Liquid dispensing device

Abstract

To select the optimal determination processing according to a prescribed condition, and restrict prolongation of time required for the determination processing.SOLUTION: A control unit of a printer executes, in a selective manner according to whether a prescribed condition is satisfied or not: first determination processing for determining whether or not a nozzle is an abnormal nozzle on the basis of a determining signal outputted from a signal processing circuit; and second determination processing for generating a differential signal that is a signal of a difference between a non-driving time signal outputted from the signal processing circuit when inspecting drive is not performed and the determining signal, in order to determine whether or not the nozzle is an abnormal nozzle on the basis of the differential signal.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] The present inventors have developed a determination technique for suppressing the effects of noise and accurately determining whether or not a nozzle is abnormal, but have found the following problems. If the above-mentioned determination technique is employed every time a discharge inspection is performed, the determination accuracy can be maintained, but there is a problem in that the time required for the determination process is long, taking up the user's time.

[0007] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a liquid ejection apparatus capable of selecting an optimal determination process in accordance with predetermined conditions and preventing the time required for the determination process from becoming long. [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; 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. the control unit selectively executes a first judgment process in which the nozzle is judged to be abnormal or not based on the judgment signal output from the signal output unit by having the liquid ejection head perform the inspection drive, and a second judgment process in which a differential signal is generated which is a difference signal between a non-driven signal output from the signal output unit when the liquid ejection head is not performing the inspection drive and the judgment signal output from the signal output unit by having the liquid ejection head perform the inspection drive, and the nozzle is judged to be abnormal or not based on the differential signal depending on whether a predetermined condition is satisfied. Effect of the Invention

[0009] According to the liquid ejection device of the present invention, it is possible to selectively execute a first determination process that does not require the generation of a differential signal and a second determination process that takes more time than the first determination process but allows for determination while suppressing the effects of noise, depending on whether a predetermined condition is satisfied. This makes it possible to prevent the time required for the determination process from becoming too long. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating a printer according to an embodiment of the present invention. [Diagram 2] 4A to 4C 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 signal processing 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 a flow of the first determination process shown in FIG. 5. [Figure 7] 6 is a flowchart showing a flow of the second determination process shown in FIG. 5. [Figure 8] 8 is a flowchart showing the flow of the differential signal generation process shown in FIG. 7. [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 a process flow when a time signal indicating a predetermined time of a printer according to a first modified example is received. [Figure 11] 13 is a flowchart showing a process flow when a print command signal is received by a printer according to a second modified example. [Figure 12] 13 is a flowchart showing a process flow when a print command signal is received by a printer according to a third modified example. [Figure 13]13 is a flowchart showing a process flow when an ON signal or a recovery instruction signal is received in a printer according to a fourth modified example. [Figure 14] 13 is a flowchart showing a process flow when an on-signal of a printer according to a fifth modified example is received. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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, transport rollers 6 and 7, a maintenance unit 8, an outlet 19, etc.

[0013] 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.

[0014] 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.

[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, 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.

[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 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.

[0017] The maintenance unit 8 (the "recovery means" of the present invention) 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, 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.

[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 (the "recovery operation" of the present invention) in which ink is discharged from within 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 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.

[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 (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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] <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.

[0031] In addition to the components described above, the printer 1 also has a display unit 69, an operation unit 70, and a clock unit 68. The display unit 69 is, for example, a liquid crystal display provided on the housing of the printer 1. The control unit 80 controls the display unit 69 to display information necessary for the operation of the printer 1. The operation unit 70 is, for example, buttons provided on the housing of the printer 1, a touch panel provided on the display unit 69, etc. A user can input signals to the control unit 80 by operating the operation unit 70.

[0032] In this embodiment, the operation unit 70 includes a power switch (not shown). The user can turn the printer 1 on and off by operating the power switch. When the user operates the power switch of the operation unit 70 to turn on the printer 1, an ON signal indicating that the printer 1 has been turned on is output from the operation unit 70, and the control unit 80 receives this ON signal. The clock unit 68 keeps time, and the control unit 80 receives a time signal indicating the time from the clock unit 68.

[0033] 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.

[0034] <Processing when receiving an inspection command signal> Next, the flow of processing by the control unit 80 when an inspection instruction signal is received to instruct whether or not the nozzle 10 is an abnormal nozzle will be described. For example, when a user operates the operation unit 70 of the printer 1 or a PC connected to the printer to instruct whether or not the nozzle 10 is an abnormal nozzle, an inspection instruction signal is transmitted from the operation unit 70, PC, etc., and the control unit 80 receives this inspection instruction signal. Alternatively, in a case where an inspection is set to be performed every time a predetermined time is reached, when a time signal indicating that the predetermined time has been reached is transmitted from the clock unit 68, the control unit 80 receives this signal as an inspection instruction signal. Also, for example, when a user operates a power switch (not shown) of the operation unit 70 of the printer 1 and an on signal is transmitted from the power switch, the control unit 80 receives this signal as an inspection instruction signal.

[0035] 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).

[0036] Next, the control unit 80 executes a non-driven signal acquisition process (S102) and resets the values ​​of variables N1 and N2 to 0 (S103). In the non-driven signal acquisition process, the control unit 80 acquires a signal output from the signal processing circuit 78 in a state where the inspection drive is not being performed as a non-driven signal. 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 repeated with a period T of the power supplied from the AC power source, as shown in FIG. 9(a), for example. The maximum value of the non-driven signal output from the signal processing circuit 78 is voltage H, and the minimum value is voltage h. 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. The non-driven signal acquired in S102 is a signal with a time longer than the period T. The variable N1 corresponds to the number of times a first determination process, described later, has been performed since the non-driven signal was acquired. Moreover, the variable N2 corresponds to the number of times that the second determination process, which will be described later, has been performed since the non-driven signal was acquired.

[0037] 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.

[0038] Next, the control unit 80 judges whether the acquired value of the non-driven signal is equal to or greater than a first threshold (S105). The value of the non-driven signal here is the difference [Hh] between the maximum value H and the minimum value h of the non-driven signal. If the value [Hh] is equal to or greater than the first threshold (S105: YES), the control unit 80 judges whether the value [Hh] is equal to or greater than a second threshold (S106). The second threshold is a value greater than the first threshold, and if the value is equal to or greater than the first threshold, it is a boundary value indicating that the disturbance of the non-driven signal is too large, i.e., the noise is very large, and a good differential signal cannot be generated in the subsequent differential signal generation process. On the other hand, the first threshold is a boundary value indicating that the noise is extremely small and the nozzle state can be judged with sufficient accuracy even with the judgment signal. If the value [Hh] is equal to or greater than the second threshold (S106: YES), the control unit 80 ends the inspection. In this way, the inspection flow ends.

[0039] If the value [Hh] is less than the first threshold in S105 (S105: NO), the control unit 80 executes a first determination process (S107). In the first determination process of S107, the control unit 80 determines whether or not the target nozzle is an abnormal nozzle based on the determination signal. Details of the first determination process will be explained later. Next, the control unit 80 increments the value of the variable N1 by 1 (S108) and proceeds to S112.

[0040] If the value [Hh] is less than the second threshold in S106 (S106: NO), the control unit 80 executes the second judgment process (S109). In the second judgment process, the control unit 80 generates a differential signal, which is a signal of the difference between the value of the non-driven signal acquired in the non-driven signal acquisition process in S102 and the value of the judgment signal acquired in S104. Here, the non-driven signal acquired in the non-driven signal acquisition process in S102 and the judgment signal acquired in S104 contain noise components, but the differential signal obtained in S109 is a signal in which the noise components have been reduced from the judgment signal. The generation of the differential signal will be described later. In addition, the control unit 80 judges whether the target nozzle is an abnormal nozzle or not based on the generated differential signal. The details of the second judgment process will be described later. Next, the control unit 80 increments the value of the variable N2 by 1 (S110) and proceeds to S111.

[0041] Next, in S111, the control unit 80 determines whether there is an undetermined nozzle 10 that has not been determined whether it is an abnormal nozzle. If there is an undetermined nozzle 10 (S111: YES), the control unit 80 changes the target nozzle to one of the undetermined nozzles 10 (S112). Then, if the variable N1 is less than the predetermined value Nt (S113: NO), the control unit 80 proceeds to S114, and if the variable N2 is less than the predetermined value Nt (S114: NO), the control unit 80 returns to S104. If the variable N1 is equal to or greater than the predetermined value Nt (S113: YES), the control unit 80 returns to S102. Also, if the variable N2 is equal to or greater than the predetermined value Nt (S114: YES) in S114, the control unit 80 returns to S102. Thus, it is determined whether each of the multiple nozzles 10 of the inkjet head 4 is an abnormal nozzle by the processes of S104 to S111 in order. Furthermore, the non-driven signal acquisition process is executed each time the variable N1 or variable N2 reaches a predetermined value Nt, that is, each time it is determined whether or not a nozzle is abnormal for Nt nozzles 10. Note that the predetermined value Nt in this embodiment is approximately 1 / 6 of the total number of nozzles 10, but may be set appropriately.

[0042] If there is no undetermined nozzle 10 in S111 (S111: NO), the control unit 80 determines whether or not there is an abnormal nozzle based on the result of at least one of the determination processes in S107 and S109 for the multiple nozzles 10 of the inkjet head 4 (S115). If there is no abnormal nozzle (S115: NO), the process ends. If there is an abnormal nozzle (S115: YES), the control unit 80 executes a purge process (S116) 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.

[0043] <First Judgment Process> Next, the first determination process in S107 will be described. In the first determination process, the control unit 80 performs processing according to the flow of FIG.

[0044] More specifically, the control unit 80 determines whether the difference [M1-m1] between the maximum value M1 and the minimum value m1 of the judgment signal acquired in the test drive process of S104 is equal to or greater than the threshold value Jt1 (S201). If [M1-m1] is equal to or greater than the threshold value Jt1 (S201: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S202) and returns to the flow of Fig. 5. If [M1-m1] is less than the threshold value Jt1 (S201: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S203) and returns to the flow of Fig. 5.

[0045] In this embodiment, the judgment signal can accurately determine whether or not a nozzle is abnormal based on whether the difference [M1-m1] between the maximum value M1 and the minimum value m1 of the judgment signal is less than the threshold value Jt1.

[0046] <Second Judgment Process> Next, the second determination process of S109 will be described. In the second determination process, the control unit 80 performs processing according to the flow of FIG.

[0047] More specifically, the control unit 80 first executes a differential signal generation process for generating a differential signal (S301). The details of the differential signal generation process will be described later. Next, the control unit 80 determines whether or not the difference [M2-m2] between the maximum value M2 and the minimum value m2 of the differential signal generated in the differential signal generation process of S301 is equal to or greater than a threshold value Jt2 (S302). If [M2-m2] is equal to or greater than the threshold value Jt2 (S302: YES), the control unit 80 stores in the flash memory 84 that the target nozzle is not an abnormal nozzle (S303) and returns to the flow of FIG. 5. If [M2-m2] is less than the threshold value Jt2 (S302: NO), the control unit 80 stores in the flash memory 84 that the target nozzle is an abnormal nozzle (S304) and returns to the flow of FIG. 5.

[0048] <Differential signal generation processing> Next, the differential signal generation process in S301 will be described. In the differential signal generation process, the control unit 80 performs processing according to the flow of FIG.

[0049] More specifically, the control unit 80 first resets the value of the variable K to 0 (S401). The variable K corresponds to the number of times that the sum of squares A0, 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 (S402). 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 S402 and the portion corresponding to the second signal portion R2 of the non-driven signal, the control unit 80 calculates the sum of squares A0, 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 (S403), stores this sum of squares A0 in the flash memory 84 as the sum of squares A (S404), and increments the value of the variable K by 1 (S405). Here, the above timing refers to each position on the time axis where the values ​​of two signals overlap when the two signals are superimposed at a certain position on the time axis. Hereafter, this will be referred to simply as timing.

[0050] Next, the control unit 80 overlaps the determination signal and the non-driven signal with a time ΔT shift (S406), calculates the sum of squares A0, 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 S406 and the portion corresponding to the second signal portion R2 of the non-driven signal (S407), and increases the value of the variable K by 1 (S408). Here, the time ΔT is shorter than the period T.

[0051] If the sum of squares A0 calculated in S407 is equal to or greater than the sum of squares A stored in the flash memory 84 (S409: NO), the process proceeds directly to S411. If the sum of squares A0 calculated in S407 is less than the sum of squares A stored in the flash memory 84 (S409: YES), the control unit 80 updates the sum of squares A stored in the flash memory 84 to the sum of squares A0 calculated in S407, and updates the settings relating to the positions on the time axis where the determination signal and the non-driven signal stored in the flash memory 84 are superimposed to those at the time of the calculation of the sum of squares A0 in S407 (S410), and then proceeds to S411.

[0052] In S411, it is determined whether (K×ΔT) is equal to or greater than the period T. If (K×ΔT) is less than the period T (S411: NO), the process returns to S406. If (K×ΔT) is equal to or greater than the period T (S411: 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 (S412), and the process returns to the flow of FIG.

[0053] Here, if the target nozzle is an abnormal nozzle, the judgment signal will be 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 will be 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 A0 is minimum, and the differential signal, which is the difference between the judgment signal value and the non-driven signal value at each timing, will be approximately the same as FIG. 3(a) if the target nozzle is not an abnormal nozzle, and will be approximately the same as FIG. 3(b) if the target nozzle is an abnormal nozzle. However, in the differential signal, the voltage V0 in FIG. 3(a) and (b) will be approximately 0.

[0054] In this embodiment, the noise components are common to the judgment signal and the non-driven signal. Therefore, the difference 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 difference signal in the second judgment process.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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 [M2-m2] between the maximum value M2 and the minimum value m2 of the differential signal is less than the threshold value Jt2.

[0060] 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.

[0061] In addition, in this embodiment, the non-driven signal acquisition 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.

[0062] Moreover, the noise components in the signal output from the signal processing circuit 78 may change over time. In this embodiment, the non-driven signal is acquired and updated each time a predetermined number (Nt) of nozzles 10 are judged to be abnormal, that is, when the number of times the first judgment process is executed reaches a predetermined value Nt, and when the number of times the second judgment process is executed reaches a predetermined value Nt. By updating the non-driven signal, the judgment results of S105 and S106 may change from before the update. That is, as time passes, the noise increases, and the first judgment process is executed before the non-driven signal is updated, but after the update, the second judgment process is executed. In this case, it is possible to perform judgment processing with high accuracy. Conversely, as time passes, the noise decreases, and the second judgment process is executed before the non-driven signal is updated, but after the update, the first judgment process is executed. In this case, the time required for the judgment process is shortened. Based on the value of the non-driven signal reacquired in this way, it is possible to reselect either the first judgment process or the second judgment process. Furthermore, when the number of times the second determination process has been executed reaches a predetermined value Nt, the non-driven signal is updated, so that even if the noise components in the signal output from the signal processing circuit 78 change over time, a differential signal that is less affected by noise can be obtained. Here, in this embodiment, N1 and N2 are counted separately, but they may be counted together. That is, if N1+N2 is less than the predetermined value Nt (S114: NO), the process returns to S104, and if the variable N1+N2 is equal to or greater than the predetermined value Nt (S113: YES), the process may be performed. In this way, the non-driven signal can be updated according to the total number of times the first determination process and the second determination process have been executed.

[0063] As described above, according to the printer 1 of this embodiment, if the predetermined condition that the value [Hh] of the non-driven signal is equal to or greater than the first threshold value is not met in S105, the process proceeds to S107, where the first determination process is executed, and if the predetermined condition that the value [Hh] of the non-driven signal is equal to or greater than the first threshold value and less than the second threshold value is met in S105 and S106, the process proceeds to S109, where the second determination process is executed. In this manner, in this embodiment, depending on whether the predetermined condition is met or not, it is possible to selectively execute the first determination process, which does not require the generation of a difference signal, and the second determination process, which requires the generation of a difference signal and takes more time than the first determination process but can accurately determine whether the target nozzle is an abnormal nozzle while suppressing the effects of noise. This makes it possible to prevent the time required for the determination process from becoming too long.

[0064] Furthermore, in S105, if the predetermined condition that the value [Hh] of the non-driven signal is equal to or greater than the first threshold is not satisfied, the noise is small, and therefore it is possible to determine whether the target nozzle is an abnormal nozzle or not using the determination signal without generating a differential signal (first determination process). Therefore, it is not necessary to take time to generate a differential signal while maintaining the determination accuracy, and it is possible to suppress the time required for the determination process. Furthermore, in S105 and S106, if the predetermined condition that the value [Hh] of the non-driven signal is equal to or greater than the first threshold and less than the second threshold is satisfied, even if a certain amount of noise occurs, it is possible to determine whether the target nozzle is an abnormal nozzle or not while suppressing the influence of the noise (second determination process). Therefore, it is necessary to take more time to generate a differential signal and the determination process takes more time than when the first determination process is performed, but it is possible to perform the determination while suppressing the influence of the noise. In other words, it is possible to suppress a decrease in the determination accuracy.

[0065] Since the value of the non-driven signal is the difference between the maximum and minimum values ​​of the non-driven signal, it is possible to selectively execute the first judgment process and the second judgment process based on the difference between the maximum and minimum values ​​of the driven signal.

[0066] Furthermore, in S106, when the value of the non-driven signal is equal to or greater than the second threshold, the control unit 80 does not execute either the first or second judgment process. For example, the printer 1 may receive sudden noise from the outside. In this case, the non-driven signal may contain a component of the sudden noise, but the judgment signal may not contain the component of the sudden noise. In this case, if a differential signal is generated using the non-driven signal containing the component of the sudden noise, the differential signal will be a signal that is significantly affected by the sudden noise component. In other words, when the noise is significantly large, neither the first nor the second judgment process is executed because the judgment accuracy is reduced. As a result, no time is required for the judgment process.

[0067] <First Modification> Next, as a first modified example, when the control unit 80 receives a time signal (inspection instruction signal) indicating a predetermined time transmitted from the clock unit 68, even if the value of the non-driven time signal is less than the first threshold value, the control unit 80 may perform the second determination process without performing the first determination process. That is, in this modified example, the control unit 80 performs the second determination process based on receiving a time signal indicating a predetermined time from the clock unit 68. Hereinafter, a description will be given with reference to FIG. 10, and the same reference numerals will be used to denote the same parts as those in the above-mentioned embodiment, and description thereof will be omitted.

[0068] The control unit 80 first determines whether or not a time signal indicating a predetermined time has been received (S501). If the time signal indicating the predetermined time has not been received (S501: NO), the control unit 80 repeats S501. On the other hand, if the time signal indicating the predetermined time has been received (S501: YES), the control unit 80 performs the above-mentioned S101 and S102. Then, the control unit 80 resets the value of the variable N2 to 0 (S502).

[0069] Next, the control unit 80 performs the above-mentioned steps S104, S109 to S112, and S114 to S116. In this manner, the inspection flow ends.

[0070] In this manner, in the printer of this modified example, it is preset to acquire a judgment signal based on receipt of a time signal indicating a predetermined time (S104), which is the predetermined condition. Then, if the predetermined condition is met, the second judgment process of S109 is executed. If the judgment process is performed at a predetermined time, there is ample time. Therefore, by performing the second judgment process when a time signal indicating the predetermined time is received, it is possible to suppress a decrease in the accuracy of judging whether or not the target nozzle is an abnormal nozzle.

[0071] <Second Modification> Next, as a second modified example, when the control unit 80 receives a recording command signal (the "ejection command signal" of the present invention) instructing to perform recording on the recording paper P, it may execute a first determination process before executing a printing process based on the recording command signal, and execute a second determination process after the printing process is completed if another recording command signal has not been received by the time the printing process is completed. That is, in this modified example, the control unit 80 executes a first determination process before the printing process based on the reception of a recording command signal, and executes a second determination process after the printing process. The following description will be given with reference to FIG. 11, and the same reference numerals will be used to denote the same parts as in the above-described embodiment, and description thereof will be omitted.

[0072] The control unit 80 first judges whether or not a recording command signal has been received (S601). If a recording command signal has not been received (S601: NO), S601 is repeated. If a recording command signal has been received (S601: YES), the control unit 80 performs the above-mentioned S101, S104, S107, S111, S112, S115, and S116. In S112, the target nozzle is changed, and then the process returns to S104. Note that in the first judgment process in this modified example, since the non-driven signal is not used, the non-driven signal is not acquired until the printing process. This makes it possible to prevent the time required from receiving the recording command signal to executing the printing process from becoming long.

[0073] After S116, the control unit 80 executes the printing process (S602). That is, the control unit 80 controls the transport motor 87 based on the recording command signal to cause the transport rollers 6 and 7 to transport the recording paper P to a position where an area of ​​the recording paper P on which an image is to be recorded in the first recording pass faces the multiple nozzles 10 of the inkjet head 4. Then, the control unit 80 controls the carriage motor 86 to move the carriage 2 in the scanning direction, while controlling the inkjet head 4 to perform a recording pass in which ink is ejected from the multiple nozzles 10 toward the recording paper P.

[0074] Thereafter, if recording on one sheet of recording paper P is not complete, the control unit 80 controls the conveying motor 87 to cause the conveying rollers 6, 7 to convey the recording paper P a predetermined distance and repeats the operation of making the conveying rollers 6, 7 perform a recording pass again until recording on one sheet of recording paper P is complete. If recording of an image on one sheet of recording paper P is complete, the control unit 80 controls the conveying motor 87 to cause the conveying rollers 6, 7 to discharge the recording paper P on which recording has been completed.

[0075] Next, the control unit 80 determines whether or not a recording command signal other than the recording command signal received in S601 has been received (S603). That is, the control unit 80 determines whether or not a different recording command signal has been received before executing the second inspection process described below after the printing process in S602. If a different recording command signal has been received (S603: YES), the control unit 80 executes the printing process based on the different recording command signal received, as in S602.

[0076] If another recording command signal has not been received in S603 (S603: NO), the control unit 80 performs S604 to S614 similar to the above-mentioned S101, S102, S502, S104, S109 to S112, and S114 to S116. Then, the flow ends.

[0077] In this manner, in the printer of this modified example, it is preset to obtain a determination signal before the printing process based on the reception of a recording command signal, and to obtain a determination signal after the printing process, which is a predetermined condition. If the predetermined condition is satisfied, the first determination process of S107 is executed before the printing process. If another recording command signal is not received by the time the printing process is completed, the predetermined condition is satisfied, and the second determination process of S608 is executed after the printing process. If the determination process is executed before the printing process, there is no time to spare. Therefore, by executing the first determination process, it is possible to determine the state of the nozzles while suppressing the time required for the determination process. On the other hand, if the determination process is executed after the printing process, there is time to spare because the printing process has been completed. Therefore, by executing the second determination process, it is possible to suppress a decrease in the determination accuracy.

[0078] <Third Modification> Next, as a third modified example, when the control unit 80 receives a recording command signal, if printing based on the recording command signal is set to a low image quality that is less than a predetermined image quality, a first determination process is performed, and if printing is set to a high image quality that is equal to or higher than the predetermined image quality, a second determination process is performed. High image quality printing in this modified example means printing such that the resolution of the image printed on the recording paper P is equal to or higher than the predetermined resolution. On the other hand, low image quality printing means printing such that the resolution of the image printed on the recording paper P is less than the predetermined resolution. The following description will be made with reference to FIG. 12, and parts similar to those in the above-mentioned embodiment will be denoted by the same reference numerals and description will be omitted.

[0079] First, in S601, the control unit 80 determines whether or not a recording command signal has been received, and if a recording command signal has not been received (S601: NO), S601 is repeated. If a recording command signal has been received (S601: YES), the control unit 80 determines whether or not printing based on the received recording command signal is set to high-quality printing (S701).

[0080] When printing based on the recording command signal is set to low-quality printing (S701: NO), the control unit 80 performs the above-mentioned S101, S104, S107, S111, S112, S115, S116, and S602. Note that in the first determination process in this modified example, the non-driven signal is not used, so the non-driven signal is not acquired until the printing process. This makes it possible to prevent the time required from receiving the recording command signal to executing the printing process from becoming long.

[0081] If printing based on the recording command signal is set to high quality printing (S701: YES), the control unit 80 performs S702 to S710 similar to the above-mentioned S101, S102, S502, S104, S109 to S112, and S114. Then, if there are no undetermined nozzles in S708 (S708: NO), the process proceeds to S115, where S116 and S602 are performed. Then, the flow ends.

[0082] In this way, in the printer of this modified example, the determination signal is acquired before the print process based on the reception of the recording command signal, and if the printing based on the recording command signal is set to high image quality, the second determination process is performed, which is a predetermined condition. If the predetermined condition is met, there is no time to execute the determination process before the print process, but since the user requests high image quality printing, it is possible to suppress a decrease in the determination accuracy by executing the second determination process (S706) before the print process.

[0083] <Fourth Modification> Next, as a fourth modified example, the control unit 80 performs the first determination process when it receives an ON signal from the power switch by user operation, and when it receives a recovery instruction signal to perform suction purging by operating the printer's operation unit 70 or a PC connected to the printer. The following description will be given with reference to Fig. 13, and parts similar to those in the above-mentioned embodiment will be denoted by the same reference numerals and description will be omitted.

[0084] The control unit 80 first judges whether or not an ON signal has been received (S801). If an ON signal has not been received (S801: NO), the control unit 80 judges whether or not a recovery instruction signal has been received (S802). If a recovery instruction signal has not been received (S802: NO), the process returns to S801. On the other hand, if the control unit 80 has received either an ON signal or a recovery instruction signal (S801, S802: YES), the above-mentioned S101, S104, S107, S111, S112, S115, and S116 are performed. In this way, the flow ends.

[0085] In this way, in the printer of this modified example, it is preset to acquire a judgment signal (S104) before performing a purge process (S106) based on the reception of an ON signal and a recovery instruction signal, and this is a predetermined condition. Then, when the predetermined condition is satisfied, the first judgment process of S107 is executed. When a recovery instruction signal is received by an operation from a user, it is highly likely that an operation such as a printing process will be executed next, and there is no time to spare. Therefore, it is possible to perform the first judgment process and suppress the time required for the judgment process. In addition, it is possible to perform the first judgment process immediately after the power is turned on and suppress the time required for the judgment process. As a result, it is possible to quickly perform a printing process, etc. immediately after the power is turned on.

[0086] <Fifth Modification> Next, as a fifth modified example, when the control unit 80 receives an ON signal from the power switch by the user's operation, the second determination process is performed. Hereinafter, a description will be given with reference to FIG. 14, and the same reference numerals will be used to denote the same parts as those in the above-mentioned embodiment, and the description will be omitted.

[0087] The control unit 80 first determines whether or not an ON signal has been received (S901). If an ON signal has not been received (S901: NO), S901 is repeated. On the other hand, if an ON signal has been received (S901: YES), the control unit 80 performs the above-mentioned S101, S102, S502, S104, S109 to S112, and S114 to S116. Then, the flow ends.

[0088] In this way, in the printer of this modified example, it is preset to acquire a judgment signal based on receiving an ON signal (S104), which is a predetermined condition. If the predetermined condition is met, the second judgment process of S109 is executed. By performing the second judgment process immediately after turning on the power, it is possible to suppress a decrease in judgment accuracy. As a result, it is possible to perform printing processes and the like well immediately after turning on the power.

[0089] 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.

[0090] In the above embodiment, the value of the non-driven signal is the difference between the maximum value H and the minimum value h, and it is determined whether the value is equal to or greater than the first threshold value and whether the value is equal to or greater than the second threshold value, but the value may be the absolute value of any of the values ​​in the non-driven signal and may be set appropriately. Also, the first threshold value in the above embodiment is a fixed value set in advance, but it may be 1 / 2 the amplitude (maximum value-minimum value) of the judgment signal for a specific nozzle that is assumed to be a normal nozzle, and may be changed appropriately. Also, the first threshold value may be changed depending on the temperature, humidity, cumulative number of printed sheets, etc. of the environment in which the printer is installed.

[0091] Furthermore, even if the number of times the first determination process or the number of times the second determination process has been performed reaches the predetermined value Nt, it is not necessary to reacquire the non-driven signal.

[0092] The first, second, fourth, or fifth modified examples described above may be combined with each other. In this case, the process from receiving the recording instruction signal to executing the printing process in the second modified example may be replaced with the third modified example.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[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 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.

[0102] 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.

[0103] 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.

[0104] 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]

[0105] 1. Printer (liquid ejection device) 4. Inkjet head (liquid ejection head) 8 Maintenance Unit (Recovery Method) 10 Nozzles 68 Clock Section 76 Detection electrode (part of the signal output section) 77 High voltage power supply circuit (part of the signal output section) 78 Signal processing circuit (part of the signal output section) 79 Resistor (part of signal output section) 80 Control section

Claims

1. a liquid ejection head having a 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 a first determination process for determining whether or not the nozzle is the abnormal nozzle based on the determination signal output from the signal output unit by driving the liquid ejection head for the inspection; a second judgment process for generating a differential signal which is the difference between the non-driven signal output from the signal output unit when the liquid ejection head is not driven for inspection and the judgment signal output from the signal output unit by driving the liquid ejection head for inspection, and for determining whether the nozzle is an abnormal nozzle based on the differential signal, depending on whether a predetermined condition is satisfied.

2. the predetermined condition is that the value of the non-driven signal is equal to or greater than a first threshold value; The control unit is When the value of the non-driven signal is less than the first threshold value, the first determination process is executed; The liquid ejection device according to claim 1 , wherein the second determination process is executed when the value of the non-driven signal is equal to or greater than the first threshold value.

3. 3. The liquid ejection device according to claim 2, wherein the value of the non-driven signal is a difference between a maximum value and a minimum value of the non-driven signal.

4. The control unit is When the number of times that the first determination process has been executed reaches a first predetermined number of times, the non-driven signal is acquired again; 4. The liquid ejection apparatus according to claim 2, wherein the first determination process and the second determination process are selectively executed based on a value of the non-driven signal that has been reacquired.

5. The control unit is When the number of times that the second determination process has been executed reaches a second predetermined number of times, the non-driven signal is acquired again; 4. The liquid ejection apparatus according to claim 2, wherein the first determination process and the second determination process are selectively executed based on a value of the non-driven signal that has been reacquired.

6. The control unit is A liquid ejection device described in any one of claims 2 to 5, characterized in that when the value of the non-driven signal is equal to or greater than a second threshold value that is greater than the first threshold value, neither the first judgment process nor the second judgment process is executed.

7. A clock unit that outputs a time signal indicating the time is further provided, The control unit is when the time signal indicating a predetermined time is received, the test drive is performed to obtain the determination signal; the predetermined condition is that the determination signal is acquired based on reception of the time signal, The control unit is The liquid ejection device according to claim 1 , wherein the second determination process is executed when the determination signal is acquired based on reception of the time signal.

8. The control unit is when receiving an ejection instruction signal instructing the liquid ejection head to eject liquid from the nozzles toward the ejection receiving medium, ejecting liquid based on the ejection instruction signal, and when no other ejection instruction signal is received by the time the liquid ejection is completed, performing the test drive after the completion of the liquid ejection to obtain the judgment signal; the predetermined condition is that the determination signal is acquired after the liquid ejection is completed, The control unit is 8. The liquid ejection apparatus according to claim 1, wherein the second determination process is executed when the determination signal is acquired after the liquid ejection based on the ejection instruction signal is completed.

9. The control unit is when receiving an ejection instruction signal that instructs the liquid ejection head to eject liquid from the nozzles toward the ejection receiving medium, before ejecting liquid based on the ejection instruction signal, the test drive is performed to acquire the judgment signal; the predetermined condition is that the determination signal is acquired before the liquid is ejected, The control unit is 9. The liquid ejection apparatus according to claim 1, wherein the first determination process is executed when the determination signal is acquired before the liquid is ejected based on the ejection instruction signal.

10. The control unit is when receiving an ejection instruction signal that instructs the liquid ejection head to eject liquid from the nozzles toward the ejection receiving medium, before ejecting liquid based on the ejection instruction signal, the test drive is performed to acquire the judgment signal; the predetermined condition is set so that image quality obtained by liquid ejection based on the ejection instruction signal is equal to or higher than a predetermined image quality; The control unit is A liquid ejection device as described in any one of claims 1, 7 and 8, characterized in that when the judgment signal is acquired before performing the liquid ejection based on the ejection instruction signal, and when the image quality obtained by the liquid ejection is set to be equal to or higher than the specified image quality, the second judgment process is executed.

11. Further, a recovery means is provided for performing a recovery operation to discharge liquid from the nozzle, The control unit is when a recovery instruction signal for performing the recovery operation is received, the inspection driving is performed before performing the recovery operation to obtain the determination signal; the predetermined condition is that the determination signal is acquired based on receipt of the recovery instruction signal, The control unit is 11. The liquid ejection device according to claim 1, wherein the first determination process is executed when the determination signal is obtained based on the reception of the recovery instruction signal.

12. The control unit is When an ON signal is received when the power is turned on, the inspection drive is performed to obtain the judgment signal; the predetermined condition is that the determination signal is acquired based on reception of the ON signal, The control unit is 12. The liquid ejection device according to claim 1, wherein the first determination process is executed when the determination signal is obtained based on the reception of the ON signal.

13. The control unit is When an ON signal is received when the power is turned on, the inspection drive is performed to obtain the judgment signal; the predetermined condition is that the determination signal is acquired based on reception of the ON signal, The control unit is 12. The liquid ejection apparatus according to claim 1, wherein the second determination process is executed when the determination signal is obtained based on the reception of the ON signal.

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