JP2016179558A - inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in which an image quality defect continues from the time when a nozzle defect occurs since a defective nozzle occurring in the middle of printing cannot be detected even though the image quality defect can be prevented by allocating data to be input to the nozzle having the nozzle defect that can be detected before printing to another nozzle in a conventional technique.SOLUTION: An inkjet printer includes a roll sheet different from a recording medium, discharges ink to the roll sheet for each fixed scan during printing, compares the surface states between a non-discharged portion of the roll sheet and a discharged portion, changes the nozzle compared to non-discharging when the surface states are within a certain threshold, and allocates printing data to be input to the nozzle to another nozzle being in the complementary relationship to eliminate a continuous nozzle defect. After discharging ink from all the nozzles to the roll sheet, a carriage is returned to a printing operation, detection of the nozzle defect can be performed in parallel with printing, and thereby the state of the nozzle can be evaluated without stopping printing.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an inkjet printer that records an image by ejecting ink.

  2. Related Art Inkjet printers that record images by ejecting ink from an inkjet head onto a recording medium such as paper or a resin film are known. Inkjet printers are required to improve performance such as high image quality, durability, and reliability. However, if foreign matter adheres to the nozzle surface of the ink jet head, ejection failure such as ink not being ejected or bending may occur due to the influence. For this reason, in general inkjet printers, deposits such as ink and foreign matter adhering to the nozzle surface of the inkjet head are periodically wiped and removed with an elastic wiper blade such as rubber. However, in the wiping operation for removing the dust, the dust may enter the nozzle, the nozzle may be clogged, and a defect that causes non-ejection may occur. Also, nozzle failures such as nozzle clogging can occur during printing.

  In some ink jet printers, when such a nozzle failure occurs, an alternative control for a nozzle that records an image recorded by the defective nozzle with another nozzle is employed. For example, Japanese Patent Application Laid-Open No. 2011-156732 describes a technique for detecting whether or not an optical axis of a sensor including a light emitting unit and a light receiving unit is a non-ejection nozzle by whether or not the ink ejected from the nozzle is blocked. ing. Then, printing is performed by substituting other nozzles for non-ejection nozzles, thereby preventing image quality defects due to nozzle defects from being visually recognized.

JP 2011-156732 A

  In the conventional technique, defective nozzles that can be detected before printing can be prevented by allocating input data to other nozzles. However, since a defective nozzle that occurs during printing cannot be detected, an image quality defect occurs from the point in time when the nozzle defect occurs. Also, detection based on whether or not the optical axis is blocked may be erroneously detected by ink mist. Also, a large amount of ink is wasted when checking repeatedly. In this case, an inkjet printer that periodically wipes the nozzle surface during printing cannot replace the nozzle failure that occurs at that time.

  The present invention has been made in view of the above circumstances, and has a simple configuration, detects a nozzle failure during printing, and performs control to replace a nozzle that becomes defective during printing, thereby continuously. An object of the present invention is to provide an ink jet printer capable of preventing image quality deterioration.

  An inkjet printer according to the present invention includes a recording head in which a nozzle array including a plurality of nozzles that eject ink is disposed, a carriage that mounts the recording head and moves in the main scanning direction, and intersects the main scanning direction. An inkjet printer that discharges the ink from the nozzles to the recording medium to record an image, and conveys the roll paper along the recording medium conveyance direction. A roll paper conveying means for detecting the image recorded on the roll paper, and changing the position of the carriage to the roll paper for each nozzle and changing the position of the ink for each nozzle. To form dots, detect the dots by the detection means, and the nozzles discharge the ink based on the detection result If the result of the determination is non-ejection, the nozzle that is not ejecting is replaced by another nozzle, the image is recorded on the recording medium, and the result of the judgment is ejection In this case, the image is recorded on the recording medium by the nozzle that is the ejection.

  According to the present invention, nozzle defects due to wiping operations performed during printing or long printing are detected without stopping printing during printing, and replacement of the output at an early stage prevents deterioration of image quality of continuous output products. Can be prevented.

FIG. 1 is a schematic view of an ink jet printer. FIG. 2 is a block diagram of the ink jet printer. FIG. 3 is a schematic diagram of the discharge confirmation mechanism. FIG. 4 is a flowchart of print control. FIG. 5 is a flowchart of the discharge confirmation.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an ink jet printer. As shown in FIG. 1, the inkjet printer 1 of the present embodiment horizontally arranges a recording medium 50 and conveys it from the back of the paper surface of FIG. 1 to eject ink from an inkjet recording head 9. Images, characters and the like corresponding to the recording data are recorded on the surface of the recording medium 50. The recording medium 50 is paper, a resin film, or the like. The front direction from the back of this page is called the sub-scanning direction.

  The ink jet printer 1 includes a plurality of recording heads 9, a carriage 4 that reciprocally scans in a direction that intersects the conveyance direction of the recording medium 50, for example, a direction that is orthogonal to the recording medium 50, and a wipe unit that wipes the nozzle surface of the recording head 9. 10 and a capping unit 12 that caps the recording head 9. The direction of reciprocating scanning is called the main scanning direction. The ink jet printer 1 includes control means for controlling the entire apparatus including reception of recording data and control of recording operation. In addition, a transport unit that transports the recording medium 50 is provided. The transport unit includes a plurality of transport roller pairs 3 that are rotated about a horizontal axis along the paper surface by a motor 5 in order to feed the paper onto the substantially flat platen 2 that extends in the depth direction of the paper surface of FIG. The transport roller pair 3 includes a grid roller that is rotatably supported around a rotation axis that is parallel to the rotation axis, and a pinch roller that is energized by the grid roller. The grid roller is rotated by the motor 5. The recording medium 50 is conveyed while being sandwiched between the grid roller and the pinch roller. As the grid roller rotates, the recording medium 50 can be conveyed in the sub-scanning direction.

  The carriage 4 is provided so as to be movable along a carriage rail 17 that extends in a direction perpendicular to the conveyance direction of the recording medium 50 above the conveyance unit, the wipe unit 10, and the capping unit 12. Further, a motor 6 is provided for reciprocating the carriage 4 on the carriage rail 17 so as to be capable of position control and speed control. The motor 6 drives an endless belt 7 disposed along the carriage rail 17. A carriage 4 is fixed to the endless belt 7. The endless belt 7 is wound around pulleys disposed on both ends in the moving direction of the carriage 4. A linear scale 8 is provided along the carriage rail 17, and a linear sensor 16 that detects the scale of the linear scale 8 is provided in the carriage 4. The position of the carriage 4 can be detected, and the positions of a plurality of recording heads 9 fixed to the carriage 4 at fixed positions can also be detected accordingly.

  Further, a detachable ink cartridge 14 for supplying recording ink to the recording head 9 is provided, and the ink cartridge 14 and the recording head 9 are connected by an ink tube 15 for supplying ink.

  In the present embodiment, the ink cartridge 14 is provided with a plurality of colors of ink for performing color recording, and can be supplied to the recording head 9 for each color via a plurality of ink tubes 15 as pipes. ing. The ink cartridge 14 is provided with a plurality of ink tanks corresponding to each ink, and each ink is accommodated in a corresponding ink tank.

  The carriage 4 is provided with a plurality of recording heads 9 on the lower surface side in accordance with the ink color, recording range, and the like, and the ink supplied from the ink tube 15 is supplied to the recording head 9 that performs recording of the same color. .

  Although details of the recording head 9 are not shown, a plurality of ink ejection holes are provided in an ink chamber for supplying ink to each nozzle and a nozzle surface facing the recording medium. The nozzles can be provided with an appropriate number and arrangement pitch according to the configuration of the ejection mechanism, the recording pixel pitch, and the like. For example, a large number of nozzles such as 256 can be arranged. For example, the recording head 9 may use a piezoelectric element as a recording element, or may be a recording head using a heater as a recording element.

  The position control and speed control of the motor 6 are performed according to the control signal of the control means. During the recording operation, the motor 6 is controlled so that the recording head 9 reciprocates on the recording medium 50 at a predetermined speed. Further, the motor 6 can move the recording head 9 to a predetermined wiping position of the wipe unit 10 during the cleaning operation. The capping unit 12 cleans the inside of the nozzle hole of the recording head 9 by sucking the ink of the recording head 9 from the nozzle to the outside. Also, the ink is prevented from drying by capping when not in use. The schematic configuration of the capping unit 12 includes a cap 11, a cap driving unit, a suction pump, a waste ink bottle 13, and an air release valve. The air release valve is a valve that introduces outside air with the nozzle surface sealed with a cap 11.

  Among these, at least the cap 11 is provided for each recording head 9. However, the cap drive unit, the suction pump, and the air release valve may be provided for each of the plurality of caps 11 when the operations of the recording heads 9 can be made common.

  The cap drive unit moves up and down to selectively switch the position of the cap 11 in the vertical direction, and includes, for example, appropriate mechanical, electromagnetic, and fluid lifting means. Therefore, the cap drive unit moves the cap 11 up and down in the vertical direction with respect to the recording head 9 which is moved on the carriage rail 17 by the motor 6 and positioned above the capping unit 12. It is possible to switch between a state in which the nozzle surface is sealed and a state in which it is released.

  The suction pump is for sucking contents such as air and ink in the sealed space of the cap and discharging them to the outside. For example, a rotary pump or the like can be adopted. A suction pump can also be used as a liquid passing means for passing ink from the ink cartridge 14 to the recording head 9. The suction pump has a suction port connected to the cap 11 and a discharge port connected to the waste ink bottle 13. It is necessary to seal the nozzle surface with the cap 11, and it is desirable that the contact surface between the recording head 9 and the cap 11 is free from dust and ink clumps.

  The wipe unit 10 wipes and cleans the nozzle surface of the recording head 9 by moving the wipe blade relative to the nozzle surface of the recording head 9 while the recording head 9 is moved above the wipe unit 10. To do.

  The discharge confirmation mechanism 32 is a means for confirming the state of each nozzle of the recording head 9. It is possible to detect whether or not each nozzle has recorded on the roll paper. It is arranged on the side of the platen 2. Each nozzle can be confirmed in parallel with the image recording on the recording medium 50 on the platen 2.

  FIG. 2 is a block diagram of the ink jet printer. The control unit 20 is a control unit including a CPU that executes processing operations such as calculation, control, determination, and setting. The control means 20 operates according to a control program stored in the ROM 21. The RAM 22 is used as a recording data buffer, a work area for arithmetic processing by the control means 20, and the like. The carriage movement motor drive circuit 23 operates under the control of the control unit 20 and drives the motor 6 that moves the carriage 4 on which the recording head 9 is mounted. The carriage position detection sensor 24 includes a linear sensor 16 that detects the scale of the linear scale 8 disposed along the carriage rail 17 that guides the movement of the carriage 4. Based on the sensor output, the controller 20 calculates and acquires the position of the carriage 4. The head drive circuit 25 is controlled by the control means 20. The recording head 9 is operated via the head driving circuit 25. When a plurality of recording heads 9 are mounted, the control unit 20 and the head driving circuit 25 can drive each recording head 9 individually. The head drive circuit 25 generates ink ejection timing or non-ejection timing for each recording head 9 based on the information input from the control means 20 and drives the recording head 9. When ink ejection is performed, an ON waveform is generated. When ink ejection is not performed, an OFF waveform is generated and transferred to each recording head 9. The ejection timing is determined according to the position of the carriage 4 calculated by the control means 20 based on information from the carriage position detection sensor 24.

  The recording medium transport unit 26 operates under the control of the control unit 20. The recording medium transport unit 26 includes a transport unit that transports the recording medium 50. The pair of transport rollers 3 is driven by the motor 5 to transport the recording medium 50. The wipe blade moving motor drive circuit 27 operates under the control of the control means 20. The wipe blade moving motor drive circuit 27 drives a motor that moves the belt to which the wipe blade is fixed.

  The detection unit 39 detects the color of the roll paper 19 before starting printing, and stores the output result in the RAM 22. Next, after the ink ejected portion is conveyed, the color of the roll paper 19 is detected and output to a different area from the RAM 22. The control means 20 compares the original color of the roll paper 19 recorded in the RAM 22 with the color of the portion where the ink is ejected, and if the color difference exceeds a certain threshold, the ejected nozzle is regarded as defective, and the use of the nozzle The data that should have been input is assigned to other nozzles and is recorded instead. The detection means 39 can use a colorimeter that detects a color difference and outputs an Lab value. Moreover, the photodetector which lights each color LED of RGB and detects the reflected light may be sufficient. In that case, an LED having a color that easily reacts to the ink color is used.

  The roll paper transport motor 18 is controlled by the control means 20 and transports the recording medium 50. Further, the number of scans in the sub-scanning direction of the carriage 4 during recording is counted, and ink is ejected every several nozzles onto the roll paper 19 outside the image recording area every predetermined number of times. When the roll paper is conveyed so that the first discharged portion falls within the detection range of the detection means 39, the state of the nozzle used for the first discharge is determined using the detection means 39, and when the determination is completed, The roll paper 19 is transported to a position where the state of the nozzle used for the second ejection can be detected, and the nozzle used for the second ejection is determined by the detection means 39. This is performed for all the nozzles that discharge.

  For example, assume that all nozzles are 20 nozzles. For the sake of explanation, the numbers 1 to 20 are assigned in order from the nozzles at one end. The nozzles used for the first discharge are the first, sixth, eleventh and sixteenth nozzles. The nozzles used for the second discharge are the second, seventh, twelfth and seventeenth nozzles. The nozzles used for the third discharge are the third, eighth, thirteenth and eighteenth nozzles. The nozzles used for the fourth discharge are the fourth, ninth, fourteenth, and nineteenth nozzles. The nozzles used for the fifth discharge are the first, fifth, tenth and fifteenth nozzles. The nozzles used for the fifth discharge are the fifth, tenth, fifteenth and twentieth nozzles. In this way, test printing is performed in five steps. By separating the nozzles and recording, it is possible to prevent erroneous detection due to overlapping of other dots due to bleeding or the like. The control means 20 detects the result of this test printing, that is, whether or not ink is ejected, by the detection means 39. Based on the result, the control means 20 calculates the difference between the initial value and the detected value, and if there is a difference greater than or equal to a predetermined value, it indicates that the nozzle is normal, and if there is no difference, there is some abnormality, It is judged that. This is performed for each recording head arranged for each color. The recording positions of the roll paper of the recording heads are arranged so as not to overlap with the carriage moving direction.

  FIG. 3 is a schematic diagram of the discharge confirmation mechanism. A roll paper 19, a roll paper transport motor 18 for transporting the roll paper 19, and a detecting means 39 for detecting a test pattern recorded on the roll paper are provided. The roll paper 19 is set in the discharge confirmation mechanism 32 and is moved by the roll paper transport motor 18. That is, the roll paper 19 is moved by winding the roll paper 19 on the side where the roll paper transport motor 18 is disposed. The roll paper transport motor 18 is controlled by the control means 20, and the nozzles of the recording head 9 are divided into a plurality of nozzle groups, and after the ink is ejected by the nozzle groups, the portion where the ejected ink droplets land is the detection means 39. Transport to be within the detection range. After detecting the surface state of the roll paper 19 by the detection means 39, the roll paper 19 is transported again so that the portion where the ink droplets ejected by the next nozzle group landed falls within the detection range of the detection means 39. This operation is repeated until all nozzles are finished. When the detection means 39 performs the detection operation, if the ink droplet 30 is ejected normally, an output value different from the initial value obtained by measuring the surface of the roll paper 19 is stored in the RAM 22. When the ink droplet 31 is not ejected normally, the same output value as the initial value obtained by measuring the surface of the roll paper 19 is stored in the RAM 22. The detection means 39 may be equipped with a mechanism for scanning in the width direction of the roll paper, or may be arranged in the width direction to expand the detection range. In addition, detection accuracy can be improved by increasing the dot size of the ink that has landed. For example, the roll paper is preferably a film having a two-layer structure of a sheet formed of a porous member, and the upper layer is a film in which the lower layer is difficult to soak ink. Further, the upper layer is preferably provided with a high-contrast color sheet corresponding to each ink for each color.

  FIG. 4 is a flowchart for ejecting ink to the ejection confirmation mechanism during printing. After printing is started, it is determined in step S1 whether the carriage 4 has been scanned a predetermined number of times. If yes, the process proceeds to step S2, and if not, the process proceeds to step S7. For example, detection is performed every 100 scans. Alternatively, the nozzle group detected for each scan may be changed, and the nozzle group corresponding to the scan may be detected for each scan. In step S <b> 2, the carriage 4 is moved to a predetermined position of the discharge confirmation mechanism 32. In step S <b> 3, one of several nozzle groups allocated in advance ejects ink onto the roll paper 19. The ejection method is performed according to a predetermined pattern. For example, 10 dots are ejected, the carriage is moved in the scanning direction by 1 dot, and 10 dots are ejected there again. It is possible to record dots that are dark and large to some extent. While the image is printed, it is folded back at the edge of the platen 2. However, when the nozzle is checked, it is moved back to the position of the ejection confirmation mechanism 32 without being folded back. When ink is ejected from a predetermined nozzle onto the roll paper, the process returns to the platen 2 to continue printing. You can check without taking time even during printing.

  In step S4, it is determined whether all of the nozzles of the recording head 9 have been ejected. If so, the process proceeds to step S6, and if not, the process proceeds to step S5. In step S5, the carriage 4 is moved in the width direction of the roll paper by a predetermined amount, and the next nozzle set is discharged onto the roll paper. For example, the carriage is moved to a position that does not overlap the previously recorded dots. When a nozzle confirmation process or a defect is confirmed, a nozzle substitution process is performed.

  In step S6, the confirmation of the state of the nozzle and the substitution process when the nozzle is defective are terminated, and the printing operation is resumed. Next, in step S7, it is determined whether printing has been completed. If it has been completed, control is terminated. Otherwise, the process proceeds to step S1.

  FIG. 5 is a flowchart for detecting a nozzle defect. In step S 8, the surface of the roll paper 19 is measured, and the Lab value as a detection result is stored in the RAM 22. The output result at this time may be a value obtained by emitting white light, detecting reflected light from the RGB color sensors, and AD converting the result.

  In step S9, ink is ejected from the first nozzle group divided into a plurality of groups on the roll paper 19. Next, the roll paper 19 is conveyed and detected. When the discharge is completed, the roll paper transport motor 18 is driven and transported so that the portion ejected from the first nozzle group is within the detection range of the detection means 39 in step S10. In step S11, the surface of the roll paper 19 is measured by the detection means 39. That is, the dots recorded by the first nozzle group are detected at the respective dot positions. The transport amount of the roll paper 19 is controlled by the control means 20 by the roll paper transport motor 18 and the transport amount is also controlled. From which nozzle the dots recorded by the nozzle group are ejected are controlled by the control means 20, and the correspondence between the dots and the nozzles can be calculated from the transport quantity.

  In step S12, it is determined whether the difference between the measurement result stored in the RAM 22 in step S8, that is, the initial value is equal to or greater than a threshold value. The threshold value is obtained from a predetermined experiment and stored in the ROM 21. If it is equal to or greater than the threshold value, the process proceeds to step S13, and the nozzle number detected at that time is stored in the RAM 22. If it is less than the threshold value, the process proceeds to step S14.

  In step S14, it is determined whether or not the determination for all discharged nozzles has been completed. If all the nozzles have not been detected yet, the process proceeds to step S15, the roll paper is conveyed so that the position of the next nozzle row is within the detection range of the detection means 39, and step S11 and subsequent steps are performed again. If the detection of all nozzles has been completed, the process proceeds to step S16, and the nozzle corresponding to the nozzle number stored in the RAM 22 in step S13 is set to non-ejection from the scan for recording the next image. An alternative nozzle is calculated and obtained for the nozzle of the stored nozzle number, and printing is performed by the alternative nozzle instead of the ejection by the defective nozzle. At this time, the print data can be changed and allocated for replacement.

  The present invention can be used in an ink jet printer.

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Platen 3 Carrying roller pair 4 Carriage 5 Motor 6 Motor 7 Carriage rail 8 Linear scale 9 Recording head 10 Wipe unit 18 Roll paper conveyance means 19 Roll paper 30 Normal ejection ink 31 Defective ejection ink 50 Recording medium

Claims (3)

A recording head in which a nozzle array composed of a plurality of nozzles for ejecting ink is arranged, a carriage mounted with the recording head and moving in the main scanning direction, and a recording medium conveyed in a direction intersecting the main scanning direction An inkjet printer that records an image by ejecting the ink from the nozzles onto the recording medium.
Roll paper transport means for transporting roll paper along the transport direction of the recording medium;
Detecting means for detecting an image recorded on the roll paper,
Each time the carriage is scanned a predetermined number of times, the ink is ejected at different positions on the roll paper for each nozzle to form dots,
The dot is detected by the detection means, and it is determined whether or not the nozzle ejects the ink based on the detection result. If the determination result is non-ejection, the nozzle that is not ejecting is determined. The image is recorded on the recording medium in place of the other nozzles, and when the determination result is ejection, the image is recorded on the recording medium by the nozzle that is ejection. inkjet printer.   2. The ink jet printer according to claim 1, wherein when the ink is ejected onto the roll paper, the ink is recorded on the roll paper for every predetermined number of the nozzles.   The inkjet printer according to claim 1, wherein the detection unit is a colorimetric sensor that detects a color difference.

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