JP2012111174A - Recorder and method of recovering discharge performance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To readily recover discharge performance while suppressing consumption of a liquid.SOLUTION: When defective discharge occurs at a discharge port because meniscus is destroyed and bubbles are mixed into an individual ink passage (step S21, bubble-mixing), a meniscus restoring operation (step S22) is executed. In the meniscus restoring operation, first, a discharge face is covered with a cap, and the cap inside is sucked for pressure reduction. Then, a voltage pulse signal of a pulse width T satisfying T>Tis supplied to an individual electrode corresponding to the defective discharge occurring discharge port. Tcorresponds to the magnitude of the pulse width with which a speed at which the liquid is discharged from the discharge port is maximized and locally maximized.

Description

  The present invention relates to a recording apparatus having a liquid ejection head provided with an ejection port for ejecting liquid, and an ejection performance recovery method.

  Japanese Patent Laid-Open No. 2004-228561 is to prevent the ink from drying by moving the ink meniscus inside the nozzle by moving the ink meniscus by lowering the pressure in the nozzle cap after covering the nozzle with the nozzle cap. .

JP-A-6-336018

  When air stays in the liquid flow path that supplies the liquid to the discharge port that discharges the liquid, there may be a problem that the liquid discharge performance deteriorates. Therefore, in order to recover the discharge performance, it is conceivable to discharge the staying air from the discharge port to the outside by forcibly discharging the liquid. For example, it is conceivable to use the technique of Patent Document 1 described above to reduce the pressure in the cap to suck the liquid in the discharge port and discharge the staying air together with the liquid from the discharge port.

  However, it is not preferable to discharge the liquid every time the discharge performance is recovered, because wasteful consumption of the liquid increases.

  An object of the present invention is to provide a recording apparatus and a discharge performance recovery method that can easily recover discharge performance while suppressing liquid consumption.

  The recording apparatus of the present invention includes a discharge port that discharges a liquid, a liquid channel that supplies the liquid to the discharge port, a pressure chamber provided in the middle of the liquid channel, and a volume of the pressure chamber that is V1. After changing from V1 to V2 greater than V1, a volume changing operation for returning to V1 is performed, and a liquid discharge head having an actuator that discharges liquid from the discharge port and the discharge port of the liquid discharge head are opened. A capping unit that covers the ejection region in contact with the ejection surface and in which the ejection port is formed, and a pressure in an inclusion space surrounded by the capping unit and the ejection surface in a state where the capping unit covers the ejection region. Pressure changing means for changing, and recovery operation control means for controlling the pressure changing means and the actuator to execute recovery operation processing of the discharge performance of the discharge port, When the volume changing operation is executed such that T = To (To> 0) with respect to the time T from when the actuator starts to change the volume of the pressure chamber from V1 to V2 until it starts to return to V1, The discharge speed of the liquid discharged from the discharge port has a maximum and maximum characteristic, and the recovery operation process is performed within the range in which the liquid is not discharged from the discharge port where the liquid meniscus is formed. And a process of causing the actuator to perform the volume changing operation in a range where T> To and no liquid is discharged from the discharge port after the pressure changing operation for reducing the pressure in the space is executed by the pressure changing unit. .

  A recording apparatus according to another aspect of the present invention includes a discharge port for discharging a liquid, a liquid channel for supplying a liquid to the discharge port, a pressure chamber provided in the middle of the liquid channel, and the pressure chamber A liquid discharge head having an actuator for discharging the liquid from the discharge port by executing a volume changing operation for changing the volume of the liquid from V1 to V2 larger than V1 and then returning to V1; A liquid inflow means for causing the liquid in the liquid storage means to flow into the liquid flow path, and a recovery operation control means for controlling the liquid inflow means and the actuator to execute the recovery operation processing of the discharge performance of the discharge port With respect to the time T from when the actuator starts to change the volume of the pressure chamber from V1 to V2 until it starts to return to V1, T = To (To> 0). Thus, when the volume changing operation is executed, the discharge speed of the liquid discharged from the discharge port has a maximum and maximum characteristic, and the recovery operation process is performed on the liquid inflow means to the discharge port. A process of causing the actuator to perform the volume changing operation in a range where T> To and no liquid is discharged from the discharge port after the liquid is flowed into the liquid flow path at a pressure in a range where no liquid is discharged from Contains.

  The discharge performance recovery method of the present invention is a discharge performance recovery method for recovering the discharge performance of the discharge port in the recording apparatus, wherein the recording device discharges liquid from each of the plurality of discharge ports to a recording medium. A step of forming an inspection pattern on a recording medium by discharging, and a step of identifying one of the plurality of discharge ports having a reduced discharge performance based on the inspection pattern formed on the recording medium; After the recovery operation control means causes the pressure changing means to execute the pressure lowering operation, only T> To and only the actuator corresponding to the discharge port identified as having a reduced discharge performance. And a step of executing the volume changing operation in a range in which liquid is not discharged from the outlet.

  According to the recording apparatus of the present invention, first, the liquid in the liquid flow path can be drawn out to a certain extent by reducing the pressure in the internal space. Thereby, a part of the air staying in the vicinity of the discharge port can be discharged from the discharge port. At this time, since the inside space is depressurized in a range where the liquid is not discharged from the discharge port where the liquid meniscus is formed, consumption of the liquid is suppressed. After that, when the volume changing operation is executed by the actuator, when the volume of the pressure chamber is changed from V1 to V2, the liquid in the liquid flow path is further moved to the discharge port side, and the remaining air is further pushed out. Can do. Here, if the actuator is operated so that T = To, liquid may be discharged from the discharge port. When the actuator is operated so that T <To, the volume of the pressure chamber returns to V1 before the liquid in the liquid flow path is sufficiently moved to the discharge port side. For this reason, the air staying in the vicinity of the discharge port cannot be sufficiently pushed out. On the other hand, as in the present invention, by operating the actuator so that T> To, the liquid in the liquid channel is sufficiently discharged toward the discharge port while preventing the liquid from being discharged from the discharge port. Can be moved. That is, the air staying in the vicinity of the discharge port can be sufficiently pushed out.

  In the recording apparatus according to another aspect, the same effect as described above can be obtained by flowing a liquid instead of depressurizing the internal space. Furthermore, according to the discharge performance recovery method of the present invention, since the volume changing operation can be executed only for the discharge port identified as having the discharge performance deteriorated based on the inspection pattern, the discharge performance is not deteriorated. The volume changing operation does not have to be performed unnecessarily up to the exit.

It is the schematic diagram seen from the front which shows roughly the internal structure of the inkjet printer which concerns on one embodiment of this invention. FIG. 2A is a side view showing a state where the wiper wipes the ejection surface of the head in the printer of FIG. FIG. 2B is a side view including a cross section of the cap, showing a state where the cap covers the head. FIG.2 (c) is a top view of the cap of FIG.2 (b). FIG. 2 is a plan view of the head body of FIG. 1. FIG. 4 is an enlarged view of a portion surrounded by an alternate long and short dash line in FIG. 3. It is the elements on larger scale of a head discharge surface. FIG. 4 is a partial cross-sectional view of the head body of FIG. 3. It is a fragmentary sectional view of the actuator unit of FIG. FIG. 8A shows the waveform of the voltage pulse signal supplied to the individual electrode of FIG. FIG. 8B is a graph showing the relationship between the pulse width of FIG. 8A and the liquid ejection speed. FIG. 2 is a block diagram illustrating a configuration of a printer control system. It is a test | inspection pattern for test | inspecting the discharge defect of the head for precoat. It is an inspection pattern for inspecting ejection failure of an ink head. It is a flowchart which shows a series of flows of operation | movement by a printer. It is a flowchart which shows the flow of the recovery operation step of FIG. It is a schematic diagram which shows roughly the structure of the head periphery which concerns on a 1st modification. FIG. 15A shows an inspection pattern for inspecting ejection failure of the precoat head according to the second modification. FIG. 15B is an enlarged view of the discharge surface and a schematic diagram showing the relationship between the discharge port and the group of the discharge port group. It is a test | inspection pattern for test | inspecting the discharge defect of the head for precoat which concerns on the 3rd-6th modification.

  A preferred embodiment of the present invention will be described below with reference to the drawings.

  First, an overall configuration of an inkjet printer 1 according to an embodiment of the present invention will be described with reference to FIG. The ink jet printer 1 includes a precoat head 2 that ejects a transparent precoat liquid for improving image quality, and an ink jet head 3 that ejects ink. The heads 2 and 3 are both line heads that are long along one direction (the direction perpendicular to the paper surface of FIG. 1), and are incorporated in the ink jet printer 1 with the longitudinal direction as the main scanning direction. The printer 1 is a line type color ink jet printer.

  As the precoat liquid component, a pigment ink is used for aggregating pigment pigments, and a dye ink is used for depositing dye pigments. The precoat solution is prepared by appropriately selecting a polyvalent metal salt such as magnesium salt and calcium salt in addition to cationic polymers such as diallyldimethylammonium chloride polymer and diallylmethylammonium salt polymer, using water as the main solvent. . When the ink lands on the region of the paper P to which such precoat liquid has been applied in advance, the polyvalent metal salt or the like acts on the dye or pigment that is the colorant of the ink to form an insoluble or hardly soluble metal composite or the like ( Agglomerated or precipitated). As a result, the penetrability of the adhering ink into the paper P is reduced, and the ink is easily fixed on the paper P. In this embodiment, pigment ink is used for image formation.

  The printer 1 has a rectangular parallelepiped housing 501a. A paper discharge unit 531 is provided on the top plate of the housing 501a. The internal space of the housing 501a can be divided into spaces A, B, and C in order from the top. Spaces A and B are spaces in which a paper transport path that continues to the paper discharge unit 531 is formed. In the space A, conveyance of the paper P and image formation on the paper P are performed. In the space B, an operation related to paper feeding is performed. In the space C, a tank unit 60 that stores an image forming liquid is detachably attached to the housing 501a. The tank unit 60 includes a tray 63, one tank 61, and four tanks 62. In the tray 63, the tanks 61 and 62 are juxtaposed in the sub-scanning direction. The tank 61 stores a precoat liquid, and the tank 62 stores ink.

  In the space A, one head 2, four heads 3, a maintenance unit 80, a transport unit 521 that transports the paper P, a guide unit that guides the paper P, and the like are arranged. In the upper part of the space A, a controller 100 that controls the operation of each part of the printer 1 and controls the operation of the entire printer 1 is disposed. The controller 100 is connected to a print data acquisition unit 110 that acquires image data for printing from the outside of the printer 1. The print data acquisition unit 110 may read image data recorded on a digital data recording medium such as a USB memory, or may acquire image data from a computer connected to the printer 1 via an interface or a network. Also good.

  Each of the heads 2 and 3 has a substantially rectangular parallelepiped shape. One head 2 is arranged at the most upstream side along the sheet conveying direction, and four heads 3 are arranged at a predetermined pitch in the downstream side. The head 2 and the four heads 3 are fixed to a head frame 503, and are installed in the housing 501a so as to be movable in the vertical direction by a driving mechanism (not shown). The heads 2 and 3 are supplied with precoat liquid, magenta ink, cyan ink, yellow ink and black ink from the tank 61 and tank 62 through ink tubes (not shown).

  The lower surface of the head 2 for the precoat liquid is a flat discharge surface 2a, and a plurality of discharge ports 8 for discharging droplets are opened. Inside the head 2, a liquid flow path for leading the precoat liquid to the discharge port is formed. The ink head 3 has the same structure as the head 2, and a plurality of discharge ports 8 are opened on the discharge surface 3 a and a liquid flow path is formed therein. The four heads 3 eject magenta, cyan, yellow, and black ink droplets, respectively. The discharge surfaces 2a and 3a are arranged in parallel to each other.

  The conveyance unit 521 includes two belt rollers 506 and 507, an endless conveyance belt 508 wound between both rollers 506 and 507, a nip roller 504 and a peeling plate 505 disposed outside the conveyance belt 508, and a conveyance belt 508. It has a platen 519 and the like arranged inside. The belt roller 507 is a driving roller, and is rotated by driving a conveyance motor (not shown) under the control of the controller 100, and rotates clockwise in FIG. As the belt roller 507 rotates, the conveyance belt 508 travels in the direction of the arrow in FIG. The belt roller 506 is a driven roller and rotates clockwise in FIG. 1 as the transport belt 508 travels. The nip roller 504 is disposed to face the belt roller 506 and presses the paper P supplied from the upstream guide portion (described later) against the outer peripheral surface 508 a of the transport belt 508. A weak adhesive silicon layer is formed on the outer peripheral surface 508a. The peeling plate 505 is disposed to face the belt roller 507, peels the paper P from the outer peripheral surface 508a, and guides the paper P to a downstream guide portion (described later). The platen 519 is disposed to face the five heads 2 and 3, and supports the upper loop of the conveyor belt 508 from the belt inner peripheral surface side. As a result, a predetermined gap suitable for image formation is formed between the outer peripheral surface 508a and the ejection surfaces 2a and 3a.

  The guide portions are arranged on both sides of the transport unit 521. The upstream guide portion includes two guides 527 a and 527 b and a pair of feed rollers 526. The guide unit connects a paper feed unit 501b (described later) and the transport unit 521. The downstream guide unit includes two guides 529 a and 529 b and two pairs of feed rollers 528. The guide unit connects the transport unit 521 and the paper discharge unit 531.

  In the space B, a paper feeding unit 501b is arranged. The paper feed unit 501b includes a paper feed tray 523 and a paper feed roller 525, and the paper feed tray 523 can be attached to and detached from the housing 501a. The paper feed tray 523 is a box that opens upward, and can store a plurality of papers P. Under the control of the controller 100, the paper feed roller 525 sends out the paper P located on the uppermost side of the paper feed tray 523 and supplies it to the upstream guide unit.

  In the spaces A and B, as described above, a paper transport path is formed from the paper feed unit 501b to the paper discharge unit 531 via the transport unit 521. Based on the recording command, the image recording control unit 101 (see FIG. 9) of the controller 100 sends out the paper P from the paper supply tray 523. The paper P is sent to the transport unit 20 through the upstream guide portion. When the paper P passes directly under the head 2 along the sub-scanning direction (paper transport direction), pre-coated liquid droplets are ejected from the head 2. Ink droplets are sequentially ejected from the respective heads 3 on the downstream side, and a desired color image is formed on the paper P. At this time, the landing position of the pre-coated liquid droplets that land on the paper P first is adjusted to coincide with the landing position of the ink droplets that land next. Thus, when ink droplets land on the paper P, pigment aggregation occurs due to the pre-coated droplets that have landed first. As a result, the ink droplet that has landed next does not easily permeate the paper P, and the quality of the image formed on the paper P is improved. afterwards. The paper P is sent upward by the downstream guide portion and discharged from the opening 530 to the paper discharge portion 531. The sub-scanning direction is a direction parallel to the paper transport direction, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along the horizontal plane.

  A line-type image sensor 71 is installed downstream of the four heads 3 in the paper transport direction. A CCD (Charge Coupled Device) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like is used as the image sensor 71. The image sensor 71 captures an image on the paper P formed by the heads 2 and 3. The image sensor 71 has a plurality of light receiving elements arranged in the main scanning direction, and can capture the maximum width of the image forming area on the paper P. The image sensor 71 transmits the captured image to the controller 100 as image data. As will be described later, such image data is used for analysis of an inspection pattern related to ejection performance.

  The maintenance unit 80 in the space A includes a wiper 81 that wipes the ejection surface 2a of the head 2 and the ejection surface 3a of the head 3, and a cap 82 (capping means) that covers the ejection surfaces 2a and 3a. The wiper 81 and the cap 82 are provided on each of the heads 2 and 3. In the following, the wiper 81 and the cap 82 provided for the head 3 will be described, but the same applies to the head 2. The heads 2 and 3 appropriately move between an image forming position where an image is formed on the paper P, a wiping position where the wiper 81 can be wiped, and a covering position where the cap 82 can be covered.

  The wiper 81 has a wiper blade 81a and a support base that supports the wiper blade 81a. As shown in FIG. 2A, the tip of the wiper blade 81a is disposed at a position where it comes into contact with the ejection surface 3a at the wiping position. The wiper 81 reciprocates along the arrow D1. At this time, the tip of the wiper blade 81a wipes the ejection surface 3a.

  As shown in FIG. 2B, the cap 82 covers the ejection surface 3a at the coating position and prevents the ink in the ejection port 8 from drying. The cap 82 includes a cap base 82a having a flat upper surface and a lip 82b protruding upward from the upper surface. As shown in FIG. 2C, the cap base 82a has a rectangular planar shape, and a lip 82b is disposed along the outer edge of the rectangle. A hollow channel 82c is formed in the cap table 82a. One end of the flow path 82c opens to the center of the upper surface of the cap table 82a, and the other end opens to the side surface of the cap table 82a. An air tube 83 is connected to the opening on the side surface side, and a pump 85 (pressure changing means) is connected via the air tube 83. The lip 82b is an elastic member that comes into contact with the discharge surface 3a and is in close contact with the discharge surface 3a. When the cap 82 covers the discharge surface 3a, a gap is formed between the discharge surface 3a and the cap base 82a, and all the discharge ports 8 are surrounded by the lip 82b in plan view.

  The cap 82 can reciprocate along the arrow D2 in FIG. In a state where the head 3 is disposed above the cap 82, after the cap 82 moves below the head 3, the head 3 is lowered to the covering position, whereby the tip of the lip 82b is pressed against the ejection surface 2a. . Thereby, an inclusion space (gap) 84 surrounded by the cap 82 and the ejection surface 3a is formed. The air in the internal space 84 is sucked by the pump 85 through the flow path 82 c and the air tube 83.

  The configuration of the heads 2 and 3 will be described in more detail with reference to FIGS. Each of the heads 2 and 3 is a laminate of an upper structure in which ink is temporarily stored and a head body 4 that ejects ink. The heads 2 and 3 have the same configuration, and the head 2 has a head body 4 at the lower part. The head 3 also has a head body 5 at the bottom. In the following, only the head body 5 will be mainly described. The head body 5 includes a flow path unit 9 and eight actuator units 21 attached to the upper surface thereof. The eight actuator units 21 have a trapezoidal planar shape, and are arranged in two rows of staggered shapes as shown in FIG. A flexible printed board (not shown) that supplies a drive signal from the controller 100 is connected to the upper surface of the actuator unit 21. An ink supply port 5 x is formed on the upper surface of the flow path unit 9 so as to avoid the arrangement area of the actuator unit 21, and is covered with a filter 72. The filter 72 filters ink flowing from the upper structure into the flow path unit 9.

  As shown in FIG. 6, the flow path unit 9 is a laminate of a plurality of metal plates 22 to 30 made of stainless steel. A plurality of through holes are formed in each of the plates 22 to 30. The plates 22 to 30 are aligned and stacked, and have an ink flow path in which each through hole communicates. The ink flow path includes a manifold flow path 51, a sub-manifold flow path 51a, and an individual ink flow path 32. As shown in FIGS. 3 and 4, one end of the manifold channel 51 communicates with the ink supply port 5x, and the other end communicates with the sub-manifold channel 51a extending in the head longitudinal direction. A plurality of individual ink channels 32 are branched from the sub-manifold channel 51a. As shown in FIG. 6, the individual ink flow path 32 has the outlet of the sub-manifold flow path 51 a as one end, and reaches the discharge port 8 of the discharge surface 3 a through the pressure chamber 10 and the aperture 12. In FIG. 4, for convenience of explanation, the pressure chamber 10, the aperture 12, and the discharge port 8 that are located below the actuator unit 21 and should be drawn with broken lines are drawn with solid lines.

  On the ejection surface 3a, as shown in FIG. 5, a plurality of ejection ports 8 are arranged at equal intervals along the main scanning direction. These discharge ports 8 are arranged at intervals of n times (n: natural number) the unit distance p corresponding to the printing resolution in the main scanning direction to form a discharge port array. There are n ejection port arrays, and adjacent arrays are arranged at equal intervals in the sub-scanning direction while shifting by an interval p in the main scanning direction. As a result, the projection points created in the sub-scanning direction are aligned at equal intervals p on the virtual straight line L0 extending in the main scanning direction. The ejection ports 8 of the head 2 are also arranged in the same manner. Further, the ejection port 8 of the head 2 and the ejection port 8 of the head 3 are arranged at the same position in the main scanning direction, and overlap each other in the sub scanning direction.

  The ink flow in the flow path unit 9 will be described. The ink supplied to the ink supply port 5x is distributed from the manifold channel 51 to the sub-manifold channel 51a. The ink in the sub-manifold channel 51 a flows into each individual ink channel 32 and reaches the ejection port 8 via the pressure chamber 10.

  Next, the actuator unit 21 will be described in more detail. The actuator unit 21 includes a plurality of actuators corresponding to the pressure chambers 10 and selectively applies ejection energy to the ink in the pressure chambers 10. As shown in FIG. 7, the actuator unit 21 is made of a lead zirconate titanate (PZT) -based ceramic material having ferroelectricity, and includes three piezoelectric layers 41 to 43. The uppermost piezoelectric layer 41 is polarized in the thickness direction. A plurality of individual electrodes 35 are formed on the upper surface of the piezoelectric layer 41. A common electrode 34 formed on the entire surface of the sheet is interposed between the piezoelectric layer 41 and the lower piezoelectric layer 42.

  The individual electrode 35 faces the pressure chamber 10. An individual land 36 is electrically connected to the tip of the individual electrode 35. When the electric field in the polarization direction is applied to the piezoelectric layer 41 by setting the individual electrode 35 to a potential different from that of the common electrode 34, the electric field application portion in the piezoelectric layer 41 functions as a drive active portion that is distorted by the piezoelectric effect. The two lower piezoelectric layers 42 and 43 close to the pressure chamber 10 are inactive layers and do not spontaneously deform even when an electric field is applied. For this reason, the portion sandwiched between the individual electrode 35 and the pressure chamber 10 functions as an individual unimorph type actuator. That is, the actuator unit 21 is a piezoelectric element in which a plurality of actuators corresponding to the number of pressure chambers 10 are built.

  The common electrode 34 is equally grounded in the region corresponding to all the pressure chambers 10. On the other hand, a drive signal is selectively supplied to the individual electrode 35.

  Here, a driving method of the actuator unit 21 will be described. For example, if the polarization direction and the electric field application direction are the same, the drive active portion contracts in a direction (plane direction) orthogonal to the polarization direction. On the other hand, the piezoelectric layers 42 and 43 are not spontaneously deformed. When a difference in strain in the plane direction occurs between the piezoelectric layer 41 and the piezoelectric layers 42 and 43, the entire piezoelectric layers 41 to 43 are deformed so as to be convex toward the pressure chamber 10 (unimorph deformation).

  The head 2 has a drive control unit 2b, and the head 3 has a drive control unit 3b (see FIG. 9). As shown in FIG. 8A, a voltage pulse signal S that is a drive signal is supplied from the drive control unit 3b (2b) to the individual electrodes 35. The voltage pulse signal S includes a square pulse having a width T and a height E. In this embodiment, each individual electrode 35 is maintained in a state of potential E (> 0) in advance. Accordingly, the piezoelectric layers 41 to 43 are on standby in a unimorph deformed state. The volume of the pressure chamber 10 at this time is set to V1. The voltage pulse signal S is supplied to the individual electrode 35 every time an ink ejection request occurs. When one voltage pulse signal S is supplied, the potential of the individual electrode 35 starts to drop to the ground potential at time t1. When the individual electrode 35 becomes the ground potential, the piezoelectric layers 41 to 43 return to the state before the deformation, and the volume of the pressure chamber 10 becomes V2 (> V1). By this volume increasing operation, a negative pressure is applied to the ink in the pressure chamber 10, and the ink is sucked from the sub manifold channel 51 a into the individual ink channel 32. At time t2 when time T has elapsed from time t1, the potential of the individual electrode 35 starts to return to E. When the potential of the individual electrode 35 returns to E, the piezoelectric layers 41 to 43 are unimorph deformed again, and the volume of the pressure chamber 10 also returns to V1. By this volume reduction operation, positive pressure is applied to the ink in the pressure chamber 10, and ink is ejected from the ejection port 8. A series of operations of the actuator unit 21 that returns the volume of the pressure chamber 10 to V1 from V1 through V2 by supplying the voltage pulse signal S corresponds to the volume changing operation in the present invention.

  The speed of the ink ejected from the ejection port 8 varies depending on the pulse width T when the pulse height E is the same. When a negative pressure is applied to the pressure chamber 10 at time t1, natural vibration is excited in the ink in the individual ink flow path 32 (a pressure wave is generated). When a positive pressure is applied at a timing at which the positive pressure in the pressure chamber 10 is maximized due to this natural vibration, this positive pressure is most effectively superimposed on the natural vibration. At this time, ink droplets are ejected at the maximum ejection speed. Such a pulse width T is assumed to be To. The graph of FIG. 8 shows the relationship between the pulse width T and the ink ejection speed. The ink ejection speed becomes maximum at T = To, and decreases as T becomes farther from To. Also, the discharge speed can be maximized at other time points where T = (odd multiple of To) starting from time t1, such as T = 3 * To, T = 5 * To, and the like. However, if the magnification with respect to To is large, the vibration will attenuate with time, so even if ink is ejected, the ejection speed is lower than when T = To. On the other hand, when T = (even multiples of To), the natural vibration generated at time t1 and the positive pressure applied at time t2 are superimposed in opposite phases, canceling each other and not ejecting ink. To depends on the natural vibration period of the ink in the individual ink flow path 32. In the present embodiment, the time AL and To required for the pressure wave to propagate through the ink from the outlet of the sub-manifold channel 51a to the discharge port 8 are designed to be equal.

  FIG. 8C shows voltage pulse signals Sa to Sc used in the present embodiment. In either case, the pulse height E is the same, but the pulse widths are different from each other. Regarding the pulse width, the voltage pulse signal Sa is smaller than To, the voltage pulse signal Sb is equal to To, and the voltage pulse signal Sc is larger than To. The voltage pulse signal Sb is used when ink or precoat liquid is ejected from the heads 2 and 3. The pulse widths of the voltage pulse signals Sa and Sc are adjusted so that ink or the like is not ejected from the ejection port 8 when supplied to the individual electrode 35. The case where the voltage pulse signal Sa or Sc is used will be described later.

  Hereinafter, the control by the controller 100 will be described in more detail with reference to FIGS. 9 to 13. The controller 100 performs image recording control for forming an image on the paper P based on image data for printing, and discharge performance evaluation for evaluating whether or not the discharge performance of the discharge ports 8 in the heads 2 and 3 has deteriorated. The control and the recovery operation control for recovering the discharge performance of the discharge port 8 are executed.

  In the image recording control, the image recording control unit 101 provided in the controller 100 controls the heads 2 and 3 and the transport unit 521 based on the printing image data acquired by the print data acquisition unit 110. Thereby, the image corresponding to the image data is formed on the paper P as described above.

  The discharge performance evaluation control is as follows. As shown in FIG. 9, the controller 100 includes an inspection pattern recording control unit 104 that forms an inspection pattern on the paper P, and a non-ejection information acquisition unit 102 (performance degradation information) that acquires information regarding ejection defects based on the inspection pattern. Acquisition means). The inspection pattern differs between the head 2 and the head 3. A pattern 121 shown in FIG. 10 is used as the inspection pattern for the head 2. In order to form the pattern 121 on the paper P, as shown in the pattern 131, droplets of precoat liquid and ink droplets are landed on the paper P. In the pattern 131, the white circle s1 corresponds to the landing position of the droplet of the precoat liquid, and the black circle s2 corresponds to the landing position of the ink droplet. In the pattern 131, dot rows 131a in which white circles s1 and black circles s2 are alternately arranged along the main scanning direction are repeatedly arranged in the sub-scanning direction. That is, dot rows 131b in which white circles s1 are arranged along the sub-scanning direction and dot rows 131c in which black circles s2 are arranged in the sub-scanning direction are alternately arranged in the main scanning direction.

  The inspection pattern recording control unit 104 causes the precoat liquid droplets and ink droplets to be ejected to the dot positions indicated by the pattern 131 as follows. First, in the head 2, droplets of the precoat liquid are ejected from the ejection port group composed of the ejection ports 8 arranged alternately every other in the main scanning direction to each dot position s1 included in one dot row 131a. In any of the heads 3 (for example, the black head 3), the discharge ports 8 are included in the dot row 131a from the discharge port group including the discharge ports 8 arranged alternately with respect to the main scanning direction. Ink droplets are ejected to each dot position s2. For example, as shown in FIG. 5, a droplet of the precoat liquid is ejected from the ejection port group 8x including the odd-numbered ejection ports 8 from the left to the dot position s1 in the head 2. Then, an ink droplet is ejected from the ejection port group 8y including the even-numbered ejection ports 8 from the left to the dot position s2 in the head 3. Thus, one dot row 131a is formed on the paper P. By repeating such ejection to the dot row 131a in the sub-scanning direction, the droplets and ink droplets of the precoat liquid are landed on all the dot positions s1 and s2 shown in the pattern 131. As a result, a pattern 121 is formed on the paper P.

  In the pattern 121, since ink droplets land on the dot row 131c, an ink color line 121c is formed on the paper P. Here, the ink droplet landed at the adjacent dot position s2 is less likely to enter the dot position s1 where the precoat liquid droplet has landed appropriately. Therefore, a line 121a in which the color of the paper P appears as it is is formed at the position of the dot row 131b. On the other hand, ink droplets that have landed on the adjacent dot position s2 are likely to enter the dot position s1 where the droplet of the precoat liquid has not landed properly. Therefore, a line 121b in which ink has blotted from the adjacent dot position s2 is formed at the position of the dot row 131b where the precoat liquid has not landed. In particular, in the dot row 131b sandwiched between the dot rows 131c from both sides in the main scanning direction, the ink bleeds from both sides like a line 121b. The line 121b is thinner than the line 121a or is generally lighter and has an ink color. Due to the difference between the two lines 121a and 121b, it is clearly shown on the pattern 121 that a discharge failure has occurred at the discharge port 8 of the head 2.

  Next, the inspection pattern recording control unit 104 forms a pattern in which the dot position s1 and the dot position s2 are replaced with the pattern 131 at another position (or another sheet P) on the sheet P. For example, when the pattern 121 is first formed using the discharge port groups 8x and 8y of FIG. 5, next, the discharge ports 8 other than the discharge port group 8x in the head 2 and the discharge ports other than the discharge port group 8y in the head 3 are used. A pattern is formed using the outlet 8. Thereby, it is clearly shown on the pattern whether or not the ejection failure has occurred in the remaining ejection ports 8.

  As the inspection pattern for the head 3, the pattern 122 or 123 shown in FIGS. 11A and 11B is used. The pattern 122 is a rectangular pattern whose inside is filled, and is a so-called solid image pattern. The pattern 122 is formed by ejecting ink from all the ejection ports 8 in one head 3 to form lines along the main scanning direction and repeating this line formation in the sub-scanning direction. A hollow arrow in FIG. 11A indicates a correspondence relationship between each actuator unit 21 and a pattern formation portion by ink ejected from the ejection port 8 corresponding to the actuator unit 21. In the head 3, when a discharge failure has occurred in any of the discharge ports 8 corresponding to any of the actuator units 21 (for example, the actuator unit 21a in FIG. 11A), the position corresponding to the discharge port 8 is A line 122a based on the background color of the paper P appears. The pattern 123 is a brick-like pattern in which horizontal lines along the main scanning direction and vertical lines along the sub-scanning direction are regularly arranged. In the pattern 123, it is easy to visually determine which discharge port 8 has a discharge failure based on the positional relationship between the line 123a corresponding to the discharge failure and the vertical line.

  When an inspection pattern is formed on the paper P, in this embodiment, the image sensor 71 sequentially reads the inspection pattern and outputs read image data corresponding to the read pattern to the non-ejection information acquisition unit 102. . The non-ejection information acquisition unit 102 evaluates the presence or absence of ejection failure in the head 2 or 3 based on the read image data, and identifies the defective ejection port 8. The ejection port 8 is specified by detecting the position of the line 121b, 122a, or 123a in the main scanning direction in the patterns 121-123. The non-ejection information acquisition unit 102 has information indicating the relationship between the position in the main scanning direction and the ejection port 8. Based on this information and the detected position, the ejection port 8 in which ejection failure has occurred. Identify. In particular, the non-ejection information acquisition unit 102 evaluates the degree of bleeding at a portion where ink bleeding occurs, such as the line 121b. This evaluation is performed, for example, by comparing with other lines such as the line 121a or by evaluating the degree of ink density by comparing with a reference value.

  Causes of ejection failure are (1) clogging with the adhesive in the flow path, (2) the viscosity of the precoat liquid or ink is increased, and (3) the meniscus is destroyed and individually There are mainly three types of bubbles entering the ink flow path 32. Among these, the ejection failure due to the cause of (1) is a permanent ejection failure, and is extracted and removed, for example, at the initial shipment stage of the apparatus. Further, in the case of ejection failure due to the cause of (2), it is gradually improved by repeating the ejection operation. For this reason, unlike the line 121b, 122a, or 123a having a constant density, a line in which the density gradually recovers in the sub-scanning direction appears in the inspection pattern.

  On the other hand, the discharge failure due to the cause of (3) occurs when bubbles enter and stay from the discharge port 8 and the meniscus moves backward to the back of the flow path, as indicated by a broken line Q in FIG. In such a case, it is often the case that the meniscus does not return to the end of the discharge port only by repeating the normal discharge operation. Therefore, in the case of ejection failure due to (3), the line 121b, 122a or 123a is likely to appear in the inspection pattern. Therefore, the non-ejection information acquisition unit 102 determines whether or not the ejection failure is caused by (3) based on whether or not the density change occurs in the line. At this time, if there is no density change between the predetermined line lengths, it is determined that the defect is caused by the cause of (3), and if the density is monotonously changed, it is determined that the defect is caused by the cause of (2).

  Recovery operation control is as follows. The controller 100 includes a recovery operation control unit 103 that causes the heads 2 and 3 and the maintenance unit 80 to execute a predetermined recovery operation process. There are the following three types of recovery operations of the present embodiment.

  The first recovery operation is a meniscus restoration operation that restores the meniscus at the ejection port 8 in which ejection failure has occurred due to the cause of (3) above. In this operation, first, the recovery operation control unit 103 controls the maintenance unit 80 to cover the ejection surfaces 2a and 3a with the cap 82 as shown in FIG. Then, the pump 85 sucks the air in the internal space 84 and depressurizes the internal space 84 (the pressure in the internal space 84 is negative compared to the atmospheric pressure). At this time, the inner space 84 is depressurized to a pressure close to the meniscus withstand pressure within a range in which ink and precoat liquid do not leak. The meniscus pressure resistance is the maximum pressure at which the meniscus is maintained against the external air pressure at the discharge port 8. The pressure in the internal space 84 may be managed by providing pressure measuring means for the internal space 84 and reducing the pressure so that the meniscus is not destroyed. Alternatively, the pump 85 may be driven with a driving amount that is adjusted in advance to such a pressure range. In the case of a discharge failure due to the cause of (3), as shown in FIG. 6, the meniscus of the discharge port 8 is broken and air bubbles enter. As the internal space 84 is depressurized, the meniscus inside the individual ink flow path 32 is pulled out toward the ejection port 8. With respect to this decompression, the meniscus remains at the opening of the discharge port 8 at the discharge port 8 where there is no discharge failure.

  Here, even if the meniscus in the individual ink flow path 32 is pulled out to the portion 29a, it is difficult to reach the opening of the discharge port 8 for the following reason. The magnitude of the force acting on the meniscus by the reduced pressure is smaller as the area of the meniscus is smaller. As shown in FIG. 6, the individual ink flow path 32 is tapered toward the opening of the ejection port 8. That is, in the vicinity of the opening end, the force acting on the meniscus is also reduced, making it difficult to move the meniscus.

  Therefore, after the decompression of the internal space 84, the recovery operation control unit 103 controls the drive control unit 2b or 3b to drive the actuator corresponding to the discharge port 8 that is identified as having a discharge failure. Specifically, a plurality of voltage pulse signals Sc shown in FIG. 8C are supplied from the drive control unit 2b or 3b to the individual electrode 35 corresponding to the specified ejection port 8. The pulse width T of the voltage pulse signal Sc preferably satisfies 1.5 * To <T <2.5 * To. By applying such a pulse, ink or the like is supplied from the sub-manifold channel 51a to the individual ink channel 32 in question while reliably suppressing the ejection of ink or the like from the other ejection ports 8, and the meniscus is supplied. Can be pushed out toward the discharge port 8 side. As a result, air bubbles can be pushed out from the discharge port 8 to restore the meniscus. Note that an additional voltage pulse signal S that cancels meniscus vibration may be supplied immediately after supplying several voltage pulse signals Sc to the individual electrodes 35.

  In addition, when decompressing the inside of the inclusion space 84, it is preferable to vibrate a normal meniscus minutely. It has been confirmed that the meniscus pressure resistance is improved when the meniscus vibrates minutely. In other words, due to the minute vibration of the meniscus, it is difficult for liquid such as ink to be discharged from the normal ejection port 8 even if the inside space 84 is depressurized. Specifically, the voltage pulse signal Sa shown in FIG. 8C is continuously supplied to the individual electrode 35 corresponding to the normal ejection port 8 where no ejection failure has occurred. Thereby, the meniscus vibrates minutely.

  The second recovery operation is a flushing operation for recovering the ejection failure due to the cause (2). In this operation, first, the recovery operation control unit 103 controls the maintenance unit 80 to cover the ejection surfaces 2a and 3a with the cap 82 as shown in FIG. Then, the ink or the precoat liquid is forcibly discharged from the discharge port 8 into the internal space 84. Specifically, a large number of voltage pulse signals S satisfying T = To are supplied to the individual electrodes 35, or a voltage pulse signal S having a large pulse height E is supplied. As a result, the ink having increased viscosity is discharged from the discharge port 8 and the discharge failure is eliminated.

  The third recovery operation is a wiper operation for adjusting the meniscus. In this operation, the recovery operation control unit 103 controls the maintenance unit 80 so that the wiper 81 wipes the ejection surfaces 2a and 3a as shown in FIG. Thereby, the state of the meniscus is uniformly arranged at each discharge port 8. At this time, prior to wiping by the wiper 81, the ink or the like is forcibly discharged from each discharge port 8. The discharge of ink or the like is performed by applying a positive pressure from the ink supply side, for example, without driving the actuator. If the size of the head 2 or 3 is small, the inside of the inclusion space 84 may be decompressed so that the discharge surface 2a or 3a is covered with the cap 82 and the meniscus is destroyed by the pump 85 as described above.

  Hereinafter, a series of steps of operations performed by the printer 1 will be described with reference to FIG. First, the controller 100 determines whether or not the user has instructed to inspect the ejection performance (step S1). An instruction from the user is input from an operation panel of the printer 1 or a computer connected to the printer 1. When an instruction is given to inspect the ejection performance (step S1, Yes), the controller 100 controls the paper feed unit 501b, the transport unit 521, and the like to transport the inspection paper to the heads 2 and 3. (Step S2). At this time, a normal recording sheet may be used as an inspection sheet, or a dedicated sheet different from the recording sheet may be used.

  Next, the precoat liquid is discharged from the head 2 and the ink is discharged from the head 3 to form patterns 121 to 123 on the paper (step S3). Then, based on the image data relating to the inspection patterns 121 to 123 generated by the image sensor 71, the non-ejection information acquisition unit 102 determines whether ejection failure has occurred in the ejection port 8 (S4). At this time, the non-ejection information acquisition unit 102 identifies the ejection port 8 in which ejection failure has occurred and evaluates the cause of ejection failure. In this evaluation step, for example, a color difference corresponding to each dot row 131b is obtained and compared with the color difference of the paper P itself. A threshold is provided for the color difference, and if the color difference measured with respect to this threshold is close to the paper P itself, the discharge is good, and if it is close to the color ink of the head 3, the discharge is poor.

  If there is no ejection failure (No at Step S4), the printer 1 returns to the operation at Step S1. If ejection failure has occurred (step S4, Yes), the printer 1 issues a warning to the user by a display display, an alarm, or the like (step S5). Then, an instruction is received from the user as to whether or not to perform a recovery operation for eliminating the ejection failure. If there is an instruction (Yes in step S6), the printer 1 executes a recovery operation (step S7). If there is no instruction (No at Step S6), the operation returns to Step S1. Details of the recovery operation step will be described later.

  If there is no inspection instruction in step S1 (step S1, No), the controller 100 determines whether or not a predetermined time has elapsed since the previous inspection (step S8). When the controller 100 determines that a predetermined time has passed since the previous inspection (step S8, Yes), the printer 1 executes the operation from step S2. That is, even when there is no inspection instruction, when a predetermined time has elapsed since the previous inspection, the discharge performance inspection is executed. When it is determined that the predetermined time has not elapsed since the previous inspection (step S8, No), the controller 100 determines whether there is a print job (step S9) and determines that there is a print job. If so (step S9, Yes), the print job is executed (step S10). While the print job is not completed, the printer 1 continues to execute the print job (No at Step S11, Step S10). When the print job is completed (Yes at Step S11), the operation returns to Step S1. . If it is determined in step S9 that there is no print job (step S9, No), the printer 1 stands by until a print job is generated.

  The recovery operation step of step S7 will be described in more detail with reference to FIG. First, the controller 100 is based on the result of evaluation by the non-ejection information acquisition unit 102, and the cause of ejection failure is due to the increase in viscosity in (2) above or due to the inclusion of bubbles in (3) above. Is determined (step S21). When the controller 100 determines that the cause of the ejection failure is due to (2) (step S21, viscosity increase), the recovery operation control unit 103 causes the heads 2, 3 and the maintenance unit 80 to perform the above-described flushing operation. . Thereafter, the printer 1 returns to the operation of step S1. On the other hand, when the controller 100 determines that the cause of the ejection failure is due to (3) (step S21, mixing of bubbles), the recovery operation control unit 103 causes the heads 2, 3 and the maintenance unit 80 to perform the meniscus restoration operation described above. Is executed (step S22). In step S24, the recovery operation control unit 103 causes the maintenance unit 80 to execute the above-described wiper operation. Then, the printer 1 returns to the operation of step S1.

  According to the present embodiment described above, when it is detected that the meniscus is broken and bubbles are mixed into the flow path as shown in FIG. Perform a restore operation. According to the meniscus restoration operation, first, the internal space 84 is depressurized to the vicinity of the meniscus pressure resistance within a range where the meniscus is not destroyed. As a result, the meniscus retracted into the flow path can be pulled out toward the ejection port 8 while preventing ink or the like from being ejected from the normal ejection port 8.

  Next, a voltage pulse signal S that satisfies 1.5 * To <T <2.0 * To is supplied to the individual electrode 35 corresponding to the ejection port 8 in which ejection failure has occurred. As a result, the meniscus can be restored while preventing ink or the like from being discharged from the discharge port 8. Here, when the voltage pulse signal S that satisfies T <To is supplied, the next positive pressure is applied in a short time from the application of the first negative pressure. There is a risk that ink or the like may not be sufficiently supplied to the ink flow path 32. On the other hand, by setting To <T, the ink or the like is sufficiently supplied from the sub-manifold channel 51a to the individual ink channel 32, and the meniscus can be sufficiently moved to the ejection port 8 side. When 1.5 * To <T <2.5 * To is satisfied, the pulse width T is a value in the vicinity of 2 * To where the negative pressure and the positive pressure cancel each other. For this reason, it can suppress reliably that ink etc. discharge from the discharge outlet 8. FIG. Thus, in the meniscus restoration operation of this embodiment, the meniscus can be restored without wasting ink or the like.

  In the present embodiment, the pattern 121 shown in FIG. 10 is used to inspect the ejection failure of the head 2. This is due to the following reason. In order to inspect the ejection failure, since the precoat liquid is transparent, it is very difficult to inspect the precoat liquid alone. Also, the droplets of the precoat liquid and the ink droplets are landed on the same position on the paper P, and the difference in the color of the ink between the position where the precoat liquid has landed properly and the position where it has not landed properly is visually detected. It is also possible. However, the presence or absence of the precoat solution appears as a difference in color density. That is, since it is necessary to determine the difference in density between inks of the same color, it is difficult to determine the difference with an image sensor or visual observation. Furthermore, the difference in color development depending on the presence or absence of the precoat solution may not be so noticeable. Therefore, there is a limit to the inspection by these methods. On the other hand, when the pattern 121 of FIG. 10 is used, the ejection failure at the ejection port 8 appears as a difference between the color of the paper P and the color of the ink, as indicated by lines 121a and 121b. Therefore, since the difference is remarkable as compared with other inspection patterns that appear as the difference in color density in the same color ink, it is easy to inspect the ejection failure of the ejection port 8.

  Further, according to the pattern 121, since the ink bleeds from the dot position s2 on both sides in the main scanning direction to the dot position s1, the difference from the line 121a is clearly shown like the line 121b. Furthermore, the dot row 121b in which the dot positions s1 corresponding to the same ejection port 8 are arranged is adjacent to the dot row 121c in which the dot positions s2 corresponding to the same ejection port 8 are arranged. For this reason, when there is a discharge failure at the discharge port 8, the ink that has landed on the dot row 121c oozes from the entire row to the dot row 121b, and as shown by the line 121b, The difference is clearly visible. Accordingly, it is easy to inspect the discharge failure of the discharge port 8.

  Further, according to the pattern 121, the dot positions s1 and the dot positions s2 are alternately arranged in the main scanning direction, and droplets are discharged from the different discharge ports 8 to the dot positions s1, respectively. In this case, it is possible to grasp which ejection port 8 has ejection failure by grasping in which line the ink bleeding such as the line 121b appears. Therefore, it is easy to identify the discharge port 8 where the discharge failure has occurred.

  Hereinafter, various modifications of the present embodiment will be described. In the first modified example, as shown in FIG. 14, a pump 91 (liquid inflow unit) for allowing ink to flow is provided for each of the head 2 and the head 3. Hereinafter, in order to avoid duplication, the head 3 will be described, and the description of the head 2 will be omitted. A flow path 33 is formed inside the upper structure of the head 3. The flow path 33 is branched into a plurality of flow paths 33a, and each flow path 33a communicates with each ink supply port 5x. The pump 91 forcibly causes the ink in the tank 62 to flow into the head 3. The ink that has flowed into the flow path 33 flows into the head body 5 via the flow path 33a and the ink supply port 5x. In the first modified example, during the meniscus restoration operation, the recovery operation control is performed so that the ink is caused to flow into the head 3 at a pressure within a range in which the ink is not ejected from the ejection port 8 instead of decompressing the internal space 84. The unit 103 controls the pump 91. As a result, the meniscus (see FIG. 6) retracted into the flow path can be pushed out to the discharge port 8 side, similarly to the decompression of the internal space 84. Other operations are the same as those in the above-described embodiment.

  The second modified example relates to a pattern 231 used instead of the pattern 131. In the pattern 231, as shown in FIG. 15A, three black circles s2 are arranged between the white circles s1. Each of the white circles s1 is sandwiched between two black circles s2 in the main scanning direction. The dot rows 231a thus formed are repeatedly arranged in the sub-scanning direction. In the second modification, the ejection ports 8 of the head 2 are divided into a plurality of ejection port groups, and an inspection pattern corresponding to the pattern 231 is formed for each ejection port group. Each discharge port group is composed of discharge ports 8 spaced apart by placing three discharge ports 8 in the main scanning direction. FIG. 15B is a specific example of the discharge port group. As shown in FIG. 15B, the discharge ports 8 are formed at intervals corresponding to 2400 dpi as a whole. On the other hand, in each of the discharge port groups 8a to 8d, the discharge ports 8 are arranged at intervals corresponding to 600 dpi. Then, the precoat liquid is discharged from the discharge port group 8a to each position s1 of the pattern 231. Further, ink is ejected from the head 3 to the position s2 from the ejection ports 8 sandwiched between the ejection ports 8 of the ejection port group 8a in the main scanning direction. As a result, one inspection pattern corresponding to the pattern 231 is formed on the paper P. Similarly, for each of the ejection port groups 8b to 8d, one inspection pattern corresponding to the pattern 231 is formed at a different position on the paper P (or on another paper P).

  According to the second modified example, in each inspection pattern, lines with the precoat liquid are formed at relatively wide intervals and constant intervals, so that the discharge port 8 where the precoat liquid discharge failure has occurred can be easily identified. In addition, since a line of the precoat liquid is formed at 600 dpi with respect to the 2400 dpi discharge port 8, it is possible to detect a discharge failure by a 600 dpi low resolution image sensor.

  As shown in FIG. 16A, in the pattern 331 according to the third modification, eight dot positions s2 are adjacent to each other around one dot position s1, and these dot positions s2 are the dot positions s1. Surrounding. When the inspection pattern is formed based on the pattern 331, the ink bleeding from the dot position s2 is suppressed when the droplet of the precoat liquid has appropriately landed on the dot position s1. Therefore, as shown in the pattern 332a, an inspection pattern in which the ground color of the paper P appears as it is at the center is formed on the paper P. On the other hand, when the droplet of the precoat liquid does not land at the position s2, since the ink bleeds from the surrounding dot position s2, as shown in the pattern 332b, an inspection pattern in which the center is thinly painted with the ink, It is formed on the paper P. By determining whether the inspection pattern is 332a or 332b, it is possible to detect a discharge failure at the discharge port 8.

  As shown in FIG. 16B, the pattern 431 according to the fourth modification is simply one dot position s1 and one dot position s2 adjacent to each other. Even in such a case, since the degree of ink bleeding changes from the dot position s2 to the dot position s1 depending on whether or not the droplet of the precoat liquid has appropriately landed on the dot position s1, the ejection failure of the ejection port 8 is reduced. Can be inspected. However, rather than merely adjoining the dot positions s1 and s2, the dot position s2 adjacent to the dot position s1 sandwiches the dot position s1, as in the pattern 532 of FIG. 16C according to the fifth modification. In the pattern, the difference that occurs to the extent that the ink spreads according to the presence or absence of ejection failure of the ejection port 8 becomes larger. Further, as in the pattern 631 of FIG. 16D according to the sixth modification, two or more dot positions s2 may be adjacent to the dot position s1 in different directions.

  The seventh modification relates to a method for identifying ejection failure. In the above-described embodiment, the ejection port 8 in which the ejection failure has occurred is specified, but the seventh example is configured to determine the ejection port group in which the ejection failure has occurred. For example, the discharge ports 8 may be divided into one discharge port group for each actuator unit 21, and it may be determined from the inspection pattern which discharge port group corresponding to which actuator unit 21 has a discharge failure. In the example of FIG. 11, since a discharge failure has occurred in the discharge port group corresponding to the actuator unit 21a, this discharge port group is determined as a discharge port group in which a discharge failure has occurred. In the recovery operation process, various recovery operations are executed for each discharge port group. In other words, the meniscus restoration operation and the flushing operation are executed for all the discharge ports 8 belonging to the discharge port group that is determined to have a discharge failure, but the other discharge ports 8 are not executed. According to the seventh embodiment, since the recovery operation is performed in units of discharge port groups, simple control is achieved, and it is not necessary to wastefully execute the recovery operation for the discharge port groups in which no discharge failure has occurred.

<Modification>
The above is a description of a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the means for solving the problem. It is possible.

  For example, in the above-described embodiment, it is assumed that only the precoat liquid droplets land on the white circle s1 and only the ink droplets land on the black circle s2. However, both the precoat liquid droplet and the ink droplet may land at the position of the black circle s2. In this case, the ink bleeding from the black circle s2 to the white circle s1 may be slightly weakened. However, if the droplet of the precoat liquid does not land at the position of the white circle s1, the ink is still transferred from the black circle s2 to the white circle s1. It becomes easy to bleed. Therefore, in this case as well, it is possible to detect a discharge failure at the discharge port 8.

  In the above-described embodiment, it is assumed that no ink or precoat liquid is discharged at all as a discharge failure of the discharge port 8. However, it may be assumed that the discharge performance is decreased due to a decrease in the discharge performance of the discharge port 8, but the discharge amount is smaller than the specified amount. For example, in the pattern 131, it may be assumed that no droplet of the precoat liquid has landed at the position of the white circle s1, or a case where some droplets have landed. Even when the liquid droplets land slightly, the ink easily bleeds when the amount of liquid droplets is small as compared with the case where the liquid droplets land appropriately. In addition, if the degree of bleeding can be accurately detected, it is possible to evaluate how low the discharge performance of the discharge port 8 is.

  In the above-described embodiment, the patterns 122 and 123 are used as the inspection pattern for the head 3. Among these, for the pattern 122, from the viewpoint of improving the readability after pattern formation, the dots of the precoat liquid may be formed in advance in the pattern formation region in the same pattern as the inspection pattern.

  Further, in the above-described embodiment, the ejection failure of the ejection port 8 is detected based on the image data of the inspection pattern read by the image sensor 71. However, when the user visually observes the inspection pattern formed on the paper P and finds that the lines 122b, 122a, or 123a indicating the ejection failure are generated, the user instructs the printer 1 to perform the recovery operation. May be. At this time, the user determines to which discharge port group or which discharge port 8 a discharge failure has occurred, and the user inputs the discharge port group or discharge port 8 that has been determined to have a discharge failure to the printer 1. You may comprise so that it can do. In this case, the means for receiving input from the user corresponds to the performance degradation information acquisition means in the present invention.

S, Sa to Sc Voltage pulse signals s1, s2 Dot positions 121-123 Inspection pattern 1 Inkjet printer (printer)
2 Precoat head (head)
2a Discharge surface 3 Inkjet head (head)
3a Ejection surface 8 Ejection port 10 Pressure chamber 21 Actuator unit 32 Individual ink flow path 35 Individual electrode 71 Image sensor 80 Maintenance unit 82 Cap 84 Enclosure space 85 Pump 100 Controller 101 Image recording control unit 102 Non-ejection information acquisition unit 103 Recovery operation control Unit 104 inspection pattern recording control unit 110 print data acquisition unit

Claims (9)

A discharge port for discharging liquid, a liquid channel for supplying liquid to the discharge port, a pressure chamber provided in the middle of the liquid channel, and a volume of the pressure chamber changed from V1 to V2 larger than V1 Then, a liquid discharge head having an actuator that discharges liquid from the discharge port by performing a volume changing operation to return to V1;
Capping means for covering the discharge region in which the discharge port is formed in contact with the discharge surface where the discharge port of the liquid discharge head is opened;
Pressure changing means for changing the pressure in the inclusion space surrounded by the capping means and the discharge surface in a state where the capping means covers the discharge area;
A recovery operation control unit that controls the pressure changing unit and the actuator to execute a recovery operation process of the discharge performance of the discharge port,
When the volume changing operation is executed such that T = To (To> 0) with respect to the time T from when the actuator starts changing the volume of the pressure chamber from V1 to V2 until it starts to return to V1. The discharge speed of the liquid discharged from the discharge port has a maximum and maximum characteristic,
The recovery operation process
After causing the pressure changing means to perform a pressure lowering operation for depressurizing the interior space within a range in which liquid is not discharged from the discharge port in which a liquid meniscus is formed, T> To and the liquid from the discharge port A recording apparatus comprising: processing for causing the actuator to perform the volume changing operation within a range where no ink is discharged. The liquid discharge head has a plurality of the discharge ports,
The apparatus further comprises performance deterioration information acquisition means for acquiring information for determining a discharge port group composed of one or a plurality of the discharge ports including the discharge port in which the discharge performance has decreased.
In the recovery operation process, based on the information acquired by the performance deterioration information acquisition unit, only the actuator corresponding to the discharge port group in which the discharge failure has occurred is T> To and liquid is discharged from the discharge port group. The recording apparatus according to claim 1, wherein the volume changing operation is executed within a range not to be performed. The performance deterioration information acquisition means acquires information for specifying the discharge port where the discharge performance has decreased,
In the recovery operation process, only the actuator corresponding to the discharge port specified by the information acquired by the performance deterioration information acquisition unit is T> To, and the volume changing operation is performed in a range where liquid is not discharged from the discharge port. The recording apparatus according to claim 2, wherein: In the recovery operation process,
Based on the information acquired by the performance deterioration information acquisition means, the actuators corresponding to the discharge ports other than the discharge port group in which the discharge failure has occurred satisfy 0 <T <To and no liquid is discharged from the discharge ports. The recording apparatus according to claim 2, wherein the volume changing operation is executed in a range. In the recovery operation process,
The recording apparatus according to claim 1, wherein the actuator performs the volume changing operation so that 1.5 * To <T <2.5 * To. In the recovery operation process,
The recording apparatus according to claim 1, wherein the actuator executes the volume changing operation a plurality of times after the pressure changing operation is executed by the pressure changing unit.   The cross section of the liquid channel along a plane orthogonal to the discharge direction in the vicinity of the discharge port is changed so as to become smaller toward the discharge port. The recording device according to item. The recording apparatus according to any one of claims 1 to 7, wherein a plurality of the discharge ports are formed in the liquid discharge head, wherein the discharge performance of the discharge port is recovered.
The recording apparatus ejecting liquid from each of the plurality of ejection openings to a recording medium to form an inspection pattern on the recording medium;
Based on the inspection pattern formed on the recording medium, the step of identifying a discharge performance of the plurality of discharge ports is reduced;
After the recovery operation control means causes the pressure changing means to execute the pressure lowering operation, only T> To and only the actuator corresponding to the discharge port identified as having a reduced discharge performance. And a step of executing the volume changing operation in a range in which liquid is not discharged from the outlet. A discharge port for discharging liquid, a liquid channel for supplying liquid to the discharge port, a pressure chamber provided in the middle of the liquid channel, and a volume of the pressure chamber changed from V1 to V2 larger than V1 Then, a liquid discharge head having an actuator that discharges liquid from the discharge port by performing a volume changing operation to return to V1;
Liquid storage means for storing liquid;
Liquid inflow means for causing the liquid in the liquid storage means to flow into the liquid flow path;
A recovery operation control unit that controls the liquid inflow unit and the actuator to execute a recovery operation process of the discharge performance of the discharge port;
When the volume changing operation is executed such that T = To (To> 0) with respect to the time T from when the actuator starts changing the volume of the pressure chamber from V1 to V2 until it starts to return to V1. The discharge speed of the liquid discharged from the discharge port has a maximum and maximum characteristic,
The recovery operation process
The volume changing operation in a range where T> To and no liquid is discharged from the discharge port after the liquid flows into the liquid flow path to the liquid inflow means at a pressure in a range where the liquid is not discharged from the discharge port. The recording apparatus characterized by including the process which makes the said actuator perform.

Images