JP6740585B2 - INKJET RECORDING APPARATUS, INKJET RECORDING APPARATUS CONTROL METHOD, AND PROGRAM - Google Patents

Description

The present invention relates to an inkjet recording apparatus, a method for controlling the inkjet recording apparatus, and a program.

As an image recording apparatus or an image forming apparatus such as a printer, a facsimile, and a copying machine, an inkjet recording apparatus is known, for example. An inkjet recording apparatus includes a nozzle for ejecting ink droplets, a pressure chamber communicating with the nozzle, a piezoelectric element for pressurizing ink in the pressure chamber, and the like, and a recording medium (paper, metal, wood, ceramics, Etc.) to form an image (characters, figures, etc.).

There is known a droplet ejection device that suppresses image deterioration by correcting image data based on the determination result of the presence or absence of crosstalk and the crosstalk amount and suppressing the occurrence of crosstalk (for example, See Patent Document 1).

However, in the inkjet recording apparatus, if the image data cannot be corrected based on the ink viscosity, variations in droplet speed and ejection amount, nozzle clogging, and the like are likely to occur, so it is difficult to stabilize the image quality with high accuracy. become.

The present invention has been made in view of the above problems, and an object thereof is to improve the image quality of an inkjet recording apparatus.

The inkjet recording apparatus according to the present embodiment includes a plurality of nozzles, a plurality of pressure chambers that communicate with the nozzles and store ink, and pressure generating elements that are arranged to face the plurality of pressure chambers, respectively. A drive waveform that drives the pressure generating element to pressurize the pressure chamber to eject ink droplets from the nozzles, and a droplet ejection head that ejects ink droplets from a plurality of nozzles based on image data. A drive waveform generating section, a residual vibration detecting section for detecting residual vibration of ink in the pressure chamber after driving the pressure generating element, and a plurality of amplitude values of residual vibration detected by the residual vibration detecting section. based on, to calculate the damping ratio, to obtain the ink viscosity on the basis of the damping ratio, and arithmetic unit, based on the obtained ink viscosity, have a, an image processing unit for correcting the image data, The image processing unit includes a correction rate calculation unit that calculates a correction rate α for each nozzle, a correction unit that multiplies the image data by the correction rate α, and outputs image data that is multiplied by the correction rate α, and the correction rate. The requirement is to have a gradation processing unit that performs gradation processing on the image data multiplied by α .

According to this embodiment, the image quality of the inkjet recording device can be improved.

It is a figure which illustrates the inkjet recording device which concerns on this Embodiment. It is a figure which illustrates the droplet discharge device which concerns on this Embodiment. It is a figure which illustrates the droplet discharge device which concerns on this Embodiment. FIG. 4 is a plan view illustrating a recording unit according to the present embodiment. FIG. 3 is a bottom view illustrating the inkjet recording head according to the present embodiment. FIG. 3 is a perspective view illustrating the inkjet recording head according to the present embodiment. It is an operation conceptual diagram which shows the residual vibration which concerns on this Embodiment. It is a figure which illustrates the drive waveform application period and residual vibration waveform generation period which concern on this Embodiment. It is a figure which illustrates the damping vibration which concerns on this Embodiment. It is a figure which shows the relationship between the residual vibration actual measurement waveform and ink viscosity which concern on this Embodiment. FIG. 7 is a diagram showing a relationship between the damping ratio ζ and the ink viscosity μ according to the present embodiment. FIG. 3 is a block diagram illustrating a droplet discharge device according to the first embodiment. It is a block diagram which illustrates the droplet discharge device concerning a 2nd embodiment. It is a block diagram which illustrates the image processing part concerning this embodiment. 6A and 6B are diagrams illustrating a prediction characteristic obtained by a correction rate calculation unit of the image processing unit, where FIG. 9A shows nozzle characteristics that change with time, and FIG. 9B shows dot positions between pages and in a printing period. It is a table which illustrates the correction rate which concerns on this Embodiment. It is a schematic diagram which shows notionally the image correction by the bicubic method which concerns on this Embodiment. FIG. 12 is a circuit diagram illustrating the inkjet recording head shown in FIG. 11. FIG. 19 is a diagram showing a generated residual vibration waveform and an amplitude value detected by the circuit of FIG. 18. It is a figure explaining the flow chart of nozzle characteristic judgment and image data amendment in an ink jet recorder.

Hereinafter, modes for carrying out the invention will be described with reference to the drawings and tables. In each drawing, the same components may be denoted by the same reference numerals, and duplicate description may be omitted.

In this specification, a case where a piezoelectric element is used as a pressure generating element that pressurizes ink in the pressure chamber will be described.

<Inkjet recording device>
FIG. 1 is a schematic configuration diagram showing an example of a line scanning type inkjet recording apparatus in the on-demand system according to the present embodiment.

As shown in FIG. 1, the inkjet recording apparatus 100 is disposed between a recording medium supply unit 111 and a recording medium recovery unit 112, and has a recording unit 101, a platen 102 provided facing the recording unit 101, and a drying unit. 103, a recording medium transport device, and the like.

A continuous recording medium (also referred to as roll paper, continuous paper, or the like) 113 is delivered from the recording medium supply unit 111 at high speed, and is wound and collected by the recording medium collecting unit 112.

The recording unit 101 has a line-shaped inkjet recording head in which nozzles (printing nozzles) are arranged in the entire printing width. Color printing is performed by inkjet recording heads for each color of black, cyan, magenta, and yellow. The nozzle surface of each inkjet recording head is supported on the platen 102 with a predetermined gap. The recording unit 101 forms a color image on the printing surface of the recording medium 113 by ejecting ink droplets in synchronization with the conveying speed of the recording medium conveying device. The drying unit 103 dries and fixes the ink printed on the recording medium 113 to prevent the ink from adhering to other portions. As the drying means 103, a non-contact type drying device or a contact type drying device may be used.

The recording medium conveying device includes a regulation guide 104, an infeed unit 105, a dancer roller 106, an EPC (Edge Position Control) 107, a meandering amount detector 108, an outfeed unit 109, a puller 110, and the like.

The regulation guide 104 positions the recording medium 113 supplied from the recording medium supply unit 111 in the width direction. The infeed unit 105 includes a driven roller and a driving roller, and keeps the tension of the recording medium 113 constant. The dancer roller 106 moves up and down according to the tension of the recording medium 113 and outputs a position signal. The EPC 107 controls the meandering of the recording medium 113. The meandering amount detector 108 is used for feedback of the meandering amount. The outfeed unit 109 includes a driven roller and a driving roller, and rotates at a constant speed to convey the recording medium 113 at a set speed. The puller 110 includes a driven roller and a drive roller, and ejects the recording medium 113 to the outside of the apparatus. The recording medium conveyance device is a tension control type conveyance device that detects the position of the dancer roller 106 and controls the rotation of the infeed unit 105 to keep the tension of the recording medium 113 during conveyance constant.

The line scanning type inkjet recording apparatus 100 discharges the thickened ink by performing a star flushing operation and a line flushing operation (for example, an idle discharge operation at the A4 sheet boundary). The star flushing operation has a demerit that it is difficult to sufficiently obtain the discarding effect in an image having a low humidity environment and a small print duty, but has a merit that a waste paper is not generated. The line flushing operation has a demerit that waste paper is generated because it is necessary to cut the area where the ink droplets are ejected later, while it has a merit that powerful discarding can be performed.

<Inkjet recording head module>
FIG. 2 is a schematic side view showing an example of an inkjet recording head module mounted on the inkjet recording apparatus 100. FIG. 2A is a side view and FIG. 2B is a perspective view.

As shown in FIG. 2, the inkjet recording head module (droplet ejection device) 200 includes a drive control substrate 210, an inkjet recording head 220, a cable 230, an adjusting plate 270, and the like.

The drive control board 210 includes a control unit 211, a drive waveform generation unit 212 that generates a drive waveform to be applied to the piezoelectric element, a storage unit 213, and an image processing unit 214 that corrects image data based on ink viscosity. It is a rigid substrate.

The control unit 211 is provided with a drive control unit 215 that transmits drive waveform data to the drive waveform generation unit 212, a calculation unit 216 that calculates ink viscosity, an image processing unit 214 that corrects image data, and the like.

The inkjet recording head 220 includes a head substrate 221, a residual vibration detection substrate 222, a head drive IC substrate 223, an ink tank 224, a rigid plate 225, and the like. The inkjet recording head 220 drives the piezoelectric element based on the drive waveform generated by the drive waveform generation unit 212 to eject ink droplets from the plurality of nozzles.

The cable 230 is electrically connected to the drive control board side connector 231 and the head side connector 232, and is responsible for analog signal communication and digital signal communication between the drive control board 210 and the head board 221.

In the line scanning type inkjet recording apparatus, one or a plurality of inkjet recording heads 220 are arranged side by side in a direction perpendicular to the conveyance direction of the recording medium 113, and the print nozzles are arranged in the entire printing width (FIG. 2). (See (B)). By ejecting ink droplets from the inkjet recording head 220 fixed by the adjusting plate 270, high-speed image formation on the recording medium 113 becomes possible. When the droplet discharge device according to the present embodiment is applied to the line scanning type inkjet recording device, it is not necessary to mount the forward and backward data rearrangement section described later, so that the circuit scale can be reduced.

The liquid droplet ejection apparatus according to the present embodiment is a serial scanning type inkjet recording apparatus that forms an image by moving one or a plurality of inkjet recording heads in a direction perpendicular to the transport direction of the recording medium 113. It is also possible to apply When the droplet discharge device according to the present embodiment is applied to the serial scanning type inkjet recording device, it is not necessary to use two or more inkjet recording heads.

FIG. 3 is a top view showing the internal mechanical configuration of the serial scanning type inkjet recording apparatus.

The ink carriage unit 301 reciprocates in the main scanning direction (direction of arrow A in the drawing) and forms an image on the recording medium 309 which is intermittently conveyed in the sub-scanning direction (direction of arrow B in the drawing). The ink carriage portion 301 is supported by a main guide rod that extends along the main scanning direction. Further, the ink carriage portion 301 is provided with a connecting piece, and the connecting piece engages with a sub guide member provided in parallel with the main guide rod to stabilize the posture of the ink carriage portion 301.

The ink carriage portion 301 is connected to a timing belt 306 stretched between a gear 304 and a pressure roller 305. The ink carriage unit 301 reciprocates in the main scanning direction by the driving force of the main scanning motor 303 being transmitted via the gear 304, the pressure roller 305, the timing belt 306, and the like. When the ink carriage unit 301 starts reciprocating movement, recording on the recording medium 309 is started, and the recording medium 309 is conveyed to the platen 310 via the paper feeding unit, the conveying unit, and the like. The pressure roller 305 adjusts the distance between the pressure roller 305 and the gear 304 and applies a predetermined tension to the timing belt 306.

The movement of the ink carriage unit 301 in the main scanning direction is controlled based on an encoder value obtained by detecting a mark on the encoder sheet 308 by the encoder sensor 307 provided in the ink carriage unit 301 along the main scanning direction. The encoder sensor 307 detects the position of the ink carriage unit 301 by reading the encoder sheet 308 provided along the main scanning direction.

On the ink carriage portion 301, an inkjet recording head 302y that ejects yellow (Y) ink, an inkjet recording head 302m that ejects magenta (M) ink, an inkjet recording head 302c that ejects cyan (C) ink, and a black (K) ink jet recording head 302c. An inkjet recording head 302k that ejects ink is mounted. The recording unit 302 (302y, 302m, 302c, 302k) is installed so that the ejection surface faces the recording medium 309 side. Each inkjet recording head has a plurality of nozzles, and an image is formed on the recording medium 309 by ejecting ink droplets from the nozzle row onto the recording medium 309 being conveyed.

A cartridge, which is an ink supply body that supplies ink to the recording unit 302, is arranged at a predetermined position in the inkjet recording apparatus. The recording unit 302 and the cartridge are connected by a pipe, and the ink is supplied from the cartridge to the recording unit 302 via the pipe.

A platen 310 is provided at a position facing the ejection surface of the inkjet recording head. The platen 310 supports the recording medium 309 when ejecting ink from the recording unit 302 to the recording medium 309. The inkjet recording apparatus shown in FIG. 3 is a wide-width machine in which the moving distance of the ink carriage unit 301 in the main scanning direction is long, and the platen 310 is composed of a plurality of plate-shaped members connected in the main scanning direction.

The recording medium 309 is nipped by conveyance rollers and conveyed in the sub-scanning direction. The recording medium 309 is sucked by a suction fan provided on the back surface (the surface opposite to the surface on which the recording medium is placed) of the platen 310 while the conveyance in the sub-scanning direction is stopped. It is held on the surface of the platen 310. When a thick paper such as a postcard, a strongly curled paper such as a coated paper, or a paper having a rough surface such as a matte film is used as the recording medium 309, a space between the recording medium 309 and the ink carriage unit 301 is used. It is preferable to increase the distance.

The serial scanning type inkjet recording apparatus may include a maintenance mechanism for maintaining the reliability of the inkjet recording head. The maintenance mechanism can perform cleaning and capping of the ejection surface of the inkjet recording head, discharge of unnecessary ink from the inkjet recording head, and the like. Further, as the drive control board, a board having the same configuration and function as the board mounted in the line scanning type ink jet recording apparatus can be applied.

Although details will be described later, the droplet discharge device according to the present embodiment acquires the ink viscosity based on the residual vibration generated in the ink in the pressure chamber after the ink droplet is discharged (after the piezoelectric element 35 is driven). The image data is corrected based on the acquired ink viscosity. As a result, the droplet discharge device can suppress variations in the droplet speed and the discharge amount due to inclusion of bubbles and can perform interpolation and the like for the non-discharge nozzles, and thus the image quality of the inkjet recording device can be improved.

FIG. 4 is an enlarged plan view showing an example of a head unit in the recording unit 101 mounted on the inkjet recording apparatus 100.

The recording unit 101 includes a black head array 101K, a cyan head array 101C, a magenta head array 101M, and a yellow head array 101Y, and each color head array includes a plurality of inkjet recording heads 220. The black head array 101K ejects black ink drops, the cyan head array 101C ejects cyan ink drops, the magenta head array 101M ejects magenta ink drops, and the yellow head array 101Y. Ejects a yellow ink drop.

The head arrays (101K, 101C, 101M, 101Y) of the respective colors are arranged in a direction parallel to the transport direction of the recording medium 113. The plurality of inkjet recording heads 220 are arranged in a zigzag pattern in a direction perpendicular to the transport direction of the recording medium 113. By arranging a plurality of inkjet recording heads in a staggered pattern, the width of the printing area can be widened.

FIG. 5 is an enlarged bottom view of the inkjet recording head 220 in the head section.

The inkjet recording head 220 includes a plurality of nozzles 20, and the plurality of nozzles 20 are arranged in a zigzag pattern in a direction perpendicular to the transport direction of the recording medium 113. By arranging a plurality of nozzles in a staggered pattern, the resolution of the printing area can be increased.

In the configuration of FIG. 5, the inkjet recording heads 220 are arranged in a staggered pattern of three rows and two rows, and the nozzles 20 are arranged in a zigzag pattern of 32 rows in two rows and two rows. However, the number of columns and the number arranged in each column are not particularly limited.

<Inkjet recording head>
FIG. 6 is a perspective view showing an example of the inkjet recording head 220 mounted on the inkjet recording apparatus 100.

As shown in FIG. 6, the inkjet recording head 220 includes a nozzle plate 21, a pressure chamber plate 22, a restrictor plate 23, a diaphragm plate 24, a rigid plate 225, a piezoelectric element group 26, and the like. The piezoelectric element group 26 includes a support member 34, a plurality of piezoelectric elements 35, a piezoelectric element connection substrate 36, a piezoelectric element drive IC 37, and the like.

A plurality of nozzles 20 are formed on the nozzle plate 21, and pressure chambers 27 corresponding to the nozzles 20 are formed on the pressure chamber plate 22. The restrictor plate 23 is formed with a restrictor 29 that communicates the pressure chamber 27 and the common ink flow path 28 and controls the ink flow rate to the pressure chamber 27. The diaphragm plate 24 has a diaphragm (elastic wall). 30 and the filter 31 are formed. These plates are sequentially stacked, positioned, and joined to form a flow path plate. The flow path plate is joined to the rigid plate 225, the filter 31 and the opening 32 of the common ink flow path 28 face each other, and the piezoelectric element group 26 is inserted into the opening 32. An upper opening end of the ink introducing pipe 33 is connected to the common ink flow path 28, and a lower opening end of the ink introducing pipe 33 is connected to a head tank filled with ink.

A plurality of piezoelectric elements 35 are formed on the surface of the support member 34, and the free ends of the piezoelectric elements 35 are adhesively fixed to the vibration plate 30. A piezoelectric element drive IC 37 is formed on the surface of the piezoelectric element connection substrate 36, and the piezoelectric element 35 and the piezoelectric element connection substrate 36 are electrically connected. The piezoelectric element 35 is controlled by the piezoelectric element drive IC 37 based on the drive waveform (for example, drive voltage waveform) generated by the drive waveform generation unit. The piezoelectric element drive IC 37 is controlled based on the image data transmitted from the host controller, the timing signal output from the drive control unit 215 of the control unit 211, and the like.

Note that in FIG. 6, for simplification of the drawing, the nozzle 20, the pressure chamber 27, the restrictor 29, the piezoelectric element 35, and the like are illustrated in a smaller number than they actually are.

<Detection of residual vibration>
An example of residual vibration detection in the droplet discharge device according to the present embodiment will be described with reference to FIGS. 7 to 11.

FIG. 7 is an operation conceptual diagram showing residual vibration generated in the ink contained in the pressure chamber of the inkjet recording head 220. FIG. 7(A) is during ejection of ink droplets, and FIG. 7(B) is after ejection of ink droplets. Both figures schematically show changes in pressure generated in the pressure chamber.

FIG. 8 is a schematic diagram showing an example of a drive waveform application period and a residual vibration waveform generation period. The horizontal axis represents time [s] and the vertical axis represents voltage [V]. The drive waveform application period corresponds to FIG. 7A, and the residual vibration waveform generation period corresponds to FIG. 7B.

As shown in FIG. 7A, when the drive waveform generated by the drive waveform generation unit 212 is applied to the piezoelectric element 35 (specifically, the electrode of the piezoelectric element connection substrate 36), the piezoelectric element 35 , Expand and contract. An expansion and contraction force acts on the ink in the pressure chamber 27 from the piezoelectric element 35 via the vibration plate 30, and a pressure change occurs in the pressure chamber 27, whereby an ink droplet is ejected from the nozzle 20. For example, the pressure in the pressure chamber 27 decreases due to the drive waveform falling operation, and the pressure in the pressure chamber 27 increases due to the drive waveform rising operation (see the drive waveform application period shown in FIG. 8).

As shown in FIG. 7B, after the drive waveform is applied to the piezoelectric element 35 (after ink droplet ejection), residual pressure vibration occurs in the ink in the pressure chamber 27, and The residual pressure wave propagates from the ink to the piezoelectric element 35 via the vibration plate 30. The residual vibration waveform of the residual pressure wave is a damped vibration waveform (see the residual vibration waveform generation period shown in FIG. 8). As a result, a residual vibration voltage is induced in the piezoelectric element 35 (specifically, the electrode of the piezoelectric element connection substrate 36). The residual vibration detection unit detects the residual vibration voltage and outputs the detection result (for example, a digital signal obtained by AD converting the amplitude value of the residual vibration waveform fixed at the peak value) to the control unit 211 as the output of the residual vibration detection unit. Is output.

As described above, in the droplet discharge device according to the present embodiment, the residual vibration detection unit detects the residual vibration based on the expansion and contraction of the piezoelectric element, and the control unit acquires the ink viscosity based on the detection result. The droplet discharge device according to the present embodiment can detect the ink viscosity by using, for example, a viscometer, without using the residual vibration detecting unit.

Here, since the residual vibration waveform is the damping vibration, attention is paid to the damping ratio of the damping vibration as the output of the residual vibration detecting unit. The process of calculating the damping ratio of the damping vibration from the amplitude value of the residual vibration waveform and the relationship between the damping ratio of the residual vibration waveform and the ink viscosity will be described with reference to FIGS. 9 to 11.

The theoretical formula of the damping vibration is as follows: x is the damping vibration displacement with respect to time, x ₀ is the initial displacement, ζ is the damping ratio, ω ₀ is the natural vibration frequency, ω _d is the natural vibration frequency of the damping system, and v ₀ is the initial change amount. The time can be represented by [Equation 1].

減衰系の固有振動周波数ω_ｄは、式（２）で表せる。

The natural vibration frequency ω _d of the damping system can be expressed by equation (2).

対数減衰率δは、ａ_ｎをｎ番目の振幅値、ａ_ｎ＋ｍをｎ＋ｍ番目の振幅値として、式（３）で表せる。対数減衰率δは、減衰比ζを算出する為に必要なパラメータである。

The logarithmic decrement δ can be expressed by Equation (3), _{where an} is the n-th amplitude value and an _+m is the n+m-th amplitude value. The logarithmic damping rate δ is a parameter necessary for calculating the damping ratio ζ.

図９において、Ｔは１周期、ｍＴはｍ周期、ａ_ｎはｎ番目の振幅値、ａ_ｎ＋１はｎ＋１番目の振幅値、ａ_ｎ＋２はｎ＋２番目の振幅値、ａ_ｎ＋ｍはｎ＋ｍ番目の振幅値である（但し、ｎ、ｍは自然数）。

In FIG. 9, T is 1 cycle, mT is m cycle, a _n is the nth amplitude value, a _n+1 is the n+1th amplitude value, a _n+2 is the n+2nd amplitude value, and a _n+m is the n+mth amplitude value. Yes (however, n and m are natural numbers).

Since the logarithmic attenuation rate δ is a value obtained by averaging per cycle by dividing the rate of amplitude change into logarithms and dividing by m, the damping ratio ζ is calculated by using the logarithmic attenuation rate δ as shown in equation (4 ).

減衰比ζは、複数周期分の振幅値の減衰率を、１周期分で平均化した情報を有する。

The damping ratio ζ has information obtained by averaging the damping rates of the amplitude values for a plurality of cycles for one cycle.

Therefore, in order to calculate the damping ratio ζ of the damping vibration from the equations (1) to (4), the logarithmic damping rate δ may be obtained, and in order to obtain the logarithmic damping rate δ, at least two residual It can be seen that it is sufficient to recognize the amplitude value of the vibration waveform.

FIG. 10 shows the relationship between the residual vibration actual measurement waveform and the ink viscosity. The vertical axis represents voltage [V], the horizontal axis represents time [s], and the zero point on the time axis represents the switching timing from the drive waveform application period to the residual vibration waveform generation period. The magnitude relationship of the ink viscosities can be expressed as viscosity B=1.7 and viscosity C=3 when viscosity A=1.

From FIG. 10, it can be seen that the amplitude value in the residual vibration actual measurement waveform of viscosity A=1 is the largest and the amplitude value in the residual vibration actual measurement waveform of viscosity C=3 is the smallest. That is, it can be seen that the lower the ink viscosity, the larger the amplitude of the damping vibration and the smaller the damping ratio of the damping vibration.

FIG. 11 shows the relationship between the damping ratio and the ink viscosity calculated based on the residual vibration actual measurement waveform.

It can be seen from FIG. 11 that as the ink viscosity μ increases with μ _A , μ _B , and μ _C , the damping ratio ζ also increases with μ _A , μ _B , and μ _C.

As shown in FIG. 11, the droplet discharge device 200 generates a drive waveform (for example, a μ _A drive waveform, a μ _B drive waveform, a μ _C drive waveform) corresponding to each ink viscosity, and each piezoelectric element. Apply to. Further, the droplet discharge device 200 corrects the image data in consideration of the actual ink state (for example, air bubble mixing, ink thickening).

As a result, the droplet discharge device 200 can suppress variations in the discharge speed and the discharge amount, and can stably discharge the ink droplets from each nozzle. Further, the droplet discharge device 200 can prevent nozzle clogging and can appropriately perform interpolation for non-discharge nozzles.

In the case of critical damping (damping ratio ζ=1), the droplet discharge device 200 determines that the nozzle is completely clogged. However, even when the damping is not critical (damping ratio ζ<1), the ink viscosity becomes extremely large depending on the nozzle diameter, the nozzle shape, the constituent components of the ink, etc., and thus the nozzle clogging occurs. Sometimes. In this case, the droplet discharge device 200 determines that the closer the damping ratio ζ is to 1, the higher the probability that nozzle clogging will occur.

FIG. 12 is a block diagram showing an example of an inkjet recording head module mounted in the inkjet recording apparatus according to this embodiment.

The inkjet recording head module 200 includes a drive control board 210, an inkjet recording head 220, and the like. The drive control board 210 is equipped with a control unit 211, a drive waveform generation unit 212, a storage unit 213, an image processing unit 214, and the like. The inkjet recording head 220 includes a head substrate 221 on which a control unit 226 is mounted, a residual vibration detection substrate 222 on which a residual vibration detection unit 240 is mounted, a piezoelectric element connection substrate 36 on which a piezoelectric element driving IC 37 is mounted, and a piezoelectric element 35 ( Piezoelectric elements 35a to 35x) and the like. A waveform processing circuit 250, a switching unit 241, an A/D converter 242, and the like are mounted on the residual vibration detection substrate 222. The waveform processing circuit 250 includes a filter circuit 251, an amplifier circuit 252, a peak hold circuit 253, and the like.

The control unit 211 mounted on the drive control board 210 and the control unit 226 mounted on the head board 221 may have some or all of the functions unified. Further, some or all of the functions mounted on the residual vibration detection board 222 may be unified into the drive control board 210 or the head board 221. Further, the image processing unit 214 may be provided inside the control unit 211 or may be provided outside the control unit 211.

The controller 211 includes a drive controller 215 that controls the drive waveform generator 212, an image processor 214, and a calculator 216 that calculates ink viscosity.

The drive control unit 215 of the control unit 211 generates drive waveform data based on the image data received from the host controller 260, and outputs the drive waveform data to the drive waveform generation unit 212, the inkjet recording head 220, and the like. The drive control unit 215111 transmits the timing control signal (digital signal) to the piezoelectric element drive IC 37 and the switching unit 241 by serial communication, and transmits the switching signal synchronized with the timing control signal to the switching unit 241. The drive control unit 215211 can control the timing at which the residual vibration voltage induced in the electrode of the piezoelectric element connection substrate 36 is taken into the residual vibration detection substrate 222 by synchronizing the timing control signal and the switching signal. ..

The calculation unit 216 of the control unit 211 selects at least two digital signals from the output of the residual vibration detection unit 240 (for example, a digital signal obtained by AD converting the amplitude value of the residual vibration waveform fixed at the peak value). The damping ratio of the damping vibration is calculated by using the equations (1) to (4). The larger the number of amplitude values selected, the higher the accuracy of calculating the damping ratio.

Further, the calculation unit 216 acquires the ink viscosity in the pressure chamber by comparing the calculated attenuation ratio with the attenuation ratio data stored in the storage unit 213, and the acquired ink viscosity is sent to the image processing unit 214. Is output.

The drive waveform generation unit 212 D/A converts the drive waveform data, performs voltage amplification and current amplification to generate a drive waveform, and outputs the drive waveform to the piezoelectric element drive IC 37. The drive waveform generation unit 212 applies the optimum drive waveform for each nozzle 20 to drive the piezoelectric elements 35 (piezoelectric elements 35a to 35x).

The storage unit 213 stores in advance attenuation ratio data and ejection characteristic data (ink viscosity prediction data) used for correction in image processing.

The image processing unit 214 corrects the image data received from the host controller 260 based on the ink viscosity. Specifically, the image processing unit 214 calculates a correction factor based on the ink viscosity, multiplies the image data received by the I/F by the correction factor, and the image data obtained by multiplying the correction factor by gradation processing and forward/backward pass. Perform data rearrangement processing. Thereby, the image processing unit 214 can correct the image data in consideration of the inclusion of bubbles in the pressure chamber, the nozzle clogging, the ink temperature, and the like.

Incidentally, the forward pass/return pass data rearrangement processing means that when the droplet discharge device is applied to a serial scanning type ink jet recording device (see FIG. 3), image data is sent to the serial head in the forward pass and the backward pass. Refers to the sorting process. Therefore, when the droplet discharge device is applied to a line scanning type inkjet recording device, the image processing unit 214 does not need to perform the forward and backward data rearrangement processing.

The controller 226 deserializes the timing control signal and sends it to the piezoelectric element drive IC 37.

The piezoelectric element drive IC 37 is ON/OFF controlled based on the timing control signal, and when ON (OFF), for example, applies (non-applies) the drive waveform generated by the drive waveform generation unit 212 to the piezoelectric element 35. (See the drive waveform application period shown in FIG. 7). The piezoelectric element 35 expands and contracts based on the drive waveform falling operation and the rising operation, and ink droplets are ejected from each nozzle in response to the driving of the piezoelectric element 35.

In the waveform processing circuit 250, the filter circuit 251 and the amplifier circuit 252 filter and amplify the residual vibration waveform, and the peak hold circuit 253 recognizes the peak value (for example, the maximum value) of the amplitude value of the residual vibration waveform.・Extract and fix at peak value.

The switching unit 241 switches connection/disconnection between the piezoelectric element 35 and the waveform processing circuit 250. For example, when the piezoelectric element 35 and the waveform processing circuit 250 are connected by the switching unit 241, the residual oscillating voltage induced in the electrode of the piezoelectric element connection substrate 36 is taken into the waveform processing circuit 250.

The A/D converter 242 converts the amplitude value (analog signal) fixed by the waveform processing circuit 250 into a digital signal, and outputs it to the arithmetic unit 216 of the control unit 211 (feedback). The calculation unit 216 may be provided in the control unit 226, and the calculation unit 216 can calculate the damping ratio of the damping vibration based on the feedback output of the residual vibration detection unit 240.

In the present embodiment, the residual vibration detection unit 240 and the calculation unit 216 constitute a viscosity acquisition unit.

In FIG. 12, the residual vibration voltage of the piezoelectric elements 35a to 35x is sequentially switched and detected using a set of residual vibration detection units (switching unit 241, waveform processing circuit 250, A/D converter 242). However, the configuration of the residual vibration detection unit is not particularly limited. For example, a configuration may be adopted in which residual vibration detection units are formed for all the piezoelectric elements and the ink viscosities in all the pressure chambers are detected at the same time. In addition, for example, the piezoelectric element may be divided into several groups, a residual vibration detecting portion may be formed for each group, and the ink viscosity in the pressure chamber may be detected by sequentially switching each group. By grouping, it is possible to increase the number of nozzles that can be simultaneously detected while suppressing an increase in circuit scale.

In addition, the inkjet recording head module 200 may not include the residual vibration detection unit. For example, as in the second embodiment shown in FIG. 13, a viscometer 312 (viscosimeters 312a to 312x) is provided so as to correspond to all the pressure chambers, and the viscosity of ink in each pressure chamber is calculated by the viscometer. It may be configured to detect.

In the present embodiment, the viscometer 312 constitutes the viscosity acquisition means. In this case, since it is not necessary to detect the residual vibration, it is not necessary to provide the waveform processing circuit 250 between the switching unit 241 and the A/D converter 242.

FIG. 14 is a block diagram showing an example of the image processing unit according to the present embodiment. The image processing unit 214 executes the following processing, for example, according to the control program.

The image processing unit 214 includes a correction rate calculation unit 2141, a correction unit 2142, a gradation processing unit 2143, a forward/return data rearrangement unit 2144, an ejection elapsed time calculation unit 2145, and the like.

The ejection elapsed time calculation unit (ejection interval calculation unit) 2145 receives the image data (for example, [7:0]) received from the host controller 260. The ejection elapsed time calculation unit 2145 calculates in advance the ejection interval for each nozzle based on the printing shape droplets and the printing positions that contribute to the image shape included in the image data.

The correction rate calculation unit 2141 calculates the correction rates α1 to α192 (for example, the number of nozzles is 192) based on the ink viscosity, and outputs it to the correction unit 2142.

The correction unit 2142 multiplies the image data (for example, [7:0]) received from the host controller 260 by the correction factors α1 to α192, and outputs the image data obtained by multiplying the image data to the gradation processing unit 2143. .. The correction unit 2142 corrects the image data for each nozzle by using the correction rate calculated for each nozzle.

The gradation processing unit 2143 performs gradation processing on the image data multiplied by the correction rate, and the data (for example, KD′ [1:0]) subjected to the gradation processing is changed to the forward return data rearrangement unit 2144. Output to.

The forward pass/return pass data rearranging unit 2144 performs the forward pass/return pass data rearrangement process on the image data that has been subjected to the gradation process, and the forward pass/return pass data rearrangement process is performed (for example, SD′[1:0]). ) Is output to the inkjet recording head 220.

When the droplet discharge device according to the present embodiment is applied to a line scanning type inkjet recording device, it is not necessary to mount the forward/return data rearrangement unit 2144 in the image processing unit 214, and it is not necessary. In order to interpolate the ejection nozzles, two heads may be arranged.

Here, the prediction characteristic obtained by the correction rate calculation unit 2141 of the image processing unit 214 will be described with reference to FIG. FIG. 15A shows nozzle characteristics that change with time, and FIG. 15B shows dot positions between pages and in the printing period.

During printing, during the printing period (image area), since the drive waveform is applied to the piezoelectric element 35, residual vibration detection is not performed, and residual vibration detection (first time) is performed at the position Pa between pages (non-image area). ..

Therefore, assuming that the characteristics (viscosity, damping ratio, etc.) for each nozzle obtained are a, it is predicted how the ejection characteristics will change with time from the ejection characteristic prediction data that is prepared in advance and stored in the storage unit 213. You can As can be seen from FIG. 15A, the value of the ejection characteristic prediction data (ink viscosity prediction data) increases as the standing time increases.

By correcting each nozzle according to the amount of change, it is possible to stabilize the image quality with high accuracy. For example, when the discharge position in the printing period when focusing on a certain nozzle is referred to as being Pb → Pc → Pd and 3 times, the elapsed time T _B from the position Pa which detects the residual vibration of the first to Pb, the image data It is calculated based on For example, to the image data based on the elapsed time T _B from the residual vibration detection position Pa to the discharge Pb can be calculated with reference to the discharge gap for each nozzle output from the discharge interval calculation section 415.

15 from (A), as the first of the residual vibration detected by the position Pa by the acquired characteristic a time T _A the time axis origin (initial value), determined predicted characteristic and elapsed time T _B from the ejection characteristic estimation data c is determined, and appropriate correction can be performed according to the prediction characteristic c.

The nozzle ejected at the time T _B is refreshed (discharging the thickened ink by applying a drive waveform having a larger amplitude than that at the time of image formation, and performing idle ejection), and the characteristic returns to a. Return.

At the next ejection position Pc, since the elapsed time T _C from the position Pb to Pc can be calculated from the image data, similarly, the time T _A at the position Pa at which the first residual vibration is detected is the origin of the time axis (initial value). As the value), the prediction characteristic d is determined from the ejection characteristic prediction data, and appropriate correction becomes possible.

The same is true after the ejection positions Pc→Pd.

Further, even if the refreshing (discharging, blank ejection) is performed by the ejection performed during the printing period, the thickened ink is not always completely ejected depending on the ejected droplet amount. Therefore, on the next page, based on the characteristic b acquired at the position of residual vibration detection (for example, Pe in FIG. 15B) between the two times after the refreshing between pages in which stronger discarding is performed, It is set to T a _'the time axis origin (the initial value of the next page). In this way, by setting the origin again between the next pages, that is, by repeatedly determining the ejection characteristics in the period of the non-image area, more accurate prediction characteristics can be obtained.

The above can be applied to all of the nozzles individually, and even in the scanning operation of the carriage such as the serial head (between the forward and backward passes), it is possible to make predictions not only between pages based on the flushing performed last time.

Here, as an example, a method of obtaining and correcting the correction rate from the prediction characteristic will be shown using a table and an algorithm (bicubic method) described later. The tables and algorithms used are stored in the storage unit 213. Alternatively, another storage unit may be provided in the image processing unit 214 to store the table and algorithm used for correction.

The residual vibration detected by the residual vibration detector 240 is input to the correction factor calculator 2141. Alternatively, the ink viscosity (or damping ratio) calculated by the calculation unit 216 based on the detected residual vibration is input to the correction factor calculation unit 2141.

The correction factor calculation unit 2141 determines the ejection characteristics for each nozzle by comparing the ink viscosity (or residual vibration, damping ratio) acquired by the detection with the stored table or algorithm. The ejection correction rate for each nozzle is determined by determining the ejection characteristics for each nozzle. Further, by identifying the non-ejection nozzle by determining the ejection characteristics for each nozzle, it becomes possible to interpolate the position of the non-ejection nozzle with another nozzle.

FIG. 16 is a table showing correction factors corresponding to nozzles and ink viscosities. The number of nozzles is 192, and the ink viscosity increases in alphabetical order.

For example, when the ink viscosity of the third nozzle is c, the correction rate is +0.6 dot, and when the ink viscosity of the 28th nozzle is e, the correction rate is +0.3 dot.

Further, for example, when the ink viscosity of all nozzles is g or more, the ink droplets are not ejected from the nozzles, and thus the image processing unit 214 determines that there is a non-ejection nozzle and determines that the non-ejection nozzle is present. Interpolate with another discharge nozzle.

In the line scanning type inkjet recording apparatus (FIG. 1), when non-ejection nozzles occur, two heads may be arranged and the heads with non-ejection nozzles may be interpolated with the heads without non-ejection nozzles.

On the other hand, in the serial scanning type inkjet recording apparatus (FIG. 3), when a non-ejection nozzle occurs, the head may perform several scans (a plurality of passes) and eject ink droplets from other nozzles to perform interpolation. ..

The image processing unit 214 may have a table corresponding to the correction rate for each temperature calculated from the attenuation ratio, or may have another table in which the positive and negative correction amounts are different between the forward path and the return path. May be. The image processing unit 214 may also use a circuit to invert the sign.

Next, the algorithm of the correction unit 2142 will be described.

When the correction amount is 1 dot, it is sufficient to shift the landing position of the ink droplet by 1 dot by delaying the image data. However, when the correction amount is less than 1 dot (for example, when the correction amount is 0.6 dot), the distance between the dots is constant, and therefore the ink droplet cannot be landed between the dots.

Therefore, in such a case, a pseudo shifted dot is reproduced by changing the pixel value of the image data. As a result, even if the landing position of the ink droplet is the same as before correction, it is possible to artificially shift the landing position of the ink droplet by 0.6 dot.

FIG. 17 is a schematic diagram conceptually showing image correction by the bicubic method.

A case where the pixel value of a certain pixel in the image data needs to be corrected by 0.6 dot (when the correction rate α is 0.6 dot) will be described as an example.

The pixel value before correction is n, the pixel value after correction is n′, and the pixel values of three points existing in the vicinity of the pixel value n are (n−1), (n+1), and (n+2).

Assuming that the distance between the pixel value n and the pixel value n′ is d=0.6 dot, the distance between the pixel value n′ and the pixel value (n−1) is (1+d)=1.6 dot, The distance between n′ and the pixel value (n+1) is (1-d)=0.4 dot, and the distance between the pixel value n′ and the pixel value (n+2) is (2-d)=1.4 dot. Become.

In this case, the pixel value n before correction and the pixel values (n−1, n+1, n+2) at three points existing in the vicinity of the pixel value n are substituted into the following equation to obtain the pixel value n after correction. 'Can be asked.

n′=W1×(n−1)+W2×n+W3×(n+1)+W4×(n+2)
For example, in the case of performing the double density processing for enlarging an image twice in the main scanning direction and the sub scanning direction, if the coefficients are fixed values and W1=W4=-0.125 and W2=W3=0.625,
n'=0.5 (2n+1).

That is, by performing the interpolation calculation using the bicubic method, the pixel value n′ of a certain pixel in the image data can be artificially obtained, for example, by a pixel value n′ shifted by 0.6 dot.

By changing the values of the coefficients W1, W2, W3, and W4, the pixel value n of a certain pixel in the image data is pseudo-shifted by the correction rate α to obtain the pixel value n′ at an arbitrary position. It is possible to ask.

For example, the position correction of the timing deviation of the landing position of the ink droplet is adjusted by adjusting the timing of the generated timing control signal in the drive control unit 215 of the control unit 211. The adjusted timing control signal is transmitted to the piezoelectric element drive IC 37 via the deserializing control unit 226, and the drive waveform is applied to a predetermined piezoelectric element at an adjusted timing.

Further, the interpolation of the timing of the ink droplet landing position is adjusted by adding the target of the drive waveform data generated in the drive control unit 215 of the control unit 211. A drive waveform is generated by the drive waveform generation unit 212 based on the adjusted (added) image waveform data, and the drive waveform is transmitted to the piezoelectric element drive IC 37 and corresponds to the nozzle in the vicinity of the nozzle to be interpolated. It is applied to the piezoelectric element.

FIG. 18 is a circuit diagram showing an example of the residual vibration detecting unit according to the present embodiment.

The piezoelectric element drive IC 37 includes a plurality of switching elements, and ON/OFF of the piezoelectric element drive IC 37 is controlled by ON/OFF of a switching element formed corresponding to each piezoelectric element. After the ink droplets are ejected (the piezoelectric element driving IC 37 is turned off), the piezoelectric element 35 and the waveform processing circuit 250 are connected via the switching means 241, so that the residual vibration detecting section 240 is induced in the piezoelectric element 35. It is possible to detect the residual vibration voltage and recognize the amplitude value of the residual vibration waveform.

The waveform processing circuit 250 suppresses the adverse effect of the detection circuit on the residual vibration waveform by receiving the minute residual vibration waveform in the high impedance buffer section. The passive element constants of the resistors R1 to R5, the capacitors C1 to C3, etc. mounted on the waveform processing circuit 250 are driven by the drive control unit of the control unit 211 according to the difference in natural vibration frequency due to the characteristics of the inkjet recording head 220. Preferably, it is variably controlled by 215.

The filter circuit 251 filters the residual vibration waveform. The filter circuit 251 has a predetermined pass band width with the natural vibration frequency as the center frequency, and, for example, the band width of −3 dB from both ends of the pass band width is set to about 3 times the pass band width. Preferably. This makes it possible to absorb variations in natural vibration frequency caused by variations in manufacturing of the inkjet recording head 220, and to efficiently remove high frequency noise and low frequency noise.

The amplifier circuit 252 amplifies the residual vibration waveform that has been subjected to the filtering process (see the dotted line shown in FIG. 18). In the amplifier circuit 252, the amplification factor is preferably set so that the waveform is amplified within the inputtable range of the A/D converter 242.

Note that the filter circuit 251 and the amplifier circuit 252 can be efficiently removed of noise components and extracted of signal components by being configured as a bandpass filter amplification type (Salenki type), but the configuration is particularly It is not limited. It is sufficient that at least a filter having a high-pass characteristic and a low-pass characteristic is combined with a non-inverting amplification section or an inverting amplification section.

The peak hold circuit 253 recognizes and extracts the peak value of the amplitude value of the residual vibration waveform, and fixes the peak value (see the solid line shown in FIG. 19). In the peak hold circuit 253, it is preferable that the discharge time of the resistor R6 and the capacitor C3 is set to be 1/2 or less of the residual vibration cycle. The reset of the peak hold circuit 253 is performed by the drive control unit 215 of the control unit 211 outputting a reset signal to the switching element SW1 at the timing when the rising edge of the damped oscillation waveform crosses the reference voltage Vref. The reset timing may be any timing at which the peak hold circuit 253 can recognize the amplitude value of the damped oscillation waveform, and the reset timing can be detected by a comparison unit or the like. The configuration of the peak hold circuit 253 is not limited to the configuration shown in FIG. 18, and may be at least a circuit capable of fixing the peak value of the amplitude value of the residual vibration waveform.

FIG. 19 shows an example of a waveform that is filtered and amplified by the circuit shown in FIG. 18 (shown by a dotted line) and a waveform fixed by the peak value of the amplitude value (shown by a solid line).

The amplitude value is fixed at five peak values, the amplitude value of the first half wave is amplitude value 1, the amplitude value of the second half wave is amplitude value 2, and the amplitude value of the third half wave is amplitude value 3, respectively. , The amplitude value of the fourth half-wave is amplitude value 4, and the amplitude value of the fifth half-wave is amplitude value 5. The steep waveform seen below the reference voltage Vref is an undershoot due to instantaneous discharge of the capacitor C3.

The damping ratio ζ can be calculated by selecting at least two amplitude values from the amplitude values 1 to 5 by the calculation unit 216 of the control unit 211 and using Expression (3) and Expression (4). Since FIG. 19 shows the waveforms when the amplitude values 1 to 5 on the upper side of the vertical amplitude are detected, the damping ratio ζ can be calculated by averaging four cycles. It is also possible to detect the lower amplitude value and calculate the damping ratio ζ. When the upper amplitude value of the upper and lower amplitude is used to calculate the damping ratio ζ, an amplifier circuit may be applied to the waveform processing circuit 250, and the upper amplitude value of the upper and lower amplitude is used to calculate the damping ratio ζ. In that case, an inverting amplifier circuit may be applied to the waveform processing circuit 250.

Note that the calculation unit 216 of the control unit 211 can improve the calculation accuracy of the damping ratio ζ by appropriately selecting the amplitude value. For example, the calculation unit 216 selects an amplitude value to be used for calculation from the amplitude value 2, the amplitude value 3, the amplitude value 4, and the amplitude value 5 except for the amplitude value 1 which is easily affected by the variation of the switching means. Is also good. In addition, for example, the calculation unit 216 calculates from the amplitude value 1, the amplitude value 2, the amplitude value 3, and the amplitude value 4 except for the smallest amplitude value (for example, the amplitude value 5) in which the detection error is likely to be large. The amplitude value used may be selected. Further, for example, the calculation unit 216 may select the amplitude value used for the calculation from the amplitude value 2, the amplitude value 3, and the amplitude value 4 except for both the amplitude value 1 and the amplitude value 5. Alternatively, the damping ratio ζ may be calculated by averaging the periods excluding half-waves having a large influence of disturbance and noise.

The overall control method of the inkjet recording apparatus 100 will be described below. FIG. 20 is a flowchart illustrating a timing operation of image data of the image forming apparatus according to the embodiment of the present invention.

First, the correction factor calculation unit 2141 reads residual vibration prediction data for each nozzle, which has been recorded in advance (S1).

Then, residual vibration detection is performed after the nozzles are refreshed by the inter-page blank ejection (S2) (S3).

The correction rate calculation unit 2141 determines the initial value (a, see FIG. 15A) of the residual vibration prediction data by the characteristic determination for each nozzle (S4).

The ejection elapsed time calculation unit 2145 reads the original image data [7:0] (S5) and calculates the ejection elapsed time from ejection to the next ejection for each nozzle (S6).

In the correction factor calculation unit 2141. A correction factor is calculated based on the residual vibration prediction data based on the elapsed time from the initial value (S7).

The correction unit 2142 corrects the calculated correction rate α and the original image [7:0] into the original image [7:0]×α.

After that, in the gradation processing unit 2143, gradation processing is performed to create data KD'[1:0] (S8), and then in the forward and return data rearranging unit 2144, it is converted into data SD'[1:0]. Yes (S9).

The ejection timing is adjusted by the controller 226 of the recording head 220 based on the data SD′[1:0] corrected in this way (see FIG. 17). In addition, and/or based on the corrected data SD′[1:0], the drive waveform data is adjusted in the drive control unit 215 of the control unit 211 so as to interpolate the non-ejection nozzle. The drive waveform adjusted in 212 is generated.

A drive waveform for image formation is applied to the piezoelectric element 35 based on the adjusted data, and printing is started (S10).

The same process is repeated when the second page is printed by the print end determination (S11).

If the droplet discharge head shown in FIG. 1 has a line head configuration, the step of rearranging the forward and backward data (S9) is not necessary.

According to the droplet discharge device according to the present embodiment, the ink viscosity is acquired by utilizing the residual vibration generated in the ink in the pressure chamber after the ink droplet is discharged, and the image data is obtained based on the ink viscosity. to correct. As a result, it is possible to suppress the occurrence of variations in droplet speed and ejection amount, nozzle clogging, and the like, and perform highly accurate correction, so that it is possible to improve the image quality of the inkjet recording apparatus.

Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the specific embodiments, and within the scope of the gist of the embodiments of the present invention described in the claims, Various modifications and changes are possible.

20 Nozzle 27 Pressure Chamber 30 Vibration Plate 35 Piezoelectric Element 100 Inkjet Recording Device 200 Inkjet Recording Head Module (Droplet Ejection Device)
211 Control unit (acquisition unit)
212 Drive Waveform Generation Unit 214 Image Processing Unit 215 Drive Control Unit 216 Calculation Unit (Viscosity Acquisition Unit)
240 Residual vibration detection unit (viscosity acquisition means)
311 Piezoelectric element for driving 312 Viscometer (viscosity acquisition means)
2141 Correction rate calculation unit 2145 Ejection elapsed time calculation unit (ejection interval calculation unit)

JP, 2008-132658, A

Claims (12)

A plurality of nozzles, a plurality of pressure chambers communicating with the nozzles for accommodating the ink, and pressure generating elements arranged so as to face the plurality of pressure chambers, respectively. A droplet discharge head for discharging ink droplets from the nozzle of
A drive waveform generation unit that drives the pressure generation element to pressurize the pressure chamber to eject ink droplets from the nozzle, generate a drive waveform, and
A residual vibration detecting section for detecting residual vibration of ink in the pressure chamber after driving the pressure generating element;
A calculation unit that calculates a damping ratio based on a plurality of amplitude values of the residual vibration detected by the residual vibration detection unit and acquires the ink viscosity based on the damping ratio;
Based on the obtained ink viscosity, have a, an image processing unit for correcting the image data,
The image processing unit,
A correction rate calculation unit for calculating the correction rate α for each nozzle,
A correction unit for multiplying the image data by the correction rate α and outputting image data obtained by multiplying the correction rate α;
An inkjet recording apparatus comprising: a gradation processing unit that performs gradation processing on image data obtained by multiplying the correction rate α . The correction unit is
When the nozzle correction amount is 1 dot, the image data is delayed to shift the ink droplet landing position,
When the correction amount of the nozzle is less than 1 dot, interpolation processing using the bicubic method is performed on the pixel value n before correction and the pixel values of three points existing in the vicinity of the pixel value n to obtain the image data. Correct the landing position of the pixel value n of a certain pixel in
The inkjet recording apparatus according to claim 1. When the nozzle correction amount is less than 1 dot, the correction unit sets the pixel value before correction to n, the pixel value after correction to n′, and the pixel values of three points existing in the vicinity of the pixel value n (n−1). ), (n+1), (n+2),
n′=W1×(n−1)+W2×n+W3×(n+1)+W4×(n+2) is calculated,
By changing the values of the coefficients W1, W2, W3, and W4, the pixel value n of a certain pixel in the image data is pseudo-shifted by the correction rate α to obtain the pixel value n′ at an arbitrary position.
The inkjet recording apparatus according to claim 2. The correction rate calculation unit of the image processing unit determines an ejection characteristic based on the ink viscosity and identifies a non-ejection nozzle,
The inkjet recording device according to claim 1 . It has a storage means for storing the ink viscosity prediction data corresponding to the nozzle,
The correction rate calculation unit compares the acquired ink viscosity with the ink viscosity prediction data stored in the storage unit to determine ejection characteristics and identify a non-ejection nozzle.
The inkjet recording device according to claim 4 . The inkjet recording apparatus forms an image by ejecting ink droplets onto a continuous recording medium,
In the printed continuous recording medium, an image area and a non-image area are present, and in a period in which the nozzle faces the non-image area, the residual vibration detection unit detects the ink in the pressure chamber communicating with the nozzle. Obtaining residual vibration, the calculation unit calculates the ink viscosity, the correction factor calculation unit repeatedly determines the ejection characteristics based on the ink viscosity in the non-image area,
The inkjet recording device according to claim 4 or 5 . The storage unit stores the correction rate of the image data for each temperature.
The inkjet recording device according to claim 5 . The image processing unit further includes a discharge interval calculation unit that calculates a discharge interval for each nozzle based on the image data,
The image processing unit corrects the image data based on the acquired ink viscosity and the ejection interval for each nozzle calculated from the image data.
An ink jet recording apparatus according to any one of claims 1 to 7. The droplet discharge head provided with the plurality of nozzles has a line scanning type head configuration,
An ink jet recording apparatus according to any one of claims 1 to 8. The droplet discharge head provided with the plurality of nozzles has a serial scanning type head configuration,
The image processing unit further includes a forward return data rearrangement unit that performs a process of rearranging the image data on the forward pass and the return pass on the data subjected to the gradation process.
An ink jet recording apparatus according to any one of claims 1 to 8. A method for controlling an inkjet recording apparatus, which ejects ink droplets from a plurality of nozzles based on image data,
A drive waveform generating step of driving a pressure generating element arranged to face each of the plurality of pressure chambers, pressurizing the pressure chambers to eject ink droplets from the nozzles, generating a drive waveform,
A residual vibration detecting step of detecting residual vibration of ink in the pressure chamber after driving the pressure generating element;
A calculation step of calculating a damping ratio based on a plurality of amplitude values of the residual vibration detected by the residual vibration detecting step, and acquiring an ink viscosity based on the damping ratio;
Correcting the image data based on the ink viscosity,
In the correcting step, a correction rate for each nozzle is calculated, the image data is multiplied by the correction rate, and gradation processing is performed on the image data multiplied by the correction rate.
Ink jet recording apparatus control method. A program executed by a droplet discharge device that discharges ink droplets from a plurality of nozzles based on image data,
A driving waveform generating process for driving a pressure generating element arranged to face each of the plurality of pressure chambers to pressurize the pressure chambers to eject ink droplets from the nozzles;
Residual vibration detection processing for detecting residual vibration of ink in the pressure chamber after driving the pressure generating element,
An arithmetic process that calculates a damping ratio based on a plurality of amplitude values of the residual vibration detected by the residual vibration detection process, and acquires an ink viscosity based on the damping ratio;
A process of correcting the image data based on the ink viscosity,
In the correction process, a correction rate is calculated for each nozzle, the image data is multiplied by the correction rate, and gradation processing is performed on the image data multiplied by the correction rate.
program.

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