JP2022015776A - Image formation system and image formation method - Google Patents

Abstract

To provide an image formation system and image formation method which can more surely suppress the image quality reduction due to a defective nozzle.SOLUTION: An image formation system comprises: a first image formation apparatus 1a including a first ink discharge part having a first nozzle group, a first image reading part and a first control part; and a second image formation apparatus including a second ink discharge part having a second nozzle group and a second control part. The first control part generates first alternative discharge information for causing the second ink discharge part to perform the alternative discharge of ink to a first alternative discharge region including a region corresponding to a first discharge failure region on a recording medium in a case where the first discharge failure region due to such a fact that a defective nozzle is included in the first nozzle group is detected in an image read by the first image reading part. The second control part causes the second ink discharge part to perform the alternative discharge to the first alternative discharge region on the basis of the first alternative discharge information.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming system and an image forming method.

Conventionally, an inkjet method in which an ink ejection unit provided with a nozzle group for ejecting ink is provided, and an image is formed by ejecting ink from the nozzle group to a recording medium while moving the recording medium and the ink ejection unit relative to each other. There is an image forming device. In such an image forming apparatus, when there is a defective nozzle such that ink is not ejected or the ink ejection amount or ejection direction is incorrect, there is a problem that the influence of the defective nozzle appears in the image and the image quality is deteriorated.

On the other hand, technology is known to prevent deterioration of image quality by preventing ink from being ejected from defective nozzles and increasing the amount of ink ejected from adjacent nozzles of defective nozzles to supplement non-ejection of ink by defective nozzles. (For example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2002-19101

However, if the adjacent nozzle is originally the target of ink ejection, or if the adjacent nozzle is also a defective nozzle, the amount of ink ejected from the adjacent nozzle cannot be increased for complementation, which is appropriate. Cannot be complemented. Therefore, the above-mentioned conventional technique has a problem that the deterioration of image quality due to a defective nozzle may not be suppressed.

An object of the present invention is to provide an image forming system and an image forming method capable of more reliably suppressing image quality deterioration caused by a defective nozzle.

In order to achieve the above object, the invention of the image forming system according to claim 1 is
An image forming system including a first image forming apparatus and a second image forming apparatus.
The first image forming apparatus is
A first ink ejection unit having a first nozzle group and ejecting ink from the first nozzle group to a recording medium,
A first image reading unit that reads an image formed on a recording medium by ejecting ink by the first ink ejection unit, and a first image reading unit.
The first control unit and
Have,
The second image forming apparatus is
A second ink ejection unit having a second nozzle group and ejecting ink from the second nozzle group to a recording medium delivered from the first image forming apparatus.
The second control unit and
Have,
The first control unit is the first in which ink is not normally ejected due to the inclusion of defective nozzles in the first nozzle group in the image read by the first image reading unit. When a ejection failure region is detected, the ink alternative ejection by the second ink ejection unit is performed on the recording medium with respect to the first alternative ejection region including the region corresponding to the first ejection failure region. Generate a first alternative discharge information to be done,
The second control unit causes the second ink ejection unit to perform the alternative ejection to the first alternative ejection region based on the first alternative ejection information.

The invention according to claim 2 is the image forming system according to claim 1.
The second control unit causes the second ink ejection unit to perform the alternative ejection to the first alternative ejection region on the recording medium in which the first ejection defective region is detected.

The invention according to claim 3 is the image forming system according to claim 1 or 2.
The first alternative ejection information includes information for identifying the defective nozzle of the first nozzle group.
The second control unit causes the alternative ejection to be performed by the nozzle of the second nozzle group whose ink ejection position corresponds to the defective nozzle of the first ink ejection unit.

The invention according to claim 4 is the image forming system according to claim 1.
The first alternative ejection information includes information that is composed of a part of the first nozzle group and identifies a sub-nozzle group that includes the defective nozzle and whose ink ejection positions are adjacent to each other.
In the image formation after the first alternative discharge information is generated,
The first control unit ejects ink from the nozzles of the first nozzle group excluding the sub-nozzle group specified by the first alternative ejection information by the first ink ejection unit.
The second control unit causes the second nozzle group to perform the alternative ejection by the sub-nozzle group whose ink ejection position corresponds to the sub-nozzle group specified by the first alternative ejection information.

The invention according to claim 5 is the image forming system according to claim 1.
The first ink ejection unit has a plurality of first head units that eject inks of different colors from the nozzles.
The second ink ejection unit has a plurality of second head units that eject ink of the same color as each of the plurality of first head units from a nozzle.
The first alternative discharge information includes information for identifying a head unit having the defective nozzle among the plurality of first head units.
In the image formation after the first alternative discharge information is generated,
The first control unit uses the first ink ejection unit to ink from the remaining head units of the plurality of first head units excluding the head unit specified by the first alternative ejection information. Is discharged,
The second control unit performs the alternative ejection by the head unit that ejects ink of the same color as the head unit specified by the first alternative ejection information among the plurality of second head units. Let me.

The invention according to claim 6 is the image forming system according to claim 1 or 2.
The first alternative ejection information is partial image data including a portion corresponding to the first alternative ejection region in the image data of the image to be formed.
The second control unit causes the second ink ejection unit to eject ink based on the partial image data to perform the alternative ejection.

The invention according to claim 7 is the image forming system according to any one of claims 1 to 6.
The second control unit causes the alternative discharge to be performed when a predetermined alternative discharge execution condition is satisfied.

The invention according to claim 8 is the image forming system according to any one of claims 1 to 7.
The first image forming apparatus has an inversion portion that inverts the front and back of the recording medium.
The first ink ejection unit of the first image forming apparatus ejects ink to the first surface of the recording medium.
In the second ink ejection unit of the second image forming apparatus, a recording medium whose front and back sides are reversed by the inversion portion after the ink is ejected by the first ink ejection unit is delivered from the first image forming apparatus. In this case, ink is ejected to the second surface opposite to the first surface, and after the ink is ejected by the first ink ejection portion, the front and back sides are recorded without being inverted by the inversion portion. When the medium is delivered from the first image forming apparatus, ink is ejected to the first surface.
When the first alternative ejection information is generated, the first control unit causes the second image forming apparatus to send the recording medium without inverting the recording medium by the inversion unit.

The invention according to claim 9 is the image forming system according to claim 1.
The second image forming apparatus has a second image reading unit that reads an image formed on a recording medium by ejecting ink by the second ink ejection unit.
In the image read by the second image reading unit, the second control unit is not ejected ink normally due to the inclusion of defective nozzles in the second nozzle group. When a ejection failure region is detected, the ink alternative ejection by the first ink ejection unit is performed on the recording medium with respect to the second alternative ejection region including the region corresponding to the second ejection failure region. Generate a second alternative discharge information to be done,
The first control unit causes the first ink ejection unit to perform the alternative ejection to the second alternative ejection region based on the second alternative ejection information.

The invention according to claim 10 is the image forming system according to claim 9.
The second alternative ejection information includes information for identifying the defective nozzle of the second nozzle group.
The first control unit causes the alternative ejection to be performed by the nozzle of the first nozzle group whose ink ejection position corresponds to the defective nozzle of the second ink ejection unit.

The invention according to claim 11 is the image forming system according to claim 9.
The second alternative ejection information includes information for identifying a sub-nozzle group including the defective nozzle and having ink ejection positions adjacent to each other, which is a part of the second nozzle group.
In the image formation after the second alternative discharge information is generated,
The first control unit causes the alternative nozzle group to perform the alternative ejection by the sub-nozzle group whose ink ejection position corresponds to the sub-nozzle group specified by the second alternative ejection information among the first nozzle group.
The second control unit ejects ink from the nozzles of the second nozzle group excluding the sub-nozzle group specified by the second alternative ejection information by the second ink ejection unit.

The invention according to claim 12 is the image forming system according to claim 9.
The first ink ejection unit has a plurality of first head units that eject inks of different colors from the nozzles.
The second ink ejection unit has a plurality of second head units that eject ink of the same color as each of the plurality of first head units from a nozzle.
The second alternative discharge information includes information for identifying a head unit having the defective nozzle among the plurality of second head units.
In the image formation after the second alternative discharge information is generated,
The first control unit performs the alternative ejection by the head unit that ejects ink of the same color as the head unit specified by the second alternative ejection information among the plurality of first head units. Let me,
The second control unit uses the second ink ejection unit to ink from the remaining head units of the plurality of second head units excluding the head unit specified by the second alternative ejection information. Is discharged.

The invention according to claim 13 is the image forming system according to claim 9.
The second alternative ejection information is partial image data including a portion corresponding to the second alternative ejection region in the image data of the image to be formed.
The first control unit causes the first ink ejection unit to eject ink based on the partial image data to perform the alternative ejection.

The invention according to claim 14 is the image forming system according to any one of claims 9 to 13.
The first control unit causes the alternative discharge to be performed when a predetermined alternative discharge execution condition is satisfied.

The invention according to claim 15 is the image forming system according to any one of claims 9 to 14.
The first image forming apparatus has an inversion portion that inverts the front and back of the recording medium.
The first ink ejection unit of the first image forming apparatus ejects ink to the first surface of the recording medium.
When the second alternative ejection information is generated, the first control unit ejects ink to the first surface of the recording medium by the first ink ejection unit, and then reverses the ink. The front and back sides of the recording medium are reversed by the unit, and the alternative ink ejection unit causes the second surface of the recording medium to be ejected to the second surface opposite to the first surface.

The invention according to claim 16 is the image forming system according to claim 7 or 14.
The alternative ejection execution condition is at least one of the quality level of the formed image, the position of the defective nozzle, the color of the ink corresponding to the defective nozzle, the presence or absence of an adjacent defective nozzle, the object attribute of the formed image, and the resolution of the formed image. It is about the department.

The invention according to claim 17 is the image forming system according to any one of claims 7, 14 and 16.
An input unit that accepts an input operation for setting the alternative discharge execution condition,
A display unit that displays the alternative discharge execution conditions and
To prepare for.

Further, in order to achieve the above object, the invention of the image forming method according to claim 18 is described.
It has a first nozzle group, and is formed on a recording medium by a first ink ejection unit that ejects ink from the first nozzle group to a recording medium and ink ejection by the first ink ejection unit. A first image forming apparatus having a first image reading unit for reading an image, and a first image forming apparatus.
A second image forming apparatus having a second nozzle group and having a second ink ejection portion for ejecting ink from the second nozzle group with respect to the recording medium delivered from the first image forming apparatus. It is an image formation method by an image formation system equipped with
In the image read by the first image reading unit, when a first ejection defective region in which ink is not ejected normally due to the inclusion of defective nozzles in the first nozzle group is detected. First alternative for causing the second ink ejection unit to perform alternative ejection of ink to the first alternative ejection region including the region corresponding to the first ejection defective region on the recording medium. The process of generating discharge information and
A step of causing the second ink ejection unit to perform the alternative ejection to the first alternative ejection region based on the first alternative ejection information.
including.

The invention according to claim 19 is the image forming method according to claim 18.
The second image forming apparatus has a second image reading unit that reads an image formed on a recording medium by ejecting ink by the second ink ejection unit.
The image formation method is
In the image read by the second image reading unit, there is a second ejection defective region in which ink is not ejected normally due to the inclusion of a defective nozzle in the nozzle of the second ink ejection unit. When detected, in order to cause the first ink ejection unit to perform alternative ejection of ink to the second alternative ejection region including the region corresponding to the second ejection failure region on the recording medium. The process of generating the second alternative discharge information and
A step of causing the first ink ejection unit to perform the alternative ejection to the second alternative ejection region based on the second alternative ejection information.
including.

According to the present invention, deterioration of image quality due to defective nozzles can be more reliably suppressed.

It is a figure which shows the schematic structure of the image formation system which is 1st Embodiment of this invention. It is a schematic diagram which shows the structure of a head unit. It is a block diagram which shows the main functional composition of the 1st image forming apparatus and the 2nd image forming apparatus. It is a figure explaining the alternative ejection of ink. It is a figure which shows the alternative discharge setting screen. It is a flowchart which shows the control procedure of the image formation process executed by the 1st image formation apparatus. It is a flowchart which shows the control procedure of the image formation process which is executed by the 2nd image formation apparatus. It is a figure which shows the image formation process in the image formation process of FIGS. 6 and 7. It is a flowchart which shows the control procedure of the alternative discharge setting process. It is a figure which shows the example of the test image. It is a figure explaining the alternative ejection by the 2nd image forming apparatus for complementing the ejection failure of the 1st image forming apparatus. It is a figure explaining the alternative ejection by the 1st image forming apparatus for complementing the ejection failure of the 2nd image forming apparatus. It is a figure which shows the control procedure of the image formation processing in 2nd Embodiment. It is a figure which shows the image formation process in the image formation process of FIG. It is a flowchart which shows the control procedure of the image formation processing in the modification 2-1. It is a figure which shows the image formation process in the image formation process of FIG. It is a figure which shows the image formation process in the image formation process of FIG.

Hereinafter, embodiments of the image forming system and the image forming method of the present invention will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a diagram showing a schematic configuration of an image forming system 100 according to a first embodiment of the present invention.
The image forming system 100 is connected to the paper feeding unit 2, the first image forming apparatus 1a for forming an image on the recording medium M supplied from the feeding unit 2, and the first image forming apparatus 1a. It includes a second image forming apparatus 1b that forms an image on the recording medium M delivered from the image forming apparatus 1a, and a paper ejection unit 3 from which the recording medium M on which the image is formed is discharged. The image forming system 100 is a series tandem system in which an image is formed on one recording medium M by a first image forming apparatus 1a and a second image forming apparatus 1b connected in series. As the recording medium M, in addition to paper such as plain paper and coated paper, various media such as cloth or sheet-shaped resin capable of fixing the ink landed on the surface can be used.

The paper feed unit 2 has a paper feed tray for storing the recording medium M, and supplies the recording media M one by one to the first image forming apparatus 1a by a paper feed mechanism (not shown).

The first image forming apparatus 1a includes a first transport unit 10a, a first ink ejection unit 20a, a first image reading unit 30a, a first reversing unit 40a, a first control unit 50a, and the like. To prepare for.

The first transport unit 10a includes a transport belt 11, a plurality of transport rollers 12, a medium detection unit 14, a rotary encoder 15, and the like.
The conveyor belt 11 is a ring-shaped belt whose inside is supported by a plurality of conveyor rollers 12. A specific drive roller among the plurality of transfer rollers 12 is driven by the transfer drive unit 13 (see FIG. 3) and rotates about a rotation axis extending in the X direction of FIG. The transport belt 11 orbits around the plurality of transport rollers 12 as the drive rollers rotate. The first transport unit 10a transports the recording medium M by rotating the transport belt 11 at a speed corresponding to the rotation speed of the transport roller 12 in a state where the recording medium M is placed on the transport belt 11. It is conveyed in the moving direction of 11 (Y direction in FIG. 1). The first transport portion 10a is provided with a guide member (not shown) that abuts and guides the side end portion of the recording medium M. With this guide member, the misalignment of the recording medium M in the X direction can be corrected, and the recording medium M can be placed at a predetermined position in the X direction.

The medium detection unit 14 detects the tip end portion and the side end portion of the recording medium M mounted on the transport belt 11 and is conveyed, and outputs the detection result to the first control unit 50a. As the detection method of the medium detection unit 14, for example, an optical method for specifying the positions of the tip portion and the side end portion from the image pickup result of the tip portion and the side end portion of the recording medium M can be used. However, the present invention is not limited to this, and a method of contact-detecting the tip end portion and the side end portion of the recording medium M may be used.

The rotary encoder 15 is attached to the drive roller of the transfer rollers 12, and outputs a pulse signal to the first control unit 50a each time the drive roller rotates by a predetermined angle. From the signal from the rotary encoder 15, the amount of rotation of the drive roller, that is, the amount of movement of the conveyor belt 11 (and the recording medium M) can be detected.

The first ink ejection unit 20a has a plurality of head units 21 (plurality of first head units) that eject inks of different colors from the nozzles. Specifically, the first ink ejection unit 20a has four head units 21Y and 21M corresponding to four colors of ink of yellow (Y), magenta (M), cyan (C), and black (K), respectively. It is equipped with 21C and 21K. In the following, when referring to any one of the head units 21Y, 21M, 21C, and 21K, it is referred to as "head unit 21". In the head unit 21, the nozzle surface provided with openings of a plurality of nozzles for ejecting ink is exposed to the outside thereof, and the head unit 21 has an appropriate timing according to the rotation of the transport belt 11 on which the recording medium M is placed. An image is recorded by ejecting ink to the recording medium M from the nozzle opening on the nozzle surface facing the outer peripheral surface of the transport belt 11. The head unit 21 is arranged so that the nozzle surface and the outer peripheral surface are separated by a predetermined distance. In the present embodiment, the head units 21Y, 21M, 21C, and 21K are arranged so as to be arranged at predetermined intervals in this order from the upstream side in the transport direction of the recording medium M. The entire nozzle provided in the first ink ejection portion 20a is hereinafter referred to as a "first nozzle group".

FIG. 2 is a schematic diagram showing the configuration of the head unit 21. FIG. 2 is a plan view of the entire head unit 21 as viewed from the side facing the outer peripheral surface of the transport belt 11.
In the present embodiment, the head unit 21 includes 16 recording heads 211 each having a nozzle array consisting of nozzles N arranged in the X direction (that is, in the width direction orthogonal to the transport direction). These 16 recording heads 211 are combined by two to form eight head modules 211M. The positions of the plurality of nozzle rows included in each head module 211M are adjusted in the X direction so that the positions of the nozzles in the X direction do not overlap. The set of a plurality of nozzles N provided in one head module 211M is hereinafter referred to as "sub-nozzle group G". The arrangement direction of the nozzles N in each recording head 211 is not limited to the width direction orthogonal to the transport direction, and may be a direction intersecting the transport direction at an angle other than a right angle.

The ink ejection mechanism for ejecting ink from each nozzle N is not particularly limited, but a piezo type using a piezoelectric material can be used. As a piezo type ink ejection mechanism, a shear mode and a vent mode are known. The shear mode ink ejection mechanism causes a shear mode type displacement in the piezoelectric body on the wall surface of the pressure chamber communicating with the nozzle N to fluctuate the pressure of the ink in the pressure chamber to eject the ink. Further, the ink ejection mechanism in the vent mode fluctuates the pressure of the ink in the pressure chamber by deforming the piezoelectric body fixed to the diaphragm constituting the wall surface of the pressure chamber to eject the ink.

Each head module 211M fits into an opening provided in the support plate 21a of the head unit 21, and the nozzle surface of the recording head 211 is formed from the bottom surface of the support plate 21a (the surface facing the transport belt 11). It is held by the support plate 21a in an exposed state. Further, the eight head modules 211M have a positional relationship in which the range in which ink can be ejected from the nozzle N is continuously connected in the X direction, and the houndstooth so that the arrangement ranges in the X direction partially overlap each other. The line heads are arranged in a shape.

The arrangement range of the nozzle N in the X direction of the head unit 21 covers the width in the X direction of the region of the recording medium M conveyed by the transfer belt 11 in which an image can be recorded. The head unit 21 is fixedly used when recording an image, and is used by sequentially ejecting ink to positions having different transport directions at predetermined intervals (conveyance direction intervals) according to the transport of the recording medium M, thereby making a single pass. Record the image by the method.

The first image reading unit 30a shown in FIG. 1 is provided at a position facing the outer peripheral surface of the transport belt 11 on the downstream side of the first ink ejection section 20a in the transport direction. The first image reading unit 30a reads the first image formed on the recording medium M by ejecting ink by the first conveying unit 10a, and outputs the reading result to the first control unit 50a. The first image reading unit 30a includes a linear image sensor in which a plurality of image pickup devices such as a CCD (charge-coupled device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor are arranged along the X direction, and an image pickup device. It has a generation unit that generates image data (imaging data) according to an electric signal output from the recording medium M, and a light source that irradiates the recording medium M with light.

The first inversion unit 40a inverts the front and back of the recording medium M, and sends the inverted recording medium M to the second image forming apparatus 1b. The first reversing unit 40a includes a plurality of roller pairs 41 that sandwich and convey the recording medium M. When the front and back of the recording medium M are inverted, the first inversion unit 40a once draws the recording medium M transmitted from the transport belt 11 toward the second image forming apparatus 1b into the inversion path 42. By reversing the traveling direction of the recording medium M and returning it to the transport path to the second image forming apparatus 1b again, the recording medium M is sent out to the second image forming apparatus 1b with the front and back reversed. be able to.
Further, by advancing the recording medium M from the inversion path 42 to the return path 43, the recording medium M can be supplied to the transfer belt 11 of the first transfer unit 10a again in a state where the front and back sides are inverted. As a result, the first ink ejection unit 20a can record an image on the second surface (the surface opposite to the first surface) of the recording medium M. As described above, the first image forming apparatus 1a can also form an image on the front and back of the recording medium M.
The configuration of the first reversing unit 40a is not limited to that shown in FIG. 1, and any configuration can be used as long as the front and back surfaces of the recording medium M can be inverted.

The first control unit 50a collectively controls the operation of each unit of the first image forming apparatus 1a.
For example, the first control unit 50a conveys the recording medium M by the first conveying unit 10a, and at the same time, the first ink ejection unit 20a is conveyed to the recording medium M based on the image data of the image to be formed. Ink is ejected from the nozzle of No. 1 to form an image. In this image formation, the first control unit 50a identifies the position of the recording medium M based on the detection result of the tip portion of the recording medium M by the medium detection unit 14 and the output signal from the rotary encoder 15, and records the image. Ink is ejected from the nozzle at the timing when the nozzle of the head unit 21 faces the ink ejection target position on the medium M. Further, when it is determined from the detection result of the side end portion of the recording medium M by the medium detection unit 14 that the position of the recording medium M in the X direction deviates from a predetermined position, the first control unit 50a is used. The range of the nozzle used for image formation is shifted in the X direction according to the amount of deviation, and adjustment is made so that an image is formed in a predetermined image formation range on the recording medium M.
Further, the first control unit 50a has a defective nozzle in the nozzle (first nozzle group) of the first ink ejection unit 20a in the scanned image based on the reading result by the first image reading unit 30a. It is detected whether or not there is an ejection defective region (first ejection defective region) in which ink is not normally ejected due to inclusion. When the discharge defective region is detected, the first control unit 50a executes various processes related to dealing with the discharge defect. The measures to deal with the ejection failure will be described in detail later.

The second image forming apparatus 1b includes a second transport unit 10b, a second ink ejection unit 20b, a second image reading unit 30b, a second reversing unit 40b, a second control unit 50b, and the like. To prepare for.
The configuration of the second transport unit 10b, the second ink ejection unit 20b, the second image reading unit 30b, the second reversing unit 40b, and the second control unit 50b is the first in the first image forming apparatus 1a. Since the configuration is the same as that of the transport unit 10a, the first ink ejection unit 20a, the first image reading unit 30a, the first reversing unit 40a, and the first control unit 50a, detailed description thereof will be omitted.
The second ink ejection unit 20b is a four head units 21Y, 21M, 21C, 21K (a plurality of second heads) that eject ink of the same color as each of the first ink ejection portions 20a from the nozzles. Unit). Further, the entire nozzle provided in the second ink ejection unit 20b is hereinafter referred to as a "second nozzle group".

The second image forming apparatus 1b conveys the recording medium M delivered from the first image forming apparatus 1a in the Y direction by the second conveying unit 10b, and the second ink ejection unit with respect to the recording medium M. Ink is ejected from 20b to form an image.
After the first ink ejection unit 20a of the first image forming apparatus 1a ejects ink to the first surface, the recording medium M whose front and back sides are inverted by the first inversion portion 40a is delivered from the first image forming apparatus 1a. In this case, the second ink ejection unit 20b ejects ink to the second surface. On the other hand, when the recording medium M is handed over from the first image forming apparatus 1a without the front and back being reversed by the first reversing unit 40a after the ink is ejected by the first ink ejection unit 20a, the second The ink ejection unit 20b ejects ink to the first surface.

The second control unit 50b collectively controls the operation of each unit of the second image forming apparatus 1b.
For example, the second control unit 50b conveys the recording medium M by the second conveying unit 10b, and the second ink ejection unit 20b is transferred to the recording medium M based on the image data of the image to be formed. Ink is ejected from the nozzle of No. 1 to form an image.
Further, the second control unit 50b has a defective nozzle in the nozzle (second nozzle group) of the second ink ejection unit 20b in the scanned image based on the reading result by the second image reading unit 30b. It is detected whether or not there is an ejection defective region (second ejection defective region) in which ink is not normally ejected due to inclusion. When the discharge defective region is detected, the second control unit 50b executes various processes related to dealing with the discharge defect. The measures to deal with the ejection failure will be described in detail later.

The paper ejection unit 3 has a paper ejection tray on which the recording medium M for which image formation by the second image forming apparatus 1b has been completed is placed.

FIG. 3 is a block diagram showing the main functional configurations of the first image forming apparatus 1a and the second image forming apparatus 1b.
In FIG. 3 and the following description, the first image forming apparatus 1a or the second image forming apparatus 1b is referred to as an “image forming apparatus 1”, and the first conveying portion 10a or the second conveying portion 10b is referred to as a “conveying portion 10”. , The first ink ejection unit 20a or the second ink ejection unit 20b is the "ink ejection unit 20", the first image reading unit 30a or the second image reading unit 30b is the "image reading unit 30", the first The reversing unit 40a or the second reversing unit 40b is referred to as a "reversing unit 40", and the first control unit 50a or the second control unit 50b is referred to as a "control unit 50".
The image forming apparatus 1 includes a transport unit 10, a transport unit 10 having a transport drive unit 13, a medium detection unit 14, and a rotary encoder 15, an ink ejection unit 20 having a recording head 211 and a recording head drive unit 212, an image reading unit 30, and a roller. It includes an inversion unit 40 having a drive unit 44, a control unit 50, an image processing unit 61, an operation display unit 62 (input unit, display unit), a communication unit 63, a bus 64, and the like. In the following, description of the components already described will be omitted.

The transfer drive unit 13 supplies a drive signal to the motor that drives the transfer belt 11 based on the control signal supplied from the control unit 50, and rotates the transfer belt 11 at a predetermined speed and timing.

The recording head drive unit 212 supplies a drive signal for deforming the piezoelectric body according to the image data at an appropriate timing to the ink ejection mechanism of the recording head 211, so that the image data can be obtained from the nozzle N of the recording head 211. The amount of ink corresponding to the pixel value is ejected.

The roller drive unit 44 rotates the roller pair 41 of the reversing unit 40 in a rotation amount and a rotation direction according to a control signal from the control unit 50, and moves the recording medium M in the reversing unit 40.

The control unit 50 includes a CPU 51 (Central Processing Unit), a RAM 52 (Random Access Memory), a ROM 53 (Read Only Memory), and a storage unit 54.
The CPU 51 reads out various control programs and setting data stored in the ROM 53 and stores them in the RAM 52, and executes the program to perform various arithmetic processes. The control unit 50 collectively controls the overall operation of the image forming apparatus 1 by the CPU 51 performing these arithmetic processes.
The RAM 52 provides a working memory space to the CPU 51 and stores temporary data. The RAM 52 may include a non-volatile memory.
The ROM 53 stores various control programs, setting data, and the like executed by the CPU 51. A rewritable non-volatile memory such as a flash memory may be used instead of the ROM 53.

The storage unit 54 stores a print job (image recording command) input from an external device via the communication unit 63 and image data 543 of the image to be recorded related to the print job. Further, the storage unit 54 stores the first alternative discharge information 541 and the second alternative discharge information 542. Of these, the first alternative ejection information 541 is information for causing the second image forming apparatus 1b to perform alternative ejection when an ejection defective region caused by a defective nozzle of the first image forming apparatus 1a is detected. It is generated by the first image forming apparatus 1a. Further, the second alternative ejection information 542 is information for causing the first image forming apparatus 1a to perform alternative ejection when the ejection defective region caused by the defective nozzle of the second image forming apparatus 1b is detected. And is generated by the second image forming apparatus 1b. Further, the storage unit 54 stores the partial image data 544 generated for the alternative ejection. As the storage unit 54, for example, an HDD (Hard Disk Drive) may be used, or a DRAM (Dynamic Random Access Memory) or the like may be used in combination.

The image processing unit 61 performs various image processing. The image processing unit 61, for example, analyzes data in the page description language included in the job data input via the communication unit to generate vector data, and generates bitmap data of a raster image from the vector data. Performs image processing such as rasterization processing. Each data string in the bitmap data corresponds to one nozzle of the head unit 21, and an image can be formed by ejecting ink from each nozzle according to the pixel value of the bitmap data. In this way, the image processing unit 61 functions as a RIP (raster image processor). The image processing executed by the image processing unit 61 is not limited to the one illustrated above.

The operation display unit 62 performs various display outputs related to the operation of the image forming apparatus 1, and also receives various input operations from the user related to the operation of the image forming apparatus 1. Specifically, the operation display unit 62 includes, for example, a display device including a touch panel type input device, a switch provided according to various input operation contents, and the like.

The communication unit 63 is a communication interface that controls a communication operation with the other image forming apparatus 1 or an external device. Here, the other image forming apparatus 1 refers to the second image forming apparatus 1b for the communication unit 63 of the first image forming apparatus 1a, and the first for the communication unit 63 of the second image forming apparatus 1b. Refers to the image forming apparatus 1a of. The communication interface includes one or a plurality of communication interfaces corresponding to various communication protocols, such as a network interface card. The communication unit 63 transmits various commands including the first alternative discharge information 541 and the second alternative discharge information 542 to the other image forming apparatus 1 based on the control of the control unit 50. In addition, the image data to be recorded and the setting data (job data) related to the image recording are acquired from the external device, and the status information and the like are transmitted to the external device.

The bus 64 is a path for transmitting and receiving signals between the control unit 50 and other configurations.

Next, the image forming operation of the image forming system 100 will be described.
In the image forming system 100, in the case of performing normal image forming, a first image is formed by the first image forming apparatus 1a with respect to the first surface (surface) of the recording medium M, and the recording medium M is formed. A second image is formed by the second image forming apparatus 1b with respect to the second surface (back surface).
Further, when a ejection defect is detected in the first image formed by the first image forming apparatus 1a, the ink is applied to the first surface by the second image forming apparatus 1b so as to supplement the ejection defect. Alternative discharge is performed. After this alternative ejection, a second image is formed on the second surface.

FIG. 4 is a diagram illustrating alternative ejection of ink.
FIG. 4A shows a first image formed on the first surface of the recording medium M by the first image forming apparatus 1a. Here, it is assumed that the nozzle of the first ink ejection unit 20a contains a defective nozzle that cannot eject ink. Therefore, in the first image of FIG. 4A, the ejection defective region r1 is generated due to the non-ejection of ink from the defective nozzle. The ejection failure region r1 is an region in which the ink of the color corresponding to the defective nozzle is not ejected, but in FIG. 4A, dots are added to the ejection failure region r1 for convenience of explanation. .. Further, the discharge defective region r1 is usually an extremely narrow region corresponding to one nozzle, but in FIG. 4A, the width of the discharge defective region r1 is exaggerated.

The ejection failure region r1 is detected by the first control unit 50a based on the reading result of the first image by the first image reading unit 30a. In the present embodiment, the image data read by the first image reading unit 30a and the image data 543 (bitmap data generated by the image processing unit 61) used for forming the first image are used. The discharge defective region r1 is detected by comparing and analyzing the above. Further, the defective nozzle is identified from the position of the ejection defective region r1 in the image.

When the discharge defective region r1 is detected in the first image, the first control unit 50a of the first image forming apparatus 1a performs alternative ejection to the ejection defective region r1 by the second image forming apparatus 1b. The first alternative discharge information 541 is generated and transmitted to the second image forming apparatus 1b. Specifically, the first alternative ejection information 541 is a second image forming apparatus 1b with respect to the alternative ejection region R1 (first alternative ejection region) including the region corresponding to the ejection defective region r1 on the recording medium M. This is information for causing the second ink ejection unit 20b of the above to perform alternative ejection of ink. In the present embodiment, the discharge defective region r1 and the alternative discharge region R1 are the same region. Further, in the present embodiment, the first alternative ejection information 541 includes information for identifying a defective nozzle among the first nozzle group included in the first ink ejection unit 20a. The information is, for example, a nozzle array number in the X direction.

When the second control unit 50b of the second image forming apparatus 1b receives the first alternative ejection information 541, the second ink ejection with respect to the alternative ejection region R1 is based on the first alternative ejection information 541. The alternative discharge is performed by the portion 20b. That is, the second control unit 50b uses a nozzle in which the defective nozzle of the first ink ejection unit 20a and the ink ejection position in the X direction correspond to the second nozzle group of the second ink ejection unit 20b. Have an alternative discharge performed. Further, in the present embodiment, the second control unit 50b causes the alternative ejection region R1 (that is, the ejection defective region r1) on the same recording medium M in which the ejection defective region r1 is detected to perform alternative ejection. .. Further, from the detection result of the side end portion of the recording medium M by the medium detection unit 14, the mounting position of the recording medium M on the transport belt 11 of the second transport unit 10b in the X direction is the position of the first transport unit 10a. When it is detected that the recording medium M is displaced from the mounting position in the X direction on the transport belt 11, the second transport unit 10b sets a nozzle for performing alternative discharge to the displacement amount of the mounting position. Shifts in the X direction according to.

FIG. 4B shows an extracted partial image formed in the alternative discharge region R1 by this alternative discharge. A partial image of FIG. 4B is formed on the first surface of the recording medium M by superimposing it on the first image of FIG. 4A, so that ejection failure is performed as shown in FIG. 4C. A first image complemented with is formed. After the first image is formed, the front and back sides of the recording medium M are inverted by the second inversion portion 40b of the second image forming apparatus 1b, and the second ink ejection portion 20b is used to make a second surface on the second surface. Image is formed.

Such alternative discharge is executed when a predetermined alternative discharge execution condition is satisfied when the discharge defective region r1 is detected. That is, the first control unit 50a generates the first alternative discharge information 541 when the alternative discharge execution condition is satisfied. Therefore, the second control unit 50b causes the alternative discharge to be performed based on the first alternative discharge information 541 when the alternative discharge execution condition is satisfied. The alternative discharge execution condition can be set by the user by an input operation on the alternative discharge setting screen 621 displayed on the operation display unit 62.

FIG. 5 is a diagram showing an alternative discharge setting screen 621.
The alternative discharge setting screen 621 shows the alternative discharge execution condition, and is displayed on the display device of the operation display unit 62. On the alternative discharge setting screen 621, various condition items related to the alternative discharge execution condition and candidates for setting contents in each item are displayed. Specifically, "quality level", "detection color", "detection position", "number of continuous defective nozzles", "image attribute" and "image resolution" are displayed as condition items. Of these, "detection color", "detection position", and "number of continuous defective nozzles" are condition items related to the detection result of defective nozzles. The operation buttons or text boxes provided for each condition item, which indicate candidates for setting contents, can be selected or input by the user's contact operation with the touch panel. That is, the operation display unit 62 can accept an input operation for setting an alternative discharge execution condition.

The "quality level" is a condition item relating to the quality level of the formed image, and represents the quality of the formed image desired by the user.
When "High" is selected for "Quality level" as shown in FIG. 5, alternative ejection is performed even if the ejection defect is slight or inconspicuous, and a high-quality image with accurate complement to the ejection defect is made. Is formed.
On the other hand, if "Low" is selected, the image quality is not prioritized and alternative ejection is not performed. Alternatively, only alternative ejection may be performed for ejection defects in a large area or ejection defects in a conspicuous position. "Low" is selected when the quality of the formed image is not important, for example, for test printing.
When "Medium" is selected, an alternative discharge between "High" and "Low" is performed.

The “detection color” is a condition item relating to the color of the ink corresponding to the defective nozzle, and indicates the color of Y, M, C, and K to be replaced. If the ejection defect is K (black), it is easily recognized as a white streak, but if it is Y (yellow), it is inconspicuous, and the ease of recognition differs depending on the color. Therefore, by omitting the alternative ejection of the color that is inconspicuous, it is possible to reduce the frequency of the alternative ejection while suppressing the influence on the quality and improve the productivity. In FIG. 5, C, M, and K, in which discharge defects are easily noticeable, are selected as targets for alternative discharge.

The "detection position" is a condition item relating to the position of the detected defective nozzle. When a register mark (trim mark) other than the main image is printed at the edge of the recording medium, the quality of the image at the edge may not be important. In such a case, as shown in FIG. 5, by selecting the “central portion” as the target of the alternative discharge, the alternative discharge when a defective nozzle is detected at the end portion can be omitted.

The "number of continuously defective nozzles" is a condition item relating to the presence or absence of adjacent defective nozzles and the number of consecutively adjacent defective nozzles. When "1" is selected, alternative ejection is performed regardless of the adjacent status of defective nozzles, and when "2" is selected, alternative ejection is performed only when two or more defective nozzles are adjacent to each other. When ejection is performed and "3" is selected, alternative ejection is performed only when three or more defective nozzles are adjacent to each other. Here, "adjacent" means that the ink ejection positions (landing positions) in the X direction on the recording medium M are adjacent to each other, and are not necessarily adjacent to each other in the nozzle row of the recording head 211. As the number of consecutively adjacent defective nozzles increases, ejection defects are more likely to be recognized as white streaks. Therefore, by setting this condition item, it is possible to select how much white streaks are allowed.

The "image attribute" is a condition item related to the object attribute of the formed image. The ease of recognition of ejection defects differs depending on the object attributes (here, text, graphics, and image) of the formed image. Here, "text" is an attribute of an image mainly composed of characters, "graphics" is an attribute of an image mainly composed of figures, and "image" is a multi-gradation mainly composed of photographs and the like. It is an attribute of the image of. Of these, ejection defects are easily recognized as white streaks in texts and graphics, but ejection defects may not be noticeable in images because a plurality of colors and gradations are mixed. In the condition item of this "image attribute", it is possible to select for which object attribute the alternative ejection is performed.

"Image resolution" is a condition item relating to the resolution of the formed image. When an image is formed by a high-resolution (for example, 1200 dpi) image forming apparatus 1 based on low-resolution (for example, 150 dpi) image data, a large number of nozzles are used for a region corresponding to one pixel of the original image data. Ink is ejected. For this reason, ejection defects may not be noticeable in the formation of low-resolution images. Therefore, by specifying the lower limit image resolution for performing alternative ejection in the condition item of this "image resolution", it is possible to prevent the alternative ejection from being performed for an image having a resolution lower than the lower limit.

When the discharge defect is detected, the first control unit 50a determines whether or not the alternative output execution condition consisting of the above condition items is satisfied, and if it is satisfied, the first alternative discharge is satisfied. Generate information 541.

Next, the control procedure of the image forming process executed by the image forming system 100 will be described separately for the processing performed by the first image forming apparatus 1a and the processing performed by the second image forming apparatus 1b.

FIG. 6 is a flowchart showing a control procedure of the image forming process executed by the first image forming apparatus 1a.
This image forming process is executed when, for example, a print job and image data 543 are input to the first control unit 50a from an external device via the communication unit 63.

When the image formation process is started, the first control unit 50a forms a first image on the first surface of the recording medium M based on the image data 543 (step S101). Specifically, the first control unit 50a conveys the recording medium M by the first transfer unit 10a, and at an appropriate timing according to the image data 543 from the nozzle of each head unit 21 of the first ink ejection unit 20a. Ink is ejected to form a first image on the first surface.

The first control unit 50a causes the first image reading unit 30a to read the first image formed on the first surface (step S102). Further, the image data 543 used for image formation in step S101 is compared with the scanned image data acquired in step S102 to detect a ejection defect, and if a ejection defect is detected, a defective nozzle is specified. (Step S103).

When a discharge defect is detected (“YES” in step S104), the first control unit 50a determines whether or not the preset alternative discharge execution condition is satisfied (step S105). When it is determined that the alternative discharge execution condition is satisfied (“YES” in step S105), the first control unit 50a generates the first alternative discharge information 541 including the information for identifying the defective nozzle (step). S106), an image forming command (alternative ejection command) to the first surface based on the first alternative ejection information 541 is transmitted to the second image forming apparatus 1b (step S107).

On the other hand, if no discharge defect is detected in step S104 (“NO” in step S104), or if it is determined in step S105 that the alternative discharge execution condition is not satisfied (“NO” in step S105), the first step is made. The control unit 50a of 1 reverses the front and back of the recording medium M by the first inversion unit 40a (step S108), and transmits an image formation command to the second surface to the second image forming apparatus 1b (step S109). ).

When step S107 or step S109 is completed, the first control unit 50a causes the second image forming apparatus 1b to send out the recording medium M (step S110).
Here, when passing through steps S106 and S107, since the front and back of the recording medium M are not inverted, the recording medium M is sent to the second image forming apparatus 1b with the first surface facing upward. That is, when the first alternative discharge information 541 is generated, the first control unit 50a sends the recording medium M to the second image forming apparatus 1b without inverting the recording medium M by the first inverting unit 40a.
Further, when passing through steps S108 and S109, since the front and back of the recording medium M are reversed, the recording medium M is sent to the second image forming apparatus 1b with the second surface facing upward.
When the step S110 is completed, the first control unit 50a ends the image forming process on the first image forming apparatus 1a side.

FIG. 7 is a flowchart showing a control procedure of the image forming process executed by the second image forming apparatus 1b.
When the image forming process is started, the second control unit 50b determines whether or not an image forming command has been received from the first image forming device 1a (step S201), and has not received the image forming command. If it is determined (“NO” in step S201), the process of step S201 is executed again. If it is determined that the image formation command has been received (“YES” in step S201), the second control unit 50b determines whether or not the first alternative discharge information 541 has been received (step S202). ..

When it is determined that the first alternative discharge information 541 has been received (“YES” in step S202), the second control unit 50b has a partial image for alternative discharge based on the first alternative discharge information 541. Data 544 is generated (step S203). Here, the partial image data 544 includes a data string corresponding to a defective nozzle identified by the first alternative discharge information 541 among the image data related to the first image formed on the first surface, and the data string is included. The pixels excluding the above are image data having values corresponding to non-ejection of ink.

The first control unit 50a causes the second ink ejection unit 20b to perform alternative ejection to the first surface of the recording medium M based on the partial image data 544 (step S204). Specifically, the second control unit 50b conveys the recording medium M by the second transfer unit 10b, and the appropriate timing according to the partial image data 544 from the nozzle of each head unit 21 of the second ink ejection unit 20b. By ejecting ink with, alternative ejection is performed on the first surface. Here, by using the partial image data 544, ink is ejected only from the nozzles whose ink ejection positions correspond to the defective nozzles of the first ink ejection portion 20a. As a result, the ink is ejected and complemented to the ejection defective region r1 (alternative ejection region R1) in which the ink was not ejected from the defective nozzle in the first image forming apparatus 1a.

When the alternative discharge is completed, the second control unit 50b reverses the front and back of the recording medium M by the second reversing unit 40b and places it on the transport belt 11 again (step S205).

When the process of step S205 is completed, or when it is determined in the process of step S202 that the first alternative discharge information 541 has not been received (“NO” in step S202), the second control unit 50b , A second image is formed on the second surface of the recording medium M (step S206).
When the process of step S206 is completed, the second control unit 50b ends the image forming process.
The image forming processes of FIGS. 6 and 7 are performed in parallel for each of the colors Y, M, C, and K. The determination of the presence or absence of a discharge defect in step S104 branches to "YES" when a discharge defect is detected for any one color. As a result, the four-color images are superimposed on one recording medium M to form a color image.

FIG. 8 is a diagram showing an image forming process in the image forming process of FIGS. 6 and 7.
The left side of FIG. 8 shows the process of forming an image on the first surface of the recording medium M, and the left side shows the process of forming an image on the first surface.
As shown in the upper part of FIG. 8, in step S101, the first image forming apparatus 1a forms the first image with respect to the first surface. Here, the ejection failure region r1 is generated due to the nozzle failure.
As shown in the middle stage of FIG. 8, in step S204, the second image forming apparatus 1b performs alternative ejection to the alternative ejection region R1 (discharge defective region r1) on the first surface, and the ejection defect is complemented. ..
Then, as shown in the lower part of FIG. 8, in step S205, the second image forming apparatus 1b forms a second image with respect to the second surface.

(Modification 1-1)
Subsequently, a modification 1-1 of the first embodiment will be described.
In the first embodiment, the first alternative ejection information 541 includes information for identifying a defective nozzle, and the second image forming apparatus 1b includes partial image data 544 based on the first alternative ejection information 541. Was generated, and alternative ejection was executed based on the partial image data 544.
On the other hand, in this modification, the same image data as the partial image data 544 is directly generated as the first alternative discharge information 541. That is, the first control unit 50a of the first image forming apparatus 1a is based on the identified defective nozzle, and is the first alternative ejection which is the image data having the same contents as the partial image data 544 in the first embodiment. Information 541 is generated and transmitted to the second image forming apparatus 1b. The second image forming apparatus 1b uses the first alternative ejection information 541 as partial image data to execute alternative ejection.
Also by such a method, the alternative ejection by the second image forming apparatus 1b can be executed.

As described above, the image forming system 100 according to the first embodiment includes the first image forming apparatus 1a and the second image forming apparatus 1b, and the first image forming apparatus 1a is a first nozzle group. The image formed on the recording medium M by the first ink ejection unit 20a for ejecting ink from the first nozzle group to the recording medium M and the ink ejection by the first ink ejection unit 20a is read. It has a first image reading unit 30a and a first control unit 50a, and the second image forming apparatus 1b has a second nozzle group and is delivered from the first image forming apparatus 1a. It has a second ink ejection unit 20b for ejecting ink from a second nozzle group with respect to the recording medium M, and a second control unit 50b, and the first control unit 50a reads a first image. In the image read by the unit 30a, when the ejection defective region r1 in which the ink is not ejected normally due to the inclusion of the defective nozzle in the first nozzle group is detected, the ejection defective region r1 on the recording medium M is detected. The first alternative ejection information 541 for causing the second ink ejection unit 20b to perform alternative ejection of ink to the alternative ejection region R1 including the region corresponding to the ejection failure region r1 is generated, and the second control unit The 50b causes the alternative ejection region R1 to perform alternative ejection by the second ink ejection unit 20b based on the first alternative ejection information 541.
As described above, by supplementing the ejection defect in the first image forming apparatus 1a with the alternative ejection by the second image forming apparatus 1b, it is possible to more reliably suppress the deterioration of the image quality due to the defective nozzle. That is, in the conventional technique in which alternative ejection is performed by an adjacent nozzle of a defective nozzle, appropriate complementation is performed when the adjacent nozzle of the defective nozzle is originally the target of ink ejection or when the adjacent nozzle is also a defective nozzle. However, according to the configuration of the present embodiment, complementary ejection can be executed regardless of the situation of the nozzle adjacent to the defective nozzle.
As a result, it is possible to reduce the occurrence of waste paper (spoiled paper) due to the formation of an image that does not meet a predetermined quality standard.
Further, even if a defective nozzle occurs in the first image forming apparatus 1a, the second image forming apparatus 1b can perform complementary ejection, so that the frequency of parts replacement such as the head module 211M and the head unit 21 can be suppressed. .. Therefore, the cost of replacement parts can be reduced, and the decrease in productivity due to parts replacement work can be suppressed.

Further, the second control unit 50b causes the second ink ejection unit 20b to perform alternative ejection to the alternative ejection region R1 on the recording medium M in which the ejection failure region r1 is detected. In this way, it is possible to suppress the occurrence of waste paper by performing alternative ejection to the recording medium M itself in which ejection failure is detected.

Further, the first alternative ejection information 541 includes information for identifying a defective nozzle of the first nozzle group, and the second control unit 50b is the first ink ejection unit 20a of the second nozzle group. Alternative ejection is performed by a nozzle whose defective nozzle and ink ejection position correspond to each other. As a result, alternative ejection can be selectively performed only for the detected ejection defect region r1, so that alternative ejection can be performed for the recording medium M itself in which the ejection defect is detected.

Further, the second control unit 50b causes the alternative discharge to be performed when a predetermined alternative discharge execution condition is satisfied. As a result, the alternative discharge can be performed in just proportion, and the decrease in productivity due to the execution of unnecessary alternative discharge can be suppressed.

Further, the first image forming apparatus 1a has a first inversion portion 40a for inverting the front and back of the recording medium M, and the first ink ejection portion 20a of the first image forming apparatus 1a is a recording medium M. Ink is ejected to the first surface, and the second ink ejection portion 20b of the second image forming apparatus 1b is inverted on the front and back by the first reversing portion 40a after the ink is ejected by the first ink ejection unit 20a. When the recorded recording medium M is delivered from the first image forming apparatus 1a, ink is ejected to the second surface opposite to the first surface, and the ink by the first ink ejection unit 20a is ejected. When the recording medium M is delivered from the first image forming apparatus 1a without being inverted by the first reversing unit 40a after ejection, ink is ejected to the first surface and the first control is performed. When the first alternative ejection information 541 is generated, the unit 50a sends the recording medium M to the second image forming apparatus 1b without inverting the recording medium M by the first inverting unit 40a. According to this, the second image forming apparatus 1b can perform alternative ejection to the ejection defective region r generated on the first surface without inverting the front and back of the delivered recording medium M.

The alternative ejection execution conditions are the quality level of the formed image, the position of the defective nozzle, the color of the ink corresponding to the defective nozzle, the presence or absence of the adjacent defective nozzle, the object attribute of the formed image, and at least a part of the resolution of the formed image. It is about. This makes it possible to flexibly set the conditions for performing alternative ejection according to the quality level desired by the user, the use of the image, and the like.

Further, the image forming system 100 includes an operation display unit 62, and the operation display unit 62 functions as an input unit that accepts an input operation for setting an alternative discharge execution condition and a display unit that displays an alternative discharge execution condition. do. As a result, the user can easily set the alternative discharge execution condition.

Further, in the image forming method of the present embodiment, in the image read by the first image reading unit 30a, ink is not normally ejected due to the inclusion of defective nozzles in the first nozzle group. When the defective region r1 is detected, the alternative ejection region R1 including the region corresponding to the ejection defective region r1 on the recording medium M is made to perform alternative ejection of ink by the second ink ejection unit 20b. A step of generating the first alternative ejection information 541 and a step of causing the alternative ejection region R1 to perform alternative ejection by the second ink ejection unit 20b based on the first alternative ejection information 541 are included. As a result, deterioration of image quality due to defective nozzles can be more reliably suppressed, and the occurrence of waste paper can be reduced. In addition, the frequency of parts replacement can be suppressed, the cost of replacement parts can be reduced, and the decrease in productivity due to parts replacement work can be suppressed.

(Second embodiment)
Next, the second embodiment will be described.
In the second embodiment, defective nozzles of the first image forming apparatus 1a and the second image forming apparatus 1b are detected in advance using a predetermined test image, and the first image forming apparatus 1a is detected based on the detection result. It is different from the first embodiment in that the second image forming apparatus 1b performs alternative ejection for the ejection defect of the other image forming apparatus 1, respectively. In the following, the differences from the first embodiment will be mainly described, and the contents common to the first embodiment will be omitted.

In the second embodiment, the alternative ejection setting process for identifying the defective nozzle and setting the alternative ejection is executed before the execution of the normal image formation.

FIG. 9 is a flowchart showing a control procedure of the alternative discharge setting process.
In the flowchart, steps S301 to S305 are executed by the first control unit 50a of the first image forming apparatus 1a, and steps S306 to S309 are executed by the second control unit 50b of the second image forming apparatus 1b. ..

When the alternative ejection setting process is started, the first control unit 50a of the first image forming apparatus 1a is a test image with respect to the first surface of the recording medium M based on the image data of the predetermined test image T. T is formed (step S301).

FIG. 10 is a diagram showing an example of the test image T.
The test image T is an image arranged in a houndstooth pattern so that a plurality of lines L do not overlap each other. Each line L is formed by continuously ejecting ink from one nozzle, and the plurality of lines L correspond one-to-one with a plurality of nozzles of the head unit 21. Therefore, when the line L is missing or blurred, the nozzle corresponding to the line L can be specified as a defective nozzle.
The test image T is not limited to the one shown in FIG. 10, and can be any image in which the ink ejection status from each nozzle can be confirmed.

Returning to FIG. 9, the first control unit 50a causes the first image reading unit 30a to read the test image T, and based on the reading result, identifies the defective nozzle of the first ink ejection unit 20a by the above-mentioned method. (Step S302).

When a defective nozzle is detected (“YES” in step S303), the first control unit 50a generates the first alternative ejection information 541 for causing the second image forming apparatus 1b to perform the alternative ejection. (Step S304).

When the process of step S304 is completed, or when it is determined that the defective nozzle is not detected in step S303 (“NO” in step S303), the first control unit 50a is the first reversing unit 40a. The front and back of the recording medium M are inverted and sent to the second image forming apparatus 1b (step S305).

When the recording medium M is delivered, the second control unit 50b of the second image forming apparatus 1b forms the test image T with respect to the second surface of the recording medium M based on the image data of the test image T (. Step S306).

The second control unit 50b causes the second image reading unit 30b to read the test image T, and based on the reading result, identifies the defective nozzle of the second ink ejection unit 20b by the method described above (step S307). ..

When a defective nozzle is detected (“YES” in step S308), the second control unit 50b generates the second alternative ejection information 542 for causing the first image forming apparatus 1a to perform the alternative ejection. (Step S309).

If it is determined that the defective nozzle is not detected in step S309 or if it is determined in step S308 (“NO” in step S308), the second control unit 50b ends the alternative discharge setting process.
It should be noted that, before step S304, it may be determined whether or not the alternative discharge execution condition is satisfied, and the first alternative discharge information 541 may be generated in step S304 only when the alternative discharge execution condition is satisfied. Further, before step S309, it may be determined whether or not the alternative discharge execution condition is satisfied, and the second alternative discharge information 542 may be generated in step S309 only when the alternative discharge execution condition is satisfied.

The first alternative discharge information 541 and the second alternative discharge information 542 generated in the alternative discharge setting process are shared by the first image forming apparatus 1a and the second image forming apparatus 1b. That is, the first alternative ejection information 541 generated by the first image forming apparatus 1a is transmitted to the second image forming apparatus 1b, and the second alternative ejection information 542 generated by the second image forming apparatus 1b. Is transmitted to the first image forming apparatus 1a.
The alternative discharge setting process is performed for each of the four colors Y, M, C, and K. Alternatively, a test image T for four colors may be formed on one recording medium M, and alternative ejection setting processing may be performed for the four colors in parallel.

As described above, in the present embodiment, the defective nozzles of the first image forming apparatus 1a and the second image forming apparatus 1b are identified in advance using the test image T, and the first alternative ejection information 541 and the second alternative are used. Discharge information 542 is generated. Then, in normal image formation, the ejection failure caused by the defective nozzle of the first image forming apparatus 1a is supplemented by the alternative ejection by the second image forming apparatus 1b, and the ejection defect caused by the defective nozzle of the second image forming apparatus 1b is complemented. The ejection failure to be performed is supplemented by the alternative ejection by the first image forming apparatus 1a.
That is, when the ejection failure region r2 is detected in the image formed on the second surface, the second control unit 50b of the second image forming apparatus 1b of the present embodiment uses the first image forming apparatus 1a. The second alternative discharge information 542 for causing the alternative discharge is generated and transmitted to the first image forming apparatus 1a. Specifically, the second alternative ejection information 542 is the first image forming apparatus 1a with respect to the alternative ejection region R2 (second alternative ejection region) including the region corresponding to the ejection defective region r2 on the recording medium M. This is information for causing the first ink ejection unit 20a of the above to perform alternative ejection of ink.
In the following, when any one of the combination of the "discharge defective region r1 and the alternative discharge region R1" and the combination of the "discharge defective region r2 and the alternative discharge region R2" is referred to, the "discharge defective region r and the alternative discharge region r" are referred to. It is written as "R".

Here, in the present embodiment, since the defective nozzle is specified before the execution of the normal image formation, the ejection defective region r itself corresponding to the defective nozzle is used as the alternative ejection region R as in the first embodiment. In addition to the mode of performing the alternative discharge, it is also possible to perform the alternative discharge to the alternative discharge region R including the discharge defective region r and wider than the discharge defective region r. In the following, an example of making the alternative discharge region R wider than the discharge defective region r will be described.

FIG. 11 is a diagram illustrating alternative ejection by the second image forming apparatus 1b for compensating for the ejection defect of the first image forming apparatus 1a.
FIG. 11 shows an alternative discharge related to an image of a color in which a discharge defect is detected among Y, M, C, and K.
FIG. 11A shows a first image formed on the first surface of the recording medium M by the first image forming apparatus 1a in which a defective nozzle is detected. Here, ink is not ejected to the alternative ejection region R1 including the region corresponding to the ejection failure region r1, and an image is formed in the region excluding the alternative ejection region R1.

The alternative ejection region R1 can be, for example, an region corresponding to a sub-nozzle group G, that is, one head module 211M, which includes the specified defective nozzle and whose ink ejection positions in the X direction are adjacent to each other.
In order to perform such control, the first alternative discharge information 541 includes information for identifying the head module 211M including the defective nozzle. The first control unit 50a is a nozzle of the head module 211M excluding the head module 211M specified by the first alternative ejection information 541 among the first nozzle group of the head unit 21 by the first ink ejection unit 20a. Ink is ejected from.

Further, the second control unit 50b of the second image forming apparatus 1b has a head whose ink ejection position corresponds to the head module 211M specified by the first alternative ejection information 541 among the second ink ejection units 20b. Alternative ejection is performed by the module 211M.
FIG. 11B shows a partial image formed in the alternative discharge region R1 by this alternative discharge. A partial image of FIG. 11B is formed on the first surface of the recording medium M by superimposing it on the first image of FIG. 11A, so that ejection failure is performed as shown in FIG. 11C. A first image complemented with is formed.

FIG. 12 is a diagram illustrating alternative ejection by the first image forming apparatus 1a for compensating for the ejection defect of the second image forming apparatus 1b.
Similarly in this case, the alternative ejection region R2 is defined as a region corresponding to the sub-nozzle group G, that is, one head module 211M, in which the ink ejection positions in the X direction include the specified defective nozzles and are adjacent to each other. .. In order to perform such control, the second alternative ejection information 542 includes information identifying the head module 211M including the defective nozzle.

When the ejection defect of the second image forming apparatus 1b is supplemented by the alternative ejection by the first image forming apparatus 1a, the substitution by the first image forming apparatus 1a is performed prior to the image forming by the second image forming apparatus 1b. Discharge is performed. This is because in the image forming system 100, the first image forming apparatus 1a is located on the upstream side of the second image forming apparatus 1b.

That is, as shown in FIG. 12A, first, the first control unit 50a of the first image forming apparatus 1a is specified by the second alternative ejection information 542 of the first ink ejection unit 20a. Alternative ejection is performed by the head module 211M whose ink ejection position corresponds to that of the head module 211M. As a result, a partial image is formed in the alternative discharge region R2.

Next, as shown in FIG. 12B, the second control unit 50b of the second image forming apparatus 1b is
The second ink ejection unit 20b ejects ink from the nozzles of the head module 211M excluding the head module 211M specified by the second alternative ejection information 542 in the second nozzle group of the head unit 21. As a result, the second image is formed in the region excluding the alternative discharge region R2.
As shown in FIG. 12 (c), ejection failure is caused by forming the second image of FIG. 12 (b) on the second surface of the recording medium M by superimposing it on the partial image of FIG. 12 (a). A second image complemented by is formed.

FIG. 13 is a diagram showing a control procedure of the image forming process in the second embodiment.
In the flowchart, steps S401 to S407 and S409 are executed by the first control unit 50a of the first image forming apparatus 1a, and steps S408 and S410 to S413 are executed by the second control unit 50b of the second image forming apparatus 1b. Is executed by.

When the image forming process is started, the first control unit 50a of the first image forming apparatus 1a generates the first alternative ejection information 541 in the alternative ejection setting process, and satisfies the alternative ejection execution execution condition. Whether or not it is determined (step S401).

When the first alternative discharge information 541 is generated and it is determined that the alternative discharge execution condition is satisfied (“YES” in step S401), the first control unit 50a uses the first alternative discharge information. By supplying the image data 543 of the first image to the head module 211M excluding the head module 211M specified in 541, the first surface of the recording medium M is the region excluding the alternative ejection region R1. The image of 1 is formed (step S402).

When it is determined that the first alternative discharge information 541 is not generated or the alternative discharge execution condition is not satisfied (“NO” in step S401), the first control unit 50a is the recording medium M. A first image is formed on the first surface by using all the head modules 211M (step S403).

When the step S402 or S403 is completed, the first control unit 50a inverts the front and back of the recording medium M by the first inversion unit 40a (step S404).

The first control unit 50a determines whether or not the second alternative discharge information 542 is generated in the alternative discharge setting process and the alternative discharge execution condition is satisfied (step S405). When the second alternative discharge information 542 is generated and it is determined that the alternative discharge execution condition is satisfied (“NO” in step S405), the first control unit 50a is the first transfer unit 10a. Of these, the image data 543 of the second image is recorded by supplying the image data 543 of the second image to the head module 211M and the head module 211M of the second image forming apparatus 1b specified by the second alternative ejection information 542. Alternate ejection is executed for the alternative ejection region R2 on the second surface of the medium M (step S406).
After that, the first control unit 50a causes the second image forming apparatus 1b to send out the recording medium M (step S407).

When the recording medium M is delivered, the second control unit 50b of the second image forming apparatus 1b is second to the head module 211M excluding the head module 211M specified in the second alternative ejection information 542. By supplying the image data 543 of the image, the second image is formed in the region of the second surface of the recording medium M excluding the alternative ejection region R2 (step S408).

On the other hand, if it is determined in step S405 that the second alternative discharge information 542 is not generated or the alternative discharge execution condition is not satisfied (“NO” in step S405), the first control unit 50a , The recording medium M is sent out to the second image forming apparatus 1b (step S409).

When the recording medium M is delivered, the second control unit 50b of the second image forming apparatus 1b causes the second surface of the recording medium M to form a second image using all the head modules 211M (the second control unit 50b). Step S410).

When the process of step S408 or S410 is completed, the second control unit 50b determines whether or not the first alternative discharge information 541 is generated and the alternative discharge execution condition is satisfied (step S411). When the first alternative discharge information 541 is generated and it is determined that the alternative discharge execution condition is satisfied (“YES” in step S411), the second control unit 50b is the second inversion unit 40b. The front and back of the recording medium M are inverted and placed on the transport belt 11 again (step S412). Further, the second control unit 50b has image data 543 of the first image with respect to the head module 211M of the first image forming apparatus 1a specified in the first alternative discharge information 541 and the head module 211M corresponding to the head module 211M. Is supplied to the alternative ejection region R1 on the first surface of the recording medium M to execute the alternative ejection (step S413).
When the process of step S413 is completed, or when it is determined in step S411 that the first alternative discharge information 541 is not generated or the alternative discharge execution condition is not satisfied (“NO” in step S411), The second control unit 50b ends the image forming process.
The image forming process of FIG. 13 is performed in parallel for each of the colors Y, M, C, and K. As a result, the four-color images are superimposed on one recording medium M to form a color image.

FIG. 14 is a diagram showing an image forming process in the image forming process of FIG.
As shown in the first stage of FIG. 14, in step S402, the first image forming apparatus 1a forms a first image on the first surface in a region other than the alternative ejection region R1.
As shown in the second stage of FIG. 14, in step S406, alternative ejection is performed with respect to the alternative ejection region R2 on the second surface by the first image forming apparatus 1a.
As shown in the third stage of FIG. 14, in step S408, a second image is formed on the second surface by the second image forming apparatus 1b with respect to the region excluding the alternative discharge region R2. This completes the second image on the second surface.
As shown in the fourth stage of FIG. 14, in step S413, the second image forming apparatus 1b performs alternative ejection to the alternative ejection region R1 on the first surface. As a result, the first image of the first surface is completed.

As described above, in the image forming system 100 according to the second embodiment, the second image forming apparatus 1b reads the image formed on the recording medium M by the ink ejection by the second ink ejection unit 20b. It has an image reading unit 30b of. Further, the first control unit 50a has a ejection defect in which ink is not normally ejected due to the inclusion of defective nozzles in the first nozzle group in the image read by the first image reading unit 30a. When the region r1 is detected, the second ink ejection unit 20b causes alternative ejection of ink to the alternative ejection region R1 including the region corresponding to the ejection failure region r1 on the recording medium M. The alternative ejection information 541 of 1 is generated, and the second control unit 50b causes the alternative ejection region R1 to perform alternative ejection by the second ink ejection unit 20b based on the first alternative ejection information 541. Further, the second control unit 50b has a ejection defect in which ink is not normally ejected due to the inclusion of defective nozzles in the second nozzle group in the image read by the second image reading unit 30b. When the region r2 is detected, the first ink ejection unit 20a causes alternative ejection of ink to the alternative ejection region R2 including the region corresponding to the ejection failure region r2 on the recording medium M. The alternative ejection information 542 of 2 is generated, and the first control unit 50a causes the alternative ejection region R2 to perform alternative ejection by the first ink ejection unit 20a based on the second alternative ejection information 542. Thereby, the ejection defect generated in one of the first image forming apparatus 1a and the second image forming apparatus 1b can be supplemented by the alternative ejection by the other. Therefore, it is possible to further reduce the occurrence of waste paper. Further, the frequency of replacement of parts such as the head module 211M can be further suppressed.

Further, the first alternative ejection information 541 is information specifying the head module 211M including the defective nozzle, which is a part of the first nozzle group (information specifying the sub-nozzle group G in which the ink ejection positions are adjacent to each other. ) Is included, and in image formation after the first alternative ejection information 541 is generated, the first control unit 50a is subjected to the first alternative ejection of the first nozzle group by the first ink ejection unit 20a. Ink is ejected from the sub-nozzle group G of the head module 211M excluding the head module 211M specified by the information 541, and the second control unit 50b is based on the first alternative ejection information 541 of the second nozzle group. Alternative ejection is performed by the sub-nozzle group G of the head module 211M whose ink ejection position corresponds to the specified head module 211M. As a result, when a defective nozzle is detected in the first image forming apparatus 1a, alternative ejection can be performed by the second image forming apparatus 1b in units of the head module 211M. Further, even when a defective nozzle cannot be specified exactly, supplementation by alternative ejection can be appropriately performed.

Further, the second alternative ejection information 542 is information for specifying the head module 211M including the defective nozzle, which is a part of the second nozzle group (information for specifying the sub-nozzle group G in which the ink ejection positions are adjacent to each other. ), In the image formation after the second alternative ejection information 542 is generated, the first control unit 50a is the head module specified by the second alternative ejection information 542 in the first nozzle group. Alternative ejection is performed by the sub-nozzle group G of the head module 211M whose ink ejection position corresponds to the 211M, and the second control unit 50b is the second of the second nozzle group by the second ink ejection unit 20b. Ink is ejected from the sub-nozzle group G of the head module 211M excluding the head module 211M specified by the alternative ejection information 542. As a result, when a defective nozzle is detected in the second image forming apparatus 1b, alternative ejection can be performed by the first image forming apparatus 1a in units of the head module 211M. Further, even when a defective nozzle cannot be specified exactly, supplementation by alternative ejection can be appropriately performed.

Further, the first control unit 50a causes the alternative discharge to be performed when the predetermined alternative discharge execution condition is satisfied, and the second control unit 50b performs the alternative discharge when the predetermined alternative discharge execution condition is satisfied. Have alternative discharge performed. As a result, the alternative discharge can be performed in just proportion, and the decrease in productivity due to the execution of unnecessary alternative discharge can be suppressed.

Further, when the second alternative ejection information 542 is generated, the first control unit 50a ejects ink to the first surface of the recording medium M by the first ink ejection unit 20a, and then ejects the ink. The front and back sides of the recording medium M are inverted by the first inversion unit 40a, and the first ink ejection unit 20a causes alternative ejection to the second surface on the side opposite to the first surface of the recording medium M. As a result, in the first image forming apparatus 1a, alternative ejection to the alternative ejection region R2 on the second surface can be performed.

Further, in the image forming method of the present embodiment, in the image read by the first image reading unit 30a, ink is not normally ejected due to the inclusion of defective nozzles in the first nozzle group. When a defective region r1 is detected, the second ink ejection unit 20b causes alternative ejection of ink to the alternative ejection region R1 including the region corresponding to the ejection defective region r1 on the recording medium M. A step of generating the first alternative ejection information 541, a step of causing the alternative ejection region R1 to perform alternative ejection by the second ink ejection unit 20b based on the first alternative ejection information 541, and a second. In the second image read by the image reading unit 30b, the ejection defective region r2 in which the ink is not ejected normally due to the inclusion of the defective nozzle in the nozzle of the second ink ejection unit 20b is detected. In this case, the second alternative ejection information for causing the first ink ejection unit 20a to perform alternative ejection of ink to the alternative ejection region R2 including the region corresponding to the ejection failure region r2 on the recording medium M. A step of generating 542 and a step of causing the alternative ejection region R2 to perform alternative ejection by the first ink ejection unit based on the second alternative ejection information 542 are included. Thereby, the ejection defect generated in one of the first image forming apparatus 1a and the second image forming apparatus 1b can be supplemented by the alternative ejection by the other. Therefore, it is possible to further reduce the occurrence of waste paper. Further, the frequency of replacement of parts such as the head module 211M can be further suppressed.

(Modification 2-1)
Next, a modification 2-1 of the second embodiment will be described.
In FIGS. 13 and 14, when a defective nozzle is detected in the second image forming apparatus 1b, the second image forming apparatus 1a performs alternative ejection to the alternative ejection region R2, and then the second image forming apparatus 1a. The image forming apparatus 1b ejects ink to the remaining region to form a second image, but the following method may be used instead.
That is, when a defective nozzle is detected in the second image forming apparatus 1b, the first image forming apparatus 1a forms the entire second image with respect to the second surface. As a result, the ejection failure region r2 included in the alternative ejection region R2 is complemented by the first image forming apparatus 1a. However, when the first image forming apparatus 1a has a defective nozzle and the first alternative ejection information 541 is generated, the portion corresponding to the alternative ejection region R1 in the second image on the second surface Since the ink is not ejected, the alternative ejection region R1 is ejected by the second image forming apparatus 1b.

FIG. 15 is a flowchart showing a control procedure of the image forming process in the modified example 2-1.
The flowchart of FIG. 15 corresponds to a flow chart of FIG. 13 in which step S406 is changed to step S406a, step S408 is deleted, and steps S414 to 417 are added. Hereinafter, the differences from the flowchart of FIG. 13 will be described.

When the second alternative discharge information 542 is generated in step S405 and it is determined that the alternative discharge execution condition is satisfied (“YES” in step S405), the first control unit 50a is the recording medium. A second image is formed on the second surface of M (step S406a). Specifically, when it is determined in step S401 that the first alternative discharge information 541 is generated, the first control unit 50a uses the head module 211M specified in the first alternative discharge information 541. By supplying the image data 543 of the second image to the removed head module 211M, the second image is formed in the region of the second surface of the recording medium M excluding the alternative ejection region R1. Further, when it is determined in step S401 that the first alternative discharge information 541 is not generated, the first control unit 50a causes all the head modules 211M with respect to the second surface of the recording medium M. Used to form a second image.

The second control unit 50b of the second image forming apparatus 1b determines that the recording medium M is delivered, the first alternative ejection information 541 is generated in step S411, and the alternative ejection execution condition is satisfied. In this case (“YES” in step S411), the second image is taken with respect to the head module 211M of the first image forming apparatus 1a and the corresponding head module 211M specified in the first alternative ejection information 541. By supplying the image data 543, the alternative ejection is executed for the alternative ejection region R1 on the second surface of the recording medium M (step S414). After that, the second control unit 50b inverts the recording medium M (step S412) and causes the alternative discharge region R1 on the first surface to execute the alternative discharge (step S413).

On the other hand, if it is determined in step S405 that the second alternative discharge information 542 is not generated or does not satisfy the alternative discharge execution condition (“NO” in step S405), the procedure is the same as in FIG. Processing proceeds. That is, the recording medium M is sent to the second image forming apparatus 1b (step S409), and the second image forming apparatus 1b forms the second image on the entire second surface (step S410). Further, when the first alternative discharge information 541 is generated and the alternative discharge execution condition is satisfied (“YES” in step S415), the front and back of the recording medium M are reversed (step S416), and the recording medium is recorded. Alternative ejection is executed by the second image forming apparatus 1b with respect to the alternative ejection region R1 on the first surface of M (step S417). The processing of steps S415 to S417 is the same as the processing of steps S411 to S413 of FIG.

When the processing of step S413 or step S417 is completed, or when it is determined in steps S411 and S415 that the first alternative discharge information 541 is not generated or the alternative discharge execution condition is not satisfied (step S411). , S415 “NO”), the second control unit 50b ends the image forming process.

16 and 17 are diagrams showing an image forming process in the image forming process of FIG.
Of these, FIG. 16 is a diagram showing an image forming process when all of steps S401, S405 and S411 are branched to “YES”.
As shown in the first stage of FIG. 16, in step S402, the first image forming apparatus 1a forms a first image on the first surface in a region other than the alternative ejection region R1.
As shown in the second stage of FIG. 16, in step S406a, a second image is formed on the second surface by the first image forming apparatus 1a with respect to the region other than the alternative discharge region R1. At this time, since the ink is ejected to the alternative ejection region R2 (see FIG. 14) on the second surface, the alternative ejection for compensating for the ejection failure of the second image forming apparatus 1b is completed.
As shown in the third stage of FIG. 16, in step S414, the second image forming apparatus 1b performs alternative ejection to the alternative ejection region R1 on the second surface. This completes the second image on the second surface.
As shown in the fourth stage of FIG. 16, in step S413, the second image forming apparatus 1b performs alternative ejection to the alternative ejection region R1 on the first surface. As a result, the first image of the first surface is completed.

FIG. 17 is a diagram showing an image forming process when the image is branched into “YES” in step S401, “NO” in S405, and “YES” in S411.
As shown in the first stage of FIG. 17, in step S402, the first image forming apparatus 1a forms a first image on the first surface in a region other than the alternative ejection region R1.
As shown in the second stage of FIG. 17, in step S410, the entire second image is formed with respect to the second surface by the second image forming apparatus 1b.
As shown in the third stage of FIG. 17, in step S417, the second image forming apparatus 1b performs alternative ejection to the alternative ejection region R1 on the first surface. As a result, the first image of the first surface is completed.

(Modification 2-2)
Next, a modification 2-2 of the second embodiment will be described. This modification may be combined with the modification 2-1.
In the second embodiment, the alternative ejection is performed with the head module 211M including the defective nozzle as a unit, but instead, the alternative ejection may be performed with the head unit 21 as a unit.

In order to perform such alternative ejection, the first alternative ejection information 541 is a head unit 21 having a defective nozzle among a plurality of head units 21 possessed by the first ink ejection unit 20a of the first image forming apparatus 1a. Contains information that identifies.
Further, in the image formation after the first alternative ejection information 541 is generated, the first control unit 50a of the first image forming apparatus 1a is the head unit 21 of the plurality of head units 21 due to the first ink ejection unit 20a. Of these, ink is ejected from the remaining head units 21 excluding the head unit 21 specified by the first alternative ejection information 541, and the second control unit 50b of the second image forming apparatus 1b is a plurality of head units 21. Of these, the head unit 21 that ejects ink of the same color as the head unit 21 specified by the first alternative ejection information 541 causes the alternative ejection to be performed.
As a result, when a defective nozzle is detected in the first image forming apparatus 1a, alternative ejection can be performed by the second image forming apparatus 1b with the head unit 21 as a unit. By using the head unit 21 as a unit, images of the same color are formed by the same image forming apparatus 1, so that deterioration of image quality due to displacement of ejection positions in images of the same color can be suppressed. Can be done.

Similarly, the second alternative ejection information 542 includes information for identifying the head unit 21 having a defective nozzle among the plurality of head units 21 included in the second ink ejection unit 20b of the second image forming apparatus 1b.
Further, in the image formation after the second alternative ejection information 542 is generated, the first control unit 50a of the first image forming apparatus 1a uses the second alternative ejection information 542 among the plurality of head units. An alternative ejection is performed by a head unit that ejects ink of the same color as the specified head unit, and the first control unit 50a of the second image forming apparatus 1b has a plurality of ink ejection units 20b. Ink is ejected from the remaining head units of the head units excluding the head unit specified by the second alternative ejection information 542.
As a result, when a defective nozzle is detected in the second image forming apparatus 1b, alternative ejection can be performed by the first image forming apparatus 1a with the head unit 21 as a unit. By using the head unit 21 as a unit, images of the same color are formed by the same image forming apparatus 1, so that deterioration of image quality due to displacement of ejection positions in images of the same color can be suppressed. Can be done.

(Modification 2-3)
Next, Modifications 2-3 of the second embodiment will be described. This modification may be combined with the modification 2-1.
In this modification, as in the first embodiment, ink ejection from the identified defective nozzle is stopped, and alternative ejection is performed by the nozzle corresponding to the ink ejection position in the other image forming apparatus 1. ..

That is, the first alternative ejection information 541 includes information for identifying a defective nozzle of the first nozzle group possessed by the head unit 21 of the first ink ejection unit 20a, and is a second image forming apparatus 1b. The control unit 50b causes the head unit 21 of the second ink ejection unit 20b to perform alternative ejection by using a nozzle whose ink ejection position corresponds to that of the defective nozzle of the first ink ejection unit 20a among the second nozzle group. ..
Further, the second alternative ejection information 542 includes information for identifying a defective nozzle of the second nozzle group possessed by the head unit 21 of the second ink ejection unit 20b, and is the first of the first image forming apparatus 1a. The control unit 50a causes the head unit 21 of the first ink ejection unit 20a to perform alternative ejection by using a nozzle whose ink ejection position corresponds to that of the defective nozzle of the second ink ejection unit 20b among the first nozzle group. ..
As a result, alternative ejection can be performed with the minimum required nozzles.

(Modification 2-4)
Next, a modification 2-4 of the second embodiment will be described. This modification may be combined with the modification 2-1.
In this modification, the same image data as the partial image data 544 for the alternative discharge is directly generated as the first alternative discharge information 541 and the second alternative discharge information 542. This modification corresponds to the modification 1-1 of the first embodiment.

That is, the first alternative ejection information 541 of this modification is partial image data including a portion corresponding to the alternative ejection region R1 in the image data of the image to be formed, and is the second image forming apparatus 1b. The control unit 50b of the above causes the second ink ejection unit 20b to eject ink based on the partial image data to perform alternative ejection.
Further, the second alternative ejection information 542 is partial image data including a portion corresponding to the alternative ejection region R2 in the image data of the image to be formed, and is the first control unit 50a of the first image forming apparatus 1a. Is to eject ink to the first ink ejection unit 20a based on the partial image data to perform alternative ejection.
According to this, it is possible to reduce the process of data processing for alternative discharge.

The present invention is not limited to the above embodiment and each modification, and various modifications can be made.
For example, in the above embodiment, a plurality of head modules 211M are arranged in a houndstooth pattern in the head unit 21, but instead, the recording heads 211 are arranged in a houndstooth pattern. May be. In this case, alternative ejection may be performed using the recording head 211 as a unit.
Further, the head unit 21 may be configured to have a single recording head 211 or a single head module 211M.

Further, in the above embodiment, the nozzle group provided in one head module 211M is exemplified as the "secondary nozzle group", but the present invention is not limited to this. The sub-nozzle group may be a part of a predetermined number of nozzles including defective nozzles and whose ink ejection positions are adjacent to each other, that is, a plurality of nozzles included in the head module 211M.

Further, in the above embodiment, the example in which the image is formed on both sides of the recording medium M has been described, but the present invention is not limited to this, and the image may be formed only on one side (first surface) of the recording medium M. The alternative ejection in this case is performed only by the second image forming apparatus 1b. That is, when a defective nozzle is detected in the first image forming apparatus 1a and the first alternative ejection information 541 is generated, after the first image forming apparatus 1a forms an image on the first surface, the first image is formed. The recording medium M is sent to the second image forming apparatus 1b without being inverted by the inversion unit 40a of 1, and the second image forming apparatus 1b performs alternative ejection to the first surface.

Further, in the above embodiment, the description has been made using an example in which the content of the alternative discharge execution condition is set by the user, but the present invention is not limited to this, and whether or not to execute the alternative discharge based on the fixed alternative discharge execution condition is performed. A determination may be made.

Further, in the above embodiment, the alternative discharge is performed only when the alternative discharge execution condition is satisfied, but the present invention is not limited to this, and the alternative discharge may always be performed when a discharge defect is detected.

Further, in the above embodiment, the example in which the recording medium M is transported by the transport unit 10 provided with the transport belt 11 has been described, but the purpose is not limited to this, and the transport unit 10 is, for example, the outer periphery of the rotating transport drum. The recording medium M may be held and conveyed on the surface.

Although some embodiments of the present invention have been described, the scope of the invention is not limited to the embodiments described above, but includes the scope of the invention described in the claims and the equivalent scope thereof. ..

1a First image forming device 1b Second image forming device 2 Feeding section 3 Paper ejection section 10a First transport section 10b Second transport section 11 Transport belt 12 Transport roller 13 Transport drive section 14 Medium detection section 15 Rotary Encoder 20a First ink ejection unit 20b Second ink ejection unit 21, 21Y, 21M, 21C, 21K Head unit 21a Support plate 211 Recording head 211M Head module 212 Recording head driving unit 30a First image reading unit 30b Second Image reading unit 40a First reversing unit 40b Second reversing unit 41 Roller pair 42 Reversing path 43 Return path 44 Roller driving unit 50a First control unit 50b Second control unit 51 CPU
52 RAM
53 ROM
54 Storage unit 541 First alternative discharge information 542 Second alternative discharge information 543 Image data 544 Partial image data 61 Image processing unit 62 Operation display unit (input unit, display unit)
621 Alternative ejection setting screen 63 Communication unit 64 Bus 100 Image formation system G Sub-nozzle group M Recording medium N Nozzle R1 Alternative ejection area (first alternative ejection area)
R2 alternative discharge area (second alternative discharge area)
r1 Discharge failure area (first discharge failure area)
r2 Discharge failure area (second discharge failure area)
T-test image

Claims (19)

An image forming system including a first image forming apparatus and a second image forming apparatus.
The first image forming apparatus is
A first ink ejection unit having a first nozzle group and ejecting ink from the first nozzle group to a recording medium,
A first image reading unit that reads an image formed on a recording medium by ejecting ink by the first ink ejection unit, and a first image reading unit.
The first control unit and
Have,
The second image forming apparatus is
A second ink ejection unit having a second nozzle group and ejecting ink from the second nozzle group to a recording medium delivered from the first image forming apparatus.
The second control unit and
Have,
The first control unit is the first in which ink is not normally ejected due to the inclusion of defective nozzles in the first nozzle group in the image read by the first image reading unit. When a ejection failure region is detected, the ink alternative ejection by the second ink ejection unit is performed on the recording medium with respect to the first alternative ejection region including the region corresponding to the first ejection failure region. Generate a first alternative discharge information to be done,
The second control unit is an image forming system that causes the second ink ejection unit to perform the alternative ejection to the first alternative ejection region based on the first alternative ejection information. The second control unit claims that the second ink ejection unit performs the alternative ejection to the first alternative ejection region on the recording medium in which the first ejection failure region is detected. Item 1. The image forming system according to item 1. The first alternative ejection information includes information for identifying the defective nozzle of the first nozzle group.
According to claim 1 or 2, the second control unit causes the alternative ejection to be performed by a nozzle of the second nozzle group whose ink ejection position corresponds to the defective nozzle of the first ink ejection unit. The image forming system described. The first alternative ejection information includes information that is composed of a part of the first nozzle group and identifies a sub-nozzle group that includes the defective nozzle and whose ink ejection positions are adjacent to each other.
In the image formation after the first alternative discharge information is generated,
The first control unit ejects ink from the nozzles of the first nozzle group excluding the sub-nozzle group specified by the first alternative ejection information by the first ink ejection unit.
The second control unit causes the second nozzle group to perform the alternative ejection by the sub-nozzle group whose ink ejection position corresponds to the sub-nozzle group specified by the first alternative ejection information. The image forming system according to claim 1. The first ink ejection unit has a plurality of first head units that eject inks of different colors from the nozzles.
The second ink ejection unit has a plurality of second head units that eject ink of the same color as each of the plurality of first head units from a nozzle.
The first alternative discharge information includes information for identifying a head unit having the defective nozzle among the plurality of first head units.
In the image formation after the first alternative discharge information is generated,
The first control unit uses the first ink ejection unit to ink from the remaining head units of the plurality of first head units excluding the head unit specified by the first alternative ejection information. Is discharged,
The second control unit performs the alternative ejection by the head unit that ejects ink of the same color as the head unit specified by the first alternative ejection information among the plurality of second head units. The image forming system according to claim 1. The first alternative ejection information is partial image data including a portion corresponding to the first alternative ejection region in the image data of the image to be formed.
The image forming system according to claim 1 or 2, wherein the second control unit causes the second ink ejection unit to eject ink based on the partial image data to perform the alternative ejection. The image forming system according to any one of claims 1 to 6, wherein the second control unit performs the alternative discharge when a predetermined alternative discharge execution condition is satisfied. The first image forming apparatus has an inversion portion that inverts the front and back of the recording medium.
The first ink ejection unit of the first image forming apparatus ejects ink to the first surface of the recording medium.
In the second ink ejection unit of the second image forming apparatus, a recording medium whose front and back sides are reversed by the inversion portion after the ink is ejected by the first ink ejection unit is delivered from the first image forming apparatus. In this case, ink is ejected to the second surface opposite to the first surface, and after the ink is ejected by the first ink ejection portion, the front and back sides are recorded without being inverted by the inversion portion. When the medium is delivered from the first image forming apparatus, ink is ejected to the first surface.
Any of claims 1 to 7, wherein when the first control unit generates the first alternative ejection information, the recording medium is sent to the second image forming apparatus without being inverted by the inversion unit. The image forming system according to claim 1. The second image forming apparatus has a second image reading unit that reads an image formed on a recording medium by ejecting ink by the second ink ejection unit.
In the image read by the second image reading unit, the second control unit is not ejected ink normally due to the inclusion of defective nozzles in the second nozzle group. When a ejection failure region is detected, the ink alternative ejection by the first ink ejection unit is performed on the recording medium with respect to the second alternative ejection region including the region corresponding to the second ejection failure region. Generate a second alternative discharge information to be done,
The first control unit according to claim 1, wherein the first control unit causes the first ink ejection unit to perform the alternative ejection to the second alternative ejection region based on the second alternative ejection information. Image formation system. The second alternative ejection information includes information for identifying the defective nozzle of the second nozzle group.
The ninth aspect of the present invention, wherein the first control unit causes the alternative ejection to be performed by a nozzle of the first nozzle group whose ink ejection position corresponds to the defective nozzle of the second ink ejection unit. Image formation system. The second alternative ejection information includes information for identifying a sub-nozzle group including the defective nozzle and having ink ejection positions adjacent to each other, which is a part of the second nozzle group.
In the image formation after the second alternative discharge information is generated,
The first control unit causes the alternative nozzle group to perform the alternative ejection by the sub-nozzle group whose ink ejection position corresponds to the sub-nozzle group specified by the second alternative ejection information among the first nozzle group.
The second control unit ejects ink from the nozzles of the second nozzle group excluding the sub-nozzle group specified by the second alternative ejection information by the second ink ejection unit. The image forming system according to claim 9. The first ink ejection unit has a plurality of first head units that eject inks of different colors from the nozzles.
The second ink ejection unit has a plurality of second head units that eject ink of the same color as each of the plurality of first head units from a nozzle.
The second alternative discharge information includes information for identifying a head unit having the defective nozzle among the plurality of second head units.
In the image formation after the second alternative discharge information is generated,
The first control unit performs the alternative ejection by the head unit that ejects ink of the same color as the head unit specified by the second alternative ejection information among the plurality of first head units. Let me,
The second control unit uses the second ink ejection unit to ink from the remaining head units of the plurality of second head units excluding the head unit specified by the second alternative ejection information. 9. The image forming system according to claim 9. The second alternative ejection information is partial image data including a portion corresponding to the second alternative ejection region in the image data of the image to be formed.
The image forming system according to claim 9, wherein the first control unit causes the first ink ejection unit to eject ink based on the partial image data to perform the alternative ejection. The image forming system according to any one of claims 9 to 13, wherein the first control unit performs the alternative discharge when a predetermined alternative discharge execution condition is satisfied. The first image forming apparatus has an inversion portion that inverts the front and back of the recording medium.
The first ink ejection unit of the first image forming apparatus ejects ink to the first surface of the recording medium.
When the second alternative ejection information is generated, the first control unit ejects ink to the first surface of the recording medium by the first ink ejection unit, and then reverses the ink. Claims 9 to 14 in which the front and back sides of the recording medium are inverted by the unit, and the alternative ejection is performed by the first ink ejection unit on the second surface of the recording medium opposite to the first surface. The image forming system according to any one of the above. The alternative ejection execution condition is at least one of the quality level of the formed image, the position of the defective nozzle, the color of the ink corresponding to the defective nozzle, the presence or absence of an adjacent defective nozzle, the object attribute of the formed image, and the resolution of the formed image. The image forming system according to claim 7 or 14, which relates to a unit. An input unit that accepts an input operation for setting the alternative discharge execution condition,
A display unit that displays the alternative discharge execution conditions and
The image forming system according to any one of claims 7, 14 and 16. It has a first nozzle group, and is formed on a recording medium by a first ink ejection unit that ejects ink from the first nozzle group to a recording medium and ink ejection by the first ink ejection unit. A first image forming apparatus having a first image reading unit for reading an image, and a first image forming apparatus.
A second image forming apparatus having a second nozzle group and having a second ink ejection portion for ejecting ink from the second nozzle group with respect to the recording medium delivered from the first image forming apparatus. It is an image formation method by an image formation system equipped with
In the image read by the first image reading unit, when a first ejection defective region in which ink is not ejected normally due to the inclusion of defective nozzles in the first nozzle group is detected. First alternative for causing the second ink ejection unit to perform alternative ejection of ink to the first alternative ejection region including the region corresponding to the first ejection defective region on the recording medium. The process of generating discharge information and
A step of causing the second ink ejection unit to perform the alternative ejection to the first alternative ejection region based on the first alternative ejection information.
Image forming method including. The second image forming apparatus has a second image reading unit that reads an image formed on a recording medium by ejecting ink by the second ink ejection unit.
The image formation method is
In the image read by the second image reading unit, there is a second ejection defective region in which ink is not ejected normally due to the inclusion of a defective nozzle in the nozzle of the second ink ejection unit. When detected, in order to cause the first ink ejection unit to perform alternative ejection of ink to the second alternative ejection region including the region corresponding to the second ejection failure region on the recording medium. The process of generating the second alternative discharge information and
A step of causing the first ink ejection unit to perform the alternative ejection to the second alternative ejection region based on the second alternative ejection information.
18. The image forming method according to claim 18.

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