JP2006240049A - Liquid droplet ejecting head and liquid droplet ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet ejecting head which can apply a non-ejection waveform while preventing a recording speed from being decreased by a simple constitution. <P>SOLUTION: The liquid droplet ejecting head comprises: a liquid droplet ejecting head body which includes nozzles for ejecting liquid droplets, pressure generation chambers communicating with the nozzles, and a pressure applying means driven on the basis of ejection data to apply a pressure into the pressure generating chambers, thereby making liquid droplets ejected from the nozzles; and a driving circuit that drives the pressure applying means. The driving circuit of the liquid droplet ejecting head comprises a first storage means for storing the ejection data, and a second storage means for storing information that regulates a relationship between the ejection data and driving waveform pattern data corresponding to a driving waveform for driving the pressure applying means. The driving waveform is any of a non-action waveform, the non-ejection waveform and an ejection waveform. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet discharge head and a droplet discharge device that discharge droplets from nozzles.

  In a liquid droplet ejection head that ejects liquid droplets from a nozzle, such as an ink jet recording head for recording an image using minute ink droplets (hereinafter sometimes simply referred to as a recording head), the pressure applying means is driven, By applying pressure in the pressure generating chamber, droplets are ejected from the nozzle and landed on a recording medium such as recording paper.

  A recording apparatus such as a printer, a copying machine, or a facsimile is configured to record dots on a recording material such as paper or a plastic thin plate based on image information, and to record an image composed of the dots.

  The ink jet printer is configured to record an image by ejecting and ejecting ink droplets from nozzles of a recording head and attaching them to a recording material.

  In recent years, gradation recording has been performed by various printers, and ink jet printers have also been performed in the same manner as other printers. As one of gradation recordings, there is a method in which the ejection nozzle diameter is reduced, the size of one ink droplet is reduced, and the number of dots ejected per pixel is changed. According to this method, by changing the number of dots to be ejected, the same effect as changing the size of the dots at the time of ejection can be obtained.

  In addition, in order to increase the printing speed, ink having a quick drying property is used so that the inks do not mix even if they are overprinted immediately.

  By the way, when the diameter of the discharge nozzle is reduced in this way and quick-drying ink is used, drying of the ink surface of the discharge nozzle starts abruptly immediately after the ink is discharged.

  For this reason, when the time until the next ink discharge is long, the discharge is not performed even if the drive signal is given, or even if the discharge is performed, the speed and trajectory become unstable and normal droplets are not generated. There is also a problem that it cannot be obtained. As a result, the formed image is blurred, resulting in a decrease in image quality.

In order to avoid such a problem, a drive signal is used to apply pressure to the liquid storage chamber to eject liquid droplets from the nozzle tip, and a drive signal for each pixel corresponding to image data is generated in the image forming area. Drive means, and the drive means generates a drive signal including a pulse for vibrating the liquid surface at the tip of the nozzle without discharging a droplet from the nozzle to a pixel that does not discharge ink. An ink jet printer is disclosed. (See Patent Document 1)
That is, in the invention of Patent Document 1, a drive signal including a pulse for vibrating the liquid surface at the tip of the nozzle is generated without discharging a droplet from the nozzle to a pixel to which ink is not discharged. . By oscillating the droplet surface even for pixels that do not eject ink droplets in the image forming area by such a drive signal, droplets are ejected from the nozzle for each pixel regardless of whether ink droplets are ejected or not. Since the ink surface at the tip of the nozzle is kept in a vibrating state without being discharged, the ink is prevented from drying.
Japanese Patent Laid-Open No. 10-250064

  In the prior art disclosed in Patent Document 1, the ink droplet is driven by a drive signal including a non-discharge pulse for vibrating the liquid surface at the nozzle tip before or after the discharge pulse separately from the discharge pulse. During the application of a pulse for this purpose, ejection cannot be performed, and the recording speed decreases.

  The present invention has been made in view of the above situation, and can apply a non-ejection waveform with a simple configuration without reducing the recording speed. As a result, a droplet is ejected by the non-ejection waveform. By vibrating the droplet surface even for pixels that do not, the liquid surface at the tip of the nozzle is kept in a vibrating state without ejecting droplets from the nozzle regardless of whether droplets are ejected for each pixel. Therefore, an object of the present invention is to provide a droplet discharge head and a droplet discharge device that can prevent the liquid from drying and that can heat the liquid by the heat generated by driving the pressure applying means using a non-discharge waveform. To do.

The object of the present invention is achieved by the following configurations.
(Claim 1)
A nozzle for discharging a droplet, a pressure generation chamber communicating with the nozzle, and a pressure applying unit that is driven based on discharge data and discharges the droplet from the nozzle by applying pressure to the pressure generation chamber A liquid droplet discharge head having a liquid droplet discharge head main body having a driving circuit for driving the pressure applying unit,
The drive circuit stores a first storage unit that stores the discharge data, and a second unit that stores information defining a relationship between the discharge data and drive waveform pattern data corresponding to a drive waveform for driving the pressure applying unit. Storage means,
The liquid droplet ejection head, wherein the drive waveform is any one of a non-operation waveform, a non-ejection waveform, and an ejection waveform.
(Claim 2)
The droplet discharge head according to claim 1, wherein the second storage unit is rewritable.
(Claim 3)
The droplet discharge head main body has a nozzle row including a plurality of the nozzles, and the drive circuit divides the nozzles of the nozzle row into M (M is an integer of 2 or more) sets, and The droplet discharge head according to claim 1, further comprising a control unit that sequentially discharges droplets from the nozzles for each set.
(Claim 4)
The pressure applying means is formed of a piezoelectric material that forms at least a part of a partition wall of the pressure generating chamber and is deformed in a shear mode by application of the driving waveform, and the M is 3, and the non-ejection waveform The droplet discharge head according to claim 3, wherein is a GND waveform.
(Claim 5)
A liquid droplet ejection apparatus using the liquid droplet ejection head according to claim 1.
(Claim 6)
3. A droplet discharge apparatus using the droplet discharge head according to claim 2, wherein the second storage means is set to a preset value when the apparatus is turned on.

  The inventor includes a nozzle for discharging a droplet, a pressure generation chamber communicating with the nozzle, and a droplet generated from the nozzle by being driven based on discharge data to apply pressure to the pressure generation chamber. A droplet discharge head having a droplet discharge head main body having a pressure applying unit for discharging and a drive circuit for driving the pressure applying unit, wherein the drive circuit stores a first memory for storing the discharge data. And second storage means for storing information defining a relationship between the ejection data and drive waveform pattern data corresponding to a drive waveform for driving the pressure applying means, the drive waveform being non-operating Select a non-operating waveform, non-ejection waveform, or ejection waveform according to the ejection data by using a droplet ejection head that is either a waveform, non-ejection waveform, or ejection waveform It is possible to apply a non-ejection waveform with a simple configuration without reducing the recording speed. As a result, the non-ejection waveform causes the droplet surface to vibrate even for pixels that do not eject the droplet. As a result, the liquid surface at the tip of the nozzle is kept in a vibrating state without discharging a droplet from the nozzle regardless of whether the droplet is discharged for each pixel, so that drying of the liquid is prevented. The present inventors have considered that the liquid can be heated by the heat generated by the driving of the pressure applying means by the non-ejection waveform.

  Here, the driving of the pressure applying means by the non-ejection waveform means that the pressure applying means is driven such that a pressure is applied to the pressure generating chamber so as not to eject the liquid droplets from the nozzles.

  According to the first aspect of the present invention, it is possible to apply a non-ejection waveform with a simple configuration without reducing the recording speed. As a result, even for a pixel that does not eject droplets due to the non-ejection waveform. By vibrating the liquid surface, the liquid surface at the tip of the nozzle is kept in a vibrating state without ejecting liquid droplets from the nozzle regardless of whether liquid droplets are ejected for each pixel. In addition, the liquid can be heated by the heat generated by driving the pressure applying means by the non-ejection waveform.

  According to the second aspect of the present invention, the combination of the ejection data and the drive waveform pattern data can be freely rewritten and set as necessary.

  According to invention of Claim 3, the number of the pressure provision means driven simultaneously can be reduced, and the burden of a drive circuit can be reduced.

  According to the invention described in claim 4, in the head in which the pressure applying means is formed of a piezoelectric material that forms at least a part of the partition wall of the pressure generating chamber and is deformed in a shear mode by applying a driving waveform. By dividing and driving the nozzle row into three groups and using the GND waveform as the non-ejection waveform, it becomes possible to configure all the waveforms related to the driving with a single-pole waveform. Therefore, the power supply cost can be reduced.

  According to the fifth aspect of the present invention, the same effects as in the first to fourth aspects can be obtained by the droplet discharge device using the droplet discharge head according to any one of the first to fourth aspects.

  According to the sixth aspect of the present invention, when there is no operation for rewriting the second storage means, the information in the second storage means is automatically set to the preset value when the apparatus is turned on. In the case where the operation of rewriting the second storage means is unnecessary, the operation procedure can be omitted.

  Although the example of embodiment regarding this invention is shown below, the aspect of this invention is not limited to these.

  The droplet discharge head body according to the present invention includes a nozzle for discharging a droplet, a pressure generation chamber communicating with the nozzle, and a pressure application for applying a pressure to the pressure generation chamber and discharging the droplet from the nozzle. As long as the liquid droplet ejection head body is provided with the means, the liquid ejection head body can be applied to any type of liquid droplet ejection head body, and the liquid filled in the pressure generation chamber may be any liquid. In the following description, the shear mode (share mode) is a droplet discharge head body that includes pressure applying means that changes pressure by expanding or contracting the volume in the pressure generating chamber, and uses ink as the liquid that fills the pressure generating chamber. A mode) type ink jet head main body will be described.

  In the shear mode type head main body, at least a part of the partition wall of the pressure generating chamber is constituted by a piezoelectric element as pressure applying means, and ink droplets are ejected from the nozzle by deforming the piezoelectric element.

  The droplet discharge head body and the drive circuit are collectively defined as a droplet discharge head.

  As a droplet discharge device using such a droplet discharge head, an ink jet printer will be described.

<Mechanical configuration of inkjet printer>
Hereinafter, the mechanical configuration of the main part of the serial type ink jet printer 1 of FIG. 1 will be described, but the present invention is not limited to this embodiment.

  In this embodiment, an example of a printer having an inkjet head body having two nozzle rows for each color and having nozzle rows for Y, M, C, and K colors is shown. The present invention can also be applied to a head body having a row or a printer that performs recording with a single-color head body.

  In the following description, since the configuration relating to the head body 17 and the drive circuit 16 is common to each of the colors Y, M, C, and K, the alphabetic suffixes that indicate the configuration relating to each color are omitted and are collectively described. There is.

  The carriage 2 is a resin case in which a head main body 17, which will be described later, and a drive circuit 16 for four colors for driving pressure applying means of the head main body 17 and an ink cartridge (not shown) are housed. The drive circuit 16 housed in the carriage 2 is composed of an IC, and is connected to the control board 9 by a flexible cable 5 drawn from the carriage 2.

  The head main body 17 which is a droplet discharge head main body is composed of four color main bodies 17Y, 17M, 17C and 17K, and the head main bodies 17 of the respective colors are arranged in the X direction which is the main scanning direction with respect to the recording medium. It has a row of nozzles. The number of nozzles is 256 per row, and they are arranged in the Y direction, which is the sub-scanning direction. Each nozzle array has a drive circuit 16.

  The carriage 2 is reciprocated in the main scanning direction indicated by an arrow X in the figure by the carriage driving mechanism 6. The carriage drive mechanism 6 includes a motor 6a, a pulley 6b, a toothed belt 6c, and a guide rail 6d, and the carriage 2 is fixed to the toothed belt 6c.

  When the pulley 6b is rotated by the motor 6a, the carriage 2 fixed to the toothed belt 6c is moved along the direction of the arrow X in the drawing. The guide rail 6d is two cylinders parallel to each other and penetrates the insertion hole of the carriage 2 so that the carriage 2 slides.

  For this reason, the toothed belt 6c is not bent by the weight of the carriage 2, and the reciprocating direction of the carriage 2 is in a straight line. The direction in which the carriage 2 moves can be changed by reversing the rotation direction of the motor 6a, and the moving speed of the carriage 2 can be changed by changing the number of rotations.

  The ink cartridge has an ink tank inside. The ink supply port of the ink tank opens when the ink cartridge is set in the carriage 2 and is connected to the ink supply pipe, and is closed when the connection is released, and ink is supplied to the head body 17.

  The carriage 2 is provided with an ink cartridge mounting portion so that an ink cartridge containing Y, M, C, and K inks for ejection can be attached and detached.

  The flexible cable 5 is a data transfer means for transferring image data or the like as ejection data. The flexible cable 5 is a flexible film in which a wiring pattern including data signal lines, power supply lines and the like is printed. Data is transferred to and from the control board 9 to follow the movement of the carriage 2.

  The encoder 7 is a resin transparent film with a scale at predetermined intervals, and the scale is detected by an optical sensor provided on the carriage 2 to detect the moving speed of the carriage 2.

  The paper transport mechanism 8 is a mechanism for transporting the recording paper P in the sub-scanning direction indicated by an arrow Y in the figure, and includes a transport motor 8a and transport roller pairs 8b and 8c. The transport roller pair 8b and the transport roller pair 8c are driven by a transport motor 8a and are roller pairs that are substantially equal to each other by a gear train (not shown), but the transport roller pair 8c rotates at a slightly faster peripheral speed.

  The recording paper P is sandwiched between a pair of transport rollers 8b that have been fed from a paper feed mechanism (not shown) and rotated at a constant speed, and the direction of transport in the sub-scanning direction is controlled by a paper feed guide (not shown). After being corrected, the sheet is sandwiched and transported by the transport roller pair 8c.

  Since the peripheral speed of the conveyance roller pair 8c is slightly faster than that of the conveyance roller pair 8b, the recording paper P passes through the recording unit without causing slack. The speed at which the recording paper P moves in the sub-scanning direction is set to a constant speed.

  In this way, while moving the recording paper P at a constant speed in the sub-scanning direction, the carriage 2 is moved at a constant speed in the main scanning direction, and the ink ejected from the head 17 is adhered to a predetermined range on one side of the recording paper P. Record an image on

  The printer can record an image by ejecting ink droplets during reciprocal bidirectional scanning in the main scanning direction in order to improve the recording speed. (Hereinafter, such a recording method may be referred to as bidirectional recording.)

<Configuration of inkjet head body>
Hereinafter, an embodiment of a head body in the ink jet printer of FIG. 1 will be described with reference to the drawings, but the present invention is not limited to this embodiment.

  FIG. 2 is an enlarged view of the nozzle portion when the ink jet head main body 17 in FIG. 1 is viewed from the direction of the recording paper P. In this figure, 15 nozzles per color corresponding to a part of 512 nozzles per color are shown.

  The nozzle portions of 17Y, 17M, 17C, and 17K constituting the inkjet head main body 17 are arranged in this order at a predetermined distance in the main scanning direction X. The inkjet head main body of each color has, for example, 17Y in the main scanning direction X with respect to the recording medium, the first nozzle row 102Y of the nozzle 18Y1 and the second nozzle row 103Y of the nozzle 18Y2. That is, a total of 8 nozzle rows are arranged in the main scanning direction. These nozzle rows are separated by a distance L1 between nozzle rows and a distance L2 between colors within the same color. In order to land the ink droplets ejected from these eight nozzle rows at a predetermined position and form a straight line image in the sub-scanning direction, it is necessary to adjust the ejection timing of the ink droplets from each nozzle row. is there. The image printing start is driven in accordance with the ejection cycle determined by the main scanning speed of the recording head and the above-mentioned distance with respect to the preceding nozzle row in the main scanning direction of the head, and printing is delayed by a predetermined cycle. Start. In the case of reciprocal printing, the drive waveform application timing between nozzle rows is shifted in the reverse order of the forward path in the return path. Details will be described later.

  When driving a shear mode type recording head having a plurality of pressure generating chambers separated by a partition wall made of a piezoelectric material as described above, when the partition wall of one pressure generation chamber performs an ejection operation, Since the adjacent pressure generation chambers are affected, of the plurality of pressure generation chambers (nozzles), one pressure generation chamber (nozzle) separated from each other with one or more pressure generation chambers (nozzles) interposed therebetween It is divided into M groups (M is an integer of 2 or more) so as to form a set, and drive control is performed so that the ink discharge operation is sequentially performed in time division for each set. In this embodiment, a so-called three-cycle discharge method is employed in which every two pressure generation chambers (nozzles) are selected and discharged in three sets.

  In this embodiment, each nozzle row is composed of 256 nozzles, and the nozzles in each row are arranged with a period of 3 nozzles and adjacent nozzles are shifted by 1/3 of the minimum pixel pitch in the main scanning direction. Each row is driven in three cycles of A set, B set, and C set every two nozzles in accordance with the discharge cycle determined by the main scanning speed of the recording head and the shift amount of 1/3 of the minimum pixel pitch. Thus, the landing positions of the ink droplets ejected from the nozzles of the A group, the B group, and the C group are aligned, and a linear line image is formed in the sub-scanning direction.

  By dividing the nozzle row in this way, the number of pressure applying means that are driven simultaneously can be reduced, the load on the drive circuit is reduced, the drive capability of the drive circuit is suppressed, and a small-capacity drive source is used. Cost reduction is possible.

  The nozzle pitch in the nozzle row direction within the row is 180 dpi (141 μm), the two rows are arranged in parallel, and are shifted by 70.5 μm (equivalent to 360 dpi) in the nozzle row direction with respect to each nozzle. The nozzle density in the nozzle row direction is 360 dpi, and 512 nozzle groups are configured. That is, the nozzle positions of the nozzle arrays 102 and 103 are arranged so as to be interpolated and shifted in the nozzle array direction so as to correspond to the image grid, and all pixels are recorded in one scan.

FIG. 3 is a schematic view showing a shear mode type ink jet head main body for one color and a manufacturing process thereof.
FIG. Here, the configuration of the head main body 17Y is shown, but the heads 17M to 17K have the same configuration.

  First, a first piezoelectric material substrate 10a and a second piezoelectric material substrate 10b having different polarization directions are prepared. The first piezoelectric material substrate 10a includes a thick substrate 26a and a thin substrate 22a. Similarly, the second piezoelectric material substrate 10b also includes a thick substrate 26b and a thin substrate 22b (FIG. 3A).

  A dry film 130a is pasted on the thin substrate 22a of the first piezoelectric material substrate 10a, and the dry film 130a is exposed and developed to create a mask for setting the processing positions of the ink channels and electrodes serving as pressure generation chambers ( FIG. 3 (b)). In the first piezoelectric material substrate 10a, 258 grooves are processed by a diamond blade or the like at a position set by a mask to form a pressure generating chamber 28a that is an ink channel. Thereby, the adjacent pressure generation chambers are partitioned by the partition walls of the piezoelectric material. A drive electrode 25a is formed in the pressure generating chamber 28a by aluminum vapor deposition, and an extraction electrode 160a connected to the drive electrode 25a is formed (FIG. 3C).

  Here, after the 258 pressure generating chambers, the two pressure generating chambers at both ends are dummy pressure generating chambers that are not accompanied by ink ejection from the nozzles. In this way, dummy pressure generation chambers that do not discharge ink are provided on both outer sides of the 256 pressure generation chambers that discharge ink through the partition walls of the piezoelectric material, so that they are positioned at both ends of the 256 pressure generation chambers. Prevents a drop in ink discharge from the pressure generation chamber As will be described later, ink is supplied to the dummy pressure generation chamber, but no corresponding nozzle is provided.

  Similarly, a dry film 130b is pasted on the thin substrate 22b of the second piezoelectric material substrate 10b, and a mask for setting the processing positions of the ink channels and electrodes is created by exposing and developing the dry film 130b. In the second piezoelectric material substrate 10b, 258 grooves are formed by a diamond blade or the like at a position set by a mask to form a pressure generation chamber 28b. Thereby, the adjacent pressure generation chambers are partitioned by the partition walls of the piezoelectric material. A drive electrode 25b is formed in the pressure generating chamber 28b by aluminum vapor deposition, and an extraction electrode 160b connected to the drive electrode 25b is formed.

  Next, cover substrates 24a and 24b covering pressure generation chambers 28a and 28b are provided on first piezoelectric material substrate 10a and second piezoelectric material substrate 10b, leaving extraction electrodes 160a and 160b (FIG. 3D). )), The first piezoelectric material substrate 10a and the second piezoelectric material substrate 10b are bonded to the side opposite to the side where the cover substrates 24a and 24b are provided, and the center portion is cut (FIG. 3E). ), A nozzle plate 180 having 256 × 2 rows of nozzles 18a, 18b is provided in a portion corresponding to the pressure generating chambers 28a, 28b to manufacture two head bodies 17Y (FIG. 3F).

  At the time of bonding, the pressure generating chambers of the heads are shifted from each other by ½ pitch, and the heads are 180 dpi by bonding them so that they are arranged in a staggered manner. By shifting each other by ½, it can be used as a 360 dpi recording head, the number of nozzles can be increased, and a high-density recording head can be obtained.

  Thereafter, manifolds 19b and 19b for supplying ink to the pressure generating chambers 28a and 28b are connected to the first piezoelectric material substrate 10a and the second piezoelectric material substrate 10b, respectively, to the two head bodies. At the same time, flexible cables 5a and 5b, which are wiring boards provided with drive circuits 16a and 16b, are connected to the extraction electrodes 160a and 160b to simultaneously manufacture two inkjet heads (FIG. 3G). Since two two-row heads can be manufactured at the same time, the manufacturing cost of the head can be reduced. The yellow ink of the same color is supplied to the pressure generation chambers of the two-row heads and discharged from the nozzles.

  In this embodiment, the nozzles 18a and 18b of the plurality of nozzle rows are integrally formed on a single nozzle plate substrate, and the positioning of the nozzles 18a and 18b of the plurality of nozzle rows is accurate and errors are reduced. Thus, ink droplets can be ejected with high accuracy.

  The piezoelectric material used for the piezoelectric material substrate 10 is not particularly limited as long as it deforms when a voltage is applied, and a known material may be used, and a substrate made of an organic material may be used. A substrate made of a piezoelectric non-metallic material is preferable, and a substrate made of a piezoelectric non-metallic material such as a ceramic substrate formed through a process such as molding or firing, or a substrate formed through a coating or lamination process, etc. There is. Examples of the organic material include organic polymers and hybrid materials of organic polymers and inorganic materials.

Ceramic substrates include PZT (PbZrO ₃ —PbTiO ₃ ) and third component added PZT. The third component includes Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Mn _1/3 Sb _{2 / 3} ) O ₃ , Pb (Co _1/3 Nb _2/3 ) O _{3, and the} like, and further, BaTiO ₃ , ZnO, LiNbO ₃ , LiTaO _{3, and the} like can be used.

  Moreover, as a board | substrate formed through the process of application | coating or lamination, it can form by the sol-gel method, laminated substrate coating, etc., for example.

  The material of the cover substrate 24 is not particularly limited, and may be a substrate made of an organic material. However, a substrate made of a non-piezoelectric nonmetallic material is preferable. As the substrate made of this non-piezoelectric nonmetallic material, alumina, It is preferably selected from at least one of aluminum nitride, zirconia, silicon, silicon nitride, silicon carbide, quartz, and unpolarized PZT. Examples of the organic material include organic polymers and hybrid materials of organic polymers and inorganic materials.

  Further, as a material of the nozzle plate 180, a synthetic resin such as polyimide resin, polyethylene terephthalate resin, liquid crystal polymer, aromatic polyamide resin, polyethylene naphthalate resin, polysulfone resin, or a metal material such as stainless steel can be used.

  Platinum, gold, silver, copper, aluminum, palladium, nickel, tantalum, and titanium can be used as the metal used for the drive electrode 25 and the extraction electrode 160. In particular, from the viewpoint of electrical characteristics and workability, gold Aluminum, copper, and nickel are preferable, and are formed by plating, vapor deposition, or sputtering.

  In this embodiment, the partition wall of the pressure generation chamber is constituted by a thin substrate and a thick substrate, which are two piezoelectric material substrates having different polarization directions. For example, the piezoelectric material substrate is only a portion of the thin substrate. It may be at least part of the partition wall.

  The shear mode type recording head is easy to manufacture because the main part of the head can be constructed simply by forming the pressure generating chamber in the piezoelectric material and forming the metal electrode on the partition wall as described above. Since the pressure generating chambers can be arranged at high density, this is a preferable mode for recording high-definition images.

  As described above, the head main bodies 17Y, 17M, 17C, and 17K of the respective colors are produced, and the head main body 17 is obtained.

  In the head main body 17, as described above, positive and negative pressures are applied to the ink in the pressure generating chamber by deformation of the partition walls, and the partition walls constitute pressure applying means.

<Electrical configuration of the entire inkjet printer>
FIG. 4 is a block diagram showing an example of the electrical configuration of the entire inkjet printer according to the embodiment of the present invention shown in FIG.

  In FIG. 4, a control board 9 indicated by a broken line is mounted with a CPU 11 as a control means for controlling the entire inkjet printer 1 and is connected to the drive circuit 16 of the carriage 2 by the flexible cable 5 as described above. ing.

  The control board 9 uses the same timing for storing the image data, which is the ejection data corresponding to the nozzle row, in the shift register, which is the first storage means of the drive circuit corresponding to the nozzle row, among the plurality of nozzle rows. It is also a control means that makes the timing for ejecting droplets from a row independent for each of a plurality of nozzle rows.

  The page memory 12 stores image data that is ejection data received from a personal computer or the like that uses the inkjet printer 1 itself as a peripheral device. The storage capacity of the page memory 12 may be determined by the number of bits of image data handled by a personal computer or the like, the number of dots, the signal transfer speed, the processing speed of the CPU, and the like.

  The line memories 13a and 13b are used as line memories for storing the image data of each pixel recorded in a line in the sub-scanning direction when recording on the recording paper P, and each image data has a gradation of several bits. Data is transferred from the page memory 12. In the present embodiment, two 12-bit processing line memories 13a and 13b are used in parallel. However, a single line memory for 24-bit processing may be used.

  The data signal line (data BUS) from the page memory 12 is 24 bits and branches to each line memory 13 by 12 bits. The image data in the line memories 13a and 13b is transferred to the drive circuit 16 via the flexible cable 5.

  The interfaces 14a and 14b are means for exchanging data with an external personal computer, and are configured by any of various serial interfaces and various parallel interfaces.

  In addition, it has both display and input functions, such as one-way recording (forward direction) or bidirectional recording setting, various settings such as setting data in a table of an output pattern register 34 to be described later, recording commands, etc. Operation input means (not shown) for performing an instruction operation on the control board 9 is provided.

The drive circuits 16Y1, 16Y2 to 16K1, 16K2 are constituted by ICs. In this embodiment, one (total 8) is provided for each nozzle row for four colors of YMCK.
Each drive circuit 16 includes two cascade-connected 128-channel × 3-bit shift registers, and image data from the line memories 13a and 13b is temporarily stored in the shift registers. This shift register constitutes first storage means.

  In the present embodiment, the image data of the first nozzle row of yellow (Y) is transferred from the line memory 13a to the drive circuit 16Y1 via a 3-bit data signal line, and the image data of the second nozzle row of yellow (Y) is similarly used. It is transferred to the drive circuit 16Y2. The 512 pieces of yellow image data transferred to the drive circuits 16Y1 and 16Y2 are processed in parallel, and recording is performed by the head main body 17Y.

  Similarly, the magenta (M) image data is transferred from the line memory 13a to the drive circuits 16M1 and 16M2, and is recorded by the head body 17M. The cyan (C) image data is transferred from the line memory 13b to the drive circuits 16C1 and 16C2, and recording is performed by the head main body 17C. The black (K) image data is transferred from the line memory 13b to the drive circuits 16K1 and 16K2, and recording is performed by the head main body 17K. The detailed operation of these drive circuits 16 will be described later. As described above, the timing for transferring and storing the image data corresponding to the nozzle row to the shift register of each drive circuit 16 corresponding to the nozzle row is common among the plurality of nozzle rows, that is, the same. The timing is controlled to be As a result, data transfer to the shift registers of a plurality of drive circuits corresponding to a plurality of nozzle rows can be performed simultaneously, and a data transfer trigger process can be performed efficiently. In addition, the configuration of the control system can be simplified.

  The AND gate 200 controls a TRGIN signal for starting ink discharge when the carriage 2 starts one reciprocating movement and reaches a predetermined position on the forward path or the backward path based on the information detected by the encoder 7. The signal is output to each drive circuit 16 via the circuit 23. Each drive circuit 16 receives this TRGIN signal, sends a drive waveform, and ejects ink from each nozzle row.

  As described above, the timing at which droplets are ejected from each nozzle row is controlled independently for each of the plurality of nozzle rows by the control substrate 9. As a result, the landing position of the droplet for each nozzle row can be adjusted more finely than the pixel pitch.

  Each of the drive circuits 16Y1 to 16K2 supplies a drive waveform to a shear mode piezoelectric element provided in each nozzle of the head bodies 17Y to 17K through a 256-bit data signal line, and receives the drive waveform to receive a shear mode piezoelectric element. Is deformed, the ink in the head of each color is ejected.

  The drive signal generation circuit 15 generates a single drive signal composed of a plurality of drive waveforms and supplies it to each drive circuit 16 as will be described later. Since the drive waveform needs to be changed depending on the image data, three types of drive signals (pulse_timing0 drive signal including a non-discharge waveform as a basic waveform, pulse_timing1 drive signal including a non-operation waveform as a basic waveform, and a discharge waveform as a basic waveform) 3 types of drive signals of pulse_timing2 included) are stored as digital data in a line memory (not shown) in the drive signal generation circuit 15. This line memory can be configured using an SRAM or the like.

  In this embodiment, since data of 3 bits (8 gradations) per color is output, the waveform data stored in the line memory is converted to digital data by adding a GND waveform to the head and repeating the basic waveform seven times. Is. Although details of these basic waveforms will be described later, both the ejection waveform and the non-operation waveform are rectangular wave pulses.

  With a plurality of ejection waveforms, a plurality of ink droplets are recorded on the recording paper P within one pixel period, and an area corresponding to the number of droplets can be recorded by image data, and gradation recording can be performed. .

  Furthermore, if a different waveform is used for the ejection waveform, the appropriate amount of ink to be ejected can be changed, and the gradation can be further improved.

  In this example, 3 bits (eight gradations) are used as an example, but other numbers are possible. If the number of bits (number of gradations) of each data and the data in the line memory are changed in conjunction with each other, they can be changed. Good.

  The present invention can also be applied to binary recording with 1-bit (two gradations) image data.

<Electrical Configuration of Inkjet Head Drive Circuit>
Hereinafter, the electrical configuration of the head drive circuit 16, which is a characteristic configuration of the present invention, will be described with reference to block diagrams showing details of the drive circuit shown in FIGS. 5 and 6.

  FIG. 5 is a diagram showing details of the driving circuit 16 for one row of each color head shown in FIG. 4, that is, for 256 nozzles. FIG. 6 is a block diagram showing details of a driving IC for 128 nozzles in FIG. Here, the configuration of the drive circuit 16Y1 of the head body 17Y is shown, but the drive circuits 16M1 to 16K2 of 16Y2 and the head bodies 17M to 17K have the same configuration.

  As shown in FIG. 5, the drive circuit 16Y1 of this embodiment includes two 128-channel (nozzle) drive ICs, and the 3-bit × 128-channel (nozzle) shift register 31 in each drive IC is cascaded. Connected. The piezoelectric elements for 256 channels (nozzles) are driven. Further, the drive electrodes of the dummy pressure generating chambers located at both ends and the drive circuit are connected (out-D corresponds to this), and a drive waveform pattern to be described later is applied.

  Since these two drive ICs have basically the same configuration, one of them is shown in detail in FIG.

  The 128-channel driver IC shown in FIG. 6 has a first latch circuit 32A of 3 bits × 128 channels (nozzles) as the first latch means, and a 3 bits × 128 channels (nozzles) as the second latch means. A second latch circuit 32B, a shift register 31 as a first storage means for outputting image data to the first latch circuit 32A, a gray scale controller 33 as a drive means for driving a pressure applying means based on the ejection data, An output pattern register 34 as a second storage means, a three-phase buffer amplifier 35, and the like are included. It is preferable to use a register such as the output pattern register 34 as the second storage means.

  In this embodiment, in order to process image data consisting of 8 gradations per pixel, each means constituting the drive circuit 16 has a configuration corresponding to 3 bits. In synchronization with the transfer clock DCLK input from the control circuit 23, image data consisting of a plurality of bits, here 3 bits, is transferred from the line memory 13 to the shift register 31 of the drive circuit 16 in units of pixels. Come. This transfer timing is common among the nozzle rows.

  FIG. 6 shows a state in which the first 3-bit pixel data Sin0, Sin1, and Sin2 are transferred via a 3-bit data signal line. The image data that could not be stored in the shift register is output to and stored in a subsequent shift register that is cascade-connected as Sout0, Sout1, and Sout2.

  The shift register 31 has a capacity capable of storing image data of a number of pixels corresponding to one ejection of 128 nozzles by the nozzle head 17. By connecting two shift registers 31, image data for 256 pixels corresponding to one column of nozzles arranged in the sub-scanning direction is stored in the present embodiment. When the carriage 2 reaches a predetermined position, the control circuit 23 outputs a LAT1 signal which is a first trigger signal for instructing the latch timing, and the first latch circuit 32A shifts when receiving this LAT1 signal. The image data output in parallel from the register 31 is latched.

  When the carriage 2 reaches a predetermined position, the control circuit 23 outputs a LAT2 signal that is a second trigger signal for instructing the latch timing, and when the second latch circuit 32B receives the LAT2 signal, the first latch signal 32B is output. The image data output in parallel from the latch circuit 32A is latched.

  The first trigger signal and the second trigger signal are preferably a common trigger signal. As a result, the signal line for the trigger input of the latch timing can be reduced.

  Specifically, a common trigger signal is a pulse signal having two edges, a rising edge and a falling edge, one of the two edges is a first trigger signal, and the other edge is The second trigger signal may be used. This makes it possible to generate a common trigger signal for latch timing with a simple configuration. Further, the two latch timings can be easily changed by changing the pulse width.

  As described above, the image data output from the shift register 31 is latched by the second latch circuit 32B via the first latch circuit 32A.

  When the carriage 2 reaches a position suitable for recording, the control circuit 23 outputs a TRGIN signal for starting ink ejection, and when the second latch circuit 32B receives this TRGIN signal, the second latch circuit The image data latched in 32B is output to the gray scale controller 33.

  As described above, by providing two latch means, the data transfer speed is not increased more than necessary, and the recording speed is not lowered. Data transfer can be performed simultaneously, and data transfer trigger processing can be performed efficiently. Further, the configuration of the control system can be simplified, and the landing position of the droplet for each nozzle row can be adjusted more finely than the pixel pitch.

  The gray scale controller 33 receives three types of drive signals from the drive signal generation circuit (pulse_timing0 drive signal including a non-discharge waveform, pulse_timing1 drive signal including a non-operation waveform, and pulse_timing2 drive signal including a discharge waveform). Is input through the input terminal.

  Further, the gray scale controller 33 converts the pressure generating chambers corresponding to the 256 nozzles into three sets of A set, B set, and C set by selection signals STB-1, 2, and 3 supplied from the input terminals. A control unit is configured to divide and sequentially drive the corresponding piezoelectric elements. In STB-1, group A is selected, group B is selected in STB-2, group C is selected in STB-3, and ink droplets are sequentially ejected from the corresponding nozzles.

  Further, the gray scale controller 33 has a counting means 50 that counts what number waveform in the drive waveform pattern is output. The GSC (gray scale count) that is a count value of the counting means 50 is set to 0 to 0. Count to 7.

  Further, the gray scale controller 33 includes an output pattern register 34 that stores a conversion table that is information defining the relationship between the image data that is ejection data and the drive waveform pattern data corresponding to the drive waveform that drives the pressure applying means. Have. In this embodiment, drive waveform pattern data corresponding to a plurality of drive waveforms is shown.

  First, the counting means is reset by the input LOAD signal. STB-1 is selected, and A set of pressure generation chambers (nozzles) are selected. The drive waveform pattern data is determined from the image data corresponding to each pressure generation chamber (each nozzle) of A set by the conversion table stored in the output pattern register 34. In addition, predetermined drive waveform pattern data is selected for the pressure generation chambers of the B group and the C group that are not driven. GSC, which is the count value of the counting means, is incremented by 1 from 0 to determine the drive waveform to be output. The drive waveform is selected from three types of drive waveforms, ie, a non-operation waveform, a non-discharge waveform, and a discharge waveform, according to the image data and the count value of the counting means. These waveforms are selected and output by the switching means (not shown) from the above-described three types of drive signals in synchronization with the input GSCLK timing signal.

  The three-phase buffer amplifier 35 shifts the level of the drive waveform output from the gray scale controller 33 to the power supply voltage necessary for driving the piezoelectric element. At this time, the drive voltage of the ejection waveform is determined by the voltage value VH1 input from the input terminal, and the drive voltage of the non-operation waveform is determined by the voltage value VH2 input in the same manner. Output to the piezoelectric element, and ink droplets are ejected from the corresponding nozzle. By changing the voltage values of VH1 and VH2, the drive voltages of the ejection waveform and the non-operation waveform can be changed to optimum values.

  When the count value of the counting means reaches GSC = 7, it is determined that the ejection of ink droplets from the A set of pressure generating chambers (nozzles) has been completed, the counting means 50 is reset by the LOAD signal, and the STB-2 signal The group B is selected by the above, and ink droplets are similarly ejected from the group B. When the B set is completed, the ink discharge for the C set is similarly performed. This completes the ink ejection for all the nozzles for one row, and the recording is repeated again based on the next image data.

<Relationship between image data and drive waveform pattern>
FIG. 7 is a diagram showing an example of a conversion table between image data and drive waveform pattern data.

  Since the image data is 3 bits and 8 gradations, gradation value 0 is (0, 0, 0), gradation value 1 is (0, 0, 1), gradation value 2 is (0, 1, 0) , Tone value 3 is (0, 1, 1), tone value 4 is (1, 0, 0), tone value 5 is (1, 0, 1), tone value 6 is (1, 1, 0), the gradation value 7 is represented as (1, 1, 1).

  The drive waveform pattern data is data corresponding to eight drive waveforms from the first drive waveform to the eighth drive waveform corresponding to GSC = 0 to 7 of the count value of the counting means described above. 2 can take three values.

  Further, since the data is output from the bit positioned later, for example, in the case of the gradation value (0, 1, 1) in the table of FIG. 7, (1, 1, 1, 2, 2, 2, 1 , 0) is selected and drive waveform pattern data (0, 1, 2, 2, 2, 1, 1, 1) is output. The output drive waveform pattern corresponds to the count value GSC = 0 to 7 described above. In this case, the count value of the count means is 0 when GSC = 0, and when GSC = 1. 1 if GSC = 2, 2 if GSC = 3, 2 if GSC = 4, 1 if GSC = 5, 1 if GSC = 6, 1 if GSC = 6 In the case of = 7, 1 is output as drive waveform data.

  As described above, the STB signal divides the pressure generating chamber corresponding to 256 nozzles into three groups A, B, and C according to the three divided signals STB-1, STB-2, and STB-3. Thus, the corresponding piezoelectric elements are sequentially divided and driven.

  In the table of FIG. 7, when n = 1 and driving the piezoelectric elements of the A set of pressure generating chambers, the A waveform of the pressure generating chambers of the A set of pressure generating chambers has drive waveform pattern data according to the image data as described above. Although selected, the B and C pressure generation chambers corresponding to n = 2 and 3 have a drive waveform of (1, 1, 1, 1, 1, 1, 1, 0) regardless of the image data. The pattern data is selected and (0, 1, 1, 1, 1, 1, 1, 1, 1) is output.

  Similarly, when driving the piezoelectric elements of the pressure generation chambers of the group B with n = 2, the drive waveform pattern data is selected for the pressure generation chambers of the group B according to the image data as described above. However, the A and C pressure generation chambers corresponding to n = 1, 3 have (1, 1, 1, 1, 1, 1, 1, 0) drive waveform pattern data regardless of the image data. Is selected and (0, 1, 1, 1, 1, 1, 1, 1) is output.

  Similarly, when driving the piezoelectric elements of the C pressure generating chambers with n = 3, the driving waveform pattern data is selected for the C generating pressure chambers according to the image data as described above. However, the A, B pressure generation chambers corresponding to n = 1, 2 have (1, 1, 1, 1, 1, 1, 1, 0) drive waveform pattern data regardless of the image data. Is selected and (0, 1, 1, 1, 1, 1, 1, 1) is output.

  Therefore, when the count value of the counting means is GSC = 0, the driving waveform data of 0 is selected in any pressure generation chamber of the A group, the B group, and the C group, and the piezoelectric element is not driven, but the GSC = In 1 to 7, the piezoelectric element is driven as shown below according to the drive waveform data.

  In addition, drive waveform pattern data of (1, 1, 1, 1, 1, 1, 1, 0) is selected as out-D for the drive electrode of the dummy pressure generation chamber described above, and (0, 1 , 1, 1, 1, 1, 1, 1) is output. As a result, the partition walls of the dummy pressure generating chambers are driven in accordance with the driving waveform applied to the electrodes corresponding to the image data of the pressure generating chambers at both ends of the 256 pressure generating chambers.

  FIG. 8 shows drive waveform data, a drive waveform output to the piezoelectric element, and timing.

  In FIG. 8, the horizontal axis represents time, and the vertical axis of the drive waveform represents the drive voltage. In the figure, a section corresponding to one drive waveform, that is, one count of GSC is shown.

FIG. 9 is a diagram showing the basic operation of the shear mode head by the drive waveform. Here, three pressure generating chambers 28A, 28B, and 28C, which are a part of one nozzle row of the 17Y head body, are shown, and the 28B pressure generating chamber is selected by the STB signal that is a divided drive signal. It is assumed that 28A and 28C are pressure generation chambers that are not selected, and are driven according to image data.
FIG. 10 is a diagram showing the split drive operation of the shear mode inkjet head, and shows the state in which the volume of the pressure generating chamber is contracted.

  9 and 10 show a cross section of the head main body, and the description of the nozzles is omitted. In FIG. 10, the drive electrodes are omitted. Moreover, the same reference numerals in the figure denote the same members as those in FIG. 3, and 27 denotes a partition.

  Here, one nozzle row of 17Y is shown, but the same applies to the other nozzle rows.

  In FIG. 8, during the period in which the drive waveform data is “0”, the pulse_timing0 drive signal corresponding to the non-ejection waveform is selected, and the GND (earth) which is the non-ejection waveform generates pressure corresponding to the image data. Applied to the piezoelectric element of the chamber. As described above, the drive waveform data “1” is selected for the pressure generation chambers of the unselected group, the drive signal of pulse_timing1 corresponding to the non-operation waveform is selected, and the positive voltage of the voltage value VH2 which is the non-operation waveform Are applied to the piezoelectric element in the pressure generating chamber.

  Accordingly, in the recording head main body 17Y, in the state shown in FIG. 9A, the electrode 25B of the pressure generation chamber corresponding to the image data is connected to the ground, and the electrodes 25A, 25A, When a positive rectangular wave pulse having a voltage value VH2 which is a non-operating waveform is applied to 25C, first, in the polarization direction of the piezoelectric materials 27a and 27b constituting the partition walls 27B and 27C by the first rising of the pulse. An electric field in a perpendicular direction is generated, and both 27a and 27b are deformed at the joint surfaces of the partition walls. As shown in FIG. 9C, the partition walls 27B and 27C are deformed inward and the volume of the pressure generating chamber 28B is increased. Shrink. Due to this contraction, a pressure is applied to the extent that ink droplets in the pressure generating chamber 28B are not ejected.

When a predetermined time elapses, the potential of the electrodes 25A and 25C returns to 0 due to the falling of the pulse, and the partition walls 27B and 27C return from the contracted position to the neutral position in FIG.
Accordingly, the partition walls 27B and 27C of the piezoelectric element of the pressure generating chamber 28B corresponding to the image data are deformed to the extent that ink droplets are not ejected from the nozzles according to the drive waveform, and the ink at the nozzle tip is not ejected from the nozzles. Since the surface is kept in a vibrating state, drying of the ink is prevented. Further, the ink can be heated by the heat generated by driving the pressure applying means by the non-ejection waveform. Heating reduces the ink viscosity and facilitates ejection. Further, when there is an ink temperature distribution between the pressure generation chambers, this can be corrected.

  In FIG. 8, during the period in which the drive waveform data is “1”, the drive signal of pulse_timing1 corresponding to the non-operation waveform is selected, and a positive voltage rectangular wave pulse having the voltage value VH2 that is the non-operation waveform is displayed in the image data. Applied to the piezoelectric element of the corresponding pressure generating chamber. As described above, the drive waveform data “1” is selected for the pressure generation chambers of the unselected group, and the drive signal of pulse_timing1 corresponding to the non-operation waveform is selected. Similarly, the voltage value VH2 which is the non-operation waveform is selected. A square wave pulse of positive voltage is applied to the piezoelectric element in the pressure generating chamber.

  As a result, in the state shown in FIG. 9A, the recording head main body 17Y has a non-operating waveform for both the pressure generating chamber electrode 25B corresponding to the image data and the unselected pressure generating chamber electrodes 25A and 25C. A square wave pulse having a positive voltage value of VH2 is applied. Accordingly, the partition walls 27B and 27C of the piezoelectric element of the pressure generating chamber 28B corresponding to the image data are not driven and are not deformed because no potential difference is generated. .

  In FIG. 8, during the period in which the drive waveform data is “2”, the drive signal of pulse_timing2 corresponding to the discharge waveform is selected, and the rectangular wave pulse of the voltage value VH1 which is the discharge waveform corresponds to the image data. Applied to the piezoelectric element. As described above, the drive waveform data “1” is selected for the pressure generation chambers of the set that is not driven, the drive signal of pulse_timing1 corresponding to the non-operation waveform is selected, and the positive voltage of the voltage value VH2 that is the non-operation waveform Are applied to the piezoelectric element in the pressure generating chamber. The rectangular waveform pulse of the ejection waveform and the rectangular waveform pulse of the non-operation waveform are shifted in timing, and the rectangular waveform pulse of the non-operation waveform is output following the rectangular waveform pulse of the ejection waveform.

  As a result, in the state shown in FIG. 9A, the recording head main body 17Y applies a rectangular wave pulse of the voltage value VH1 to the electrode 25B of the pressure generating chamber corresponding to the image data, and a set of pressures that are not driven. When the first ground portion of the non-operating waveform is applied to the electrodes 25A and 25C in the generation chamber, first, at the first rising edge of the pulse, perpendicular to the polarization direction of the piezoelectric materials 27a and 27b constituting the partition walls 27B and 27C. As a result, an electric field is generated in both directions, and both 27a and 27b are deformed in the joint surfaces of the partition walls. As shown in FIG. 9B, the partition walls 27B and 27C are deformed outward, and the volume of the pressure generating chamber 28B is expanded. To do. As a result, a negative pressure is generated in the ink in the pressure generating chamber 28B, and the ink flows. When the pulse potential is returned to 0 after a predetermined time, the partition walls 27B and 27C return from the expanded position to the neutral position shown in FIG. 9A, and high pressure is applied to the ink in the pressure generating chamber 28B.

  Subsequently, when a rectangular wave pulse of VH2 is applied to the electrodes 25A and 25C of the pair of pressure generation chambers that are not driven while the electrode 25B of the pressure generation chamber corresponding to the image data is connected to the ground, By rising, as shown in FIG. 9C, the partition walls 27B and 27C are deformed inward, and the volume of the pressure generating chamber 28B is contracted. Due to this contraction, a higher pressure is applied to the ink in the pressure generating chamber 28 </ b> B, and ink droplets are ejected from the nozzle 28. When a predetermined time elapses, the pulse potential is returned to 0, and the partition walls 27B and 27C are returned from the contracted position to the neutral position in FIG.

  In this embodiment, since the drive waveform pattern includes 8 drive gradation patterns except for the leading earth portion, the above operation is repeated 7 times within one pixel period. A multi-drop ejection is performed by ejecting a maximum of 7 ink droplets.

  In the present invention, one drive waveform may be selected as a drive waveform pattern with 1-bit image data, and one ink droplet may be ejected within one pixel period. At this time, any one of the non-ejection waveform, the ejection waveform, and the non-operation waveform is selected based on the image data. Since the ejection can be performed while the non-ejection waveform is applied, the recording speed does not decrease and the non-ejection waveform can be applied.

  As described above, the multi-channel shear mode ink jet head is driven in three cycles of A group, B group, and C group.

  Such a three-cycle discharge operation will be further described with reference to FIG. In the example shown in FIG. 10, the head main body 17Y includes nine pressure generation chambers A1, B1, C1, A2, B2, C2, A3, B3, and C3, which are a part of one row of 256 pressure generation chambers. It is shown.

  At the time of ink ejection, first, a drive waveform is applied to the electrodes of the pressure generation chambers 28 of the A group (A1, A2, A3) according to the image data, and the pressure generation chambers of the B group (B1, B2, B3) and C A non-operation waveform is applied to the pair (C1, C2, C3) pressure generation chamber.

  Subsequently, the operation is performed in the same manner as described above for each pressure generating chamber 28 of the B group (B1, B2, B3) and further to each pressure generating chamber 28 of the C group (C1, C2, C3).

  In such a shear mode type ink jet recording head, the deformation of the partition wall 27 is caused by a voltage difference applied to the electrodes provided on both sides of the wall. Therefore, as in this embodiment, a negative voltage is applied to the electrode of the pressure generating chamber for discharging ink. Instead of applying the voltage, it is possible to operate the device by grounding the electrode of the pressure generating chamber for discharging ink and applying a positive voltage to the electrodes of the pressure generating chambers on both sides. This is a preferred embodiment.

  The discharge waveform and non-operation waveform are rectangular wave pulses with a constant voltage peak value. When 0V is 0% and the peak voltage is 100%, the pulse width is the rise of the voltage from 0V. It is defined as the time between 10% at the beginning or the beginning of falling and 10% at the beginning of falling or rising from the peak voltage. Further, the rectangular wave refers to a waveform in which both the rise time and fall time between 10% and 90% of the voltage are 0.5 μsec or less. By using a rectangular wave, the inkjet head can be driven with good responsiveness to eject droplets. In the method of ejecting droplets by resonance of pressure waves, the inkjet head is driven more efficiently and with high sensitivity. be able to.

  Note that AL (Acoustic Length) is ½ of the acoustic resonance period of the pressure generating chamber. This AL is obtained when a rectangular wave pulse is applied to the partition wall 27 which is a pressure applying unit to measure the speed of an ink droplet to be ejected, and the rectangular wave voltage value is made constant to change the pulse width of the rectangular wave. The pulse width at which the flying speed of the ink droplet is maximized is obtained.

  Further, as in the above embodiment, the ratio of the drive voltage VH1 (V) of the rectangular wave pulse having the ejection waveform to the drive voltage VH2 (V) of the rectangular wave pulse having the non-operating waveform is expressed by the relationship of | VH1 |> | VH2 | Then, it is easy to cancel the residual pressure wave after discharging the ink droplet, and stable ejection by high frequency driving can be achieved, and the ink in the nozzle can be appropriately shaken by the non-operation waveform, which is preferable.

  The pulse width of the rectangular wave pulse of the ejection waveform is preferably 0.5AL to 1.4AL, which is in the vicinity of 1AL. This increases the discharge pressure (discharge speed) of the droplets, and the most efficient discharge force can be obtained.

  In addition, the pulse width of the non-operating waveform rectangular wave pulse is preferably 1.6 to 2.5 AL in the vicinity of 2 AL. This facilitates cancellation of the residual pressure wave.

  Note that the reference voltage of the voltage VH1 and the voltage VH2 is not necessarily zero. The voltage VH1 and the voltage VH2 are differential voltages.

  FIG. 11 shows a drive waveform pattern, drive waveform output, and timing chart corresponding to the table of FIG. Here, the driving for one pixel of the pressure generation chamber selected by the division driving, for example, A set is shown. Although the drive waveform pattern applied to the dummy pressure generation chamber is omitted, the drive waveform pattern when the image data of FIG. 11 is (H, I, J) is applied to the drive electrode of the dummy pressure generation chamber. Is done.

  First, the counting means is reset by the input LOAD signal. For example, STB-1 is selected and A set of pressure generation chambers are selected. The drive waveform pattern data is determined from the image data corresponding to the A set by the conversion table stored in the output pattern register 34. In addition, a predetermined drive waveform pattern is selected for the pressure generation chambers of the B group and the C group that are not driven. GSC which is the count value of the counting means is incremented by 1 from 0 to 7 to determine the drive waveform to be output. The drive waveform is selected from three types of drive waveforms, ie, a non-operation waveform, a non-discharge waveform, and a discharge waveform, according to the image data and the count value of the counting means. These waveforms are selected and output by the switching means (not shown) from the above-described three types of drive signals in synchronization with the input GSCLK timing signal.

  In the present embodiment, when the image data has a gradation value 0 of (0, 0, 0), a non-ejection waveform is applied with a count of GSC = 3, that is, a fourth waveform. The ink surface at the tip of the nozzle can be vibrated substantially at the center of the non-ejection pixel, and the drying of the ink is prevented effectively and efficiently.

  In addition, when the image data is (0, 0, 1) and the gradation value is 1, the ink is ejected with the count of GSC = 3 and the fourth drive waveform, so the first dot is one pixel. Can be arranged in the approximate center. When the image data is (0, 1, 0) and the gradation value is 2, ink is generated with the fourth drive waveform with a count of GSC = 3 and the fifth drive waveform with a count of GSC = 4. Is discharged, so that a total of two drops of dots can be arranged almost at the center of one pixel. Similarly, by arranging dots from the center to the periphery of the pixel as the gradation value increases, the center of gravity of the dots can be made uniform between the low gradation dots and the high gradation dots.

  As described above, if the drive waveform pattern data is configured by assigning bit data to each drive waveform, a desired waveform can be selected according to the value of each bit, and the ejection data and the drive waveform pattern data can be easily configured. These combinations can be freely set, and since the ejection can be performed while the non-ejection waveform is applied, the recording speed is not lowered and the non-ejection waveform can be applied.

  The program is programmed to upload the value of a nonvolatile memory (not shown) in the CPU 11 to the output pattern register 34 every time the printer is turned on.

  Therefore, the output pattern register 34 is automatically set to a preset value when the printer is turned on when there is no rewriting operation. Therefore, the operation procedure is omitted when the operation for rewriting the output pattern register is unnecessary. it can.

  If necessary, the output pattern register table can be rewritten by rewriting the value of a nonvolatile memory (not shown) in the CPU 11.

  In the case where a plurality of droplets are ejected from a drive waveform pattern in which a plurality of the same waveforms are continued, only the unit waveform may be created by the memory of the drive circuit.

  In this embodiment, the drive signal is input from the drive signal generation circuit 15 of the control board 9, but may be generated by a memory in the drive circuit.

<Adjusting the dot position of multiple rows of nozzles in inkjet head>
Hereinafter, the dot position adjustment of a plurality of nozzles of the inkjet head in the inkjet printer of FIG. 1 will be described.

  In the head main body of this embodiment, in order to land ink droplets ejected from the eight nozzle rows at predetermined positions and form a straight line image in the sub-scanning direction, ink droplet ejection from each nozzle row Timing needs to be adjusted.

  Further, the ink jet printer of the present embodiment shown in FIG. 1 has a mode in which dots are formed during reciprocal bidirectional scanning in the main scanning direction in order to improve the recording speed. In such an ink jet printer, in order to print a good image, it is necessary to match the positions in the main scanning direction between the dots formed during the forward movement and the dots formed during the backward movement. This is because if the relative deviation between the dots formed during the forward movement and the dots formed during the backward movement occurs, the image becomes rough and the image quality deteriorates.

  When bidirectional recording is performed, a slight shift in the dot formation position tends to greatly affect the image quality. For example, when the recording head performs main scanning from left to right, if the dot position has a characteristic of shifting to the left side, the main scanning is performed in the reverse direction on the return path, so the dot position is shifted to the right side. As a result, the deviation that occurs in either one of the reciprocations is doubled by performing bidirectional recording. As described above, in bidirectional recording, image quality deterioration due to poor adjustment of the reciprocating dot position becomes severe, so it is necessary to adjust the dot formation timing easily and accurately.

  Therefore, in order to correct such a deviation, the ink jet printer according to the present embodiment performs adjustment using a so-called test pattern described below.

  In the test pattern, dots are formed from each nozzle row by forward movement. From nozzle rows other than the reference nozzle row, the timing for ejecting ink to each pixel is shifted in several stages, and the relative positional relationship is changed to form dots. The same goes for the backward movement.

  Further, with respect to the reference nozzle row, dots are formed from the nozzle row by forward movement, and dots are formed by backward movement without performing sub-scanning. At this time, at the time of backward movement, the timing of ejecting ink to each pixel is shifted in several stages, and dots are formed by changing the relative positional relationship of dots during forward movement and backward movement.

  By looking at the test pattern printed in this way and selecting the optimum timing, the ink ejection timing can be adjusted so that there is no positional deviation of the reciprocating dots from each nozzle row.

  In the ink jet printer of this embodiment, the timing adjustment in units of pixels is adjusted by shifting the image data in the page memory 12, and the adjustment in a range finer than the units of pixels is performed by using the first latch circuit 32A and the second adjustment described above. The latch circuit 32B is used to adjust the ejection timing of ink droplets from the nozzles independently.

  First, the former will be described.

  In the non-volatile memory (not shown) of the CPU 11 in FIG. 4, positional shift data (shift amount from the reference position) for each nozzle row measured at the time of manufacture of the ink jet printer is respectively stored in the main scanning direction X. Are stored in the forward and backward directions.

  In the page memory 12 of FIG. 4, for example, when the ink jet printer is powered on, positional deviation data is read from the CPU 11, and image data that does not eject any ink corresponding to that data, that is, zero value (hereinafter referred to as correction data). ) Is memorized. The zero value is (0, 0, 0) when expressed in 3 bits.

  Here, since the first nozzle row of Y color is at the head in the forward direction of the main scanning direction, that is, at the front reference position, it is necessary to add correction data to the front (in this case, meaning to come before the image data in the forward direction). There is no. For the second nozzle row of Y color and the nozzle rows of other colors, correction data that becomes longer according to the positional deviation of the nozzles is added before the image data. On the other hand, after the image data of the nozzle rows other than the K second nozzle row (here, meaning that the data comes after the image data in the forward direction), post-data is added. Since the second nozzle row for K color is positioned at the rear reference position when the carriage moves to the rightmost, it is not necessary to add rear data. The post data consists of the same zero value as that of the correction data, but does not need to correspond exactly to the positional deviation, and is used to make the data length constant. Thus, the forward direction composite image data for driving the nozzle is created.

  The creation of composite image data in the backward direction will be described. Since the second row nozzle of K color is at the head, that is, the rear reference position in the backward direction in the main scanning direction, it is not necessary to add correction data to the front (in this case, meaning to come before the image data in the backward direction). For the K-color first row nozzle and the other color nozzle rows, correction data that is longer in accordance with the displacement of the nozzle is added to the front of the image data. On the other hand, after the image data of the nozzle rows other than the Y first nozzle row (in this case, meaning to come after the image data in the backward direction), post-data is added. Thus, backward composite image data for driving the nozzles is created.

  The image data of each nozzle row formed in this way is sent to the line memos 13a and 13b in FIG. 4 for each line, and is input to the drive circuits 16Y1 to 16K2 at the same timing in the eight nozzle rows. The timing to be supplied to the piezoelectric element is awaited. When the carriage 2, that is, the head main body 17 starts moving in the forward direction and determines that each nozzle row has reached the ejection position based on the signal from the encoder, the CPU 11 drives the control circuit 23 to output the timing signal. Each drive circuit 16 transmits.

  Then, each drive circuit 16 outputs the composite image data to each piezoelectric element. Here, since the correction data is not added to the composite image data output to the Y-color first nozzle row, the Y-color first nozzle row immediately starts ink ejection based on the image data. To do. However, since the other nozzle rows are first driven based on the correction data, the head main body 17 moves in the forward direction while being maintained in a state where ink is not ejected.

  After that, when the head main body 17 moves in the forward direction from the previous reference position by the positional deviation of the Y-color second nozzle array, the driving based on the correction data ends, so that the Y-color second nozzle array is based on the image data. Starts ink ejection. Further, when the head 17 moves in the forward direction by the positional deviation of the first nozzle row of M color from the previous reference position, the driving based on the correction data is completed, so that the nozzle row starts ink ejection based on the image data. . Thereafter, when the head 17 moves in the forward direction by the positional deviation from the previous reference position sequentially in the order of the M color second nozzle row to the K color second nozzle row, the driving based on the correction data is completed, so the image Based on the data, the nozzle starts ink ejection.

  Finally, when the ink ejection of the nozzle row based on the image data of the K second nozzle row is completed, the carriage 2 reaches the rear reference position, and then the scanning direction is reversed in the backward direction. Also in the backward direction, nozzle drive control is performed based on the composite image data in the same manner as described above.

This makes it possible to adjust the landing position for each nozzle row in pixel pitch units. Next, adjustment that is finer than pixel units will be described. FIG. 12 shows an example of a data processing timing chart of two nozzle rows taking 17Y as an example. The horizontal axis of FIG. 12 represents time. A similar processing method is used for 17M, 17C, and 17K.

  In this embodiment, according to the transfer clock DCLK, the yellow (Y) first nozzle row image data is transferred from the line memory 13a to the shift register of the drive circuit 16Y1 via the 3-bit data signal line. Similarly, the image data of the nozzle row is transferred to the shift register of the drive circuit 16Y2 at the same timing. The magenta (M) image data is transferred from the line memory 13a to the shift registers of the drive circuits 16M1 and 16M2, and the cyan (C) image data is transferred from the line memory 13b to the shift registers of the drive circuits 16C1 and 16C2. Black (K) image data is transferred from the line memory 13b to the shift registers of the drive circuits 16K1 and 16K2.

  As described above, the control board 9 transfers the image data corresponding to the nozzle row to the shift register of each drive circuit 16 corresponding to the nozzle row, and stores the timing between a plurality of nozzle rows (here, eight rows). Are controlled in common, that is, at the same timing. As a result, data transfer to the shift registers of a plurality of drive circuits corresponding to a plurality of nozzle rows can be performed simultaneously, and a data transfer trigger process can be performed efficiently. In addition, the configuration of the control system can be simplified.

  When the carriage 2 reaches a predetermined position, when the data transfer for 256 channels is completed, the control circuit 23 displays a LAT1 signal (an arrow in the figure) that is a first trigger signal for instructing the latch timing. When the LAT1 signal is received, the first latch circuit 32A latches the image data output in parallel from the shift register 31. In this embodiment, the output timing of the LAT1 signal is common among the eight nozzle rows. That is, the image data transferred to the shift register at the same time in 8 columns is simultaneously latched by the first latch circuit 32A in 8 columns.

  Here, in the non-volatile memory (not shown) of the CPU 11 in FIG. 4, the ejection timing shift time data in units smaller than the pixel pitch between the nozzle rows measured at the time of manufacturing the ink jet printer is respectively stored in the main scanning direction X. Are stored in the forward and backward directions.

  4 reads out the deviation time data from the nonvolatile memory when the ink jet printer is turned on, for example, and the control circuit 23 generates the latch timing signal LAT2 (falling edge) for each nozzle row based on this deviation time. The output timing is controlled independently to output to each drive circuit corresponding to the nozzle row.

  When receiving the LAT2 signal, the second latch circuit 32B latches the image data output in parallel from the first latch circuit 32A.

  When the carriage 2 reaches a position suitable for recording, the control circuit 23 outputs a TRGIN signal for starting ink ejection, and when the second latch circuit 32B receives this TRGIN signal, the second latch circuit The image data latched by 32B is sequentially output to the gray scale controller 33 from the A set of nozzle rows, and then the pressure applying unit is driven to eject ink droplets.

  As described above, by providing two latch means, the data transfer speed is not increased more than necessary, and the recording speed is not lowered. Data transfer can be performed simultaneously, and data transfer trigger processing can be performed efficiently. In addition, the control system configuration is simplified, and the timing at which droplets are ejected from each nozzle array is controlled independently for each nozzle array, and the droplet landing position for each nozzle array is adjusted more finely than the pixel pitch. It becomes possible to do.

  FIG. 13 shows a preferred example of a data processing timing chart of two nozzle rows, taking 17Y as an example. The horizontal axis of FIG. 12 represents time. A similar processing method is used for 17M, 17C, and 17K.

  In this example, the first trigger signal LAT1 (rising edge) and the second trigger signal LAT2 (falling edge) of each column are common triggers composed of pulse signals having two edges, a rising edge and a falling edge. It is a signal. This makes it possible to generate a common trigger signal for latch timing with a simple configuration. In addition, the signal line for the trigger input of the latch timing can be reduced, and the two latch timings can be easily changed by changing the pulse width.

The pulse signal may be a downward pulse, the falling edge may be the LAT1 signal, and the rising edge may be the LAT2 signal.

<Line-type inkjet printer>
FIG. 14 is a perspective view showing a main part of an example in which the present invention is applied to an ink jet printer 100 having a line head main body. In the figure, the same reference numerals are given to the same members as the means or members in the case of the serial head.

  A line head main body 117 (the number of nozzles is 512 × 4 per color) in which four head main bodies 17 having 512 nozzles per color shown in FIG. 1 are arranged along the Y direction in the sub-scanning direction is provided for each color head. In the order of 117Y, 117M, 117C, and 117K, four are stacked in the X direction of the main scanning direction and stored in the outer case 117a. Similarly, the ink droplet ejection operation is controlled by the drive circuit 16 of the present invention housed in the outer case 117a.

  The paper transport mechanism 8 transports the recording paper P in the X direction, which is the main scanning direction, by the transport motor 8a transport roller pair 8b and transport roller pair 8c, as in the inkjet printer 1. Other basic configurations of the control board 9, the integrated drive circuit 16, and the like are the same as those of the ink jet printer 1 except that they are changed so as to correspond to 512 × 4 nozzles.

  As with the inkjet printer 1, the inkjet printer 100 transfers image data transferred from a personal computer or the like to the line memories 13a and 13b, and the line memory 13a and 13b expresses image data expressed in a gradation of 3 bits per pixel. Is transferred to the drive circuit 16 connected by the flexible cable 5. When the trigger circuit TRGIN is input, the drive circuit 16 ejects ink from the nozzle head 17 and performs recording on the recording paper P, as in the drive circuit 16 of the inkjet printer 1.

  As described above, in the above embodiment, a rectangular waveform having a sufficiently short rise time and fall time as compared with AL is applied to the piezoelectric element. By using the rectangular wave, it is possible to perform driving using the acoustic resonance of the pressure wave more effectively. Compared with a method using a trapezoidal wave, the ink droplets are ejected more efficiently, and can be driven with a lower drive voltage. In addition, the drive circuit can be designed with a simple digital circuit. In addition, the pulse width can be easily set.

  In the above embodiment, a shear mode type piezoelectric element that deforms in a shear mode by applying an electric field is used as the pressure applying means. The shear mode type piezoelectric element is preferable because a rectangular-wave drive pulse can be used more effectively, the drive voltage is lowered, and more efficient drive is possible. In addition, an example of a head in which ink channels that are pressure generation chambers are continuous across a partition wall has been shown. However, ink channels and dummy channels are alternately arranged so that every other ink channel is arranged. The present invention can also be applied to a dummy channel head that discharges ink from an ink channel. In this case, even if the partition wall of the ink channel is shear-deformed, the ink channel is easily driven without affecting other adjacent ink channels.

  However, the present invention is not limited to these, and other types of piezoelectric elements such as a single plate type piezoelectric actuator and a longitudinal vibration type stacked piezoelectric element may be used as the piezoelectric element. Also, other pressure applying means such as an electromechanical conversion element using electrostatic force or magnetic force, or an electrothermal conversion element for applying pressure using a boiling phenomenon may be used.

  In the above description, an application example of an inkjet printer is shown as a droplet discharge device, and an inkjet recording head for performing image recording is used as a droplet discharge head. However, the present invention is not limited to this. And a nozzle for discharging droplets, a pressure generation chamber communicating with the nozzle, and a pressure that is driven based on discharge data to discharge the droplets from the nozzle by applying pressure to the pressure generation chamber A droplet discharge head main body having an application unit and a drive circuit for driving the pressure application unit, and can be widely applied as a droplet discharge head and a droplet discharge device that discharge liquid from a pressure generating chamber as droplets from a nozzle. is there. For example, it is also effective in industrial applications such as liquid crystal color filter manufacturing applications. In particular, this is particularly effective when a nozzle having a small diameter or a quick-drying liquid is used, and a liquid in which the liquid surface of the discharge nozzle is likely to dry rapidly is generated immediately after the liquid droplet is discharged.

It is a perspective view which shows the principal part of a serial type inkjet printer. It is an enlarged view of the nozzle part of an inkjet head. It is the schematic which shows a shear mode type inkjet head main body and its manufacturing process. 1 is a circuit block diagram illustrating a circuit configuration of the entire inkjet printer 1. It is a block diagram which shows the structure of a drive circuit. It is a block diagram which shows the structure of a drive circuit in detail. It is a figure which shows the table which prescribed | regulated the relationship between image data and the drive waveform pattern data corresponding to the several drive waveform which drives a pressure provision means. It is a figure which shows the relationship between the data of a drive waveform, and the output of a drive waveform. It is a figure which shows the basic operation | movement of the shear mode inkjet head by a drive waveform. It is a figure which shows the operation | movement of the division drive of a shear mode inkjet head. It is a figure which shows image data and a drive waveform pattern. It is a figure which shows an example of the data processing timing chart of a multiple row nozzle. It is a figure which shows the preferable example of the data processing timing chart of a multiple row nozzle. It is a perspective view which shows the principal part of a line type inkjet printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Serial type inkjet printer 2 Carriage 5 Flexible cable 7 Encoder 9 Control board 10, 10a, 10b Piezoelectric material board 11 CPU
12 page memory 13, 13a, 13b line memory 14, 14a, 14b interface 15 drive signal generation circuit 16, 16Y1, 16Y2, 16M1, 16M2, 16C1, 16C2, 16K1, 16K2 drive circuit 17, 17Y, 17M, 17C, 17K head Main body 18, 18a, 18b, 18Y1, 18Y2, 18M1, 18M2, 18C1, 18C2, 18K1, 18K2 Nozzle 19, 19a, 19b Manifold 20 ROM
23 Control circuit 24, 24a, 24b Cover substrate 25, 25a, 25b, 25A, 25B, 25C Drive electrode 28, 28a, 28b, 28A, 28B, 28C Pressure generating chamber 31 Shift register 32A First latch circuit 32B Second latch Latch circuit 33 Gray scale controller 34 Output pattern register 35 Three-phase buffer amplifier 50 Count means 100 Line type inkjet printer 102, 102Y, 102M, 102C, 102K First nozzle row,
103, 103Y, 103M, 103C, 103K Second nozzle row 117, 117Y, 117M, 117C, 117K Line head body 160, 160a, 160b Extraction electrode 180 Nozzle plate 200 AND gate L1 Distance between nozzle rows L2 Head distance X Main scan Direction Y Sub-scanning direction

Claims (6)

A nozzle for discharging a droplet, a pressure generation chamber communicating with the nozzle, and a pressure applying unit that is driven based on discharge data and discharges the droplet from the nozzle by applying pressure to the pressure generation chamber A liquid droplet discharge head having a liquid droplet discharge head main body having a driving circuit for driving the pressure applying unit,
The drive circuit stores a first storage unit that stores the discharge data, and a second unit that stores information defining a relationship between the discharge data and drive waveform pattern data corresponding to a drive waveform for driving the pressure applying unit. Storage means,
The droplet discharge head according to claim 1, wherein the drive waveform is any one of a non-operation waveform, a non-discharge waveform, and a discharge waveform. The droplet discharge head according to claim 1, wherein the second storage unit is rewritable. The droplet discharge head main body has a nozzle row including a plurality of the nozzles, and the drive circuit divides the nozzles of the nozzle row into M (M is an integer of 2 or more) sets, and The droplet discharge head according to claim 1, further comprising a control unit that sequentially discharges droplets from the nozzles for each set. The pressure applying means is formed of a piezoelectric material that forms at least a part of a partition wall of the pressure generation chamber and is deformed in a shear mode by application of the driving waveform, and M is 3, and the non-ejection waveform The droplet discharge head according to claim 3, wherein is a GND waveform. 5. A liquid droplet ejection apparatus using the liquid droplet ejection head according to claim 1. 3. A droplet discharge apparatus using the droplet discharge head according to claim 2, wherein the second storage means is set to a preset value when the apparatus is turned on.

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