JP2009148974A - Discharge state detector, liquid-droplet discharger, and discharge state detection program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge state detector which can detect the state of a liquid-droplet discharge means from the current value of drive power without altering a circuit for driving the liquid-droplet discharge means, and to provide a liquid-droplet discharger and a discharge state detection program. <P>SOLUTION: When the state of a discharge nozzle for discharging a liquid-droplet from a discharge port communicating with a pressure chamber and the outside thereof is detected by varying the pressure in a pressure chamber for containing liquid by means of a piezoelectric element 62C, a substrate voltage VDD being applied to a CMOS inverter circuit 52 for switching a voltage being applied to the piezoelectric element 62C is switched to a voltage VDD2 which is lower than a substrate voltage VDD1 at the time of image recording to apply a detection waveform to a CMOS inverter circuit 52, and a physical quantity corresponding to the current value Is of power being supplied to the CMOS inverter circuit 52 at a drive voltage VH2 is detected to derive a variation period of the current value Is from the detection result, so that a determination is made that a liquid-droplet discharge means is not in a normal state if the variation period thus derived does not satisfy preset conditions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, as a droplet discharge device, for example, there is an ink jet recording head incorporated in an image recording device. In an inkjet recording head, a part of a wall constituting a pressure chamber for containing ink droplets is configured as a deformable diaphragm, and the diaphragm is deformed by a piezoelectric element, and pressure is applied from a nozzle communicating the pressure chamber and the outside. There is one that ejects liquid droplets in a room.

  The driving of the piezoelectric element can be classified into an analog waveform driving and a rectangular wave driving depending on a driving voltage application method. In the analog waveform driving, the voltage applied to the piezoelectric element can be freely changed, so that fine discharge control can be executed. On the other hand, in the rectangular wave driving, since the circuit can be reduced in size, the image recording apparatus has been downsized in recent years, and the rectangular wave driving inkjet recording head has been attracting attention.

  In this type of ink jet recording head, ejection cannot be performed normally due to a change in the state of the head, such as air bubbles entering the pressure chamber from the nozzle or the viscosity of the ink adhering to the nozzle surface increasing. Discharge state) occurs.

  Conventionally, it has been proposed to detect a non-ejection state from a change in the resonance frequency of a piezoelectric element in an analog-driven recording head (see, for example, Patent Document 1). In Patent Document 1, it is proposed that the input voltage is a sine wave and is compared with the output voltage on the low potential side of the piezoelectric element in order to detect a change in the resonance frequency.

  In the case of rectangular wave drive, the drive circuit is configured by a switching circuit that turns on and off the voltage. This switching circuit is generally designed to have a high on-resistance because it is designed so that ejection can be performed satisfactorily according to the ejection characteristics of the head.

Conventionally, as a technique for controlling on-resistance, a technique that uses a constant current control (current mirror) system to drive regardless of a change in on-resistance (see, for example, Patent Document 2) or a resistance switching system is used. Have been proposed (for example, see Patent Documents 3 to 5).
JP 2005-355100 A JP 2002-316414 A JP 2002-178510 A JP 2003-276188 A JP 2002-094346 A

  The present invention relates to a discharge state detection device, a droplet discharge device, and a discharge state capable of detecting the state of a droplet discharge unit based on a current value of driving power without changing the configuration of a drive circuit for driving the droplet discharge unit The purpose is to provide a detection program.

  According to a first aspect of the present invention, there is provided a droplet discharge means for discharging a droplet from a discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber in which the liquid is accommodated by a driving element. First power supply means for supplying power at a substrate voltage level to a drive circuit having a switching element for switching a voltage level applied to the drive element; and power at a drive voltage level lower than the substrate voltage level for the drive circuit. A second power supply means for supplying, a detection means for detecting a physical quantity according to a current value of power supplied from the second power supply means to the drive circuit, and a detection waveform applied to the switching element. A state in which a change period of the current value is derived based on a detection result by the detection unit, and when the derived change period does not satisfy a preset condition, it is detected that the droplet discharge unit is not in a normal state. When detecting the state of the droplet discharge means by the detection means, the first switching means for switching the voltage level of the power supplied to the drive circuit by the first power supply means, and the state detection means, The first switching means is controlled to switch the substrate voltage level of the power supplied to the drive circuit to a substrate voltage level lower than the substrate voltage level supplied when performing droplet ejection using the droplet ejection means. And a control means.

  According to a second aspect of the present invention, in the ejection state detecting device according to the first aspect, the switching element is a CMOS inverter circuit configured by a pair of pMOS transistors and an nMOS transistor, and the first power supply means is a pMOS Power is supplied to the back gate of the transistor, and the second power supply means supplies power to the source of the pMOS transistor.

  According to a third aspect of the present invention, there is provided the discharge state detecting device according to the first or second aspect, further comprising second switching means for switching a voltage level of power supplied to the drive circuit by the second power supply means. The control means is configured to reduce the drive voltage level when the substrate voltage level is lowered so that the difference between the substrate voltage level and the drive voltage level becomes a predetermined potential. The switching means and the second switching means are controlled.

  A fourth aspect of the present invention is the ejection state detection device according to any one of the first to third aspects, wherein the drive circuit drives each of the drive elements of the plurality of droplet ejection means, The control means sequentially drives the drive elements of the plurality of droplet discharge means one by one by the drive circuit when the state detection means detects the state of the droplet discharge means, and the state detection means Thus, the state detection for each droplet discharge means is controlled to be executed sequentially.

  According to a fifth aspect of the present invention, there is provided a droplet discharge means for discharging a droplet from a discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber in which the liquid is stored by a driving element. A drive circuit having a switching element for switching a voltage level applied to the drive element; first power supply means for supplying power at a substrate voltage level to the drive circuit; and Second power supply means for supplying power at a low drive voltage level, detection means for detecting a physical quantity corresponding to a current value of power supplied from the second power supply means to the drive circuit, and the switching element A change waveform of the current value is derived based on the detection result by the detection means by applying a detection waveform to the liquid crystal, and when the derived change period is included in a preset normal period, the droplet discharge means is correct. A state detecting means for detecting that the current is in a state, a first switching means for switching a voltage level of power supplied to the drive circuit by the first power supply means, and a droplet discharge means by the state detecting means. When detecting the state, the substrate voltage level of the electric power supplied to the drive circuit is switched to a substrate voltage level lower than the substrate voltage level supplied when the droplet discharge using the droplet discharge means is executed. Control means for controlling the first switching means.

  According to a sixth aspect of the present invention, there is provided a droplet discharge means for discharging a droplet from a discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber in which the liquid is accommodated by a driving element. When detecting the state of the substrate, the substrate voltage level supplied to the computer when the droplet discharge using the droplet discharge means is executed is applied to the switching element that switches the voltage applied to the drive element. A voltage switching step for switching to a lower voltage level, applying a detection waveform to the switching element, and detecting a physical quantity corresponding to a current value of power supplied to the drive circuit at a drive voltage level lower than the substrate voltage level A change period of the current value is derived based on the detection step and the detection result, and when the derived change period does not satisfy a preset condition, the droplet discharge means corrects. State detection step of detecting a non-state, thereby executing.

  According to the first aspect of the present invention, the state of the droplet discharge means can be detected based on the current value of the drive power without changing the configuration of the drive circuit for driving the drive circuit.

  According to the second aspect of the present invention, the state of the droplet discharge means can be detected based on the current value of the drive power without changing the configuration of the drive circuit for the droplet discharge means using the CMOS inverter circuit.

According to the invention described in claim 3, the state detection can be executed so that the droplets are not discharged even if the substrate voltage level is changed. According to the invention described in claim 4, a plurality of droplets are discharged by one drive circuit. Even when the means is controlled, the state detection can be executed for each discharge means.

  According to the fifth aspect of the present invention, the state of the droplet discharge means can be detected based on the current value of the driving power without changing the configuration of the drive circuit for driving the droplet discharge means.

  According to the sixth aspect of the invention, it is possible to detect the state of the droplet discharge means based on the current value of the drive power without changing the configuration of the drive circuit for driving the droplet discharge means.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows the configuration of an image recording apparatus 10 according to the first embodiment. As shown in FIG. 1, the image recording apparatus 10 includes a paper feed tray 20 and a paper discharge tray 22 and a plurality of rollers 24.

  The recording paper P is accommodated in the paper feed tray 20, and when recording an image, the recording paper P in the paper feed tray 20 is taken out one by one by the roller 24 to pass through the image recording apparatus 10 in a predetermined transport path F. Are discharged to the discharge tray 22.

  In the conveyance path F of the recording paper P, a conveyance belt 14 stretched between a drive roll 11 that rotates in the direction of arrow E and a driven roll 12 that rotates as the drive roll 11 rotates, and an adsorber 16 are disposed. The adsorber 16 presses the recording paper P conveyed on the conveying path F against the conveying belt 14, applies electric charges to the recording paper P, and electrostatically adsorbs the recording paper P to the conveying belt 14.

  A registration roll 26 is disposed on the upstream side of the conveyance belt 14 in the conveyance path F of the recording paper P. The registration roll 26 performs paper skew correction to prevent the recording paper P transported along the transport path F from being attracted to the transport belt 14 in a distorted state in the transport direction.

  Further, in the conveyance path F of the recording paper P, yellow (Y), magenta (M), cyan (C), black (black) at positions facing the recording surface of the recording paper P electrostatically attracted to the conveyance belt 14. A recording head array 18 including four recording heads 18Y, 18M, 18C, and 18K for ejecting ink of four colors K) is provided.

  Each of the recording heads 18Y, 18M, 18C, and 18K for each color has a plurality of head units each having a plurality of ejection nozzles 62 (not shown in the figure, see FIG. 3) arranged over the entire width direction of the conveying belt 14. The discharge nozzle 62 is of the FWA (Full Width Array) type.

  In the following description, the members provided for each color are indicated by adding alphabets (Y / M / C / K) indicating the respective colors to the end of the reference numerals, but will be described without particularly distinguishing the colors. In this case, the explanation will be made by omitting the alphabet at the end of the code.

  Also, as shown in the figure, the image recording apparatus 10 according to the present embodiment is configured to include a front / back reversing conveyance path R. When performing double-sided printing, after forming an image on one side, the recording paper P is transported along the transport path R so that the back side of the surface on which the image is formed is placed on each recording head 18Y, 18M, 18C, 18K. Turn the front and back so that they face each other.

  In addition, ink tanks 19Y, 19M, 19C, and 19K are provided between the conveyor belt 14 and the paper discharge tray 22 to store the inks of the respective colors. The ink in the ink tanks 19Y, 19M, 19C, and 19K is supplied to the recording heads 18Y, 18M, 18C, and 18K via an ink supply pipe (not shown).

  In addition, examples of inks that can be used in the image recording apparatus 10 shown in FIG.

  Here, the recording heads 18Y, 18M, 18C, and 18K are configured to be separated from the transport belt 14 by a drive mechanism (not shown).

  Furthermore, maintenance devices 28A and 28B are provided on the upstream side and the downstream side of the transport path F of the recording heads 18Y, 18M, 18C, and 18K, respectively. The maintenance device 28A includes maintenance units 30K and 30C for black and cyan, and the maintenance device 28B includes maintenance units 30M and 30Y for magenta and yellow. Each of the maintenance devices 28A and 28B is configured to be movable in a direction approaching each other by a drive mechanism (not shown).

  As shown in FIG. 2, the recording heads 18Y, 18M, 18C, and 18K are moved away from the conveying belt 14 during maintenance. Further, at the time of maintenance, the maintenance devices 28A, 28B are moved to the space between the recording heads 18Y, 18M, 18C, 18K generated by the separation movement of the recording heads 18Y, 18M, 18C, 18K and the conveying belt 14.

  As a result, the maintenance units 30Y, 30M, 30C, and 30K of the maintenance devices 28A and 28B are opposed to the four recording heads 18Y, 18M, 18C, and 18K of the recording heads 18Y, 18M, 18C, and 18K, respectively. The maintenance process is executed as appropriate.

  The maintenance process executed by the maintenance unit 30 includes suction of ink liquid in the discharge nozzle 62, wiping of ink droplets attached to the discharge port 62A of the discharge nozzle 62, supply of ink liquid into the discharge nozzle 62, and the like. Can be given.

  FIG. 3 is a cross-sectional view of the discharge nozzle 62 of the recording head 18 according to the present embodiment. As shown in the figure, the discharge nozzle 62 includes a discharge port 62A, a pressure chamber 62B, a piezoelectric element 62C, a pressure adjustment plate 62D, and an ink supply path 62E.

  An appropriate amount of ink is supplied to the pressure chamber 62B from the ink tank 19 of the color corresponding to each recording head 18 via the ink supply path 62E, and is temporarily stored. The pressure chamber 62B communicates with the outside via the discharge port 62A.

  Further, a part of the wall surface of the pressure chamber 62B is configured as a pressure adjustment plate 62D that is deformed when a pressing force or pressure is applied, and a piezoelectric element 62C is attached to the pressure adjustment plate 62D.

  The piezoelectric element 62C has a property of changing its shape when a voltage is applied. By using this property, a voltage is applied to the piezoelectric element 62C to change the pressing force on the pressure adjusting plate 62D. The volume in the pressure chamber 62B is contracted or expanded.

  By thus changing the volume in the pressure chamber 62B, a vibration wave (pressure wave) is generated in the ink. This vibration wave vibrates the liquid level of the ink discharge port 62A, thereby discharging an ink droplet from the discharge port 62A.

  The image recording apparatus 10 includes a motor (not shown) for driving the roller 24, the drive roll 11, the maintenance device 28, and the like. These motors are driven by a control unit (not shown) that controls the entire apparatus via a conveyance system drive control circuit (not shown) that controls the conveyance and maintenance operations of the recording paper P.

  FIG. 4 is a functional block diagram schematically showing the configuration of the recording head control device 40 of the image recording apparatus 10 according to the present embodiment. The recording head control device 40 is provided by the number of the recording heads 18 such as the recording head control devices 40Y, 40M, 40C, and 40K. Description will be made with the reference numerals omitted.

  As shown in the figure, the recording head control device 40 includes a CPU (central processing unit) 42 that controls the operation of the entire recording head 18 and a control memory 44. The CPU 42 and the control memory 44 are each connected to the bus 41.

  The control memory 44 includes a ROM (Read Only Memory) and a RAM (Random Access Memory). The control memory 44 stores various control programs of the recording head control device 40 executed by the CPU 42 and various parameters used for executing the programs. It is stored and used as a work area for the CPU 42.

  The CPU 42 drives the recording head 18 by executing various programs stored in the control memory 44 based on instructions from a control unit (not shown) that controls the operation of the entire apparatus.

  In addition, the recording head control device 40 includes an image memory 46 that stores recording data generated based on image data to be subjected to image recording processing, and a piezoelectric element provided in each discharge nozzle 62 provided in the recording head 18. And a nozzle selection circuit 48 for independently controlling each piezoelectric element 62C using a drive circuit 50 for driving the element 62C. These image memory 46 and nozzle selection circuit 48 are also connected to the bus 41.

  In this embodiment, since the FWA type recording head 18 is used, a plurality of drive circuits 50 are actually connected to the recording head control device 40, but here, the explanation is not complicated. Therefore, one drive circuit 50 will be taken up and described.

  The image memory 46 stores recording data for image recording that is created by a recording data control unit that is controlled by a general control unit (not shown) and that is input to the recording head control device 40. As this recording data, for example, multi-gradation (for example, 256 gradations) image data to be image-recorded is converted into image data for each CMYK color by color conversion. The image data for each CMYK color obtained by the color conversion is converted (quantized) into dot data of a predetermined value number (for example, binary) for each color for each pixel. At this time, a method such as an error diffusion method or a dither method for diffusing a quantization error caused by quantization to peripheral pixels may be used as appropriate. Further, the quantized dot data for each CMYK color is converted into a data structure that can be decoded by the recording head control device 40, and the arrangement of the ejection nozzles 62 of the recording heads 18C, 18M, 18Y, and 18K is considered. The data is rearranged in the recording order (transfer order) to create recording data for each CMYK color. The print data is output to the print head control device 40 of the corresponding color.

  The nozzle selection circuit 48 reads out the recording data from the image memory 44, and the piezoelectric element corresponding to the ejection nozzle 62 that ejects droplets at a timing according to a droplet trigger signal input from an unillustrated ejection timing generation unit. 62C is selectively driven. In the present embodiment, the nozzle selection circuit 48 is included in the drive circuit 50 for driving the piezoelectric element 62 </ b> C provided in the discharge nozzle 62.

  The drive circuit 50 is configured as an integrated circuit on which a plurality of CMOS (Complementary Metal Oxide Semiconductor) inverter circuits 52 for applying a drive waveform to the piezoelectric elements 62C corresponding to the plurality of ejection nozzles 62 are mounted.

  The recording head control device 40 includes a substrate power supply circuit 70 and a drive power supply circuit 72 that supply drive power to the drive circuit 50. The substrate power supply circuit 70 outputs the power of the substrate voltage VDD by constant voltage control, and the drive power supply circuit 72 outputs the power of the drive voltage VH by constant voltage control.

  Here, FIG. 5A shows one ejection nozzle 62 extracted from the configuration of the drive circuit 50. As shown in the figure, the CMOS inverter circuit 52 includes a pair of pMOSFETs (p-channel metal oxide semiconductor field effect transistors) 52A and nMOSFETs (n-channel metal oxide semiconductor field effect transistors) 52B. Are connected to the gate of the nMOSFET 52B, and a drive waveform is inputted from the nozzle selection circuit 48.

  The source of the pMOSFET 52A is connected to the output terminal of the drive power supply circuit 72 described above, and the drive voltage VH is applied. Further, the back gate of the pMOSFET 52A is connected to the output terminal of the substrate power supply circuit 70 described above, and the substrate voltage VDD is applied. On the other hand, the source and back gate of the nMOSFET 52B are grounded. Further, the drain of the pMOSFET 52A and the drain of the nMOSFET 52B are connected, and are connected to the high potential side of the piezoelectric element 62C.

  With this configuration, when a drive waveform is input from the nozzle selection circuit 48, if the drive waveform is LOW, the pMOSFET 52A is turned on, the nMOSFET 52B is turned off, the drive voltage VH is applied to the piezoelectric element 62C, and the piezoelectric element 62C. Is charged. On the other hand, when the drive waveform is HIGH, the nMOSFET 62B is turned on and the pMOSFET 52B is turned off, and the charge charged in the piezoelectric element 62C is discharged.

  Here, FIG. 5B shows an equivalent circuit when the pMOSFET 52A is ON and the nMOSFET 52B is OFF in FIG. As shown in the figure, the CMOS inverter circuit 52 can be represented by the on-resistance Rd of the pMOSFET 52A. The on-resistance Rd is a resistance value based on the substrate voltage VDD, the drive voltage VH, the potential difference between the substrate voltage VDD and the drive voltage VH, and the like.

  As shown in the figure, the piezoelectric element 62C is generally equivalent to a parallel circuit of a series circuit of an equivalent inductance L0, an equivalent capacity C0, a resonance resistance R0, and a braking capacity Cd, and L0, C0, It can be regarded as a resonance circuit having a resonance frequency fr derived based on R0. Further, the impedance Z shown in the figure varies depending on the state of the discharge port 62A, the pressure chamber 62B, the pressure adjusting plate 62D, the ink supply path 62E, and the like of the discharge nozzle 62 that interacts with the piezoelectric element 62C. As the impedance Z changes, the resonance frequency fr of the equivalent circuit also changes.

  Therefore, when the resonance frequency fr varies, it may be determined that the state of the discharge nozzle 62 has changed. The fluctuation of the resonance frequency fr can be detected based on the current value Is of the power supplied from the drive power supply circuit 72 to the drive circuit 50.

  The factors that change the state of the discharge nozzle 62 include generation of bubbles in the pressure chamber 62B, clogging of the discharge port 62A, increase in ink viscosity, and the like.

  FIG. 6 shows frequency characteristics of admittance Y = Is / Vs based on the current value Is of the equivalent circuit shown in FIG. 5B and the voltage Vs applied to the piezoelectric element 62C. In the figure, the characteristic indicated by the thin line indicates the case where the on-resistance Rd = 300Ω, and the characteristic indicated by the thick line indicates the case where the on-resistance R = 1000Ω. In addition, the characteristic indicated by the solid line indicates a state where the ejection can be performed normally, and the characteristic indicated by the broken line indicates a case where there is a possibility that the ejection cannot be performed normally (non-ejection).

  In addition, the frequency at which each characteristic shown in the figure has a peak is the resonance frequency fr. As shown in the figure, when the on-resistance Rd is large, the resonance position can be understood as compared with the case where the on-resistance Rd is small. In addition, since the SNR (Signal to Noise Ratio) is small (bad), the resonance position may not be accurately grasped. Therefore, when detecting the current value Is in order to detect the state of the discharge nozzle 62, it is preferable to reduce the on-resistance Rd.

  FIG. 7A shows a change in on-resistance Rd when the substrate voltage VDD is changed, and FIG. 7B shows a change in on-resistance Rd when the drive voltage VH is changed. ing. As shown in the figure, the lower the substrate voltage VDD, the smaller the on-resistance Rd, and the higher the driving voltage VH, the smaller the on-resistance Rd.

  However, since the substrate voltage VDD and the drive voltage VH are set according to the ejection characteristics of the ejection nozzle 62, it is not easy to change the on-resistance Rd during ejection control. In order to prevent latch-up of the CMOS inverter circuit 52, it is necessary to set the relationship between the drive voltage VH and the substrate voltage VDD so that VH <VDD.

  Therefore, as shown in FIG. 4, the recording head controller 40 includes a substrate voltage switching circuit 74 and a drive voltage switching circuit 76, and the substrate voltage switching circuit 74 is connected to the substrate power supply circuit 70. The voltage switching circuit 76 is connected to the driving power supply circuit 72, respectively. The substrate voltage switching circuit 74 and the drive voltage switching circuit 76 are each connected to the bus 41 and controlled by the CPU 42.

  The substrate voltage switching circuit 74 switches the voltage level of the power supplied to the drive circuit 50 by the substrate power supply circuit 70 between the substrate voltage VDD1 for image recording and the substrate voltage VDD2 for state detection. The drive voltage switching circuit 76 switches the voltage level of the power supplied to the drive circuit 50 by the drive power supply circuit 72 between the image recording drive voltage VH1 and the state detection drive voltage VH2.

  A detection changeover switch 80 and a current detection circuit 82 are connected in parallel to the output terminal of the drive power supply circuit 72. Thus, the power output from the drive power supply circuit 72 is supplied to the drive circuit 50 via the detection changeover switch 80 when the detection changeover switch 80 is ON, and the current detection circuit when the detection changeover switch 80 is OFF. It is supplied to the drive circuit 50 via 82. A control signal from the CPU 42 is output to the detection switch 80 via the output port 78, and the detection switch 80 performs an ON / OFF operation based on the control signal.

  Further, the current value Is detected by the current detection circuit 82 is converted into digital data via the band-pass filter 84 and the digital analog (A / D) converter 86. The current value Is converted into digital data is buffered in a predetermined area of the control memory 44 via the input port 88 connected to the bus 41.

  Further, when detecting the ejection state, the CPU 42 changes the substrate voltage VDD and the drive voltage VH to the substrate voltage VDD2 and the drive voltage VH2 via the substrate voltage switching circuit 74 and the drive voltage switching circuit 76, respectively. In addition, a control signal is output so that the detection changeover switch 80 is turned off, and a control signal is output so as to execute a detection operation for applying a detection waveform to the nozzle selection circuit 48 one by one. Further, the CPU 42 identifies the resonance frequency based on the current value Is stored in the control memory 44 and detects the state of each discharge nozzle 62. Further, the result of the state detection (normal state or non-discharge state) is stored in the control memory 44 as status information indicating the state of each discharge nozzle 62.

  When a plurality of drive circuits 50 are connected to the recording head controller 40, the substrate power supply circuit 70 and the drive power supply circuit 72 may be shared by the drive circuits 50, but the detection changeover switch 80, current The detection circuit 82 is provided for each drive circuit 50. Further, when the state detection process for each drive circuit 50 is executed in parallel, a buffer region for the band pass filter 84, the A / D converter 86, and the control memory 44 is also provided for each drive circuit 50.

  The operation of the present embodiment will be described below.

  The image recording apparatus 10 executes image recording when image data is input together with an image recording instruction. At the time of image recording, first, recording data is generated based on the input image data, and the piezoelectric elements 62C corresponding to the respective ejection nozzles 62 provided in the recording head 18 are driven based on the generated recording data.

  Here, in the image recording apparatus 10, the state detection process of the ejection nozzle 62 is executed by the recording head control apparatus 40 during non-image recording.

  FIG. 8 is a flowchart showing a flow of state detection processing executed by the CPU 42 of the recording head control device 40. Hereinafter, the state detection process according to the present embodiment will be described with reference to FIG.

  First, in step 100, the voltage level of the power supplied to the drive circuit 50 by the substrate power supply circuit 70 (substrate voltage VDD) and the drive power supply circuit 72 are driven via the substrate voltage switch circuit 74 and the drive voltage switch circuit 76. The voltage level (drive voltage VH) of the power supplied to the circuit 50 is switched to VDD2 and VH2, respectively, and then the process proceeds to step 102 to output a control signal for switching off the detection selector switch 80 via the output port 78. .

  The substrate voltage VDD2 and the drive voltage VH need to be set so as to satisfy the relationship VH <VDD. Further, in this embodiment, in order to prevent the ink liquid stored in the pressure chamber 62B from being thickened, the pressure wave is applied to the ink liquid to the extent that the ink droplets applied to the piezoelectric element 62C during non-image recording are not ejected. Even when the preliminary waveform is applied, VDD2 and VH2 are set so that ink droplets are not ejected from the ejection port 62A.

  In the next step 104, an instruction to execute the detection waveform application process is output to the nozzle selection circuit 48, and then the process proceeds to step 106, 1 is set in the variable n, and then the process proceeds to step 108. Thereby, in the nozzle selection circuit 48, a detection waveform is sequentially applied to each discharge nozzle 62 every time the trigger signal becomes HIGH. In the present embodiment, the number of types of waveforms applied to the piezoelectric element 62C is reduced by using a preliminary waveform as the detection waveform.

  In step 108, it is determined whether or not the trigger signal becomes HIGH, and the process waits for the determination to be affirmative. If the determination is affirmative, the process proceeds to the next step 110, where the current detection circuit 82 detects the current value Is detected by the current detection circuit 82 and input as digital data via the band pass filter 84 and the A / D converter 86. Start buffering to 44.

  In the next step 112, the process waits for the trigger signal to become HIGH again, and then proceeds to step 114. In step 114, the resonance frequency frn of the piezoelectric element 62Cn is derived based on the current value Is when the detection waveform is applied to the buffered discharge nozzle 62n, and then the process proceeds to step 116 where the resonance frequency frn is normal. It is determined whether or not the resonance frequency is within the range of the dischargeable frequency. In addition, the range of the resonance frequency that can be normally discharged can be set as appropriate based on the result of an experiment using an actual machine or a computer simulation based on the specifications of the actual machine.

  If a negative determination is made in step 116, the process proceeds to step 118 where the status information indicating the state of the discharge nozzle 62 n stored in the control memory 44 is changed to the non-discharge state, and then the process proceeds to step 120.

  If the determination in step 116 is affirmative, it is determined that no discharge has occurred, and the process proceeds to step 120 without executing the process in step 118.

  In step 120, it is determined whether or not the variable n is equal to or greater than the number of nozzles provided in the drive circuit 50. If the determination is negative, the process proceeds to step 122. In step 122, the variable n is incremented ("1" is added to the variable n), and then the process returns to step 112 again.

  On the other hand, if an affirmative determination is made in step 120, the process proceeds to step 124, the detection changeover switch 80 is switched to the ON state, and then the process proceeds to step 126 to set the substrate voltage VDD and the drive voltage VH for image recording. Switching to the substrate voltage VDD1 and the drive voltage VH1, and then this state detection process is terminated.

  The status information changed by this state detection process is referred to and used in subsequent maintenance processes and image recording.

  FIG. 9 shows the flow of the detection waveform application process executed by the nozzle selection circuit 48 based on the execution instruction of the detection waveform application process output by the process of step 104 in FIG. Hereinafter, the detection waveform application processing according to the present embodiment will be described with reference to FIG.

  First, in step 140, 1 is set in the variable n, and thereafter, the process proceeds to step 142 to determine whether or not the trigger signal becomes HIGH. If the determination is affirmative, the process proceeds to the next step 144, where the detection waveform (preliminary waveform in the present embodiment) is applied to the piezoelectric element 62Cn of the discharge nozzle 62n, and then the process proceeds to step 146.

  In step 146, it is determined whether or not the variable n is equal to or greater than the number of nozzles provided in the drive circuit 50. If the determination is negative, the process proceeds to step 148. In step 148, the variable n is incremented ("1" is added to the variable n), and then the process returns to step 142 again. On the other hand, if the determination in step 146 is affirmative, the detection waveform application process is terminated.

  In this way, the detection waveform is applied to all the piezoelectric elements 62 </ b> C driven by the drive circuit 50, and the current value Is is sequentially detected by the current detection circuit 82.

  In FIG. 10, the supply power voltage of the image recording apparatus 10 according to the present embodiment, the voltage applied to the piezoelectric element 62C, the operation of the detection changeover switch 80, and the current value Is detected by the current detection circuit 82 are shown as a timing chart. It is shown.

  As shown in the figure, when the image recording operation by the image recording apparatus 10 is stopped, the supply of power to the drive circuit 50 is stopped, and when the image recording is started, the substrate voltage VDD1 and the drive are stopped. Supply of the power of the voltage VH1 to the drive circuit 50 is started. In addition, application of the ejection waveform based on the recording data is started via the nozzle selection circuit 48. The ejection waveform is applied at a timing based on a trigger signal (not shown).

  When the image recording for one page is completed, the voltage level of the power supplied to the drive circuit 50 is switched to the substrate voltage VDD2 and the drive voltage VH2, and the detection switch 80 is turned off to start the state detection process.

  Thereafter, when the state detection processing is completed, the voltage level of the power supplied to the drive circuit 50 is switched to the substrate voltage VDD1 and the drive voltage VH1, and the detection changeover switch 80 is turned on to start image recording for the next page. .

  FIG. 11 shows the execution timing of each process during the state detection process. As shown in the figure, the discharge nozzles 62 are selected one by one by the nozzle selection circuit 48 at the timing when the trigger signal becomes HIGH, and the detection waveforms are sequentially applied. Accordingly, the current value Is detected by the current detection circuit 82 becomes a current value flowing through the CMOS inverter circuit 52 of the piezoelectric element 62C of the ejection nozzle 62 selected by the nozzle selection circuit 48.

  On the other hand, the state detection based on the current value Is is processed after the detected current value Is is buffered, so that the processing timing is delayed by one trigger signal from the detection waveform application timing.

  FIG. 12 shows an enlarged view of the applied voltage to the piezoelectric element 62C and the detected value of the current value Is during state detection. As shown in the figure, the current value Is greatly changes at the timing when the application of voltage to the piezoelectric element 62C starts and ends. That is, accumulation of electric charge (charging) in the piezoelectric element 62C starts when voltage application is started, and the current value Is stabilizes when charging is completed. On the other hand, when the application of the voltage is finished, the electric charge charged in the piezoelectric element 62C is discharged, and when the electric charge is discharged, the current value Is is stabilized.

  In addition, since the pressure wave generated by the piezoelectric element 62C propagates while being attenuated at a constant period (reverberation vibration), the current value Is also varies periodically while the amplitude is attenuated during the period A between charging and discharging. .

  FIG. 13 shows the current value Is in the period A in an enlarged manner. As shown in the figure, the resonance period becomes longer in the non-ejection state between the normal fluctuation period (reverberation vibration period) TA and the non-ejection fluctuation period TB. Therefore, in the state detection process according to the present embodiment, the fluctuation period Tn of the detection value Is obtained by applying the detection waveform to the piezoelectric element 62Cn of each discharge nozzle 62n is derived, and the difference from the fluctuation period TA at normal time is derived. Is determined as a non-ejection state (step 114 and step 116 in FIG. 8).

  In the present embodiment, the method of comparing the reverberation vibration periods has been described. However, the resonance is detected by performing the spectrum detection by the fast Fourier transform based on the current value Is using the software (program) incorporated in the control memory 44 by the CPU 42. The frequency Frn may be obtained.

  The configuration of the image recording apparatus 10 according to each of the above embodiments is an example, and can be changed as appropriate without departing from the gist of the present invention.

  Further, the flow of processing according to each of the above embodiments is an example, and it is needless to say that the flow can be appropriately changed without departing from the gist of the present invention.

  For example, in each of the above-described embodiments, the description has been given of the embodiment using the FWA type recording head in which the nozzles are provided in the entire width direction of the recording medium different from the conveying direction of the recording medium. A PWA (Partial Width Array) type in which an image is formed by scanning and moving a recording head having nozzles arranged so as to face a part in the width direction different from the recording medium width direction of the recording medium. The present invention can also be applied to the recording head.

  In this embodiment, the state detection process is executed using a preliminary waveform between sheets (between pages). However, when non-image formation is performed, at what timing such as when the power is turned on. Also good. For example, when applied to a PWA type recording head, it is also possible to execute a state detection process between line breaks.

  In each of the above embodiments, the gradation that can be expressed by the recording head 18 has been described as two gradations, but the present invention is not limited to this, and is a case where quantization is performed to three gradations or more. Can also be applied.

  FIG. 14 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and an example of a computer when various processing functions executed by the image recording apparatus of the present invention are realized by the computer program. In the figure, 550 is a program, 552 is a computer, 554 is a magneto-optical disk, 556 is an optical disk, 558 is a magnetic disk, 560 is a memory, 562 is an internal memory, 566 is a reading unit, 570 is a hard disk, 568 and 574 are interfaces, Reference numeral 572 denotes a communication unit.

  Part or all of the functions of the respective units of the image recording apparatus of the present invention described in the above embodiments can be realized by a program 550 that can be executed by a computer. In that case, the program 550, data used by the program, and the like can be stored in a computer-readable storage medium. As a storage medium, the reading unit 566 provided in the hardware resource of the computer causes a change state of energy such as magnetism, light, electricity, etc. according to the description content of the program, and a signal corresponding thereto is generated. In this format, the description content of the program can be transmitted to the reading unit 566. For example, a magneto-optical disk 554, an optical disk 556 (including a CD and a DVD), a magnetic disk 558, a memory 560 (including an IC card and a memory card), and the like. Of course, these storage media are not limited to portable types.

  The program 550 is stored in these storage media, and the program 550 is read from the computer by, for example, mounting these storage media on the reading unit 566 or the interface 574 of the computer 552, and stored in the internal memory 562 or the hard disk 570. The function of the image processing apparatus of the present invention can be realized by executing the program 550 by the CPU 564. Alternatively, the program 550 is transferred to the computer 552 via a network or the like, and the computer 552 receives the program 550 by the communication unit 572, stores the program 550 in the internal memory 562 or the hard disk 570, and executes the program 550 by the CPU 564. You may implement | achieve the function of the image processing apparatus of invention. In addition, the computer 552 can be connected to various devices via an interface 568. For example, a display device for displaying information and an input device for inputting information by a user are also connected.

  Of course, some functions may be configured by hardware, or all may be configured by hardware. Alternatively, it can be configured as a program including the present invention together with other configurations.

  In the present embodiment, the present invention has been described by taking an ink jet image recording apparatus as an example. However, the present invention is not limited to an ink jet image recording apparatus, and the present invention is not limited to an ink jet image recording apparatus. The present invention can be applied to general droplet discharge devices for various industrial uses such as production of a filter and formation of an EL display panel by discharging an organic EL solution onto a substrate.

  Further, the recording paper P that is the target of image recording in the image recording apparatus 10 is not limited to a recording paper or an OHP sheet, as long as the droplet discharge head is a target for discharging droplets. In addition, for example, polymer films are widely included.

1 is a schematic diagram illustrating a configuration of an image recording apparatus according to an embodiment. FIG. 3 is a schematic diagram illustrating a positional relationship among a recording head, a maintenance device, and a conveyor belt during maintenance of the image recording apparatus. FIG. 2 is a schematic diagram illustrating a configuration of a discharge nozzle of a recording head. 1 is a block diagram illustrating a configuration of a recording head control device of an image recording apparatus according to an embodiment. (A) is a circuit diagram showing a configuration of a drive circuit for one ejection nozzle, and (B) is a circuit diagram showing an equivalent circuit when a voltage is applied to a piezoelectric element. It is a graph which shows the frequency characteristic of the admittance of a drive circuit. (A) is a graph showing the relationship between the substrate voltage and the on-resistance of the drive circuit, and (B) is a graph showing the relationship between the drive voltage and the on-resistance of the drive circuit. It is a flowchart which shows the flow of the state detection process which concerns on embodiment. It is a flowchart which shows the flow of the detection waveform application process which concerns on embodiment. 6 is a timing chart showing an example of an operation pattern of the image recording apparatus according to the embodiment. It is a timing chart which shows the processing timing of each part at the time of state detection. It is a graph which shows the time-dependent change of electric current value Is. 13 is a graph obtained by enlarging FIG. It is explanatory drawing of an example of a computer program in the case of implement | achieving the function of various processes with a computer program, the storage medium which stored the computer program, and a computer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image recording apparatus 11 Drive roll 12 Driven roll 14 Conveyor belt 18 Recording head array 20 Paper tray 22 Paper discharge tray 24 Roll 40 Recording head control apparatus 42 CPU (state detection means, control means)
44 Control memory 46 Image memory 48 Nozzle selection circuit 50 Drive circuit 52 CMOS inverter circuit (switching element)
70 Substrate power supply circuit (first power supply means)
72 Drive power supply circuit (second power supply means)
74 Substrate voltage switching circuit 76 Drive voltage switching circuit 80 Detection switching switch 82 Current detection circuit (detection means)
84 Band pass filter 86 A / D converter 62 Discharge nozzle (droplet discharge means)

Claims (6)

The voltage applied to the drive element of the droplet discharge means for discharging the droplet from the discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber containing the liquid by the drive element First power supply means for supplying power at a substrate voltage level to a drive circuit having a switching element for switching levels;
Second power supply means for supplying power to the drive circuit at a drive voltage level lower than the substrate voltage level;
Detection means for detecting a physical quantity according to a current value of power supplied from the second power supply means to the drive circuit;
A detection waveform is applied to the switching element to derive a change period of the current value based on a detection result by the detection means, and the droplet discharge means is normal when the derived change period does not satisfy a preset condition. State detection means for detecting that the state is not correct,
First switching means for switching a voltage level of power supplied to the drive circuit by the first power supply means;
When detecting the state of the droplet discharge unit by the state detection unit, the substrate voltage level of the power supplied to the drive circuit is the substrate voltage supplied when performing droplet discharge using the droplet discharge unit Control means for controlling the first switching means to switch to a substrate voltage level lower than the level;
A discharge state detection device. The switching element is a CMOS inverter circuit composed of a pair of pMOS transistors and nMOS transistors,
The first power supply means supplies power to the back gate of the pMOS transistor,
The ejection state detection device according to claim 1, wherein the second power supply unit supplies power to a source of the pMOS transistor. A second switching means for switching a voltage level of power supplied to the drive circuit by the second power supply means;
The control means is configured to reduce the drive voltage level when the substrate voltage level is lowered so that a difference between the substrate voltage level and the drive voltage level becomes a predetermined potential. 3. The discharge state detection device according to claim 1, wherein the discharge state detection device controls the first switching unit and the second switching unit. The drive circuit is configured to respectively drive a plurality of drive elements of the droplet discharge means,
The control means sequentially drives the drive elements of the plurality of droplet discharge means one by one by the drive circuit when the state detection means detects the state of the droplet discharge means, and the state detection means The discharge state detection apparatus according to claim 1, wherein control is performed so that state detection for each droplet discharge unit is sequentially executed by the control. Droplet discharge means for discharging droplets from the discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber in which the liquid is stored by a driving element;
A drive circuit having a switching element for switching a voltage level applied to the drive element;
First power supply means for supplying power at a substrate voltage level to the drive circuit;
Second power supply means for supplying power to the drive circuit at a drive voltage level lower than the substrate voltage level;
Detection means for detecting a physical quantity according to a current value of power supplied from the second power supply means to the drive circuit;
Applying a detection waveform to the switching element to derive a change period of the current value based on a detection result by the detection means, and the droplet discharge means when the derived change period is included in a preset normal period A state detection means for detecting that is in a normal state;
First switching means for switching a voltage level of power supplied to the drive circuit by the first power supply means;
When detecting the state of the droplet discharge unit by the state detection unit, the substrate voltage level of the power supplied to the drive circuit is the substrate voltage supplied when performing droplet discharge using the droplet discharge unit Control means for controlling the first switching means to switch to a substrate voltage level lower than the level;
A droplet discharge device comprising: When detecting the state of the droplet discharge means for discharging droplets from the discharge port communicating with the pressure chamber and the outside of the pressure chamber by changing the pressure inside the pressure chamber containing the liquid by the driving element ,
On the computer,
A voltage switching step of switching the substrate voltage level applied to the switching element for switching the voltage applied to the driving element to a voltage level lower than the substrate voltage level supplied when performing droplet ejection using the droplet ejection means;
A detection step of applying a detection waveform to the switching element and detecting a physical quantity corresponding to a current value of power supplied to the drive circuit at a drive voltage level lower than the substrate voltage level;
A state detection step of deriving a change period of the current value based on the detection result and detecting that the droplet discharge means is not in a normal state when the derived change period does not satisfy a preset condition;
A discharge state detection program for executing

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