Liquid dispensing device

Abstract

To detect that continued short-circuit and temporary short-circuit occur between a liquid discharge head and an electrode.SOLUTION: A voltage supply circuit 51 generates a potential difference between an inkjet head and an electrode 26. The electrode 26 is connected with a first output part 58 that outputs a first signal according to change in voltage of the electrode 26 at the time of making the inkjet head perform driving for an inspection. The electrode 26 is connected with a second output part 60 through low-pass filters 59 and 71. Further, the electrode 26 is connected with a third output part 62 through a high-pass filter 56. It is determined on the basis of the first signal whether ink is normally discharged from a nozzle by the driving for an inspection. It is determined on the basis of a second signal outputted from the second output part 60 whether continued short-circuit occurs or not. It is determined on the basis of a third signal outputted from the third output part 62 whether temporary short-circuit occurs or not.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] As an example of a liquid ejection device that ejects liquid from a nozzle, Patent Document 1 describes an inkjet printer that ejects ink from a nozzle to perform recording. The inkjet printer described in Patent Document 1 has an inspection area including an electrode member in a capping member that covers the nozzle. Then, in a state where a potential difference is generated between the print head and the inspection area, the print head is caused to perform an operation to eject ink from the nozzle toward the inspection area, and based on the change in voltage in the inspection area, it is inspected whether ink has been ejected normally from the nozzle. Furthermore, Patent Document 1 measures the actual voltage between the print head and the inspection area when performing the above inspection. Then, when the actual measured voltage is below the inspection tolerance range, it is determined that the print head and the electrode member are short-circuited and a leak current is flowing, and the print head and the capping member are separated, and the ink accumulated in the capping member is discharged by a suction pump. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-136858 A Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in the inkjet printer of Patent Document 1, when a continuous short circuit occurs between the print head and the inspection area, a leak current flows continuously between the print head and the inspection area, so that the voltage between the print head and the inspection area continues to be below the inspection tolerance range. In Patent Document 1, whether or not a continuous short circuit occurs between the print head and the inspection area is determined based on whether or not the voltage between the print head and the inspection area is below the inspection tolerance range. On the other hand, for example, a temporary short circuit may occur between the print head and the inspection area due to a temporary discharge between the print head and the inspection area. In this case, since only a leak current flows between the print head and the electrode member temporarily, it is necessary to capture a temporary voltage change. However, in the configuration for detecting a continuous short circuit between the print head and the inspection area as described in Patent Document 1, there is a risk that the above-mentioned temporary voltage change cannot be captured. When a temporary short circuit occurs between the print head and the inspection area, there is a risk that a similar temporary short circuit may occur repeatedly or that it may shift to a continuous short circuit between the print head and the inspection area. Therefore, it is preferable to be able to detect the occurrence of a short circuit between the print head and the inspection area not only when a continuous short circuit occurs between the print head and the inspection area, but also when a temporary short circuit occurs between the print head and the inspection area.

[0005] An object of the present invention is to provide a liquid ejection device that is capable of more accurately detecting both the occurrence of a continuous short circuit and the occurrence of a temporary short circuit between a liquid ejection head and an electrode that receives liquid ejected from a nozzle. [Means for solving the problem]

[0006] a first output section electrically connected to either the electrode or the liquid ejection head and configured to output a first signal corresponding to an electrical change that occurs when the liquid ejection head is driven for testing to eject liquid from the nozzle toward the electrode while the liquid ejection head is opposed to the electrode; a low-pass filter electrically connected to the electrode; a second output section electrically connected to the electrode via the low-pass filter; a high-pass filter electrically connected to the electrode; a third output section electrically connected to the electrode via the high-pass filter; and a control section. The control section determines whether or not liquid has been normally ejected from the nozzle based on the first signal, and determines whether or not a short circuit has occurred between the liquid ejection head and the electrode based on the second signal output from the second output section and the third signal output from the third output section. Effect of the Invention

[0007] According to the present invention, it is possible to determine whether or not liquid has been normally ejected from the nozzle based on the first signal output from the first output unit. Also, when a continuous short circuit occurs between the liquid ejection head and the electrode, the DC component of the voltage of the electrode changes. In the present invention, since the second output unit is connected to the electrode via a low-pass filter, the second signal output from the second output unit is a signal corresponding to the DC component of the voltage of the electrode. As a result, it is possible to detect that a continuous short circuit occurs between the liquid ejection head and the electrode based on the second signal. Also, when a temporary short circuit occurs between the liquid ejection head and the electrode, the voltage of the electrode changes suddenly, causing a high-frequency component to occur in the voltage of the electrode. In the present invention, since the third output unit is connected to the electrode via a high-pass filter, the third signal output from the third output unit is a signal corresponding to the high-frequency component of the voltage of the electrode. As a result, it is possible to detect that a temporary short circuit occurs between the liquid ejection head and the electrode based on the third signal. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a printer according to an embodiment of the present invention; [Diagram 2] 4A to 4C are diagrams for explaining electrodes and the like arranged inside the cap. [Diagram 3] FIG. 2 is a block diagram showing the electrical configuration of the printer. [Figure 4] FIG. 2 is a block diagram showing a configuration of a testing circuit; [Diagram 5] (a) is a diagram to explain the signal sent from the high-pass filter to the first output unit when ink is not ejected from the nozzle during test drive, and the signal output from the first output unit, (b) is a diagram to explain the signal sent from the high-pass filter to the first output unit when ink is ejected from the nozzle during test drive, and (c) is a diagram to explain the signal output from the first output unit when ink is ejected from the nozzle during test drive. [Figure 6] 6 is a diagram for explaining a signal output from a second output section. FIG. [Figure 7] FIG. 1A is a diagram for explaining a signal received by the latch circuit when no temporary short circuit occurs, FIG. 1B is a diagram for explaining a signal received by the latch circuit when a temporary short circuit occurs, and FIG. 1C is a diagram for explaining a signal output from the latch circuit (third output section). [Figure 8] 10 is a flowchart showing a process flow when an inspection instruction signal is received. [Figure 9] 13 is a block diagram showing a configuration of an inspection circuit in an example in which a discharge instruction signal is output from a control unit to a discharge circuit; FIG. [Figure 10] 10 is a flowchart showing a process flow when an inspection instruction signal is received in the example of FIG. 9. [Figure 11] 6 is a diagram for explaining an example in which the inkjet head and a first output section are electrically connected. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will now be described.

[0010] <Overall printer configuration> As shown in FIG. 1, the printer 1 (the "liquid ejection device" of the present invention) according to this embodiment includes a carriage 2, a subtank 3, an inkjet head 4 (the "liquid ejection head" of the present invention), a platen 5, transport rollers 6 and 7, a maintenance unit 8, etc.

[0011] 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 36 (see FIG. 3) via a belt (not shown) or the like, and when the carriage motor 36 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.

[0012] The subtank 3 is mounted on the carriage 2. Here, the printer 1 is equipped with a cartridge holder 13, in which four ink cartridges 14 are removably attached. The four ink cartridges 14 are lined up in the scanning direction, and store black, yellow, cyan, and magenta inks ("liquids" of the present invention) from the one arranged on the right side in the scanning direction. The subtank 3 is connected to the four ink cartridges 14 attached to the cartridge holder 13 via four tubes 15. In this way, the four colors of ink are supplied to the subtank 3 from the four ink cartridges 14.

[0013] 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.

[0014] 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 37 (see FIG. 3) via gears (not shown). When the transport motor 37 is driven, the transport rollers 6 and 7 rotate and the recording paper P is transported in the transport direction.

[0015] The maintenance unit 8 includes a cap 21, a suction pump 22, and a waste liquid tank 23. The cap 21 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 21.

[0016] The cap 21 can be raised and lowered by a cap lifting mechanism 38 (see FIG. 3). When the carriage 2 is positioned at the maintenance position so that the nozzles 10 and the cap 21 face each other, the cap 21 is raised by the cap lifting mechanism 38, and the upper end of the cap 21 comes into close contact with the nozzle surface 4a, resulting in a capped state in which the nozzles 10 are covered by the cap 21. When the cap 21 is lowered by the cap lifting mechanism 38, the nozzles 10 are in an uncapped state in which they are not covered by the cap 21. The cap 21 is not limited to a cap that covers the nozzles 10 by coming into close contact with the nozzle surface 4a. The cap 21 may cover the 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.

[0017] The suction pump 22 is a tube pump or the like, and is connected to the cap 21 and the waste liquid tank 23. In the maintenance unit 8, when the suction pump 22 is driven in the above-mentioned capped state, it is possible to perform a so-called suction purge, 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 23.

[0018] For convenience, the cap 21 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 21 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 may selectively discharge either the black ink or the color ink in the inkjet head 4 during suction purge. Alternatively, for example, the cap 21 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.

[0019] In addition, in the maintenance unit 8, when the suction pump 22 is driven in the uncapped state, the ink accumulated in the cap 21 can be discharged by suction purging, inspection driving (described later), or the like, thereby performing so-called idle suction. The ink discharged from the cap 21 by idle suction is also stored in the waste liquid tank 23.

[0020] As shown in Fig. 2, an electrode 26 having a rectangular planar shape is disposed within the cap 21. The electrode 26 constitutes a test circuit 27 (see Figs. 3 and 4) described later. The test circuit 27 is controlled by a control unit 30 (see Figs. 3 and 4). In this embodiment, in the above-mentioned capped state, while a potential difference is generated between the inkjet head 4 and the electrode 26 as described later, it is possible to determine whether ink has been ejected from the nozzle 10 based on a change in voltage of the electrode 26 when the inkjet head 4 is driven for testing to eject ink from the nozzle 10.

[0021] <Printer electrical configuration> Next, the electrical configuration of the printer 1 will be described. As shown in Fig. 3, the printer 1 includes a control unit 30. The control unit 30 includes a central processing unit (CPU) 31, a read only memory (ROM) 32, a random access memory (RAM) 33, a memory 34, and an application specific integrated circuit (ASIC) 35. The control unit 30 controls the operations of a carriage motor 36, an inkjet head 4, a conveying motor 37, a cap lifting mechanism 38, a suction pump 22, an inspection circuit 27, and the like. The control unit 30 also receives signals from the inspection circuit 27.

[0022] The control unit 30 may be one in which only the CPU 31 performs various processes, one in which only the ASIC 35 performs various processes, or one in which the CPU 31 and the ASIC 35 work together to perform various processes. The control unit 30 may be one in which one CPU 31 performs processes independently, or one in which multiple CPUs 31 share the processes. The control unit 30 may be one in which one ASIC 35 performs processes independently, or one in which multiple ASICs 35 share the processes.

[0023] <Test circuit> Next, the inspection circuit 27 will be described. As shown in Fig. 4, the inspection circuit 27 includes the above-mentioned electrode 26, a voltage supply circuit 51 (the "voltage supply section" of the present invention), a main circuit 52, a voltage dividing circuit 53, a comparison voltage generating circuit 54, a comparison circuit 55, a high-pass filter 56, an amplifier circuit 57, a first output section 58, a low-pass filter 59 (the "other low-pass filter" of the present invention), a second output section 60, a latch circuit 61, a third output section 62, and a discharge circuit 63 (the "discharge section" of the present invention).

[0024] The voltage supply circuit 51 applies a voltage to the electrode 26 to generate a potential difference between the inkjet head 4 and the electrode 26. As will be described later, the voltage supply circuit 51 adjusts the output voltage by switching between boosting the output voltage and stopping boosting the voltage. The operation of the voltage supply circuit 51 will be described in detail later.

[0025] The voltage supply circuit 51 also includes a comparison signal receiving section 51a, an enable signal receiving section 51b, and an on / off signal receiving section 51c.

[0026] The comparison signal receiving unit 51a is a unit that receives a comparison signal output from the comparison circuit 55 as described below. The permission signal receiving unit 51b is a unit that receives a permission signal output from the control unit 30. The permission signal is a signal that indicates whether or not to permit boosting in the voltage supply circuit 51. The on / off signal receiving unit 51c is a unit that receives an on / off signal output from the control unit 30. The on / off signal is a signal that indicates whether the voltage supply circuit 51 should be in an on state in which boosting is possible, or an off state in which boosting is not possible.

[0027] The main circuit 52 is a circuit that connects the voltage supply circuit 51 and the electrode 26. A low-pass filter 71 is connected to a portion of the main circuit 52 between the voltage supply circuit 51 and the electrode 26. The low-pass filter 71 is a filter that attenuates components of a frequency higher than a cutoff frequency in a voltage fluctuation on the electrode 26 side, which is downstream of the low-pass filter 71 in the voltage supply, in the main circuit 52, with respect to the voltage supply circuit 51 side, which is upstream of the low-pass filter 71 in the voltage supply. In other words, mainly a DC component of the voltage input from the downstream side of the voltage supply is output from the low-pass filter 71 to the upstream side of the voltage supply.

[0028] The voltage dividing circuit 53 is connected to a connection part 52a between the voltage supply circuit 51 and the low pass filter 71 of the main circuit 52. The voltage dividing circuit 53 outputs a voltage Vd obtained by dividing the voltage V output from the voltage supply circuit 51 at a predetermined ratio. The voltage Vd output from the voltage dividing circuit 53 is a voltage that can be input to the comparison circuit 55.

[0029] The comparison voltage generating circuit 54 generates a comparison voltage Vda to be compared with the voltage Vd output from the voltage dividing circuit 53. The comparison voltage Vda is a voltage corresponding to the predetermined voltage Va. More specifically, the magnitude |Vda| of the comparison voltage Vda is the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 when the magnitude |V| of the voltage V output from the voltage supply circuit 51 is the magnitude |Va| of the predetermined voltage Va. In other words, the magnitude |Vda| of the comparison voltage Vda is set so that the magnitude |V| of the voltage V output from the voltage supply circuit 51 becomes the predetermined voltage Va. The comparison voltage generating circuit 54 has a PWM signal receiving unit 54a that receives a PWM (Pulse Width Modulation) signal output from the control unit 30. The comparison voltage generating circuit 54 generates a comparison voltage based on the PWM signal received by the PWM signal receiving circuit 54a. Specifically, the comparison voltage generating circuit 54 generates a comparison voltage Vda with a larger magnitude as the proportion R of the PWM signal with a value of High becomes higher.

[0030] The comparison circuit 55 is electrically connected to the voltage divider circuit 53, the comparison voltage generation circuit 54, and the voltage supply circuit 51. The comparison circuit 55 compares the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 with the magnitude |Vda| of the comparison voltage Vda output from the comparison voltage generation circuit 54, and outputs a comparison signal according to the result to the voltage supply circuit 51. That is, the comparison signal is a signal indicating whether the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 is greater than the magnitude |Vda| of the comparison voltage Vda. The comparison signal output from the comparison circuit 55 is received by a comparison signal receiving unit 51a of the voltage supply circuit 51.

[0031] Here, the operation of the voltage supply circuit 51 will be described. When the permission signal received by the permission signal receiving unit 51b indicates that boosting in the voltage supply circuit 51 is permitted and the on / off signal received by the on / off signal receiving unit 51c indicates that the voltage supply circuit 51 is to be turned on, the voltage supply circuit 51 switches between boosting and stopping the boosting based on the comparison signal. Specifically, the voltage supply circuit 51 boosts the voltage when the comparison signal indicates that |Vd| is equal to or smaller than |Vda|. On the other hand, when the comparison signal indicates that |Vd| is greater than |Vda|, the voltage supply circuit 51 stops boosting the voltage. As a result, the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 is held at the magnitude |Vda| of the comparison voltage Vda. And the magnitude |V| of the voltage V output from the voltage supply circuit 51 is held at the magnitude |Va| of the predetermined voltage Va.

[0032] Here, the predetermined voltage Va is, for example, a positive voltage of about 500V, and the comparison voltage Vda is, for example, a positive voltage of about 1.7V. In this case, the voltages V and Vd are voltages of 0V or higher. Alternatively, the predetermined voltage Va may be, for example, a negative voltage of about -500V, and the comparison voltage Vda may be, for example, a negative voltage of about -1.7V. In this case, the voltages V and Vd are voltages of 0V or lower.

[0033] The high-pass filter 56 is connected to a connection portion 52b (the "second connection portion" of the present invention) between the electrode 26 of the main circuit 52 and the low-pass filter 71. The amplifier circuit 57 is connected to the high-pass filter 56. The first output portion 58 is connected to the amplifier circuit 57. That is, the amplifier circuit 57 is connected between the high-pass filter 56 and the first output portion 58. Furthermore, the high-pass filter 56 is connected between the voltage supply circuit 51 and the first output portion 58.

[0034] When a voltage fluctuation occurs at electrode 26 upstream of high-pass filter 56 in the voltage supply, the DC component of the voltage (the high voltage component applied by voltage supply circuit 51) is removed by high-pass filter 56 downstream of high-pass filter 56 in the voltage supply. The voltage that has passed through high-pass filter 56 is amplified by amplifier circuit 57 and output from first output unit 58. As a result, the signal output from first output unit 58 is a signal in which the high-frequency component of the voltage of electrode 26 has been amplified.

[0035] Here, the voltage of the electrode 26 will be described when the inkjet head 4 is driven for testing to eject ink from the nozzle 10 in the above-mentioned capped state and a potential difference is generated between the inkjet head 4 and the electrode 26 by applying a voltage to the electrode 26 by the voltage supply circuit 51. When ink is not ejected from the nozzle 10 by the test driving, the voltage of the electrode 26 hardly changes. When ink is ejected from the nozzle 10 by the test driving, the voltage of the electrode 26 changes. Furthermore, the change in the voltage of the electrode 26 at this time is rapid. Therefore, the high-frequency component of the voltage of the electrode 26 differs depending on whether ink is ejected from the nozzle 10 by the test driving.

[0036] As a result, when ink is not ejected from the nozzle 10 by the test driving, the signal output from the high-pass filter 56 to the amplifier circuit 57 and the signal output from the first output section 58 become signals whose voltages hardly change from V0, as shown in Fig. 5(a), where V0 is, for example, a voltage close to the ground potential.

[0037] On the other hand, when ink is ejected from the nozzle 10 by the inspection drive and the voltage of the electrode 26 changes, the signal output from the high-pass filter 56 toward the amplifier circuit 57 becomes a signal whose voltage changes with respect to V0 as shown in FIG. 5(b). However, the amount of change in the voltage of the electrode 26 when ink is ejected from the nozzle 10 by the inspection drive is smaller than the amount of change in the voltage of the electrode 26 when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, as will be described later. Therefore, the signal output from the high-pass filter 56 toward the amplifier circuit 57 when ink is ejected from the nozzle 10 by the inspection drive also becomes a signal with a small amount of voltage change as shown in FIG. 5(b).

[0038] Further, the signal output from the first output unit 58 becomes a signal obtained by amplifying the signal in FIG. 5(b) as shown in FIG. 5(c). Therefore, the signal output from the first output unit 58 has a larger voltage change than the signal output from the high-pass filter 56 toward the amplifier circuit 57. Specifically, the signal output from the first output unit 58 when ink is ejected from the nozzle 10 by the inspection drive is a signal whose maximum value Vh of the voltage V1 is larger than Vh1 (>V0), and whose minimum value Vm of the voltage V1 is smaller than Vm1 (<V0).

[0039] In this way, the signal output from the first output unit 58 becomes a signal indicating whether or not ink is ejected from the nozzle 10 by the inspection drive. Further, since the signal output from the first output unit 58 is a signal amplified by the amplifier circuit 57, it becomes a signal with a certain amount of voltage change when ink is ejected from the nozzle 10 by the inspection drive.

[0040] The low-pass filter 59 is connected to a connection portion 52c (the "first connection portion" of the present invention) between the voltage supply circuit 51 and the low-pass filter 71 of the main circuit 52. Here, the connection portion 52c is also a portion of the main circuit 52 between the voltage supply circuit 51 and the electrode 26. The second output portion 60 is connected to the low-pass filter 59. As a result, in this embodiment, the second output portion 60 is connected to the connection portion 52c, and the low-pass filter 59 is connected between the connection portion 52c and the second output portion 60.

[0041] The second signal output from the second output section 60 is a signal in which high frequency components have been removed by the low pass filters 59 and 71 in response to fluctuations in the voltage of the electrode 26. That is, the second signal output from the second output section 60 is mainly a signal of the DC component of the voltage of the electrode 26.

[0042] Here, for example, a connection between the inkjet head 4 and the electrode 26 via the ink in the cap 21 may cause a continuous short circuit between the inkjet head 4 and the electrode 26. A continuous short circuit between the inkjet head 4 and the electrode 26 means that the inkjet head 4 and the electrode 26 remain short-circuited and a leak current continues to flow between the inkjet head 4 and the electrode 26. When a continuous short circuit occurs between the inkjet head 4 and the electrode 26, a leak current continues to flow between the inkjet head 4 and the electrode 26, causing the magnitude of the voltage of the electrode 26 to decrease.

[0043] Therefore, as shown in FIG. 6, when there is no continuous short circuit between the inkjet head 4 and the electrode 26, the magnitude |V2| of the voltage V2 of the second signal output from the second output unit 60 is about the voltage V2a (V2a>0). When there is a continuous short circuit between the inkjet head 4 and the electrode 26, the magnitude |V2| of the voltage V2 of the second signal output from the second output unit 60 becomes smaller than the voltage V2b (<V2a). Thus, the second signal becomes a signal indicating whether there is a continuous short circuit between the inkjet head 4 and the electrode 26. Note that FIG. 6 shows a case where there is no continuous short circuit between the inkjet head 4 and the electrode 26 until time T1, and a continuous short circuit occurs between the inkjet head 4 and the electrode 26 from time T1.

[0044] The latch circuit 61 is connected in parallel with the amplifier circuit 57 to the high-pass filter 56. The third output unit 62 is connected to the latch circuit 61. Thus, the third output unit 62 is connected to the high-pass filter 56 without passing through the amplifier circuit 57, and the latch circuit 61 is connected between the high-pass filter 56 and the third output unit 62. The latch circuit 61 receives a signal from which the DC component (the high voltage component applied by the voltage supply circuit 51) has been removed by the high-pass filter 56 from the voltage of the electrode 26. The latch circuit 61 is configured to output a signal when a voltage equal to or higher than a predetermined voltage is input, and not to output a signal when a voltage lower than the predetermined voltage is input. Further, the latch circuit 61 has a circuit that maintains its output once it outputs a signal. The latch circuit 61 includes a release signal receiving unit 61a that receives a release signal instructing the release of the output from the control unit 30, and the maintenance of the output of the latch circuit 61 continues until a release command is received from the control unit 30.

[0045] Here, if a temporary short circuit occurs between the inkjet head 4 and the electrode 26, for example, due to a temporary discharge occurring in the gap between the ink in the cap 21 and the nozzle surface 4a, a temporary voltage change occurs in the electrode 26. The temporary short circuit occurs between the inkjet head 4 and the electrode 26 when the inkjet head 4 and the electrode 26 are temporarily short-circuited and a leakage current flows between the inkjet head 4 and the electrode 26. In addition, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, the temporary voltage change of the electrode 26 is abrupt. Therefore, the high-frequency component of the voltage of the electrode 26 differs depending on whether or not a temporary short circuit occurs between the inkjet head 4 and the electrode 26. In addition, the amount of change in the voltage of the electrode 26 at this time is larger than the amount of change in the voltage of the electrode 26 when ink is ejected from the nozzle 10 by the test drive.

[0046] Therefore, when no temporary short circuit occurs between the inkjet head 4 and the electrode 26, as shown in Fig. 7(a), the voltage of the signal output from the high-pass filter 56 and received by the latch circuit 61 hardly changes. In other words, the latch circuit 61 does not output a signal. On the other hand, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, as shown in Fig. 7(b), the voltage of the signal received by the latch circuit 61 changes temporarily. However, this voltage change lasts for a short period of time.

[0047] When a voltage change occurs in the signal received by the latch circuit 61 due to a temporary short circuit occurring between the inkjet head 4 and the electrode 26, the latch circuit 61 outputs a signal. In addition, since the latch circuit 61 has a circuit for maintaining the output, the signal continues to be output. As a result, the latch signal output from the latch circuit 61 has a voltage of V0 when no temporary short circuit occurs between the inkjet head 4 and the electrode 26, as shown in FIG. 7(c), and has a voltage of V3a (>V0) when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, and the output of the signal is maintained. That is, the latch signal output from the latch circuit 61 is a signal indicating whether or not a temporary short circuit has occurred between the inkjet head 4 and the electrode 26. Note that FIGS. 7(b) and (c) show a case where a temporary short circuit has occurred between the inkjet head 4 and the electrode 26 at time T2. In addition, when temporary short circuits occur continuously between the inkjet head 4 and the electrode 26, the latch signal output from the latch circuit 61 continues to have a voltage of V3a. The control unit 30 outputs a release signal when it determines that it is not necessary to maintain the output from the latch circuit 61, and the latch circuit 61 receives the release signal from the control unit 30 at the release signal receiving unit 61a. The latch circuit 61 receives the release signal and stops outputting the latch signal. Note that FIG. 7(c) shows a case where the latch circuit 61 receives the release signal at time T3, which is later than time T2. The third signal output from the third output unit 62 connected to the latch circuit 61 is also the same signal as the latch signal.

[0048] The discharge circuit 63 is connected to a connection portion 52d (the "third connection portion" of the present invention) between the electrode 26 and the connection portion 52b of the main circuit 52. The connection portion 52d is also a portion of the main circuit 52 between the electrode 26 and the low-pass filter 71. The connection portion 52d is closer to the electrode 26 than the connection portion 52c to which the second output portion 60 is connected and the connection portion 52b to which the third output portion 62 is connected of the main circuit 52. The discharge circuit 63 discharges at a position close to the electrode 26 in order to rapidly lower the voltage of the electrode 26 without waiting for the voltage supplied from the voltage supply circuit 51 to drop.

[0049] The discharge circuit 63 has a second signal receiving section 63a that receives the second signal output from the second output section 60, and a latch signal receiving section 63b that receives the signal output from the latch circuit 61. The second signal receiving section 63a is electrically connected to the second output section 60. The latch signal receiving section 63b is electrically connected to the latch circuit 61. The discharge circuit 63 discharges from the electrode 26 when the second signal received by the second signal receiving section 63a indicates that a continuous short circuit has occurred between the inkjet head 4 and the electrode 26. The discharge circuit 63 also discharges from the electrode 26 when the latch signal received by the latch signal receiving section 63b indicates that a temporary short circuit has occurred between the inkjet head 4 and the electrode 26.

[0050] <Processing when receiving an inspection command signal> Next, a process flow of the control unit 30 when an inspection instruction signal is received to instruct to inspect whether or not ink is ejected from the nozzle 10 will be described. In this embodiment, 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 or not ink is ejected normally from the nozzle 10, an inspection instruction signal is transmitted from the operation unit, PC, etc. of the printer 1, and the control unit 30 receives this inspection instruction signal. Then, when the control unit 30 receives the inspection instruction signal, it performs processing according to the flow of FIG. 8.

[0051] 8 is started, the on / off signal output from the control unit 30 indicates that the voltage supply circuit 51 is to be turned off. The permission signal output from the control unit 30 indicates that the voltage supply circuit 51 is not permitted to boost the voltage. At this point in time, the control unit 30 is not outputting a PWM signal.

[0052] 8 in more detail, the control unit 30 first executes the capping process (S101). In the capping process, the control unit 30 controls the carriage motor 36 and the cap lifting mechanism 38 to bring the device into the above-mentioned capped state. If the device is in the capped state when the inspection instruction signal is received, the device maintains the capped state in S101.

[0053] Next, the control unit 30 switches the on / off signal it is outputting to one indicating that the voltage supply circuit 51 is turned on (S102). Next, the control unit 30 switches the permission signal it is outputting to one indicating that boosting is permitted (S103). Next, the control unit 30 starts outputting the PWM signal (S104). Through the processes of S102 to S104, the voltage supply circuit 51 switches between boosting and stopping boosting based on the comparison signal, as described above.

[0054] As a result, the voltage supply circuit 51 boosts the voltage until the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 becomes the magnitude |Vda| of the comparison voltage Vda, that is, until the magnitude |V| of the voltage V output from the voltage supply circuit 51 becomes the magnitude |Va| of the predetermined voltage Va. Then, a comparison signal is received indicating that the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 has reached the magnitude |Vda| of the comparison voltage Vda, and the voltage supply circuit 51 stops boosting the voltage. In this way, the voltage supply circuit 51 repeats boosting and stopping the boosting based on the comparison signal so that the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 is held at the magnitude |Vda| of the comparison voltage Vda. That is, the magnitude |V| of the voltage V output from the voltage supply circuit 51 is held at the magnitude |Va| of the predetermined voltage Va.

[0055] Next, the control unit 30 starts the ejection detection process after the voltage supplied to the electrode 26 reaches a predetermined voltage Va (S105). In the ejection detection process, the control unit 30 sequentially drives each of the multiple nozzles 10 of the inkjet head 4 for inspection. Then, based on a first signal output from the first output unit 58 when the inspection drive is performed, the control unit 30 determines whether or not ink has been ejected normally from the nozzle 10, and stores the result in the memory 34.

[0056] If a continuous short circuit has not occurred between the inkjet head 4 and the electrode 26 (S106: NO) and a temporary short circuit has not occurred between the inkjet head 4 and the electrode 26 (S107: NO), the control unit 30 continues the ejection detection process until the ejection detection process is completed (S108: NO). Here, in S106, the control unit 30 determines whether or not a continuous short circuit has occurred between the inkjet head 4 and the electrode 26 based on the second signal output from the second output unit 60. Also, in S107, the control unit 30 determines whether or not a temporary short circuit has occurred between the inkjet head 4 and the electrode 26 based on the third signal output from the third output unit 62.

[0057] When the ejection detection process is completed (S108: YES), the control unit 30 stops outputting the PWM signal (S109). This reduces the magnitude |Vda| of the comparison voltage Vd (for example, to ground potential). As a result, boosting is no longer performed in the voltage supply circuit 51, and the magnitude |Va| of the voltage V output from the voltage supply circuit 51 gradually decreases and finally reaches, for example, ground potential. That is, the output of the voltage from the voltage supply circuit 51 is stopped.

[0058] Next, the control unit 30 switches the output permission signal to one indicating that boosting is not permitted (S110), and then switches the output on / off signal to one indicating that the voltage supply circuit 51 is to be turned off (S111).

[0059] On the other hand, when a continuous short circuit occurs between the inkjet head 4 and the electrode 26 during the ejection inspection process (S106: YES), and when a temporary short circuit occurs between the inkjet head 4 and the electrode 26 during the ejection inspection process (S107: YES), the control unit 30 interrupts the ejection detection process (S112), executes an uncap process (S113), and then executes the processes of S109 to S111. In the uncap process of S113, the control unit 30 controls the cap lift mechanism 38 to lower the cap 21 to bring the cap into an uncapped state. This makes it difficult for a leak current to flow between the inkjet head 4 and the electrode 26, and prevents the nozzle 10 from being damaged.

[0060] Furthermore, when a continuous short circuit occurs between the inkjet head 4 and the electrode 26 during the ejection inspection process, the second signal received by the second signal receiving section 63a of the discharge circuit 63 indicates that a continuous short circuit has occurred between the inkjet head 4 and the electrode 26. This causes the discharge circuit 63 to discharge from the electrode 26. Furthermore, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26 during the ejection inspection process, the latch signal received by the latch signal receiving section 63b of the discharge circuit 63 indicates that a temporary short circuit has occurred between the inkjet head 4 and the electrode 26. This causes the discharge circuit 63 to discharge from the electrode 26. In a state in which the discharge circuit 63 is discharging from the electrode 26, a leak current is unlikely to flow between the inkjet head 4 and the electrode 26, and this prevents the nozzle 10 from being damaged.

[0061] Furthermore, if the discharge inspection process is not interrupted after the process of S111, that is, if the discharge inspection process is completed (S114: NO), the control unit 30 ends the process as it is. If the discharge inspection process is interrupted (S114: YES), the control unit 30 executes an idle suction process (S115) and returns to S101. In the idle suction process, the control unit 30 drives the suction pump 22 in an uncapped state to perform idle suction. In the discharge inspection process that starts in S105 after the idle suction process of S114, it may be determined whether ink is normally discharged only for nozzles 10 other than the nozzles 10 for which it has been determined whether ink was normally discharged before the interruption, or it may be determined whether ink is normally discharged for all nozzles 10 of the inkjet head 4.

[0062] <Effects> According to this embodiment, it is possible to determine whether or not liquid has been normally ejected from the nozzles 10 based on the first signal output from the first output section 58 when the test drive is performed.

[0063] Furthermore, when a continuous short circuit occurs between the inkjet head 4 and the electrode 26, the DC component of the voltage of the electrode 26 changes. In this embodiment, the second output section 60 is connected to the electrode 26 via the low-pass filters 59 and 71, and therefore the second signal output from the second output section 60 is a signal containing a DC component in response to the voltage fluctuation of the electrode 26. This makes it possible to more accurately detect the occurrence of a continuous short circuit between the inkjet head 4 and the electrode 26 based on the second signal.

[0064] Furthermore, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, the voltage of the electrode 26 changes suddenly, generating high-frequency components in the voltage of the electrode 26. In this embodiment, since the third output section 62 is connected to the electrode 26 via the high-pass filter 56, the third signal output from the third output section 62 is a signal containing high-frequency components in response to the voltage fluctuation of the electrode 26. As a result, it is possible to detect the occurrence of a temporary short circuit between the inkjet head 4 and the electrode 26 based on the third signal.

[0065] Furthermore, in this embodiment, a low-pass filter 71 having an effect in the direction from the electrode 26 to the voltage supply circuit 51 is connected between the voltage supply circuit 51 and the electrode 26. Therefore, even if voltage fluctuation occurs at the electrode 26 due to a temporary short circuit or discharge, this voltage fluctuation is unlikely to be transmitted to the voltage supply circuit 51. This makes it possible to suppress fluctuations in the voltage Vd output from the voltage divider circuit 53, so that the voltage V supplied from the voltage supply circuit 51 becomes stable.

[0066] In this embodiment, a low-pass filter 71 and a low-pass filter 59 are connected between the electrode 26 and the second output section 60. This makes it possible for these two low-pass filters 59 and 71 to effectively remove high-frequency components of the voltage of the electrode 26.

[0067] In this embodiment, the third output section 62 is electrically connected to a connection section 52b between the electrode 26 and the low-pass filter 71 of the main circuit 52, and the high-pass filter 56 is connected between the third output section 62 and the connection section 52b. This makes it possible to achieve a structure in which the high-pass filter 56 is connected between the electrode 26 and the third output section 62.

[0068] Furthermore, by connecting the third output section 62 and the high-pass filter 56 in this manner, the electrode 26 and the third output section 62 can be connected without passing through the low-pass filter 71. This makes it possible to accurately determine whether or not a temporary short circuit has occurred between the inkjet head 4 and the electrode 26, based on the third signal output from the third output section 62.

[0069] Furthermore, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, the voltage of the electrode 26 changes for a short period of time. Therefore, unlike the present embodiment, if the latch circuit 61 is not connected between the high-pass filter 56 and the third output unit, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, the third signal output from the third output unit 62 will also be a signal whose voltage changes for a short period of time. As a result, there is a risk that the control unit 30 will not be able to detect the occurrence of a temporary short circuit between the inkjet head 4 and the electrode 26 based on the third signal.

[0070] In contrast, in this embodiment, a latch circuit 61 is connected between the high-pass filter 56 and the third output section. Therefore, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, causing a short-term change in the voltage of the electrode 26, information indicating the occurrence of such a short-term voltage change is held in the latch circuit 61. The third signal output from the third output section 62 is a signal corresponding to the information held in the latch circuit 61. This allows the control section 30 to accurately detect the occurrence of a temporary short circuit between the inkjet head 4 and the electrode 26 based on the third signal.

[0071] Furthermore, once a temporary short circuit has occurred, there is a high possibility that it will occur again unless the state of the ink between the electrode 26 and the inkjet head 4 changes. In this case, the presence of the latch circuit 61 that can maintain output even after a temporary short circuit has occurred makes it possible to continue outputting the latch signal until the state of the ink between the electrode 26 and the inkjet head 4 is improved. This makes it possible to prevent the recurrence of a temporary short circuit.

[0072] Furthermore, in this embodiment, in order to generate a detectable voltage change in the electrode 26 when ink is ejected from the nozzle 10 toward the electrode 26 by the test drive, it is necessary to increase the potential difference generated between the inkjet head 4 and the electrode 26 by the voltage supply circuit 51. Therefore, the DC component of the voltage output from the electrode 26 becomes a high voltage, for example, about 500 V. On the other hand, the amount of change in the voltage of the electrode 26 when ink is ejected from the nozzle 10 by the test drive is smaller than the magnitude of the DC component of the voltage of the electrode 26.

[0073] In this embodiment, since the high-pass filter 56 is connected between the electrode 26 and the first output section 58, the voltage of the electrode 26 from which the DC component (high voltage component) has been removed is sent to the first output section 58. Therefore, the first signal output from the first output section 58 makes it easy to determine whether or not ink has been normally ejected from the nozzle 10 by the test drive. In addition, since the first output section 58 and the third output section 62 are connected to a common high-pass filter 56, the circuit configuration of the test circuit 27 can be simplified.

[0074] Furthermore, in this embodiment, the amount of change in the voltage of the electrode 26 when ink is ejected from the nozzle 10 toward the electrode 26 by the test drive is smaller than the amount of change in the voltage of the electrode 26 when a temporary short circuit occurs between the inkjet head 4 and the electrode 26.

[0075] Therefore, in this embodiment, an amplifier circuit 57 is connected between the high-pass filter 56 and the first output section 58. As a result, when ink is ejected from the nozzle 10 toward the electrode 26 by the test driving, the voltage of the first signal output from the first output section 58 does not become too small, and it is possible to accurately determine whether or not ink has been normally ejected from the nozzle 10 by the test driving based on the first signal.

[0076] On the other hand, the third output part 62 is connected to the high-pass filter 56 without passing through the amplifier circuit 57. This makes it possible to prevent the voltage of the third signal output from the third output part 62 from becoming too large.

[0077] Furthermore, in this embodiment, when a continuous or temporary short circuit occurs between the inkjet head 4 and the electrode 26, the discharge circuit 63 discharges from the electrode 26. This makes it possible to suppress the leakage current flowing between the inkjet head 4 and the electrode 26, and to prevent the nozzle 10 from being damaged by the leakage current. Furthermore, since the discharge circuit 63 is connected to the connection portion 52d between the electrode 26 of the main circuit 52 and the low-pass filter 71, which is close to the electrode 26, it is possible to discharge from the electrode 26 as quickly as possible when a continuous or temporary short circuit occurs between the inkjet head 4 and the electrode 26.

[0078] Furthermore, the connection portion 52d to which the discharge circuit 63 is connected is closer to the electrode 26 than the connection portion 52c to which the second output portion 60 is connected and the connection portion 52b to which the third output portion 62 is connected of the main circuit 52. From this point of view, when a continuous or temporary short circuit occurs between the inkjet head 4 and the electrode 26, discharge from the electrode 26 can be performed as quickly as possible.

[0079] In this embodiment, the latch circuit 61 and the discharge circuit 63 are electrically connected, and the discharge circuit 63 switches whether or not to discharge from the electrode 26 based on the latch signal output from the latch circuit 61. This allows the electrode 26 to discharge as quickly as possible based on the latch signal output from the latch circuit 61 when a temporary short circuit occurs between the inkjet head 4 and the electrode 26. In addition, when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, there is a high possibility that such a temporary short circuit will occur again. In this embodiment, the latch signal output from the latch circuit 61 is directly input to the discharge circuit 63, so that the electrode 26 can continue to discharge until the fluctuation in voltage of the electrode 26 caused by the temporary short circuit subsides.

[0080] In this embodiment, the second output unit 60 and the discharge circuit 63 are electrically connected, and the discharge circuit 63 switches whether or not to discharge from the electrode 26 based on the second signal output from the second output unit 60. This makes it possible to discharge from the electrode 26 as quickly as possible based on the second signal output from the second output unit 60 when a continuous short circuit occurs between the inkjet head 4 and the electrode 26.

[0081] <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.

[0082] In the above embodiment, the second signal receiving section 63a of the discharge circuit 63 and the second output section 60 are electrically connected, and the latch signal receiving section 63b of the discharge circuit 63 and the latch circuit 61 are electrically connected. Then, when the second signal received by the second signal receiving section 63a indicates that a continuous short circuit has occurred, and when the latch signal received by the latch signal receiving section 63b of the discharge circuit 63 indicates that a temporary short circuit has occurred, the discharge circuit 63 is configured to discharge from the electrode 26, but this is not limiting.

[0083] In the first modification, as shown in FIG. 9, the control unit 30 can output a discharge instruction signal to the discharge circuit 101 to instruct the discharge circuit 101 to discharge from the electrode 26. The discharge circuit 101 has a discharge instruction signal receiving unit 101a that receives the discharge instruction signal. The discharge circuit 101 is configured to discharge from the electrode 26 when the discharge instruction signal receiving unit 101a receives the discharge instruction signal. That is, in the above embodiment, the discharge circuit 63 receives the signal corresponding to the occurrence of a short circuit output from the second output unit 60 and the latch circuit 61 without going through the control unit 30. In contrast, in the first modification, the control unit 30 receives the signal corresponding to the occurrence of a short circuit output from the second output unit 60 and the latch circuit 61, and outputs a discharge instruction signal to instruct the discharge circuit 101 to discharge based on this signal.

[0084] In the first modification, when an inspection command signal is received, the control unit 30 performs processing according to the flow of Fig. 10. More specifically, when an inspection command signal is received, the control unit 30 executes the same processes of S101 to S115 as in the above-described embodiment. However, in the first modification, unlike the above-described embodiment, when the control unit 30 receives a signal in response to the occurrence of a short circuit between the inkjet head 4 and the electrode 26 in S106 or S107, it outputs a discharge command signal to the discharge circuit 101 (S201) and then proceeds to S112.

[0085] In the first modification, when the control unit 30 determines that a continuous or temporary short circuit has occurred between the inkjet head 4 and the electrode 26, it outputs a discharge instruction signal to the discharge circuit 101. Then, when the discharge circuit 101 receives the discharge instruction signal, it performs discharge from the electrode 26. In this way, when a continuous or temporary short circuit has occurred between the inkjet head 4 and the electrode 26, it is possible to perform discharge from the electrode 26.

[0086] The discharge circuit may have both the second signal receiving section 63a and the latch signal receiving section 63b of the above embodiment and the discharge instruction signal receiving section 101a of the first modification. The discharge circuit 63 may be configured to discharge from the electrode 26 when the second signal received by the second signal receiving section 63a indicates that a continuous short circuit has occurred, when the latch signal received by the latch signal receiving section 63b of the discharge circuit 63 indicates that a temporary short circuit has occurred, and when the discharge instruction signal receiving section 101a receives a discharge instruction signal. The discharge circuit may have either the second signal receiving section 63a or the latch signal receiving section 63b of the above embodiment and the discharge instruction signal receiving section 101a of the first modification.

[0087] In the above embodiment, the discharge circuit 63 is connected to the connection portion 52d of the main circuit 52 between the electrode 26 and the low-pass filter 71. The connection portion 52d is a portion of the main circuit 52 closer to the electrode 26 than the connection portion 52c to which the second output portion 60 is connected and the connection portion 52b to which the third output portion 62 is connected. However, this is not limited to this.

[0088] For example, the discharge circuit 63 may be connected to a connection portion of the main circuit 52 between the electrode 26 and the low-pass filter 71, and which is farther from the electrode 26 than at least one of the connections 52b, 52c (the "third connection portion" of the present invention).

[0089] Also, for example, the discharge circuit 63 may be connected to a connection part (the "third connection part" of the present invention) in a part of the main circuit 52 other than the part between the electrode 26 and the low-pass filter 71, and closer to the electrode 26 than the connection parts 52b, 52c.

[0090] Also, for example, the discharge circuit 63 may be connected to a connection part of the main circuit 52 other than the part between the electrode 26 and the low-pass filter 71 and farther from the electrode 26 than at least one of the connections 52b, 52c. The discharge circuit 63 may be connected to the electrode 26 without passing through the main circuit 52. Furthermore, a discharge circuit that discharges from the electrode 26 may not be provided.

[0091] In addition, in the above embodiment, the high-pass filter 56 and the first output section 58 are connected via the amplifier circuit 57, and the high-pass filter 56 is connected to the third output section 62 without via the amplifier circuit 57, but this is not limited thereto. For example, when the control section 30 can detect a small voltage change in the first output section 58, the amplifier circuit 57 does not need to be connected between the high-pass filter 56 and the first output section 58.

[0092] In the above embodiment, the high-pass filter 56 is connected between the first output section 58 and the connection section 52, and thus the high-pass filter 56 is connected to the first output section 58 and the third output section 62. However, this is not limited to the above. For example, the electrode 26 and the third output section 62 may be connected via the high-pass filter 56, and the electrode 26 and the first output section 58 may be connected without the high-pass filter 56. In this case, a high-pass filter other than the high-pass filter 56 may be connected between the electrode 26 and the first output section 58. That is, the high-pass filter connected between the electrode 26 and the first output section 58 and the high-pass filter connected between the electrode 26 and the third output section 62 may be separate. Alternatively, a high-pass filter may not be connected between the electrode 26 and the first output section 58.

[0093] In the above embodiment, the latch circuit 61 is connected between the high-pass filter 56 and the third output unit 62, but this is not limiting. For example, if the discharge circuit 63 and the control unit 30 can accurately detect a short-term voltage change received, the latch circuit 61 does not need to be connected between the high-pass filter 56 and the third output unit 62.

[0094] In the above embodiment, the third output section 62 is connected to the connection section 52b of the main circuit 52, and the high-pass filter 56 is connected between the connection section 52b and the third output section 62, but this is not limited thereto. For example, the electrode 26 and the third output section 62 may be connected without passing through the main circuit 52, and the high-pass filter 56 may be connected between the electrode 26 and the third output section 62. In the above embodiment, the low-pass filter 71 provided in the main circuit 52 and the low-pass filter 59 provided outside the main circuit 52 are connected between the electrode 26 and the second output section 60, but this is not limited thereto. Only the low-pass filter 59 provided in the main circuit 52 may be connected between the electrode 26 and the second output section 60. Alternatively, only the low-pass filter 59 provided outside the main circuit 52 may be connected between the electrode 26 and the second output section 60.

[0095] In the above embodiment, the first output unit 58 is electrically connected to the electrode 26, but this is not limiting. For example, in Modification 2, as shown in Fig. 11, the first output unit 111 is connected to the inkjet head 4, and an amplifier circuit 112 is connected between the first output unit 111 and the inkjet head 4. The inkjet head 4 is also connected to a brand. Although not shown in the drawings, in Modification 2, the first output unit and the amplifier circuit are not connected to the electrode 26.

[0096] When the test drive is performed with a potential difference being generated between the inkjet head 4 and the electrode 26, a voltage change occurs in both the inkjet head 4 and the electrode 26. Therefore, even when the first output unit 111 is connected to the inkjet head 4, it is possible to determine whether or not ink has been normally ejected from the nozzle 10 based on the first signal output from the first output unit 111. As described above, in the second modification, the amplifier circuit 112 does not have to be connected between the inkjet head 4 and the first output unit 111. Also, a filter may be connected between the inkjet head 4 and the ground. This filter is for preventing the amplitude of the signal caused by the ejection of ink from the inkjet head 4 from becoming small in a configuration in which the first output unit 111 is connected to the inkjet head 4 while a voltage is supplied to the electrode 26, and the signal output from the first output unit 111 can be made larger by providing the filter.

[0097] In the above embodiment, a comparison signal is output from the comparison circuit 55 based on the magnitude relationship between the magnitude |Vd| of the voltage Vd output from the voltage divider circuit 53 and the magnitude |Va| of the comparison voltage Va generated by the comparison voltage generation circuit 54. Then, based on the comparison signal, whether or not to boost the voltage is switched in the voltage supply circuit 51, thereby outputting a voltage from the voltage supply circuit 51 and applying the voltage to the electrode 26. However, this is not limited to this. A voltage supply unit having a configuration different from that described above may apply a voltage to the electrode 26.

[0098] In the above embodiment, the test drive is performed for all the nozzles 10 of the inkjet head 4 to determine whether or not ink is ejected normally from the nozzles 10, but this is not limited to the above. For example, the test drive may be performed for only some of the nozzles 10 of the inkjet head 4, such as every other nozzle 10 in each nozzle row 9, to determine whether or not ink is ejected normally from the nozzles 10. Then, for the other nozzles 10, it may be estimated whether or not ink is ejected normally from the nozzles 10 based on the determination results for the some of the nozzles 10.

[0099] In the above example, the first signal output from the first output unit is a signal corresponding to whether or not ink has been ejected from the nozzle 10. When the first signal indicates that ink has been ejected from the nozzle 10, it is determined that ink has been ejected normally from the nozzle 10. However, this is not limited to this. The first signal may be a signal corresponding to an ejection mode other than whether or not ink has been ejected, such as the ink ejection direction or ejection speed. When the first signal indicates that ink has been ejected from the nozzle 10 in a predetermined ejection mode, it may be determined that ink has been ejected normally from the nozzle 10.

[0100] In the above, an example has been described in which the present invention is applied to a printer equipped with a so-called serial head that ejects ink from multiple nozzles while moving in the scanning direction together with the carriage, but the present invention is not limited to this. For example, the present invention can also be applied to a printer equipped with a so-called line head that extends across the entire length of the recording paper in the scanning direction.

[0101] 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]

[0102] 1: Printer 4: Inkjet head 26: Electrode 51: Voltage supply circuit 52: Main circuit 56: High pass filter 57: Amplification circuit 58: First output section 59: Low-pass filter 60: Second output section 61: Latch circuit 62: Third output section 63:Discharge circuit 71: Low pass filter 101:Discharge circuit 111: First output section 112: Amplification circuit

Claims

1. a liquid ejection head having a nozzle for ejecting liquid; an electrode arranged to be able to face the nozzle; a voltage supply unit that applies a voltage to the electrode to generate a potential difference between the liquid ejection head and the electrode; a first output section that is electrically connected to either the electrode or the liquid ejection head, and outputs a first signal corresponding to an electrical change when the liquid ejection head is driven for testing to eject liquid from the nozzle toward the electrode in a state in which the liquid ejection head and the electrode are opposed to each other; a low pass filter electrically connected to the electrodes; a second output section electrically connected to the electrode via the low pass filter; a high pass filter electrically connected to the electrode; a third output section electrically connected to the electrode via the high-pass filter; A control unit, The control unit is determining whether or not liquid has been normally ejected from the nozzle based on the first signal; A liquid ejection device characterized in that it determines whether a short circuit has occurred between the liquid ejection head and the electrode based on a second signal output from the second output section and a third signal output from the third output section.

2. a main circuit electrically connecting the voltage supply unit and the electrodes; the low-pass filter is provided in the main circuit, 2. The liquid ejection device according to claim 1, wherein the second output section is electrically connected to a first connection section of the main circuit between the voltage supply section and the low pass filter.

3. A low-pass filter other than the low-pass filter is provided, 3. The liquid ejection device according to claim 2, wherein the other low-pass filter is connected between the first connection portion and the second output portion.

4. the third output is electrically connected to a second connection of the main circuit between the electrode and the low pass filter; 4. The liquid ejection device according to claim 2, wherein the high-pass filter is connected between the third output portion and the second connection portion.

5. The liquid ejection device according to claim 4, further comprising a latch circuit connected between the high-pass filter and the third output section.

6. the first output portion is electrically connected to the second connection portion; 6. The liquid ejection device according to claim 4, wherein the high-pass filter is connected between the first output portion and the second connection portion.

7. an amplifier circuit connected between the high-pass filter and the first output section; The liquid ejection device according to claim 6 , wherein the third output portion is connected to the high-pass filter without passing through the amplifier circuit.

8. A discharge unit that discharges from the electrode, A liquid ejection device according to any one of claims 2 to 7, characterized in that the discharge section is electrically connected to a third connection section of the main circuit between the electrode and the low-pass filter.

9. a main circuit electrically connecting the voltage supply unit and the electrodes; A discharge unit that discharges from the electrode, the second output section and the third output section are each electrically connected to the main circuit; A liquid ejection device as described in any one of claims 1 to 8, characterized in that the discharge section is electrically connected to a third connection section of the main circuit that is closer to the electrode than the section to which the second output section and the third output section are connected.

10. A discharge unit that discharges from the electrode, The discharge unit is 6. The liquid ejection device according to claim 5, further comprising: a latch circuit that is electrically connected to the electrode and that switches whether or not to perform discharge based on a signal output from the latch circuit.

11. A discharge unit that discharges from the electrode, The discharge unit is A liquid ejection device as described in any one of claims 1 to 10, characterized in that it is electrically connected to the second output section and configured to switch whether or not to discharge from the electrode based on the second signal.

12. A discharge unit that discharges from the electrode, The control unit is when it is determined that the liquid ejection head and the electrode are short-circuited based on the second signal and the third signal, a discharge instruction signal is output to the discharge unit to instruct the electrode to discharge; The discharge unit is 12. The liquid ejection device according to claim 1, wherein the liquid ejection device is configured to perform discharge from the electrodes when the discharge instruction signal is received.

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