JPH11334047A - Line type ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an imperfect image resulting from defect of a nozzle by providing a control section for forming an image with an auxiliary head when information from a nozzle head check means for a line head arranged with the auxiliary head indicates defect of a nozzle. SOLUTION: A recording sheet P is held by carrying rollers 31, 32 and carried by the roller 31. A line head 2 faces the surface PS of the recording sheet P between the rollers 31, 32 and an auxiliary head 2' of same image recording width is juxtaposed thereto. These heads 2, 2' are connected through flexible cables 4, 4', with a control board 51 having a control section. A laser nozzle check means 6 comprising a laser light source 61 for irradiating an ink drop ejected from a nozzle with a laser beam, and a light receiving element 62 receiving the laser beam is disposed on one side of the line head 2. When the beam arrives at the element 62, a detective nozzle ejecting no ink or ejecting an ink drop in curved course is specified and an image is formed using the auxiliary head 2'.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A line head having a plurality of nozzles arranged at a length corresponding to the width of a recording medium is provided. The nozzle discharges ink from the nozzles to the recording medium and moves the recording medium in a sub-scanning direction. The present invention relates to a line-type inkjet printer that forms an image on the recording medium by being conveyed.

[0002]

2. Description of the Related Art An image is formed on an ink-jet printer by moving a head in a main scanning direction while discharging small droplets of ink, which are controlled by a nozzle of the head according to an image signal, onto a recording medium. When recording is performed for one line, the recording medium is conveyed for one line in the sub-scanning direction, and a small droplet of ink is ejected again from the nozzles of the head onto the recording medium, and the image is recorded for one line. By repeating this, an image is formed on the recording medium.

[0003] Another configuration is disclosed in Japanese Patent Laid-Open No. 62-161547.
As described in Japanese Patent Application Laid-Open Publication No. H10-264, there is a fixed line head in which ink nozzles of a head are arranged at a substantially equal pitch at a length substantially equal to a maximum recording width of a recording medium.

According to this configuration, it is not necessary to move the head in the main scanning direction, and the image can be formed only by conveying the recording medium perpendicular to the main scanning direction in the sub scanning direction.
High-speed image formation can be performed.

[0005]

As described above, in an ink jet printer having a fixed line head in which the head does not move in the main scanning direction, for example, the nozzles are clogged with dust and the like, and ink cannot be ejected (hereinafter, ink insufficiency). In some cases, the periphery of the discharge port of the nozzle is wet with ink, the droplet of the discharged ink is pulled toward it, and ink is not recorded at a target position on the recording medium (hereinafter, ink landing bending). In other words, when there is a nozzle defect, an image defect occurs in an image formed on a recording medium.

More specifically, when ink is not ejected, a vertical streak in the sub-scanning direction is formed on the recording medium. In addition, in the case of the ink landing bend, as shown in FIG. 12, the discharge ink C from the nozzle c causes the ink landing bend due to the wetting of the ink around the nozzle periphery, and the ink is discharged when the CC line is formed. The CC line formed by the dots of the ink approached the BB line formed in the same way, and at the same time, was further away from the DD line, and the pitch between the lines was different from other AA lines, EE lines, etc. Vertical stripes in the sub-scanning direction are formed as an image formed by the points (1) and (2).

When an image defect due to such a nozzle defect occurs, the image defect cannot be eliminated unless the head is replaced. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide a line type ink jet printer that can improve image defects due to nozzle defects.

It is a second object of the present invention to provide a line type ink jet printer which can reduce the frequency of replacing a line head, reduce replacement cost, and improve reliability.

[0009]

Means for Solving the Problems A first method for solving the above problems is described below.
The present invention has a line head in which a plurality of nozzles are arranged at a length corresponding to the width of a recording medium, ejects ink from the nozzles to the recording medium, and conveys the recording medium in a sub-scanning direction. A line-type inkjet printer that forms an image on the recording medium by using a nozzle check unit that detects a defect in a nozzle of the line head, an auxiliary head that is provided in parallel with the line head, and a nozzle check unit. And a control unit that takes in the above information and forms an image using the auxiliary head when there is a defect in the nozzle of the line head.

If the nozzle of the line head is defective,
By performing image formation using the auxiliary head provided in parallel with the line head, image defects due to nozzle defects can be improved.

Here, as an example of the auxiliary head, there is an auxiliary head having an image recording width equal to or larger than the image recording width of the line head. In this case, an image defect can be improved by using an auxiliary head instead of the line head, or by driving a nozzle of the auxiliary head corresponding to a defective nozzle of the line head.

In particular, when the nozzles of the auxiliary head are driven in response to the defective nozzles of the line head, the frequency of replacement of the line head is reduced, the replacement cost is reduced, and the reliability can be improved.

As another example of the auxiliary head, there is an auxiliary head that can move in the line direction of the line head. In this case, the auxiliary head is moved so that the nozzle of the auxiliary head is located at a position corresponding to the defective nozzle of the line head, and image formation is performed by using the nozzle of the auxiliary head instead of the defective nozzle of the line head. Image defects can be improved, the frequency of line head replacement can be reduced, replacement costs can be reduced, and reliability can be improved.

According to a second aspect of the present invention, there is provided a line head having a plurality of nozzles arranged at a length corresponding to the width of the recording medium, and ejecting ink from the nozzles to the recording medium and sub-scanning the recording medium. A line-type inkjet printer that forms an image on the recording medium by transporting the line head in a direction, a nozzle check unit that detects a defect of a nozzle of the line head, and a driving unit that drives the line head in a line direction. When the information from the nozzle check unit is taken in and the nozzle of the line head has a defect, a plurality of image formations are performed on the same recording medium, and at least one of the plurality of image formations is performed. In the image forming, the line head is moved in the line direction of the line head using the driving unit, and the defective portion is moved to another normal nozzle. A line type inkjet printer and performs image formation by using.

At least one of the plural times of image formation performed on the same recording medium is performed by moving the line head in the line direction of the line head and using another normal nozzle to form a defective portion. Image formation can improve image defects due to nozzle defects.

Further, the frequency of replacement of the line head is reduced, the replacement cost is reduced, and the reliability can be improved. Here, from the viewpoint of simplification of the mechanism, the recording medium is provided on a circumferential surface of a drum rotatable around an axis, and the shaft of the drum is rotationally driven, as in the invention according to claim 5. It is desirable to convey the recording medium in the sub-scanning direction.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to the drawings. (1) First Embodiment (Corresponding to Claims 1 and 2) First, the overall configuration of a line-type inkjet printer according to this embodiment will be described with reference to FIG.

In the line type ink jet printer 1, a recording paper P as a recording medium is sandwiched between a pair of transport rollers 31 and 32 of a transport mechanism 3, and is further rotated by a transport roller pair 31 driven by a transport motor 33 in FIG. It is designed to be transported in the Y direction.

The line head 2 and the auxiliary head 2 'are arranged side by side so as to face the surface PS of the recording paper P between the pair of transport rollers 31,32. The auxiliary head 2 ′ is a line head having the same image recording width as the line head 2.

The line head 2 and the auxiliary head 2 'are connected to flexible cables (hereinafter referred to as FPC) 4,
A control board 51 on which a control unit described later is provided via 4 '
It is connected to the.

Next, the line head will be described with reference to FIG. The structure of the auxiliary head 2 ′ is the same as that of the line head 2, and redundant description will be omitted. As shown in the figure,
The line head 2 can be divided into a base substrate 24 and a lid substrate 25. The piezoelectric element 22 is provided on the base substrate 24.
Are arranged in a line, and each piezoelectric element 22 is connected to the FPC 4 via a circuit conductor 23.

On the lid substrate 25, nozzles 21 forming pairs with the respective piezoelectric elements 22 are formed in a line at the same pitch, and each nozzle 21 is connected to a thin tube provided with a place for receiving the ink discharge pressure by the piezoelectric elements 22. , This thin tube is the lid substrate 25
Are connected to the ink tank provided in the printer.

On one side of the line head 2,
A laser nozzle check means 6 comprising a laser light source 61 for irradiating a laser beam to ink droplets discharged from the nozzle 21 and a light receiving element 62 for receiving the laser beam is provided.

Next, the electrical connection of the above configuration will be described with reference to FIG. In the figure, reference numeral 5 denotes a control unit which is provided on the control board 51 and takes in an image signal and drives the line head 2, the auxiliary head 2 ', the transport mechanism 3, and the laser nozzle check means 6.

Next, the operation of the above configuration will be described with reference to FIG. First, the presence / absence of a nozzle defect in the line head 2 is checked using a laser nozzle check unit (step 1).

More specifically, the plurality of nozzles 21 of the line head 2 are sequentially driven one by one while the laser beam is emitted from the laser light source 61. If ink is not ejected or the ink is bent, the light receiving element 62
When the laser beam reaches the nozzle, a defective nozzle can be specified.

Here, when there is no defective nozzle,
The control unit 5 conveys the recording paper P at a constant speed by the conveyance mechanism 3, drives the piezoelectric element 22 according to the image signal, and simultaneously ejects ink droplets one line at a time from the nozzle 21 of the line head 2. Then, an image is formed on the recording paper P (steps 2 and 3).

If there is a defective nozzle in step 1, an image is formed using the auxiliary head 2 '(steps 2, 4). According to the above configuration, the nozzle 2 of the line head 2
If there is a defect in 1, an image defect due to a defect in the nozzle 21 can be improved by forming an image using the auxiliary head 2 ′ arranged in parallel with the line head 2.

The present invention is not limited to the above embodiment. In the above-described embodiment, the description has been made of the inkjet using the piezoelectric element 22 as an element for discharging ink.
A bubble burst type inkjet may be used.

(2) Second Embodiment (corresponding to Claims 1 and 2) Next, a second embodiment of the present invention will be described with reference to FIG.

The configuration of this embodiment is the same as that of the first embodiment, and the operation is different. Therefore, only the operation will be described, and the description of the configuration will be omitted. As shown in FIG. 5, first, the presence / absence of a nozzle defect of the line head 2 is checked using a laser nozzle check unit (step 1).

Here, when there is no defective nozzle,
The control unit 5 conveys the recording paper P at a constant speed by the conveyance mechanism 3, drives the piezoelectric element 22 according to the image signal, and simultaneously ejects ink droplets one line at a time from the nozzle 21 of the line head 2. Then, an image is formed on the recording paper P (steps 2 and 3).

If there is a defective nozzle in step 1, the line head 2 is used for a part other than the defective nozzle, and the auxiliary head 2 'is used instead for the defective nozzle.
Is used to form an image (steps 2 and 4).

According to the above configuration, when the nozzle 21 of the line head 2 has a defect, an image is formed by using the auxiliary head 2 ′ arranged in parallel with the line head 2, so that an image defect due to the defect of the nozzle 21 is formed. Can be improved.

Further, the frequency of replacement of the line head 2 is reduced, the replacement cost is reduced, and the reliability can be improved. (3) Third Embodiment (Corresponding to Claims 1 and 3) First, the overall configuration of a line-type inkjet printer according to this embodiment will be described with reference to FIG. The same parts as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and
Their description is omitted.

The first and second guides 100 and 101 are arranged side by side along the line direction of the line head 2.
Each of the first and second guides 100 and 101 has at least one nozzle, and the auxiliary head 1 facing the surface PS of the recording paper P between the pair of transport rollers 31 and 32.
A slider 105 provided with 10 is movably engaged.

The slider (auxiliary head) 105
(110) denotes pulleys 121 and 122 and pulleys 121 and 1
And a motor 127 that drives the pulley 121.
The line head 2 is driven in the line direction by an auxiliary head moving mechanism 120 composed of

Next, the electrical connection of the above configuration will be described with reference to FIG. In the figure, reference numeral 5 denotes a control unit which is provided on the control board 51 and takes in an image signal and drives the line head 2, the auxiliary head 110, the transport mechanism 3, the auxiliary head moving mechanism 120, and the laser nozzle check means 6.

Next, the operation of the above configuration will be described with reference to FIG. First, the presence / absence of a nozzle defect in the line head 2 is checked using a laser nozzle check unit (step 1).

Here, when there is no defective nozzle,
The control unit 5 conveys the recording paper P at a constant speed by the conveyance mechanism 3, drives the piezoelectric element 22 according to the image signal, and simultaneously ejects ink droplets one line at a time from the nozzle 21 of the line head 2. Then, an image is formed on the recording paper P (steps 2 and 3).

If there is a defective nozzle in step 1, the auxiliary head moving mechanism 120 is driven to move the auxiliary head 110 to a position corresponding to the defective nozzle (steps 2, 4).

Then, an image is formed on the portion other than the defective nozzle using the line head 2 and on the defective nozzle portion using the auxiliary head 110 instead (step 5). According to the above configuration, when the nozzle 21 of the line head 2 has a defect, an image defect due to the defect of the nozzle 21 can be improved by forming an image using the auxiliary head 110 in the line head 2.

Further, the frequency of replacement of the line head 2 is reduced, the replacement cost is reduced, and the reliability can be improved. (4) Fourth Embodiment (Corresponding to Claims 4 and 5) First, the overall configuration of a line-type inkjet printer according to this embodiment will be described with reference to FIG. The same parts as those in FIG. 1 showing the first embodiment are denoted by the same reference numerals, and
Their description is omitted.

The transport mechanism 400 of the present embodiment comprises a drum 403 on which recording paper P is provided on a circumference, and a drum drive motor 401 for rotating the drum 403 in the axial direction.
It consists of

The line head 2 has a guide 411 provided in the line direction of the line head 2, a slider 413 provided with the line head 2 and movably engaged with the guide 411, and a guide 411. A line head moving mechanism 450 including a screw rod 423 provided, a screw rod driving motor 421 for driving the screw rod 423 to rotate, and a nut member 415 attached to the side surface of the slider 413 and screwed to the screw rod 423. The line head 2 is movable in the line direction of the line head 2.

Next, the electrical connection of the above configuration will be described with reference to FIG. In the figure, reference numeral 5 denotes a control unit which receives an image signal and drives the line head 2, the transport mechanism 400, the line head moving mechanism 450, and the laser nozzle check unit 6.

Next, the operation of the above configuration will be described with reference to FIG. First, the presence / absence of a nozzle defect of the line head 2 is checked by using the laser nozzle check means (step
1).

Here, when there is no defective nozzle,
The control unit 5 drives the recording paper P to rotate at a constant angular velocity by the transport mechanism 400, drives the piezoelectric element 22 according to the image signal, and simultaneously ejects ink droplets one line at a time from the nozzle 21 of the line head 2. The recording medium is ejected to form an image on the recording paper P (steps 2 and 3).

If there is a defective nozzle in step 1, image formation is performed a plurality of times. That is, the control unit 5
The recording paper P is driven to rotate at a constant angular velocity by the transport mechanism 400, the piezoelectric element 22 is driven in accordance with the image signal, and ink droplets are ejected from the nozzles 21 of the line head 2 one line at a time. Perform the first image formation on P
(Steps 2, 4).

Next, the control section 5 drives the line head moving mechanism 450 to move the line head 2 in the line direction (step 5). Then, the control unit 5 controls the transport mechanism 4
00, the recording paper P is rotationally driven at a constant angular velocity, the piezoelectric element 22 is driven in accordance with the image signal, and the ink droplets are ejected from the nozzles 21 of the line head 2 one line at a time. Perform the second image formation (step
6).

According to the above-described configuration, when the nozzle 21 of the line head 2 has a defect, of the plurality of times (two times in this embodiment) of the image formation, the second By moving the line head 2 in the line direction and forming an image of the defective portion using another normal nozzle 21, an image defect due to a defect of the nozzle 21 can be improved.

Further, the frequency of replacement of the line head 2 is reduced, the replacement cost is reduced, and the reliability can be improved. Further, the present embodiment can be applied to the line type ink jet printer as in the first to third embodiments, but if one image formation is completed, the recording is performed manually or by a mechanism. It is necessary to set the paper P again.

On the other hand, in the line type ink jet printer according to the present embodiment, the recording paper P is provided on the circumferential surface of the drum 403, and the drum 403 is driven to rotate to carry the paper in the sub-scanning direction. .

With this configuration, it is not necessary to reset the recording paper P when performing image formation a plurality of times, as compared with the line type ink jet printer of the first to third embodiments. , The mechanism becomes simple.

The present invention is not limited to the above embodiment. In the above embodiment, a total of two image formations are performed. However, three or more image formations are performed, and at least one of the image formations is performed by moving the line head 2 in the line direction. The effects of the embodiment can be obtained.

[0056]

As described above, according to the first aspect, when a nozzle of a line head has a defect, an image is formed by using an auxiliary head provided in parallel with the line head, whereby the nozzle of the line head is formed. Image defects due to defects can be improved.

Here, when an auxiliary head having an image recording width larger than the image recording width of the line head is used, an auxiliary head may be used instead of the line head, or a defective nozzle of the line head may be used. By driving the nozzles of the auxiliary head corresponding to the above, image defects can be improved.

In particular, when the nozzles of the auxiliary head are driven corresponding to the defective nozzles of the line head, the frequency of replacement of the line head is reduced, the replacement cost is reduced, and the reliability can be improved.

When an auxiliary head that can move in the line direction of the line head is used, the auxiliary head is moved so that the nozzle of the auxiliary head is located at a position corresponding to the defective nozzle of the line head. By performing image formation using the nozzles of the auxiliary head instead of the defective nozzles of the head, image defects can be improved,
According to the second aspect of the present invention, in which the frequency of replacement of the line head is reduced, the replacement cost is reduced, and the reliability is improved, at least one of the plurality of image formations performed on the same recording medium is performed. In the image formation at one time, the line head is moved in the line direction of the line head, and the defective portion is formed using another normal nozzle, whereby an image defect due to a nozzle defect can be improved.

Further, the frequency of replacement of the line head is reduced, the replacement cost is reduced, and the reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an overall configuration of a line-type inkjet printer according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of a line head shown in FIG.

FIG. 3 is a diagram illustrating electrical connection of the line-type inkjet printer according to the first embodiment.

FIG. 4 is a flowchart illustrating an operation of the line-type inkjet printer according to the first embodiment.

FIG. 5 is a flowchart illustrating an operation of the line-type inkjet printer according to the second embodiment.

FIG. 6 is a diagram illustrating an overall configuration of a line-type inkjet printer according to a third embodiment.

FIG. 7 is a diagram illustrating electrical connection of a line-type inkjet printer according to a third embodiment.

FIG. 8 is a flowchart illustrating the operation of a line-type inkjet printer according to a third embodiment.

FIG. 9 is a diagram illustrating an overall configuration of a line-type inkjet printer according to a fourth embodiment.

FIG. 10 is a diagram illustrating electrical connection of a line-type inkjet printer according to a fourth embodiment.

FIG. 11 is a flowchart illustrating the operation of a line-type inkjet printer according to a fourth embodiment.

FIG. 12 is an enlarged view of a dot image formed on a recording medium by ink ejected from nozzles of a line head.

[Explanation of symbols]

 2 line head 2 'auxiliary head 6 laser nozzle check means (nozzle check means) 5 control unit

Claims (5)

[Claims] A line head having a plurality of nozzles arranged at a length corresponding to a width of a recording medium, for discharging ink from the nozzles to the recording medium and conveying the recording medium in a sub-scanning direction. A line-type inkjet printer that forms an image on the recording medium by performing a nozzle check unit that detects a defect of a nozzle of the line head; an auxiliary head provided in parallel with the line head; and the nozzle check unit. And a control unit that takes in information from the control unit and forms an image using the auxiliary head when there is a defect in the nozzle of the line head. 2. The line type ink jet printer according to claim 1, wherein the auxiliary head has an image recording width equal to or larger than the image recording width of the line head. 3. The apparatus according to claim 1, wherein the auxiliary head is movable in a line direction of the line head.
The line-type inkjet printer as described in the above. 4. A line head having a plurality of nozzles arranged at a length corresponding to a width of a recording medium, and ejecting ink from the nozzles to the recording medium and conveying the recording medium in a sub-scanning direction. A line-type inkjet printer that forms an image on the recording medium by performing a nozzle check that detects a nozzle defect of the line head; a driving unit that drives the line head in a line direction; When the information from the means is taken in and the nozzle of the line head has a defect, the image is formed a plurality of times on the same recording medium, and at least one of the plurality of times of the image formation is scanned by the method described above. The line head is moved in the line direction of the line head using a driving unit, and a defective portion is formed using another normal nozzle to form an image. A line-type ink jet printer. 5. The recording medium is provided on a circumferential surface of a drum rotatable about an axis, and the shaft of the drum is rotationally driven to convey the recording medium in a sub-scanning direction. Item 5. A line type ink jet printer according to item 4.