JP2020055297A - Liquid discharge device, liquid discharge head and driving method of the same - Google Patents

Abstract

To provide a driving circuit which can suppress a potential change in switching a driving signal.SOLUTION: A liquid discharge device having a driving signal substrate 51 for inputting a driving signal in response to waveform data to a liquid discharge head, includes a driving element 86 for driving a nozzle, a plurality of switching elements 231a, b connected in parallel to the driving element, a first signal transmission part which is connected to the driving element through the respective switching elements and is formed of a plurality of signal lines for transmitting the driving signal, a potential difference detection part 233 which detects a potential difference on the basis of an intermediate potential of the driving signal transmitted to the respective signal lines, a correction signal generation part 234 which generates a correction signal on the basis of the potential difference, a correction processing part 222 which corrects the waveform data on the basis of the correction signal, and driving signal generation parts 223a, b which are arranged for the signal lines respectively and generate the driving signal on the basis of the waveform data corrected by the correction processing part and output to the signal lines.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a liquid ejection device, a liquid ejection head, and a driving method thereof.

  A so-called piezo that discharges liquid by changing the volume in the liquid flow path by deforming a diaphragm that forms the wall of the liquid flow path by using a driving element such as a piezoelectric element as a liquid discharge apparatus including a liquid discharge head. Devices of the type are known.

  This type of liquid ejection device electrically controls the liquid (droplets) to be ejected, so that the droplet size and the like can be finely controlled. This is advantageous when used in a recording device for forming an image.

  The liquid ejection device includes a drive signal generation circuit for generating a drive signal applied to a drive element provided in the liquid ejection head. It is known that waveform data corresponding to a droplet size, ink temperature, and the like is recorded in the drive signal generation circuit, and the waveform data can be selected (for example, see Patent Document 1).

  It is conceivable that a plurality of drive signal generation circuits are provided for one drive element, and the drive signal generation circuit is switched by a switch, so that a drive signal input to the drive element can be switched. According to this configuration, the drive signal can be switched at high speed in accordance with the droplet size and the like.

  However, a plurality of drive signals input to one drive element may have different intermediate potentials (reference potentials) due to manufacturing variations in a drive signal generation circuit and transmission paths. In this case, an instantaneous potential change occurs when the drive signal is switched, and an unexpected current is input to the drive element, causing a malfunction or failure of the drive element.

  The disclosed technology has been made in view of the above circumstances and has been made to solve the problem, and has as its object to suppress a potential change at the time of switching a drive signal.

  The disclosed technology is a driving element for driving the nozzle in a liquid discharging apparatus having a liquid discharging head for discharging liquid from a nozzle, and a driving signal substrate for inputting a driving signal corresponding to waveform data to the liquid discharging head. A plurality of switching elements connected in parallel to the driving element, and a first signal transmission unit including a plurality of signal lines connected to the driving element via the switching elements and transmitting the driving signal, A switching control unit that performs switching control to selectively turn on the plurality of switching elements; a potential difference detection unit that detects a potential difference based on an intermediate potential of a drive signal transmitted to each of the signal lines; A correction signal generation unit that generates a correction signal based on the correction signal, a correction processing unit that corrects the waveform data based on the correction signal, and a correction processing unit. And outputs to the signal line to generate the drive signal based on the corrected waveform data Ri, a drive signal generation unit provided for each of the signal line, a liquid discharge apparatus having a.

  A change in potential at the time of switching of the drive signal can be suppressed.

FIG. 1 is an external perspective view of a liquid ejection device according to the present embodiment as viewed from the front side. FIG. 3 is a schematic plan view of a mechanism of the liquid ejection device. FIG. 3 is a cross-sectional view of a liquid ejection head. FIG. 3 is a block diagram illustrating a configuration of a control unit. FIG. 3 is a block diagram illustrating an electrical configuration of a drive signal substrate and a liquid ejection head. FIG. 3 is a block diagram illustrating a configuration of a first drive signal generator and a second drive signal generator. FIG. 3 is a diagram illustrating waveforms of drive signals and the like in an ideal state. FIG. 9 is a diagram illustrating, as a comparative example, a waveform of a drive signal and the like in a case where a shift occurs in an intermediate potential but offset correction is not performed. FIG. 4 is a diagram illustrating waveforms of a drive signal and the like when a shift occurs in an intermediate potential and offset correction is performed. 6 is a flowchart illustrating an operation of the liquid ejection device. It is a figure showing composition of a correction processing part in a 2nd embodiment. 5 is a flowchart illustrating an initial operation after power is turned on. FIG. 11 is a block diagram illustrating an electrical configuration of a drive signal substrate and a liquid ejection head according to a third embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted. In the embodiments described below, an ink jet printer that forms an image by discharging ink on a recording medium will be described as an example of a liquid discharge apparatus to which the present invention is applied.

[First Embodiment]
Hereinafter, the liquid ejection device according to the first embodiment of the present invention will be described.

<Configuration of liquid ejection device>
FIG. 1 is an external perspective view of a liquid ejection apparatus 1 according to the present embodiment as viewed from the front side.

  The liquid ejecting apparatus 1 has an apparatus main body 1 a, a sheet feeding tray 2, and a sheet discharging tray 3. The paper feed tray 2 is detachably mounted on the apparatus main body 1a, and supplies paper 11 (see FIG. 2) as a recording medium to the apparatus main body 1a. The paper discharge tray 3 is detachably mounted on the apparatus main body 1a, and stocks the paper 11 on which an image is recorded (formed) by the apparatus main body 1a.

  At one end of the front surface of the apparatus main body 1a, a cartridge loading section 4 for loading an ink cartridge is provided. An operation display unit 5 having operation buttons, a display, and the like is provided on an upper surface of the cartridge loading unit 4.

  The cartridge loading section 4 is configured to be able to insert and load a plurality of ink cartridges 10k, 10c, 10m, and 10y having different ink colors from the front side to the back side of the apparatus main body 1a.

  The ink cartridge 10k contains black (K) ink. The ink cartridge 10c contains cyan (C) ink. The ink cartridge 10m contains magenta (M) ink. The ink cartridge 10y contains yellow (Y) ink. In addition, when the color of the ink is not distinguished, it is simply referred to as the ink cartridge 10.

  On the front side of the cartridge loading section 4, a front cover 6 that is opened when the ink cartridge 10 is attached and detached is provided so as to be openable and closable. Further, the ink cartridges 10k, 10c, 10m, and 10y are configured to be loaded side by side in a horizontal state in a vertically installed state.

  The operation display unit 5 includes a remaining amount display unit for displaying the remaining amount of each of the ink cartridges 10k, 10c, 10m, and 10y, a power button, a paper feed / print restart button, a cancel button, and the like.

  Next, the mechanism of the liquid ejection apparatus 1 will be described with reference to FIG. FIG. 2 is a schematic plan view of a mechanism of the liquid ejection device 1.

  The carriage 25 is slidably held in the main scanning direction (longitudinal direction of the guide rod) by the guide rod 22 as the main guide member and the sub guide members (guide rod, guide stay, etc.). The guide rod 22 is horizontally mounted on main side plates 21A and 21B constituting a frame member of the apparatus main body 1a.

  The carriage 25 is moved and scanned in the main scanning direction by a main scanning mechanism including a main scanning motor 26, a driving pulley 27, a driven pulley 28, and a timing belt 29.

  On the carriage 25, for example, four sub-tank-integrated liquid ejection heads 31 for ejecting ink droplets (droplets) of each color of black (K), cyan (C), magenta (M), and yellow (Y) are provided. It is installed.

  In the liquid discharge head 31, a nozzle row including a plurality of nozzles 98a (see FIG. 3) is formed in a sub-scanning direction orthogonal to the main scanning direction. The carriage 25 is mounted on the carriage 25 with the liquid ejection direction facing downward.

  In the carriage 25, a driving signal from a driving signal substrate 51 is input to the liquid ejection head 31 via a flexible flat cable (FFC) 12 as a wiring member and a relay substrate 56. The relay board 56 is provided on the carriage 25.

  On the other hand, below the carriage 25, a transport belt 41 is disposed as transport means for transporting the paper 11 fed from the paper feed tray 2 in the sub-scanning direction. The transport belt 41 is an endless belt, and is stretched between the transport roller 42 and the tension roller 43. The transport belt 41 is circulated in the belt transport direction by rotating the transport roller 42 by the sub-scanning motor 210 (see FIG. 4).

<Structure of liquid ejection head>
Next, the structure of the liquid ejection head 31 will be described. FIG. 3 is a cross-sectional view of the liquid ejection head 31.

  The liquid ejection head 31 has a drive unit 102 and a liquid chamber unit 104. The drive unit 102 is made of, for example, a thermoplastic resin, and has a frame member 80 having a hollow portion 80a as a pressure generating device storage space formed in a central portion, and a pressure generating device 82 disposed in the hollow portion 80a. .

  In the frame member 80, a pair of common liquid chambers 80b and 80c are formed on both sides of the hollow portion 80a in a direction orthogonal to the longitudinal direction.

  The pressure generating device 82 includes a rectangular parallelepiped base member 84 formed of a hard material such as ceramics or metal, for example, stainless steel, and a plurality of piezoelectric elements 86 arranged on the base member 84 in a matrix of 2 rows and n columns. Having.

  Each piezoelectric element 86 is a piezo-type laminated piezoelectric element. A large number of internal electrodes 90 of each piezoelectric element 86 are alternately taken out on both end faces every other layer and connected to individual end face electrodes formed of, for example, an AgPd alloy or the like formed on both end faces. Further, the individual end face electrodes on the end face side of each piezoelectric element 86 facing the other piezoelectric element in the same row are connected to a common electrode on the base member 84.

  An FPC is joined by soldering to the individual end face electrodes and the common electrode on the end face side of each piezoelectric element 86 that are not opposed to other piezoelectric elements in the same row, and the common electrode is connected to the ground potential.

  Each piezoelectric element 86 generates an electric field in the stacking direction when a drive signal is applied, and displaces in the stacking direction, thereby changing the internal volume of the liquid chamber and discharging a liquid (droplet) from the nozzle 98a. . Therefore, the piezoelectric element 86 is a driving element that drives the nozzle 98a.

<Configuration of control unit>
Next, the configuration of the control unit of the liquid ejection device 1 will be described. FIG. 4 is a block diagram showing a configuration of the control unit 200.

  The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, a RAM 204, and a host I / F 205.

  The CPU 201 controls the entire liquid ejecting apparatus 1. The ROM 202 stores programs executed by the CPU 201 and various data. The RAM 203 temporarily stores image data and the like. The RAM 204 stores data that needs to be held when the power is turned off.

  The host I / F 205 receives image data transmitted from a host device such as a personal computer in a wired or wireless manner.

  Further, the control unit 200 includes the drive signal substrate 51 described above, a main scanning motor driving unit 206 that drives the main scanning motor 26, and a sub-scanning motor driving unit 207 that drives the sub-scanning motor 210. The CPU 201 controls the drive signal substrate 51, the main scanning motor driving unit 206, and the sub-scanning motor driving unit 207 to perform an image recording operation on the paper 11.

<Electrical Configuration of Drive Signal Substrate and Liquid Discharge Head>
FIG. 5 is a block diagram illustrating an electrical configuration of the drive signal substrate 51 and the liquid ejection head 31. The liquid discharge device 1 is configured to discharge a liquid (droplet) by inputting a drive signal generated in the drive signal substrate 51 to each piezoelectric element 86 in the liquid discharge head 31.

  The drive signal substrate 51 includes a drive waveform information storage unit 220, a waveform selection unit 221, a correction processing unit 222, a first drive signal generation unit 223a, a second drive signal generation unit 223b, and an ejection timing control unit 224. And a droplet size selection unit 225.

  The liquid ejection head 31 includes a head temperature detection unit 230, a first switching element (hereinafter, referred to as a first SW) 231a, a second switching element (hereinafter, referred to as a second SW) 231b, a switching control unit 232, and a potential difference. It has a detection unit 233 and a correction signal generation unit 234.

  The drive waveform information storage unit 220 stores waveform data corresponding to a droplet size, a droplet temperature, and the like. The waveform selection unit 221 selects waveform data from the drive waveform information storage unit 220 based on a head temperature detection signal detected by the head temperature detection unit 230 in the liquid ejection head 31 and outputs the waveform data to the correction processing unit 222. .

  The correction processing unit 222 holds correction signals (first offset signal and second offset signal) supplied from a correction signal generation unit 234 described later, and corrects waveform data based on the correction signals. The corrected waveform data is input to the first drive signal generator 223a and the second drive signal generator 223b.

  Different waveform data is input to the first drive signal generator 223a and the second drive signal generator 223b. For example, waveform data for different droplet sizes is input to the first drive signal generator 223a and the second drive signal generator 223b. For example, the first drive signal generation unit 223a receives waveform data for generating a small droplet having a small droplet size, and the second drive signal generation unit 223b receives waveform data for generating a large droplet having a large droplet size. Is entered.

  The first drive signal generation unit 223a transmits the first drive signal Va (t) to the liquid ejection head 31 by generating the first drive signal Va (t) for droplet generation and outputting the first drive signal Va (t) to the signal line 240a. Let it. The second drive signal generation unit 223b transmits the second drive signal Vb (t) to the liquid ejection head 31 by generating the second drive signal Vb (t) for large droplet generation and outputting the generated second drive signal Vb (t) to the signal line 240b. Let it. The signal lines 240a and 240b are first signal transmission units for driving signal transmission formed via the FFC 12 and the relay board 56.

  FIG. 6 is a block diagram illustrating the configuration of the first drive signal generator 223a and the second drive signal generator 223b. The first drive signal generator 223a and the second drive signal generator 223b each include a waveform data memory 250, a D / A converter 251, a voltage amplifier 252, and a current amplifier 253.

  The waveform data memory 250 stores the waveform data input from the correction processing unit 222. When new waveform data is input from the correction processing unit 222, the waveform data memory 250 deletes the stored waveform data and updates it with new waveform data.

  The D / A converter 251 converts the waveform data output from the waveform data memory 250 into an analog signal. The voltage amplification circuit 252 performs voltage amplification on the analog signal converted by the D / A converter 251. The current amplification circuit 253 current-amplifies the signal that has been voltage-amplified by the voltage amplification circuit 252. A signal output from the current amplification circuit 253 is a drive signal.

  The first drive signal generator 223a and the second drive signal generator 223b operate at a constant ejection cycle T in synchronization with a predetermined clock signal. The first drive signal Va (t) and the second drive signal Vb (t) change periodically depending on time t.

  Returning to FIG. 5, a first SW 231a and a second SW 231b are connected in parallel to one electrode of each piezoelectric element 86. The other electrode of each piezoelectric element 86 is connected to ground (GND).

  The terminal of each first SW 231a on the side opposite to the piezoelectric element 86 is connected to a signal line 240a to which the first drive signal Va (t) is transmitted. The terminal of each second SW 231b on the side opposite to the piezoelectric element 86 is connected to a signal line 240b to which the second drive signal Vb (t) is transmitted. That is, the first SW 231a switches the connection state between the piezoelectric element 86 and the signal line 240a between on and off. The second SW 231b switches the connection state between the piezoelectric element 86 and the signal line 240b between on and off.

  The switching of the first SW 231a and the second SW 231b is controlled by the switching control unit 232.

  The switching control unit 232 selectively turns on the first SW 231a and the second SW 231b based on the timing control signal from the ejection timing control unit 224 and the droplet size selection signal from the droplet size selection unit 225. That is, one of the first drive signal Va (t) and the second drive signal Vb (t) is selected and input to the piezoelectric element 86 as the drive signal V (t).

  The ejection timing control unit 224 generates an ejection timing control signal based on an instruction from the CPU 201 based on the image data, and outputs the signal to each switching control unit 232. The droplet size selection unit 225 generates a droplet size selection signal based on an instruction from the CPU 201 based on the image data, and outputs the signal to each switching control unit 232. Each switching control unit 232 controls which one of the first SW 231a and the second SW 231b is turned on, and controls the timing of turning on, based on the ejection timing control signal and the droplet size selection signal.

  The potential difference detecting section 233 is connected to the signal lines 240a and 240b. The potential difference detection unit 233 includes a first potential difference that is a potential difference between an intermediate potential of the first drive signal Va (t) transmitted to the signal line 240a and the ideal potential Vi, and a second drive signal Vb transmitted to the signal line 240b. A second potential difference which is a potential difference between the intermediate potential of (t) and the ideal potential Vi is calculated. Here, the intermediate potential is a reference potential of the first drive signal Va (t) and the second drive signal Vb (t), and is an initial potential (t = 0) and an end (t = T) of each ejection T. Potential. The ideal potential is an ideal intermediate potential Vi when no potential shift occurs.

  The potential difference detection unit 233 holds the value of the ideal potential Vi, and detects a first potential difference ΔVa and a second potential difference ΔVb represented by the following equations (1) and (2).

ΔVa = Va (0) −Vi (1)
ΔVb = Vb (0) −Vi (2)
The correction signal generation unit 234 generates and outputs a first offset signal representing the first potential difference ΔVa and a second offset signal representing the second potential difference ΔVb. The correction signal generation unit 234 transmits the first offset signal and the second offset signal as correction signals to the drive signal substrate 51 via the signal line 241. The signal line 241 is a second signal transmission unit for transmitting a correction signal, which is formed via the FFC 12 and the relay board 56.

  The correction processing unit 222 in the drive signal substrate 51 performs offset correction of the droplet generation waveform data input from the waveform selection unit 221 based on the first offset signal, and converts the large droplet generation waveform data into the second droplet generation waveform data. Offset correction is performed based on the offset signal. As a result, the offset-corrected waveform data for droplet generation is input to the first drive signal generation unit 223a. The offset-corrected large drop generation waveform data is input to the second drive signal generation unit 223b.

  As a result, the first drive signal Va (t) and the second drive signal Vb (t) generated by the first drive signal generation unit 223a and the second drive signal generation unit 223b are expressed by the following equations (3) and (4), respectively. ) Is corrected.

Va ′ (t) = Va (t) −ΔVa (3)
Vb ′ (t) = Vb (t) −ΔVb (4)
Here, Va ′ (t) and Vb ′ (t) represent the corrected first drive signal and the second drive signal, respectively.

<Driving signal offset correction>
Next, offset correction of the first drive signal Va (t) and the second drive signal Vb (t) will be described.

  FIG. 7 is a diagram illustrating waveforms of drive signals and the like in an ideal state. FIG. 7A shows the waveform of the first drive signal Va (t). FIG. 7B shows the waveform of the second drive signal Vb (t). FIG. 7C shows a first switching signal supplied to the first SW 231a. FIG. 7D shows a second switching signal supplied to the second SW 231b. FIG. 7E shows a drive signal V (t) input to the piezoelectric element 86.

  The first and second switching signals select the first drive signal Va (t) in the first discharge cycle, select the second drive signal Vb (t) in the second discharge cycle, and select the first drive signal Vb (t) in the third discharge cycle. The drive signal Va (t) has been selected.

  FIG. 7 illustrates a case where the intermediate potential Va (0) of the first drive signal Va (t) and the intermediate potential Vb (0) of the second drive signal Vb (t) both match the ideal potential Vi. Is shown. In this case, there is no potential difference when the drive signal is switched between the ejection cycles.

  FIG. 8 is a diagram illustrating, as a comparative example, a waveform of a drive signal and the like in a case where offset correction is not performed although a shift occurs in the intermediate potential. FIGS. 8A to 8E show waveforms of signals similar to FIGS. 7A to 7E, respectively.

  FIG. 8A shows a case where the potential difference ΔVa between the intermediate potential Va (0) of the first drive signal Va (t) and the ideal potential Vi is not zero. FIG. 8B shows a case where the potential difference ΔVb between the intermediate potential Vb (0) of the second drive signal Vb (t) and the ideal potential Vi is not zero. These potential differences can be caused by differences in the signal amplification factor and the attenuation factor during transmission due to manufacturing variations of the first drive signal generation unit 223a and the second drive signal generation unit 223b, manufacturing variations of the first signal transmission unit, and the like. .

  In this case, as shown in FIG. 8E, when the drive signal is switched between the ejection cycles, a sharp change in the potential occurs, and an unexpected current flows through the piezoelectric element 86, causing a failure or malfunction of the piezoelectric element 86. Can cause.

  For example, when the potential changes from a high potential Va (T) to a low potential Vb (0), such as between the first ejection cycle and the second ejection cycle, the piezoelectric element 86 contracts and the liquid ejection is performed. Pressure is generated in the direction of drawing the meniscus surface of the head 31 into the nozzle 98a. Abnormal ejection does not occur in the pull-in operation itself, but interference may occur in the subsequent meniscus operation by the second drive signal Vb (t), and normal ejection may not be performed.

  Conversely, when the potential changes from low potential Vb (T) to high potential Va (0), such as between the second ejection cycle and the third ejection cycle, the meniscus surface of the liquid ejection head 31 is changed to the nozzle 98a. Pressure is generated in the direction of pushing out the outside. This is an operation in the direction in which ejection is performed, and may lead to abnormal ejection. Even if abnormal ejection does not occur, interference may occur in the subsequent meniscus operation by the first drive signal Va (t), and normal ejection may not be performed.

  Further, if the steep change of the potential is repeated many times at high speed, the first SW 231a and the second SW 231b may be damaged, and the image quality may be significantly impaired.

  FIG. 9 is a diagram showing waveforms of drive signals and the like when a shift occurs in the intermediate potential and offset correction is performed. FIGS. 9A to 9E show waveforms of signals similar to FIGS. 7A to 7E, respectively.

  As shown in FIGS. 9A and 9B, when the potential difference ΔVa and the potential difference ΔVb are not zero, the potential difference is detected by the potential difference detection unit 233, and the first offset signal and the The two offset signals are generated by the correction signal generation unit 234 and input to the correction processing unit 222. The correction processing unit 222 corrects the waveform data based on the input correction signal and inputs the corrected waveform data to the first drive signal generation unit 223a and the second drive signal generation unit 223b. These processes are performed within the first ejection cycle.

  After the first ejection cycle, the first drive signal generation unit 223a and the second drive signal generation unit 223b output the corrected first drive signal Va ′ (t) and the second drive signal Vb after offset correction. '(T) is output.

  As a result, as shown in FIG. 9E, after the second ejection cycle, the intermediate potential Va (0) and the intermediate potential Vb (0) substantially coincide with the ideal potential Vi, and when the drive signal is switched (ejection time). The potential change during the period is suppressed. This prevents the piezoelectric element 86 from malfunctioning or malfunctioning.

<Operation flow>
Next, an operation flow of the liquid ejection device 1 will be described. FIG. 10 is a flowchart illustrating the operation of the liquid ejection device 1.

  Each operation of the liquid ejection device 1 illustrated in FIG. 10 is performed based on control by the CPU 201. When starting the image recording operation on the sheet 11, first, the CPU 201 sends the first drive signal Va (t) and the second drive signal Vb (t) to the first drive signal generator 223a and the second drive signal generator 223b. ) Is started (step S10).

  Next, the CPU 201 selects a drive signal corresponding to the ejection information based on the ejection information (step S11). The switching control of the switching control unit 232 is performed via the ejection timing control unit 224 and the droplet size selection unit 225. Is executed (step S12). For example, when it is necessary to discharge a small droplet, the first drive signal Va (t) is selected (step S11), and the first SW 231a is turned on. As a result, the drive signal V (t) is input to the piezoelectric element 86, and the ejection operation in the first ejection period starts.

  Next, the CPU 201 selects a drive signal for the next ejection period based on the ejection information (Step S13). Then, the CPU 201 determines whether or not the drive signal needs to be switched in the next ejection period (step S14). For example, when the first drive signal Va (t) is selected in the first ejection period and the second drive signal Vb (t) is selected in the second ejection period, it is determined that the drive signal needs to be switched. .

  When the switching of the drive signal is necessary (Step S14: Yes), the CPU 201 causes the potential difference detection unit 233 to perform the above-described operation of detecting the potential difference (Step S15), and the correction signal generation unit 234 generates a correction signal. At the same time, the offset processing is performed by the correction processing unit 222 (step S16). As a result, the first drive signal Va ′ (t) and the second drive signal Vb ′ (t) after correction are output from the first drive signal generator 223a and the second drive signal generator 223b. Then, the CPU 201 causes the switching control unit 232 to execute switching control (step S17).

  Next, the CPU 201 determines whether or not to end the image recording operation (step S18), and when it is to be ended (step S18: Yes), ends the processing. On the other hand, if the image recording operation is not to be ended, the CPU 201 returns the processing to step S13. If the CPU 201 determines in step S14 that switching of the drive signal is not necessary (step S14: No), the process proceeds to step S18.

  As described above, by performing the potential difference detection and the offset correction for each ejection cycle, the potential change when the drive signal is switched is always suppressed.

  The CPU 201 may execute the potential difference detection and the offset correction when the power of the liquid ejection apparatus 1 is turned on. When the correction processing unit 222 holds the correction signal, the correction signal is updated with a new correction signal.

<Effect>
According to the liquid ejecting apparatus 1 according to the present embodiment, by performing the potential difference detection and the offset correction as described above, the potential change when the drive signal is switched is suppressed. Further, by performing the potential difference detection and the offset correction for each ejection cycle, it is possible to cope with a potential change depending on a temperature change during the ejection operation.

  In the present embodiment, since the first SW 231a and the second SW 231b and the potential difference detection unit 233 are provided in the liquid ejection head 31 having the piezoelectric element 86, the potential difference detection unit 233 has the characteristics of the first signal transmission unit and the like. , The potential difference can be detected with high accuracy, and the accuracy of offset correction is improved.

  Further, in the present embodiment, since the correction signal generation unit 234 is provided in the liquid ejection head 31, it is possible to suppress deterioration of the potential difference information and generate a highly accurate correction signal.

[Second embodiment]
Hereinafter, a liquid ejection device according to a second embodiment of the present invention will be described.

  FIG. 11 is a diagram illustrating a configuration of the correction processing unit 222 according to the second embodiment. In the present embodiment, the correction processing unit 222 includes an offset correction processing unit 300, a voltage magnification correction processing unit 301, and a voltage magnification storage unit 302.

  The offset correction processing unit 300 performs an offset process based on the correction signals (the first offset signal and the second offset signal) described in the first embodiment. The voltage magnification correction processing unit 301 performs voltage magnification correction processing for adjusting the speed and weight of the liquid (droplet) discharged from the nozzle 98a on the offset-processed waveform data. The voltage magnification storage unit 302 stores the voltage magnification used for the voltage magnification correction processing. This voltage magnification is stored in advance in the voltage magnification storage unit 302 from an external PC or the like.

  The voltage magnification correction is a correction process for performing an operation of multiplying a voltage signal constituting the waveform data by a voltage magnification, and aims at enlarging or reducing the voltage magnification with reference to an intermediate potential. Therefore, if the voltage magnification correction is simply performed, the voltage value based on the GND potential is corrected. Therefore, if a deviation occurs in the intermediate potential, the deviation amount influences and the voltage magnification is affected. There is a possibility that a further potential shift will occur in the corrected waveform data.

  Therefore, in the present embodiment, the correction processing unit 222 is configured to perform the voltage magnification correction processing by the voltage magnification correction processing unit 301 after the offset correction processing by the offset correction processing unit 300 is performed.

  Specifically, assuming that the waveform after the offset correction is expressed by the above equations (3) and (4), the voltage magnification correction processing unit 301 performs the correction processing based on the following equations (5) and (6). .

Va ″ (t) = (Va ′ (t) −Vi) × X + Vi (5)
Vb ″ (t) = (Vb ′ (t) −Vi) × X + Vi (6)
Here, X is the voltage magnification stored in the voltage magnification storage unit 302. Va ″ (t) and Vb ″ (t) represent the first drive signal and the second drive signal after the voltage magnification correction, respectively.

  That is, the voltage magnification correction processing unit 301 multiplies the waveform obtained by subtracting the ideal potential Vi from the waveform after the offset correction (the waveform whose intermediate potential is the GND potential) by the voltage magnification, and adds the ideal potential Vi.

  The waveform data subjected to the voltage magnification correction by the voltage magnification correction processing unit 301 is input to the first drive signal generation unit 223a and the second drive signal generation unit 223b, and the first drive signal Va ″ (t) and the second drive signal A signal Vb ″ (t) is generated.

  This voltage magnification correction processing is performed after the offset correction processing in step S16 in the flowchart of the first embodiment shown in FIG.

  Other configurations and operations of the liquid ejection device according to the second embodiment are the same as those of the liquid ejection device according to the first embodiment.

  In the second embodiment, it is preferable that the liquid discharge device performs the initial operation shown in FIG. 12 after the power is turned on.

  FIG. 12 is a flowchart illustrating an initial operation after power is turned on. When the power button of the operation display unit 5 is operated to turn on the power (step S30), the CPU 201 determines whether or not the offset values (the first offset signal and the second offset signal) are stored in the offset correction processing unit 300. Is determined (step S31).

  When the offset value is stored in the offset correction processing unit 300 (Step S31: Yes), the CPU 201 determines whether or not the correction value needs to be updated (Step S32). For example, the CPU 201 displays a message on the operation display unit 5 and allows the user to select whether or not the update is necessary.

  When the offset value is not stored in the offset correction processing unit 300 (Step S31: No), and when the correction value needs to be updated (Step S32: Yes), the CPU 201 operates the respective units to perform the above-described operation. Is performed (step S33). Thus, the offset value (correction signal) is obtained and stored in the offset correction processing unit 300.

  Next, the CPU 201 determines whether or not the voltage magnification is stored in the voltage magnification storage unit 302 (step S34). When the voltage magnification is not stored in the voltage magnification storage unit 302 (step S34: No), the CPU 201 executes a process of acquiring the voltage magnification, and stores the acquired voltage magnification in the voltage magnification storage unit 302 (step S35). ).

  Thereafter, the CPU 201 controls each unit to start an image recording operation on the sheet 11 (step S36). If it is determined in step S32 that the correction value does not need to be updated (step S32: No), the CPU 201 skips steps S33 to S35 and starts the image recording operation.

  As described above, in the second embodiment, since the voltage magnification correction is performed in a state where the intermediate potential is set to zero after the offset correction, the potential deviation is suppressed by the voltage magnification correction.

[Third embodiment]
Hereinafter, a liquid ejection device according to a third embodiment of the present invention will be described.

  FIG. 13 is a block diagram illustrating an electrical configuration of the drive signal substrate 51a and the liquid ejection head 31 according to the third embodiment. The drive signal substrate 51a of the present embodiment further includes a temperature difference detection unit 400 and a temperature difference correction processing unit 401.

  The temperature difference detector 400 is a temperature sensor that detects a temperature difference between the first drive signal generator 223a and the second drive signal generator 223b. Since the first drive signal generation unit 223a and the second drive signal generation unit 223b are each configured by a separate circuit, a temperature difference may occur between them due to a difference in heat generation amount or the like.

  The temperature difference correction processing unit 401 corrects the waveform based on the temperature difference detected by the temperature difference detection unit 400 so that the difference between the first drive signal and the second drive signal caused by the temperature difference disappears.

  This temperature difference detection and temperature difference correction processing is performed in step S16 in the flowchart shown in FIG.

  Other configurations and operations of the liquid ejection device according to the third embodiment are the same as the configurations and operations of the liquid ejection device according to the first embodiment or the second embodiment.

  As described above, in the third embodiment, the drive signal is corrected based on the temperature difference between the drive signal generation units, so that more accurate correction can be performed.

<Modification>
In each of the above embodiments, two drive signal generation units, the first drive signal generation unit 223a and the second drive signal generation unit 223b, are provided. However, the number of drive signal generation units is not limited to two and may be three. It is good also as above. In this case, a signal line for transmitting a drive signal to each drive signal generation unit is provided in the first signal transmission unit. The potential difference detection unit 233 detects a potential difference between the intermediate potential of each drive signal and the ideal potential Vi. The correction signal generator 234 generates a correction signal (offset signal) corresponding to each potential difference.

  In each of the above embodiments, the waveform data for generating small droplets or the waveform data for generating large droplets is input to the drive signal generation unit. However, the waveform data is not limited to these, and can be changed as appropriate. For example, waveform data for fine drive may be input to the drive signal generator. The fine drive is an operation of inputting a drive signal to the piezoelectric element 86 such that a liquid is not discharged from the nozzle 98a and stirring the nozzle surface when the pixel corresponds to a white area on the image data.

  As the potential difference between the ideal potential and the intermediate potential used for the correction, a value other than that described above may be used. For example, when the intermediate potential Va (0) of the first drive signal Va (t) is different from the intermediate potential Vb (0) of the second drive signal Vb (t), the intermediate potential is the first drive signal Va. It may be adjusted to one of the intermediate potential Va (0) of (t) and the intermediate potential Vb (0) of the second drive signal Vb (t). A potential difference calculated based on such an intermediate potential may be used to generate a correction signal.

  Note that the present invention is not limited to the requirements described in the above embodiments. Regarding these points, the gist of the present invention can be changed within a range that does not impair the gist, and can be appropriately determined according to the application form.

DESCRIPTION OF SYMBOLS 1 Liquid discharge device 10 Ink cartridge 11 Paper 31 Liquid discharge head 51, 51a Drive signal board 86 Piezoelectric element (drive element)
98a Nozzle 200 control section 220 drive waveform information storage section 221 waveform selection section 222 correction processing section 223a first drive signal generation section 223b second drive signal generation section 224 ejection timing control section 225 droplet size selection section 230 head temperature detection section 231a First switching element 231b Second switching element 232 Switching control unit 233 Potential difference detection unit 234 Correction signal generation unit 240a Signal line 240b Signal line 241 Signal line 300 Offset correction processing unit 301 Voltage magnification correction processing unit 302 Voltage magnification storage unit 400 Temperature difference Detector 401 Temperature difference correction processor

JP 2018-83405 A

Claims (11)

A liquid discharge apparatus comprising: a liquid discharge head that discharges liquid from a nozzle; and a drive signal substrate that inputs a drive signal corresponding to waveform data to the liquid discharge head,
A driving element for driving the nozzle,
A plurality of switching elements connected in parallel to the driving element;
A first signal transmission unit including a plurality of signal lines connected to the drive element via the switching elements and transmitting the drive signal;
A switching control unit that performs switching control to selectively turn on the plurality of switching elements;
A potential difference detection unit that detects a potential difference based on an intermediate potential of the drive signal transmitted to each signal line,
A correction signal generation unit that generates a correction signal based on the potential difference,
A correction processing unit that corrects the waveform data based on the correction signal,
A drive signal generation unit provided for each signal line, the drive signal generation unit generating the drive signal based on the waveform data corrected by the correction processing unit and outputting the drive signal to the signal line,
A liquid ejection device having:   The liquid ejection apparatus according to claim 1, wherein the correction processing unit includes an offset correction processing unit that performs an offset correction for correcting the waveform data so as to eliminate the potential difference based on the correction signal.   The correction processing unit further includes a voltage magnification correction processing unit that multiplies a waveform obtained by subtracting an ideal potential from the waveform subjected to the offset correction by a voltage magnification and performs a voltage magnification correction to add the ideal potential. 3. The liquid ejection device according to 2. The drive signal generator outputs the drive signal based on waveform data that is different from each other periodically at a constant ejection cycle,
4. The liquid ejection device according to claim 1, wherein the drive signal input to the drive element is selected by the switching control. 5.   The liquid ejecting apparatus according to claim 1, further comprising a second signal transmission unit that transmits the correction signal from the correction signal generation unit to the correction processing unit.   The method according to claim 1, wherein the detection of the potential difference by the potential difference detection unit, the generation of the correction signal by the correction signal generation unit, and the correction by the correction processing unit are performed for each ejection cycle. The liquid ejection device according to claim 1.   The detection of the potential difference by the potential difference detection unit, the generation of the correction signal by the correction signal generation unit, and the correction by the correction processing unit are executed before an image recording operation on a recording medium by the liquid ejection head. The liquid ejection device according to claim 1.   The liquid ejection device according to claim 1, wherein the driving element is a piezoelectric element.   9. The liquid ejecting apparatus according to claim 1, wherein the potential difference is a potential difference between an intermediate potential and an ideal potential. A driving element for driving a nozzle for discharging liquid,
A plurality of switching elements connected in parallel to the driving element;
A first signal transmission unit connected to the drive element via each of the switching elements and configured to transmit a drive signal corresponding to waveform data;
A potential difference detection unit that detects a potential difference based on an intermediate potential of the drive signal transmitted to each of the signal lines. A driving element for driving a nozzle for discharging liquid,
A plurality of switching elements connected in parallel to the driving element;
A first signal transmission unit connected to the drive element via each of the switching elements and configured to transmit a drive signal corresponding to waveform data;
A potential difference detection unit that detects a potential difference based on an intermediate potential of the drive signal transmitted to each of the signal lines.
A correction signal is generated based on the potential difference detected by the potential difference detection unit, the waveform data is corrected based on the correction signal, and the drive signal is generated based on the waveform data corrected by the correction signal. And driving the driving element by outputting the signal to the signal line.

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