JP2011212932A - Inkjet recording apparatus and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce maculature and to enhance reliability of continuous drawing record in an inkjet recording apparatus.SOLUTION: In an inkjet recording apparatus, discharge for abnormality detection is performed by applying a waveform for abnormal nozzle detection, a waveform different from a driving signal of a recording waveform which is applied when a target image is drawn/recorded on a recording medium, wherein an abnormal nozzle is made undeliverable on the basis of the discharge result, with correction performed with a nozzle other than the abnormal nozzle. After discharge is done for abnormal nozzle detection, before the target image is drawn/recorded, an implement for performing dischargeability recovery operation is provided. For example, recovery discharge is performed by applying a waveform that increases a discharging force more than a recording waveform or a waveform that makes stable discharge possible. Discharge may be implemented based on specific recovery image data. Also, a mode for cleaning a nozzle surface is possible in which nozzle surface is flooded with a washing liquid from a recovery hole of a nozzle surface and in which an adhesion liquid of the nozzle surface is recovered from the recovery hole together with the washing liquid.

Description

  The present invention relates to an inkjet recording apparatus and a recording method, and in particular, a technique for detecting ejection failure (such as flying bend, droplet volume abnormality, splash, non-ejection) occurring in an inkjet head having a large number of nozzles (droplet ejection ports). In addition, the present invention relates to a technique for suppressing a reduction in image quality caused by the abnormal nozzle.

  An inkjet apparatus that forms an image by ejecting a functional material (hereinafter also referred to as “ink”) onto a recording medium using an inkjet head is environmentally friendly and can record on various recording media at high speed. Further, it has features such as a high-definition image that is difficult to bleed.

  However, in the ink jet recording, ejection failure occurs with a certain probability for the nozzles in the head, and streak unevenness and density unevenness occur at the image position corresponding to the defective nozzle. Such a discharge failure that leads to a reduction in image quality leads to an increase in the number of waste papers and a reduction in throughput due to the execution of head maintenance.

  In particular, in a single pass method in which drawing is performed by one recording scan, ejection failure of one nozzle greatly affects the overall image quality. Further, in the single-pass method in which productivity is important, since the inkjet head is always on the recording medium, it is difficult to perform head maintenance during the drawing operation.

  Causes of ejection failure in the ink jet head include a decrease in ejection force due to bubbles mixed in the inside of the nozzle, adhesion of foreign matter near the nozzle, abnormal liquid repellency near the nozzle, abnormal nozzle shape, and the like. In addition, the nozzles that have failed to discharge are likely to generate ink mist due to unstable discharge, and this mist may also cause the surrounding normal nozzles to become defective. Various countermeasures such as degassing of ink (Patent Document 1) and suction of ink mist (Patent Document 2) have been proposed as countermeasures for suppressing the occurrence of ejection failure. However, it is difficult to completely prevent ejection failure.

  In order to solve this problem, methods for detecting in advance nozzles that are likely to cause ejection failures have been studied (Patent Documents 3 and 4). Japanese Patent Application Laid-Open No. 2003-228620 describes that a non-ejection nozzle is detected at a maintenance position outside the drawing area using a waveform different from the recording waveform, and maintenance is performed when non-ejection is detected.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a technique for detecting nozzles that are abnormally discharged and performing correction using surrounding normal nozzles.

Japanese Patent Laid-Open No. 5-17712 JP-A-2005-205766 JP 2003-205623 A JP 11-348246 A

  However, the technique disclosed in Patent Document 3 has a configuration in which the print head is moved to a maintenance position outside the drawing area, and non-ejection nozzle detection and maintenance are performed at the maintenance position. Further, there is no description regarding the detection of ejection failures other than non-ejection (flying bending, splash), and no specific detection waveform is disclosed.

  The technique of Patent Document 4 is a high-resolution imaging device (CCD) that can accurately read the landing of ink droplets, a means that can observe the flying state of ink droplets, etc., in order to detect abnormal ejection that is visually recognized. Expensive detection means is necessary and detection time is also required. Furthermore, since the abnormality detection by this technique cannot be performed during drawing, the throughput is reduced.

  As described above, it has been difficult to achieve both recording stability and throughput with the conventionally proposed technology. In addition, there is a possibility that a defective image is output (damaged paper is generated) during a time lag period from when the abnormal discharge detection result is obtained until non-discharge correction is applied based on the detection result.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ink jet recording apparatus and a recording method capable of reducing waste paper and improving the reliability of drawing recording and the stability of recording quality. And In this specification, the term “scrap paper” is used for convenience, but in the application of the present invention, the material of the recording medium (recording material) is not limited to “paper”. In addition to paper, recording media of various materials such as resin, metal, silicon (Si), and glass can be used.

  In order to achieve the above object, the following invention modes are provided.

  (Invention 1): An inkjet recording apparatus according to Invention 1 includes an inkjet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to each nozzle are provided, a conveying unit that conveys a recording medium, Recording waveform signal generating means for generating a recording waveform drive signal applied to the pressure generating element when a target image is drawn and recorded on the recording medium by the inkjet head, and detecting an abnormal nozzle of the inkjet head An abnormal nozzle detection waveform signal generating means for generating a drive signal of an abnormal nozzle detection waveform having a waveform different from the recording waveform when performing ejection for performing, and a head position capable of being ejected onto the recording medium Applying the abnormal nozzle detection waveform drive signal to the pressure generating element with the inkjet head disposed A discharge control means for detection that causes discharge for abnormality detection from the nozzle, an abnormal nozzle detection means for specifying an abnormal nozzle that indicates discharge abnormality from the discharge result for abnormality detection, and discharge of the specified abnormal nozzle Correction control means for correcting the image data so as to draw and record a target image with a nozzle other than the abnormal nozzle, and ejection from nozzles other than the abnormal nozzle according to the image data corrected by the correction control means A recording discharge control means for controlling drawing and recording operation, and an operation for recovering the discharge performance of the ink jet head after the abnormality detection discharge is performed and before drawing and recording the target image. Recovery means to perform.

According to the present invention, an abnormal nozzle detection waveform is used in an early stage before an image defect in which density unevenness (streaks unevenness) due to ejection failure is visually recognized in an output image drawn and recorded by a recording waveform drive signal. The occurrence of abnormal discharge is detected. Detect abnormal nozzles that are becoming poorly discharged early, and before they appear as defects in the output image, discharge the abnormal nozzles (discontinue discharge), and the effects of image quality degradation due to the abnormal discharge of these abnormal nozzles. Correct with surrounding normal nozzles.
Thereby, the recording stability can be maintained, and continuous recording with little loss of paper becomes possible.

  In particular, in the present invention, after the ejection for detecting an abnormality, the ejection recovery operation is performed before the ejection (drawing recording ejection) for drawing and recording a desired image (target image). As a result, it is possible to recover the discharge performance of the nozzle whose discharge performance has deteriorated due to the abnormality detection discharge, and to maintain the discharge performance for at least a certain time (temporarily).

  According to the present invention, it is possible to reduce the waste paper generated in the time lag from abnormality detection until the non-ejection correction works effectively, and it is possible to improve the reliability of continuous printing.

  Further, in the present invention, an abnormal nozzle is detected at a head position (drawable area) that can be ejected onto a recording medium without retracting an inkjet head (hereinafter sometimes referred to simply as “head”) to a maintenance position or the like. Since the discharge performance can be recovered, a decrease in throughput can be avoided.

  (Invention 2): An ink jet recording apparatus according to Invention 2, in Invention 1, wherein the recovery means applies a recovery waveform drive signal different from the recording waveform or the detection waveform to the pressure generating element. It is characterized by having a recovery discharge control means for performing recovery discharge.

  The recovery waveform is preferably a waveform that enhances the ejection force (ejection speed) or a waveform that enables stable ejection compared to a recording waveform for drawing and recording a desired image. By using such a waveform, the effect of recovering the discharge property is enhanced.

  (Invention 3) The inkjet recording apparatus according to Invention 3 is characterized in that, in Invention 2, the recovery waveform is a waveform having a larger potential difference than the recording waveform.

  Increasing the drive voltage tends to increase the ejection force, and increasing the ejection force (ejection speed) increases the effect of discharging thickened ink. However, if the drive voltage is set too high, mist and satellites (sub-droplets) increase and the discharge performance deteriorates. Therefore, from the viewpoint of achieving both enhanced recovery effect and good discharge performance, drive for recovery discharge The signal voltage is preferably 1.1 to 1.6 times the voltage of the recording waveform, and more preferably 1.2 to 1.5 times.

(Invention 4): In the inkjet recording apparatus according to Invention 4, in the invention 2 or 3, the recovery waveform is obtained by dividing the wavelength (period T ₀ ) of the recording waveform by an integer N (where N ≧ 2). It is a waveform in which pulses are applied at intervals.

  According to this aspect, the apparent frequency can be increased by N times, and ejection can be performed in a region where the frequency characteristics are stable. By continuing such stable discharge, the discharge property can be recovered.

  (Invention 5): The ink jet recording apparatus according to Invention 5 is the ink jet recording apparatus according to any one of Inventions 2 to 4, wherein the droplets ejected by applying the recovery waveform drive signal are adhered to the recording medium. It is characterized by.

  Continuous drawing with little loss of paper without lowering throughput by moving the head to a maintenance position outside the recording medium and performing abnormal nozzle detection and recovery operations at the head position where ejection is possible on the recording medium. Output is possible.

  (Invention 6): The ink jet recording apparatus according to Invention 6 is the inkjet recording apparatus according to Invention 1, wherein the recovery means performs ejection based on recovery image data representing a predetermined recovery drawing pattern, and the recovery medium is recorded on the recording medium. It has a recovery pattern formation control means for forming a drawing pattern.

  As recovery image data, discharge characteristics are restored by pre-determining a specific pattern that is less affected by crosstalk and expected stable discharge, and performing discharge according to the specific recovery image data. Can be made. According to this aspect, the ejection for recovery of the present invention can be carried out with only the commanded image data without adding any improvement to the apparatus, such as addition of waveform data or addition of waveform generation means.

  (Invention 7): In the inkjet recording apparatus according to Invention 7, in the invention 6, the recovery drawing pattern is a pattern having a coverage of 10% or less, and discharge is performed with respect to the nozzle on which the abnormality detection discharge has been performed. It is characterized by being.

  From the viewpoint of performing stable ejection while suppressing the influence of crosstalk, for example, a pattern in which dots are sparsely distributed with a coverage (coverage ratio, image area ratio) of 10% or less can be employed.

  Note that it is preferable that the recovery image data is determined so that the recovery discharge is performed for all the nozzles that have been subjected to the abnormality detection discharge. If it is difficult to perform abnormality detection ejection and recovery ejection for all nozzles on a single recording medium, divide the nozzles into multiple nozzle groups, and divide the recording medium into groups for ejection and recovery for abnormality detection. Discharging may be performed.

  (Invention 8): The inkjet recording apparatus according to Invention 8 is the inkjet recording apparatus according to Invention 6, wherein the recovery drawing pattern is a ratio of the number of nozzles simultaneously ejected from the nozzle groups connected to the same flow path in the inkjet head. The simultaneous drive rate shown is a pattern that is 10% or less.

  In general, an inkjet head tends to cause crosstalk when the number of simultaneous ejections of nozzles belonging to the same flow path is large. Therefore, in order to suppress the influence of crosstalk and perform stable discharge, it is preferable that the simultaneous drive rate of the nozzles in the same flow path be 10% or less.

  (Invention 9): The inkjet recording apparatus according to Invention 9, in Invention 1, the recovery means includes a nozzle surface cleaning means for cleaning the nozzle surface provided with the plurality of nozzles of the inkjet head, The nozzle surface cleaning means is provided on the nozzle surface, and a recovery hole for recovering the adhering liquid adhering to the nozzle surface, and the recovery liquid overflows the nozzle surface from the recovery hole, and the overflowed And a recovery means for recovering the recovery liquid from the recovery hole together with the adhering liquid.

  According to this aspect, the recovery liquid overflowing from the recovery hole to the nozzle surface is bonded (unified) with the adhesion liquid around the recovery hole by surface tension. Thereafter, the collected liquid and the attached liquid are collected together from the collection hole, whereby the attached liquid can be collected (removed) from the nozzle surface. As a result, it is possible to improve (recover) the deterioration of the discharge performance caused by the attached liquid adhering to the nozzle surface.

  (Invention 10): The inkjet recording apparatus according to Invention 10 is characterized in that, in Invention 9, the adhesion liquid is collected by the nozzle surface cleaning means at a position where the inkjet head faces the recording medium.

  The cleaning operation by the nozzle surface cleaning means can be performed at a head position (drawable area) that can be ejected onto the recording medium without retracting the head to a maintenance position outside the recording medium. Therefore, without interrupting continuous drawing and recording, on a non-image area (margin portion) of the recording medium, between recording media (between sheets), or during a recording ejection operation (during drawing and recording of the image portion), etc. The nozzle surface can be cleaned at an appropriate timing.

  (Invention 11): The inkjet recording apparatus according to Invention 11 is the inkjet recording apparatus according to any one of Inventions 1 to 10, wherein the target image is drawn and recorded in an image forming area on the recording medium, and the image on the recording medium is recorded. The abnormality detection ejection is performed in a non-image area other than the formation area.

  There is a mode in which an abnormal nozzle is specified by reading a pattern or the like formed in a non-image area on a recording medium by an abnormality detection discharge by using an optical sensor or the like, and analyzing and measuring it. There is also an aspect in which an abnormal nozzle is identified by detecting a droplet in flight by ejection for detecting an abnormality with an optical sensor or the like, and analyzing and measuring the detection signal.

  (Invention 12): The ink jet recording apparatus according to Invention 12 is the invention 11, wherein at least one of the test pattern for detecting abnormal nozzles and the test pattern for correcting density unevenness is formed in the non-image area on the recording medium. Is formed.

There is a mode in which test pattern output control means for outputting each of these test patterns is provided, and any one of the test patterns is selectively output as necessary. For example, during the process of continuously drawing and recording (continuous printing) an image to be output, the presence or absence of abnormal nozzles is constantly monitored while forming a test pattern for detecting abnormal nozzles in a non-image area of the recording medium. When abnormal nozzles are detected during monitoring during recording, density unevenness is detected in the non-image area of the recording medium in order to obtain density data necessary for correction processing that improves the influence of the ejection failure processing of the abnormal nozzles. A test pattern for correction is formed. Then, this test pattern is read, and based on the read result, the image data is corrected so that the required image quality can be achieved with only nozzles other than the abnormal nozzle. Thereafter, drawing recording is performed in accordance with the corrected data. The drawing and recording of the target image can be continued in accordance with the data before correction after the occurrence of the abnormal nozzle is detected until the drawing is switched to the corrected data, and the occurrence of damaged paper can also be suppressed.
(Invention 13): The inkjet recording apparatus according to Invention 13 is characterized in that, in Invention 11 or 12, the abnormal nozzle detection waveform is a waveform that lowers the ejection speed than the recording waveform.

  According to this aspect, since the ejection force at the time of ejection for detecting an abnormal nozzle is weaker than the ejection force at the time of drawing and recording an image using the recording waveform, bubbles are mixed into the nozzle, This is highly effective for detecting abnormal discharge due to abnormal factors inside the nozzle, such as adhesion of foreign matter and reduction in volume deformation of the pressure chamber.

  As a waveform for lowering the ejection speed than the recording waveform, a waveform having a smaller potential difference than the recording waveform, a waveform with a pulse width changed compared to the recording waveform pulse, and a comparison with the recording waveform pulse Then, a waveform in which the slope of the pulse is changed, and a waveform obtained by adding a pre-pulse having a potential difference of not discharging (Tc / 2) × n before applying the discharge pulse when the head resonance period is Tc (however, n is a natural number), and at least one waveform can be used. The waveform exemplified here can lower the ejection speed than the recording waveform. It is also possible to appropriately combine the waveform characteristics exemplified here.

  (Invention 14) In the ink jet recording apparatus according to Invention 14, in any one of Inventions 11 to 13, the abnormal nozzle detection waveform has a larger amount of liquid rising from the nozzle than the recording waveform. It is a waveform.

  According to this aspect, there is an effect on detection of ejection failure due to an abnormal factor outside the nozzle, such as adhesion of ink mist or paper dust.

  As a waveform in which the amount of liquid rising from the nozzle is larger than the recording waveform, a waveform having a larger potential difference than the recording waveform, a waveform obtained by adding a signal element that contracts the pressure chamber to the extent that ejection is not performed, before ejection, When the head resonance period is Tc, a waveform in which two pulses obtained by adding a signal element that contracts the pressure chamber to such an extent that ejection is not performed before ejection is continuously applied at a time interval of Tc × n (where n is a natural number) ) Before applying a discharge pulse, a waveform that applies another pulse with a potential difference that does not discharge, or when the pulse is applied alone, the first pulse that does not discharge normally is applied and the liquid overflows from the nozzle It is possible to use at least one of the waveforms in which ejection is performed by applying the subsequent second pulse after the discharge. With the waveform illustrated here, the amount of liquid rising from the nozzle can be made larger than that of the recording waveform. It is also possible to appropriately combine the waveform characteristics exemplified here.

  (Invention 15): The inkjet recording method according to Invention 15 is for drawing and recording a target image on a recording medium by an inkjet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to each nozzle is provided. A recording waveform signal generating step for generating a recording waveform drive signal to be applied to the pressure generating element when performing a discharge, and a waveform different from the recording waveform when performing ejection for detecting an abnormal nozzle of the inkjet head An abnormal nozzle detection waveform signal generating step for generating an abnormal nozzle detection waveform drive signal, and driving the abnormal nozzle detection waveform in a state where the inkjet head is disposed at a position where the ink can be ejected onto the recording medium. Discharge control process for detection for applying a signal to the pressure generating element and discharging discharge for abnormality from the nozzle , An abnormal nozzle detection process for specifying an abnormal nozzle that indicates a discharge abnormality from the discharge result for abnormality detection, and the discharge of the specified abnormal nozzle is stopped, and a target image is drawn and recorded by a nozzle other than the abnormal nozzle A correction control step for correcting the image data, a recording discharge control step for controlling the discharge from the nozzles other than the abnormal nozzles according to the image data corrected by the correction control step, and drawing recording, and the abnormality detection And a recovery step of performing an operation of recovering the ejection performance of the inkjet head before performing drawing and recording of the target image.

  As specific contents in the recovery step, the same means and steps (operations and processes) as the means described in each section of the inventions 2 to 14 can be applied.

  According to the present invention, it is possible to achieve reduction in waste paper and improvement in reliability.

Enlarged view of the nozzle section schematically showing the cause of ejection failure Waveform diagram showing an example of drive signal for recording waveform Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle internal factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle external factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle external factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle external factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle external factors Waveform diagram showing an example of abnormal nozzle detection waveform suitable for detection of nozzle external factors Top view of paper Waveform diagram showing examples of drive signals for recording waveforms Waveform diagram showing examples of recovery waveform drive signals Waveform diagram showing examples of recovery waveform drive signals A diagram showing an example of recovery image data A diagram showing an example of recovery image data Cross-sectional view of an inkjet head having nozzle surface cleaning means The figure which shows the example of the arrangement pattern of the nozzle and collection | recovery hole in the head of FIG. The figure which shows the example of the arrangement pattern of a nozzle and a recovery hole The figure which shows the example of the arrangement pattern of a nozzle and a recovery hole Diagram showing configuration of ink circulation system and recovery device Explanatory drawing which shows a mode that the adhesion ink adhering to a nozzle surface is collect | recovered Explanatory drawing which shows a mode that the adhesion ink which covered the nozzle is collect | recovered 1 is a configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. Plane perspective view showing structural example of head Plane perspective view showing another structural example of the head 250 Sectional drawing which follows the AA line in FIG. Plane perspective view showing an example of the flow path structure inside the head Schematic diagram showing another example of the flow path structure inside the head Main block diagram showing the system configuration of the inkjet recording apparatus of this example Configuration diagram of inline detector Explanatory drawing showing an example of test chart formation 6 is a flowchart showing a sequence of unevenness correction in the ink jet recording apparatus according to the embodiment of the present invention. Flow chart showing pre-correction sequence Plan view showing an example of a test chart for detecting defective on-line discharge Plan view showing test chart for concentration measurement The flowchart which shows the detail of the correction process of the image data in step S38 of FIG. The figure for demonstrating the detail of the correction process of the density data in step S118 of FIG. The figure for demonstrating the detail of the calculation process of the density nonuniformity correction value in step S120 of FIG. The figure for demonstrating the detail of the process in step S122 of FIG. The figure which shows other embodiment regarding the correction process of the density data in step S118 of FIG. Flowchart showing another example of unevenness correction

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Cause of ejection failure>
First, the cause of ejection failure will be considered. FIG. 1 is an enlarged view of the nozzle portion schematically showing the cause of ejection failure. In FIG. 1, reference numeral 1 denotes a nozzle, 2 denotes ink filled in the nozzle 1, and 3 denotes a meniscus (gas-liquid interface). FIG. 2A shows a state where bubbles 4 are mixed in the ink 2 in the nozzle 1. The nozzle 1 communicates with a pressure chamber (not shown), and the pressure chamber is provided with a piezoelectric element (piezoactuator) as pressure generating means. By driving the piezoelectric element to change the volume of the pressure chamber, droplets are ejected from the nozzle 1. At this time, if bubbles 4 are present in the nozzle 1, the pressure is absorbed by the bubbles 4 or the flow of liquid is hindered, resulting in ejection failure.

  FIG. 1B shows a state in which the foreign material 5 adheres to the inner wall surface of the nozzle 1. When the foreign matter 5 adheres to the inside of the nozzle, the foreign matter 5 obstructs the flow of the liquid and causes ejection defects such as flying bends.

  FIG. 1 (c) shows a case where foreign matter 6 is attached in the vicinity of the nozzle hole outside the nozzle 1. When foreign matter 6 adheres to the vicinity of the nozzle outside the nozzle, the liquid comes into contact with the foreign matter 6 and the axial symmetry of the meniscus is lost, which causes discharge failure such as flying bend.

  In the case of a partial decrease in liquid repellency in the vicinity of the nozzle on the nozzle surface 1A (for example, peeling of the liquid repellent film) instead of the adhesion of the foreign matter 6, this is the same as in FIG. Examples of the foreign substances 5 and 6 include agglomerates of ink components, dried substances, paper powder, dust, ink mist, and residues that remain unintentionally in the head manufacturing process.

<Detection method of abnormal nozzle>
As shown in FIG. 1, the causes of ejection failure are roughly divided into the nozzle internal factors described in (a) and (b) and the nozzle external factors described in (c). In the case where bubbles 4 or foreign substances 5 are present in the nozzle (abnormal nozzle due to nozzle internal factor), if the ejection force is reduced, ejection failure due to the nozzle internal factor is promoted. That is, the influence of the bubbles 4 and the foreign matter 5 is exerted by driving to reduce the ejection speed by reducing the displacement amount of the piezoelectric element or applying pressure fluctuation at a frequency shifted from the head resonance frequency. This is more remarkably reflected in the discharge result. As a result, undischarge is promoted or the amount of bending of the flying curve is amplified.

  On the other hand, if there is foreign matter 6 or poor liquid repellency outside the nozzle, the ink overflows from the hole of the nozzle 1 (pumps the ink), and the ink contacts the foreign matter 6 or poor liquid repellency outside the nozzle. By doing so, ejection failure due to external factors of the nozzle is promoted.

  In the present embodiment, when a discharge failure is detected, a test pattern is drawn using a drive signal having a waveform that promotes the discharge failure separately from the drive waveform for drawing recording, and the print result is measured. That is, even when the piezoelectric element is driven using the ejection drive waveform at the time of normal drawing, even if there is a state of bubbles 4 or foreign substances 5 and 6 at a level that does not appear (cannot be detected) as ejection failure. By using a detection waveform that promotes and amplifies the ejection failure, it can be expressed as a detectable failure. As a result, it is possible to detect an ejection failure at an initial stage level that cannot be recognized as an ejection failure in the drawing recording drive waveform at an early stage.

  A specific waveform example will be described below.

(About drive waveforms during drawing and recording)
FIG. 2 is an example of an ejection drive waveform (hereinafter referred to as “recording waveform”) during normal drawing and recording. Here, in order to simplify the description, a so-called pull-push type drive waveform is illustrated. However, in the implementation of the present invention, the form of the drive waveform is not particularly limited, and a pull-push-pull waveform and other various drive waveforms can be used.

  The driving signal of the recording waveform 10 shown in FIG. 2 drives the first signal element 10a that outputs a reference potential for maintaining the volume of the pressure chamber in a steady state, and drives the piezoelectric element in the direction of expanding the pressure chamber from the steady state. A second signal element (pulling waveform section) 10b that performs, a third signal element 10c that maintains the pressure chamber in an expanded state, and a fourth signal element (pushing waveform section) that drives the piezoelectric element in a direction to compress and compress the pressure chamber. 10d.

  That is, the first signal element 10a is a waveform part that maintains the reference potential, and the second signal element 10b is a falling waveform part that lowers the potential from the reference potential. The third signal element 10c is a waveform part that maintains the potential lowered by the second signal element 10b, and the fourth signal element 10d is a rising waveform part that raises the potential of the third signal element 10c to the reference potential.

Pulse interval of the pull-push waveform, it is preferable to match the head resonance period (Helmholtz resonance vibration period) Tc, the pulse width Tp is that the head resonance period natural number fraction of (Helmholtz natural oscillation period) T _C Is desirable. The head resonance period refers to the natural period of the entire vibration system determined from the ink flow path system, ink (acoustic element), dimensions, materials, physical properties, etc. of the piezoelectric element.

(Example of abnormal nozzle detection waveform suitable for detecting defects in nozzle internal factors)
When detecting an abnormal nozzle, a special waveform (referred to as “abnormal nozzle detection waveform”) different from the recording waveform described in FIG. 2 is used to promote and amplify the ejection failure, thereby detecting sensitivity and accuracy. To improve.

  Examples of abnormal nozzle detection waveforms suitable for detecting abnormal nozzles caused by internal nozzle factors are shown in FIGS.

  In FIG. 3, the potential difference Vpp (difference between the maximum value and the minimum value of the voltage waveform) is smaller than that of the recording waveform of FIG. It is preferable to reduce the potential difference of the recording waveform by 10% or more, and more preferable to decrease in the range of 15% to 25%.

  In FIG. 4, the pulse width Tp is changed as compared with the recording waveform of FIG. It is preferably increased or decreased by 10% or more with respect to the pulse width of the recording waveform, and more preferably increased or decreased in the range of 20% to 50%.

  The ink jet head has a pulse width that can be stably discharged due to the flow path structure and the physical properties of the liquid used. The pulse width of the recording waveform is determined to be a pulse width that enables stable ejection. On the other hand, in the abnormal nozzle detection waveform, in order to weaken the ejection force, a waveform with a changed pulse width is used.

  In FIG. 5, the slope of the pulse waveform (the slope of the rise of the fourth signal element 10d) is changed as compared with the recording waveform of FIG. It is preferable to increase or decrease the slope by 20% or more with respect to the slope of the recording waveform, and more preferably to increase or decrease within the range of 50% to 200%.

  FIG. 6 shows an example in which a waveform signal (pre-pulse) that weakens the ejection force is applied before the ejection pulse 12. When the head resonance frequency is 1 / Tc, a pulse with a small potential difference (a weak pulse that cannot be ejected from the nozzle only by applying this pulse) is applied to (Tc / 2) × n before the ejection pulse 12 (Where n is a natural number).

  The pre-pulse 14 includes a waveform portion (fifth signal element 14a) that lowers the potential from the reference potential, a sixth signal element 14b that maintains the potential lowered by the fifth signal element 14a, and the potential of the sixth signal element 14b. A seventh signal element that raises to a reference potential. The vibration wave generated by the application of the pre-pulse 14 inhibits the subsequent drawing of the ejection pulse 12 (the drawing operation by the first signal element 10a), and the ejection force by the ejection pulse 12 is reduced. That is, by applying the pre-pulse 14, the meniscus in the nozzle is once drawn into the nozzle and then pushed out so as to rise out of the nozzle. At the timing when this vibration remains and the meniscus is drawn again and pushed out, the drawing signal element (10a) of the next ejection pulse 12 is added. For this reason, the pulling operation of the pull-in signal element (10a) overlapping the swell operation of the residual vibration of the prepulse 14 is hindered, and the ejection force is weakened. In addition, the structure demonstrated in FIGS. 3-6 can also be combined suitably.

(Example of abnormal nozzle detection waveform suitable for detecting defects of nozzle external factors)
Next, examples of abnormal nozzle detection waveforms suitable for detecting abnormal nozzles caused by nozzle external factors are shown in FIGS.

  In FIG. 7, the potential difference Vpp (difference between the maximum value and the minimum value of the voltage waveform) is larger than that of the recording waveform of FIG. It is preferable to increase the potential difference of the recording waveform by 10% or more.

  In FIG. 8, before the drawing signal element (reference numeral 10b) of the ejection pulse 20, the pressure chamber is contracted and the signal element (reference numeral 10e) for raising ink from the nozzle (expanding ink) and its potential are maintained. This is an example in which a signal element 10f is added.

  By these signal elements 10e and 10f, the ink rises from the nozzle before ejection, and the ink can come into contact with the foreign matter 6 and the like outside the nozzle.

  In addition to the waveform of FIG. 8, FIG. 9 further applies the ejection pulse 20 at a time interval of n × Tc. According to the configuration of FIG. 9, ink can be further raised from the nozzle by the pressure chamber contraction signal element (10e) before the next ejection by the residual vibration generated by the application of the previous ejection pulse 20. By adding an extrusion operation at a timing that is an integral multiple of the vibration period Tc, vibration can be amplified.

  In FIG. 10, a pre-pulse 22 having a small potential difference is applied before the ejection pulse 20. The pre-pulse 22 is applied at a timing “n × Tc” before the ejection pulse 20. The pre-pulse 22 includes a pushing signal element (eighth signal element) 22a that raises the potential from the reference potential to contract the pressure chamber, a ninth signal element 22b that maintains the potential raised by the eighth signal element 22a, And a tenth signal element 22c for returning the potential of the ninth signal element 22b to the reference potential. The ink cannot be ejected from the nozzle only by applying the prepulse 22 alone.

  By causing the vibration wave generated by the application of the prepulse 22 to resonate with the vibration caused by the ejection pulse 20 that follows, that is, the swell from the nozzle can be amplified by the residual vibration of the prepulse.

  In FIG. 11, before the ejection pulse 20, a first pulse 24 that is not normally ejected alone (for example, ejection speed is 4 m / s or less) is applied, and the first pulse 24 causes ink to overflow. After that, ejection is performed with the subsequent second pulse (reference numeral 20). The potential difference Va of the first pulse 24 is adjusted to a value smaller than the potential difference of the second pulse 20.

In addition, a mode in which ink is swelled from the nozzle and a discharge speed is slower than the drawing waveform is also possible. By adjusting the voltage of the “waveform that causes ink overflow” illustrated in FIGS. 7 to 11, it is possible to obtain a waveform that reduces ejection force and generates swell.
As a result, it is possible to detect and promote the ejection failure caused by the internal and external factors of the nozzle.

  As described with reference to FIGS. 3 to 11, a test pattern (also referred to as “test chart”) is ejected using a special waveform (abnormal nozzle detection waveform) different from the drive waveform for drawing and recording. The presence or absence of abnormal nozzles is detected from the test chart printing results.

  This abnormal nozzle detection can amplify the degree of abnormality in the nozzle as compared with the recording waveform. Therefore, it is possible to detect an abnormality at an early stage before a recording failure occurs during drawing / recording using the recording waveform. In addition, detection with a low-resolution detector is possible, and high-speed detection and high-sensitivity detection are possible.

  In addition, by detecting abnormal nozzles using multiple types of abnormal nozzle detection waveforms corresponding to both internal and external nozzle failure causes, high-sensitivity detection of ejection failures due to each failure cause is possible. Is possible.

(About test pattern drawing position on paper)
The test pattern according to the present embodiment may be formed at any position on the paper. However, when detecting abnormal nozzles while executing printing of a plurality of sheets, a print target image (actual image) is drawn. It is preferable to form a test pattern in a blank portion (referred to as “non-drawing area” or “non-image portion”) outside the image forming area (referred to as “drawing area” or “image portion”).

  As shown in FIG. 12, it is possible to record all or part of the test pattern in the image forming area (drawing area) 42 on the paper 40. However, the paper is wasted and the effective printing speed ( Throughput) also decreases. On the other hand, in the image forming area 42, a target image (corresponding to a “desired image”) is drawn, and the outer margins (“non-image forming areas”) 44A, 44B, 46A, 46B are tested. By recording all or part of the pattern, paper waste can be reduced and throughput can be improved. After the target image is drawn and recorded in the image forming area 42, the image is cut along the cutting line 48, the surrounding non-image portion is removed, and the image portion of the image forming area 42 is left as a printed product.

  In particular, in the case of an ink jet printing apparatus that performs single-pass drawing using a page wide head (full line type head) having a nozzle row corresponding to the entire width of the image forming area 42, a margin portion (44 </ b> A) on the leading end side of the paper 40. ) And the trailing edge side blank portion (44B), it is preferable to record all or part of the test pattern.

  A test chart is formed on the non-image portion (44A, 44B, etc.) of the paper 40 using the abnormal nozzle detection waveform before the start of the print job (JOB) for drawing the target image or during the execution of the print job. Then, the abnormal nozzle can be detected from the print result of the test chart. When an abnormal nozzle is detected, the use of the abnormal nozzle is stopped and the image data is corrected so that a good image can be output only with the remaining normal nozzles. Based on the corrected image data, the target image is corrected. Printing can be continued. In this way, an abnormal nozzle is discovered and dealt with early before a problem occurs in drawing recording of the image portion using the drive signal of the recording waveform, and continuous recording (continuous printing) becomes possible. In other words, before an actual malfunction occurs in the drawing of the image area, an abnormal nozzle that is likely to cause ejection failure is detected at an early stage, and this is subjected to an ejection failure process, and the remaining nozzles compensate for the effects of the ejection failure. The image data is corrected as follows. For this reason, it is possible to continue printing while avoiding the occurrence of lost paper and a decrease in throughput with respect to problems occurring during continuous recording.

  FIG. 12 shows an example (an example in which the sheet is conveyed in a direction parallel to the short side of the sheet) in which the sheet is conveyed with the long side of the rectangular sheet orthogonal to the sheet conveyance direction. Is not limited to this. For example, the sheet may be rotated 90 degrees in FIG. 12 and conveyed in the direction of the sheet with the short side of the sheet orthogonal to the sheet conveying direction.

<Problem when using abnormal nozzle detection waveform>
In the method using the abnormal nozzle detection waveform described above, the waveform that deteriorates the discharge performance is used as the detection waveform, and the discharge performance is deteriorated in advance. there's a possibility that. In this case, the correction cannot be made in time, and as a result, it is expected that the waste paper cannot be reduced. To solve such problems, the following measures are taken. That is, a recovery means is provided for temporarily recovering the discharge performance after the abnormal nozzle detection discharge is performed and before the actual drawing recording is performed.

<Example of Recovery Means 1: Form of Applying Recovery Waveform Signal>
The ejection performance can be recovered by applying the recovery waveform drive signal after the ejection by applying the abnormal nozzle detection waveform described in FIGS. 3 to 11 and before the drawing of the image portion. FIG. 13A shows an example of a general recording waveform (drawing waveform) for comparison. Here, the continuous discharge by the rectangular wave is illustrated as in FIG. Since one discharge (one drop) is performed by pull-pushing a rectangular wave, FIG. 13A shows an example of three consecutive firings. The number of fires is not limited to this. Further, it is not necessary that the pulses are equally spaced, and the potential differences of the pulses need not be all equal.

In addition, the waveform illustrated in FIG. 13A is obtained by using only one pulse out of one wavelength (period T ₀ ) including three pulses, and a small dot is obtained when two pulses are used. When 3 pulses are used, a large dot with 3 drops is obtained.

  FIG. 13B shows a modification of the waveform shown in FIG. As shown in FIG. 13B, a waveform element portion (reference numeral 52) for suppressing reverberation may be added behind the waveform of the recording discharge shown in FIG.

  FIG. 14 is a first example of a recovery waveform signal. FIG. 14 shows a recovery waveform (dedicated waveform) specially devised with the intention of increasing the recovery effect. As is clear from comparison with FIG. 13A, the recovery waveform of FIG. 14 is a waveform having a larger potential difference Vpp than the normal drawing waveform.

  After the ejection due to the application of the abnormal nozzle detection waveform described in FIGS. 3 to 11, before the drawing of the image portion, the drive signal of the recovery waveform shown in FIG. 14 is generated in the non-image portion (margin portion) region. Application is performed, and recovery droplet ejection (continuous firing) is performed on the non-image area. This recovery droplet ejection applies a waveform having a larger potential difference Vpp compared to a normal drawing waveform and improves ejection energy (ejection speed), so that defects are promoted by application of the abnormal nozzle detection waveform. The ink around the nozzles is blown off with strong discharge energy, and the discharge performance is temporarily recovered.

  The term “temporarily” as used herein refers to a level that does not cause a loss of paper within a period until at least non-ejection correction involving non-ejection processing of the defective nozzle is effectively performed for a nozzle detected as a defective nozzle. This means that it is not required until the defective nozzles are completely normalized, as long as it is sufficient to restore the discharge performance and maintain the image quality. In other words, unlike full-scale maintenance (head pressurization, nozzle suction, wiping, etc.) that is performed by retracting the head out of the paper, the ejection performance is a temporary period until non-ejection correction is effective. This means that it is only necessary to be secured.

  As a condition of the potential difference Vpp (difference between the maximum value and the minimum value) at which a good recovery effect is expected, the recording waveform (1.1 to 1.6 times the potential difference of FIG. 13A), More preferably, the ratio is 1.2 times or more and 1.5 times or less, and if the potential difference is increased too much, mist and satellite increase, which may deteriorate the discharge performance. The upper limit of the potential difference is set, and the upper limit of the potential difference may be determined by a design other than the ejection property, in which case it is necessary not to exceed the upper limit determined by the design.

FIG. 15 is a second example of a recovery waveform signal. The recovery waveform in FIG. 15 is a waveform in which a pulse is applied at the timing of equally dividing the wavelength (period T ₀ ) in FIG. 13A (the potential difference is the same). That is, the ejection pulse interval (T ₂ ) in the waveform of FIG. 15 is an interval that divides the wavelength (period T ₀ ) of FIG. 13A into two equal parts (T ₂ = T _0/2 ). In this way, the apparent discharge frequency in the recovery discharge operation is doubled by using a waveform (recovery waveform) that applies a pulse at the timing of equally dividing the wavelength of the recording waveform (FIG. 13A). In addition, it is possible to perform ejection in a region where the frequency characteristics are stable. By continuing stable ejection, the ejection performance can be recovered.

Not limited to the waveform illustrated in FIG. 15, a waveform in which a pulse is applied at an interval obtained by dividing the wavelength (period T ₀ ) of the recording waveform by an integer N (where N ≧ 2) can be used as the recovery waveform.

  Note that the phenomenon in which the ejection stability changes depending on the ejection frequency is considered to be mainly caused by fluid interaction (crosstalk). That is, when a droplet is ejected from a nozzle, the meniscus in the nozzle will sway, but if it is low frequency driving that has a sufficiently long ejection cycle relative to the swaying cycle (period of meniscus vibration), The next discharge can be performed after the shaking due to the discharge is settled. That is, a low frequency region having a low frequency that can secure a discharge interval longer than the meniscus vibration attenuation time is not affected by the residual vibration of the meniscus and stable discharge is possible.

  In addition, pressure waves from other nozzles in the head may be transmitted to cause the meniscus to rise or be dented, but when this meniscus is fluctuating, if a discharge command is issued, depending on the timing Becomes poor in dischargeability. When discharging is performed before a pressure wave from a neighboring nozzle arrives (high-frequency discharging), there is no such problem and stable discharging is possible.

<Example of Recovery Means 2: Mode of Performing Discharge According to Image Data for Recovery>
In FIGS. 14 to 15, the example of changing the waveform of the drive signal at the time of recovery ejection has been described. However, the recovery effect can also be obtained by performing ejection according to the image data for recovery.

  FIG. 16 shows a first example of image data for recovery (dot arrangement data). A small square point 56 in FIG. 16 represents the position of a dot (position where a corresponding nozzle is ejected) recorded by a head (not shown). Here, it is assumed that the drawing proceeds from the right to the left in FIG. For example, a nozzle array of a page wide head (not shown) is arranged along the vertical direction of FIG. 16, and droplet ejection is performed while transporting paper from the left to the right of FIG. 16 (opposite to the drawing direction). I do. In addition, the paper may be fixed and the droplet may be ejected while moving the page wide head from right to left (along the drawing direction) in FIG. 16, or both the paper and the page wide head may be moved. I do not care.

  FIG. 16 is an image with a coverage (coverage) of 5%. A pattern with a coverage of 10% or less is preferable from the viewpoint of reducing the influence of crosstalk by reducing the number of nozzles to be simultaneously ejected while giving an opportunity for recovery ejection for all nozzles, and performing stable ejection.

  FIG. 17 shows a second example of image data for recovery. Due to the flow path structure inside the head and the like, there are various conditions under which the head can stably discharge. For example, with respect to a specific head, nozzles in the same common flow path (nozzle groups in which ink supply ports of pressure chambers corresponding to the nozzles are connected to the same common flow path, and ink is distributed and supplied from the same common flow path Nozzles belonging to (2) have a characteristic that enables stable ejection when the simultaneous drive rate is 10% or less.

  Rather than sporadically discharging from a single nozzle (with a sufficiently long discharge interval), it is easier to discharge continuously from the same nozzle at a somewhat shorter time interval (for example, in a cycle of several kHz). The recovery effect is high.

  Under such circumstances, there is also a form of drawing a line pattern for performing a predetermined number of continuous discharges from each nozzle as shown in FIG. As an example, in a page wide head having a recording resolution of 1200 dpi, image data that draws a line 62 at 75 dpi along the drawing direction at an appropriate interval in the paper width direction (x direction) orthogonal to the drawing direction is used. . The number of lines 62 corresponding to each nozzle is, for example, about 50, and the discharge frequency is 25.276 kHz (line length is about 1 mm). These conditions are merely examples, and appropriate conditions are set as long as the drawing area on the paper is not eroded.

  In FIG. 17, a line pattern block 64 in which a plurality of lines 62 are arranged in the vertical direction is drawn by a group of nozzles that are simultaneously ejected (simultaneously driven). The simultaneous drive rate of the nozzles in the same common flow path is suppressed to 10% or less. Although FIG. 17 shows an example in which the line pattern block 64 having 16 stages is drawn by changing the position in the drawing direction, the number of stages of the line pattern blocks is not limited to this. In accordance with the image data of FIG. 17, each line pattern block 64 is formed while changing the nozzle group used for ejection, and recovery ejection is performed for all nozzles.

<Example 3 of Recovery Means: Mode for Implementing Nozzle Face Cleaning Operation>
Further, as another embodiment, a nozzle having a means (nozzle face cleaning means) for recovering the adhering liquid adhering to the nozzle face (droplet ejection face) is used, and after ejection by the abnormal nozzle detection waveform, the nozzle It is also possible to obtain a recovery effect by performing the surface cleaning operation.

  FIG. 18 is a cross-sectional view showing a configuration example of a head provided with nozzle surface cleaning means. The head 200 is provided with a plurality of nozzles 202 (ink ejection ports) for ejecting ink droplets on an ink ejection surface (the lower surface in FIG. 18, hereinafter referred to as a nozzle surface, denoted by reference numeral “201”). . FIG. 18 shows an enlarged configuration of a droplet discharge element for one channel (an ink chamber unit corresponding to one nozzle 202) serving as a recording element unit.

  A liquid repellent film is formed over the entire surface of the ink ejection surface (nozzle surface 201) of the nozzle plate 201P on which the nozzles 202 are formed so that the liquid attached to the nozzle surface 201 can be easily collected. Furthermore, the nozzle surface 201 is a flat surface.

  The nozzle 202 communicates with the pressure chamber 204 via the nozzle flow path 203. The pressure chamber 204 communicates with a common flow path 208 for supplying ink via a supply port 206 (individual supply path). The common flow path 208 communicates with an ink tank (reference numeral 223 in FIG. 22) described later, and ink supplied from the ink tank 223 is distributed and supplied to each pressure chamber 204 via the common flow path 208.

  An actuator 212 having individual electrodes 211 is joined to a diaphragm 210 that constitutes a part of the pressure chamber 204 (the top surface in FIG. 18). The diaphragm 210 of this example is made of silicon (Si) with a nickel (Ni) conductive layer functioning as a common electrode 213 corresponding to the lower electrode of the actuator 212, and is arranged corresponding to each pressure chamber 204. Also serves as a common electrode. It is also possible to form the diaphragm with a non-conductive material such as resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member. Moreover, you may comprise the diaphragm which serves as a common electrode with metals (conductive material), such as stainless steel (SUS).

  By applying a driving voltage between the individual electrode 211 and the common electrode 213, the actuator 212 is deformed to change the volume of the pressure chamber 204, and ink is ejected from the nozzle 202 due to the pressure change accompanying this. For the actuator 212, a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate is preferably used. After the ink is ejected, when the displacement of the actuator 212 is restored, new ink is refilled into the pressure chamber 204 from the common flow path 208 through the supply port 206.

  By controlling the driving of the actuator 212 corresponding to each nozzle 202 according to the image data, ink droplets can be ejected from the nozzle 202. By controlling the ink ejection timing of each nozzle 202 in accordance with the transport speed while transporting the paper at a constant speed, a desired image can be recorded on the paper.

  In addition, the head 200 collects excess liquid from the nozzle channel 203 on the opposite side (left side in FIG. 18) of the common channel 208 across the nozzle channel 203 connected to the nozzle 202 from the pressure chamber 204. Common return flow path 220 is provided. The nozzle channel 203 of each nozzle 202 is connected to the common return channel 220 via the individual return channel 221, and excess ink that is not used for ejection passes from the nozzle channel 203 via the individual return channel 221. Collected in the common return channel 220. The common return flow path 220 is connected to a return tank (reference numeral 224 in FIG. 22) of an ink return portion via an ink return pipe line (reference numeral 226 in FIG. 22) described later.

  Further, a recovery hole 230 is formed in the vicinity of the nozzle 202 on the nozzle surface 201 of the head 200 shown in FIG. The recovery hole 230 communicates with a recovery liquid chamber 232 formed in the head 200. The recovery liquid chamber 232 is connected to a recovery device (FIG. 22) via a recovery flow path (reference numeral 243 in FIG. 22) described later. , 240). The adhering liquid adhering to the nozzle surface 201 is combined with the recovered liquid overflowing from the recovery hole 230 to the nozzle surface 201 (hereinafter sometimes referred to as “cleaning liquid”) and recovered from the recovery hole 230 together with the recovered liquid. It is accommodated in the liquid chamber 232 (see FIG. 18) and sent to the storage tank (reference numeral 241 in FIG. 22) of the recovery device 240 via the recovery flow path 243.

FIG. 19 is an example of an arrangement pattern of the nozzles 202 and the collection holes 230. In the example of FIG. 19, the nozzles 202 are arranged in two rows, and the recovery holes 230 are arranged in two rows between these nozzle rows. The distance d _N from each nozzle 202 to the nearest collection hole 230 is not more than a certain value for any nozzle 202. FIG. 19 shows a symmetrical arrangement in which the distance d _N between the nozzle 202 and the nearest adjacent collection hole 230 is constant for any nozzle 202.

  Here, the two-row nozzles and the two-row collection holes are shown, but a multi-row configuration in which the arrangement is repeated periodically or symmetrically using this arrangement pattern as a repeating unit is also possible. 18 is a cross-sectional view taken along line 18-18 in FIG.

(Variation of arrangement pattern of nozzle 202 and recovery hole 230)
The arrangement pattern of the nozzles 202 and the collection holes 230 is not limited to the example of FIG. 19, and various forms are possible. Some of these are illustrated in FIGS. In FIG. 20A, the nozzles 202 are arranged in a line at a constant interval P _NZ , and the recovery holes 230 are arranged at a constant interval Pr (where Pr = 2 × P _NZ ) in parallel with the nozzle array. It is an array pattern arranged in a line.

  FIG. 20B shows an example in which one collection hole row is formed between two nozzle rows. FIG. 20B shows a preferred arrangement pattern when the distance between nozzles between nozzle rows is less than 1400 μm. When the inter-nozzle distance between the nozzle rows is 1400 μm or more, the pattern described in FIG. 19 is suitable.

  The reason why the inter-nozzle distance and the arrangement of the recovery holes 230 are defined in this way is as follows. In general, the nozzle 202 is often placed about 0.7 mm to 1.0 mm away from the paper (recording medium). If the size of the droplets adhering to the nozzle surface 201 is 2000 μm or more in diameter, the droplets may come into contact with the paper and stain the paper.

  For this reason, it is preferable that the range in which the cleaning liquid overflows (wettes and spreads) from the recovery hole 230 is less than 1000 μm (in a circle having a radius of less than 1000 μm) from the center of the recovery hole 230.

  Furthermore, it is more preferable to control the liquid so that it overflows from the center of the recovery hole 230 to about 700 μm in consideration of an increase in the amount of liquid that is combined (unified) with the attached liquid adhering to the nozzle surface 201. . The arrangement relationship (relative positional relationship) between the nozzle 202 and the recovery hole 230 is designed so as to satisfy such a condition.

  21A to 21D illustrate the arrangement pattern of the collection holes 230 when the nozzles 202 are arranged in a matrix. In FIG. 21A, one row of recovery holes 230 is arranged for one row of nozzles 202. In FIG. 21B, one row of collection holes 230 having a smaller number than that in FIG. 21A is arranged for one row of nozzles 202. In FIG. 21C, the same number of recovery holes 230 as the nozzles 202 are arranged in the vicinity of the nozzles 202 for one row of nozzles 202. FIG. 21D is a modification similar to FIG. 21C, and the positions of one row of recovery holes 230 arranged close to the nozzle 202 row are alternately opposite to the nozzle 202 row. The arrangement pattern is arranged as shown in FIG.

(Description of collection device)
FIG. 22 shows the configuration of the ink circulation system 222 and the recovery device 240 of the head 200. The ink circulation system 222 and the collection device 240 are provided corresponding to each head for each ink color (here, four heads for each color corresponding to four colors of CMYK). Since the ink circulation system and the collection device corresponding to each head have the same configuration, the ink circulation system 222 and the collection device 240 related to one head 200 are shown here.

  As shown in FIG. 22, the ink circulation system 222 temporarily stores an ink supply unit (hereinafter referred to as “ink tank”) 223 that stores ink as an ink supply source, and ink collected from the head 200. An ink return portion (hereinafter referred to as “return tank”) 224 for storing is provided. The ink tank 223 and the head 200 are connected via an ink supply path 225, and ink is supplied from the ink tank 223 to the common flow path 208 in the head 200 through the ink supply path 225. The return tank 224 and the head 200 are connected via an ink return path 226, and the ink is returned from the common return flow path 220 in the head 200 to the return tank 224 through the ink return path 226. .

  The ink that has returned (collected) to the return tank 224 returns to the ink tank 223 through a communication path 227 that connects the return tank 224 and the ink tank 223. The ink circulation path includes an ink tank 223, an ink supply path 225, an internal flow path (common flow path 208, common return flow path 220) in the head 200, an ink return path 226, a return tank 224, and a communication path 227. Has been. Note that an arrow R1 shown in the figure indicates an ink supply direction, and an arrow R2 indicates an ink return direction. The ink circulation system 222 is provided with a circulation flow generator (a pump or the like (not shown)) that generates a circulation flow for circulation in the ink.

(About collection device)
The head 200 is provided with a recovery device 240. The recovery device 240 is a device that causes the cleaning liquid to overflow the nozzle surface 201 from the recovery hole 230 formed in the nozzle surface 201 and recovers the overflowing cleaning liquid together with the adhering ink adhering to the nozzle surface 201.

  As shown in FIG. 22, the recovery device 240 includes a storage tank 241 that stores the cleaning liquid, a syringe pump 242 that applies pressure to the cleaning liquid stored in the storage tank 241, and a recovery liquid chamber 232 (see FIG. 18) and the storage tank 241, a valve 244 provided in the middle of the recovery channel 243, and a controller 300 for controlling the syringe pump 242, the valve 244, and the like.

  A first connection port 241A and a second connection port 241B are provided in the upper part of the storage tank 241, and a third connection port 241C is provided in the lower part. A syringe pump 242 is connected to the first connection port 241A, and a recovery channel 243 is connected to the second connection port 241B. A recovery liquid supply path 245 is connected to the third connection port 241C. A valve 246 that is controlled by the control unit 300 is provided in the middle of the recovered liquid supply path 245. The valve 246 is opened by the control unit 300 so as to open during an exchange operation for exchanging the collected liquid (cleaning liquid) between the storage tank 241 and the collected tank 247, and to be closed at other times. Yes. In addition, since each member (242, 243, 245) is connected to each connection port 241A-C, the storage tank 241 is substantially sealed.

  A recovery liquid supply path 245 that connects the storage tank 241 and the recovery tank 247 is connected to an upper portion of the recovery tank 247, and one end of the recovery liquid supply path 245 is drawn into the recovery tank 247. A bidirectional pump 248 is provided between the valve 246 and the recovery tank 247 in the middle of the recovery liquid supply path 245. The pump 248 is controlled by the control unit 300. By switching the driving direction of the pump 248, the flow of the collected liquid from the storage tank 241 to the collection tank 247 side (arrow x1) and the flow of the collected liquid from the collection tank 247 to the storage tank 241 side can be switched. It has become. An air communication port 249 that communicates with the atmosphere is formed in the upper part of the recovery tank 247.

  One end of the recovery flow path 243 connecting the head 200 and the storage tank 241 is connected to the head 200 and connected to the recovery liquid chamber 232 (see FIG. 18) and the recovery hole 230 in the head 200, and the other end is a second connection. It passes through the opening 241B and is disposed inside the storage tank 241 (in the liquid layer in the tank). The valve 244 provided on the recovery flow path 243 is controlled by the control unit 300 to open when performing the recovery operation and the replacement operation, and to close at other times. The recovery operation refers to a series of operations for overflowing the recovery liquid from the recovery hole 230 through the recovery flow path 243 and recovering the overflowed recovery liquid.

  The syringe pump 242 is controlled by the control unit 300 and can increase or decrease the pressure of the air layer G formed in the upper part of the storage tank 241. Specifically, by expanding and contracting the internal space of the syringe pump 242, the pressure of the air layer G communicating with the internal space is also increased or decreased. When the pressure of the air layer G is increased by reducing the internal space of the syringe pump 242 (in FIG. 22, the pushing direction of the syringe is indicated by a white arrow), the liquid level of the recovered liquid stored in the storage tank 241 is The recovered liquid pressed by the air layer G whose pressure has increased is sent to the head 200 through the recovery flow path 243 and overflows from the recovery hole 230 to the nozzle surface 201. In the figure, black arrows indicate the flow of ink, and white arrows indicate the flow of air.

  Conversely, when the internal space of the syringe pump 242 is enlarged to reduce the pressure of the air layer G, the liquid level of the recovered liquid stored in the storage tank 241 is pulled by a negative pressure, and the recovered liquid in the head 200 is recovered. It is collected in the storage tank 241 through the flow path 243. At this time, the recovered liquid overflowing the nozzle surface 201 is recovered through the recovery hole 230.

  The controller 300 controls the pressure that acts on the air layer G by controlling the syringe pump 242. The pressure applied to the air layer G is set so as to be a predetermined amount (predetermined value) that does not reach the nozzle 202 adjacent to the recovery hole 230 when the recovery liquid overflows the nozzle surface 201. Has been. Further, when recovering the recovered liquid overflowing the nozzle surface 201, the recovery force (suction force) is set so that the recovered liquid on the nozzle surface 201 can be recovered reliably. In addition, since these predetermined values change according to a design value and an environment, it is preferable to obtain a suitable range by conducting a plurality of experiments in advance.

  In addition, the control unit 300 controls the syringe pump 242 according to the number of recovery operations or a measurement value from a sensor (not shown) that measures the viscosity of the recovery liquid to set a pressure that acts on the air layer G to a predetermined value. Fluctuate from.

  The recovered liquid stored in the storage tank 241 is preferably a liquid that can dissolve or disperse the adhering ink adhering to the nozzle surface 201. In this embodiment, a liquid that can dissolve the adhering ink is used. In addition, you may use adhesion ink as a collection | recovery liquid. Moreover, it is preferable that the color of a collection | recovery liquid is the same color as an adhesion liquid, or is transparent. In addition, it is preferable to use a recovery liquid having a surface tension of 40 mN / m or less and 10 mN / m or more so that it does not drop when it overflows from the recovery hole 230 or tears at the time of recovery and no recovery residue occurs. 35 mN / m or less and 25 mN / m or more are more preferable.

(Explanation of collection operation)
FIG. 23A is a schematic diagram illustrating a state where ink mist or the like is attached to the nozzle surface 201. In the figure, the black dots represent the adhered ink. When ejection for drawing recording or abnormal nozzle detection is performed, ink mist or the like adheres to the nozzle surface 201 of the head 200. Adhering ink adheres irregularly around the nozzles 202 and the recovery holes 230, and the adhering droplet size varies.

  In order to remove such adhering ink, first, the recovered liquid overflows from the recovery hole 230 (FIG. 23B). That is, by opening the valve 244 of the recovery flow path 243 described in FIG. 22 and driving the syringe pump 242 (driving in the direction of reducing the pump internal space), a predetermined amount of recovered liquid is discharged from the recovery hole 230 of the head 200. The pressure of the air layer G of the storage tank 241 is increased so as to overflow the nozzle surface 201.

  As shown in FIG. 23 (b), the recovered liquid overflowing from the recovery hole 230 spreads in the radial direction around the recovery hole 230, and is combined with the adhered ink on the nozzle surface by surface tension to be integrated (contacted). The liquids are united).

  Next, it drives in the direction which expands the internal space of the syringe pump 242, and the pressure of the air layer G of the storage tank 241 is decreased. As a result, a negative pressure acts on the recovered liquid in the recovery flow path 243 via the storage tank 241, and the recovered liquid overflowing the nozzle surface 201 is collected from the recovery hole 230 into the head 200 together with the integrated attached ink. And collected on the storage tank 241 side (see FIG. 23C).

  Thereafter, the valve 244 of the recovery channel 243 is closed. The control unit 300 in FIG. 22 transmits a signal (the valve 244 opening signal, the syringe pump 242 drive command signal, the valve 244 closing signal, etc.) for performing the above-described collecting operation, and the valve 244 and the syringe pump 242. Operates in response to a signal from the control unit 300.

  According to such a nozzle surface cleaning means, the recovery liquid overflows from the recovery hole 230, and the recovered recovery liquid and attached ink are recovered together from the recovery hole 230, so that the recovery liquid does not overflow from the recovery hole. In comparison with the one that collects adhering ink, the adhering liquid can be collected over a wider range on the nozzle surface 201. Further, when compared with a liquid that requires a wiping operation (so-called wiping operation) to collect the adhering liquid adhering to the nozzle surface 201, the adhering ink can be collected without interrupting the recording operation. As a result, the nozzle surface cleaning means according to this example can maintain stable image quality without reducing productivity.

(About other effects)
Further, since the pressure generated by the syringe pump 242 is transmitted to the recovered liquid via the air layer G of the storage tank 241, it is easier to finely adjust the pressure applied to the recovered liquid than to directly transmit the pressure to the recovered liquid. The recovery device 240 recovers the adhering liquid together with the recovering liquid. Therefore, it is assumed that the recovering liquid is mixed with the adhering liquid and the viscosity increases and it is difficult to overflow from the recovery hole 230. By controlling the syringe pump 242 and varying the pressure applied to the recovered liquid in accordance with the viscosity of the liquid, a predetermined amount of the recovered liquid can always overflow the nozzle surface 201.

  In addition, since the liquid repellent film is formed over the entire nozzle surface 201 of the present example, the recovery liquid overflowing from the recovery hole 230 and the adhering liquid coupled to the recovery liquid are recovered without leaving them. be able to. Further, in this example, since the nozzle surface 201 is formed smoothly over the entire surface, the recovered liquid overflowing from the recovery hole 230 spreads substantially uniformly on the nozzle surface 201, and reliably adheres liquid within a predetermined range. Can be recovered. Even if the viscosity of the adhering ink is increased, the recovered liquid dissolves or disperses the adhering ink, so that the adhering ink can be reliably recovered together with the recovered liquid.

  By using a liquid that is the same color or transparent as the attached ink as the recovery liquid, it is possible to maintain the color of the droplets discharged from the nozzle 202 after cleaning the nozzle surface.

(Regarding the effect of the collecting operation when the nozzle 202 is covered with the adhered ink)
As shown in FIG. 24A, even if the nozzle 202 is covered with the adhering ink, the recovery liquid overflows from the recovery hole 230, and after the adhering ink and the recovery liquid are combined, the recovery hole 230 is obtained. By collecting the recovered liquid from the ink, the adhered ink covering the nozzle 202 is recovered together with the recovered liquid (see FIG. 24B).

(Recovery liquid exchange operation between the storage tank 241 and the recovery tank 247)
Next, the recovery liquid exchange operation performed between the storage tank 241 and the recovery tank 247 shown in FIG. 22 will be described. When the operation of collecting the ink adhering to the nozzle surface 201 (nozzle surface cleaning operation) is performed a predetermined number of times, or when the sensor (not shown) for measuring the viscosity of the recovered liquid reaches a predetermined value, the control unit 300 Operates the pump 248 to send the recovered liquid in the storage tank 241 and the recovery flow path 243 to the empty recovery tank 247 through the recovery liquid supply path 245 for recovery.

  When the collected liquid is collected in the collection tank 247, the control unit 300 displays a display notifying the completion of collection on a display (not shown). Thereafter, the user removes the collection tank 247 from which the collected liquid has been collected from the inkjet recording apparatus and replaces it with a new collection tank 247. When the recovery tank 247 is replaced, the control unit 300 operates the pump 248 to supply new recovery liquid in the recovery tank 247 to the storage tank 241 through the recovery liquid supply path 245. In this way, the recovered liquid is exchanged between the storage tank 241 and the recovery tank 247.

  In this embodiment, the control unit 300 opens the valve 244 at the time of the replacement operation. However, the present invention is not limited to this configuration, and the control unit 300 performs the valve operation at a time other than the recovery operation. You may comprise so that 244 may close. In this case, since the recovery efficiency of the recovered liquid increases when the inside of the substantially closed storage tank 241 is opened to the atmosphere, for example, an openable atmosphere opening unit (not shown) or the like is provided at the top of the storage tank 241. It may be provided.

<Variation 1 of nozzle surface cleaning means>
In the recovery operation of the present embodiment, the recovery liquid overflows the nozzle surface 201, and the operation of recovering the adhering liquid bound to the recovery liquid together with the overflowed recovery liquid is performed. However, the present invention is not limited to this. Before the recovered liquid overflows the nozzle surface 201, an operation of recovering the adhering ink adhering to the nozzle surface 201 by setting the inside of the recovery hole 230 to a negative pressure may be performed. By adding such an operation, there are the following advantages.

  For example, if the adhering ink already covers the recovery hole 230 before performing the recovery operation, and the recovery liquid overflows from the recovery hole 230 in this state, the amount of liquid around the recovery hole 230 increases so that the recovery liquid and adhesion When there is a possibility that the liquid may spill from the nozzle surface 201, the recovery hole 230 is covered with the negative pressure applied to the recovery hole 230 before the recovery liquid overflows the nozzle surface (droplet discharge surface) 201 from the recovery hole 230. If the collected liquid overflows the nozzle surface 201 after the adhered ink is collected, a predetermined amount of the collected liquid can always overflow the nozzle surface 201. Moreover, it is possible to suppress the collected liquid from spilling.

<Variation 2 of nozzle surface cleaning means>
In FIG. 22, the pressure adjustment by the syringe pump 242 is performed via the air in the storage tank 241. However, the present invention is not limited to this, and the pressure adjustment by the syringe pump 242 is not limited to this. It is good also as a structure performed through the collection | recovery liquid.

<Modification 3 of nozzle surface cleaning means>
In FIG. 22, although the example which attached the syringe pump 242 to the storage tank 241 was demonstrated, it replaced with this structure and the syringe pump 242 is arrange | positioned rather than the valve 244 on the collection | recovery flow path 243 at the head 200 side, and 1st connection A configuration in which the opening 241A is opened to the atmosphere may be employed (not shown).

  In such a form, when the collected liquid overflows from the collection hole 230, that is, when a positive pressure is applied to the collected liquid in the collection flow path 243 by the syringe pump 242, the valve 244 is closed. Further, when a negative pressure is applied to the recovery liquid in the recovery flow path 243 by the syringe pump 242, the valve 244 is opened.

<Variation 4 of nozzle surface cleaning means>
In place of the syringe pump 242 in FIG. 22, an elevating device that moves the storage tank 241 up and down is provided, and pressurization / depressurization of the recovered liquid in the recovery flow path 243 due to a difference in height (water head difference) between the storage tank 241 and the head 200. It is also possible to perform the configuration (not shown). In the case of this form, the first connection port 241A of the storage tank 241 is opened to the atmosphere. Further, the valve 238 on the recovery channel 243 is controlled so as to be closed only during the replacement operation of the recovery liquid.

<Variation 5 of nozzle surface cleaning means>
In FIG. 22, the syringe pump 242, the valve 244, and the pump 248 are omitted, and instead, a tube pump for deforming the recovery liquid supply path 245 is provided on the recovery tank 247 side of the recovery liquid supply path 245 from the valve 246. A configuration can be adopted (not shown). In the case of this configuration, the first connection port 241A of the storage tank 241 is closed, and the storage tank 241 is substantially sealed.

  The tube pump includes a roller and is arranged so that a part of the recovered liquid supply path 245 is wound around. This roller rotates using a motor controlled by the control unit 300 as a drive source. The roller crushes the recovered liquid supply path 245 (tube) and rotates while deforming it, thereby causing the recovered liquid in the recovered liquid supply path 245 to flow in one direction. In such a configuration, the valve 246 is controlled by the control unit 300 so that the valve 246 is opened when the collecting device performs the collecting operation, and is closed at other times.

  At the time of the recovery operation, first, the tube pump rotates forward while crushing the recovery liquid supply path 245 so that a predetermined amount of the recovery liquid overflows the nozzle surface 201, thereby causing the recovery liquid to flow to the recovery hole 230. At this time, since the flow of the recovery liquid by the tube pump is transmitted to the recovery flow path 243 via the storage tank 241, pressure fluctuation (pulsation) by the tube pump is suppressed. Note that, also in the embodiment according to the fifth modification, the amount of the recovered liquid overflowing from the nozzle surface 201 due to the pressure applied by the tube pump is obtained in advance through experiments or the like.

  As described with reference to FIGS. 23B and 24A, the recovery liquid overflowing from the recovery hole 230 spreads in the radial direction around the recovery hole 230, and is caused by the adhered ink on the nozzle surface 201 and the surface tension. Combine to become one.

  Thereafter, the tube pump starts to rotate in reverse while crushing the recovered liquid supply path 245. As a result, the pressure of the recovery liquid in the recovery flow path 243 decreases, a negative pressure acts on the recovery liquid in the recovery flow path 243, and the recovery liquid overflowing on the nozzle surface 201 is collected together with the adhering ink to the recovery hole 230. To the recovery channel 243 (see FIG. 23C and FIG. 24B).

  The nozzle surface cleaning means described above can clean the nozzle surface without moving the head to the maintenance position and with the head placed at the printing position (position facing the paper). For this reason, it is possible to clean the nozzle surface between sheets of continuous printing or during the margin of the sheet.

  By performing drawing of the image portion (reference numeral 42 in FIG. 12) after such nozzle surface cleaning, it is possible to reduce waste paper without reducing productivity.

<Configuration example of inkjet recording apparatus>
Next, a configuration example of an ink jet recording apparatus to which the undischarge detection technique and the recovery technique are applied will be described. FIG. 25 is a configuration diagram of the ink jet recording apparatus according to the embodiment of the present invention. In the ink jet recording apparatus 100, a plurality of colors of ink are directly ejected onto a recording medium 114 (sometimes referred to as “paper” for convenience) held on the pressure drum 126 c of the ink droplet ejecting unit 108. An impression cylinder direct drawing type ink jet recording apparatus for forming a color image, which uses a two-liquid reaction (aggregation) system in which an image is formed on a recording medium 114 using ink and a processing liquid (here, an aggregation processing liquid). This is an on-demand type image forming apparatus.

  The ink jet recording apparatus 100 mainly includes a paper supply unit 102 that supplies a recording medium 114, a permeation suppression agent applying unit 104 that applies a permeation suppression agent to the recording medium 114, and a process that applies a treatment liquid to the recording medium 114. The liquid application unit 106, the ink droplet ejection unit 108 that ejects ink onto the recording medium 114, the fixing unit 110 that fixes the image formed on the recording medium 114, and the recording medium 114 on which the image is formed are conveyed. The paper discharge unit 112 is configured to be discharged.

  The paper supply unit 102 is provided with a paper supply table 120 on which a sheet recording medium 114 is stacked. The recording media 114 loaded on the paper feed table 120 are sent one by one to the feeder board 122 in order from the top, and received by the pressure drum (permeation inhibitor drum) 126a of the permeation suppression agent applying unit 104 via the transfer drum 124a. Passed.

  Holding claws 115a and 115b (grippers) for holding the leading end of the recording medium 114 are formed on the surface (circumferential surface) of the pressure drum 126a. The recording medium 114 transferred from the transfer drum 124a to the pressure drum 126a is in close contact with the surface of the pressure drum 126a while being held at the front end by the holding claws 115a and 115b (that is, the state wound around the pressure drum 126a). ) In the rotational direction of the impression cylinder 126a (counterclockwise direction in FIG. 25). The same configuration is applied to other impression cylinders 126b to 126d described later. A member 116 is formed on the surface (circumferential surface) of the transfer drum 124a to transfer the tip of the recording medium 114 to the holding claws 115a and 115b of the pressure drum 126a. The same configuration is applied to other transfer cylinders 124b to 124d described later.

(Penetration inhibitor application part)
In the permeation suppression agent applying unit 104, a sheet preheating unit 128 and a permeation suppression agent discharge are disposed at positions facing the surface of the pressure drum 126a in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 25) of the pressure drum 126a. A head 130 and a permeation suppression agent drying unit 132 are provided.

  Each of the paper preheating unit 128 and the permeation suppression agent drying unit 132 is provided with a hot air dryer capable of controlling temperature and air volume within a predetermined range. When the recording medium 114 held on the impression cylinder 126a passes through a position facing the paper preheating unit 128 and the permeation suppression agent drying unit 132, the air heated by the hot air dryer (hot air) is applied to the surface of the recording medium 114. It is configured to be sprayed toward.

  The permeation suppression agent discharge head 130 discharges a solution containing a permeation suppression agent (hereinafter also simply referred to as “permeation suppression agent”) to the recording medium 114 held on the pressure drum 126a. In this example, a droplet ejection method is applied as a means for applying a permeation inhibitor to the surface of the recording medium 114, but the present invention is not limited to this, and various methods such as a roller coating method and a spray method are applied. It is also possible to do.

  The permeation suppressor suppresses permeation into the recording medium 114 of a solvent (and a solvophilic organic solvent) contained in a processing liquid and an ink liquid described later. As the permeation inhibitor, a resin particle dispersed (or dissolved) in a solution is used. For example, an organic solvent or water is used as the solution of the penetration inhibitor. As the organic solvent for the penetration inhibitor, methyl ethyl ketone, petroleum, and the like are preferably used.

  The paper preheating unit 128 makes the temperature Tm1 of the recording medium 114 higher than the minimum film-forming temperature Tf1 of the resin particles of the permeation suppression agent. As a method for adjusting the temperature Tm1, there are a method of heating the recording medium 114 from the lower surface using a heating element such as a heater installed inside the pressure drum 126a, and a method of heating the upper surface of the recording medium 114 by applying hot air. In this example, a method of heating from the upper surface of the recording medium 114 using an infrared heater or the like is used. These methods may be combined.

  For the method of applying the penetration inhibitor, droplet ejection, spray coating, roller coating or the like is preferably used. In the case of droplet ejection, a permeation inhibitor can be selectively applied only to the ink droplet ejection location and its surroundings, which will be described later, which is preferable. Further, in the case of the recording medium 114 where curling is unlikely to occur, the application of the permeation inhibitor may be omitted.

  A treatment liquid application unit 106 is provided following the permeation suppression agent application unit 104. A transfer drum 124b is provided between the pressure drum (penetration inhibitor drum) 126a of the permeation suppression agent applying unit 104 and the pressure drum (processing liquid drum) 126b of the treatment liquid applying unit 106 so as to be in contact therewith. ing. As a result, the recording medium 114 held on the pressure drum 126a of the permeation suppression agent applying unit 104 is delivered to the pressure drum 126b of the treatment liquid application unit 106 via the transfer drum 124b after the permeation suppression agent is applied. .

(Processing liquid application part)
In the treatment liquid application unit 106, a sheet preheating unit 134 and a treatment liquid discharge head 136 are disposed at positions facing the surface of the pressure drum 126 b in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 25) of the pressure drum 126 b. , And a processing liquid drying unit 138 are provided.

  Since the paper preheating unit 134 has the same configuration as that of the paper preheating unit 128 of the permeation suppression agent applying unit 104, the description thereof is omitted here. Of course, different configurations may be applied.

  The treatment liquid ejection head 136 is for ejecting treatment liquid onto the recording medium 114 held by the pressure drum 126b, and is the same as each ink ejection head 140C, 140M, 140Y, 140K of the ink ejection unit 108. Configuration is applied.

  The processing liquid used in this example agglomerates color materials contained in the ink ejected from the ink ejection heads 140M, 140K, 140C, and 140Y disposed in the ink ejection unit 108 toward the recording medium 114. It is an acidic liquid having an action.

  The processing liquid drying unit 138 is provided with a hot air dryer capable of controlling the temperature and the air volume within a predetermined range, and the recording medium 114 held on the impression cylinder 126 b faces the hot air dryer of the processing liquid drying unit 138. When passing through the position, air heated by a hot air dryer (hot air) is sprayed onto the processing liquid on the recording medium 114.

  The temperature and air volume of the hot air dryer are adjusted so that the processing liquid applied on the recording medium 114 is dried by the processing liquid discharge head 136 disposed on the upstream side in the rotation direction of the impression cylinder 126 b, and the solid is formed on the surface of the recording medium 114. Or a semi-solid solution aggregation treatment agent layer (thin film layer in which the treatment liquid is dried) is set to such a value.

  The “solid or semi-solid flocculating agent layer” as used herein refers to one having a moisture content in the range of 0 to 70% as defined below.

The “aggregation treatment agent” is used not only in a solid or semi-solid solution but also in a broad concept including other liquids, and particularly in a liquid state with a solvent content of 70% or more. The aggregating agent thus obtained is referred to as “aggregating treatment liquid”.

  According to the evaluation experiment on the movement of the coloring material when the solvent content of the treatment liquid (aggregation treatment agent layer) on the recording medium 114 is changed, the solvent content of the treatment liquid is 70% or less after the treatment liquid is applied. When the treatment liquid is dried until the colorant moves, the colorant movement becomes inconspicuous. When the treatment liquid is further dried to 50% or less, the colorant movement becomes so good that visual confirmation of colorant movement cannot be confirmed, which is effective in preventing image deterioration. It was confirmed.

  In this way, drying is performed until the solvent content of the treatment liquid on the recording medium 114 becomes 70% or less (preferably 50% or less), and a solid or semi-solid aggregation treatment agent layer is formed on the recording medium 114. By forming the image, it is possible to prevent image deterioration due to color material movement.

[Ink ejection part]
An ink droplet ejection unit 108 is provided following the treatment liquid application unit 106. A transfer cylinder 124c is provided between the pressure drum (processing liquid drum) 126b of the treatment liquid application unit 106 and the pressure drum 126c of the ink droplet ejection unit 108 so as to be in contact therewith. As a result, the recording medium 114 held on the pressure drum 126b of the treatment liquid application unit 106 is applied with the treatment liquid to form a solid or semi-solid aggregating treatment agent layer, and then via the transfer cylinder 124c. The ink is transferred to a pressure drum (drawing drum) 126c of the ink droplet ejection unit 108.

  The ink droplet ejecting section 108 corresponds to each of the four color inks CMYK at positions facing the surface of the pressure drum 126c in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 25) of the pressure drum 126c. Ink droplet ejection heads 140C, 140M, 140Y and 140K are provided side by side, and further, solvent drying units 142a and 142b are provided on the downstream side thereof.

  As each of the ink droplet ejection heads 140C, 140M, 140Y, and 140K, a recording head (liquid droplet ejection head) of a system that ejects liquid is applied in the same manner as the processing liquid ejection head 136 described above. That is, each of the ink droplet ejection heads 140C, 140M, 140Y, and 140K ejects the corresponding color ink droplets toward the recording medium 114 held by the pressure drum 126c.

  The ink storage / loading unit (not shown) includes an ink tank that stores ink supplied to each of the ink droplet ejection heads 140C, 140M, 140Y, and 140K. Each ink tank communicates with a corresponding head via a required flow path, and supplies a corresponding ink to each ink droplet ejection head. The ink storage / loading unit includes notifying means (display means, warning sound generating means) for notifying when the remaining amount of liquid in the tank is low, and has a mechanism for preventing erroneous loading between colors. ing.

  Ink is supplied from each ink tank of the ink storage / loading unit to each ink droplet ejection head 140C, 140M, 140Y, 140K, and from each ink droplet ejection head 140C, 140M, 140Y, 140K to the recording medium 114 according to an image signal. On the other hand, corresponding color inks are ejected.

  Each of the ink droplet ejection heads 140C, 140M, 140Y, and 140K has a length corresponding to the maximum width of the image forming area in the recording medium 114 held by the impression cylinder 126c, and the image forming area is disposed on the ink ejection surface. This is a full-line head in which a plurality of nozzles for ink ejection (not shown in FIG. 25) are arranged over the entire width (see FIG. 26). The ink droplet ejection heads 140C, 140M, 140Y, and 140K are installed so as to extend in a direction orthogonal to the rotation direction of the impression cylinder 126c (conveying direction of the recording medium 114).

  According to the configuration in which a full line head having a nozzle row covering the entire width of the image forming area of the recording medium 114 is provided for each ink color, the recording medium 114 is conveyed at a constant speed by the impression cylinder 126c, and this conveying direction ( With respect to the sub-scanning direction), the image of the recording medium 114 can be obtained by performing the operation of relatively moving the recording medium 114 and the ink ejection heads 140C, 140M, 140Y, and 140K once (that is, in one sub-scanning). An image can be recorded in the formation area. Single-pass image formation with such a full-line (page wide) head is a multi-pass with a serial (shuttle) type head that reciprocates in the direction (main scanning direction) orthogonal to the recording medium conveyance direction (sub-scanning direction). High-speed printing is possible as compared with the case where the method is applied, and print productivity can be improved.

  The ink jet recording apparatus 100 of the present example is capable of recording up to, for example, a recording medium (recording paper) having a maximum chrysanthemum half size. Is used. The ink ejection volumes of the ink ejection heads 140C, 140M, 140Y, and 140K are, for example, 2 pl, and the recording density is the main scanning direction (width direction of the recording medium 114) and the sub-scanning direction (conveyance direction of the recording medium 114). Both are 1200 dpi, for example.

  Further, in this example, the configuration of four colors of CMYK is illustrated, but the combination of ink colors and the number of colors is not limited to the present embodiment, and R (red), G (green), and B as necessary. (Blue) ink, light ink, dark ink, and special color ink may be added. For example, it is possible to add a head for ejecting light ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  Although not shown in the drawing, head maintenance such as preliminary discharge and suction operation is performed by moving the head from an image recording position (drawing position) immediately above the impression cylinder 126c (drawing drum) to a predetermined maintenance position (for example, pressure). The cylinder 126c is configured to be executed in a state of being retracted to a position outside the drum in the axial direction.

  The solvent drying units 142a and 142b include hot air dryers that can control the temperature and the air volume within a predetermined range, like the paper preheating units 128 and 134, the permeation suppression agent drying unit 132, and the treatment liquid drying unit 138 described above. Composed. When ink droplets are ejected onto a solid or semi-solid aggregation processing agent layer formed on the surface of the recording medium 114, ink aggregates (coloring material aggregates) are formed on the recording medium 114. At the same time, the ink solvent separated from the color material spreads to form a liquid layer in which the aggregation treatment agent is dissolved. In this way, the solvent component (liquid component) remaining on the recording medium 114 causes not only curling of the recording medium 114 but also image degradation. Therefore, in this example, after the corresponding color inks are ejected onto the recording medium 114 from the respective ink ejection heads 140C, 140M, 140Y, and 140K, the solvent components are dried by the hot air dryers of the solvent drying units 142a and 142b. Is evaporated and dried.

  A fixing unit 110 is provided following the ink ejection unit 108. A transfer drum 124d is provided between the pressure drum (drawing drum) 126c of the ink droplet ejection unit 108 and the pressure drum (fixing drum) 126d of the fixing unit 110 so as to be in contact therewith. As a result, the recording medium 114 held on the pressure drum 126c of the ink droplet ejection unit 108 is delivered to the pressure drum 126d of the fixing unit 110 via the transfer drum 124d after each color ink is applied.

[Fixing part]
In the fixing unit 110, in-line detection is performed in which the printing result by the ink droplet ejection unit 108 is read at a position facing the surface of the pressure drum 126d in order from the upstream side in the rotation direction (counterclockwise direction in FIG. 25) of the pressure drum 126d. A portion 144 and heating rollers 148a and 148b are provided.

  The in-line detection unit 144 is a reading unit that reads an output image, and includes an image sensor for imaging a printing result of the ink droplet ejection unit 108 (a droplet ejection result of each ink droplet ejection head 140C, 140M, 140Y, 140K). It functions as a means for checking nozzle clogging and other ejection defects from a droplet ejection image read by the image sensor, or as a colorimetric means for acquiring color information.

  In this example, a test pattern based on a line pattern, a density pattern, or a combination of these is formed in the image recording area or non-image area (so-called blank area) of the recording medium 114, and this test pattern is read by the inline detection unit 144. Based on the reading result, inline detection is performed such as acquisition of color information (colorimetry), detection of density unevenness, and determination of the presence or absence of ejection abnormality for each nozzle.

  The heating rollers 148a and 148b are rollers capable of controlling the temperature within a predetermined range (for example, 100 ° C. to 180 ° C.), and heat the recording medium 114 sandwiched between the heating rollers 148a and 148b and the impression cylinder 126d. While pressing, the image formed on the recording medium 114 is fixed. The heating temperature of the heating rollers 148a and 148b is preferably set according to the glass transition temperature of the polymer fine particles contained in the treatment liquid or ink.

  In addition, it may replace with the ink containing the high boiling point solvent and the thermoplastic resin particle, and may contain the monomer component which can be polymerized and hardened by UV exposure. In this case, the inkjet recording apparatus 100 includes a UV exposure unit that exposes the ink on the recording medium 114 to UV light instead of the heat-pressure fixing unit using a heat roller. In this way, when ink containing an actinic ray curable resin such as a UV curable resin is used, an actinic ray is irradiated, such as a UV lamp or an ultraviolet LD (laser diode) array, instead of a fixing roller for heat fixing. Means are provided.

[Paper output section]
Subsequent to the fixing unit 110, a paper discharge unit 112 is provided. The paper discharge unit 112 includes a paper discharge drum 150 that receives the recording medium 114 on which an image is fixed, a paper discharge tray 152 on which the recording medium 114 is loaded, and a sprocket and a paper discharge tray 152 provided on the paper discharge drum 150. And a paper discharge chain 154 provided with a plurality of paper discharge grippers. Although the details of the paper transport mechanism by the paper discharge chain 154 are not shown, the recording medium 114 after printing is held at the leading edge of the paper by a gripper of a bar (not shown) passed between the endless paper discharge chains 154. Then, the sheet is transported above the sheet discharge table 152 by the rotation of the sheet discharge chain 154.

<Head structure>
Next, the structure of the head will be described. Since the structures of the heads 130, 136, 140C, 140M, 140Y, and 140K are common, the heads will be represented by the reference numeral 250 in the following.
FIG. 26 (a) is a plan perspective view showing an example of the structure of the head 250, and FIG. 26 (b) is an enlarged view of a part thereof. 27 is a perspective plan view showing another example of the structure of the head 250, and FIG. 28 is a three-dimensional configuration of one-channel droplet discharge elements (ink chamber units corresponding to one nozzle 251) serving as a recording element unit. It is sectional drawing (sectional drawing in alignment with the AA in FIG. 26) which shows these.

  As shown in FIG. 26, the head 250 of this example has a matrix of a plurality of ink chamber units (droplet discharge elements) 253 including nozzles 251 serving as ink discharge ports and pressure chambers 252 corresponding to the nozzles 251. The nozzle spacing (projection nozzle pitch) is projected (orthogonally projected) so as to be aligned along the longitudinal direction of the head (direction perpendicular to the paper feed direction). High density is achieved.

  Nozzle rows having a length corresponding to the entire width Wm of the drawing area of the recording medium 114 are configured in a direction (arrow M direction; main scanning direction) substantially orthogonal to the feeding direction of the recording medium 114 (arrow S direction; sub-scanning direction). The form to do is not limited to this example. For example, instead of the configuration of FIG. 26A, as shown in FIG. 27A, short head modules 250 ′ in which a plurality of nozzles 251 are two-dimensionally arranged are arranged in a staggered manner and connected. Thus, there are a mode in which a line head having a nozzle row having a length corresponding to the full width of the recording medium 114 and a mode in which the head modules 250 ″ are arranged in a row and connected as shown in FIG.

  The pressure chamber 252 provided corresponding to each nozzle 251 has a substantially square planar shape (see FIGS. 26A and 26B), and the nozzle 251 is provided at one of the diagonal corners. An outlet for supplying ink (supply port) 254 is provided on the other side. Note that the shape of the pressure chamber 252 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse. As shown in FIG. 28, the head 250 has a structure in which a nozzle plate 251A in which nozzles 251 are formed and a flow path plate 252P in which flow paths such as a pressure chamber 252 and a common flow path 255 are formed are laminated and joined. . The nozzle plate 251A constitutes a nozzle surface (ink ejection surface) 250A of the head 250, and a plurality of nozzles 251 communicating with the pressure chambers 252 are two-dimensionally formed.

  The flow path plate 252P forms a side wall of the pressure chamber 252 and a flow path that forms a supply port 254 as a narrowed portion (most narrowed portion) of an individual supply path that guides ink from the common flow path 255 to the pressure chamber 252. It is a forming member. For convenience of explanation, the flow path plate 252P has a structure in which one or a plurality of substrates are stacked, although it is illustrated schematically in FIG.

  The nozzle plate 251A and the flow path plate 252P can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow channel 255 communicates with an ink tank (not shown) as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 252 via the common flow channel 255.

  A piezoelectric actuator 258 including an individual electrode 257 is joined to a diaphragm 256 that constitutes a part of the pressure chamber 252 (the top surface in FIG. 28). The diaphragm 256 of this example is made of silicon (Si) with a nickel (Ni) conductive layer functioning as a common electrode 259 corresponding to the lower electrode of the piezoelectric actuator 258, and is arranged corresponding to each pressure chamber 252. It also serves as a common electrode for the actuator 258. It is also possible to form the diaphragm with a non-conductive material such as resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member. Moreover, you may comprise the diaphragm which serves as a common electrode with metals (conductive material), such as stainless steel (SUS).

  By applying a driving voltage to the individual electrode 257, the piezo actuator 258 is deformed and the volume of the pressure chamber 252 is changed, and ink is ejected from the nozzle 251 due to the pressure change accompanying this. When the piezo actuator 258 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 252 from the common channel 255 through the supply port 254.

  As shown in FIG. 26B, the ink chamber units 253 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized. In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is Ls, in the main scanning direction, each nozzle 251 is substantially equivalent to a linear arrangement with a constant pitch P = Ls / tan θ. It can be handled.

  In the implementation of the present invention, the arrangement form of the nozzles 251 in the head 250 is not limited to the illustrated example, and various nozzle arrangement structures can be applied. For example, instead of the matrix array described in FIG. 26, a linear array of lines, a V-shaped nozzle array, and a zigzag (W-shaped) nozzle array having a V-shaped array as a repeating unit. Etc. are also possible.

  The means for generating the discharge pressure (discharge energy) for discharging the droplets from each nozzle in the inkjet head is not limited to the piezo actuator (piezoelectric element), but the thermal method (the pressure of film boiling due to the heating of the heater) Various pressure generating elements (energy generating elements) such as heaters (heating elements) and other actuators based on other systems can be applied. Corresponding energy generating elements are provided in the flow path structure according to the ejection method of the head.

  FIG. 29 is a plan view showing a flow channel structure in the head 250. As shown in the figure, the head 250 includes a flow path structure for ink supply including main flow paths 320 and 321, a branch flow path 322, and ink introduction ports (main supply ports) 324 to 2327. A branch channel 322 in FIG. 29 corresponds to the common channel denoted by reference numeral 255 in FIG.

  As shown in FIG. 29, a plurality of rows of branch channels 322 are provided in the same row as the arrangement of the pressure chambers 252 arranged along the direction of the angle θ, and are connected to the upper and lower main channels 320 and 321. Therefore, the branch flow path 322 is arranged so as to be bridged between the main flow paths 320 and 321. In addition, a supply port 254 of each pressure chamber 252 is connected to each branch channel 322. That is, in FIG. 29, a branch channel 322 is provided for each group of nozzle rows (here, six nozzles are illustrated) arranged along the direction of the angle θ. If nozzles (six nozzles in this example) connected to the same branch flow path 322 are simultaneously ejected, there is a possibility of being affected by crosstalk. Therefore, when printing a test pattern, the same branch flow path is used. It is desirable to control the nozzles that receive ink supply from 322 so that they are not driven simultaneously. When performing recovery discharge, the simultaneous drive rate of nozzle groups belonging to the same flow path (here, a group of nozzles 251 directly connected to the same branch flow path 322 via the supply port 254) is set. It is desirable to make it 10% or less. In FIG. 29, for convenience of illustration, the number of nozzles connected to the same branch flow path 322 is reduced, but in an actual head, several tens (for example, about 20 to 50) nozzles have the same flow path. May be connected to.

  The structure of the flow path in the head is not limited to the example of FIG. FIG. 30 shows another example. 30, elements that are the same as or similar to those in the example of FIG. 29 are given the same reference numerals, and descriptions thereof are omitted.

  Since crosstalk affects the discharge of other nozzles due to the propagation of reverberant sound waves during discharge, strictly speaking, all the connected flow paths are affected. However, the degree of influence depends on the resistance between the nozzle and each flow path. Accordingly, the crosstalk between the nozzle groups in the same branch flow path 322 has a high influence.

  When the common return flow path 220 is provided in addition to the common flow path 208 on the ink supply side as in the head 200 described with reference to FIG. 18, not only the flow path (208) on the supply side but also the return flow path. The side flow path (220) can also be a flow path that mediates crosstalk. In other words, the “same flow path” in the present invention means “only the flow path on the supply side”, “only the flow path on the return side (collection side)”, or “the flow path on the supply side”. And both of the flow paths on the return side ”.

  Instead of the head 250 described with reference to FIGS. 26 to 30, the head 200 described with reference to FIG. 18 may be used.

<Description of control system>
FIG. 31 is a block diagram illustrating a system configuration of the inkjet recording apparatus 100. As shown in FIG. 31, the inkjet recording apparatus 100 includes a communication interface 170, a system controller 172, an image memory 174, a ROM 175, a motor driver 176, a heater driver 178, a print control unit 180, an image buffer memory 182, a head driver 184, and the like. I have.

  The communication interface 170 is an interface unit (image input means) that receives image data sent from the host computer 186. As the communication interface 170, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 186 is taken into the inkjet recording apparatus 100 via the communication interface 170 and temporarily stored in the image memory 174. The image memory 174 is a storage unit that stores an image input via the communication interface 170, and data is read and written through the system controller 172. The image memory 174 is not limited to a memory composed of semiconductor elements, and a magnetic medium such as a hard disk may be used.

  The system controller 172 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 172 controls the communication interface 170, the image memory 174, the motor driver 176, the heater driver 178, and the like, and performs communication control with the host computer 186, read / write control of the image memory 174 and ROM 175, and the like. At the same time, a control signal for controlling the motor 188 and the heater 189 of the transport system is generated.

  The system controller 172 includes an impact error measurement computation unit 172A that performs computation processing to generate impact position error data and data (density data) indicating density distribution from the test chart read data read from the inline detection unit 144; It includes a density correction coefficient calculation unit 172B that calculates a density correction coefficient from the measured landing position error information and density information. The processing functions of the landing error measurement calculation unit 172A and the density correction coefficient calculation unit 172B can be realized by ASIC, software, or an appropriate combination.

  The density correction coefficient data obtained by the density correction coefficient calculation unit 172B is stored in the density correction coefficient storage unit 190.

  The ROM 175 stores programs executed by the CPU of the system controller 172 and various data necessary for control (data for ejecting test charts, waveform data for detecting abnormal nozzles, waveform data for drawing and recording, abnormal nozzle information, etc.) Is stored). The ROM 175 may be a non-rewritable storage unit or a rewritable storage unit such as an EEPROM. Further, by utilizing the storage area of the ROM 175, a configuration in which the ROM 175 is also used as the density correction coefficient storage unit 190 is possible.

  The image memory 174 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 176 is a driver (driving circuit) that drives the conveyance motor 188 in accordance with an instruction from the system controller 172. The heater driver 178 is a driver that drives the heater 189 such as the post-drying unit 142 in accordance with an instruction from the system controller 172.

  In accordance with the control of the system controller 172, the print control unit 180 performs various processes, corrections, and the like for generating a droplet ejection control signal from image data (multi-value input image data) in the image memory 174. In addition to functioning as signal processing means, it also functions as drive control means for supplying the generated ink discharge data to the head driver 184 to control the discharge drive of the head 250.

  That is, the print control unit 180 includes a density data generation unit 180A, a correction processing unit 180B, an ink ejection data generation unit 180C, and a drive waveform generation unit 180D. Each of these functional blocks (180A to 180D) can be realized by ASIC, software, or an appropriate combination.

  The density data generation unit 180A is a signal processing unit that generates initial density data for each ink color from input image data, and performs density conversion processing (including UCR processing and color conversion) and, if necessary, pixel number conversion. Process.

  The correction processing unit 180B is a processing unit that performs density correction using the density correction coefficient stored in the density correction coefficient storage unit 190, and performs unevenness correction processing. The correction processing unit 180B performs processing according to each of a first correction method and a second correction method described later.

  The ink ejection data generation unit 180C is a signal processing unit including a halftoning processing unit that converts the corrected image data (density data) generated by the correction processing unit 180B into binary or multivalued dot data. Value (multi-value) conversion processing is performed. Various known means such as an error diffusion method, a dither method, a threshold matrix method, and a density pattern method can be applied as the halftone processing means. In the halftone process, generally, gradation image data having an M value (M ≧ 3) is converted into gradation image data having an N value (N <M). In the simplest example, the image data is converted into binary (dot on / off) dot image data. However, in the halftone process, the dot size type (for example, three types such as a large dot, a medium dot, and a small dot) is converted. It is also possible to perform corresponding multi-level quantization.

  The ink discharge data generated by the ink discharge data generation unit 180C is given to the head driver 184, and the ink discharge operation of the head 250 is controlled.

  The drive waveform generation unit 180D is a unit that generates a drive signal waveform for driving the actuator 258 (see FIG. 28) corresponding to each nozzle 251 of the head 250, and the signal generated by the drive waveform generation unit 180D ( Drive waveform) is supplied to the head driver 184. The signal output from the drive waveform generator 180D may be digital waveform data or an analog voltage signal.

  The drive waveform generation unit 180D selectively generates a drive signal for a recording waveform and a drive signal for an abnormal nozzle detection waveform. Various waveform data are stored in the ROM 175 in advance, and waveform data to be used is selectively output as necessary.

  The print control unit 180 includes an image buffer memory 182, and image data, parameters, and other data are temporarily stored in the image buffer memory 182 when image data is processed in the print control unit 180. In FIG. 31, the image buffer memory 182 is shown in a form associated with the print control unit 180, but it can also be used as the image memory 174. Also possible is an aspect in which the print controller 180 and the system controller 172 are integrated and configured with one processor.

  An outline of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 170 and stored in the image memory 174. At this stage, for example, RGB multivalued image data is stored in the image memory 174.

  In the inkjet recording apparatus 100, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image (RGB) data stored in the image memory 174 is sent to the print control unit 180 via the system controller 172, and the density data generation unit 180A, the correction processing unit 180B of the print control unit 180, the ink It is converted into dot data for each ink color via the ejection data generation unit 180C.

  That is, the print control unit 180 performs a process of converting the input RGB image data into dot data of four colors K, C, M, and Y. Thus, the dot data generated by the print control unit 180 is stored in the image buffer memory 182. The dot data for each color is converted into CMYK droplet ejection data for ejecting ink from the nozzles of the head 250, and the ink ejection data to be printed is determined.

  The head driver 184 outputs a drive signal for driving the actuator 258 corresponding to each nozzle 251 of the head 250 according to the print contents based on the ink ejection data and the drive waveform signal given from the print control unit 180. The head driver 184 may include a feedback control system for keeping the head driving condition constant.

  In this manner, the drive signal output from the head driver 184 is applied to the head 250, whereby ink is ejected from the corresponding nozzle 251. An image is formed on the recording medium 114 by controlling ink ejection from the head 250 in synchronization with the conveyance speed of the recording medium 114.

  As described above, based on the ink discharge data and the drive signal waveform generated through the required signal processing in the print control unit 180, control of the discharge amount and discharge timing of the ink droplets from each nozzle through the head driver 184. Is done. Thereby, a desired dot size and dot arrangement are realized.

  As described with reference to FIG. 25, the inline detection unit 144 is a block including an image sensor, reads an image printed on the recording medium 114, performs necessary signal processing, and the like to perform a printing situation (whether ejection is performed, droplet ejection Variation, optical density, etc.) and the detection result is provided to the print controller 180 and the system controller 172.

  The print control unit 180 performs various corrections on the head 250 based on information obtained from the in-line detection unit 144 as necessary, and performs cleaning operations (nozzle recovery operation) such as preliminary ejection, suction, and wiping as necessary. Perform the controls to be implemented.

  The maintenance mechanism 194 in the drawing includes members necessary for head maintenance, such as an ink receiver, a suction cap, a suction pump, and a wiper blade.

  The operation unit 196 as a user interface includes an input device 197 and a display unit (display) 198 for an operator (user) to make various inputs. The input device 197 may employ various forms such as a keyboard, a mouse, a touch panel, and buttons. By operating the input device 197, an operator can input printing conditions, select an image quality mode, input / edit attached information, search information, and the like. This can be confirmed through the display on the display unit 198. The display unit 198 also functions as means for displaying a warning such as an error message.

  The inkjet recording apparatus 100 of the present embodiment has a plurality of image quality modes, and the image quality mode is set by a user's selection operation or by automatic selection by a program. The criterion for determining an abnormal nozzle is changed according to the output image quality level required in the set image quality mode. The higher the required quality, the more severe the criteria.

  Information regarding the printing conditions and abnormal nozzle determination criteria for each image quality mode is stored in the ROM 175.

  A mode in which all or a part of the processing functions of the landing error measurement calculation unit 172A, the density correction coefficient calculation unit 172B, the density data generation unit 180A, and the correction processing unit 180B described in FIG. 31 is mounted on the host computer 186 side is also possible. is there. The drive waveform generation unit 180D in FIG. 31 corresponds to “recording waveform signal generation means” and “abnormal nozzle detection waveform generation means”. Further, the combination of the system controller 172 and the print control unit 180 includes “detection discharge control means”, “correction control means”, “printing discharge control means”, “recovery discharge control means”, and “recovery pattern formation control”. It corresponds to “means”.

Further, the system controller 172 in FIG. 31 functions as the control unit described with reference numeral 300 in FIG.

<Configuration example of inline detection unit>
FIG. 32 is a configuration diagram of the inline detection unit 144. The in-line detection unit 144 includes a reading sensor unit 274 in which a line CCD 270 (corresponding to “image reading unit”), a lens 272 that forms an image on the light receiving surface of the line CCD 270, and a mirror 273 that bends the optical path. Arranged in parallel, each image on the recording medium is read. The line CCD 270 has a photocell (pixel) array for each color provided with RGB color filters, and a color image can be read by RGB color separation. For example, a CCD analog shift register for separately transferring the charges of even-numbered pixels and odd-numbered pixels in one line is provided next to the photocell array for each of RGB3 lines.

  Specifically, a line CCD “μPD8827A” (trade name) manufactured by NEC Electronics Corporation having a pixel pitch of 9.325 μm, 7600 pixels × RGB, and an element length (sensor width in the photocell arrangement direction) of 70.87 mm can be used.

  The line CCD 270 is fixed so that the arrangement direction of the photocells and the axis of the drum on which the recording medium is conveyed are parallel to each other.

  The lens 272 is a lens of a reduction optical system that forms an image on a recording medium wound on a conveyance drum (an impression cylinder 126d in FIG. 25) with a predetermined reduction ratio. For example, when a lens that reduces an image by 0.19 times is employed, a 373 mm width on the recording medium is imaged on the line CCD 270. At this time, the reading resolution on the recording medium is 518 dpi.

  As shown in FIG. 32, the read sensor unit 274 in which the line CCD 270, the lens 272, and the mirror 273 are integrated can be moved and adjusted in parallel with the axis of the transport drum, and the positions of the two read sensor units 274 are adjusted, respectively. The image read by the reading sensor unit 274 is slightly overlapped. Although not shown in FIG. 32, as an illumination means for detection, for example, a xenon fluorescent lamp is arranged on the back surface of the bracket 275, on the recording medium side, and a white reference plate is periodically provided between the image and the illumination. To measure the white reference. In this state, the lamp is turned off and the black reference level is measured.

  The reading width of the line CCD 270 (the range that can be inspected at one time) can be designed in various ways in relation to the width of the image recording area on the recording medium. From the viewpoint of lens performance and resolution, for example, the reading width of the line CCD 270 is about ½ of the width of the image recording area (the maximum width that can be inspected).

  Image data obtained by the line CCD 270 is converted into digital data by an A / D converter or the like, stored in a temporary memory, processed through the system controller 172, and stored in the image memory 174.

<Example of pattern formation for detecting online ejection defects>
FIG. 33 is an example of forming a detection pattern (test chart) for early detection of abnormal nozzles during printing. Here, the detection pattern 310 is formed in a blank portion (“non-image area”) 304 outside the image forming area 302 on the recording medium 114. In FIG. 33, the downward direction in the vertical direction is the recording medium conveyance direction. Although the detection pattern 310 is formed in the margin portion 304 on the leading end side of the sheet in the conveyance direction of the recording medium 114, the detection pattern may be formed in the margin portion on the trailing end of the sheet.

  The image forming area 302 is an area for drawing a target image. After the target image is drawn and recorded in the image forming area 302, the image is cut along the cutting line 306, the surrounding non-image portion is removed, and the image portion of the image forming area 302 is left as a printed product.

  As the detection pattern 310, for example, a so-called “1 on n off” type line pattern that can form independent sub-scanning direction lines for each nozzle in the head is formed.

  By transporting the recording medium 114 while discharging droplets continuously from one nozzle, a dot row (dots) in which dots formed by the landing ink from the nozzle are arranged in a line on the recording medium 114 in the sub-scanning direction ( In the case of a line head having a high recording density, if dots are simultaneously ejected from all nozzles, dots from adjacent nozzles partially overlap each other, so that the line for each nozzle cannot be determined. In order to be able to distinguish the lines formed by each nozzle individually, the line group is formed with at least one nozzle, preferably 3 nozzles or more, between the nozzles that discharge simultaneously.

  In this example, in one line head, nozzles constituting a nozzle row (substantially nozzle row obtained by orthographic projection) arranged in a line substantially along the main scanning direction from the end in the main scanning direction. When the nozzle numbers are assigned in order, the nozzle groups for simultaneous ejection are grouped according to the remainder number “B” (B = 0, 1,..., A−1) when the nozzle number is divided by an integer “A” of 2 or more. Then, the droplet ejection timing is changed for each nozzle number group of AN + 0, AN + 1,... AN + B, and a line group is formed by continuous droplet ejection from each nozzle (where N is an integer of 0 or more).

  Thereby, adjacent lines do not overlap in each line block, and independent lines can be formed for all the nozzles. Similar detection patterns are formed for the heads corresponding to the CMYK ink colors.

  However, since the area of the non-image portion 304 in the recording medium 114 is limited, a line pattern (test chart) for all nozzles of all heads may not be formed in the non-image portion 304 of one recording medium 114. In such a case, the test chart is formed separately on a plurality of recording media 114. For example, if the test chart that can be formed on the non-image portion 304 of one recording medium 114 is 1/8 of all the nozzles, the droplet ejection results of all the nozzles are checked separately for eight recording media 114. Become.

  If two types of waveforms are used as abnormal nozzle detection waveforms, one suitable for amplification of internal factors of the nozzle and one suitable for amplification of external factors of the nozzles, the recording medium can be doubled by 16 recording media. It is possible to check by factor for all heads and all nozzles. Then, it is possible to continue drawing recording on the image portion until all nozzles of all heads are checked for abnormality and correction processing for the detected abnormal nozzle is performed.

  However, since it takes a large number of sheets to complete the check of all nozzles, only one of the waveforms suitable for amplifying the nozzle internal factors or the waveform suitable for amplifying the nozzle external factors is used. A configuration using can also be used. In addition, it is possible to adopt a configuration in which the detection frequency based on the waveform suitable for amplification of the nozzle internal factor and the detection frequency based on the waveform suitable for amplification of the nozzle external factor are different.

<Flowchart of Unevenness Correction Sequence (Example 1)>
FIG. 34 is a flowchart showing a non-uniformity correction sequence in the ink jet recording apparatus according to the embodiment of the present invention. In this example, the unevenness correction includes a pre-correction process (step S11) in which a test chart is measured by a sensor (inline detection unit 144) in the apparatus to acquire correction data before the start of continuous printing by a print job. Combined with the on-line correction process (steps S20 to S38) for adaptive correction while continuously printing (without interrupting printing) by measuring the test chart with the inline detection unit 144 during printing It has become.

  In the pre-correction step (step S11), the pre-discharge failure detection process is performed in parallel with the pre-uniformity correction process.

  FIG. 35 shows a flowchart of the pre-correction process. As shown in FIG. 35, in the pre-correction process, first, an on-line ejection failure detection unevenness correction pattern is drawn on the image portion of the recording medium (paper) using the drawing drive waveform (step S101). This online discharge failure detection unevenness correction pattern is a line pattern suitable for measuring the landing position variation (landing error) of each nozzle, a line pattern suitable for specifying the undischarge nozzle position, and density unevenness measurement. A density pattern suitable for the case may be included. These test patterns may be combined and printed on one recording medium, or the elements of each test pattern may be divided and printed on a plurality of recording media.

  Further, after the above-described on-line ejection failure detection unevenness correction pattern is drawn, the recovery ejection described in FIGS. 14 to 17 and the nozzle surface cleaning operation described in FIGS. 18 to 24 are performed.

  The printing result of the unevenness correction pattern output in this way is read using the in-line detection unit 144 in the apparatus, density data, landing error data indicating landing position error of each nozzle, and non-ejection specifying the position of the non-ejection nozzle Various data necessary for processing such as image correction such as nozzle data is generated (step S102).

  Using the measurement result of the unevenness correction pattern, the inkjet recording apparatus 100 performs unevenness correction by applying a predetermined correction method (step S103). Here, as a correction method, any one of the correction methods described later is applied.

  In parallel with the prior unevenness correction shown in steps S101 to S103, the predischarge failure detection shown in steps S104 to S109 is performed. That is, an on-line ejection failure detection pattern (test chart) is formed with an abnormal nozzle detection waveform at the leading edge or image portion of the paper (step S104), and this is measured by the inline detection unit 144 (step S105). One or more types of abnormal nozzle detection waveforms are used. It is preferable to use a waveform or a plurality of types of waveforms that can cope with abnormal causes inside and outside the nozzle.

  A discharge failure nozzle is detected from the measurement result (step S106), and the specified discharge failure nozzle is subjected to non-discharge processing (step S107). That is, it is not used for droplet ejection at the time of drawing. Further, information on non-ejection nozzles in the head (non-ejection nozzle data) is generated (step S108), and this is stored in storage means such as a memory.

  Then, unevenness correction processing corresponding to these non-ejection nozzles is performed (step S109). As the unevenness correction method at this time, the same method as the correction method employed in step S103 can be employed. Further, a correction method different from that in step S103 may be adopted.

  The correction coefficient data, non-ejection nozzle data, and landing error data acquired by the pre-correction step (steps S101 to S109) as described above are stored in the inkjet recording apparatus 100 (preferably nonvolatile storage means). For example, stored in the ROM 175).

  The timing for performing the pre-correction described with reference to FIG. 35 is not particularly limited. For example, it is performed once every few days when the apparatus is started up.

(About the first correction method)
As the first correction method, for example, a known correction unit disclosed in JP-A-2006-347164 can be used. This method can correct density unevenness due to landing errors. This publication discloses image recording apparatuses (1) to (8) having the following configurations.

  (1) A recording head having a plurality of recording elements, conveying means for conveying at least one of the recording head and the recording medium and relatively moving the recording head and the recording medium, and recording characteristics of the recording element Characteristic information acquisition means for acquiring information indicating the above, a determination means for determining a correction target recording element for correcting density unevenness due to recording characteristics of the recording element, and the plurality of recording elements among the plurality of recording elements Among them, a correction range setting means for setting N (N is an integer of 2 or more) correction recording elements used for output density correction, and density unevenness due to the recording characteristics of the correction target recording elements are calculated. Correction coefficient determining means for determining density correction coefficients of the N correction recording elements based on correction conditions for reducing low frequency components of a power spectrum representing the spatial frequency characteristics of the same density unevenness Correction processing means for performing an operation for correcting the output density using the density correction coefficient determined by the correction coefficient determining means, and drive control means for controlling the driving of the recording element based on a correction result by the correction processing means. And an image recording apparatus.

  (2) The image recording according to (1), wherein the correction condition is a condition in which a differential coefficient at a frequency origin (f = 0) of a power spectrum representing a spatial frequency characteristic of density unevenness is substantially zero. apparatus.

  (3) The correction condition is expressed by N simultaneous equations obtained from a condition for preserving the direct current component of the spatial frequency and a condition in which the differential coefficients up to the (N−1) th order are substantially zero ( 2) The image recording apparatus described.

  (4) The image recording apparatus according to any one of (1) to (3), wherein the recording characteristic is a recording position error.

  (5) When the index for specifying the position of the recording element is i and the recording position of the recording element i is xi, the density correction coefficient di of the recording element i is given by

(4) The image recording apparatus described in (4),

(6) comprising storage means for storing a printing model of the recording element;
The image recording apparatus according to (1) or (2), wherein the correction coefficient determining unit determines the correction coefficient based on the print model.

  (7) The image recording apparatus according to (6), further comprising changing means for changing the print model based on a recording state of the recording element.

  (8) The image recording apparatus according to (6) or (7), wherein the printing model is a hemispherical model.

  The density non-uniformity (density unevenness) in the recorded image can be expressed by the intensity in the spatial frequency characteristic (power spectrum), and the visibility of the density unevenness can be evaluated by the low frequency component of the power spectrum. For example, by determining the density correction coefficient using a condition that the differential coefficient at the frequency origin (f = 0) of the power spectrum after correction using the density correction data is approximately 0, the intensity of the power spectrum at the frequency origin can be increased. The power spectrum in the vicinity of the origin (that is, the low frequency region) can be kept small. Thereby, accurate unevenness correction can be realized.

  Using the correction method disclosed in Japanese Patent Application Laid-Open No. 2006-347164, density correction coefficients corresponding to the correction target nozzles and the nozzles included in the peripheral correction range are obtained. Density unevenness due to nozzle recording characteristics (landing error, etc.) is calculated, and density correction data is calculated based on correction conditions for reducing low frequency components of the power spectrum representing the spatial frequency characteristics of the density unevenness. Using the density correction data, the image data is corrected for the input image data for printing.

  This image data correction processing is preferably performed on the continuous tone image data at the stage before halftoning processing (processing to convert to binary or multi-value dot data).

(About the second correction method)
As the second correction method, the correction method proposed in the specification of Japanese Patent Application No. 2008-254809 can be applied. In the second correction method, a non-ejection nozzle is specified, and a correction coefficient for correcting image data so as to compensate for the density of the non-ejection nozzle is calculated by surrounding nozzles other than the non-ejection nozzle. The specification of Japanese Patent Application No. 2008-254809 proposes the following configurations ([1], [2]).

  [1] Means for reading a density measurement test chart image recorded by a recording head having a plurality of recording elements arranged in a predetermined direction and acquiring density information indicating the recording density of each recording element. Density information acquisition means whose reading resolution in the direction along the array of the recording elements is smaller than the recording resolution of the recording elements, and non-ejection information acquisition means for acquiring non-ejection information indicating the non-ejection of the recording elements And density information correction means for correcting the density information acquired by the density information acquisition means based on the non-ejection information acquired by the non-ejection acquisition means, and density unevenness correction information is calculated from the corrected density information. Density unevenness correction information calculating means, non-ejection correction information calculating means for calculating non-ejection correction information for correcting non-ejection based on the non-ejection information; Image processing apparatus including an image data correction information calculation means for calculating the summed image data correction information and the correction information and the ejection failure correction information.

  [2] The density information correcting unit identifies a non-ejection recording element based on the non-ejection information, and corrects density information corresponding to the non-ejection recording element to be higher than density information before correction. 1] The image processing apparatus according to item 1.

  A specific method will be described with reference to FIGS.

  Returning to the description of the flowchart in FIG. 34, a pre-correction process is performed in step S11, and after acquiring data necessary for the correction, a print job for continuously printing a large number of sheets at an appropriate timing is started (step S20). After printing is started, online correction is performed by a correction method according to the second correction method. That is, when printing is started, an on-line ejection failure detection pattern (test chart) is formed on the non-image portion at the leading end of the paper with an abnormal nozzle detection waveform (step S22), and the image portion is used for normal drawing. A target image is drawn and recorded by the drive signal of the drive waveform (step S24).

  FIG. 36 is a plan view illustrating an example of an online ejection failure detection test chart. As shown in FIG. 36, this test chart C1 uses an ink droplet ejection head 250 to form a linear pattern 400 substantially parallel to the y direction (sub-scanning direction) at a predetermined interval in the x direction (main scanning direction). It is printed. Here, the interval d in the x direction of the pattern 400 is set according to the resolution of the inline detection unit 144. For example, when the substantial nozzle density N in the x direction of the ink droplet ejection head 250 is 1200 npi and the reading resolution R in the x direction of the inline detection unit 144 is 400 dpi, the interval d in the x direction of the pattern 400 is d ≧ 1. / R = 1/400 [inch].

  When creating the non-ejection detection test chart C1, specifically, ink is ejected every n (≧ 3 (= N ÷ R = 1200 ÷ 400)) nozzles in the x direction to form a pattern 400L for one line. Print. Next, printing is performed every n nozzles by shifting the nozzle for discharging ink by one in the x direction. By repeating this n times, the pattern 2400 by the liquid ejection from all the nozzles is printed. Thereby, it is possible to create a test chart C1 that can determine whether or not the nozzles are non-ejection nozzles with the resolution of the inline detection unit 144 for all the nozzles.

  The recording medium 114 on which the drawing and recording of the test chart C1 and the image portion has been completed is transported by transport means such as the transfer drum 124d and the impression drum 126d, and the print result of the on-line ejection failure detection pattern is read by the inline detection unit 144 ( Step S26). Based on this read information, the presence or absence of ejection failure is determined (step S28).

  Information relating to the abnormal nozzle determination criterion is stored in advance in the ROM 175 or the like, and a determination criterion value corresponding to the image quality mode is set. For example, reference values relating to one or a plurality of evaluation items such as an allowable value of landing error due to a flying curve, an allowable value of line width (allowable value of discharge amount), and a density value are defined. The presence or absence of an abnormal nozzle is determined according to this reference value, and the abnormal nozzle is specified.

  If there is no ejection failure (non-ejection or flying curve) nozzle in step S28, the process returns to step S22, and the above processing (steps S22 to S28) is repeated while continuing to print the target image.

  On the other hand, if there is a defective nozzle in step S28, the position of the abnormal nozzle is specified, and in order to handle this abnormal nozzle as a non-discharge nozzle that is not used when drawing the image portion, The non-ejection nozzle data shown is updated (step S30). Then, a nonuniformity correction pattern corresponding to the ejection failure is created in the non-image portion of the next recording medium 114 (step S32). This unevenness correction pattern is one in which droplet ejection from the specified abnormal nozzle is prohibited (discharging is stopped), and a pattern for density measurement is printed only with the remaining normal nozzles.

  When the unevenness correction pattern is drawn in the non-image portion, the drawing recording for the image portion of the recording medium 114 is performed using the nozzle detected as an abnormal nozzle in step S28 (discharged), and for normal recording. This is performed using a waveform drive signal (step S32). That is, drawing is continued under the same conditions as when printing the previous page.

  FIG. 37 is a plan view showing an example of a density measurement test chart (unevenness correction pattern). As shown in FIG. 37, the density measurement test chart C2 is obtained by printing a density pattern in which the density is constant in the x direction and the density changes stepwise in the y direction. By reading the image of the density measurement test chart C2 by the inline detection unit 144, density data corresponding to the pixel position (measurement density position) in the nozzle row direction of the inline detection unit 144 can be obtained. Note that the test chart C <b> 2 may be formed separately for a plurality of recording media 114 due to the limitation of the blank area of the recording media 114.

  The recording medium 114 on which the unevenness correction pattern (test chart C2) and the drawing and recording of the image portion have been completed is transported by transport means such as the transfer drum 124d and the impression drum 126d, and the print result of the test chart C2 is printed by the inline detection unit 144. Is read (step S36 in FIG. 34). Data is obtained from the read information, and density data representing the density distribution in the main scanning direction is obtained.

  Then, the image data is corrected based on the measurement result (step S38).

  FIG. 38 is a flowchart of the image data correction process in step S38.

  From the result of measuring the density of the density measurement chart, density data indicating the density distribution in the nozzle row direction (main scanning direction; referred to as x direction) is acquired (step S116). Next, the density data in the nozzle row direction is corrected based on the non-ejection nozzle data (step S118).

  FIG. 39 is a diagram for explaining the details of the density data correction processing in step S118 of FIG.

  First, a non-ejection density correction value (m1) is set for the nozzles specified as non-ejection nozzles for nozzles adjacent in the x direction (step S180). Here, the non-ejection density correction value (m1) is a value experimentally determined in advance and held in the ink jet recording apparatus 100, and m1 ≧ 1 (m1 = 1.4 to 1.6 in one example). . The value of m1 for the nozzles other than the nozzles on both sides of the non-ejection nozzle is 1.0. Then, as shown by m1 'in FIG. 39, the non-ejection density correction value is smoothed (smoothed) in the x direction by a low-pass filter (LPF) or moving average calculation (step S182).

  Next, the non-ejection chamber correction value m1 ′ corresponding to the nozzle position (nozzle number) is converted into a measured density correction value m1 ″ for each pixel position (measured density position) of the in-line detection unit 144 (step S184). 39, for convenience of explanation, the nozzle density in the x direction of the head 250 is 1200 npi, and the reading resolution in the x direction of the inline detection unit 144 is 400 dpi, in which case the non-ejection density correction value (m1 ′) is 3 (= (1200 ÷ 400) A measured density correction value is obtained by averaging in nozzle units.

  Next, the density data (measured density value) is corrected according to the following (Equation 1) using the measured density correction value m ″ obtained in step S184 (step S186).

(Corrected measured density value) = (measured density value) × (measured density corrected value) (Equation 1)
In the example shown in FIG. 39, the measured density correction value is set to a value larger than 1.0 at the measured density position including the non-ejection nozzle and the neighboring measured density position, and the measured density value at the measured density position is corrected. It is getting higher.

  Next, the process proceeds to step S120 in FIG. 38, and a density unevenness correction value (shading unevenness correction value) is calculated based on the density data for each measured density position of the inline detection unit 144 corrected in step S118 (step S120). ).

  FIG. 40 is a diagram for explaining the details of the density unevenness correction value calculation process in step S120 of FIG.

  As shown in FIG. 40, first, according to the resolution conversion curve indicating the correspondence between the pixel position (measured density position) of the inline detection unit 144 and the nozzle position, the measured density value for each measured density position corrected in step S118 is obtained. It is converted into density data for each nozzle position (step S200).

  Next, the difference between the density data D1 for each nozzle position obtained in step S200 and the target density value D0 is calculated (step S202).

  Next, according to the pixel value-density value curve indicating the correspondence between the pixel value and the density value, the density value difference calculated in step S202 is converted into a pixel value difference (step S204). The pixel value difference is stored in the image buffer memory 182 as a density unevenness correction value for each nozzle position (step S206).

  Next, the process proceeds to step S122 in FIG. 38, and the density unevenness correction value is corrected with the non-ejection correction value using the non-ejection nozzle data (step S122). That is, as shown in FIG. 41, the non-ejection correction value (m2) is set to the nozzles on both sides of the non-ejection nozzle. Here, the non-ejection correction value (m2) is a value experimentally determined in advance and held in the inkjet recording apparatus 100, and m2 ≧ 1.0 (m2 = 1.4 to 1.6 in one example). is there. Note that the value of m2 for nozzles other than the nozzles on both sides of the non-ejection nozzle is 1.0. Then, the density unevenness correction value is corrected by the following (Equation 2). In the following (Expression 2), the density unevenness correction value is multiplied by the non-ejection correction value, but may be added.

(Corrected density unevenness correction value) = (density unevenness correction value) × (non-ejection correction value) (Expression 2)
Next, using the density unevenness correction value, the input image data is corrected to generate output image data (step S124 in FIG. 38). Based on the corrected output image data obtained in this way, an image is drawn on the recording medium in the next drawing process.

  That is, after step S38 in FIG. 34, it is determined whether or not the print job is completed in step S40. If it is not completed, the process returns to step S22 and drawing on the next recording medium 114 is performed. When drawing the image part after correcting the image data in step S38, the nozzles that are recognized as abnormal nozzles in the previous ejection failure detection are not used (no discharge), and recording is performed only with other normal nozzles. Done.

  Thus, the above processing (steps S22 to S40) is repeated until the print job is completed. When the completion of the print job is confirmed in step S40, the printing is finished (step S42).

  As described above, the test chart is formed in the non-image portion and the test chart is read in the non-image portion while the image portion is drawn and recorded during continuous printing, and online correction is performed from the read result.

  According to the present embodiment, when correcting density unevenness due to the presence of a non-ejection nozzle, accurate density correction is performed regardless of the resolution of the in-line detection unit 144 used for reading the density measurement test chart. be able to. In addition, since the resolution of the inline detection unit 144 can be lowered, the amount of data related to density unevenness correction can be reduced and the processing can be lightened. In addition, since the inline detection unit 144 can be an inexpensive one with a low resolution, the cost of the apparatus can be reduced.

[Other correction methods]
Next, another correction method will be described. In the following description, the description of the same configuration as that of the embodiment described in FIGS. 34 to 41 is omitted.

  FIG. 42 is a diagram showing details of the density data correction processing in step S118 of FIG.

  As shown in FIG. 42, in the present embodiment, when correcting the density data, first, based on the resolution conversion curve, the position of the non-ejection nozzle of the non-ejection nozzle data is determined based on the measured density position of the in-line detection unit 144. (Step S180).

  Next, based on the non-ejection nozzle data updated and acquired in step S30 of FIG. 34, the number of non-ejection nozzles at the measured concentration position of the inline detection unit 144 is obtained and stored in the non-ejection occurrence number table T1 (step S1). S182). In the example shown in FIG. 42, since the nozzle density in the x direction of the head 250 is 1200 npi and the reading resolution in the x direction of the inline detection unit 144 is 400 dpi, the non-ejection occurrence number data at each measurement density position in the non-ejection occurrence number table T1. Values from 0 to 3 are stored.

  Next, based on the non-ejection occurrence number data, the density data in the nozzle row direction is corrected by the following (Equation 3) (steps S184 and S186).

(Corrected measured concentration value) = (measured concentration value) × (measured concentration corrected value) (Equation 3)
Here, the measured density correction value is an experimentally determined parameter and is stored in advance in the ROM 175 of the inkjet recording apparatus 100. In the example shown in FIG. 42, the measured density correction value increases as the number of non-ejection nozzles at the measured density position increases and as the measured density value increases. That is, in step S186, the corrected density value (density data) at the position is corrected so as to increase as the number of non-ejection nozzles at the position increases and as the measured density value increases.

  According to the present embodiment, as in the embodiments described with reference to FIGS. 38 to 41, when correcting density unevenness due to the presence of a non-ejection nozzle, an inline detection unit used for reading a density measurement test chart Regardless of the resolution of 144, accurate density correction can be performed.

[Countermeasures when many abnormal nozzles are detected]
In the process described in steps S28 to S30 in FIG. 34, it is preferable to warn the user (user) when the number of nozzles detected as abnormal nozzles exceeds a predetermined specified value. For example, a warning message is displayed on the display unit 198 to alert the user about the necessity of head maintenance.

  Alternatively, a mode in which the head maintenance is automatically executed instead of or in combination with the above warning is also preferable. In this case, since it is necessary to move the head to the maintenance position, printing is interrupted, and maintenance operations such as pressure purge, ink suction, idle ejection, and nozzle surface wiping are performed in the maintenance unit.

<Example 2 of flowchart of unevenness correction sequence>
FIG. 43 is a flowchart showing a second example of the unevenness correction sequence in the ink jet recording apparatus according to the embodiment of the present invention. In FIG. 43, steps that are the same as or similar to those in the flowchart described in FIG. 34 are given the same step numbers, and descriptions thereof are omitted.

  The unevenness correction sequence shown in FIG. 43 is to perform pre-correction offline, instead of pre-correction using the inline detection unit in FIG. That is, the unevenness correction shown in FIG. 43 includes a pre-correction (offline correction) step (steps S12 to S16) in which a test chart is measured offline to acquire correction data before starting continuous printing by a print job (steps S12 to S16). An online correction process (step S20) in which correction is performed adaptively while performing continuous printing (without interrupting printing) by measuring a test chart with a sensor (inline detection unit 144) in the apparatus during printing. To S40).

  As shown in FIG. 43, first, a test chart for offline measurement is output (step S12), and the print result is measured in detail by an offline scanner (not shown) (step S14). The test chart here shows a line pattern suitable for measuring the landing position variation (landing error) of each nozzle, a line pattern suitable for specifying the position of an undischarge nozzle, and a density suitable for measuring density unevenness, etc. Includes patterns. In the case of off-line measurement, a test pattern can be formed on the entire recording surface (image forming area and non-image area) of the recording medium 114.

  These test patterns may be combined and printed on one recording medium, or the elements of each test pattern may be divided and printed on a plurality of recording media. The printing result of the test chart output in this way is read using an image reading device such as a flat bed scanner, landing error data indicating the landing position error of each nozzle, non-ejection nozzle data specifying the position of the non-ejection nozzle, etc. Various data necessary for processing such as image correction are generated. Note that it is desirable to use an offline scanner having a higher resolution (higher resolution) than the inline detection unit 144 in the apparatus.

  Various data thus obtained is input to the inkjet recording apparatus 100 via a communication interface, an external storage medium (removable medium), or the like.

  Using the off-line measurement result, the inkjet recording apparatus 100 has two types of methods, a first correction method for correcting density unevenness due to landing errors and a second correction method for correcting density unevenness due to non-ejection nozzles. Apply the correction method.

  Thus, the correction coefficient data calculated by each of the first correction method and the second correction method, the non-ejection nozzle data, and the landing error data are stored in a storage unit (preferably a non-volatile storage unit, For example, it is stored in the ROM 175).

  The timing for performing offline measurement is not particularly limited. For example, it is performed once every few days when the apparatus is started up. Further, when forming a test chart for off-line measurement, it is possible to use a recording waveform drive signal, or an abnormal nozzle detection waveform drive signal, using both waveforms. It is also possible to measure in detail. However, it is preferable to use a recording waveform drive signal for the test chart for measuring the landing position error.

  The steps after step S20 (steps S20 to S42) in the flowchart of FIG. 43 are the same as those in FIG.

<About fine adjustment of drive waveform signal for each head>
Depending on the individual characteristics, the CMYK heads (or head modules) may have different droplet amounts and ejection speeds even when the same drive signal is given. For this reason, it is also preferable to finely adjust the waveform for each head (or for each head module).

  For example, a correction parameter for correcting the abnormal nozzle detection waveform for each head may be stored in the ROM 175 or the like, and the waveform of the drive signal applied to each head may be corrected using this correction parameter. Further, this correction parameter may be commonly used as a correction parameter for a drawing (recording) waveform.

  As an example of a specific method, a test pattern is drawn in advance with a drawing (recording) waveform at the time of shipment of the apparatus, and the correction parameter (for example, the waveform of the waveform) is measured from the measurement result of the image density (or dot diameter). (Voltage magnification) is determined in advance. Information on this correction parameter is stored in the ROM 175 or the like, and is used for waveform correction during ejection driving. The correction parameter is also applied to the correction of the abnormal nozzle detection waveform.

<About recording media>
“Recording medium” is a generic term for media on which dots formed by droplets ejected from a nozzle are recorded, and is called by various terms such as a printing medium, a recording medium, an image forming medium, an image receiving medium, and a discharging medium. Is included. In carrying out the present invention, the material and shape of the recording medium are not particularly limited, and a printed sheet on which a continuous sheet, a cut sheet, a seal sheet, a resin sheet such as an OHP sheet, a film, a cloth, a wiring pattern, and the like are formed, It can be applied to various media regardless of rubber sheet and other materials and shapes.

<Means for moving the head and paper relative to each other>
In the above-described embodiment, the configuration in which the recording medium is transported to the stopped head is exemplified. However, in the implementation of the present invention, a configuration in which the head is moved with respect to the stopped recording medium (the drawing medium) is also possible. In addition, a configuration in which both the head and the recording medium are moved is also possible. A single-pass type full-line type recording head is usually arranged along a direction orthogonal to the feeding direction (conveying direction) of the recording medium. There may be a mode in which the head is disposed along an oblique direction with an angle.

<Application examples to other devices>
In the above embodiment, application to an inkjet recording apparatus for graphic printing has been described as an example, but the scope of application of the present invention is not limited to this example. For example, a wiring drawing device that draws a wiring pattern of an electronic circuit, a manufacturing device for various devices, a resist printing device that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing device, and a material deposition material. The present invention can be widely applied to inkjet systems that obtain various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus for forming a structure.

<Appendix>
In this specification, the following invention aspects are also disclosed regarding the non-ejection correction technique and the nozzle surface cleaning technique.

  (Invention 16): In any one of inventions 1 to 14, as the abnormal nozzle detection means, an optical sensor for optically detecting a discharge result for abnormality detection by application of a drive signal of the abnormal nozzle detection waveform Is used. An ink jet recording apparatus comprising:

  As an example of the optical sensor, an image reading unit that reads a drawing result such as a pattern formed on a recording medium can be used. Further, instead of the image reading means, an optical sensor that captures a droplet in flight can be used. The optical sensor is not limited to the one installed in the ink jet recording apparatus, and may be an external apparatus such as a scanner configured separately from the apparatus. In this case, the entire inkjet system including the external device is interpreted as an “ink jet recording device”. Furthermore, an aspect including a plurality of optical sensors is also possible. For example, a plurality of sensors having different reading resolutions can be provided.

  (Invention 17): In the invention 16, the optical sensor is disposed opposite to a conveying unit that conveys the recording medium after drawing by the inkjet head, and an image that reads the recording surface of the recording medium being conveyed by the conveying unit. An ink jet recording apparatus which is a reading unit.

  According to this aspect, the test pattern on the recording medium can be read during the printing process in which the target image is drawn and recorded (without stopping drawing), and the reading result can be reflected in the correction. it can. In this manner, since abnormal nozzles can be detected during drawing and correction processing reflecting the detection results can be performed, throughput is improved while maintaining recording quality.

  (Invention 18): In Invention 17, prior to drawing and recording the target image on the recording medium, pre-detection by the optical sensor and pre-correction using the detection result are performed, and drawing and recording of the target image is performed. An ink jet recording apparatus, wherein detection by the optical sensor and correction using the detection result are performed.

  According to this aspect, it is possible to perform both pre-correction before drawing recording and online detection and correction during drawing recording of the target image using the optical sensor. Pre-correction enables high-precision detection and correction, and detection and correction during drawing and recording can also deal with ejection abnormalities that can occur during continuous recording.

  (Invention 19): In the invention 18, in the prior detection, a plurality of types of waveforms are used as the abnormal nozzle detection waveform, and in the detection during drawing and recording of the target image, one type of the abnormal nozzle detection waveform is used. An inkjet recording apparatus using a waveform.

  When a test pattern for detecting abnormal nozzles is formed in a non-image area (margin portion) of a recording medium, a plurality of recording media may be required to evaluate all nozzles due to the limitation of the margin area. In this way, when evaluating the presence / absence of abnormality of all nozzles with a test pattern divided into a plurality of sheets, if a plurality of types of abnormal nozzle detection waveforms are used, the combination of each waveform type is completed for all nozzles. It is conceivable that the number of recording media required for the process increases.

  In the detection during drawing and recording, by using only one type of waveform, the number of sheets required for one cycle of the detection pattern can be reduced, and the amount of waste paper generated can be reduced.

  (Invention 20): Ink jet, characterized in that, in Invention 16 or 17, in addition to the optical sensor arranged to face the conveying means, a second optical sensor having detection performance different from the optical sensor is provided. Recording device.

  The optical sensor to be used can be selectively changed according to the purpose such as the quality and throughput of the target output image. In addition to a mode in which switching control means for automatically switching the optical sensor to be used is provided, the sensor may be changed by a manual operation of the user.

  (Invention 21): The ink jet recording apparatus according to Invention 20, wherein the second optical sensor has a resolution different from that of the optical sensor arranged to face the conveying means.

  For example, regarding the first optical sensor installed in the apparatus and the second optical sensor installed outside the apparatus, the second optical sensor has a higher resolution than the first optical sensor.

  (Invention 22): In Invention 20 or 21, the second optical sensor is offline image reading means for reading a recording surface on a recording medium offline, and before drawing and recording the target image on the recording medium. In addition, prior detection using the second optical sensor and preliminary correction using the detection result are performed, and detection using the optical sensor and correction using the detection result are performed during drawing and recording of a target image. An inkjet recording apparatus.

  According to this aspect, it is possible to perform both pre-correction (offline detection and correction) by the second optical sensor and online detection and correction during drawing and recording of the target image. Pre-correction enables high-precision detection and correction, and detection and correction during drawing and recording can also deal with ejection abnormalities that can occur during continuous recording.

  (Invention 23): The inkjet recording apparatus according to Invention 20, in Invention 19, in the prior detection, a plurality of types of waveforms are used as the abnormal nozzle detection waveform, and in the detection during drawing and recording of the target image, One type of waveform is used as the abnormal nozzle detection waveform.

  In the detection during drawing and recording, by using only one type of waveform, the number of sheets required for one cycle of the detection pattern can be reduced, and the amount of waste paper generated can be reduced.

  (Invention 24): In any one of Inventions 16 to 24, there is provided information storage means for storing information defining a criterion for judging whether or not there is an ejection abnormality with respect to the information obtained from the optical sensor. An ink jet recording apparatus characterized in that an abnormal nozzle indicating an ejection abnormality is specified in accordance with the reference.

  By applying the drive signal of the abnormal nozzle detection waveform, ejection failure is promoted and amplified. By comparing the information (sensor output signal, etc.) obtained by detecting this with the specified standard, it is displayed on the drawn image. The presence or absence of an abnormal nozzle can be determined at a stage before an image defect occurs.

  (Invention 25): An inkjet recording apparatus according to Invention 24, comprising a plurality of image quality modes, and comprising control means for changing the reference according to the set image quality mode.

  According to this aspect, the throughput and reliability can be changed according to the required image quality.

  (Invention 26): An inkjet recording apparatus according to any one of Inventions 1 to 25, further comprising warning output means for outputting a warning based on the number determined as the abnormal nozzle.

  If the number of nozzles detected as abnormal nozzles becomes very large, there may be a case where the effect of performing the non-discharge process on these nozzles cannot be sufficiently compensated by other nozzles. Therefore, it is also preferable to perform a control in which a predetermined determination reference value is stored in advance in a memory or the like and a warning is given to the user (user) when the number of abnormal nozzles exceeds the reference value.

  (Invention 27): The inkjet according to any one of Inventions 1 to 26, further comprising a maintenance control means for performing a control for performing a maintenance operation of the inkjet head based on the number determined as the abnormal nozzle. Recording device.

  When the number of abnormal nozzles exceeds a certain amount, it is preferable to perform a control for automatically performing head maintenance. For example, as a maintenance operation, a control unit and a maintenance mechanism for performing at least one of pressure purge, ink suction, idle ejection, and nozzle surface wiping are provided. Thereby, it is possible to prevent a drawing defect when the number of abnormal nozzles is excessive.

  (Invention 28): An ink jet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to each nozzle are provided, a transporting means for transporting the recording medium, and the ink jet head on the recording medium. A recording waveform signal generating means for generating a recording waveform drive signal applied to the pressure generating element when drawing and recording a target image, and the ejection when detecting an abnormal nozzle of the inkjet head First abnormal nozzle detection waveform signal generating means for generating a drive signal of a first abnormal nozzle detection waveform having a waveform that lowers the ejection speed than the recording waveform, and detecting an abnormal nozzle of the inkjet head When the liquid is discharged, the first waveform is formed of a waveform in which the amount of liquid rising from the nozzle is larger than the recording waveform. Second abnormal nozzle detection waveform signal generating means for generating a drive signal of the abnormal nozzle detection waveform, and the first abnormal nozzle detection waveform or the drive signal of the second abnormal nozzle detection waveform as the pressure. A discharge control means for detection that applies a discharge to the generation element to perform discharge for abnormality detection, and an abnormal nozzle detection means that identifies an abnormal nozzle that indicates discharge abnormality from the discharge result for abnormality detection. An ink jet recording apparatus.

  According to the present invention, it is possible to promote and amplify each defect and effectively detect an abnormality inside the nozzle and an abnormality outside the nozzle. For this reason, highly accurate detection is possible, and it is possible to detect with a low resolution sensor.

  (Invention 29): When a target image is drawn and recorded on a recording medium by an inkjet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to each nozzle is provided, the pressure generating elements are given Separately from the drive signal for the recording waveform, when the ejection for detecting the abnormal nozzle of the ink jet head is performed, the first abnormal nozzle detection waveform is driven, which has a waveform that lowers the ejection speed than the recording waveform. When the first abnormal nozzle detection waveform signal generating step for generating a signal and ejection for detecting the abnormal nozzle of the inkjet head are performed, the amount of liquid rising from the nozzle is larger than the recording waveform. A second abnormal nozzle detection waveform signal generating step for generating a drive signal of a second abnormal nozzle detection waveform comprising a waveform; An abnormal nozzle detection waveform or a drive signal of the second abnormal nozzle detection waveform is applied to the pressure generating element to perform discharge for abnormality detection from the nozzle, and the abnormality detection An abnormal nozzle detection method comprising: an abnormal nozzle detection step of identifying an abnormal nozzle that indicates an abnormal discharge from the discharge result of the step.

  (Invention 30): In Invention 9 or 10, the recovery means stores a liquid storage part that stores the recovery liquid, a recovery flow path that connects the liquid storage part and the recovery hole, and storage in the liquid storage part. And a pressure increasing / decreasing means for increasing / decreasing the pressure applied to the recovered liquid.

  (Invention 31): In the invention 9 or 10, the recovery means includes a liquid storage section that stores the recovery liquid, a recovery flow path that connects the liquid storage section and the recovery hole, Pressure increasing / decreasing means for increasing or decreasing the pressure applied to the recovered liquid.

  (Invention 32): The ink jet recording apparatus according to Invention 30 or 31, wherein the pressure increasing / decreasing means varies the pressure applied to the recovered liquid according to the viscosity of the recovered liquid.

  (Invention 33): In any one of Inventions 9 to 32, the pressure increasing / decreasing means applies a negative pressure to the recovery hole before the recovery liquid overflows the droplet discharge surface from the recovery hole. Inkjet recording device.

  (Invention 34): The inkjet recording apparatus according to any one of Inventions 9, 10, and 30 to 33, wherein the recovered liquid is a liquid that dissolves or disperses the attached liquid.

  (Invention 35): The ink jet recording apparatus according to any one of Inventions 9, 10, 30 to 34, wherein the color of the recovered liquid is the same color as the adhesion liquid or is transparent.

  DESCRIPTION OF SYMBOLS 1 ... Nozzle, 2 ... Ink, 3 ... Meniscus, 4 ... Bubble, 5, 6 ... Foreign matter, 10 ... Recording waveform, 12, 20 ... Discharge pulse, 14, 22 ... Pre-pulse, 40 ... Paper, 42 ... Image formation area 62 ... Line, 100 ... Inkjet recording device, 126c, 126d ... Impression cylinder (conveying means), 144 ... Inline detection unit, 140C, 140M, 140Y, 140K ... Ink droplet ejection head (inkjet head), 172 ... System controller, 175 ... ROM, 180 ... print control unit, 196 ... operation unit, 200 ... head, 201 ... nozzle surface, 202 ... nozzle, 204 ... pressure chamber, 208 ... common flow path, 220 ... common return flow path, 230 ... collection hole , 212 ... Actuator, 240 ... Recovery device, 242 ... Syringe pump, 300 ... Control unit, 251 ... Nozzle, 252 Pressure chamber, 258 ... actuator, 302 ... image forming region, 304 ... non-image portion

Claims (15)

An inkjet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to each nozzle are provided;
Conveying means for conveying the recording medium;
A recording waveform signal generating means for generating a recording waveform drive signal applied to the pressure generating element when the target image is drawn and recorded on the recording medium by the inkjet head;
An abnormal nozzle detection waveform signal generating means for generating a drive signal of an abnormal nozzle detection waveform comprising a waveform different from the recording waveform when performing ejection for detecting an abnormal nozzle of the inkjet head;
For detection that causes the abnormal nozzle detection waveform drive signal to be applied to the pressure generating element to discharge the abnormal detection from the nozzle in a state where the inkjet head is disposed at a position where the ink can be discharged onto the recording medium. A discharge control means;
An abnormal nozzle detecting means for specifying an abnormal nozzle indicating a discharge abnormality from the discharge result for abnormality detection;
Correction control means for correcting the image data so as to stop the discharge of the specified abnormal nozzle and draw and record a target image with a nozzle other than the abnormal nozzle;
A discharge control means for recording that performs drawing recording by controlling discharge from nozzles other than the abnormal nozzle according to the image data corrected by the correction control means;
A recovery means for performing an operation of recovering the discharge performance of the inkjet head before performing the drawing and recording of the target image after the discharge for abnormality detection is performed;
An ink jet recording apparatus comprising: In claim 1,
The recovery means includes recovery discharge control means for applying a recovery waveform drive signal different from the recording waveform and the detection waveform to the pressure generating element to perform recovery discharge. Inkjet recording apparatus. In claim 2,
The inkjet recording apparatus, wherein the recovery waveform is a waveform having a larger potential difference than the recording waveform. In claim 2 or 3,
The inkjet recording apparatus, wherein the recovery waveform is a waveform in which a pulse is applied at an interval obtained by dividing the wavelength (period T ₀ ) of the recording waveform by an integer N (where N ≧ 2). In any one of Claims 2 thru | or 4,
An ink jet recording apparatus, wherein droplets ejected by applying a drive signal having the recovery waveform are attached to the recording medium. In claim 1,
The recovery means includes recovery pattern formation control means for performing ejection based on recovery image data representing a predetermined recovery drawing pattern and forming the recovery drawing pattern on the recording medium. Inkjet recording apparatus. In claim 6,
The ink jet recording apparatus, wherein the recovery drawing pattern is a pattern having a coverage of 10% or less, and discharges the nozzle on which the abnormality detection discharge has been performed. In claim 6,
The recovery drawing pattern is a pattern in which a simultaneous drive rate indicating a ratio of the number of nozzles to be simultaneously ejected among nozzle groups connected to the same flow path in the inkjet head is 10% or less. Inkjet recording device. In claim 1,
The recovery means includes nozzle surface cleaning means for cleaning a nozzle surface provided with the plurality of nozzles of the inkjet head;
The nozzle surface cleaning means includes
A recovery hole provided on the nozzle surface for recovering the adhering liquid adhering to the nozzle surface;
An ink jet recording apparatus comprising: a recovery unit that causes the recovery liquid to overflow from the recovery hole to the nozzle surface and recovers the overflowed recovery liquid from the recovery hole together with the adhering liquid. In claim 9,
The inkjet recording apparatus, wherein the attached liquid is collected by the nozzle surface cleaning means at a position where the inkjet head faces the recording medium. In any one of Claims 1 thru | or 10,
The target image is drawn and recorded in an image forming area on the recording medium,
The inkjet recording apparatus, wherein the abnormality detection ejection is performed in a non-image area other than the image forming area on the recording medium. In claim 11,
An ink jet recording apparatus, wherein at least one of a test pattern for detecting abnormal nozzles and a test pattern for correcting density unevenness is formed in the non-image area on the recording medium. In claim 11 or 12,
The ink jet recording apparatus according to claim 1, wherein the abnormal nozzle detection waveform is a waveform that causes a discharge speed to be lower than that of the recording waveform. In any one of Claims 11 thru | or 13,
2. The ink jet recording apparatus according to claim 1, wherein the abnormal nozzle detection waveform is a waveform in which a rising amount of liquid from the nozzle is larger than the recording waveform. Driving a recording waveform to be applied to the pressure generating element when a target image is drawn and recorded on a recording medium by an inkjet head in which a plurality of nozzles are arranged and a plurality of pressure generating elements corresponding to the nozzles are provided. A recording waveform signal generating step for generating a signal;
An abnormal nozzle detection waveform signal generating step for generating a drive signal of an abnormal nozzle detection waveform comprising a waveform different from the recording waveform when performing ejection for detecting an abnormal nozzle of the inkjet head;
For detection that causes the abnormal nozzle detection waveform drive signal to be applied to the pressure generating element to discharge the abnormal detection from the nozzle in a state where the inkjet head is disposed at a position where the ink can be discharged onto the recording medium. A discharge control process;
An abnormal nozzle detection step for identifying an abnormal nozzle indicating a discharge abnormality from the discharge result for abnormality detection;
A correction control step of correcting the image data so as to stop the discharge of the specified abnormal nozzle and draw and record a target image with a nozzle other than the abnormal nozzle;
A recording discharge control step of performing drawing recording by controlling discharge from nozzles other than the abnormal nozzle according to the image data corrected by the correction control step;
A recovery step of performing an operation of recovering the discharge performance of the inkjet head after performing the abnormality detection discharge and before drawing and recording the target image;
An ink jet recording method comprising: