Control method, liquid ejection device, and inkjet system

Abstract

To accurately determine whether or not an abnormality has occurred in which liquid accumulation is forming on the nozzle surface. [Solution] A liquid dispensing device that dispenses liquid onto a medium has a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is discharged, and the control method for dispensing liquid onto a medium includes an acquisition step of acquiring residual vibration information relating to residual vibration in the pressure chamber after applying a voltage to one or more of the plurality of piezoelectric elements, and a determination step of determining whether or not a first abnormality has occurred, which is an abnormality in which liquid puddles are formed on the nozzle surface provided with the plurality of nozzles, based on the residual vibration information.

Description

Technical Field

[0001] The present invention relates to a control method, a liquid ejection device, and an inkjet system.

Background Art

[0002] Conventionally, a liquid ejection device having a liquid ejection head for ejecting a liquid onto a medium such as printing paper has been provided. In such a liquid ejection device, ejection abnormalities may occur where the liquid cannot be normally ejected from the nozzles due to the liquid ejection head, such as thickening of the liquid in the liquid ejection head. For example, in Patent Document 1, based on residual vibrations generated after driving the liquid ejection head, it is described a technique for determining the presence or absence of ejection abnormalities of the liquid ejection head, such as air bubbles being mixed into the liquid of the liquid ejection head, the liquid of the liquid ejection head thickening, and paper dust adhering to the nozzle surface of the liquid ejection head.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described liquid ejection head, in addition to the mixing of air bubbles, thickening of the liquid, and adhesion of paper dust, ejection abnormalities may occur due to the formation of liquid pools on the nozzle surface. However, with conventional techniques, it has been difficult to determine whether an abnormality in which a liquid pool is formed has occurred.

Means for Solving the Problems

[0005] A control method according to one aspect of the present disclosure is a control method for a liquid dispensing device that dispenses liquid onto a medium, the device having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a liquid dispensing head having a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is dispensed, the method comprising: an acquisition step of acquiring residual vibration information relating to residual vibration in the pressure chamber after applying a voltage to one or more of the plurality of piezoelectric elements; and a determination step of determining whether or not a first abnormality has occurred, which is an abnormality in which liquid puddles are formed on the nozzle surface provided with the plurality of nozzles, based on the residual vibration information.

[0006] A liquid dispensing device according to one aspect of the present disclosure is a liquid dispensing device for dispensing liquid onto a medium, having a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is discharged, and comprising: an acquisition unit that acquires residual vibration information relating to residual vibration in the pressure chamber after a voltage is applied to one or more of the plurality of piezoelectric elements; and a determination unit that determines, based on the residual vibration information, whether or not a first abnormality has occurred, which is an abnormality in which liquid puddles are formed on the nozzle surface provided with the plurality of nozzles.

[0007] An inkjet system according to one aspect of the present disclosure is an inkjet system comprising: a liquid ejection device that ejects liquid onto a medium having a liquid ejection head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is ejected; and a server provided outside the liquid ejection device, wherein the liquid ejection device acquires residual vibration information relating to residual vibration in the pressure chamber after applying a voltage to one or more of the plurality of piezoelectric elements, transmits the residual vibration information from the liquid ejection device to the server, the server determines, based on the residual vibration information, whether or not a first abnormality has occurred, which is an abnormality in which liquid puddles are formed on the nozzle surface provided with the plurality of nozzles, and transmits determination information indicating the determination result of whether or not the first abnormality has occurred to the liquid ejection device. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing an example configuration of the inkjet system 10 according to the first embodiment. [Figure 2] A diagram showing an example of the configuration of Server 300. [Figure 3] A diagram showing the configuration of the processing unit 200. [Figure 4] A schematic diagram illustrating an example of the configuration of inkjet printer 100. [Figure 5] A block diagram showing an example configuration of inkjet printer 100. [Figure 6] A cross-sectional view showing an example configuration of the head tip 111. [Figure 7] An enlarged cross-sectional view of the vicinity of the piezoelectric element 111f. [Figure 8] A block diagram showing an example of the configuration of a liquid dispensing head HU. [Figure 9] A diagram showing a timing chart to explain the operation of inkjet printer 100 during the recording period Tu. [Figure 10] A diagram illustrating residual vibrations in the liquid reservoir generation nozzle (Nz-M). [Figure 11] Figure showing the functions of the inkjet system 10. [Figure 12] Figure showing a flowchart illustrating the operation of the inkjet system 10. [Figure 13] Figure showing a flowchart illustrating the liquid accumulation flag setting process. [Figure 14] Figure for explaining the relationship between the threshold value λA and the threshold value λB. [Figure 15] Figure showing a flowchart illustrating the liquid accumulation determination process. [Figure 16] Figure showing a flowchart illustrating the liquid accumulation flag setting process in the second embodiment. [Figure 17] Figure showing a flowchart illustrating the liquid accumulation flag setting process in the first modification. [Figure 18] Figure showing a flowchart illustrating the operation of the inkjet system 10 in the second modification. [Figure 19] Figure showing the functions of the inkjet printer 100C in the third modification. [Figure 20] Schematic diagram exemplifying an example of the configuration of the inkjet printer 100D in the eighth modification.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for implementing the present disclosure will be described with reference to the drawings. However, in each figure, the dimensions and scales of each part are appropriately different from the actual ones. Also, the embodiments described below are preferred specific examples of the present disclosure, and thus various technically preferable limitations are imposed. However, the scope of the present disclosure is not limited to these embodiments unless there is a description to specifically limit the present disclosure in the following description.

[0010] 1. First Embodiment 1-1. Outline of the Inkjet System 10 FIG. 1 is a schematic diagram showing a configuration example of an inkjet system 10 according to the first embodiment. The inkjet system 10 is a system that performs a recording process on a medium PP, which will be described later, by an inkjet method. In the example shown in FIG. 1, the inkjet system 10 includes inkjet printers 100_1 to 100_3, processing devices 200_1 to 200_3, and a server 300.

[0011] Here, the inkjet printers 100_1 to 100_3 are devices provided by the manufacturers of the inkjet printers 100_1 to 100_3. In the following description, each of the inkjet printers 100_1 to 100_3 may be generically referred to as an inkjet printer 100 without distinction. The inkjet printer 100 is a liquid ejection device that ejects ink, which is an example of a liquid. The manufacturer of the inkjet printer 100 is a vendor that manufactures the inkjet printer 100. The manufacturer of the inkjet printer 100 may be described as the "printer manufacturer". Each of the inkjet printers 100_1 to 100_3 may be provided by the same printer manufacturer or different printer manufacturers. However, the liquid ejection head HU incorporated in the inkjet printers 100_1 to 100_3 is provided by the manufacturer of the liquid ejection head HU. The manufacturer of the liquid ejection head HU is a vendor that manufactures the liquid ejection head HU. Hereinafter, the manufacturer of the liquid ejection head HU may be described as the "head manufacturer". The printer manufacturer manufactures the inkjet printer 100 by receiving the liquid ejection head HU from the head manufacturer and incorporating the provided liquid ejection head HU into the inkjet printer 100. The inkjet printer 100 is an example of a "liquid ejection device".

[0012] Figure 1 shows user U_1 using inkjet printer 100_1, user U_2 using inkjet printer 100_2, and user U_3 using inkjet printer 100_3. In the following description, users U_1 to U_3 may be collectively referred to as user U without distinction. User U is, for example, an employee belonging to the printer manufacturer who uses inkjet printer 100. Also, for example, a third party who has received inkjet printer 100 from the printer manufacturer and uses it is also user U. In the following description, a third party who has received inkjet printer 100 from the printer manufacturer may be referred to as an "end user". For each integer i from 1 to 3, user U_i uses processing unit 200_i in addition to inkjet printer 100_i.

[0013] Inkjet printer 100_1 is connected to processing unit 200_1 in a communicative manner. Inkjet printer 100_2 is connected to processing unit 200_2 in a communicative manner. Inkjet printer 100_3 is connected to processing unit 200_3 in a communicative manner. Thus, inkjet printers 100_1 to 100_3 correspond to processing units 200_1 to 200_3 respectively and are connected to processing units 200_1 to 200_3 in a communicative manner. In the following description, processing units 200_1 to 200_3 may be referred to collectively as processing unit 200 without distinction.

[0014] Furthermore, below, the recording system 20_i may be described for each integer i from 1 to 3. The recording system 20_i includes the inkjet printer 100_i and the processing unit 200_i. In the following description, the recording systems 20_1 to 20_3 may be referred to collectively as the recording system 20 without distinction. It can also be said that the inkjet system 10 has the recording systems 20_1 to 20_3 and the server 300.

[0015] In the example shown in Figure 1, the inkjet system 10 has three inkjet printers 100 and three processing units 200, but this number is not limited to these three; it may be one, two, or four or more. In other words, the number of sets of inkjet printers 100 and processing units 200 is not limited to three; it may be one, two, or four or more.

[0016] The inkjet printer 100 receives image data Img from the processing unit 200. The inkjet printer 100 forms an image on the medium PP based on the image data Img. Hereinafter, the process of forming an image on the medium PP by ejecting ink onto the medium PP may be referred to as "recording process".

[0017] The PP medium is not particularly limited as long as it is a medium that the inkjet printer 100 can print on, for example, various types of paper, various types of fabric, or various types of film.

[0018] The inkjet printer 100 has one liquid ejection head HU. In the following description, the liquid ejection head HU ejects ink from a nozzle Nz provided on the liquid ejection head HU. Hereafter, the elements constituting the inkjet printer 100, excluding the liquid ejection head HU, may be referred to as the "printer body".

[0019] In the example shown in Figure 1, the inkjet printer 100 has one liquid ejection head HU, but the number of liquid ejection heads HU is not limited to one; there may be two or more.

[0020] The processing unit 200 is a computer, such as a desktop or notebook computer. The processing unit 200 is connected to the server 300 via a network NW such as a LAN, WAN, or the Internet. LAN is an abbreviation for Local Area Network. WAN is an abbreviation for Wide Area Network.

[0021] Server 300 is a computer that functions as a cloud server CS, as described later. Server 300 is managed by a different business operator than, for example, the head manufacturer, the printer manufacturer, and the end user. Hereafter, the business operator that manages Server 300 may be referred to as the "server operator." The head manufacturer uses a portion of Server 300.

[0022] 1-2. Server 300 Configuration Figure 2 shows an example of the configuration of server 300. Server 300 includes a control circuit 310, a memory circuit 320, and a communication device 380. The control circuit 310, the memory circuit 320, and the communication device 380 are interconnected by a bus 390 for communicating information.

[0023] The control circuit 310 includes, for example, one or more processors such as CPUs. CPU is an abbreviation for Central Processing Unit. The control circuit 310 may also include a programmable logic device such as an FPGA in place of, or in addition to, a CPU. FPGA is an abbreviation for Field Programmable Gate Array.

[0024] The memory circuit 320 is composed of a magnetic memory device or flash ROM, etc. The memory circuit 320 is readable by the control circuit 310 and stores multiple programs, including the virtualization program VM and control program PM1 executed by the control circuit 310, as well as various information used by the control circuit 310. The virtualization program VM divides the resources of the server 300, such as the control circuit 310 and the memory circuit 320, into multiple parts, and operates each of the divided resources as a cloud server CS. The headmaker uses some of the multiple cloud servers CS as part of the server 300. The control program PM1 is developed by the headmaker.

[0025] However, the memory circuit 320 does not need to have a virtualization program VM, and the processing unit 200 may access the server 300 instead of the cloud server CS.

[0026] The memory circuit 320 includes, for example, one or more volatile memories such as RAM and one or more non-volatile memories such as ROM, EEPROM, or PROM, or both, as semiconductor memory. RAM is an abbreviation for Random Access Memory. ROM is an abbreviation for Read Only Memory. EEPROM is an abbreviation for Electrically Erasable Programmable Read-Only Memory. PROM is an abbreviation for Programmable ROM.

[0027] The communication device 380 is hardware having a communication circuit for communicating with the processing unit 200 via a network NW. The communication device 380 may also be referred to as a network device, network controller, network card, or communication module, for example.

[0028] 1-3. Configuration of the processing unit 200 Figure 3 shows the configuration of the processing unit 200. The processing unit 200 includes a control circuit 210, a memory circuit 220, a communication device 230, an input device 260, and a display device 270. The control circuit 210, the memory circuit 220, the communication device 230, the input device 260, and the display device 270 are interconnected by a bus 290 for communicating information.

[0029] The control circuit 210 includes, for example, one or more processors such as CPUs. The control circuit 210 may also include a programmable logic device such as an FPGA in place of, or in addition to, a CPU.

[0030] The memory circuit 220 is composed of a magnetic memory device or flash ROM, etc. The memory circuit 220 is readable by the control circuit 210 and stores multiple programs, including the inkjet program PM2 executed by the control circuit 210, and various information used by the control circuit 210. The memory circuit 220 includes, for example, one or more volatile memories such as RAM and one or more non-volatile memories such as ROM, EEPROM, or PROM, or both, as semiconductor memory. The inkjet program PM2 is downloaded from the cloud server CS running on the server 300 and installed on the processing unit 200, for example, when the processing unit 200 is connected to the inkjet printer 100. The inkjet program PM2 is, for example, a program that generates image data Img. More specifically, the inkjet program PM2 generates image data Img that shows the image generated by the application program. The application program is, for example, an application program that creates documents and an application program that creates images.

[0031] The communication device 230 is hardware having a communication circuit for communicating with the processing unit 200 via a network NW. The communication device 230 may also be referred to as a network device, network controller, network card, or communication module, for example.

[0032] The communication device 240 is a circuit capable of communicating with the inkjet printer 100. For example, the communication device 240 is a network card such as USB or Bluetooth. USB is an abbreviation for Universal Serial Bus. USB and Bluetooth are registered trademarks.

[0033] The input device 260 is a device that outputs operation information in response to user U's actions. The input device 260 is, for example, a mouse and a keyboard.

[0034] The display device 270 displays an image containing some information to the user U. The display device 270 is an organic EL display, an LED display, or an LCD. EL is an abbreviation for Electro-Luminescence. LED is an abbreviation for Light Emitting Diode. LCD is an abbreviation for Liquid Crystal Display. Alternatively, the input device 260 and the display device 270 may be integrated into a single unit. An example of an integrated configuration of the input device 260 and the display device 270 is a touch panel.

[0035] As shown in Figures 1 to 3, there is a business model in which a head manufacturer provides a liquid ejection head HU to a printer manufacturer, and the printer manufacturer manufactures an inkjet printer 100 by incorporating the liquid ejection head HU into the printer body. In this business model, it is common for the printer manufacturer to design and manufacture everything except the liquid ejection head HU. In this embodiment, the head manufacturer provides a cloud server CS and an inkjet program PM2 that runs on the processing unit 200, and the user U connects the processing unit 200 to the cloud server CS and runs the inkjet program PM2 on the processing unit 200. As a result, in this embodiment, the printer manufacturer does not need to prepare the inkjet program PM2, thus reducing the design and manufacturing burden on the printer manufacturer.

[0036] 1-4. Configuration of the 100 Inkjet Printer Figure 4 is a schematic diagram illustrating an example of the configuration of the inkjet printer 100. Figure 5 is a block diagram illustrating an example of the configuration of the inkjet printer 100. In the following explanation, we assume mutually orthogonal X, Y, and Z axes. One direction along the X axis from any point is denoted as the X1 direction, and the opposite direction to the X1 direction is denoted as the X2 direction. Similarly, mutually opposite directions along the Y axis from any point are denoted as the Y1 and Y2 directions, and mutually opposite directions along the Z axis from any point are denoted as the Z1 and Z2 directions. The XY plane, which includes the X and Y axes, corresponds to the horizontal plane. The Z axis is an axis along the vertical direction, and the Z2 direction corresponds to the downward direction in the vertical direction.

[0037] The inkjet printer 100 according to the first embodiment is a serial printer that reciprocates the liquid ejection head HU along the X axis. Specifically, as shown in Figure 4, the inkjet printer 100 according to the first embodiment performs an ejection operation to form an image on the medium PP by transporting the medium PP in the Y1 direction, which is the sub-scanning direction, and moving the liquid ejection head HU in the X1 and X2 directions, which are the main scanning directions, while ejecting ink from the nozzles Nz. In Figure 4, some of the nozzles Nz of the liquid ejection head HU are typically shown.

[0038] As shown in Figure 4, the multiple nozzles Nz of the liquid discharge head HU are divided into nozzle rows La and nozzle row Lb, which are spaced apart from each other in the direction along the X axis. Each of nozzle row La and nozzle row Lb is a set of multiple nozzles Nz arranged linearly in the direction along the Y axis. In the following description, it is assumed that the number of nozzles Nz included in nozzle row La and nozzle row Lb is M, which is between 1 and 1. Therefore, the number of nozzles Nz that the liquid discharge head HU has is 2M. In order to distinguish each of the 2M nozzles Nz, the nozzles Nz in nozzle row La may be written as nozzle Nz[am1], and the nozzles Nz in nozzle row Lb may be written as nozzle Nz[bm2]. m1 and m2 are integers between 1 and M, inclusive. Also, in the following, nozzles Nz[a1] to nozzle Nz[aM] and nozzles Nz[b1] to nozzle Nz[bM] may be written as nozzle Nz without distinction.

[0039] In this embodiment, as shown in Figure 4, among the M nozzles Nz divided into nozzle row La, the nozzle Nz furthest in the Y2 direction is denoted as nozzle Nz[a1], and the nozzle Nz furthest in the Y1 direction is denoted as nozzle Nz[aM]. Similarly, among the M nozzles Nz divided into nozzle row Lb, the nozzle Nz furthest in the Y2 direction is denoted as nozzle Nz[b1], and the nozzle Nz furthest in the Y1 direction is denoted as nozzle Nz[bM].

[0040] As shown in Figures 4 and 5, the inkjet printer 100 includes a control module CM, a liquid ejection head HU, a liquid container 120, a moving mechanism 130, a transport mechanism 140, a maintenance mechanism 145, a communication device 150, a memory circuit 160, and a control circuit 170.

[0041] The control module CM includes a power supply circuit 113 and a drive signal generation circuit 114. The liquid discharge head HU is an assembly that includes a head chip 111 and a drive circuit 112. The liquid discharge head HU may incorporate part or all of the control module CM.

[0042] The print head 111 ejects ink toward the PP medium. Figure 4 shows a representative example of the 2M piezoelectric elements 111f that make up the print head 111. A detailed example of the print head 111 will be explained later based on Figure 6.

[0043] In the example shown in Figure 5, the liquid discharge head HU has one head tip 111, but this number may be two or more. One or more head tips 111 are arranged so that multiple nozzles Nz are distributed across a portion of the width direction of the medium PP.

[0044] The drive circuit 112, under the control of the control circuit 170, switches whether or not to supply a drive signal Com output from the drive signal generation circuit 114 to each of the multiple piezoelectric elements 111f of the head chip 111.

[0045] The drive circuit 112 includes a switching circuit 115 and a detection circuit 117. The switching circuit 115, under the control of the control circuit 170, switches whether or not to supply a drive signal Com output from the drive signal generation circuit 114 to each of the 2M piezoelectric elements 111f on the head chip 111 connected to the drive circuit 112. The switching circuit 115 also switches whether or not to electrically connect each piezoelectric element 111f to the detection circuit 117. In this embodiment, it is assumed that the drive signal Com includes drive signal Com-A and drive signal Com-B. Furthermore, the signal actually supplied to the piezoelectric element 111f from drive signals Com-A and Com-B may be described as the supplied drive signal Vin. The switching circuit 115 includes, for example, a group of switches such as a transmission gate for the switching. Details of the switching circuit 115 will be described later with reference to Figure 7. The detection circuit 117 outputs a residual vibration signal NES, which indicates the vibration remaining in the pressure chamber CV (described later), to the generation circuit 190 after the piezoelectric element 111f has been driven. More specifically, the detection circuit 117 generates the residual vibration signal NES based on the detection signal Vout detected from the piezoelectric element 111f driven by the drive signal Com.

[0046] The power supply circuit 113 receives power from a commercial power source (not shown) and generates various predetermined potentials. The generated potentials are supplied to various parts of the inkjet printer 100 as appropriate. In the example shown in Figure 5, the power supply circuit 113 generates a power supply potential VHV and an offset potential VBS. The offset potential VBS is supplied to the head chip 111, etc. The power supply potential VHV is supplied to the drive signal generation circuit 114, etc.

[0047] The drive signal generation circuit 114 is a circuit that generates a drive signal Com for driving each piezoelectric element 111f of the head chip 111. Specifically, the drive signal generation circuit 114 includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 114, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 170 (described later) from a digital signal to an analog signal, and the amplification circuit generates the drive signal Com by amplifying the analog signal using the power supply potential VHV from the power supply circuit 113.

[0048] As illustrated in Figure 4, the inkjet printer 100 is equipped with a liquid container 120 for storing ink. For example, a cartridge that can be attached to the inkjet printer 100, a bag-shaped ink pack made of flexible film, or an ink tank that can be refilled with ink can be used as the liquid container 120.

[0049] The moving mechanism 130 and the transport mechanism 140 move the relative positions of the medium PP and the liquid discharge head HU under the control of the control circuit 170. Moving the relative positions means that the liquid discharge head HU may be moved while the position of the medium PP is fixed, or the medium PP may be moved while the position of the liquid discharge head HU is fixed. In this embodiment, with respect to the direction along the X-axis, which is the main scanning direction, the liquid discharge head HU is moved in the direction along the X-axis while the position of the medium PP in the X-axis is fixed, and with respect to the Y1 direction, which is the sub-scanning direction, the medium PP is moved in the Y1 direction while the position of the liquid discharge head HU in the direction along the Y-axis is fixed.

[0050] The moving mechanism 130 reciprocates the liquid discharge head HU along the X-axis under the control of the control circuit 170. As shown in Figure 4, the moving mechanism 130 comprises a roughly box-shaped carriage 131 that houses the liquid discharge head HU and an endless belt 132 to which the liquid discharge head HU is fixed. A configuration in which the liquid container 120 is mounted on the carriage 131 together with the liquid discharge head HU can also be adopted.

[0051] The transport mechanism 140 transports the medium PP in the Y1 direction under the control of the control circuit 170. Specifically, the transport mechanism 140 comprises a transport roller (not shown) whose rotation axis is parallel to the X axis, and a motor (not shown) that rotates the transport roller under the control of the control circuit 170.

[0052] The communication device 150 is a circuit capable of communicating with the processing unit 200. For example, the communication device 150 is a network card such as a USB or Bluetooth card. Alternatively, the communication device 150 may be integrated with the control circuit 170.

[0053] The memory circuit 160 stores various programs, including the control program PM3 executed by the control circuit 170, and various data, such as image data Img, processed by the control circuit 170. The memory circuit 160 includes, for example, one or more volatile memories such as RAM and one or more non-volatile memories such as ROM, EEPROM, or PROM, or both, as semiconductor memory. The memory circuit 160 may be configured as part of the control circuit 170.

[0054] The control circuit 170 has the function of controlling the operation of each part of the inkjet printer 100 and the function of processing various data. The control circuit 170 includes, for example, one or more processors such as CPUs. The control circuit 170 may also include a programmable logic device such as an FPGA instead of a CPU, or in addition to a CPU.

[0055] The control circuit 170 controls the operation of each part of the inkjet printer 100 by executing a program stored in the memory circuit 160. Here, the control circuit 170 generates signals such as control signals Sk1, Sk2, Sk3, print signal SI, and waveform specification signal dCom as signals to control the operation of each part of the inkjet printer 100.

[0056] Control signal Sk1 is a signal for controlling the drive of the moving mechanism 130. Control signal Sk2 is a signal for controlling the drive of the transport mechanism 140. Control signal Sk3 is a signal for controlling the maintenance mechanism 145. Print signal SI is a signal for controlling the drive of the drive circuit 112. Specifically, print signal SI specifies at predetermined intervals whether or not the drive circuit 112 supplies the drive signal Com from the drive signal generation circuit 114 to the piezoelectric element 111f. This specification determines the amount of ink ejected from the head chip 111, etc. Waveform specification signal dCom is a digital signal for defining the waveform of the drive signal Com generated by the drive signal generation circuit 114.

[0057] When recording is performed, the control circuit 170 first stores the image data Img supplied from the processing unit 200 in the storage circuit 160. Next, the control circuit 170 generates various control signals such as the print signal SI, the waveform specification signal dCom, the control signal Sk1, the control signal Sk2, and the control signal Sk3 based on the image data Img stored in the storage circuit 160. Then, based on the various control signals and the various data stored in the storage circuit 160, the control circuit 170 controls the transport mechanism 140 and the moving mechanism 130 to change the relative position of the medium PP with respect to the liquid ejection head HU, while controlling the liquid ejection head HU so that the piezoelectric element 111f is driven. As a result, the control circuit 170 adjusts the presence or absence of ink ejection from the piezoelectric element 111f, the amount of ink ejected, and the timing of ink ejection, and controls the execution of the recording process to form an image on the medium PP based on the image data Img.

[0058] Furthermore, the inkjet printer 100 according to this embodiment may perform an ejection state determination process to determine whether the ink ejection state from each nozzle Nz is normal or defective. In addition, if an ejection defect occurs in a nozzle Nz included in the liquid ejection head HU, it may be described as an ejection defect of the liquid ejection head HU. Furthermore, a nozzle Nz that has experienced an ejection defect may be described as "defective nozzle Nz-T". On the other hand, a nozzle Nz that does not experience an ejection defect may be described as "normal ejection nozzle Nz-S".

[0059] Here, a discharge failure refers to a state in which, even when the piezoelectric element 111f is driven by the drive signal Com to attempt to discharge ink from the nozzle Nz, the ink cannot be discharged in the manner specified by the drive signal Com, resulting in a decrease in the discharge characteristics of the nozzle Nz. Discharge characteristics include, for example, the discharge volume and / or discharge speed. Causes of discharge failure include air bubbles being mixed into the ink in the liquid discharge head HU, the ink in the liquid discharge head HU becoming more viscous, and paper dust adhering to the nozzle surface FN of the liquid discharge head HU, which will be described later. Here, the ink discharge manner specified by the drive signal Com means that the piezoelectric element 111f discharges an amount of ink specified by the waveform of the drive signal Com, and the piezoelectric element 111f discharges the ink at a discharge speed specified by the waveform of the drive signal Com. In other words, a state in which ink cannot be ejected according to the ink ejection pattern defined by the drive signal Com includes not only a state in which ink cannot be ejected from nozzle Nz, but also a state in which less ink than the amount of ink ejected defined by the drive signal Com is ejected from nozzle Nz, a state in which more ink than the amount of ink ejected defined by the drive signal Com is ejected from nozzle Nz, or a state in which the ink cannot be ejected at the desired landing position on the medium PP because the ink is ejected at a speed different from the ink ejection speed defined by the drive signal Com. In the following, nozzle Nz that is the subject of the ejection state determination may be referred to as "determined nozzle Nz-H".

[0060] In the ejection state determination process, the inkjet printer 100 first selects a nozzle Nz-H to be determined from among 2M nozzles Nz using a control circuit 170, second drives the nozzle Nz-H to be determined under the control of the control circuit 170 to generate residual vibration in the pressure chamber CV communicating with the nozzle Nz-H, third generates a residual vibration signal NES based on the detection signal Vout detected from the piezoelectric element 111f that detected the residual vibration using a detection circuit 117, and fourth generates individual residual vibration information NEI related to the residual vibration based on the residual vibration signal NES using a generation circuit 190.

[0061] Furthermore, the inkjet printer 100 according to this embodiment performs maintenance processing to restore the ejection failure of a nozzle Nz having ejection failure using a maintenance mechanism 145. The maintenance processing includes a flushing process to discharge ink from the nozzle Nz, a wiping process to wipe off foreign matter such as paper dust attached to the vicinity of the nozzle Nz with a wiper 147, and a pumping process to suck up ink, air bubbles, etc. from inside the nozzle Nz with a tube pump. The flushing process is a process that forcibly removes thickened ink and air bubbles mixed in the ink by repeatedly driving a piezoelectric element 111f with a drive signal Com for the flushing process. The maintenance mechanism 145 includes a cap 146 for covering the liquid ejection head HU so as to seal the nozzle Nz, a wiper 147, a tube pump (not shown) for sucking up ink, air bubbles, etc., and an ink receiving unit (not shown) for receiving the discharged ink when discharging ink. The maintenance mechanism 145 is provided in a region that does not overlap with the medium PP when viewed in the Z-axis direction.

[0062] Figure 6 is a cross-sectional view showing an example configuration of the head chip 111. However, in Figure 6, the drive circuit 112 is also shown in addition to the head chip 111. The head chip 111 has a configuration that is approximately symmetrical with respect to the X-axis. However, the positions of the nozzles Nz in nozzle row La and the multiple nozzles Nz in nozzle row Lb along the Y-axis may coincide or differ. In Figure 6, a configuration in which the positions of the multiple nozzles Nz in nozzle row La and the multiple nozzles Nz in nozzle row Lb along the Y-axis coincide is illustrated.

[0063] As shown in Figure 6, the head chip 111 includes a flow channel substrate 111a, a pressure chamber substrate 111b, a nozzle plate 111c, a vibration absorber 111d, a diaphragm 111e, a plurality of piezoelectric elements 111f, a protective plate 111g, a case 111h, and a wiring board 111i.

[0064] The flow channel substrate 111a and the pressure chamber substrate 111b are stacked in this order in the Z1 direction, forming a flow channel for supplying ink to multiple nozzles Nz. In the region located in the Z1 direction from the stack consisting of the flow channel substrate 111a and the pressure chamber substrate 111b, the diaphragm 111e, multiple piezoelectric elements 111f, a protective plate 111g, a case 111h, and a wiring board 111i are installed. On the other hand, in the region located in the Z2 direction from the said stack, the nozzle plate 111c and a vibration absorber 111d are installed. Each element of the head chip 111 is generally a plate-shaped member that is elongated in the Y direction, and is joined to each other, for example, by adhesive. The elements of the head chip 111 will be described in order below.

[0065] The nozzle plate 111c is a plate-shaped member provided with multiple nozzles Nz in nozzle rows La and Lb, respectively. Each of the multiple nozzles Nz is a through-hole through which ink passes. Here, the surface of the nozzle plate 111c facing the Z2 direction is the nozzle surface FN. The nozzle plate 111c is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, such as dry etching or wet etching. However, other known methods and materials may be used in the manufacture of the nozzle plate 111c as appropriate. Furthermore, the cross-sectional shape of the nozzles Nz is typically circular, but is not limited to this, and may be non-circular, such as polygonal or elliptical.

[0066] The flow channel substrate 111a is provided with a space R1, a plurality of supply channels Ra, and a plurality of communication channels Na for each of the nozzle rows La and Lb. Space R1 is an elongated opening extending in the direction along the Y axis when viewed in a plan view along the Z axis. Each of the supply channels Ra and communication channels Na is a through-hole formed for each nozzle Nz. Each supply channel Ra communicates with space R1.

[0067] The pressure chamber substrate 111b is a plate-shaped member provided with a plurality of pressure chambers CV, called cavities, for each of the nozzle rows La and Lb. The plurality of pressure chambers CV are arranged in the direction along the Y axis. Each pressure chamber CV is formed for each nozzle Nz and is a long space extending in the direction along the X axis in a plan view. The flow channel substrate 111a and the pressure chamber substrate 111b are manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology, similar to the nozzle plate 111c described above. However, other known methods and materials may be used as appropriate for the manufacture of the flow channel substrate 111a and the pressure chamber substrate 111b.

[0068] The pressure chamber CV is a space located between the flow channel substrate 111a and the diaphragm 111e. For each of the nozzle rows La and Lb, multiple pressure chambers CV are arranged in a direction along the Y axis. The pressure chambers CV also communicate with the communication channel Na and the supply channel Ra, respectively. Therefore, the pressure chambers CV communicate with the nozzle Nz via the communication channel Na and with the space R1 via the supply channel Ra.

[0069] A diaphragm 111e is positioned on the surface of the pressure chamber substrate 111b facing the Z1 direction. The diaphragm 111e is an elastically vibrating plate-shaped member. The diaphragm 111e has, for example, a first layer and a second layer, which are stacked in this order in the Z1 direction. The first layer is, for example, an elastic film composed of silicon oxide (SiO2). This elastic film is formed, for example, by thermal oxidation of one surface of a silicon single crystal substrate. The second layer is, for example, an insulating film composed of zirconium oxide (ZrO2). This insulating film is formed, for example, by forming a zirconium layer by sputtering and then thermally oxidizing the layer. Note that the diaphragm 111e is not limited to the stacked configuration of the first and second layers described above, and may be composed of, for example, a single layer or three or more layers.

[0070] On the surface of the diaphragm 111e facing the Z1 direction, multiple piezoelectric elements 111f are arranged for each nozzle row La and nozzle row Lb, corresponding to the nozzle Nz. Each piezoelectric element 111f is a passive element that deforms in response to the supply of a drive signal Com. Each piezoelectric element 111f is elongated in shape, extending along the X-axis in a plan view. The multiple piezoelectric elements 111f are arranged along the Y-axis to correspond to the multiple pressure chambers CV. The piezoelectric elements 111f overlap the pressure chambers CV in a plan view.

[0071] Figure 7 is an enlarged cross-sectional view of the vicinity of the piezoelectric element 111f. However, in Figure 7, the protective plate 111g is omitted from the drawing to avoid complexity.

[0072] As illustrated in Figure 7, the piezoelectric element 111f is a laminate in which a piezoelectric material Zm is interposed between an upper electrode Zu to which an offset potential VBS is supplied and a lower electrode Zd to which a drive signal Com is supplied. The piezoelectric element 111f is, for example, the portion where the lower electrode Zd, the upper electrode Zu, and the piezoelectric material Zm overlap when viewed from the Z1 direction. A pressure chamber CV is provided in the Z2 direction of the piezoelectric element 111f. In the first embodiment, the offset potential VBS is supplied to the upper electrode Zu and the drive signal Com is supplied to the lower electrode Zd, but it is also possible that the drive signal Com is supplied to the upper electrode Zu and the offset potential VBS is supplied to the lower electrode Zd.

[0073] In the first embodiment, the lower electrode Zd is an individual electrode arranged spaced apart from each other for each piezoelectric element 111f. On the other hand, the upper electrode Zu is a strip-shaped common electrode extending in the direction along the Y axis so as to be continuous across multiple piezoelectric elements 111f. Examples of metallic materials for the lower electrode Zd and the upper electrode Zu include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), and copper (Cu). One of these can be used alone, or two or more can be used in combination in the form of an alloy or laminate.

[0074] The piezoelectric element Zm is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3) and, for example, is a strip-shaped material that extends along the Y-axis so as to be continuous across multiple piezoelectric elements 111f. However, the piezoelectric element Zm may be a single unit across multiple piezoelectric elements 111f. In this case, the piezoelectric element Zm is provided with through-holes extending along the X-axis in regions corresponding to the gaps between adjacent pressure chambers CV in a plan view. When the diaphragm 111e vibrates in conjunction with the deformation of the piezoelectric elements 111f, the pressure in the pressure chamber CV fluctuates, causing ink to be ejected from the nozzle Nz.

[0075] Let's return to the explanation in Figure 6. The protective plate 111g is a plate-shaped member installed on the surface of the diaphragm 111e facing the Z1 direction, protecting the multiple piezoelectric elements 111f and reinforcing the mechanical strength of the diaphragm 111e. Here, the multiple piezoelectric elements 111f are housed between the protective plate 111g and the diaphragm 111e. The protective plate 111g is made of, for example, a resin material.

[0076] Case 111h is a component for storing ink supplied to multiple pressure chambers CV. Case 111h is made of, for example, a resin material. Each nozzle row La and nozzle row Lb in case 111h is provided with a space R2. Space R2 is in communication with the aforementioned space R1 and, together with space R1, functions as a reservoir R for storing ink supplied to the multiple pressure chambers CV. Case 111h is provided with an inlet IH for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chambers CV via each supply channel Ra.

[0077] The vibration absorber 111d, also called the compliance substrate, is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink in the reservoir R. The vibration absorber 111d may also be a thin, flexible metal plate. The surface of the vibration absorber 111d facing the Z1 direction is joined to the flow channel substrate 111a by adhesive or the like.

[0078] The wiring board 111i is mounted on the surface of the diaphragm 111e facing the Z1 direction and is a mounting component for electrically connecting the head chip 111, the drive circuit 112, and the control module CM, etc. The wiring board 111i is a flexible wiring board such as COF, FPC, or FFC. The aforementioned drive circuit 112 is mounted on the wiring board 111i of this embodiment. COF is an abbreviation for Chip On Film. FPC is an abbreviation for Flexible Printed Circuit. FFC is an abbreviation for Flexible Flat Cable.

[0079] In the following, assuming that n1 is a or b and m1 is any integer from 1 to M, elements related to nozzle Nz[n1m1] may be described with the prefix [n1m1]. For example, a pressure chamber CV communicating with nozzle Nz[n1m1] may be described as pressure chamber CV[n1m1], and a piezoelectric element 111f that applies pressure to pressure chamber CV[n1m1] may be described as piezoelectric element 111f[n1m1]. Similarly, elements related to the nozzle Nz-H to be judged may be described with the prefix "-H". For example, a pressure chamber CV communicating with the nozzle Nz-H to be judged may be described as "pressure chamber CV-H to be judged", and a piezoelectric element 111f that applies pressure to pressure chamber CV-H to be judged may be described as "pressure chamber 111f-H to be judged".

[0080] 1-5. Configuration of the liquid dispensing head HU The configuration of the liquid discharge head HU will be described below with reference to Figure 8.

[0081] Figure 8 is a block diagram showing an example of the configuration of a liquid discharge head HU. Figure 8 shows the head chip 111 and the drive circuit 112 provided on the liquid discharge head HU.

[0082] In addition to the head chip 111 and the drive circuit 112, the liquid discharge head HU includes internal wiring LHa to which the drive signal Com-A is supplied from the drive signal generation circuit 114, internal wiring LHb to which the drive signal Com-B is supplied from the drive signal generation circuit 114, internal wiring LHs for supplying the detection signal Vout detected from the piezoelectric element 111f to the detection circuit 117, and internal wiring LHd to which the offset potential VBS is supplied.

[0083] As shown in Figure 8, the switching circuit 115 comprises 2M switches SWa[a1] to SWa[bM], 2M switches SWb[a1] to SWb[bM], 2M switches SWs[a1] to SWs[bM], and a connection state specification circuit 116 that specifies the connection state of each switch. For example, transmission gates can be used as each switch. The connection status specification circuit 116 generates connection status specification signals SLa[a1]~SLa[bM] that specify the on / off state of switches SWa[a1]~SWa[bM], connection status specification signals SLb[a1]~SLb[bM] that specify the on / off state of switches SWb[a1]~SWb[bM], and connection status specification signals SLs[a1]~SLs[bM] that specify the on / off state of switches SWs[a1]~SWs[bM], based on at least some of the print signal SI, latch signal LAT, and period specification signal Tsig supplied from the control circuit 170.

[0084] If n1 is a or b and m1 is any integer from 1 to M, the switch SWa[n1m1] switches between conduction and non-conductivity between the internal wiring LHa and the lower electrode Zd[n1m1] of the piezoelectric element 111f[n1m1], according to the connection status signal SLa[n1m1]. For example, the switch SWa[n1m1] turns on when the connection status signal SLa[n1m1] is high level and turns off when it is low level. If n1 is a or b and m1 is any integer from 1 to M, the switch SWb[n1m1] switches between conduction and non-conductivity between the internal wiring LHb and the lower electrode Zd[n1m1] of the piezoelectric element 111f[n1m1], according to the connection status signal SLb[n1m1]. For example, the switch SWb[n1m1] turns on when the connection status signal SLb[n1m1] is high level and turns off when it is low level. If n1 is a or b and m1 is any integer from 1 to M, the switch SWs[n1m1] switches between conduction and non-conductivity between the internal wiring LHs and the lower electrode Zd[n1m1] of the piezoelectric element 111f[n1m1], according to the connection status signal SLs[n1m1]. For example, the switch SWs[n1m1] turns on when the connection status signal SLs[n1m1] is high level and turns off when it is low level.

[0085] When n1 is a or b and m1 is any integer from 1 to M, the detection circuit 117 receives the detection signal Vout[n1m1] output from the piezoelectric element 111f[n1m1] via the internal wiring LHs. The detection circuit 117 then generates a residual vibration signal NES based on this detection signal Vout[n1m1]. The residual vibration signal NES is an analog signal.

[0086] The detection circuit 117 may include, for example, a negative feedback amplifier for amplifying the detection signal Vout, a low-pass filter for attenuating the high-frequency components of the detection signal Vout, and a voltage follower that converts impedance to output a low-impedance residual vibration signal NES.

[0087] The generation circuit 190 generates individual residual vibration information NEI based on the residual vibration signal NES. Individual residual vibration information NEI is a digital signal. For example, the generation circuit 190 samples the residual vibration signal NES at regular intervals and generates individual residual vibration information NEI by associating time information, which indicates the time of sampling with respect to an arbitrary starting point, with a value indicating the potential obtained from the sampling.

[0088] 1-6. Operation of the liquid dispensing head HU The operation of the liquid ejection head HU will be described below with reference to Figure 9. In this embodiment, the operating period of the inkjet printer 100 includes one or more recording periods Tu. In this embodiment, the inkjet printer 100 is assumed to perform either driving each piezoelectric element 111f in the recording process or driving the target piezoelectric element 111f-H and detecting residual vibration in the preparation process for the ejection state determination process during each recording period Tu. However, this disclosure is not limited to this embodiment, and it may be possible to perform both driving each piezoelectric element 111f in the recording process and driving the target piezoelectric element 111f-H and detecting residual vibration in the preparation process for the ejection state determination process during each recording period Tu. Generally, an inkjet printer 100 forms an image based on image data Img by ejecting ink from each nozzle Nz one or more times over multiple continuous or intermittent recording periods Tu. In addition, the inkjet printer 100 according to this embodiment performs a preparatory process for ejection state determination processing 2M times over 2M recording periods Tu which are provided continuously or intermittently, thereby performing an ejection state determination process with each of the 2M nozzles Nz[a1] to D[bM] as the nozzle Nz-H to be determined.

[0089] Figure 9 is a timing chart illustrating the operation of the inkjet printer 100 during the recording period Tu. As shown in Figure 9, the control circuit 170 outputs a latch signal LAT having a pulse PlsL. Thus, the control circuit 170 defines the recording period Tu as the period from the rising edge of pulse PlsL to the rising edge of the next pulse PlsL.

[0090] The print signal SI includes individual designation signals Sd[a1] to Sd[bM] that specify the mode of driving the piezoelectric elements 111f[a1] to D[bM] during each recording period Tu. When at least one of the recording process and the ejection state determination process is performed during the recording period Tu, the control circuit 170 supplies the print signal SI, including the individual designation signals Sd[a1] to Sd[bM], to the connection state designation circuit 116 in synchronization with the clock signal CL prior to the start of the recording period Tu, as shown in Figure 9. In this case, if n1 is a or b and m1 is any integer from 1 to M, the connection state designation circuit 116 generates connection state designation signals SLa[n1m1], SLb[n1m1], and SLs[n1m1] during the recording period Tu based on the individual designation signal Sd[n1m1].

[0091] Furthermore, if n1 is a or b and m1 is any integer from 1 to M, the individual designation signal Sd[n1m1] according to this embodiment is a signal that, for each recording period Tu, specifies to the piezoelectric element 111f[n1m1] one of three drive modes: ink ejection, non-ejection of ink, and drive as the target of determination in the ejection state determination process.

[0092] As shown in Figure 9, the drive signal generation circuit 114 outputs a drive signal Com-A having an output waveform PX. The output waveform PX has a minimum potential VLX and a maximum potential VHX. The output waveform PX has its start and end potentials set to the reference potential V0.

[0093] Then, assuming that n1 is a or b and m1 is any integer from 1 to M, if the individual designation signal Sd[n1m1] specifies ink ejection to the piezoelectric element 111f[n1m1], the connection state designation circuit 116 sets the connection state designation signal SLa[n1m1] to a high level during the recording period Tu, and sets the connection state designation signals SLb[n1m1] and SLs[n1m1] to low levels during the recording period Tu. In this case, the nozzle Nz[n1m1] ejects ink during the recording period Tu, and dots are formed on the medium PP.

[0094] As shown in Figure 9, the drive signal generation circuit 114 outputs a drive signal Com-B having a test waveform PS provided during the recording period Tu. In this embodiment, the test waveform PS is determined such that the potential difference between the highest potential VHS and the lowest potential VLS of the test waveform PS is smaller than the potential difference between the highest potential VHX and the lowest potential VLX of the ejection waveform PX. Specifically, assuming that n1 is a or b and m1 is any integer from 1 to M, when the drive signal Com-B having the test waveform PS is supplied to the piezoelectric element 111f[n1m1], the test waveform PS is determined such that the piezoelectric element 111f[n1m1] is driven to the extent that no ink is ejected from the nozzle Nz[n1m1]. Note that the potential of the test waveform PS at the start and end is set to the reference potential V0.

[0095] Furthermore, the control circuit 170 outputs a period specification signal Tsig having pulses PlsT1 and PlsT2. As a result, the control circuit 170 divides the recording period Tu into three control periods: TSS1, from the start of pulse PlsL to the start of pulse PlsT1; TSS2, from the start of pulse PlsT1 to the start of pulse PlsT2; and TSS3, from the start of pulse PlsT2 to the start of the next pulse PlsL.

[0096] Furthermore, assuming that n1 is a or b and m1 is any integer from 1 to M, if the individual designation signal Sd[n1m1] designates nozzle Nz[n1m1] as the nozzle Nz-H to be determined, the connection state designation circuit 116 sets the connection state designation signal SLa[n1m1] to a low level during the recording period Tu, sets the connection state designation signal SLb[n1m1] to a high level during the control periods TSS1 and TSS3 and to a low level during the control period TSS2, and sets the connection state designation signal SLs[n1m1] to a low level during the control periods TSS1 and TSS3 and to a high level during the control period TSS2. In this case, the piezoelectric element 111f-H to be judged is driven by the drive signal Com-B of the inspection waveform PS during the control period TSS1. The piezoelectric element 111f is displaced by the drive signal Com-B of the inspection waveform PS during the control period TSS1. As a result, vibration occurs in the pressure chamber CV-H to be judged, and this vibration persists during the control period TSS2. During the control period TSS2, the lower electrode Zd of the piezoelectric element 111f-H changes its potential in accordance with the residual vibration occurring in the pressure chamber CV-H. In other words, during the control period TSS2, the lower electrode Zd of the piezoelectric element 111f-H exhibits a potential corresponding to the electromotive force of the piezoelectric element 111f caused by the residual vibration occurring in the pressure chamber CV-H. The potential of the lower electrode Zd can be detected as a detection signal Vout during the control period TSS2.

[0097] 1-7. Causes of dispensing failure As mentioned above, the causes of ejection failure are the inclusion of air bubbles, increased ink viscosity, and adhesion of paper dust. However, experiments by the inventors have revealed that other factors can also cause ejection failure. Specifically, it has been found that if the wiping process is not performed sufficiently, or if the negative pressure setting of the pressure chamber CV is insufficient, a small amount of liquid droplet may overflow from the nozzle Nz, resulting in the formation of a liquid reservoir on the nozzle surface FN. This liquid reservoir may slightly adversely affect the ejection characteristics. Hereafter, nozzles Nz whose ejection characteristics are deteriorated due to the occurrence of liquid reservoirs may be referred to as liquid reservoir-occurring nozzles Nz-M.

[0098] When we attempted to detect the presence or absence of liquid accumulation using residual vibration, we found that the residual vibration for the liquid accumulation-generating nozzle Nz-M was slightly different from the residual vibration for the normal-discharge nozzle Nz-S. This difference is explained using Figure 10.

[0099] Figure 10 is a diagram illustrating the residual vibrations of the liquid accumulation nozzle Nz-M. Graph g1 in Figure 10 shows the residual vibration characteristics of the liquid accumulation nozzle Nz-M and the normal discharge nozzle Nz-S. The horizontal axis of graph g1 represents time, and the vertical axis represents potential. The residual vibration characteristic NCS shown in graph g1 shows the residual vibration characteristics for the normal discharge nozzle Nz-S. The residual vibration characteristic NCM shown in graph g1 shows the residual vibration characteristics for the liquid accumulation nozzle Nz-M.

[0100] As shown in the residual vibration characteristics NCM and NCS in Figure 10, the amplitude AM1 of the residual vibration for the liquid pooling nozzle Nz-M is slightly smaller than the amplitude AS1 of the residual vibration for the normal discharge nozzle Nz-S. Amplitudes AM1 and AS1 are the absolute values ​​of the difference between the potential of the first extreme of the residual vibration and the potential Ac at the center of the residual vibration amplitude. Furthermore, the period TM1 of the residual vibration for the liquid pooling nozzle Nz-M is slightly longer than the period TS1 of the residual vibration for the normal discharge nozzle Nz-S. Periods TM1 and TS1 represent the period from the first to the third extreme of the residual vibration. Also, the time HM1 at which the residual vibration amplitude becomes centered for the liquid pooling nozzle Nz-M is slightly later than the time HS1 at which the residual vibration amplitude becomes centered for the normal discharge nozzle Nz-S. Time HM1 and HS1 represent the first time the residual vibration amplitude becomes centered. The residual vibration being at the center of the amplitude occurs when, assuming the residual vibration is a sine wave whose amplitude is decreasing, its phase is 0 degrees or 180 degrees.

[0101] As shown above by the residual vibration characteristics NCM and NCS, there is a difference between the residual vibration of the nozzle Nz-M where liquid pooling occurs and the residual vibration of the nozzle Nz-S where discharge is normal. However, because this difference is minute, it is difficult to distinguish from the error range, and even using the residual vibration of a single nozzle Nz, it was not possible to accurately detect whether or not liquid pooling has occurred. Here, liquid pooling does not occur in only one nozzle Nz, but extends across multiple adjacent nozzles Nz. Because the nozzles Nz are of a very small size, and the liquid pooling spreads to some extent due to surface tension, a liquid pool formed by one nozzle Nz covers adjacent nozzles Nz as well. In other words, when liquid pooling occurs, the residual vibration of a single nozzle Nz-M where liquid pooling occurs cannot be distinguished from the error range, but the residual vibrations of multiple adjacent nozzles Nz show the same trend, as obtained from the inventor's experiments. In this embodiment, the fact that the residual vibrations of multiple adjacent nozzles Nz show the same trend is utilized to determine whether or not liquid pooling has occurred.

[0102] In the following description, an abnormality in which liquid pooling occurs may be referred to as "liquid pooling abnormality," and among the abnormalities resulting in poor ejection, abnormalities other than liquid pooling abnormality, such as the inclusion of air bubbles, increased ink viscosity, and paper dust adhesion, which involve abnormalities of the liquid ejection head HU, may be referred to as "previously described head abnormalities." Note that liquid pooling abnormality is an example of "Type 1 abnormality," and previously described head abnormalities are an example of "Type 2 abnormality."

[0103] 1-8. Functions and Operation of Inkjet System 10 The functions and operation of the inkjet system 10 will be explained using Figures 11 to 15. In this embodiment, the cloud server CS performs an abnormality determination process and provides the inkjet printer 100 with a service that provides determination information JI indicating the determination result. The abnormality determination process is a process that determines, based on residual vibration information NI, whether there is an abnormality in ink pool formation, an abnormality in the previously ejected head, or normal ejection that is neither an abnormality in ink pool formation nor an abnormality in the previously ejected head. The residual vibration information NI has 2M individual residual vibration information NEI.

[0104] Figure 11 is a diagram showing the functions of the inkjet system 10. Figure 12 is a flowchart showing the operation of the inkjet system 10. The control circuit 170 functions as the acquisition unit 171, the first transmission unit 173, the first reception unit 175, and the maintenance control unit 177 by reading the control program PM3 and executing the read control program PM3. The server 300 functions as the cloud server CS by reading the virtualization program VM and executing the read virtualization program VM. The cloud server CS reads the control program PM1 and executes the control program PM1, thereby functioning as the second reception unit 301, the determination unit 303, and the second transmission unit 305.

[0105] The flowchart shown in Figure 12 is executed, for example, when the inkjet printer 100 receives image data Img from the processing unit 200, before executing the recording process. In step SJ2, the control circuit 170 functions as an acquisition unit 171 to acquire residual vibration information NI. Specifically, the control circuit 170 acquires 2M individual residual vibration information NEI corresponding to 2M nozzles Nz, which will be contained in the residual vibration information NI, from the generation circuit 190. More specifically, the control circuit 170 sets the nozzle Nz[x] to the nozzle Nz-H to be determined for each of a1 to bM, and acquires the individual residual vibration information NEI[x] by executing an ejection state determination process on the nozzle Nz-H to be determined. Step SJ2 is an example of the "acquisition process". After the processing in step SJ2 is completed, in step SJ4, the control circuit 170 functions as the first transmission unit 173 and controls the communication device 150 to transmit residual vibration information NI, which has 2M individual residual vibration information NEI acquired by the acquisition unit 171, to the cloud server CS. More specifically, the first transmission unit 173 transmits the residual vibration information NI to the cloud server CS via the processing unit 200. Step SJ4 is an example of the "transmission process". After the processing in step SJ4 is completed, the control circuit 170 waits for a response from the cloud server CS.

[0106] In step SC2, the cloud server CS functions as the second receiving unit 301 and receives residual vibration information NI from the inkjet printer 100. After the processing in step SC2 is completed, in step SC4, the cloud server CS functions as the determination unit 303 and performs abnormality determination processing. Step SC4 is an example of a "determination process". As shown in Figure 12, the abnormality determination processing includes the liquid accumulation flag setting process, which is the process in step SC6, and the liquid accumulation determination process, which is the process in step SC8. The liquid accumulation determination process will be explained using Figure 13, and the liquid accumulation determination process will be explained using Figure 15.

[0107] Figure 13 is a flowchart showing the liquid accumulation flag setting process. The liquid accumulation flag setting process sets a liquid accumulation flag for nozzles Nz whose discharge characteristics may be degraded due to liquid accumulation. However, nozzles Nz with the liquid accumulation flag set may still have normal discharge. The liquid accumulation flag setting process also determines whether or not there is a previously reported head abnormality. In addition, in the series of processes shown in Figure 13, the determination unit 303 uses the amplitude and period of residual vibration to determine which nozzles Nz may have degraded discharge characteristics due to liquid accumulation.

[0108] In step SC12, the determination unit 303 selects the first nozzle Nz out of 2M nozzles Nz. The first nozzle Nz out of 2M nozzles Nz can be any nozzle Nz out of 2M nozzles Nz, but in this embodiment, it is nozzle Nz[a1].

[0109] After the processing in step SC12 is completed, in step SC14, the determination unit 303 selects the individual residual vibration information NEI corresponding to the selected nozzle Nz from among the 2M individual residual vibration information NEI included in the residual vibration information NI. Then, in step SC16, the determination unit 303 uses the selected individual residual vibration information NEI to determine whether the following equation (1) holds true. |Amplitude AM - Amplitude Reference Value AS| > Threshold λA (1)

[0110] However, |x| represents the absolute value of x. Amplitude AM is the absolute value of the difference between the potential of the first extreme of the residual vibration of the selected individual residual vibration information NEI and the potential of the center of the residual vibration amplitude. Amplitude reference value AS is the absolute value of the difference between the potential of the first extreme of the residual vibration for a discharge normal nozzle Nz-S and the potential of the center of the residual vibration amplitude. Threshold λA is the amplitude threshold for determining whether or not a previously reported head abnormality exists. The amplitude reference value AS and threshold λA are set in advance by the head manufacturer's experiments or experience. The head manufacturer stores the amplitude reference value AS and threshold λA in the memory circuit 320.

[0111] If the result of step SC16 is negative, the determination unit 303 determines in step SC18 whether the following equation (2) holds true using the selected individual residual vibration information NEI. |Periodic TM - Periodic reference value TS| > Threshold TA (2)

[0112] The period TM is the period from the first to the third extreme value of the residual vibration of the selected individual residual vibration information NEI. The period reference value TS is the period from the first to the third extreme value of the residual vibration for a discharge normal nozzle Nz-S. The threshold value TA is the period threshold for determining whether or not a previously reported head abnormality exists. The period reference value TS and the threshold value TA are set in advance by the head manufacturer's experiments or experience. The head manufacturer stores the period reference value TS and the threshold value TA in the memory circuit 320.

[0113] If the result of step SC18 is negative, the determination unit 303 determines in step SC20 whether the following equation (3) holds true using the selected individual residual vibration information NEI. |Amplitude AM - Amplitude reference value AS|>Threshold λB (3)

[0114] The threshold λB is an amplitude threshold used to determine whether or not the discharge characteristics may be degraded due to liquid accumulation. The threshold λB is set in advance by the head maker's experiments or experience. The head maker stores the threshold λB in the memory circuit 320. The threshold λB is smaller than the threshold λA. For example, the threshold λB may be less than or equal to 1 / 10 of the threshold λA, or less than or equal to 1 / 100 of the threshold λA. The relationship between the threshold λA and the threshold λB will be explained after the explanation of the process in step SC28.

[0115] If the result of step SC20 is negative, the determination unit 303 determines in step SC22 whether the following equation (4) holds true using the selected individual residual vibration information NEI. |Periodic TM - Periodic reference value TS| > Threshold TB (4)

[0116] The threshold TB is a periodic threshold used to determine whether or not the discharge characteristics may be degraded due to liquid accumulation. The threshold TB is set in advance by the head maker's experiments or experience. The head maker stores the threshold TB in the memory circuit 320. For example, the threshold TB may be 1 / 10 or less of the threshold TA, or 1 / 100 or less of the threshold TA.

[0117] If the result of step SC22 is negative, the determination unit 303 determines in step SC24 that the selected nozzle Nz is ejecting normally. Also, if the result of step SC20 is positive, or if the result of step SC22 is positive, the determination unit 303 sets a liquid accumulation flag for the selected nozzle Nz in step SC26. Specifically, the determination unit 303 stores the information identifying the selected nozzle Nz and the liquid accumulation flag in the memory circuit 320 in association with each other. Also, if the result of step SC16 is positive, or if the result of step SC18 is positive, the determination unit 303 determines in step SC28 that a previously ejected head abnormality has occurred at the selected nozzle Nz. Although not shown in the figures, the determination unit 303 uses a known method to determine whether the selected individual residual vibration information NEI is due to air bubbles, ink viscosity, or paper dust adhesion. The relationship between threshold λA and threshold λB will be explained using Figure 14.

[0118] Figure 14 is a diagram illustrating the relationship between threshold values ​​λA and λB. Graph g2 in Figure 14 is an enlarged view of the area near the first extreme value of the residual vibration in graph g1. However, for ease of understanding, graph g2 shows the potential Ac at the center of the residual vibration amplitude as 0[V]. Furthermore, in graph g2, in order to match the notation of equations (1) and (3) shown in Figure 13, the absolute value of the difference between the potential of the first extreme value of the residual vibration and the potential Ac at the center of the residual vibration amplitude for the liquid accumulation nozzle Nz-M is written as amplitude AM, and the absolute value of the difference between the potential of the first extreme value of the residual vibration and the potential Ac at the center of the residual vibration amplitude for the normal discharge nozzle Nz-S is written as amplitude reference value AS.

[0119] Regarding the amplitude of residual vibration, the selected nozzle Nz is determined to be a previously reported head abnormality if equation (1) holds true. And, as can be seen from Figure 14, if equation (1) holds true, then either equation (1-a) or (1-b) below also holds true. Amplitude AM > Amplitude reference value AS + threshold λA (1-a) Amplitude AM < Amplitude reference value AS - threshold λA (1-b)

[0120] Furthermore, the case in which a liquid reservoir flag is set for the selected nozzle Nz is when equation (1) does not hold and equation (3) holds. And, as can be seen from Figure 14, when equation (1) does not hold and equation (3) holds, it is when either equation (3-a) or (3-b) below holds. Amplitude reference value AS + threshold λB < Amplitude AM ≤ Amplitude reference value AS + threshold λA (3-a) Amplitude reference value AS - threshold λA ≤ Amplitude AM < Amplitude reference value AS - threshold λB (3-b)

[0121] As shown in equations (3-a) and (3-b), in the first embodiment, when liquid accumulation occurs at the selected nozzle Nz, the possibility that the amplitude AM of the residual vibration for the selected nozzle Nz will be greater than the amplitude reference value AS + threshold λB, and the possibility that it will be less than the amplitude reference value AS - threshold λB are considered.

[0122] Furthermore, the case in which the selected nozzle Nz is discharging normally is when equation (3) does not hold. And, as can be seen from Figure 14, when equation (3) does not hold, it is when the following equation (3-c) holds. Amplitude reference value AS - threshold λB ≤ Amplitude AM ≤ Amplitude reference value AS + threshold λB (3-c)

[0123] As can be seen from Figure 14, since threshold λB is smaller than threshold λA, amplitude reference value AS-threshold λA is smaller than amplitude reference value AS-threshold λB. Note that amplitude reference value AS-threshold λA is an example of a "second threshold," and amplitude reference value AS-threshold λB is an example of a "first threshold."

[0124] In the example in Figure 14, since equation (3-b) holds true, the determination unit 303 sets a liquid accumulation flag for the selected nozzle Nz.

[0125] Although not shown in the diagram, the relationship between threshold TA and threshold TB is the same as the relationship between threshold λA and threshold λB. Specifically, with respect to the period of residual vibration, the selected nozzle Nz is determined to be a previously reported head abnormality when equation (2) holds true. And when equation (2) holds true, either equation (2-a) or (2-b) below also holds true. Period TM > Period Reference Value TS + Threshold TA (2-a) Period TM < Period Reference Value TS - Threshold TA (2-b)

[0126] Furthermore, the case in which the liquid reservoir flag is set for the selected nozzle Nz is when equation (2) does not hold and equation (4) holds. And when equation (2) does not hold and equation (4) holds, it is when either equation (4-a) or (4-b) below holds. Periodic reference value TS + threshold TB < period TM ≤ periodic reference value TS + threshold TA (4-a) Period criterion value TS - threshold value TA ≤ period TM < period criterion value TS - threshold value TB (4-b)

[0127] As shown in equations (4-a) and (4-b), in the first embodiment, when liquid accumulation occurs at the selected nozzle Nz, the possibility that the period TM of the residual vibration for the selected nozzle Nz may be longer than the period reference value TS + threshold TB, and the possibility that it may be shorter than the period reference value TS - threshold TB are considered.

[0128] The selected nozzle Nz is considered to be dispensing normally if equation (4) does not hold. And if equation (4) does not hold, then equation (4-c) below must hold. Periodic reference value TS - threshold value TB ≤ Period TM ≤ Periodic reference value TS + threshold value TB (4-c)

[0129] Since threshold TB is smaller than threshold TA, periodic reference value TS + threshold TA is longer than periodic reference value TS + threshold TB. Note that periodic reference value TS + threshold TA is an example of a "fourth threshold," and periodic reference value TS + threshold TB is an example of a "third threshold."

[0130] The explanation returns to Figure 13. After the processing of step SC24, step SC26, or step SC28 is completed, the determination unit 303 determines in step SC30 whether all nozzles Nz have been selected. If the determination result of step SC30 is negative, the determination unit 303 selects the next nozzle Nz in step SC32. In this embodiment, the next nozzle Nz is the nozzle Nz adjacent to the selected nozzle Nz in the Y1 direction. Specifically, if n1 is either a or b and m1 is an integer from 1 to M-1, and the selected nozzle Nz is nozzle Nz[n1m1], then the next nozzle Nz is nozzle Nz[n1m1+1]. However, if the selected nozzle Nz is nozzle Nz[aM], then the next nozzle Nz is nozzle Nz[b1]. After the processing of step SC32 is completed, the determination unit 303 returns to step SC14. If the result of step SC30 is positive, the determination unit 303 terminates the series of processes shown in Figure 13.

[0131] In the flowchart shown in Figure 13, the amplitude of the residual vibration is expressed as the absolute value of the difference between the potential of the first extreme value of the residual vibration and the potential of the center of the residual vibration amplitude. However, this is not the only method. For example, the amplitude of the residual vibration may also be expressed as the absolute value of the difference between the potential of the second and subsequent extreme values ​​of the residual vibration and the potential of the center of the residual vibration amplitude. However, since the amplitude of the residual vibration decreases over time, the absolute value of the difference between the potential of the first extreme value of the residual vibration and the potential of the center of the residual vibration amplitude is greater than the absolute value of the difference between the potential of the second and subsequent extreme values ​​and the potential of the center of the residual vibration amplitude. Therefore, by using the potential of the first extreme value of the residual vibration, the influence of noise is relatively smaller compared to using the potential of the second and subsequent extreme values, thus improving the measurement accuracy of the residual vibration amplitude.

[0132] Furthermore, in the flowchart shown in Figure 13, the period of residual vibration is defined as the period from the first to the third extreme value of the residual vibration, but this is not limited to this. For example, the period of residual vibration may be the period from the nth extreme value (after the second) to the (n+2th)th extreme value. Moreover, the period of residual vibration does not necessarily have to use the extreme values ​​of the residual vibration. Since the period of a sine wave is the period from a time of any phase until it returns to the same phase, for example, it may be the period from the nth time (1 or more) when the residual vibration is at the center of its amplitude to the (n+2th) time when the residual vibration is at the center of its amplitude. Because the amplitude of residual vibration is related to the extreme values ​​of the residual vibration after the first, it is preferable not to use the extreme values ​​of the residual vibration for the period of residual vibration. This is because if any noise is affecting the extreme values ​​of the residual vibration, this noise will affect not only the amplitude of the residual vibration but also the period of the residual vibration.

[0133] Figure 15 is a flowchart illustrating the liquid accumulation detection process. The flowchart in Figure 15 shows the liquid accumulation detection process for M nozzles Nz divided into nozzle row La. The liquid accumulation detection process for M nozzles Nz divided into nozzle row Lb is simply the same as replacing nozzle Nz[am1] with nozzle Nz[bm1] in the flowchart in Figure 15, so the illustration and explanation are omitted. In addition, in the flowchart in Figure 15, the determination unit 303 determines that a liquid accumulation abnormality has occurred if the liquid accumulation flag is set for three consecutive nozzles Nz.

[0134] In step SC42, the determination unit 303 assigns 2 to the variable m1. Next, in step SC44, the determination unit 303 determines whether the liquid accumulation flag is set for nozzle Nz[am1-1]. If the determination result in step SC44 is positive, the determination unit 303 determines in step SC46 whether the liquid accumulation flag is set for nozzle Nz[am1]. If the determination result in step SC46 is positive, the determination unit 303 determines in step SC48 whether the liquid accumulation flag is set for nozzle Nz[am1+1].

[0135] If the result of step SC48 is positive, the determination unit 303 determines in step SC50 that an abnormality in liquid pooling formation has occurred. After the processing of step SC50 is completed, the determination unit 303 determines in step SC52 whether the value of variable m1 is M-1, which is the number of nozzles Nz that are divided into nozzle row La. If the result of step SC44 is negative, if the result of step SC46 is negative, or if the result of step SC48 is negative, the determination unit 303 also executes the processing of step SC52.

[0136] As can be understood from the processing from step SC44 to step SC48, even if the liquid accumulation flag is set for nozzle Nz[am1], if the liquid accumulation flag is not set for at least one of nozzles Nz[am1-1] and nozzle Nz[am1+1], the determination unit 303 does not determine that a liquid accumulation abnormality has occurred for nozzle Nz[am1].

[0137] If the result of step SC52 is negative, the determination unit 303 assigns the value of variable m1 (1) plus 1 to the variable m1 in step SC54. After the processing of step SC54 is completed, the determination unit 303 returns to step SC44. If the result of step SC52 is positive, the determination unit 303 terminates the series of processes shown in Figure 15.

[0138] To rephrase the processes in Figure 13 and Figure 15, if nozzle Nz[am1] is the target nozzle Nz, then nozzles Nz[am1-1] and Nz[am1+1] are adjacent nozzles Nz adjacent to nozzle Nz[am1], and can also be said to be surrounding nozzles Nz located around nozzle Nz[am1]. Surrounding nozzles Nz of nozzle Nz[am1] are, for example, nozzles Nz that are included within a predetermined distance range defined by the head manufacturer. For example, the head manufacturer measures the shape of the liquid reservoir through experiments, etc., and if the target nozzle Nz is included in the liquid reservoir, it generates a program that executes the series of processes shown in Figure 15, treating the nozzles Nz that are likely to be included in the liquid reservoir as surrounding nozzles Nz. The number of surrounding nozzles Nz is not limited to two; at least one is sufficient.

[0139] The determination unit 303 determines that a liquid pooling abnormality has occurred if the amplitude of the residual vibration related to the individual residual vibration information NEI for nozzle Nz[am1] is smaller than the amplitude reference value AS-threshold λB, and the amplitude of the residual vibration related to the individual residual vibration information NEI for nozzles Nz[am1-1] and nozzles Nz[am+1] is smaller than the amplitude reference value AS-threshold λB. Note that nozzle Nz[am1] is an example of a "target nozzle," and the individual residual vibration information NEI for nozzle Nz[am1] is an example of "first individual information related to residual vibration in the pressure chamber communicating with the target nozzle." Nozzle Nz[am1-1] and nozzle Nz[am1+1] are examples of "adjacent nozzles" and "surrounding nozzles," and the individual residual vibration information NEI for nozzle Nz[am1-1] and the individual residual vibration information NEI for nozzle Nz[am1+1] are examples of "second individual information regarding residual vibration in the pressure chamber CV communicating with the surrounding nozzle Nz."

[0140] In the series of processes shown in Figure 15, the determination unit 303 determined that a liquid pooling abnormality had occurred when the liquid pooling flag was set for three consecutive nozzles Nz. However, the number of consecutive nozzles Nz is not limited to three; it can be two or more. For example, the determination unit 303 may determine that a liquid pooling abnormality has occurred when the liquid pooling flag is set for five consecutive nozzles Nz. For example, if m1 is any integer between 3 and M-2, the determination unit 303 may determine that a liquid pooling abnormality has occurred if the liquid pooling flag is set for all of nozzles Nz[am1-2], nozzle Nz[am1-1], nozzle Nz[am1], nozzle Nz[am1+1], and nozzle Nz[am1+2]. In this case, nozzle Nz[am1] is an example of a "target nozzle," nozzles Nz[am1-1] and Nz[am1+1] are examples of "adjacent nozzles" and "surrounding nozzles," and nozzles Nz[am1-2] and Nz[am1+2] are examples of "surrounding nozzles."

[0141] Furthermore, in the series of processes shown in Figure 15, the determination unit 303 determined that a liquid pooling abnormality had occurred when the liquid pooling flag was set on three consecutive nozzles Nz. However, it is not necessary for the nozzles Nz to be two or more consecutive nozzles Nz; the determination unit 303 may also determine that a liquid pooling abnormality has occurred if the liquid pooling flag is set on the surrounding nozzles Nz of the target nozzle Nz, excluding the adjacent nozzles Nz. For example, the determination unit 303 may determine that a liquid pooling abnormality has occurred if m1 is any integer between 3 and M-2, and the liquid pooling flag is set on all of nozzles Nz[am1-2], nozzle Nz[am1], and nozzle Nz[am1+2].

[0142] Furthermore, in the series of processes shown in Figure 15, the determination unit 303 determined that a liquid pooling abnormality has occurred when a liquid pooling flag is set for nozzles Nz that are continuous in the direction along the Y axis, but it is not limited to this. For example, surrounding nozzles Nz may include nozzles Nz adjacent to the target nozzle Nz in the direction along the X axis. In this embodiment, when m1 is any integer between 1 and M, the nozzle Nz adjacent to nozzle Nz[am1] in the direction along the X axis is nozzle Nz[bm1]. For example, the determination unit 303 may determine that a liquid pooling abnormality has occurred when m1 is any integer between 1 and M, and both nozzles Nz[am1] and nozzle Nz[bm1] have liquid pooling flags set. Alternatively, the determination unit 303 may determine that a liquid pooling abnormality has occurred if m1 is any integer between 2 and M-1, and the liquid pooling flag is set for both nozzle Nz[am1-1], nozzle Nz[am1], nozzle Nz[am1+1], and nozzle Nz[bm1].

[0143] Let's return to the explanation in Figures 11 and 12. After the processing in step SC4 is completed, in step SC10, the cloud server CS functions as the second transmission unit 305 and transmits judgment information JI, which indicates the judgment result of the determination unit 303, to the inkjet printer 100. The judgment information JI includes one or more identifiers from among a first identifier indicating that ejection is normal, a second identifier indicating that a previously ejected head abnormality has occurred, and a third identifier indicating that an abnormal liquid pooling formation has occurred. For example, if the series of processes shown in Figure 13 does not determine that a previously ejected head abnormality has occurred, and the series of processes shown in Figure 15 does not determine that an abnormal liquid pooling formation has occurred, the judgment information JI includes the first identifier. Also, if the series of processes shown in Figure 13 determines that a previously ejected head abnormality has occurred, the judgment information JI includes the second identifier. Also, if the series of processes shown in Figure 13 determines that an abnormal liquid pooling formation has occurred in the series of processes shown in Figure 15, the judgment information JI includes the third identifier. Furthermore, if the judgment information JI includes a second identifier, it includes an identifier indicating that it is one of the following: air bubbles, increased ink viscosity, or paper dust adhesion. After the processing in step SC10 is completed, the cloud server CS terminates the series of processes shown in Figure 12.

[0144] Furthermore, after the processing of step SC10 is completed, the cloud server CS may store the judgment information JI in the memory circuit 320. The head manufacturer can improve the liquid discharge head HU by analyzing the judgment information JI. In addition, in order to improve the liquid discharge head HU by the head manufacturer more efficiently, the cloud server CS may store the residual vibration information NI and the judgment information JI in association with each other in the memory circuit 320. Furthermore, in order to reduce the capacity used by the memory circuit 320, the cloud server CS may store the residual vibration information NI and the judgment information JI in association with each other in the memory circuit 320 only if the judgment information JI contains one or more identifiers from the second identifier and the third identifier.

[0145] After the processing in step SJ4 is completed, the control circuit 170 waits for a response from the cloud server CS, and in step SJ6, the control circuit 170 functions as the first receiving unit 175 and receives judgment information JI from the cloud server CS. Step SJ6 is an example of a "receiving process". After the processing in step SJ6 is completed, in step SJ8, the control circuit 170 functions as the maintenance control unit 177 and controls the maintenance mechanism 145 based on the judgment information JI to resolve the previously reported head abnormality.

[0146] For example, if the judgment information JI contains an identifier indicating the presence of air bubbles, the maintenance control unit 177 instructs the maintenance mechanism 145 to perform a pumping process. Also, if the judgment information JI contains an identifier indicating increased ink viscosity, the maintenance control unit 177 instructs the maintenance mechanism 145 to perform a flushing process or a pumping process. Also, if the judgment information JI contains an identifier indicating the adhesion of paper dust, the maintenance control unit 177 instructs the maintenance mechanism 145 to perform a wiping process. Also, if the judgment information JI contains a third identifier, the maintenance control unit 177 instructs the maintenance mechanism 145 to perform a wiping process. After the processing in step SJ8 is completed, the control circuit 170 terminates the series of processes shown in Figure 12.

[0147] 1-9. Summary of the First Embodiment To facilitate understanding, the amplitude reference value AS-threshold λB, an example of a "first threshold" used to determine abnormal liquid pooling formation, will be referred to as the "first lower amplitude threshold," and the amplitude reference value AS-threshold λA, an example of a "second threshold" used to determine previously identified head abnormalities, will be referred to as the "second lower amplitude threshold." Furthermore, the individual residual vibration information NEI concerning residual vibration in the pressure chamber CV communicating with the target nozzle Nz will be referred to as the "first individual information," and the individual residual vibration information NEI concerning residual vibration in the pressure chamber CV communicating with at least one surrounding nozzle Nz located around the target nozzle Nz will be referred to as the "second individual information." In addition, the period reference value TS+threshold TB, an example of a "third threshold" used to determine abnormal liquid pooling formation, will be referred to as the "first upper period threshold," and the period reference value TS+threshold TA, an example of a "fourth threshold" used to determine previously identified head abnormalities, will be referred to as the "second upper period threshold," thus concluding the first embodiment.

[0148] The first embodiment defines a control method for an inkjet printer 100 that ejects ink onto a medium PP, having 2M piezoelectric elements 111f, 2M pressure chambers CV that apply pressure to the ink inside by driving each of the 2M piezoelectric elements 111f, and a liquid ejection head HU having a plurality of nozzles Nz that communicate with each of the 2M pressure chambers CV and eject ink. This control method involves a process SJ2 to acquire residual vibration information NI having 2M individual residual vibration information NEI in the pressure chambers CV after applying voltage to the 2M piezoelectric elements 111f, and a process SC4 to determine whether or not an abnormal liquid pooling formation has occurred based on the residual vibration information NI. According to the first embodiment, it is possible to accurately determine whether or not a liquid pooling abnormality has occurred by utilizing the fact that the residual vibration of multiple nozzles Nz causes deviations with the same tendency. If the accuracy of determining liquid pooling abnormalities decreases, for example, if it is incorrectly determined that a liquid pooling abnormality has occurred even though no liquid pool has actually been formed, the recording process will be delayed due to unnecessary wiping, and the liquid-repellent film provided on the nozzle surface FN may be worn or peeled off due to excessive wiping. If the liquid-repellent film is worn or peeled off, liquid droplets will be more likely to adhere to the nozzle surface, which may degrade the ejection performance. On the other hand, if it is incorrectly determined that no liquid pooling abnormality has occurred even though a liquid pool has actually been formed, the recording process will be performed with the liquid pool still formed, which will degrade the quality of the image formed on the medium PP.

[0149] Furthermore, the residual vibration information NI includes first individual information and second individual information. Then, in step SC4, the determination unit 303 determines whether or not a liquid pooling abnormality has occurred based on the first individual information and the second individual information. As described above, if the discharge characteristics of the target nozzle Nz are reduced due to liquid accumulation, the liquid accumulation will spread to some extent due to surface tension, and therefore the liquid accumulation may also adversely affect the surrounding nozzles Nz. Accordingly, the first embodiment can improve the accuracy of determining whether or not a liquid accumulation abnormality has occurred compared to the embodiment that determines whether or not a liquid accumulation abnormality has occurred without using second individual information.

[0150] Furthermore, the surrounding nozzle Nz includes the target nozzle Nz and adjacent nozzles Nz. As described above, if the discharge characteristics of the target nozzle Nz are reduced due to liquid accumulation, the liquid accumulation will spread to some extent due to surface tension, and therefore, the liquid accumulation may also adversely affect the adjacent nozzle Nz. Furthermore, the possibility that the liquid accumulation is adversely affecting the adjacent nozzle Nz is higher than the possibility that it is adversely affecting surrounding nozzles Nz that are not adjacent nozzles Nz. Therefore, according to the first embodiment, the accuracy of determining whether or not a liquid accumulation abnormality has occurred can be improved compared to the method of determining whether or not a liquid accumulation abnormality has occurred without using individual residual vibration information NEI for the adjacent nozzle Nz.

[0151] Furthermore, in step SC4, the determination unit 303 further determines whether or not a previously reported head abnormality has occurred based on the first individual information. According to the first embodiment, it is possible to accurately determine whether or not a liquid pooling abnormality has occurred while simultaneously determining whether or not a previously reported head abnormality has occurred.

[0152] Furthermore, in step SC4, the determination unit 303 determines that a liquid pooling abnormality has occurred if the amplitude of the residual vibration related to the first individual information is smaller than the first lower amplitude threshold, and the amplitude of the residual vibration related to the second individual information is smaller than the first lower amplitude threshold. According to the first embodiment, it is possible to accurately determine whether or not a liquid pooling abnormality has occurred using the amplitude of residual vibration and a first lower amplitude threshold.

[0153] Furthermore, in step SC4, the determination unit 303 determines that no liquid pooling abnormality or previously reported head abnormality has occurred if the amplitude of residual vibration related to the first individual information or the second individual information is greater than the first lower limit amplitude threshold. For example, even if the amplitude of residual vibration with respect to the target nozzle Nz is smaller than the first lower amplitude threshold, if the amplitude of residual vibration with respect to the surrounding nozzle Nz is larger than the first lower amplitude threshold, then liquid pooling has not occurred, and it is highly likely that the amplitude of residual vibration with respect to the target nozzle Nz is smaller than the first lower amplitude threshold due to errors such as noise. Therefore, according to the first embodiment, even if the amplitude of residual vibration of either the first individual information or the second individual information is affected by noise, it can be correctly determined that no liquid pooling abnormality or previously reported head abnormality has occurred.

[0154] Furthermore, in step SC4, the determination unit 303 determines that a previously reported head abnormality has occurred if the amplitude of the residual vibration related to the first individual information is smaller than the second lower amplitude threshold, and the second lower amplitude threshold is smaller than the first lower amplitude threshold. According to the first embodiment, when the amplitude of residual vibration related to the target individual residual vibration information NEI decreases significantly and falls below the second lower amplitude threshold, it can be determined that a previously reported head abnormality has occurred.

[0155] Furthermore, in step SC4, the determination unit 303 determines that a liquid pooling abnormality has occurred if the period of residual vibration related to the first individual information is longer than the first upper limit period threshold, and the amplitude of residual vibration related to the second individual information is longer than the first upper limit period threshold. According to the first embodiment, it is possible to accurately determine whether or not a liquid pooling abnormality has occurred using the period of residual vibration and a first upper period threshold.

[0156] Furthermore, in step SC4, the determination unit 303 determines that no liquid pooling abnormality or previously reported head abnormality has occurred if the period of residual vibration related to the first individual information or the second individual information is shorter than the first upper limit period threshold. According to the first embodiment, even if the period of residual vibration of either the first individual information or the second individual information is affected by noise, it can be correctly determined that no liquid pooling abnormality or previously reported head abnormality has occurred.

[0157] Furthermore, in step SC4, the determination unit 303 determines that a previously reported head abnormality has occurred if the period of residual vibration related to the first individual information is longer than the second upper period threshold, and the second upper period threshold is longer than the first upper period threshold. According to the first embodiment, when the period of residual vibration related to the first individual information becomes longer than the second upper period threshold, it can be determined that a previously reported head abnormality has occurred.

[0158] Furthermore, the control method for the inkjet printer 100 uses a cloud server CS located outside the inkjet printer 100. This control method involves the process in step SJ4, which transmits the residual vibration information NI acquired by the process in step SJ2 from the inkjet printer 100 to the cloud server CS, and the process in step SJ6, which receives judgment information JI indicating the judgment result by the judgment unit 303 from the cloud server CS. The cloud server CS then performs the process in step SC4 as the judgment unit 303. In other words, the cloud server CS performs abnormality judgment processing and provides the inkjet printer 100 with a service that provides judgment information JI indicating the judgment result. A service that provides judgment information JI may be offered for a limited time. It is also possible for the inkjet printer 100 to perform abnormality detection processing. Therefore, one possible configuration in which the inkjet printer 100 performs abnormality detection processing is to provide the service that provides judgment information JI to the printer manufacturer for a limited time. However, in the configuration in which the inkjet printer 100 performs abnormality detection processing, the program that performs abnormality detection processing is stored in the memory circuit 160. As a result of the printer manufacturer illegally analyzing the program that performs abnormality detection processing, there is a risk that after the period for which the service that provides judgment information JI is offered has expired, the printer manufacturer may use the results of the illegal analysis to independently implement abnormality detection processing. In the first embodiment, since the entity that executes the abnormality detection processing is the cloud server CS, it is possible to provide the service that provides judgment information JI to the printer manufacturer for a limited time while suppressing the leakage of the program that performs abnormality detection processing.

[0159] 2. Second Embodiment In the first embodiment, as shown by equations (3-a) and (3-b), when liquid accumulation occurs at the selected nozzle Nz, the first embodiment considers the possibility that the amplitude AM of the residual vibration for the selected nozzle Nz may be greater than the amplitude reference value AS + threshold λB, and the possibility that it may be less than the amplitude reference value AS - threshold λB. However, as shown in Figure 10, the amplitude of the residual vibration for the liquid accumulation-occurring nozzle Nz-M is slightly smaller than the amplitude of the residual vibration for the normal discharge nozzle Nz-S. Therefore, when liquid accumulation occurs at the selected nozzle Nz, it is also possible to consider only the possibility that the amplitude AM of the residual vibration for the selected nozzle Nz may be less than the amplitude reference value AS - threshold λB. Similarly, as shown by equations (4-a) and (4-b), in the first embodiment, when liquid accumulation occurs at the selected nozzle Nz, the possibility that the period TM of the residual vibration for the selected nozzle Nz may be longer than the period reference value TS + threshold TB, and the possibility that it may be shorter than the period reference value TS - threshold TB. However, as shown in Figure 10, the period of residual vibration for the nozzle Nz-M where liquid accumulation occurs is slightly longer than the period of residual vibration for the nozzle Nz-S where discharge is normal. Therefore, if liquid accumulation occurs in the selected nozzle Nz, it is only possible to consider the possibility that the period TM of the residual vibration for the selected nozzle Nz will be longer than the period reference value TS + threshold TB. The second embodiment will be described below.

[0160] Figure 16 is a flowchart showing the liquid reservoir flag setting process in the second embodiment. The flowchart in Figure 16 differs from the flowchart in Figure 13 in that step SC16A is executed instead of step SC16, step SC18A is executed instead of step SC18, step SC20A is executed instead of step SC20, and step SC22A is executed instead of step SC22, but otherwise they are the same. Below, only the differences from the flowchart in Figure 13 will be explained.

[0161] After the processing in step SC14 is completed, the determination unit 303 determines in step SC16A whether the following equation (1A) holds true using the selected individual residual vibration information NEI. Amplitude reference value AS - Amplitude AM > Threshold λA' (1A)

[0162] In the second embodiment, the threshold λA' is an amplitude threshold for determining whether or not a previously reported head abnormality has occurred. The threshold λA' is set in advance by the head manufacturer's experiments or experience. The head manufacturer stores the threshold λA' in the memory circuit 320.

[0163] If the result of step SC16A is negative, the determination unit 303 determines in step SC18A whether the following equation (2A) holds true using the selected individual residual vibration information NEI. Period TM - Period Reference Value TS > Threshold TA' (2A)

[0164] The threshold value TA' is a periodic threshold used to determine whether or not a previously reported head malfunction has occurred. The threshold value TA' is pre-set based on the head manufacturer's experiments or experience. The head manufacturer stores the threshold value TA' in the memory circuit 320.

[0165] If the result of step SC18A is negative, the determination unit 303 determines in step SC20A whether the following equation (3A) holds true using the selected individual residual vibration information NEI. Amplitude reference value AS - Amplitude AM > Threshold λB' (3A)

[0166] In the second embodiment, the threshold λB' is an amplitude threshold for determining whether or not the discharge characteristics may be degraded due to liquid accumulation. The threshold λB' is set in advance by the head maker's experiments or experience. The head maker stores the threshold λB' in the memory circuit 320. The threshold λB' is smaller than the threshold λA'. For example, the threshold λB' may be 1 / 10 or less of the threshold λA', or 1 / 100 or less of the threshold λA.

[0167] If the result of step SC20A is negative, the determination unit 303 determines in step SC22A whether the following equation (4A) holds true using the selected individual residual vibration information NEI. Period TM - Period Reference Value TS > Threshold TB' (4A)

[0168] In the second embodiment, threshold TB' is a period threshold for determining whether or not the discharge characteristics may be degraded due to liquid accumulation. Threshold TB' is preset by the head maker's experiments or experience. The head maker stores threshold TB' in the memory circuit 320. For example, threshold TB' may be 1 / 10 or less of threshold TA', or 1 / 100 or less of threshold TA'.

[0169] Furthermore, equation (1A) can be transformed into equation (1A-a) below, and equation (3A) can be transformed into equation (3A-a) below. Amplitude AM < Amplitude reference value AS - threshold λA' (1A-a) Amplitude AM < Amplitude reference value AS - threshold λB' (3A-a)

[0170] Since threshold λB' is smaller than threshold λA', amplitude reference value AS-threshold λA' is smaller than amplitude reference value AS-threshold λB'. In the second embodiment, amplitude reference value AS-threshold λA' is an example of a "second threshold," and amplitude reference value AS-threshold λB' is an example of a "first threshold."

[0171] Furthermore, equation (2A) can be transformed into equation (2A-a) below, and equation (4A) can be transformed into equation (4A-a) below. Period TM > Period Reference Value TS + Threshold TA' (2A-a) Period TM > Period Reference Value TS + Threshold TB' (4A-a)

[0172] In the second embodiment, the periodic reference value TS + threshold TA' is an example of a "fourth threshold," and the periodic reference value TS + threshold TB' is an example of a "third threshold."

[0173] 3. Variant Each of the embodiments exemplified above can be modified in various ways. Specific examples of modifications that can be applied to each of the embodiments described above are given below. Two or more embodiments arbitrarily selected from the following examples can be merged as appropriate, provided they do not contradict each other.

[0174] 3-1. First variation In the liquid reservoir flag setting process of the first embodiment described above, the amplitude and period of residual vibration were used, but the phase of residual vibration may also be used.

[0175] 3-1-1. Operation of the first modified example Figure 17 is a flowchart showing the liquid reservoir flag setting process in the first modified example. The flowchart in Figure 17 differs from the flowchart in Figure 13 in that step SC18B is executed instead of step SC18, and step SC22B is executed instead of step SC22, but otherwise they are the same. Below, only the differences from the flowchart in Figure 13 will be explained.

[0176] If the result of step SC16 is negative, the determination unit 303 determines in step SC18B whether the following equation (5) holds true using the selected individual residual vibration information NEI. |Phase time HM - Phase reference value HS|> Threshold HA (5)

[0177] Phase time HM is a value indicating the first time when the residual vibration of the selected individual residual vibration information NEI reaches the center of its amplitude. Phase reference value HS is a value indicating the first time when the residual vibration for the discharge normal nozzle Nz-S reaches the center of its amplitude. Threshold HA is a threshold used to determine whether or not a previously reported head abnormality exists, and is the threshold for the time when the phase is 180 degrees, in other words, the threshold for the first time when the residual vibration reaches the center of its amplitude. This 180 degrees is an example of a "specific phase". The phase reference value HS and threshold HA are set in advance by the head manufacturer's experiments or experience. The head manufacturer stores the phase reference value HS and threshold HA in the memory circuit 320.

[0178] If the result of step SC20 is negative, the determination unit 303 determines in step SC22 whether the following equation (6) holds true using the selected individual residual vibration information NEI. |Phase time HM - Phase reference value HS| > Threshold HB (6)

[0179] The threshold HB is a threshold used to determine whether or not the discharge characteristics may be degraded due to liquid accumulation, and is the threshold value at the first time when the residual vibration is at the center of its amplitude. The threshold HB is set in advance by the head maker's experiments or experience. The head maker stores the threshold HB in the memory circuit 320. The threshold HB is smaller than the threshold HA. For example, the threshold HB may be 1 / 10 or less of the threshold HA, or 1 / 100 or less of the threshold HA.

[0180] Regarding the phase of residual vibration, the selected nozzle Nz is determined to be a previously reported head abnormality if equation (5) holds true. And if equation (5) holds true, then either equation (5-a) or (5-b) below also holds true. Phase time HM > Phase reference value HS + Threshold HA (5-a) Phase time HM < Phase reference value HS - Threshold HA (5-b)

[0181] Furthermore, the case in which the liquid reservoir flag is set for the selected nozzle Nz is when equation (5) does not hold and equation (6) holds. And when equation (5) does not hold and equation (6) holds, it is when either equation (6-a) or (6-b) below holds. Phase reference value HS + threshold HB < Phase time HM ≤ Phase reference value HS + threshold HA (6-a) Phase reference value HS - Threshold value HA ≤ Phase time HM < Phase reference value HS - Threshold value HB (6-b)

[0182] The selected nozzle Nz is considered to be dispensing normally if equation (6) does not hold. And if equation (6) does not hold, then equation (6-c) below must hold. Phase reference value HS - Threshold HB ≤ Phase time HM ≤ Phase reference value HS + Threshold HB (6-c)

[0183] Since threshold HB is smaller than threshold HA, the phase reference value HS + threshold HA is longer than the phase reference value HS + threshold HB. Note that the phase reference value HS + threshold HA is an example of a "sixth threshold," and the phase reference value HS + threshold HB is an example of a "fifth threshold."

[0184] In the flowchart shown in Figure 17, the time at which the potential of the residual vibration reaches 180 degrees is the value representing the first time when the residual vibration reaches its amplitude center, but this is not the only option. For example, the phase of the residual vibration may be a value representing the second or subsequent times when the residual vibration reaches its amplitude center. Furthermore, the phase of the residual vibration does not have to be the time when the residual vibration reaches its amplitude center; for example, it may be the time when the phase reaches 90 degrees or 270 degrees, specifically the time when the residual vibration reaches its extremum. However, since the amplitude of the residual vibration is related to the extremum of the residual vibration from the first time onward, it is preferable not to use the extremum of the residual vibration for the phase of the residual vibration. This is because if any noise is affecting the extremum of the residual vibration, this noise will affect not only the amplitude of the residual vibration but also its phase.

[0185] Furthermore, in the flowchart shown in Figure 17, the determination unit 303 uses the amplitude and phase of the residual vibration to determine the nozzle Nz that may have reduced discharge characteristics due to liquid accumulation, but it is not limited to this. For example, the determination unit 303 may use the period and phase of the residual vibration to determine the nozzle Nz that may have reduced discharge characteristics due to liquid accumulation. Alternatively, the determination unit 303 may use the amplitude, period, and phase of the residual vibration to determine the nozzle Nz that may have reduced discharge characteristics due to liquid accumulation. Alternatively, the determination unit 303 may use one of the elements of the amplitude, period, and phase of the residual vibration to determine the nozzle Nz that may have reduced discharge characteristics due to liquid accumulation.

[0186] In addition, the first modified example is a form in which the phase of the residual vibration is used instead of the period of the residual vibration in the first embodiment, but in the second embodiment, a form in which the phase of the residual vibration is used instead of the period of the residual vibration is also possible. For example, in step SC18A, the determination unit 303 uses the selected individual residual vibration information NEI to determine whether the following equation (2B) holds true. Phase time HM - Phase reference value HS > Threshold HA' (2B)

[0187] The threshold HA' is a threshold used to determine whether or not a previously reported head anomaly has occurred. It is the threshold for the time when the phase becomes 180 degrees, or in other words, the threshold for the first time when the residual vibration is at the center of its amplitude. The threshold HA' is set in advance by the head manufacturer's experiments or experience. The head manufacturer stores the threshold HA' in the memory circuit 320.

[0188] Furthermore, in step SC22A, the determination unit 303 uses the selected individual residual vibration information NEI to determine whether the following equation (4B) holds true. Period TM - Period Reference Value TS > Threshold TB' (4B)

[0189] The threshold HB' is a threshold used to determine whether or not the discharge characteristics may be degraded due to liquid accumulation, and is the threshold value at the first time when the residual vibration is at the center of its amplitude. The threshold HB' is set in advance by the head maker's experiments or experience. The head maker stores the threshold HB' in the memory circuit 320. The threshold HB' is smaller than the threshold HA'. For example, the threshold HB' may be 1 / 10 or less of the threshold HA', or 1 / 100 or less of the threshold HA'.

[0190] 3-1-2. Summary of the first variation To facilitate understanding, an example of a "specific phase" is described as "180 degrees" below. Individual residual vibration information NEI relating to residual vibration in the pressure chamber CV communicating with the target nozzle Nz is described as "first individual information," and individual residual vibration information NEI relating to residual vibration in the pressure chamber CV communicating with at least one surrounding nozzle Nz located around the target nozzle Nz is described as "second individual information." Furthermore, a phase reference value HS + threshold HB, which is an example of a "fifth threshold" used to determine abnormal liquid pooling, is described as the "first upper limit phase threshold," and a phase reference value HS + threshold HA, which is an example of a "sixth threshold" used to determine previously mentioned head abnormalities, is described as the "second upper limit phase threshold." A summary of the first modified example is then provided.

[0191] In step SC4, the determination unit 303 determines that a liquid pooling abnormality has occurred if the time at which the residual vibration related to the first individual information reaches a specific phase is later than the first upper limit phase threshold, and the time at which the residual vibration related to the second individual information reaches 180 degrees is later than the first upper limit phase threshold. According to the first modified example, it is possible to accurately determine whether or not a liquid pooling abnormality has occurred using the phase of residual vibration and the first upper limit phase threshold.

[0192] Furthermore, in step SC4, the determination unit 303 determines that no liquid pooling abnormality or previously reported head abnormality has occurred if the time at which the residual vibration related to the first individual information or the second individual information becomes 180 degrees is earlier than the first upper limit phase threshold. According to the first modified example, even if the period of residual vibration of either the first individual information or the second individual information is affected by noise, it can be correctly determined that no liquid pooling abnormality or previously reported head abnormality has occurred.

[0193] Furthermore, in step SC4, the determination unit 303 determines that a previously reported head abnormality has occurred if the time at which the residual vibration related to the first individual information becomes 180 degrees is later than the second upper limit phase threshold, and the second upper limit phase threshold is later than the first upper limit phase threshold. According to the first modified example, if the period of residual vibration related to the first individual information becomes longer than the second upper period threshold, it can be determined that a previously described head abnormality has occurred.

[0194] 3-2. Second Variation If the inkjet printer 100 is temporarily unable to connect to the cloud server CS, it stores residual vibration information NI in the memory circuit 160 of the inkjet printer 100. The second modified example is described below.

[0195] 3-2-1. Operation of the second modified example Figure 18 is a flowchart showing the operation of the inkjet system 10 in the second modified example. The flowchart in Figure 18 differs from the flowchart in Figure 12 in that it performs the processes of step SJ12 and step SJ14 between the processes of step SJ2 and step SJ4, but otherwise it is the same. Below, only the differences from the flowchart in Figure 12 will be explained.

[0196] After the processing in step SJ2 is completed, in step SJ12, the control circuit 170 functions as the first transmission unit 173 to determine whether or not it is connected to the cloud server CS. If the result of the determination in step SJ12 is negative, the control circuit 170 stores the residual vibration information NI acquired in step SJ2 in the memory circuit 160 in step SJ14. The memory circuit 160 is an example of a "memory unit". After the processing in step SJ14 is completed, the control circuit 170 executes the processing in step SJ12 again. If the result of the determination in step SJ12 is positive, the control circuit 170 executes the processing in step SJ4. In the processing of step SJ4, if the processing in step SJ14 was executed, the control circuit 170 transmits the residual vibration information NI stored in the memory circuit 160 to the cloud server CS.

[0197] Although not shown in Figure 18, the process in step SJ14 only needs to be executed once. Also, if the result of the judgment in step SJ12 is negative multiple times, the control circuit 170 may terminate the series of processes shown in Figure 18. The control circuit 170 then sends information to the processing unit 200 indicating that it was not possible to send the residual vibration information NI to the cloud server CS. The processing unit 200 displays a dialog box on the display device 270 informing the user U that it was not possible to send the residual vibration information NI to the cloud server CS and asking whether or not to have the inkjet printer 100 perform the recording process of the image data Img. If the user U chooses to have the inkjet printer 100 perform the recording process, the inkjet printer 100 performs the recording process.

[0198] Furthermore, as shown in Figure 5, although the inkjet printer 100 has a memory circuit 160 in the printer body, the liquid ejection head HU may also have a memory circuit. Then, in step SJ14, the residual vibration information NI may be stored in the memory circuit of the liquid ejection head HU.

[0199] 3-2-2. Summary of the second variation In the second modified example described above, the inkjet printer 100 is provided with a memory circuit 160, and in step SJ14, if the inkjet printer 100 and the cloud server CS cannot be connected, the first transmission unit 173 stores the residual vibration information NI obtained by the processing in step SJ4 in the memory circuit 160. The inkjet printer 100 and the cloud server CS may be temporarily unable to connect due to reasons such as a temporary interruption of the cloud server CS service or congestion in communication between the inkjet printer 100 and the cloud server CS. According to the second modification, even if the inkjet printer 100 and the cloud server CS are unable to connect, the residual vibration information NI can be stored in the memory circuit 160, so that the residual vibration information NI can be sent to the cloud server CS when the inkjet printer 100 and the cloud server CS become connected.

[0200] 3-3. Third Variation In each of the embodiments described above, the cloud server CS functioned as the determination unit 303, but the control circuit 170 may also function as the determination unit 303.

[0201] Figure 19 shows the function of the inkjet printer 100C in the third modified example. The inkjet printer 100C differs from the inkjet printer 100 in that it has a control circuit 170C instead of the control circuit 170. The control circuit 170C differs from the control circuit 170 in that it functions as an acquisition unit 171, a determination unit 303, and a maintenance control unit 177. That is, the control circuit 170C functions as a determination unit 303 and performs the processing of step SC4. According to the third modification, the control circuit 170C performs the processing in step SC4, which improves the speed of obtaining the determination information JI compared to the inkjet system 10 in the first embodiment, because it does not need to transmit the residual vibration information NI and receive the determination information JI. For example, the third modification may be applied when a head manufacturer manufactures the printer body in addition to the liquid ejection head HU.

[0202] In the third modified example, the control circuit 170C performs the processing in step SC4, but the control circuit 170C may also transmit residual vibration information NI to the processing unit 200, and the control circuit 210 of the processing unit 200 may perform the processing in step SC4.

[0203] In the third modified example, after the control circuit 170C has performed the processing in step SC4, the control circuit 170C may transmit the judgment information JI to the cloud server CS. When the cloud server CS receives the judgment information JI, it stores the judgment information JI in the memory circuit 320. The control circuit 170C may also transmit the residual vibration information NI and the judgment information JI to the cloud server CS. When the cloud server CS receives the residual vibration information NI and the judgment information JI, it stores the residual vibration information NI and the judgment information JI in association with each other in the memory circuit 320. The control circuit 170C may also transmit the residual vibration information NI and the judgment information JI to the cloud server CS only if the judgment information JI contains one or more identifiers from the second identifier and the third identifier.

[0204] Furthermore, the inkjet printer 100C in the third modified example does not need to be connected to the cloud server CS. When a service support person from the head manufacturer visits the printer manufacturer or user U, the inkjet printer 100C or processing unit 200 copies the judgment information JI, etc., to a portable storage device brought by the service support person. The portable storage device is, for example, an SSD. SSD is an abbreviation for Solid State Drive. Then, when the service support person returns to the head manufacturer's office, a PC that can connect to the cloud server CS transmits the judgment information JI, etc., stored in the portable storage device to the cloud server CS.

[0205] 3-4. Fourth variation In each of the above embodiments, the cloud server CS determines, based on the residual vibration information NI, whether or not a liquid pooling abnormality has occurred, as well as whether or not a previously reported head abnormality has occurred, but is not limited to this. For example, the cloud server CS may determine only whether or not a liquid pooling abnormality has occurred based on the residual vibration information NI, and may not determine whether or not a previously reported head abnormality has occurred.

[0206] 3-5. Fifth variation In each of the above embodiments, the cloud server CS acquires residual vibration information NI having 2M individual residual vibration information NEIs, but is not limited to this. The cloud server CS may acquire residual vibration information NI having 2 or more individual residual vibration information NEIs, and determine whether or not a liquid pooling abnormality has occurred based on this residual vibration information NI.

[0207] 3-6. Sixth Variation In each of the embodiments described above, if the inkjet printer 100 is connectable to a network NW, the communication device 150 connects to the network NW, but is not limited to this. For example, if the liquid ejection head HU has a communication device, this communication device may communicate with the network NW.

[0208] 3-7. Seventh Variation In each of the above embodiments, the individual residual vibration information NEI is information that associates time information with potential values, but the individual residual vibration information NEI is not limited to information that associates time information with potential values. For example, the individual residual vibration information NEI may be one or more values ​​among a value indicating the amplitude of the residual vibration, a value indicating the period of the residual vibration, and a value indicating the time at which the residual vibration is in a specific phase. For example, the generation circuit 190 identifies the amplitude of the residual vibration from the residual vibration signal NES and outputs a value indicating the identified amplitude as the individual residual vibration information NEI to the control circuit 170.

[0209] 3-8. Variation 8 The liquid discharge head HU may be a circulating head having a so-called circulation channel. The eighth modified example will be explained below with reference to Figure 20.

[0210] Figure 20 is a schematic diagram illustrating an example of the configuration of the inkjet printer 100D in the eighth modified example. The inkjet printer 100D differs from the inkjet printer 100 in that it has a liquid ejection head HUD instead of a liquid ejection head HU, a control circuit 170D instead of a control circuit 170, and further includes a pump 121, a liquid reservoir 122, and a circulation mechanism 125. The liquid ejection head HUD has a circulation channel inside, although it is not shown in the figure. Also, as shown in Figure 20, the liquid ejection head HUD has one nozzle row La. Thus, this disclosure can also be applied to the inkjet printer 100 which has one nozzle row.

[0211] Pump 121 is provided between liquid container 120 and liquid storage unit 122. Liquid storage unit 93 stores ink to be supplied to liquid discharge head HUD. Circulation mechanism 125 is a mechanism that supplies ink to liquid discharge head HUD and recovers ink discharged from liquid discharge head HUD for resupply to liquid discharge head HUD. Circulation mechanism 125 includes a supply path 1251 for supplying ink from liquid storage unit 122 to liquid discharge head HU, a recovery path 1252 for recovering ink from liquid discharge head HU to liquid storage unit 122, and a flow mechanism 1253 for appropriately flowing the ink. Flow mechanism 1253 is provided between supply paths 1251. Under the control of control circuit 170D, flow mechanism 1253 causes the ink in supply paths 1251 to flow. Flow mechanism 1253 is, for example, a pump and / or a compressor.

[0212] When the control circuit 170D receives judgment information JI from the cloud server CS, it functions as the maintenance control unit 177 in the eighth modified example. If the judgment information JI includes a third identifier indicating that an abnormal liquid pooling has occurred, the maintenance control unit 177 in the eighth modified example controls the fluid mechanism 1253 to increase or decrease the ink pressure in the circulating channel within the liquid discharge head HUD, either instead of or in addition to the wiping process.

[0213] 3-9. Variation 9 In the embodiments described above, a serial-type inkjet printer 100 is exemplified in which the liquid ejection head HU is reciprocated in a direction along the X axis, but the present disclosure is not limited to such embodiments. The inkjet printer 100 may also be a line-type liquid ejection device in which a plurality of nozzles Nz are distributed over the entire width of the medium PP.

[0214] 3-10. Other variations The inkjet printer 100 described above can be used in various devices such as facsimile machines and photocopiers, in addition to devices dedicated to printing. However, the use of the recording device of the present invention is not limited to printing. For example, a recording device that ejects a colorant solution can be used as a manufacturing device for forming color filters for liquid crystal display devices. Also, a recording device that ejects a conductive material solution can be used as a manufacturing device for forming wiring and electrodes for wiring boards. [Explanation of Symbols]

[0215] 10...Inkjet system, 20...Recording system, 100, 100C, 100D...Inkjet printer, 111...Head chip, 111a...Flow channel substrate, 111b...Pressure chamber substrate, 111c...Nozzle plate, 111d...Vibration absorber, 111e...Diaphragm, 111f...Piezoelectric element, 111g...Protective plate, 111h...Case, 111i...Wiring board, 112...Drive circuit, 113...Power supply circuit, 114...Drive signal generation circuit, 115...Switching circuit, 116...Connection status specification circuit, 117...Detection circuit, 120...Liquid container, 121...Pump, 122...Liquid storage section, 125...Circulation mechanism, 1 30...Moving mechanism, 131...Carriage, 132...Endless belt, 140...Conveying mechanism, 145...Maintenance mechanism, 146...Cap, 147...Wiper, 150...Communication device, 160...Memory circuit, 170,170C,170D...Control circuit, 171...Acquisition unit, 173...First transmission unit, 175...First reception unit, 177...Maintenance control unit, 190...Generation circuit, 200...Processing device, 210...Control circuit, 220...Memory circuit, 230,240...Communication device, 260...Input device, 270...Display device, 290...Bus, 300...Server, 301...Second reception unit, 303...Determination unit, 30 5…Second transmitter, 310…Control circuit, 320…Memory circuit, 380…Communication device, 390…Bus, 1251…Supply path, 1252…Recovery path, 1253…Flow mechanism, AM, AM1…Amplitude, AS…Amplitude reference value, AS1…Amplitude, Ac…Potential, CL…Clock signal, CM…Control module, CS…Cloud server, CV…Pressure chamber, Com, Com-A, Com-B…Drive signal, FN…Nozzle surface, HA, HA', HB, HB'…Threshold, HM…Phase time, HS…Phase reference value, HU…Liquid discharge head, IH…Inlet, Img…Image data, JI…Decision information, LAT…Latch signal No., LHa, LHb, LHd, LHs…Internal wiring, La, Lb…Nozzle row, NCM, NCS…Residual vibration characteristics, NEI…Individual residual vibration information, NES…Residual vibration signal, NI…Residual vibration information, NW…Network, Na…Communication channel, Nz…Nozzle, PM1…Control program, PM2…Inkjet program, PM3…Control program, PP…Media, PS…Inspection waveform, PX…Ejection waveform, PlsL, PlsT1, PlsT2…Pulse, R…Reservoir, R1, R2…Space, Ra…Supply channel, SI…Printing signal, SLa, SLb, SLs…Connection status specification signal, SWa,SWb, SWs…Switch, Sd…Individual designation signal, Sk1, Sk2, Sk3…Control signal, TM, TM1…Period, TS…Period reference value, TS1…Period, TSS1, TSS2, TSS3…Control period, Tsig…Period designation signal, Tu…Recording period, U…User, V0…Reference potential, VBS…Offset potential, VHS…Maximum potential, VHV…Power supply potential, VHX…Maximum potential, VLS, VLX…Minimum potential, VM…Virtualization program, Vin…Supply drive signal, Vout…Detection signal, Zd…Lower electrode, Zm…Piezoelectric material, Zu…Upper electrode, dCom…Waveform designation signal, g1, g2…Graph.

Claims

1. A control method for a liquid dispensing device that dispenses liquid onto a medium, comprising a liquid dispensing head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is discharged, An acquisition step to acquire residual vibration information relating to residual vibration in a pressure chamber after applying a voltage to one or more piezoelectric elements among the plurality of piezoelectric elements, A control method characterized by performing a determination step of determining whether or not a first abnormality has occurred, which is an abnormality in which liquid accumulation is formed on the nozzle surface provided with the plurality of nozzles, based on the residual vibration information.

2. The residual vibration information includes first individual information relating to residual vibration in a pressure chamber communicating with a target nozzle among the plurality of nozzles, and second individual information relating to residual vibration in a pressure chamber communicating with at least one surrounding nozzle located around the target nozzle. The control method according to claim 1, characterized in that the determination step determines whether or not the first abnormality has occurred based on the first individual information and the second individual information.

3. The control method according to claim 2, characterized in that the surrounding nozzles include adjacent nozzles adjacent to the target nozzle.

4. The control method according to claim 2, characterized in that the determination step further determines, based on the first individual information, whether a second abnormality has occurred, which is an abnormality different from the first abnormality and is an abnormality of the liquid discharge head caused by the liquid discharge head.

5. The control method according to claim 4, characterized in that the determination step determines that the first abnormality has occurred when the amplitude of the residual vibration relating to the first individual information is smaller than the first threshold and the amplitude of the residual vibration relating to the second individual information is smaller than the first threshold.

6. The control method according to claim 5, characterized in that the determination step determines that the first abnormality and the second abnormality have not occurred if the amplitude of the residual vibration relating to the first individual information or the second individual information is greater than the first threshold.

7. The determination step determines that the second abnormality has occurred if the amplitude of the residual vibration related to the first individual information is smaller than the second threshold. The control method according to claim 6, characterized in that the second threshold is smaller than the first threshold.

8. The control method according to claim 4, characterized in that the determination step determines that the first abnormality has occurred if the period of residual vibration relating to the first individual information is longer than the third threshold and the amplitude of residual vibration relating to the second individual information is longer than the third threshold.

9. The control method according to claim 8, characterized in that the determination step determines that the first abnormality and the second abnormality have not occurred if the period of residual vibration relating to the first individual information or the second individual information is shorter than the third threshold.

10. The determination step determines that the second abnormality has occurred if the period of the residual vibration related to the first individual information is longer than the fourth threshold. The control method according to claim 9, characterized in that the fourth threshold is longer than the third threshold.

11. The control method according to claim 4, characterized in that the determination step determines that the first abnormality has occurred if the time at which the residual vibration relating to the first individual information reaches a specific phase is later than the fifth threshold, and the time at which the residual vibration relating to the second individual information reaches the specific phase is later than the fifth threshold.

12. The control method according to claim 11, characterized in that the determination step determines that the first abnormality and the second abnormality have not occurred if the time at which the residual vibration relating to the first individual information or the second individual information reaches the specific phase is earlier than the fifth threshold.

13. The determination step determines that the second abnormality has occurred if the time at which the residual vibration relating to the first individual information reaches the specific phase is later than the sixth threshold. The control method according to claim 12, characterized in that the sixth threshold is slower than the fifth threshold.

14. Using a server located outside the aforementioned liquid dispensing device, A transmission step involves transmitting the residual vibration information acquired in the acquisition step from the liquid dispensing device to the server. The process further includes a receiving step of receiving determination information from the server that indicates the determination result obtained in the aforementioned determination step, The control method according to claim 1, characterized in that the server performs the determination step.

15. The liquid dispensing device is provided with a storage unit, The control method according to claim 14, characterized in that, when the liquid dispensing device and the server cannot be connected, the transmission step stores the residual vibration information acquired by the acquisition step in the storage unit.

16. The control method according to claim 1, characterized in that the liquid dispensing device performs the determination step.

17. A liquid dispensing device for dispensing liquid onto a medium, comprising: a plurality of piezoelectric elements; a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements; and a liquid dispensing head having a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is discharged, An acquisition unit that acquires residual vibration information relating to residual vibration in a pressure chamber after applying a voltage to one or more piezoelectric elements among the plurality of piezoelectric elements, A determination unit that determines whether or not a first abnormality has occurred, which is an abnormality in which liquid accumulation is formed on the nozzle surface provided with the plurality of nozzles, based on the residual vibration information, A liquid dispensing device characterized by having the following features.

18. An inkjet system comprising: a liquid ejection device that ejects liquid onto a medium, having a liquid ejection head having a plurality of piezoelectric elements, a plurality of pressure chambers that apply pressure to the liquid inside by driving each of the plurality of piezoelectric elements, and a plurality of nozzles that communicate with each of the plurality of pressure chambers and from which the liquid is ejected; and a server provided outside the liquid ejection device, The aforementioned liquid discharge device is Residual vibration information regarding residual vibration in the pressure chamber after applying a voltage to one or more of the plurality of piezoelectric elements is acquired. The residual vibration information is transmitted from the liquid dispensing device to the server. The aforementioned server, Based on the residual vibration information, it is determined whether or not a first abnormality has occurred, which is an abnormality in which liquid accumulation is formed on the nozzle surface provided with the plurality of nozzles. The liquid dispensing device is sent judgment information indicating whether or not the first abnormality has occurred. An inkjet system characterized by the following features.

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