Patent Publication Number: US-11648767-B2

Title: Printing system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. 2020-064877 filed on Mar. 31, 2020, the content of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     Aspects of the disclosure relate to a printing system including a server and a printer that performs maintenance of an ejection head. 
     BACKGROUND 
     A known maintenance system includes an estimation model used for estimating a recommended timing of a nozzle performance check based on use conditions. In such a maintenance system, the estimation model is updated based on a history of the actual use conditions after an ejection head is cleaned. This update improves appropriateness of the estimation model. The improvement of the appropriateness narrows a gap between the recommended timing of the nozzle performance check determined based on the estimation model and a timing at which an ejection failure actually occurs, thereby improving determination accuracy of the recommended timing. 
     SUMMARY 
     In the known maintenance system, the determination accuracy of the recommended timing at which maintenance is to be performed next and subsequent times may be improved by updating the estimation model based on the history of the actual use conditions after maintenance is performed. In other words, the timing at which maintenance was actually performed may be evaluated and the estimation model may be updated based on the evaluation result. The update of the estimation model may improve reliability of the recommended timing at which maintenance is to be performed. Nevertheless, in the known maintenance system, a manner of the performed maintenance might not be evaluated, and consideration might not be given to re-evaluation of the same maintenance according to situations in which an ejection failure has occurred after the maintenance. 
     Accordingly, aspects of the disclosure provide a printing system that may recommend a suitable maintenance manner for resolving an ejection failure by evaluating the maintenance manner using an evaluation index and re-evaluating the maintenance manner according to the degree of improving ejection performance after maintenance is performed in the maintenance manner. 
     In one or more aspects of the disclosure, a printing system includes a controller. The controller is configured to: receive first condition information related to an ejection failure in a printer; determine a maintenance manner applicable to the first condition information; cause the printer to perform a maintenance in the determined maintenance manner; receive second condition information related to the ejection failure in the printer after the maintenance is performed; determine whether an ejection performance in the printer has been improved based on the second condition information in response to performing the maintenance; update an evaluation index in accordance with determination of whether the ejection performance in the printer has been improved, the evaluation index corresponding to the determined maintenance manner. 
     According to one or more aspects of the disclosure, the printing system may recommend a suitable maintenance manner for resolving an ejection failure by evaluating the maintenance manner using an evaluation index and re-evaluating the maintenance manner according to the degree of improving ejection performance after maintenance is performed in the maintenance manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a general configuration of one of printers included in a printing system according to one or more illustrative embodiments of the disclosure. 
         FIG.  2    is a block diagram illustrating a configuration of the printing system including the printer of  FIG.  1    and other printers and an electrical configuration of one of the printers according to one or more illustrative embodiments of the disclosure. 
         FIG.  3 A  is a table showing an example database stored in a memory of a server according to one or more illustrative embodiments of the disclosure. 
         FIG.  3 B  is a continuation of the table of  FIG.  3 A  according to one or more illustrative embodiments of the disclosure. 
         FIG.  4    is a flowchart of a control procedure executed by a CPU of the printer and a CPU of the server in cooperation with each other according to one or more illustrative embodiments of the disclosure. 
         FIG.  5    is a continuation of the flowchart of  FIG.  4    according to one or more illustrative embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an illustrative embodiment will be described with reference to the accompanying drawings. In the illustrative embodiment, a description will be provided on a printing system including one or more printers. The printing system may enable a service provider to offer a printing service using the one or more printer to a customer (i.e., a user) who pays a fee for the service. 
     General Configuration of Printer 
     Referring to  FIG.  1   , a description will be provided on one of printers  1  that is included in a printing system  100  (refer to  FIG.  2   ) and owned by a service provider that offers a printing service using the printer  1  to a customer. The printers  1  may be owned by different service providers that offer the printing service using the respective printers  1 . All of the printers  1  have an identical configuration, and therefore, the description will be provided on one of the printers  1 . As illustrated in  FIG.  1   , the printer  1  includes a carriage  2 , an inkjet head  3 , a platen  4 , conveyance rollers  5  and  6 , a foam  7 , and a purging unit  8 . A side of the printer  1 , in which the purging unit  8  may be located, may be defined as the right of the printer  1 . A side of the printer  1 , in which the foam  7  may be located, may be defined as the left of the printer  1 . A side of the printer  1 , in which the conveyance roller  6  may be located, may be defined as the front of the printer  1 . A side of the printer  1 , in which the conveyance roller  5  may be located, may be defined as the rear of the printer  1 . A right-left direction corresponds to a main scanning direction. A frontward direction corresponds to a conveyance direction in which a recording sheet P is conveyed. The printer  1  may be an example of a printing apparatus. The carriage  2  may be an example of a moving unit and also an example of a printing unit. The inkjet head  3  may be an example of an ejection head. 
     The carriage  2  is connected to a carriage motor  56  (refer to  FIG.  2   ) via a belt. The carriage  2  is configured to move in the main scanning direction along guide rails  11  and  12 , in response to the carriage motor  56  being driven. 
     The inkjet head  3  is connected to a plurality of tubes, for example, four tubes  31 . The tubes  31  are connected to four ink cartridges  32 , respectively. The ink cartridges  32  are disposed next to each other in the main scanning direction at a right front corner portion of the printer  1 . The inkjet head  3  is supplied with black ink, yellow ink, cyan ink, and magenta ink stored in the respective ink cartridges  32  via the respective tubes  31 . 
     The inkjet head  3  is mounted on the carriage  2 . While the carriage  2  moves the inkjet head  3  in the main scanning direction, the inkjet head  3  ejects ink to perform printing. The inkjet head  3  includes a channel unit  13  and an actuator  14 . 
     The channel unit  13  has a nozzle surface  13 A that may be its lower surface. The nozzle surface  13 A has nozzles  10 . The channel unit  13  includes ink channels including the nozzles  10 . The nozzles  10  are arranged in four rows in the conveyance direction orthogonal to the main scanning direction to form nozzle rows  9 . The nozzle rows  9  are disposed next to each other in the main scanning direction at the nozzle surface  13 A. In each nozzle row  9 , the nozzles  10  are substantially equally spaced in the conveyance direction. The nozzles  10  in adjacent nozzle rows  9  are aligned in the main scanning direction. 
     The nozzle rows  9  include a black nozzle row, a yellow nozzle row, a cyan nozzle row, and a magenta nozzle row in this order from the right. The inkjet head  3  is configured to eject black ink, yellow ink, cyan ink, and magenta ink from the nozzles  10  belonging to the respective corresponding nozzle rows  9 . The nozzles  10  included in a single nozzle row  9  are provided for a single color of ink. A corresponding color of ink is supplied to the nozzles  10  included in a single nozzle row  9  via a common tube  31  and a common ink channel. That is, ink stored in an ink cartridge  32  flows to each nozzle  10  included in a single nozzle row  9  through a corresponding common tube  31  and a corresponding common ink channel in this order. Thus, each nozzle row  9  includes an upstream nozzle  10  and a downstream nozzle  10  located relative to each other in a direction in which ink flows in a corresponding ink channel. 
     The actuator  14  is configured to apply ejection energy to ink stored in each nozzle  10  individually, in response to the actuator  14  being driven. 
     The platen  4  is disposed below the inkjet head  3 . The platen  4  faces the nozzle surface  13 A during printing. The platen  4  has a size that extends over the entire width of a recording sheet P in the main scanning direction. The platen  4  may support a recording sheet P from below. The recording sheet P may be an example of a recording medium. The conveyance roller  5  is located upstream from the platen  4  in the conveyance direction. The conveyance roller  6  is located downstream from the platen  4  in the conveyance direction. The conveyance rollers  5  and  6  are connected to a conveyance motor  57  (refer to  FIG.  2   ) via gears. The conveyance rollers  5  and  6  are configured to rotate to convey a recording sheet P in the conveyance direction, in response to the conveyance motor  57  being driven. 
     Such a configuration may enable the printer  1  to perform printing on a recording sheet P. More specifically, every time the conveyance rollers  5  and  6  convey a recording sheet P by a certain distance, the inkjet head  3  ejects ink from one or more nozzles  10  while the carriage  2  moves in the main scanning direction. 
     Foam 
     The foam  7  includes ink absorbable material such as sponge, and is disposed further to the left than the platen  4 . In the printer  1 , thus, the carriage  2  is movable to position at a flushing position where the nozzle surface  13 A faces the form  7  under control of a controller  50  of the printer  1 . Such a configuration may thus enable the printer  1  to perform flushing. 
     Purging Unit 
     The purging unit  8  includes a cap  21 , a switching unit  22 , a suction pump  23 , and a waste liquid tank  24 . 
     The cap  21  is disposed further to the right than the platen  4 . In the printer  1 , thus, the carriage  2  is movable to position at a maintenance position where the nozzle surface  13 A faces the cap  21  under control of the controller  50 . The cap  21  includes a capping portion  21 A and a capping portion  21 B disposed to the left of the capping portion  21 A. In a state where the carriage  2  is positioned at the maintenance position, the nozzles  10  belonging to the rightmost nozzle row  9  face the capping portion  21 A and the nozzles  10  belonging to the other three nozzle rows  9  face the capping portion  21 B. 
     The cap  21  is movable upward and downward selectively under control of a cap up-and-down device  58  (refer to  FIG.  2   ). That is, the cap  21  is movable in a direction intersecting the nozzle surface  13 A between a capping position and an uncapping position. When the cap  21  is moved upward in a state where the carriage  2  is positioned at the maintenance position, the cap  21  comes into intimate contact with the nozzle surface  13 A of the inkjet head  3  to cover the nozzles  10 . More specifically, the capping portion  21 A covers the nozzles  10  belonging to the rightmost nozzle row  9  and the capping portion  21 B covers the nozzles  10  belonging to the other three nozzle rows  9 . Hereinafter, the state where the cap  21  covers the nozzles may be referred to as a “capping state”. The state where the cap  21  is not in the capping state may be referred to as an “uncapping state”. As described above, the cap up-and-down device  58  is configured to move the cap  21  upward and downward between the capping position and the uncapping position. When the cap  21  is located at the capping position, the cap  21  is in the capping state. The uncapping position is lower than the capping position. 
     The cap  21  may have an alternative configuration to intimately contact the nozzle surface  13 A to cover the nozzles  10 . Such alternative configuration may include the channel unit  13  including a frame that surrounds the nozzle surface  13 A for protecting the nozzles  10 . In this case, the cap  21  may intimately contact the frame to cover the nozzles  10 . 
     The switching unit  22  is connected to the capping portions  21 A and  21 B via tubes  29 A and  29 B, respectively. The switching unit  22  is also connected to the suction pump  23  via a tube  29 C. The switching unit  22  switches a connection destination of the suction pump  23  between the capping portion  21 A and the capping portion  21 B. The suction pump  23  may be a peristaltic pump. The suction pump  23  has one end connected to the waste liquid tank  24  via a tube  29 D and the other end connected to the switching unit  22  via the tube  29 C. 
     The purging unit  8  and the foam  7  may be examples of a maintenance unit. 
     Printing System 
     Referring to  FIG.  2   , a description will be provided on a configuration of the printing system  100  including the printers  1 . The printing system  100  includes a plurality of the printers  1  and a server  200 . Each printer  1  and the server  200  are connected to a network NT. Each printer  1  is thus communicable with the server  200  via the network NT. 
     Server 
     The server  200  includes a memory  210  and a CPU  220 . The memory  210  stores a database DB (refer to  FIGS.  3 A and  3 B ). The CPU  220  may be an example of a second controller. The memory  210  may be an example of a storage. 
     Printer 
     Referring to  FIG.  2   , a description will be provided on an electrical configuration of the printer  1 . The printer  1  further includes the controller  50 . The controller  50  controls operation of the printer  1 . 
     The controller  50  includes a CPU  51 , a ROM  52 , a RAM  53 , an EEPROM  54 , an ASIC  55 , and an interface  90 . The CPU  51  may be an example of a first controller. Such a configuration enables the controller  50  to control the carriage motor  56 , the actuator  14 , the conveyance motor  57 , the cap up-and-down device  58 , the switching unit  22 , and the suction pump  23 . 
     The controller  50  further includes a failure nozzle detector  84  configured to detect an ink ejection failure caused by clogging of a nozzle  10  in the inkjet head  3  or other causes. The failure nozzle detector  84  is connected to an ejection detector  64  disposed at a position where the ejection detector  64  faces the inkjet head  3 . The ejection detector  64  includes a conductive material that may be electrically connected to an ink absorbing material. The failure nozzle detector  84  is configured to detect an electrical signal traveling through the conductive material. More specifically, the failure nozzle detector  84  is configured to detect a signal indicating changes in current caused in response to driving the inkjet head  3  to eject a charged ink droplet toward the absorbing material. In a case where a value of the signal is less than or equal to a certain threshold, the failure nozzle detector  84  determines that a certain amount of ink has not been ejected from the particular nozzle  10  or no ink has been ejected from the particular nozzle  10 . In other words, the failure nozzle detector  84  is configured to detect a failure nozzle  10  that has failed to eject ink. The failure nozzle detector  84  may be an example of an ejection failure detector. 
     Nevertheless, the detection of a failure nozzle  10  may be implemented in another manner. For example, the controller  50  may control the carriage motor  56  and the conveyance rollers  5  and  6  to cause the inkjet head  3  to print an appropriate test pattern. Then, the test pattern may be scanned using a CCD or another photosensor to detect which nozzle  10  is a failure nozzle. 
     The interface  90  may be a wired or wireless LAN interface that enables the printer  1  to communicate with another device. The interface  90  is connected to the network NT. 
     Although, as illustrated in  FIG.  2   , the controller  50  includes a single CPU  51 , the controller  50  may include a plurality of CPUs  51 . In this case, processing tasks may be divided among the CPUs  51 . Although, as illustrated in  FIG.  2   , the controller  50  includes a single ASIC  55 , the controller  50  may include a plurality of ASICs  55 . In this case, processing tasks may be divided among the ASICs  55 . 
     Flushing 
     Next, a description will be provided on flushing to be performed as the maintenance described above. 
     The printer  1  performs flushing under control of the controller  50 . The flushing is that, in a state where the carriage  2  is located at the flushing position, the controller  50  drives the actuator  14  to cause the inkjet head  3  to discharge from the nozzles  10  ink that may have high viscosity. The details of flushing are as described below. 
     When the printer  1  is in a standby mode, the cap  21  is in the capping state to reduce ink evaporation due to evaporation of moisture in ink at the nozzles  10 . During printing, first, the controller  50  controls the cap up-and-down device  58  to move the cap  21  downward. Then, the controller  50  controls the carriage motor  56  to move the carriage  2  to stop at the flushing position, and controls the actuator  14  to perform flushing. A intensity mode of flushing may be controlled between a high intensity mode and a low intensity mode under control of the controller  50 . More specifically, the controller  50  switches voltage to be applied to the actuator  14  between a high voltage and a low voltage to change the intensity mode of flushing. The controller  50  may control the actuator  14  for each individual nozzle  10 . After flushing, while the controller  50  controls the carriage motor  56  to move the carriage  2  in the main scanning direction within a range in which the nozzle surface  13 A faces a recording sheet P, the controller  50  controls the actuator  14  to cause the inkjet head  3  to eject ink from appropriate one or more nozzles  10  to perform printing. After printing, the controller  50  controls the carriage motor  56  to move the carriage  2  to stop at the maintenance position. Then, the controller  50  controls the cap up-and-down device  58  to move the cap  21  upward to bring the cap  21  into the capping state. 
     Purge 
     Next, a description will be provided on a purge to be performed by the purging unit  8  as the maintenance described above. 
     In a state where the cap  21  is in the capping state, the controller  50  controls the switching unit  22  to connect the suction pump  23  to the capping portion  21 A and then drives the suction pump  23 . That is, the printer  1  performs a suction purge for discharging black ink in the channel unit  13  from the nozzles  10  belonging to the rightmost nozzle row  9 . 
     Thereafter, in the printer  1 , while the cap  21  is maintained in the capping state, the controller  50  controls the switching unit  22  to connect the suction pump  23  to the capping portion  21 B and then drives the suction pump  23 . That is, the printer  1  performs a suction purge for discharging color inks such as yellow ink, cyan ink, and magenta ink in the respective channel units  13  from the nozzles  10  belonging to the other three nozzle rows  9 . Ink discharged from the inkjet head  3  by the respective suction purges is collected in the waste liquid tank  24 . 
     In addition to the suction purges, the printer  1  may perform an exhaust purge for discharging air entered and trapped in an air trap chamber from the nozzles  10 . The air trap chamber is disposed above the nozzles  10  in the inkjet head  3 . The exhaust purge may be implemented by a known configuration and manner. 
     In the illustrative embodiment, as described above, the printer  1  performs a purge or flushing as maintenance. In both of the purge and flushing, ink is consumed due to discharging. Nevertheless, in other embodiments, the printer  1  may perform another operation as maintenance. For example, ink may be circulated such that ink may be supplied from a cartridge to an inkjet head and residual ink after printing may be supplied to the inkjet head again via a circulation channel. An ink circulation speed may be increased as maintenance. Such a circulation may reduce increase of the ink viscosity without wasting ink, thereby improving the ink ejection performance of the inkjet head  3 . 
     Maintenance Evaluation 
     In the printing system  100 , a respective printer  1  performs maintenance in a particular maintenance manner. The particular maintenance manner adopted in the maintenance is rated on a scale of points that may be an evaluation index. The evaluation index indicates effectiveness of the maintenance manner for recovering ejection performance of the nozzles  10 . The evaluation history and the evaluation indexes are stored in the database DB stored in the memory  210  of the server  200 . 
     Database 
     Referring to  FIGS.  3 A and  3 B , a description will be provided on the database DB. The database DB is a merely example. The database DB includes twenty-two records with record numbers from 1 to 22. The database DB includes fields for “failure nozzle percentage/pattern”, “occurrence area”, “printer condition”, “maintenance manner”, “rank”, and “rank update date”. Each record includes a value or details of each field. 
     The field “failure nozzle percentage/pattern” indicates a percentage of failure nozzles  10  detected by the failure nozzle detector  84  with respect to the total number of nozzles  10  in the inkjet head  3 , or a location pattern of detected failure nozzles  10 . The percentage of failure nozzles  10  may be an example of first data. The percentage of failure nozzles  10  is hereinafter referred to as a “failure nozzle percentage”. The location pattern of detected failure nozzles  10  may be an example of second data. The details of the field “failure nozzle percentage/pattern” may be hereinafter simply referred to as “failure nozzle data”. 
     In this example, in each of the records of Nos. 1 to 4, the failure nozzle data indicates that the failure nozzle percentage is 50% or more. In each of the records of Nos. 5 to 10, the failure nozzle data indicates that the failure nozzle percentage is 12.5% or more but less than 50%. In each of the records of Nos. 11 to 18, the failure nozzle data indicates that the failure nozzle percentage is less than 12.5%. In each of the records of Nos. 19 to 22, the failure nozzle data indicates that the nozzles  10  includes two or more failure nozzles  10  that are located next to each other in the main scanning direction and included in two or more of the nozzle rows  9 . 
     The field “occurrence area” indicates an area where the failure nozzles  10  are detected in the inkjet head  3  by the failure nozzle detector  84 . Hereinafter, such an area may be simply referred to as an “occurrence area”. The occurrence area is another example of the second data. The details of the field “occurrence area” may be hereinafter simply referred to as “occurrence area data”. 
     In this example, in each of the records of Nos. 5 and 6, the occurrence area data indicates that most of the failure nozzles  10  are located in an upstream portion of the inkjet head  3  along the one or more ink channels. In each of the records of Nos. 7 and 8, the occurrence area data indicates that most of the failure nozzles  10  are located in a downstream portion of the inkjet head  3  along the one or more ink channels. In each of the records Nos. 9 and 10, the occurrence area data indicates that the failure nozzles  10  are randomly located in both the upstream portion and the downstream portion of the inkjet head  3 . In each of the records of Nos. 11 to 14, the occurrence area data indicates that all of the failure nozzles  10  is located in the upstream portion or in the downstream portion of the inkjet head  3  along the one or more ink channels. In each of the records Nos. 15 to 18, the occurrence area data indicates that the failure nozzles  10  are randomly located in both of the upstream portion and the downstream portion of the inkjet head  3 . 
     The database DB may include both or only one of the first data and the second data. That is, in this illustrative embodiment, the database DB only need to include at least one of the first data or the second data, and the at least one of the first data or the second data only need to be taken into consideration in selecting and determining a maintenance manner to be adopted. 
     The field “printer condition” indicates temperature detected by a temperature sensor and humidity detected by a humidity sensor. The sensors are disposed in the printer  1 . The temperature sensor detects temperature at the printer  1 . The temperature may be an example of a detector that detects a condition of the printer  1 . The humidity sensor detects humidity at the printer  1 . The humidity sensor may be another example of the detector. The field “printer condition” also indicates the presence or absence of a sheet conveyance failure. The printer  1  further includes a sensor that determines a sheet conveyance condition. An occurrence of a sheet conveyance failure is detected based on, for example, a detection result of the sensor and a drive control condition of the conveyance motor  57 . The function of detecting a sheet conveyance failure using such a sensor may be another example of the detector. 
     The details of the field “printer condition” may be hereinafter simply referred to as “printer condition data”. 
     In each of the records of Nos. 1 and 2, the printer condition data indicates that an average temperature between the previous ejection failure detection and the latest ejection failure detection by the failure nozzle detector  84  is Y1 [° C.] or higher. In each of the records of Nos. 3 and 4, the printer condition data indicates that the average temperature is lower than Y1 [° C.]. 
     Hereinafter, the average temperature between the previous ejection failure detection and the latest ejection failure detection by the failure nozzle detector  84  may be simply referred to as an “average temperature since the last ejection failure detection”. The value “Y1” is a threshold specified in advance, and may be a criterion for occurrence of inhibition of ink flow due to a growth of air mass intruded into the ink channels. 
     In each of the records of Nos. 11, 12, 15, and 16, the printer condition data indicates that the average temperature since the last ejection failure detection is Y2 [° C.] or higher. In each of the records of Nos. 13, 14, 17, and 18, the printer condition data indicates that the average temperature since last ejection failure detection is lower than Y2 [° C.]. The value “Y2” is a threshold specified in advance, and may be a criterion for occurrence of, for example, inhibition of ink flow due to increase of the ink viscosity under low temperature environment. The value “Y2” is less than the value “Y1”. 
     In each of the records of Nos. 19 and 20, the printer condition data indicates that a sheet conveyance failure has occurred due to a contact between the inkjet head  3  and a recording sheet P immediately before an ejection failure detection by the failure nozzle detector  84  is performed. More specifically, for example, the occurrence of such a sheet conveyance failure may be detected when, for example, the carriage  2  moves in a state where a floating recording sheet P contacts the lower surface of the inkjet head  3 . In each of the records of Nos. 21 and 22, the printer condition data indicates that such a conveyance failure has not occurred immediately before an ejection failure detection. 
     The field “maintenance manner” indicates a maintenance manner that has been adopted in previous maintenance, and a suction intensity mode. Nevertheless, the field “maintenance manner” might not necessarily include all the data but only need to include at least one of the maintenance manner or the suction intensity mode. Hereinafter, the details of the field “maintenance manner” may be simply referred to as “maintenance manner data”. 
     In each of the records Nos. 1, 2, 3, and 8, the maintenance manner data indicates that a suction purge was performed by the purging unit  8  at a high intensity mode. In the record of No. 2, the maintenance manner data indicates that an exhaust purge was performed in addition to a suction purge. In each of the records of Nos. 4, 6, 7, 10, 12, 16, 20, and 22, the maintenance manner data indicates that a suction purge was performed by the purging unit  8  at a medium intensity mode. In each of the records of Nos. 5, 9, 11, 14, 15, 18, 19, and 21, the maintenance manner data indicates that a suction purge was performed by the purging unit  8  at a low intensity mode. In the illustrative embodiment, for example, the suction intensity modes “high”, “medium”, and “low” in a suction purge are realized by respective different operating durations of the suction pump  23 . In other words, the suction intensity modes “high”, “medium”, and “low” are realized by a long operating duration, a medium operating duration, and a short operating duration of the suction pump  23  relative to each other. 
     In each of the records of Nos. 13 and 17, the maintenance manner data indicates that flushing using the foam  7  was performed. In flushing according to the records of Nos. 13 and 17, a relatively high voltage is applied by the controller  50  to a particular portion of the actuator  14  corresponding to a failure nozzle  10  detected by the failure nozzle detector  84  to perform flushing on the failure nozzle  10  at a high intensity mode. For example, the flushing intensity modes “high” and “low” are realized by a high voltage and a low voltage, respectively, to be applied by the controller  50 . 
     In each record, the field “rank” indicates a rank representing an evaluation index for the maintenance manner adopted in previous maintenance. In each record, the maintenance manner data indicates the details of a maintenance manner adopted in particular maintenance for an ejection failure identified by the failure nozzle data, the occurrence area data, and the printer condition data in a corresponding record. A rank as an evaluation index is assigned to a maintenance manner adopted in each maintenance performed on a respective ejection failure according to the degree of improving ejection performance. The rank initially has a value of 5 that is an intermediate value of the scale. The greater the value, the higher the rank and the higher the evaluation. In a case where the ejection performance has been improved by a certain extent (e.g., not less than 50% of the failure nozzles  10  has been recovered) by maintenance in a particular maintenance manner having rank “5”, the rank of the particular maintenance manner is raised (i.e., rank “6”). That is, the value indicating the rank is incremented by one, and thus, the rank becomes higher than rank “5”. In a case where the ejection performance has not been changed or has not been improved by the certain extent (e.g., less than 50% of the failure nozzles  10  has been recovered) although maintenance was performed in the particular maintenance manner having rank “5”, the rank of the particular maintenance manner is lowered (i.e., rank “4”). That is, the value indicating the rank is decremented by one, and thus, the rank becomes lower than rank “5”. After that, in a case where maintenance is performed in the same particular maintenance manner for an ejection failure occurred in the same situation, if the ejection performance has been improved by the certain extent by the maintenance, the rank of the adopted maintenance manner is raised, that is, the value indicating the rank is incremented by one. If the ejection performance has not been changed or has not been improved by the certain extent by the maintenance, the rank is lowered, that is, the value indicating the rank is decremented by one. 
     In each record, the field “rank update date” indicates the last date on which the rank was updated based on the evaluation of a maintenance manner adopted in maintenance that has been performed on an ejection failure identified by the failure nozzle data, the occurrence area data, and the printer condition data. In a case where a maintenance manner included in a particular record has not been adopted more than once, the date on which the maintenance manner was first adopted is indicated in the field “rank update date”. 
     For example, the record of No. 1 indicates a case where a maintenance manner that is a suction purge at a high intensity mode was adopted in particular maintenance in a situation where the failure nozzle percentage is 50% or more and the average temperature since the last ejection failure detection is Y1 [° C.] or higher. The record of No. 1 further indicates that the last date on which such a maintenance manner was adopted is Feb. 5, 2020 and the evaluation index that has been updated on the same day, that is, the current rank indicates rank “9”. 
     The record of No. 2 indicates another case where another maintenance manner that is a suction purge at a high intensity mode and an exhaust purge were both adopted in another particular maintenance in a situation where the failure nozzle percentage is 50% or more and the average temperature since the last ejection failure detection is Y1 [° C.] or higher. The record of No. 2 further indicates that the last date on which such a maintenance manner was adopted is Feb. 10, 2020 that is later than that in the record of No. 1. Nevertheless, the record of No. 2 indicates that the evaluation index that has been updated on the same day, that is, the current rank indicates rank “8” that is lower than that in the record of No. 1. 
     Different maintenance manners may be adopted for ejection failures occurred in the same situation. In this case, the respective cases are recorded as different cases in the database DB. In a case where an ejection failure occurs in the same situation as the situation indicated in those records, in the illustrative embodiment, the maintenance manner having the highest rank thereamong is to be adopted. More specifically, for example, it is assumed that the rank of the maintenance manner in the record of No. 2 has rank “10” as of Feb. 9, 2020 and an ejection failure has occurred twice on Feb. 10, 2020 in a situation where the failure nozzle percentage is 50% or more and the average temperature since the last ejection failure detection is Y1 [° C.] or higher. That is, an ejection failure has occurred twice on Feb. 10, 2020 in the same situation as the situation indicated in each of the records of Nos. 1 and 2. When the first ejection failure occurred, the maintenance manner in the record of No. 2 has rank “10” that was higher than the rank “9” of the maintenance manner in the record of No. 1. Thus, the maintenance manner in the record of No. 2 was adopted in maintenance for the first ejection failure. That is, a suction purge at a high intensity mode and an exhaust purge were both performed as the maintenance. Nevertheless, the ejection performance has not been changed or has not been improved by the certain extent. Thus, the rank of the maintenance manner in the record of No. 2 was lowered by one rank from rank “10” to rank “9”. When the second ejection failure occurred, the maintenance manner in the record of No. 2 has the same rank as the rank of the maintenance manner in the record of No. 1. In this case, the maintenance manner with the latest update date is determined as a maintenance manner to be adopted. Thus, the maintenance manner in the record of No. 2 was again adopted in maintenance for the second ejection failure. Nevertheless, the ejection performance has not been changed or has not been improved by the certain extent. Thus, the rank of the maintenance manner in the record of No. 2 was further lowered by one rank from rank “9” to rank “8”. Accordingly, in a case where an ejection failure occurs in the same situation after the rank of the maintenance manner in the record of No. 2 was updated twice on Feb. 10, 2020, the maintenance manner in the record of No. 1 is to be adopted in maintenance for the ejection failure. 
     The records of Nos. 1 and 2 may indicate the evaluation results of the respective maintenance manners adopted in maintenance performed in the same printer  1  or in different printers  1 . 
     For example, the record of No. 9 indicates another case where another maintenance manner that is a suction purge at a low intensity mode was adopted in another particular maintenance in a situation where the failure nozzle percentage is 12.5% or more but less than 50% and failure nozzles are located randomly. The record of No. 9 further indicates that the last date on which such a maintenance manner was adopted is Jan. 30, 2020 and the evaluation index that has been updated on the same day, that is, the current rank indicates rank “7”. 
     The record of No. 10 indicates another case where another maintenance manner that is a suction purge at a medium intensity mode was adopted in another particular maintenance in a situation where the failure nozzle percentage is 12.5% or more but less than 50% and the failure nozzles are located randomly. The record of No. 10 further indicates that the last date on which such a maintenance manner was adopted is Feb. 11, 2020 that is later than that in the record of No. 9. Nevertheless, the record of No. 10 indicates that the evaluation index that has been updated on the same day, that is, the current rank indicates rank “9” that is higher than that in the record of No. 9. 
     More specifically, for example, it is assumed that the maintenance manner in the record of No. 10 has rank “8” as of Feb. 11, 2020 and an ejection failure has occurred on Feb. 11, 2020 in a situation where the failure nozzle percentage is 12.5% or more but less than 50% and the failure nozzles are located randomly. That is, an ejection failure has occurred in the same situation as the situation indicated in each of the records of Nos. 9 and 10. When the ejection failure occurred, the maintenance manner in the record of No. 10 has rank “8” that was higher than rank “7” of the maintenance manner in the record of No. 9. Thus, the maintenance manner in the record of No. 10 was adopted in maintenance for the ejection failure. That is, a suction purge at a medium intensity mode was performed as the maintenance. As a result of the maintenance, the ejection performance has been improved by the certain extent. Thus, the rank of the maintenance manner in the record of No. 10 was raised by one rank from rank “8” to rank “9”. Accordingly, in a case where an ejection failure occurs in the same situation after the rank of the maintenance manner in the record of No. 10 was updated on Feb. 11, 2020, the maintenance manner in the record of No. 10 is to be adopted in maintenance for the ejection failure. 
     Control Procedure for Maintenance 
     Referring to  FIGS.  4  and  5   , a description will be provided on a control procedure executed by the CPU  51  of the printer  1  and the CPU  220  of the server  200  in cooperation with each other with reference to the database DB (refer to  FIGS.  3 A and  3 B ). The following maintenance processing is implemented by the control procedure in which the CPU  51  of the printer  1  and the CPU  220  of the server  200  execute a maintenance processing program included in programs stored in the ROM  52  and the memory  210 . 
     As illustrated in  FIG.  4   , in the printer  1 , the CPU  51  determines whether the timing of periodic maintenance has come (e.g., step S 11 ). If the CPU  51  determines that the timing of periodic maintenance has come (e.g., YES in step S 11 ), the CPU  51  initializes a variable N to 0 (zero) (e.g., step S 13 ). The variable N indicates the number of times maintenance has been performed. Subsequent to step S 13 , the CPU  51  executes an ejection failure detection (e.g., step S 15 ). More specifically, the CPU  51  causes the failure nozzle detector  84  to detect a failure nozzle  10  via the ejection detector  64 , that is, determines whether an ejection failure has occurred. At step S 15 , the CPU  51  also causes each sensor (e.g., the temperature sensor) to detect a corresponding condition. Subsequent to step S 15 , the CPU  51  transmits, to the server  200 , a result of the ejection failure detection executed by the failure nozzle detector  84  (e.g., step S 17 ). The result of the ejection failure detection includes information corresponding to the failure nozzle data, information corresponding to the occurrence area data, and information corresponding to the printer condition data. Hereinafter, the information corresponding to the failure nozzle data, the information corresponding to the occurrence area data, and the information corresponding to the printer condition data are collectively referred to as “ejection failure information”. The information corresponding to the failure nozzle data and the information corresponding to the occurrence area data both transmitted to the server  200  in step S 17  may be examples of first condition information. The information corresponding to the printer condition data transmitted to the server  200  in step S 17  may be an example of third condition information. In the illustrative embodiment, if the CPU  51  determines, in step S 11 , that the timing of periodic maintenance has come (e.g., YES in step S 11 ), the CPU  51  executes step S 13  and the subsequent steps. Nevertheless, in other embodiments, the CPU  51  may execute step S 13  and the subsequent steps in response to receiving an instruction to start printing or in response to the power of the printer  1  being turned on. 
     In the server  200 , in response to the printer  1  transmitting the ejection failure information to the server  200 , the CPU  220  receives the ejection failure information from the printer  1  (e.g., step S 19 ). Subsequent to step S 19 , the CPU  220  determines, based on the received ejection failure information, whether all the nozzles  10  are normal, that is, whether the failure nozzle percentage is 0% (e.g., step S 21 ). If the CPU  220  determines that the failure nozzle percentage is 0% (e.g., YES in step S 21 ), no maintenance is to be performed on the inkjet head  3 . Thus, the routine ends. If the CPU  220  determines that the failure nozzle percentage is more than 0% (e.g., NO in step S 21 ), the CPU  220  accesses the database DB stored in the memory  210 . The CPU  220  searches the database DB for a record applicable to the ejection failure information (e.g., step S 23 ). The applicable record includes a record indicating the same or similar situation to the situation where the currently ejection failure has occurred described in the ejection failure information. In this illustrative embodiment, “the record indicating similar situation” may be a record in which a condition indicated by at least one of the failure nozzle data, the occurrence area data, or the printer condition data includes a condition indicated by the ejection failure information. 
     Subsequent to step S 23 , the CPU  220  determines whether the database DB includes at least one record including the same or similar situation (e.g., step S 25 ). If the CPU  220  determines that the database DB does not include any of such record (e.g., NO in step S 25 ), the routine proceeds to step S 27 . In this illustrative embodiment, the CPU  220  determines that the database DB does not include at least one record including the same or similar situation in a case where the database DB does not include a record in which a condition indicated by at least one of the failure nozzle data, the occurrence area data, or the printer condition data includes a condition indicated by the ejection failure information. In step S 27 , the CPU  220  determines a default manner as a maintenance manner to be adopted. Details of the default manner is predetermined. The default manner includes, for example, a suction purge at a medium intensity mode. Subsequent to step S 27 , the routine proceeds to step S 33 . The default manner may be an example of a specific maintenance manner. 
     If the CPU  220  determines that the database DB includes at least one record including the same or similar situation (e.g., YES in step S 25 ), the routine proceeds to step S 29 . In step S 29 , the CPU  220  selects each maintenance manner included in the at least one record including the same or similar situation. 
     In a case where the received ejection failure information indicates that an ejection failure has occurred in a situation where the failure nozzle percentage is 50% or more and the average temperature since the last ejection failure detection is Y1 [° C.] or higher, the CPU  220  selects the maintenance manners included in the respective records of Nos. 1 and 2. The maintenance manner in the record of No. 1 includes a suction purge at a high intensity mode. The maintenance manner in the record of No. 2 includes a suction purge at a high intensity mode and an exhaust purge. In a case where the received ejection failure information indicates that an ejection failure has occurred in a situation where the failure nozzle percentage is 12.5% or more but less than 50% and the failure nozzles are located randomly, the CPU  220  selects the maintenance manners included in the respective records of Nos. 9 and 10. The maintenance manner in the record of No. 9 includes a suction purge at a low intensity mode. The maintenance manner in the record of No. 10 includes a suction purge at a medium intensity mode. 
     Subsequent to step S 29 , the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner having the highest rank at this moment among the maintenance manners selected in step S 29  (e.g., step S 31 ). 
     More specifically, for example, in a case where the CPU  220  selects the maintenance manners in the respective records of Nos. 1 and 2 (e.g., step S 29 ), the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner in the record of No. 1 that has a higher rank than the rank of the maintenance manner in the record of No. 2. That is, a suction purge at a high intensity mode is to be adopted. In a case where the CPU  220  selects the maintenance manners in the respective records of Nos. 9 and 10 (e.g., step S 29 ), the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner in the record of No. 10 that has a higher rank than the rank of the maintenance manner in the record of No. 9. That is, a suction purge at a medium intensity mode is to be adopted. 
     In a case where the CPU  220  selects different maintenance manners having the same rank from two or more applicable records (e.g., step S 29 ), the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner that was adopted in the latest maintenance, that is, the maintenance manner with the latest update date. More specifically, for example, in a case where the CPU  220  selects the maintenance manners in the respective records of Nos. 15 and 16, the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner in the record of No. 16. That is, a suction purge at a medium intensity mode is to be adopted for an ejection failure currently occurring in a situation where the failure nozzle percentage is less than 12.5% and the average temperature since the last ejection failure detection is Y2 [° C.] or higher. 
     Nevertheless, in other embodiments, in a case where the CPU  220  selects the maintenance manners having the same rank (e.g., step S 29 ), the CPU  220  may determine, as a maintenance manner to be adopted, the maintenance manner in which less ink is consumed during maintenance as compared with the other maintenance manners. For example, ink consumption amount increases in the order of flushing, a suction purge at a low intensity mode, a suction purge at a medium intensity mode, and a suction purge at a high intensity mode. 
     As described above, in steps S 27  and S 31 , a maintenance manner to be adopted is determined based on the search for an applicable record in the database DB in step S 23  and based on the sameness or similarity of the ejection failure information with respect to the ejection failure data, the occurrence area data, and the printer condition data in each record. 
     That is, in regard to the field “failure nozzle percentage/pattern” and the field “occurrence area” in the database DB, a maintenance manner to be adopted may be determined based on at least one of the information corresponding to the failure nozzle data (e.g., the first data) or the information corresponding to the occurrence area data (e.g., the second data) included in the ejection failure information. More specifically, for example, as described above, a maintenance manner to be adopted may be determined based on the percentage of failure nozzles with respect to the total number of nozzles  10 , whether the failure nozzles  10  are located next to each other in the main scanning direction, and where the failure nozzles are located with respect to an ink channel (e.g., an upstream portion or a downstream portion of the inkjet head  3 ). 
     In regard to the field “printer condition” in the database DB, a maintenance manner to be adopted may be determined based on the information corresponding to the printer condition data included in the ejection failure information. 
     In particular, in the illustrative embodiment, a maintenance manner to be adopted may be determined based on the information corresponding to the failure nozzle data, the information corresponding to the occurrence area data, and the information corresponding to the printer condition data. 
     Subsequent to step S 31  or S 27 , the CPU  220  transmits, to the printer  1 , an instruction to perform maintenance in the maintenance manner determined in step S 31  or S 27  (hereinafter, simply referred to as a maintenance instruction) (e.g., step S 33 ). In response to this, in the printer  1 , the CPU  51  receives the maintenance instruction from the server  200  (e.g., step S 35 ). Subsequent to step S 35 , in the printer  1 , the CPU  51  causes the printer  1  to perform maintenance in the maintenance manner specified in the received maintenance instruction (e.g., step S 37 ). The maintenance instruction may be an example of maintenance information. Subsequent to step S 37 , the CPU  51  increments the variable N by 1 (one) (e.g., step S 39 ). 
     Subsequent to step S 39 , as illustrated in  FIG.  5   , in the printer  1 , as with step S 15 , the CPU  51  determines, via the ejection detector  64 , whether an ejection failure has occurred with respect to each nozzle  10  (e.g., step S 41 ). Subsequent to step S 41 , as with step S 17 , the CPU  51  transmits, to the server  200 , ejection failure information as the result of the ejection failure detection (e.g., step S 43 ). The ejection failure information transmitted to the server  200  in step S 43  may be an example of second condition information. 
     In the server  200 , in response to the printer  1  transmitting the ejection failure information to the server  200 , as with step S 19 , the CPU  220  receives the ejection failure information from the printer  1  (e.g., step S 45 ). Subsequent to step S 45 , as with step S 21 , the CPU  220  determines, based on the received ejection failure information, whether the failure nozzle percentage is 0% (e.g., step S 47 ). If the CPU  220  determines that the failure nozzle percentage is 0% (e.g., YES in step S 47 ), the CPU  220  determines that the maintenance manner adopted in the maintenance performed in step S 37  was effective for the currently-occurring ejection failure, and thus increments the evaluation index of the adopted maintenance manner by one (e.g., step S 49 ). That is, the rank of the maintenance manner is raised. Facts that the maintenance manner adopted in the maintenance performed in step S 37  was effective for the currently-occurring ejection failure refers to the ejection performance having been improved by the certain extent. Thus, the updated rank of the maintenance manner adopted for the currently-occurring ejection failure is recorded in the database DB. 
     In other words, in a case where, in step S 25 , the CPU  220  determines that the database DB includes the record including same situation as the situation when the current ejection failure has occurred, the printer  1  performs maintenance in the same maintenance manner as the maintenance manner in the record in step S 37 . Thereafter, in the server  200 , the CPU  220  increments the value indicating the current rank of the adopted maintenance manner by one and overwrites the current rank with a new rank. 
     In a case where, in step S 25 , the CPU  220  determines that the database DB includes the record including similar situation to the situation when the current ejection failure has occurred, the printer  1  performs maintenance in the same maintenance manner as the maintenance manner in the record in step S 37 . Thereafter, in the server  200 , the CPU  220  generates a new record that is different from the record including the similar situation, and stores the generated record in the database DB. That is, the newly-generated record includes the details of the ejection failure information transmitted in step S 17  and received in step S 19 , the maintenance manner adopted in the maintenance performed in step S 37 , and the updated rank. The details of the ejection failure information include the information corresponding to the failure nozzle data, the information corresponding to the occurrence area data, and the information corresponding to the printer condition data detected in step S 15 . In response to completion of step S 49 , the routine proceeds to step S 55 . 
     If the CPU  220  determines that the failure nozzle percentage is not 0% (e.g., NO in step S 47 ), the CPU  220  determines whether the failure nozzle percentage is 50% or less (e.g., step S 51 ). If the CPU  220  determines that the failure nozzle percentage is higher than 50% (e.g., NO in step S 51 ), the CPU  220  determines that the maintenance manner adopted in the maintenance performed in step S 37  is not effective for the currently-occurring ejection failure, and thus decrements the evaluation index by one (e.g., step S 53 ). That is, the rank of the maintenance manner is lowered. Thus, the updated rank of the maintenance manner adopted for the currently-occurring ejection failure is recorded in the database DB. 
     In other words, in a case where, in step S 25 , the CPU  220  determines that the database DB includes the record including same situation as the situation when the current ejection failure has occurred, the printer  1  performs maintenance in the same maintenance manner as the maintenance manner in the record in step S 37 . Thereafter, in the server  200 , the CPU  220  decrements the value indicating the current rank of the adopted maintenance manner by one and overwrites the current rank with a new rank. 
     In a case where, in step S 25 , the CPU  220  determines that the database DB includes the record including similar situation to the situation when the current ejection failure has occurred, the printer  1  performs maintenance in the same maintenance manner as the maintenance manner in the record in step S 37 . Thereafter, in the server  200 , the CPU  220  generates a new record that is different from the record including the similar situation, and stores the generated record in the database DB. That is, the newly-generated record includes the details of the ejection failure information transmitted in step S 17  and received in step S 19 , the maintenance manner adopted in the maintenance performed in step S 37 , and the updated rank. The details of the ejection failure information include the information corresponding to the failure nozzle data, the information corresponding to the occurrence area data, and the information corresponding to the printer condition data detected in step S 15 . In response to completion of step S 53 , the routine proceeds to step S 55 . 
     If the CPU  220  determines that the failure nozzle percentage is 50% or less (e.g., YES in step S 51 ), the CPU  220  determines that the maintenance manner adopted in the maintenance performed in step S 37  was effective for the currently-occurring ejection failure but the ejection performance has not been completely recovered, and thus increments or decrements by one the evaluation index according to the degree of improvement (e.g., step S 57 ). That is, the rank of the maintenance manner is raised or lowered. Thus, the updated rank of the maintenance manner adopted for the currently-occurring ejection failure is recorded in the database DB. The updated rank is recorded in the database DB in the same manner as the other cases described above. If, in step S 51 , the CPU  220  determines that the failure nozzle percentage is 50% or less (e.g., YES in step S 51 ), the failure nozzle percentage is more than 0%. This refers that ejection performance has not been completely recovered, that is, the nozzles  10  still include at least one failure nozzle. Thus, in other embodiments, in step S 57 , the CPU  220  may decrement by one the evaluation index in all cases. Nevertheless, in other embodiments, in step S 57 , the CPU  220  may not change the evaluation index. In response to completion of step S 57 , the routine proceeds to step S 55 . 
     Subsequent to step S 49 , S 53 , or S 57 , the routine proceeds to step S 55 . In step S 55 , the CPU  220  determines whether the variable N is equal to 2. In a case where the variable N is equal to 1 (one) (i.e., N=1), the CPU  220  determines that the variable N is not equal to 2 (e.g., NO in step S 55 ). Thus, the routine returns to step S 23 . In step S 23 , the CPU  220  searches the database DB for an applicable record and executes the subsequent steps. If the CPU  220  determines that the variable N is equal to 2 (e.g., YES in step S 55 ), the CPU  220  transmits an evaluation completion notification to the printer  1  (e.g., step S 59 ). That is, in this illustrative embodiment, the CPU  220  executes steps S 23  to S 57  in  FIGS.  4  and  5    two times. Nevertheless, in other embodiments, the CPU  220  may execute steps S 23  to S 57  in  FIGS.  4  and  5    only one time, or three or more times. In response to the server  200  transmitting the notification to the printer  1 , the CPU  51  receives the notification from the server  200  (e.g., step S 61 ). Then, the control procedure ends. In other embodiments, the transmission (e.g., step S 59 ) and reception (e.g., step S 61 ) of the evaluation completion notification may be skipped. 
     Effects Achieved by Illustrative Embodiment 
     As described above, in the illustrative embodiment, each maintenance manner is rated on a scale of points that indicates a rank of a respective maintenance manner. The rank corresponds to an evaluation index indicating effectiveness of a maintenance manner for recovering ejection performance. Each time maintenance is performed, the rank of the maintenance manner adopted in the maintenance is reviewed. 
     In other words, in a case where the failure nozzle detector  84  determines that an ejection failure has occurred in the printer  1 , the CPU  51  transmits, to the server  200 , the detection result of the failure nozzle detector  84  (e.g., step S 17 ). The detection result includes information corresponding to the failure nozzle data and information corresponding to the occurrence area data, both of which are related to a situation when the detected ejection failure has occurred. Subsequent to step S 17 , the CPU  51  causes the printer  1  to perform maintenance in a suitable maintenance manner determined based on the information corresponding to the failure nozzle data and the information corresponding to the occurrence area data (e.g., step S 37 ). Thereafter, the CPU  51  transmits, to the server  200 , the detection result of the failure nozzle detector  84  again (e.g., step S 43 ). The detection result includes information corresponding to the failure nozzle data and the occurrence area data, both of which are related to the situation when the detected ejection failure has occurred. Based on both information transmitted to the server  200  from the printer  1  in steps S 17  and S 43 , in the server  200 , the CPU  220  updates the rank of the adopted maintenance manner, that is, rates again the adopted maintenance manner (e.g., step S 49 , S 53 , or S 57 ). More specifically, in a case where the information received by the server  200  in step S 45  indicates that the ejection performance has been improved by the certain extent as compared with the information received by the server  200  in step S 19 , the CPU  220  determines that the maintenance manner adopted in the performed maintenance was effective for the currently-occurring ejection failure, and thus the rank of the maintenance manner is raised (e.g., step S 49  or S 57 ). In a case where the information received by the server  200  in step S 45  indicates that the ejection performance has not been changed or has not been improved by the certain extent as compared with the information received by the server  200  in step S 19 , the CPU  220  determines that the maintenance manner adopted in the performed maintenance is not effective for the currently-occurring ejection failure, and thus the rank of the maintenance manner is lowered (e.g., step S 53  or S 57 ). 
     According to the illustrative embodiment, each time maintenance is performed in the determined maintenance manner, the rank of the maintenance manner adopted in the maintenance is reviewed. Thus, the maintenance manner that is not effective for a particular ejection failure has a lower rank and the maintenance manner that is effective for the particular ejection failure has a higher rank. Consequently, the printing system may recommend a suitable maintenance manner to the owner of the printer  1 . 
     Nevertheless, in other embodiments, in a case where the information received by the server  200  in step S 45  indicates that the ejection failure has been resolved, the rank may be raised (e.g., step S 49 ). In a case where the ejection failure information indicates that the ejection failure has not been resolved, the rank may be lowered. Such a rating may explicitly indicate that the ejection failure has been resolved by maintenance in the adopted maintenance manner and thus the ejection performance has been completely recovered. Consequently, the printing system may recommend a suitable maintenance manner to the owner of the printer  1  reliably. 
     In the illustrative embodiment, in step S 17 , in response to the printer  1  transmitting, to the server  200 , information regarding a situation when an ejection failure has occurred based on a result of an ejection failure detection, the CPU  220  of the server  200  determines a maintenance manner to be adopted that may be suitable for the received information (e.g., step S 31 ). Subsequent to step S 31 , the CPU  220  transmits, to the printer  1 , a maintenance instruction to perform maintenance in the maintenance manner determined in step S 31  (e.g., step S 33 ). In response to receiving the maintenance instruction, the CPU  51  causes the printer  1  to perform maintenance in the maintenance manner specified in the maintenance instruction (e.g., step S 37 ). Thus, the CPU  220  of the server  200  may determine a maintenance manner suitable for the detected ejection failure at that moment and enable the printer  1  to perform maintenance in the determined maintenance manner. After the printer  1  performs the maintenance in the determined maintenance manner, the CPU  220  of the server  200  reviews the evaluation index, that is, the rank of the maintenance manner adopted in the maintenance (e.g., step S 49 , S 53 , or S 57 ). 
     Consequently, the printing system may recommend a suitable maintenance manner to the owner of the printer  1  more reliably. 
     In the illustrative embodiment, in the server  200 , in step S 31 , the CPU  220  determines a maintenance manner to be adopted based on at least one of the information corresponding to the failure nozzle data (e.g., the first data) or the information corresponding to the occurrence area data (e.g., the second data). Thus, the CPU  220  may determine a maintenance manner to be adopted in detail based on at least one of the information indicating what percentage of failure nozzles are included or the information indicating an occurrence area of the failure nozzles. 
     In the illustrative embodiment, in step S 31 , the CPU  220  of the server  200  determines a maintenance manner to be adopted based on the percentage of failure nozzles with respect to the total number of nozzles  10 . Thus, depending on the percentage of failure nozzles  10  with respect to the total number of nozzles  10 , the CPU  220  of the server  200  may determine a suitable maintenance manner in detail. More specifically, the higher percentage of failure nozzles  10 , the CPU  220  may determine a maintenance manner in which a stronger suction power is achieved or a maintenance manner in which a relatively longer duration of a suction time is achieved. 
     In the illustrative embodiment, in the server  200 , in step S 31 , the CPU  220  determines a maintenance manner to be adopted based on the occurrence area of the failure nozzles  10 . Examples of the occurrence areas of the failure nozzles  10  include an upstream portion of the inkjet head  3  along an ink channel and a downstream portion of the inkjet head  3  along an ink channel. Thus, the CPU  220  of the server  200  may determine a suitable maintenance manner to be adopted in detail. More specifically, in a case where the failure nozzles  10  are located at the downstream portion of the inkjet head  3 , the CPU  220  may determines, as a maintenance manner to be adopted, a maintenance manner in which a higher intensity mode or a longer time duration is achieved as compared with a case where the failure nozzles  10  are located at the upstream portion of the inkjet head  3 . 
     In the illustrative embodiment, in the server  200 , in step S 31 , the CPU  220  determines a maintenance manner to be adopted based on whether the failure nozzles  10  are located next to each other in the main scanning direction. Thus, in such a case, the CPU  220  may determine a suitable maintenance manner in detail on an assumption that, the inkjet head  3  is adversely affected by a recording sheet P during sheet conveyance. 
     In the illustrative embodiment, in the server  200 , in step S 31 , the CPU  220  determines a maintenance manner to be adopted based on the information corresponding to the printer condition data. Examples of the information corresponding to the printer condition data include temperature, humidity, and the presence or absence of a sheet conveyance failure. The temperature and the humidity may be the average temperature and the average humidity, respectively. The temperature and the humidity may alternatively be detected timely. The average temperature and the average humidity may be obtained based on a plurality of values detected in a certain cycle. According to the illustrative embodiment, a maintenance manner to be adopted may be determined in detail based on the various information. 
     Examples of the information corresponding to the printer condition data may further include environment information such as the presence or absence of paper particles and dust detected by an appropriate detector. Examples of the information corresponding to the printer condition data may further include various values counted by respective appropriate counters such as a total use time of a respective ink cartridge  32 , the number of times of a respective ink cartridge  32  replaced, a total time during which the cap  21  is in the uncapping state where the nozzles  10  are not covered by the cap  21 , and the number of printed pages. In a case where a maintenance manner to be adopted is determined based on such information, the database DB may include various data corresponding to the various information. 
     In the illustrative embodiment, an update history of each maintenance manner that has been adopted is stored in the database DB of the server  200  in association with the information corresponding to the failure nozzle data and the information corresponding to the occurrence area data both related to the ejection failure occurring at that time. 
     In response to the server  200  receiving new information corresponding to the failure nozzle data and new information corresponding to the occurrence area data from the printer  1 , the CPU  220  selects at least one maintenance manner applicable to the received information by referring to the database DB (e.g., step S 29 ). Subsequent to step S 29 , the CPU  220  determines, as a maintenance manner to be adopted, a single maintenance manner among the at least one maintenance manner selected in step S 29  (e.g., step S 31 ). Thus, the CPU  220  may effectively and appropriately determine a maintenance manner to be adopted based on the at least one maintenance manner that has been actually adopted in maintenance performed before. 
     In the illustrative embodiment, the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner rated in the highest rank among the at least one maintenance manner selected in step S 29  (e.g., step S 31 ). Thus, the CPU  220  may determine a maintenance manner suitable for the information corresponding to the failure nozzle data and the information corresponding to the occurrence area data among the at least one maintenance manner that has been actually adopted in maintenance performed before. 
     In the illustrative embodiment, in a case where the CPU  220  selects two or more maintenance manners rated in the same rank in step S 29 , the CPU  220  determines, as a maintenance manner to be adopted, the maintenance manner with the latest update date or the maintenance manner in which less ink is consumed during maintenance as compared with the other maintenance manners. Thus, the CPU  220  may reliably determine a maintenance manner suitable for the information corresponding to the failure nozzle data and the information corresponding to the occurrence area data among the at least one maintenance manner that has been actually adopted in maintenance performed before. 
     In the illustrative embodiment, in a case where the database DB does not include a maintenance manner applicable to the information corresponding to the failure nozzle data and the information corresponding to the occurrence area data both received from the printer  1 , the CPU  220  determines the default manner as a maintenance manner to be adopted (e.g., step S 27 ). Thus, even when the CPU  220  determines that the database DB does not include an applicable maintenance manner although the CPU  220  searches the database DB including the maintenance manners, each of which has been actually adopted in maintenance performed before, such a determination control may enable the printer  1  to perform maintenance in at least some maintenance manner. 
     In the illustrative embodiment, the maintenance manner data includes at least one of a maintenance type or a suction intensity mode. In other embodiments, for example, the maintenance manner data may include an operating duration. Thus, maintenance cases may be classified by maintenance type (e.g., suction or flushing). Further, even when maintenance cases include the same maintenance types, the maintenance cases may be classified by intensity mode (e.g., high, medium or low) or operating duration. The different maintenance cases may be rated individually using a respective evaluation index. 
     Modifications 
     In the illustrative embodiment, a numerical value is used to indicate the rank as the evaluation index. In a case where the ejection performance has been improved by the certain extent, the value indicating the rank is incremented. In a case where the ejection performance has not been changed or has not been improved by the certain extent, the value indicating the rank is decremented. Nevertheless, such a numerical value might not necessarily be used as the evaluation index. In other embodiments, as the evaluation index, a non-numerical value may be used, such as “A”, “B”, or “C”, or “excellent”, “good”, or “poor”. In any case using such a non-numerical value, the rank only need to be raised to a higher evaluation in a case where the ejection performance has been improved by the certain extent, and the rank only need to be lowered by a lower evaluation in a case where the ejection performance has not been changed or has not been improved by the certain extent. 
     In the illustrative embodiment, the description has been provided on the example in which the printer  1  is owned by a service provider that offers a printing service and a customer (i.e., a user) obtains the printing service using the printer  1 . Nevertheless, in other embodiments, the disclosure may be applied to another case where a user owns and uses the printer  1 . In this case, the same effects as described above may be achieved. 
     In this illustrative embodiment, in S 17  the printer  1  transmits, to the server  200 , a result of the ejection failure detection. In response to receiving the result, the server  200  executes the steps S 19  to S 31 . In S 33  the server  200  transmits, to the printer  1 , the instruction to perform maintenance in the maintenance manner determined in step S 31  or S 27 . In S 43  the printer  1  transmits, to the server  200 , the ejection failure information as the result of the ejection failure detection. In response to receiving the ejection failure information, the server  200  executes the steps S 47  to S 55 . In S 59  the server  200  transmits the evaluation completion notification to the printer  1 . Nevertheless, in modification, instead of the server  200 , the printer  1  may execute the steps S 19  to S 31  and S 47  to S 55 . That is, in this modification, the printer  1  may execute the steps described in  FIGS.  4  and  5    without communicating with the server  200 . 
     In the illustrative embodiments, the controller  50  of the printer  1  includes a single CPU  51 . Nevertheless, in other embodiments, for example, the controller  50  may include a plurality of CPUs  51 . In still other embodiments, for example, the controller  50  may include a combination of a CPU  51  and a hardware circuit such as the ASIC  55  or hardware circuits only. 
     In the above description, the sequence in the flowcharts of  FIGS.  4  and  5    is merely an example, and therefore, may include another step or skip one or more steps or the sequence of steps may be changed without departing from the spirit and technical idea of the disclosure. 
     Further, one or more aspects of the illustrative embodiment and the modifications may be combined appropriately. 
     Various modifications may be made to the disclosure without departing from the spirit and scope of the disclosure.