EP3556561B1

EP3556561B1 - Inkjet recording device and ink discharge control method of inkjet recording device

Info

Publication number: EP3556561B1
Application number: EP17879773.4A
Authority: EP
Inventors: Yuki Watanabe; Akira Takeya; Masakazu Mori
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2016-12-16
Filing date: 2017-11-08
Publication date: 2022-08-17
Anticipated expiration: 2037-11-08
Also published as: EP3556561A4; CN110087888A; EP3556561A1; JPWO2018110153A1; JP6988825B2; WO2018110153A1

Description

TECHNICAL FIELD

The present invention relates to an inkjet recording device and an ink discharge control method of the inkjet recording device.

BACKGROUND ART

Conventionally, there has been known an inkjet recording device which records an image by discharging ink onto a recording medium from an opening of a nozzle provided on an ink discharge surface of an ink discharger. In such an inkjet recording device, a foreign material flowing into the nozzle from the nozzle opening or the ink solidified at the nozzle opening may result in a faulty nozzle which does not discharge ink normally. Examples of an ink discharge fault of the faulty nozzle include abnormal discharge amount, abnormal discharge direction of the ink, and the like. Further, fine mist of ink (ink mist) generated from the faulty nozzle may be more than that from the normal nozzle during an ink discharge operation.
Such a faulty nozzle leads to image quality deterioration of the recorded image. Therefore, conventionally, there have been techniques for repairing a faulty nozzle to its normal state by performing ink discharge (ink ejection) not based on image data of an image to be recorded but at a predetermined timing or based on a user's instruction, such that inflow of foreign materials and solidification of ink are prevented for prevention of faulty nozzle generation and elimination of nozzle clogging (for example, see Patent Document 1).

CITATION LIST

PATENT LITERATURE

[Patent Document 1] Japanese Patent Application Laid Open Publication No. 2008-149629
US 2006/125869 A1 and JP 2005 088307 A disclose further relevant prior art.

SUMMARY OF INVENTION

TECHNICAL PROBLEM

However, depending on the opening state of the nozzle opening of the faulty nozzle, there is a problem that, during ejection, the faulty nozzle abnormally discharges ink or ink mist which adheres to the ink discharge surface and with which the ink discharge surface is contaminated. If the ink discharge surface is thus contaminated, the ink or ink mist adhering to the ink discharge surface falls onto the recording medium so as to cause the recording medium to be contaminated, and is solidified so as to plug a part of the nozzle opening and result in another faulty nozzle.
Objects of the present invention include providing an inkjet recording device and an ink discharge control method of the inkjet recording device by which contamination of an ink discharge surface due to ejection can be suppressed.

SOLUTION TO PROBLEM

In order to achieve the above-described object, according to the invention, an inkjet recording device according to claim 1 is disclosed.
According to the invention, an ink discharge control method of an inkjet recording device according to claim 4 is disclosed.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to suppress contamination of an ink discharge surface due to ejection.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a schematic configuration of an inkjet recording device according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a main functional configuration of the inkjet recording device.
FIG. 3 is a schematic view showing a configuration of cleaning rollers.
FIG. 4 is a schematic view showing a configuration of an inspection unit.
FIG. 5 is a diagram for explaining an operation of faulty nozzle detection.
FIG. 6 is a view for explaining an ejection area for ink ejection on a recording medium.
FIG. 7 is a block diagram showing a functional configuration regarding ejection control by a head controller.
FIG. 8 is a flowchart showing a control procedure for image record processing.
FIG. 9 is a flowchart showing a control procedure of image record processing according to Modification 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment according to an inkjet recording device and an ink discharge control method of the inkjet recording device of the present invention will be described on the basis of the drawings.
FIG. 1 is a view showing a schematic configuration of an inkjet recording device 1 according to an embodiment of the present invention.
FIG. 2 is a block diagram showing the main functional configuration of the inkjet recording device 1.
The inkjet recording device 1 includes a conveyor 10, a head unit 20 (ink discharger), a controller 30 (faulty nozzle identifier or cleaning controller), a head unit mover 41, a maintenance unit 42, an inspection unit 43 (discharge state detector), an operation unit/display 44, an input/output interface 45, and a bus 46.
The conveyor 10 has a driving roller 11, a driven roller 12, a conveyance belt 13, and the like.
The driving roller 11 is driven by a conveyance motor (not shown) and rotates around a rotation shaft. The conveyance belt 13 is a loop belt which is supported from inside by the driving roller 11 and the driven roller 12 and circles according to rotation of the driving roller 11. The driven roller 12 rotates on a rotation shaft parallel to the rotation shaft of the driving roller 11 according to the circling movement of the conveyance belt 13. A material used for the conveyance belt 13 flexibly bends on contacting faces with the driving roller 11 and with the driven roller 12 and reliably supports a recording medium M. For example, a belt of resin such as rubber, and a steel belt may be used. The recording medium M may be placed on the conveyance belt 13 more stably when the conveyance belt 13 includes a material and/or configuration which causes the recording medium M to be sucked. The conveyer 10 circulates the conveyance belt 13 at a rate depending on the rotational rate of the driving roller 11 with the recording medium M placed on the conveyance surface of the conveyance belt 13, so as to convey the recording medium M in the moving direction (conveying direction: Y direction in FIG. 1) of the conveyance belt 13. An encoder (rotary encoder) (not shown) is provided on the drive shaft of the driving roller 11 such that the circling movement distance of the conveyance belt 13 can be calculated.
The recording medium M may be conveyed intermittently, with a break during the ink discharge in the conveyor 10, for example. The conveyance by the conveyor 10 includes actions of taking a break during conveyance, as described above.
In the present embodiment, fabric is used as the recording medium M. The recording medium M is pulled out (wound) from a roll on which the recording medium M is rolled, and is supplied onto the conveyance belt 13. The recording medium M has a rectangular shape having a width of two meters in width direction (X direction in FIG.1) which is perpendicular to the conveyance direction and a length of approximately 4000 meters in the conveyance direction. The conveyor 10 may convey a recording medium M having a width of less than two meters in the width direction. The conveyor 10 may be configured to be able to convey a recording medium M having a width of more than two meters (for example, about 4 meters) in the width direction, or may be configured to be able to convey a recording medium M having a width of less than two meters in the width direction at a maximum.
The recording medium M is not limited to fabric as mentioned above, and various kinds of media such as paper and sheet resin may be used, as long as ink can be fixed on its surface.
The head unit 20 records an image on the recording medium M conveyed by the conveyor 10 by discharging ink from the nozzle onto the recording medium M on the basis of image data. In the inkjet recording device 1 according to the present embodiment, four head units 20 each corresponding to ink of four colors (yellow (Y), magenta (M), cyan (C), and black (K)) are arranged from the upstream side of the conveyance direction of the recording medium M in order of Y, M, C, K at a predetermined interval.
The head units 20 each have multiple (seven in the present embodiment) recording heads 22 in each of which multiple recording elements are arranged in a direction intersecting with the conveyance direction of the recording medium M (in the width direction perpendicular to the conveyance direction in the present embodiment, that is, in the X direction) and a head controller 21 which controls the ink discharge operation by the recording heads 22. The recording heads 22 each have the corresponding ink discharge surface where opening(s) of the nozzle are formed and which is arranged so as to face the conveyance surface of the conveyance belt 13. Further, the head units 20 each have a first storage 23 (a storage or an initial faulty nozzle information storage) integrated with the head unit 20.
Each of the recording elements of the recording heads 22 includes a pressure chamber to store ink, a piezoelectric element attached on a wall surface of the pressure chamber, and the nozzle(s) to discharge ink. When a driving signal is transmitted from the driving circuit in the recording head 22 to the piezoelectric element, deformation of the piezoelectric element depending on the driving signal causes pressure in the pressure chamber to vary so that ink is discharged from the nozzle communicating with the pressure chamber. Hereinafter, the operation regarding the discharge of ink from the nozzles depending on the driving signal may be referred to as an ink discharge operation. The ink discharge operation includes the case where ink is not discharged depending on the driving signal as the nozzle has become a faulty nozzle described later.
The arrangement range in the X direction of the recording elements included in the head unit 20 covers the width in the X direction of an area in which an image can be recorded in the recording medium M conveyed by the conveyor 10. The head unit 20 is used at a fixed position with respect to the conveyor 10 during image recording. That is, the inkjet recording device 1 records an image by a single pass method.
A part of the nozzles in the head unit 20 may be a faulty nozzle(s) that does not discharge ink normally on manufacturing the head unit 20, as a result of processing variation in forming nozzles and characteristic variation in the piezoelectric elements. In addition, a fault of the nozzle may be caused later as a result of using the head unit 20 in the inkjet recording device 1, since foreign materials from the nozzle opening may flow into and stop the nozzle or the ink may solidify in the nozzle opening. Examples of the ink discharge fault in the faulty nozzle includes non-discharge of ink and abnormality in discharge amount and discharge direction of ink. Further, in the case of a faulty nozzle showing abnormality in the discharge amount and the discharge direction of the ink, the fine mist of ink (ink mist) may be generated more than the normal nozzle during the ink discharge.
The head unit 20 in which a faulty nozzle (initial faulty nozzle) regarding an initial fault has been detected on manufacturing is used in the present embodiment. Further, in the present embodiment, a faulty nozzle which was not detected in the detection of the initial faulty nozzle will be referred to as a later faulty nozzle.
The initial faulty nozzle is detected by an external inspection device (different from the inkjet recording device 1). For example, ink (or a droplet for inspection) is discharged from each nozzle of the head unit 20, and the discharged ink is photographed by the inspection device from the side of the ink discharge direction so that an ink discharge state is determined. If no ink is detected in the photograph data, it is determined that the ink is not discharged. If inclination of the ink discharge direction is detected, it is determined that the ink discharge direction is abnormal. If ink does not fly at a normal speed, it is determined that the ink discharge amount is abnormal. The nozzles determined as described above are detected as the initial faulty nozzles. Here, the inclination of the ink discharge direction means that the ink is discharged in a direction different from the normal discharge direction.
The head controller 21 outputs various control signals and image data to a head driver of the recording head 22 at appropriate timing according to the control signal from controller 30 or the number of counted pulse signals input from the rotary encoder attached to driving roller. The head driver of the recording head 22 transmits a driving signal for deforming the piezoelectric element to the recording element of the recording head 22 according to the control signal and image data input from the head controller 21, and causes the ink to be discharged from the opening of respective nozzles. In the present embodiment, an ejection controller is configured by the controller 30 and the head controller 21.
The first storage 23 includes a non-volatile memory such as a flash memory or an EEPROM (Electrically Erasable Programmable Read Only Memory), and stores initial faulty nozzle data D1 (initial faulty nozzle information) regarding the above-described initial faulty nozzle. In the initial faulty nozzle data D1, the initial faulty nozzle is identified by array numbers of the nozzles in the head unit 20. The first storage 23 may be configured by a ROM (Read Only Memory).
The head unit mover 41 raises or lowers the head unit 20 in the Z direction (distance direction) which is perpendicular to the conveyance surface of the conveyance belt 13. Further, the head unit mover 41 moves the head unit 20 which has been raised to a predetermined position in the Z direction to a position facing the ink receiver of the maintenance unit 42 described later in the X direction. As a mechanism for raising and lowering the head unit 20 in the Z direction, the head unit mover 41 includes, for example, a support extending in the Z direction and a moving unit to which the head unit 20 is fixed and which can move in the Z direction along the support by rotation of the stepping motor. Further, as a mechanism for moving the head unit 20 in the X direction, the head unit mover 41 includes, for example, a guide rail extending in the X direction and a slide member to which the head unit 20 is fixed and which moves along the guide rail..
Four head unit movers 41 are provided corresponding to the respective four head units 20.
The maintenance unit 42 includes an ink receiver (not shown) that receives the ink discharged by ink ejection (flushing) from the nozzles of the head unit 20. The ejection is an ink discharge operation from a nozzle by the head unit 20 such that a repairable faulty nozzle which can be repaired to a normal state where ink is normally discharged is repaired to the normal state or such that no fault is newly caused in the nozzle. This ejection includes, on the whole, the ink discharge operation from the nozzles of the head unit 20 not based on the image data of the image to be recorded (a normal image instructed to record by a print job, various test images, etc.) in the inkjet recording device 1. The discharging includes, for example, ejection performed to an area outside of the image recording area on the recording medium M during execution of the print job (hereinafter also referred to as first ejection), as well as ejection performed on the ink receiver of the maintenance unit 42 (hereinafter also referred to as the second ejection). The details of the ejection will be described later.
Also, the maintenance unit 42 includes a cleaning roller (cleaner) that performs a cleaning operation (hereinafter also referred to as "wiping") for wiping and cleaning of the ink discharge surface of the head unit 20.
FIG. 3 is a schematic view showing the configuration of the cleaning roller 421.
The cleaning roller 421 has an outer peripheral surface which a wiping cloth containing a predetermined chemical solution is wound around and is arranged such a rotation shaft which is parallel to the Y direction. The maintenance unit 42 has a rotating motor and a conveyance motor (not shown). While the cleaning roller 421 rotates in response to the operation of the rotating motor, it moves in the Z direction and the X direction in response to the operation of the conveyance motor. During the above-described wiping, the cleaning roller 421 contacts the ink discharge surface of the head unit 20 by moving in the Z direction as a result of the operation of the conveyance motor. The cleaning roller 421 wipes, in such a contacting state, the ink discharge surface of the head unit 20 by moving in the X direction in response to the operation of the conveyance motor during rotation by the operation of the rotating motor. Four cleaning rollers 421 are provided corresponding to the respective four head units 20.
The inspection unit 43 performs a predetermined measurement operation for detecting the ink discharge state from each nozzle.
FIG. 4 is a schematic view showing the configuration of the inspection unit 43.
The inspection unit 43 includes a light emitter 431, a light receiver 432, a moving unit 433, a moving belt 434, rollers 435a and 435b, a motor 436, a linear encoder 437, and the like. In the inspection unit 43, the light emitter 431 irradiates the flying path of the ink from the nozzle with light, and the light receiver 432 measures the quantity of the light. The ink discharge state from each nozzle is inspected by determining whether or not the measured light quantity decreases at a position appropriate for the nozzle due to ink. For example, as shown in FIG. 4, the inspection unit 43 performs the measurement operation on the head unit 20 when it has moved to the side of +Z direction by the head unit mover 41 after the recording operation. Alternatively, the head unit 20 may be moved to the position of the inspection unit 43 for the measurement operation.
The light emitter 431 outputs light (here, visible light) in the direction of a light axis (optical axis) L. The light receiver 432 detects the light output from the light emitter 431. The light output from the light emitter 431 has directivity, and is substantially detected by the light receiver 432 in the state where there is no light-shielding object, that is, there is no ink in between. Meanwhile, the light receiver 432 is set to be narrow in a range where a ratio of attenuated light quantity to the total incident light quantity is a detectable level or more when ink to be detected enters the light receiving area and is set to be wide in a range where the ink position does not deviate from the light receiving area even if there is a positional deviation regarding attaching accuracy of the inspection unit 43 or rotational operation accuracy of the motor 436.
The moving unit 433 is a plate member on whose surface are fixed the light emitter 431 and the light receiver 432. One end of the moving unit 433 is fixed to the moving belt 434.
The moving belt 434 has a ring shape and is rotationally driven by the rollers 435a and 435b provided on the inner circumferential surface. The moving belt 434 is rotationally driven so as to move the moving unit 433 in the X direction.
The motor 436 rotates the roller 435a. The rotational rate of the motor 436 can be appropriately changed on the basis of the control signal from the controller 30.
The linear encoder 437 outputs a signal indicating movement of the moving unit 433. The linear encoder 437 is not particularly limited, but may be one which reads a scale with an optical sensor, for example.
The operation unit/display 44 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as an operation key or a touch panel disposed overlapping the screen of the display device. The operation unit/display 44 displays various kinds of information on the display device, and converts the user's input operation to the input device into an operation signal and outputs the operation signal to the controller 30.
The input/output interface 45 is a means for transmitting and receiving data to and from an external device 2. As the input/output interface 45 are configured various serial interfaces, various parallel interfaces, or a combination thereof.
The bus 46 is a path for the controller 30 to transmit and receive signals to and from other components.
The controller 30 includes a CPU 31 (Central Processing Unit), a RAM 32 (Random Access Memory), a ROM 33, and a second storage 34 (storage).
The CPU 31 reads programs for various kinds of control and setting data stored in the ROM 33, stores the read programs and the setting data in the RAM 32, executes the programs, and performs various arithmetic processes. The CPU 31 thereby integrally controls the overall operations of the inkjet recording device 1. For example, while causing the conveyer 10 to convey the recording medium M, the CPU 31 causes the head unit 20 to discharge ink from the nozzles to the recording medium M based on the image data of an image stored in the second storage 34 so as to record the image.
The RAM 32 is a working memory space in the CPU 31 and stores temporary data. The RAM 32 stores a maintenance complete flag used to determine the state where a maintenance operation is performed. Here, the maintenance complete flag is binary data represented by one bit. The RAM 32 may include a non-volatile memory.
The ROM 33 stores programs for various kinds of control executed by the CPU 31, setting data, and the like. Instead of the ROM 33, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.
The second storage 34 stores faulty nozzle data D2 (faulty nozzle information) on faulty nozzle(s) including the initial faulty nozzle(s) indicated by the initial faulty nozzle data D1 in the first storage 23 and/or the later faulty nozzle(s) detected by the operation of the inspection unit 43. In the faulty nozzle data D2, the faulty nozzle is identified by a nozzle array number in each head unit 20. The faulty nozzle data D2 is generated in the operation of faulty nozzle detection described later. The faulty nozzle data D2 may include only data on the faulty nozzles exclusive of the initial faulty nozzles (that is, data on the later faulty nozzles). In this case, the initial faulty nozzle is identified by referring to the initial faulty nozzle data D1 in the first storage 23.
The second storage 34 stores a print job (image recording command) and image data input from the external device 2 via the input/output interface 45 and image data corrected by the CPU 31. For example, an HDD (hard disk drive) may be used as the second storage 34, and a DRAM (dynamic random access memory) may be used together.
The external device 2 is, for example, a personal computer, and transmits the print job, image data, and the like to the controller 30 via the input/output interface 45.
Next, various operations regarding management of the faulty nozzle in the inkjet recording device 1 will be described. Here, management of the faulty nozzle includes detection of the faulty nozzle, compensation setting of non-discharge of ink from the faulty nozzle by correction of image data, ejection during printing job execution, the maintenance operation of the head unit 20, and replacement of the head unit 20.
First, the operation of faulty nozzle detection performed in the inkjet recording device 1 will be described.
In the inkjet recording device 1, detection of a faulty nozzle in the head unit 20 is performed when a predetermined faulty nozzle detection start condition is satisfied. Here, the faulty nozzle detection start condition is, for example, performing recording operations of more than a predetermined number of times by the head unit 20 after the last operation of faulty nozzle detection. Alternatively, the condition may be consumption of ink by a predetermined amount or more after the last operation of faulty nozzle detection. Alternatively, the faulty nozzle detection may be started according to the instruction of a user.
FIG. 5 is a diagram for explaining the operation of faulty nozzle detection.
In this drawing, the positions of the nozzles 221 on the ink discharge surfaces 222 of the recording heads 22 are schematically shown in a plan view of the recording heads 22 of the head unit 20 and the moving unit 433 of the inspection unit 43 as viewed from the side facing the conveyance surface of the conveyance belt 13.
When the faulty nozzle detection is started, the head unit 20 is moved to the side of +Z direction by the head unit mover 41 after the recording operation, and the inspection unit 43 is arranged between the head unit 20 and the conveyor belt 13. Alternatively, the head unit 20 may be moved to a position above the inspection unit 43.
Then, the moving unit 433 is moved to a position facing the recording head 22 on the basis of the signal regarding measurement from the linear encoder 437. That is, the moving unit 433 is moved to a position where the light axis L of the light output from the light emitter 431 and detected by the light receiver 432 crosses the ink flying path from the leading nozzle 221. Here, among the nozzles 221, the leading nozzle 221 is the one located at an end of the +X direction (the left end in FIG. 5) of the endmost recording head 22 in the +X direction. Subsequently, while ink is discharged from the respective nozzles 221 of the recording heads 22 sequentially for a predetermined time, the light emitter 431 and the light receiver 432 moved to the position corresponding to the nozzle 221 operate to inspect the ink discharge state on the basis of the measurement result of the light amount by the light receiver 432. That is, if decrease in light quantity due to ink is not detected at the position corresponding to the nozzle 221, the non-discharge of the ink is detected. If the position at which the decrease in light quantity is detected is out of the position corresponding to the nozzle 221, inclination of the ink discharge direction is detected. The nozzle 221 from which ink is discharged sequentially changes one by one in the -X direction in FIG. 5, toward the one at the end (right end in FIG. 5) of the endmost recording head in the -X direction. The changing speed at this time is set to be constant, and the moving unit 433 is moved at a constant speed corresponding to the constant changing speed.
The operation of faulty nozzle detection is performed on all the nozzles including the nozzle(s) that have already been identified as the faulty nozzle(s) according to the faulty nozzle data D2. The above-described operation of faulty nozzle detection is performed on each of the four head units 20.
Thus, light quantity reflecting the ink discharge state is measured from each of the nozzles 221 of the head units 20 by the operations of the light emitter 431 and the light receiver 432, and the ink discharge state from the nozzles 221 is inspected as a result of the measurement result. If non-discharge of ink or inclination of the ink discharge direction is detected as a result of the inspection, a nozzle corresponding thereto is identified as the faulty nozzle. When the faulty nozzle is identified, the faulty nozzle data D2 indicating the faulty nozzle is generated on the basis of the array number of the identified nozzle 221 in the head unit 20 and stored in the second storage 34.
Here, if the faulty nozzle data D2 has been already stored in the second storage 34, the new faulty nozzle data D2 overwrites the existing faulty nozzle data D2. If it is necessary to refer to the history of the generation status of the later faulty nozzles, new faulty nozzle data D2 may be generated and stored independently of the existing faulty nozzle data.
Next, image data correction based on the faulty nozzle data D2 will be described.
When the faulty nozzle is identified by the faulty nozzle data D2 in the inkjet recording device 1, an image identified by the print job is recorded after image data correction of the image for suppressing disorder of the recorded image caused by the faulty nozzle. For example, if the nozzle 221a in FIG. 5 is identified as a faulty nozzle, image data of the image is corrected such that ink is not discharged from the nozzle 221a and such that compensation for the non-discharge of ink from the faulty nozzle is made by an increase in the amount of ink discharged from the nozzles (the nozzles 221b in FIG. 5) next to the faulty nozzle or the nozzles (for example, nozzles 221b and 123c in FIG. 5) adjacent to the faulty nozzle. Then, an image in which the image quality deterioration due to the faulty nozzle is suppressed is recorded with the ink discharged from the head unit 20 to the recording medium M on the basis of the corrected image data.
When an image is recorded by an unused head unit 20 after replacement of the head unit 20, the faulty nozzle data D2 regarding the head unit 20 is reset. That is, since the head unit 20 has no later faulty nozzle, the faulty nozzle data D2 to be stored in the second storage 34 is generated based on the initial faulty nozzle data D1 stored in the first storage 23 of the head unit 20. Then, the image data of the image is corrected based on the new faulty nozzle data D2. Therefore, when the head unit 20 is replaced with an unused one, it is possible to correct the image data without the operation of faulty nozzle detection, and the image is recorded based on the corrected image data.
Next, ink ejection (first ejection) performed during print job execution will be described.
In the inkjet recording device 1, when viscosity of ink in the vicinity of an opening of the nozzle 221 is increased due to evaporation of solvent in the ink in the vicinity of the opening, the nozzle becomes a faulty nozzle with the ink discharge fault such as deviations of the amount, flying direction, flying speed, and the like of ink to be discharged from the original setting. In particular, since a normal image(s) to be recorded is successively recorded on the recording medium M of 4000 meters in length in the present embodiment, if the conveyance speed is 60 [m/min], for example, the image recording operation continues for one hour or more after the start of the image recording operation. In this image recording operation, depending on the contents of the normal image, there may be a nozzle 221 from which ink is discharged at an extremely low frequency or is not discharged. Such a nozzle 221 tends to become a faulty nozzle due to the above-described ink viscosity increased during the successive period of the image recording operation.
Therefore, in the inkjet recording device 1 according to the present embodiment, the head unit 20 performs the first ejection including discharge of ink from the nozzle 221 to an area outside of the recording area of the normal image on the recording medium M under conveyance, so that the nozzle 221 does not become a faulty nozzle.
FIG. 6 is a view for explaining an ejection area for ink ejection on the recording medium M.
As shown in FIG. 6, in the present embodiment, the first ejection is performed on the band-shaped ejection area 52 which extends in the X direction in the recording medium M. A normal image 51 is recorded on the upstream side and the downstream side of the ejection area 52 in the Y direction. That is, the ejection area 52 is set outside the recording area of the normal image 51. The normal image 51 is a long image in which a plurality of unit images are connected to one another at the front end and rear end of the respective unit images in the Y direction. The normal image 51 is recorded continuously in the recording area of the normal image 51.
The ejection area 52 is composed of color- specific ejection areas 52Y, 52M, 52C, and 52K in which the head units 20 corresponding to Y, M, C, and K respectively discharge ink. The color- specific ejection areas 52Y, 52M, 52C, and 52K are band-shaped areas next to one another in the Y direction and extending over the recording range by the nozzles 221 of the head unit 20 in the X direction. Ink is successively discharged about 1000 times from each of the nozzles of the head units 20 to the respective color- specific ejection areas 52Y, 52M, 52C, and 52K. The range of the ejection area 52 in the X direction is equal to the range for recording the normal image 51 in the X direction. The ranges of the color- specific ejection areas 52Y, 52M, 52C, and 52K are determined so as not to overlap with each other mainly for reducing set-off of ink by suppressing the ink discharge amount per unit area. They may overlap with each other if it does not matter whether or not set-off of ink is caused.
In the first ejection, ink discharge timing is adjusted depending on the Y-directional position of the nozzles 221 arranged in each recording head 22, so that ink is discharged in a band-shaped (long rectangular-shaped) range in the Y direction on the recording medium M.
Further, in the present embodiment, in ejection of ink, it is possible to select whether or not to discharge ink from the nozzle(s) 221 identified as the faulty nozzle(s) according to the faulty nozzle data D2. In the first ejection described above, ink is not discharged from the nozzle(s) 221 identified as the faulty nozzle(s) according to the faulty nozzle data D2, and the ink is discharged only from the normal nozzle(s) 221. This suppresses contamination of the ink discharge surface 222 with ink or ink mist which has been abnormally discharged from the faulty nozzle in the first ejection and adhering to the ink discharge surface 222. The contamination causes problems such as dropping of ink onto the recording medium M at unintended timing due to air flow, cloth powder, etc. and occurrence of a new faulty nozzle due to solidification of the ink blocking a part of the nozzle opening. In particular, if the ejection is performed outside the recording area of the normal image 51 of the recording medium M as shown in FIG. 6, since the normal image 51 is recorded immediately after the ejection without cleaning the ink discharge surface 222, the contamination of the ink discharge surface 222 caused by the ink from the faulty nozzle leads to dropping of the ink which in turn contaminates the recording medium M. However, occurrence of such a problem is effectively suppressed according to the invention by discharging no ink from the faulty nozzle in the ejection.
Thus, in the present embodiment, ink discharge from the nozzle(s) 221 identified as the faulty nozzle(s) according to the faulty nozzle data D2 is not performed in the ejection if any of the following conditions is satisfied: a condition (predetermined condition) that an image is recorded subsequently to the ink discharge by the ejection; a condition (predetermined condition) that an image is recorded after the ink discharge by the discharge and before the cleaning operation for cleaning the ink discharge surface 222; and a condition (predetermined condition) that ink is discharged from the nozzle(s) 221 outside the image recording area of the recording medium M.
Hereinafter, a control operation for the first ejection in the inkjet recording device 1 will be described.
Each of the head units 20 starts ejection during execution of the print job when a predetermined position which is a target for ink ejection (the front end of each of the color separated ejection areas 52Y, 52M, 52C, and 52K) moves to a position where ink is discharged by each of the head units 20 as the conveyor 10 conveys the recording medium M (hereinafter, the predetermined position is also referred to as an ejection start position.). It is determined that the ejection start position has moved to the ink discharge position when a predetermined number of pulse signals for each of the head units 20 are output from the rotary encoder attached to the driving roller.
FIG. 7 is a block diagram showing a functional configuration regarding ejection control by the head controller 21.
As shown in FIG. 7, the head controller 21 includes a control circuit 21a, a switch 21b, and an image data storage 21c. The head controller 21 may have a configuration including, for example, a circuit board and an FPGA (Field Programmable Gate Array) mounted on the circuit board. In the present embodiment, the FPGA includes the control circuit 21a, the switch 21b, and the image data storage 21c. The image data storage 21c may be provided outside the FPGA. Also, instead of the FPGA may be used other semiconductor integrated circuits such as an ASIC (Application Specific Integrated Circuits).
The image data storage 21c stores image data Da of the normal image 51 and ejection data Db used for ejection. Here, the ejection data Db is used to generate a drive signal(s) for ejection of ink from the nozzles 221 of each head unit 20, and is equivalent to date of a solid image, in which every pixel takes a maximum gradation value.
The image data Da and the ejection data Db are output to the switch 21b under the control of the control circuit 21a. Either the image data Da or the ejection data Db is output from the switch 21b to the head driver 22a of the recording head 22 in accordance with the switching control signal output from the control circuit 21a to the switch 21b.
The control circuit 21a outputs a control signal for performing the ink discharge operation at an appropriate timing to the head driver 22a. Further, the control circuit 21a outputs the switching control signal to the switch 21b to cause the switch 21b to output either the image data Da or the ejection data Db to the head driver 22a for each line. That is, in recording the normal image 51, the control circuit 21a causes the switch 21b to output the image data Da to the head driver 22a. Further, in starting the ejection, the control circuit 21a switches the switch 21b to start supplying the ejection data Db to the head driver 22a. The ejection data Db is successively supplied until the ejection operation is ended. Further, the control circuit 21a refers to the faulty nozzle data D2 stored in the second storage 34 and supplies control signals to the head driver 22a so that drive signal is not supplied from the head driver 22a to the recording element having the nozzle 221 identified as the faulty nozzle.
Since the ejection data Db is data having a configuration equivalent to solid image data consisting of data on equivalent pixels, predetermined pixel data may be repeatedly supplied to the switch 21b under the control of the control circuit 21a instead of reading out the ejection data Db from the image data storage 21c and supplying it to the switch 21b.
Under such control, while the normal image 51 is recorded in the recording area for the normal image 51, ejection is performed toward the outside of the recording area for the normal image 51.
Next, the maintenance operation by the head unit 20 based on the faulty nozzle data D2 will be described.
In the inkjet recording device 1, a predetermined maintenance operation is started when at least one of the number and the arrangement of faulty nozzle(s) in each head unit 20 indicated by the faulty nozzle data D2 satisfies a predetermined maintenance start condition. In the maintenance operation of the present embodiment, the second ejection and wiping are subsequently performed.
Here, the maintenance start condition according to the number of faulty nozzles may be that the number of faulty nozzles indicated by the faulty nozzle data D2 is more than a predetermined first reference number. The first reference number is set within a range of the number of faulty nozzle(s) surrounded by nozzles which compensate for the non-discharge of ink from the faulty nozzle(s) so that image quality deterioration in the recorded image is so suppressed that the image quality fault due to the faulty nozzle(s) is hardly visible. The first reference number is preferably set to a large value for reduction in the maintenance operation frequency.
The maintenance start condition according to the arrangement of faulty nozzle(s) may be that there are successive faulty nozzles of more than a predetermined second reference number, and that these faulty nozzles include the later faulty nozzle(s). Here, the second reference number is set within a range of the number of successive faulty nozzles surrounded by nozzles which compensate for the non-discharge of ink from the adjacent faulty nozzles so that image quality deterioration in the recorded image is so suppressed that the image quality fault due to the faulty nozzles is hardly visible.
The second ejection in the above maintenance operation is performed by discharge of ink from the respective nozzles 221 while the head unit 20 has been moved to the position facing the ink receiver of the maintenance unit 42. The number of ink discharge operations in the second ejection is not particularly limited, but can be about 1000 as in the first ejection described above.
Here, in the second ejection, ink is discharged from all the nozzles including the faulty nozzle(s). This is because, even if ink discharge surface 222 is contaminated with ink or ink mist due to the ink discharge from the faulty nozzle(s) in the second ejection, wiping is subsequently performed after the second ejection such that ink discharge surface 222 is cleaned. The control operation for the second ejection in the inkjet recording device 1 is similar to the control operation for the first ejection except that the drive signal is also supplied to the faulty nozzle(s) to discharge ink.
In the maintenance operation, wiping is performed when the second ejection is ended. In this wiping, the head units 20 are each moved to a predetermined cleaning position where the cleaning roller 421 is disposed, and the cleaning roller 421 is moved so as to abut on the ink discharge surface 222 of the head unit 20. The cleaning roller 421 in this state then moves in the X direction while rotating and being in contact with the ink discharge surface 222 depending on the operation of the rotation motor of the maintenance unit 42 and the conveyance motor. As a result, the entire ink discharge surface 222 is wiped with a wiping cloth wound around the outer peripheral surface of the cleaning roller 421 to remove the ink and foreign materials adhering to the ink discharge surface 222 and the openings of the nozzles 221.
The maintenance operation of the present embodiment dissolves blocking of the nozzle opening due to clogging or contamination of the nozzle which has been caused later. Therefore, as a natural result of the maintenance operation, the later faulty nozzle may be repaired to the normal state, but the initial faulty nozzle can be rarely repaired to the normal state.
Next, display of head unit replacement information for prompting replacement of the head unit 20 will be described.
In the inkjet recording device 1, after the above-described maintenance operation, faulty nozzle detection based on the inspection result by the inspection unit 43 is performed before the next normal image recording. The later faulty nozzle detected as a result is a later faulty nozzle which is not repaired to the normal state by the maintenance operation (hereinafter referred to as a later faulty unfixable nozzle). In the inkjet recording device 1, if at least one of the number and the arrangement of the later faulty unfixable nozzles in each head unit 20 satisfies a predetermined condition equal to the condition under which the above maintenance operation is started, the head unit replacement information indicating that it is time to replace the head unit 20 is displayed by the operation unit/display 44, and prompts the user to replace the head unit 20.
Whether or not the head unit 20 needs to be replaced may be determined on the basis of a condition in which the number and arrangement of the initial faulty nozzle(s) are added to the number and arrangement of the later faulty unfixable nozzle(s).
Next, image record processing performed in the inkjet recording device 1 will be described.
FIG. 8 is a flowchart showing a control procedure for the image record processing.
This image record processing is started when the image data of the normal image recorded on the recording medium M and the print job for instruction of the recording of the normal image are supplied from the external device 2 through the input/output interface 45 and stored in the second storage 34.
When the image record processing is started, the controller 30 determines whether or not there is an unexecuted print job stored in the second storage 34 (step S101). If it is determined that the unexecuted print job is not stored in the second storage 34 ("NO" in step S101), the controller 30 ends the image record processing.
If it is determined that an unexecuted print job is stored in the second storage 34 ("YES" in step S101), the controller 30 determines whether or not the faulty nozzle detection start condition is satisfied. (Step S102). Here, the controller 30 determines that the faulty nozzle detection start condition is satisfied if the image recording operation by the head unit 20 is performed a predetermined number of times or more after the last faulty nozzle detection (step S103)o
If it is determined that the faulty nozzle detection start condition is satisfied ("YES" in step S102), the controller 30 detects a faulty nozzle (step S103). That is, the controller 30 operates the motor of the head unit mover 41 to move the head unit 20 in the +Z direction, and moves the inspection unit 43 so as to be between the head unit 20 and the conveyor belt 13. Then, the controller 30 and the head controller 21 cause the head driver 22a of the recording head 22 to output a drive signal to the recording element, and cause ink to be discharged from the nozzles 221 of the recording element. Here, the controller 30 and the head controller 21 cause ink to be discharged from the respective nozzles 221 several times or several tens of times. As a result, there is no contamination or, if any, a little contamination of the ink discharge surface. Further, during the operation of the motor 436 of the inspection unit 43 to move the moving unit 433 depending on the ink discharge, the controller 30 operates the light emitter 431 and the light receiver 432 in synchronization with the ink discharge timing to obtain a light detection signal output from the light receiver 432. The controller 30 detects the later faulty nozzle on the basis of the obtained detection signal, generates faulty nozzle data D2 (overwrites the faulty nozzle data D2 if there has been some already), and stores it in the second storage 34.
The controller 30 determines whether or not the maintenance start condition is satisfied (step S104). Here, the controller 30 determines that the maintenance start condition regarding the number of faulty nozzles is satisfied if the faulty nozzle data D2 indicates larger number of faulty nozzles than the first reference number. Further, the controller 30 determines that the maintenance start condition regarding the arrangement of the faulty nozzle is satisfied if the faulty nozzle data D2 indicates successive faulty nozzles of more than a predetermined second reference number.
If it is determined that the maintenance start condition is not satisfied ("NO" in step S104), or if it is determined that the faulty nozzle detection start condition is not satisfied in step S102 ("NO" in step S102), the controller 30 determines whether or not there is a faulty nozzle in any of the head units 20 (step S105).
If it is determined that there is a faulty nozzle in any of the head units 20 ("YES" in step S105), the controller 30 corrects the image data on the basis of the faulty nozzle data D2 (step S106). That is, with reference to the faulty nozzle data D2, the controller 30 corrects the image data of the normal image regarding the print job such that ink is not discharged from the faulty nozzle and compensation for the non-discharge of ink from the faulty nozzle is performed. The corrected image data is stored in the second storage 34.
The controller 30 starts the image recording operation regarding the print job based on the image data corrected in step S106.
That is, the controller 30 causes the conveyor 10 to start conveyance of the recording medium M. In addition, when the ejection start position moves to the ink discharge position of each head unit 20, the controller 30 and the head controller 21 causes each nozzle 221 except the faulty nozzle in each head unit 20 to perform the first ejection onto the ejection area 52 (step S107: ejection step). Further, when the recording area of the normal image 51 moves to the ink discharge position of each head unit 20, the controller 30 and the head controller 21 starts ink discharge from the nozzle 221 based on the image data after correction to record the normal image 51 on recording medium M (step S108).
When it is determined in step S105 that all the head units 20 have no faulty nozzles ("NO" in step S105), the controller 30 causes the normal image 51 to be recorded based on the image data regarding the print job without correction.
When the recording of one normal image 51 is ended, the controller 30 determines whether or not the recording of all the normal images 51 according to the instruction by the print job has been ended (step S109). If there remains an unrecorded normal image 51, the process proceeds to the process of step S107 ("NO" in step S109). If all the normal images 51 have been recorded, the process proceeds to the process of step S101 ("YES" in step S109).
If it is determined in step S104 that the maintenance start condition is satisfied ("YES" in step S104), the controller 30 determines whether or not the maintenance complete flag is set to OFF (step S110).
If it is determined that the maintenance complete flag is set to OFF ("YES" in step S110), the controller causes the predetermined maintenance operation to be performed. That is, the controller 30 operates the head unit mover 41 such that the head unit 20 moves to a position facing the ink receiver of the maintenance unit 42. Then, the controller 30 and the head controller 21 cause all the nozzles including the faulty nozzle in the head unit 20 to perform the second ejection, in which ink is ejected to the ink receiver (step S111: ejection step). When the second ejection is ended, the controller 30 moves the head unit 20 to a predetermined cleaning position, operates the rotating motor and the conveyance motor of the maintenance unit 42, and causes the cleaning roller 421 to perform wiping (step S112).
When the process of step S112 is ended, the controller 30 sets the maintenance complete flag to ON (step S113). When the process of step S113 is ended, the controller 30 causes the process to proceed to the process of step S103.
If it is determined in step S110 that the maintenance complete flag is set to ON ("NO" in step S110), the controller 30 causes the operation unit/display 44 to display the head unit replacement information (step S114).
When the process of step S114 is ended, the controller 30 ends the image record processing.
In the above-described image record processing, the control for ejection in step S107 and step S111 corresponds to the ejection control by the controller 30 and the head controller 21.

(Modification 1)

Next, modification 1 of the above embodiment will be described. The present modification is different from the above embodiment in that the detection of the faulty nozzle is performed only immediately after the maintenance operation. The other points are the same as those in the above embodiment.
FIG. 9 is a flowchart showing a control procedure of image record processing according to the present modification. The image record processing shown in FIG. 9 is the image record processing of the above embodiment shown in FIG. 8 modified by changing step S102 for step S115, performing step S111 and step S112 before step S103, and deleting step S110 and step S113. In the following, differences from the image record processing shown in FIG. 8 will be mainly described.
When the process of step S101 is ended, the controller 30 determines whether or not the initial maintenance start condition is satisfied (step S115). Here, if ink of a predetermined amount or more has been consumed by image recording in the head unit 20 after the last maintenance operation (steps S111 and S112), the controller 30 determines that the initial maintenance start condition is satisfied. If it is determined that the initial maintenance start condition is not satisfied ("NO" in step S115), the controller 30 causes the process to proceed to the process of step S105.
If it is determined that the initial maintenance start condition is satisfied ("YES" in step S115), the controller 30 performs the maintenance operation (step S111 and step S112). When the process of step S112 is ended, the controller 30 detects the faulty nozzle (step S103). Further, in step S104 performed after step S103, if it is determined that the maintenance start condition is satisfied ("YES" in step S104), the controller 30 causes the operation unit/display 44 to display the head unit replacement information (step S114).
According to such an image record processing of the present modification, detection of a faulty nozzle is performed only immediately after the maintenance operation, so the frequency of execution of detection of a faulty nozzle can be suppressed.

(Modification 2)

Next, modification 2 of the above embodiment will be described. The present modification is different from the above embodiment in that ink is not discharged from the initial faulty nozzle in the second ejection. Unlike the later faulty nozzle that occurs due to clogging of the nozzle opening, etc., the initial faulty nozzle is less likely to be repaired to the normal nozzle by ejection since it has a defect due to the manufacturing process of the recording element. From this point of view, ink is not discharged from the initial faulty nozzle in the second discharge in the present modification. This reduces the amount of ink consumed by the ejection.
Since the initial faulty nozzle is not used (the ink ejection operation is not performed) in the first ejection or recording operations of various images, the initial faulty nozzle of this modification is never used, and is treated as an unfixable (unrepairable) faulty nozzle. Therefore, the initial faulty nozzle may be excluded from the target to detect the faulty nozzle in this modification.
As described above, the inkjet recording device 1 according to the present embodiment and according to the invention defined in claim 1 includes the head unit 20 having an ink discharge surface 222 provided with an opening of a nozzle 221 for discharging ink; the controller 30 and the head controller 21 (ejection controller) performing ejection control to discharge ink from the nozzles 221 not based on image data of the normal image 51 to be recorded; and the first storage 23 and the second storage 34 (storage) respectively storing initial faulty nozzle data D1 and faulty nozzle data D2 regarding a faulty nozzle that does not discharge ink normally among the nozzles 221. In the ejection control, the controller 30 and the head controller 21 (ejection controller) can select whether or not ink is to be discharged from the nozzle 221 which is identified as the faulty nozzle among the nozzle 221 according to the faulty nozzle data D2.
This makes it possible to discharge no ink from the faulty nozzle according to necessity in the ejection control, thereby suppressing contamination of the ink discharge surface 222 by the ink or ink mist abnormally which has been discharged from the faulty nozzle and adheres to the ink discharge surface 222. As a result, it is possible to suppress the occurrence of a problem such as contamination due to drop of ink adhering to the ink discharge surface 222 onto the recording medium M or the conveyor belt 13, and occurrence of a new faulty nozzle due to solidification of the ink adhering to the ink discharge surface 222 so as to plug a part of the nozzle opening.
According to a further preferred embodiment, the inkjet recording device 1 includes the inspection unit 43 detecting the ink discharge state from the nozzle 221. The controller 30 identifies a faulty nozzle from the detection result by the inspection unit 43, and stores the faulty nozzle data D2 in the second storage 34 on the basis of the identification result (faulty nozzle identifier). With such a configuration, the faulty nozzle can be accurately identified on the basis of the ink discharge state from the nozzle 221. Further, by determining a faulty nozzle not discharging ink in the ejection control with reference to the faulty nozzle data D2 based on the faulty nozzle detection result, it is possible to perform appropriate ejection control which reflects the latest faulty nozzle detection result. For example, if a nozzle has been identified as a faulty nozzle in the past but determined to have been repaired to be a normal nozzle according to the latest faulty nozzle detection result, it is possible to prevent the nozzle from becoming a faulty nozzle again by ink discharge in the ejection control. Also, if a nozzle is newly determined to be a faulty nozzle according to the latest faulty nozzle detection result, it is possible to reliably prevent contamination of the ink discharge surface 222 by stopping the ink discharge in the ejection control.
According to a further preferred embodiment, if a predetermined condition is satisfied in the ejection control, the controller 30 and the head controller 21 select not to discharge ink from a nozzle 221 identified to be a faulty nozzle according to the faulty nozzle data D2 among the nozzles 221 (ejection controller). Therefore, discharge of ink from a faulty nozzle is stopped according to the predetermined condition for suppressing contamination of the ink discharge surface 222, and it is possible to effectively realize both suppression of faulty nozzle generation and recovery from faulty nozzle by the ejection.
Further, if the normal image 51 is recorded subsequently to the ink discharge by the ejection control, the controller 30 and the head controller 21 determine that the above predetermined condition is satisfied (ejection controller). This makes it possible to record the normal image 51 by the head unit 20 where contamination of the ink discharge surface 222 is suppressed. As a result, it is possible to suppress the occurrence of a problem that the ink adhering to the ink discharge surface 222 drops onto the recording medium M during the recording of the normal image 51.
The inkjet recording device 1 has the cleaning roller 421 that cleans the ink discharge surface 222. The controller 30 causes the cleaning roller 421 to perform a cleaning operation of the ink discharge surface 222 (cleaning controller). If the normal image 51 is recorded after the ink discharge according to the ejection control and before the cleaning operation, the controller 30 and the head controller 21 determines that the above predetermined condition is satisfied (ejection controller). This makes it possible to record the normal image 51 with the head unit 20 in which contamination of the ink discharge surface 222 is suppressed. As a result, it is possible to suppress the occurrence of a problem that ink adhering to the ink discharge surface 222 drops onto the recording medium M during recording of the normal image 51.
Further, in the ejection control, if ink is discharged from the nozzle 221 to outside the recording area of the normal image 51 of the recording medium M, the controller 30 and the head controller 21 determine that the above predetermined condition is satisfied (ejection controller). This makes it possible to keep the ink discharge surface 222 of the head unit 20 in a state where contamination is suppressed if the ejection and the recording of the normal image 51 are successively performed on the same recording medium M. As a result, it is possible to suppress the occurrence of a problem that ink adhering to the ink discharge surface 222 drops onto the recording medium M during recording of the normal image 51.
According to a comparative example, not according to the invention, the controller 30 and the head controller 21 can perform a multiple kinds of ejection control (first and second ejection) different from each other, and determines that the above predetermined condition is satisfied if a predetermined ejection control (first ejection) among the multiple kinds of ejection control is performed (ejection controller). This makes it possible to perform the ink discharge from the faulty nozzle in the ejection control at the timing when contamination of the ink discharge surface 222 does not cause a problem, and to repair the faulty nozzle to a normal nozzle.
According to a comparative example, not according to the invention, the first storage 23 for storing the initial faulty nozzle data D1 regarding the initial faulty nozzle is provided integrally with the head unit 20. This makes it possible to identify a faulty nozzle of the head unit 20 (that is, an initial faulty nozzle) without detecting a faulty nozzle on replacement of the head unit 20.
According to a comparative example, not according to the invention, the faulty nozzle data D2 includes information on the initial faulty nozzle associated with the initial fault of the head unit 20. In the ejection control, the controller 30 and the head controller 21 performs selection such that ink is not discharged from a nozzle identified as an initial faulty nozzle according to the information on the initial faulty nozzle (ejection controller). This makes it possible to suppress ink consumption by omitting ink discharge from the initial faulty nozzle which is unlikely to be repaired to the normal nozzle.
Further, the ink discharge control method of the inkjet recording device 1 according to the above embodiment and according to the invention as defined in claim 4 includes the ejection step in which ink is discharged from the nozzle 221 not based on the image data of the normal image 51 to be recorded. It is selected whether or not to perform ink discharge in the ejection step from the nozzle 221 identified as a faulty nozzle according to the faulty nozzle data D2 among the nozzles 221 when a predetermined condition is satisfied. Thus, by discharging no ink from the faulty nozzle according to necessity in the ejection step, it is possible to suppress contamination of the ink discharge surface 222 due to the ink or ink mist discharged abnormally from the faulty nozzle and adhering to the ink discharge surface 222.
The present invention is not limited to the abovementioned embodiment(s) or modifications, and can be variously modified.
For example, the second ejection and wiping are performed as the maintenance operation in the above embodiment and each modification, however, instead of or in addition to the second ejection, pressure purge may be performed in which the ink is forcibly discharged from the nozzles 221 as the maintenance operation. For performing the pressure purge, the maintenance unit 42 may be provided with a pressure pump which pressurizes the ink at a predetermined pressure position in the ink supply path communicating with the pressure chamber of the recording element. By pressurizing ink in this way, the ink is forcibly discharged from the nozzle 221 of the recording element, and the clogging of the nozzle 221 is eliminated. The pressure purge is performed while the ink discharge surface 222 of the head unit 20 faces the ink receiver.
After wiping subsequent to the pressure purge, ejection may be further performed. In this case, since wiping of the ink discharge surface 222 is not usually performed before the recording operation of the normal image 51 after the ejection, it is preferable that ink is not discharged from the faulty nozzle in the ejection so as to prevent contamination of the ink discharge surface 222.
In the above embodiment and each modification, the ejection control is exemplified by, but not limited to, the ejection control for performing the first ejection for discharging ink from the normal nozzle(s) to outside the recording area of the normal image 51 on the recording medium M, and the ejection control for performing the second ejection for discharging ink from all the nozzles to the ink receiver. For example, in the ejection by the first ejection control, ink may be discharged in a small amount with a frequency such that visual recognition is not possible within a recording area of the normal image 51 during recording of the normal image 51. Also in the case of such an embodiment of the first ejection, since the ink discharge surface 222 of the head unit 20 is facing the recording medium M, in order to prevent the adhesion of the ink to the ink discharge surface 222 and dropping of the adhering ink onto the recording medium M, according to the invention, ink is not discharged from a faulty nozzle. In addition to the ejection control according to the invention, according to further preferred embodiments, multiple kinds of discharge control may be performed where at least a part of the followings are different from each other: the start condition; the frequency of ink discharge from each nozzle 221; a drive signal used for ink discharge; an object to which ink is discharged, etc. Among these multiple kinds of ejection control, ink is discharged from all the nozzles by ejection control that causes little or no contamination of the ink discharge surface 222 by ink discharged abnormally from a faulty nozzle, or by ejection control of discharging ink when the ink discharge surface 222 is cleaned subsequently. By predetermined ejection control other than the above and other than the second ejection control, ink is not discharged from faulty nozzle(s), such as in the first ejection control. Contamination of the ink discharge surface 222 can be thereby suppressed.
In the above embodiment and each modification, it is described that each head unit 20 is provided with the first storage 23 storing the initial faulty nozzle data D1 regarding the initial faulty nozzle, for example. However, the head unit 20 may not be provided with the first storage 23, but the second storage 34 of the controller 30 may store the faulty nozzle data D2 regarding the initial faulty nozzle and the later faulty nozzle. In this case, faulty nozzle detection may be performed at the time of replacing the head unit 20 for an update of the faulty nozzle data D2. Alternatively, the faulty nozzle data D2 may be generated on the basis of information regarding the initial faulty nozzle detected in advance by an external detection device and stored in the second storage 34.
In the above embodiment and each modification, the inspection unit 43 is described using, but not limited to, an example which measures light quantity as a physical quantity reflecting the ink discharge state from the nozzles 221 and identifies the later faulty nozzle from the measurement result. For example, the faulty nozzle may be identified by recording a predetermined inspection image on the recording medium M and analyzing imaging data obtained by imaging this inspection image by an image reading unit such as a line sensor or an area sensor. Here, the predetermined inspection image may be, for example, a line pattern of a plurality of lines recorded by ink discharged from each of the plurality of nozzles 221 of the head unit 20. If there is a broken line or a line not recorded at an appropriate position corresponding to the nozzle 221 according to the imaging data obtained by imaging this line pattern, the nozzle 221 corresponding to the line can be identified as a faulty nozzle.
Also, prior to the faulty nozzle detection in the inspection unit 43, the ejection may be performed from respective nozzles including the faulty nozzle(s). As a result, it is possible to suppress determination of a nozzle that is easily repairable to a normal state as a faulty nozzle. In this case, the ink discharge surface 222 is preferably cleaned by wiping before faulty nozzle detection after ejection, however, the wiping may be omitted if there is no contamination or, if any, a little contamination of the ink discharge surface 222, for example, if the frequency of ink discharge in the ejection is sufficiently low.
In the above embodiment and each modification, the cleaner for cleaning the ink discharge surface 222 is exemplified by the cleaning roller 421, but the invention is not limited thereto. For example, cleaner may have a blade for scraping foreign materials or ink on the ink discharge surface 222.
The above embodiment and each modification is described by an example of recording on a long recording medium M unwound from a roll is described, but the invention is not limited thereto. For example, the recording medium is not limited to be unwound from a roll, but may be folded in zigzag, for example. The recording medium may be short sheets of paper.
The above embodiment and each modification is described by an example of conveying the recording medium M with the conveyor 10 having the conveyance belt 13, but the invention is not limited thereto. The conveyor 10 may hold and convey the recording medium M on the outer peripheral surface of a rotating conveyance drum, for example.
In the above description in the embodiment and each modification, a single-pass inkjet recording device 1 is described as an example, but the present invention may be applied to an inkjet recording device which records an image during a scan by a recording head.
Although some embodiments of the present invention have been described, the scope of the present invention is not limited to them, but includes the scope of the invention recited in the claims.

INDUSTRIAL APPLICABILITY

The present invention is applicable to an inkjet recording device and an ink discharge control method of the inkjet recording device.

REFERENCE SIGNS LIST

1: Inkjet Recording Device
2: External Device
10: Conveyor
11: Driving Roller
12: Driven roller
13: Conveyance Belt
20: Head Unit
21: Head Controller
21a: Control circuit
21b: Switch
21c: Image Data Storage
22: Recording Head
22a: Head Driver
221: Nozzle
222: Ink Discharge Surface
23: First Storage
30: Controller
31: CPU
32: RAM
33: ROM
34: Second Storage
41: Head Unit Mover
42: Maintenance Unit
421: Cleaning Roller
43: Inspection Unit
431: Light Emitter
432: Light Receiver
433: Moving Unit
434: Moving Belt
435a, 435b: Roller
436: motor
437: linear Encoder
44: Operation Unit/Display
45: Input/Output Interface
46: Bus
51: Normal Image
52: Ejection Area
52Y, 52M, 52C, 52K: Color-Specific Ejection Image
D1: Initial Faulty Nozzle Data
D2: Faulty Nozzle Data
Da: Image Data Of Normal image
Db: Ejection Data
L: Light Axis
M: Recording Medium

Claims

An inkjet recording device (1) comprising:
an ink discharger (20) having an ink discharge surface on which an opening of at least one nozzle (221) that discharges ink is formed;

an ejection controller (21) for performing ejection control to discharge ink from the at least one nozzle not based on image data of an image to be recorded; and

a storage (34) for storing faulty nozzle information regarding a faulty nozzle that does not discharge ink normally among the at least one nozzle,

wherein, in the ejection control, the ejection controller can select whether or not to discharge ink from a nozzle identified as a faulty nozzle among the at least one nozzle according to the faulty nozzle information, characterized in that
the ejection controller is configured to perform a first ejection control to discharge ink during print job execution onto a recording medium (M) from at least one nozzle not based on image data of an image to be recorded,

wherein, in the first ejection, ink is not discharged from a nozzle identified as a faulty nozzle according to the faulty nozzle information and ink is discharged from a normal nozzle which is not a faulty nozzle,

wherein the inkjet recording device is configured to carry out a maintenance operation over a maintenance unit displaced from the recording medium,

wherein, in the maintenance operation, a second ejection control and subsequent cleaning operation is performed,

wherein the ejection controller is configured to discharge ink from all nozzles including faulty nozzles in the second ejection,

wherein the ejection controller can select whether to discharge ink according to the first ink ejection control or the second ink ejection control.
The inkjet recording device according to claim 1, comprising:
a discharge state detector (43) for detecting an ink discharge state from the nozzle; and

a faulty nozzle identifier (30) for identifying a faulty nozzle on a basis of a result of detection by the discharge state detector and for causing the storage to store the faulty nozzle information on a basis of a result of identifying the faulty nozzle.
The inkjet recording device according to claim 1 or 2,
wherein, in the ejection control, the ejection controller selects not to discharge ink from a nozzle identified as a faulty nozzle among the at least one nozzle according to the faulty nozzle information if a predetermined condition is satisfied,

wherein, if an image is recorded subsequently to ink discharge in the first ejection control, the ejection controller determines that the predetermined condition is satisfied,

or

wherein, if ink is discharged from a nozzle to outside of a recording area of an image in a recording medium (M) in the ejection control, the ejection controller determines that the predetermined condition is satisfied,

or

wherein the inkjet recording device comprising:
a cleaner (421) for cleaning the ink discharge surface; and

a cleaning controller (30) for causing the cleaner to perform a cleaning operation of the ink discharge surface,

wherein, if an image is recorded after the ink discharge in the ejection control and before the cleaning operation is performed, the ejection controller determines that the predetermined condition is satisfied.
An ink discharge control method of an inkjet recording device (1) including an ink discharger (20) and a storage (34),
wherein the ink discharger has an ink discharge surface on which an opening of at least one nozzle (221) that discharges ink is formed, and

wherein the storage stores faulty nozzle information regarding a faulty nozzle that does not discharge ink normally among the at least one nozzle,

the method comprising:
an ejection step (step S107, S111) of discharging ink from the at least one nozzle not based on image data of an image to be recorded;

wherein, in the ejection step, it is determined whether or not to discharge ink from a nozzle identified as a faulty nozzle among the at least one nozzle according to the faulty nozzle information, characterized by the ejection controller performing a first ejection control (step S107) to discharge ink during print job execution onto a recording medium (M) from at least one nozzle not based on image data of an image to be recorded,

wherein, in the first ejection, ink is not discharged from a nozzle identified as a faulty nozzle according to the faulty nozzle information and ink is discharged from a normal nozzle which is not a faulty nozzle,

the inkjet recording device carrying out a maintenance operation over a maintenance unit displaced from the recording medium,

wherein, in the maintenance operation, a second ejection control (S111) and subsequent cleaning operation (S112) is performed,

the ejection controller discharging ink from all nozzles including faulty nozzles in the second ejection,

wherein the ejection controller selects whether to discharge ink according to the first ink ejection control or the second ink ejection control.