JP2885964B2 - Ink jet recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, as an image recording apparatus, an ink jet recording apparatus which performs recording by discharging ink onto a recording material has been known. Ink jet recording apparatuses are non-impact type recording apparatuses and have features such as low noise and easy color image recording by using multi-color inks. is there.

In a serial scan type ink jet recording apparatus, a multi-nozzle head in which a plurality of nozzles are arranged in parallel is scanned in a direction A shown in FIG. 8A to record an image having a width d, and recording of one line is completed. Every time, the recording is intermittently fed in the direction opposite to the direction B shown in FIG. 8A by the recording width of the multi-nozzle head. That is, recording is performed as shown in (1), (2), and (3) of FIG.

The recording width d is determined by the number of nozzles and the recording density of the head. For example, when the number of nozzles is 256 and the recording density is 400 dots / inch (dpi), 16.25.
6 mm (= 256 × 25.4 / 400).

When the amount of ink to be recorded is large, the ink bleeds and the recording width increases to d + Δd as shown in FIG. In such a case, the ink overlaps at the seam of scanning, the density of that portion increases, and black streaks appear.

To prevent this, there is a method in which the sub-scanning width in the direction B in FIG. 8 is set to d + Δd. However, according to this method, when the amount of ink to be printed is small, the seam of scanning becomes white streaks. There was a problem of becoming.

As a method for preventing black streaks, there is, for example, a method disclosed by the present applicant in Japanese Patent Application No. 63-148229. In this method, the input signal corresponding to each nozzle is converted using the table shown in FIG. 9, and each nozzle is driven by a drive signal (output signal) whose maximum value is suppressed to F. A large amount is suppressed to a predetermined amount.

[0008]

However, when the environmental temperature is high, or when the temperature of the head increases due to continuous recording of a high-density image, the viscosity of the ink decreases as the temperature increases. There has been a problem that the ink ejection amount increases and black streaks appear at the seam of scanning. SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording apparatus which solves the above-described problems and can make black or white streaks of scanning joints inconspicuous even when the temperature changes.

[0009]

SUMMARY OF THE INVENTION The present invention relates to an ink jet recording apparatus provided with a plurality of ink jet heads having a nozzle row composed of a plurality of nozzles, wherein head temperature detecting means for detecting the temperature of each of the ink jet heads is provided. Limiting means for limiting the maximum image signal level corresponding to the end nozzle of each ink jet head to a predetermined value or less in accordance with the temperature detected by the head temperature detecting means.

The present invention relates to an ink jet recording apparatus provided with a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, wherein head temperature detecting means for detecting the temperature of each of the ink jet heads, and a position of a pixel in a matrix. Calculating means for calculating the sum of the image data weighted according to the following formulas: and a temperature corresponding to the end nozzle of each inkjet head based on the sum obtained by the calculating means and the temperature detected by the head temperature detecting means. And limiting means for limiting the maximum image signal level to a predetermined value or less.

The present invention relates to an ink jet recording apparatus provided with a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, wherein head temperature detecting means for detecting the temperature of each of the ink jet heads, and weighted ink jet heads. Sum calculating means for calculating the sum of image signals corresponding to the heads; and a maximum image corresponding to the end nozzle of each inkjet head based on the sum obtained by the sum calculating means and the temperature detected by the temperature detecting means. Limiting means for limiting the signal level to a predetermined value or less.

The present invention relates to an ink jet recording apparatus provided with a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, wherein head group temperature detecting means for detecting the temperature of the ink jet head group, and head group temperature detecting means Limiting means for limiting the maximum image signal level corresponding to the end nozzle of each ink jet head to a predetermined value or less in accordance with the temperature detected by the means.

[0013]

[0014]

[0015]

[0016]

[0017]

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

First Embodiment FIG. 1 shows a first embodiment of the present invention. FIG. 2 shows the structure of the ink jet recording apparatus of this embodiment.

In FIG. 2, reference numeral 5 denotes a roll-shaped recording material. Reference numerals 1 and 2 denote transport rollers for regulating the recording surface of the recording material 5 to be flat. Reference numeral 3 denotes a feeding roller for nipping the recording material 5 and feeding the recording material 5 in the direction f in FIG. A sub-scanning motor 15 drives the feed roller 3. Reference numeral 8 denotes a carriage on which a recording head unit 9 is mounted. The recording head unit 9 includes four color ink jet heads 9Y, 9M, 9C, and 9Bk of yellow, magenta, cyan, and black, and four color ink tanks are arranged for each ink jet head. Each inkjet head has nozzles arranged in a straight line. FIG. 3 shows an inkjet head 9C in which the nozzles 51 are linearly arranged. Reference numerals 6 and 7 are guide rails which are arranged in parallel to each other and cross the recording surface of the recording material 5 to guide the carriage 8.

The recording material 5 includes ink jet heads 9Y,
When the recording material 5 is stopped intermittently by the print width of 9M, 9C, and 9Bk, and the feeding of the recording material 5 is stopped, the recording head unit 9 is scanned in the P direction to eject ink droplets corresponding to the image signal. Has become.

FIG. 1 shows four ink jet heads 9Y, 9M, 9C, 9Bk shown in FIG.
Among them, only the inkjet head 9C for cyan is shown. Further, the inkjet heads 9Y, 9M, 9C, 9
Only the temperature sensor 24C among the four temperature sensors for detecting the temperature of Bk is shown. The γ table ROM 22 includes a control signal indicating whether or not the input signal corresponds to the end nozzle,
The input image signal is converted into a table according to the temperature signal from the temperature sensor 24C.

FIG. 4 shows an example of the γ table stored in the γ table ROM 22. In the figure, A is a table when no conversion is performed, and B to G are γ tables used when the input signal is large. The γ tables BG are selected in this order as the temperature increases.

In this embodiment, the configuration is as described above.
When the control signal indicates a nozzle other than the end nozzle, the straight line A (FIG. 4) is selected from the γ table ROM 22, and the input signal is set to each of the inkjet heads 9Y, 9M, 9
C, 9Bk is output as it is.

On the other hand, when the control signal indicates the end nozzle, one γ table is selected from the γ tables B to G according to the temperature signal from the temperature sensor 24C, and the selected γ table is used. The input image signal is converted, and the converted image signal is output to the inkjet heads 9Y, 9M, 9
C, 9Bk.

In this embodiment, since the configuration is made as described above,
Even when the temperature increases and the ink ejection amount increases, the maximum level of the image signal applied to the end nozzle is appropriately suppressed. Therefore, even if the temperature changes, the white streak and the black streak at the scanning joint become inconspicuous.

Second Embodiment FIG. 5 shows a second embodiment of the present invention.

In FIG. 5, reference numerals 9C and 24C denote the same parts as in FIG. Buffers 60a to 60i temporarily store image data corresponding to the pixels shown in FIG.
61a to 61i are multipliers for multiplying image data from the buffers 60a to 60i by coefficients α1 to α9, respectively. An adder 62 adds all outputs from the multipliers 61a to 61i. A ROM 30 outputs a γ table selection signal in accordance with a combination of an output signal from the adder 62 and a temperature signal from the temperature sensor 24. Reference numeral 31 denotes a γ table ROM for converting an input image signal into a table according to a γ table selection signal from the ROM 30.

This embodiment is different from the first embodiment in that:
The input image signal conversion method is different.

In the first embodiment, the determination as to whether or not the image is a high-density portion is made by focusing only on the image signal given to the end nozzle. Therefore, when only the image signal has a high density by chance, the dots of the end nozzles are thinned out even though the spread of the image width due to the bleeding is small, which may cause inconvenience. Further, when the amount of ink printed on the periphery is large, the ink is affected by the bleeding, so that a sufficient effect may not be obtained unless the printing amount of the end nozzle is further reduced.

In this embodiment, such inconvenience is improved, and a 3 × 3 pixel matrix (see FIG. 6) centering on the pixel (j, m) recorded by the end nozzle is used. The degree of suppression of the amount of ink recorded by the end nozzles was changed according to the sum of the image data of the pixels inside. In the matrix of the image data shown in FIG. 6, the i-th row is the image data given to the end nozzle in the previous scan, the j-th row is the image data given to the end nozzle in the current scan, and the k-th row is 2 from the shortest part. This is the image data given to the nozzle. Further, the m-th column is a pixel of interest in the current recording, the l (ell) column is a pixel in the previous recording, and the m-th column is a pixel in the next recording.

In this embodiment, the temperature of each of the ink jet heads 9Y, 9M, 9C, 9Bk of the recording head unit 9 is detected by a temperature sensor including a temperature sensor 24C, and a multiplier 61a is provided according to the position of the pixel in the matrix.
The weighting coefficient is multiplied by the pixel data according to .about.61i and weighted, and the sum of the image data is calculated by the adder 62. Then, a γ table selection signal is generated based on the obtained sum and the temperature detected by the temperature sensor, the input image signal is converted by the selected γ table, and a predetermined position of each of the inkjet heads 9Y, 9M, 9C, 9Bk is determined. Input to the nozzle. Therefore, when the sum obtained by the calculation is large, the value of the image data given to the end nozzle becomes small. That is, referring to FIG. 4 as an example, the higher the added output signal level and the higher the temperature, the larger the signal suppression amount, that is, the γ table selection signal of the γ table close to G is output. Accordingly, the ink amount of not only the end nozzles but also the peripheral nozzles is suppressed according to the temperature, and the black streak is more appropriately prevented.

Third Embodiment FIG. 7 shows a third embodiment of the present invention.

In FIG. 7, reference numerals 9C and 24C denote the same parts as in FIG. An arithmetic processing unit 40 weights image signals for cyan, magenta, yellow, and black, and then sums the image signals.

[0034]

S = α ₁ C + α ₂ M + α ₃ Y + α ₄ Bk (1) α _{1 to} α ₄ : A weighting coefficient experimentally obtained from the magnitude of the bleeding rate of each color ink. Here, if a sufficient effect can be obtained with a simple sum, α ₁ = α ₂ = α ₃ = α ₄ = 1. A ROM 42 outputs a γ table selection signal in accordance with a combination of the sum signal from the arithmetic processing unit 40 and the temperature signal from the temperature sensor 24.
Reference numeral 43 denotes a γ table ROM which stores input image signals in the ROM 42.
Table conversion is performed in accordance with the γ table selection signal from.

This embodiment is different from the first embodiment in that:
The input image signal conversion method is different.

In this embodiment, the temperature of a predetermined ink jet head of the recording head unit 9, for example, the ink jet head 9C for cyan is detected by the temperature sensor 24C, and the arithmetic processing unit 40 is used to correspond to each ink jet head. The image signal is multiplied by a weighting coefficient, and the sum is calculated. Then, a γ table is selected from the γ table ROM 43 based on the obtained sum and the detected temperature, the input image signal is converted by the selected γ table, and each of the inkjet heads 9Y, 9M, 9C,
Input to 9Bk. Therefore, the image signal level corresponding to the nozzle at the predetermined position of each ink jet head is suppressed, and the occurrence of black streaks at the ends is prevented.

As described above, in the first to third embodiments, the example of directly detecting the temperature of the ink jet head has been described.
The average temperature of each inkjet head is detected, for example, the temperature of the recording head unit 9 is detected, and each of the inkjet heads 9Y, 9M, 9 according to the detected temperature is detected.
You may make it suppress the input image signal level corresponding to the nozzle of the predetermined position of C, 9Bk. Also in this case, the image signal level corresponding to the nozzle at the predetermined position of the inkjet head is suppressed, and the occurrence of black streaks at the end is prevented.

In the first to third embodiments, the example in which the ink ejection amount is directly controlled has been described. However, the input signal is binarized by using dithering, error diffusion, or the like to control the number of dots. May be.

[0039]

As described above, according to the present invention,
With the configuration described above, there is an effect that the black streak or the white streak at the scanning joint caused by the change in the temperature can be made inconspicuous.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an inkjet recording apparatus according to a first embodiment.

FIG. 3 is a diagram showing an example of the arrangement of nozzles of the cyan inkjet head shown in FIG. 2;

FIG. 4 is a diagram showing an example of a γ table stored in a γ table ROM 22 shown in FIG. 1;

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of image data corresponding to a pixel.

FIG. 7 is a block diagram showing a third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the occurrence of black streaks at a seam of scanning.

FIG. 9 is a diagram illustrating an example of a conventional conversion table for end nozzles.

[Explanation of symbols]

 9C inkjet head 22 γ table ROM 24C temperature sensor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41J 2/21 B41J 2/205

Claims (4)

(57) [Claims] 1. An ink jet recording apparatus comprising a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, comprising: a head temperature detecting means for detecting a temperature of each of the ink jet heads; An ink jet recording apparatus comprising: a limiter that limits a maximum image signal level corresponding to an end nozzle of each ink jet head to a predetermined value or less in accordance with the set temperature. 2. An ink jet recording apparatus comprising a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, comprising: a head temperature detecting means for detecting a temperature of each of the ink jet heads; Calculating means for calculating the sum of the weighted image data, based on the sum obtained by the calculating means and the temperature detected by the head temperature detecting means, the maximum value corresponding to the end nozzle of each inkjet head. An ink jet recording apparatus comprising: a limiting unit that limits an image signal level to a predetermined value or less. 3. An ink jet recording apparatus comprising a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, wherein: a head temperature detecting means for detecting a temperature of each of the ink jet heads; Sum calculating means for calculating a sum of corresponding image signals; and a maximum image signal level corresponding to an end nozzle of each ink jet head based on the sum obtained by the sum calculating means and the temperature detected by the temperature detecting means. An ink jet recording apparatus comprising: a restricting unit that restricts a value to a predetermined value or less. 4. An ink jet recording apparatus comprising a plurality of ink jet heads each having a nozzle row composed of a plurality of nozzles, comprising: a head group temperature detecting means for detecting a temperature of the ink jet head group; An ink jet recording apparatus comprising: a limiter that limits a maximum image signal level corresponding to an end nozzle of each ink jet head to a predetermined value or less in accordance with the detected temperature.