JP2000006389A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image of a high quality by arranging a plurality of line heads for discharging ink liquid droplets of the same color to a recording medium. SOLUTION: A controller conveys a recording sheet P at a constant speed via a conveying mechanism 3, drives piezoelectric elements of respective line heads 121 to 124 according to an image signal, and discharges ink liquid droplets from nozzles 131 to 134 to form an image on the sheet P. With the thus constitution, four line heads 121 to 124 having a pitch P of 180 dpi of the nozzles 131 to 134 are respectively deviated at 720 (180×4) dpi and disposed so that a resolution of the formed image becomes 720 dpi of a high image quality. Even if a nozzle fault such as no discharge of an ink, an ink injecting bend or the like exists in any of the heads 121 to 124 so that a noise occurs at the image, the noise is alleviated by forming the image via other line head, thereby obtaining a high image quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink jet printer, and more particularly, to an ink jet printer suitable for high-speed image formation and high-resolution image formation.

[0002]

2. Description of the Related Art FIG. 8 is a view showing an example of a conventional line type ink jet printer having a line head.

In the line type ink jet printer 1, a recording paper P is nipped by a pair of conveying rollers 31 and 32 of a conveying mechanism 3 and further conveyed in a Y direction in FIG. It is supposed to be.

[0006] A line head 2 is provided between the pair of transport rollers 31 and 32 so as to face the surface PS of the recording paper P as a recording medium. The line head 2 is connected via a flexible cable (hereinafter referred to as FPC) 4 to a control board 51 provided with a control unit.

Next, the line head will be described with reference to FIG. As shown in the figure, the line head 2 is
4 and a lid substrate 25. The piezoelectric elements 22 are arranged in a row on the base substrate 24, and each of the piezoelectric elements 22 is connected to the FPC 4 via a circuit conductor 23.

[0006] 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.

Next, the operation of the above configuration will be described. The control unit on the control board 51 transports the recording paper P at a constant speed by the transport mechanism 3, drives the piezoelectric element 22 according to the image signal, and collects the ink from the nozzle 21 of the line head 2 one line at a time. The droplet is ejected to form an image on the recording paper P.

[0008]

The line-type ink jet printer having the above structure does not need to move the head in the main scanning direction, as compared with a so-called shuttle type ink jet printer in which the head is driven in the main scanning direction. Since image formation can be performed only by conveying the recording paper P orthogonally in the sub-scanning direction, high-speed image formation can be performed.

However, in a line type ink jet printer having only one such line head 2, for example, dust cannot be ejected due to clogging of the nozzle 21 of the line head 2 (hereinafter referred to as ink non-ejection). ), Or when the peripheral edge of the nozzle 21 is wet with ink, the ejected ink droplet is pulled toward it, and the ink is not recorded at the target position on the recording medium (hereinafter referred to as ink landing bending). If the nozzle 21 has a defect, there is a problem that an image defect (noise) occurs in an image formed on the recording paper P.

Each of the nozzles 21
Therefore, since the piezoelectric element 22, the ink tank, the thin tube, and the like must be provided correspondingly, there is a limit in making the pitch of the nozzle 21 fine, and there is also a problem that a high-resolution image cannot be obtained.

In this case, by disposing the line head 2 at an angle to the main scanning direction, the pitch of the nozzles in the main scanning direction is narrowed, and the resolution can be increased.
Another problem occurs in that the distance for moving the recording paper P in the sub-scanning direction increases, and the image forming speed decreases.

In addition, regardless of the type of ink jet head using a piezoelectric element, high voltage type, bubble burst type, etc.
The specific driving frequency is determined. Therefore, there is a problem that the image forming speed is also determined by the driving frequency of the head.

Further, in the case of manufacturing a line head, at present, it is costly to manufacture a long line head of 5 inches or more. Therefore, a single line head is manufactured by connecting a plurality of small-width line heads. ing.

On the other hand, in the line head, the droplet discharge characteristics of the nozzles at both ends which are affected only by the nozzles on one side, and the droplet discharge characteristics of the nozzles other than both ends which are affected by the nozzles on both sides. Is different.

Therefore, in a line head manufactured by connecting narrow line heads, there is a problem that nozzles having different droplet discharge characteristics are mixed in one line, and an image defect occurs on the recording paper P.

In the case where line heads having a small width are connected to each other, it is difficult to accurately adjust the nozzle pitch at the joints. This also causes a problem that an image defect occurs on the recording paper P.

The present invention has been made in view of the above problems, and a first object of the present invention is to provide an ink jet printer capable of forming a high quality image. A second object is to provide an ink jet printer capable of forming images at high speed.

[0018]

According to a first aspect of the present invention, there is provided an ink jet printer comprising a plurality of line heads for discharging ink droplets of the same color onto a recording medium. is there.

By providing a plurality of line heads for ejecting ink droplets of the same color to a recording medium, it is possible to form high-quality images and high-speed images. According to a second aspect of the present invention, in the first aspect, a nozzle of another line head is located between adjacent nozzles of one of the plurality of heads in the main scanning direction. An ink jet printer characterized in that:

In the main scanning direction, by arranging the nozzles of another line head between adjacent nozzles of one of the plurality of heads, the resolution in the main scanning direction is increased. High quality image formation is possible.

Further, even if any one of the plurality of line heads has a nozzle defect such as a non-ejection of ink or a bent ink landing, noise may occur in an image.
Noise is reduced by image formation by other line heads,
High image quality.

As an example, when the pitch of the nozzles of each line head in the main scanning direction is P (dpi) and the number of line heads is N, the nozzles of each line head are P / N (dpi) in the main scanning direction. By displacing the images, the resolution of the formed image becomes P × N (dpi), the resolution increases, and a high-quality image can be formed.

According to a third aspect of the present invention, there is provided an ink jet printer according to the first or second aspect, wherein the plurality of line heads are arranged in a direction crossing a main scanning direction.

By arranging a plurality of line heads in a direction intersecting the main scanning direction, the pitch of the nozzles in the main scanning direction is narrowed, the resolution is increased, and a high quality image can be formed.

Further, by providing a plurality of line heads, the distance for moving the recording medium in the sub-scanning direction is reduced, and the image forming speed is not reduced. According to a fourth aspect of the invention, there is provided an ink jet printer according to the first aspect, wherein each nozzle of the plurality of line heads is located at the same position in the main scanning direction.

Since the nozzles of a plurality of line heads are located at the same position in the main scanning direction, a plurality of line images can be formed at the same time, so that a high-speed image can be formed. In addition, the relative movement of the recording medium and the line head in the sub-scanning direction is such that the band images obtained by a single image formation by a plurality of line heads overlap each other, so that the ink in one line head is Noise due to non-ejection of ink and bending of ink landing,
High quality image formation is possible.

Further, when each line head is manufactured by joining small line heads, the joint of the small line heads of each line head is individually shifted in the main scanning direction to connect the small line heads. It is possible to prevent image defects caused by the alignment.

According to a fifth aspect of the present invention, in the first aspect of the present invention, a plurality of line head groups each including a plurality of line heads having nozzles located at the same position in the main scanning direction are provided. An ink jet printer wherein nozzles of another line head group are located between adjacent nozzles of one line head group among a plurality of line head groups.

In the line head group, by setting the nozzles of each line head at the same position in the main scanning direction, a plurality of line images can be formed at the same time, so that high-speed image formation can be performed.

Further, the relative movement between the recording medium and the line head group in the sub-scanning direction is such that the band images obtained by one image formation by the line head group are overlapped, so that one line is formed. Noise due to non-ejection of ink in the head and bending due to landing of ink is reduced, and a high-quality image can be formed.

In the case where each line head is manufactured by joining small line heads, joining the small line heads by shifting the joints of the small line heads individually in the main scanning direction. , It is possible to prevent image defects caused by the above.

Further, by arranging the nozzles of another line head group between adjacent nozzles of one of the plurality of line head groups, the resolution in the main scanning direction is increased. High quality image formation is possible.

Further, even if any one of the plurality of line heads has a nozzle defect such as non-ejection of ink or a bent ink landing, noise may occur in an image.
Noise is reduced by image formation by other line heads,
High image quality.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. (First Embodiment) An overall configuration of an ink jet printer according to a first embodiment will be described with reference to FIG. still,
8 and 9 showing the conventional example are denoted by the same reference numerals, and their description is omitted.

In the figure, first to fourth line heads 121, 122, 12 are stacked between a pair of conveying rollers 31, 32 so as to face a surface PS of a recording paper P as a recording medium.
3,124 are provided. These first to fourth line heads 121, 122, 123, and 124 eject ink droplets of the same color, and their individual structures are the same as those of the line head 2 described in the conventional example.

The first to fourth line heads 1 will be described with reference to FIG.
The nozzle-side surfaces 21, 122, 123, and 124 will be described. The first to fourth line heads 121, 122, 123,
Reference numeral 124 denotes a plurality of nozzles 131, 132, 133, and 134 having a pitch (P) of 180 dpi (dot per inch) in the main scanning direction.
Are formed.

The first to fourth line heads 121, 122,
Reference numerals 123 and 124 are arranged with a shift of 720 dpi in the main scanning direction. That is, the second to fourth line heads 12
One nozzle 132 ', 133', 1 of 2,123,124
Reference numeral 34 'is located between adjacent nozzles 131' and 131 "of the first line head 121.

Next, the operation of the above configuration will be described. The control unit transports the recording paper P at a constant speed by the transport mechanism 3,
Each line head 121, 122, 12 according to the image signal
3,124 piezoelectric elements 22 are driven, and each line head 1
21,122,123,124 nozzles 131,132,1
Ink droplets are ejected from 33 and 134 to form an image on the recording paper P.

According to the ink jet printer having the above configuration, the pitch (P) of the nozzles 131, 132, 133, 134 is
Four line heads 121, 122, 123, 1 of 180 dpi
By arranging the 24 pixels at a displacement of 720 (180 × 4) dpi, the resolution of the formed image becomes 720 dpi, and the image quality is high.

Further, a plurality of line heads 121, 122,
If any one of the line heads 123 and 124 has a nozzle defect such as non-ejection of ink or bending of ink landing, and noise occurs in the image, noise is reduced by image formation by another line head. High image quality.

The present invention is not limited to the above embodiment. In the above-described embodiment, an ink jet using the piezoelectric element 22 as an element for ejecting ink has been described. Alternatively, a high voltage ink jet or a bubble burst ink jet may be used.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. The difference between this embodiment and the first embodiment is that the first to fourth heads 1
In the first embodiment, the nozzles 131, 132, 133, and 134 of the line heads 121, 122, 123, and 124 are arranged along the main scanning direction in the first embodiment. The embodiment is different from the first embodiment in that it is provided so as to intersect with the main scanning direction.

According to the above configuration, in addition to the effects of the first embodiment, each line head 121, 1 in the main scanning direction is provided.
22,123,124 nozzles 131,132,133,1
34, the pitch is narrowed, the resolution is increased, and a high quality image can be formed.

Further, a plurality of line heads 121, 122,
By providing 123 and 124, the distance for moving the recording medium P in the sub-scanning direction is also reduced, and the image forming speed is not reduced.

(Third Embodiment) An overall configuration of an ink jet printer according to a third embodiment will be described with reference to FIG. 8 and 9 showing the conventional example are denoted by the same reference numerals, and the description thereof will be omitted.

In the figure, first to third line heads 221, 222, 22 are stacked between a pair of conveying rollers 31, 32 so as to face a surface PS of a recording sheet P as a recording medium.
3 are provided. These first to sixth line heads 221, 222, 223, 224, 225, and 226 eject ink droplets of the same color, and their individual structures are the same as those of the line head 2 described in the conventional example. .

Next, the nozzle-side surfaces of the first to third line heads 221, 222, 223 will be described with reference to FIG.
In the first to third line heads 221, 222, 223,
A plurality of nozzles 231, 232 having the same pitch in the main scanning direction,
233 are formed.

The first to third line heads 22
1, 222, 223 are the respective nozzles 231, 232, 2
33 are arranged at the same position in the main scanning direction. Next, the operation of the above configuration will be described. The controller transports the recording paper P at a constant speed by the transport mechanism 3.

The first line head 22 according to the image signal
The first piezoelectric element 22 is driven, and the first line head 221 is driven.
Ink droplets are ejected from the nozzle 231 of the recording paper P
First, an image for one line in the main scanning direction is formed.

At the same time, the second line head 222 is used to form an image of a line next to the line image formed by the first line head 221. Further, an image of a line next to the line image formed by the second line head 222 is formed by using the third line head 223.

According to the ink jet printer having the above structure, a plurality of line images can be simultaneously formed, so that high-speed image formation can be performed. (Fourth Embodiment) A fourth embodiment will be described with reference to FIG. FIG. 6 is a configuration diagram on the nozzle side of a line head according to a fourth embodiment of the present invention. The same parts as those in FIG. 5 showing the third embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the first line heads 221 are line heads 221a, 221b, 22
1c,... Are connected. The second line head 222 is a small line head 222a, 2
22b, 222c, and so on.

The third line head 222 is manufactured by connecting small-width line heads 223a, 223b, 223c,... And each line head 22
1,222,223 small-width line heads 221a, 221
1b, 221c, ..., 222a, 222b, 222c, ...
.., 223a, 223b, 223c,... Are individually shifted in the main scanning direction.

With such a configuration, in addition to the effect of the third embodiment, there is a problem of image defects caused by connecting small-width line heads, that is, different droplet ejections in one line. Mixed nozzles with characteristic nozzles
It is possible to solve the problem that an image defect occurs in P and the problem that the nozzle pitch does not match at the joint.

(Fifth Embodiment) A fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a configuration diagram on the nozzle side of a line head according to a fifth embodiment of the present invention.

In the figure, reference numeral 415 denotes nozzles 413, 41
Line head 4 whose position is at the same position in the main scanning direction
This is a first line head group consisting of 11,412. A second line head group 425 includes line heads 421 and 422 in which the positions of the nozzles 423 and 424 are at the same position in the main scanning direction.

Reference numeral 435 denotes line heads 431 and 432 in which the positions of the nozzles 433 and 434 are the same in the main scanning direction.
Is a third line head group consisting of: These first to third line head groups 415, 425, 43
5 nozzles 413, 414, 423, 424, 433, 4
Numerals 34 are shifted from each other by a predetermined pitch in the main scanning direction.

That is, the nozzles of the other line head groups are arranged between adjacent nozzles of one of the first to third line head groups 415, 425, and 435. I have.

According to such a configuration, in each line head group 415, 425, 435, the nozzles of each line head are located at the same position in the main scanning direction, so that a plurality of line images can be simultaneously displayed. Can be formed,
High-speed image formation is possible.

The recording paper P and the line head group 4
By making the relative movement in the sub-scanning direction with respect to 15, 425, 435 such that the band images obtained by one image formation by the plurality of line head groups 415, 425, 435 overlap, one movement is achieved. Noise due to non-ejection of ink and bending of ink landing in the line head group is reduced, and a high-quality image can be formed.

Line head groups 415, 425, 43
5 line heads 411, 412, 421, 422, 43
In the case where 1,432 are manufactured by joining small line heads, each line head 411,412,42
By shifting the joints of the small-width line heads of 1,422,431,432 individually in the main scanning direction, it is possible to prevent an image defect caused by joining the small-width line heads.

Further, the line head groups 415 and 42
By arranging the nozzles of another line head group between the adjacent nozzles of one of the 5,435 line head groups, the resolution in the main scanning direction is increased, and a high-quality image can be formed. .

The line heads 411, 412, 42
If one of the line heads 1, 422, 431, and 432 has a nozzle defect such as non-ejection of ink or a bent ink landing, and noise occurs in the image, the noise is not generated by image formation by another line head. Is reduced, and high image quality is obtained.

[0064]

As described above, according to the first aspect of the present invention, by providing a plurality of line heads for ejecting ink droplets of the same color to a recording medium, it is possible to form a high-quality image. High-speed image formation can be performed.

According to the second aspect of the present invention, in the main scanning direction, nozzles of another line head are located between nozzles adjacent to one line head of the plurality of heads. Accordingly, the resolution in the main scanning direction is increased, and a high-quality image can be formed.

Even if any one of the plurality of line heads has a nozzle defect such as non-ejection of ink or a bent ink landing, noise may occur in an image.
Noise is reduced by image formation by other line heads,
High image quality.

According to the third aspect of the present invention, by arranging a plurality of line heads in a direction intersecting the main scanning direction, the pitch of the nozzles in the main scanning direction is narrowed, the resolution is increased, and high image quality is achieved. An image can be formed.

Further, by providing a plurality of line heads, the distance for moving the recording medium in the sub-scanning direction is reduced, and the image forming speed is not reduced. According to the fourth aspect of the invention, since the nozzles of the plurality of line heads are located at the same position in the main scanning direction, a plurality of line images can be formed simultaneously, so that high-speed image formation can be performed.

Further, the relative movement of the recording medium and the line head in the sub-scanning direction is such that the band images obtained by one image formation by a plurality of line heads are overlapped, so that one line head is formed. Noise due to non-ejection of ink and bending of ink landing is reduced, and a high-quality image can be formed.

Further, when each line head is manufactured by joining small line heads, the joints of the small line heads of each line head are individually shifted in the main scanning direction to connect the small line heads. It is possible to prevent image defects caused by the alignment.

According to the fifth aspect of the present invention, in the line head group, since the nozzles of each line head are located at the same position in the main scanning direction, a plurality of line images can be formed simultaneously. High-speed image formation is possible.

Further, the relative movement between the recording medium and the line head group in the sub-scanning direction is such that the band images obtained by one image formation by the line head group are overlapped, so that one line is formed. Noise due to non-ejection of ink in the head and bending due to landing of ink is reduced, and a high-quality image can be formed.

In the case where each line head is manufactured by joining small line heads, the joints of the small line heads are shifted in the main scanning direction individually to join the small line heads. , It is possible to prevent image defects caused by the above.

Further, by arranging the nozzles of another line head group between adjacent nozzles of one of the plurality of line head groups, the resolution in the main scanning direction is increased. High quality image formation is possible.

Further, even if any one of the plurality of line heads has a nozzle defect such as non-ejection of ink or a bent ink landing, and noise occurs in an image,
Noise is reduced by image formation by other line heads,
High image quality.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram illustrating nozzle-side surfaces of first to fourth line heads in FIG.

FIG. 3 is a configuration diagram of an inventive portion of a second embodiment.

FIG. 4 is a diagram illustrating an overall configuration of an inkjet printer according to a third embodiment.

FIG. 5 is a configuration diagram illustrating a nozzle-side surface of first to third line heads in FIG. 4;

FIG. 6 is a configuration diagram on the nozzle side of a line head according to a fourth embodiment.

FIG. 7 is a configuration diagram on the nozzle side of a line head according to a fifth embodiment.

FIG. 8 is a diagram illustrating an example of an ink jet printer having a conventional line head.

FIG. 9 is an exploded perspective view of the line head in FIG.

[Explanation of symbols]

 121 first line head 122 second line head 123 third line head 124 fourth line head 221, 222, 223, 224 nozzle

Claims (5)

[Claims] 1. An ink jet printer comprising a plurality of line heads for discharging ink droplets of the same color onto a recording medium. 2. In a main scanning direction, between adjacent nozzles of one line head of the plurality of heads,
2. The ink jet printer according to claim 1, wherein nozzles of another line head are located. 3. The apparatus according to claim 1, wherein the plurality of line heads are arranged in a direction crossing a main scanning direction.
Or the inkjet printer according to 2. 4. The ink jet printer according to claim 1, wherein each nozzle of the plurality of line heads is located at the same position in the main scanning direction. 5. A plurality of line head groups each including a plurality of line heads having nozzles located at the same position in the main scanning direction, wherein one of the plurality of line head groups is located in the main scanning direction. 2. The ink jet printer according to claim 1, wherein nozzles of another line head group are located between adjacent nozzles.