JPH04363256A - Ink jet recording device - Google Patents

Abstract

PURPOSE:To prevent the black or white line at a scanning joint from inconspicuous by providing a head temp. detecting means and a means for controlling the level of the image signal corresponding to a nozzle in a predetermined position of each ink jet according to the detected temp. CONSTITUTION:Transfer rollers 1 and 2 regulate uniformly the surface of a recording material 5 and a feed roller 3 sends the recording material 5 in the direction f. A recording head 9 consists of ink jet heads 9Y, 9M, 9C and 9BK having the four colors of yellow, magenta, cyan and black respectively. The recording material 5 is fed intermittently by steps of the printing width of each of the ink jet heads 9Y, 9M, 9C and 9BK and, when it is stopped, a recording head unit 9 is scanned in the direction p to deliver the ink drops according to the image signal. A secondary scanning motor 15 drives the feed roller 3 and the recording head units 9 are mounted on a carriage 8.

Description

[Detailed description of the invention]

0001

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

0002

2. Description of the Related Art Inkjet recording apparatuses have been known as image recording apparatuses that perform recording by ejecting ink onto a recording material. Inkjet recording devices are non-impact recording devices with features such as low noise and the ability to easily record color images by using multicolored inks, and have become rapidly popular in recent years. be.

[0003] In a serial scan type inkjet recording device, a multi-nozzle head in which a plurality of nozzles are arranged in parallel scans in the direction A shown in FIG. Each time, the recording head is intermittently fed in the direction opposite to the B direction shown in FIG. 8(A) by the recording width of the multi-nozzle head. In other words, (
1), (2), and (3).

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

[0005] When a large amount of ink is recorded, the ink bleeds and the recording width widens to d+Δd as shown in FIG. 8(B). In such a case, the ink overlaps at the joint between scans, and the density of that part becomes high, resulting in the appearance of black streaks.

To prevent this, there is a method of setting the sub-scanning width in the B direction in FIG. There was a problem with that.

Further, as a method for preventing black streaks, there is, for example, a method disclosed in Japanese Patent Application No. 148229/1983 by the present applicant. This method converts the input signal corresponding to each nozzle using the table shown in Figure 9, drives each nozzle with a drive signal (output signal) whose maximum value is suppressed to The large amount is suppressed to a predetermined amount.

[0008]

[Problems to be Solved by the Invention] However, when the environmental temperature is high or when the head temperature rises due to continuous recording of high-density images, the viscosity of the ink decreases as the temperature rises. There was a problem in that the amount of ink ejected increased and black streaks appeared at the joints between scans. SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus that solves the above-mentioned problems and can make black lines or white lines at scan connections less noticeable even when the temperature changes.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an inkjet head group consisting of a plurality of inkjet heads, each inkjet head having a plurality of nozzles arranged in a straight line. In the inkjet recording apparatus, head temperature detection means detects the temperature of each inkjet head of the inkjet head group, and an image corresponding to a nozzle at a predetermined position of each inkjet head according to the temperature detected by the head temperature detection means. The first step is to suppress the signal level.
The invention is characterized by comprising a suppressing means.

Further, the present invention provides an inkjet recording apparatus including an inkjet head group consisting of a plurality of inkjet heads, each inkjet head having a plurality of nozzles arranged in a straight line, in which each inkjet head of the inkjet head group has a plurality of nozzles arranged in a straight line. head temperature detection means for detecting the respective temperatures of the pixels; a calculation means for calculating the sum of the image data weighted according to the position of the pixel in the matrix; and a head temperature detection means for detecting the sum obtained by the calculation means and the head temperature detection means. and a second suppressing means for suppressing the image signal level corresponding to the nozzle at a predetermined position of each inkjet head based on the determined temperature.

Further, the present invention provides an inkjet recording apparatus including an inkjet head group consisting of a plurality of inkjet heads, each inkjet head having a plurality of nozzles arranged in a straight line, in which a predetermined inkjet of the inkjet head group is provided. temperature detection means for detecting the temperature of the head; sum calculation means for calculating the sum of weighted image signals corresponding to each inkjet head; The present invention is characterized by comprising a third suppressing means for suppressing the image signal level corresponding to the nozzle at a predetermined position of each inkjet head based on the temperature.

Furthermore, in an inkjet recording apparatus comprising an inkjet head group, each inkjet head having a plurality of nozzles arranged in a straight line, the head group detects the temperature of the inkjet head group. temperature detection means;
The present invention is characterized by comprising a fourth suppressing means for suppressing an image signal level corresponding to a nozzle at a predetermined position of each inkjet head in accordance with the temperature detected by the head group temperature detecting means.

[0013]

[Operation] In the present invention, the temperature of each inkjet head of the inkjet head group is detected by the head temperature detection means, and an image is displayed corresponding to the nozzle at a predetermined position of each inkjet head according to the temperature detected by the head temperature detection means. The signal level is suppressed by the first suppressing means.

Further, in the present invention, the temperature of each inkjet head of the inkjet head group is detected by the head temperature detection means, and the sum of the image data weighted according to the position of the pixel in the matrix is calculated by the calculation means, Based on the sum obtained by the calculating means and the temperature detected by the head temperature detecting means, the second suppressing means suppresses the image signal level corresponding to the nozzle at a predetermined position of each inkjet head.

Furthermore, the temperature of a predetermined inkjet head of the inkjet head group is detected by the temperature detection means, the sum of the weighted image signals corresponding to each inkjet head is calculated by the calculation means, and the sum obtained by the calculation means is calculated. Based on the temperature detected by the temperature detection means, the third suppression means suppresses the image signal level corresponding to the nozzle at a predetermined position of each inkjet head.

Furthermore, the temperature of the inkjet head group is detected by the head group temperature detection means, and the image signal level corresponding to the nozzle at a predetermined position of each inkjet head is adjusted according to the temperature detected by the head group temperature detection means. 4 Suppression by suppression means.

[0017]

Embodiments Hereinafter, embodiments of the present invention will be described 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 inkjet recording apparatus of this example.

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

The recording material 5 is an inkjet head 9Y,
It is intermittently fed by the printing widths of 9M, 9C, and 9Bk, and when the feeding of the recording material 5 is stopped, the recording head unit 9 is scanned in the P direction to eject ink droplets according to the image signal. It has become.

For simplicity of explanation, FIG. 1 shows four inkjet heads 9Y, 9M, 9C, and 9Bk shown in FIG.
Of these, only the cyan inkjet head 9C is shown. In addition, inkjet heads 9Y, 9M, 9C, 9B
Of the four temperature sensors that detect the temperature of k, only the temperature sensor 24C is shown. The γ table ROM 22 converts the input image signal into a table according to a control signal indicating whether the input signal corresponds to an end nozzle and a 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. γ tables B to G are selected in this order as the temperature increases.

[0023] In this embodiment, since the configuration is as described above,
When the control signal indicates a nozzle other than the end nozzle, straight line A (FIG. 4) is selected from the γ table ROM 22, and the input signal is applied to each inkjet head 9Y, 9M, 9C.
, 9Bk as is.

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

[0025] In this embodiment, since the configuration is as described above,
Even if the temperature rises 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, white streaks and black streaks at the joints between scans become less noticeable.

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

In FIG. 5, 9C and 24C indicate the same parts as in FIG. Buffers 60a to 60i temporarily store image data corresponding to the pixels shown in FIG. Multipliers 61a to 61i multiply the image data from the buffers 60a to 60i by coefficients α1 to α9, respectively. 62 is an adder that adds all the outputs from the multipliers 61a to 61i. 30 is a ROM which outputs a γ table selection signal in accordance with the combination of the output signal from the adder 62 and the temperature signal from the temperature sensor 24. Reference numeral 31 denotes a γ table ROM, which converts an input image signal into a table according to a γ table selection signal from the ROM 30.

[0028] In comparison with the first embodiment, this embodiment has the following points:
The method of converting the input image signal is different.

In the first embodiment, the judgment as to whether or not it is a high-density portion was made by paying attention only to the image signal applied to the end nozzle. Therefore, if only that image signal happens to have a high density, the dots of the end nozzle may be thinned out even though the image width is not widened due to blurring, which may cause problems. Furthermore, if there is a large amount of ink printed on the periphery, the ink will be affected by the bleeding, so a sufficient effect may not be obtained unless the amount of printing from the end nozzles is further reduced.

The present embodiment improves this inconvenience by using a 3×3 pixel matrix (see FIG. 6) centered on the pixel (j, m) recorded by the end nozzle, and The degree of suppression of the amount of ink recorded by the end nozzles was varied depending on the sum of the image data of the pixels within. In the image data matrix shown in FIG. 6, the i row is the image data given to the end nozzle during the previous scan, the j row is the image data given to the end nozzle during the current scan, and the k row is the image data given to the end nozzle during the current scan. This is the image data given to the th nozzle. Further, the m column is a pixel of interest related to the current recording, the l (L) column is a pixel related to the previous recording, and the m column is a pixel related to the next recording.

In this embodiment, the temperature of each inkjet head 9Y, 9M, 9C, and 9Bk of the recording head unit 9 is detected by a temperature sensor including a temperature sensor 24C, and the multiplier 61a is detected depending on the position of the pixel in the matrix.
.about.61i, the pixel data is weighted by multiplying it by a weighting coefficient, 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, and the selected γ
The input image signal is converted using a table and input to the nozzles at predetermined positions of each inkjet head 9Y, 9M, 9C, and 9Bk. 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, using FIG. 4 as an example, the higher the addition output signal level and the higher the temperature, the greater the amount of signal suppression, that is, the γ table selection signal of the γ table closer to G is output. Therefore, the amount of ink not only in the end nozzles but also in the surrounding nozzles is suppressed depending on the temperature, and black streaks are more appropriately prevented.

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

In FIG. 7, 9C and 24C indicate the same parts as in FIG. 40 is an arithmetic processing unit that weights the image signals for cyan, magenta, yellow, and black, and then calculates the sum of the weights.

[0034]

[Math. 1] S=α1 C+α2 M+α3 Y+α4 Bk
(1) α1 to α4: Weighting coefficients are determined experimentally 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 = α2 = α3 = α4 = 1. 42 is a ROM that outputs a γ table selection signal in accordance with the combination of the sum signal from the arithmetic processing unit 40 and the temperature signal from the temperature sensor 24; 43 is a γ table ROM, and the input image signal is stored in the ROM 42.
Table conversion is performed in response to a γ table selection signal from .

[0035] In comparison with the first embodiment, this embodiment has the following points.
The method of converting the input image signal is different.

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

In the first to third embodiments above, an example of directly detecting the temperature of the inkjet 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 inkjet head 9Y, 9M, 9C is
, 9Bk may be suppressed. In this case as well, the image signal level corresponding to the nozzle at a predetermined position of the inkjet head is suppressed, and the occurrence of black streaks at the edges is prevented.

Furthermore, in the first to third embodiments, an example was explained in which the amount of ink discharged is directly controlled, but the number of dots may be controlled by converting the input signal into a binary value using dither, error diffusion method, etc. It's okay.

[0039]

[Effects of the Invention] As explained above, according to the present invention,
With the above configuration, there is an effect that black lines or white lines at scan joints caused by temperature changes can be made less noticeable.

[Brief explanation of drawings]

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

FIG. 2 is a diagram showing the 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;

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

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

FIG. 6 is a diagram showing an example of image data corresponding to pixels.

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 scan joints.

FIG. 9 is a diagram showing an example of a conversion table for a conventional end nozzle.

[Explanation of symbols]

9C Inkjet head 22 γ table ROM 24C Temperature sensor

Claims (4)

[Claims] 1. In an inkjet recording apparatus comprising a group of inkjet heads each including a plurality of inkjet heads and each inkjet head having a plurality of nozzles arranged in a straight line, the temperature of each inkjet head of the group of inkjet heads is measured. The apparatus is characterized by comprising a head temperature detection means for detecting the temperature, and a first suppression means for suppressing the image signal level corresponding to a nozzle at a predetermined position of each inkjet head in accordance with the temperature detected by the head temperature detection means. Inkjet recording device. 2. In an inkjet recording apparatus comprising a group of inkjet heads each including a plurality of inkjet heads and each inkjet head having a plurality of nozzles arranged in a straight line, the temperature of each inkjet head of the group of inkjet heads is measured. head temperature detection means for detecting; a calculation means for calculating the sum of image data weighted according to the position of the pixel in the matrix; and a calculation means for calculating the sum obtained by the calculation means and the temperature detected by the head temperature detection means. An inkjet recording apparatus comprising: a second suppressing means for suppressing an image signal level corresponding to a nozzle at a predetermined position of each inkjet head. 3. In an inkjet recording apparatus comprising a group of inkjet heads, each inkjet head having a plurality of nozzles arranged in a straight line, the temperature of a predetermined inkjet head of the group of inkjet heads is determined. temperature detection means for detecting; sum calculation means for calculating the sum of weighted image signals corresponding to each inkjet head; and based on the sum obtained by the sum calculation means and the temperature detected by the temperature detection means, An inkjet recording apparatus comprising: a third suppressing means for suppressing an image signal level corresponding to a nozzle at a predetermined position of each inkjet head. 4. In an inkjet recording apparatus including an inkjet head group consisting of a plurality of inkjet heads, each inkjet head having a plurality of nozzles arranged in a straight line, a head group temperature for detecting the temperature of the inkjet head group. Inkjet recording characterized by comprising a detection means and a fourth suppression means for suppressing the image signal level corresponding to a nozzle at a predetermined position of each inkjet head according to the temperature detected by the head group temperature detection means. Device.