Driving device and liquid discharge head

Abstract

To provide a driving device and a liquid discharge head that can obtain an appropriate discharge amount and can prevent a latch-up phenomenon.SOLUTION: A driving device according to an embodiment outputs a driving signal. The driving signal includes, in this order, an auxiliary pulse that contracts a volume of a pressure chamber communicating with a nozzle that discharges liquid from a reference state, a discharge pulse that expands the volume of the pressure chamber beyond the reference state and then returns the volume to the reference state to thereby discharge a liquid droplet from the nozzle communicating with the pressure chamber, a cancel pulse that contracts the volume of the pressure chamber from the reference state after discharge of the liquid droplet and then returns the volume to the reference state to thereby attenuate residual vibration, and a damping pulse that expands, to an extent that liquid is not discharged, the volume of the pressure chamber after attenuation of the residual vibration in which the volume of the pressure chamber has been returned to the reference state by application of the cancel pulse. An application time of the damping pulse is shorter than an application time of the cancel pulse, and is at least 0.5 times a half period of a primary acoustic resonance frequency of liquid in the pressure chamber or at least 1 μs.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a driving device and a liquid ejection head. [Background technology]

[0002] In recent years, various printing performances such as high image quality and high resolution have been required for liquid ejection devices such as inkjet printers, and ejection stability has become necessary. For example, a liquid ejection head is known that includes a plurality of nozzles, a plurality of pressure chambers that are provided corresponding to each of the nozzles and filled with ink, a plurality of piezoelectric elements that correspond to the pressure chambers, and a drive device that applies drive signals to the piezoelectric elements.

[0003] In such liquid ejection heads, in order to suppress the occurrence of satellites and ink mist without impairing the ejection stability of the main ink droplets, a drive waveform may be used that applies to the actuator: a first pulse that ejects the ink droplets; a second pulse that contracts the pressure chamber from a steady state after the ink droplets are ejected and then returns it to the steady state, thereby damping residual vibration; and an expansion pulse that expands the volume within the pressure chamber to a level where ink is not ejected after the residual vibration has damped, thereby preventing the occurrence of satellite drops.

[0004] In addition, in order to change the ejection volume without changing the head structure, it is possible to use a drive waveform that includes an auxiliary pulse, an ejection pulse, a cancel pulse, and a damping pulse in that order, but if the width of the expansion pulse or damping pulse is short, electrical crosstalk can cause large voltage fluctuations in adjacent actuators, which can lead to latch-up. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-181210 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a drive device and a liquid ejection head that can obtain an appropriate ejection amount and prevent the latch-up phenomenon. [Means for solving the problem]

[0007] A driving device according to an embodiment outputs a driving signal. The driving signal includes, in this order: an auxiliary pulse that contracts the volume of a pressure chamber communicating with a nozzle that ejects liquid from a reference state; an ejection pulse that expands the volume of the pressure chamber from the reference state and then returns it to the reference state, thereby ejecting a droplet from the nozzle communicating with the pressure chamber; a cancel pulse that contracts the volume of the pressure chamber from the reference state after the droplet is ejected and then returns it to the reference state, thereby attenuating residual vibration; and a damping pulse that expands the volume of the pressure chamber to a level that prevents liquid from being ejected after the volume of the pressure chamber is returned to the reference state by application of the cancel pulse and the residual vibration has attenuated. The application time of the damping pulse is shorter than the application time of the cancel pulse, and is at least 0.5 times a half cycle of the main acoustic resonance frequency of the liquid in the pressure chamber or at least 1 μs. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing an inkjet head according to an embodiment. [Figure 2] FIG. 2 is a plan view showing the configuration of an inkjet head according to the embodiment. [Figure 3] FIG. 2 is a plan view showing a configuration of a part of the inkjet head. [Figure 4] FIG. 2 is a cross-sectional view showing a configuration of a part of the inkjet head. [Figure 5] FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. [Figure 6] FIG. 3 is an explanatory diagram showing a driving waveform according to the embodiment; [Figure 7] 3A and 3B are explanatory diagrams showing the liquid ejection state of the liquid ejection head. DETAILED DESCRIPTION OF THE INVENTION

[0009] An inkjet head 10 according to a first embodiment and an inkjet printer 100 using the inkjet head 10 will be described below with reference to FIGS. 1 to 5. FIG. 1 is a perspective view of an inkjet head according to the embodiment, and FIG. 2 is a plan view showing the configuration of the inkjet head according to the embodiment. FIG. 3 is a plan view showing the configuration of a portion of the inkjet head, and FIG. 4 is a cross-sectional view. FIG. 5 is a schematic diagram showing an inkjet printer according to the embodiment. FIG. 6 is an explanatory diagram showing a drive waveform PP. FIG. 7 is an explanatory diagram showing the liquid ejection state of the liquid ejection head 1 in accordance with the drive waveform PP. Note that in each figure, the configuration is enlarged, reduced, or omitted as appropriate for ease of explanation.

[0010] The inkjet head 10 is a so-called side-shooter, share-mode, share-wall inkjet head. Two inkjet heads 10, each with a pair of actuators, may be combined to form a four-row integrated head unit. The inkjet head 10 is a device for ejecting ink, and is mounted inside an inkjet printer, for example. For example, the inkjet head 10 is supplied with ink as a liquid stored in an ink tank 132. The liquid ejection head 1 may be a non-circulation head that does not circulate ink, or a circulation head that circulates ink.

[0011] 1 and other figures show only one head body of the inkjet head 10. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and dummy chambers 32 are alternately arranged. The dummy chambers 32 are air chambers to which ink is not supplied, and do not have nozzles 28.

[0012] 1 to 4, the inkjet head 10 includes an actuator base 11, a nozzle plate 12, and a frame 13. The actuator base 11 is an example of a substrate. An ink chamber 27 to which ink, as an example of a liquid, is supplied is formed inside the inkjet head 10. The inkjet head 10 also includes components such as a drive circuit 17, as an example of a drive device, that controls the inkjet head 10, and a manifold 18 that forms part of a path between the inkjet head 10 and an ink tank.

[0013] The actuator base 11 includes a substrate 21, a pair of actuators 22, and a cover member 24.

[0014] The substrate 21 is formed in the shape of a rectangular plate from ceramics such as alumina. The substrate 21 has a flat mounting surface. A pair of actuators 22 are bonded to the mounting surface of the substrate 21. A supply hole 25 and a discharge hole 26 are formed in the substrate 21. Pattern wiring 211 (electrode wiring) that constitutes an electrode is formed on the substrate 21 of the actuator base 11.

[0015] The supply hole 25 is a through-hole that extends in the longitudinal direction of the actuators 22, between the pair of actuators 22, at the center of the substrate 21. The supply hole 25 communicates with the ink supply portion of the manifold 18. The supply hole 25 is connected to an ink tank via the ink supply portion. The supply hole 25 supplies ink from the ink tank to the ink chamber 27.

[0016] The discharge holes 26 are outlets for discharging ink. The discharge holes 26 are through-holes that penetrate the substrate 21, and a plurality of, for example, four, discharge holes 26 are provided. The discharge holes 26 communicate with the ink discharge portion of the manifold 18, and discharge the ink from the ink chambers 27.

[0017] A pair of actuators 22 is bonded to the mounting surface of the substrate 21. The pair of actuators 22 are arranged in two rows on the substrate 21 with a supply hole 25 between them. Each actuator 22 is formed of two plate-shaped piezoelectric elements made of, for example, lead zirconate titanate (PZT). The two piezoelectric elements are bonded together so that their polarization directions are opposite to each other in the thickness direction.

[0018] The actuators 22 correspond to the two rows of nozzles 28 and are arranged in parallel inside the ink chamber 27. The actuators 22 divide the ink chamber 27 into a first common chamber 271 and two second common chambers 272.

[0019] The actuator 22 is formed to have a trapezoidal cross section. The side surface 221 of the actuator 22 has a longitudinal direction extending along the column direction and has an inclined surface that is inclined with respect to the extension direction and the ejection direction. In other words, the cross section of the actuator 22 perpendicular to the column direction is trapezoidal. The top portion 222 of the actuator 22 is bonded to the nozzle plate 12. The actuator 22 has a plurality of wall-shaped drive elements 33, and grooves that form pressure chambers 31 and dummy chambers 32 are formed between the drive elements 33. In other words, the drive elements 33 are formed between the grooves that form the pressure chambers 31 and dummy chambers 32.

[0020] The pressure chambers 31 and the dummy chambers 32 are arranged alternately. The pressure chambers 31 and the dummy chambers 32 each extend in a direction intersecting the longitudinal direction of the actuator 22, and a plurality of them are arranged in parallel in a first direction (X-axis in the drawing), which is the longitudinal direction of the actuator 22.

[0021] The drive element 33 is formed between the pressure chamber 31 and the dummy chamber 32, and changes the volume of the pressure chamber 31 by deforming in response to a drive signal.

[0022] The multiple pressure chambers 31 communicate with multiple nozzles 28 in the nozzle plate 12 joined to the top portion 222. Both ends of the pressure chambers 31 in the second direction communicate with the ink chambers 27. That is, one end opens to a first common chamber 271 of the ink chambers 27, and the other end opens to a second common chamber 272 of the ink chambers 27. Therefore, ink flows in from one end of the pressure chambers 31 and flows out from the other end. The pressure chambers 31 may have throttling sections 240 that partially block the openings at both ends in the second direction, thereby increasing the flow path resistance. The throttling sections 240 increase the fluid resistance, for example, by reducing the cross-sectional area of ​​the flow path of the pressure chambers 31 perpendicular to the second direction compared to the inside of the pressure chambers 31. The throttling sections 240 are configured, for example, so that the width dimension in a direction intersecting the second direction, which is the extension direction of the pressure chambers 31, in the first direction or the third direction, is narrowed at the inlets and outlets at both ends of the pressure chambers 31. For example, the throttle portion 240 is formed by blocking a part of the flow path between the pressure chamber 31 and the ink chamber 27 .

[0023] The dummy chamber 32 is closed on one side in the third direction by the nozzle plate 12 joined to the top portion 222, and is closed on both sides in the second direction by the cover member 24.

[0024] The groove that constitutes the pressure chamber 31 communicates with the first common chamber 271 and the second common chamber 272.

[0025] An electrode layer 34 is provided on the driving element 33. The electrode layer 34 is formed of, for example, a nickel thin film. The electrode layer 34 extends from the bottom of the grooves forming the pressure chambers 31 and dummy chambers 32 onto the substrate 21 and is connected to the pattern wiring 211. For example, the electrode layer 34 of the pressure chamber 31 is connected to the individual wiring 2111 on the mounting surface of the actuator base 11 and forms an individual electrode. The electrode layer 34 of the dummy chamber 32 is connected to the common wiring 2112 on the mounting surface of the actuator base 11 and forms a common electrode. The electrode layer 34 is connected to the control unit 116 via the pattern wiring 211 and driving circuit 17 and is configured to be drive-controllable by control by a processor.

[0026] The nozzle plate 12 is formed of, for example, a rectangular film made of polyimide. The nozzle plate 12 faces the mounting surface of the actuator base 11. The nozzle plate 12 has a plurality of nozzles 28 formed therein, which penetrate the nozzle plate 12 in the thickness direction.

[0027] The nozzles 28 are provided in the same number as the pressure chambers 31 and are arranged opposite each pressure chamber 31. The nozzles 28 are aligned along the first direction and arranged in two rows corresponding to the pair of actuators 22. Each nozzle 28 is configured in a cylindrical shape with its axis extending in the third direction. For example, the nozzles 28 may have a constant diameter or may have a shape that narrows toward the center or tip. The nozzles 28 are arranged opposite to the midpoints of the pressure chambers 31 formed in the pair of actuators 22 in the extension direction and are each connected to the pressure chambers 31. One nozzle 28 is arranged in the longitudinal center of each pressure chamber 31.

[0028] The frame 13 is formed into a rectangular frame shape from, for example, a nickel alloy. The frame 13 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12. The frame 13 is bonded to both the mounting surface of the actuator base 11 and the nozzle plate 12. In other words, the nozzle plate 12 is attached to the actuator base 11 via the frame 13.

[0029] The manifold 18 is joined to the actuator base 11 on the side opposite to the nozzle plate 12. Inside the manifold 18, an ink supply portion, which is a flow path communicating with the supply hole 25, and an ink discharge portion, which is a flow path communicating with the discharge hole 26, are formed.

[0030] The drive circuit 17 includes various wiring boards 51 and a driver IC 52. The drive circuit 17 drives the drive elements 33 by applying a drive voltage to the wiring pattern via the driver IC 52, thereby increasing or decreasing the volume of the pressure chambers 31 and causing droplets to be ejected from the nozzles 28 arranged opposite to them. The driver IC 52 is electrically connected to the electrode layer 34 via the wiring of the wiring board 51 and the pattern wiring 211.

[0031] An ink chamber 27 is formed inside the inkjet head 10 configured as described above and is surrounded by the actuator base 11, the nozzle plate 12, and the frame 13. That is, the ink chamber 27 is formed between the actuator base 11 and the nozzle plate 12. For example, the ink chamber 27 is divided into three sections in the second direction by the two actuators 22, and has two second common chambers 272 as common chambers into which the discharge holes 26 open, and a first common chamber 271 as common chamber into which the supply hole 25 opens. The first common chamber 271 and the second common chamber 272 are in communication with a plurality of pressure chambers 31.

[0032] In the inkjet head 10 configured as described above, ink circulates between the ink tank and the ink chamber 27 through the supply hole, pressure chamber, and discharge hole. For example, in response to a signal input from the control unit 116 of the inkjet printer 100, the driver IC 52 applies a drive voltage to the electrode layer 34 via wiring on the wiring board 51, such as a film, thereby generating a potential difference between the electrode layer 34 of the pressure chamber 31 and the electrode layer 34 of the dummy chamber 32, thereby selectively deforming the drive element 33 into a shear mode. In other words, the control unit 116 and drive circuit 17, which serve as a drive device, deform the drive element 33 formed between the pressure chamber 31 and the dummy chamber 32 in response to the drive signal, thereby changing the volume of the pressure chamber 31 and ejecting a droplet from the nozzle 28.

[0033] An example of an inkjet printer 100 equipped with an inkjet head 10 will be described below with reference to Fig. 5. The inkjet printer 100 includes a housing 111, a medium supply unit 112, an image forming unit 113, a medium discharge unit 114, a conveying device 115, and a control unit 116 as an example of a drive device.

[0034] The inkjet printer 100 is a liquid ejection device that performs an image formation process on a sheet of paper P by ejecting a liquid such as ink while transporting the sheet of paper P as a recording medium, which is the object of ejection, along a predetermined transport path A that runs from a medium supply section 112 through an image forming section 113 to a medium ejection section 114.

[0035] The housing 111 forms the outer shell of the inkjet printer 100. The housing 111 has an outlet at a predetermined location for discharging the paper P to the outside.

[0036] The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to hold a stack of multiple sheets of paper P of various sizes.

[0037] The medium discharge unit 114 includes a paper discharge tray configured to be able to hold the paper P discharged from the discharge port.

[0038] The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 that are disposed above the support section 117 and face each other.

[0039] The support section 117 includes a conveyor belt 118 that is looped in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back side, and a plurality of belt rollers 120 that are provided on the back side of the conveyor belt 118.

[0040] During image formation, the support unit 117 supports the paper P on a holding surface, which is the upper surface of the conveyor belt 118, and conveys the paper P downstream by moving the conveyor belt 118 at a predetermined timing by the rotation of the belt roller 120.

[0041] The head unit 130 includes a plurality of inkjet heads 10, ink tanks 132 as liquid tanks mounted on each inkjet head 10, a connection flow path 133 connecting the inkjet heads 10 and the ink tanks 132, and a circulation pump 134 as a circulation unit. The head unit 130 is a circulation type head unit that constantly circulates liquid in the ink tanks 132 and the pressure chambers 31, dummy chambers 32, and ink chambers 27 built inside the inkjet heads 10.

[0042] In this embodiment, the system includes inkjet heads 10 of four colors, cyan, magenta, yellow, and black, and ink tanks 132 that store ink of each color. The ink tanks 132 are connected to the inkjet heads 10 by connection flow paths 133. The connection flow paths 133 include a supply flow path that is connected to the supply port of the inkjet head 10, and a recovery flow path that is connected to the discharge port of the inkjet head 10.

[0043] A negative pressure control device such as a pump (not shown) is connected to the ink tank 132. The negative pressure control device controls the negative pressure inside the ink tank 132 in accordance with the head value between the inkjet head 10 and the ink tank 132, thereby causing the ink supplied to each nozzle 28 of the inkjet head 10 to form a meniscus of a predetermined shape.

[0044] The circulation pump 134 is a liquid feed pump configured, for example, as a piezoelectric pump. The circulation pump 134 is provided in the supply flow path. The circulation pump 134 is connected to a drive circuit of the control unit 116 by wiring, and is configured to be controllable by a CPU (Central Processing Unit). The circulation pump 134 circulates the liquid in the circulation flow path including the inkjet head 10 and the ink tank 132.

[0045] The conveying device 115 conveys the paper P along a conveying path A that runs from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114. The conveying device 115 includes a plurality of guide plate pairs 121 and a plurality of conveying rollers 122 that are arranged along the conveying path A.

[0046] Each of the guide plate pairs 121 includes a pair of plate members arranged opposite each other with the paper P being conveyed therebetween, and guides the paper P along the conveying path A.

[0047] The conveying rollers 122 are driven to rotate under the control of the control unit 116, thereby sending the paper P downstream along the conveying path A. Sensors for detecting the conveying status of the paper are arranged at various points along the conveying path A.

[0048] The control unit 116 is, for example, a control board, and includes a processor, a ROM (Read Only Memory), a RAM (Random Access Memory), an I / O port which is an input / output port, and an image memory.

[0049] The processor is a processing circuit such as a CPU (Central Processing Unit) that serves as a controller. The processor controls the head unit, drive motor, operation unit, various sensors, etc. through an I / O port. The processor transmits the print data stored in the image memory to the drive circuit 17 in the order of drawing.

[0050] The print data is data that is converted from image data including information on the color and density of each area and input to the head in order to eject liquid. The liquid ejection head 1 inputs a drive signal corresponding to the input print data to the drive circuit 17, and applies a drive waveform to each drive element 33 of the actuator section via the drive circuit 17.

[0051] In the inkjet printer 100 configured as described above, when the control unit 116 detects a print instruction entered by a user operating the operation input unit via an interface, for example, it drives the transport device 115 to transport the paper P and outputs a print signal to the head unit 130 at a predetermined timing, thereby driving the inkjet head 10. For a liquid ejection operation, the inkjet head 10 sends a drive signal to the driver IC 52 in response to an image signal corresponding to image data, which applies a drive voltage to the electrode layer 34 of the actuator 22 via wiring, selectively driving the drive elements 33 that form the side walls of the actuator 22, thereby ejecting ink from the nozzles 28 and forming an image on the paper P held on the transport belt 118. For a liquid ejection operation, the control unit 116 drives the circulation pump 134 to circulate liquid through a circulation flow path that passes through the ink tank 132 and the inkjet head 10. By the circulation operation, the ink in the ink tank 132 is supplied from the supply hole 25 to the first common chamber 271 of the ink chamber 27 through the ink supply portion of the manifold 18 by driving the circulation pump 134. This ink is supplied to the multiple pressure chambers 31 and multiple dummy chambers 32 of the pair of actuators 22. The ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chambers 31 and dummy chambers 32. This ink is discharged from the discharge hole 26 to the ink tank 132 through the ink discharge portion of the manifold 18.

[0052] The following describes the characteristics of the liquid ejection head 1 in this embodiment and the drive waveform of the drive signal generated by the drive circuit 17 or control unit 116 of the liquid ejection head 1. For example, the liquid ejection head 1 supplies an ejection waveform as a drive waveform to the drive element of the actuator to eject ink and form pixels.

[0053] For example, the control unit 116 and the drive circuit 17 function as a drive waveform generating means that generates and outputs a predetermined drive waveform by switching the voltage value to be applied to the target drive element 33 between three or more types of voltage based on the print data and setting the drive waveform to be applied to each drive element.

[0054] FIG. 6 is an explanatory diagram showing a drive waveform according to this embodiment. In the drive waveform of FIG. 6, the vertical axis represents potential and the horizontal axis represents time. The drive waveform PP according to this embodiment is an ejection waveform that ejects liquid once from the nozzle 28 by expanding and contracting the pressure chamber. In the drive waveform of FIG. 6, the potential difference between adjacent pressure chambers is shown as the actual waveform. As an example, an example is shown in which switching is performed between three voltage values: an expansion voltage (V0) that expands the pressure chamber, a contraction voltage (V1) that contracts the pressure chamber, and a steady voltage (V2) that serves as a reference voltage and is a voltage between the expansion voltage and the contraction voltage.

[0055] 6 shows a drive waveform PP according to the first embodiment. This drive waveform PP includes, in this order, an auxiliary pulse Pb, an ejection pulse Pe, a cancel pulse Pc, and a damping pulse Pd. The time period of this drive waveform PP is a drive period Tc. The drive waveform PP also includes steady-state elements Pf, Pg, and Ph that maintain a steady state (reference state), which is a state during print standby in which a steady voltage V2 is applied to the piezoelectric element, for a predetermined time after each of the ejection pulse Pe, cancel pulse Pc, and damping pulse Pd.

[0056] That is, the drive circuit 17 first applies an auxiliary pulse Pb that sets the voltage to contraction (V1) from the steady state (V2), then applies an ejection pulse Pe that sets the voltage to expansion (V0) without returning to the steady state, then maintains the steady state (V2) for a predetermined time (t2 → t3), then applies a cancel pulse Pc that sets the voltage to contraction (V1), then maintains the steady state for a predetermined time (t4 → t5), then applies a damping pulse (Pd) that sets the voltage to expansion (V0) and maintains this for a predetermined time (t5 → t6), and then maintains the steady state for a predetermined time.

[0057] The auxiliary pulse Pb is a waveform that contracts the pressure chamber just before the expansion element of the ejection pulse Pe, accelerating the speed of the ejected ink droplet. For the auxiliary pulse Pb, the drive circuit 17 increases the voltage from a steady voltage V2 to a contraction voltage V1, and then decreases the voltage to an expansion voltage V0 at timing t1 after a predetermined time has elapsed. The application time of the auxiliary pulse (Pb) is preferably a half cycle (1AL) of the main acoustic resonance frequency of the liquid in the pressure chamber, but may also be less than a half cycle (1AL) of the main acoustic resonance frequency, or more than three times the half cycle of the main acoustic resonance frequency.

[0058] The ejection pulse Pe has a waveform that reduces the voltage from a contraction voltage V1 to an expansion voltage V0, and then increases the voltage to a steady voltage V2 at timing t2 after a predetermined time has passed. That is, after the auxiliary pulse Pb, the drive circuit 17 does not return to the steady state, but instead maintains the expansion voltage V0 as the ejection pulse Pe for a predetermined time (t1 → t2), and then returns to the steady voltage V2, thereby returning the pressure chamber from the expansion state to the steady state and ejecting an ink droplet from the nozzle. The application time (t1 → t2) of the ejection pulse Pe is preferably set to half a cycle (1AL) of the main acoustic resonance frequency of the liquid in the pressure chamber.

[0059] The cancel pulse Pc has a waveform that increases the voltage from the steady voltage V2 to the contraction voltage V1 after the steady element Pf following the ejection pulse Pe. After returning to the steady state with the ejection pulse Pe and allowing a predetermined time (t2 to t3) to pass, the drive circuit 17 applies the cancel pulse Pc at timing t3 to increase the voltage from the steady voltage V2 to the contraction voltage V1, thereby contracting the volume of the pressure chamber from the steady state. The application of this cancel pulse Pc damps residual vibration. After applying the cancel pulse Pc, the drive circuit 17 returns the voltage to the steady voltage V2 again, thereby returning the volume of the pressure chamber to the steady state. Note that to obtain a sufficient ejection volume, the waiting time in the steady state after the ejection pulse Pe (Pf: t2 to t3) is preferably 0.5 AL or less. The application time of the cancel pulse Pc (t3 to t4) is set to 1.9 AL or more and 2.0 AL or less.

[0060] Furthermore, after applying the cancel pulse Pc, the drive circuit 17 returns to a steady state and waits a predetermined time (t4→t5) before applying a damping pulse Pd under conditions such that ink is not ejected, thereby performing damping to prevent latch-up.

[0061] The damping pulse Pd has a waveform that reduces the voltage from the steady voltage V2 to the extended voltage V0 after the steady element Pg following the cancel pulse Pc. The extended voltage is 0V, for example. To suppress large voltage fluctuations, the application time of the damping pulse Pd (t5 → t6) is set to 0.5 AL or more, or 1 μs or more. To ensure stable ejection, the application time of the damping pulse Pd (t5 → t6) is shorter than the application time of the cancel pulse Pc (t3 → t4). After applying the damping pulse Pd, the drive circuit 17 returns the voltage to the steady voltage V2 again, and has a steady element Ph that maintains a steady state for a predetermined time.

[0062] The time from the center of the pulse width of the cancel pulse Pc to the center of the pulse width of the damping pulse Pd is 1.5 AL or more and 2.5 AL or less, and is set to 2.0 AL in this embodiment as an example.

[0063] Figure 7 shows the impact positions of droplets ejected sequentially from multiple nozzles 28 under different conditions as an example of evaluation results obtained by varying the pulse width of the cancel pulse Pc. The vertical direction in Figure 7 corresponds to the arrangement direction of the nozzles 28, and droplets are ejected from eight nozzles 28, landing sequentially from right to left along the horizontal direction. In other words, the rightmost dot in each row in Figure 7 indicates the impact position of the first droplet, with subsequent droplets being placed sequentially to the left. The experimental conditions were a steady-state waiting time (Pf: t2 → t3) of 0.25 AL after the ejection pulse Pe, an application time of the damping pulse Pd of 0.6 AL, and a time difference between the centers of the cancel pulse Pc and the damping pulse Pd of 2 AL. The application time of the cancel pulse Pc was varied between 1.7 AL and 2.2 AL, and the application time of the damping pulse Pd was 0.6 AL.

[0064] Figure 7 shows that when the Pc pulse width is 1.7AL or 1.8AL, the distance between the two rightmost dots in the first horizontal row is narrow. On the other hand, when the pulse width is 2.1AL or 2.2AL, the distance between the two rightmost dots is greater. On the other hand, when the application time is 1.9 to 2.0AL, the landing positions in the horizontal row are evenly spaced.

[0065] These experimental results show that when ejecting 8 dots at a drive frequency of 26 kHz, the application time of the cancel pulse (Pc) that provides an appropriate inter-dot distance is approximately 1.9 to 2.0 AL.

[0066] With the drive device and liquid ejection head 1 configured in this way, ejection can be stabilized by shortening the application time of the damping pulse in a drive waveform including an auxiliary pulse, an ejection pulse, a cancel pulse, and a damping pulse. Furthermore, by setting the application time (t5→t6) of the damping pulse (Pd) to 0.5 AL or more, or 1 μs or more, electrical crosstalk can be suppressed, suppressing large voltage fluctuations in adjacent drive elements, thereby preventing latch-up.

[0067] Furthermore, with the above-described driving device and liquid ejection head 1, the application time of the auxiliary pulse is set to 1 time or less, or 3 times or more, of AL, thereby making it possible to maintain high ejection performance.

[0068] Furthermore, in the above-described driving device and liquid ejection head 1, the time required for contraction from a steady state after ejection of a droplet is set to 0.5 times or less AL, thereby ensuring the ejection amount.

[0069] Furthermore, in the above-described driving device and liquid ejection head 1, the time difference between the centers of the damping pulse and the cancel pulse is 1.5 to 2.5 times AL, so that the ejection speed can be made uniform and the landing positions can be arranged evenly.

[0070] It should be noted that the embodiments of the present invention are not limited to the above-described configuration. For example, in the above-described embodiment, the drive circuit 17 having the driver IC 52 provided in the liquid ejection head 1 and the control unit 116 are exemplified as examples of the drive device, but the present invention is not limited to this. For example, various control devices, such as a control device connected to the liquid ejection head 1 and provided outside the liquid ejection head 1, may also be used as the drive device.

[0071] The waveform does not have to be one type, but may be a combination of multiple or more types of waveforms. For example, it may be applied to any one of the multiple drive elements 33 at any timing, and it is also possible to drive them in combination with different waveforms. For example, the drive waveform PP may be part of a multi-drop waveform that ejects droplets using multiple ejection waveforms, or it may be a single waveform that ejects droplets using a single ejection waveform.

[0072] Furthermore, although the first potential and the second potential are set to the maximum voltage and the minimum voltage, respectively, they are not limited to this and may be set to other voltage values.

[0073] Each potential of the drive waveform can be changed as needed, and the voltage value applied to each piezoelectric pillar can be adjusted as needed depending on various conditions. For example, a potential difference can be generated by grounding one of adjacent piezoelectric pillars and applying a voltage to the other, or by applying a voltage to both of them. Furthermore, the example is not limited to switching between three potentials, and a configuration in which switching between four or more potentials is also possible.

[0074] The configuration of the liquid ejection head 1 is not limited to the above example, and may be used for other types of heads. For example, the liquid ejection head may be configured to drive the liquid ejection unit by vibrating a diaphragm provided between the pressure chamber and the drive element unit through deformation of the drive element unit.

[0075] According to at least one of the embodiments described above, it is possible to ensure an appropriate ejection amount and prevent latch-up.

[0076] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0077] 1...liquid ejection head, 10...inkjet head, 11...actuator base, 12...nozzle plate, 13...frame, 17...drive circuit, 18...manifold, 21...substrate, 22...actuator, 24...cover member, 25...supply hole, 26...discharge hole, 27...ink chamber, 28...nozzle, 31...pressure chamber, 32...dummy chamber, 33...drive element, 34...electrode layer, 51...wiring board, 52...driver IC, 100...inkjet printer, 111...casing, 112...medium supply section , 113...image forming section, 114...medium discharge section, 115...conveying device, 116...control section, 117...support section, 118...conveying belt, 119...support plate, 120...belt roller, 121...pair of guide plates, 122...conveying roller, 130...head unit, 132...ink tank, 133...connecting flow path, 134...circulation pump, 211...pattern wiring, 221...side section, 222...top, 240...throttle section, 271, 272...common chamber, 2111...individual wiring, 2112...common wiring.

Claims

1. an auxiliary pulse for contracting the volume of a pressure chamber communicating with a nozzle that ejects liquid from a reference state; an ejection pulse that expands the volume of the pressure chamber from the reference state and then returns it to the reference state, thereby ejecting droplets from a nozzle communicating with the pressure chamber; a cancel pulse that reduces the volume of the pressure chamber from the reference state after the droplet is ejected and then returns it to the reference state, thereby attenuating residual vibration; a damping pulse that expands the volume of the pressure chamber to a level where liquid is not ejected, after residual vibration has been attenuated by applying the cancel pulse to return the volume of the pressure chamber to the reference state; A drive device that outputs a drive signal in which the application time of the damping pulse is shorter than the application time of the cancel pulse and is 0.5 times or more the half cycle of the main acoustic resonance frequency of the liquid in the pressure chamber or 1 μs or more.

2. 2. The driving device according to claim 1, wherein the application time of the auxiliary pulse is equal to or less than one half cycle of the main acoustic resonance frequency of the liquid in the pressure chamber, or equal to or more than three half cycles.

3. 2. The driving device according to claim 1, wherein the time required for the volume of the pressure chamber to contract from the reference state after the droplet is ejected is equal to or less than 0.5 times a half cycle of a main acoustic resonance frequency of the liquid in the pressure chamber.

4. 2. The drive device of claim 1, wherein the center-to-center time difference between the damping pulse and the cancellation pulse is twice a half-cycle of the main acoustic resonant frequency of the liquid in the pressure chamber.

5. A drive device according to any one of claims 1 to 4; a liquid ejection head that is driven by the drive device to eject liquid, Liquid discharge device.

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