JP2018043370A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device in which a discharge failure caused by sedimentation of ink components and the like in a non-discharge period is suppressed.SOLUTION: A printer 100 comprises: a print head 13 having nozzles 74 discharging ink, cavities 73 communicating with the nozzles 74, and a pressure fluctuation induction section 72 inducing pressure fluctuation in the cavities 73; and a drive signal generating circuit 37 generating a discharge drive waveform for driving the pressure fluctuation induction section 72 so as to cause the ink to be discharged from the nozzles 74 and a non-discharge drive waveform for driving the pressure fluctuation induction section 72 at a degree for not causing the ink to be discharged from the nozzles 74. The non-discharge drive waveform is a waveform obtained by superposing a waveform of a second frequency higher than a first frequency on a waveform of the first frequency for vibrating menisci of the ink formed on the nozzles 74 in a direction along a direction in which the ink is discharged from the nozzles 74.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a liquid ejection apparatus.

  For example, an ink jet printer as a liquid ejecting apparatus may not normally eject ink due to thickening of ink during a non-ejection period when ink (liquid) is not ejected. In contrast, for example, as in the ink jet recording apparatus described in Patent Document 1, the ink is finely vibrated at the nozzle tip by finely vibrating the meniscus of the ink formed at the nozzle tip to the extent that the ink is not ejected during the non-ejection period. There is known a liquid ejecting apparatus configured to suppress thickening and sticking and prevent occurrence of ejection failure.

JP 2004-181676 A

  However, in the ink jet recording apparatus described in Patent Document 1, it is possible to suppress the ink from being thickened and fixed at the tip of the nozzle, but depending on the specifications of the ink used, the components in the ink in the ink storage chamber over time As a result, there is a problem that discharge failure may occur due to uneven viscosity. Also, if the ink in the ink storage chamber cannot be re-stirred, it is necessary to discharge all the ink in the ink storage chamber in order to eliminate the state. There has been a problem that the amount of (discarded) ink increases.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or forms.

  Application Example 1 A liquid discharge apparatus according to this application example includes a liquid discharge head including a nozzle that discharges a liquid, a pressure chamber that communicates with the nozzle, a pressure variation inducing unit that induces a pressure variation in the pressure chamber, Drive waveform generating means for generating a discharge drive waveform for driving the pressure fluctuation inducing section so that the liquid is discharged from the nozzle and a non-discharge drive waveform for driving the pressure fluctuation inducing section to the extent that the liquid is not discharged from the nozzle. And the non-ejection drive waveform has a first frequency waveform that vibrates a meniscus of the liquid formed in the nozzle in a direction along a direction in which the liquid is ejected from the nozzle. It is a waveform in which a waveform of a second frequency higher than the frequency is superimposed.

  According to this application example, the non-ejection drive waveform that drives the pressure fluctuation inducing unit to the extent that liquid is not ejected from the nozzle is changed to the waveform of the first frequency that vibrates the meniscus in the direction along the direction in which the liquid is ejected from the nozzle. , A waveform obtained by superimposing a waveform having a second frequency higher than the first frequency. That is, by driving the pressure fluctuation inducing portion with this non-ejection driving waveform, the meniscus is vibrated to the extent that liquid is not ejected from the nozzle, and is accommodated in the pressure chamber (and the region from the pressure chamber to the nozzle tip). It is possible to propagate the vibration of the first frequency and the second frequency waveform higher than the first frequency to the liquid. As a result, the liquid in the vicinity of the meniscus can be prevented from thickening and sticking to the nozzle, and the liquid contained in the pressure chamber (and the region from the pressure chamber to the nozzle tip) can be more effectively stirred. Can do. That is, for example, even when a liquid includes a sedimentation component, the occurrence of liquid discharge failure due to sedimentation can be suppressed by suppressing sedimentation by more effective stirring. Further, since the frequency of eliminating (returning) the liquid ejection failure is reduced by discharging the liquid from the pressure chamber, the amount of liquid consumed (discarded) for the return can be reduced.

  Application Example 2 In the liquid ejection apparatus according to the application example, the waveform of the second frequency is a waveform that causes the surface of the meniscus to vibrate in-plane.

  According to this application example, the non-ejection drive waveform that drives the pressure fluctuation inducing unit to the extent that liquid is not ejected from the nozzle is changed to the waveform of the first frequency that vibrates the meniscus in the direction along the direction in which the liquid is ejected from the nozzle. The waveform of the second frequency that causes the surface of the meniscus to vibrate in-plane is superimposed. That is, by driving the pressure fluctuation inducing portion with this non-ejection driving waveform, the meniscus can be vibrated to the extent that no liquid is ejected from the nozzle while vibrating the surface of the meniscus in-plane. Here, since the second frequency is high enough to cause the meniscus surface to vibrate in-plane (that is, because the waveform of the second frequency has greater energy), the pressure chamber (and the nozzle tip from the pressure chamber) It is possible to stir the liquid contained in the region up to) more effectively. In addition, since the surface of the vibrating meniscus is vibrated in-plane, the liquid in the vicinity of the meniscus is vibrated in a local range near the interface in contact with the air at the nozzle tip region. Even when the liquid thickens in the meniscus due to volatilization of the liquid, the thickening range is kept in the vicinity of the meniscus. That is, the sticking due to the thickening of the liquid is suppressed, and the thickened liquid can be kept in the vicinity of the meniscus. As a result, even when a predetermined discharge is not performed due to the thickened liquid, it is only necessary to discharge the thickened liquid retained in the vicinity of the meniscus. Can be canceled (returned). Further, the amount of liquid consumed (discarded) for returning can be reduced to a smaller amount.

  Application Example 3 In the liquid ejection apparatus according to the application example described above, the amplitude of the waveform of the second frequency is smaller than the amplitude of the waveform of the first frequency.

  According to this application example, the amplitude of the vibration of the waveform of the second frequency (the waveform of the frequency higher than the frequency of vibrating the meniscus) is smaller than the amplitude of the vibration of the waveform of the first frequency (waveform of vibrating the meniscus). . That is, the vibration of the waveform of the second frequency is smaller than the amplitude of the waveform that vibrates the meniscus and the frequency is increased, so that the liquid is suppressed from being ejected and is also affected by the meniscus vibration. The vibration of the waveform of the second frequency can be propagated in the liquid without any problem.

  Application Example 4 In the liquid ejection device according to the application example, the ejection driving waveform is a waveform on which the waveform of the second frequency is superimposed.

  As in this application example, the discharge drive waveform is also a waveform in which the waveform of the second frequency is superimposed, and the pressure chamber (and the nozzle from the pressure chamber to the nozzle due to the effect of the waveform of the second frequency even during liquid discharge). It is possible to stir the liquid contained in the region up to the tip (at any time by the waveform of the second frequency).

  Application Example 5 In the liquid ejection device according to the application example, the second frequency is a natural number multiple of the frequency of the ejection drive waveform.

  According to this application example, since the second frequency is a natural number multiple of the frequency of the ejection drive waveform, timing control for generating the ejection drive waveform becomes easier, and the ejection drive waveform is generated with higher reproducibility. be able to. As a result, liquid discharge control can be performed with higher accuracy.

  Application Example 6 In the liquid ejection apparatus according to the application example described above, the amplitude of vibration based on the second frequency waveform of the ejection drive waveform is vibration based on the second frequency waveform of the non-ejection drive waveform. It is smaller than the amplitude of.

  According to this application example, the amplitude of the vibration based on the second frequency waveform of the ejection driving waveform is smaller than the amplitude of the vibration based on the second frequency waveform of the non-ejection driving waveform. By virtue of the effect of the waveform having the frequency of 2, the liquid accommodated in the pressure chamber (and the region from the pressure chamber to the tip of the nozzle) can be agitated. The influence of can be suppressed.

  Application Example 7 A liquid discharge apparatus according to this application example includes a liquid discharge head including a nozzle that discharges a liquid, a pressure chamber that communicates with the nozzle, a pressure variation inducing unit that induces a pressure variation in the pressure chamber, Drive waveform generating means for generating a discharge drive waveform for driving the pressure fluctuation inducing section so that the liquid is discharged from the nozzle and a non-discharge drive waveform for driving the pressure fluctuation inducing section to the extent that the liquid is not discharged from the nozzle. The ejection drive waveform is a waveform in which the non-ejection drive waveform is superimposed.

  According to this application example, since the non-ejection drive waveform is superimposed on the ejection drive waveform that drives the pressure variation inducing unit so that liquid is ejected from the nozzle, only the ejection drive waveform is applied to the pressure variation inducing unit. Thus, during the liquid discharge period and the non-discharge period, vibration based on the non-discharge drive waveform can be propagated to the liquid stored in the pressure chamber (and the region from the pressure chamber to the nozzle tip). As a result, the liquid in the vicinity of the meniscus can be prevented from thickening and adhering to the nozzle during the non-ejection period of the liquid, and the pressure chamber (and the pressure chamber can also be reduced during the liquid ejection period due to the effect of the non-ejection driving waveform. The liquid accommodated in the region from the nozzle tip to the nozzle tip can be stirred. Further, since it is only necessary to apply the ejection drive waveform to the pressure fluctuation inducing part, the drive control for the pressure fluctuation inducing part can be simplified.

  Application Example 8 In the liquid ejection device according to the application example, the non-ejection driving waveform is a waveform that causes in-plane vibration of the surface of the liquid meniscus formed in the nozzle.

  According to this application example, the non-ejection driving waveform that causes the surface of the meniscus of the liquid formed on the nozzle to vibrate in-plane is superimposed on the ejection driving waveform that drives the pressure fluctuation inducing section so that the liquid is ejected from the nozzle. Therefore, by simply applying a discharge drive waveform to the pressure fluctuation inducing section, the liquid stored in the pressure chamber (and the region from the pressure chamber to the nozzle tip) is non-removed during the liquid discharge period and the non-discharge period. The vibration based on the ejection driving waveform can be propagated, and the surface of the meniscus formed on the nozzle can be vibrated in-plane. Here, since the non-ejection driving waveform has a frequency that is high enough to cause the meniscus surface to vibrate in-plane (that is, because the non-ejection driving waveform has more energy), the pressure chamber (and the pressure chamber to the nozzle tip) The liquid contained in the region) can be stirred more effectively. In addition, since the surface of the vibrating meniscus is vibrated in-plane, the liquid in the vicinity of the meniscus is vibrated in a local range near the interface in contact with the air at the nozzle tip region. Even when the liquid thickens in the meniscus due to volatilization of the liquid, the thickening range is kept in the vicinity of the meniscus. That is, the sticking due to the thickening of the liquid is suppressed, and the thickened liquid can be kept in the vicinity of the meniscus. As a result, even when a predetermined discharge is not performed due to the thickened liquid, it is only necessary to discharge the thickened liquid retained in the vicinity of the meniscus. Can be canceled (returned). Further, the amount of liquid consumed (discarded) for returning can be reduced to a smaller amount.

1 is a front view illustrating a configuration of a printer as a liquid ejection apparatus according to Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of a printer as a liquid ejection apparatus according to a first embodiment. Illustration of basic functions of the printer driver Schematic diagram showing an example of nozzle arrangement as seen from the bottom of the print head Cross section of the main part of the print head Block diagram for explaining an example of the configuration of a drive control system for driving a print head Timing chart showing drive signals generated by a drive signal generation circuit in the prior art Timing chart for explaining waveform of first frequency and waveform of second frequency Timing chart showing an example of a drive signal of Example 1 in the present embodiment Timing chart showing an example of a drive signal according to the first embodiment Timing chart showing an example of a drive signal of Example 2 in the present embodiment Timing chart showing an example of a drive signal according to the second embodiment Conceptual diagram explaining in-plane vibration of meniscus A diagram conceptually showing the vibration of the meniscus surface Timing chart showing an example of a drive signal according to Modification 1 Timing chart showing an example of a drive signal according to Modification 2 Timing chart showing an example of a drive signal according to Modification 2

  DESCRIPTION OF EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention. In the following drawings, the scale may be different from the actual scale for easy understanding. Further, in the coordinates added to the drawings, the Z-axis direction is the vertical direction, the + Z direction is the upward direction, the X-axis direction is the front-rear direction, the -X direction is the forward direction, the Y-axis direction is the left-right direction, and the + Y direction is the left direction. The XY plane is a horizontal plane.

(Embodiment 1)
FIG. 1 is a front view illustrating a configuration of a printer 100 as a “liquid ejecting apparatus” according to the first embodiment, and FIG. 2 is a block diagram of the same.
The printer 100 constitutes the printing system 1 together with the image processing apparatus 110 connected to the printer 100. Based on print data including pixel data received from the image processing apparatus 110, the printer 100 prints a desired image on a roll paper 5 as a long print medium supplied in a rolled state. Inkjet printer.

<Basic configuration of image processing apparatus>
The image processing apparatus 110 includes a printer control unit 111, an input unit 112, a display unit 113, a storage unit 114, and the like, and controls a print job that causes the printer 100 to perform printing. The image processing apparatus 110 is configured using a personal computer as a preferred example.
Software that operates the image processing apparatus 110 includes general image processing application software (hereinafter referred to as an application) that handles image data to be printed, print data for controlling the printer 100 and causing the printer 100 to execute printing. Includes printer driver software to be generated (hereinafter referred to as printer driver).

The printer control unit 111 includes a central processing unit (CPU) 115, an application specific integrated circuit (ASIC) 116, a digital signal processor (DSP) 117, a memory 118, a printer interface unit 119, and the like. I do.
The input unit 112 is information input means as a human interface. Specifically, for example, a port to which a keyboard or an information input device is connected.
The display unit 113 is an information display unit (display) as a human interface, and is related to information input from the input unit 112, an image to be printed on the printer 100, and a print job under the control of the printer control unit 111. Information etc. are displayed.
The storage unit 114 is a rewritable storage medium such as a hard disk drive (HDD) or a memory card. The storage unit 114 stores software (a program operated by the printer control unit 111) that operates the image processing apparatus 110, images to be printed, and print jobs. Related information and the like are stored.
The memory 118 is a storage medium that secures an area for storing a program for the CPU 115 to operate, a work area for the operation, and the like, and includes a storage element such as a RAM or an EEPROM.

<Basic configuration of printer 100>
The printer 100 includes a printing unit 10, a moving unit 20, a control unit 30, and the like. The printer 100 that has received the print data from the image processing apparatus 110 controls the printing unit 10 and the moving unit 20 by the control unit 30 to print an image on the roll paper 5 (image formation).
For the print data, for example, general image data (for example, RGB digital image information) obtained by a digital camera or the like is converted so that it can be printed by the printer 100 by an application and printer driver included in the image processing apparatus 110. This is data for image formation, and includes commands for controlling the printer 100.

The printing unit 10 includes a head unit 11, an ink supply unit 12, and the like.
The moving unit 20 includes a scanning unit 40, a transport unit 50, and the like. The scanning unit 40 includes a carriage 41, a guide shaft 42, a carriage motor (not shown), and the like. The conveyance unit 50 includes a supply unit 51, a storage unit 52, a conveyance roller 53, a platen 55, and the like.

  The head unit 11 includes a print head 13 and a head driver 14 as a “liquid discharge head” having a plurality of nozzles (nozzle rows) that discharge printing ink (hereinafter referred to as ink) as “liquid” as ink droplets. ing. The head unit 11 is mounted on the carriage 41 and reciprocates in the scanning direction along with the carriage 41 moving in the scanning direction (X-axis direction shown in FIG. 1). While the head unit 11 (printing head 13) moves in the scanning direction, the ink droplets are ejected onto the roll paper 5 supported by the platen 55 under the control of the control unit 30 to thereby form a row of dots along the scanning direction. (Raster line) is formed on the roll paper 5.

The ink supply unit 12 includes an ink tank and an ink supply path (not shown) that supplies ink from the ink tank to the print head 13.
As the ink, for example, as an ink set made of a dark ink composition, a four-color ink set obtained by adding black (K) to a three-color ink set of cyan (C), magenta (M), and yellow (Y), etc. There is. Further, for example, eight colors including ink sets such as light cyan (Lc), light magenta (Lm), light yellow (Ly), and light black (Lk) made of a light ink composition in which the density of each color material is lightened. There are ink sets. The ink tank, the ink supply path, and the ink supply path to the nozzle that ejects the same ink are provided independently for each ink.

  A piezo method is used as a method for ejecting ink droplets (inkjet method). In the piezo method, a pressure corresponding to a print information signal is applied to ink stored in a pressure chamber by an actuator using a piezoelectric element (piezo element), and ink droplets are ejected (discharged) from a nozzle communicating with the pressure chamber for printing. It is a method.

The moving unit 20 (scanning unit 40, conveying unit 50) moves the roll paper 5 relative to the printing unit 10 under the control of the control unit 30.
The guide shaft 42 extends in the scanning direction and supports the carriage 41 in a slidable contact state, and the carriage motor serves as a driving source for reciprocating the carriage 41 along the guide shaft 42. That is, the scanning unit 40 (carriage 41, guide shaft 42, carriage motor) moves the carriage 41 (that is, the print head 13) in the scanning direction along the guide shaft 42 under the control of the control unit 30.

The supply unit 51 rotatably supports a reel on which the roll paper 5 is wound in a roll shape, and sends the roll paper 5 to the conveyance path. The storage unit 52 rotatably supports a reel that winds up the roll paper 5, and winds up the roll paper 5 that has been printed from the conveyance path.
The transport roller 53 includes a drive roller that moves the roll paper 5 in the transport direction (Y-axis direction shown in FIG. 1) that intersects the scanning direction, a driven roller that rotates as the roll paper 5 moves, and the like. Is conveyed from the supply unit 51 to the storage unit 52 via the printing region of the printing unit 10 (the region in which the print head 13 scans and moves on the upper surface of the platen 55).

The control unit 30 includes an interface unit 31, a CPU (Central Processing Unit) 32, a memory 33, a drive control unit 34, and the like, and controls the printer 100.
The interface unit 31 is connected to the printer interface unit 119 of the image processing apparatus 110 and transmits / receives data between the image processing apparatus 110 and the printer 100.
The CPU 32 is an arithmetic processing device for controlling the entire printer 100.
The memory 33 is a storage medium that secures an area for storing a program for the CPU 32 to operate, a work area for the operation, and the like, and includes a storage element such as a RAM or an EEPROM.
The CPU 32 controls the printing unit 10 and the moving unit 20 via the drive control unit 34 according to the program stored in the memory 33 and the print data received from the image processing apparatus 110.

The drive control unit 34 controls the drive of the printing unit 10 (head unit 11 and ink supply unit 12) and the moving unit 20 (scanning unit 40 and transport unit 50) based on the control of the CPU 32. The drive control unit 34 includes a movement control signal generation circuit 35, a discharge control signal generation circuit 36, and a drive signal generation circuit 37 as “drive waveform generation means”.
The movement control signal generation circuit 35 is a circuit that generates a signal for controlling the movement unit 20 (scanning unit 40, conveyance unit 50) in accordance with an instruction from the CPU 32.
The ejection control signal generation circuit 36 generates a head control signal for selecting a nozzle for ejecting ink, selecting an ejection amount, controlling ejection timing, and the like according to an instruction from the CPU 32 based on the print data. It is.
The drive signal generation circuit 37 is a circuit that generates a drive signal for driving an actuator 77 (described later). The drive signal will be described later.

  With the above configuration, the control unit 30 moves the carriage 41 that supports the print head 13 along the guide shaft 42 with respect to the roll paper 5 supplied to the printing region by the conveyance unit 50 (the supply unit 51 and the conveyance roller 53). An operation of ejecting ink droplets from the print head 13 while moving in the scanning direction (X-axis direction), and an operation of moving the roll paper 5 in the transport direction (+ Y direction) intersecting the scanning direction by the transport unit 50 (transport roller 53). Is repeated to form (print) a desired image on the roll paper 5.

<Basic functions of the printer driver>
FIG. 3 is an explanatory diagram of the basic functions of the printer driver.
Printing on the roll paper 5 is started when print data is transmitted from the image processing apparatus 110 to the printer 100. The print data is generated by the printer driver.
The print data generation process will be described below with reference to FIG.

  The printer driver receives image data (for example, text data or full-color image data) from the application, converts the print data into a format that can be interpreted by the printer 100, and outputs the print data to the printer 100. When converting image data from an application into print data, the printer driver performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, command addition processing, and the like.

The resolution conversion process is a process for converting the image data output from the application into a resolution (printing resolution) when printing on the roll paper 5. For example, when the print resolution is specified as 720 × 720 dpi, the vector format image data received from the application is converted into bitmap format image data with a resolution of 720 × 720 dpi. Each pixel data of the image data after the resolution conversion process is composed of pixels arranged in a matrix. Each pixel has a gradation value of, for example, 256 gradations in the RGB color space. That is, the pixel data after resolution conversion indicates the gradation value of the corresponding pixel.
Pixel data corresponding to one column of pixels arranged in a predetermined direction among pixels arranged in a matrix is called raster data. The predetermined direction in which the pixels corresponding to the raster data are arranged corresponds to the moving direction (scanning direction) of the print head 13 when printing an image.

The color conversion process is a process for converting RGB data into data in the CMYK color system space. The CMYK colors are cyan (C), magenta (M), yellow (Y), and black (K), and the image data in the CMYK color system space is data corresponding to the ink color that the printer 100 has. Therefore, for example, when the printer 100 uses 10 types of inks of the CMYK color system, the printer driver generates image data in a 10-dimensional space of the CMYK color system based on the RGB data.
This color conversion processing is performed based on a table (color conversion lookup table LUT) in which gradation values of RGB data and gradation values of CMYK color system data are associated with each other. Note that the pixel data after the color conversion processing is, for example, CMYK color system data of 256 gradations represented by the CMYK color system space.

  The halftone process is a process of converting high gradation number (256 gradations) data into gradation number data that can be formed by the printer 100. By this halftone processing, data indicating 256 gradations indicates, for example, 1-bit data indicating 2 gradations (with or without dots) or 4 gradations (without dots, small dots, medium dots, large dots). Converted to 2-bit data. Specifically, from the dot generation rate table corresponding to the gradation value (0 to 255) and the dot generation rate, the dot generation rate corresponding to the gradation value (for example, in the case of 4 gradations, no dot, small Pixel data is created so that dots are formed in a dispersed manner using the dither method, error diffusion method, etc. at the obtained generation rate. The

  The rasterizing process is a process of rearranging pixel data arranged in a matrix (for example, 1-bit or 2-bit data as described above) according to the dot formation order at the time of printing. The rasterizing process includes a path allocating process in which image data composed of pixel data after halftone processing is allocated to each path in which ink droplets are ejected while the print head 13 (nozzle array) scans and moves. When the pass assignment is completed, the actual nozzles forming each raster line constituting the print image are assigned.

The command addition process is a process for adding command data corresponding to the printing method to the rasterized data. The command data includes, for example, transport data related to the transport specifications of the medium (the amount of movement in the transport direction, the speed, etc.).
These processes by the printer driver are performed by the ASIC 116 and the DSP 117 (see FIG. 2) under the control of the CPU 115, and the generated print data is transmitted to the printer 100 via the printer interface unit 119.

<Nozzle row>
FIG. 4 is a schematic diagram illustrating an example of the arrangement of nozzles as viewed from the lower surface of the print head 13.
As shown in FIG. 4, the print head 13 has a nozzle row in which a plurality of nozzles 74 for discharging ink of each color are formed side by side (in the example shown in FIG. A black ink nozzle row K, a cyan ink nozzle row C, a magenta ink nozzle row M, a yellow ink nozzle row Y, a gray ink nozzle row LK, and a light cyan ink nozzle row LC).

  The plurality of nozzles 74 in each nozzle row are aligned and arranged at regular intervals (nozzle pitch) along the transport direction (Y-axis direction). In FIG. 4, the nozzles 74 of each nozzle row are assigned a lower number than the nozzles 74 on the downstream side (# 1 to # 400). That is, the # 1 nozzle 74 is positioned downstream of the # 400 nozzle 74 in the transport direction. Each nozzle 74 is provided with a pressure fluctuation inducing section 72 (see FIG. 5) for driving each nozzle 74 to eject ink droplets.

FIG. 5 is a cross-sectional view of the main part of the print head 13.
The print head 13 includes a nozzle 74 for ejecting ink, a cavity 73 as a “pressure chamber” communicating with the nozzle 74, a pressure fluctuation inducing section 72 for inducing pressure fluctuation in the cavity 73, and the like. Further, the pressure fluctuation inducing unit 72 includes a diaphragm 71, an actuator 77, and the like.

The diaphragm 71 constitutes at least a part of the surface constituting the cavity 73 (in the example shown in FIG. 5, the ceiling surface of the cavity 73 is constituted), and the displacement (deflection) of the diaphragm 71 is caused. The volume of the cavity 73 (that is, the internal pressure) increases or decreases.
The actuator 77 includes a piezoelectric thin film 77a (piezo element), an electrode 77b provided to cover one surface of the piezoelectric thin film 77a, and an electrode 77c provided to cover the other surface of the piezoelectric thin film 77a. It is constituted by. The actuator 77 is provided so as to be laminated on the diaphragm 71 so as to sandwich the diaphragm 71 with the cavity 73, and can bend (bend and vibrate) the diaphragm 71.

  The nozzle 74 is formed on the nozzle plate 75. In addition, a cavity 73 and a reservoir 78 communicating with this via an ink supply port 83 are formed in a cavity substrate 76 positioned so as to be sandwiched between the nozzle plate 75 and the vibration plate 71. The reservoir 78 communicates with an ink tank (not shown) via an ink supply path.

  In the pressure fluctuation inducing section 72 having such a configuration, by applying a drive signal between the electrodes 77b and 77c, the diaphragm 71 is flexed and vibrated as shown by an arrow in FIG. The pressure fluctuation can be induced to vibrate the ink inside the cavity 73, and the ink droplets can be ejected from the nozzle 74.

<Print head drive control>
Next, the drive control of the print head 13 will be described with reference to FIG. FIG. 6 is a block diagram illustrating an example of a configuration of a drive control system that drives the print head 13.
As described above, the head unit 11 includes the print head 13, the head driver 14, and the like. The drive control unit 34 includes an ejection control signal generation circuit 36 and a drive signal generation circuit 37, and drives and controls the print head 13 via the head driver 14.
More specifically, the drive control unit 34, based on the head control signal generated by the ejection control signal generation circuit 36 and the drive signal generated by the drive signal generation circuit 37, passes through each head 74 via the head driver 14. The corresponding pressure fluctuation inducing units 72 (actuators 77) are selectively driven.

The waveform of the drive signal generated by the drive signal generation circuit 37 includes a discharge drive waveform that drives the pressure fluctuation inducing unit 72 (actuator 77) so that ink is discharged from the nozzle 74, and a pressure that does not cause ink to be discharged from the nozzle 74. There is a non-ejection driving waveform for driving the fluctuation inducing unit 72 (actuator 77).
The ejection drive waveform is a signal for causing the head driver 14 to eject ink from the nozzle 74 by driving the actuator 77 to cause pressure fluctuation in the ink in the cavity 73.
The non-ejection drive waveform is a signal for the head driver 14 to drive the actuator 77 to cause the ink in the cavity 73 to vibrate (vibrates the ink meniscus formed on the nozzle 74).
The head driver 14 selects an ejection drive waveform and a non-ejection drive waveform based on the head control signal, and controls the timing to drive the actuator 77.

  The head control signal includes a signal based on pixel data designating the actuator 77 corresponding to the nozzle 74 to which ink droplets are to be ejected, waveform pattern data of the ejection driving waveform relating to the ejection amount, and a control signal that determines the timing of the ejection driving waveform. (Clock signal, latch signal, channel signal) and the like.

<Ink ejection drive>
Next, the drive signal generated by the drive signal generation circuit 37 will be described.
FIG. 7 is a timing chart showing drive signals generated by the drive signal generation circuit 37 in the prior art.
In FIG. 7, drive pulses PS <b> 1 to PS <b> 3 indicate ejection drive waveforms that drive the pressure fluctuation inducing unit 72 (actuator 77) with an amplitude V <b> 1 so that ink is ejected from the nozzles 74. The drive pulses MS1 to MS4 show non-ejection drive waveforms that drive the pressure fluctuation inducing unit 72 (actuator 77) with an amplitude V2 smaller than the amplitude V1 to the extent that ink is not ejected from the nozzles 74.
In FIG. 7, a period T (period T) that is a repetition period corresponds to a period during which the nozzle 74 moves in the scanning direction by one pixel. For example, when the print resolution is 720 dpi, the period T corresponds to a period for the nozzle 74 to move 1/720 inch with respect to the roll paper 5.

Since the ejection drive waveform (drive pulses PS1 to PS3) needs to accurately control the timing of ejecting ink droplets and the ejection amount per time, the trapezoidal wave, that is, the output value with a predetermined value over time. It has a waveform that can be changed (that is, changed at a predetermined speed). Further, the amplitude is sufficient to cause a necessary and sufficient pressure fluctuation in the ink in the cavity 73 to be ejected.
The non-ejection drive waveforms (drive pulses MS1 to MS4) are waveforms that cause pressure fluctuations in the ink in the cavity 73 to the extent that ink is not ejected. Therefore, the amplitude is smaller than the ejection drive waveform (drive pulses PS1 to PS3). Further, it is not necessarily a trapezoidal wave, and may be a sine wave or a rectangular wave, for example.

The drive signal generation circuit 37 generates the four types of drive signals shown in FIG. 7 and sends them to the head driver 14 in synchronization with the head control signal.
The four types of drive signals are drive signal 0 when no dot is formed (when the 2-bit pixel data (dot gradation value) is [00]), and small dot formation (when the dot gradation value is [01]. )), Driving signal 2 when medium dots are formed (when the dot gradation value is [10]), driving when large dots are formed (when the dot gradation value is [11]) Signal 3.
The drive signal 0 that does not form a dot is a signal that does not include the ejection drive waveform over the period T. The drive pulse MS1 during the period T1, the drive pulse MS2 during the period T2, the drive pulse MS3 during the period T3, and the period T4. This is a signal for generating the drive pulse MS4.
The drive signal 1 at the time of forming a small dot is a signal for generating the drive pulse PS1 in the period T1, generating the drive pulse MS2 in the period T2, the drive pulse MS3 in the period T3, and the drive pulse MS4 in the period T4.
The drive signal 2 for forming the medium dots is a signal for generating the drive pulse PS1 in the period T1, the drive pulse PS2 in the period T2, the drive pulse MS3 in the period T3, and the drive pulse MS4 in the period T4.
The driving signal 3 at the time of forming a large dot is a signal for generating the driving pulse PS1 in the period T1, the driving pulse PS2 in the period T2, the driving pulse PS3 in the period T3, and the driving pulse MS4 in the period T4.
Note that the lengths of the periods T1 to T4 are the same length as shown in FIG.

  The head driver 14 selects the corresponding drive signal from the drive signals 0 to 3 based on the head control signal, that is, based on the pixel data, controls the timing, and selects the corresponding actuator 77 to drive. To do. As a result, ink droplets based on the pixel data are ejected at positions based on the pixel data, and printing is performed.

<Ink fine vibration drive>
By the way, when the ink inside the cavity 73 continues to be stationary, the viscosity of the ink may change and the ink ejection characteristics may change. For example, in the case of ink using water or a volatile solvent as the solvent, the viscosity of the ink in the portion (meniscus region) that touches the air at the tip of the nozzle 74 may increase due to volatilization of the solvent. Further, when a thixotropic liquid is used for the ink, the apparent viscosity differs between the stirring state and the stationary state, and the viscosity increases when the stationary state continues. Therefore, in order to stably eject ink, the printer 100 always has a cavity that does not eject ink by a non-ejection drive waveform (drive pulses MS1 to MS4) during a period when ejection is not performed. The pressure in the ink in 73 is caused to vary. Specifically, the ink meniscus formed on the nozzle 74 is vibrated by the non-ejection drive waveform (drive pulses MS1 to MS4), thereby suppressing the thickening and solidification of the ink at the tip of the nozzle 74, and the cavity By propagating vibrations to the ink stored in 73 (and the region from the cavity 73 to the tip of the nozzle 74), an increase in viscosity is suppressed even when the ink is a thixotropic liquid.

In the printer 100 having the basic configuration described so far, there is a problem that the non-ejection period becomes longer, leading to ejection failure, and in that case, it may not be possible to easily resolve it. .
Specifically, for example, as described above, the ink in the cavity 73 is slightly affected by the problem that the viscosity of the nozzle 74 increases due to the volatilization of the solvent and the nozzle 74 becomes clogged. By applying the vibration, the meniscus vibrates at the tip of the nozzle 74, the ink is stirred, and the ink in the meniscus region can be prevented from solidifying. However, depending on the frequency and amplitude at which the ink is vibrated, if the situation where the ink is not ejected continues for a long time, the thickened ink in the vicinity of the meniscus continuously diffuses into the cavity 73 communicating with the nozzle. As a result, there is a case where the viscosity of the ink is increased over the entire cavity 73, leading to defective ink ejection.
Further, when the solute constituting the ink contains a sediment component, when the non-ejection period becomes longer, the sedimentation is also advanced by the non-ejection drive waveform (drive pulses MS1 to MS4), and the entire cavity 73 is spread. As a result, uneven viscosity of the ink may occur, leading to ejection failure.
In order to eliminate these conditions, it is necessary to discharge all of the ink stored in the cavity 73, and it takes time to recover, and the amount of ink consumed (discarded) for recovery increases. There was a problem of being fooled.

Therefore, in the printer 100 of the present embodiment, the non-ejection drive waveform generated by the drive signal generation circuit 37 causes the first meniscus of the ink formed on the nozzle 74 to vibrate in a direction along the direction in which the ink is ejected from the nozzle 74. In addition, a waveform having a second frequency higher than the first frequency is superimposed on the waveform having the above frequency.
This will be specifically described below.

FIG. 8 is a timing chart for explaining the waveform of the first frequency and the waveform of the second frequency.
A waveform W1 shown in FIG. 8 is the waveform of the drive signal 0 described above in the periods T1 to T2, and this shows a non-ejection drive waveform of the first frequency. That is, the drive pulses MS1 to MS4 form a waveform that vibrates the ink meniscus formed in the nozzle 74 in the direction along which the ink is ejected from the nozzle 74.
The first frequency is f1 = 4 / T, where f1 is the first frequency.
The waveform W2 is a second frequency waveform to be superimposed on the first frequency waveform (the waveform of the drive signal 0).
The second frequency is a frequency higher than the first frequency, that is, the waveform W2 is a waveform having a frequency higher than the waveform W1 (the waveform of the drive signal 0) that vibrates the ink meniscus formed on the nozzle 74. . For example, the first frequency is 10 kHz, while the second frequency is 100 kHz. The second frequency is a sine wave or a rectangular wave, but may be a trapezoidal wave. The amplitude V3 of the second frequency waveform (waveform W2) is smaller than the amplitude V2 of the non-ejection drive waveform (waveform W1) of the first frequency. This is because if the amplitude V3 of the waveform W2 is increased, the ink meniscus formed on the nozzle 74 may not be vibrated and the ink may be ejected.

A waveform W3 shown in FIG. 8 is a waveform in which the waveform W2 is superimposed on the waveform W1. Here, the vibration amplitude V3 of the second frequency waveform (non-ejection drive waveform) is smaller than the vibration amplitude V2 of the first frequency waveform (non-ejection drive waveform).
The drive signal generation circuit 37 has a superimposition circuit that superimposes two waveforms, outputs a waveform W3 in which the waveform W2 is superimposed on the waveform W1, and sends it to the head driver 14.
The drive signal generation circuit 37 according to the related art described above has been described as generating four types of drive signals and sending them to the head driver 14 in synchronization with the head control signal as shown in FIG. Similarly to the drive signal 0, the drive signal generation circuit 37 outputs a waveform W3 in which the waveform W2 is superimposed on the non-ejection drive waveforms (drive pulses MS1 to MS4) included in the drive signals 0 to 3 and sends them to the head driver. . That is, the first frequency waveform is the above-described non-ejection drive waveform (drive pulses MS1 to MS4).

Example 1
FIG. 9 is a timing chart showing an example of drive signals (drive signals 0 to 3) of Example 1 in the present embodiment. FIG. 10 is a timing chart illustrating an example of the drive signal 1 (waveform W4) according to the first embodiment.
The drive signal as Example 1 in the present embodiment is a non-ejection drive waveform (drive pulse MS1 to MS4) portion (portion indicated by a thick line in FIG. 9) in the drive signals 0 to 3 (see FIG. 7) in the prior art. The waveform W2 is superimposed only on.
For example, the drive signal (waveform W4) of Example 1 shown in FIG. 10 shows a state in which the waveform W2 is superimposed on the non-ejection drive waveforms of the drive pulses MS2 to MS4 of the drive signal 1 (see FIG. 7) in the prior art. It is a waveform, The period T1-T2 in it is shown. The waveform W4 is a waveform in which the waveform W2 is superimposed only after the drive pulse MS2 of the non-ejection drive waveform, and the waveform W2 is not superimposed on the ejection drive waveform (drive pulse PS1).
As shown in FIG. 9, the same applies to the other drive signals (drive signals 0, 2, 3), and the non-ejection drive waveforms of the respective drive waveforms among the drive pulses MS1 to MS4 of the non-ejection drive waveforms. Waveform W2 is superimposed on (drive pulses MS1 to MS4).

  In the drive signal of the first embodiment, the drive signal generation circuit 37 selectively selects a non-ejection drive waveform (drive pulses MS1 to MS4) on which the waveform W2 is superimposed and an ejection drive waveform (drive pulses PS1 to PS3). It is obtained by combining and outputting.

(Example 2)
FIG. 11 is a timing chart showing an example of drive signals (drive signals 0 to 3) of Example 2 in the present embodiment. FIG. 12 is a timing chart illustrating an example of the drive signal 1 (waveform W5) according to the second embodiment.
In the drive signal as Example 2 in the present embodiment, the waveform W2 is superimposed on all of the drive signals 0 to 3 (see FIG. 7) in the prior art. That is, the non-ejection drive waveform generated by the drive signal generation circuit 37 is a waveform in which the waveform of the second frequency is superimposed, and the ejection drive waveform is also a waveform in which the waveform of the second frequency is superimposed.
For example, the drive signal (waveform W5) of the second embodiment shown in FIG. 12 is a waveform showing a state in which the waveform W2 is superimposed on the entire drive signal 1 (see FIG. 7) in the prior art, and the period T1 within that waveform ~ T2 is shown.
As shown in FIG. 11, the same applies to the other drive signals (drive signals 0, 2, and 3), and the waveform W2 is superimposed on the entire drive signals 0 to 3 (see FIG. 7).

  The drive signal of the second embodiment is obtained by superimposing the waveform W2 on the entire drive signals 0 to 3 and outputting them in the drive signal generation circuit 37.

In the second embodiment, it is preferable that the second frequency is a natural number multiple of the frequency of the ejection drive waveform. This is because the second frequency waveform (waveform W2) is also superimposed on the ejection drive waveform (drive pulses PS1 to PS3), and therefore the second frequency is a natural number multiple of the frequency of the ejection drive waveform. This is because the timing control (waveform rising / falling waveform control and generation timing control thereof) when generating the ejection driving waveform becomes easier, and the ejection driving waveform can be generated with higher reproducibility. As a result, ink ejection can be controlled with higher accuracy.
The frequency of the ejection driving waveform is the same frequency (f1 = 4 / T) as the first frequency.

(Example 3)
The drive signal as Example 3 in the present embodiment is the second superimposed on the waveform of the first frequency that vibrates the meniscus in the drive signal output from the drive signal generation circuit 37 of Example 1 and Example 2 described above. The frequency waveform is a waveform that vibrates the surface of the meniscus in-plane.
Here, the in-plane vibration means vibration in which a vibration wave is formed on the meniscus surface as conceptually shown in FIG. On the other hand, FIG. 14 is a diagram conceptually showing the vibration of the meniscus surface. The amplitude V3 (see FIG. 10) of the second frequency waveform that causes the meniscus to vibrate in-plane is extremely smaller than the amplitude V2 of the first frequency waveform, and is a signal that does not cause ink to be ejected. Is higher frequency than the frequency of the first frequency waveform and higher than the ultrasonic band.

As described above, according to the liquid ejection apparatus according to the present embodiment, the following effects can be obtained.
The non-ejection drive waveform that drives the pressure fluctuation inducing unit 72 to such an extent that ink is not ejected from the nozzle 74 has a first frequency waveform that causes the meniscus to vibrate in a direction along the direction in which ink is ejected from the nozzle 74. This is a waveform in which a waveform having a second frequency higher than the frequency is superimposed. That is, by driving the pressure fluctuation inducing portion 72 with this non-ejection driving waveform, the meniscus is vibrated to the extent that ink is not ejected from the nozzle 74, and the cavity 73 (and the region from the cavity 73 to the tip of the nozzle 74) is also generated. It is possible to propagate the vibration of the first frequency and the waveform of the second frequency higher than the first frequency to the ink to be stored. As a result, it is possible to prevent the ink in the vicinity of the meniscus from thickening and sticking to the nozzle 74 and to stir the ink contained in the cavity 73 (and the region from the cavity 73 to the tip of the nozzle 74) more effectively. can do. That is, for example, even when the ink contains a sediment component, the sedimentation is suppressed by more effective agitation, thereby suppressing the occurrence of ink ejection failure due to sedimentation. Moreover, since the frequency of eliminating (returning) ink discharge defects is reduced by discharging ink from the cavity 73, the amount of ink consumed (discarded) for recovery can be reduced. Further, since the frequency of returning the defect is reduced, the productivity can be improved. In particular, in a printer 100 in which the print head 13 is a line head type, when performing flushing for discharging ink from the cavity 73, it is necessary to move the line head or a member that receives the flushed ink, which reduces productivity. . On the other hand, since the number of times flushing is performed can be reduced, productivity can be improved.

  The amplitude of the vibration of the second frequency waveform (non-ejection drive waveform (waveform having a frequency higher than the frequency for vibrating the meniscus)) is the same as the first frequency waveform (non-ejection drive waveform (waveform for vibrating the meniscus)). ) Is smaller than the vibration amplitude. That is, when the vibration of the waveform of the second frequency is smaller than the amplitude of the waveform of vibrating the meniscus and the frequency is increased, ink ejection is suppressed and the vibration of the meniscus is affected. The vibration of the waveform of the second frequency can be propagated in the ink without any problem.

  Further, according to Example 2 of the present embodiment, the ejection driving waveform is also a waveform in which the waveform of the second frequency is superimposed, so that the cavity 73 can be obtained due to the effect of the waveform of the second frequency even during ink ejection. The ink accommodated in (and the region from the cavity 73 to the tip of the nozzle 74) can be agitated (at any time by the waveform of the second frequency).

  In Example 2 of the present embodiment, in particular, by setting the second frequency to be a natural number multiple of the frequency of the ejection drive waveform, timing control for generating the ejection drive waveform becomes easier, and ejection is performed with higher reproducibility. A drive waveform can be generated. As a result, ink ejection can be controlled with higher accuracy.

  Further, according to Example 3 of the present embodiment, the non-ejection drive waveform that drives the pressure fluctuation inducing unit 72 to the extent that ink is not ejected from the nozzle 74 causes the meniscus to extend in the direction along which the ink is ejected from the nozzle 74. This is a waveform obtained by superimposing a second frequency waveform for in-plane vibration of the meniscus surface on the first frequency waveform to be vibrated. That is, by driving the pressure fluctuation inducing portion 72 with this non-ejection driving waveform, the meniscus can be vibrated to the extent that ink is not ejected from the nozzle 74 while vibrating the meniscus surface in-plane. Here, since the second frequency is high enough to cause the surface of the meniscus to vibrate in-plane (that is, the waveform of the second frequency has a larger energy), the cavity 73 (and the cavity 73 to the nozzle 74). The ink stored in the region up to the tip can be stirred more effectively. Further, by vibrating the surface of the vibrating meniscus in-plane, the vibration of the ink in the vicinity of the meniscus is performed in a local range in the vicinity of the interface in contact with the air at the nozzle 74 tip region. Even when the ink thickens in the meniscus due to the volatilization of the components, the thickening range is kept in the vicinity of the meniscus. That is, the sticking due to the thickening of the ink is suppressed, and the thickened ink can be kept in the vicinity of the meniscus. As a result, even when a predetermined discharge is not performed due to the thickened ink, it is only necessary to discharge the thickened ink that remains in the vicinity of the meniscus, so it is easier to discharge the defect. Can be canceled (returned). In addition, the amount of ink consumed (discarded) for return can be reduced to a smaller amount.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below. Here, the same components as those in the above-described embodiment are denoted by the same reference numerals, and redundant description is omitted.

(Modification 1)
FIG. 15 is a timing chart illustrating an example of a drive signal (waveform W5a) according to the first modification.
In the second example of the first embodiment, as illustrated in FIG. 12, the driving signal is obtained by superimposing the waveform W2 on the driving signals 0 to 3 and outputting the driving signal 0 to 3 in the driving signal generation circuit 37. . In this case, the amplitude of the vibration based on the second frequency waveform of the ejection drive waveform is V3, similar to the amplitude of the vibration based on the second frequency waveform of the non-ejection drive waveform, but the second of the ejection drive waveform. The vibration amplitude based on the second frequency may be smaller than the vibration amplitude based on the second frequency waveform of the non-ejection drive waveform. That is, as shown in FIG. 15, in the vibration amplitude V2 based on the second frequency waveform of the ejection drive waveform and the vibration amplitude V3 based on the second frequency waveform of the non-ejection drive waveform, V2 <V3. May be.

  According to this modification, the vibration amplitude V2 based on the second frequency waveform of the ejection drive waveform is smaller than the vibration amplitude V3 based on the second frequency waveform of the non-ejection drive waveform. In addition, the ink contained in the cavity 73 (and the region from the cavity 73 to the tip of the nozzle 74) can be agitated by the effect of the waveform of the second frequency. The influence of vibration based on the waveform can be suppressed.

(Modification 2)
FIG. 16 is a timing chart illustrating an example of drive signals (drive signals 0 to 3) according to the second modification. FIG. 17 is a timing chart showing an example of the drive signal 1 (waveform W5b) according to the second modification. FIG. 17 shows periods T1 to T2 of the waveform W5b.
In the above-described embodiment, the non-ejection drive waveform generated by the drive signal generation circuit 37 is the waveform of the first frequency that vibrates the ink meniscus formed in the nozzle 74 in the direction along which the ink is ejected from the nozzle 74. Furthermore, although it has been described that the waveform of the second frequency higher than the first frequency is superimposed, in the second modification, the non-ejection drive waveform is included in the ejection drive waveform generated by the drive signal generation circuit 37. Are superimposed.
Here, the non-ejection drive waveform superimposed on the ejection drive waveform is the second frequency waveform (waveform W2) in the first embodiment. In this modification, the waveform W1 that vibrates the meniscus of ink formed on the nozzle 74 is not used. That is, the non-ejection drive waveform that drives the pressure fluctuation inducing unit 72 (actuator 77) to the extent that ink is not ejected from the nozzle 74 is the waveform (waveform W2) of the second frequency in the first embodiment.

  According to this modification, since the non-ejection drive waveform is superimposed on the entire ejection drive waveform for driving the pressure fluctuation inducing unit 72 so as to eject ink from the nozzles 74, the pressure fluctuation inducing unit 72 is driven to eject. By simply applying the waveform, vibration based on the non-ejection drive waveform is propagated to the ink stored in the cavity 73 (and the region from the cavity 73 to the tip of the nozzle 74) during the ink ejection period and the non-ejection period. Can be made. As a result, the ink in the vicinity of the meniscus can be prevented from thickening and adhering to the nozzle 74 during the ink non-ejection period, and the cavity 73 (and cavity) can also be produced during the ink ejection period due to the effect of the non-ejection drive waveform. The ink stored in the region 73 to the tip of the nozzle 74 can be agitated. Further, since it is only necessary to apply the ejection drive waveform to the pressure fluctuation inducing section 72, the drive control for the pressure fluctuation inducing section 72 can be simplified.

  In the present modification, the non-ejection drive waveform superimposed on the entire ejection drive waveform is preferably a waveform that causes the surface of the ink meniscus formed in the nozzle 74 to vibrate in-plane. In other words, the non-ejection drive waveform that causes the surface of the ink meniscus formed in the nozzle 74 to vibrate in-plane is superimposed on the ejection drive waveform that drives the pressure fluctuation inducing unit 72 so as to eject ink from the nozzle 74. By simply applying an ejection driving waveform to the pressure fluctuation inducing section 72, non-ejection is performed on the ink stored in the cavity 73 (and the region from the cavity 73 to the tip of the nozzle 74) during the ink ejection period and the non-ejection period. Vibration based on the driving waveform can be propagated, and the surface of the meniscus formed on the nozzle 74 can be vibrated in-plane. Here, since the non-ejection driving waveform has a frequency that is high enough to cause the meniscus surface to vibrate in-plane (that is, the non-ejection driving waveform has a larger energy), the cavity 73 (and from the cavity 73 to the tip of the nozzle 74) The ink accommodated in the (region) can be stirred more effectively. Further, by vibrating the surface of the vibrating meniscus in-plane, the vibration of the ink in the vicinity of the meniscus is performed in a local range in the vicinity of the interface in contact with the air at the nozzle 74 tip region. Even when the ink thickens in the meniscus due to the volatilization of the components, the thickening range is kept in the vicinity of the meniscus. That is, the sticking due to the thickening of the ink is suppressed, and the thickened ink can be kept in the vicinity of the meniscus. As a result, even when a predetermined discharge is not performed due to the thickened ink, it is only necessary to discharge the thickened ink that remains in the vicinity of the meniscus, so it is easier to discharge the defect. Can be canceled (returned). In addition, the amount of ink consumed (discarded) for return can be reduced to a smaller amount.

Note that, in the above description, in the portion described as further superimposing the waveform of the second frequency higher than the first frequency on the waveform of the first frequency, the waveform of the first frequency is not necessarily limited in advance. The method is not limited to the method of generating the waveform of the second frequency and superimposing the waveform of the second frequency on the waveform of the first frequency. That is, when the waveform of the first frequency includes the waveform component of the second frequency in the stage of generating the waveform of the first frequency, a method of leaving the waveform component of the second frequency may be used. .
Specifically, for example, a method of leaving a ripple of the second frequency remaining in the waveform of the first frequency may be used. More specifically, for example, when a waveform of the first frequency is generated via a digital amplifier using a PDM (Pulse Density Modulation) method or a PWM (Pulse Width Modulation) method, a frequency higher than the first frequency is used. If there is a residual ripple component due to the basic pulse, a method of generating a drive signal having the waveform component of the second frequency by leaving the ripple may be used.
Even with such a method, the same effects as those of the above-described embodiment can be obtained.

  By the way, various types can be combined with the drive signal which the drive signal generation circuit 37 produces | generates like the Example and modified example of embodiment mentioned above. Therefore, ink is not ejected from the nozzles 74 in accordance with the usage state of the nozzles 74 provided in the printer 100 and the ink specifications (for example, the time during which ink is not ejected, the temperature of the environment, the viscosity of the ink, the ink composition, etc.). A non-ejection driving waveform for driving the pressure fluctuation inducing unit 72 (that is, a vibration (stirring) mode related to suppression of ink thickening and viscosity unevenness) can be considered. For example, several methods may be set in advance as the vibration (stirring) mode, and the method may be selected or selected depending on the situation.

As vibration (stirring) modes set in advance, for example, three modes of strong, medium and weak are prepared.
The strong mode is, for example, a mode in which Example 2 is combined with Example 2 in the first embodiment.
The middle mode is, for example, the mode of Example 1 in the first embodiment.
The weak mode is, for example, a mode according to the prior art.

  Further, the amplitude V3 of the waveform of the second frequency to be superimposed may be changeable according to the mode. For example, it is possible to save power by keeping the required minimum strength.

  DESCRIPTION OF SYMBOLS 1 ... Printing system, 5 ... Roll paper, 10 ... Printing part, 11 ... Head unit, 12 ... Ink supply part, 13 ... Print head, 14 ... Head driver, 20 ... Moving part, 30 ... Control part, 31 ... Interface part 32 ... CPU, 33 ... memory, 34 ... drive control unit, 35 ... movement control signal generation circuit, 36 ... discharge control signal generation circuit, 37 ... drive signal generation circuit, 40 ... scanning unit, 41 ... carriage, 42 ... guide Axis 50 ... Conveying section 51 ... Supplying section 52 ... Storage section 53 ... Conveying roller 55 ... Platen 71 ... Vibration plate 72 ... Pressure fluctuation inducing section 73 ... Cavity 74 ... Nozzle 75 ... Nozzle plate 76 ... Cavity substrate, 77 ... Actuator, 77a ... Piezoelectric thin film, 77b, 77c ... Electrode, 78 ... Reservoir, 83 ... Ink supply port, 100 ... Printer , 110 ... image processing apparatus, 111 ... printer controller, 112 ... input unit, 113 ... display unit, 114 ... storage unit, 115 ... CPU, 116 ... ASIC, 117 ... DSP, 118 ... memory, 119 ... printer interface unit.

Claims (8)

A liquid ejection head having a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a pressure fluctuation inducing section for inducing pressure fluctuation in the pressure chamber;
Drive waveform generation for generating a discharge driving waveform for driving the pressure fluctuation inducing unit so that the liquid is discharged from the nozzle and a non-discharge driving waveform for driving the pressure fluctuation inducing unit to the extent that the liquid is not discharged from the nozzle Means, and
The non-ejection drive waveform has a second frequency higher than the first frequency in a waveform of a first frequency that vibrates the meniscus of the liquid formed in the nozzle in a direction along the direction in which the liquid is ejected from the nozzle. A liquid ejecting apparatus having a waveform in which a waveform of the frequency is superimposed.   The liquid ejection apparatus according to claim 1, wherein the waveform of the second frequency is a waveform that vibrates the surface of the meniscus in-plane.   The liquid ejection apparatus according to claim 1, wherein an amplitude of the waveform of the second frequency is smaller than an amplitude of the waveform of the first frequency.   4. The liquid ejection apparatus according to claim 1, wherein the ejection driving waveform is a waveform in which the waveform of the second frequency is superimposed. 5.   The liquid ejection apparatus according to claim 4, wherein the second frequency is a natural number multiple of the frequency of the ejection drive waveform.   The amplitude of vibration based on the waveform of the second frequency of the ejection drive waveform is smaller than the amplitude of vibration based on the waveform of the second frequency of the non-ejection drive waveform. 5. The liquid ejection device according to 5. A liquid ejection head having a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and a pressure fluctuation inducing section for inducing pressure fluctuation in the pressure chamber;
Drive waveform generation for generating a discharge driving waveform for driving the pressure fluctuation inducing unit so that the liquid is discharged from the nozzle and a non-discharge driving waveform for driving the pressure fluctuation inducing unit to the extent that the liquid is not discharged from the nozzle Means, and
The liquid ejection apparatus, wherein the ejection drive waveform is a waveform in which the non-ejection drive waveform is superimposed.   The liquid ejection apparatus according to claim 7, wherein the non-ejection driving waveform is a waveform that causes in-plane vibration of a surface of the liquid meniscus formed on the nozzle.

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