JP4725307B2 - Inkjet printer - Google Patents

Description

  In the present invention, for example, minute characters of liquid inks of a plurality of colors are ejected from a plurality of nozzles to form fine particles (ink dots) on a print medium, thereby drawing a predetermined character or image. The present invention relates to an inkjet printer driving apparatus and a driving method thereof.

Such an inkjet printer is generally inexpensive and can easily obtain a high-quality color printed matter. Accordingly, along with the widespread use of personal computers and digital cameras, it has become widespread not only in offices but also in general users.
In such an ink jet printer, a moving body called a carriage or the like, which is integrally provided with an ink cartridge and a print head (also referred to as an ink jet head), generally reciprocates on a print medium in a direction intersecting the transport direction. While ejecting (injecting) liquid ink droplets from the nozzles of the print head to form minute ink dots on the print medium, a predetermined character or image is drawn on the print medium to produce a desired printed matter. It is designed to create. The carriage is equipped with four color (yellow, magenta, cyan) ink cartridges including black (black) and a print head for each color, so that not only monochrome printing but also full-color printing combining each color is easy. (Furthermore, 6 colors, 7 colors, or 8 colors in which light cyan, light magenta, etc. are added to these colors are also put into practical use).

  In such an ink jet printer, the actuator is driven by a drive signal to change the pressure in the pressure chamber, and the ink in the pressure chamber is ejected as an ink droplet from a nozzle communicating with the pressure chamber by the pressure change. There are also several types of actuators. For example, in a piezoelectric inkjet printer, when a drive signal is applied to a piezoelectric (piezoelectric) element, which is an actuator, the diaphragm in contact with the pressure chamber is displaced, thereby changing the pressure in the pressure chamber. Ink droplets are discharged.

In this type of ink jet printer, a common drive signal is applied to actuators of a plurality of nozzles for the purpose of shortening the time required for printing, simplifying the drive circuit, and reducing the number of signal lines. That is, the same drive signal is simultaneously supplied to a plurality of actuators. In such a case, a plurality of actuators are connected in parallel to one drive signal. The actuator to be connected is selected according to the nozzle that should eject ink droplets, that is, print data. As described above, when the number of actuators connected to one drive signal changes, it has become clear that the ink droplet ejection characteristics change according to the number of connections. Therefore, in the inkjet printer described in Patent Document 1 below, the number of actuators (or nozzles) that are actually driven is obtained, and the drive signal itself for ink droplet ejection is changed and set according to the number. Specifically, the ink droplet ejection characteristics are stabilized by changing the slope of the voltage increase or decrease of the drive signal composed of the trapezoidal wave voltage signal or the peak value itself.
JP 2000-238262 A

  However, in the conventional ink jet printer, although the ink droplet ejection characteristics can be stabilized to some extent, further improvement is desired. In other words, actuators composed of piezo elements have individual differences such as processing variations and heat generation coefficients. Cumulative differences occur for the number of actuators that are actually driven, and the cumulative values also differ depending on the selected actuator. . This becomes remarkable in a line head type ink jet printer that simultaneously drives more actuators.

  The present invention has been made paying attention to the above-described problems, and a component having a frequency characteristic opposite to the frequency characteristic of a drive circuit including an actually driven actuator is used as an original ink droplet ejection drive signal. It is an object of the present invention to provide an ink jet printer that can stabilize ink droplet ejection characteristics by adding.

[Invention 1] In order to solve the above problems, an ink jet printer of the invention 1, an ink jet printer having a driving means to apply a drive signal for ink droplet ejection actuator of nozzles for ejecting Lee ink droplets, detecting the frequency characteristic of the driving circuit including the actuator upon application of a frequency characteristic detection drive signal to the actuator of nozzles for discharging the ink droplets, the ink in the filter of the frequency characteristic and the inverse of the frequency characteristic through droplet ejection drive signal, and characterized by supplying a filter pass component of the frequency characteristic and the inverse of the frequency characteristics to hear dynamic circuit before addition to the ink droplet ejection drive signal.

  The inventors of the present application, for example, form a low-pass filter in which the capacitance of the actuator made of a piezoelectric element and the parasitic inductance and resistance component of the wiring form a kind of low-pass filter, thereby removing the high-frequency component of the drive signal, so-called dullness occurs. It was found that the drive signal is distorted. Moreover, the frequency characteristics of the low-pass filter differ depending on the selected actuator and the number thereof as described above. Therefore, according to the ink jet printer according to the first aspect of the present invention, the frequency characteristic detection drive signal is applied to the actuator of the nozzle that should eject ink droplets, and the frequency characteristic of the drive circuit including the actuator at that time is detected. Since the ink droplet ejection drive signal is passed through a filter having a frequency characteristic opposite to that frequency characteristic, the filter passing component is supplied to the drive circuit including the actuator in addition to the original ink droplet ejection drive signal. In addition, the drive signal applied to the actuator coincides with or substantially coincides with the original ink droplet ejection drive signal, and the ink droplet ejection characteristics of the individual nozzles can be stabilized close to the ideal state.

[Invention 2] invention 2 of the ink jet printer, outputs print data representing the actuator provided for the Bruno nozzle, or to discharge ink droplets of the amount of the degree of any nozzle or rads based on the print data comprising: a print data output means, and driving means for pre-applying a drive signal for ink droplet ejection actuator of the nozzles which eject ink droplets based on Kishirushi character data for ejecting ink droplets from the nozzle, the drive means, before Symbol ink droplet ejection drive signal preceding the ink droplet non-ejection frequency characteristic detection drive signal setting means to sequence chronological order frequency characteristic detection drive signal of any based on said print data actuator to the frequency characteristic detection drive signal and the ink droplet ejection driving signals one is selected-option selection whether to apply or to a plurality of actuators same Serial frequency characteristic detection drive signal and selection means to apply the ink droplet ejection driving signal, the frequency characteristic of detecting a frequency characteristic of the drive circuit including the actuator when the frequency characteristic detection drive signal is applied detection hand stage, the inverse frequency characteristic filter setting means to set the inverse frequency characteristic filter of the frequency characteristic detected by the detecting means that said frequency characteristic opposite frequency characteristics, the ink droplet ejection driving signal is the inverse frequency characteristic filter it is characterized in that it comprises a frequency characteristic amended driving signal output hands stage supplied to the drive circuit frequency components in addition to the initial ink droplet ejection drive signal that has passed through the.

  According to the ink jet printer of the second aspect, in order to detect the frequency characteristic of the drive circuit including the actuator, the frequency characteristic detection drive signal for non-ink droplet ejection is arranged in time series before the ink droplet ejection drive signal. And selecting which actuator to apply the frequency characteristic detection drive signal and the ink droplet ejection drive signal to the actuator based on the print data, and the same frequency characteristic detection drive signal to one or more selected actuators. In addition, the ink droplet ejection drive signal is applied, and the frequency characteristic of the drive circuit including the actuator is detected when the frequency characteristic detection drive signal is applied, and the reverse frequency of the frequency characteristic opposite to the detected frequency characteristic is detected. Set the characteristic filter, and pass the ink droplet ejection drive signal through the inverse frequency characteristic filter. In addition to the ink droplet discharge drive signal, the drive signal is supplied to the drive circuit including the actuator. Therefore, the drive signal actually applied to the actuator matches or substantially matches the original ink droplet discharge drive signal. The ink droplet ejection characteristics can be stabilized close to the ideal state.

[Invention 3] invention 3 of the ink jet printer is an ink jet printer of the invention 2, wherein the frequency characteristic detection drive signal setting means, each of the case where the ink droplet ejection driving signal is coupled to a time-series manner the ink droplet ejection by arranging the frequency characteristic detection drive signal to the previous stage of all of the drive signal, the inverse frequency characteristic filter setting unit, the frequency characteristic at respective frequency characteristics detection drive signal applied which is detected by the detection means it is characterized in that on the basis of the frequency characteristic setting the inverse frequency characteristic filter of the frequency characteristic and the inverse of the frequency characteristics.

  According to the ink jet printer according to the third aspect of the present invention, when the ink droplet ejection drive signals are connected in time series, the frequency characteristic detection drive signals are arranged in all preceding stages of the individual ink droplet ejection drive signals, Based on the detected frequency characteristics when the frequency characteristic detection drive signal is applied, the inverse frequency characteristic filter of the opposite frequency characteristic is set, so that, for example, ink droplet ejection is performed to eject ink droplets of different resolutions. Even in the case where the driving signals are connected in time series, the actual driving signals applied to the actuator can be matched or substantially matched with the original ink droplet ejection driving signal.

[Invention 4] The ink jet printer according to invention 4 is the ink jet printer according to invention 2 or 3, wherein the frequency characteristic detecting means detects an actual signal value when the frequency characteristic detecting drive signal is applied, and performs fast Fourier transform. It performs the inverse frequency characteristic filter setting means is characterized by setting the inverse frequency characteristic filter based on the power spectrum value of the specific high frequency component of the fast Fourier transformed real signal values .

  According to the ink jet printer according to the fourth aspect of the present invention, the actual signal value at the time of applying the frequency characteristic detection drive signal is detected, the fast Fourier transform is performed, and the specific high frequency component of the actual signal value obtained by the fast Fourier transform is detected. Since the reverse frequency characteristic filter is set based on the power spectrum value, it is possible to set the reverse frequency characteristic filter accurately and easily.

Next, a first embodiment of an ink jet printer drive device according to the present invention will be described with reference to the drawings.
FIG. 1 is a plan view showing a schematic configuration of the ink jet printer 1 of the present embodiment. As shown in FIG. 1, the ink jet printer 1 includes a carriage 4 on which a head unit 2 and an ink cartridge 3 are mounted. The carriage 4 is guided by a set of carriage shafts 5 and can move in the main scanning direction. It has become. A part of the carriage 4 is fixed to a toothed belt 9, and the toothed belt 9 is stretched between a driving pulley 7 and a driven pulley 8 fixed to a rotating shaft of the motor 6.

  Further, an encoder 10 is attached to the carriage 4, and a linear scale 11 is provided along the moving direction of the carriage 4. Thereby, the position of the head unit 2 on the carriage 4 is detected by the encoder 10. In FIG. 1, reference numeral 12 denotes a cable for electrically connecting the head unit 2 and the system controller, reference numeral 13 denotes a wiper for cleaning the surface of an ink jet head described later, and reference numeral 14 denotes the ink jet. It is a cap for capping the nozzle substrate (see FIG. 3) of the head.

  In the ink jet printer 1 having such a configuration, when the detection signal of the encoder 10 is input to a motor control circuit (not shown), the motor control circuit causes the rotational operation of the motor 6 to be accelerated, constant speed, decelerated, Inversion, acceleration, constant speed, deceleration, inversion, etc. are controlled. Along with the operation of the motor 6, the carriage 4 repeats reciprocating movement in the main scanning direction, and the constant speed section corresponds to the printing area. Therefore, the head unit 2 mounted on the carriage 4 at the constant speed. Ink droplets are ejected from the nozzles onto the print medium a. As a result, predetermined characters and images are recorded (printed) on the printing medium a by the ink dots formed by the ink droplets.

  Next, a specific configuration of the head unit 2 shown in FIG. 1 will be described with reference to FIGS. 2A and 3. The head unit 2 includes a plurality of inkjet heads (nozzle heads) 20 as shown in FIG. 2a, and each inkjet head 20 uses a piezoelectric actuator. As shown in FIG. 2 a, the inkjet head 20 includes a vibration plate 21, a piezoelectric actuator 22 that displaces the vibration plate 21, an ink that is liquid inside, and an internal pressure caused by the displacement of the vibration plate 21. A cavity (pressure chamber) 23 that is increased or decreased, and a nozzle 24 that communicates with the cavity 23 and ejects ink as droplets by increasing or decreasing the pressure in the cavity 23 are provided.

  More specifically, the inkjet head 20 includes a nozzle substrate 25 on which nozzles 24 are formed, a cavity substrate 26, a vibration plate 21, and a laminated piezoelectric actuator 22 in which a plurality of piezoelectric elements 27 are laminated. Yes. The cavity substrate 26 is formed in a predetermined shape as shown in the figure, whereby a cavity 23 and a reservoir 28 communicating with the cavity 23 are formed. The reservoir 28 is connected to the ink cartridge 3 via the ink supply tube 29. The piezoelectric actuator 22 includes comb-shaped electrodes 31 and 32 arranged opposite to each other, and piezoelectric elements 27 arranged alternately with the comb teeth of the electrodes 31 and 32. The piezoelectric actuator 22 is joined to the diaphragm 21 through an intermediate layer 30 at one end side thereof as shown in FIG.

  In the piezoelectric actuator 22 having such a configuration, the drive signal from the drive signal source applied between the first electrode 31 and the second electrode 32 expands and contracts in the vertical direction as indicated by an arrow in FIG. The mode to use is used. Therefore, in the piezoelectric actuator 22, for example, when a drive signal as shown in FIG. 2A is applied, the vibration plate 21 is displaced, the pressure in the cavity 23 changes, and an ink droplet is ejected from the nozzle 24. It has become. Specifically, as will be described in detail later, the volume of the cavity 23 is expanded (expanded) to draw ink, and then the volume of the cavity 23 is reduced (shrinked) to eject the ink, thereby Ink droplets are ejected from the nozzles. The nozzles 24 for each inkjet head 20 formed on the nozzle substrate 26 shown in FIG. 2a are arranged as shown in FIG. 3, for example. In the example of FIG. 3, an arrangement pattern of the nozzles 24 when applied to four colors of ink (Y: yellow, M: magenta, C: cyan, K: black) is shown. Full color printing is possible.

  Another example of the piezoelectric actuator 22 is shown in FIG. The reference numerals in the figure are the same as those in FIG. 2a. This piezoelectric actuator is generally called a unimorph actuator and has a simple structure in which the piezoelectric element 27 is sandwiched between two electrodes 31 and 32. By applying a drive signal, the piezoelectric actuator is similar to the stacked actuator of FIG. 2a. Then, the ink expands and contracts in the vertical direction in the figure, expands the volume of the cavity 23 and draws ink, and then reduces the volume of the cavity 23 and discharges ink droplets from the nozzles 24.

  The inkjet printer 1 is provided with a control device for controlling itself. For example, as shown in FIG. 4, the control device prints on a print medium by controlling a printing device, a paper feeding device, and the like based on print data input from a host computer 60 such as a personal computer or a digital camera. The processing is performed. An input interface unit 61 that receives print data input from the host computer 60, a control unit 62 configured by, for example, a microcomputer that executes print processing based on the print data input from the input interface unit 61, A carriage motor driver 63 that drives and controls the carriage motor 41, a paper feed motor driver 64 that drives and controls the paper feed motor 51, a head driver 65 that drives and controls the inkjet head 20, and output signals of the drivers 63, 64, and 65 And an interface 67 that converts the output signal into a control signal used by the inkjet head 20 and outputs the control signal.

  The control unit 62 temporarily stores a CPU (Central Processing Unit) 62a that executes various processes such as a print process, and print data input through the input interface 61 or various data when the print data print process is executed. A ROM (Read-Only ROM) comprising a RAM (Random Access Memory) 62c that temporarily stores an application program such as print processing or the like, and a non-volatile semiconductor memory that stores a control program executed by the CPU 62a Memory) 62d. When the control unit 62 obtains print data (image data) from the host computer 60 via the interface unit 61, the CPU 62a performs a predetermined process on the print data and ejects ink droplets from any nozzle. Alternatively, print data indicating how many ink droplets are to be ejected is output, and control signals are output to the drivers 63 to 65 based on the print data and input data from various sensors. When the control signals are output from the drivers 63 to 65, they are converted into drive signals by the interface unit 67, and the piezoelectric actuators 22, the carriage motors 41, and the paper feed motors 51 corresponding to the plurality of nozzles 24 of the inkjet head 20. Each of which operates to perform a printing process on the print medium. Each component in the control unit 62 is electrically connected through a bus (not shown).

  Further, the control unit 62 writes the write enable signal DEN, the write clock signal WCLK, and the write address data A0 to A0 in order to write the waveform forming data DATA for forming the drive signal described later into the waveform memory 701 described later. A3 is output to write, for example, 16-bit waveform forming data DATA into the waveform memory 701, and read address data A0 to A3 for reading out the waveform forming data DATA stored in the waveform memory 701. The first clock signal ACLK that sets the timing for latching the waveform forming data DATA read from the waveform memory 701, the second clock signal BCLK that sets the timing for adding the latched waveform data, and the latch data are cleared. Outputs clear signal CLER to head driver 65 That.

The head driver 65 includes a drive signal generation circuit 70 that generates a drive signal COM and an oscillation circuit 71 that outputs a clock signal SCK. As shown in FIG. 5, the drive signal generation circuit 70 includes a waveform memory 701 for storing waveform formation data DATA for generating a drive signal input from the control unit 62 in a storage element corresponding to a predetermined address, A latch circuit 702 that latches the waveform forming data DATA read from the waveform memory 701 by the first clock signal ACLK described above, an output of the latch circuit 702, and waveform generation data WDATA output from a latch circuit 704 described later. An adder 703 for adding, a latch circuit 704 for latching the addition output of the adder 703 by the above-described second clock signal BCLK, and a predetermined high-pass filter process on the waveform generation data WDATA output from the latch circuit 704 Digital filter circuit 708 to be applied and the digital filter A switch 709 for selecting passed in accordance with the waveform generation data and high frequency components WDATAH output from the road 70 8 the selection signal WN, the waveform generation data high which has passed through the waveform generation data WDATA and a switch 709 which is output from the latch circuit 704 An adder 710 that adds the frequency component WDATAH, an output of the adder 710, that is, a D / A converter 705 that converts the frequency characteristic corrected waveform generation data WDATAS into an analog signal, and the D / A converter 705 A voltage amplifying unit 706 that amplifies the output analog signal, a current amplifying unit 707 that amplifies the output signal of the voltage amplifying unit 706 and outputs the drive signal COM to the piezoelectric actuator 22, and a piezoelectric actuator The frequency characteristics of the actual drive signal COM of the drive circuit including A frequency characteristic calculator 712 detected by the D conversion, and an inverse frequency characteristic filter (high-pass filter) having a frequency characteristic opposite to the frequency characteristic of the actual drive signal COM detected by the frequency characteristic calculator 712. And an inverse frequency characteristic filter selection circuit 711 for selecting from among the digital filter circuit 708. Here, the clear signal CLER output from the control unit 62 is input to the latch circuits 702 and 704, and the latch data is cleared when the clear signal CLER is turned off.

  As shown in FIG. 6, in the waveform memory 701, memory elements each having several bits are arranged at the designated address, and waveform data DATA is stored together with the addresses A0 to A3. Specifically, the waveform data DATA is input together with the clock signal WCLK to the addresses A0 to A3 instructed from the control unit 62, and the waveform data DATA is stored in the memory element by the input of the write enable signal DEN.

  The inkjet head 20 selects a nozzle to be ejected based on the drive signal COM generated by the drive signal generation circuit 70 and the print data via the input / output interface unit 67 and outputs the drive signal COM to the piezoelectric actuator 22. After the drive waveform signal selection data signal SI for determining the connection timing and the nozzle selection data are input to all the nozzles, the drive signal COM and the piezoelectric actuator 22 of the inkjet head 20 are connected based on the drive waveform signal selection data SI. A clock signal SCK for transmitting the latch signal LAT, the channel signal CH, and the drive waveform signal selection data signal SI to the inkjet head 20 as a serial signal is input.

  Next, a configuration for connecting the drive signal COM output from the drive signal generation circuit 70 and the piezoelectric element 71 will be described. FIG. 7 is a block diagram of a selection unit that connects the drive signal COM and the piezoelectric element 71. The selection unit temporarily stores drive register signal selection data SI for designating the piezoelectric actuator 22 corresponding to the nozzle 24 to which ink droplets are to be ejected, and data of the shift register 211. The latch circuit 212 includes a level shifter 213 that converts the output of the latch circuit 212 and a selection switch 201 that connects the drive signal COM to the piezoelectric actuator 22 in accordance with the output of the level shifter.

  The drive waveform signal selection data signal SI is sequentially input to the shift register 211, and the storage area is sequentially shifted from the first stage to the subsequent stage according to the input pulse of the clock signal SCK. The latch circuit 212 latches each output signal of the shift register 211 by the input latch signal LAT after the drive waveform signal selection data SI for the number of nozzles is stored in the shift register 211. The signal stored in the latch circuit 212 is converted by the level shifter 213 to a voltage level at which the selection switch 201 at the next stage can be turned on / off. This is because the drive signal COM is higher than the output voltage of the latch circuit 212, and the operating voltage range of the selection switch 201 is set higher accordingly. The selection switch 201 is composed of an analog switch having a transmission gate in which a P-channel FET and an N-channel FET are combined, and the gate voltage is level-converted to a high value in order to sufficiently operate the analog switch. The piezoelectric actuator 22 of the nozzle to which the gate voltage of the selection switch 201 is applied by the level shifter 213 is connected to the drive signal COM at the connection timing of the drive waveform signal selection data SI. In addition, after the drive waveform signal selection data signal SI of the shift register 211 is stored in the latch circuit 212, the next print information is input to the shift register 211, and the storage data of the latch circuit 212 is stored in accordance with the ink droplet ejection timing. Update sequentially. Reference numeral HGND in the figure is the ground end of the piezoelectric actuator 22. Further, according to the selection switch 201, even after the piezoelectric actuator 22 is disconnected from the drive signal COM, the input voltage of the piezoelectric actuator 22 is maintained at the voltage just before the disconnection.

  Next, the principle of drive signal generation will be described. First, waveform data that is 0 as a voltage change amount per unit time is written in the address A0. Similarly, waveform data of + ΔV1 is written in the address A1, −ΔV2 is written in the address A2, and + ΔV3 is written in the address A3. In addition, the data stored in the latch circuits 702 and 704 is cleared by the clear signal CLER. The drive signal COM is raised to an intermediate potential (offset) by the waveform data.

  From this state, for example, as shown in FIG. 8, when the waveform data at the address A1 is read and the first clock signal ACLK is input, the digital data of + ΔV1 is stored in the latch circuit 702. The stored digital data of + ΔV1 is input to the latch circuit 704 via the adder 703, and the latch circuit 704 stores the output of the adder 703 in synchronization with the rise of the second clock signal BCLK. Since the output of the latch circuit 704 is also input to the adder 703, the output of the latch circuit 704, that is, the drive signal COM is added by + ΔV1 at the rising timing of the second clock signal BCLK. In this example, the waveform data at the address A1 is read during the time width T1, and as a result, the digital data of + ΔV1 is added until it is tripled.

  Next, when the waveform data at the address A0 is read and the first clock signal ACLK is input, the digital data stored in the latch circuit 702 is switched to zero. The digital data of 0 is added at the rising timing of the second clock signal BCLK through the adder 703 as described above, but since the digital data is 0, the value before that is substantially the same. Is retained. In this example, the drive signal COM is held at a constant value during the time width T0.

  Next, when the waveform data at the address A2 is read and the first clock signal ACLK is input, the digital data stored in the latch circuit 702 is switched to -ΔV2. The digital data of −ΔV2 passes through the adder 703 and is added at the rising timing of the second clock signal BCLK as described above. However, since the digital data is −ΔV2, the second clock is practically set. The drive signal COM is subtracted by −ΔV2 in accordance with the signal. In this example, the digital data of −ΔV2 is subtracted until it becomes 6 times during the time width T2.

  The drive signal COM thus generated and output after being subjected to analog conversion and voltage-current amplification is a waveform signal as shown in FIG. 2a. Of these, the rising portion of the drive signal COM is a stage where the volume of the cavity 23 is enlarged and ink is drawn (which can be said to draw the meniscus when the ink discharge surface is considered), and the falling portion of the drive signal COM is the volume of the cavity 23. Is reduced and the ink is ejected (which can be said to be a meniscus when the ink ejection surface is considered). As a result of ejecting the ink, ink droplets are ejected from the nozzles. Incidentally, the waveform of the drive signal depends on the waveform data 0, + ΔV1, −ΔV2, + ΔV3, the first clock signal ACLK, and the second clock signal BCLK written to the addresses A0 to A3, as can be easily guessed from the above. It can be adjusted.

  By variously changing the voltage increase / decrease slope and peak value of the drive signal COM consisting of this voltage trapezoidal wave, the ink drawing amount and drawing speed, the ink pushing amount and the pushing speed can be changed. It is possible to obtain different ink dot sizes by changing the amount of ink discharged. Therefore, for example, as shown in FIG. 9, even when a plurality of drive signals COM are connected in time series, a single drive signal COM is selected and supplied to the piezoelectric actuator 22 to eject ink droplets. A variety of ink dot sizes can be obtained by selecting a plurality of drive signals COM and supplying them to the piezoelectric actuator 22 and ejecting ink droplets a plurality of times. That is, if a plurality of ink droplets land on the same position before the ink is dried, it is substantially the same as ejecting a large ink droplet, and the size of the ink dot can be increased.

  By combining such techniques, it is possible to increase the number of gradations. The gradation is a state of density of each color included in a so-called pixel represented by ink dots, and the size of the ink dot corresponding to the color density of each pixel is called gradation, and can be expressed by ink dots. The number of furniture is called the number of gradations. High gradation means that the number of gradations is large. Note that the drive signal COM at the left end in FIG. 9 only draws ink and does not push it out. This is called microvibration, and is used, for example, to prevent or prevent nozzle drying and to detect how the actual drive signal changes as will be described later, without ejecting ink droplets.

  By the way, the trapezoidal wave drive signal COM as shown in FIG. 10a also has a trapezoidal corner as shown in FIG. This is because the piezoelectric actuators 22 are connected in parallel by the selection unit described above. The piezoelectric actuator 22 has a capacitance C. For example, in addition to the resistance R or parasitic inductance of the wiring itself shown in FIG. 11a, each time the piezoelectric actuator 22 is connected, as shown in FIGS. 11b, 11c, and 11d. Capacitance C is connected in parallel one after another, and a low-pass filter is configured by the entire drive circuit. Naturally, the drive signal COM supplied to the drive circuit constituting this low-pass filter is free from high-frequency components, that is, has a corner. The problem here is that the electrostatic capacitance C of the piezoelectric actuator 22 differs individually due to individual differences, and the frequency characteristics of the low-pass filter of the entire drive circuit differ depending on the selected piezoelectric actuator 22.

  Therefore, in the present embodiment, as shown in FIG. 12, the above-described fine vibration drive signals are arranged in the preceding stage of each drive signal COM, and this fine vibration drive signal is supplied to the drive circuit including the piezoelectric actuator 22. Is detected by a frequency characteristic calculator 712, and a digital filter having a frequency characteristic opposite to the frequency characteristic of the drive circuit detected by the frequency characteristic calculator 712, that is, a high-pass (high frequency) filter is included in the digital filter circuit 708. The component of the drive signal COM for ink droplet ejection that has passed through the digital filter circuit 708 is passed from the switch 709 and added to the original drive signal COM by the adder 710, and this is the frequency characteristic corrected drive signal. As a drive circuit including the piezoelectric actuator 22. That is, the minute vibration drive signal corresponds to the frequency characteristic detection drive signal of the present invention. The switch 709 is closed only when the selection signal WN is supplied. The digital filter circuit 708 includes a plurality of high-pass (high-frequency) filters having frequency characteristics.

  That is, in the present embodiment, a fine vibration drive signal, that is, a frequency characteristic detection drive signal and a frequency characteristic corrected drive signal are supplied to the drive circuit including the piezoelectric actuator 22 of the nozzle that should eject ink droplets based on the print data. Although supplied, the component that has passed through the digital filter 708 is removed by the drive circuit, so that the original ink droplet ejection drive signal is applied to the piezoelectric actuator 22. The frequency characteristic calculator 712 performs a fast Fourier transform FFT on the micro vibration drive signal COM detected only when the latch signal LAT and the channel signal CH are input. As is well known, when fast Fourier transform is performed, a power spectrum PS is obtained for each frequency f as shown in FIG. In the present embodiment, a power spectrum PS having a preset high frequency fa is obtained, and an inverse frequency characteristic filter is set based on the value of the power spectrum PS. In the inverse frequency characteristic filter, the pass frequency band and the gain are adjusted.

  Therefore, according to the ink jet printer of this embodiment, in order to detect the frequency characteristics of the drive circuit including the piezoelectric actuator 22, the ink droplet non-ejection frequency characteristic detection drive signal (slightly before the ink droplet ejection drive signal) Vibration drive signals) are arranged in time series, and the piezoelectric actuator 22 to which the frequency characteristic detection drive signal and the ink droplet ejection drive signal are applied is selected based on the print data. Alternatively, the same frequency characteristic detection drive signal and ink droplet ejection drive signal are applied to a plurality of actuators, and the frequency characteristics of the drive circuit including the piezoelectric actuator 22 when the frequency characteristic detection drive signal is applied are detected. Then, an inverse frequency characteristic filter having a frequency characteristic opposite to the detected frequency characteristic is set, and the inverse frequency characteristic filter is set to Since the ink droplet ejection drive signal is passed and the passed component is supplied to the drive circuit including the piezoelectric actuator 22 in addition to the original ink droplet ejection drive signal, it is actually applied to the piezoelectric actuator 22. The drive signal coincides with or substantially coincides with the original ink droplet ejection drive signal, and the ink droplet ejection characteristics of the individual nozzles can be stabilized close to the ideal state.

  In addition, when the ink droplet ejection drive signals are connected in time series, the frequency characteristic detection drive signals are arranged in all preceding stages of the individual ink droplet ejection drive signals, and the detected individual frequency characteristic detection drives. Since the inverse frequency characteristic filter of the opposite frequency characteristic is set based on the frequency characteristic at the time of signal application, for example, ink droplet ejection drive signals are connected in time series in order to eject ink droplets of different resolutions. Even in this case, each actual drive signal applied to the piezoelectric actuator 22 can be matched or substantially matched with the original ink droplet ejection drive signal.

In addition, the actual signal value at the time of applying the frequency characteristic detection drive signal is detected and fast Fourier transform is performed, and the inverse frequency based on the power spectrum value of the specific high frequency component of the actual signal value obtained by the fast Fourier transform. Since the characteristic filter is set, the inverse frequency characteristic filter can be set accurately and easily.
FIG. 14 shows a different embodiment of the drive signal generation circuit 70 of the ink jet printer of the present invention. In this embodiment, the digital filter circuit 708 of the drive signal generation circuit 70 in FIG. 5 is changed to an analog filter circuit 718. Along with this, the position of the D / A converter 705 is changed, and the adder 710 and the inverse frequency characteristic filter selection circuit 711 have analog functions, but the operation as the drive signal generation circuit 70 is almost the same. is there.

  In each of the above-described embodiments, only an example in which the inkjet printer drive device of the present invention is applied to a so-called multi-pass inkjet printer is described in detail. However, the inkjet printer head drive device of the present invention is a line head type. The present invention can be applied to all types of ink jet printers including printers.

1 is a plan view of an ink jet printer showing an embodiment of a head driving device of an ink jet printer of the present invention. It is a schematic block diagram of the inkjet head of the inkjet printer of FIG. It is explanatory drawing of the nozzle of the inkjet head of FIG. It is a block diagram of the control apparatus provided in the inkjet printer of FIG. FIG. 5 is a block diagram of the drive signal generation circuit of FIG. 4. It is explanatory drawing of the waveform memory of FIG. It is a block diagram of the selection part which connects a drive signal to a piezoelectric actuator. It is explanatory drawing of drive signal generation. It is explanatory drawing which shows an example of the drive signal which arranged the ink drop ejection drive signal in time series. It is explanatory drawing of the state from which a drive signal changes with the number of actuators connected. It is explanatory drawing of the low-pass filter comprised by the actuator connected. It is explanatory drawing which shows an example of the arrangement | sequence of the drive signal for ink droplet discharge, and the drive signal for frequency characteristic detection. It is explanatory drawing of the power spectrum of the drive signal for a frequency characteristic detection by which the fast Fourier transform was carried out. FIG. 5 is a block diagram illustrating another example of the drive signal generation circuit of FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 is an inkjet printer, 15 is a selection switch, 20 is an inkjet head, 21 is a diaphragm, 22 is a piezoelectric actuator, 23 is a cavity, 24 is a nozzle, 62 is a control part, 70 is a drive signal generation circuit, a is a printing medium

Claims (4)

An inkjet printer provided with a drive means to apply a drive signal for ink droplet ejection actuator of nozzles for ejecting Lee ink droplets,
Detecting the frequency characteristic of the driving circuit including the actuator upon application of a frequency characteristic detection drive signal to the actuator of nozzles for discharging the ink droplets, the ink in the filter of the frequency characteristic and the inverse of the frequency characteristic through droplet ejection drive signals, inkjet printer and supplying the filter pass component of the frequency characteristic and the inverse of the frequency characteristics to hear dynamic circuit before addition to the ink droplet ejection drive signal. An actuator which is provided for the mounting nozzle, the printing data output means for outputting the print data indicating for ejecting ink droplets of the amount of the degree of any nozzle or rads based on the print data, before Kishirushi shaped Drive means for applying an ink droplet ejection drive signal to an actuator of a nozzle that ejects ink droplets based on data and ejecting ink droplets from the nozzle;
Said driving means, before Symbol ink droplet ejection drive signal preceding the ink droplet non-ejection time series sequence to the frequency characteristics detection drive signal setting hand stage frequency characteristic detection drive signal of, based on said print data wherein the frequency characteristic detection drive signal and the ink droplet ejection driving signals one is selected-option selection whether to apply or more actuator same said frequency characteristic detection drive signal and the ink droplet to any of the actuator selection means to apply an ejection driving signal, the frequency characteristics detection means to detect the frequency characteristic of the drive circuit including the actuator when the frequency characteristic detection drive signal is applied, detected by the frequency characteristics detection means inverse frequency characteristic filter setting means to set the inverse frequency characteristic filter of the frequency characteristic and the inverse of the frequency characteristics, the ink droplet ejection drive signal Inkjet printers but that comprising the frequency characteristic amended driving signal output hands stage supplied to the driving circuit in addition to the initial ink droplet ejection drive signal frequency components having passed through the inverse frequency characteristic filter. Wherein the frequency characteristic detection drive signal setting means, the frequency characteristic detection drive signal to all the preceding stage of each of the ink droplet ejection drive signal when the ink droplet ejection driving signal is chronologically linked Array
The inverse frequency characteristic filter setting means sets the inverse frequency characteristic filter of the frequency characteristic and the inverse of the frequency characteristics based on the frequency characteristics at the time of the detected individual frequency characteristics detection drive signal applied at the frequency characteristic detecting means The inkjet printer according to claim 2, wherein: The frequency characteristic detection means detects an actual signal value when the frequency characteristic detection drive signal is applied, and performs a fast Fourier transform.
The inverse frequency characteristic filter setting means, according to claim 2 or 3, characterized in that to set the inverse frequency characteristic filter based on the power spectrum value of the specific high frequency component of the Fast Fourier transformed real signal values The inkjet printer described in 1.

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