Driving device

Abstract

To provide a driving device capable of suppressing satellite mist during discharge.SOLUTION: A driving device includes a driving unit for applying a driving signal for driving a pressure chamber communicating with a nozzle that discharges liquid, to an actuator. The waveform of the driving signal includes a normal state, an expanded state, a first contracted state, and a second contracted state. The waveform of the driving signal includes a first waveform that causes the pressure chamber to be in the first contracted state after the volume of the pressure chamber is expanded, a second waveform that causes the pressure chamber to be changed into the second contracted state at a timing after a point at which a flow velocity of the pressure chamber becomes 0 for the first time after the application of the first waveform, and a third waveform that causes the pressure chamber to be changed from the second contracted state to the normal state after the point at which the flow velocity becomes 0 for the first time after the application of the second waveform. The timing of the application of the second waveform is 1.5 AL or more after the timing of the application of the first waveform.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to a drive device. [Background technology]

[0002] Inkjet heads mounted on inkjet printers are known as liquid ejection devices. Inkjet printers eject ink droplets from the inkjet head to form images on the surface of a recording medium. Inkjet heads eject ink droplets from nozzles connected to pressure chambers by changing the volume of the pressure chambers using a piezoelectric actuator. The operation of the actuator is controlled by a drive waveform input to the actuator.

[0003] When ejecting liquid, droplets called satellite mist may be generated in addition to the ejected droplets. Because satellite mist can cause print quality to deteriorate due to irregular landing, it is necessary to suppress satellite mist. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-208411 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a drive device that can suppress satellite mist during ejection. [Means for solving the problem]

[0006] The driving device according to the embodiment includes a driving unit that applies to an actuator a driving signal that drives a pressure chamber that communicates with a nozzle that ejects liquid, and the waveform of the driving signal has a steady state, an expanded state, a first contracted state, and a second contracted state, and includes a first waveform that expands the volume of the pressure chamber and then changes it to the first contracted state, a second waveform that changes it to the second contracted state at a timing after the point at which the flow rate in the pressure chamber first becomes 0 after application of the first waveform, and a third waveform that changes it from the second contracted state to the steady state after the point at which the flow rate first becomes 0 after application of the second waveform, and the timing of application of the second waveform is 1.5 AL or more after the timing of application of the first waveform. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a liquid ejection device according to a first embodiment. [Figure 2] FIG. 2 is a perspective view showing the configuration of the liquid ejection head. [Figure 3] FIG. 2 is a cross-sectional view showing a part of the configuration of the liquid ejection head. [Figure 4] 4A and 4B are explanatory diagrams showing drive waveforms and vibration analysis results of Comparative Example 1 and Example 1. [Figure 5] 10A and 10B are explanatory diagrams showing drive waveforms and vibration analysis results of Examples 2 and 3. [Figure 6] 10A and 10B are explanatory diagrams showing drive waveforms and vibration analysis results of Example 4. [Figure 7] 5A to 5C are explanatory diagrams illustrating the printing operation of the liquid ejection head. [Figure 8] 5A and 5B are explanatory diagrams illustrating the landing accuracy of droplets ejected by a liquid ejection head. [Figure 9] FIG. 2 is an explanatory diagram showing the printing characteristics of Example 1, Example 3, and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0008] A liquid ejection head 10 and a liquid ejection device 100 according to a first embodiment will be described below with reference to Fig. 1 to Fig. 9. Fig. 1 is a block diagram showing the configuration of the liquid ejection device 100 according to the first embodiment. Fig. 2 is a perspective view showing the configuration of the liquid ejection head, and Fig. 3 is a cross-sectional view showing the configuration of the actuator of the liquid ejection head.

[0009] As shown in FIG. 1, the liquid ejection device 100, which is a driving device, includes a liquid ejection head 10, a liquid supply unit 21, a transport unit 22, an operation unit 25, a display unit 26, and a control unit 30, which is a driving unit.

[0010] As shown in Figure 10, the liquid ejection device 100 is an inkjet printer that performs an image formation process on a medium P such as paper by ejecting liquid such as ink from the liquid ejection head 10 while transporting the medium P, which is the ejection target, along a predetermined transport path that passes through a printing position opposite the liquid ejection head 10.

[0011] The liquid ejection head 10 is, for example, a shared-mode shared-wall type inkjet head. The liquid ejection head 10 may be a non-circulation type head that does not circulate ink, or a circulation type head that circulates ink. In this embodiment, the liquid ejection head 10 will be described using an example of a non-circulation type head.

[0012] For example, the liquid ejection head 10 includes an actuator 11 having a plurality of piezoelectric elements that communicate with the nozzles, and a drive circuit 12 that drives the actuator 11.

[0013] For example, the liquid ejection head 10 has a plurality of nozzles 111 that eject liquid, a plurality of pressure chambers 112 that communicate with the nozzles, and a flow path that includes a common chamber that communicates with the plurality of pressure chambers 112. The flow path of the liquid ejection head 10 is connected to a liquid supply unit 21, and ink is supplied to the flow path of the liquid ejection head 10 from the liquid supply unit.

[0014] The actuator 11 is, for example, an actuator plate made of a piezoelectric material in the shape of a plate, and includes a plurality of piezoelectric elements 115 and electrodes 116 formed on the piezoelectric elements 115. For example, groove-shaped pressure chambers 112 are formed between the plurality of piezoelectric elements 115. When a voltage is applied to the electrodes 116 of the piezoelectric elements 115 provided corresponding to each pressure chamber 112, the piezoelectric elements 115 are deformed, and the actuator 11 increases or decreases the volume of the pressure chambers 112, causing ink to be ejected from the nozzles.

[0015] The drive circuit 12 drives the actuator 11 by applying a drive voltage to the electrodes of the piezoelectric body. The drive circuit 12 generates a control signal and a drive signal for operating the piezoelectric element 115. The drive circuit 12 generates a control signal for control purposes such as selecting the timing of ejecting liquid and the piezoelectric element 115 that will eject the liquid, in accordance with an image signal input from the control unit 30 of the liquid ejection device 100. The drive circuit 12 also generates a voltage to be applied to the electrode 116 of the piezoelectric element 115, i.e., a drive signal (electrical signal), in accordance with the control signal. When the drive circuit 12 applies the drive signal to the piezoelectric element 115, the piezoelectric element 115 is driven to change the volume of the pressure chamber 112. In other words, the actuator 11 is configured to be drive-controllable by the control unit 30.

[0016] As shown in Figure 1, the drive circuit 12 includes a data buffer 13, a decoder 14, and a driver 15. The data buffer 13 stores print data in chronological order for each piezoelectric element of the actuator 11. The decoder 14 controls the driver 15 for each piezoelectric element based on the print data stored in the data buffer 13. The driver 15 outputs a drive signal that operates each piezoelectric element 115 under the control of the decoder 14. The drive signal is a voltage that is applied to the electrode 116 of each piezoelectric element 115.

[0017] The liquid supply unit 21 is connected to the primary side of the flow path of the liquid ejection head 10, and supplies liquid to the flow path of the liquid ejection head 10. For example, the liquid supply unit 21 includes a tank that stores liquid, a connecting flow path that connects the tank with the flow path of the liquid ejection head 10, and a liquid feed pump that sends the liquid from the tank to the liquid ejection head 10.

[0018] The transport unit 22 transports a medium such as paper along a predetermined transport path and supplies it to a printing position. The transport unit 22 includes, for example, a plurality of transport rollers and transport guides arranged along the transport path. The transport unit 22 supports the medium so that it can move relative to the liquid ejection head 10.

[0019] The operation unit 25 includes function keys such as a power key, a paper feed key, and an error reset key.

[0020] The display unit 26 has a display that can display various states of the image printing device.

[0021] The control unit 30 is, for example, a control board, and includes a processor 31, a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, an image memory 34, and an I / O port 35 which is an input / output port.

[0022] The processor 31 is a processing circuit such as a CPU (Central Processing Unit) that serves as a controller. The processor 31 corresponds to the central part of a computer. The processor 31 controls each part to realize various functions of the printer in accordance with an operating system and application programs. For example, the processor 31 controls the operation of the liquid ejection head 10, the liquid supply unit 21, and the transport unit 22 that are provided in the liquid ejection device 100. During printing, the processor 31 also transmits print data stored in the image memory 34 to the drive circuit 12 in the order of drawing.

[0023] The ROM 32 corresponds to the read-only main memory of the computer. The ROM 32 stores the operating system and application programs. The ROM 32 may also store data necessary for the processor 31 to execute processes for controlling each unit.

[0024] The RAM 33 corresponds to the rewritable main memory of the computer. The RAM 33 stores data necessary for the processor 31 to execute processing. The RAM 33 is also used as a work area where information is rewritten as needed by the processor 31. The work area may include an image memory where print data is developed.

[0025] The image memory 34 stores print data from the externally connected device 200, for example.

[0026] The I / O port 35 is an interface unit that inputs data from the externally connected device 200 and outputs data to the outside. Print data from the externally connected device 200 is sent to the control unit 30 through the I / O port 35 and stored in the image memory 34.

[0027] In the liquid ejection device 100 configured as described above, the control unit 30 inputs a signal to the liquid ejection head 10, thereby applying a drive voltage to the drive circuit 12, generating a potential difference across the multiple piezoelectric elements 115, selectively deforming the piezoelectric elements 115, and increasing or decreasing the volume of the pressure chambers 112, thereby ejecting liquid from the nozzles 111. For example, if the volume of the pressure chambers 112 expands or contracts during driving, pressure vibrations occur within the pressure chambers 112. These pressure vibrations increase the pressure within the pressure chambers 112, causing droplets (ink droplets) to be ejected from the nozzles 111 communicating with the pressure chambers 112. For example, in response to a signal input from the control unit 30, the driver 15 applies a drive voltage to the electrodes of the pressure chambers 112 via the electrodes 116, thereby generating a potential difference across the multiple piezoelectric elements 115, selectively deforming the piezoelectric elements 115, and changing the volume of the pressure chambers 112. For example, when a voltage that serves as an expansion element is applied, the piezoelectric element 115 deforms, the volume of the corresponding pressure chamber 112 increases, the pressure decreases, and ink in the common chamber flows into that pressure chamber 112. Then, when a drive voltage of reverse potential is applied to the electrode 116 of the piezoelectric element 115 while the volume of the pressure chamber 112 is in an increased state, the piezoelectric element 115 deforms, the volume of the pressure chamber 112 decreases, and the pressure increases. As a result, the ink in the pressure chamber 112 is pressurized and ejected from the nozzle 111.

[0028] The drive waveforms of the drive signals generated by the drive circuit 12 of the liquid ejection head 10 will be described with reference to FIGS.

[0029] FIG. 4 shows the drive waveforms and vibration analysis results for Comparative Example 1 and Example 1. FIG. 5 shows the drive waveforms and vibration analysis results for Examples 2 and 3. FIG. 6 shows the drive waveforms and vibration analysis results for Example 4. In each waveform diagram, the horizontal axis represents time, and the vertical axis represents voltage, ink flow velocity, and ink pressure. In each diagram, voltage is represented by a solid line, flow velocity at the nozzle surface by a dashed line, and pressure at the nozzle by a dot-dash line. FIGS. 7 and 8 are explanatory diagrams of the printing operation and impact accuracy of a liquid ejection head. FIG. 9 is an explanatory diagram showing the printing characteristics in Comparative Example 1, Example 1, and Example 3.

[0030] 4 shows the ejection waveform Pa according to Comparative Example 1 and the ejection waveform Pb according to Example 1. Waveform data of the drive waveform is stored, for example, in a memory in the drive circuit 12. The IC of the drive circuit 12 selects which drive waveform to input to the actuator 11 based on the gradation data sent from the control board.

[0031] The reference ejection waveform Pa of Comparative Example 1 and the ejection waveform Pb of Example 1 each have a steady waveform, an expansion waveform that expands the pressure chamber 112, a first contraction waveform that contracts the pressure chamber 112, and a second contraction waveform that further contracts the pressure chamber 112.

[0032] The ejection waveforms Pa and Pb are controlled by switching the voltage level of the drive waveform for ejecting liquid between at least four levels (-V2, 0, +V1, +V2). As an example, voltage is applied in four levels: a first voltage (0) which is an intermediate voltage, a second voltage (-V2) which is lower than the intermediate voltage, a third voltage (+V1) which is higher than the intermediate voltage, and a fourth voltage (+V2) which is higher than the third voltage.

[0033] Both ejection waveforms Pa and Pb are waveforms that expand the pressure chamber from an intermediate voltage, maintain this state for AL, and then contract. The ejection waveforms Pa and Pb contract in two stages, maintaining the first contraction state for a certain period of time, then maintaining the second contraction state for a certain period of time, and then returning to the initial steady state. In the ejection waveform Pb, satellites are reduced by adjusting the time of the first contraction state and the time of the second contraction state based on the ejection waveform Pa.

[0034] Here, the voltage condition is V1=1 / 2xV2 |-V2|=|+V2| In addition, in the time direction, for the reference ejection waveform Pa, the expansion time = first contraction time = second contraction time = AL (2.50 μs). On the other hand, for the ejection waveform Pb, the expansion time = second contraction time = AL (2.50 μs). In other words, the width of the expansion pulse, the width of the first contraction pulse, and the width of the second contraction pulse of the ejection waveform Pa are each set to the width of AL (Acoustic Length). AL is half the natural vibration period λ, which is determined by the ink characteristics and the internal structure of the head.

[0035] On the other hand, in the ejection waveform Pb, the width of the expansion pulse and the width of the second contraction pulse are each set to the width of AL (Acoustic Length). The width of the first contraction pulse is set to 1.5 AL or more. In the ejection waveform Pb, the timing for switching the voltage to enter the second contraction state is 1.5 AL or more after the timing for entering the first contraction state.

[0036] As a specific example, starting from a steady state, at a predetermined timing ta, the voltage is reduced from a first intermediate voltage (-V2) to a second voltage lower than the intermediate voltage (0V) using an expansion waveform PPa, and maintained at the second voltage for a predetermined time (first predetermined time). Then, after the first predetermined time tb, the voltage is returned to the first voltage (+V1) (PPb). After maintaining the first voltage for a predetermined time tc, a third voltage higher than the first voltage is applied as a first contraction waveform PPc, and maintained for a predetermined time. Then, at a timing td after the predetermined time, a fourth voltage higher than the first voltage is applied as a second contraction waveform PPd for a predetermined time. After a predetermined time, te, the voltage is gradually returned to the first voltage using third waveforms PPe and PPf. In the third waveform, the voltage is gradually switched, first reduced from the fourth voltage to the third voltage, and then reduced to the first voltage. This ejection waveform Pb is a waveform that ejects with an expansion waveform and suppresses vibration with a contraction waveform. The intermediate voltage is, for example, 0V and is also called the reference voltage.

[0037] In the ejection waveform Pb of Example 1, applying a first voltage (-V2) to the actuator for time AL as an expansion waveform causes the pressure chamber 112 to expand. Then, after time AL has elapsed, switching to apply (+V1) to the actuator causes the pressure chamber 112 to transition from the expansion state to the first contraction state, the pressure at the nozzle face peaks, and ejection begins (the nozzle face flow velocity increases). The first contraction state is maintained for at least the time at which the flow velocity at the nozzle face first becomes zero after the start of ejection, and after point tv0 at which this flow velocity becomes zero, the pressure chamber 112 transitions from the expansion state to the second contraction state (+V2 is applied). By transitioning to the second contraction state, the absolute value of the flow velocity at the nozzle face tends to be suppressed. The ejection waveform Pa can suppress vibrations in flow velocity and pressure by returning from the second contraction state to its initial flat state at the point at which the flow velocity becomes zero after the second contraction.

[0038] In the ejection waveform Pb of Example 1, the timing of returning from the second contracted state to the initial state is delayed compared to the ejection waveform Pa of Comparative Example 1, and is shifted to a timing later than the point at which the second flow velocity becomes 0, thereby changing the flow velocity in the positive direction and pushing out the ink liquid pillar. By returning from the second contracted state to the initial state after pushing out the ink liquid pillar for a predetermined time, the generation of satellite drops can be suppressed.

[0039] Note that, as a method of shifting the timing of returning from the second contraction state to the initial state to later than point tv1 where the second flow velocity becomes 0, there are two possible methods: extending the second contraction time and extending the first contraction time, but extending the first contraction time will result in a larger flow velocity value after ejection. Therefore, the ejection waveform Pb of Example 1 applies a waveform that sets the pressure chamber 112 to the first contraction state after expanding the volume of the pressure chamber 112, and then applies a waveform that sets the pressure chamber to the second contraction state after point tv1 where the flow velocity in the pressure chamber first becomes zero.

[0040] The timing of application of the fourth voltage (+V2) to achieve the second contraction state is after point tv1 where the flow velocity becomes zero. For example, timing td at which the voltage is switched to achieve the second contraction state is after 1.5 AL or more has elapsed since the timing at which the first contraction state was achieved.

[0041] In other words, the ejection waveform Pb has a first waveform that expands the volume 112 of the pressure chamber and then sets it to a first contraction state, a second waveform that changes it to a second contraction state at a timing after the point at which the flow rate in the pressure chamber first becomes 0 after the application of the first waveform, and a third waveform that changes it from the second contraction state to a steady state after the point at which the flow rate first becomes 0 after the application of the second waveform.

[0042] Furthermore, if the timing for returning from the second contraction state to the initial state is shifted to a point after point tv1 where the flow velocity becomes 0 for the second time, delaying the time condition by 0.5 times or more than AL will increase the first flow velocity oscillation peak Pka after ejection, making it possible to further reduce satellites. However, it will also increase the second flow velocity oscillation peak Pkb after ejection, which may result in erroneous ejection, or the next ejection may be affected by this oscillation, disrupting impact accuracy.

[0043] FIG. 5 is an explanatory diagram showing the drive waveforms Pb' and Pc and vibration analysis results for Examples 2 and 3. Example 2 includes a return waveform PPe that directly returns from the fourth voltage to the first voltage, instead of the waveforms PPe and PPf that gradually return the ejection waveform Pb of Example 1 from the fourth voltage to the first voltage. Other aspects are similar to Example 1. Example 3 includes a fourth waveform that, after applying the third waveform in Example 2, restores the contraction state and then returns to the steady state. That is, in Example 3, in order to suppress flow velocity vibration, in addition to the waveform of Example 2, fourth waveforms PPg and PPh are placed after the return waveform PPe, which contract and return the pressure chamber 112 at a timing between the first flow velocity vibration peak Pka (first peak) and the second flow velocity vibration peak Pkb (second peak) of the flow velocity vibration.

[0044] The ejection waveform Pc of Example 3 has a steady waveform, an expansion waveform that expands the pressure chamber 112, a first contraction waveform that contracts the pressure chamber 112, a second contraction waveform that further contracts the pressure chamber 112, and a third contraction waveform that further contracts the pressure chamber 112 after returning it to a steady state. The ejection waveform Pc controls the voltage level of the drive waveform for ejecting liquid by switching between at least four levels (-V2, 0, +V1, +V2). As an example, voltage is applied in four levels: a first voltage which is an intermediate voltage, a second voltage lower than the intermediate voltage, a third voltage higher than the intermediate voltage, and a fourth voltage higher than the third voltage.

[0045] The ejection waveform Pc, like Pa and Pb, is a waveform that expands the pressure chamber from the 0 level, maintains it for AL time, and then contracts. In the ejection waveform Pc, for example, the contraction waveform has two stages, maintaining a first contraction state for a certain time, then maintaining a second contraction state for a certain time, and then returning to the initial 0 level. Furthermore, the ejection waveform Pc has a fourth waveform that contracts the pressure chamber again during the peak of the flow velocity oscillation after returning from the second contraction state to the 0 level. In other words, the ejection waveform Pc can suppress flow velocity oscillation by adding an additional contraction waveform to the ejection waveforms Pb and Pb'.

[0046] Here, the conditions for the voltage of the ejection waveform Pc and the time direction are the same as those for Pb and Pb'.

[0047] In the ejection waveform Pc, the width of the expansion pulse and the width of the second contraction pulse are set to the width of AL (Acoustic Length), and the width of the first contraction pulse is set to 1.5AL or more.

[0048] In other words, the ejection waveform Pc has a first waveform that sets the volume of the pressure chamber to a first contraction state after expanding it, a second waveform that changes the state to a second contraction state at a timing after the point where the flow velocity in the pressure chamber first becomes 0 after application of the first waveform, a third waveform that changes the state from the second contraction state to a steady state after the point where the flow velocity first becomes 0 after application of the second waveform, and a fourth waveform that sets the state to a contraction state again after application of the third waveform and then returns to the steady state. The rest is the same as the ejection waveform Pb in Example 1 above.

[0049] FIG. 6 shows the drive waveform and vibration analysis results for Example 4, where the timing td for entering the second contraction state is set 2 AL after the timing for entering the first contraction state. In FIG. 6, the horizontal axis represents time, and the vertical axis represents voltage, ink flow velocity, and ink pressure. In each figure, the voltage is represented by a solid line, the flow velocity at the nozzle surface by a dashed line, and the pressure at the nozzle by a dashed-dotted line. As shown in FIG. 6, when the timing td for entering the second contraction state is set 2 AL after the timing for entering the first contraction state, the first peak Pka can be made larger than when the timing td is set 1.5 AL in Example 3 shown in FIG. 5. Therefore, depending on the physical properties of the ink, it is preferable to set the width of the first contraction pulse to 2.0 AL or less.

[0050] That is, in this embodiment, the timing td at which the voltage is switched to achieve the second contraction state is preferably adjusted to a timing in the range of 1.5 AL or more and less than 2.0 AL after the timing at which the first contraction state is achieved.

[0051] Fig. 7 is an explanatory diagram showing the liquid ejection head 10 and the medium P during the printing operation of the liquid ejection device 100. As shown in Fig. 7, in the liquid ejection device 100, when the liquid ejection head 10 is moved relative to the medium P along the transport direction indicated by the arrow and ejects liquid, dots D, which are multiple droplets, are formed on the medium P, as shown in Fig. 7. The waveform of Example 3 has improved landing accuracy compared to Example 1.

[0052] FIG. 9 is an explanatory diagram showing the print state using the ejection waveform Pa of Comparative Example 1, the ejection waveform Pb of Example 1, and the ejection waveform Pc of Example 3. FIG. 9 shows that the ejection waveform Pa of Comparative Example 1 forms satellite mist, which is a small droplet, around the dot D, and that the print state using the ejection waveform Pb of Example 1 can suppress satellite mist better. Furthermore, as shown in FIG. 9, the ejection waveform Pc of Example 3 reduces the disturbance of landing droplets and suppresses satellite mist better than the ejection waveform Pb of Example 1 by varying the drive voltage. It can be seen that Comparative Example 1 has good landing accuracy, but satellite mist Ds is generated. Example 1 produces less satellite mist. On the other hand, it can be seen that Example 3 has more consistent landing positions and better landing accuracy than Example 1.

[0053] According to the liquid ejection head 10 and the liquid ejection device 100 of this embodiment, satellite mists can be reduced by delaying the time from the first contraction to the second contraction, for example.

[0054] Furthermore, the ejection waveform Pc of the third embodiment has a waveform that contracts the pressure chamber again between the peaks of the flow velocity oscillations after returning from the second contraction state to the steady state, thereby improving the landing accuracy. Therefore, as shown in FIG. 9, for example, it is possible to obtain a printing result with less satellite mist Ds and suppress the variation in landing position. Therefore, it is possible to achieve both landing accuracy and reduction of satellite mist.

[0055] The embodiment of the present invention is not limited to the above-described configuration.

[0056] For example, although the above embodiment has been described using a single-drop ejection waveform, multiple drops may be used. For example, the ejection waveforms Pb, Pc, Pd, etc. of the above embodiments may be applied to any of the drop ejection waveforms.

[0057] Furthermore, the voltage value applied to each piezoelectric element 115 can be adjusted appropriately depending on various conditions. For example, a potential difference may be generated by grounding one of adjacent piezoelectric elements 115 and applying a voltage to the other, or by applying a voltage to both of them.

[0058] For example, the configuration of the liquid ejection head 10 is not limited to the above example, and may be used in other types of heads. For example, the liquid ejection head may be configured to drive the liquid ejection unit by vibrating a vibration plate provided between the pressure chamber 112 and the drive element unit through deformation of the drive element unit.

[0059] Furthermore, although the time conditions are based on AL, they may be slightly different. For example, the expansion time and the first contraction time may be set in the range of 0.9 AL to 1.1 AL.

[0060] Furthermore, each potential of the drive waveform can be changed as appropriate, and the voltage value applied to each piezoelectric element 115 can be adjusted as appropriate according to various conditions. For example, a potential difference may be generated by grounding one of adjacent piezoelectric elements 115 and applying a voltage to the other, or by applying a voltage to both of them.

[0061] The drive waveform is not limited to a pull-fire waveform, and may be a push-fire waveform or a push-pull-fire waveform. For example, the configuration of the liquid ejection head 10 is not limited to the above example, and may be used in other types of heads. For example, it may have a structure in which ink is ejected by deforming a diaphragm using static electricity, or a heat-generating element type structure in which ink is ejected from a nozzle using thermal energy from a heater or the like. In these cases, the diaphragm or heater or the like serves as an actuator for applying pressure vibrations to the inside of the pressure chamber 112.

[0062] Although the liquid ejection device 100 is exemplified as an inkjet printer that forms a two-dimensional image using ink on an image formation medium, it is not limited to this and may be, for example, a 3D printer, industrial manufacturing machinery, medical machinery, etc. The liquid ejection device may be a 3D printer, industrial manufacturing machinery, medical machinery, etc., and may form a three-dimensional object by ejecting, for example, a material substance or a binder for solidifying the material from an inkjet head.

[0063] According to at least one of the embodiments described above, it is possible to achieve both high impact accuracy and a reduction in satellite mist.

[0064] 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]

[0065] 10...liquid ejection head, 11...actuator, 12...drive circuit, 13...data buffer, 14...decoder, 15...driver, 21...liquid supply unit, 22...transport unit, 25...operation unit, 26...display unit, 30...control unit, 31...processor, 32...ROM, 33...RAM, 34...image memory, 35...I / O port, 100...liquid ejection device, 111...nozzle, 112...pressure chamber, 115...piezoelectric element, 116...electrode, 200...externally connected device

Claims

1. a drive unit that applies a drive signal to the actuator to drive a pressure chamber that communicates with a nozzle that ejects liquid; The waveform of the drive signal is having a steady state, an expanded state, a first contracted state, and a second contracted state; a first waveform that expands the volume of the pressure chamber and then causes the pressure chamber to enter a first contracted state; a second waveform that changes the state to a second contraction state at a timing after the point at which the flow velocity in the pressure chamber first becomes 0 after application of the first waveform; and a third waveform that changes the second contraction state to a steady state after the point at which the flow rate first becomes zero after application of the second waveform; and The timing of application of the second waveform is 1.5 AL or more after the timing of application of the first waveform.

2. The drive device according to claim 1 , further comprising: a fourth waveform that, after application of the third waveform, causes the contraction state again and then returns to the steady state.

3. 2. The drive device according to claim 1, wherein the second waveform is applied within 2 AL after the timing of application of the first waveform.

4. 3. The drive device according to claim 2, wherein the timing at which the fourth waveform is brought into the contracted state is between a first peak and a second peak of the flow velocity vibration after ejection.

5. 2. The drive device of claim 1, wherein the expansion time and the second contraction time are between 0.9 AL and 1.1 AL.

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