Printing device and head

Abstract

To provide a printing device in which a common electrode can be suppressed from producing heat, and a head.SOLUTION: A printing device comprises: a nozzle plate which has a first nozzle row having at least one nozzle that discharges liquid by an applied voltage and a second nozzle row having at least one nozzle that discharges liquid by an applied voltage; a common electrode arranged across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzle of the first nozzle row, to which a voltage is applied; a second individual electrode corresponding to the nozzle of the second nozzle row. to which a voltage is applied; and a control circuit. The control circuit allows a driving waveform for making the nozzle discharge liquid to be inputted at a predetermined driving cycle and makes a cycle at which the voltage is applied to the second individual electrode delay, by time shorter than the driving cycle, than a cycle at which the voltage is applied to the first individual electrode.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present technology relates to a printing device and a head that prints by ejecting liquid from nozzles. [Background technology]

[0002] A liquid ejection head has been proposed that includes an actuator having two common electrode layers, one individual electrode layer, a piezoelectric element, and a vibration plate, and ejects liquid from nozzles by vibration of the actuator. The common electrode layer has a strip-shaped first portion extending in a direction perpendicular to the nozzle row, and a plurality of second portions extending perpendicularly from the first portion (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-96070 A Summary of the Invention [Problem to be solved by the invention]

[0004] When power is supplied to the actuator, the actuator vibrates. At this time, a current flows from the second portions to the first portion. The current is concentrated in the first portion, and the first portion is likely to become hot.

[0005] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a printing device and a head that are capable of suppressing heat generation in the common electrode. [Means for solving the problem]

[0006] A printing device according to one embodiment of the present disclosure comprises a nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, a common electrode arranged across the first nozzle row and the second nozzle row, first individual electrodes corresponding to the nozzles of the first nozzle row and to which a voltage is applied, second individual electrodes corresponding to the nozzles of the second nozzle row and to which a voltage is applied, and a control circuit, wherein the control circuit inputs a drive waveform for ejecting liquid from the nozzles at a predetermined drive period, and delays the period for applying a voltage to the second individual electrode by a time shorter than the drive period relative to the period for applying a voltage to the first individual electrode.

[0007] A head according to one embodiment of the present disclosure comprises a nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, a common electrode arranged across the first nozzle row and the second nozzle row, first individual electrodes corresponding to the nozzles of the first nozzle row and to which a voltage is periodically applied, second individual electrodes corresponding to the nozzles of the second nozzle row and to which a voltage is periodically applied, and a control circuit, wherein the control circuit inputs a drive waveform for ejecting liquid from the nozzles at a predetermined drive period, and delays the period for applying a voltage to the second individual electrode by a time shorter than the drive period relative to the period for applying a voltage to the first individual electrode. Effect of the Invention

[0008] In a printing device and a head according to an embodiment of the present disclosure, a drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle. The control circuit delays the cycle for applying a voltage to the second individual electrode by a time shorter than the drive cycle with respect to the cycle for applying a voltage to the first individual electrode, thereby canceling out the current flowing through the common electrode and suppressing heat generation in the common electrode. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view illustrating a printing device according to a first embodiment. [Diagram 2] FIG. 4 is an explanatory diagram illustrating the flow of ink between a subtank and an inkjet head. [Diagram 3] FIG. 2 is a simplified partial enlarged cross-sectional view of an ink-jet head. [Figure 4] FIG. 2 is a block diagram of a printing device. [Diagram 5] FIG. 4 is a schematic plan view of a common electrode. [Figure 6] FIG. 2 is a schematic circuit diagram of a mainstream electrode and an actuator. [Figure 7] 13 is a timing chart showing the first to sixth voltage waveforms, the first to sixth current waveforms, and the total current when actuators are driven simultaneously. [Figure 8] 13 is a timing chart showing a first voltage waveform to a sixth voltage waveform and a first current waveform to a sixth current waveform in a case where an actuator is driven with a delay of Δt. [Figure 9] 13 is a timing chart showing a first current waveform to a sixth current waveform and a total current when an actuator is driven with a delay of Δt. [Figure 10] 13 is a timing chart showing a first voltage waveform to a sixth voltage waveform, a first current waveform to a sixth current waveform, and a total current when the actuator is driven with a delay of ΔT. [Figure 11] 10 is a flowchart illustrating a printing process performed by the control device. [Figure 12] FIG. 11 is a simplified partial enlarged cross-sectional view of an ink-jet head according to a second embodiment. [Figure 13] FIG. 2 is a block diagram of a printing device. [Figure 14] FIG. 4 is a schematic plan view of a common electrode and a second common electrode. [Figure 15] FIG. 2 is a schematic circuit diagram of a mainstream electrode and an actuator. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Embodiment 1) The present invention will be described below based on the drawings showing a printing device according to a first embodiment. Fig. 1 is a plan view showing the printing device, and Fig. 2 is an explanatory diagram showing the flow of ink between a sub-tank and an inkjet head. In the following description, the front, back, left and right directions shown in Fig. 1 will be used. The front and back directions correspond to the transport direction, and the left and right directions correspond to the scanning direction. The front side of Fig. 1 corresponds to the upper side, and the back side corresponds to the lower side, and up and down will also be used.

[0011] 1, the printing device 1 includes a platen 2, an ink ejection device 3, and transport rollers 4 and 5. A recording medium, that is, a recording paper 200, is placed on the upper surface of the platen 2. The ink ejection device 3 ejects ink onto the recording paper 200 placed on the platen 2 to record an image. The ink ejection device 3 includes a carriage 6, a sub-tank 7, four inkjet heads 8, a circulation pump 10, and the like.

[0012] Two guide rails 11, 12 extending to the left and right are provided above the platen 2 to guide the carriage 6. An endless belt 13 extending to the left and right is connected to the carriage 6. The endless belt 13 is driven by a carriage drive motor 14. As the endless belt 13 is driven, the carriage 6 is guided by the guide rails 11, 12 and moves back and forth in the scanning direction in an area facing the platen 2.

[0013] A cap 20 and a flushing receiver 21 are provided between the guide rails 11 and 12. The cap 20 and the flushing receiver 21 are disposed below the ink ejection device 3. The cap 20 is disposed at the right end of the guide rails 11 and 12, and the flushing receiver 21 is disposed at the left end of the guide rails 11 and 12. The cap 20 and the flushing receiver 21 may be disposed left and right reversed.

[0014] The sub-tank 7 and the four inkjet heads 8 are mounted on a carriage 6 and move back and forth in the scanning direction together with the carriage 6. The sub-tank 7 is connected to a cartridge holder 15 via a tube 17. Ink cartridges 16 of one or more colors (four colors in this embodiment) are attached to the cartridge holder 15. Examples of the four colors include black, yellow, cyan, and magenta.

[0015] Four ink chambers 19 are formed inside the subtank 7. The four ink chambers 19 store four colors of ink supplied from the four ink cartridges 16, respectively.

[0016] The four inkjet heads 8 are aligned in the scanning direction below the subtank 7. A plurality of nozzles 80 are formed on the bottom surface of each inkjet head 8. As shown in Fig. 2, one inkjet head 8 corresponds to one color of ink and is connected to one ink chamber 19. That is, the four inkjet heads 8 correspond to four colors of ink, respectively, and are connected to four ink chambers 19, respectively.

[0017] An ink supply port 83 and an ink discharge port 84 are provided on the upper surface of the inkjet head 8. The ink supply port 83 and the ink discharge port 84 are connected to the ink chamber 19 via a tube or the like. A circulation pump 10 is interposed between the ink supply port 83 and the ink chamber 19.

[0018] The circulation pump 10 is a tube pump that pushes out the liquid in a tube by, for example, squeezing the tube with a rotor. The circulation pump 10 sends the ink in the ink chamber 19 to the inkjet head 8.

[0019] Ink sent from the ink chamber 19 by the circulation pump 10 flows into the inkjet head 8 through the ink supply port 83 and is ejected from the nozzle 80. Ink that is not ejected from the nozzle 80 returns to the ink chamber 19 through the ink discharge port 84. The ink circulates between the ink chamber 19 and the inkjet head 8. Note that instead of the circulation pump 10, another power source for circulation, such as a device that sends compressed air into the subtank 7 to send the ink to the inkjet head 8, may be used. The four inkjet heads 8 eject the four colors of ink supplied from the subtank 7 onto the recording paper 200 while moving in the scanning direction together with the carriage.

[0020] As shown in FIG. 1, the transport roller 4 is disposed upstream (rear) of the platen 2 in the transport direction. The transport roller 5 is disposed downstream (front) of the platen 2 in the transport direction. The two transport rollers 4, 5 are driven synchronously by a motor (not shown). The two transport rollers 4, 5 transport the recording paper 200 placed on the platen 2 in a transport direction perpendicular to the scanning direction. The printing device 1 includes a control device 50. The control device 50 includes a CPU, a non-volatile memory, a RAM, a logic circuit (e.g., FPGA), etc. The control device 50 receives a print job from an external device 100, controls the driving of the ink ejection device 3 and the transport rollers 4, etc., and executes the print process.

[0021] FIG. 3 is a schematic partially enlarged cross-sectional view of the inkjet head 8. The inkjet head 8 includes a plurality of pressure chambers 81. The pressure chambers 81 form a plurality of pressure chamber rows. A vibration plate 82 is formed above the pressure chambers 81. A layered piezoelectric body 83 is formed above the vibration plate 82. A common electrode 84 is formed between the piezoelectric body 83 and the vibration plate 82 above each pressure chamber 81. An individual electrode 85 is formed on the upper surface of the piezoelectric body 83 above each pressure chamber 81. The individual electrode 85 and the common electrode 84 face each other vertically with the piezoelectric body 83 in between. A nozzle plate 87 is provided below each pressure chamber 81. A plurality of nozzles 80 are formed in the nozzle plate 87, penetrating vertically. Each nozzle 80 is disposed below each pressure chamber 81. The plurality of nozzles 80 form a plurality of nozzle rows, including a first nozzle row 80a and a second nozzle row 80b (see FIG. 5). The nozzle rows extend along the pressure chamber rows. The common electrode 84 is arranged across the first nozzle row 80a and the second nozzle row 80b.

[0022] The common electrode 84 is connected to a COM terminal, which is connected to ground in this embodiment. The individual electrode 85 is connected to the switch control unit 67. When a high or low voltage is applied to the individual electrode 85, the piezoelectric body 81 deforms and the diaphragm 82 vibrates. The vibration of the diaphragm 82 causes ink to be ejected from the pressure chamber 81 via the nozzle 80.

[0023] 4 is a block diagram of the printing device 1. The printing device 1 includes an AC / DC converter 62 connected to an AC power source 61. The AC / DC converter 62 converts AC voltage into DC voltage and outputs it to a DC / DC converter 63. The DC / DC converter 63 changes the voltage and outputs it to a switch control unit (SW control unit) 67.

[0024] The switch control unit 67 includes a plurality of n-th switches 67(n) (n=1, 2,...) and a switch 67a. The n-th switch 67(n) and the detection switch 67a are configured by, for example, an analog switch IC. One end of each of the n-th switches 67(n) and one end of the detection switch 67a are connected to an individual electrode 85 via a common bus.

[0025] The other ends of the multiple nth switches 67(n) are connected to multiple nth waveform generating units 66(n) (n = 1, 2, ...), respectively. That is, the first switch 67(1) is connected to the first waveform generating unit 66(1), the second switch 67(2) is connected to the second waveform generating unit 66(2), and the nth switch 67(n) is connected to the nth waveform generating unit 66(n).

[0026] The other end of the detection switch 67a is connected to the detection circuit 65. The detection circuit 65 detects the capacitance of the actuator 88, in other words, the capacitance of a capacitor formed by the common electrode 84, the individual electrode 85, and the piezoelectric body 83. The printing device 1 includes a control circuit 64. The control circuit 64 includes a CPU, a non-volatile memory, a RAM, a logic circuit (e.g., an FPGA), or the like. The control circuit 64 causes the switch control unit 67 to connect or disconnect the nth switch 67(n) and the detection amount switch 67a. The control circuit 64 causes each nth waveform generating unit 66(n) to output a drive waveform. Each nth waveform generating unit 66(n) outputs a different waveform. The control circuit 64 causes the detection circuit 65 to detect the capacitance.

[0027] A case where the actuator 88 is driven will be described. For example, when the actuator 88 is driven by a drive waveform generated by the first waveform generating unit 66(1), the control circuit 64 causes the switch control unit 67 to connect only the first switch 67(1) and output a drive waveform from the first waveform generating unit 66(1) to the actuator 88. At this time, all other switches, that is, the second switch 67(2), the third switch 67(3), ..., the nth switch 67(n), and the detection switch 67a, are disconnected. The same process is performed when the actuator 88 is driven by a drive waveform generated by the second waveform generating unit 66(2), the third waveform generating unit 66(3), ..., or the nth waveform generating unit 66(n).

[0028] A case where the capacitance is detected will be described. The control circuit 64 connects only the detection switch 67a to the switch control unit 67. The detection circuit 65, for example, charges and discharges the capacitance to measure the capacitance. At this time, all of the n-th switches 67(n), i.e., the first switch 67(1), the second switch 67(2), ..., the n-th switch 67(n), are disconnected.

[0029] 5 is a schematic plan view of the common electrode 84. In FIG. 5, the X direction indicates a direction parallel to the nozzle row, and the Y direction indicates a direction intersecting the nozzle row. The common electrode 84 includes two mainstream electrodes 90, 90. The two mainstream electrodes 90, 90 are spaced apart in the X direction. The mainstream electrodes 90 are strip-shaped and extend in the Y direction. One end of each mainstream electrode 90 is connected to the COM electrode. The other end of each mainstream electrode 90 is connected via a connecting portion 93.

[0030] A plurality of tributary electrodes 91 are connected to the mainstream electrode 90. The tributary electrodes 91 are strip-shaped and extend in the X direction. The plurality of tributary electrodes 91 are arranged at approximately equal intervals in the Y direction. That is, the common electrode 84 is comb-shaped. In this embodiment, as an example, six tributary electrodes 91 are connected to one mainstream electrode 90, but the number of tributary electrodes 91 is not limited to six. Hereinafter, the six tributary electrodes 91 are also referred to as a first tributary electrode 91(1), a second tributary electrode 91(2), a third tributary electrode 91(3), a fourth tributary electrode 91(4), a fifth tributary electrode 91(5), and a sixth tributary electrode 91(6). The first branch electrode 91(1) to the sixth branch electrode 91(6) are arranged in order from the other end of the mainstream electrode 90 (the part closest to the connecting portion 93) to one end of the mainstream electrode 90 (the part closest to the COM electrode).

[0031] A row of pressure chambers is arranged below the branch electrode 91, and a row of nozzles is arranged below the pressure chambers. Fig. 5 shows a state in which a first nozzle row 80a is arranged below the first branch electrode 91(1), and a second nozzle row 80b is arranged below the second branch electrode 91(2). Although not shown in Fig. 5, a third nozzle row 80c to a sixth nozzle row 80f (see Fig. 6) are also arranged below the third branch electrode 91(3) to the sixth branch electrode 91(6), respectively. Each nozzle row is arranged between two main electrodes 90, 90.

[0032] If the width of the main electrode 90 in the X direction is d1 and the width of the tributary electrode 91 in the Y direction is d2, then d1 is shorter than the sum of the widths d2 of the multiple tributary electrodes 91. For example, d1 is 1000 μm, d2 is 600 μm, and there are 12 tributary electrodes 91.

[0033] For example, as shown in FIG. 5 , in the mainstream electrode 90, the region between the first tributary electrode 91(1) and the second tributary electrode 91(2) is defined as a first region 90(1), the region between the second tributary electrode 91(2) and the second tributary electrode 91(3) is defined as a second region 90(2), the region between the third tributary electrode 91(3) and the fourth tributary electrode 91(4) is defined as a third region 90(3), the region between the fourth tributary electrode 91(4) and the fifth tributary electrode 91(5) is defined as a fourth region 90(4), the region between the fifth tributary electrode 91(5) and the sixth tributary electrode 91(6) is defined as a fifth region, and the region between the sixth tributary electrode 91(6) and one end of the mainstream electrode 90 (the portion closest to the COM electrode) is defined as a sixth region 90(6). The resistances of the first region 90(1) to the sixth region 90(6) are respectively a first resistance r1 to a sixth resistance r6.

[0034] Fig. 6 is a schematic circuit diagram of the mainstream electrode 90 and the actuators 88a to 88f. In Fig. 6, the actuator 88 of each nozzle 80 in the first nozzle row 80a is representatively represented as one actuator 88a. Similarly, the actuators in the second nozzle row 80b to the sixth nozzle row 80f are represented as one actuator 88b to 88f.

[0035] Fig. 7 is a timing chart showing the first to sixth voltage waveforms, the first to sixth current waveforms, and the total current when the actuators 88a to 88f are driven simultaneously. In Fig. 7, the first to sixth voltage waveforms indicate voltage waveforms applied to the actuators 88a to 88f, the first to sixth current waveforms indicate current waveforms flowing through the first to sixth branch electrodes 91(1) to 91(6), and the total current indicates the amount of current flowing through the main electrode 90. Here, the first to sixth voltage waveforms have the same waveform shape.

[0036] As shown in FIG. 7, when the first voltage waveform to the sixth voltage waveform are input to the individual electrodes 85 of the actuators 88a to 88f at the same timing, a current also flows through the first branch electrode 91(1) to the sixth branch electrode 91(6) at the same timing, and a current flows through the first resistor r1 to the sixth resistor r6, as shown by the arrows in FIG. 5. In detail, the current flowing through the first tributary electrode 91(1) flows through the first resistor r1, the current flowing through the first tributary electrode 91(1) and the second tributary electrode 91(2) flows through the second resistor r2, the current flowing through the first tributary electrode 91(1) to the third tributary electrode 91(3) flows through the third resistor r3, the current flowing through the first tributary electrode 91(1) to the fourth tributary electrode 91(4) flows through the fourth resistor r4, the current flowing through the first tributary electrode 91(1) to the fifth tributary electrode 91(5) flows through the fifth resistor r5, and the current flowing through the first tributary electrode 91(1) to the sixth tributary electrode 91(6) flows through the sixth resistor r6. The amount of current flowing through the sixth resistor r6 corresponds to the total current. Since the first to sixth current waveforms have the same rising and falling points, the currents flowing through the first to sixth tributary electrodes 91(1) to 91(6) in the mainstream electrode 90 are sequentially added toward the COM electrode. Therefore, a larger current flows through the mainstream electrode 90 than through each of the tributary electrodes 91, and the amount of heat generated by the mainstream electrode 90 tends to be large.

[0037] Fig. 8 is a timing chart showing the first to sixth voltage waveforms and the first to sixth current waveforms when the actuators 88a to 88f are driven with a delay of Δt each, and Fig. 9 is a timing chart showing the first to sixth current waveforms and the total current when the actuators 88a to 88f are driven with a delay of Δt each. In Fig. 8, S is the drive period of the first to sixth voltage waveforms, and Δt is shorter than the drive period S. When the individual electrode 85 of actuator 88a is the first individual electrode 85a and the individual electrode 85 of actuator 88b is the second individual electrode 85b (see FIG. 3), the period in which a voltage is applied to the second individual electrode 85b is delayed by Δt from the period in which a voltage is applied to the first individual electrode 85a.

[0038] Here, the pulse width of the current waveform is 2Δt, the rising point of the first current waveform is t1, the rising point of the second current waveform is t2, the rising point of the third current waveform and the falling point of the first current waveform is t3, the rising point of the fourth current waveform and the falling point of the second current waveform is t4, the rising point of the fifth current waveform and the falling point of the third current waveform is t5, the rising point of the sixth current waveform and the falling point of the fourth current waveform is t6, the falling point of the fifth current waveform is t7, and the falling point of the sixth current waveform is t8.

[0039] When the drive timing of actuators 88a to 88f is delayed by Δt, the total current at time t1 is the current flowing through the first tributary electrode 91(1), the current amount at time t2 is the current flowing through the first tributary electrode 91(1) and the second tributary electrode 91(2), the total current at time t3 is the current flowing through the second tributary electrode 91(2) and the third tributary electrode 91(3), the total current at time t4 is the current flowing through the third tributary electrode 91(3) and the fourth tributary electrode 91(4), the total current at time t5 is the current flowing through the fourth tributary electrode 91(4) and the fifth tributary electrode 91(5), the total current at time t6 is the current flowing through the fifth tributary electrode 91(3) and the sixth tributary electrode 91(6), and the total current at time t7 is the current flowing through the sixth tributary electrode 91(6). At time t8, no current flows through the mainstream electrode 90. In this way, when the drive timings of the actuators 88a to 88f are delayed by Δt each, the effective value of the total current amount can be made smaller than when the actuators 88a to 88f are driven simultaneously.

[0040] 10 is a timing chart showing the first to sixth voltage waveforms, the first to sixth current waveforms, and the total current when the actuators 88a to 88f are driven with a delay of ΔT each. Here, ΔT is shorter than the drive period S of the first to sixth voltage waveforms. That is, the period in which a voltage is applied to the second individual electrode 85b is delayed by ΔT from the period in which a voltage is applied to the first individual electrode 85a.

[0041] By delaying by ΔT, the falling start time k1 of the first voltage waveform and the rising start time k1 of the second voltage waveform become the same, and the falling end time k2 of the first voltage waveform and the rising end time k2 of the second voltage waveform become the same. That is, the first time when the slope of the first voltage waveform becomes negative and the second time when the slope of the second voltage waveform becomes positive overlap so as to be the same.

[0042] Similarly, the start point of the falling edge of the second voltage waveform is the same as the start point of the rising edge of the third voltage waveform, and the end point of the falling edge of the second voltage waveform is the same as the end point of the rising edge of the third voltage waveform. The start point of the falling edge of the third voltage waveform is the same as the start point of the rising edge of the fourth voltage waveform, and the end point of the falling edge of the third voltage waveform is the same as the end point of the rising edge of the fourth voltage waveform. The start point of the falling edge of the fourth voltage waveform is the same as the start point of the rising edge of the fifth voltage waveform, and the end point of the falling edge of the fourth voltage waveform is the same as the end point of the rising edge of the fifth voltage waveform. The start point of the falling edge of the fifth voltage waveform is the same as the start point of the rising edge of the sixth voltage waveform, and the end point of the falling edge of the fifth voltage waveform is the same as the end point of the rising edge of the sixth voltage waveform. It should be noted that ΔT may be set so that the first time period and the second time period at least partially overlap each other.

[0043] As shown in FIG. 10, when the actuator 88a starts to drive, the first current waveform is generated by the rise of the first voltage waveform, that is, a current flows through the first branch electrode 91(1). Next, when the actuator 88b starts to drive, the second voltage waveform rises, but the first voltage waveform falls at the same time, so the first current waveform and the second current waveform are offset. Next, when the actuator 88c starts to drive, the third voltage waveform rises, but the second voltage waveform falls at the same time, so the second current waveform and the third current waveform are offset. Next, when the actuator 88d starts to drive, the fourth voltage waveform rises, but the third voltage waveform falls at the same time, so the third current waveform and the fourth current waveform are offset. Next, when the actuator 88e starts to drive, the fifth voltage waveform rises, but the fourth voltage waveform falls at the same time, so the fourth current waveform and the fifth current waveform are offset. Next, when actuator 88f starts to drive, the sixth voltage waveform rises but at the same time the fifth voltage waveform falls, so the fifth and sixth current waveforms are offset. Next, when actuator 88a starts to drive, the first voltage waveform rises but at the same time the sixth voltage waveform falls, so the sixth and first current waveforms are offset.

[0044] These are repeated, and only the first current waveform generated by the initial rising edge of the first voltage waveform flows through the mainstream electrode 90. Therefore, the total amount of current flowing through the mainstream electrode 90 is suppressed.

[0045] 11 is a flow chart for explaining the printing process by the control device 50. The control device 50 judges whether or not a print job has been received from the external device 100 (S1). If a print job has not been received (S1: NO), the control device 50 returns the process to step S1. If a print job has been received (S1: YES), the control device 50 executes a flushing process (S2). The flushing process is a process for ejecting ink from the nozzles 80 for purposes other than printing. At this time, the control device 50 outputs a delay execution command to the control circuit 64, and the control circuit 64 drives the actuators 88a to 88f with a delay of Δt or ΔT as described above.

[0046] Next, the control device 50 executes a capacitance detection process (S3). The control device 50 outputs a detection execution command to the control circuit 64, and the control circuit 64 causes the detection circuit 65 to detect the capacitance of the capacitor formed by the individual electrode 85, the common electrode 84, and the piezoelectric body 83. Next, the control device 50 executes one print task (S4). A print task is a unit that constitutes a print job. Specifically, it is a liquid ejection process performed while the inkjet head 8 moves right or left by the left and right width of the recording paper 200. Next, the control device 50 determines whether the one print task is completed (S5). If the one print task is not completed (S5: NO), the process returns to step S5. If the one print task is completed (S5: YES), the control device 50 determines whether the print job is completed (S6).

[0047] If the print job is completed (S6: YES), the control device 50 ends the print process. If the print job is not completed (S6: NO), the control device 50 judges whether it is time to perform the capacitance detection process (S7). The capacitance detection process is periodically executed to detect the temperature of the inkjet head 8. If it is time to perform the capacitance detection process (S7: YES), the control device 50 judges whether it is time to perform the flushing process (S8). The flushing process is periodically executed for the maintenance of the nozzle 80. If it is time to perform the flushing process (S8: YES), the control device 50 executes the flushing process (S9). In step S9, the control device 50 outputs a delay execution command to the control circuit 64, and the control circuit 64 drives the actuators 88a to 88f with a delay of Δt or ΔT as described above. The control device 50 causes the control circuit 67 to execute the capacitance detection process (S10), and returns the process to step S4. In step S10, the control circuit 67 executes the capacitance detection process.

[0048] In step S8, if it is not the timing to perform the flushing process (S8: NO), that is, if it is the timing to perform the capacitance detection process but not the timing to perform the flushing process, the control device 50 causes the control circuit 67 to perform the capacitance detection process (S15) and returns the process to step S4. In step S15, the control circuit 67 performs the capacitance detection process.

[0049] In step S7, if it is not the timing to perform the capacitance detection process (S7: NO), the control device 50 determines whether it is the timing to perform the flushing process (S11). If it is the timing to perform the flushing process (S11: YES), the control device 50 executes the flushing process (S12) and returns the process to step S4. In step S12, the control device 50 may or may not output a delay execution command to the control circuit 64.

[0050] In step S11, if it is not the timing to perform the flushing process (S11: NO), the control device 50 judges whether it is the timing to perform the non-ejection flushing process (S13). The non-ejection flushing process is a process for preventing the nozzle 80 from drying without ejecting liquid, and more specifically, it is a process for slightly deforming the piezoelectric body 83 to vibrate the surface (meniscus) of the liquid. The non-ejection flushing process is periodically performed. If it is the timing to perform the non-ejection flushing process (S13: YES), the control device 50 performs the non-ejection flushing process (S14) and returns the process to step S4. In step S14, the control device 50 outputs a command to perform the non-ejection flushing process to the control circuit 64, and the control circuit 64 causes the n-th waveform generating unit 66(n) to generate a drive waveform corresponding to the non-ejection flushing process and supply it to the individual electrode 85. Furthermore, the control device 50 outputs a delay execution command to the control circuit 64, and the control circuit 64 drives the actuators 88a to 88f with a delay of Δt or ΔT as described above. If it is not the timing to execute the non-ejection flushing process (S13: NO), the control device 50 returns the process to step S4.

[0051] Although the control device 50 executes the capacitance detection process via the control circuit 64, the control device 50 may directly control the switch control circuit 67 and the detection circuit 65 to execute the capacitance detection process.

[0052] In the first embodiment, a drive waveform for ejecting liquid from the nozzles is input at a predetermined drive period S. The control circuit 64 delays the period for applying a voltage to the second individual electrode 85b from the period for applying a voltage to the first individual electrode 85a by a time Δt shorter than the drive period S, thereby canceling out the current flowing through the common electrode 84 and suppressing heat generation in the common electrode 84.

[0053] In addition, the control circuit 64 delays the cycle so that the first time when the slope of the first voltage waveform is negative and the second time when the slope of the second voltage waveform is positive overlap at least partially, so that the current flowing through the first branch electrode 91(1) and the current flowing through the second branch electrode 91(2) are at least partially offset.

[0054] In addition, the control circuit 64 delays the period so that the start point k1 of the first period and the start point k2 of the second period become the same, which makes it easier for the current flowing through the first branch electrode 91(1) and the current flowing through the second branch electrode 91(2) to cancel each other out.

[0055] Furthermore, when the control circuit 64 executes the flushing process before the capacitance detection process, it delays the cycle, thereby suppressing the temperature rise of the common electrode 84 caused by the flushing process and suppressing the influence of the temperature rise of the common electrode 84 on the capacitance detection process.

[0056] Furthermore, if the capacitance detection process is not executed after the flushing process, the control circuit 64 can not delay the cycle in the flushing process. By not delaying the cycle, the time required for the flushing process can be shortened.

[0057] When the control device 50 executes the flushing process and the capacitance detection process, the control circuit 64 can delay the cycle to suppress the amount of heat generated by the common electrode 84.

[0058] When the control device 50 executes the flushing process, the control circuit 64 can delay the cycle to suppress the amount of heat generated by the common electrode 84.

[0059] When the non-ejection flushing process is executed, the control circuit 64 can delay the cycle to suppress the amount of heat generated by the common electrode 84.

[0060] The width d1 in the X direction of the mainstream electrode 90 is shorter than the sum of the widths d2 of the multiple tributary electrodes 91. Increasing the width d1 increases the dimension of the inkjet head 8 in the X direction. By reducing the size of the width d1, the increase in the dimension of the inkjet head 8 in the X direction can be reduced, and the inkjet head 8 can be made smaller in size in the X direction. Although the common electrode 84 is comb-shaped in the first embodiment, it may be formed in a plate shape.

[0061] (Embodiment 2) The present invention will be described below with reference to the drawings showing a printing device according to embodiment 2. Among the configurations according to embodiment 2, the same configurations as those in embodiment 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0062] 12 is a simplified partial enlarged cross-sectional view of the inkjet head 8. A second common electrode 86 is provided inside the piezoelectric body 83. The second common electrode 86 is disposed above each pressure chamber 81. The second common electrode 86 faces the individual electrode 85, but does not face the common electrode 84. The common electrode 84 is disposed at a position facing the individual electrode 85, but does not face the second common electrode 86. The vibration plate 82, the piezoelectric body 83, the common electrode 84, the individual electrode 85, and the second common electrode 86 constitute an actuator 88.

[0063] 13 is a block diagram of the printing device 1. The AC / DC converter 62 converts AC voltage into DC voltage and outputs it to the DC / DC converter 63 and the second DC / DC converter 68. The second DC / DC converter 68 changes the voltage to a VCOM voltage. The VCOM voltage is higher than the COM voltage. The second DC / DC converter 68 is connected to the second common electrode 86 and applies the VCOM voltage to the second common electrode 86. When a HIgh or LOW voltage is applied to the individual electrodes 85, the piezoelectric body 83 deforms and the diaphragm 82 vibrates.

[0064] FIG. 14 is a schematic plan view of the common electrode 84 and the second common electrode 86. In FIG. 14, the first nozzle row 80a and the second nozzle row 80b are omitted. The second common electrode 86 includes one mainstream electrode 94 and multiple tributary electrodes. The mainstream electrode 94 is strip-shaped and extends in the Y direction. The mainstream electrode 94 is disposed at a position away from the mainstream electrode 90 of the common electrode 84 in the X direction so as to face the mainstream electrode 90 of the common electrode 84. One end of the mainstream electrode 94 is connected to the VCOM electrode. Each tributary electrode 95 is strip-shaped and extends in the X direction from the mainstream electrode 94. The multiple tributary electrodes 95 are arranged at approximately equal intervals in the Y direction so as to alternate with the multiple tributary electrodes 91.

[0065] In this embodiment, as an example, six tributary electrodes 95 are connected to one mainstream electrode 94. The number of tributary electrodes 95 is not limited to six. Hereinafter, the six tributary electrodes 95 are referred to as the first tributary electrode 95(1) to the sixth tributary electrode 95(6), respectively. The first tributary electrode 95(1) to the sixth tributary electrode 95(6) are arranged in order from the other end of the mainstream electrode 94 (the part farthest from the VCOM electrode) to one end of the mainstream electrode 95 (the part closest to the VCOM electrode).

[0066] 14, in the mainstream electrode 94, the regions between the first tributary electrode 95(1) to the sixth tributary electrode 95(6) are designated as a first region 94(1) to a fifth region 94(5), and the region between the sixth tributary electrode 95(6) and one end of the mainstream electrode 94 is designated as a sixth region 94(6). In addition, the resistances of the first region 94(1) to the sixth region 94(6) are designated as a seventh resistor r7 to a twelfth resistor r12, respectively.

[0067] Fig. 15 is a simplified circuit diagram of the main electrodes 90, 94 and the actuators 88a to 88f. The first to sixth voltage waveforms are input to the individual electrodes 85 of the actuators 88a to 88f, and as shown by the arrows in Fig. 14, current flows through the first to sixth branch electrodes 95(1) to 95(6) and through the seventh resistor r7 to twelfth resistor r12.

[0068] The seventh resistor r7 to the twelfth resistor r12 correspond to the first resistor r1 to the sixth resistor r6. Therefore, similarly to the first embodiment, by driving the actuators 88a to 88f with a delay of Δt or ΔT each, the current flowing through the second common electrode 86 can be offset, thereby suppressing heat generation in the second common electrode 86. That is, heat generation in both the common electrode 84 and the second common electrode 86 can be suppressed.

[0069] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the scope of the claims and the scope equivalent to the claims. [Explanation of symbols]

[0070] 1 Printing device 8 Inkjet head 50 Control device (control unit) 64 Control circuit 80a First nozzle row 80b Second nozzle row 83 Piezoelectric 84 Common electrode 85a 1st individual electrode 85b 2nd individual electrode 86 2nd common electrode 90, 94 Main flow electrode (first electrode, fourth electrode) 91, 95 Tributary electrode (2nd electrode, 3rd electrode)

Claims

1. a nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; The control circuit delays the period so that a first time when a slope of a first voltage waveform applied to the first individual electrode becomes negative and a second time when a slope of a second voltage waveform applied to the second individual electrode becomes positive overlap at least partially. Printing device.

2. The control circuit delays the period so that a start point of the first time period and a start point of the second time period are the same. The printing device of claim 1 .

3. A nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; a piezoelectric body on which the common electrode, a first individual electrode, and a second individual electrode are arranged, The control circuit includes: a flushing process for ejecting liquid from the nozzle, and a capacitance detection process for detecting a capacitance of a capacitor formed by the first individual electrode or the second individual electrode, the common electrode, and the piezoelectric body; When the flushing process is executed before the capacitance detection process, the period is delayed. Printing device.

4. The control circuit includes: When the capacitance detection process is not executed after the flushing process, the control circuit does not delay the cycle in the flushing process. The printing device according to claim 3 .

5. A nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; a piezoelectric body on which the common electrode, a first individual electrode, and a second individual electrode are arranged; A control unit different from the control circuit is provided, The control unit is a flushing process for ejecting liquid from a nozzle, and a capacitance detection process for detecting a capacitance of a capacitor formed by the first individual electrode or the second individual electrode, the common electrode, and the piezoelectric body; When the flushing process is executed before the capacitance detection process, the control circuit delays the period. Printing device.

6. A nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; a piezoelectric body on which the common electrode, a first individual electrode, and a second individual electrode are arranged; A control unit different from the control circuit is provided, the control circuit executes a capacitance detection process to detect a capacitance of a capacitor formed by the first individual electrode or the second individual electrode, the common electrode, and the piezoelectric body; The control unit executes a flushing process for ejecting liquid from a nozzle, When the control unit executes the flushing process before the capacitance detection process, the control circuit delays the period. Printing device.

7. A nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; The common electrode is A strip-shaped first electrode; a strip-shaped second electrode extending from the first electrode in a direction intersecting the first electrode, the second electrode being disposed at a position overlapping the first nozzle row in the up-down direction; a third electrode having a strip shape extending from the first electrode in a direction intersecting with the first electrode, the third electrode being disposed at a position overlapping with the second nozzle row in the up-down direction; a strip-shaped fourth electrode having the same potential as the first electrode and disposed at a position away from the first electrode in a direction intersecting the first electrode; having the first nozzle row and the second nozzle row are disposed between the first electrode and the fourth electrode, The width of the first electrode is smaller than the sum of the width of the second electrode and the width of the third electrode. Printing device.

8. A nozzle plate having a first nozzle row having at least one nozzle that ejects liquid in response to an applied voltage, and a second nozzle row having at least one nozzle that ejects liquid in response to an applied voltage; a common electrode disposed across the first nozzle row and the second nozzle row; a first individual electrode corresponding to the nozzles of the first nozzle row and to which a voltage is applied; a second individual electrode to which a voltage is applied, the second individual electrode corresponding to the nozzles of the second nozzle row; Control circuit Equipped with The control circuit includes: A drive waveform for ejecting liquid from a nozzle is input at a predetermined drive cycle, a period in which a voltage is applied to the second individual electrode is delayed from a period in which a voltage is applied to the first individual electrode by a time shorter than the drive period; A second common electrode to which a voltage different from that of the common electrode is applied is provided. Printing device.

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