JP2017209790A - Droplet ejection apparatus and droplet ejection method - Google Patents

Abstract

Disclosed is a droplet ejection device that prevents ejection failure such as instability in droplet ejection characteristics and missing dots due to residual vibration of an ink meniscus in a nozzle opening without newly providing a special circuit.
A printing apparatus includes a print head having nozzles that eject ink droplets, and a print head control unit that controls driving of the print head based on ink droplet ejection data. When a predetermined data pattern is detected in the ink droplet ejection data, the residual vibration of the ink droplet in the nozzle that occurs due to the ejection of the ink droplet affects the ejection of the next ink droplet. Has a discharge data conversion unit 90 for converting into a reduced data pattern that reduces the influence of residual vibration.
[Selection] Figure 6

Description

  The present invention relates to a droplet discharge device and a droplet discharge method.

  As a droplet discharge device, for example, an inkjet printer using a droplet discharge head that discharges droplets (ink droplets) is known. In the droplet discharge head, when a discharge pulse is applied to a pressure generating element provided in a pressure chamber communicating with the nozzle, a pressure fluctuation occurs in the liquid in the pressure chamber, and the droplet is discharged from the nozzle. In this droplet discharge head, the next droplet discharge may become unstable due to the residual vibration of the liquid in the pressure chamber after the droplet discharge (residual vibration of the ink meniscus in the nozzle opening). On the other hand, for example, Patent Document 1 describes a droplet discharge apparatus (inkjet recording apparatus) that uses a technique of applying an auxiliary pulse for suppressing residual vibration of an ink meniscus to a pressure generating element.

JP 2004-66727 A

  However, in the droplet discharge device described in Patent Document 1, a residual signal is generated by using a drive signal generation circuit for generating an auxiliary pulse for suppressing residual vibration of the ink meniscus and a selection circuit for selecting and applying the auxiliary pulse. There has been a problem in that it has to be provided as a circuit of a dedicated design that matches the waveform (that is, the specification of the droplet discharge head).

  The present invention has been made to solve the above-described problems, and can be implemented as the following application examples or forms.

  Application Example 1 A liquid droplet ejection apparatus according to this application example includes a liquid droplet ejection head having a nozzle that ejects liquid droplets, and a control unit that drives and controls the liquid droplet ejection head based on liquid droplet ejection data. A predetermined data pattern in which the residual vibration of the liquid droplets in the nozzle generated by the discharge of the liquid droplets affects the discharge of the next liquid droplets in the liquid droplet discharge data. And a droplet discharge data conversion unit that converts the predetermined data pattern into a reduced data pattern that reduces the influence of the residual vibration.

According to this application example, when the predetermined data pattern in which the residual vibration generated by the discharge of the droplet affects the discharge of the next droplet is included in the droplet discharge data, the liquid included in the control unit The droplet ejection data conversion unit converts the predetermined data pattern into a reduced data pattern that reduces the influence of residual vibration. The controller controls driving of the droplet discharge head based on the converted droplet discharge data, thereby suppressing a drop in droplet discharge quality due to the influence of residual vibration. That is, for example, in an inkjet printer, it is possible to suppress a decrease in print quality.
In addition, since the droplet discharge data conversion unit that converts the droplet discharge data can be simply configured as a function unit by software or firmware, it can be realized without any special control circuit.

  Application Example 2 In the droplet discharge device according to the above application example, n is a natural number, m is a natural number smaller than n, and the predetermined data pattern causes the droplet to be discharged at any timing in a predetermined cycle. When the discharge affected by the residual vibration is the nth counted from the discharge affected by the residual vibration, the droplet discharge data conversion unit performs the nth discharge. The predetermined data pattern is converted into the reduced data pattern by changing the data pattern so that the (n−m) th or (n + m) th ejection is performed.

  According to this application example, the timing of ejecting droplets is shifted from the timing (n-th) of ejection affected by the residual vibration (shifted to the (n−m) th or n + m-th), whereby the influence of the residual vibration is reduced. Droplet discharge data for performing reduced discharge can be obtained.

  Application Example 3 In the droplet discharge device according to the application example, m = 1.

  According to this application example, the ejection of the influence of the residual vibration is performed by shifting the timing of ejecting the droplet to the timing before or after the ejection timing (nth) affected by the residual vibration. Droplet discharge data can be obtained. Since the amount by which the timing is shifted is minimum, for example, in an ink jet printer, it is possible to perform good printing in which deterioration in print quality due to residual vibration is suppressed while minimizing the influence on the printed image.

  Application Example 4 In the droplet discharge device according to the application example described above, the predetermined period is at least twice the shortest period that the droplet discharge head can discharge.

  According to this application example, the predetermined period for ejecting droplets is at least twice the shortest period at which the droplet ejection head can eject, so that the influence of the residual vibration is affected to reduce the influence of the residual vibration. Even when the ejection timing is shifted, it is possible to provide a margin with respect to the ejection limit period of the liquid droplet ejection head, so that it is possible to perform satisfactory liquid droplet ejection.

  Application Example 5 A droplet discharge method according to this application example is a droplet discharge method in which a droplet discharge head is driven and controlled based on droplet discharge data, and droplets are discharged from nozzles of the droplet discharge head. In the droplet discharge data, a predetermined data pattern is detected in which residual vibration of the droplet in the nozzle that occurs with the discharge of the droplet affects the next droplet discharge. A droplet discharge data conversion step for converting the predetermined data pattern into a reduced data pattern that reduces the influence of the residual vibration.

  According to this application example, when the predetermined data pattern in which the residual vibration generated by the discharge of the droplet affects the discharge of the next droplet is included in the droplet discharge data, the droplet discharge data conversion is performed. According to the process, the predetermined data pattern is converted into a reduced data pattern in which the influence of the residual vibration is reduced. By controlling the droplet discharge head based on the converted droplet discharge data, it is possible to suppress the drop in droplet discharge quality due to the influence of residual vibration. That is, for example, in an inkjet printer, it is possible to suppress a decrease in print quality.

1 is a front view illustrating a configuration of a printing apparatus as a droplet discharge apparatus according to Embodiment 1. FIG. 1 is a block diagram of a printing apparatus as a droplet discharge 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 schematically showing the configuration of the print head controller Timing chart showing ejection pulse and vibration waveform of meniscus surface Schematic diagram showing examples of predetermined data patterns and reduced data patterns Flow chart showing processing of the print head controller Block diagram showing a configuration of a print head control unit according to Modification 1

  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-back direction, the -X direction is the forward direction, the Y-axis direction is the left-right direction, The XY plane is a horizontal plane.

(Embodiment 1)
FIG. 1 is a front view showing a configuration of a printing apparatus 100 as a droplet discharge apparatus according to Embodiment 1, and FIG. 2 is a block diagram of the same.
The printing apparatus 100 constitutes a printing system 1 together with an image processing apparatus 110 connected to the printing apparatus 100. Based on the print data including pixel data as “droplet discharge data” received from the image processing apparatus 110, the printing apparatus 100 is desired to use a long print medium 5 that is supplied in a rolled state. This is an ink jet printer that prints the image.

<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 printing apparatus 100 to perform printing. The image processing apparatus 110 is configured using a personal computer as a preferred example.
Software for operating the image processing apparatus 110 includes general image processing application software (hereinafter referred to as an application) that handles image data to be printed, control of the printing apparatus 100, and printing for causing the printing apparatus 100 to execute printing. Includes printer driver software (hereinafter referred to as printer driver) that generates data.

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, images to be printed on the printing apparatus 100, and print jobs under the control of the printer control unit 111. Information to be 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 Printing Apparatus 100>
The printing apparatus 100 includes a printing unit 10, a print medium moving unit 20, a control unit 30, and the like. The printing apparatus 100 that has received the print data from the image processing apparatus 110 controls the printing unit 10 and the printing medium moving unit 20 by the control unit 30 to print an image on the printing medium 5 (image formation).
The print data is converted so that, for example, general image data (for example, RGB digital image information) obtained by a digital camera or the like can be printed by the printing apparatus 100 by the application and printer driver included in the image processing apparatus 110. The image forming data includes a command for controlling the printing apparatus 100.

The printing unit 10 includes a printing head 11 as a “droplet ejection head”, an ink supply unit 12, and the like.
The print medium moving unit 20 includes a scanning unit 40, a conveyance 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 print head 11 has a plurality of nozzles (nozzle rows) that eject printing ink (hereinafter referred to as ink) as ink droplets as “droplets”. The print head 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). By ejecting ink droplets onto the printing medium 5 supported by the platen 55 under the control of the control unit 30 while the print head 11 moves in the scanning direction, a row of dots (raster lines) along the scanning direction is formed. It is formed on the print medium 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 11.
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.

As a method for ejecting ink droplets (inkjet method), a piezo method is used as a preferred example. The piezo method is a method in which a pressure corresponding to a print information signal is applied to ink stored in a pressure chamber by a piezoelectric element (piezo element), and ink droplets are ejected (discharged) from a nozzle communicating with the pressure chamber for printing.
The method for ejecting ink droplets is not limited to this, and other recording methods for ejecting ink into droplets to form dot groups on a print medium may be used. For example, pressure is applied to the ink with a small pump and the nozzle is mechanically vibrated with a quartz crystal vibrator, etc. to forcibly eject ink droplets. A method of jetting and recording a droplet (thermal jet method) may be used.

The print medium moving unit 20 (scanning unit 40, transport unit 50) moves the print medium 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 11) 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 print medium 5 is wound in a roll shape, and sends the print medium 5 to the transport path. The storage unit 52 rotatably supports a reel around which the print medium 5 is wound, and winds the print medium 5 that has been printed from the conveyance path.
The conveyance roller 53 includes a drive roller that moves the print medium 5 in the conveyance direction (Y-axis direction shown in FIG. 1) that intersects the scanning direction, a driven roller that rotates as the print medium 5 moves, and the like. From the supply unit 51 through the printing region of the printing unit 10 (the region in which the print head 11 scans and moves on the upper surface of the platen 55) to form a conveyance path.

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 printing apparatus 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 printing apparatus 100.
The CPU 32 is an arithmetic processing device for controlling the entire printing apparatus 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, according to the program stored in the memory 33 and the print data received from the image processing apparatus 110, via the drive control unit 34, the print medium moving unit 20 (scanning unit 40, transport unit 50), the printing unit 10 ( The print head 11) is controlled.

  The drive control unit 34 controls the drive of the print medium moving unit 20 (scanning unit 40 and transport unit 50) and the printing unit 10 (print head 11 and ink supply unit 12) based on the control of the CPU 32. The drive control unit 34 includes a print head control unit 35 as a “control unit”. The print head controller 35 will be described later.

  With the above configuration, the control unit 30 moves the carriage 41 that supports the print head 11 along the guide shaft 42 with respect to the printing medium 5 supplied to the printing area by the conveyance unit 50 (the supply unit 51 and the conveyance roller 53). An operation of ejecting ink droplets from the print head 11 while moving in the scanning direction (X-axis direction), and an operation of moving the print medium 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 print medium 5.

<Basic functions of the printer driver>
FIG. 3 is an explanatory diagram of the basic functions of the printer driver.
Printing on the print medium 5 is started when print data is transmitted from the image processing apparatus 110 to the printing apparatus 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, full-color image data, etc.) from the application, converts the print data into a format that can be interpreted by the printing apparatus 100, and outputs the print data to the printing apparatus 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 of converting the image data output from the application into a resolution (print resolution) when printing on the print medium 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 11 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 printing apparatus 100 has. . Therefore, for example, when the printing apparatus 100 uses 10 types of CMYK color inks, 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 for converting high gradation number (256 gradations) data into gradation number data that can be formed by the printing apparatus 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 rasterization process includes a path allocation 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 11 (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 printing apparatus 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 11.
As shown in FIG. 4, the print head 11 includes a nozzle array in which a plurality of nozzles for ejecting ink of each color are formed side by side (in the example shown in FIG. 4, 400 nozzles # 1 to # 400, respectively). 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 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 in each nozzle row are assigned a lower number as the nozzles on the downstream side (# 1 to # 400). That is, the nozzle # 1 is located downstream of the nozzle # 400 in the transport direction. Each nozzle is provided with a drive element (the above-described piezo element) for driving each nozzle to eject ink droplets.

FIG. 5 is a cross-sectional view of the main part of the print head 11.
The print head 11 includes a vibration plate 71, a piezoelectric actuator 72 as a pressure generating unit that displaces the vibration plate 71, and a pressure chamber in which ink is filled and the internal pressure is increased or decreased by the displacement of the vibration plate 71. And a nozzle 74 that communicates with the cavity 73 and discharges ink as droplets by increasing or decreasing the pressure in the cavity 73.

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

  The actuator 72 includes comb-shaped electrodes 79a and 79b arranged opposite to each other, and piezoelectric elements 77 (piezo elements) alternately stacked with the comb teeth of the electrodes 79a and 79b. As shown in FIG. 5, the actuator 72 has one end fixed to a fixed plate 81 fixed to the casing 80 of the print head 11, and the other end connected to a vibration plate via a joining plate 82. 71 is joined.

  In the actuator 72 having such a configuration, by applying a drive signal between the electrodes 79a and 79b, the diaphragm 71 is moved up and down as shown by arrows in FIG. Thus, the ink inside the cavity 73 can be vibrated, or ink droplets can be ejected from the nozzles 74.

<Print head drive control>
FIG. 6 is a block diagram schematically showing the configuration of the print head control unit 35.
The print head control unit 35 has a function of driving and controlling the print head 11. Specifically, the print head control unit 35 selectively drives the actuator 72 (piezoelectric element 77) corresponding to each nozzle 74 based on the head control signal (pixel data) and the basic drive signal. A drive signal is generated and applied. That is, the basic drive signal is selectively applied to the actuator 72 based on the print data.
The print head control unit 35 includes an ejection data conversion unit 90 having a function as a “droplet ejection data conversion unit” characterizing the present invention, a shift register 91, a latch 92, a level shifter 93, a switch 94, and the like. The ejection data conversion unit 90, the shift register 91, the latch 92, the level shifter 93, and the switch 94 are provided corresponding to each of the plurality of nozzles 74 included in the print head 11.

Among the basic drive signals, the drive signal COM shown in FIG. 6 is used for causing the print head control unit 35 to drive the actuator 72 and cause the ink in the cavity 73 to vary in pressure, thereby ejecting ink from the nozzles 74. Basic signal. The drive signal COM is generated by a drive signal generation circuit (not shown) included in the drive control unit 34.
Note that the basic drive signal includes a basic signal (not shown) for driving the actuator 72 to apply fine vibration to the ink in the cavity 73.

The head control signal includes a clock signal CLK, a latch signal LAT, a pixel data signal SI, and the like.
The clock signal CLK and the latch signal LAT are generated by an oscillation circuit (not shown) included in the drive control unit 34.
The pixel data signal SI is a serial signal generated by the ejection data conversion unit 90 based on the rasterized pixel data (“droplet ejection data” in the present invention, hereinafter also referred to as ink droplet ejection data).
The pixel data signal SI input to the shift register 91 in synchronization with the clock signal CLK is latched by the latch 92 by the latch signal LAT, and the switch 94 is driven via the level shifter 93, so that the piezoelectric element 77 of the nozzle 74 is obtained. The selected drive signal COM is applied as the ejection pulse PS.

FIG. 7 is a timing chart showing the ejection pulse PS applied to the piezoelectric element 77 and the vibration waveform MW of the meniscus liquid level at the opening of the nozzle 74.
The drive signal COM is a signal having a period T. Therefore, the print head 11 can eject ink droplets at any timing of the cycle T as the “predetermined cycle”.
The graph shown by the solid line in FIG. 7 shows the waveform of the ejection pulse PS0 applied at the first timing T0 of the period T and the vibration waveform MW of the meniscus liquid surface of the corresponding nozzle 74 opening. The meniscus liquid surface is damped (residual vibration) at timings T1 to T3 (or thereafter) after the nozzle 74 ejects ink droplets during the period of timing T0.

  In order to perform the next ejection from the same nozzle 74 following the ejection at the timing T0, the ejection pulses PS1 to the ejection pulses PS3 (or later) are applied at the timing T1 to the timing T3 (or later) following the ejection pulse PS0. be able to. However, since there is such residual vibration, the subsequent ejection may be unstable due to the influence. Specifically, as shown in FIG. 7, at the timings T1 and T2, the residual vibration of the meniscus liquid surface and the vibration by the discharge pulses PS1 and PS2 for discharge are in phase, so the movement of the meniscus liquid surface However, the movement of the meniscus liquid surface becomes unstable because the residual vibration of the meniscus liquid surface and the vibration by the discharge pulse PS3 for discharging are in opposite phases at the timing T3. There is. Further, depending on the degree, there is a case where ejection is not performed.

That is, in the case of the example shown in FIG. 7, when the pixel data signal SI (that is, pixel data) is such that ink droplets are ejected at the timing T3 following the ejection at the timing T0, the predetermined data is obtained at the timing T3. In some cases, ejection may not be performed, and printing may not be performed with a desired print quality. In this case, for example, by changing the discharge at the timing T3 to be discharged at the timing T2 or the timing T4, the discharge following the discharge at the timing T0 can be made more stable.
The print head controller 35 can change this timing. That is, the print head control unit 35 as the “control unit” causes the residual vibration of the ink droplets in the nozzles 74 generated by the ejection of the ink droplets to occur in the ink droplet ejection data (in the rasterized pixel data). “Droplet ejection data conversion” that converts “predetermined data pattern” to “reduced data pattern” that reduces the effects of residual vibration when a “predetermined data pattern” that affects the ejection of ink droplets is detected A discharge data conversion unit 90 as a “part”.
This will be specifically described below.

<Discharge data conversion unit>
The frequency of the residual vibration is determined by the configuration specifications of the print head 11. Therefore, when the specification of the print head 11 is determined (that is, in advance), it is possible to know the ejection timing that is affected by the residual vibration. Accordingly, whether or not there is ejection at the timing affected by the residual vibration in the ink droplet ejection data can be grasped in advance by referring to (analyzing) the data pattern.
For example, as described above, the “predetermined data pattern” in which the residual vibration generated by the ejection of the ink droplet affects the ejection of the next ink droplet is the next ejection in the third period T from the previous ejection. If it is known that the pattern is to be performed, the ink droplet discharge data is analyzed in order, and when the corresponding data pattern (predetermined data pattern) is detected, the next discharge timing is set to the second discharge timing from the previous discharge. By performing processing to change to the timing or the fourth timing, a data pattern (reduced data pattern) that can perform more stable ejection can be obtained.

  Note that when the timing of the next ejection following the previous ejection is changed, there is a case where an influence due to the residual vibration is newly generated at another timing following the next ejection. In the case of such a data pattern, for example, a process such as no change may be included for ejection at the next timing following the previous ejection.

FIG. 8 is a schematic diagram illustrating an example of a “predetermined data pattern” and a converted “reduced data pattern”.
The input pattern shown in FIG. 8 indicates that when the ink droplet ejection data is analyzed in units of 8 bits when the pixel data constituting the ink droplet ejection data is composed of 1-bit data, the “predetermined data pattern” "Is an example of an input pattern in which" is detected. In this example, the “predetermined data pattern” is a pattern having the next discharge in the third cycle T from the previous discharge. That is, a pattern in which ejection is performed in the third bit after ejection of the second bit and ejection in the third bit corresponds to the “predetermined data pattern”.
As shown in FIG. 6, the ejection data conversion unit 90 analyzes the ink droplet ejection data, and when a “predetermined data pattern” is detected, converts the corresponding portion into a “reduced data pattern”.

The output pattern shown in FIG. 8 is an example in which the input pattern is converted into a “reduced data pattern”. The ejection timing is changed as indicated by the arrow shown in the input pattern, and as a result, the ejection timing is converted into a data pattern (reduced data pattern) having no “predetermined data pattern”.
As described above, the ejection data conversion unit 90 recognizes in advance the “predetermined data pattern” to be detected, analyzes the ink droplet ejection data, and detects the “predetermined data pattern” therein. , An algorithm for converting the corresponding part into a corresponding “reduced data pattern” is provided.
The ejection data converter 90 outputs the pixel data signal SI based on the “reduction data pattern” to the shift register 91 (see FIG. 6).

That is, when n is a natural number and m is a natural number smaller than n, the “predetermined data pattern” is composed of a data pattern that ejects ink droplets at any timing of the cycle T, and the influence of residual vibration is reduced. When the discharge received is the nth counted from the discharge having the influence of the residual vibration, the discharge data conversion unit 90 sets the data pattern so that the nth discharge becomes the (n−m) th or n + mth discharge. By changing “predetermined data pattern” to “reduced data pattern”.
That is, the amount by which the timing is shifted is not limited to the adjacent ejection timing (that is, m = 1) as described above, and may be a timing at which the influence of residual vibration is reduced. However, as the amount of shift increases, the ideal dot position in printing will shift, so for example, there is a trade-off between print quality that causes non-ejection due to residual vibration and print quality that decreases due to timing shift. It is desirable to determine m.

  The function of the ejection data conversion unit 90 described above may be configured by firmware in the control unit 30, or may be configured as a function unit by software processed by the CPU 32.

  It has been described that the frequency of residual vibration (that is, the ejection timing affected by the residual vibration) can be known in advance when the configuration specifications of the print head 11 are determined. May not be accurately derived from manufacturing specifications. In that case, analyze the vibration of the ink meniscus when the ink droplets are actually ejected, or analyze the state of the dots formed on the print medium by ejecting the ink droplets. A method of obtaining the ejection timing (the predetermined data pattern described above) for receiving the ink may be used.

  Further, in the printing apparatus 100 having the function of the ejection data conversion unit 90, the predetermined period (period T) is preferably at least twice the shortest period that the print head 11 can eject.

FIG. 9 is a flowchart illustrating processing of the print head control unit 35 when the characteristic ink droplet ejection method of the printing apparatus 100 is regarded as a “droplet ejection method”.
That is, the “droplet discharge method” is a droplet discharge method in which the print head 11 is driven and controlled based on ink drop discharge data (rasterized pixel data) and ink droplets are discharged from the nozzles 74 of the print head 11. In the case where a “predetermined data pattern” is detected in the ink droplet ejection data, the residual vibration of the ink droplet in the nozzle 74 that occurs with the ejection of the ink droplet affects the ejection of the next ink droplet. In addition, a “droplet ejection data conversion step” for converting the “predetermined data pattern” into a “reduced data pattern” that reduces the influence of residual vibration is included.

First, the print head controller 35 receives print data (step S1), and analyzes ink droplet ejection data included in the print data (step S2).
It is determined whether or not the “predetermined data pattern” is included in the ink droplet ejection data (step S3). If it is included (Yes in step S3), the corresponding pattern is changed to the “reduction data pattern”. Conversion is performed (step S4).
While performing the necessary data pattern conversion, the converted ink droplet ejection data is transmitted to the shift register 91 as the pixel data signal SI (step S5).
It is determined whether the transmission of the pixel data signal SI based on the print data is completed (step S6), and the processing from step S2 is continued until the transmission is completed.
Steps S2 to S4 correspond to the “droplet ejection data conversion step” in the present invention.

As described above, according to the droplet discharge apparatus and the droplet discharge method according to the present embodiment, the following effects can be obtained.
When the ink droplet ejection data includes a “predetermined data pattern” in which residual vibration generated by ejection of an ink droplet affects the ejection of the next ink droplet, ejection data conversion included in the print head control unit 35 The unit 90 converts the “predetermined data pattern” into a “reduced data pattern” that reduces the influence of residual vibration. The print head control unit 35 controls driving of the print head 11 based on the converted ink droplet ejection data, thereby suppressing a drop in ink droplet ejection quality due to the influence of residual vibration. That is, for example, in an inkjet printer, it is possible to suppress a decrease in print quality.
In addition, since the ejection data conversion unit 90 that converts ink droplet ejection data can be simply configured as a function unit by software or firmware, it can be realized without a special control circuit.

  Further, by shifting the ink droplet ejection timing from the ejection timing (n-th) affected by the residual vibration (shifted to the (n−m) th or n + m-th), the ejection in which the influence of the residual vibration is reduced is performed. Ink droplet ejection data to be performed can be obtained. In particular, when m = 1 and the timing of ejecting ink droplets is shifted to the timing before or after the ejection timing (n-th) affected by the residual vibration, the amount of timing shift is minimum. For example, in an ink jet printer, it is possible to perform good printing in which deterioration in print quality due to residual vibration is suppressed while minimizing the influence on the printed image.

  Further, when the predetermined period (period T) for ejecting ink droplets is twice or more the shortest period that the print head 11 can eject, it is affected by the residual vibration in order to reduce the influence of the residual vibration. Even when the ejection timing is shifted, it is possible to provide a margin with respect to the ejection limit period of the print head 11, so that it is possible to eject ink droplets favorably.

  In addition, when viewed as a droplet ejection method including a droplet ejection data conversion step, residual vibrations that occur with the ejection of an ink droplet in the ink droplet ejection data affect the ejection of the next ink droplet. When the “data pattern” is included, the “predetermined data pattern” is converted into the “reduced data pattern” in which the influence of the residual vibration is reduced by the droplet discharge data conversion process. By controlling the drive of the print head 11 based on the converted ink droplet ejection data, it is possible to suppress a drop in ink droplet ejection quality due to the influence of residual vibration. That is, for example, in an inkjet printer, it is possible to suppress a decrease in print quality.

  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. 10 is a block diagram illustrating a configuration of a print head control unit 35B included in the printing apparatus 100 according to the first modification.
In the embodiment described above, as shown in FIG. 6, in the print head control unit 35, a “droplet ejection data conversion unit” is provided as the ejection data conversion unit 90 in the previous stage of the shift register 91 to form the pixel data signal SI. Although it has been described that the previous ink droplet ejection data (pixel data subjected to rasterization processing) is converted, the present invention is not limited to such a configuration.
For example, the “predetermined data pattern” included in the data pattern after the ink droplet ejection data is converted into the pixel data signal SI may be detected and converted into the “reduced data pattern”.

As shown in FIG. 10, the print head control unit 35B according to the first modification includes a “droplet discharge data conversion unit” as a discharge data conversion unit 90B in the subsequent stage of the latch 92, and data before being transmitted to the level shifter 93. Pattern analysis (detects “predetermined data pattern”) and conversion (conversion to “reduced data pattern” when “predetermined data pattern” is detected).
The ejection data conversion unit 90B can be configured by a PLD (programmable logic device), an ASIC (Application Specific Integrated Circuit), or the like as a data conversion circuit.

The configuration other than the print head control unit 35B is the same as that of the first embodiment, and the same effect as described above can be obtained also by this modification.
Even when the ink droplet ejection data (rasterized pixel data) is composed of data of 2 bits or more, the data pattern after the ink droplet ejection data is converted into the pixel data signal SI Since analysis and conversion are performed, conversion can be performed relatively easily.

(Modification 2)
In the above-described embodiment, the “droplet discharge data conversion unit” is provided in the printing apparatus 100. However, as in the case of the first embodiment, at the stage of ink droplet discharge data (rasterized pixel data), FIG. 8 can analyze a data pattern for driving the nozzle 74 (specifically, a bit pattern for driving the switch 94), the image processing apparatus 110 is provided with a “droplet ejection data conversion unit”. May be.
Specifically, a printer driver that generates print data is provided with a function as a “droplet discharge data conversion unit”, and pixel data that has been rasterized once is subjected to “predetermined” as in the first embodiment. Detection of “data pattern” and conversion to “reduced data pattern” when “predetermined data pattern” is detected. By generating print data including pixel data that has been converted and transmitting the print data to the printing apparatus 100, it is possible to perform printing with reduced influence of residual vibration due to ejection. In this case, the printer driver needs to acquire the configuration specifications of the print head 11 used in the printing apparatus 100 in advance.
Note that the “droplet discharge device” includes the image processing device 110 in the light of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Printing system, 5 ... Printing medium, 10 ... Printing part, 11 ... Print head, 12 ... Ink supply part, 20 ... Print medium moving part, 30 ... Control part, 31 ... Interface part, 32 ... CPU (Central Processing Unit) , 33 ... Memory, 34 ... Drive control unit, 35 and 35B ... Print head control unit, 40 ... Scanning unit, 41 ... Carriage, 42 ... Guide shaft, 50 ... Conveyance unit, 51 ... Supply unit, 52 ... Storage unit, 53 ... Conveying roller, 55 ... Platen, 71 ... Vibration plate, 72 ... Actuator, 73 ... Cavity, 74 ... Nozzle, 75 ... Nozzle plate, 76 ... Cavity substrate, 77 ... Piezoelectric element, 78 ... Reservoir, 79a, 79b ... Electrode , 80, housing, 81, fixing plate, 82, bonding plate, 83, ink supply port, 90, 90 B, ejection data conversion unit, 91, shift register, 92, rack , 93 ... Level shifter, 94 ... Switch, 100 ... Printing device, 110 ... Image processing device, 111 ... Printer control unit, 112 ... Input unit, 113 ... Display unit, 114 ... Storage unit, 115 ... CPU, 116 ... ASIC, 117: DSP (Digital Signal Processor), 118: Memory, 119: Printer interface unit.

Claims (5)

A droplet discharge head having a nozzle for discharging droplets;
A control unit that drives and controls the droplet discharge head based on the droplet discharge data,
The control unit is
In the droplet discharge data, when a predetermined data pattern is detected in which residual vibration of the droplet in the nozzle that occurs due to the discharge of the droplet affects the discharge of the next droplet, A droplet discharge apparatus comprising: a droplet discharge data conversion unit that converts the predetermined data pattern into a reduced data pattern that reduces the influence of the residual vibration. n is a natural number, m is a natural number smaller than n,
The predetermined data pattern is constituted by a data pattern for discharging the droplets at any timing of a predetermined cycle, and the discharge affected by the residual vibration is counted from the discharge affected by the residual vibration. If it is nth,
The droplet discharge data conversion unit converts the predetermined data pattern into the reduced data pattern by changing the data pattern so that the nth discharge becomes the (n−m) th or n + mth discharge. The droplet discharge device according to claim 1, wherein:   The droplet discharge device according to claim 2, wherein m = 1.   4. The droplet discharge device according to claim 2, wherein the predetermined period is at least twice as short as a minimum period that the droplet discharge head can discharge. 5. A droplet discharge method for driving and controlling a droplet discharge head based on droplet discharge data and discharging a droplet from a nozzle of the droplet discharge head,
In the droplet discharge data, when a predetermined data pattern is detected in which residual vibration of the droplet in the nozzle that occurs due to the discharge of the droplet affects the discharge of the next droplet, A droplet discharge method comprising: a droplet discharge data conversion step of converting the predetermined data pattern into a reduced data pattern that reduces the influence of the residual vibration.

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