JP2004174816A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an excellent ink jet recorder in which normal image formation is not damaged by nonejection of ink, total recording time lag is suppressed in recording operation and high quality image formation is ensured with no unevenness in density. <P>SOLUTION: The ink jet recorder has a recording head constituted of six color inks, i.e. Y, M, C, K, light M and light C, and (1) if the nozzle of C does not eject ink, printing is performed by replacing that nozzle with the nozzle of light C in the identical pass. (2) If the nozzle of M does not eject ink, that nozzle is replaced with the nozzle of light M in the identical pass. (3) It is also true in the reverse case of C and light C, and in the reverse case of M and light M. (4) If the nozzle of K does not eject ink, printing is performed by replacing that nozzle with that for the mixed color of C, M and Y. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet printer that interpolates and prints dots to be recorded by a non-ejection nozzle when ejection failure occurs among a plurality of nozzles of a multi-head. Is involved.
[0002]
[Prior art]
In general, a color ink jet recording apparatus includes a recording head on which four color inks of cyan (C), magenta (H), yellow (Y), and black (K) are mounted, and conveying means for conveying recording paper. And control means for controlling these. Then, a recording head for ejecting ink droplets from a plurality of nozzles is scanned on recording paper, and a color image is formed by superimposing the ejected ink droplets.
[0003]
In such a color ink jet recording apparatus, different from a monochrome ink jet recording apparatus that prints only characters, various elements such as color development, gradation, and uniformity are required for recording a color image image.
[0004]
However, the quality of an image to be printed largely depends on the performance of the print head alone. Slight differences between the nozzles that occur during the print head manufacturing process, such as variations in the shape of the discharge ports of the print head and the electrical / thermal converters (discharge heaters), indicate the amount of ink discharged and the direction of the discharge direction. , And the image quality is deteriorated as the density unevenness of the finally formed recorded image. As a result, there may be "white" portions which cannot periodically satisfy the area factor of 100 g in the main scanning direction of the head, or dots may overlap more than necessary, or white stripes may occur. It becomes. These phenomena are usually perceived by human eyes as density unevenness.
[0005]
In addition, in the recording head of an ink jet recording apparatus, when the ink is not discharged, the ink thickens particularly in an ink liquid passage near a discharge port, and normal discharge is not performed. There is. Further, in the case where the recording operation with a high recording dot ratio (high recording duty) is continuous or the like, fine bubbles are generated in the ink in the liquid path as the ink is ejected, and these bubbles grow and grow. Bubbles may remain in the liquid path and affect the ejection, and similarly, normal ejection may not be performed. In addition to the bubbles generated by the above-described ejection, some of the bubbles are mixed into the ink in an ink supply system such as a connection portion of an ink supply path.
[0006]
Due to the non-ejection of ink caused by these causes, various problems occur as compared with the normal case. First, what can be considered is deterioration of the image quality of the print result. Due to the non-ejection of the ink, not only the density does not reach the predetermined density, but also an image with noticeable uneven streaks. Furthermore, if printing is continued in a state in which normal ejection is not possible, the print head will rise to a much higher temperature than in a normal case, causing damage to the print head itself and possibly impairing durability. .
[0007]
In an ink jet recording apparatus in which ejection failure is caused by these various causes, (1) capping processing for covering the ejection port surface of the recording head when ejection is not performed to prevent thickening of ink, and (2) capping state. (3) an ink suction process for sucking ink from a discharge port to forcibly discharge the thickened ink; (3) a preliminary discharge process for discharging the thickened ink by discharging the ink to a predetermined ink receiver including an ink absorber; Failures have been avoided by performing such recovery processing.
[0008]
However, there are some ejection failure nozzles that cannot be completely removed even if such a recovery process is performed. In such a case, it is said that replacing the head itself with a new head is the quickest method, but this increases the economic burden on the user, and furthermore, the inkjet itself This can lead to a loss of reliability.
[0009]
Therefore, in recent years, means for preventing deterioration of a printed image even when there is a nozzle having a discharge failure has been considered.
[0010]
This is a method of guaranteeing a recorded image by interpolating with another nozzle in another pass without using a defective nozzle, and is described in JP-A-6-226982. That is the non-ejection nozzle interpolation method.
[0011]
According to this method, in a multi-nozzle head having a plurality of nozzles, for example, if the X-th nozzle has a discharge failure, this is stored in the control means.
[0012]
First, the X-th missing one-time printing is performed, then Ydot line feed is performed, and the missing portion is interpolated by the Z-th normal nozzle, and normal printing is performed by the two-time printing.
[0013]
[Problems to be solved by the invention]
However, the following problem exists in the non-ejection nozzle interpolation method in the conventional inkjet recording apparatus.
[0014]
First, the total time required for recording is described.
[0015]
In the non-ejection nozzle interpolation method described as a conventional example, print data of a nozzle in which ink is not ejected is interpolated by another nozzle in the same head. Only a line feed (recording paper conveyance) is performed, and a pass occurs in which printing is performed only by another nozzle designated for interpolation. That is, the number of passes increases by the number of the non-ejection nozzles, and the total printing time is delayed. Further, accuracy for paper feeding only for a predetermined amount, sometimes paper feeding accuracy in units of one dot, and ink landing accuracy are required, and this is not a practical method.
[0016]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to prevent a delay in a total recording time in a recording process without impairing normal image formation due to non-ejection of ink, and to reduce a density. An object of the present invention is to provide an excellent ink jet recording apparatus capable of forming a uniform high-quality image.
[0017]
[Means for Solving the Problems]
In order to solve the above problems, an ink jet recording apparatus according to the present invention has the following configuration.
[0018]
That is, an ink jet recording apparatus that forms an image by ejecting ink to a recording medium based on input image information, comprising: a recording head having a plurality of nozzles; and an ejection failure for each of the plurality of nozzles. The apparatus further comprises: an ejection failure detection means for detecting; and an interpolation control means for controlling assignment of a recording dot assigned to a nozzle of the recording head for which ejection failure has been detected by the ejection failure detection means to another recording head.
[0019]
According to the above configuration, it is possible to interpolate and print the recording dots to be recorded by the nozzles in which the ejection failure has been detected by another recording head.
[0020]
Further, an ink jet recording apparatus according to a second aspect of the present invention has the following configuration.
[0021]
This is an inkjet recording apparatus having a recording head composed of six color inks of Y (yellow), H (dark magenta), C (dark cyan), K (black), LM (light magenta), and LC (light cyan). If a discharge failure is detected in the M ink print head, the print dots allocated to the discharge failure nozzles are allocated to the LM ink print head, and control is performed so that printing is performed in the same pass. When the ejection failure is detected, the recording dot assigned to the ejection failure nozzle is assigned to the recording head of the LC ink, and the printing is controlled in the same pass, and the ejection failure is detected in the recording head of the LM ink. In this case, the recording dots assigned to the ejection failure nozzles are assigned to the recording head of M ink, and control is performed so that printing is performed in the same pass. When a discharge failure is detected in the recording head of the ink, the recording dot allocated to the discharge defective nozzle is allocated to the recording head of the C ink, and control is performed so that printing is performed in the same pass. Is detected, the recording dots assigned to the ejection failure nozzles are assigned to the Y, M, and C ink recording heads, and control is performed so that printing is performed in the same pass.
[0022]
With the above configuration, even when a discharge failure occurs in the print head, a pass for interpolation does not occur, so that it is possible to obtain a print image equivalent to that when there is no discharge failure without delaying the printing time. Become.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0024]
FIG. 1 is a perspective view showing the configuration of an ink jet recording image forming apparatus according to the present invention.
[0025]
A recording head 101 includes an ink tank in which a plurality of color inks are respectively sealed, and a multi-head in which heads corresponding to the respective ink tanks are integrated.
[0026]
Reference numeral 102 denotes a non-ejection nozzle detection unit that positions light receiving elements for detecting two beams in positions opposite to each other in the sub-scanning direction outside a printable area where a print head in which a number of nozzles are arranged in the sub-scanning direction can scan. And using nozzles at positions close to the light receiving elements, while sequentially controlling the ejection of ink droplets from these nozzles toward the beam in a time-series manner, based on the ejection timing of the ink drops and the detection timing of the light receiving element. This is to specify a discharge failure nozzle. It is composed of a light emitting element for generating two beams and a light receiving element for detecting the light. A belt 103 moves the print head 101 together with printing.
[0027]
Reference numeral 104 denotes a paper feed roller which rotates while holding down the recording paper 106 and feeds the recording paper 106 in the Y direction as needed. Reference numeral 105 denotes a paper feed roller, which feeds the recording paper 106 and plays a role of suppressing the recording paper 106 similarly to the paper feed roller 104.
[0028]
FIG. 2 is a block diagram of an ink jet recording image forming apparatus according to the present invention.
[0029]
Reference numeral 201 denotes a memory unit which temporarily stores, from outside the figure, print data on which image processing for printing has been performed.
[0030]
Reference numeral 202 denotes a head data generation unit that performs read processing of print data based on a relative position on a print sheet for each ink color in the print head, and generates pass data for each print scan according to the number of print passes. I do.
[0031]
A control unit 203 monitors the state of each unit and performs various controls related to driving of the print head.
[0032]
A printhead control unit 204 generates various control signals for driving the printhead 205.
[0033]
Reference numeral 205 denotes a recording head, which discharges ink onto a recording sheet according to the path data.
[0034]
Reference numeral 206 denotes a non-discharge detection unit which detects non-discharge of each nozzle of the print head.
[0035]
A basic recording operation in the above configuration will be described.
[0036]
During standby, the print head 101 at the home position moves in the X direction according to a print start command, and discharges ink onto the print paper 106 in accordance with print data by a plurality of nozzles to perform printing. When printing of the print data is completed to the end of the print paper 106, the paper feed roller 104 rotates in the direction of the arrow to feed the paper by a predetermined width in the Y direction. Subsequently, while the recording head moves in the -X direction, ink is ejected onto the recording paper 106 in accordance with the recording data by a plurality of nozzles in the same manner, printing is performed, and the print position returns to the original home position. When the paper feed roller 104 rotates again in the direction of the arrow, the paper is fed by a predetermined width in the Y direction. Data recording is realized by repeating such a scanning operation and a paper feeding operation.
[0037]
The recording head will be described as an example of a multi-head in which six chips are integrated. The ink arrangement of this recording head is arranged in cyan (C), magenta (H), yellow (Y), black (K), light cyan (LC) and light magenta (LM) from the front side in the forward scanning direction.
[0038]
FIG. 3 illustrates this state. This drawing does not limit the arrangement of ink, and the order of arrangement may be changed.
[0039]
Next, the interpolation control operation responding to the ink non-discharge detection characteristic of the present invention will be described in detail.
[0040]
FIG. 4 is a diagram in the case where a non-ejection nozzle 401 occurs in cyan (C) of the print head. Here, the number of nozzles is illustrated as 16 as an example, and the number of nozzles is not limited.
[0041]
For example, if a non-ejection nozzle 401 is generated in cyan (C) of the recording head, if printing is performed in this state, one dot of C will be missing, and it will appear as a blank area to the user. Would. Alternatively, when a color is expressed by mixing colors with other inks, an image is discolored at a missing one dot portion.
[0042]
Therefore, a control operation of the interpolation method according to the present invention will be described as a method for coping with the case where non-ejection has occurred.
[0043]
The non-discharge detection unit monitors the discharge state of each nozzle before printing is started and each time reciprocal scanning is performed. The non-ejection nozzle detection unit detects ink droplets that have been ejection-controlled in a time-sequential manner by two beams, and can specify an ejection failure nozzle without an error of one nozzle.
[0044]
FIG. 5 shows the non-ejection nozzle interpolation operation of the cyan head.
[0045]
If the non-ejection detecting unit detects an ejection failure nozzle 501 in cyan (C) of the recording head in the middle of page recording, the control unit 203 is notified immediately to that effect. The control unit 203 requests an interpolation instruction to the head data generation unit 202 in response to the notification of non-ejection detection at the 501 nozzle of the print head. In response to this, the head data generation unit operates to allocate all print dots to be assigned to the 501 nozzles of the printhead to the light cyan (LC) nozzles 511 of the printhead. Similarly to 501, the nozzle 511 is the n-th nozzle from the top (fourth from the top in the figure), that is, another nozzle located at the same n-th place from the non-ejection nozzle and offset from the head. assign. Then, at the time of printing, the print head scans by the offset in the direction of the arrow, and discharges ink when 512 nozzles have come to the position where the nozzles 502 should originally discharge ink. As described above, it is not necessary to prepare a new pass for the interpolation, and the interpolation printing can be completed in the same pass.
[0046]
However, there is a concern about subtle differences in density by replacing the dark cyan dots with light cyan, but originally, the input image data was sorted to either dark or light ink according to the threshold value, so the threshold If the image data is in the vicinity of the value, it can be said that there is no problem in the difference in density. Further, when an image is actually printed, it is often printed in a plurality of passes (two or more passes), and the density distribution in recording dot units is dispersed, so that the image quality is deteriorated due to the difference in the density of the same color ink. This is not a problem because there is almost no problem.
[0047]
As described above, the printing dots for the 501 nozzles of the cyan head in the printing scan after the ejection failure detection are all interpolated by the 511 nozzles of the light cyan head, so that the interpolated printing can be completed in the same pass. This makes it possible not only to prevent a delay in printing time, but also to prevent deterioration of a recorded image.
[0048]
FIG. 6 shows the interpolation operation of the magenta head.
[0049]
In the same manner as described above, when the ejection failure nozzle 502 of the magenta head (M) is detected, the printing dots to be assigned to the 502 nozzles of the magenta head are all assigned to the 512 nozzles of the light magenta head (LM).
[0050]
Until now, the interpolation operation in the case where the ejection failure has occurred in the cyan head (C) and the magenta head (M) has been described, but the interpolation operation is the same in the opposite case.
[0051]
That is, when an ejection failure occurs in the light cyan head (LC), all the recording dots are assigned to the cyan head (C). When an ejection failure occurs in the light magenta head (LM), all the recording dots are magenta. An interpolation operation is performed so as to allocate the head (M).
[0052]
Next, the interpolation operation of the black head will be described. See FIG.
[0053]
When a discharge failure nozzle is detected in the black head, the treatment is slightly different.
[0054]
When the ejection failure detection unit detects the ejection failure nozzle 503 in black (K) of the recording head, it is notified to the control unit 203 and requests the head data generation unit 202 to perform an interpolation instruction. In response to this, the head data generation unit allocates recording dots to be assigned to the 503 nozzles of the black head to the nozzles 513, 514, and 515 of the cyan (C), magenta (H), and yellow (Y) heads. Operate.
[0055]
The nozzles 513, 514, and 515 are the n-th nozzle from the top (the 13th from the top in the figure), that is, the offset separation between the non-ejection nozzle and the head, and the same n-th location from the top Assign to another nozzle located at.
[0056]
At the time of printing, each print head scans by an offset in the direction of the arrow, and when the cyan head comes to the position where the nozzle 503 should originally discharge ink, the nozzle 513 discharges the ink. When the magenta head comes to the position where the nozzle should have ejected the ink, the nozzle 514 ejects the ink, and when the yellow head comes to the position where the nozzle 503 should originally have ejected the ink, Nozzles eject ink.
[0057]
That is, the recording dots for the 503 nozzles of the black head are recorded instead by creating black by mixing the three colors of cyan, magenta, and yellow.
[0058]
As described above, it is not necessary to prepare a new pass for the interpolation, and the interpolation printing can be completed in the same pass.
[0059]
However, there is some concern about differences in tint and density by replacing the genuine black dots with three-color mixed black. However, the recording dot size is originally very small, and furthermore, a plurality of passes (two-pass) are required. In many cases, the genuine black dot and the three-color mixed black are indistinguishable when viewed in recording dot units, and it can be said that there is no problem.
[0060]
Although not shown, for yellow (Y), even if an ejection failure nozzle occurs, the process of replacing the recording dot with another head is not performed. This is because originally, it is difficult for human eyes to determine the density of yellow, and even if some ejection failure nozzles occur, they do not cause a decrease in density or image quality.
[0061]
Next, a flowchart showing the flow of the processing of the present invention will be described. See FIG.
[0062]
First, the non-ejection detection unit detects whether or not an ejection failure has occurred in the nozzles of the print head. (S11) If no ejection failure nozzle has occurred, the normal printing process is performed.
[0063]
If an ejection failure nozzle has occurred, the nozzle number of the ejection failure nozzle is specified and notified to the control unit (S12). When notified, the control unit controls the head data generation unit, and allocates data to be recorded by the ejection failure nozzle to another nozzle that can perform interpolation printing in the same pass (S13). Interpolation recording is performed using the allocated data (S14).
[0064]
As described above, when an ink ejection failure is detected in the recording head, a defective dot is detected by allocating the recording dot to be recorded by the nozzle where ejection failure has occurred to another nozzle and performing an interpolation recording operation. However, it is possible to realize normal image formation without density unevenness without being affected by it.
[0065]
Furthermore, since data is assigned to nozzles of the same nozzle number that are offset by the offset amount from the ejection failure nozzle, interpolation printing can be performed in the same pass without the need for an interpolation pass, thereby extending the printing time. And realizes image formation.
[0066]
【The invention's effect】
As described in detail above, in an ink jet recording apparatus that forms an image by discharging ink on a recording medium based on input image information, a plurality of recording heads having a plurality of discharging units, and the plurality of discharging units A defective discharge detecting means for detecting a defective discharge with respect to each of the recording heads, and controlling the recording dots allocated to the discharge section of the recording head in which the defective discharge is detected by the defective discharge detecting means to be allocated to another recording head. Interpolating control means for detecting non-ejection of ink on a nozzle-by-nozzle basis, and recording a recording dot to be recorded by the non-ejection-detected nozzle by a nozzle of another recording head. It is possible to prevent the image quality from deteriorating even when the nozzles are present.
[0067]
Further, the interpolation printing is performed in the same pass, and there is no pass for the interpolation printing, so that the total printing time is the same.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an ink jet recording apparatus according to the present invention.
FIG. 2 is a block diagram of an ink jet recording apparatus according to the present invention.
FIG. 3 is a diagram illustrating a head and an ink arrangement of the inkjet recording apparatus according to the present invention.
FIG. 4 is a diagram when a defective ejection nozzle occurs in a cyan head according to the embodiment of the present invention.
FIG. 5 is a diagram in which dots to be printed by ejection failure nozzles of a cyan head in the embodiment of the present invention are replaced by nozzles of a light cyan head.
FIG. 6 is a diagram in which dots to be printed by ejection failure nozzles of a magenta head according to the embodiment of the present invention are replaced by nozzles of a light magenta head.
FIG. 7 is a diagram in which dots to be printed by ejection failure nozzles of a black head according to the embodiment of the present invention are replaced by a mixed color of three colors of cyan, magenta, and yellow.
FIG. 8 is a flowchart showing the processing of the present invention.

Claims (2)

In an ink jet recording apparatus that prints by discharging ink droplets onto a recording medium, a recording head having a plurality of nozzles,
A discharge failure detection unit that detects a discharge failure for each of the plurality of nozzles;
Interpolation control means for controlling the recording dots to be assigned to the nozzles where ejection failures are detected, by the ejection failure detection means, so as to assign them to other nozzles.
An ink jet recording apparatus comprising: This is an inkjet recording apparatus having a recording head composed of six color inks of Y (yellow), H (dark magenta), C (dark cyan), K (black), LH (light magenta), and LC (light cyan). hand,
When an ejection failure is detected in the M ink recording head, control is performed so that the recording dots assigned to the ejection failure nozzles are assigned to the LH ink recording head.
If ejection failure is detected in the C ink recording head, control is performed so that the recording dots assigned to the ejection failure nozzle are assigned to the LC ink recording head,
When an ejection failure is detected in the LM ink recording head, control is performed so that the recording dots assigned to the ejection failure nozzle are assigned to the M ink recording head.
If ejection failure is detected in the recording head of the LC ink, control is performed such that the recording dots assigned to the ejection failure nozzle are assigned to the recording head of the C ink.
The method according to claim 1, wherein when a discharge failure is detected in the K ink recording head, control is performed such that the recording dots allocated to the discharge defective nozzles are allocated to the Y, M, and C ink recording heads. Ink jet recording device.

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