JPH09290532A - Sub-scanning control method and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printer where a deterioration in quality of printed images caused by a tilt of a print head is prevented. SOLUTION: A printer includes a print head 2 having two or more dot forming elements arranged at a constant nozzle pitch, a main scanning driver 3 that drives the print head 2 over printing paper in the specific main scanning direction, a sub-scanning driver 4 that carries the printing paper in the sub- scanning direction and a main controller 5, and printing is carried out while the print head 2 scans over the printing paper relatively in the main and sub- scanning directions. The main controller 5 controls the sub-scanning driver 4 so as to satisfy such conditions that f and k are mutually prime number, f=n and f=M×k+α (α=1 when M is an even number, and α=k-1 when M is an odd number), where n is the number of nozzles that actually spout ink in the print head 2, k is the intervals of the nozzles, and f is a unit transfer amount of the printing paper in the sub-scanning direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus, such as a serial scan type printer (hereinafter, serial printer), which prints on a print medium while scanning a print head.

[0002]

2. Description of the Related Art Conventionally, various types of printers such as a dot impact printer, a thermal transfer printer, and an inkjet printer are known as serial printers that print while scanning a print head on a print medium. A serial printer is a printer that performs printing while the print head scans the surface of a print medium, for example, print paper in a raster shape. Specifically, the print head moves the print head onto the print paper in the main scanning direction (paper feed direction). Vertical direction, the same applies hereinafter)
Printing is performed by combining the main scanning operation of scanning in the sub-scanning direction and the sub-scanning operation of conveying the printing paper in the sub-scanning direction (paper feeding direction, the same applies below).

The print head has a dot forming element array in which a large number of dot forming elements, for example, a multi-pin needle head, a thermal head, an ink jet nozzle, etc. are arranged in the sub-scanning direction. A plurality of lines can be printed at the same time by one main scanning pass. The print medium is a sheet material that can be printed by a print head, such as O.
It may be an HP film or the like, and is not limited to printing paper.

By the way, in such a serial printer, when graphic printing is performed while sub-scanning at pitch intervals in the sub-scanning direction of the dot-forming element array, the characteristics of individual dot-forming elements in the print head, variations in dot pitch, and printing. Due to the paper feed accuracy of the paper,
There is a problem that overlaps and gaps are generated in the sub-scanning direction of the printed matter. Occurrence of this overlap or the like appears as a horizontal striped pattern with respect to the printed image, which causes deterioration of print quality.

As a measure against such a problem, for example, US Pat. No. 4,1986,642 and JP-A-53-2040 are known.
A recording method based on "constant pitch sub-scanning" shown in Japanese Patent Publication has been proposed. This recording method is a method that enables high-quality printing by dispersing the ejection characteristics of the inkjet nozzles, variations in nozzle pitch, and the like on the printed image to make them inconspicuous.

More specifically, the constant pitch sub-scan recording method uses a nozzle array in which n ink jet nozzles are arranged in a row in the sub-scanning direction at a pitch corresponding to a k dot pitch in the printing resolution. For the nozzle pitch k of the print head, an integer less than or equal to n, which is relatively prime to the number of nozzles n, is selected, and each time the nozzle array completes one main scanning pass, a sub-scan corresponding to an n-dot pitch is performed. Set to feed paper by the distance.

As a result, when each line is printed by each nozzle in one main scanning pass, adjacent lines above each line are printed by nozzles at different positions in the next main scanning pass. , In the next main scanning pass, the adjacent lines above each adjacent line are
It will be printed by nozzles at other different positions. In this way, in the recording method by constant pitch sub-scanning,
Adjacent lines are always printed by different nozzles, so even if there is some variation in the ejection characteristics or nozzle pitch of each nozzle, the variation will not be noticeable on the print screen and the print image quality can be improved. .

By the way, recently, the print head has been made narrower in pitch with the improvement of the printing resolution.
Only narrowing the pitch interval is limited due to manufacturing problems. Therefore, in general, as shown in FIG. 11, a plurality of nozzles (# 0, # 1, ...) Are arranged so as to be displaced in the sub-scanning direction to achieve a pseudo narrow pitch. In FIG. 11, an example in which a print head having a nozzle pitch k is obtained by a nozzle array in which even nozzle rows (# 0, # 2, ...) And odd nozzle rows (# 1, # 3, ...) Are combined. Is shown.

[0009]

However, in order to improve the print image quality in the conventional ink jet printer which employs the sub-scanning system with a constant pitch, the line formed by each nozzle array of the print head is set in the main scanning direction. It is essential that it is completely vertical and does not displace. Therefore, when the print head is tilted as shown in FIG. 12, the following problems will occur.

That is, as shown in FIG. 12, when the print head is tilted by Δd, each nozzle position is displaced from its original point. Then, depending on the relationship between the type of so-called raster continuous pattern in which adjacent dots are continuous and the paper feed error, so-called white stripes occur and the print image quality deteriorates.

Specifically, a print pattern that should originally be formed by overlapping all four dots as shown in FIG. 13A is a center of four dots as shown in FIG. 13B. A white streak is formed in the main scanning direction due to white spots in the portion, and as shown in FIG. 14A, a print pattern which is supposed to be continuous in the main scanning direction due to two dots overlapping each other is shown in FIG. As shown in b), white spots are formed in the main scanning direction due to white spots in the middle of the two dots.

In a print head of an actual serial printer, it is costly to completely adjust the dot forming elements such as the nozzle array to proper positions in the manufacturing process of the serial printer, and there are some differences. Most of them are attached in a slightly tilted state. In other words, it is not an exaggeration to say that the dot forming elements in the print head always have an inclination. If a raster continuous pattern is formed by
It has been confirmed by the present inventors that a large number of white lines are generated in combination with a paper feed error. Therefore, in such sub-scanning control, white stripes are generated regardless of whether the paper feed error is offset to the + side or the − side, and the print image quality is degraded.

An object of the present invention is to provide a method for suppressing deterioration of print image quality due to tilt of a print head, and a printing apparatus suitable for carrying out the method.

[0014]

SUMMARY OF THE INVENTION The method provided by the present invention is directed to a printhead having a plurality of rows of dot forming element arrays in which a predetermined number (N) of dot forming elements are arranged at a constant nozzle pitch. In a sub-scanning control method in a printing apparatus that drives in the scanning direction and conveys a print medium in the sub-scanning direction orthogonal to the main scanning direction for printing, the number of dot forming elements used for printing in the print head is n. When a value obtained by multiplying the desired printing resolution by the nozzle pitch is represented by a nozzle interval k, and a unit carry amount of the print medium in the sub-scanning direction is represented by f, f and k are relatively prime, Further, the print medium so as to satisfy the conditions of f = n and f = M × k + α (M is a positive integer less than n, α is 1, when M is an even number, and k−1 when M is an odd number). Control the amount of conveyance in the sub-scanning direction. The features.

Further, the printing apparatus of the present invention suitable for carrying out the above method is a print head having a predetermined number of dot forming elements arranged at a constant nozzle pitch, and the print head with respect to a print medium. The main scanning driving unit that drives in the main scanning direction, the sub scanning driving unit that conveys the print medium in the sub scanning direction orthogonal to the main scanning direction, and the operations of the main scanning driving unit and the sub scanning driving unit are performed. In a printing apparatus that includes a main control unit that controls and prints by displacing the relative position of the print head with respect to the surface of the print medium, the main control unit causes f and k to be relatively prime as described above. And f
= N, f = M × k + α, the sub-scanning drive unit is controlled so as to satisfy the conditions.

In the above print head, for example, a plurality of dot forming element arrays in which a predetermined number of dot forming elements are arranged in a row in the sub-scanning direction are provided between corresponding dot forming elements of other dot forming element arrays. They are arranged side by side in the main scanning direction so as to be interpolated with each other.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of the essential parts of a printing apparatus according to an embodiment of the present invention.

The printing apparatus 1 has a print head 2 in which ink-jet nozzles serving as dot forming elements are arranged at a fixed nozzle pitch, and the print head 2 is driven in the main scanning direction with respect to a printing paper. The main scanning drive unit 3, the sub-scanning drive unit 4 that drives the printing paper so as to convey the printing paper in the sub-scanning direction orthogonal to the main scanning direction, the printing operation by the print head 2, and the print head in the main scanning drive unit 3. Drive amount,
The sub-scanning drive unit 4 includes a main control unit 5 that controls the amount of printing paper conveyed.

In order to obtain the above nozzle pitch in the print head 2, in the present embodiment, a plurality of nozzle arrays in which N (integer) nozzles are arranged in a row in the sub-scanning direction are used as the other nozzle arrays of the same structure. The corresponding nozzles are arranged side by side in the main scanning direction so as to be interpolated with each other, whereby a pseudo narrow pitch is achieved.

The main scanning drive unit 3 and the sub-scanning drive unit 4 can be replaced with those of a conventional printing apparatus of this type.

The main control section 5 outputs various control signals to the print head 2, the main scanning drive section 3 and the sub-scanning drive section 4 in a predetermined procedure. As a result, the printing operation is performed while the print head 2 moves on the surface of the printing paper in the main scanning direction, and the printing paper is conveyed in the sub scanning direction, so that a predetermined image is formed on the printing paper. It has become.

As a result of analyzing white stripes generated due to the relationship between the type of raster continuous pattern and the paper feed error, the present inventors have four types of white stripe generation patterns. Of these four types, I found that some of the white stripes are relatively inconspicuous. Furthermore, the offset direction of the paper feed error and the tilt direction of the print head are
It has been found that there is a correlation as shown in the table of FIG. 2 and the occurrence of white streaks can be reduced depending on the combination of these conditions.

That is, when a raster continuous pattern is formed by printing from even-numbered dots to even-numbered dots or from odd-numbered dots to odd-numbered dots during printing, the odd-numbered dots to the even-numbered dots It was found that white stripes occur less frequently than in the case where a raster continuous pattern is formed by continuous dots of 1 or even dots from odd dots. This tendency becomes more remarkable when the head inclination is large even if the paper feed error is "0".

In the present embodiment, as described above, the sub-scanning control is performed so that the adjacent passes continue from the even-numbered dots to the even-numbered dots or from the odd-numbered dots to the odd-numbered dots. is there.

In the sub-scanning control as described above, in the printing apparatus 1, of the N nozzles used for printing in the print head 2, the number of nozzles that actually eject ink is n, and the printing resolution is the nozzle pitch. Assuming that the multiplied value is the nozzle interval k and the unit feed amount in the sub-scanning direction by the sub-scanning drive unit 4, that is, the paper feed amount, f and k are relatively prime and f
= N, f = M × k + α (α = 1 when M is even, α = k−1 when M is odd), the main controller 5 controls the sub-scanning driver 4. It can be realized by doing. At this time, if M is even, the raster continuous pattern is in descending order, and if M is odd, the raster continuous pattern is in ascending order.

Hereinafter, based on FIGS. 2 and 3 to 10,
A specific example of the sub-scanning control according to this embodiment will be described.

3 to 10 are explanatory views showing examples of printing states under various conditions shown in FIG.

3 to 6 are examples when M is an even number (α = 1), and in FIGS. 7 to 10, M is an odd number (α = k−1).
This is an example in the case of. And FIG. 3, FIG. 4, FIG. 7, and FIG.
Shows an example in which the offset direction of the paper feed error is on the − (minus) side, and FIGS. 5, 6, 9 and 10 show examples in which the offset direction of the paper feed error is on the + (plus) side. Furthermore, depending on the tilt direction of the print head, the case of + side is shown in FIG.
5, FIG. 7, FIG. 9, and FIG. 4, FIG.
It is divided into FIG. 8 and FIG.

Further, in the examples shown in FIGS. 3 to 10, the reference symbol A indicates a white streak occurrence point having a relatively large influence on the print image quality, and the reference symbol B indicates a white streak occurrence point having almost no influence. .

As is apparent from these figures, when the paper feed error is offset in the + direction during sub-scan control, the raster continuous patterns are arranged in descending order, and when the paper feed error is offset in the-direction. By selecting each raster continuous pattern in ascending order, the occurrence of white stripes can be reduced. As a result, even if the print head 2 is tilted, only the inconspicuous white stripe pattern is selected. That is, by limiting the raster continuous pattern to even-numbered dots-even-numbered dots and odd-numbered dots-odd-numbered dots, the generation level of white stripes can be significantly reduced compared to the conventional case, and the print quality can be improved. Can be suppressed.

This is particularly effective when the distance between the rows of ink jet nozzles arranged in the print head 2 is large.

[0033]

As is apparent from the above description, according to the present invention, even if the print head is tilted, the deterioration of print image quality is suppressed by controlling the unit carry amount of the print medium in the sub-scanning direction. effective.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a relationship between a raster continuous pattern, a paper feed error offset direction, and a print head inclination.

FIG. 3 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 4 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 5 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 6 is a diagram showing a printing example under various conditions shown in FIG.

FIG. 7 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 8 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 9 is a diagram showing an example of printing under various conditions shown in FIG.

FIG. 10 is a diagram showing a printing example under various conditions shown in FIG.

FIG. 11 is a diagram showing an example of a nozzle pattern in a conventional print head.

FIG. 12 is a diagram showing an example of a nozzle pattern when a conventional print head is tilted.

FIG. 13 is a diagram showing an example of a print pattern that causes deterioration of print quality.

FIG. 14 is a diagram showing an example of a print pattern that causes deterioration of print quality.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printing device 2 Print head 3 Main scanning drive section 4 Sub-scanning drive section 5 Main control section

Claims (3)

[Claims] 1. A print head having a plurality of rows of dot forming element arrays in which a predetermined number of dot forming elements are arranged at a constant nozzle pitch is driven in the main scanning direction, and a print medium is orthogonal to the main scanning direction. In the sub-scanning control method in a printing apparatus that performs printing while conveying in the sub-scanning direction, the number of dot forming elements used for printing in the print head is n, and a value obtained by multiplying a desired print resolution by the nozzle pitch is the nozzle. When the interval k and the unit carry amount of the print medium in the sub-scanning direction are represented by f, in the printing apparatus, f and k are relatively prime, and f = n,
The conveyance of the print medium in the sub-scanning direction so that the condition of f = M × k + α (M is a positive integer less than n, α is 1 when M is an even number, and k−1 when M is an odd number) is satisfied. A sub-scanning control method for a printing apparatus, characterized by controlling an amount. 2. A print head having a plurality of rows of dot forming element arrays in which a predetermined number of dot forming elements are arranged at a constant nozzle pitch, and the print head is driven in the main scanning direction with respect to a print medium. A main scanning drive unit, a sub scanning drive unit that conveys the print medium in a sub scanning direction orthogonal to the main scanning direction, and a main control unit that controls the operations of the main scanning drive unit and the sub scanning drive unit. In a printing device that performs printing by displacing the relative position of the print head with respect to the surface of the print medium, the main controller controls the number of dot forming elements used for printing in the print head to be n, When a value obtained by multiplying the desired print resolution by the nozzle pitch is represented by a nozzle interval k and a unit carry amount of the print medium in the sub-scanning direction is represented by f, f and k are relatively prime, and f = n, f = M × k + α
(M is a positive integer less than n, α is 1, M when M is an even number,
Is configured to control the sub-scanning drive unit so as to satisfy the condition of k-1) when is an odd number. 3. The print head comprises a plurality of dot forming element arrays in which a predetermined number of dot forming elements are arranged in a row in the sub-scanning direction, and the corresponding dot forming elements of other dot forming element arrays are mutually arranged. The printing apparatus according to claim 2, wherein the printing apparatuses are arranged side by side in the main scanning direction so as to be interpolated.