Liquid discharge head, recording device, and driving method for liquid discharge head

Abstract

This liquid discharge head comprises: an actuator that generates pressure for discharging a liquid from a nozzle; and a drive assembly that outputs, to the actuator, a drive signal having a drive waveform corresponding to a discharge amount of the liquid such that the liquid is discharged or not discharged at the nozzle at a prescribed drive frequency. The drive assembly changes the drive waveform in response to a change in the drive frequency.

Description

Liquid ejection head, recording device, and method for driving the liquid ejection head

[0001] This disclosure relates to a liquid ejection head such as an inkjet head, a recording device having the liquid ejection head, and a method for driving the liquid ejection head.

[0002] Liquid ejection heads (e.g., inkjet heads) are known that eject liquid (e.g., ink) toward a medium (e.g., paper) (see, for example, Patent Documents 1 and 2 below). Such liquid ejection heads eject or not eject (in other words, remain in standby mode) liquid at a predetermined drive frequency. From another perspective, focusing on a single nozzle, and calling the reciprocal of the drive frequency the drive cycle, at each drive cycle, liquid is ejected to print on one pixel, or liquid is not ejected to prevent printing on the said pixel. Furthermore, the ejection of liquid in each drive cycle is performed by inputting a drive signal having a drive waveform corresponding to the amount of liquid ejected to an actuator that applies pressure to the liquid.

[0003] Here, for example, if liquid was discharged in the previous drive cycle and if no liquid was discharged in the previous drive cycle, the discharge characteristics (e.g., droplet flight velocity) may differ even if the same drive waveform drive signal is input to the actuator in the next drive cycle. This is due to factors such as the presence or absence of residual vibration of the liquid caused by the discharge in the previous drive cycle. Therefore, in Patent Documents 1 and 2, when discharging, the drive waveform is corrected according to the number of drive cycles in which no discharge has occurred since the last time a discharge occurred.

[0004] Japanese Patent Publication No. 2016-150548 Japanese Patent Publication No. 2020-142490

[0005] A liquid discharge head according to one aspect of the present disclosure comprises an actuator and a drive assembly. The actuator generates pressure for discharging liquid from a nozzle. The drive assembly outputs a drive signal having a drive waveform corresponding to the amount of liquid to be discharged to the actuator, such that the liquid is discharged or not discharged from the nozzle at a predetermined drive frequency. The drive assembly changes the drive waveform in response to a change in the drive frequency.

[0006] A recording device according to one aspect of the present disclosure includes a liquid discharge head and a controller that inputs control data to the liquid discharge head. The liquid discharge head includes an actuator and a drive assembly. The actuator generates pressure to discharge liquid from a nozzle. The drive assembly outputs a drive signal having a drive waveform corresponding to the amount of liquid discharged to the actuator so that the liquid is discharged or not discharged from the nozzle at a drive frequency specified from the control data. The controller changes the drive frequency. At least one of the drive assembly and the controller performs a process to change the drive waveform in response to the change in the drive frequency.

[0007] A method for driving a liquid discharge head according to one aspect of the present disclosure relates to a method for controlling a liquid discharge head having an actuator that generates pressure for discharging liquid from a nozzle. The driving method includes inputting a drive signal having a drive waveform corresponding to the amount of liquid discharged to the actuator so that the liquid is discharged or not discharged from the nozzle at a predetermined drive frequency. By inputting the signal, the drive frequency is changed, and the drive waveform is changed in accordance with the change in the drive frequency.

[0008] A side view of the recording device according to the embodiment. A plan view of the recording device of Figure 1. An exploded perspective view of the liquid discharge head according to the embodiment. A cross-sectional view of a part of the liquid discharge head of Figure 3. A diagram showing an example of a change in the drive frequency in the liquid discharge head. A diagram showing an example of the effect of a change in the drive frequency on liquid discharge. A diagram showing an example of a method for correcting the drive waveform in response to a change in the drive frequency. A diagram explaining the discharge frequency. A block diagram showing the configuration of the signal processing system of the recording device of Figure 1. A block diagram showing the configuration of the signal processing system of the liquid discharge head. A schematic diagram showing an example of a correction table that defines the correction rules for the drive waveform. A schematic diagram showing an example of a waveform table that defines the drive waveform. A part of a flowchart showing the procedure for the correction process according to the first example. Another part of the flowchart of Figure 13. Yet another part of the flowchart of Figure 14. A flowchart showing the procedure for the correction process according to the second example. A flowchart showing the procedure for the correction process according to the third example. A flowchart showing the procedure for a process that may be added to the correction process according to the first example.

[0009] (Outline of Embodiments) Figure 1 is a side view showing a printer 1 (an example of a recording device) according to an embodiment. Figure 2 is a top view of the printer 1. For convenience, Figure 1 is shown with a Cartesian coordinate system D1D2D3. The recording device, etc., according to the embodiment may be used in any orientation. However, for convenience, without further notice, an example may be given where the +D3 side is at the top, and expressions based on this configuration may be used.

[0010] The printer 1 includes one or more (multiple in the illustrated example) heads 3 (an example of a liquid ejection head) that eject liquid (e.g., ink), a transport device 5 that transports media P, and a controller 7 (Figure 1) that controls these. The transport device 5 transports the media P so that it passes below the head 3 on the +D2 side or the -D2 side. Then, an image is printed on the upper surface of the media P by ejecting liquid downward from the head 3.

[0011] In the description of the embodiments, for convenience, the terms "image" and "image data" may not be strictly distinguished. These terms may be substituted for each other as long as no inconsistencies arise.

[0012] Figure 4 is a cross-sectional view of the front part 9 that constitutes the lower surface of the head 3. The front part 9 (head 3) has a plurality of nozzles 11 that open on its lower surface. Figure 4 shows the portion corresponding to one nozzle 11. From the nozzles 11, droplets (e.g., ink droplets) for forming an image on the upper surface of the media P are ejected. The ejection of the droplets is achieved by applying pressure to the liquid by an actuator 13. The actuator 13 is driven when a drive signal is input.

[0013] Figure 6A shows an example of a drive signal SgD input to actuator 13. Note that a number may be added to the code "SgD" to distinguish between different drive signals, such as "SgD1". In Figure 6A, the horizontal axis represents time t, and the vertical axis represents potential V. The potential of the drive signal SgD changes over time. That is, the drive signal SgD has a waveform (sometimes called a "drive waveform"). In the illustrated example, the drive waveform is composed of a single rectangular pulse. The shape of the drive waveform corresponds to the discharge rate. For example, the larger the discharge rate, the larger the pulse height (potential difference) or the number of pulses.

[0014] Note that one drive signal SgD is a signal corresponding to the printing of one pixel (formation of one dot) on the media P. One dot may be formed by one droplet, or by multiple droplets landing at the same or close positions on the media P. When printing is not performed on a pixel (when no liquid is discharged), a signal (or, from another perspective, a potential that replaces the drive signal SgD) may or may not be input to the actuator 13. For convenience in describing the embodiments, the former signal may also be treated as a type of drive signal SgD.

[0015] Figure 5 is a schematic diagram illustrating the drive frequency F in printer 1. In this figure, the horizontal axis represents time. In the lower figure, the vertical axis represents the transport speed v of the media P. The upper figure schematically shows the situation in which a droplet LD is flying from top to bottom.

[0016] Figure 5 focuses on one nozzle 11 responsible for printing at a predetermined position in the D1 direction (a direction perpendicular to the media P transport direction). It also assumes a situation where no liquid is discharged and printing is continuously performed in the D2 direction (the media P transport direction) at the predetermined position.

[0017] The transport speed v of the media P gradually increases from, for example, the start of the transport device 5's operation (time t0), and remains constant from time t1 onward. From time t1 onward, droplets LD are ejected at regular drive cycles T. Because the transport speed v and drive cycle T are constant, pixels are printed on the media P at regular intervals (dots are formed at regular intervals).

[0018] The reciprocal of the drive cycle T is the drive frequency F (= 1 / T). In general printers, printing occurs only from time t1 onward, and never before time t1. The transport speed v and the constant drive frequency F from time t1 onward may be set by the manufacturer of the printer 1, or they may be set by the user before printing.

[0019] Here, for example, when printing is performed before time t1, the drive frequency F is changed in accordance with the change in transport speed v in order to keep the spacing of pixels on the media P in the D2 direction constant. Specifically, the faster the transport speed v, the higher the drive frequency F (shorter the drive period T). In this way, there are cases where it is desirable to change the drive frequency F during printing.

[0020] Furthermore, the printer 1 according to this embodiment changes the waveform of the drive signal SgD in accordance with the change in the drive frequency F during printing. For example, it changes the number of pulses, the pulse height, the pulse width, and / or the relative relationship of multiple pulses (relationship such as magnitude and / or timing).

[0021] Furthermore, if the drive frequency F is changed before or during printing, the length of the drive period T changes. For example, the duration of the portion of the drive signal SgD where the potential is constant at the beginning and / or end (the portion that does not constitute a pulse) changes. Changes in such portions that do not directly affect the ejection characteristics are not included in the changes in the drive waveform as referred to here.

[0022] Discharge characteristics include, for example, the velocity of the dispensed droplets (discharge rate) and / or the amount of liquid dispensed corresponding to one dot. In the description of the embodiments, only one of the discharge rate and the discharge rate may be mentioned as an example of discharge characteristics, but the terms discharge rate and discharge rate may be substituted for each other as long as no inconsistencies arise.

[0023] The effects of changing the waveform of the drive signal SgD in response to changes in the drive frequency F are as follows, for example:

[0024] Figure 6 is a schematic diagram showing the effect of changes in the drive frequency F on liquid discharge. Figure A has already been described. In Figure B, the horizontal axis corresponds to Figure A. The vertical axis shows the displacement x of the meniscus (not shown) in the nozzle 11 in the D3 direction. Line Ln1 shows an example of the change over time of the meniscus displacement x caused by the drive signal SgD1 in Figure A.

[0025] This example illustrates a so-called pull-and-shoot operation. Specifically, as the drive signal SgD falls, the meniscus is drawn into the nozzle 11 (see the first trough of line Ln1). Next, as the drive signal SgD rises, the meniscus moves in the direction of ejection from the nozzle 11 (see the first peak of line Ln1). This causes a droplet to be ejected. The meniscus continues to vibrate even after the droplet is ejected (residual vibration occurs).

[0026] Figure 6C illustrates the displacement x of the meniscus, assuming that a drive signal SgD with the same drive waveform is continuously input at a constant drive frequency F. In this figure, line Ln2 shows the change in displacement x over time caused by drive signal SgD2 in the next drive period T following drive signal SgD1. However, residual vibration of line Ln1 is not considered in line Ln2. Lines Ln3, Ln4, and Ln5, similar to line Ln2, show the change in displacement x over time caused by drive signals SgD that follow drive signal SgD2 in sequence.

[0027] In Figure 6, Part C, the first peak of each vibration shown by lines Ln2 to Ln5, corresponding to the ejection, overlaps with the trough of the residual vibration generated by the ejection preceding that peak. As a result, the vibrations shown by lines Ln1 to Ln5 cancel each other out. In this case, for example, the ejection velocity of the droplets corresponding to lines Ln2 to Ln5 will be slower than the expected ejection velocity. Also, the ejection amount corresponding to one pixel will be less than the intended amount.

[0028] Figure 6D is similar to Figure C. However, the drive period T in Figure D is different from the drive period T in Figure C. Furthermore, in each of the vibrations shown by lines Ln2 to Ln5, the first peak corresponding to the ejection overlaps with the peak of the residual vibration generated by the ejection preceding that peak. As a result, the vibrations shown by lines Ln1 to Ln5 reinforce each other. In this case, for example, the ejection velocity of the droplets corresponding to lines Ln2 to Ln5 will be faster than the expected ejection velocity. Also, the ejection amount corresponding to one pixel will be greater than the intended amount.

[0029] As shown after time t1 in Figure 5, when a single nozzle 11 continuously discharges at a constant drive frequency F, the influence each discharge receives from the previous discharge is the same across multiple discharges, as can be seen from Figure C or D in Figure 6. Therefore, the probability of variations in discharge characteristics is low. However, as shown before time t1, when the drive frequency F changes, the influence each discharge receives from the previous discharge changes, as can be seen from the different effects of residual vibration in Figures C and D in Figure 6. As a result, the probability of variations in discharge characteristics increases.

[0030] Accordingly, by changing the drive waveform in accordance with the change of the drive frequency F, the variation in the ejection characteristics as described above can be reduced. For example, when the drive frequency F changes and the state shown in diagram C of FIG. 6 is reached, the drive waveform is corrected so as to increase the ejection speed. Further, for example, when the drive frequency F changes and the state shown in diagram D of FIG. 6 is reached, the drive waveform is corrected so as to decrease the ejection speed.

[0031] It should be noted that the above-described effects do not necessarily have to be achieved. FIG. 5 is merely an example of a case where it is desired to change the drive frequency F, and the change of the drive frequency F does not presuppose the change of the conveyance speed v shown in FIG. 5. For example, the drive frequency F may be changed in order to change the resolution in the D2 direction. Further, although attention is focused on acceleration in FIG. 5, the same applies to deceleration. Different technical ideas may be extracted from the present disclosure from the above viewpoint. In this case, for example, a change in the drive frequency F does not have to be an essential requirement, and changing the drive waveform in accordance with a change in the drive frequency F does not have to be an essential requirement.

[0032] The above is the outline of the embodiment. Hereinafter, the details of the embodiment will be generally described in the following order. 1. Printer (Figs. 1 and 2) 2. Head (Figs. 3 and 4) 2.1. Entire head 2.2. Front part 3. Correction method for drive waveform 3.1. Specific example of correction method (Fig. 7) 3.2. Ejection frequency (Fig. 8) 4. Configuration of signal processing system 4.1. Functional blocks 4.1.1. Functional block of controller (Fig. 9) 4.1.2. Functional block of head (Fig. 10) 4.2. Data (Figs. 11 and 12) 5. Specific procedure of correction 5.1. First example (Figs. 13 to 15) 5.2. Second example (Fig. 16) 5.3. Third example (Fig. 17) 5.4. Additional processing (Fig. 18) 6. Summary of the embodiment

[0033] (1. Printer) The configuration of the printer 1 may be various configurations except for the configuration for changing the drive waveform in accordance with a change in the drive frequency F. For example, the printer 1 may have a known configuration. The printer 1 illustrated in FIG. 1 and FIG. 2 is merely an example. Hereinafter, the overall printer 1 will be briefly described by taking the printer 1 shown in FIG. 1 and FIG. 2 as an example.

[0034] In the printer 1, as shown in FIG. 2, one head unit 15 is constituted by a plurality of (five in the illustrated example) heads 3. In each head unit 15, the five heads 3 are arranged in a staggered manner so that no gap is generated in the D1 direction when viewed in the D2 direction. The printable range of each head unit 15 substantially covers the width (the D1 direction) of the medium P. An image is formed when the head 3 ejects ink droplets while the medium P passes under the head 3.

[0035] As can be understood from the above, the printer 1 is configured as a so-called line printer. However, the printer 1 is not limited to a line printer. For example, the printer 1 may be a serial printer. In a serial printer, for example, the operation of moving a head (head unit) in a direction intersecting the conveyance direction of the medium P and the conveyance of the medium P are alternately performed. In the description of the embodiment, for convenience, description may be made on the premise of a line printer without particular notice.

[0036] The printer 1 includes a plurality of (four in the illustrated example) head units 15. The four head units 15 are arranged, for example, in the conveyance direction of the medium P. The five heads 3 in each head unit 15 correspond to ink of the same color. The four head units 15 correspond to inks of different colors (four-color inks). The four-color inks are, for example, magenta (M), yellow (Y), cyan (C) and black (K). Accordingly, the printer 1 functions as a color printer.

[0037] Contrary to the above explanation, printer 1 may perform single-color printing, or conversely, print with more than four colors. In other words, the number of colors is arbitrary. Also, two or more head units 15 may correspond to one color. Conversely, one head unit 15 may correspond to two or more colors, for example, by having one head 3 correspond to two or more colors. The number of heads 3 included in one head unit 15 is arbitrary, and it may be just one. As can be understood from the above, the number of heads 3 that printer 1 has is arbitrary.

[0038] In each head unit 15, the configuration for fixing the multiple heads 3 to each other is arbitrary. Figures 1 and 2 illustrate a frame 17 having an opening (not shown) that exposes the lower surface of the head 3.

[0039] Printer 1 prints on, for example, a roll of paper, which is media P. However, media P may also be sheet-fed paper. The size of media P is also arbitrary. For example, media P can be as small as a receipt, as a size commonly used in offices, or as large as a poster.

[0040] The configuration of the conveying device 5 for transporting the media P is arbitrary. Figures 1 and 2 illustrate a configuration in which the media P is transported by rotating rollers that are in contact with the media P. Other configurations include, for example, a configuration in which the media P is transported by transporting a belt that holds the media P, and a configuration in which the media P is transported by rotating a drum around which the media P is wound. In a broader sense, the conveying device 5 is a moving device that moves the head 3 and the media P relative to each other.

[0041] The controller 7 is comprised of, for example, a computer. The computer may comprise, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and an external storage device (e.g., an HDD (Hard Disk Drive) or SSD (Solid State Drive)), although these are not specifically shown in the diagram. The CPU executes programs stored in the ROM and / or external storage device, thereby constructing various functional units that perform various calculations (including control). The controller 7 may also include logic circuits that perform certain operations, power supply circuits, or drivers. The controller 7 may be hardware-integrated in one location or distributed across multiple locations. The controller 7 controls the head 3 and transport device 5 based on print data that includes image data (a broad concept including characters).

[0042] Printer 1 may have various other components in addition to those described above. Examples are given below, although they are not specifically shown in the diagrams. • Drying device: For example, to accelerate the drying of the ink. • Coating device: For example, to uniformly apply a transparent coating agent to the media P. • Cleaning device: For example, to clean the head 3. Note that Printer 1 may use the head 3 for coating an agent in addition to, or instead of, printing with colored ink.

[0043] (2. Head) (2.1. Overall Head) Figure 3 is an exploded perspective view of head 3. The configuration of head 3 can be various, except for the configuration for changing the drive waveform in response to changes in the drive frequency F, and may be a known configuration, for example. The configuration shown in Figure 3 is just one example. In the following, we will take the configuration shown in Figure 3 as an example and briefly describe the head 3 in general.

[0044] The manner in which head 3 (or actuator, from another perspective) applies pressure to the liquid for discharge is arbitrary. For example, head 3 may be piezoelectric or thermal. Piezoelectric type applies pressure to the liquid by utilizing the deformation of a piezoelectric element. Thermal type applies pressure to the liquid by heating the liquid to generate bubbles. The mode of deformation of the piezoelectric element used by the piezoelectric head 3 is also arbitrary, and may be, for example, a bending mode, a vertical mode, or a shear mode. In the description of the embodiment, the bending mode will be taken as an example.

[0045] The print head 3 may simply be a device that supplies ink, or it may not only supply ink but also recover any undischarged ink (in other words, a circulating type). For convenience, the former will be used as an example in the description of the embodiment.

[0046] Head 3 has the following components in order from the -D3 side, for example: • Front part 9: For example, as described above, it has a nozzle 11 and an actuator 13. • Flexible substrate 19: For example, it contributes to the transmission of the drive signal SgD to the actuator 13. • Drive IC (integrated circuit) 21: For example, it generates and outputs the drive signal SgD. • Back part 23: For example, it supplies liquid to the front part 9. • Circuit board 25: For example, it contributes to the transmission of signals from the FPGA (Field Programmable Gate Array) 27 to the drive IC 21. • FPGA 27: For example, it contributes to determining the correction rule for the drive waveform.

[0047] In head 3, the entire configuration for inputting the drive signal SgD to actuator 13 is sometimes referred to as the drive assembly 29. In the illustrated example, the drive assembly 29 includes a flexible substrate 19, a drive IC 21, a circuit board 25, and an FPGA 27.

[0048] One or more (two in the illustrated example) flexible substrates 19 are joined to a plurality of actuators 13 on the upper surface of the front part 9 by bumps 31 (Figure 4). The drive IC 21 is mounted on the flexible substrate 19. The circuit board 25 is connected to the flexible substrate 19 via connectors (not shown) or other circuit boards. The FPGA 27 is mounted on the circuit board 25. The drive IC 21 and FPGA 27 may include a CPU, ROM, and RAM, and may also include an external storage device. Any part of the above description of the computer may be applied to the drive IC 21 and FPGA 27.

[0049] Although not specifically shown in the figures, the head 3 may have other appropriate components in addition to those described above. For example, the head 3 may have a housing that covers the upper surface of the back part 23 and houses the flexible substrate 19 and the circuit board 25, etc. Regardless of whether the head 3 has any additional components, the combination of the front part 9 and the drive assembly 29 may be considered as an example of the liquid discharge head of this disclosure.

[0050] (2.2. Front Part) As shown in Figure 4, the front part 9 has a flow channel member 33 and an actuator substrate 35 including a plurality of actuators 13. The flow channel member 33 is, for example, a plate with the same width as the front part 9. The actuator substrate 35 is, for example, a plate that is slightly smaller than the flow channel member 33 (however, it has the width to span the plurality of pressurized chambers 43 described later).

[0051] The flow channel member 33 has one or more flow channels 37, each containing a plurality of nozzles 11. The flow channel 37 includes a common flow channel 39 extending from an inlet (not shown) into which liquid is supplied from outside the flow channel member 33 (back part 23 in the illustrated example), and a plurality of individual flow channels 41 branching off from the common flow channel 39. Each individual flow channel 41 contains a nozzle 11. The individual flow channels 41 also have a pressurized chamber 43 that opens onto the upper surface of the flow channel member 33. The flow channel member 33 is constructed, for example, by laminating a plurality of plate-shaped plates (not shown) via an adhesive (not shown).

[0052] The actuator substrate 35 is a piezoelectric type that utilizes bending deformation. The specific type of such actuator 13 is arbitrary and may be, for example, a unimorph type or a bimorph type. The unimorph type utilizes the deformation of one piezoelectric layer. The bimorph type utilizes the deformation of two piezoelectric layers stacked on top of each other. Furthermore, deformation of three or more piezoelectric layers may be used (a type not classified as any of the above may also be adopted).

[0053] Figure 4 illustrates a unimorph-type actuator 13. The actuator 13 has, for example, a diaphragm 45, a common electrode 47, a piezoelectric layer 49, and individual electrodes 51, in that order from the flow path member 33 side.

[0054] The diaphragm 45, common electrode 47, and piezoelectric layer 49 extend across multiple pressurized chambers 43 in a plan view. That is, they are provided in common to multiple pressurized chambers 43. For convenience, the terms diaphragm 45, common electrode 47, and piezoelectric layer 49 may refer to the parts located in each actuator 13, or to the entire actuator substrate 35. Individual electrodes 51 are provided in each pressurized chamber 43, facing the pressurized chamber 43. The number of individual electrodes 51 is basically the same as the number of pressurized chambers 43.

[0055] The portion of the piezoelectric layer 49 sandwiched between the individual electrodes 51 and the common electrode 47 is polarized in the thickness direction. Therefore, for example, when an electric field (voltage) is applied in the polarization direction of the piezoelectric layer 49 by the individual electrodes 51 and the common electrode 47, the piezoelectric layer 49 contracts in the direction along the layer. This contraction is restricted by the diaphragm 45. As a result, the actuator 13 deforms by bending so that it becomes convex toward the pressurizing chamber 43. When an electric field (voltage) is applied in the opposite direction by the individual electrodes 51 and the common electrode 47, the actuator 13 deforms by bending toward the opposite side of the pressurizing chamber 43. One or both of these bending deformations are used to apply pressure to the liquid in the pressurizing chamber 43.

[0056] Each individual electrode 51 has an electrode body 51a that overlaps the pressurizing chamber 43 in a plan view, and a lead electrode 51b extending from the electrode body 51a. The lead electrode 51b is joined to the flexible substrate 19 via a conductive bump 31. Although not shown, a common electrode 47 is also connected to the flexible substrate 19 via a through-conductor (not shown) and a bonding material (not shown) that penetrates the piezoelectric layer 49.

[0057] The specific driving method of the actuator 13 (or, from another perspective, the specific form of the driving signal SgD input to the actuator 13) is arbitrary. For example, the driving method may be a so-called pull-type, a push-type, or a combination of both. The pull-type is briefly described below.

[0058] In this explanation, it is assumed that when the potential of the individual electrodes 51 is higher than the potential of the common electrode 47, an electric field is applied to the piezoelectric layer 49 in the same direction as the polarization direction, causing the actuator 13 to bend toward the pressurizing chamber 43. It is also assumed that a reference potential is applied to the common electrode 47. Furthermore, it is assumed that a drive signal SgD is input to the individual electrodes 51.

[0059] Before a discharge request is made, the potential applied to the individual electrode 51 (a broad signal including the drive signal SgD) is set to a potential higher than the reference potential (hereinafter referred to as "high potential"). Then, each time a discharge request is made, the potential of the individual electrode 51 is set to a potential lower than the high potential (hereinafter referred to as "low potential"), and then set to the high potential again at a predetermined timing. That is, the pulses containing the drive signal SgD are input to the individual electrode 51. The low potential may be set as appropriate, but for example, it may be the same potential as the reference potential.

[0060] Before an ejection request, since the potential of the individual electrode 51 is at a high potential, the actuator 13 is bent toward the pressure chamber 43 side. Then, when the potential (drive signal SgD) of the individual electrode 51 becomes low potential, the actuator 13 starts returning to the shape before deformation (the flat shape), the volume of the pressure chamber 43 increases, and ink begins to vibrate at the natural vibration period. This vibration increases the pressure inside the pressure chamber 43. At this timing, the drive signal SgD is set to low potential, the actuator 13 bends toward the pressure chamber 43 side again, and applies pressure to the pressure chamber 43. The former pressure and the latter pressure are superimposed, and liquid is ejected from the nozzle 11.

[0061] (3. Correction method for drive waveform) (3.1. Specific example of correction method) FIG. 7 is a schematic diagram showing a specific example of a method for correcting a drive waveform in accordance with a change in drive frequency F. The upper part of FIG. 7 shows an example of the influence of the drive frequency F on ejection characteristics. In this figure, the horizontal axis represents the drive frequency F (kHz). The vertical axis represents the ejection velocity magnification u Ｆ / u ０ (%). u ０ is the ejection velocity when there is no influence of residual vibration. u Ｆ is the ejection velocity when the drive frequency F is the value shown on the horizontal axis.

[0062] FIG. 7 is obtained through experiments. Specifically, liquid ejection using the same drive waveform at a constant drive frequency F was performed continuously (that is, in all drive cycles T), and the average value of the ejection velocity u Ｆ at that time was obtained. Measurement of such ejection velocity u Ｆ was performed for various values of drive frequency F, and line Ln11 in FIG. 7 was obtained.

[0063] As described above, depending on the drive frequency F, the residual vibration and the vibration for the next ejection weaken each other or strengthen each other, and as a result, the ejection velocity becomes slower or faster. In the illustrated example, it is as follows: • In a range lower than frequency f １ : The change in ejection velocity is small. • Frequency f １ to f ２Range (Range α): Discharge speed becomes slower. • Frequency f ２ ~f ３ Range: The change in discharge speed is small. • Frequency f ３ ~f ４ Range (Range β): Discharge speed becomes slower. • Frequency f ４ ~f ５ Range (range γ): Discharge rate increases.

[0064] As described above, the effect of the drive frequency F can be evaluated by dividing the range in which the drive frequency F can change into multiple frequency ranges and evaluating each frequency range. Therefore, as shown in the lower part of Figure 7, a correction rule is defined for each frequency range.

[0065] The lower part of Figure 7 is a conceptual diagram showing the record R1 held by the printer 1. Record R1 holds multiple frequency ranges (more precisely, frequency range information DF that defines the frequency ranges) and multiple correction information DA that define correction rules (whether or not correction is performed and the correction method), each associated with the other. The printer 1 then identifies the correction information DA associated with the frequency range (DF) that includes the drive frequency F (or the ejection frequency f described later), which is the reciprocal of the drive period T, for each drive cycle T, and corrects the drive waveform based on that correction information DA.

[0066] More specifically, the frequency range information DF may include, for example, information on the lower and upper limits of the frequency range. The lower limit of the lowest frequency range may be 0, not 0, or not specified. The upper limit of the highest frequency range may or may not be specified. When the drive frequency F (or ejection frequency f, described later) for the next ejection is lower or higher than the entire range of multiple frequency ranges defined by multiple frequency range information DFs, correction is optional, and the printing process may be terminated abnormally.

[0067] Correction information DA corresponding to ranges α and β where the discharge speed slows down specifies, for example, a correction rule for increasing the discharge speed. Correction information DA corresponding to range γ where the discharge speed increases specifies, for example, a correction rule for decreasing the discharge speed. Ranges where the change in discharge speed is relatively small (0 to f) １ and f ２ ~f ３ The correction information DA corresponding to ) defines a correction rule that does not correct the drive waveform.

[0068] Note that, as shown in the example, a specific frequency range (0 to f) １ and f ２ ~f ３ Even if no correction is performed in the specified frequency range (ranges α, β, and γ), if the drive waveform is corrected in other frequency ranges (ranges α, β, and γ), it can still be said that the drive waveform as a whole is corrected (changed) according to the drive frequency F. Furthermore, in the description of the embodiments, for convenience, the drive waveform that has not been corrected may also be referred to as the corrected drive waveform, etc.

[0069] The specific method of correction when performing correction is arbitrary. Figure 7 illustrates an example of changing from the initially set drive waveform to another drive waveform whose shape is predetermined. Specifically, in Figure 7, "FIRE" indicates the type of drive waveform, and "FIRE" with different numbers attached indicates that they are of different types.

[0070] For example, in the illustrated example, the drive waveform initially set for the next discharge is "FIRE1". In range α, it is specified that "FIRE4" is used instead of "FIRE1". Similarly, in range β or γ, it is specified that "FIRE5" or "FIRE6" is used instead of "FIRE1". In other ranges, it is specified that "FIRE1" is used.

[0071] Discharge speed u with respect to drive frequency F ＦThe manner of change (shape of line Ln11) differs depending on, for example, the specific shape of the individual flow path 41, the specific configuration of the actuator 13, and the specific drive waveform of the drive signal SgD. Line Ln11 shown in Figure 7 is merely an example. As can be understood from this, in record R1, the number of frequency ranges is arbitrary, the lower and upper limits of each frequency range are arbitrary, and the content of the correction rules set for each frequency range is also arbitrary.

[0072] In one head 3, the discharge speed u in response to the change in the drive frequency F. Ｆ The manner in which the discharge speed u changes may be determined for various drive waveforms by experiment, simulation calculations, and / or theoretical calculations. Ｆ The manner of change may be determined by using different drive waveforms in a predetermined order (for example, two types of drive waveforms alternately). Furthermore, for example, the referenced record D1 may differ depending on the drive waveform of the past and most recent discharge (sometimes referred to as the "previous discharge," not necessarily the discharge in the immediately preceding drive cycle T) and / or the drive waveform of the next discharge.

[0073] There are various methods other than those described above for changing the drive waveform according to the drive frequency F (or discharge frequency f, which will be described later; the same applies hereafter in this paragraph). For example, a correction amount for the parameters that define the drive waveform (e.g., number of pulses, pulse height, pulse width, and / or relative relationship between multiple pulses) may be calculated by a function that includes the drive frequency F as a variable, and the correction may be performed based on this correction amount. Such a function may be set for each of the multiple frequency ranges (DF). In addition, the correction amount for the above parameters may be set to a predetermined value (i.e., a value that does not depend on the change in frequency within each frequency range) for each of the multiple frequency ranges (DF).

[0074] (3.2. Discharge Frequency) Figure 8 is a schematic diagram illustrating the discharge frequency f. Up to this point, as shown in Figure 8A, the explanation has basically been based on the assumption that droplets are continuously discharged from a single nozzle 11 (i.e., throughout all drive cycles T). However, as shown in Figures 8B and C, in actual image printing, droplets may not be discharged at all. As a result, the discharge characteristics are affected in essentially the same way as when the drive frequency F changes.

[0075] Specifically, in Figure B, one discharge and one non-discharge occur alternately, and the drive frequency F is effectively halved. In Figure C, one discharge and two non-discharges occur alternately, and the drive frequency F is effectively 1 / 3. Therefore, the discharge frequency f is defined as follows, using the number of non-discharges N from the previous discharge to the next discharge: f = F / (N + 1)

[0076] In the previous section, it was explained that correction information DA associated with the frequency range (frequency range information DF) that includes the drive frequency F for the next discharge was referred to. Instead of the drive frequency F for the next discharge, correction information DA associated with the frequency range that includes the discharge frequency f for the next discharge may be referred to. In a higher-level concept, the drive waveform may change according to the discharge frequency f. In the description of the embodiment, this embodiment will be taken as an example. Note that since the discharge frequency f is based on the drive frequency F, even if the drive waveform changes according to the discharge frequency f, the drive waveform will still change according to the change in drive frequency F, as explained above.

[0077] (4. Signal Processing System Configuration) (4.1. Functional Blocks) The actuator 13 driving method (drive waveform correction method) described above may be implemented by constructing various functional units in the controller 7 and the drive assembly 29. Furthermore, the division of roles between the controller 7 and the drive assembly 29 of the head 3 is arbitrary. The division of roles between the FPGA 27 and the drive IC 21 is also arbitrary. An example is shown below. In the following, we will outline the functional units that contribute to changing the drive waveform according to the drive frequency F. It goes without saying that functional units not mentioned below may be provided as appropriate.

[0078] (4.1.1. Controller Functional Blocks) Figure 9 is a block diagram showing the configuration of the signal processing system of the printer 1. The controller 7 has, for example, the following functional units: ・Print processing unit 53: For example, controls the head 3. ・Transportation control unit 55: For example, controls the transport device 5.

[0079] The transport control unit 55 controls, for example, the electric motor 57, which is the drive source for the transport device 5. The control of the transport control unit 55 may be, for example, open-loop control or closed-loop control. Figure 9 illustrates an example in which semi-closed-loop control is performed in which the detected value of a sensor 59 (e.g., an encoder or resolver) that detects the rotational speed of the electric motor 57 is fed back.

[0080] The printing processing unit 53 has, for example, the following functional units: • Initial waveform setting unit 61: For example, sets the drive waveform of the drive signal SgD (the waveform before correction according to the ejection frequency f). • F setting unit 63: For example, holds information on the drive frequency F. It may also set and / or calculate the drive frequency F.

[0081] The initial waveform setting unit 61 sets a drive waveform for each drive cycle T for a plurality of nozzles 11, for example. More specifically, for example, when the printing processing unit 53 receives a print command based on predetermined image data from an unillustrated operation unit for the printer 1 or from an external device connected to the printer 1, it quantizes the gradation value of each pixel of the image data or assigns a plurality of pixels of the image data to a plurality of nozzles 11 to set the gradation value (after quantization) for each nozzle 11 for each drive cycle T. The initial waveform setting unit 61 selects a drive waveform (for example, one of "FIRE1" to "FIRE3") corresponding to the quantized gradation value.

[0082] The drive frequency F and the transport speed v may be set, for example, with one value being set first and the other value being set based on the first value. Which is set first may vary depending on the operating state of the transport device 5 (acceleration state, constant speed state, or deceleration state). Furthermore, the drive frequency F and / or transport speed v may be set by the manufacturer of the printer 1, the user, and / or the printing processing unit 53 (F setting unit 63 and / or transport control unit 55). An example is given below.

[0083] In one example, the drive frequency F and transport speed v (target value) for the acceleration, constant speed, and deceleration states are all set by the manufacturer of the printer 1. The F setting unit 63 and the transport control unit 55 retain the set values. The retained values ​​are referenced by other functional units as needed (the reference of values ​​is the same in other examples as well).

[0084] In one example, the constant-speed drive frequency F is set by the user through operations on an unillustrated control unit of the printer 1. The F setting unit 63 holds this value. The transport control unit 55 sets the transport speed v (target value) for the acceleration state, constant-speed state, and deceleration state based on the constant-speed drive frequency F held by the F setting unit 63. The F setting unit 63 sets the drive frequency F for the acceleration state and deceleration state based on the target value (or detected value) of the transport speed v for the acceleration state and deceleration state.

[0085] The printing processing unit 53 outputs control data D11 to the head 3. The control data D11 is, for example, data for each drive cycle T. The control data D11 includes, for example, identification information ID (see "ID" in Figure 12, described later) that identifies the drive waveform set for each of the multiple nozzles 11 in each drive cycle T, information on the drive frequency F in each drive cycle T, and information on the ejection timing (for example, the time difference from receiving the control data D11 to ejection). The format for transmitting this information is arbitrary. For example, the information on the drive frequency F may be represented by the period of continuously transmitted pulses, or it may be a numerical value held in data of a predetermined number of bits. The control data D11 is output together with the clock signal in synchronization with the clock signal, for example.

[0086] Furthermore, the control data D11 currently being transmitted may not relate to the discharge immediately after its transmission, but rather to a discharge that occurs multiple drive cycles T later than the current time. Within the head 3, the various signals or data being transmitted do not necessarily relate to the discharge immediately after their transmission. For convenience, terms such as "next discharge" and "previous discharge" are used, but these do not necessarily refer to the current time and the "next" and "previous" relative to the nozzle 11. They may also refer to the "next" and "previous" relative to the various signals or data being transmitted, or to the functional unit processing those signals or data. Therefore, for example, the "next" and "previous" for any functional unit of the controller 7 may be out of sync with the "next" and "previous" for any functional unit of the head 3.

[0087] (4.1.2. Functional Block of the Head) Figure 10 is a block diagram showing the configuration of the signal processing system of the head 3. As previously described, the head 3 has a drive assembly 29. The drive assembly 29 also has an FPGA 27 and a drive IC 21. The control data D11 in Figure 9 is input to the FPGA 27.

[0088] FPGA 27 has, for example, the following functional units: • f calculation unit 65: For example, calculates the discharge frequency f based on the control data D11. • Waveform reset unit 67: For example, resets the identification information ID of the drive waveform specified for each nozzle 11 by the control data D11 (including maintaining the same identification information ID).

[0089] As previously described, the control data D11 includes identification information ID for the drive waveform specified for each nozzle 11 for each drive cycle T. The f calculation unit 65 counts the number of non-discharges N from the identification information ID corresponding to non-discharges. Then, the f calculation unit 65 calculates the discharge frequency f for each nozzle 11 based on the identified number N and the drive frequency F information included in the control data D11.

[0090] The waveform resetting unit 67 resets the drive waveform identification information ID specified by the control data D11 for each nozzle 11, based on the discharge frequency f calculated by the f calculation unit 65, by referring to record R1 as described with reference to Figures 7 and 8. This operation may be considered as correction of the drive waveform or as part of the correction.

[0091] The drive IC 21 has, for example, the following functional units: • Distribution unit 69: Distributes the identification information ID of the reset drive waveform to the following multiple individual control units 71 for each of the multiple nozzles 11 for each drive cycle T. • Individual control unit 71: Each corresponds to an actuator 13 and inputs a drive signal SgD to the corresponding actuator 13. • Waveform storage unit 73: Stores information (waveform table TW in Figure 12, described later) that defines multiple drive waveforms corresponding to each of the multiple identification information IDs.

[0092] The individual control unit 71 generates a drive signal SgD having a drive waveform corresponding to the identification information ID distributed from the distribution unit 69, based on the waveform table TW stored in the waveform storage unit 73, and outputs it to the actuator 13 (more specifically, the individual electrode 51). The specific method by which the individual control unit 71 generates the drive signal SgD is arbitrary.

[0093] For example, although not specifically shown in the figures, the individual control unit 71 may have multiple wires to which multiple potentials are supplied from a constant voltage source, one wire to the actuator 13, and multiple switches to switch the connection relationship between the former and the latter. The individual control unit 71 may then turn the multiple switches ON or OFF in a predetermined order based on waveform information DW (see Figure 12) corresponding to the identification information ID assigned to it, and generate and output a drive signal SgD.

[0094] Furthermore, for example, a waveform generation unit (not shown) provided in common to multiple individual control units 71 may generate drive signals SgD for all types of drive waveforms based on a waveform table TW, and output all generated drive signals SgD in parallel to each individual electrode 51 (and by extension to multiple individual electrodes 51). Each individual control unit 71 may have multiple wires to which multiple drive signals SgD are input in parallel, one wire to the actuator 13, and multiple switches to switch the connection state between the former and the latter. The individual control unit 71 may then control the multiple switches so that it outputs only the drive signal SgD corresponding to the identification information ID assigned to it from all the input drive signals SgD to the actuator 13.

[0095] (4.2. Data) Figure 11 is a schematic diagram conceptually showing the configuration of the table group STA held by the head 3 (more specifically the FPGA 27, and even more specifically the waveform resetting unit 67). The table group STA holds multiple identification information IDs (for convenience, referred to as "ID2") related to the drive waveform in the previous ejection, associated with multiple correction tables TA. Each correction table TA holds multiple identification information IDs (for convenience, referred to as "ID1") related to the drive waveform in the next ejection, associated with multiple records R1. As a result, for example, the waveform resetting unit 67 can refer to the records R1 corresponding to the type of drive waveform (before correction) of the previous ejection and the type of drive waveform (before correction) of the next ejection, and select the drive waveform (after correction) for the next ejection according to the drive frequency F of the next ejection.

[0096] In Figure 11, the number of correction tables TA included in the table group STA, the number of records R1 included in each correction table TA, the number of frequency ranges (frequency range information DF (Figure 7)) in each record R1, the size of each frequency range, and the type of drive waveform (correction information DA) associated with each frequency range are for illustrative purposes only and may be changed as appropriate. Furthermore, Figure 11 is merely for conceptually explaining the data content, and the actual data structure is arbitrary. For example, the table group STA may have a data structure that can be treated as a three-dimensional data table, and the positional relationship between data cells in the physical domain is also arbitrary.

[0097] In the illustrated example, it is assumed that the drive waveforms before correction are "FIRE1" to "FIRE3", and the drive waveforms selected when correcting them are "FIRE4" to "FIRE7". However, the drive waveform used as the drive waveform before correction may also be used as the drive waveform selected when correction is performed. Also, the drive waveform referenced as the previous discharge may be the corrected one, not the pre-correction one. In other words, seven correction tables TA corresponding to "FIRE1" to "FIRE7" may be prepared. Furthermore, the number of pre-correction drive waveforms is not limited to three types, nor is the number of corrected drive waveforms limited to four types, nor is the total number of drive waveforms limited to seven types. For example, more drive waveforms than those in the illustrated example may be prepared. However, for convenience in describing the embodiment, the number of drive waveform types and the mode of operation shown in the illustration will be used as an example.

[0098] Figure 12 is a schematic diagram conceptually showing the configuration of the waveform table TW held by the head 3 (more specifically, the drive assembly 29, drive IC 21, and waveform storage unit 73). The waveform table TW holds multiple identification information IDs that identify the type of drive waveform and multiple waveform information DWs that define the drive waveform, in association with each other.

[0099] The waveform information DW may be data that holds values ​​for parameters that define, for example, the number of pulses, pulse height, pulse width, and / or the relative relationship of multiple pulses contained in the drive signal SgD, or it may be time-series data that holds the change in the potential of the drive signal SgD over time. In Figure 12, the drive waveform is schematically shown in the field of the waveform information DW, but its shape is for illustrative purposes only and does not correspond to that of reality.

[0100] In the illustrated example, eight waveform information DWs, labeled "FIRE0" to "FIRE7," are stored. "FIRE0" corresponds to non-discharge, and its data format may be the same as or different from the data format of the other waveform information DWs. In the illustrated example, the signal for non-discharge is depicted as a signal whose potential does not change over time. Unlike the illustrated example, the signal for non-discharge may have a waveform (pulse) that imparts vibrations to the liquid at a level that does not cause liquid to be discharged. Such vibrations contribute, for example, to reducing the probability of the liquid solidifying.

[0101] (5. Specific Correction Procedure) The following shows an example of the procedure performed by head 3 (more specifically, FPGA 27). In the following explanation, "FIRE1", "FIRE2", and "FIRE3", which are set as pre-correction drive waveforms, are assumed to correspond to large droplets, medium droplets, and small droplets, respectively. As previously mentioned, the pre-correction drive waveforms corresponding to discharge are not limited to three types.

[0102] Furthermore, the following explanation will focus on only one nozzle 11. The process described below may be performed substantially in parallel for multiple nozzles 11, for example.

[0103] (5.1. First Example) Figures 13 to 15 are flowcharts showing the processing steps for the first example. In Figures 13 to 15, "A" in Figure 13 leads to "A" in Figure 14, "B" in Figure 14 leads to "B" in Figure 15, and "C" in Figures 14 and 15 leads to "C" in Figure 13.

[0104] This process begins when a SIN signal is input from the controller 7 (more specifically the printing processing unit 53) to the head 3 (more specifically the FPGA 27) and ends when a SIN signal is output. The SIN signal includes, for example, information about the type of drive waveform selected (identification information ID), and is part or all of the control data D11. The input SIN signal includes information about the drive waveform before correction (ID1), and the output SIN signal includes information about the drive waveform after correction (ID2).

[0105] Steps ST1 to ST3 are processes to differentiate based on which drive waveform the previous discharge (past and most recent discharge; not necessarily the discharge in the immediately preceding drive cycle T) was. For example, in step ST1, head 3 (more specifically, waveform reset unit 67) determines whether the previous discharge was "FIRE1". If the determination is positive, proceed to step ST4; otherwise, proceed to step ST2. In step ST2, head 3 determines whether the previous discharge was "FIRE2". If the determination is positive, proceed to step ST4; otherwise, proceed to step ST3. In step ST3, head 3 determines whether the previous discharge was "FIRE3". If the determination is positive, proceed to step ST4; otherwise, proceed to "C".

[0106] Cases in which a negative determination is made in step ST4 include, for example, the fact that information about the previous ejection has not yet been generated, such as immediately after printing has started. Also, as can be understood from step ST12 in Figure 18, which will be described later, cases where the previous ejection occurred relatively far in the past than the next ejection, and the information about that previous ejection has been erased. Furthermore, cases where "FIRE0" continues from a drive cycle T in which no information about the previous ejection exists. In these cases, the head 3 (waveform resetting unit 67) outputs a SIN output without correcting the drive waveform.

[0107] The processing after a positive determination is made in each of steps ST1 to ST3 is common to all except that the record R1 referenced later is different. For this reason, the common ST4 to ST6 codes are assigned to the three flows separated by steps ST1 to ST3, while the ST7 to ST9 codes are assigned only to the leftmost step.

[0108] Steps ST4 to ST6 are processes to differentiate based on which drive waveform the next discharge will be. For example, in step ST4, head 3 determines whether the next discharge is "FIRE1" or not. If the determination is positive, proceed to step ST7; otherwise, proceed to step ST5. In step ST5, head 3 determines whether the next discharge is "FIRE2" or not. If the determination is positive, proceed to step ST7; otherwise, proceed to step ST6. In step ST6, head 3 determines whether the next discharge is "FIRE3" or not. If the determination is positive, proceed to step ST7; otherwise, proceed to "C".

[0109] One example of a case where a negative determination is made in step ST6 is when the next discharge is not discharged ("FIRE0"). In this case, head 3 (waveform resetting unit 67) outputs a SIN without correcting the drive waveform.

[0110] In steps ST7 to ST9, the head 3 selects a corrected drive waveform according to the drive waveforms for the previous and next discharges identified in steps ST1 to ST6. For example, in step ST7, the head 3 (more specifically, the f calculation unit 65) obtains the drive frequency F from the control data D11 (or SIN signal) that triggered the illustrated process. In step ST8, the head 3 (f calculation unit 65) obtains the number of non-discharges N from the control data D11 received so far. Although not shown in the illustration, the head 3 (f calculation unit 65) then calculates the discharge frequency f. In step ST9, the head 3 (more specifically, the waveform reset unit 67) refers to record R1 corresponding to the types of drive waveforms (identification information ID1 and ID2) for the previous and next discharges, and identifies the type of drive waveform (correction information DA) associated with the frequency range (frequency range information DF) that includes the calculated discharge frequency f.

[0111] The head 3 (waveform resetting unit 67) then generates and outputs a SIN signal in which the identification information ID that identifies the drive waveform included in the SIN signal is replaced with the identification information ID held by the identified correction information DA. Note that the input SIN signal and the SIN signal output with the identification information ID replaced may differ only in the content of the identification information ID (the data format may be maintained), or the information held and / or the data format may be different.

[0112] Figures 13 to 15 (and Figures 16 to 18, described later) are merely conceptual illustrations of the processing procedure, and the actual processing and / or program may differ from the illustrated examples. For example, in Figures 13 to 15, steps ST1 to ST6 identify the "FIRE" values ​​of the previous and next discharges (before correction), and steps ST7 to ST9 are shown in parallel to make it clear that the corrected "FIRE" value differs depending on the combination. In practice, these processes may be implemented by the same program (same functional unit) that takes the previous and next discharges (before correction) as input.

[0113] (5.2. Second Example) Figure 16 is a flowchart showing the processing procedure for the second example. The second example can be described as a simplified version of the first example. In the first example, the drive waveform of the next discharge was corrected for all combinations of the drive waveform of the previous discharge and the drive waveform of the next discharge. In the second example, the drive waveform of the next discharge is corrected only when the drive waveform of the previous discharge and the drive waveform of the next discharge are the same. Specifically, for example, it is as follows.

[0114] Steps ST1a to ST3a perform the same determination as steps ST1 to ST3 in the first example. Steps ST4a to ST6a perform the same determination as steps ST4 to ST6 in the first example. However, after the case is divided according to the type of drive waveform of the previous discharge (after steps ST1a to ST3a), only whether or not the type of drive waveform of the next discharge is the same as the type of drive waveform of the previous discharge is determined (steps ST4a to ST6a), and differences from other types are not determined. If a negative determination is made in steps ST4a to ST6a, the head 3 (waveform resetting unit 67) outputs a SIN output without correcting the drive waveform. The processing when an affirmative determination is made in steps ST4a to ST6a (steps ST7 to ST9) is the same as steps ST7 to ST9 in the first example.

[0115] In the second example, the number of records R1 may be less than in the first example. For example, assuming the example in Figure 11, in the first example, nine records R1 are prepared in a 3x3 (waveform type x waveform type) configuration. On the other hand, in the second example, only three records R1 (a table containing these three records R1) are needed, one extracted from each correction table TA.

[0116] (5.3. Third Example) Figure 17 is a flowchart showing the processing procedure for the third example. The third example can be described as a simplified version of the first example. In the first example, the drive waveform of the next discharge was corrected for all combinations of the drive waveform of the previous discharge and the drive waveform of the next discharge. In the third example, the drive waveform of the next discharge is corrected only when the drive waveform of the previous discharge is a large drop (the highest discharge volume, "FIRE1"). Specifically, for example, it is as follows.

[0117] In step ST1b, the head 3 (waveform resetting unit 67) makes the same determination as in step ST1 of the first example. If a negative determination is made, the head 3 (waveform resetting unit 67) outputs a SIN signal and terminates the process without correcting the drive waveform. The processing after a positive determination is made in step ST1b (steps ST4 to ST9) is the same as the processing after a positive determination is made in step ST1 of the first example.

[0118] In the third example, the number of records R1 may be less than in the first example. For example, assuming the example in Figure 11, in the third example, only one correction table TA is needed for the previous discharge to be "FIRE1".

[0119] (5.4. Additional Processing) Figure 18 shows an example of a processing procedure that may be added to the first to third examples. Here, it is expressed based on the first example. When applied to the second and third examples, "C" in Figure 18 may be considered to be connected immediately before the SIN output in the second and third examples. Also, step ST1 in Figure 18 may be replaced with steps ST1a and ST1b in the second and third examples. This processing may be inserted, for example, between the "SIN input" and step ST1 in Figure 13.

[0120] In step ST11, the head 3 (more specifically, the drive assembly 29 and FPGA 27) determines whether or not to start printing. If the determination is positive, the head 3 proceeds to "C"; if it is negative, it proceeds to step ST12 (or step ST1 from another perspective). As a result, when printing is started, the head 3 outputs a SIN without performing any processing to correct the drive waveform.

[0121] In step ST12, the head 3 (more specifically, the drive assembly 29 and FPGA 27) determines whether the number of non-ejection cycles N is 3 or greater. If the determination is positive, the head 3 proceeds to "C"; otherwise, it proceeds to step ST1. As a result, if the number of cycles N is 3 or greater than a predetermined number (3 in the illustrated example), the head 3 outputs a SIN without performing any processing to correct the drive waveform.

[0122] In the example shown in Figure 13, when printing starts, a negative determination is made in step ST3 (or ST3a or ST1b), and the process proceeds to "SIN output". Therefore, even if step ST11 is not inserted, no processing is performed to correct the drive waveform. However, while step ST3 is performed for each nozzle 11, step ST11 is performed in common for all nozzles 11. When a positive determination is made in step ST11, the execution of steps ST1 to ST3 is omitted for all nozzles 11, and SIN output is performed.

[0123] The start of printing in step ST11 is, for example, the start of printing an image, and is not necessarily immediately after the printer 1 starts operating. The start of printing an image may be, for example, the start of printing a long image in the D2 direction on a roll of paper. This long image may be based on a single image data in the internal processing of the printer 1, or it may be formed by arranging multiple images based on multiple image data without any gaps. Also, the start of printing a single image may be, for example, the start of printing each image when multiple images are printed sequentially at predetermined time intervals. The predetermined time interval may be, for example, at least longer than the drive cycle T (the time when the next image starts printing), and may be greater than or equal to the time length obtained by multiplying the drive cycle T (the time when the next image starts printing) by the threshold of the number of steps N in step ST12 (3 in the illustrated example).

[0124] The head 3 may determine whether or not to start printing as appropriate. For example, the printer 1 (more specifically the controller 7 and print processing unit 53) may include information indicating the start of image printing in the control data D11. Alternatively, the head 3 may determine that printing has started if the time interval between receiving the previous control data D11 and receiving the current control data D11, or the time interval between the ejection time specified by the previous control data D11 (the start time of output of the drive signal SgD) and the ejection time specified by the current control data D11, is longer than a predetermined time interval. The predetermined time interval may be, for example, the same as the time interval described in the previous paragraph.

[0125] Furthermore, when focusing on a single nozzle 11, in both cases where a positive determination is made in step ST11 and step ST12, the processing for correcting the drive waveform is skipped, and the process proceeds to "SIN output". In other words, when a positive determination is made in step ST11, the head 3 performs the same processing as when a positive determination is made in step ST12. To put it another way, when the head 3 first ejects liquid from the nozzle 11 after being instructed to start printing a predetermined image, it can be said that it outputs a drive signal SgD with the same drive waveform as the drive waveform when the number of consecutive non-ejection cycles N is greater than or equal to a predetermined number (for example, 3) (and all other conditions are the same).

[0126] When the process in step ST12 is applied, for example, head 3 (FPGA 27) does not need to retain information about ejections prior to two previous ejections. That is, head 3 (FPGA 27) may erase information about ejections that occurred more than a predetermined number of times (3 times) ago (for example, whether it was "FIRE0" to "FIRE3").

[0127] (6. Summary of Embodiments) Below, we will extract configurations according to the embodiments and describe examples of their effects. Note that the extracted configurations do not necessarily have to produce the effects exemplified below. Also, for convenience, the reference numerals of one of the multiple embodiments may be used as representative. The following explanation may also apply to embodiments in which reference numerals are not used, as long as no inconsistencies arise. Also, for convenience, the drive frequency F and the discharge frequency f may not be strictly distinguished.

[0128] The head 3 according to this embodiment (an example of a liquid discharge head) includes an actuator 13 and a drive assembly 29. The actuator 13 generates pressure to discharge liquid from the nozzle 11. A drive signal SgD having a drive waveform corresponding to the amount of liquid discharged is output to the actuator 13 so that liquid is discharged or not discharged from the nozzle 11 at a predetermined drive frequency F. The drive assembly 29 changes the drive waveform in accordance with the change in the drive frequency F.

[0129] From another perspective, the printer 1 according to the embodiment includes a head 3 and a controller 7 that inputs control data D11 to the head 3. The drive assembly 29 outputs a drive signal SgD having a drive waveform corresponding to the amount of liquid to be discharged to the actuator 13 so that liquid is discharged or not discharged from the nozzle 11 at a drive frequency F specified by the control data D11. The controller 7 changes the drive frequency F. At least one of the drive assembly 29 and the controller 7 (the former in the description of the embodiment) performs a process to change the drive waveform in response to the change in the drive frequency F.

[0130] From yet another perspective, the control method according to the embodiment is a control method for a head 3 having an actuator 13 that generates pressure for discharging liquid from a nozzle 11. The control method includes inputting a drive signal SgD having a drive waveform corresponding to the amount of liquid to the actuator 13 so that liquid is discharged or not discharged from the nozzle 11 at a predetermined drive frequency F. This input changes the drive frequency F and changes the drive waveform in accordance with the change in drive frequency F.

[0131] Therefore, for example, even if the drive frequency F changes and the effect of residual vibration on the ejection characteristics (e.g., ejection speed) changes (Figures 6 and 7 (upper panel)), the change in ejection characteristics can be reduced. As a result, the probability of maintaining image quality even when the drive frequency F changes is improved. Furthermore, as shown in Figure 5, printing can be performed even during the acceleration or deceleration period of the transport device 5. Consequently, waste of media P can be reduced.

[0132] The drive assembly 29 may change the drive waveform for the next discharge in accordance with the change in the discharge frequency f (Figure 8), which is obtained by dividing the drive frequency F by the number of consecutive non-discharge periods N from the nozzle 11 to the next discharge plus 1.

[0133] In this case, the drive waveform is corrected according to the effective drive frequency (i.e., the ejection frequency f) corresponding to the image content, thus improving the effect of reducing the influence of residual vibration on the ejection characteristics. Furthermore, the effects of the drive frequency F and the effects of ejection / non-ejection can be handled in a unified manner, resulting in simplified processing.

[0134] As shown in Figure 7, the drive assembly 29 may hold a record R1 that associates multiple non-overlapping frequency ranges (frequency range information DF) with multiple correction information DA that define correction rules for the drive waveform (such as whether or not correction is performed and the corrected drive waveform). The drive assembly 29 may change the drive waveform for the next ejection based on the correction information DA in record R1 that is associated with the frequency range (DF) that includes the ejection frequency f for the next ejection.

[0135] In this case, for example, a correction rule for the drive waveform can be defined simply and flexibly in response to changes in the ejection characteristics with respect to the drive frequency F (e.g., increase, no change, and decrease in ejection speed). As a result, it becomes easier to reduce variations in ejection speed caused by changes in the ejection frequency f, and consequently, it becomes easier to improve image quality. Furthermore, since the head 3 determines whether or not to correct and how to correct based on the ejection frequency f, the configuration of the controller 7 may be the same as that of a conventional configuration. As a result, for example, it becomes easier to apply the technology of this embodiment to an existing printer 1.

[0136] Record R1 is located in a frequency range (range f in Figure 7) that lies between two frequency ranges (see ranges α and β in Figure 7) to which correction information DA, which specifies how to correct the drive waveform, is associated. ２ ~f ３ (See reference) and correction information DA which specifies that the drive waveform should not be corrected may be included in the data.

[0137] In this case, for example, the flexibility of the correspondence between the drive frequency F (discharge frequency f) and the correction rule is improved. Furthermore, between the frequency ranges (ranges α and β) in which residual vibration affects the discharge characteristics, there is a frequency range (f) in which the effect of residual vibration on the discharge characteristics is small. ２ ~f ３The fact that this can occur is a finding obtained by focusing on the continuous (or near-continuous) change of the drive frequency F. In other words, assuming that the drive frequency F is constant, it is difficult to obtain the above finding by simply focusing on whether the effective drive frequency (see discharge frequency f) becomes F, F / 2, or F / 3 depending on the number of non-discharge cycles.

[0138] When the drive assembly 29 first ejects liquid from the nozzle 11 after being instructed to start printing a predetermined image (see affirmative determination in step ST11), it may output a drive signal SgD with the same drive waveform as the drive waveform (for example, an uncorrected drive waveform) when the number of consecutive non-ejections N is equal to or greater than a predetermined number (3 in the example in Figure 18) (and all other conditions are the same) (see affirmative determination in step ST12).

[0139] In this case, for example, the processing can be simplified when there is a high probability that the effect of residual vibration is small. Also, since there are usually many nozzles 11, the load on the CPU and other components can be reduced. As a result, for example, the probability of a delay in the timing of the initial discharge can be reduced.

[0140] The drive assembly 29 may be configured so as not to cause a change in the drive waveform in accordance with the change in the number of consecutive non-discharge cycles N if the number of consecutive non-discharge cycles N is three or more (see the affirmative determination in step ST12). In other words, the drive assembly 29 may output a drive signal SgD with the same drive waveform (for example, an uncorrected drive waveform) even if the number of cycles N is different.

[0141] In this case, for example, the processing when the effect of residual vibration is small can be simplified. Also, since head 3 no longer needs to retain and manage control data D11 from three or more previous values, memory capacity is saved.

[0142] The drive assembly 29 may change the drive waveform according to the liquid discharge rate (for example, one of "FIRE1" to "FIRE3" may be selected). Also, as shown in Figure 17, the drive assembly 29 may change the drive waveform according to the drive frequency F only when the past and most recent discharge (previous discharge) at the nozzle 11 corresponds to the maximum discharge rate ("FIRE1").

[0143] In this case, for example, correction is performed only when the effect of residual vibration is significant, thus reducing the load on the CPU of head 3 involved in the correction. Also, when head 3 holds record R1 as shown in Figure 11, its storage capacity can be saved. On the other hand, as in the example in Figure 17, for the next ejection, by performing correction considering the difference in ejection amount, the probability of changes in ejection characteristics can be reduced, thereby improving image quality.

[0144] As shown in Figure 16, the drive assembly 29 may change the drive waveform according to the drive frequency F only when the discharge amount corresponding to the past and most recent discharge (previous discharge) at the nozzle 11 is the same as the discharge amount corresponding to the next discharge.

[0145] In this case, for example, it is easy to obtain frequency characteristics (data useful for generating record R1) as shown in the upper part of Figure 7. Furthermore, since it is not necessary to store record R1 or correct the drive waveform for all combinations of drive waveforms, for example, the load on the CPU of head 3 can be reduced and storage capacity can be saved.

[0146] The drive assembly 29 may include an FPGA 27 (an example of a control circuit) and a drive IC 21. The FPGA 27 may hold record R1 and may identify correction information DA associated with a frequency range (DF) that includes the ejection frequency f of the next ejection. The drive IC 21 may output a drive signal SgD to the actuator 13 based on the correction information DA identified by the FPGA 27. The correction information DA may be identification information IDs that identify multiple types of drive waveforms (for example, "FIRE4" to "FIRE7"). The drive IC 21 may hold a waveform table TW (Figure 12) that associates multiple identification information IDs with waveform information DW that defines multiple types of drive waveforms. The drive IC 21 may also generate a drive signal SgD of the drive waveform defined by the waveform information DW corresponding to the identification information ID identified by the FPGA 27 based on the waveform table TW.

[0147] In this case, for example, since the head 3 has information that defines the corrected drive waveform, the configuration of the controller 7 may be the same as in the conventional configuration. As a result, for example, it is made easier to apply the technology of this embodiment to an existing printer 1.

[0148] In the above embodiments, printer 1 is an example of a recording device. Head 3 is an example of a liquid ejection head. FPGA 27 is an example of a control circuit.

[0149] The technology relating to this disclosure is not limited to the embodiments described above and may be implemented in various forms.

[0150] For example, the recording device is not limited to those generally classified as printers. For example, the recording device may be a plotter. Furthermore, the recording device may be one in which a liquid ejection head is moved by a robot to print on stationary media, or it may be a handheld printer in which the liquid ejection head (or the entire recording device including the head) is moved by a human hand to print on stationary media. As can be understood from the above, the moving device is not limited to a transport device that moves the media, but may be one that moves the head, or one that moves both the head and the media.

[0151] When the moving device is a robot that moves the head, it is clear that an external controller of the head (including a controller that controls the robot) may set the relative movement speed between the head and the media, and / or the drive frequency F. In the case of a handheld printer, for example, the relative movement speed may be detected by a sensor provided on the head (or a part that moves with the head; the same applies hereinafter), and the head's calculation unit may set the drive frequency F based on that speed.

[0152] Furthermore, the liquid is not limited to ink; for example, it could be a paint or a conductive material for patterning on a circuit board (although all of these can be considered types of ink). Also, for example, the liquid may exhibit the properties of a Newtonian fluid or the properties of a non-Newtonian fluid (e.g., pseudoplasticity).

[0153] Furthermore, the media is not limited to paper. For example, it may be resin, cloth, wood, metal, or ceramic. Also, the media is not limited to paper (film) form, but may be, for example, a sheet, a vehicle body, or a building.

[0154] The liquid dispensing head may be used for purposes other than recording. For example, the liquid dispensing head may be used to dispense a chemical substance from a nozzle toward another chemical substance to induce a chemical reaction.

[0155] In this embodiment, the head determines whether or not to perform correction and how to perform the correction based on the drive frequency F, and also holds waveform information DW that defines the drive waveform. However, the division of roles between the controller 7 and the head 3 is arbitrary. For example, unlike in this embodiment, the controller 7 may hold a table group STA and determine whether or not to perform correction and how to perform the correction, and / or the controller 7 may hold waveform information DW and generate the drive signal SgD (before being selected and amplified by the drive IC 21).

[0156] 1...Printer (recording device), 3...Head (liquid ejection head), 11...Nozzle, 13...Actuator, 29...Drive assembly, D11...Control data, F...Drive frequency, SgD...Drive signal.

Claims

1. A liquid discharge head comprising: an actuator that generates pressure to discharge liquid from a nozzle; and a drive assembly that outputs a drive signal having a drive waveform corresponding to the amount of liquid discharged to the actuator so that the liquid is discharged or not discharged from the nozzle at a predetermined drive frequency, wherein the drive assembly changes the drive waveform in accordance with the change in the drive frequency.

2. The liquid dispensing head according to claim 1, wherein the drive assembly changes the drive waveform in the next discharge in accordance with the change in the discharge frequency obtained by dividing the drive frequency by the number of consecutive non-discharges from the nozzle plus 1.

3. The liquid dispensing head according to claim 2, wherein the drive assembly holds records that associate a plurality of non-overlapping frequency ranges with a plurality of correction information that defines correction rules for the drive waveform, and the drive waveform for the next dispensing is changed based on the correction information in the record that is associated with the frequency range including the dispensing frequency for the next dispensing.

4. The liquid discharge head according to claim 3, wherein the record includes data relating a frequency range located between two frequency ranges to which the correction information specifying that the drive waveform should be corrected is associated, and the correction information specifying that the drive waveform should not be corrected.

5. The liquid ejection head according to any one of claims 2 to 4, wherein the drive assembly outputs the same drive signal as the drive waveform when the number of consecutive non-ejections is greater than or equal to a predetermined number of times, when the drive assembly first ejects the liquid from the nozzle after being instructed to start printing a predetermined image.

6. The liquid discharge head according to any one of claims 2 to 4, wherein the drive assembly does not cause a change in the drive waveform in accordance with the change in the number of consecutive non-discharges if the number of such non-discharges is three or more.

7. The liquid dispensing head according to any one of claims 1 to 6, wherein the drive assembly changes the drive waveform according to the amount of liquid to be dispensed, and changes the drive waveform according to the drive frequency only when the past and most recent dispensing at the nozzle corresponds to the maximum amount of liquid to be dispensed.

8. The liquid dispensing head according to any one of claims 1 to 6, wherein the drive assembly changes the drive waveform according to the amount of liquid to be dispensed, and changes the drive waveform according to the drive frequency only when the amount of liquid to which the past and most recent dispensed at the nozzle corresponds is the same as the amount of liquid to which the next dispensed dispensed.

9. The drive assembly comprises a control circuit that holds the record and identifies the correction information associated with the frequency range including the discharge frequency of the next discharge, and a drive IC that outputs the drive signal to the actuator based on the correction information identified by the control circuit, wherein the correction information is identification information that identifies a plurality of types of drive waveforms, and the drive IC holds a waveform table that associates a plurality of the identification information with waveform information that defines the plurality of types of drive waveforms, and generates the drive signal having the drive waveform defined by the waveform information corresponding to the identification information identified by the control circuit based on the waveform table, or the liquid discharge head according to any one of claims 4 to 8 that directly or indirectly references claim 3.

10. A recording device comprising: a liquid discharge head; a controller for inputting control data to the liquid discharge head, wherein the liquid discharge head comprises: an actuator that generates pressure for discharging liquid from a nozzle; and a drive assembly that outputs a drive signal having a drive waveform corresponding to the amount of liquid discharged to the actuator so that the liquid is discharged or not discharged from the nozzle at a drive frequency specified from the control data; the controller changes the drive frequency; and at least one of the drive assembly and the controller is a recording device that performs a process to change the drive waveform in accordance with the change in the drive frequency.

11. A method for controlling a liquid discharge head having an actuator that generates pressure for discharging liquid from a nozzle, comprising inputting a drive signal having a drive waveform corresponding to the amount of liquid to the actuator so that the liquid is discharged or not discharged from the nozzle at a predetermined drive frequency, wherein the input changes the drive frequency and changes the drive waveform in accordance with the change in the drive frequency.

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