Liquid ejecting head

Abstract

The liquid ejection head includes a nozzle plate, a pressure chamber, an actuator, and a drive circuit. The drive circuit generates a drive signal that drives the actuator. The drive signal includes a plurality of ejection waveforms that cause the plurality of droplets to be ejected from the nozzle. The waveform widths of the plurality of ejection waveforms are the same. The discharge waveform of the drive signal includes an expansion potential difference that expands the volume of the pressure chamber, a reduction potential difference that reduces the volume of the pressure chamber, and at least one intermediate potential difference between the expansion potential difference and the reduction potential difference. The drive circuit counteracts vibration of an acoustic resonance frequency in a frequency domain higher than a main acoustic resonance frequency of the liquid in the pressure chamber generated by the change of the potential difference by at least one or more changes of the potential difference after the change of the potential difference. The interval between the plurality of discharge waveforms coincides with the period in which the residual vibration of the liquid in the pressure chamber generated by the previously generated discharge waveform and the vibration of the liquid in the pressure chamber generated by the subsequently generated discharge waveform are enhanced.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a liquid ejection head. BACKGROUND

[0002] In the past, in a liquid ejection head that ejects liquid, a dot diameter when a liquid droplet lands on a medium is increased by continuously ejecting a plurality of liquid droplets, thereby realizing gray scale expression of ink density on the medium. However, in a case where there is a deviation in a main acoustic vibration frequency of a plurality of pressure chambers, if a plurality of liquid droplets are continuously ejected by inputting the same drive waveform (a drive waveform in which a width of an ejection waveform of a first droplet and a last droplet is different) to the plurality of pressure chambers, a situation where the continuously ejected liquid droplets do not coalesce occurs, which becomes a cause of deterioration of print quality.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-045797 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] An object of the present application is to provide a liquid ejection head in which ejection forces of liquid droplets are substantially the same and in which an ejection speed of a subsequent liquid droplet can be increased.

[0008] TECHNICAL SOLUTION FOR SOLVING THE PROBLEM

[0009] A liquid ejection head includes a nozzle plate, a pressure chamber, an actuator, and a drive circuit. The nozzle plate includes a nozzle that ejects liquid. The pressure chamber communicates with the nozzle. The actuator changes a volume of the pressure chamber in accordance with a drive signal. The drive circuit generates the drive signal that drives the actuator. The drive signal includes a plurality of ejection waveforms that cause a plurality of liquid droplets to be ejected from the nozzle. The plurality of ejection waveforms have the same waveform width. The ejection waveform of the drive signal includes an expansion potential difference that causes the volume of the pressure chamber to expand, a contraction potential difference that causes the volume of the pressure chamber to contract, and at least one or more intermediate potential differences between the expansion potential difference and the contraction potential difference. The drive circuit cancels vibration of an acoustic resonance frequency in a frequency domain that is higher than a main acoustic resonance frequency of liquid in the pressure chamber that is generated by a change in potential difference, by at least one or more changes in potential difference that are performed after the change in potential difference. The interval of the plurality of ejection waveforms coincides with a period in which a residual vibration of liquid in the pressure chamber that is generated by a previously generated ejection waveform and a vibration of liquid in the pressure chamber that is generated by a subsequently generated ejection waveform are enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1is a cross-sectional view showing a liquid ejection head according to an embodiment, with parts of the configuration omitted.

[0011] Figure 2 is a cross-sectional view showing a liquid ejection head according to an embodiment, with parts of the configuration omitted.

[0012] Figure 3 is a block diagram schematically showing the configuration of a drive circuit of a liquid ejection head according to an embodiment.

[0013] Figure 4 is an explanatory diagram showing the configuration of a liquid ejection apparatus using a liquid ejection head according to an embodiment.

[0014] Figure 5 is a block diagram showing an example of the configuration of a liquid ejection apparatus according to an embodiment.

[0015] Figure 6 is an explanatory diagram showing an example of a drive waveform including an ejection waveform and a cancellation waveform of a liquid ejection head according to a comparative example.

[0016] Figure 7 is an explanatory diagram showing an example of a drive waveform and acoustic vibration of a liquid ejection head according to an embodiment.

[0017] Figure 8 is an explanatory diagram showing the relationship between a drive waveform and an ejected droplet in an example of a liquid ejection head according to an embodiment.

[0018] Figure 9 is an explanatory diagram showing an example of an ejected droplet of a liquid ejection head according to an embodiment.

[0019] Figure 10 is an explanatory diagram showing an example of a frequency analysis of a liquid ejection head according to a comparative example.

[0020] Figure 11 is an explanatory diagram showing an example in which a main acoustic vibration and a parasitic vibration of a liquid ejection head according to a comparative example are synthesized.

[0021] Figure 12 is an explanatory diagram showing an example of a frequency analysis of a liquid ejection head according to a comparative example.

[0022] Figure 13 is an explanatory diagram showing an example of a drive waveform and acoustic vibration of a liquid ejection head according to a comparative example.

[0023] Figure 14 is an explanatory diagram showing an example of a drive waveform and acoustic vibration of a liquid ejection head according to a comparative example.

[0024] Figure 15This is an explanatory diagram showing an example of the drive waveform of the liquid ejector head according to the embodiment.

[0025] Figure 16 This is an illustrative diagram showing an example of the drive waveform of a liquid ejector head according to another embodiment.

[0026] Figure 17 This is an explanatory diagram showing an example of the drive waveform of the liquid ejector head according to the embodiment and comparative example.

[0027] Figure 18 This is an illustrative diagram showing an example of the drive waveform of a liquid ejector head according to another embodiment.

[0028] Figure 19 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0029] Figure 20 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0030] Figure 21 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0031] Figure 22 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0032] Figure 23 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0033] Figure 24 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0034] Figure 25 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0035] Figure 26 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0036] Figure 27 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0037] Figure 28 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0038] Figure 29 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0039] Figure 30 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0040] Figure 31 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0041] Figure 32 This is an explanatory diagram showing the relationship between the waveform width and the ejection force in an ejection waveform that ejects two droplets, based on the time width Dp of the preceding and subsequent droplets.

[0042] Explanation of reference numerals in the attached figures

[0043] 1: Liquid ejector head; 10: Base; 20: Actuator; 21: Piezoelectric column; 22: Non-driven piezoelectric column; 30: Vibrating plate; 40: Flow channel plate; 42: Partition wall; 45: Flow channel; 46: Pressure chamber; 47: Individual flow channel; 48: Common flow channel; 50: Nozzle plate; 51: Nozzle; 70: Drive circuit; 71: Wiring membrane; 72: Driver IC; 81: First voltage source; 82: Second voltage source; 83: Third voltage source; 84: Fourth voltage source; 85: Fifth voltage source; 100: Liquid ejection device; 111: Housing; 112: Medium supply unit; 113: Image forming unit; 114: Medium discharge unit; 115: Conveying device. 117: Support unit; 118: Conveyor belt; 119: Support plate; 120: Belt roller; 121: Guide plate pair; 122: Conveyor roller; 130: Head unit; 132: Ink tank; 133: Connecting flow channel; 134: Supply pump; 150: Control unit; 151: Processor; 154: I / O port; 155: Image memory; 161: Drive motor; 162: Operation unit; 163: Various sensors; 200: External connection device; 301: Vibration part; 721: Data buffer; 722: Decoder; 723: Driver; 724: Voltage control unit; 725: Voltage switching unit; 726: Wiring electrode; 727: Wiring electrode. Detailed Implementation

[0044] The following is for reference Figures 1 to 5 The configuration of the liquid nozzle 1 and the liquid ejection device 100 using the liquid nozzle 1 according to the embodiment will be described. Figure 1 This is a cross-sectional view showing a partial omission of the components of the liquid ejector head 1 according to the embodiment. Figure 2 This is a cross-sectional view showing a portion of the liquid ejector head 1 without any visible components. Figure 3 This is a block diagram schematically showing the configuration of the drive circuit 70 of the liquid ejector head 1. Figure 4 This is an explanatory diagram showing the configuration of the liquid ejection device 100 using the liquid ejection head 1 according to the embodiment. Figure 5 This is a block diagram showing an example of the configuration of the liquid ejection device 100. It should be noted that, in each figure, the configuration is shown in appropriate enlargements, reductions, or omissions for illustrative purposes.

[0045] The liquid ejector head 1 involved in this embodiment is, for example, an inkjet head that ejects ink as a liquid. Figure 1 and Figure 2 As shown, the liquid ejector head 1 includes a base 10, an actuator 20, a vibrating plate 30, a flow channel plate 40, a nozzle plate 50 having multiple nozzles 51, and a drive circuit 70.

[0046] The base 10 is formed, for example, in the shape of a rectangular plate. The actuator 20 is engaged with the base 10.

[0047] The actuator 20 is, for example, a piezoelectric component having a plurality of piezoelectric pillars 21 and a plurality of non-driven piezoelectric pillars 22 arranged alternately with the plurality of piezoelectric pillars 21. The actuator 20 is formed in a comb-like shape by arranging the plurality of piezoelectric pillars 21 and the plurality of non-driven piezoelectric pillars 22 at predetermined intervals in one direction. For example, such an actuator 20 is formed by cutting grooves from the end face opposite to the base 10 side of the stacked piezoelectric component that is joined to the base 10, thereby forming a plurality of piezoelectric elements in the shape of rectangular pillars at predetermined intervals relative to a piezoelectric component. Furthermore, the formed plurality of piezoelectric elements constitute a plurality of piezoelectric pillars 21 and a plurality of non-driven piezoelectric pillars 22 arranged alternately as piezoelectric elements by providing electrodes or the like. That is, the actuator 20 is divided into a plurality of sections at one end (vibrating plate 30 side) by the formed grooves, and the other end (base 10 side) is connected.

[0048] For example, the stacked piezoelectric component constituting actuator 20 is formed by stacking and sintering sheet-like piezoelectric materials. As a specific example, such as... Figure 1 and Figure 2 As shown, the piezoelectric pillar 21 and the non-driven piezoelectric pillar 22 are, for example, stacked piezoelectric elements serving as driving elements. The piezoelectric pillar 21 and the non-driven piezoelectric pillar 22 each have multiple stacked piezoelectric layers, multiple internal electrodes formed on the main surface of each piezoelectric layer, and multiple external electrodes. It should be noted that, as an example, the piezoelectric pillar 21 and the non-driven piezoelectric pillar 22 have the same configuration.

[0049] The piezoelectric layer is formed into a thin plate, for example, by a piezoelectric material such as PZT (lead zirconate titanate) or lead-free KNN (sodium potassium niobate). Multiple piezoelectric layers are stacked in the thickness direction and bonded together by sintering. It should be noted that the stacking direction of the multiple piezoelectric layers is orthogonal to the arrangement direction of the multiple piezoelectric pillars 21 and the multiple non-driven piezoelectric pillars 22.

[0050] The internal electrodes are conductive films of a predetermined shape, made of conductive materials such as silver and palladium that can be sintered. The internal electrodes are formed in predetermined regions on the main surface of each piezoelectric layer. Multiple internal electrodes are alternately configured as different poles in the arrangement direction.

[0051] External electrodes are formed on the surfaces of multiple piezoelectric pillars 21 and multiple non-driven piezoelectric pillars 22, converging the ends of the internal electrodes. The external electrodes are formed from Ni, Cr, Au, or other materials using known methods such as electroplating or sputtering. The multiple external electrodes are respectively disposed on different side surfaces of the multiple piezoelectric pillars 21 and multiple non-driven piezoelectric pillars 22, and are configured as different electrodes. It should be noted that external electrodes of different electrodes can also be arranged in different regions of the same side surface of the multiple piezoelectric pillars 21 and multiple non-driven piezoelectric pillars 22.

[0052] In this embodiment, as an example, the plurality of external electrodes have individual electrodes formed on the plurality of piezoelectric pillars 21 and the plurality of non-driven piezoelectric pillars 22, respectively, and a common electrode continuously formed on the plurality of piezoelectric pillars 21 and the plurality of non-driven piezoelectric pillars 22. The plurality of individual electrodes formed on the plurality of piezoelectric pillars 21 and the plurality of non-driven piezoelectric pillars 22 are arranged independently of each other. The common electrode is grounded, for example.

[0053] These external electrodes are connected to the drive circuit 70, for example. Each external electrode is connected to the control unit 150, which is a drive unit, via wiring through the driver 723 described later in the drive circuit 70, and is configured to be able to be driven and controlled by the processor 151.

[0054] The piezoelectric column 21 and the non-driven piezoelectric column 22 vibrate longitudinally along the stacking direction of the piezoelectric layers by applying a voltage to the internal electrodes via the external electrodes. The longitudinal vibration referred to here, for example, means "vibration in the thickness direction as defined by the piezoelectric constant d33". For example, as... Figure 2 As shown, a plurality of piezoelectric columns 21, spaced apart by one, are arranged corresponding to the pressure chamber 46 via the vibrating plate 30, while the remaining non-driven piezoelectric columns 22 are arranged opposite the partition wall 42 via the vibrating plate 30.

[0055] The piezoelectric column 21 vibrates longitudinally when a voltage is applied, causing displacement of the vibrating plate 30. That is, the piezoelectric column 21 deforms the pressure chamber 46. The non-driven piezoelectric column 22 is positioned opposite the partition wall 42. No voltage is applied to the non-driven piezoelectric column 22. In other words, each piezoelectric column 21 constitutes an actuator that deforms the pressure chamber 46 by driving it, and each non-driven piezoelectric column 22 constitutes a support. That is, the piezoelectric column 21 causes the pressure chamber 46 to expand and contract, thereby changing the volume of the pressure chamber.

[0056] The vibrating plate 30 is engaged with one side of the piezoelectric layer of the plurality of piezoelectric pillars 21, 22, i.e., the side of the nozzle plate 50. The vibrating plate 30 is deformed, for example, by driving the piezoelectric pillars 21. The vibrating plate 30 is engaged with the piezoelectric pillars 21 and the non-driven piezoelectric pillars 22 of the actuator 20.

[0057] The vibrating plate 30 is, for example, a flat plate configured such that its thickness direction is the stacking direction of the piezoelectric layers. The surface direction of the vibrating plate 30 extends in the arrangement direction of the plurality of piezoelectric pillars 21 and the plurality of non-driven piezoelectric pillars 22. The vibrating plate 30 is, for example, a metal plate. The vibrating plate 30 has a plurality of vibrating portions 301 opposite to each pressure chamber 46 and capable of independent displacement. The vibrating plate 30 is formed by connecting the plurality of vibrating portions 301 into a single unit.

[0058] For example, the vibrating plate 30 is configured as a flat plate, and the areas that are connected to the piezoelectric post 21 are displaced individually. The vibrating plate 30 is, for example, made of SUS plate. The vibrating plate 30 may also have creases or steps formed in the parts adjacent to the vibrating parts 301 or between adjacent vibrating parts 301 to facilitate the displacement of multiple vibrating parts 301.

[0059] The vibrating plate 30 expands and contracts the pressure chamber 46 by shifting the portion opposite to the piezoelectric column 21 due to the elongation and compression of the piezoelectric column 21, thereby changing the volume of the pressure chamber 46. The elongation and compression of the piezoelectric column 21 are generated by the longitudinal vibration of the piezoelectric column 21.

[0060] One side of the vibrating plate 30 is engaged with the actuator 20, and the other side of the vibrating plate 30 is engaged with the flow channel plate 40. A pressure chamber 46 capable of containing ink is formed between the vibrating plate 30 and the flow channel plate 40.

[0061] The main surface of one side of the vibrating plate 30 faces the piezoelectric columns 21 and 22 respectively, and the main surface of the other side faces the pressure chamber 46 and the partition wall 42 respectively.

[0062] The flow channel plate 40 is joined to the vibrating plate 30. The flow channel plate 40 is disposed between the nozzle plate 50 and the vibrating plate 30. The flow channel plate 40 has a plurality of partition wall portions 42. In addition, the flow channel plate 40 forms a defined flow channel 45. The flow channel plate 40 is formed, for example, by stacking a plurality of plates 401 with partial openings to form a plurality of partition wall portions 42 and a defined flow channel 45.

[0063] The partition wall 42 is arranged in a plurality of directions in which the plurality of piezoelectric columns 21, 22 are arranged, and is positioned opposite the non-driven piezoelectric columns 22 across the vibrating plate 30. The partition wall 42 separates the plurality of pressure chambers 46 of the defined flow channel 45 (described later) and the plurality of individual flow channels 47.

[0064] The defined flow channel 45 includes: a plurality of pressure chambers 46 separated by partition walls 42 of the flow channel plate 40; a plurality of individual flow channels 47 separated by partition walls 42; and a common flow channel 48 communicating with the plurality of individual flow channels 47.

[0065] Multiple pressure chambers 46 are arranged in the direction of the arrangement of multiple piezoelectric columns 21 and multiple non-driven piezoelectric columns 22, and are positioned opposite to the multiple piezoelectric columns 21 through a vibrating plate 30. The multiple pressure chambers 46 arranged in one direction are separated by partition walls 42. Multiple partition walls 42 disposed between the multiple pressure chambers 46 are positioned opposite to the multiple non-driven piezoelectric columns 22 through a vibrating plate 30. The multiple pressure chambers 46 are formed by sealing one side of the flow channel plate 40 using a vibrating plate 30 and sealing the other side using a nozzle plate 50 in the piezoelectric layer stacking direction. Additionally, a nozzle 51 formed on the nozzle plate 50 is disposed in the pressure chamber 46.

[0066] Multiple pressure chambers 46 are connected to a common flow channel 48 via individual flow channels 47. Each pressure chamber 46 holds liquid supplied from the common flow channel 48 via the individual flow channels 47 and is deformed by the vibration of a vibrating plate 30 forming part of the pressure chamber 46, thereby ejecting liquid from a nozzle 51. The individual flow channels 47 connect the common flow channel 48 and the pressure chambers 46. The number of individual flow channels 47 is the same as the number of pressure chambers 46. The cross-sectional shape of the individual flow channels 47 differs from that of the pressure chambers 46. The cross-sectional area of ​​the individual flow channels 47 is smaller than that of the pressure chambers 46. The common flow channel 48 is fluidly connected to the multiple individual flow channels 47 and communicates with the pressure chambers 46 through each individual flow channel 47.

[0067] The nozzle plate 50 is formed, for example, of a metal such as SUS·Ni or a resin material such as polyimide. The nozzle plate 50 is joined to the flow channel plate 40, covering a plurality of pressure chambers 46. The nozzle plate 50 has a plurality of nozzles 51 formed at positions opposite to the plurality of pressure chambers 46 and extending through in the thickness direction. A nozzle array is formed by the plurality of nozzles 51.

[0068] like Figure 5 As shown, the drive circuit 70 includes a data buffer 721, a decoder 722, and a driver 723. The data buffer 721 stores print data sequentially for each of the piezoelectric posts 21 and 22. The decoder 722 controls the driver 723 for each of the piezoelectric posts 21 and 22 based on the print data stored in the data buffer 721. The driver 723 outputs a drive signal to activate each piezoelectric post 21 and 22 based on the control of the decoder 722. The drive signal is a voltage applied to each piezoelectric post 21 and 22.

[0069] As a specific example, such as Figure 1 As shown, the driving circuit 70 includes: a wiring film 71 with one end connected to an external electrode, a driver IC 72 mounted on the wiring film 71, and a printed wiring substrate mounted on the other end of the wiring film 71. For example, the driver IC 72 includes a data buffer 721, a decoder 722, and a driver 723. It should be noted that the driver IC 72 may also have a configuration in which the data buffer 721, decoder 722, and driver 723 are partially represented, while the printed wiring substrate and the like have the remaining portion represented.

[0070] The drive circuit 70 applies a drive voltage to the external electrode through the driver IC 72, thereby driving the piezoelectric column 21, changing the volume of the pressure chamber 46, and causing the droplet to be ejected from the nozzle 51.

[0071] Wiring film 71 is connected to multiple individual electrodes and a common electrode. For example, wiring film 71 is fixed to the connection portion of an external electrode by means of thermoforming or the like. Wiring film 71 is, for example, a chip-on-film (COF) on which a driver IC 72 is mounted.

[0072] The driver IC72 is connected to the external electrode via the wiring film 71. It should be noted that the driver IC72 can also be connected to the external electrode via other means such as ACP (anisotropic conductive paste), NCF (non-conductive film), and NCP (non-conductive paste) without using the wiring film 71.

[0073] The driver IC 72 generates control signals and drive signals applied to each piezoelectric post 21, 22 to activate the piezoelectric posts 21. Based on the image signal input from the control unit 150 of the liquid ejection device 100, the driver IC 72 generates control signals for controlling the timing of ink ejection and the selection of the piezoelectric post 21 for ink ejection. Additionally, the driver IC 72 generates a voltage, i.e., a drive signal (electrical signal), applied to the piezoelectric post 21 according to the control signals. When the driver IC 72 applies a drive signal to the piezoelectric post 21, the piezoelectric post 21 is driven, causing the vibrating plate 30 to shift and change the volume of the pressure chamber 46, causing it to expand and contract. This causes the ink filling the pressure chamber 46 to vibrate under pressure. Through this pressure vibration, ink is ejected from the nozzle 51 provided in the pressure chamber 46. It should be noted that the liquid ejection head 1 can also achieve grayscale representation by changing the amount of ink droplets falling on a pixel. Furthermore, the liquid ejection head 1 can also change the amount of ink droplets falling on a pixel by changing the number of ink ejections. Thus, the driver IC72 is an example of an application unit that applies a drive signal to the piezoelectric column 21.

[0074] Next, as Figure 3 As shown, an example of the drive circuit 70 will be described. The drive circuit 70, for example, includes a voltage control unit 724 and a voltage switching unit 725, the same number as the pressure chamber 46, within the driver IC 72. However, in... Figure 3 The diagram shows two voltage switching units 725, while other voltage switching units 725 are omitted.

[0075] The drive circuit 70 is connected to the first voltage source 81, the second voltage source 82, the third voltage source 83, the fourth voltage source 84, and the fifth voltage source 85. The drive circuit 70 applies the voltage supplied from the first voltage source 81 to each wiring electrode 726. Additionally, the drive circuit 70 selectively applies the voltages supplied from the first voltage source 81, the second voltage source 82, the third voltage source 83, the fourth voltage source 84, and the fifth voltage source 85 to each wiring electrode 727. Here, in the case where the actuator 20 is a stacked PZT, there is a tendency for degradation if a bipolar voltage is applied; therefore, the voltages supplied by the first voltage source 81, the second voltage source 82, the third voltage source 83, the fourth voltage source 84, and the fifth voltage source 85 are of either positive or negative polarity relative to the ground voltage.

[0076] The output voltage of the first voltage source 81 is, for example, the ground voltage, and its value is set to V0 (V0=0[V]). The output voltage of the second voltage source 82 represents a voltage value of V1. It should be noted that voltage value V1 is set to be a voltage higher than V0. The output voltage of the third voltage source 83 represents a voltage value of, for example, V2. For example, voltage value V2 is set to be a voltage higher than V0 and lower than V1. The output voltage of the fourth voltage source 84 represents a voltage value of V3. It should be noted that voltage value V3 is set to be a voltage lower than V0. The output voltage of the fifth voltage source 85 represents a voltage value of, for example, V4. For example, voltage value V4 is set to be a voltage lower than V0 and higher than V3.

[0077] Wiring electrode 726 is connected to a common electrode that serves as the ground electrode of actuator 20. Multiple wiring electrodes 727 are each connected to an individual electrode that serves as a non-ground electrode of actuator 20.

[0078] The voltage control unit 724 is connected to multiple voltage switching units 725 respectively. The voltage control unit 724 outputs a command to each voltage switching unit 725 indicating which voltage source among the first voltage source 81, second voltage source 82, third voltage source 83, fourth voltage source 84, and fifth voltage source 85 to select. For example, the voltage control unit 724 receives an image signal from the control unit 150 and determines the switching timing of the voltage source in each voltage switching unit 725. Furthermore, at the determined switching timing, the voltage control unit 724 outputs a command to the voltage switching unit 725 to select any one of the first voltage source 81, second voltage source 82, third voltage source 83, fourth voltage source 84, and fifth voltage source 85. The voltage switching unit 725 switches the voltage source connected to the wiring electrode 727 according to the command from the voltage control unit 724.

[0079] The voltage switching unit 725 is, for example, composed of a semiconductor switch. The voltage switching unit 725, under the control of the voltage control unit 724, connects any one of the first voltage source 81, the second voltage source 82, the third voltage source 83, the fourth voltage source 84, and the fifth voltage source 85 to the wiring electrode 727. Therefore, the internal electrodes of different poles of the piezoelectric post 21 are connected to the wiring electrode 726 and the wiring electrode 727 via external electrodes (a common electrode and individual electrodes).

[0080] In this drive circuit 70, the drive circuit switches the connection wiring between voltage sources 81, 82, 83, 84, and 85 and actuator 20 via a switching circuit composed of a voltage control unit 724 and multiple voltage switching units 725, thereby inputting drive waveforms with at least three potential differences as drive signals to the electrode space of actuator 20. Here, the drive waveform is the ejection waveform of droplets ejected by driving actuator 20. It should be noted that, in this embodiment, potential differences other than the largest and smallest potential differences are referred to as intermediate potential differences.

[0081] The printed wiring board is a PWA (Printed Wiring Assembly) that houses various electronic components and connectors. The printed wiring board is connected to the control unit 150 of the liquid ejection device 100.

[0082] Next, refer to Figure 4 and Figure 5 An example of a liquid ejection device 100 equipped with a liquid ejection head 1 will be described. The liquid ejection device 100 is, for example, an inkjet recording device. The liquid ejection device 100 includes a housing 111, a media supply unit 112, an image forming unit 113, a media discharge unit 114, and a transport device 115. In addition, the liquid ejection device 100 includes a control unit 150.

[0083] The liquid ejection device 100 is a liquid ejection device that performs image forming processing on paper P by ejecting liquid such as ink while conveying the object to be ejected, i.e., paper P, which is a printing medium, along a predetermined conveying path A. The predetermined conveying path A extends from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114.

[0084] The housing 111 forms the outline of the liquid ejection device 100. A discharge port for discharging paper P to the outside is provided at a designated location on the housing 111.

[0085] The media supply unit 112 has multiple paper feed boxes, which are configured to stack and hold multiple sheets of paper P of various sizes.

[0086] The media discharge section 114 is equipped with a paper discharge tray, which is configured to hold the paper P discharged from the discharge port.

[0087] The image forming unit 113 includes a support portion 117 for supporting the paper P and a plurality of head units 130 disposed opposite to each other above the support portion 117.

[0088] The support portion 117 includes: a conveyor belt 118 arranged in a ring in a predetermined area for image formation; a support plate 119 supporting the conveyor belt 118 from the back side; and a plurality of belt rollers 120 arranged on the back side of the conveyor belt 118.

[0089] The support portion 117 supports the paper P on the upper surface, i.e. the holding surface, of the conveyor belt 118 when forming an image, and conveys the conveyor belt 118 at a predetermined time by the rotation of the belt roller 120, thereby conveying the paper P to the downstream side.

[0090] The head unit 130 includes a liquid ejector head 1, a plurality of ink tanks 132 mounted on the liquid ejector head 1 as liquid containers, a connecting channel 133 connecting the liquid ejector head 1 and the ink tanks 132, and a supply pump 134.

[0091] In this embodiment, multiple head units 130 are provided. Each head unit 130 uses ink of a different color. For example, the multiple head units 130 include liquid ejector heads 1 of four colors: cyan, magenta, yellow, and black, and ink tanks 132 that respectively contain these inks of various colors. The ink tanks 132 are connected to the common flow channel 48 of the liquid ejector heads 1 via a connecting flow channel 133.

[0092] Additionally, a negative pressure control device, such as a pump (not shown), is connected to the ink tank 132. Thus, by controlling the negative pressure inside the ink tank 132 in accordance with the head value of the liquid nozzle 1 and the ink tank 132, the ink supplied to each nozzle 51 of the liquid nozzle 1 is formed into a curved surface of a predetermined shape.

[0093] The supply pump 134 is, for example, a liquid delivery pump composed of a piezoelectric pump. The supply pump 134 is provided in the supply flow channel. The supply pump 134 is connected to the control unit 150 via wiring and is controlled by the control unit 150. The supply pump 134 supplies liquid to the liquid nozzle 1.

[0094] The conveying device 115 conveys paper P along a conveying path A from the media supply unit 112 through the image forming unit 113 to the media discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 arranged along the conveying path A.

[0095] Multiple guide plates 121 each have a pair of plate components arranged opposite each other across the conveyed paper P, guiding the paper P along the conveying path A.

[0096] The conveying roller 122 is driven to rotate under the control of the control unit 150, thereby conveying the paper P downstream along the conveying path A. It should be noted that sensors for detecting the conveying status of the paper are arranged at various points along the conveying path A.

[0097] The control unit 150 is, for example, a control board. The control unit 150 is equipped with a processor 151, a ROM (Read Only Memory) 152, a RAM (Random Access Memory) 153, an I / O port 154 as an input / output port, and an image memory 155.

[0098] The processor 151 is a processing circuit, including a CPU (Central Processing Unit), which acts as a controller. The processor 151 controls the head unit 130, drive motor 161, operating unit 162, and various sensors 163 located in the liquid dispensing device 100 via I / O port 154. The processor 151 sends the print data stored in the image memory 155 to the drive circuit 70 in the order it is drawn.

[0099] ROM 152 stores various programs, etc. RAM 153 temporarily stores various variable data, image data, etc. It should be noted that ROM 152 and RAM 153 are just examples of storage media; any other storage medium can be used as long as it can store various programs and data. I / O port 154 is an interface for inputting data from external devices such as external connection device 200 and outputting data to external devices. Print data from external connection device 200 is sent to control unit 150 through I / O port 154 and saved to image memory 155.

[0100] The characteristics of the liquid ejection head 1 used in the liquid ejection device 100 and the drive waveform (ejection waveform of the drive signal) of the liquid ejection head 1 as a comparative example of the prior art will be described below.

[0101] First, use Figures 6 to 14 The driving waveform of the liquid ejector head 1 involved in the comparative example will be explained. It should be noted that... Figure 6 This is an explanatory diagram showing an example of the driving waveform of the liquid ejection head 1 involved in the comparative example, which includes a multi-drop ejection waveform of continuously ejecting multiple droplets and an elimination waveform. Figure 7 This is an explanatory diagram showing an example of an ejection waveform and acoustic vibration of the liquid ejection head 1 according to the embodiment. Figure 8 This is an explanatory diagram showing the relationship between the ejection waveform and the ejected droplets in an example of a liquid ejector head 1. Figure 9 This is an explanatory diagram showing an example of liquid droplets ejected from liquid nozzle 1. Figures 10 to 14The attached diagram is provided as a comparative example to illustrate a conventional liquid ejector head. Figure 10 This is an explanatory diagram illustrating an example of frequency analysis of pressure vibrations in a liquid ejector head involved in a comparative example. Figure 11 It shows that Figure 10 An illustrative diagram illustrating an example of the synthesis of primary acoustic vibration and parasitic vibration. Figure 12 This is an explanatory diagram illustrating an example of frequency analysis of the liquid ejector involved in the comparative example. Figure 13 This is an explanatory diagram showing an example of the drive waveform and acoustic vibration of the liquid ejector head involved in the comparative example. Figure 14 This is an explanatory diagram showing an example of the driving waveform and acoustic vibration of the liquid ejector head involved in the comparative example.

[0102] First, existing liquid ejection heads employ a driving method known as so-called pull-jet, which increases the ejection force by driving the piezoelectric column 21 according to the half-cycle AL of the dominant acoustic vibration of the pressure chamber. However, as Figure 10 As shown in the example of frequency analysis of pressure vibration in the nozzle section, when a liquid ejector head (actuator) is driven to eject droplets from the nozzle, in the pressure chamber, in addition to the main acoustic vibration caused by the fluidity of the ink, parasitic vibrations sometimes occur in the frequency domain higher than the main acoustic vibration.

[0103] When a parasitic vibration with a higher frequency than the primary acoustic vibration is generated when the actuator drives the ejection of droplets from the nozzle, such as... Figure 11 As shown, the pressure in the pressure chamber generates a pressure peak with a period shorter than the half-cycle of the primary acoustic vibration. That is, the synthesized wave obtained by combining the primary acoustic vibration and the parasitic vibration becomes steep in the initial stage of vibration. The short-period pressure peak increases the ejection velocity of the leading portion of the ejected droplet, but on the other hand, it does not persist until the end of ejection, thus decreasing the ejection velocity of the trailing portion of the droplet. Therefore, as... Figure 9 As shown in Figure (a) above, when the droplets are ejected, the volume of the satellite droplets relative to the front droplets increases, resulting in a deterioration in print quality. Here, satellite droplets refer to droplets that are ejected at intervals from the front droplets as they follow the initially ejected droplets (front droplets) when the pressure chamber is deformed by driving the piezoelectric column 21 to eject liquid from the nozzle.

[0104] Additionally, for example, in a prior art liquid nozzle similar to the liquid nozzle 1 of this embodiment, such as... Figure 12 Frequency analysis shows that, in addition to the primary acoustic vibration, a parasitic vibration of approximately 3 times (e.g., 2.8 times) is generated. Here, the following reasons are considered as the cause of the parasitic vibration with a frequency higher than the primary acoustic vibration generated in the pressure chamber of the liquid ejector head.

[0105] One example of the cause is the vibration of a liquid column in a closed tube at odd multiples of 3 or higher. Examples of such liquid ejector heads include... Figure 12 The liquid nozzle shown is similar to the liquid nozzle 1 of the embodiment, with the connection point to the common flow channel being an open end of the end ejector.

[0106] Another example of the cause is the vibration of the liquid column in the open pipe being an integer multiple of 2. Examples of such liquid ejection heads include... Figure 13 The diagram shows a side-mounted injector with its connection point to the common flow channel at an open end. It should be noted that in the main acoustic vibration of the open pipe, the amplitude of the pressure vibration reaches its maximum at the center of the open pipe; therefore, the nozzle is positioned near the center of the open pipe. For example... Figure 13 As shown, when an even multiple of 2 or higher vibrations occur in the liquid column vibration of an open tube, the center of the open tube becomes a node of a small-amplitude pressure vibration. Therefore, when the nozzle is positioned near the center of the open tube, the shape of the ejected droplets is less affected by even multiples of 2 or higher vibrations. Consequently, when the nozzle is positioned near the center of the open tube, odd multiples of 3 or higher vibrations are more likely to be the main cause of increased satellite droplet volume and deterioration of print quality compared to even multiples of 2 or higher vibrations.

[0107] Another example of the cause is that when the cross-sections of the pressure chamber and the individual flow channels are different, the sound velocity in each flow channel changes, and the vibration is mainly caused by the reflection of pressure vibration.

[0108] Another example of vibration caused primarily by the following situation: when the rigidity of the wall or part of the wall of a separate flow channel is less than that of the pressure chamber, the pressure generated in the pressure chamber is reduced in the less rigid flow channel, thereby creating pressure vibration nodes between the pressure chamber and the less rigid flow channel. This is such a situation, for example, as... Figure 1 Like the actuator (piezoelectric column 21) shown by the solid line in the middle, Figure 1 The area of ​​the PZT actuator (piezoelectric column 21) shown by the double-dotted line is offset relative to the area of ​​the vibrating plate on the pressure chamber wall due to manufacturing errors, etc. The area on the pressure chamber wall where only the vibrating plate exists without actuator support is relatively large. It should be noted that... Figure 10 and Figure 12 The graph shown is for Figure 1 The area above the right side of the pressure chamber, where only a vibrating plate exists but no actuator is supported, is slightly shorter than the length of the pressure chamber in the longitudinal direction. Figure 1 The following simulation was performed on the nozzle pressure vibration frequency analysis results when the pressure chamber 46 was within 30% of the lateral width of the head. The simulation refers to the structural analysis of PZT and pressure chamber deformation, the compressibility fluid analysis of the liquid behavior of the flow channel, and the fluid surface analysis of the droplet ejection from the nozzle.

[0109] Moreover, such as Figure 14 As shown, when the rectangular wave width Dp of the ejection waveform is set to AL, the third harmonic vibration AI generated by expanding the pressure chamber before ejection (falling waveform) and the third harmonic vibration AII generated by shrinking the pressure chamber during ejection (rising waveform) reinforce each other. Therefore, short-period pressure peaks are generated by the third harmonic vibration, resulting in deterioration of print quality.

[0110] Next, as an existing example, the driving and driving waveform of the liquid ejector head 1 involved in the comparative example will be described. In this comparative example, the pressure vibration of the pressure chamber 46 of the liquid ejector head 1 is regarded as the vibration of the liquid column in a closed tube, and is set as a driving waveform that suppresses the acoustic resonance frequency (parasitic vibration) of a frequency range higher than the main acoustic resonance frequency (main acoustic vibration) of the liquid in the pressure chamber 46, which is approximately three times or more of the main acoustic resonance frequency, and is approximately an odd multiple of the third harmonic vibration. Here, as Figure 10 As shown, approximately 3 times includes 2.8 times. Furthermore, in this example, regarding the drive waveform of liquid ejector head 1, as an example of multiple drops continuously ejected, such as... Figure 6 As shown, an example of two consecutive ejections of droplets is illustrated.

[0111] First, when the potential difference is at its minimum, the liquid ejector head 1 expands the pressure chamber 46 to its maximum size via the piezoelectric column 21 of the actuator 20; when the potential difference is at its maximum, the ink pressure chamber is reduced to its minimum size via the piezoelectric column 21 of the actuator 20. Furthermore, when ejecting ink using the liquid ejector head 1, ink is ejected by reducing the pressure chamber 46 before ejection, expanding it just before ejection, and reducing it at the moment of ejection. In this example, the ejection waveform of the drive waveform of the liquid ejector head 1 continuously decreases the potential difference (expansion potential difference), including the intermediate potential difference, twice as multiple times, when expanding the pressure chamber 46 just before ejection, or continuously increases the potential difference (contraction potential difference), including the intermediate potential difference, twice as multiple times, when reducing the pressure chamber 46 at the moment of ejection. More preferably, the ejection waveform causes the potential difference to change continuously twice during both the expansion and contraction of the pressure chamber 46. Therefore, the liquid ejector head 1 ejects two droplets by inputting such an ejection waveform twice in succession.

[0112] Additionally, after continuously inputting the second ejection waveform to eject ink multiple times (in this example, twice) through the liquid ejector head, an elimination waveform is input to counteract residual vibrations generated after ink ejection. In the following description, the first ejection waveform may sometimes be referred to as the ejection waveform of the first drop, and the second ejection waveform as the ejection waveform of the second drop.

[0113] In this example, the elimination waveform of the driving waveform of the liquid ejector head 1 makes the waveform width (elimination width) Cp of the elimination waveform less than AL. Furthermore, in this example, in addition to the reduction of the pressure chamber during ejection, the potential difference, including the intermediate potential difference, is continuously increased twice during the reduction of the pressure chamber 46, and the potential difference, including the intermediate potential difference, is continuously decreased twice during the expansion of the pressure chamber 46. More appropriately, similar to the ejection waveform, the elimination waveform causes the potential difference to change twice continuously during both the expansion and reduction of the pressure chamber 46.

[0114] Figure 6 The example shown depicts a drive waveform input twice consecutively at predetermined intervals when ink is ejected from the liquid ejector head 1. Additionally, Figure 7 An example of the ejection waveform is shown below. Figure 6 and Figure 7 In the diagram, the vertical axis represents voltage (potential difference), and the horizontal axis represents time. It should be noted that the driving waveform is generated by the driver IC72 of the driving circuit 70. For example... Figure 6 As shown, in both the ejection waveform and the elimination waveform, the driving waveform reduces the expansion potential difference twice when the pressure chamber 46 expands, and increases the contraction potential difference twice when the pressure chamber 46 contracts during ejection. Furthermore, when the potential difference is changed during both the expansion and contraction of the pressure chamber 46, after applying the first potential difference, the first potential difference is maintained for a predetermined time before the second potential difference is applied. It should be noted that when the pressure chamber expands while the voltage (potential difference) is reduced, the voltage (potential difference) is increased to pre-contract the pressure chamber before the input ejection waveform.

[0115] First, use Figure 6 and Figure 7 A specific example of the ejection waveform of the first droplet in the driving waveform is provided. For example... Figure 7 As shown, when the pressure chamber 46 is pre-expanded before ink is ejected, the time interval from the moment when the expansion potential difference first begins to expand after the potential difference has decreased twice consecutively to the moment when the contraction potential difference first begins to contract after the expansion potential difference has decreased twice consecutively is set as Dp. Additionally, as... Figure 7 As shown, when the pressure chamber 46 is reduced during ejection, the time interval from the moment when the expanding potential difference begins to expand for the second time after decreasing twice consecutively before increasing the potential difference to the moment when the shrinking potential difference begins to shrink for the second time after decreasing twice consecutively after decreasing the expanding potential difference to increasing twice consecutively after decreasing the shrinking potential difference is set as Dp.

[0116] Furthermore, the time width Dp is greater than 0.5AL and less than 1.5AL. More appropriately, Dp = AL. This is because if Dp is greater than 0.5AL and less than 1.5AL, the primary acoustic vibration generated by pre-expanding the pressure chamber 46 before ejection and the primary acoustic vibration generated by shrinking the pressure chamber 46 during ejection will mutually reinforce each other.

[0117] Here, when the period of parasitic vibrations such as the third harmonic is set to λn in the driving waveform, and the time interval between the start time of the first potential difference change and the start time of the second potential difference change when the potential difference increases twice consecutively or decreases twice consecutively is set to Tm, then Tm = λn / 2. When the piezoelectric column 21 (actuator) is driven with such a driving waveform, as... Figure 7 As shown, the parasitic vibrations generated during the first potential difference change and those generated during the second potential difference change have a 180-degree phase difference, thus canceling each other out. This suppresses print quality degradation caused by parasitic vibrations such as third harmonics. It should be noted that... Figure 7 In the middle, the pressure reaches its maximum at the instant when the pressure chamber contracts due to the rising waveform. Additionally, in situations such as... Figure 1 In the case of the downward-facing nozzle with a meniscus flow velocity, the center of the amplitude is the instant when the pressure chamber contracts due to the rising waveform, and the velocity reaches its maximum downward after 1 / 4 of a cycle. Subsequently, vibrations with a 2AL period are shown for the primary acoustic vibration, and vibrations with a λn period are shown for the third harmonic.

[0118] More appropriately, such as Figure 7 As shown, the driving waveform makes the potential difference change of the first potential difference change the same as that of the second potential difference change, so that the parasitic vibrations in the pressure chamber 46 with approximately the same amplitude and a phase difference of 180 degrees cancel each other out, which can greatly suppress the residual vibrations originating from the parasitic vibrations.

[0119] Thus, when the time width Dp of the ejection waveform (driving waveform) that causes the potential difference to increase twice consecutively or decrease twice consecutively is set to AL, and the time interval Tm is set to λn / 2, as follows: Figure 7As shown, the parasitic vibration (third harmonic vibration AI) generated by the pressure chamber shrinkage (rising waveform) during the first potential difference change and the parasitic vibration (third harmonic vibration AII) generated by the pressure chamber shrinkage (rising waveform) during the second potential difference change have a phase difference of 180 degrees, thus canceling each other out. Furthermore, if the time interval Tm is less than 0.5AL, the main acoustic vibration generated by the pressure chamber shrinkage (rising waveform) during the first potential difference change and the main acoustic vibration generated by the pressure chamber shrinkage (rising waveform) during the second potential difference change mutually reinforce each other. Additionally, by setting Dp to AL, the main acoustic vibration generated by pre-expanding the pressure chamber (falling waveform) before ejection and the main acoustic vibration generated by shrinking the pressure chamber (rising waveform) during ejection mutually reinforce each other, increasing the ejection force generated by the main acoustic vibration. It should be noted that when the pressure chamber expands with a reduced voltage (potential difference), the voltage (potential difference) is increased to pre-shrink the pressure chamber before inputting the ejection waveform.

[0120] Here, the condition Tm for the mutual attenuation of parasitic vibrations of period λn in the driving waveform is explained. First, let the vibration of period λn generated during the first potential difference change be A, and let the vibration vector after time Tm of A be A'. Let the vibration vector of period λn generated during the second potential difference change after Tm be B. When Tm is an odd multiple of λn / 2 (the phase difference between A' and B is 180 degrees), the absolute value of the resultant vector of A' and B reaches its minimum. When the absolute value of the resultant vector of A' and B, calculated from the synthesis formula of a single vibration of period λn, is less than or equal to the larger of the absolute values ​​of A' and B (or less than or equal to the absolute values ​​of A' and B if they are the same), the phase difference between vibration vectors A' and B becomes within 180 degrees ± 60 degrees.

[0121] The absolute value of the composite vector of A' and B can be transformed into the following formula. Here, if we let θA be the phase of A' and θB be the phase of B, then A' = |A'|(cosθA, sinθA), B = |B|(cosθB, sinθB). In this case, the absolute value of the composite vector of A' and B becomes:

[0122] …(Equation 1).

[0123] Here, if we assume |A'|≤|B|, then the phase difference (θA-θB) between A' and B, for which |B|≥Equation 1 holds, becomes the condition for the mutual weakening of oscillations with period λn. If we square both sides of Equation 1 and transform it, we get:

[0124] …(Equation 2).

[0125] As can be seen from the above, if the phase difference (θA-θB) between A' and B is within the range of 180 degrees ± 60 degrees, then Equation 2 holds true.

[0126] Furthermore, when |B|≤|A'|, if we square both sides of the expression |A'|≥1 and then transform it, it becomes:

[0127] …(Equation 3).

[0128] As can be seen from the above, if the phase difference (θA-θB) between A' and B is within the range of 180 degrees ± 60 degrees, then Equation 3 holds true.

[0129] Therefore, the condition for the mutual weakening of parasitic vibrations with period λn becomes:

[0130] …(Equation 4).

[0131] Here, k is an odd number greater than or equal to 1.

[0132] In addition, when the potential difference changes twice continuously during the expansion and contraction of the pressure chamber 46, the driving waveform Tm is preferably set to both the holding time of the intermediate potential difference during the expansion of the pressure chamber and the holding time of the intermediate potential difference during the contraction of the pressure chamber as (k / 2-1 / 6)λn≤Tm≤(k / 2+1 / 6)λn (k is an odd number greater than or equal to 1).

[0133] Furthermore, from the viewpoint that the primary acoustic vibrations generated when the potential difference changes from the previous potential difference to the next potential difference mutually reinforce each other, thereby reducing power consumption, a shorter Tm is more ideal.

[0134] From the above points, it can be seen that, taking into account the reduction in power consumption, the Tm of the driving waveform becomes:

[0135] …(Equation 5).

[0136] Here, k is an odd number greater than or equal to 1.

[0137] Next, the evaluation of the ejection waveform of the first droplet in the driving waveform of liquid ejector head 1 is performed. Figure 8 The image shows the results of ejecting a single drop of ink using a liquid ejector head 1 driven with various waveforms (2AL = 5.24 μs). It should be noted that... Figure 8 In all the results of various waveforms, the initial droplet velocity is adjusted to approximately 8 m / s by adjusting the voltage.

[0138] Figure 8 The topmost driving waveform, used as a comparison example, has a rise time tr of 0.2 μs. Figure 14The trapezoidal drive waveform shown, in addition to this, becomes Figure 7 The driving waveform shown represents two potential difference changes, with different Tm values ​​and a rise time of 0.2 μs for both. Furthermore, the ejection voltage represents the difference between the expansion and contraction potential differences. It should be noted that the intermediate potential difference is the midpoint between the expansion and contraction potential differences.

[0139] For example, such as Figure 12 Frequency analysis shows that, in addition to the main acoustic vibration, the liquid ejector head 1 also generates approximately three times the amount of parasitic vibration. The period λn of the parasitic vibration is 1.85 μs, and λn / 2 becomes 0.925 μs.

[0140] in addition, Figure 9 The image shows simulation results of the ejected droplet state when the ink is a single droplet. Figure 9 In the figure above (a), an example of ejected droplets under a trapezoidal driving waveform with tr=0.2μs is shown. The figure in the middle (b) shows an example of ejected droplets under a driving waveform with Tm=0.62μs and two potential difference changes. The figure below (c) shows an example of ejected droplets under a driving waveform with Tm=0.93μs and two potential difference changes.

[0141] like Figure 8 and Figure 9 As shown in Figure (c) below, in the waveform with Tm = 0.93 μs, which is closest to the half-cycle of the parasitic vibration, the ratio of the leading droplet volume to the total ejection volume is the largest, as shown in Figure (c). Figure 8 and Figure 9 As shown in the central diagram (b), it can be observed that the further Tm deviates from 0.925 μs, the lower the proportion of the leading droplet volume. Furthermore, it is known that the smaller Tm is, the lower the ejection voltage per unit volume (ejection voltage / total ejection volume). These results also indicate that, based on the driving waveform of the first droplet ejection head 1, it is possible to suppress both power consumption and vibrations with frequencies higher than the dominant acoustic vibration.

[0142] Next, use Figure 6 A specific example of the ejection waveform of the second droplet in the driving waveform will be provided. It should be noted that, in this comparative example, compared to the ejection waveform of the first droplet, the time width Dp of the second droplet's ejection waveform, from the moment the potential difference begins to decrease for the first time after decreasing twice through expansion, is shorter. For example, if the Dp21 of the first droplet's ejection waveform is the same as AL, then the Dp22 of the second droplet's ejection waveform is set to be less than AL.

[0143] Here, for simplicity, vibration attenuation caused by viscous resistance of the flow channel is ignored. When the occurrence time of the potential difference change based on tr is set to tin, and the time of the reference point (0) of the phase is set to t0, and the pressure vibration of the pressure chamber caused by pressurization is schematically represented, it becomes cos((t0-tin)*(π / AL)). Furthermore, the velocity of the liquid in the nozzle section is -sin((t0-tin)*(π / AL)). It should be noted that when the nozzle is facing downwards, the liquid velocity in the nozzle section changes downwards due to pressurization of the pressure chamber; therefore, a negative sign is marked in the formula for the liquid velocity in the nozzle section. Furthermore, when the occurrence time of the potential difference change based on tf is set to tin, and the pressure vibration of the pressure chamber caused by depressurization is schematically represented, it becomes cos(-π+(t0-tin)*(π / AL)). Furthermore, the velocity of the liquid in the nozzle section is -sin(-π+(t0-tin)*(π / AL)). It should be noted that when the nozzle is oriented downwards, the liquid velocity in the nozzle changes upwards due to the pressure reduction in the pressure chamber. Therefore, a negative sign is marked in the formula for the liquid velocity in the nozzle.

[0144] Subsequently, based primarily on the reference point (0) or (0'') of the phase, the time elapsed from the occurrence of each voltage step input to the reference point (in the case of phase lead) is substituted into (t0-tin). Thus, the phase is described with reference point (0) or (0'') regarding the changes in each potential difference and their composite waves.

[0145] For ease of explanation, the following will be... Figure 6 The first to fourth potential difference changes in the ejection waveform of the first drop are defined as (1) to (4), and the first to fourth potential difference changes in the ejection waveform of the second drop are defined as (21) to (24). Furthermore, the reference point for the phase of the ejection waveform of the first drop is defined as (0), and the reference point for the phase of the ejection waveform of the second drop is defined as (0''). It should be noted that here, the reference point for the phase of the ejection waveform of the first drop is set at the midpoint between potential difference changes (2) and (3), and the reference point for the phase of the ejection waveform of the second drop is set at the midpoint between potential difference changes (22) and (23). Additionally, the voltage drop time tf and the voltage rise time tr in the figure are approximately the same. Furthermore, the amount of potential difference change between (1) and (2) and the amount of potential difference change between (21) and (22) are... Figure 6 The changes in height in (3) and (4) are roughly the same, and the changes in potential difference between (23) and (24) are also roughly the same.

[0146] First, show Figure 6 The dominant acoustic vibration of the ejection waveform. When inFigure 6 When a potential difference change is made in the ejection waveform of the first droplet, and an intermediate voltage is input as shown in (1) to expand the pressure chamber 46, the pressure chamber 46 expands through the potential difference in (1), thus depressurizing the pressure chamber 46. The resulting vibration is a vibration with a phase leading by -π + (Dp21 + Tm21) / 2 * (π / AL). Furthermore, when the potential difference change shown in (2) is made, it becomes a vibration with a phase leading by -π + (Dp21 - Tm21) / 2 * (π / AL) in (2). The composite wave of (1) and (2) becomes a vibration with a phase leading by -π + Dp21 / 2 * (π / AL).

[0147] The potential differences (3) and (4), which are used to reduce the pressure chamber 46, change in the opposite direction to the potential differences (1) and (2), which are used to expand the pressure chamber 46, thus reducing the pressure chamber 46 and pressurizing it. Therefore, (3) becomes a vibration with a phase leading by -(Dp21-Tm21) / 2*(π / AL). Furthermore, (4) can be considered a vibration with a phase leading by -(Dp21+Tm21) / 2*(π / AL). Therefore, the composite wave of (3) and (4) becomes a vibration with a phase leading by -Dp21 / 2*(π / AL).

[0148] Here, if we assume that the composite wave of (1), (2), (3) and (4) at time (0) is a vibration with a phase leading by -π / 2.

[0149] Next, it is shown Figure 6 The main acoustic vibration of the second drop ejection waveform. When the potential difference is changed and the intermediate voltage for expanding the pressure chamber 46 is input as shown in (21), the pressure chamber 46 is expanded by the potential difference in (21), and the pressure inside the pressure chamber 46 is reduced. Therefore, when the width of the second drop ejection waveform is set to Dp22, it becomes a vibration with a phase leading by -π + (Dp22 + Tm22) / 2 * (π / AL). Furthermore, when the potential difference is changed as shown in (22), it can be considered that the vibration in (22) is a vibration with a phase leading by -π + (Dp22 - Tm22) / 2 * (π / AL). Therefore, the composite wave of (21) and (22) becomes a vibration with a phase leading by -π + Dp22 / 2 * (π / AL).

[0150] The potential differences (23) and (24), which are used to reduce the pressure chamber 46, change in the opposite direction to the potential differences (21) and (22), which are used to expand the pressure chamber 46, thus reducing the pressure chamber 46 and pressurizing it. Therefore, (23) becomes a vibration with a phase leading by -(Dp22-Tm22) / 2*(π / AL). Similarly, (24) becomes a vibration with a phase leading by -(Dp22+Tm22) / 2*(π / AL). Therefore, the composite wave of (23) and (24) becomes a vibration with a phase leading by -Dp22 / 2*(π / AL).

[0151] Here, if we assume that the composite waves of (21), (22), (23) and (24) at time (0'') are the composite waves, then the composite waves of (21), (22), (23) and (24) are vibrations with a phase lead of -π / 2.

[0152] Therefore, if the phase difference between (0) and (0'') is set to an even multiple of π (or AL if it is a time interval), then the composite waves of (1), (2), (3), and (4) have the same phase as the composite waves of (21), (22), (23), and (24) and thus reinforce each other. Figure 6 In the example, the time difference (time interval) between (0) and (0'') is 2AL. Furthermore, by reducing the time width Dp22 of (21) and (23), the amplitude of the composite wave (ejection waveform of the second drop) of (21), (22), (23) and (24) can be adjusted. Therefore, the ejection speed of the second drop ejected by the mutual reinforcement of the residual vibration generated by the composite wave of (1), (2), (3) and (4) and the composite wave of (21), (22), (23) and (24) can be adjusted. In this way, in the drive waveform of multiple drops of ink being continuously ejected by the liquid ejector head 1, by adjusting Dp in the ejection waveform after any ejection waveform, the ejection speed of the ink ejected later can be adjusted to a speed greater than the ejection speed of the droplets ejected earlier.

[0153] However, in Figure 6 In the comparative example shown, the drive waveforms involved produce significantly different waveform widths for Dp21 and Dp22 due to variations in ink viscosity and flow resistance along the ink supply path up to each nozzle 51. When a liquid ejector head 1 with significantly different Dp21 and Dp22 waveform widths is driven by a drive waveform that drives multiple pressure chambers 46, resulting in significantly different main acoustic vibration frequencies due to manufacturing deviations, etc., print quality deteriorates.

[0154] In this embodiment, the liquid ejector head 1 expresses grayscale by the number of continuously ejected droplets. Here, when multiple nozzles 51 eject the same number of droplets, the same drive waveform is input to multiple piezoelectric columns 21 that change the volume of multiple pressure chambers 46 connected to these multiple nozzles 51. On the other hand, the main acoustic vibration frequencies of the multiple pressure chambers 46 may not be the same due to manufacturing deviations, etc. For example, the drive waveform of an inkjet head with a maximum half-cycle AL of 3.5 μs, a minimum half-cycle AL of 2.5 μs, and an average half-cycle AL of 3.0 μs driving the main acoustic vibration frequencies of the multiple pressure chambers 46 will be described below.

[0155] It should be noted that the AL of the multiple pressure chambers 46 can be investigated by individually inputting a rectangular wave into the piezoelectric column 21 that changes the volume of each pressure chamber 46, and measuring the velocity of the droplets ejected from the nozzle 51 at that time. For example, by changing the time width Dp of the rectangular wave and measuring the velocity of the ejected droplets, if the ejection velocity of the droplets reaches its maximum when the time width Dp of the rectangular wave is 3.0 μs, then 3.0 μs can be considered as the AL of the corresponding pressure chamber.

[0156] Next, the problems with the existing drive waveform will be explained. For example, when printing by ejecting droplets from the liquid ejector head 1 while conveying the medium (e.g., paper P) of the object to be printed, it is necessary to adjust the speed of each volume of droplet so that even if the volume of the droplets ejected from the nozzle 51 changes, the landing position of the droplets on the medium will not change.

[0157] first, Figure 17 The image shows an example of a driving waveform (droplet waveform) for ejecting a single droplet. For example... Figure 17 As shown, the time width Dp11 of the ejection waveform is set to Dp11 = AL. Furthermore, the period of the ejection waveform is 2UL = 2AL. Moreover, the wavelength λn of the parasitic vibration is the wavelength of the third harmonic of the primary acoustic vibration, Tm11 = λn / 2 (= UL / 3). Furthermore, regarding the drive waveform (n-droplet waveform) for continuously ejecting multiple droplets, the waveform width Dp of the ejection waveform of each droplet is set to 1AL for the preceding or last droplet, and the waveform width Dp of the ejection waveform of other droplets is set to be smaller than 1AL (Dp < AL) or larger than 1AL (Dp > AL). Thus, the velocity of the droplets during continuous ejection is adjusted to be close to the ejection velocity of a single droplet. For example, Figure 6An example is setting the waveform width Dp21 of the ejection waveform of the preceding droplet to 1AL, and setting the waveform width Dp22 of the ejection waveform of other droplets to be smaller than 1AL. In the case of continuous droplet ejection, since the residual vibration of the pressure chamber is generated by the ejection of the first droplet, the ejection velocity of the subsequent droplet is increased by ejecting the next droplet according to the phase of the residual vibration. In the case of a single droplet, since it is not possible to expect an increase in velocity through residual vibration, the waveform width Dp11 of the ejection waveform of a single droplet is set to 1AL, and the ejection waveform width is adjusted when ejecting droplets continuously.

[0158] Furthermore, considering that the wavelength λn of the parasitic vibration also deviates from the half-cycle AL of the dominant acoustic vibration frequency, in this example, to reduce the parasitic vibration in more pressure chambers, the average λn / 2 is set to 1 μs, so that Tm11 is consistent with the average λn / 2.

[0159] For example, in pressure chamber 46 where AL is approximately 3.0 μs in multiple pressure chambers 46, such as Figure 6 As shown, the waveform of two consecutively ejected drops is adjusted, with the two drop waveforms set to Dp21=3.0μs, UL=3.0μs, Dp22=2.1μs, Cp=1.5μs, and Tm21=Tm22=1.0μs (=UL / 3). In this case, the velocity of the second ejected droplet in the two-drop waveform is considered to be greater than the velocity of the first ejected droplet in the two-drop waveform.

[0160] The two droplet waveforms cause the residual vibration generated by the ejection waveform of Dp21 to be in phase with the ejection waveform of Dp22. Therefore, the center distance 2UL between the ejection waveforms of Dp21 and Dp22 is twice the AL of the pressure chamber. Moreover, even if the waveform width of Dp22 is smaller than the AL of the pressure chamber, the velocity of the second ejected droplet of the two-drop waveform is greater than the velocity of the first ejected droplet of the two-drop waveform.

[0161] Here, the two droplet waveforms are input to a piezoelectric column 21 that can change the volume of pressure chamber 46, which has an AL value of 3.5 μs among multiple pressure chambers 46. In this case, in addition to the difference between the waveform width of Dp22 and the AL of the pressure chamber becoming larger, the difference between the center distance 2UL of the ejection waveforms of Dp21 and Dp22 and the 2AL of the pressure chamber also becomes larger. Therefore, there is a concern that the velocity of the second ejection droplet is smaller compared to the velocity of the first ejection droplet of the two droplet waveforms. If the second ejection droplet lands on the medium later than the first ejection droplet, it leads to a decrease in print quality.

[0162] For example, Figures 19 to 32The diagram shows the relationship between waveform width and ejection force based on the time width Dp of the preceding and subsequent droplets. Figures 19 to 32 The graph shows the ejection force characteristics of pressure chamber 46 schematically with the horizontal axis set as the waveform width of the ejection waveform and the vertical axis set as the ejection force relative to the waveform width when there is no residual vibration. Figures 19 to 26 This shows an example where the time width Dp21 of the ejection waveform of the preceding droplet is different from the time width Dp22 of the ejection waveform of the subsequent droplet (Dp21≠Dp22). Figures 27 to 32 An example is shown where the Dp21 of the preceding droplet is the same as or approximately the same as the Dp22 of the subsequent droplet (Dp21≈Dp22). Here, avrAL is the average AL of multiple pressure chambers 46 with the same input drive waveform. minAL is the minimum AL of multiple pressure chambers 46 with the same input drive waveform. maxAL is the maximum AL of multiple pressure chambers 46 with the same input drive waveform. Additionally, Figures 19 to 22 and Figure 27 and Figure 28 The upward-convex, bow-shaped dashed line represents the ejection force characteristics in pressure chamber 46, which are roughly the same as those in AL and avrAL.

[0163] Figure 21 It is shown in Figure 6 The waveform shows the relationship between waveform width and ejection force when Dp21 is set to the same time width as avrAL and Dp22 is set to a time width smaller than avrAL. Figure 21 In the middle, the DP22's ejection force is slightly less than that of the DP21, but... Figure 6 In the waveform, the residual vibration generated by Dp21 and Dp22 reinforce each other, so that the velocity of the droplets ejected through Dp22 becomes equal to or greater than the velocity of the droplets ejected through Dp21.

[0164] Figure 25 It is shown to have Figure 21 The waveform widths of Dp21 and Dp22 shown are Figure 6 The graph shows the relationship between the waveform width and the ejection force when the pressure chamber AL is 46° and the driving waveform is driven by AL. Because... Figure 25 The waveform width of Dp21 is avrAL, thus becoming the ejection force near the peak of the ejection force characteristic of the pressure chamber, with relatively small changes in ejection force. On the other hand, due to Figure 25 The waveform width of Dp22 is very small compared to avrAL, therefore the change in ejection force caused by the elongation of AL in pressure chamber 46 is large. Furthermore, the difference between the center distance 2UL of the ejection waveforms of Dp21 and Dp22 and the 2AL (=2*maxAL) of the pressure chamber increases, therefore, compared to... Figure 21 In comparison, Figure 25In the process, the ejection force of both Dp21 and Dp22 decreases, but the decrease is greater for Dp22. Therefore, even if Dp22 and the residual vibration reinforce each other, the droplet velocity ejected through Dp22 may still be lower than that ejected through Dp21.

[0165] Next, the waveform of the two consecutively ejected drops was adjusted in one of the plurality of pressure chambers where AL was approximately 3.0 μs, setting the two drop waveforms to Dp21 = 2.1 μs, UL = 3.0 μs, Dp22 = 3.0 μs, Cp = 1.5 μs, and Tm21 = Tm22 = 1.0 μs (= UL / 3). In this case, the velocity of the second ejected droplet in the two-drop waveform is considered to be greater than the velocity of the first ejected droplet in the two-drop waveform.

[0166] The two-drop waveform also causes the residual vibration generated by the ejection waveform of Dp21 to be in phase with the ejection waveform of Dp22. Therefore, the center distance 2UL between the ejection waveforms of Dp21 and Dp22 is twice the AL of the pressure chamber. For this reason, the velocity of the second ejection droplet of the two-drop waveform is greater than the velocity of the first ejection droplet of the two-drop waveform.

[0167] Here, the two droplet waveforms are input to the piezoelectric column 21, which changes the volume of the pressure chamber 46 to a minimum value of 2.5 μs among the plurality of pressure chambers 46. In this case, the ejection velocity of the first droplet increases as the difference between the waveform width of Dp21 and the AL of the pressure chamber decreases. On the other hand, the difference between the waveform width of Dp22 and the AL of the pressure chamber increases, further increasing the difference between the center distance 2UL of the ejection waveforms of Dp21 and Dp22 and the 2AL of the pressure chamber. Therefore, there is a concern that the ejection velocity of the second droplet is lower than that of the first droplet in the two droplet waveforms. As a result, since the second droplet lands on the medium later than the first droplet, the print quality is reduced.

[0168] Figure 19 This illustrates the relationship between waveform width and ejection force when Dp22 is set to the same time width as avrAL and Dp21 is set to a time width smaller than avrAL. For example... Figure 19 As shown, Dp22 has a greater ejection force compared to Dp21. Furthermore, the residual vibrations generated by Dp21 and Dp22 reinforce each other, resulting in a higher droplet velocity ejected through Dp22 than that ejected through Dp21.

[0169] Figure 23The diagram shows the relationship between the waveform width and the ejection force when a drive waveform with Dp22 set to the same time width as avrAL and Dp21 set to a time width smaller than avrAL is input to pressure chamber 46, where AL is minAL.

[0170] like Figure 23 As shown, Dp21 has a waveform width closer to the value of minAL than Dp22, thus increasing the ejection force of Dp21. Furthermore, since the difference between the center distance 2UL between the ejection waveforms of Dp21 and Dp22 and the pressure chamber's 2AL (2*minAL) increases, even if Dp22 and the residual vibration reinforce each other, the droplet velocity ejected through Dp22 may be lower than the droplet velocity ejected through Dp21.

[0171] Next, use Figure 15 The driving waveform of this embodiment will be described. In the driving waveform of this embodiment, the time width Dp21 of the ejection waveform of the first drop (initial) is the same as the time width Dp22 of the ejection waveform of the second drop (subsequent) (here, "same" includes being substantially the same), and the interval of the ejection waveform is consistent with the period of the residual vibration of the liquid in the pressure chamber 46 generated by the first ejection waveform and the period of the vibration of the liquid in the pressure chamber 46 generated by the subsequently generated ejection waveform. In addition, for example, Dp21 and Dp22 are made different from 1AL. For example, in a pressure chamber 46 where AL is approximately 3.0 μs, the driving waveform is driven by the second ejection waveform. Figure 15 The waveform of two consecutively ejected drops, as shown, is adjusted such that, with the waveforms Dp21=Dp22=2.4μs, UL=3.0μs, Cp=1.5μs, and Tm21=Tm22=1.0μs (=UL / 3), the velocity of the second ejected droplet is greater than that of the first ejected droplet, and the velocity of the ejected droplet of the single-drop waveform becomes close to the velocity of either droplet in the two-drop waveform. More appropriately, Dp21=Dp22 is adjusted so that the velocity of the combined droplet is approximately the same as the ejection velocity of the single-drop waveform droplet.

[0172] exist Figure 15 When the waveform widths of Dp21 and Dp22 are the same or approximately the same, the pressure exerted by the ejection waveforms of Dp21 and Dp22 on the liquid in pressure chamber 46 is the same or approximately the same. Furthermore, by making the center-to-center spacing between the ejection waveforms of Dp21 and Dp22 approximately the same as 2AL, the residual vibration of pressure chamber 46 generated by Dp21 and the pressure exerted on the liquid in pressure chamber 46 by Dp22 mutually reinforce each other. Therefore, the velocity of the droplets ejected by Dp22 is typically greater than that of the droplets ejected by Dp21.

[0173] Figure 27 , Figure 29 as well as Figure 31 Shown in Figure 15 The waveform width and ejection force are related when Dp21 and Dp22 are set to time widths smaller than minAL. Figure 27 , Figure 29 as well as Figure 31 In this context, the ejection forces of Dp22 and Dp21 are equivalent. Figure 15 In the waveform, the residual vibration generated by Dp21 and Dp22 reinforce each other, so that the velocity of the droplets ejected through Dp22 becomes equal to or greater than the velocity of the droplets ejected through Dp21.

[0174] Next, use Figure 15 The condition under which the residual vibration of the pressure chamber generated by Dp21 and the pressure applied to the liquid in the pressure chamber by Dp22 mutually reinforce each other will be explained in detail. It should be noted that, in this embodiment, the waveform width of the second droplet ejection is approximately the same as that of the first droplet ejection. Furthermore, in order to make the velocity of the ejected droplet of one waveform approximately the same as the velocity of the ejected droplets of two waveforms, Dp21 and Dp22 are set to be smaller than the average half-cycle AL of the principal acoustic vibration frequency of the plurality of pressure chambers, which is 3.0 μs.

[0175] Here, in a droplet waveform... Figure 17 In such a waveform configuration, residual vibrations will not reinforce each other. Therefore, when the voltage height of the ejected waveforms is the same in both single-drop and multi-drop waveforms, to obtain the same ejection velocity as the multi-drop waveform, a larger ejection force is required in the single-drop waveform. For example, the ejection waveform width of a single drop is preferably set between minAL and maxAL to increase the ejection force. In this case, consider setting the waveform width of each ejection waveform of the multi-drop waveform to minAL. In a pressure chamber where AL is minAL, the multi-drop waveform with an ejection width of minAL has a greater ejection force than the single-drop waveform with an average ejection width of AL.

[0176] Furthermore, since residual vibrations can reinforce each other, the ejection velocities of multiple droplets can be significantly higher than those of a single droplet. This raises the same concern when the waveform widths of the individual ejection waveforms of the multiple droplets are set between minAL and maxAL, in any pressure chamber 46 where AL is between minAL and maxAL. Therefore, it is preferable to set the waveform widths of the individual ejection waveforms of the multiple droplets to be smaller than minAL or larger than maxAL.

[0177] For ease of explanation, the following will be... Figure 15The first to fourth potential difference changes in the ejection waveform of the first drop are defined as (1) to (4), and the first to fourth potential difference changes in the ejection waveform of the second drop are defined as (21) to (24). Furthermore, the reference point for the phase of the ejection waveform of the first drop is defined as (0), and the reference point for the phase of the ejection waveform of the second drop is defined as (0''). It should be noted that here, the reference point (0) for the phase of the ejection waveform of the first drop is set between potential difference changes (2) and (3), and the reference point (0'') for the phase of the ejection waveform of the second drop is set between potential difference changes (22) and (23). Additionally, Figure 15 The voltage fall time tf in Figure 15 The voltage rise time tr in each case is approximately the same. Additionally, the change in potential difference in (1), (2), (21), and (22) is similar to the change in potential difference in (3), (4), (23), and (24). Figure 15 The changes in height are roughly the same.

[0178] right Figure 15 The dominant acoustic vibration of the ejected waveform of the first droplet is illustrated. Figure 15 As shown, when a potential difference change is performed in the ejection waveform of the first drop, and a voltage is input as shown in (1) to expand the pressure chamber 46, the pressure chamber 46 expands through the potential difference in (1), thus depressurizing the pressure chamber 46. The resulting vibration is a vibration with a phase leading by -π + (Dp21 + Tm21) / 2 * (π / AL). Further, when the potential difference change shown in (2) is performed, it becomes a vibration with a phase leading by -π + (Dp21 - Tm21) / 2 * (π / AL) in (2). The composite wave of (1) and (2) becomes a vibration with a phase leading by -π + Dp21 / 2 * (π / AL).

[0179] As the potential difference changes (3) and (4) used to reduce the pressure chamber 46, the potential difference changes (1) and (2) used to expand, which are opposite to the potential difference changes (3) and (4), thus reducing the pressure chamber 46 and pressurizing it. Therefore, (3) becomes a vibration with a phase lead of -(Dp21-Tm21) / 2*(π / AL). Furthermore, (4) can be considered a vibration with a phase lead of -(Dp21+Tm21) / 2*(π / AL). Therefore, the composite wave of (3) and (4) becomes a vibration with a phase lead of -Dp21 / 2*(π / AL).

[0180] Here, if we assume that the composite wave of (1), (2), (3) and (4) at time (0) is a vibration with a phase leading by -π / 2.

[0181] Next, it is shownFigure 15 The main acoustic vibration of the second drop ejection waveform. When the potential difference is changed and a voltage is input as shown in (21) to expand the pressure chamber 46, the pressure chamber 46 is expanded through the potential difference in (21), and the pressure inside the pressure chamber 46 is reduced. Therefore, when the width of the second drop ejection waveform is set to Dp22, it becomes a vibration with a phase leading by -π + (Dp22 + Tm22) / 2 * (π / AL). Furthermore, when the potential difference is changed as shown in (22), it can be considered that the vibration in (22) is a vibration with a phase leading by -π + (Dp22 - Tm22) / 2 * (π / AL). Therefore, the composite wave of (21) and (22) becomes a vibration with a phase leading by -π + Dp22 / 2 * (π / AL).

[0182] The potential differences (23) and (24), which are used to reduce the pressure chamber 46, change in the opposite direction to the potential differences (21) and (22), which are used to expand the pressure chamber 46, thus reducing the pressure chamber 46 and pressurizing it. Therefore, (23) becomes a vibration with a phase leading by -(Dp22-Tm22) / 2*(π / AL). Similarly, (24) becomes a vibration with a phase leading by -(Dp22+Tm22) / 2*(π / AL). Therefore, the composite wave of (23) and (24) becomes a vibration with a phase leading by -Dp22 / 2*(π / AL).

[0183] Here, if we assume that the composite waves of (21), (22), (23) and (24) at time (0'') are the composite waves, then the composite waves of (21), (22), (23) and (24) are vibrations with a phase lead of -π / 2.

[0184] Therefore, if the phase difference between (0) and (0'') is set to an even multiple of π (or AL if it is a time interval), then the composite waves of (1), (2), (3), and (4) will have the same phase as the composite waves of (21), (22), (23), and (24) and will mutually reinforce each other. In the example in the attached figure, the time difference (time interval) between (0) and (0'') is 2AL.

[0185] Here, the condition of the time difference (time interval) between (0) and (0'') for the amplitude of the composite waves of (1), (2), (3) and (4) and the composite waves of (21), (22), (23) and (24) mutually reinforcing each other is considered. If the time difference 2UL between (0) and (0'') is greater than 1.5AL and less than 2.5AL, then the composite waves of (1), (2), (3) and (4) mutually reinforce each other with the composite waves of (21), (22), (23) and (24).

[0186] Furthermore, the half-cycle AL of the main acoustic vibration frequency of the multiple pressure chambers 46 of the liquid ejector head 1 varies due to manufacturing deviations. Here, the maximum value of the half-cycle AL of the main acoustic vibration frequency of the multiple pressure chambers 46 is set as maxAL, and the minimum value is set as minAL. In this case, among the multiple pressure chambers 46, the value when 1.5AL becomes the maximum is 1.5maxAL, and the value when 2.5AL becomes the minimum is 2.5minAL. Therefore, it is sufficient to set 2UL, where 1.5AL≤1.5maxAL<2U<2.5minAL≤2.5AL, to the time difference between (0) and (0''). It can be seen that as long as 1.5AL≤1.5maxAL<2U<2.5minAL≤2.5AL is set as 2UL, it is sufficient to set 2UL to the time difference between (0) and (0''). Figure 15 The time difference 2UL between (0) and (0'') of the two drop waveforms shown is set to be greater than 1.5maxAL and less than 2.5minAL. Then, in all of the plurality of pressure chambers, the phase difference between the composite waves of (1), (2), (3) and (4) and the composite waves of (21), (22), (23) and (24) is less than ±90 degrees, and the composite waves of (1), (2), (3) and (4) and the composite waves of (21), (22), (23) and (24) mutually reinforce each other.

[0187] Furthermore, since the time widths Dp21 of (1) and (3) and Dp22 of (21) and (23) are approximately the same, even if the half-cycle AL of the main acoustic vibration frequency of the pressure chamber is different from the waveform UL, the pressure exerted on the liquid in the corresponding pressure chamber by the ejection waveforms with time widths Dp21 and Dp22 is the same. In addition, the ejection velocity of the second droplet, caused by the mutual reinforcement of the residual vibrations resulting from the composite waves of (1), (2), (3), and (4) and the composite waves of (21), (22), (23), and (24), is greater than that of the first droplet. Thus, through... Figure 15 The driving waveform shown depicts the continuous ejection of multiple drops of ink. In all of the multiple pressure chambers 46, the ejection speed of the ink ejected later, due to the residual vibration generated by the previous ejection waveform, can be adjusted to a speed higher than that of the previously ejected droplets.

[0188] Furthermore, the time interval between (1) and (2) depressurizing the pressure chamber is Tm21, and the time interval between (3) and (4) pressurizing the pressure chamber 46 is also Tm21. Therefore, if Tm21 is set according to the conditions of the above formula 4, the parasitic vibrations of (1) and (2) cancel each other out, and the parasitic vibrations of (3) and (4) also cancel each other out. Further, the time interval between (21) and (22) depressurizing the pressure chamber is Tm22, and the time interval between (23) and (24) pressurizing the pressure chamber 46 is also Tm22. Therefore, if Tm22 is set according to the conditions of the above formula 4, the parasitic vibrations of (21) and (22) cancel each other out, and the parasitic vibrations of (23) and (24) also cancel each other out.

[0189] It should be noted that while the method described involves adjusting the ejection speed of subsequently ejected ink, which is generated by the residual vibration of the previous ejection waveform, to a speed exceeding the ejection speed of the previously ejected droplets, it is also possible to adjust the speed to exceed the ejection speed of the previously ejected droplets by making the Tm of the subsequently input ejection waveform shorter than the Tm of the previous ejection waveform. This is because a shorter Tm results in, for example,... Figure 7 The greater the mutual reinforcement of the principal acoustic vibrations caused by the rising and falling waveforms, the better. Specifically, in Figure 15 With that driving waveform, the droplet velocity of the second drop can be made greater than that of the first drop by making the time width of Tm22 shorter than that of Tm21. In addition, if the time widths of Tm21 and Tm22 are set within the range of the conditions in Equation 4 above, parasitic vibrations can also be reduced.

[0190] For example, consider the case where the period λn of the parasitic vibration is the third harmonic of the principal acoustic vibration. Here, let λn be 2AL / 3, AL = 3.0 μs. With k = 1, substituting λn into equation 4 yields 2 / 3 μs ≤ Tm ≤ 4 / 3 μs. For example, in... Figure 16 In another example of the implementation, if Tm21=1.3μs and Tm22=0.7μs, then it becomes the driving waveform of Tm with the formula 4 set to be true.

[0191] It should be noted that the period λn of the parasitic vibration of the multiple pressure chambers 46 of the liquid ejector head 1 may differ due to manufacturing deviations. Here, the maximum value of the period λn of the parasitic vibration of the multiple pressure chambers 46 is set as maxλn, and the minimum value is set as minλn. In this case, among the multiple pressure chambers 46, the lower limit of equation 4 reaches its maximum when it becomes (k / 2 - 1 / 6)maxλn, and the upper limit of equation 4 reaches its minimum when it becomes (k / 2 + 1 / 6)minλn. Therefore, it becomes:

[0192] …(Equation 6).

[0193] Here, k is an odd number greater than or equal to 1.

[0194] If Tm is set within the range where Equation 6 holds, parasitic vibrations can be reduced in all of the plurality of pressure chambers 46.

[0195] Here, considering the case where the period λn of the parasitic vibration is the third harmonic of the principal acoustic vibration, we set minλn to 2*minAL / 3 = 5 / 3 μs and maxλn to 2*maxAL / 3 = 7 / 3 μs. With k=1, substituting minλn and maxλn into Equation 6 yields 7 / 9 μs ≤ Tm ≤ 10 / 9 μs. Setting Tm within this range allows us to reduce parasitic vibrations in all of the plurality of pressure chambers 46. For example, in... Figure 16 If Tm21 = 1.1 μs and Tm22 = 0.8 μs, then it becomes the driving waveform of Tm with the set equation 6 being true.

[0196] It should be noted that, in the example of this implementation, Figure 17 The time, voltage height, and ejection waveform of the droplet shown are related to the tf and tr of the ejection waveform. Figure 15 The two droplet waveforms shown are identical, but a single droplet waveform can be completely different from the two. In this case, to maintain print quality, it is also necessary to reduce the droplet velocity difference between the single-drop and two-drop waveforms. At this point, it is only necessary to... Figure 15 The time width Dp21 (=Dp22) of the two droplet waveforms shown is adjusted to be close to the velocity of each droplet in the two droplet waveforms, or the velocity of the droplet formed by the combination of droplets ejected through Dp21 and Dp22. Figure 17 The velocity of a droplet with different waveforms can be determined.

[0197] It should be noted that even when it is desired to make Dp21 and Dp22 different values ​​to fine-tune the droplet velocities of the two droplet waveforms, it is best to make Dp21 and Dp22 as close as possible to ensure that the pressures of Dp21 and Dp22 on the liquid in the pressure chamber are similar. For example, the time difference between Dp21 and Dp22 is preferably the smallest time difference other than zero that can be set in the drive circuit 70 that generates the corresponding drive waveform.

[0198] For example, when the two drop waveforms are set to Dp21=Dp22=2.4μs, Tm21=Tm22=1.0μs, UL=3.0μs, and Cp=1.5μs, the velocity of the combined droplet in the two drop waveforms is greater than the velocity of the ejected droplet in the single drop waveform. When the two drop waveforms are set to Dp21=Dp22=2.3μs, Tm21=Tm22=1.0μs, UL=3.0μs, and Cp=1.5μs, the velocity of the combined droplet in the two drop waveforms is less than the velocity of the ejected droplet in the single drop waveform.

[0199] Furthermore, in the corresponding liquid ejector head 1 drive circuit 70, if it is not possible to set the values ​​of Dp21 and Dp22 to values ​​between 2.3μs and 2.4μs, it is sufficient to set them to, for example, Dp21=2.3μs, Dp22=2.4μs, Tm21=Tm22=1.0μs, UL=3.0μs, and Cp=1.5μs.

[0200] It should be noted that the driving waveform for ejecting multiple droplets in the liquid ejection head 1 of this embodiment is not limited to a two-drop waveform, but can also be a three-drop waveform that ejects three or more droplets, or an n-drop waveform that ejects a predetermined number of droplets n. Figure 18 The image shows an example of a three-drop waveform ejected as another implementation of the driving waveform. It should be noted that, in... Figure 18 In the example of the ejected waveform, the elimination waveform is omitted. For example... Figure 18 As shown, if the time difference between (0) and (0'') is set to be greater than 1.5maxAL and less than 2.5minAL, then in all of the plurality of pressure chambers, the phase difference between the composite waves of (1), (2), (3), and (4) and the composite waves of (21), (22), (23), and (24) is less than ±90 degrees. Thus, the composite waves of (1), (2), (3), and (4) and the composite waves of (21), (22), (23), and (24) mutually reinforce each other.

[0201] In addition, such as Figure 18As shown, if the time difference between (0'') and (0''') is set to be greater than 1.5maxAL and less than 2.5minAL, then in all of the plurality of pressure chambers, the phase difference between the composite waves of (21), (22), (23), and (24) and the composite waves of (31), (32), (33), and (34) is less than ±90 degrees. Thus, the composite waves of (21), (22), (23), and (24) and the composite waves of (31), (32), (33), and (34) mutually reinforce each other. In addition, by setting it to Dp31 (=Dp32=Dp33) and adjusting the time width of Dp31 (=Dp32=Dp33), even if the half-cycle AL of the main acoustic vibration frequency of pressure chamber 46 is different from the waveform UL, the ejection waveforms with time widths of Dp31, Dp32, and Dp33 exert the same pressure on the liquid in the corresponding pressure chamber. In addition, the ejection velocity of the second droplet, which is ejected through the mutual reinforcement of the residual vibrations caused by the composite waves of (1), (2), (3), and (4) and the composite waves of (21), (22), (23), and (24), is greater than that of the first droplet. Furthermore, the ejection velocity of the third droplet, which is ejected through the mutual reinforcement of the residual vibrations caused by the composite waves of (21), (22), (23), and (24) and the composite waves of (31), (32), (33), and (34), is greater than that of the second droplet.

[0202] In this way, by continuously ejecting multiple drops of ink using a drive waveform (n-drop waveform), the ejection speed of the ink ejected later, through the residual vibration generated by the previous ejection waveform, can be adjusted in all of the multiple pressure chambers 46 to a speed higher than the ejection speed of the previously ejected droplets.

[0203] Furthermore, the time interval between (1) and (2) depressurizing pressure chamber 46 is Tm31, and the time interval between (3) and (4) pressurizing pressure chamber 46 is also Tm31. Therefore, if Tm31 is set according to the conditions of the above formula 4, the parasitic vibrations of (1) and (2) cancel each other out, and the parasitic vibrations of (3) and (4) also cancel each other out. Further, the time interval between (21) and (22) depressurizing pressure chamber 46 is Tm32, and the time interval between (23) and (24) pressurizing pressure chamber 46 is also Tm32. Therefore, if Tm32 is set according to the conditions of the above formula 4, the parasitic vibrations of (21) and (22) cancel each other out, and the parasitic vibrations of (23) and (24) also cancel each other out. Furthermore, the time interval between (31) and (32) depressurizing the pressure chamber 46 is called Tm33, and the time interval between (33) and (34) pressurizing the pressure chamber 46 is also called Tm33. Therefore, if Tm33 is set according to the conditions of the above formula 4, the parasitic vibrations of (31) and (32) cancel each other out, and the parasitic vibrations of (33) and (34) also cancel each other out.

[0204] This describes adjusting the ejection speed of ink ejected subsequently due to residual vibrations generated by the previous ejection waveform to a speed exceeding the ejection speed of previously ejected droplets. However, it is also possible to adjust the speed to exceed the ejection speed of previously ejected droplets by making the Tm of the subsequently input ejection waveform shorter than the Tm of the previous ejection waveform. This is because a shorter Tm results in a higher ejection speed, for example, from... Figure 7 The greater the mutual reinforcement of the principal acoustic vibrations caused by the rising and falling waveforms shown, the more pronounced the effect. Specifically, in Figure 18 In the case of the three-drop waveform shown, the droplet velocity of the second drop can be made greater than that of the first drop by making the time width of Tm32 shorter than that of Tm31. Furthermore, the droplet velocity of the third drop can be made greater than that of the second drop by making the time width of Tm33 shorter than that of Tm32. Additionally, if the time widths of Tm31, Tm32, and Tm33 are set within the range of the conditions in Equation 4, parasitic vibrations can also be reduced.

[0205] It should be pointed out that, such as Figure 15 and Figure 17 As shown, the time, voltage height, and tf and tr of the ejection waveforms of one drop and two drops are related to... Figure 18 The three droplet waveforms shown are identical, but the waveforms of the one-drop and two-drop waveforms can be completely different from the three-drop waveform. In this case, to maintain print quality, it is also necessary to reduce the difference in droplet velocity between the one-drop, two-drop, and three-drop waveforms. Here, we assume that the one-drop and two-drop waveforms are adjusted to reduce the difference in droplet velocity. This can be achieved by adjusting... Figure 18The time width Dp31 (=Dp32=Dp33) of the three-drop waveform is adjusted to be close to the velocity of each droplet in the three-drop waveform, or the velocity of the droplet formed by the combination of droplets ejected through Dp31, Dp32, and Dp33. Figure 17 A drop of waveform Figure 15 The velocity of the two droplets with different waveforms can be determined.

[0206] It should be noted that even when it is desired to make Dp31, Dp32, and Dp33 different values ​​to fine-tune the droplet velocities of the three-drop waveform, it is best to make Dp31, Dp32, and Dp33 as close as possible to ensure that the pressures exerted by Dp31, Dp32, and Dp33 on the liquid in pressure chamber 46 are similar. For example, the time difference between Dp31, Dp32, and Dp33 is preferably the smallest time difference other than zero that can be set in the drive circuit 70 that generates the corresponding drive waveform.

[0207] For example, when the three-drop waveform is set to Dp31=Dp32=Dp33=2.4μs, Tm31=Tm32=Tm33=1.0μs, UL=3.0μs, and Cp=1.5μs, the velocity of the combined droplet in the three-drop waveform is greater than the velocity of the ejected droplet in the single-drop waveform. When the three-drop waveform is set to Dp31=Dp32=Dp33=2.3μs, Tm31=Tm32=Tm33=1.0μs, UL=3.0μs, and Cp=1.5μs, the velocity of the combined droplet in the three-drop waveform is less than the velocity of the ejected droplet in the single-drop waveform.

[0208] In the drive circuit 70 of the corresponding liquid nozzle 1, if it is not possible to set the values ​​of Dp31, Dp32, and Dp33 to values ​​between 2.4μs and 2.3μs, for example, they can be set to Dp31=Dp32=2.3μs, Dp33=2.4μs, Tm31=Tm32=Tm33=1.0μs, UL=3.0μs, and Cp=1.5μs. Alternatively, they can be set to Dp31=2.3μs, Dp32=Dp33=2.4μs, Tm31=Tm32=Tm33=1.0μs, UL=3.0μs, and Cp=1.5μs.

[0209] Furthermore, even for multi-drop drive waveforms (n-drop waveforms) that differ from two-drop and three-drop waveforms, if the reference point of the phase of the first ejected waveform within two consecutive ejected waveforms is set to (0), and the reference point of the phase of the next ejected waveform is set to (0''), and the time difference between (0) and (0'') is set to be greater than 1.5maxAL and less than 2.5minAL, then in all of the plurality of pressure chambers, the residual vibration of all ejected waveforms ejected after the second drop mutually reinforces the previous ejected waveform. Additionally, by setting the width of all ejected waveforms to Dpn1 (=Dpn2=~=Dpnn) and adjusting the time width of Dpn1 (=Dpn2=~=Dpnn), even if the half-cycle AL of the main acoustic vibration frequency of pressure chamber 46 differs from the waveform UL, the pressure exerted on the liquid in the corresponding pressure chamber 46 by ejected waveforms with time widths of Dpn1~Dpnn is the same. In this way, by continuously ejecting multiple drops of ink using a drive waveform (n-drop waveform), the ejection speed of the ink ejected later, through the residual vibration generated by the previous ejection waveform, can be adjusted to a speed greater than the ejection speed of the previously ejected droplets in all of the multiple pressure chambers 46.

[0210] Furthermore, if Tmn1 (=Tmn2=~=Tmnn) is set according to the conditions of Equation 4 above, then the parasitic vibrations caused by the initial and final pressure changes of each Tm will cancel each other out.

[0211] It should be noted that the ejection waveforms of the n-drop waveform and the waveforms of the waveforms ejecting more than n drops can be completely different. In this case, to maintain print quality, it is also necessary to reduce the difference in droplet velocity between the n-drop waveform and the waveforms of the waveforms ejecting more than n drops. Here, the waveforms of the waveforms ejecting more than n drops are adjusted to reduce the difference in droplet velocity. Moreover, this can be achieved by adjusting the time width Dpn1 (=Dpn2=~=Dpnn) of the n-drop waveform, setting it so that the velocity of each droplet in the n-drop waveform, or the velocity of the combined droplet after the droplets ejected through Dpn1~Dpnn, are close to the droplet velocity of the waveforms ejecting more than n drops.

[0212] It should be noted that even when it is desired to make Dpn1 to Dpnn different values ​​to fine-tune the droplet velocity of each droplet in the n-droplet waveform, it is best to make Dpn1 to Dpnn as close as possible to ensure that the pressure of the liquid in the pressure chamber 46 is similar. For example, the time difference between Dpn1, Dpn2, ..., Dpnn is preferably the smallest time difference other than zero that can be set in the drive circuit 70 that generates the corresponding drive waveform.

[0213] According to the liquid ejector head 1 described above, the time width of the initial ejection waveform is the same (including approximately the same) as the time width of the subsequent ejection waveform, and the interval of the ejection waveform is consistent with the period of the residual vibration of the liquid in the pressure chamber generated by the first ejection waveform and the vibration of the liquid in the pressure chamber generated by the subsequent ejection waveform. That is, the drive waveform has approximately the same width as the ejection waveform when multiple droplets are ejected continuously, and the center-to-center distance of the ejection waveform when multiple droplets are ejected continuously is 2AL. The liquid ejector head can make the ejection force of each droplet approximately the same and increase the ejection speed of subsequent droplets. Since the ejection waveform width is approximately the same, the ejection force of the droplets in each ejection waveform is approximately the same. Since the center-to-center distance of the ejection waveform is 2AL, the ejection waveform of subsequent droplets and the residual vibration mutually reinforce each other, and the ejection speed is increased. The liquid ejector head improves print quality by counteracting parasitic vibrations.

[0214] Furthermore, when multiple droplets are continuously ejected at approximately the same speed, the liquid ejector head 1 can adjust the width of the ejection waveform regardless of the number of droplets. Additionally, the liquid ejector head 1 sets the intermediate voltage time to approximately half a cycle of the parasitic vibration, thus canceling out the parasitic vibration. Furthermore, the intermediate voltage time of the ejection waveform after the final droplet is ejected can be made shorter than the intermediate voltage time of the previous ejection waveforms.

[0215] Some embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and their equivalents.

Claims

1. A liquid ejector head, comprising: Nozzle plate, equipped with nozzles for spraying liquid; The pressure chamber is connected to the nozzle; The actuator changes the volume of the pressure chamber according to the drive signal; and The drive circuit generates the drive signal that drives the actuator. The driving signal includes multiple ejection waveforms that cause multiple droplets to be ejected from the nozzle. The waveform widths of the multiple ejected waveforms are the same. The ejection waveform of the driving signal includes an expansion potential difference that expands the volume of the pressure chamber, a contraction potential difference that reduces the volume of the pressure chamber, and at least one intermediate potential difference between the expansion potential difference and the contraction potential difference. The drive circuit cancels out vibrations at an acoustic resonant frequency higher than the primary acoustic resonant frequency of the liquid in the pressure chamber caused by the change in potential difference, by performing at least one potential difference change after the change in potential difference. The intervals of the plurality of ejection waveforms are consistent with the period of the residual vibration of the liquid in the pressure chamber generated by the first ejection waveform and the vibration of the liquid in the pressure chamber generated by the subsequent ejection waveform.

2. The liquid ejector head according to claim 1, wherein, When the period of the acoustic resonant frequency in the frequency domain higher than the main acoustic resonant frequency of the liquid in the pressure chamber is set as λn, and when the number of potential difference changes included in the driving signal is h times, one of the potential difference changes from the first to the (h-1)th time in which the volume of the pressure chamber expands or shrinks is designated as the i-th potential difference change, and one of the potential difference changes from the (i+1)th time in which the volume of the pressure chamber expands or shrinks is designated as the j-th potential difference change, the time interval Tij between any two i-th and j-th potential difference changes in the h times is: (k / 2-1 / 6)λn≤Tij≤(k / 2+1 / 6)λn, where k is an odd number greater than or equal to 1.

3. The liquid ejector head according to claim 2, wherein, The time interval Tij is: (k / 2-1 / 6)λn≤Tij≤kλn / 2, where k is an odd number greater than or equal to 1.

4. The liquid ejector head according to claim 1, wherein, The driving circuit has a switching circuit that connects the electrode and the voltage source, and the driving signal is generated by switching the switching circuit.

5. The liquid ejector head according to claim 1, wherein, The time interval between the centers of the plurality of ejected waveforms is greater than 1.5 times the maximum value of the half-cycle of the principal acoustic vibration frequency of the plurality of pressure chambers and less than 2.5 times the minimum value of the cycle. The plurality of pressure chambers change volume by means of the actuator that receives the drive signal.

6. The liquid ejector head according to claim 1, wherein, The acoustic resonant frequency in the frequency domain higher than the primary acoustic resonant frequency of the liquid in the pressure chamber is an odd multiple of more than three times the primary acoustic resonant frequency.

7. The liquid ejector head according to any one of claims 1 to 6, wherein, The interval between the plurality of ejection waveforms is the waveform width such that the ejection velocity of the last ejected droplet within the plurality of droplets is greater than the ejection velocity of the first ejected droplet.

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