JP2007090631A - Head drive device for inkjet printer and method for driving head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid enlargement of a size of a drive circuit and to reduce a cycle of ejecting an ink droplet from one nozzle by precisely correcting an ejection characteristic of an ink droplet from a nozzle in a nozzle array. <P>SOLUTION: Drive waveform signals WCOM1-WCOM8 are arranged by each four signals in a time series manner to form two drive signals COM1, COM2, and then the drive signals COM1, COM2 are synchronously output. As one or more of the drive waveform signals WCOM1-WCOM8 are selected from the output two drive signals COM1, COM2 to be supplied to a piezoelectric actuator 22 of a nozzle which is ready to eject an ink droplet, it is possible to precisely correct the ejection characteristic of the ink droplet from the nozzle in the nozzle array by virtue of the combination of the selected drive waveform signals WCOM1-WCOM8, and unnecessary enlargement of the drive circuit can be avoided at the same time. In addition, by selecting the drive waveform signals WCOM1-WCOM8 from the two drive signals COM1, COM2, it is possible to reduce a cycle of ejecting the ink droplets from one nozzle. <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 a head driving device and a head driving method for an ink jet printer.

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.

  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. For this reason, manufacturing variations occur in parts, actuators, and the like constituting the pressure chambers and ink flow paths, and variations in pressure changes in the individual pressure chambers occur. The variation in the pressure change in the pressure chamber is a variation in the ink droplet ejection characteristics between the nozzles. This variation in the ink droplet ejection characteristics between the nozzles of the ink jet head results in fluctuations in the size and position of ink dots formed by ejecting ink droplets onto the print medium, leading to a decrease in image quality of printed matter such as density unevenness.

  On the other hand, in order to improve the printing speed and improve the image quality, there is an increasing demand for so-called multiple nozzles in which the number of nozzles is further increased than before. By increasing the number of nozzles in the nozzle row, the number of scans of the ink jet head can be reduced, so that the printing speed is improved. However, the increase in the number of nozzles in the nozzle row is strongly influenced by the manufacturing variation of the inkjet head described above, and even if the drive signal is adjusted for each nozzle row, ink droplet ejection characteristics between the nozzles in the nozzle row Cannot be corrected, and as a result, the image quality of the printed matter is reduced. Furthermore, there may be an increase in the number of ink jet heads that cannot obtain predetermined ejection characteristics, and the production yield may be deteriorated.

Therefore, in Patent Document 1 below, the nozzles in the nozzle row are divided into regions having different ink droplet ejection characteristics, and a drive circuit is provided for each of the divided regions, so that the nozzle ink droplet ejection characteristics in the nozzle row are arranged. Is corrected.
JP 2005-88436 A

However, in the head drive device of the conventional ink jet printer, it is possible to finely correct the ink droplet ejection characteristics by increasing the number of regions in the nozzle row to be divided. However, a drive circuit is necessary for that amount. There is a problem that the drive circuit becomes large.
The present invention has been made by paying attention to the above-described problems, and it is possible to finely correct the nozzle ink droplet ejection characteristics in the nozzle row, while avoiding an increase in the size of the drive circuit and a single nozzle. It is an object of the present invention to provide a head driving device and a head driving method for an ink jet printer having a short ink droplet ejection cycle from the head.

  [Invention 1] In order to solve the above-described problems, an ink jet printer head drive device according to Invention 1 corresponds to each of a plurality of nozzles provided in the head, a pressure chamber communicating with each nozzle, and each pressure chamber. An actuator provided; print data output means for outputting print data indicating which ink droplets are to be ejected or how much ink droplets are to be ejected based on the print data; and from the print data output means A head drive device for an ink jet printer, comprising: a drive unit that discharges ink droplets from nozzles by applying a drive signal to the actuator based on print data to change the pressure in the pressure chamber; A plurality of drive signals are generated by arranging one or more drive waveform signals for driving the actuator in time series. A drive signal generating means for synchronously outputting the drive signals, and one or more drive waveform signals selected from a plurality of drive signals output from the drive signal generating means to be used as an actuator for a nozzle to eject ink droplets A drive waveform signal selection means for supplying is provided.

  According to the head drive device of the ink jet printer according to the first aspect of the present invention, one or more drive waveform signals for driving the actuator are arranged in time series to generate a plurality of drive signals, and the plurality of drive signals are synchronized. Since the output is selected and one or more drive waveform signals are selected from the output drive signals and supplied to the actuators of the nozzles to which ink droplets are to be ejected, the nozzle array is selected according to the combination of the selected drive waveform signals. The nozzle ink droplet ejection characteristics can be finely corrected, and unnecessary increase in the size of the drive circuit can be avoided at the same time, and the drive waveform signal can be selectively supplied to the actuator from a plurality of drive signals, so The ink droplet ejection cycle can be shortened.

[Invention 2] The head drive device for an ink jet printer according to invention 2 is the head drive device for an ink jet printer according to invention 1, wherein the drive signal generating means includes two drive waveform signals arranged in time series. One drive signal unit is used as the drive signal, and two drive signal units are arranged and output in time series.
According to the head drive device of the ink jet printer according to the second aspect of the present invention, two drive signals obtained by arranging two drive waveform signals in time series are used as one drive signal unit, and the drive signal units are arranged in time series. Since it is configured to output two in a row, the combination of drive waveform signals that can be selected can be dramatically increased so that the nozzle ink droplet ejection characteristics in the nozzle array can be finely corrected, and the drive signal generating means can be reduced in size. Can be

  [Invention 3] The head drive device of the ink jet printer according to invention 3 is the head drive device of the ink jet printer according to invention 2, wherein the drive waveform signal selection means is a selection switch capable of connecting each of the two drive signals to an actuator. Storage means for storing drive waveform signal selection data for defining a drive waveform signal to be selected corresponding to the print data and drive signal selection data for defining a drive signal to be selected corresponding to the print data; A drive waveform signal selection means for selecting a drive waveform signal based on the print data and drive waveform signal selection data stored in the storage means; and a drive signal selection data stored in the print data and storage means. Drive signal selection means for selecting a drive signal and the drive waveform signal selected by the drive waveform signal selection means It is characterized in that a switch driving means for driving the selection switch on the basis of the drive signal selected by the fine drive signal selecting means.

  According to the head drive device of the ink jet printer according to the third aspect of the present invention, the drive waveform signal selection data for specifying the drive waveform signal to be selected corresponding to the print data and the drive signal to be selected corresponding to the print data are specified. The drive signal selection data to be stored is stored, the drive waveform signal is selected based on the print data and the stored drive waveform signal selection data, and the drive is selected based on the print data and the stored drive signal selection data. The drive waveform signal selection data corresponding to the print data is selected because the signal is selected and the selection switch is driven based on the selected drive waveform signal and the drive signal to supply the drive waveform signal in the drive signal to the actuator. And the drive signal selection data for each nozzle, the nozzle ink droplet ejection characteristics in the nozzle array can be controlled. It can be finely corrected for each Le.

[Invention 4] The head drive device for an ink jet printer according to the invention 4 is the head drive device for an ink jet printer according to the above item 3, wherein the storage means corrects a variation in ink droplet ejection characteristics between nozzles. Signal selection data and drive signal selection data are stored.
According to the head drive device of the ink jet printer according to the fourth aspect of the present invention, the configuration is such that the drive waveform signal selection data and the drive signal selection data for ink droplet ejection for correcting variations in ink droplet ejection characteristics between nozzles are stored. The nozzle ink droplet ejection characteristics in the row can be finely corrected for each nozzle.

[Invention 5] The head drive device for an inkjet printer according to Invention 5 is the head drive device for an inkjet printer according to Invention 4, wherein the drive means is the storage means based on a correction amount of variation in ink droplet ejection characteristics between nozzles. And a data updating means for storing drive waveform signal selection data and drive signal selection data.
According to the head drive device of the ink jet printer according to the fifth aspect of the present invention, the drive waveform signal selection data and the drive signal selection data are stored based on the correction amount of the variation in the ink droplet ejection characteristics between the nozzles. The nozzle ink droplet ejection characteristics in the row can be finely corrected for each nozzle.

 [Invention 6] A head driving method of an ink jet printer according to Invention 6 is based on print data, and from which of a plurality of nozzles provided in the head, which ink droplet is ejected or how much ink droplet is ejected. A head of an ink jet printer that outputs print data indicating whether or not to discharge 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 A driving method, wherein a plurality of driving signals generated by arranging one or more driving waveform signals for driving an actuator in time series are synchronously output, and one or more driving waveform signals are generated from the plurality of driving signals. Is selected and supplied to an actuator of a nozzle to which ink droplets are to be ejected.

  According to the head driving method of the ink jet printer according to the sixth aspect of the present invention, one or more drive waveform signals for driving the actuator are arranged in time series to generate a plurality of drive signals, and the plurality of drive signals are synchronized. Since the output is selected and one or more drive waveform signals are selected from the output drive signals and supplied to the actuators of the nozzles to which ink droplets are to be ejected, the nozzle array is selected according to the combination of the selected drive waveform signals. The ink droplet ejection characteristics within the nozzle can be finely corrected, and an unnecessary increase in the size of the drive circuit can be avoided at the same time. In addition, drive waveform signals from a plurality of drive signals can be simultaneously supplied to the actuator, so ink droplets from one nozzle can be supplied. The discharge cycle can be shortened.

Next, an embodiment of a head driving device for an inkjet printer 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 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. The adjustment of the amount of ink droplets ejected from the nozzle is referred to as gradation, and as will be described later, in this embodiment, three gradations of L, M, and S (four gradations including the case where ink droplets are not ejected) are included. Express. 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. Note that the address data A0 to A3 output to the first drive signal generation circuit 69 and the second drive signal generation circuit 70 have different values.

  The head driver 65 includes a first drive signal generation circuit 69 that forms a first drive signal COM1, a first drive signal generation circuit 70 that forms a second drive signal COM2, and an oscillation circuit 71 that outputs a clock signal SCK. I have. The first and second drive signal generation circuits 69 and 70 have the same configuration. As a representative, the first drive signal generation circuit 69 has a waveform for generating a drive signal input from the control unit 62 as shown in FIG. A waveform memory 701 for storing the formation data DATA in a storage element corresponding to a predetermined address, and a latch circuit 702 for latching the waveform formation data DATA read from the waveform memory 701 by the first clock signal ACLK. , An adder 703 for adding the output of the latch circuit 702 and waveform generation data WDATA output from the latch circuit 704 described later, and a latch circuit for latching the added output of the adder 703 by the second clock signal BCLK described above. 704 and the waveform generation data WDATA output from the latch circuit 704 are converted into analog signals. A D / A converter 705, a voltage amplifying unit 706 that amplifies the analog signal output from the D / A converter 705, and an output signal of the voltage amplifying unit 706 is current-amplified to generate a first drive signal COM1 ( Or a current amplifying unit 707 that outputs a second drive signal COM2). 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 is connected to the first drive signal COM1 generated by the first drive signal generation circuit 69, the second drive signal COM2 generated by the second drive signal generation circuit 70, and the printing via the input / output interface unit 67. The drive waveform signal selection data signal SI and the first drive signal COM1 or the second drive signal COM2 for selecting the nozzle to be ejected based on the data and selecting the drive waveform signal in the first drive signal COM1 and the second drive signal COM2. After the drive signal selection data signal SEL for selecting one of them and the nozzle selection data are input to all the nozzles, the first drive signal COM1 and the second drive signal COM2 and the piezoelectric actuator 22 of the inkjet head 20 are determined based on these data. Latch signal LAT and channel signal CH to be connected, drive waveform signal selection data signal Clock signal SCK for transmitting the inkjet head 20 to I and the drive signal selection data signal SEL as a serial signal is input.

  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. 7, 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 first drive signal COM1 (or the second drive signal COM2) is + ΔV1 at the rising timing of the second clock signal BCLK. It is added one by one. 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 first drive signal COM1 (or the second drive signal COM2) 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 first drive signal COM1 (or the second drive signal COM2) 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 first drive signal COM1 or the second drive signal COM2 thus generated and output after being subjected to analog conversion and voltage-current amplification becomes a waveform signal as shown in FIG. Among these, the rising portion of the first drive signal COM1 or the second drive signal 2COM expands the volume of the cavity 23 and draws ink (it can be said that the meniscus is drawn in view of the ink ejection surface), and the first drive signal The falling portion of COM1 or the second drive signal COM2 is a stage in which the volume of the cavity 23 is reduced and ink droplets are ejected (it can be said that the meniscus is pushed out considering the ink ejection surface). 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 drive signal obtained by arranging the drive waveform signals in time series is defined as a drive signal.

  Next, a configuration for connecting the first drive signal COM1 output from the first drive signal generation circuit 69 and the second drive signal COM2 output from the second drive signal generation circuit 70 and the piezoelectric actuator 22 will be described. . FIG. 8 is a block diagram of a selection unit that connects the first drive signal COM <b> 1 and the second drive signal COM <b> 2 and the piezoelectric actuator 22. The selection unit includes a shift register 210 that stores drive signal selection data SEL (SELH, SELL) and drive waveform signal selection data SI among pixel data that designates the piezoelectric actuator 22 corresponding to the nozzle that should eject ink droplets. (SIH, SIL) for the shift register 211, the latch circuit 212 for temporarily storing the data of the shift registers 210, 211, the flip-flop circuit 213, and the drive waveform signal selection data SI stored in the latch circuit 212 A drive waveform signal selection circuit 214 that selects a drive waveform signal based on the first drive signal, a drive signal selection data SEL stored in the latch circuit 212, and a first drive signal based on the drive waveform signal selected by the drive waveform signal selection circuit 214 By selecting COM1 and the second drive signal COM2, the final A drive signal selection circuit 217 for selecting a drive waveform signal, and a level shifter 218 for driving the selection switches 15 and output of the drive signal selection circuit 217 level conversion to. The drive signal selection data SEL of this embodiment is SELH and SELL 2-bit data, and the drive waveform signal selection data SI is also SIH and SIL 2-bit data.

  The shift register 210 selects whether or not either one or both of the first drive signal COM1 and the second drive signal COM2 are selected from the print data read for each pixel, that is, each nozzle. The prescribed drive signal selection data SEL is sequentially input, and the storage area is sequentially shifted from the first stage to the subsequent stage in accordance with the input pulse of the section dock signal SCK. Similarly, drive waveform signal selection data SI that specifies which drive waveform signal in each drive signal is selected from the print data or none of the print data is sequentially input to the shift register 211 and the clock signal SCK. In response to the input pulse, the storage area sequentially shifts from the first stage to the subsequent stage. The latch circuit 212 stores the print data for the number of nozzles, that is, the drive signal selection data SEL and the drive waveform signal selection data SI in the shift registers 210 and 211, and then receives the latch signals LAT of the shift registers 210 and 211. Each output signal is latched. The flip-flop circuit 213 is reset by the latch signal LAT and is inverted every time the channel signal CH is input. The signal output from the drive signal selection circuit 217 is converted to a voltage level by which the selection switch 15 can be turned on / off by the level shifter 218. This is because the first drive signal COM1 and the second drive signal COM2 are higher in voltage than the output voltage of the drive signal selection circuit 217, so that the operating voltage range of the selection switch 15 is also set high.

  FIG. 9 shows the configuration of the drive waveform signal selection circuit 214. The drive waveform signal selection circuit 214 includes two AND circuits AND1 and AND2 and one OR circuit OR1. Among these, the upper bit data SIH of the drive waveform signal selection data SI and the inverted output NOTQ of the flip-flop circuit 213 are input to the first AND circuit AND1. Further, the lower bit data SIL of the drive waveform signal selection data SI and the output Q of the flip-flop circuit 213 are input to the second AND circuit AND2. The output of the first AND circuit AND1 and the output of the second AND circuit AND2 are input to the OR circuit OR1, and the drive waveform signal selection result WSEL is output.

  FIG. 10 shows a configuration from the drive signal selection circuit 217 to the piezoelectric actuator 22. The selection switch 15 includes two analog switches SW1 and SW2 for each piezoelectric actuator 22 corresponding to each nozzle, and connects the first drive signal COM1 and the second drive signal COM2 to the piezoelectric actuator 22 in parallel. To do. Accordingly, the level shifter 218 also includes a level shifter LV1 corresponding to the switch SW1 and a level shifter LV2 corresponding to the switch SW2. On the other hand, the drive signal selection circuit 217 includes eight AND circuits AND3 to AND10, two OR circuits OR2 and OR3, and two inverter circuits INV1 and INV2. Among these, the upper bit data SELH of the drive signal selection data SEL and the inverted output NOTQ of the flip-flop circuit 213 are input to the third AND circuit AND3. The fourth AND circuit AND4 receives the lower bit data SELL of the drive signal selection data SEL and the output Q of the flip-flop circuit 213. The fifth AND circuit AND5 receives the output obtained by inverting the upper bit data SELH of the drive signal selection data SEL by the first inverter circuit INV1 and the inverted output NOTQ of the flip-flop circuit 213. The sixth AND circuit AND6 receives an output obtained by inverting the lower bit data SELL of the drive signal selection data SEL by the second inverter circuit INV2 and the output Q of the flip-flop circuit 213. The seventh AND circuit AND7 receives the output of the third AND circuit AND3 and the drive waveform signal selection result WSEL. The output of the fourth AND circuit AND4 and the drive waveform signal selection result WSEL are input to the eighth AND circuit AND8. The ninth AND circuit AND9 receives the output of the fifth AND circuit AND5 and the drive waveform signal selection result WSEL. The tenth AND circuit AND10 receives the output of the sixth AND circuit AND6 and the drive waveform signal selection result WSEL. The output of the seventh AND circuit AND7 and the output of the eighth AND circuit AND8 are input to the second OR circuit OR2. The outputs of the ninth AND circuit AND9 and the tenth AND circuit AND10 are input to the third OR circuit OR3. The first level shifter LV1 receives the output of the second OR circuit OR2, and the second level shifter LV2 receives the output of the third OR circuit OR3.

  As shown in FIG. 11, the first drive signal COM1 and the second drive signal COM2 of the present embodiment are configured by arranging four drive waveform signals WCOM1 to WCOM8 in time series and are synchronously output. . The total of the eight drive waveform signals WCOM1 to WCOM8 are different, and therefore the volume of ink droplets ejected by the respective drive waveform signals WCOM1 to WCOM8 is also different, resulting in the size of the ink dots formed on the print medium. It is also different. In the present embodiment, the selection unit described above selects any one or more of these drive waveform signals WCOM1 to WCOM8 and supplies them to the piezoelectric actuator 22, whereby ink droplets of various capacities, that is, various sizes. Attempt to form an ink dot. The drive waveform signals WCOM1 to WCOM8 are selected and combined in 81 ways as will be described later, and the variations in ink droplet ejection characteristics between the nozzles are corrected using them. That is, the cycle of the first drive signal COM1 and the second drive signal COM2 including all of these drive waveform signals WCOM1 to WCOM8 is an ink droplet ejection cycle TA for ejecting ink droplets from one nozzle.

  In the present embodiment, the two drive waveform signals WCOM1, WCOM2 preceded by the first drive signal COM1 and the two drive waveform signals WCOM3, WCOM4 preceded by the second drive signal COM2 synchronized with the first drive signal COM1 are defined as the first unit UNIT1. Two drive waveform signals WCOM5 and WCOM6 following the one drive signal COM1 and two drive waveform signals WCOM7 and WCOM8 following the second drive signal COM2 synchronized therewith are defined as a second unit UNIT2. Then, the selection of the drive waveform signals WCOM1 to WCOM4 from the first unit UNIT1 is performed, and the first upper bit data SIH1, the first lower bit data SIL1 and the drive signal of the drive waveform signal selection data SI read before that are selected. The drive waveform signal selection data read before the selection of the drive waveform signals WCOM5 to WCOM8 from the second unit UNIT2 is performed with the first upper bit data SELH1 and the first lower bit data SELL1 of the selection data SEL. The second upper bit data SIH2 and the second lower bit data SIL2 of SI and the second upper bit data SELH2 and the second lower bit data SELL2 of the drive signal selection data SEL are used.

  Among these, FIG. 12 is a table showing the selection procedure of the drive waveform signals WCOM1 to WCOM4 of the first unit UNIT1. According to the drive waveform signal selection circuit 214, the drive waveform signals WCOM1 to WCOM4 are selected when the drive waveform signal SI is at a high level, that is, a logical value 1, and are not selected when the drive waveform signal SI is at a low level, that is, a logical value 0. On the other hand, according to the drive signal selection circuit 217, the first drive signal COM1 is selected when the drive signal selection data SEL is high level, that is, the logical value 1, and the second drive signal is selected when the drive signal selection data SEL is low level, that is, the logical value 0. COM2 is selected. Then, the first drive signal COM1 and the second drive signal COM2 in the stage division of the preceding drive waveform signals WCOM1 and WCOM3 are selected by the upper bit data SELH of the drive signal selection data SEL, and are followed by the lower bit data SELL. The first drive signal COM1 and the second drive signal COM2 in the stage division of the drive waveform signals WCOM2 and WCOM4 are selected. Therefore, when there is no drive signal selection data SEL and both the upper bit data SIH and the lower bit data SIL of the drive waveform signal selection data SI are at the logical value 0, no drive waveform signal is selected. Further, both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have a logical value 1, the upper bit data SIH of the drive waveform signal selection data SI has a logical value 0, and the lower bits of the drive waveform signal selection data SI. When the data SIL has a logical value 1, only the second drive waveform signal WCOM2 is selected. Further, both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have a logical value 1, the upper bit data SIH of the drive waveform signal selection data SI has a logical value 1, and the lower bits of the drive waveform signal selection data SI. When the data SIL has a logical value 0, only the first drive waveform signal WCOM1 is selected. Further, when both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have a logical value 1, and both the upper bit data SIH and the lower bit data SIL of the drive waveform signal selection data SI have a logical value 1, The drive waveform signal WCOM1 and the second drive waveform signal WCOM2 are selected. Further, both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have a logical value of 0, the upper bit data SIH of the drive waveform signal selection data SI has a logical value of 0, and the lower bits of the drive waveform signal selection data SI. When the data SIL has a logical value 1, only the fourth drive waveform signal WCOM4 is selected. Further, both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have a logical value 0, the upper bit data SIH of the drive waveform signal selection data SI has a logical value 1, and the lower bits of the drive waveform signal selection data SI. When the data SIL is a logical value 0, only the third drive waveform signal WCOM3 is selected. Further, when both the upper bit data SELH and the lower bit data SELL of the drive signal selection data SEL have the logical value 0 and both the upper bit data SIH and the lower bit data SIL of the drive waveform signal selection data SI have the logical value 3, The drive waveform signal WCOM3 and the fourth drive waveform signal WCOM4 are selected. Further, the upper bit data SELH of the drive signal selection data SEL is a logical value 1, the lower bit data SELL of the drive signal selection data SEL is a logical value 0, and the upper bit data SIH and the lower bit data SIL of the drive waveform signal selection data SI. When both are logical values 1, the first drive waveform signal WCOM1 and the fourth drive waveform signal WCOM4 are selected. Also, the upper bit data SELH of the drive signal selection data SEL is a logical value 0, the lower bit data SELL of the drive signal selection data SEL is a logical value 1, and the upper bit data SIH and the lower bit data SIL of the drive waveform signal selection data SI. When both are logical values 1, the third drive waveform signal WCOM3 and the second drive waveform signal WCOM2 are selected.

  In this way, there are nine selection patterns just by selecting the drive waveform signals WCOM1 to WCOM4 from the first unit UNIT1 (the drive waveform signals WCOM5 to WCOM8 are not selected from the second unit UNIT2). Further, when the fifth drive waveform signal WCOM5 is selected in the second unit UNIT2, there are nine selection patterns (the fifth drive waveform signal WCOM5 is selected and the drive waveform signals WCOM1 to WCOM4 are selected from the first unit UNIT1). Similarly, since there are nine selection patterns when the seventh driving waveform signal WCOM7 is selected, 27 selection patterns including the nine selection patterns for selecting the driving waveform signals WCOM1 to WCOM4 only from the first unit UNIT1. The selection pattern occurs. Furthermore, since there are 27 selection patterns when the sixth drive waveform signal WCOM6 is selected in the second unit UNIT2, and 27 selection patterns when the eighth drive waveform signal WCOM8 is selected, the fifth drive waveform There are 81 selection patterns including 27 selection patterns up to the signal WCOM5 or the seventh drive waveform signal WCOM7.

  When ink droplets were actually ejected using these 81 drive waveform signals WCOM1 to WCOM8, 39 patterns with substantially different ink dot sizes were confirmed. FIG. 13 shows the drive waveform signal selection patterns arranged in the order of the ink dot size, that is, the dot area and numbered. In the present embodiment, this dot area is divided into three stages, and three gradations of sizes L, M, and S (4 gradations when adding no dot) are expressed in order of increasing dot area. Each gradation can have substantially 13 types of ink dot areas. The dot number corresponding to the median of the ink dot areas of each gradation is set as a reference value for each of the L, M, and S gradations, and the nozzle For nozzles that deviate from the ink dot area reference value due to variations in ink droplet ejection characteristics, the dot number is shifted up and down to approach the reference value.

  FIG. 14 shows the dot area and the nozzle number before the gradation M is corrected. That is, 180 drive waveform signal selection patterns corresponding to the dot numbers serving as reference values are output for all nozzles. FIG. 15 shows the correction amount obtained by measuring all the ink dot areas and determining how many dot numbers shown in FIG. 13 should be corrected vertically. A positive value of the correction amount means that the dot number is corrected to be large (correcting the dot area is small), and a negative value is to correct the dot number to be small (correcting the dot area is large). That is, a drive waveform signal selection pattern corresponding to dot number 18 is output to the nozzle of nozzle number 1, and a drive waveform signal selection pattern corresponding to dot number 17 is output to the nozzle of nozzle number 2. FIG. 16 shows that the drive waveform signal selection pattern is corrected in this way and ink droplets are ejected from all nozzles. The corrected ink dot area is almost uniform.

  In the present embodiment, the drive waveform signal selection pattern for each gradation corrected in this way is combined with the drive waveform signal selection data SI and the drive signal selection data SEL described above, for example, as shown in a table shown in FIG. Then, it is stored in the RAM 62c which is a storage means. In this calculation process, first, in step S1, the drive waveform signal selection data SI and the drive signal selection data SEL stored in the RAM 62c are read.

Next, the process proceeds to step S <b> 2, and the correction amount of variation in ink droplet ejection characteristics of each nozzle obtained by the dot area measurement described above is read.
In step S3, the drive waveform signal selection data SI and the drive signal selection data SEL read in step S1 are corrected with the correction amount read in step S2, and the ink droplet ejection characteristics of each nozzle are corrected. Drive waveform signal selection data SI and drive signal selection data SEL for correcting the variation are calculated.

Next, the process proceeds to step S4, and the drive waveform signal selection data SI and the drive signal selection data SEL calculated in step S3 are updated and stored in the RAM 62c.
Next, the process proceeds to step S5, where it is determined whether or not the update of the drive waveform signal selection data SI and the drive signal selection data SEL for all the nozzles is completed. If the update is completed, the process returns to the main program. Otherwise, the process proceeds to step S1.

Further, FIG. 19 shows a calculation process for a printing operation using the drive waveform signal selection data SI and the drive signal selection data SEL. In this calculation process, first, in step S11, the print timing of the corresponding nozzle calculated in the individual calculation process is read.
Next, the process proceeds to step S12, and the print data of the corresponding nozzle calculated in the individual calculation process, in this case, the gradation data L, M, S (and not printed) is read.

In step S13, the drive waveform signal selection data SI and the drive signal selection data SEL corresponding to the gradation data read in step S12 are read from the storage table of the RAM 62c and output to the inkjet head. .
Next, the process proceeds to step S14, where it is determined whether or not it is the print timing. If it is the print timing, the process proceeds to step S15, and if not, the process waits.

In step S15, the first drive signal COM1 and the second drive signal COM2 are output in synchronization.
Next, the process proceeds to step S16, and the drive waveform signal is selected by the selection unit.
Next, the process proceeds to step S17, where it is determined whether or not the printing operation has been completed. If the printing operation has been completed, the process returns to the main program, and if not, the process proceeds to step S11.

  According to these calculation processes, when ink droplets are actually ejected from each nozzle and the ink dot area is measured, and a correction amount for correcting variations in ink droplet ejection characteristics between the nozzles is obtained from the measurement results, a drive waveform is obtained. The signal selection data SI and the drive signal selection data SEL are updated and stored, and printing is performed using the updated and stored drive waveform signal selection data SI and drive signal selection data SEL.

  Therefore, according to the head drive device of the inkjet printer of this embodiment, one or more drive waveform signals WCOM1 to WCOM8 for driving the piezoelectric actuator 22 are arranged in time series to generate a plurality of drive signals COM1 and COM2. The plurality of drive signals COM1 and COM2 are output in synchronism, and one or more drive waveform signals WCOM1 to WCOM8 are selected from the output drive signals COM1 and COM2 and the ink droplets are to be ejected. By supplying the piezoelectric actuator 22, the nozzle ink droplet ejection characteristics in the nozzle array can be finely corrected by the combination of the selected drive waveform signals WCOM1 to WCOM8, and unnecessary enlargement of the drive circuit can be avoided at the same time. Drive waveform signals WCOM1 to WCOM8 from the drive signals COM1 and COM2. It is possible to shorten the ink ejection period of from one nozzle it is possible to selectively supplied to the piezoelectric actuator 22.

  Also, two drive signals COM1 and COM2 formed by arranging two drive waveform signals WCOM1 to WCOM8 in time series are set as one drive signal unit UNIT1 and UNIT2, and the drive signal units UNIT1 and UNIT2 are set in time series two. By arranging and outputting them, the combination of selectable drive waveform signals WCOM1 to WCOM8 can be dramatically increased so that the nozzle ink droplet ejection characteristics in the nozzle array can be finely corrected, and the drive signal generation circuit 69 , 70 can be reduced to only two.

  Further, the drive waveform signal selection data SI that defines the drive waveform signals WCOM1 to WCOM8 to be selected corresponding to the print data and the drive signal selection data SEL that defines the drive signals COM1 and COM2 to be selected corresponding to the print data. Are selected, the drive waveform signals WCOM1 to WCOM8 are selected based on the print data and the stored drive waveform signal selection data SI, and the drive is performed based on the print data and the stored drive signal selection data SEL. The signals COM1 and COM2 are selected, the selection switch 15 is driven based on the selected drive waveform signals WCOM1 to WCOM8 and the drive signals COM1 and COM2, and the drive waveform signals WCOM1 to WCOM8 in the drive signals COM1 and COM2 are piezoelectric. By supplying the actuator 22, The a drive waveform signal selection data SI corresponding to the motor drive signal selection data SEL and are stored in each nozzle can be finely corrected nozzle ink drop ejection characteristics of the nozzle row for each nozzle.

In addition, since the drive waveform signal selection data SI and the drive signal selection data SEL for discharging ink droplets for correcting variations in the ink droplet discharge characteristics between nozzles are stored, the nozzle ink droplet discharge characteristics in the nozzle row are changed for each nozzle. Can be finely corrected.
Further, since the drive waveform signal selection data SI and the drive signal selection data SEL are stored on the basis of the correction amount of the variation in the ink droplet discharge characteristics between the nozzles, the nozzle ink droplet discharge characteristics in the nozzle row can be changed for each nozzle at any time. Can be finely corrected.

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

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 explanatory drawing of drive signal generation. It is a block diagram of the selection part which connects a drive signal to a piezoelectric actuator. FIG. 9 is a block diagram of a drive waveform signal selection circuit in FIG. 8. It is a block diagram from the drive signal selection circuit of FIG. 8 to a piezoelectric actuator. It is explanatory drawing of a drive waveform signal and a drive signal. It is explanatory drawing of the drive signal and drive waveform signal which are selected by drive waveform signal selection data and drive signal selection data. It is explanatory drawing of the ink dot area formed by the combination of a drive waveform signal. It is explanatory drawing of the ink dot area before correct | amending an ink droplet discharge characteristic. It is explanatory drawing of the correction amount of an ink droplet discharge characteristic. It is explanatory drawing of the ink dot area after correct | amending an ink droplet discharge characteristic. The drive is a drive waveform signal selection pattern table composed of a combination of waveform signal selection data and drive signal selection data. It is a flowchart of the arithmetic processing for updating and storing drive waveform signal selection data and drive signal selection data. It is a flowchart of a printing process.

Explanation 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 unit, 62c is a RAM, 69 is a first drive signal generator Circuit, 70 a second drive signal generation circuit, 214 a drive waveform signal selection circuit, 217 a drive signal selection circuit, and a a print medium

Claims (6)

 A plurality of nozzles provided in the head, a pressure chamber communicating with each nozzle, an actuator provided corresponding to each pressure chamber, and from which nozzle ink droplets are ejected based on print data or which Print data output means for outputting print data indicating whether or not ink droplets are to be ejected, and applying a drive signal to the actuator based on the print data from the print data output means to change the pressure in the pressure chamber An ink jet printer head drive device comprising a drive means for ejecting ink droplets from nozzles, wherein the drive means arranges one or more drive waveform signals for driving an actuator in time series to provide a plurality of drive signals. Drive signal generating means for generating a plurality of drive signals in synchronization with each other, and a plurality of output signals from the drive signal generating means. Head drive apparatus of an ink jet printer, characterized in that it comprises one or more the selected drive waveform signal selecting means for supplying the actuators of the nozzles to eject ink droplets of the drive waveform signal from the drive signal.  The drive signal generating means uses two drive signals obtained by arranging two drive waveform signals in time series as one drive signal unit, and outputs the two drive signal units arranged in time series. The head driving device for an ink jet printer according to claim 1.   The drive waveform signal selection means includes a selection switch that can connect each of the two drive signals to an actuator, drive waveform signal selection data that defines a drive waveform signal to be selected corresponding to the print data, and the print data Storage means for storing drive signal selection data for defining a drive signal to be selected corresponding to the driving signal, and driving for selecting a drive waveform signal based on the print data and the drive waveform signal selection data stored in the storage means Waveform signal selection means, drive signal selection means for selecting a drive signal based on the print data and drive signal selection data stored in the storage means, and the drive waveform signal and drive selected by the drive waveform signal selection means The switch driving means for driving the selection switch based on the drive signal selected by the signal selection means. Head drive apparatus of an ink jet printer according to.   4. The head of an ink jet printer according to claim 3, wherein the storage unit stores drive waveform signal selection data and drive signal selection data for ink droplet ejection that correct variations in ink droplet ejection characteristics between nozzles. Drive device.  The drive means includes data update means for storing drive waveform signal selection data and drive signal selection data in the storage means based on a correction amount of variation in ink droplet ejection characteristics between nozzles. 4. A head driving device for an inkjet printer according to item 4.  Based on the print data, print data indicating which ink droplet is to be ejected from which of the plurality of nozzles provided in the head or how much ink droplet is to be ejected, and based on the print data An ink jet printer head driving method for ejecting ink droplets from nozzles communicating with a pressure chamber by applying a driving signal to the actuator to change the pressure in the pressure chamber. Synchronously output multiple drive signals created by arranging one or more in time series, select one or more drive waveform signals from the multiple drive signals, and supply them to the actuator of the nozzle that should eject ink droplets A head driving method for an ink jet printer.

Images