JP2003118149A - Ink-jet printer and method of recovering therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a total number of heads when a recovery head is provided in a full-line type ink-jet printer. SOLUTION: When a defective nozzle is detected by test printing, a recovery operation is executed by means of the recovery head provided beforehand. When a head generating a defective nozzle is one for a K color, printing is executed by a K color recovery mode. The K color is complemented by a mixed color of C, M, Y colors in the recovery mode. In a line where the defective nozzle occurs in the K color, a pixel of image data of C, M, Y colors is added to a position corresponding to the position where the K color pixel exists. As a result, it is possible thereby to prevent a white stripe from occurring by the mixed pixel of the C, M, Y colors even when drop-out of the K color occurs. Therefore, in the case where the recovery heads are provided, it is possible to cope with the above problems without providing a recovery head for the K color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printing apparatus having a full line type ink jet head in a width direction of a printing paper to be conveyed, and more particularly to an ink jet printing apparatus capable of recovering a nozzle missing defect of the ink jet head. Regarding the recovery method.

[0002]

2. Description of the Related Art Conventionally, an ink jet type printing apparatus has a type in which an ink jet head moves along the width direction of a printing paper to be conveyed and an ink jet head having a full line width fixed along the width direction. There is a format. In the former type of inkjet printing apparatus, since the head is moved, the printing speed is slow but the head may be short (that is, the number of nozzles may be small), and the apparatus can be manufactured relatively inexpensively. Therefore, it is mainly used for home and office use. The latter type of inkjet printing apparatus is expensive because a large number of nozzles have to be arranged in parallel, but it has the advantage that high-speed printing can be performed because the head is not moved. Therefore, it is suitable for commercial printing.

On the other hand, in any of the above-mentioned types of ink jet printing apparatuses, there is a problem that ink jet nozzles are clogged due to an increase in ink viscosity and mixing of paper powder. When such nozzle clogging occurs, ink cannot be ejected from the nozzle, and white lines appear on the corresponding line. (Hereinafter, this phenomenon is referred to as nozzle omission.) Therefore, the conventional inkjet printing device is equipped with a detection device that detects the nozzle clogging, and issues an error alarm when clogging occurs, or nozzle clogging is detected. Some have a cleaning device to solve the problem.

[0004]

Although the above-described cleaning device is effective, the nozzle omission may occur without eliminating the clogging of the nozzle even if such cleaning is performed. Here, in the case of the head-moving type inkjet printing device like the former, there is a solution that complements a missing line by performing scanning twice using another usable nozzle, but a full line type Is impossible because the nozzle position is fixed. Therefore, in the case of the full line type, to use when the nozzle of either head is clogged,
It is conceivable to have a preliminary head.

However, such a spare head requires the same structure as the original head. Considering for general color printing, full line heads are required for four CMYK colors, and if each of these is equipped with auxiliary heads, a total of 4 × 2 = 8 heads must be provided. There is a problem that the price of the device is further increased because it is a large size of full line type.

According to the present invention, in an inkjet printing apparatus having a spare head, the number of heads can be reduced and the apparatus price can be made relatively low. It is an object of the present invention to provide a recovering method that can reduce the number.

[0007]

According to a first aspect of the present invention, C, M, Y, and
An inkjet printing apparatus including an inkjet head having a full line width corresponding to each color of K, in order to recover a nozzle missing defect of an inkjet nozzle,
It is characterized in that a spare inkjet head corresponding to each of the C and M colors is provided, and a spare inkjet head for Y and K colors is not provided.

According to a second aspect of the present invention, there is provided an ink jet printing apparatus provided with an ink jet head having a full line width corresponding to each color of C, M, Y and K in a direction orthogonal to a printing paper conveyance direction. In order to recover the nozzle missing defect of the inkjet nozzle, a spare inkjet head corresponding to each of the C, M and Y colors is provided, and a spare inkjet head for the K color is not provided.

According to a third aspect of the present invention, in the ink jet printing apparatus according to the first or second aspect, with respect to the nozzle missing defect of K color, C, M, Y color or C,
The feature is that recovery is performed by mixing any one of M colors.

According to a fourth aspect of the present invention, in the ink jet printing apparatus provided with an ink jet head having a full line width corresponding to each color of C, M, Y and K in the direction orthogonal to the conveying direction of the printing paper, the K color is used. A recovering method for recovering a defective nozzle omission, comprising the step of detecting a defective nozzle omission of the K color inkjet head and specifying the position of the corresponding defective nozzle, and a K-color image corresponding to the position of the defective nozzle. Based on the data string, the C,
Modifying the image data of the corresponding columns of M, Y colors or C, M colors.

A fifth aspect of the present invention is the recovering method according to the fourth aspect, wherein the C, M, Y colors or C,
The modification of the M color image data is characterized by taking the logical sum of the K color image data for each of the C, M, Y color or C, M color image data.

[0012]

DETAILED DESCRIPTION OF THE INVENTION An example of an inkjet printing apparatus according to the present invention will be described with reference to FIGS. 1 is a schematic side view showing the configuration of the main part of the inkjet printing apparatus, and FIG. 2 is a schematic top view showing the structure of the head section.

In the drawing, the ink jet printing apparatus is provided with a movable platen 1 for carrying a web-shaped printing paper p.
And heads 2 to 4 for respectively recording CMYK color ink images on the printing paper conveyed by the movable platen 1,
The spare heads 6 and 7 provided as spares for the C and M color heads 2 and 3 are provided. Further, it is provided with a detection means 8 for reading the printed image and detecting nozzle missing of each head.

The movable platen 1 includes a pair of rollers 10 and 1.
Endless belt 12 hung between 1 and this belt 12
And a suction means 13 for sucking the printing paper p via the sheet, and holds the printing paper flat during ink jet recording.

The rollers 10 and 11 are driven to rotate by a motor (not shown), and the rotation speed thereof is synchronized with the recording timing of the head. Endless belt 1
Reference numeral 2 denotes a smooth belt that can run with the printing paper p placed on the surface thereof, and a large number of fine through holes are formed on the belt surface. For example, the endless belt 12 is made of durable steel or the like. Endless belt 1 running above
Adsorption means 13 is provided immediately below the traveling path 2.
The suction means 13 is composed of a suction box having a large number of suction holes on its upper surface, that is, on the surface contacting the rear surface of the endless belt 12, and the inside thereof is connected to a vacuum pump (not shown) to apply a vacuum negative pressure.

In this movable platen 1, the printing paper p travels in a state where it is attracted to the endless belt 12 by the negative pressure of the attraction means 13, so that the feeding accuracy is higher than that of the type in which it is conveyed only by the pair of conveying rollers. can get. Also, the lower surface of the printing paper is not rubbed as compared with a general fixed type platen. It is effective in preventing scratches during double-sided printing and preventing the generation of static electricity. The printing paper p may be in the form of a cut sheet instead of the web.

The heads 2 to 5 are full-line type ink jet heads, each of which is provided with a nozzle array along the width direction of the printing paper p (the direction perpendicular to the paper surface in FIG. 1 and the left-right direction on the paper surface in FIG. 2). The print sheets p are arranged in parallel along the transport direction of the printing paper p traveling by the movable platen 1 (direction from right to left in FIG. 1, direction from top to bottom in FIG. 2). The heads 2 to 5 achieve a full line width by connecting a number of small heads L each having a plurality of nozzle rows. Specifically, as shown in FIG.
The n small heads L1 to Ln are arranged in two rows in a zigzag pattern to form a substantially full line. As described above, in the present embodiment, since the n small heads L are arranged in a zigzag manner, the existing small head L is used to form a printing apparatus having a desired width without using a full-sized head of a custom size. be able to. Although the small heads L are arranged in two rows in this embodiment, they may be arranged in three or more rows.

On the other hand, the C and M colors are provided with spare heads 6 and 7 for recovery. The configuration of the spare heads 6 and 7 is the same as that of the heads 2 and 3. All heads 2-7
Are arranged side by side at a predetermined interval in the order of printing according to each printing color, and are provided with an ink tank, an ink supply pump, and the like, which are not shown.

The detecting means 8 comprises a CCD line sensor provided along the width direction of the printing paper p, and is capable of photoelectrically detecting the ink image on the printing paper. In the present embodiment, a predetermined pattern is printed from a previously designated nozzle, and it is determined whether or not the nozzle is operating normally by detecting whether or not this pattern is formed.

FIG. 3 shows an operation block diagram of each of the heads 2 to 7. As shown in the figure, this inkjet printing apparatus uses each head 2 to 2 based on image data to be printed.
A control means 9 for supplying necessary image data to each of the seven is provided. In addition, each head 2 to 7 has a corresponding head 2
Drivers 2d to 7d for driving .about.7 and image memories 2m to 7m as output buffers are connected.

The control means 9 in this embodiment comprises a microcomputer having various input / output means,
The input image data is RIP-developed into bit map data for each color of YMCK. The image data that has been bit-mapped is stored in each of the image memories 2m to 7m.
and the drivers 2d to 7d are transferred to the image memory 2
Each head 2 corresponding to image data within m to 7 m
Drive 7 The RIP development as described above may be performed by an image processing device or the like provided in the preceding stage of the inkjet printing device.

The printing operation procedure according to this embodiment will be described below with reference to the flowchart shown in FIG. 4 in combination with FIG. First, test printing is performed in advance in step S1, and the presence or absence of nozzle omission is determined by checking the test result in the detection means 8 in step S2.

FIG. 6 is a diagram showing an example of a pattern drawn when the detecting means 8 detects nozzle missing. In this test print pattern, several dots are printed from the nozzles n1, n2, ... Ni at predetermined intervals. Then, test printing is performed while sequentially shifting the nozzles to be operated. This test pattern is read by the detection means 8, and if the recording pattern is missing, it can be determined that the corresponding nozzle is clogged. In this embodiment, the test printing is performed by each head, and the control unit 9 determines which nozzle on which head the nozzle is clogged. The test pattern is not limited to the above, and may be any pattern as long as it can identify the operating nozzle.

If there is no nozzle omission here, the process proceeds to step S3 and printing is performed in the normal printing mode. In this normal printing mode, the control means 9 transfers the bitmap data corresponding to CMYK colors to the image memories 2m to 5m for the heads 2 to 5, respectively. Then, each of the drivers 2d to 5d records an image at a predetermined drawing timing according to the image data in the image memories 2m to 5m. That is, each of the drivers 2d to 5d further reduces each of the small heads L according to the position where each of the heads 2 to 5 is arranged.
The image recording timing is sequentially adjusted according to the zigzag arrangement, and the images of the respective colors are controlled so as to match the same register position.
In this normal print mode, image data is not transferred to the image memories 6m and 7m, and therefore the spare heads 6 and 7 are not used. Therefore, printing is performed only by the original heads 2 to 5.

If there is a nozzle missing, the process proceeds to step S4, and the control means 9 sets the number of colors to be recovered. In this embodiment, the recovering method differs depending on the colors of C and M or K. In this embodiment, Y color is not recovered. This is because a slight drop in Y color is virtually invisible to the human eye. If the color to be recovered is C or M, the process proceeds to step S5, and printing is performed in the C or M recover mode.

Here, for ease of understanding, the case of C color recovery will be described. For example, if nozzle omission occurs in the i-th nozzle of the C-color head 2 due to the test printing, the i-th line of C-color is drawn by the spare head 6 in this embodiment. That is,
The control means 9 transfers the image data for the other nozzles except the i-th nozzle to the image memory 2m, and transfers only the image data for the i-th nozzle to the image memory 6m. As a result, the spare head 6 performs the recovery operation for the i-th nozzle position instead of the head 2.

The heads 2 and 6 and the heads 3 and 7 are configured such that the same C and M colors of ink are supplied from separate ink tanks (not shown), but if necessary. You may make it supply the same ink by switching a distribution route etc. from the same tank.

When the color to be recovered next is K, the process proceeds from step S4 to S6. In this embodiment, the K color spare head is not provided, and the K color is achieved by mixing CMY colors. That is, when nozzle missing occurs in the K-color head 5, reproduction is performed by superimposing CMY pixels instead of K-color pixels.

This K-color recovery method is the procedure shown in steps S21 to S24 of FIG. First, step S21
Then, based on the K color image data k, the image data of the pixel row corresponding to the nozzle missing position of the K color head 5 (hereinafter,
The symbol k1) is extracted. And the following step S
At 22, the image data k1 is added and calculated only at the positions corresponding to the image data c, m, y, and the corrected image data c1, m1, y1 is obtained. For example, the above calculation is 2
If the value is bitmap data, it can be easily obtained by performing a logical sum operation on the image data of image data c and k1, m and k1, and image data of y and k1.

It should be noted that the K color recovery is preferably complemented by mixing the colors of the CMY colors, but a similar effect can be achieved even if the Y colors are omitted and only the CM colors are mixed. In this case, blue pixels are recorded due to the color mixture of CM, but it is generally difficult to distinguish between blue and black, and there are many cases where there is no problem visually.

In step S23, the image data c
Image memories 2m to 4 corresponding to 1, m1 and y1 respectively
forwarded to m. The image data k corresponding to the other nozzles except the image data k1 of the pixel row corresponding to the nozzle missing position is transferred to the memory 5m. Step S24
Then, printing is performed based on this. According to this embodiment, only the portion where the K color nozzle is missing can be complemented by the CMY mixed color pixels.

The procedure and operation example shown in the above flow are specific examples in this embodiment, and can be executed by a modified procedure or other operation procedure. Shall be included. Main modifications will be described below as other embodiments.

[Other Embodiments] (1) In the above embodiment, the Y-color spare head is not provided, but it may be provided. Of course, if the Y-color spare head is not provided, the total number of heads is reduced and the product can be constructed at low cost. The recovering method when the Y-color spare head is provided may be the same as the recovering methods for the C and M colors described above.

(2) LC in addition to YMCK four-color head
(Light cyan), LM (light magenta) 6
The present invention can be applied to an inkjet printing apparatus having a color head.

(3) In the above embodiment, the spare head recovers only the line where the nozzles are missing. However, if nozzles are missing in the heads 2 and 3, all of them are replaced with the heads 2 and 3. Drawing the spare head 6,
7 may be substituted. In this case, it is not necessary to accurately specify the nozzle missing position, but simply the heads 2, 3
Since it is only necessary to detect whether or not the nozzle omission has occurred, it is possible to deal with it by visual inspection or the like. The recovering method in this case can be achieved by simply transferring the image data to the spare head side instead of the normal head.

(4) Even when the K color is complemented by a mixture of CMY colors, the spare heads may be used for the C and M colors. For example, the original C color head 2 and K color head 5
When the nozzle omission occurs at the same time, the spare head 6 is used in place of the head 2 to recover the C color, and the spare head 6 and the M and Y color heads 3 and 4 are used to recover the K color. May be.

(5) In the above embodiment, the heads 2 to 5 are used during normal printing, and the spare heads 6 and 7 are not used. However, stopping one of the heads in this way may not be desirable because it may remain unused for a long period of time. Therefore, in the normal print mode, the heads 2 and 6 and the heads 3 and 7 are
Printing may be performed by alternately operating and. For example, the printing may be switched at an appropriate timing such as one sheet for each print or a predetermined number of jobs.

On the other hand, even in the recover mode, printing may be performed by alternately using the heads. For example, in the case of C color, when the i-th line of the head 2 causes nozzle omission and the j-th line of the head 6 causes nozzle omission, the head 6 is always used for the i-th line. However, the head 2 is always used for the j-th line.
However, in other lines, the head 2 and the head 6 can be used alternately. In such a configuration, the heads 2 and 6 and the heads 3 and 7 do not function as spares, but both heads are treated equally.

(6) In the above embodiment, the detection means 8 detects the nozzle missing position from the test print, but other methods may be used. For example, FIG. 6 is a diagram for explaining an alternative nozzle clogging detection method. First, the first clogging detection device detects the ejection of ink droplets with an optical sensor. FIG. 6A shows this principle diagram. In the figure, this detection apparatus projects a laser beam B onto a head 100 in which a plurality of nozzles are arranged so as to cross a line on which ink droplets of all nozzles are ejected, and the laser beam B. And a light receiving means 102 for receiving the light. The beam diameter of the laser beam B is set smaller than the diameter of the ink droplet, and if the ink droplet exists on the optical axis, the light receiving unit 102 does not receive the light.

In this detecting device, ink droplets are ejected one by one from each nozzle on the head 100 while projecting and receiving the laser beam B. If the light reception of the light receiving unit 102 is blocked at the corresponding timing according to the ejection timing, it means that the nozzle is not clogged and the ink droplet is ejected. On the contrary, even if the head 100 is driven so as to eject the ink droplets, if the light reception of the light receiving unit 102 is not interrupted, it can be determined that the droplets are not ejected, that is, the corresponding nozzle is clogged.

When adopted in the ink jet printing apparatus according to the present embodiment, each head 2 to 7 is in the form of two staggered lines, so it is necessary to provide a light projecting and light receiving means for at least each line. . However, if the distance between the light projecting and light receiving means is long, the accuracy of each mounting position becomes severe. Therefore, n detection means may be provided so as to detect each small head L.

FIG. 6B is an explanatory view showing the principle of the second clogging detection device of another method. In the figure, the head 10
A diaphragm 103 and a vibration detecting means 104 for detecting the vibration of the diaphragm 103 are provided below the nozzle 0. In this device, some ink droplets are dropped from the nozzle onto the vibration plate 103, and the vibration due to this dropping is detected by the vibration detecting means. As this vibration detecting means, for example, a microphone or the like for detecting a minute vibration wave of the diaphragm is known. Since this detection device must be provided below the nozzle, in a full line type inkjet printing device in which the head does not move, it is necessary to provide the detection device so that it can retreat below the nozzle during non-printing. .

[0043]

According to the present invention, there is an effect that a defective nozzle missing of K color can be recovered by mixing CMY colors. Accordingly, even when the spare head for nozzle missing is provided, the K-color head does not have to be provided.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an inkjet printing apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a head configuration in an inkjet printing apparatus according to the present invention.

FIG. 3 is a block diagram of a main part of the inkjet printing apparatus according to the present invention.

FIG. 4 is a flowchart showing a print mode setting procedure and a K color recovery procedure in the inkjet printing apparatus according to the present invention.

FIG. 5 is a diagram showing an example of a test print pattern for detecting nozzle clogging.

FIG. 6 is a diagram for explaining another detection method for detecting nozzle clogging.

[Explanation of symbols]

1 movable platen 2 heads (for C color) 3 heads (for M color) 4 heads (for Y color) 5 heads (for K color) 6 Spare head (for C color) 7 Spare head (for M color) 8 Detection means 9 Control means

Claims (5)

[Claims] 1. An inkjet printing apparatus, comprising an inkjet head having a full line width corresponding to each color of C, M, Y, and K in a direction orthogonal to a transport direction of a printing sheet, the nozzle missing defect of an inkjet nozzle being recovered. In order to do so, an inkjet printing apparatus is provided, which is provided with a spare inkjet head corresponding to each of the C and M colors, and is not provided with a spare inkjet head for the Y and K colors. 2. A direction perpendicular to the conveying direction of the printing paper,
An inkjet printing apparatus including an inkjet head having a full line width corresponding to each color of C, M, Y, and K, in order to recover a nozzle missing defect of an inkjet nozzle, each of the C, M, and Y colors is supported. An inkjet printing apparatus having a spare inkjet head that does not include a spare inkjet head for K color. 3. With respect to the nozzle defect of K color,
The inkjet printing apparatus according to claim 1 or 2, wherein the inkjet printing apparatus recovers by mixing any of C, M, Y colors or C, M colors. 4. A recovery for recovering a nozzle missing defect of K color in an inkjet printing apparatus including an inkjet head having a full line width corresponding to each color of C, M, Y, and K in a direction orthogonal to a printing paper conveyance direction. A method of detecting a nozzle missing defect of the K color inkjet head and specifying a position of the corresponding defective nozzle; and a method of calculating the K color image data string corresponding to the position of the defective nozzle. And C. M, Y colors or image data of corresponding columns of C, M colors. 5. The C, M, Y color or C, M color image data is modified by modifying the C, M, Y color or C, M color image data with the K color image data. 5. The recovering method according to claim 4, wherein the logical sum of is taken.