JP7639491B2 - Liquid ejection device - Google Patents

Description

The present invention relates to a liquid ejection device that ejects liquid from a nozzle.

As a liquid ejection device that ejects liquid from nozzles, Patent Document 1 describes an inkjet printer that prints by ejecting ink from nozzles. The inkjet printer described in Patent Document 1 executes a head inspection routine that inspects whether ink is ejected normally from each nozzle of the print head. In the head inspection routine, a predetermined potential difference is generated between the print head and an inspection area in the capping member, and the head is positioned in the normal inspection position, thereby bringing the nozzle plate of the print head into contact with the inspection area. Then, it is determined whether the actual measured voltage between the cavity plate of the print head and the inspection area is below the inspection tolerance range. If the actual measured voltage is not below the inspection tolerance range, the system proceeds to inspect whether ink is ejected normally from each nozzle.

If the measured voltage is below the inspection tolerance range, it is assumed that a large current leak is occurring, and the print head is moved away from the capping member to perform an empty suction process. The empty 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 empty 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.

JP 2007-136858 A

In Patent Document 1, as described above, the nozzle plate of the print head is brought into contact with the inspection area in the capping member while a predetermined potential difference is generated between the inspection area and the capping member. If the measured voltage is below the inspection tolerance range in this state, an empty suction process is executed, and it is determined again whether the measured voltage is below the inspection tolerance range. In Patent Document 1, the state in which a predetermined potential difference is generated between the inspection area and the capping member continues during this time. Therefore, if a large current leak occurs, the ink in the capping member is discharged by the empty suction process, and the state in which a large current leak occurs continues for the period until the measured voltage rises within the inspection tolerance range, which may damage the nozzle.

The object of the present invention is to provide a liquid ejection device that can prevent damage to the nozzle caused by current leakage.

The liquid ejection device of the present invention includes a liquid ejection head having a nozzle that ejects liquid, a cap that covers the nozzle, a liquid amount detection means that detects the amount of liquid in the cap, an electrode arranged in the cap, and a voltage application unit that applies a voltage to the electrode. The liquid ejection device is equipped with a signal output unit that outputs a judgment signal according to an electrical change in the electrode, a memory unit that stores a threshold value related to the amount of liquid in the cap, and a control unit. When the control unit receives an inspection instruction signal that instructs the inspection of whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, if the amount of liquid in the cap detected by the liquid amount detection means is less than the threshold value, the control unit causes the liquid ejection head to perform an inspection drive to eject liquid from the nozzle toward the electrode in an inspection acceptance state in which the nozzle is covered by the cap and a voltage is applied to the electrode by the voltage application unit, obtains the judgment signal from the signal output unit, and performs an inspection process to determine whether the nozzle is the abnormal nozzle based on the judgment signal. If the amount of liquid in the cap is equal to or greater than the threshold value, the control unit does not perform the inspection process.

The liquid ejection device of the present invention includes a liquid ejection head having a nozzle that ejects liquid, a cap that covers the nozzle, a liquid amount detection means that detects the amount of liquid in the cap, an electrode arranged in the cap, and a voltage application unit that applies a voltage to the electrode, and includes a signal output unit that outputs a judgment signal corresponding to an electrical change in the electrode, a memory unit that stores a threshold value related to the amount of liquid in the cap, and a control unit. When the control unit receives an inspection instruction signal that instructs the inspection of whether the nozzle is an abnormal nozzle having an abnormality in ejecting liquid, if the amount of liquid in the cap detected by the liquid amount detection means is less than the threshold value, the control unit causes the liquid ejection head to perform an inspection drive to eject liquid from the nozzle toward the electrode in an inspection acceptance state in which the nozzle is covered by the cap and a voltage is applied to the electrode by the voltage application unit, obtains the judgment signal from the signal output unit, and performs an inspection process to determine whether the nozzle is the abnormal nozzle based on the judgment signal. If the amount of liquid in the cap is equal to or greater than the threshold value, the control unit performs a predetermined process different from the inspection process and then performs the inspection process.

This invention can prevent short circuits between the electrodes and the liquid ejection head, which could damage the nozzles.

1 is a schematic diagram illustrating a configuration of a printer according to an embodiment of the present invention. 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. FIG. 1A is a diagram showing the change in potential of the detection electrode when ink is ejected from the nozzle, and FIG. 1B is a diagram showing the change in potential of the detection electrode when ink is not ejected from the nozzle. FIG. 2 is a block diagram showing the electrical configuration of the printer. 10A is a flowchart showing a flow of processing by the control unit when an inspection instruction signal is received, and FIG. 10B is a flowchart showing a flow of processing by the control unit when a recording command is received. 11A and 11B are diagrams for explaining discharge between the ink in the cap and the nozzle surface. 10 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in the first modified example. 13 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in Modification 2. 13A is a flowchart showing the flow of processing by the control unit when an inspection instruction signal is received in variant example 3, and FIG. 13B is a flowchart showing the flow of processing by the control unit when a recording command is received in variant example 3. 13A is a flowchart showing the processing flow by the control unit when an inspection instruction signal is received in variant example 4, and FIG. 13B is a diagram for explaining a table that associates the voltage applied to the detection electrode with a threshold value in variant example 4. 13 is a flowchart showing a flow of processing by a control unit when an inspection instruction signal is received in Modification 5. 13A is a flowchart showing the flow of processing performed by the control unit when power is supplied to the printer in variant example 6, and FIG. 13B is a flowchart showing the flow of processing by the control unit when an inspection instruction signal is received in variant example 6. FIG. 4A is a diagram illustrating the case where ink in the cap comes into contact with the nozzle surface, and FIG. 4B is a diagram illustrating the case where an ink column is formed between the detection electrode and the nozzle surface.

A preferred embodiment of the present invention is described below.

<Overall printer configuration>
As shown in FIG. 1, a printer 1 according to this embodiment (the "liquid ejection device" of the present invention) 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 (the "recovery means" of the present invention), and the like.

The carriage 2 is supported by two guide rails 11, 12 that extend 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.

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 from the one positioned to the right in the scanning direction, they store black, yellow, cyan, and magenta ink (the "liquid" of the present invention). The subtank 3 is connected to the four ink cartridges 14 attached to the cartridge holder 13 via four tubes 15. In this way, the four colors of ink are supplied to the subtank 3 from the four ink cartridges 14.

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 also ejects ink from multiple nozzles 10 formed on its lower surface, the nozzle surface 4a. More specifically, the multiple 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. From the multiple nozzles 10, black, yellow, cyan, and magenta inks are ejected from the nozzle row 9 on the right side of the scanning direction.

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

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 the maintenance position to the right of the platen 5 in the scanning direction, the multiple nozzles 10 face the cap 71.

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 multiple 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 contact with the nozzle surface 4a, resulting in a capped state in which the multiple 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 covering the multiple nozzles 10 by coming into contact with the nozzle surface 4a. The cap 71 may cover the multiple nozzles 10 by coming into contact with a frame (not shown) or the like that is arranged around the nozzle surface 4a of the inkjet head 4, for example.

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 to perform a so-called suction purge (the "recovery operation" of the present invention) in which ink is discharged from inside the inkjet head 4 through the multiple nozzles 10. The ink discharged by the suction purge is stored in the waste liquid tank 73.

For the sake of 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 purging. However, this is not limited to the above. 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 purging. 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 purging.

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

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 (the "voltage application section" of the present invention) via a resistor 79. The high-voltage power supply circuit 77 applies a predetermined positive voltage (e.g., about 600 V) to the detection electrode 76. Meanwhile, the inkjet head 4 is held at ground potential. This creates a predetermined potential difference between the inkjet head 4 and the detection electrode 76. A determination circuit 78 is connected to the detection electrode 76. The determination circuit 78 compares the voltage value of the signal output from the detection electrode 76 with a threshold value Vt, and outputs a signal according to the result.

To explain in more detail, since a potential difference occurs between the inkjet head 4 and the detection electrode 76, the ink ejected from the nozzle 10 is charged. When ink is ejected from the nozzle 10 toward the detection electrode 76 with the carriage 2 positioned in the maintenance position, as shown in FIG. 3(a), the charged ink approaches the detection electrode 76, and the potential of the detection electrode 76 drops from the voltage Va when the inkjet head 4 is not driven until the ink lands on the detection electrode 76, and reaches a voltage Vb lower than the voltage Va. Then, after the charged ink lands on the detection electrode 76, the voltage of the detection electrode 76 gradually rises and returns to the voltage Va. That is, the voltage of the detection electrode 76 changes during the drive period Td of the inkjet head 4.

On the other hand, when ink is not being ejected from the nozzle 10, as shown in FIG. 3B, the voltage of the detection electrode 76 hardly changes from the voltage Va during the drive period Td of the inkjet head 4. Therefore, the judgment circuit 78 is set with a threshold value Vt (Vb<Vt<Va) to distinguish between these. The judgment circuit 78 compares the minimum value of the voltage output from the detection electrode 76 with the threshold value Vt during the drive period Td of the inkjet head 4, and outputs a judgment signal according to the judgment result. In this embodiment, the combination of the detection electrode 76, the high voltage power supply circuit 77, the resistor 79, and the judgment circuit 78 corresponds to the "signal output unit" of the present invention. The signal output unit outputs a judgment signal according to whether the nozzle 10 is an abnormal nozzle that does not eject ink.

In addition, here, a positive voltage is applied to the detection electrode 76 by the high voltage power supply circuit 77, but a negative voltage (for example, about -600V) may be applied to the detection electrode 76 by the high voltage power supply circuit 77. In this case, contrary to the above, when ink is ejected from the nozzle 10 toward the detection electrode 76 with the carriage 2 positioned in the maintenance position, the charged ink approaches the detection electrode 76, and the potential of the detection electrode 76 rises from voltage Va until the ink lands on the detection electrode 76, and after the ink lands on the detection electrode 76, the voltage of the detection electrode 76 gradually decreases and returns to voltage Va.

<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 transport 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 a determination signal from a determination circuit 78.

In addition to the components described above, the printer 1 also includes a clock unit 67. The clock unit 67 keeps track of time and outputs a time signal indicating the current time. The control unit 80 receives the time signal from the clock unit 67.

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 a single CPU 81 performs processes independently, or one in which multiple CPUs 81 share the processing. The control unit 80 may be one in which a single ASIC 85 performs processes independently, or one in which multiple ASICs 85 share the processing.

<Processing upon receipt of inspection instruction signal>
Next, the process performed 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. When an inspection instruction signal is received, the control unit 80 performs the process according to the flow of FIG. 5A. For example, when a user operates an operation unit (not shown) 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, 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 signal indicating that the predetermined time has been reached is transmitted from the clock unit 67, the control unit 80 receives this signal as an inspection instruction signal.

To explain the flow of FIG. 5(a) in more detail, when the inspection instruction signal is received, the control unit 80 judges whether the ink amount X in the cap 71 is less than the threshold value Xt (S101) (the "liquid amount judgment process" of the present invention). Here, the control unit 80 stores the number of ink ejections from each nozzle 10 and the number of suction purges since the last empty suction in the flash memory 84. In S101, the ink amount X is calculated based on these, and it is judged whether the calculated ink amount X is less than the threshold value Xt. In this case, the control unit 80 also serves as the "liquid amount detection unit" of the present invention. Alternatively, the cap 71 is provided with a liquid amount sensor that detects that the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, and in S101, it is judged whether the ink amount X is less than the threshold value Xt based on the detection result of this liquid amount sensor. In this case, the liquid amount sensor corresponds to the "liquid amount detection unit" of the present invention.

In addition, as shown in FIG. 6, when a voltage is applied to the detection electrode 76 in the capped state, the threshold value Xt is set to an amount of ink that is less than the minimum amount of ink that would cause a short circuit between the detection electrode 76 and the nozzle surface 4a due to a discharge occurring between the ink I in the cap 71 and the ink in the nozzle 10.

If the ink amount X is equal to or greater than the threshold value Xt (S101: NO), the process ends. In other words, the control unit 80 does not perform the inspection to determine whether the nozzle 10 is an abnormal nozzle, which will be described next.

If the ink amount X is less than the threshold value Xt (S101: YES), the control unit 80 then executes the capping process (S102). In the capping process, the control unit 80 controls the carriage motor 86, the cap lifting mechanism 88, etc. to achieve the above-mentioned capped state. If the capped state is reached when the inspection instruction signal is received, the capped state is maintained in S102. Next, the control unit 80 controls the high-voltage power supply circuit 77 to apply a voltage to the detection electrode 76 (S103). This results in a state in which a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77 in the capped state (the "inspection acceptance state" of the present invention).

Then, in the above-mentioned inspection acceptance state, the control unit 80 executes the inspection drive process (S104). In the inspection drive process, the control unit 80 controls the inkjet head 4 to perform inspection drive for each of the multiple nozzles 10 of the inkjet head 4, and acquires a judgment signal from the judgment circuit 78. The inspection drive refers to driving the inkjet head 4 to eject ink from the nozzles 10. Note that in this embodiment, the process of S102 to S104 in combination corresponds to the "inspection process" of the present invention.

After the above test drive process, the control unit 80 controls the high voltage power supply circuit 77 to stop applying voltage to the detection electrode 76 (S105). Next, the control unit 80 determines whether or not there is an abnormal nozzle based on the determination signal acquired during the test drive process (S106). If there is no abnormal nozzle (S106: NO), the process ends. If there is an abnormal nozzle (S106: YES), the control unit 80 stores a recovery flag in the flash memory 84 (S107) and then ends the process.

<Processing when a recording command is received>
Next, there will be described the process that the control unit 80 performs when it receives a recording command (the "ejection command signal" of the present invention) that instructs recording on the recording paper P. When it receives the recording command, the control unit 80 performs the process according to the flow of FIG.

In more detail, when a recording command is received, the control unit 80 determines whether a recovery flag is stored in the flash memory 84 (S201). If a recovery flag is not stored in the flash memory 84 (S201: NO), the process proceeds directly to S204. If a recovery flag is stored in the flash memory 84 (S201: YES), the control unit 80 executes a purge process (S202), erases the recovery flag stored in the flash memory 84 (S203), and then proceeds to S204. In the purge process of S202, the control unit 80 controls the suction pump 72 and the like to perform suction purging. As a result, in this embodiment, if it is determined that an abnormal nozzle exists in the inspection process, the abnormal nozzle is recovered by suction purging when the first recording command is received after the inspection process.

In S204, the control unit 80 executes a recording process. In the recording process, 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 the inkjet head 4 ejects ink from the multiple nozzles 10 toward the recording paper P, and a transport motor 87 to cause the transport rollers 6 and 7 to transport the recording paper P a predetermined distance, thereby recording on the recording paper P.

＜Effects＞
In this embodiment, the detection electrode 76 and the inkjet head 4 may be shorted out via the ink in the cap 71. If the detection electrode 76 and the inkjet head 4 are shorted out, a large leakage current flows through the inkjet head 4 when a voltage is applied to the detection electrode 76 by the high-voltage power supply circuit 77, causing damage to the nozzles 10. On the other hand, when the amount of ink X in the cap 71 is small (less than the threshold value Xt), the detection electrode 76 and the inkjet head 4 are unlikely to be shorted out via the ink in the cap 71. On the other hand, when the amount of ink X in the cap 71 is large (greater than the threshold value Xt), the detection electrode 76 and the inkjet head 4 are likely to be shorted out via the ink in the cap 71.

In this embodiment, when an inspection command signal is received, if the ink amount X in the cap 71 is less than the threshold value Xt, the inspection process is executed. This allows the inspection process to be executed in a state where there is a low possibility of a short circuit between the detection electrode 76 and the inkjet head 4.

On the other hand, when an inspection instruction signal is received, if the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, the inspection process is not executed. This prevents a short circuit between the detection electrode 76 and the inkjet head 4 and damage to the nozzle 10 by not executing the inspection process that involves applying an electrode voltage to the detection electrode 76 when there is a high possibility of the detection electrode 76 and the inkjet head 4 shorting out.

In addition, in this embodiment, the threshold value Xt is set to an amount equal to or less than the minimum amount of ink that causes a short circuit between the detection electrode 76 and the inkjet head 4 due to discharge between the ink I in the cap 71 and the ink in the nozzle 10 when a voltage is applied to the detection electrode 76. In this way, it is possible to determine whether or not a short circuit will occur between the detection electrode 76 and the inkjet head 4 based on whether or not the ink amount X in the cap 71 is less than the threshold value Xt.

In addition, in this embodiment, if an abnormal nozzle is present, the abnormal nozzle can be restored by suction purging.

In addition, in this embodiment, if an abnormal nozzle is present, the abnormal nozzle is restored by suction purging when the first ejection instruction signal is received after the inspection process. This allows the abnormal nozzle to be restored immediately before ink is ejected from the nozzle 10 toward the recording paper P to perform recording.

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

In the above embodiment, when the ink amount X is equal to or greater than the threshold value Xt, the nozzle 10 is not inspected to see if it is an abnormal nozzle, but this is not limited to the above.

In the first modification, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow in FIG. 7. To explain in more detail, in the first modification, similar to the above embodiment, if the ink amount X is less than the threshold value Xt (S101: YES), the control unit 80 performs the processing in S102 to S107.

On the other hand, in variant 1, if the ink amount X is equal to or greater than the threshold value Xt (S101: NO), the control unit 80 executes an empty suction process (the "predetermined process" and "discharge process" of the present invention) (S301), and then executes the processes of S102 to S107. In the empty suction process of S301, the control unit 80 controls the cap lift mechanism 88 to enter the uncapped state, and then drives the suction pump 72 to perform empty suction. Note that in variant 1, the maintenance unit 8 for performing suction purge and empty suction doubles as the "recovery means" and "discharge means" of the present invention.

In the first modification, when an inspection command signal is received, if the ink amount X in the cap 71 is less than the threshold value Xt, the inspection process is executed. This allows the inspection process to be executed in a state where there is a low possibility of a short circuit between the detection electrode 76 and the inkjet head 4.

On the other hand, when an inspection instruction signal is received, if the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, the ink in the cap 71 is discharged by empty suction, and then the inspection process is performed. This makes it possible to perform the inspection process in a state where there is a low possibility of a short circuit between the detection electrode 76 and the inkjet head 4.

In addition, in the first modified example, when the ink amount X is equal to or greater than the threshold value Xt, empty suction is performed immediately, but this is not limited to this.

In the second modification, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow in FIG. 8. To explain in more detail, in the second modification, similar to the above embodiment, when the ink amount X is less than the threshold value Xt (S101: YES), the control unit 80 performs processing from S102 to S107.

On the other hand, in the second modification, when the ink amount X is equal to or greater than the threshold value Xt (S101: NO), the control unit 80 controls the high-voltage power supply circuit 77 in the above-mentioned capped state to apply a voltage to the detection electrode 76 temporarily (for example, for about 10 ms) (S401). Then, based on the voltage of the detection electrode 76 when the voltage is temporarily applied to the detection electrode 76, it is determined whether or not the detection electrode 76 and the inkjet head 4 are actually shorted (S402, the "short circuit determination process" of the present invention). When the detection electrode 76 and the inkjet head 4 are shorted, a current flows between the detection electrode 76 and the inkjet head 4, so that the absolute value of the voltage of the detection electrode 76 when a voltage is applied to the detection electrode 76 becomes smaller. Therefore, based on whether the voltage of the detection electrode 76 is lower than a predetermined voltage, it is possible to determine whether or not the detection electrode 76 and the inkjet head 4 are actually shorted.

If the detection electrode 76 and the inkjet head 4 are not actually shorted (S402: NO), the control unit 80 executes the processes of S102 to S107 as is. If the detection electrode 76 and the inkjet head 4 are actually shorted based on the potential of the detection electrode 76 (S402: YES), the control unit 80 executes the empty suction process (S301) as in the first modification, and then executes the processes of S102 to S107.

Here, even if the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, when a voltage is applied to the detection electrode 76 in the capped state, a short circuit may not actually occur between the detection electrode 76 and the inkjet head 4.

In the second modification, when an inspection instruction signal is received and the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, a voltage is temporarily applied to the detection electrode 76 in the capped state, and a short circuit determination process is executed to determine whether or not the detection electrode 76 and the inkjet head 4 are shorted based on the signal output from the determination circuit 78. If the detection electrode 76 and the inkjet head 4 are not shorted, an inspection process is executed. This allows the inspection process to be executed in a state where the detection electrode 76 and the inkjet head 4 are not shorted. Furthermore, since a voltage is only temporarily applied to the detection electrode 76 at this time, even if the detection electrode 76 and the inkjet head 4 are shorted, the nozzle 10 will not be significantly damaged.

On the other hand, if the detection electrode 76 and the inkjet head 4 are actually shorted, empty suction is performed to drain the ink from within the cap 71 before the inspection process is performed. This makes it possible to perform the inspection process in a state where there is a low possibility of the detection electrode 76 and the inkjet head 4 shorting out.

In addition, in the second modification, when the detection electrode 76 and the inkjet head 4 are actually shorted, the ink in the cap 71 is discharged by performing empty suction before the inspection process is performed, but this is not limited to the above. When the detection electrode 76 and the inkjet head 4 are actually shorted, the inspection process may not be performed.

Also, if it is determined that the detection electrode 76 and the inkjet head 4 are actually shorted, the inkjet head 4 may be uncapped and an inspection process may be performed.

In addition, in the above embodiment, the same process is executed when the ink amount X is equal to or greater than the threshold value Xt, regardless of whether the inspection instruction signal is an inspection instruction signal sent by user operation or a signal indicating that a specified time has arrived, but this is not limited to the above.

In the third modification, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow in FIG. 9(a). To explain in more detail, in the third modification, similar to the above embodiment, when the ink amount X is less than the threshold value Xt (S101: YES), the control unit 80 performs processing in S102 to S107.

On the other hand, in the third modification, if the ink amount X is equal to or greater than the threshold value Xt (S101: NO), the control unit 80 determines whether the received inspection instruction signal is a time signal indicating that it is a predetermined time (S501). If the received inspection instruction signal is not a time signal indicating that it is a predetermined time (S501: NO), the control unit 80 performs the empty suction process (S301) as in the first modification, and then performs the processes of S102 to S107 as in the above embodiment.

If the received inspection instruction signal is a time signal indicating that it is the specified time (S501: YES), the control unit 80 stores the inspection flag in the flash memory 84 (S502) and ends the process without executing the processes of S102 to S107.

In addition, in the third modification, when the control unit 80 receives a recording command, it performs processing according to the flow in FIG. 9(b). More specifically, when the control unit 80 receives a recording command, it determines whether or not an inspection flag is stored in the flash memory 84 (S601). If an inspection flag is not stored in the flash memory 84 (S601: NO), the control unit 80 performs the same processing of S201 to S204 as in the above embodiment.

If an inspection flag is stored in the flash memory 84 (S601: YES), the control unit 80 executes the same empty suction process as S301 (S602), and then executes the same processes of S603 to S606 as S102 to S105.

If there is no abnormal nozzle (S607: NO), the control unit 80 executes the recording process of S204. If there is an abnormal nozzle (S607: YES), the control unit 80 executes the processes of S202 to S204.

In variant 3, an inspection instruction signal is received each time a specified time is reached. In such cases, the specified time is often set to a time when it is undesirable for the printer 1 to generate noise, such as late at night when the printer 1 is not in use. On the other hand, dry suction generates a louder noise than inspection drive because the cap 71 is lowered to achieve an uncapped state and the suction pump 72 is driven. Therefore, unlike variant 3, if dry suction is performed and then inspection processing is executed when the ink amount X in the cap 71 is equal to or greater than the threshold value Xt at the specified time, the sound generated by dry suction becomes audible noise.

Therefore, in the third modification, when a signal indicating that the specified time has come is received as an inspection instruction signal, if the ink amount X in the cap 71 is equal to or greater than the threshold value Xt, the inspection process is not executed at the specified time. Then, when a recording command is first received thereafter, dry suction is performed, followed by the inspection process, and then the recording process. This makes it possible to execute the inspection process in a state where there is a low possibility of a short circuit between the detection electrode 76 and the inkjet head 4. Also, the inspection process can be executed immediately before ink is ejected from the nozzle 10 toward the recording paper P to perform recording. Also, by not executing dry suction at the specified time, it is possible to prevent a loud noise that could become a disturbance from being generated at the specified time.

In addition, in the above embodiment, one type of voltage is applied to the detection electrode 76, and correspondingly, one type of threshold value Xt is also applied, but this is not limited to the above.

In the fourth modification, the high voltage power supply circuit 77 selectively applies either the first voltage V1 or the second voltage V2, which is lower than the first voltage, to the detection electrode 76 depending on, for example, the environment in which the printer 1 is used. For example, when the outside air temperature is high, the moisture in the ink evaporates more easily in the cap 71 than when the outside air temperature is low, and the amount of moisture in the air in the cap 71 is greater, so that leakage current is more likely to flow. Also, for example, when the humidity is high, the amount of moisture in the air in the cap 71 is greater than when the humidity is low, so that leakage current is more likely to flow. Also, for example, immediately after flushing is performed to eject ink from the nozzle 10 toward the cap 71, the amount of moisture in the air in the cap 71 is greater, so that leakage current is more likely to flow. Therefore, in the fourth modification, for example, when the amount of moisture in the air in the cap 71 is estimated to be low, the first voltage V1 is applied to the detection electrode 76, and when the amount of moisture in the air in the cap 71 is estimated to be high, the second voltage V2 is applied to the detection electrode 76.

When the control unit 80 receives an inspection instruction signal, it performs processing according to the flow in FIG. 10(a). To explain in more detail, in the fourth modification, when the control unit 80 receives an inspection instruction signal, it sets the threshold value Xt (S701) and then performs the same processing of S101 to S107 as in the above embodiment.

In the fourth modification, a table is stored in the flash memory 84 that associates the voltage V applied to the detection electrode 76 with the threshold value Xt, as shown in FIG. 10(b). In S701, the threshold value Xt is set based on the voltage applied to the detection electrode 76 by the high-voltage power supply circuit 77 and the table in FIG. 10(b).

The first threshold value Xt1 in FIG. 10(b) is set to an amount less than the minimum amount at which a discharge occurs between the ink I in the cap 71 and the nozzle surface 4a when the first voltage V1 is applied to the detection electrode 76 in the capped state, causing a short circuit between the detection electrode 76 and the nozzle surface 4a. The second threshold value Xt2 in FIG. 10(b) is greater than the first threshold value Xt1. The second threshold value Xt2 is set to an amount less than the minimum amount at which a discharge occurs between the ink I in the cap 71 and the nozzle surface 4a when the second voltage V2 is applied to the detection electrode 76 in the capped state, causing a short circuit between the detection electrode 76 and the nozzle surface 4a.

The higher the voltage applied to the detection electrode 76, the greater the potential difference between the detection electrode 76 and the inkjet head 4, and the greater the change in voltage of the detection electrode 76 when the test drive is performed; however, when the ink amount X in the cap 71 is small, the detection electrode 76 and the inkjet head 4 are more likely to short out. On the other hand, in the fourth modification, during the test process, either the first voltage V1 or the second voltage V2 is selectively applied to the detection electrode 76 depending on the environment in which the printer 1 is used, etc.

Therefore, in the fourth modification, when the first voltage V1 is applied to the detection electrode 76 in the inspection process, the inspection process is executed when the ink amount X in the cap 71 is less than the first threshold value Xt1. When the second voltage V2 is applied to the detection electrode 76 in the inspection process, the inspection process is executed when the ink amount X in the cap 71 is less than the second threshold value Xt2. This makes it possible to execute the inspection process in a state where the detection electrode 76 and the inkjet head 4 are unlikely to short out, regardless of the voltage applied between them. It is also possible to make it less likely that the inspection process will not be executed even when there is a high possibility of the detection electrode 76 and the inkjet head 4 shorting out.

In the fourth modification, an example was described in which the threshold value Xt was set according to the voltage V applied to the detection electrode 76 in the above embodiment, but this is not limiting. In the first to third modifications, the threshold value Xt may be set according to the voltage V applied to the detection electrode 76, as in the fourth modification.

In the fifth modification, the high voltage power supply circuit 77 selectively applies either a first voltage V1 or a second voltage V2 lower than the first voltage to the detection electrode 76. Furthermore, when the control unit 80 receives an inspection instruction signal, it performs processing according to the flow of FIG. 11.

In more detail, in the fifth modification, if the ink amount X is less than the first threshold value Xt1 (S801: YES), the control unit 80 sets the voltage V to be applied to the detection electrode 76 to the first voltage V1 (S802), and executes the same processes of S102 to S107 as in the above embodiment. In this case, in S103, the first voltage V1 is applied to the detection electrode 76.

If the ink amount X is equal to or greater than the first threshold value Xt1 (S801: NO) and is less than the second threshold value Xt2, which is greater than the first threshold value Xt1 (S803: YES), the control unit 80 sets the voltage V to be applied to the detection electrode 76 to the second voltage V2 (S804) and executes the same processes of S102 to S107 as in the above embodiment. In this case, the second voltage V2 is applied to the detection electrode 76 in S103.

If the ink amount X is equal to or greater than the second threshold value Xt2 (S803: NO), the control unit 80 performs the same idle suction process as in S301 (S805), sets the voltage V to be applied to the detection electrode 76 to the first voltage V1 (S806), and performs the same processes of S102 to S107 as in the above embodiment. In this case, in S103, the first voltage V1 is applied to the detection electrode 76.

The higher the voltage applied to the detection electrode 76, the larger the potential difference between the detection electrode 76 and the inkjet head 4, and the larger the change in voltage of the detection electrode 76 when the test drive is performed. In other words, from the viewpoint of increasing the change in voltage of the detection electrode 76 when the test drive is performed, it is preferable to apply a high voltage to the test electrode 76. On the other hand, the higher the voltage of the test electrode 76, the more likely it is that the detection electrode 76 and the inkjet head 4 will short out when the ink amount X in the cap 71 is smaller. In other words, from the viewpoint of preventing the detection electrode 76 and the inkjet head 4 from shorting out, it is preferable to apply a low voltage to the test electrode 76.

Therefore, in the fifth modification, if the ink amount X in the cap 71 is less than the first threshold value Xt1, a first voltage V1 is applied to the detection electrode 76 in the inspection process. If the ink amount X in the cap 71 is equal to or greater than the first threshold value Xt1 and less than the second threshold value Xt2, a second voltage V2 is applied to the detection electrode 76 in the inspection process. This allows the inspection drive to be performed by applying as high a voltage as possible to the detection electrode 76 according to the ink amount X in the cap 71, within a range where the possibility of a short circuit between the detection electrode 76 and the inkjet head 4 is low.

In the sixth modification, while power is being supplied to the printer 1, the control unit 80 performs processing in accordance with the flow in FIG. 12(a). Also, in the sixth modification, when the control unit 80 receives an inspection instruction signal, it performs processing in accordance with the flow in FIG. 12(b).

To explain the flow of FIG. 12(a) in detail, the control unit 80 is in standby when it has not received a signal from the clock unit 67 indicating that the second time has arrived (S901: NO). Here, the second time is a time prior to the first time. The first time is a time, such as late at night, when it is undesirable for the printer 1 to generate sound. The second time is a time, such as early evening, when it is permissible for the printer 1 to generate sound.

When a signal indicating that the second time has arrived is received from the clock unit 67 (S901: YES), the control unit 80 determines whether the ink amount X is less than the threshold value Xt (S902, the "previous liquid amount determination process" of the present invention). If the ink amount X is less than the threshold value Xt (S902: YES), the process returns to S901. If the ink amount X is equal to or greater than the threshold value Xt (S902: NO), the control unit 80 performs the same empty suction process as S301 (S903) and then returns to S901.

To explain the flow of FIG. 12(b) in more detail, when the inspection instruction signal is received, if the ink amount X is less than the threshold value Xt (S101: YES), the control unit 80 executes the same processes of S102 to S107 as in the above embodiment.

If the ink amount X is equal to or greater than the threshold value Xt (S101: NO) and the inspection instruction signal is a time signal indicating that it is the first time received from the clock unit 67 (S1001: YES), the process ends without executing S102 to S107. If the inspection instruction signal is a signal other than a time signal indicating that it is the first time received from the clock unit 67 (S1001: NO), the control unit 80 executes the same empty suction process as S301 (S1002), and then executes S102 to S107 as in the above embodiment.

In variant 6, an inspection instruction signal is received each time the first time occurs. In such a case, the first time is often set to a time when it is undesirable for the printer 1 to generate noise, such as late at night when the printer 1 is not in use. On the other hand, dry suction generates a louder noise than inspection drive because the cap 71 is lowered to achieve the uncapped state and the suction pump 72 is driven. Therefore, unlike variant 6, if dry suction is performed and then inspection processing is executed when the ink amount X in the cap 71 is equal to or greater than the threshold value Xt at the first time, the sound generated by dry suction becomes audible noise.

Therefore, in variant 6, if the ink amount X in the cap 71 at a second time before the first time is equal to or greater than the threshold value Xt, empty suction is performed at the second time to drain the ink in the cap 71. This increases the likelihood that the ink amount X in the cap 71 will be less than the threshold value Xt at the first time. As a result, it increases the likelihood that the inspection process can be performed when the first time arrives.

In addition, in the sixth modified example, if the ink amount X is equal to or greater than the threshold value Xt (S101: NO) and the inspection instruction signal is a signal indicating that it is the first time received from the clock unit 67 (S1001: YES), the process is terminated as is, but this is not limited to this. For example, if the ink amount X is equal to or greater than the threshold value Xt (S101: NO), the process of S102 to S107 may be performed after the empty suction process is performed regardless of whether the inspection instruction signal is a signal indicating that it is the first time received from the clock unit 67. In this case, the empty suction process may be performed at the first time. However, even in this case, the empty suction process is performed at the second time if the ink amount X is equal to or greater than the threshold value Xt, so that the ink amount X is less likely to be equal to or greater than the threshold value Xt at the first time compared to the case where the empty suction process is not performed at the second time. Therefore, the frequency of empty suction, which causes noise problems, at the first time can be reduced.

In addition, in the above embodiment, the threshold value Xt was set to an amount less than the minimum amount at which a short circuit occurs between the detection electrode 76 and the nozzle surface 4a due to discharge occurring between the ink I in the cap 71 and the nozzle surface 4a when a voltage is applied to the detection electrode 76 in the capped state, but this is not limited to this.

For example, the threshold value Xt may be set to an amount less than the minimum amount of ink that allows the ink I in the cap 71 to come into contact with the nozzle surface 4a in the capped state, as shown in FIG. 13(a).

If the threshold value Xt is set to an amount equal to or less than the minimum amount of ink at which the ink in the cap 71 and the ink in the nozzle 10 come into contact and cause a short circuit between the detection electrode 76 and the inkjet head 4, it is possible to determine whether or not a short circuit will occur between the detection electrode 76 and the inkjet head 4 based on whether or not the ink amount X in the cap 71 is less than the threshold value Xt.

Alternatively, for example, as shown in FIG. 13(b), the threshold value Xt may be set to an amount less than the minimum amount of ink that would form a liquid column J of ink connecting the detection electrode 76 and the nozzle surface 4a in the capped state. The liquid column J is a portion of the ink I in the cap 71 that extends between the detection electrode 76 and the nozzle surface 4a due to its own surface tension, connecting them.

If the threshold value Xt is set to an amount equal to or less than the minimum amount of ink at which a short circuit occurs between the detection electrode 76 and the inkjet head 4 via the liquid column J formed between the nozzle surface 4a and the detection electrode 76, it is possible to determine whether or not a short circuit occurs between the detection electrode 76 and the inkjet head 4 based on whether or not the amount of ink X in the cap 71 is less than the threshold value Xt.

Alternatively, the threshold value Xt may be set to another value within a range in which the detection electrode 76 and the inkjet head 4 are not shorted out via the ink in the cap 71 when a voltage is applied to the detection electrode 76 in the capped state.

In the above example, if an abnormal nozzle is present, a recovery flag is stored in the flash memory 84, and if a recovery flag is stored in the flash memory 84 when a recording command is input, a suction purge is performed by the purge process before the recording process is executed, but this is not limited to the above. For example, if an abnormal nozzle is present, a suction purge may be performed immediately.

In the above example, when an abnormal nozzle is present, a uniform suction purge is performed as a recovery operation to discharge ink from the nozzle 10 and recover the 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 that is performed.

In the above example, suction purging is performed as the purging, but this is not limited to this. For example, a pressure pump may be provided midway through the tube 15 connecting the subtank 3 and the ink cartridge 14. Alternatively, a pressure pump connected to the ink cartridge may be provided in the printer. Then, with the multiple nozzles 10 covered with 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 a so-called pressure purging. In this case, the pressure pump corresponds to the "recovery means" of the present invention.

Furthermore, during purging, both suction by the suction pump 72 and pressurization by the pressurization pump may be performed. In this case, the combination of the maintenance unit 8 and the pressurization pump corresponds to the "recovery means" of the present invention.

The recovery operation for discharging ink from the nozzle 10 to recover the abnormal nozzle is not limited to purging. For example, the recovery operation may be to control the inkjet head 4 to perform flushing to discharge ink from at least the abnormal nozzle, thereby recovering the abnormal nozzle. In this case, the inkjet head 4 serves as both the "liquid ejection head" and the "recovery means" of the present invention. The abnormal nozzle may also be recovered by purging and flushing.

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.

In addition, 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 result of the determination as to whether the nozzles 10 that have been subjected to the inspection drive are abnormal or not.

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, a nozzle 10 that has an abnormality other than whether ink is ejected, such as a nozzle 10 that has an abnormality in the direction of ink ejection, may be determined to be an abnormal nozzle.

In the above, we have described an example 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.

Although the above describes an example in which the present invention is applied to a printer that ejects ink from a nozzle to record on recording paper P, the present invention is not limited to this. It 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 devices such as smartphones, cardboard, and plastic members. It can also be applied to liquid ejection devices that eject liquids other than ink, such as liquid resins and metals.

REFERENCE SIGNS LIST 1 printer 4 inkjet head 8 maintenance unit 10 nozzle 67 clock unit 71 cap 76 detection electrode 77 high voltage power supply circuit 78 determination circuit 79 resistor 80 control unit 84 flash memory

Claims (14)

a liquid ejection head having a nozzle for ejecting liquid;
A cap for covering the nozzle;
a liquid amount detection means for detecting the amount of liquid in the cap;
a signal output section that has an electrode disposed in the cap and a voltage application section that applies a voltage to the electrode and outputs a determination signal corresponding to an electrical change in the electrode;
A storage unit that stores a threshold value related to the amount of liquid in the cap;
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,
when the amount of liquid in the cap detected by the liquid amount detection means is less than the threshold value, the nozzle is covered with the cap, and in an inspection acceptance state in which a voltage is applied to the electrode by the voltage application unit, an inspection drive is performed on the liquid ejection head for ejecting liquid from the nozzle toward the electrode, the determination signal is obtained from the signal output unit, and an inspection process is executed to determine whether or not the nozzle is an abnormal nozzle based on the determination signal;
The liquid ejection device is characterized in that, when the amount of liquid in the cap is equal to or greater than the threshold value, the inspection process is not executed. a liquid ejection head having a nozzle for ejecting liquid;
A cap for covering the nozzle;
a liquid amount detection means for detecting the amount of liquid in the cap;
a signal output section that has an electrode disposed in the cap and a voltage application section that applies a voltage to the electrode and outputs a determination signal corresponding to an electrical change in the electrode;
A storage unit that stores a threshold value related to the amount of liquid in the cap;
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,
when the amount of liquid in the cap detected by the liquid amount detection means is less than the threshold value, the nozzle is covered with the cap, and in an inspection acceptance state in which a voltage is applied to the electrode by the voltage application unit, an inspection drive is performed on the liquid ejection head for ejecting liquid from the nozzle toward the electrode, the determination signal is obtained from the signal output unit, and an inspection process is executed to determine whether or not the nozzle is an abnormal nozzle based on the determination signal;
The liquid ejection device according to claim 1, further comprising: a step of: executing a predetermined process different from the inspection process before executing the inspection process when the amount of liquid in the cap is equal to or greater than the threshold value. a liquid discharge means for performing a discharge operation to discharge the liquid in the cap,
3. The liquid ejection device according to claim 2, wherein the predetermined process is a discharge process that causes the liquid discharge means to perform the discharge operation. the predetermined process includes a short circuit determination process for controlling the voltage application unit to temporarily bring the device into the test acceptance state, and determining whether or not a short circuit occurs between the electrode and the liquid ejection head in the test acceptance state based on a signal output from the signal output unit at this time,
The control unit is
The liquid ejection device according to claim 2 , wherein the inspection process is executed when it is determined in the short-circuit determination process that no short circuit occurs between the electrodes and the liquid ejection head in the inspection acceptance state. a liquid discharge means for performing a discharge operation to discharge the liquid in the cap,
The predetermined process further includes a discharge process of causing the liquid discharge means to perform the discharge operation,
The control unit is
When it is determined in the short circuit determination process that the electrode and the liquid ejection head are short-circuited in the inspection acceptance state,
The liquid ejection apparatus according to claim 4 , wherein the inspection process is carried out after the ejection process is carried out. a liquid discharge means for performing a discharge operation to discharge the liquid in the cap;
A clock unit that outputs a time signal indicating the time,
the inspection instruction signal includes the time signal from the clock unit indicating that a predetermined time has arrived,
The control unit is
a liquid amount determination process for determining whether or not the liquid amount in the cap detected by the liquid amount detection means is less than the threshold value when the time signal indicating that the predetermined time has arrived is received;
When the liquid amount determination process determines that the liquid amount in the cap is less than the threshold value,
Executing the inspection process;
When the liquid amount determination process determines that the liquid amount in the cap is equal to or greater than the threshold value,
The inspection process is not executed at the predetermined time,
Then, when a discharge instruction signal for instructing to discharge liquid from the nozzle toward the discharge receiving medium is received for the first time,
causing the liquid discharging means to perform the discharging operation, and then executing the inspection process;
3. The liquid ejection apparatus according to claim 1, wherein after the inspection process is performed, the liquid ejection head is caused to eject liquid from the nozzles toward the ejection receiving medium. the voltage application unit selectively applies to the electrode either a first voltage or a second voltage lower than the first voltage;
The storage unit is
a first threshold value corresponding to a case where the first voltage is applied to the electrodes by the voltage application unit in the test acceptance state; and
a second threshold value corresponding to a case where the second voltage is applied to the electrodes by the voltage application unit in the test acceptance state, the second threshold value being greater than the first threshold value;
The control unit is
When the inspection instruction signal is received, a liquid amount determination process is executed to determine whether or not the liquid amount in the cap detected by the liquid amount detection means is less than the threshold value;
When the voltage application unit applies the first voltage to the electrodes in the test acceptance state,
In the liquid amount determination process, it is determined whether or not the liquid amount in the cap is less than the first threshold value;
When the voltage application unit applies the second voltage to the electrodes in the test acceptance state,
7. The liquid ejection device according to claim 1, wherein in the liquid amount determination process, it is determined whether or not the amount of liquid in the cap is less than the second threshold value. the voltage application unit selectively applies to the electrode either a first voltage or a second voltage lower than the first voltage;
The storage unit is
a first threshold value corresponding to a case where the first voltage is applied to the electrodes by the voltage application unit in the test acceptance state; and
a second threshold value corresponding to a case where the second voltage is applied to the electrodes by the voltage application unit in the test acceptance state, the second threshold value being greater than the first threshold value;
The control unit is
When the inspection instruction signal is received, a liquid amount determination process is executed to determine whether or not the liquid amount in the cap detected by the liquid amount detection means is less than the threshold value;
When it is determined in the liquid amount determination process that the liquid amount in the cap is less than the first threshold value,
In the test processing, the voltage application unit is controlled to apply the first voltage to the electrodes to enter the test acceptance state;
When it is determined in the liquid amount determination process that the liquid amount in the cap is equal to or greater than the first threshold value and less than the second threshold value,
7. The liquid ejection device according to claim 1, wherein, in the inspection process, the voltage application unit is controlled to apply the second voltage to the electrode, thereby entering the inspection acceptance state. A liquid discharge means for performing a discharge operation to discharge the liquid in the cap;
A clock unit that outputs a time signal indicating the time,
the inspection instruction signal includes the time signal output from the clock unit, the time signal indicating that a first time has arrived,
The control unit is
when receiving the time signal from the clock unit, the time signal indicating that a second time has come, which is earlier than the first time, a previous liquid level determination process is executed to determine whether or not the liquid level in the cap detected by the liquid level detection means is less than the threshold value;
A liquid ejection device according to any one of claims 1 to 8, characterized in that, when the previous liquid amount determination process determines that the amount of liquid in the cap is equal to or greater than the threshold value, the liquid ejection means is caused to perform the ejection operation. A liquid ejection device according to any one of claims 1 to 9, characterized in that the threshold value is equal to or less than the minimum amount of liquid at which the liquid in the cap and the liquid in the nozzle are not in contact with each other and discharge occurs between the liquid in the cap and the liquid in the nozzle in the inspection acceptance state. The liquid ejection device according to any one of claims 1 to 9, characterized in that the threshold value is equal to or less than the minimum amount of liquid at which the liquid in the cap and the liquid in the nozzle come into contact. The liquid ejection device according to any one of claims 1 to 9, characterized in that the threshold value is equal to or less than the minimum amount of liquid in the cap that generates a liquid column connecting the liquid ejection head and the electrode. A recovery means for performing a recovery operation to discharge liquid from the nozzle,
The control unit is
13. The liquid ejection apparatus according to claim 1, wherein, when the nozzle determined to be the abnormal nozzle in the inspection process is present, the recovery means is caused to perform the recovery operation. The control unit is
If there is a nozzle that is determined to be an abnormal nozzle in the inspection process,
When an ejection instruction signal for instructing to eject liquid from the nozzle toward the ejection receiving medium is received for the first time after the inspection process,
14. The liquid ejection apparatus according to claim 13, wherein the liquid ejection head is caused to eject liquid from the nozzles toward the ejection receiving medium after the recovery unit has performed the recovery operation.

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