JP2005104037A - Image forming device and recording control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device which can form a preferable image even if abnormal ejection occurs at one of ejection nozzles, and can reduce the number of the nozzles in a recording head, and to provide a recording control method. <P>SOLUTION: The print head 50 has fundamental nozzles 51A for use in formation of an image, and redundant nozzles 51B for use in substitute ejection when the fundamental nozzles 51A undergo ejection failure. The number of the redundant nozzles 51B is a half of the number of the fundamental nozzles 51A, and therefore the total number of the nozzles in the print head 50 can be reduced. When the fundamental nozzle 51-2 undergoes ejection failure, the redundant nozzle 51-21 is controlled so as to carry out substitute ejection for formation of a dot row 102, and therefore the ejection failure of the fundamental nozzle 51-2 is complemented. When the fundamental nozzle 51-3 undergoes ejection failure, at least one of the spare nozzles 51-21 and 51-41 is controlled so as to carry out substitute ejection, and therefore the ejection failure of the fundamental nozzle 51-3 is complemented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and a recording control method, and more particularly to a complementary recording control technique for an abnormality of a recording element.

  In recent years, inkjet recording apparatuses (inkjet printers) have become widespread as recording apparatuses that print and record images taken by digital still cameras. An ink jet recording apparatus includes a plurality of recording elements in a head. The recording head is scanned while ejecting ink droplets from the recording elements onto the recording medium, and when one line of an image is recorded on the recording paper, one recording medium is recorded. An image is formed on the recording paper by conveying the line and repeating this process.

  Ink jet printers use a single serial head and perform recording while scanning the head in the width direction of the recording medium, and recording elements are arranged corresponding to the entire area of one side of the recording medium. Some use a line head. In the case of using a line head, image recording can be performed on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements. A printer using a line head does not require a transport system such as a carriage that scans a short head, and does not require complicated scanning control between the carriage movement and the recording medium. In addition, since only the recording medium moves, the recording speed can be increased as compared with a printer using a serial head.

  In an ink jet printer, ink thickening, solidification, mixing of bubbles into the nozzle, and the like may occur, and an ejection abnormality may occur in which ink is not ejected normally from the nozzle. Such ejection abnormal nozzles cause image deterioration such as streaks and unevenness. In particular, in an inkjet printer using a line head, unevenness occurs along the recording medium conveyance direction, and the image is significantly deteriorated.

  Therefore, in an inkjet printer, not only is it controlled to quickly find a nozzle with an abnormal discharge and perform a recovery operation on the nozzle, but each nozzle is equipped with a redundant nozzle. A method has been proposed in which the redundant nozzle is operated instead of the abnormal nozzle to complement the nozzle.

  In the ink jet recording method and apparatus disclosed in Patent Document 1, image data is divided so as to complement and record corresponding to two nozzle rows in the recording head, and any nozzle is detected by the non-ejection detection means. When non-ejection is detected in a row, check whether the nozzles in the other nozzle row at the same position as the non-ejection nozzle are normal. Control is performed to add image data corresponding to the non-ejection nozzle.

  In addition, the ink jet head and the ink jet recording apparatus described in Patent Document 2 include a plurality of pressure chamber rows in which a plurality of pressure chambers are arranged in a direction inclined from the longitudinal direction of the head, and are arranged in the same straight line in the scanning direction. Control is performed so that ink is alternately ejected from the nozzle corresponding to the pressure chamber.

Furthermore, the ink jet recording apparatus and the ink jet recording method described in Patent Document 3 increase the ejection amount from the nozzle adjacent to the non-ejection nozzle detected by the non-ejection nozzle detection means for detecting the non-ejection nozzle, thereby causing a non-ejection. Completion processing of the discharge nozzle is performed.
Japanese Patent Laid-Open No. 10-6488 JP 2002-225265 A JP 2001-315318 A

  However, in order to cope with the non-ejection of all the nozzles, it is necessary to provide N times as many redundant nozzles (an integer of N ≧ 1) as the number of nozzles, which increases the size of the recording head and increases the cost. Further, by providing redundant nozzles, the total number of nozzles in the recording head increases, so that the maintenance mechanism is expected to increase in size and control load.

  In the ink jet recording method and apparatus disclosed in Patent Document 1, since the nozzles at the same position must be provided for each nozzle, the number of nozzles in the recording head cannot be reduced. In addition, since the nozzle that complements the non-ejection of other nozzles is also used for image formation, the recording control becomes complicated.

  Further, in the ink jet head and the ink jet recording apparatus described in Patent Document 2, it is necessary to provide nozzles at the same position for each nozzle, and the number of nozzles in the recording head cannot be reduced.

  Further, the ink jet recording apparatus and the ink jet recording method described in Patent Document 3 require a discharge amount control unit that controls the ink discharge amount of the nozzle adjacent to the non-discharge nozzle.

  The present invention has been made in view of such circumstances, and an image forming apparatus and recording control capable of forming a preferable image even when an abnormal ejection nozzle occurs and reducing the number of nozzles in the recording head. It aims to provide a method.

  In order to achieve the above object, an invention according to claim 1 is an image forming apparatus for forming an image on a recording medium, and discharges droplets that are mainly used during image formation and form dots on the recording medium. A basic nozzle row in which basic nozzles to be arranged are arranged, a print head having a redundant nozzle row in which a smaller number of redundant nozzles are arranged than the basic nozzles, and the redundant nozzles are substituted when the basic nozzles become abnormal in discharge. And a droplet ejection control means for controlling droplet ejection.

  That is, since the number of redundant nozzles smaller than that of the basic nozzles makes it possible to perform complementary discharge when the basic nozzles become abnormally discharged, image deterioration due to abnormal discharge of the basic nozzles can be reduced.

  By operating only the basic nozzle, it is possible to form the desired image on the recording medium (by realizing the desired dot diameter, dot pitch, and resolution), but the basic nozzle performs normal ejection. Even during the operation, it is preferable to control the redundant nozzles to operate at regular intervals.

  Discharge abnormalities include discharge amount abnormality in which the actual discharge amount is smaller (larger) than the predetermined discharge amount, non-discharge without droplets being discharged at all, discharge direction abnormality in which the discharge direction deviates from the predetermined discharge direction, etc. The present invention is applicable to any ejection abnormality.

  A mode provided with a discharge detection means for detecting a discharge abnormality of the basic nozzle is preferable. The discharge detection means may pick up an image (recording result) formed on the recording medium using an image pickup means such as a line sensor, or a non-contact measurement means using a laser or the like for a droplet discharged from the nozzle. May be used for observation. When the droplets discharged from the nozzle are monitored, a complementary operation can be realized in real time.

  The recording head may be a full-line type recording head in which nozzle openings are arranged over the entire printable area in a direction substantially perpendicular to the recording medium conveyance direction, or a short recording head in the recording medium conveyance direction. A serial type recording head that ejects droplets while moving in a substantially orthogonal direction may be used. Further, it may be a split type head having a plurality of recording heads in a direction substantially orthogonal to the recording medium conveyance direction.

  The recording medium is a medium (image forming medium) that receives printing by a recording head, and is various regardless of material or shape such as continuous paper, cut paper, sealing paper, resin sheet such as OHP sheet, film, cloth, and the like. Media.

  According to a second aspect of the present invention, the number of the redundant nozzles is ½ of the number of the basic nozzles.

  That is, by setting the number of redundant nozzles to ½ of the basic number of nozzles, the total number of nozzles in the print head can be reduced, and the print head can be reduced in size.

  As shown in claim 3, in the invention according to claim 1 or 2, the redundant nozzles are arranged in a staggered manner with respect to the basic nozzles.

  If the basic nozzles and the redundant nozzles are arranged in a staggered manner, the space in the recording head can be used efficiently.

  The arrangement interval of the redundant nozzles may be based on the actual basic nozzle interval, or may be based on the projection nozzle interval when projected in the longitudinal direction of the recording head.

  As shown in claim 4, in the invention according to claim 1, 2 or 3, the droplet ejection control means, when the basic nozzle becomes abnormal discharge, among the redundant nozzles adjacent to the basic nozzle which has abnormal discharge, Control is performed so that substitute droplet ejection is performed from at least one redundant nozzle.

  For example, when a certain basic nozzle becomes abnormal in discharge, if there is one redundant nozzle adjacent to the abnormal discharge nozzle, substitute droplet ejection may be performed from now on, or if there are two or more adjacent redundant nozzles, these Substitute droplet ejection may be performed from one redundant nozzle. Further, substitute droplet ejection may be performed from two or more adjacent redundant nozzles.

  The adjacent redundant nozzle may be a nozzle that is closest to the basic nozzle, or may be a redundant nozzle that forms a dot closest to the dot formed by the basic nozzle.

  According to a fifth aspect of the present invention, in the first or second aspect of the present invention, the recording apparatus includes a transport unit that relatively moves the recording medium and the recording head in the recording medium transport direction, and the redundant nozzle is the basic nozzle. The nozzles are arranged on the same straight line substantially parallel to the recording medium conveyance direction of the nozzles, and are arranged every other basic nozzle.

  A mode in which the redundant nozzle is arranged upstream of the basic nozzle in the recording medium conveyance direction is preferable. Of course, the redundant nozzle may be arranged downstream of the basic nozzle in the recording medium conveyance direction.

  According to a sixth aspect of the present invention, in the invention according to the fifth aspect, the droplet ejection control means is configured such that the basic nozzle in which redundant nozzles are arranged on the same straight line substantially parallel to the recording medium conveyance direction causes abnormal discharge. In this case, the control is performed so that substitute ejection is performed in place of the basic nozzle in which the ejection is abnormal from the redundant nozzle arranged on the same straight line substantially parallel to the recording medium conveyance direction. It is said.

  If a basic nozzle in which redundant nozzles are arranged on the same straight line that is substantially parallel to the recording medium conveyance direction becomes abnormal, it will be replaced by the redundant nozzles on the same straight line that is substantially parallel to the recording medium conveyance direction. Since the substitute droplet ejection is performed, it is possible to supplement the basic nozzle in which the ejection is abnormal.

  In particular, in a full-line type recording head, if redundant nozzles are placed on the same straight line that is substantially parallel to the recording medium conveyance direction, the same position as the basic nozzle that caused the ejection failure. Therefore, it is possible to reliably compensate for the ejection abnormality.

  According to a seventh aspect of the present invention, in the invention according to the fifth or sixth aspect, the discharge control means discharges a basic nozzle in which the redundant nozzle is not disposed on the same straight line substantially parallel to the recording medium conveyance direction. When an abnormality occurs, substitute droplet ejection is performed by at least one basic nozzle among the basic nozzles adjacent to the basic nozzle in which ejection abnormality has occurred and redundant nozzles arranged on the same straight line substantially parallel to the recording medium conveyance direction. It is characterized by control.

  That is, even when the redundant nozzle is not arranged on the same straight line substantially parallel to the recording medium conveyance direction and the basic nozzle in which ejection abnormality has occurred, the recording medium of the basic nozzle adjacent to the basic nozzle in which ejection abnormality has occurred. Substitute droplet ejection can be performed from redundant nozzles arranged on the same straight line substantially parallel to the transport direction, so that the ejection abnormality of the basic nozzle can be complemented, and the visibility of image deterioration due to ejection abnormality can be reduced.

  Further, in the invention according to claim 7, the discharge control means is configured such that the basic nozzle in which the redundant nozzle is not arranged on the same straight line substantially parallel to the recording medium conveyance direction causes abnormal discharge. In this case, at least one of the basic nozzles adjacent to the basic nozzle that is abnormally discharged performs the droplet ejection for the basic nozzle that is abnormally ejected, and the basic nozzle that performs the droplet ejection and the recording medium conveyance Control is performed so that substitute droplet ejection is performed by redundant nozzles arranged on the same straight line substantially parallel to the direction.

  That is, when a basic nozzle that does not have redundant nozzles arranged on the same straight line substantially parallel to the recording medium conveyance direction has an ejection failure, at least one basic nozzle that is adjacent to the basic nozzle in which the ejection failure has occurred Substitute droplet ejection is performed from the redundant nozzles arranged on the same straight line substantially parallel to the recording medium conveyance direction of the basic nozzle used for substitution droplet substitution. Dots formed by the ejected droplets become dots larger than a predetermined size, and the visibility of image deterioration due to ejection abnormality can be lowered.

  Further, as shown in claim 9, in the invention according to any one of claims 1 to 8, when the basic nozzle in which ejection abnormality has occurred is not ejected, the ejection control means It is characterized by controlling so as not to perform substitute droplet ejection.

  That is, if the basic nozzle in which ejection is abnormal is not ejected, substitute ejection is not performed, and the control load can be reduced.

  Further, according to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the discharge control means is configured to provide the redundant nozzle at a predetermined ratio with respect to the operation of the basic nozzle during image formation. It is characterized by controlling to operate.

  Since the basic nozzle and the redundant nozzle are operated at a predetermined ratio at the time of image formation, even when the basic nozzle is abnormally discharged, the redundant nozzle complements. Further, since the redundant nozzles are driven at regular intervals, the maintenance load on the redundant nozzles can be reduced.

  Further, as described in claim 11, in the invention according to any one of claims 1 to 10, the recording head includes two or more nozzle rows in which nozzles for discharging ink droplets are arranged, The nozzle row includes a redundant nozzle row in which redundant nozzles of the same color dark ink and redundant nozzles of the same color light ink are arranged.

  In other words, since the redundant nozzles of the same color dark and light ink are arranged in the same nozzle row, the recording head can be reduced in size.

  The redundant nozzles for dark ink and the redundant nozzles for light ink may be arranged alternately or in groups of several. Further, a plurality of redundant nozzles of light ink may be arranged between redundant nozzles of dark ink, or a plurality of redundant nozzles of dark ink may be arranged between redundant nozzles of light ink.

  The number of the dark ink redundant nozzles and the light ink redundant nozzles may be the same, or one of them may be large.

  The present invention also provides a method invention for achieving the above object. According to a twelfth aspect of the present invention, there is provided an image forming apparatus for forming an image by ejecting liquid droplets onto a recording medium from a recording head provided with basic nozzles used for image formation and fewer redundant nozzles than the basic nozzles. An image recording step of discharging droplets from the basic nozzle to form an image on the recording medium, a discharge detecting step of detecting a discharge abnormality of the basic nozzle, and the discharge detecting step. And a substitute droplet ejecting step of performing substitute droplet ejection from a predetermined redundant nozzle when a discharge abnormality of the basic nozzle is detected.

  An aspect including a basic nozzle recovery step of executing a recovery operation of the basic nozzle that has become abnormal in discharge is preferable.

  According to the present invention, a recording head for forming an image on a recording medium is provided with a number of redundant nozzles less than the number of basic nozzles and basic nozzles, and when the basic nozzles become abnormal in discharge, the redundant nozzles are operated. Therefore, even if the basic nozzle is abnormally discharged, it is complemented by the redundant nozzle, and the number of nozzles in the recording head can be reduced.

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

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a print unit 12 having a plurality of print heads 12K, 12C, 12M, and 12Y provided for each ink color, and each print head 12K, 12C, 12M, An ink storage / loading unit 14 for storing ink to be supplied to 12Y, a paper feeding unit 18 for supplying recording paper 16, a decurling unit 20 for removing curling of the recording paper 16, and a nozzle of the printing unit 12 A suction belt transport unit 22 that is disposed to face a surface (ink ejection surface) and transports the recording paper 16 while maintaining the flatness of the recording paper 16, and a print detection unit 24 that reads a printing result by the printing unit 12, A paper discharge unit 26 that discharges printed recording paper (printed matter) to the outside.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration that uses roll paper, a cutter (first cutter) 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is disposed on the printing surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least portions facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 are horizontal ( Flat surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, a suction chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  When the power of a motor (not shown in FIG. 1, described as reference numeral 88 in FIG. 6) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 rotates in the clockwise direction in FIG. , And the recording paper 16 held on the belt 33 is conveyed from left to right in FIG. Details of the belt 33 will be described later.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blow method of blowing clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although a mode using a roller / nip conveyance mechanism instead of the suction belt conveyance unit 22 is also conceivable, if the roller / nip conveyance is performed in the print area, the image easily spreads because the roller contacts the printing surface of the sheet immediately after printing. There is a problem. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 is a so-called full-line head in which a line-type head having a length corresponding to the maximum paper width is arranged in a direction orthogonal to the paper feeding direction (recording paper conveyance direction) (see FIG. 2). Although a detailed structural example will be described later, each of the print heads 12K, 12C, 12M, and 12Y has a length that exceeds at least one side of the maximum size recording paper 16 targeted by the inkjet recording apparatus 10, as shown in FIG. A line type head in which a plurality of ink discharge ports (nozzles) are arranged is formed.

  Printing corresponding to each color ink in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16 (hereinafter referred to as the recording paper transport direction). Heads 12K, 12C, 12M and 12Y are arranged. A color image can be formed on the recording paper 16 by discharging the color inks from the print heads 12K, 12C, 12M, and 12Y while the recording paper 16 is conveyed.

  As described above, according to the printing unit 12 in which the full line head that covers the entire width of the paper is provided for each ink color, the operation of relatively moving the recording paper 16 and the printing unit 12 in the recording paper transport direction is performed. The image can be recorded on the entire surface of the recording paper 16 only by performing it once (that is, by scanning once in the recording paper conveyance direction). Thus, high-speed printing is possible and productivity can be improved as compared with a serial (shuttle scan) type head in which the print head reciprocates in a direction substantially perpendicular to the recording paper conveyance direction.

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink and dark ink are added as necessary. May be. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta.

  As shown in FIG. 1, the ink storage / loading unit 14 has tanks that store inks of colors corresponding to the print heads 12K, 12C, 12M, and 12Y, and each tank is connected via a conduit (not shown). The print heads 12K, 12C, 12M, and 12Y communicate with each other. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means, etc.) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. doing.

  The print detection unit 24 includes an image sensor for imaging the droplet ejection result of the print unit 12, and functions as a means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor.

  The print detection unit 24 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink ejection width (image recording width) by the print heads 12K, 12C, 12M, and 12Y. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor is composed of a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads test patterns (or actual images) printed by the print heads 12K, 12C, 12M, and 12Y of the respective colors, and detects ejection of each head. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like. In addition, the print detection unit 24 includes a light source (not shown) that irradiates light to the ejected dots.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  When printing on porous paper with dye-based ink, the weather resistance of the image is prevented by blocking the paper holes by pressurization and preventing contact with ozone or other substances that cause dye molecules to break. There is an effect to improve.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined surface uneven shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown in FIG. 1, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders. Reference numeral 26B denotes a test print discharge unit.

  Next, the structure of the print head 50 will be described. Since the structures of the print heads 12K, 12C, 12M, and 12Y provided for the respective ink colors are common, the print heads are represented by reference numeral 50 in the following.

  FIG. 3A is a plan view showing the arrangement of the nozzle openings 51 on the nozzle opening forming surface of the print head 50. Hereinafter, the nozzle opening 51 is simply referred to as the nozzle 51.

  As shown in FIG. 3A, the print head 50 according to the present embodiment is used at the time of image formation (printing), and mainly includes basic nozzles 51A arranged along a direction substantially orthogonal to the recording paper conveyance direction. The redundant nozzle 51B is used for complementary droplet ejection of the basic nozzle 51A and is arranged in parallel with the basic nozzle row.

  The basic nozzle 51A (for example, the basic nozzle 51-2) and the corresponding redundant nozzle 51B (for example, the redundant nozzle 51-21) are arranged on the same straight line substantially parallel to the recording paper conveyance direction, and the redundant nozzle 51B is the basic nozzle. 51A is provided upstream of the recording paper conveyance direction.

  The number of redundant nozzles 51B is ½ of the basic nozzle 51A, and the pitch of the redundant nozzle 51B in the direction substantially orthogonal to the recording paper conveyance direction is the pitch of the basic nozzle 51A in the direction substantially orthogonal to the recording paper conveyance direction. Is approximately twice as large as

  That is, as shown in FIG. 3 (a), the print head 50 includes the basic nozzle 51A along the direction substantially orthogonal to the recording paper transport direction, 51-1, 51-2, 51-3, 51-4, 51-5,... Are arranged in this order, and among them, the basic nozzle 51-2 and the basic nozzle 51-4 are respectively the redundant nozzle 51-21 and the redundant nozzle 51 on the same straight line substantially parallel to the recording paper transport direction. -41. In other words, every other basic nozzle 51A includes redundant nozzles 51B that can eject droplets at the same droplet ejection point.

  Here, the nozzle pitch may be an interval (distance) between the nozzles, or a projected nozzle pitch projected so as to be aligned in a direction substantially perpendicular to the recording paper conveyance direction or the recording paper conveyance direction.

  FIG. 3B is a plan perspective view (enlarged view) showing an example of the structure of the print head 50, and shows the arrangement of the pressure chambers 52 communicated with the nozzle openings 51. 4 is a cross-sectional view (a cross-sectional view taken along line 4-4 in FIG. 3B) showing a three-dimensional configuration of the ink chamber unit.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. Each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54.

  An actuator 58 having an individual electrode 57 is joined to the pressure plate 56 constituting the top surface of the pressure chamber 52, and the actuator 58 is deformed by applying a driving voltage to the individual electrode 57, and the nozzle 51 Ink is ejected. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example. In this example, the print head having one basic nozzle row and one redundant nozzle row is illustrated, but a matrix head in which these nozzles are two-dimensionally arranged may be used.

  In the present embodiment, a method of ejecting ink droplets by deformation of an actuator 58 typified by a piezo element (piezoelectric element) is employed. In carrying out the present invention, the method for ejecting ink is not particularly limited. Instead of the piezo method, a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure. Various methods can be applied.

  FIG. 5 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10.

  The ink supply tank 60 is a base tank for supplying ink, and is installed in the ink storage / loading unit 14 described with reference to FIG. There are two types of ink supply tank 60: a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the ink remaining amount is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type. The ink supply tank 60 of FIG. 5 is equivalent to the ink storage / loading unit 14 of FIG. 1 described above.

  As shown in FIG. 5, a filter 62 is provided between the ink supply tank 60 and the print head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 5, a configuration in which a sub tank is provided in the vicinity of the print head 50 or integrally with the print head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  The mode in which the internal pressure is controlled by the sub-tank includes a mode in which the internal pressure in the ink chamber unit 53 is controlled by the difference in ink water level between the sub-tank opened to the atmosphere and the ink chamber unit 53 in the print head 50, or a sealed sub-tank. There are modes in which the internal pressures of the sub tank and the ink chamber are controlled by a connected pump, and any mode may be applied.

  Further, the inkjet recording apparatus 10 is provided with a cap 64 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle 51 and a cleaning blade 66 as a means for cleaning the surface of the nozzle 51. Yes.

  The maintenance unit including the cap 64 and the cleaning blade 66 can be moved relative to the print head 50 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the print head 50 as necessary. The

  The cap 64 is displaced up and down relatively with respect to the print head 50 by an elevator mechanism (not shown). The cap 64 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the print head 50, thereby covering the nozzle surface (ink ejection surface) with the cap 64.

  During printing or standby, if the frequency of use of a specific nozzle 51 is reduced and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, ink cannot be ejected from the nozzle 51 even if the actuator 58 operates.

  Before such a state is reached (within the range of the viscosity that can be discharged by the operation of the actuator 58), the actuator 58 is operated, and the cap 64 (ink near the nozzle whose viscosity has increased) is discharged. Preliminary ejection (purging, idle ejection, brim ejection) is performed toward the ink receiver.

  Further, when air bubbles are mixed into the ink in the print head 50 (in the pressure chamber 52), the ink cannot be ejected from the nozzle even if the actuator 58 is operated. In such a case, the cap 64 is applied to the print head 50, the ink in the pressure chamber 52 (ink mixed with bubbles) is removed by suction with the suction pump 67, and the suctioned and removed ink is sent to the collection tank 68. .

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

  The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the ink discharge surface (surface of the nozzle plate) of the print head 50 by a blade moving mechanism (wiper) (not shown). When ink droplets or foreign substances adhere to the nozzle plate, the nozzle plate surface is wiped by sliding the cleaning blade 66 on the nozzle plate to clean the nozzle plate surface. It should be noted that when the ink ejection surface is cleaned by the blade mechanism, preliminary ejection is performed in order to prevent foreign matter from being mixed into the nozzle 51 by the blade.

  FIG. 6 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and 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 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 is a control unit that controls each unit such as the communication interface 70, the image memory 74, the motor driver 76, and the heater driver 78. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, and the like, as well as a transport system motor 88 and heater 89. A control signal for controlling is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. FIG. 6 shows only the motor driver 76 and the motor 88, but the system controller 72 controls a plurality of motor drivers and motors.

  The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from the image data in the image memory 74 according to the control of the system controller 72, and the generated print A control unit that supplies a control signal (print data) to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing of the ink droplets of the print head 50 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 6, the image buffer memory 82 is shown in a form associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with a single processor.

  The head driver 84 drives the actuators of the print heads 12K, 12C, 12M, and 12Y for each color based on the print data given from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor, reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, droplet ejection And the detection result is provided to the print control unit 80.

  The print control unit 80 performs various corrections of the print head 50 based on information obtained from the print detection unit 24 as necessary. In the ink jet recording apparatus 10, when ejection abnormality of the basic nozzle 51 </ b> A is detected, droplet ejection control is performed in which the redundant nozzle 51 </ b> B is operated to perform droplet ejection in place of the ejection abnormality nozzle. Details of the droplet ejection control will be described later.

  Further, in the example shown in FIG. 1, the print detection unit 24 is provided on the print surface side, and the print surface is illuminated by a light source (not shown) such as a cold cathode tube arranged near the line sensor. Although the configuration is such that the reflected light is read by the line sensor, other configurations may be used in the implementation of the present invention.

[First Embodiment]
Next, details of droplet ejection control in the inkjet recording apparatus 10 will be described.

  In general, when ink is exposed to the atmosphere, moisture such as glycerin or alcohol having a high boiling point evaporates, and the viscosity gradually increases to form a thickened layer. Accordingly, in a nozzle that does not discharge for a long time, the ink thickens from the vicinity of the discharge opening, and these thickened inks cause discharge abnormalities. In addition, air bubbles mixed into the nozzle 51 and the pressure chamber 52 also cause abnormal discharge.

  Discharge abnormalities include discharge volume abnormalities in which the amount of discharged ink droplets is less than a predetermined discharge amount, abnormal discharge directions in which the ink droplet discharge direction deviates from the original discharge direction, and non-ejection in which no ink droplets are discharged. There is. When the ejection amount is abnormal, the size of the formed dot is smaller than the original size, and when the ejection direction is abnormal, the dot is formed at a position shifted from the original droplet ejection point. In addition, the non-ejection dots are not formed.

  When an abnormal discharge is detected by the print detection unit 24 shown in FIG. 1, the recovery operation of the abnormal discharge nozzle is performed using the maintenance mechanism shown in FIG. On the other hand, when an ejection abnormality is detected during image recording, a complementary operation is performed in which the redundant nozzle 51B shown in FIG.

  The detection of the print result by the print detection unit 24 may be performed by picking up a print result (actual image, test pattern, etc.) using an image pickup means such as a line sensor and analyzing the result to identify an abnormal discharge nozzle. Good. Here, since a known method can be applied to the method for identifying the ejection abnormal nozzle from the printing result, a detailed description thereof is omitted.

  Further, as a method other than imaging the printing result, there is a method of detecting an ejection abnormal nozzle by directly observing the state of ink droplets flying by a non-contact measuring means using a laser or the like. Of course, various methods other than the method described above can be applied.

  FIG. 7 shows a configuration of a print head 50 according to a conventional example. The print head 50 has the same number of redundant nozzles 51B as the basic nozzles 51A. That is, the basic nozzle 51A is arranged in the order of 51-1, 51-2, 51-3, 51-4, 51-5,... In the direction substantially orthogonal to the recording paper conveyance direction, and the redundant nozzle 51B is the basic nozzle. Arranged in the order of 51-11, 51-21, 51-31, 51-41, 51-51,... Parallel to the direction substantially perpendicular to the row and the recording paper conveyance direction.

  Further, the redundant nozzles 51-11, 51-21, 51-31, 51-41, 51-51 are respectively connected to the basic nozzles 51-1, 51-2, 51-3, 51-4, 51-5. The redundant nozzles 51B are arranged on the same straight line substantially parallel to the recording medium conveyance direction, and the redundant nozzles 51B are provided upstream of the basic nozzles 51A in the recording paper conveyance direction.

  In the print head 50 having such a structure, for example, when the basic nozzle 51-1 is detected as non-ejection (ejection abnormality), the redundant nozzle 51-11 is operated to perform substituting for the basic nozzle 51-1. The non-ejection can be complemented. This is because the basic nozzle 51-1 and the redundant nozzle 51-11 can eject ink droplets at the same droplet ejection point. Similarly, when non-ejection of each basic nozzle is detected, the redundant nozzle corresponding to each basic nozzle can be operated to complement non-ejection.

  However, since the conventional example shown in FIG. 7 includes the same number of redundant nozzles as the number of nozzles (basic nozzles) necessary for image formation (recording), the number of nozzles is twice that of the basic nozzles, and the print head 50 is provided. Will increase the size and cost. Further, the increase in the size of the print head 50 leads to an increase in the size of maintenance members such as the cap 64 and the blade 66 shown in FIG.

  Therefore, in order to reduce the number of nozzles in the print head 50, the number of redundant nozzles 51B is halved of the basic nozzle 51A in the inkjet recording apparatus 10 to reduce the total number of nozzles in the print head 50. Is realized.

  Next, the droplet ejection control of the print head 50 will be described in detail. Hereinafter, the same or similar parts as those in FIG. 3A are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 8 is a diagram for explaining the nozzle arrangement of the print head 50 shown in FIG. 3A and the droplet ejection control when the basic nozzle 51-2 does not discharge.

  When ink droplets are normally ejected from the basic nozzle 51A, as shown in FIG. 8, dots (images) 100 are formed on the recording paper 16 at positions where dots are originally formed.

  Here, when the nozzle 51-2 is not ejected, dots are not formed in the dot row indicated by the reference numeral 102, and the print result image is uneven in the recording paper transport direction. In the inkjet recording apparatus 10, when the print detection unit 24 shown in FIG. 1 detects the non-ejection of the basic nozzle 51-2, it corresponds to the basic nozzle 51-2 (the same straight line substantially parallel to the recording paper transport direction). The droplet ejection control is performed so that the redundant nozzle 51-21 (provided on the line) is operated to eject the dot row 102. Accordingly, no streaks are generated in the print result image along the recording paper conveyance direction.

  The droplet ejection timing of the redundant nozzle 51-21 is controlled so as to be shifted from the droplet ejection timing of the basic nozzle 51-2 according to the recording paper conveyance speed.

  With reference to FIG. 9, the droplet ejection control when the basic nozzle 51-3 having no redundant nozzles on the same straight line substantially parallel to the recording paper conveyance direction fails to discharge will be described.

  When the basic nozzle 51-3 fails to discharge, the redundant nozzle is not provided on the same straight line substantially parallel to the recording paper conveyance direction, and the substitute droplet ejection described with reference to FIG. 8 cannot be performed. Therefore, the droplet ejection control is performed so that the redundant nozzles 51-21 and 51-41 located after the basic nozzle 51-2 and the basic nozzle 51-4 adjacent to the basic nozzle 51-3 are operated to perform substitute droplet ejection. Done. As a result, a dot row 102A and a dot row 104A are formed. In FIG. 9, the dots included in the dot row 102 </ b> A and the dot row 104 </ b> A are indicated by a dashed line.

  By performing substitution droplet ejection in this way, it is possible to reduce the visibility of uneven stripes in the recording paper conveyance direction caused by non-ejection of the basic nozzle 51-3 (basic nozzle having no redundant nozzle).

  Here, if the basic nozzle 51-2 and the basic nozzle 51-4 are not ejecting droplets, if the basic nozzle 51-2 and the basic nozzle 51-4 are controlled to operate simultaneously, the dot row 102A and the dot row 104A are displayed. The dot rows 102B and 104B composed of dots larger than a predetermined size are formed, and it becomes possible to further reduce the visibility of uneven stripes occurring in the recording paper conveyance direction.

  When the non-ejected basic nozzle is not ejected, it is not necessary to perform substitute droplet ejection (complementary operation), so that the redundant nozzle is controlled not to operate. Furthermore, it is possible to perform control so that redundant nozzles are selectively used according to whether the basic nozzles are on or off.

  For example, when the basic nozzle 51-3 is not ejecting and the basic nozzle 51-2 is ejected and the basic nozzle 51-4 is ejected, the droplet ejection control described with reference to FIG. 9 is executed.

  On the other hand, if the basic nozzle 51-2 is not ejected and the basic nozzle 51-4 is ejected, the redundant nozzle 51-41 is activated (the redundant nozzle 51-21 is not activated), and the basic nozzle 51-2 is ejected. In the case of droplets and basic nozzle 51-4 non-droplet ejection, the redundant nozzle 51-21 is operated (the redundant nozzle 51-41 is not operated).

  Further, if both the basic nozzle 51-2 and the basic nozzle 51-4 are not ejecting droplets, control is performed to activate either the redundant nozzle 51-21 or the redundant nozzle 51-41. At this time, it may be controlled to operate the redundant nozzle closer to the ideal droplet ejection position of the basic nozzle 51-3.

  In the present embodiment, the non-ejection of the basic nozzle has been described. However, the present invention can also be applied to ejection abnormalities other than non-ejection.

  In the ink jet recording apparatus 10 configured as described above, the basic nozzles 51A are positioned upstream on the same straight line substantially parallel to the basic nozzle 51A and the recording paper conveyance direction, and are arranged in a direction substantially orthogonal to the recording paper conveyance direction. When the non-ejection of the basic nozzle 51A is detected using the redundant nozzles 51B provided for every other nozzle, control is performed to perform substitute droplet ejection. The non-ejection of the basic nozzle 51A can be complemented and the total number of nozzles in the print head 50 can be reduced.

  On the other hand, since it is not necessary to control the discharge amount of the redundant nozzle 51B, the discharge amount control means is unnecessary.

  Further, the control for operating the redundant nozzle 51B may be performed by switching the redundant nozzle 51B that is operated in accordance with the ON / OFF of the basic nozzle 51A. Further, a basic nozzle adjacent to a basic nozzle that has failed in ejection when the redundant nozzle 51B is operating may be operated.

  Next, FIG. 10 shows a modified example of the redundant nozzle 51B described above.

  The print head 50 shown in FIG. 10 is provided with a nozzle that discharges the same color dark and light ink. In the print head 50, dark ink nozzles 200 (200-1, 200-2,...) Are arranged along a direction substantially perpendicular to the recording paper conveyance direction, and light nozzles 204 (discharge light ink). , 204-1, 204-2, 204-3,...) Are arranged along a direction substantially perpendicular to the recording paper conveyance direction, and dark ink redundant nozzles 208 (208-21, 208-41,. ..), Redundant nozzle rows 212 in which light ink redundant nozzles 210 (210-21, 210-41,...) Are alternately arranged along a direction substantially orthogonal to the recording paper transport direction are provided. 212 is disposed between the dark ink row 202 and the light ink row 206.

  That is, the dark ink redundant nozzle 208-21 is arranged on the same straight line substantially parallel to the recording paper transport direction upstream of the dark ink nozzle 200-2 in the recording paper transport direction, and the recording paper transport of the light ink nozzle 204-2 is performed. A light ink redundant nozzle 210-21 is arranged on the same straight line substantially parallel to the recording paper conveyance direction on the upstream side in the direction. Further, the dark ink redundant nozzle 208-21 and the light ink redundant nozzle 210-21 are adjacent to each other in a direction substantially orthogonal to the recording paper conveyance direction.

  In the print head 50 configured as described above, it is possible to complement between dark ink and light ink.

  For example, when the dark ink nozzle 200-1 is not ejected, the light ink redundant nozzle 210-21 can be operated to perform substitute droplet ejection. Further, when the light ink nozzle 204-2 is operated, non-ejection of the dark ink nozzle 200-1 can be complemented by two droplets of light ink.

  On the other hand, when the light ink nozzle 204-3 does not eject, the dark ink nozzle 200-2 and the dark ink redundant nozzle 208-21 can be operated. In this case, it can be supplemented by operating any one of the nozzles and adjusting the number of times of droplet ejection according to the density difference between the dark ink and the light ink.

  In FIG. 10, the light ink nozzle row 206, the redundant nozzle row 212, and the dark ink nozzle row 202 are arranged in this order from the upstream side to the downstream side in the recording paper conveyance direction. The dark ink nozzle row 202 and the redundant nozzle row 212 may be exchanged. Further, the light ink nozzle row 206 and the redundant nozzle row 212 may be interchanged.

  The nozzle arrangement in the redundant nozzle row 212 is not limited to the arrangement shown in FIG. 10, and any arrangement that combines the dark ink redundant nozzle 208 and the light ink redundant nozzle 210 may be used.

  Furthermore, the nozzles of the redundant nozzle row 212 may be configured by only one of the dark ink redundant nozzle 208 and the light ink redundant nozzle 210.

  In the print head 50 described above, the number of nozzle rows can be reduced and the size of the head can be reduced by combining nozzles of the same color dark and light ink. Moreover, non-ejection can be complemented with high accuracy by using the same color ink.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described.

  FIG. 11 is a diagram for explaining nozzle arrangement of the print head 50 provided in the inkjet recording apparatus 10 according to the second embodiment of the present invention and its droplet ejection control.

  As described with reference to FIGS. 8 to 10, the print head 50 includes basic nozzle rows in which basic nozzles 51A are arranged in a direction substantially orthogonal to the recording paper conveyance direction, and redundant nozzles 51B substantially in the recording paper conveyance direction. Redundant nozzle rows arranged in an orthogonal direction, and the redundant nozzle rows are arranged upstream of the basic nozzle rows in the recording paper conveyance direction.

  Here, in the print head 50 shown in FIG. 11, when the basic nozzle 51A and the redundant nozzle 51B are projected so as to be aligned in the direction orthogonal to the recording paper conveyance direction, the redundant nozzle 51B is arranged approximately in the middle of the adjacent basic nozzle 51A. It has become a staggered arrangement.

  In other words, the redundant nozzle 51-21 is arranged between the basic nozzle 51-2 and the basic nozzle 51-3 on the upstream side of the basic nozzle row in the recording paper conveyance direction, while the basic nozzle 51-3 and the basic nozzle 51-3 are arranged. No redundant nozzles are arranged between the nozzles 51-4 and the upstream side of the basic nozzle row in the recording paper conveyance direction.

  In the print head 50 in which the basic nozzle 51A and the redundant nozzle 51B are arranged in this way, when the basic nozzle 51-2 does not discharge, the redundant nozzle 51-21 is operated to perform substitute ejection. Be controlled. FIG. 11 shows dots (images) 300 ejected from the print head 50.

  That is, when the basic nozzle 51-2 is not ejected, dots (not shown) that are originally formed by the ink droplets ejected from the basic nozzle 51-2 are not formed. The non-ejection of the basic nozzle 51-2 can be supplemented by the dot row 302 formed by the ink droplets.

  FIG. 12 is a diagram for explaining droplet ejection control when the basic nozzle 51-3 fails to discharge. When the basic nozzle 51-3 is not ejected, the dots (not shown) that are originally formed by the ink droplets ejected from the basic nozzle 51-3 are not formed, so the ink ejected from the redundant nozzle 51-21 The non-ejection of the basic nozzle 51-3 can be complemented by the dot row 302 formed by droplets.

  Similarly, when the basic nozzle 51-4 and the basic nozzle 51-5 fail to discharge, the redundant nozzle 51-41 is operated, and the basic nozzle 51-6 and the basic nozzle 51-7 fail to discharge. In this case, the redundant nozzle 51-61 is operated to perform droplet ejection, and it is possible to supplement when the basic nozzle 51A fails to discharge.

  In the inkjet recording apparatus 10 configured as described above, since the basic nozzles 51A and the redundant nozzles 51B are arranged in a staggered arrangement, the redundant nozzles are more efficiently performed than the substitute droplet ejection control described in the first embodiment. 51B can be operated.

  Although FIG. 12 illustrates an aspect in which the redundant nozzle 51B is arranged at the approximate center between the basic nozzles 51A, the arrangement of the redundant nozzle 51B may be offset from the approximate center between the basic nozzles 51A.

  Further, as shown in FIG. 13, the present embodiment can also be applied to a print head in which the same color inks described with reference to FIG. 10 are combined. 13 that are the same as or similar to those in FIG. 10 are assigned the same reference numerals, and descriptions thereof are omitted.

  In FIG. 13, a dark ink redundant nozzle 208-21 is provided upstream of the dark ink nozzle 200-2 and dark ink nozzle 200-3 in the conveyance direction of the recording paper, and the dark ink nozzle 200-2 and the dark ink nozzle. When 200-3 fails to discharge, the dark ink redundant nozzle 208-21 can be operated to compensate.

  On the other hand, a light ink redundant nozzle 210-21 is provided on the upstream side in the recording paper conveyance direction between the light ink nozzle 204-2 and the light ink 204-3, and the light ink nozzle 204-2 and the light ink 204-3 are provided. In the case of non-ejection, the light ink redundant nozzle 210-21 can be operated to compensate.

[Application example]
Next, application examples of the first embodiment and the second embodiment described above will be described. As described above, the basic nozzle 51A and the redundant nozzle 51B are provided in the print head, and the ejection abnormality of the basic nozzle 51A is detected. When the ejection abnormality of the basic nozzle 51A is detected, the redundant nozzle 51B is used to perform substitute droplet ejection. Although the droplet ejection control to be performed has been disclosed, if ejection abnormality detection does not function due to a failure or the like, even if ejection abnormality occurs in the basic nozzle by performing droplet ejection replacement (droplet ejection control) described below, the result Generation of uneven stripes in an image can be reduced.

  First, in the nozzle arrangement shown in FIG. 8, the redundant nozzle 51-21 is replaced at a frequency of about 1/3 with respect to the droplet ejection of the basic nozzle 51-2. In other words, control is performed so that one of the four basic droplets 51-2 is ejected using the redundant nozzle 51-21 instead of the basic nozzle 51-2. Similarly, the redundant nozzle 51-41 is replaced with the frequency of about 1/3 with respect to the droplet ejection of the basic nozzle 51-4.

  Further, the redundant nozzle 51-21 is replaced with the redundant nozzle 51-21 at a frequency of about 1/6 with respect to the droplets ejected from the basic nozzle 51-3, and the redundant nozzle 51 with a frequency of about 1/6 with respect to the droplets ejected from the basic nozzle 51-3. Replace with -41.

  By performing droplet ejection in this manner, the droplet ejection frequencies of the basic nozzle 51A and the redundant nozzle 51B are equalized. By equalizing the nozzle frequency, the nozzle standby time (time interval between discharge and discharge) is equalized between the basic nozzle 51A and the redundant nozzle 51B.

  Furthermore, about 1/3 of the non-ejections of the basic nozzle 51A can be supplemented by redundant nozzles.

  Next, in the nozzle arrangement shown in FIG. 11, the redundant nozzle 51-21 is replaced at a frequency of about 1/3 with respect to the droplet ejection of the basic nozzle 51-2. Similarly, the redundant nozzle 51-21 is replaced at a frequency of about 1/3 with respect to the droplet ejection of the basic nozzle 51-3.

  Also, it is replaced with the redundant nozzle 51-41 at a frequency of about 1/6 with respect to the droplets of the basic nozzle 51-4. Replace with nozzle 51-41.

  By performing droplet ejection in this manner, the droplet ejection frequencies of the basic nozzle 51A and the redundant nozzle 51B are equalized. By equalizing the nozzle frequency, the nozzle standby time (time interval between discharge and discharge) is equalized between the basic nozzle 51A and the redundant nozzle 51B.

  Furthermore, about 1/3 of the non-ejections of the basic nozzle 51A can be supplemented by redundant nozzles.

  In the application example described above, it is possible to complement without detecting the ejection abnormality of the basic nozzle 51A, and further, by using the redundant nozzle 51B for droplet ejection other than the substitute ejection, non-ejection of the redundant nozzle 51B can be prevented. Can be prevented. Thus, in order to prevent the discharge abnormality of the redundant nozzle 51B, a mode in which the redundant nozzle 51B is periodically operated is preferable.

  In the present embodiment, an inkjet recording apparatus including a full-line type print head has been exemplified. However, the scope of application of the present invention is not limited to this, and serial (printing while scanning the print head in the width direction of the paper) The present invention is also applicable to an ink jet recording apparatus having a (shuttle scan) type head.

  Further, in this embodiment, a piezo method using a piezoelectric element for ejecting ink droplets is illustrated, but the present invention includes an energy generator in the ink chamber, and the energy generator generates heat by heating the ink in the ink chamber. The present invention can also be applied to a thermal ink jet recording apparatus that discharges ink using bubbles. However, it is difficult to control the meniscus with bubbles generated by heating ink in a thermal ink jet recording apparatus.

  The scope of application of the present invention is not limited to an ink jet recording apparatus, and can be applied to a liquid discharge apparatus that discharges liquids such as water, chemicals, and processing liquid from discharge holes (nozzles) provided in a head.

1 is a basic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a plan view of a main part around a printing unit of the ink jet recording apparatus shown in FIG. Illustration of print head structure Sectional drawing which follows the 4-4 line in FIG. Schematic diagram showing the configuration of the ink supply unit in the inkjet recording apparatus according to the present embodiment Main part block diagram which shows the system configuration | structure of the inkjet recording device which concerns on this embodiment. The figure which shows the prior art example of the print head which has a redundant nozzle The figure explaining the nozzle arrangement of the print head in the inkjet recording device which concerns on 1st Embodiment. The figure explaining the droplet ejection control in the inkjet recording device which concerns on 1st Embodiment. The figure which shows the modification of the nozzle arrangement | positioning shown in FIG. The figure explaining the nozzle arrangement and droplet ejection control of the print head in the ink jet recording apparatus according to the second embodiment. The figure explaining the droplet ejection control in the inkjet recording device which concerns on 2nd Embodiment. The figure which shows the application example of the nozzle arrangement | positioning shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 24 ... Print detection part, 50 ... Print head, 51 ... Nozzle, 51A, 200, 204 ... Basic nozzle, 51B, 208, 210 ... Redundant nozzle, 72 ... System controller, 80 ... Print control part

Claims (12)

An image forming apparatus for forming an image on a recording medium,
It has a basic nozzle row in which basic nozzles that are mainly used during image formation and ejects droplets that form dots on a recording medium are arranged, and a redundant nozzle row in which fewer redundant nozzles are arranged than the basic nozzles. A recording head;
A droplet ejection control means for controlling to perform substitution droplet ejection from the redundant nozzle when the basic nozzle is abnormally discharged;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the number of redundant nozzles is ½ of the number of basic nozzles.   The image forming apparatus according to claim 1, wherein the redundant nozzles are arranged in a staggered manner with respect to the basic nozzles.   When the basic nozzle becomes abnormal in ejection, the droplet ejection control means controls to perform substitution ejection from at least one redundant nozzle among redundant nozzles adjacent to the basic nozzle in which ejection abnormalities occur. The image forming apparatus according to claim 1, 2 or 3. Transport means for relatively moving the recording medium and the recording head in the recording medium transport direction;
3. The image according to claim 1, wherein the redundant nozzles are arranged on the same straight line substantially parallel to the recording medium conveyance direction of the basic nozzles, and are arranged every other basic nozzle. Forming equipment.   When the basic nozzle in which the redundant nozzle is arranged on the same straight line substantially parallel to the recording medium conveyance direction becomes abnormal in ejection, the droplet ejection control means moves in the ejection direction of the basic nozzle and the recording medium in the recording medium conveyance direction. The image forming apparatus according to claim 5, wherein the control is performed so as to perform substitute droplet ejection from a redundant nozzle arranged on a substantially parallel straight line in place of a basic nozzle in which ejection abnormality has occurred.   When the basic nozzle in which the redundant nozzle is not arranged on the same straight line substantially parallel to the recording medium conveyance direction becomes abnormal in discharge, the discharge control means is at least one of the basic nozzles adjacent to the basic nozzle that is abnormal in discharge. 7. The image forming apparatus according to claim 5 or 6, wherein one droplet is ejected by one basic nozzle and redundant nozzles arranged on the same straight line substantially parallel to the recording medium conveyance direction.   When the basic nozzle in which the redundant nozzle is not arranged on the same straight line substantially parallel to the recording medium conveyance direction becomes abnormal in discharge, the discharge control means is at least one of the basic nozzles adjacent to the basic nozzle that is abnormal in discharge. In addition to performing basic droplet ejection for a basic nozzle that has failed to be ejected by one basic nozzle, the basic nozzle for performing the alternate droplet ejection and redundant nozzles arranged on the same straight line substantially parallel to the recording medium conveyance direction The image forming apparatus according to claim 7, wherein the image forming apparatus is controlled to perform droplets.   9. The discharge control unit according to claim 1, wherein when the basic nozzle in which discharge is abnormal is not ejected, the ejection control unit performs control so as not to perform substituting for the basic nozzle. The image forming apparatus described in 1.   10. The apparatus according to claim 1, wherein the ejection control unit controls the redundant nozzles to operate at a predetermined ratio with respect to the operation of the basic nozzles during image formation. 11. Image forming apparatus.   The recording head includes two or more nozzle rows in which nozzles for discharging ink droplets are arranged, and the nozzle row is a redundant nozzle row in which redundant nozzles of the same color dark ink and redundant nozzles of the same color light ink are arranged. The image forming apparatus according to claim 1, further comprising: A recording control method of an image forming apparatus for forming an image by discharging droplets onto a recording medium from a recording head provided with basic nozzles used for image formation and a number of redundant nozzles less than the basic nozzles,
An image recording step of discharging droplets from the basic nozzle to form an image on the recording medium;
A discharge detection step of detecting discharge abnormality of the basic nozzle;
When a discharge abnormality of the basic nozzle is detected by the discharge detection step, a substitute droplet ejecting step of performing substitute droplet ejection from a predetermined redundant nozzle,
Including a recording control method.

Images