JP2003063043A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer which can correct a bad ejection of ink from a defective ejecting hole without setting up a spare ejecting hole and can make even an ink jet head having a defective ink ejecting hole usable. SOLUTION: An image processing part 22 grasps color information and the position of a defective ejecting hole of a print head 1 by referring to a defective ejecting hole position storing part 21a of a memory 21. When the defective ejecting hole is for black color ink, the poor ink ejection due to the defective ejecting hole is compensated by forming black color dots by mixture of colors through ejecting inks from yellow, magenta, and cyan color ink ejecting holes which can eject the ink at the same position of that of the defective ejecting hole. If the defective ejecting holes is for other than black color, the ink is ejected from the ejecting hole for the same color adjacent to the defective ejecting hole and compensates the bad ink ejection by the defective ejection hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer used for a printer of a facsimile machine, a copying machine, an OA equipment or the like, and more specifically, it can remedy a defective ink ejection hole in a print head. It is about technology.

[0002]

2. Description of the Related Art Ink jet printing is advantageous in facsimile machines, copiers, printers for office automation equipment, etc. because it produces less noise and can easily print on plain paper.

An ink jet printer using this method is equipped with an ink jet head (hereinafter, referred to as a print head) having a plurality of fine ink discharge holes generally called orifices, and its drive is controlled by a drive controller. The ink is ejected only from the ejection holes necessary for the character or the image to print on the recording material.

The print head is provided with one or two characters and has one or two rows of ink ejection holes in the vertical direction (the sub-scanning direction, which is the recording material conveying direction). It is mounted on a so-called moving body, and while moving in the horizontal direction (main scanning direction), every one line in the horizontal direction (one line for a length of one character, two for a length of two characters). Some lines are printed. In this case, after the printing of one line in the horizontal direction is completed, the print head moves in the opposite direction and returns to the original position, and during that time, the recording material is conveyed by one line in the vertical direction,
The next line is printed.

In the case of an ink jet printer having a print head having such a structure, which is compatible with full color, the above-mentioned print heads have a total of 4 for black ink, yellow ink, magenta ink, and cyan ink.
On the other hand, they are mounted on the carriage side by side in the lateral direction, and ink of each color is ejected when the carriage moves once in the lateral direction. Note that the four print heads do not have to be separately configured, but may be integrally configured.

A long head having the same size as the width of the recording material, which is called a line head, is fixed in the lateral direction and arranged.
There is also a type of print head that does not use a carriage. In this case, since it is not necessary to move the print head in the horizontal direction, the drive system for moving the print head in the horizontal direction is not necessary in comparison with the former configuration, so that the printer can be downsized.
Moreover, there is an advantage that the printing speed can be increased.

In an ink jet printer equipped with a print head having such a structure, in the case of full-color printing, the above long print head is used for black ink, yellow ink, magenta ink, and cyan ink. 4 in total are arranged side by side in the vertical direction. Again, the printheads do not have to be four separate configurations,
It may be configured integrally.

By the way, since the diameter of the ink ejection hole in such a print head is very small, about 30 to 60 μm, defects such as clogging and inability to eject ink in a set shape occur during manufacture. In some cases, as the number of ejection holes formed increases, the probability that one or two ejection holes in the ejection holes will have such a defect increases. At the current technical level, it is difficult to correct the ejection hole that has caused such a defect and is discarded, so that the yield of the print head is reduced and the cost of the inkjet printer is increased.

In view of the above problems, Japanese Patent Laid-Open No. 8-174805 discloses that the above-described line head includes a first ejection array having normal ejection holes and a second ejection array having auxiliary ejection holes. When two ejection hole arrays are arranged side by side and a defect occurs in the ejection hole having the first ejection hole array, the second ejection lined up with the defective ejection hole is used instead of the defective ejection hole. A configuration is described which uses the spare ejection holes of the hole array.

[0010]

However, in the structure in which the second ejection hole array is provided in advance as a spare as in the above publication, the ejection holes having the first ejection hole array are certainly defective. Even if there is a spare ejection hole, the print head itself can be used and the yield can be improved by substituting a spare ejection hole, but most ejection holes of the second ejection hole array are wasteful ejections that are not used until the end. Since a large number of such wasteful ejection holes are formed in advance, the structure of the print head is complicated and the size of the print head itself is increased. There is a problem in adopting it in the print head.

The present invention has been made in view of the above problems, and is an ink jet head having a defective ejection hole by correcting defective ejection of ink from the defective ejection hole without providing a preliminary ejection hole. It is to provide an inkjet printer that can be used.

[0012]

In order to solve the above-mentioned problems, the first ink jet printer of the present invention has a plurality of ejection holes for ejecting ink of a predetermined color, and a plurality of ejection holes which exhibit a black color by mixing colors. In an inkjet printer that has a print head provided for each color and forms a color image on a recording material by ejecting ink from each ejection hole, when the ejection hole of black ink is defective, the defective ejection is performed. Instead of ejecting black ink from the holes, ink is ejected from each of the plurality of color ejection holes capable of ejecting the ink to the same position on the recording material as the defective ejection hole to form black dots by mixed colors. It is characterized in that it comprises a control means for controlling the drive of the print head.

Here, as a plurality of colors that exhibit a black color by mixing colors, for example, three colors of yellow, magenta, and cyan can be cited.

According to the above arrangement, when the black ink ejection hole is defective, the control means controls the drive of the print head to eject the ink to the same position on the recording material as the defective ejection hole. Ink is ejected from each of the ejection holes of a plurality of colors to form black dots of mixed colors in the area where the defective ejection holes are assigned.

Therefore, even if a spare ejection hole is not provided as a substitute in the case of a defect, a missing dot position that should be formed by ejecting ink from the defective ejection hole can be eliminated from other normal ejection holes. By covering with ejection, it is possible to form an image without problems, and it is possible to use even a print head having defective ejection holes.

Since the structure of the print head is simple and does not increase in size because a spare ejection hole is not provided as a substitute, there is no need to use it for a movable print head mounted on a carriage. no problem.

Further, the above control means can be easily realized by software improvement of the drive control unit of the ink jet head mounted in the conventional ink jet printer, so that the cost reduction effect by the improvement of the print head yield is sufficient. It is reflected in the price of the inkjet printer, and the price reduction of the inkjet printer can be promoted.

In order to solve the above problems, the second ink jet printer of the present invention is provided with a print head having a plurality of ejection holes for ejecting ink of the same color, and ink is ejected from each ejection hole for recording. In an inkjet printer that forms an image on a material, when there is a defective ejection hole, the ejection hole ejects ink of the same color as the defective ejection hole, and the ejection hole is adjacent to the defective ejection hole. When the ink is ejected, the control means for controlling the drive of the print head is provided so as to compensate the ink ejection failure due to the defective ejection hole.

This corresponds to the case where the ejection holes for the color inks other than black are defective, or the ejection holes for the black ink are defective in the apparatus configuration in which black dots cannot be formed by mixed colors.

Here, the adjacent ejection holes are movable heads in which the print head is mounted on the carriage, and when the ejection holes of the same color are arranged in one line in the sub-scanning direction, they are adjacent to each other in the sub-scanning direction. Becomes In the mobile head,
When a plurality of rows of ejection holes arranged in the sub-scanning direction are arranged in parallel in the main scanning direction, the ejection holes of different rows arranged in the main scanning direction may be used.

The same applies to the case of a fixed type line head in which the print heads are linearly arranged in the main scanning direction which is the width direction of the recording material, and the discharge holes of the same color are arranged in one line in the main scanning direction. In the lined single line configuration, the adjacent ejection holes are ejection holes adjacent to each other in the main scanning direction, and in the plural line configuration in which a plurality of rows of ejection holes arranged in the main scanning direction are juxtaposed, The ejection holes to be formed may be ejection holes adjacent to each other in the sub-scanning direction.

According to the above construction, when there is a defective ejection hole, the control means controls the drive of the print head to eject ink from at least one ejection hole of the same color adjacent to the defective ejection hole. Colors are placed in the areas to which the discharge holes are assigned.

Therefore, even if a spare ejection hole is not provided as a substitute in the case of a defect, a missing dot position that should be formed by ejecting ink from the defective ejection hole can be prevented from being ejected from other normal ejection holes. By covering with ejection, it is possible to form an image without problems, and it is possible to use even a print head having defective ejection holes.

Since the structure of the print head is simple and does not increase in size because a spare ejection hole is not provided as a substitute, there is no need to use it for a movable print head mounted on a carriage. no problem.

Further, the above control means can be easily realized by a software improvement of the drive control unit of the ink jet head mounted in the conventional ink jet printer, so that the cost reduction effect by the improvement of the yield of the print head is sufficient. It is reflected in the price of the inkjet printer, and the price reduction of the inkjet printer can be promoted.

In the above-mentioned second ink jet printer of the present invention, when forming a solid image, the control means increases the ink ejection amount from the adjacent ejection holes.

When the image to be formed is a solid image, the ejection failure of ink due to the defective ejection hole can be compensated by controlling so that the ink ejection amount from the adjacent ejection hole is increased.

In the case of forming a solid image,
In addition, when a plurality of inks of different colors are ejected to the same position on the recording material to form one dot in a mixed color, the control means sets the other dots formed by ink ejection from normal ejection holes. It is desirable that the ink ejection amount to be increased is determined so that the color difference becomes small.

When a solid image is formed, and
When a plurality of inks of different colors are ejected at the same position on the recording material to form one dot in a mixed color, the ink ejection amount to be increased is different from that of other dots formed by ejecting ink from a normal ejection hole. By deciding so as to be small, the color difference (gradation unevenness) can be suppressed and the image quality can be improved.

In the above-described second ink jet printer of the present invention, when a single dot image or a fine line image is formed, the control means sets the ink ejection amount from the adjacent ejection holes from the normal ink ejection amount. Reduce.

When the image to be formed is a single-dot image or a thin line image, the ink ejection amount from the adjacent ejection holes is controlled so as to be smaller than the regular ink ejection amount, so that the ink due to the defective ejection holes is ejected. The ejection failure can be compensated without making it noticeable.

In the above-described second ink jet printer of the present invention, the control means determines whether or not there is an adjacent dot adjacent to a dot formed by ejecting ink from the defective ejection hole, If there is, the amount of ink ejected from the adjacent ejection hole is made larger than the regular ink ejection amount, and if there is no adjacent dot, the amount of ink ejected from the adjacent ejection hole is made smaller than the regular ink ejection amount. Can also be characterized.

In the above arrangement, the presence / absence of an adjacent dot adjacent to the dot formed by ejecting ink from the defective ejection hole is first determined. In the case of a solid image, there is an adjacent dot, and in the case of a single dot image or a thin line image, there is no adjacent dot, so the formed image can be discriminated by the presence or absence of the adjacent dot. Then, when there is an adjacent dot, the ink ejection amount from the adjacent ejection hole is made larger than the regular ink ejection amount,
When there is no adjacent dot, the amount of ink ejected from the adjacent ejection hole is made smaller than the regular ink ejection amount. Therefore, as described above, in solid images, single dot images and thin line images, ink due to defective ejection holes is used. It is possible to make up for the ejection failure of (1) without making it noticeable.

In the above-described first and second ink jet printers of the present invention, when gradation expression is performed using a dither matrix pattern, a predetermined number of ejection holes used for expressing the dither matrix pattern are arranged at each position. Further, a storage means for storing the dither matrix pattern when the ejection holes at each position become defective is further provided,
The control means may switch the dither matrix pattern when the defective ejection hole is used to the dither matrix pattern corresponding to the position of the defective ejection hole by referring to the storage means.

In gradation expression using a dither matrix pattern, according to a predetermined matrix order,
Since the matrix pixels are filled up, if the matrix order of the matrix pixels assigned to the defective ejection holes is a small number, the number of matrix pixels in which dots are formed in the alternative ejection holes increases.

According to the above arrangement, the storage unit stores the dither matrix pattern for each position of the predetermined number of ejection holes used for expressing the dither matrix pattern when the ejection holes at each position become defective. Each is remembered. The dither matrix pattern when the ejection holes at each position become defective is, in other words, the matrix order of the matrix pixels formed by the defective ejection holes is large.

Then, the control means switches the dither matrix pattern when the defective ejection hole is used to the dither matrix pattern corresponding to the position of the defective ejection hole by referring to the storage means, so that the alternative ejection hole is selected. Thus, it is possible to reduce the number of matrix pixels in which dots are formed and to achieve more accurate gradation expression.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS.

The ink jet printer of the present embodiment to which the configuration of the present invention is applied is, as shown in FIG. 2 and FIG.
A print head 1 that ejects ink onto a recording material P is an ink tank 2 that supplies ink to the print head 1.
At the same time, it is configured to be mounted on the ink carriage 3.
The ink carriage 3 is slidably supported by a shaft 4, and is reciprocally moved by a timing belt 5 in a main scanning direction indicated by an arrow A and a return direction which is the opposite direction thereof. .

The print head 1 is capable of independently ejecting four color inks of black (K), yellow (Y), magenta (M), and cyan (C). As shown in the drawing, a plurality of ejection holes 20 for ejecting the same color ink are provided side by side in the sub-scanning direction which is a direction orthogonal to the main scanning direction and which is the conveyance direction of the recording material P. Here, since black, cyan, magenta, and yellow are arranged in this order from the upstream side in the main scanning direction, ink is ejected in the order of yellow, magenta, cyan, and black.
Note that the print head 1 has a structure in which a total of four print heads configured separately for each of the above colors are mounted on one carriage 3, and the ejection holes 20 for the four colors are included in one print head. It may be an integrated one-body configuration.

On the other hand, the recording material P on which an image is formed by the ink ejected from the print head 1 is stacked on the paper feed tray 6 and fed by the pickup roller 7 as shown in FIGS. The sheets are separated and fed one by one from the paper tray 6, and are conveyed below the print head 1 by the conveying roller pair 8 in the sub-scanning direction shown by an arrow B, and are discharged onto the discharge tray 11 by the discharging roller pair 9. The paper is ejected. A platen 12 that supports the recording material from the back side is provided at a portion of the conveyance path of the recording material P that faces the print head 1.

In such a structure, the print head 1
Ejects the ink supplied from the ink tank 2 onto the recording material P from the ejection holes 20 corresponding to the image signal while moving in the main scanning direction. Then, when the movement in the main scanning direction is completed, the movement in the return direction is started, and printing of the next one line is started. Further, while the print head 1 is moving in the return direction, the recording material P has a width of one line (a dimension of one line in the sub-scanning direction) in which the print head 1 forms an image by one scan. It is transported in the sub-transport direction. An image is formed on the recording material P by sequentially repeating such writing scanning for each line.

FIG. 1 is a block diagram showing the electrical construction of the ink jet printer of this embodiment. Control unit 1
Reference numeral 9 denotes a control center that controls each unit of the inkjet printer, which includes a CPU (Central Processing Unit), and includes an interface unit 25, an image processing unit 22, a drive control unit 23, a memory 21, and the like.

The interface section 25 receives print commands and print data transmitted from an external personal computer or the like to the ink jet printer, and the print commands and print data received by the interface section 25. Is transmitted to the image processing unit 22 and the drive system control unit 23.

The image processing section 22 transmits a drive signal to the head drive circuit 26 based on the transmitted print data, and the head drive circuit 26 uses the drive signal to output the print head 1 described above. Are driven to control the ink ejection operation from each ejection hole 20.

On the other hand, when the print command is transmitted, the drive system control section 23 transmits each drive signal to the carriage drive circuit 27 and the recording material transport drive circuit 29.

The carriage drive circuit 27 supplies electric power to the carriage motor 28 which drives the timing belt 5 in response to the drive signal, and causes the ink carriage 3 to perform a predetermined operation related to the ejection operation of the print head 1 based on print data. The print head 1 is moved in the main scanning direction at a timing, and is also moved in the return direction at a predetermined timing when the ink ejection operation by the print head 1 is stopped.

The recording material conveying drive circuit 29 supplies electric power to the recording material conveying motor 30 for driving the conveying roller pair 8 and the paper discharge roller pair 9 in response to the drive signal to sub-scan the recording material P at a predetermined timing. It is to be transported in the direction.

The memory 21 is a RAM (Random Acc
ESS Memory) and ROM (Read Only Memory). The RAM mainly stores the print data temporarily under the control of the image processing unit 22, and the ROM stores the control program of the inkjet printer and various tables in advance.

By the way, as described above, in the print head in which the plurality of ejection holes 20 are formed like the above-mentioned print head 1 in the ink jet printer, one of the plurality of ejection holes 20 is defective. However, the print head 1 is a defective head, cannot be used as it is, and is discarded, which is a factor of increasing the price of the inkjet printer.

In the ink jet printer of the present embodiment, the control section (control means) 19 shown in FIG. 1 drives the head through the image processing section 22 so that such a defective head can be used. By controlling the drive of the circuit 26, dot formation by the defective ejection hole 20 in the print head 1 is compensated by ejecting ink from another favorable ejection hole.

This will be described in detail below.

First, as shown in FIG. 5, actual printing is performed using the print head 1 to check the state of each discharge hole 20 of each color and detect the position of the defective discharge hole 20. Figure 5
In the above example, a total of 30 ejection holes 2 are arranged in parallel in the sub-scanning direction.
The 0s are divided into 3 groups A to C, each of which is numbered 0 to 9 to identify the positions of the 30 ejection holes and the positions of the defective ejection holes 20. ing. The defective ejection hole 20 is detected for each color, and the defective ejection hole 20 in the print head 1 is the ejection hole 20 of what color and at what number (downstream in the sub-scanning direction, which is the front end of the image). It can be specified as color information and position information such as Y-N (where N is an integer from 1 to 30).

The color information and the position information of the defective ejection holes 20 thus obtained are stored in the RAM of the memory 21 in FIG. 1 described above, and the defective ejection hole position storage for storing the positional information of the defective ejection holes is stored. It is stored in the section 21a.

The image processing section 22 has an interface section 25.
When the print head 1 is driven by the image data received by, the defective ejection hole position storage portion 21a is checked, and first, the defective ejection hole 20 forms a black dot based on the color information. Or to form a color dot other than black.

When a black dot is to be formed, the position of the ejection hole 20 is judged based on the position information. For example, when the ejection hole 20 is the fifth ejection hole, , The yellow, magenta, and cyan discharge holes 20 at the same fifth position, the three color dots are formed at the positions on the recording material P where the defective discharge holes 20 should form dots. , And sends a drive signal to the head drive circuit 26 so that black dots due to mixed colors are formed.

As a result, as shown in FIG. 6 (a), the line-shaped missing due to the black dots not being formed by the defective ejection holes 20 is changed to black dots by the mixed colors as shown in FIG. 6 (b). Can be filled.

On the other hand, in the case of forming yellow, magenta, and cyan color dots, it is judged based on the position information which ejection hole 20 is, for example, the ejection hole 20 is the fifth. In the case of the ejection holes of the defective ejection hole 20, the ink is ejected from the ejection hole 20 of the same color as the defective ejection hole 20 and adjacent to the fifth ejection hole 20, that is, the fourth and sixth ejection holes 20. When the recording material P is discharged,
A drive signal is transmitted to the head drive circuit 26 as formed above. Specifically, the ink ejection amount from the adjacent ejection holes 20 corresponding to the print data is made larger than the regular ejection amount according to the image to be formed.

As a result, as shown in FIG. 7A, in the case of a solid image, if the defective dots are not formed due to the ejection holes 20, and a line-shaped drop occurs,
As shown in (b) of the figure, by increasing the amount of ink ejected from the adjacent ejection holes 20, it is possible to fill the gap. Further, in the case of forming a solid image in this way, and in the case where a plurality of inks of different colors are ejected to the same position on the recording material to form one dot in a mixed color, the ink ejection amount to be increased is normally increased. The color difference (gradation unevenness) can be suppressed and the image quality can be improved by determining so that the color difference with other dots formed by ejecting ink from the appropriate ejection holes 20 is reduced.

Further, as shown in FIG. 8A, in the case of a single dot image such as a halftone dot image, a defective ejection hole 20n
So as to form color dots that are not formed by the ejection holes 20n + 1 and the ejection holes 2 adjacent to the defective ejection hole 20n.
From 0n-1, the amount of ink that is smaller than the regular dot formation amount from the other ejection holes 20 is ejected, and two color dots smaller than the regular size are formed. As a result, in the case of a single dot image such as a halftone image,
It is possible to fill the dot omission caused by the color dots not being formed by the defective ejection holes 20.

Whether the image to be formed is a solid image, a single dot image, or a fine line image is determined by, for example, adjoining a dot formed in a defective ejection hole 20. It can be judged based on the presence / absence of dots to be printed. That is, if there is an adjacent dot, it is a solid image, and if there is no adjacent dot, it is a single dot image or a thin line image.

In this case, since the black dots can be formed by mixing colors, the alternative method for black dots is different from that for other color dots, but black dots cannot be formed by mixing colors. In the case of an inkjet printer, an alternative method similar to that for color dots may be adopted.

Further, in the ink jet printer according to the present embodiment, the black ink is formed by the pigment and the color ink is formed by using the dye. Therefore, in the image processing unit 22, the image processing unit 22 shown in FIGS. As shown in, it is determined whether or not the dot area ratio, which is a value obtained by dividing the total number of dots per unit area by the number of black dots, exceeds 50%.
Even if the black ejection holes 20 are normal, the black dots made of black ink and the black dots formed by color mixing of the color inks are mixedly arranged. This makes it possible to obtain a beautiful image in a shorter time while covering the drawback that the black ink formed of the pigment is difficult to dry.

Further, in the ink jet printer of the present embodiment, the image processing unit 22 is adapted to perform gradation expression using a dither matrix pattern. However, in gradation expression using a dither matrix pattern, Since the matrix pixels are filled in according to the determined matrix order, if the matrix order of the matrix pixel assigned to the defective ejection hole is a small number, dots are formed in the alternative ejection holes. The number of matrix pixels will increase.

Therefore, in the ink jet printer of the present embodiment, the ejection holes 20 at each position become defective in the memory 21 for each position of the predetermined number of ejection holes 20 used for expressing the dither matrix pattern. The dither matrix pattern for each case is stored, and the image processing unit 22 refers to the memory 21 to determine the dither matrix pattern when the defective ejection hole 20 is used, by referring to the position of the defective ejection hole 20. The dither matrix pattern according to the above is switched. The dither matrix pattern when the ejection holes 20 at each position are defective is that the matrix order of the matrix pixels formed in the defective ejection holes 20 is large.

For example, reference numeral 32 in FIG.
When multi-valued dither processing is performed using a 4 × 4 dither matrix having 8 bits (256 gradations) per pixel, 4
Each pixel of the × 4 matrix is filled in the matrix order represented by numerical values in each pixel. Here, as indicated by reference numeral 33, in the dither matrix pattern that fills 10 pixels out of 16, if the pattern is fixed, the four ejection holes 20-1 to 20-4 that fill the pixels are provided. If there is a defective one, dots are formed by the alternative ejection holes 20. For example, when the ejection hole 20-1 is defective, 8 pixels are filled with normal dots and 2 pixels are filled with the alternative ejection hole 20. If the ejection hole 20-2 is defective, 6 pixels are filled with normal dots, and 4 pixels are filled with the alternative ejection hole 20.

On the other hand, in the ink jet printer according to the present embodiment, the image processing unit 22 changes the dither matrix pattern to the defective ejection hole 20 according to the position, as indicated by reference numeral 34, and gives priority. Since the number of pixels filled with normal dots is increased,
The number of pixels in which dots are formed is reduced, and more accurate gradation expression can be performed.

[0068]

As described above, in the first ink jet printer of the present invention, the ejection holes for ejecting the ink of the predetermined color are provided in accordance with the black color and a plurality of colors exhibiting the black color by mixing the colors. In an inkjet printer that includes a print head and forms a color image on a recording material by ejecting ink from each ejection hole, when the ejection hole of the black ink is defective, the ejection of the black ink by the defective ejection hole is performed. Instead, the drive of the print head is controlled so that ink is ejected from each of the ejection holes of the plurality of colors capable of ejecting the ink to the same position on the recording material as the defective ejection hole to form a black dot by color mixture. It is characterized in that it is provided with a control means.

With this arrangement, even if a spare ejection hole is not provided as a substitute in the case of a defect, a dot position drop that should be formed by ejecting ink from the defective ejection hole can be eliminated from other normal ejection holes. The image can be formed without any problem by covering the ejection head with the ejection, and even a print head having a defective ejection hole can be used.

Since the structure of the print head is simple and does not increase in size because a spare ejection hole is not provided for substitution, it can be used for a movable print head mounted on a carriage. no problem.

Further, the above control means can be easily realized by a software improvement of the drive control unit of the ink jet head mounted in the conventional ink jet printer, so that the cost reduction effect by the improvement of the yield of the print head is sufficient. It is reflected in the price of the inkjet printer, and the price reduction of the inkjet printer can be promoted.

As described above, the second ink jet printer of the present invention includes the print head having a plurality of ejection holes for ejecting the same color ink, and ejects the ink from each ejection hole onto the recording material. In an inkjet printer for forming an image, when there is a defective ejection hole, the ejection hole ejects ink of the same color as the defective ejection hole,
It is characterized in that a control means is provided for controlling the drive of the print head so as to compensate the defective ejection of the ink due to the defective ejection hole by ejecting the ink from at least one ejection hole adjacent to the defective ejection hole. .

Thus, even if a spare ejection hole is not provided as a substitute in the case of a defect, a missing dot position that should be formed by ejecting ink from the defective ejection hole can be eliminated from other normal ejection holes. The image can be formed without any problem by covering the ejection head with the ejection, and even a print head having a defective ejection hole can be used.

Since the structure of the print head is simple and does not increase in size because a spare ejection hole is not provided as a substitute, there is no need to use it for a movable print head mounted on a carriage. no problem.

Further, since the above-mentioned control means can be easily realized by a software improvement of the drive control unit of the ink jet head mounted in the conventional ink jet printer, the cost reduction effect due to the improvement of the print head yield is sufficient. It is reflected in the price of the inkjet printer, and the price reduction of the inkjet printer can be promoted.

In the above-mentioned second ink jet printer of the present invention, when forming a solid image, the control means increases the ink ejection amount from the adjacent ejection holes. As a result, it is possible to compensate for the defective ejection of ink due to the defective ejection hole when the image to be formed is a solid image.

In the case of forming a solid image,
In addition, when a plurality of inks of different colors are ejected to the same position on the recording material to form one dot in a mixed color, the control means sets the other dots formed by ink ejection from normal ejection holes. It is desirable to adopt a configuration in which the ink ejection amount to be increased is determined so that the color difference becomes small, and by doing so, the color difference (gradation unevenness) can be suppressed and the image quality can be improved.

In the above-described second ink jet printer of the present invention, when a single dot image or a fine line image is formed, the control means sets the ink ejection amount from the adjacent ejection holes from the regular ink ejection amount. Reduce.

When the image thus formed is a single-dot image or a thin line image, it is possible to compensate the ink ejection failure due to the defective ejection hole without making it conspicuous.

In the above-described second ink jet printer of the present invention, the control means determines whether or not there is an adjacent dot adjacent to a dot formed by ejecting ink from the defective ejection hole, and the adjacent dot is detected. If there is, the amount of ink ejected from the adjacent ejection hole is made larger than the regular ink ejection amount, and if there is no adjacent dot, the amount of ink ejected from the adjacent ejection hole is made smaller than the regular ink ejection amount. Can also be characterized.

As a result, as described above, in the solid image, the single dot image and the fine line image, the defective ejection of ink due to the defective ejection hole can be compensated for without being conspicuous.

In the above-described first and second ink jet printers of the present invention, when gradation expression is performed using a dither matrix pattern, a predetermined number of ejection holes used for expressing the dither matrix pattern are arranged at each position. Further, a storage means for storing the dither matrix pattern when the ejection holes at each position become defective is further provided,
The control means may switch the dither matrix pattern when the defective ejection hole is used to the dither matrix pattern corresponding to the position of the defective ejection hole by referring to the storage means.

As a result, the dither matrix pattern when the defective ejection hole is used is switched to the dither matrix pattern corresponding to the position of the defective ejection hole, so that the matrix pixel in which dots are formed in the alternative ejection hole. More accurate gradation expression can be obtained by reducing the number of.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an inkjet printer according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of the inkjet printer.

FIG. 3 is an explanatory diagram showing a configuration of the inkjet printer.

FIG. 4 is an explanatory diagram showing an arrangement state of ejection holes in a print head included in the inkjet printer.

FIG. 5 is an explanatory diagram showing a method of detecting a defective ejection hole of a print head in the inkjet printer.

6 (a) and 6 (b) are explanatory views showing a method for relieving dot formation of defective ejection holes in the inkjet printer.

7A and 7B are explanatory views showing a method of remedying dot formation of defective ejection holes in the inkjet printer.

8A and 8B are explanatory views showing a method of remedying dot formation of defective ejection holes in the inkjet printer.

9A and 9B are explanatory diagrams showing a method of remedying dot formation of defective ejection holes in the inkjet printer.

FIG. 10 is an explanatory diagram showing switching of a dither matrix pattern in the inkjet printer.

[Explanation of symbols]

1 print head 20 discharge holes 21 memory (control means, storage means) 22 Image processing unit (control means)

Claims (7)

[Claims] 1. A print head having ejection holes for ejecting ink of a predetermined color is provided for black and a plurality of colors exhibiting black by mixing colors, and ink is ejected from each ejection hole. In an inkjet printer that forms a color image on a recording material, if the black ink ejection hole is defective, instead of ejecting the black ink by the defective ejection hole, the defective ejection hole and the same position on the recording material are replaced. An ink jet printer comprising a control means for controlling the drive of the print head so that ink is ejected from each of the ejection holes of the plurality of colors capable of ejecting ink to form a black dot by color mixing. 2. An ink jet printer, comprising a print head provided with a plurality of ejection holes for ejecting ink of the same color, wherein an image is formed on a recording material by ejecting ink from each ejection hole. In some cases, an ejection hole that ejects ink of the same color as the defective ejection hole, and the ejection failure of the ink due to the defective ejection hole is supplemented by the ink ejection from at least one ejection hole adjacent to the defective ejection hole. An ink jet printer comprising the control means for controlling the drive of the print head as described above. 3. The ink jet printer according to claim 2, wherein when forming a solid image, the control means increases the ink ejection amount from the adjacent ejection holes. 4. When a plurality of inks of different colors are ejected at the same position on a recording material to form one dot in a mixed color, the control means controls the other dots formed by ink ejection from normal ejection holes. The ink jet printer according to claim 3, wherein the ink ejection amount to be increased is determined such that the color difference between the ink jet printer and the ink is reduced. 5. When the single dot image or the thin line image is formed, the control means sets the ink ejection amount from the adjacent ejection holes to be smaller than the regular ink ejection amount. The described inkjet printer. 6. The control means determines the presence or absence of an adjacent dot adjacent to a dot formed by ejecting ink from the defective ejection hole, and if there is an adjacent dot, the ink from the adjacent ejection hole is detected. The inkjet amount according to claim 2, wherein the ejection amount is larger than the regular ink ejection amount, and when there is no adjacent dot, the ejection amount of the ink from the adjacent ejection hole is smaller than the regular ink ejection amount. Printer. 7. When the gradation expression is performed by using a dither matrix pattern, dither when the discharge holes at each position become defective for each position of a predetermined number of discharge holes used for expressing the dither matrix pattern. Storage means for respectively storing matrix patterns is further provided, and the control means refers to the storage means to determine the dither matrix pattern when a defective ejection hole is used, according to the position of the defective ejection hole. The inkjet printer according to claim 1, wherein the inkjet printer is switched to a dither matrix pattern.