Liquid ejection device, liquid ejection system, and control method for liquid ejection device

Abstract

To quickly generate data and shorten a time taken to start liquid ejection, even when dedicated dot size data for complementing a missing dot is provided.SOLUTION: When it is determined that an abnormal nozzle exists, a control unit of a printer controls an ink jet head such that first ejection data including first data for selecting a size of at least some dots is generated, and based on the first ejection data, dots are formed on recording paper by ejecting ink from a plurality of nozzles. When it is determined that an abnormal nozzle does not exist, the control unit controls the ink jet head such that second ejection data including second data for selecting a size of dots to be formed by a plurality of nozzles is generated, and based on the second ejection data, dots are formed on the recording paper by ejecting ink from the plurality of nozzles.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a liquid ejection device that ejects a liquid from a nozzle, a liquid ejection system including the liquid ejection device and an external device, and a control method for the liquid ejection device.

Background Art

[0002] As an example of a liquid ejection device that ejects a liquid from a nozzle, Patent Document 1 describes a liquid ejection device that ejects ink from a nozzle to perform recording. In the liquid ejection device of Patent Document 1, when a defective ejection nozzle (abnormal nozzle) is detected by a detection unit that detects the ejection state of the nozzle, the size of the ink droplets ejected from the nozzle adjacent to the defective ejection nozzle is increased to complement the image of the missing dots caused by the defective ejection nozzle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the liquid ejection device described in Patent Document 1 above, a dedicated large-sized ink droplet for complementing the image of missing dots can be selectively ejected from the nozzle. That is, even in a state where a defective ejection nozzle has not been detected, an ink droplet of a complementary size and a plurality of types of normal-sized ink droplets smaller than this complementary size and used for normal ejection can be selectively ejected from the nozzle. When creating ejection data that enables selective ejection of ink droplets of a plurality of types including such a complementary size from the nozzle, the amount of such data may become large. For example, when the ejection data enabling ejection of a plurality of types of normal-sized ink droplets from the nozzle is data of 2 bits per dot, by adding the complementary size to the plurality of types of normal sizes, the data may become 3 bits or more per dot. In this case, regardless of whether or not to use an ink droplet of a dedicated size for complementing the image of missing dots, the amount of ejection data is always large. When the amount of data becomes large, there is a problem that the time required to generate the ejection data and the like increases, and it takes time until the liquid ejection starts.

[0005] Therefore, an object of the present invention is to provide a liquid ejection device, a liquid ejection system, and a control method for a liquid ejection device, which can quickly generate data and shorten the time required until the liquid ejection starts, in a liquid ejection device having dedicated dot size data for complementing missing dots.

Means for Solving the Problems

[0006] The liquid ejection device of the present invention includes a liquid ejection head having a plurality of nozzles that eject liquid to form dots of a plurality of types of sizes on a medium to be ejected, and a signal output unit that outputs a determination signal corresponding to whether or not the nozzle is an abnormal nozzle having an abnormality in liquid ejection when performing inspection driving for the liquid ejection head to check whether or not the nozzle is an abnormal nozzle, and a control unit. Then, the control unit executes a determination process for determining whether or not at least one of the plurality of nozzles is the abnormal nozzle based on the determination signal. When it is determined in the determination process that at least one of the plurality of nozzles is the abnormal nozzle, first data for selection from the first type is generated as data for selecting the size of at least some of the dots formed by the plurality of nozzles from among a plurality of types, and the liquid ejection head is controlled to eject liquid from the plurality of nozzles to form the dots on the medium to be ejected based on the first data. When it is determined in the determination process that the abnormal nozzle does not exist among the plurality of nozzles, second data having a smaller data amount than the first data is generated as data for selecting the size of the dots formed by the plurality of nozzles from among a second type smaller than the first type, and the liquid ejection head is controlled to eject liquid from the plurality of nozzles to form the dots on the medium to be ejected based on the second data. Record dots.

[0007] Further, the liquid ejection system of the present invention includes a liquid ejection head having a plurality of nozzles that eject liquid to form dots of a plurality of types of sizes on a medium to be ejected, a signal output unit that outputs a determination signal according to whether or not the nozzle is an abnormal nozzle having an abnormality in liquid ejection when causing the liquid ejection head to perform inspection driving for checking whether or not the nozzle is an abnormal nozzle, a control unit, and an external device connected to the control unit so as to be able to transmit and receive information based on the signal obtained from the signal output unit. Then, the control unit executes a determination process for determining whether or not at least one of the plurality of nozzles is the abnormal nozzle based on the determination signal, transmits data regarding the determination result in the determination process to the external device, and when the data regarding the determination result transmitted from the control unit indicates the presence of at least one abnormal nozzle among the plurality of nozzles, the external device generates first data for selecting from among a plurality of types as data for selecting the size of at least a part of the dots formed by the plurality of nozzles, transmits the first data to the control unit, and when the data regarding the determination result transmitted from the control unit does not indicate the presence of the abnormal nozzle among the plurality of nozzles, the external device generates second data having a smaller data amount than the first data as data for selecting the size of the dots formed by the plurality of nozzles from among a second type smaller than the first type, transmits the second data to the control unit, and the control unit controls the liquid ejection head to eject liquid from the plurality of nozzles to form the dots on the medium to be ejected based on either the first data or the second data transmitted from the external device.

[0008] Further, a control method for a liquid ejection apparatus according to the present invention includes a liquid ejection head having a plurality of nozzles that eject liquid to form dots of a plurality of types of sizes on a medium to be ejected, and an inspection drive for checking whether or not the nozzles are abnormal nozzles with an abnormality in liquid ejection is performed on the liquid ejection head. A signal output unit that outputs a determination signal according to whether or not the nozzle is the abnormal nozzle, and a control unit connected to an external device so as to be able to transmit and receive information based on the signal obtained from the signal output unit. A control method for a liquid ejection apparatus, comprising: executing a determination process for determining whether or not at least one of the plurality of nozzles is the abnormal nozzle based on information based on the determination signal; and data related to the determination process is among the plurality of nozzles When indicating the presence of at least one abnormal nozzle, as data for selecting the size of at least a part of the dots formed by the plurality of nozzles from a plurality of types, first data for selecting from the first type is generated, and the data related to the determination process does not indicate the presence of the abnormal nozzle among the plurality of nozzles. In this case, as data for selecting the size of the dots formed by the plurality of nozzles from a second type smaller than the first type, second data having a smaller data amount than the first data is generated, and based on either the first data or the second data, the liquid ejection head is controlled to eject liquid from the plurality of nozzles to form the dots on the medium to be ejected.

Effects of the Invention

[0009] According to the liquid ejection apparatus, liquid ejection system, and control method for a liquid ejection apparatus of the present invention, it is possible to generate second data having a smaller data amount than the first data. Therefore, even when having dedicated dot size data for complementing missing dots, it is possible to generate data quickly, and it is possible to shorten the time required until the start of liquid ejection.

Brief Description of the Drawings

[0010]

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Best Mode for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described.

[0012] <Overall Configuration of Printer> As shown in FIG. 1, a printer system 100 (the "liquid ejection system" of the present invention) according to this embodiment includes a printer 1 (the "liquid ejection device" of the present invention) and a PC 90 (personal computer: the "external device" of the present invention) that is connected to be able to transmit and receive information with a control unit 80 (described later) of the printer 1. The printer 1 includes a carriage 2, a sub-tank 3, an inkjet head 4 (the "liquid ejection head" of the present invention), a platen 5, conveyance rollers 6, 7, a maintenance unit 8, and the like.

[0013] The carriage 2 (a "part of the moving mechanism" of the present invention) is supported by two guide rails 11, 12 (a "part of the moving mechanism" of the present invention) extending in the scanning direction. The carriage 2 is connected to a carriage motor 86 (see FIG. 6) via a belt or the like not shown. When the carriage motor 86 (a "part of the moving mechanism" of the present invention) is driven, the carriage 2 moves in the scanning direction along the guide rails 11, 12. Hereinafter, as shown in FIG. 1, the right side and the left side in the scanning direction will be defined for the description.

[0014] The sub-tank 3 is mounted on the carriage 2. Here, the printer 1 has a cartridge holder 13, and four ink cartridges 14 are removably mounted on the cartridge holder 13. The four ink cartridges 14 are arranged side by side in the scanning direction, and store black, yellow, cyan, and magenta inks (the "liquid" of the present invention) in order from the one arranged on the right side in the scanning direction. The sub-tank 3 is connected to the four ink cartridges 14 mounted on the cartridge holder 13 via four tubes 15. Thereby, the above four-color inks are supplied from the four ink cartridges 14 to the sub-tank 3.

[0015] The inkjet head 4 is mounted on the carriage 2 and connected to the lower end of the sub-tank 3. The four-color ink is supplied from the sub-tank 3 to the inkjet head 4. Further, the inkjet head 4 discharges ink from a plurality of nozzles 10 formed on the nozzle surface 4a which is the lower surface thereof. More specifically, the plurality of nozzles 10 are arranged in the conveyance direction orthogonal to the scanning direction to form a nozzle row 9, and on the nozzle surface 4a, four rows of nozzle rows 9 are arranged in the scanning direction. From the plurality of nozzles 10, black, yellow, cyan, and magenta inks are discharged in order from those constituting the nozzle row 9 on the right side in the scanning direction.

[0016] The platen 5 is disposed below the inkjet head 4 and faces the plurality of nozzles 10. The platen 5 extends over the entire length of the recording paper P (the "medium to be discharged" in the present invention) in the scanning direction and supports the recording paper P from below. The conveyance roller 6 is disposed upstream of the inkjet head 4 and the platen 5 in the conveyance direction. The conveyance roller 7 is disposed downstream of the inkjet head 4 and the platen 5 in the conveyance direction. The conveyance rollers 6 and 7 are connected to a conveyance motor 87 (see FIG. 6) via gears or the like not shown. When the conveyance motor 87 is driven, the conveyance rollers 6 and 7 rotate, and the recording paper P is conveyed in the conveyance direction.

[0017] The maintenance unit 8 includes a cap 71, a suction pump 72, and a waste liquid tank 73. The cap 71 is disposed on the right side of the platen 5 in the scanning direction. When the carriage 2 is positioned at the maintenance position on the right side of the platen 5 in the scanning direction, the plurality of nozzles 10 face the cap 71.

[0018] In addition, the cap 71 can be raised and lowered by a cap lifting mechanism 88 (see FIG. 6). When the carriage 2 is positioned at the above maintenance position so that the plurality of nozzles 10 and the cap 71 face each other, and the cap 71 is raised by the cap lifting mechanism 88, the upper end of the cap 71 is in close contact with the nozzle surface 4a, and the plurality of nozzles 10 are covered by the cap 71. Note that the cap 71 is not necessarily limited to covering the plurality of nozzles 10 by being in close contact with the nozzle surface 4a. The cap 71 may cover the plurality of nozzles 10 by being in close contact with, for example, a frame (not shown) disposed around the nozzle surface 4a of the inkjet head 4.

[0019] The suction pump 72 is a tube pump or the like and is connected to the cap 71 and the waste liquid tank 73. In the maintenance unit 8, when the suction pump 72 is driven with the plurality of nozzles 10 covered by the cap 71 as described above, so-called suction purge can be performed to discharge the ink in the inkjet head 4 from the plurality of nozzles 10. The ink discharged by the suction purge is stored in the waste liquid tank 73.

[0020] Here, for the sake of convenience, the description has been made on the assumption that the cap 71 covers all the nozzles 10 together and discharges the ink in the inkjet head 4 from all the nozzles 10 during suction purge, but this is not limitative. For example, the cap 71 may be separately provided with a portion covering the plurality of nozzles 10 constituting the rightmost nozzle row 9 that discharges black ink and a portion covering the plurality of nozzles 10 constituting the three leftmost nozzle rows 9 that discharge color ink (yellow, cyan, and magenta inks), and in the suction purge, either the black ink or the color ink in the inkjet head 4 can be selectively discharged. Alternatively, for example, the cap 71 may be provided individually for each nozzle row 9, and in the suction purge, ink can be discharged from the nozzles 10 individually for each nozzle row 9.

[0021] Also, as shown in FIG. 2, a detection electrode 76 having a rectangular planar shape is disposed within the cap 71. The detection electrode 76 is connected to a high-voltage power supply circuit 77 via a resistor 79. And, during the inspection drive described later, a predetermined potential (e.g., about 600 V) is applied to the detection electrode 76 by the high-voltage power supply circuit 77. On the other hand, the inkjet head 4 is held at the ground potential. Thereby, a predetermined potential difference is generated between the inkjet head 4 and the detection electrode 76. A signal processing circuit 78 is connected to the detection electrode 76. The signal processing circuit 78 includes a differentiating circuit and the like, and outputs a signal obtained by performing a process including differentiation processing on the potential signal output from the detection electrode 76. That is, the signal output from the signal processing circuit 78 is a voltage signal corresponding to the voltage of the detection electrode 76. However, the signal output from the signal processing circuit 78 may be a current signal. In the present embodiment, the combination of the detection electrode 76, the high-voltage power supply circuit 77, the signal processing circuit 78, and the resistor 79 corresponds to the "signal output unit" of the present invention.

[0022] After positioning the carriage 2 at the above maintenance position, a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77. At this time, in a state where the inspection drive described later is not performed, the voltage of the signal output from the signal processing circuit 78 becomes the voltage V0 shown in FIGS. 3(a) and 3(b).

[0023] In the present embodiment, after positioning the carriage 2 at the above maintenance position, an inspection drive is performed to drive the inkjet head 4 so as to eject ink from the nozzle 10 toward the detection electrode 76 in a state where a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77. In the inspection drive, it is driven based on ejection waveform data for ejecting any one of small, medium, and large ink droplet sizes described later.

[0024] If the nozzle 10 is not an abnormal nozzle with an abnormality in ink ejection, when inspection driving is performed, charged ink is ejected from the nozzle 10. As a result, the charged ink approaches the detection electrode 76, and the potential of the detection electrode 76 changes until the ink lands on the detection electrode 76. Then, after the charged ink lands on the detection electrode 76, the potential of the detection electrode 76 returns to the potential before ink ejection while decaying.

[0025] At this time, the signal (the "determination signal" of the present invention) output from the signal processing circuit 78 rises from the voltage V0 to a voltage V1 greater than the voltage V0 as shown in FIG. 3(a), and then decreases to a voltage V2 smaller than the voltage V0, and then repeats rising and falling while decaying and returns to the voltage V0. As a result, the signal output from the signal processing circuit 78 becomes a signal with a maximum value of voltage V1 and a minimum value of voltage V2.

[0026] On the other hand, when the nozzle 10 is an abnormal nozzle, ink is not ejected from the nozzle 10 even when inspection driving is performed. Therefore, the signal output from the signal processing circuit 78 does not change from the voltage V0 as shown in FIG. 3(b).

[0027] As described above, in the present embodiment, depending on whether the nozzle 10 is an abnormal nozzle or not, the signal output from the signal processing circuit 78 when inspection driving is performed is different. And in the present embodiment, this is utilized to determine whether the nozzle 10 is an abnormal nozzle as described later.

[0028] <Inkjet head> Next, the structure of the inkjet head 4 will be described in detail. As shown in FIGS. 4 and 5, the inkjet head 4 includes a flow path unit 21 and a piezoelectric actuator 22.

[0029] The flow path unit 21 is formed by laminating plates 31 to 35 vertically in this order from below. The flow path unit 21 includes a plurality of individual flow paths 41 each including a nozzle 10 and four common flow paths 42.

[0030] Corresponding to the fact that the plurality of nozzles 10 form a nozzle row 9 of four columns as described above, the plurality of individual flow paths 41 form an individual flow path row 29 by being arranged in the conveyance direction, and the flow path unit 21 has four rows of individual flow path rows 29 arranged in the scanning direction.

[0031] Each individual flow path 41 has a nozzle 10, a pressure chamber 51, a descender 52, and a throttle flow path 53. The nozzle 10 and the left end portion of the pressure chamber 51 in the scanning direction are connected via the descender 52, and the throttle flow path 53 is connected to the right end portion of the pressure chamber 51 in the scanning direction.

[0032] The four common flow paths 42 correspond to the four rows of individual flow path rows 29, extend in the conveyance direction, and vertically overlap with the right side portions in the scanning direction of the plurality of individual flow paths 41 that constitute the corresponding individual flow path rows 29. And the common flow path 42 is connected to the right end portions in the scanning direction of the throttle flow paths 53 that constitute these individual flow paths 41. Also, ink is supplied to each common flow path 42 from a supply port 42a provided at the upstream end portion in the conveyance direction.

[0033] The piezoelectric actuator 22 has a diaphragm 61, a piezoelectric layer 62, a common electrode 63, and a plurality of individual electrodes 64. The diaphragm 61 is made of a piezoelectric material mainly composed of lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate, is disposed on the upper surface of the flow path unit 21 (the upper surface of the plate 35), and covers the plurality of pressure chambers 51. The piezoelectric layer 62 is made of the above-described piezoelectric material, is disposed on the upper surface of the diaphragm 61, and continuously extends over the plurality of pressure chambers 51. In this embodiment, the diaphragm 61 and the piezoelectric layer 62 are made of a piezoelectric material, but the diaphragm 61 may be made of an insulating material other than the piezoelectric material, such as a synthetic resin material.

[0034] The common electrode 63 is disposed between the diaphragm 61 and the piezoelectric layer 62 and extends over the entire area thereof. The common electrode 63 is connected to a power source (not shown) via a wiring (not shown) and is held at the ground potential. The plurality of individual electrodes 64 are disposed on the upper surface of the piezoelectric layer 62. The plurality of individual electrodes 64 are individual for the plurality of pressure chambers 51 and vertically overlap the central portions of the corresponding pressure chambers 51. The plurality of individual electrodes 64 are each connected to a driver IC 89 (see FIG. 6) via a wiring (not shown).

[0035] The driver IC 89 is connected to the control unit 80 and supplies drive signals having pulse-shaped drive waveforms, which are generated based on respective ejection data (described later) transmitted from the control unit 80, to the respective individual electrodes 64. That is, according to the drive waveform, the potential of the individual electrode 84 is switched between a predetermined drive potential (for example, about 20 to 30 V) corresponding to the height of the pulse and the ground potential and applied. Thus, like the control unit 80, the driver IC 89 also constitutes a part of the control unit of the present invention. Also, portions sandwiched between the common electrode 63 of the piezoelectric layer 62 and the respective individual electrodes 64 are polarized in the thickness direction, respectively.

[0036] In the piezoelectric actuator 22, a portion vertically overlapping each pressure chamber 51 serves as a drive element 22a for applying pressure to the ink in the pressure chamber 51. Then, by switching the potential of the individual electrode 64 between the ground potential and the drive potential by the driver IC 89, the drive element 22a can be driven. When the drive element 22a is driven, the potential difference between the individual electrode 64 and the common electrode 63 changes, so that portions of the piezoelectric layer 62 and the diaphragm 61 vertically overlapping the pressure chamber 51 are deformed. Due to this deformation, the pressure of the ink in the pressure chamber 51 fluctuates, and ink droplets can be ejected from the nozzle 10 communicating with the pressure chamber 51.

[0037] Note that in this embodiment, the drive element for ejecting ink droplets from the nozzle 10 is a piezoelectric element, but the drive element is not limited to the piezoelectric element. For example, a method of heating the ink by a heating element to cause film boiling, and ejecting ink droplets from the nozzle 10 by the energy at that time, the heating element may be used as the drive element.

[0038] Further, in order to enable multi-tone expression and achieve high-quality printing, the printer 1 of this embodiment can select the sizes of ink droplets with different ink ejection amounts from each nozzle 10 from among five types. That is, for one nozzle 10, it is configured to be able to selectively adopt one operation mode from a total of five operation modes, namely, a non-ejection mode in which no ink droplets are ejected and four ejection modes with different ink droplet volumes corresponding to four ejection amounts of small, medium, large, and extra-large.

[0039] <Electrical Configuration of Printer> Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 6, the printer 1 includes a control unit 80. The control unit 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a flash memory (the "memory unit" of the present invention) 84, an ASIC (Application Specific Integrated Circuit) 85, and the like. The control unit 80 controls the operations of the carriage motor 86, the inkjet head 4 (driver IC 89), the conveyance motor 87, the cap lifting mechanism 88, the suction pump 72, the high-voltage power supply circuit 77, and the like. Further, the control unit 80 receives a signal from the signal processing circuit 78.

[0040] The flash memory 84 includes a first table 84a and a second table 84b. The first table 84a has five ejection waveform data (ejection waveform data with different ejection amounts) respectively corresponding to the above five types (the "first type" in the present invention) of ink droplet sizes shown in FIG. 7(a). The ejection waveform data for no ejection can hold a constant potential without pulses. The ejection waveform data corresponding to small-sized ink droplets has one pulse that can switch the potential between the driving potential and the ground potential, enabling the ejection of a small amount of ink droplets. The ejection waveform data corresponding to medium-sized ink droplets has two of the above pulses, enabling the ejection of a medium amount of ink droplets. The ejection waveform data corresponding to large-sized ink droplets has three of the above pulses, enabling the ejection of a large amount of ink droplets. The ejection waveform data corresponding to extra-large-sized ink droplets has four of the above pulses, enabling the ejection of an extra-large amount of ink droplets. When ejecting extra-large-sized ink droplets, the first period TS1, which is the period during which ink droplets are ejected from the inkjet head 4 onto the recording paper P, is set to a time longer than the four pulses for ejecting extra-large-sized ink droplets. That is, the moving speed of the carriage 2 in the scanning direction when ejecting extra-large-sized ink droplets is determined based on the first period TS1 and the printing resolution. Here, the correspondence between the ejection data and the ejection waveform data is shown. When the ejection data is 2 bits, it is no ejection: 00, ink droplet (small): 01, ink droplet (medium) 10, ink droplet (large) 11, and an ink droplet (extra-large) cannot be assigned with 2 bits. When the ejection data is 3 bits, it is no ejection: 000, ink droplet (small): 001, ink droplet (medium) 010, ink droplet (large) 011, ink droplet (extra-large): 100. When the ejection data is 4 bits, it is no ejection: 0000, ink droplet (small): 0001, ink droplet (medium) 0010, ink droplet (large) 0011, ink droplet (extra-large): 0100. Thus, an extra-large-sized ink droplet can be assigned with 3 bits or 4 bits.

[0041] The second table 84b has four ejection waveform data corresponding to four ink droplet sizes (no ejection, small, medium, large) out of the above five types of ink droplet sizes shown in FIG. 7(b) (the "second type" in the present invention), excluding the extra-large size. These four ejection waveform data only have the corresponding period changed from the first period TS1 to the second period TS2, and the number of pulses contributing to the ink ejection amount is the same as that of the four ejection waveform data in the first table 84a. The second period TS2, which is the period when ink droplets are ejected from the inkjet head 4 onto the recording paper P, is set to a time longer than the three pulses for ejecting large-size ink droplets. At this time, the moving speed of the carriage 2 in the scanning direction is determined based on the second period TS2 and the printing resolution. From the above description, when forming an image on the recording paper P at a specific printing resolution, the moving speed of the carriage 2 in the scanning direction can be increased when printing in the second period TS2 compared to when printing in the first period TS1. Here, the correspondence between the ejection data and the ejection waveform data is shown. When the ejection data is 2 bits, no ejection: 00, ink droplet (small): 01, ink droplet (medium) 10, ink droplet (large) 11.

[0042] Note that the control unit 80 may be configured such that only the CPU 81 performs various processes, or only the ASIC 85 performs various processes, or the CPU 81 and the ASIC 85 cooperate to perform various processes. Also, the control unit 80 may be configured such that one CPU 81 performs processes alone, or a plurality of CPUs 81 share the processes. Further, the control unit 80 may be configured such that one ASIC 85 performs processes alone, or a plurality of ASICs 85 share the processes.

[0043] <Processing at the time of receiving the inspection instruction signal> Next, the process flow of the control unit 80 when receiving an inspection instruction signal instructing to inspect whether the nozzle 10 is an abnormal nozzle will be described. For example, when the user operates an operation unit (not shown) of the printer 1, a PC 90 connected to the printer 1, etc., and instructs to inspect whether the nozzle 10 is an abnormal nozzle, an inspection instruction signal is transmitted from the operation unit, the PC 90, etc., and the control unit 80 receives this inspection instruction signal. Alternatively, for example, when the printer 1 has a clock unit (not shown) that outputs a signal indicating the time, and is set to perform an inspection of whether it is an abnormal nozzle every time a predetermined time arrives, when a signal indicating that the predetermined time has arrived is transmitted from the clock unit, the control unit 80 receives this signal as an inspection instruction signal.

[0044] When receiving the inspection instruction signal, the control unit 80 performs processing along the flow chart of FIG. 8. More specifically, the control unit 80 first sets any one of the plurality of nozzles 10 of the inkjet head 4 as a target nozzle to be inspected for whether it is an abnormal nozzle (S101).

[0045] Subsequently, the control unit 80 executes an inspection drive process (S102). In the inspection drive process, the control unit 80 causes the inkjet head 4 to perform inspection drive for the target nozzle in a state where a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77, and acquires a determination signal output from the signal processing circuit 78 at this time.

[0046] Next, when the inspection drive is performed in S102, the control unit 80 determines whether the difference [Va - Vb] between the maximum value Va and the minimum value Vb in the first period T1 of the determination signal is equal to or greater than the threshold value Vt based on the determination signal output from the signal processing circuit 78 (S103: determination process).

[0047] Here, as shown in FIG. 3(a), the first period T1 is a part of the determination period T. When inspection driving is performed and ink is ejected from the nozzle 10, it is assumed that the value of the determination signal becomes the maximum value V1 at the first timing U1 and the value of the determination signal becomes the minimum value V2 at the second timing U2. The determination period T is a period starting from the start point of the inspection driving as shown in FIG. 3(a) and ending when the signal output from the signal processing circuit 78 sufficiently attenuates when ink is ejected from the nozzle 10 by the inspection driving. In this embodiment, at the manufacturing stage of the printer 1 or the like, the first timing U1 and the second timing U2 are obtained through experiments or the like, and based on this, information on the first period T1 is stored in the flash memory 84.

[0048] When the difference [Va - Vb] between the maximum value Va and the minimum value Vb of the determination signal is equal to or greater than the threshold value Vt (S103: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S104).

[0049] When the difference [Va - Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the threshold value Vt (S103: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S105).

[0050] After S104 or S105, the control unit 80 determines whether the inspection for whether each nozzle 10 of the inkjet head 4 is an abnormal nozzle has been completed (S106). If there is a nozzle 10 for which the inspection for whether it is an abnormal nozzle has not been completed (S106: NO), the control unit 80 changes the target nozzle to any nozzle 10 for which the inspection for whether it is an abnormal nozzle has not been completed (S107), and returns to S102.

[0051] If the inspection for whether each nozzle 10 of the inkjet head 4 is an abnormal nozzle has been completed (S106: YES), the control unit 80 controls the high-voltage power supply circuit 77 to cancel the application of voltage to the detection electrode 76 (S108).

[0052] Next, based on the result of the determination process of S103 for the plurality of nozzles 10 of the inkjet head 4, the control unit 80 determines whether the number of abnormal nozzles is 1 or more (S109). When the number of abnormal nozzles is 1 or more (S109: YES), the control unit 80 stores the abnormal nozzle flag information in the flash memory 84 (S110). The abnormal nozzle flag information here is flag information indicating that an abnormal nozzle has occurred. When there is no abnormal nozzle (S109: NO), the process proceeds to S111. In S111, if the abnormal nozzle flag information is stored in the flash memory 84, the control unit 80 erases the flag information. Thus, the process ends.

[0053] <Control during recording> Subsequently, the control when recording on the recording paper P in the printer 1 will be described. In the printer 1, for example, when a user operates the PC90 (external device) and receives a recording command signal including image data for recording an image on the recording paper P transmitted from the PC90, the control unit 80 performs processing along the flow of FIG. 9.

[0054] Explaining the flow of FIG. 9 in more detail, the control unit 80 first determines whether a recording command signal has been received (S201). When the recording command signal has not been received (S201: NO), S201 is repeated. When the recording command signal has been received (S201: YES), the control unit 80 determines whether abnormal nozzle flag information is stored in the flash memory 84 (S202).

[0055] When the abnormal nozzle flag information is stored in the flash memory 84 (S202: YES), the process proceeds to S203. When the abnormal nozzle flag information is not stored in the flash memory 84 (S202: NO), the process proceeds to S204.

[0056] In S203, the control unit 80 executes the first ejection data generation process. The first ejection data is ejection data in all image formation paths executed based on the recording command signal. One image formation path in the present embodiment refers to a path in which the carriage 2 moves in one or the other direction in the scanning direction while the conveyance of the recording paper P in the conveyance direction is stopped. As a modification, one image formation path may be a path in which the carriage 2 reciprocates in the scanning direction while the conveyance of the recording paper P in the conveyance direction is stopped.

[0057] When the information indicating that ink droplets are ejected from an abnormal nozzle to form dots on the recording paper P is included in the recording command signal, the control unit 80 generates first ejection data including first data for selecting an extra-large size for the ink droplet size corresponding to the adjacent dots formed adjacent to the dots (i.e., the dots that were supposed to be formed by the abnormal nozzle). In the first data in the present embodiment, 4 bits are allocated. For this reason, it is possible to use data that can select up to 16 types of dot sizes. In the present embodiment, the first data is used as data for selecting specific ejection waveform data from among the five types of ejection waveform data in the first table 84a. When using the first data, as described above, among the five types of ejection waveform data, "0000" is used when selecting no ejection, "0001" is used when selecting a small ink droplet size, "0010" is used when selecting a medium ink droplet size, "0011" is used when selecting a large ink droplet size, and "0100" is used when selecting an extra-large ink droplet size.

[0058] Also, when executing one or more image formation paths, the control unit 80 generates first ejection data in which the data for selecting the size of all dots formed in one image formation path in which dots that were supposed to be formed by an abnormal nozzle exist is the first data.

[0059] Further, when there are no dots that were supposed to be formed by the abnormal nozzle among the plurality of dots formed in one image formation path, the control unit 80 generates first ejection data including second data for selecting the ink droplet sizes of the plurality of dots. At this time, when there are no dots that were supposed to be formed by the abnormal nozzle among the plurality of dots formed in one image formation path and information indicating that ink droplets are not ejected from the abnormal nozzle to form blank dots is included in the recording command signal, the control unit 80 selects the ink droplet size corresponding to the adjacent dots formed adjacent to the blank dots, and generates first ejection data including second data for selecting the ink droplet size that is selected when there is no abnormal nozzle. The first ejection data thus generated is transmitted to the driver IC 89, and the process proceeds to S205.

[0060] On the other hand, in S204, the control unit 80 executes the second ejection data generation process. The second ejection data is ejection data in all image formation paths executed based on the recording command signal. The control unit 80 generates second ejection data including second data for selecting the ink droplet sizes of a plurality of dots based on the recording command signal. In the present embodiment, 2 bits are allocated to the second data. Therefore, it is possible to use data that can select up to four types of dot sizes. In the present embodiment, the second data is used as data for selecting specific ejection waveform data from the four types of ejection waveform data in the second table 84b, but the second data may also be used as data for selecting specific ejection waveform data from the five types of ejection waveform data in the first table 84a. When using the second data, as described above, among the four types of ejection waveform data, "00" is used when selecting no ejection, "01" is used when selecting a small ink droplet size, "10" is used when selecting a medium ink droplet size, and "11" is used when selecting a large ink droplet size. Since such second data has a smaller data amount than the first data, the second ejection data is smaller than the first ejection data including the first data generated based on the same recording command signal. The second ejection data thus generated is transmitted to the driver IC 89, and the process proceeds to S205.

[0061] Here, a case will be described where, based on a received recording command signal, image recording forms solid lines of different colors on a recording paper P for each image forming path. On the left side of FIG. 10, a state where a plurality of nozzles 10 are arranged along the conveyance direction is shown. In the center of FIG. 10, a part of a solid line composed of a plurality of dots formed by ejecting ink droplets from these nozzles 10 is shown. On the right side of FIG. 10, ejection data for ejecting ink droplets from the nozzles 10 is shown. For example, in the first image forming path, ink is ejected from all the nozzles that eject black ink to form a black line. After the recording paper P is conveyed by a predetermined conveyance amount, in the next image forming path, ink is ejected from all the nozzles that eject magenta ink to form a magenta line. Thereafter, lines of yellow and cyan are formed in order.

[0062] As shown in FIG. 10(a), when there are no abnormal nozzles in the nozzles 10 for each color, a plurality of dot trains DT in which dots D are arranged in the scanning direction are formed in the conveyance direction on the recording paper P by ejecting ink droplets from each nozzle 10, and a solid line is formed. At this time, the control unit 80 generates second ejection data as shown on the right side of FIG. 10(a) corresponding to the arrangement order of the nozzles 10 in FIG. 10(a) in S204. The second ejection data at this time is data in which second data corresponding to each nozzle 10 is arranged in order. More specifically, 2 bits are allocated to the second data. Although the ink droplet size indicated by the second data in the present embodiment is a large size, it may be changed as appropriate.

[0063] On the other hand, as shown in FIG. 10(b), for example, among a plurality of nozzles 10 that eject black ink (the "first liquid" of the present invention), even though only the third nozzle 10 from the top is an abnormal nozzle (indicated by a black circle in the figure), when performing normal image formation, the control unit 80 generates second ejection data as shown on the right side of FIG. 10(b) corresponding to the arrangement order of the nozzles 10 in FIG. 10(b). In this case, a blank dot sequence DT1 is formed by dots (dots D1 indicated by broken lines) that were supposed to be formed by the abnormal nozzle, and except for this, the above-described dot sequence DT is formed. When this blank dot sequence DT1 is formed, it becomes a white streak and the image quality deteriorates.

[0064] In the present embodiment, in order to suppress such white streaks, the above-described control is performed. As shown in FIG. 10(c), an adjacent dot D2 adjacent to dot D1 is set to an extra-large dot size larger than dot D. That is, in S203, the control unit 80 selects an extra-large size for the ink droplet size corresponding to the adjacent dot D2 formed adjacent to the dot D1 that was supposed to be formed by the abnormal nozzle (the "nozzle for the first liquid" of the present invention), and generates first ejection data including the first data for selecting the ink droplet size corresponding to the dots D other than the adjacent dot D2. In other words, in S203, the control unit 80 selects an extra-large size for the ink droplet size corresponding to the adjacent dot D2 formed by the nozzle 10 (the "second nozzle" of the present invention) adjacent to the nozzle 10 corresponding to the abnormal nozzle (the "first nozzle" of the present invention) in the conveyance direction, and generates first ejection data including the first data for selecting the ink droplet size corresponding to the dots D formed by the nozzles 10 other than the nozzles 10 adjacent to the abnormal nozzle.

[0065] As a result, a dot sequence DT2 formed by adjacent dots D2 is formed at a position sandwiching the dot sequence DT1 in the conveyance direction, and the above-described dot sequence DT is formed otherwise. By forming adjacent dots D2 that are larger than the size of dots D formed when there are no abnormal nozzles in this way, the blank portion of the dot sequence DT1 is filled by the dot sequence DT2, making the white streaks less prominent.

[0066] At this time, the control unit 80 generates first ejection data as shown on the right side of FIG. 10(c), corresponding to the arrangement order of the nozzles 10 in FIG. 10(c), in S203. In the image formation path when forming a black line, the first ejection data is a plurality of first data not including the second data arranged in a row. More specifically, 4 bits are allocated to the first data. Among the plurality of first data in the present embodiment, the first data corresponding to the two nozzles 10 sandwiching the abnormal nozzle in the conveyance direction is data "0100" that selects an extra-large size for the ink droplet size, and the first data corresponding to the other nozzles 10 is data "0011" that selects a large size for the ink droplet size. Note that the ink droplet size for forming the adjacent dots D2 may be any size as long as it is larger than the dots formed when there are no abnormal nozzles. Also, in the present embodiment, at the abnormal nozzle, ink is not ejected using "00" or "0000" that selects no ejection, but as a modification, data for ejecting ink from the abnormal nozzle may be selected. For example, the presence or absence of ejection may be changed due to states such as splashes or bends in the state of the abnormal nozzle.

[0067] On the other hand, in S203, when forming a color line other than the black line (that is, when forming a color line by the nozzle 10 (the "nozzle for the second liquid" of the present invention) that discharges the color ink (the "second liquid" of the present invention)), the control unit 80 generates first discharge data in which a plurality of second data not including the first data are arranged. As a result, it becomes possible to use the second data as the data for discharging the color ink from the nozzle 10 that does not have an abnormal nozzle. Therefore, even if there is an abnormal nozzle in the nozzle 10 that discharges the black ink, the control unit 80 can quickly generate the data for the nozzle 10 that discharges the color ink, and can effectively shorten the time required until the start of image recording. Note that the ink droplet size indicated by the second data in the present embodiment is a large size, but it may be changed as appropriate.

[0068] In addition, when a plurality of dots formed in one image forming pass when forming a line with mixed colors include dots that were supposed to be formed by an abnormal nozzle, all of the discharge data of black, yellow, cyan, and magenta in the one image forming pass may be formed with the first data, or only the discharge data of black with an abnormal nozzle may be formed with the first data, and yellow, cyan, and magenta without an abnormal nozzle may be formed with the second data.

[0069] Next, in S205, the control unit 80 executes image recording processing. That is, based on the received recording command signal, the control unit 80 controls a paper feeding mechanism (not shown) and a conveyance motor 87 to supply the recording paper P to the paper feeding mechanism, and conveys the recording paper P to the conveyance rollers 6 and 7 until the area where an image is to be recorded in the first recording path of the recording paper P faces a plurality of nozzles 10 of the inkjet head 4. Then, the control unit 80 controls the carriage motor 86 to move the carriage 2 in the scanning direction, and causes an image forming path in which ink is ejected from the plurality of nozzles 10 toward the recording paper P to be performed. At this time, when executing one image forming path in which ink droplets are ejected from the nozzles 10 based on the first ejection data including the first data, the control unit 80 controls the carriage motor 86 so that the carriage 2 moves in the scanning direction at a first moving speed based on the first cycle TS1 and the printing resolution. Further, when executing another image forming path in which ink droplets are ejected from the nozzles 10 based on the first ejection data or the second ejection data including only the second data, the control unit 80 controls the carriage motor 86 so that the carriage 2 moves in the scanning direction at a second moving speed based on the second cycle TS2 and the printing resolution. Thus, in the first ejection data or the second ejection data that does not include the first data and includes only the second data, when the printing resolution is the same, the carriage 2 moves at a second moving speed that is faster than the first moving speed. Thereby, in one image forming path, when there are no abnormal nozzles, the time required from the start to the end of image recording on the recording paper P is shortened.

[0070] Also, when progressing from S203 to S205 (i.e., when the first ejection data is transmitted to the driver IC89), the driver IC89 selects ejection waveform data from the first table 84a and the second table 84b based on the first ejection data, generates a drive signal having a pulsed drive waveform, and supplies it to each individual electrode 64 so as to eject ink droplets of a desired size from each nozzle 10. On the other hand, when progressing from S204 to S205 (i.e., when the second ejection data is transmitted to the driver IC89), the driver IC89 selects an ejection waveform from the second table 84b based on the second ejection data, generates a drive signal having a pulsed drive waveform, and supplies it to each individual electrode 64 so as to eject ink droplets of a desired size from each nozzle 10. In this way, a plurality of dots are formed on the recording paper P and an image is recorded.

[0071] After that, when the recording on one sheet of recording paper P is not completed, the control unit 80 controls the conveyance motor 87 to convey the recording paper P a predetermined distance by the conveyance rollers 6 and 7, and repeats the operation of causing the image formation path to be performed again until the recording on one sheet of recording paper P is completed. When the recording of the image on one sheet of recording paper P is completed, the control unit 80 controls the conveyance motor 87 to discharge the recording paper P on which the recording is completed by the conveyance rollers 6 and 7. In this way, the control during recording is terminated.

[0072] As described above, according to the printer 1 of the present embodiment, when there is no abnormal nozzle, the control unit 80 can generate second ejection data having second data with a smaller data amount than the first data. Therefore, even if it has dedicated dot size data for complementing missing dots, the control unit 80 can quickly generate the data to be transmitted to the driver IC89, and can shorten the time required until the start of image recording.

[0073] For the first data, 4 bits are allocated to each dot, and for the second data, 2 bits are allocated to each dot. The ejection data (data for selecting the size of each dot) generally deals with binary data composed of 0 or 1. When 4 bits (first data) are allocated to each dot, it can be data that can select 16 types of dot sizes, but the data amount increases accordingly. However, when 2 bits (second data) are allocated to each dot, 4 types of dot sizes can be selected, and the data amount can be reduced to approximately half compared to 4 bits. For this reason, the second ejection data becomes even smaller than the first ejection data. Also, data that is a power of 2 such as 2 bits and 4 bits can fit within 8 bits without a remainder, so the arithmetic processing can be performed with a simpler program. For this reason, the control unit 80 can generate or process data quickly, and it is possible to shorten the time required to start image recording.

[0074] As a modification, as shown in FIGS. 7 and 12, instead of 4 bits for the first data, 3 bits may be allocated. In this case, for example, among 5 types of ejection waveform data, when no ejection is selected, "000" is used, when a small ink droplet size is selected, "001" is used, when a medium ink droplet size is selected, "010" is used, when a large ink droplet size is selected, "011" is used, and when an extra-large ink droplet size is selected, "100" is used. Otherwise, the same applies to the first data with 4 bits allocated as described above. When 4 bits are allocated to each dot, it can be data that can select 16 types of dot sizes, but the data amount increases accordingly. However, by allocating 3 bits to each dot, 8 types of dot sizes can be selected, and moreover, the data amount can be reduced compared to 4 bits.

[0075] The dot with the largest size in the second table 84b (the ink droplet size is large) is smaller than the dot with the largest size in the first table 84a (the ink droplet size is extremely large). As a result, it becomes possible to make the dots formed based on the first data larger than the dots formed based on the second data.

[0076] The dot sizes that can be selected from the first table 84a include all of the dot sizes that can be selected from the second table 84b. As a result, since it includes the sizes of common image dots, image processing becomes easier. More specifically, the ink ejected from the inkjet head 4 includes four types: yellow, cyan, magenta, and black. When expressing other colors, the respective colors are mixed (or two or more colors are arranged at adjacent close positions) to express colors such as green, purple, and orange. For example, when expressing orange with the dots selected by the first data and the dots selected by the second data, there may be a case where yellow with an abnormal nozzle is the first data and magenta without an abnormal nozzle is the second data. At this time, if there is no common dot size to select, image processing (color expression) becomes difficult. However, in this embodiment, since the dot sizes other than extremely large are common between the first data and the second data, it becomes possible to select the same dot size, and image processing becomes easier.

[0077] The second table 84b has five ejection waveform data corresponding to four ink droplet sizes corresponding to no ejection and three types of ejection amounts: small, medium, and large, respectively. The first table 84a has four ejection waveform data corresponding to five ink droplet sizes obtained by adding an extremely large ejection amount to the above four types, respectively. As a result, it becomes possible to make the maximum size of the dots formed based on the first data larger than the dots formed based on the second data.

[0078] When it is determined that there is an abnormal nozzle, in S203, the control unit 80 generates first data as data for selecting the size of an adjacent dot adjacent to a dot that was supposed to be formed by the abnormal nozzle. Thereby, it becomes possible to select and form the size of the adjacent dot adjacent to the dot that was supposed to be formed by the abnormal nozzle from among the five types in the first table 84a.

[0079] In S203, when the abnormal nozzle is a nozzle that forms a blank dot without discharging an ink droplet, the control unit 80 generates first ejection data including second data for selecting the ink droplet size corresponding to the adjacent dot formed adjacent to the blank dot, which is the ink droplet size selected when there is no abnormal nozzle. Thereby, even when there is an abnormal nozzle, when the abnormal nozzle is a nozzle that forms a blank dot, it becomes possible to generate the second data. For this reason, it becomes possible to effectively generate data quickly and shorten the time required until the start of image recording.

[0080] The driver IC (control unit) 89 generates a drive signal based on the first data and the first table 84a, discharges an ink droplet from the nozzle 10 onto the recording paper P to form a dot, generates a drive signal based on the second data and the second table 84b, and discharges an ink droplet from the nozzle 10 onto the recording paper P to form a dot. Thereby, when the control unit 80 generates the first data, dots can be formed using the ejection waveform data in the first table 84a, and when the second data is generated, dots can be formed using the ejection waveform data in the second table 84b.

[0081] In addition, when an adjacent dot adjacent to a dot that was supposed to be formed by an abnormal nozzle (the "first nozzle" of the present invention) is formed by a nozzle (the "second nozzle" of the present invention) adjacent to the abnormal nozzle along the conveyance direction, it is larger than the size of the dot formed by the adjacent nozzle when the abnormal nozzle was not an abnormal nozzle. As a result, it is possible to make the adjacent dot adjacent to the dot that was supposed to be formed by the abnormal nozzle (first nozzle) based on the first data larger in size, and to form the adjacent dot by the nozzle adjacent to the abnormal nozzle.

[0082] Further, when there is no abnormal nozzle among the plurality of nozzles that form a plurality of dots in one image formation path, and both of the two nozzles 10 (first nozzle and second nozzle) adjacent in the conveyance direction are not abnormal nozzles, the control unit 80 generates second discharge data including second data as data for selecting the sizes of the dots in both the first dot row and the second dot row along the scanning direction formed by these two nozzles 10. Then, when there is an abnormal nozzle among the plurality of nozzles that form a plurality of dots in one image formation path, first discharge data including first data is generated as data for selecting the size of the dot by the nozzle adjacent to the abnormal nozzle. As a result, it is possible to reduce the data amount related to the dots for both of the two nozzles 10.

[0083] In addition, the control unit 80 generates first discharge data including first data as data for forming an image formation path in which there is a dot that was supposed to be formed by an abnormal nozzle, and generates first discharge data or second discharge data including second data as data for forming another image formation path in which there is no dot that was supposed to be formed by an abnormal nozzle. As a result, it is possible to generate either the first data or the second data for each image formation path.

[0084] In the above-described embodiment, in one image formation path, the first data and the second data were not mixed in the first ejection data. However, the first data and the second data may be mixed in the first ejection data. For example, as shown in FIG. 13, the second data may be used as data for forming dots D other than the adjacent dots D2. In this case, the control unit 80 may generate the first ejection data as shown in FIG. 13. At this time, additional data for causing the first table 84a to select ejection waveform data corresponding to ink droplets of the same size according to the size of the ink droplets indicated by the second data is included in the first ejection data. As a result, since the data for forming the dots D other than the adjacent dots D2 decreases in data amount from the first data to the second data, in one image formation path, the data amount of the first ejection data becomes smaller than that including only the first data. Therefore, as described above, the control unit 80 can generate the data to be transmitted to the driver IC89 earlier, and can shorten the time required until the start of image recording. Also, when forming an image in which colors are mixed in one image formation path, the first data and the second data may be mixed in the first ejection data as described above. That is, it becomes possible to use the second data as data for ejecting the color ink from the nozzle 10 that ejects the color ink without abnormal nozzles. For this reason, even if there are abnormal nozzles in the nozzle 10 that ejects the black ink, the control unit 80 can generate the data for the nozzle 10 that ejects the color ink earlier, and can effectively shorten the time required until the start of image recording.

[0085] In the above-described embodiment, the control unit 80 generated each ejection data. However, each ejection data may be generated by the PC 90, and the driver IC 89 may generate a drive signal based on the ejection data transmitted from the PC 90 to the control unit 80, and eject ink droplets from the nozzle 10 onto the recording paper P to perform image recording. The control during recording in the printer system 100 in this modification will be described below with reference to FIG. 11. Note that the processing at the time of receiving the inspection instruction signal is the same as in the above-described embodiment.

[0086] As shown in FIG. 11, the control unit 80 first executes S301 similar to the above-described S201. In S301, when a recording command signal is received (S301: YES), the control unit 80 transmits data (abnormal nozzle information stored in the flash memory 84) indicating the determination result in the determination process of S103 to the PC 90 (S302).

[0087] Next, in S303, the PC 90 determines whether there is an abnormal nozzle from the transmitted data. When there is an abnormal nozzle (S303: YES), the PC 90 executes a first ejection data generation process similar to the above-described S203 (S304). The first ejection data generated in S304 is transmitted from the PC 90 to the control unit 80 and then from the control unit 80 to the driver IC 89.

[0088] On the other hand, when there is no abnormal nozzle (S303: NO), the PC 90 executes a second ejection data generation process similar to the above-described S204 (S305). The second ejection data generated in S305 is transmitted from the PC 90 to the control unit 80 and then from the control unit 80 to the driver IC 89.

[0089] Next, the control unit 80 executes an image recording process similar to the above-described S205 (S306). When the recording of an image on one sheet of recording paper P is thus completed, the control unit 80 controls the conveyance motor 87 to discharge the recording paper P on which the recording has been completed from the conveyance rollers 6 and 7. Thus, the control during recording ends.

[0090] According to the control method of the printer system 100 and the printer 1 according to such a modification, when there is no abnormal nozzle, it is possible to generate second ejection data having second data with a smaller data amount than the first data. Therefore, even if there is dedicated dot size data for complementing missing dots, it is possible to quickly generate the data to be transmitted to the driver IC 89, and it is possible to shorten the time required until the start of image recording.

[0091] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications are possible as long as they are within the scope described in the claims.

[0092] In the above-described embodiments and each modification, when there is no abnormal nozzle, the second ejection data generated based on the recording command signal does not include the first data. However, when there is an abnormal nozzle, if the data amount of the second ejection data generated based on the recording command signal is smaller than that of the first ejection data generated based on the recording command signal, the first data may be included in the second ejection data.

[0093] In the above-described embodiments and each modification, when dots are expected to be formed by an abnormal nozzle, the size of the dots formed by ejection from nozzle 10 adjacent to the abnormal nozzle is made larger than the dot size formed when there is no abnormal nozzle. However, for any nozzle that forms dots adjacent to the dots expected to be formed by the abnormal nozzle, the size of the dots formed by ejection from nozzle 10 not adjacent to the abnormal nozzle may be made larger than the dot size formed when there is no abnormal nozzle. By doing so, the same effect as described above can be obtained.

[0094] Also, in the above-described embodiments and each modification, when dots are expected to be formed by an abnormal nozzle, only the size of the dots adjacent to the dots expected to be formed by the abnormal nozzle is made larger than the dot size formed when there is no abnormal nozzle. However, the size of the dots around the dots adjacent to the dots expected to be formed by the abnormal nozzle may be made larger than the dot size formed when there is no abnormal nozzle. In this way, the dot omission due to the abnormal nozzle may be distributed to the dot group near the dot omission, and interpolation by error diffusion may be performed. In this case, the same effect as described above can be obtained.

[0095] In the above embodiments and each modification example, although the size of the adjacent dot of the dot that was supposed to be formed by the abnormal nozzle was an extremely large ink droplet size, it may be a size other than the extremely large ink droplet size as long as it is larger than the dot size formed when there is no abnormal nozzle.

[0096] In the above embodiments and each modification example, although the size of the adjacent dot of the dot that was supposed to be formed by the abnormal nozzle was an extremely large ink droplet size, it does not have to be an adjacent dot. Also, the size of the ink droplet added in the first data may be a dot with a size smaller than the large ink droplet size. This also increases the types of dots used when complementing the abnormal nozzle, making it easier to complement the nozzle that was supposed to be formed by the abnormal nozzle.

[0097] At least a part of the discharge amount of the ink droplet size corresponding to each of the four types of discharge waveform data excluding the discharge waveform data corresponding to the extremely large ink droplet size of the first table 84a may be different from the discharge amount of the ink droplet size corresponding to each of the four types of discharge waveform data of the second table 84b. Also, the first table 84a and the second table 84b may be composed of one table. Further, if the number of types of ink droplet sizes mainly selected by the first data is larger than the number of types of ink droplet sizes mainly selected by the second data, the number of types may be determined as appropriate.

[0098] In the above-described embodiments and each modification, when information indicating that ink droplets are to be ejected from an abnormal nozzle to form dots on the recording paper P is included in the recording command signal, the control unit 80 generates first ejection data including first data for selecting an extra-large size for the ink droplet size corresponding to adjacent dots formed adjacent to the dots (i.e., the dots that were supposed to be formed by the abnormal nozzle). However, the present invention is not limited to this. For example, when there is an abnormal nozzle, regardless of whether information indicating that ink droplets are to be ejected to form dots on the recording paper P is included in the recording command signal, first ejection data using the first data may be generated. In this case, since it is not determined whether to eject ink droplets from the abnormal nozzle, for all colors with abnormal nozzles, first ejection data using the first data may be generated in all passes. This simplifies the control process and can shorten the time required to start image recording.

[0099] Also, in the above examples, the timing of suction purge and the like were omitted. For example, at the timing of S109 described above, when the number of abnormal nozzles is equal to or more than a predetermined number, the control unit 80 may execute a purge process. At this time, as the number of abnormal nozzles increases, the amount of ink discharged in the suction purge may be increased or the like.

[0100] Also, the purge is not limited to being a suction purge. For example, a pressure pump may be provided in the middle of the tube 15 connecting the sub-tank 3 and the ink cartridge 14. Alternatively, a pressure pump connected to the ink cartridge may be provided in the printer. Then, with the plurality of nozzles 10 covered with the cap 71, by driving the pressure pump, the ink in the inkjet head 4 is pressurized to discharge the ink in the inkjet head 4 from the nozzles 10, and a so-called pressure purge may be performed.

[0101] Furthermore, during purging, both suction by the suction pump 72 and pressurization by the pressure pump may be performed. Alternatively, instead of purging, the inkjet head 4 may be caused to perform flushing for discharging ink from at least the abnormal nozzles. Further, both purging and flushing may be performed.

[0102] Also, when there are abnormal nozzles, the control unit 80 is not necessarily limited to automatically performing suction purging or the like. For example, when there are abnormal nozzles, the user may be notified and the user may be allowed to select whether to perform suction purging, and suction purging may be performed when it is selected to perform suction purging.

[0103] In the above-described embodiment, inspection driving is performed for all the nozzles 10 of the inkjet head 4, but this is not limiting. For example, inspection driving may be performed only for some of the nozzles 10 of the inkjet head 4, such as every other nozzle 10 in each nozzle row 9, and for the other nozzles 10, it may be estimated whether they are abnormal nozzles based on the determination result for the above-mentioned some nozzles 10.

[0104] In the above-described embodiment, the signal processing circuit 78 outputs a signal corresponding to whether or not it is an abnormal nozzle according to the change in the voltage of the detection electrode 76 when ink is ejected from the nozzle 10 toward the detection electrode 76, but this is not limiting.

[0105] For example, a detection electrode extending in the vertical direction may be arranged, and a signal corresponding to whether or not it is an abnormal nozzle may be output from a determination circuit according to the change in the voltage of the detection electrode when ink is ejected so as to pass through a region facing the detection electrode from the nozzle 10. Alternatively, an optical sensor (the "signal output unit" of the present invention) for detecting the ink ejected from the nozzle 10 may be provided, and a signal corresponding to whether or not it is an abnormal nozzle may be output from the optical sensor.

[0106] Alternatively, for example, similar to that described in Japanese Patent No. 4929699, a voltage detection circuit (the "signal output unit" of the present invention) that detects a change in voltage when ink is ejected from a nozzle may be connected to a plate on which nozzles of an inkjet head are formed, and a signal corresponding to whether or not a nozzle is an abnormal nozzle may be output from the voltage detection circuit to the control unit 80.

[0107] Alternatively, for example, similar to that described in Japanese Patent No. 6231759, the substrate of the inkjet head may be provided with a temperature detection element (the "signal output unit" of the present invention). Then, after applying a first applied voltage to drive the heater for ink ejection and then applying a second applied voltage to drive the heater so that ink is not ejected, based on the change in temperature detected by the temperature detection element after applying the second applied voltage and until a predetermined time elapses, a signal corresponding to whether or not the nozzle 10 is an abnormal nozzle may be output.

[0108] In the above examples, the signal output unit outputs a signal corresponding to whether or not ink has been ejected from the nozzle 10, but it is not limited to this. The signal output unit may output a signal corresponding to whether or not a nozzle is an abnormal nozzle with an abnormality other than non-ejection of ink. An abnormality other than non-ejection of ink is, for example, an abnormality in the ejection direction of the ink.

[0109] In the above, an example in which the present invention is applied to a printer equipped with a so-called serial head that ejects ink from a plurality of nozzles while moving in the scanning direction together with a carriage has been described, but it is not limited to this. For example, the present invention can also be applied to a printer equipped with a so-called line head that extends over the entire length of a recording sheet in the scanning direction. Further, in order to relatively move the inkjet head 4 and the recording sheet P, the carriage 2 is moved in the scanning direction, but the recording sheet P or both the recording sheet and the carriage 2 may be moved.

[0110] In addition, in the above description, an example of applying the present invention to a printer that discharges ink from a nozzle to perform recording on a recording paper P has been described, but the present invention is not limited thereto. The present invention can also be applied to printers that record images on recording media other than recording paper, such as T-shirts, sheets for outdoor advertisements, cases of portable terminals such as smartphones, cardboard, and resin members. Further, the present invention can also be applied to liquid ejection devices that eject liquids other than ink, for example, resins or metals in a liquid state.

Explanation of Reference Numerals

[0111] 1 Printer (liquid ejection device) 2 Carriage (part of the moving mechanism) 4 Inkjet head (liquid ejection head) 10 Nozzle 11, 12 Guide rail (part of the moving mechanism) 76 Detection electrode (part of the signal output unit) 77 High-voltage power supply circuit (part of the signal output unit) 78 Signal processing circuit (part of the signal output unit) 79 Resistor (part of the signal output unit) 80 Control unit 84 Flash memory (storage unit) 86 Carriage motor (part of the moving mechanism) 90 PC (external device)

Claims

1. A liquid ejection head having a plurality of nozzles that eject a liquid to form dots of a plurality of sizes on a medium to be ejected, a signal output unit that outputs a determination signal according to whether or not the nozzle is an abnormal nozzle when the liquid ejection head is subjected to an inspection drive for checking whether or not the nozzle is an abnormal nozzle in liquid ejection, and a control unit, wherein the control unit executes a determination process for determining whether or not at least one of the plurality of nozzles is the abnormal nozzle based on the determination signal, when it is determined in the determination process that at least one of the plurality of nozzles is the abnormal nozzle, generates first data for selection from a first type as data for selecting the size of at least some of the dots formed by the plurality of nozzles from among a plurality of types, and controls the liquid ejection head to eject a liquid from the plurality of nozzles to form the dots on the medium to be ejected based on the first data, when it is determined in the determination process that the abnormal nozzle does not exist among the plurality of nozzles, generates second data having a smaller data amount than the first data as data for selecting the size of the dots formed by the plurality of nozzles from a second type smaller than the first type, and controls the liquid ejection head to eject a liquid from the plurality of nozzles to form the dots on the medium to be ejected based on the second data. A liquid ejection device characterized by the above.

2. 4 bits are allocated to one dot in the first data, The liquid ejection device according to claim 1, wherein 2 bits are allocated to one dot in the second data.

3. 3 bits are allocated to one dot in the first data, The liquid ejection device according to claim 1, wherein 2 bits are allocated to one dot in the second data.

4. The liquid ejection device according to any one of claims 1 to 3, wherein the dot having the largest size among the second type is smaller than the dot having the largest size among the first type.

5. The liquid ejection device according to any one of claims 1 to 4, characterized in that the dot sizes that can be selected from the first type include all of the dot sizes that can be selected from the second type.

6. The second type includes four types corresponding to no ejection and three types of ejection amounts, namely small, medium, and large. The liquid ejection device according to any one of claims 1 to 5, characterized in that the first type includes five types obtained by adding an extra-large ejection amount greater than the large ejection amount to the four types.

7. The liquid ejection device according to any one of claims 1 to 6, characterized in that at least some of the dots include adjacent dots adjacent to the dots that were supposed to be formed by the abnormal nozzle.

8. The control unit When it is determined in the determination process that at least one of the plurality of nozzles is the abnormal nozzle, and when the abnormal nozzle is a nozzle that forms blank dots without ejecting liquid, the liquid ejection device according to any one of claims 1 to 7, characterized in that the second data is generated.

9. Further comprising a storage unit The storage unit A first table having a plurality of ejection waveform data with different ejection amounts corresponding to the first type, and A second table having a plurality of ejection waveform data with different ejection amounts corresponding to the second type, and stores them. The control unit When the first data is generated, the dots are formed on the medium to be ejected based on the first data and the first table. The liquid ejection device according to any one of claims 1 to 8, characterized in that when the second data is generated, the dots are formed on the medium to be ejected based on the second data and the second table.

10. The plurality of nozzles include a plurality of first liquid nozzles for ejecting a first liquid and a plurality of second liquid nozzles for ejecting a second liquid different from the first liquid. The control unit When the abnormal nozzle exists in the first liquid nozzles and does not exist in the second liquid nozzles, data for selecting the sizes of at least some of the dots formed by the first liquid nozzles is generated as the first data, and data for selecting the sizes of the dots formed by the second liquid nozzles is generated as the second data. The liquid ejection device according to any one of claims 1 to 9, characterized in that.

11. further comprising a moving mechanism for moving at least one of the liquid ejection head and the medium to be ejected so that the liquid ejection head moves relative to the medium to be ejected in one direction when the liquid ejection head ejects liquid; the plurality of nozzles includes a first nozzle and a second nozzle arranged adjacent to the first nozzle in an intersecting direction intersecting the one direction; The liquid ejection apparatus according to claim 7, wherein when the first nozzle is the abnormal nozzle and the adjacent dot is formed by the second nozzle, the size of the adjacent dot formed by the second nozzle based on the first data is larger than the size of the dot formed by the second nozzle based on the second data when the first nozzle is not the abnormal nozzle.

12. further comprising a moving mechanism for moving at least one of the liquid ejection head and the medium to be ejected so that the liquid ejection head moves relative to the medium to be ejected in one direction when the liquid ejection head ejects liquid; the control unit is configured to: control the moving mechanism such that a relative movement speed of the liquid ejection head with respect to the medium to be ejected when the second data is generated is higher than a relative movement speed of the liquid ejection head when the first data is generated, according to any one of claims 1 to 10.

13. further comprising a moving mechanism for moving at least one of the liquid ejection head and the medium to be ejected so that the liquid ejection head moves relative to the medium to be ejected in one direction when the liquid ejection head ejects liquid; the plurality of nozzles includes a first nozzle and a second nozzle arranged adjacent to the first nozzle in an intersecting direction intersecting the one direction; the control unit is configured to: when moving the liquid ejection head relative to the medium to be ejected in the one direction and forming the dot on the medium to be ejected with at least one of the plurality of nozzles, when neither the first nozzle nor the second nozzle is an abnormal nozzle, Generate the second data as data for selecting the sizes of both the dots of a first dot array in which the dots formed by the first nozzle are arranged in the one direction and the dots formed by the second nozzle are arranged in the one direction and adjacent to the first dot array when the liquid ejection head relatively moves in the one direction. When the first nozzle is an abnormal nozzle and the second nozzle is not an abnormal nozzle, The liquid ejection apparatus according to any one of claims 1 to 10, which generates the first data as data for selecting the sizes of the dots of the second dot array when the liquid ejection head relatively moves in the one direction.

14. Further include a moving mechanism for moving at least one of the liquid ejection head and the medium to be ejected so that the liquid ejection head relatively moves in one direction with respect to the medium to be ejected when the liquid ejection head ejects liquid. The control unit, When it is determined in the determination process that there is at least one abnormal nozzle among the plurality of nozzles, when executing a plurality of image formation passes for forming an image on the medium to be ejected by ejecting liquid from the nozzles while relatively moving the liquid ejection head in the one direction with respect to the medium to be ejected, Generate the first data as data for forming one image formation pass in which dots that were supposed to be formed by the abnormal nozzle exist. The liquid ejection apparatus according to any one of claims 1 to 10, characterized in that the second data is generated as data for forming other image formation passes in which dots that were supposed to be formed by the abnormal nozzle do not exist.

15. A liquid ejection head having a plurality of nozzles for ejecting liquid to form dots of a plurality of types of sizes on a medium to be ejected, A signal output unit that outputs a determination signal according to whether the nozzle is an abnormal nozzle when the liquid ejection head is caused to perform an inspection drive for checking whether the nozzle is an abnormal nozzle in liquid ejection, A control unit, An external device connected to be able to transmit and receive information based on the signal obtained from the signal output unit to and from the control unit, Comprising, The control unit, Execute a determination process for determining whether at least one of the plurality of nozzles is an abnormal nozzle based on the determination signal, Transmit data regarding the determination result in the determination process to the external device, The external device When the data regarding the determination result transmitted from the control unit indicates the presence of at least one of the abnormal nozzles among the plurality of nozzles, as data for selecting the size of at least a part of the dots formed by the plurality of nozzles from among a plurality of types, generate first data for selecting from among the first type, and transmit the first data to the control unit. When the data regarding the determination result transmitted from the control unit does not indicate the presence of the abnormal nozzle among the plurality of nozzles, as data for selecting the size of the dots formed by the plurality of nozzles from among a second type that is less than the first type, generate second data having a smaller data amount than the first data, and transmit the second data to the control unit. The control unit A liquid ejection system, wherein the liquid ejection head is controlled to eject liquid from the plurality of nozzles based on any one of the first data and the second data transmitted from the external device to form the dots on the ejection target medium.

16. A liquid ejection head having a plurality of nozzles for ejecting liquid to form dots of a plurality of types of sizes on an ejection target medium, a signal output unit that outputs a determination signal corresponding to whether or not the nozzle is an abnormal nozzle having an abnormality in liquid ejection when the liquid ejection head is caused to perform an inspection drive for confirming whether or not the nozzle is an abnormal nozzle, and a control unit connected to an external device so as to be able to transmit and receive information based on the signal obtained from the signal output unit. A control method for a liquid ejection device, comprising: Performing a determination process for determining whether or not at least one of the plurality of nozzles is an abnormal nozzle based on the information in the determination signal. When the data regarding the determination process indicates the presence of at least one of the abnormal nozzles among the plurality of nozzles, generate first data for selecting from among the first type as data for selecting the size of at least a part of the dots formed by the plurality of nozzles from among a plurality of types. When the data regarding the determination process does not indicate the presence of the abnormal nozzle among the plurality of nozzles, generate second data having a smaller data amount than the first data as data for selecting the size of the dots formed by the plurality of nozzles from among a second type that is less than the first type. A control method, characterized by controlling the liquid ejection head so as to eject a liquid from the plurality of nozzles based on either the first data or the second data to form the dots on a medium to be ejected.

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