Liquid dispensing device

Abstract

To more accurately determine whether or not a nozzle is an abnormal nozzle.SOLUTION: A determination signal for determining whether or not a nozzle is an abnormal nozzle is output from a signal processing circuit. When ink is normally discharged from the nozzle, the determination signal is assumed to be maximum at a first timing U1 and be minimum at a timing U2 later the first timing U1 in a determination period T. When a difference (Va-Vb) between a maximum value Va in a first continuous period T1 including the first timing U1 and a minimum value Vb in a second continuous period T2 including the second timing U2 but not including the first timing is equal to or more than a threshold Vt, the determination signal determines that the nozzle is not the abnormal nozzle, and when the difference is less than the threshold Vt, the determination signal determines that the nozzle is the abnormal nozzle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] As an example of a liquid ejection device that ejects liquid from nozzles, Patent Document 1 describes a printer that performs recording by ejecting ink from nozzles. The printer in Patent Document 1 performs an ejection test to check whether ink can be ejected properly. In the ejection test, whether ink can be ejected properly is determined based on whether the amplitude of the detection signal (the difference between the maximum and minimum potentials) detected when a drive signal is applied to a piezoelectric element in the head exceeds a threshold.

[0003] Furthermore, the printer in Patent Document 1 performs a noise test to determine whether or not noise is present, and when the noise test determines that there is no noise, it determines whether or not ink can be ejected well based on the results of the ejection test. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-210768 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, as described above, a noise test is performed, and if it is determined that there is no noise, it is determined whether or not the ink can be ejected satisfactorily based on the results of the ejection test. However, in a printer such as that described in Patent Document 1, it can actually be difficult to perform an ejection test in a noise-free state, for example, because a certain amount of noise is always present from the AC power supply.

[0006] Furthermore, as in Patent Document 1, when determining whether ink can be ejected well based on whether the amplitude of the detection signal detected when a drive signal is applied to the piezoelectric element of the head exceeds a threshold, if the detection signal contains large noise, it may not be possible to accurately determine whether ink can be ejected well.

[0007] An object of the present invention is to provide a liquid ejection device that can more accurately determine whether or not a nozzle is abnormal by suppressing the influence of noise. [Means for solving the problem]

[0008] The liquid ejection device of the present invention comprises: a liquid ejection head having a nozzle for ejecting liquid; a signal output unit that outputs a determination signal for determining whether or not the nozzle is an abnormal nozzle when the liquid ejection head is driven for inspection to confirm whether or not the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; a control device; the determination signal is a signal whose value changes during a determination period that begins at the start of the test driving when the nozzle is not an abnormal nozzle, the determination period has a first period and a second period different from the first period, The control device determining that the nozzle is not the abnormal nozzle when a difference between a maximum value of the determination signal in the first period and a minimum value of the determination signal in the second period is equal to or greater than a first threshold value; determining that the nozzle is the abnormal nozzle when a difference between a maximum value of the determination signal in the first period and a minimum value of the determination signal in the second period is less than a second threshold value that is smaller than the first threshold value; When the difference between the maximum value of the determination signal in the first period and the minimum value of the determination signal in the second period is less than the first threshold value and is equal to or greater than the second threshold value, a determination is not made as to whether the nozzle is an abnormal nozzle. 。 [Effects of the Invention]

[0009] Whether or not a nozzle is abnormal is determined based on at least one of the maximum value of the determination signal during the first period and the minimum value of the determination signal during the second period. In this case, if the first period is set to a period during which the value of the determination signal is estimated to be somewhat large if the nozzle is not abnormal, then even if the value of the determination signal increases due to noise at times other than the first period, this value will not be used to determine whether or not the nozzle is abnormal. Alternatively, if the second period is set to a period during which the value of the determination signal is estimated to be somewhat small if there is no abnormal noise, then even if the value of the determination signal decreases due to noise at times other than the second period, this value will not be used to determine whether or not the nozzle is abnormal. For these reasons, with this invention, even if the determination signal contains noise, it is possible to more accurately determine whether or not a nozzle is abnormal based on at least one of the maximum value and the minimum value. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. [Figure 2] 10A and 10B are diagrams for explaining detection electrodes arranged in a cap, and the connection relationship between the detection electrodes and a high-voltage power supply circuit and a determination circuit. [Figure 3] FIG. 10A is a diagram showing the determination signal when there is no noise and ink is ejected from the nozzle, and FIG. 10B is a diagram showing the determination signal when there is no noise and ink is not ejected from the nozzle. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Figure 5] 10 is a flowchart showing a process flow when an inspection instruction signal is received. [Figure 6] 10 is a flowchart showing a process flow when an inspection instruction signal is received in the first modification. [Figure 7] 10 is a flowchart showing a process flow when an inspection instruction signal is received in Modification 2. [Figure 8] 13 is a flowchart showing a process flow when an inspection instruction signal is received in Modification 3. [Figure 9] FIG. 10 is a diagram for explaining a first period and a second period in Modification 4. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will now be described.

[0012] <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, conveying rollers 6 and 7, a maintenance unit 8, an outlet 19, etc.

[0013] The carriage 2 is supported by two guide rails 11 and 12 extending in the scanning direction. The carriage 2 is connected to a carriage motor 86 (see FIG. 4) via a belt or the like (not shown), and when the carriage motor 86 is driven, the carriage 2 moves in the scanning direction along the guide rails 11 and 12. In the following description, the right and left sides of the scanning direction are defined as shown in FIG.

[0014] The subtank 3 is mounted on the carriage 2. 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 right side in the scanning direction, they store black, yellow, cyan, and magenta inks ("liquids" according to the present invention). The subtank 3 is connected to the four ink cartridges 14 attached to the cartridge holder 13 via four tubes 15. This allows the four colors of ink to be supplied from the four ink cartridges 14 to the subtank 3.

[0015] 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, the nozzle face 4a. More specifically, the plurality of nozzles 10 are arranged in a transport direction perpendicular to the scanning direction to form nozzle rows 9, and on the nozzle face 4a, four nozzle rows 9 are aligned in the scanning direction. From the plurality of nozzles 10, black, yellow, cyan, and magenta inks are ejected, starting with the nozzles 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 multiple nozzles 10. The platen 5 extends over the entire length of the recording paper P (the "ejection receiving medium" of the present invention) 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 and the like (not shown). 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.

[0017] 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.

[0018] 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, and the cap 71 is raised by the cap lifting mechanism 88, 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, for example, cover the plurality of nozzles 10 by coming into close contact with a frame or the like (not shown) that is arranged 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, 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.

[0020] For convenience, the cap 71 has been described as covering all of the nozzles 10 together, and ink in the inkjet head 4 is discharged from all of the nozzles 10 during suction purging. However, this is not limiting. For example, the cap 71 may have separate portions covering the nozzles 10 constituting the rightmost nozzle row 9 that ejects black ink and the nozzles 10 constituting the three leftmost nozzle rows 9 that eject color inks (yellow, cyan, and magenta ink), so that either the black ink or the color ink in the inkjet head 4 can be selectively discharged during suction purging. Alternatively, for example, a separate cap 71 may be provided for each nozzle row 9, so that ink can be discharged from the nozzles 10 for each nozzle row 9 individually during suction purging.

[0021] 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 (e.g., approximately 600 V) is applied to the detection electrode 76 by the high-voltage power supply circuit 77 during the determination drive described below. 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 outputs a signal obtained by processing the potential signal output from the detection electrode 76, including differentiation. In other words, 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 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 section" of the present invention.

[0022] After the carriage 2 is positioned at the maintenance position, a potential difference is generated between the inkjet head 4 and the detection electrode 76 by the high-voltage power supply circuit 77. At this time, when the inspection drive described below is not being performed and there is no noise, the value of the signal (non-drive signal) output from the signal processing circuit 78 becomes a predetermined reference value V0, as shown in Figures 3(a) and 3(b).

[0023] In this embodiment, after the carriage 2 is positioned at the maintenance position, a potential difference is generated between the inkjet head 4 and the detection electrode 76 by the high-voltage power supply circuit 77, and an inspection drive is performed to drive the inkjet head 4 so as to eject ink from the nozzles 10 toward the detection electrode 76.

[0024] During the test drive, if the nozzle 10 is not an abnormal nozzle having an abnormality in ink ejection, charged ink is ejected from the nozzle 10. 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.

[0025] At this time, if there is no noise, the signal (determination signal) output from the signal processing circuit 78 rises from the moment ink starts to be ejected from the nozzle 10, reaches a maximum value V1 that is higher than the reference value V0, and then drops to a minimum value V2 that is lower than the reference value V0, as shown in Figure 3(a).After that, the signal increases and decreases while attenuating, and converges to the reference value V0.

[0026] On the other hand, if the nozzle 10 is an abnormal nozzle, even if the nozzle 10 is driven for testing, ink will not be ejected from the nozzle 10. Therefore, if there is no noise, the signal (determination signal) output from the signal processing circuit 78 regarding the potential of the detection electrode 76 will not change from a predetermined reference value V0, as shown in FIG. 3(b).

[0027] In this manner, in this embodiment, the signal output from the signal processing circuit 78 when the determination drive is performed differs depending on whether the nozzle 10 is an abnormal nozzle. This fact is then utilized in this embodiment to determine whether the nozzle 10 is an abnormal nozzle, as will be described later.

[0028] The outlet 19 can be connected to an AC power source 90 (see FIG. 4) such as a commercial power source. When the outlet 19 is inserted and connected to the AC power source 90, AC power is supplied to the printer 1.

[0029] <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 transport 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 a determination signal from a signal processing circuit 78.

[0030] 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.

[0031] <Processing when receiving an inspection instruction signal> Next, we will explain the flow of processing by the control device 80 when it receives an inspection instruction signal that instructs it to inspect whether or not the nozzle 10 is an abnormal nozzle. The control device 80 receives an inspection instruction signal when, for example, a user operates an operation unit (not shown) of the printer 1 or a PC connected to the printer to instruct it to inspect whether or not the nozzle 10 is an abnormal nozzle, thereby sending an inspection instruction signal to the control device 80.

[0032] When the inspection instruction signal is received, the control device 80 performs processing in accordance with the flow of Fig. 5. First, the control device 80 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.

[0033] 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 acquires the non-driven signal output from the signal processing circuit 78 for a predetermined period (S103). Here, the predetermined period is the time during which the non-driven signal is acquired in order to determine whether or not the non-driven signal contains significant noise. From the viewpoint of more accurately determining whether or not the non-driven signal contains significant noise, the predetermined period may be set to a relatively long period, such as a period equal to or longer than the determination period T. Alternatively, from the viewpoint of shortening the time required to determine whether or not the non-driven signal contains significant noise, the predetermined period may be set to a period shorter than the determination period T. Here, the determination period T refers to the period from the start of the test drive as shown in FIG. 3(a) until the signal output from the signal processing circuit 78 is sufficiently attenuated when ink is ejected from the nozzle 10 by the test drive.

[0034] Next, the control device 80 determines whether the difference [Vna - Vna] between the maximum value Vna and the minimum value Vnb of the non-driven signal acquired in S103 is smaller than a predetermined value Vnt (S104). If the difference [Vna - Vnb] between the maximum value Vna and the minimum value Vnb is equal to or greater than the predetermined value Vnt (S104: NO), and if a predetermined time has not elapsed since the start of the first non-driven signal (S105: NO), the process returns to S103. If the difference [Vna - Vnb] between the maximum value Vna and the minimum value Vnb is equal to or greater than the predetermined value Vnt (S104: NO), and if a predetermined time has elapsed since the start of the first non-driven signal (S105: YES), the control device 80 outputs an error signal (S106) and ends the process. The error signal is a signal for displaying an error message, for example, on a display unit (not shown) of the printer 1 or on a display of a PC connected to the printer 1.

[0035] If the difference [Vna-Vnb] between the maximum value Vna and the minimum value Vnb is less than the predetermined value Vnt (S104: YES), the control device 80 sets one of the multiple nozzles 10 of the inkjet head 4 as the target nozzle to be determined as to whether it is an abnormal nozzle (S107).

[0036] Next, the control device 80 executes a test drive process (S108). In S108, the control device 80 causes the inkjet head 4 to perform a test drive for ejecting ink from the target nozzles.

[0037] Next, when the test drive is performed by S108, the control device 80 determines, based on the judgment signal output from the signal processing circuit 78, whether the difference [Va-Vb] between the maximum value Va of the judgment signal in the first period T1 and the minimum value Vb of the judgment signal in the second period T2 is greater than or equal to the threshold value Vt (S109).

[0038] 3A, the first period T1 is a part of the determination period T and is a continuous period including a first timing U1 at which the value of the determination signal is expected to reach a maximum value V1 when test driving is performed in a noise-free state and ink is ejected from the nozzles 10. The second period T2 is a part of the determination period T and is a continuous period including a second timing U2 at which the value of the determination signal is expected to reach a minimum value V2 when test driving is performed in a noise-free state and ink is ejected from the nozzles 10, and does not overlap with the first period T1. In this embodiment, the first timing U1 and the second timing U2 are obtained by experiment or the like during the manufacturing stage of the printer 1, and information about the first period T1 and the second period T2 is stored in the flash memory 84 based on this information.

[0039] If 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 (S109: YES), the control device 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S110). If 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 (S109: NO), the control device 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S111).

[0040] After storing in the flash memory 84 in S110 or S111 whether the target nozzle is an abnormal nozzle, the control device 80 determines whether or not the inspection of all nozzles 10 in the inkjet head 4 to determine whether or not they are abnormal has been completed (S112). If there is a nozzle 10 for which the inspection to determine whether or not it is an abnormal nozzle has not been completed (S112: NO), the control device 80 changes the target nozzle to any of the nozzles 10 for which the inspection to determine whether or not it is an abnormal nozzle has not been completed (S113), and returns to S108.

[0041] If inspection of all nozzles 10 of the inkjet head 4 to determine whether they are abnormal has been completed (S112: YES), the control device 80 controls the high-voltage power supply circuit 77 to stop applying voltage to the detection electrode 76 (S114). Next, the control device 80 determines whether any of the nozzles 10 of the inkjet head 4 are abnormal, based on the information stored in the flash memory 84 in S110 or S111 (S115).

[0042] If there are no abnormal nozzles (S115: NO), the process ends. If there are abnormal nozzles (S115: YES), the control device 80 executes a purge process (S116) and then ends the process. In the purge process, the control device 80 controls the suction pump 72 to perform a suction purge. This allows the abnormal nozzles to be restored.

[0043] In the purge process, suction purging may be performed uniformly regardless of the number of abnormal nozzles, or suction purging may be performed so that the greater the number of abnormal nozzles, the greater the amount of ink discharged.

[0044] <Effects> In this embodiment, whether or not a nozzle is abnormal is determined based on the maximum value Va of the determination signal during a first period T1 of the determination period T and the minimum value Vb of the determination signal during a second period T2 of the determination period T, which is different from the first period T1. In this case, if the first period T1 is set to a period during which the value of the determination signal is estimated to be large, even if the value of the determination signal increases due to noise at times other than the first period T1, this value will not be used to determine whether or not the nozzle is abnormal. Furthermore, if the second period T2 is set to a period during which the value of the determination signal is estimated to be small, even if the value of the determination signal decreases due to noise at times other than the second period T2, this value will not be used to determine whether or not the nozzle is abnormal. For these reasons, in this embodiment, even if the determination signal contains noise, it is possible to more accurately determine whether or not the nozzle 10 is abnormal based on the maximum value Va and the minimum value Vb.

[0045] Furthermore, in this embodiment, the first period T1 is a continuous period that includes a first timing U1 at which the value of the determination signal is estimated to be maximum if there is no noise and the nozzle is not abnormal. The second period T2 is a continuous period that includes a second timing U2 at which the value of the determination signal is estimated to be minimum if there is no noise and the nozzle is not abnormal, but does not include the first timing U1. This makes it possible to more accurately determine whether or not the nozzle 10 is an abnormal nozzle based on the maximum value Va of the determination signal during the first period T1 and the minimum value Vb during the second period T2.

[0046] Furthermore, in this embodiment, it is possible to more accurately determine whether or not a nozzle 10 is an abnormal nozzle based on whether or not the difference [Va-Vb] between the maximum value Va of the judgment signal in the first period T1 and the minimum value Vb in the second period T2 is greater than or equal to the threshold value Vt.

[0047] Furthermore, in this embodiment, when an inspection instruction signal is received, a non-driven signal is also received. Then, if the difference [Vna-Vnb] between the maximum value Vna and the minimum value Vnb of the non-driven signal is less than a predetermined value Vnt, an inspection drive process is executed. This allows the inspection drive to be performed when there is a low possibility that the determination signal will contain significant noise, making it possible to more accurately determine whether or not the nozzle 10 is an abnormal nozzle.

[0048] On the other hand, if the difference [Vna-Vnb] between the maximum value Vna and the minimum value Vnb of the non-driven signal is equal to or greater than a predetermined value Vnt, the test driving process is not executed. This prevents erroneous determination by not executing the test driving process when there is a high possibility that the determination signal contains large noise.

[0049] <Modification> Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims.

[0050] In the above-described embodiment, the condition that the difference [Vna-Vnb] between the maximum value Vna and the minimum value Vnb of the non-driven signal is less than a predetermined value Vnt is set as the predetermined condition for determining whether or not to perform test driving, but this is not limited to this.

[0051] Another condition for the maximum value Vna and minimum value Vnb of the non-driven signal may be set as a predetermined condition for determining whether or not to perform test driving. For example, the other condition is a condition that both the absolute value |Vna-V0| of the difference between the maximum value Vna of the non-driven signal and a reference value V0 and the absolute value |Vnb-V0| of the difference between the minimum value Vnb of the non-driven signal and the reference value V0 are smaller than a predetermined value.

[0052] Furthermore, the determination as to whether or not to perform test driving is not limited to whether or not a predetermined condition is satisfied for the maximum value Vna and the minimum value Vnb of the non-driving signal.

[0053] In the first modification, when the control device 80 receives an inspection instruction signal, it performs processing according to the flow of FIG.

[0054] More specifically, the control device 80 executes the same processes of S101 to S103 as in the above-described embodiment. However, in the first modification, in S103, a non-driving signal for a period longer than the determination period T is acquired.

[0055] Next, the control device 80 determines whether the non-driving signal acquired in S103 is a periodically repeated signal (S201).

[0056] Here, power is supplied to the printer 1 from an AC power supply 90. Therefore, due to the influence of noise caused by the AC voltage applied from the AC power supply, the non-driving signal includes a signal that repeats at a fixed cycle corresponding to the cycle of this AC voltage. The cycle of the AC voltage is, for example, 1 / 50 second when the AC power supply is 50 Hz, and 1 / 60 second when the AC power supply is 60 Hz. Furthermore, the fixed cycle corresponding to the cycle of the AC voltage is a cycle longer than the determination period T, for example, a cycle that is an integer multiple of the cycle of the AC voltage.

[0057] Therefore, if the noise contained in the non-driven signal is mainly noise caused by the AC voltage and no other large noise is contained, the non-driven signal will be a signal that repeats at the above-mentioned regular cycle. On the other hand, if the non-driven signal contains large noise that has suddenly occurred due to environmental changes or the like in addition to noise caused by the AC voltage, the non-driven signal will not be a signal that repeats at the above-mentioned regular cycle.

[0058] In S201, it is determined whether the non-driven signal is a signal that repeats at the above-mentioned constant period, thereby determining whether the non-driven signal contains sudden large noise. Also, in S201, for example, multiple signals that repeat at the above-mentioned constant period are extracted from the non-driven signal, and values of the extracted multiple signals at corresponding timings are obtained. If the variation in these values is within a predetermined range, it is determined that the non-driven signal is a periodically repeating signal. On the other hand, if the variation in these values exceeds the predetermined range, it is determined that the non-driven signal is not a periodically repeating signal.

[0059] If the non-driven signal is not a periodically repeated signal (S201: NO), the process proceeds to S105. If the non-driven signal is a periodically repeated signal (S201: YES), the control device 80 then acquires information about the minimum noise period of the non-driven signal (S202).

[0060] The minimum noise period is a period within the cycle of the non-driven signal that has the same length as the determination period T and is a period in which the difference between the maximum and minimum values of the non-driven signal is smallest. In S202, the control device 80, for example, acquires the maximum and minimum values for each of a plurality of different periods of the non-driven signal that have the same length as the determination period T, and acquires information about the period among these plurality of periods that has the smallest difference between the maximum and minimum values as information about the minimum noise period.

[0061] Then, the control device 80 executes the processes of S107 to S116 as in the above-described embodiment. However, in Modification 1, in S107, the control device 80 causes the inkjet head 4 to perform the test drive so that the determination period coincides with the minimum noise period in the cycle of the non-drive signal.

[0062] If the noise is caused by the AC voltage applied from the AC power supply 90, the non-driven signal will be a signal that repeats at a fixed cycle corresponding to the cycle of the AC voltage. In Modification 1, the test drive is performed so that the determination period T coincides with the minimum noise period. This allows the test drive to be performed during a period with as little noise as possible, making it possible to more accurately determine whether or not the nozzle 10 is an abnormal nozzle.

[0063] However, if the noise is not periodic, even if information on the minimum noise period is obtained before the test drive and the test drive is performed so that the judgment period T matches the noise period, it may not be possible to reduce the noise during the test drive.

[0064] Therefore, in Modification 1, if the non-drive signal is a signal that is repeated at a constant cycle, the liquid ejection head is driven for inspection so that the determination period T coincides with the minimum noise period. As a result, as described above, if the signal output from the signal processing circuit 78 contains periodic noise, by driving for inspection during a period with as little noise as possible, it is possible to more accurately determine whether the nozzle is an abnormal nozzle.

[0065] On the other hand, if the non-drive signal does not change periodically, the test drive process is not executed. This prevents erroneous determination by not executing the test drive at a timing when there is a high possibility that the signal output from the signal processing circuit 78 contains non-periodic noise.

[0066] Furthermore, in the first modification, it is determined whether the non-driven signal is a periodically repeating signal, and information on the minimum noise period is acquired only when it is determined that the non-driven signal is a periodically repeating signal, but this is not limited to this. Because the non-driven signal is not likely to contain sudden large noise, for example, information on the minimum noise period may be acquired without determining whether the non-driven signal is a periodically repeating signal.

[0067] In addition, in the above-described embodiment and modified example 1, the test driving is performed at a timing that minimizes noise in the determination signal, but this is not limiting. For example, in the above-described embodiment, S103 to S106 may be omitted, and the process may proceed to S107 after processing S102.

[0068] Furthermore, in the above-described embodiment, whether or not the nozzle 10 is an abnormal nozzle is determined based on whether or not the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the judgment signal is greater than or equal to the threshold value Vt, but this is not limited to this.

[0069] In Modification 2, when an inspection instruction signal is received, the control device 80 performs processing according to the flow of Fig. 7. However, in Modification 2, the processing of S101 to S107 and S112 to S116 is the same as in the above-described embodiment, and therefore S101 to S107 and S112 to S116 are not shown in Fig. 7.

[0070] More specifically, in Modification 2, after setting the target nozzle in S107, the control device 80 resets the value of variable N to 0 (S301). Variable N corresponds to the number of times that test driving has been repeated for the same nozzle 10. Next, the control device 80 executes test driving processing similar to S108 in the above embodiment (S302), and increments the value of variable N by 1.

[0071] If 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 first threshold value Vt1 (S304: YES), the control device 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S110). Here, the first threshold value Vt1 is a value greater than the threshold value Vt in the above-described embodiment.

[0072] If the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the first threshold value Vt1 (S304: NO) and is also less than the second threshold value Vt2 (S305: NO), the control device 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S111). Here, the second threshold value Vt2 is a value smaller than both the first threshold value Vt1 and the threshold value Vt in the above-described embodiment.

[0073] If the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the judgment signal is less than the first threshold value Vt1 (S304: NO) and is greater than or equal to the second threshold value Vt2 (S305: YES), and if the variable N is less than the predetermined value Nt (S306: NO), return to S302.

[0074] As a result, until the variable N reaches a predetermined value Nt, as long as the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the judgment signal is less than the first threshold value Vt1 and greater than or equal to the second threshold value Vt2, inspection driving for the same nozzle 10 is repeated, and judgments S304 and S305 are made.

[0075] Then, as described above, when the test drive for the same nozzle 10 is repeatedly performed and the variable N reaches a predetermined value Nt (S306: YES), if 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 (S307: YES), the control device 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S110). On the other hand, if 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 (S307: NO), the control device 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S111). Then, after storing in the flash memory 84 in S110 or S111 whether the target nozzle is an abnormal nozzle or not, the process proceeds to S112.

[0076] In Modification 2, if 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 first threshold value Vt1, it is possible to more accurately determine that the nozzle 10 is an abnormal nozzle. Furthermore, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the second threshold value Vt2, it is possible to more accurately determine that the nozzle 10 is not an abnormal nozzle. On the other hand, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the first threshold value Vt1 and equal to or greater than the second threshold value Vt2, it is highly likely that the determination signal contains significant noise. Therefore, in this case, by not determining whether the nozzle 10 is an abnormal nozzle, it is possible to prevent erroneous determination.

[0077] Furthermore, in Modification 2, if the difference [Va-Vb] between the maximum value Va and minimum value Vb of the determination signal is less than the first threshold value Vt1 and greater than or equal to the second threshold value Vt2, i.e., if there is a high possibility that the determination signal contains large noise, the test drive is performed again, and it is determined whether the nozzle 10 is an abnormal nozzle based on the difference between the maximum value Va and minimum value Vb of the determination signal output from the signal output unit during this test drive again. This makes it possible to more accurately determine whether the nozzle 10 is an abnormal nozzle.

[0078] Furthermore, in Modification 2, the test driving for the same target nozzle is repeatedly performed only until the variable N reaches a predetermined value Nt, while the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the first threshold value Vt1 and greater than or equal to the second threshold value Vt2, but this is not limiting. For example, the test driving may be repeatedly performed until the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is greater than or equal to the first threshold value Vt1 or less than the second threshold value Vt2.

[0079] Furthermore, in Modification 2, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the first threshold value Vt1 and is equal to or greater than the second threshold value Vt2, then the test drive is performed again and the determination of S304 and S305 is made, but this is not limiting. For example, if the difference [Va-Vb] between the maximum value Va and the minimum value Vb of the determination signal is less than the first threshold value Vt1 and is equal to or greater than the second threshold value Vt2, then the test drive may not be performed again and the fact that it was not possible to determine whether or not the nozzle is abnormal may be stored in flash memory 84.

[0080] Furthermore, in variant 2, as described above, when inspection driving is repeatedly performed on the same nozzle 10 and the variable N reaches a predetermined value Nt (S307: YES), it may be stored in flash memory 84 that it is impossible to determine whether the nozzle is abnormal or not.

[0081] Furthermore, in the above example, whether or not the nozzle 10 is an abnormal nozzle is determined based on the difference [Va-Vb] between the maximum value Va of the judgment signal in the first period T1 and the minimum value Vb in the second period T2, but this is not limited to this.

[0082] In Modification 3, when an inspection instruction signal is received, the control device 80 performs processing according to the flow of Fig. 8. However, in Modification 3, the processing of S101 to S108 and S112 to S116 is the same as in the above-described embodiment, and therefore S101 to S108 and S112 to S116 are not shown in Fig. 8.

[0083] Explaining the flow of FIG. 8 in more detail, the control device 80, after executing the test driving process in S108, as in the above-described embodiment, determines whether the maximum value Va of the determination signal in the first period T1 is equal to or greater than the threshold value Vat, and whether the minimum value Vb of the determination signal in the second period T2 is equal to or less than the threshold value Vbt (S401, S402).

[0084] If the maximum value Va is equal to or greater than the threshold value Vat (S401: YES) and the minimum value Vb is equal to or less than the threshold value Vbt (S402: YES), the control device 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S110).

[0085] If the maximum value Va is smaller than the threshold value Vat (S401: NO) and if the minimum value Vb is greater than the threshold value Vbt (S402: NO), the control device 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S111).

[0086] In addition, in the above example, whether or not the nozzle 10 is an abnormal nozzle is determined based on both the maximum value Va of the determination signal in the first period T1 and the minimum value Vb of the determination signal in the second period T2, but this is not limited to this.

[0087] For example, in variant example 3, of S401 and S402, only the determination of S401 is performed, and if the maximum value Va is equal to or greater than the threshold value Vat (S401: YES), the flash memory 84 stores the fact that the target nozzle is not an abnormal nozzle, and if the maximum value Va is smaller than the threshold value Vat (S401: NO), the flash memory 84 stores the fact that the target nozzle is an abnormal nozzle.

[0088] Alternatively, in variant example 3, of S401 and S402, only the determination of S402 may be performed, and if the minimum value Vb is equal to or less than the threshold value Vbt (S402: YES), the flash memory 84 may store the fact that the target nozzle is not an abnormal nozzle, and if the minimum value Vb is greater than the threshold value Vbt (S402: NO), the flash memory 84 may store the fact that the target nozzle is an abnormal nozzle.

[0089] In the above example, the first period T1 is a continuous period including a first timing U1 at which the value of the determination signal is expected to reach the maximum value V1 when test driving is performed in a noise-free state and ink is ejected from the nozzles 10. The second period T2 is a continuous period that does not overlap with the first period T1 and includes a second timing U2 at which the value of the determination signal is expected to reach the minimum value V2 when test driving is performed in a noise-free state and ink is ejected from the nozzles 10. However, this is not limited to this.

[0090] 9, in Modification 4, the first period T1 is set to be the first period during which the value of the determination signal is expected to be greater than the reference value V0 when test driving is performed in a noise-free state and ink is ejected from the nozzle 10. The second period T2 is set to be the first period during which the value of the determination signal is expected to be smaller than the reference value V0 when test driving is performed in a noise-free state and ink is ejected from the nozzle 10.

[0091] In variant example 4, the first period T1 is set as a period during which it is estimated that the value of the judgment signal will be greater than the reference value V0 if there is no noise and the nozzle is not an abnormal nozzle, so it is possible to more accurately determine whether or not the nozzle 10 is an abnormal nozzle based on the maximum value Va of the judgment signal in the first period T1.

[0092] Furthermore, in variant example 4, the second period T2 is set to a period during which the value of the judgment signal is estimated to be smaller than the reference value V0 when there is no noise and the nozzle is not an abnormal nozzle, so it is possible to more accurately determine whether or not the nozzle 10 is an abnormal nozzle based on the minimum value of the judgment signal during the second period T2.

[0093] Furthermore, in the above example, suction purging is performed to restore the abnormal nozzle, but this is not limiting. For example, a pressure pump may be provided midway along the tube 15 connecting 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 multiple nozzles 10 covered with caps 71, the pressure pump may be driven to pressurize the ink in the inkjet head 4 and discharge the ink from the inkjet head 4 through the nozzles 10, thereby performing so-called pressure purging.

[0094] Furthermore, during purging, both suction by the suction pump 72 and pressurization by the pressure pump may be performed.

[0095] Furthermore, the method of recovering abnormal nozzles is not limited to purging. For example, abnormal nozzles may be recovered by flushing, which causes the inkjet head 4 to discharge ink from the nozzles 10. Alternatively, abnormal nozzles may be recovered by both purging and flushing. Alternatively, abnormal nozzles may be recovered by selectively performing either purging or flushing depending on the number of abnormal nozzles, etc.

[0096] Furthermore, in the above-described embodiment, in S107 and S113, one nozzle 10 out of the multiple nozzles 10 of the inkjet head 4 is set as the target nozzle for determining whether it is an abnormal nozzle, but this is not limited to this. Two or more nozzles may be set as the target nozzle for the inspection drive process (S108). In this case, the threshold value may be set according to the number of target nozzles. For example, the greater the number of target nozzles, the greater the threshold value may be set.

[0097] Furthermore, in the above embodiment, the test drive is performed on all of the nozzles 10 of the inkjet head 4, but this is not limited to this. For example, the test 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 determination signal output from the signal processing circuit 78 during the test drive.

[0098] Furthermore, in the above-described embodiment, the signal processing circuit 78 outputs a signal indicating whether or not the nozzle is abnormal based on the change in 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 this.

[0099] For example, a detection electrode extending in the vertical direction may be disposed, and a signal indicating whether or not the nozzle is abnormal may be output from the signal processing circuit in response to a change in the potential of the detection electrode when ink is ejected from the nozzle 10 so as to pass through an area 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 a signal indicating whether or not the nozzle is abnormal may be output from the optical sensor.

[0100] Alternatively, for example, as described in Patent Publication No. 4929699, a voltage detection circuit (the "signal output unit" of the present invention) that detects changes in voltage when ink is ejected from the nozzles can be connected to the plate on which the nozzles of the inkjet head are formed, and the voltage detection circuit can output a signal indicating whether or not the nozzle is abnormal.

[0101] 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 to eject ink, a second applied voltage is applied to drive the heater so that ink is not ejected, and a signal indicating whether the nozzle is an abnormal nozzle or not may be output based on the change in temperature detected by the temperature detection element during the period from when the second applied voltage was applied until a predetermined time has elapsed.

[0102] Furthermore, in the above example, the signal output section outputs a signal according to whether or not ink has been ejected from the nozzle 10, but the present invention is not limited to this.

[0103] For example, a signal output unit may be provided that outputs a signal corresponding to an abnormal nozzle state other than the state of ink not being ejected. An abnormal nozzle state may be, for example, an abnormality in the direction of ink ejection, the generation of droplets, the presence of air bubbles, or the presence of paper dust.

[0104] 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 P in the scanning direction.

[0105] Although the above description has been given of an example in which the present invention is applied to a printer that ejects ink from nozzles to record on recording paper P, 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, outdoor advertising sheets, cases for mobile devices such as smartphones, cardboard, and resin materials. 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]

[0106] 1. Printer 4 Inkjet head 10 nozzles 76 Detection electrode 77 High-voltage power supply circuit 78 Signal Processing Circuit 79 Resistance 80 Control device 84 Flash memory 90 AC power supply

Claims

1. a liquid ejection head having nozzles for ejecting liquid; a signal output unit that outputs a determination signal for determining whether or not the nozzle is an abnormal nozzle when the liquid ejection head is driven for inspection to confirm whether or not the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; a control device; the determination signal is a signal whose value changes during a determination period that begins at the start of the test driving when the nozzle is not an abnormal nozzle, the determination period has a first period and a second period different from the first period, The control device determining that the nozzle is not an abnormal nozzle when a difference between a maximum value of the determination signal in the first period and a minimum value of the determination signal in the second period is equal to or greater than a first threshold value; determining that the nozzle is the abnormal nozzle when a difference between a maximum value of the determination signal in the first period and a minimum value of the determination signal in the second period is less than a second threshold value that is smaller than the first threshold value; A liquid ejection device characterized in that when the difference between the maximum value of the judgment signal during the first period and the minimum value of the judgment signal during the second period is less than the first threshold value and greater than or equal to the second threshold value, no determination is made as to whether the nozzle is an abnormal nozzle.

2. a storage unit, the storage unit stores information about the first period; the first period is the first period of the determination period during which, if the nozzle is not the abnormal nozzle, the value of the determination signal is estimated to be greater than the value of the non-driven signal, which is a signal output from the signal output section when the test driving is not being performed; The control device 2. The liquid ejection device according to claim 1, wherein the determination as to whether the nozzle is the abnormal nozzle is determined based on the maximum value of the determination signal during the first period stored in the storage unit.

3. a storage unit, the storage unit stores information about the second period; the second period is the first period of the determination period during which, if the nozzle is not the abnormal nozzle, the value of the determination signal is estimated to be smaller than the value of the non-driven signal, which is a signal output from the signal output section when the test driving is not being performed; The control device 2. The liquid ejection device according to claim 1, wherein the determination as to whether the nozzle is the abnormal nozzle is based on the minimum value of the determination signal during the second period stored in the storage unit.

4. a storage unit, the storage unit stores information about the first period and information about the second period; the first period is a continuous period within the determination period that includes a first timing at which the value of the determination signal is estimated to be maximum if the nozzle is not the abnormal nozzle, the second period is a continuous period of the determination period that includes a second timing at which the value of the determination signal is estimated to be minimum if the nozzle is not the abnormal nozzle, and does not include the first timing, The control device The liquid ejection device according to claim 1, characterized in that it determines whether the nozzle is an abnormal nozzle based on the maximum value of the judgment signal during the first period stored in the memory unit and the minimum value of the judgment signal during the second period stored in the memory unit.

5. The control device When a difference between a maximum value of the determination signal in the first period and a minimum value of the determination signal in the second period is less than the first threshold value and is equal to or greater than the second threshold value, causing the liquid ejection head to perform the inspection driving again; A liquid ejection device as described in any one of claims 1 to 4, characterized in that it determines whether the nozzle is an abnormal nozzle based on the difference between the maximum value of the judgment signal output from the signal output unit during the second inspection drive in the first period and the minimum value of the judgment signal during the second period.

6. The control device When an inspection instruction signal instructing that the inspection driving be performed is received, acquiring a non-driven signal that is a signal output from the signal output unit when the test driving is not being performed; When a predetermined condition regarding at least one of a maximum value and a minimum value of the non-drive signal in a predetermined period is satisfied, the liquid ejection head is driven for inspection; 6. The liquid ejection apparatus according to claim 1, wherein the liquid ejection head is not driven for inspection when the predetermined condition is not satisfied.

7. The predetermined condition is:

7. The liquid ejection device according to claim 6, wherein the condition is that the difference between the maximum value and the minimum value of the non-driven signal during the predetermined period is less than a predetermined value.

8. Power is supplied from an AC power source, a non-drive signal that is a signal output from the signal output unit when the test drive is not being performed includes a signal that is repeated at a constant cycle corresponding to the cycle of an AC voltage applied from an AC power supply, The control device When an inspection instruction signal instructing that the inspection driving be performed is received, acquire information on a minimum noise period within the period of the non-driven signal, the minimum noise period being the same length as the determination period and in which the difference between the maximum value and the minimum value of the non-driven signal is smallest; The liquid ejection device according to any one of claims 1 to 5, wherein the liquid ejection head is driven for inspection so that the determination period coincides with the minimum noise period in the cycle of the non-drive signal.

9. The control device determining whether the non-driven signal is a signal that is repeated at a constant cycle; When the non-driven signal is a signal that is repeated at a constant cycle, driving the liquid ejection head for inspection so that the determination period coincides with the minimum noise period in the cycle of the non-drive signal; If the non-driven signal is not a signal that is repeated at a constant cycle, 9. The liquid ejection apparatus according to claim 8, wherein the liquid ejection head is not driven for inspection.

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