JP2018111318A - Ink discharge device, discharge amount correction method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an image quality of an ink-jet recording device.SOLUTION: A droplet discharge device includes: a plurality of pressure chambers which are communicated with a plurality of nozzles and store ink; a diaphragm arranged over each of the pressure chambers so as to form an elastic wall of each of the pressure chambers; pressure generating elements arranged so as to face each of the plurality of pressure chambers through the diaphragm; a drive waveform generating section which inputs drive waveform data indicating the shape of the drive waveform driving the pressure generating elements to generate the drive waveform for each of the nozzles; a residual vibration detection part which detects a residual vibration generated in each of the pressure chambers after the pressure generating element has been driven; and a control section which corrects drive waveform data for each of the nozzles during printing based on the detection result of the residual vibration detection part.SELECTED DRAWING: Figure 10

Description

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

  For example, an ink jet recording apparatus is known as an image recording apparatus or an image forming apparatus such as a printer, a facsimile machine, and a copying apparatus. An ink jet recording apparatus includes a recording medium (paper, metal, wood, ceramics) using an ink jet recording head including a nozzle that ejects ink droplets, a pressure chamber that communicates with the nozzle, and a piezoelectric element that pressurizes ink in the pressure chamber. , Etc.) to form desired characters, figures, etc.

  A liquid ejecting apparatus that ejects ink droplets from a recording head under optimum ejection conditions by setting an initial value of a driving voltage for oscillating a flexible electrode for each nozzle or nozzle group based on a residual vibration waveform. It is known (see, for example, Patent Document 1).

  However, the conventional ink jet recording apparatus cannot correct the drive voltage for each nozzle based on the residual vibration waveform detected during printing. For this reason, there has been a problem that the image quality is lowered in the apparatus.

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

  The droplet discharge device according to the present embodiment includes a plurality of pressure chambers that communicate with a plurality of nozzles to store ink, a vibration plate that is disposed over each pressure chamber so as to form an elastic wall of each pressure chamber, and a vibration A drive waveform is generated for each nozzle by receiving, as input, a pressure generating element arranged to face each of the plurality of pressure chambers via a plate, and drive waveform data indicating the shape of the drive waveform for driving the pressure generating element. Drive waveform data for each nozzle during printing based on the detection result of the drive waveform generator, the residual vibration detector that detects residual vibration generated in each pressure chamber after driving the pressure generating element, and the residual vibration detector And a control unit that corrects.

  According to this embodiment, the image quality of the ink jet recording apparatus can be improved.

1 is a diagram illustrating an ink jet recording apparatus according to Embodiment 1. FIG. 1 is a side view illustrating a droplet discharge device according to a first embodiment. 2 is a plan view illustrating a recording unit according to Embodiment 1. FIG. 2 is a bottom view illustrating the ink jet recording head according to Embodiment 1. FIG. 2 is a perspective view illustrating the ink jet recording head according to Embodiment 1. FIG. FIG. 6 is an operation concept diagram showing residual vibration according to the first embodiment. FIG. 6 is a diagram illustrating a drive waveform application period and a residual vibration waveform generation period according to the first embodiment. 3 is a diagram illustrating a damped vibration according to Embodiment 1. FIG. It is a figure which shows the relationship between the residual vibration measurement waveform and ink viscosity which concern on Embodiment 1. FIG. 1 is a block diagram illustrating a droplet discharge device according to a first embodiment. 2 is a circuit diagram illustrating a droplet discharge device according to Embodiment 1. FIG. 6 is a diagram illustrating a residual vibration waveform according to the first embodiment. FIG. It is a figure which shows the relationship between damping ratio (zeta) concerning Embodiment 1, and ink viscosity (micro | micron | mu). 6 is a diagram illustrating drive waveforms according to the first embodiment. FIG. 6 is a diagram illustrating correction timing according to Embodiment 1. FIG. 6 is a diagram illustrating correction timing according to Embodiment 1. FIG. FIG. 6 is a diagram illustrating a relationship between an ink viscosity μ and a temperature T according to the first embodiment. 6 is a cross-sectional view illustrating an ink jet recording head according to Embodiment 2. FIG. 6 is a block diagram illustrating a droplet discharge device according to a second embodiment. FIG. 6 is a block diagram illustrating a droplet discharge device according to a second embodiment. FIG. FIG. 6 is a circuit diagram illustrating a droplet discharge device according to a second embodiment. 6 is a control flowchart according to the second embodiment. 10 is a control flowchart according to the third embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings and tables. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

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

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

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

  A continuous recording medium (also called roll paper, continuous paper, etc.) 113 is fed out from the recording medium supply unit 111 at a high speed, and is wound and collected by the recording medium collection unit 112.

  The recording means 101 has a line-shaped inkjet recording head in which nozzles (print nozzles) are arranged over the entire printing width. Color printing is performed by inkjet recording heads of each color of black, cyan, magenta, and yellow. The nozzle surface of each ink jet 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 conveyance speed of the recording medium conveyance device. The drying unit 103 performs drying and fixing of the ink in order to prevent the ink printed on the recording medium 113 from adhering to other portions. As the drying means 103, a non-contact type drying device may be used, or a contact type drying device may be used.

  The recording medium conveyance device includes a regulation guide 104 that positions the recording medium 113 supplied from the recording medium supply unit 111 in the width direction, a driven roller, and a driving roller, and an infeed unit that keeps the tension of the recording medium 113 constant. 105, a dancer roller 106 that moves up and down according to the tension of the recording medium 113 and outputs a position signal, an EPC (Edge Position Control) 107 that controls the meandering of the recording medium 113, and a meandering amount detector 108 used for meandering amount feedback. , Which is composed of a driven roller and a driving roller, and is composed of an outfeed unit 109 that rotates at a constant speed to convey the recording medium 113 at a set speed, a driven roller and a driving roller, and discharges the recording medium 113 to the outside of the apparatus. Including a puller 110. 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 being conveyed constant.

  The line scanning ink jet recording apparatus 100 discharges thickened ink by performing a star flushing operation and a labyrinth operation (for example, an empty ejection operation at an A4 sheet boundary). The star flushing operation has a demerit that it is difficult to sufficiently obtain a discarding effect in an image with a low humidity environment and a small print duty, and has an advantage that no waste paper is generated. The labyrinth operation has a demerit that a waste paper is generated because an area where ink droplets are ejected needs to be cut later.

  Here, a control method for recovering the ejection performance of the head will be described. During printing, since the ink in the pressure chamber is in contact with the outside air through the nozzle openings, the solvent evaporates and the viscosity increases due to the influence of changes in ambient temperature and humidity, self-heating due to continuous driving, etc. End up. In addition, during the time other than during printing, the ink in the pressure chamber is moisturized by covering the nozzle with a dedicated cap (heat retaining cap) etc., but if the nozzle is covered for a long time, the viscosity increases. Resulting in. As a result, there is a problem in that the ink ejection speed varies from nozzle to nozzle, causing abnormal images such as density unevenness, streaks, and color changes. Furthermore, when the ink viscosity increases, the thick ink becomes clogged with the nozzles (ejection failure), and dot missing (pixel loss) occurs in the image forming area. Therefore, in order to restore the ejection performance of the head, it is preferable that the control unit can correct the drive waveform data for each nozzle based on the feedback result of the residual vibration fed back during printing.

  Although details will be described later, the droplet discharge device according to the present embodiment can detect a change in liquid viscosity (ink viscosity) over time during printing for each nozzle and correct drive waveform data in real time. it can. As a result, it is possible to suppress the occurrence of abnormal images in the page and improve the image quality of the ink jet recording apparatus.

<Inkjet recording head module>
FIG. 2 is a schematic side view showing an example of an ink jet recording head module mounted on the ink jet recording apparatus 100.

  As shown in FIG. 2, the ink jet recording head module (droplet discharge device) 200 includes a drive control board 210, an ink jet recording head 220, a cable 230, and the like.

  A control unit 211, a storage unit 213, and the like are mounted on the drive control board 210. The ink jet recording head 220 includes a residual vibration detection substrate 222, a head drive IC substrate 223, an ink tank 224, a rigid plate 225, a piezoelectric element connection substrate, and the like. The cable 230 is connected to the drive control board side connector 231 and the head side connector 232 and performs analog signal communication and digital signal communication between the drive control board 210 and the piezoelectric element connection board.

  In the line scanning type inkjet recording apparatus 100, 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. By ejecting ink droplets from the line scanning ink jet recording head 220 to the recording medium 113, high-speed image formation becomes possible. Note that the droplet discharge apparatus according to the present embodiment is a serial scanning inkjet recording apparatus that forms an image by moving one or more inkjet recording heads in a direction perpendicular to the conveyance direction of the recording medium 113. , Etc. are also applicable.

  FIG. 3 is an enlarged plan view showing an example of a head portion in the recording means 101 mounted on the ink jet recording apparatus 100.

  The recording means 101 includes a black head array 101K, a cyan head array 101C, a magenta head array 101M, and a yellow head array 101Y. Each color head array includes a plurality of ink jet recording heads 220. The black head array 101K discharges black ink droplets, the cyan head array 101C discharges cyan ink droplets, and the magenta head array 101M discharges magenta ink droplets. The head array 101Y ejects yellow ink droplets.

  The head arrays (101K, 101C, 101M, 101Y) for each color are arranged in a direction parallel to the conveyance direction of the recording medium 113. The plurality of inkjet recording heads 220 are arranged in a staggered manner in a direction perpendicular to the conveyance direction of the recording medium 113. By arranging a plurality of ink jet recording heads in a staggered manner, the width of the print area can be increased.

  FIG. 4 is an enlarged bottom view of the ink jet recording head 220 in the head portion.

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

  In this embodiment, the inkjet recording heads 220 are arranged in three and two rows in a staggered manner, and the nozzles 20 are arranged in thirty two and two rows in a staggered manner. However, the number of columns and the number of columns arranged in each column are not particularly limited.

<Inkjet recording head>
FIG. 5 is a perspective view showing an example of an ink jet recording head 220 mounted on the ink jet recording apparatus 100.

  As shown in FIG. 5, 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 driving 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 with 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. The upper opening end of the ink introduction pipe 33 is connected to the common ink flow path 28, and the lower opening end of the ink introduction 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 bonded and fixed to the diaphragm 30. A piezoelectric element driving 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 driving IC 37 is controlled based on image data transmitted from the host controller, a timing signal output from the control unit 211, and the like.

  In FIG. 5, the nozzle 20, the pressure chamber 27, the restrictor 29, the piezoelectric element 35, and the like are shown in a smaller number than the actual number for simplification of the drawing.

<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.

  FIG. 6 is an operation conceptual diagram showing residual vibration generated in the ink in the pressure chamber in the inkjet recording head 220. 6A is during ink droplet ejection, FIG. 6B is after ink droplet ejection, and both figures schematically show changes in pressure generated in the pressure chamber.

  FIG. 7 is a schematic diagram illustrating 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. 6A, and the residual vibration waveform generation period corresponds to FIG.

  As shown in FIG. 6A, when the drive waveform generated by the drive waveform generator 212 is applied to the piezoelectric element 35 (specifically, the electrode of the piezoelectric element connection substrate 36), the piezoelectric element 35 is , Expand and contract. A stretching force acts on the ink in the pressure chamber 27 from the piezoelectric element 35 via the vibration plate 30, and a pressure change is generated in the pressure chamber 27, whereby an ink droplet is ejected from the nozzle 20. For example, the pressure in the pressure chamber 27 is lowered by the drive waveform falling operation, and the pressure in the pressure chamber 27 is raised by the drive waveform rising operation (see the drive waveform application period shown in FIG. 7).

  As shown in FIG. 6B, after a 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 pressure chamber 27 The residual pressure wave propagates from the ink to the piezoelectric element 35 through 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. 7). 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 uses 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) as an output of the residual vibration detection unit to the control unit 211. Is output.

  Thus, in the droplet discharge device according to the present embodiment, the residual vibration detection unit detects residual vibration based on the expansion and contraction of the piezoelectric element, and the control unit detects ink based on the output of the residual vibration detection unit. Determine viscosity. Here, since the residual vibration waveform is a damped vibration, attention is paid to the damping ratio of the damped vibration as one means for determining the ink viscosity based on the output of the residual vibration detecting unit. By paying attention to the damping ratio of the damped vibration, the controller can accurately determine the ink viscosity with a simple circuit configuration.

  Next, 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 amplitude value of the residual vibration waveform and the ink viscosity will be described with reference to FIGS.

The theoretical expression of the damped vibration is as follows: x is the damped 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, t can be expressed as [Expression 1].

The natural vibration frequency ω _d of the damping system can be expressed by [Equation 2].

The logarithmic decay rate δ can be expressed by [Equation 3] where an is an _nth amplitude value and an _{+ m} is an n + mth amplitude value. The logarithmic attenuation rate δ is a parameter necessary for calculating the attenuation ratio ζ.

In FIG. 8, T is one period, mT is m cycles, _{a n} is the n-th amplitude _{value, a n + 1} is n + 1 th amplitude _{value, a n + 2} is (n + 2) -th amplitude _{value, a n + m} is n + m-th amplitude value Yes (where n and m are natural numbers).

  Since the logarithmic attenuation rate δ is a value averaged per one cycle by logarithmizing the ratio of amplitude change and dividing by m, the attenuation ratio ζ is expressed by [Equation 4 ].

The attenuation ratio ζ has information obtained by averaging attenuation rates of amplitude values for a plurality of periods over one period.

  Therefore, in order to calculate the damping ratio ζ of the damped vibration from [Equation 1] to [Equation 4], the logarithmic attenuation rate δ may be obtained, and in order to obtain the logarithmic attenuation rate δ, at least two residuals are obtained. It can be seen that it is sufficient to recognize the amplitude value of the vibration waveform.

  FIG. 9 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 relationship of the viscosity of each ink can be expressed as viscosity B = 1.7 and viscosity C = 3 when the viscosity A = 1.

  FIG. 9 shows that the amplitude value in the residual vibration actual measurement waveform with viscosity A = 1 is the largest and the amplitude value in the residual vibration actual measurement waveform with viscosity C = 3 is the smallest.

  That is, as the ink viscosity is lower, the amplitude of the damped vibration is larger and the damping ratio of the damped vibration is smaller, and it can be seen that the residual vibration measured waveform and the ink viscosity are correlated.

  FIG. 10 is a block diagram showing an example of an ink jet recording head module mounted on the ink jet recording apparatus according to the present embodiment.

  The ink jet recording head module 200 includes a drive control board 210, an ink jet recording head 220, and the like. A control unit 211, a storage unit 213, and the like are mounted on the drive control board 210. The ink jet recording head 220 includes a residual vibration detection substrate 222 on which the residual vibration detection unit 240 is mounted, a piezoelectric element connection substrate 36 on which the piezoelectric element driving IC 37 is mounted, 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 board 222. The piezoelectric element drive IC 37 includes a drive waveform generation unit 212, a serial / para conversion unit 371, a control unit 372, and the like. The waveform processing circuit 250 includes a filter circuit 251, an amplifier circuit 252, a peak hold circuit 253, and the like.

  It should be noted that the control unit 211 mounted on the drive control board 210 and the control unit 372 mounted on the piezoelectric element drive IC 37 may have some functions or all functions unified. In addition, some or all of the functions mounted on the residual vibration detection board 222 may be unified with the drive control board 210.

  The control unit 211 generates drive waveform data based on image data received from a host controller (not shown) and outputs the drive waveform data to the piezoelectric element drive IC 37. The control unit 211 transmits a timing control signal (digital signal) to the piezoelectric element driving IC 37 and the switching unit 241 by serial communication, and transmits a switching signal synchronized with the timing control signal to the switching unit 241. The controller 211 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.

  Further, the control unit 211 outputs from the output of the residual vibration detection unit 240 fed back for each nozzle from 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). At least two or more digital signals are selected, and the damping ratio of the damping vibration is calculated using [Formula 1] to [Formula 4]. The greater the number of amplitude values selected, the greater the accuracy of calculating the attenuation ratio.

  Further, the control unit 211 accurately detects the ink viscosity in the pressure chamber by comparing the calculated attenuation ratio with the attenuation ratio data stored in the storage unit 213. Then, the control unit 211 corrects the drive waveform data for each nozzle 20 based on the ink viscosity. Accordingly, the drive waveform generation unit 212 can drive the piezoelectric element 35 (piezoelectric elements 35a to 35x) by applying an optimum drive waveform for each nozzle 20.

  The storage unit 213 stores attenuation ratio data in advance.

  The serial / para conversion unit 371 converts the drive waveform data (serial data) corrected by the control unit 211 into a parallel signal and outputs the parallel signal to the drive waveform generation unit 212 and the control unit 372.

  The control unit 372 deserializes the timing control signal and outputs a signal corresponding to the timing control signal to the drive waveform generation unit 212.

  The drive waveform generation unit 212 performs D / A conversion on the drive waveform data (parallel signal), performs voltage amplification and current amplification, generates a drive waveform, and outputs the drive waveform to the piezoelectric element drive IC 37.

  The piezoelectric element drive IC 37 is ON / OFF controlled based on the timing control signal. For example, when the piezoelectric element drive IC 37 is ON (OFF), the drive waveform generation unit 212 applies a drive waveform generated for each nozzle to the piezoelectric element 35 ( (Refer to the drive waveform application period shown in FIG. 7). The piezoelectric element 35 expands and contracts based on the drive waveform falling operation and startup operation, and ink droplets are ejected from each nozzle in accordance with the drive of the piezoelectric element 35.

  The waveform processing circuit 250 performs filter processing on the residual vibration waveform by the filter circuit 251 and the amplification circuit 252 and amplifies it, and recognizes the peak value (for example, the maximum value) of the amplitude value of the residual vibration waveform by the peak hold circuit 253.・ 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 vibration 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 the digital signal (feedback). The control unit 211 (or the control unit 226) may calculate the damping ratio of the damped vibration based on the output (detection result) of the residual vibration detection unit 240 fed back.

  In FIG. 10, the residual vibration voltages of the piezoelectric elements 35a to 35x are sequentially switched and detected using a set of residual vibration detection units (switching means 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 residual vibration detection unit may be formed for each of the piezoelectric elements, and the ink viscosity in all the pressure chambers may be detected simultaneously. Further, for example, the piezoelectric elements may be divided into several groups, a residual vibration detection unit 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 detected simultaneously while suppressing an increase in circuit scale.

  FIG. 11 is a circuit diagram illustrating an example of a residual vibration detection unit according to the present embodiment.

  The piezoelectric element driving IC 37 includes a plurality of switching elements, and ON / OFF of the piezoelectric element driving IC 37 is controlled by ON / OFF of switching elements formed corresponding to each piezoelectric element. After ink droplet ejection (piezoelectric element drive IC 37 is OFF), the residual vibration detector 240 is induced by the piezoelectric element 35 by connecting the piezoelectric element 35 and the waveform processing circuit 250 via the switching unit 241. The residual vibration voltage can be detected and the amplitude value of the residual vibration waveform can be recognized.

  The waveform processing circuit 250 receives a minute residual vibration waveform by the high impedance buffer unit, thereby suppressing the adverse effect of the detection circuit on the residual vibration waveform. Passive element constants such as resistors R1 to R5 and capacitors C1 to C3 mounted on the waveform processing circuit 250 are variably controlled by the control unit 211 in accordance with a difference in natural vibration frequency caused by characteristics of the ink jet recording head 220. It is preferable.

  The filter circuit 251 performs a filtering process on the residual vibration waveform. The filter circuit 251 has a predetermined pass bandwidth with the natural vibration frequency as the center frequency. For example, a bandwidth of −3 dB from each end of the pass bandwidth is set to about three times the pass bandwidth. It is preferable. Thereby, it is possible to absorb the variation of the natural vibration frequency caused by the manufacturing variation of the ink jet recording head 220 and to efficiently remove the high frequency noise and the low frequency noise.

  The amplifier circuit 252 amplifies the residual vibration waveform that has been subjected to the filter processing (see the dotted line in FIG. 12). In the amplifier circuit 252, the amplification factor is preferably set so that the waveform is amplified within the input possible range of the A / D converter 242.

  Note that the filter circuit 251 and the amplifier circuit 252 are configured by a band-pass filter amplification type (Salenki type), thereby enabling efficient noise component removal and signal component extraction. It is not limited. What is necessary is just to be comprised with the circuit which combined the filter which has a high-pass characteristic and a low-pass characteristic at least, and a non-inverting amplification part or an inverting amplification part.

  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. 12). In the peak hold circuit 253, the discharge time of the resistor R6 and the capacitor C3 is preferably set so as to be ½ or less of the residual vibration period. The reset of the peak hold circuit 253 is performed when the control unit 211 outputs a reset signal to the switching element SW1 at a timing when the rising of the damped oscillation waveform crosses the reference voltage Vref. The reset timing may be any timing as long as the peak hold circuit 253 can recognize the amplitude value of the damped vibration waveform, and the reset timing can also be detected by a comparison unit (not shown). Note that the configuration of the peak hold circuit 253 is not limited to the configuration illustrated in FIG. 11, and it is sufficient that the peak hold circuit 253 is configured with at least a circuit capable of fixing the peak value of the amplitude value of the residual vibration waveform.

  FIG. 12 shows an example of a waveform (shown by a dotted line) that has been filtered and amplified using the circuit shown in FIG. 11 and a waveform (shown by a solid line) that is fixed at the peak value of the amplitude value.

  The amplitude values are 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. The amplitude value of the fourth half wave is assumed to be amplitude value 4, and the amplitude value of the fifth half wave is assumed to be amplitude value 5. The steep waveform seen below the reference voltage Vref is an undershoot caused by instantaneously discharging the capacitor C3.

  The attenuation ratio ζ can be calculated using [Equation 3] and [Equation 4] by selecting at least two amplitude values among the amplitude values 1 to 5 by the control unit 211. In FIG. 12, since the waveform is shown when amplitude values 1 to 5 above the upper and lower amplitudes are detected, the attenuation ratio ζ can be calculated by averaging four periods. It is also possible to calculate the attenuation ratio ζ by detecting the lower amplitude value. When the upper amplitude value of the upper and lower amplitudes is used for calculating the attenuation ratio ζ, an amplification circuit may be applied to the waveform processing circuit 250, and the upper amplitude value of the upper and lower amplitudes is used for calculating the attenuation ratio ζ. In this case, an inverting amplifier circuit may be applied to the waveform processing circuit 250.

  Note that the control unit 211 can increase the calculation accuracy of the attenuation ratio ζ by appropriately selecting the amplitude value. For example, the control unit 211 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 that is easily affected by the variation of the switching unit. Also good. Further, for example, the control unit 211 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 tends to increase. The amplitude value to be used may be selected. For example, the control unit 211 may select an amplitude value used for 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 the half wave having a large influence of disturbance or noise.

  FIG. 13 shows the relationship between the attenuation ratio ζ calculated using the amplitude value (amplitude value 1, amplitude value 2, amplitude value 3, amplitude value 4, or amplitude value 5) shown in FIG. 12 and the ink viscosity μ. FIG.

  FIG. 13 shows that the damping ratio ζ of the damping vibration increases as the ink viscosity μ increases, and the damping ratio ζ of the damping vibration has a correlation with the ink viscosity.

  FIG. 14 is a diagram illustrating an example of a drive waveform. The horizontal axis represents time [s], and the vertical axis represents voltage [V].

  The voltage amplitude Vpp of the trapezoidal driving waveform shown in FIG. 14 is proportional to the droplet discharge speed and the discharge amount. For example, when the control unit 211 determines that the ink viscosity has increased based on the calculated attenuation ratio, the droplet discharge speed and the discharge amount are decreased. Therefore, in this case, the droplet discharge speed and the discharge amount can be corrected by increasing the voltage gain of the drive waveform and increasing the voltage amplitude Vpp.

  That is, in correspondence with the ink viscosity determined by the control unit 211, the drive waveform generation unit 212 generates a drive waveform having a different voltage amplitude Vpp for each ink viscosity (see FIG. 13), and generates a drive waveform for each piezoelectric element. Apply. Thereby, the drive waveform generation unit 212 can apply an optimum drive waveform to each piezoelectric element.

  The control unit 211 may repeat detection and correction as needed so that the detected attenuation ratio satisfies a predetermined range without converting the output of the residual vibration detection unit 240 into ink viscosity. The predetermined range is not particularly limited, but may be a range in which the droplet discharge speed and the discharge amount are kept constant.

  FIG. 15 is a diagram illustrating an example of timing at which the control unit corrects drive waveform data.

  A case where the residual vibration detection unit 240 detects a change in ink viscosity in the process of forming an image on the recording medium 113 while conveying the recording medium 113 in the conveyance direction (see the arrow in the figure) will be described.

  In this case, the control unit 211 corrects the drive waveform data from the next droplet of the droplet in which the ink viscosity change is detected. Thereby, the droplet discharge device can suppress the occurrence of an abnormal image in the page.

  FIG. 16 is a diagram illustrating an example of timing at which the control unit corrects drive waveform data.

  In the process of forming an image on the recording medium 113 while conveying the recording medium 113 in the conveying direction (see the arrow in the figure), the residual vibration detection unit 240 is printing a certain page (for example, page 1). A case where a change in ink viscosity is detected will be described.

  In this case, the control unit 211 does not correct the drive waveform data in the page 1, and drives the drive waveform data from the blank portion (for example, between pages) between the page 1 and the next page (for example, page 2). Correct. Thereby, the droplet discharge device can suppress the occurrence of abnormal images on the next page and thereafter.

  FIG. 17 is a diagram showing the relationship between the temperature T and the ink viscosity μ.

  The control unit 211 can calculate the ink viscosity μ from the calculated attenuation ratio ζ based on FIG. 13, and can calculate the ink temperature T from the ink viscosity μ based on FIG. That is, the control unit 211 can calculate the ink temperature based on the calculated attenuation ratio ζ. Thus, the ink temperature can be monitored without installing a thermistor or the like.

  According to the droplet discharge device according to the present embodiment, the residual vibration generated in the ink in the pressure chamber after the ink droplet discharge is effectively used, and the control unit outputs the feedback result of the residual vibration detection unit. Based on the ink viscosity, the drive waveform data is corrected for each nozzle. As a result, an optimum drive waveform can be applied to each piezoelectric element according to the state of the ink, so that the image quality of the ink jet recording apparatus can be improved.

<Second Embodiment>
In the present embodiment, the case where the piezoelectric element mounted on the ink jet recording head 220 is different from the piezoelectric element according to the first embodiment will be described. Unlike the piezoelectric element according to the first embodiment, the piezoelectric element according to the second embodiment includes a driving piezoelectric element and a support piezoelectric element (see Japanese Patent No. 3933506).

  FIG. 18 is a schematic cross-sectional view showing an example of the ink jet recording head 220 according to the present embodiment.

  As shown in FIG. 18, the piezoelectric element includes a driving piezoelectric element 311 and a support piezoelectric element 312, and the driving piezoelectric element 311 and the support piezoelectric element 312 are alternately arranged. The driving piezoelectric element 311 is formed via the diaphragm 30 at a position corresponding to the opening of the pressure chamber 27. The support piezoelectric element 312 is formed via the diaphragm 30 at a position corresponding to the partition wall of the pressure chamber 27.

  With the configuration shown in FIG. 18, not only the driving piezoelectric element 311 but also the support piezoelectric element 312 can be used for residual vibration detection. In other words, the support piezoelectric element 311 is always used for residual vibration detection, and the drive piezoelectric element 311 is used for residual vibration detection when there is no adverse effect on ejection (when the piezoelectric element is not driven). be able to. Therefore, in the line scanning type inkjet recording apparatus 100, the time required to detect the ink viscosity of all the nozzles 20 (residual vibration detection time) is increased during printing, increasing the degree of freedom of the timing for detecting the residual vibration. It can be shortened. Further, since it is not necessary to provide a new sensor, the ink jet recording head 220 can have a relatively simple configuration.

  Furthermore, with the configuration shown in FIG. 18, even if a displacement occurs when the diaphragm 30 and the piezoelectric element are connected, characteristic fluctuations that occur in the piezoelectric element can be suppressed. The injection characteristic can be stabilized.

  The configuration of the piezoelectric element is not particularly limited to the configuration shown in FIG. 18, and at least the support piezoelectric element 312 can detect residual vibration independently of the driving piezoelectric element 311. Any configuration can be used. It is also possible to adopt a configuration in which another sensor is provided so that all the piezoelectric elements can be used for residual vibration detection at all times. Examples of other sensors include a pressure sensor that detects the pressure in the pressure chamber 27, and an optical sensor (displacement sensor, speed sensor, camera) that detects fluctuations in the meniscus.

  FIG. 19 is a block diagram showing an example of an ink jet recording head module mounted on the ink jet recording apparatus according to the present embodiment.

  As shown in FIG. 19, the driving piezoelectric element 311 (driving piezoelectric elements 311 a to 311 x) is connected to the piezoelectric element driving IC 37 and the switching unit 241 and controlled based on the driving waveform output from the piezoelectric element driving IC 37. The The driving piezoelectric element 311 is controlled by the piezoelectric element driving IC 37 so as not to detect residual vibration when driven, and to detect residual vibration when not driven.

  As shown in FIG. 19, the support piezoelectric element 312 (supporting piezoelectric elements 312 a to 312 x) is connected to the switching unit 241 and controlled based on a switching signal output from the control unit 211. Therefore, the piezoelectric element 312 for support is controlled by the piezoelectric element driving IC 37 so that the residual vibration is always detected.

  FIG. 19 shows a configuration in which the residual vibration is detected not only by the supporting piezoelectric element 312 but also by the driving piezoelectric element 311. For example, as shown in FIG. It is also possible to adopt a configuration used for residual vibration detection.

  FIG. 21 is a circuit diagram illustrating an example of a residual vibration detection unit according to the present embodiment. The circuit diagram of the residual vibration detection part in the case of adopting a configuration in which only the support piezoelectric element 312 is used for residual vibration detection (see FIG. 20) is shown.

  10 and FIG. 21 are different in the piezoelectric element connected to the waveform processing circuit 250 via the switching unit 241. In FIG. 10, the waveform processing circuit 250 and the driving piezoelectric element are connected. In FIG. 21, the waveform processing circuit 250 and the support piezoelectric element are connected. Since other configurations are all equal, detailed description is omitted.

  In FIG. 21, the piezoelectric element 312 and the waveform processing circuit 250 are connected from the piezoelectric element driving IC 37 to the piezoelectric element 311 via the switching unit 241 in accordance with the timing of applying the driving waveform. Thereby, the residual vibration detection unit 240 can detect the residual vibration voltage induced in the piezoelectric element 312 and recognize the amplitude value of the residual vibration waveform.

<Control flow chart>
FIG. 22 is a diagram showing an example of a control flowchart of the line scanning ink jet recording apparatus in the on-demand method according to the present embodiment. The control flowchart shown in FIG. 22 is executed by the control unit 211 according to the control program, for example.

  In step S1, the control unit 211 sets n = 1 in order to perform correction for each nozzle.

  In step S <b> 2, the control unit 211 applies a driving waveform (for standard viscosity) to the piezoelectric element 311 (piezoelectric elements 311 a to 311 x) via the driving waveform generation unit 212.

  In step S3, the control unit 211 monitors the piezoelectric element driving IC 37 and determines whether or not the piezoelectric element driving IC 37 is turned off. When it determines with the piezoelectric element drive IC37 having been turned off (YES), the control part 211 performs the process of step S4. When it is determined that the piezoelectric element driving IC 37 is not OFF (NO), the control unit 211 continues monitoring the piezoelectric element driving IC 37 (the process of step S3 is performed again).

  In step S <b> 4, the control unit 211 connects the piezoelectric element 312 (piezoelectric elements 312 a to 312 x) to be detected and the waveform processing circuit 250 using the switching unit 241.

  In step S5, the control unit 211 calculates the damping ratio ζdet from the detection result (amplitude value) by the residual vibration detection.

  In step S6, the control unit 211 compares the damping ratio ζdet with the ink viscosity μ using a table (see FIG. 13).

  In step S7, the control unit 211 determines whether the ink viscosity has changed as a result of the comparison. When it is determined that the ink viscosity has changed (YES), the control unit 211 performs the process of step S8. When it is determined that the ink viscosity has not changed (NO), the control unit 211 performs the process of step S9.

  In step S8, the control unit 211 corrects the drive waveform data and applies a drive waveform corresponding to the detected ink viscosity to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212.

  In step S9, the control unit 211 applies a drive waveform for standard viscosity to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212 without correcting the drive waveform data.

  In step S10, the control unit 211 determines whether or not the nozzle has reached the final nozzle. When it is determined that the nozzle has reached the final nozzle (YES), the control unit 211 ends the process. When it is determined that the nozzle has not reached the final nozzle (NO), the control unit 211 performs the process of step S11.

  In step S10, the control unit 211 increments n by 1 and applies a drive waveform for printing to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212 (processing in step S2 again). I do).

<Third Embodiment>
In the present embodiment, a control flowchart different from that of the second embodiment when a configuration in which the support piezoelectric element 312 is used for residual vibration detection will be described. FIG. 23 is a diagram showing an example of a control flowchart of the line scanning ink jet recording apparatus in the on-demand system according to the present embodiment. The control flowchart shown in FIG. 23 is executed by the control unit 211 according to the control program, for example.

  In step S1, the control unit 211 sets n = 1 in order to perform correction for each nozzle.

  In step S <b> 2, the control unit 211 applies a driving waveform (for standard viscosity) to the piezoelectric element 311 (piezoelectric elements 311 a to 311 x) via the driving waveform generation unit 212.

  In step S3, the control unit 211 monitors the piezoelectric element driving IC 37 and determines whether or not the piezoelectric element driving IC 37 is turned off. When it determines with the piezoelectric element drive IC37 having been turned off (YES), the control part 211 performs the process of step S4. When it is determined that the piezoelectric element driving IC 37 is not OFF (NO), the control unit 211 continues monitoring the piezoelectric element driving IC 37 (the process of step S3 is performed again).

  In step S <b> 4, the control unit 211 connects the piezoelectric element 312 (piezoelectric elements 312 a to 312 x) to be detected and the waveform processing circuit 250 using the switching unit 241.

  In step S5, the control unit 211 calculates the damping ratio ζdet from the detection result (amplitude value) by the residual vibration detection.

  In step S6, the control unit 211 compares the damping ratio ζdet with the ink viscosity μ using a table (see FIG. 13).

  In step S7, the control unit 211 determines whether the ink viscosity has changed as a result of the comparison. When it is determined that the ink viscosity has changed (YES), the control unit 211 performs the process of step S8. When it is determined that the ink viscosity has not changed (NO), the control unit 211 performs the process of step S11.

In step S8, the control unit 211 determines whether or not the damping ratio ζdet is larger than the damping ratio of the standard viscosity. When it is determined that the damping ratio ζdet is larger than the damping ratio of the standard viscosity (YES), the control unit 211 performs the process of step S9.
When it is determined that the damping ratio ζdet is equal to or less than the damping ratio of the standard viscosity (NO), the control unit 211 performs the process of step S10.

  In step S <b> 9, the control unit 211 corrects the drive waveform data, and moves the drive waveform shifted by one to the piezoelectric element 311 (piezoelectric elements 311 a to 311 x) via the drive waveform generation unit 212 toward the high viscosity side in the table. Apply. Thereby, the ink discharge speed and the discharge amount can be corrected without giving a sudden voltage change to the piezoelectric element, so that the deterioration of the piezoelectric element can be prevented.

  In step S10, the control unit 211 corrects the drive waveform data and shifts the drive waveform by one to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212 to the low viscosity side in the table. Apply. Thereby, the ink discharge speed and the discharge amount can be corrected without giving a sudden voltage change to the piezoelectric element, so that the deterioration of the piezoelectric element can be prevented.

  In step S11, the control unit 211 applies a drive waveform for standard viscosity to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212 without correcting the drive waveform data.

  In step S12, the control unit 211 determines whether the nozzle has reached the last nozzle. When it is determined that the nozzle has reached the final nozzle (YES), the control unit 211 ends the process. When it is determined that the nozzle has not reached the final nozzle (NO), the control unit 211 performs the process of step S13.

  In step S13, the control unit 211 increments n by 1 and applies a drive waveform for printing to the piezoelectric element 311 (piezoelectric elements 311a to 311x) via the drive waveform generation unit 212 (processing in step S2 again). I do).

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and within the scope of the gist of the embodiment of the present invention described in the claims, Various modifications and changes are possible.

20 Nozzle 27 Pressure chamber 30 Diaphragm 35 Piezoelectric element (pressure generating element)
113 Recording medium 200 Inkjet recording head module (droplet ejection device)
211 Control Unit 212 Drive Waveform Generation Unit 240 Residual Vibration Detection Unit 311 Drive Piezoelectric Element 312 Support Piezoelectric Element

JP 2007-98691 A

The present invention relates to an ink discharge apparatus, a discharge amount correction method, and a program.

However, in the conventional ink jet recording apparatus, there is a possibility that image quality is degraded.

The ink ejection device of the present embodiment includes a plurality of nozzles that eject ink, a plurality of pressure chambers that communicate with the plurality of nozzles and store ink, a vibration plate that forms walls of each pressure chamber, and the vibration A plurality of pressure generating elements generating pressure to each of the plurality of pressure chambers via a plate, and detecting residual vibration propagating from the diaphragm to the pressure generating element after pressure is generated by the pressure generating element ; A residual vibration detection unit; and a control unit that corrects an ink ejection amount based on a detection result of the residual vibration detection unit, and the control unit forms an image after the detection of the residual vibration detection unit. It is a requirement that the ink ejection amount is corrected when an image is formed on the next and subsequent pages .

Claims (10)

A plurality of pressure chambers communicating with a plurality of nozzles and storing ink;
A diaphragm disposed across each pressure chamber to form an elastic wall of each pressure chamber;
A pressure generating element disposed to face each of the plurality of pressure chambers via the diaphragm;
A drive waveform generator for generating a drive waveform for each nozzle, with drive waveform data indicating the shape of a drive waveform for driving the pressure generating element as an input;
A residual vibration detector that detects residual vibration generated in each pressure chamber after driving the pressure generating element;
And a controller that corrects the drive waveform data for each nozzle during printing based on a detection result of the residual vibration detector. The controller is
The droplet discharge device according to claim 1, wherein the drive waveform data is corrected from the next droplet of the droplet in which a change in liquid viscosity is detected. The controller is
The droplet discharge device according to claim 1, wherein the drive waveform data is corrected from a margin portion of the recording medium.   The droplet ejection apparatus according to claim 1, wherein the residual vibration detection unit uses the pressure generating element.   The droplet ejection device according to claim 4, wherein the residual vibration detection unit uses a pressure generating element for a column.   The droplet discharge device according to claim 5, wherein the support pressure generating element is disposed so as to face a partition existing between the plurality of pressure chambers.   The liquid droplet ejection apparatus according to claim 1, wherein the output of the residual vibration detection unit is a damping ratio of a residual vibration waveform. The controller is
The liquid droplet ejection apparatus according to claim 7, wherein the drive waveform data is corrected so that the attenuation ratio satisfies a predetermined range. A plurality of pressure chambers communicating with a plurality of nozzles for storing ink; a diaphragm disposed over each pressure chamber so as to form an elastic wall of each pressure chamber; and the plurality of pressure chambers via the diaphragm A pressure generating element disposed so as to face each other, a driving waveform generating unit that generates a driving waveform for each nozzle by using driving waveform data indicating a shape of a driving waveform for driving the pressure generating element, and the pressure A droplet ejection method for a droplet ejection apparatus, comprising: a residual vibration detection unit that detects residual vibration generated in each pressure chamber after driving the generating element;
Correcting the drive waveform data for each nozzle during printing based on the detection result of the residual vibration detection unit. A plurality of pressure chambers communicating with a plurality of nozzles for storing ink; a diaphragm disposed over each pressure chamber so as to form an elastic wall of each pressure chamber; and the plurality of pressure chambers via the diaphragm A pressure generating element disposed so as to face each other, a driving waveform generating unit that generates a driving waveform for each nozzle by using driving waveform data indicating a shape of a driving waveform for driving the pressure generating element, and the pressure A program that is executed by a droplet discharge device that includes a residual vibration detection unit that detects residual vibration generated in each pressure chamber after driving the generating element,
And a process of correcting the drive waveform data for each nozzle during printing based on a detection result of the residual vibration detection unit.