Liquid ejection device

Abstract

To accurately determine whether liquid is discharged normally from a nozzle or not.SOLUTION: It is determined whether ink is discharged normally from a nozzle or not, on the basis of change in voltage of an electrode 26, at the time of making an inkjet head perform driving for an inspection, in a state where a voltage supply circuit 51 outputs a voltage and a potential difference is generated between the inkjet head and the electrode 26. When magnitude of a voltage outputted from a voltage-dividing circuit 53 that divides the voltage outputted from the voltage supply circuit 51 is equal to or below magnitude of a comparison voltage outputted from a comparison circuit 55, the voltage supply circuit 51 performs boosting for rising the outputted voltage. When the magnitude of the voltage outputted from the voltage-dividing circuit 53 is larger than the magnitude of the comparison voltage outputted from the comparison circuit 55, the voltage supply circuit 51 stops the boosting.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a droplet discharge device that discharges a liquid from a nozzle.

Background Art

[0002] As an example of a liquid discharge device that discharges a liquid from a nozzle, Patent Document 1 describes an inkjet printer that discharges ink from a nozzle to perform recording. The inkjet printer described in Patent Document 1 has an inspection region in which a capping member that covers the nozzle includes an electrode member. Then, by applying a voltage to the cavity plate that constitutes the print head by a booster circuit, a potential difference is generated between the print head and the inspection region, and in this state, based on the change in the voltage of the inspection region when an operation for discharging ink from the nozzle toward the inspection region is performed on the print head, it is inspected whether or not ink is normally discharged from the nozzle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in Patent Document 1, as described above, when inspecting whether or not ink is normally discharged from the nozzle, if the potential difference generated between the print head and the inspection region fluctuates, the amount of change in the voltage of the inspection region when ink is discharged from the nozzle fluctuates. Therefore, in Patent Document 1, in order to obtain an accurate inspection result, it is preferable to stabilize the voltage applied to the cavity plate.

[0005] An object of the present invention is to stabilize the potential difference between a liquid ejection head and an electrode to which liquid is ejected for inspection of liquid ejection from a nozzle, and to more accurately determine whether or not liquid is normally ejected from the nozzle. To provide a liquid ejection device capable of

Means for Solving the Problems

[0006] The liquid ejection device of the present invention includes a liquid ejection head having a nozzle for ejecting liquid, an electrode disposed to face the nozzle, and applying a voltage to either the liquid ejection head or the electrode to cause a potential difference between the liquid ejection head and the electrode. A voltage supply unit, and either the liquid ejection head or the electrode is electrically connected, and in a state where the liquid ejection head and the electrode are opposed to each other, an inspection drive for ejecting liquid from the nozzle toward the electrode is performed on the liquid ejection head. A first output unit that outputs a voltage corresponding to an electrical change when the voltage is applied, a voltage comparison unit electrically connected to the voltage supply unit, and the voltage comparison unit outputs a comparison signal according to whether the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of a predetermined voltage. A comparison signal output unit, the voltage supply unit having a comparison signal receiving unit that receives the comparison signal electrically connected to the comparison signal output unit, and when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, boosting is performed to increase the magnitude of the output voltage, and when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, the boosting is stopped.

[0007] In addition, the liquid ejection device according to the present invention includes a liquid ejection head having nozzles for ejecting liquid, an electrode disposed to face the nozzles, a voltage supply unit that generates a potential difference between the liquid ejection head and the electrode by applying a voltage to either the liquid ejection head or the electrode, a first output unit that is electrically connected to either the liquid ejection head or the electrode and outputs a voltage corresponding to an electrical change when the liquid ejection head is caused to perform inspection driving for ejecting liquid from the nozzles toward the electrode in a state where the liquid ejection head and the electrode face each other, a voltage comparison unit electrically connected to the voltage supply unit, and a control unit. The voltage comparison unit has a comparison signal output unit that outputs a comparison signal to the control unit according to whether the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of a predetermined voltage. When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, the control unit outputs a control signal for controlling the voltage supply unit, the control signal instructing to perform a voltage boost to increase the magnitude of the voltage output from the voltage supply unit. When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, the control unit outputs the control signal instructing to stop the voltage boost. The voltage supply unit has a control signal reception unit that receives the control signal. When the control signal instructs to perform the voltage boost, the voltage supply unit performs the voltage boost, and when the control signal instructs to stop the voltage boost, the voltage supply unit stops the voltage boost.

Advantages of the Invention

[0008] According to the present invention, it is possible to stabilize the magnitude of the voltage output from the voltage supply unit, and it is possible to accurately determine whether or not liquid is normally ejected from the nozzles.

Brief Description of the Drawings

[0009]

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[0010] [First Embodiment] Hereinafter, a preferred first embodiment of the present invention will be described.

[0011] <Overall Configuration of the Printer> As shown in FIG. 1, a printer 1 (the "liquid ejection device" of the present invention) according to the first embodiment includes a carriage 2, a sub-tank 3, an inkjet head 4 (the "liquid ejection head" of the present invention), a platen 5, conveyance rollers 6 and 7, a maintenance unit 8, and the like.

[0012] The carriage 2 is supported by two guide rails 11 and 12 extending in the scanning direction. The carriage 2 is connected to a carriage motor 36 (see FIG. 3) via a belt (not shown). When the carriage motor 36 is driven, the carriage 2 moves in the scanning direction along the guide rails 11 and 12. Hereinafter, as shown in FIG. 1, the right side and the left side in the scanning direction will be defined for explanation.

[0013] The sub-tank 3 is mounted on the carriage 2. Here, the printer 1 includes a cartridge holder 13, and four ink cartridges 14 are detachably mounted on the cartridge holder 13. The four ink cartridges 14 are arranged side by side in the scanning direction, and store black, yellow, cyan, and magenta inks (the "liquid" of the present invention) in order from the one arranged on the right side in the scanning direction. The sub-tank 3 is connected to the four ink cartridges 14 mounted on the cartridge holder 13 via four tubes 15. Thereby, the four-color inks are supplied from the four ink cartridges 14 to the sub-tank 3.

[0014] The inkjet head 4 is mounted on the carriage 2 and connected to the lower end of the sub-tank 3. The four-color inks are supplied from the sub-tank 3 to the inkjet head 4. Further, the inkjet head 4 ejects ink from a plurality of nozzles 10 formed on a nozzle surface 4a which is the lower surface thereof. More specifically, the plurality of nozzles 10 are arranged in a conveyance direction orthogonal to the scanning direction to form a nozzle row 9, and on the nozzle surface 4a, four rows of nozzle rows 9 are arranged side by side in the scanning direction. From the plurality of nozzles 10, black, yellow, cyan, and magenta inks are ejected in order from the ones constituting the nozzle row 9 on the right side in the scanning direction.

[0015] The platen 5 is disposed below the inkjet head 4 and faces a plurality of 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 conveyance roller 6 is disposed upstream of the inkjet head 4 and the platen 5 in the conveyance direction. The conveyance roller 7 is disposed downstream of the inkjet head 4 and the platen 5 in the conveyance direction. The conveyance rollers 6 and 7 are connected to a conveyance motor 37 (see FIG. 3) via gears (not shown). When the conveyance motor 37 is driven, the conveyance rollers 6 and 7 rotate, and the recording paper P is conveyed in the conveyance direction.

[0016] The maintenance unit 8 includes a cap 21, a suction pump 22, and a waste liquid tank 23. The cap 21 is disposed on the right side of the platen 5 in the scanning direction. When the carriage 2 is positioned at a maintenance position on the right side of the platen 5 in the scanning direction, the plurality of nozzles 10 face the cap 21.

[0017] Further, the cap 21 is vertically movable by a cap elevating mechanism 38 (see FIG. 3). When the carriage 2 is positioned at the maintenance position so that the plurality of nozzles 10 face the cap 21, and the cap 21 is lifted by the cap elevating mechanism 38, the upper end portion of the cap 21 comes into close contact with the nozzle surface 4a, and the plurality of nozzles 10 are covered by the cap 21 in a capped state. Also, when the cap 21 is lowered by the cap elevating mechanism 38, the plurality of nozzles 10 are in an uncapped state where they are not covered by the cap 21. Note that the cap 21 is not necessarily limited to covering the plurality of nozzles 10 by coming into close contact with the nozzle surface 4a. The cap 21 may cover the plurality of nozzles 10, for example, by coming into close contact with a frame (not shown) disposed around the nozzle surface 4a of the inkjet head 4.

[0018] 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 cap state, so-called suction purge can be performed to discharge the ink in the inkjet head 4 from the plurality of nozzles 10. The ink discharged by the suction purge is stored in the waste liquid tank 23.

[0019] Here, for the sake of convenience, it has been described that the cap 21 covers all the nozzles 10 together and discharges the ink in the inkjet head 4 from all the nozzles 10 in the suction purge, but this is not limitative. For example, the cap 21 may separately include a portion covering the plurality of nozzles 10 constituting the rightmost nozzle row 9 that discharges black ink and a portion covering the plurality of nozzles 10 constituting the three leftmost nozzle rows 9 that discharge color ink (yellow, cyan, magenta inks), and in the suction purge, either the black ink or the color ink in the inkjet head 4 may be selectively discharged. Alternatively, for example, the cap 21 may be provided individually for each nozzle row 9, and in the suction purge, ink may be discharged from the nozzles 10 individually for each nozzle row 9.

[0020] Also, in the maintenance unit 8, when the suction pump 22 is driven in the above uncapped state, so-called air suction can be performed to discharge the ink accumulated in the cap 21 by suction purge, inspection drive, etc. to be described later. The ink discharged from the cap 21 by the air suction is also stored in the waste liquid tank 23.

[0021] Also, as shown in FIG. 2, an electrode 26 having a rectangular planar shape is disposed inside the cap 21. The electrode 26 constitutes an inspection circuit 27 (see FIGS. 3 and 4) described later. The inspection circuit 27 is controlled by a control unit 30 (see FIGS. 3 and 4). In the first embodiment, while setting the cap state and causing a potential difference to occur between the inkjet head 4 and the electrode 26 as described later, based on the change in the voltage of the electrode 26 when the inkjet head 4 is caused to perform an inspection drive for discharging ink from the nozzle 10, it is possible to determine whether or not ink has been discharged from the nozzle 10.

[0022] <Electrical Configuration of Printer> 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 CPU (Central Processing Unit) 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a memory 34, an ASIC (Application Specific Integrated Circuit) 35, and the like. The control unit 30 controls the operations of a carriage motor 36, an inkjet head 4, a conveyance motor 37, a cap lifting mechanism 38, a suction pump 22, an inspection circuit 27, and the like. Further, the control unit 30 receives a signal from the inspection circuit 27.

[0023] Note that the control unit 30 may be configured such that only the CPU 31 performs various processes, or only the ASIC 35 performs various processes, or the CPU 31 and the ASIC 35 cooperate to perform various processes. Also, the control unit 30 may be configured such that one CPU 31 performs processing alone, or a plurality of CPUs 31 perform processing in a shared manner. Further, the control unit 30 may be configured such that one ASIC 35 performs processing alone, or a plurality of ASICs 35 perform processing in a shared manner.

[0024] <Inspection Circuit> Next, the inspection circuit 27 will be described. As shown in FIG. 4, the inspection circuit 27 includes the above-described electrode 26, a voltage supply circuit 51 (the "voltage supply unit" of the present invention), a main circuit 52, a voltage dividing circuit 53, a comparison voltage generation circuit 54, a comparison circuit 55, a high-pass filter 56, an amplification circuit 57, a discharge detection output unit 58 (the "first output unit" of the present invention), a low-pass filter 59 (the "another low-pass filter" of the present invention), a first short-circuit output unit 60, a latch circuit 61, a second short-circuit output unit 62, and a discharge circuit 63. In the first embodiment, the combination of the voltage dividing circuit 53, the comparison voltage generation circuit 54, and the comparison circuit 55 corresponds to the "voltage comparison unit" of the present invention. Also, in the first embodiment, the first short-circuit output unit 60 and the second short-circuit output unit 62 correspond to the "second output unit" of the present invention.

[0025] The voltage supply circuit 51 is for generating a potential difference between the inkjet head 4 and the electrode 26 by applying a voltage to 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 the boosting. The operation of the voltage supply circuit 51 will be described in detail later.

[0026] The voltage supply circuit 51 also includes a comparison signal receiving unit 51a, a permission signal receiving unit 51b, and an on-off signal receiving unit 51c.

[0027] The comparison signal receiving unit 51a is a part that receives a comparison signal output from the comparison circuit 55 as will be described later. The permission signal receiving unit 51b is a part that receives a permission signal output from the control unit 30. The permission signal is a signal indicating whether to permit boosting in the voltage supply circuit 51. The on-off signal receiving unit 51c is a part that receives an on-off signal output from the control unit 30. The on-off signal is a signal indicating whether to set the voltage supply circuit 51 to an on state in which boosting is possible or an off state in which boosting cannot be performed.

[0028] 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 the cut-off frequency in the voltage fluctuation on the side of the electrode 26, which is on the downstream side of the voltage supply in the main circuit 52, with respect to the side of the voltage supply circuit 51, which is on the upstream side of the voltage supply in the main circuit 52 and is upstream of the low-pass filter 71. That is, mainly the 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.

[0029] The voltage dividing circuit 53 is connected to a connection portion 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 of a magnitude that can be input to the comparison circuit 55.

[0030] The comparison voltage generation circuit 54 generates a comparison voltage Vda for comparison with the voltage Vd output from the voltage dividing circuit 53. The comparison voltage Vda is a voltage corresponding to a 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 such that the magnitude |V| of the voltage V output from the voltage supply circuit 51 becomes the predetermined voltage Va. The comparison voltage generation circuit 54 includes a PWM signal reception unit 54a that receives the PWM (Pulse Width Modulation) signal output from the control unit 30. The comparison voltage generation circuit 54 generates a comparison voltage based on the PWM signal received by the PWM signal reception unit 54a. Specifically, the comparison voltage generation circuit 54 generates a comparison voltage Vda with a larger magnitude as the ratio R at which the value is High in the PWM signal is higher.

[0031] The comparison circuit 55 is electrically connected to the voltage division 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 division circuit 53 with the magnitude |Vda| of the comparison voltage Vda output from the comparison voltage generation circuit 54, and outputs a comparison signal corresponding 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 division 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 the comparison signal receiving unit 51a of the voltage supply circuit 51.

[0032] Here, the operation of the voltage supply circuit 51 will be described. The permission signal received by the permission signal receiving unit 51b of the voltage supply circuit 51 indicates that the voltage supply circuit 51 is permitted to perform step-up, and when the on-off signal received by the on-off signal receiving unit 51c indicates that the voltage supply circuit 51 is in the on state, based on the comparison signal, it switches whether to perform step-up or stop step-up. Specifically, the voltage supply circuit 51 performs step-up when the comparison signal indicates that |Vd| is less than or equal to |Vda|. On the other hand, when the comparison signal indicates that |Vd| is greater than |Vda|, the step-up is stopped. Thereby, the magnitude |Vd| of the voltage Vd output from the voltage division circuit 53 is maintained 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 maintained at the magnitude |Va| of the predetermined voltage Va.

[0033] 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.

[0034] The high-pass filter 56 is connected to a connection part 52b 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 ejection detection output part 58 is connected to the amplifier circuit 57. That is, the amplifier circuit 57 is connected between the high-pass filter 56 and the ejection detection output part 58. Also, the high-pass filter 56 is connected between the voltage supply circuit 51 and the first output part 58.

[0035] When a voltage fluctuation occurs at the electrode 26 on the upstream side of the voltage supply with respect to the high-pass filter 56, the DC component of the voltage (the high voltage component applied by the voltage supply circuit 51) is removed by the high-pass filter 56 on the downstream side of the voltage supply with respect to the high-pass filter 56. The voltage passing through the high-pass filter 56 is amplified by the amplifier circuit 57 and output from the ejection detection output part 58. Thereby, the signal output from the ejection detection output part 58 becomes a signal in which the high-frequency component of the voltage of the electrode 26 is amplified.

[0036] Here, while setting the above cap state and applying a voltage to the electrode 26 by the voltage supply circuit 51 to generate a potential difference between the inkjet head 4 and the electrode 26, the voltage of the electrode 26 when inspection driving for ejecting ink from the nozzle 10 is performed on the inkjet head 4 will be described. When ink is not ejected from the nozzle 10 by the inspection driving, the voltage of the electrode 26 hardly changes. When ink is ejected from the nozzle 10 by the inspection driving, the voltage of the electrode 26 changes. Also, the change in the voltage of the electrode 26 at this time is abrupt. 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 inspection driving.

[0037] Accordingly, when ink is not ejected from the nozzle 10 by the inspection drive, the signal output from the high-pass filter 56 toward the amplifier circuit 57 and the signal output from the ejection detection output unit 58 are signals whose voltage hardly changes from V0 as shown in FIG. 5(a). Here, V0 is a voltage close to the ground potential, for example.

[0038] 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 is 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 is also a signal with a small amount of voltage change as shown in FIG. 5(b).

[0039] Also, the signal output from the ejection detection output unit 58 is a signal obtained by amplifying the signal of FIG. 5(b) as shown in FIG. 5(c). Therefore, the signal output from the ejection detection 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 ejection detection 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).

[0040] In this way, the signal output from the ejection detection output unit 58 is a signal indicating whether ink is ejected from the nozzle 10 by the inspection drive. Also, since the signal output from the ejection detection output unit 58 is a signal amplified by the amplifier circuit 57, it is a signal with a certain amount of voltage change when ink is ejected from the nozzle 10 by the inspection drive.

[0041] The low-pass filter 59 is connected to a connection portion 52c 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 first short-circuit output portion 60 is connected to the low-pass filter 59. Thus, in the first embodiment, the first short-circuit 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 first short-circuit output portion 60.

[0042] The first short-circuit signal output from the first short-circuit output portion 60 becomes a signal from which high-frequency components are removed by the low-pass filters 59 and 71 with respect to fluctuations in the voltage of the electrode 26. That is, the first short-circuit signal output from the first short-circuit output portion 60 mainly becomes a signal of the DC component of the voltage of the electrode 26.

[0043] Here, for example, when the inkjet head 4 and the electrode 26 are connected via the ink in the cap 21, a continuous short circuit may occur between the inkjet head 4 and the electrode 26. The occurrence of a continuous short circuit between the inkjet head 4 and the electrode 26 means that the state in which the inkjet head 4 and the electrode 26 are short-circuited continues, and a leakage 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 leakage current continues to flow between the inkjet head 4 and the electrode 26, so that the magnitude of the voltage of the electrode 26 decreases.

[0044] 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 first short-circuit signal output from the first short-circuit 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 first short-circuit signal output from the first short-circuit output unit 60 becomes smaller than the voltage V2b (<V2a). Thus, the first short-circuit signal becomes a signal indicating whether or not 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.

[0045] The latch circuit 61 is connected in parallel with the amplifier circuit 57 to the high-pass filter 56. The second short-circuit output unit 62 is connected to the latch circuit 61. As a result, the second short-circuit 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 second short-circuit output unit 62. The latch circuit 61 receives, from the voltage of the electrode 26, a signal from which a DC component (a high voltage component applied by the voltage supply circuit 51) has been removed by the high-pass filter 56. 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 the signal has been output. The latch circuit 61 includes a release signal receiving unit 61a that receives a release signal for 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.

[0046] Here, for example, if a temporary discharge occurs in the gap between the ink in the cap 21 and the nozzle surface 4a, a temporary short circuit occurs between the inkjet head 4 and the electrode 26, and a temporary voltage change occurs in the electrode 26. A temporary short circuit between the inkjet head 4 and the electrode 26 means that the inkjet head 4 and the electrode 26 are temporarily short circuited, and a temporary leakage current flows between the inkjet head 4 and the electrode 26. Also, the temporary voltage change of the electrode 26 when a temporary short circuit occurs between the inkjet head 4 and the electrode 26 is rapid. Therefore, the high-frequency component of the voltage of the electrode 26 differs depending on whether or not a temporary short circuit has occurred between the inkjet head 4 and the electrode 26. Also, 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 inspection driving.

[0047] Therefore, when no temporary short circuit occurs between the inkjet head 4 and the electrode 26, as shown in FIG. 7(a), in the signal output from the high-pass filter 56 and received by the latch circuit 61, the voltage hardly changes. That is, 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), in the signal received by the latch circuit 61, the voltage temporarily changes. However, this voltage change is for a short time.

[0048] When a change in voltage 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. Also, since it 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, for example, as shown in FIG. 7(c), has a voltage of V0 when there is no temporary short circuit between the inkjet head 4 and the electrode 26, and becomes a signal with a voltage of V3a (>V0) when a temporary short circuit occurs between the inkjet head 4 and the electrode 26, and the output of that 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 the case where a temporary short circuit occurs between the inkjet head 4 and the electrode 26 at time T2. Also, when a temporary short circuit continuously occurs between the inkjet head 4 and the electrode 26, the latch signal output from the latch circuit 61 will be in a state where the voltage of V3a continues. When the control unit 30 determines that it is not necessary to maintain the output from the latch circuit 61, it outputs a release signal, and the latch circuit 61 receives the release signal from the control unit 30 at the release signal reception unit 61a. The latch circuit 61 stops outputting the latch signal upon receiving the release signal. Note that FIG. 7(c) shows the case where the latch circuit 61 receives the release signal at time T3 after time T2. Also, the second short circuit signal output from the second short circuit output unit 62 connected to the latch circuit 61 is the same signal as the latch signal.

[0049] The discharge circuit 63 is connected to a connection portion 52d between the connection portion 52b and the electrode 26 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. Also, the connection portion 52d is closer to the electrode 26 than the connection portion 52c to which the first short circuit output unit 60 of the main circuit 52 is connected and the connection portion 52b to which the second short circuit output unit 62 is connected. 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.

[0050] The discharge circuit 63 includes a first short - circuit signal receiving unit 63a that receives the first short - circuit signal output from the first short - circuit output unit 60, and a latch signal receiving unit 63b that receives the signal output from the latch circuit 61. The first short - circuit signal receiving unit 63a is electrically connected to the first short - circuit output unit 60. Also, the latch signal receiving unit 63b is electrically connected to the latch circuit 61. The discharge circuit 63 performs discharge from the electrode 26 when the first short - circuit signal received by the first short - circuit signal receiving unit 63a indicates that a continuous short - circuit has occurred between the inkjet head 4 and the electrode 26. Also, the discharge circuit 63 performs discharge from the electrode 26 even when the latch signal received by the latch signal receiving unit 63b indicates that a temporary short - circuit has occurred between the inkjet head 4 and the electrode 26.

[0051] <Processing at the time of receiving the inspection instruction signal> Next, the processing flow of the control unit 30 when receiving an inspection instruction signal instructing to inspect whether ink has been ejected from the nozzle 10 will be described. In the first embodiment, for example, when the user operates an operation unit (not shown) of the printer 1, a PC connected to the printer, etc., to instruct an inspection of whether ink is normally ejected from the nozzle 10, an inspection instruction signal is transmitted from the operation unit of the printer 1, the PC, etc., and the control unit 30 receives this inspection instruction signal. Then, when receiving the inspection instruction signal, the control unit 30 performs processing along the flow of FIG. 8.

[0052] Note that at the time when the flow of FIG. 8 is started, the on - off signal output from the control unit 30 indicates that the voltage supply circuit 51 is in an off state. Also, the permission signal output from the control unit 30 indicates that the voltage supply circuit 51 is not permitted to perform boosting. Also, at this time, the control unit 30 is not outputting a PWM signal.

[0053] Explaining the flow of FIG. 8 in more detail, the control unit 30 first executes a capping process (S101). In the capping process, the control unit 30 controls the carriage motor 36 and the cap lifting mechanism 38 to set the above-described cap state. If the cap state is already set at the time of receiving the inspection instruction signal, the cap state is maintained in S101.

[0054] Subsequently, the control unit 30 switches the output on-off signal to indicate that the voltage supply circuit 51 is turned on (S102). Subsequently, the control unit 30 switches the output permission signal to indicate that boosting is permitted (S103). Subsequently, the control unit 30 starts outputting the PWM signal (S104). By 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.

[0055] As a result, boosting is performed in the voltage supply circuit 51 until the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 becomes equal to 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 equal to the magnitude |Va| of the predetermined voltage Va. Then, upon receiving the comparison signal due to the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 reaching the magnitude |Vda| of the comparison voltage Vda, boosting is stopped in the voltage supply circuit 51. In this way, the voltage supply circuit 51 repeats boosting and stopping boosting based on the comparison signal so that the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is maintained at the magnitude |Vda| of the comparison voltage Vd. That is, the magnitude |V| of the voltage V output from the voltage supply circuit 51 is maintained at the magnitude |Va| of the predetermined voltage Va.

[0056] Subsequently, the control unit 30 starts the ejection detection process after the voltage supplied to the electrode 26 reaches the predetermined voltage Va (S105). In the ejection detection process, the control unit 30 causes the inspection drive to be performed in order for each of the plurality of nozzles 10 of the inkjet head 4. Then, based on the ejection detection signal output from the ejection detection output unit 58 when the inspection drive is performed, it is determined whether or not ink is ejected normally from the nozzle 10, and the result is stored in the memory 34.

[0057] If a continuous short circuit does not occur between the inkjet head 4 and the electrode 26 (S106: NO), and a temporary short circuit does not occur 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 first short circuit signal output from the first short circuit 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 second short circuit signal output from the second short circuit output unit 62.

[0058] When the ejection detection process is completed (S108: YES), the control unit 30 stops the output of the PWM signal (S109). As a result, the magnitude |Vda| of the comparison voltage Vd becomes small (for example, the ground potential). As a result, boosting is not performed in the voltage supply circuit 51, and the magnitude |V| of the voltage V output from the voltage supply circuit 51 gradually becomes small and finally becomes, for example, the ground potential. That is, the voltage output from the voltage supply circuit 51 is stopped.

[0059] Subsequently, the control unit 30 switches the output permission signal to indicate that boosting is not permitted (S110). Subsequently, the output on-off signal is switched to indicate that the voltage supply circuit 51 is in the off state (S111).

[0060] 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 the uncapping process (S113), and then executes the processes of S108 to S111. In the uncapping process of S112, the control unit 30 controls the cap lifting mechanism 38 to lower the cap 21 to put it in the uncapped state. Thereby, it becomes difficult for a leakage current to flow between the inkjet head 4 and the electrode 26, and it is possible to prevent the nozzles 10 from being damaged.

[0061] Also, when a continuous short circuit occurs between the inkjet head 4 and the electrode 26 during the ejection inspection process, the first short circuit signal received by the first short circuit signal receiving unit 63a of the discharge circuit 63 indicates that a continuous short circuit has occurred between the inkjet head 4 and the electrode 26. Thereby, the discharge circuit 63 discharges from the electrode 26. Also, 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 unit 63b of the discharge circuit 63 indicates that a temporary short circuit has occurred between the inkjet head 4 and the electrode 26. Thereby, the discharge circuit 63 discharges from the electrode 26. In a state where the discharge circuit 63 is discharging from the electrode 26, it becomes difficult for a leakage current to flow between the inkjet head 4 and the electrode 26, and thereby, it is possible to prevent the nozzles 10 from being damaged.

[0062] Also, after the process of S111, if the ejection inspection process has not been interrupted, that is, if the ejection inspection process has been completed (S114: NO), the control unit 30 ends the process as it is. If the ejection inspection process has been interrupted (S114: YES), the control unit 30 executes an air suction process (S115) and returns to S101. In the air suction process, the control unit 30 causes air suction by driving the suction pump 22 in the uncapped state. In addition, in the ejection inspection process starting at S105 after the air suction process of S114, it may be determined whether ink is normally ejected or not only for nozzles 10 other than the nozzle 10 for which it has been determined whether ink was normally ejected or not before being interrupted, or it may be determined whether ink is normally ejected or not for all nozzles 10 of the inkjet head 4.

[0063] <Effect> In the first embodiment, the comparison circuit 55 outputs a comparison signal according to whether the magnitude |V| of the voltage V output from the voltage supply circuit 51 is greater than the magnitude |Va| of a predetermined voltage Va. When the comparison signal indicates that the magnitude |V| of the voltage V output from the voltage supply circuit 51 is less than or equal to the magnitude |Va| of the predetermined voltage Va, the voltage supply circuit 51 performs boosting. Also, when the comparison signal indicates that the magnitude |V| of the voltage V output from the voltage supply circuit 51 is greater than the magnitude |Va| of the predetermined voltage Va, the voltage supply circuit 51 stops boosting. Thereby, the magnitude |V| of the voltage V output from the voltage supply circuit 51 can be stabilized to the magnitude |Va| of the predetermined voltage Va, and it is possible to accurately determine whether ink is normally ejected from the nozzle 10.

[0064] Also, in the first embodiment, since the comparison circuit 55 is electrically connected to the comparison signal receiving unit 51a of the voltage supply circuit 51, the responsiveness is high. Thereby, the voltage supplied from the voltage supply circuit 51 can be made more stable, and it is possible to accurately determine whether ink is normally ejected from the nozzle 10.

[0065] Also, in the first embodiment, when determining whether or not ink is normally ejected from the nozzle 10, the magnitude |V| of the voltage V output from the voltage supply circuit 51 is as large as, for example, about 500 V. On the other hand, the magnitude of the voltage that a general comparison circuit can handle is, for example, about several V, which is smaller than the magnitude |V| of the voltage V output from the voltage supply circuit 51.

[0066] Therefore, in the first embodiment, the voltage output from the voltage supply circuit 51 is divided by the voltage dividing circuit 53. Then, as a comparison signal, a signal is output according to whether or not the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is larger than the magnitude |Vda| of the comparison voltage Vda generated by the comparison voltage generation circuit 54. Thereby, even if the magnitude |V| of the voltage V output from the voltage supply circuit 51 is large, it is possible to determine whether or not the magnitude |V| of the voltage V output from the voltage supply circuit 51 is larger than the magnitude |Va| of a predetermined voltage Va by using a general comparison circuit.

[0067] Also, in the first embodiment, by generating a comparison voltage based on the PWM signal output from the control unit 30, it becomes easy to set the magnitude |Vda| of the comparison voltage Vda to a desired magnitude.

[0068] Also, in the first embodiment, when it is shown that the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is less than or equal to the magnitude |Vda| of the comparison voltage Vda (the magnitude |V| of the voltage V output from the voltage supply circuit 51 is less than or equal to the magnitude |Va| of the predetermined voltage Va), and it is shown that the permission signal permits boosting, and it is shown that the on-off signal turns on the voltage supply circuit 51, boosting is performed only in this case. Thereby, it is possible to prevent boosting from being performed unintentionally due to circuit failures, malfunctions, etc., and to ensure the safety of the device.

[0069] [Second Embodiment] Next, a preferred second embodiment of the present invention will be described. However, since the configuration of the second embodiment is only partially different from that of the first embodiment, the differences from the first embodiment will mainly be described below.

[0070] As shown in FIG. 9, in the second embodiment, in the inspection circuit 100, the comparison circuit 55 outputs a comparison signal to the control unit 30. Further, the control unit 30 outputs a control signal for controlling the voltage supply circuit 111 based on the comparison signal. The control unit 30 selectively outputs either a signal instructing the voltage supply circuit 111 to step up the voltage or a signal instructing the voltage supply circuit 111 to stop stepping up the voltage as the control signal.

[0071] The voltage supply circuit 101 is obtained by replacing the comparison signal receiving unit 51a (see FIG. 4) in the voltage supply circuit 51 of the first embodiment with a control signal receiving unit 101a that receives the control signal output from the control unit 30. The voltage supply circuit 101 steps up the voltage when the on-off signal indicates an on state, the permission signal indicates permission to step up the voltage, and the control signal instructing to step up the voltage is received. Also, the voltage supply circuit 101 stops stepping up the voltage when the on-off signal indicates an off state, the permission signal indicates non-permission to step up the voltage, and the control signal instructing to stop stepping up the voltage is received.

[0072] Then, in the second embodiment, when the control unit 30 receives an inspection instruction signal, it performs processing along the flow of FIG. 10 in parallel with performing processing along the flow of FIG. 8 in the same manner as in the first embodiment.

[0073] Regarding the flow of FIG. 10, the control unit 30 determines whether the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is less than or equal to the magnitude |Vda| of the comparison voltage Vda based on the comparison signal (S201). When the magnitude |Vd| of the voltage Vd is less than or equal to the magnitude |Vda| of the comparison voltage Vda (S201: YES), the control unit 30 outputs a control signal instructing boosting to the voltage supply circuit 51 (S202). When the magnitude |Vd| of the voltage Vd is greater than the magnitude |Vda| of the comparison voltage Vda (S201: NO), the control unit 30 outputs a control signal instructing to stop boosting to the voltage supply circuit 51 (S203).

[0074] After the processes of S202 and S203, if the discharge detection process is not completed (S204: NO), the process returns to S201, and when the discharge detection process is completed (S204: YES), the process ends.

[0075] As a result, in the second embodiment, while the discharge detection process is being performed, in the voltage supply circuit 51, boosting and its stop are switched based on the control signal, so that the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is maintained at the magnitude |Vda| of the comparison voltage Vda, similar to that described in the first embodiment. As a result, the magnitude |V| of the voltage V output from the voltage supply circuit 51 is maintained at the magnitude |Va| of the predetermined voltage Va.

[0076] <Effect> In the second embodiment, the comparison circuit 55 outputs a comparison signal according to whether the magnitude |V| of the voltage V output from the voltage supply circuit 1011 is greater than the magnitude |Va| of a predetermined voltage Va (whether the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is greater than the magnitude |Vda| of the comparison voltage Vda). The control unit 30 transmits a control signal indicating whether to perform boosting or stop based on whether the comparison signal indicates that the magnitude |V| of the voltage V output from the voltage supply circuit 101 is greater than the magnitude |Va| of the predetermined voltage Va. The voltage supply circuit 101 switches whether to perform boosting or stop based on the control signal. Thereby, the magnitude |V| of the voltage V output from the voltage supply circuit 101 can be stabilized to the magnitude |Va| of the predetermined voltage Va, and it is possible to accurately determine whether ink has been normally ejected from the nozzle 10.

[0077] Also, in the second embodiment, since the comparison circuit 55 outputs a comparison signal to the control unit 30 and the voltage supply circuit 101 receives the control signal at the control signal receiving unit 101a, in the inspection circuit 100, it is not necessary to connect the comparison circuit 55 and the voltage supply circuit 101, and the configuration of the inspection circuit 100 can be simplified.

[0078] Also, in the second embodiment, boosting is performed only when the control signal indicates that boosting is to be performed, the permission signal indicates that boosting is permitted, and the on-off signal indicates that the voltage supply unit is in the on state. Thereby, it is possible to prevent boosting from being performed unintentionally due to circuit failures, malfunctions, etc., and ensure the safety of the device.

[0079] [Modification Example] As described above, the preferred first and second embodiments of the present invention have been described. However, the present invention is not limited to the first and second embodiments, and various modifications are possible within the scope described in the claims.

[0080] In the first embodiment, the voltage supply circuit 51 includes an on-off signal receiving unit 51c, a permission signal receiving unit 51b, and a comparison signal receiving unit 51a. The voltage supply circuit 51 switches between boosting and stopping boosting based on the comparison signal only when the on-off signal indicates that the voltage supply circuit 51 is turned on and the permission signal indicates that boosting is permitted. However, this is not limiting.

[0081] In Modification 1, as shown in FIG. 11, the inspection circuit 110 is obtained by replacing the voltage supply circuit 51 with a voltage supply circuit 111 in the inspection circuit 27 of the first embodiment. Different from the voltage supply circuit 51, the voltage supply circuit 111 does not have an on-off signal receiving unit 51c (see FIG. 4). In Modification 1, for example, when the printer is powered on, the voltage supply circuit 111 is always in the on state. The voltage supply circuit 111 switches between boosting and stopping boosting based on the comparison signal only when the permission signal indicates that boosting is permitted.

[0082] Also, in Modification 1, when the control unit 30 receives an inspection instruction signal, it performs processing according to the flow of FIG. 12. The flow of FIG. 12 is obtained by removing the processing of S102 and S111 from the flow of FIG. 8.

[0083] In Modification 1, boosting is performed only when it is indicated that the magnitude |V| of the voltage V output from the voltage supply circuit 51 is less than or equal to the magnitude |Va| of a predetermined voltage Va (the magnitude |Vd| of the voltage Vd output from the voltage dividing circuit 53 is less than or equal to the magnitude |Vda| of the comparison voltage Vda) and the permission signal indicates that boosting is permitted. This prevents boosting from being unintentionally performed due to circuit failures, malfunctions, etc., and ensures the safety of the device.

[0084] Also, in Modification 1, the voltage supply circuit 111 switches whether to perform boosting or stop boosting based on the comparison signal only when the permission signal indicates that boosting is permitted. However, this is not the only case. For example, if the voltage supply circuit does not have a permission signal receiving unit and always switches whether to perform boosting or stop boosting based on the comparison signal when it receives a control signal, it may also be acceptable.

[0085] Also, in the second embodiment, the voltage supply circuit 101 includes an on / off signal receiving unit 51c, a permission signal receiving unit 51b, and a control signal receiving unit 101a. Then, the voltage supply circuit 101 switches whether to perform boosting or stop boosting based on whether the control signal instructs to perform boosting or stop boosting only when the on / off signal indicates that the voltage supply circuit 101 is in the on state and the permission signal indicates that boosting is permitted. However, this is not the only case.

[0086] In Modification 2, as shown in FIG. 13, the inspection circuit 120 is obtained by replacing the voltage supply circuit 101 in the inspection circuit 100 of the second embodiment with a voltage supply circuit 121. Different from the voltage supply circuit 101, the voltage supply circuit 121 does not have an on / off signal receiving unit 51c (see FIG. 9). In Modification 2, for example, when the printer is powered on, the voltage supply circuit 121 is always in the on state. Then, the voltage supply circuit 121 switches whether to perform boosting or stop boosting based on whether the control signal instructs to perform boosting or stop boosting only when the permission signal indicates that boosting is permitted.

[0087] Also, in Modification 2, when the control unit 30 receives an inspection instruction signal, it performs processing along the flowcharts of FIGS. 10 and 12 in the same manner as in Modification 1.

[0088] In Modification 2, boosting is performed only when the control signal indicates boosting and the permission signal indicates permission to perform boosting. This prevents unintentional boosting due to circuit failures, malfunctions, etc., and ensures the safety of the device.

[0089] Also, in Modification 2, the voltage supply circuit 111 switches between boosting and stopping boosting based on the control signal only when the permission signal indicates permission to perform boosting, but this is not limiting. For example, even if the voltage supply circuit does not have a permission signal receiving unit and always switches between boosting and stopping boosting based on the control signal when the control signal is received, it may be acceptable.

[0090] Also, in the first and second embodiments, the comparison voltage generation circuit 54 generates a comparison voltage based on the received PWM signal. Therefore, as described below, the comparison voltage may be changed by changing the PWM signal output from the control unit 30 according to conditions.

[0091] In Modification 3, the control unit 30 changes the PWM signal by performing processing along the flow of FIG. 14(a). In Modification 3, when the output of the PWM signal is started at S104, the processing of the flow of FIG. 14(a) is started.

[0092] Explaining the flow of FIG. 14(a) in detail, the control unit 30 performs the processing of S302 to S307 described below until the output of the PWM signal is stopped at S108 (S301: NO). Then, when the output of the PWM signal is stopped at S109 (S301: YES), the processing ends.

[0093] In S302, the control unit 30 waits while the maximum value Vh of the voltage of the ejection detection signal output from the ejection detection output unit 58 is less than or equal to Vh1, or the minimum value Vm of the voltage of the ejection detection signal output from the ejection detection output unit 58 is greater than or equal to Vm1 (S302: NO). Here, the time when the maximum value Vh is less than or equal to Vh1, or the minimum value Vm is greater than or equal to Vm1 is when the inspection drive is not being performed and when ink is not ejected from the nozzle 10 by the inspection drive.

[0094] Then, when the maximum value Vh of the voltage of the ejection detection signal output from the ejection detection output unit 58 becomes greater than Vh1 and the minimum value Vm of the voltage of the ejection detection signal output from the ejection detection output unit 58 becomes less than Vm1 (S302: YES), the process proceeds to S303. Here, the time when the maximum value Vh is greater than Vh1 and the minimum value Vm is less than Vm1 is when ink is ejected from the nozzle 10 by the inspection drive.

[0095] In S303, the control unit 30 determines whether the maximum value Vh is less than Vh2 (>Vh1). If the maximum value Vh is less than Vh2 (S303: YES), the control unit 30 increases the ratio R of the time during which the value in the PWM signal becomes High by ΔR (S305) and returns to S301. As a result, the magnitude |Vda| of the comparison voltage Vda generated in the comparison voltage generation circuit 54 increases.

[0096] If the maximum value Vh is greater than or equal to Vh2 (S303: NO), the control unit 30 determines whether the minimum value Vm is greater than Vm2 (<Vm1). If the minimum value Vm is greater than Vm2 (S304: YES), the process proceeds to S305.

[0097] When the minimum value Vm is less than or equal to Vm2 (S304: NO), the control unit 30 determines whether the maximum value Vh is greater than Vh3 (>Vh2) and the minimum value Vm is less than Vm3 (<Vm2) (S306).

[0098] When the maximum value Vh is less than or equal to Vh3, or the minimum value Vm is greater than or equal to Vm3 (S306: NO), the process directly returns to S301. When the maximum value Vh is greater than Vh3 and the minimum value Vm is less than Vm3 (S306: YES), the control unit 30 decreases the ratio R of the time during which the value in the PWM signal is High by ΔR (S307) and returns to S301. As a result, the magnitude |Vda| of the comparison voltage Vda generated by the comparison voltage generation circuit 54 decreases.

[0099] Here, when inspection driving is performed, in the ejection detection signal output from the ejection detection output unit 58, when the maximum value Vh is greater than Vh1 and the minimum value Vm is less than Vm1, it is determined that ink is ejected from the nozzle 10. On the other hand, the relationship between the magnitude |V| of the voltage V output from the voltage supply circuit 51 and the maximum value Vh and the minimum value Vm of the voltage V1 of the ejection detection signal output from the ejection detection output unit 58 when ink is ejected from the nozzle 10 by inspection driving may vary due to environmental factors and various errors in the printer. And, for example, as shown by the dashed line in FIG. 14(b), if the difference between the maximum value Vh and Vh1 and the difference between the minimum value Vm and Vm1 are too small, even if ink is ejected from the nozzle 10 in subsequent inspection driving, the maximum value Vh may be less than or equal to Vh1, or the minimum value Vm may be greater than or equal to Vm1, resulting in a risk of misjudging that ink is not ejected from the nozzle 10. On the other hand, as shown by the dash-dotted line in FIG. 14(b), if the magnitude |Vh| of the maximum value Vh and the magnitude |Vm| of the minimum value Vm when ink is ejected from the nozzle 10 by inspection driving are too large, a signal of a large voltage will be input to the control unit 30, which may cause factors such as a malfunction. That is, the maximum value Vh when ink is ejected from the nozzle 10 by inspection driving is preferably within a certain range higher than Vh1 (for example, within the range of Vh2 or more and Vh3 or less), and the minimum value Vm is preferably within a certain range lower than Vm2 (for example, within the range of V2a or less and V2b or more).

[0100] Therefore, in Modification 3, as described above, when ink is ejected from the nozzle 10 by inspection driving, the PWM signal is changed based on the maximum value Vh and the minimum value Vm of the voltage V1 of the ejection detection signal output from the ejection detection output unit 58. As a result, the voltage output from the voltage supply circuit 51 is changed according to the change in the PWM signal. As a result, the maximum value Vh and the minimum value Vm of the ejection detection signal output from the ejection detection output unit 58 can be kept within an appropriate range.

[0101] In Modification 4, the control unit 30 changes the PWM signal by performing processing along the flow of FIG. 15(a). In Modification 4, when the output of the PWM signal is started in S104, the processing of the flow of FIG. 15(a) is started.

[0102] Explaining the flow of FIG. 15(a) in detail, the control unit 30 performs the processing of S402 to S407 described below until the output of the PWM signal is stopped in S108 (S401: NO). Then, when the output of the PWM signal is stopped in S109 (S401: YES), the processing ends.

[0103] In S402, the control unit 30 determines whether or not the magnitude |V2| of the voltage V2 of the first short-circuit signal output from the first short-circuit output unit 60 is smaller than V2b. That is, the control unit 30 determines whether or not a continuous short circuit has occurred between the inkjet head 4 and the electrode 26.

[0104] When the magnitude |V2| of the voltage V2 is smaller than V2b (S402: YES), the process returns to S401. When the magnitude |V2| of the voltage V2 is smaller than V2b, as described in the first embodiment, it is determined that a continuous short circuit has occurred between the inkjet head 4 and the electrode 26, and the output of the PWM signal is stopped in S108. Therefore, the processing of the flow of FIG. 15(a) ends.

[0105] When the magnitude |V2| of the voltage V2 is equal to or greater than V2b (S402: NO), the control unit 30 determines whether the magnitude |V2| of the voltage V2 of the first short-circuit signal output from the first short-circuit output unit 60 is smaller than V2c (V2b < V2c < V2a) (S403). When the magnitude |V2| of the voltage V2 is smaller than V2c (S403: YES), the control unit 30 increases the ratio R of the time during which the value in the PWM signal becomes High by ΔR (S404), and returns to S401. As a result, the magnitude |Vda| of the comparison voltage Vda generated in the comparison voltage generation circuit 54 increases.

[0106] When the magnitude |V2| of the voltage V2 is equal to or greater than V2c (S403: NO), the control unit 30 then determines whether the magnitude |V2| of the voltage V2 is greater than V2d (> V2a) (S405). When the magnitude |V2| of the voltage V2 is equal to or less than V2d (S405: NO), it returns to S401 as it is. When the magnitude |V2| of the voltage V2 is greater than V2d (S405: YES), the control unit 30 decreases the ratio R of the time during which the value in the PWM signal becomes High by ΔR (S406), and returns to S401. As a result, the magnitude |Vda| of the comparison voltage Vda generated in the comparison voltage generation circuit 54 decreases.

[0107] Here, when a continuous short circuit occurs between the inkjet head 4 and the electrode 26, the voltage V2 output from the first short-circuit output unit 60 significantly decreases and the magnitude |V2| of the voltage V2 becomes smaller than V2b. On the other hand, even when no continuous short circuit occurs between the inkjet head 4 and the electrode 26, it may be difficult to completely reduce the leakage current flowing between the inkjet head 4 and the electrode 26 to zero.

[0108] Also, as described in Modification Example 3, when performing inspection driving, it is preferable that the maximum value Vh and the minimum value Vm of the voltage V1 of the ejection detection signal output from the ejection detection output unit 58 fall within a certain range. On the other hand, the relationship between the magnitude |V| of the voltage V output from the voltage supply circuit 51 and the maximum value Vh and the minimum value Vs of the voltage of the ejection detection signal output from the ejection detection output unit 58 changes due to the influence of the leakage current flowing between the inkjet head 4 and the electrode 26.

[0109] For example, if a slight leakage current flows between the inkjet head 4 and the electrode 26, the voltage V output from the first short - circuit output unit 60 decreases. Also, the amount of voltage drop at this time is smaller than when a continuous short - circuit occurs between the inkjet head 4 and the electrode 26. Further, when time elapses, this leakage current may become smaller or zero, and in these cases, the voltage V output from the first short - circuit output unit 60 increases.

[0110] Therefore, in Modification Example 4, as described above, the PWM signal is changed based on the voltage V2 of the first short - circuit signal output from the first short - circuit output unit 60. As a result, the voltage output from the voltage supply circuit 51 is changed according to the change in the PWM signal. As a result, the maximum value Vh and the minimum value Vm of the voltage V1 of the ejection detection signal output from the ejection detection output unit 58 can be made to fall within an appropriate range.

[0111] For example, as shown in FIG. 15(b), when a leakage current smaller than when a continuous short - circuit occurs between the inkjet head 4 and the electrode 26 starts to flow at time T3a, the voltage V2 output from the first short - circuit output unit 60 decreases to a voltage within the range of V2b≦V2<V2c. At this time, by increasing the ratio R of the PWM signal, the voltage V2 output from the first short - circuit output unit 60 rises above V2c.

[0112] Also, for example, when the leakage current flowing between the inkjet head 4 and the electrode 26 becomes small or zero at a subsequent time T3b, the voltage V2 output from the first short - circuit output unit 60 rises and becomes higher than V2d. At this time, by decreasing the ratio R of the PWM signal, the voltage V2 output from the first short - circuit output unit 60 decreases and becomes lower than V2d.

[0113] In Modification 5, as shown in FIG. 16(a), in addition to the same configuration as the printer 1 of the first and second embodiments, the printer 130 includes a temperature sensor 131 and a humidity sensor 132. In Modification 5, the temperature sensor and the humidity sensor 132 correspond to the "information acquisition unit" of the present invention.

[0114] The temperature sensor 131 acquires information on temperature such as the ambient air temperature, etc., and outputs a temperature signal indicating the acquired temperature information to the control unit 30. The humidity sensor 132 acquires information on humidity such as the ambient humidity, etc., and outputs a humidity signal indicating the acquired humidity information to the control unit 30. Also, in Modification 5, as shown in FIG. 16(b), in the memory 34 (the "storage unit" of the present invention), a table (the "association information" of the present invention) in which the ranges of temperature X and humidity Y are associated with the ratio R of the time during which the value in the PWM signal becomes High is stored.

[0115] Then, in Modification 5, based on the temperature X indicated by the temperature signal received from the temperature sensor 131, the humidity Y indicated by the humidity signal received from the humidity sensor 131, and the table in FIG. 16(b), the control unit 30 determines the ratio R of the time during which the value in the PWM signal becomes High, and outputs a PWM signal corresponding to the determined ratio R.

[0116] As described in Modification 3, when performing the inspection drive, it is preferable to make the maximum value Vh and the minimum value Vm of the voltage of the ejection detection signal output from the ejection detection output unit 58 fall within a certain range. On the other hand, the relationship between the magnitude |V| of the voltage V output from the voltage supply circuit 51 and the maximum value Vh and the minimum value Vm of the voltage output from the ejection detection output unit 58 may vary depending on the influence of temperature and humidity.

[0117] Therefore, in Modification 5, based on the temperature information acquired by the temperature sensor 131, the humidity information acquired by the humidity sensor 132, and the table stored in the memory 34, the ratio R of the time during which the value in the PWM signal becomes High is determined. Then, based on the determined ratio R, by outputting the PWM signal, the comparison voltage is changed. As a result, the maximum value Vh and the minimum value Vm of the voltage of the ejection detection signal output from the ejection detection output unit 58 can be made to fall within an appropriate range regardless of the influence of temperature and humidity.

[0118] Also, in Modification 5, the printer 130 includes the temperature sensor 131 and the humidity sensor 132, and determines the ratio R in the PWM signal using the temperature information acquired by the temperature sensor 131 and the humidity information acquired by the humidity sensor 132, but it is not limited to this. The printer may include only one of the temperature sensor 131 and the humidity sensor 132, and determine the ratio R in the PWM signal based on one of the temperature and humidity information detected by this one sensor.

[0119] Also, in the first and second embodiments, the voltage supply circuit applies a voltage to the electrode 26 to generate a potential difference between the inkjet head 4 and the electrode 26, and the ejection detection output unit 58, the first short-circuit output unit 60, and the second short-circuit output unit 62 are all electrically connected to the electrode 26, but it is not limited to this.

[0120] In Modification 6, as shown in FIG. 17, an inspection circuit 141 is connected to the inkjet head 4. Also, the electrode 26 is held at the ground potential. Further, as shown in FIG. 18, the inspection circuit 141 is the inspection circuit 27 excluding the electrode 26, and the inkjet head 4 is electrically connected to the connection portion 52d. As a result, in Modification 6, when a voltage is applied to the inkjet head 4 by the voltage supply circuit 51, a potential difference is generated between the inkjet head 4 and the electrode 26.

[0121] In Modification 7, as shown in Fig. 19(a), in a configuration where a voltage is applied to the electrode 26 by the voltage supply circuit 51 in the same manner as in the first embodiment, a discharge detection output unit 151 is connected to the inkjet head 4, and an amplifier circuit 152 is connected between the discharge detection output unit 151 and the inkjet head 4. Further, in Modification 7, the inkjet head 4 is connected to the ground. Although not shown, in Modification 7, the discharge detection output unit and the amplifier circuit are not connected to the electrode 26.

[0122] In Modification 8, as shown in Fig. 19(b), in a configuration where a voltage is applied to the inkjet head 4 by the voltage supply circuit 51, a discharge detection output unit 151 is connected to the electrode 26, and an amplifier circuit 152 is connected between the discharge detection output unit 151 and the electrode 26. Further, in Modification 8, the electrode 26 is connected to the ground. Although not shown, in Modification 8, the discharge detection output unit and the amplifier circuit are not connected to the inkjet head 4. As described above, a voltage may be supplied to either the inkjet head 4 or the electrode 26, and the discharge detection output unit 151 may be connected to either of them.

[0123] Even when a potential difference is generated between the inkjet head 4 and the electrode 26 by applying a voltage to either the inkjet head 4 or the electrode 26, when ink is discharged from the nozzle 10 by inspection driving, a voltage change occurs in the inkjet head 4 and the electrode 26. Therefore, even in the configurations of Modifications 6 to 8, it is possible to determine whether or not ink is normally discharged from the nozzle 10 based on the voltage of the discharge detection signal output from the discharge detection output unit. And even in the configurations of Modifications 6 to 8, when performing inspection driving, the magnitude of the voltage applied to the inkjet head 4 or the electrode 26 can be stabilized, and it is possible to accurately determine whether or not ink is normally discharged from the nozzle 10.

[0124] In addition, in Modification 7, a filter may be connected between the inkjet head 4 and the ground. Also, in Modification 8, a filter may be connected between the electrode 26 and the ground. These filters are used to prevent the amplitude of the signal from decreasing due to ink ejection from the inkjet head 4 in a configuration where a voltage is supplied to one of the inkjet head 4 and the electrode 26 while the ejection detection output unit is connected to the other. By providing the filter, the signal output from the ejection detection output unit can be made larger.

[0125] Also, in the above example, the comparison voltage generation circuit 54 generates a comparison voltage based on the PWM signal received from the control unit 30, but this is not limiting. The comparison voltage generation circuit may generate a comparison voltage with a different configuration. For example, the comparison voltage generation circuit may generate a comparison voltage by dividing the voltage supplied from the power source with a resistor. Also, in this case, a plurality of resistors connectable to the power source and a switch for switching the connection and disconnection between the power source and each of these resistors are provided, and the voltage division ratio is changed by switching the resistor connected to the power source with the switch, thereby changing the generated comparison voltage.

[0126] Also, in the above example, the inspection circuit 27 has a voltage division circuit 53 that divides the voltage output from the voltage supply unit. Then, 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 division 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, the voltage supply circuit 51 outputs a voltage to apply a voltage to the electrode 26 by switching whether to perform boosting in the voltage supply circuit 51. However, this is not limiting.

[0127] For example, a comparison circuit may be made capable of receiving a high voltage input without providing a voltage division circuit. Then, the voltage V output from the voltage supply circuit 51 and a predetermined voltage Va are input to the comparison circuit, and the comparison circuit may output a comparison signal according to whether the magnitude |V| of the voltage V output from the voltage supply circuit 51 is greater than the magnitude |Va| of the predetermined voltage Va.

[0128] Also, in the above example, the inspection circuit has the first short-circuit output unit 60 that outputs a signal according to whether a continuous short circuit has occurred between the inkjet head 4 and the electrode 26, and the second short-circuit output unit 62 that outputs a signal according to whether a temporary short circuit has occurred between the inkjet head 4 and the electrode 26, but it is not limited to this. The inspection circuit may have only one of the first short-circuit output unit 60 and the second short-circuit output unit 62. Also, the inspection circuit may not have either the first short-circuit output unit 60 or the second short-circuit output unit 62.

[0129] Also, in the above example, the inspection circuit has the discharge circuit 63, but the discharge circuit may have a configuration different from that described above. Alternatively, the inspection circuit may not have a discharge circuit.

[0130] Also, in the above-described embodiment, inspection driving was performed for all the nozzles 10 of the inkjet head 4 to determine whether ink was normally ejected from the nozzles 10, but it is not limited to this. For example, inspection driving may be performed only for some of the nozzles 10 of the inkjet head 4, such as every other nozzle 10 in each nozzle row 9, to determine whether ink was normally ejected from the nozzles 10. Then, for the other nozzles 10, it may be estimated whether ink is normally ejected from the nozzles 10 based on the determination result for the some of the nozzles 10.

[0131] Also, in the above example, the ejection detection signal output from the ejection detection output unit is a signal corresponding to whether or not ink is ejected from the nozzle 10. And when the ejection detection signal indicates that ink has been ejected from the nozzle 10, it is determined that ink has been normally ejected from the nozzle 10. However, this is not limited thereto. The ejection detection signal may be a signal corresponding to an ejection mode different from whether or not ink has been ejected, such as the ejection direction or ejection speed of the ink. And when the ejection detection signal indicates that ink has been ejected from the nozzle 10 in a predetermined ejection mode, it may be determined that ink has been normally ejected from the nozzle 10.

[0132] Also, in the above, an example in which the present invention is applied to a printer including a so-called serial head that ejects ink from a plurality of nozzles while moving in the scanning direction together with the carriage has been described, but this is not limited thereto. For example, it is also possible to apply the present invention to a printer including a so-called line head that extends over the entire length of the recording paper in the scanning direction.

[0133] Also, in the above, an example in which the present invention is applied to a printer that ejects ink from a nozzle to perform recording on a recording paper P has been described, but this is not limited thereto. 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 advertisements, cases of mobile terminals such as smartphones, cardboard, and resin members. Further, the present invention can also be applied to liquid ejection devices that eject liquids other than ink, such as resins or metals in a liquid state.

Explanation of Reference Numerals

[0134] 1: Printer 4: Inkjet head 26: Electrode 51: Voltage supply circuit 52: Main circuit 53: Voltage dividing circuit 54: Comparative voltage generation circuit 55: Comparison circuit 58: Ejection detection output unit 60: Short-circuit detection output unit 62: Short-circuit detection output unit 101: Voltage supply circuit 101a: Control signal receiving section 111: Voltage supply circuit 121: Voltage supply circuit 130: Printer 131: Temperature sensor 132: Humidity sensor 151: Discharge detection output section 161: Discharge detection output section

Claims

1. A liquid ejection head having a nozzle for ejecting a liquid, An electrode disposed to face the nozzle, A voltage supply unit that generates a potential difference between the liquid ejection head and the electrode by applying a voltage to either the liquid ejection head or the electrode, A first output unit that is electrically connected to either the liquid ejection head or the electrode, and outputs a voltage corresponding to an electrical change when the liquid ejection head is caused to perform a test drive for ejecting a liquid from the nozzle toward the electrode with the liquid ejection head and the electrode facing each other, A voltage comparison unit electrically connected to the voltage supply unit, The voltage comparison unit has a comparison signal output unit that outputs a comparison signal according to whether the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of a predetermined voltage, The voltage supply unit, Has a comparison signal receiving unit that receives the comparison signal electrically connected to the comparison signal output unit, When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, a boosting operation is performed to increase the magnitude of the output voltage, When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, the boosting operation is stopped. A liquid ejection device characterized by this.

2. A liquid ejection head having a nozzle for ejecting a liquid, An electrode disposed to face the nozzle, A voltage supply unit that generates a potential difference between the liquid ejection head and the electrode by applying a voltage to either the liquid ejection head or the electrode, A first output unit that is electrically connected to either the liquid ejection head or the electrode, and outputs a voltage corresponding to an electrical change when the liquid ejection head is caused to perform inspection driving for ejecting liquid from the nozzle toward the electrode in a state where the liquid ejection head and the electrode face each other; A voltage comparison unit electrically connected to the voltage supply unit; A control unit; and The voltage comparison unit includes a comparison signal output unit that outputs a comparison signal to the control unit according to whether the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of a predetermined voltage. The control unit: When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, outputs a control signal for controlling the voltage supply unit, the control signal instructing to perform a voltage boost to increase the magnitude of the voltage output from the voltage supply unit; When the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, outputs the control signal instructing to stop the voltage boost; The voltage supply unit: Includes a control signal receiving unit that receives the control signal; When the control signal instructs to perform the voltage boost, performs the voltage boost; When the control signal instructs to stop the voltage boost, stops the voltage boost. A liquid ejection device characterized by the above.

3. A main circuit that connects either the liquid ejection head or the electrode to the voltage supply unit; The voltage comparison unit: A voltage dividing circuit that is connected to the main circuit and divides the voltage output from the voltage supply unit; A comparison voltage generation circuit that generates a comparison voltage corresponding to the predetermined voltage, the comparison voltage being a voltage for comparing with the voltage output from the voltage dividing circuit; The liquid discharge device according to claim 1 or 2, further comprising: a comparison circuit that outputs a signal according to whether the magnitude of the voltage output from the voltage dividing circuit is greater than the magnitude of the comparison voltage as the comparison signal.

4. comprising a control unit, the control unit outputs a PWM signal for generating the comparison voltage, the comparison voltage generation circuit, has a PWM signal receiving unit that receives the PWM signal, The liquid discharge device according to claim 3, wherein the comparison voltage is generated based on the PWM signal.

5. the control unit, is configured to be able to change the PWM signal, The liquid discharge device according to claim 4, wherein the PWM signal corresponding to the magnitude of the voltage output from the first output unit is output.

6. comprising a second output unit connected to the main circuit and outputting a voltage according to the magnitude of the leakage current flowing between the liquid discharge head and the electrode, the control unit, is configured to be able to change the PWM signal, The liquid discharge device according to claim 4, wherein the PWM signal corresponding to the magnitude of the voltage output from the second output unit is output.

7. an information acquisition unit that acquires environment information which is information on at least one of temperature and humidity; a storage unit that stores association information associating the environment information and the comparison voltage, the control unit, is configured to be able to change the PWM signal, The liquid discharge device according to claim 5, wherein the PWM signal corresponding to the environment information acquired by the information acquisition unit and the association information stored in the storage unit is output.

8. comprising a control unit, the control unit outputs a permission signal indicating whether to permit the boosting in the voltage supply unit, the voltage supply unit has a permission signal receiving unit that receives the permission signal, when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, and the permission signal indicates permission to perform the boosting, the boosting is performed, when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, and when the permission signal indicates non - permission to perform the boosting, the boosting is stopped. The liquid ejection device according to claim 1, characterized in that.

9. the control unit outputs a permission signal indicating whether to permit the boosting in the voltage supply unit, the voltage supply unit has a permission signal receiving unit that receives the permission signal, when the control signal instructs to perform the boosting and the permission signal indicates permission to perform the boosting, the boosting is performed, when the control signal instructs to stop the boosting and when the permission signal indicates non - permission to perform the boosting, the boosting is stopped. The liquid ejection device according to claim 2, characterized in that.

10. comprising a control unit, the control unit outputs a permission signal indicating whether to permit the boosting in the voltage supply unit and an on - off signal indicating whether to set the voltage supply unit to an on state in which the boosting can be performed or an off state in which the boosting cannot be performed, the voltage supply unit A permission signal receiving unit that receives the permission signal, An on-off signal receiving unit that receives the on-off signal, and when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is less than or equal to the magnitude of the predetermined voltage, and the permission signal indicates permission to perform the boosting, and the on-off signal indicates that the voltage supply unit is in the on state, perform the boosting, when the comparison signal indicates that the magnitude of the voltage output from the voltage supply unit is greater than the magnitude of the predetermined voltage, the permission signal indicates non-permission to perform the boosting, and the on-off signal indicates that the voltage supply unit is in the off state, stop the boosting. The liquid discharge device according to claim 1, characterized in that

11. The control unit outputs a permission signal indicating whether to permit the boosting in the voltage supply unit, and an on-off signal indicating whether to set the voltage supply unit to an on state in which the boosting can be performed or an off state in which the boosting cannot be performed, and The voltage supply unit has a permission signal receiving unit that receives the permission signal, and an on-off signal receiving unit that receives the on-off signal, and when the control signal instructs to perform the boosting, the permission signal indicates permission to perform the boosting, and the on-off signal indicates that the voltage supply unit is in the on state, perform the boosting, when the control signal instructs to stop the boosting, the permission signal indicates non-permission to perform the boosting, and the on-off signal indicates that the voltage supply unit is in the off state, stop the boosting. The liquid discharge device according to claim 2, characterized in that

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