JP4501476B2 - Liquid ejecting apparatus and liquid ejecting method - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus and a liquid ejecting method capable of ejecting various liquids toward a medium, and more particularly, to a liquid ejecting apparatus in which a plurality of nozzles arranged in a line are provided on a medium facing surface of a head.

  The liquid ejecting apparatus is an apparatus that ejects liquid. Examples of the liquid ejecting apparatus include a printing apparatus, a color filter manufacturing apparatus, and a dyeing apparatus. The liquid ejecting apparatus includes a head that ejects liquid from a nozzle. Then, the liquid is ejected toward the medium while moving the head in a predetermined direction along the surface of the medium. For this reason, nozzles serving as liquid ejection ports are provided on the medium facing surface of the head. Further, in order to eject a large amount of liquid in a short time, the nozzles are arranged in a line, and constitute a nozzle line.

By the way, in this type of liquid ejecting apparatus, it is required to shorten the process of ejecting liquid. For this reason, regarding the head, the number of nozzles per nozzle row tends to increase. For example, a head having 180 nozzles per nozzle row has also been proposed (see, for example, Patent Document 1). If these nozzles are provided at a pitch corresponding to 180 dpi, the length of the nozzle row is 1 inch (2.54 cm). In addition, a high speed is also required for the liquid ejection frequency (see, for example, Patent Document 2). In such a liquid ejecting apparatus, the moving speed of the head is increased as the liquid ejecting frequency is increased.
Japanese Patent Laid-Open No. 2003-53968 (page 4, FIG. 1) Japanese Patent Laid-Open No. 2003-326716 (page 10, FIG. 5)

In this type of liquid ejecting apparatus, it is known that the droplets ejected from the nozzles are divided into main droplets and satellite droplets and fly. In the conventional apparatus, the flight trajectory of the main droplet and the flight trajectory of the satellite droplet have a substantially constant relationship, and the amount of landing position deviation between them is also substantially constant. For this reason, it is possible to control injection in consideration of this landing position deviation.
However, due to the increase in the number of nozzles per nozzle row, the increase in the liquid ejection frequency, and the increase in the moving speed of the head, satellite droplets flew far from the normal flight trajectory. The phenomenon that caused the landing position shift of was confirmed. This unexpected landing position deviation causes various problems. For example, in a printing apparatus or a textile printing apparatus, it causes color unevenness. Moreover, in a color filter manufacturing apparatus, it becomes a cause of color mixing.

  The present invention has been made in view of such a problem, and an object of the present invention is to realize a liquid ejecting apparatus and a liquid ejecting method that can prevent an unexpected landing position shift of satellite droplets.

The main invention is
A head provided with a nozzle row composed of a plurality of nozzles arranged in a row on the medium facing surface;
A head moving unit that moves the head in a predetermined direction along the surface of the medium;
An interval adjusting unit for adjusting an interval between the head and the medium;
An injection control unit that performs liquid injection control;
A liquid ejecting apparatus comprising:
The injection control unit
Among the plurality of nozzles sandwiched between the nozzle at one end and the nozzle at the other end of the nozzle row,
The number of non-ejecting nozzles that do not eject liquid is determined according to an interval from the medium facing surface to the surface of the medium.

=== Summary of disclosure ===
At least the following will be made clear by the description of the present specification and the accompanying drawings.

  A head provided with a nozzle array composed of a plurality of nozzles arranged in a line on a medium facing surface, a head moving unit that moves the head in a predetermined direction along the surface of the medium, the head and the medium; A liquid ejecting apparatus including an interval adjusting unit that adjusts an interval between the nozzles and an ejection control unit that performs ejection control of the liquid, wherein the ejection control unit applies the nozzle at one end and the nozzle at the other end of the nozzle row. The number of non-ejection nozzles that do not eject liquid is determined in accordance with the interval from the medium facing surface to the surface of the medium among the plurality of nozzles sandwiched.

According to such a liquid ejecting apparatus, the portion of the non-ejection nozzle in the nozzle row is equal to the state in which the interval between adjacent nozzles is wider than the other portions in the nozzle row. For this reason, when the liquid is ejected, an air flow in the direction of the medium accompanying the liquid ejection occurs. However, the air flow is weaker than the other portions in the portion corresponding to the non-ejection nozzle. It may not occur.
Thereby, the flow of air generated as the head moves in a predetermined direction, that is, the flow of air along the medium surface flows through the portion corresponding to the non-ejection nozzle. Therefore, the air flow along the medium surface is less affected by the air flow in the medium direction and flows smoothly. As a result, it is possible to prevent an unexpected landing position shift with respect to the satellite droplet.

In this liquid ejecting apparatus, the ejection control unit determines the non-ejecting nozzles for each predetermined number of nozzles.
According to such a liquid ejecting apparatus, a portion where the air flow in the medium direction is weak or a portion where this flow does not occur occurs at regular intervals. That is, a portion where air along the medium surface passes is formed at regular intervals. As a result, the entire plurality of nozzles belonging to the nozzle row can be used effectively.

In this liquid ejecting apparatus, the non-ejection nozzle is constituted by a plurality of adjacent nozzles.
According to such a liquid ejecting apparatus, the width of the portion through which the air flow along the medium surface passes can be adjusted. Thereby, the non-ejecting nozzle can be arranged optimally for the liquid ejecting apparatus.

In this liquid ejecting apparatus, the number of the adjacent nozzles is determined according to the predetermined number of nozzles.
According to such a liquid ejecting apparatus, the predetermined number of nozzles corresponds to the number of continuous nozzles capable of ejecting liquid. For this reason, the width of the portion through which the air flow along the surface of the medium passes can be matched to the number of nozzles that can eject the liquid.

In this liquid ejecting apparatus, the ejection control unit determines the non-ejection nozzle according to the ejection frequency of the liquid.
According to such a liquid ejecting apparatus, the strength of the air flow in the medium direction changes according to the liquid ejecting frequency, but it can cope with the change.

The liquid ejecting apparatus includes a medium placement unit on which the medium is placed, and the ejection control unit includes information regarding a distance from a surface of the medium placement unit to the medium facing surface, Obtaining a distance from the medium facing surface to the surface of the medium based on the information on the thickness;
According to such a liquid ejecting apparatus, information on the distance from the surface of the medium placement unit to the medium facing surface that can be easily obtained from the apparatus side, and information on the thickness of the medium determined by the type of medium used. Based on this, since the distance from the medium facing surface to the surface of the medium is acquired, there is no need to provide a dedicated measuring unit for measuring the distance from the medium facing surface to the surface of the medium. For this reason, the number of parts can be reduced.

In this liquid ejecting apparatus, the interval adjusting unit is another head moving unit that moves the head in a direction approaching and separating from the medium, and from the surface of the medium mounting unit to the medium The information about the distance to the facing surface is information indicating the position of the head determined by the other head moving unit.
According to such a liquid ejecting apparatus, the distance from the medium facing surface of the head to the surface of the medium is acquired based on the information indicating the position of the head that is easier to move than the medium placement unit. For this reason, the structure can be simplified.

In the liquid ejecting apparatus, the information regarding the thickness of the medium is information indicating a type of the medium.
According to such a liquid ejecting apparatus, since the information on the type of medium used when determining the liquid ejecting frequency or the like is used as information on the thickness of the medium, the number of types of input information is reduced. can do.

Further, a head provided with a nozzle row composed of a plurality of nozzles arranged in a row on a medium facing surface, a head moving unit that moves the head in a predetermined direction along the surface of the medium, the head, and the head A liquid ejecting apparatus comprising: an interval adjusting unit that adjusts an interval with a medium; and an ejection control unit that performs liquid ejection control. The liquid ejecting apparatus includes a medium placing unit on which the medium is placed, and the interval adjustment The unit is another head moving unit that moves the head in a direction approaching and separating from the medium, and the ejection control unit includes a distance from the surface of the medium mounting unit to the medium facing surface. And the information about the thickness of the medium, the distance from the medium facing surface to the surface of the medium is acquired, the distance from the medium facing surface to the surface of the medium, and the ejection frequency of the liquid Depending on the adjacent Non-ejection nozzles that are configured by a plurality of nozzles and do not eject liquid are determined for each predetermined number of nozzles among a plurality of nozzles sandwiched between one end nozzle and the other end nozzle of the nozzle row, and the adjacent plurality The number of the nozzles is determined according to the predetermined number of nozzles, and the information on the distance from the surface of the medium placement unit to the medium facing surface is the position of the head determined by the other head moving unit. The information regarding the thickness of the medium is information indicating the type of the medium.
According to such a liquid ejecting apparatus, since almost all the effects described above are exhibited, the object of the present invention is achieved most effectively.

  Also, a liquid ejecting method for ejecting liquid from the nozzles while moving a head provided with a nozzle array composed of a plurality of nozzles arranged in a line on a medium facing surface in a predetermined direction along the surface of the medium. A step of acquiring a distance from the medium facing surface to the surface of the medium, and a non-ejection nozzle that does not eject liquid according to the distance from the medium facing surface to the surface of the medium. It is also possible to realize a liquid ejecting method including a step defined in a plurality of nozzles sandwiched between one end nozzle and the other end nozzle.

=== Printing system ===
<About the subject of explanation>
There are various types of liquid ejecting apparatuses such as a printing apparatus, a color filter manufacturing apparatus, a display manufacturing apparatus, a semiconductor manufacturing apparatus, and a DNA chip manufacturing apparatus, and it is difficult to describe all of them. Therefore, in this specification, a printing system including a printer as a printing apparatus will be described as an example.

<About the configuration of the printing system>
FIG. 1 is an explanatory diagram showing an external configuration of the printing system 100. The printing system 100 includes a printer 1, a computer 110, a display device 120, an input device 130, and a recording / reproducing device 140. The printer 1 is a printing apparatus that prints an image on a medium such as paper, cloth, or film. In the following description, a sheet S (see FIG. 5), which is a typical medium, will be described as an example. The computer 110 is communicably connected to the printer 1 and outputs a print signal PRT corresponding to the image to the printer 1 in order to cause the printer 1 to print an image. The display device 120 includes a display and displays a user interface such as an application program 114 and a printer driver 116 (see FIG. 2). The input device 130 is, for example, a keyboard 131 or a mouse 132, and is used for operating the application program 114, setting the printer driver 116, or the like along the user interface displayed on the display device 120. The recording / reproducing device 140 is, for example, a flexible disk drive device 141 or a CD-ROM drive device 142.

  A printer driver 116 is installed in the computer 110. The printer driver 116 is a program for realizing the function of displaying the user interface on the display device 120 and the function of converting the image data output from the application program 114 into the print signal PRT. The printer driver 116 is recorded on a recording medium (computer-readable recording medium) such as a flexible disk FD or a CD-ROM. The printer driver 116 can also be downloaded to the computer 110 via the Internet. And this program is comprised from the code | cord | chord for implement | achieving various functions.

  The “printing apparatus” means the printer 1 in a narrow sense, but means a system of the printer 1 and the computer 110 in a broad sense. Accordingly, a printer incorporating the printer driver 116 and the application program 114 described above is also included in the “printing apparatus”. The “liquid ejecting apparatus” according to the claims is also interpreted in the same manner.

=== Printer driver ===
<About the printer driver>
FIG. 2 is a schematic explanatory diagram of basic processing performed by the printer driver 116. In addition, about the component already demonstrated, since the same code | symbol is attached | subjected, description is abbreviate | omitted. In the computer 110, computer programs such as a video driver 112, an application program 114, and a printer driver 116 are operating under an operating system installed in the computer 110. The video driver 112 has a function of causing the display device 120 to display a user interface, for example, in accordance with display commands from the application program 114 and the printer driver 116. The application program 114 has a function of performing image editing, for example, and creates data related to an image (image data). The user can give an instruction for printing an image edited by the application program 114 via the user interface of the application program 114. Upon receiving a print instruction, the application program 114 outputs image data to the printer driver 116.

  The printer driver 116 receives image data from the application program 114, converts the image data into a print signal PRT, and outputs the print signal PRT to the printer 1. Here, the print signal PRT is data in a format that can be interpreted by the printer 1 and includes various command data and pixel data. The command data is data for instructing the printer 1 to execute a specific operation. The pixel data is data relating to pixels constituting an image (printed image) printed on the paper S. For example, the color and size of dots formed at positions on the paper corresponding to certain pixels. It is the data which shows. The printer driver 116 performs resolution conversion processing, color conversion processing, halftone processing, rasterization processing, and the like, converts the image data into a print signal PRT, and outputs the converted print signal PRT to the printer 1. Hereinafter, various processes performed by the printer driver 116 will be described.

  The resolution conversion process is the resolution when printing image data (text data, image data, etc.) output from the application program 114 on the paper S (the interval between dots when printing), and is also called the print resolution. ). For example, when the print resolution is specified as 720 × 720 dpi, the image data received from the application program 114 is converted into image data having a resolution of 720 × 720 dpi.

  Examples of this conversion method include interpolation and thinning of pixel data. For example, when the resolution of the image data is lower than the designated printing resolution, new pixel data is generated between adjacent pixel data by performing linear interpolation or the like. On the contrary, when the resolution of the image data is higher than the print resolution, the resolution of the image data is made equal to the print resolution by thinning out pixel data at a certain rate.

  Note that each pixel data in the image data is data having gradation values in multiple stages (for example, 256 stages) represented by an RGB color space. Hereinafter, the pixel data having RGB gradation values is referred to as RGB pixel data, and image data composed of the RGB pixel data is referred to as RGB image data.

  The color conversion process is a process of converting each RGB pixel data of the RGB image data into data having gradation values of multiple levels (for example, 256 levels) represented by a CMYK color space. This CMYK is the color of the ink that the printer 1 has. That is, C means cyan. M represents magenta, Y represents yellow, and K represents black. Hereinafter, the pixel data having CMYK gradation values is referred to as CMYK pixel data, and the image data composed of these CMYK pixel data is referred to as CMYK image data. This color conversion process is performed by the printer driver 116 referring to a table (color conversion lookup table LUT) in which RGB gradation values and CMYK gradation values are associated with each other.

  The halftone process is a process of converting CMYK pixel data having multi-stage gradation values into CMYK pixel data having small-stage gradation values that can be expressed by the printer 1. For example, CMYK pixel data indicating 256 gradation values is converted into 2-bit CMYK pixel data indicating 4 gradation values by halftone processing. The 2-bit CMYK pixel data includes, for example, “no dot formation” (binary value “00”), “small dot formation” (also “01”), and “medium dot formation” for each color. (Also “10”) and “large dot formation” (also “11”).

  For such halftone processing, for example, a dither method or the like is used, and 2-bit CMKY pixel data is created so that the printer 1 can form dots dispersedly. Note that the method used for the halftone process is not limited to the dither method, and a γ correction method, an error diffusion method, or the like may be used.

  The rasterizing process is a process for changing the CMYK image data subjected to the halftone process in the order of data to be transferred to the printer 1. The rasterized data is output to the printer 1 as the print signal PRT. In this embodiment, non-ejection nozzles that do not eject ink are determined in this rasterization process. The process for determining the non-injection nozzle will be described in detail later.

<Setting by printer driver>
FIG. 3 is an explanatory diagram of a user interface of the printer driver 116. The user interface of the printer driver 116 is displayed on the display device 120 via the video driver 112. The user can make various settings of the printer driver 116 using the input device 130. Basic settings include image quality settings and paper type settings. These settings will be described later.

=== Configuration of Printer ===
<About printer configuration>
FIG. 4 is a block diagram of the overall configuration of the printer 1 of the present embodiment. FIG. 5 is a schematic diagram of the overall configuration of the printer 1 of the present embodiment. FIG. 6 is a cross-sectional view of the overall configuration of the printer 1 of the present embodiment. Hereinafter, the basic configuration of the printer 1 of the present embodiment will be described with reference to these drawings.

  The ink jet printer 1 according to the present embodiment includes a transport unit 20, a carriage unit 30, a head unit 40, a sensor group 50, and a controller 60. The printer 1 that has received the print signal PRT from the computer 110, which is an external device, controls each unit (conveyance unit 20, carriage unit 30, head unit 40) by the controller 60. The controller 60 controls each unit based on the print signal PRT received from the computer 110 and prints an image on the paper S. The status in the printer is monitored by each sensor of the sensor group 50, and each sensor outputs a detection result to the controller 60. The controller 60 that receives the detection result from each sensor controls each unit based on the detection result.

The transport unit 20 feeds the paper S to a printable position, and transports the paper S by a predetermined transport amount in a predetermined direction (hereinafter referred to as a transport direction) during printing. Here, the transport direction of the paper S is a direction that intersects the carriage movement direction described below, and can also be expressed as a sub-scanning direction. The transport unit 20 functions as a transport mechanism that transports the paper S. The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25.
The paper feed roller 21 is a roller for automatically feeding the paper S inserted into the paper insertion slot into the printer 1. The paper feed roller 21 has a D-shaped cross-sectional shape, and the length of the circumferential portion is set longer than the transport distance to the transport roller 23. For this reason, the sheet S can be sent to the transport roller 23 by rotating the sheet feeding roller 21 in a state where the circumferential portion is in contact with the surface of the sheet. The carry motor 22 is a motor for carrying the paper S in the carrying direction, and is constituted by, for example, a DC motor. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper S being printed from the back side of the paper S. That is, the sheet S as a medium is placed on the platen 24. Accordingly, the platen 24 corresponds to a “medium mounting portion” according to the claims. The paper discharge roller 25 is a roller for transporting the printed paper S in the transport direction. The paper discharge roller 25 rotates in synchronization with the transport roller 23.

  The carriage unit 30 includes a carriage 31, a carriage motor 32 (also referred to as a CR motor), a guide shaft 33, and a gap adjustment lever 34. An ink cartridge 35 that contains ink is detachably attached to the carriage 31. A head 41 that ejects ink from nozzles is attached to the carriage 31. The carriage motor 32 is a motor for reciprocating the carriage 31 in a predetermined direction (hereinafter referred to as a carriage movement direction), and is constituted by, for example, a DC motor. Since the head 41 is attached to the carriage 31, the head 41 and the nozzle move in the same direction as the carriage 31 moves in the carriage movement direction. Therefore, this carriage movement direction corresponds to the “predetermined direction along the surface of the medium” according to the claims. The carriage movement direction can also be expressed as the main scanning direction.

  The guide shaft 33 is a member that supports the carriage 31. The guide shaft 33 of the present embodiment is configured by a metal rod having a circular cross section, and is attached in the carriage movement direction. Accordingly, when the carriage motor 32 operates, the carriage 31 moves along the guide shaft 33 in the carriage movement direction. For this reason, the carriage motor 32, the guide shaft 33, and the like correspond to a “head moving portion” according to the claims.

  The gap adjusting lever 34 is used to adjust the distance between the paper facing surface of the head 41, that is, the “medium facing surface” according to the claims, and the surface of the platen 24, ie, the “surface of the medium placing portion” according to the claims. It is a lever. The gap adjusting lever 34 is attached so as to be tiltable about the rotation shaft 34a. The guide shaft 33 is attached to the gap adjusting lever 34 at a position shifted from the rotation shaft 34a. Therefore, by tilting the gap adjustment lever 34, the guide shaft 33 is moved in the vertical direction. Accordingly, the head 41 is moved in a direction approaching the paper S and a direction away from the paper S.

  The height adjusting mechanism of the head 41 using the guide shaft 33 and the gap adjusting lever 34 adjusts the position of the head 41 in the height direction by moving the guide shaft 33 in the vertical direction. The structure can be simplified. Further, the gap adjusting lever 34 and the guide shaft 33 are “interval adjusting portions” according to claims and correspond to “other head moving portions”. The vertical movement of the head 41 by the gap adjusting lever 34 and the guide shaft 33 will be described later.

  The head unit 40 is for ejecting ink onto the paper S. The head unit 40 has a head 41. As shown in FIG. 8, a nozzle row 42 including a plurality of nozzles (# 1 to # 180) arranged in a row is provided on the paper facing surface 41a of the head 41. Ink is intermittently ejected from each nozzle. When the ink is intermittently ejected from the nozzles while the head 41 is moving in the carriage movement direction, a raster line composed of dots along the carriage movement direction is formed on the paper S. The structure of the head 41, a drive circuit for driving the head 41, and a method for driving the head 41 will be described later.

  The sensor group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, a paper width sensor 54, a head position detection sensor 55 (see FIG. 21), and the like.

  The linear encoder 51 is for detecting a position in the carriage movement direction, and detects a slit formed in the slit plate and a belt-like slit plate installed along the carriage movement direction. A photo interrupter. The rotary encoder 52 is for detecting the amount of rotation of the transport roller 23, and is a disc-shaped slit plate that rotates as the transport roller 23 rotates, and a photo interrupter that detects a slit formed in the slit plate. Have

  The paper detection sensor 53 is for detecting the leading end position of the paper S to be printed. The paper detection sensor 53 is provided at a position where the front end position of the paper S can be detected while the paper feed roller 21 is transporting the paper S toward the transport roller 23. The paper detection sensor 53 is a mechanical sensor that detects the leading edge of the paper S by a mechanical mechanism. More specifically, the paper detection sensor 53 has a lever that can rotate in the paper transport direction, and this lever is disposed so as to protrude into the transport path of the paper S. As the paper S is transported, the front end of the paper comes into contact with the lever, and the lever is rotated. Therefore, the paper detection sensor 53 detects the position of the leading edge of the paper S and the presence or absence of the paper S by detecting the movement of the lever with a photo interrupter or the like.

  The paper width sensor 54 is attached to the carriage 31. The paper width sensor 54 is an optical sensor, and receives the reflected light of the light irradiated on the paper S from the light emitting unit at the light receiving unit, and detects the presence or absence of the paper S based on the received light intensity at the light receiving unit. The paper width sensor 54 detects the position of the edge of the paper S while being moved by the carriage 31 and detects the width of the paper S. It is also possible to detect the leading edge of the paper S by the paper width sensor 54.

  The head position detection sensor 55 is for detecting the position of the head 41 in the height direction. In other words, the head position detection sensor 55 is for detecting the position of the head 41 determined by the guide shaft 33 and the gap adjusting lever 34 as another head moving unit. The head position detection sensor 55 is configured by a switch that detects the tilt state of the gap adjustment lever 34. The head position detection sensor 55 will be described in detail later.

  The controller 60 is a control unit for controlling the printer 1. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 is for transmitting and receiving data between the computer 110 which is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer 1. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and has storage means such as a RAM, an EEPROM, and a ROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

<About the configuration of the head>
FIG. 7A is a cross-sectional view of a part of the head 41 cut in a direction perpendicular to the nozzle row 42. FIG. 7B is an enlarged view of the vicinity of the pressure chamber in FIG. 7A. FIG. 8 is a diagram for explaining the arrangement of nozzles #i on the paper facing surface 41 a of the head 41.

  The head 41 includes a case 411, a flow path unit 412 bonded to the front end surface of the case 411, and a piezo element unit 413 attached inside the case 411. The case 411 is a block-shaped member in which an accommodation chamber 411a for accommodating the piezo element unit 413 is formed. The case 411 is made of a resin such as an epoxy resin, for example. The accommodation chamber 411a is provided through the case 411. Specifically, it is provided from the adhesion surface with the flow path unit 412 to the attachment surface to the carriage 31. One accommodation chamber 411 a is provided for one piezo element unit 413. The piezo element unit 413 is attached to each nozzle row 42. In this embodiment, as will be described later, since eight nozzle rows 42 are provided, the case 411 is provided with eight storage chambers 411a, and the piezoelectric element unit 413 is attached to each storage chamber 411a. .

  The channel unit 412 includes a channel forming plate 412a, an elastic plate 412b bonded to one surface of the channel forming plate 412a, and a nozzle plate 412c bonded to the other surface of the channel forming plate 412a. . The flow path forming plate 412a is formed from a silicon wafer, a metal plate, or the like. The channel forming plate 412a is formed with a groove and a through hole having a predetermined shape. For example, a groove serving as a pressure chamber 412d, a through-hole serving as a nozzle communication port 412e communicating between the pressure chamber 412d and the nozzle #i, and a through-hole serving as a common ink chamber 412f (corresponding to a “common liquid chamber”). And a groove serving as an ink supply path 412g (corresponding to a “liquid supply path”) communicating between the pressure chamber 412d and the common ink chamber 412f.

  The elastic plate 412b includes a support frame 412h, an elastic film 412i supported by the support frame 412h, and an island portion 412j with which the tip surface of the piezo element comes into contact. In the elastic plate 412b, an island portion 412j is formed at a portion corresponding to the pressure chamber 412d. The bonding surface of the island portion 412j with the elastic film 412i is slightly smaller than the opening shape of the groove portion that becomes the pressure chamber 412d. For this reason, an elastic region is formed by the elastic film 412i around the island portion 412j.

  The nozzle plate 412c is a thin plate material provided with a plurality of nozzles #i. Stainless steel is suitably used for the nozzle plate 412c. The nozzle plate 412c is provided with eight nozzle rows 42 including A rows to H rows. Each nozzle row 42 is provided such that the arrangement direction of the nozzles #i is the transport direction. In this embodiment, one nozzle row 42 has 180 nozzles. Each nozzle #i is formed at an interval corresponding to 180 dpi. Accordingly, the length of each nozzle row 42 is about 1 inch. Further, the nozzle rows 42 are provided in a state of being arranged in the carriage movement direction. These nozzle rows 42 are grouped by two rows. In the example of FIG. 8, the nozzle row 42 of the A row and the nozzle row 42 of the B row belong to the same group, and the nozzle row 42 of the C row and the nozzle row 42 of the D row belong to the same group. Similarly, the E-row nozzle row 42 and the F-row nozzle row 42 belong to the same group, and the G-row nozzle row 42 and the H-row nozzle row 42 belong to the same group. The nozzle rows belonging to the same group are provided at positions close to each other. The nozzle rows belonging to the same group are formed with a half-pitch shift in the nozzle row direction (conveyance direction). On the other hand, the interval between groups is wider than the interval between nozzle rows belonging to the same group.

  The piezo element unit 413 includes a piezo element group 413a, and an adhesive substrate 413b in which the piezo element group 413a is bonded to one surface and the other surface is bonded to the case 411. The piezoelectric element group 413a is formed in a comb-like shape by forming slits at a predetermined pitch corresponding to each pressure chamber 412d of the flow path unit 412 on a piezoelectric substrate in which piezoelectric bodies and electrode layers are alternately stacked. Yes. Each of the comb teeth is a piezo element PZT. Accordingly, one piezo element unit 413 has 180 piezo elements PZT (comb teeth). In addition, each piezo element PZT is bonded in a state in which a part on the tip side protrudes outward from the edge of the adhesive substrate 413b. That is, each piezo element PZT is bonded to the adhesive substrate 413b in a cantilever state.

  The piezo element unit 413 is inserted into the housing chamber 411a of the case 411 with the piezo element group 413a tip directed toward the flow path unit 412. In this inserted state, the bonding surface of the bonding substrate 413 b with the case 411 is bonded to the inner wall of the case 411. Further, in this bonded state, each tip surface of the piezo element PZT is bonded to the corresponding island portion 412j. Each piezoelectric element PZT expands and contracts in the element longitudinal direction perpendicular to the stacking direction by applying a potential difference between the opposing electrodes. Due to the expansion and contraction of the piezo element PZT, the island portion 412j is pushed toward the pressure chamber 412d or pulled away from the pressure chamber 412d. At this time, since the elastic film 412i around the island portion is deformed, ink droplets can be ejected from the nozzles.

<About driving the head>
9 and 10 are diagrams for explaining the head driving unit 43 that drives the head 41 and its peripheral part. FIG. 11 is a diagram for explaining the original drive signal ODRV generated from the original drive signal generator 44. FIG. 12 is a diagram illustrating the drive signal DRV (i) for each nozzle.

  The head drive unit 43 drives the corresponding piezo element PZT based on the serially transmitted print signal PRT in order to eject ink droplets from each nozzle #i. The head driving unit 43 is provided for each nozzle row 42. The head driving unit 43 includes a first shift register group 431, a second shift register group 432, a latch circuit group 433, a decoder group 434, and a switch group SW. Then, the first shift registers 431 (1) to 431 (180) of the first shift register group 431, the second shift registers 432 (1) to 432 (180) of the second shift register group 432, and the latch circuit group 433. The first latch circuit and the second latch circuit (both not shown), the decoder (not shown) of the decoder group 434, and the switches SW (1) to SW (180) of the switch group SW are nozzles. A number corresponding to the nozzle #i in the row 42 is provided. In the present embodiment, one nozzle row 42 includes 180 nozzles. For this reason, 180 of these first shift registers, second shift registers, decoders, and switches are also provided for one nozzle row 42. Here, the numbers in parentheses in FIG. 10 indicate the numbers of the nozzles #i corresponding to the members (or signals).

  First shift registers 431 (1) to 431 (180), second shift registers 432 (1) to 432 (180), first latch circuit, second latch circuit, decoder, and switches SW (1) to SW (180 ) Are grouped by nozzle. The input of the first latch circuit is connected to the corresponding first shift registers 431 (1) to 431 (180), and the input of the second latch circuit is the corresponding second shift registers 432 (1) to 432 ( 180). The outputs of the first latch circuit and the second latch circuit are connected to corresponding decoders. Further, the output of this decoder is connected to the corresponding switches SW (1) to SW (180).

  The original drive signal ODRV is a signal that is the basis of the drive signal DRV (i) for each nozzle, and is used in common for each piezo element PZT. The original drive signal ODRV in the present embodiment has four drive pulses of a first drive pulse W1 to a fourth drive pulse W4 within a time T during which the nozzle crosses the distance of one pixel. Here, the first drive pulse W1 is a drive pulse for medium dots. That is, when the first drive pulse W1 is supplied to the piezo element PZT, an amount of medium ink droplets corresponding to the medium dots is ejected from the nozzle #i. The second driving pulse W2 is a driving pulse for small dots. That is, when the second drive pulse W2 is supplied to the piezo element PZT, a small ink droplet corresponding to a small dot is ejected from the nozzle #i. The third drive pulse W3 is a drive pulse for medium dots, like the first drive pulse W1. The fourth drive pulse W4 is a drive pulse for fine vibration. That is, when the fourth pulse W4 is supplied to the piezo element PZT, the meniscus slightly vibrates and ink thickening is prevented.

  The print signal PRT is a signal for serially transmitting pixel data for the number of nozzles. The serially transmitted print signal PRT is input to the head drive unit 43 and converted into a print signal PRT (i) that is pulse selection data for each nozzle. The print signal PRT (i) is a signal corresponding to the pixel data, and is assigned to one pixel assigned to the nozzle #i. In the present embodiment, since there are four drive pulses (first pulse W1 to fourth pulse W4) within a time T crossing the distance of one pixel, the print signal PRT (i) is 4-bit data per pixel. Have Each bit of the print signal PRT (i) indicates ON / OFF of the corresponding drive pulse. The print signal PRT (i) is output from the decoder to the switch SW (i).

  The drive signal DRV (i) is a signal for driving each piezo element PZT (i). The drive signal DRV (i) of this embodiment is obtained by controlling the supply of the original drive signal ODRV to the piezo element PZT (i) based on the print signal PRT (i). When the drive signal DRV (i) is input to the piezo element PZT (i), the piezo element PZT (i) is deformed according to the voltage change of the drive signal DRV (i). When the piezo element PZT (i) is deformed, the elastic film 412i (side wall) defining a part of the pressure chamber 412d is deformed, and ink is ejected from the nozzle #i, or the meniscus of the nozzle #i is slightly vibrated. .

  The first control signal S1 is input to the latch circuit group 433 and the decoder group 434. The second control signal S2 is input to the decoder group 434. The first control signal S1 and the second control signal S2 have a pulse indicating the timing at which the print signal PRT (i) changes.

  The print signal PRT serially transmitted to the head drive unit 43 is converted into a print signal PRT (i) that is 4-bit data for each nozzle, for example, as described below. First, the upper bits of the pixel data constituting the print signal PRT are input to the first shift register group 431 in the order of nozzles. Next, the lower bits of the pixel data are input to the first shift register group 431 in the order of nozzles. Here, since the second shift register group 432 is connected in series downstream of the first shift register group 431, when the lower bits of the pixel data are input to the first shift register group, the upper bits of the pixel data Shift from the first shift register group 431 to the second shift register group 432.

  When all the print signals PRT (pixel data) are set in the shift register groups 431 and 432, the pulse of the first control signal S1 is input to the latch circuit group 433. As a result, the data of the shift register groups 431 and 432 are latched by the latch circuit group 433. That is, the print signal PRT (for example, the lower bits of the pixel data) set in the first shift register is latched by the first latch circuit, and the print signal PRT (for example, the upper bits of the pixel data) is set in the second shift register. Bit) is latched by the second latch circuit.

  When the pulse of the first control signal S1 is input to the latch circuit group 433, the pulse of the first control signal S1 is also input to the decoder group 434. When the first control signal S1 is input, the decoder group 434 translates the print signal PRT (that is, 2-bit pixel data) latched by the latch circuit group 433, and outputs the print signal PRT ( i) is obtained. The obtained print signal PRT (i) is output to the switch group SW in order from the most significant bit. That is, when the pulse of the first control signal S1 is input to the latch circuit group 433, the most significant bit of the print signal PRT (i) is output to the switch group SW. Next, when the first pulse of the second control signal S2 is input to the decoder group 434, the second most significant bit of the print signal PRT (i) is output to the switch group SW. Similarly, when the second pulse of the second control signal S2 is input to the decoder group 434, the third bit from the most significant bit of the print signal PRT (i) is output to the switch group SW, and the second control signal S2 When the third pulse is input to the decoder group 434, the least significant bit of the print signal PRT (i) is output to the switch group SW. In this way, the serially transmitted print signal PRT is converted into 180 pieces of 4-bit data and output to the switch group SW.

  When the level of the print signal PRT (i) is “1”, the switch SW (i) passes the drive pulse corresponding to the original drive signal ODRV as it is to obtain the drive signal DRV (i). On the other hand, when the level of the print signal PRT (i) is “0”, the switch SW (i) cuts off the drive pulse corresponding to the original drive signal ODRV.

  In this embodiment, when the print signal PRT (i) is “00”, the corresponding decoder of the decoder group 434 outputs “0001” as the print signal PRT (i). Accordingly, the fourth pulse W4 is supplied to the piezo element PZT (i), and the meniscus is slightly vibrated. When the print signal PRT (i) is “01”, the decoder outputs “0100” as the print signal PRT (i). Thus, the second pulse W2 is supplied to the piezo element PZT (i), and a small dot is formed. When the pixel data is “10”, the decoder outputs “0010” as the print signal PRT (i). As a result, the third pulse W3 is supplied to the piezo element PZT (i) to form a medium dot. If the pixel data is “10”, “1000” may be output from the decoder as the print signal PRT (i), and the first pulse W1 may be supplied to the piezo element PZT (i). Further, when the pixel data included in the print signal PRT is “11”, the decoder outputs “1010” as the print signal PRT (i). Accordingly, the first pulse W1 and the third pulse W3 are supplied to the piezo element PZT (i), and a large dot is formed by two medium ink droplets.

  A plurality of types of original drive signals ODRV are prepared according to the print mode. For each original drive signal, the supply frequency of the drive pulse to the piezo element PZT (i) is determined. For example, when “normal” is set as the image quality, the supply frequency of the drive pulse is, for example, 14.4 kHz. In this case, the ejection frequency of the ink droplet is also 14.4 kHz. On the other hand, when “beautiful” is set as the image quality, the supply frequency of the drive pulse is, for example, 7.2 kHz. In this case, the ejection frequency of the ink droplet is also 7.2 kHz.

<About printing operation>
FIG. 13 is a flowchart of the operation during printing. Each operation described below is executed by the controller 60 controlling each unit in accordance with a program stored in the memory 63. This program has code for executing each operation.

  Print command reception (S001): The controller 60 receives a print command from the computer 110 via the interface unit 61. This print command is included in the header of the print signal PRT transmitted from the computer 110. Then, the controller 60 analyzes the contents of various commands included in the received print signal PRT, controls each unit, and performs the following paper feed operation, transport operation, dot formation operation, and the like.

  Paper Feed Operation (S002): Next, the controller 60 performs a paper feed operation. The paper feeding operation is a process of moving the paper S to be printed and positioning it at a printing start position (so-called cueing position). That is, the controller 60 rotates the paper feed roller 21 and sends the paper S to be printed to the transport roller 23. Subsequently, the controller 60 rotates the transport roller 23 to position the paper S sent from the paper feed roller 21 at the print start position.

  Dot Forming Operation (S003): Next, the controller 60 performs a dot forming operation. The dot forming operation is an operation of forming dots on the paper S by intermittently ejecting ink from the head 41 moving along the carriage movement direction. The controller 60 drives the carriage motor 32 to move the carriage 31 in the carriage movement direction. Further, the controller 60 ejects ink from the head 41 (nozzles) based on the print signal PRT while the carriage 31 is moving. When the ink ejected from the head 41 lands on the paper, dots are formed on the paper.

  Transport Operation (S004): Next, the controller 60 performs a transport operation. The transport operation is a process of moving the paper S relative to the head 41 along the transport direction. The controller 60 drives the transport motor 22 and rotates the transport roller 23 to transport the paper S in the transport direction. By this transport operation, the head 41 can form dots at positions different from the positions of the dots formed by the previous dot formation operation.

  Paper discharge determination (S005): Next, the controller 60 determines whether or not to discharge the paper S being printed. If data for printing on the paper S being printed remains at the time of this determination, the paper is not discharged. Then, the controller 60 alternately repeats the dot formation operation and the transport operation until there is no data to be printed, and gradually prints an image composed of dots on the paper S. If there is no more data for printing on the paper S being printed, the controller 60 determines to discharge the paper.

  Paper Discharge Processing (S006): Next, the controller 60 causes the printed paper S to be discharged. That is, the controller 60 rotates the paper discharge roller 25 to discharge the printed paper S to the outside.

  Print end determination (S007): Next, the controller 60 determines whether or not to continue printing. If printing is to be performed on the next sheet S, the printing is continued and the feeding operation of the next sheet S is started. If printing is not performed on the next sheet S, the printing operation is terminated.

=== Characteristics of the present embodiment ===
<About landing position deviation of satellite ink>
Before describing the features of this embodiment, first, the landing position deviation of satellite ink droplets will be described. Here, FIG. 14A and FIG. 14B are schematic diagrams for explaining the ink droplet generation process. FIG. 15A is a schematic diagram illustrating the flight trajectory of ink droplets. FIG. 15B is a schematic diagram showing the landing position deviation between the main ink droplet and the satellite ink droplet, and shows the landing position deviation that usually occurs.

  In this type of printer 1, the ink droplets ejected from the nozzle #i are divided into a main ink droplet Im and a satellite ink droplet Is and fly. This is because the ink pushed out from the nozzle #i extends in a columnar shape (see FIG. 14A) and the ink column is divided by the surface tension (see FIG. 14B). )). The ease with which satellite ink droplets Is are generated varies depending on the viscosity of the ink and the flying speed of the ink.

  For example, as the viscosity of the ink to be used, an ink having a viscosity within a range of about 2.0 to 12.0 mPa · sec in a temperature range of about 10 to 40 ° C. is used. Specifically, examples of the normal ink include those having a viscosity in the range of about 2.0 to 6.5 mPa · sec, and the pigment ink having a high viscosity has a viscosity of about 8 to 11 mPa · sec. Although those within the range are mentioned, it is difficult to control so as not to generate the satellite ink droplet Is when the ink that can be ejected by the head 41 having the above-described configuration is considered.

  The main ink droplet Im and the satellite ink droplet Is generated in this way are air flowing along the paper surface (corresponding to the “medium surface” according to the claims) as the carriage 31 moves (in this example, For the sake of convenience, in the following description, it is also affected by the horizontal wind. These ink droplets have different flying speeds in the paper direction (vertical direction in this example), and the satellite ink droplet Is has a lower flying velocity than the main ink droplet Im. Furthermore, the amount of satellite ink droplet Is is smaller than that of the main ink droplet Im. Accordingly, the satellite ink droplet Is is more influenced by the cross wind Ws than the main ink droplet Im. As a result, the satellite ink droplet Is is landed on the leeward side of the cross wind Ws than the main ink droplet Im. The amount of deviation between the landing positions of the satellite ink droplet Is and the main ink droplet Im is the difference between the flying speeds of the two ink droplets Im and Is, the distance from the paper facing surface 41a of the head 41 to the paper surface (the ink droplets). It varies depending on the flight distance in the vertical direction), the speed of the cross wind Ws (the moving speed Vcr of the carriage 31), and the like.

<About wind phenomenon>
By the way, as described above, when the number of nozzles #i constituting one nozzle row 42 is increased, the moving speed of the carriage 31 (head 41) is increased, and the ink droplet ejection frequency is increased, the satellite ink is increased. As for the droplet Is, its landing position greatly deviates from the normal position, and an unexpected landing position deviation occurs. Here, FIG. 16 is a diagram schematically showing an unexpected landing position deviation in the satellite ink droplet Is. FIG. 17 is an enlarged schematic view showing a portion where an unexpected landing position deviation occurs.

  As shown in FIG. 16, due to an unexpected landing position shift in the satellite ink droplet Is, a pattern similar to a pattern (that is, a wind pattern) formed by wind is formed on the surface of the paper. For convenience, in the following description, a phenomenon in which a pattern similar to the wind pattern is formed is referred to as a wind pattern phenomenon. Then, as shown in FIG. 17, a pattern similar to this wind pattern is formed mainly due to a landing position shift of the satellite ink droplet Is. Specifically, as shown in FIG. 15B, the main ink droplet Im and the satellite ink droplet Is are landed side by side in the carriage movement direction. However, the landing position of the satellite ink droplet Is is greatly deviated in a place where the wind ripple phenomenon occurs. Such a pattern resembling a wind pattern causes a reduction in image quality and hinders the improvement of image quality. Therefore, it is desired to prevent the occurrence of the wind ripple phenomenon.

  Here, the cause of the occurrence of the wind ripple phenomenon will be considered. As described above, the wind ripple phenomenon is caused mainly by the landing of the satellite ink droplet Is from a normal position. From this, it is considered that the size and weight of the satellite ink droplet Is and the flying speed and the disturbance of the cross wind Ws are involved in the wind ripple phenomenon. That is, since the satellite ink droplet Is is sufficiently smaller than the main ink droplet Im, the degree of deceleration during flight is larger than that of the main ink droplet Im. As an example, the main ink droplet Im has an ink weight of 5.0 ng and a flying speed of 9 m / s. On the other hand, the satellite ink droplet Is has an ink weight of 2.7 ng and a flying speed of 6 m / s. Since the weight is small and the flying speed is slow, the satellite ink droplet Is is more susceptible to the cross wind Ws than the main ink droplet Im. As a result, it is considered that the landing position deviation of the satellite ink droplet Is is caused by the disturbance of the cross wind Ws.

  Next, the disturbance of the cross wind Ws will be examined. Here, FIG. 18A is a diagram schematically showing the cross wind Ws when ink droplets (Im, Is) are ejected from one nozzle #i. FIG. 18B is a diagram schematically showing the cross wind Ws when ink droplets (Im, Is) are ejected from a plurality of continuous nozzles #i. FIG. 19 is a diagram schematically showing the relationship between the flow of air generated by the ejected ink droplets (for convenience, also referred to as downward wind Wv in the following description) and the cross wind Ws. FIG. 20 is a diagram schematically showing a state in which the downward wind Wv is broken by the cross wind Ws.

  According to the simulation, during the movement of the carriage 31, the cross wind Ws flows in a direction opposite to the direction in which the carriage 31 travels. When ink droplets are ejected from one nozzle #i, as shown in FIG. 18A, the cross wind Ws flows while avoiding the ink droplets. This is presumably because, as shown in FIG. 19, the downward air flow Wv, that is, the air flow toward the paper S, is generated by the repeated ejection of ink droplets. In this case, the cross wind Ws flows smoothly because it is sufficient to change the flow by one nozzle.

  When ink droplets are ejected from a plurality of continuous nozzles #i, as shown in FIG. 18B, it is necessary to change the flow of the cross wind Ws by an amount corresponding to these nozzles #i. That is, it is considered that the downward wind Wv performs the same function as the air curtain by repeatedly ejecting ink droplets from these nozzles #i. Therefore, in this case, it is considered that the cross wind Ws hits the downward wind Wv and changes its direction. The downward wind Wv (air curtain) is subjected to a force opposite to the direction in which the carriage 31 travels (hereinafter also referred to as a force due to the lateral wind Ws) when the lateral wind Ws hits it.

  The force due to the cross wind Ws increases as the number of continuous nozzles #i increases. In addition, this force increases as the moving speed Vcr of the carriage 31 increases, that is, as the flow of the cross wind Ws increases. On the other hand, the force of the downward wind Wv decreases as the distance from the sheet facing surface 41a of the head 41 to the sheet surface increases. And when the force by this cross wind Ws becomes stronger than the force of the down wind Wv, for example, as shown in FIG. 20, the cross wind Ws penetrates the down wind Wv. In this state, the flow of the cross wind Ws is disturbed by the interaction with the downward wind Wv. The landing position of the satellite ink droplet Is is shifted from the normal position by the cross wind Ws whose flow is disturbed, and the above-described wind ripple phenomenon is considered to have occurred.

Here, Table 1 and Table 2 show the experimental results of examining the state of occurrence of the wind ripple phenomenon when the number of continuous nozzles #i that eject ink droplets is changed.

  Under the conditions of this experiment, when the number of continuous nozzles #i was 33 or more, the occurrence of the wind ripple phenomenon was visually confirmed. And it was also confirmed that this wind ripple phenomenon becomes remarkable as the number of continuous nozzles #i increases. Note that the number of nozzles #i at which the occurrence of the wind ripple phenomenon is confirmed is the distance PGa (see FIG. 15) from the paper facing surface 41a of the head 41 to the paper surface, the moving speed Vcr of the carriage 31, and the nozzle #i. It is considered that it changes according to the density (formation pitch).

Table 3 shows the experimental results of examining the state of occurrence of the wind ripple phenomenon when the distance PGa from the paper facing surface 41a of the head 41 to the paper surface is changed.

  Under the conditions of this experiment, when the distance PGa from the paper facing surface 41a of the head 41 to the paper surface was 1.2 mm, the occurrence of the wind ripple phenomenon was visually confirmed. It has also been confirmed that this wind ripple phenomenon becomes more prominent as the distance PGa from the paper facing surface 41a of the head 41 to the paper surface becomes larger. Note that the interval at which the occurrence of the wind ripple phenomenon is confirmed also varies depending on the interval PGa from the sheet facing surface 41a of the head 41 to the sheet surface, the moving speed Vcr of the carriage 31, the density of the nozzle #i, and the like.

<The main points of this embodiment>
Thus, the wind ripple phenomenon is considered to be caused by the flying speed of the satellite ink droplet Is and the disturbance of the cross wind Ws. Here, the satellite ink droplet Is is greatly affected by the viscous resistance of air. For this reason, the flying speed of the satellite ink droplet Is decreases as the flying distance of the ink droplet increases. In consideration of this point, in the present embodiment, among the plurality of nozzles #i sandwiched between the nozzle # 1 at one end and the nozzle # 180 at the other end of the nozzle row 42, the distance from the sheet facing surface 41a to the sheet surface The number of non-ejecting nozzles that do not eject ink corresponding to PGa is determined. That is, the number of non-injection nozzles is determined according to the interval PGa. In this case, the number corresponding to the interval PGa includes “0”. For this reason, the non-injection nozzle is not set under the condition where the wind ripple phenomenon does not occur. Then, under the condition where the wind ripple phenomenon occurs, the number of non-injection nozzles corresponding to the remarkableness of the wind ripple phenomenon is set.

  By configuring in this way, the portion of the non-ejection nozzle in the nozzle row 42 becomes the same as the state in which the interval between the adjacent nozzles #i is wider than the other portions in the nozzle row 42. For this reason, at the time of ink ejection, the downward wind Wv may be weaker than the other portions or may not occur at the portions corresponding to the non-ejection nozzles. As a result, the cross wind Ws is less affected by the downward flow and flows smoothly. As a result, it is possible to prevent an unexpected landing position shift related to the satellite ink droplet Is.

<Head height adjustment>
First, the height adjustment mechanism of the head 41 will be described. Here, FIG. 21 is a diagram for explaining the vertical movement of the head 41 by the gap adjusting lever 34 and the guide shaft 33. That is, FIG. 21A is a diagram illustrating a state in which the sheet facing surface 41 a of the head 41 is close to the surface of the platen 24. FIG. 21B is a diagram illustrating a state where the sheet facing surface 41 a of the head 41 is separated from the surface of the platen 24. FIG. 21C is a diagram for explaining the difference in the position of the paper facing surface 41 a of the head 41.

  As shown in FIG. 21A, the sheet facing surface 41a of the head 41 is in a state closest to the platen surface when the gap adjusting lever 34 is directed substantially upward. At the lowered position of the head 41, the interval PG1 from the sheet facing surface 41a of the head 41 to the platen surface is 1.5 mm. Then, as shown in FIG. 21B, when the gap adjusting lever 34 is tilted to the upstream side (the right side in this figure) in the paper transport direction, the guide shaft 33 is raised by about 0.5 mm. As a result, the sheet facing surface 41a of the head 41 is also raised. That is, as shown in FIG. 21C, the sheet facing surface 41a of the head 41 moves from the lowest position indicated by the dotted line to the raised position indicated by the solid line. At this raised position, the distance PG2 from the sheet facing surface 41a of the head 41 to the platen surface is 2.0 mm. Further, when the sheet facing surface 41a of the head 41 is in the raised position, that is, when the gap adjusting lever 34 is in a tilted state, the head position detection sensor 55 is turned on and outputs a detection signal. In this example, the head position detection sensor 55 is configured by a micro switch, and the switch is turned on when the gap adjustment lever 34 abuts.

  As described above, in the present embodiment, the height of the head 41 is switched between the two levels. When the height of the head 41 is “high”, a detection signal from the head position detection sensor 55 is input to the controller 60. For this reason, the controller 60 can recognize the height of the head 41 by monitoring the detection signal from the head position detection sensor 55.

  For example, as shown in FIG. 22, the memory 63 (see FIG. 4) of the printer 1 includes the state of the head position detection sensor 55 based on the detection signal, the position of the head 41 in the height direction, and the sheet facing surface. Table information indicating the relationship with the distance from 41a to the platen surface is stored.

  Then, the controller 60 recognizes the height of the head 41 by referring to this table information. Further, the controller 60 acquires the distances PG1 and PG2 from the sheet facing surface 41a of the head 41 to the platen surface based on the recognized height information of the head 41. The acquired intervals PG1 and PG2 from the sheet facing surface 41a of the head 41 to the platen surface are transmitted to the printer driver 116.

<Recognizing the thickness of the paper and the distance from the paper facing surface to the paper surface>
Further, the controller 60 acquires the information on the thickness of the paper S based on the information on the paper type input via the user interface of the printer driver 116.
For example, as shown in FIG. 23, the memory 63 of the printer 1 stores table information indicating the relationship between the paper type and the paper thickness. Then, the controller 60 refers to the table information, and acquires information on the thickness of the paper S from the input paper type information. This paper type information is used for other purposes such as setting the print mode. By using such information as the thickness information of the paper S, the number of input information can be reduced, and the usability can be improved.
The acquired information on the thickness of the sheet S is also transmitted to the printer driver 116.

<Recognizing ink droplet ejection frequency>
The controller 60 also acquires print mode information based on image quality information input via the user interface of the printer driver 116. For example, as shown in FIG. 24, the memory 63 of the printer 1 stores table information indicating the relationship between image quality and print mode. As shown in FIG. 24, the ink droplet ejection frequency and carriage movement speed are determined by the printing mode.

For example, when the image quality is “normal”, “high speed” is set as the print mode. In the “high-speed” printing mode, the ejection frequency of the ink droplets is set to “high”. The injection frequency in this case is, for example, 14.4 kHz. The carriage moving speed is set to “high speed”. In this case, the moving speed is, for example, 76.2 cm / sec (300 cps).
On the other hand, when the image quality is “beautiful”, “high image quality” is set as the print mode. In the “high image quality” printing mode, the ink droplet ejection frequency is set to “low”. In this case, the injection frequency is, for example, 7.2 kHz. The carriage moving speed is set to “low speed”. The moving speed in this case is, for example, 47.0 cm / sec (185 cps).
The ink droplet ejection frequency affects the strength of the downward wind Wv. That is, as the ink droplet ejection frequency increases, the downward wind Wv increases. For this reason, the ease of occurrence of the wind ripple phenomenon changes according to the ejection frequency of the ink droplets.

<Regarding control to suppress wind ripple phenomenon>
The printer driver 116 functions as an “ejection control unit” according to the claims. That is, the printer driver 116 determines the distance from the paper facing surface 41a of the head 41 to the paper surface based on the information on the distances PG1 and PG2 from the paper facing surface 41a to the platen surface of the head 41 and the information on the thickness of the paper S. The interval PGa is acquired. Next, the printer driver 116 determines whether or not to set a non-ejecting nozzle from the acquired interval and print mode information. Thereafter, the printer driver 116 transmits the halftone-processed pixel data to the printer 1 based on the determination result. Details will be described below.

  FIG. 25 is a flowchart for explaining each operation of the rasterizing process performed by the printer driver 116. The printer driver 116 has a code for executing each operation.

  In this rasterization process, the printer driver 116 first acquires the interval PGa from the paper facing surface 41a of the head 41 to the paper surface (S011). This operation is performed based on the information on the distances PG1 and PG2 from the sheet facing surface 41a of the head 41 to the platen surface and the information on the thickness of the sheet S transmitted from the controller 60. For example, the printer driver 116 subtracts the thickness of the paper S from the distance from the paper facing surface 41a of the head 41 to the platen surface, thereby obtaining the distance PGa from the paper facing surface 41a of the head 41 to the paper surface. With such a configuration, the interval PGa can be acquired without providing a dedicated measurement unit. Thereby, the number of parts can be reduced.

Here, Table 4 shows the interval PGa from the sheet facing surface 41a of the head 41 to the sheet surface for each type of sheet S when the distance from the sheet facing surface 41a of the head 41 to the platen surface is 1.5 mm. It is a table. Table 5 shows the interval PGa from the sheet facing surface 41a of the head 41 to the sheet surface for each type of sheet S when the distance from the sheet facing surface 41a of the head 41 to the platen surface is 2.0 mm. It is a table. As shown in these tables, when the distance PG1 from the sheet facing surface 41a to the platen surface is 1.5 mm, the distance PGa from the sheet facing surface 41a of the head 41 to the sheet surface is 1.5 mm or less. When the distance PG2 from the paper facing surface 41a to the platen surface is 2.0 mm, the distance PGa from the paper facing surface 41a of the head 41 to the paper surface is 1.7 mm or more.

  If the distance PGa from the paper facing surface 41a of the head 41 to the paper surface is acquired, the printer driver 116 acquires the set print mode (S012). In this embodiment, two types of “normal” and “beautiful” are prepared as print modes. For this reason, the printer driver 116 acquires one of the printing modes of “normal” or “beautiful”.

  If the set print mode is acquired, the printer driver 116 determines whether or not to set a non-ejecting nozzle (S013). The criteria for this determination differ depending on the type of the printer 1, but in this embodiment, the interval PGa from the paper facing surface 41a of the head 41 to the paper surface is wider than 1.5 mm and the print mode is “normal”. Is set, the non-injection nozzle is set. This is for the reason described above. As described above, the wind ripple phenomenon is more likely to occur as the interval PGa from the paper facing surface 41a of the head 41 to the paper surface is wider, and is more likely to occur as the carriage 31 moves faster. Furthermore, it is because it is easy to generate | occur | produce, so that the ejection frequency of an ink drop is high. In the present embodiment, determination criteria are determined in consideration of these conditions. That is, when “normal” is set as the print mode and the head 41 is positioned at the above-described raised position, it is determined that the non-ejection nozzle is determined. In addition, when any one of the conditions is not satisfied, the non-injection nozzle is not determined.

  If the above-described conditions are not satisfied, that is, if the head 41 is positioned at the lowered position, or if “clean” is set as the print mode, the non-ejection nozzle is not set (S014). ). In this case, all nozzles #i constituting the nozzle row 42 are in a state where ink can be ejected. In this case, in the rearrangement operation (S015), rearrangement is performed for the number of pixel data corresponding to all the nozzles #i, and the data is transmitted to the printer 1.

  On the other hand, when the above-described conditions are satisfied, a non-injection nozzle is set (S016). In this embodiment, as shown in FIG. 26A, odd nozzles (# 1, # 3, # 5) are used in the forward path in the movement of the carriage 31, and even nozzles (# 2, # 4, # 6, # 6 are used in the return path. ). That is, the non-injection nozzle is determined for each nozzle. By defining the non-injection nozzles in this way, as shown in FIG. 26B, the nozzle #i formation pitch is equal to a doubled state. Thereby, in the dot formation process mentioned above, the cross wind Ws flows through the part corresponding to a non-ejection nozzle. Thereby, the disturbance of the air flow is prevented with respect to the cross wind Ws, and the unexpected landing position deviation of the satellite droplets can be prevented.

<About non-injection nozzle setting>
By the way, in the setting operation (S016) of the non-ejecting nozzle described above, the non-ejecting nozzle is determined for each nozzle. However, if a large number of non-ejecting nozzles are determined, the printing speed is reduced by that amount. It is desirable to have as few nozzles as possible. That is, it is desirable to provide a minimum number for each predetermined nozzle that does not cause a wind ripple phenomenon. Therefore, the state of occurrence of an unexpected satellite misalignment (wind ripple phenomenon) when the set ratio of the non-injection nozzles was changed was confirmed by experiments.
The confirmation results are shown in Table 6.

  In Table 6, “Duty” indicates the ratio of non-injection nozzles to the number of nozzles #i constituting the nozzle row 42. In this embodiment, since one nozzle row 42 has 180 nozzles #i, a duty of 95% means that the liquid is ejected by using 95% of the 180 nozzles #i. Means that. In this case, 171 nozzles are used for ink ejection.

  From Table 6, it has been confirmed that in the printer 1 of this embodiment, the occurrence of the wind ripple phenomenon can be reliably prevented by setting the non-ejecting nozzles to a number with a Duty of 75%. That is, one unused nozzle may be provided for three nozzles #i. In this case, it is preferable that the non-injection nozzles have a uniform interval, that is, be determined for each predetermined number of nozzles. This is because a portion where the downward wind Wv is weak or a portion where this wind is not generated occurs at regular intervals. In other words, the portion through which the cross wind Ws passes is formed at regular intervals. As a result, the entire plurality of nozzles belonging to the nozzle row 42 can be used effectively.

  Further, regarding the non-injection nozzles, it is preferable to set the number according to the interval PGa from the sheet facing surface 41a to the sheet surface. This is because the required number of non-injection nozzles changes according to the interval PGa. In this case, it is preferable that the height adjustment mechanism of the head 41 can adjust the height of the head 41 in a plurality of stages. For example, instead of the gap adjustment lever 34, a gear with the guide shaft 33 attached in an eccentric state is provided, and this gear is preferably rotated by a drive source such as a step motor that can control the amount and direction of rotation. With this configuration, it is possible to minimize the number of non-ejection nozzles, and it is possible to achieve both improvement in printing speed and prevention of wind ripples at a high level.

  Moreover, as shown in an example in FIG. 27, the non-injecting nozzle may be a plurality of continuous nozzles #i. By comprising in this way, the width | variety of the part through which the cross wind Ws passes can be adjusted. As a result, the non-ejecting nozzles can be optimally arranged for the printer 1. The number of non-injection nozzles is preferably determined according to the number of injection nozzles #i sandwiched between non-injection nozzles. This is because the width of the portion through which the cross wind Ws passes can be adapted to the number of nozzles #i that can eject ink. As a result, the non-injection nozzle can be optimized. Further, the number of non-ejection nozzles may be determined according to the ejection frequency of the ink droplets. This is because the width of the portion through which the cross wind Ws passes can be optimized according to the strength of the downward wind Wv, and the occurrence of the wind ripple phenomenon can be reliably prevented.

=== Other Embodiments ===
<About non-injection nozzle setting>
In the above-described embodiment, the non-ejection nozzles are set by the printer driver 116, but may instead be set by the controller 60 of the printer 1.

<About the printer>
In the above-described embodiment, the printer 1 has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technique as that of the present embodiment may be applied to various recording apparatuses to which an ink jet technique is applied such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

<About ink>
Since the above-described embodiment is an embodiment of the printer 1, the dye ink or the pigment ink is ejected from the nozzle #i. However, the ink ejected from the nozzle #i is not limited to such ink.

<About nozzle>
In the above-described embodiment, ink is ejected using the piezo element PZT. However, the method of ejecting ink is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<Nozzle rows used for printing>
In the above-described embodiment, different color inks can be ejected from each of the eight nozzle rows 42, but the present invention is not limited to this. The nozzle rows 42 may be 4 rows, 6 rows, or 2 rows.

It is explanatory drawing which showed the external appearance structure of the printing system. FIG. 3 is a schematic explanatory diagram of basic processing performed by a printer driver. 3 is an explanatory diagram of a user interface of a printer driver. FIG. 1 is a block diagram of an overall configuration of a printer. 1 is a schematic diagram of an overall configuration of a printer. 1 is a cross-sectional view of the overall configuration of a printer. FIG. 7A is a cross-sectional view of a portion of the head cut in a direction perpendicular to the nozzle row. FIG. 7B is an enlarged view of the vicinity of the pressure chamber in FIG. 7A. FIG. 8 is a diagram illustrating the arrangement of nozzles on the paper facing surface of the head. It is a figure explaining the head drive part which drives a head, and its peripheral part. It is a figure explaining the head drive part which drives a head, and its peripheral part. It is a figure explaining the original drive signal generated from an original drive signal generating part. It is a figure explaining the drive signal for every nozzle. It is a flowchart of the operation | movement at the time of printing. 14A and 14B are schematic diagrams for explaining the ink droplet generation process. FIG. 15A is a schematic diagram illustrating the flight trajectory of ink droplets. FIG. 15B is a schematic diagram showing the landing position deviation between the main ink droplet and the satellite ink droplet, and shows the landing position deviation that usually occurs. It is the figure which showed typically the unexpected landing position shift in the ink droplet of a satellite. It is the schematic diagram which expanded and showed the part which the unexpected landing position shift has arisen. FIG. 18A is a diagram schematically showing a cross wind when an ink droplet is ejected from one nozzle. FIG. 18B is a diagram schematically showing a cross wind when ink droplets are ejected from a plurality of continuous nozzles. It is the figure which showed typically the relationship between the downward wind produced by the ejected ink droplet, and a cross wind. It is the figure which showed typically the state where the downward wind was broken by the crosswind. FIG. 21A is a diagram illustrating a state in which the sheet facing surface approaches the platen surface. FIG. 21B is a diagram illustrating a state where the sheet facing surface is separated from the platen surface. FIG. 21C is a diagram illustrating the difference in the position of the sheet facing surface. It is a figure explaining the table information stored in a memory. It is a figure explaining the table information stored in a memory. It is a figure explaining the table information stored in a memory. 4 is a flowchart for explaining operations of rasterization processing performed by a printer driver. FIG. 26A and FIG. 26B are diagrams schematically illustrating a state in which a non-injection nozzle is set. It is the figure which illustrated a plurality of continuous non-injection nozzles.

Explanation of symbols

1 printer, 20 transport unit, 21 paper feed roller, 22 transport motor,
23 transport roller, 24 platen, 25 paper discharge roller, 30 carriage unit,
31 Carriage, 32 Carriage motor, 33 Guide shaft,
34 Gap adjustment lever, 34a Rotating shaft, 35 Ink cartridge,
40 head units, 41 heads, 41a paper facing surface, 411 case,
411a storage chamber, 412 flow path unit, 412a flow path forming plate, 412b elastic plate,
412c nozzle plate, 412d pressure chamber, 412e nozzle communication port,
412f common ink chamber, 412g ink supply path, 412h support frame,
412i elastic film, 412j island, 413 piezo element unit,
413a piezo element group, 413b adhesive substrate, 42 nozzle array, 43 head drive unit,
431 first shift register group, 432 second shift register group,
433 latch circuit group, 434 decoder group, 44 original drive signal generator,
50 sensor groups, 51 linear encoder, 52 rotary encoder,
53 Paper detection sensor, 54 Paper width sensor, 55 Head position detection sensor,
60 controller, 61 interface unit, 62 CPU, 63 memory,
64 unit control circuit,
100 printing system, 110 computer, 112 video driver,
114 application programs, 116 printer drivers, 120 display devices,
130 input device, 131 keyboard, 132 mouse, 140 recording / reproducing device,
141 flexible disk drive device, 142 CD-ROM drive device,
PZT piezo element, SW switch group, Ws crosswind, Wv downward wind

Claims (10)

A head provided with a nozzle row composed of a plurality of nozzles arranged in a row on the medium facing surface;
A head moving unit that moves the head in a predetermined direction along the surface of the medium;
An interval adjusting unit for adjusting an interval between the head and the medium;
An injection control unit that performs liquid injection control;
A liquid ejecting apparatus comprising:
The injection control unit
Among the plurality of nozzles sandwiched between the nozzle at one end and the nozzle at the other end of the nozzle row,
A liquid ejecting apparatus, wherein the number of non-ejection nozzles that do not eject liquid is determined in accordance with an interval from the medium facing surface to the surface of the medium. The liquid ejecting apparatus according to claim 1,
The injection control unit
The liquid ejecting apparatus, wherein the non-ejecting nozzle is determined for each predetermined number of nozzles. The liquid ejecting apparatus according to claim 2,
The non-injection nozzle is
A liquid ejecting apparatus comprising a plurality of adjacent nozzles. The liquid ejecting apparatus according to claim 3,
The plurality of adjacent nozzles are
The liquid ejecting apparatus, wherein the number is determined according to the predetermined number of nozzles. The liquid ejecting apparatus according to any one of claims 1 to 4,
The injection control unit
The liquid ejecting apparatus, wherein the non-ejection nozzle is determined according to the ejection frequency of the liquid. The liquid ejecting apparatus according to any one of claims 1 to 5,
A medium placement unit on which the medium is placed;
The injection control unit
The distance from the medium facing surface to the surface of the medium is acquired based on information on the distance from the surface of the medium placement unit to the medium facing surface and information on the thickness of the medium. Liquid ejector. The liquid ejecting apparatus according to claim 6,
The interval adjusting unit is
Another head moving unit that moves the head in a direction approaching and separating from the medium;
Information on the distance from the surface of the medium placement unit to the medium facing surface is
The liquid ejecting apparatus is information indicating a head position determined by the other head moving unit. The liquid ejecting apparatus according to claim 6 or 7,
Information on the thickness of the medium is
The liquid ejecting apparatus is information indicating a type of the medium. A head provided with a nozzle row composed of a plurality of nozzles arranged in a row on the medium facing surface;
A head moving unit that moves the head in a predetermined direction along the surface of the medium;
An interval adjusting unit for adjusting an interval between the head and the medium;
An injection control unit that performs liquid injection control;
A liquid ejecting apparatus comprising:
A medium placement unit on which the medium is placed;
The interval adjusting unit is
Another head moving unit that moves the head in a direction approaching and separating from the medium;
The injection control unit
Based on the information on the distance from the surface of the medium placement unit to the medium facing surface and the information on the thickness of the medium, the distance from the medium facing surface to the surface of the medium is acquired,
Among the plurality of nozzles sandwiched between the nozzle at one end and the nozzle at the other end of the nozzle row,
A non-ejecting nozzle that is configured by a plurality of adjacent nozzles and that does not eject liquid according to the interval from the medium facing surface to the surface of the medium, and the interval from the medium facing surface to the surface of the medium; and According to the ejection frequency of the liquid, determined for each predetermined number of nozzles,
The number of the adjacent nozzles is determined according to the predetermined number of nozzles,
Information on the distance from the surface of the medium placement unit to the medium facing surface is information indicating the position of the head determined by the other head moving unit,
The information related to the thickness of the medium is information indicating a type of the medium. A liquid ejecting method for ejecting liquid from the nozzles while moving a head provided with a nozzle array composed of a plurality of nozzles arranged in a line on a medium facing surface in a predetermined direction along the surface of the medium. ,
Obtaining a distance from the medium facing surface to the surface of the medium;
Determining a non-ejecting nozzle that does not eject liquid according to an interval from the medium facing surface to the surface of the medium, among a plurality of nozzles sandwiched between one end nozzle and the other end nozzle of the nozzle row; The
A liquid ejecting method comprising:

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