Liquid dispensing device

Abstract

To more accurately determine whether a nozzle is abnormal or not while suppressing the influence of noise.SOLUTION: A liquid discharge device obtains a signal during non-driving that is output from a signal processing circuit in a state where driving for inspection is not performed (S102); obtains a signal for determination for determining whether a nozzle is abnormal or not, which is output from the signal processing circuit when making an inkjet head perform the driving for inspection (S104); overlaps the signal for determination with the signal during non-driving so that a difference between a value of the signal for determination and a value of signal during non-driving becomes minimum to generate a differential signal that is a signal showing the difference between the value of the signal for determination and the value of the signal during non-driving at each timing (S105); and determines whether the nozzle is abnormal or not on the basis of the differential signal (S106).SELECTED DRAWING: Figure 5

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 satisfactorily. In the ejection test, it is determined whether ink can be ejected satisfactorily based on whether the amplitude (the difference between the maximum potential and the minimum potential) of a detection signal detected when a drive signal is applied to a piezoelectric element of a head exceeds a threshold value.

[0003] In addition, 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] JP 2012-210768 A 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 discharged satisfactorily based on the results of the discharge test. However, in a printer such as that in Patent Document 1, for example, a certain amount of noise always enters from the AC power supply, and in reality, it can be difficult to perform the discharge test in a noise-free state.

[0006] An object of the present invention is to provide a liquid ejection device that can suppress the effects of noise and more accurately determine whether or not a nozzle is abnormal. [Means for solving the problem]

[0007] The liquid ejection device of the present invention includes a liquid ejection head having at least one nozzle for ejecting liquid, an electrode for receiving the liquid ejected from the nozzle; When the liquid ejection head is driven for inspection to check whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, A change in the voltage of the electrode when liquid is ejected from the nozzle toward the electrode. a signal output unit that outputs a judgment signal in response to the driving of the liquid ejection head for inspection, and a control unit, wherein the control unit causes the liquid ejection head to perform the driving for inspection and acquires the judgment signal output from the signal output unit, and acquires a signal output from the signal output unit as a non-driving signal when the liquid ejection head is not being driven for inspection, The difference between the value of the judgment signal and the value of the non-driven signal is minimized. The judgment signal and the non-driven signal are superimposed to generate a differential signal, which is the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and it is determined whether the nozzle is an abnormal nozzle based on the differential signal. A liquid ejection device according to the present invention includes a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform an inspection drive for checking whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, and a control unit, wherein the control unit causes the liquid ejection head to perform the inspection drive, and acquires the judgment signal output from the signal output unit. When the liquid ejection head is not being driven for inspection, the signal output from the signal output unit is obtained as a non-driven signal, and the judgment signal and the non-driven signal are superimposed to generate a differential signal which is the difference between the value of the judgment signal at each timing and the value of the non-driven signal.If the sum of the values ​​obtained by squaring the values ​​of the differential signal at each timing is less than a threshold value, it is determined that the nozzle is an abnormal nozzle, and if the sum of the values ​​obtained by squaring the values ​​of the differential signal at each timing is equal to or greater than the threshold value, it is determined that the nozzle is not an abnormal nozzle. In addition, the liquid ejection device of the present invention comprises a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives the liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform an inspection drive to check whether the nozzle is an abnormal nozzle having an abnormality in liquid ejection, and a control unit, wherein the control unit causes the liquid ejection head to perform the inspection drive and acquires the judgment signal output from the signal output unit, and when the liquid ejection head is not caused to perform the inspection drive, acquires the signal output from the signal output unit as a non-driven signal, superimposes the judgment signal and the non-driven signal to generate a differential signal that is a signal of the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and if the sum of the values ​​of the differential signal at each timing is less than a threshold value, determines that the nozzle is the abnormal nozzle, and if the sum of the values ​​of the differential signal at each timing is equal to or greater than the threshold value, determines that the nozzle is not the abnormal nozzle. a control unit configured to output a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform a test drive for checking whether the nozzle is an abnormal nozzle having an abnormality in liquid ejection, and a control unit, wherein the control unit causes the liquid ejection head to perform the test drive and acquires the judgment signal output from the signal output unit, and when the liquid ejection head is not caused to perform the test drive, acquires a signal output from the signal output unit as a non-driven signal, superimposes the judgment signal and the non-driven signal to generate a differential signal which is a signal that is the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and determines whether the nozzle is the abnormal nozzle based on the differential signal, and power is supplied from an AC power source, and the non-driven signal is a signal with a length greater than or equal to the period of the power supplied from the AC power source. In addition, the liquid ejection device of the present invention comprises a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives the liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform a test drive to check whether the nozzle is an abnormal nozzle having an abnormality in liquid ejection, and a control unit, wherein the control unit causes the liquid ejection head to perform the test drive and acquires the judgment signal output from the signal output unit, and acquires the signal output from the signal output unit as a non-driven signal just before causing the liquid ejection head to perform the test drive, superimposes the judgment signal and the non-driven signal to generate a differential signal that is a signal of the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and judges whether the nozzle is the abnormal nozzle based on the differential signal. Furthermore, a liquid ejection device of the present invention includes a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform a test drive for checking whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, and a control unit, wherein the control unit causes the liquid ejection head to perform the test drive and acquires the judgment signal output from the signal output unit, and when the liquid ejection head is not caused to perform the test drive, The signal output from the signal output unit is acquired as a non-driven signal, the judgment signal and the non-driven signal are superimposed to generate a differential signal which is the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and it is determined whether or not the nozzle is an abnormal nozzle based on the differential signal. A plurality of the non-driven signals are acquired continuously, and if the variation in the plurality of non-driven signals is within a predetermined range, the acquired non-driven signal is used to generate the differential signal, and if the variation in the plurality of non-driven signals is not within the predetermined range, the plurality of non-driven signals are acquired again. A liquid ejection device according to the present invention includes a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform an inspection drive for checking whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, and a control unit, wherein the control unit causes the liquid ejection head to perform the inspection drive, and receives the judgment signal output from the signal output unit. When the liquid ejection head is not being driven for inspection, the signal output from the signal output unit is obtained as a non-driven signal, the judgment signal and the non-driven signal are superimposed to generate a differential signal which is the difference between the value of the judgment signal at each timing and the value of the non-driven signal, and based on the differential signal, it is determined whether or not the nozzle is an abnormal nozzle, and if the sum of the squares of the values ​​of the differential signal at each timing exceeds a predetermined value, the non-driven signal is obtained again, and the non-driven signal is used to generate the differential signal. In addition, the liquid ejection device of the present invention comprises a liquid ejection head having at least one nozzle that ejects liquid, an electrode that receives the liquid ejected from the nozzle, a signal output unit that outputs a judgment signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is caused to perform a test drive to check whether the nozzle is an abnormal nozzle having an abnormality in liquid ejection, and a control unit, wherein the control unit causes the liquid ejection head to perform the test drive and acquires the judgment signal output from the signal output unit, and when the liquid ejection head is not caused to perform the test drive, acquires the signal output from the signal output unit as a non-driven signal, superimposes the judgment signal and the non-driven signal to generate a differential signal which is a signal of the difference between the value of the judgment signal and the value of the non-driven signal at each timing, and judges whether the nozzle is the abnormal nozzle based on the differential signal, and if the sum of the values ​​of the differential signal at each timing exceeds a predetermined value, acquires the non-driven signal again and generates the differential signal using the non-driven signal. Effect of the Invention

[0008] In the present invention, the noise components are common to the judgment signals and the non-driven signals. Therefore, the differential signal, which is the difference between the value of each judgment signal and the value of the non-driven signal, is a judgment signal in which the noise components have been reduced. This makes it possible to accurately determine whether or not a nozzle is abnormal based on the differential signal. [Brief description of the drawings]

[0009] [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 the signal processing circuit when ink is ejected from a nozzle during test drive when there is no noise, and FIG. 1B is a diagram showing a signal output from the signal processing circuit when ink is not ejected from a nozzle during test drive when there is no noise. [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 non-driven signal setting process in FIG. 5. [Figure 7] 6 is a flowchart showing the flow of the differential signal generation process in FIG. 5. [Figure 8] 6 is a flowchart showing the flow of the determination process in FIG. 5. [Figure 9] FIG. 1A is a diagram showing an example of an actual non-driven signal including noise, and FIG. 1B is a diagram showing an example of an actual judgment signal including noise when ink is ejected by test driving. [Figure 10] 13 is a flowchart showing the flow of a non-driven signal setting process in the first modified example. [Figure 11] 13 is a flowchart showing a process flow when an inspection instruction signal is received in the second modification. [Figure 12] 13 is a flowchart showing a process flow when an inspection instruction signal is received in the third modification example. [Figure 13] 13 is a flowchart showing a process flow when an inspection instruction signal is received in the fourth modification example. [Figure 14] 13 is a flowchart showing the flow of a differential signal generation process according to the fifth modified example. [Figure 15] 13A is a flowchart showing the flow of the determination process in the sixth modification, and FIG. 13B is a flowchart showing the flow of the determination process in the seventh modification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Preferred embodiments of the present invention will now be described.

[0011] <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, an outlet 19, etc.

[0012] 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.

[0013] 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 lined up in the scanning direction, and store black, yellow, cyan, and magenta inks ("liquids" of the present invention) from the one arranged on the right side in the scanning direction. 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 to the subtank 3 from the four ink cartridges 14.

[0014] 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 surface 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 surface 4a, four nozzle rows 9 are lined up in the scanning direction. The nozzles 10 eject black, yellow, cyan, and magenta inks in that order, starting from the nozzles constituting the nozzle row 9 on the right side of the scanning direction.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 driving for inspection, which will be 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 subjected to processing including differentiation processing on the potential signal output from the detection electrode 76. That is, the signal output from the signal processing circuit 78 is a voltage signal corresponding to the voltage of the detection electrode 76. However, the signal output from the signal processing circuit 78 may be a current signal. In 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.

[0021] With the carriage 2 positioned in 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 voltage of the signal (non-driven signal) output from the signal processing circuit 78 becomes voltage V0 as shown in Figures 3(a) and (b), assuming that there is no influence of noise.

[0022] 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.

[0023] 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.

[0024] At this time, assuming that there is no effect of noise, the signal output from the signal processing circuit 78 rises from voltage V0 to voltage V1, which is greater than voltage V0, then drops to voltage V2, which is less than voltage V0, and then repeats rising and dropping while attenuating, before returning to voltage V0, as shown in Fig. 3(a). As a result, the signal output from the signal processing circuit 78 becomes a signal whose maximum value is voltage V1 and whose minimum value is voltage V2.

[0025] 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 voltage V0, as shown in FIG.

[0026] In addition, the signal output from the signal processing circuit 78 has a first signal portion R1 whose value changes due to inspection driving when the nozzle 10 is not an abnormal nozzle (when it is a normal nozzle), and a second signal portion R2 following the first signal portion whose value does not change due to inspection driving regardless of whether the nozzle 10 is an abnormal nozzle or not.

[0027] 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.

[0028] The outlet 19 can be connected to an AC power source (not shown). When the outlet 19 is plugged in and connected to the AC power source, power is supplied to the printer 1 from the outlet 19. When the outlet 19 is unplugged, the supply of power from the outlet 19 is cut off.

[0029] <Printer electrical configuration> Next, the electrical configuration of the printer 1 will be described. As shown in Fig. 4, the printer 1 includes a control unit 80. The control unit 80 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a flash memory 84, and an ASIC (Application Specific Integrated Circuit) 85. The control unit 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 unit 80 also receives signals from a signal processing circuit 78.

[0030] The control unit 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 unit 80 may be one in which one CPU 81 performs processes independently, or one in which multiple CPUs 81 share the processes. The control unit 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 command signal> Next, a process flow of the control unit 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 unit 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 unit 80 receives this signal as an inspection instruction signal.

[0032] When receiving the inspection command signal, the control unit 80 performs processing according to the flow of Fig. 5. To explain in more detail, the control unit 80 first sets one of the nozzles 10 of the inkjet head 4 as a target nozzle to be inspected to see whether it is an abnormal nozzle or not (S101).

[0033] Next, the control unit 80 executes a non-driven signal setting process (S102) and resets the value of the variable N to 0 (S103). In the non-driven signal setting process, the control unit 80 sets the non-driven signal based on the signal output from the signal processing circuit 78 when the test drive is not being performed. The non-driven signal setting process will be described in detail later. The variable N corresponds to the number of nozzles 10 that have been determined to be abnormal or not since the non-driven signal was set.

[0034] Next, the control unit 80 executes a test drive process (S104). In the test drive process, the control unit 80 causes the inkjet head 4 to perform test drive for the target nozzle while applying a voltage to the detection electrode 76 by the high voltage power supply circuit 77, and acquires a determination signal output from the signal processing circuit 78 at this time.

[0035] Next, the control unit 80 executes a differential signal generation process (S105). In the differential signal generation process, the control unit 80 superimposes the non-driven signal set in the non-driven signal setting process in S102 and the judgment signal acquired in S104, and generates a differential signal that is a signal of the difference between the judgment signal value and the non-driven signal value at each timing. Here, the above timing refers to each position on the time axis where the values ​​of the two signals overlap when the two signals are superimposed at a certain position on the time axis. Hereinafter, it will be simply referred to as timing. Here, the non-driven signal set in the non-driven signal setting process in S102 and the judgment signal acquired in S104 contain noise components, but the differential signal obtained by the differential signal generation process in S105 is a signal in which the noise components are reduced from the judgment signal. The details of the differential signal generation process will be described later.

[0036] Next, the control unit 80 executes a determination process (S106) and increments the value of the variable N by 1 (S107). In the determination process of S106, the control unit 80 determines whether or not the target nozzle is an abnormal nozzle based on the difference signal. Details of the determination process will be described later.

[0037] Next, the control unit 80 judges whether there is an undetermined nozzle 10 that has not been determined whether it is an abnormal nozzle or not (S108). If there is an undetermined nozzle 10 (S108: YES), the control unit 80 changes the target nozzle to one of the undetermined nozzles 10 (S109). If the variable N is less than the predetermined value Nt (S110: NO), the process returns to S104. If the variable N is equal to or greater than the predetermined value Nt (S110: YES), the process returns to S102. As a result, each of the multiple nozzles 10 of the inkjet head 4 is sequentially judged whether it is an abnormal nozzle or not by the processes of S104 to S106. Furthermore, every time the variable N reaches the predetermined value Nt, that is, every time it is judged whether Nt nozzles 10 are abnormal or not, the non-driven signal setting process is executed.

[0038] If there are no undetermined nozzles 10 (S108: NO), the control unit 80 determines whether or not there are any abnormal nozzles based on the results of the determination process in S106 for the multiple nozzles 10 of the inkjet head 4 (S111). If there are no abnormal nozzles (S111: NO), the process ends as is. If there are abnormal nozzles (S111: YES), the control unit 80 executes a purge process (S112) and then ends the process. In the purge process, the control unit 80 controls the suction pump 72 and the like to perform a suction purge to recover the abnormal nozzle.

[0039] <Signal setting process when not in operation> Next, the non-driven signal setting process of S102 will be described in detail. In the non-driven signal setting process, the control unit 80 performs processing according to the flow of FIG.

[0040] To explain in more detail, in the non-driven signal setting process, the control unit 80 continuously acquires multiple (e.g., about 3 to 5) non-driven signals based on the signal output from the signal processing circuit 78 when test driving is not being performed (S201).

[0041] Here, the non-driven signal includes noise due to the influence of power supplied from the AC power source via the outlet 19, and includes a signal that is repeated with a period T of the power supplied from the AC power source, as shown in Fig. 9(a), for example. The period T is (1 / 60) seconds when the AC power source is 60 Hz, and (1 / 50) seconds when the AC power source is 50 Hz. Also, each non-driven signal acquired in S201 is a signal with a duration longer than the period T.

[0042] Next, the control unit 80 calculates a sum of squares A for each combination of two non-driven signals among the multiple non-driven signals acquired in S201 (S202). In S202, the control unit 80 overlaps the two non-driven signals by shifting their positions on the time axis slightly from each other, and calculates a sum of squares A0, which is the sum of the squares of the differences between the values ​​of the two non-driven signals at each timing, for each case. Then, the smallest of the multiple calculated sums of squares A0 is set as the sum of squares A.

[0043] If there is no sum of squares A calculated for each of the two non-driven signals for all combinations of the non-driven signals obtained in S201 that is equal to or greater than the predetermined value At (S203: NO), the control unit 80 sets one of the non-driven signals obtained in S201 as the non-driven signal to be used for generating the difference signal (S204) and returns to the flow of FIG. 5. If there is any sum of squares A calculated that is equal to or greater than the predetermined value At (S203: YES), the control unit 80 returns to S201. As a result, the acquisition of the non-driven signals is repeated until all the sums of squares A calculated for all combinations are less than the predetermined value At. At this time, even if the acquisition of the non-driven signals is repeated a predetermined number of times, if there is any sum of squares A calculated that is equal to or greater than the predetermined value At, the control unit 80 may notify the user of an error and end the process.

[0044] <Differential signal generation processing> Next, the differential signal generation process in S105 will be described. In the differential signal generation process, the control unit 80 performs the process according to the flow of FIG.

[0045] More specifically, the control unit 80 first resets the value of the variable K to 0 (S301). The variable K corresponds to the number of times that the sum of squares B0, which will be described later, has been calculated. Next, the control unit 80 overlaps the determination signal and the non-driven signal based on an initial setting regarding the positions on the time axis at which the determination signal and the non-driven signal are overlapped (S302). The initial setting is, for example, stored in advance in the flash memory 84. Next, for the second signal portion R2 of the determination signal overlapped in S302 and the portion corresponding to the second signal portion R2 of the non-driven signal, the control unit 80 calculates the sum of squares B0, which is the sum of the squares of the differences between the values ​​of the determination signal and the non-driven signal at each timing (S303), stores this sum of squares B0 in the flash memory 84 as the sum of squares B (S304), and increments the value of the variable K by 1 (S305).

[0046] Next, the control unit 80 overlaps the determination signal and the non-driven signal with a time ΔT shift (S306), calculates the sum of squares B0, which is the sum of the values ​​obtained by squaring the differences between the determination signal value and the non-driven signal value at each timing, for the second signal portion R2 of the determination signal overlapped in S306 and the portion corresponding to the second signal portion R2 of the non-driven signal (S307), and increases the value of the variable K by 1 (S308). Here, the time ΔT is shorter than the period T.

[0047] If the sum of squares B0 calculated in S307 is equal to or greater than the sum of squares B stored in flash memory 84 (S309: NO), the process proceeds directly to S311. If the sum of squares B0 calculated in S307 is less than the sum of squares B stored in flash memory 84 (S309: YES), the control unit 80 updates the sum of squares B stored in flash memory 84 to the sum of squares B0 calculated in S307, and updates the settings relating to the positions on the time axis where the determination signal and the non-driven signal stored in flash memory 84 are superimposed to those at the time of calculation of the sum of squares B0 in S307 (S310), and then proceeds to S311.

[0048] In S311, it is determined whether (K×ΔT) is equal to or greater than the period T. If (K×ΔT) is less than the period T (S311: NO), the process returns to S306. If (K×ΔT) is equal to or greater than the period T (S311: YES), the control unit 80 generates a differential signal by superimposing the determination signal and the non-driven signal based on the settings stored in the flash memory 84 regarding the positions on the time axis at which the determination signal and the non-driven signal are superimposed, and then returns to the flow of FIG.

[0049] Here, if the target nozzle is an abnormal nozzle, the judgment signal is the same as the non-driven signal, as shown in FIG. 9(a). On the other hand, if the target nozzle is not an abnormal nozzle, the judgment signal is a signal that has changed from the signal in FIG. 9(a) in response to the change in the voltage of the detection electrode 76 during the driving for inspection, as shown in FIG. 9(b). Therefore, as described above, the judgment signal and the non-driven signal are overlapped at the position on the time axis where the sum of squares B0 is minimum, and the differential signal, which is the difference between the judgment signal value and the non-driven signal value at each timing, is approximately the same as FIG. 3(a) when the target nozzle is not an abnormal nozzle, and is approximately the same as FIG. 3(b) when the target nozzle is an abnormal nozzle. However, in the differential signal, the voltage V0 in FIG. 3(a) and (b) is approximately 0.

[0050] <Determination process> Next, the determination process of S106 will be described. In the determination process, the control unit 80 performs processing according to the flow of FIG.

[0051] More specifically, the control unit 80 determines whether the difference [Mm] between the maximum value M and the minimum value m of the differential signal generated in the differential signal generation process of S105 is equal to or greater than the threshold value Jt (S401). If [Mm] is equal to or greater than the threshold value Jt (S401: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S402) and returns to the flow of Fig. 5. If [Mm] is less than the threshold value Jt (S501: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S403) and returns to the flow of Fig. 5.

[0052] <Effects> In this embodiment, the noise components are common to the judgment signal and the non-driven signal. Therefore, the differential signal, which is the difference between the judgment signal value and the non-driven signal value at each timing, is a judgment signal with reduced noise components. This makes it possible to accurately determine whether or not a nozzle is abnormal based on the differential signal.

[0053] In addition, in this embodiment, the difference signal is generated by overlapping the judgment signal and the non-driven signal on the time axis so that the difference between the value of the judgment signal and the value of the non-driven signal is minimized, thereby making the difference signal a signal that is less affected by noise.

[0054] In this embodiment, the difference signal is generated by overlapping the judgment signal and the non-driven signal on the time axis so that the sum of the squared values ​​of the differences between the judgment signal value and the non-driven signal value at each timing is minimized. This makes it possible to minimize the difference between the judgment signal value and the non-driven signal value.

[0055] In this embodiment, the difference between the value of the judgment signal and the value of the non-driven signal is squared. By squaring the difference, a larger difference value is weighted more than a smaller difference value, and affects the sum value more. This makes it easier to extract values ​​that are significantly out of line.

[0056] Furthermore, if the noise components are the same, the second signal portion of the judgment signal and the portion corresponding to the second signal portion of the non-driven signal will be substantially the same signal. Therefore, in this embodiment, the judgment signal and the non-driven signal are overlapped to generate a differential signal so that the difference between the second signal portion of the judgment signal and the non-driven signal is minimized. This makes it possible to reduce the influence of noise on the differential signal.

[0057] Furthermore, in this embodiment, the differential signal is a signal in which the noise components have been reduced in the judgment signal, so it is possible to accurately determine whether or not a nozzle is abnormal based on whether the difference [Mm] between the maximum value M and minimum value m of the differential signal is less than the threshold value Jt.

[0058] Noise in the non-driven signal changes with the period T of the power supplied from the AC power supply. Therefore, in this embodiment, the non-driven signal is made to be a signal longer than the period T. This makes it possible to make the non-driven signal sufficiently long to adjust the positions on the time axis at which the determination signal and the non-driven signal overlap, according to the period T of the power supplied from the AC power supply.

[0059] In this embodiment, the non-driven signal setting process is executed immediately before the test drive process. That is, the non-driven signal is acquired immediately before the test drive. This makes it possible to make the noise components contained in the judgment signal and the non-driven signal similar to each other.

[0060] Furthermore, the noise components in the signal output from the signal processing circuit 78 may change over time. In this embodiment, each time a predetermined number (Nt) of nozzles 10 are determined to be abnormal, a non-driven signal is acquired and the non-driven signal used to generate the differential signal is updated. This makes it possible to acquire a differential signal that is less affected by noise, even if the noise components in the signal output from the signal processing circuit 78 change over time.

[0061] In addition, the printer 1 may be subjected to sudden noise from the outside. In this case, the non-driven signal may contain a component of the sudden noise, and the judgment signal may not contain the component of the sudden noise. In this case, if a differential signal is generated using a non-driven signal containing a component of the sudden noise, the differential signal will be a signal that is significantly affected by the sudden noise component. Therefore, in this embodiment, a plurality of non-driven signals are continuously acquired, and if the variation of these non-driven signals is large and does not fall within a predetermined range, the non-driven signals are acquired again. This makes it possible to generate a differential signal based on a non-driven signal that does not contain sudden noise, and to make the differential signal not affected by the sudden noise.

[0062] Furthermore, in this embodiment, it is possible to determine whether the variation in the multiple non-driven signals falls within a predetermined range based on whether any of the square sums A calculated for all combinations of two non-driven signals in the multiple non-driven signals is greater than or equal to a predetermined value At.

[0063] <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.

[0064] In the above-described embodiment, a plurality of non-driven signals are continuously acquired, and the sum of squares A is calculated for every combination of two non-driven signals among the plurality of non-driven signals. Then, if there is no sum of squares A that is equal to or greater than the predetermined value At, a difference signal is generated using the acquired non-driven signals. If there is a sum of squares A that is equal to or greater than the predetermined value At, the non-driven signals are reacquired. However, this is not limited to the above.

[0065] In the first modification, in the non-driving signal setting process, the control unit 80 performs the process according to the flow of Fig. 10. In the flow of Fig. 10, S202 and S203 in the flow of Fig. 6 are replaced with S501 and S502, respectively.

[0066] In S501, the control unit 80 calculates the sum C for each combination of two non-driven signals among the multiple non-driven signals acquired in S201. At this time, the control unit 80 overlaps the two non-driven signals by shifting their positions on the time axis slightly from each other, and calculates the sum C0 of the difference between the values ​​of the two non-driven signals at each timing for each case. Then, the smallest of the multiple calculated sums C0 is set as the sum C.

[0067] Then, when there is no sum C calculated for each of the two non-driven signals for all combinations of the multiple non-driven signals acquired in S201 that is equal to or greater than the predetermined value Ct (S502: NO), the control unit 80 sets one of the multiple non-driven signals acquired in S201 as the non-driven signal to be used for generating the differential signal (S803), and returns to the flow of Fig. 5. When there is a sum C calculated for all combinations that is equal to or greater than the predetermined value Ct (S203: YES), the process returns to S201.

[0068] In variant example 1, it is possible to determine whether the variation in the multiple non-driven signals falls within a predetermined range based on whether there is any two non-driven signals in all combinations of the multiple non-driven signals whose sum C of the differences in values ​​at each timing is greater than or equal to a predetermined value Ct.

[0069] Furthermore, it may be possible to determine whether the variation in the multiple non-driven signals is within a predetermined range by a method other than the above-described embodiment and modification example 1. For example, the above determination may be made based on whether the average value of the difference in values ​​at each timing among all combinations of two non-driven signals in the multiple non-driven signals is equal to or greater than a predetermined value. Alternatively, for example, the above determination may be made based on whether the maximum value of the difference in values ​​at each timing among all combinations of two non-driven signals in the multiple non-driven signals is equal to or greater than a predetermined value.

[0070] In addition, it is not limited to acquiring a plurality of non-driven signals and generating a differential signal using the acquired non-driven signals when the variation of the plurality of non-driven signals is within a predetermined range. For example, in the second modification, when the control unit 80 receives an inspection instruction signal, the control unit 80 performs processing according to the flow of FIG.

[0071] More specifically, in Modification 2, the control unit 80, like the embodiment described above, sets the target nozzles (S101), and then acquires the non-driven signal output from the signal processing circuit 78 (S601). Thereafter, the control unit 80 executes the processes of S103 to S105 similar to those in the embodiment described above.

[0072] Next, the control unit 80 calculates the sum of squares X, which is the sum of the values ​​obtained by squaring the values ​​at each timing of the portion corresponding to the second signal portion R2 of the differential signal generated in S105 (S602). If the sum of squares X exceeds the predetermined value Xt (S603: YES), the control unit 80 reacquires the non-driven signal in the same manner as in S601 (S604), resets the value of the variable N to 0 (S605), and returns to S105. If the sum of squares X is equal to or less than the predetermined value Xt (S603: NO), the control unit 80 executes the processes of S106 to S112 as in the above-mentioned embodiment.

[0073] If the noise components in the signal output from the signal processing circuit 78 are the same when the non-driven signal is acquired and when the judgment signal is acquired, the sum of squares X in the portion corresponding to the second signal portion R2 of the differential signal will be approximately 0. In contrast, if the noise components in the signal output from the signal processing circuit 78 are significantly different when the non-driven signal is acquired and when the judgment signal is acquired, the sum of squares X in the portion corresponding to the second signal portion R2 of the differential signal will be large. Therefore, in Modification 2, if the sum of squares X exceeds the predetermined value Xt, the non-driven signal is acquired again, and this non-driven signal is used to generate the differential signal.

[0074] In the third modification, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of Fig. 12. In the flow of Fig. 12, S602 and S603 in the flow of Fig. 11 are replaced with S701 and S702, respectively.

[0075] In S701, the control unit 80 calculates the sum Y of the values ​​at each timing of the portion corresponding to the second signal portion R2 of the differential signal generated in S105. If the sum Y exceeds a predetermined value Yt (S702: YES), the control unit 80 executes the processes of S604 and S605 and returns to S105. If the sum Y is equal to or less than the predetermined value Yt (S702: NO), the control unit 80 executes the processes of S106 to S112 as in the above embodiment.

[0076] If the noise components in the signal output from the signal processing circuit 78 are the same when the non-driven signal is acquired and when the judgment signal is acquired, the sum Y in the portion corresponding to the second signal portion R2 of the differential signal will be approximately 0. In contrast, if the noise components in the signal output from the signal processing circuit 78 are significantly different when the non-driven signal is acquired and when the judgment signal is acquired, the sum Y in the portion corresponding to the second signal portion R2 of the differential signal will be large. Therefore, in Modification 3, if the sum Y exceeds the predetermined value Yt, the non-driven signal is acquired again to generate a differential signal.

[0077] In the second and third modifications, it is determined whether the sum of squares X and the sum of sums Y for the portion corresponding to the second signal portion R2 of the differential signal exceed the predetermined values ​​Xt and Yt, respectively, but this is not limiting. In the second and third modifications, it may be determined whether the sum of squares and the sum of sums for the entire portion corresponding to the first and second signal portions R1 and R2 of the differential signal exceed a threshold value. In this case, the calculated sum of squares and the sum of sums are larger than those in the second and third modifications, but if the difference in noise components between the non-driven signal and the judgment signal is small, the sum of squares and the sum of sums are smaller than when this difference is large. Therefore, if the predetermined value is set to a value slightly larger than those in the second and third modifications, the differential signal can be generated in a state where the difference in noise components between the non-driven signal and the judgment signal is small.

[0078] In the fourth modification, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of Fig. 13. In the flow of Fig. 13, S602 and S603 in the flow of Fig. 11 are replaced with S801 and S802, respectively.

[0079] In S801, the control unit 80 counts the number Z of points where the value exceeds a predetermined value in the portion corresponding to the second signal portion R2 of the differential signal generated in S105. If the number Z exceeds the predetermined number Zt (S802: YES), the process of S604 and S605 is executed, and the process returns to S105. If the number Z is equal to or less than the predetermined number Zt, the process of S106 to S112 is executed as in the above embodiment.

[0080] If the noise components in the signal output from the signal processing circuit 78 are the same when the non-driven signal is acquired and when the judgment signal is acquired, the difference in value between the second signal portion R2 of the judgment division signal and the portion corresponding to the second signal portion R2 of the non-driven signal is approximately 0. In contrast, if the noise components in the signal output from the signal processing circuit 78 are significantly different when the non-driven signal is acquired and when the judgment signal is acquired, the difference in value between the second signal portion R2 of the judgment division signal and the portion corresponding to the second signal portion R2 of the non-driven signal becomes large, and the number of portions with large values ​​increases in the signal portion corresponding to the second signal portion R2 of the differential signal. Therefore, in the fourth modification, when the number Z of portions whose values ​​exceed a predetermined value in the signal portion corresponding to the second signal portion of the differential signal exceeds a predetermined number Zt, the non-driven signal is acquired again to generate a differential signal.

[0081] In the above embodiment, in the differential signal generation process, the non-driven signal and the judgment signal are overlapped with their positions on the time axis shifted by ΔT, and the square sum B0 is calculated for each case. Then, the non-driven signal and the judgment signal are overlapped so that the square sum B0 is minimized to generate a differential signal. However, this is not limited to this.

[0082] In the fifth modification, in the differential signal generation process, the control unit 80 performs the process according to the flow of Fig. 14. The flow of Fig. 14 is obtained by replacing S303, S304, S307, S309, and S310 in the flow of Fig. 7 with S901, S902, S903, S904, and S905, respectively.

[0083] In S901, the sum E0 of the difference between the value of the judgment signal and the value of the non-driven signal at each timing is calculated for the second signal portion R2 of the judgment signal superimposed in the initial setting and the portion corresponding to the second signal portion R2 of the non-driven signal. In S902, the sum E0 calculated in S901 is stored in the flash memory 84 as the sum E. In S903, the sum E0 of the difference between the value of the judgment signal and the value of the non-driven signal at each timing is calculated for the second signal portion R2 of the judgment signal superimposed in the setting after shifting their positions on the time axis by ΔT in the immediately preceding S306 and the portion corresponding to the second signal portion R2 of the non-driven signal. In S904, it is determined whether the sum E0 calculated in S903 is smaller than the sum E stored in the flash memory 84.

[0084] If the sum E0 is equal to or greater than the sum E (S904: NO), the process proceeds directly to S311. If the sum E0 is smaller than the sum E (S904: YES), the control unit 80 updates the sum E stored in the flash memory 84 to the sum E0 calculated in S903, and updates the settings relating to the positions on the time axis where the determination signals and non-driven signals stored in the flash memory 84 overlap with each other to those at the time of the calculation of the sum E0 in S903 (S905), and then proceeds to S311.

[0085] In the fifth modification, the signal for judgment and the signal when not driven are overlapped to generate a differential signal so that the sum E0 of the difference between the value of the signal for judgment and the value of the signal when not driven at each timing is minimized. This makes it possible to minimize the difference between the value of the signal for judgment and the value of the signal when not driven.

[0086] Furthermore, when generating a differential signal, the method of overlapping the judgment signal and the non-driven signal so as to minimize the difference between the value of the judgment signal and the value of the non-driven signal is not limited to that described in the above embodiment and modification example 5. The judgment signal and the non-driven signal may be overlapped by another method so as to minimize the difference between the value of the judgment signal and the value of the non-driven signal.

[0087] For example, the non-driven signal and the judgment signal may be overlapped by shifting their positions on the time axis by ΔT, and the average value of the difference between the value of the second signal portion of the judgment signal and the value of the non-driven signal may be calculated, and the positions on the time axis where the judgment signal and the non-driven signal are overlapped may be set so that this average value is smallest.

[0088] Alternatively, for example, the non-driven signal and the judgment signal may be overlapped by shifting their positions on the time axis by ΔT, and the maximum value of the difference between the value of the second signal portion of the judgment signal and the value of the non-driven signal may be calculated, and the positions on the time axis where the judgment signal and the non-driven signal are overlapped may be set so that this maximum value is smallest.

[0089] In addition, the present invention is not limited to generating a differential signal by overlapping the judgment signal and the non-driven signal so that the difference between the value of the second signal portion of the judgment signal and the value of the non-driven signal is minimized. For example, the judgment signal and the non-driven signal may be overlapped to generate a differential signal so that the difference between the value of the judgment signal and the value of the non-driven signal is minimized for the entire judgment signal including the portion corresponding to the first signal portion R1 and the portion corresponding to the second signal portion R2.

[0090] In addition, the present invention is not limited to generating a differential signal by overlapping the judgment signal and the non-driven signal so that the difference between the value of the judgment signal and the value of the non-driven signal is minimized. For example, the differential signal may be generated by overlapping the judgment signal and the non-driven signal so that the positions of the judgment signal and the non-driven signal on the time axis are slightly shifted from the position on the time axis where the difference between the judgment signal value and the non-driven signal value is minimized.

[0091] In the above embodiment, whether or not the target nozzle is an abnormal nozzle is determined based on whether the difference [Mm] between the maximum value M and the minimum value m of the differential signal is greater than or equal to the threshold value Jt, but this is not limited to the above.

[0092] In the sixth modification, in the judgment process, the control unit 80 performs the process according to the flow of Fig. 15(a). To explain in more detail, in the judgment process, the control unit 80 first calculates the sum of squares F of the values ​​of the difference signal at each timing (S1001). Then, if the sum of squares F is less than the threshold value Ft (S1002: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S1003). If the sum of squares F is equal to or greater than the threshold value Ft (S1002: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S1004).

[0093] If the nozzle 10 is an abnormal nozzle, the determination signal and the non-driven signal will be substantially the same signal, and the difference signal will have a value of substantially 0. Therefore, it is possible to determine whether or not the nozzle is an abnormal nozzle based on whether or not the sum of squares F of the difference signal is less than the threshold value Ft.

[0094] In the seventh modification, in the judgment process, the control unit 80 performs the process according to the flow of Fig. 15(b). More specifically, in the judgment process, the control unit 80 first calculates the sum G of the values ​​of the difference signals at each timing (S1101). Then, if the sum G is less than the threshold value Gt (S1102: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S1103). If the sum G is equal to or greater than the threshold value Gt (S1102: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S1104).

[0095] If the nozzle 10 is an abnormal nozzle, the determination signal and the non-driven signal will be substantially the same signal, and the differential signal will have a value of substantially 0. Therefore, it is possible to determine whether or not the nozzle is an abnormal nozzle based on whether or not the sum G of the differential signals is less than the threshold value Gt.

[0096] Furthermore, it may be possible to determine whether or not the nozzle 10 is an abnormal nozzle based on the differential signal using a method other than those of the embodiment and modified examples 6 and 7 described above.

[0097] In addition, in the above embodiment, a non-driven signal is set each time a determination is made as to whether or not a predetermined number of nozzles 10 are abnormal, but this is not limited to this. For example, a differential signal may be generated for all nozzles 10 based on the initially set non-driven signal, and then a determination may be made as to whether or not a nozzle is abnormal.

[0098] In the above example, the non-driven signal is acquired immediately before the test drive is performed, but this is not limited to the above. For example, the non-driven signal may be acquired after the test drive is performed and a time required for the change in voltage of the detection electrode 76 due to the test drive to be sufficiently attenuated has elapsed. Alternatively, for example, if the noise does not vary significantly with time, the non-driven signal may be acquired in advance and information on the non-driven signal may be stored in the flash memory 84.

[0099] In the above example, the non-driven signal is a signal having a length equal to or longer than the period T of the power supplied from the AC power supply, but this is not limited to this. The non-driven signal may be a signal having a length slightly shorter than the period T of the power supplied from the AC power supply.

[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 unit 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 for 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 for 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 or not based on the determination results for the some of the nozzles 10.

[0105] Furthermore, in the above-described embodiment, the signal processing circuit 78 outputs a signal indicating whether or not the nozzle is abnormal in response to the change in voltage 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 in response to a change in voltage 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 a signal indicating whether or not the nozzle is abnormal may be output from the optical sensor.

[0107] Alternatively, for example, as described in Patent Gazette No. 4,929,699, a voltage detection circuit (the "signal output unit" 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 control unit 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 section 84 Flash Memory

Claims

1. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; superimposing the judgment signal and the non-driven signal so as to minimize a difference between the value of the judgment signal and the value of the non-driven signal, thereby generating a differential signal which is a signal representing the difference between the value of the judgment signal and the value of the non-driven signal at each timing; The liquid ejection device further comprises a step of determining whether or not the nozzle is an abnormal nozzle based on the difference signal.

2. The control unit is A liquid ejection device as described in claim 1, characterized in that the differential signal is generated by overlapping the judgment signal and the non-driven signal so that the sum of the squared values ​​of the differences between the values ​​of the judgment signal and the non-driven signal at each timing is smallest.

3. The control unit is A liquid ejection device as described in claim 1, characterized in that the differential signal is generated by overlapping the judgment signal and the non-driven signal so that the sum of the differences between the values ​​of the judgment signal and the non-driven signal at each timing is minimized.

4. The determination signal is a first signal portion whose value changes due to the test drive when the nozzle is not the abnormal nozzle; a second signal portion whose value does not change due to the test drive; The control unit is A liquid ejection device as described in any one of claims 1 to 3, characterized in that the differential signal is generated by overlapping the judgment signal and the non-driven signal so that the difference between the value of the second signal portion of the judgment signal and the value of the non-driven signal is minimized.

5. The control unit is If the difference between the maximum value and the minimum value of the differential signal is equal to or greater than a threshold value, it is determined that the nozzle is not an abnormal nozzle; 5. The liquid ejection device according to claim 1, wherein the nozzle is determined to be the abnormal nozzle when the difference between the maximum value and the minimum value of the differential signal is less than the threshold value.

6. The control unit is When a sum of values ​​obtained by squaring the values ​​of the difference signal at each timing is less than a threshold value, the nozzle is determined to be the abnormal nozzle; A liquid ejection device according to any one of claims 1 to 4, characterized in that if the sum of the squared values ​​of the difference signal at each timing is greater than or equal to the threshold value, it is determined that the nozzle is not an abnormal nozzle.

7. The control unit is When the sum of the values ​​of the difference signals at each timing is less than a threshold value, the nozzle is determined to be the abnormal nozzle; 5. The liquid ejection device according to claim 1, wherein the nozzle is determined to be not the abnormal nozzle when the sum of the values ​​of the difference signals at each timing is equal to or greater than the threshold value.

8. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; When a sum of values ​​obtained by squaring the values ​​of the difference signal at each timing is less than a threshold value, the nozzle is determined to be the abnormal nozzle; A liquid ejection device, comprising: a nozzle detecting unit that detects whether a nozzle is abnormal, the nozzle being determined to be abnormal when a sum of squares of values ​​of the difference signal at each timing is equal to or greater than the threshold value.

9. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; When the sum of the values ​​of the difference signals at each timing is less than a threshold value, the nozzle is determined to be the abnormal nozzle; A liquid ejection device comprising: a nozzle that is determined to be not an abnormal nozzle when a sum of values ​​of the difference signal at each timing is equal to or greater than the threshold value.

10. Power is supplied from an AC power source, 10. The liquid ejection device according to claim 1, wherein the non-driving signal is a signal having a length equal to or longer than the period of the power supplied from the AC power source.

11. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; determining whether the nozzle is an abnormal nozzle based on the difference signal; Power is supplied from an AC power source, The liquid ejection device according to claim 1, wherein the non-driving signal is a signal having a length equal to or greater than the period of the power supplied from the AC power source.

12. 12. The liquid ejection apparatus according to claim 1, wherein the control unit acquires the non-driving time signal immediately before causing the liquid ejection head to perform the inspection driving.

13. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal immediately before driving the liquid ejection head for the test; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; The liquid ejection device further comprises a step of determining whether or not the nozzle is an abnormal nozzle based on the difference signal.

14. the liquid ejection head has a plurality of the nozzles, The control unit is performing the test drive on the liquid ejection head in sequence for the plurality of nozzles, thereby acquiring the judgment signals for the plurality of nozzles; The non-driven signal is acquired immediately before the liquid ejection head is driven for the test. A liquid ejection device as described in claim 12 or 13, characterized in that thereafter, the non-driven signal is acquired each time the judgment signal is acquired for a predetermined number of the nozzles, and the non-driven signal used to generate the differential signal is updated.

15. The control unit is A plurality of the non-driven signals are continuously acquired; If the variation in the plurality of non-driven signals is within a predetermined range, the non-driven signals are used to generate the differential signal; 15. The liquid ejection device according to claim 1, wherein, when the variation in the plurality of non-driven signals is not within the predetermined range, the plurality of non-driven signals are acquired again.

16. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; determining whether the nozzle is an abnormal nozzle based on the difference signal; A plurality of the non-driven signals are continuously acquired; If the variation in the plurality of non-driven signals is within a predetermined range, the non-driven signals are used to generate the differential signal; The liquid ejection device according to claim 1, wherein, when the variation in the non-driven signals is not within the predetermined range, the non-driven signals are acquired again.

17. The control unit is determining that the variation in the plurality of non-driven signals falls within the predetermined range when a sum of squares of differences between values ​​of any two of the plurality of non-driven signals at each timing is less than a predetermined value; A liquid ejection device as described in claim 15 or 16, characterized in that if the sum of the squared values ​​of the differences between the values ​​of any two of the non-driven signals at each timing of the multiple non-driven signals is greater than or equal to the specified value, it is determined that the variation of the multiple non-driven signals is not within the specified range.

18. The control unit is determining that the variation in the plurality of non-driven signals falls within the predetermined range when a sum of differences in values ​​of any two of the plurality of non-driven signals at each timing is less than a predetermined value; A liquid ejection device as described in claim 15 or 16, characterized in that if the sum of the differences in values ​​of any two of the non-driven signals at each timing of the multiple non-driven signals is greater than or equal to the specified value, it is determined that the variation in the multiple non-driven signals is not within the specified range.

19. The control unit is A liquid ejection device as described in any one of claims 1 to 14, characterized in that when the sum of the squared values ​​of the differential signal at each timing exceeds a predetermined value, the non-driven signal is acquired again, and the differential signal is generated using the non-driven signal.

20. The control unit is A liquid ejection device described in any one of claims 1 to 14, characterized in that when the sum of the values ​​of the differential signal at each timing exceeds a predetermined value, the non-driven signal is acquired again, and the differential signal is generated using the non-driven signal.

21. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; determining whether the nozzle is an abnormal nozzle based on the difference signal; A liquid ejection device characterized in that, when the sum of the squared values ​​of the differential signal at each timing exceeds a predetermined value, the non-driven signal is acquired again, and the differential signal is generated using the non-driven signal.

22. a liquid ejection head having at least one nozzle for ejecting liquid; an electrode for receiving the liquid ejected from the nozzle; a signal output section that outputs a determination signal corresponding to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode when the liquid ejection head is driven for inspection to confirm whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid; A control unit, The control unit is causing the liquid ejection head to perform the inspection drive and acquiring the judgment signal output from the signal output unit; acquiring a signal output from the signal output unit as a non-driven signal when the liquid ejection head is not driven for testing; the determination signal and the non-driven signal are superimposed to generate a differential signal which is a signal representing a difference between a value of the determination signal and a value of the non-driven signal at each timing; determining whether the nozzle is an abnormal nozzle based on the difference signal; A liquid ejection device characterized in that, when the sum of the values ​​of the differential signal at each timing exceeds a predetermined value, the non-driven signal is acquired again, and the differential signal is generated using the non-driven signal.

23. The control unit is A liquid ejection device as described in claim 4, characterized in that when there are a predetermined number or more parts whose values ​​exceed a predetermined value in the signal portion corresponding to the second signal portion of the differential signal, the non-driven signal is acquired again, and the differential signal is generated using the non-driven signal.

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