JP2007015194A - Maintenance method of recording head and inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a maintenance method of a recording head wherein defective nozzles can be detected without impeding the printing work, and the productivity of printing images of a high quality can be enhanced, and to provide an inkjet printer. <P>SOLUTION: The inkjet printer forms an image to a recording medium by delivering ink droplets d from nozzles 1a and 1d on the basis of image data in a process of scanning the recording heads 1A and 1D with a plurality of the arranged nozzles 1a and 1d back and forth along a direction orthogonal to a conveying direction of the recording medium. A detection light L which detects the presence or absence of passing of the ink droplet d is formed at the lateral side of the recording medium of the inkjet printer, along an arrangement direction of the nozzles 1a and 1d of the recording heads 1A and 1D to intersect a trajectory of the ink droplets d delivered from the nozzles 1a and 1d. In a process where nozzle arrays of the recording heads 1A and 1D pass the detection light L during continuous printing to the recording medium by scanning the recording heads 1A and 1D, the ink droplets d are sequentially delivered from the nozzles 1a and 1d of not fewer than one nozzle and fewer than all nozzles of the recording heads 1A and 1D. All nozzles are detected by a plurality of the number of scanning times. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a recording head maintenance method and an ink jet printer, and more particularly to a recording head maintenance method and an ink jet printer capable of detecting a defective nozzle that does not normally eject ink droplets without interfering with printing operations. .

  An ink jet printer that reciprocally scans a recording head composed of a plurality of nozzles along a direction orthogonal to the recording medium conveyance direction discharges ink droplets during the reciprocating scan to form an image for one reciprocating scan. After that, a predetermined image is formed in the recording area of the recording medium by repeating a series of operations of intermittently conveying the recording medium by a predetermined amount and performing the next one reciprocating scan.

  In such an ink jet printer, it is an indispensable technique for improving image quality to detect defective nozzles in which ink droplets are not ejected from the nozzles or ejection bends occur. As a countermeasure, in addition to a method of actually printing on a recording medium and detecting the printed matter using a sensor, a detection light is formed between the light emitting part and the light receiving part, and ink is directed toward the detection light. A method for optically detecting the presence of a defective nozzle from a change in the amount of light at the time of ejecting a droplet is known.

  However, the former method requires a recording medium for each detection and is uneconomical. In the latter method, it is not necessary to prepare a recording medium for each detection, but it is necessary to narrow the width of the optical path of the detection light in order to improve detection sensitivity. It is difficult to guide to the optical axis of the detection light.

  Therefore, in Patent Document 1, in the detection method using detection light, the detection light is allowed to pass while ejecting ink droplets, the position where the sensor output at that time is maximum is specified, and the recording head is stopped at that position. Ink droplets are ejected from all nozzles simultaneously, and the presence or absence of ejection failure is detected from the absolute value.

  In Patent Document 2, the recording head is moved to the position of the detection light and stopped, and then an ink droplet is ejected one nozzle at a time to detect a defective nozzle.

Further, in Patent Document 3, the detection light is formed obliquely with respect to the direction of the nozzle row of the recording head, and each recording nozzle is sequentially aligned with the optical axis of the detection light by scanning the recording head. All nozzles are detected by sequentially discharging the nozzles.
Japanese Patent No. 3145898 JP 2003-127430 A Japanese Patent No. 3535723

  In the technique described in Patent Document 1, it takes time to identify the position where the sensor output is maximum and confirm the coincidence between the nozzle row and the detection light, and in addition, the ink droplets are ejected from all the nozzles at the same time. There is a problem that the discharge failure cannot be detected. Also, since the detection work is performed with the recording head stopped, it must be performed separately from the printing work.

  Although the technique described in Patent Document 2 can detect one nozzle at a time, in order to detect all the nozzles for each nozzle, a detection time different from the printing operation is provided, and the recording head is temporarily set. Must be done after stopping.

  As described above, in the techniques described in Patent Documents 1 and 2, for example, it is necessary to interrupt the printing operation periodically to detect defective nozzles at regular intervals, which causes a decrease in print productivity. It becomes.

  Furthermore, in the technique described in Patent Document 3, it is not necessary to provide another detection time as in Patent Documents 1 and 2 in that it can be detected during scanning of the recording head, but the ink droplets ejected from each nozzle are not necessary. Therefore, it is necessary to accurately measure the timing at which each nozzle in the nozzle row coincides with the optical axis of the detection light so that each ink droplet can be ejected. However, in this case, since the angle of the detection light, the nozzle position, the scanning speed of the recording head, and the like must be synchronized in a complicated manner, it is precisely performed in the process of scanning the recording head during the normal printing operation. It is extremely difficult.

  SUMMARY OF THE INVENTION Accordingly, the present invention provides a recording head maintenance method and an ink jet printer that can detect defective nozzles without interfering with the printing operation and can enhance the productivity of high-quality printed images. Is an issue.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

  According to a first aspect of the present invention, in the process of reciprocally scanning a recording head in which a plurality of nozzles are arranged along a direction perpendicular to the conveyance direction of the recording medium, ink droplets are ejected from the nozzles based on image data. In a recording head maintenance method in an ink jet printer for forming an image on a recording medium, it crosses a side of the recording medium along a direction in which the nozzles of the recording head are arranged and a flight path of ink droplets ejected from the nozzles. As described above, a process of forming detection light for detecting the presence or absence of the passage of the ink droplet, scanning the recording head, and the nozzle array of the recording head passing the detection light during continuous printing on the recording medium Then, ink droplets are ejected sequentially from nozzles of the recording head that are at least one nozzle but less than all nozzles, and all the nozzles are detected by multiple scans. Is a maintenance method of the recording head, characterized by.

  According to a second aspect of the present invention, the nozzles are provided in a plurality of rows along the scanning direction, and each nozzle is scanned in the process of scanning the recording head and passing the detection light during continuous printing on the recording medium. 2. The recording head maintenance method according to claim 1, wherein ink droplets are sequentially ejected from one nozzle and less than all nozzles in a row, and all nozzles in each nozzle row are detected by a plurality of scans.

  The invention according to claim 3 is characterized in that the detection light is arranged on both sides of the recording medium, and the detection light is detected on both sides of the recording medium in the process of reciprocating scanning of the recording head. The recording head maintenance method according to 1 or 2.

  According to a fourth aspect of the present invention, the ejection of ink droplets in the process of passing the detection light is performed in the forward path and the backward path of the recording head, respectively. This is a maintenance method.

  According to a fifth aspect of the present invention, preliminary ejection for ejecting ink droplets from all nozzles is executed immediately before and / or immediately after ejection of ink droplets in the process of passing the detection light. A maintenance method for a recording head according to any one of items 1 to 4.

  According to a sixth aspect of the present invention, when a defective nozzle is detected by detecting the nozzle, the image data is corrected so that an image to be printed by the nozzle is printed by another nozzle. A maintenance method for a recording head according to any one of 1 to 5.

  According to a seventh aspect of the present invention, when a defective nozzle is detected by the detection of the nozzle, the continuous printing operation of the recording medium is interrupted and a nozzle recovery operation is executed. A maintenance method for a recording head according to any one of the above.

  According to an eighth aspect of the present invention, in the process of reciprocally scanning a recording head formed by arranging a plurality of nozzles along a direction perpendicular to the recording medium conveyance direction, ink droplets are ejected based on image data to perform the recording. In an ink jet printer that forms an image on a medium, the detection light is arranged so as to intersect with a flight path of an ink droplet that is arranged on the side of the recording medium and that is arranged along the nozzle arrangement direction of the recording head and is ejected from the nozzle. In the process of forming and passing the detection light during continuous printing on the recording medium by scanning the recording head and detecting the presence or absence of passage of the ink droplet, the recording head 1 Control means for sequentially ejecting ink droplets from nozzles not less than all nozzles and detecting all nozzles by a plurality of scans. An ink jet printer to.

  According to a ninth aspect of the present invention, the nozzles are provided in a plurality of rows along the scanning direction, and the control means scans the recording head and passes the detection light during continuous printing on the recording medium. 9. The method according to claim 8, wherein in the process, control is performed so that ink droplets are sequentially ejected from one nozzle and less than all nozzles in each nozzle row, and all nozzles in each nozzle row are detected by a plurality of scans. Inkjet printer.

  The invention according to claim 10 is characterized in that the ink droplet detection means is arranged on both sides of the recording medium, and the control means controls to perform detection on both sides of the recording medium. The inkjet printer according to 8 or 9.

  An eleventh aspect of the invention is the ink jet printer according to the eighth, ninth, or tenth aspect, wherein the control unit performs control so as to perform detection on the forward path and the return path of the recording head.

  According to a twelfth aspect of the present invention, the control means performs control so as to perform preliminary ejection for ejecting ink droplets from all nozzles immediately before and / or immediately after ejection of ink droplets in the process of passing the detection light. The ink jet printer according to claim 8, wherein the ink jet printer is provided.

  According to a thirteenth aspect of the present invention, when the defective nozzle is detected by the detection of the nozzle, the control means corrects the image data so that an image to be printed by the nozzle is printed by another nozzle. It is an inkjet printer in any one of Claims 8-12 characterized by the above-mentioned.

  According to a fourteenth aspect of the present invention, when the defective nozzle is detected by the detection of the nozzle, the control means controls to interrupt the continuous printing operation of the recording medium and execute the nozzle recovery operation. It is an inkjet printer in any one of Claims 8-12 characterized by the above-mentioned.

  According to the first and eighth aspects of the present invention, there is provided a recording head maintenance method capable of detecting a defective nozzle without interfering with the printing operation and enhancing the productivity of high-quality printed images, and An ink jet printer can be provided.

  According to the second and ninth aspects of the invention, even when a plurality of nozzle rows are provided, defective nozzles can be detected without interfering with the printing operation, and productivity of high-quality printed images is achieved. It is possible to provide a recording head maintenance method and an ink jet printer capable of improving the recording efficiency.

  According to the third and tenth aspects of the present invention, since it is possible to detect ink droplets on both sides of the recording medium, detection of all nozzles can be completed at an early stage.

  According to the fourth and eleventh aspects of the present invention, since it is possible to detect ink droplets in each of the forward path and the return path, detection of all nozzles can be completed early.

  According to invention of Claim 5, 12, a nozzle can be stabilized by preliminary discharge.

  According to the sixth and thirteenth aspects of the invention, even if a defective nozzle is detected, there is no need to interrupt the printing operation, and the printing operation can be continued without reducing the printing speed.

  According to the seventh and fourteenth aspects of the present invention, when a defective nozzle is detected, the defective nozzle can be recovered early.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing a schematic configuration of a main part of the ink jet printer, FIG. 2 is a view of the recording head viewed from the nozzle surface side, and FIG. 3 is a block diagram showing a configuration of the main part of the ink jet printer.

  In FIG. 1, reference numerals 1 </ b> A to 1 </ b> D denote four recording heads that eject four colors of YMCK, and are mounted on a common carriage 2. Both ends of the wire 4 spanned between two pulleys 4a and 4b are attached to the carriage 2, and slide along two parallel guide rails 3 extending along the main scanning direction indicated by A in the figure. It is provided as possible. A main scanning motor 5 is connected to one pulley 4a, and the carriage 2 is pulled by the wire 4 when the main scanning motor 5 is driven to rotate and slides on the guide rail 3 in the main scanning direction A. It is designed to reciprocate along.

  As shown in FIG. 2, each of the recording heads 1A to 1D mounted on the carriage 2 includes a plurality of nozzles 1a,..., 1b, 1c, 1d, which are parallel to the sub-scanning direction indicated by B in the drawing. And they are arranged in one row along the direction orthogonal to the main scanning direction A.

  A transport belt 6 is disposed below the carriage 2. The conveyor belt 6 is stretched between two conveyor rollers 6a and 6b arranged at a predetermined interval in the sub-scanning direction B. One transport roller 6b is connected to a sub-scanning motor 7 composed of a stepping motor so as to be able to transmit a driving force. When the sub-scanning motor 7 is rotationally driven, the transport belt 6 is rotationally driven. The recording medium M placed thereon is conveyed along the sub-scanning direction B.

  In this inkjet printer, the control unit 100 drives the main scanning motor 5 to move the carriage 2 along the main scanning direction A. In the course of this movement, the control unit 100 prints the recording heads 1A to 1D at a predetermined timing. By driving the drive circuits 101A to 101D provided for each, the ink droplets are ejected from the nozzles 1a to 1d of the recording heads 1A to 1D toward the recording medium M stopped on the conveying belt 6, respectively. When one main scanning (outward path) of the carriage 2 is completed, the control unit 100 drives the sub-scanning motor 7 to rotate the transport roller 6b and intermittently rotate the transport belt 6 to move the recording medium M by a predetermined amount. A desired image corresponding to the image data is formed on the recording medium M by repeating the operation of carrying and performing the next main scanning (return path) in the same manner as described above.

  1 is a linear encoder for detecting a position of the carriage 2 along the main scanning direction A. The carriage 2 is provided with an encoder sensor 103 (see FIG. 3) not shown in FIG. 1, and the position of the carriage 2 along the main scanning direction A is detected from the linear encoder 102 and controlled as position information of the carriage 2. It is to be sent to the part 100.

  An ink droplet detection device 200 is disposed further to the side of the outer side of the conveyance belt 6 of the recording medium M. The ink droplet detection apparatus 200 includes a light emitting element 201 having a light emitting element that emits a light beam such as an LED (light emitting diode) or a laser, and a light receiving element that receives a light beam emitted from the light emitting part 201. And a light receiving unit 202 having a distance between them so that the nozzle rows of the recording heads 1A to 1D can be sandwiched in a reciprocating scanning region along the main scanning direction A of the recording heads 1A to 1D. The detection light L is formed by emitting a light beam from the light emitting unit 201 toward the light receiving unit 202. At this time, the detection light L is formed so as to be able to cross the flight path of the ink droplets ejected from the nozzles 1a to 1d along the arrangement directions of the nozzles 1a to 1d.

  Accordingly, when an ink droplet is ejected from any one of the nozzles 1 a to 1 d at the position of the detection light L, the ink droplet passes through the detection light L, and a shadow at that time is captured by the light receiving unit 202. The shadow of the ink droplet captured by the light receiving unit 202 is converted into an electrical signal and sent to the detecting unit 204 (see FIG. 3) as a change in signal output. The detection unit 204 detects a large signal change when the ink droplet has passed by comparing the change in the signal output sent from the light receiving unit 202 with the reference signal, and if there is a large signal change, the control unit A signal is output to 100.

  The control unit 100 controls the ejection of the ink droplets by controlling the drive circuits 101A to 101D that drive the recording heads 1A to 1D, and the ink from the output of the ejection start signal to the drive circuits 101A to 101D. Whether or not ink droplets are ejected is determined based on whether or not there is a signal output from the detection unit 204 within a sufficient set time during which the droplets will pass the detection light L.

  As shown in FIG. 1, an ink tray 203 is arranged between the light emitting unit 201 and the light receiving unit 202 so as to receive ink droplets ejected when ink droplets are detected.

  In the present invention, detecting ink droplets ejected from the nozzles 1a to 1d using such an ink droplet detection apparatus 200 is sometimes simply referred to as “nozzle detection”.

  In FIG. 1, reference numeral 300 denotes a recording head recovery device, which is disposed further outside the ink droplet detection device 200. The recovery device 300 is in close contact with any one of the nozzle surfaces of the recording heads 1A to 1D, and a suction cap 301 that forcibly sucks ink from the nozzles, a suction pump 302 for making the inside of the suction cap 301 a negative pressure, and a suction cap A suction pipe 303 that communicates the inside of the suction pump 302 with the suction pump 302 and discharges the sucked ink, and a suction cap lifting / lowering motor that moves the suction cap 301 up and down between a position close to the nozzle surface and a position away from the nozzle surface. 304 (see FIG. 3). The suction pump 302 and the suction cap lifting / lowering motor 304 are controlled by the control unit 100.

  Next, the operation of the ink jet printer will be described with reference to FIGS. 4 is a diagram showing a flow of maintenance operation when the recording heads 1A to 1D are moved forward, FIG. 5 is a diagram showing a flow of maintenance operation when the recording heads 1A to 1D are moved backward, and FIG. It is a figure explaining the relationship between a range and the ink droplet d. Here, in FIG. 1, the case where the recording heads 1A to 1D move from the left to the right is the forward movement, and the reverse is the backward movement.

  Maintenance refers to detecting defective nozzles, preliminary ejection that ejects ink droplets from all nozzles at once, forcibly sucking ink from the nozzles, and wiping the nozzle surface to recover the defective state. Although including cleaning and the like, in the present invention, maintenance means to include at least a defective nozzle detection operation.

  Further, in the present invention, the defective nozzle includes not only a nozzle missing state in which ink droplets are not ejected from the nozzles but also a state of ejection bending in which ink droplets are bent and ejected from the nozzles.

  First, when the carriage 2 is positioned on the left side of the recording medium M and stopped, the forward movement is started in the right direction, and the position information read from the linear encoder 102 has reached the recording area of the recording medium M. At the time of detection, printing for one scan is performed, and the recording medium M moves to the outside of the recording area on the right side.

  The nozzle row of the recording head 1D on the carriage 2 positioned at the head during forward movement has come to a position P1 that is closer to the front position P1 than the detection range P2-P3 of the detection light L of the ink droplet detection device 200 shown in FIG. Is detected from the position information read from the linear encoder 102 (S1), the control unit 100 continuously ejects ink droplets d from one nozzle (here, nozzle No. 1) to the drive circuit 101D. A signal is output to (S2). In the meantime, the carriage 2 continues to move at a constant speed that is the same as the printing speed. The ink droplet d passes through the detection range P2-P3 of the detection light L while ejecting the ink droplet d continuously from 1, and the detection light L is blocked by the ink droplet d ejected at this time.

  When the nozzle array of the recording head 1D moves to a position P4 slightly beyond the detection range P2-P3 of the detection light L (S3), the control unit 100 stops the ejection of ink droplets from the recording head 1D (S4). Thereafter, whether or not the ink droplets d continuously ejected from the recording head 1D have passed through the detection light L during the forward movement and are captured by the light receiving unit 202, that is, the nozzle No. of the recording head 1D. 1 determines whether or not the ink droplet d is a defective nozzle that does not normally discharge (S5). Here, when the ink droplet d is not detected, the control unit 100 determines the nozzle No. of the recording head 1D. 1 is determined to be a defective nozzle, recovery processing (which will be described later) is executed (S6), and when an ink droplet d is detected, nozzle No. 1 is detected. 1 is determined to be normal and the detection operation is terminated.

  Thereafter, as the carriage 2 further moves forward, each nozzle row of the adjacent recording heads 1C, 1B, and 1A also reaches the position P1 before the detection range P2-P3 in the same manner as described above. By continuously ejecting ink droplets d from 1b and 1a, the presence or absence of a defective nozzle is detected.

  When each of the nozzles 1a to 1d to be detected at the time of the forward movement is normal, the carriage 2 moves to the reverse position at the rightmost end, reverses there and moves to the reverse movement.

  When the carriage 2 reverses and starts moving backward in the left direction, it first passes through the ink droplet detection device 200. Then, the nozzle row of the recording head 1A on the carriage 2 positioned at the head during the backward movement comes to a position P4 in front of the detection range P3-P2 of the detection light L of the ink droplet detection device 200 shown in FIG. Is detected from the position information read from the linear encoder 102 (S11), the control unit 100 causes the drive circuit 101A to send one nozzle other than the nozzle that ejected the ink droplet d during the forward movement (here, the nozzle No. 1). A signal is output so that ink droplets d are continuously ejected from nozzle No. 2 adjacent to nozzle 1 (S12). In the meantime, the carriage 2 continues to move back at a constant speed that is the same as the speed during printing. The ink droplet d passes through the detection range P3-P2 of the detection light L while continuously ejecting the ink droplet d from 2, and the detection light L is blocked by the ink droplet d ejected at this time.

  When the nozzle row of the recording head 1A moves to a position P1 slightly past the detection range P3-P2 of the detection light L (S13), the control unit 100 stops the ejection of ink droplets from the recording head 1A (S14). Thereafter, whether or not the ink droplets d continuously ejected from the recording head 1A have passed through the detection light L during the backward movement and are captured by the light receiving unit 202, that is, the nozzle No. of the recording head 1A. 2 determines whether or not the ink droplet d is a defective nozzle that is not ejected normally (S15). Here, when the ink droplet d is not detected, the control unit 100 determines the nozzle No. of the recording head 1A. 2 is determined to be a defective nozzle, recovery processing (which will be described later) is executed (S16), and when an ink droplet d is detected, nozzle No. 2 is detected. 2 is judged to be normal, and the detection operation is terminated.

  Thereafter, as the carriage 2 further moves backward, each nozzle row of the adjacent recording heads 1B, 1C, and 1D also reaches the position P4 before the detection range P3-P2 in the same manner as described above. By continuously ejecting ink droplets d from 1c and 1d, the presence or absence of a defective nozzle is detected.

  Next, when it is detected from the position information read from the linear encoder 102 that the recording area of the recording medium M has been reached, printing for one scan is performed, and the recording medium M is moved to the outside of the recording area on the left side. Move on to reverse operation.

  Thereafter, the above operation is repeated, but each time the recording heads 1A to 1D on the carriage 2 pass above the detection light L of the ink droplet detection device 200, the nozzle positions for ejecting the ink droplets d are sequentially changed. Then, the ink droplet d is ejected from all the nozzles by repeating the upper passage of the detection light L a plurality of times. For example, when each of the recording heads 1A to 1D has 256 nozzles and detects one nozzle each time the detection light L passes once, the printing operation is repeated 128 times, that is, the printing operation for 128 scans is repeated. Nozzle detection ends. At this time, the ink droplet d is ejected to a wide range including the detection range P2-P3 of the detection light L, that is, a position P4 (P1) slightly passing from the position P1 (P4) slightly before the detection range P2-P3 of the detection light L. Therefore, it is not necessary to perform an accurate alignment so that the carriage 2 is stopped and the optical axis of the detection light L and the nozzle row coincide with each other, and it is extremely simple and can perform a normal printing operation. The nozzle can be detected without any interruption.

  The number of nozzles to be detected when the detection light L passes once is not limited to one nozzle per recording head as described above, but depends on the detection range P2-P3 of the detection light L and the moving speed of the carriage 2. Depending on the situation, it can be set appropriately, and if there is a margin, it is possible to execute a plurality of nozzles per recording head by sequentially ejecting from a plurality of nozzles. However, from the viewpoint of enabling accurate detection during the movement of the carriage 2, it is necessary to make the number less than the total number of nozzles per recording head, and preferably a number of one or more nozzles and ½ or less of the total number of nozzles. More preferably, the number is 1 nozzle or more and 1/3 or less of the total number of nozzles, most preferably 1 to 5 nozzles.

  The nozzles to be detected may be sequentially detected from the nozzle at the end, or may be preferentially detected from nozzles that are less frequently used during one scan and are likely to be defective nozzles. .

  As a result of detection by the ink droplet detection device 200, when it is determined that the nozzle is a defective nozzle that does not eject the ink droplet d normally, the control unit 100 executes a recovery process by the recovery device 300 in steps S6 and S16.

  FIG. 7 is a flowchart showing the operation of the recovery process. If it is determined that there is a defective nozzle, the control unit 100 moves the recording head including the defective nozzle on the carriage 2 to a position where the suction cap 301 of the recovery device 300 is installed and stops it (S21). Next, the suction cap lifting / lowering motor 304 is driven to raise the suction cap 301 (S22). As a result, the suction cap 301 comes into contact with and closely contacts the nozzle surface of the recording head including the defective nozzle. Next, the control unit 100 drives the suction pump 302 to make negative pressure in the suction cap 301, thereby forcibly sucking ink from each nozzle and recovering problems such as nozzle clogging (S23). After a predetermined time, the suction pump 302 is stopped (S24), and the suction pump lift motor 304 is driven in the reverse direction to lower the suction cap 301 away from the nozzle surface (S25), thereby completing the recovery process.

  By executing the recovery process in this manner, defective nozzles can be recovered at an early stage, which is effective in maintaining image quality and forming a high-quality image.

  If the recovery process is executed every time a defective nozzle is detected, there is a concern that the printing operation is interrupted each time. In general, in an ink jet printer in which a recording head is moved by main scanning with a carriage, when the number of defective nozzles is as small as about 1 to 2 nozzles, an image to be printed by the defective nozzles is printed using other nozzles. Is possible. Accordingly, the control unit 100 does not execute the recovery process each time a defective nozzle is detected, and corrects the image data so that an image to be printed with the defective nozzle is printed with another nozzle. Is also preferable. As a result, even if a defective nozzle is detected, it is not necessary to perform the recovery process. Therefore, it is not necessary to interrupt the printing operation, and it is possible to continue the printing operation without reducing the printing speed. In this case, the recovery process may be executed collectively at the end of the printing operation.

  In the present invention, it is also preferable to execute preliminary ejection in which a plurality of ink droplets are continuously ejected from all nozzles immediately before and / or immediately after ejection of ink droplets for detection by the ink droplet detection device 200. Since all the nozzles can be stabilized by performing preliminary ejection, if performed immediately before detection, ejection of ink droplets for detection becomes stable, and accurate detection becomes possible. Moreover, if it is executed immediately after detection, the ejection of ink droplets during the printing operation is stabilized, which is effective in maintaining the image quality.

  In the above description, the detection operation by the ink droplet detection device 200 is executed both during the forward movement and during the backward movement. However, either the forward movement (forward path) or the backward movement (return path) is performed. It may be only. However, if it is executed both during the forward movement and during the backward movement, the detection of all the nozzles can be completed early, so that defective nozzles can be found early and effective in maintaining image quality. It is.

  Further, in the above description, only one ink droplet detection device 200 is arranged on one side of the recording medium M. However, as shown in FIG. 8, ink droplet detection devices 200A and 200B are provided on both sides. Each may be arranged. In this case, every time the carriage 2 reciprocates, each ink droplet detection device 200A, 200B can detect in the same manner, so that the detection of all the nozzles can be completed earlier. Of course, if the detection by each of the ink droplet detection devices 200A and 200B is executed both during the forward movement and during the backward movement of the carriage 2, the detection can be completed earlier, so that the image quality can be maintained. It is more effective.

  Further, the ink droplet detection device 200 is not limited to one arranged on one side of the recording medium M, and a plurality of ink droplet detection devices 200 are arranged in parallel according to the scanning width of the carriage 2, thereby detecting a plurality of detections per one scan. A plurality of nozzles may be detected through light.

  In the present invention, the number of recording heads is not limited at all. Further, the number of nozzle rows arranged in one recording head is not limited to one, and may be a plurality of rows.

The perspective view which shows schematic structure of the principal part of an inkjet printer View of the recording head viewed from the nozzle side Block diagram showing the configuration of the main part of an inkjet printer Diagram showing the flow of maintenance operation when the print head moves forward and backward Diagram showing the flow of maintenance operation when the recording head is moved backward (A) is a diagram for explaining the relationship between the detection range of detection light during forward movement and ink droplets, and (b) is a diagram for explaining the relationship between the detection range of detection light during backward movement and ink droplets. Flow chart showing the operation of recovery processing The top view which shows other embodiment of the recording part of an inkjet printer

Explanation of symbols

1A to 1D: Recording heads 1a to 1d: Nozzle 2: Carriage 3: Guide rail 4: Wire 4a, 4b: Pulley 5: Main scanning motor 6: Conveying belt 6a, 6b: Conveying roller 7: Sub scanning motor 100: Control unit 101A to 101D: Drive circuit 200, 200A, 200B: Ink droplet detection device 201: Light emitting unit 202: Light receiving unit 203: Ink tray 204: Detection unit 300: Recovery device 301: Suction cap 302: Suction pump 303: Suction pipe M: Recording medium L: Detection light d: Ink droplet

Claims (14)

Inkjet for forming an image on the recording medium by ejecting ink droplets from the nozzle based on image data in a process of reciprocating scanning a recording head in which a plurality of nozzles are arranged along a direction orthogonal to the conveyance direction of the recording medium In a recording head maintenance method in a printer,
Detection light for detecting the presence / absence of the passage of the ink droplets on the side of the recording medium along the arrangement direction of the nozzles of the recording head and crossing the flight path of the ink droplets ejected from the nozzles Form the
During the process of scanning the recording head and continuously printing on the recording medium, ink droplets are sequentially ejected from one or more nozzles of the recording head to less than all nozzles while the nozzle array of the recording head passes the detection light. A maintenance method for a recording head, wherein all nozzles are detected by scanning a plurality of times. The nozzles are provided in a plurality of rows along the scanning direction,
In the process of scanning the recording head and passing the detection light during continuous printing on the recording medium, each nozzle row sequentially ejects ink droplets from one or more nozzles and less than all nozzles, 2. The maintenance method for a recording head according to claim 1, wherein all nozzles of the nozzle array are detected.   3. The recording head according to claim 1, wherein the detection light is disposed on both sides of the recording medium, and detection is performed on both sides of the recording medium in a process of reciprocating scanning of the recording head. Maintenance method.   4. The recording head maintenance method according to claim 1, wherein the ejection of ink droplets in the process of passing the detection light is performed respectively in the forward path and the backward path of the recording head.   The preliminary ejection for ejecting ink droplets from all the nozzles is executed immediately before and / or immediately after the ejection of the ink droplets in the process of passing the detection light. Maintenance method of the recording head.   The image data is corrected so that an image to be printed by the nozzle is printed by another nozzle when a defective nozzle is detected by the nozzle detection. Recording head maintenance method.   The recording head according to claim 1, wherein when a defective nozzle is detected by the detection of the nozzle, the continuous printing operation of the recording medium is interrupted and a nozzle recovery operation is executed. Maintenance method. Inkjet printer for forming an image on the recording medium by ejecting ink droplets based on image data in a process of reciprocating scanning a recording head formed by arranging a plurality of nozzles along a direction orthogonal to the conveyance direction of the recording medium In
The detection light is arranged on the side of the recording medium, along the arrangement direction of the nozzles of the recording head, and intersects the flight path of the ink droplets ejected from the nozzles, and the presence or absence of the passage of the ink droplets Ink droplet detection means for detecting
In the process of scanning the recording head and passing the detection light during continuous printing on the recording medium, ink droplets are sequentially ejected from nozzles of one or more nozzles and less than all nozzles of the recording head, and all of them are scanned by a plurality of scans. An ink jet printer comprising: control means for controlling to detect nozzles. The nozzles are provided in a plurality of rows along the scanning direction,
In the process of scanning the recording head and passing the detection light during continuous printing on the recording medium, the control means sequentially discharges ink droplets from nozzles of 1 nozzle or more and less than all nozzles in each nozzle row, 9. The ink jet printer according to claim 8, wherein control is performed so that all nozzles of each nozzle row are detected by one scan. The ink droplet detection means is disposed on both sides of the recording medium,
The ink jet printer according to claim 8 or 9, wherein the control means controls to perform detection on both sides of the recording medium.   11. The ink jet printer according to claim 8, 9 or 10, wherein the control means performs control so as to perform detection in each of a forward path and a return path of the recording head.   9. The control unit according to claim 8, wherein control is performed so as to perform preliminary ejection for ejecting ink droplets from all nozzles immediately before and / or immediately after ejection of ink droplets in the process of passing the detection light. The inkjet printer in any one of -11.   The control means corrects the image data so that an image to be printed by the nozzle is printed by another nozzle when a defective nozzle is detected by the detection of the nozzle. An inkjet printer according to any one of the above. 13. The control unit according to claim 8, wherein when a defective nozzle is detected by the detection of the nozzle, the control unit performs control so as to interrupt the continuous printing operation of the recording medium and execute a nozzle recovery operation. An inkjet printer according to any one of the above.

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