Liquid ejection apparatus and method for driving liquid ejection apparatus

Abstract

To provide a liquid ejection apparatus capable of ejecting liquid droplets at a high frequency and stably ejecting the liquid droplets, and to provide a method for driving the liquid ejection apparatus.SOLUTION: The liquid ejection apparatus includes: an ejection unit including a nozzle that discharges liquid droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in the liquid in the pressure chamber in response to a supplied individual drive signal; and a drive control unit 111 that supplies the individual drive signals to the drive elements for each of a plurality of consecutive individual cycles. The drive control unit 111 supplies a first individual drive signal according to situation information including an ejection history within a first period having a predetermined length immediately before a first individual cycle to the drive element as the individual drive signal when ejecting a liquid droplet from the nozzle in the first individual cycle included in the plurality of individual cycles.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a liquid ejecting apparatus having an ejection section that ejects liquid from a nozzle and a method for driving the liquid ejecting apparatus, and more particularly to an ink jet recording apparatus that ejects ink as the liquid and a method for driving the ink jet recording apparatus. [Background technology]

[0002] 2. Description of the Related Art A liquid ejecting apparatus, typified by an ink jet recording apparatus such as an ink jet printer or plotter, is provided with an ejection unit capable of ejecting liquid such as ink stored in a cartridge or tank as droplets.

[0003] The ejection unit includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a drive element for generating pressure fluctuations in the liquid in the pressure chamber. The liquid ejection device prints a desired image by selecting pulses included in a drive waveform for each drive cycle, depending on image data to be printed on a medium, and supplying the pulses to the drive element, or by not selecting a pulse and not supplying it to the drive element (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-40408 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the drive element is driven at high speed, residual vibrations of the liquid inside the nozzle caused by driving the drive element in a previous drive cycle affect the drive element when it is driven in a later drive cycle, resulting in variations in the amount of droplets ejected when driven in the later drive cycle. [Means for solving the problem]

[0006] An aspect of the present invention that solves the above problem is a liquid ejection device comprising: an ejection unit having a nozzle that ejects droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that causes pressure fluctuations in the liquid in the pressure chamber in response to a supplied individual drive signal; and a drive control unit that supplies the individual drive signal to the drive element for each of a plurality of consecutive individual periods, wherein, when ejecting droplets from the nozzle in a first individual period included in the plurality of individual periods, the drive control unit supplies to the drive element as the individual drive signal a first individual drive signal that corresponds to status information including an ejection history within a first period of a predetermined length immediately before the first individual period.

[0007] Another aspect of the present invention is a method for driving a liquid ejection device having an ejection section having a nozzle that ejects droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that causes pressure fluctuations in the liquid in the pressure chamber in response to a supplied individual drive signal, characterized in that the individual drive signal is supplied to the drive element for each of a plurality of consecutive individual periods, and when ejecting droplets from the nozzle in a first individual period included in the plurality of individual periods, a first individual drive signal corresponding to status information including an ejection history within a first period of a predetermined length immediately before the first individual period is supplied to the drive element as the individual drive signal. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejecting apparatus. [Figure 2] FIG. [Figure 3] FIG. 2 is a block diagram showing an electrical configuration of the liquid ejection device. [Figure 4] 10 is a drive waveform of a first common drive signal. [Figure 5] 10 is a drive waveform of a second common drive signal. [Figure 6] 10 is a drive waveform of a third common drive signal. [Figure 7]10 shows the drive waveforms of a common drive signal, a head control signal, and an individual drive signal. [Figure 8] FIG. 2 is a block diagram showing a function realization unit of a control unit. [Figure 9] 10 is a graph showing the relationship between the ratio of the ejection cycle and the amount of droplets ejected. [Figure 10] 10A and 10B are diagrams illustrating ejection and non-ejection in a plurality of consecutive individual periods. [Figure 11] 10A and 10B are diagrams illustrating ejection and non-ejection in a plurality of consecutive individual periods. [Figure 12] 10A and 10B are diagrams illustrating ejection and non-ejection in a plurality of consecutive individual periods. [Figure 13] 10 is a table showing the relationship between the ejection interval and the natural vibration period Tc. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below based on embodiments. However, the following description illustrates one aspect of the present invention and can be modified as desired within the scope of the present invention. In each drawing, the same reference numerals indicate the same components, and their description will be omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, the directions along these axes are referred to as the X direction, Y direction, and Z direction. In each drawing, the direction indicated by the arrow is the positive (+) direction, and the direction opposite the arrow is the negative (-) direction. The Z direction indicates the vertical direction, the +Z direction indicates a vertically downward direction, and the -Z direction indicates a vertically upward direction. Furthermore, the directions of the three spatial axes, which are not limited to positive and negative directions, will be described as the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0010] (Embodiment 1) FIG. 1 is a diagram showing a schematic configuration of a liquid ejecting apparatus 1 of the present invention.

[0011] As shown in the figure, the liquid ejecting device 1 is a so-called serial printer that includes a discharge unit 2 and prints by conveying a medium S in the X-axis direction while reciprocating the discharge unit 2 in the Y-axis direction and discharging (also called spraying) liquid from the discharge unit 2 toward the medium S in the +Z direction. Note that the medium S can be made of any material, such as recording paper, resin film, cloth, etc.

[0012] The liquid ejecting device 1 includes a discharge unit 2, a liquid storage unit 3, a control unit 4, a transport mechanism 5 that feeds the medium S, and a movement mechanism 6.

[0013] The ejection unit 2 ejects the liquid supplied from the liquid storage unit 3 in the form of droplets in the +Z direction.

[0014] The liquid storage section 3 stores the liquid to be ejected from the ejection section 2. Examples of the liquid storage section 3 include a cartridge that can be attached to and detached from the liquid ejection device 1, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. Although not specifically shown, the liquid storage section 3 may store multiple types of ink with different colors, ingredients, etc. individually. The liquid storage section 3 may also be separated into a main tank and a sub-tank. The sub-tank may be connected to the ejection section 2, and the liquid consumed when droplets are ejected from the ejection section 2 may be replenished from the main tank to the sub-tank. The liquid may also be circulated between the liquid storage section 3 and the ejection section 2.

[0015] The control unit 4 includes, for example, a control device such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage device such as a semiconductor memory. The control unit 4 also includes a power supply device that supplies power from an external power source such as a commercial power source to each element of the liquid ejection device 1. The control unit 4 is electrically connected to the ejection unit 2 via external wiring (not shown). The control unit 4 comprehensively controls each element of the liquid ejection device 1 by the control device executing a program stored in the storage device.

[0016] The transport mechanism 5 transports the medium S in the X-axis direction, and includes, for example, a transport roller 5a that is rotated by a transport motor that is driven under the control of the control unit 4.

[0017] The movement mechanism 6 is a mechanism for reciprocating the discharge unit 2 in the Y-axis direction, and includes a holder 6a that holds the discharge unit 2, and a conveyor belt 6b that is an endless belt that is installed along the Y-axis direction. The control unit 4 controls the driving of a conveyor motor (not shown) to rotate the conveyor belt 6b, and moves the discharge unit 2 reciprocally in the Y-axis direction together with the holder 6a fixed to the conveyor belt 6b.

[0018] The discharge unit 2 performs a jetting operation of jetting ink supplied from the liquid storage unit 3 as droplets in the +Z direction from each of the multiple nozzles 21 (see FIG. 2) under the control of the control unit 4. This jetting operation by the discharge unit 2 is performed in parallel with the transport of the medium S by the transport mechanism 5 and the reciprocating movement of the discharge unit 2 by the movement mechanism 6, thereby applying ink to the medium S, or so-called printing.

[0019] 2 is a cross-sectional view of the discharge section 2 according to one embodiment of the present invention. Note that the directions of the discharge section 2 will be described based on the directions when the discharge section 2 is mounted on the liquid ejecting device 1, i.e., the X-axis direction, the Y-axis direction, and the Z-axis direction.

[0020] As shown in the figure, the ejection section 2 of this embodiment includes a pressure chamber substrate 10, a communication plate 15, a nozzle plate 20 having a plurality of nozzles 21 formed therein, a protective substrate 30, a case member 40, a piezoelectric actuator 300, and a wiring member 110.

[0021] The pressure chamber substrate 10 is made of, for example, a silicon substrate. In the pressure chamber substrate 10, a plurality of pressure chambers 12 are arranged side by side along the X-axis direction. The plurality of pressure chambers 12 are arranged side by side along the X-axis direction so as to be at the same position in the Y-axis direction. Two pressure chambers 12 adjacent to each other in the X-axis direction are separated by a partition wall (not shown). In this embodiment, two pressure chamber rows in which the pressure chambers 12 are arranged side by side along the X-axis direction are provided in the Y-axis direction.

[0022] A communication plate 15 and a nozzle plate 20 are stacked in this order on the surface of the pressure chamber substrate 10 facing the +Z direction. A vibration plate 50 and a piezoelectric actuator 300 are stacked in this order on the surface of the pressure chamber substrate 10 facing the -Z direction.

[0023] The communicating plate 15 is made of a plate-like member bonded to the surface of the pressure chamber substrate 10 facing the +Z direction. The communicating plate 15 is provided with nozzle communicating passages 16 that communicate between the pressure chambers 12 and the nozzles 21. The communicating plate 15 is also provided with a first common liquid chamber section 17 and a second common liquid chamber section 18 that constitute a common liquid chamber 100 that communicates with a plurality of pressure chambers 12. The first common liquid chamber section 17 is provided by penetrating the communicating plate 15 in the Z-axis direction. The second common liquid chamber section 18 is provided by opening onto the surface facing the +Z direction without penetrating the communicating plate 15 in the Z-axis direction. Furthermore, the communicating plate 15 is provided with supply communicating passages 19 that communicate with one end of the pressure chambers 12 in the Y-axis direction, independently for each pressure chamber 12. The supply communication passage 19 communicates the second common liquid chamber portion 18 with the pressure chamber 12, and supplies ink in the common liquid chamber 100 to the pressure chamber 12. As such a communication plate 15, a silicon substrate or the like can be used.

[0024] The nozzle plate 20 is bonded to the surface of the communication plate 15 facing the +Z direction. Nozzles 21 are formed in the nozzle plate 20, which communicate with each pressure chamber 12 via nozzle communication passages 16. In this embodiment, the multiple nozzles 21 are arranged in a row along the X-axis direction. Also, in this embodiment, two nozzle rows, in which the nozzles 21 are arranged side by side along the X-axis direction, are provided spaced apart in the Y-axis direction.

[0025] The material of the nozzle plate 20 is not particularly limited, and for example, a silicon substrate or the like can be used.

[0026] The vibration plate 50 has, for example, an elastic film 51 made of silicon oxide provided on the pressure chamber substrate 10 side, and an insulating film 52 made of zirconium oxide provided on the surface of the elastic film 51 facing the -Z direction.

[0027] The piezoelectric actuator 300 includes a first electrode 60 sequentially stacked in the -Z direction on the diaphragm 50, a piezoelectric layer 70 formed using a piezoelectric material, for example, a composite oxide with a perovskite structure represented by the general formula ABO3, and a second electrode 80. Such a piezoelectric actuator 300 is also referred to as a piezoelectric element, and refers to a portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. Furthermore, a portion of the piezoelectric layer 70 where piezoelectric strain occurs when a voltage is applied between the first electrode 60 and the second electrode 80 is referred to as an active portion 310. In contrast, a portion of the piezoelectric layer 70 where no piezoelectric strain occurs is referred to as an inactive portion. In other words, the active portion 310 refers to the portion of the piezoelectric layer 70 sandwiched between the first electrode 60 and the second electrode 80. In this embodiment, an active portion 310 is formed for each pressure chamber 12. In other words, the piezoelectric actuator 300 is formed with multiple active portions 310. The plurality of active portions 310 serve as driving elements that cause pressure changes in the ink within the pressure chambers 12. Generally, one of the electrodes of the active portions 310 is configured as an individual electrode that is independent for each active portion 310, and the other electrode is configured as a common electrode that is common to the plurality of active portions 310. In this embodiment, the first electrode 60 constitutes the individual electrode, and the second electrode 80 constitutes the common electrode.

[0028] Furthermore, lead electrodes 91, which are lead wiring, are drawn out from each electrode of the piezoelectric actuator 300. A wiring member 110 made of a flexible substrate is connected to the end of the lead electrode 91 opposite to the end connected to the piezoelectric actuator 300. The wiring member 110 is mounted with a drive circuit 111 having a plurality of switching elements that select whether or not to supply a drive signal for driving each active portion 310 to each active portion 310. In other words, the wiring member 110 in this embodiment is a COF (Chip On Film). Note that the wiring member 110 does not necessarily have to be provided with the drive circuit 111. In other words, the wiring member 110 may be an FFC (Flexible Flat Cable), an FPC (Flexible Printed Circuits), or the like.

[0029] A protective substrate 30 having approximately the same size as the pressure chamber substrate 10 is bonded to the surface of the pressure chamber substrate 10 facing the -Z direction. The protective substrate 30 has accommodation sections 31, which are spaces for protecting the piezoelectric actuators 300. The accommodation sections 31 are provided independently for each row of piezoelectric actuators 300 arranged side by side in the X-axis direction, with two accommodation sections 31 formed side by side in the Y-axis direction. The protective substrate 30 also has a through hole 32 penetrating in the Z-axis direction between the two accommodation sections 31 arranged side by side in the Y-axis direction. Ends of lead electrodes 91 drawn from each electrode of the piezoelectric actuators 300 extend so as to be exposed within the through hole 32, and the lead electrodes 91 and the wiring member 110 are electrically connected within the through hole 32. Such a protective substrate 30 may be made of, for example, a silicon substrate.

[0030] In addition, a case member 40 that defines a common liquid chamber 100 that communicates with the multiple pressure chambers 12 is fixed on the protective substrate 30. The case member 40 has substantially the same shape as the above-mentioned communicating plate 15 in a plan view, and is bonded to the protective substrate 30 as well as to the above-mentioned communicating plate 15.

[0031] The case member 40 has a recess 41 on the protective substrate 30 side that is deep enough to accommodate the pressure chamber substrate 10 and the protective substrate 30. This recess 41 has an opening area that is larger than the surface of the protective substrate 30 that is bonded to the pressure chamber substrate 10. Then, with the pressure chamber substrate 10 and the protective substrate 30 accommodated in the recess 41, the opening surface of the recess 41 on the nozzle plate 20 side is sealed by the communicating plate 15.

[0032] The case member 40 is also provided with a third common liquid chamber 42 that communicates with the first common liquid chamber 17 of the communication plate 15. The first common liquid chamber 17 and second common liquid chamber 18 provided in the communication plate 15 and the third common liquid chamber 42 provided in the case member 40 constitute a common liquid chamber 100 of this embodiment. A common liquid chamber 100 is provided for each row of pressure chambers 12, i.e., two common liquid chambers 100 in total. Each common liquid chamber 100 is provided continuously along the X-axis direction in which the pressure chambers 12 are arranged side by side, and the supply communication paths 19 that communicate each pressure chamber 12 with the common liquid chamber 100 are arranged side by side in the X-axis direction. The case member 40 is also provided with an inlet 44 that communicates with the common liquid chamber 100 and supplies ink to each common liquid chamber 100. The case member 40 is also provided with a connection port 43 that communicates with the through-hole 32 of the protection substrate 30 and through which the wiring member 110 is inserted. The case member 40 is made of a material such as a metal material or a resin material.

[0033] Furthermore, a compliance substrate 45 is provided on the surface of the communicating plate 15 on the +Z direction side where the first common liquid chamber portion 17 and the second common liquid chamber portion 18 open. This compliance substrate 45 seals the openings on the ejection surface side of the first common liquid chamber portion 17 and the second common liquid chamber portion 18. In this embodiment, such a compliance substrate 45 includes a sealing film 46 made of a flexible thin film, and a fixed substrate 47 made of a hard material such as metal. The area of ​​the fixed substrate 47 facing the common liquid chamber 100 is an opening 48 that is completely removed in the thickness direction, and therefore one side of the common liquid chamber 100 forms a compliance portion 49 that is a flexible portion sealed only by the flexible sealing film 46.

[0034] The ejection unit 2 takes in liquid from the liquid storage unit 3 into the common liquid chamber 100 via the inlet 44, filling the interior from the common liquid chamber 100 to the nozzles 21, and then applies a voltage to each active portion 310 corresponding to the pressure chambers 12 in accordance with an individual drive signal COMout from the drive circuit 111. This causes the diaphragm 50 to flex and deform together with the active portion 310, increasing the pressure of the liquid in each pressure chamber 12 and causing droplets to be ejected from each nozzle 21.

[0035] 3 is a block diagram showing the electrical configuration of the liquid ejection device 1. The control unit 4 is an element that performs overall control of the liquid ejection device 1. The control unit 4 includes an external interface 211 (hereinafter referred to as the external I / F 211), a RAM 212 that temporarily stores various data, a ROM 213 that stores control programs and the like, a control processing unit 214 that includes a CPU and the like, an oscillation circuit 215 that generates a clock signal (CK), a drive signal generation circuit 216 that generates a drive signal to be supplied to the discharge unit 2, and an internal interface 217 (hereinafter referred to as the internal I / F 217).

[0036] The external I / F 211 is an interface for transmitting and receiving data to and from a host computer (not shown). Examples of data received by the control unit 4 from the host computer via the external I / F 211 include print data composed of character codes, graphic functions, image data, and the like. Examples of data transmitted by the control unit 4 via the external I / F 211 include a busy signal (BUSY) and an acknowledge signal (ACK). The RAM 212 functions as a receive buffer 212A, an intermediate buffer 212B, an output buffer 212C, and a work memory (not shown). The receive buffer 212A temporarily stores print data received by the external I / F 211, the intermediate buffer 212B stores intermediate code data converted by the control processing unit 214, and the output buffer 212C stores dot pattern data. The dot pattern data is composed of recording data (SI) obtained by decoding (translating) gradation data.

[0037] In this embodiment, the drive signal generation circuit 216 generates multiple common drive signals with different waveforms. In this embodiment, it includes a first drive signal generation circuit 216A that generates the first common drive signal COM1, a second drive signal generation circuit 216B that generates the second drive signal COM2, and a third drive signal generation circuit 216C that generates the third common drive signal COM3. The first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 have different waveforms. When the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 are not distinguished from one another, they will be referred to as the common drive signal COM. Details of each common drive signal COM will be described later.

[0038] The ROM 213 stores font data, graphic functions, and the like, as well as control programs (control routines) for causing the control processing unit 214 to perform various data processing operations. The control processing unit 214 reads print data from the receive buffer 212A and converts the print data to generate intermediate code data, which it then stores in the intermediate buffer 212B. The control processing unit 214 also analyzes the intermediate code data read from the intermediate buffer 212B and converts the intermediate code data into pixel data by referencing the font data and graphic functions stored in the ROM 213. The control processing unit 214 then applies any necessary decoration processing and stores the converted pixel data in the output buffer 212C. The control program may be loaded from a recording medium, such as a floppy disk, CD-ROM, DVD-ROM, or USB memory, connected directly via the external I / F 211 or via the host computer. The control program may also be provided in the host computer as a printer driver.

[0039] Then, during printing, when the control processing unit 214 obtains recording data equivalent to one line of the discharge unit 2, it outputs this one line of recording data to the discharge unit 2 via the internal I / F 217. Furthermore, when one line of recording data is output from the output buffer 212C, the expanded intermediate code data is erased from the intermediate buffer 212B, and expansion processing is performed on the next intermediate code data.

[0040] The ejection unit 2 includes a drive circuit 111, which is a drive control unit. The drive circuit 111 has a shift register 112, a latch circuit 113, a decoder 114, a level shifter 115, and a switch 116. The shift register 112, the latch circuit 113, the decoder 114, the level shifter 115, and the switch 116 are composed of a shift register element, a latch element, a decoder element, a level shifter element, and a switch element (not shown) that are provided for each nozzle 21. Furthermore, a shift register element, a latch element, a level shifter element, and a switch element are provided for each of the multiple common drive signals input to the drive circuit 111. The shift register 112, the latch circuit 113, the decoder 114, the level shifter 115, the switch 116, and the activation unit 310 are electrically connected in this order. The drive circuit 111 also includes a control logic 117 that transmits to the decoder 114 a selection signal that selects the optimal common drive signal COM from the multiple common drive signals COM generated by the drive signal generation circuit 216 and sent from the control unit 4 via the internal I / F.

[0041] The drive circuit 111 generates an individual drive signal COMout from a head control signal including recording data (SI) sent from the control unit 4 via the internal I / F and a common drive signal COM selected by the control logic 117 from among multiple common drive signals COM, and supplies the individual drive signal COMout to the active unit 310. Note that the individual drive signal COMout is an applied pulse that is actually supplied to the active unit 310. The recording data (SI) is also referred to as pixel data or print data.

[0042] The print data SI is composed of multiple print data to be ejected for each of the multiple dots that make up one line. For example, the print data may be binary, with "1" indicating that a dot is to be formed and "0" indicating that a dot is not to be formed. If the print data is "1," the drive circuit 111 supplies an ejection pulse included in the common drive signal COM to the activation unit 310 that causes droplets to be ejected from the nozzle 21 corresponding to that print data. If the print data is "0," the drive circuit 111 does not supply an ejection pulse to the activation unit 310.

[0043] In this way, the discharge unit 2 discharges droplets from each nozzle 21 at a timing defined by the recording data SI and the like under the control of the control unit 4. The control unit 4 then controls the transport mechanism 5 to transport the medium S and the movement mechanism 6 to move the discharge unit 2 back and forth via the internal I / F 217 in parallel with the discharge operation by the discharge unit 2. Printing is performed on the medium S under such control of the control unit 4.

[0044] Here, the head control signal, common drive signal COM, and individual drive signal COMout will be described with reference to Figs. 4 to 7. Fig. 4 shows a drive waveform representing a first common drive signal COM1. Fig. 5 shows a drive waveform representing a second common drive signal COM2. Fig. 6 shows a drive waveform representing a third common drive signal COM3. Fig. 7 shows drive waveforms representing the first common drive signal COM1 and individual drive signal COMout as examples of head control signals and common drive signals COM. In Fig. 7, droplet ejection is indicated by a circle (○), and non-ejection is indicated by a cross (×).

[0045] 4 to 7, the common drive signal COM is repeatedly generated by the drive signal generation circuit 216 at unit cycles T defined by a clock signal transmitted from the oscillation circuit 215. The unit cycle T is also called the recording cycle T, and corresponds to one pixel of an image to be printed on the medium S. The unit cycle T is also called the ejection cycle. Note that the common drive signal COM in this embodiment is configured to include one ejection pulse within one unit cycle T, so the unit cycle T and the ejection cycle are equal; however, the common drive signal COM can also be configured to include multiple ejection pulses within one unit cycle T, with the pulse interval between the multiple ejection pulses being the ejection cycle.

[0046] In this embodiment, the individual drive signal COMout generated from the common drive signal COM and the head control signal is supplied to the first electrode 60, which is an individual electrode, with the second electrode 80, which is the common electrode of the active section 310, as a reference potential. That is, the voltage applied to the second electrode 80 by the individual drive signal COMout is expressed as a potential with the reference potential as a reference. Furthermore, the common drive signal COM and the individual drive signal COMout are drive potentials in a broad sense.

[0047] Here, the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3, which are examples of the plurality of common drive signals COM, will be described.

[0048] 4 is a reference common drive signal, which has a long enough ejection period so that residual vibrations from the ejection of the previous droplet do not affect the ejection of the subsequent droplet, in other words, a waveform suitable for low-frequency ejection.

[0049] The first common drive signal COM1 is a signal that has a first ejection pulse DP1 within a unit period T, and is repeatedly generated for each unit period T by the first drive signal generation circuit 216A.

[0050] The first ejection pulse DP1 has a first expansion element P1, a first expansion maintaining element P2, a first contraction element P3, a first contraction maintaining element P4, and a first expansion returning element P5, which are arranged in this order in time series. Note that the first ejection pulse DP1 is a reference ejection pulse, and the first expansion element P1, the first expansion maintaining element P2, the first contraction element P3, the first contraction maintaining element P4, and the first expansion returning element P5 are also referred to as the expansion element P1, the expansion maintaining element P2, the contraction element P3, the contraction maintaining element P4, and the expansion returning element P5.

[0051] The first expansion element P1 changes the potential from the intermediate potential Vm to the first potential V1, expanding the volume of the pressure chamber 12 from the reference volume. This first expansion element P1 draws the liquid level in the nozzle 21 toward the pressure chamber 12, and liquid is supplied to the pressure chamber 12 from the common liquid chamber 100 side.

[0052] The first expansion maintaining element P2 maintains the first potential V1 for a certain period of time. While the first expansion maintaining element P2 is being supplied, pressure oscillations occur in the liquid within the pressure chamber 12 with a natural oscillation period Tc. The period of the pressure oscillations of the liquid within the pressure chamber 12, the so-called natural oscillation period Tc, can generally be expressed by the following equation (1):

[0053]

number

number

number

[0054] The first contraction element P3 changes the potential from the first potential V1 to the second potential V2, contracting the volume of the pressure chamber 12 and ejecting a droplet from the nozzle 21. In other words, the first contraction element P3 corresponds to the ejection element. The potential difference from the first potential V1 to the second potential V2 is the maximum voltage Vh in the first ejection pulse DP1. In this embodiment, the maximum voltage Vh of the first ejection pulse DP1 is referred to as the first maximum voltage Vh1. In contrast, the potential change width between the intermediate potential Vm of the first expansion element P1 and the first potential V1 is referred to as the first potential difference Vc1. In this embodiment, for example, the first potential difference Vc1 of the first ejection pulse DP1 is 70% of the first maximum voltage Vh1.

[0055] The first contraction maintaining element P4 maintains the second potential V2 for a certain period of time. While the first contraction maintaining element P4 is supplied to the active portion 310, pressure vibrations occur in the liquid within the pressure chamber 12 with the natural vibration period Tc.

[0056] The first expansion return element P5 changes the potential from the second potential V2 to the intermediate potential Vm, thereby expanding the volume of the pressure chamber 12. This first expansion return element P5 weakens the pressure vibration of the liquid inside the pressure chamber 12. In other words, the first contraction maintenance element P4 and the first expansion return element P5 function as so-called vibration damping elements that weaken the vibration of the liquid surface inside the nozzle 21 after the droplets are ejected.

[0057] The second common drive signal COM2 shown in FIG. 5 is a signal that has a second ejection pulse DP2 within a unit period T, and is repeatedly generated for each unit period T by the second drive signal generation circuit 216B.

[0058] The second ejection pulse DP2 has a second expansion element P11, a second expansion maintaining element P12, a second contraction element P13, a second contraction maintaining element P14, and a second expansion returning element P15, which are arranged in this order in time series.

[0059] The second expansion element P11 changes the potential from the intermediate potential Vm to the third potential V3, expanding the volume of the pressure chamber 12 from the reference volume. This second expansion element P11 draws the liquid level in the nozzle 21 toward the pressure chamber 12, and liquid is supplied to the pressure chamber 12 from the common liquid chamber 100 side.

[0060] The second expansion maintaining element P12 maintains the third potential V3 for a certain period of time. While the second expansion maintaining element P12 is being supplied, pressure oscillation occurs in the liquid within the pressure chamber 12 with the natural oscillation period Tc.

[0061] The second contraction element P13 changes the potential from the third potential V3 to the fourth potential V4, contracting the volume of the pressure chamber 12 and ejecting a droplet from the nozzle 21. In other words, the second contraction element P13 corresponds to an ejection element. The potential difference from the third potential V3 to the fourth potential V4 is referred to as a second maximum voltage Vh2. Furthermore, the potential change width between the intermediate potential Vm of the second expansion element P11 and the third potential V3 is referred to as a second potential difference Vc2. In this embodiment, for example, the second potential difference Vc2 of the second ejection pulse DP2 is 95% of the second maximum voltage Vh2. Note that, as will be described in more detail later, the second maximum voltage Vh2 is slightly greater than the first maximum voltage Vh1.

[0062] The second contraction maintaining element P14 maintains the fourth potential V4 for a certain period of time. While the second contraction maintaining element P14 is being supplied to the active portion 310, pressure vibrations occur in the liquid within the pressure chamber 12 with the natural vibration period Tc.

[0063] The second expansion return element P15 changes the potential from the fourth potential V4 to the intermediate potential Vm, thereby expanding the volume of the pressure chamber 12. This first expansion return element P5 weakens the pressure vibration of the liquid inside the pressure chamber 12. In other words, the second contraction maintenance element P14 and the second expansion return element P15 function as so-called vibration damping elements that weaken the vibration of the liquid surface inside the nozzle 21 after the droplets are ejected.

[0064] The second ejection pulse DP2 has a second potential difference Vc2 that is 95% of the second maximum voltage Vh2. Therefore, when comparing the case where the first ejection pulse DP1 is supplied to the active portion 310 with the case where the second ejection pulse DP2 is supplied to the active portion 310 in a state where no residual vibration is generated in the liquid in the pressure chamber 12 or the nozzle 21, the amount of liquid supplied into the pressure chamber 12 by the second expansion element P11 is greater than that by the first expansion element P1, and the ejection amount of droplets ejected by the second ejection pulse DP2 is greater than that by the first ejection pulse DP1.

[0065] The third common drive signal COM3 shown in FIG. 6 is a signal that has a third ejection pulse DP3 within the unit period T, and is repeatedly generated for each unit period T by the third drive signal generation circuit 216C.

[0066] The third ejection pulse DP3 has a third expansion element P21, a third expansion maintaining element P22, a third contraction element P23, a third contraction maintaining element P24, and a third expansion returning element P25, which are arranged in this order in time series.

[0067] The third expansion element P21 changes the potential from the intermediate potential Vm to the fifth potential V5, expanding the volume of the pressure chamber 12 from the reference volume. This third expansion element P21 draws the liquid level in the nozzle 21 toward the pressure chamber 12, and liquid is supplied to the pressure chamber 12 from the common liquid chamber 100 side.

[0068] The third expansion maintaining element P22 maintains the fifth potential V5 for a certain period of time. While the third expansion maintaining element P22 is being supplied, pressure oscillation occurs in the liquid within the pressure chamber 12 with the natural oscillation period Tc.

[0069] The third contraction element P23 changes the potential from the fifth potential V5 to the sixth potential V6, contracting the volume of the pressure chamber 12 and ejecting a droplet from the nozzle 21. In other words, the third contraction element P23 corresponds to the ejection element. The potential difference from the fifth potential V5 to the sixth potential V6 is referred to as the third maximum voltage Vh3. Furthermore, the potential change width between the intermediate potential Vm of the third expansion element P21 and the fifth potential V5 is referred to as the third potential difference Vc3. In this embodiment, for example, the third potential difference Vc3 of the third ejection pulse DP3 is 40% of the third maximum voltage Vh3. Furthermore, the third maximum voltage Vh3 is the same as the first maximum voltage Vh1.

[0070] The third contraction maintaining element P24 maintains the sixth potential V6 for a certain period of time. While the third contraction maintaining element P24 is being supplied to the active portion 310, pressure vibrations occur in the liquid within the pressure chamber 12 with the natural vibration period Tc.

[0071] The third expansion return element P25 changes the potential from the sixth potential V6 to the intermediate potential Vm, thereby expanding the volume of the pressure chamber 12. This third expansion return element P25 weakens the pressure vibration of the liquid inside the pressure chamber 12. In other words, the third contraction maintenance element P24 and the third expansion return element P25 function as so-called vibration damping elements that weaken the vibration of the liquid surface inside the nozzle 21 after the droplets are ejected.

[0072] The third ejection pulse DP3 has a third potential difference Vc3 that is 40% of the third maximum voltage Vh3. The third maximum voltage Vh3 is the same as the first maximum voltage Vh1. Therefore, when comparing the case where the first ejection pulse DP1 is supplied to the active portion 310 with the case where the third ejection pulse DP3 is supplied to the active portion 310 in a state where no residual vibration is generated in the liquid in the pressure chamber 12 and the nozzle 21, the amount of liquid supplied into the pressure chamber 12 by the third expansion element P21 is less than that by the first expansion element P2, and the ejection volume of droplets ejected by the third ejection pulse DP3 is smaller than that by the first ejection pulse DP1.

[0073] When the first ejection pulse DP1 of the first common drive signal COM1, the second ejection pulse DP2 of the second common drive signal COM2, and the third ejection pulse DP3 of the third common drive signal COM3 are not distinguished from one another, they are referred to as ejection pulses.

[0074] 7 is a signal that defines the unit period T for discharging ink from the nozzle 21 to one pixel, and indicates the unit period T, i.e., the period during which the discharge unit 2 moves across the section of one pixel. The latch signal LAT is generated by the control unit 4, and is input to the control logic 117 and latch circuit 113 included in the drive circuit 111.

[0075] The change signal CH is a signal that indicates a section during which an ejection pulse included in the common drive signal COM is applied to the active section 310. The change signal CH is generated by the control section 4 and input to the control logic 117 included in the drive circuit 111.

[0076] The print data SI is a signal that indicates whether or not a dot should be formed in each pixel, i.e., whether or not a droplet should be ejected from the nozzle 21. This print data SI is composed of one bit for each nozzle 21. For example, if there are 180 nozzles 21, then 1 bit x 180 print data SI is sent from the control unit 4 for each unit period T. The print data SI is input to a shift register 112.

[0077] The clock signal CLK is a signal used when recording data SI, a change signal CH, a latch signal LAT, etc. sent from the control unit 4 are set in the control logic 117 of the drive circuit 111, the shift register 112, etc.

[0078] The control logic 117 generates a selection signal for each nozzle 21 that selects which of the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 to supply to the active unit 310, and inputs the selection signal to the decoder 114. The decoder 114 selects one common drive signal from the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 based on the selection signal, and generates an individual drive signal COMout to supply to the active unit 310 for each individual period. The method by which the control unit 4 selects the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 will be described later. The individual period of the individual drive signal COMout is the same as the unit period T of the first common drive signal COM1 to the third common drive signal COM3.

[0079] Here, an example of ejection control of the individual periods I to V of the individual drive signal COMout generated using the first common drive signal COM1 will be described.

[0080] In the recording data SI, the recording data SI is formed so that the period corresponding to the first ejection pulse DP1 is "1" so that droplets are ejected in the individual cycle I, and during the period in which the recording data is "1", the switch is brought into a connected state by the latch signal LAT, so that the individual drive signal COMout can be supplied to the active section 310. Then, the active section 310 is deformed by this supplied individual drive signal COMout, and droplets corresponding to the first ejection pulse DP1 are ejected.

[0081] In the individual period II, the print data is "1", and similarly, the individual drive signal COMout including the first ejection pulse DP1 is supplied to the active section 310, and droplets corresponding to the first ejection pulse DP1 are ejected.

[0082] In individual period III, the recording data is "0", and while the recording data is "0", the switch is in a non-connected state, so the supply of the first ejection pulse DP1 to the active portion 310 is cut off and no droplets are ejected. During this period when the recording data is "0", each active portion 310 holds its immediately previous potential, so the immediately previous displacement state is maintained.

[0083] Similarly, in the individual period IV, no droplets are ejected, and in the individual period V, as in the individual period I, droplets are ejected corresponding to the first ejection pulse DP1.

[0084] Furthermore, when ejecting droplets in any one of the multiple individual periods (referred to as the first individual period), the control logic 117 selects a common drive signal COM according to the ejection history within a first period of a predetermined length immediately preceding the first individual period, generates an individual drive signal COMout, and drives the active section 310, thereby suppressing variation in the ejection amount of droplets ejected regardless of the ejection history.

[0085] FIG. 8 is a block diagram showing the function realization units of the control unit 4. As shown in FIG.

[0086] As shown in FIG. 8, the control unit 4 includes a natural vibration period acquisition unit 200 and a situation information acquisition unit 201.

[0087] The natural vibration period acquisition unit 200 acquires information regarding the natural vibration period Tc of the ejection unit 2. The natural vibration period acquisition unit 200 can acquire the natural vibration period Tc by, for example, detecting a residual vibration signal indicating fluctuations in the electromotive force generated in the active unit 310 due to the active unit 310 vibrating due to pressure vibrations remaining in the liquid in the pressure chamber 12 after the active unit 310 is driven, and analyzing the residual vibration signal. Note that the natural vibration period acquisition unit 200 acquires the natural vibration period Tc by detecting a residual vibration signal indicating fluctuations in the electromotive force due to residual vibrations after the active unit 310 is driven, but this is not particularly limited. The natural vibration period Tc may be acquired in advance by calculation or experiment, and information regarding the acquired natural vibration period Tc may be stored in a memory element mounted on the ejection unit 2, for example, a memory element built into the drive circuit 111 in this embodiment, before shipping the ejection unit 2. The natural vibration period acquisition unit 200 may then acquire information regarding the natural vibration period Tc stored in the memory element. Of course, if the ejection unit 2 is equipped with a storage element other than the drive circuit 111, the natural vibration period Tc may be stored therein. By storing the natural vibration period Tc, which varies from ejection unit 2 to ejection unit 2, in its own storage element in this way, it is possible to easily select a drive signal corresponding to the first individual period in accordance with the natural vibration period Tc of the ejection unit 2, as will be described in detail later. Of course, the storage element that stores the natural vibration period Tc may be a storage element provided in the control unit 4 of the liquid ejection device 1.

[0088] The status information acquisition unit 201 acquires status information including the ejection history of a first period of a predetermined length immediately preceding a first individual period in a first individual period included in the plurality of individual periods. The status information including the ejection history within the first period indicates the period elapsed since the ejection of the droplet immediately preceding the first individual period. The first period of a predetermined length is, for example, at least one individual period and preferably within six times the natural vibration period Tc. This is because, as will be described in detail later, if the ejection interval is greater than six times the natural vibration period Tc, the subsequent droplet can be ejected with almost no influence from residual vibrations caused by the ejection of the previous droplet, and there is no significant variation in the ejection amount between the ejection of the previous droplet and the ejection of the subsequent droplet.

[0089] The control unit 4 transmits status information to the control logic 117, the status information including information regarding the natural vibration period Tc acquired by the natural vibration period acquisition unit 200 and information including the discharge history for the first period acquired by the status information acquisition unit 201.

[0090] The control logic 117 selects the common drive signal COM corresponding to the first individual period based on the received status information. Then, the drive circuit 111 generates an individual drive signal COMout from the common drive signal COM selected by the control logic 117, supplies it to the active unit 310, and drives the active unit 310 with the individual drive signal COMout.

[0091] When high-speed driving is performed, the residual vibration of the liquid in the nozzle 21 caused by driving the active portion 310 in the previous individual period affects the pressure fluctuation of the liquid caused by driving the active portion 310 in the subsequent individual period, resulting in fluctuations in the amount of liquid ejected in the subsequent individual period. FIG. 9 is a graph showing the relationship between the ratio of the ejection period to the natural vibration period Tc and the amount of liquid ejected. The ejection period refers to the ejection interval between ejection pulses in the individual drive signal COMout in the subsequent individual periods. In the graph shown in FIG. 9, the ejection amount is expressed as a ratio to the ejection period long enough so that the residual vibration caused by the ejection of the previous droplet does not affect the ejection of the subsequent droplet, in other words, the ejection amount in the case of low-frequency ejection.

[0092] As shown in the figure, when the ejection period is n times the natural vibration period Tc (n is an integer), the ejection volume of the ejected droplets is maximized. When the ejection period is (n+0.5) times the natural vibration period Tc (n is an integer), the ejection volume of the ejected droplets is minimized. That is, since the meniscus inside the nozzle 21 after droplet ejection oscillates at the natural vibration period Tc, when the ejection period is n times the natural vibration period Tc (n is an integer), the pressure fluctuation caused by driving the active portion 310 acts in the same direction as the meniscus flow inside the nozzle 21, resulting in a resonance period. This means that the pressure fluctuations are multiplied, resulting in a maximum ejection volume of the droplets. On the other hand, when the ejection period is (n+0.5) times (n is an integer), the pressure fluctuation caused by driving the active portion 310 acts in the opposite direction to the meniscus flow inside the nozzle 21, resulting in an anti-resonance period. This means that the pressure fluctuations are canceled out, resulting in a minimum ejection volume of the droplets. Note that a minimum ejection volume also includes non-ejection. However, as shown in Figure 9, when the magnification n of the ejection cycle relative to the natural vibration period Tc is large, specifically when it is greater than 6 times (n>6), the ejection of subsequent droplets is performed after the residual vibration caused by the ejection of the previous droplet has sufficiently attenuated, so that fluctuations are unlikely to affect the ejection amount of the subsequent droplets.

[0093] For example, if the ejection interval of the maximum ejection frequency at which droplets are continuously ejected is "1×m" as shown in FIG. 10, then if droplets are ejected every other individual period, i.e., if there is one non-ejection between ejections, the ejection interval will be "2×m" as shown in FIG. 11. Furthermore, as shown in FIG. 12, if there are two non-ejections between ejections, the ejection interval will be "3×m," and if there are three non-ejections between ejections, the ejection interval will be "4×m." Note that FIGS. 10 to 12 are diagrams illustrating ejection and non-ejection in multiple consecutive individual periods I to IX, with ejection indicated by a circle (○) and non-ejection indicated by a cross (×). In this embodiment, "m" is the ejection period of the maximum ejection frequency, and may also be referred to as the ejection period m of the maximum ejection frequency.

[0094] The relationship between these ejection intervals and the natural vibration period Tc is shown in Table Ta1 in Figure 13. The leftmost column of Table Ta1 shows the ratio (m / Tc) between the ejection period m of the maximum ejection frequency and the natural vibration period Tc, and the second column from the left shows the ratio n of the ejection interval to the natural vibration period Tc according to the ratio (m / Tc) for each ejection interval. In addition, in each individual period, the ejection of droplets is indicated by a circle (○) and the non-ejection is indicated by a cross (×).

[0095] As shown in Table Ta1, for example, if the ejection period m of the maximum ejection frequency is 2.5 times the natural vibration period Tc, the ratio n of the ejection interval to the natural vibration period Tc when performing continuous ejection (1 x m) is 2.5 times, and as shown in Figure 9, the amount of droplets ejected after continuous ejection is 15% less than at a low frequency.

[0096] Therefore, to set the droplet ejection volume to a target value, for example, within ±3% (within the range indicated by the dashed line in FIG. 9 ), the potential change rate of the expansion element P1 of the reference ejection pulse of the reference common drive signal is changed as the ejection pulse for later ejection in the chronological order. The potential change rate of the expansion element P1 is set to be larger than the potential change rate of the reference expansion element P1. An example of a common drive signal in which the potential change rate of the expansion element P1 is changed to be larger is the second ejection pulse DP2 of the second common drive signal COM2. That is, the second ejection pulse DP2 has a second potential difference Vc2 with respect to the second maximum voltage Vh2 set to 90% so that the ejection volume is larger than that of the first ejection pulse DP1. Therefore, when the ejection interval ratio n is 2.5, by using the second ejection pulse DP2 for later ejection in the chronological order of continuous ejection, droplets can be ejected at a target ejection volume within ±3%. However, due to the influence of residual vibration, simply making the second potential difference Vc2 of the second expansion element P11 larger than the first potential difference Vc1 may not be enough to increase the ejection rate. Therefore, by making the second maximum voltage Vh2 slightly larger than the first maximum voltage Vh1, the ejection rate can be set to the target value.

[0097] Furthermore, as shown in Table Ta1, when the ratio (m / Tc) is 2.5, the ratio n of the ejection interval to the natural vibration period Tc when performing an ejection (2 × m) with one non-ejection between ejections is 5.0. As shown in Figure 9, the ejection volume of subsequent droplets is 6% larger than that at a low frequency. Therefore, to achieve the target droplet ejection volume (within ±3%), the potential change rate of the expansion element P1 of the reference ejection pulse of the reference common drive signal is changed as the ejection pulse for subsequent ejections. The potential change rate of the expansion element P1 is set to be smaller than the potential change rate of the reference expansion element P1. An example of a common drive signal in which the potential change rate of the expansion element P1 is changed to be smaller is the third ejection pulse DP3 of the third common drive signal COM3. In other words, the third potential difference Vc3 of the third ejection pulse DP3 with respect to the third maximum voltage Vh3 is set to 40% so that the ejection volume of the third ejection pulse DP3 is smaller than that of the first ejection pulse DP1. Therefore, when the ejection interval ratio n is 5.0, by using the third ejection pulse DP3 when ejecting later in the continuous ejection time series, droplets can be ejected with the droplet ejection amount set to the target value within ±3%.

[0098] 9, the closer the ratio of the ejection period to the natural vibration period Tc is to n times (n is an integer), the larger the potential change width of the first expansion element P1 as shown by the second ejection pulse DP2, like the potential change width of the second expansion element P11, and the closer the ratio of the ejection period to the natural vibration period Tc is to (n+0.5) times, the smaller the potential change width of the first expansion element P1 as shown by the third ejection pulse DP3, like the potential change width of the third expansion element P21. This makes it possible to suppress variations in the ejection amount due to residual vibration from the previous ejection.

[0099] As shown in Table Ta1, when the ratio (m / Tc) is 2.5, the ratio n of the ejection interval to the natural vibration period Tc when performing an ejection (3 x m) with two non-ejections between ejections is 7.5, and the residual vibration of the previous ejection does not significantly affect the subsequent ejection. For this reason, the first ejection pulse DP1 is used when ejecting later. This allows droplets to be ejected at a target ejection volume within ±3% of the target value.

[0100] Furthermore, when the ratio (m / Tc) is 2.5 and the ratio n is 10 when performing ejection (4×m) with three non-ejections between ejections, or when the ratio n is 12.5 when performing ejection (5×m) with four non-ejections between ejections, the first ejection pulse DP1 is used in the same way as when the ratio n is 7.5.

[0101] That is, when performing the ejection shown in FIG. 12, if the ratio (m / Tc) is 2.5, droplets are ejected using the first ejection pulse DP1 in individual period I. In the next individual period V, the ejection interval ratio n becomes 10, so droplets are ejected using the first ejection pulse DP1. In the next individual period VI, the ratio n becomes 2.5, so droplets are ejected using the second ejection pulse DP2. In the next individual period IX, the ratio n becomes 7.5, so droplets are ejected using the first ejection pulse DP1.

[0102] As described above, when the ratio n of the ejection period m of the maximum ejection frequency to the natural vibration period Tc is 2.5, the ejection interval is within six times the natural vibration period Tc when there is one or less non-ejection between ejections. Therefore, the first period acquired by the status information acquisition unit 201 is the two shots before the first individual period (ejection period m × 2), and the ejection history for these two shots before that can be acquired as status information.

[0103] For example, when the ratio (m / Tc) of the ejection interval m of the maximum ejection frequency to the natural vibration period Tc is 2.5 and the first individual period is the individual period V shown in FIG. 12, the status information acquisition unit 201 acquires, as the first period, the ejection history of the individual periods III and IV, which are the two shots immediately preceding the individual period V shown in FIG. 12, as the status information. In other words, the status information includes information related to the natural vibration period Tc and the ejection history of non-ejection in the individual period III and non-ejection in the individual period IV. Then, based on the status information received from the control unit 4, the control logic 117 sends a selection command to the decoder 114 to select the first common drive signal COM1 (first ejection pulse DP1) as the drive waveform COM to be used in the individual period V. In other words, when the first individual period is the individual period V shown in FIG. 12, the drive circuit 111 generates the first individual drive signal COMout having the first ejection pulse DP1 of the first common drive signal COM1 and supplies it to the activation unit 310.

[0104] For example, when the ratio (m / Tc) of the ejection interval m of the maximum ejection frequency to the natural vibration period Tc is 2.5 and the first individual period is individual period VI in FIG. 12, the status information acquisition unit 201 acquires, as status information, the ejection history of individual periods IV and V, which are the two shots immediately preceding individual period VI shown in FIG. 12 as the first period. In other words, the status information includes information related to the natural vibration period Tc and the ejection history of non-ejection in individual period IV and ejection in individual period V. Then, based on the information status received from the control unit 4, the control logic 117 transmits a selection command to the decoder to select the second common drive signal COM2 (second ejection pulse DP2) as the common drive signal COM to be used in individual period VI. In other words, when the first individual period is individual period VI in FIG. 12, the drive circuit 111 supplies the first individual drive signal COMout having the second ejection pulse DP2 of the second common drive signal COM2 to the activation unit 310. That is, the status information including the ejection history of non-ejection in the individual period IV and ejection in the individual period V is referred to as first status information, and the waveform shape of the second ejection pulse DP2 is referred to as the first waveform shape.

[0105] Furthermore, for example, when the ratio (m / Tc) of the ejection period m of the maximum ejection frequency to the natural vibration period Tc is 2.5, and the first individual period is individual period III shown in FIG. 11, the status information acquisition unit 201 acquires, as status information, the ejection history of individual periods I and II, which are the two shots immediately preceding individual period III in FIG. 11, as the first period. In other words, the status information includes information about the natural vibration period Tc and information about ejection during individual period I and non-ejection during individual period II. Then, based on the status information received from the control unit 4, the control logic 117 sends a selection command to the decoder to select the third common drive signal COM3 as the common drive signal COM to be used during individual period III. In other words, when the first individual period is individual period III in FIG. 11, the drive circuit 111 generates a first individual drive signal COMout having the third ejection pulse DP3 of the third common drive signal COM3 and supplies it to the activation unit 310. In this embodiment, the status information including the ejection history of ejection in individual period I and non-ejection in individual period II is referred to as the second status information, and the waveform shape of the third ejection pulse DP3 is referred to as the second waveform shape. In other words, this is status information that is different from the first status information and the second status information described above, and has a waveform shape that is different from the first waveform shape and the second waveform shape. Therefore, the second potential difference Vc2 of the second expansion element P11 of the second ejection pulse DP2 is different from the third potential difference Vc3 of the third expansion element P21 of the third ejection pulse DP3. In this embodiment, the second expansion element P11 is an example of the "first expansion element," and the third expansion element P21 is an example of the "second expansion element."

[0106] Furthermore, for example, when the ratio (m / Tc) of the ejection period m of the maximum ejection frequency to the natural vibration period Tc is 2.5, and the first individual period is individual period III shown in FIG. 10, the status information acquisition unit 201 acquires, as status information, the ejection history of individual periods I and II, which are the two shots immediately preceding individual period III in FIG. 10, as the first period. That is, the status information includes information about the natural vibration period Tc and information about the ejection in individual period I and the ejection in individual period II. Then, based on the status information received from the control unit 4, the control logic 117 sends a selection command to the decoder to select the second common drive signal COM2 as the common drive signal COM to be used in individual period III. That is, when the first individual period is individual period III in FIG. 10, the drive circuit 111 generates a first individual drive signal COMout having the second ejection pulse DP2 of the second common drive signal COM2 and supplies it to the activation unit 310. This control is the same as when the first individual period is individual period VI shown in FIG. 12. That is, the status information including the ejection history within the first period may include the period elapsed since the ejection of the droplet immediately before the first individual cycle. That is, the amount of time elapsed since the ejection of the droplet immediately before the first individual cycle is calculated as a multiple of the fixed vibration cycle Tc, and a common drive signal COM whose ejection amount does not increase or decrease depending on the magnification is selected from the multiple common drive signals COM, and the first individual drive signal COMout is generated to drive the active unit 310.

[0107] In this way, when ejecting droplets in the first individual period, the control logic 117 selects the optimal common drive signal from the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3 based on status information including information about the natural vibration period Tc received from the control unit 4 and the ejection history within a first period of a predetermined length immediately preceding the first individual period. The drive circuit 111 then generates an individual drive signal COMout based on the common drive signal selected by the control logic 117 and drives the active unit 310 with this individual drive signal COMout. This makes it possible to suppress variations in the ejection volume of droplets ejected from the nozzles 21, even when high-frequency ejection is performed, regardless of the ejection history, i.e., without being affected by residual vibrations from the previous ejection. Therefore, high-quality printing can be performed even when high-frequency ejection is performed.

[0108] In the above example, the ratio (m / Tc) of the ejection period m of the maximum ejection frequency during continuous ejection to the natural vibration period Tc in Table Ta1 is 2.5. However, the same applies to other ratios (m / Tc). For example, when the maximum ejection frequency ratio (m / Tc) is 2.0, the ratio n of the ejection interval to the natural vibration period Tc when performing continuous ejection (1×m) is 2.0, resulting in a 6% increase in the ejection volume of subsequent droplets. Therefore, in subsequent ejections, an individual drive signal COMout having a third ejection pulse DP3 is generated and supplied to the activation unit 310. Also, when the ratio (m / Tc) is 2.0, the ratio n of the ejection interval to the natural vibration period Tc when performing ejection with one non-ejection between ejections (2×m) is 4.0, resulting in an 8% increase in the ejection volume of subsequent droplets. Therefore, an individual drive signal COMout having an ejection pulse with a lower Vc1 to Vh3 than the third ejection pulse DP3 is generated and supplied to the activation unit 310. Furthermore, when (m / Tc) is 2.0, if the ratio n of the ejection interval to the natural vibration period Tc when performing an ejection (3×m) with two non-ejections between ejections is 6.0, the ejection amount of the subsequent droplets is within ±3% of the target value, so an individual drive signal COMout having a first ejection pulse DP1 is generated and supplied to the active section 310.

[0109] (Other embodiments) Although the embodiments of the present invention have been described above, the basic configuration of the present invention is not limited to those described above.

[0110] In the first embodiment described above, three common drive signals COM—the first common drive signal COM1, the second common drive signal COM2, and the third common drive signal COM3—are prepared in advance. However, three or more common drive signals may be generated from a reference common drive signal COM based on multiple maximum ejection frequencies and natural vibration periods Tc, and a selection may be made from the multiple common drive signals in accordance with status information including information on the natural vibration period Tc and the ejection history, thereby suppressing variations in the ejection volume. In other words, the natural vibration period Tc varies depending on the physical properties of the droplets and the structure of the ejection unit 2, and the maximum ejection frequency varies depending on the reference common drive signal. Therefore, it is possible to prepare the first common drive signal COM1 through the third common drive signal COM3 in advance as described above. Alternatively, the control unit 4 may generate multiple common drive signals, and the control logic 117 may select the optimal common drive signal from the multiple common drive signals during ejection to prevent variations in the ejection volume based on the natural vibration period Tc and the reference common drive signal.

[0111] In the first embodiment described above, the first common drive signal COM1 to the third common drive signal COM3 and the second common drive signal COM2 and the third common drive signal COM3 are prepared in advance as multiple common drive signals, but this is not particularly limited. For example, using the first common drive signal COM1 as a reference common drive signal, the control unit 4 may correct the waveform shape of the basic first common drive signal COM1 each time in accordance with situation information including the natural vibration period Tc and the ejection history, and appropriately modify it to have waveform shapes similar to those of the second common drive signal COM2 and the third common drive signal COM3.

[0112] In the first embodiment described above, the second potential difference Vc2, which is the potential change width of the second expansion element P11 of the second common drive signal COM2, and the third potential difference Vc3, which is the potential change width of the third expansion element P21 of the third common drive signal COM3, are varied relative to the first potential difference Vc1, which is the potential change width of the first expansion element P1 of the first common drive signal COM1. However, this is not particularly limited. For example, the potential change rate per unit time of the second expansion element P11 and the third expansion element P21 relative to the first expansion element P1 may be varied in accordance with the situation information. Furthermore, the period from the start of the second expansion element P11 to the start of the second contraction element P13 and the period from the start of the third expansion element P21 to the start of the third contraction element P23 may be varied in accordance with the situation information, relative to the period from the start of the first expansion element P1 to the start of the first contraction element P3.

[0113] Furthermore, in the above-described first embodiment, in the individual non-ejection cycles, the previous potential, i.e., the intermediate potential Vm, is applied, but this is not particularly limited to this. In the individual non-ejection cycles, the active section 310 may be driven to the extent that liquid is not ejected, i.e., so-called micro-vibration driving may be performed, thereby vibrating the meniscus of the nozzle 21 and stirring the liquid in the pressure chamber 12, thereby suppressing settling and thickening of the components contained in the ink.

[0114] Furthermore, the control logic 117 is configured to select a common drive signal COM from a plurality of common drive signals COM based on situation information including information on the natural vibration period Tc and the ejection history, but this is not particularly limited to this, and the control unit 4 may also select the common drive signal COM.

[0115] In the above-described embodiments, the thin-film piezoelectric actuator 300 is used as the driving element for generating a pressure change in the pressure chamber 12. However, the driving element is not limited to this, and other types of driving elements can be used, such as a thick-film piezoelectric actuator formed by attaching a green sheet or a longitudinal vibration type piezoelectric actuator in which piezoelectric material and electrode forming material are alternately laminated to expand and contract in the axial direction. Furthermore, the driving element can be a so-called electrostatic actuator that uses electrostatic force to deform a vibration plate and eject droplets from the nozzle 21.

[0116] Furthermore, the present invention is broadly applicable to liquid ejection devices in general that include a liquid ejection head. Examples of liquid ejection heads include various inkjet recording heads used in image recording devices such as printers, and colorant ejection heads used in manufacturing color filters for liquid crystal displays and the like. Examples of liquid ejection heads include electrode material ejection heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and the like, and bioorganic material ejection heads used in biochip manufacturing, and the present invention can also be applied to liquid ejection devices that include these liquid ejection heads.

[0117] (Addendum) From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0118] A preferred embodiment of a liquid ejection device according to Aspect 1 includes a nozzle that ejects droplets to be deposited on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in the liquid in the pressure chamber in response to a supplied individual drive signal. The drive control unit supplies the individual drive signal to the drive element for each of a plurality of consecutive individual periods. When ejecting droplets from the nozzle in a first individual period included in the plurality of individual periods, the drive control unit supplies the drive element with a first individual drive signal corresponding to status information including an ejection history within a first period of a predetermined length immediately preceding the first individual period. By supplying the first individual drive signal corresponding to the status information including the ejection history to the drive element, the drive control unit can suppress fluctuations in the ejection amount between droplets ejected at high frequency due to residual vibrations from the ejection of the previous droplet, thereby suppressing variations in the ejection amount. This enables droplets to be ejected at high frequency while achieving high-quality printing.

[0119] In Aspect 2, which is a specific example of Aspect 1, the first individual drive signal has a first waveform when the status information including the ejection history within the first period is first status information, and has a second waveform different from the first waveform when the status information including the ejection history within the first period is second status information different from the first status information. Thus, by driving the drive elements with different waveforms depending on the first status information and the second status information, when droplets are ejected at a high frequency, it is possible to suppress fluctuations in the ejection amount between droplets due to residual vibrations caused by the ejection of the immediately preceding droplet, thereby suppressing variations in the ejection amount.

[0120] In Aspect 3, which is a specific example of Aspect 2, the first waveform shape includes a first expansion element that changes in potential to expand the volume of the pressure chamber and a first contraction element that changes in potential to contract the volume of the pressure chamber expanded by the first expansion element, thereby causing a droplet to be ejected from the nozzle, and the second waveform shape includes a second expansion element that changes in potential to expand the volume of the pressure chamber and a second contraction element that changes in potential to contract the volume of the pressure chamber expanded by the second expansion element, thereby causing a droplet to be ejected from the nozzle, wherein the potential change width of the first expansion element is different from the potential change width of the second expansion element. Thus, by making the potential change width of the first expansion element different from the potential change width of the second expansion element, the ejection amount can be easily changed.

[0121] In Aspect 4, which is a specific example of Aspect 2, the device further includes a drive signal generation circuit that generates a first common drive signal having the first waveform shape and a second common drive signal having the second waveform shape, wherein the drive control unit, when ejecting droplets from the nozzles in the first individual period included in the plurality of individual periods, selects the first common drive signal and supplies the generated first individual drive signal to the drive elements as the individual drive signal if the status information including the ejection history within the first period is the first status information, and the drive control unit, when ejecting droplets from the nozzles in the first individual period included in the plurality of individual periods, selects the second common drive signal and supplies the generated first individual drive signal to the drive elements as the individual drive signal if the status information including the ejection history within the first period is the second status information. This allows the first individual drive signal to be easily generated by selecting one of the first common drive signal and the second common drive signal.

[0122] In Aspect 5, which is a specific example of Aspect 2, the device further includes a drive signal generation circuit that generates a common drive signal, wherein the drive signal generation circuit, when ejecting liquid from the nozzle during the first individual period included in the plurality of individual periods, sets the waveform shape of the common drive signal to the first waveform shape if the status information including the ejection history within the first period is the first status information, and the drive signal generation circuit, when ejecting liquid from the nozzle during the first individual period included in the plurality of individual periods, sets the waveform shape of the common drive signal to the second waveform shape if the status information including the ejection history within the first period is the second status information, and the drive control unit, when ejecting liquid from the nozzle during the first individual period included in the plurality of individual periods, supplies the first individual drive signal generated from the common drive signal to the drive element as the individual drive signal. This allows the first individual drive signal to be easily generated by changing the waveform shape of the common drive signal.

[0123] In Aspect 6, which is a specific example of Aspect 1, the status information including the ejection history within the first period indicates the period that has elapsed since the ejection immediately preceding the first individual cycle.

[0124] In aspect 7, which is a specific example of aspect 6, when the status information including the ejection history within the first period is first status information, the first individual drive signal has a first waveform shape, the first waveform shape having a first expansion element whose potential changes to expand the volume of the pressure chamber, and a first ejection element whose potential changes to contract the volume of the pressure chamber expanded by the first expansion element, causing a droplet to be ejected from the nozzle, and the closer the elapsed period is to n times (n is an integer) the natural vibration period of the ejection unit, the smaller the potential change width of the first expansion element. According to this, the closer the elapsed period is to an integer multiple, the greater the ejection amount due to residual vibration from the immediately preceding ejection, so by reducing the potential change width of the first expansion element, the ejection amount can be reduced and variation in the ejection amount can be suppressed.

[0125] In Aspect 8, which is a specific example of Aspect 1, the status information including the ejection history within the first period includes information related to the natural vibration period of the ejection unit. Since the increase or decrease in the ejection amount is affected by the magnification of the elapsed time relative to the natural vibration period, supplying individual drive signals to the drive elements based on the status information including the natural vibration period can suppress variations in the ejection amount.

[0126] A ninth aspect, which is a specific example of the eighth aspect, further comprises a natural vibration period acquisition unit that acquires information about the natural vibration period of the ejection portion.

[0127] In Aspect 10, which is a specific example of Aspect 9, the drive element is a piezoelectric element, and the natural vibration period acquisition unit acquires the natural vibration period from an electromotive force signal due to residual vibration after driving the piezoelectric element. This allows the natural vibration period to be easily measured and acquired using the piezoelectric element.

[0128] In Aspect 11, which is a specific example of Aspect 1, the predetermined length is equal to or greater than one individual cycle and is equal to or less than six times the natural vibration period of the ejection part. According to this, when the predetermined length is greater than six times the natural vibration period, residual vibrations generated by the immediately preceding ejection are attenuated and have almost no effect, so there is no need to acquire an ejection history of an unnecessarily long length.

[0129] A preferred embodiment of a driving method for a liquid ejection device according to Aspect 12 is a driving method for a liquid ejection device having an ejection unit including a nozzle that ejects droplets to land on a medium, a pressure chamber communicating with the nozzle, and a drive element that generates pressure fluctuations in the liquid in the pressure chamber in response to a supplied individual drive signal. The method includes: supplying the individual drive signal to the drive element for each of a plurality of consecutive individual periods; and, when ejecting droplets from the nozzle in a first individual period included in the plurality of individual periods, supplying the drive element with a first individual drive signal corresponding to status information including an ejection history within a first period of a predetermined length immediately preceding the first individual period. By supplying the first individual drive signal corresponding to status information including the ejection history to the drive element, when ejecting droplets at high frequency, it is possible to suppress fluctuations in the ejection amount between droplets ejected due to residual vibrations from the ejection of the previous droplet, thereby suppressing variations in the ejection amount. This enables droplets to be ejected at high frequency while achieving high-quality printing. [Explanation of symbols]

[0130] COM...common drive signal, COM1 to COM3...first common drive signal to third common drive signal, DP1 to DP3...first ejection pulse to third ejection pulse, P1...first expansion element, P2...first contraction element, P11...second expansion element, P12...second contraction element, P21...third expansion element, P22...third contraction element, T...unit cycle, 1...liquid injection device, 2...ejection section, 3...liquid storage section, 4...control section, 5...transport mechanism, 6...movement mechanism, 10...pressure chamber substrate, 12...pressure chamber, 15...communicating plate, 20...nozzle plate, 21...nozzle, 30...protective substrate, 32... Through hole, 40...case member, 45...compliance substrate, 50...diaphragm, 60...first electrode, 70...piezoelectric layer, 80...second electrode, 91...lead electrode, 100...common liquid chamber, 110...wiring member, 111...drive circuit, 117...control logic, 211...external interface, 212A...receiving buffer, 212B...intermediate buffer, 212C...output buffer, 214...control processing unit, 215...oscillating circuit, 216...drive signal generating circuit, 217...internal interface, 300...piezoelectric actuator, 310...active part.

Claims

1. a discharge unit having a nozzle that discharges droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in the liquid within the pressure chamber in response to a supplied individual drive signal; a drive control unit that supplies the individual drive signal to the drive element for each of a plurality of consecutive individual periods, the drive control unit, when ejecting a droplet from the nozzle in a first individual period included in the plurality of individual periods, supplies, as the individual drive signal, a first individual drive signal to the drive element according to status information including an ejection history within a first period of a predetermined length immediately before the first individual period; A liquid ejection device characterized by:

2. The first individual drive signal is When the status information including the ejection history within the first period is first status information, the status information has a first waveform shape, When the status information including the ejection history within the first period is second status information different from the first status information, the ink droplet has a second waveform shape different from the first waveform shape. The liquid ejection apparatus according to claim 1 .

3. the first waveform shape has a first expansion element that changes in potential so as to expand the volume of the pressure chamber, and a first contraction element that changes in potential so as to contract the volume of the pressure chamber expanded by the first expansion element, thereby ejecting a droplet from the nozzle, the second waveform shape has a second expansion element whose potential changes so as to expand the volume of the pressure chamber, and a second contraction element whose potential changes so as to contract the volume of the pressure chamber expanded by the second expansion element, thereby ejecting a droplet from the nozzle, The potential change width of the first expansion element is different from the potential change width of the second expansion element. The liquid ejection apparatus according to claim 2 .

4. a drive signal generating circuit that generates a first common drive signal having the first waveform shape and a second common drive signal having the second waveform shape; the drive control unit, when ejecting droplets from the nozzles in the first individual period included in the plurality of individual periods, if the status information including the ejection history within the first period is the first status information, supplies the first individual drive signal generated by selecting the first common drive signal to the drive elements as the individual drive signal; the drive control unit, when ejecting droplets from the nozzles in the first individual period included in the plurality of individual periods, if the status information including the ejection history within the first period is the second status information, supplies the first individual drive signal generated by selecting the second common drive signal to the drive elements as the individual drive signal; The liquid ejection apparatus according to claim 2 .

5. further comprising a drive signal generating circuit for generating a common drive signal; the drive signal generation circuit, when ejecting liquid from the nozzle in the first individual period included in the plurality of individual periods, if the status information including the ejection history within the first period is the first status information, sets the waveform shape of the common drive signal to the first waveform shape; the drive signal generation circuit, when ejecting liquid from the nozzle in the first individual period included in the plurality of individual periods, if the status information including the ejection history within the first period is the second status information, sets the waveform shape of the common drive signal to the second waveform shape; the drive control unit supplies the first individual drive signal generated from the common drive signal to the drive element as the individual drive signal when ejecting liquid from the nozzle in the first individual period included in the plurality of individual periods; The liquid ejection apparatus according to claim 2 .

6. the status information including the ejection history within the first period indicates a period of time elapsed since the ejection immediately before the first individual period; The liquid ejection apparatus according to claim 1 .

7. The first individual drive signal is When the status information including the ejection history within the first period is first status information, the status information has a first waveform shape, the first waveform shape has a first expansion element that changes in potential so as to expand the volume of the pressure chamber, and a first ejection element that changes in potential so as to contract the volume of the pressure chamber expanded by the first expansion element, thereby ejecting a droplet from the nozzle, the potential change width of the first expansion element becomes smaller as the elapsed period approaches n times (n is an integer) the natural vibration period of the ejection portion; The liquid ejection apparatus according to claim 6 .

8. the status information including the ejection history within the first period includes information regarding a natural vibration period of the ejection section; The liquid ejection apparatus according to claim 1 .

9. a natural vibration period acquisition unit that acquires information about the natural vibration period of the ejection unit, The liquid ejection apparatus according to claim 8 .

10. The driving element is a piezoelectric element, the natural vibration period acquisition unit acquires the natural vibration period from an electromotive force signal due to residual vibration after driving the piezoelectric element. The liquid ejection apparatus according to claim 9 .

11. The predetermined length is equal to or greater than one individual period and is equal to or less than six times the natural vibration period of the ejection portion. The liquid ejection apparatus according to claim 1 .

12. A method for driving a liquid ejecting device having a discharge unit including a nozzle that discharges droplets to be landed on a medium, a pressure chamber that communicates with the nozzle, and a drive element that generates pressure fluctuations in liquid within the pressure chamber in response to a supplied individual drive signal, the method comprising: supplying the individual drive signal to the drive element for each of a plurality of consecutive individual periods; supplying, to the drive element, a first individual drive signal corresponding to status information including an ejection history within a first period of a predetermined length immediately before the first individual period, when ejecting a droplet from the nozzle in a first individual period included in the plurality of individual periods; A method for driving a liquid ejection device.

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