JP2002144549A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer in which the effect of a defective nozzle unrecoverable by a wiping means onto adjacent nozzles, and missing of print dots due to defective nozzle can be avoided. SOLUTION: The ink jet printer comprises a print head provided with a plurality of nozzles ejecting identical ink dots, and performs printing by moving the print head in a direction intersecting the carrying direction of sheet. The ink jet printer further comprises means for registering defective nozzles ejecting no ink dot among a plurality of nozzles provided in the print head, means for prohibiting dot ejecting operation of registered defective nozzle, and means for performing dot ejection of registered defective nozzle through an alternative nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print head provided with a plurality of nozzles for jetting the same ink by dots, and to cause the print head to scan dots in a direction intersecting the paper transport direction to cause the ink to be jetted. The present invention relates to an ink jet printer that performs printing by using a printer.

[0002]

2. Description of the Related Art In general, an ink jet printing apparatus scans a print head having a plurality of nozzles in a line direction orthogonal to a paper feed direction (hereinafter, referred to as scan) to print a plurality of lines (hereinafter, referred to as scan). Scan printing) is performed at the same time, and the above-described scan printing is repeatedly performed while intermittently feeding the paper, thereby performing printing on one sheet of paper.

[0003] The number of ink jet nozzles provided in one print head varies depending on the type of printer.
For example, an enormous number of ink jet printers for printing on long paper or A0 size large paper are provided, for example, 510 printers are provided for each color for a total of four colors. The nozzles are divided into blocks for each color and are arranged separately. In the blocks, nozzles that handle ink of the same color are arranged substantially in a line in a direction orthogonal to the scanning direction.

The interval between nozzles in a block is a parameter that determines the printing resolution, and cannot be made too large. If printing at 360 dpi is performed by one scan, the interval between nozzles is 70 μm, which is equivalent to 360 dpi. (Micrometers). In actuality, by performing scan printing by overlapping the previous scan printing so that the positions of the print dots are slightly displaced, processing such as printing with a resolution finer than the nozzle interval is performed. On the other hand, the nozzle interval is generally formed to be twice or four times wider, but the nozzle interval is still 140 μm or 280 μm.
And so on.

[0005] In addition, it is also common to employ a configuration in which one line is not printed by one nozzle, but one line is printed by two scans, for example, with two nozzles sharing one half at a time. is there. For example, each dot on one line is divided into two systems, odd-numbered dots and even-numbered dots, and these two systems of dots are assigned to two nozzles, respectively, so that one line can be printed by two scans. To be fulfilled. Specifically, as shown in FIG. 3A, in the first scan, the even-numbered nozzles N6, N8, and N10 eject ink to the even-numbered dots in the arrangement order, while the odd-numbered nozzles N7, N9
Performs ink ejection on odd-numbered dots, and then
The second scan is performed by feeding the paper by half the total nozzle width L. In the second scan, as shown in FIG. 3B, the odd-numbered nozzles N1, N3, and N5 eject ink from left to right to even-numbered dots, while the even-numbered nozzles N2 and N4 emit odd-numbered dots. Ink ejection is performed for the third dot. By configuring such that one line is printed by a plurality of nozzles by scanning a plurality of times, variations in dot ejection characteristics and formation positions of each nozzle appear in all dots on one line. Can be avoided, and deterioration of print quality can be prevented.

[0006]

By the way, in a printer which performs printing by ejecting ink from nozzles, there is generally a problem that dust adheres to the nozzles to cause nozzle clogging. In addition, when a problem occurs in one nozzle, as described below, the nozzle may adversely affect surrounding nozzles and widen a defective portion.

FIG. 7 shows a process in which a clogged nozzle adversely affects the surrounding nozzles. A cross-sectional view of a plurality of nozzles is shown on the left, and the result of dot ejection is shown on the right. FIG. 7A shows a normal state, and FIG. 7B shows an initial state in which dust has clogged the nozzle “c”. As shown in FIG. 7B, when the nozzle is clogged with dust, ink may still be ejected from the nozzle at an initial stage. In this case, the ink ejection is affected by the dust and causes a flight bend. , Overlapping with the next dot. Next, as shown in FIG. 7 (C), an ink reservoir is generated at the tip of the clogged nozzle,
Dot ejection is not performed from the defective nozzle. When the dot ejection is not performed, as shown in FIGS. 7D and 7E, the ink supplied for the dot ejection is pushed out from the tip of the nozzle to grow an ink reservoir, and the adjacent nozzle, The nozzle spreads to the next adjacent nozzle, and a state is reached in which dot ejection cannot be performed from a plurality of continuous nozzles.

[0008] With respect to an abnormality of the print head such as nozzle clogging, the wiping means such as a wiper blade is used to perform printing at the start and end of one printing process, or at the time of one scan printing or predetermined scan printing. A printer that wipes the nozzles of the nozzles of the head to recover the nozzle abnormality to a normal state is also common.

However, in the method of wiping the nozzle orifice by the wiping means, even if the above-described ink pool or large dust adhering to the outside of the nozzle orifice can be removed, the inside of the nozzle orifice can be removed. Clogged trash and small adhesive trash cannot be removed. Therefore, in the case where dust is clogged inside the nozzle ejection port, even if the nozzle ejection port is wiped by the wiping means, the ink pool grows in the middle of one scan, and the print quality may be visually reduced. There was a problem of reaching the state.

[0010] Therefore, when dust is clogged inside the injection port, there is no other way but to remove the dust by a special method other than the wiping means or to replace the print head. There was a problem of soaring significantly.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the deterioration of print quality by avoiding the influence on adjacent nozzles and the loss of print dots due to defective nozzles, even if a nozzle failure that cannot be improved by the wiping means occurs. Accordingly, it is an object of the present invention to provide an ink jet printer that can extend a period for replacing a print head and reduce running costs.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a print head provided with a plurality of nozzles for ejecting the same kind of ink by dots, and the print head is moved in a direction intersecting the paper transport direction. In an ink-jet printer that performs printing by ejecting ink by dot ejection while scanning to, a defective nozzle registration unit that registers a defective nozzle that does not eject dot among a plurality of nozzles provided in the print head, The configuration includes a defective nozzle masking unit that prohibits a dot ejection operation at a defective nozzle, and a defective nozzle substitution unit that substitutes another nozzle for dot ejection that should be performed by a registered defective nozzle.

According to such means, when a defective nozzle that has caused nozzle clogging is found, the defective nozzle is registered in the defective nozzle registration means such as a memory.
Thereafter, the dot ejection operation is prohibited in the defective nozzle. As a result, it is possible to prevent the ink from being pushed out of the nozzle and causing a pool of ink at the tip of the nozzle to adversely affect adjacent normal nozzles. In addition, since the defective nozzle replacement means replaces the dot ejection that should be performed by the defective nozzle with another nozzle, it is possible to avoid the print nozzle missing due to the defective nozzle.
Therefore, unless the number of defective nozzles increases significantly,
It is possible to maintain print quality that is almost the same as in a normal case. Further, thereby, even if the above-mentioned defective nozzles are generated, it is possible to continue printing almost normally without replacing the print head, and it is possible to reduce the running cost of the printing apparatus.

Preferably, the plurality of nozzles are arranged side by side in a direction intersecting the scanning direction of the print head, and two or more nozzles are formed by a plurality of scans performed while intermittently feeding the paper in one direction. A plurality of dots on one print line are scanned, and a plurality of dots on one print line are divided into a plurality of system dots. In the ink jet printer configured to perform printing by performing dot ejection while sharing one system at a time, the defective nozzle replacement unit is configured such that the registered defective nozzle scans the defective nozzle in the print line. It is preferable that the dot ejection for the assigned dot is performed by a nozzle assigned to another dot on the print line.

With this configuration, even when the dot ejection of the defective nozzle is replaced by another nozzle, unnecessary scanning of the print head is unnecessary, and the same printing speed as in the normal case can be maintained. .

More preferably, the print head has pixel data indicating whether or not to perform dot ejection at each coordinate point of the printing coordinates (the ink ejection amount is "0", "1", "1/2", etc. (Including pixel data capable of performing typical dot ejection), and passes pixel data of one print line sent to the print head side for each of the plurality of dot systems. And mask means capable of controlling the non-passing of the print head, the pixel data of the same print line is sent to the print head side a plurality of times while the scan by the print head is performed a plurality of times, and the mask is By switching the system of the pixel data to be passed by the means, the plurality of nozzles perform printing while sharing one system at a time for a plurality of system dots on one print line. In the ink jet printer, the defective nozzle masking means is configured to forcibly block the pixel data corresponding to the registered defective nozzle out of the pixel data sent to the print head side, while When another nozzle scans the same print line as the print line scanned by the registered defective nozzle, the nozzle replacement means replaces the dot assigned by the registered defective nozzle among the pixel data of the print line. It is preferable that the control of the mask means is released and the pixel data is passed to the print head side.

According to such a configuration, the stop of dot ejection from the defective nozzle and the replacement by another nozzle are performed by masking and unmasking the pixel data.
These controls can be easily and quickly performed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing a hardware configuration of an ink jet printer 1 which is an embodiment of the printing apparatus of the present invention, and FIG. 2 is a functional block diagram showing the functions of the printer 1 according to functions.

The printer 1 of this embodiment is, for example, an A1
For large-format paper, such as large-format paper, such as large-format, A0-size, and large-size roll paper, which prints while intermittently sending large-format paper in the vertical direction and scanning the print head that ejects ink in the horizontal direction. Is an inkjet printer.

This printer 1 has, as shown in FIG.
A CPU 11 for performing overall control of the printer 1, a program ROM 12 in which a control program and control data executed by the CPU 11 are stored, and a display unit for displaying input keys that can be operated by a user and details of the operation , An operation panel 13 functioning as a defective nozzle registration unit, an interface 14 for transmitting and receiving data to and from the host computer 2 connected via the network 4, an inkjet print head, and control for controlling the same. Printer engine 1 equipped with circuits, etc.
5, a spool memory 16 capable of temporarily storing pixel data sent from the host computer 2
A band memory 17 for storing pixel data of a plurality of print lines scanned by a plurality of nozzles provided in a print head in one scan, a defective nozzle registration memory 18 for storing data relating to defective nozzles, Band memory 17
Circuit 19 as a masking means capable of masking pixel data sent from the printer engine 15 to the printer engine 15
And a mask control circuit 20 for controlling the mask circuit 19 and constituting a defective nozzle mask means and a defective nozzle replacement means.

As shown in FIG. 2, the printer engine 15 includes a print control unit 15A, a media transport unit 15B, a carriage transport unit 15C, a print head drive unit 15D, and the like. The print head driving unit 15D is a mechanism for ejecting ink from each nozzle of the print head in accordance with the input pixel data. For example, by applying a current to a piezoelectric element provided corresponding to each nozzle, pressure is applied to the ink in the nozzle. In addition, ink is ejected from a nozzle. The carriage transport unit 15C is a mechanism that scans or moves the print head in a direction perpendicular to the paper feed direction in accordance with the ink ejection, and the media transport unit 15B intermittently feeds the print paper in accordance with the scan operation of the print head. Mechanism. The print control unit 15A is a control circuit that receives the pixel data read from the band memory 17 and controls the operation of each mechanism based on the input of the pixel data.

The defective nozzle registration memory 18 is constituted by a nonvolatile memory such as a flash ROM, for example, and has a storage capacity of a plurality of bits corresponding to each nozzle of 510 × 6 colors provided in the print head. "0" is stored when the nozzle corresponding to the bit is a defective nozzle, and "1" is stored when the nozzle is a used nozzle.

The operation panel 13 is used to register a defective nozzle in the defective nozzle registration memory 18 by operating an operation button, and to give an instruction to execute a test print of a predetermined pattern for finding a defective nozzle. The registration of these defective nozzles and the instruction to execute test printing can also be performed by data transmission from the host computer 2 via the interface 14.

The CPU 11 fetches pixel data and various control data supplied from the host computer 2 via the interface 14, stores the pixel data in the spool memory 16, and transmits various commands and control data from the operation panel 13. Perform input processing to input. Also, C
The PU 11 also functions as a band memory control unit 111 (FIG. 2) that reads and writes data from and to the band memory 17, sequentially reads pixel data for printing processing from the spool memory 16 to the band memory 17, and sets the band data at a predetermined timing. From the memory 17 to the printer engine 15
Print control such as sending to the side. In addition, it also functions as a defective nozzle registration unit 112 (FIG. 2) for reading and writing data in the defective nozzle registration memory 18 based on an input from the operation panel 13.

The band memory 17 is a memory for storing a plurality of lines of pixel data to be printed in one scan (eg, rightward scan or leftward scan).

In this embodiment, one normal printing line is set so that two different nozzles share the printing by half over two scans during normal operation with no defective nozzles. That is, among the plurality of dots on one print line, the odd-numbered dots from the left as the first system and the even-numbered dots as the second system are referred to as the second system. Printing is performed over two scans by sharing the two types of dots with the two nozzles. However, if the pixel data is divided into the first system and the second system by the software processing, the processing speed is reduced. Therefore, the first system and the second system are always transferred from the band memory 17 to the printer engine 15 side. Pixel data for all coordinates of each print line including
By masking the pixel data in a hardware manner by a mask circuit 19 such as an ND logic gate, only the first system pixel data and the second system pixel data are stored in the printer engine 1.
It is configured to be sent to the fifth side. Accordingly, the pixel data of the same print line is written twice in the band memory 17 in total, and is sent to the printer engine 15 twice as pixel data for different nozzles.

The mask circuit 19 masks the pixel data of the first system or the pixel data of the second system for each pixel data of one print line in order to enable the transfer of the pixel data as described above. To prevent the light from passing through the printer engine 15.

The mask control circuit 20 performs pixel data transmission from the band memory 17 for each pixel data of each print line in order to transmit the pixel data as described above in a normal state in which no defective nozzle is registered. 1 system or 2nd
Control for masking the system pixel data is performed. next,
The details will be described.

FIG. 3 is an explanatory diagram of mask processing in a normal state where there is no registration of a defective nozzle. In the figure,
To simplify the description, the ten single color nozzles N1
N10 indicates a process of printing a rectangle of 16 dots in width × 10 dots in height. In the figure, white circles indicate dots before ink ejection, and black circles indicate dots after ink ejection.

In a normal state in which no defective nozzle is registered, the mask control circuit performs the following control. That is, as shown in FIG. 3A, at the time of the first scan sliding rightward, the odd-numbered nozzles N1, N3
, N9 are masked with pixel data of the second system for pixel data corresponding to the even-numbered nozzles N2, N4,.
Control is performed on the pixel data corresponding to N10 such that the first-system pixel data is masked. Thereby,
As shown in FIG. 3A, dot printing is performed in an oblique lattice arrangement in a range where printing is performed.

Next, after a sheet is fed by half the width L of all the nozzles N1 to N10, a second scan of sliding to the left is performed. At the time of the second scan, the mask circuit 19 is controlled so as to mask the pixel data opposite to that at the time of the rightward scan. As a result, in a print line in which both the first scan and the second scan have already been performed (the first line to the fifth line in FIG. 3B), dot ejection is performed in the entire print range, and the second line is ejected. The print line where only the scan was performed (from the sixth line to the
In the tenth line), dot ejection is performed in an oblique lattice pattern in the printing range. Then, the same processing is repeated, and, for example, in the third scan, dot ejection is performed on all the dots of a rectangle of 16 dots × 10 dots.

FIG. 4 is a diagram for explaining the mask processing when a defective nozzle is registered. Also in the figure, in order to simplify the explanation, ten single-color nozzles N1 to N1 are used.
0 indicates a process of printing a rectangle of 16 dots in width × 10 dots in height. In the figure, white circles indicate dots before ink ejection, and black circles indicate dots after ink ejection.

The above-mentioned mask control circuit 20, when there is a registration of a defective nozzle, performs the defective nozzle masking means 20 shown in FIG.
1 and a function as a defective nozzle replacement unit 202. More specifically, when a defective nozzle is registered in the defective nozzle registration memory 18, the mask control circuit 20 acts as a defective nozzle masking unit 201 thereafter, and FIG.
As shown in (b), the mask circuit 19 is controlled so that the pixel data corresponding to the defective nozzle N7 is masked in both the first system and the second system. Similarly, when a defective nozzle is similarly registered,
The mask control circuit 20 acts as the defective nozzle replacement means 202, and as shown in FIG. 4B, the first and second systems are used for the pixel data of the replacement nozzle N2 that scans the same print line as the defective nozzle N7. The mask circuit 19 is controlled so that any pixel data is not masked. By such control, the operation of the registered defective nozzle N7 is not forcibly performed for the dot ejection, and the replacement of the substitute nozzle N7 corresponding to the defective nozzle N7 is performed for the dot missing due to the suppression of the operation of the defective nozzle N7.
2 replaces dot ejection.

Next, the procedure of the registration process of the defective nozzle for registering the defective nozzle in the printer 1 having the above configuration and the printing process executed by the printer 1 will be described with reference to the flowcharts of FIGS.

FIG. 5 is a flowchart showing a procedure for registering a defective nozzle in the printer 1.

The registration process of the defective nozzle is performed, for example, after the user visually confirms that there is a dot where printing is not performed normally by visually observing the print result, and cleans the print head by wiping means such as a wiper blade. This is also performed when such an abnormality immediately recurs. In such a case, among the plurality of nozzles provided in the print head, there must be a nozzle that has become defective due to dust clogging or the like, and the user first specifies the defective nozzle (step S1).

The defective nozzle can be specified, for example, by performing one scan print as test print, visually finding out which nozzle is abnormal from the result of the scan print, or providing a print head. The test is performed by driving a plurality of nozzles one by one one by one in a test print called a nozzlelet pattern in which a short line of one vertical dot is drawn in a stepwise manner, and a nozzle having an abnormality is found from the pattern print. The identification of the defective nozzle is as follows.
For example, it may be configured to be automatically performed by image input by a CCD camera and image analysis processing by a CPU.

When the defective nozzle can be identified, the operation panel 1
By operating the key 3 or inputting data from the host computer 2, the printer 1 is first set to the registration mode of a defective nozzle (step S2), and then data indicating the defective nozzle (for example, the ink color to be handled and the number of the nozzle). Is input (step S3). Then, CP
The defective nozzle registration unit 112 functioned by U11 fetches the input data and writes "0" data indicating a defect in the bit area of the defective nozzle registration memory 18 corresponding to the defective nozzle (step S4). This completes the registration processing of the defective nozzle.

FIG. 6 is a flowchart showing the procedure of the printing process executed by the printer 1.

The printing process is started when an instruction to execute the printing process and pixel data indicating the print content are received from the host computer 2 via the interface 14.
The received pixel data is temporarily stored in the spool memory 16 and then written out to the band memory 17 one pixel data for one scan at a predetermined timing. In this embodiment, printing of one line is performed by sharing two nozzles in two scans. Therefore, pixel data of each print line is written to the band memory 17 twice in total as described above. It is supposed to be.

When pixel data for one scan is written to the band memory 17, the pixel data is read out by the band memory control means 111 and transferred to the printer engine 15 via the mask circuit 19 (step S1).
1).

The mask circuit 19 first performs a mask process in a normal state on the sent pixel data (step S12). That is, when scanning in the right direction, the first-system pixel data is masked for pixel data corresponding to odd-numbered nozzles, and the second-system pixel data is masked for pixel data corresponding to even-numbered nozzles. I do. On the other hand, when scanning in the left direction, the pixel data is masked so as to be reversed.

Further, when the defective nozzle is registered in the defective nozzle registration memory 18, pixel data of the remaining system which is not masked for the pixel data corresponding to the defective nozzle is also masked (step S13).

Further, when there is a registration of a defective nozzle,
The mask in the normal mode performed in step S12 is canceled for the pixel data corresponding to the substitute nozzle that scans the same line as the defective nozzle (step S14).

The mask processing in steps S12 to S14 is not performed one by one, but is performed at a time by simultaneously changing the circuit state of the mask circuit 19 under the control of the mask control circuit 20. .

Then, the pixel data masked by the mask circuit 19 is transferred to the printer engine (step S15). Based on the pixel data, the print head is driven and the carriage on which the print head is mounted is conveyed to 1.
The printing process for the scan is performed (step S16).

Thereafter, the paper is fed by half the total nozzle width (step S17), and it is determined whether or not all printing has been completed (step S18). Are repeated, and if all printing has been completed, the printing process ends.

As described above, according to the printer 1 of this embodiment, when a defective nozzle that has caused nozzle clogging is found, the defective nozzle is registered in the defective nozzle registration memory 18.
Then, the dot ejection operation is prohibited in the defective nozzle, whereby the ink is pushed out from the defective nozzle and ink is accumulated at the tip of the defective nozzle, which adversely affects the adjacent normal nozzle. Is avoided. Also, defective nozzle replacement means 2
With 02, the dot ejection that should be performed by the defective nozzle is performed by substituting with another nozzle, so that the missing of the print dot due to the defective nozzle can be avoided. Therefore, as long as the number of defective nozzles does not increase significantly, it is possible to maintain print quality that is almost the same as in the normal case. Also,
As a result, even if a defective nozzle as described above occurs, printing can be continued almost normally without replacing the print head, and the running cost of the printer 1 can be reduced.

In addition, the defective nozzle replacement means 202 performs dot ejection for the first or second system of dots that the defective nozzle has shared in the print line on which the registered defective nozzle is scanned. Since the configuration is performed by the nozzles sharing the other dots above, no extra scanning of the print head is required to replace the defective nozzle, and the printing speed can be maintained as normal.

The defective nozzle masking means 201 forcibly masks the pixel data corresponding to the registered defective nozzle among the pixel data sent to the print head side. Is a configuration that cancels the mask of the normal mode of the pixel data corresponding to the substitute nozzle that scans the same line as the registered defective nozzle, so that the operation of the defective nozzle is suppressed and the dot ejection by the substitute nozzle is replaced. It is possible to perform the control easily and at high speed.

Note that the ink jet printer of the present invention is not limited to the printer 1 of this embodiment. For example, in this embodiment, one print line is configured to be shared by two nozzles by half over two scans, but printing of one print line is performed by three or more nozzles. The present invention can be similarly applied to a configuration in which the present invention is shared.

In the above embodiment, the nozzle spacing and the vertical resolution of the print dots have been described as being equal. However, scan printing is performed so as to overlap the previous scan print so that the positions of the print dots are slightly shifted. Thus, the present invention can be similarly applied to an ink jet printer of a type that performs printing with a resolution smaller than the interval between nozzles.

Further, as an example of a method of prohibiting an ink ejection operation of a defective nozzle, a method of performing data processing such as masking pixel data of the nozzle has been described. For example, the ink supply to the nozzles may be cut off by a control valve or the like, or the ink supply to the nozzles may be cut off.

Further, the replacement of the defective nozzle by the substitute nozzle is performed by performing a scan operation for replacement processing in addition to the scan operation similar to the normal operation, and performing dot ejection that should be performed by the defective nozzle to any normal nozzle. May be performed.

The mask processing of the pixel data by the defective nozzle masking means and the cancellation of the masking processing by the defective nozzle replacement means can be performed by a hardware configuration using logic gates or the like, or can be executed by software processing of the CPU. You can do it.

The mask circuit 19 is connected to the band memory 1.
7 is provided between the printer engine 15 and the pixel data, and the mask processing is performed on the pixel data during the transfer of the pixel data from the band memory 17 to the printer engine 15. A mask circuit 19 may be provided between the means 15A and the print head driving unit 15D, and the same mask processing may be performed on the pixel data transferred between them.

In the above-described embodiment, an example in which the present invention is applied to an ink jet printer for large-size paper has been described. However, the present invention can be applied to various types of ink jet printers.

[0059]

As described above, according to the present invention,
When a defective nozzle that has caused nozzle clogging is found, the defective nozzle is registered in a defective nozzle registration unit such as a memory, and thereafter, the dot ejection operation is prohibited in the defective nozzle. In addition, it is possible to prevent the ink from being pushed out of the nozzle to form an ink pool at the tip of the nozzle and adversely affecting adjacent normal nozzles. In addition, the defective nozzle replacement means replaces the dot ejection that should be performed by the defective nozzle with another nozzle, so that it is possible to avoid the print nozzle missing due to the defective nozzle. Therefore, as long as the number of defective nozzles does not increase significantly, it is possible to maintain print quality that is almost the same as in the normal case. Then, even if a defective nozzle occurs, it is possible to continue almost normal printing without replacing the print head,
There is an effect that the running cost of the printing apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an ink jet printer suitable for applying the present invention.

FIG. 2 is a functional block diagram illustrating a functional configuration of the printer according to the embodiment.

FIGS. 3A and 3B are diagrams for explaining mask processing in a normal state where no defective nozzle is registered; FIG.
(B) is for the second scan.

FIGS. 4A and 4B are diagrams for explaining a mask process when a defective nozzle is registered, wherein FIG. 4A is for a first scan, and FIG. 4B is for a second scan.

FIG. 5 is a flowchart illustrating a procedure for registering a defective nozzle in the printer of the embodiment.

FIG. 6 is a flowchart illustrating a procedure of a printing process performed by the printer according to the embodiment.

FIG. 7 shows a process in which the clogged nozzle has an effect on the surroundings.
The result of the dot ejection is shown on the right.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer 2 Host computer 4 Network 11 CPU 12 Program ROM 13 Operation panel 14 Interface 15 Printer engine 15A Print control means 15B Media transport unit 15C Carriage transport unit 15D Print head drive unit 16 Spool memory 17 Band memory 18 Defective nozzle registration memory 19 Mask Circuit 20 Mask control circuit 111 Band memory control means 112 Defective nozzle registration means 201 Defective nozzle mask means 202 Defective nozzle replacement means

Claims (3)

[Claims] A print head provided with a plurality of nozzles for ejecting the same type of ink by dot ejection, and printing by performing dot ejection of ink while scanning the print head in a direction intersecting with a paper transport direction. In some inkjet printers, a defective nozzle registration unit that registers a defective nozzle that does not perform dot ejection among a plurality of nozzles provided in the print head; a defective nozzle mask unit that prohibits a dot ejection operation on the registered defective nozzle; An ink jet printer comprising: a defective nozzle substitution unit that substitutes another nozzle for dot ejection that should be performed by a registered defective nozzle. 2. The method according to claim 1, wherein the plurality of nozzles are arranged side by side in a direction intersecting with a scanning direction of a print head, and are formed by a plurality of scans performed while intermittently feeding the paper in one direction.
More than one nozzle scans over one print line, and
A plurality of dots on one print line are divided into a plurality of system dots, and a plurality of nozzles scanning on the same print line share and eject one of the plurality of system dots. And the defective nozzle replacement means, in a print line on which the registered defective nozzle is scanned, emits a dot ejection for a dot shared by the defective nozzle in the print line. 2. The ink jet printer according to claim 1, wherein the printing is performed by a nozzle sharing another dot. 3. The print head performs dot ejection from each nozzle according to pixel data indicating whether or not to perform dot ejection at each coordinate point of print coordinates, and a pixel of one print line sent to the print head side. Mask means capable of controlling passing and non-passing of data for each of the plurality of systems of dots, wherein a plurality of pixel data of the same print line are provided during a plurality of scans by the print head. A plurality of nozzles are assigned to a plurality of system dots on one print line by switching the system of pixel data sent to the print head side and passed by the mask means each time. The defective nozzle masking means corresponds to a registered defective nozzle among the pixel data sent to the print head side. Means for forcibly not passing the pixel data to be passed. The defective nozzle replacement means, when another nozzle scans the same print line as the print line scanned by the registered defective nozzle, the print line 3. An ink jet printer according to claim 2, wherein the pixel data of the dot which is assigned to the registered defective nozzle among the pixel data of (c) is released from the control of the mask means and passed to the print head side. .