JP6561645B2 - Droplet ejection apparatus, image forming apparatus, droplet ejection apparatus control method, and program - Google Patents

Description

  The present invention relates to a droplet discharge device, an image forming apparatus, a method for controlling a droplet discharge device, 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.

  In a device that ejects ink droplets from an ink chamber by driving a piezoelectric element that is an actuator with an electrical signal, the period and amplitude of residual vibration are detected from an electromotive voltage generated in the piezoelectric element after the piezoelectric element is driven. It is already known that it is possible to determine the presence or absence of bubbles and ink not filled, and to prevent malfunctions such as printing mistakes due to nozzle failures (Patent Document 1).

  Alternatively, in Patent Document 2, the purpose is to detect residual vibration due to a change in state, and a piezoelectric actuator is driven by a trapezoidal pulse drive signal to detect the generated residual vibration. It is disclosed that when detecting the state, the amplitude of the residual vibration is made constant by setting a detection waveform for detecting the residual vibration in accordance with the ink temperature.

  However, since there are variations for each nozzle such as the nozzle diameter and the capacitance of the piezo, the natural frequencies vary. Accordingly, there is a possibility that the state for each nozzle cannot be accurately detected with the same detection waveform.

  In view of the above circumstances, an object of one embodiment of the present invention is to provide a droplet discharge device that can detect an abnormal state with high accuracy.

According to one aspect of the present invention, a droplet discharge device includes a plurality of nozzles, a plurality of pressure chambers that communicate with the plurality of nozzles and store liquid, respectively, and are provided corresponding to the plurality of nozzles. A plurality of piezoelectric elements arranged to face the plurality of pressure chambers via the pressure chamber, and a state detection for detecting residual liquid in the pressure chamber to detect the state of the nozzle or the liquid in the pressure chamber A waveform generating unit that applies a waveform to the piezoelectric element, a storage unit that stores a nozzle diameter for each nozzle as a unique value for each nozzle, and a reference waveform for detection is corrected according to the nozzle diameter for each nozzle , And a control unit that generates the state detection waveform used in the waveform generation unit.

  According to the present embodiment, an abnormal state can be detected with high accuracy in the droplet discharge device.

It is a figure which illustrates the inkjet recording device which concerns on embodiment of this invention. It is the side view and perspective view of the ink carriage part of a line head structure. It is the schematic of the ink carriage part of a serial head structure. It is a bottom view illustrating an inkjet recording head array having a line head configuration. 2 is a perspective view illustrating an example of an inkjet recording head. FIG. It is a perspective view which illustrates the composition of an ink jet recording head. FIG. 5 is an operation conceptual diagram showing ink ejection and residual vibration in a pressure chamber. It is a figure which illustrates the drive waveform application period and residual vibration waveform generation period of FIG. It is a figure which shows the relationship between a damped vibration waveform and a damping ratio. It is a figure which shows the relationship between residual vibration measurement waveform and ink viscosity. It is a figure which shows the relationship between damping ratio (zeta) and ink viscosity (micro | micron | mu). 1 is a block diagram of a droplet discharge device according to a first embodiment. 2 is a circuit diagram of an ink jet recording head according to the present embodiment. FIG. It is a figure which shows a residual vibration waveform and the detected amplitude value. It is a figure which illustrates the ink in a pressure chamber at the time of normal discharge, and a residual vibration waveform. It is a figure which illustrates the ink in a pressure chamber when a nozzle surface dries, and a residual vibration waveform. It is a figure which illustrates waveform control of the waveform for a state detection when a nozzle diameter varies. It is a figure which illustrates waveform control of the waveform for a state detection when the electrostatic capacitance of a piezoelectric element varies. It is a table which illustrates the correction factor of the amplitude and frequency of the state detection waveform according to the nozzle diameter and the capacitance of the piezoelectric element. A control example in which the state detection waveform is corrected based on the table shown in FIG. It is a figure explaining the flow which acquires the specific value for every nozzle in the 2nd Embodiment of this invention. It is a table which illustrates the correction factor of the state detection waveform according to the frequency and damping ratio of the residual vibration waveform of the eigenvalue detection waveform. It is a figure which illustrates the waveform control of the state detection waveform according to the residual vibration waveform of the eigenvalue detection waveform.

  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, “normal state” refers to a state in which ink droplets are normally ejected from the nozzle, and “abnormal state” refers to an abnormality in the liquid in the nozzle or the pressure chamber. For example, a state where ink droplets are not ejected from the nozzle (non-ejection), a state where an appropriate amount of ink droplets are not ejected from the nozzle, a state where ink droplets are not landed at an appropriate position, a nozzle It shall refer to the state where something is attached to.

  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.

<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. , Maintenance / recovery means 114, a recording medium transport device, and the like.

  The recording medium conveyance 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.

  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.

<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. 2A and 2B show an ink carriage portion having a line head configuration, in which FIG. 2A is a side view and FIG. 2B is a perspective view.

  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, an adjustment plate 270, and the like.

  The drive control board 210 includes an acquisition unit (control unit) 211 that acquires ink viscosity, a drive waveform generation unit 212 that generates a drive waveform to be applied to the piezoelectric element, storage units 213 and 214, and image data based on the ink viscosity. This is a rigid board on which an image processing unit to be corrected is mounted.

  The ink jet 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 ink jet recording head 220 drives the piezoelectric element based on the drive waveform generated by the drive waveform generator 212 and ejects ink droplets from a 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 ink jet recording apparatus, one or a plurality of ink jet 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 over the entire printing width (FIG. 2). (See (B)). By ejecting ink droplets from the inkjet recording head 220 fixed by the adjustment plate 270, high-speed image formation on the recording medium 113 becomes possible. When the liquid droplet ejection apparatus according to the present embodiment is applied to a line scanning type ink jet recording apparatus, it is not necessary to mount a forward path return data rearrangement unit, which will be described later, and the circuit scale can be reduced.

  Note that the liquid droplet ejection apparatus according to this embodiment is applied to 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 conveyance direction of the recording medium 113. It is also possible to apply. When the liquid droplet ejection apparatus according to the present embodiment is applied to a serial scanning type ink jet recording apparatus, it is not necessary to use two or more ink jet recording heads.

  FIG. 3 is a schematic view (top view) of an ink carriage portion having a serial head configuration. FIG. 3 shows an internal mechanical configuration of the serial scanning type ink jet recording apparatus.

  The ink carriage unit 301 reciprocates in the main scanning direction (arrow A direction in the figure) and forms an image on the recording medium 309 that is intermittently conveyed in the sub-scanning direction (arrow B direction in the figure). The ink carriage unit 301 is supported by a main guide rod extending along the main scanning direction. 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 unit 301 is connected to a timing belt 306 that is stretched between a gear 304 and a pressure roller 305. The ink carriage unit 301 reciprocates in the main scanning direction when the driving force of the main scanning motor 303 is transmitted through 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 a paper feeding unit, a conveying unit, and the like. The pressure roller 305 adjusts the distance between the gear 304 and gives 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 the encoder value obtained by the encoder sensor 307 provided in the ink carriage unit 301 detecting the mark on the encoder sheet 308 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.

  The ink carriage unit 301 includes 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. An ink jet recording head 302k that discharges ink is mounted. The recording means 302 (302y, 302m, 302c, 302k) is installed such that the ejection surface faces the recording medium 309 side. Each inkjet recording head includes a plurality of nozzles, and forms an image on the recording medium 309 by ejecting ink droplets from the nozzle row to the recording medium 309 being conveyed.

  A cartridge that is an ink supply body that supplies ink to the recording unit 302 is disposed at a predetermined position in the ink jet recording apparatus. The recording unit 302 and the cartridge are connected by a pipe, and 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 ink is ejected from the recording unit 302 to the recording medium 309. The ink jet recording apparatus shown in FIG. 3 is a wide-width machine having a long moving distance in the main scanning direction in the ink carriage section 301, and the platen 310 is configured by connecting a plurality of plate-like members in the main scanning direction.

  The recording medium 309 is sandwiched between transport rollers and transported 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 paper with a strong curl such as a coated paper, a paper with a rough surface such as a mat film, or the like is used as the recording medium 309, the space between the recording medium 309 and the ink carriage unit 301 is used. It is preferable to increase the distance.

  Note that the serial scanning ink jet recording apparatus may include a maintenance mechanism for maintaining the reliability of the ink jet recording head. The maintenance mechanism can perform, for example, cleaning and capping of the ejection surface of the ink jet recording head, discharging unnecessary ink from the ink jet recording head, and the like. As the drive control board, a board having the same configuration and function as a board mounted on a 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 detects the residual vibration to be applied when generating the residual vibration in order to find out whether there is an abnormality in the liquid in the nozzle or the pressure chamber. The waveform for detection (reference waveform for detection) is corrected according to the eigenvalue of the nozzle, and a waveform for detecting the state is generated. For this reason, in the droplet discharge device, the ink state (abnormal state) for each nozzle can be detected more accurately.

<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, an electrode pad 38, 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.

  Here, as an example, the nozzle surface that is the ink discharge portion of the head in the nozzle plate 21 is formed of Ni / PTFE eutectoid, silicone resin, and fluorine-based water repellency imparting agent in order to improve ejection stability and wiping properties. Layer is provided. When the surface energy of the nozzle surface is also matched with that of the inner wall of the nozzle hole, it becomes more effective. Therefore, the inner wall of the nozzle hole may be subjected to the same treatment as the nozzle surface as necessary. When forming the silicone layer, portions other than the electrode plate other than the electrode plate, such as the back side of the nozzle plate, where the silicone layer is not formed are masked with a photoresist, a water-soluble resin, or the like.

  Since the coating treatment is performed on the inner wall of the nozzle hole in this manner, the nozzle diameter of the nozzle 20 may vary slightly depending on the coating state.

  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. Here, the piezoelectric element used in the embodiment of the present invention is a piezo-type electro-mechanical conversion element, and the piezoelectric element 35 includes a lower electrode (first electrode), an electromechanical conversion layer, an upper electrode ( And a second electrode). In order to generate the pressure of each ink discharge, an individual piezoelectric element 35 is arranged for each pressure chamber 27 corresponding to the nozzle 20.

  As an example of the electromechanical conversion layer, lead zirconate titanate (PZT) ceramics or the like is used, and these are formed as a metal composite oxide produced by laminating a plurality of metal oxides as a main component.

  Since the electromechanical conversion layer is formed by being cut after lamination, the film thickness may slightly vary in the manufacturing process. When the film thickness of the electromechanical conversion layer is reduced, the capacitance increases, and when the film thickness is increased, the capacitance decreases.

  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, state detection waveform, standard 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.

  FIG. 6 is an enlarged bottom view of the inkjet 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.

  As shown in FIG. 6, the diameter of the nozzle (hole) 20 arranged in the head portion of the ink jet recording head 220 is the nozzle diameter D, and the number of nozzles 20 corresponds to N used in the flow of FIG. .

  In the present embodiment, a configuration in which four nozzles are arranged per row and nozzles 20 are arranged in a staggered manner of 32 rows per row and two rows is shown as an example. The number to be formed is not particularly limited.

<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. 7 is an operation concept diagram showing residual vibration generated in the ink in the pressure chamber in the inkjet recording head 220. 7A is during ink droplet ejection, FIG. 7B is after ink droplet ejection, and both figures schematically show changes in pressure generated in the pressure chamber.

  FIG. 8 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. 7A, and the residual vibration waveform generation period corresponds to FIG.

  As shown in FIG. 7A, when the drive waveform generated by the drive waveform generator 212 is applied to the piezoelectric element 35 (specifically, the electrode pad 38 of the piezoelectric element connection substrate 36), the piezoelectric element 35 expands and contracts. 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. 8).

  As shown in FIG. 7B, 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 pad 38 of the piezoelectric element connection substrate 36). The residual vibration detection unit detects the residual vibration voltage and outputs the detection result to the control unit 211 as an output of the residual vibration detection unit.

  As described above, in the droplet discharge device according to the present embodiment, the residual vibration detection unit detects the induced residual vibration voltage, and the control unit determines the residual vibration attenuation ratio based on the output of the residual vibration detection unit. Alternatively, it is possible to determine a discharge abnormality by calculating a frequency.

  In FIG. 7, the residual vibration voltage when the drive waveform is applied and the ink droplet is ejected is described. However, the residual vibration is such that a fine drive waveform smaller than the drive waveform is applied and ink is not ejected. Even when the ink surface (meniscus) is vibrated. In order to detect an abnormal state, which will be described later, a waveform (state detection waveform and a predetermined standard waveform) that generates residual vibration is preferably a fine driving waveform that does not eject droplets when running costs are considered. .

  If the peak width tp of the state detection waveform is too long, the ink vibration speed reaches the liquid discharge speed, and the liquid droplets are discharged. Therefore, for example, if the natural vibration period of the pressure chamber 27 communicating with the nozzle 20 is fc and the natural vibration period obtained by (1 / fc) is Tc, the Tp of the state detection credit waveform is (1/3) Tc. It is preferable to set as follows.

  Next, the process of calculating the damping ratio of the damped vibration from the amplitude value of the residual vibration waveform and the amplitude value of the residual vibration waveform for determining the presence or absence of ejection abnormality will be described using FIG.

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 by the following equation (1).

減衰系の固有振動周波数ω_ｄは、数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、数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。

Logarithmic decrement δ is the amplitude value of n-th to _{a n,} the _{a n + m} as n + m-th amplitude values, expressed by the number 3. The logarithmic attenuation rate δ is a parameter necessary for calculating the attenuation 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 Figure 9, 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 period by logarithmizing the rate of amplitude change and dividing by m, the attenuation ratio ζ is expressed by Equation 4 using the logarithmic attenuation rate δ. I can express.

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 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 the equations 1 to 4, the logarithmic damping rate δ may be obtained, and in order to obtain the logarithmic damping rate δ, the amplitudes of at least two residual vibration waveforms are obtained. You can see that it is enough to recognize the value.

  FIG. 10 shows the relationship between the residual vibration measured 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. 10 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, it can be seen that the lower the ink viscosity, the larger the amplitude of the damped vibration and the smaller the damping ratio of the damped vibration.

  Further, it can be seen from FIG. 10 that noise is superimposed on the actually measured waveform, the variation of the first half-wave is large, and the correlation of the amplitude value with respect to the magnitude relationship of each ink viscosity cannot be seen. For example, if an ink viscosity change is detected using the magnitude of the amplitude value of the first half-wave, the viscosity B and the viscosity C in FIG. 10 cannot be separated.

  Therefore, in the embodiment of the present invention, an ink viscosity detection method using an attenuation ratio that can suppress variation in the first half-wave is applied while being configured with a band-pass filter that cuts high-frequency / low-frequency noise components. The viscosity can be detected appropriately.

  The ink viscosity can be obtained without using the attenuation ratio, but the detection can be performed with higher accuracy by using the attenuation ratio.

  FIG. 11 shows the relationship between the damping ratio calculated based on the residual vibration actual measurement waveform and the ink viscosity. From FIG. 11, it can be seen that as the ink viscosity μ increases as μA, μB, and μC, the damping ratio ζ increases as μA, μB, and μC.

  As shown in FIG. 11, the droplet discharge device 200 generates a drive waveform (for example, a μA drive waveform, a μB drive waveform, and a μC drive waveform) corresponding to each ink viscosity and applies it to each piezoelectric element. . In addition, the droplet discharge device 200 corrects the image data in consideration of the actual ink state (for example, mixing of bubbles and ink thickening).

  Thereby, the droplet discharge device 200 can suppress the fluctuation of the discharge speed and the discharge amount, and can stably discharge the ink droplet from each nozzle. Furthermore, the droplet discharge device 200 can prevent nozzle clogging and 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 critical damping is not achieved (attenuation ratio ζ <1), nozzle clogging occurs due to an extremely large ink viscosity depending on the nozzle diameter, nozzle shape, ink components, and the like. Sometimes. In this case, the droplet discharge device 200 determines that the closer the attenuation ratio ζ is to 1, the higher the probability that an abnormal state such as nozzle clogging occurs and ink is not discharged is high.

<Driving of droplet discharge device>
FIG. 12 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. The drive control board 210 is equipped with a control unit 211, a drive waveform generation unit 212, an eigenvalue storage unit 213 for each nozzle, an attenuation ratio data storage unit 214, and the like.

  The ink jet 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, 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, a comparator 243, and the like are mounted on the residual vibration detection board 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 unify some functions or all functions into one of them. Further, some or all of the functions mounted on the residual vibration detection substrate 222 may be unified with the drive control substrate 210 or the head substrate 221.

  The control unit 211 includes a drive control unit 215, a detection waveform control unit 216, a calculation unit 217, and a determination unit 218. Although an example in which individual control units corresponding to these functions are provided in the control unit 211 is shown in FIG. 12, all the functions may be configured by one circuit.

  The drive control unit 215 of the control unit 211 generates drive waveform data based on the image data received from the host controller 120 (= control unit of the inkjet recording apparatus 100) and outputs the drive waveform data to the drive waveform generation unit 212. The drive control unit 215 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 drive control unit 215 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 detection waveform control unit (waveform control unit) 216 of the control unit 211 corrects the reference waveform data for detection according to the eigenvalue for each nozzle stored in the eigenvalue storage unit 213 for each nozzle, and the waveform generation unit The state detection waveform data used in the above is generated. Details of the correction will be described later with reference to FIGS.

  The calculation unit 217 of the control unit 211 selects at least two or more 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 using Equations 1 to 4. The greater the number of amplitude values selected, the greater the accuracy of calculating the attenuation ratio.

  The determination unit 218 of the control unit 211 compares the calculated attenuation ratio with the attenuation ratio data stored in the attenuation ratio data storage unit 214, thereby determining whether or not an ejection abnormality has occurred in the inkjet recording head 220 (ejection). Existence of abnormality is accurately determined. Based on the determination result, the control unit 211 instructs the inkjet recording head module 200 to perform an appropriate maintenance / recovery operation (suction operation, wiping operation, flushing operation, etc.) using the maintenance / recovery unit 114. May be.

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

  The specific value storage unit 213 for each nozzle stores the correlation between the attenuation ratio data serving as a reference and the variation for each nozzle.

  For example, the unique value storage unit 213 for each nozzle stores a correlation table between the unique value for each nozzle and the waveform for state detection as shown in FIG. 19 in the first embodiment. In this case, the waveform control unit 216 corrects the reference waveform data for detection according to the correlation table stored in the eigenvalue storage unit 213 for each nozzle and converts it into waveform data for state detection.

  Here, the eigenvalue for each nozzle is the nozzle diameter D (μm) for each nozzle generated at the time of manufacture and / or the electrostatic capacitance C (pF) of the piezoelectric elements 35a to 35x (opposite to the nozzle) for each nozzle. Since variations in the nozzle diameter D and / or the electrostatic capacitance C of the piezoelectric elements 35a to 35x for each nozzle occur at the time of manufacture, they are stored in the nozzle specific value storage means 213 in advance.

  Alternatively, in a second embodiment to be described later, the waveform generation unit 212 applies a predetermined standard waveform to the piezoelectric element 35 in a normal nozzle state, and the residual vibration detection unit 240 applies the standard waveform to the piezoelectric element. Later, residual vibration generated in the liquid in the pressure chamber 27 is detected. And the calculating part 37 calculates the eigenvalue for every nozzle based on the said residual vibration generated after the application of the said standard waveform.

  In this case, the waveform control unit 216 corrects the detection reference waveform data according to the calculated unique value for each nozzle and converts it into state detection waveform data. The calculated characteristic value for each nozzle is a damping ratio of residual vibration generated after application of the standard waveform and / or a frequency of the residual vibration.

  The attenuation ratio data storage unit 214 stores in advance attenuation ratio data such as a look-up table LT indicating the correlation between the attenuation ratio and the viscosity. The attenuation ratio data is used when the determination unit 218 of the control unit 211 determines the state.

  The control unit 226 deserializes the timing control signal and transmits it to the piezoelectric element driving 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 generated by the drive waveform generation unit 212 is applied (non-applied) to the piezoelectric element 35. (Refer to the drive waveform application period shown in FIG. 8). 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) can calculate the damping ratio of the damped vibration based on the output of the residual vibration detection unit 240 fed back.

  The comparator 243 also inputs the output of the amplifier circuit 252 to the comparator 243 and feeds back the waveform output from the comparator 243 to the control unit 211. The control unit 211 (or the control unit 226) can calculate the frequency of the damped vibration based on the output of the residual vibration detection unit 240 fed back.

  In FIG. 12, the residual vibration voltages of the piezoelectric elements 35a to 35x are sequentially switched using a set of residual vibration detectors (switching means 241, waveform processing circuit 250, A / D converter 242, comparator 243). However, the configuration of the residual vibration detection unit is not particularly limited. For example, it is possible to form a residual vibration detection unit corresponding to all the piezoelectric elements and detect the damping ratio of the damped vibration at the same time. 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 attenuation ratio of the damped vibration 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. 13 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. Thereby, selective state detection becomes possible. The waveform processing circuit 250 can detect residual vibration with a simple circuit configuration of a general-purpose operational amplifier, a passive element, and a switch. Thereby, the increase in the circuit scale in the droplet discharge device can be suppressed, and the cost can be suppressed.

  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.

  As a result, variations in the natural vibration frequency caused by manufacturing variations in the ink jet recording head 220 can be absorbed to some extent, and high-frequency noise and low-frequency noise can be efficiently removed.

  The amplifier circuit 252 amplifies the residual vibration waveform that has been subjected to the filter processing (see the dotted line shown in FIG. 14). 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. 14). 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 comparator 243 becomes a High output when the inputted damped oscillation waveform becomes equal to or higher than the reference voltage Vref. The output of the comparator 243 is input to the control unit 211 (calculation unit 217). The control unit 211 detects the frequency from the rising cycle or the falling cycle (cycle Td) (see FIG. 23, (b)).

  The reset of the peak hold circuit 253 is performed by the control unit 211 outputting a reset signal to the switching element SW1 at a timing when the rising of the damped oscillation waveform detected by the comparator 243 crosses the reference voltage Vref.

  The reset timing is not limited to the above as long as the peak hold circuit 253 can recognize the amplitude value of the damped vibration waveform. Note that the configuration of the peak hold circuit 253 is not limited to the configuration shown in FIG. 13, 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. 14 shows an example of a waveform (shown by a dotted line) that has been filtered and amplified using the circuit shown in FIG. 13 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 by using the equations 3 and 4 by selecting at least two, preferably three or more amplitude values among the amplitude values 1 to 5 by the control unit 211. In FIG. 15, 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.

  Here, the residual vibration waveform of the damped vibration in the normal discharge state and the residual vibration waveform of the damped vibration in the abnormal discharge state will be described with reference to FIGS. 15 and 16.

  In a droplet discharge device, even if a discharge operation is performed, a phenomenon that ink is not normally discharged from the nozzle 20, that is, an ink droplet discharge abnormality may occur. Causes of ejection abnormalities include thickening of the ink viscosity due to drying of the nozzle surface, which is ejected for a long time, mixing of bubbles in the pressure chamber 27, liquid pooling near the nozzle 20 and adhesion of paper dust. . When this ejection abnormality occurs, ink is not ejected from the nozzle 20 (non-ejection), the ink cannot eject an appropriate appropriate amount, or the ink does not land at an appropriate position.

  FIG. 15 shows a case where the ink in the pressure chamber 27 is normal, and FIG. 16 shows a case where the viscosity of the ink in the pressure chamber 27 increases due to drying of the nozzle 20 with little ejection for a long time.

  FIGS. 15A and 16A are schematic views showing the state of ink in the pressure chamber 27. FIGS. 15B to 16B are schematic diagrams 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]. In FIGS. 16B and 16B, the drive waveform application period corresponds to FIG. 7A, and the residual vibration waveform generation period corresponds to FIG. 7B.

  In the case of FIG. 15A, the inside of the pressure chamber 27 is normal, and the residual vibration waveform is also normal in FIG. 16B. Therefore, the control unit 211 satisfies the predetermined range of the residual vibration waveform attenuation ratio. , “It is determined that there is no abnormality (a state in which only ink is filled and nothing is attached to the nozzle)”.

  In the case of FIG. 15A, the viscosity of the ink in the pressure chamber 27 increases. In FIG. 16B, the amplitude value of the first half wave is not substantially different from that in the normal ejection state, but the second half wave. Subsequent amplitude values (the amplitude value of the second half wave, the amplitude value of the third half wave) are smaller than in the normal ejection state. That is, the damping ratio of the residual vibration in the case of FIG. 16B has a waveform shape that is larger than the damping ratio of the residual vibration in the case of FIG.

  Therefore, in the case of FIG. 16B, the control unit 211 determines that the attenuation ratio of the residual vibration waveform does not satisfy the predetermined range and is in an abnormal discharge state (there is a discharge abnormality).

  In addition, even when bubbles are mixed in the liquid chamber, liquid pools near the nozzle surface, and paper dust adherence, the damping ratio of the residual vibration is increased as compared with the normal state. Therefore. When the residual vibration damping ratio is greater than a predetermined value, it can be determined that the nozzle is in an abnormal state.

  However, since this residual vibration varies depending on the nozzle diameter and the capacitance of the piezo, it cannot be accurately detected with the same residual vibration waveform due to variations among nozzles.

<Abnormality detection operation>
In the embodiment of the present invention, residual vibration is generated at times other than printing in order to find a defect (abnormal state) of ink in the nozzle. At this time, the control for correcting the drive signal (state detection signal) for detecting the residual vibration state according to the specific value of the nozzle will be described below.

<< First Embodiment >>
((Correction by nozzle diameter))
With reference to FIGS. 17A to 19 below, the variation of the residual vibration and the countermeasure against the variation in the first embodiment of the present invention will be described.

FIGS. 17A and 17B are diagrams exemplifying waveform control of a state detection waveform when the nozzle diameter varies when the nozzle conditions (temperature, ink viscosity, etc.) are constant.
17A shows the residual vibration waveform when the nozzle diameter varies in the normal ejection state, and FIG. 17B shows the residual vibration waveform when the state detection waveform corrected according to the nozzle diameter is applied. Indicates.

  In FIG. 17A, a waveform b2 is a residual vibration waveform when the nozzle diameter D is a predetermined value (standard value). In this case, the waveform b1 shows the residual vibration waveform when the nozzle diameter D is smaller than the standard value, and the waveform b3 shows the residual vibration waveform when the nozzle diameter D is larger than the predetermined value.

  As shown in FIG. 17A, when the nozzle diameter varies, the frequency in the residual vibration varies. Specifically, since the frequency of the residual vibration that is generated is determined by the volume of the pressure chamber 27 that communicates with each nozzle 20, it is substantially equal to the natural vibration frequency fc of the pressure chamber 27. Therefore, assuming that the natural vibration period obtained by (1 / fc) is Tc, the vibration period of the generated residual vibration is approximately equal to Tc. Furthermore, when the same detection waveform is applied, the amplitude Am increases as the frequency increases. For example, in FIG. 17A, the amplitude of the first half-wave is (Am1-1)> (Am1-2)> (Am1-3).

  Therefore, if the nozzle diameter that determines the volume of the communicating pressure chamber 27 is different, even if the same drive waveform (detection drive waveform) is applied, the residual vibration fluctuates due to variations in the specific value (nozzle diameter D) for each nozzle, A difference occurs in the damping ratio detected from the residual vibration.

  As can be seen from FIG. 17A, the frequency decreases and the amplitude decreases as the nozzle diameter increases as in the waveform b3 (Am1-3), and the frequency increases and the amplitude decreases as the nozzle diameter decreases as in the waveform b1. Increases (Am1-1).

  Therefore, in the embodiment of the present invention, when residual vibration is generated in order to find a defect in the ink in the nozzle, the state detection waveform to be applied is corrected according to the nozzle diameter of the nozzle, thereby more accurately. The ink state for each nozzle is detected.

  Here, the relationship between the shape of the state detection waveform for detecting an abnormal state and the generated residual vibration will be described. As an example, a correction method when a trapezoidal waveform is used as the state detection waveform will be described below. It is known that there is a proportional relationship with the trapezoidal waveform frequency (peak width (pulse width) tp) and the residual vibration speed.

  FIG. 17B shows the residual vibration waveform when the state detection waveform corrected according to the nozzle diameter is applied.

  In the trapezoidal wave, the meniscus is pulled inward by the piezoelectric element contracting due to the falling waveform. Thereafter, due to the rising waveform, the piezoelectric element expands, whereby a droplet is ejected or the meniscus is pushed outward.

As described above, when the natural vibration periods of the pressure chamber 27 determined by the nozzle diameter are Tc1, Tc2, and Tc3, respectively, the ratio of the pulse width tp to the period Tc is set to equalize the amplitude of the generated residual vibration. To be equal,
tp1 / Tc1 = tp2 / Tc2 = tp3 / Tc3 (5)
It may be set so as to hold.

  Therefore, if the timing of the rising waveform is the same, the peak width tp becomes longer as it falls earlier (tp1 <tp2 <tp3). Therefore, in order to increase the peak width tp, the frequency is slowed down. .

  Specifically, for a nozzle having a small nozzle diameter D where the frequency is high and the cycle is short as in the waveform b1 of FIG. 17A, the cycle is short so that the peak width tp1 of (B) is short. A state detection waveform d1 having a high frequency is applied.

  On the other hand, for a nozzle having a large nozzle diameter D having a low frequency and a long cycle as shown by a waveform b3 in FIG. 17A, a state detection in which the cycle is long and the frequency is low so that the peak width tp3 is long. Application waveform d3 is applied.

  As described above, when it is assumed that the residual vibration varies according to the variation in the nozzle diameter as shown in FIG. 17A, the variation due to the nozzle diameter (the natural vibration frequency of the pressure chamber) is grasped in advance. The peak width tp of the trapezoidal wave may be adjusted by adjusting the frequency as shown in B).

  The nozzle diameter for each nozzle is stored in advance in the nozzle eigenvalue storage means 213, the waveform control unit 216 of the control unit 211 corrects the detection waveform (detection reference waveform (data)), and is generated by the waveform generation unit 212. A state detection waveform to be applied to the piezoelectric element 35 is created.

  Alternatively, a state detection waveform having a different peak width tp may be prepared in advance, and the state detection waveform may be adjusted by selecting a state detection waveform for each corresponding nozzle diameter.

  As shown in FIG. 17B, when a state detection waveform with a corrected peak width is applied according to the nozzle diameter, the first half wave, the second half wave, and the third half wave of the residual vibration are applied. Each amplitude value (Am1 ′, Am2 ′, Am3 ′) does not vary between waveforms having different nozzle diameters.

  Since the frequency of residual vibration is the natural vibration frequency Tc of the pressure chamber 27 determined by the nozzle diameter as described above, the frequency may remain different. Even if the frequencies are different, the attenuation ratio can be calculated when the amplitudes are equal. Therefore, the nozzle state can be accurately detected by adjusting (correcting) the peak width tp of the waveform to be applied (detection reference waveform) by changing the frequency in accordance with the nozzle diameter described above. is there.

((Correction by capacitance))
FIG. 18 is a diagram illustrating waveform control of a state detection waveform when the capacitance of the piezoelectric element varies when the nozzle conditions (temperature, ink viscosity, etc.) are constant.

  FIG. 18A shows the residual vibration waveform when the capacitance of the piezoelectric element varies, and FIG. 18B shows the residual vibration when the state detection waveform corrected according to the capacitance of the piezoelectric element is applied. Waveform is shown.

  In FIG. 18A, a waveform a2 is a residual vibration waveform when the capacitance C of the piezoelectric element is a predetermined value (standard value). In this case, the waveform a1 shows the residual vibration waveform when the electrostatic capacitance C of the piezoelectric element is smaller than a predetermined value, and the waveform a3 shows the residual vibration waveform when the electrostatic capacitance C of the piezoelectric element is larger than the predetermined value.

As shown in (A), when the capacitance C of the piezoelectric element varies, the amplitude value in the residual vibration varies. Specifically, since the piezoelectric element has a function as a capacitor having electrostatic capacity, when a driving waveform having the same capacitance (C) and voltage (amplitude Vpp) is applied, the piezoelectric element 35 generates an angular velocity (ω). The residual vibration amplitude Amp is
Amp = ωCVpp (6)
Can be set.

  Therefore, as can be seen from the above equation (6) and FIG. 18A, the larger the electrostatic capacitance C of the piezoelectric element, the larger the amplitude value of the generated residual vibration (waveform a3), and the smaller the electrostatic capacitance C becomes. The amplitude of the residual vibration becomes small (waveform a1).

  Therefore, in the embodiment of the present invention, when residual vibration is generated in order to find a defect in the ink in the nozzle, the state detection waveform to be applied is arranged for each nozzle so as to face the nozzle. By correcting from the reference waveform for detection according to the capacitance of ˜35x, the ink state for each nozzle is detected more accurately.

  Here, the relationship between the shape of the state detection waveform used for detecting the residual vibration and the generated residual vibration will be described. As an example, a correction method when a trapezoidal waveform is used as the state detection waveform will be described below. It has been found that the amplitude Vpp of the trapezoidal waveform is proportional to the intensity of residual vibration.

  FIG. 18B shows a control example in which the corrected waveform is applied to a nozzle having an appropriate capacitance of a piezoelectric element.

  The larger the voltage amplitude Vpp of the trapezoidal waveform of the state detection waveform to be applied (Vpp1 <Vpp2 <Vpp3), the larger the contraction / expansion operation of the piezoelectric element, the larger the amplitude of the residual vibration that occurs.

  Therefore, in order to equalize the amplitude of the generated residual vibration, when the same voltage is applied, the amplitude of the residual vibration (Amp) proportional to the size of the capacitance C and the trapezoidal waveform of the state detection waveform What is necessary is just to set so that the magnitude of amplitude Vpp may be reversed.

  Specifically, the amplitude Vpp1 of the trapezoidal waveform of (B) with respect to a nozzle having a small electrostatic capacitance C of the piezoelectric element and a small amplitude (Amp-1) as in the waveform a1 shown in FIG. Is applied to the state detection waveform c1.

  On the contrary, the amplitude Vpp3 of the trapezoidal waveform of (B) is small for a nozzle having a large capacitance C of the piezoelectric element and a large amplitude (Amp-3) as shown by a waveform a3 shown in FIG. A state detection waveform c3 is applied.

  As shown in FIG. 18A, when it is assumed that the residual vibration varies depending on the variation in the capacitance of the piezoelectric element, the variation in the capacitance C of the piezoelectric element is grasped in advance and shown in FIG. Thus, the trapezoidal wave amplitude Vpp may be adjusted. The capacitance of the piezoelectric element for each nozzle is stored in advance in the nozzle eigenvalue storage unit 213, and the waveform (reference waveform for detection) is corrected by the waveform control unit 216 of the control unit 211.

  As described above, when the state detection waveform to be applied is applied according to the capacitance of the piezoelectric element, the generated residual vibration waveform does not vary. Thereby, it is possible to detect a nozzle state correctly.

  Alternatively, as shown in FIG. 18B, detection waveforms having different amplitudes Vpp may be prepared, and the detection waveform may be adjusted by selecting the detection waveform for each corresponding nozzle diameter.

  In the examples of FIGS. 17 and 18, the example in which either the nozzle diameter or the capacitance of the piezoelectric element varies has been described, but in actuality, both the nozzle diameter and the capacitance of the piezoelectric element may vary. . Therefore, it is preferable to adjust both the frequency (peak width) and the amplitude Vpp of the trapezoidal waveform that becomes the state detection waveform.

  Here, as an example of correction, a method of calculating based on a table storing a state detection waveform from the nozzle diameter and the piezoelectric capacitance will be described.

  FIG. 19 is a table illustrating the amplitude and frequency correction rate of the state detection waveform according to the nozzle diameter and the capacitance of the piezoelectric element. The vertical length of the table is the capacitance C of the piezoelectric element, and the horizontal length is the nozzle diameter D.

  In the results derived from these eigenvalues, the upper cell indicates the amplitude Vpp in the state detection waveform, and the lower cell indicates the correction factor for the frequency f. From this table, the frequency and amplitude correction factors in the state detection waveform for detecting residual vibration can be derived.

  The average value constituting the reference waveform data for detection is a nozzle diameter of D4 and a capacitance of C4 in the table. At this time, the correction factor is 1. As an example of the correction rate derivation using this table, when the nozzle diameter is D5 and the capacitance is C2, the frequency correction rate in the state detection waveform data is 0.9, and the amplitude correction rate is 1.45. It becomes. Similarly, when the nozzle diameter is D2 and the capacitance is C5, the frequency correction rate in the state detection waveform is 1.2, and the amplitude correction rate is 0.75.

  By controlling using the table in this way, the vibration frequency and amplitude are grasped from the nozzle diameter, capacitance, etc., and the state detection waveform for each nozzle obtained from this vibration frequency is used. Each abnormal state can be detected with high accuracy.

  FIG. 20 is an example of a residual vibration waveform when a state detection waveform is applied, corrected based on the table shown in FIG.

  For example, in FIG. 19, when the nozzle diameter is D4 and the capacitance is C4 as shown at the center, a detection reference waveform having {frequency 1f, trapezoidal waveform amplitude 1Vpp} is applied.

  As shown in the upper left of FIG. 19, when nozzle diameter = D2 and capacitance = C2, the nozzle diameter is small, so the frequency is high, and the capacitance is small, so the amplitude is small. Therefore, as shown in FIG. 20, a state detection waveform of {frequency 1.2f, trapezoidal waveform amplitude 1.45Vpp} obtained by correcting the detection reference waveform is applied.

  For example, in FIG. 19, when the nozzle diameter is D5 and the capacitance is C5, the frequency is low because the nozzle diameter is large and the amplitude is large because the capacitance is large. Therefore, as shown in FIG. 20, a state detection waveform of {frequency 1.2f, trapezoidal waveform amplitude 1.45Vpp} obtained by correcting the detection reference waveform is applied.

<Second Embodiment>
In this embodiment, unlike the first embodiment, the nozzle eigenvalue storage means 213 (see FIG. 12) is calculated based on the residual vibration waveform detected after applying the standard waveform (eigenvalue detection waveform), not in advance. The nozzle unique value is stored.

  Specifically, the waveform generation unit 212 applies a predetermined standard waveform to the piezoelectric element 35 in a normal nozzle state before abnormality occurs, and the residual vibration detection unit 240 applies the standard waveform to the piezoelectric element. Later, residual vibration generated in the liquid in the pressure chamber 27 is detected. And the calculating part 37 calculates the eigenvalue for every nozzle based on the said residual vibration generated after the application of the said standard waveform.

  In this case, the calculated eigenvalue for each nozzle is a damping ratio of residual vibration generated after application of the standard waveform and / or a frequency of the residual vibration.

  For example, as described above, when the unique value of the nozzle at the time of manufacture is stored in advance as in the first embodiment, for example, the value measured at the standard temperature is stored. However, if the temperature of the ink changes due to a change in the outside air, the behavior of residual vibration differs even with the same ink. In such a case, it is more preferable to apply a state detection vibration to detect the residual vibration by applying a standard waveform and reset the eigenvalue for each nozzle before detecting the residual vibration waveform.

  Then, the waveform control unit 216 corrects the detection reference waveform data according to the calculated unique value for each nozzle, and generates state detection waveform data. Then, the waveform generation unit 212 generates a state detection waveform based on the state detection waveform data and applies it to the piezoelectric element 35.

  FIG. 21 is a flowchart for explaining a flow for acquiring eigenvalues for each nozzle in the second embodiment of the present invention.

  First, the control unit 211 (drive control unit 215) designates the first nozzle (S1).

  The waveform generator 212 applies a predetermined standard waveform to the designated nozzle (corresponding to the piezoelectric element 35x), and the residual vibration detector 240 detects the residual vibration (S2).

  Next, the calculation unit 217 of the control unit 211 calculates and obtains the attenuation ratio and frequency of the residual vibration waveform generated after the application of the standard waveform, and stores it as the eigenvalue in the nozzle eigenvalue storage unit 213 (S3).

  This is repeated until eigenvalues for each nozzle are obtained for all nozzles (for α) (S4, S5).

  In this way, by calculating and obtaining the unique value for each nozzle, the shape of the nozzle of the ink jet recording head generated after manufacture, the secular change (deterioration) of the capacitance of the piezoelectric element, and the temperature change are also taken into consideration. It is possible to determine the status abnormality. Therefore, it is possible to determine the abnormality with higher accuracy.

  Here, as an example, a method for correcting the state detection waveform from the frequency and amplitude of the residual vibration detected in advance is shown using a table. FIG. 22 is a table illustrating the correction factor of the state detection waveform according to the frequency and damping ratio of the residual vibration waveform of the eigenvalue detection waveform.

  In FIG. 22, the vertical length of the table is the residual vibration attenuation ratio detected, and the horizontal frequency is the detected residual vibration frequency. In the results derived from these eigenvalues, the upper cell is the amplitude in the state detection waveform, and the lower cell is the correction factor for the frequency. From this table, the frequency and amplitude correction factors in the applied state detection waveform can be derived.

  The average value is the period T4 in the detected residual vibration and the damping ratio ζ4 in the residual vibration in the table. At this time, the correction factor is 1.

  As an example of deriving the correction factor using this table, when the detected period Td of the residual vibration waveform of the eigenvalue detection waveform (standard waveform) is T2 and the damping ratio is ζ5, the frequency f in the state detection waveform is The correction rate is 1.2, and the amplitude correction rate is 0.75.

  Similarly, when the period Td of the residual vibration waveform of the eigenvalue detection waveform is T5 and the damping ratio is ζ2, the correction rate of the frequency f in the state detection waveform is 0.9, and the correction rate of the amplitude Vpp is 0. 75.

  FIG. 23 is a diagram illustrating waveform control of the state detection waveform according to the residual vibration waveform of the eigenvalue detection waveform. (A) shows a residual vibration waveform when the same state detection waveform (standard waveform) is applied to a plurality of nozzles. (B) is the output waveform from the comparator at the time of acquiring the waveform of (A) (from the rise of the second mountain to the rise of the third mountain), (C) is corrected from the waveform detected by the residual vibration in (A) 6 is a residual vibration waveform when the state detection waveform is applied.

  In FIG. 23A, a waveform e2 is a residual vibration waveform at the nozzle set as a target value, and waveforms e1 and e3 are residual vibration waveforms at nozzles with large variations. FIG. 23A shows that the amplitude of the residual vibration waveform varies. The attenuation ratio calculated from the amplitude of the waveform in FIG. 23A has a large e1 attenuation ratio and a small e3 attenuation ratio. For example, referring to the correlation table in FIG. 22 for the waveform in FIG. 23A, the waveform e1 has an attenuation rate ζ5 (large), the waveform e2 has an attenuation rate ζ4 (standard), and the waveform e3 has The attenuation rate is ζ2 (small).

  Further, FIG. 22B shows a result of detecting periods Td1, Td2, and Td3 by the comparator 243 (see FIGS. 12 and 13). Since the detected period is Td1 (waveform e1) <Td2 (waveform e2) <Td3 (waveform e3), the frequency of the residual vibration waveform is f (waveform e1)> f2 (waveform e2)> f1 (waveform e3). I understand that. For example, referring to the correlation table of FIG. 22 for the waveform of FIG. 23B, the waveform e1 has a cycle Td1 = T2 (short), the waveform e2 has a cycle Td2 = T4 (standard), and the waveform e3. Is the cycle Td3 = T5 (long).

  In the nozzle that has detected the waveforms e1 and e3, in order to make the detected waveform equal to the waveform e2, the waveform detected by the residual vibration is recorded in the nozzle-specific eigenvalue storage unit 213 and corrected by the drive waveform generator 212. By applying the waveform e′1 and the waveform e′3, which are detection waveforms, it is possible to accurately detect the nozzle state.

  FIG. 23C is an example of a residual vibration waveform when a waveform for state detection is applied by correcting the waveform of FIG. 23A based on the table shown in FIG.

  For example, the waveform e2 shown in FIG. 22 (A) has a frequency of residual vibration detected as shown in the center of FIG. 22 = T4 and a damping ratio = ζ4, so {frequency 1f, amplitude of trapezoidal waveform A reference waveform for detection (e2 ′) of 1 Vpp} is applied as a state detection waveform.

  The waveform e1 in FIG. 23A has a short residual vibration period T2 and a large damping ratio ζ5. Therefore, as shown in FIG. 23C, a state detection waveform (e1 ′) of {frequency 1.2f, trapezoidal waveform amplitude 0.75 Vpp} obtained by correcting the detection reference waveform is applied.

  Further, in the waveform e1 in FIG. 23A, the period of the residual vibration is long and short T5, and the damping ratio is large and ζ2. Therefore, as shown in FIG. 23C, a state detection waveform (e3 ′) of {frequency 0.9f, trapezoidal waveform amplitude 1.45 Vpp} obtained by correcting the detection reference waveform is applied.

  In this way, the characteristic value for each nozzle is generated separately from the state detection waveform to generate residual vibration and the calculated value is obtained using a table, so that the shape of the nozzle of the inkjet recording head generated after manufacture and the capacitance of the piezoelectric element An abnormal state can be determined in consideration of the secular change (deterioration) and temperature. Therefore, it is possible to determine the abnormality with higher accuracy.

  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 Vibration plate (vibration plate)
35 Piezoelectric Element 200 Inkjet Recording Head Module (Droplet Discharge Device)
211 Control unit 212 Drive waveform generation unit (waveform generation unit)
213 Eigenvalue storage means (storage means) for each nozzle
214 Attenuation ratio data storage means 215 Drive control unit 216 Waveform control unit (detection waveform control unit)
217 Calculation unit 218 Determination unit 240 Residual vibration detection unit

Japanese Patent Laid-Open No. 10-11068 JP 2007-001028 A

Claims (13)

Multiple nozzles,
A plurality of pressure chambers respectively communicating with the plurality of nozzles and containing a liquid;
A plurality of piezoelectric elements provided corresponding to the plurality of nozzles, respectively, and arranged to face the plurality of pressure chambers via the diaphragm,
Waveform generation that generates a state detection waveform based on the state detection waveform data and applies it to the piezoelectric element in order to generate residual vibration in the pressure chamber and detect the state of the liquid in the nozzle or the pressure chamber And
Storage means for storing the nozzle diameter for each nozzle as a unique value for each nozzle ;
A controller that corrects reference waveform data for detection according to the nozzle diameter of each nozzle and generates the waveform data for state detection used in the waveform generator;
Droplet discharge device. Multiple nozzles,
A plurality of pressure chambers respectively communicating with the plurality of nozzles and containing a liquid;
A plurality of piezoelectric elements provided corresponding to the plurality of nozzles, respectively, and arranged to face the plurality of pressure chambers via the diaphragm,
Waveform generation that generates a state detection waveform based on the state detection waveform data and applies it to the piezoelectric element in order to generate residual vibration in the pressure chamber and detect the state of the liquid in the nozzle or the pressure chamber And
Storage means for storing the capacitance of each piezoelectric element as a specific value for each nozzle;
A control unit that corrects the reference waveform data for detection according to the capacitance of each piezoelectric element corresponding to each nozzle and generates the waveform data for state detection used in the waveform generation unit; Prepare
Droplet discharge device. Multiple nozzles,
A plurality of pressure chambers respectively communicating with the plurality of nozzles and containing a liquid;
A plurality of piezoelectric elements provided corresponding to the plurality of nozzles, respectively, and arranged to face the plurality of pressure chambers via the diaphragm,
Waveform generation that generates a state detection waveform based on the state detection waveform data and applies it to the piezoelectric element in order to generate residual vibration in the pressure chamber and detect the state of the liquid in the nozzle or the pressure chamber And
Storage means for storing the nozzle diameter and the capacitance of the piezoelectric element as the eigenvalue for each nozzle;
According to the nozzle diameter for each nozzle and the electrostatic capacity for each piezoelectric element corresponding to each nozzle, the reference waveform data for detection is corrected, and the waveform data for state detection used in the waveform generation unit is corrected. Generating a control unit,
Droplet discharge device. Multiple nozzles,
A plurality of pressure chambers respectively communicating with the plurality of nozzles and containing a liquid;
A plurality of piezoelectric elements provided corresponding to the plurality of nozzles, respectively, and arranged to face the plurality of pressure chambers via the diaphragm,
Waveform generation that generates a state detection waveform based on the state detection waveform data and applies it to the piezoelectric element in order to generate residual vibration in the pressure chamber and detect the state of the liquid in the nozzle or the pressure chamber And
Storage means for storing eigenvalues for each nozzle;
A control unit that corrects reference waveform data for detection according to the eigenvalue for each nozzle and generates the waveform data for state detection used in the waveform generation unit;
A residual vibration detector,
An arithmetic unit,
The waveform generator applies a predetermined standard waveform to the piezoelectric element in a normal nozzle state,
The residual vibration detection unit detects the residual vibration generated in the liquid in the pressure chamber after applying the standard waveform to the piezoelectric element,
The calculation unit calculates a specific value for each nozzle based on the residual vibration generated after application of the standard waveform,
The control unit generates the state detection waveform data by correcting the reference waveform data for detection according to the calculated eigenvalue for each nozzle.
Droplet discharge device. The calculated eigenvalue for each nozzle is a damping ratio of the residual vibration generated after application of the standard waveform.
The droplet discharge device according to claim 4 . The calculated characteristic value for each nozzle is a frequency of the residual vibration generated after application of the standard waveform.
The droplet discharge device according to claim 4 . A residual vibration detector for detecting the residual vibration generated in the liquid in the pressure chamber;
An arithmetic unit that calculates a detection value based on the detected residual vibration,
Based on the detection value calculated based on the residual vibration in the pressure chamber generated after applying the state detection waveform to the piezoelectric element, it is determined whether there is an abnormality in the nozzle or the liquid in the pressure chamber. the apparatus according to any one of claims 1 to 6 further comprising a determination unit, a. The detection value used for determination in the determination unit is an attenuation ratio calculated by the calculation unit based on the residual vibration generated after application of the state detection waveform.
The liquid droplet ejection apparatus according to claim 7 . The detection value used for determination in the determination unit is a frequency calculated by the calculation unit based on the residual vibration generated after application of the state detection waveform.
The liquid droplet ejection apparatus according to claim 7 . The storage means stores a correlation table between the eigenvalue for each nozzle and the waveform for state detection,
The control unit corrects the detection reference waveform data according to the correlation table to obtain the state detection waveform data.
What Re or liquid ejecting device according to one of claims 1 to 9. A droplet discharge device according to any one of claims 1 to 10 , comprising:
Image forming apparatus. A method for controlling a droplet discharge device according to any one of claims 1 to 10 ,
Generating reference waveform data for detection;
According to the nozzle diameter for each nozzle as the eigenvalue for each nozzle , correcting the reference waveform data for detection and generating waveform data for state detection;
Generating a state detection waveform based on the state detection waveform data and applying the waveform to the piezoelectric element;
Detecting a state by causing residual vibration of the liquid in the pressure chamber by the state detection waveform; and
A method for controlling a droplet discharge device. A program to be executed by the droplet discharge device according to any one of claims 1 to 10 ,
Processing for generating reference waveform data for detection;
According to the nozzle diameter for each nozzle as the eigenvalue for each nozzle , processing for correcting the reference waveform data for detection and generating waveform data for state detection;
Processing for generating a state detection waveform based on the state detection waveform data and applying the waveform to the piezoelectric element;
And a process for detecting a state by causing residual vibration of the liquid in the pressure chamber by the state detection waveform.

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