JP2007098804A - Driver of inkjet printer and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the unevenness of nozzle ink-droplet delivery properties between heads even when forming and outputting a drive signal with connecting two or more drive waveform signals and feeding it to an actuator. <P>SOLUTION: Intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 for actuating a piezoelectric-type actuator 22 are corrected based on the information of the ink-droplet delivery properties acquired from the nozzles for every head, and the drive signal COM is formed and outputted by connecting in time series two or more drive waveform signals of WCOM1 to WCOM3 with the corrected intervals T1 and T2. Thereby, the influence of the pressure change in a cavity 23 due to the connected drive waveform signals of WCOM1 to WCOM3 in front and behind becomes possible to be suppressed, and then the unevenness of the nozzle ink-droplet delivery properties between heads becomes possible to be suppressed even when connecting two or more drive waveform signals of WCOM1 to WCOM3 and feeding them to the piezoelectric-type actuator 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 inkjet printers are generally inexpensive and can easily obtain high-quality color prints, and therefore have become widespread not only in offices but also in general users with the spread of personal computers and digital cameras.
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 called 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.

  By the way, in this type of ink jet printer, higher gradation is required. 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. The size of the ink dot depends on the amount of ink droplets. In order to change the gradation, for example, it is necessary to change a drive signal to an actuator provided in the ink jet head. For example, when the actuator is a piezo element (piezoelectric element), the displacement (strain) of the actuator (more precisely, the diaphragm) increases as the voltage value applied to the actuator increases. The gradation of dots can be changed.

  Therefore, in Patent Document 1 listed below, a drive signal is created by combining drive waveform signals corresponding to each gradation degree of the number of gradations that can be achieved, and this is generated for each pixel, that is, for each actuator provided in the inkjet head. From this drive signal, a drive waveform signal corresponding to the gradation of the ink dot to be formed is selected, and the drive waveform signal is supplied to the actuator to eject ink droplets. The required gradation of ink dots is achieved.

  By the way, in such an ink jet head, a plurality of nozzles are formed with high density by fine processing in order to perform high-resolution printing. However, in reality, variations in nozzle ink droplet ejection characteristics between the heads occur due to actuator mounting errors and processing accuracy of components constituting the pressure chamber and the ink flow path. This variation in nozzle ink droplet ejection characteristics between inkjet heads results in variations in the size and position of ink dots formed by ejecting ink droplets onto a print medium, leading to a decrease in image quality of printed matter such as density unevenness.

Therefore, for example, by correcting the voltage value of the drive signal (drive waveform signal) to the actuator for each head according to the nozzle ink droplet ejection characteristics of each head, variations in the nozzle ink droplet ejection characteristics between the heads are suppressed. Like that. Further, in Patent Document 2 below, among the drive waveform signals, the process of ejecting ink droplets by contracting the pressure chamber from the expanded state and the contracted state of the pressure chamber after ejecting the ink droplet are described as the nozzle ink droplets of each head. By correcting according to the ejection characteristics, variations in the nozzle ink droplet ejection characteristics between the heads are suppressed.
Japanese Patent Laid-Open No. 2003-1824 JP 2001-270092 A

  However, even if it is possible to suppress variations in the nozzle ink droplet ejection characteristics between the heads due to a single driving waveform signal by the conventional inkjet printer driving device and driving method thereof, as described above, a plurality of driving waveform signals are used. It has been clarified that variations in nozzle ink droplet ejection characteristics between the heads cannot always be suppressed when they are connected to generate and output a drive signal and supplied to the actuator.

  The present invention has been made paying attention to the above-described problems. Even when a plurality of drive waveform signals are concatenated to generate and output a drive signal and supplied to the actuator, the nozzle ink between the heads can be obtained. An object of the present invention is to provide an ink jet printer driving device and a driving method thereof capable of suppressing variations in droplet discharge characteristics.

  [Invention 1] In order to solve the above-mentioned problems, an ink jet printer drive device according to Invention 1 corresponds to a plurality of nozzles provided for each of a plurality of heads, a pressure chamber communicating with each nozzle, and each pressure chamber. Ink jet printer drive device comprising an actuator provided as an output, and outputs print data indicating which ink droplets are ejected from which nozzle or how much ink droplets are ejected based on the print data Print data output means, and drive means for discharging ink droplets from the nozzles by applying a drive signal to the actuator based on print data from the print data output means to change the pressure in the pressure chamber, The drive means generates a drive signal for generating and outputting a drive signal by connecting a plurality of drive waveform signals for driving the actuator in time series. And drive waveform signal interval correction means for correcting the interval of the drive waveform signals connected by the drive signal generation means based on ink droplet ejection characteristic information from the nozzles for each head. Is.

  According to the ink jet printer driving apparatus of the first aspect of the present invention, the interval of the drive waveform signal for driving the actuator is corrected based on the ink droplet ejection characteristic information from the nozzle for each head, and the corrected interval is used. Since the drive signal is generated and output by connecting a plurality of drive waveform signals in time series, it is possible to suppress the effect of pressure change in the pressure chamber due to the connected drive waveform signals before and after the drive signal. Even when a plurality of waveform signals are connected and supplied to the actuator, it is possible to suppress variations in nozzle ink droplet ejection characteristics between the heads.

[Invention 2] The ink jet printer drive apparatus according to the invention 2 is the ink jet printer drive apparatus according to the invention 1, wherein the drive waveform signal interval correction means is based on ink droplet ejection characteristic information from the nozzles of each head. It is characterized in that the interval between the drive waveform signals is corrected so that the ink droplet ejection amount by the combination of a plurality of drive waveform signals becomes a predetermined value.

  According to the ink jet printer driving apparatus of the second aspect of the invention, the driving waveform signal interval correction means has a predetermined ink droplet ejection amount based on a combination of a plurality of driving waveform signals based on the ink droplet ejection characteristic information from each nozzle. Since the drive waveform signal interval is corrected so as to be a value, the output times of a plurality of drive waveform signals connected in the drive signal can be made to coincide between different heads. It is possible to suppress the landing position deviation of the droplets.

[Invention 3] The ink jet printer drive apparatus according to the invention 3 is the ink jet printer drive apparatus according to the invention 1 or 2, wherein the drive means is a drive waveform signal based on ink droplet ejection characteristic information from the nozzle of each head. Drive waveform signal correcting means for correcting the above is provided.
According to the drive device for an ink jet printer according to the invention 3, since the drive waveform signal itself is corrected based on the ink droplet ejection characteristic information from the nozzles for each head, the nozzles between the heads by a single drive waveform signal are used. Variations in ink droplet ejection characteristics can also be corrected.

  [Invention 4] The driving method of the ink jet printer of Invention 4 is based on print data, from which nozzle among a plurality of nozzles provided for each of a plurality of heads, or how much ink is ejected. An ink jet printer that outputs print data as to whether or not to discharge droplets and applies a drive signal to the actuator based on the print data to change the pressure in the pressure chamber to discharge ink droplets from nozzles communicating with the pressure chamber The drive waveform signal for driving the actuator is corrected based on the ink droplet ejection characteristic information from the nozzles for each head, and a plurality of drive waveform signals are timed at the corrected intervals. The drive signals are generated and output by connecting them in series.

  According to the driving method of the ink jet printer according to the fourth aspect of the present invention, the interval of the drive waveform signal for driving the actuator is corrected based on the ink droplet ejection characteristic information from the nozzle for each head, and the corrected interval is used. Since the drive signal is generated and output by connecting a plurality of drive waveform signals in time series, it is possible to suppress the effect of pressure change in the pressure chamber due to the connected drive waveform signals before and after the drive signal. Even when a plurality of waveform signals are connected and supplied to the actuator, it is possible to suppress variations in nozzle ink droplet ejection characteristics between the heads.

Next, an embodiment of a drive device for an ink jet printer of 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 enlarged to draw ink, and then the volume of the cavity 23 is reduced to eject ink droplets. 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. The example of FIG. 3 shows an arrangement pattern of the nozzles 24 when applied to four colors of ink (Y: yellow, M: magenta, C: cyan, K: black). 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, and a control unit 62 configured by, for example, a microcomputer that executes print processing based on the check data input from the input interface unit 61; The carriage motor driver 63 for driving and controlling the carriage motor 41, the paper feeding motor driver 64 for driving and controlling the paper feeding motor 51, the head driver 65 for driving and controlling the inkjet head 20, and the outputs of the drivers 63, 64 and 65 An interface 67 that converts the signal into a control signal used by the external carriage motor 41, the paper feed motor 51, and the inkjet head 20 and outputs the control signal is configured.

  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. In addition, each component in the control unit 62 is electrically connected via 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 D for converting the waveform generation data WDATA output from the latch circuit 704 into an analog signal / A converter 705 and the analog output from this D / A converter 705 A voltage amplifier 706 amplifies the voltage signal, and a current amplifier 707 for outputting a drive signal COM output signal of the voltage amplifier 706 current amplification to. 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 the 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 the drive waveform signal in the drive signal COM. After the drive waveform signal selection data signal SI and the nozzle selection data are input to all the nozzles, the latch signal LAT and the channel signal CH for connecting the drive signal COM and the piezoelectric actuator 22 of the inkjet head 20 based on these data, the drive A clock signal SCK for transmitting the waveform signal selection data signal SI as a serial signal to the inkjet head 20 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 designates the piezoelectric actuator 22 corresponding to the nozzle 24 to which ink droplets are to be ejected, and shifts a shift register 211 that stores drive waveform signal selection data SI for selecting a drive waveform signal in the drive signal COM, and a shift register 211 A latch circuit 212 that temporarily stores data in the register 211, a level shifter 213 that converts the level of 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. Has been.

  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. 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.

  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 first drive signal COM1 (or the second drive signal COM2) 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. Of these, the rising portion of the drive signal COM is a stage in which the volume of the cavity 23 is enlarged and ink is drawn in (it can be said that the meniscus is drawn in consideration of the ink discharge surface), and the falling portion of the drive signal COM is the volume of the cavity 23. Is reduced and the ink droplets are ejected (it can be said that the meniscus is extruded if the ink ejection surface is considered). 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. A drive signal having a single waveform is defined as a drive waveform signal, and a signal obtained by connecting the drive waveform signals in time series is defined as a drive signal.

  Thus, even with a single drive waveform signal, ink droplets can be ejected from the nozzles by pulling the meniscus (also referred to as pull) and then extruding the meniscus (also referred to as push). Therefore, even when a drive signal is created by connecting drive waveform signals in time series, an independent drive waveform signal may be selected and supplied to the piezoelectric actuator 22 to eject ink droplets. In some cases, a plurality of drive waveform signals are selected and supplied to the piezoelectric actuator 22 to eject ink droplets a plurality of times. If a plurality of ink droplets land at 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. Multi-gradation is achieved by a combination of such techniques.

  In either case of ejecting ink droplets by a single drive waveform signal or ejecting ink droplets by a plurality of drive waveform signals, the ink droplet ejection characteristics from the nozzles are different for each of the inkjet heads 20 provided. Different. As described above, this is due to manufacturing errors and assembly errors of each inkjet head 20. However, the singularization or reduction of the number of inkjet heads 20 only requires higher accuracy. That's not realistic.

  Of these, the variation in the nozzle ink droplet ejection characteristics between the heads when ejecting ink droplets with a single drive waveform signal should also correct the waveform of the drive waveform signal itself. For example, as shown in FIG. 9, the waveform of the drive waveform signal is obtained by converting the pull-push voltage value or potential difference (crest value in terms of waveform) ΔV in the drive waveform signal WCOM into the nozzle ink droplet ejection characteristics for each head. Correct accordingly. In the correction, when ink droplets are actually ejected from the nozzles of each head and it is desired to enlarge the ink dots from the size of the ink dots formed on the print medium, that is, when it is desired to increase the amount of ejected ink droplets. When it is desired to increase the pull-push voltage value ΔV and reduce the ink dots, that is, to reduce the amount of ejected ink droplets, the pull-push voltage value ΔV may be decreased. Waveform data + ΔV1, −ΔV2, + ΔV3 for correcting this single drive waveform signal WCOM is stored in the waveform correction table of the RAM 62c in the control unit 62.

  Even when the nozzle ink ejection characteristics for each head are corrected by the single drive waveform signal WCOM as described above, when a plurality of drive waveform signals WCOM are selected and supplied to the piezoelectric actuator 22, Variations in nozzle ink discharge characteristics occur. FIG. 10 shows that when different drive waveform signals WCOM1 to WCOM are supplied to the piezoelectric actuators 22 of the inkjet heads A and B in different inkjet heads A and B, the first drive waveform signal WCOM1 and the second drive waveform. When the signal WCOM2 is selected and supplied to the piezoelectric actuators 22 of the inkjet heads A and B, the third drive waveform signal WCOM2 and the third drive waveform signal WCOM3 are selected and the piezoelectric types of the inkjet heads A and B are selected. When supplied to the actuator 22, the ink dot area when all the first to third drive waveform signals WCOM 1 to WCOM 3 are selected and supplied to the inkjet heads A and B is measured. The intervals between the drive waveform signals when the plurality of drive waveform signals WCOM1 to WCOM3 are selected and supplied to the piezoelectric actuator 22 are fixed. As is apparent from the figure, the ink dot areas when the single drive waveform signals WCOM1 to WCOM3 are supplied are the same for both the ink jet heads A and B, but a plurality of drive waveform signals WCOM1 to WCOM3 are selected. The ink dot area when supplied differs for each of the inkjet heads A and B.

  When the drive waveform signals WCOM1 to WCOM3 are continuously supplied to the piezoelectric actuator 22 as a result of intensive studies on the cause of the variation in the ink dot area for each head, that is, the variation in the nozzle ink droplet ejection characteristics for each head. Focusing on the pressure fluctuation in the cavity 23, it was found that this pressure fluctuation depends on the interval between the drive waveform signals WCOM1 to WCOM3 to be connected. FIG. 11 shows the ink dot area measured when the intervals of the drive waveform signals WCOM1 to WCOM3 to be connected are variously changed. In the present embodiment, since it is necessary to output a drive signal composed of a series of drive waveform signals to the piezoelectric actuator 22 of each nozzle, the smaller the interval between the drive waveform signals, the more required the drive signal per nozzle. It is possible to shorten the time required for printing by shortening the time, that is, the driving cycle. In this embodiment, as shown in FIG. 11, there is a minimum value of the ink dot area in the drive waveform signal interval of 4 μsec, and the ink dot area gradually increases as the drive waveform signal interval becomes shorter. Therefore, in this embodiment, in the region where the drive waveform signal interval is 4 μsec or less, the variation in the ink dot area is suppressed, that is, the variation in the nozzle ink droplet ejection characteristics for each head is suppressed. The interval of the drive waveform signal is set according to the nozzle ink droplet ejection characteristics for each head.

  For example, when the ink dots of the ink droplets ejected from the nozzles of the inkjet head A are larger than the ink dots of the ink droplets ejected from the nozzles of the inkjet head B, each drive of the inkjet head A is performed as shown in FIG. By adjusting the push-pull voltage values of the waveform signals WCOM1 to WCOM3 to be smaller than the push-pull voltage values of the drive waveform signals WCOM1 to WCOM3 of the inkjet head B, between the inkjet heads by the single drive waveform signals WCOM1 to WCOM3 The variation of the nozzle ink droplet ejection characteristics is suppressed. Further, the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 of the inkjet head B are adjusted so that the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 of the inkjet head A are increased, so that the plurality of drive waveform signals WCOM1. -Variation in nozzle ink droplet ejection characteristics between inkjet heads due to WCOM3 is suppressed. The table of FIG. 13 summarizes the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3. In this embodiment, the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 of the inkjet head A are both 3.5 μsec., And the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 of the inkjet head B are both 4 μsec. It was. The intervals T1 and T2 between the drive waveform signals WCOM1 to WCOM3 are corrected so that the ink droplet ejection amount by the plurality of drive waveform signals WCOM1 to WCOM3 becomes a predetermined value.

  As shown in FIG. 14, the intervals T1 and T2 between the drive waveform signals WCOM1 to WCOM3 are adjusted by adjusting the first clock signal ACLK for reading the waveform data + ΔV1 written at the address A1 at the stage of drawing the meniscus described above. What is necessary is just to adjust timing. The adjusted first clock signal ACLK is also stored in the waveform correction table of the RAM 62 c in the control unit 62. Further, the drive waveform signal WCOM0 in FIG. 12 is called so-called micro vibration, and ink droplets are not actually ejected. For this reason, pressure fluctuation does not occur in the cavity 23 due to the fine vibration drive waveform signal WCOM0, so the interval T0 between the fine vibration drive waveform signal WCOM0 and the first drive waveform signal WCOM1 is not adjusted. Further, even if the intervals T1 and T2 between the drive waveform signals WCOM1 to WCOM3 are adjusted, the time required for the drive signal COM, that is, the so-called drive cycle is fixed.

A flowchart of FIG. 15 shows a calculation process for generating and outputting the drive signal COM by connecting such drive waveform signals WCOM in time series. In this calculation process, the drive waveform data DATA corrected based on the nozzle ink droplet ejection characteristic information for each head as described above is read from the waveform correction table of the RAM 62c.
Next, the process proceeds to step S2, and the waveform data DATA read from the waveform correction table in step S1 is written into the waveform memory 701.

Next, the process proceeds to step S3, where it is determined whether or not it is the output timing of the drive signal COM. If it is the output timing of the drive signal COM, the process proceeds to step S4, and if not, the process waits.
In step S4, as described above, the waveform data DATA written in the waveform memory 701 according to the first clock signal ACLK and the second clock signal BCLK, that is, 0, + ΔV1, -ΔV2, and + ΔV3 are read.

In step S5, the waveform data DATA read in step S4 is D / A converted and output.
Next, the process proceeds to step S6, where it is determined whether or not the generation output of the drive signal COM is completed. When the generation output of the drive signal COM is completed, the process returns to the main program. Migrate to

  FIG. 16 shows the ink dot area from the nozzle of the ink jet head A and the ink dot area from the nozzle of the ink jet head B formed by this arithmetic processing. As is apparent from the figure, according to the driving apparatus and driving method of the ink jet printer of the present embodiment, the ink dot area when ink droplets are ejected with the single driving waveform signal WCOM1 to WCOM3, that is, the nozzle for each head. Variations in the ink droplet ejection characteristics are also suppressed in the ink dot area when ink droplets are ejected with a plurality of drive waveform signals WCOM1 to WCOM3, that is, the nozzle ink droplet ejection characteristics for each head.

  Further, as apparent from FIG. 12, based on the ink droplet ejection characteristic information from the nozzles of each head, the drive waveform signal WCOM1 is set so that the ink droplet ejection amounts by the plurality of drive waveform signals WCOM1 to WCOM3 become a predetermined value. By correcting the intervals T1 and T2 of .about.WCOM3 and matching the time t0 at the center of the drive signal COM formed by connecting a plurality of drive waveform signals WCOM1 (WCOM0) to WCOM3 between different heads, ink from each head It is possible to suppress the landing position deviation of the droplets.

  Next, another embodiment of the ink jet printer drive device of the present invention will be described. For example, in the ink dot area characteristic of FIG. 11 described above, that is, the nozzle ink droplet ejection characteristic for each head, for example, a characteristic curve such as a parabola is obtained with a minimum interval of 4 μsec. Between drive waveform signals that minimize the ink dot area. It is drawn. Then, when the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 of the inkjet head B are both 4 μsec., In the inkjet head A having a smaller dot area than the inkjet head B, that is, having a smaller nozzle ink droplet ejection characteristic, For example, as shown in FIG. 17, the interval T1 between the first drive waveform signal WCOM1 and the second drive waveform signal WCOM2 is set to 3.5 μsec., And the interval T2 between the second drive waveform signal WCOM2 and the third drive waveform signal WCOM3 is set. Even when 4.5 μsec. Is used, the nozzle ink droplet ejection characteristics can be similarly increased.

  FIG. 18 shows the drive signal COM generated and output by the arithmetic processing of FIG. 15 by setting the intervals T1 and T2 between the drive waveform signals WCOM1 to WCOM3 in this way. In this drive signal COM, the timings of the first drive waveform signal WCOM1 and the third drive waveform signal WCOM3 of the ink jet head A and the ink jet head B, including the micro vibration drive waveform signal WCOM0, can be matched. As described above, according to the driving device of the ink jet printer of the present embodiment, based on the ink droplet ejection characteristic information from each nozzle, the total time of the intervals T1 and T2 between different heads is made equal, and a plurality of driving waveforms is obtained. By correcting the intervals T1 and T2 of the drive waveform signals WCOM1 to WCOM3 so that the ink droplet ejection amount based on the combination of the signals WCOM1 to WCOM3 becomes a predetermined value, the output times of a plurality of drive waveform signals connected in the drive signal Can be matched between different heads, and it is possible to suppress landing position deviation of ink droplets from each head.

  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. In particular, in a line head type ink jet printer in which a large number of ink jet heads are arranged in a direction crossing the print medium conveyance direction, the effect of suppressing variation in nozzle ink droplet ejection characteristics between the heads according to the present invention is large.

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 of the waveform correction of a drive waveform signal. It is explanatory drawing of the nozzle ink droplet discharge characteristic for every head. It is explanatory drawing of the space | interval of a drive waveform signal, and a nozzle ink discharge characteristic. It is explanatory drawing of one Embodiment of the drive signal which connected the drive waveform signal. 13 is a storage table of drive waveform signal intervals in FIG. 12. It is explanatory drawing of the space | interval adjustment of a drive waveform signal. It is a flowchart which shows the arithmetic processing for a drive signal output. It is explanatory drawing of the nozzle ink discharge characteristic for every head by the arithmetic processing of FIG. It is a storage table of intervals of drive waveform signals with different settings. It is explanatory drawing of other embodiment of the drive signal by the space | interval of the drive waveform signal of FIG.

Explanation of symbols

  1 is an ink jet printer, 15 is a selection switch, 20 is an ink jet head, 21 is a diaphragm, 22 is a piezoelectric actuator, 23 is a cavity, 24 is a nozzle, 62 is a control unit, 62c is a RAM, 70 is a drive signal generation circuit, a is the print medium

Claims (4)

  An ink-jet printer drive device comprising a plurality of nozzles provided for each of a plurality of heads, a pressure chamber communicating with each nozzle, and an actuator provided corresponding to each pressure chamber. Print data output means for outputting print data indicating which ink droplets are ejected from which nozzles or how much ink droplets are ejected based on the nozzles, and driving the actuator based on the print data from the print data output means Drive means for ejecting ink droplets from the nozzles by applying a signal to change the pressure in the pressure chamber, and the drive means is driven by connecting a plurality of drive waveform signals for driving the actuator in time series. Drive signal generation means for generating and generating a signal, and generation of the drive signal based on ink droplet ejection characteristic information from the nozzles of each head Drive apparatus of an ink jet printer, characterized in that a drive waveform signal interval correcting means for correcting the distance of the driving waveform signals to be connected by the step.   The drive waveform signal interval correction means adjusts the interval between the drive waveform signals so that the ink droplet discharge amount based on the combination of the plurality of drive waveform signals becomes a predetermined value based on the ink droplet discharge characteristic information from the nozzles for each head. The ink jet printer drive device according to claim 1, wherein correction is performed.   3. The inkjet printer according to claim 1, wherein the driving unit includes a driving waveform signal correcting unit that corrects a driving waveform signal based on ink droplet ejection characteristic information from a nozzle for each head. Drive device.   Based on the print data, print data indicating which ink droplets are to be ejected or how many ink droplets are to be ejected from among the plurality of nozzles provided for each of the plurality of heads is printed. A method of driving an ink jet printer that ejects ink droplets from nozzles communicating with a pressure chamber by applying a drive signal to an actuator based on data to change the pressure in the pressure chamber. Based on the ink droplet ejection characteristic information, the drive waveform signal interval for driving the actuator is corrected, and a plurality of drive waveform signals are connected in time series at the corrected interval to generate and output a drive signal. A method of driving an inkjet printer, characterized by the following.

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