) for cleaning modes in which the percentage of the number of times used is less than 5% is set to 0, but the present invention is not limited to this. The cleaning purpose determination threshold TH(1) for cleaning modes in which the percentage of the number of times used is less than P%, where P is a constant of 10 or less, may be set to 0. Furthermore, the cleaning purpose determination threshold TH(1) may be calculated using the above formula (1) for all cleaning modes, regardless of the percentage of the number of times used.

[0085] 13, the cleaning purpose determination threshold value TH(1) is calculated for each cleaning mode, for each ink color and for each front and back side (i.e., for each head unit 13). Thereafter, the processing of steps S200 to S250 is performed, for example, once a week, as described above. The period (for example, one week) representing the interval between the processing of steps S200 to S250 corresponds to the specified period.

[0086] In step S200, logs for a predetermined extraction period are acquired from the logs stored in the database server 20. Hereinafter, the logs acquired in step S200 (i.e., logs for the extraction period) are referred to as "extracted logs." If the processes of steps S200 to S250 are performed weekly, the extraction period is, for example, two weeks. In this example, a health score is calculated for each week based on two weeks' worth of logs. Regarding the relationship between the extraction period and the aforementioned preliminary period, the preliminary period is a period that precedes the extraction period but is longer than the extraction period. Furthermore, the unit period (e.g., one day) used as a unit for counting the number of cleanings in the process of step S210 is shorter than the extraction period (e.g., two weeks) and the specified period (e.g., one week). Furthermore, it is preferable that the unit period be an integer fraction of the extraction period and the specified period.

[0087] After the extraction log is acquired, the number of cleanings per unit period in the extraction period is counted for each cleaning mode, for each ink color and for both the front and back sides, based on the extraction log (step S210).

[0088] Next, for each cleaning mode, for each ink color and for the front and back sides, the number of unit periods in which the cleaning count exceeds the cleaning purpose determination threshold during the extraction period (hereinafter referred to as the "threshold exceedance count") is counted based on the count values ​​(the cleaning count per unit period during the extraction period) obtained in step S210 (step S220). In this regard, for example, if the change in the cleaning count per unit period during the extraction period is as shown in FIG. 18 and the cleaning purpose determination threshold TH(1) is the value indicated by the dashed-dotted line indicated by reference numeral 71 in FIG. 18, the cleaning count per unit period exceeds the cleaning purpose determination threshold TH(1) in the dotted line indicated by reference numeral 72 in FIG. 18 and the dotted line indicated by reference numeral 73 in FIG. 18. In this way, the number of times the cleaning count exceeds the cleaning purpose determination threshold TH(1) is counted as the threshold exceedance count.

[0089] Next, a weighting factor for each cleaning mode is assigned to the threshold exceedance count obtained in step S220 (step S230). A weighting factor is set in advance for each cleaning mode, and the product of the threshold exceedance count obtained in step S220 and the weighting factor is calculated for each ink color and for each front and back side (i.e., for each head unit 13) for each cleaning mode. For example, the weighting factor for Normal mode is set to "1," the weighting factor for Strong mode is set to "3," and the weighting factor for Extreme mode is set to "5." In this way, the weighting factor for Strong mode is set to a value greater than the weighting factor for Normal mode, and the weighting factor for Extreme mode is set to a value greater than the weighting factor for Strong mode.

[0090] Then, a health score is calculated for each ink color and for each front and back side (i.e., for each head unit 13) using the following formula (2) (step S240). The condition score is realized from this health score: S = V(1) x K(1) + V(2) x K(2) + V(3) x K(3) ... (2) where S represents the health score, V(1) represents the number of times the threshold is exceeded for the normal mode, K(1) represents the weighting coefficient for the normal mode, V(2) represents the number of times the threshold is exceeded for the strong mode, K(2) represents the weighting coefficient for the strong mode, V(3) represents the number of times the threshold is exceeded for the extreme mode, and K(3) represents the weighting coefficient for the extreme mode.

[0091] In this embodiment, three cleaning modes (Normal mode, Strong mode, and Extreme mode) are provided, but if n cleaning modes from the first to the nth are provided, the health score is calculated using the following equation (3). where S represents the health score, V(i) represents the number of threshold exceedances for the i-th cleaning mode, and K(i) represents the weighting factor for the i-th cleaning mode.

[0092] After calculating the health score based on the extracted log, the health scores calculated over a predetermined period in the past are statistically processed to calculate a threshold value (hereinafter referred to as the "deterioration threshold value") for determining whether the condition of the print head 130 has deteriorated (step S250). Specifically, the deterioration threshold value is calculated using the following equation (4). Note that this deterioration threshold value serves as the second threshold value: TH(2) = AV(2) + CO(2) × σ(2) (4) Here, TH(2) represents the deterioration threshold value, AV(2) represents the average value of the health scores over the predetermined period, CO(2) represents a coefficient greater than or equal to 1, and σ(2) represents the standard deviation of the health scores over the predetermined period.

[0093] In the above equation (4), the coefficient CO(2) is set to, for example, 1.5. In this case, the relationship between the health scores of each of the four colors (K, C, M, and Y) during the predetermined period and the deterioration threshold value is, for example, as shown in Figure 19. In Figure 19, the value indicated by the dashed dotted line labeled 75 is the deterioration threshold value TH(2).

[0094] In this way, the head condition estimation process is carried out in the application server 30. Then, a result display image is generated in which the state of the print head 130 is digitized and visualized based on the results obtained from the head condition estimation process, and this result display image is displayed on the display unit 400 (see FIG. 1) of the administrator's computer 40. Details of the result display image will be described later.

[0095] Note that the health score calculated in step S240 may be normalized so that the user can easily recognize the degree of deterioration of the print head 130.

[0096] In this embodiment, step S200 realizes a first log acquisition step, step S210 realizes a first cleaning number count step, and step S240 realizes a condition score calculation step.

[0097] 6.3 Functional Configuration The functional configuration for realizing the above-described head condition estimation process will be described with reference to the block diagram shown in Fig. 20. The print control device 110 includes a log output unit 111, a log temporary storage unit 112, and a log transmission unit 113. The application server 30 includes a first log acquisition unit 31, a first cleaning count count unit 32, a second log acquisition unit 33, a second cleaning count count unit 34, a cleaning purpose determination threshold calculation unit 35, a health score calculation unit 36, a health score storage unit 37, a deterioration threshold calculation unit 38, and a result display image generation unit 39. Note that each component within the application server 30 is realized by the application server 30 executing the above-described head condition estimation program.

[0098] The log output unit 111 outputs a log 61 that includes information about cleaning of the print head 130. In this embodiment, the log 61 output from the log output unit 111 includes the cleaning log (see FIG. 7) and the startup information log (see FIG. 8) described above. The log temporary storage unit 112 temporarily stores the log 61 output from the log output unit 111. The log transmission unit 113 transmits the log 61 stored in the log temporary storage unit 112 to the database server 20 at predetermined time intervals. The database server 20 holds the logs 61 transmitted from a large number of inkjet printing devices 10 (see FIG. 1).

[0099] The first log acquisition unit 31 acquires, as an extracted log 61a, logs for the above-mentioned extraction period from among the logs 61 held in the database server 20 (in other words, logs output during the extraction period from among the logs output by the log output unit 111). The first cleaning counting unit 32 counts the number of cleanings 62 per unit period during the extraction period for each ink color and for the front and back sides for each cleaning mode, based on the extracted log 61a.

[0100] The second log acquisition unit 33 acquires, as a preliminary log 61b, the logs for the above-mentioned preliminary period from among the logs 61 held in the database server 20 (in other words, the logs output during the preliminary period from among the logs output by the log output unit 111). The second cleaning counting unit 34 counts the number of cleanings 63 per unit period in the preliminary period for each cleaning mode, for each ink color and for both the front and back sides, based on the preliminary log 61b.

[0101] The cleaning purpose determination threshold calculation unit 35 calculates the above-mentioned cleaning purpose determination threshold TH(1) for each cleaning mode, for each ink color and for each front and back side, based on the cleaning count 63 per unit period in the preliminary period. As described above, the percentage of the number of times each cleaning mode has been used is calculated, and for cleaning modes whose percentage of the number of times used is less than 5%, the cleaning purpose determination threshold TH(1) is set to 0, and for cleaning modes whose percentage of the number of times used is 5% or more, the cleaning purpose determination threshold TH(1) is calculated using the above formula (1). The cleaning purpose determination threshold calculation unit 35 serves as a first threshold calculation unit.

[0102] The health score calculation unit 36 ​​calculates a health score S for each ink color and for the front and back sides based on the results of comparing the cleaning count 62 per unit period during the extraction period with the cleaning purpose determination threshold TH(1). As described above, the threshold exceedance count (the number of unit periods during the extraction period during which the cleaning count exceeds the cleaning purpose determination threshold TH(1)) is calculated for each ink color and for the front and back sides, and the health score S is calculated for each ink color and for the front and back sides using the above formula (2). The threshold exceedance count is weighted according to the cleaning mode. That is, the health score calculation unit 36 ​​calculates the health score S based on a value obtained by weighting the threshold exceedance count according to the cleaning mode. The health score calculation unit 36 ​​functions as a condition score calculation unit. The health score storage unit 37 stores the health scores S calculated by the health score calculation unit 36.

[0103] The deterioration threshold calculation unit 38 calculates the deterioration threshold TH(2) using the above formula (4) by statistically processing the health scores S for a predetermined period of time in the past that are stored in the health score storage unit 37 (in other words, the health scores S calculated by the health score calculation unit 36 ​​during a predetermined period of time in the past). Note that the deterioration threshold calculation unit 38 implements a second threshold calculation unit.

[0104] The result display image generation unit 39 generates a result display image 64 to be displayed on the display unit of the administrator's computer 40 based on the most recent health score S, the past health score S (the health score S stored in the health score memory unit 37), and the deterioration threshold TH (2).

[0105] 7. Result Display Image The following describes the result display image 64 generated by the result display image generation unit 39. The result display image 64 is typically displayed on the display unit 400 of the administrator's computer 40. However, this is not limiting, and for example, the result display image 64 may be output from the inkjet printing device 10 as a print image.

[0106] In this embodiment, as described above, a deterioration threshold TH(2) is calculated as a threshold for determining whether the condition of the print head 130 has deteriorated. By visually displaying the magnitude relationship between the deterioration threshold TH(2) and the health score S, the user can easily grasp the degree of deterioration in the condition of the print head 130. Therefore, an image (such as the image shown in FIG. 19 ) that graphically represents the relationship between the health score S for each of the four colors (K, C, M, and Y) over a predetermined past period and the deterioration threshold TH(2) is generated as the result display image 64. Displaying such an image allows the user to visually grasp the degree of deterioration in the print head 130, enabling the user to quickly determine, for example, whether or not to replace the print head 130. Note that if the print head 130 has been replaced, the result display image 64 may include an image such as a mark indicating the color of ink used to replace the print head 130 and the timing of replacement.

[0107] Furthermore, an image such as that shown in FIG. 21 is generated as the result display image 64, which includes numerical values ​​representing the health score S for each ink color and for the front and back sides, and arcs of a predetermined width having arc lengths corresponding to the health score S. In the example shown in FIG. 21 , the numerical values ​​representing the health score S are displayed inside the arcs. These numerical values ​​are values ​​obtained by normalizing the health score S so that the maximum possible value is 100. Also, with reference to FIG. 21 , for example, the arc labeled 801 is displayed in red, the arc labeled 802 is displayed in yellow, and the arc labeled 803 is displayed in green. In this way, the result display image 64 includes an image of a mark colored according to the magnitude of the health score S. This allows the user to visually grasp the imminent need to replace the print head 130. A warning message urging replacement of the print head 130 may be displayed when the arc remains displayed in red or yellow for a predetermined period of time. For example, a warning message may be displayed if the arc is displayed in red for two consecutive days, or if the arc is displayed in yellow or red for five consecutive days.

[0108] It is preferable for the user to be able to grasp the increase / decrease trend of the health score S. This is because, for example, even if the health score S is high, if the health score S is on a decreasing trend, the user can determine that there is no need to replace the print head 130. Therefore, an image such as that shown in FIG. 22 may be generated as the result display image 64, in which arrows indicating the increase / decrease trend of the health score S are added to the image shown in FIG. 21 . In FIG. 22 , the arrow labeled 811 indicates that the health score S is on an increasing trend, the arrow labeled 812 indicates that there is almost no increase / decrease in the health score S, and the arrow labeled 813 indicates that the health score S is on a decreasing trend. Furthermore, in FIG. 22 , for example, the arrow labeled 811 is displayed in red, the arrow labeled 812 is displayed in gray, and the arrow labeled 813 is displayed in green. Displaying the result display image 64 such as that shown in FIG. 22 allows the user to grasp not only the current state of the print head 130 but also the trend of changes in the state of the print head 130.

[0109] In the example shown in Figure 22, the increase / decrease trend of the health score S is determined by comparing the health score S based on the most recent extraction period with the health score S based on the immediately preceding extraction period. Here, if two consecutive extraction periods are defined as the preceding extraction period and the subsequent extraction period, then a result display image 64 (the image shown in Figure 22) based on the health score S for the subsequent extraction period includes an image (specifically, an arrow image) that indicates the increase / decrease trend of the health score S since the preceding extraction period. This configuration visually displays whether the condition of the print head 130 is getting worse or better, making it possible, for example, to prevent unnecessary replacement of the print head 130.

[0110] 8. Effects According to this embodiment, the number of cleanings 62 per unit period during the extraction period is calculated based on the logs (cleaning log and startup information log) 61 output from the inkjet printing apparatus 10 during a predetermined extraction period. The number of times the threshold is exceeded is calculated by comparing the number of cleanings 62 per unit period during the extraction period with a threshold (cleaning purpose determination threshold TH(1)). A health score S representing the condition of the print head 130 is calculated based on a value obtained by weighting the number of times the threshold is exceeded according to the cleaning mode. Generally, when color unevenness occurs in a printed image, the number of cleanings increases to prevent further deterioration in print quality, and as the degree of color unevenness worsens, the number of cleanings increases further. Furthermore, the worse the degree of color unevenness, the more intensive the cleaning mode selected. Therefore, the value of the health score S calculated in this embodiment accurately reflects the deterioration of the print head 130. Furthermore, it is believed that the number of cleanings increases if the condition of the print head 130 deteriorates, and decreases if the condition of the print head 130 improves. Therefore, the health score S calculated in this embodiment reflects the transition of the print head 130's condition, such as when the print head 130 recovers from a deteriorated state. Furthermore, because the health score S can be calculated with the logs (cleaning log and startup information log) 61, an imaging device is not required to calculate the health score S. As described above, this embodiment makes it possible to accurately estimate the condition of the print head 130 without the need for an imaging device (i.e., at low cost). Furthermore, because the print head 130 can be replaced at an appropriate time, wasteful consumption of resources (such as ink and printing paper 6) is reduced. In this way, it is possible to contribute to the achievement of the SDGs (Sustainable Development Goals).

[0111] Furthermore, for example, by determining whether or not the print head 130 needs to be replaced based on the health score S during regular maintenance of the inkjet printing device 10 and then performing the print head 130 replacement in a planned manner, the occurrence of unexpected head failure and the resulting downtime can be reduced. Furthermore, because non-steady cleaning is generally performed when a user confirms a decline in print quality (such as the occurrence of color unevenness) through sensory testing, the method according to this embodiment allows the user's judgment to be reflected in the value of the health score S. Furthermore, because it is believed that the number of cleanings increases as the degree of color unevenness worsens, the method according to this embodiment allows the degree of color unevenness, which is difficult to quantify, to be reflected in the value of the health score S.

[0112] 9. Modifications Modifications of the above embodiment will now be described.

[0113] 9.1 First Modification In the above embodiment, the health score S was calculated using the above formula (2). In this case, if the number of times the threshold was exceeded for each cleaning mode during the extraction period was the same, the same value was obtained as the health score S, regardless of the trend in the number of cleanings during the extraction period. In contrast, in this modification, the health score S is calculated taking into account the trend in the number of cleanings during the extraction period. The method for calculating the health score S in this modification will be described below.

[0114] In this modification, before calculating the health score S in step S240 of FIG. 13 , a line is calculated that indicates the increase / decrease trend in the number of cleanings during the extraction period for each ink color and for both the front and back sides. The value of the slope of this line is then used to calculate the health score S. Specifically, a regression line (linear equation) is calculated by the least squares method using data on the number of cleanings per unit period during the extraction period. For example, if the number of cleanings per unit period during the extraction period is as shown in part A of FIG. 23 , the line labeled 81 in part B of FIG. 23 is calculated as the regression line. Then, a coefficient (hereinafter referred to as the “correction coefficient”) to be multiplied by the health score S calculated using equation (2) above is calculated according to a predetermined rule based on the value of the slope of the regression line (the coefficient of the first-order term in the linear equation). The correction coefficient is calculated, for example, using the following equation (5): Z=1+J×G (5) Here, Z represents a correction coefficient, J represents an adjustment coefficient that is set appropriately, and G represents the value of the slope of the regression line.

[0115] After the correction coefficient Z is calculated as described above, the health score S is calculated for each ink color and for the front and back sides. In this modified example, if the health score S calculated by the above formula (2) is replaced with Sa, the health score S is calculated by the following formula (6): S = Sa × Z (6)

[0116] As described above, the health score S is calculated taking into account the slope of the regression line, which indicates the trend of increases and decreases in the number of cleanings during the extraction period. Here, it is assumed that the adjustment coefficient J is set to 0.1. In this case, if the health score calculated using the above formula (2) is 80 and the slope of the regression line is 0.5, then the health score S in this modified example is calculated to be 84 based on the above formulas (5) and (6). Furthermore, if the health score calculated using the above formula (2) is 90 and the slope of the regression line is -1, then the health score S in this modified example is calculated to be 81 based on the above formulas (5) and (6).

[0117] In this modified example, when the slope of the regression line is positive, i.e., when the number of cleanings during the extraction period is on an increasing trend, the value of health score S is larger than in the above embodiment, and when the slope of the regression line is negative, i.e., when the number of cleanings during the extraction period is on a decreasing trend, the value of health score S is smaller than in the above embodiment. In this way, the increasing or decreasing trend of the number of cleanings during the extraction period is reflected in the value of health score S.

[0118] By the way, when the calculation of the health score S is generalized, if n cleaning modes from 1st to nth are prepared, the health score S is calculated for each ink color and for the front and back sides separately using the following equation (7). where S represents the health score, Z represents the correction factor, V(i) represents the number of threshold exceedances for the i-th cleaning mode, and K(i) represents the weighting factor for the i-th cleaning mode.

[0119] In this modification, the correction coefficient Z is determined according to the value of the slope of the regression line obtained using the least squares method, but the invention is not limited to this. For example, the correction coefficient Z can also be determined according to the value of the slope of the nearest portion of a curve (Loess curve) obtained using a method called "Loess" (a method for determining the tendency of local changes in data).

[0120] 9.2 Second Modification In this modification, a result display image 64 that includes an image showing the increase / decrease trend of the health score and is different from the result display image 64 shown in Fig. 22 is displayed on the display unit of administrator's computer 40. Specifically, a result display image 64 such as that shown in Fig. 24 is displayed on the display unit of administrator's computer 40.

[0121] As shown in FIG. 24 , in this modification, a line graph shows the change in the average value of health score S (weekly average value) for each ink color over the past four weeks, for both the front and back sides. Note that in FIG. 24 , the lines labeled 821, 822, 823, and 824 show the change in the average value of health score S for black, cyan, magenta, and yellow, respectively. The lines labeled 821, 822, 823, and 824 are displayed in black, cyan, magenta, and yellow, respectively. On the right side of the line graph, the average value of health score S for each ink color over the past week is shown numerically. Values ​​greater than or equal to 90 are marked red 831, and values ​​greater than or equal to 70 but less than 90 are marked yellow 832.

[0122] In this modified example, the user can also grasp not only the current state of the print head 130 but also the tendency of changes in the state of the print head 130 .

[0123] 9.3 Third Modification In the above embodiment, the health score S was calculated for each ink color and for each front and back side. In other words, in the above embodiment, the health score S was calculated for each head unit 13. However, the present invention is not limited to this. In this modification, the health score S is calculated for each print head 130.

[0124] In this modified example, in step S210 of FIG. 13 , the number of cleanings per unit period in the extraction period is counted for each print head 130 for each cleaning mode. In step S220 of FIG. 13 , the number of times the threshold is exceeded is counted for each print head 130 for each cleaning mode. In this regard, since each head unit 13 is composed of ten print heads 130 (see FIG. 4 ), the cleaning purpose determination threshold TH(1) used to count the number of times the threshold is exceeded is set to, for example, one-tenth the value in the above embodiment. In step S230 of FIG. 13 , the product of the number of times the threshold is exceeded and the weighting coefficient is calculated for each print head 130 for each cleaning mode. In step S240 of FIG. 13 , the health score S is calculated for each print head 130 using equation (2) above. In step S250 of FIG. 13 , the deterioration threshold TH(2) is calculated in the same manner as in the above embodiment.

[0125] As the result display image 64, for example, an image that visualizes the current health score S of each of the 10 print heads 130 included in the head unit 13 and the increase / decrease trend of the health score S is displayed on the display unit 400 of the administrator's computer 40.

[0126] 9.4 Fourth Modification In the above embodiment, the head condition estimation process was performed by the application server 30 (see FIG. 1 ) connected to multiple inkjet printing devices 10 via the communication line 5. However, the present invention is not limited to this. In this modification, the head condition estimation process is performed by the print control device 110 within the inkjet printing device 10.

[0127] 25 is a block diagram showing the functional configuration for realizing the head condition estimation process in this modified example. As shown in Fig. 25, the print control device 110 includes a log output unit 111, a log storage unit 120, a first log acquisition unit 131, a first cleaning count count unit 132, a second log acquisition unit 133, a second cleaning count count unit 134, a cleaning purpose determination threshold calculation unit 135, a health score calculation unit 136, a health score storage unit 137, a deterioration threshold calculation unit 138, and a result display image generation unit 139.

[0128] The operation of the log output unit 111, first cleaning count count unit 132, second cleaning count unit 134, cleaning purpose determination threshold calculation unit 135, health score calculation unit 136, health score memory unit 137, deterioration threshold calculation unit 138, and result display image generation unit 139 is similar to that of the log output unit 111, first cleaning count count unit 32, second cleaning count unit 34, cleaning purpose determination threshold calculation unit 35, health score calculation unit 36, health score memory unit 37, deterioration threshold calculation unit 38, and result display image generation unit 39 in the above embodiment (see Figure 20).

[0129] The log storage unit 120 holds the logs 61 output from the log output unit 111. The first log acquisition unit 131 acquires, from the logs 61 held in the log storage unit 120, logs based on cleaning performed during the above-mentioned extraction period (logs output from the log output unit 111 during the extraction period) as extracted logs 61a. The second log acquisition unit 133 acquires, from the logs 61 held in the log storage unit 120, logs based on cleaning performed during the above-mentioned preliminary period (logs output from the log output unit 111 during the preliminary period) as preliminary logs 61b.

[0130] The result display image 64 is displayed on the display unit of the print control device 110 or on the display unit of a personal computer connected to the print control device 110 via a LAN or the like.

[0131] 10. Others The present invention is not limited to the above-described embodiment (including modifications) and can be implemented in various modifications without departing from the spirit of the present invention. For example, the above-described embodiment (including modifications) employs an inkjet printing apparatus 10 that performs color printing. However, the present invention is not limited to this, and an inkjet printing apparatus that performs monochrome printing may also be employed. Furthermore, the above-described embodiment (including modifications) employs an inkjet printing apparatus 10 that uses aqueous ink. However, the present invention is not limited to this, and an inkjet printing apparatus that uses UV ink (ultraviolet-curable ink), such as an inkjet printing apparatus for label printing, may also be employed. In this case, an ultraviolet irradiation mechanism that cures the UV ink on the printing paper 6 by ultraviolet irradiation is provided inside the printing mechanism 11 (see FIGS. 2 and 3 ), instead of the drying mechanism 106. Furthermore, the inkjet printing apparatus 10 in the above-described embodiment (including modifications) includes multiple print heads 130. However, the present invention is not limited to this, and the inkjet printing apparatus 10 may include a single print head 130.

[0132] 11. Supplementary Notes Based on the above disclosure, printing systems and printing devices having the following configurations are also conceivable.

[0133] (Supplementary Note 1) A printing system including a printing device having a print head that ejects ink onto a print medium and a cleaning mechanism that cleans the print head, and a head condition estimation device that estimates the condition of the print head, wherein the printing device and the head condition estimation device are connected via a communication line, the printing device has a log output unit that outputs a log including information about the cleaning of the print head, and the head condition estimation device has: a first log acquisition unit that acquires, as an extracted log, logs output during an extraction period that is a predetermined period from among the logs output by the log output unit; a first cleaning counting unit that counts the number of cleanings per unit period during the extraction period based on the extracted log; and a condition score calculation unit that calculates a condition score that represents the condition of the print head based on a result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0134] (Supplementary Note 2) The printing system described in Supplementary Note 1 is characterized in that the head condition estimation device further comprises: a second log acquisition unit that acquires, as a preliminary log, a log output by the log output unit that was output during a preliminary period that is a period that precedes the extraction period and is longer than the extraction period; a second cleaning counting unit that counts the number of cleanings per unit period in the preliminary period based on the preliminary log; and a first threshold calculation unit that calculates the first threshold by statistically processing the number of cleanings per unit period in the preliminary period.

[0135] (Supplementary Note 3) The printing system according to Supplementary Note 2, characterized in that: the printing device has a plurality of print heads, each of which ejects a different color of ink onto the print medium; the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes; the log includes information on the cleaning mode used when cleaning was performed; and the first threshold calculation unit calculates a usage rate for each cleaning mode, where P is a constant of 10 or less; for cleaning modes whose usage rate is less than P percent, sets the first threshold to 0; and for cleaning modes whose usage rate is P percent or more, calculates the first threshold for each ink color using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average value of the number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

[0136] (Supplementary Note 4) The printing system described in Supplementary Note 2 is characterized in that: the printing device has a plurality of print heads, each of which ejects a different color of ink onto the printing medium; the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes; the log includes information on the cleaning mode used when cleaning was performed; and the first threshold calculation unit calculates the first threshold for each cleaning mode for each ink color using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

[0137] (Appendix 5) The printing system described in Appendix 1 is characterized in that the condition score calculation unit counts the number of unit periods in which the number of cleanings exceeds the first threshold value during the extraction period as the number of times the threshold value is exceeded based on the number of cleanings per unit period during the extraction period, and calculates the condition score based on the number of times the threshold value is exceeded.

[0138] (Appendix 6) The printing system described in Appendix 5 is characterized in that the cleaning mechanism is configured to be able to perform cleaning of the print head in multiple cleaning modes, the log includes information on the cleaning mode used when cleaning was performed, and the condition score calculation unit counts the number of times the threshold is exceeded for each cleaning mode and calculates the condition score based on a value obtained by assigning a weight to the number of times the threshold is exceeded according to the cleaning mode.

[0139] (Supplementary Note 7) The printing system according to Supplementary Note 6, wherein the printing device has a plurality of print heads each ejecting a different color of ink onto the printing medium, and the plurality of cleaning modes include n cleaning modes from first to nth cleaning modes, and the condition score calculation unit calculates the condition score for each ink color using the following formula: where S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents the weighting factor for the i-th cleaning mode.

[0140] (Appendix 8) The printing system described in Appendix 5 is characterized in that the condition score calculation unit obtains a regression line showing the trend of increase or decrease in the number of cleanings during the extraction period based on the number of cleanings per unit period during the extraction period, and calculates the condition score taking into account the slope of the regression line.

[0141] (Supplementary Note 9) The printing device has a plurality of print heads, each of which ejects ink of a different color onto the print medium, and the cleaning mechanism is configured to be able to clean the plurality of print heads in n cleaning modes, numbered from first to nth, and the log includes information on the cleaning mode used when cleaning was performed, and the head condition estimation device further comprises: a second log acquisition unit that acquires, from among the logs output by the log output unit, logs output during a preliminary period that is a period before the extraction period and longer than the extraction period, as a preliminary log; a second cleaning counting unit that counts the number of cleanings per unit period in the preliminary period based on the preliminary log; and a first threshold calculation unit that calculates the first threshold by statistically processing the number of cleanings per unit period in the preliminary period, where P is a constant not greater than 10, and the first threshold calculation unit calculates a usage rate for each cleaning mode, and sets the first threshold to 0 for cleaning modes whose usage rate is less than P percent, and calculates the first threshold for cleaning modes whose usage rate is P percent or more using the following formula: TH(1)=AV(1)+CO(1)×σ(1) The printing system according to Supplementary Note 1, wherein the condition score calculation unit counts, for each cleaning mode, the number of unit periods in which the number of cleanings exceeds the first threshold value in the extraction period as the number of times that the threshold value is exceeded, based on the number of cleanings per unit period in the extraction period, and calculates the condition score for each ink color using the following formula: Here, TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient greater than or equal to 1, σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period, S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents a weighting coefficient for the i-th cleaning mode.

[0142] (Appendix 10) The printing system described in Appendix 9 is characterized in that the printing device includes a double-sided printing device having a print head that ejects ink onto the front side of the printing medium and a print head that ejects ink onto the back side of the printing medium, the first threshold calculation unit calculates the first threshold for each cleaning mode for each side that ejects ink and for each color of ink for the double-sided printing device, and the condition score calculation unit calculates the condition score for each side that ejects ink and for each color of ink for the double-sided printing device.

[0143] (Appendix 11) The printing system described in Appendix 1 is characterized in that the first log acquisition unit acquires the extraction log for each specified period set to a period shorter than the extraction period, the first cleaning count unit counts the number of cleanings per unit period in the extraction period for each specified period, and the status score calculation unit calculates the status score for each specified period.

[0144] (Appendix 12) A printing system as described in Appendix 1, further comprising a management device having a display unit and connected to the head condition estimation device via the communication line, wherein the head condition estimation device further comprises a result display image generation unit that generates a result display image based on the condition score, and wherein the result display image is displayed on the display unit.

[0145] (Appendix 13) The printing system described in Appendix 12 is characterized in that the head condition estimation device further includes a second threshold calculation unit that calculates a second threshold by statistically processing the condition scores calculated by the condition score calculation unit over a predetermined period in the past, and the result display image includes an image that graphically represents the relationship between the condition scores over the predetermined period and the second threshold.

[0146] (Appendix 14) The printing system described in Appendix 13, wherein the second threshold calculation unit calculates the second threshold using the following formula: TH(2) = AV(2) + CO(2) × σ(2), where TH(2) represents the second threshold, AV(2) represents the average value of the condition score for the specified period, CO(2) represents a coefficient of 1 or more, and σ(2) represents the standard deviation of the condition score for the specified period.

[0147] (Supplementary Note 15) The printing system according to Supplementary Note 12, wherein the result display image includes an image of a mark that is color-coded according to the condition score.

[0148] (Appendix 16) The printing system described in Appendix 12, characterized in that when two consecutive extraction periods are defined as an earlier extraction period and a later extraction period, the result display image based on the status score in the later extraction period includes an image showing an increase / decrease trend of the status score from the earlier extraction period.

[0149] (Supplementary Note 17) The printing system according to Supplementary Note 1, wherein the log output unit outputs information about the serial number of the print head as the log when the printing device is started.

[0150] (Appendix 18) A printing system described in any one of Appendices 1 to 17, characterized in that the head condition estimation device is connected to each printing device of a plurality of users via the communication line, and the condition score calculation unit calculates the condition score for each user based on a log output from the log output unit contained only in the printing device of that user.

[0151] (Appendix 19) A head condition estimation method for estimating the condition of a print head of a printing device having a print head that ejects ink onto a printing medium, a cleaning mechanism that cleans the print head, and a log output unit that outputs a log including information regarding the cleaning of the print head, comprising: a first log acquisition step of acquiring, as an extracted log, logs output by the log output unit that are output during an extraction period, which is a predetermined period; a first cleaning number count step of counting the number of cleanings per unit period during the extraction period based on the extracted log; and a condition score calculation step of calculating a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0152] (Appendix 20) A printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, characterized in that the printing device comprises: a log output unit that outputs a log including information regarding the cleaning of the print head; a first log acquisition unit that acquires, as an extracted log, logs output by the log output unit that are output during an extraction period, which is a predetermined period; a first cleaning count unit that counts the number of cleanings per unit period during the extraction period based on the extracted log; and a condition score calculation unit that calculates a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

[0153] DESCRIPTION OF SYMBOLS 10... Inkjet printing device 13... Head unit 20... Database server 30... Application server 31, 131... First log acquisition unit 32, 132... First cleaning count count unit 33, 133... Second log acquisition unit 34, 134... Second cleaning count count unit 35, 135... Cleaning purpose determination threshold calculation unit 36, 136... Health score calculation unit 37, 137... Health score storage unit 38, 138... Deterioration threshold calculation unit 39, 139... Result display image generation unit 40... Administrator's personal computer 100... Printing machine main body 110... Print control device 111... Log output unit 112... Log temporary storage unit 113... Log transmission unit 120... Log storage unit 130... Print head S... Health score (status score) TH(1)... Cleaning purpose determination threshold (first threshold) TH(2)... Deterioration threshold (second threshold)

Claims

1. A printing system including a printing device having a print head that ejects ink onto a print medium and a cleaning mechanism that cleans the print head, and a head condition estimation device that estimates the condition of the print head, wherein the printing device and the head condition estimation device are connected via a communication line, and the printing device outputs a log that includes information regarding the cleaning of the print head, and the head condition estimation device has a processor and a memory that stores a program, and based on the program stored in the memory, the processor acquires, as an extracted log, logs that were output during a predetermined extraction period from the logs output from the printing device, counts the number of cleanings per unit period during the extraction period based on the extracted log, and calculates a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold.

2. The printing system described in claim 1, wherein the processor, based on the program stored in the memory, further acquires logs output from the printing device that were output during a preliminary period that is a period that precedes the extraction period and is longer than the extraction period as preliminary logs, counts the number of cleanings per unit period during the preliminary period based on the preliminary logs, and determines the first threshold value by statistically processing the number of cleanings per unit period during the preliminary period.

3. The printing system of claim 2, wherein the printing device has a plurality of print heads, each of which ejects a different color of ink onto the print medium; the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes; the log includes information on the cleaning mode used when cleaning was performed; and the processor calculates a usage rate for each cleaning mode, where P is a constant of 10 or less; sets the first threshold to 0 for cleaning modes whose usage rate is less than P percent; and calculates the first threshold for each ink color for cleaning modes whose usage rate is P percent or more using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

4. The printing system of claim 2, wherein the printing device has a plurality of print heads, each of which ejects a different color of ink onto the printing medium; the cleaning mechanism is configured to be able to perform cleaning of the plurality of print heads in a plurality of cleaning modes; the log includes information on the cleaning mode used when cleaning was performed; and the processor calculates the first threshold for each cleaning mode for each ink color using the following formula: TH(1) = AV(1) + CO(1) × σ(1), where TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient of 1 or more, and σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period.

5. The printing system of claim 1, wherein the processor counts the number of unit periods in which the number of cleanings exceeds the first threshold value during the extraction period as the number of times the threshold value is exceeded based on the number of cleanings per unit period during the extraction period, and calculates the status score based on the number of times the threshold value is exceeded.

6. The printing system described in claim 5, wherein the cleaning mechanism is configured to be able to perform cleaning of the print head in a plurality of cleaning modes, the log includes information on the cleaning mode used when cleaning was performed, and the processor counts the number of times the threshold is exceeded for each cleaning mode and calculates the condition score based on a value obtained by assigning a weight to the number of times the threshold is exceeded according to the cleaning mode.

7. The printing system according to claim 6, wherein the printing device has a plurality of print heads each ejecting a different color of ink onto the printing medium, and n cleaning modes, numbered 1 to n, are prepared as the plurality of cleaning modes, and the processor calculates the condition score for each ink color using the following formula: where S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents the weighting factor for the i-th cleaning mode.

8. The printing system of claim 5, wherein the processor determines a regression line showing the trend of increase or decrease in the number of cleanings during the extraction period based on the number of cleanings per unit period during the extraction period, and calculates the condition score taking into account the slope of the regression line.

9. The printing device has a plurality of print heads, each of which ejects a different color of ink onto the printing medium; the cleaning mechanism is configured to be able to clean the plurality of print heads in n cleaning modes, numbered from first to nth; the log includes information on the cleaning mode used when cleaning was performed; and the processor, based on the program stored in the memory, further: acquires, from among the logs output from the printing device, logs output during a preliminary period that is a period before the extraction period and longer than the extraction period, as preliminary logs; counts the number of cleanings per unit period during the preliminary period based on the preliminary logs; and determines the first threshold value by statistically processing the number of cleanings per unit period during the preliminary period; where P is a constant of 10 or less, the processor: calculates a usage rate for each cleaning mode; sets the first threshold value to 0 for cleaning modes whose usage rate is less than P percent; and calculates the first threshold value for cleaning modes whose usage rate is P percent or more using the following formula for each ink color: TH(1) = AV(1) + CO(1) × σ(1) The printing system according to claim 1 , wherein the processor counts, for each cleaning mode, the number of unit periods in which the number of cleanings exceeds the first threshold value during the extraction period based on the number of cleanings per unit period during the extraction period, and calculates the condition score for each ink color using the following formula: Here, TH(1) represents the first threshold, AV(1) represents the average number of cleanings per unit period in the preliminary period, CO(1) represents a coefficient greater than or equal to 1, σ(1) represents the standard deviation of the number of cleanings per unit period in the preliminary period, S represents the condition score, V(i) represents the number of times the threshold is exceeded for the i-th cleaning mode, and K(i) represents a weighting coefficient for the i-th cleaning mode.

10. The printing system described in claim 9, wherein the printing device includes a double-sided printing device having a print head that ejects ink onto the front side of the printing medium and a print head that ejects ink onto the back side of the printing medium, and the processor calculates the first threshold value for each cleaning mode for each side that ejects ink and for each color of ink for the double-sided printing device, and the processor calculates the condition score for each side that ejects ink and for each color of ink for the double-sided printing device.

11. The printing system of claim 1, wherein the processor: acquires the extraction log for each specified period set to a period shorter than the extraction period; counts the number of cleanings per unit period in the extraction period; and calculates the status score for each specified period.

12. The printing system described in claim 1 further includes a management device having a display unit and connected to the head condition estimation device via the communication line, wherein the processor further generates a result display image based on the condition score based on the program stored in the memory, and the result display image is displayed on the display unit.

13. The printing system described in claim 12, wherein the processor further determines a second threshold value by statistically processing the condition score calculated over a predetermined period of time in the past based on the program stored in the memory, and the result display image includes an image that graphically represents the relationship between the condition score over the predetermined period of time and the second threshold value.

14. The printing system of claim 13, wherein the processor calculates the second threshold value using the following formula: TH(2) = AV(2) + CO(2) × σ(2), where TH(2) represents the second threshold value, AV(2) represents the average value of the condition score during the specified period, CO(2) represents a coefficient of 1 or more, and σ(2) represents the standard deviation of the condition score during the specified period.

15. The printing system of claim 12, wherein the result display image includes an image of a mark that is color-coded according to the condition score.

16. The printing system of claim 12, wherein when two consecutive extraction periods are defined as an earlier extraction period and a later extraction period, the result display image based on the status score in the later extraction period includes an image showing an increase / decrease trend of the status score from the earlier extraction period.

17. The printing system according to claim 1, wherein when the printing device is started, the printing device outputs information about the serial number of the print head as the log.

18. A printing system described in any one of claims 1 to 17, wherein the head condition estimation device is connected to each printing device of a plurality of users via the communication line, and the processor calculates the condition score for each user based on logs output only from the printing device of that user.

19. A head condition estimation method for estimating the condition of a print head of a printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, wherein the printing device outputs a log containing information regarding cleaning of the print head, and the head condition estimation method includes: a first log acquisition step of acquiring, as an extracted log, logs output during an extraction period, which is a predetermined period, from the logs output from the printing device; a first cleaning frequency count step of counting the number of cleanings per unit period during the extraction period based on the extracted log; and a condition score calculation step of calculating a condition score representing the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

20. A printing device having a print head that ejects ink onto a printing medium and a cleaning mechanism that cleans the print head, comprising: a storage device that stores a log containing information regarding the cleaning of the print head; a processor; and a memory that stores a program, wherein the processor, based on the program stored in the memory, obtains, as an extracted log, a log based on cleaning performed during an extraction period, which is a predetermined period, from the logs stored in the storage device; counts the number of cleanings per unit period during the extraction period based on the extracted log; and calculates a condition score that represents the condition of the print head based on the result of comparing the number of cleanings per unit period during the extraction period with a first threshold value.

Images