Head unit, liquid ejection device, and control method

Abstract

The present application provides a head unit, a liquid ejection device, and a control method that improve the detection accuracy of residual vibrations. The head unit includes: an ejection section that ejects a liquid using a piezoelectric element that is displaced by being supplied with a drive signal; a residual vibration detection section that detects a residual vibration signal that is generated due to residual vibrations of the ejection section, the residual vibrations of the ejection section being generated in conjunction with the displacement of the piezoelectric element; a first switch that switches whether or not to supply the piezoelectric element with a first drive signal; a second switch that switches whether or not to supply the residual vibration detection section with the residual vibration signal; and a control section that controls the first switch and the second switch, the control section acquiring a detection start timing based on a pole of the residual vibration signal detected by the residual vibration detection section, the first switch being switched so as not to supply the piezoelectric element with the first drive signal at the detection start timing, and the second switch being switched so as to supply the residual vibration detection section with the residual vibration signal at the detection start timing.

Description

Technical Field

[0001] This disclosure relates to a head unit, a liquid ejection device, and a control method. Background Technology

[0002] For example, in an inkjet printer, an image is printed on the medium by ejecting ink from a cavity onto the medium.

[0003] In such a printer, piezoelectric elements can be used to obtain information related to the state of the ink within the nozzle from the residual vibration of the ink inside the nozzle.

[0004] Patent Document 1 describes a method for determining the ejection state by using a piezoelectric element to vibrate ink within a cavity and detecting the ink's behavior relative to the residual vibration. Furthermore, Patent Document 1 describes a circuit that applies a drive signal to the piezoelectric element during the process of vibrating the ink and detects changes in the electromotive force of the piezoelectric element during the process of checking the residual vibration of the ink (see Patent Document 1).

[0005] Patent Document 1: Japanese Patent No. 6323585

[0006] However, in the existing technology, the timing of the process of applying vibration to the ink by switching and the process of detecting the residual vibration of the ink have not been sufficiently studied. Sometimes the detection accuracy of residual vibration deteriorates, which in turn leads to a decrease in accuracy when making judgments based on the detection results of residual vibration. Summary of the Invention

[0007] To solve the aforementioned technical problems, one aspect of the head unit includes: an ejection section that ejects liquid using a piezoelectric element, the piezoelectric element being displaced by a supplied drive signal; a residual vibration detection section that detects a residual vibration signal generated by the residual vibration of the ejection section, the residual vibration of the ejection section being generated as the piezoelectric element is displaced; a first switch that switches whether to supply a first drive signal to the piezoelectric element; a second switch that switches whether to supply the residual vibration signal to the residual vibration detection section; and a control section that controls the first switch and the second switch, the control section obtaining a detection start timing based on the pole of the residual vibration signal detected by the residual vibration detection section, the first switch being switched at the detection start timing to not supply the first drive signal to the piezoelectric element, and the second switch being switched at the detection start timing to supply the residual vibration signal to the residual vibration detection section.

[0008] To address the aforementioned technical problems, one aspect of a liquid ejection device includes a conveying mechanism and a head unit. The head unit comprises: an ejection section that ejects liquid using a piezoelectric element, the piezoelectric element being displaced by a supplied drive signal; a residual vibration detection section that detects a residual vibration signal generated by the residual vibration of the ejection section, the residual vibration of the ejection section being generated with the displacement of the piezoelectric element; a first switch that switches whether to supply a first drive signal to the piezoelectric element; a second switch that switches whether to supply the residual vibration signal to the residual vibration detection section; and a control section that controls the first switch and the second switch. The control section obtains a detection start timing based on the pole of the residual vibration signal detected by the residual vibration detection section. At the detection start timing, the first switch is switched to not supply the first drive signal to the piezoelectric element, and the second switch is switched to supply the residual vibration signal to the residual vibration detection section.

[0009] To address the aforementioned technical problems, one aspect of the control method is a control method in a head unit, the head unit comprising: an ejection section that ejects liquid using a piezoelectric element, the piezoelectric element being displaced by a supplied drive signal; a residual vibration detection section that detects a residual vibration signal generated by the residual vibration of the ejection section, the residual vibration of the ejection section being generated with the displacement of the piezoelectric element; a first switch that switches whether to supply a first drive signal to the piezoelectric element; a second switch that switches whether to supply the residual vibration signal to the residual vibration detection section; and a control section that controls the first switch and the second switch, wherein in the control method, the control section obtains a detection start timing based on the pole of the residual vibration signal detected by the residual vibration detection section, the first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element, and the second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection section. Attached Figure Description

[0010] Figure 1 This is a simplified diagram illustrating the configuration of an inkjet printer, which is a liquid ejection device according to an embodiment.

[0011] Figure 2 This illustrates the implementation methods involved. Figure 1 An exploded perspective view illustrating an example of the configuration of the head unit 35 in the inkjet printer shown.

[0012] Figure 3 This is a block diagram that schematically illustrates the main parts of the inkjet printer involved in the embodiment.

[0013] Figure 4 This illustrates the implementation methods involved. Figure 1A schematic cross-sectional view of an example of a head unit in an inkjet printer.

[0014] Figure 5 This is an example of a nozzle configuration pattern for a nozzle plate of a head unit using four-color inks, as described in the implementation method.

[0015] Figure 6 This is a schematic cross-sectional view illustrating other examples of the head unit involved in the implementation.

[0016] Figure 7 This is a state diagram showing the various states of the head unit when the drive signal is input according to the embodiment.

[0017] Figure 8 This illustrates the concept involved in the implementation method. Figure 4 The circuit diagram of the calculation model for the residual vibration of the vibrating plate.

[0018] Figure 9 This is a diagram showing an example of the circuit of a head unit having a residual vibration detection section according to an embodiment.

[0019] Figure 10 This is a diagram illustrating an example of the control content involved in the implementation method.

[0020] Figure 11 This is an explanatory diagram showing the on and off states of the switch during states ST1 and ST5.

[0021] Figure 12 This is an explanatory diagram showing the on and off states of the switch during states ST2 and ST4.

[0022] Figure 13 This is an explanatory diagram showing the on and off states of the switch during state ST3.

[0023] Figure 14 This is a diagram illustrating an example of the correspondence between the timing of the signal TSIG and the output signal NVTS in an embodiment.

[0024] Figure 15 This diagram illustrates an example of the processing procedure performed in the control unit involved in the embodiment.

[0025] Figure 16 This is a diagram illustrating an example of the timing for determining the start of detection of residual vibration signals according to an embodiment.

[0026] Figure 17 This is a diagram illustrating an example of the timing for the start of detection of residual vibration signals according to an embodiment.

[0027] Figure 18This is a diagram illustrating an example of the effect of adjusting the timing of the start of residual vibration signal detection according to the embodiment.

[0028] Explanation of reference numerals in the attached figures

[0029] 1…Inkjet printer, 2…Main unit, 3…Printing section, 4…Printing device, 5…Paper feeding device, 6…Control unit, 7…Operation panel, 8…Main computer, 9…Interface section, 10…Ejection anomaly detection unit, 21…Tray, 22…Paper outlet, 24…Recovery mechanism, 25…Flow path substrate, 26…Common liquid chamber substrate, 26a…Through-through space, 26b…Wiring space, 27…Moldable substrate, 27a…Ink inlet, 27b…Through-through, 27c…Flexible part, 28…Unit housing, 28a…Space, 28b…Ink inlet channel, 29…Flexible cable, 29a…One end, 29b…Main unit, 29c…End, 29d…Control IC, 30…Elastic film, 31…Ink cartridge, 32… Carriage, 33… Drive signal generation unit, 35… Head unit, 35A… Head unit A, 41… Carriage motor, 42… Reciprocating movement mechanism, 43… Carriage motor driver, 51… Paper feed motor, 52… Paper feed roller, 52a… Driven roller, 52b… Drive roller, 53… Paper feed motor driver, 61… CPU, 62… Storage unit, 200… Piezoelectric element, 201… Stacked piezoelectric element, 240… Nozzle plate, 241… Nozzle, 242… Cavity plate, 243… Vibrating plate, 244… Intermediate layer, 245… Cavity, 246… Liquid reservoir, 247… Ink supply port, 248… External electrode, 249… Internal electrode, 251… Connecting space, 252… Nozzle plate A, 253… Nozzle A, 2 54…Metal plate, 255…Adhesive film, 256…Connecting port forming plate, 257…Cavity A plate, 258…Cavity A, 259…Liquid reservoir A, 260…Ink supply port A, 261…Ink inlet port, 262…Vibrating plate A, 263…Lower electrode, 264…Upper electrode, 301…First head unit, 311a…Piezoelectric element 1a, 311b…Piezoelectric element 1b, 312a…Electrode 1a, 312b…Electrode 1b, 313a…Electrode 2a, 313b…Electrode 2b, 321a, 321b, 321c…Drive switch, 321s…Nozzle selection switch, 322a, 322b, 322c…Bias switch, 331…First resistor, 341…First capacitor, 342…Second resistor, 343…Detection switch, 351…First operational amplifier, 352…Third resistor, 353…Fourth resistor, 361…Second operational amplifier, 362…Peak hold circuit, 371…3s switch, 391…A / D converter, 411…High-pass filter, 412…Gain adjustment section, 413…Buffer section, 414…Residual vibration waveform acquisition section, 421…Timing band, 422…Carriage guide shaft, 431…Ink supply tube, 511…First residual vibration signal, 511a…1a residual vibration signal, 521…First maximum point, 522…Second maximum point, 531…First detection start timing, 531a…1a detection start timing.611…Residual vibration signal with offset, 612…Residual vibration signal without offset, 621…Offset, 631…Threshold, 641…Error, 2011…First control unit, 2021…First drive signal generation unit, 2111…First CPU, 2112…First storage unit, 2031…Drive control unit, 2041…Constant voltage signal generation unit, 3011…Control content table, 3023…Piezoelectric element drive signal, Ca…Parasitic capacitance, L1…Conveying mechanism, N1…First node, N2…Second node, N3…Third node, N4…Fourth node, N5…Fifth node, P…Recording paper, P1…Check pulse, Vx…Specified potential, W1…Ejection section, S1~S7…Processing steps. Detailed Implementation

[0030] The embodiments will now be described with reference to the accompanying drawings.

[0031] The embodiments of the liquid ejection device disclosed herein will be described in detail below.

[0032] This embodiment is provided as an example and should not be construed as limiting the content of this disclosure.

[0033] In this embodiment, an inkjet printer that prints images on recording paper using ejected ink will be described as an example of a liquid ejection device. Ink is an example of a liquid material. Recording paper is an example of a droplet receiver.

[0034] Figure 1 This is a simplified diagram showing the configuration of an inkjet printer 1, which is a liquid ejection device in the embodiment.

[0035] It should be noted that in the following explanation, Figure 1 The upper side is referred to as the upper part, and the lower side as the lower part. First, the structure of the inkjet printer 1 will be explained.

[0036] Figure 1 The inkjet printer 1 shown has a main body 2, and has a tray 21 for holding recording paper P at the upper rear, a paper discharge port 22 for discharging recording paper P at the lower front, and an operation panel 7 on the upper surface.

[0037] The operation panel 7 may be composed of, for example, a liquid crystal display, an organic EL (Electroluminescence) display, or an LED (Light Emitting Diode) lamp, and includes a display section (not shown) for displaying error messages and an operation section (not shown) composed of various switches. The display section of the operation panel 7 functions as a notification unit.

[0038] In addition, the main body 2 of the device mainly includes: a printing device 4, which has a printing section 3 as a reciprocating moving body; a paper feeding device 5, which supplies recording paper P to the printing device 4 and discharges recording paper P from the printing device 4; and a control unit 6, which controls the printing device 4 and the paper feeding device 5.

[0039] Under the control of the control unit 6, the paper feeding device 5 intermittently feeds recording paper P one sheet at a time. The recording paper P passes near the lower part of the printing unit 3. At this time, the printing unit 3 reciprocates in a direction approximately orthogonal to the feeding direction of the recording paper P, performing printing on the recording paper P. That is, the reciprocating movement of the printing unit 3 and the intermittent feeding of the recording paper P constitute the main scan and sub-scan in printing, performing inkjet printing.

[0040] The printing apparatus 4 includes a printing unit 3, a carriage motor 41, and a reciprocating movement mechanism 42. The carriage motor 41 is a drive source that moves the printing unit 3 in a reciprocating manner in the main scanning direction. The reciprocating movement mechanism 42 receives the rotation of the carriage motor 41 and moves the printing unit 3 reciprocally.

[0041] The printing section 3 includes multiple head units 35, ink cartridges (I / C) 31 that supply ink to each head unit 35, and a carriage 32 that mounts each head unit 35 and the ink cartridge 31. It should be noted that in the case of inkjet printers with high ink consumption, the ink cartridge 31 may not be mounted on the carriage 32, but may be located in another location and supplied with ink via a tube connected to the head unit 35, but this is not shown in the figure.

[0042] It should be noted that full-color printing is possible by using ink cartridges 31 filled with yellow, cyan, magenta, and black inks. In this case, a head unit 35 corresponding to each color is provided in the printing section 3. Here, in Figure 1 The image shows four ink cartridges 31 corresponding to four colors of ink, but the printing unit 3 can also be configured to have ink cartridges 31 with other colors, such as light cyan, light magenta, dark yellow, special color inks, etc.

[0043] Figure 2 This is a schematic exploded perspective view showing the structure of the head unit 35.

[0044] like Figure 2 As shown, the head unit 35 in the embodiment is generally composed of a nozzle plate 240, a flow path substrate 25, a common liquid chamber substrate 26, a plastic substrate 27, etc., and these components are installed on the unit housing 28 in a stacked state.

[0045] The nozzle plate 240 is a plate-shaped component in which a plurality of nozzles 241 are arranged in rows at a pitch corresponding to the dot formation density. For example, a nozzle array is formed by arranging 300 nozzles 241 in rows at a pitch corresponding to 300 dpi. In an embodiment, two nozzle arrays are formed on the nozzle plate 240. Here, the two nozzle arrays are formed by offsetting the nozzles 241 by half the pitch between them in the arrangement direction of the nozzles 241. The nozzle plate 240 can be formed, for example, from glass ceramic, a single-crystal silicon substrate, or stainless steel.

[0046] A very thin elastic film 30 made of silicon dioxide is formed on the upper surface of the flow path substrate 25, i.e., on the side of the common liquid chamber substrate 26, through thermal oxidation. On the flow path substrate 25, a plurality of cavities 245, divided by multiple partition walls, are formed corresponding to each nozzle 241 through anisotropic etching. The cavities 245 are as follows... Figure 4 As shown.

[0047] Therefore, the cavities 245 are also formed in a row, offset by half the pitch between the nozzles 241 in the arrangement direction of the nozzles 241. A communicating space 251 is formed on the outer side of the row of cavities 245 in the flow path substrate 25. The communicating space 251 communicates with each cavity 245.

[0048] Additionally, a piezoelectric element 200 is formed for each cavity 245 in the flow path substrate 25. The piezoelectric element 200 deforms the elastic membrane 30 to pressurize the ink in the cavity 245.

[0049] A common liquid chamber substrate 26 having a through space 26a extending along the thickness direction is disposed on a flow path substrate 25 on which the piezoelectric element 200 is formed. Examples of materials for the common liquid chamber substrate 26 include glass, ceramic materials, metals, and resins. For example, it can also be formed from a material with approximately the same coefficient of thermal expansion as the flow path substrate 25. For example, a monocrystalline silicon substrate made of the same material as when the flow path substrate 25 is a monocrystalline silicon substrate can also be used to form the common liquid chamber substrate 26.

[0050] Furthermore, the through space 26a in the common liquid chamber substrate 26 is connected to the communication space 251 of the flow path substrate 25. In addition, in the common liquid chamber substrate 26, a wiring space 26b extending through the substrate thickness direction is formed between adjacent rows of piezoelectric elements.

[0051] Additionally, a malleable substrate 27 is disposed on the upper surface side of the common liquid chamber substrate 26. In the region of the malleable substrate 27 opposite to the through space 26a of the common liquid chamber substrate 26, an ink inlet 27a is formed in a manner that extends through the thickness direction for supplying ink from the ink inlet needle side to the common liquid chamber.

[0052] Furthermore, the area of ​​the malleable substrate 27 opposite to the through-space 26a, excluding the ink inlet 27a and the through-hole 27b, becomes an extremely thin flexible portion 27c. This flexible portion 27c seals the upper opening of the through-space 26a, thus forming a common liquid chamber. Moreover, this flexible portion 27c functions as a malleable portion that absorbs pressure changes in the ink within the common liquid chamber. Furthermore, a through-hole 27b is formed in the center of the malleable substrate 27. This through-hole 27b communicates with the space 28a of the unit housing 28.

[0053] The unit housing 28 is a component with an ink inlet channel 28b and a recess in the region opposite the flexible portion 27c that allows the flexible portion 27c to expand. The ink inlet channel 28b communicates with the ink inlet port 27a and is used to supply ink introduced from the ink inlet needle side to the common liquid chamber side. A space 28a extending along the thickness direction is provided in the center of the unit housing 28. One end of the flexible cable 29 is inserted into the space 28a along the insertion direction indicated by the hollow arrow, and is connected to the terminal led out from the piezoelectric element 200 and fixed by adhesive. Examples of materials for the unit housing 28 include stainless steel and other metal materials.

[0054] The flexible cable 29 has a control IC (Integrated Circuit) 29d mounted on one side of a rectangular base film such as polyimide for controlling the application of a driving voltage toward the piezoelectric element 200, and a pattern of independent electrode wiring connected to the control IC 29d is formed therein. Furthermore, at one end of the flexible cable 29, a plurality of connection terminals (not shown) are arranged in a row corresponding to each external electrode 248 extending from the piezoelectric element 200, and at the other end, a plurality of other-end connection terminals are arranged in a row. These other-end connection terminals are connected to the substrate terminal portion of a substrate that relays signals from the main body of the inkjet printer 1. In addition, in the flexible cable 29, the wiring pattern other than the connection terminals at both ends and the surface of the control IC 29d are covered with a photoresist. The external electrodes 248 are as follows... Figure 4 As shown.

[0055] One end 29a of the flexible cable 29, which is connected to the external electrode 248 and the internal electrode 249, is bent in a convex manner. More specifically, the front end of one end 29a is bent in a mountain-shaped manner from the body 29b of the flexible cable 29 in a ridge-like manner, and the end 29c is bent back in the opposite direction to the insertion direction of the flexible cable 29. The internal electrode 249 is as follows: Figure 4 As shown.

[0056] The nozzle plate 240, flow path substrate 25, common liquid chamber substrate 26, plastic substrate 27, and unit housing 28 are joined together by heating in a state in which adhesive or hot melt film is disposed between them and they are stacked together.

[0057] return Figure 1 The reciprocating movement mechanism 42 has a carriage guide shaft 422 and a timing belt 421. The two ends of the carriage guide shaft 422 are supported by a frame (not shown), and the timing belt 421 extends parallel to the carriage guide shaft 422.

[0058] The carriage 32 is supported by the carriage guide shaft 422 of the reciprocating movement mechanism 42 and fixed to a part of the timing belt 421.

[0059] When the timing belt 421 is rotated forward and backward via the pulley by the operation of the carriage motor 41, the printing unit 3 reciprocates under the guidance of the carriage guide shaft 422. During this reciprocating movement, ink droplets are appropriately ejected from each inkjet head 100 of the print head unit 35 corresponding to the image data to be printed, and printed on the recording paper P. It should be noted that this image data can also be referred to as printing data, etc.

[0060] The paper feeding device 5 has a paper feeding motor 51 as its driving source and a paper feeding roller 52 that rotates by the action of the paper feeding motor 51.

[0061] The paper feed roller 52 consists of a driven roller 52a and a drive roller 52b. The driven roller 52a and drive roller 52b are positioned vertically opposite each other across the transport path of the recording paper P, holding the recording paper P in place. The drive roller 52b is connected to the paper feed motor 51. Thus, the paper feed roller 52 feeds multiple sheets of recording paper P, which are placed on the tray 21, one by one into the printing unit 4, or discharges them one by one from the printing unit 4. It should be noted that the tray 21 can also be replaced by a paper feed box that can be easily installed and removed to store the recording paper P.

[0062] Furthermore, the paper feed motor 51 also feeds the recording paper P, corresponding to the resolution of the image, in conjunction with the reciprocating motion of the printing unit 3. The paper feeding and paper delivery actions can be performed using different motors, or they can be performed using the same motor by means of a torque transmission switching component such as an electromagnetic clutch.

[0063] In this embodiment, the paper feeding motor 51 and the paper feeding roller 52 constitute the conveying mechanism L1.

[0064] The control unit 6 controls the printing apparatus 4 and the paper feeding device 5, etc., based on printing data input from the main computer 8, such as a personal computer or digital camera, thereby performing printing processing on the recording paper P. Furthermore, the control unit 6 causes the display unit of the operation panel 7 to display error messages, or to illuminate / flash LEDs, and causes each unit to perform corresponding processing based on the pressed signals of various switches input from the operation unit. Furthermore, the control unit 6 transmits error messages or printing abnormalities to the main computer 8 as needed. The main computer 8, for example... Figure 3 As shown.

[0065] Figure 3 This is a block diagram schematically showing the main parts of the inkjet printer of this disclosure. Figure 3 The inkjet printer 1 disclosed herein includes an interface unit 9, a control unit 6, a carriage motor 41, a carriage motor driver 43, a paper feed motor 51, a paper feed motor driver 53, a head unit 35, a drive signal generation unit 33, an ejection abnormality detection unit 10, a recovery mechanism 24, and an operation panel 7. The interface unit 9 receives printing data input from a host computer 8, the carriage motor driver 43 drives and controls the carriage motor 41, the paper feed motor driver 53 drives and controls the paper feed motor 51, and the drive signal generation unit 33 drives and controls the head unit 35.

[0066] The recovery mechanism 24 is used to restore the function of the head unit 35 so that it can function normally when ink droplets cannot be ejected from the head unit 35. Specifically, the recovery mechanism 24 performs a rinsing action and a wiping action. The rinsing action is a head cleaning action that ejects ink droplets from all or all of the nozzles 241 of the head unit 35 when the cover of the head unit 35 is installed or in a place where ink droplets are not applied to the recording paper. In addition, during the wiping action, paper dust or debris adhering to the head surface is wiped away by a wiper to clean the nozzle plate. At this time, the nozzles 241 are under negative pressure, which may introduce ink of other colors. Therefore, after the wiping action, a certain amount of ink droplets are ejected from all the nozzles 241 of the head unit 35 to perform the rinsing action.

[0067] It should be noted that the ejection anomaly detection unit 10 and the drive signal generation unit 33 will be described in detail later.

[0068] In Figure 3In this unit, the control unit 6 includes a CPU (Central Processing Unit) 61 and a storage unit 62. The CPU 61 performs various processes such as printing processing and ejection anomaly detection processing. The storage unit 62 includes an EEPROM (Electrically Erasable Programmable Read-Only Memory), RAM (Random Access Memory), and a PROM, which are all types of non-volatile semiconductor memory. The EEPROM stores printing data input from the host computer 8 via the interface unit 9 in a data storage area (not shown). The RAM temporarily stores various data or temporarily executes application programs for printing processing during ejection anomaly detection processing. The PROM stores control programs for each control unit. It should be noted that the components of the control unit 6 are electrically connected via a bus (not shown).

[0069] As described above, the printing unit 3 includes multiple head units 35 corresponding to inks of various colors. Furthermore, each head unit 35 includes multiple nozzles 241 and piezoelectric elements 200 corresponding to each of these nozzles 241. That is, the head unit 35 is configured to include multiple inkjet heads 100, each inkjet head 100 having a set of nozzles 241 and piezoelectric elements 200. The inkjet head 100 is a droplet ejection head.

[0070] In addition, although not shown, various sensors that can detect the ink level in the ink cartridge 31, the position of the printing section 3, the temperature, humidity and other printing environment are electrically connected to the control unit 6.

[0071] When the control unit 6 obtains printing data from the host computer 8 via the interface unit 9, it stores the printing data in the storage unit 62. Then, the CPU 61 performs prescribed processing on the printing data and outputs control signals to each of the drivers in the drive signal generation unit 33, carriage motor driver 43, and paper feed motor driver 53, as well as the head unit 35, based on the processed data and input data from various sensors. When these control signals are input via the carriage motor driver 43 and the paper feed motor driver 53, the carriage motor 41 and the paper feed device 5 of the printing apparatus 4 operate respectively. Thus, printing processing is performed on the recording paper P.

[0072] Next, the structure of each head unit 35 will be described.

[0073] Figure 4 yes Figure 1 The diagram shows a schematic cross-sectional view of the head unit 35. The head unit 35 corresponds to the inkjet head 100.

[0074] pass Figure 4 The component shown constitutes the ejection part W1.

[0075] Figure 5 It shows that it has been applied. Figure 4 A top view of an example of the nozzle surface of the printing section 3 of the head unit 35 shown.

[0076] Figure 4 The head unit 35 shown ejects liquid, i.e. ink, from the cavity 245 through the nozzle 241 driven by the piezoelectric element 200. The head unit 35 includes a nozzle plate 240 with the nozzle 241 formed thereon, a cavity plate 242, a vibrating plate 243, and a stacked piezoelectric element 201 formed by stacking multiple piezoelectric elements 200.

[0077] The cavity plate 242 is formed into a predetermined shape, thereby forming the cavity 245 and the reservoir 246. The predetermined shape is one in which a recess is formed.

[0078] The cavity 245 is connected to the reservoir 246 via the ink supply port 247. In addition, the reservoir 246 is connected to the ink cartridge 31 via the ink supply pipe 431.

[0079] 201 of laminated piezoelectric elements Figure 4 The lower end of the piezoelectric element 201 is connected to the vibrating plate 243 via an intermediate layer 244. Multiple external electrodes 248 and internal electrodes 249 are connected to the stacked piezoelectric element 201. Specifically, external electrodes 248 are connected to the outer surface of the stacked piezoelectric element 201, and internal electrodes 249 are disposed between each piezoelectric element 200 constituting the stacked piezoelectric element 201 or within each piezoelectric element. In this case, a portion of the external electrodes 248 and internal electrodes 249 are alternately arranged in a manner that overlaps in the thickness direction of the piezoelectric element 200.

[0080] Therefore, by applying a driving voltage waveform from the driving signal generation unit 33 between the external electrode 248 and the internal electrode 249, the stacked piezoelectric element 201... Figure 4 The arrow in the image indicates the deformation. Figure 4 The device extends and vibrates in the vertical direction, causing the vibrating plate 243 to vibrate. The vibration of the vibrating plate 243 causes a change in the volume of the cavity 245, resulting in a change in the pressure inside the cavity 245. The liquid ink filling the cavity 245 is then ejected as droplets from the nozzle 241.

[0081] The amount of liquid lost in cavity 245 due to ejected droplets is replenished by supplying ink from reservoir 246. Additionally, ink is supplied from ink cartridge 31 to reservoir 246 via ink supply pipe 431.

[0082] It should be pointed out that it was formed in Figure 4The arrangement of the nozzles 241 on the nozzle plate 240 shown is, for example, as follows: Figure 5 The nozzles are configured in a staggered manner as shown in the diagram. Furthermore, the pitch between these nozzles 241 can be appropriately set according to the printing resolution (dpi: dots per inch).

[0083] exist Figure 6 The diagram shows the configuration of the nozzle 241 when the ink cartridge 31 uses four colors of ink.

[0084] Next, other examples of head unit 35 will be explained. Figure 6 The A-head unit 35A shown is driven by the piezoelectric element 200 to vibrate the A-vibrating plate 262, ejecting liquid ink from the A-cavity 258 through the A-nozzle 253. A stainless steel metal plate 254 is bonded to the A-nozzle plate 252, which has the A-nozzle 253 forming holes, via an adhesive film 255, and then another stainless steel metal plate 254 is bonded to it via an adhesive film 255. Then, a communication port forming plate 256 and an A-cavity plate 257 are sequentially bonded to it.

[0085] The nozzle plate 252, metal plate 254, adhesive film 255, communication port forming plate 256, and cavity plate 257 are each formed into a predetermined shape, and are overlapped to form cavity 258 and reservoir 259. The predetermined shape is one in which a recess is formed. Cavity 258 and reservoir 259 are connected via ink supply port 260. Reservoir 259 is also connected to ink inlet port 261.

[0086] An A-thrusting plate 262 is provided at the opening on the upper surface of the A-thrusting plate 257, and the piezoelectric element 200 is connected to the A-thrusting plate 262 via a lower electrode 263. Additionally, an upper electrode 264 is connected to the piezoelectric element 200 on the side opposite to the lower electrode 263. A drive signal generation unit 33 applies and supplies a drive voltage waveform between the upper electrode 264 and the lower electrode 263, thereby causing the piezoelectric element 200 to vibrate, which in turn causes the A-thrusting plate 262 connected to it to vibrate. The vibration of the A-thrusting plate 262 causes a change in the volume of the A-thrusting cavity 258, resulting in a change in pressure within the A-thrusting cavity 258. The ink, which is filled with liquid within the A-thrusting cavity 258, is ejected as droplets from the A-thrusting nozzle 253.

[0087] The amount of liquid reduced in cavity A 258 due to the ejected droplets is replenished by supplying ink from reservoir A 259. Additionally, ink is supplied to reservoir A 259 from ink inlet 261.

[0088] Next, refer to Figure 7The ejection of ink droplets is explained.

[0089] Figure 7 This is a state diagram showing the various states of the head unit when the drive signal is input according to the embodiment.

[0090] When from the drive signal generation unit 33 to Figure 4 or Figure 6 When a driving voltage is applied to the piezoelectric element 200, mechanical forces such as stretching or warping are generated in the piezoelectric element 200. Therefore, the vibrating plate 243 or the Ath vibrating plate 262 relative to... Figure 7 The initial state shown in (a) is directed towards Figure 4 or Figure 6 The upper part of the bending is as follows: Figure 7 As shown in (b), the volume of cavity 245 or cavity A 258 is expanded. In this state, when the drive voltage is changed under the control of the drive signal generation unit 33, the vibrating plate 243 or vibrating plate A 262 recovers due to its elastic restoring force and moves downward beyond the position of the vibrating plate 243 or vibrating plate A 262 in the initial state, as shown in (b). Figure 7 As shown in (c), the volume of cavity 245 or cavity A 258 shrinks drastically. At this time, due to the compression pressure generated within cavity 245 or cavity A 258, a portion of the ink, which is a liquid material, filling cavity 245 or cavity A 258 is ejected as ink droplets from nozzle 241 or nozzle A 253 that communicates with cavity 245 or cavity A 258.

[0091] Due to this series of actions, namely the ink ejection action based on the drive signal of the drive signal generation unit 33, the vibrating plate 243 of each cavity 245 undergoes damped vibration until it ejects ink droplets again according to the input drive voltage of the next drive signal. Hereinafter, this damped vibration is also referred to as residual vibration. It is assumed that the residual vibration of the vibrating plate 243 has an inherent vibration frequency determined by the acoustic resistance r caused by the shape of the nozzle 241 and ink supply port 247 or the ink viscosity, the inertia m caused by the weight of the ink in the flow path, and the compliance Cm of the vibrating plate 243.

[0092] The calculation model for the residual vibration of the vibrating plate 243 based on the above assumption is explained.

[0093] Figure 8 This is a circuit diagram illustrating the calculation model of the simple harmonic motion of the residual vibration of the vibrating plate 243. Thus, the calculation model of the residual vibration of the vibrating plate 243 is represented by the sound pressure p, as well as the aforementioned inertia m, compliance Cm, and acoustic impedance r. Therefore, when calculating the volume velocity u... Figure 8 When the circuit imparts a step response to the sound pressure p, the following equation is obtained.

[0094] u={p / (ω·m)}e -ωt ·sinωt

[0095] ω={1 / (m·Cm)-α 2} 1 / 2

[0096] α=r / 2m

[0097] Figure 9 This is a diagram showing an example of the circuit of the first head unit 301 having the residual vibration detection unit according to the embodiment.

[0098] It should be pointed out that, Figure 9 The diagram shows a first control unit 2011, a first drive signal generation unit 2021, a drive control unit 2031, a constant voltage signal generation unit 2041, and an A / D (Analog to Digital) converter 391, all housed inside the first head unit 301. Alternatively, the first drive signal generation unit 2021 could be located outside the first head unit 301, while the first control unit 2011, drive control unit 2031, constant voltage signal generation unit 2041, and A / D converter 391 could be located inside the first head unit 301.

[0099] In this embodiment, the first control unit 2011 is an example of a residual vibration detection unit. That is, in this embodiment, the first control unit 2011 has the function of detecting residual vibration signals. The residual vibration detection unit may also include an A / D converter 391.

[0100] It should be noted that components other than the first control unit 2011 may also have the function of a residual vibration detection unit. For example, in this embodiment, the first control unit 2011 is shown to have both the function of a residual vibration detection unit and the function of a control unit, but these functions may also be provided in different components.

[0101] The first control unit 2011 includes a first CPU 2111 and a first storage unit 2112.

[0102] The first storage unit 2112 may, for example, include various types of memory.

[0103] It should be noted that the first control unit 2011 may also be constructed using a microcomputer, for example.

[0104] The constant voltage signal generation unit 2041 generates and supplies a signal with a constant voltage. In this embodiment, the constant voltage is equivalent to a fixed potential VBS.

[0105] In this embodiment, the state in which the switch in the circuit is turned on is also called "on", and the state in which the switch is not turned on is also called "off".

[0106] It should be pointed out that, Figure 9 The first control unit 2011, first CPU 2111, first storage unit 2112, first drive signal generation unit 2021, and first head unit 301 shown are respectively located in... Figure 3 In the example, this corresponds to the control unit 6, CPU 61, storage unit 62, drive signal generation unit 33, and head unit 35.

[0107] The first head unit 301 includes a first a piezoelectric element 311a, a first a piezoelectric element 311b, a first a electrode 312a and a second a electrode 313a disposed above and below the first a piezoelectric element 311a, and a first a electrode 312b and a second a electrode 313b disposed above and below the first a piezoelectric element 311b.

[0108] Electrode 313a (2a) and electrode 313b (2b) are connected to a fixed potential VBS generated by the constant voltage signal generation unit 2041.

[0109] In this embodiment, two piezoelectric elements are shown in parallel, but the number of such piezoelectric elements can be arbitrary.

[0110] The first head unit 301 and the drive signals COMA, COMB, and COMC each have corresponding drive switches 321a, 321b, and 321c.

[0111] In this embodiment, a configuration is shown that allows switching between drive signals COMA, COMB, and COMC, each with a different waveform as the drive signal. However, the number of drive signals that can be switched is not particularly limited; for example, a single drive signal may also be used. That is, although three switches, drive switch 321a, drive switch 321b, and drive switch 321c, are shown in this embodiment, one or two of them may also be used.

[0112] One end of the drive switch 321a is connected to the terminal of the drive signal COMA.

[0113] One end of the drive switch 321b is connected to the terminal of the drive signal COMB.

[0114] One end of the drive switch 321c is connected to the terminal of the drive signal COMC.

[0115] The other end of drive switch 321a, the other end of drive switch 321b, the other end of drive switch 321c, one end of detection nozzle selection switch 321s, the first a electrode 312a, and the first b electrode 312b are electrically connected at the first node N1.

[0116] One end of the bias switch 322a is connected to the terminal of the drive signal COMA.

[0117] One end of the bias switch 322b is connected to the terminal of the drive signal COMB.

[0118] One end of the bias switch 322c is connected to the terminal of the drive signal COMC.

[0119] The other end of the nozzle selection switch 321s, one end of the first resistor 331, and one end of the first capacitor 341 are electrically connected at the third node N3.

[0120] The other ends of the first resistor 331, the other ends of the bias switch 322a, the other ends of the bias switch 322b, and the other ends of the bias switch 322c are electrically connected at the second node N2.

[0121] The drive switch 321a switches the connection state between the drive signal COMA and the first node N1 between being on and off.

[0122] The drive switch 321b switches the connection state between the drive signal COMB and the first node N1 between on and off states.

[0123] The drive switch 321c switches the connection state between the drive signal COMC and the first node N1 between on and off states.

[0124] Here, the three drive signals COMA to COMC are generated by the first drive signal generation unit 2021. The first drive signal generation unit 2021 is controlled by the first control unit 2011.

[0125] The first head unit 301 is equipped with a nozzle selection switch 321s.

[0126] The nozzle selection switch 321s is used to switch the connection status of the first node N1 and the third node N3 between on and off states.

[0127] Here, drive switches 321a, 321b, 321c, and the detection nozzle selection switch 321s are controlled by drive control unit 2031. Drive control unit 2031 is controlled by first control unit 2011.

[0128] Here, drive switches 321a, 321b, 321c and the detection nozzle selection switch 321s can also be constructed using a transfer gate (TG).

[0129] It should be noted that a transmission gate may have, for example, a P-channel transistor and an N-channel transistor connected in parallel, but it may also be constructed from transistors of either channel.

[0130] The first head unit 301 and the drive signals COMA, COMB, and COMC each have a bias switch 322a, a bias switch 322b, and a bias switch 322c respectively.

[0131] Here, bias switches 322a, 322b, and 322c correspond to drive switches 321a, 321b, and 321c, respectively. If a portion of drive switches 321a, 321b, and 321c is not present, then a portion of bias switches 322a, 322b, and 322c is also not present.

[0132] The bias switch 322a switches the connection state between node N3 and drive signal COMA between on and off.

[0133] The bias switch 322b switches the connection state between node N3 and drive signal COMB between on and off.

[0134] The bias switch 322c switches the connection state between node N3 and drive signal COMC between on and off.

[0135] Here, bias switches 322a, 322b, and 322c are controlled by drive control unit 2031. Drive control unit 2031 is controlled by first control unit 2011.

[0136] Here, bias switches 322a, 322b, and 322c can also be constructed using transmission gates, for example.

[0137] The first head unit 301 includes a first resistor 331, a high-pass filter (HPF) 411, a gain adjustment unit 412, a buffer unit 413, and a third-second switch 371.

[0138] In this embodiment, a residual vibration waveform acquisition unit 414 is configured by a high-pass filter 411, a gain adjustment unit 412, and a buffer unit 413 to acquire the waveform of the residual vibration.

[0139] The high-pass filter 411 includes a first capacitor 341, a second resistor 342, and a detection switch 343.

[0140] The gain adjustment unit 412 includes a first operational amplifier 351, a third resistor 352, and a fourth resistor 353.

[0141] The buffer section 413 includes a second operational amplifier 361 and a peak hold circuit 362.

[0142] In this embodiment, the peak value of the signal detected by the second operational amplifier 361 can be held and output by the peak hold circuit 362. This peak value is, for example, the maximum or minimum point of the signal.

[0143] In this embodiment, the buffer unit 413 is shown to have a peak holding circuit 362 for peak holding. However, as another example, the buffer unit 413 may not have the peak holding circuit 362, but the first control unit 2011 may have the function of a peak holding circuit. In this case, the function of the peak holding circuit may be implemented, for example, by a processor executing a predetermined program. In this way, the peak value of the detection signal may also be processed by the first control unit 2011, etc.

[0144] In this embodiment, the gain adjustment unit 412 is composed of a negative feedback type amplifier using the first operational amplifier 351. By adjusting the midpoint of the third resistor 352 and the fourth resistor 353, which are variable resistors that divide the output signal, the amplitude of the output signal can be adjusted.

[0145] Furthermore, the second operational amplifier 361 of the buffer section 413 performs impedance conversion to output a low-impedance detection signal. In this embodiment, the second operational amplifier 361, which functions as a buffer, is composed of a voltage follower.

[0146] It should be noted that, for example, a low-pass filter may also be provided between the gain adjustment unit 412 and the buffer unit 413.

[0147] This low-pass filter attenuates the high-frequency components of the signal. For example, it can be a multiple-feedback type using an operational amplifier, attenuating frequency components higher than the residual vibration frequency band. By using this low-pass filter to limit the detection frequency range, noise components can be removed.

[0148] The first resistor 331 functions as a bias resistor to supply the voltage of the drive signal COMA, drive signal COMB, or drive signal COMC.

[0149] The other end of the first capacitor 341 is connected to the + input terminal of the first operational amplifier 351.

[0150] The other end of the first capacitor 341, the + input terminal of the first operational amplifier 351, one end of the second resistor 342, and one end of the detection switch 343 are electrically connected at the fourth node N4.

[0151] The other end of the second resistor and the other end of the detection switch 343 are connected to analog ground AGND.

[0152] The detection switch 343 is controlled by the drive control unit 2031. The drive control unit 2031 is controlled by the first control unit 2011.

[0153] Here, the potential of the simulated ground AGND is set, for example, to the center potential between the high power supply potential and the low power supply potential of the buffer section 413.

[0154] The detection switch 343 can also be constructed using a transmission gate, for example.

[0155] The output terminal of the first operational amplifier 351 is connected to the + input terminal of the second operational amplifier 361.

[0156] The third resistor 352 and the fourth resistor 353 are connected in series between the point between the output terminal of the first operational amplifier 351 and the + input terminal of the second operational amplifier 361 and the analog ground AGND.

[0157] The input terminal of the first operational amplifier 351, one end of the third resistor 352, and one end of the fourth resistor 353 are electrically connected at the fifth node N5.

[0158] The input terminal of the second operational amplifier 361 is connected to the output terminal.

[0159] The output terminal of the second operational amplifier 361 is connected to one end of the third switch 371.

[0160] The other end of the 3s switch 371 is connected to the output terminal of the residual vibration signal.

[0161] The 3s switch 371 is controlled by the drive control unit 2031. The drive control unit 2031 is controlled by the first control unit 2011.

[0162] The 3s switch 371 can also be constructed using a transmission gate, for example.

[0163] The residual vibration signal of the waveform acquired by the residual vibration waveform acquisition unit 414 is output from the output terminal via the buffer unit 413 and the 3s switch 371.

[0164] The NVTS terminal output, which is the output from this output terminal, is input to the first control unit 2011 via the A / D converter 391.

[0165] The A / D converter 391 performs A / D conversion on the residual vibration signal, which is an analog signal output from the output terminal, and outputs the resulting digital signal to the first control unit 2011.

[0166] It should be noted that the function of the A / D converter 391 can also be implemented in other parts, for example, the function of the A / D converter 391 can also be implemented inside the first control unit 2011.

[0167] exist Figure 9 In the example, drive switches 321a, 321b, and 321c are switches used to selectively apply drive signals COMA, COMB, and COMC to the first node N1, respectively.

[0168] In addition, the detection nozzle selection switch 321s is a switch used to switch between a state in which residual vibration signals can be supplied to the residual vibration signal detection unit and a state in which residual vibration signals cannot be supplied to the residual vibration signal detection unit by switching the connection state of the first node N1 and the third node N3 between on and off.

[0169] In addition, bias switches 322a, 322b, and 322c are used to selectively apply drive signals COMA, COMB, and COMC to the second node N2, respectively.

[0170] In addition, the detection switch 343 is a switch used to switch between a state where residual vibration signals cannot be supplied to the residual vibration signal detection unit and a state where residual vibration signals can be supplied to the residual vibration signal detection unit by switching the connection state of the fourth node N4 and AGND between on and off.

[0171] Additionally, the third switch 371 is a switch used to switch between a state in which residual vibration signals can be supplied to the residual vibration signal detection unit and a state in which residual vibration signals cannot be supplied to the residual vibration signal detection unit by switching the connection state between the peak holding circuit 362 and the NVTS terminal, which is the output terminal, between on and off.

[0172] In this embodiment, during the printing operation, a test drive signal is applied to the first a piezoelectric element 311a and the first b piezoelectric element 311b, and the residual vibration detection unit detects the residual vibration, which is a pressure change within the cavity, as a change in the electromotive force of the first a piezoelectric element 311a and the first b piezoelectric element 311b. The drive control unit 2031 supplies the test drive signal to the first a piezoelectric element 311a and the first b piezoelectric element 311b based on the control signal. On the other hand, when detecting residual vibration, the electromotive force of the first a piezoelectric element 311a and the first b piezoelectric element 311b is supplied to the residual vibration detection unit.

[0173] The residual vibration detection unit detects the signal representing the change in electromotive force of the first piezoelectric element 311a and the first piezoelectric element 311b as a residual vibration signal.

[0174] Although Figure 9Detailed illustrations are omitted in the example, but the first head unit 301 and each of the multiple nozzles are equipped with multiple piezoelectric element sections. Each piezoelectric element section is composed of one or more piezoelectric elements.

[0175] exist Figure 9 In the example shown, a combination of two piezoelectric elements, namely piezoelectric element 311a and piezoelectric element 311b, is used as the piezoelectric element part, but it is not limited to this. For example, one piezoelectric element can also be used as a single unit.

[0176] Drive switches 321a to 321c are in an ON state when their respective control signals are high, applying drive signals to the first a piezoelectric element 311a and the first b piezoelectric element 311b. Conversely, they are in an OFF state when their respective control signals are low, not applying drive signals to the first a piezoelectric element 311a and the first b piezoelectric element 311b. In other words, drive switches 321a to 321c are configured to switch between applying each drive signal to the first a piezoelectric element 311a and the first b piezoelectric element 311b.

[0177] On the other hand, when the nozzle selection switch 321s is in the ON state with a high control signal, it applies the electromotive force change of the first a piezoelectric element 311a and the first b piezoelectric element 311b to the third node N3. Conversely, when the control signal is in the OFF state with a low control signal, it does not apply the electromotive force change of the first a piezoelectric element 311a and the first b piezoelectric element 311b to the third node N3. That is, the nozzle selection switch 321s can switch whether the electromotive force change of the first a piezoelectric element 311a and the first b piezoelectric element 311b is applied to the third node N3.

[0178] Thus, when the nozzle selection switch 321s is in the off state, it is in a state where it cannot supply a signal to the residual vibration signal detection unit, and when it is in the on state, it is in a state where it can supply a signal to the residual vibration signal detection unit.

[0179] It should be noted that in this embodiment, the timing for switching drive switches 321a to 321c from on to off and the timing for switching detection switch 343 from on to off are set to the same timing.

[0180] In other words, at the same time that the drive switches 321a to 321c switch from being on to being off and stop supplying drive signals to the first piezoelectric element 311a and the first piezoelectric element 311b, the detection switch 343 switches from being on to being off and applies the electromotive force change of the first piezoelectric element 311a and the first piezoelectric element 311b to the fourth node N4, thereby becoming a state in which a signal can be supplied to the residual vibration signal detection unit.

[0181] Bias switches 322a to 322c are in the ON state when their respective control signals are high, and in the OFF state when their respective control signals are low.

[0182] The detection switch 343 is in the ON state when the control signal is high and in the OFF state when the control signal is low.

[0183] By turning on the detection switch 343, the potential of the input terminal of the buffer section 413 can be clamped to analog ground AGND.

[0184] The 3s switch 371 is in the ON state when the control signal is high, and in the OFF state when the control signal is low.

[0185] However, the maximum potential of the drive signal in this embodiment is 42V, while the high power supply potential of the buffer unit 413 is 3.3V and the low power supply potential is 0V. This is because a large-amplitude drive signal is required to drive the first a piezoelectric element 311a and the first b piezoelectric element 311b, while the buffer unit 413 is an analog signal processing circuit and does not require a large dynamic range.

[0186] The changes in the electromotive force (starting voltage) of the first piezoelectric element 311a and the first piezoelectric element 311b reflect the changes in pressure inside the cavity. Therefore, the frequency band of the residual vibration is narrower than the frequency band of the driving signal. On the other hand, noise may sometimes be superimposed on the signal path of the residual vibration. The high-pass filter 411 attenuates frequency components in the frequency band lower than that of the residual vibration. This improves the accuracy of the residual vibration detected by the residual vibration detection unit.

[0187] Furthermore, in the high-pass filter 411, the DC component is cut off by the first capacitor 341. Since the potential of the residual vibration amplitude is low compared to the maximum potential of the drive signal, it is not suitable for DC coupling. In this embodiment, by cutting off the DC component with the high-pass filter 411, the buffer section 413 of the subsequent stage can operate normally.

[0188] Furthermore, the detection switch 343 becomes closed except during the period of detecting residual vibration, and the fourth node N4 is clamped to the analog ground AGND.

[0189] That is, during the period when the drive signal of the first capacitor 341 and the potential on the piezoelectric element side change significantly, the detection switch 343 is turned on. Even if the DC component is cut off by the first capacitor 341, when the potential changes significantly, the potential of the fourth node N4 also changes significantly.

[0190] In electronic circuits, when a large-amplitude signal exceeding the dynamic range is supplied, charge is deposited throughout the circuit components, sometimes requiring a long time to return to normal operation. Furthermore, it is necessary to increase the voltage withstand capability of components such as transistors that make up the electronic circuit.

[0191] In contrast, in this embodiment, by turning on the detection switch 343 during the period of a large change in the potential on the piezoelectric element side of the drive signal of the first capacitor 341 and clamping the potential of the input terminal of the buffer section 413 to analog ground AGND, the detection of residual vibration can be started immediately during the detection period, thereby reducing the withstand voltage of the components constituting the buffer section 413.

[0192] Figure 10 This is a diagram illustrating an example of the control content involved in the implementation method.

[0193] Figure 10 The control contents table 3011, LAT internal signal 3021, TSIG internal signal 3022, states ST1 to ST5, and piezoelectric element drive signal 3023 for drive signal COM are shown.

[0194] Control content table 3011 shows timing, pulse edge, status, action, and detection status.

[0195] As an example, the NVTS terminal outputs, TG_A / B / C, TG_N, SW_A / B / C, and SHT_SW are shown.

[0196] As a timing indicator, the first pulse of TSIG and the second pulse of TSIG are shown after the rise of LAT.

[0197] As pulse edges, rising edge and falling edge are shown.

[0198] The states ST1 to ST5 are shown as states.

[0199] The NVTS terminal output represents the output of the residual vibration signal. As the NVTS terminal output, the HiZ value representing high impedance and the detection state representing the state of residual vibration detection are shown.

[0200] As shown in TG_A / B / C, the on / off switching states of drive switches 321a, 321b, and 321c are illustrated. It should be noted that... Figure 10 In the example, for the sake of simplicity, the on / off state of the three switches is shown in summary.

[0201] As TG_N, the on / off switching state of the nozzle selection switch 321s is displayed.

[0202] As shown in SW_A / B / C, the on / off switching states of bias switches 322a, 322b, and 322c are illustrated. It should be noted that... Figure 10 In the example, for the sake of simplicity, the on / off state of the three switches is shown in summary.

[0203] As SHT_SW, the on / off switching state is shown for detection switch 343.

[0204] Next, the operation of each switch will be explained.

[0205] To show Figure 10 The timing diagrams of the actions of each switch shown are used as an example for explanation.

[0206] Figure 11 This is an explanatory diagram showing the on and off states of the switches during states ST1 and ST5.

[0207] Figure 12 This is an explanatory diagram showing the on and off states of the switches during states ST2 and ST4.

[0208] Figure 13 This is an explanatory diagram showing the on and off states of the switch during state ST3.

[0209] It should be noted that, in this example, it is assumed that the target is the same as the target. Figure 9 The nozzles 241 corresponding to the first piezoelectric element 311a and the first piezoelectric element 311b shown detect the ejection state of ink droplets.

[0210] In addition, in this example, the case where the drive is performed according to the drive signal COMA is shown. Regarding the drive signals COMB and COMC, which are other drive signals, the drive switches 321b and 321c are always off, and the bias switches 322b and 322c are always off.

[0211] exist Figures 11 to 13 In the example, the circuit section related to the drive signal COMA is shown, while the circuit sections related to the drive signals COMB and COMC are omitted.

[0212] It should be noted that the operation is the same when driving based on drive signal COMB or drive signal COMC, which are other drive signals, as it is when driving based on drive signal COMA.

[0213] During state ST1, the drive signal COMA includes a check pulse P1. During state ST1, TG_A is on, TG_N is off, SW_A is off, and SHT_SW is on. Therefore, the states of drive switch 321a, nozzle selection switch 321s, and detection switch 343 become... Figure 11 The state shown.

[0214] When the drive switch 321a is turned on and a test pulse P1 is applied to the first a electrode 312a and the first b electrode 312b, the first a piezoelectric element 311a and the first b piezoelectric element 311b flex in the direction of introducing the ink droplet into the cavity in sync with the rising edge of the test pulse P1, and flex in the direction of expelling the ink droplet from the cavity in sync with the falling edge of the test pulse P1.

[0215] Here, the amplitude, phase, and fall time of the inspection pulse P1 can be adjusted so that ink droplets are not ejected from the nozzle 241, or ink droplets can be ejected from the nozzle 241 using the inspection pulse P1. When the inspection pulse P1 is a waveform corresponding to no ejection, residual vibration can be detected during normal printing. On the other hand, when the inspection pulse P1 is a waveform corresponding to ejection, it is sufficient to move the head unit 35 to a position offset from the recording paper and eject ink droplets.

[0216] Next, during state ST2, the drive signal COMA is at the specified potential Vx. During state ST2, TG_A, TG_N, SW_A, and SHT_SW are on, therefore the drive switch 321a, the detection nozzle selection switch 321s, the bias switch 322a, and the detection switch 343 are on. As a result, as... Figure 12 As shown, the potential of the second node N2 becomes the specified potential Vx, and the potential of the third node N3 also becomes the specified potential Vx.

[0217] Next, during state ST3, the drive signal COMA is at the specified potential Vx. During state ST3, TG_N and SW_A remain on, therefore the nozzle selection switch 321s is on. On the other hand, since TG_A and SHT_SW are off, the drive switch 321a and the detection switch 343 are off. As a result, as Figure 13 As shown, with the potential of the second node N2 becoming the specified potential Vx and the potential of the third node N3 being biased through the first resistor 331, the electromotive force generated in the first a piezoelectric element 311a and the first b piezoelectric element 311b is extracted as the first output signal OUT1 via the high-pass filter 411.

[0218] In this example, the detection start timing is the timing of the switch from state ST2 to state ST3, which is the timing of the TSIG pulse falling.

[0219] Next, during state ST4, the drive signal COMA is at the specified potential Vx. During state ST4, similarly to state ST2, TG_A, TG_N, SW_A, and SHT_SW are on, therefore drive switch 321a, nozzle selection switch 321s, bias switch 322a, and detection switch 343 are on. As a result, as... Figure 12 As shown, the potential of the second node N2 becomes the specified potential Vx, and the potential of the third node N3 also becomes the specified potential Vx.

[0220] Next, during state ST5, similarly to state ST1, TG_A is on and SHT_SW is on, thus driving switch 321a and detection switch 343 are on. On the other hand, since TG_N is off, the detection nozzle selection switch 321s is off. As a result, as Figure 11 As shown, the drive signal COMA is applied to the first a electrode 312a and the first b electrode 312b via the drive switch 321a. Additionally, since SHT_SW is turned on, the potential of the fourth node N4 is clamped to analog ground AGND.

[0221] Here, if the first state is when the drive switch 321a is on and the nozzle selection switch 321s is off, the second state is when the drive switch 321a is on and the nozzle selection switch 321s is on, and the third state is when the drive switch 321a is off and the nozzle selection switch 321s is on, then the drive control unit 2031 controls the drive switch 321a and the nozzle selection switch 321s in the order of state ST1 (first state) → state ST2 (second state) → state ST3 (third state). Alternatively, the drive control unit 2031 controls the drive switch 321a and the nozzle selection switch 321s in the order of state ST3 (third state) → state ST4 (second state) → state ST5 (first state).

[0222] Thus, the reason for setting the second state midway through the transition from the first state to the third state and midway through the transition from the third state to the first state is to prevent switching noise from occurring due to the change in the potential of the third node N3 at the time points when switching the on state of the drive switch 321a and the on state of the nozzle selection switch 321s.

[0223] That is, in the second state, the specified potential Vx of the drive signal COMA is supplied to the third node N3 via the path of drive switch 321a → first node N1 → detection nozzle selection switch 321s, and the specified potential Vx of the drive signal COMA is supplied to the third node N3 via the path of second node N2 → first resistor 331.

[0224] When transitioning from the second state to the third state, the drive switch 321a turns off, but the path from the second node N2 to the first resistor 331 remains open. The specified potential Vx of the drive signal COMA is biased to the third node N3 through the first resistor 331. Therefore, the potential of the third node N3 does not change significantly when transitioning from the first state to the third state, thus reducing switching noise. Furthermore, by controlling the drive switch 321a and the detection nozzle selection switch 321s in the order of first state → second state → third state, the current from the first piezoelectric element 311a and the first piezoelectric element 311b can flow continuously, thus eliminating the generation of surge voltage during switching due to the back electromotive force of the coil. As a result, residual vibration can be detected simultaneously with the start state ST3.

[0225] Furthermore, when transitioning from the second state to the first state, the detection nozzle selection switch 321s is switched to the off state. However, in the second state, a drive signal COMA is also applied to the first a piezoelectric element 311a and the first b piezoelectric element 311b via the drive switch 321a. The potential of the second node N2 becomes the specified potential Vx of the drive signal COMA. Therefore, the noise of the applied voltage superimposed on the first a piezoelectric element 311a and the first b piezoelectric element 311b can be reduced.

[0226] In addition, during states ST1 and ST5 (first state) and ST2 and ST4 (second state), the detection switch 343 is in the ON state, therefore the potential of the fourth node N4 is clamped to analog ground AGND. Figures 11 to 13 As shown, a parasitic capacitance Ca exists between the supply line to which the drive signal COMA is supplied and the supply line connected to the third node N3 and supplied with an electromotive force based on residual vibration. Therefore, during state ST1, even if the detection nozzle selection switch 321s is in the off state, the large-amplitude inspection pulse P1 will still be transmitted to the third node N3 via the parasitic capacitance Ca. According to this embodiment, during state ST1 and state ST2, the detection switch 343 is in the on state, and the fourth node N4 is clamped to the analog ground AGND. Therefore, it is possible to prevent the inspection pulse P1 from interfering with the residual vibration detection unit.

[0227] Figure 14This is a diagram illustrating an example of the correspondence between the timing of the signal TSIG and the output signal NVTS in an embodiment.

[0228] exist Figure 14 In the diagram, the horizontal axis represents time, and the vertical axis represents various voltage levels.

[0229] exist Figure 14 The diagram shows a single-timing piezoelectric element drive signal 3023, 10 signals TSIG1 to TSIG10 for each of the different timing input TSIG internal signals, and 10 output signals NVTS1 to NVTS10 generated by each of the 10 signals TSIG1 to TSIG10.

[0230] Here, the piezoelectric element drive signal 3023 is in Figure 9 In the example, the signal corresponds to the voltage of the drive signal COMA, drive signal COMB, or drive signal COMC.

[0231] Furthermore, since the pulse falling timings of signals TSIG1 to TSIG10 are different, therefore, Figure 9 The timing for switching the drive switches 321a, 321b, and 321c from on to off, as well as the timing for switching the detection switch 343 from on to off, also change to the corresponding timing.

[0232] In addition, output signals NVTS1 to NVTS10 are in Figure 9 In the example, the signal corresponds to the signal output from the NVTS terminal.

[0233] The following describes the changes in the output signal of the NVTS terminal when the internal signal of TSIG is input at different timings.

[0234] Generally, piezoelectric elements have the following properties: they deform when a voltage is applied by a drive signal, etc., and then return to their original shape when the applied voltage is stopped. Furthermore, it is known that the mechanical damping vibration generated when returning to the original shape becomes the back electromotive force (EMF) of the piezoelectric element. In this embodiment, when the deformed first piezoelectric element 311a and first piezoelectric element 311b return to their original shape, a back EMF originating from the mechanical damping vibration occurs in the first a electrode 312a and the first b electrode 312b, resulting in an electrically damped EMF. Assuming that the drive switches 321a, 321b, and 321c remain closed, the potential of the first a electrode 312a and the first b electrode 312b is fixed by the potential of the piezoelectric element drive signal 3023, therefore no back EMF occurs in the first a electrode 312a and the first b electrode 312b. On the other hand, when the drive switches 321a, 321b, and 321c switch from on to off, at that timing, the potential fixation of the first a electrode 312a and the first b electrode 312b generated by the potential of the piezoelectric element drive signal 3023 is eliminated. Therefore, a back electromotive force (EMF) appears in the first a electrode 312a and the first b electrode 312b, starting from the potential of the piezoelectric element drive signal 3023. Here, the back EMF is detected as a residual vibration signal at the NVTS terminal by the high-pass filter 411 at the timing when the detection switch 343 switches from on to off. Since this signal passes through the high-pass filter 411, it absorbs the difference of DC offset with a predetermined time constant, like... Figure 14 That is, the waveforms of the output signals NVTS1 to NVTS10 will be as shown. In other words, the greater the amplitude of the back electromotive force of the input high-pass filter 411 during the timing of the switching of the driving switches 321a, 321b, and 321c from on to off, the greater the influence caused by the transient response of the high-pass filter 411, and the greater the impact on the waveform of the residual vibration signal appearing in the output signal NVTS.

[0235] Because the residual vibration signal undergoes attenuation, the earlier the wave is detected at a given time, the larger the amplitude of the residual vibration signal. Therefore, the absolute value of this amplitude is more valuable for determining the nozzle condition. However, for the reasons mentioned above, based on the timing of the TSIG signal, the absolute value of the amplitude is like... Figure 14 If the output signals NVTS1 to NVTS10 deviate, the possibility of misjudgment increases.

[0236] Figure 15 This is a diagram illustrating an example of the processing performed in the first control unit 2011 according to the embodiment.

[0237] The processing of steps S1 to S7 will be explained.

[0238] In step S1, the first control unit 2011 performs initial settings to start detecting residual vibration signals. Then, it moves on to the processing in step S2.

[0239] Here, the timing used for this initial setting can be any timing, such as using the earliest possible timing.

[0240] In step S2, the first control unit 2011 detects the residual vibration signal using the function of the residual vibration detection unit and acquires the residual vibration signal detected by the residual vibration signal detection unit. Then, it transfers to the processing in step S3.

[0241] In step S3, the first control unit 2011 searches for the first maximum point of the residual vibration signal based on the acquired residual vibration signal and holds the result for a time A1. Then, it transfers to the processing in step S4.

[0242] In step S4, the first control unit 2011 searches for the next maximum point of the residual vibration signal based on the acquired residual vibration signal and holds the result for a time A2. Then, it transfers to the processing in step S5.

[0243] Here, the cases where the maxima of the residual vibration signal are used in the processing of step S4 and step S5 are shown, but as other examples, the minima can also be used instead of the maxima. For example, the period of the residual vibration can be determined based on one or more of the following: the time between adjacent maxima, the time between adjacent minima, the time between a maxima and its next adjacent minima, and the time between a minima and its next adjacent maxima.

[0244] In step S5, the first control unit 2011 calculates the period of the residual vibration signal based on the value obtained by subtracting time A1 from time A2, and calculates 1 / 4 of that period as the detection start shift timing. Then, it transfers to the processing in step S6.

[0245] In step S6, the first control unit 2011 sets the detection start timing to the value obtained by adding the detection start shift timing to time A1. Then, it transfers to the processing in step S7.

[0246] In step S7, the first control unit 2011 stores the detection start timing in the storage unit.

[0247] Then, the process ends.

[0248] As described above, in the first head unit 301 of this embodiment, when the timing of the residual vibration signal is misaligned, the level of the DC offset included in the detection result changes. Correspondingly, as a calibration process, control is performed to disconnect the piezoelectric element's drive at the convergence point of the residual vibration waveform based on information from at least two points of the residual vibration signal. This information may, for example, be information from the maximum or minimum points.

[0249] Therefore, in the first head unit 301 of this embodiment, the detection accuracy of residual vibration signals can be improved.

[0250] As one example, the first head unit 301 includes: an ejection section W1 that ejects liquid using a piezoelectric element, the piezoelectric element being displaced by a supplied drive signal; a residual vibration detection section that detects a residual vibration signal generated by the residual vibration of the ejection section W1, the residual vibration of the ejection section W1 being generated as the piezoelectric element is displaced; a first switch that switches whether a first drive signal is supplied to the piezoelectric element; a second switch that switches whether a residual vibration signal is supplied to the residual vibration detection section; and a control section that controls the first switch and the second switch.

[0251] The control unit obtains the detection start timing based on the poles of the residual vibration signal detected by the residual vibration detection unit.

[0252] The first switch is switched to not supply the first drive signal to the piezoelectric element at the start of the detection timing.

[0253] The second switch is switched at the start timing of the detection to supply a residual vibration signal to the residual vibration detection unit.

[0254] exist Figure 9 , Figure 10 , Figure 15 In the example, piezoelectric element 311a (1a) and piezoelectric element 311b (1b) are examples of piezoelectric elements.

[0255] exist Figure 9 , Figure 10 , Figure 15 In the example, drive signals COMA, COMB, and COMC are examples of the first drive signal.

[0256] exist Figure 9 , Figure 10 , Figure 15 In the example, drive switches 321a, 321b, and 321c are examples of the first switch.

[0257] exist Figure 9 , Figure 10 , Figure 15In the example, detection switch 343 is an example of a second switch.

[0258] exist Figure 9 , Figure 10 , Figure 15 In the example, the first control unit 2011 is an example of a control unit and also an example of a residual vibration detection unit.

[0259] exist Figure 9 , Figure 10 , Figure 15 In the examples, the maxima and minima are examples of poles.

[0260] As an example, the first head unit 301 includes a storage unit for storing the detection start timing obtained by the control unit.

[0261] Here, in Figure 9 , Figure 10 , Figure 15 In the example, the first storage unit 2112 is an example of a storage unit.

[0262] It should be noted that such a storage unit can also be located outside the first head unit 301.

[0263] As an example, in the first head unit 301, the residual vibration detection unit has a peak hold circuit.

[0264] Here, in Figure 9 , Figure 10 , Figure 15 In the example, the peak hold circuit 362 is one example of a peak hold circuit, but the first control unit 2011 can also have the function of a peak hold circuit. In this case, the function of the peak hold circuit can also be integrated with the function of the residual vibration detection unit.

[0265] It should be noted that the residual vibration detection unit can also be configured without a peak hold circuit.

[0266] As an example, in the first head unit 301, a high-pass filter 411 is provided in the front stage of the residual vibration detection unit.

[0267] It should be noted that the first head unit 301 can also be configured without a high-pass filter 411.

[0268] As an example, in the first head unit 301, a piezoelectric element is used to spray liquid into a medium.

[0269] As an example, in the first head unit 301, the piezoelectric element is a piezoelectric element used for inspection that is not used to spray liquid into the medium.

[0270] As an example, the liquid ejection device has a conveying mechanism L1 and a head unit.

[0271] As an example, the control method in the first head unit 301 performs control as described in this embodiment.

[0272] Reference Figures 16 to 18 This illustrates a specific example of the process for determining the timing of the start of detection.

[0273] Figure 16 This is a diagram illustrating an example of determining the start timing of residual vibration signal detection according to an embodiment.

[0274] exist Figure 16 In the diagram, the horizontal axis represents time, and the vertical axis represents the voltage level.

[0275] exist Figure 16 The first residual vibration signal 511 is shown in the figure.

[0276] In the first residual vibration signal 511, the time between the first maximum point 521 and the adjacent second maximum point 522 is determined as the difference time Tc.

[0277] Then, calculate 1 / 4 of the difference time Tc as the first shift time Ts.

[0278] The time of the result obtained by adding the first shift time Ts to the first maximum point 521 is set as the first detection start time 531.

[0279] Figure 17 This is a diagram illustrating an example of the timing for the start of detection of residual vibration signals according to an embodiment.

[0280] exist Figure 17 In the diagram, the horizontal axis represents time, and the vertical axis represents the voltage level.

[0281] exist Figure 17 The diagram shows the residual vibration signal 511a of the first a and its detection start timing 531a of the first a.

[0282] Figure 18 This is a diagram illustrating an example of the effect of adjusting the timing of the start of residual vibration signal detection according to the embodiment.

[0283] exist Figure 18 In the diagram, the horizontal axis represents time, and the vertical axis represents the voltage level.

[0284] exist Figure 18 The diagram shows a residual vibration signal 611 with offset, a residual vibration signal 612 without offset, an offset 621, and a threshold 631.

[0285] As time passes, the offset component of the offset residual vibration signal 611 decreases, and after a sufficient period of time, the offset residual vibration signal 611 overlaps with the unoffset residual vibration signal 612.

[0286] An error 641 occurs between the binarization result of threshold 631 used for the offset residual vibration signal 611 and the binarization result of threshold 631 used for the non-offset residual vibration signal 612.

[0287] In this embodiment, the error problem can be eliminated by adjusting the timing of the detection start of the residual vibration signal.

[0288] Typically, when analyzing waveforms obtained by piezoelectric conversion of residual vibrations, noise needs to be removed, and a high-pass filter is used to reduce the DC component.

[0289] However, when analyzing ejection correlation information based on the waveform of residual vibration, the action becomes unstable for the first waveform due to the transient response of the high-pass filter, resulting in waveform distortion. Therefore, for example, the first waveform may be masked, and a second and subsequent waveforms may be used for determination.

[0290] In response to this, in the first head unit 301 of this embodiment, the influence of waveform distortion caused by the transient response of the high-pass filter 411 used to remove DC components is reduced by bringing the timing of the convergence point of the residual vibration waveform.

[0291] Here, the convergence point of the residual vibration waveform is the point where the amplitude varies by ±0 in the direction of the amplitude.

[0292] As a calibration process, residual vibration is temporarily detected, and the period of residual vibration is inferred based on the time difference between the maximum and minimum values. At the start timing of residual vibration detection, the drive of the piezoelectric element is disconnected, and a residual vibration signal is supplied to the residual vibration detection unit. Therefore, in this embodiment, the first waveform of the residual vibration can be used for analysis.

[0293] Thus, in the first head unit 301 according to this embodiment, even when the front stage of the residual vibration detection unit is equipped with a high-pass filter 411, the influence of the transient response of the high-pass filter 411 can be reduced, and a residual vibration waveform with reduced waveform distortion caused by the transient response of the high-pass filter 411 can be obtained. Therefore, in the first head unit 301 according to this embodiment, the first waveform of the residual vibration is not distorted, and ejection correlation information can be obtained with excellent accuracy.

[0294] As a specific example, for the residual vibration signal after the actuator is driven, an example of timing optimization processing to start sensing the residual vibration signal is given.

[0295] For example, as a circuit to remove noise other than the main frequency components of residual vibration signals, an active bandpass filter (Act. BPF) using an operational amplifier is sometimes employed. In this case, a transient response occurs in the high-pass filter characteristics of the input stage of this circuit when the input voltage produces a DC step.

[0296] Furthermore, as a subsequent stage of an active bandpass filter, a circuit is sometimes used to convert the residual vibration signal of an analog quantity into a binary pulse using a comparator and to measure the period and phase of the residual vibration signal. As a method for converting to a binary pulse, for example, one can use one or more threshold voltages to convert it into one or more binary pulses.

[0297] In this case, the amplitude of the residual vibration signal is calculated based on the residual vibration signal as a decaying sine wave, and the pulse width of multiple pulses is converted.

[0298] However, in this configuration, the transient response component of the DC offset affects the accuracy of the period measurement.

[0299] For example, when using only information from the binarized pulse obtained through the comparator, even if the sensing timing that minimizes the transient response component is calculated, the accuracy of specifying the times of the maxima and minima will be insufficient, resulting in a decrease in the optimal accuracy of the timing for the start of detection of the residual vibration signal.

[0300] In this embodiment, such transient response components can be reduced, ideally minimizing them.

[0301] In this embodiment, for example, by storing information on the timing of the detection start of the residual vibration signal for each individual inkjet head, errors such as periodic measurements in subsequent stages of residual vibration signal processing can be reduced.

[0302] Specifically, in Figure 16 In the example, the period of the residual vibration signal becomes close to the value of the inherent vibration of the piezoelectric element.

[0303] In addition, such as Figure 17 As in the example, the timing of the switch that causes the switching drive signal applied to the piezoelectric element to be turned off is adjusted to the timing of the convergence point of the residual vibration waveform.

[0304] Here, the timing of the convergence point of the residual vibration waveform can, for example, be the point after 1 / 4 of the period from the maximum point of the waveform.

[0305] It should be noted that a minimum point can also be used instead of a maximum point.

[0306] Thus, for example, even if the residual vibration signal is distorted relative to the original actuator power-on signal at the sensing start timing due to the DC offset transient response when the residual vibration signal passes through the active bandpass filter, in this embodiment, the distortion can be reduced by adjusting the sensing start timing, and ideally minimized.

[0307] Therefore, in this embodiment, it is possible to infer the nozzle state by sensing the reverse-energizing signal caused by the residual vibration after being driven by the PZT actuator.

[0308] In this embodiment, by reducing the influence of the DC offset transient response of the active bandpass filter, it is possible to detect the component of the residual vibration signal caused by the original actuator drive.

[0309] Therefore, in this embodiment, for example, as Figure 18 In the example where the center level of the residual vibration signal is set as a threshold, and the period is calculated based on the time it takes for the residual vibration signal level to pass through the threshold, as in the case where the residual vibration signal level changes from a value less than the threshold to a value greater than the threshold or from a value greater than the threshold to a value less than the threshold, the error can be reduced and ideally minimized.

[0310] Furthermore, in this embodiment, for example, regarding the residual vibration signal, since the excess transient response component can be sufficiently reduced from the initial stage of sensing, high-precision amplitude measurement can be performed from the timing when the amplitude is large in the initial stage of the decay waveform.

[0311] For example, even if the amplitude of the residual vibration signal changes depending on the viscosity or other physical properties of the ejected liquid, this embodiment can use high-precision amplitude information to improve the accuracy of various determinations.

[0312] For example, the following process can be performed during the shipment inspection of inkjet heads: for each individual head, information on the optimal timing for sensing residual vibration signals is obtained according to the technology of this embodiment, and this information is stored in the memory built into the head. Thus, in a printer with the heads assembled, this information can be read from the memory and used as the timing information for sensing residual vibration signals.

[0313] For example, in a printer with a nozzle assembly, the following process can be performed: before determining nozzle leakage based on the sensing result of the residual vibration signal, information on the optimal timing for sensing the residual vibration signal is obtained according to the technology of this embodiment, and this timing information is stored as one of the information associated with the nozzle. Therefore, in this printer, when actually determining nozzle leakage, the timing information can be used as the sensing timing information when sensing the residual vibration signal.

[0314] For example, by optimizing the timing of the sensing start of the residual vibration signal according to the technique of this embodiment, the amplitude of the first waveform in the decay waveform can be obtained with excellent accuracy. This improves the accuracy of detecting or determining changes in residual vibrations caused by actuator displacement characteristics or time-deteriorated vibrations, and also improves the accuracy of detecting or determining changes in the attenuation ratio of residual vibrations caused by changes in the viscosity of the ejected liquid.

[0315] Here, the piezoelectric element used for detecting residual vibration in order to determine the detection start timing and the piezoelectric element used for detecting residual vibration using the detection start timing determined therefrom can, for example, be the same piezoelectric element, or different piezoelectric elements can be used.

[0316] For example, in a configuration that uses a piezoelectric element that is actually used for ejection for detection of the start timing, there is an effect that the head unit can be omitted.

[0317] As another example, a configuration can be used that has a separate piezoelectric element for detecting the start timing, from the piezoelectric element actually used for ejection.

[0318] In addition, in this embodiment, the following situation is shown: when the residual vibration has multiple decaying waveforms, the detection accuracy is improved by detecting the first waveform of the residual vibration, and the accuracy of the ejection correlation information is improved by obtaining the ejection correlation information based on its detection result. However, as another example, the configuration of detecting the second or subsequent waveforms of the residual vibration can also be used.

[0319] Alternatively, it can be used to detect the composition of any two or more waveforms when the residual vibration has multiple decaying waveforms.

[0320] In addition, in this embodiment, the point offset from the maximum or minimum point of the residual vibration by 1 / 4 period is regarded as the convergence point of the residual vibration waveform and is set as the start timing for residual vibration detection. However, as another example, the period obtained by adding an integer multiple of 1 / 2 period to 1 / 4 period, such as 3 / 4 period or 5 / 4 period, can be used instead of 1 / 4 period.

[0321] Furthermore, the convergence point of the residual vibration waveform may not necessarily be a strict convergence point location, and may also include errors.

[0322] This error can be, for example, 1 / 8 of a period, which is equivalent to 360 degrees, and therefore can also be ±45 degrees.

[0323] In this embodiment, when there are multiple nozzles that each use a piezoelectric element, the control of the detection start timing of residual vibration detection and the application of the detection start timing can be performed, for example, on a per-nozzle basis or on a per-nozzle array consisting of a predetermined number of nozzles.

[0324] For example, the detection start time can be set for each of the multiple nozzles, and the average or median of their detection results can be applied to these multiple nozzles.

[0325] For example, the detection start timing can be tested for one or more representative nozzles, and the detection start timing based on the test results can be applied to one or more other nozzles.

[0326] For example, multiple tests can be performed on the same nozzle at the start time, and the average or median of these multiple test results can be applied.

[0327] In this embodiment, the timing of the detection of residual vibration needs to be performed at least once, but it can also be performed more than twice.

[0328] For example, in the head unit, the following process can also be performed: when using the nozzle, the detection start timing of residual vibration is detected and updated each time.

[0329] For example, in the head unit, the following process can also be performed: the detection start time of residual vibration is detected and updated at specified intervals. This specified interval can also be a periodic period.

[0330] For example, in the head unit, the following process can also be performed: if the ink used or the air pressure during use changes, the detection start timing of residual vibration can be detected and updated.

[0331] In this embodiment, the process of detecting and storing the detection start timing of residual vibration can be performed, for example, before the head unit or the liquid ejection device equipped with the head unit is shipped, or it can be performed after they are shipped.

[0332] For example, in inkjet printers, residual vibration detection can be performed and stored at any time after shipment, starting the timing process.

[0333] In head units or liquid ejection devices equipped with head units, a mode can also be set up to detect and store residual vibration at the start time of detection. This mode can also be called a calibration mode, etc.

[0334] In the head unit or liquid ejection device equipped with a head unit, for example, calibration mode processing can be performed at the power-on timing or the reset timing.

[0335] In a head unit or a liquid ejection device equipped with a head unit, it is also possible to switch between a calibration mode and a mode that applies the detection start timing detected in the calibration mode. This mode may also be referred to as a sensing mode, for example.

[0336] A program for implementing the functions of any component in any of the devices described above can also be recorded on a computer-readable recording medium, and the computer system can read and execute the program. The term "computer system" here includes hardware such as an operating system or peripheral devices. "Computer-readable recording medium" refers to removable media such as floppy disks, optical disks, ROM (Read Only Memory), and CD (Compact Disc)-ROM, as well as storage devices such as hard disks built into a computer system. "Computer-readable recording medium" also includes media that retain programs for a certain period of time, such as volatile memory within a computer system acting as a server or client when the program is transmitted via a network such as the Internet or a communication line such as a telephone line. This volatile memory can also be RAM. The recording medium can also be a non-transitory recording medium.

[0337] The aforementioned program can also be transmitted from a computer system storing the program in a storage device or similar device to other computer systems via a transmission medium or through transmission waves in the transmission medium. The "transmission medium" for transmitting the program refers to a medium with the function of transmitting information, such as a network like the Internet or a communication line like a telephone line.

[0338] The program described above can also be a part of a program used to achieve the aforementioned functions. Alternatively, the program can be a program that can achieve the aforementioned functions by combining with programs already recorded in the computer system; this is known as a differential file. A differential file can also be called a differential program.

[0339] The functions of any component in any of the devices described above can also be implemented by a processor. The various processes in the embodiments can also be implemented by a processor that operates based on information such as programs and a computer-readable recording medium that stores such information. The processor can implement the functions of each component using separate hardware, or it can implement the functions of each component using integrated hardware. The processor includes hardware, which may include at least one of circuitry for processing digital signals and circuitry for processing analog signals. The processor may also be configured using one or more circuit devices or one or more circuit elements mounted on a circuit board, or both. As circuit devices, ICs or the like may be used; as circuit elements, resistors or capacitors or the like may be used.

[0340] A processor can also be a CPU. However, a processor is not limited to a CPU; it can also be various processors such as a GPU (Graphics Processing Unit) or a DSP (Digital Signal Processor). A processor can also be a hardware circuit formed by an ASIC (Application Specific Integrated Circuit). A processor can consist of multiple CPUs, or multiple hardware circuits formed by ASICs. A processor can also be a combination of multiple CPUs and multiple hardware circuits formed by ASICs. A processor can also include one or more amplifier circuits or filter circuits for processing analog signals.

[0341] The embodiments have been described in detail above with reference to the accompanying drawings, but the specific configuration is not limited to these embodiments, and also includes designs that do not depart from the spirit of this disclosure.

[0342] appendix

[0343] Example 1

[0344] A head unit, comprising:

[0345] The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal;

[0346] The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, which is generated as the piezoelectric element is displaced.

[0347] The first switch switches whether to supply a first drive signal to the piezoelectric element.

[0348] The second switch toggles whether to supply the residual vibration signal to the residual vibration detection unit; and

[0349] The control unit controls the first switch and the second switch.

[0350] The control unit determines the detection start timing based on the poles of the residual vibration signal detected by the residual vibration detection unit.

[0351] The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element.

[0352] The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

[0353] Example 2

[0354] According to the head unit described in Example 1, wherein...

[0355] The head unit includes a storage unit that stores the detection start timing acquired by the control unit.

[0356] Example 3

[0357] According to the head unit described in Configuration Example 1 or Configuration Example 2, wherein,

[0358] The residual vibration detection unit has a peak hold circuit.

[0359] Example 4

[0360] According to any one of the configuration examples 1 to 3, the head unit, wherein,

[0361] The stage before the residual vibration detection unit is equipped with a high-pass filter.

[0362] Example 5

[0363] According to any one of the configuration examples 1 to 4, the head unit, wherein,

[0364] The piezoelectric element is used to spray the liquid into the medium.

[0365] Example 6

[0366] According to any one of the configuration examples 1 to 4, the head unit, wherein,

[0367] The piezoelectric element is a piezoelectric element used for inspection that is not used to spray the liquid into the medium.

[0368] Example 7

[0369] A liquid ejection device comprising a conveying mechanism and a head unit,

[0370] The head unit includes:

[0371] The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal;

[0372] The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, which is generated as the piezoelectric element is displaced.

[0373] The first switch switches whether to supply a first drive signal to the piezoelectric element.

[0374] The second switch toggles whether to supply the residual vibration signal to the residual vibration detection unit; and

[0375] The control unit controls the first switch and the second switch.

[0376] The control unit determines the detection start timing based on the poles of the residual vibration signal detected by the residual vibration detection unit.

[0377] The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element.

[0378] The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

[0379] Example 8

[0380] One control method is the control method in the head unit.

[0381] The head unit includes:

[0382] The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal;

[0383] The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, which is generated as the piezoelectric element is displaced.

[0384] The first switch switches whether to supply a first drive signal to the piezoelectric element.

[0385] The second switch toggles whether to supply the residual vibration signal to the residual vibration detection unit; and

[0386] The control unit controls the first switch and the second switch.

[0387] In the control method,

[0388] The control unit determines the detection start timing based on the poles of the residual vibration signal detected by the residual vibration detection unit.

[0389] The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element.

[0390] The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

Claims

1. A head unit, characterized by, have: The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal; The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, the residual vibration of the ejector being generated with the displacement of the piezoelectric element, and the residual vibration detection unit includes a peak hold circuit for detecting the poles of the residual vibration signal. The first switch switches whether to supply a first drive signal to the piezoelectric element. The second switch switches whether to supply the residual vibration signal to the residual vibration detection unit. as well as The control unit controls the first switch and the second switch. The control unit determines the detection start timing based on the time difference between the poles of the residual vibration signal detected by the peak hold circuit of the residual vibration detection unit, and between adjacent maxima or minima of the residual vibration signal. The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element. The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

2. The head unit according to claim 1, characterized in that, The head unit includes a storage unit that stores the detection start timing obtained by the control unit.

3. The head unit according to claim 1 or 2, characterized in that, The head unit has a high-pass filter in front of the residual vibration detection unit.

4. The head unit according to claim 1 or 2, characterized in that, The piezoelectric element is used to spray the liquid into the medium.

5. The head unit according to claim 1 or 2, characterized in that, The piezoelectric element is a piezoelectric element used for inspection that is not used to spray the liquid into the medium.

6. A liquid discharge apparatus characterized by comprising: It has a conveying mechanism and a head unit. The head unit includes: The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal; The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, the residual vibration of the ejector being generated with the displacement of the piezoelectric element, and the residual vibration detection unit includes a peak hold circuit for detecting the poles of the residual vibration signal. The first switch switches whether to supply a first drive signal to the piezoelectric element. The second switch switches whether to supply the residual vibration signal to the residual vibration detection unit. as well as The control unit controls the first switch and the second switch. The control unit determines the detection start timing based on the time difference between the poles of the residual vibration signal detected by the peak hold circuit of the residual vibration detection unit, and between adjacent maxima or minima of the residual vibration signal. The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element. The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

7. A control method characterized by, It is the control method in the header unit. The head unit includes: The ejection section uses a piezoelectric element to eject liquid, and the piezoelectric element is displaced by being supplied with a drive signal; The residual vibration detection unit detects the residual vibration signal generated by the residual vibration of the ejector, the residual vibration of the ejector being generated with the displacement of the piezoelectric element, and the residual vibration detection unit includes a peak hold circuit for detecting the poles of the residual vibration signal. The first switch switches whether to supply a first drive signal to the piezoelectric element. The second switch switches whether to supply the residual vibration signal to the residual vibration detection unit. as well as The control unit controls the first switch and the second switch. In the control method, The control unit determines the detection start timing based on the time difference between the poles of the residual vibration signal detected by the peak hold circuit of the residual vibration detection unit, and between adjacent maxima or minima of the residual vibration signal. The first switch is switched at the detection start timing to not supply the first drive signal to the piezoelectric element. The second switch is switched at the detection start timing to supply the residual vibration signal to the residual vibration detection unit.

Images