JPH08323992A - Ink-jet recording device - Google Patents

Abstract

PURPOSE: To prevent printing quality from lowering even in the presence of a nozzle which does not discharge ink in a print head. CONSTITUTION: A pattern which is recorded on a recording sheet by a print head 103 having a plurality of nozzles is read by a sensor 110, and a pattern width detection part 106 and CPU 108 judge whether the pattern is a regular one or not. When the pattern is not regular, an image is formed by a method in which only the normal nozzles of the print head 103 are made to discharge ink through a head control part 104 under the control by CPU 108.

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, and more particularly to an inkjet recording apparatus having a plurality of print heads.

[0002]

2. Description of the Related Art There is an ink jet method as one type of ink recording method, and a bubble jet method is known as one type of the ink jet method. In such an ink jet method, a heater is attached to each nozzle for ejecting ink, a heating pulse signal is applied to the heater to heat the ink through the heater, and the ink filled in the nozzle by the bubble pressure generated. Is discharged. When the inkjet method is applied to an image forming apparatus, usually 100 nozzles are arranged back and forth to form one print head to form an image.

FIG. 15 is an example of an image printed by a print head composed of a plurality of nozzles. As shown in FIG. 15, one line is printed by using a plurality of nozzles of the print head (solid portion), and one band is printed by moving the print head in the main scanning direction (horizontal direction) for printing. Then, the printing paper is fed in the sub-scanning direction (vertical direction in the figure) to print the next band, and the above operation is repeated to form an image composed of several bands.

FIGS. 16A and 16B are perspective views showing the structure of the print head. FIG. 16A shows a separate type print head in which the print head and the ink tank are formed separately, and FIG. 16B is an integrated print head in which the print head and the ink tank are integrally formed. .

In the separate type print head, only the ink tank can be replaced when the ink tank becomes empty, and the positional relationship between the ink ejection ports of the nozzles of the print head remains unchanged. On the other hand, in the integrated print head, each print head (for example, the print head for yellow Y) is treated as a consumable item, and when the ink becomes empty, the print head that has become empty (in this case, for yellow Y) It is necessary to replace the print head).

Therefore, when some of the print heads in the integrated print head are replaced, as shown in FIG.
As shown in (b), horizontal and vertical mounting misalignment X1 and Y1 between individual print heads occurs, and when printing is performed as it is, streaks X2 and Y2 occur in the horizontal and vertical directions, resulting in image unevenness. There is.

That is, in the case of the horizontal mounting displacement of the individual print heads, as shown in the center of FIG. 17A, black K, cyan C and yellow Y are printed at the same position. On the other hand, only magenta M is printed with a slight shift (displayed in solid lines) (displayed in diagonal lines). Therefore vertical stripe X2
Will occur. Similarly, as shown in FIG. 17B, in the case of a vertical mounting misalignment, black K, cyan C, and yellow Y are printed at the same position (solid display), while magenta M. Only the mark is printed at the position shifted downward (hatched display). As a result, a streak Y2 is generated in which only magenta M extends laterally downward. In addition,
In the above explanation, "black K, cyan C, and yellow Y are printed at the same position", but strictly speaking, FIG.
As shown in the enlarged views on the right side of (a) and (b), black K, cyan C, and yellow Y are printed with a slight deviation in the lateral direction, but this does not pose a practical problem.

Therefore, when some of the print heads in the integrated print head are replaced, the mounting position of the replaced print head is confirmed, and the mounting position can be adjusted (deviation correction) if necessary. Will be needed.

Therefore, when some of the integrated print heads are replaced, as shown in FIGS. 18 (a) and 18 (b),
Reference print head K1 and other print heads K2, C,
Using M and Y, the pattern of the reference print head K1 and the pattern K2 of the print head after replacement are printed in parallel in the vertical direction (FIG. 18A) and the horizontal direction (FIG. 18B). . Next, the width (pattern interval) between the center dots of each pattern is obtained, and the "first reference print head K1 and each print head (the pattern interval between the first reference print head K1 and the second reference print head K2)" is calculated. For example, the second reference print head K2
The misregistration amounts of the other print heads C, M, and Y with respect to are calculated.

Using the calculated values, the vertical and horizontal misalignment between the print heads due to the mounting position of the print heads is corrected.

[0011]

However, in an ink jet type nozzle, ink may not be ejected depending on the nozzle. If misalignment correction in the vertical direction is performed without considering the fact that the nozzles are not ejecting, even if the mounting position of the print head is not misaligned originally, FIG.
As shown in (b), there is a case where the correction is performed with an extra deviation.

That is, in the case of the deviation correction, as described with reference to FIG. 18, the sensor 110 performs the deviation correction based on the difference between the pattern interval between the reference print head pattern and the other print head patterns. It was However, FIG.
As shown on the left side of (a), A1 -C
Assuming that ink ejection failure has occurred between A1 and B1 of the print width (print area) between 1 and 1, the result of misalignment correction is as shown on the right side of FIG. Moves to the original midpoint between A1 and B1. As a result, as shown by the dotted lines above and below, areas where ink is not attached are formed. The reason is that the center line S1 of the portion printed by the sensor 110 is read, and the center line S1 is corrected to be shifted to the center line S2 of the area to be originally printed.

This phenomenon occurs when the nozzle in the center of the print area of the print head does not eject, because the sensor 110 for resist adjustment itself is not highly accurate and cannot detect ink ejection. Will never occur.
Here, the resist adjustment means adjusting the positional deviation of the ink ejected onto the recording member.

However, when the non-ejection nozzles are present at the upper and lower ends of the printing area, the above-mentioned unfavorable deviation correction is performed, which may affect the image quality. As a specific example, as shown in FIG.
When the character "mountain" is output by K, the result of misalignment is "black", "magenta", and "mixed color of black and magenta".
Will result in a patchy output.

As described above, when the misfiring nozzle is located at the end and the misalignment is corrected, the output image is misaligned, resulting in deterioration of the image quality.

Therefore, an object of the present invention is to provide an ink jet recording apparatus capable of preventing deterioration of image quality even if ink is not ejected in the print head.

[0017]

In order to solve the above-mentioned problems, the invention according to claim 1 is an ink jet recording apparatus provided with a print head having a plurality of nozzles, in which ink in the print head is not ejected. And an ink non-ejection nozzle identifying unit that identifies the ink ejection nozzle, and a first print control unit that controls to perform printing by a nozzle other than the ink non-ejection nozzle detected by the ink non-ejection nozzle identifying unit.

According to a second aspect of the present invention, the ink non-ejection nozzle specifying means controls the second print control means and the second print control means that causes the individual nozzles to print a plurality of times. A first reading sensor for reading a pattern printed below is provided.

According to a third aspect of the present invention, the ink non-ejection nozzle specifying means includes a print width storage means for storing a reference print width and a second reading sensor for reading a pattern printed by the print head. And a print width comparison means for comparing the data read by the second reading sensor with the reference print width stored in the print width storage means.

The invention according to claim 4 is characterized by further comprising means for adjusting a resist by a pattern printed under the control of the first print control means.

[0021]

According to the first aspect of the invention, the non-ejection nozzle identifying means detects the non-ejection nozzle in the print head. First
The print control unit controls the nozzles other than the non-ejection nozzle detected by the non-ejection nozzle identifying unit to perform printing.

According to the second aspect of the invention, the second aspect
The print control unit controls to print a plurality of times for each nozzle. The first reading sensor reads the pattern printed under the control of the second print control means. The non-ejection nozzle is specified by the output signal based on the read pattern (see FIG. 7).

According to the third aspect of the invention, the print width as a reference is stored in advance in the print width storage means. The second reading sensor reads the pattern printed by the print head. The print width comparison means compares the data read by the second reading sensor with the reference print width stored in the print width storage means (see FIGS. 9 and 12). The non-ejection nozzle is specified based on the comparison result.

According to the fourth aspect of the present invention, since the pattern printing is performed by the nozzles other than the ink non-ejection nozzles and the resist adjustment is performed, erroneous misalignment correction due to the non-ejection nozzles cannot occur. The inconvenience as shown in 1 does not occur.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments. In addition, the same reference numerals are given to the parts already described, and the duplicated description will be omitted.

(1) First Embodiment FIG. 1 is a perspective view of an essential part of an ink jet recording apparatus of this embodiment, and FIG. 2 is an enlarged perspective view of a linear scale and the like in FIG. 3 is a block diagram of the control system of this embodiment, and FIG. 4 is a block diagram of the print head (in the case of one) in FIG.

First, the structure of the essential parts of the mechanical system of the ink jet recording apparatus will be described with reference to FIGS. 1 and 2.

As shown in FIGS. 1 and 2, a carriage (not shown) is attached to the belt 2 driven by the main scanning motor 1, and the print head 103 is attached to the carriage.
And a sensor 110 for reading the print pattern are attached. Then, in order to perform printing at an accurate position with respect to variations in the carriage speed, a linear scale 109 in which slits of a predetermined pitch are formed for each dot is arranged along the scan direction of the print head. Is read by the linear sensor 109a attached to the print head 103. The linear sensor 10
Ink ejection is synchronized based on the output signal of 9a,
The ink is controlled to be ejected to a predetermined position on the recording paper 5.

Further, the sub-scanning motor 3 rotationally drives the roller 4, and the rotation of the roller 4 drives the recording paper 5 in the paper feeding direction.

An upper cover 6 is arranged so as to cover the ink jet recording apparatus constructed as described above, and an upper cover open / close detection sensor 111 for detecting opening / closing of the cover 6 is arranged on the right side of the upper cover 6. Has been done.

Next, the structure of the main part of the control system of the ink jet recording apparatus will be described with reference to FIGS. 3 and 4.

As shown in FIGS. 3 and 4, the main parts of the control system are the external device 101, the print controller 102, and the print head 1.
03, and the outline of the function of this control system is image image data (serial image data) transferred from an external device 101 such as an image scanner, a personal computer, and a CAD.
Based on the VDI, under the control of the print control unit 102, control for forming an image on the recording paper 5 (see FIG. 1) using the print head 103 is performed.

First, the print control unit 102 for generating the signals necessary for performing the above-mentioned functions will be described. Print control unit 1
Reference numeral 02 is composed of a CPU 108, a print head control unit 104, a pattern detection unit 105, a pattern width detection unit 106, a print head misregistration amount detection unit 107, various memories (such as an image memory not shown), and I / O.

The CPU 108 interfaces with the external device 101 and controls the overall operation of the print controller 102. That is, when the serial image data VDI is transferred from the external device 101, the CPU 10
A print head control unit 10 to be described below according to a command from
In 4, the image data VDI for several bands is temporarily held in the image memory. Various image processes are applied to the held image data VDI, and the image data VDO is output in synchronization with the scan of the print head 103.

In FIG. 4, 201 is a shift register, 202 is a latch circuit, 203 to 206 are AND circuits, 207 to 210 are transistors, and 211 is a heater.

Then, the image data VDO is transferred from the head control unit 104 to the transfer clock CLK as serial binary data.
Are transferred in synchronism with, and serial-parallel conversion is sequentially performed by the shift register 201. The print head (not shown) has 128 nozzles, and after 128 image data VDOs have been transferred, the nozzles are held by the LAT (latch) signal. Further, 128 nozzles of the print head are divided into 8 blocks, and a block enable signal BENB0 to 1 pulse of 1 pulse per 1 block.
7 and heater drive pulse signal (heat enable signal)
HENB is given, the transistor is turned on only for the nozzles for which image data is enabled and held, the heater 211 is heated, and ink is ejected.

Next, the operation will be described with reference to FIGS.

As shown in FIG. 5, when the upper cover 6 is opened (step S1), the upper cover open / close detection sensor 11 is opened.
1 detects opening of the cover. Then, the print head 103
When the print head is replaced, a print head replacement detecting means (not shown) detects the print head replacement (step S2) and automatically prints for each nozzle several times as shown in FIG.
Print pattern (test pattern) P (see Fig. 1) on top
Are formed (step S3).

Next, when the carriage is driven, the sensor 110 reads the print pattern P, and this sensor 110
The output of is monitored by the CPU 108 to determine whether or not the pattern for each nozzle is printed (step S4).

Next, the detection of the non-ejection nozzle in step S5 will be described in detail. Print pattern P shown in FIG.
Is a print pattern for each nozzle of the above-mentioned replaced print head nozzles. This print is the same as the above 12
8 nozzles divided into 8 blocks
After the scanning, the recording paper 5 is fed by one dot in the upward direction in the drawing, and the second scanning is performed. That is, as indicated by reference numeral Z1 in FIG. 7, printing is performed in the first scan by the 0th nozzle on the top of the print head 103, and then the recording paper 5 is advanced by one dot in the upward direction in the drawing. The 0th
Printing is performed in the second scan with the nozzles, and then 0th
Printing is performed by the nozzle up to the 127th scan. This 0th
In the case of the nozzle, lines are printed from the first scan to the 127th scan as shown in the figure, and this print is read by the sensor 110 to obtain the output W1.

Similarly, even when the first scan to the 127th scan are performed by the second first nozzle from the top of the print head 103 to perform the printing, the print pattern is not drawn as indicated by the symbol Z2. This is because the first nozzle is not ejecting ink, and the code W is read even if the sensor 110 reads it.
No output, as shown by 2.

After the printing of all patterns is completed, the sensor 110 detects the presence or absence of a print pattern, and from the detection result, the nozzles that have not ejected ink are determined by the CPU 108 and used by the print head controller 102 for printing. Control the nozzle.

In the case shown in FIG. 7, as described above, the first
No nozzle is printed, and this sensor output W2 is CP
It is read in U108, and as shown in FIG. 8, the nozzles are controlled so that the nozzles that have failed to eject are not used (step S6).

That is, among the 128 nozzles, the nozzles actually used for printing are the eighth to 120th nozzles, and the 0th to 7th nozzles and the 121st to 121st nozzles at both ends.
The 127th nozzle is not used for printing. Therefore, as described above, when ejection failure occurs in the first nozzle,
No. 0 to No. 8 nozzles are not used, and No. 120 to No. 1 are used instead.
Use 27 nozzles. By doing so, even if there is a non-ejection nozzle, it is possible to avoid the non-ejection nozzle when actually printing.

Therefore, after the nozzles to be used are determined, the registration of each print head is adjusted. Therefore, as shown in FIG.
The image shift as shown in (1) does not occur. In this embodiment, the presence or absence of ink ejection from all nozzles is detected. However, what is necessary for the resist adjustment is the detection of ejection failure at the edges, so it suffices if there is a print pattern for the nozzles at the upper and lower edges. Easy to judge.

(2) Second Embodiment In the first embodiment, as described with reference to FIG. 7, since printing is performed for each nozzle, it takes a considerable amount of time to replace a plurality of print heads. This embodiment provides a means for detecting a non-ejection nozzle in a short time. This means will be described with reference to FIGS. 9 to 11.

First, one line is printed in the printing direction using the reference print head K (see FIG. 9). Furthermore, the other three print heads M, C, and Y also perform 1-line printing (steps S11 to S14). Next, the width of this one-line printing is detected by the sensor 110 (step S
15).

Then, the output result of the sensor 110 is compared with the reference print width stored in advance in the memory,
A narrow print is detected (step S16). In the case shown in FIG. 9, it is clear from the output result of the sensor 110 that the print width of the print head M is narrow.
Further, as shown in FIG. 10, the nozzles of the print head M causing the non-ejection are divided into several blocks (three blocks in this case) to print a pattern (step S17), and this pattern is detected by the sensor 110. The position of the non-ejection nozzle is specified by scanning (step S18). Then, this output (pattern) is read by the CPU 108, and the same nozzle control (execution of printing while avoiding non-ejection nozzles) is performed using the print head control unit 102 (step S1).
9).

By doing so, the non-ejection nozzle can be specified in a short time.

(3) Third Embodiment This embodiment is also a case where a non-ejection nozzle is specified within a short time.

This embodiment will be described with reference to FIGS. 12 to 14.

As shown in FIG. 12, the encoder 7 is attached to the shaft of the sub-scanning motor (paper feed motor) 3 and the position of the print pattern is detected by the photo interrupter 8. FIG. 13 is a block diagram of the control system.

First, after detecting that the print head has been replaced in the same manner as described above, a pattern is printed by each print head (steps S21 to S23). After that, in order to detect the edge of the recording paper 5, the recording paper 5 is once fed in the reverse direction to detect the paper edge (steps S24 and S25), and the photo interrupter 8 is started with this paper edge as a starting point.
Is output by the CPU 108 (step S2)
6).

Next, the print pattern is scanned by the sensor 110, and the print start position of the print pattern from the paper edge (see FIG.
2) and the end position (reference V in FIG. 12) (step S27), it is possible to know which nozzle of which print head is causing the ejection failure (step S28). .

Even in this way, the non-ejection nozzle can be specified in a short time.

[0056]

As described above, according to the present invention, the ink non-ejection nozzle specifying means for specifying the nozzle in the print head in which the ink is not discharged, and the ink non-ejection specified by the ink non-ejection nozzle specifying means. Since the print control means for controlling the printing to be performed by the nozzle other than the nozzle is provided, it is possible to avoid the printing by the ink non-ejection nozzle. In addition, since erroneous resist adjustment by the ink non-ejecting nozzles is prevented, the inconvenience (deterioration of print quality) associated with the misregistration correction as in the past does not occur.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part of a mechanism system according to a first embodiment of the present invention.

FIG. 2 is a perspective view around a print head in the first embodiment.

FIG. 3 is a block diagram of a main part of a control system in the first embodiment.

FIG. 4 is a block diagram of a print head controller in FIG.

FIG. 5 is an operation flowchart of the first embodiment.

FIG. 6 is a diagram showing a print pattern of the first embodiment.

FIG. 7 is a diagram illustrating details of FIG. 6;

FIG. 8 is a diagram showing a state of print nozzle control according to the first embodiment.

FIG. 9 is a first print pattern for detecting a non-ejection nozzle in the second embodiment.

FIG. 10 is a second print pattern for detecting a non-ejection nozzle in the second embodiment.

FIG. 11 is an operation flowchart of the second embodiment.

FIG. 12 is a first print pattern according to the third embodiment.

FIG. 13 is a block diagram of a control system of the third embodiment.

FIG. 14 is an operation flowchart of the third embodiment.

FIG. 15 is a diagram showing one-band printing by one conventional print head.

FIG. 16 is a perspective view showing a conventional print head,
(A) is a separate type, and (b) is an integral type.

17A and 17B are diagrams illustrating a conventional resist adjustment problem, in which FIG. 17A is an explanatory diagram in the case of a horizontal mounting displacement and FIG. 17B is an explanatory diagram in the case of a vertical mounting displacement.

18A and 18B are diagrams showing a print pattern for adjusting the deviation of the print head, in which FIG. 18A is a lateral deviation and FIG. 18B is a longitudinal deviation.

19A and 19B are diagrams illustrating a defect of conventional resist adjustment, in which FIG. 19A is a diagram illustrating a principle of vertical misalignment, and FIG. 19B is a diagram illustrating misalignment in the Chinese character “mountain”.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 main scanning motor 3 sub-scanning motor 5 recording paper 102 print control device (first and second print control means) 103 print head 106 pattern width detection section (ink non-ejection nozzle identification means) 107 head deviation amount detection section (ink non-ejection) Nozzle specifying means) 108 CPU 109 Linear scale 110 Sensor (first and second reading sensor)

Claims (4)

[Claims] 1. An ink jet recording apparatus comprising a print head having a plurality of nozzles, comprising: an ink non-ejection nozzle identifying means for identifying a nozzle in which the ink in the print head is non-ejection; and an ink non-ejection nozzle identifying means. An inkjet recording apparatus, comprising: a first print control unit that controls printing by a nozzle other than the detected ink non-ejection nozzle. 2. The ink non-ejecting nozzle specifying means reads a pattern printed under the control of a second print control means for printing a plurality of times for each of the individual nozzles, and the second print control means. The inkjet recording apparatus according to claim 1, further comprising a first reading sensor. 3. The ink non-ejection nozzle specifying means, a print width storage means for storing a reference print width, a second reading sensor for reading a pattern printed by the print head, and the second reading sensor. 2. The ink jet recording apparatus according to claim 1, further comprising a print width comparison unit that compares the read data with a reference print width stored in the print width storage unit. 4. The ink jet recording apparatus according to claim 1, further comprising means for adjusting a resist by a pattern printed under the control of the first print control means.