JP2001270155A - Line printer - Google Patents

Abstract

(57) [Problem] To provide a line printer capable of favorably suppressing disturbance of a formed image such as a streak appearing in a transport direction even if positioning accuracy of a unit head is not so high. When forming a series of dots 40 arranged in the width direction in a region including a pair of nozzles 31a adjacent at a pitch P1 smaller than the pitch P of the nozzles 31 in each unit head 3, a pair of nozzles is used. Only one of 31a is alternately driven for each row. For this reason, in the joint portion 41 of the dots 40 formed by the unit heads 3, the dots 40 formed by the nozzles 31a of one unit head 3 and the dots 40 formed by the nozzles 31a of the other unit head 3 alternate. It is arranged in. by this,
A portion where the density of the dots 40 becomes coarse can be blurred to make it less noticeable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line printer, and more particularly to a line printer having a recording head formed by arranging a plurality of unit heads in a width direction.

[0002]

2. Description of the Related Art Conventionally, in a line printer of an ink jet type, a wire dot type or the like, a dot forming portion for forming dots on a recording medium such as a roll paper has a direction (hereinafter referred to as a width) which is orthogonal to a conveying direction of the recording medium. The recording heads are arranged at a predetermined pitch in the direction (referred to as a direction), and the dot forming unit is driven at a predetermined timing while conveying the recording medium, thereby forming an image on the recording medium. In addition, when it is difficult to provide a dot forming portion over the entire width of the recording medium in one recording head, the recording head is divided into a plurality of unit heads, and the unit heads are arranged in the width direction. ing. That is, when the width of the recording medium is wide, the recording head becomes long and large, so that it is difficult to manufacture the recording head accurately. Therefore, in such a case, a recording head is configured by arranging a plurality of small unit heads that can be manufactured relatively accurately in the width direction.

When the recording head is composed of a plurality of unit heads, it is necessary to accurately position each unit head. That is, the interval between the closest dot forming portions of a pair of adjacent unit heads must be matched with the pitch at which the dot forming portions are arranged in each unit head, and if this condition is not satisfied Has the following problems.

FIG. 7 is an explanatory diagram showing the above problem. Although FIG. 7 illustrates an ink jet printer as an example, a similar problem occurs in a wire dot printer. FIG. 7A shows the arrangement of the ideal unit heads 3 positioned as described above and the dots 40 formed by the arrangement. As shown in FIG. 7A, nozzles 31 as dot forming portions are arranged at a predetermined pitch P in the width direction in each unit head 3. Also, the pitch P1 between the nozzles 31a closest to each other of the pair of adjacent unit heads 3 (that is, the right end nozzle 31a of the left unit head 3 and the left end of the right unit head 3 in FIG. 7A). The interval between the nozzle 31a and the nozzle 31a in the width direction also matches the pitch P described above. Therefore, the dots 40 can be formed uniformly on the recording medium. In FIG. 7,
The dots 40 are formed at a pitch of about half of the pitch P. This is because each unit head 3 is fixed while the recording medium is fixed.
Is moved in the width direction by P / 2 to perform a so-called shuttle drive for forming new dots 40 between the dots 40 formed last time. The dots 41 formed by the unit heads 3 have the same color (the same applies to the embodiments described later).

However, when the positioning of the unit heads 3 is inappropriate, for example, when P1> P as shown in FIG. 7 (B), the dots 40 at the joint portions 41 of the dots 40 formed by the unit heads 3 are formed. Density becomes coarse and whitish streaks appear. Conversely, if P1 <P, the density of the dots 40 becomes high at the joints, and a streak of dark color appears.

[0006]

However, in recent years,
An extremely high resolution is required for the printer, and it is difficult to accurately and accurately position the unit head. For example, in order to realize a resolution of 300 dpi (dot per inch), the pitch of a dot forming unit (for example, a nozzle in the case of an ink jet printer) is set to 8
It must be 5 μm. Although the dot forming section in each unit head can be arranged at a relatively accurate pitch,
It is almost impossible to position each unit head with an accuracy of less than 10 μm. Therefore, an object of the present invention is to provide a line printer capable of favorably suppressing disturbance of a formed image such as a streak as described above even if the positioning accuracy of a unit head is not so high. .

[0007]

Means for Solving the Problems and Effects of the Invention According to the first aspect of the present invention, there is provided a conveying means for conveying a recording medium in a predetermined direction, and forming dots on the recording medium. A recording head comprising a plurality of unit heads in which a plurality of dot forming units are arranged at a predetermined pitch in a width direction orthogonal to the predetermined direction, and the dot forming unit according to conveyance of the recording medium. And a recording control unit for driving at least one pair of the unit heads adjacent to each other by arranging the unit heads alternately before and after in the predetermined direction. The interval in the width direction of the portion is close to the predetermined pitch or less, and the recording control means is arranged in a series including the pair of dot forming portions in the width direction. When forming the Tsu bets, and drives only one of the dot forming portion to be paired.

In the present invention, the unit heads are alternately arranged before and after in the predetermined direction (for example, partially overlap in the width direction), whereby at least one pair of dot forming portions of the unit heads adjacent to each other are arranged. Are close to each other at a predetermined pitch or less. For this reason, when forming a series of dots arranged in the width direction in the area including the paired dot forming units, if the paired dot forming units are driven together, the dots formed by each unit head are formed. Although the density of the dots may be high at the joints, it is not low. Therefore, when forming the series of dots, the recording control unit drives only one of the pair of dot forming units.

In this case, it is possible to prevent the density of the dots from becoming denser than other portions, and to prevent a gap of one dot or more from being left. Therefore, in the present invention, even if the positioning accuracy of the unit head is not so high, it is possible to satisfactorily suppress the disturbance of the formed image such as a streak as described above.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, when the recording control means forms the series of dots a plurality of times, at least one time the pair of dot forming sections is formed. It is characterized in that only one of them is driven, and at least one other time, only the other of the pair of dot forming units is driven.

In the present invention, when the series of dots are formed a plurality of times, at least one of the paired dot forming units is at least once, and at least the other is at least one of the paired dot forming units. Only the other of them is driven. For this reason, even if the dot density differs from the other portions at the joint portions of the dots formed by the unit heads, the portions having different densities are not arranged linearly in the predetermined direction. For this reason, the portions having different densities are blurred and less noticeable. Therefore, in the present invention, in addition to the effect of the first aspect, even if the dot density is different from the other portions at the joint portion, the portions having different densities are less noticeable, and the formed image is disturbed. Is more effectively suppressed.

According to a third aspect of the present invention, in addition to the configuration of the second aspect, when the recording control unit forms the series of dots a plurality of times, the recording control unit alternately drives the pair of dot forming units. It is characterized by the following. In the present invention, when forming the series of dots a plurality of times, the pair of dot forming units are alternately driven. For this reason, even if the dot density is different from that of the other portions at the joint portion, the portion having the different density can be more favorably blurred to be less noticeable. Therefore, according to the present invention, in addition to the effect of the second aspect of the invention, there is an effect that disturbance of a formed image can be more favorably suppressed.

According to a fourth aspect of the present invention, in addition to any one of the first to third aspects, the pair of dot forming portions of each of the unit heads is disposed along the predetermined direction. It is characterized by the following. In the present invention, since the pair of dot forming units are arranged along the predetermined direction, the pair of dot forming units can form dots at substantially the same location on the recording medium. For this reason, when only one of the paired dot forming units is driven, the dots arranged almost in the same manner as the dots 40 corresponding to the ideal arrangement of the unit heads 3 in FIG. Can be formed. Therefore, in the present invention, in addition to the effect of any one of the first to third aspects, the disturbance of the formed image can be more favorably suppressed by making the arrangement of the dots closer to the ideal state. Such an effect is produced.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing a configuration of a line printer 1 to which the present invention is applied. In the following embodiments, an ink jet printer will be described as an example. However, the present invention can be applied to a wire dot printer in the same manner.

As shown in FIG. 1, a line printer 1 according to the present embodiment has a width direction (direction of an arrow A) of a recording medium 99 made of, for example, roll paper (may be a film or the like).
Is provided with a recording head 5 in which a plurality of unit heads 3 are arranged, and each unit head 3 has a nozzle 31 as a dot forming unit for discharging ink facing a recording medium 99. The nozzles 31 are arranged at a predetermined pitch P in the width direction, and the unit heads 3 are alternately arranged (so-called staggered) before and after in the transport direction of the recording medium 99 (the direction of arrow B). I have. With such an arrangement of the unit heads 3, the nozzles 31a closest to each other of the pair of adjacent unit heads 3 are arranged substantially in a straight line along the transport direction.

Next, the recording head 5 constructed as described above
Is connected to an electronic control circuit 50 as recording control means as shown in FIG. 2 to control the state of ink ejection from each nozzle 31. The electronic control circuit 50 includes a CPU 51, R
An interface 61 to which image data and the like are externally input, a transport motor 63 as transport means for transporting the recording medium 99 in the transport direction (corresponding to a predetermined direction), Also, it is connected to a so-called shuttle driving head moving motor 65 that moves the recording head 5 in the width direction by P / 2 and forms a new dot 40 between the dots 40 formed last time (see FIG. 3). I have. Then, while transporting the recording medium 99 by the transport motor 63, the corresponding nozzle 31 is driven at a predetermined timing corresponding to the image data or the like input to the interface 61.

When forming a series of dots 40 arranged in the width direction in a region including the above-mentioned pair of nozzles 31a, the electronic control circuit 50 only shows one of the pair of nozzles 31a. As shown in FIG. 3, driving is performed alternately for each row. For this reason, in the joint portion 41 of the dots 40 formed by the unit heads 3, the dots 40 formed by the nozzles 31a of one unit head 3 and the dots 40 formed by the nozzles 31a of the other unit head 3 alternate. It is arranged in.

As described above, since the nozzles 31a are arranged substantially in a straight line along the direction in which the recording medium 99 is conveyed, the pitch P1 between the pair of nozzles 31a should be normal.
Is 0, and the dots 4 arranged substantially in the same manner as the dots 40 corresponding to the ideal arrangement of the unit heads 3 in FIG.
0 should be able to be formed. However,
The pitch P1 is not always 0 due to an assembling error of the unit head 3, and a gap corresponding to the pitch P1 is generated between the dots 40 in the joint portion 41. On the other hand, in the present embodiment, by alternately arranging the dots 40 formed by the nozzles 31a, it is possible to prevent the gaps from being arranged on a straight line, and to reduce the density of the dots 40. Can be made inconspicuous by blurring the portion that becomes Therefore, even if the positioning accuracy of the unit head 3 is not so high, disturbance of a formed image such as a streak appearing at the joint portion 41 can be favorably suppressed.

In the above embodiment, the pair of nozzles 31a are alternately driven for each row, but may be alternately driven for every two rows as shown in FIG. The driving may be performed alternately for each row. However, the nozzle 3 on the driving side
The more frequently the 1a is switched, the better the joint portion 41 can be blurred, and the more the switching is performed for each row as in the above-described embodiment, the more the disturbance of the formed image can be more effectively suppressed.

As shown in FIG. 5, both nozzles 31a may be driven in some rows. In this case, a dark portion where the dots 40 formed by the nozzles 31a overlap each other is also formed in the joint portion 41. In the case of P1 ≠ 0, there is a gap between the dots 40 near the joint portion 41, so that the color of the portion tends to be lighter.
When the overlapping portions of the dots 40 are appropriately interwoven in this manner, the joint portions 41 may be more appropriately blurred, and the disturbance of the formed image may be more appropriately suppressed. Further, although the effect is considerably reduced as compared with the above embodiments, an embodiment of the present invention includes a pair of nozzles 3.
It is sufficient that at least one row for driving only one of 1a is provided, and such a row is also included.

Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above-described embodiments, but may be implemented in various other forms without departing from the spirit of the present invention. Can be implemented. For example, the arrangement of the unit heads in the present invention is not limited to the staggered arrangement as described above.
The form arrange | positioned in steps or more is also included. Also in this case, if attention is paid to a pair of adjacent unit heads 3, the disturbance of the formed image can be suppressed by the same processing as in the above embodiments.

The unit heads 3 do not necessarily have to overlap in the width direction. As shown in FIG. 6B, a pitch P1 between the nozzles 31a of the pair of adjacent unit heads 3 which is closest to each other. Is smaller than the pitch P, an effect can be obtained to some extent. Further, there may be a plurality of nozzles 31 of a pair of adjacent unit heads 3 that approach each other at a pitch P1 smaller than the pitch P as shown in FIG. 6C. Also in this case, the same effect as in each of the above-described embodiments can be obtained by, for example, alternately driving the pair of adjacent nozzles 31.

In the example of FIG. 6C, the pitch P1
, There are three pairs of nozzles 31 that are close to each other, of which nozzles 31b and 31c, nozzles 31d and 31e
Is a pitch smaller than the pitch P1 (P-P1).
In close proximity. Therefore, in such a case, one of the nozzle 31b or the nozzle 31c and the nozzle 31d or the nozzle 31e may be driven alternately or every plural rows. In this case, there is a portion where the dots 40 are densely arranged. However, it is possible to prevent the densely arranged portions from being arranged in a straight line and to blur them, thereby suppressing disturbance of a formed image. Can be. Embodiments of the present invention include such a form.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a configuration of a line printer to which the present invention is applied.

FIG. 2 is a block diagram illustrating a configuration of a control system of the line printer.

FIG. 3 is an explanatory diagram illustrating a driving state of the line printer.

FIG. 4 is an explanatory diagram showing a modification of the driving state.

FIG. 5 is an explanatory diagram showing another modification of the driving state.

FIG. 6 is an explanatory diagram illustrating a modification of the unit head arrangement of the line printer.

FIG. 7 is an explanatory diagram showing a problem of a conventional line printer.

[Explanation of symbols]

1. Line printer 3. Unit head 5
... recording head 31 ... nozzle 40 ... dot 4
DESCRIPTION OF SYMBOLS 1 ... Joint part 50 ... Electronic control circuit 63 ... Transport motor 9
9 Recording medium

Claims (4)

[Claims] A transport unit that transports a recording medium in a predetermined direction; and a unit head in which dot forming units that form dots on the recording medium are arranged at a predetermined pitch in a width direction orthogonal to the predetermined direction. A line printer comprising: a plurality of recording heads arranged in the width direction; and recording control means for driving the dot forming unit in accordance with the conveyance of the recording medium, wherein each of the unit heads has a predetermined length. By being alternately arranged before and after in the direction, the interval in the width direction between at least one pair of dot forming portions of the unit heads adjacent to each other is close to the predetermined pitch or less, and the recording control means When forming a series of dots arranged in the width direction in a region including the paired dot forming units, only one of the paired dot forming units is driven. Line printer according to claim. 2. When the recording control unit forms the series of dots a plurality of times, at least one of the pair of dot forming units is formed at least once, and the other is formed of the pair at least once. 2. The line printer according to claim 1, wherein only the other one of the dot forming units is driven. 3. A line printer according to claim 2, wherein said recording control means alternately drives said pair of dot forming portions when said series of dots are formed a plurality of times. 4. The line printer according to claim 1, wherein the pair of dot forming sections of each of the unit heads are arranged along the predetermined direction.