Liquid ejecting head

Abstract

Provided is a liquid ejection head that can be adapted to any installation site and use. According to one embodiment, a liquid ejection head includes a nozzle plate, a piezoelectric element, a drive circuit, first and second power supply lines, a first capacitor, and a selection circuit. The nozzle plate is provided with a plurality of nozzles which eject liquid, and piezoelectric elements are arranged corresponding to the nozzles. The drive circuit applies a drive waveform corresponding to the discharged liquid to each piezoelectric element. A fixed specific potential is input into the first power line, a common waveform shared by the plurality of piezoelectric elements is input into the second power line, and the first power line and the second power line are connected with the driving circuit. The selection circuit selects whether to connect a first power supply line and a first capacitor connected to the first power supply line to the driving circuit. The first capacitance has a capacitance equal to or greater than the total capacitance of all of the plurality of piezoelectric elements. The drive circuit creates a drive waveform using an input from the first power supply line or the second power supply line.

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejector head. Background Technology

[0002] A liquid ejector head is known for supplying a predetermined amount of liquid to a specified location. The liquid ejector head is, for example, mounted on an inkjet printer, a 3D printer, or a dispensing device. An inkjet printer ejects droplets of ink from its printhead, forming images on the surface of a recording medium. A 3D printer ejects droplets of modeling material from its modeling material ejector head, causing them to solidify and form a three-dimensional model. A dispensing device ejects droplets of a sample, supplying a predetermined amount to multiple containers.

[0003] The liquid ejector head has multiple channels for ejecting liquid. Each channel includes a nozzle for ejecting liquid, a pressure chamber connected to the nozzle, and an actuator for changing the volume of the pressure chamber. The liquid ejector head selects the channel from the multiple channels for ejecting liquid and drives the actuator by supplying a drive waveform. When the actuator is driven, the volume of the pressure chamber filled with liquid changes, and liquid is ejected from the nozzle.

[0004] Multiple fixed potentials are input to the liquid ejector head. In the drive circuit, an arbitrary fixed potential is selected from these multiple potentials to generate a drive waveform (for example, see Patent Document 1). Such a structure for generating drive waveforms inside the liquid ejector head enables the miniaturization and cost reduction of an IC (Integrated Circuit) that integrates multiple channel drive circuits corresponding to multiple channels.

[0005] However, in such liquid nozzles that internally generate drive waveforms, the drive waveform is generated from a fixed potential by rapidly switching the switch within the drive circuit on and off. Therefore, the switches generate significant heat, limiting the use of such liquid nozzles in heat-sensitive applications and applications.

[0006] In addition, a liquid ejector head is proposed in which multiple drive waveforms with different volumes of ejected liquid are generated outside the liquid ejector head. These multiple drive waveforms are input to the liquid ejector head and selected by a drive circuit (for example, see Patent Document 2). Such a structure of selecting external drive waveforms can effectively generate multiple drive waveforms that are different from each other.

[0007] However, in liquid ejector heads that utilize externally generated drive waveforms, there is a distance between the source of the drive waveform and the drive circuit. Therefore, due to the influence of cable wiring resistance, connector contact resistance, and other factors, the generated drive waveform deteriorates during its journey to the drive circuit. Consequently, the use of such liquid ejector heads is limited in applications requiring rapidly generated drive waveforms.

[0008] Therefore, a liquid nozzle that can handle any installation location and application is desired.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 2014-04792

[0012] Patent Document 2: Japanese Patent Application Publication No. 2024-30510 Summary of the Invention

[0013] The technical problem that the invention aims to solve

[0014] The technical problem to be solved by the embodiments of the present invention is to provide a liquid nozzle that can be used in any installation location and for any purpose.

[0015] Technical solutions for solving technical problems

[0016] According to one embodiment, a liquid ejector head includes a nozzle plate, piezoelectric elements, a drive circuit, a first power line and a second power line, a first capacitor, and a selection circuit. The nozzle plate has multiple nozzles arranged to eject liquid. Piezoelectric elements are respectively arranged corresponding to the nozzles. The drive circuit applies a drive waveform to each of the multiple piezoelectric elements, corresponding to the liquid ejected from the nozzle corresponding to that piezoelectric element. The first power line has a fixed specific potential input and is connected to the drive circuit. The second power line has a common waveform shared by the multiple piezoelectric elements input and is connected to the drive circuit. The first capacitor is connected to the first power line. The selection circuit selects whether to connect the first power line and the first capacitor to the drive circuit. The first capacitor has a total electrostatic capacitance greater than or equal to the sum of all the multiple piezoelectric elements connected to the drive circuit. The drive circuit uses input from either the first power line or the second power line to generate the drive waveform. Attached Figure Description

[0017] Figure 1 This is a structural block diagram of an inkjet printer equipped with an inkjet head, which is the liquid ejection head according to the first embodiment.

[0018] Figure 2 This is a 3D view of the inkjet head.

[0019] Figure 3 This is a cross-sectional view of the piezoelectric actuator in the inkjet head.

[0020] Figure 4 This is a circuit diagram of an existing inkjet head.

[0021] Figure 5 This is a circuit diagram of an existing inkjet head.

[0022] Figure 6 This is a circuit diagram of the inkjet head of the liquid ejection head according to the first embodiment.

[0023] Figure 7 This is a circuit diagram of an inkjet head for a liquid ejector, as a variation of the first embodiment.

[0024] Figure 8 This is a circuit diagram of the inkjet head of the liquid ejector head according to the second embodiment.

[0025] Figure 9 This is a circuit diagram of the inkjet head of the liquid ejector head, which is a variation of the second embodiment.

[0026] 1: Inkjet printer; 2: Host PC; 3: Network; 11: Control unit; 12: Display; 13: Operation unit; 14: Communication interface; 15: Conveyor motor; 16: Motor drive circuit; 17: Pump; 18: Pump drive circuit; 19, 19-1~19-n: Inkjet head; 20: Head controller; 21: Power supply; 22: Processor; 23: Memory; 24: In-head control circuit; 25: Head unit; 26: Nozzle head; 27: Flexible printed wiring board; 28: Nozzle board; 29: Actuator board; 3 0: Sealing component; 31: Ink supply port; 32: Pressure chamber; 33: Air chamber; 34: Printed substrate; 35: Driver IC; 36: Piezoelectric actuator; 37: Nozzle; 38, 39: Piezoelectric components; 40, 42: Electrodes; 41: Individual wiring; 43: Common wiring; 44: Drive circuit; 45: First power supply line; 46: Reference (GND) potential line; 47: Connector; 48: Drive auxiliary capacitor; 49: Second power supply line; 50: Power supply line; 51, 53: Selection circuit; 54: Buck circuit. Detailed Implementation

[0027] Hereinafter, the liquid ejector head according to the embodiments will be described in detail with reference to the accompanying drawings. In the embodiments, an inkjet head will be used as an example of a liquid ejector head. It should be noted that the same symbols are used for the same structures in each figure.

[0028] [First Implementation Method]

[0029] Figure 1 This is a structural block diagram of the inkjet printer 1 in the first embodiment. The inkjet printer 1 forms an image on the printing medium while conveying the printing medium as a recording medium.

[0030] like Figure 1As shown, the inkjet printer 1 includes: a control unit 11, a display 12, an operation unit 13, a communication interface 14, a transport motor 15, a motor drive circuit 16, a pump 17, a pump drive circuit 18, a plurality of inkjet heads 19-1, 19-2, ..., 19-n, which are liquid ejection heads according to the first embodiment, a head controller 20, and a power supply 21. Furthermore, the inkjet printer 1 includes a transport mechanism (not shown), a paper feed tray, and a paper discharge tray. It should be noted that... Figure 1 In this document, the interface will be abbreviated as "IF". Furthermore, in subsequent descriptions, when not distinguishing between multiple inkjet heads 19-1 to 19-n, they will only be referred to as "inkjet head 19".

[0031] The control unit 11 includes a processor 22 and a memory 23, and performs various controls on the inkjet printer 1. The processor 22 is an arithmetic element that performs arithmetic processing. The processor 22 performs various processes, for example, based on a program stored in the memory 23 and the data used in the program. The memory 23 stores programs, data used in the program, etc., in a rewritable manner.

[0032] The display 12 is a display device such as a liquid crystal display, which displays images based on image signals input from the processor 22 or a graphics controller (not shown) for image processing.

[0033] The operation unit 13 has an operation section that generates operation signals based on user operations. The operation unit 13 may be, for example, a touch sensor, numeric keys, a power button, a paper feed button, various function keys, or a keyboard. The touch sensor may be, for example, a resistive film touch sensor or an electrostatic capacitive touch sensor. The touch sensor acquires information indicating a specified position within a certain area. Alternatively, the touch sensor may also be used as a touch panel integrally formed and disposed on the upper surface of the display 12. In this case, the touch sensor generates a signal indicating the touched position on the screen displayed on the display 12.

[0034] Communication interface 14 is an interface for communicating with external devices. In this embodiment, communication interface 14 is used, for example, to communicate with at least one host PC 2 that sends printing data to inkjet printer 1. Communication interface 14 communicates with host PC 2 via a wired or wireless network 3, such as a LAN (Local Area Network).

[0035] The conveyor motor 15, by rotating, becomes the drive source for a conveyor mechanism (not shown) used to convey printing media. The conveyor mechanism consists of a conveyor belt for conveying the printing media, multiple rollers (drive rollers and driven rollers) mounted on the conveyor belt, and guide members. The conveyor motor 15 rotates the drive rollers, thereby moving the conveyor belt. The printing media moves along a predetermined conveying path via guide members positioned near the conveyor belt.

[0036] The motor drive circuit 16 drives the transport motor 15 according to the transport control signal input from the control unit 11. Through the motor drive circuit 16, the transport motor 15, and the transport mechanism, the printed media taken from the paper feed cassette (not shown) is transported via multiple inkjet heads 19 to the paper discharge tray (not shown). It should be noted that the paper feed cassette is a box that holds multiple printed media. The paper discharge tray is a tray that holds the printed media discharged from the inkjet printer 1.

[0037] Pump 17 supplies ink from the ink tank through the ink flow path to the ink chamber of the printhead 19. Pump 17 is positioned on the ink flow path, which connects the ink tank to the pressure chamber 32 of the piezoelectric actuator 36, which serves as the ink chamber of the printhead 19 (see reference). Figure 3 It consists of pipes connected together.

[0038] The pump drive circuit 18 drives the pump 17 according to the ink supply control signal input from the processor 22.

[0039] The inkjet head 19 ejects ink onto the printing medium to form an image. Based on the drive power and control signals supplied by the head controller 20, an image is formed by ejecting ink onto the printing medium being transported to the conveyor mechanism. Multiple inkjet heads 19 are provided, each corresponding to a different ink color, such as cyan, magenta, yellow, and black.

[0040] The printhead controller 20 is a circuit connected to the control unit 11, the power supply 21, and the host PC2, and controls the multiple connected printheads 19. The printhead controller 20 actuates the printheads 19, causing ink to be ejected from the piezoelectric actuators 36 inside the printheads 19, forming an image on the printing medium.

[0041] Power supply 21 converts AC power supplied from commercial power supply into DC power (DC voltage DCV). Power supply 21 supplies DC power as a drive power to various structural parts within inkjet printer 1.

[0042] Next, the structure of the inkjet head 19 will be described. The inkjet head 19 has an in-head control circuit 24 and a head unit 25. The head unit 25 is equipped with a plurality of piezoelectric actuators 36 for ejecting ink. The in-head control circuit 24 is a control circuit that controls the head unit 25. Figure 2 This is a 3D view of the inkjet head 19. Figure 3 This is a cross-sectional view of the piezoelectric actuator 36 provided with the inkjet head 19. Below, refer to these... Figure 2 and Figure 3 Please provide an explanation.

[0043] like Figure 2As shown, the inkjet head 19 includes a nozzle head 26, which is an example of a liquid ejection section. The nozzle head 26 is connected to a flexible printed wiring board 27, which is an example of a printed wiring board with an in-head control circuit 24. The nozzle head 26 includes a nozzle plate 28, an actuator board 29, a sealing member 30, and an ink supply port 31. The sealing member 30 seals the openings of the pressure chamber 32 and the air chamber 33 formed on the actuator board 29. The ink supply port 31 is connected to an ink tank (not shown) via an ink flow path (not shown).

[0044] The flexible printed wiring board 27 is connected to the actuator substrate 29 of the nozzle head 26, and via connector 47 (see reference). Figure 6 The flexible printed wiring board 27 is connected to the printed circuit board 34, which serves as a relay substrate. The flexible printed wiring board 27 is equipped with a driver IC 35 included in the head control circuit 24. The driver IC 35 is a dedicated driver circuit 44 that integrates multiple piezoelectric actuators 36 of the head unit 25 (see reference). Figure 6 The drive chip is located within the printhead. The internal control circuit 24 temporarily stores printing data received from the printhead controller 20 via the printed circuit board 34. Based on this printing data, it determines the operating mode of each channel's piezoelectric actuator 36 and generates control signals to achieve the determined operating modes. The drive IC 35 takes multiple fixed potentials or multiple drive waveforms received from the printhead controller 20 via the printed circuit board 34 as input. Based on these control signals, it applies drive signals to the piezoelectric actuators 36 of each channel to eject ink at a predetermined timing.

[0045] The nozzle plate 28 is, for example, a rectangular plate formed of resin such as polyimide or metal such as stainless steel. Multiple ink-ejecting nozzles 37 are formed on the surface of the nozzle plate 28. The nozzle density is, for example, set in the range of 150 to 1200 dpi.

[0046] The actuator substrate 29 is, for example, a rectangular substrate formed of insulating ceramic. Figure 3As shown, multiple ink pressure chambers 32 and air chambers 33 are alternately formed on the actuator substrate 29 along a first direction, such as the X direction. The pressure chambers 32 are in communication with the nozzle 37. The pressure chambers 32 are in communication with the ink supply port 31, for example, via a common ink chamber (not shown) formed on the actuator substrate 29 or the sealing member 30. That is, the nozzle head 26 supplies ink to the pressure chambers 32 of each channel through the ink supply port 31. In other words, the nozzle head 26 serves as both a liquid ejection section and a liquid supply section. On the other hand, the air chambers 33, which are arranged adjacent to the pressure chambers 32, are closed spaces that are not in communication with the nozzles 37 and the common ink chamber (not shown). The pressure chambers 32 and the air chambers 33 are formed by cutting two piezoelectric members 38 and 39, which are stacked in a direction opposite to the polarization direction (for example, opposite directions), into a rectangular groove shape in a second direction, such as the Z direction, on the actuator substrate 29. That is, the pressure chamber 32 and the air chamber 33 are separated by piezoelectric components 38 and 39 stacked in a third direction, such as the Y direction, as sidewalls.

[0047] Electrode 40 is integrally formed with the bottom surface and both sides of pressure chamber 32. Electrode 40 of pressure chamber 32 is connected to a separate wiring 41, which serves as a wiring component. Electrode 42 is integrally formed with the bottom surface and both sides of air chamber 33. Electrode 42 of air chamber 33 is connected to a common wiring 43, which serves as a wiring component. That is, the connection point between electrode 40 of pressure chamber 32 and the separate wiring 41 is one terminal of piezoelectric actuator 36. The connection point between electrode 42 of air chamber 33 and the common wiring 43 is the other terminal of piezoelectric actuator 36. Electrodes 40 and 42, separate wiring 41, and common wiring 43 are formed, for example, from a nickel film. Separate wiring 41 is connected to drive IC 35 (i.e., drive circuit 44 for each channel). Drive IC 35 applies a drive voltage as a drive signal to each piezoelectric actuator 36 of each channel. Common wiring 43 is connected to a reference potential (e.g., ground (GND)). With this structure, the piezoelectric actuator 36, which is given a driving voltage, is subjected to an electric field in a direction that intersects (preferably orthogonal) with the polarization axes of the piezoelectric components 38 and 39, and the piezoelectric components 38 and 39, which form the sidewalls of the piezoelectric actuator 36 in the X direction, deform symmetrically in the X direction in a shear mode.

[0048] Specifically, the ink pressure chamber 32 is formed between a pair of cylindrical piezoelectric actuators 36 using piezoelectric components 38 and 39. A potential difference is applied to the two walls of the cylindrical piezoelectric actuators 36, i.e., the inner and outer walls of the pressure chamber 32. By charging / discharging the electrostatically capacitive piezoelectric elements 38 and 39, i.e., the piezoelectric actuators 36, the piezoelectric actuators 36 deform. That is, the piezoelectric components 38 and 39 drive the pressure chamber 32. As a result, the volume of the pressure chamber 32 changes, and consequently, the ink pressure within the pressure chamber 32 changes. By adjusting the magnitude and timing of this change, ink droplets are ejected from the nozzle 37.

[0049] Next, the circuit structure of the inkjet head 19 will be described. Before describing the circuit structure involved in this embodiment, firstly, refer to... Figure 4 and Figure 5 The circuit structure of the existing inkjet head 190 will be explained.

[0050] Figure 4 This diagram illustrates the circuit structure in the case where a drive waveform is generated internally within the existing inkjet head 190. The piezoelectric actuator 36 is connected to the drive circuit 44 integrated into the drive IC 35 via a separate wiring 41. The drive circuit 44 is connected to two first power supply lines 45 and a reference (GND) potential line 46. Additionally, the piezoelectric actuator 36 is connected to the reference (GND) potential line 46 via a common wiring 43. The two first power supply lines 45 and the reference (GND) potential line 46 are respectively connected to an input terminal (not shown) of connector 47. Fixed potentials V1, V2, and the reference (GND) potential, which are arbitrary potentials, are input from the head controller 20 via the printed circuit board 34 at the input terminal of connector 47. The drive circuit 44 selects the input first fixed potentials V1, V2, and the reference (GND) potential and generates a drive waveform. The piezoelectric actuator 36 charges and discharges according to the selected potential and the charging potential of the piezoelectric actuator 36. Due to the impedance of the power supply (fixed potential) line input to the inkjet head, there is a possibility of delayed charging and discharging. To prevent this, a drive auxiliary capacitor 48 is connected to the first power line 45 to reduce the impact of impedance.

[0051] Figure 5This diagram illustrates the circuit structure when the input is a drive waveform generated externally to the existing inkjet head 190. In this case, the drive circuit 44 is connected to two second power supply lines 49 and a reference (GND) potential line 46. The two second power supply lines 49 and the reference (GND) potential line 46 are respectively connected to an input terminal (not shown) of connector 47. At the input terminal (not shown) of connector 47, the drive waveforms AC1 and AC2, which are variable potentials, and the reference (GND) potential, which is an arbitrary fixed potential, are input from the head controller 20 via printed circuit board 34. The drive circuit 44 selects the input drive waveforms AC1, AC2, and the reference (GND) potential and inputs them to the piezoelectric actuator 36 via separate wiring 41. The larger the electrostatic capacitance, the more difficult it is to generate a drive waveform external to the inkjet head 190; therefore, the drive auxiliary capacitor 48 is not connected.

[0052] Thus, due to the presence or absence of the auxiliary driving capacitor 48, it is impossible to simultaneously address all factors. Figure 4 The internal waveform generation and shown Figure 5 The external waveform selection is shown.

[0053] Figure 6 This is a circuit diagram of the inkjet head 19, which is the liquid ejector head according to the first embodiment. The piezoelectric actuator 36 is connected to the drive circuit 44 integrated in the driver IC 35 via a separate wiring 41. The drive circuit 44 is connected to two power lines 50 and a reference (GND) potential line 46. Additionally, the piezoelectric actuator 36 is connected to the reference (GND) potential line 46 via a common wiring 43. The reference (GND) potential line 46 is connected to an input terminal (not shown) of the connector 47. Each power line 50 is connected to the output terminal of a selection circuit 51, which functions as a dual-input selection switch. One input terminal of the selection circuit 51 is connected to the first power line 45, and the other input terminal is connected to the second power line 49. Therefore, the selection circuit 51 switches the connection of the power lines 50 between the first power line 45 and the second power line 49. Both selection circuits 51 select the same input terminal. The first and second power lines 45 and 49 are connected to an input terminal (not shown) of the connector 47. At the input terminal of connector 47, fixed potentials V1 and V2 and a reference (GND) potential, as arbitrary potentials, and drive waveforms AC1 and AC2, as variable potentials, are input from the head controller 20 via printed circuit board 34. Additionally, a drive auxiliary capacitor 48 is connected to the first power line 45.

[0054] It should be noted that the selection circuit 51 is configured as a physical switching component, capable of switching the selected input, for example, when assembled into the inkjet printer 1. Alternatively, the selection circuit 51 may also be a circuit using semiconductor switching elements such as FET (Field Effect Transistor), MOS (Metal Oxide Semiconductor), and Photo MOS. The selection control of this semiconductor switching element can be performed either by the driver IC 35 or by the processor 22 via connector 47. It should be noted that the selection of the selection circuit 51 can be the same for all the multiple inkjet heads 19 of the inkjet printer 1, or the selections for the different inkjet heads 19 can be different. That is, the selection of the selection circuit 51 can be different depending on the location and purpose of each inkjet head 19.

[0055] The drive auxiliary capacitor 48 needs to have a sufficiently large electrostatic capacitance relative to the piezoelectric actuator 36 connected via the drive circuit 44. If the drive auxiliary capacitor 48 is not large, the voltage drops instantaneously and crosstalk increases due to the number of drive circuits 44 and the power supply impedance. The difference in load on the piezoelectric actuator 36 between the case where the number of drive circuits 44 is 1 channel and the case where all channels are connected contributes to crosstalk. To reduce this effect, each drive auxiliary capacitor 48 should have at least the same electrostatic capacitance as the piezoelectric actuator 36 connected via the drive circuit 44. Furthermore, the drive auxiliary capacitor 48 is not connected to the second power line 49 on the drive waveform selection side. This is because additional drive capability is required for external drive waveform generation.

[0056] The inkjet head 19 according to the first embodiment includes: a nozzle plate 28 with a plurality of nozzles 37 for ejecting ink; piezoelectric actuators 36, which are multiple piezoelectric elements, respectively provided corresponding to the nozzles 37; a drive circuit 44 that supplies a drive waveform to the plurality of piezoelectric actuators 36 corresponding to the ink ejected from the nozzles 37 corresponding to the piezoelectric actuators 36; a first power line 45 that receives a fixed specific potential and is connected to the drive circuit 44; a second power line 49 that receives drive waveforms AC1 and AC2, which are common waveforms shared by the plurality of piezoelectric actuators 36, and is connected to the drive circuit 44; a drive auxiliary capacitor 48, which is a first capacitor and is connected to the first power line 45; and a selection circuit 51 that selects whether to connect the first power line 45 and the drive auxiliary capacitor 48 to the drive circuit 44. Then, the drive auxiliary capacitor 48 has the total electrostatic capacitance of all the piezoelectric actuators 36 connected to the drive circuit 44, and the drive circuit 44 uses input from either the first or second power line 45, 49 to create the drive waveform.

[0057] Therefore, according to the inkjet head 19 of the liquid ejector head according to the first embodiment, by selecting the selection circuit 51, it is possible to switch between a method of selecting an arbitrary potential from multiple fixed potentials V1, V2 and a reference (GND) potential to generate a drive waveform, and a method of selecting a common drive waveform AC1, AC2 and a reference (GND) potential. Thus, a liquid ejector head that can accommodate any installation location and application can be provided. That is, by using the optimal drive waveform with a common circuit, the print quality of various inkjet printers 1 can be guaranteed.

[0058] It should be noted that in the inkjet head 19, which is the liquid ejector head according to the first embodiment, no drive auxiliary capacitor 48 is connected to the second power line 49, that is, there is no load.

[0059] Therefore, according to the inkjet head 19 of the liquid ejection head according to the first embodiment, it is possible to eliminate the need to create the required high-driving-capability drive waveforms AC1 and AC2 in the external circuit of the inkjet head 19, such as the head controller 20.

[0060] Furthermore, in the inkjet head 19, which is the liquid ejection head according to the first embodiment, the selection circuit 51 can be a selection switch that switches the input of the drive circuit 44 between the first power line 45 and the second power line 49.

[0061] [Variation Example]

[0062] Figure 7 This is a circuit diagram of the inkjet head 19 of the liquid ejector head according to a variation of the first embodiment. In the first embodiment, the drive auxiliary capacitor 48 is not connected to the second power line 49, but it is also possible to... Figure 7 A small-capacity bypass capacitor 52 is connected as shown, which does not affect the degree to which the drive waveforms AC1 and AC2 from the external input are affected.

[0063] The bypass capacitor 52 removes high-frequency noise and suppresses resonance. Even with a large capacitance, the bypass capacitor 52 has a smaller electrostatic capacitance than the piezoelectric actuator 36 connected through the drive circuit 44.

[0064] Thus, the inkjet head 19 of the liquid ejector head involved in the modification of the first embodiment may also have a bypass capacitor 52 as a second capacitor connected to the second power line 49, and the capacitance of the bypass capacitor 52 may also have an electrostatic capacitance smaller than the total of the plurality of piezoelectric actuators 36 connected to the drive circuit 44.

[0065] [Second Implementation]

[0066] Next, the inkjet head 19, which is the liquid ejection head according to the second embodiment, will be described. It should be noted that detailed descriptions of structures identical to those in the first embodiment will be omitted.

[0067] Figure 8 This is a circuit diagram of the inkjet head 19, which is the liquid ejection head according to the second embodiment. In this second embodiment, each power line 50 is connected to the first power line 45 via a selection circuit 53 and is directly connected to the second power line 49. The selection circuit 53 can be an on / off switch. As an on / off switch, it can be a semiconductor switching element such as FET, MOS, or PhotoMOS. Therefore, the selection circuit 53 switches the connection and disconnection of the first power line 45 and the drive auxiliary capacitor 48, which is the first capacitor, to the power line 50, i.e., the drive circuit 44. The selection control of this semiconductor switching element can be performed either by the driver IC 35 or by the processor 22 via the connector 47. The on / off of the two selection circuits 53 is synchronized.

[0068] The inkjet head 19 according to the second embodiment includes: a nozzle plate 28 with a plurality of nozzles 37 for ejecting ink; piezoelectric actuators 36, which are multiple piezoelectric elements, respectively provided corresponding to the nozzles 37; a drive circuit 44 that supplies a drive waveform to the plurality of piezoelectric actuators 36 corresponding to the ink ejected from the nozzles 37 corresponding to the piezoelectric actuators 36; a first power line 45 that receives a fixed specific potential and is connected to the drive circuit 44; a second power line 49 that receives drive waveforms AC1 and AC2, which are common waveforms shared by the plurality of piezoelectric actuators 36, and is connected to the drive circuit 44; a drive auxiliary capacitor 48, which is a first capacitor and is connected to the first power line 45; and a selection circuit 53 that selects whether to connect the first power line 45 and the drive auxiliary capacitor 48 to the drive circuit 44. Then, the drive auxiliary capacitor 48 has the total electrostatic capacitance of all the piezoelectric actuators 36 connected to the drive circuit 44, and the drive circuit 44 uses input from either the first or second power line 45, 49 to create the drive waveform.

[0069] Therefore, in the inkjet head 19 as a liquid ejector head according to the second embodiment, by turning the selection circuit 53 on / off, it is possible to switch between a method of selecting an arbitrary potential from multiple fixed potentials V1, V2 and a reference (GND) potential to generate a drive waveform, and a method of selecting a common drive waveform AC1, AC2 and a reference (GND) potential. Thus, a liquid ejector head that can accommodate any installation location and application can be provided. That is, by using the optimal drive waveform with a common circuit, the print quality of various inkjet printers 1 can be guaranteed.

[0070] It should be noted that, in this second embodiment, the selection circuit 53 is an on / off switch that switches the connection and disconnection of the first power line 45 and the driving auxiliary capacitor 48, which serves as the first capacitor, to the driving circuit 44.

[0071] Therefore, the inkjet head 19 according to the liquid ejection head of the second embodiment can be a selection circuit 53 that switches on / off, thus reducing the number and size of terminals.

[0072] [Variation Example]

[0073] Figure 9 This is a circuit diagram of the inkjet head 19 of the liquid ejector head according to a variation of the second embodiment. In this variation, a step-down circuit 54 is included. This step-down circuit 54 takes a fixed potential V1 input to one of the two first power lines 45 as input, steps down the fixed potential V1, and generates a fixed potential V2. Then, the step-down circuit 54 applies the generated fixed potential V2 to the other first power line 45. Therefore, no fixed potential V2 is input to the connector 47. The step-down circuit 54 is a DC-DC converter, serving as a linear regulator or switching regulator. It should be noted that, for the stabilization of the step-down circuit 54, a sufficiently large capacitor is required on both the input and output sides. This capacitor can be used in conjunction with the drive auxiliary capacitor 48.

[0074] Thus, in the inkjet head 19 of the modified embodiment of the second embodiment, one of the fixed potentials is generated by the step-down circuit 54 inside the inkjet head 19. As a result, the number of power lines input from the head controller 20 can be reduced.

[0075] However, in this modified example, attention should be paid to the driving waveform generated by the driving circuit 44 connected to the fixed potential V2. The fixed potential V2 charges and discharges the piezoelectric actuator 36, which is smoothed by the driving auxiliary capacitor 48. Therefore, the step-down circuit 54 needs to have sufficient performance to handle the smoothed charging and discharging current.

[0076] It should be noted that the step-down circuit 54 can be configured as a standalone IC or it can be built into the same driver IC 35 as the driver circuit 44 of each channel.

[0077] The first and second embodiments and their variations have been described above, but the embodiments are not limited to the above embodiments.

[0078] For example, the piezoelectric actuator 36 can be a stacked type with multiple piezoelectric elements, or the piezoelectric element can be a single-layer piezoelectric actuator.

[0079] In the above embodiments, the inkjet head 19 of the inkjet printer 1 was described as an example of a liquid ejection device, but the liquid ejection device may also be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0080] The embodiments of the present invention are presented merely as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are similarly included within the scope of the invention as described in the claims and their equivalents.

Claims

1. A liquid ejection head, comprising: a nozzle plate in which a plurality of nozzles that eject liquid are arranged; a plurality of piezoelectric elements that are respectively provided corresponding to the nozzles; a drive circuit that applies a drive waveform corresponding to ejection of the liquid from the nozzle corresponding to the piezoelectric element to each of the plurality of piezoelectric elements; a first power supply line to which a fixed specific potential is input and which is connected to the drive circuit; a second power supply line to which a common waveform that is common to the plurality of piezoelectric elements is input and which is connected to the drive circuit; a first capacitor that is connected to the first power supply line; and a selection circuit that selects whether or not the first power supply line and the first capacitor are connected to the drive circuit, wherein the first capacitor has an electrostatic capacity that is greater than the sum of the plurality of piezoelectric elements connected to the drive circuit, and the drive circuit uses input from either of the first power supply line and the second power supply line to create the drive waveform.

2. The liquid ejection head according to claim 1, wherein the liquid ejection head further comprises a second capacitor that is connected to the second power supply line, and the second capacitor has an electrostatic capacity that is less than the sum of the plurality of piezoelectric elements connected to the drive circuit.

3. The liquid ejection head according to claim 1, wherein the second power supply line is ungrounded.

4. The liquid ejection head according to claim 1, wherein the selection circuit switches the input of the drive circuit between the first power supply line and the second power supply line.

5. The liquid ejection head according to claim 1, wherein the selection circuit switches the connection and disconnection of the first power supply line and the first capacitor to the drive circuit. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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