Liquid dispensing device

Abstract

To determine whether a leak current properly flows or not regardless of an environment.SOLUTION: When receiving an inspection instructing signal that instructs to inspect whether a nozzle is an anomalous nozzle or not, a control unit switches to a capping state (S101) in which a plurality of nozzles are capped through capping processing, and while a voltage is applied to a detecting electrode 76 in the cap (S102), the control unit determines whether a leak current flows or not (S103) based on whether a value V of a signal corresponding to a DC component of the voltage of the detecting electrode is less than a threshold Vt or not. When the value V of the signal is equal to or larger than the threshold Vt and it is determined that the leak current flows (S103: NO), the control unit ejects ink in the cap through emptying suction processing (S105) and updates the threshold Vt based on the value of the signal corresponding to the DC component of the voltage of the detecting electrode 76 when the voltage is applied to the detecting electrode 76 in an uncapped state in which the cap is separated from the nozzle.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 a liquid ejection device that ejects liquid from a nozzle, Patent Document 1 describes an inkjet printer that ejects ink from a nozzle to perform printing. The inkjet printer described in Patent Document 1 executes a head inspection routine to inspect whether ink is ejected normally from each nozzle of a print head. In the head inspection routine, a predetermined potential difference is generated between the print head and an inspection area in a capping member, and the head is positioned in a normal inspection position to bring the nozzle plate of the print head into contact with the inspection area. Then, it is determined whether the actual voltage between the cavity plate of the print head and the inspection area is below the inspection tolerance range. If the actual voltage is not below the inspection tolerance range, the process proceeds to an inspection of whether ink is ejected normally from each nozzle.

[0003] If the measured voltage is below the inspection tolerance range, it is determined that a large current leak is occurring, and the print head is separated from the capping member to perform an idle suction process. The idle suction process is a process in which a suction pump connected to the capping member is driven to drain the ink that has accumulated inside the capping member. After the idle suction process, it is determined whether the measured voltage is below the inspection tolerance range, and if it is below the inspection tolerance range, the process proceeds to an inspection of whether ink is being ejected normally from each nozzle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-136858 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, in Patent Document 1, as described above, whether or not a large current leak is occurring is determined by determining whether or not the measured voltage between the cavity plate of the print head and the inspection area is below the inspection tolerance range. However, if the inspection tolerance range is fixed, depending on the environment, there is a risk that it will only be possible to determine that a leak is occurring when a fairly large current leak is occurring, or that a leak will be determined to be occurring when in fact no leak is occurring, resulting in unnecessary execution of an empty suction process.

[0006] An object of the present invention is to provide a liquid ejection device that is capable of appropriately determining whether or not a leak has occurred regardless of the environment. [Means for solving the problem]

[0007] A liquid ejection device of the present invention has a liquid ejection head having a nozzle for ejecting liquid, an electrode, and a voltage application unit that applies a voltage to the electrode, and is equipped with a signal output unit that outputs a signal corresponding to an electrical change in the electrode, a memory unit that stores a threshold value, and a control unit, and when the control unit receives an inspection instruction signal instructing to inspect whether or not the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, the control unit controls the voltage application unit to bring the electrode into an applied state in which a voltage is applied, and determines whether or not the liquid ejection head is driven and the value of a non-driven signal, which is a signal obtained from the signal output unit, is equal to or less than the threshold value. A leak determination process is executed to determine whether or not a leak current is flowing between the ejection head and the electrode, and if it is determined in the leak determination process that the leak current is not flowing, the voltage application unit is controlled to put it in the applied state, and a test drive is performed to cause the liquid ejection head to eject liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit, and at a predetermined timing when the leak determination process and the test drive are not performed, the voltage application unit is controlled to put it in the applied state, and an update process is executed to update the threshold information stored in the memory unit based on the value of the non-driven signal at this time.

[0008] Further, a liquid ejection device of the present invention has a liquid ejection head having a nozzle for ejecting liquid, an electrode, and a voltage application unit that applies a voltage to the electrode, and is equipped with a signal output unit that outputs a signal corresponding to an electrical change in the electrode, a memory unit that stores a threshold value, a temperature detection unit that detects a temperature, and a control unit, wherein the control unit, upon receiving an inspection instruction signal instructing to inspect whether or not the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, updates the threshold value stored in the memory unit, controls the voltage application unit to bring the electrode into an applied state in which a voltage is applied, and determines whether or not a leak current is flowing between the liquid ejection head and the electrode based on whether or not a value of a non-driven signal, which is a signal obtained from the signal output unit without driving the liquid ejection head, is equal to or lower than the threshold value. a leakage determination process for determining whether or not a leakage current is flowing, and if it is determined in the leakage determination process that no leakage current is flowing, the voltage application unit is controlled to put the voltage application unit into the applied state, and an inspection drive is performed to cause the liquid ejection head to eject liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit, the memory unit stores information on the temperature detected by the temperature detection unit when the threshold value stored in the memory unit is updated, and when updating the threshold value stored in the memory unit, the control unit updates the threshold value stored in the memory unit based on the temperature difference between the temperature detected by the temperature detection unit when the inspection instruction signal was received and the temperature detected by the temperature detection unit the previous time the threshold value stored in the memory unit was updated.

[0009] Further, a liquid ejection device of the present invention has a liquid ejection head having a nozzle for ejecting liquid, an electrode, and a voltage application unit that applies a voltage to the electrode, and is equipped with a signal output unit that outputs a signal corresponding to an electrical change in the electrode, a memory unit that stores a threshold value, a temperature detection unit that detects a temperature, and a control unit, wherein the control unit, when receiving an inspection instruction signal instructing to inspect whether or not the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, updates the threshold value stored in the memory unit, controls the voltage application unit to bring the electrode into an applied state in which a voltage is applied, and executes a leak determination process to determine whether or not a leak current is flowing between the liquid ejection head and the electrode based on whether or not a value of a non-driven signal, which is a signal obtained from the signal output unit without driving the liquid ejection head, is equal to or lower than the threshold value, and If it is determined that no liquid is flowing, the voltage application unit is controlled to put it in the applied state, and an inspection drive is performed to cause the liquid ejection head to eject liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit, and the memory unit stores information on multiple non-overlapping temperature ranges and information on which temperature range, among the multiple temperature ranges, the temperature detected by the temperature detection unit when the threshold value stored in the memory unit is updated falls within the information, and when updating the threshold value stored in the memory unit, the control unit updates the threshold value stored in the memory unit based on the temperature range that includes the temperature detected by the temperature detection unit when the inspection instruction signal was received and the temperature range that includes the temperature detected by the temperature detection unit when the threshold value stored in the memory unit was last updated. Effect of the Invention

[0010] According to the present invention, it is possible to more accurately determine whether or not a leakage current is flowing between the electrode and the liquid ejection head. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a printer according to a first embodiment. [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] 1A is a diagram showing a signal output from the second circuit when a voltage is applied to the detection electrode and test driving is not being performed, and when ink is not ejected from the nozzle by the test driving, and FIG. 1B is a diagram showing a signal output from the second circuit when ink is ejected from the nozzle by the test driving. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Diagram 5] 5 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the first embodiment. [Figure 6] 10 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the second embodiment. [Figure 7] 10 is a flowchart showing a flow of processing by a control unit when ink is introduced in a second embodiment. [Figure 8] 13 is a flowchart showing a flow of processing by a control unit at the time of initial installation in the third embodiment. [Figure 9] 13 is a flowchart showing the flow of processing performed by a control unit while power is being supplied to a printer in a fourth embodiment. [Figure 10] 13 is a flowchart showing the flow of processing performed by a control unit while power is being supplied to a printer in a fifth embodiment. [Figure 11] 23 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the sixth embodiment. [Figure 12] 13(a) is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the seventh embodiment, and (b) is a diagram for explaining information on a temperature range. FIG. [Figure 13] 20 is a flowchart showing a flow of processing by a control unit when a recording command is received in the eighth embodiment. [Figure 14] 13 is a flowchart showing a flow of processes performed by a control unit when an inspection instruction signal is received in the ninth embodiment. [Figure 15] 13 is a flowchart showing a flow of processing by a control unit when a recording command is received in the ninth embodiment. [Figure 16] 23 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the tenth and eleventh embodiments. [Figure 17] FIG. 17(a) is a diagram for explaining a table relating the amount of change in temperature to the amount of change in threshold in the tenth embodiment, and FIG. 17(b) is a diagram for explaining a table relating the amount of change in temperature range to the amount of change in threshold in the eleventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [First embodiment] A first preferred embodiment of the present invention will now be described.

[0013] <Overall printer configuration> As shown in FIG. 1, the printer 1 (the "liquid ejection device" of the present invention) according to the first 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, and a maintenance unit 8 (the "purging means" of the present invention).

[0014] 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.

[0015] 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 ("liquid tanks" of the present invention) are removably mounted. The four ink cartridges 14 are aligned in the scanning direction, and from the one positioned on the right side in the scanning direction, they store black, yellow, cyan, and magenta inks ("liquids" of the present invention). The subtank 3 is connected to the four ink cartridges 14 mounted on the cartridge holder 13 via four tubes 15. In this way, the four colors of ink are supplied from the four ink cartridges 14 to the subtank 3.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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, and the upper end of the cap 71 comes into close contact with the nozzle surface 4a, resulting in a capped state in which the plurality of nozzles 10 are covered by the cap 71. When the cap 71 is lowered by the cap lifting mechanism 88, the cap 71 comes into an uncapped state in which the cap 71 is separated from the nozzle surface 4a. Note that the cap 71 is not limited to a cap that covers 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.

[0020] 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, the suction pump 72 is driven in the above-mentioned capped state, thereby discharging ink from inside the inkjet head 4 through the multiple nozzles 10, that is, performing a so-called suction purge. The ink discharged by the suction purge is stored in the waste liquid tank 73.

[0021] 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.

[0022] In addition, in the maintenance unit 8, by driving the suction pump 72 in the uncapped state, it is possible to perform idle suction to discharge the ink inside the cap 71. The ink discharged by idle suction is also stored in the waste liquid tank 73.

[0023] 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 (the "voltage application section" of the present invention) via a resistor 79. A predetermined voltage (e.g., about 600 V) is applied to the detection electrode 76 by the high-voltage power supply circuit 77 during a determination drive, which will be described later. Meanwhile, the inkjet head 4 is held at the ground potential. This generates a predetermined potential difference between the inkjet head 4 and the detection electrode 76.

[0024] In the first embodiment, while a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77, a test drive can be performed in which the inkjet head 4 is driven to eject ink from the nozzle 10 toward the detection electrode 76.

[0025] Since a potential difference occurs between the inkjet head 4 and the detection electrode 76, when ink is ejected from the nozzle 10 by the test drive, the ejected ink is charged. Then, when this charged ink is ejected from the nozzle 10 toward the detection electrode 76, the potential of the detection electrode 76 changes. On the other hand, if ink is not ejected from the nozzle 10 by the test drive, the potential of the detection electrode 76 does not change.

[0026] Thus, in the first embodiment, whether or not the potential of the detection electrode 76 changes when the test drive is performed depends on whether or not the nozzle 10 is an abnormal nozzle that does not eject ink.

[0027] Further, a signal processing circuit 78 is connected to the detection electrode 76. The signal processing circuit 78 has a first circuit 78a and a second circuit 78b.

[0028] The first circuit 78a is a circuit for outputting a signal corresponding to the voltage of the detection electrode 76 when the inkjet head 4 is not driven (the "non-driven signal" of the present invention). The first circuit 78a is configured to continue to output a voltage corresponding to the magnitude of the DC component of the voltage of the detection electrode 76. More specifically, the first circuit 78a includes, for example, a filter circuit that cuts out the periodic component of the change in voltage of the detection electrode 76 when the inspection drive is performed, and the signal output from the first circuit 78a is configured to cut out the change in voltage of the detection electrode 76 due to the inspection drive.

[0029] In addition, the signal output from the first circuit 78a may be an analog signal whose value changes continuously in response to changes in the magnitude of the DC component of the detection electrode 76, or it may be a digital signal whose value changes in stages in response to changes in the magnitude of the DC component of the detection electrode 76.

[0030] The second circuit 78b is a circuit for outputting a signal according to the amount of change in the voltage of the detection electrode 76 when the test drive is performed. The second circuit 78b includes a differentiation circuit and the like, and power is supplied to the differentiation circuit in conjunction with a control signal that applies a voltage to the detection electrode 76, and a signal differentiated according to the change in the voltage of the detection electrode 76 is output. For example, when a high voltage is applied to the detection electrode 76 by the high voltage power supply circuit 77 and the test drive is not performed, and when ink is not ejected from the nozzle 10 by the test drive, as shown in FIG. 3(a), the value of the signal output from the second circuit 78b is a constant V0. When ink is ejected from the nozzle 10 by the test drive, as shown in FIG. 3(b), the signal output from the second circuit 78b becomes a signal that changes at a predetermined period. At this time, the value of the signal output from the second circuit 78b rises from V0 to a maximum value V1, then falls to a minimum value V2 smaller than V0, and then becomes a signal that repeats increasing and decreasing while attenuating.

[0031] In the first embodiment, the detection electrode 76, the high-voltage power supply circuit 77, the resistor 79, and the signal processing circuit 78 together correspond to the "signal output section" of the present invention.

[0032] <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 central processing unit (CPU) 81, a read only memory (ROM) 82, a random access memory (RAM) 83, a memory 84, and an application specific integrated circuit (ASIC) 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 (a first circuit 78a and a second circuit 78b).

[0033] In addition to the components described above, the printer 1 also includes a clock unit 70 and a temperature sensor 69. The clock unit 70 keeps time and outputs a time signal indicating the current time. The control unit 80 receives the time signal from the clock unit 70. The temperature sensor 69 detects the temperature and outputs a temperature signal indicating the temperature. The control unit 80 receives the temperature signal from the temperature sensor 69.

[0034] 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.

[0035] <Processing when a recording command is received> Next, a process performed by the control unit 80 when a recording command to perform recording on the recording paper P is received will be described. When a recording command is received, the control unit 80 controls the cap lifting mechanism 88 to lower the cap 71 to an uncapped state. Thereafter, the control unit 80 controls the carriage motor 86 to move the carriage 2 in the scanning direction, while repeatedly performing a recording pass in which ink is ejected from the multiple nozzles 10 toward the recording paper P, and a conveying operation in which the conveying motor 87 is controlled to cause the conveying rollers 6 and 7 to convey the recording paper P a predetermined distance, thereby performing recording on the recording paper P.

[0036] <Processing when receiving an inspection command signal> Next, the process performed by 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. When an inspection instruction signal is received, the control unit 80 performs the process according to the flow of FIG. 5. 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, in the case where an inspection to inspect whether the nozzle is an abnormal nozzle is performed every time a predetermined time is reached, when a signal indicating that the predetermined time has been reached is transmitted from the clock unit 76, the control unit 80 receives this signal as an inspection instruction signal.

[0037] 5 in more detail, when an inspection instruction signal is received, the control unit 80 executes the capping process (S101). In the capping process, the control unit 80 controls the cap lifting mechanism 88 to lift the cap 71 to the above-mentioned capped state. However, if the capped state is established immediately before the capping process, the capped state is maintained in the capping process of S101. The same applies to the following capping processes. Next, the control unit 80 controls the high-voltage power supply circuit 77 to apply a voltage to the detection electrode 76 (S102).

[0038] Next, the control unit 80 judges whether or not the value V of the signal output from the first circuit 78a is less than the threshold value Vt (S103, the "leak judgment process" of the present invention). In the first embodiment, the detection electrode 76 and the inkjet head 4 may be shorted via the ink in the cap 71. In this case, if a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77 in the capped state, a large leakage current flows between the detection electrode 76 and the inkjet head 4, damaging the nozzle 10.

[0039] Furthermore, when a leak current flows between the detection electrode 76 and the inkjet head 4, the voltage of the detection electrode 76 is lower and the value of the signal output from the first circuit 78a is smaller than when no leak current flows. Therefore, in S103, it is possible to determine whether or not the leak current flows based on whether or not the value V of the signal output from the first circuit 78a is less than the threshold value Vt. The threshold value Vt is stored in the memory 84.

[0040] When the value V of the signal output from the first circuit 78a is equal to or greater than the threshold value Vt (S103: NO), the process proceeds directly to S109. When the value V of the signal output from the first circuit 78a is less than the threshold value Vt (S103: YES), the control unit 80 controls the high voltage power supply circuit 77 to stop the application of voltage to the detection electrode 76 (S104). Next, the control unit 80 executes an empty suction process (S105). In the empty suction process, the control unit 80 controls the cap lifting mechanism 88 to lower the cap 71 to the uncapped state, and then drives the suction pump 72 to perform the empty suction.

[0041] Next, the control unit 80 controls the high voltage power supply circuit 77 to apply a voltage to the detection electrode 76 again (S106). Since the detection electrode 76 is in an uncapped state in the idle suction process of S105, a voltage is applied to the detection electrode 76 in the uncapped state in S106. Then, the control unit 80 updates the threshold Vt stored in the memory 84 based on the value of the signal output from the first circuit 78a (S107). In S107, the control unit 80 updates the threshold Vt to a value that is larger or smaller than the value of the signal output from the first circuit 78a by a predetermined amount, that is, a value whose difference from the value of the signal output from the first circuit 78a is a predetermined amount. In the first embodiment, the processes of S106 and S107 correspond to the "update process" of the present invention. Then, after the process of S107, the control unit 80 executes a cap process similar to S101 (S108) and then proceeds to S109.

[0042] In S109, the control unit 80 executes a test drive process (S109). In the test drive process, the control unit 80 performs test drive for each of the multiple nozzles 10 of the inkjet head 4, and acquires a signal output from the second circuit 78b.

[0043] Next, the control unit 80 judges whether or not there is an abnormal nozzle based on the signal acquired in the inspection drive process (S110). If there is no abnormal nozzle (S110: NO), the process ends. If there is an abnormal nozzle (S110: YES), the control unit 80 executes a purge process (S111) and ends the process. In the purge process, the control unit 80 controls the suction pump 72 and the like to perform a suction purge.

[0044] <Effects> In the first embodiment, whether or not a leak current flows between the detection electrode 76 and the inkjet head 4 can be determined depending on whether the value V of the signal output from the first circuit 78a is less than the threshold value Vt, depending on the voltage of the detection electrode 76 when a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77. Also, in the first embodiment, the threshold value Vt stored in the memory 84 is updated based on the signal output from the first circuit 78a at a predetermined timing when the inspection drive is not performed. This allows the threshold value Vt to be appropriate for determining whether or not a leak current flows between the detection electrode 76 and the inkjet head 4 even when the environment changes.

[0045] Furthermore, in the first embodiment, by performing the test drive in the capped state, the detection electrode 76 and the inkjet head 4 can be brought closer to each other during the test drive. This allows a larger electrical change in the detection electrode 76 when the test drive is performed. Furthermore, when updating the threshold value Vt stored in the memory 84, a voltage is applied to the detection electrode 76 in the uncapped state. Therefore, even in a situation where a large leakage current would flow if a voltage were applied to the detection electrode 76 in the capped state, the threshold value Vt can be updated to an appropriate value.

[0046] In the first embodiment, when updating the threshold value Vt stored in the memory 84, the threshold value Vt is updated to a value that is different from the value of the signal output from the first circuit 78a by a predetermined amount. This makes it possible to set the threshold value Vt to a value appropriate for determining whether or not a leak current is flowing.

[0047] Furthermore, in the first embodiment, the signal processing circuit 78 has a first circuit 78a that outputs a signal corresponding to the voltage (DC component of the voltage of the detection electrode 76) applied to the detection electrode 76 by the high voltage power supply circuit 77, and a second circuit 78b that outputs a signal corresponding to a change in the voltage of the detection electrode 76 in a predetermined cycle due to inspection driving. This makes it possible to separately acquire a signal of the change in the DC component of the voltage of the detection electrode 76, which is used to determine whether or not a leak current is flowing, and a signal of the change in the voltage of the detection electrode 76 in a predetermined cycle, which is used to determine whether or not the nozzle is abnormal.

[0048] In the first embodiment, when the value V of the signal output from the first circuit 78a is equal to or greater than the threshold Vt in S103 and it is determined that a leak current is flowing, there are two cases: a leak current is actually flowing, and a leak current is not actually flowing but the threshold Vt is not appropriate for the current environment, so that it is erroneously determined that a leak current is flowing. Therefore, in the first embodiment, the threshold Vt stored in the memory 84 is updated immediately after it is determined that the value V of the signal output from the first circuit 78a is equal to or greater than the threshold Vt and that a leak current is flowing. This allows the threshold Vt stored in the memory 84 to be updated to an appropriate one when the threshold Vt stored in the memory 84 is not appropriate for the current environment.

[0049] [Second embodiment] Next, a second preferred embodiment of the present invention will be described. Like the first embodiment, the second embodiment also relates to a printer 1. However, unlike the first embodiment, the second embodiment has a feature that the control unit 80 performs processing according to the flow of FIG. 6 when it receives an inspection instruction signal.

[0050] More specifically, when the control unit 80 receives an inspection command signal, it executes the processes of S101 and S102 as in the first embodiment. Then, if the value V of the signal output from the first circuit 78a is equal to or greater than the threshold Vt (S103: NO), the process proceeds to S109. If the value V of the signal output from the first circuit 78a is less than the threshold Vt (S103: YES), it executes the processes of S104 and S105 as in the first embodiment. However, unlike the first embodiment, the second embodiment does not subsequently execute the processes of S106 and S107 for updating the threshold Vt, but instead executes the processes of S201 and S202 in order.

[0051] In S201, the control unit 80 executes the same capping process as in S108. In S202, the control unit 80 controls the high voltage power supply circuit 77 to apply a voltage to the detection electrode 76 (S202). Thereafter, the control unit 80 executes the processes of S109 to S111 as in the first embodiment.

[0052] In the second embodiment, an initial value of the threshold value Vt is stored in the memory 84 when the printer 1 is manufactured, and then ink is introduced into the inkjet head 4, etc. Then, when ink is introduced into the inkjet head 4, etc., the control unit 80 performs processing according to the flow of FIG.

[0053] More specifically, the control unit 80 executes an ink introduction process (S301). In the ink introduction process, the control unit 80 introduces ink into the inkjet head 4 by performing a suction purge.

[0054] Next, the control unit 80 executes an uncap process (S302), and controls the high-voltage power supply circuit 77 to apply a voltage to the detection electrode 76 (S303). In the uncap process of S302, the control unit 80 controls the cap lift mechanism 88 to lower the cap 71 to bring the cap into an uncapped state. Then, in this state, the control unit 80 updates the threshold value Vt stored in the memory 84, as in S107 (S304). Thereafter, the control unit 80 controls the high-voltage power supply circuit 77 to stop applying a voltage to the detection electrode 76 (S305), and ends the process.

[0055] <Effects> In the second embodiment, the threshold value Vt stored in the memory 84 is updated when the introduction of ink into the inkjet head 4 is completed. This makes it possible to make the threshold value Vt stored in the memory 84 appropriate for the environment at the time when the introduction of ink into the inkjet head 4 is completed.

[0056] In the second embodiment, ink is introduced into the inkjet head 4 by performing suction purging, but this is not limiting. For example, ink may be introduced into the inkjet head 4 using a dedicated device provided in the manufacturing facility of the printer 1, and after the ink is introduced into the inkjet head 4, the control unit 80 may execute the processes of S302 to S305.

[0057] [Third embodiment] Next, a third preferred embodiment of the present invention will be described. Like the first and second embodiments, the third embodiment also relates to the printer 1. Also, in the third embodiment, like the second embodiment, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of FIG.

[0058] Also, in the third embodiment, unlike the second embodiment, ink is not introduced into the inkjet head 4 etc. when the printer 1 is manufactured, but instead a preservation liquid of a different type from ink is introduced. Then, when the printer 1 is used for the first time, that is, when the ink cartridge 14 is attached to the cartridge holder 13 for the first time in the printer 1 and the power is turned on, the control unit 80 performs processing according to the flow of FIG.

[0059] More specifically, the control unit 80 executes an initial introduction process (S401). In the initial introduction process, the control unit 80 performs suction purging to discharge the storage liquid in the inkjet head 4 from the nozzles 10, and also performs initial introduction to introduce ink from the ink cartridge 14 to the inkjet head 4. Then, after the initial introduction, the control unit 80 executes processes of S402 to S405 similar to S301 to S304.

[0060] <Effects> In the third embodiment, immediately after the completion of the initial installation, the threshold value Vt stored in the memory 84 is updated. This makes it possible to make the threshold value Vt stored in the memory 84 appropriate for the environment immediately after the initial installation.

[0061] [Fourth embodiment] Next, a fourth preferred embodiment of the present invention will be described. Like the first to third embodiments, the fourth embodiment also relates to the printer 1. Also in the fourth embodiment, like the second and third embodiments, when the control unit 80 receives an inspection instruction signal, the control unit 80 performs processing according to the flow of FIG. 6.

[0062] In the fourth embodiment, while power is being supplied to the printer 1, the control unit 80 performs processing according to the flow of Fig. 9. To explain in more detail, the control unit 80 waits until a predetermined time has elapsed since the threshold value Vt stored in the memory 84 was last updated (S501: NO). Then, when the predetermined time has elapsed since the threshold value Vt stored in the memory 84 was last updated (S501: YES), the control unit 80 performs the processing of S502 to S505 similar to S301 to S304, thereby updating the threshold value Vt stored in the memory 84. That is, in the fourth embodiment, the threshold value Vt stored in the memory 84 is updated every time a predetermined time elapses.

[0063] <Effects> In the fourth embodiment, every time a predetermined time elapses, the threshold value Vt stored in the memory 84 is updated. This allows the threshold value Vt stored in the memory 84 to be made appropriate in response to changes in the environment over time.

[0064] [Fifth embodiment] Next, a fifth preferred embodiment of the present invention will be described. Like the first to fourth embodiments, the fifth embodiment also relates to the printer 1. Also in the fifth embodiment, like the second to fourth embodiments, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of FIG. 6.

[0065] In the fifth embodiment, while power is being supplied to the printer 1, the control unit 80 performs processing according to the flow of FIG. 10. To explain in more detail, the control unit 80 waits until a predetermined time has elapsed since the previous suction purge was performed (S601: NO). Then, when the predetermined time has elapsed since the previous suction purge was performed (S601: YES), the control unit 80 performs a purge process similar to S111, and then performs the processes of S603 to S606 similar to S301 to S304, thereby updating the threshold value Vt stored in the memory 84. That is, in the fifth embodiment, the suction purge is performed periodically, and the threshold value Vt stored in the memory 84 is updated when the suction purge is performed periodically.

[0066] <Effects> In the fifth embodiment, periodic suction purge is performed, and the threshold value Vt stored in the memory 84 is updated at the timing of performing the periodic suction purge. This makes it possible to make the threshold value Vt stored in the memory 84 appropriate in response to changes in the environment over time.

[0067] In the fifth embodiment, the processes of S603 to S606 are executed after the purge process of S602, but the processes of S603 to S606 may be executed before the purge process of S602.

[0068] [Sixth embodiment] Next, a sixth preferred embodiment of the present invention will be described. Like the first to fifth embodiments, the sixth embodiment also relates to the printer 1. In the sixth embodiment, when the control unit 80 receives an inspection instruction signal, the control unit 80 performs processing according to the flow of FIG.

[0069] More specifically, if the temperature difference ΔT between the temperature detected by the temperature sensor 69 when the inspection instruction signal is received and the temperature detected by the temperature sensor 69 when the inspection instruction signal was received the previous time is equal to or less than a predetermined value ΔTt (S701: NO), the control unit 80 executes a capping process (S702), controls the high voltage power supply 77 to apply a voltage to the detection electrode 76 (S703), and proceeds to S709.

[0070] If the temperature difference ΔT is greater than the predetermined value ΔTt (S701: YES), the control unit 80 executes an uncap process (S704), controls the high voltage power supply 77 to apply a voltage to the detection electrode 76 (S705), and updates the threshold value Vt stored in the memory 84 (S706). Next, the control unit 80 stores information on the temperature detected by the temperature sensor 69 in the memory 84 (S707). Thereafter, the control unit 80 executes a cap process (S708) and proceeds to S709.

[0071] In S709, similarly to S103, it is determined whether or not the value V of the signal output from the first circuit 78a is smaller than the threshold value Vt. If the value V of the signal output from the first circuit 78a is smaller than the threshold value Vt (S709: YES), the processes of S109 to S111 are executed similarly to the first embodiment.

[0072] When the value V of the signal output from the first circuit 78a is equal to or greater than the threshold value Vt (S709: NO), the control unit 80 controls the high voltage power supply circuit 77 to stop the application of voltage to the detection electrode 76 (S710) and executes an idle suction process (S711). Next, the control unit 80 executes a cap process (S712), and then controls the high voltage power supply circuit 77 to apply voltage to the detection electrode 76 again (S713). Then, the process of S109 to S111 is executed in the same manner as in the first embodiment.

[0073] <Effects> In the sixth embodiment, the threshold value Vt stored in the memory 84 is updated immediately before determining whether or not a leak current is flowing based on whether or not the value V of the signal output from the first circuit 78a is less than the threshold value Vt. Therefore, the threshold value Vt stored in the memory 84 can be made appropriate for the environment when determining whether or not a leak current is flowing.

[0074] Also, when the temperature has changed significantly, it is highly likely that the appropriate threshold value Vt has changed. Therefore, in the sixth embodiment, when the temperature difference ΔT between the temperature when the inspection instruction signal is received and the temperature when the threshold value Vt stored in the memory 84 is updated last time is equal to or greater than a predetermined temperature difference ΔTt, the threshold value Vt stored in the memory 84 is updated immediately before determining whether or not a leak current is flowing. As a result, when the temperature has changed significantly since the last update of the threshold value Vt and it is highly likely that the appropriate threshold value Vt has changed, it is possible to determine whether or not a leak current is flowing after updating the threshold value Vt to one appropriate for the environment when determining whether or not a leak current is flowing. On the other hand, when the temperature has not changed much since the last update of the threshold value Vt and it is highly unlikely that the appropriate threshold value Vt has changed, it is possible to avoid unnecessary updating of the threshold value Vt.

[0075] [Seventh embodiment] Next, a second preferred embodiment of the present invention will be described. The seventh embodiment, like the first to sixth embodiments, also relates to the printer 1. In the seventh embodiment, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of FIG. 12(a). The flow of FIG. 12(a) is obtained by replacing S701 with S801 in the flow of FIG. 11.

[0076] Here, in the seventh embodiment, the memory 84 stores information on a plurality of types of temperature ranges as shown in Fig. 12(b). In S801, the control unit 80 determines whether or not a temperature range including a temperature detected by the temperature sensor 69 when an inspection instruction signal is received, among the plurality of types of temperature ranges shown in Fig. 12(b), has changed from a temperature range including a temperature detected by the temperature sensor 69 when an inspection instruction signal was received the previous time. If the temperature range has not changed (S801: NO), the process proceeds to S702. If the temperature range has changed (S801: YES), the process proceeds to S704.

[0077] In the seventh embodiment, information on the temperature detected by the temperature sensor 69 is stored in S707, and a temperature range including the temperature detected by the temperature sensor 69 can be obtained from this temperature information and the table of Fig. 12(b). That is, in the seventh embodiment, the temperature information stored in the memory 84 in S707 indicates information on the temperature range. However, in the seventh embodiment, information on the temperature range itself including the temperature detected by the temperature sensor 69 may be stored in the memory 84 in S707 instead of the information on the temperature detected by the temperature sensor 69.

[0078] <Effects> In the seventh embodiment, the threshold value Vt stored in the memory 84 is updated immediately before determining whether or not a leak current is flowing based on whether or not the value V of the signal output from the first circuit 78a is less than the threshold value Vt. Therefore, the threshold value Vt stored in the memory 84 can be made appropriate for the environment when determining whether or not a leak current is flowing.

[0079] Also, when the temperature has changed significantly, it is highly likely that the appropriate threshold Vt has changed. Therefore, in the seventh embodiment, when the temperature range including the temperature when the inspection instruction signal is received is different from the temperature range including the temperature when the threshold Vt was last updated, the threshold Vt stored in the memory 84 is updated immediately before determining whether or not a leak current is flowing. As a result, when the temperature has changed significantly since the last update of the threshold Vt and it is highly likely that the appropriate threshold Vt has changed, it is possible to determine whether or not a leak current is flowing by updating the threshold Vt to one appropriate for the environment when determining whether or not a leak current is flowing. On the other hand, when the temperature has not changed much since the last update of the threshold Vt and it is highly likely that the appropriate threshold Vt has changed, it is possible to avoid unnecessary updating of the threshold Vt.

[0080] [Eighth embodiment] Next, an eighth preferred embodiment of the present invention will be described. The eighth embodiment, like the first to seventh embodiments, also relates to the printer 1. In the eighth embodiment, the control unit 80 performs processing along the flow of Fig. 6 when it receives an inspection instruction signal, like the second and third embodiments. In the seventh embodiment, the control unit 80 performs processing along the flow of Fig. 13 when it receives a recording command.

[0081] More specifically, when the control unit 80 receives a recording command, it executes an uncap process (S901) and controls the high voltage power supply circuit 77 to apply a voltage to the detection electrode 76 (S902). Then, similar to S107, it updates the threshold value Vt stored in the memory 84 (S903). Thereafter, the control unit 80 controls the high voltage power supply circuit 77 to stop applying the voltage to the detection electrode 76 (S904) and executes a recording process (S905). In the recording process, the control unit 80 causes the recording pass and the conveying operation to be repeated, as described in the first embodiment, to perform recording on the recording paper P.

[0082] <Effects> Here, when updating the threshold value Vt stored in the memory 84, the state is set to the uncapped state, and a voltage is applied to the detection electrode 76 by the high voltage power supply circuit 77. On the other hand, when recording on the recording paper P, it is necessary to switch from the capped state to the uncapped state. Therefore, in the eighth embodiment, the threshold value Vt stored in the memory 84 is updated at the timing of recording on the recording paper P. In this way, the threshold value Vt stored in the memory 84 can be updated by utilizing the switch from the capped state to the uncapped state when recording on the recording paper P.

[0083] [Ninth embodiment] Next, a ninth preferred embodiment of the present invention will be described. As with the first to eighth embodiments, the ninth embodiment also relates to the printer 1. In the ninth embodiment, the control unit 80 receives, as an inspection instruction signal, a time signal indicating that a predetermined time has arrived, transmitted from the clock unit 76, and an inspection instruction signal different from the time signal, transmitted from an operation unit (not shown) of the printer 1, a PC, or the like.

[0084] In the ninth embodiment, when the control unit 80 receives an inspection instruction signal, the control unit 80 performs processing along the flow of Fig. 14. In the ninth embodiment, when the control unit 80 receives a recording command, the control unit 80 performs processing along the flow of Fig. 15.

[0085] Describing the flow of FIG. 14 in detail, when the control unit 80 receives an inspection instruction signal, the control unit 80 first determines whether the received inspection instruction signal is a time signal indicating that a predetermined time has arrived (S1001).

[0086] If the received inspection instruction signal is a time signal indicating that the predetermined time has arrived (S1001: YES), the control unit 80 executes the processes of S702 and S703 similar to those of the seventh and eighth embodiments, and then executes the processes of S709 to S713, S109, and S110. If the received inspection instruction signal is not a time signal indicating that the predetermined time has arrived (S1001: NO), the control unit 80 executes the processes of S704 to S706, and S708 similar to those of the seventh and eighth embodiments, and then executes the processes of S709 to S713, S109, and S110.

[0087] Furthermore, in the ninth embodiment, if it is determined in S110 that there is no abnormal nozzle (S110: NO), the process ends immediately.

[0088] Furthermore, if it is determined in S110 that there are no abnormal nozzles (S110: YES) and the received inspection instruction signal is a time signal indicating that a specified time has arrived (S1002: YES), the control unit 80 stores a recovery flag in the memory 84 (S1003) and terminates the process.

[0089] Furthermore, if it is determined in S110 that there are no abnormal nozzles (S110: YES) and the received inspection instruction signal is not a time signal indicating that a specified time has arrived (S1002: NO), the control unit 80 executes a purge process (S1004) and ends the process.

[0090] To explain the flow of Figure 15 in more detail, when the control unit 80 receives a recording command, if a recovery flag is not stored in the memory 84 (S1101: NO), the control unit 80 executes a recording process similar to S905 (S1104).

[0091] If a recovery flag is stored in memory 84 (S1101: YES), the control unit 80 executes a purge process (S1102), erases the recovery flag stored in memory 84 (S1103), and then executes a recording process (S1104).

[0092] <Effects> In the ninth embodiment, an inspection is performed to determine whether or not there is an abnormal nozzle at each predetermined time. In this case, the predetermined time is often set to a time period when the printer 1 is not in use, such as late at night. On the other hand, when updating the threshold value Vt stored in the memory 84, it is necessary to switch from the capped state to the uncapped state, and the movement of the cap 71 at this time generates a relatively loud noise. For these reasons, unlike the ninth embodiment, when the threshold value Vt stored in the memory 84 is updated at a predetermined time, noise may become a problem.

[0093] Therefore, in the ninth embodiment, when a time signal indicating that a predetermined time has arrived is received as an inspection instruction signal, the threshold value Vt stored in memory 84 is not updated, and the threshold value Vt stored in memory 84 by the previous update is used to determine whether or not a leak current is flowing. On the other hand, when an inspection instruction signal other than the time signal indicating that the predetermined time has arrived is received, the threshold value Vt stored in memory 84 is updated, and the updated threshold value Vt is used to determine whether or not a leak current is flowing.

[0094] [Tenth and Eleventh Embodiments] Next, preferred tenth and eleventh embodiments of the present invention will be described. The tenth and eleventh embodiments, like the first to ninth embodiments, relate to the printer 1. In the tenth and eleventh embodiments, for example, when the printer 1 is manufactured, information on the temperature at that time and a threshold value Vt set according to this temperature are stored in the memory 84. In the tenth and eleventh embodiments, when an inspection instruction signal is received, processing is performed according to the flow of FIG.

[0095] More specifically, when the control unit 80 receives the inspection command signal, the control unit 80 updates the threshold Vt stored in the memory 84 based on the temperature difference between the temperature detected by the temperature sensor 69 and the temperature detected by the temperature sensor 69 at the previous update of the threshold Vt stored in the memory 84 (S1201), and stores information on the temperature detected by the temperature sensor 69 in the memory 84 (S1202). Then, after the processes of S1201 and S1202, the control unit 80 executes the processes of S101 to S105, S201, S202, and S109 to S111, similarly to the second embodiment.

[0096] However, the method of updating the threshold value Vt in S1201 is different between the tenth and eleventh embodiments.

[0097] To explain in more detail, in the tenth embodiment, the memory 84 stores a table as shown in FIG. 17(a), which associates the range of the temperature change amount ΔT obtained by subtracting the temperature detected by the temperature sensor 69 at the time of the previous update of the threshold value Vt stored in the memory 84 from the temperature detected by the temperature sensor 69 when the inspection instruction signal is received, with the change amount ΔVt of the threshold value Vt.

[0098] 17(a), a positive value for the change amount ΔVt indicates that the threshold Vt is increased, a negative value indicates that the threshold Vt is decreased, and ±0 indicates that the threshold Vt is not changed. Also, in FIG. 17(a), ΔVt1 and ΔVt2 have a magnitude relationship of |ΔVt2|>|ΔVt1|>0.

[0099] Then, in the tenth embodiment, in S1201, the change amount ΔVt of the threshold value Vt is determined based on the temperature change amount ΔT at the time when the inspection instruction signal is received and the table of Figure 16 (b), and the threshold value Vt stored in the memory 84 is updated to a value changed by the change amount ΔVt from the current value.

[0100] Meanwhile, in the eleventh embodiment, similarly to the seventh embodiment, information on a plurality of types of temperature ranges as shown in Fig. 12(b) is stored in the memory 84. Also, in the eleventh embodiment, a table as shown in Fig. 17(b) is stored in the memory 84, which associates the amount of change in the temperature range including the temperature detected by the temperature sensor 69 when the inspection instruction signal is received from the temperature range including the temperature detected by the temperature sensor 69 at the time of the previous update of the threshold value Vt stored in the memory 84 with the amount of change ΔVt in the threshold value Vt.

[0101] Then, in the eleventh embodiment, in S1201, the change amount ΔVt of the threshold value Vt is determined based on the change amount of the above-mentioned temperature range when the inspection instruction signal is received and the table of Figure 17 (b), and the threshold value Vt stored in the memory 84 is updated to a value changed by the change amount ΔVt from the current value.

[0102] In the eleventh embodiment, in S1202, instead of storing information on the temperature detected by the temperature sensor 69, as in the seventh embodiment, information on a temperature range including the temperature detected by the temperature sensor 69 may be stored.

[0103] <Effects> The appropriate threshold value changes depending on the temperature. Therefore, in the tenth embodiment, the threshold value Vt stored in the memory 84 is updated based on the temperature difference ΔT between the temperature when the inspection command signal is received and the temperature when the threshold value Vt is last updated. This allows the threshold value Vt to be appropriate according to the temperature. Also, in the eleventh embodiment, the threshold value Vt stored in the memory 84 is updated based on the change in the temperature range including the temperature when the inspection command signal is received from the temperature range including the temperature when the threshold value Vt was last updated. This allows the threshold value Vt to be appropriate according to the temperature.

[0104] <Modification> Although the first to eleventh preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments and various modifications are possible within the scope of the claims.

[0105] In the sixth and seventh embodiments, the threshold value Vt stored in the memory 84 is updated immediately before determining whether or not a leak current is flowing only when the temperature at the time of receiving the inspection command signal has changed significantly from the temperature at the time of the previous update of the threshold value Vt, but this is not limiting. For example, the threshold value Vt stored in the memory 84 may be updated at all times immediately before determining whether or not a leak current is flowing.

[0106] In the eighth embodiment, the threshold value Vt stored in the memory 84 is updated at the timing of recording on the recording paper P by utilizing the switching from the capped state to the uncapped state during recording, but this is not limited to this. The threshold value Vt stored in the memory 84 may be updated at the timing of a predetermined operation other than recording on the recording paper P, including switching from the capped state to the uncapped state, by utilizing the switching from the capped state to the uncapped state during the predetermined operation.

[0107] In addition, in the first to eleventh embodiments, various examples of the timing for updating the threshold value Vt stored in memory 84 have been described, but the threshold value Vt stored in memory 84 may be updated at two or more of these timings.

[0108] In the above example, the signal processing circuit 78 has the first circuit 78a and the second circuit 78b, but is not limited to this. For example, the signal processing circuit 78 may output a signal corresponding to a change in the voltage (DC component) applied to the detection electrode 76 by the high voltage power supply circuit 77 and a change in the voltage of the detection electrode 76 due to the inspection drive.

[0109] In the above example, when updating the threshold value Vt stored in the memory 84, the threshold value Vt is updated to a value that is different from the value of the signal output from the first circuit 78a by a predetermined amount, but this is not limited to this. For example, when updating the threshold value Vt stored in the memory 84, the threshold value Vt may be updated to the same value as the value of the signal output from the first circuit 78a.

[0110] Furthermore, in the first to eighth, tenth and eleventh embodiments, if an abnormal nozzle is present, and in the ninth embodiment, if an abnormal nozzle is present and the inspection command signal is a signal other than a time signal indicating that the predetermined time has arrived, suction purging is immediately performed. Also, in the ninth embodiment, if an abnormal nozzle is present and the inspection command signal is a time signal indicating that the predetermined time has arrived, a recovery flag is stored in the memory 84, and if the recovery flag is stored in the memory 84 when a recording command is received, suction purging is performed before recording on the recording paper P, but this is not limited to the above.

[0111] For example, in the first to eighth, tenth and eleventh embodiments, if an abnormal nozzle is present, a recovery flag may be stored in the memory 84, and if a recording command is received and the recovery flag is stored in the memory 84, suction purging may be performed before recording on the recording paper P. Also, in the ninth embodiment, if an abnormal nozzle is present, suction purging may be performed immediately regardless of whether the inspection command signal is a time signal indicating that a predetermined time has been reached. Alternatively, in the ninth embodiment, if an abnormal nozzle is present, a recovery flag may be stored in the memory 84, and if a recording command is received and the recovery flag is stored in the memory 84, suction purging may be performed before recording on the recording paper P.

[0112] In the above example, a voltage is applied to the detection electrodes 76 in the capped state when driving for inspection is performed, and a voltage is applied to the detection electrodes 76 in the uncapped state when updating the threshold Vt stored in the memory 84, but this is not limited to the above. For example, a voltage may be applied to the detection electrodes 76 in the capped state both when driving for inspection is performed and when updating the threshold Vt stored in the memory 84. Alternatively, a voltage may be applied to the detection electrodes 76 in the uncapped state both when driving for inspection is performed and when updating the threshold Vt stored in the memory 84.

[0113] In the above example, the high voltage power supply circuit 77 applies a voltage to the detection electrode 76, and when the value V of the signal corresponding to the voltage of the detection electrode 76 when the inkjet head 4 is not driven is equal to or greater than the threshold value Vt, that is, when it is determined that a leak current is flowing, the printer performs idle suction so that the detection electrode 76 and the inkjet head 4 are not shorted, and then performs the test drive. However, this is not limited to the above. For example, the printer may be provided with a wiper for wiping off ink adhering to the nozzle surface 4a, and when it is determined that a leak current is flowing, the wiper may be caused to wipe the nozzle surface 4a so that the detection electrode 76 and the inkjet head 4 are not shorted, and then the test drive may be performed. Alternatively, when it is determined that a leak current is flowing, the process may be terminated without performing the test drive by not performing an operation for preventing a short between the detection electrode 76 and the inkjet head 4.

[0114] In the above example, a uniform suction purge is performed when there is an abnormal nozzle, but this is not limited to the above. For example, the greater the number of abnormal nozzles, the greater the amount of ink discharged by the suction purge may be.

[0115] In the above example, suction purging is performed as purging, but this is not limiting. 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 from the inkjet head 4 through the nozzles 10, thereby performing so-called pressure purging.

[0116] Furthermore, during purging, both suction by the suction pump 72 and pressurization by the pressurizing pump may be performed.

[0117] Furthermore, the method of recovering an abnormal nozzle is not limited to purging. For example, the inkjet head 4 may be controlled to perform flushing to discharge ink from at least the abnormal nozzle, thereby recovering the abnormal nozzle. Alternatively, the abnormal nozzle may be recovered by purging and flushing.

[0118] In the above example, when an abnormal nozzle is present, the control unit 80 automatically performs suction purging or the like to recover the abnormal nozzle, but this is not limited to the above. For example, when an abnormal nozzle is present, the user may be notified of this and allowed to select whether or not to perform suction purging. Then, when the user selects to perform suction purging, suction purging may be performed.

[0119] In the above embodiment, the inspection drive is performed on all the nozzles 10 of the inkjet head 4, but this is not limited to the above. For example, the inspection drive may be performed on only some of the nozzles 10 of the inkjet head 4, such as every other nozzle 10 in each nozzle row 9, and the remaining nozzles 10 may be determined to be abnormal or not based on the determination result of whether the nozzles 10 that have been subjected to the inspection drive are abnormal or not.

[0120] In the above example, the nozzle 10 from which ink is not ejected is determined to be an abnormal nozzle, but this is not limited to the above. For example, the nozzle 10 having an abnormality other than whether ink is ejected, such as a nozzle 10 having an abnormality in the ink ejection direction, may be determined to be an abnormal nozzle.

[0121] In the above, an example has been described in which the present invention is applied to a printer equipped with a so-called serial head that ejects ink from multiple nozzles while moving in the scanning direction together with the carriage, but the present invention is not limited to this. For example, the present invention can also be applied to a printer equipped with a so-called line head that extends across the entire length of the recording paper P in the scanning direction.

[0122] 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]

[0123] 1. Printer 4 Inkjet head 10 Nozzles 14 Ink Cartridges 69 Temperature Sensor 70 Clock section 71 Cap 76 Detection electrode 76 77 High Voltage Power Supply Circuit 78 Signal Processing Circuit 78a 1st circuit 78b 2nd circuit 79 Resistance 80 Control section 84 Memory 88 Cap lifting mechanism

Claims

1. a liquid ejection head having a nozzle for ejecting liquid; a signal output section having an electrode and a voltage application section for applying a voltage to the electrode and for outputting a signal corresponding to an electrical change in the electrode; A storage unit that stores a threshold value; A control unit, The control unit is When an inspection instruction signal is received instructing to inspect whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, a leakage determination process is executed to determine whether or not a leakage current is flowing between the liquid ejection head and the electrode based on whether or not a value of a non-driven signal, which is a signal acquired from the signal output unit without driving the liquid ejection head, is equal to or less than the threshold value by controlling the voltage application unit to apply a voltage to the electrode, and when it is determined in the leak determination process that the leak current is not flowing, the voltage application unit is controlled to be in the applied state, and the liquid ejection head is caused to perform an inspection drive for ejecting liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit; A liquid ejection device characterized in that, at a predetermined timing when the leak determination process and the inspection drive are not performed, the voltage application unit is controlled to put it in the applied state, and an update process is performed to update the threshold value information stored in the memory unit based on the value of the non-driven signal at this time.

2. a cap in which the electrode is housed and which covers the nozzle; a switching means for switching between a capped state in which the nozzle is covered with the cap and an uncapped state in which the cap is separated from the nozzle, The control unit is When the inspection drive is performed, the switching means is controlled to set the cap state, 2. The liquid ejection device according to claim 1, wherein when the voltage application unit is controlled to be in the voltage applied state in the renewal process, the switching means is controlled to be in the uncapped state.

3. The control unit is A liquid ejection device as described in claim 1 or 2, characterized in that, in the update process, the threshold information stored in the memory unit is updated to a value whose difference from the value of the non-driven signal when the voltage application unit is controlled to be in the voltage applied state is a predetermined amount.

4. The signal output unit is a first circuit that outputs a signal corresponding to a DC component of the voltage of the electrode; A liquid ejection device as described in any one of claims 1 to 3, characterized in that it has a second circuit that outputs a signal that changes at a predetermined period in response to a change in voltage of the electrode when liquid is ejected from the nozzle toward the electrode in the applied state.

5. 5. The liquid ejection device according to claim 1, wherein the predetermined timing includes a timing immediately after it is determined in the leak determination process that the leak current is flowing.

6. 6. The liquid ejection device according to claim 1, wherein the predetermined timing includes a timing immediately after the introduction of liquid into the liquid ejection head is completed during the manufacture of the liquid ejection device.

7. a purge means for purging the liquid inside the liquid ejection head; a liquid tank connected to the liquid ejection head and storing liquid to be ejected from the nozzles; When the liquid ejection device is manufactured, the liquid ejection head is filled with a storage liquid different from the liquid to be ejected from the nozzles, The control unit is before a first use of the liquid ejection device, the purging means is caused to perform the purging, thereby discharging the storage liquid from within the liquid ejection head, and an initial introduction is performed in which liquid is introduced from the liquid tank to the liquid ejection head for ejection from the nozzles; 7. The liquid ejection apparatus according to claim 1, wherein the predetermined timing includes a timing immediately after the initial introduction is completed.

8. 8. The liquid ejection device according to claim 1, wherein the predetermined timing includes a timing when a predetermined time has elapsed since a previous update process.

9. a purge means for purging the liquid inside the liquid ejection head, The control unit periodically causes the purging means to perform the purging, 9. The liquid ejection device according to claim 1, wherein the predetermined timing includes a timing for causing the purging means to periodically perform the purging.

10. 10. The liquid ejection device according to claim 1, wherein the predetermined timing includes a timing immediately before the leak determination process after the inspection instruction signal is received.

11. A temperature detection unit for detecting a temperature, The storage unit stores information on the temperature detected by the temperature detection unit when the update process is executed, The predetermined timing is A liquid ejection device as described in claim 10, characterized in that it includes a timing after receiving the inspection instruction signal and before the leak determination process when the temperature difference between the temperature detected by the temperature detection unit when the inspection instruction signal is received and the temperature detected by the temperature detection unit and stored in the memory unit the last time the update process was performed is a predetermined temperature difference or more.

12. A temperature detection unit for detecting a temperature, The storage unit is Information on multiple types of temperature ranges that do not overlap with each other, and information indicating which of the plurality of temperature ranges the temperature detected by the temperature detection unit when the update process is executed falls within; The predetermined timing is A liquid ejection device as described in claim 10, characterized in that it includes a timing after receiving the inspection instruction signal and before the judgment process, when the temperature range including the temperature detected by the temperature detection unit when the inspection instruction signal is received is different from the temperature range including the temperature detected by the temperature detection unit and stored in the memory unit the last time the update process was performed.

13. 3. The liquid ejection apparatus according to claim 2, wherein the predetermined timing includes a timing at which a predetermined operation including switching from the capped state to the uncapped state by the switching means is performed.

14. A clock unit that outputs a time signal indicating the time, When the time signal indicating that a predetermined time has come is received as the inspection instruction signal, The update process is not executed, and the leak determination process is executed using the threshold value stored in the storage unit by the previous update process. When the inspection instruction signal, which is different from the time signal indicating that the predetermined time has arrived, is received, Execute the update process, The liquid ejection device according to claim 2 , wherein the leak determination process is performed using the threshold value updated by the update process.

15. a liquid ejection head having a nozzle for ejecting liquid; a signal output section having an electrode and a voltage application section for applying a voltage to the electrode and for outputting a signal corresponding to an electrical change in the electrode; A storage unit that stores a threshold value; A temperature detection unit that detects a temperature; A control unit, The control unit is When an inspection instruction signal is received instructing to inspect whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, updating the threshold value stored in the storage unit; a leakage determination process is executed to determine whether or not a leakage current is flowing between the liquid ejection head and the electrode based on whether or not a value of a non-driven signal, which is a signal acquired from the signal output unit without driving the liquid ejection head, is equal to or less than the threshold value by controlling the voltage application unit to apply a voltage to the electrode; when it is determined in the leak determination process that the leak current is not flowing, the voltage application unit is controlled to be in the applied state, and the liquid ejection head is caused to perform an inspection drive for ejecting liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit; the storage unit stores information on the temperature detected by the temperature detection unit when the threshold value stored in the storage unit is updated; The control unit is When updating the threshold value stored in the storage unit, A liquid ejection device characterized in that the threshold value stored in the memory unit is updated based on the temperature difference between the temperature detected by the temperature detection unit when the inspection instruction signal is received and the temperature detected by the temperature detection unit the last time the threshold value stored in the memory unit was updated.

16. a liquid ejection head having a nozzle for ejecting liquid; a signal output section having an electrode and a voltage application section for applying a voltage to the electrode and for outputting a signal corresponding to an electrical change in the electrode; A storage unit that stores a threshold value; A temperature detection unit that detects a temperature; A control unit, The control unit is When an inspection instruction signal is received instructing to inspect whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, updating the threshold value stored in the storage unit; a leakage determination process is executed to determine whether or not a leakage current is flowing between the liquid ejection head and the electrode based on whether or not a value of a non-driven signal, which is a signal acquired from the signal output unit without driving the liquid ejection head, is equal to or less than the threshold value by controlling the voltage application unit to apply a voltage to the electrode; when it is determined in the leak determination process that the leak current is not flowing, the voltage application unit is controlled to be in the applied state, and the liquid ejection head is caused to perform an inspection drive for ejecting liquid from the nozzle toward the electrode, and a signal is obtained from the signal output unit; The storage unit is Information on multiple types of temperature ranges that do not overlap with each other, and information indicating in which of the plurality of temperature ranges the temperature detected by the temperature detection unit falls when the threshold value stored in the storage unit is updated; The control unit is When updating the threshold value stored in the storage unit, A liquid ejection device characterized in that the threshold value stored in the memory unit is updated based on the temperature range that includes the temperature detected by the temperature detection unit when the inspection instruction signal is received and the temperature range that includes the temperature detected by the temperature detection unit the last time the threshold value stored in the memory unit was updated.

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