JP2010058406A - Ejection inspecting method and liquid ejecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejecting apparatus such as an inkjet printer which can carry out proper inspection of ejection. <P>SOLUTION: (1) The inspection of ejection is repeated up to a predetermined number of times until the ejection of the liquid ejecting apparatus which ejects the liquid from nozzles is normally inspected. When the ejection is inspected normally, the liquid ejecting apparatus carries out the next predetermined action. If the ejection cannot be normally inspected even after the inspection is repeated to the predetermined number of times, the liquid ejecting apparatus carries out the next predetermined action storing abnormality information of the ejection inspection in a memory. (2) After the next predetermined action is carried out, the inspection is repeated up to the predetermined number of times until the ejection is inspected normally. If the ejection cannot be normally inspected even after the inspection is repeated to the predetermined number of times, the liquid ejecting apparatus checks the memory and decides it as an abnormality of the apparatus if the abnormality information is stored in the memory. The ejection inspecting method includes the (1) and (2). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a discharge inspection method and a liquid discharge apparatus.

As a liquid ejection apparatus such as an ink jet printer, there has been proposed an apparatus in which charged ink is ejected toward a detection electrode and a liquid ejection inspection is performed based on an electrical change generated in the electrode. (See Patent Document 1)
JP 2007-152888 A

  As described above, in a printer that performs an ejection inspection based on an electrical change, if noise occurs, the inspection cannot be performed accurately. However, noise includes noise that occurs in the short term and noise that occurs in the long term. If the noise is generated in the short term, if the inspection is performed again after a predetermined time, the inspection can be performed accurately. Discharge inspection cannot be performed. On the other hand, even though the discharge inspection cannot be performed due to long-term noise, if the inspection is repeatedly performed until the discharge inspection is normally performed, the discharge inspection is wasted.

  Accordingly, an object of the present invention is to perform an appropriate ejection inspection.

  The main inventions for solving the problems are as follows: (1) The discharge inspection was repeated a predetermined number of times until the discharge inspection of the liquid discharge device that discharges liquid from the nozzles was normally performed, and the discharge inspection was normally performed. In this case, the liquid ejecting apparatus performs the next predetermined operation, and when the ejection inspection is not performed normally even after the ejection inspection is repeated up to the predetermined number of times, the liquid ejecting apparatus stores the liquid ejecting apparatus in the memory. Storing the abnormal information of the discharge inspection and performing the next predetermined operation; and (2) performing the discharge inspection up to the predetermined number of times until the discharge inspection is normally performed after the next predetermined operation is performed. If the discharge inspection is not performed normally even after repeating the discharge inspection up to the predetermined number of times, the liquid discharge apparatus checks the memory and stores the abnormal information in the memory. There possible to determine an abnormality of the liquid ejection device if it is stored, a discharge inspection method having.

  Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following will become apparent from the description of the present specification and the accompanying drawings.

That is, (1) The discharge inspection is repeatedly performed a predetermined number of times until the discharge inspection of the liquid discharge device that discharges the liquid from the nozzle is normally performed, and when the discharge inspection is performed normally, the liquid discharge device Performs the following predetermined operation, and if the discharge inspection is not performed normally even after repeating the discharge inspection up to the predetermined number of times, the liquid discharge apparatus stores the abnormality information of the discharge inspection in a memory. (2) after the next predetermined operation is performed, the discharge inspection is repeatedly performed up to the predetermined number of times until the discharge inspection is normally performed, and the discharge inspection is performed. If the ejection test is not performed normally even after repeated up to a predetermined number of times, the liquid ejection device checks the memory, and if the abnormality information is stored in the memory, the liquid Determining abnormality of the detection device and a discharge inspection method having.
According to such a discharge inspection method, the timing of performing the discharge inspection is shifted. Therefore, if the noise is short, the inspection can be normally performed while repeating the discharge inspection up to a predetermined number of times. The inspection can be normally performed when performing the discharge inspection after performing the predetermined operation. By doing so, it is possible to prevent the discharge inspection time from being unnecessarily prolonged, and the discharge inspection can be properly terminated. Further, if the inspection cannot be performed normally after the next predetermined operation, it can be determined that the liquid ejection device is in an abnormal state. In addition, by performing a predetermined operation between ejection inspections, the state of the liquid ejection apparatus changes and the probability that the ejection inspection can be performed normally increases.

In this discharge inspection method, when the abnormality information is stored in the memory, the discharge inspection in the operation of (1) is compared with the case where the abnormality information is not stored in the memory. Shortening the time until the ejection inspection performed after the next predetermined operation is performed.
According to such a discharge inspection method, the fact that abnormality information is stored in the memory means that the discharge inspection for all nozzles has not been completed, and if there is a nozzle that generates a discharge failure, a printed image Therefore, it is possible to suppress the deterioration of the printed image by performing the next ejection inspection as soon as possible.

In this discharge inspection method, in the discharge inspection, the liquid discharged from the nozzle by the first electrode is set to a first potential, and the liquid at the first potential is set to a second potential different from the first potential. Inspecting the presence or absence of liquid ejection from the nozzle based on a potential change generated in at least one of the first electrode and the second electrode due to liquid ejection from the nozzle and liquid ejection from the nozzle. .
According to such a discharge inspection method, when a discharge inspection is performed based on a potential change, the discharge inspection may not be performed normally due to noise, but by varying the discharge inspection timing, noise of different lengths may be generated. By avoiding this, the discharge inspection can be performed normally.

In such a discharge inspection method, a non-discharge period in which liquid is not discharged from all nozzles is provided between the discharge inspection for one nozzle and the discharge inspection for another nozzle, and the potential change in the non-discharge period is provided. Based on this, it is determined whether or not the discharge inspection for the certain nozzle has been performed normally.
According to such a discharge inspection method, it is possible to determine whether noise has occurred during the discharge inspection period, and it is possible to determine whether the discharge inspection has been performed normally.

In this discharge inspection method, the nozzle and the second electrode are not opposed to each other in the next predetermined operation.
According to such a discharge inspection method, for example, it is possible to remove noise generated when a foreign substance adheres between the nozzle and the second electrode and current leaks, and the probability that a discharge inspection can be performed normally is increased. .

In this discharge inspection method, the next predetermined operation is a printing operation.
According to such a discharge inspection method, the state of the liquid discharge apparatus changes, and the probability that a discharge inspection can be performed normally increases.

In such a discharge inspection method, the next predetermined operation is a recovery operation in which liquid is normally discharged from a nozzle that generates a discharge failure.
According to such a discharge inspection method, the state of the liquid discharge apparatus changes, and the probability that a discharge inspection can be performed normally increases. In addition, deterioration of the printed image can be suppressed.

And (1) a nozzle that discharges liquid, (2) a memory, and (3) a control unit that performs a discharge inspection of the nozzle, wherein the discharge inspection is performed a predetermined number of times until the discharge inspection is normally performed. Repeatedly, if the ejection inspection is normally performed, the next predetermined operation is performed. If the ejection inspection is not performed normally even if the ejection inspection is repeated up to the predetermined number of times, the memory is performed. Storing the abnormal information of the discharge inspection to the next predetermined operation, after performing the next predetermined operation, the discharge inspection is repeatedly performed up to the predetermined number of times until the discharge inspection is normally performed, If the discharge inspection is not performed normally even after repeating the discharge inspection up to the predetermined number of times, the memory is checked, and if the abnormality information is stored in the memory, the control for determining the abnormal state When a liquid discharge apparatus having a.
According to such a liquid ejecting apparatus, since the timing of performing the ejection inspection is shifted, it is possible to normally perform the ejection inspection while avoiding noise having different lengths. By doing so, it is possible to prevent the discharge inspection time from being unnecessarily prolonged, and the discharge inspection can be properly terminated. Further, if the inspection cannot be performed normally after the next predetermined operation, it can be determined that the liquid ejection device is in an abnormal state. In addition, by performing a predetermined operation between ejection inspections, the state of the liquid ejection apparatus changes and the probability that the ejection inspection can be performed normally increases.

=== About Inkjet Printers ===
In the embodiments described below, an ink jet printer (hereinafter also referred to as a printer 1) will be described as an example of the liquid ejection device.

  FIG. 1A is a block diagram illustrating a printing system having a printer 1 and a computer CP, and FIG. 1B is a perspective view of the printer 1. The printer 1 ejects ink, which is a kind of liquid, toward a medium such as paper, cloth, or film. The medium is an object to which liquid is ejected. The computer CP is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer CP transmits print data corresponding to the image to the printer 1. The printer 1 includes a paper transport mechanism 10, a carriage moving mechanism 20, a head unit 30, a drive signal generation circuit 40, a dot dropout detection unit 50, a cap mechanism 60, a detector group 70, and a printer-side controller 80.

  The paper transport mechanism 10 transports the paper in the transport direction. The carriage moving mechanism 20 moves the carriage 21 to which the head unit 30 is attached in a predetermined movement direction (a direction intersecting the transport direction).

  The head unit 30 includes a head 31 and a head controller HC. The head 31 ejects ink toward the paper. The head controller HC controls the head 31 based on a head control signal from the controller 80 of the printer 1.

  FIG. 2A is a cross-sectional view of the head 31. The head 31 includes a case 32, a flow path unit 33, and a piezo element unit 34. The case 32 is a member for housing and fixing the piezo element unit 34 and is made of, for example, a non-conductive resin material such as an epoxy resin.

  The flow path unit 33 includes a flow path forming substrate 33a, a nozzle plate 33b, and a vibration plate 33c. The nozzle plate 33b is bonded to one surface of the flow path forming substrate 33a, and the vibration plate 33c is bonded to the other surface. The flow path forming substrate 33 a is formed with a pressure chamber 331, an ink supply path 332, and voids and grooves that become the common ink chamber 333. The flow path forming substrate 33a is made of, for example, a silicon substrate. The nozzle plate 33b is provided with a nozzle group including a plurality of nozzles Nz. The nozzle plate 33b is made of a conductive plate-like member, for example, a thin metal plate. The nozzle plate 33b is connected to a ground line and has a ground potential. A diaphragm portion 334 is provided in a portion corresponding to each pressure chamber 331 in the diaphragm 33c. The diaphragm portion 334 is deformed by the piezo element PZT and changes the volume of the pressure chamber 331. In addition, the piezoelectric element PZT and the nozzle plate 33b are electrically insulated by interposing the vibration plate 33c, the adhesive layer, and the like.

  The piezo element unit 34 includes a piezo element group 341 and a fixed plate 342. The piezo element group 341 has a comb shape. Each of the comb teeth is a piezo element PZT. The front end surface of each piezo element PZT is bonded to an island portion 335 included in the corresponding diaphragm portion 334. The fixing plate 342 supports the piezo element group 341 and serves as a mounting portion for the case 32. The piezo element PZT is a kind of electromechanical conversion element. When a drive signal COM is applied, the piezo element PZT expands and contracts in the longitudinal direction and gives a pressure change to the liquid in the pressure chamber 331. The ink in the pressure chamber 331 undergoes a pressure change due to a change in the volume of the pressure chamber 331. By utilizing this pressure change, ink droplets can be ejected from the nozzle Nz.

  FIG. 2B is a diagram illustrating an arrangement of nozzles Nz provided on the nozzle plate 33b. The nozzle plate is provided with a plurality of nozzle rows in which 180 nozzles are arranged at intervals of 180 dpi along the paper conveyance direction. Each nozzle row ejects ink of a different color, and this nozzle plate 33b is provided with six nozzle rows. Specifically, the black ink nozzle row Nk, the yellow ink nozzle row Ny, the cyan ink nozzle row Nc, the magenta ink nozzle row Nm, the light cyan ink nozzle row Nlc, and the light magenta ink nozzle row Nlm. For the sake of explanation, young numbers are assigned in order from the nozzle Nz on the upstream side in the paper transport direction (# 1 to # 180).

  The drive signal generation circuit 40 generates a drive signal COM. When the drive signal COM is applied to the piezo element PZT, the piezo element expands and contracts, and the volume of the pressure chamber 331 corresponding to each nozzle Nz changes. Therefore, the drive signal COM is applied to the head 31 at the time of printing, at the time of dot missing inspection (described later), at the time of flushing that is the recovery operation of the nozzle Nz that is missing dots. The waveform of the drive signal COM is appropriately determined at each time of printing, dot missing inspection, and flushing.

  The missing dot detection unit 50 detects whether ink is ejected from each nozzle Nz. The cap mechanism 60 performs a suction operation for sucking ink from each nozzle Nz in order to suppress the evaporation of the ink solvent from the nozzle Nz or to restore the discharge capability of the nozzle Nz. The detector group 70 includes a plurality of detectors that monitor the status of the printer 1. Detection results by these detectors are output to the printer-side controller 80.

  The printer-side controller 80 performs overall control in the printer 1, and includes an interface unit 80a, a CPU 80b, and a memory 80c. The interface unit 80a exchanges data with the computer CP. The memory 80c secures an area for storing a computer program, a work area, and the like. The CPU 80b, according to the computer program stored in the memory 80c, controls each control target unit (the paper transport mechanism 10, the carriage movement mechanism 20, the head unit 30, the drive signal generation circuit 40, the missing dot detection unit, the cap mechanism 60, the detector. Group 70) is controlled.

  In such a printer 1, the ink is intermittently ejected from the head 31 moving along the carriage movement direction to form dots on the sheet, and the conveyance process for conveying the sheet in the conveyance direction. By repeating alternately, dots are formed at positions different from the positions of the dots formed by the previous dot formation process, and the image is completed.

=== About missing dots and recovery operation ===
If ink (liquid) is not ejected from the nozzle Nz for a long time or if foreign matter such as paper dust adheres to the nozzle Nz, the nozzle Nz may be clogged. When the nozzle Nz is clogged in this way, ink is not ejected when ink should be ejected from the nozzle Nz, and dot missing occurs. The missing dot means a phenomenon in which dots are not formed where ink is originally ejected from the nozzles Nz and dots are to be formed. If dot omission occurs, it causes image quality degradation. Therefore, in this embodiment, when a dot missing nozzle Nz (hereinafter also referred to as a dot missing nozzle) is detected by the dot missing detector 50 (described later), the recovery operation is performed, so that the ink is normally discharged from the dot missing nozzle. To be discharged.

  3A to 3C are views showing the positional relationship between the head 31 and the cap mechanism 60 during the recovery operation. First, the cap mechanism 60 will be described. The cap mechanism 60 includes a cap 61 and a slider member 62 that supports the cap 61 and is movable in a slanting vertical direction. The cap 61 has a rectangular bottom portion (not shown) and a side wall portion 611 that stands up from the periphery of the bottom portion, and has a thin box shape with an open upper surface facing the nozzle plate 33b. In a space surrounded by the bottom portion and the side wall portion 611, a sheet-like moisture retaining member made of a porous member such as felt or sponge is disposed.

  As shown in FIG. 3A, in a state where the carriage 21 is out of the home position (where the carriage 21 is located on the rightmost side in the movement direction), the cap 61 is more than the surface of the nozzle plate 33b (hereinafter also referred to as the nozzle surface). Positioned sufficiently low. 3B, when the carriage 21 moves to the home position side, the carriage 21 contacts the contact portion 63 provided on the slider member 62, and the contact portion 63 moves together with the carriage 21 to the home position side. To do. When the contact portion 63 moves to the home position side, the slider member 62 rises along the guide slot 64, and the cap 61 also rises accordingly. Finally, as shown in FIG. 3C, when the carriage 21 is positioned at the home position, the side wall 611 (porous member) of the cap 61 and the nozzle plate 33b are brought into close contact with each other. Therefore, the evaporation of the ink solvent from the nozzles Nz can be suppressed by positioning the carriage 21 at the home position when the power is turned off or during a long pause.

  Next, the recovery operation will be described. One of the recovery operations for the missing dot nozzle is a “flushing operation”. As shown in FIG. 3B, the flushing operation forcibly and continuously ejects ink droplets from each nozzle Nz with a slight gap between the nozzle surface and the opening edge of the cap 61 (the upper end of the side wall portion 611). It is an operation to make.

  A waste liquid tube 65 is connected to the space between the bottom surface of the cap 61 and the side wall portion 611, and a suction pump (not shown) is connected to the middle of the waste liquid tube 65. As another recovery operation, “pump suction” is performed with the opening edge of the cap 61 in contact with the nozzle surface as shown in FIG. 3C. When the suction pump is operated in a state where the side wall portion 611 of the cap 61 and the nozzle surface are in close contact, the space of the cap 61 can be negatively pressured. Thereby, the ink in the head 31 can be sucked together with the thickened ink and paper dust, and the dot missing nozzle can be recovered.

  Another recovery operation is a “fine vibration operation”. The micro-vibration operation moves the meniscus (the free surface of the ink exposed by the nozzle Nz) to the ejection side and the drawing side by applying a pressure change that does not eject ink droplets to the ink in the pressure chamber 331. The thickened ink in the vicinity of the nozzle is dispersed by stirring. In addition, by maintaining the cap mechanism 60 at the position shown in FIG. 3B and moving the carriage 21 in the moving direction, the ink droplets adhered to the nozzle surface by the wiper 66 protruding above the side wall portion 611 of the cap 61. And foreign matter can be removed.

  That is, in the printer 1 of the present embodiment, the ink is normally ejected from the nozzles where dots are missing by the recovery operation such as the flushing operation, the pump suction, the fine vibration operation, and the nozzle surface cleaning operation by the wiper 66. Can do.

=== Discharge inspection ===
<About the missing dot detection unit 50>
4 is a diagram of the cap 61 as viewed from above, FIG. 5A is a diagram illustrating the dot dropout detection unit 50, and FIG. 5B is a block diagram illustrating the detection control unit 57. The missing dot detection unit 50 actually ejects ink from each nozzle, and detects a missing nozzle depending on whether the ink has been ejected normally. First, the configuration of the missing dot detection unit 50 will be described. As shown in FIG. 5A, the missing dot detection unit 50 includes a high voltage power supply unit 51, a first limiting resistor 52, a second limiting resistor 53, a detection capacitor 54, an amplifier 55, a smoothing capacitor 56, and a detection control unit 57. Have.

  When detecting missing dots, the nozzle surface and the cap 61 face each other as shown in FIGS. 3B and 5A. In the space surrounded by the side wall 611 of the cap 61, as shown in FIG. 4, a moisturizing member 612 and a wire-like detection electrode 613 are arranged. The detection electrode 613 has a high potential of about 600 V to 1 kV during the dot missing detection operation. The detection electrode 613 illustrated in FIG. 4 includes a frame portion provided in a double rectangular shape, a diagonal line portion that connects the diagonal portions of the frame portion, and a cross portion that connects the midpoints on each side of the frame portion. Have. With this structure, it is uniformly charged over a wide range. In addition, when the ink solvent of the present embodiment is a liquid having conductivity (for example, water) and the detection electrode 613 is set to a high potential while the moisturizing member 612 is wet, the surface of the moisturizing member 612 also has the same potential. Also in this respect, the area where ink is ejected from the nozzle is uniformly charged over a wide range.

  The high-voltage power supply unit 51 is a type of power supply that makes the detection electrode 613 in the cap 61 have a predetermined potential. The high-voltage power supply unit 51 of this embodiment is configured by a DC power supply of about 600 V to 1 kV, and the operation is controlled by a control signal from the detection control unit 57.

  The first limiting resistor 52 and the second limiting resistor 53 are disposed between the output terminal of the high-voltage power supply unit 51 and the detection electrode 613, and limit the current flowing between the high-voltage power supply unit 51 and the detection electrode 613. . In the present embodiment, the first limiting resistor 52 and the second limiting resistor 53 have the same resistance value (for example, 1.6 MΩ), and the first limiting resistor 52 and the second limiting resistor 53 are connected in series. As shown in the figure, one end of the first limiting resistor 52 is connected to the output terminal of the high voltage power supply unit 51, the other end is connected to one end of the second limiting resistor 53, and the other end of the second limiting resistor 53 is connected to the detection electrode. Connect to 613.

  The detection capacitor 54 is an element for extracting a potential change component of the detection electrode 613, and one conductor is connected to the detection electrode 613 and the other conductor is connected to the amplifier 55. By interposing the detection capacitor 54, the bias component (DC component) of the detection electrode 613 can be removed, and the signal can be easily handled. In this embodiment, the detection capacitor 54 has a capacity of 4700 pF.

  The amplifier 55 amplifies and outputs a signal (potential change) appearing at the other end of the detection capacitor 54. The amplifier 55 of this embodiment is configured with a gain of 4000 times. As a result, the potential change component can be acquired as a voltage signal having a change width of about 2 to 3V. The set of the detection capacitor 54 and the amplifier 55 corresponds to a kind of detection unit, and detects a potential change of the detection electrode 613 caused by ejection of an ink droplet.

  The smoothing capacitor 56 suppresses a rapid change in potential. The smoothing capacitor 56 of this embodiment has one end connected to a signal line connecting the first limiting resistor 52 and the second limiting resistor 53, and the other end connected to the ground. And the capacity | capacitance is 0.1 micro F.

  The detection control unit 57 is a part that controls the missing dot detection unit 50. As shown in FIG. 5B, the detection control unit 57 includes a register group 57a, an AD conversion unit 57b, a voltage comparison unit 57c, and a control signal output unit 57d. The register group 57a includes a plurality of registers. Each register stores a determination result for each nozzle Nz, a voltage threshold for determination, and the like. The AD converter 57b converts the amplified voltage signal (analog value) output from the amplifier 55 into a digital value. The voltage comparison unit 57c compares the magnitude of the amplitude value based on the amplified voltage signal with a voltage threshold value. The control signal output unit 57d outputs a control signal for controlling the operation of the high voltage power supply unit 51.

<Outline of discharge inspection>
Next, an outline of the ejection inspection performed by the dot missing detection unit 50 will be described. As described above, in this printer 1, the nozzle plate 33 b (corresponding to the first electrode) is connected to the ground so as to have the ground potential (corresponding to the first potential), and the detection electrode 613 (second electrode) disposed on the cap 61. (Corresponding to the electrode) is set to a high potential (corresponding to the second potential) of about 600 V to 1 kV. The ink droplet ejected from the nozzle Nz becomes the ground potential by the nozzle plate having the ground potential. The nozzle plate 33b and the detection electrode 613 are arranged with a predetermined interval d (see FIG. 5A), and ink droplets are ejected from the detection target nozzle Nz. The detection control unit 57 acquires an electrical change (periodic change in potential) caused on the detection electrode 613 side due to ejection of the ink droplets via the detection capacitor 54 and the amplifier 55. The detection control unit 57 determines whether ink droplets are normally ejected from the detection target nozzle Nz based on the acquired electrical change.

  Although the principle of detection has not been clarified accurately, it is considered that these members can behave like a capacitor by arranging the nozzle plate 33b and the detection electrode 613 at a predetermined interval d. . As shown in FIG. 5A, by contacting the nozzle plate 33b connected to the ground, the ink extending in a columnar shape from the nozzle Nz also becomes the ground potential. The presence of such ink is considered to change the capacitance of the capacitor. In other words, the ground potential ink and the detection electrode 613 constitute a capacitor, and the capacitance changes as the ink is ejected (elongation of the columnar ink). In this case, as the capacitance decreases, the amount of charge that can be stored between the nozzle plate 33b and the detection electrode 613 decreases. For this reason, surplus charges move from the detection electrode 613 to the high-voltage power supply unit 51 side through the limiting resistors 52 and 53. That is, a current flows toward the high voltage power supply unit 51. Further, when the capacitance increases or the decreased capacitance returns, the charge moves from the high-voltage power supply unit 51 to the detection electrode 613 through the limiting resistors 52 and 53. That is, a current flows toward the detection electrode 613. When such a current (also referred to as a discharge inspection current If for convenience) flows, the potential of the detection electrode 613 changes. The change in the potential of the detection electrode 613 also appears as a change in the potential of the other conductor (the conductor on the amplifier 55 side) in the detection capacitor 54. Therefore, it is possible to determine whether or not an ink droplet has been ejected by monitoring the potential change of the other conductor.

  FIG. 6A is a diagram illustrating an example of the drive signal COM used during the ejection inspection, and FIG. 6B illustrates the voltage signal SG output from the amplifier 55 when ink is ejected from the nozzle Nz with the drive signal COM of FIG. 6A. It is a figure explaining. The drive signal COM has a plurality of ejection pulses PS (20 to 30 in a 50 kHz period) for ejecting ink from the nozzles Nz in the first half period TA of the repetition period T, and a constant potential at an intermediate potential in the second half period TB. Is preserved. The drive signal generation circuit 40 repeatedly generates the drive signal COM every repetition period T. This repetition period T corresponds to the time required for inspection of one nozzle Nz (for example, 1 kHz).

  When such a drive signal COM is applied to the piezo element PZT, ink droplets are continuously ejected from the nozzle Nz corresponding to the piezo element PZT 20 to 30 times at a cycle of 50 kHz. As a result, the potential of the detection electrode 613 changes, and the amplifier 55 outputs the potential change to the detection control unit 57 as the voltage signal SG shown in FIG. 6B. The detection control unit 57 calculates the maximum amplitude Vmax (difference between the highest voltage VH and the lowest voltage VL) from the voltage signal SG during the inspection period of the nozzle Nz to be inspected, and compares the maximum amplitude Vmax with a predetermined threshold value TH. As shown in FIG. 6B, when ink is ejected from the detection target nozzle Nz, the maximum amplitude Vmax becomes larger than the threshold value TH. On the other hand, if ink is not ejected from the inspection target nozzle Nz due to clogging or the like, the potential of the detection electrode 613 does not change, and the maximum amplitude Vmax of the voltage signal SG is also equal to or less than the threshold value TH.

  In summary, in the present embodiment, the presence or absence of a dot missing nozzle is determined based on whether or not an ink droplet is actually ejected from the nozzle Nz to be inspected. For this purpose, an inspection drive signal COM (FIG. 6A) is applied to the piezo element PZT corresponding to the nozzle Nz to be inspected. Further, by keeping the nozzle plate 33b at the ground potential and providing the high potential detection electrode 613 in the cap 61, it is known from the change in the potential of the detection electrode 613 that an ink droplet has been ejected from the nozzle Nz. be able to. Specifically, the detection control unit 57 compares the maximum amplitude Vmax of the voltage signal SG (FIG. 6B) based on the potential change of the detection electrode 613 with a predetermined threshold value, and thereby the ink from the nozzle Nz to be inspected. It is determined whether or not a droplet has been ejected.

=== About the non-ejection dummy period ===
FIG. 7A is a diagram illustrating a voltage signal SG when the inspection is normally performed without generating noise during the ejection inspection, and FIG. 7B is a diagram illustrating the voltage signal SG when noise is generated during the ejection inspection. It is. In the figure, the result of discharge inspection (voltage signal SG) from nozzle # 1 to nozzle # 15 is shown. As described above, in the ejection inspection, whether or not the nozzles Nz are missing is inspected by comparing the maximum amplitude Vmax in the inspection period T of each nozzle Nz with the threshold value TH. For example, in the voltage signal SG of FIG. 7A, since the maximum amplitude Vmax of the nozzle # 1 is larger than the threshold value TH, it can be determined that no missing dot occurs in the nozzle # 1. On the other hand, since the maximum amplitude Vmax of the nozzle # 5 is equal to or less than the threshold value TH, it can be determined that a missing dot has occurred in the nozzle # 5.

  However, if mechanical vibration (impact) occurs during the discharge inspection or the discharge inspection current If flowing to the detection electrode 613 leaks, noise may occur in the voltage signal SG as shown in FIG. 7B. . For example, when the user sets paper on the tray of the printer 1, mechanical vibration may occur in the printer 1 and noise may occur in the voltage signal SG. In addition, a conductive foreign substance adheres between the nozzle surface and the detection electrode 613 and the discharge inspection current If leaks, or the discharge inspection current If leaks through the ink overflowing from the cap 61 and the ink adhering to the wiper 66. As a result, noise may occur in the voltage signal SG.

  As shown in FIG. 7B, if noise that causes the maximum amplitude to exceed the threshold value TH occurs during the discharge inspection period, the discharge inspection cannot be performed normally. For example, nozzle # 5 is a dot missing nozzle. If no noise is generated during the ejection inspection period, the change in potential (maximum amplitude Vmax) during the inspection period of nozzle # 5 does not exceed the threshold TH as shown in FIG. 7A. However, if noise occurs during the ejection inspection period, the change in the noise potential (maximum amplitude Vmax) during the inspection period of nozzle # 5 exceeds the threshold value, so that the detection control unit 57 normally ejects ink droplets from nozzle # 5. Is mistakenly determined to have been discharged. Then, nozzle # 5 is not detected as a missing dot nozzle, and printing is performed without performing a recovery operation or the like. As a result, the image quality of the printed image is degraded.

  Thus, when noise occurs in the voltage signal SG during the ejection inspection period, the missing dot nozzle cannot be accurately detected. Therefore, in this embodiment, a “non-ejection dummy period (corresponding to a non-ejection period)” is provided during the ejection inspection period, and it is determined whether noise has occurred during the ejection inspection period. The non-ejection dummy period is a period in which ink droplets are not ejected from all the nozzles Nz. The non-ejection dummy period is provided between ejection inspections of the plurality of nozzles Nz. For example, in FIG. 7A, the non-ejection dummy period is provided after the ejection inspection of nozzle # 1 to nozzle # 15 is performed.

  If no noise is generated in the ejection inspection period as shown in FIG. 7A, the maximum value (maximum amplitude Vmax) of the voltage change in the non-ejection dummy period is also equal to or less than the threshold value TH. If the maximum amplitude Vmax of the non-ejection dummy period is equal to or less than the threshold value TH, it can be determined that no noise is generated in the voltage signal SG in the ejection inspection period of nozzle # 1 to nozzle # 15 before the non-ejection dummy period. . That is, it can be determined that the ejection inspection from nozzle # 1 to nozzle # 15 is normally performed, and the inspection result in which the missing dot is detected by the voltage signal SG is correct.

  On the other hand, when noise is generated during the ejection inspection period as shown in FIG. 7B, the maximum amplitude Vmax of the non-ejection dummy period becomes larger than the threshold value TH. Therefore, if the maximum value of the voltage change in the non-ejection dummy period is larger than the threshold value TH, noise is generated in the voltage signal SG in the ejection inspection period from nozzle # 1 to nozzle # 15 before the non-ejection dummy period. Can be judged. That is, it can be determined that the ejection inspection from nozzle # 1 to nozzle # 15 is performed in an abnormal state of the function of the printer 1, and the inspection result in which the missing dot is detected by the voltage signal SG is not correct.

  In this way, by providing the non-ejection dummy period between the ejection inspections of the nozzles Nz, it is possible to accurately detect the missing dot nozzles with the voltage signal SG in which no noise is generated. Then, if a dot missing nozzle is detected, printing is performed after performing a recovery operation or the like, whereby image quality deterioration of the printed image can be suppressed. In addition, since there is a noise factor in the resistance element of the missing dot detection unit 50, as shown in the non-ejection dummy period in FIG. 7A, a large noise due to leakage of the mechanical vibration and the ejection inspection current If does not occur. In both cases, noise with a small amplitude may occur.

  FIG. 8 is a diagram for explaining a block serving as a discharge inspection unit. Incidentally, as described with reference to FIG. 2B, the head 31 used in the printer 1 of the present embodiment is provided with six nozzle rows Nk to Nlm. Each nozzle row Nk to Nlm is composed of 180 nozzles Nz. For this reason, 1080 (180 × 6 columns) nozzles Nz are targets for ejection inspection. In the present embodiment, it is assumed that 15 nozzles Nz are used as units for ejection inspection (hereinafter also referred to as blocks), and inspection is performed in units of blocks. That is, one nozzle row is divided into 12 blocks, and a discharge inspection of a total of 72 blocks is performed. Then, a “non-ejection dummy period” for confirming whether or not noise has occurred in the voltage signal SG is provided between the inspection period of a certain block and the inspection period of the next block. Therefore, when the maximum amplitude Vmax of a certain non-ejection dummy period exceeds the threshold value TH, the ejection inspection of the previous block (discharge inspection of 15 nozzles) is invalidated. When the ejection inspection of a certain block becomes invalid, the ejection inspection is performed again. If the maximum amplitude Vmax of a certain non-ejection dummy period is equal to or smaller than the threshold value TH, the ejection inspection of the previous block is validated and the ejection inspection of the next block is performed (details will be described later).

  Further, it is preferable that the non-ejection dummy period has a length comparable to the period required for the inspection for one nozzle Nz, that is, the repetition period T of the drive signal COM shown in FIG. 6A. If the non-ejection dummy period is shorter than the repetition period T, the non-ejection dummy period becomes shorter than one cycle of noise, and the maximum amplitude Vmax of noise may not be detected. Then, the presence or absence of noise cannot be accurately detected. Conversely, if the non-ejection dummy period is approximately the same as the inspection period of one nozzle Nz, it is sufficient to obtain the maximum noise amplitude Vmax. Therefore, if the non-ejection dummy period is made longer than the period required for the inspection for one nozzle Nz, the ejection inspection time becomes longer.

  In addition, in the discharge inspection of each nozzle Nz, the voltage comparison unit 57c of the detection control unit 57 acquires the maximum amplitude Vmax from the maximum value VH and the minimum value VL of the voltage signal SG (digital signal) for each repetition period T. For this reason, the control of period management can also be facilitated by confirming the presence or absence of noise in the non-ejection dummy period by allowing the voltage comparison unit 57c to acquire the maximum amplitude Vmax from the voltage change in the same period (repetition period T). . In other words, in the non-ejection dummy period, the length is approximately the same as the period T required for the inspection of one nozzle, so that the control can be facilitated, the presence or absence of noise can be as accurate as possible, and the inspection time is long. It can suppress becoming.

=== About the optimal number of non-ejection dummy periods ===
In the present embodiment, as shown in FIG. 8, 15 nozzles are set as one block (unit of ejection inspection), and one non-ejection dummy period is provided every time the ejection inspection of 15 nozzles Nz is performed. By the way, when the number of non-ejection dummy periods is increased, noise generated in a short period (hereinafter also referred to as short-term noise) can be detected, so that noise detection accuracy can be improved. On the other hand, if the number of non-ejection dummy periods is increased too much, the ejection inspection takes time. Therefore, a method for determining the optimum number of non-ejection dummy periods, that is, the optimum number of nozzles belonging to one block (hereinafter also referred to as a unit block) will be described below.

  FIG. 9A is a diagram showing a difference in inspection time due to a difference in the number of nozzles belonging to a unit block, FIG. 9B is a diagram showing a difference in false detection rate due to a difference in the number of nozzles belonging to a unit block, and FIG. FIG. 6 is a diagram showing a table summarizing the results of a test for determining the optimum number of nozzles belonging to a unit block (hereinafter also referred to as a nozzle number determination test). In the present embodiment, an optimum nozzle per unit block that suppresses an excessively long inspection time while obtaining the required dot missing nozzle detection accuracy by performing a nozzle number determination test in the manufacturing process of the printer 1. Determine the number. Specifically, a plurality of nozzles belonging to the unit block are changed, and the ejection inspection is actually performed.

  In the nozzle number determination test, similarly to the actual ejection inspection of the printer 1, the ejection inspection is performed for each nozzle belonging to the block, and a non-ejection dummy period is provided between the ejection inspections for each block. Further, a test in which disturbance is intentionally given during the test period to generate noise in the voltage signal SG and a test in which no disturbance is given are performed. As a main cause of noise (mechanical vibration) generated during the ejection inspection period, an action of the user setting paper on the printer 1 can be considered. Therefore, disturbance is given by actually setting the paper in the printer 1 during the test period, and noise is generated in the voltage signal SG. In the test with disturbance, when the maximum amplitude Vmax of the voltage change in the non-ejection dummy period exceeds the threshold as shown in FIG. 7B, the block inspection before the ejection inspection period is invalidated, and the ejection inspection is performed again. Execute (re-inspection). If the maximum amplitude Vmax of the non-ejection dummy period is equal to or less than the threshold value, the process proceeds to the ejection inspection of the next block. Note that the result of the nozzle number determination test in FIG. 9C is the result of the ejection inspection of one nozzle row.

  In this embodiment, as shown in FIG. 9C, the number of nozzles belonging to the unit block is three. “45 nozzles” belong to the first unit block, “15 nozzles” belong to the second unit block, and “4 nozzles” belong to the third unit block. Assume that the discharge inspection is performed for each of the three types of unit blocks. Here, the number of nozzles belonging to the unit block is preferably a common divisor (for example, 45, 15, 4) of the number of nozzles “180” in the nozzle row. By doing so, the number of nozzles for ejection inspection in all the blocks becomes equal, and control of ejection inspection becomes easy.

  First, the inspection time is compared in the result of the nozzle number determination test. FIG. 9A shows the difference in inspection time between the second unit block and the third unit block. In FIG. 9A, the discharge inspection time of 30 nozzles is shown. As shown in the figure, as the number of nozzles in the unit block decreases, the number of non-ejection dummy periods increases, so the inspection time increases. 9C also shows that the smaller the number of nozzles belonging to a unit block, the greater the number of non-ejection dummy periods and the longer the inspection time. Also, as the number of nozzles belonging to a unit block decreases, it becomes easier to detect short-term noise, and therefore the number of re-inspections during an inspection with a disturbance increases. Therefore, the inspection time increases as the number of nozzles in the unit block decreases.

  Next, the false detection rate when a disturbance is given during the test is compared. FIG. 9B shows a state where noise of the same length is generated at the same timing in the first unit block and the second unit block. As the number of nozzles in the unit block increases, the interval between the non-ejection dummy periods becomes longer, so the probability that short-term noise will occur in the non-ejection dummy period decreases. That is, even if noise is generated during the period during which dot missing detection is performed for each nozzle Nz, noise often does not occur during the non-ejection dummy period. As a result, the missing dot of the nozzle Nz is often determined based on the voltage signal SG in which noise is generated.

  The error detection rate shown in FIG. 9C is a ratio between the number of nozzles for which dot missing has been determined based on the maximum amplitude Vmax of the voltage signal SG during a period in which noise has occurred due to disturbance and the number of nozzles to be inspected (180). . 9C also shows that the false detection rate increases as the number of nozzles belonging to the unit block increases.

  Also, the inspection time without disturbance and the inspection time with disturbance in FIG. 9C are compared. In the first unit block and the second unit block, the difference in the inspection time without disturbance is “0.5 seconds”, while the difference in the inspection time with disturbance is “0.38 seconds”. The difference in inspection time is small. This is because if the number of nozzles belonging to a unit block is excessively increased, noise is generated in the non-ejection dummy period, and the time required for re-inspection increases when re-inspection is performed. That is, when the number of nozzles belonging to a unit block is large, the number of nozzles that are normally inspected during a period in which noise is not generated is larger than the number of nozzles that are inspected in a period in which short-term noise is generated. Nevertheless, the re-inspection means that the period during which the ejection inspection is repeated unnecessarily becomes longer.

  In this way, as a “nozzle number determination test”, a discharge inspection is performed by changing the number of nozzles belonging to a unit block, and an inspection time and a false detection rate are calculated. In the result of FIG. 9C, the inspection time of the third unit block is longer by about 3 seconds than the first unit block and the second unit block. On the other hand, the inspection time of the second unit block is only 0.5 seconds longer than that of the first unit block. Nevertheless, the second unit block can have a lower false detection rate than the first unit block. Therefore, in the present embodiment, it is determined that 15 nozzles are optimal for the unit block.

  That is, in the present embodiment, the number of nozzles belonging to a unit block is determined in consideration of the time required for ejection inspection and the false detection rate. Then, the number of nozzles belonging to the unit block is stored in the memory 80c of the printer 1. By doing so, a non-ejection dummy period is provided every time the printer-side controller 80 conducts ejection inspection of 15 nozzles based on the ejection inspection drive signal COM (FIG. 6A) when performing ejection inspection. Can be controlled. As a result, the inspection time can be shortened as much as possible while maintaining the detection accuracy of the discharge inspection.

  Further, without fixing the number of nozzles belonging to the unit block to 15, for example, the memory 80c of the printer 1 stores the result of the inspection time and the false detection rate when the number of nozzles belonging to the unit block is different. Depending on the selection, the number of nozzles belonging to the unit block may be determined. For example, the user is allowed to determine which of the inspection time and the false detection rate is important. When the user attaches importance to the erroneous detection rate, it is preferable to determine the number of nozzles belonging to the unit block so that the allowable inspection time is determined and the erroneous detection rate is the lowest among the allowable inspection times. Conversely, if the user places importance on the inspection time, let the allowed false detection rate be determined, and determine the number of nozzles belonging to the unit block so that the inspection time is the shortest among the allowable false detection rates. Good.

=== Detection of Abnormality in Detection Electrode 613 ===
In the missing dot detection unit 50, the detection electrode 613 is charged to a high potential of 600V to 1kV. As described above, a conductive foreign matter adheres between the nozzle surface and the detection electrode 613 and the discharge inspection current If leaks, or the discharge inspection current flows through the ink overflowing from the cap 61 or the ink attached to the wiper 66. There is a possibility that If leaks and an abnormality such as a short circuit occurs in the detection electrode 613. If an abnormality occurs in the detection electrode 613, ink ejection cannot be detected normally.

  In order to detect an abnormality in the detection electrode 613, a voltage dividing circuit is generally provided in a power supply line for charging the detection electrode 613. That is, the power supply voltage is divided by a voltage dividing circuit, and a detection voltage having a voltage level suitable for detection is acquired. Then, the abnormality of the detection electrode 613 is detected by digitally converting the voltage value of the detection voltage.

  However, when detection is performed using a voltage dividing circuit, there is a problem in that charge as a signal source to be used for dot dropout detection leaks through the voltage dividing circuit and detection sensitivity is lowered. In addition, there is a cause of noise (noise) in the resistance element itself, and there is a problem that current noise and thermal noise increase by providing many resistance elements. It is difficult to completely remove such noise in a circuit that handles a high voltage signal.

  In view of such circumstances, the dot dropout detection unit 50 of the present embodiment does not monitor the voltage level using the voltage dividing circuit, but detects based on the change in the electrical state caused by the discharge inspection current If. An abnormality of the electrode 613 is detected. That is, the potential change of the other conductor of the detection capacitor 54 is amplified by the amplifier 55, and it is determined whether the detection electrode 613 is normal or not based on the amplitude of the obtained voltage signal SG. To do.

  FIG. 10 is a diagram for explaining the detection of abnormality of the detection electrode 613. Here, when the discharge inspection current If leaks from the detection electrode 613 and an abnormality occurs in the detection electrode 613, the maximum amplitude Vmax decreases for all the nozzles Nz. Therefore, a first threshold value TH1 (corresponding to the aforementioned threshold value TH, here 3V) is set with respect to the maximum amplitude Vmax of the voltage signal SG obtained during the ejection inspection. When the maximum amplitude Vmax for all the nozzles Nz belonging to a certain block is 3 V or more (and no noise is generated in the non-ejection dummy period), the detection electrode during the ejection inspection of that block No abnormality occurs in 613, and it can be determined that all nozzles belonging to the block have no missing dots.

  The missing dot detection unit 50 pays attention to the fact that the maximum amplitude Vmax becomes smaller for all the nozzles Nz at the time of abnormality, and determines a second threshold value TH2 that is lower than the first threshold value TH1 by a predetermined voltage level. That is, as shown in FIG. 10, when the maximum amplitude Vmax for all the nozzles Nz is equal to or less than the first threshold value TH1, the threshold value is changed to the second threshold value TH2 (for example, 2.5 V) and the discharge inspection is performed again. Do. Then, in the inspection period excluding the non-ejection dummy period, the detection control unit 57 determines that the maximum amplitude Vmax for all the nozzles Nz is equal to or smaller than the first threshold value TH1 and is larger than the second threshold value TH2, in other words, an amplifier. When the magnitude of the potential change amplified by 55 is within the range defined by the first threshold value TH1 and the second threshold value TH2, it is determined that the discharge inspection current If is leaked due to a short circuit or the like. The determination result is output to the printer-side controller 80. The printer-side controller 80 performs processing such as stopping the operation of the printer 1 in response to the determination result (described later).

  The second threshold value TH2 is preferably set to a value higher than the noise that normally occurs during the non-ejection dummy period. As described above, the resistance element has a noise factor. Since this noise is amplified by the amplifier 55, it becomes a certain level. As in this embodiment, by setting the second threshold value TH2 higher than the noise that normally occurs during the non-ejection dummy period, it is difficult to be affected by the small noise that normally occurs. Thereby, the detection accuracy of an electrical change caused by ink ejection can be increased.

=== About the flow of detecting missing dots ===
FIG. 11 is a flowchart of the printing operation of the printer 1. This printing operation is controlled by the printer-side controller 80. First, when the printer-side controller 80 receives a print command (S001), a “dot missing detection operation” is performed (S002). In this dot missing detection operation, the presence or absence of a dot missing nozzle is determined (details will be described later). If no dot missing nozzle is detected (N in S003), a printing operation is performed (S004). On the other hand, when a dot missing nozzle is detected (Y in S003), the recovery operation (for example, pump suction, flushing operation, fine vibration operation, etc.) for the dot missing nozzle is performed (S005).

  After the recovery operation is completed, the missing dot detection operation is performed again to check whether or not ink droplets are normally ejected from the missing dot nozzle by the recovery operation. At this time, if a missing dot nozzle is detected even if the recovery operation is repeated a predetermined number of times, that is, if the missing dot detection operation is repeated a predetermined number of times (Y in S006), the leakage of current from the detection electrode 613 occurs. It is determined whether or not there is (S007, based on register storage). If it is determined that the current leak through the detection electrode 613 has not been eliminated (Y in S007), it is considered that there is a current leak that is difficult to eliminate by the recovery operation. Therefore, a series of processing is terminated as abnormal termination due to current leakage. On the other hand, if there is no current leakage (N in S007), the user selects whether to perform the printing operation with a missing dot nozzle or to forcibly terminate without performing the printing operation (S008). ). When the user selects forced termination, the printer-side controller 80 terminates a series of processes as abnormal termination due to user selection. If the user selects printing, a printing operation is executed (S004). In the case where the printing operation is performed in a state where there are dot missing nozzles, the print data may be complemented by increasing the dot diameter formed on the nozzles in the vicinity of the dot missing nozzles.

  When one unit of printing operation, for example, printing operation on one sheet or a series of printing operations corresponding to one job is completed, the printer-side controller 80 confirms whether there is data to be continuously printed (S008). If there is data to be continuously printed (Y in S008), the presence / absence of a function abnormality flag (described later) is confirmed (S009). If the function abnormality flag is set in the register (corresponding to the memory) of the detection control unit 57 (Y in S009), the dot missing detection operation is performed before the next printing operation (S002). If the function abnormality flag is not set in the register (N in S009) and a predetermined time has not yet elapsed since the previous dot dropout inspection operation was performed (N in S010), the next printing is performed. Operation is performed. On the other hand, even if the function abnormality flag is not set in the register (N in S009), if a predetermined time has elapsed since the previous dot missing detection operation (Y in S010), the dot missing detection operation is performed (S002). ). Over time, the ink around the nozzles that are not frequently used increases in viscosity, which may cause missing dots. Therefore, a missing dot detection operation is performed every predetermined time.

<About missing dot detection operation>
FIG. 12 is a diagram illustrating a flow of the dot missing detection operation (S002 in FIG. 11). Next, the missing dot detection operation will be described. The missing dot detection operation is performed in a state where the carriage 21 is moved to the inspection position as shown in FIG. 3B. First, the detection control unit 57 sets the first threshold value TH1 (S101). As described above, the first threshold value TH1 is a threshold value for determining whether or not ink droplets are normally ejected (see FIG. 10). Next, a discharge inspection operation for each nozzle Nz is performed (S102, details will be described later). Whether or not the maximum amplitude Vmax of the voltage signal SG corresponding to at least one nozzle is larger than the first threshold value when the ejection inspection for all the blocks is normally completed without generating noise in the non-ejection dummy period. Determination is made (S103). If the maximum amplitude Vmax for one or more nozzles Nz is greater than the first threshold value TH1, it is determined that there is no abnormality in the detection electrode 613 (for example, current leakage) (“No leak”) (Y in S103). If “leak is present” is stored in the register, it is rewritten as “no leak”. Then, returning from the dot missing detection operation (to the flow of FIG. 11), when the maximum amplitude Vmax for all the nozzles Nz is larger than the first threshold value TH1, it can be determined that there is no dot missing nozzle (FIG. 11). In S003, the process proceeds to the next predetermined operation (printing operation).

  If the maximum amplitude Vmax for all the nozzles Nz is equal to or less than the first threshold value TH1 (N in S103), it is considered that a hardware abnormality such as current leakage or disconnection through the detection electrode 613 has occurred. In this case, the detection control unit 57 sets the second threshold value TH2 (S104). As described above, the second threshold value TH2 is a threshold value for determining whether or not the detection electrode 613 is abnormal (abnormality due to current leakage) due to a short circuit or the like (see FIG. 10). Thereafter, the discharge inspection operation is performed again (S105), and it is determined whether or not the maximum amplitude Vmax corresponding to all the nozzles Nz is larger than the second threshold value TH2 (S106). If this condition is satisfied (Y in S106), it is considered that an abnormality such as current leakage through the detection electrode 613 has occurred. For this reason, abnormal termination processing due to current leakage is performed. For example, the energization to the detection electrode 613 is stopped, and a message indicating that an abnormality has occurred is displayed on the display.

  If this condition is not satisfied (N in S106), it is determined whether or not the maximum amplitude Vmax corresponding to all the nozzles Nz is smaller than the second threshold value TH2 (S107). When this condition is satisfied (Y in S107), it is recognized that ink droplets are not ejected from all the nozzles Nz for control. Therefore, whether or not the same recognition has been made in the past ejection inspection is determined based on whether or not the “all-dot missing flag” is set in the register (S109). If the all-dot missing flag is set (Y in S109), it is assumed that an abnormality has occurred in the hardware (printer 1), and an abnormality due to all-dot missing (no ink droplets are ejected from all nozzles Nz). As a result of the abnormality), a series of processing is terminated. On the other hand, if the all-dot missing flag is not set (N in S109), the all-dot missing flag is set in the register (S110), and the register is “stored as leak / dot missing”. Thereafter, a recovery operation is performed (S111), and a discharge inspection operation is performed again (S102). Thus, even if the above-described processing is repeated and the recovery operation is performed (S111), if the maximum amplitude Vmax for all the nozzles Nz is smaller than the second threshold value TH2 (Y in S107), an abnormal end is caused by missing all dots. . Further, as a result of performing the recovery operation (S111) and the ejection inspection operation (S102), the fact that there is one or more nozzles having the maximum amplitude Vmax larger than the first threshold value is not the “all-dot missing” state. That is. Therefore, when the “all dot missing flag” is set in the register, the all dot missing flag may be cleared.

  On the other hand, if the maximum amplitude Vmax for some nozzles Nz is greater than or equal to the second threshold value in S107 (N in S107), current leakage has occurred and dot missing (ink) has occurred for some nozzles Nz. It is considered that droplet non-ejection) has occurred. In this case, the all missing dots flag is cleared (S108). Then, the information with missing dots and the information with current leakage are set in the register, and the operation returns from this missing dot detection operation. Thereafter, it is determined that there is a missing dot in S003 of the flow of FIG. 11, and a recovery operation is performed (S005). If the current leakage is not recovered even after the recovery operation, “abnormal termination due to leakage” is caused as described above.

  The reason why the abnormal termination is not immediately caused by the leak when there is a current leak and there is a missing dot (N in S107) will be described. This is because the recovery operation may remove ink and foreign matter between the detection electrode 613 and the nozzle surface, possibly eliminating current leakage. Further, even when the ink discharge amount at each nozzle Nz decreases, the maximum amplitude Vmax of the voltage signal SG for each nozzle Nz may be equal to or lower than the first threshold value TH1 and equal to or higher than the second threshold value. In this case, in terms of control, it is difficult to distinguish from the case where there is current leakage and dot missing (N in S107). In such a case, it is possible to distinguish by performing the recovery operation (S005 in FIG. 11).

  In S106 of the flow of FIG. 12, when there is a current leak but no dot dropout (Y), the abnormal end is immediately caused by the current leak, but a recovery operation may be performed before that. If the current leakage is not resolved even after the recovery operation, it is preferable to terminate the operation abnormally.

<Discharge inspection operation>
FIG. 13 is a diagram showing a flow of the ejection inspection operation, and FIG. 14 is a diagram for explaining the ejection inspection operation. Next, a specific procedure of the discharge inspection operation (S102 in FIG. 12) will be described. In the discharge inspection operation, first, a nozzle row to be inspected is determined from the six nozzle rows of the head 31 (S201). Next, the nozzle row to be inspected is divided into 12 blocks (see FIG. 8), and the block to be inspected is determined from among them (S202).

  Then, the ejection inspection is sequentially performed on the nozzles Nz belonging to the inspection target block (S203). Specifically, based on the drive signal COM shown in FIG. 6A, ink droplets are continuously ejected from the nozzle Nz 20 to 30 times. The detection control unit 57 acquires an electrical change of the detection electrode 613 caused by the ejection of the ink droplet as a voltage signal SG shown in FIG. 6B. Note that after the detection control unit 57 acquires the voltage signal SG, the voltage signal SG is converted into a digital signal by the AD conversion unit 57b of the detection control unit 57. Based on the digital signal, the maximum amplitude Vmax, which is the inspection result for each nozzle Nz, is calculated. Thereafter, the voltage comparison unit 57c compares the maximum amplitude Vmax with a threshold value (first threshold value TH1 or second threshold value TH2), and the comparison result is stored in a register of the detection control unit 57. For example, when the register for the comparison result is 1 bit, the comparison result is stored with two types of contents such as “higher than threshold” and “below threshold”.

  Further, not only the comparison result between the maximum amplitude Vmax of each nozzle Nz and the threshold value, but also the maximum amplitude Vmax (maximum value of voltage change) and the threshold value (first threshold value TH1) in the non-ejection dummy period are compared. If the maximum amplitude Vmax in the non-ejection dummy period is smaller than the threshold value, it can be determined that no noise has occurred during the previous inspection period of the target block (N in S204). In this case, the comparison result of the target block is held in the register (S205). In this case, if it is the final block (Y in S207), the next nozzle row is the inspection target, and if it is not the final block (N in S207), the next block is the inspection target. Similarly, if it is the last nozzle row (Y in S207), it returns from the discharge inspection operation, and if it is not the last nozzle row (N in S207), the next nozzle row is set as the inspection target.

  On the other hand, when the maximum amplitude Vmax of the non-ejection dummy period is larger than the threshold value, it can be determined that noise has occurred during the previous inspection period of the target block, and it is determined that the detection is abnormal (Y in S204). Therefore, the comparison result of the previous target block is invalid. If there is a detection abnormality in this way, the discharge inspection (S203 and S204) is repeated a predetermined number of times (here, 130 times) (N in S208) until the discharge inspection is normally performed on the target block.

  Even if the ejection inspection for the target block is repeated up to a predetermined number of times (here, 130 times) in S208, if a detection abnormality occurs (Y in S208), an improvement operation is performed (S209). The improvement operation includes, for example, movement of the carriage 21, and the carriage 21 is temporarily moved from the inspection position (for example, the position in FIG. 3B) to the printing area side (left side in the movement direction), and then the inspection position. It is the operation to return to. By performing this operation, there are cases where an abnormality caused by a mechanical factor can be resolved. For example, the short-circuit state between the detection electrode 613 and the nozzle plate 33b due to ink or foreign matter adhering to the wiper 66 may be eliminated.

  After the improvement operation, the process is repeated a predetermined number of times (13 times) until the ejection inspection is normally performed on the target block. The improvement operation is also repeated up to a predetermined number of times (here, 3 times). In other words, in the present embodiment, a maximum of 390 times (= 130 times × 3 times) of discharge inspection is performed for one target block in one discharge inspection operation. If the discharge inspection is still not performed normally (Y in S210), it is confirmed whether the function abnormality flag is set in the register (S211). Note that the ejection inspection for each block may be repeatedly performed without interposing the improvement operation.

  If the function abnormality flag is not set in the register (N in S211), the function abnormality flag is set in the register (S212, storing the abnormality information of the discharge inspection in the memory), and the process returns from the discharge inspection operation. To do. In this case, the ejection inspection of the block after the target block is not performed, and the process proceeds to the printing operation (S004 in FIG. 11, corresponding to the next predetermined operation). On the other hand, if the function abnormality flag has already been set (Y in S211), it is determined that an abnormality has occurred in the printer 1, and the series of processing ends.

<Discharge inspection timing>
In the present embodiment, the detection control unit 57 acquires an electrical change that occurs in the detection electrode 613 due to the ejection of the ink droplet from the nozzle Nz as a voltage signal SG (FIG. 6B), and based on the voltage signal SG. Detect dot missing nozzles. If noise occurs in the voltage signal SG as shown in FIG. 7B, the dot missing nozzle cannot be detected accurately. Therefore, a discharge inspection is performed for each block composed of a plurality of nozzles Nz, and a non-discharge dummy period is provided between the discharge inspections of each block. Then, the maximum amplitude Vmax in the non-ejection dummy period is compared with a threshold value to determine whether noise has occurred during the inspection period. As shown in FIG. 7B, when the maximum amplitude Vmax of the non-ejection dummy period is larger than the threshold value, it is determined that noise has occurred during the inspection period, and the inspection result of the block before the non-ejection dummy period is invalidated. To do.

  The discharge inspection operation is controlled by a printer-side controller 80 (corresponding to a control unit). In the discharge inspection operation, when it is determined that noise has occurred during the discharge inspection period for each block (Y in S204 in FIG. 13), one block is checked until the inspection is normally performed. The discharge inspection is repeated up to 390 times. Note that the maximum number of times that repeated ejection inspection is performed on one target block may be determined based on, for example, an allowable time during which the nozzle surface (meniscus) is kept moisturized.

  Incidentally, noise generated in the voltage signal SG includes noise having a short generation period and noise having a long generation period. In addition, there are noises that are not cured by the above-described improvement operation. It is assumed that when a discharge inspection is performed on a certain target block, it is found that noise has occurred during the inspection period due to a subsequent non-discharge dummy period. Here, if noise is generated in the non-ejection dummy period in one ejection test, it will end abnormally immediately, or the next predetermined operation without performing the ejection test on the target block or other blocks. It is assumed that the process moves to (for example, printing operation). Then, for example, noise generated during the discharge inspection period of the target block is short-term noise, and when the discharge inspection is performed again, the discharge inspection ends even though no noise is generated. As described above, when noise is generated in one discharge inspection, if the discharge inspection is immediately finished, the discharge inspection cannot be performed properly. As a result, an image is printed in a state where there is a dot missing nozzle, or the user is burdened with unnecessary work by post-processing of the printer 1 that has ended abnormally.

  Therefore, in the present embodiment, in one discharge inspection operation (FIG. 13), when noise occurs in the discharge inspection of a certain target block and the inspection is abnormal, the discharge inspection of the target block is normal. Until a predetermined number of times (here, 390 times) is repeated. By doing so, in the case of short-term noise, the noise subsides during repeated ejection inspections up to a predetermined number of times, and the ejection inspection can be performed normally.

  Here, it is assumed that there is no restriction on the number of repetitions of ejection inspection of a certain target block in one ejection inspection operation (FIG. 13). That is, it is assumed that the discharge inspection is repeatedly performed even if the predetermined number of times (390 times) defined in the present embodiment is exceeded until the discharge inspection is normally performed. Then, for example, if the noise generated during the discharge inspection period of the target block is long-term noise, the discharge inspection is repeated wastefully during a long period when the noise is generated, so the discharge inspection time becomes longer. As a result, the print processing time also becomes longer. In addition, by repeatedly performing the ejection inspection, the ink is wasted. In addition, the nozzle surface dries during the ejection inspection period, causing dot dropout.

  Therefore, in the present embodiment, even if the discharge inspection is not performed normally even if the discharge inspection is repeatedly performed up to a predetermined number of times (here, 390 times) within one discharge inspection operation (FIG. 13) (FIG. 13). 13), the temporary discharge inspection is interrupted. Then, it is confirmed whether the function abnormality flag is set in the register (S211). If the function abnormality flag is not set (N in S211), the function abnormality flag is set in the register, and the process proceeds to the next predetermined operation (printing operation in S004 in FIG. 11). When printing is continued after the next printing operation is completed (Y in S008), it is confirmed that the function abnormality flag is set (Y in S009), and the ejection inspection (dot missing detection operation) is performed again. I do.

  In the second discharge inspection operation after the next printing operation (FIG. 13), if the discharge inspection is not performed normally even after repeated discharge inspections up to a predetermined number of times (390 times), the register malfunctions. It is confirmed that the flag is set (Y in S211), and it is determined that an abnormality has occurred in the printer 1, and the series of processing is terminated. Note that when the discharge inspection is normally performed in the discharge inspection operation after setting the function abnormality flag, the setting of the function abnormality flag may be canceled (not shown).

  By doing so, long-term noise is generated in the first ejection inspection operation, and even if the ejection inspection is repeated up to a predetermined number of times and the inspection cannot be performed normally, the next printing operation is performed. In the meantime, long-term noise may subside. Then, in the second discharge inspection operation, the discharge inspection can be normally performed. Even if the ejection inspection is repeated up to a predetermined number of times and the inspection cannot be normally performed, various operations such as movement of the carriage 21, conveyance of the paper, and ejection of ink droplets from the nozzles are performed by performing the printing operation. Since the state of the printer 1 is changed, there is a case where the inspection abnormality is resolved by performing the ejection inspection after the printing operation.

  In other words, if it cannot be performed normally even after repeated ejection inspections a predetermined number of times, the timing of the ejection inspection can be shifted by performing the next predetermined operation (for example, printing operation), and no noise is generated. The probability that the ejection inspection can be performed at the timing is increased. In addition, the state of the printer 1 (for example, the state of the nozzle surface and the cap mechanism 60) is changed by performing the next predetermined operation, the cause of the noise is removed, and a normal inspection is performed in the discharge inspection after the next predetermined operation. The probability of being able to do it increases.

  Also, in the second discharge inspection operation after the next predetermined operation, if the discharge inspection cannot be performed normally, it is considered that some abnormality has occurred. For example, when the installation location of the printer 1 is poor and noise is generated by continuously applying vibration to the printer 1, the installation location of the printer 1 is not changed even if the next predetermined operation (printing operation) is sandwiched. As long as the noise is not cured. Therefore, if the inspection cannot be normally performed even in the ejection inspection operation after the next predetermined operation (when the function abnormality flag is set), it is determined that an abnormality has occurred in the printer 1 and the series of processes is terminated.

  To summarize the above, in this embodiment, the discharge inspection is repeatedly performed a predetermined number of times until the discharge inspection is normally performed. If the discharge inspection is not performed normally, the function abnormality flag is set, and the next Perform a predetermined action. Then, after the next predetermined operation, if the discharge inspection cannot be performed normally even if the discharge inspection is repeated a predetermined number of times again, it is determined that the printer 1 is abnormal. By doing so, the discharge inspection can be performed while avoiding various noises such as long-term noise and short-term noise, and the discharge inspection can be appropriately performed. Further, it is possible to prevent the ejection inspection from being repeated unnecessarily, and the inspection time can be prolonged and the ink consumption can be suppressed.

  Heretofore, when a print command is received (S001 in FIG. 11) or after the recovery operation for the dot missing nozzle is performed (S005 in FIG. 11), the dot missing detection operation (ejection inspection operation) is performed. However, it is not limited to this. For example, when the printer 1 is turned on, a missing dot detection operation (ejection inspection operation) may be performed. In many cases, the user sets paper in the printer 1 after the printer 1 is turned on. As described above, the main cause of the noise generated in the voltage signal SG is the action of the user setting paper on the printer 1. Therefore, immediately after turning on the power of the printer 1, even if repeated ejection inspection (dot missing detection operation) is performed, normal inspection cannot be performed, the next predetermined operation (for example, standby operation) is performed, and then another ejection inspection is performed. It may be confirmed that a sheet is set in the printer 1 before the operation is performed.

  Further, in the flow of FIG. 11 and FIG. 13, when a normal inspection cannot be performed even if the discharge inspection is repeated a predetermined number of times (FIG. 13), after setting a function abnormality flag (S <b> 212 in FIG. 13), Although the printing operation is performed (S004 in FIG. 11), the present invention is not limited to this. The “next predetermined operation” after setting the malfunction flag may be, for example, a standby operation or a recovery operation. By doing so, the timing of performing the ejection inspection can be shifted. Further, for example, by performing a flushing operation in the recovery operation, foreign matter or the like attached to the nozzle surface can be removed, and noise generated by current leakage from the detection electrode 613 through the foreign matter can be removed. . Further, as the “next predetermined operation”, the carriage 21 may be moved, or the carriage 21 may be moved while maintaining the state of FIG. 3B. As a result, the nozzle surface (nozzle) and the detection electrode 613 are not opposed to each other. By doing so, it is possible to remove noise generated due to current leakage through ink or foreign matter between the nozzle surface and the detection electrode 613, and the probability that the ejection inspection after a predetermined operation is normally performed increases. . In particular, when the carriage 21 is moved while maintaining the state shown in FIG. 3B, the wiper 66 can remove the deposits on the nozzle surface, which makes it easier to remove noise.

  Further, after the function abnormality flag is set, the recovery operation may be performed before the printing operation (S004 in FIG. 11). By doing so, if the printing operation is performed in a state where the ejection inspection of all the nozzles is not normally performed, that is, even if the printing is performed without knowing the presence or absence of the missing dot nozzle, the recovery operation is performed before the printing operation. If this is done, the missing dot nozzle is recovered, so that it is possible to suppress deterioration in the image quality of the printed image.

  In the flow of FIG. 11, after the printing operation is performed (S004), when the next printing operation is subsequently performed (Y in S008), if the function abnormality flag is set (S009), the dot dropout is immediately performed again. Although the detection operation is performed, the present invention is not limited to this. For example, when the function abnormality flag is not set, the dot omission detection operation is performed after a predetermined time (for example, after one hour), whereas when the function abnormality flag is set, the predetermined time. The dot missing detection operation may be performed after a shorter time (for example, after 30 minutes). In other words, when the function abnormality flag is set, the discharge inspection for all nozzles is not normally performed in the previous dot missing detection operation, so if dot missing nozzles occur, the image quality deteriorates. I will let you. Therefore, when the function abnormality flag is set, the next dot missing detection operation (discharge inspection operation) is performed from the previous dot missing detection operation (discharge inspection operation) more than when the function abnormality flag is not set. Shorten the time until it is done. By doing so, it is possible to suppress image quality degradation that occurs due to the failure to perform the ejection inspection normally.

=== Other Embodiments ===
Each of the above embodiments has been described mainly with respect to a printing system having an ink jet printer, but includes disclosure of a discharge inspection method and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Non-ejection dummy period>
In the above-described embodiment, in order to confirm whether noise is generated in the voltage signal SG acquired from the detection electrode 613, a non-ejection dummy period is provided between the nozzle ejection inspection period (discharge inspection for each block). However, it is not limited to this. For example, the presence or absence of noise may be confirmed based on the frequency of the voltage signal SG. For example, it can be determined that noise has occurred when a signal having a frequency higher than the frequency of the voltage signal SG to be originally obtained is obtained in the detection period for one nozzle. In the above-described embodiment, the non-ejection dummy period is provided for each block composed of a plurality of nozzles. However, the present invention is not limited to this. For example, a non-ejection dummy period may be provided for each ejection inspection for one nozzle. In addition, a non-ejection dummy period is provided after ejection inspection of one block, and when noise is generated in a certain non-ejection dummy period, it is determined whether or not noise is generated in the block before that non-ejection dummy period. However, it is not limited to this. For example, a non-ejection dummy period may be provided before the ejection inspection of the block, and the presence or absence of noise in the subsequent ejection inspection may be determined, or a non-ejection dummy period may be provided between the ejection inspections of the block.

<About the missing dot detection unit 50>
In the above-described embodiment, an abnormality of the detection electrode 613 is detected based on a change in the electrical state caused by the discharge inspection current If without providing a voltage dividing circuit in the dot dropout detection unit 50. However, the present invention is not limited to this, and the power supply voltage may be divided by a voltage dividing circuit, and an abnormality of the detection electrode 613 may be detected based on the detected voltage.

  In the above-described embodiment, based on the electrical change of the detection electrode 613 generated by ejecting ink droplets from the nozzles in the high potential detection electrode 613 and the ground potential nozzle plate 33b, the dot missing nozzles. Although the presence or absence is detected, it is not restricted to this. In the case where the presence or absence of a missing dot nozzle is detected based on an electrical change as in the above-described embodiment, the present invention is effective because the inspection may not be performed accurately due to the influence of noise.

  In the above-described embodiment, as shown in FIG. 5A, the detection electrode is set to a higher potential than the nozzle surface, and the potential change of the detection electrode 613 caused by the ejection of the ink droplet is extracted by the detection capacitor 54. Not limited to this. 15A to 15C are diagrams illustrating other configurations of the dot missing nozzle portion. In FIG. 15A, the high voltage power supply unit 51 is connected to the nozzle plate 33b (corresponding to the first electrode) to make it high potential (corresponding to the first potential), and the detection electrode 613 (corresponding to the second electrode) is connected to the ground. To ground potential (corresponding to the second potential). Then, a missing dot nozzle is detected by a change in the potential of the nozzle plate caused by ink ejection. In FIG. 15B, the detection electrode 613 is set to a high potential, the nozzle plate 33b is set to the ground potential, and a dot missing nozzle is detected by a change in the potential of the nozzle plate due to ink ejection. Further, as shown in FIG. 15C, the detection electrode 613 is set to the ground potential, the nozzle plate 33b is set to the high potential, and the dot missing nozzle is detected by the potential change of the detection electrode 613 due to ink ejection.

  In the above-described embodiment, the ink ejected from the nozzle is set to the ground potential by setting the nozzle plate to the first potential (ground potential). However, the present invention is not limited to this. If the ink ejected from the nozzle is configured to have the first potential (ground potential), the nozzle plate may not be used as an electrode. For example, a conductive member that is provided on a wall surface such as the ink flow path or the pressure chamber 331 and that is electrically connected to the ink in the nozzle Nz may be provided, and this conductive member may be set to the ground potential. Further, the ink is not limited to the ground potential, and any potential difference necessary for detection may be required between the detection electrode 613 and the ink.

<Discharge inspection abnormality>
In the above-described embodiment, in the ejection inspection operation, the same operation is performed when the ejection inspection is not normally performed even if the ejection inspection is repeatedly performed for a certain block, or when the ejection inspection is normally completed (see FIG. However, the present invention is not limited to this, and another operation may be performed.

<About line printers>
In the above-described embodiment, the printer 1 that alternately performs the image forming operation of ejecting ink droplets while the head 31 moves in the movement direction and the conveyance operation of relatively moving the head 31 and the medium in the conveyance direction that intersects the movement direction. However, the present invention is not limited to this. For example, a line head printer that forms an image by arranging heads (nozzles) in the paper width direction intersecting the medium conveyance direction and ejecting ink droplets toward the medium conveyed under the head may be used.

<About liquid ejection device>
In the above-described embodiment, the ink jet printer is exemplified as the liquid ejecting apparatus (part) for performing the liquid ejecting method, but is not limited thereto. If it is a liquid ejection device, it can be applied to various industrial devices, not a printer (printing device). For example, a textile printing apparatus for applying a pattern to a fabric, a display manufacturing apparatus such as a color filter manufacturing apparatus or an organic EL display, a DNA chip manufacturing apparatus for manufacturing a DNA chip by applying a solution in which DNA is dissolved to a chip, and the like. Also, the present invention can be applied.
The liquid discharge method may be a piezo method that discharges liquid by applying voltage to the drive element (piezo element) to expand and contract the ink chamber, or generates bubbles in the nozzle using a heating element. It is also possible to use a thermal method in which liquid is discharged by the bubbles.

FIG. 1A is a block diagram illustrating a printing system, and FIG. 1B is a perspective view of a printer. FIG. 2A is a sectional view of the head, and FIG. 2B is a diagram showing an arrangement of nozzles. 3A to 3C are views showing the positional relationship between the head and the cap mechanism during the recovery operation. It is the figure which looked at the cap from the upper part FIG. 5A is a diagram for explaining the missing dot detection unit, and FIG. 5B is a block diagram for explaining the detection control unit. 6A is a diagram illustrating a drive signal, and FIG. 6B is a diagram illustrating a voltage signal. FIG. 7A is a diagram illustrating a voltage signal in which noise is not generated, and FIG. 7B is a diagram illustrating a voltage signal in which noise is generated. It is a figure explaining the block used as a discharge inspection unit. It is a diagram showing the difference in inspection time, It is a diagram showing the difference in false detection rate, It is a figure which shows the table | surface which put together the result of the nozzle number determination test. It is a figure for demonstrating the detection of abnormality of the electrode for a detection. It is a flow of printing operation of the printer. It is a figure which shows the flow of dot missing detection operation | movement. It is a diagram showing a flow of discharge inspection operation, It is a figure for demonstrating a discharge test | inspection operation | movement. 15A to 15C are diagrams showing another configuration for detecting a missing dot nozzle.

Explanation of symbols

1 printer, 10 paper transport mechanism, 20 carriage movement mechanism, 21 carriage,
30 head units, 31 heads, HC head control unit, 32 cases,
33 channel unit, 33a channel forming substrate, 33b nozzle plate,
33c diaphragm, 331 pressure chamber, 332 ink supply path, 333 common ink chamber,
334 Diaphragm part, 335 island part, 34 piezo element unit,
341 piezoelectric element group, 342 fixed plate, 40 drive signal generation circuit,
50 missing dot detector, 51 high voltage power supply unit, 52 first limiting resistor,
53 second limiting resistor, 54 detecting capacitor, 55 amplifier,
56 smoothing capacitor, 57 detection control unit, 57a register group,
57b AD conversion unit, 57c voltage comparison unit, 57d control signal output unit,
60 cap mechanism, 61 cap, 611 side wall, 612 moisturizing member,
613 electrode for detection, 62 slider member, 63 contact part, 64 long hole,
65 waste tube, 66 wiper, 70 detector group, 80 controller,
80a interface unit, 80b CPU, 80c memory,
CP computer

Claims (8)

(1) The discharge inspection is repeatedly performed a predetermined number of times until the discharge inspection of the liquid discharge apparatus that discharges liquid from the nozzles is normally performed, and when the discharge inspection is normally performed, the liquid discharge apparatus In the case where the discharge inspection is not performed normally even if the discharge inspection is repeated up to the predetermined number of times, the liquid discharge apparatus stores the abnormality information of the discharge inspection in a memory and stores the abnormality information. Performing the following predetermined actions:
(2) After the next predetermined operation is performed, the discharge inspection is repeated up to the predetermined number of times until the discharge inspection is normally performed, and the discharge inspection is performed even if the discharge inspection is repeated up to the predetermined number of times. If not normally performed, the liquid ejection device checks the memory, and determines that the liquid ejection device is abnormal if the abnormality information is stored in the memory;
A discharge inspection method comprising: The discharge inspection method according to claim 1,
When the abnormality information is stored in the memory, the next predetermined operation is performed from the ejection inspection in the operation (1) as compared to the case where the abnormality information is not stored in the memory. A discharge inspection method for shortening a time until the discharge inspection is performed. The discharge inspection method according to claim 1 or 2,
In the ejection inspection, the liquid ejected from the nozzle by the first electrode is set to a first potential, and the liquid having the first potential is ejected toward the second electrode having a second potential different from the first potential. ,
Inspecting the presence or absence of liquid ejection from the nozzle based on a potential change occurring in at least one of the first electrode and the second electrode due to liquid ejection from the nozzle;
Discharge inspection method. The discharge inspection method according to claim 3,
A non-ejection period in which liquid is not ejected from all nozzles is provided between the ejection inspection for one nozzle and the ejection inspection for another nozzle,
Based on the potential change in the non-ejection period, it is determined whether or not the ejection inspection for the certain nozzle has been performed normally.
Discharge inspection method. The discharge inspection method according to claim 3 or 4,
In the next predetermined operation, the discharge inspection method in which the nozzle and the second electrode are not opposed to each other. A discharge inspection method according to any one of claims 1 to 5,
The next predetermined operation is a discharge inspection method which is a printing operation. A discharge inspection method according to any one of claims 1 to 4,
The next predetermined operation is a discharge inspection method that is a recovery operation in which liquid is normally discharged from a nozzle that generates a discharge failure. (1) a nozzle for discharging liquid;
(2) memory,
(3) A control unit that performs discharge inspection of the nozzle,
The discharge inspection is repeated a predetermined number of times until the discharge inspection is normally performed. When the discharge inspection is performed normally, the next predetermined operation is performed, and the discharge inspection is repeatedly performed the predetermined number of times. If the discharge inspection is not performed normally, the memory stores the abnormality information of the discharge inspection in the memory and performs the next predetermined operation,
After the next predetermined operation, the discharge inspection is repeated up to the predetermined number of times until the discharge inspection is normally performed, and the discharge inspection is performed normally even if the discharge inspection is repeated up to the predetermined number of times. If not, the control unit checks the memory, and if the abnormality information is stored in the memory, the controller determines an abnormal state;
A liquid ejection apparatus having

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