JP2005205649A - Inkjet printer, and method for sensing nonejection of ink from nozzle thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer which is equipped with a simple and inexpensive nonejection sensing means, and a method for sensing the nonejection of ink from a nozzle of the inkjet printer. <P>SOLUTION: In this method for sensing the nonejection of the ink from the nozzle of the inkjet printer which prints by ejecting the ink from a nozzle array while relatively moving a recording medium P and a printhead 121, a predetermined pattern for sensing is printed by means of a plurality of nozzles which are selected every n nozzles from the nozzle array of the printhead 121; a pattern for sensing, similar to the above pattern for sensing, is sequentially printed by means of the plurality of nozzles selected every n nozzles, in terms of the respective intermediate nozzles; and all the patterns for sensing are sequentially read while a reading sensor array 125 is oscillated in the direction of the nozzle array. When the pattern is not in place, the nozzle corresponding to the pattern can be determined not to eject the ink. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet printer, and more particularly to a technique for detecting non-ejection of nozzles.

  In an inkjet printer that ejects ink from nozzles to form an image, non-ejection of ink from the nozzles is a major factor that degrades the image. Therefore, methods for detecting non-ejection by various methods have been proposed.

  For example, Patent Document 1 proposes a method in which a patch is created using one nozzle, light is emitted from a light emitting diode, and reflected light from the patch is received by a phototransistor for determination.

  In Patent Document 2, a transparent tape as a recording medium for detection is conveyed in the nozzle row direction, and ink is ejected from every first nozzle to four nozzles to draw a straight line. Then, a method has been devised in which the state of the ink ejected on the transparent tape by the encoder sensor is repeated four times to detect non-ejection for all nozzles.

Patent Document 3 proposes a non-ejection detection means when a line head having a length substantially the same as the paper feed width is used as the print head. Here, a non-ejection detection method is proposed in which ink is drawn from every tenth nozzle and a line is drawn, and this is repeated 10 times to draw a line for all the nozzles and this is detected by a reading sensor. There is also a description that a reading sensor having a structure arranged in an array can be used.
JP-A-5-338199 JP 2003-127420 A JP-A-10-138513

  However, Patent Document 1 has a problem that it takes time to create a detection pattern for creating a patch with one nozzle.

  Moreover, in patent document 2, the mechanism which conveys the transparent tape which is a recording medium for a detection is complicated, and there exists a problem that a transparent tape needs to be replenished regularly.

  In Patent Document 3, since straight lines are drawn by every ten nozzles, there is an advantage in that even a print head with a fine print density can create a blank between lines and can be easily identified. However, there is a problem that it takes time to detect the line while moving the reading sensor in the scanning direction. On the other hand, the use of an array in which a large number of reading sensors are arranged in the scanning direction is also described, but a reading sensor array having the same density as the printing density is required, and there is a problem that the reading sensor array becomes expensive. It was.

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and is intended to provide an ink jet printer provided with a simple and inexpensive non-ejection detection means, and a method for detecting non-ejection of nozzles in the ink jet printer. .

  In order to achieve the above object, an ink jet printer according to claim 1 of the present application is an ink jet printer that performs printing by ejecting ink from a nozzle array while relatively moving a recording medium and a print head. And a reading sensor array that reads the detection pattern printed by the nozzles, and a swinging means that swings the reading sensor array in the nozzle array direction of the print head.

  The ink jet printer according to claim 2 of the present application is characterized in that a reading density of the reading sensor array is coarser than a printing density of the print head.

  In the ink jet printer according to claim 3 of the present application, the amplitude width of the reading sensor array by the swinging unit is ½ or more of the pitch between a plurality of nozzles taken every n from the nozzle row of the print head. It is characterized by that.

  According to a fourth aspect of the present invention, there is provided a method for detecting ink non-ejection of a nozzle in an ink jet printer that performs printing by ejecting ink from a nozzle array while relatively moving a recording medium and a print head. A step of printing a predetermined detection pattern by a plurality of nozzles taken every n from the row, and a detection pattern similar to the detection pattern by a plurality of nozzles every n of the intermediate nozzles are sequentially printed. Each step includes a step of sequentially reading all the detection patterns while swinging the reading sensor in the nozzle row direction.

  The method according to claim 5 of the present application is characterized in that the detection pattern is a pattern in which straight lines printed by one nozzle are arranged in parallel at equal intervals.

  According to the above means, it operates as follows. In the print head, a predetermined pattern for detection is printed by a plurality of nozzles taken every n from the nozzle rows arranged in a row. This is similarly performed for the intermediate nozzles, and a predetermined detection pattern is printed by all the nozzles constituting the print head. The pattern printed by each nozzle has an interval of n nozzles between adjacent patterns.

  The detection pattern thus formed is moved and brought under the reading sensor array. When the reading sensor array is swung in the nozzle row direction, the pattern printed by each nozzle enters the reading range of the reading sensor, and the pattern is detected. If there is no pattern at the position where the pattern should be, it can be understood that ink was not ejected from the nozzle corresponding thereto, and the non-ejection nozzle can be specified.

  According to the first aspect of the present invention, since the pattern can be detected by swinging the reading sensor array, it is possible to recognize the pattern reliably with a simple configuration, and it is possible to specify a non-ejection nozzle. Can play.

  According to the invention of claim 2, since the reading density of the reading sensor array is coarser than the printing density of the print head, the reading sensor array can be made inexpensive.

  According to the invention of claim 3, since the amplitude width of the reading sensor array by the swinging means is ½ or more of the pitch between patterns printed by every n nozzles of the reading sensor array, the reading sensor array Can reliably read the pattern.

  According to the method of claim 4, even with a print head having a high print density, the pattern is formed by every n nozzles, so that the read density of the read sensor array can be made coarse, and an inexpensive read sensor array can be used reliably. The pattern can be read and the non-ejection nozzle can be easily identified.

  According to the method of claim 5, since the pattern is a straight line, printing can be easily performed. Moreover, reading is also easy.

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

  FIG. 1 is an overall view showing the configuration of an ink jet printer. In FIG. 1, the inkjet printer 100 includes a cassette 110 in which sheets P as recording media are stacked and accommodated, a printing unit 120, a sheet conveyance unit 130, and a sheet discharge unit 140.

  The paper P in the cassette 110 is sent out one by one by the paper feed roller 111 and fed into the paper transport unit 130. A registration roller 131 is provided at the entrance of the paper conveyance unit 130, and an endless conveyance belt 133 wound around a plurality of conveyance rollers 132 is provided at a position passing through the registration roller 131. The paper P transported on the transport belt 133 is printed by the print head 121 of the printing unit 120, and is discharged onto the paper discharge tray 142 by the paper discharge roller 141 when printing is finished. Four print heads 121 are provided corresponding to each color of Y (yellow), M (magenta), C (cyan), and K (black).

  A reading sensor array 125 as a detection unit is provided on the discharge tray 142 side below the print head 121. The reading sensor array 125 has a large number of reading sensors arranged in a line, and each reading sensor is composed of a light emitting diode and a light receiving element. Further, the reading sensor array 125 has a swinging means 126, which can swing in the direction of the nozzle row of the print head 121 (main scanning direction).

  FIG. 2 is an enlarged view of the nozzles of one print head 121. An arrow indicates the conveyance direction of the paper P. The print head 121 is a line head type, and a large number of nozzles 123 corresponding to a print density such as 300 dpi or 600 dpi are arranged in a line in the scanning direction, and the length W thereof is approximately the width direction of the paper P (the conveyance direction). It is in agreement with the size in the direction orthogonal.

  FIG. 3 is a block diagram of the ink jet printer of the present invention. The controller 150 uses a computer to control the entire inkjet printer. The control unit 150 includes a CPU, a memory, a storage device, and the like, and controls the entire inkjet printer according to an installed program. The control unit 150 includes a print data storage unit 151 and a detection pattern storage unit 152. The print head drive unit 122 draws ink from the nozzle rows of the print heads 121 of YMCK in accordance with a drive signal based on print data and detection pattern data sent from the control unit 150 to draw a document image and a detection pattern. . The detection pattern will be described later.

  Printing on the paper P is performed as follows. The paper P in the cassette 110 is sent out by the paper feed roller 111, temporarily stopped by the registration roller 131, and the posture is corrected. The registration roller 131 causes the paper P to be printed on the print head in accordance with the timing at which the print head 121 ejects ink. Feed under 121.

  The print head 121 drives each of the YMCK print heads 121 based on the print data input to the print data storage unit 151 of the control unit 150 to discharge each color ink at a necessary timing, thereby forming a color image.

  The sheet P is transported while being electrostatically attracted to the transport belt 133 while passing under the print head 121. The posture holding means of the paper P at the time of printing is not limited to the transport belt 133, and a drum winding method, an air suction method, or the like may be used. The paper P printed by the printing unit 120 is discharged to the paper discharge tray 142. Alternatively, in the case of double-sided printing, it is sent to a reversing unit (not shown) and conveyed again to the printing unit, or sent to a post-processing machine (not shown), and predetermined post-processing such as punching and stapling is performed.

  Next, detection of a non-ejection nozzle will be described. If the ink is not ejected or becomes insufficient, the quality of the image is greatly affected. Therefore, it is necessary to detect the occurrence at an early stage and perform recovery or image correction. Non-ejection detection is performed when nozzle clogging can be predicted to some extent, such as when the power is turned on or when it has not been used for a long time. This can be automatically performed by inputting the control unit 150 in advance. Also, detection can be started manually in case of unexpected such as when dust or the like adheres to the nozzle surface.

  FIG. 4 is a diagram illustrating the relationship between the detection pattern and the reading sensor array 125. When ink non-ejection detection starts, first, a detection pattern shown in FIG. 4 is created. FIG. 4 shows an example in which 256 nozzle rows are ejected at intervals of every four. Further, the detection pattern shown in FIG. 4 is printed on the paper P by any one of the YMCK print heads 121. A thick straight line shown in the figure indicates a straight line as a pattern drawn by one nozzle 123 of the print head 121. The number attached to each straight line is the nozzle number. That is, the leftmost first column in FIG. 3 is a straight line group drawn by the nozzles of nozzle numbers 1, 5, 9,..., 249, 253. In the next second column, a straight line group with nozzle numbers 2, 6, 10,..., 250, 254 is shown. In the following, the third column shows a straight line group with nozzle numbers 3, 7, 11,..., 251 and 255, and the fourth column shows a straight line group with nozzle numbers 4, 8, 12,. In each row, ink is ejected from every fourth nozzle 123 to draw a linear pattern. Of course, every fourth is only an example, and generally every n.

  If each straight line is a print head of 600 dpi, the thickness is about 60 μm, and this is printed with a length of about 20 mm. However, the length of the line and the interval between adjacent rows (every four lines, etc.) The interval such as every other 10) can be set in advance by the nozzle to be used.

  When the paper P is conveyed in the direction of the paper discharge tray 142 and the straight line in the first row reaches just below the reading sensor array 125, the reading sensor array 125 detects the presence or absence of the straight line. In the reading sensor array 125, a large number of reading sensors are arranged in a line. As long as the number of reading sensors can detect the presence or absence of a straight line, the pitch does not need to be the same as the printing density. If the printing density is 600 dpi, the reading density may be about 90 to 400 dpi. Moreover, the number of reading sensors should just be more than the number of the straight lines described in the pattern in one row | line. In the embodiment, since every fourth nozzle 123 is detected, 256/4 = 64, that is, 64, and the detection ranges of these reading sensors are displayed as S1, S2, S3... S63, S64. .

  Each reading sensor has a light emitting diode and a light receiving element, and detects when the light receiving element receives reflected light reflected by the light irradiated by the light emitting diode hitting an object. If the object is a white portion of the paper P, the reflected light is strong, and if the object is a line, the reflected light is weak so that the presence or absence of a straight line can be detected.

  By the way, if the light receiving element has a detection range wider than the width of the straight line drawn in the detection pattern, it is easy to capture the straight line pattern within the detection range. However, for example, if there is a detection range that is 10 times the width of the straight line, the difference in the amount of received light between when the straight line is detected and when it is not detected becomes small, making it difficult to determine the presence or absence of the straight line. On the other hand, if the detection range is equal to or smaller than the width of the straight line, the difference in the amount of received light becomes large and detection is easy. Therefore, in the embodiment, the detection range is set to be slightly larger than the width of the pattern (straight line).

  When the straight line in the first row reaches just below the reading sensor array 125, the detection ranges S1, S2,... Of each reading sensor are the straight lines drawn by the nozzle numbers 1, 5, 9,. If it is above, it can be detected, but if it is in the middle of the straight line as shown in FIG. 4, the line drawn by the nozzle cannot be detected. In addition, the narrower the detection range, the greater the possibility that it cannot be detected.

  Therefore, in the present invention, the swinging means 126 is provided so that the reading sensor array 125 swings in the sensor array column direction (direction A in FIG. 4) during reading. As a result, even if the straight line of the detection pattern is out of the readable range of the reading sensor, the straight line can be caught within the detection range while swinging, so the presence or absence of the straight line is accurately detected. It becomes possible. The swinging means 126 is driven by a motor or a solenoid, and has a cycle shorter than the time for one straight line to pass through the reading sensor array 125. The amplitude width of the reading sensor array 125 is not less than ½ of the pitch m between the patterns (straight lines) so that the detection pattern can be read even when the straight line of the detection pattern is located near the center of the reading sensor. Amplitude.

  If a straight line drawn by the nozzles is detected by each reading sensor of the reading sensor array 125 and there is no line at a desired position, it can be determined that the nozzle corresponding to the line does not eject. If non-ejection nozzles cannot be identified, all modules must be restored, and the recovery process takes time and increases waste ink. In the invention, this can be prevented.

  FIG. 5 is an example showing the output of the reading sensor array 125 when a straight line of the detection pattern of one row is detected. FIG. 5A shows a case where there is no non-ejection nozzle, and FIG. This is the case when there is a nozzle. In (a), all the reading sensors of the reading sensor array 125 detect the straight line drawn by the nozzle 123, and the output is regularly reduced. On the other hand, in (b), since there is no decrease in the output of the reading sensor at the two locations indicated by the arrows, it can be seen that the nozzle 123 corresponding thereto does not discharge. From this result, the non-ejection nozzle determination unit 160 notifies the control unit 150 that the nozzle 123 having the nozzle number XX of the Y print head 121 is non-ejection. Only the print head 121 including the ink is discharged by a recovery means such as a suction stroke. After passing through the reading sensor array 125, the paper P used for ejection failure detection is guided by a switching gate (not shown) to a path different from that of a normal printed material, stored in the machine, and periodically discarded by an operator.

  As another countermeasure when the ejection failure is detected, it is possible to continue printing and correct the image using a good nozzle adjacent to the non-ejection nozzle. Alternatively, when there is a defect in the printed image during printing and the operator finds a discharge failure, the operator can execute the discharge failure detection mode to recover the discharge failure.

  Or, when a predetermined time or a predetermined number of printed sheets have passed, ejection failure detection is performed periodically, and when ejection failure is detected, printing is temporarily interrupted and ejection failure is recovered by recovery means. However, printing may be resumed thereafter.

  In the above embodiment, as shown in FIG. 4, all nozzles 123 are divided into four groups, and all of the four groups of straight lines are printed, and then a straight line is detected by the reading sensor array 125. Is printed, the straight line may be detected and the next group of straight lines may be printed.

  If the above detection is performed from the second column to the fourth column of the detection pattern shown in FIG. 3, the non-ejection detection of all nozzles is completed for the four print heads 121 of YMCK.

  The color of ink ejected from each print head 121 is different from Y (yellow), M (magenta), C (cyan), and K (black). For this reason, there are colors that are difficult to read with a reading head, such as yellow. In that case, non-ejection is detected separately for each color, and in the case of a color that is difficult to read, such as yellow, a filter is provided in the reading sensor.

  In the above embodiment, the number of reading sensors and the number of straight lines coincided. Therefore, each reading sensor and the nozzle have a 1: 1 correspondence, and a reading sensor that does not detect a straight line can be easily determined to mean a non-ejection nozzle. However, the number of reading sensors is not limited to the same as the number of straight lines, and may be large. In that case, even when there is no non-ejection nozzle, a reading sensor that detects a straight line and a reading sensor that does not detect a straight line are generated. Even in such a case, for example, if several reading sensors that do not detect a straight line are generated in succession, it can be dealt with by determining that the corresponding nozzle is not ejecting.

  In the above-described embodiment, the print head 121 is a line head having nozzle rows over the entire area in the paper width direction, and the heads for each color YMCK are arranged in parallel in the paper conveyance direction. The nozzle rows are arranged so that the print density is 600 dpi.

  However, it is difficult to create a 600 dpi line head in one row due to manufacturing problems. For example, four 150 dpi pitch nozzle rows are arranged in parallel, and the phase is shifted by 1/4 in the nozzle row direction. 600 dpi can be printed.

  Further, as in the embodiment shown in FIG. 1, when a long head having the same length as the paper width is integrally formed, if a nozzle defect occurs due to a manufacturing defect, the entire head becomes defective and yield increases. Incurs a decline. Therefore, as a module configuration divided by an appropriate length in the nozzle row direction, a configuration in which the modules are connected in the paper width direction is preferable.

  6A shows a module configuration in which any one of the print heads 121 of YMCK in FIG. 1 is divided into two nozzles 121a and 121b in the nozzle row direction, and each module has four 150 dpi nozzles arranged in parallel. This is an example configured. The print head 121a is composed of 150 dpi print heads 121a1, 121a2, 121a3, 121a4 as shown in FIG. 6A, and the nozzles of each print head are arranged at 1/4 pitch as shown in FIG. 6B. By shifting, the print head is 600 dpi. The other print head 121b is similarly composed of 150 dpi print heads 121b1, 121b2, 121b3, 121b4.

  In order to detect non-ejection of the ink for the print head 121 shown in FIG. 6, first, ink is ejected from all nozzles of the print head 121a4 and the print head 121b4, and a straight line group corresponding to the first row in FIG. Print. Next, ink is ejected from all the nozzles of the print head 121a3 and the print head 121b3, and a straight line group corresponding to the second column in FIG. 4 is printed. Similarly, a straight line group in the third and fourth columns is printed. The non-ejection can be detected by the same method as described above.

1 is an overall view illustrating a configuration of an inkjet printer. 2 is an enlarged view of nozzles of one print head 121. FIG. 1 is a block diagram of an ink jet printer of the present invention. It is a figure which shows the relationship between the pattern for a detection, and a reading sensor array. An example of the output of the reading sensor array when a straight line of the detection pattern of one row is detected. (A) shows a case where there is no non-ejection nozzle, and (b) shows a case where there is a non-ejection nozzle. is there. (A) is a diagram showing a nozzle having a module configuration in which one print head is divided in the nozzle row direction and a print head with a fine pitch is formed by combining a plurality of print heads with a coarse pitch, and (b) is one module. It is the figure which expanded the principal part.

Explanation of symbols

P paper (recording medium)
m Pitch between patterns 100 Inkjet printer 121 Print head 121a Print head 121a1, 121a2, 121a3, 121a4 Print head 121b Print head 121b1, 121b2, 121b3, 121b4 Print head 123 Nozzle 125 Read sensor array 126 Swing means 150 Control unit 151 Print Data storage unit 152 Detection pattern storage unit 160 Non-ejection nozzle determination unit

Claims (5)

An inkjet printer that prints by ejecting ink from a nozzle row while relatively moving a recording medium and a print head, and a reading sensor array that is arranged in parallel with the print head and reads a detection pattern printed by the nozzle; An ink jet printer comprising: swinging means for swinging the reading sensor array in the nozzle row direction of the print head. The inkjet printer according to claim 1, wherein a reading density of the reading sensor array is coarser than a printing density of the print head. 3. The amplitude width of the reading sensor array by the swinging means is 1/2 or more of the pitch between a plurality of nozzles taken every n nozzle rows from the print head nozzle row. Inkjet printer. In a non-ejection detection method for nozzles in an ink jet printer that prints by ejecting ink from nozzle rows while relatively moving a recording medium and a print head,
A step of printing a predetermined detection pattern by a plurality of nozzles taken every n from the nozzle row of the print head, and a detection for the same as the detection pattern by a plurality of nozzles every n of the intermediate nozzles An ink non-ejection detection method for a nozzle in an ink jet printer, comprising: sequentially printing patterns; and sequentially reading all detection patterns while swinging a reading sensor array in a nozzle row direction. 5. The method of detecting non-ejection of nozzles in an ink jet printer according to claim 4, wherein the detection pattern is a pattern in which straight lines printed by one nozzle are arranged in parallel at equal intervals.

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