JP4576940B2 - Inkjet recording device - Google Patents

Description

The present invention relates to an ink jet recording apparatus for recording an image by ejecting ink droplets onto a recording medium by an ink jet recording head.

  2. Description of the Related Art Conventionally, an ink jet recording apparatus that records an image on a recording medium such as recording paper by ejecting ink droplets from nozzles of an ink jet recording head is known. In recent years, in such an ink jet recording apparatus, it has been proposed to use a line type recording head having a length substantially the same as the width of the recording medium in response to a demand for high speed. In such a line type recording head, since the number of nozzles is particularly large, there is a tendency that nozzles are clogged and defective discharge is likely to occur.

  For this reason, in order to cope with such a problem, a method has been conventionally proposed in which an image defect is reduced by detecting and correcting an ejection failure. For example, there are a plurality of image recording rows in which a plurality of nozzles are arranged in one row in the paper conveyance direction, and usually, the image recording rows are recorded so as to complement each other. A method is disclosed in which recording is performed using normal nozzles that are on the same line as the ejection failure nozzle and the paper conveyance direction (see, for example, Patent Document 1).

  In this case, since a line that should be recorded by a defective ejection nozzle is recorded by another normal nozzle, a blank line (white streak) does not occur, and an image defect can be avoided. However, since it is necessary to provide a plurality of nozzles on the same line, there is a problem that the recording resolution cannot be increased.

  Also, a method has been proposed in which an auxiliary head is mounted and when there is a nozzle ejection failure, the auxiliary head is used to avoid image defects (for example, see Patent Document 2). However, there is a problem in that the auxiliary head itself increases the cost because the auxiliary head itself is not normally used.

Further, a method is disclosed in which the drive conditions of the nozzles on both sides of the defective ejection nozzle are changed to increase the ink ejection amount so that the line blanks (white lines) that should have been recorded by the defective ejection nozzle become inconspicuous. (For example, refer to Patent Document 3). However, when two defective nozzles are generated consecutively, there is a problem that correction cannot be performed sufficiently and image defects cannot be reduced.
Japanese Patent Laid-Open No. 10-6488 Japanese Patent Laid-Open No. 11-334047 JP 11-348246 A

Therefore, in view of the above circumstances, the present invention can maintain the recording resolution at a high level, and can appropriately reduce image defects caused by defective discharge even when two or more nozzles are continuously generated (white lines are not noticeable). An object is to obtain an inkjet recording apparatus.

In order to achieve the above object, an ink jet recording apparatus according to claim 1 of the present invention includes a first nozzle array having a width substantially equal to a print area and a second nozzle array having a width equal to or greater than the print area. Inkjet recording heads arranged in parallel so that the nozzles are arranged in a staggered manner, detection means for detecting the ejection states of the nozzles of the first nozzle array and the nozzles of the second nozzle array, and the detection means of the detection result, when consecutive ejection failure than 2 nozzle was observed, the second nozzle array, and a moving mechanism for moving to the discharge failure is continuously not become more than the nozzle dispersing position, It is characterized in that the ink discharge amount of the nozzles adjacent to the nozzles judged to be defective is increased by a predetermined amount .

  According to the first aspect of the invention, since the nozzles of the first nozzle array and the nozzles of the second nozzle array are arranged in a staggered manner, the recording resolution can be maintained at a high level. In addition, even if ejection failures are continuously recognized for 2 nozzles or more, the second nozzle array having a width (number of nozzles) larger than the printing area is moved to a dispersion position where ejection failures do not continuously become 2 nozzles or more. Therefore, white streaks can be made inconspicuous in the printed image. That is, it is possible to reduce image defects.

In addition, since the ink discharge amount of the nozzles adjacent to the nozzles determined to be defective in discharge is increased by a predetermined amount, white streaks can be made less noticeable in the printed image. That is, it is possible to further reduce image defects.

According to a second aspect of the present invention, in the inkjet recording apparatus, the first nozzle array having a width substantially equal to the print area and the second nozzle array having a width equal to or larger than the print area are arranged in a staggered manner. The inkjet recording heads arranged in parallel so as to be arranged, detection means for detecting the ejection states of the nozzles of the first nozzle array and the nozzles of the second nozzle array, and the detection result of the detection means A nozzle that has been determined to be defective in discharge, and includes a moving mechanism that moves the second nozzle array to a dispersion position where the defective discharge does not continuously become two or more nozzles. The driving of is stopped.

According to the invention of claim 2, since the nozzles of the first nozzle array and the nozzles of the second nozzle array are arranged in a staggered manner, the recording resolution can be maintained at a high level. In addition, even if ejection failures are continuously recognized for 2 nozzles or more, the second nozzle array having a width (number of nozzles) larger than the printing area is moved to a dispersion position where ejection failures do not continuously become 2 nozzles or more. Therefore, white streaks can be made inconspicuous in the printed image. That is, it is possible to reduce image defects.

In addition, since the driving of the nozzle determined to be defective is stopped, it is possible to avoid the influence on the printing due to bubbles remaining in the nozzle.

The ink jet recording apparatus according to claim 3, in the ink jet recording apparatus according to claim 1, the driving of the nozzles is determined that discharge failure is characterized by being stopped.

According to the invention of claim 3 , since the drive of the nozzle determined to be defective in ejection is stopped, it is possible to avoid the influence on the printing due to bubbles remaining in the nozzle .

The inkjet recording apparatus according to claim 4 is the inkjet recording apparatus according to any one of claims 1 to 3 , wherein the number of dispersed positions is two or more at a nozzle pitch of the second nozzle array. It is characterized by the moved position .

According to the invention of claim 4 , white streaks can be surely not conspicuous in the printed image. That is, this makes it possible to suitably reduce image defects .

The inkjet recording apparatus according to claim 5 is the inkjet recording apparatus according to any one of claims 1 to 4, wherein the maximum movement distance of the second nozzle array is that of the second nozzle array. It is a difference between the number of nozzles and the number of nozzles of the first nozzle array .

According to the invention of claim 5 , since the second nozzle array can be moved by a difference between the number of nozzles of the first nozzle array and the number of nozzles of the second nozzle array, it can flexibly cope with white streak (image defect). can do.

As described above, according to the present invention, the recording resolution can be maintained at a high level, and even when ejection failures occur continuously for two or more nozzles, image defects caused thereby can be suitably reduced (white streaks are conspicuous). without it) it is possible to provide an ink jet recording apparatus.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below in detail based on the embodiments shown in the drawings. 1 and 2 show a schematic configuration of an ink jet recording apparatus according to the present invention. As shown in FIGS. 1 and 2, the ink jet recording apparatus 10 includes a paper feed tray 12 in which the recording paper P is accommodated, and a recording unit 14 that records an image on the recording paper P supplied from the paper feed tray 12. The first conveyance unit 16 that conveys the recording paper P to the recording unit 14, the paper discharge tray 18 that stores the recording paper P on which the image is recorded by the recording unit 14, and the recording in which the image is recorded on the paper discharge tray 18 A second transport unit 20 that transports the paper P, and a reversing unit 22 that is provided between the second transport unit 20 and the first transport unit 16 and that reverses the recording paper P and re-feeds it to the recording unit 14 during duplex printing. And have.

  The recording unit 14 has an inkjet recording head 24. As shown in FIG. 4, the inkjet recording head 24 is a so-called full width array (FWA) capable of single-pass printing, and yellow (Y) from the upstream side in the transport direction of the recording paper P. , Magenta (M), cyan (C), and black (K).

  Each of the inkjet recording heads 24 </ b> Y to 24 </ b> K is a nozzle that can cover a width that is substantially the same as the maximum width (printing area) of the recording paper P on which image recording in the inkjet recording apparatus 10 is assumed, that is, the maximum width (printing area). The first nozzle array 26 having a number and the second nozzle array 28 having a printable area (number of nozzles, for example, 100 spare nozzles) larger than the first nozzle array 26, each nozzle 66, 68. (See FIG. 5), ink droplets are ejected by known means such as a thermal method or a piezoelectric method.

  Furthermore, the inkjet recording heads 24Y to 24K are provided with maintenance units 30Y to 30K. The maintenance units 30Y to 30K are divided into two groups of black (K), cyan (C), magenta (M), and yellow (Y), and the retreat positions at the time of printing and the respective inkjet recording heads 24Y to 24K. It is configured to be movable to a maintenance position.

  Each maintenance unit 30Y-30K has a dummy jet receiver, a wiping member, a cap, etc., and when maintaining each inkjet recording head 24Y-24K, each inkjet recording head 24Y-24K raises predetermined height. It has become. The maintenance units 30Y to 30K are arranged to face the nozzle surfaces (not shown) of the respective ink jet recording heads 24Y to 24K.

  As shown in FIG. 3, the ink jet recording apparatus (printer) 10 is connected to a control apparatus 34 such as a computer (PC) using an external interface 32. Accordingly, when a print command is issued by the application 36 on the control device 34, the print driver 38 receives the print command, and transmits the print command and print data to the inkjet recording apparatus 10 through the external interface 32 through an image conversion process. .

  When an image signal such as a print command and print data is transmitted, the inkjet recording apparatus 10 determines a droplet ejection timing and a nozzle to be used by the print head controller 40 and applies a drive signal to the nozzle. Accordingly, the inkjet recording heads 24Y to 24K are configured to record images on the recording paper P. In addition, as illustrated, the inkjet recording apparatus 10 includes a defective ejection detection mechanism 42 that detects ejection states of the inkjet recording heads 24Y to 24K, a CPU 44 that controls the overall operation, and the like.

  The recording paper P in the paper feed tray 12 is picked up one by one by the pickup roller 46 and is sent to the recording unit 14 by the first transport unit 16. The first transport unit 16 includes a plurality of transport roller pairs 48 for transporting paper disposed at appropriate positions, and the recording paper P is re-supplied to the predetermined transport roller pair 48A from the reversing unit 22 described later. It has come to be.

  The recording unit 14 is wound around a driving roller 52 disposed on the upstream side in the sheet conveyance direction and a driven roller 54 disposed on the downstream side so that the printing surface of the recording sheet P faces the inkjet recording head 24. A conveyor belt 50 is provided, and this conveyor belt 50 is configured to circulate (rotate) in the direction of arrow A (counterclockwise) in FIG. A nip roller 56 that is in sliding contact with the transport belt 50 from the front side is disposed above the drive roller 52.

  The second transport unit 20 includes a plurality of transport roller pairs 58 for transporting paper disposed at appropriate positions, and the predetermined transport roller pair 58A can send the recording paper P to the reversing unit 22 described later. It has become. The reversing unit 22 has a plurality of conveyance roller pairs 60 for conveying the paper disposed at appropriate positions, and the recording sheet P is conveyed from the conveyance roller pair 58A to the conveyance roller pair 48A with the printed surface facing up. It is designed to be transported in a directed state.

  That is, the recording paper P that is supplied to the recording unit 14 and has an image formed on one surface (front surface) by passing below the ink jet recording heads 24Y to 24K is sandwiched between the conveyance roller pair 58A at the end. Then, the transport roller pair 58 </ b> A rotates reversely and is sent to the reversing unit 22, and is sent by the transport roller pair 60 to the transport roller pair 48 </ b> A.

  Then, the sheet is sandwiched between the conveying roller pair 48A and supplied again between the conveying belt 50 and the nip roller 56. At this time, the non-printed surface is supplied so as to face the ink jet recording heads 24Y to 24K. The In this way, the recording paper P that has been turned upside down and on which the image is formed on the other side (back side) is discharged to the discharge tray 18 by the second transport unit 20 as it is.

  As shown in FIGS. 1 and 2, the ink jet recording apparatus 10 includes ink tanks 62Y, 62M, 62C, and 62K that supply ink to the ink jet recording heads 24Y to 24K. Each of the ink tanks 62Y to 62K is filled with, for example, an aqueous pigment ink.

  Next, in the inkjet recording apparatus 10 having the above-described configuration, a means for reducing image defects (white streaks) caused when defective discharge continuously occurs in two or more nozzles will be described with reference to FIGS. Explained. As described above, each of the ink jet recording heads 24Y to 24K includes the first nozzle array 26Y to 26K and the second nozzle array 28Y to 28K, respectively. As illustrated in FIG. The second nozzle array 28 is arranged in parallel so that the respective nozzles 66 and 68 are staggered in a direction orthogonal to the paper transport direction (in a zigzag pattern).

  Further, the nozzles 66 and 68 of the first nozzle array 26 and the second nozzle array 28 are both arranged at an interval of 300 npi, and the first nozzle array 26 and the second nozzle array 28 are respectively arranged in a staggered manner. Therefore, 600 dpi recording can be performed in the nozzle arrangement direction. Accordingly, the recording of 600 × 600 dpi is possible together with the conveyance of the recording paper P, and high-resolution recording is possible.

  As shown in FIG. 4, each of the second nozzle arrays 28 </ b> Y to 28 </ b> K is configured to be movable in a direction orthogonal to the paper transport direction (hereinafter referred to as “width direction”). Arbitrary configurations can be adopted as the moving mechanism 70 that allows the second nozzle arrays 28Y to 28K to move in the width direction (the direction of the arrow B in the drawing).

  For example, one end face of each of the second nozzle arrays 28Y to 28K is connected to the other end of a coil spring 72, one end of which is fixed to the device frame or the like, and the other end face is fixed to the rotating shaft 64 and is independent of each other. The second nozzle arrays 28Y to 28K are moved in the width direction against the urging force of the coil spring 72 or the urging force by abutting the eccentric cams 74 that are driven to rotate and rotating the eccentric cams 74. Such a configuration can be adopted.

  The maximum movement distance of the second nozzle arrays 28Y to 28K is a difference between the number of nozzles of the first nozzle arrays 26Y to 26K and the number of nozzles of the second nozzle arrays 28Y to 28K. For example, if the number of nozzles of the first nozzle arrays 26Y to 26K is 8000 and the number of nozzles of the second nozzle arrays 28Y to 28K is 8100, the maximum movement distance of the second nozzle arrays 28Y to 28K is The pitch is 100 pieces, which is the number of spare nozzles.

  Next, a control method for the inkjet recording heads 24Y to 24K having the above-described configuration will be described with reference to the flowchart shown in FIG. First, before executing the normal printing process, trial printing is performed for each color, and the ejection states of the ink jet recording heads 24Y to 24K are detected. That is, the defective discharge detection mechanism 42 detects whether or not there is a defective discharge nozzle in the first nozzle array 26 and the second nozzle array 28 (S1). Then, in the inkjet recording heads 24Y to 24K of the respective colors, when there is no ejection failure nozzle or when there are not 2 or more ejection failure nozzles continuous, normal printing processing is performed (S2).

  In the present invention, “continuous” means continuous when printed on the recording paper P, and the nozzles 66 of the first nozzle array 26 and the nozzles 68 of the second nozzle array 28 arranged in a staggered manner. It is judged across. That is, the case where two or more ejection failure nozzles are continuous means a case where the nozzle 66 and the nozzle 68 become ejection failures adjacent to each other in a staggered arrangement as shown in FIG.

  Now, as shown in FIG. 7, for example, when trial printing is performed with the black (K) inkjet recording head 24K, white streaks (image defects) are continuously generated in the printed image. Assuming that a defective ejection beyond the nozzle is detected (recognized) by the defective ejection detection mechanism 42, the controller 34 instructs the inkjet recording apparatus 10 to move the second nozzle array 28K of the inkjet recording head 24K in the width direction. Send to.

  When the inkjet recording apparatus 10 receives a command to move the second nozzle array 28K of the inkjet recording head 24K in the width direction, the inkjet recording apparatus 10 rotates the eccentric cam 74 that is in contact with the second nozzle array 28K by a predetermined angle. As a result, the second nozzle array 28K is moved to a position where the white streaks are dispersed and become inconspicuous (dispersion position) (S3).

  That is, for example, as shown in FIG. 8, the nozzle pitch of the second nozzle array 28K is moved in the width direction by one (2 dots in recording resolution). As shown in the figure, the moving distance at this time may be one for the nozzle pitch of the second nozzle array 28K, but in order to make sure that white streaks (image defects) are not noticeable when printed. Is preferably at least two nozzle pitches (four dots at recording resolution).

  In particular, as shown in FIG. 9, it is preferable to move the second nozzle array 28 to the maximum movable range because white streaks (image defects) when printed can be reliably dispersed. Note that the maximum moving distance at this time is the number of spare nozzles (for example, 100). The larger the number of spare nozzles, the more flexibly cope with the occurrence of white lines (image defects). For example, if the nozzles that have failed to discharge are nozzles on both ends (within 100 nozzles from both ends) of the second nozzle array 28, the nozzles are removed from the print area (substantially equal to the width of the first nozzle array 26). It is also possible.

  In any case, since the second nozzle array 28K is moved in the width direction so as not to cause ejection failure continuously for two or more nozzles, there is no problem that white streaks are conspicuous in the printed image. That is, printing with reduced image defects is possible. At this time, it is preferable that the driving of the nozzle that has caused the ejection failure is appropriately stopped. According to this, it is possible to avoid the influence on printing due to bubbles remaining in the nozzle.

  Further, as shown in FIG. 10, after the second nozzle array 28K is moved, the drive conditions of the nozzles 66A, 68A that are regarded as defective in ejection and the nozzles 66B, 66C, 68B, 68C adjacent to the nozzles 66A, 68A are changed. You may comprise as follows. That is, the nozzles 68B and 68C of the second nozzle array 28K adjacent in a staggered manner to the nozzles 66A determined to be defective in the first nozzle array 26K and the nozzles 68A determined to be defective in the second nozzle array 28K. Alternatively, the ink discharge amount of the nozzles 66B and 66C of the first nozzle array 26K adjacent in a staggered manner may be increased by a predetermined amount. According to this, white streaks (image defects) when printed can be made more inconspicuous (reduced).

  In addition, the first nozzle array 26 may be moved in the width direction, but in this case, the recording paper P needs to be moved in the width direction, which is not preferable in terms of the structure of the inkjet recording apparatus 10. Therefore, although the size in the width direction of the ink jet recording apparatus 10 itself increases, the configuration in which the first nozzle array 26 is fixed and the second nozzle array 28 is movable does not move the recording paper P in the width direction. This is preferable.

  Further, the inkjet recording heads 24Y to 24K are limited to those in which the nozzles 66 and 68 are arranged one-dimensionally (aligned on one straight line) in each of the first nozzle arrays 26Y to 26K and the second nozzle arrays 28Y to 28K. Needless to say, the same effect can be obtained even when two-dimensionally arranged (a plurality of rows arranged in the paper conveyance direction).

  As described above, the first nozzle array 26 that covers the printing area is detected even when ejection defects of two or more nozzles are detected continuously such that white lines (image defects) occur in the test printed image. Since the second nozzle array 28 having a larger number of nozzles (having spare nozzles) can be moved in the width direction, the white stripes (image defects) can be dispersed and made inconspicuous.

  In other words, in the FWA inkjet recording heads 24Y to 24K, even if ejection failures of 2 nozzles or more occur continuously, the inkjet recording heads 24Y to 24K are not replaced, and image defects (white streaks) are thereby reduced. It is possible to print an image in a state where

  The ink jet recording apparatus 10 according to the present invention is limited to a device used for recording general images (characters, pictures, photographs, etc.) on the recording paper P, such as a facsimile, a copying machine, and a printer complex machine. It is not a thing. For example, the present invention can also be applied to production of a color filter for display performed by discharging colored ink on a polymer film or glass, formation of a wiring pattern on a substrate, and the like.

  Further, the liquid to be ejected is not limited to ink. For example, liquids intended for various industrial applications such as the formation of bumps for component mounting by discharging molten solder onto the substrate, and the formation of EL display panels by discharging organic EL solution onto the substrate The ink jet recording apparatus 10 according to the present invention can be applied to a general droplet ejecting apparatus.

Schematic side view showing the configuration of the ink jet recording apparatus during printing Schematic side view showing configuration during maintenance of inkjet recording apparatus Schematic block diagram showing a system of an ink jet recording apparatus Schematic perspective view schematically showing the configuration of an ink jet recording head Schematic plan view showing the printing state with an inkjet recording head Flowchart for explaining means for reducing image quality defects due to defective nozzle ejection Schematic plan view showing the printing state when two nozzle ejection failures occur continuously Schematic plan view showing a printing state when image quality defects are reduced by moving the second nozzle array Schematic plan view showing the printing state when image quality defects are reduced by maximally moving the second nozzle array Schematic plan view showing the printing state when moving the second nozzle array and increasing the ink discharge amount of the adjacent nozzles to reduce image quality defects

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording device 14 Recording part 24 Inkjet recording head 26 1st nozzle array 28 2nd nozzle array 30 Maintenance unit 34 Control apparatus 42 Defect discharge detection mechanism (detection means)
50 Conveying belt 66 Nozzle 68 Nozzle 70 Moving mechanism 72 Coil spring 74 Eccentric cam

Claims (5)

An ink jet recording head in which a first nozzle array having a width substantially equal to the print area and a second nozzle array having a width equal to or greater than the print area are arranged in parallel so that the nozzles are arranged in a staggered manner;
Detecting means for detecting a discharge state of the nozzles of the first nozzle array and the nozzles of the second nozzle array;
A moving mechanism for moving the second nozzle array to a dispersion position where the discharge failure does not continuously become 2 nozzles or more when a discharge failure of 2 nozzles or more is continuously recognized according to the detection result of the detection means;
Equipped with a,
An ink jet recording apparatus, wherein an ink discharge amount of nozzles adjacent to a nozzle determined to be defective is increased by a predetermined amount . An ink jet recording head in which a first nozzle array having a width substantially equal to the print area and a second nozzle array having a width equal to or greater than the print area are arranged in parallel so that the nozzles are arranged in a staggered manner;
Detecting means for detecting a discharge state of the nozzles of the first nozzle array and the nozzles of the second nozzle array;
A moving mechanism for moving the second nozzle array to a dispersion position where the discharge failure does not continuously become 2 nozzles or more when a discharge failure of 2 nozzles or more is continuously recognized according to the detection result of the detection means;
With
An ink jet recording apparatus you characterized in that driving of is determined that ejection failure nozzle is stopped. The ink jet recording apparatus according to claim 1 , wherein the driving of the nozzle determined to be an ejection failure is stopped . 4. The ink jet recording apparatus according to claim 1 , wherein the dispersion position is a position where two or more nozzles are moved at a nozzle pitch of the second nozzle array . 5. The maximum movement distance of the second nozzle array, in any one of claims 1 to 4, characterized in that the number of nozzles of the difference of the nozzle number of the second nozzle array the first nozzle array The ink jet recording apparatus described.

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