JP2004174750A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high quality image formation without causing a void or uneven density upon occurrence of nonejection. <P>SOLUTION: The ink jet recorder performing multipass recording comprises a means for detecting nonejection of a recording head, and a control means for altering the combination of nozzles forming a line depending on the detection results. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet recording apparatus that forms an image by discharging ink on a recording medium, and more specifically, relates to non-discharge detection / complementary control that detects non-discharge of ink and performs complementary recording. It is.
[0002]
[Prior art]
In recent years, OA equipment such as a personal computer, a copying apparatus, and a word processor has become widespread, and an apparatus for performing digital image recording by an ink jet system as one type of image forming (recording) apparatus of these apparatuses has been rapidly developed. Widespread. In particular, the colorization of OA equipment has been advanced along with the enhancement of its functions, and accordingly, various color ink jet recording apparatuses have been developed.
[0003]
Generally, an ink jet recording apparatus includes a carriage on which a recording unit (recording head) and an ink tank are mounted, a conveying unit for conveying a recording sheet, and a control unit for controlling these. Then, the recording head for ejecting ink droplets from the plurality of ejection ports is serially scanned in a direction (main scanning direction) orthogonal to the recording paper conveyance direction (sub-scanning direction), while an amount equal to the recording width during non-recording. For intermittent conveyance. Furthermore, in the case of a color-compatible inkjet recording apparatus, a color image is formed by superimposing ink droplets ejected by recording heads of a plurality of colors.
[0004]
In an ink jet recording apparatus, as a method of ejecting ink, a heating element (electric / thermal energy converter) is provided in the vicinity of an ejection port, and an electric signal is applied to the heating element to locally heat the ink to change the pressure. And a method using an electric / thermal energy converter that causes ink to be ejected from an ejection port, and a method using an electric / mechanical converter such as a piezoelectric element. In addition, a configuration in which an electric / pressure conversion unit such as a piezo element is used as a unit for discharging ink and a mechanical pressure is applied to the ink to discharge the ink has been conventionally known.
[0005]
This recording method records characters and graphics by discharging ink onto a recording medium from a discharge port as a minute liquid in response to a recording signal, and has low noise because it is non-impact. It has advantages such as low running cost, easy downsizing of the device, and relatively easy colorization, so it can be used together with a computer or word processor, or used alone. It is widely used as an image forming (recording) means in recording apparatuses such as copying machines, printers, and facsimile machines.
[0006]
FIG. 16 is a block diagram showing a schematic configuration of an entire control circuit of the ink jet recording apparatus.
[0007]
A CPU 601 in the form of a microprocessor is connected to a host 624 via an interface 605, and a ROM 602 storing a control program, an EEPROM 603 storing an updatable control program, a processing program, various constant data, and the like, and an interface 605 from the host 624. The RAM 604 for storing a command signal and recording information received via the RAM is accessed, and the recording operation is controlled based on the information stored in these memories. Further, the CPU 601 moves the carriage 620 by operating the carriage motor 611 via the output port 608 and the carriage motor control circuit 610, and operates the paper feed motor 614 via the output port 608 and the paper feed motor control circuit 613. This causes the paper transport mechanism 612 such as a transport roller to operate. Further, the CPU 601 can record a desired image on a recording medium by driving the recording head 622 via the recording head control circuit 621 based on the recording information stored in the RAM 604. The power supply circuit 619 outputs a logic drive voltage Vcc (for example, 5 V) for operating the CPU 601 and the printhead control circuit 621, various motor drive voltages Vm (for example, 24 V), and a heat voltage Vh for driving the printhead 622. (For example, 12 V). Further, instruction information input from the conversion key 607 is transmitted to the CPU 601 via the input port 606, and an instruction from the CPU 601 is transmitted to the LED control circuit 615 via the output port 609 to turn on an LED or to control display. When transmitted to the circuit 617, a message is displayed on the LCD 618. A CPU bus 623 connects the above-described various components to each other.
[0008]
In the conventional ink jet recording method, it was necessary to use a special coated paper having an ink absorbing layer in order to obtain a high-colored color image without bleeding of the ink. A method of giving printability to plain paper used in large quantities in machines and the like has also been put to practical use. Further, it is desired to support various recording media such as OHP sheets, cloths, plastic sheets, and the like. To meet such demands, recording media (recording media) having different ink absorption characteristics were selected as necessary. At this time, a recording apparatus capable of performing the best recording irrespective of the type of the recording medium has been developed and commercialized. Also, regarding the size of the recording medium, large-sized woven fabrics such as posters for advertising and garments are required. The demand for such an ink jet recording apparatus has been increasing in a wide range of industrial fields as an excellent recording means, the provision of higher quality images has been demanded, and the demand for higher speed has been increasing more and more. It can be said.
[0009]
Generally, a color ink jet recording method uses three color inks of cyan (Cy), magenta (Mg) and yellow (Ye), and further uses four color inks added with black (Bk). To realize color recording. Unlike a monochrome ink jet recording device that prints only characters, such a color ink jet recording device requires various elements such as color development, gradation, and uniformity in recording a color image image. It becomes.
[0010]
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 is a "white" portion where the area factor 100% cannot be periodically satisfied in the main scanning direction of the head, or dots overlap more than necessary, or white streaks occur. It will be. These phenomena are usually perceived by human eyes as density unevenness. Therefore, a method called a multi-pass printing method has been proposed as a measure against the density unevenness. Here, for simplicity, a case where a single ink color head having 12 nozzles is used will be described as an example. The state of recording is shown in FIG.
[0011]
In the first scan, the zigzag pattern is recorded, the paper is fed by half of the recording width (6 dot width), and then the inverted zigzag pattern is recorded in the second scan to complete the recording. That is, by alternately performing paper feeding in a unit of 6 dots and recording in a staggered / inverted zigzag pattern, a recording area in units of 6 dots is completed for each scan. In this way, by printing one line using two different nozzles, a high-quality image with reduced density unevenness can be formed. In addition, the multi-pass printing method has the effect of suppressing bleeding by printing while drying the ink, and the increase in the temperature of the print head that causes ejection failure by reducing the number of print dots for each scan. The suppression effect can be achieved at the same time.
[0012]
As a method of generating pass data for each scan, a method of generating pass data by thinning out print data using a staggered / inverted zigzag pattern as described above (referred to as a fixed thinning method), a print dot A method of generating pass data by thinning out print data using a random mask pattern or the like in which dots and non-print dots are arranged in a random manner (referred to as a table method), or thinning out only print dots There is known a method of generating path data (hereinafter referred to as a data thinning method).
[0013]
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 in which the ratio of recording dots is high (recording duty is high) is continuous or the like, fine bubbles are generated in the ink in the liquid path along with the ink ejection, 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.
[0014]
Due to the non-ejection of ink due to these causes, not only does the reliability of the printing apparatus decrease, but if printing is continued in a state where it can not be ejected normally, the print head heats up to a much higher temperature than in the normal case. As a result, the recording head itself may be damaged, and the durability may be impaired.
[0015]
In order to prevent such a discharge failure, the ink jet recording apparatus performs (1) a capping process for covering the discharge port surface of the recording head to prevent the viscosity of the ink from being increased when the discharge is not performed, and (2) a discharge process in a capping state. Recovery of ink suction processing for sucking ink and forcibly discharging thickened ink, and (3) preliminary discharge processing for discharging ink to a predetermined ink receiver composed of an ink absorber and discharging thickened ink. Processing is performed.
[0016]
In connection with such recovery processing, it is preferable to provide a means for detecting non-ejection of ink for the purpose of improving the reliability of the printing apparatus. Further, it is preferable that an ejection failure can be individually detected for each of the plurality of ejection units included in the recording head. As the detection means, a method using an optical sensor arranged on the side of the ink flight path, a method for determining based on a temperature rise and a subsequent temperature drop generated in the print head due to idle discharge, and recording and reading a predetermined test pattern In many cases, such a method is used for detection.
[0017]
As a method of complementing the detected non-ejection nozzle, a method has been proposed in which a nozzle that is not used in normal printing is provided in advance, and the non-ejection complement nozzle performs complementary recording in place of the non-ejection nozzle. However, providing the recording head with extra nozzles not only hinders the miniaturization of the recording head, but also increases the cost of the consumable recording head.
[0018]
As still another method, a method of realizing complementary printing by assigning dots to be printed by a non-ejection nozzle to other nozzles forming the same line in multi-pass printing for a nozzle in which non-ejection is detected. is there. In addition, for the purpose of speeding up the printing process, a type having a plurality of sets of print heads has been proposed. In such an ink jet printing apparatus, non-discharge nozzles print on nozzles of other heads forming the same line. Negative printing can be realized by assigning power dots.
[0019]
[Problems to be solved by the invention]
However, in the above-mentioned conventional ink jet recording apparatus, there are the following problems related to measures against non-ejection of ink.
[0020]
Generally, when non-ejection is detected during page recording, recovery processing is promptly performed. That is, the recovery process is performed by temporarily suspending the recording process, which causes a problem that the total recording processing time is delayed. Furthermore, in an inkjet printing apparatus that performs multi-pass printing, the time interval between a plurality of printing scans on the same area is longer than the time required for a normal printing scan by the time required for the recovery process. In general, ink droplets ejected later penetrate in a direction perpendicular to the paper surface and in a direction along the paper surface, but do not penetrate and fix to a region where the ink droplets landed first penetrate. The ink droplets ejected later penetrate and fix further below the region where the ink droplets ejected earlier penetrate. However, when the next ink droplet lands at a long time interval after the ejection in the previous recording scan, the ink droplet permeates relatively much into the area where the previous ink droplet has penetrated and fixed. It is known that the printing density becomes higher when the time interval of the printing scan is longer. That is, density unevenness may occur in an area where the time interval of recording has been increased by the recovery processing. In addition, since a large amount of ink is consumed particularly in the ink suction processing, it is not preferable to perform the recovery processing unnecessarily.
[0021]
If normal ink ejection cannot be resumed even after executing the recovery process, it is necessary to replace the unrecoverable print head with a new print head that can operate normally. That is, until the recording head is replaced, density unevenness and white streaks due to non-ejection are allowed, or the recording function itself is completely stopped.
[0022]
On the other hand, problems have been pointed out regarding the image quality formed as a result of the complementing process. With reference to FIG. 17, a method of performing complementary printing by other nozzles forming the same line in multi-pass printing will be described using two-pass printing as an example. In ordinary two-pass printing, thinning-out printing is performed at a duty of 50% in the first pass, and printing of the remaining 50% is performed in the second pass. Here, if non-ejection occurs in a certain nozzle, no dot is formed in the first pass (or second pass) for the line to be formed by the non-ejection nozzle, and in the second pass (or first pass), no dot is formed. All dots are formed. In other words, printing with a very different duty for each printing scan as compared with the other lines is performed.
[0023]
Such a difference in dot formation for each line is that if it is a single line, it is buried in an adjacent line and it is relatively difficult to recognize, but if such lines are present continuously, it becomes conspicuous, and it is noticeable to human eyes as unevenness. There is a problem that it is recognized. Further, even when many nozzles forming the same line become non-ejection and the deviation of duty becomes large, the image quality is adversely affected. Furthermore, if all the nozzles forming the same line become non-ejection, the complementary control itself becomes impossible, causing a large image quality deterioration due to white spots.
[0024]
SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to prevent a recording process from being stopped frequently by a recovery operation or the like, and to avoid white spots caused by ink non-ejection as much as possible. An object of the present invention is to provide a highly reliable and excellent ink jet recording apparatus which enables high quality image formation without unevenness by useless complementary recording.
[0025]
[Means for Solving the Problems]
In order to solve the above problems, an ink jet recording apparatus according to a first aspect of the present invention has the following configuration.
[0026]
That is, multi-pass printing is performed in which a print head having a plurality of discharge units is scanned a plurality of times over the same area on a print medium and ink is formed on the print medium based on input image information to form an image. In the inkjet recording apparatus, a combination of a failure detection unit that detects a discharge failure of a discharge unit of the recording head and the ink discharge unit that forms a row is changed according to a failure detection result by the failure detection unit. Control means for controlling the combination. According to the above configuration, it is possible to change the combination of the ejection units forming the rows according to the detection result of the ejection failure of the recording head.
[0027]
Further, an ink jet recording apparatus according to a second aspect of the present invention has the following configuration.
[0028]
That is, in the ink jet recording apparatus according to the first aspect, the combination control unit includes a unit that changes a number used for image formation of the ink ejection unit of the recording head, and the number of the ink ejection unit that forms a row is changed. Controlling to change the combination. According to the above configuration, it is possible to change the combination of the ejection units forming the rows by changing the number used for image formation of the ejection units according to the detection result of the ejection failure of the recording head.
[0029]
Further, an ink jet recording apparatus according to a third aspect of the present invention has the following configuration.
[0030]
That is, in the ink jet recording apparatus according to the first aspect, the image forming apparatus includes a plurality of image forming modes in which the same region is scanned a different number of times, the combination control unit includes a mode changing unit that changes the image forming mode, and Controlling to change the combination of the formed ink discharge units. According to the above configuration, it is possible to change the combination of the discharge units that form the rows by changing the image forming mode according to the detection result of the discharge failure of the print head.
[0031]
Further, an ink jet recording apparatus according to a fourth aspect of the present invention has the following configuration.
[0032]
That is, in the ink jet recording apparatus according to the first invention, the combination control unit includes a conveyance amount control unit that changes a conveyance amount of the recording medium between each printing scan, and determines a combination of the ink ejection units that form a row. Control to change. According to the above configuration, it is possible to change the combination of the discharge units forming the rows by changing the transport amount of the print medium in accordance with the detection result of the discharge failure of the print head.
[0033]
Further, an ink jet recording apparatus according to a fifth aspect of the present invention has the following configuration.
[0034]
That is, in the ink jet recording apparatus according to the first invention, the ink jet recording apparatus further includes a first determination unit that determines whether a plurality of rows to be formed by the plurality of failure ejection units detected by the failure detection unit overlap by a predetermined number, The combination control unit controls in response to the output of the first determination unit to change the combination of the ink ejection units that form the rows when the rows to be formed by the plurality of failure ejection units overlap by a predetermined number. It is characterized by. According to the above configuration, it is possible to change the combination of the ejection units forming the row in response to the failure detection of the predetermined number of ejection units forming the same row.
[0035]
Further, an ink jet recording apparatus according to a sixth aspect of the present invention has the following configuration.
[0036]
That is, in the ink jet recording apparatus according to the fifth aspect, the first determination unit determines whether or not the overlap of the rows to be formed by the plurality of obstacle ejection units is equal to the same row scanning count. I do. According to the above configuration, it is possible to change the combination of the ejection units forming the row in response to the number of the faulty ejection units forming the same row being detected equal to the number of print passes.
[0037]
Further, an ink jet recording apparatus according to a seventh aspect of the present invention has the following configuration.
[0038]
That is, in the ink jet recording apparatus according to the first aspect of the present invention, the inkjet recording apparatus further includes a second determination unit that determines whether a predetermined number of rows to be formed by the plurality of failure ejection units detected by the failure detection unit are adjacent to each other, The combination control means controls in response to the output of the second determination means to change the combination of the ink ejection parts forming a line when a predetermined number of rows to be formed by the plurality of failure ejection parts are adjacent to each other. It is characterized by. According to the above configuration, it is possible to change the combination of the ejection units forming the rows in response to the failure detection of the predetermined number of ejection units forming the continuous rows.
[0039]
Further, an ink jet recording apparatus according to an eighth aspect of the present invention has the following configuration.
[0040]
That is, the inkjet recording apparatus according to the first aspect of the invention is characterized in that the inkjet recording apparatus further comprises a complementary control means for allocating a pixel to be formed by the failure ejection unit to another ejection unit in response to the failure detection output. According to the above configuration, it is possible to apply the present invention to an ink jet recording apparatus that performs complementary recording control of a failure ejection unit.
[0041]
Further, an ink jet recording apparatus according to a ninth aspect of the present invention has the following configuration.
[0042]
That is, in the ink jet recording apparatus according to the first invention, the recording head has an electric / heat converting means for discharging ink. According to the above configuration, it is possible to apply the present invention to an ink jet recording apparatus having an electric / heat converting means.
[0043]
Further, an ink jet recording apparatus according to a tenth aspect of the present invention has the following configuration.
[0044]
That is, in the ink jet recording apparatus according to the first invention, the recording head has an electric / pressure conversion unit for discharging ink. According to the above configuration, it is possible to apply the present invention to an ink jet recording apparatus having an electric / pressure conversion unit.
[0045]
BEST MODE FOR CARRYING OUT THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.
[0046]
FIG. 3 shows the configuration of the recording section of the ink jet recording apparatus according to the present invention.
[0047]
Reference numeral 301 denotes a recording head, which includes an ink tank in which four color inks (Bk, Cy, Mg, and Ye) are respectively sealed, and a multi-head in which four heads corresponding to the respective inks are integrated. I have. Reference numeral 302 denotes a carriage that supports the recording head 301 and moves them together with recording. The carriage 302 is at the home position shown in a standby state such as a non-printing state. Reference numeral 303 denotes a paper feed roller, which rotates in the direction of the arrow in the figure while holding down the recording paper 306 together with the auxiliary roller 304, and feeds the recording paper 306 in the Y direction as needed. Reference numeral 305 denotes a paper feed roller that feeds the recording paper 306 and plays a role of suppressing the recording paper 306 similarly to the paper feed roller 303 and the auxiliary roller 304. Here, the recording head 301 has 64 nozzles each arranged in the paper feed direction for four colors of Bk, Cy, Mg, and Ye.
[0048]
A basic recording operation in the above configuration will be described.
[0049]
During standby, the carriage 302 at the home position ◎ ejects ink onto the recording paper 306 in accordance with the recording data by the plurality of nozzles of the recording head 301 and performs recording while moving in the X direction according to the recording start command. When the recording of the recording data is completed to the end of the recording paper 306, the carriage returns to the original home position. By rotating the paper feed roller 304 in the direction of the mark, the paper is fed by a predetermined width in the Y direction, and recording in the X direction is started again. Data recording is realized by repeating such a scanning operation and a paper feeding operation.
[0050]
Although not shown, the inkjet recording apparatus according to the present embodiment includes a CPU configured to control and execute recording and image processing, a control unit including a ROM, a RAM, a dedicated circuit, an external host computer, and the like. Interface unit for exchanging image information and various control information among them, a carriage motor for driving a carriage, a paper feed motor for driving a paper feed roller, a motor for driving a paper transport motor for driving a paper transport, etc. A driver, a driver for driving the printhead for driving the printhead, a replacement panel for inputting control information by a user, and the like.
[0051]
The ink jet printing apparatus according to the present embodiment employs a multi-pass printing method in which an image is formed by scanning the same printing area a plurality of times. As described above, in multi-pass printing, an image is formed using a plurality of nozzles on one line, thereby suppressing density unevenness due to a slight difference in the ink ejection amount and ejection direction of each nozzle. This is a printing method in which the print duty for each is reduced to prevent image quality deterioration due to ink bleeding or the like.
[0052]
In the present embodiment, a table thinning-out method of generating pass data by masking image data with a mask table is adopted. Here, a 4-pass printing will be described as an example. The number of nozzles of the recording head is 64 nozzles.
[0053]
FIG. 2 is a schematic block diagram of a pass data generation block for generating pass data which is print data for each print scan for realizing multi-pass printing. Here, a single ink color will be described for simplicity.
[0054]
Reference numeral 201 denotes a memory unit that temporarily stores image data that has been subjected to image processing for recording and input from outside the figure. Reference numeral 202 denotes an input control unit which performs a process of writing recording data to the memory unit 201. An output control unit 203 reads out print data based on the position of the print head on the print sheet. A table storage unit 204 stores mask tables A, B, C, and D (described later). A mask processing unit 205 performs mask processing of image data using a mask table in the table storage unit 204 to generate path data. Reference numeral 206 denotes an original table storage in the control unit 210, which stores table data (described later) on which each of the mask tables A, B, C, and D is generated. Reference numeral 207 denotes a table generation unit in the control unit 210, which generates each of the mask tables A, B, C, and D based on the original mask table stored in the original table storage unit 206, and generates a table storage unit. Output to 204. Reference numeral 208 denotes a non-discharge complementing control unit in the control unit 210, which controls change of the table generation process of the table generation unit 207 in response to a detection result input from a non-discharge nozzle detection block (not shown). A control unit 210 monitors the status of each unit and performs various controls related to path data generation in response to control signals from inside and outside the drawing.
[0055]
First, a basic path data generation operation of the entire path data generation block will be described.
[0056]
Raster-scanned binary image data is input from outside the figure, and is temporarily stored in the memory unit 201 via the input control unit 202. The output control unit 203 sequentially converts the binary image data stored in the memory unit 201 for each scan in accordance with the position on the paper surface of the nozzle group corresponding to each ink color based on the print area control from the control unit 210. Read and output. Here, one data transfer unit is 64 pixel data corresponding to the number of nozzles. The mask processing unit 205 performs mask processing of image data (replaces recording dots with non-recording dots) using the mask table stored in the table storage unit 204, and generates and outputs pass data.
[0057]
The path data generation processing based on the table reference method will be described with reference to the drawings.
[0058]
FIG. 4 is a diagram showing an example of a mask table for each print scan. A, B, C, and D are complementary mask tables used in the first, second, third, and fourth passes, respectively. It is a table. The mask tables A to D are tables each having a size corresponding to 1024 pixels in the main scanning direction * 16 pixels in the sub-scanning direction. These tables are repeatedly developed in each direction and used as mask data. The number of nozzles included in the print head is 64, and the number of pixels corresponding to the paper transport amount in 4-pass printing is 64/4 = 16, which is equal to the size of the mask table in the sub-scanning direction.
[0059]
FIG. 5 is a diagram for explaining a printing scan using the mask table shown in FIG. A, B, C, and D are applied as mask patterns every 16 to 64 lines of data corresponding to 64 nozzles. All image areas are always subjected to mask processing in the order of A, B, C, and D to generate print data.
[0060]
Next, table generation control will be described with a simple example.
[0061]
First, a basic table generation method will be described. The table generation unit 207 generates each of the mask tables A, B, C, and D based on the original mask table stored in the original table storage unit 206, and outputs it to the table storage unit 204. The original table is basically each 8-bit data consisting of a random number sequence, and has a size corresponding to 1024 pixels in the main scanning direction and 32 pixels in the sub-scanning direction. First, in 4-pass printing, each 8-bit data is divided by 4 to generate remainders 0, 1, 2, and 3. Then, four tables A, B, C, and D in which 1 is generated corresponding to each of the remainders 0, 1, 2, and 3 are created and stored in the table storage unit 104. Each table size in the sub-scanning direction is 16 pixels. On the other hand, in two-pass printing, two tables A and B are created using remainders 0 and 1 obtained by dividing each 8-bit data by two. In this case, the size in the sub-scanning direction is 32 pixels.
[0062]
Next, a table generation method when a non-ejection nozzle is detected will be described. The basic generation procedure is the same as the normal table generation. Here, non-ejection nozzles are not limited to nozzles that cannot eject ink at all, but nozzles that have ejection failure phenomena such that the size and flying direction of ink droplets are extremely unstable or normal ejection may not be possible. Is shown. In the non-ejection nozzle detection block outside of FIG. 2, ink non-ejection detection is performed for each nozzle. The non-discharge detection operation is executed at the start of page printing or during page printing as needed. When the non-ejection nozzle is detected, the non-ejection nozzle number is notified to the non-ejection complement control unit 208 in the control unit 210. In the non-ejection complementing control unit 208, during a period until the non-ejection is avoided and the restart of a good ejection operation is confirmed, one of the nozzles forming a part of the same line as the non-ejection nozzle according to the notified nozzle number. Instruct the generation change of the table to be applied to one. In response to this, the table generator 207 generates each of the mask tables A, B, C, and D based on the original mask table. In 4-pass printing, image formation is completed by complementarily printing a line in a certain main scanning direction by different nozzles in four scans. That is, another three nozzles are involved in the printing in three scans separately from the line printed by the nozzle that has been detected as non-ejection. One of these three nozzles controls a non-ejection nozzle to form a dot to be recorded, thereby realizing normal image formation.
[0063]
A specific example will be described. It is assumed that a non-ejection of ink is detected at nozzle # 20. The nozzle # 20 is a nozzle area to which the table B is applied, and corresponds to the fifth line of the table B. The other three nozzles that form dots on the same line as the dots printed by nozzle # 20 are nozzle # (table A), nozzle # 36 (table C), and nozzle # 52 (table D). Here, it is assumed that the nozzle # 36 to which the table C is applied complements the dot to be recorded by the non-ejection nozzle # 20 instead of the nozzle # 20. The table data generation processing of the fifth line of the table C used for the nozzle # 36 is controlled differently from the normal processing.
[0064]
That is, when generating the mask data of the fifth line of the table C from the original table, the dot position corresponding to the remainder 1 in addition to the dot position corresponding to the remainder 2 divided by 4 as usual. By generating No. 1, normal image formation is realized by distributing dots to be printed by the non-ejection nozzle # 20 to the nozzle # 36 capable of normal ejection. Further, for the fifth line of the table B corresponding to the non-ejection nozzle # 20, all the dots are controlled to be 0 so that no recording dot is given regardless of the value stored in the original table.
[0065]
That is, by allocating dots to be printed by the nozzles in which the ink ejection failure has been detected to nozzles forming the same line by another scan, image omission due to ejection failure can be avoided and normal image formation can be realized. In this example, the recording dots of the non-ejection nozzles of the table B are allocated to the table C of the same line. However, the recording dots may be allocated to the corresponding nozzles of the tables A and D, or may be equally allocated to all of them. FIG. 6 is an example of a mask table that implements a complementing process when the nozzle # 1 is not ejected with respect to FIG. In this example, nozzle # 17 performs complementary printing in place of non-ejection nozzle # 1.
[0066]
Next, nozzle combination control for line formation in response to non-discharge detection characteristic of the present invention will be described in detail.
[0067]
As described above, when non-ejection is detected during printing, it is necessary to promptly perform recovery processing to return to a normal ejection state. This causes a problem that the total recording processing time is delayed. Further, since a large amount of ink is consumed particularly in the ink suction processing or the like, it is not preferable to perform the recovery processing unnecessarily.
[0068]
On the other hand, in the non-ejection complemented line, dot formation significantly different from other normally formed lines is performed. For example, in the case of four-pass printing, the mask tables A, B, C, and D for four printing scans for each line are normally generated so that the masks are turned off with almost the same duty. In each of the fourth passes, an image is uniformly formed by approximately 25%. However, for example, in the case where the nozzle # 20 using the table B does not discharge and is complemented by the nozzle # 36 using the table C as in the above example, the dot formation duty on the corresponding line is the first pass, Deviations such as 25%, 0%, 50%, and 25% are generated for the second, third, and fourth passes. Further, the nozzle # 4 and the nozzle # 52 forming the same line also become non-discharge, and if all of them are complemented by the nozzle # 36, the dot formation duty on the corresponding line becomes the first pass, the second pass, the third pass, The values are 0%, 0%, 100%, and 0% for each of the fourth passes, and dot formation that is significantly different from a normally formed line is performed. Differences in dot formation in such image formation are more likely to be perceived by human eyes as density unevenness as the number of nozzles forming the same line increases and as such lines are adjacent to each other.
[0069]
In this embodiment, when it is detected that a predetermined number of lines formed by a plurality of non-ejection nozzles overlap or are adjacent to each other, the number of nozzles (effective nozzles) used for image formation is changed. Here, an example will be described in which the number of effective nozzles is changed from 64 to 60 when lines formed by non-ejection nozzles overlap by 2 or by 3 (continuous) lines.
[0070]
FIG. 1 is a flowchart illustrating an effective nozzle number control operation in response to a non-ejection nozzle detection. First, a non-discharge detection operation is performed for all nozzles. All the non-ejection nozzle numbers are sequentially notified, and the non-ejection nozzle number is obtained by dividing the non-ejection nozzle number by 16. 16 is a value obtained by dividing 64, which is the number of mounted nozzles (= standard number of effective nozzles), by 4, which is the number of print passes. Next, it is checked whether two or more overlapping non-ejection lines exist for all the non-ejection nozzles. When two or more nozzles forming the same line do not discharge, 60 is selected as the number of effective nozzles instead of 64. On the other hand, it is checked whether four or more non-ejection lines are continuous. When four or more lines are formed by non-ejection nozzles, 60 is similarly selected as the number of effective nozzles. In other cases, that is, when there is no overlap of the nozzles formed by the same line and the continuation of the non-ejection line is 3 or less, the standard effective nozzle number 64 is selected.
[0071]
That is, when the lines to be formed by the non-ejection nozzles overlap by a predetermined number (2 in this embodiment) or continue by a predetermined number (4 in this embodiment), the effective nozzle number is changed from 64 to 60. 3) By controlling to change the combination of the nozzles that form the line by changing the line, and avoiding the generation and continuation of the line having a remarkably different printing duty, it is possible to suppress the density unevenness due to the easy complementation processing.
[0072]
As described in detail above, by controlling the number of effective nozzles with respect to the occurrence of non-ejection of the print head, the number of effective nozzles is changed by changing the number of effective nozzles when a predetermined number of lines to be formed by the non-ejection nozzles overlap or are adjacent to each other. , And high quality image formation without density unevenness can be realized.
[0073]
(Second embodiment)
In the first embodiment, the ink jet recording apparatus that changes and controls the number of effective nozzles according to the detection result of the non-ejection nozzle has been described in detail. In the second embodiment, an ink jet printing apparatus that changes the combination of nozzles in line formation by changing the number of printing passes according to the detection result of a non-ejection nozzle will be described.
[0074]
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings. The basic configuration of the entire apparatus and the path data generation block is the same as in the first embodiment. However, the recording head in this embodiment has 60 nozzles arranged for each color in the paper feed direction.
[0075]
In this embodiment, when it is detected that a predetermined number of lines formed by a plurality of non-ejection nozzles overlap or are adjacent to each other, the number of print passes is changed. Here, an example will be described in which the number of print passes is changed from 4 to 5 when the lines formed by the non-ejection nozzles overlap by 2 or by 3 (continuous).
[0076]
FIG. 7 is a flowchart for explaining the print pass number control operation in response to the non-ejection nozzle detection. First, a non-discharge detection operation is performed for all nozzles. All the non-ejection nozzle numbers are sequentially notified, and the non-ejection nozzle number is obtained by dividing the non-ejection nozzle number by 15. 15 is a value obtained by dividing 60, which is the number of mounted nozzles (= effective nozzle number), by 4, which is the standard number of printing passes. Next, it is checked whether or not two or more overlapping non-ejection lines exist for all the non-ejection nozzles. When two or more nozzles forming the same line do not discharge, the number of printing passes is changed to five instead of the standard four. On the other hand, it is checked whether four or more non-ejection lines are continuous. When four or more lines formed by the non-ejection nozzles are continuous, 5 is similarly selected as the number of print passes. In other cases, that is, when there is no overlap of nozzles formed by the same line and the number of consecutive non-ejection lines is 3 or less, 4-pass printing, which is the standard number of printing passes, is performed.
[0077]
That is, when the lines to be formed by the non-ejection nozzles overlap by a predetermined number (2 in this embodiment) or continue by a predetermined number (4 in this embodiment), the number of print passes is changed from (4 to 5). 3) By controlling to change the combination of the nozzles that form the line by changing the line, and avoiding the generation and continuation of the line having a remarkably different printing duty, it is possible to suppress the density unevenness due to the easy complementation processing.
[0078]
As described in detail above, by controlling the number of print passes in response to the occurrence of non-ejection of the print head, this is achieved by changing the number of print passes when a predetermined number of lines to be formed by the non-ejection nozzles overlap or are adjacent. , And high quality image formation without density unevenness can be realized.
[0079]
(Third embodiment)
In the first and second embodiments, when the lines to be formed by the non-ejection nozzles overlap by two or by three in a row, the inkjet recording apparatus controls to change the combination of the nozzles forming the lines. Was explained. This takes into account deterioration in image quality due to uneven printing duty due to the non-ejection complementing process.
[0080]
However, reducing the number of effective nozzles as in the first embodiment or increasing the number of printing passes as in the second embodiment leads to an increase in the total time required for image formation. Further, it is known that the influence on the image quality due to the deviation of the recording duty as described above largely depends on the ink absorption characteristics of the recording medium. That is, the degree of unevenness perceived by human eyes varies greatly depending on the type of recording medium used.
[0081]
If emphasis is placed on the high speed of the image forming process, it is desirable to avoid reducing the number of effective nozzles (increase the number of print passes) for the occurrence of unacceptable non-ejection. That is, while the first and second embodiments change the number of effective nozzles (change the number of printing positions) when the number of non-ejection lines overlaps 2 or more or the number of continuations reaches 4 or more. In the third embodiment, the combination of nozzles forming lines is changed and controlled only when the non-ejection complementing process becomes impossible and white spots occur.
[0082]
FIG. 8 is a flowchart illustrating the effective nozzle number control operation in response to the non-ejection nozzle detection. First, a non-discharge detection operation is performed for all nozzles. All the non-ejection nozzle numbers are sequentially notified, and the non-ejection nozzle number is obtained by dividing the non-ejection nozzle number by 16. 16 is a value obtained by dividing 64, which is the number of mounted nozzles (= standard number of effective nozzles), by 4, which is the number of print passes. Next, it is checked whether or not four overlapping non-ejection lines exist for all the non-ejection nozzles. When all four nozzles forming the same line do not discharge, 60 is selected as the number of effective nozzles instead of 64. In other cases, that is, when the overlap of the nozzles formed by the same line is 3 or less, 64, which is the standard number of effective nozzles, is selected.
[0083]
That is, in a case where the number of effective nozzles is changed and controlled according to the result of detecting a non-ejection nozzle as in the first embodiment, all the nozzles forming the same line (by the same number as the number of print passes) are incorrect. When the ejection is detected, the number of print passes is changed. That is, in the 4 (2) pass printing, when 4 (2) nozzles forming the same line fail to discharge, the number of printing passes is changed (increased), so that white spots due to the non-discharge can be avoided.
[0084]
As described in detail above, when complementary print control becomes impossible for the non-ejection of the print head, the combination of the nozzles that form the lines is changed to avoid white spots in the image. High quality image formation can be realized.
[0085]
(Fourth embodiment)
In the first and second embodiments, the ink jet printing apparatus adopting the table reference system for generating print data for each print scan by referring to the mask table has been described. It is not limited to. A fixed thinning method for regularly allocating recording dots based on pixel coordinates, a data culling method for allocating recording dots by thinning recording dots (recording data '1'), or a combination of these methods may be used. Correspondingly, the complement of the non-ejection nozzle is not limited to the complement control method by changing the mask table.
[0086]
A fixed thinning method for regularly allocating recording dots based on pixel coordinates will be briefly described. This is to perform multi-pass printing by regularly assigning print pass numbers according to the X coordinate and / or Y coordinate of the image data. FIG. 9 shows an example of a thinning pattern in 4-pass printing. Print dots with X coordinates X = 4N, 4N + 1, 4N + 2, and 4N + 3 are assigned to the pass numbers 4P, 4P + 1, 4P + 2, and 4P + 3, respectively.
[0087]
FIG. 10 shows an example of non-ejection complement in such a thinning method. Here, nozzle # 1 does not discharge, and nozzle # 17 performs complementary printing instead.
[0088]
Next, a brief description will be given of a data thinning method in which recording dots are sorted by a recording dot thinning process. In this method, only data “1” (data indicating a recording dot) included in image data is counted, and multi-pass printing is performed by associating a number obtained by dividing by the number of printing passes with a printing pass number. FIG. 11 shows an example of a thinning pattern in 4-pass printing. The 4S-th, 4S + 2nd, 4S + 1-th, and 4S + 3rd recording dots are assigned to the pass numbers 4P, 4P + 1, 4P + 2, and 4P + 3, respectively.
[0089]
FIG. 12 shows an example of non-ejection complement in such a thinning method. Here, nozzle # 1 does not discharge, and nozzle # 17 performs complementary printing instead.
[0090]
(Fifth embodiment)
In the first embodiment, the description has been given of the ink jet recording apparatus that controls the change of the combination of a plurality of nozzles forming each line by changing the effective nozzle number. In the second embodiment, the description has been given of the ink jet printing apparatus which changes and controls the combination of a plurality of nozzles forming each line by changing the number of printing passes. The means for changing the combination of nozzles forming the line is not limited to these. Fourth Embodiment In a fourth embodiment, an ink jet recording apparatus will be described in which the combination of nozzles forming lines is changed and controlled by changing the paper transport amount control during scanning.
[0091]
Hereinafter, a fourth embodiment of the present invention will be described in detail with reference to the drawings. The print head in this embodiment has 64 nozzles arranged in the paper feed direction for each color, and performs four-pass printing.
[0092]
In the present embodiment, when it is detected that a predetermined number of lines formed by a plurality of non-ejection nozzles overlap or are adjacent to each other, the paper transport amount between printing scans is changed. FIG. 9 shows how two different paper transport controls are performed. Here, normally, paper transport control equivalent to 16 (= 64/4) is always performed between print scans (paper transport mode 1). However, when the lines formed by the non-ejection nozzles overlap by 2 or continue by 4 (adjacent), uneven lines such as 14, 14, 14, 22, 14, 14, 14, 22,. A case in which the mode is switched to the paper transport control (paper transport mode 2) will be described as an example. FIG. 14 shows how these two types of paper transport control are performed.
[0093]
FIG. 13 is a flowchart for explaining the paper transport amount control operation in response to the non-ejection nozzle detection. First, a non-discharge detection operation is performed for all nozzles. All the non-ejection nozzle numbers are sequentially notified, and the non-ejection nozzle number is obtained by dividing the non-ejection nozzle number by 15. 15 is a value obtained by dividing 60, which is the number of mounted nozzles (= effective nozzle number), by 4, which is the standard number of printing passes. Next, it is checked whether or not two or more overlapping non-ejection lines exist for all the non-ejection nozzles. If two or more nozzles forming the same line do not discharge, the paper transport amount is changed to non-uniform control. On the other hand, it is checked whether four or more non-ejection lines are continuous. When four or more lines formed by the non-ejection nozzles are continuous, the paper transport amount is similarly switched to non-uniform control. In other cases, that is, when there is no overlap of the nozzles formed by the same line and the continuation of the non-ejection line is 3 or less, the uniform feed with the transport amount of 16 is always performed.
[0094]
That is, when the lines to be formed by the non-ejection nozzles overlap by a predetermined number (2 in this embodiment) or continue by a predetermined number (4 in this embodiment), the paper transport amount control between the printing scans is performed. By controlling to change the combination of the nozzles that form the line by changing the line, and avoiding the generation and the continuation of the line whose recording duty is remarkably different, it is possible to suppress the density unevenness due to the easy complementation processing.
[0095]
As described in detail above, by changing the paper transport amount control for the occurrence of non-discharge of the print head, the paper transport between print scans is performed when a predetermined number of lines to be formed by the non-discharge nozzles overlap or are adjacent. This can be avoided by changing the control, and high-quality image formation without density unevenness can be realized.
[0096]
(Other Examples)
In the above embodiment, an ink jet recording apparatus equipped with an ink tank in which four color (Bk, Cy, Mg, Ye) color inks are respectively sealed and a multi-head in which four heads corresponding to the respective ink tanks are integrated. As described above, a multi-head including an independent one-color head corresponding to each ink may be mounted. Further, the ink color is not limited to four, and a configuration using a plurality of inks having different densities using light colors such as L-Cy and L-Mg may be used. The number of nozzles is not limited to 64 or 60. Furthermore, although the ink jet recording apparatus for recording one dot per pixel for each ink color has been described, the same ink may be overprinted.
[0097]
Further, the number of recording heads to be mounted is not limited to one set (one for each color), and the present invention can be applied to an ink jet recording apparatus including a plurality of sets (two or more for each color). FIG. 18 is a schematic diagram showing a configuration of a recording unit of an ink jet recording apparatus equipped with two sets of recording heads. The carriage 302 has a first recording head 301 and a second recording head 307 mounted thereon, and corresponds to six color (Bk, Cy, Mg, Ye, L-Cy, L-Mg) inks, respectively. FIG. 19 is a diagram showing an example of the ink arrangement of two sets of recording heads. Here, the ink arrangement is configured to be symmetric.
[0098]
Further, the form of the ink jet recording apparatus according to the present invention is not limited to those provided integrally or separately as an image output apparatus of an information processing apparatus such as a computer or a word processor. It may be a facsimile machine having a communication function.
[0099]
【The invention's effect】
As described in detail above, according to the present invention, a recording head having a plurality of ejection sections is scanned a plurality of times over the same area on a recording medium, and ink is applied to the recording medium based on input image information. An inkjet printing apparatus that performs multi-pass printing by forming an image by discharging, comprising: a failure detection unit configured to detect a discharge failure of a discharge unit of the recording head; and And a combination control means for controlling a combination of the ink ejection units to be formed, by detecting a non-ejection of ink for each nozzle of the recording head, and forming a plurality of ejections according to the detection result. By changing the combination of the units, density unevenness caused by the complementing process is reduced, white spots due to inability to complement are avoided, Always enabling efficient image formation, high-performance ink jet recording apparatus for realizing high-speed and high-quality image formation is excellent effect that can be provided
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating a state of a combination change control of the same line according to a non-ejection nozzle state according to a first embodiment of the present invention.
FIG. 2 is a schematic block diagram of a path data generation block according to the first embodiment of the present invention.
FIG. 3 is a schematic diagram illustrating an ink jet recording apparatus according to a first embodiment of the present invention.
FIG. 4 is a diagram showing an example of a mask table according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating a state of a mask process for each print scan in the first embodiment of the present invention.
FIG. 6 is a diagram showing an example of a mask table for implementing non-ejection complement in the first embodiment of the present invention.
FIG. 7 is a flowchart illustrating a state of changing the combination of the same lines according to the state of a non-ejection nozzle according to the second embodiment of the present invention.
FIG. 8 is a flowchart illustrating a state of a combination change control of the same line according to a non-ejection nozzle state according to a third embodiment of the present invention.
FIG. 9 is a diagram illustrating a state of recording dots for each recording scan in a fixed thinning method according to a fourth embodiment of the present invention.
FIG. 10 is a diagram illustrating a state of print dots for each print scan for implementing non-ejection complementation in a fixed thinning method according to a fourth embodiment of the present invention.
FIG. 11 is a diagram illustrating a state of recording dots for each recording scan in a data thinning method according to a fourth embodiment of the present invention.
FIG. 12 is a diagram illustrating a state of print dots for each print scan for implementing non-ejection complementation in a data thinning method according to a fourth embodiment of the present invention.
FIG. 13 is a flowchart illustrating a state of a combination change control of the same line according to a non-ejection nozzle state according to a fifth embodiment of the present invention.
FIG. 14 is a diagram illustrating an example of a paper transport control mode according to a fifth embodiment of the present invention.
FIG. 15 is a diagram illustrating an example of a paper transport control mode according to a fifth embodiment of the present invention.
FIG. 16 is a schematic block diagram illustrating a configuration example of an overall control circuit of the inkjet recording apparatus.
FIG. 17 is a diagram illustrating multi-pass printing.
FIG. 18 is a schematic view showing an ink jet recording apparatus according to another embodiment of the present invention.
FIG. 19 is a diagram illustrating an example of an ink arrangement of a two-set recording head according to another embodiment of the present invention.

Claims (10)

Ink jet printing that performs multi-pass printing in which a print head having a plurality of discharge units is scanned a plurality of times over the same area on a print medium and ink is discharged onto the print medium based on input image information to form an image. A device,
Failure detection means for detecting a discharge failure of a discharge unit of the recording head,
Combination control means for controlling to change the combination of the ink ejection units forming a row, according to the failure detection result by the failure detection means,
An ink jet recording apparatus comprising: The combination control unit has a unit that changes a number used for image formation of the ink ejection unit of the recording head, and controls to change a combination of the ink ejection unit that forms a row.
The ink jet recording apparatus according to claim 1, wherein: A plurality of image forming modes with different numbers of times of scanning the same area are provided,
The combination control unit includes a mode change unit that changes the image forming mode, and controls to change a combination of the ink discharge units that form a row.
The ink jet recording apparatus according to claim 1, wherein: The combination control unit includes a conveyance amount control unit that changes a conveyance amount of a printing medium between each printing scan, and controls to change a combination of the ink ejection units that form a row.
The ink jet recording apparatus according to claim 1, wherein: A first determination unit that determines whether or not the rows to be formed by the plurality of failure ejection units detected by the failure detection unit overlap by a predetermined number,
In response to the output of the first determination unit, the combination control unit controls to change the combination of the ink ejection units that form the rows when the rows to be formed by the plurality of failure ejection units overlap by a predetermined number.
The ink jet recording apparatus according to claim 1, wherein: The first determination unit determines whether or not the overlap of the rows to be formed by the plurality of fault ejection units is equal to the same row scan count.
The ink jet recording apparatus according to claim 5, wherein: The apparatus further includes a second determination unit configured to determine whether a predetermined number of rows to be formed by the plurality of failure ejection units whose failures have been detected by the failure detection unit are adjacent to each other,
In response to the output of the second determination unit, the combination control unit controls to change the combination of the ink ejection units that form a line when the rows to be formed by the plurality of failure ejection units are adjacent by a predetermined number,
The ink jet recording apparatus according to claim 1, wherein: Complementary control means for allocating a pixel to be formed by the failure ejection unit to another ejection unit in response to the failure detection output,
The ink jet recording apparatus according to claim 1, wherein: 2. The ink-jet recording apparatus according to claim 1, wherein the recording head has an electric / heat conversion unit for discharging ink. 2. The ink jet recording apparatus according to claim 1, wherein the recording head has an electric / pressure conversion unit for discharging ink.

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