Printing device and printing method

Abstract

To suppress a reduction in printing speed caused by an increase in number of passes.SOLUTION: A printer performs printing by combining conveyance of a printing medium by a conveyance part and main scanning in which a printing head discharges ink on the basis of printing data with a scan part moving. The control part executes printing by: calculating, on the basis of a positional relation in a conveyance direction between defective nozzles and normal nozzles included in a nozzle array, a possible complementary conveyance amount capable of complementing no ink discharge by the defective nozzles with discharge of ink by the normal nozzles in a relation between one main scanning and the other main scanning with conveyance therebetween, which is a conveyance amount per conveyance by the conveyance part, for each nozzle array by nozzle array position; determining a common conveyance amount for nozzle arrays by nozzle array position; and employing the determined common conveyance amount as the conveyance amount per conveyance by the conveyance part.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a printing apparatus and a printing method. [Background technology]

[0002] In an inkjet printer, if the ink thickens in the nozzles of the print head or if air bubbles or dust get into the nozzles, the nozzles become clogged and cannot eject ink properly, which makes them defective nozzles. Defective nozzles result in missing dots in the printed output.

[0003] There is known a technique for compensating for missing prints caused by faulty nozzles with functioning nozzles. A printing device is disclosed in which each nozzle row is divided into a plurality of regions in a first direction in which the nozzles are arranged, and for each of the set regions, it is determined whether it contains a defective nozzle that is interfering with ink ejection, and the region determined to contain a defective nozzle is designated as an unused region, and printing is performed using the remaining regions after excluding the unused regions from the plurality of regions (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-215900 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the range of nozzles to be used for printing within a nozzle row is determined in order to compensate for defective nozzles with working nozzles, the nozzle range is significantly restricted, which creates the problem of an increased number of passes required to complete printing, slowing down the printing speed. [Means for solving the problem]

[0006] a scanning unit that moves the print head in a main scanning direction that intersects with the transport direction; a control unit that controls the transport unit, the print head, and the scanning unit; and a defective nozzle detection unit that detects defective nozzles that are unable to eject ink from the multiple nozzles of the print head, and the printing device performs printing on the print medium by a combination of transport by the transport unit and main scanning in which the print head ejects ink based on print data as the scanning unit moves, wherein the control unit Based on the positional relationship in the transport direction between the faulty nozzles included in the nozzle row and normal nozzles that do not correspond to the faulty nozzles, a complementable transport amount, which is a transport amount for one transport by the transport unit and which can complement the non-ejection of ink by the faulty nozzles by the ejection of ink from the normal nozzles in the relationship between one of the main scans and the other main scan that sandwich the transport, is calculated for each nozzle row by nozzle row position, and a transport amount common to the nozzle rows by nozzle row position is determined based on the complementable transport amount for each nozzle row, and the printing is performed by adopting the determined common transport amount as the transport amount for one transport by the transport unit.

[0007] a printing method for printing on a printing medium by a combination of transporting the printing medium in a transport direction, and a main scanning in which a print head having a nozzle row consisting of a plurality of nozzles capable of ejecting ink onto the printing medium at a plurality of nozzle row positions is moved in a main scanning direction intersecting the transport direction and the print head ejects ink based on print data, the method comprising: a defective nozzle detection step for detecting a defective nozzle that is unable to eject ink from the plurality of nozzles of the print head; a calculation step for calculating, for each nozzle row at a nozzle row position, a complementable transport amount which is a transport amount for one transport of the printing medium based on a positional relationship in the transport direction between the defective nozzle included in the nozzle row and a normal nozzle that is not the defective nozzle, and which is a complementable transport amount which can complement the non-ejection of ink by the defective nozzle by the ejection of ink from the normal nozzle in a relationship between one of the main scans and the other of the main scans sandwiching the transport; a determination step for determining a transport amount common to the nozzle rows at the nozzle row positions based on the complementable transport amount for each nozzle row; and a printing step for performing the printing by adopting the determined common transport amount as the transport amount for one transport. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a simplified device configuration. [Diagram 2] FIG. 4 is a diagram showing the relationship between the print medium and the horizontal array heads as viewed from above. [Diagram 3] 5 is a flowchart showing a print control process according to the first embodiment. [Figure 4] 6 is a diagram for explaining a method for determining a complementary transport amount for each nozzle row. [Diagram 5] 11A and 11B are diagrams for explaining the determination of nozzles to be used for each nozzle row according to a common carry amount. [Figure 6] FIG. 4 is a diagram showing the relationship between a print medium and vertically arranged heads as viewed from above. [Figure 7] 10 is a flowchart showing a print control process according to a second embodiment. [Figure 8] 13 is a diagram showing used nozzles and unused nozzles in a nozzle row of the smallest segment. [Figure 9] FIG. 11 is a diagram for explaining step S270 following step S260. [Figure 10] 11A and 11B are diagrams illustrating paper feeding without compensating for a defective nozzle and paper feeding for compensating for a defective nozzle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that each drawing is merely an example for explaining the present embodiment. Since each drawing is an example, the proportions and shapes may not be accurate, the drawings may not match each other, and some parts may be omitted.

[0010] 1.Device configuration: FIG. 1 shows a simplified configuration of a printing device 10 according to this embodiment. The printing device 10 includes a control unit 11, a display unit 13, an operation reception unit 14, a communication IF 15, a printing unit 16, a memory unit 22, etc. The printing unit 16 includes a transport unit 17, a carriage 18, a print head 19, a defective nozzle detection unit 21, etc. IF is an abbreviation for interface. The control unit 11 includes one or more ICs having a CPU 11a as a processor, a ROM 11b, a RAM 11c, etc., and other non-volatile memories, etc.

[0011] In the control unit 11, a processor, i.e., a CPU 11a, executes arithmetic processing according to one or more programs 12 stored in a ROM 11b or other memory, using a RAM 11c or the like as a work area, thereby controlling the printing device 10. Note that the processor is not limited to a single CPU, and may be configured to perform processing using multiple CPUs or a hardware circuit such as an ASIC, or may be configured to perform processing in cooperation with a CPU and a hardware circuit.

[0012] The display unit 13 is a means for displaying visual information, and is configured, for example, by a liquid crystal display, an organic EL display, or the like. The display unit 13 may be configured to include a display and a drive circuit for driving the display. The operation reception unit 14 is a means for receiving operations by a user, and is realized, for example, by a physical button, a touch panel, a mouse, a keyboard, or the like. Of course, the touch panel may be realized as one function of the display unit 13.

[0013] The display unit 13 and the operation reception unit 14 may be part of the configuration of the printing device 10, or may be external peripheral devices attached to the printing device 10. The communication IF 15 is a general term for one or more IFs for connecting the printing device 10 to the outside world via wired or wireless communication in compliance with a predetermined communication protocol including a known communication standard.

[0014] The printing unit 16 is a mechanism that performs printing by an inkjet method. The transport unit 17 is a means for transporting a print medium such as paper in a predetermined transport direction, and includes rollers and a motor for rotating the rollers, etc. The upstream and downstream in the transport direction are simply referred to as upstream and downstream hereinafter. The print head 19 has a plurality of nozzles 20. The print head 19 prints an image on a print medium by ejecting or not ejecting dots of ink from the nozzles 20 based on print data for printing an image with ink, generated by the control unit 11. The print head 19 is capable of ejecting ink of various colors, such as cyan (C) ink, magenta (M) ink, yellow (Y) ink, and black (K) ink. Of course, the print head 19 may also eject ink or liquid of colors other than CMYK.

[0015] The carriage 18 is a mechanism that receives power from a carriage motor (not shown) and can move back and forth along a predetermined main scanning direction. The carriage 18 corresponds to the "scanning unit." The main scanning direction intersects with the transport direction. "Intersecting" here can be understood as being perpendicular or nearly perpendicular. The carriage 18 is equipped with a print head 19. In other words, the print head 19 moves back and forth along the main scanning direction together with the carriage 18.

[0016] The storage unit 22 is configured with a storage device such as a hard disk drive or a solid state drive. The storage unit 22 may include a memory included in the control unit 11. The storage unit 22 may also be considered as a part of the control unit 11. The storage unit 22 stores various information necessary for controlling the printing device 10.

[0017] 2 shows a simplified view from above of the relationship between the print medium 30 and the print head 19. The print head 19, which is mounted on the carriage 18, moves together with the carriage 18 in the main scanning direction D1 from one end to the other end (forward movement) and from the other end to one end (return movement). FIG. 2 shows an example of the arrangement of nozzles 20 on the nozzle surface 23. The nozzle surface 23 is the bottom surface of the print head 19. Each small circle in the nozzle surface 23 is a nozzle 20.

[0018] The print head 19 is configured to receive ink of each color from a liquid holding means (not shown) called an ink cartridge or ink tank and eject the ink from the nozzles 20, and is provided with nozzle rows 26 arranged at different nozzle row positions. Fig. 2 shows an example of a print head 19 that ejects CMYK ink. The nozzle row 26 made up of nozzles 20 that eject C ink is nozzle row 26C. Similarly, the nozzle row 26 made up of nozzles 20 that eject M ink is nozzle row 26M, the nozzle row 26 made up of nozzles 20 that eject Y ink is nozzle row 26Y, and the nozzle row 26 made up of nozzles 20 that eject K ink is nozzle row 26K.

[0019] In the example of FIG. 2, the nozzle rows 26C, 26M, 26Y, and 26K are aligned along the main scanning direction D1. The print head 19 having the nozzle rows 26 aligned along the main scanning direction D1 is also called a "horizontal array head". In the horizontal array head, the nozzle rows 26 aligned along the main scanning direction D1 are arranged at the same position in the transport direction D2. Therefore, in the horizontal array head, the nozzle row positions are different positions in the main scanning direction D1. Furthermore, the nozzle rows 26 aligned along the nozzle row positions can be called nozzle rows 26 aligned along the ink color. However, each nozzle row 26 aligned along the nozzle row positions may be a nozzle row 26K that ejects ink of the same color, specifically, all of the nozzle rows 26 eject K ink. In other words, the print head 19 may be a head that is compatible only with monochrome printing. The nozzle rows 26C, 26M, and 26Y each correspond to a "chromatic nozzle row" that ejects a chromatic ink. Furthermore, the nozzle row 26K corresponds to an "achromatic nozzle row" that ejects achromatic ink.

[0020] The nozzle row 26 is composed of a plurality of nozzles 20 with a constant or nearly constant nozzle pitch, which is the distance between the nozzles 20 in the transport direction D2. The direction in which the plurality of nozzles 20 constituting the nozzle row 26 are arranged is the nozzle row direction D3. In the example of FIG. 2, the nozzle row direction D3 is parallel to the transport direction D2. In a configuration in which the nozzle row direction D3 is parallel to the transport direction D2, the nozzle row direction D3 and the main scanning direction D1 are perpendicular to each other. However, the nozzle row direction D3 may not be parallel to the transport direction D2, and may be configured to obliquely intersect with the main scanning direction D1.

[0021] The operation of the print head 19 ejecting ink based on print data as the carriage 18 moves along the main scanning direction D1 is called a "main scan" or "pass." The printing unit 16 completes printing on the print medium 30 by combining a pass with the transport unit 17 transporting the print medium 30 in the transport direction D2.

[0022] The configuration of printing device 10 shown in FIG. 1 may be realized by a single printer, or may be realized by a plurality of devices connected to each other so as to be able to communicate with each other. That is, the printing device 10 may actually be a printing system 10. The printing system 10 includes, for example, a print control device that functions as the control unit 11 and the storage unit 22, and a printer that corresponds to the printing unit 16. The printing device 10 or printing system 10 described above realizes the printing method of the present embodiment.

[0023] The faulty nozzle detection unit 21 is a means for detecting "faulty nozzles" from among the multiple nozzles 20 of the print head 19. A faulty nozzle is a nozzle 20 that is unable to eject ink due to clogging or the like, even when ink ejection operations are performed according to print data. Inability to eject ink includes cases where ink cannot be ejected at all, as well as cases where the amount of liquid ejected is too small. It also includes cases where the amount of liquid ejected is normal, but the position where the ink lands on the print medium 30 deviates from the target position, resulting in deflected flight. A faulty nozzle may also be called an abnormal nozzle, etc. A nozzle 20 that is not a faulty nozzle is also called a "normal nozzle."

[0024] The defective nozzle detection unit 21 can employ various methods for detecting defective nozzles as long as it can determine and detect whether each nozzle 20 is defective. For example, the defective nozzle detection unit 21 employs a laser method in which the light emitter and the print head 19 are aligned so that the laser light emitted from the light emitter intersects with the ink flight path of the nozzle 20 to be inspected, and the nozzle to be inspected is determined to be defective if the light receiver cannot detect the blocking of the laser light by the dots ejected from the nozzle 20. The defective nozzle detection unit 21 may also detect defective nozzles using the method disclosed in Japanese Patent Application Laid-Open No. 2013-126776. Specifically, the defective nozzle detection unit 21 detects whether ink is ejected normally from each nozzle 20 by measuring the waveform of the residual vibration of a part of the configuration of the print head 19, such as a so-called vibration plate that bends with the deformation of a drive element (piezoelectric element) due to the application of a drive signal corresponding to print data.

[0025] The faulty nozzle detection unit 21 performs faulty nozzle detection processing to generate faulty nozzle information that describes whether or not each nozzle 20 is a faulty nozzle. The faulty nozzle information is stored in the storage unit 22. There is no particular limit to the timing at which the faulty nozzle detection unit 21 performs the faulty nozzle detection processing. The faulty nozzle detection unit 21 overwrites the faulty nozzle information with the latest faulty nozzle information as needed.

[0026] 2. First embodiment: 3 is a flowchart showing a print control process according to the first embodiment, which is executed by the control unit 11 in accordance with the program 12. The print control process includes a printing method. In the first embodiment, the print head 19 is a horizontal array head. In step S100, the control unit 11 accesses the storage unit 22 and acquires the defective nozzle information. In step S110, the control unit 11 refers to the defective nozzle information and calculates a "complementable transport amount" for each nozzle row 26. The "complementable transport amount" refers to the transport amount for one transport by the transport unit 17, and means the transport amount that can compensate for non-ejection of ink by a defective nozzle by the ejection of ink from a normal nozzle in the relationship between one main scan and the other main scan sandwiching the transport. Note that in the following, when "distance" or "length" is mentioned, it means the distance or length in the transport direction D2, unless otherwise specified.

[0027] Hereinafter, one transport by the transport unit 17 for printing is also referred to as a "paper feed." Therefore, the transport amount for one transport by the transport unit 17 is the paper feed amount. In addition, in the relationship between two main scans performed with a paper feed in between, the main scan performed first is referred to as the "preceding pass," and the main scan performed later is referred to as the "following pass."

[0028] FIG. 4 is a diagram for explaining how to obtain the complementary carry amount for each nozzle row 26 in step S110. In FIG. 4, a certain pass P1 is called the preceding pass P1, and the pass 2 following the pass P1 is called the following pass P2. FIG. 4 shows the nozzle rows 26C, 26M, 26Y, and 26K when the preceding pass P1 is performed, and the nozzle rows 26C, 26M, 26Y, and 26K when the following pass P2 is performed, assuming that the complementary carry amount for each nozzle row 26 is applied. In the example of FIG. 4, due to space limitations, each of the nozzle rows 26C, 26M, 26Y, and 26K is shown with 12 nozzles 20. Of course, the number of nozzles that actually constitute the nozzle row 26 may be more than 12. In FIG. 4, the main scanning direction D1 and the carry direction D2 are also shown, as in FIG. 2.

[0029] In Fig. 4, for the sake of convenience, each nozzle 20 constituting the nozzle arrays 26C, 26M, 26Y, and 26K is assigned a nozzle number, such as #1, #2, #3, ... #12, in order from downstream to upstream. However, the nozzle numbers of the nozzle arrays 26C, 26M, 26Y, and 26K during execution of the subsequent pass P2 are omitted as appropriate. In Fig. 4, the nozzles 20 that are considered to be normal nozzles in the faulty nozzle information are shown as simple white circles, and the nozzles 20 that are considered to be faulty nozzles in the faulty nozzle information are shown as white circles with a cross mark.

[0030] 4, the position of each of the nozzle rows 26C, 26M, 26Y, and 26K when the subsequent pass P2 is performed is shifted upstream from the position when the previous pass P1 is performed, thereby representing the complementary transport amount between the previous pass P1 and the subsequent pass P2 for each of the nozzle rows 26C, 26M, 26Y, and 26K. Of course, in reality, the nozzle rows 26 do not move upstream, but the print medium 30 moves downstream due to paper feed.

[0031] In step S110, the control unit 11 calculates the maximum complementable carry distance for the nozzle row 26 based on the positional relationship between the faulty nozzles and normal nozzles included in the nozzle row 26 in the carry direction D2. First, let us look at the nozzle row 26C. In the example of FIG. 4, two nozzles 20, nozzle number #2 and nozzle number #11, are defective nozzles in the nozzle row 26C. In the nozzle row 26C, eight nozzles 20, nozzle numbers #3 to #10, are consecutively normal nozzles, so if these eight nozzles 20, nozzle numbers #3 to #10, are used in each pass, the defective nozzles will not be used. In other words, if the paper feed amount for one pass is eight times the distance of the nozzle pitch, printing can be performed using the eight nozzles 20, nozzle numbers #3 to #10, in each pass.

[0032] However, such a distance of 8 times the nozzle pitch cannot be said to be the maximum complementable transport amount for the nozzle row 26C. According to the example of FIG. 4, the position of the printing medium 30 where ink is not ejected due to a defective nozzle of nozzle number #11 of the nozzle row 26C in the preceding pass P1 can be complemented with dots by any normal nozzle downstream of the defective nozzle in the following pass P2. Also, according to the example of FIG. 4, the position of the printing medium 30 where ink is not ejected due to a defective nozzle of nozzle number #2 of the nozzle row 26C in the following pass P2 can be complemented with dots by any normal nozzle upstream of the defective nozzle in the preceding pass P1. Therefore, in the example of FIG. 4, the distance of 10 times the nozzle pitch, which corresponds to the distance from the defective nozzle of nozzle number #11 to the normal nozzle of nozzle number #1, which is the furthest downstream in the nozzle row 26C, and the distance from the defective nozzle of nozzle number #2 to the normal nozzle of nozzle number #12, which is the furthest upstream in the nozzle row 26C, is the maximum complementable transport amount Fc for the nozzle row 26C.

[0033] In the relationship between the preceding pass and the following pass, two nozzles 20 in the same nozzle row 26 that correspond to the same position on the print medium 30 are called "pair nozzles." In other words, if a faulty nozzle becomes a pair nozzle with a normal nozzle, complementation is achieved. If faulty nozzles become pair nozzles, complementation is not achieved. In step S110, the control unit 11 similarly determines the maximum complementary carry amount for each of the nozzle rows 26M, 26Y, and 26K.

[0034] 4, two nozzles 20, nozzle number #3 and nozzle number #9, are faulty nozzles in nozzle row 26M. Since five consecutive nozzles 20, nozzle numbers #4 to #8, are normal nozzles in nozzle row 26M, if the paper feed amount is five times the nozzle pitch, printing can be performed using the five normal nozzles, nozzle numbers #4 to #8, in each pass.

[0035] However, such a distance of five times the nozzle pitch cannot be said to be the maximum complementable transport amount for the nozzle row 26M. According to the example of FIG. 4, in the preceding pass P1, the position of the printing medium 30 where ink is not ejected due to a defective nozzle with nozzle number #9 of the nozzle row 26M can be complemented with dots by the normal nozzle with nozzle number #1, which is the furthest downstream from the defective nozzle, in the following pass P2. In other words, the two nozzles 20 with nozzle numbers #1 and #9 of the nozzle row 26M can become a pair nozzle. Also, in the following pass P2, the position of the printing medium 30 where ink is not ejected due to a defective nozzle with nozzle number #3 of the nozzle row 26M can be complemented with dots by the normal nozzle with nozzle number #11, which is upstream of the defective nozzle, in the preceding pass P1. Therefore, in the example of Figure 4, the maximum complementable transport amount Fm for nozzle row 26M is a distance of 8 times the nozzle pitch, which corresponds to the distance from the faulty nozzle with nozzle number #9 in nozzle row 26M to the downstream normal nozzle with nozzle number #1, and the distance from the faulty nozzle with nozzle number #3 to the upstream normal nozzle with nozzle number #11 in nozzle row 26M.

[0036] In the example of Fig. 4, in the nozzle row 26Y, only the nozzle 20 with nozzle number #1 is a defective nozzle. For the nozzle row 26Y, simply, the position on the print medium 30 where ink is not ejected due to the defective nozzle with nozzle number #1 in the subsequent pass P2 can be complemented with a dot by the normal nozzle with nozzle number #12, which is the most upstream from the defective nozzle, in the preceding pass P1. Therefore, in the example of Fig. 4, the distance of 11 times the nozzle pitch, which corresponds to the distance from the defective nozzle with nozzle number #1 to the upstream normal nozzle with nozzle number #12 in the nozzle row 26Y, becomes the maximum complementable carry amount Fy for the nozzle row 26Y.

[0037] In the example of Figure 4, there are no faulty nozzles in nozzle row 26K. When there are no faulty nozzles, the term "complementable" is unnecessary, but here, the expression "complementable carry amount" is used for nozzle row 26K in accordance with the other nozzle rows 26C, 26M, and 26Y that have faulty nozzles. For nozzle row 26K, the distance of 12 times the nozzle pitch, which corresponds to the length of nozzle row 26, is the maximum complementable carry amount Fk.

[0038] In step S120, the control unit 11 determines a common carry amount for each nozzle row 26 for each nozzle row position, based on the complementable carry amount calculated in step S110 for each nozzle row 26. According to Fig. 4, the maximum complementable carry amounts for each nozzle row 26C, 26M, 26Y, and 26K are complementable carry amounts Fc, Fm, Fy, and Fk, so the control unit 11 may determine the smallest complementable carry amount Fm among these complementable carry amounts Fc, Fm, Fy, and Fk as the common carry amount.

[0039] However, when the smallest complementable carry amount Fm among the complementable carry amounts Fc, Fm, Fy, and Fk is set as the common carry amount, if a situation occurs in which defective nozzles become paired nozzles in any of the nozzle rows 26C, 26Y, and 26K other than the nozzle row 26M for which the complementable carry amount Fm was calculated in step S110, it is necessary to adjust the common carry amount to a smaller distance. Suppose that three nozzles 20 with nozzle numbers #3, #10, and #11 are defective nozzles in the nozzle row 26C. In this case, the defective nozzles with nozzle numbers #10 and #11 can be complemented by normal nozzles with nozzle numbers #1 and #2, and the defective nozzle with nozzle number #3 can be complemented by normal nozzle with nozzle number #12, so the complementable carry amount Fc of the nozzle row 26C is 9 times the nozzle pitch. In this case, the complementable carry amount Fm, which is a distance eight times the nozzle pitch, is still smaller than the complementable carry amount Fc, but if the complementable carry amount Fm is set as a carry amount common to each nozzle row 26, the two nozzles 20 with nozzle numbers #3 and #11, which are defective nozzles, will become paired nozzles in nozzle row 26C. Therefore, the control unit 11 determines a common carry amount that is even smaller than the complementable carry amount Fm, so as to prevent paired nozzles of defective nozzles from occurring in all nozzle rows 26C, 26Y, and 26K.

[0040] In step S130, the control unit 11 determines the "used nozzles" for each nozzle row 26 when printing is performed using the common carry amount determined in step S120. The used nozzles are the nozzles 20 that are normal nozzles and will be used for printing. Using them for printing means that print data is assigned to them. The normal nozzles 20 that are not used for printing are called "unused nozzles."

[0041] A specific example of step 130 will be described with reference to FIG. 5. As in FIG. 4, FIG. 5 also shows that the relative positions of the nozzle rows 26C, 26M, 26Y, and 26K and the printing medium 30 in the transport direction D2 change for each pass. The way to read FIG. 5 is basically the same as FIG. 4. The defective nozzles in the nozzle rows 26C, 26M, 26Y, and 26K shown in FIG. 5 are the same as those in FIG. 4. In FIG. 5, pass P1 is assumed to be the first pass for the printing medium 30. Pass P2 is the following pass when pass P1 is considered to be the preceding pass, and pass P3 is the following pass when pass P2 is considered to be the preceding pass.

[0042] In Fig. 5, the symbol F is the common carry amount F determined in step S120, that is, the paper feed amount used for printing. The carry amount F is also the complementable carry amount Fm shown in Fig. 4. In Fig. 5, used nozzles are represented by white circles, and unused nozzles are represented by gray circles. When the control unit 11 adopts the carry amount F, it designates as active nozzles all the nozzles 20 that are not paired with other nozzles 20. As shown in Fig. 5, each of the nozzles 20 with nozzle numbers #5 to #8 is not paired with other nozzles 20, and therefore the control unit 11 designates each of the nozzles 20 with nozzle numbers #5 to #8 as active nozzles in all of the nozzle rows 26C, 26M, 26Y, and 26K.

[0043] In addition, when the conveyance amount F is adopted, the control unit 11 naturally sets the normal nozzle that is paired with the faulty nozzle as the used nozzle. According to FIG. 5, for example, the nozzle 20 of the nozzle row 26C with the nozzle number #10 is paired with the faulty nozzle with the nozzle number #2, and therefore is set as the used nozzle. Also, for example, the nozzle 20 of the nozzle row 26M with the nozzle number #1 is paired with the faulty nozzle with the nozzle number #9, and therefore is set as the used nozzle. In addition, the control unit 11 may set either of the paired normal nozzles as the used nozzle when the conveyance amount F is adopted, but in the example of FIG. 5, the normal nozzle that belongs to the following pass is set as the used nozzle. For example, the two normal nozzles of the nozzle row 26Y with the nozzle numbers #11 and #3 are in a pair nozzle relationship, but the nozzle 20 of the nozzle number #11, which is the normal nozzle that belongs to the preceding pass, is set as the unused nozzle, and the nozzle 20 of the nozzle number #3, which is the normal nozzle that belongs to the following pass, is set as the used nozzle.

[0044] 5, the control unit 11 determines eight nozzles 20 with nozzle numbers #1, #3 to #8, and #10 in the nozzle row 26C as the nozzles to be used. In the nozzle row 26M, eight nozzles 20 with nozzle numbers #1, #2, #4 to #8, and #11 are determined as the nozzles to be used. In the nozzle row 26Y, eight nozzles 20 with nozzle numbers #2 to #9 are determined as the nozzles to be used, and in the nozzle row 26K, eight nozzles 20 with nozzle numbers #1 to #8 are determined as the nozzles to be used.

[0045] Furthermore, in step S130, the control unit 11 determines the most downstream nozzles to be used that are common to each nozzle row 26 for pass P1, which is the first pass. In the example of FIGS. 4 and 5, due to a defective nozzle with nozzle number #3 in the nozzle row 26M, the most downstream nozzles 20 that can be used in common in the nozzle rows 26C, 26M, 26Y, and 26K in pass P1 are the nozzles 20 with nozzle number #4. Therefore, the control unit 11 uses the nozzles with nozzle numbers equal to or greater than #4 among the nozzles to be used in each nozzle row 26 determined as described above for pass P1. In other words, in pass P1, the nozzles to be used that are located upstream of the dashed line shown in FIG. 5 are used.

[0046] In step S140, the control unit 11 employs the common carry amount determined in step S120, and uses the nozzles to be used determined in each nozzle row 26 in step S130 to control the transport unit 17, carriage 18, and print head 19 to perform printing based on the print data. That is, in a pass performed by the carriage 18 and print head 19, ink is ejected from the nozzles to be used based on the print data, and between passes, the transport unit 17 advances the paper once by the common carry amount. With this type of printing, non-ejection of ink due to defective nozzles is complemented by normal nozzles, and high-quality print results can be obtained with no missing dots required on the print medium 30.

[0047] The print data is raster data that expresses an image with a number of pixels, and specifies for each pixel whether to eject a dot (dot on) or not eject a dot (dot off) for each of the CMYK inks. In the print data, a pixel row in which pixels are lined up along the main scanning direction D1 is called a raster line. The control unit 11 can cause one nozzle 20 to print one raster line by allocating the dot data of one raster line to one nozzle 20. Therefore, for a faulty nozzle and an active nozzle that are in a pair nozzle relationship in the preceding pass and the following pass due to the paper feed of this embodiment, the control unit 11 can output a high-quality print result without missing dots due to the faulty nozzle by allocating the raster line data only to the active nozzle.

[0048] 3. Second embodiment: FIG. 6 shows a simplified view of the relationship between the print head 19 and the print medium 30 according to the second embodiment from an above perspective. The way of viewing FIG. 6 is the same as that of FIG. 2. Regarding FIG. 6, only the differences from FIG. 2 will be described. In the print head 19 shown in FIG. 6, the nozzle rows 26C, 26M, and 26Y, which are chromatic nozzle rows, are arranged along the transport direction D2. From a different perspective, it can be said that the three nozzle rows 26C, 26M, and 26Y are connected to form one nozzle row. In addition, in the print head 19, the nozzle row 26K, which is an achromatic nozzle row, is arranged side by side with the chromatic nozzle row in the main scanning direction D1. The nozzle row 26K in FIG. 6 has the same length and the same position in the transport direction D2 as the nozzle row in which the nozzle rows 26C, 26M, and 26Y are connected. The print head 19 having such a configuration in which the multiple nozzle rows 26C, 26M, and 26Y for each chromatic color are arranged along the transport direction D2 is called a "vertical arrangement head." In the vertically arranged head, the nozzle row positions are different in the transport direction D2.

[0049] 7 is a flowchart showing the print control process according to the second embodiment executed by the control unit 11 in accordance with the program 12. In the second embodiment, the print head 19 is a vertically arranged head. In the description of the second embodiment, the description of the first embodiment applies mutatis mutandis as appropriate. Step S200 is the same as step S100 in FIG. 3.

[0050] In step S210, similar to step S110, the control unit 11 references the defective nozzle information and calculates the complementable carry amount for each nozzle row 26. However, in step S210, the control unit 11 calculates the complementable carry amount for each of the nozzle rows 26C, 26M, and 26Y, which are chromatic nozzle rows. Here, it is assumed that the complementable carry amounts Fc, Fm, and Fy described in FIG. 4 have been calculated as the complementable carry amounts for each of the nozzle rows 26C, 26M, and 26Y.

[0051] In step S220, the control unit 11 determines a common carry amount F based on the complementable carry amount for each chromatic nozzle array calculated in step S210. As in the first embodiment, the control unit 11 may determine the smallest complementable carry amount Fm among the complementable carry amounts Fc, Fm, and Fy as the common carry amount F.

[0052] In step S230, the control unit 11 determines which nozzles to use when printing using the common carry amount F determined in step S220 for the nozzle row 26 that corresponds to the "smallest segment." The smallest segment is the nozzle row 26 that has the smallest complementable carry amount among the chromatic nozzle rows, and in this case, this corresponds to the nozzle row 26M. The nozzles to be used in the nozzle row 26M are the nozzles 20 with nozzle numbers #1, #2, #4 to #8, and #11, as described in FIG.

[0053] In step S240, the control unit 11 refers to the defective nozzle information to determine whether or not there is a defective nozzle among the K nozzles adjacent to the working nozzles determined for the minimum segment. The K nozzle is the name of the nozzle 20 constituting the nozzle row 26K. In the second embodiment, the control unit 11 determines, as the working nozzles of the nozzle row 26K, normal nozzles among the K nozzles adjacent to the working nozzles determined in each of the nozzle rows 26C, 26M, and 26Y. Here, "adjacent" means that the positions in the transport direction D2 are the same. In step S240, if there is a defective nozzle among the K nozzles adjacent to the working nozzles determined for the minimum segment, the control unit 11 judges "Yes" and proceeds to step S250, whereas if there is no defective nozzle among such K nozzles, the control unit 11 judges "No" and proceeds to step S260.

[0054] The process of FIG. 7 will be described with reference to FIG. 8, like FIG. 5, shows that the relative positions of the nozzle rows 26C, 26M, 26Y, and 26K and the print medium 30 in the transport direction D2 change for each pass as the paper is transported by a common transport amount F. The way to read FIG. 8 is basically the same as FIG. 5. The reference numeral 26U collectively refers to the nozzle rows 26C, 26M, and 26Y, and is referred to here as the chromatic nozzle row unit 26U. Also, in FIG. 8, the nozzle numbers #1 to #12 of the 12 nozzles 20 constituting each of the nozzle rows 26C, 26M, and 26Y are indicated by adding C, M, and Y representing the corresponding ink. For example, the nozzle 20 with the nozzle number #1 of the nozzle row 26C is indicated as the nozzle number #1C.

[0055] 8, the 36 K nozzles constituting the nozzle row 26K are numbered from downstream to upstream as nozzle numbers #1K, #2K, #3K, ... #36K. In addition, in FIG. 8, in the chromatic nozzle row unit 26U and the nozzle row 26K, the range along the transport direction D2 corresponding to the nozzle row 26C is designated as a first nozzle range 27, the range along the transport direction D2 corresponding to the nozzle row 26M is designated as a second nozzle range 28, and the range along the transport direction D2 corresponding to the nozzle row 26Y is designated as a third nozzle range 29. In FIG. 8, the chromatic nozzle row unit 26U and the nozzle row 26K corresponding to the preceding pass are shown, while the nozzle row 26K of the chromatic nozzle row unit 26U and the nozzle row 26K corresponding to the following pass is omitted.

[0056] The positions of the defective nozzles in each of the nozzle rows 26C, 26M, and 26Y shown in Fig. 8 are the same as in the examples of Figs. 4 and 5. Therefore, the carry amount F determined in step S220 is a distance eight times the nozzle pitch, and the used nozzles and unused nozzles determined in step S230 for the nozzle row 26M are the same as in the example of Fig. 5. Meanwhile, in the nozzle row 26K shown in Fig. 8, the K nozzles with nozzle numbers #11K, #15K, #23K, and #31K are defective nozzles.

[0057] 8, in step S230, the control unit 11 determines each of the nozzles 20 with nozzle numbers #1M, #2M, #4M to #8M, and #11M in the nozzle row 26M, which is the smallest segment, as the active nozzles. Therefore, the K nozzles adjacent to these active nozzles are the K nozzles with nozzle numbers #13K, #14K, #16K to #20K, and #23K. And in FIG. 8, of the K nozzles adjacent to these active nozzles, the K nozzle with nozzle number #23K is a defective nozzle, so "Yes" is determined in step S240.

[0058] In step S250, the control unit 11 determines whether or not a pair nozzle is established between a defective nozzle among the K nozzles adjacent to the working nozzle of the smallest segment and a normal nozzle that is complementary to the defective nozzle. As described above, the defective nozzle among the K nozzles adjacent to the working nozzle of the smallest segment is the K nozzle with nozzle number #23K. The K nozzles that can be paired with this K nozzle are the K nozzles located at an integer multiple of the carry amount F from the nozzle number #23K, specifically, the K nozzles with nozzle numbers #31K, #15K, and #7K. If all of the K nozzles with nozzle numbers #31K, #15K, and #7K are defective nozzles, there is no normal nozzle that can complement the K nozzle with nozzle number #23K, so the control unit 11 determines "No" in step S250.

[0059] 8, of the K nozzles with nozzle numbers #31K, #15K, and #7K, the K nozzle with nozzle number #7K is a normal nozzle. Therefore, a pair is formed between the K nozzle with nozzle number #23K and a normal nozzle that can complement it, so control unit 11 determines "Yes" in step S250 and proceeds to step S260.

[0060] In step S260, the control unit 11 determines the nozzles to be used for the other segments that are not the smallest segment, that is, for each of the nozzle rows 26C and 26Y in the example of FIG. 8. The control unit 11 may determine the nozzles to be used in each of the chromatic nozzle rows so that the print results by the nozzles 20 of the same color, the number of which corresponds to the common carry amount F, are connected in the carry direction D2. For example, just as in the first embodiment, the nozzles 20 of the nozzle row 26C having the nozzle numbers #1, #3 to #8, and #10 are determined to be the nozzles to be used, in step S260, the nozzles 20 of the nozzle row 26C having the nozzle numbers #1C, #3C to #8C, and #10C can be determined to be the nozzles to be used. Similarly, just as in the first embodiment, the nozzles 20 of the nozzle row 26Y having the nozzle numbers #2 to #9 are determined to be the nozzles to be used, in step S260, the nozzles 20 of the nozzle row 26Y having the nozzle numbers #2Y to #9Y can be determined to be the nozzles to be used.

[0061] In step S260, the control unit 11 determines the nozzle to be used so that a normal nozzle that complements the defective nozzle next to the used nozzle of the smallest segment is included in the range of the used nozzles. In the example of FIG. 8, the K nozzle with nozzle number #23K should be complemented by the K nozzle with nozzle number #7K in the third nozzle range 29. Therefore, the control unit 11 determines the nozzle to be used so that the nozzle 20 with nozzle number #7Y, which is adjacent to the nozzle number #7K, is included in the used nozzles for the nozzle row 26Y. In addition, in step S260, the control unit 11 determines the nozzle to be used so that the defective nozzle of the K nozzle does not enter the range of the used nozzles as much as possible. In the example of FIG. 8, the K nozzle with nozzle number #11K in the third nozzle range 29 is a defective nozzle, so the control unit 11 may determine the nozzle to be used by avoiding the nozzle 20 with nozzle number #11Y, which is adjacent to the nozzle number #11K, for the nozzle row 26Y.

[0062] If step S240 is judged as "No", no matter how many defective nozzles are included among the K nozzles corresponding to the other segments, those defective nozzles can be complemented by the K nozzles corresponding to the smallest segment. Therefore, in step S260, which is executed after judging "No" in step S240, when determining the nozzles to be used in each of the other segments, there is less need to determine the nozzles to be used taking the K nozzles into consideration as described above, and the degree of freedom in determining the nozzles to be used increases.

[0063] In step S270, the control unit 11 employs the common transport amount determined in step S220, and uses the active nozzles determined in steps S230 and S260 for each nozzle row 26C, 26M, 26Y and the K nozzle, which is a normal nozzle adjacent to these active nozzles, to control the transport unit 17, carriage 18, and print head 19 to execute printing based on the print data. With this type of printing, non-ejection of ink due to defective nozzles is compensated for by normal nozzles, and high-quality print results can be obtained with no missing dots on the print medium 30.

[0064] As shown in FIG. 7, if the control unit 11 determines "No" in step S250, it returns to step S220. In step S220 after returning from step S250, the common carry amount is adjusted. In this case, in step S220, the control unit 11 determines the common carry amount to be a carry amount smaller than the common carry amount determined in the previous step S220. In addition, the common carry amount is determined so that no pair nozzle of a defective nozzle occurs in each of the nozzle rows 26C, 26M, and 26Y. The control unit 11 determines the nozzle to be used in the smallest segment in step S230 according to the carry amount after such adjustment, and executes steps S240 and thereafter. In this way, in the flowchart of FIG. 7, the control unit 11 determines the common carry amount based on the complementable carry amount for each chromatic nozzle array and the position of the defective nozzle in the achromatic nozzle array.

[0065] FIG. 9 is a diagram for explaining step S270 executed after step S260. FIG. 9 shows a vertically arranged head including a chromatic nozzle array unit 26U and a nozzle array 26K, as in FIG. 8. In the nozzle arrays 26C and 26Y shown in FIG. 9, nozzles to be used are determined. In the example of FIG. 9, eight consecutive normal nozzles with nozzle numbers #3C to #10C are determined as the nozzles to be used in the nozzle array 26C. Also, in the example of FIG. 9, eight consecutive normal nozzles with nozzle numbers #3Y to #10Y are determined as the nozzles to be used in the nozzle array 26Y. Also, in each of the first nozzle range 27, the second nozzle range 28, and the third nozzle range 29, the normal nozzles that are K nozzles next to the nozzles determined in the chromatic nozzle array are determined as the nozzles to be used in the nozzle array 26K.

[0066] Also, Fig. 9 shows a portion of the printing medium 30 that receives ink ejection according to the print data in each pass, such as passes P1, P2, P3, and P4, and is transported downstream by a common transport amount F each time a pass ends. Each rectangle in the printing medium 30 in Fig. 9 represents a dot ejected from the nozzle 20. Of course, the actual dots are not rectangular, but are simply shown as rectangles here. Also, in Fig. 9, the dots of each of the K, C, M and Y inks are made identifiable by changing the density of the rectangle. In actual printing, the dots of the K, C, M and Y inks overlap on the printing medium 30, but in Fig. 9, the dots of each ink are not overlapped but are shifted in the main scanning direction D1.

[0067] Focus on a certain area A on the printing medium 30. According to the example of Fig. 9, in the first pass P1, dots of K ink and dots of C ink are ejected into the area A by the used nozzles of the K nozzles in the first nozzle range 27 and the used nozzles of the nozzle row 26C. As a result, there are no missing dots of C ink in the area A, and the printing medium 30 is fed by the transport amount F and undergoes pass P2 in a state in which a missing dot corresponding to the defective nozzle with nozzle number #31K remains. In pass P2, dots of M ink are ejected into the area A by each of the nozzles 20 with nozzle numbers #7M, #8M, and #11M out of the used nozzles of the nozzle row 26M.

[0068] In pass P3, which follows paper feeding after pass P2, dots of M ink are ejected into area A by each of the nozzles 20 with nozzle numbers #1M, #2M, #4M to #6M among the used nozzles of nozzle row 26M. In other words, ejection of M ink into area A is completed by pass P2 and pass P3. At this time, the non-ejection of ink due to the faulty nozzle with nozzle number #9M is complemented by the used nozzle with nozzle number #1M, and the non-ejection of ink due to the faulty nozzle with nozzle number #3M is complemented by the used nozzle with nozzle number #11M.

[0069] In pass P4, which follows paper feeding after pass P3, K ink dots and Y ink dots are ejected into area A by the K nozzle with nozzle number #7K in the third nozzle range 29 and the used nozzles of nozzle row 26Y. As a result, in area A, the missing dots corresponding to the defective nozzle with nozzle number #31K are filled, and printing of all K, C, Y inks is completed. Needless to say, the ejection of K ink into area A may be distributed over each pass by also using the used nozzles of the K nozzles in the second nozzle range 28 and the third nozzle range 29, rather than concentrating almost all of the ejection into area A at the timing of pass P1 as in the example of Figure 9.

[0070] 9 shows how the entire area A is filled with dots of each of the KCMY inks, but whether or not each nozzle actually ejects a dot depends on the contents of the print data. In any case, this embodiment prevents dots that are specified as to be ejected by the print data from being ejected due to a faulty nozzle, resulting in missing dots in the print result.

[0071] 4. Summary: Thus, according to this embodiment, the printing device 10 includes a transport unit 17 that transports the printing medium 30 in the transport direction D2, a print head 19 having nozzle rows 26 consisting of a plurality of nozzles 20 capable of ejecting ink onto the printing medium 30 at multiple nozzle row positions, a scanning unit that moves the print head 19 in a main scanning direction D1 that intersects with the transport direction D2, a control unit 11 that controls the transport unit 17, the print head 19, and the scanning unit, and a defective nozzle detection unit 21 that detects defective nozzles that are unable to eject ink from the multiple nozzles 20 of the print head 19. The printing device 10 prints onto the printing medium 30 by a combination of transport by the transport unit 17 and main scanning in which the print head 19 ejects ink based on print data as the scanning unit moves. The control unit 11 calculates, for each nozzle row 26 by nozzle row position, a complementary transport amount that is a transport amount for one transport by the transport unit 17 and that can complement the non-ejection of ink by a defective nozzle with the ejection of ink from a normal nozzle in the relationship between one main scan and the other main scan that sandwich the transport, based on the positional relationship in the transport direction D2 between the defective nozzles included in the nozzle row 26 and the normal nozzles that are not defective nozzles, and determines a transport amount common to the nozzle rows 26 by nozzle row position based on the complementary transport amount for each nozzle row 26, and performs printing by adopting the determined common transport amount as the transport amount for one transport by the transport unit 17.

[0072] According to the above configuration, the control unit 11 calculates the complementary carry amount for each nozzle row 26 at each nozzle row position, and determines a common carry amount for each nozzle row 26 based on the complementary carry amount. This makes it easy to ensure that the largest possible carry amount is used as the common carry amount. Therefore, it is easy to prevent a decrease in printing speed by suppressing an increase in the number of passes required to complete printing due to limiting the range of nozzles used. In particular, in this embodiment, when calculating the complementable carry amount for each nozzle row 26 by nozzle row position, the maximum complementable carry amount is calculated for each nozzle row 26. Therefore, the carry amount common to each nozzle row 26, which is determined based on the complementable carry amount for each nozzle row 26, also becomes the largest possible carry amount, and it is possible to suppress an increase in the number of passes as much as possible in a situation where printing is performed while complementing defective nozzles with working nozzles.

[0073] Furthermore, according to this embodiment, the print head 19 may be a horizontally arranged head or a vertically arranged head. In the vertically arranged head, each chromatic nozzle row, which is a nozzle row for each of a plurality of chromatic inks, is arranged along the transport direction D2, and an achromatic nozzle row corresponding to the achromatic ink is arranged alongside the chromatic nozzle row in the main scanning direction D1. The control unit 11 may then calculate the complementable carry amount for each chromatic nozzle row, and determine a common carry amount based on the complementable carry amount for each chromatic nozzle row and the position of the defective nozzle in the achromatic nozzle row. According to the above configuration, when using a vertically arranged head, it is possible to determine an appropriate transport amount that can compensate for or avoid non-ejection of ink due to defective nozzles in both the chromatic nozzle row and the achromatic nozzle row.

[0074] This embodiment discloses various categories of inventions, such as not only a printing device 10 or system, but also methods executed by the device or system, and a program 12 that causes a processor to execute those methods. The printing method prints on the printing medium 30 by a combination of conveying the printing medium 30 in a conveying direction D2, and moving the print head 19, which has a nozzle row 26 consisting of a plurality of nozzles 20 capable of ejecting ink onto the printing medium 30 at each of the nozzle row positions, in a main scanning direction D1 intersecting the conveying direction D2, while causing the print head 19 to eject ink based on print data. The printing method includes a defective nozzle detection step of detecting defective nozzles that cannot eject ink from the plurality of nozzles 20 of the print head 19, and a defective nozzle detection step of detecting defective nozzles included in the nozzle row 26 and normal nozzles that do not correspond to the defective nozzles. The method includes a calculation step of calculating, for each nozzle row 26 at a nozzle row position, a complementary carry amount that is a carry amount for one carry of the printing medium 30 based on a positional relationship between the nozzle row 26 and the normal nozzle in the carry direction D2, and that is a carry amount for one carry of the printing medium 30, and that is capable of complementing non-ejection of ink by a defective nozzle with the ejection of ink from a normal nozzle in a relationship between one main scan and the other main scan sandwiching the carry; a determination step of determining a carry amount common to the nozzle rows 26 at the nozzle row position based on the complementary carry amount for each nozzle row 26; and a printing step of performing printing by adopting the determined common carry amount as the carry amount for one carry. According to the above description, the defective nozzle detection step is performed by the defective nozzle detection unit 21. Also, step S110 in FIG. 3 and step S210 in FIG. 7 correspond to the calculation step, steps S120 and S220 correspond to the determination step, and steps S140 and S270 correspond to the printing step.

[0075] 5. Other embodiments: The control unit 11 may cause a normal nozzle adjacent to the defective nozzle in the nozzle row 26 to eject ink to compensate for at least a part of the non-ejection of ink caused by the defective nozzle. Such a process is called neighborhood complementation. The neighbor here means the neighbor in the transport direction D2. The control unit 11 may execute neighborhood complementation in steps S140 and S270. As an example, attention is paid to the defective nozzle with nozzle number #2 in the nozzle row 26C in FIG. 5. According to FIG. 5, in order to compensate for the non-ejection of ink caused by the defective nozzle, the control unit 11 assigns print data for one raster line to a normal nozzle with nozzle number #10 in the nozzle row 26C, which is a pair nozzle with the defective nozzle. At this time, the control unit 11 further assigns print data for ejecting extra ink to a normal nozzle with nozzle number #1 and a normal nozzle with nozzle number #3 adjacent to the defective nozzle with nozzle number #2.

[0076] In the above example, print data that ejects extra ink is data that ejects more dots or increases the size of each dot than the data of the raster line that is originally intended to be assigned to each normal nozzle of nozzle numbers #1 and #3 in nozzle row 26C. By performing this type of neighborhood complementation, the failure to eject ink due to a defective nozzle can be compensated for not only by the normal nozzle that is paired with the defective nozzle, but also by multiple normal nozzles. In addition, by using neighborhood complementation in combination, the amount of ink ejected by the normal nozzle that is paired with the defective nozzle to complement the defective nozzle can be reduced.

[0077] The control unit 11 may cause a plurality of normal nozzles in the nozzle row 26 that are positioned so as to be able to print a common raster line that constitutes the print data and extends in the main scanning direction D1 to overlap-print the common raster line in one main scanning and the other main scanning. As is known, overlap printing is a process in which one raster line is shared and printed by a plurality of nozzles 20. The control unit 11 may execute overlap printing in steps S140 and S270. As will be understood from the above explanation, the plurality of normal nozzles that are positioned so as to be able to print a common raster line are paired nozzles consisting of normal nozzles.

[0078] For example, a normal nozzle with nozzle number #10 (#10M) and a normal nozzle with nozzle number #2 (#2M) in nozzle row 26M form a paired nozzle. Also, for example, in nozzle row K in FIG. 5, normal nozzles with nozzle numbers #9 and #1, normal nozzles with nozzle numbers #10 and #2, normal nozzles with nozzle numbers #11 and #3, and normal nozzles with nozzle numbers #12 and #4 each form a paired nozzle. With regard to such paired nozzles, control unit 11 performs overlap printing by assigning some pixel data out of the data of multiple pixels constituting the raster line to be assigned to the paired used nozzle to the normal nozzle, which has been described as an unused nozzle in the above explanation.

[0079] In overlap printing, the allocation ratio of pixels in a raster line to two normal nozzles forming a nozzle pair does not have to be 50%:50%, and may be, for example, 20%:80%, 60%:40%, etc. Furthermore, the control unit 11 may vary such allocation ratios for each raster line to be overlap-printed. By varying the allocation ratio for each raster line to be overlap-printed, it is possible to ensure gradation in areas where the overlap-printed raster lines are continuous in the transport direction D2, thereby improving image quality.

[0080] It should be noted that there is no need to compensate for a defective nozzle with a normal nozzle if there is no need to eject ink from the defective nozzle. Therefore, when a raster line that constitutes the print data and extends in the main scanning direction D1 and that is assigned to a defective nozzle has data for the ink to be ejected, the control unit 11 executes printing by adopting a common carry amount based on the complementable carry amount as the carry amount for one transport by the transport unit 17. On the other hand, when a raster line that is assigned to a defective nozzle does not have data for the ink to be ejected, the control unit 11 may execute printing by adopting a carry amount for one transport by the transport unit 17 that is a carry amount that cannot compensate for the non-ejection of ink by the defective nozzle by the ejection of ink from a normal nozzle and that is greater than the common carry amount based on the complementable carry amount.

[0081] Fig. 10, in the same manner as Fig. 5, shows that the relative positions of the nozzle rows 26C, 26M, 26Y, and 26K and the print medium 30 in the transport direction D2 change for each pass. Fig. 10 also shows a portion of the print data 40. Each rectangle that makes up the print data 40 is an individual pixel, and each pixel has dot-on and dot-off data for each of the CMYK inks.

[0082] 10, carry amount F0 corresponds to the length of nozzle row 26, and is the maximum amount of paper feed in one go. Carry amount F0 is an example of a carry amount that is greater than the common carry amount F determined in step S120 or step S220 and is an amount that cannot compensate for non-ejection of ink by a defective nozzle by ejection of ink from a normal nozzle. Control unit 11 analyzes the print data, and determines whether or not the raster line assigned to the defective nozzle does not have data of ink to be ejected if carry amount F0 is adopted as the paper feed amount.

[0083] In the print data 40, a raster line consisting of pixels with "0" written therein is a raster line that does not have dot-on data. If the raster line assigned to each defective nozzle when the paper feed amount between pass P1 and pass P2 is set to the carry amount F0 as shown in FIG. 10, the control unit 11 may set the paper feed amount between pass P1 and pass P2 to the carry amount F0 during actual printing. By adopting the carry amount F0, the number of passes required to complete printing can be reduced, and the printing speed can be improved. In the example of FIG. 10, since the raster line assigned to the defective nozzle when the paper feed amount between pass P2 and pass 3 is set to the carry amount F0 is a raster line that has dot-on data, the paper feed amount between pass P2 and pass P3 is set to the common carry amount F described above.

[0084] Naturally, such control of the transport amount is also possible in the vertically-arranged head of the second embodiment. In the vertically-arranged head, the length of each of the nozzle rows 26C, 26M, and 26Y that make up the chromatic nozzle row unit 26U is the maximum value of the paper feed amount per pass. Therefore, when the control unit 11 performs paper feed between passes at such a maximum paper feed amount, if the raster line assigned to the defective nozzle is a raster line that does not have dot-on data, it is sufficient to adopt this maximum paper feed amount in actual printing.

[0085] In addition, such control of the carry amount can be performed according to the correspondence between the defective nozzles for each nozzle row position and the print data. With reference to FIG. 10, for example, it is assumed that the raster line assigned to the nozzle 20 with nozzle number #9 in pass P1 is data that specifies dots for CYK ink but does not specify dots for M ink in all pixels. Also, it is assumed that the raster line assigned to the nozzle 20 with nozzle number #11 in pass P1 is data that specifies dots for C ink. In this case, in the relationship between pass P1 and pass P2, paper feed is not required to complement the defective nozzle with nozzle number #9 of the nozzle row 26M with a normal nozzle, but paper feed is required to complement the defective nozzle with nozzle number #11 of the nozzle row 26C. Therefore, the control unit 11 may determine the carry amount between each pass that can complement the defective nozzle that needs to be complemented by a normal nozzle according to the contents of the print data, and may employ this in actual printing. [Explanation of symbols]

[0086] 10...printing device, 11...control unit, 11a...CPU, 11b...ROM, 11c...RAM, 12...program, 16...printing unit, 17...transport unit, 18...carriage, 19...print head, 20...nozzle, 21...defective nozzle detection unit, 26, 26C, 26M, 26Y, 26K...nozzle array, 30...printing medium, 40...printing data

Claims

1. a conveying unit that conveys the print medium in a conveying direction; a print head having a nozzle row composed of a plurality of nozzles capable of ejecting ink onto the printing medium, the nozzle row being arranged at a plurality of nozzle row positions; a scanning unit that moves the print head in a main scanning direction that intersects with the transport direction; A control unit that controls the transport unit, the print head, and the scanning unit; a defective nozzle detection unit that detects defective nozzles that are unable to eject ink from the plurality of nozzles of the print head, a printing device that prints on the print medium by a combination of conveyance by the conveyance unit and main scanning in which the print head ejects ink based on print data in association with movement of the scanning unit, The control unit is calculate, for each nozzle row according to the nozzle row position, a transport amount for one transport by the transport unit based on a positional relationship in the transport direction between the faulty nozzles included in the nozzle row and normal nozzles that are not the faulty nozzles, the transport amount being a complementable transport amount that can complement non-ejection of ink by the faulty nozzles with the ejection of ink from the normal nozzles in a relationship between one of the main scans and the other of the main scans sandwiching the transport; determining a common carry amount for the nozzle rows at the nozzle row positions based on the complementary carry amount for each nozzle row; and performing the printing by adopting the determined common carry amount as the carry amount for one transport by the transport unit. when a raster line that constitutes the print data and extends in the main scanning direction and that is assigned to the defective nozzle has data of ink to be ejected, a common carry amount based on the complementable carry amount is adopted as the carry amount for one carry by the carry unit, and the printing is performed; A printing device characterized in that, when the raster line assigned to the defective nozzle does not have data for the ink to be ejected, a transport amount that cannot compensate for the non-ejection of ink by the defective nozzle by the ejection of ink from the normal nozzle, and that is greater than a common transport amount based on the complementable transport amount, is adopted as the transport amount for one transport by the transport unit, and the printing is performed.

2. 2. The printing device according to claim 1, wherein the control unit causes the normal nozzle adjacent to the defective nozzle in the nozzle row to eject ink that compensates for at least a portion of the failure to eject ink due to the defective nozzle.

3. 3. The printing device according to claim 1, wherein the control unit causes a plurality of normal nozzles in the nozzle row that are positioned so as to be able to print a common raster line that constitutes the print data and extends in the main scanning direction to overlap-print the common raster line in one main scan and the other main scan.

4. In the print head, chromatic nozzle rows, each of which corresponds to a nozzle row for each of a plurality of chromatic inks, are arranged along the transport direction, and achromatic nozzle rows corresponding to achromatic inks are arranged side by side with the chromatic nozzle rows in the main scanning direction, 4. The printing device according to claim 1, wherein the control unit calculates the complementable carry amount for each of the chromatic nozzle rows, and determines a common carry amount based on the complementable carry amount for each of the chromatic nozzle rows and the position of the defective nozzle in the achromatic nozzle row.

5. A printing method for printing on a print medium by a combination of transport of the print medium in a transport direction by a transport unit, and main scanning for causing a print head, which has a nozzle row consisting of a plurality of nozzles capable of ejecting ink onto the print medium at a plurality of nozzle row positions, to move in a main scanning direction intersecting the transport direction and eject ink from the print head based on print data, comprising: a defective nozzle detection step of detecting a defective nozzle that is unable to eject ink from among the plurality of nozzles of the print head; a calculation step of calculating, for each nozzle row according to the nozzle row position, a transport amount for one transport of the print medium based on a positional relationship in the transport direction between the faulty nozzles included in the nozzle row and normal nozzles that do not correspond to the faulty nozzles, the transport amount being a complementable transport amount that can complement non-ejection of ink by the faulty nozzles with the ejection of ink from the normal nozzles in a relationship between one of the main scans and the other of the main scans sandwiching the transport; a determination step of determining a common carry amount for the nozzle rows at the nozzle row positions based on the complementable carry amount for each nozzle row; a printing step of executing the printing by adopting the determined common carry amount as the carry amount for one carry operation, In the printing step, when a raster line that constitutes the print data and extends in the main scanning direction and that is assigned to the defective nozzle has data of ink to be ejected, a common carry amount based on the complementable carry amount is adopted as the carry amount for one carry by the carry unit, and the printing is performed; A printing method characterized in that, when the raster line assigned to the defective nozzle does not have data for the ink to be ejected, a transport amount that cannot compensate for the non-ejection of ink by the defective nozzle by the ejection of ink from the normal nozzle, and that is greater than a common transport amount based on the complementable transport amount, is adopted as the transport amount for one transport by the transport unit, and the printing is performed.

Images