JP2017170652A - Unit for ejecting droplet, droplet ejecting device, and control method for droplet ejecting head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a unit that ejects a droplet so as to hinder variation in ejection volume between a plurality of nozzles, resulting from a liquid chamber and a nozzle characteristic.SOLUTION: A drive waveform for ejecting a droplet from a nozzle by changing the volume of a liquid chamber is applied to an individual electrode 16 of each drive element 12 in which a common electrode 15 and the individual electrode 16 are formed. The drive waveform includes: a drive portion in which a potential difference between two electrodes changes so as to expand or contract the liquid chamber a plurality of times; and a voltage holding portion including an intermediate voltage at which a potential difference between two electrodes reaches a predetermined potential difference before the potential difference changes in the drive portion. In accordance with each liquid chamber and a nozzle characteristic, a drive waveform generating section 310 independently corrects an intermediate voltage of a drive waveform applied to the individual electrode 16 of each drive element 12 corresponding to each liquid chamber.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a droplet discharge unit, a droplet discharge device, and a method for controlling a droplet discharge head.

  Conventionally, in ink-jet image formation, when ink is ejected from an ink-jet head, it is known that variations occur between a plurality of nozzles that eject droplets.

  On the other hand, in Patent Document 1, the nozzles to be driven are grouped according to the nozzle arrangement position on the nozzle bottom surface, and the voltage value of the contraction pulse is changed according to the group.

  However, in Japanese Patent Laid-Open No. 2004-228867, the variation between the rows of ejected nozzles is adjusted, but the variation in the ejection volume due to the characteristics of the liquid chamber and the nozzles due to the manufacturing variation among the plurality of nozzles in the same row cannot be suppressed. It was.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a unit that ejects droplets that can suppress variations in ejection volume among a plurality of nozzles due to the characteristics of a liquid chamber and nozzles.

In order to solve the above problems, in one embodiment of the present invention, a plurality of nozzles that discharge droplets, a plurality of liquid chambers that communicate with each of the plurality of nozzles, and a plurality of volumes that change the respective volumes of the plurality of liquid chambers A droplet ejection head comprising: a drive element; and a droplet ejection head comprising two electrodes connected to each of the drive elements; and a control unit that performs control to eject the droplet;
The two electrodes connected to each drive element include a first electrode to which a voltage that changes in a waveform is individually applied to each drive element, and a second electrode,
A voltage that changes to the waveform is applied to the plurality of first electrodes, and a potential difference between the two electrodes changes to a waveform, whereby the plurality of driving elements change the volumes of the corresponding liquid chambers,
The voltage that changes in the waveform includes a driving portion where the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes before the driving portion. A voltage holding portion including a predetermined intermediate voltage, which has a predetermined potential difference, and
In the control unit, according to the characteristics of each liquid chamber and nozzle, the intermediate voltage of the voltage changing to the waveform applied to the first electrode connected to each drive element corresponding to each liquid chamber, Provided is a unit for ejecting droplets, characterized in that each is corrected independently.

  According to one embodiment of the present invention, in a unit that ejects liquid droplets, variation in ejection volume among a plurality of nozzles due to characteristics of a liquid chamber and nozzles can be suppressed.

FIG. 3 is a cross-sectional view along the longitudinal direction of the liquid chamber of the droplet discharge head according to the embodiment of the present invention. FIG. 1B is a cross-sectional explanatory view of the liquid droplet ejection head of FIG. 1 is a block diagram illustrating a hardware configuration example of an image forming apparatus according to an embodiment of the present invention. 2A and 2B are a bottom view and a side view showing a head surface of an example of a droplet discharge head included in an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration example of a print control device and a head driver according to a first embodiment of the present invention. The graph which shows an example of the drive waveform which concerns on 1st Embodiment of this invention. Explanatory drawing which shows the state of the meniscus and drive pulse in a nozzle at the time of applying a drive pulse waveform. Illustration of non-uniform droplet volume and its correction example The flowchart which shows the flow of control which concerns on 1st Embodiment of this invention. The liquid chamber schematic diagram when not applying an applied voltage. Schematic diagram around the nozzle, liquid chamber schematic diagram, and frequency characteristics when different intermediate potentials are applied to the ideal liquid chamber. The schematic diagram of a liquid chamber, explanatory drawing of a drive waveform, and a frequency characteristic explaining the correction | amendment with respect to the liquid chamber with the large fluctuation | variation amount of the liquid in a liquid chamber by the characteristic of a liquid chamber and a nozzle. The schematic diagram of a liquid chamber, the explanatory view of a drive waveform, and a frequency characteristic explaining correction | amendment with respect to the liquid chamber with the small variation | change_quantity of the liquid in a liquid chamber by the characteristic of a liquid chamber and a nozzle. Graph showing discharge droplet volume histogram before and after correction It is a block diagram which shows the structural example of the printing control apparatus which concerns on 2nd Embodiment of this invention, and a head driver. The flowchart which shows the flow of control which concerns on 2nd Embodiment of this invention. 1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic diagram illustrating an example of an overall configuration of an image forming apparatus according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that, in the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

<Discharge head>
FIG. 1 is a cross-sectional view showing an example of an ejection head (droplet ejection head) according to an embodiment of the present invention. As shown in the drawing, an individual flow path (hereinafter referred to as “pressurized liquid chamber”) 6 is formed in the ejection head. Each nozzle 4 communicates with the pressurized liquid chamber 6. Further, the ejection head has a communication part (restrictor) 9 provided with the diaphragm 2 for each pressurized liquid chamber 6. Further, the ejection head has a communication portion 9 formed in the flow path member 1.

  A common liquid chamber 8 is formed in the frame member 17. The common liquid chamber 8 supplies the recording liquid to each pressurized liquid chamber 6. Specifically, the recording liquid is supplied from the common liquid chamber 8 via the fluid resistance unit 7. A liquid, that is, a recording liquid is supplied from the common liquid chamber 8 to each pressurized liquid chamber 6 through a communication portion 9 formed in the diaphragm 2. Note that a recording liquid supply port is formed in the frame member 17 in order to supply the recording liquid from the outside to the common liquid chamber 8. The common liquid chamber 8 is formed in a rectangular shape with a planar shape in the direction in which the pressurized liquid chambers 6 are arranged, that is, in the direction in which the nozzles are arranged (hereinafter sometimes referred to as “longitudinal direction of the common liquid chamber”). The

  In addition, the flow path member 1 forms an opening, a groove | channel, etc. in the nozzle communication path 5, each pressurized liquid chamber 6, the fluid resistance part 7, the communication part 10, etc. FIG. These can be formed, for example, when anisotropic etching using an alkaline etching solution such as a potassium hydroxide aqueous solution (KOH) is performed on a single crystal silicon substrate having a crystal plane orientation (Miller index 110). In addition, when machining such as etching or punching using an acidic etchant is performed on the SUS substrate, each pressurized liquid chamber 6 can be formed. Furthermore, the flow path member 1, the nozzle plate 3, and the vibration plate 2 can be integrally formed by electroforming. Furthermore, photosensitive resin etc. may be used for these formation.

  The diaphragm 2 is formed with a nickel plate having a three-layer structure in the order of the first layer 2a, the second layer 2b, and the third layer 2c from the pressurized liquid chamber 6 side. The diaphragm 2 is formed by electroforming, for example. Furthermore, the diaphragm 2 may be formed of, for example, a laminated member of a resin member such as polyimide and a metal plate such as a SUS substrate. Furthermore, the diaphragm 2 may be formed of a resin member or the like.

  In the nozzle plate 3, a plurality of nozzles 4 are formed for each pressurized liquid chamber 6. For example, the nozzle plate 3 is a metal such as stainless steel or nickel, a resin such as a polyimide resin film, silicon, or a combination thereof.

  Further, the inner shape of the nozzle 4, that is, the inner shape, is formed in a horn shape, for example. The internal shape of the nozzle 4 may be a substantially cylindrical shape or a truncated cone shape. Furthermore, the hole diameter of the nozzle 4 is about 14 to 35 micrometers in diameter on the outlet side from which droplets are ejected.

  The nozzle plate 3 and the nozzle surface (surface in the direction in which droplets are discharged, that is, the discharge surface) are provided with a water-repellent treatment film (layer) (3a, see FIG. 6) subjected to a water-repellent surface treatment. It is done. The water repellent film is, for example, PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor deposition coating of evaporative fluororesin (for example, fluorine pitch), solvent of silicon resin or fluororesin Baking after application is selected according to the physical properties of the recording liquid. Further, the water repellent film stabilizes the droplet shape and flight characteristics of the recording liquid so that high quality image quality can be obtained.

  The diaphragm 2 is formed of the first layer 2a with respect to each pressurized liquid chamber 6, and the second layer 2b is formed at the center of the diaphragm portion (vibration region) 2A, which is a deformable region. And the convex part 2B which consists of a laminated structure of the 3rd layer 2c is formed. The laminated piezoelectric elements 121 constituting the pressure generating means (actuator) are respectively joined to the convex portions 2B.

  The peripheral edge of the diaphragm 2 is joined to the frame member 17. The frame member 17 is formed with an ink supply hole 10 which is a supply port for supplying ink to the common liquid chamber 8 from the outside.

  The plurality of piezoelectric elements 121 are formed in a comb-like shape without being divided by performing half-cut groove processing (slit processing) on one drive element (piezoelectric member, piezoelectric element member) 12. The The drive element 12 is disposed on the base member 13 along the direction in which the plurality of piezoelectric elements 121 are arranged.

  The base member 13 is preferably formed of a metal material. When the base member 13 is formed of a metal material, heat storage due to self-heating of the drive element 12 can be reduced.

  Further, the vibration region (diaphragm) 2 </ b> A is displaced by the expansion and contraction of the piezoelectric element 121. When the vibration region 2A is displaced, the pressurized liquid chamber 6 contracts or expands. Thus, when a drive signal is applied to the piezoelectric element 121 and charging is performed, the piezoelectric element 121 expands. On the other hand, when the electric charge charged in the piezoelectric element 121 is discharged, the piezoelectric element 121 contracts.

  Note that the liquid in the pressurized liquid chamber 6 may be pressurized using a displacement in the d33 direction in the piezoelectric direction of the drive element 12 that is a piezoelectric member. Alternatively, the liquid in the pressurized liquid chamber 6 may be pressurized using displacement in the so-called d31 direction in the piezoelectric direction of the piezoelectric element member 12. Hereinafter, a configuration using displacement in the d33 direction will be described as an example.

  FIG. 1B is a cross-sectional view of the liquid droplet ejection head of FIG. 1A along the liquid chamber plane direction. Here, the piezoelectric member will be described.

  A base member 13 that constitutes an actuator unit is disposed by bonding and fixing the piezoelectric member (driving element) 12. In the drive element 12, a plurality of piezoelectric elements 121 and support members 123 are formed by forming grooves by slit processing that is not divided.

  The end face electrode on one end face of the drive element 12 is divided by dicing by half-cut to be an individual electrode 16, and the end face electrode on the other end face is conducted by all the piezoelectric elements 121 without being divided by a restriction such as notch. It becomes the common electrode 15.

  The common electrode 15 is connected to the ground (GND) electrode of the FPC cable 11 by providing an electrode layer at the end of the piezoelectric element 121 and turning it around. In this example, the piezoelectric element 121 is a driving piezoelectric element column that expands and contracts due to a change in voltage difference between the common electrode 15 and the individual electrode 16 by applying a driving waveform (absolute voltage) to the individual electrode 16.

  Here, the individual electrode 16 functions as a first electrode to which a voltage changing in waveform is applied, and the common electrode 15 functions as a second electrode to which a common voltage is applied to a plurality of electrodes.

  The column member 123 is a non-driven piezoelectric element column that is not affected by the voltage difference between the common electrode 15 and the individual electrode 16.

  The FPC cable 11 connected to a drive circuit (drive IC) that selectively applies a drive waveform (drive voltage waveform) is connected to the individual electrode 16 connected to the piezoelectric element 121 of the drive element 12.

  The drive element 12 is composed of a lead zirconate titanate (PZT) piezoelectric material 151 having a thickness of 10 to 50 μm / layer and an internal electrode 152 made of silver and palladium (AgPd) having a thickness of several μm / layer. Are laminated. The internal electrodes 152 are electrically connected to the individual electrodes 16 and the common electrode 15 which are alternately end surface electrodes (external electrodes).

  The piezoelectric constant of the piezoelectric element 121 is d33, and the pressurized liquid chamber 6 is contracted and expanded by expansion and contraction due to a change in voltage difference (relative voltage) between the electrodes 15 and 16 received by the piezoelectric element 121. The piezoelectric element 121 expands when the driving signal is applied and is charged and expands the pressurized liquid chamber 6, and the piezoelectric element 121 contracts the pressurized liquid chamber 6 in the opposite direction when the charged charge is discharged. It has become.

  In the droplet discharge head configured as described above, for example, by lowering the voltage (absolute voltage) applied to the individual electrode 16 from the reference voltage Ve (applying a pulse voltage having a drive waveform of 10 to 50 V, etc.), The voltage difference between 15 becomes small, and the piezoelectric element 121 contracts. Accordingly, the diaphragm 2 descends and the volume of the liquid chamber 6 expands, so that ink flows into the liquid chamber 6.

  Thereafter, the voltage applied to the individual electrode 16 is increased, the voltage difference between the electrodes 16 and 15 increases, the piezoelectric element 121 as the driving piezoelectric element column extends in the stacking direction, and the diaphragm 2 deforms in the nozzle 4 direction. Thus, the volume of the liquid chamber 6 is contracted. By this operation, the ink in the liquid chamber 6 is pressurized, and ink droplets are ejected (ejected) from the nozzle 4.

  Then, by returning the voltage applied to the individual electrode 16 to the reference voltage, the diaphragm 2 is restored to the initial position, and the liquid chamber 6 expands to generate a negative pressure. 106 is filled with ink. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation proceeds to the next droplet discharge operation.

  In general, some ink jet heads that use diaphragms are driven by a pushing method, a striking method, or a combination of these. In driving by the pushing method, an ink droplet is ejected by pushing the diaphragm into the pressurizing chamber and reducing the volume in the pressurizing chamber.

  In the driving by the striking method, the vibration plate is deformed by a force in the outer direction of the liquid chamber, and the displacement of the vibration plate is returned to the original volume from the expanded state of the liquid chamber to return the ink droplet. To discharge.

  As described above, the driving method of the head is not limited to (pulling-pushing), and it is also possible to perform striking or pushing depending on the direction to which the drive waveform is given.

  A liquid droplet ejection apparatus including a unit for ejecting liquid droplets provided with such an ejection head is, for example, an image forming apparatus. That is, when the image forming apparatus ejects droplets, the ejected droplets are a recording liquid such as ink. Hereinafter, an example of the image forming apparatus will be described. Note that the configuration for discharging droplets may be a unit in which the configuration for discharging droplets is integrated, such as a unit for discharging droplets.

<Hardware configuration example>
FIG. 2 is a block diagram illustrating a hardware configuration example of an image forming apparatus according to an embodiment of the present invention. For example, an image forming apparatus according to an embodiment of the present invention has the illustrated hardware configuration.

  The image forming apparatus includes a CPU (Central Processing Unit) 201, a ROM (Read-Only Memory) 202, and a RAM (Random Access Memory) 203. The image forming apparatus also includes an NVRAM (Non-Volatile RAM) 204 and an ASIC (Application Specific Integrated Circuit) 205.

  Further, the image forming apparatus includes a host I / F (interface) 206, a print control device 207, a carriage 30, a motor drive device 210, an AC bias supply device 212, and an I / O (Input / Output) 213.

  Furthermore, the image forming apparatus includes an operation panel 214, a temperature sensor 215, a main scanning motor 40, an encoder sensor 43, a sub scanning motor 31, a conveyance belt 21, an encoder sensor 35, and a charging roller 26.

  The CPU 201 controls the entire image forming apparatus. That is, the CPU 201 is a calculation device that performs calculations for realizing the processing and data processing performed by the control unit 200. The CPU 201 is a control device that controls the illustrated hardware.

  The ROM 202, the RAM 203, and the NVRAM 204 are examples of storage devices. Specifically, the ROM 202 stores a program executed by the CPU 201 and data such as fixed data. The RAM 203 stores data such as image data. Further, since the NVRAM 204 can retain data even when the power of the image forming apparatus is shut off, the NVRAM 204 stores data to be retained even when the power of the image forming apparatus is shut off.

  The ASIC 205 is an electronic circuit that performs various signal processing on image data, image processing such as rearrangement, and input / output signal processing for controlling the entire image forming apparatus.

  The host I / F 206 is an interface for transmitting / receiving data to / from the host side.

  The print control apparatus 207 transmits data for driving the ejection head (droplet ejection head) 209 and the like. In addition, the print control apparatus 207 generates and transmits a drive waveform.

  The carriage 30 is realized by the head driver 208, the ejection head 209, and the like. The head driver 208 is a driver IC (Integrated Circuit) for driving the ejection head 209 provided on the carriage 30 side.

  Here, the print control apparatus 207 and the carriage 30 are combined to form a unit 300 that discharges droplets. Further, the print control device 207 and the head driver 208 are combined to form the control unit 350 of the unit 300 that discharges droplets. The control of the unit 300 for discharging droplets will be described later with reference to FIG.

  The motor driving device 210 drives the main scanning motor 40 and the sub scanning motor 31. The AC bias supply device 212 supplies an AC bias to the charging roller 26.

  The encoder sensor 43 outputs a detection signal indicating the position of the main scanning motor 40. Similarly, the encoder sensor 35 outputs a detection signal indicating the position of the sub-scanning motor 31. The temperature sensor 215 measures the environmental temperature of the image forming apparatus and outputs a detection signal.

  The I / O 213 is an interface that inputs detection signals from each sensor.

  The operation panel 214 is a display device that displays various types of information and an input device that inputs user operations.

  For example, the control unit 200 receives image data and the like from an information processing apparatus such as a PC (Personal Computer), an image reading apparatus such as an image scanner, and an imaging apparatus such as a digital camera, by the host I / F 206. Note that image data or the like is received via a cable or a network. Next, the CPU 201 included in the control unit 200 reads and analyzes image data stored in a reception buffer included in the host I / F 206.

  Then, the control unit 200 uses the ASIC 205 to perform processing such as image processing and data rearrangement. Subsequently, the image data processed by the ASIC 205 is transmitted to the head driver 208 by the print control device 207. Note that the generation of dot pattern data for image formation is performed by a printer driver on the host side.

  Further, the print control apparatus 207 converts the image data into serial data and transmits it to the head driver 208. Further, the print control device 207 transmits signals such as a clock signal, a latch signal, and a droplet control signal (mask signal) used for transmitting image data to the head driver 208.

  Furthermore, the print control apparatus 207 includes a D / A converter that performs D / A (digital-analog) conversion on data indicating a drive signal pattern stored in the ROM 202 or the like. The print control apparatus 207 also includes a common drive waveform generation unit 301 that generates a drive signal using a voltage amplifier that amplifies the signal voltage and a current amplifier that amplifies the signal current.

  The print control apparatus 207 further includes a selection unit (transmission unit) 302 that instructs selection of a drive waveform transmitted to the head driver 208. Subsequently, one or a plurality of drive waveform pulses, that is, a drive signal (common drive waveform) is transmitted to the head driver 208. Details of the print control apparatus 207 will be described later.

  Image data is transmitted serially to the head driver 208. Further, the image data is transmitted to the head driver 208 as data for one row of the ejection head 209. Based on the data for one row, the head driver 208 applies a drive signal having a drive waveform to the ejection head 209 (individual electrode 16 thereof). When a drive signal is applied, a drive element (for example, the piezoelectric member 12 including the piezoelectric element 121) included in the ejection head 209 generates energy for ejecting a droplet. In this way, the ejection head 209 is driven based on the image data.

  Further, the image forming apparatus selects one of the sizes of, for example, a large droplet (large dot), a medium droplet (medium dot), and a small droplet (small dot) by selecting a driving waveform pulse constituting the driving waveform. As can be seen, the dots can be divided.

  Further, the CPU 201 samples a detection signal transmitted from the encoder sensor 43 that constitutes a linear encoder or the like to obtain a speed detection value, a position detection value, and the like. Next, the CPU 201 drives the drive output value for controlling the main scanning motor 40 based on the speed target value and position target position obtained from the speed and position profile stored in advance, and the speed detection value and position detection value. That is, a control value is calculated. Subsequently, the CPU 201 drives the main scanning motor 40 via the motor driving device 210 based on the control value.

  Similarly, the CPU 201 samples a detection signal transmitted from the encoder sensor 35 that constitutes a rotary encoder or the like to obtain a speed detection value, a position detection value, and the like. Next, based on the speed target value and position target position obtained from the speed and position profile stored in advance, the speed detection value and the position detection value, a drive output value for controlling the sub-scanning motor 31, that is, Calculate the control value. Subsequently, the CPU 201 drives the sub-scanning motor 31 via the motor driving device 210 based on the control value.

<Nozzle arrangement>
FIG. 3 is an external view showing an example of an ejection head included in the image forming apparatus according to the embodiment of the present disclosure. The image forming apparatus according to an embodiment of the present invention includes, for example, an ejection head 209 as illustrated. FIG. 3A is a plan view (bottom view) of the ejection head 209 viewed from the so-called nozzle direction. On the other hand, FIG. 3B is a side view of the ejection head 209 viewed from the side.

  Hereinafter, the direction in which the nozzles 4 included in the ejection head 209 are arranged (corresponding to the horizontal direction in the figure) is defined as the x axis. Further, a direction orthogonal to the x axis is taken as a y axis. The vertical direction is the z-axis.

  In the example shown in the figure, there are a plurality of nozzles 4 arranged in the x-axis direction. In this example, a nozzle group 102 is configured by a plurality of nozzles 4. Specifically, as shown in the drawing, a plurality of nozzles 4 are arranged so as to form a first row 102a and a second row 102b, and a nozzle group 102 is configured. As shown in the figure, the second row 102b is a position where there is no nozzle 4 constituting the first row 102a, that is, a position for interpolating between the nozzles 4 constituting the first row 102a. Installed.

  Further, the ejection head 209 includes a flow path member 1 (also referred to as a “droplet substrate”) that forms a flow path through which droplets flow. Furthermore, the illustrated configuration is an example in which the diaphragm 2 is bonded to the lower surface of the flow path member 1. On the other hand, in this example, the nozzle plate 3 is joined to the upper surface of the flow path member 1 with an adhesive or the like. Furthermore, the frame member 17 is joined to the diaphragm 2 with an adhesive or the like.

  The flow path member 1, the vibration plate 2, the nozzle plate 3, the frame member 17, and the like form a flow path in which a liquid that is discharged from the nozzle 4 flows or a liquid chamber in which the liquid is stored.

  Further, the damper member 20 is used on at least one of the wall surfaces of the liquid chamber to be formed. The damper member 20 is less rigid than the wall surface that is the frame member 17. Furthermore, the damper member 20 is not limited to one layer, and may be two or more layers. In addition, the damper member 20 may be made of a material different from that of the diaphragm 2. For example, the damper member 20 is nickel (Ni) metal or the like. That is, the damper member 20 is preferably made of a material having low gas permeability such as nickel metal. The damper member 20 may be formed of a resin film or the like.

<Configuration example of the first embodiment>
FIG. 4 is a block diagram illustrating a configuration example of the print control apparatus 207 and the head driver 208 according to the first embodiment of the present invention. FIG. 5 is a diagram for explaining drive waveforms according to an embodiment of the present invention.

  As illustrated in FIG. 4, the print control apparatus 207 includes a common drive waveform generation unit 301 and a transmission unit 302.

  On the other hand, the head driver 208 connected to the print control apparatus 207 is provided with drive waveform generation units 310a to 310x that can apply drive waveforms to individual nozzles.

  The common drive waveform generation unit 301 generates and transmits a common drive waveform including a plurality of ejection pulses contributing to the formation of droplets having a plurality of droplet sizes in a time series within one cycle of printing.

  The transmission unit 302 transmits to the head driver 208 a droplet control signal (large droplet MN signal, medium droplet MN signal, and small application MN signal shown in FIG. 5) instructing the droplet size. Further, the transmission unit 302 transmits droplet data such as an image data signal, a latch signal, and a clock signal to the head driver 208.

  Each drive waveform generation unit 310 in the head driver 208 in the present embodiment includes an ejection pulse selection unit 311, an intermediate voltage correction value storage region 312, a drive voltage correction value storage region 313, and a selection waveform data correction unit 314.

  The ejection pulse selection unit (data selection unit) 311 selects the selection waveform data from the common drive waveform data transmitted from the drive control unit according to the droplet data (FIGS. 5C, 5D, and 5D). (See waveform in e)). The ejection pulse selection unit 311 includes, for example, a shift register, a latch circuit, a decoder, a level shifter, an analog switch, and the like.

  The intermediate voltage correction value storage area (first storage area) 312 stores the correction value (intermediate voltage correction value) of the intermediate voltage Ve in association with the characteristics of the corresponding nozzle and the drive waveform.

  The drive voltage correction value storage area (second storage area) 313 stores the correction value of the drive voltage (discharge pulse peak voltage) in association with the characteristics of the corresponding nozzle and the drive waveform.

  For example, the intermediate voltage correction value storage area 312 and the drive voltage correction value storage area 313 are formed in the same storage means 315 such as NVRAM. Alternatively, the storage areas 312 and 313 may be provided in separate storage means.

  In the drive waveform generation unit 310, the selection waveform data correction unit 314 is connected to the ejection pulse selection unit 311, the intermediate voltage correction value storage region 312, and the drive voltage correction value storage region 313.

The selected waveform data correction unit 314 converts the waveform data selected by the ejection pulse selection unit into
Correction is performed in accordance with the intermediate voltage correction value and the drive voltage correction value read according to the drive frequency (see arrows in FIGS. 5C, 5D, and 5E). The selected waveform data reflecting the correction value is a drive waveform applied (applied) to the individual electrode 16 connected to the drive element 12.

  Here, the drive waveform is a voltage that changes to a waveform. By applying a drive waveform, which is an absolute voltage that changes into a waveform (potential difference between applied voltage and ground), to the plurality of individual electrodes 16, the potential difference (relative voltage) between the electrodes of the individual electrode 16 and the common electrode 15 is waveform. To change. Due to the change in potential difference (relative voltage) between the electrodes, the drive element 12 expands and contracts, and the plurality of drive elements 12 change the volumes of the corresponding liquid chambers.

  Here, an example is shown in which the common electrode 15 is connected to the ground voltage (0 V) (absolute voltage = relative voltage), but the common electrode may be connected to a bias voltage other than the ground voltage.

  Moreover, although the common electrode 15 and the individual electrode 16 have shown the example provided in the both sides | surfaces part of the piezoelectric element 121 in the said embodiment, an electrode may exist in another places, such as an upper surface part and a lower surface part. . Further, although an example of a pair of common electrodes and individual electrodes is shown for one piezoelectric element, a plurality of pairs of common electrodes and individual electrodes may be provided in order to change the piezoelectric elements.

  The driving voltage, intermediate voltage, and the like described below mean a potential difference between the individual electrode 16 and the common electrode 15.

  With such a configuration, it is possible to correct the intermediate voltage of the drive waveform (that is, the potential difference between the individual electrode and the common electrode) applied to each individual electrode 16 and to correct the energy applied to the liquid chamber 6. . Here, the intermediate voltage means a voltage that is applied to the individual electrode 16 and before the driving portion, so that the potential difference between the electrodes of the individual electrode 16 and the common electrode 15 becomes a predetermined voltage difference.

  This correction corrects variations in the characteristics of the liquid chambers, makes the individual liquid chamber volumes (portions where the liquid in the liquid chambers can be present) uniform, and suppresses variations in the frequency fluctuation amount of the ejected droplet volume between the nozzles. It becomes possible.

  Next, the behavior around the head and the nozzle when a drive pulse is applied will be described. FIG. 6 is an explanatory diagram showing the state of the meniscus and the drive pulse in the nozzle when the drive pulse waveform is applied.

  On the right side of FIG. 6, the waveform portion of the drive pulse corresponding to the meniscus state of the nozzle 4 on the left side is indicated by a bold line. In this specification, the meniscus means the state of the surface of the liquid (ink) near the nozzle.

  In the embodiment of the present invention, when a drive voltage waveform (overall voltage) is applied to the individual electrode 16 connected to the drive element 12, the applied absolute voltage is once held at the intermediate voltage Vg. In order to perform the discharge operation, particularly the striking operation, an intermediate voltage of about several tens of volts is maintained. At this time, the volume of the liquid chamber is reduced by the drive element that is expanded by applying the intermediate voltage.

  At the reference voltage Vg, as shown in FIG. 5A, a meniscus overflow occurs (swells due to surface tension).

  Then, as shown in FIG. 5B, the meniscus is drawn into the nozzle 4 by expanding the individual liquid chamber 6 by the first drawing waveform element a1. At this time, a part of the liquid La remains in the deteriorated water repellent film 3a.

  However, as shown in FIG. 6C, the meniscus swings back (amplitude) during the intermediate voltage (Vg) which is the voltage holding portion (period) b1 from the first pulling waveform element Pa to the first ejection pulse. Occurs, and the liquid L in the nozzle 4 and the remaining liquid La are combined.

  Therefore, as shown in FIG. 6D, the individual liquid chamber 6 is expanded by the drawing waveform element a2 of the first ejection pulse, so that the remaining liquid La is also drawn into the nozzle 4, and the meniscus is centered on the nozzle. On the other hand, it has a symmetrical shape. Here, together with the remaining liquid La, the waveform element that draws the liquid L in the nozzle 4 most is the peak voltage (drive voltage) b. The drive voltage b is a voltage at which the potential difference between the individual electrode 16 and the common electrode 15 is the smallest.

  From this state, as shown in FIG. 6E, the individual liquid chamber 6 is contracted by the contraction element c of the discharge pulse, whereby the meniscus is pushed out and the droplet is discharged. At this time, the meniscus has a symmetrical shape with respect to the center of the nozzle, so that no injection bending occurs. Therefore, the injection bending can be suppressed by performing the two-stage drawing of the meniscus (two-stage expansion of the individual liquid chamber).

  In this way, droplets are ejected from the nozzle 4 by two-stage striking of the meniscus.

  Note that the drive waveform (the voltage to be a waveform) applied in the embodiment of the present invention is not limited to the two-stage waveform, and may be a waveform excluding the steps of FIGS. 6 (a) and 6 (b). In this case, since the waveform is the same before and after the waveform changes to a trapezoid, the voltage before and after the change is set as an intermediate voltage. Therefore, in the case of one-stage striking, the intermediate voltage means a reference voltage Vg that is a period for holding a predetermined potential difference between the two electrodes before the driving portion.

  FIG. 7 is an explanatory diagram of an example of variation in droplet volume and a correction example thereof. (A) has shown the discharge volume dispersion | variation by the drive frequency dispersion | variation between several nozzles. (B) shows a discharge example in which the variation of (a) is corrected.

  Here, generally, there is a manufacturing variation in the shape between a plurality of nozzles. For example, in the assembly process, the drive element is joined to the liquid chamber part via the diaphragm, and the liquid chamber is sealed to determine the volume (volume), height, width, and the like of the liquid chamber.

  Specifically, each of the plurality of nozzles 4 of the discharge head 209 has Helmholtz natural vibration mainly corresponding to the shape of the liquid chamber 6 and the characteristics of the corresponding refill cycle such as the nozzle shape and the fluid resistance portion. This characteristic is slightly different between a plurality of nozzles due to manufacturing variations.

  In this specification, Helmholtz natural vibration (natural vibration frequency) is a compliance (unit) determined by the opening of the nozzle 4, the shape of the pressure chamber (liquid chamber) 6, and the ink supply port formed by the restrictor (communication portion) 9. (Volume change per pressure, degree of softness) and inertance.

  Further, in this specification, refill means the degree of ink inflow (pull-in) from the common liquid chamber 8 to the individual liquid chamber (pressurized liquid chamber) 6 and changes according to the resistance value of the fluid resistance portion 7. The value to be When there are many refills, the meniscus of the liquid from the nozzle 4 rises due to inertia, and further the liquid overflows.

  Due to the difference between the natural vibration period of the liquid chamber 6 and the refill period of the nozzle 4, even when the same drive frequency is applied, the volume of the ejected droplet varies as shown in FIG.

  Therefore, in the present invention, by performing the correction described later between the plurality of nozzles based on the difference between the characteristics of the liquid chamber and the nozzle (volume of the nozzle + the volume of the liquid chamber) such as the natural vibration frequency unique to the nozzle, The volume of droplets discharged after correction is made uniform.

<Control Flow of First Embodiment>
FIG. 8 is a flowchart showing a control flow according to the first embodiment of the present invention.

  First, in S <b> 1, the CPU 201 (see FIG. 2) acquires sheet conveyance speed information via the host I / F 206 or the operation panel 214.

  In S <b> 2, the CPU 201 acquires image data via the host I / F 206.

  In S3, the CPU 201 sets the head moving speed in accordance with the paper speed information and the image data. For example, the head moving speed corresponding to the image data is set in advance in the ROM 202 or the like in the control unit 200 shown in FIG. 2, and the speed is read.

  In S4, the drive frequency applied by the transmission unit 302 of the print control apparatus 207 is determined in accordance with the head moving speed.

  In S5, the droplet size (droplet size) is set in the transmission unit 302 in accordance with the image data. Then, a droplet control signal (large droplet MN signal, medium droplet MN signal, small application MN signal) is transmitted to the head driver 208 in accordance with the droplet size.

  In S6, the ejection pulse selection unit 311 selects the ejection pulse from the common driving waveform in accordance with the droplet size in the drive waveform generation unit 310 provided in plural in the head driver 208 on the carriage side.

  In S <b> 7, the selected waveform data correction unit 314 reads the correlation table of the liquid chamber dimensions (characteristics), the intermediate voltage, and the peak voltage from the storage areas 312 and 313.

  In S8, the selected waveform data correction unit 314 corrects the intermediate voltage using the correlation table in accordance with the determined drive frequency or in accordance with the high frequency drive frequency.

  In S9, the peak voltage of the ejection pulse of the droplet size selected according to the droplet size is corrected by the correlation table in accordance with the driving frequency used in S8.

  In S10, liquid voltage is generated by the potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 generated by applying the intermediate voltage (absolute voltage) corrected in S8 to the individual electrode 16 connected to the drive element 12. The volume of the chamber 6 is adjusted, and the meniscus position in the nozzle 4 is adjusted.

  In S11, a potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 generated by applying the ejection pulse (= drive waveform) corrected in S9 to the individual electrode 16 connected to the piezoelectric member (drive element) 12. ), The volume of the liquid chamber 6 is adjusted, and droplets are discharged from the nozzle 4.

  Thus, the control operation ends.

<Applied voltage, head volume, and meniscus at nozzle>
First, FIG. 9 shows a schematic view of a liquid chamber when no applied voltage is applied. The case where no applied voltage is applied indicates a case where the potential difference between the individual electrode 16 and the common electrode 15 is zero. For example, this is the case when both the individual electrode 16 and the common electrode 15 are at ground voltage.

  In this state, the liquid chamber 6 is not pressed by the drive element 12 and the resistance value of the fluid resistance portion 7 is small. Therefore, as shown in the figure, the meniscus (liquid level) of the nozzle is inside the nozzle and is slightly recessed due to surface tension.

  FIG. 10 is a schematic diagram of the periphery of the liquid chamber and the nozzle when an intermediate voltage is applied to the ideal liquid chamber. Specifically, a relationship diagram regarding the intermediate voltage and the position of the meniscus when the frequency characteristic of the droplet volume to be ejected is equal to the ideal characteristic is shown.

  10, (a) is a schematic diagram of a liquid chamber when a standard intermediate voltage is applied, (b) is a schematic diagram of a liquid chamber when a high intermediate voltage is applied, and (c) is a high intermediate voltage. A schematic view of the liquid chamber is shown.

  As shown in FIG. 10, when the applied intermediate voltage is different for liquids having the same characteristics, the amount of pushing into the pressure chamber is different, and the fluid resistance is different, so that the position of the meniscus at the nozzle is different.

  The details of performing correction control to correct the intermediate voltage once held in accordance with the characteristics of each nozzle and to make the amount of decrease in the volume of the liquid chamber before discharge uniform by utilizing this property will be described below.

<When the volume fluctuates greatly>
FIG. 11 shows the liquid when the intermediate voltage and the corrected intermediate voltage are applied to the liquid chamber having a large amount of fluctuation of the liquid in the liquid chamber (for example, the volume of the liquid chamber is large) due to the characteristics of the liquid chamber and the nozzle. The schematic diagram around a chamber and a nozzle is shown.

  In FIG. 11, (a) shows the schematic diagram of the liquid chamber before the correction, the drive waveform, and the frequency fluctuation characteristics of the ejection droplet volume, and (b) shows the schematic diagram of the liquid chamber after the correction of the intermediate voltage, and the drive waveform. The frequency variation characteristics of the ejection droplet volume are shown, and (c) shows the drive waveform after the drive voltage correction and the frequency variation characteristics of the ejection droplet volume.

  As shown in FIG. 11A, due to the characteristics of the liquid chamber and the nozzle, for the drive element 12 corresponding to the liquid chamber 6 where the amount of fluctuation of the liquid in the liquid chamber is large, the reference value shown in FIG. When the same voltage (intermediate voltage) is applied, the liquid L to be accommodated tends to increase in the outward direction of the nozzle 4.

  As described above, the amount of fluctuation of the liquid in the liquid chamber depends on the natural vibration frequency caused by the volume of the liquid chamber 6, the vertical length, and the horizontal length, the volume of the nozzle 4, and the vertical length. The size at the time of manufacture is defined by the difference in the refill cycle caused by the difference in length and the horizontal length.

  Therefore, it is preferable to measure and store the relationship of the meniscus position of the liquid L of the nozzle 4 in advance after manufacturing by applying the same voltage.

  When the frequency characteristics of the ejected droplet volume fluctuate more than the ideal characteristics, especially when the ejected droplet volume at a high frequency is large, it is ejected while the meniscus on the nozzle surface is excessively raised due to refilling. It is that.

  In order to approach the ideal characteristics, it is necessary to suppress an excessive rise of the meniscus on the nozzle surface. For this reason, by increasing the amount of pushing of the drive element 12 into the liquid chamber 6, the resistance value of the fluid resistance portion 7 of the liquid chamber 6 may be increased to suppress refilling.

  Further, if the intermediate voltage is simply raised, the pulse height (amplitude) used for the ejection operation also increases, and the volume of the ejected droplet at the time of low frequency driving increases. In order to prevent this, as shown in (c), the pulse height is also adjusted, and the ejection droplet volume during low frequency driving is corrected.

<When the volume fluctuates small>
FIG. 12 shows a liquid when an intermediate voltage and a corrected intermediate voltage are applied to a liquid chamber in which the amount of fluctuation of the liquid in the liquid chamber is small (for example, the volume of the liquid chamber is small) due to characteristics of the liquid chamber and the nozzle. It is a schematic diagram around a chamber and a nozzle.

  In FIG. 12 and FIG. 13, the drive waveform diagram shown in the center is a potential difference (relative potential) between the individual electrode 16 and the common electrode 15 that directly affects the expansion and contraction of the drive element 12 and the fluctuation of the volume of the liquid chamber 6. ). In FIG. 12 and FIG. 13, the description will be made assuming that the common electrode 15 is grounded (0 V) (relative voltage = absolute voltage) for simplification of description.

  In FIG. 12, (a) shows the schematic diagram of the liquid chamber before the correction, the drive waveform, and the frequency fluctuation characteristic of the ejection droplet volume, and (b) shows the schematic diagram of the liquid chamber after the correction of the intermediate voltage, and the drive waveform. The frequency variation characteristics of the ejection droplet volume are shown, and (c) shows the drive waveform after the drive voltage correction and the frequency variation characteristics of the ejection droplet volume.

  As shown in FIG. 12A, due to the characteristics of the liquid chamber and the nozzle, the reference value shown in FIG. 10A is applied to the drive element 12 corresponding to the liquid chamber 6 in which the fluctuation amount of the liquid in the liquid chamber is small. When the same voltage (intermediate voltage) is applied, the stored liquid L tends to be drawn inward of the nozzle 4.

  When the frequency characteristics of the ejection droplet volume fluctuate smaller than the ideal characteristics, the fact that the ejection droplet volume at a high frequency is particularly small means that the meniscus of the nozzle 4 is excessively drawn due to refilling. It is to be done.

  In order to approach the ideal characteristics, it is necessary to suppress excessive refilling. For this purpose, the amount of pushing of the drive element 12 into the liquid chamber 6 is reduced, so that the resistance value of the fluid resistance portion 7 of the liquid chamber is reduced and refilling is promoted.

  If the intermediate voltage is simply lowered as shown in (b), the pulse height (amplitude) used for the ejection operation is also reduced, and the volume of the ejected droplet during low-frequency driving is reduced. In order to prevent this, as shown in (c), the pulse height is also adjusted, and the ejection droplet volume during low-frequency driving is corrected.

  As shown in FIGS. 11 and 12, the state of the meniscus with respect to the nozzle before applying the drive waveform can be made uniform by correcting the intermediate voltage in accordance with the characteristics of the individual liquid chambers and nozzles.

図１１、図１２の傾向を表１に示す。このような製造バラツキに起因する吐出液滴体積のばらつきを補正するために、表２のように補正値を記憶しておくと好適である。

The trends in FIGS. 11 and 12 are shown in Table 1. In order to correct the variation in ejected droplet volume due to such manufacturing variations, it is preferable to store the correction value as shown in Table 2.

なお、表２では、模式的に補正の大、小等の傾向のみを示したが、実際には、段階的に変化する補正値や、補正倍率等を記憶しておくとより好ましい。このような製造ばらつきを、図４に示した、中間電圧補正値記憶領域３１２及び駆動電圧補正値記憶領域３１３に保存させておき、図８に示すように制御動作を実行する際に読み出して、補正に利用される。

In Table 2, only the tendency of large and small corrections is schematically shown, but actually, it is more preferable to store correction values that change in stages, correction magnifications, and the like. Such manufacturing variations are stored in the intermediate voltage correction value storage area 312 and the drive voltage correction value storage area 313 shown in FIG. 4, and are read when the control operation is executed as shown in FIG. Used for correction.

  Accordingly, it is possible to suppress the discharge volume variation among the plurality of nozzles due to the characteristics (variation of characteristics) of the individual liquid chambers and nozzles.

<Deviation due to frequency>
FIG. 13 shows a discharge droplet volume histogram before and after the correction. In FIG. 13, the standard deviation of the discharge droplet volume distribution between a plurality of nozzles of the discharge droplet volume discharged from the nozzle 4 when the piezoelectric element 121 of the drive element 12 is driven at a low frequency is shown. The standard deviation of the volume distribution of ejected droplets among a plurality of nozzles of the volume of ejected droplets ejected from the nozzle 4 when the piezoelectric element 121 is driven at a high frequency is shown.

  As shown in FIG. 13, the ejection droplet volume variation during high-frequency driving for ejecting droplets at a high frequency is likely to be detected as an abnormal image, particularly density unevenness. For this reason, the ejection droplet volume variation during high-frequency driving is preferentially corrected.

  Specifically, the standard deviation of the discharge droplet volume distribution between multiple nozzles during high frequency driving is corrected to be smaller than the standard deviation of the discharge droplet volume distribution between multiple nozzles during low frequency driving. To do.

In the above-described embodiment, an example in which the pulse is corrected based on the characteristics specific to the nozzle after selecting the ejection pulse corresponding to the droplet size from the common drive waveform has been described. The common drive waveform before selection may be corrected.
The common drive waveform corrected for each nozzle includes the same intermediate voltage as described above and the peak voltage of the ejection pulse.

<Configuration Example of Second Embodiment>
FIG. 14 is a block diagram illustrating a configuration example of the print control apparatus 207 and the head driver 208-1 according to the second embodiment of the present invention.

  As illustrated, the print control apparatus 207 includes a common drive waveform generation unit 301 and a transmission unit 302. On the other hand, the head driver 208-1 connected to the print control apparatus 207 is provided with drive waveform generation units 320a to 320x that can apply drive waveforms to the individual nozzles.

  The common drive waveform generation unit 301 generates and transmits a common drive waveform including a plurality of ejection pulses contributing to the formation of droplets having a plurality of droplet sizes in a time series within one cycle of printing.

  The transmitting unit 302 transmits droplet data such as a droplet control signal, an image data signal, a latch signal, and a clock signal that indicate the size of the droplet to the head driver 208-1.

  Each drive waveform generation unit 320 in the head driver 208-1 in this embodiment includes an intermediate voltage correction value storage area 321, a drive voltage correction value storage area 322, a common drive waveform correction part 323, and a drive waveform selection part 324. .

  The intermediate voltage correction value storage area (first storage area) 321 stores the intermediate voltage correction value in association with the characteristics of the corresponding nozzle and the drive waveform.

  The drive voltage correction value storage area (second storage area) 322 stores a correction value of the drive voltage (discharge pulse peak voltage) in association with the characteristics of the corresponding nozzle and the drive waveform.

  For example, the intermediate voltage correction value storage area 321 and the drive voltage correction value storage area 322 are formed in the same storage unit 325 such as NVRAM. Alternatively, the storage areas 321 and 322 may be provided in separate storage means.

  The common drive waveform correction unit 323 corrects the intermediate voltage and the drive voltage (absolute voltage) of the common drive waveform according to the input intermediate voltage correction value and drive voltage correction value.

  The drive waveform selection unit (waveform selection) 324 selects the selection waveform corrected for each nozzle from the common drive waveform data corrected for each nozzle transmitted from the common drive waveform correction unit 323 according to the droplet data. To do. The drive waveform selection unit 324 includes, for example, a shift register, a latch circuit, a decoder, a level shifter, an analog switch, and the like.

  In the drive waveform generation unit 320, the common drive waveform correction unit 323 reflects the correction value, and the selected waveform selected by the drive waveform selection unit 324 is the individual electrode 16-a connected to each of the drive elements 12-a to 12x. Drive waveform applied to ˜16-x.

  With such a configuration, it is possible to correct the intermediate voltage of the drive waveform applied to each liquid chamber. Therefore, it is possible to correct the variation in characteristics, bring the individual liquid chamber volumes close to uniform, and suppress the variation in the frequency fluctuation amount of the discharge droplet volume between the nozzles.

<Control Flow of Second Embodiment>
FIG. 15 is a flowchart showing a control flow according to the second embodiment.

  First, in step S <b> 21, the CPU 201 acquires sheet conveyance speed information via the host I / F 206 or the operation panel 214.

  In step S <b> 22, the CPU 201 acquires image data via the host I / F 206.

  In S23, the CPU 201 (FIG. 2) sets the head moving speed in accordance with the paper speed information and the image data.

  In S24, the drive frequency applied by the transmission unit 302 of the print control apparatus 207 is determined in accordance with the head moving speed.

  In S25, the droplet size is set by the transmission unit 302 in accordance with the image data. Then, in accordance with the droplet size, a droplet control signal (large droplet MN signal, medium droplet MN signal, small application MN signal) is transmitted to the head driver 208-1.

  In S26, the common drive waveform correction unit 323 reads the correlation table of the liquid chamber dimensions (characteristics), the intermediate voltage, and the peak voltage in the drive waveform generation unit 320 provided in plurality in the head driver 208-1 on the carriage side.

  In S27, the common drive waveform correction unit 323 corrects the intermediate voltage and the peak voltage of the common drive waveform using the correlation table in accordance with the determined drive frequency or in accordance with the high frequency drive frequency.

  In S28, the ejection pulse corrected for each nozzle is selected from the corrected common drive waveform by the selection unit 324 in accordance with the size of the droplet.

  In S29, the intermediate voltage (absolute voltage) corrected in S27 is applied to the individual electrode 16 connected to the piezoelectric element 121, and the potential difference (relative voltage) between the individual electrode 16 and the common electrode 15 causes the liquid chamber 6 to The volume is adjusted and the meniscus position in the nozzle 4 is adjusted.

  In S31, the ejection pulse (= drive waveform, absolute voltage) corrected in S27 and selected in S28 is applied to the individual electrode 16 connected to the piezoelectric element 121, and the potential difference between the individual electrode 16 and the common electrode 15 ( The volume of the liquid chamber 6 is adjusted by relative voltage), and the droplets are ejected from the nozzle 4.

<Example of overall configuration>
FIG. 16 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 17 is a schematic diagram illustrating an example of a mechanism portion included in the image forming apparatus according to an embodiment of the present invention. An ink jet printer 500 as an example of the image forming apparatus illustrated in FIG. 16 is a so-called serial type.

  As shown in FIG. 17, the ink jet printer has side plates 221A and side plates 221B on the left and right. A guide lot 231 and a guide lot 232 are installed on the side plate 221A and the side plate 221B. The carriage 30 moves along the guide lot 231 and the guide lot 232 in the y-axis direction (hereinafter referred to as “carriage main scanning direction”) via the timing belt by the main scanning motor.

  The carriage 30 ejects droplets of each color such as yellow (Y), cyan (C), magenta (M), and black (K). In addition, the carriage 30 may be simply referred to as “recording head 234” when a plurality of recording heads 234a and recording heads 234b having the ejection head 209 (FIG. 2) are not distinguished (hereinafter, the recording heads 234a and 234b are not distinguished from each other). There is.) As shown in the figure, the carriage 30 is installed such that a plurality of nozzles are arranged in a direction perpendicular to the carriage main scanning direction (hereinafter also referred to as “sub-scanning direction”).

  In the configuration illustrated in FIG. 17, each recording head 234 has two nozzle rows. For example, the recording head 234a has, on one side, a nozzle row that ejects black (K) droplets. The recording head 234a has a nozzle row that discharges cyan (C) droplets on the other side. Similarly, the recording head 234b has a nozzle row that ejects magenta (M) droplets on one side. In addition, the recording head 234b has a nozzle row that discharges yellow (Y) droplets on the other side.

  The carriage 30 also supplies a head tank 235a and a head tank 235b for supplying ink liquids of the respective colors to the nozzle rows of the recording head 234 (hereinafter, when the head tank 235a and the head tank 235b are not distinguished from each other) It may be referred to as “head tank 235”). A supply tube 236 for each color is connected to the head tank 235. Ink liquid is supplied to the head tank 235 from the cartridges 210k, 210c, 210m, and 210y of each color via the supply tube 236.

  On the other hand, as illustrated in FIG. 16, the ink jet printer 500 includes a paper feed tray 250. The paper feed tray 250 has a paper mounting portion 241 such as a pressure plate. In addition, a sheet S, which is an example of a recording medium, is placed on the sheet mounting unit 241. In this way, the paper feed tray 250 serves as a paper feed unit that supplies the paper S.

  Then, the sheets S are separated one by one from the sheet loading unit 241 and supplied. For example, as illustrated, the inkjet printer 500 includes a paper feed roller 243 such as a half-moon roller. A separation pad 244 is provided at a position facing the paper feed roller 243. The separation pad 244 is made of a material having a large friction coefficient.

  In order to convey the paper S from the paper supply unit to the lower side of the recording head 234, a guide member 245 for guiding the paper S is provided. Similarly, in order to convey the sheet S to the lower side of the recording head 234, a counter roller 246, a conveyance guide member 247, a pressing member 248 having a tip pressure roller 249, and the like are provided.

  Further, a transport belt (transport means) 251 and the like are provided for electrostatically attracting the transported paper S and transporting it to a position facing the recording head 234. The transport belt 251 is a so-called endless belt or the like. The conveyor belt 251 is bridged between the conveyor roller 252 and the tension roller 253. As a result, the transport belt 251 circulates in the belt transport direction (sub-scanning direction). A charging roller 256 is provided for the transport belt 251. The charging roller 256 charges the surface of the conveyance belt 251. As illustrated, the charging roller 256 is provided so as to contact the surface of the transport belt 251. Further, the charging roller 256 rotates as the conveyance belt 251 rotates.

  The conveyance belt 251 rotates according to the rotation of the conveyance roller 252 when the conveyance roller 252 is rotated by the sub-scanning motor. Therefore, the conveyance belt 251 moves around in the belt conveyance direction by the sub-scanning motor.

  Next, image formation is performed on the paper S by the recording head 234 and the like. After image formation is performed by the recording head 234 and the like, the sheet S is discharged. A paper discharge unit that discharges paper is realized by a separation claw 261 that separates the paper S from the transport belt 251, a paper discharge roller 262, a paper discharge roller 263, a paper discharge tray 255, and the like.

  Note that the inkjet printer 500 may include a duplex unit 271 and the like on the back surface. The duplex unit 271 is a detachable unit or the like. The duplex unit 271 reverses the sheet S sent from the transport belt 251 and feeds it again between the counter roller 246 and the transport belt 251. The illustrated configuration is an example in which the upper surface of the duplex unit 271 is the manual feed tray 272.

  Returning to FIG. 17, the maintenance / recovery mechanism 281 is installed on one side (right side in the drawing) of the range scanned by the carriage 30. The maintenance / recovery mechanism 281 is a mechanism for maintaining and recovering the state of each nozzle of the recording head 234. It is assumed that no image is formed on the recording medium at the position where the maintenance / recovery mechanism 281 is installed. Hereinafter, an area where image formation is not performed on the recording medium is referred to as a “non-printing area”.

  The maintenance / recovery mechanism 281 includes a cap member (hereinafter referred to as “cap”) 282a and a cap member 282b (hereinafter simply referred to as “cap 282” when the cap 282a and the cap 282b are not distinguished from each other). It is done. The cap 282 is used for capping each nozzle surface of the recording head 234.

  The maintenance / recovery mechanism 281 includes a wiper blade 283. The wiper blade 283 is a blade member for wiping each nozzle surface. Further, the maintenance / recovery mechanism 281 is provided with an idle discharge receptacle 284. The idle ejection receptacle 284 receives droplets ejected by so-called idle ejection that ejects droplets that are not used for image formation in order to discharge the thickened recording liquid.

  The non-printing area is provided with an idle discharge receptacle 288 on the other side where the maintenance / recovery mechanism 281 is installed. The idle discharge receiver 288 is provided with an opening 289.

  In the image forming apparatus as described above, the sheets S are separated and fed one by one from the sheet feed tray 250 as shown in FIG. Next, the fed paper S is sent between the counter roller 246 and the conveyance belt 251 by the guide member 245. Subsequently, the sheet S is guided by the conveyance guide member 247, and the sheet S is pressed against the conveyance belt 251 by the tip pressure roller 249.

  At this time, a positive output and a negative output are alternately applied to the charging roller 256. That is, an alternating voltage is applied to the charging roller 256. By this application, the conveying belt 251 is alternately charged in a strip shape with a predetermined width in the sub-scanning direction, that is, plus and minus in an alternating charging voltage pattern. As described above, when the paper S is transported on the transport belt 251 in which plus and minus are alternately charged in a band with a predetermined width, the paper S is attracted to the transport belt 251. Further, the sheet S is conveyed in the sub-scanning direction by the conveying belt 251.

  The carriage 30 (FIG. 2) moves relative to the conveyed paper S. Further, the carriage 30 drives the recording head 234 based on the image signal. As a result, droplets are ejected onto the paper S, and image formation for one line is performed. Next, the inkjet printer 500 conveys the paper S by a predetermined amount. Similarly, droplets are ejected onto the paper S, and image formation for one line is performed. When a recording end signal or a signal indicating that the trailing edge of the paper S has reached the recording area is received, the ink jet printer 500 ends the image formation and discharges the paper S to the paper discharge tray 255 or the like.

<Full line type image forming apparatus>
Further, the image forming apparatus may be an apparatus having an overall configuration as illustrated in FIG.

  FIG. 18 is a schematic diagram illustrating an example of another overall configuration of an image forming apparatus according to an embodiment of the present invention. An ink jet printer 501 as an example of the image forming apparatus illustrated in FIG. 18 is a so-called full line type head. The ink jet printer 501 includes an image forming unit 601 and a transport mechanism 604 that transports paper. The ink jet printer 501 has a paper feed tray 603 on which a plurality of papers S are placed.

  First, the paper S is taken from the paper feed tray 603. Next, an image is formed on the sheet S conveyed by the conveyance mechanism 604 by the image forming unit 601. Thereafter, the sheet S is discharged to a discharge tray 605.

  The image forming unit 601 includes a liquid tank that stores a liquid serving as a recording liquid. The image forming unit 601 includes line-type heads 410y, 410m, 410c, and 410k for each color. The line-type heads 410y, 410m, 410c, and 410k for each color have a length corresponding to the length in the paper width direction, that is, the direction orthogonal to the transport direction. Further, the line-type heads 410y, 410m, 410c, and 410k for each color are attached to a head holder or the like. The line-type heads 410y, 410m, 410c, and 410k for each color eject droplets onto the paper S in the order of black, cyan, magenta, and yellow from the upstream side in the transport direction.

  The line heads 410y, 410m, 410c, and 410k for each color may be a single head in which a plurality of nozzles that eject droplets of each color are arranged at a predetermined interval. Further, the line-type heads 410y, 410m, 410c, and 410k for each color may have a configuration in which the head and the cartridge are separate.

  The sheets S placed on the sheet feed tray 603 are separated one by one by a sheet feed roller 421. Next, the paper S is transported to the transport mechanism 604 by the paper feed roller 425.

  The transport mechanism 604 includes a transport belt 433 that is bridged between the driving roller 431 and the driven roller 432. Further, a charging roller 434 that charges the surface of the transport belt 433 is provided.

  Further, the ink jet printer 501 includes a guide member 435 and the like at a position facing the image forming unit 601. Further, the ink jet printer 501 includes a cleaning roller made of a porous material or the like in order to remove ink adhering to the transport belt 433. Furthermore, the ink jet printer 501 has a static elimination roller made of conductive rubber or the like in order to neutralize the paper S. In addition, the ink jet printer 501 includes a pressing roller that presses the paper S against the transport belt 433.

  Further, on the downstream side of the transport mechanism 604, a paper discharge roller 438 and a paper discharge roller 439 for discharging the paper S on which image formation has been performed are provided.

  Also in the inkjet printer 501 having such a full-line type head, when the transport belt 433 is charged and the paper S is transported to the transport belt 433, the paper S is attracted to the transport belt 433. Next, the sheet S is transported by the transport belt 433. Subsequently, the image forming unit 601 forms an image on the paper S. Thereafter, the sheet S is discharged to a discharge tray 605.

  The image forming apparatus according to the present invention may be an apparatus in which a head having a carriage moves as shown in FIGS. 16 and 17, or an apparatus having a full-line type head as shown in FIG. That is, the image forming apparatus according to the present invention may be an apparatus in which the recording medium and the ejection head move relatively.

  The image forming apparatus according to the present invention can be applied to, for example, an apparatus having a single function of a printer, a facsimile, or a copy. In addition, the image forming apparatus according to the present invention can be applied to a multifunction machine having a plurality of functions such as a printer, a facsimile, and a copy. The droplets are not limited to ink, but may be other types of recording liquids or fixing processing liquids. In other words, the image forming apparatus according to the present invention may be applied to an apparatus that ejects liquid droplets other than ink.

  Therefore, the apparatus for ejecting droplets or the apparatus using the unit for ejecting droplets according to the present invention is not limited to forming an image. For example, the formed object may be a three-dimensional structure.

  Furthermore, the recording medium is not limited to paper. The recording medium may be any material that can be adhered to the droplets. For example, the material to which the liquid can be attached is not limited as long as droplets such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or combinations thereof can be attached even temporarily.

  The embodiment according to the present invention may be realized by a program for causing a computer such as an image forming apparatus to perform image formation.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and various modifications can be made within the scope of the gist of the present invention described in the claims. Or it can be changed.

300 Unit for ejecting liquid droplets 350 Control unit 4 Nozzle 6 Liquid chamber 7 Fluid resistance unit 121 Piezoelectric element 12 Drive element (piezoelectric member)
15 Common electrode (second electrode)
16 Individual electrode (first electrode)
208, 208-1 Print control device (drive control unit)
209 Discharge head (droplet discharge head)
301 common drive waveform generation unit 302 transmission unit 310 (310a to 310x), 320 (320a to 320x) drive waveform generation unit 311 ejection pulse selection unit (data selection unit)
312, 321 Intermediate voltage correction value storage area (first storage area)
313, 322 Drive voltage correction value storage area (second storage area)
315, 325 Storage unit 314 Drive waveform correction unit 323 Common drive waveform correction unit 324 Drive waveform selection unit (waveform selection unit)
209 Discharge head (droplet discharge head)
21,251 Conveyor belt (conveying means)
500,501 Inkjet printer (image forming apparatus, droplet ejection apparatus)
L Liquid S Paper (Recording medium)
a1 Intermediate voltage b Drive voltage

JP2015-212101A

Claims (10)

A plurality of nozzles for discharging droplets, a plurality of liquid chambers communicating with each of the plurality of nozzles, a plurality of driving elements for changing the respective volumes of the plurality of liquid chambers, and 2 connected to the driving elements A droplet discharge head comprising two electrodes;
A unit for discharging droplets, comprising a control unit that performs control to discharge the droplets,
The two electrodes connected to each drive element include a first electrode to which a voltage that changes in a waveform is individually applied to each drive element, and a second electrode,
A voltage that changes to the waveform is applied to the plurality of first electrodes, and a potential difference between the two electrodes changes to a waveform, whereby the plurality of driving elements change the volumes of the corresponding liquid chambers,
The voltage that changes in the waveform includes a driving portion where the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes before the driving portion. A voltage holding portion including a predetermined intermediate voltage, which has a predetermined potential difference, and
In the control unit, according to the characteristics of each liquid chamber and nozzle, the intermediate voltage of the voltage changing to the waveform applied to the first electrode connected to each drive element corresponding to each liquid chamber, It is characterized by correcting each independently,
Unit that discharges droplets. In the control unit, the drive portion of the voltage that changes to the waveform applied to the first electrode connected to the drive elements corresponding to the liquid chambers according to the characteristics of the liquid chambers and the nozzles , Each of which is corrected independently,
A unit for discharging droplets according to claim 1. The controller is
A common drive waveform generating unit that generates a common drive waveform including a plurality of drive waveform data serving as a basis of a voltage that changes to a waveform, which contributes to droplet formation of a plurality of droplet sizes;
A data selection unit that selects one or a plurality of drive waveform data from the common drive waveform according to the droplet size to be discharged;
A first storage area that stores an intermediate voltage correction value of a voltage that changes to the waveform corresponding to the characteristics of the liquid chamber and the nozzle, and a voltage that changes to the waveform corresponding to the characteristics of the liquid chamber A storage unit including a second storage area for storing the drive voltage correction value of
Voltage that changes to the waveform by reflecting the intermediate voltage correction value stored in the first storage area and the drive voltage correction value stored in the second storage area in the selected drive waveform data A drive waveform correction unit that generates a drive waveform that is,
The first storage area, the second storage area, and the drive waveform correction unit are provided corresponding to the liquid chambers, respectively.
A unit for discharging droplets according to claim 2. The controller is
A common drive waveform generating unit that generates a common drive waveform including a plurality of drive waveform data contributing to droplet formation of a plurality of droplet sizes;
A first storage area that stores an intermediate voltage correction value of a voltage that changes to the waveform corresponding to the characteristics of the liquid chamber and the nozzle, and a voltage that changes to the waveform corresponding to the characteristics of the liquid chamber A storage unit including a second storage area for storing the drive voltage correction value of
The corrected common drive waveform is generated by reflecting the intermediate voltage correction value stored in the first storage area and the drive voltage correction value stored in the second storage area in the common drive waveform. A common drive waveform correction unit,
A waveform selection unit that selects one or a plurality of corrected drive waveform data from the corrected common drive waveform, and generates a drive waveform that is a voltage that changes to the waveform;
The first storage area, the second storage area, the common drive waveform correction unit, and the waveform selection unit are provided corresponding to the liquid chambers, respectively.
A unit for discharging droplets according to claim 1. Due to the characteristics of the liquid chamber and the nozzle, the liquid chamber with a large amount of liquid fluctuation in the liquid chamber,
The intermediate voltage correction value and the drive voltage correction value are set to values that increase the potential difference between the two electrodes.
The unit which discharges the droplet according to claim 3 or 4. Due to the characteristics of the liquid chamber and the nozzle, the liquid chamber in which the amount of fluctuation of the liquid in the liquid chamber is small,
The intermediate voltage correction value and the drive voltage correction value are set to values that reduce the potential difference between the two electrodes.
The unit which discharges the droplet according to claim 3 or 4. In the control unit, when the drive element is driven at a low frequency, the standard deviation of the discharge droplet volume distribution between the plurality of nozzles is smaller than the discharge droplet volume discharged from the nozzle. ,
When the high frequency driving, the standard deviation of the ejection droplet volume distribution between the plurality of nozzles is corrected to be small,
A unit for discharging droplets according to any one of claims 1 to 6. The second electrode is a common electrode to which a voltage common to the plurality of driving elements is applied.
A unit for discharging droplets according to any one of claims 1 to 7. A unit for discharging droplets according to any one of claims 1 to 8,
A transport unit that moves the recording medium relative to the unit that ejects the droplets,
Droplet discharge device. A plurality of nozzles for discharging droplets, a plurality of liquid chambers communicating with each of the plurality of nozzles, a plurality of driving elements for changing the respective volumes of the plurality of liquid chambers, and 2 connected to the driving elements A method for controlling a droplet discharge head comprising two electrodes,
A generation step for generating drive waveform data that is a basis of a voltage that changes to a waveform;
According to the characteristics of each liquid chamber, each of the drive elements independently corrects the drive waveform data to generate voltages that change into waveforms, respectively, a correction step,
A voltage that changes in each waveform is applied to the first electrode connected to each of the drive elements, and the potential difference between the two electrodes changes in a waveform, so that the plurality of drive elements can correspond to the respective liquid chambers. An ejection step for ejecting droplets by changing the volume, and
The drive waveform data includes a drive portion where the potential difference between the two electrodes changes so as to expand or contract the liquid chamber a plurality of times, and the potential difference between the two electrodes before the drive portion. A voltage holding portion including a predetermined intermediate voltage, which is a potential difference of
In the correction step, the intermediate voltage of the voltage changing to the waveform applied to the first electrode connected to each driving element corresponding to each liquid chamber according to the characteristics of each liquid chamber is independently set. It is characterized by correcting,
Control method of droplet discharge head.

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