Liquid dispensing device

Abstract

To accurately determine whether a nozzle is anomalous or not and to suppress wasteful consumption of liquid, while reducing a time necessary to determine whether the nozzle is anomalous or not to the shortest possible time.SOLUTION: A first nozzle and a second nozzle are driven for inspection in that order. Based on whether a difference [Va-Vb] between a maximum value Va and a minimum value Vb of a signal output from a signal processing circuit when the first nozzle is driven for inspection is equal to or larger than a first threshold Vt1 or not, it is determined whether the first nozzle is an anomalous nozzle or not. In response to a signal output from the signal processing circuit when the first nozzle is driven for inspection, a second threshold Vt2 is set (S 304). The second nozzle is driven for inspection (S306), and based on the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit at this time is equal to or larger than a second threshold Vt2 or not, it is determined whether the second nozzle is an anomalous nozzle or not (S310-S312).SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a liquid ejection device that ejects liquid from a nozzle. [Background technology]

[0002] As a liquid ejection device that ejects liquid from a nozzle, Patent Document 1 describes a printer that ejects ink from a nozzle. In the printer of Patent Document 1, in order to inspect each of the nozzles of the print head, the print head is driven to eject ink from the nozzle to be inspected. Furthermore, in order to obtain a counter waveform for reducing the residual waveform of the waveform output by driving the print head, the print head is driven to eject ink from the nozzle to be inspected. Then, the print head is driven in this manner in order for the nozzles to be inspected. This makes it possible to shorten the interval period between driving the print head for a certain nozzle and driving the print head for the next nozzle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-179543 ​​A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the printer of Patent Document 1, in addition to the print head for inspecting the nozzles, a print head is also driven to obtain the counter waveform, and driving the print head to obtain the counter waveform results in ink being wasted.

[0005] The object of the present invention is to provide a liquid ejection device that can accurately determine whether or not a nozzle is abnormal while minimizing the time required to determine whether or not a nozzle is abnormal, and that can reduce unnecessary consumption of liquid. [Means for solving the problem]

[0006] The liquid ejection device of the present invention comprises a liquid ejection head having a first nozzle and a second nozzle that eject liquid, a signal output unit that outputs a signal according to whether or not the first nozzle and the second nozzle are abnormal nozzles having an abnormality in ejecting liquid when the liquid ejection head is caused to perform an inspection drive to check whether the first nozzle and the second nozzle are abnormal nozzles having an abnormality in ejecting liquid, and a control unit, wherein the signal output unit outputs a first signal during inspection drive for the first nozzle and outputs a second signal during inspection drive for the second nozzle, and the control unit causes the liquid ejection head to perform the inspection drive for the first nozzle and then the second nozzle so that the period during which the first signal is output and the period during which the second signal is output partially overlap, and determines whether or not the first nozzle is an abnormal nozzle based on at least one of the maximum and minimum values ​​of the first signal and a first threshold value, sets a second threshold value in accordance with the first signal, and determines whether or not the second nozzle is an abnormal nozzle based on at least one of the maximum and minimum values ​​of the second signal and the second threshold value. Effect of the Invention

[0007] In the present invention, while minimizing the time required to determine whether a nozzle is abnormal, it is possible to accurately determine whether a nozzle is abnormal, and also to reduce unnecessary consumption of liquid. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a printer according to an embodiment of the present invention; [Diagram 2]4A and 4B are diagrams for explaining detection electrodes disposed in a cap, and the connection relationship between the detection electrodes and a high-voltage power supply circuit and a determination circuit. [Diagram 3] FIG. 1A is a diagram showing a signal output from a signal processing circuit when ink is ejected from a nozzle during test drive, and FIG. 1B is a diagram showing a signal output from a signal processing circuit when ink is not ejected from a nozzle during test drive. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Diagram 5] 10 is a flowchart showing a process flow when an inspection instruction signal is received. [Figure 6] 6 is a flowchart showing the flow of the first determination process in FIG. 5. [Figure 7] 6A is a flowchart showing the flow of the second determination process in FIG. 5, and FIG. 6B is a diagram for explaining a table that associates whether or not a first nozzle is an abnormal nozzle with a second threshold value. [Figure 8] FIG. 1A is a diagram for explaining the timing for performing test drive on the first to third nozzles, and FIG. 1B is a diagram showing the signal output from the signal processing circuit when none of the first to third nozzles are abnormal. [Figure 9] 13 is a flowchart showing a process flow when an inspection instruction signal is received in the first modification. [Figure 10] 10 is a flowchart showing the process of a second determination process in FIG. 9. [Figure 11] 10( a ) is a flowchart showing the flow of the third judgment process in FIG. 9 , and ( b ) is a diagram for explaining a table that associates whether the first nozzle and the second nozzle are abnormal nozzles with the third threshold value. [Figure 12] 13 is a flowchart showing the flow of a first determination process in the second modification. [Figure 13] 13A is a flowchart showing the flow of the second determination process in Modification 2, and FIG. 13B is a diagram for explaining a table that associates whether or not a first nozzle is an abnormal nozzle with a second threshold value. [Figure 14]13 is a flowchart showing the flow of a third determination process in the third modification example. [Figure 15] 1A is a diagram illustrating a table correlating whether the first and second nozzles are abnormal or not with a third threshold value that is set for a maximum value, and FIG. 1B is a diagram illustrating a table correlating whether the first and second nozzles are abnormal or not with a third threshold value that is set for a minimum value. [Figure 16] 13 is a flowchart showing the flow of a second determination process in the fourth modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will now be described.

[0010] <Overall printer configuration> As shown in FIG. 1, the printer 1 (the "liquid ejection device" of the present invention) according to this embodiment includes a carriage 2, a subtank 3, an inkjet head 4 (the "liquid ejection head" of the present invention), a platen 5, transport rollers 6 and 7, a maintenance unit 8, etc.

[0011] The carriage 2 is supported by two guide rails 11, 12 extending in the scanning direction. The carriage 2 is connected to a carriage motor 86 (see FIG. 4) via a belt (not shown) or the like, and when the carriage motor 86 is driven, the carriage 2 moves in the scanning direction along the guide rails 11, 12. In the following description, the right and left sides of the scanning direction are defined as shown in FIG. 1.

[0012] The subtank 3 is mounted on the carriage 2. Here, the printer 1 is equipped with a cartridge holder 13, in which four ink cartridges 14 are removably attached. The four ink cartridges 14 are aligned in the scanning direction, and from the one arranged on the right side in the scanning direction, they store black, yellow, cyan, and magenta inks ("liquid" of the present invention). The subtank 3 is connected to the four ink cartridges 14 attached to the cartridge holder 13 via four tubes 15. In this way, the four colors of ink are supplied from the four ink cartridges 14 to the subtank 3.

[0013] The inkjet head 4 is mounted on the carriage 2 and connected to the lower end of the subtank 3. The inkjet head 4 is supplied with the four colors of ink from the subtank 3. The inkjet head 4 ejects ink from a plurality of nozzles 10 formed on its lower surface, a nozzle face 4a. More specifically, the nozzles 10 are arranged in a transport direction perpendicular to the scanning direction to form a nozzle row 9, and on the nozzle face 4a, four nozzle rows 9 are lined up in the scanning direction. From the nozzles 10, black, yellow, cyan, and magenta inks are ejected starting from the nozzle row 9 on the right side of the scanning direction.

[0014] The platen 5 is disposed below the inkjet head 4 and faces the multiple nozzles 10. The platen 5 extends over the entire length of the recording paper P in the scanning direction and supports the recording paper P from below. The transport roller 6 is disposed upstream of the inkjet head 4 and the platen 5 in the transport direction. The transport roller 7 is disposed downstream of the inkjet head 4 and the platen 5 in the transport direction. The transport rollers 6 and 7 are connected to a transport motor 87 (see FIG. 4) via gears (not shown) and the like. When the transport motor 87 is driven, the transport rollers 6 and 7 rotate and the recording paper P is transported in the transport direction.

[0015] The maintenance unit 8 includes a cap 71, a suction pump 72, and a waste liquid tank 73. The cap 71 is disposed to the right of the platen 5 in the scanning direction. When the carriage 2 is positioned at a maintenance position to the right of the platen 5 in the scanning direction, the multiple nozzles 10 face the cap 71.

[0016] The cap 71 can be raised and lowered by a cap lifting mechanism 88 (see FIG. 4). When the carriage 2 is positioned at the maintenance position so that the plurality of nozzles 10 and the cap 71 face each other, the cap 71 is raised by the cap lifting mechanism 88, whereby the upper end of the cap 71 comes into 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 limited to covering the plurality of nozzles 10 by coming into close contact with the nozzle surface 4a. The cap 71 may cover the plurality of nozzles 10 by coming into close contact with a frame (not shown) or the like that is arranged around the nozzle surface 4a of the inkjet head 4, for example.

[0017] 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 with the cap 71 as described above, it is possible to perform a so-called suction purge, in which ink is discharged from inside the inkjet head 4 through the plurality of nozzles 10. The ink discharged by the suction purge is stored in the waste liquid tank 73.

[0018] For convenience, the cap 71 covers all the nozzles 10 together, and ink in the inkjet head 4 is discharged from all the nozzles 10 during suction purge. However, the present invention is not limited to this. For example, the cap 71 may have a portion covering the nozzles 10 constituting the rightmost nozzle row 9 that ejects black ink and a portion covering the nozzles 10 constituting the three leftmost nozzle rows 9 that eject color inks (yellow, cyan, and magenta inks), and either the black ink or the color ink in the inkjet head 4 may be selectively discharged during suction purge. Alternatively, for example, the cap 71 may be provided for each nozzle row 9, and ink may be discharged from the nozzles 10 for each nozzle row 9 separately during suction purge.

[0019] 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. A predetermined potential (for example, about 600 V) is applied to the detection electrode 76 by the high-voltage power supply circuit 77 during the inspection drive described later. Meanwhile, the inkjet head 4 is held at ground potential. This generates a predetermined potential difference 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 differentiation circuit and the like, and outputs a signal that has been processed, including differentiation, with respect to the potential signal output from the detection electrode 76. That is, the signal output from the signal processing circuit 78 is a potential signal corresponding to the potential of the detection electrode 76. However, the signal output from the signal processing circuit 78 may be a current signal. In this embodiment, the detection electrode 76, the high-voltage power supply circuit 77, the signal processing circuit 78, and the resistor 79 together correspond to the "signal output unit" of the present invention.

[0020] With the carriage 2 positioned at the above-mentioned maintenance position, a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77, and the inspection drive described below is not being performed, the value of the signal (non-driven signal) output from the signal processing circuit 78 becomes a predetermined reference value V0, as shown in Figures 3(a) and (b).

[0021] In this embodiment, the carriage 2 is positioned at the maintenance position, and then a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77. In this state, the inkjet head 4 is driven to eject ink from the nozzles 10 toward the detection electrode 76, thereby performing a test drive.

[0022] If the nozzle 10 is not an abnormal nozzle having an abnormality in ink ejection, charged ink is ejected from the nozzle 10 when the test drive is performed. This causes the charged ink to approach 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 attenuates and returns to the potential before the ink was ejected.

[0023] At this time, as shown in Fig. 3(a), the signal output from the signal processing circuit 78 is a signal that alternates between a high state in which the value is greater than the reference value V0 and a low state in which the value is smaller than the reference value V0 while attenuating. Here, periods Td1, Td2, ... in Fig. 3(a) indicate periods in which the signal is in the first, second, ... high state, respectively. Furthermore, periods Ts1, Ts2, ... in Fig. 3(a) indicate periods in which the signal is in the first, second, ... low state, respectively. The signal output from the signal processing circuit 78 reaches a maximum value V1 within the period Td1 in which the signal is first in the high state, and reaches a minimum value V2 within the period Ts1 in which the signal is first in the low state.

[0024] On the other hand, if the nozzle 10 is an abnormal nozzle, even if the test drive is performed, ink will not be ejected from the nozzle 10. Therefore, the signal output from the signal processing circuit 78 does not change from the predetermined reference value V0, as shown in FIG.

[0025] In this manner, in this embodiment, the signal output from the signal processing circuit 78 when the inspection drive is performed differs depending on whether the nozzle 10 is an abnormal nozzle. This fact is utilized in this embodiment to determine whether the nozzle 10 is an abnormal nozzle, as described below.

[0026] <Printer electrical configuration> Next, the electrical configuration of the printer 1 will be described. As shown in Fig. 4, the printer 1 is equipped with a control device 80. The control device 80 is made up of a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a flash memory 84, an ASIC (Application Specific Integrated Circuit) 85, and the like. The control device 80 controls the operations of a carriage motor 86, an inkjet head 4, a conveying motor 87, a cap lifting mechanism 88, a suction pump 72, a high-voltage power supply circuit 77, and the like. The control device 80 also receives signals from a signal processing circuit 78.

[0027] The control device 80 may be one in which only the CPU 81 performs various processes, one in which only the ASIC 85 performs various processes, or one in which the CPU 81 and the ASIC 85 work together to perform various processes. The control device 80 may be one in which one CPU 81 performs processes independently, or one in which multiple CPUs 81 share the processes. The control device 80 may be one in which one ASIC 85 performs processes independently, or one in which multiple ASICs 85 share the processes.

[0028] <Processing when receiving an inspection command signal> Next, a process flow of the control device 80 when an inspection instruction signal is received instructing to inspect whether the nozzle 10 is an abnormal nozzle will be described. For example, when a user operates an operation unit (not shown) of the printer 1 or a PC connected to the printer to instruct to inspect whether the nozzle 10 is an abnormal nozzle, an inspection instruction signal is transmitted from the operation unit, PC, etc., and the control device 80 receives this inspection instruction signal. Alternatively, for example, if the printer 1 has a clock unit that outputs a signal indicating the time, and is set to inspect whether the nozzle is an abnormal nozzle every time a predetermined time is reached, when a signal indicating that the predetermined time has been reached is transmitted from the clock unit, the control device 80 receives this signal as an inspection instruction signal.

[0029] When the inspection command signal is received, the control device 80 performs processing according to the flow of Fig. 5. More specifically, the control device 80 first controls the carriage motor 86 to move the carriage 2 to the maintenance position (S101). If the carriage 2 is located at the maintenance position at the start of the flow of Fig. 5, the carriage 2 is maintained at the maintenance position in S101.

[0030] Next, the control device 80 controls the high voltage power supply circuit 77 to apply a voltage to the detection electrode 76, thereby generating a potential difference between the detection electrode 76 and the inkjet head 4 (S102). Next, the control device 80 resets a variable N to 1 (S103). The variable N corresponds to the number of times that the test driving has been performed consecutively before waiting for a certain period of time in S204 and S308 described later.

[0031] Next, if the value of the variable N is 1 (S104: YES), the control device 80 executes a first determination process (S105), and if the value of the variable N is 2 or more (S104: NO), the control device 80 executes a second determination process (S106). The first and second determination processes will be described in detail later.

[0032] Then, after executing the first judgment process or the second judgment process, the control device 80 judges whether or not the inspection of all the nozzles 10 of the inkjet head 4 as to whether they are abnormal has been completed (whether or not the inspection drive has been performed) (S107). If there are any nozzles 10 for which the inspection of whether they are abnormal has not been completed (S107: NO), the control device 80 increments the value of the variable N by 1 (S108) and returns to S104.

[0033] When all the nozzles 10 have been inspected to determine whether they are abnormal (S107: YES), the control device 80 controls the high voltage power supply circuit 77 to stop applying voltage to the detection electrode 76 (S109). Next, the control device 80 determines whether there is an abnormal nozzle based on the information on whether there is an abnormal nozzle stored in the flash memory 84 by the first and second judgment processes (S110). If there is no abnormal nozzle (S110: NO), the process ends. If there is an abnormal nozzle (S110: YES), the control device 80 controls the suction pump 72, the cap lifting mechanism 88, etc. to perform suction purging (S111), and then ends the process.

[0034] <First Judgment Process> Next, the first determination process of S105 will be described. In the first determination process, the control device 80 performs processing according to the flow of Fig. 6. More specifically, the control device 80 sets any one of the nozzles 10 of the inkjet head 4 for which the test drive has not been completed as the first nozzle (S201). Next, the control device 80 causes the inkjet head 4 to perform the test drive for the first nozzle (S202).

[0035] Then, when the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 when the test drive is performed is equal to or greater than the first threshold value Vt1 (S203: YES), the control device 80 stores in the flash memory 84 that the first nozzle is not an abnormal nozzle (S204). On the other hand, when the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 when the test drive is performed is less than the first threshold value Vt1 (S203: NO), the control device 80 stores in the flash memory 84 that the first nozzle is an abnormal nozzle (S205). Then, after storing in the flash memory 84 in S204 or S205 whether the first nozzle is an abnormal nozzle or not, the flow returns to that of FIG. 5.

[0036] <Second Judgment Process> Next, the second determination process of S106 will be described. In the second determination process, the control device 80 performs processing according to the flow of Fig. 7(a). More specifically, when the value of the variable N is 2 (S301: YES), the control device 80 sets any one of the nozzles 10 of the inkjet head 4 for which the test driving has not been completed as the second nozzle (S303).

[0037] On the other hand, if the value of the variable N is 3 or greater (S301: NO), the control device 80 sets the nozzle 10 currently set as the second nozzle to the first nozzle (S302), and then sets any nozzle 10 among the multiple nozzles 10 in the inkjet head 4 for which test driving has not been completed to the second nozzle (S303).

[0038] After setting the second nozzle in S303, the control device 80 sets the second threshold value Vt2 (S304). Here, the flash memory 84 stores a table as shown in Fig. 7(b) that associates whether the first nozzle is an abnormal nozzle with the second threshold value Vt2. In Fig. 7(a), "normal" indicates that the nozzle is not abnormal, and "abnormal" indicates that the nozzle is abnormal.

[0039] In S304, the value of the second threshold Vt2 is set based on whether the nozzle 10 set as the first nozzle is an abnormal nozzle and on the table of Fig. 7(b). Specifically, if the first nozzle is not an abnormal nozzle, the value of the second threshold Vt2 is set to [Vt1 + ΔVa]. On the other hand, if the first nozzle is an abnormal nozzle, the value of the second threshold Vt2 is set to the same value as the first threshold Vt1.

[0040] Next, the control device 80 waits until a time Tk has elapsed, which is the sum of the length of the period Td1 during which the ink droplet first reaches a large state and the length of the period Ts1 during which the ink droplet first reaches a small state, from the start of the previous test drive (test drive for the first nozzle) (S305: NO). Then, when the time Tk has elapsed from the start of the previous test drive (S305: YES), the control device 80 causes the inkjet head 4 to perform test drive for the second nozzle (S306).

[0041] 8(a), in this embodiment, the test driving is performed so that a period Td1 during which the signal output from the signal processing circuit 78 (the "second signal" of the present invention) first reaches a large state when the test driving is performed for the second nozzle overlaps with a period Td2 during which the signal output from the signal processing circuit 78 (the "first signal" of the present invention) reaches a second largest state when the test driving is performed for the first nozzle. In other words, the test driving is performed so that the period during which the first signal is output and the period during which the second signal is output overlap partially.

[0042] Here, Fig. 8(a) shows signals output from the signal processing circuit 78 when test drive is performed for three nozzles 10 that are successively driven for testing, when the nozzles are not abnormal. However, Fig. 8(a) shows signals in a case where the signals output from the signal processing circuit 78 during test drive for each nozzle 10 are not affected by signals output by the previous test drive. Also, Fig. 8(a) shows signal waveforms using a dashed line, a one-dot chain line, and a two-dot chain line, in that order, starting with the signal for the previous test signal.

[0043] Next, the control device 80 judges whether the value V of the signal output from the signal processing circuit 78 is greater than a predetermined value Vh (S307). Here, the signal processing circuit 78 has an upper limit on the value of the signal that can be output due to the circuit configuration, etc. The predetermined value Vh is, for example, a value slightly smaller than the upper limit of the signal that can be output from the signal processing circuit 78.

[0044] If the value V of the signal output from the signal processing circuit 78 is greater than the predetermined value Vh (S307: YES), the process waits for a fixed period of time (S308). This interrupts the test operation in which test driving is performed sequentially on each of the multiple nozzles 10, and the value V of the signal output from the signal processing circuit 78 decreases. Then, after waiting for a fixed period of time, the setting information for the first and second nozzles is erased (S309), and the process returns to S103 in FIG.

[0045] If the value V of the signal output from the signal processing circuit 78 is equal to or less than the predetermined value Vh (S307: NO), and if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the second threshold value Vt2 (S310: YES), the control device 80 stores in the flash memory 84 that the second nozzle is not an abnormal nozzle (S311). On the other hand, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is less than the second threshold value Vt2 (S310: NO), the control device 80 stores in the flash memory 84 that the second nozzle is an abnormal nozzle (S312). Then, after storing in the flash memory 84 in S311 or S312 whether the second nozzle is an abnormal nozzle or not, the flow returns to that of FIG. 5.

[0046] In this embodiment, the control device 80 performs the above-described process to perform an inspection operation in which the inspection operation is performed in sequence for all the nozzles 10 of the inkjet head 4. Furthermore, at each point in time of the inspection operation, between the two nozzles 10 set as the first nozzle and the second nozzle, the inspection drive is performed in the order of the first nozzle and the second nozzle.

[0047] <Effects> In this embodiment, the test drive is performed for each nozzle 10 so that the period during which a signal (first signal) for the test drive for the first nozzle is output from the signal processing circuit 78 partially overlaps with the period during which a signal (second signal) for the test drive for the second nozzle is output from the signal processing circuit 78. Therefore, the time required to perform the test drive for all nozzles 10 of the inkjet head 4 can be shortened compared to when the period during which the first signal is output and the period during which the second signal is output do not overlap, i.e., when the test drive for the second nozzle is performed after waiting for the first signal to sufficiently attenuate.

[0048] However, if the period during which the first signal is output and the period during which the second signal is output partially overlap, the value of the second signal will be affected by the first signal. Therefore, if it is determined whether or not a nozzle is abnormal based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than a uniform threshold value, there is a risk that the determination cannot be made accurately.

[0049] Therefore, in this embodiment, when determining whether the first nozzle is an abnormal nozzle, it is determined whether it is an abnormal nozzle based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the first threshold value Vt1. On the other hand, when determining whether the second nozzle is an abnormal nozzle, a second threshold value Vt2 is set in accordance with the first signal, and it is determined whether it is an abnormal nozzle based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the second threshold value Vt2. This makes it possible to accurately determine whether any nozzle 10 is an abnormal nozzle.

[0050] Furthermore, in the case of this embodiment, unlike Patent Document 1, the inkjet head 4 is not driven to attenuate the first signal after the test drive for the first nozzle and before the test drive for the second nozzle, so no ink is discharged unnecessarily.

[0051] Furthermore, in this embodiment, when the inspection drive is performed, the signals (first and second signals) output from the signal processing circuit 78 are signals that alternate between a high state and a low state while attenuating. In this embodiment, the inspection operation is performed so that the period Td2 in which the first signal is in the second highest state and the period Td1 in which the second signal is in the first highest state overlap. In such a case, a second threshold value Vt2 is set according to the first signal, and it is possible to accurately determine whether or not the nozzle is abnormal based on whether or not the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 when the inspection drive for the second nozzle is performed is equal to or greater than the second threshold value Vt2.

[0052] Furthermore, in this embodiment, when the first nozzle is not an abnormal nozzle, the maximum value Va and minimum value Vb of the second signal are significantly different between when the period when the first signal is output and when the period when the second signal is output are made to partially overlap and when they are not overlapped. On the other hand, when the first nozzle is an abnormal nozzle, the maximum value Va and minimum value Vb of the second signal are the same between when the period when the first signal is output and when the period when the second signal is output are made to partially overlap and when they are not overlapped.

[0053] Therefore, in this embodiment, when the first nozzle is not an abnormal nozzle, the second threshold Vt2 is set to a value different from the first threshold Vt1 in accordance with the first signal. Also, when the first nozzle is an abnormal nozzle, the second threshold Vt2 is set to the same value as the first threshold Vt1. This makes it possible to accurately determine whether or not the second nozzle is an abnormal nozzle, regardless of whether or not the first nozzle is an abnormal nozzle.

[0054] Furthermore, in this embodiment, the signal processing circuit 78 has an upper limit on the signal value that can be output depending on the circuit configuration, etc. Meanwhile, when the inspection drive is performed so that the first signal and the second signal partially overlap as described above, if the inspection drive is performed successively on the nozzles 10 that are not abnormal nozzles, the value of the signal output from the signal processing circuit 78 gradually increases, as shown in Fig. 8(b). Then, when the value of the signal output from the signal processing circuit 78 reaches the upper limit, the value of the signal output from the signal processing circuit 78 does not increase any more, and it becomes impossible to accurately determine whether or not the nozzle is abnormal.

[0055] Therefore, in this embodiment, when the value V of the signal output from the signal processing circuit 78 exceeds the predetermined value Vh, the liquid ejection head is made to wait for a certain period of time before restarting the inspection operation. This makes it possible to prevent the value of the signal output from the signal processing circuit 78 from reaching the upper limit value.

[0056] <Modification> Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible within the scope of the claims.

[0057] The method of setting the threshold value to be compared with the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 when the test driving is performed continuously is not limited to that in the above-described embodiment.

[0058] In the first modification, the control device 80 performs processing according to the flow of FIG. 9 when receiving an inspection instruction signal. To explain the flow of FIG. 9 in detail, the control device 80 performs the processing of S101 to S103 in the same manner as in the above-mentioned embodiment. Then, when the value of the variable N is 1 (S401: YES), the control device 80 performs the first judgment processing in the same manner as in the above-mentioned embodiment (S105). When the value of the variable N is 2 (S401: NO, S402: YES), the control device 80 performs the second judgment processing (S403). When the value of N is 3 or more (S401: NO, S402: NO), the control device 80 performs the third judgment processing (S404). Then, after performing any one of the first to third judgment processing, the control device 80 performs the processing of S107 to S111 in the same manner as in the above-mentioned embodiment.

[0059] In the second determination process of the first modification, the control device 80 performs processing according to the flow of Fig. 10. More specifically, the control device 80 performs the processing of S303 to S312 of the above-mentioned embodiment. That is, the second determination process shown in the flow of Fig. 10 is the second determination process shown in the flow of Fig. 7(a) except for the processing of S301 and S302.

[0060] In the third determination process, the control device 80 performs the process according to the flow of Fig. 11(a). More specifically, when the value of the variable N is 3 (S501: YES), the control device 80 sets any one of the nozzles 10 of the inkjet head 4 for which the test driving has not been completed as the third nozzle (S503).

[0061] On the other hand, if the value of the variable N is 4 or greater (S501: NO), the control device 80 sets the nozzles 10 currently set as the second and third nozzles to the first and second nozzles, respectively (S502), and then sets any nozzle 10 among the multiple nozzles 10 in the inkjet head 4 for which test driving has not been completed, as the third nozzle (S503).

[0062] After setting the third nozzle in S503, the control device 80 sets a third threshold value Vt3 (S504). Here, the flash memory 84 stores a table as shown in Fig. 11(b) that associates whether the first nozzle and the second nozzle are abnormal nozzles with the third threshold value Vt3.

[0063] In S504, the third threshold value Vt3 is set based on whether the nozzle 10 set as the first and second nozzles is an abnormal nozzle and on the table of FIG. 11(b). Specifically, when neither the first nozzle nor the second nozzle is an abnormal nozzle, the value of the third threshold value Vt3 is set to [Vt1+ΔVa+ΔVb]. When the first nozzle is not an abnormal nozzle and the second nozzle is abnormal, the value of the third threshold value Vt3 is set to [Vt1+ΔVa]. When the first nozzle is an abnormal nozzle and the second nozzle is not abnormal, the value of the third threshold value Vt3 is set to [Vt1+ΔVb]. When both the first nozzle and the second nozzle are abnormal, the value of the third threshold value Vt3 is set to the same value as the first threshold value Vt1.

[0064] Next, the control device 80 waits until the time Tk has elapsed from the start of the previous test drive (test drive for the second nozzle) (S505: NO). Then, when the time Tk has elapsed from the start of the test drive for the second nozzle (S505: YES), the control device 80 causes the inkjet head 4 to perform test drive for the third nozzle (S506).

[0065] Next, the control device 80 determines whether the value V of the signal output from the signal processing circuit 78 is greater than a predetermined value Vh (S507). If the value V of the signal output from the signal processing circuit 78 is greater than the predetermined value Vh (S507: YES), the control device 80 waits for a certain period of time (S508), erases the setting information for the first to third nozzles (S509), and then returns to S103 in FIG.

[0066] If the value V of the signal output from the signal processing circuit 78 is equal to or less than the predetermined value Vh (S507: NO), and if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the third threshold value Vt3 (S510: YES), the control device 80 stores in the flash memory 84 that the third nozzle is not an abnormal nozzle (S511). On the other hand, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is less than the third threshold value Vt3 (S510: NO), the control device 80 stores in the flash memory 84 that the third nozzle is an abnormal nozzle (S512). Then, after storing in the flash memory 84 in S511 or S512 whether the third nozzle is an abnormal nozzle or not, the flow returns to that of FIG. 9.

[0067] In the first modification, the control device 80 performs the above-described process to perform an inspection operation in which the inspection operation is performed in sequence for all the nozzles 10 of the inkjet head 4. Furthermore, at each point in time of the inspection operation, among the three nozzles 10 set as the first nozzle, the second nozzle, and the third nozzle, the inspection driving is performed in the order of the first nozzle, the second nozzle, and the third nozzle.

[0068] In addition, in the first modification, when the time Tk has elapsed from the start of the test drive for the first nozzle, the second nozzle is driven for test (S305, S306). Also, when the time Tk has elapsed from the start of the test drive for the second nozzle, the third nozzle is driven for test (S505, S506).

[0069] As a result, in the first modification, the inspection drive is also performed so that the period Td1 in which the second signal first reaches the large state and the period Td2 in which the first signal reaches the second largest state overlap. Also, in the first modification, the inspection drive is performed so that the period Td1 in which the signal output from the signal processing circuit 78 when the inspection drive for the third nozzle is performed (the "third signal" of the present invention) first reaches the large state and the period Td2 in which the second signal reaches the second largest state overlap. As a result, in the first modification, the period in which the first signal is output, the period in which the second signal is output, and the period in which the third signal is output partially overlap.

[0070] When the inspection drive is performed so that the period during which the first signal is output, the period during which the second signal is output, and the period during which the third signal is output partially overlap, the second signal is influenced by the first signal, and the third signal is influenced by the first signal and the second signal.

[0071] Therefore, in the first modification, when determining whether the first nozzle is an abnormal nozzle, it is determined whether it is an abnormal nozzle based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the first threshold value Vt1. When determining whether the second nozzle is an abnormal nozzle, a second threshold value Vt2 is set according to the first signal, and it is determined whether it is an abnormal nozzle based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the second threshold value Vt2. When determining whether the third nozzle is an abnormal nozzle, a third threshold value Vt3 is set according to the first signal and the second signal, and it is determined whether it is an abnormal nozzle based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or greater than the third threshold value Vt3. This makes it possible to accurately determine whether any nozzle 10 is an abnormal nozzle.

[0072] Also, in the above-described embodiment and modified example 1, the threshold value used when performing an inspection drive on a certain nozzle 10 to determine whether or not it is an abnormal nozzle is set based on the signal output from the signal processing circuit 78 when the inspection drive immediately before the inspection drive is performed. Alternatively, the threshold value used when performing an inspection drive on a certain nozzle 10 to determine whether or not it is an abnormal nozzle is set based on the signal output from the signal processing circuit 78 when the inspection drive immediately before and two inspection drives before the inspection drive are performed. However, this is not limited to this. For example, the threshold value used when performing an inspection drive on a certain nozzle 10 to determine whether or not it is an abnormal nozzle may be set based on the signal output from the signal processing circuit 78 when three or more consecutive inspection drives immediately before the inspection drive are performed.

[0073] In addition, in the above-described embodiment, whether or not a nozzle is abnormal is determined based on whether the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 is greater than or equal to a threshold value, but this is not limited to this.

[0074] In the second modification, similarly to the above-described embodiment, when the control device 80 receives an inspection instruction signal, it performs processing along the flow of Fig. 5. However, unlike the above-described embodiment, in the second modification, the control device 80 performs processing along the flow of Fig. 12 in the first determination processing, and performs processing along the flow of Fig. 13(a) in the second determination processing.

[0075] 12, the control device 80 sets the first nozzle (S201) and drives the inkjet head 4 for testing the first nozzle (S202) in the same manner as in the above-described embodiment. Then, if the maximum value Va of the signal output from the signal processing circuit 78 is equal to or greater than the first threshold value Vtc1 set for the maximum value Va (S601: YES) and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or less than the first threshold value Vtd1 set for the minimum value Vb (S602: YES), the control device 80 stores in the flash memory 84 that the first nozzle is not an abnormal nozzle (S603).

[0076] On the other hand, if the maximum value Va is less than the first threshold value Vtc1 (S601: NO) and if the minimum value Vb is greater than the first threshold value Vtd1 (S602: NO), the flash memory 84 stores the fact that the first nozzle is an abnormal nozzle (S604).

[0077] 13(a), the control device 80 executes the processes of S301 to S303 in the same manner as in the above-described embodiment. Next, the control device 80 sets second thresholds Vtc2 and Vtd2 (S701). The second threshold Vtc2 is a second threshold set for the maximum value Va of the signal output from the signal processing circuit 78 during the test drive of the second nozzle. The second threshold Vtd2 is a second threshold set for the minimum value Vb of the signal output from the signal processing circuit 78 during the test drive of the second nozzle.

[0078] In the second modification, a table as shown in FIG. 13(b) is stored in the flash memory 84, which associates whether or not the first nozzle is an abnormal nozzle with the second thresholds Vtc2 and Vtd2. In S701, the second thresholds Vtc2 and Vtd2 are set based on whether or not the first nozzle is an abnormal nozzle and the table of FIG. 13(b). Specifically, if the first nozzle is not an abnormal nozzle, the second thresholds Vtc2 and Vtd2 are set to [Vtc1+ΔVc] and [Vtd1+ΔVd], respectively. If the first nozzle is an abnormal nozzle, the second thresholds Vtc2 and Vtd2 are set to the same values ​​as the first thresholds Vtc1 and Vtd1, respectively.

[0079] Next, the control device 80 executes the processes of S305 to S309 similar to those of the above-described embodiment. Then, when it is determined in S307 that the value V of the signal output from the signal processing circuit 78 is equal to or less than the predetermined value Vh (S307: NO), if the maximum value Va of the signal output from the signal processing circuit 78 is equal to or greater than the second threshold value Vtc2 (S702: YES) and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or less than the second threshold value Vtd2 (S703: YES), the control device 80 stores in the flash memory 84 that the second nozzle is not an abnormal nozzle (S704).

[0080] On the other hand, if the maximum value Va is less than the second threshold value Vtc2 (S702: NO) and if the minimum value Vb is greater than the second threshold value Vtd2 (S703: NO), the flash memory 84 stores the fact that the second nozzle is an abnormal nozzle (S705).

[0081] In variant example 2, it is possible to determine whether or not a nozzle is abnormal based on whether the maximum value Va of the signal (first and second signals) output from the signal processing circuit 78 when test driving is performed is greater than or equal to threshold values ​​Vtc1, Vtc2, and whether the minimum value Vb of the first and second signals is less than or equal to threshold values ​​Vtd1, Vtd2.

[0082] In the third modification, similar to the first modification, the control device 80 performs processing according to the flow of FIG. 9 when it receives an inspection instruction signal. However, in the third modification, unlike the first modification, the control device 80 performs processing according to the flow of FIG. 12 in the first judgment processing, similar to the second modification. In the second judgment processing, processing is performed according to the flow of FIG. 13(a) excluding S301 and S302. At this time, the second thresholds Vtc2 and Vtd2 are set, similar to the second modification. In the third judgment processing, processing is performed according to the flow of FIG. 14.

[0083] 14, the control device 80 executes the processes of S501 to S503 as in the first modification. Next, the control device 80 sets third thresholds Vtc3 and Vtd3 (S801). The third threshold Vtc3 is a third threshold set for the maximum value Va of the signal output from the signal processing circuit 78 during the test drive of the third nozzle. The third threshold Vtd3 is a third threshold set for the minimum value Vb of the signal output from the signal processing circuit 78 during the test drive of the third nozzle.

[0084] In the third modification, a table as shown in FIG. 15(a) is stored in the flash memory 84, which associates whether the first and second nozzles are abnormal nozzles with the third threshold value Vtc2. In the third modification, a table as shown in FIG. 15(b) is stored in the flash memory 84, which associates whether the first and second nozzles are abnormal nozzles with the third threshold value Vtd2. In S801, the third threshold values ​​Vtc2 and Vtd2 are set based on whether the first and second nozzles are abnormal nozzles and the tables of FIG. 15(a) and (b). Specifically, when neither the first nor the second nozzle is abnormal, the third threshold values ​​Vtc3 and Vtd3 are set to [Vtc1+ΔVc1+ΔVc2] and [Vtd1+ΔVd1+ΔVd2]. If the first nozzle is abnormal and the second nozzle is not, the third thresholds Vtc3 and Vtd3 are set to [Vtc1+ΔVc2] and [Vtd1+ΔVd2]. If the first nozzle is not abnormal and the second nozzle is abnormal, the third thresholds Vtc3 and Vtd3 are set to [Vtc1+ΔVc1] and [Vtd1+ΔVd1]. If both the first and second nozzles are abnormal, the third thresholds Vtc3 and Vtd3 are set to the same values ​​as the first thresholds Vtc1 and Vtd1.

[0085] Next, the control device 80 executes the processes of S505 to S509 similar to those of the above-mentioned embodiment. Then, when it is determined in S507 that the value V of the signal output from the signal processing circuit 78 is equal to or less than the predetermined value Vh (S507: NO), if the maximum value Va of the signal output from the signal processing circuit 78 is equal to or greater than the third threshold value Vtc3 (S802: YES) and the minimum value Vb of the signal output from the signal processing circuit 78 is equal to or less than the third threshold value Vtd3 (S803: YES), the control device 80 stores in the flash memory 84 that the third nozzle is not an abnormal nozzle (S704).

[0086] On the other hand, if the maximum value Va is less than the third threshold value Vtc3 (S802: NO) and if the minimum value Vb is greater than the third threshold value Vtd3 (S803: NO), the third nozzle is stored as an abnormal nozzle in the flash memory 84 (S805).

[0087] In variant example 3, it is possible to determine whether or not a nozzle is abnormal based on whether the maximum value Va of the signals (first to third signals) output from the signal processing circuit 78 when a test drive is performed is greater than or equal to threshold values ​​Vtc1, Vtc2, Vtc3, and whether the minimum value Vb of the first to third signals is greater than or equal to threshold values ​​Vtd1, Vtd2, Vtd3.

[0088] In addition, it is not limited to determining whether or not a nozzle is abnormal using both the maximum value Va and the minimum value Vb of the signal output from the signal processing circuit 78 when the test drive is performed. For example, it is possible to determine whether or not a nozzle is abnormal depending on whether the maximum value Va of the signal output from the signal processing circuit 78 when the test drive is performed is equal to or greater than the threshold values ​​Vtc1, Vtc2, Vtc3 set in the same manner as in the second and third modifications, and not to use the minimum value Vb to determine whether or not a nozzle is abnormal. Alternatively, it is possible to determine whether or not a nozzle is abnormal depending on whether the minimum value Vb of the signal output from the signal processing circuit 78 when the test drive is performed is equal to or less than the threshold values ​​Vtd1, Vtd2, Vtd3 set in the same manner as in the second and third modifications, and not to use the maximum value Va to determine whether or not a nozzle is abnormal.

[0089] In the above embodiment, when the value V of the signal output from the signal processing circuit 78 exceeds a predetermined value Vh, the inspection operation is interrupted and the inspection operation is restarted after a uniformly fixed waiting time, thereby preventing the value of the signal output from the signal processing circuit 78 from becoming too large. However, this is not limited to this.

[0090] In the fourth modification, in the second judgment process, the control device 80 performs processing according to the flow of FIG. 16. The flow of FIG. 16 is obtained by replacing S308 with S901 in the flow of FIG. 7. In S901, it is determined whether the value V of the signal output from the signal processing circuit 78 is smaller than a predetermined value Vj. The predetermined value Vj is a value smaller than a predetermined value Vh. In the fourth modification, the predetermined value Vh corresponds to the "first value" of the present invention, and the predetermined value Vj corresponds to the "second value" of the present invention.

[0091] Then, the process waits while the value V of the signal output from the signal processing circuit 78 is equal to or greater than the predetermined value Vj (S901: NO), and when the value V of the signal output from the signal processing circuit 78 becomes smaller than the predetermined value Vj (S901: YES), the setting information of the first and second nozzles is erased (S309), and the process returns to S103 in Fig. 5. In other words, the inspection operation is resumed.

[0092] In the fourth modification, when the value V of the signal output from the signal processing circuit 78 exceeds the predetermined value Vh, the inspection operation is resumed after the value V of the signal output from the signal processing circuit 78 becomes smaller than the predetermined value Vj. This makes it possible to prevent the value of the signal output from the signal processing circuit 78 from reaching the upper limit value.

[0093] In addition, in the fourth modification, S308 is replaced with S901 in the flow of FIG. 7, but S308 may be replaced with S901 in the flows of FIGS.

[0094] In the above example, when the value V of the signal output from the signal processing circuit 78 exceeds the predetermined value Vh, the inspection operation is interrupted and the system waits until the value V of the signal output from the signal processing circuit 78 decreases, but this is not limiting. For example, if the upper limit value of the value V of the signal output from the signal processing circuit 78 is sufficiently larger than the maximum value that can be output from the signal processing circuit 78 during the inspection operation, it is not necessary to perform the above-mentioned process for interrupting the inspection operation based on the value V of the signal output from the signal processing circuit 78.

[0095] Furthermore, in the above examples, if it is determined that the first nozzle is not an abnormal nozzle, the second threshold is set to a value different from the first threshold depending on the first signal, and if it is determined that the first nozzle is an abnormal nozzle, the second threshold is set to the same value as the first threshold, but this is not limited to the above.

[0096] For example, even if it is determined that the first nozzle is not an abnormal nozzle, the second threshold value may be set to the same value as the first threshold value. For example, when it is determined that the first nozzle is not an abnormal nozzle, the inspection drive for each nozzle 10 may be performed so that the period Td1 in which the second signal is first in a large state overlaps with the period Td2 in which the first signal is second in a large state and the period Ts2 in which the first signal is second in a small state in a period in which the signal value near the boundary is close to the reference value V0.

[0097] Furthermore, even if the first nozzle is determined to be an abnormal nozzle, the second threshold may be set to a value different from the first threshold. For example, a threshold different from the threshold used to determine whether or not the nozzle is abnormal may be set, and even if the first nozzle is determined to be an abnormal nozzle, if the first signal satisfies a predetermined relationship with this different threshold, the second threshold may be set to a value different from the first threshold. In this way, even if the first nozzle is an abnormal nozzle, the second threshold can be changed to an appropriate value as necessary, and it can be determined more accurately whether or not the second nozzle is an abnormal nozzle.

[0098] In the above example, the test drive for each nozzle 10 is performed so that the period Td1 in which the second signal is first in the large state and the period Td2 in which the first signal is second in the large state overlap, but this is not limited to this. The first signal and the second signal may be partially overlapped in a form different from the above.

[0099] For example, the test drive for each nozzle 10 may be performed so that the period Td1 during which the second signal is first in a large state and the period Ts2 during which the first signal is second in a small state overlap. In this case, ΔVa is set to a negative value. In this way, unlike the case shown in FIG. 8(b), the value of the signal output from the signal processing circuit 78 does not increase when the test drives for the multiple nozzles 10 are performed in sequence. Therefore, the value V of the signal output from the signal processing circuit 78 is less likely to exceed the predetermined value Vh.

[0100] In the above example, suction purging is performed uniformly when there is an abnormal nozzle, but this is not limited to the above. For example, the amount of ink discharged in the suction purging may be increased as the number of abnormal nozzles increases.

[0101] Furthermore, the purging is not limited to suction purging. For example, a pressure pump may be provided in the middle of the tube 15 that connects the subtank 3 and the ink cartridge 14. Alternatively, a pressure pump connected to the ink cartridge may be provided in the printer. Then, with the nozzles 10 covered with the caps 71, the pressure pump may be driven to pressurize the ink in the inkjet head 4 and discharge the ink in the inkjet head 4 from the nozzles 10, thereby performing so-called pressure purging.

[0102] Furthermore, in purging, both suction by the suction pump 72 and pressurization by the pressurization pump may be performed. Also, instead of purging, flushing may be performed in the inkjet head 4 to discharge ink at least from the abnormal nozzles. Also, both purging and flushing may be performed.

[0103] Furthermore, when an abnormal nozzle is present, the control device 80 is not limited to automatically performing suction purging, etc. For example, when an abnormal nozzle is present, a notification may be given to the user to allow the user to select whether or not to perform suction purging, and suction purging may be performed only when the user selects to perform suction purging.

[0104] In the above embodiment, the inspection drive is performed on all the nozzles 10 of the inkjet head 4, but this is not limited to the above. For example, the inspection drive may be performed on only some of the nozzles 10 of the inkjet head 4, such as every other nozzle 10 in each nozzle row 9, and the remaining nozzles 10 may be determined to be abnormal based on the signal output from the signal processing circuit 78 during the inspection drive.

[0105] Furthermore, in the above-described embodiment, the signal processing circuit 78 outputs a signal indicating whether or not the nozzle is abnormal, depending on the potential of the detection electrode 76 when ink is ejected from the nozzle 10 toward the detection electrode 76, but this is not limited to the above.

[0106] For example, a detection electrode extending in the vertical direction may be disposed, and a determination circuit may output a signal indicating whether or not the nozzle is abnormal depending on the potential of the detection electrode when ink is ejected from the nozzle 10 so as to pass through a region facing the detection electrode. Alternatively, an optical sensor (the "signal output unit" of the present invention) may be provided to detect ink ejected from the nozzle 10, and the optical sensor may output a signal indicating whether or not the nozzle is abnormal.

[0107] Alternatively, for example, as described in Patent Gazette No. 4929699, a voltage detection circuit (the "signal output section" of the present invention) that detects the change in voltage when ink is ejected from the nozzles can be connected to a plate on which the nozzles of the inkjet head are formed, and a signal indicating whether or not the nozzle is abnormal can be output from the voltage detection circuit to the control device 80.

[0108] Alternatively, for example, the substrate of the inkjet head may be provided with a temperature detection element (the "signal output unit" of the present invention) as described in Japanese Patent No. 6231759. Then, after applying a first applied voltage to drive the heater for ejecting ink, a second applied voltage is applied to drive the heater so that ink is not ejected, and a signal is output in accordance with whether the nozzle 10 is an abnormal nozzle or not based on the change in temperature detected by the temperature detection element during the period from when the second applied voltage is applied until a predetermined time has elapsed.

[0109] Furthermore, in the above example, the signal output unit outputs a signal in response to whether or not ink is ejected from the nozzle 10, but this is not limited to the above. The signal output unit may output a signal in response to whether or not the nozzle is abnormal, that is, has an abnormality other than the nozzle not ejecting ink. An abnormality other than the nozzle not ejecting ink could be, for example, an abnormality in the direction of ink ejection.

[0110] In the above, an example has been described in which the present invention is applied to a printer equipped with a so-called serial head that ejects ink from multiple nozzles while moving in the scanning direction together with the carriage, but the present invention 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 across the entire length of the recording paper in the scanning direction.

[0111] In the above, an example of applying the present invention to a printer that ejects ink from nozzles to perform recording on recording paper P has been described, but the present invention is not limited to this. 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 advertising, cases for mobile terminals such as smartphones, cardboard, and resin members. The present invention can also be applied to liquid ejection devices that eject liquids other than ink, such as liquid resins and metals. [Explanation of symbols]

[0112] 1. Printer 4 Inkjet head 8 Maintenance Unit 10 Nozzles 76 Detection electrode 77 High Voltage Power Supply Circuit 78 Signal Processing Circuit 79 Resistance 80 Control device 84 Flash Memory

Claims

1. a liquid ejection head having a first nozzle and a second nozzle for ejecting liquid; a signal output section that outputs a signal according to whether the first nozzle and the second nozzle are abnormal nozzles having an abnormality in liquid ejection when the liquid ejection head is driven for inspection to confirm whether the first nozzle and the second nozzle are abnormal nozzles having an abnormality in liquid ejection; A control unit, the signal output unit outputs a first signal during inspection driving of the first nozzle and outputs a second signal during inspection driving of the second nozzle; The control unit is causing the liquid ejection head to perform the test driving in the order of the first nozzle and the second nozzle so that a period during which the first signal is output and a period during which the second signal is output partially overlap; determining whether the first nozzle is an abnormal nozzle based on at least one of a maximum value and a minimum value of the first signal and a first threshold value; setting a second threshold value in response to the first signal; A liquid ejection device, comprising: a liquid ejection device that determines whether or not the second nozzle is an abnormal nozzle based on at least one of a maximum value and a minimum value of the second signal and the second threshold value.

2. The value of the signal output from the signal output unit when the test driving is not performed is set as a reference value, the first signal and the second signal are signals that alternately repeat, while attenuating, a large state in which the value is greater than the reference value and a small state in which the value is smaller than the reference value when the first nozzle and the second signal are not abnormal nozzles, The control unit is The liquid ejection device according to claim 1, wherein the liquid ejection head is driven for inspection so that the period in which the first signal secondly reaches the large state and the period in which the second signal first reaches the large state overlap.

3. The control unit is when it is determined that the first nozzle is not the abnormal nozzle based on the first signal, the second threshold is set to a value different from the first threshold in response to the first signal; 3. The liquid ejection device according to claim 1, wherein when it is determined that the first nozzle is the abnormal nozzle based on the first signal, the second threshold value is set to the same value as the first threshold value.

4. the liquid ejection head further includes a third nozzle, the signal output section outputs a third signal in response to whether the third nozzle is an abnormal nozzle during inspection driving of the third nozzle; The control unit is causing the liquid ejection head to perform the test driving in the order of the first nozzle, the second nozzle, and the third nozzle so that a period during which the first signal is output, a period during which the second signal is output, and a period during which the third signal is output partially overlap; setting a third threshold value according to the first signal and the second signal; 4. The liquid ejection device according to claim 1, wherein it is determined whether or not the third nozzle is an abnormal nozzle based on at least one of a maximum value and a minimum value of the third signal and the third threshold value.

5. The control unit is A liquid ejection device as described in any one of claims 1 to 4, characterized in that when the value of the signal output from the signal output unit exceeds a predetermined value during the inspection drive, the liquid ejection head is caused to suspend the inspection drive, wait for a certain period of time, and then the liquid ejection head is caused to resume the inspection drive.

6. The control unit is A liquid ejection device as described in any one of claims 1 to 4, characterized in that when the value of the signal output from the signal output unit exceeds a first value during the inspection drive, the liquid ejection head is caused to interrupt the inspection drive, and then, when the value of the signal output from the signal output unit becomes smaller than a second value smaller than the first value, the liquid ejection head is caused to resume the inspection drive.

7. Let N be any natural number, the liquid ejection head includes an Nth nozzle, the signal output unit outputs an N-th signal corresponding to whether the N-th nozzle is an abnormal nozzle during inspection driving of the N-th nozzle, The control unit is When the difference between the maximum value and the minimum value of the N signal is equal to or greater than an N-th threshold value, it is determined that the N nozzle is not the abnormal nozzle; 7. The liquid ejection device according to claim 1, wherein the Nth nozzle is determined to be the abnormal nozzle when the difference between the maximum value and the minimum value of the Nth signal is less than the Nth threshold value.

8. Let N be any natural number, the liquid ejection head includes an Nth nozzle, the signal output unit outputs an N-th signal corresponding to whether the N-th nozzle is an abnormal nozzle during inspection driving of the N-th nozzle, The control unit is An N-th threshold value for a maximum value of the N-th signal and an N-th threshold value for a minimum value of the N-th signal are set separately; if the maximum value of the N signal is equal to or greater than the N threshold value for the maximum value and the minimum value of the N signal is equal to or less than the N threshold value for the minimum value, it is determined that the N nozzle is not the abnormal nozzle; A liquid ejection device as described in any one of claims 1 to 6, characterized in that the Nth nozzle is determined to be the abnormal nozzle when the maximum value of the Nth signal is smaller than the Nth threshold value for the maximum value, or when the minimum value of the Nth signal is greater than the Nth threshold value for the minimum value.

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