JP2000190471A - Covering method of defective nozzle in ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a printing method at a speed as high as possible by covering a poor printing even when defective ink discharging nozzle develop. SOLUTION: Whenever the number of the combinations of a nozzle train and the colors of inks changes, badnesses are counted with a counter (S1, S10). The number of the times of main scannings with a printing head is counted with a register (S2, S4). The simulation of a main scanning is performed (S3) under the confirmation that the count value (n) is smaller than the allowable value N (S5 is Y). The above performance is successively repeated just after a region, in which no printing impossible part is present (S6, S3). When the printing over the whole image region is completed (S7 is Y), the number of the times of main scannings is stored (S8). As for the whole combination, the above steps are repeated (S9 is N, S10, S2). When the whole steps come to an end (S9 is Y), the smallest counted value (n) is extracted (S11) so as to set the combination of the nozzle train and the colors of inks read out of a data region d[k] corresponding to the value (n) (S12). The corresponding sub- tank is cleansed and the set ink is poured in the sub-tank (S13) in order to execute a printing (S14).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for complementing a defective nozzle of an ink jet head.

[0002]

2. Description of the Related Art In recent years, as an image forming apparatus for individuals,
A relatively simple printer such as a thermal transfer printer that drives the heating element of the print head to thermally transfer the ink from the ink ribbon to the paper surface, or an inkjet printer that prints by discharging the ink from the ink bottle onto the paper surface. Serial printers have become mainstream and are widely used. At present, not only monochrome printing but also full-color printing is realized. Full-color printing is usually the three primary colors of subtractive color mixing: yellow (yellow), magenta (red dye name)
And three color inks of cyan (greenish blue),
In some cases, this is performed using four colors of ink in which black (black) dedicated to a black portion of a character or image is added.

[0003] In particular, an ink jet printer discharges ink droplets from nozzles of a print head and absorbs the ink droplets on a recording material such as paper or cloth to print characters or images. It is a recording method that generates little noise, does not require special fixing processing, and is easy to perform full-color printing.

FIG. 10A is a perspective view schematically showing the structure of such a serial ink jet printer (hereinafter simply referred to as a printer), and FIG. 10B is a perspective view showing the printing method shown in FIG. Enlarged view of the head viewed from the paper side (A in FIG.
FIG. The printer 1 shown in FIG. 1 is a small-sized printer used personally at home. A print head 3 for executing printing and an ink cartridge 4 containing ink are attached to a carriage 2.

The carriage 2 has a guide rail 5 on the one hand.
And slidably supported on the other hand, and is fixed to the toothed drive belt 6 on the other hand. As a result, the print head 3 and the ink tank 4 are reciprocated in the width direction of the apparatus main body (printer 1) indicated by the double-headed arrow B in the drawing, that is, in the main scanning direction of the print image. A flexible communication cable 7 is connected between the print head 3 and a control device (not shown) of the apparatus main body, and print data and a control signal are sent from the control device to the print head 3 via the flexible communication cable 7.

The print head 3 is integrally formed as a head unit together with the ink cartridge 4 from the beginning and is detachably fixed to the carriage 2, or the print head 3 is fixed to the carriage, and the print head 3 The cartridge 4 is detachably engaged and integrated.

[0007] FIG.
As shown by dashed lines in (a), there are four ink chambers 4b containing yellow (Y), magenta (M), cyan (C), and black (K) inks, respectively. The above four types (four colors) of ink are supplied to the print head 3.

The print head 3 is opposed to the print head 3.
A platen 9 is provided at the lower end of the frame 8 of the apparatus main body so as to extend in the reciprocating movement direction indicated by the double-headed arrow B in FIG. In contact with the platen 9, the paper 10 is fed by a pair of paper feed rollers 11 (the lower roller is shaded by the paper 10 and cannot be seen in the drawing) and a pair of paper ejection rollers 12 (the lower roller is similarly shaded ), The sheet is intermittently conveyed in the printing sub-scanning direction (the diagonally lower left direction in the figure) indicated by the arrow C in the figure.

As a result, the print head 3 moves intermittently in the sub-scanning direction relative to the paper 10. During the intermittent movement (intermittent transport of the paper 10), the print head 3
Is driven by the motor 13 via the toothed drive belt 6 and the carriage 2 to eject ink near the paper 10 and print on the paper. Printing can be performed on the entire surface of the paper 10 by repeating the intermittent conveyance of the paper 10 and the printing during the reciprocating movement by the print head 3.

[0010] Monochrome printers have been the mainstream of the conventional inkjet printers, but recently, full-color printers have been the mainstream as described above.
As shown in FIG. 2B, four rows of nozzles for discharging four types of inks of yellow (Y), magenta (M), cyan (C) and black (K) are provided on the ink ejection surface. Rows 14 (14y, 14m, 14c, 14k) are formed.

In one nozzle row 14, about 125 or 256 nozzles 15 are arranged in a row at a density of, for example, 300 dpi (dots / inch) (about 12 nozzles per mm). . Each nozzle row 14 has one
Each ink chamber 4b of the ink cartridge 4 corresponding to one
, The ink of the color corresponding to each nozzle row 14 is supplied.

As described above, an ink jet printer that forms an image on a sheet by ejecting ink onto the sheet at a predetermined interval from the print head uses ink as a recording agent. In addition, poor ink ejection from nozzles often occurs due to air bubbles mixed into the ink flow path of the print head, deterioration of the head material due to the ink, drying of the ink, and the state of the nozzle surface.

As described above, when a defective nozzle is generated, that is, when one of a large number of print dots is missing, if printing is performed normally with this, the missing print dot appears at the same position every main scanning. Therefore, the defect becomes visible at a glance as a blank horizontal line, which significantly reduces the quality of the image.

In order to prevent the occurrence of such defective nozzles, measures such as improvement of ink, prevention of drying by covering the print head with a cap, cleaning of the nozzle surface, and the like are employed to improve the reliability of the print head. Although endurance has been improved, it is often difficult to virtually eliminate such defects. Instead, a method of complementing the printed portion of the defective nozzle with another excellent nozzle has been conventionally proposed. Hereinafter, this will be briefly described.

FIG. 11A shows a nozzle row where a defective nozzle is located, and a position where ink is required to be ejected onto the paper 10 by the nozzle row, that is, a print area of an image to be printed (white circle).
FIGS. 9B and 9C show the first half of the state in which printing is performed while complementing defective nozzles with this nozzle row. Here, for convenience of explanation, it is assumed that the nozzle rows 14y, 14m, 14c and 14k of the print head 3 shown in FIG. 10B are each composed of four nozzles. Further, here, an example in which the image (white circle) to be printed is a print portion using only the black (K) ink, and the colors of the other inks Y, M, and C are not required. . Therefore, the nozzle row used is nozzle row 1
Only 4k.

FIGS. 12A and 12B show the above-mentioned nozzle row 14k.
FIG. 9 is a diagram illustrating a state in the latter half of performing printing while complementing a defective nozzle. 11 (a), (b), (c) and FIGS. 12 (a),
(b) In both cases, the arrow x indicates the main scanning direction of the print head 3,
The arrow y indicates the sub-scanning direction of the print head 3. In the examples shown in FIGS. 11 and 12, the nozzle row 1
One nozzle 15k-3 within 4k (hereinafter, nozzle row 14
k of the four nozzles 15 into nozzles 15k-1, 15k-
2, 15k-3, and 15k-4), but could not be discharged for some reason (the other three nozzles 15k-
1, 15k-2 and 15k-4 are normal).

As shown in FIG. 11A, the image (print dot) to be printed now has six rows (rows 16-1, 16-2, 16-3, 16-4, 16) in the main scanning direction. −
5, 16-6), and 8 rows (row 17-
1, 17-2, 17-3, 17-4, 17-5, 17-
6, 17-7, 17-8). Therefore, if all four nozzles 15 in the nozzle row 14k are normal, the printing operation of the print head 3 in the main scanning direction is completed by moving twice (8 rows / 4 nozzles = 2 times) Cover). However, in this case, since the nozzle 15k-3 is defective, the entire printing area cannot be covered by two scans.

That is, FIG. 11B is a diagram after printing is performed by the above-described print head 3 (that is, the nozzle row 14k) in one scan in the main scanning direction. As shown by a black circle in the figure, the row 17-1 is printed by the nozzle 15k-1 and the nozzle 1k-1 is printed.
Row 17-2 is printed by 5k-2, and nozzle 15k-
4 prints row 17-4, but the nozzle 15k
-3 is defective, so that row 17-3 is indicated by the hatched circle in the figure.
Is not printable.

In order to print line 17-3, FIG.
As shown in (c), the print head 3 is advanced by 2 dots in the sub-scanning direction relative to the print area (actually, FIG.
In (a), the paper 10 is conveyed by two dots in the direction of arrow C), and the row 17-3 is printed by the nozzle 15k-1. At this time, an image unprinted area is printed as much as possible by another normal nozzle. That is, the row 17-6 is printed by the nozzle 15k-4. Also in this case, the nozzle 15k
Line 17-5 cannot be printed because -3 is defective.

Subsequently, the line 17-5 where printing was not possible was performed.
As shown in FIG. 12A, the print head 3 is advanced by two dots in the sub-scanning direction relative to the print area, and the row 17-5 is printed by the nozzle 15k-1. The image unprinted area as much as printable by the other normal nozzles, that is, the row 17-8 is printed by the normal nozzles 15k-4. Also in this case, the row 17-7 corresponding to the defective nozzle 15k-3
Is not printable. Here, the print head 3 is further advanced by two dots in the sub-scanning direction, and as shown in FIG. 12B, the row 17-7 is printed by the nozzle 15k-1 to complete the printing of the entire image area. .

[0021]

As described above, in the ink jet printer in which the color of the ink ejected from the nozzle array is fixed, if any one of the many nozzles has a defective nozzle, the defective printing is repeated. There is a problem that the number of main scans becomes extremely large to complement by scanning. That is, in the above example, the entire image area to be printed is complemented with the impossibility of printing of the defective nozzle 15k-3,
This is achieved by four reciprocating movements of the print head 3 (four main scans). As described above, there is a problem that the printing time becomes longer to complement the printing of the defective nozzle.

The above nozzle rows 14k, 14k
The ink colors of c, 14m and 14y are shown in FIGS. 10 (a) and (b).
As shown in the figure, the ink chamber 4b of the ink cartridge 4
Respectively, and therefore, nozzle row 1
Even if the four nozzles 15 of each of the three nozzle rows 14c, 14m, or 14y other than 4k are normal,
Since the color of the ink to be ejected is different from the color of the ink to be ejected by the defective nozzle 15k-3 of the nozzle row 14k,
It is not possible to substitute the printing of the defective nozzle 15k-3. Therefore, there is no other method except to complement the printing of the defective nozzle by the printing method as described above.

SUMMARY OF THE INVENTION The object of the present invention is to provide
An object of the present invention is to realize a method for compensating for a printing failure by suppressing an increase in printing time as much as possible even if a nozzle failure occurs in an inkjet head.

[0024]

According to the present invention, there is provided a method for complementing a defective nozzle of an ink jet head, comprising an ink tank for supplying ink to a nozzle array, and changing the color of replenishment ink to the ink tank by changing the color of the nozzle array. A method of complementing a defective nozzle in an ink jet printer capable of changing the color of the discharged ink, comprising: a step of storing the position of the defective nozzle; and a step of storing each ink tank corresponding to each nozzle row based on the position information of the defective nozzle In all combinations of ink colors to be filled in, a step of respectively executing a simulation to complete the printing while complementing the printing portion of the defective nozzle with respect to the printing data of the printing area in a predetermined range,
A step of determining a combination of the filled ink colors in which the printing is completed with a minimum number of main scans from the result of the simulation, and a step of filling each ink tank with ink of a color corresponding to the determined replenishment ink color. And performing printing using the ink tank replenished with the ink.

The above simulation is performed, for example, in claim 2
As described, in the first main scan, the first line of the print area is scanned so that it can be printed normally, and in the second and subsequent main scans, at least the line immediately after the normally printed area can be printed. This is performed for one page of print data, for example.

[0026]

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

FIG. 1A is an exploded perspective view showing an essential part of an image forming apparatus according to an embodiment, and FIG. 1B is an enlarged perspective view showing the print head unit. is there. As shown in FIGS. 1A and 1B, a main part 20 of the image forming apparatus includes a print head unit 21, a head driving mechanism 22, a main tank unit 23, and a pair of transport rollers 24 in a housing of the apparatus main body. It has.

The print head unit 21 and the main tank unit 23 are arranged independently of each other. That is, one of the print head units 21 is connected to a control unit (to be described later) of the apparatus main body by a flexible signal cable 25 and engages with a linear rail 26 of the head drive mechanism 22.
7, the printing is performed on the paper surface (not shown) while reciprocating along the longitudinal direction of the head drive mechanism 22, as indicated by a double-headed arrow D in FIG. The sheet is conveyed by a pair of conveying rollers 24 from the front of the main part 20 to the rear as indicated by an arrow E in FIG.

The other main tank unit 23 is vertically flat and has a rectangular shape in the horizontal direction. The longitudinal direction of the rectangular shape extends in parallel with the longitudinal direction of the drive mechanism 22, and the frame of the housing of the apparatus main body. It is arranged to be removable. In FIG. 3, a part of the sealing sheet 28 that covers the upper surface of the main tank unit 23 is cut away. A plurality of liquid storage chambers 29 for storing four colors of ink and a cleaning liquid are provided inside the cutout. The liquid filling ports 31 for replenishing the plurality of liquid storage chambers 29 with ink or cleaning liquid from the outside correspond to the number of the liquid storage chambers 29 by the number corresponding to the number of the liquid storage chambers 29. (Lower left end).

Further, at the right end of the lower surface of the main tank unit 23, four ink supply ports and one cleaning liquid supply port are provided, although not shaded in FIG.
A supply port opening / closing unit, not shown, is disposed between the main tank unit 23 and the print head unit 21. The supply port opening / closing unit moves forward and backward in the longitudinal direction of the main tank unit 23. The liquid supply port is opened and closed. Although not particularly shown, the front end detection sensor of the sheet and the rear of the print head unit 21 (diagonally lower right position in FIG. 3A) and rear (diagonally upper left position in FIG. An edge detection sensor is arranged.

As shown in FIG. 2B, the print head unit 21 is attached to the rear half 33 of the head base 32.
A linear coil 34 is provided. This linear coil 34
, The linear rail 26 described above is fitted. A slit groove 35 is formed at the rear end of the rear half 33.
A mark reading sensor which is not visible in the drawing is provided with the slit groove 35 interposed therebetween. The mark reading sensor reads a mark (a bar code or a cutout slit) formed on the linear scale 27 which is relatively fitted into the slit groove 35 and transmitted to the control unit. Thereby, the control unit controls the energization of the linear coil 34 to control the moving amount of the print head unit 21.

The front half 36 of the head base 32 includes
Ink receiving ports 37 opening in parallel with each other in a slit shape
A sub-tank (ink tank) described below, which has on the upper surface, is provided. These sub-tanks hold four types of inks for performing full-color printing: yellow, magenta, cyan, and black. A print head 38 made of a chip substrate is provided on the lower surface of the first half 36, and the wiring of the flexible signal cable 25 is connected to the wiring terminal of the print head 38.

FIG. 2A is a cross-sectional view of the front half 36 of the head base 32 shown in FIG.
FIG. 2 is a view as viewed in the direction of the arrow G in FIG. 1B (a view as viewed in the direction of arrow H in FIG. 2A). The print head 38 shown in FIGS. 2A and 2B has a thickness of about 40 μm formed on a chip substrate 39 by a thin film processing technique.
Heating elements having a size of × 40 μm are arranged at a predetermined pitch, and a common ink path is formed around the periphery thereof by partition walls laminated with a thickness of about 10 μm. The common ink path is formed on the surface of the chip substrate. The ink supply groove 41 communicates with the ink supply groove, and an ink receiving hole 41 penetrating through the chip substrate and communicating with the ink supply groove is formed in the back surface. The ink supply hole 41 communicates with a sub tank (ink tank) 43 via a filter 42. In addition, the chip substrate 39
The above-mentioned wiring terminals 48 and 49 of the drive circuit
Are formed.

On the uppermost layer of the chip substrate 39, a film-like nozzle plate 4 made of polyimide or the like and having a thickness of 10 to 30 μm.
4 are stacked to cover the common ink path formed by the partition walls, thereby forming a fine pit-shaped path for the ink supplied to the heating element. Then, a nozzle 45 formed by dry etching or the like is collectively formed at a position directly above each heating element of the nozzle plate. For example, 125 or 256 nozzles 45 form one nozzle row 46, and four nozzle rows 46 are formed in parallel to form an ink ejection surface of the print head 38.

The ink receiving port 3 of the print head 38
When the print head unit 21 moves to the home position, ink or cleaning liquid is supplied to the nozzle 7 from the liquid supply port of the main tank unit 23. A micro pump mechanism (not shown) is provided at the liquid supply port of the main tank unit 23. The micropump mechanism is supported by a tank base and includes a diaphragm having a downward opening communicating with the liquid supply port or a nozzle having a large ink discharge nozzle of a print head.

When the downward opening communicating with the liquid supply port is formed by a diaphragm, an input valve is provided in the opening of the diaphragm at the communication section with the liquid conduction path of the ink tank. An output valve is provided in the communication section with the と. These valves are in close contact with the communicating portion by their own elastic force in a natural state.

A cylindrical permanent magnet is fixedly attached at one end to the outside of the upper portion of the opening and the counter electrode of the diaphragm. The magnetic poles of the permanent magnet are polarized at both ends of the cylindrical shaft, and the side peripheral surface is slidably fitted in the guide hole of the guide member. A micro coil wound in a spiral shape is disposed on the free end side of the permanent magnet.

When a current is applied to this microcoil, the permanent magnet operates in the vertical direction following the change in the polarity of the magnetic force generated by the switching current, whereby the lower end of the permanent magnet is fixed. The upper part of the diaphragm moves up and down, so that the pressure inside it increases and decreases according to the frequency of the switching current. The input valve is operated (opened) by the decrease in the internal pressure of the diaphragm (the permanent magnet moves upward), and the liquid (ink or cleaning water) flowing from the liquid storage chamber into the liquid passage is sucked into the diaphragm.

Then, the input valve closes and the output valve opens by the increase in the internal pressure of the diaphragm (the permanent magnet moves downward), and the liquid (ink or cleaning water) sucked into the diaphragm is discharged. Outflow from the supply port.
The amount of liquid supplied from the liquid supply port can be controlled by the frequency of the current applied to the microcoil. As a result, the black ink, cyan ink, magenta ink, yellow ink, and cleaning water of the main tank unit are supplied to the ink receiving port 2 of the print head unit 3 through the liquid supply port.
The amount of ink or cleaning liquid supplied to 4 can be controlled to a desired amount.

When the downward opening communicating with the liquid supply port is constituted by a nozzle having a large ink discharge nozzle, the ink supply hole penetrating the chip substrate and the communication with the ink supply hole are formed similarly to the case of the print head. An ink supply groove formed in the surface of the substrate, an ink passage formed by partition walls laminated on the substrate surface and branching from the ink supply groove in a comb-like shape, and an ink passage formed in the interior of these ink passages. Heating elements (heating elements), common electrodes and individual driving electrodes connected to these heating elements, driving circuits (diffusion units) connected to these individual driving electrodes, and stacked on these A micropump mechanism is provided which includes a nozzle plate provided and ink discharge nozzles formed at positions facing the heating resistor of the nozzle plate.

The print head unit 21 supplies desired ink or a cleaning liquid as required from the micro pump mechanism of the main tank unit 23 to the ink receiving port 3.
The printing is executed while being received by the sub-tank 43 via the printer 7. During printing, ink droplets 47 are ejected from the nozzles 45 toward the paper surface.

FIG. 3 is a block diagram showing a system configuration of the image forming apparatus having the above configuration. As shown in the figure, the system configuration of the image forming apparatus 50 is divided into a stationary unit 51 and a moving unit 52. One moving unit 52 is a print head unit 2 that reciprocates in the main scanning direction by the linear rail 26, the linear coil 34, and the linear scale 27.
It comprises a driver 53 for driving the heat generation of one heating element.

The other stationary unit 51 is a control unit, and includes an MPU (micro processing unit) 54 and this MP
An I / F (interface) 56 and a head control unit 57 connected to the U 54 via a bus 55;
Memory A58 and head control unit 57 connected to F56
Is connected to the memory B59.

The image forming apparatus 50 receives an I / F from a PC (personal computer) 60 as a host device.
Via 56, print data and control data are input.
The MPU 54 receives the above print data and control data while controlling the memory A 58 via the I / F 56.

The MPU 54 receives an output 61 of a sensor for monitoring each part. The MPU 54 controls the rotation of a motor for transporting the paper and the linear coil 34 for reciprocating the print head unit 21. A drive signal 62 for controlling the energization drive is output. Also, MPU
Reference numeral 54 expands print data including complementary data for each line described later in the memory B 59 via the head control unit 57, and controls the driver 53 via the head control unit 57 based on the expanded print data. .

The MPU 54 controls these parts while referring to the output 61 of the sensor or referring to the position of a defective nozzle described later. Also, the head control unit 57
Transfer of print data and control signals from the
This is performed via the flexible communication cable 25 shown in FIGS. 1 (a) and 1 (b). Of course, IrDA (Infared Data Assoc)
iation: an organization that standardized infrared data communication or its system, and in turn, an apparatus using that system).

FIG. 4 schematically shows the correspondence between the liquid storage chamber 29 of the main tank unit 23 and the sub tank 43 (actually, the ink receiving port 37) of the print head 38 (actually, the print head unit 21) in the above configuration. FIG. The main scanning direction indicated by a double-headed arrow X of the print head 38 shown in FIG. 1 is the same as the main scanning direction indicated by a double-headed arrow D in FIG. The sub-scanning direction indicated by arrow Y in FIG. 4 is the direction of relative movement of the print head 38 with respect to the sheet (sub-scanning direction), and is opposite to the sheet transport direction indicated by arrow E in FIG. Direction. The range indicated by the double-headed arrow J in FIG. 4 is the effective print width of the print head 38, and the right side thereof is the home position of the print head 38. FIG. 7 shows a state in which the print head 38 has moved to the rightmost end of the home position.

5 of the main tank unit 23 shown in FIG.
Main tanks 29 (29y, 29m, 29c, 29
k, 29s) contain yellow, magenta, cyan, and black inks and a cleaning liquid, respectively. At the right end of the lower surface of each main tank 29, there are four ink liquid supply ports 64 which are not visible in FIG.
y, 64m, 64c, 64k and one cleaning liquid supply port 64
s is provided.

The total of five liquid supply ports 64 are connected to any one of the ink receiving ports 3 of the print head 38 by the print head 38 sliding in the home position as appropriate.
7, ink or cleaning liquid can be supplied.

FIG. 5 shows four ink receiving ports 37 (37-1, 37-2, 37-3, 37-4) of the print head 38.
Among the five liquid supply ports 64 of each main tank 29 (64y, 64m, 64c,
64k). In this state, the ink receiving port 37 is controlled by the MPU 54.
For -1, an ink or a cleaning liquid of any color of yellow, magenta, cyan or black can be supplied.

This is the same for any of the ink receiving ports 37, that is, in FIG.
Can discharge ink of any color from the four nozzle rows 46 shown in FIG.

When a defective nozzle occurs, the position of the defective nozzle must be recognized and stored in order to complement the printed portion of the defective nozzle. Hereinafter, a method of recognizing the position of the defective nozzle will be described.

FIG. 5 is a diagram showing a test print pattern for specifying a nozzle having a defective ink ejection. In this test printing, printing is executed according to a test pattern printing instruction input by a user from an operation panel (not shown) of the image forming apparatus 50. Also in this case, for the sake of simplicity, an example is shown in which the print head has eight dots (eight nozzles) in the sub-scanning direction.

As shown in the drawing, first, a numeral (nozzle number) “1” is printed using all the dots, and a line feed is performed.
Next, solid printing (ie, printing a straight line) with a predetermined length, for example, 10 mm, is performed under the above-mentioned number "1" at the first (first) dot on the upstream side (upward direction in the drawing) in the paper transport direction. Subsequently, the number "2" is printed at the right position printed at the length of 10 mm, a line feed is performed, and the second dot is printed at the same length. The dot,..., The eighth dot are repeated. As described above, the printing start position of each dot is shifted in the main scanning direction, and each dot is printed by about 10 mm on one dot line while numbering is performed.

In the example shown in the figure, the sixth dot is a defective example. The print trace of the sixth dot is shown by a broken line in the figure for the sake of simplicity. If it is normal, a line of 10 mm is printed at the position of the broken line in the figure. Nothing is printed at the position of the broken line below the number “6”, and the space is blank.

When the method shown in FIG. 5 is used, when one of the nozzles in the print head causes an ink ejection failure and a defective portion appears in the formed print image, the position of the defective nozzle is specified. In addition, when printing is performed after a long period of suspension of use, it is possible to check in advance whether there is a nozzle having a defective ink discharge, and to identify a defective nozzle if there is a nozzle that has a defective ink discharge. it can.

In the case of an 8-dot print head as in this example, since the number is small, each dot position is visually counted from the left, and specifying a dot having an ink ejection failure means that a number is printed. It is easy even if it is not, but for example, when trying to identify a defective dot out of 128 dots, if no number is attached, especially if there is a defective dot behind (to the right of) the center. Is difficult to count. As shown in the figure, when numbered and printed,
The user can easily recognize the number of the nozzle having the ink ejection failure from the downstream side in the paper transport direction.

The number of nozzles in the nozzle row is 128 or 2
When there are a large number of nozzles, such as 56 nozzles, it is advisable to repeat the process of printing the number for one line and then drawing a straight line sequentially with each nozzle. When A4 size paper is transported vertically and numbers are printed at 10 mm intervals in the width direction,
Defective nozzles can be easily specified simply by printing a line of 18 nozzles in one line and drawing a straight line by each nozzle in one line below the line, by repeating it a little seven times.

The number of the detected (specified) ink ejection failure dot (the sixth dot in the example of FIG. 5) is entered by the user from the keyboard of the PC 60 or the operation panel of the image forming apparatus 50. When input, the MPU 54 of the image forming apparatus 50 stores the number of the defective dot in the built-in nonvolatile RAM. Thereafter, printing control is performed so that image formation is performed while complementing the ink ejection failure of the sixth dot. Thereafter, the stored location is canceled until this setting is released or the head replacement is recognized. Are controlled not to perform the printing operation.

FIG. 6A shows a print head in which a defective nozzle has occurred, and a position where the print head requires ink ejection on a sheet, that is, a print area of an image to be printed (a vertically long white rectangle). FIG. 2B shows an initial state in which printing is performed while complementing defective nozzles with the print head.

FIGS. 7 (a) and 7 (b) show a state where the printing is continued while the defective nozzle is complemented by the print head having the defective nozzle and the printing is completed. Here, for convenience of description, the four nozzle rows 46 of the print head 38 shown in FIG. 2B are replaced with the nozzle rows 46 in FIGS. 6A and 6B and FIGS. 7A and 7B. 201, 202, 203, and 204, each nozzle row has four nozzles 2010 to 2013 and nozzle 20
20 to 2023, nozzles 2030 to 2033, and nozzles 2040 to 2043.

In the reference state, the nozzle row 201 is supplied with black ink (K), the nozzle row 202 is supplied with cyan ink (C), and the nozzle row 203 is supplied with magenta ink (M). The nozzle row 204 is supplied with yellow ink (Y).

In the example shown in FIG. The number of dots of the image to be printed is six rows (320, 32) in the main scanning direction.
1, 322, 323, 324, 325), 8 rows (310, 311, 312, 313, 314, 31) in the sub-scanning direction
5, 316, 317). Also, dots P to be printed on the image are shown as being divided into four vertically long rectangles of Y, M, C and K. The dot P to be printed is divided into Y, M, C, and K from the left side of FIG. 2A, and the portion corresponding to the color portion that needs to be printed is surrounded by a solid line.

For example, dots of 310 rows and 320 columns are printed using all the inks of Y, M, C and K, and dots of 310 rows and 321 columns to the right of the dots are the solid rectangles on the leftmost vertical rectangle. Since it is enclosed, it indicates that only Y is printed. In the example shown in FIG. 7A, the nozzle row 20 among the four nozzle rows of the print head 38 is used.
The third nozzle 2033 is defective.

Here, the case where the image shown on the right side of FIG. 6A is printed by the print head 38 in which the relationship between the ink color and the nozzle row is set to the reference state while complementing the defective nozzles. If you think about it, it will be as follows.

That is, in the first main scan, as shown in FIG. 6B, since the nozzles 2033 of the magenta M nozzle row 203 are defective, 313 of the image
The magenta M in the row and 323 columns cannot be printed (hatched rectangle). Accordingly, in order to complement this, as shown in FIG. 7A, the print head 38 is moved by three dots in the sub-scanning direction, and 313 rows and 323 columns of unprinted dots are printed by the nozzles 2030. At the same time, three lines of 314 lines or less are printed using the second or less nozzles of another nozzle row. Then, all of the 316 lines of magenta M are unprintable and remain.

Again, the print head 38 is moved to the position 313 in FIG.
By moving in the sub-scanning direction by 3 dots from the line position,
The printed portion of magenta M of 316 lines is
And print the remaining 317 lines of dots (both magenta or cyan) in the nozzle rows 203 and 202.
6A, and the printing of the image shown in FIG. 6A is completed. The number of main scans by the print head 38 until the completion of the printing is three times.

By the way, the image forming apparatus 50 in this embodiment
In, it is possible to freely set the color of the ink ejected to the nozzle row. As a result, it is possible to search for the optimal combination of the nozzle row and the ink color in advance, and perform printing as fast as possible while complementing the defective nozzle 2033.

In order to find the optimal combination of the nozzle row and the ink color, first, the inks are Y, M, C and K
There are 24 combinations when there are four colors and there are four nozzle rows. Therefore, for each of the four colors, the main part of the print head 38 when the entire image area is printed while complementing the defective nozzle 2033. Check the number of scans in the scan direction,
Printing is performed using a combination of the ink and the nozzle row when the number of scans is the least.

FIG. 8 shows an MPU for optimally (as fast as possible) printing performed while complementing the defective nozzle.
FIG. 6 is a flowchart of a simulation process performed by the CPU and a process of extracting an optimal combination of a nozzle row and an ink color and executing printing.

In the flowchart of FIG. 8, first, a counter k for counting the number of combinations is initially set to "1" (step S1). Subsequently, "0" is initially set in a register n for counting the number of main scans of the print head 38 (step S2).

Next, the image shown on the right side of FIG.
(a) The print head 38 in the reference state shown on the left side of FIG.
2, the nozzle head 203 prints cyan ink (C), the nozzle row 203 prints magenta ink (M), and the nozzle row 204 prints yellow ink (Y). Length)
Is performed (step S3).

At this point, the actual printing has not been performed yet, and this is a simulation for knowing how many main scans will complete the printing. However, for convenience of explanation, the expression “printing” will be used. In the setting of the print head 38 in the reference state, three main scans are required as described above. Then, in the first main scan in the simulation, the defective nozzle 2033
In response to the above, as shown in FIG.
Three rows of M (rectangular hatched) cannot be printed.

Here, the number of main scans is counted by incrementing the register n by "1" (step S4), and subsequently, it is determined whether or not the count value n is smaller than a predetermined allowable value N (step S4). Step S5). This allowable value N is set to prevent the main scanning from being repeated indefinitely when the first nozzle of the nozzle row is defective and there is a color that cannot be printed in the first row of the image. This is an acceptable value.

In the above determination, if the value of the register n is smaller than the allowable value N (S5: Y), the line immediately after the printing is completely completed (313 in the first processing cycle in the example shown in FIG.
(In the next processing cycle, 316 rows, and in the next processing cycle, immediately after 317 rows) (in step S6).

Then, it is determined whether or not printing of the entire image area (up to 317 lines in this example) is completed (step S).
7) If not completed (N in S7), step S3
And the steps S3 to S7 are repeated. As a result, in the example shown in FIG. 6A, three main scans (simulations) are performed, and n = 3, and it is confirmed in step S7 that printing (simulation) of the entire image area has been completed (step S7). S7 is Y).

Subsequently, the above-mentioned count value n (= 3) is calculated by MP
It is stored in the k-th simulation data area d [k] of the EEPROM incorporated in U54 (step S), and it is determined whether or not the same simulation as described above has been completed for all combinations (24 in this example). (Step S9). If not completed (N in S9), in this case, the counter k is incremented by "1" (step S10), the process returns to step S2, and steps S2 to S7 are repeated. Thereby, for the 24 combinations of the nozzle row and the ink color, the number of main scans until the image is completed is two times the number of the nozzle row and the ink color.
Each of the four combinations is counted by the counter k.

On the other hand, if the simulation has been completed for all combinations in step S9 (S9 is Y), in this case, the simulation data area d
With reference to [k], the smallest number n of main scans is extracted (step S11). Then, based on the data stored in the simulation data area d [k] when the number of main scans is n, a combination of the ink color and the nozzle row is extracted (step S12). Thus, for example, in the case of the example shown in FIG. 6A, as shown in FIGS. 9A and 9B, the cyan C ink is set in the nozzle row 201, the magenta M ink is set in the nozzle row 202, and the nozzle row is set. The setting is such that black K ink is supplied to 203 and yellow Y ink is supplied to the nozzle row 204.

This setting is performed for the print head in the reference state shown in FIGS.
In all other cases, the ink colors to be ejected are changed. Therefore, the nozzle rows 201 in which these ink colors have been changed,
After the cleaning liquid is poured into the sub tanks 202 and 203 to clean the inside of the sub tanks, the set cyan C ink, magenta M ink, and black K ink are applied to the nozzle row 201, the nozzle row 202, and the nozzle row 2
03 into the sub-tanks 43 (step S1
3).

Then, printing is executed (step S1).
4). In this printing process, printing is first performed as shown in FIG. 3 corresponding to the above-mentioned defective nozzle
In the 13th row, 320 columns, 321 columns, and 322 columns are dots to be printed with yellow Y and 323 columns are dots to be printed at the magenta M. In the newly set nozzle row 204 or 202 that discharges the yellow Y or magenta M, Has no defective nozzles.

As a result, in one main scan, the image area corresponding to the length of the nozzle row, that is, the image area corresponding to 4 dots in the sub-scanning direction, is completely printed without producing unprintable dots. Therefore, in the next movement of the print head in the sub-scanning direction, as shown in FIG. 9B, normal (normal) movement of four dots is performed.

In this printing, black K is not included in the color of the dots in the image area of line 317 to which the defective nozzle 2033 corresponds. Therefore, also in this case, all printing is performed by one main scan without generating unprintable dots. That is, as shown in FIGS. 6 (b) and 7 (a) and (b), compared to the case where printing was performed by three main scans with the ink color of the nozzle row of the print head being the reference setting, When printing is performed with the optimal settings obtained by performing the simulation, printing can be completed in two main scans, and the time is reduced by 50%.

Incidentally, in the determination in step S5 in FIG.
N ≦ n occurs when the first nozzle of the nozzle row is defective. In this case, the printing is executed by suspending the first dot of all (4 rows) nozzle rows.
The print data of the image to be simulated is 1
Although it is preferable to perform the process for the page, the process is not limited to the process for one page, and the print data may be performed for the print data which is divided from the head data to an appropriate range.

Further, as shown in FIG. 5, the detection of defective nozzles is carried out visually, but the detection of defective nozzles is not limited to this, and the test print pattern is automatically scanned and scanned by a CCD. It may be.

Further, as shown in FIG. 5, the detection of the defective nozzle is performed visually, but the detection of the defective nozzle is not limited to this, and the test print pattern is automatically scanned and scanned by the CCD. It may be.

[0086]

As described above in detail, according to the present invention, when a defective nozzle is generated, a simulation is performed on print data of a print image for all combinations of nozzle rows and ink colors to perform main scanning. Since the printing is executed by determining the optimal combination of the nozzle row and the ink color that requires the minimum number of times, it is possible to obtain a printed image with high printing quality without impairing the printing speed.

[Brief description of the drawings]

FIG. 1A is an exploded perspective view showing a configuration of a main part of an image forming apparatus according to an embodiment, and FIG. 1B is an enlarged perspective view showing a print head unit taken out therefrom.

2 (a) is a cross-sectional view of the front half of the head base of FIG. 1 (b) as viewed from the direction of the arrow F, and FIG. 2 (b) is a view of the head base of FIG.

FIG. 3 is a block diagram illustrating a system configuration of the image forming apparatus.

FIG. 4 is a diagram schematically showing a correspondence relationship between a liquid storage chamber of a main tank unit and a sub tank of a print head.

FIG. 5 is a diagram showing a test print pattern for specifying a nozzle having a defective ink ejection.

6A is a diagram showing a print head of a reference setting in which a defective nozzle has occurred and a print area of an image (white vertical rectangle) to be printed by the print head, and FIG. FIG. 11 is a diagram showing an initial state in which printing is performed while complementing the above.

FIGS. 7A and 7B are diagrams showing a state in which printing is continued and completed while complementing the defective nozzles with the print head of the reference setting having the defective nozzle, following FIG. 6B.

FIG. 8 is a flowchart of a process for executing printing by setting a relationship between an optimal ink color and a nozzle row by simulation.

FIGS. 9A and 9B are diagrams illustrating an example of a case where printing is performed with an ink color and a nozzle row that are optimally set.

FIG. 10A is a perspective view schematically showing the configuration of a conventional serial ink jet printer, and FIG. 10B is an enlarged view of the print head of FIG.

FIG. 11A is a diagram showing a nozzle row having a defective nozzle and an image pattern (white circle) to be printed by the nozzle row.
(c) is a diagram illustrating a first half of a state in which printing is performed while complementing a defective nozzle with the nozzle row of (a).

FIGS. 12A and 12B are diagrams illustrating a second half state in which printing is performed while complementing a defective nozzle with the nozzle row in FIG. 8;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Printer 2 Carriage 3 Print head 4 Ink cartridge 4b Ink chamber 5 Guide rail 6 Toothed drive belt 7 Flexible communication cable 8 Frame of apparatus main body 9 Platen 10 Paper 11 Paper feed roller pair 12 Paper discharge roller pair 14 (14y, 14m, 14c, 14k) Nozzle row 15 (15k-1, 15k-2, 15k-3, 15k-
4) Nozzle 16 (16-1 to 16-6) Print row 17 (17-1 to 16-8) Print row 20 Main part of image forming apparatus of one embodiment 21 Print head unit 22 Head drive mechanism 23 Main tank unit 24 Conveyance Roller Pair 25 Flexible Signal Cable 26 Linear Rail 27 Linear Scale 28 Sealing Sheet 29 (29y, 29m, 29c, 29k, 29s) Liquid Storage Room 31 Liquid Filling Port 32 Head Base 33 Base Rear Half 34 Linear Coil 35 Slit Groove 36 Base first half 37 (37-1, 37-2, 37-3, 37-4) Ink receiving port 38 Print head 39 Chip substrate 41 Ink receiving hole 42 Filter 43 Sub-tank 44 Nozzle plate 45 Nozzle 46 Nozzle row 47 Ink drop 48 , 49 Wiring terminal 50 Image forming apparatus 51 Static Unit 52 moving unit 53 heating driver 54 MPU (micro processing unit) 55 bus 56 I / F (interface) 57 head control unit 58 memory A 59 memory B 60 PC (personal computer) 61 output of each sensor 62 various drive signals 64 (64y, 64m, 64c, 64k, 64s) Liquid supply port

Claims (3)

[Claims] 1. A method for complementing a defective nozzle in an ink jet printer, comprising an ink tank for supplying ink to a nozzle row, and changing the color of ink discharged from the nozzle row by changing the color of replenishing ink to the ink tank. A step of storing the position of the defective nozzle; and, based on the position information of the defective nozzle, in all combinations of the ink colors to be filled in the respective ink tanks corresponding to the respective nozzle arrays, A step of respectively performing a simulation for completing printing while complementing a printing portion of the defective nozzle with respect to print data, and determining a combination of the filled ink colors in which the printing is completed by a minimum number of main scans based on a result of the simulation. Filling each ink tank with ink of a color corresponding to the determined replenishment ink color. Complement method of the defective nozzle of the inkjet head which comprises a step of performing printing by using a replenishment ink tank of the ink, at least. 2. The simulation according to claim 1, wherein in the first main scan, the first line of the print area is scanned so as to be normally printed, and in the second and subsequent main scans, at least the line immediately after the normally printed area is printed. 2. The method for complementing defective nozzles of an ink jet head according to claim 1, wherein scanning is performed so that the nozzles can be scanned. 3. The simulation according to claim 1, wherein the simulation is performed on one page of print data.
Or the method of complementing defective nozzles of the inkjet head according to 2.