JP2007111983A - Image forming apparatus and image forming method - Google Patents

Abstract

An image forming apparatus and an image forming method for reducing streaks and unevenness in a recorded image due to nozzle characteristics and forming a preferable image on a medium.
A nozzle passage 51A is provided with nozzle heaters 60A and 60B which are divided in the circumferential direction and arranged along the main scanning direction. When the nozzle heater 60A is turned on and the nozzle heater 60B is turned off, the flying direction of the ink droplet ejected from the nozzle 51 is deflected by θA, and the landing position of the ink droplet can be shifted by LA in the main scanning direction. When the heating energy of the nozzle heater 60A that is turned on is increased, the flight deflection angle θA is increased, and the landing position shift amount LA in the main scanning direction can be increased. By controlling on / off of the nozzle heaters 60A and 60B based on the characteristic information of each nozzle 51, it is possible to correct the landing position deviation caused by the nozzle characteristics.
[Selection] Figure 5

Description

  The present invention relates to an image forming apparatus and an image forming method, and more particularly to an image forming technique in an image forming apparatus that forms a desired image with a liquid deposited on a medium.

  2. Description of the Related Art In recent years, an ink jet recording apparatus has been widely used as an image forming apparatus that forms an image such as a photograph or a document on a medium (recording medium). The ink jet recording apparatus drives an ejection element provided in an ink jet head in accordance with data, thereby ejecting ink (droplet ejection) from the ejection element (nozzle) and forming a desired image on the medium.

  In an inkjet head equipped with a large number of nozzles, there are variations in the amount of ejected droplets and the direction of flight of each nozzle. When this occurs, streaks and unevenness due to nozzle characteristics occur in the recorded image. In particular, in single-pass printing using a line-type head having a length corresponding to the width of the recording medium (a printing method in which an image is formed on the entire recording medium by scanning the recording medium only once), As the serial (shuttle) system cannot perform shingling correction, streaks and unevenness due to the nozzle characteristics described above are easily noticeable.

  Here, a conventional image forming method will be described. FIG. 12 shows an image (dot) recorded on the recording medium 16 by the ink jet recording apparatus according to the prior art. In the figure, a full-line type ink jet head 300 having a nozzle row having a length corresponding to the width direction of the recording medium 16 and ink droplets ejected from the head 300 are formed on the recording medium 16. An image 301 is schematically shown. The head 300 includes five nozzles i (i = 1 to 5), and ink droplets ejected from the third nozzle 3 from the right in FIG. 12 land with a shift from a predetermined landing position to the right in FIG. . In other words, the nozzle 3 has a characteristic that the flying direction of the ink droplet is shifted to the right in FIG.

  As shown in FIG. 12, the ink droplets ejected from the nozzles 1, 2, 4, and 5 land at predetermined landing positions, and dots 302 are formed at predetermined dot forming positions. On the other hand, the ink droplets ejected from the nozzle 3 land in the right direction of FIG. 12 indicated by the arrow line with a deviation of Lx from the predetermined landing position, and deviate from the predetermined dot formation position by Lx in the right direction of FIG. Dots 304 (dot groups 306 arranged along the feeding direction of the recording medium 16) are formed at the positions.

  When such landing position misalignment occurs, dots 308 (dot group 310) formed by ink droplets ejected from nozzle 2 and dots 304 (dot group) formed by ink droplets ejected from nozzle 3 are generated. 306), the streak 312 is visually recognized in the recorded image 301, and the quality of the recorded image 301 is significantly deteriorated. In particular, when a full-line type head is used, streaks and unevenness due to the characteristics of the nozzles remarkably appear.

  Causes of the ink droplet flying direction being shifted and obliquely flying include deterioration of hydrophilicity or water repellency of the nozzle and the peripheral member of the nozzle, adhesion of foreign matters around the nozzle, and the like.

  In the invention described in Patent Document 1, nozzle information representing the ejection characteristics of each nozzle is created based on the landing position of the ink droplet ejected from the nozzle of the recording head on the recording medium, and based on this nozzle information and recording data. By predicting the effect of ink droplets ejected from each nozzle on the image to be formed, creating correction information for correcting the ink ejection state based on the prediction result, and driving the nozzle based on the correction information, There is disclosed a technique for obtaining a high-quality image by suppressing the occurrence of streaks or unevenness in an image even when a defective nozzle that causes ink droplets to drastically exist in the recording head.

The invention described in Patent Document 2 discloses a technique for deflecting the flying direction of droplets ejected from a nozzle by asymmetrically heating ink in the nozzle bore by a first heater provided in the nozzle bore. Yes.
JP 2004-58282 A JP 2002-210977 A

  As a technique for correcting the misalignment of the dot formation position caused by the nozzle characteristics, there is an ejection control that increases the ejection amount of the ink droplet ejected from the nozzle and increases the size of the dot formed by the ink droplet. is there. By such a method, an attempt is made to reduce the visibility of the stripe 312 as shown in FIG.

  However, in the above-described method, as a result of increasing the appropriate amount of ink liquid, the density of the dots changes, and there is a risk that the density will be visually recognized as density unevenness.

  In the invention described in Patent Document 1, streaks and unevenness of a recorded image are reduced by image processing, and there is a limit to reducing streaks and unevenness only by image processing. In addition, the image processing algorithm becomes complicated, and the processing load on the image processing system may increase.

  Further, the invention described in Patent Document 2 does not describe a problem such as reduction of streaks or unevenness generated in a recorded image due to variations in nozzle characteristics.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image forming apparatus and an image forming method for reducing streaks and unevenness in a recorded image due to nozzle characteristics and forming a preferable image on a medium. And

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention is configured to move a head and a recording medium relative to each other and eject liquid from a plurality of nozzles of the head. An image forming apparatus for forming an image on the head, wherein the head is divided in a circumferential direction of each nozzle channel into a plurality of nozzle channels that communicate the plurality of nozzles with a plurality of pressure chambers. A heating element group comprising a plurality of heating elements for heating the liquid in the nozzle flow path provided, nozzle characteristic information acquisition means for acquiring the nozzle characteristic information, and the heating element according to the nozzle characteristic information A flying deflection control means for controlling the heating energy of the group to deflect the flying direction of the liquid ejected from the nozzle in a direction including a component substantially orthogonal to the relative movement direction of the recording medium. The features.

  According to the present invention, the liquid in the nozzle channel is heated by the heating element group provided in the vicinity of the nozzle channel, so that the liquid in the nozzle and the nozzle channel is distributed in viscosity and surface tension. The flying direction of the liquid to be discharged is corrected by the deflection. Accordingly, it is possible to shift the landing position of the liquid on the recording medium in a direction substantially orthogonal to the moving direction of the recording medium, and correct the formation position deviation of the dots formed by the liquid according to the nozzle characteristic information. Can do.

  In this way, by correcting the dot formation position deviation due to the characteristics of each nozzle, streaks and unevenness of the image formed on the recording medium are reduced, and a high-quality preferred image can be obtained.

  The image here refers to an image in a broad sense including text such as characters and symbols, figures, patterns (for example, wiring patterns formed on a wiring board), and the like.

  The head has a full line type head having a nozzle row having a length corresponding to the width direction of the recording medium, or a nozzle row having a length less than the width direction of the recording medium. There is a serial type head that forms dots arranged in the width direction of a recording medium while scanning the head. The present invention can provide a great effect in image formation using a full line type head.

  The recording medium is a medium to which a liquid is attached by a head, and includes various media regardless of the material and shape, such as a continuous sheet, a cut sheet, a seal sheet, a resin sheet such as an OHP sheet, a film, a cloth, and the like.

  The heating element group included in the heating element group has a mode in which a plurality of heating elements are arranged along a direction substantially orthogonal to the relative movement direction of the recording medium across the nozzle flow path. In addition, the aspect which provides a heating element in the nozzle vicinity is more preferable.

  The invention according to claim 2 relates to an aspect of the image forming apparatus according to claim 1, wherein the flying direction control unit changes the heating energy ratio of the plurality of heating elements included in the heating element group to change the nozzle. The flight direction of the liquid discharged from the liquid is controlled.

  For example, when two heating elements, a first heating element and a second heating element, are provided, the first heating element is turned on and the second heating element is used to change the heating energy ratio of these heating elements. There is a mode in which the heating energy of the other heating element is determined based on the heating energy of one of the first and second heating elements.

  A third aspect of the present invention relates to an aspect of the image forming apparatus according to the first or second aspect, wherein the nozzle characteristic information acquisition unit includes a reading unit that reads an image on the recording medium. The landing state of the liquid ejected from the nozzle is detected based on the obtained reading result.

  The landing state of the liquid includes information such as a positional deviation of the landing position and a droplet amount of the landing droplet. In order to accurately determine the landing state, it is preferable that the image used for image reading by the reading unit is a test image (read-only image) composed of a dot pattern suitable for reading by the reading unit. Of course, an aspect using a practical image is also possible.

  A fourth aspect of the present invention relates to an aspect of the image forming apparatus according to the first, second, or third aspect, wherein the flying deflection control unit is configured to control a heating energy of each heating element group provided in each nozzle channel. The heating energy of each heating element group is controlled so that the sum is substantially the same.

  According to the fourth aspect of the invention, since the droplet discharge amount between the nozzles is maintained uniformly, it is possible to suppress the size variation of the dots formed on the recording medium caused by the heating of the liquid.

  A fifth aspect of the present invention relates to an aspect of the image forming apparatus according to any one of the first to fourth aspects, wherein the discharge force generating element applies a discharge force to the liquid in the pressure chamber; Drive signal supply means for supplying a drive signal to the discharge force generation element; and drive signal correction means for correcting the drive signal in response to an increase in the liquid discharge amount due to heating of the heating element group. Features.

  According to the fifth aspect of the present invention, the increase in the amount of ejected droplets accompanying the heating of the liquid is corrected, and a predetermined amount of droplets land on the recording medium. Dots are formed.

  As a mode for correcting the drive signal, there is a mode in which the amplitude of the drive signal supplied to the ejection force generation element of the ejection element heated by the liquid is reduced by an amount corresponding to the increase in the droplet ejection amount.

  The discharge force generating element includes an actuator (pressurizing means) such as a piezoelectric element on at least one wall surface of the pressure chamber, and the pressure chamber is deformed by operating the actuator to correspond to the volume change. There are a mode in which liquid is discharged and a mode in which heating means for generating bubbles by heating the liquid in the pressure chamber is provided, and the liquid is discharged by the pressure of the bubbles.

  In particular, in combination with the invention described in claim 4, the dots formed on the recording medium are suppressed from variation in size, and the enlargement of the dot size due to heating of the liquid is prevented.

  A sixth aspect of the present invention relates to an aspect of the image forming apparatus according to any one of the first to fifth aspects, wherein the recording medium is a liquid ejected from the nozzle according to the nozzle characteristic information. And a discharge control means for controlling the discharge timing of the nozzle so as to correct the landing position deviation in a direction substantially parallel to the movement direction of the nozzle.

  According to the sixth aspect of the invention, it is possible to correct the landing position deviation in the direction substantially parallel to the moving direction of the recording medium due to the nozzle characteristics, and therefore it is possible to form a preferable image in which the dot position deviation in this direction is corrected. It is. More preferably, the heating element provided in each nozzle channel is divided along a direction substantially parallel to the moving direction of the recording medium.

  In particular, in the aspect including the first and second heating elements that are arranged along the direction substantially orthogonal to the moving direction of the recording medium with the nozzle flow path interposed therebetween, the configuration of the head can be simplified, and further, the recording can be performed. It is possible to correct bi-directional landing position deviations in a direction substantially orthogonal to the moving direction of the medium and in a direction substantially parallel to the moving direction of the recording medium.

  A method invention is provided to achieve the above object. That is, in the image forming method according to the seventh aspect of the invention, the head and the recording medium are relatively moved, and liquid is ejected from a plurality of nozzles of the head to form an image on the recording medium. In the image forming method, each of a plurality of nozzle flow paths for communicating the plurality of nozzles and the plurality of pressure chambers based on the step of acquiring the characteristic information of the nozzles for discharging the liquid, and the characteristic information of the nozzles In addition, the liquid in the nozzle channel is heated by a heating element group composed of a plurality of heating elements divided and provided in the circumferential direction of the nozzle channel, and the flying direction of the droplets discharged from the nozzle is determined. And a discharge step of deflecting in a direction including a component substantially orthogonal to the relative movement direction.

  According to the seventh aspect of the present invention, it is possible to form a preferable image in which the landing position deviation in the direction substantially orthogonal to the moving direction of the recording medium is corrected.

  According to the present invention, a preferable image in which streaks and unevenness due to the nozzle characteristics are reduced by shifting the landing position of the droplets ejected according to the nozzle characteristics in a direction substantially orthogonal to the moving direction of the recording medium. Can be formed.

  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 a recording medium (recording paper) 16, a decurling unit 20 for removing curl of the recording medium 16, and a printing unit An adsorption belt conveyance unit 22 that conveys the recording medium 16 while maintaining the flatness of the recording medium 16, and a print detection unit that reads a printing result by the printing unit 12. 24 and a paper discharge unit 26 for discharging the printed recording medium 16 (printed material) 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 a plurality of types of recording media can be used, an information recording body such as a barcode or wireless tag that records the medium type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Thus, it is preferable to automatically determine the type of recording medium to be used and perform ink ejection control (droplet ejection control) so as to realize appropriate ink ejection according to the type of recording medium.

  The recording medium 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 medium 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 medium 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 medium 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 greater than the width of the recording medium 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 make a negative pressure, whereby the recording medium 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 medium 16 held on the belt 33 is conveyed from left to right in FIG.

  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 an embodiment 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 printing area, the roller contacts the printing surface of the recording medium 16 immediately after printing, so that the image is printed. There is a problem of easy bleeding. 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 recording medium conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording medium 16 by blowing heated air onto the recording medium 16 before printing. By heating the recording medium 16 immediately before printing, the ink becomes easy to dry after landing.

  The printing unit 12 is a so-called full line type head in which a line type head having a length corresponding to the maximum paper width is arranged in a direction (main scanning direction) orthogonal to the recording medium conveyance direction (see FIG. 2). Although a detailed structural example will be described later (FIGS. 3 to 5), each of the print heads 12K, 12C, 12M, and 12Y is a recording medium of the maximum size targeted by the inkjet recording apparatus 10 as shown in FIG. The line head includes a plurality of ink discharge ports (nozzles) arranged over a length exceeding at least one side of 16.

  A print head 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 medium 16 (hereinafter referred to as the recording medium conveyance direction). 12K, 12C, 12M, and 12Y are arranged. A color image can be formed on the recording medium 16 by ejecting the color inks from the print heads 12K, 12C, 12M, and 12Y while conveying the recording medium 16, respectively.

  Thus, according to the printing unit 12 in which the full line head that covers the entire area of the paper width is provided for each ink color, the operation of relatively moving the recording medium 16 and the printing unit 12 in the sub-scanning direction is performed once. An image can be recorded on the entire surface of the recording medium 16 only by performing it (that is, by one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the print head reciprocates in the main scanning direction, and productivity can be improved.

  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) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  The print detection unit 24 includes an image sensor for imaging the print result of the print unit 12, and functions as a unit for checking nozzle clogging and other ejection defects from an 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 the test patterns printed by the print heads 12K, 12C, 12M, and 12Y for each color, detects the discharge of each print head, and measures (determines) the discharge characteristics of each nozzle. Characteristic information is stored. The ejection determination and the measurement of the nozzle characteristics include the presence / absence of ejection, the measurement of the dot size, and the measurement of the dot landing position.

  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 forming 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 improved by preventing contact with ozone or other things that cause dye molecules to break by pressurizing the paper holes with pressure. There is an effect to.

  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, thereby forming an uneven shape on the image forming surface. Transcript.

  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) that switches the paper discharge path so as 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.

(Composition of printing part)
As shown in FIG. 1, the printing unit 12 includes inkjet heads 12K, 12C, 12M, and 12Y corresponding to cyan, magenta, yellow, and black inks. Hereinafter, the inkjet heads 12K, 12C, 12M, and 12Y may be described as the heads 12K, 12C, 12M, and 12Y.

  Each of the heads 12K, 12C, 12M, and 12Y of the printing unit 12 has a length corresponding to the maximum paper width of the recording medium 16 targeted by the inkjet recording apparatus 10, and the nozzle surface has a recording medium of the maximum size. This is a full-line type head in which a plurality of nozzles for ink discharge are arranged over a length exceeding at least one side (full width of the drawable range) (see FIG. 2).

  Each of the heads 12K, 12C, 12M, and 12Y has black (K), cyan (C), and magenta (M) from the upstream side along the feeding direction of the recording medium 16 (paper feeding direction shown by an arrow line in FIG. 2). Are arranged in the order of yellow (Y), and the respective heads 12K, 12C, 12M, and 12Y are fixedly installed so as to extend along a direction substantially orthogonal to the paper feeding direction.

  A color image can be formed on the recording medium 16 by ejecting the treatment liquid and different color ink from the heads 12K, 12C, 12M, and 12Y while conveying the recording medium 16 by the suction belt conveyance unit 22, respectively.

  As described above, according to the configuration in which the full-line type heads 12K, 12C, 12M, and 12Y having nozzle rows covering the entire width of the paper are provided separately for the liquid, the recording medium 16 and the printing unit in the paper feeding direction (sub-scanning direction). The image can be recorded on the entire surface of the recording medium 16 by performing the operation of moving the 12 relatively once (that is, by one sub-scanning). Thereby, high-speed printing is possible and productivity can be improved as compared with a shuttle-type head in which the head reciprocates in a direction perpendicular to the paper feed 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, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta and dark ink such as dark yellow. Also, the arrangement order of the color heads is not particularly limited.

[Head structure]
Next, the structure of the head will be described. Since the structures of the heads 12K, 12C, 12M, and 12Y are common, the heads are represented by the reference numeral 50 in the following.

  FIG. 3 is a plan perspective view showing a structural example of the head 50. As shown in FIG. 3, the head 50 of this example mainly includes a plurality of ink chamber units 53 (discharge elements) including nozzles 51 serving as ink droplet discharge holes and pressure chambers 52 corresponding to the nozzles 51. It has a structure arranged along the scanning direction (direction orthogonal to the head-recording medium relative conveyance direction). In other words, the head 50 includes one nozzle row (ink chamber unit row) having a length corresponding to the width direction of the recording medium 16. An embodiment in which a plurality of the above-described nozzle rows are provided along the sub-scanning direction (head / recording medium relative conveyance direction) is also possible.

  4A shows another structural example of the head 50 shown in FIG. 3, and FIG. 4B shows an enlarged view of a part of the head 50 '. A head 50 ′ shown in FIG. 4A has a structure in which ink chamber units 53 including nozzles 51 and pressure chambers 52 shown in FIG. 3 are arranged in a two-dimensional matrix.

  In order to increase the dot pitch printed on the recording medium 16, it is necessary to increase the nozzle pitch. A head 50 'shown in FIGS. 4A and 4B includes a plurality of ink chamber units 53 each having a nozzle 51, which is an ink droplet ejection hole, and a pressure chamber 52 corresponding to each nozzle 51. (Two-dimensionally), so that the substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the head longitudinal direction (main scanning direction orthogonal to the paper feed direction) ) Is achieved.

  The form in which one or more nozzle rows are configured in the main scanning direction over a length corresponding to the entire width of the recording medium 16 is not limited to this example. For example, instead of the configuration of FIG. 4 (a), short head blocks 50 ″ in which a plurality of nozzles 51 are two-dimensionally arranged are arranged in a staggered manner and connected as shown in FIG. 4 (c). A line head having a nozzle row having a length corresponding to the entire width of the recording medium 16 may be configured.

  As shown in FIG. 4B, the ink chamber units 53 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 α 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.

  That is, with a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along the row direction at an angle α with respect to the main scanning direction, the pitch P of the nozzles projected so as to be arranged in the main scanning direction is d ×. cosα, and in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, a high-density nozzle array can be realized.

  When the nozzles are driven by a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzles are divided into blocks, and each block is sequentially driven from one side to the other, etc., and one line (in one row of dots) in the width direction (main scanning direction) of the recording medium Driving a nozzle that prints a line or a line composed of a plurality of rows of dots is defined as main scanning.

  In particular, when driving the nozzles 51 arranged in a matrix as shown in FIGS. 4A and 4B, main scanning as described in the above (3) is preferable.

  On the other hand, by moving the full line head and the recording medium 16 relative to each other, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the main scanning described above is repeatedly performed. This is defined as sub-scanning.

  In other words, the nozzles 51 that eject ink droplets that are dots formed adjacently so as to overlap on the recording medium 16 are arranged along a row direction that forms an angle α with the main scanning direction. In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example.

  5 is a cross-sectional view showing a three-dimensional structure of the head 50 (head 50 ′ shown in FIG. 4A, head 50 ″ shown in FIG. 4C) (a cross-sectional view taken along the line Va-Va in FIG. 3). The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape (see FIG. 3), and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. 5A, each pressure chamber 52 communicates with a common channel 55 provided on the upper portion of the pressure chamber 52 (on the side opposite to the nozzle 51) via a supply port. The common channel 55 communicates with a supply tank (not shown) as an ink supply source, and the ink supplied from the supply tank is distributed and supplied to each pressure chamber 52 via the common channel 55.

  A piezoelectric element (actuator) 58 having an individual electrode 57 is joined to a diaphragm 56 that constitutes the top surface of the pressure chamber 52 and also serves as a common electrode, and the piezoelectric element of the diaphragm 56 is arranged from the individual electrode 57. By applying a drive voltage to the individual electrode 57 via the individual wiring 57A drawn out to the surface 56A, the piezoelectric element 58 is deformed and ink is ejected from the nozzle 51. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  The head 50 shown in FIG. 5 has a structure in which a common channel 55 is provided on the opposite side of the pressure chamber 52 from the diaphragm 56. The member (common flow channel member) 59 forming the bottom surface (pressure chamber side surface) of the common flow channel 55 is formed with a recess 59A corresponding to the piezoelectric element 58. 59 serves as a cover that secures a space above the piezoelectric element 58 and does not restrain the deformation.

  That is, as shown in FIG. 5 (a), a structure that does not restrict the deformation of the piezoelectric element 58 is realized by providing a space on the opposite side of the diaphragm 56 of the piezoelectric element 58.

  A supply port 54 for communicating the pressure chamber 52 and the common flow channel 55 is formed in the diaphragm 56 and the common flow channel member 59, and the pressure chamber 52 and the common flow channel 55 are communicated with each other by such a short supply port 54. According to the structure, the flow path resistance on the supply side is reduced, and high-viscosity ink can be ejected at a high frequency.

As the piezoelectric element 58 shown in FIG. 5, a piezoelectric element (piezoelectric actuator) using a ceramic material such as PZT (Pb (Zr · Ti) O ₃ , lead zirconate titanate) is preferably used. Needless to say, a piezoelectric element using a fluororesin material such as PVDF (Polyvinylidene fluoride) or PVDF-TrFE (Polyvinylidene trifluoride ethylene copolymer) may be used.

  The head 50 of this example includes a nozzle heater block (heating element) having two nozzle heaters 60A and 60B that are divided and arranged in a circumferential direction of the nozzle channel 51A in a nozzle channel 51A that communicates the nozzle 51 and the pressure chamber 52. Group) (see FIG. 5 (b), FIG. 5 (b) is a cross-sectional view taken along line Vb-Vb in FIG. 5 (a)).

  In other words, the nozzle heater 60A and the nozzle heater 60B are disposed so as to face each other across the nozzle flow path 51A and to be divided along the sub-scanning direction. By controlling the ON / OFF of the nozzle heaters 60A and 60B and the heating energy (generated heat amount), the flying direction of the ink droplets ejected from the nozzle 51 can be deflected in a direction substantially parallel to the main scanning direction. By deflecting the flying direction of the ink droplet in this way, the ink droplet can be landed while being shifted in a direction substantially parallel to the main scanning direction.

  When both the nozzle heaters 60A and 60B are on (or both off), the flying direction of the ink droplet is not deflected, and if the nozzle surface and its vicinity are in a normal state, the ink droplet forms the nozzle. It is discharged in a direction substantially perpendicular to the surface.

  Although details of the control of the nozzle heaters 60A and 60B will be described later, when the nozzle heater 60A is turned on, the flying direction of the ink droplet is represented by an angle θA with reference to the vertical direction (the central axis direction of the nozzle shown by a one-dot broken line). The landing position of the ink droplet is shifted by LA from the predetermined landing position to the left in FIG. When the nozzle heater 60B is turned on, the flying direction of the ink droplet is deflected in the direction represented by the angle θB with respect to the vertical direction, and the landing position of the ink droplet is changed from the predetermined landing position to the right in FIG. Shift by LB. That is, when any one of the nozzle heaters 60A and 60B is turned on, the flying direction of the ink droplet is deflected to the opposite side to the nozzle heater that is turned on (nozzle heater having a large heating energy), and the landing position of the ink droplet is the main position. Shifted along the scanning direction.

  Further, when the heating energy of the nozzle heaters 60A and 60B is increased, the angles θA and θB (shift amounts LA and LB) are increased, and when the heating energy of the nozzle heaters 60A and 60B is decreased, the angles θA and θB (shift amounts LA and LB) are decreased. Become.

  Note that the flying direction and deflection amount (landing position shift amount) of the ink droplets ejected from the nozzle 51 may be controlled by changing the ratio of the heating energy of the nozzle heaters 60A and 60B.

  For example, assuming that the ratio (EA / EB) of the heating energy EA of the nozzle heater 60A to the heating energy EB of the nozzle heater 60B, when the heating energy ratio (EA / EB) is 1, the flying direction of the ink droplet is not deflected.

  When the heating energy ratio exceeds 1 (when the heating energy EA of the nozzle heater 60A is larger than the heating energy EB of the nozzle heater 60B), the ink droplet is deflected toward the nozzle heater 60B, and the heating energy ratio is increased. The amount of deflection becomes large.

  On the other hand, when the heating energy ratio is less than 1 (when the heating energy EB of the nozzle heater 60B is larger than the heating energy EA of the nozzle heater 60A), the ink droplet is deflected toward the nozzle heater 60A, and this heating energy ratio is reduced. Then, the amount of deflection becomes large.

  In this example, an embodiment in which the two nozzle heaters 60A and 60B are divided in the circumferential direction of the nozzle flow path 51 is shown. However, as shown in FIG. Two nozzle heaters 60A to 60D may be provided. Of course, a larger number of nozzle heaters may be provided. In the embodiment shown in FIG. 5C, the nozzle heater 60C and the nozzle heater 60D are arranged so as to be divided along the main scanning direction so as to face each other across the nozzle flow path 51A. Further, the arrangement example shown in FIG. 5C is merely an example, and other arrangements may be applied to the nozzle heaters 60A to 60D. As another example of arrangement, there is an aspect in which the arrangement shown in FIG. 5C is rotated by a predetermined angle (for example, 45 degrees).

[Explanation of control system]
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, a memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, a nozzle heater driver 85, 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 (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 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the memory 74.

  The 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 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 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls each part such as the communication interface 70, the memory 74, the motor driver 76, the heater driver 78, etc., performs communication control with the host computer 86, read / write control of the memory 74, etc. A control signal for controlling a heater 88 such as a motor 88 and a heater 89 such as a heater of the post-drying section 42 is generated.

  The memory 74 stores programs executed by the CPU of the system controller 72 and various data necessary for control. Note that the memory 74 may be a non-rewritable storage means or a rewritable storage means such as an EEPROM. The memory 74 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 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives a heater 89 such as a temperature adjusting heater in the post-drying unit 42, the inkjet recording apparatus 10, and the head 50 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 74 in accordance with the control of the system controller 72. The generated print data This is a control unit that supplies (dot data) to the head driver 84. Necessary signal processing is performed in the print control unit 80, and the ejection amount of the treatment droplets, the ejection amount of the ink droplets, and the ejection timing of the 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. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The head driver 84 drives the piezoelectric elements 58 of the heads 12K, 12C, 12M, and 12Y 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.

  The nozzle heater driver 85 is a control block that controls ON / OFF of the nozzle heaters 60A and 60B shown in FIG. 5A, heating energy (heating energy ratio), and the like. The nozzle heater driver 85 controls on / off of the nozzle heaters 60A and 60B based on a control signal given from the print control unit 80 (nozzle characteristic specifying unit 92), and sets the heating energy of the nozzle heaters 60A and 60B.

  Data of an image to be printed is input from the outside via the communication interface 70 and stored in the memory 74. At this stage, RGB image data is stored in the memory 74.

  The image data stored in the memory 74 is sent to the print control unit 80 via the system controller 72, and is converted into dot data of processing liquid and ink dot data in the print control unit 80. That is, the print control unit 80 performs processing for converting the input RGB image data into dot data of four colors of processing liquid and KCMY. Each dot data generated by the print controller 80 is stored in the image buffer memory 82.

  The head driver 84 generates a drive control signal for the head 50 based on each dot data stored in the image buffer memory 82. When the drive control signal generated by the head driver 84 is applied to the head 50, ink droplets are ejected from the head 50. An image is formed on the recording medium 16 by controlling ink ejection of the head 50 in synchronization with the conveyance speed of the recording medium 16.

  Various control programs are stored in the program storage unit 90, and the control programs are read and executed in accordance with instructions from the system controller 72. The program storage unit 90 may use a semiconductor memory such as a ROM or an EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several storage media among these storage media. The program storage unit 90 may also be used as a recording means (not shown) for operating parameters.

  In this example, the system controller 72, the memory 74, the print control unit 80, and the like are illustrated as individual blocks as functional blocks, but these may be integrated and configured as one processor. Further, a part of the function of the system controller 72 and a part of the function of the print control unit 80 can be realized as one processor.

  The nozzle characteristic specifying unit 92 is configured to include the print detection unit 24 shown in FIG. 1, and based on the image reading result obtained from the print detection unit 24, the characteristic of each nozzle (the landing position of the ink ejected from the nozzle) Etc.) and stores this. That is, the nozzle characteristic specifying unit 92 includes a print detection unit 24 shown in FIG. 1 and a signal processing unit (nozzle removal, A / D conversion, etc.) that performs predetermined signal processing on the read signal obtained from the print detection unit 24. And a storage unit (memory) that stores characteristic information of each nozzle that has been subjected to predetermined signal processing by the signal processing unit. In FIG. 6, the signal processing unit and the storage unit are not shown.

  The print control unit 80 sends a control signal to the nozzle heater driver 85 based on the characteristic data of each nozzle generated and stored by the nozzle characteristic specifying unit 92, and the drive signal adjustment unit 94 of the print control unit 80 Drive signal correction data is provided to the head driver 84 in accordance with the characteristic data of each nozzle. The details of nozzle heater control and drive signal correction based on the nozzle characteristics will be described later.

[First Embodiment, Description of Ink Droplet Flight Deflection Control]
Next, the flying direction deflection control of the ink droplets of the inkjet recording apparatus 10 according to the present invention will be described in detail. FIG. 7 is a diagram for explaining deflection control in the flight direction (an enlarged view of the vicinity of the nozzle 51 in FIG. 5A).

  As shown in FIG. 7, when the nozzle heater 60A is turned on and the nozzle heater 60B is turned off, the viscosity and surface tension of the ink on the nozzle heater 60B side (left side in FIG. 7) in the nozzle flow path 51 are relative to those of the nozzle heater 60A side. The ink droplets discharged from the nozzles 51 fly to the nozzle heater 60B side. As a result, the flying direction of the ink droplet is deflected by the angle θA1, and the landing position of the ink droplet can be shifted by LA1 in a direction substantially parallel to the main scanning direction.

  When the heating energy of the nozzle heater 60A is further increased, the deflection angle becomes θA2 (θA2> θA1), and the deflection amount becomes LA2 (LA2> LA1). When the flying direction of the ink droplet is deflected toward the nozzle heater 60A, the nozzle heater 60A may be turned off and the nozzle heater 60B may be turned on.

  In accordance with the characteristics of each nozzle stored in the nozzle characteristic specifying unit 92 shown in FIG. 6, the deflection amount of the ink droplets ejected from the nozzle is set so as to cancel out the deviation of the dot formation position due to the characteristics of the nozzle. By setting and controlling the nozzle heaters 60A and 60B so as to deflect the ink droplets in the flying direction of the deflection angle based on the deflection amount, a preferable recorded image in which the characteristics of each nozzle are corrected can be obtained.

  FIG. 8 shows an image 100 formed on the recording medium 16 by applying the flying direction deflection control of the ink droplet shown in this example. In FIG. 8, in order to make the comparison with the prior art shown in FIG. 12 easier to understand, the head 50 includes a head having five nozzles i (i = 1 to 5) as in FIG. 12 showing the prior art. To do.

  As shown in FIG. 8, the head 50 faces the nozzle heaters 60Ai and 60Bi (i is the nozzle number, i = 1 to 1) so as to face each other across the nozzle flow path 51A (see FIG. 5) corresponding to each nozzle 1 to nozzle 5. 5). Similarly to the nozzle 3 of the head 300 according to the related art shown in FIG. 12, the nozzle 3 of the head 50 has the landing position of the ejected ink droplet in the right direction in FIG. 8 (the + direction shown by the solid arrow line). ) Has a characteristic shifted by + Lx (see FIG. 12).

  When the flight deflection control of the ink droplets of this example is applied, the heating energy of the nozzle heaters 60A3 and 60B3 is set so that the deflection amount of the dots 102 formed by the ink droplets ejected from the nozzles 3 is −Lx. (For example, only the nozzle heater 60A3 is turned on). Based on the shift amount, the flying direction of the ink droplet is deflected to the left in FIG. 8 (the minus direction indicated by the broken arrow line). As a result, the ink droplet lands at a predetermined landing position. Dots 102 (dot group 104) formed by ink droplets are formed at predetermined formation positions.

  On the other hand, the nozzle heaters 60Ai, 60Bi (i = 1, 2, 4, 5) are not used in the nozzles 1, 2, 4, 5 that do not have the characteristic that the flying direction of the ink droplets is shifted (the ink droplets fly in the vertical direction). Are controlled to be turned off.

  According to the above-described flying direction control of the ink droplet, the ink discharged from the nozzle i by controlling the nozzle heaters 60Ai and 60Bi provided in the nozzle flow path 51A communicating with each nozzle according to the characteristics of each nozzle i. Since the flying direction of the liquid droplets is deflected, an image (dot) in which streaks and unevenness due to the positional deviation of the dots due to the characteristics of each nozzle i are avoided is formed on the recording medium 16.

  In this example, the control for correcting the deviation in the flying direction of the ink droplet in a direction substantially parallel to the main scanning direction has been described. However, the ink droplet in a direction having a component substantially parallel to the sub-scanning direction is determined by the nozzle ejection characteristics. This control can also be applied when the flight direction of the vehicle deviates. For example, there is a mode in which the deviation in the flying direction of the component substantially parallel to the main scanning direction is corrected by this control, and the deviation in the flying direction of the component in the sub-scanning direction and substantially parallel is corrected by controlling the ejection timing.

[Second embodiment, description of nozzle heater drive control]
In the example shown in FIG. 8, since the nozzle heater 60A3 is operated, the nozzle channel (ink in the nozzle channel) communicating with the nozzle 3 is the other nozzle 1, 2, 4, 5 (ink in the nozzle channel). ) And the viscosity of the ink in the flow path communicating with the nozzle 3 is lowered. As a result, even if the same driving voltage is applied to the piezoelectric element 58 (see FIG. 5A) corresponding to each nozzle and the ink droplets are ejected from each nozzle, the ink liquid ejected from the nozzle 3 is used. The ejection amount of the droplets is larger than the ejection amount of the ink droplets ejected from the other nozzles 1, 2, 4, 5, and the size of the dots 102 formed by the ink droplets ejected from the nozzle 3 is It becomes larger than the dots 106 formed by ink droplets ejected from other nozzles.

  If the dot sizes vary in this way, depending on the degree of variation, the dots may be visually recognized as streaks or unevenness that degrade the image quality. Accordingly, the nozzle heaters 60Ai and 60Bi corresponding to the nozzles i (i = 1, 2, 4, 5) that do not deflect the flight direction are operated so that the dot size does not vary from nozzle to nozzle. It is preferable to control the nozzle heaters 60Ai and 60Bi so that the temperature in the nozzle flow path 51A communicating with the nozzles is uniform.

  Next, control (nozzle heater drive control) of the nozzle heater 60Ai and the nozzle 60Bi for making the temperature of the ink in each nozzle and each nozzle flow path uniform will be described. FIG. 9 shows a head 50 to which the nozzle heater drive control is applied and an image 200 formed on the recording medium 16. In FIG. 9, parts that are the same as or similar to those in FIG. 8 are given the same reference numerals, and descriptions thereof are omitted.

  In the nozzle heater control, the heating energy ratio (EB3 / EA3) of the nozzle heaters 60A3 and 60B3 of the nozzle 3 is less than 1 or more than 1 with respect to the nozzle 3 where the landing position deviation of the ejected ink droplet occurs. In this way, the heating energy EA3 and EB3 of the nozzle heaters 60A3 and 60B3 is controlled, and the landing position deviation of the ink droplets ejected from the nozzle 3 is prevented.

  On the other hand, in the nozzle i (i = 1, 2, 4, 5) where the landing position deviation does not occur, the heating energy ratio (EAi / EBi) of the nozzle heaters 60Ai, 60Bi of the nozzle i becomes 1 (that is, EAi). The nozzle heaters 60Ai and 60Bi are controlled so that = EBi.

  Further, the heating energy of the nozzle heaters 60Ai and 60Bi corresponding to each nozzle is controlled so that the temperature of the ink in each nozzle and each nozzle flow path becomes uniform by controlling the balance of the heating energy of the nozzle heaters 60Ai and 60Bi of each nozzle. Is controlled to be substantially constant.

  In the example shown in FIG. 9, for example, assuming that the heating energy EA3 = 3 × s of the nozzle heater 60A3 corresponding to the nozzle 3 and the heating energy EB3 = s (where s is a constant) of the nozzle heater 60B3, the ink ejected from the nozzle 3 Since the flying direction of the droplet is deflected toward the nozzle heater 60B and the original flying direction of the nozzle 3 is canceled, the dot formed by the ink droplet lands on a predetermined dot formation position.

  Further, the heating energy EAi of the nozzle heater 60Ai corresponding to the nozzles 1, 2, 4 and 5 and the heating energy EBi of the nozzle heater 60Bi are controlled to be substantially the same, and the nozzle heaters corresponding to the nozzles 1, 2, 4 and 5 are further controlled. The sum (EAi + EBi) of the heating energy EAi of 60Ai and the heating energy EBi of the nozzle heater 60Bi is substantially the same (EA3 + EB3) of the heating energy EA3 of the nozzle heater 60A3 corresponding to the nozzle 3 and the heating energy EA3 of the nozzle heater 60B3. The nozzle heaters 60Ai and 60Bi of each nozzle i are controlled.

  That is, in the head 50 shown in FIG. 9, the nozzle heaters 60Ai and 60Bi corresponding to the respective nozzles i are controlled so as to satisfy the relationship (EA1 + EB1) = (EA2 + EB2) = (EA3 + EB3) = (EA4 + EB4) = (EA5 + EB5). .

  Specifically, when the heating energy EAi, EBi of each nozzle heater 60Ai, 60Bi is EA1 = EB1 = EA2 = EB2 = EA4 = EB4 = EA5 = EB5 = 2 × s, EA3 = 3 × s, EB3 = s, EA3 / EB3 = 3, and the flying direction of ink droplets ejected from the nozzle 3 is deflected toward the nozzle heater EB3.

  Further, the total heating energy (EAi + EBi) of the nozzle heaters 60Ai, 60Bi of each nozzle i is (EA1 + EB1) = (EA2 + EB2) = (EA3 + EB3) = (EA4 + EB4) = (EA5 + EB5) = 4 × s. The total heating energy (EAi + EBi) of 60Ai and 60Bi is equal. Accordingly, the ejection amount of the ink droplets ejected from each nozzle is substantially uniform, and the sizes of the dots 202 constituting the image 200 shown in FIG. 9 are substantially uniform.

  FIG. 10 shows an example of the relationship between the heating energy ratio (EAi / EBi) of the nozzle heaters 60Ai and 60Bi and the ink droplet deflection amount. FIG. 10 shows an example in which the ink flying direction is deflected toward the nozzle heater 60Bi (when the heating energy EAi of the nozzle heater 60Ai is larger than the heating energy EBi of the nozzle heater 60Bi).

  Such a relationship between the heating energy ratio (EAi / EBi) of the nozzle heaters 60Ai and 60Bi and the deflection amount of the ink droplets is stored in a database in advance and stored in a predetermined memory (storage means), and the nozzle in which the landing position shift occurs. On the other hand, the heating energy ratio (EAi / EBi, where n = 1, 2, 3,..., N) is set according to the amount of landing position deviation. Further, the heating energy ratio is set to 1 for a nozzle in which no landing position deviation occurs. When the flight direction is deflected toward the nozzle heater 60Ai, the heating energy ratio may be EBi / EAi, or the deflection amount L (<0) in the region where the heating energy is less than 1 (0 or more) in FIG. You may ask for it.

  According to the control (flying direction deflection control) of the nozzle heater 60Ai and the nozzle 60Bi described above, the landing position deviation of the ink droplet caused by the characteristics of the nozzle is corrected and the flying direction deflection of the ink droplet ejected from the nozzle is corrected. As a result, the variation in the dot size is corrected, so that no streak or unevenness is visually recognized on the recording medium 16, and a preferable image 200 in which the variation in the dot size is prevented is formed.

[Third Embodiment, Description of Drive Signal Correction Control]
When ink in the nozzle flow path 51A is heated by the nozzle heaters 60Ai and 60Bi, the viscosity of the ink is lowered, so that a larger amount of ink is ejected than a predetermined ejection amount. Therefore, the dots 202 constituting the image 200 shown in FIG. 9 are larger than a predetermined dot size. For example, although the predetermined dot size is the dot 106 in FIG. 8, the dot 202 in FIG. 9 has a larger size than the dot 106 in FIG.

  In the ink jet recording apparatus 10 shown in this example, when the dot size is larger than the predetermined size as described above, the drive signal given to the piezoelectric element 58 (see FIG. 5) is adjusted (for example, the amplitude of the drive signal is changed). By reducing the ink discharge amount to a predetermined discharge amount, the dot size can be corrected to a predetermined size.

  FIG. 11 shows an image 250 formed on the recording medium 16 by applying the drive signal adjustment control described above. The dots 252 constituting the image 250 shown in FIG. 11 are substantially the same size as the dots 106 shown in FIG. 8, and the dots 102 (see FIG. 8) whose size is increased by the heating of the nozzle heaters 60Ai and 60Bi, The size (predetermined size) is smaller than 202 (see FIG. 9).

  Since the dot size increases as the total heating energy (EAi + EBi) of the nozzle heaters 60Ai, 60Bi is increased, the adjustment value of the drive signal may be set based on the total heating energy (EAi + EBi). The heating control in FIG. 11 is the same as the heating control in FIG.

  Such adjustment control of the drive signal is preferable in the aspect in which the drive signal is generated by the common drive waveform method, because it is possible to avoid complication of a circuit for adjusting the drive signal. The common drive waveform method is to prepare a plurality of drive waveform elements common to all piezoelectric elements, select one drive waveform element or a plurality of drive waveform elements from them, and use them as control signals such as enable signals. Accordingly, a drive signal (drive waveform) corresponding to each piezoelectric element is supplied.

  When this common drive waveform method is used, a memory for storing drive signals can be saved as compared with a mode in which individual drive waveforms are prepared for each piezoelectric element, and a circuit block for generating drive signals can be saved. The structure is simplified.

[Application example]
Next, application examples of the first to third embodiments described above will be described. In this application example, the ejection amount of the ink droplet ejected from the nozzle i is corrected by adjusting the drive signal applied to the piezoelectric element 58 corresponding to the nozzle i on which the nozzle heaters 60Ai and 60Bi operate.

  For example, the drive signal given to the piezoelectric element 58 corresponding to the nozzle 3 shown in FIG. 8 is made smaller than the predetermined drive signal by an amount corresponding to the increase amount of the ink droplet ejection amount, thereby making the dot 102 shown in FIG. (Dots that have become larger than a predetermined size as a result of an increase in the discharge amount due to the effect of heating by the nozzle heater 60A3) are corrected to a predetermined size.

  According to this application example, only the nozzle that deflects the flying direction of the ink droplet (actuates the nozzle heater) is controlled to adjust the drive signal corresponding to the nozzle. A uniform dot size is realized between the nozzles without being operated.

  In the aspect of adjusting the drive signal of the piezoelectric element corresponding to the specific nozzle, an adjustment circuit block for adjusting the drive signal for each piezoelectric element is provided. Further, the adjusted drive signal may be stored in advance, and the adjusted drive signal may be read out as necessary.

  In order to determine the physical property value of ink, an information recording body such as a barcode or a wireless tag that records ink type information is attached to an ink cartridge, and the information on the information recording body is read by a predetermined reader. There is a method for automatically determining the type of ink used.

  The relationship between the heating energy ratio (EAi / EBi) and the deflection amount (landing position shift amount) L is stored in a table or the like in advance according to the ink physical property values (surface tension, viscosity, etc.), and the heating energy depends on the ink used. Is more preferable.

  In this example, a piezoelectric element (piezoelectric actuator) is exemplified as the ink ejection force applying means. However, the ink in the pressure chamber is heated using a heater provided in the pressure chamber to generate bubbles, and the pressure is generated by the bubbles. The present invention can also be applied to an aspect in which ejection force is applied to the ink in the room.

  The ink jet recording apparatus 10 configured as described above specifies a nozzle that deviates the flight direction (a nozzle that ejects ink droplets that cause landing position deviation), and deflects the flight direction of the specified nozzle to thereby change the flight direction. Since the nozzle heaters 60Ai and 60Bi of the nozzles are controlled so as to cancel out the deviation, a preferable image can be obtained in which no streak or unevenness due to the positional deviation of the dots occurs.

  Further, since the nozzle heaters 60Ai and 60Bi are controlled so that the total heating energy (EAi + EBi) of the nozzle heaters 60Ai and 60Bi of each nozzle is substantially uniform, the ejection amount of ink droplets ejected from each nozzle is substantially the same. Thus, a uniform dot size is realized.

  Further, when ink is heated by heating the nozzle heaters 60Ai and 60Bi, the drive signal of the piezoelectric element corresponding to the nozzle is corrected, so that a dot of a predetermined size can be formed without increasing the ink droplet discharge amount. Obtainable.

  Further, in this example, an inkjet recording apparatus that forms an image on a recording medium by ejecting ink from nozzles provided in a head (inkjet head) is shown, but the scope of the present invention is not limited to this, The present invention can be widely applied to an image forming apparatus that forms an image (three-dimensional shape) with a liquid other than ink, such as a resist, and a liquid ejecting apparatus such as a dispenser that ejects chemical liquid, water, and the like from a nozzle (ejection hole).

1 is an overall 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. Plane perspective view showing a structural example of the head shown in FIG. The figure explaining the other aspect of the head shown in FIG. Sectional view (along the Va-Va line in FIG. 3) showing the three-dimensional structure of the head shown in FIG. 1 is a principal block diagram showing the system configuration of the ink jet recording apparatus shown in FIG. Enlarged view of the vicinity of the nozzle shown in Fig. 5 (a) The figure explaining flight direction deflection | deviation control which concerns on 1st Embodiment of this invention. The figure explaining nozzle heater control concerning a 2nd embodiment of the present invention. Diagram showing the relationship between heating energy ratio and deflection amount The figure explaining the drive signal adjustment control which concerns on 3rd Embodiment of this invention. The figure explaining the image by the discharge control which concerns on a prior art

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 16 ... Recording medium, 24 ... Print detection part, 50, 50 ', 50 "300 ... Head, 1, 2, 3, 4, 5, 51 ... Nozzle, 51A ... Nozzle flow path, 52 ... Pressure chamber, 60A, 60B, 60C, 60D ... Nozzle heater, 84 ... Head driver, 85 ... Nozzle heater driver, 92 ... Nozzle characteristic specifying unit, 94 ... Drive signal adjusting unit, EA, EB ... Heating energy, LA, LB ... Shift Amount, θA, θB ... deflection amount

Claims (7)

An image forming apparatus that forms an image on the recording medium by relatively moving the head and the recording medium and discharging liquid from a plurality of nozzles of the head,
The head supplies the liquid in the nozzle channel provided in the circumferential direction of each nozzle channel to each of the plurality of nozzle channels that communicate the plurality of nozzles and the plurality of pressure chambers. A heating element group comprising a plurality of heating elements to be heated;
Nozzle characteristic information acquisition means for acquiring characteristic information of the nozzle;
Flight deflection in which the heating energy of the heating element group is controlled in accordance with the nozzle characteristic information, and the flight direction of the liquid ejected from the nozzle is deflected in a direction including a component substantially orthogonal to the relative movement direction of the recording medium. Control means;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the flying direction control unit controls a flying direction of liquid ejected from the nozzle by changing a heating energy ratio of the plurality of heating elements included in the heating element group. . The nozzle characteristic information acquisition unit includes a reading unit that reads an image on the recording medium,
The image forming apparatus according to claim 1, wherein the landing state of the liquid ejected from the nozzle is detected based on a reading result obtained from the reading unit.   The said flight deflection control means controls the heating energy of each said heating element group so that the sum of the heating energy of each said heating element group provided in each nozzle flow path becomes substantially the same. The image forming apparatus according to 1, 2, or 3. A discharge force generating element for applying a discharge force to the liquid in the pressure chamber;
Drive signal supply means for supplying a drive signal to the ejection force generating element;
Drive signal correction means for correcting the drive signal corresponding to an increase in the discharge amount of the liquid due to heating of the heating element group;
The image forming apparatus according to claim 1, further comprising:   According to the nozzle characteristic information, there is provided an ejection control means for controlling the ejection timing of the nozzle so as to correct the deviation of the landing position of the liquid ejected from the nozzle in a direction substantially parallel to the moving direction of the recording medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. An image forming method for forming an image on the recording medium by relatively moving the head and the recording medium and discharging liquid from a plurality of nozzles of the head,
Acquiring the characteristic information of the nozzle that discharges the liquid;
A plurality of heating elements provided in the circumferential direction of the nozzle flow path in each of the plurality of nozzle flow paths for communicating the plurality of nozzles and the plurality of pressure chambers based on the characteristic information of the nozzles An ejection step of heating the liquid in the nozzle flow path by a heating element group consisting of: and deflecting the flight direction of the droplets ejected from the nozzle in a direction including a component substantially orthogonal to the relative movement direction;
An image forming method comprising:

Images