Drive device

Abstract

A drive device capable of improving ejection performance includes a drive unit that outputs a drive signal for driving a pressure chamber communicating with a nozzle that ejects a liquid, the drive waveform of the drive signal including: a first ejection waveform that ejects the liquid; a first holding element that is provided after the first discharge waveform and that elapses a predetermined time; a second discharge waveform that is provided after the first holding element and discharges the liquid; a second holding element that is provided after the second discharge waveform and that elapses a predetermined time; a third discharge waveform that is provided after the second holding element and discharges the liquid; a third holding element that is provided after the third discharge waveform and that elapses a predetermined time; and a contraction waveform that is provided between the second holding element and the third discharge waveform and contracts the pressure chamber, the period between the second discharge waveform and the third discharge waveform being larger than the period between the first discharge waveform and the second discharge waveform.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to a drive device. BACKGROUND

[0002] There is known a technique in which, as a drive signal of a piezoelectric inkjet recording device, a pulse that expands the volume of a pressure chamber is applied to an actuator at a fixed period of 2AL when 1 / 2 of the main acoustic resonance period of ink of the piezoelectric inkjet pressure chamber is set as AL, and liquid droplets are continuously ejected. Since liquid droplets are ejected at a 2AL period, there is an advantage that the drive time is short and it is easy to increase the drive frequency, but in a three-droplet or more ejection operation, it is easy to entrap a bubble from a nozzle, and thus it is easy to cause a non-ejection.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-185685 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The problem to be solved by the present application is to provide a drive device capable of improving ejection performance.

[0008] MEANS OF SOLVING THE PROBLEM

[0009] The drive device according to an embodiment has a drive section that outputs a drive signal that drives a pressure chamber that communicates with a nozzle that ejects liquid, the drive waveform of the drive signal having a first ejection waveform that causes liquid to be ejected, a first holding element that is provided after the first ejection waveform and causes a prescribed time to elapse, a second ejection waveform that is provided after the first holding element and causes liquid to be ejected, a second holding element that is provided after the second ejection waveform and causes a prescribed time to elapse, a third ejection waveform that is provided after the second holding element and causes liquid to be ejected, a third holding element that is provided after the third ejection waveform and causes a prescribed time to elapse, and a contraction waveform that is provided between the second holding element and the third ejection waveform and causes the pressure chamber to contract, the period between the second ejection waveform and the third ejection waveform being greater than the period between the first ejection waveform and the second ejection waveform. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a cross-sectional view showing the structure of an inkjet head according to a first embodiment.

[0011] Figure 2 is a cross-sectional view showing the structure of an inkjet head according to a first embodiment.

[0012] Figure 3 is a waveform chart showing a drive waveform involved in this embodiment.

[0013] Figure 4 is a waveform chart showing a drive waveform involved in the comparative example.

[0014] Figure 5 is a table showing simulation results of bubble entrainment of the drive involved in this embodiment and the drive involved in the comparative example.

[0015] Figure 6 is an explanatory diagram showing a modification example of the nozzle shape of this inkjet head.

[0016] Figure 7 is a waveform chart showing a drive waveform involved in the second embodiment.

[0017] Explanation of Reference Numerals

[0018] 1: inkjet head; 20: actuator portion; 21: driven piezoelectric element (piezoelectric element); 22: non-driven piezoelectric element (piezoelectric element); 23: groove; 26: piezoelectric structure portion; 30: vibration plate; 31: pressure chamber; 32: common chamber; 33: individual liquid chamber; 34: throttle flow path; 35: ink flow path; 40: flow path substrate; 42: partition wall portion; 45: frame portion; 45a: vibration-damping member; 46: drive circuit; 50: nozzle plate; 51: nozzle; 211: piezoelectric body layer; 221: internal electrode; 222: internal electrode; 223: external electrode; 224: external electrode; 303: opening portion; 401: flow path plate; 402: flow path plate; 403: flow path plate; P1a, P1b, P1c: ejection pulse; P2a, P2b, P2c: holding element; P3: release pulse; P4: contraction pulse; W0: drive waveform; W1: drive waveform; W2: drive waveform. DETAILED DESCRIPTION

[0019] The following will be described with reference to Figures 1 to 3 An inkjet head 1 involved in the first embodiment will be described. Figure 1 and Figure 2 is a sectional view showing the structure of the inkjet head 1 involved in the first embodiment. Figure 3 is a waveform chart showing a drive waveform in the first embodiment. Note that in each drawing, the structure is shown as being appropriately enlarged, reduced, or omitted for ease of explanation.

[0020] Figure 1 , Figure 2These are longitudinal and transverse sectional views of the inkjet head 1 according to this embodiment. As an example of a driving device, the inkjet head 1 includes: an actuator section 20, a vibrating plate 30, a flow path substrate 40 as a flow path section having multiple flow path plates, a nozzle plate 50 as a nozzle section having multiple nozzles 51, a frame section 45 as a structural section, and a driving circuit 46 as a driving section. The inkjet head 1 is a liquid ejection head provided in a liquid ejection device such as an inkjet recording apparatus.

[0021] The actuator section 20 includes, for example, a plurality of driving piezoelectric elements 21 and a plurality of non-driving piezoelectric elements 22, which are arranged alternately along a column direction as actuators and are composed of piezoelectric components; and a piezoelectric structure section 26 that connects these plurality of piezoelectric elements 21 and 22 into one unit. The actuator section 20 is divided into a plurality of sections by a plurality of slots 23, and the plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are arranged at the same spacing in the column direction. The plurality of driving piezoelectric elements 21 and non-driving piezoelectric elements 22 are all configured as cuboid columns with the same external shape.

[0022] The piezoelectric components constituting the driven piezoelectric element 21 and the non-driven piezoelectric element 22 are, for example, stacked piezoelectric bodies. The driven piezoelectric element 21 and the non-driven piezoelectric element 22 each have multiple stacked piezoelectric layers 211 and internal electrodes 221, 222 formed on the main surface of each piezoelectric layer 211. It should be noted that, as an example, the driven piezoelectric element 21 and the non-driven piezoelectric element 22 have the same stacked structure. Furthermore, the driven piezoelectric element 21 and the non-driven piezoelectric element 22 each have external electrodes 223, 224 formed on their surfaces.

[0023] The piezoelectric layer 211 is made of a piezoelectric material such as PZT (lead zirconate titanate) or lead-free KNN (sodium potassium niobate). Multiple piezoelectric layers 211 are stacked with their thickness directions along the stacking direction. For example, in this embodiment, the thickness direction and stacking direction of the piezoelectric layers 211 are arranged along the vibration direction (Z direction).

[0024] The internal electrodes 221 and 222 are conductive films of a predetermined shape made of a sinterable conductive material such as silver or palladium. The internal electrodes 221 and 222 are mutually distinct electrodes. For example, one internal electrode 221 is formed in the extension direction (Y direction), which is orthogonal to both the arrangement direction (X direction) and the vibration direction (Z direction) of the plurality of driven piezoelectric elements 21 and the plurality of non-driven piezoelectric elements 22, at a region reaching one end of the piezoelectric layer 211 but not the other end. The other internal electrode 222 is formed in the extension direction at a region reaching the other end of the piezoelectric layer 211. The internal electrodes 221 and 222 are respectively connected to external electrodes 223 and 224 formed on the sides of the piezoelectric elements 21 and 22.

[0025] External electrodes 223 and 224 are formed on the surfaces of multiple driven piezoelectric elements 21 and multiple non-driven piezoelectric elements 22, and are combined with the ends of internal electrodes 221 and 222. For example, external electrodes 223 and 224 are formed on one end face and the other end face in the extension direction of piezoelectric layer 211, respectively, becoming a common electrode and a separate electrode.

[0026] External electrodes 223 and 224 are connected to the drive circuit (drive unit) via, for example, a wiring board.

[0027] In the inkjet head 1, the piezoelectric element 21 is driven to vibrate by applying a voltage from the wiring substrate to the internal electrodes 221 and 222 via external electrodes 223 and 224. In this embodiment, the piezoelectric element 21 is driven to vibrate longitudinally along the stacking direction of the piezoelectric layer 211, thereby displacing the vibrating plate 30 and deforming the pressure chamber 31.

[0028] The vibrating plate 30 extends along a surface orthogonal to the vibration direction, i.e., the Z-direction, and engages with the surface of the piezoelectric layer 211 of the plurality of piezoelectric elements 21, 22 on the side of the vibration direction, i.e., the nozzle plate 50 side. The vibrating plate 30 is opposed to the plurality of nozzles 51 via the pressure chamber 31 in the vibration direction, i.e., the Z-direction. The vibrating plate 30 is configured to be deformable, for example. The vibrating plate 30 is engaged with the driving piezoelectric element 21 and the non-driving piezoelectric element 22 of the actuator section 20, as well as the frame section 45. The vibrating plate 30 is disposed between the flow path plate 401 and the actuator section 20 in the vibration direction. The vibrating plate 30 is arranged overlappingly with the plurality of flow path plates 401, 402, 403, forming part of the ink flow path 35. The vibrating plate 30 is engaged with the end face of the actuator section 20 by bonding or the like.

[0029] The flow path substrate 40 comprises multiple flow path plates 401, 402, and 403 stacked together. For example, depending on the viscosity of the ink, the ejected volume, etc., multiple flow path plates 401, 402, and 403 having openings or grooves, nozzle plates 50, and vibrating plates 30 are combined and joined to form a desired ink flow path 35. The multiple flow path plates 401, 402, and 403 are arranged overlapping in the stacking direction, and the openings or grooves formed in each flow path plate 401, 402, and 403 constitute a predetermined ink flow path 35. The predetermined ink flow path 35 includes a pressure chamber 31 communicating with multiple nozzles 51, a separate liquid chamber 33 communicating with a common chamber 32, and a throttling flow path 34 (resistance flow path).

[0030] As an example, flow path plates 401, 402, and 403 are stacked sequentially from the vibrating plate 30 side, with flow path plate 403 positioned opposite nozzle plate 50.

[0031] A flow path substrate 40 is disposed between the nozzle plate 50 and the vibrating plate 30. The flow path substrate 40 forms a defined ink flow path 35 (liquid chamber) internally by stacking and joining multiple flow path plates 401, 402, and 403. The defined ink flow path 35 has multiple pressure chambers 31, individual liquid chambers 33 communicating with a common chamber 32, and multiple throttling flow paths 34 (throttling sections) from the individual liquid chambers 33 to the pressure chambers 31. In other words, the flow path substrate 40 constitutes, through the stacked multiple flow path plates 401, 402, and 403, a peripheral wall portion surrounding the ink flow path 35 (liquid chamber) composed of multiple pressure chambers 31, multiple throttling flow paths 34, and individual liquid chambers 33, multiple partition walls 42 separating the rows of multiple pressure chambers 31, and side walls separating the multiple throttling flow paths 34.

[0032] The nozzle plate 50 is configured as a square plate with a thickness of approximately 10µm to 100µm, made of, for example, a metal such as SUS·Ni or a resin material such as polyimide. The nozzle plate 50 is disposed on one side of the flow path substrate 40 with an opening covering one side of the pressure chamber 31. The nozzle plate 50 has a plurality of nozzles 51 for ejecting droplets. The plurality of nozzles 51 are holes that penetrate the nozzle plate 50 in the thickness direction. A plurality of nozzles 51 are arranged in the X direction, which is the same as the arrangement direction of the pressure chambers 31, forming a nozzle array. Each nozzle 51 is positioned corresponding to one of the plurality of pressure chambers 31.

[0033] The frame portion 45 is a structure that is joined to the vibrating plate 30 together with the piezoelectric elements 21 and 22. The frame portion 45 is disposed on the side of the vibrating plate 30 opposite to the flow path substrate 40, for example, in this embodiment, it is disposed adjacent to the actuator portion 20. The frame portion 45 forms the outline of the inkjet head 1. The frame portion 45 forms a flow path for the liquid inside. In this embodiment, the frame portion 45 is joined to the other side of the vibrating plate 30, and a common chamber 32 is formed between it and the vibrating plate 30. For example, the frame portion 45 may also be constituted by a portion of a wall-deformable damping member 45a.

[0034] The common chamber 32 is formed inside the frame portion 45 and is connected to the pressure chamber 31 through the opening 303 provided in the vibrating plate 30, the individual liquid chamber 33, and the throttling flow path 34.

[0035] The drive circuit 46 includes various wiring boards and driver ICs. The drive circuit 46 is a drive waveform generation unit that generates and outputs a drive waveform based on a drive signal applied to the drive element. The driver IC is electrically connected to the electrodes of the actuator section 20 via wiring on the wiring board. By outputting a drive signal, the drive circuit 46 drives the actuator section 20, causing the volume of the pressure chamber 31 to increase or decrease, and ejecting droplets from the opposing nozzle 51.

[0036] In the inkjet head 1 configured as described above, an ink flow path 35 is formed by a nozzle plate 50, a frame portion 45, a flow path substrate 40, and a vibrating plate 30. This ink flow path 35 has multiple pressure chambers 31 communicating with the nozzle 51, a separate flow path consisting of a throttling flow path 34 communicating with the multiple pressure chambers 31 and a separate liquid chamber 33, and a common chamber 32 serving as a common flow path. For example, the common chamber 32 communicates with a cartridge, and ink is supplied to each pressure chamber 31 through the common chamber 32. Piezoelectric elements are connected by wiring to apply a voltage. In the inkjet head 1, when filled with ink, if a driving voltage is applied to the electrodes 221 and 222 by the driving circuit 46, the piezoelectric element 21 to be driven vibrates in the stacking direction, i.e., the thickness direction of each piezoelectric layer 211. That is, the piezoelectric element 21 vibrates longitudinally. Specifically, the driving circuit 46 applies a driving voltage to the internal electrodes 221 and 222 of the piezoelectric element 21 to selectively drive the piezoelectric element 21 to be driven. Then, by combining the deformation in the tensile and compressive directions caused by the piezoelectric element 21, the vibrating plate 30 is deformed, causing the volume of the pressure chamber 31 to change, thereby guiding the liquid from the common chamber 32 and spraying it out from the nozzle 51.

[0037] The following describes the drive waveform W1 based on the drive signal output by the drive circuit 46. Figure 3 This is a diagram illustrating an example of a driving waveform. The driving waveform W1 according to this embodiment has three droplet waveforms (elements) in one printing cycle. Figure 3 In the diagram, the vertical axis represents voltage [V], and the horizontal axis represents time [μs]. It should be noted that in each waveform diagram, each 1AL (Acoustic Length) represents a scale line. Here, AL is half the time of the natural vibration period (primary acoustic resonance period) of the ink within the pressure chamber 31 of the inkjet head 1.

[0038] The driving waveform W1 has multiple ejection pulses P1a~P1c (ejection waveform), holding elements (holding time) P2a~P2c, release pulse P3 (release waveform), and contraction pulse P4 (contraction waveform).

[0039] The first ejection pulse P1a (first ejection waveform), which is the pulse pulse that causes the pressure chamber to expand by dropping the voltage from the standby voltage Vb (second voltage), which serves as the reference potential, to an expansion voltage Va (first voltage), which is lower than the standby voltage, and then returning to the standby voltage Vb after a certain period of time, thereby ejecting ink. For example, the ejection pulse P1a is a trapezoidal pulse waveform.

[0040] The first holding element P2a, which is the holding element of the first drop, is the waveform of the voltage that is maintained for a specified time.

[0041] The second ejection pulse P1b (second ejection waveform), which is the ejection pulse of the second droplet, is a pulse waveform in which the voltage is reduced from the standby voltage Vb to the expansion voltage Va after holding element P2a, causing the pressure chamber 31 to expand, and then returning to the standby voltage Vb after a certain period of time, thereby ejecting ink. For example, the ejection pulse P1b is a trapezoidal pulse waveform.

[0042] The holding element P2b is the waveform that maintains the voltage for a specified time.

[0043] In the inkjet head 1, when an ejection pulse P1a is applied to the actuator section 20, the volume of the pressure chamber 31 expands and then contracts. The pressure vibration during expansion overlaps with the pressure vibration during contraction, and the first drop of ink is ejected from the nozzle 51 between the holding elements P2a. When an ejection pulse P1b is applied at a timing 2AL after the application of the ejection pulse P1a, a second drop of ink is ejected between the holding elements P2b.

[0044] The driving waveform W1 has a contraction pulse P4 (contraction waveform) after the holding element P2b and before the third drop ejection pulse, i.e., the third ejection pulse P1c (third ejection waveform). That is, when the second drop is ejected, the third drop is not ejected immediately after being held at the standby voltage, but rather the pulse waveform of the contraction pressure chamber is applied before the third ejection pulse P1c.

[0045] The contraction pulse P4 is a pulse waveform that raises the voltage from the standby voltage of the second holding element P2b, which is the second holding element, to a contraction voltage Vc (third voltage) that is higher than the standby voltage, and then returns to the standby voltage Vb after a certain period of time.

[0046] For example, a third ejection pulse P1c is applied after the contraction pulse P4. Here, the third ejection waveform is a pulse waveform that drops to the expansion voltage Va, and then rises to the contraction voltage Vc after a certain time. The ejection pulse P1c is applied at a time after the application of the ejection pulse P1b, starting from 3AL.

[0047] In addition, in this embodiment, a release pulse P3 is provided after the third holding element P2c, which is a holding element, following the ejection pulse P1c of the third drop.

[0048] The release pulse P3 is a waveform that rises to a higher release voltage Vd than the contraction voltage Vc after the ejection pulse P1c is held for a certain period of time by the holding element P2c, and then returns to the standby voltage Vb after a certain period of time. By applying this release pulse P3, residual vibration is attenuated.

[0049] In the driving waveform W1, the time (period) between ejection pulses P1a and P1b is twice AL, i.e., 2AL. On the other hand, the time (period) between ejection pulses P1b and P1c is three times AL, i.e., 3AL. That is, the period of the ejection waveform of the second and third droplets is longer than the period of the ejection waveform of the first and second droplets.

[0050] According to the drive device of this embodiment, ejection performance can be improved by suppressing nozzle entrapment. That is, in the drive waveform W1, by applying a contraction pulse P4 before applying the ejection pulse P1c of the third drop, the meniscus can be stabilized, and by applying the ejection pulse P1c after the contraction pulse P4, non-ejection can be prevented.

[0051] For example, as a comparative example, Figure 4 The driving waveform W0 shown is the waveform of the third drop ejection pulse P1c applied immediately after the holding time P2b ends. That is, after the holding time P2b ends, the driving waveform W0 applies the ejection pulse P1c without applying the contraction pulse P4. If the ink ejection operation is performed at this timing, air bubbles are easily entangled in the ink constriction surface inside the nozzle 51, resulting in no ejection.

[0052] Figure 5 Compare and show the pairs Figure 3 The driving waveform W1 of the implementation method and Figure 4 The results of the simulation were performed on the bubble entanglement in the driving waveform W0 of the comparative example. Regarding each waveform W1 and W0, the shape of the nozzle was considered... Figure 6 Ink ejection simulations were performed on various nozzle shapes shown, with ejection velocities of 6 m / s, 7 m / s, and 8 m / s. Simulations were conducted for nozzles with altered taper angles, nozzles with a straight front end (as the ejection surface side) after setting the taper, and nozzles with an inverted cone shape (as the ejection surface side) after setting the taper. It should be noted that the length of the straight portion (straight line length) was set to 10 µm and 20 µm. The ink viscosity in the ink ejection simulation was set to 5 mPa·s. The absence of air bubbles in the nozzle is indicated by 〇, the presence of air bubbles by ×, and the potential for air bubble entrainment by △. Figure 5 As can be seen, compared with the driving waveform W0 involved in Comparative Example 1, the driving waveform W1 of Embodiment 1 is less likely to cause bubble entrapment and less likely to cause non-ejection.

[0053] The present invention has been described in detail above as one embodiment, but the present invention is not limited to the above embodiment and can be appropriately modified or improved.

[0054] For example, in the above embodiment, multiple examples are shown where the ejected waveforms have the same pulse width and are trapezoidal, but this is not the only example. For instance, as other embodiments, such as... Figure 7 As shown, it can be a stepped waveform with phased voltage switching, or it can be a rectangular wave with sharp rises and falls without steps. In addition, the pulse widths of multiple ejected pulses can also be different. Figure 7 The driving waveform W2 involved in other embodiments is shown. Figure 7 In the graph, the vertical axis represents voltage [V], and the horizontal axis represents time [μs]. It should be noted that in... Figure 7 In the waveform diagram, each 1AL represents an Acoustic Length (AL) scale line. Here, AL is half the time of the natural vibration period of the ink in the pressure chamber 31 of the inkjet head 1.

[0055] The driving waveform W2 has multiple ejection pulses P1a~P1c, holding elements (holding time) P2a~P2c, release pulse P3, and contraction pulse P4. Like the driving waveform W1, the driving waveform W2 is a multi-drop driving waveform with three droplet waveforms (elements) in one printing cycle.

[0056] In the driving waveform W2 of this embodiment, each ejection pulse P1a, P1b, P1c, and the release pulse P3 and contraction pulse P4 are step waveforms that periodically switch voltages. Furthermore, in the driving waveform W2, the pulse width of the second ejection pulse P1b is shorter than that of the first ejection pulse P1a. Additionally, in the driving waveform W2, the third ejection pulse P1c is a pulse waveform that decreases from the contraction voltage to the expansion voltage and then periodically returns to the standby voltage after a certain time. In W2 of this embodiment, the time (period) between ejection pulses P1a and P1b is twice AL, i.e., 2AL. On the other hand, the time (period) between ejection pulses P1b and P1c is three times AL, i.e., approximately 3AL. That is, the period of the ejection waveforms of the second and third drops is longer than the period of the ejection waveforms of the first and second drops. Regarding other structures, it is the same as the driving waveform W1 of the first embodiment described above.

[0057] In the driving waveform W2 of this embodiment, by applying a contraction pulse P4 after the holding element P2b following the second ejection pulse P1b and before the third ejection pulse P1c, the meniscus can be stabilized. By applying the ejection pulse P1c after the contraction pulse P4, non-ejection can also be prevented.

[0058] For example, in the above embodiment, an inkjet head 1 with a driver IC is shown as an example of a driving device, but it is not limited to this. For example, various control devices such as the control device of an inkjet recording device connected to the inkjet head 1 and disposed outside the inkjet head 1 may also be used as driving devices.

[0059] The potentials of each element in the driving waveform can be varied, and the voltage applied to each piezoelectric element can be adjusted appropriately according to various conditions. Furthermore, the piezoelectric element can be either a structure that elongates when the voltage is increased and contracts when the voltage is decreased, or a structure that elongates when the voltage is decreased and contracts when the voltage is increased. Additionally, the sequence of expansion and contraction in each ejection pulse can also be appropriately set according to various conditions.

[0060] The structure of the inkjet head 1 is not limited to the examples described above, and can also be used for other types of heads. For example, the inkjet head is not limited to a structure in which a vibrating plate disposed between the pressure chamber and the drive element section vibrates by deforming the drive element section, and can also be applied to various other structures such as the type in which a pressure chamber is formed between multiple columnar drive element sections.

[0061] In addition, the inkjet head can be a non-circulating head that does not circulate ink, or it can be a circulating head that circulates ink.

[0062] According to at least one embodiment described above, ejection performance can be improved by suppressing nozzle entrapment.

[0063] Several 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 new 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 similarly included within the scope of the invention as set forth in the claims and their equivalents.

Claims

1. A driving device, characterized in that, have: The drive unit outputs a drive signal to drive the pressure chamber connected to the nozzle that ejects the liquid. The driving waveform of the driving signal has: The first jet waveform causes the liquid to be ejected; A first holding element is provided after the first ejection waveform and allows a predetermined time to elapse; A second ejection waveform is provided after the first holding element, and causes the liquid to be ejected; The second holding element is provided after the second ejection waveform and allows a predetermined time to elapse; A third ejection waveform is provided after the second holding element, and causes the liquid to be ejected; The third holding element is provided after the third ejection waveform and allows a predetermined time to elapse; as well as A contraction waveform is positioned between the second retaining element and the third ejection waveform, causing the pressure chamber to contract. The period between the second ejection waveform and the third ejection waveform is greater than the period between the first ejection waveform and the second ejection waveform.

2. The driving device according to claim 1, characterized in that, When half of the main acoustic resonance period of the ink in the pressure chamber is set as AL, the period between the first ejection waveform and the second ejection waveform is 2AL, and the period between the second ejection waveform and the third ejection waveform is 3AL.

3. The driving device according to claim 1, characterized in that, The third holding element, after the third ejection waveform, allows a predetermined time to elapse, either when the waveform returns to the reference potential or when a contraction voltage is applied.

4. The driving device according to claim 3, characterized in that, The contraction waveform or at least one of the plurality of ejection waveforms has a stepped waveform that causes the voltage to change in stages.

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