JP2007168367A - Apparatus and method for driving ink jet printer head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for driving an ink jet printer head for stabilizing ink ejection properties for more nozzles, preventing upsizing of an apparatus and suppressing increase in a dynamic range of a power supply voltage for a driving signal generation circuit. <P>SOLUTION: The method for driving an ink jet printer head comprises connecting a plurality of different driving pulses incorporating frequency property opposite to that of a driving circuit including an actuator simultaneously or in time series manner for output corresponding to a number of the actuator for a nozzle for ejecting an ink droplet, selecting which driving pulse is supplied to which actuator based on printing data SI, and supplying the selected driving pulse to the selected one or more actuators, whereby ink ejection properties for more nozzles can be stabilized, and thereby an additional driving circuit is avoided to be installed and a number of the nozzle driven by a driving pulse is limited to suppress its variation. <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).

  Further, in this type of ink jet printer in which printing is executed while reciprocating the ink jet head on the carriage in a direction intersecting with the conveyance direction of the print medium, the ink jet head is set to 10 to cleanly print the entire page. Since it is necessary to reciprocate several times to several tens of times, there is a drawback in that it takes more printing time than other types of printing apparatuses, such as laser printers and copiers using electrophotographic technology.

  In contrast, in an inkjet printer of a type in which a long inkjet head (not necessarily integrated) having the same dimensions as the width of the print medium is disposed and the carriage is not used, the inkjet head is moved in the width direction of the print medium. This is not necessary, and so-called one-pass printing is possible, so that high-speed printing similar to a laser printer is possible. The former inkjet printer is generally referred to as a “multi-pass (serial) inkjet printer”, and the latter inkjet printer is generally referred to as a “line head inkjet printer”.

  In such an ink jet printer, the actuator is driven by a drive pulse 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 several types of actuators. For example, in a piezo ink jet printer, when a drive pulse is applied to a piezo (piezoelectric) element that is an actuator, the diaphragm in contact with the pressure chamber is displaced, thereby changing the pressure in the pressure chamber. Ink droplets are discharged.

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

  However, if the conventional ink jet printer is to be developed into a line head type ink jet printer, the line head type ink jet printer has an overwhelmingly large number of nozzles, that is, actuators compared to the multi-pass type ink jet printer. The change in the number of actuators connected to the drive pulse is also large (from which nozzle the ink droplets are ejected depends on the print data), and the change in the ink droplet ejection characteristics is correspondingly large. There are many types of pulses. In practice, when the slope or peak value of the voltage increase / decrease of the drive pulse consisting of the trapezoidal wave voltage signal is changed, the amount of change itself becomes large, so it is necessary to increase the dynamic range of the power supply voltage of the drive pulse. . In order to avoid this problem, for example, if a drive circuit is provided for each of several hundred nozzles, that is, actuators, the slope of increase / decrease in the voltage of the drive pulse and the amount of change in peak value can be suppressed, so that the dynamic range of the power supply voltage is increased. Can be suppressed. However, the number of drive circuits themselves increases, leading to an increase in the size of the device.

  The present invention has been made paying attention to the above-described problems, and is an inkjet printer head capable of preventing an increase in the size of the apparatus and suppressing an increase in the dynamic range of the drive signal generation circuit power supply voltage. An object of the present invention is to provide a driving device and a head driving method.

  [Invention 1] In order to solve the above-described problem, an ink jet printer head driving method according to Invention 1 includes a plurality of nozzles provided in the ink jet head and actuators provided corresponding to the nozzles, and print data. Print data indicating which ink droplets will be ejected from which nozzle or how much ink droplets will be ejected based on the nozzle, and applying drive pulses to the actuators of the nozzles that should eject ink droplets based on the print data When ejecting ink droplets from the nozzles, a plurality of different driving pulses are simultaneously applied according to the number of actuators of the nozzles that should eject the ink droplets and taking into account the frequency characteristics opposite to the frequency characteristics of the drive circuit including the actuators. Or, output in a time-series manner, and to any actuator based on the print data Select whether to supply driving pulses of les, it is characterized in that supplies a drive pulse selected for one or more actuators that are selected.

  [Invention 2] In addition, the head drive device of the ink jet printer according to Invention 2 includes a plurality of nozzles provided in the ink jet head, an actuator provided corresponding to each nozzle, and ink from any nozzle based on print data. Print data output means for outputting print data indicating how much or how much ink drops are to be ejected, and driving to the actuator of the nozzle to which ink drops are to be ejected based on the print data from the print data output means Drive means for applying pulses to eject ink droplets from the nozzles, the drive means corresponding to the number of actuators of the nozzles to which the ink droplets are to be ejected and having a frequency characteristic opposite to that of the drive circuit including the actuators A drive that outputs a plurality of different drive pulses that take frequency characteristics into account simultaneously or in time series. A pulse output unit; and a selection unit that selects which drive pulse is supplied to which actuator based on the print data and supplies the selected drive pulse to one or a plurality of selected actuators. It is characterized by that.

 According to the head drive device and the head drive device of the ink jet printer according to these inventions, the print data indicating which ink droplet is ejected from which nozzle or how much ink droplet is ejected based on the print data is output. When a drive signal is applied to the actuator of the nozzle that should eject ink droplets based on the print data and the ink droplet is ejected from the nozzle, the actuator is set according to the number of actuators of the nozzle that should eject the ink droplet. A plurality of different drive pulses that take into account the frequency characteristics opposite to the frequency characteristics of the included drive circuit are output simultaneously or in time series, and which drive pulse is supplied to which actuator based on the print data Select and supply the selected drive pulse to the selected actuator or actuators As a result, it is possible to stabilize the ink droplet ejection characteristics of more nozzles by supplying different drive pulses corresponding to the number of actuators simultaneously or in time series to the actuators, thereby increasing the number of drive circuits. Can prevent the increase in size of the device and limit the number of nozzles driven by the drive pulse, thereby suppressing the change amount and suppressing the increase in the dynamic range of the drive signal power supply voltage. can do.

[Invention 3] Further, the head drive device of the ink jet printer of the invention 3 is the head drive device of the ink jet printer of the invention 2. In the head drive device of the ink jet printer, the print data output means is independent according to the number of nozzles to eject ink droplets. Alternatively, a combination of a plurality of drive pulses is set, and the print data is set according to the combination.
According to the head drive device of the ink jet printer according to the present invention, a configuration in which a single or a combination of a plurality of drive pulses is set according to the number of nozzles that should eject ink droplets, and print data is set according to the combination. Therefore, different drive pulses corresponding to the number of actuators can be supplied to the actuators simultaneously or in time series combination, thereby stabilizing the ink droplet ejection characteristics of more nozzles.

Next, a first embodiment of the inkjet printer of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of the ink jet printer of the present embodiment, FIG. 1a is a plan view thereof, and FIG. 1b is a front view thereof. In FIG. 1, a print medium 1 is a line head type ink jet printer that is conveyed in the direction of the arrow in the figure from the upper right to the lower left of the figure, and is printed in the printing area in the middle of the conveyance. However, the ink jet head of the present embodiment is arranged not only at one place but also at two places.

  Reference numeral 2 in the figure denotes a first inkjet head provided on the upstream side in the conveyance direction of the print medium 1, and reference numeral 3 denotes a second inkjet head provided on the downstream side, and below the first inkjet head 2. Is provided with a first transport unit 4 for transporting the print medium 1, and a second transport unit 5 is provided below the second inkjet head 3. The first transport unit 4 includes four first transport belts 6 arranged at predetermined intervals in a direction intersecting with the transport direction of the print medium 1 (hereinafter also referred to as nozzle row direction). Similarly, the second transport unit 5 includes four second transport belts 7 arranged at predetermined intervals in a direction (nozzle row direction) intersecting the transport direction of the print medium 1.

 The four second conveyor belts 7 as well as the four first conveyor belts 6 are arranged alternately adjacent to each other. In the present embodiment, among these conveyor belts 6, 7, two first conveyor belts 6 and 2 on the right side in the nozzle row direction and two first conveyor belts 6 and second on the left side in the nozzle row direction. The conveyor belt 7 is separated. That is, the right driving roller 8R is disposed in the overlapping portion of the two first conveyance belts 6 and the second conveyance belt 7 on the right side in the nozzle row direction, and the two first conveyance belts 6 and the second conveyance belts on the left side in the nozzle row direction. 7 is provided with a left driving roller 8L, a right first driven roller 9R and a left first driven roller 9L on the upstream side, and a right second driven roller 10R and a second left side on the downstream side. A driven roller 10L is provided. These rollers appear as a series, but are substantially divided at the central portion of FIG. 1a. The two first conveying belts 6 on the right side in the nozzle row direction are wound around the right driving roller 8R and the first driven roller 9R on the right side, and the two first conveying belts 6 on the left side in the nozzle row direction are connected to the left driving roller 8L and the left side. The two second conveying belts 7 on the right side in the nozzle row direction are wound around the first driven roller 9L, and the two second conveying belts on the left side in the nozzle row direction are wound on the right driving roller 8R and the second right driven roller 10R. 7 is wound around the left driving roller 8L and the second left driven roller 10L. The right electric motor 11R is connected to the right driving roller 8R, and the left electric motor 11L is connected to the left driving roller 8L. Accordingly, when the right driving roller 8R is rotationally driven by the right electric motor 11R, the first conveying unit 4 composed of the two first conveying belts 6 on the right side in the nozzle row direction and the two second conveying belts on the right side in the nozzle row direction. The second conveyance unit 5 configured by 7 moves in synchronization with each other at the same speed, and is configured by two first conveyance belts 6 on the left side in the nozzle row direction when the left driving roller 8L is rotationally driven by the left electric motor 11L. The second transport unit 5 including the first transport unit 4 and the two second transport belts 7 on the left side in the nozzle row direction are synchronized with each other and move at the same speed. However, if the rotation speeds of the right electric motor 11R and the left electric motor 11L are different, the conveyance speed in the left and right directions in the nozzle row can be changed. Specifically, the rotation speed of the right electric motor 11R is changed to that of the left electric motor 11L. When the rotational speed is higher than the rotation speed, the conveyance speed on the right side in the nozzle row direction can be made larger than that on the left side, and when the rotation speed of the left electric motor 11L is higher than the rotation speed of the right electric motor 11R. The speed can be greater than the right side.

 The first ink-jet head 2 and the second ink-jet head 3 are shifted in the transport direction of the printing medium 1 for each of six colors, for example, yellow (Y), magenta (M), cyan (C), and black (K). Arranged. Ink is supplied to each inkjet head 2 and 3 from an ink tank of each color (not shown) via an ink supply tube. Each inkjet head 2, 3 is formed with a plurality of nozzles in the direction intersecting with the conveyance direction of the print medium 1 (that is, in the nozzle row direction), and a necessary amount of ink droplets are simultaneously applied from the nozzles to necessary locations. By discharging, minute ink dots are formed and output on the printing medium 1. By performing this for each color, it is possible to perform so-called one-pass printing by passing the print medium 1 conveyed by the first conveyance unit 4 and the second conveyance unit 5 once. That is, the area where the inkjet heads 2 and 3 are disposed corresponds to the print area.

  As a method for discharging and outputting ink from each nozzle of the ink jet head, there are an electrostatic method, a piezo method, a film boiling ink jet method, and the like. In the electrostatic system, when a drive signal is given to the electrostatic gap, which is an actuator, the diaphragm in the cavity is displaced, causing a pressure change in the cavity, and ink drops are ejected from the nozzle by the pressure change. It is. In the piezo method, when a drive signal is given to a piezo element that is an actuator, the diaphragm in the cavity is displaced to cause a pressure change in the cavity, and ink droplets are ejected from the nozzle by the pressure change. . In the film boiling ink jet method, there is a minute heater in the cavity, the ink is instantaneously heated to 300 ° C. or more, the ink becomes a film boiling state, bubbles are generated, and ink droplets are ejected from the nozzle by the pressure change. That's it. The present invention can be applied to any ink output method, but is particularly suitable for a piezo element that can adjust the ejection amount of ink droplets by adjusting the peak value of the drive signal and the voltage increase / decrease slope.

  The ink droplet ejection nozzles of the first inkjet head 2 are formed only between the four first conveyance belts 6 of the first conveyance unit 4, and the ink droplet ejection nozzles of the second inkjet head 3 are the second conveyance. It is formed only between the four second conveyor belts 7 of the section 5. This is because the inkjet heads 2 and 3 are cleaned by a cleaning unit, which will be described later, but in this way, one-pass printing cannot be performed with only one of the inkjet heads. Therefore, the first ink jet head 2 and the second ink jet head 3 are arranged so as to be shifted in the transport direction of the print medium 1 in order to compensate for the portions that cannot be printed with each other. Note that the first inkjet head 2 and the second inkjet head 3 each have 5400 nozzles for each color, and achieve a pixel density of 720 dpi as a whole. All the nozzles have independent actuators, each of which is provided with a selection switch which will be described later.

  Disposed below the first inkjet head 2 is the first cleaning cap 12 for cleaning the first inkjet head 2, and disposed below the second inkjet head 3 is the second inkjet head. 2 is a second cleaning cap 13 that cleans 3. Each of the cleaning caps 12 and 13 has such a size that it can pass between the four first conveying belts 6 of the first conveying unit 4 and between the four second conveying belts 7 of the second conveying unit 5. It is formed. These cleaning caps 12 and 13 are, for example, a rectangular bottomed cap body that covers the nozzles formed on the lower surfaces of the ink jet heads 2 and 3, that is, the nozzle surfaces and can be in close contact with the nozzle surfaces, and is disposed at the bottom thereof. And a tube pump connected to the bottom of the cap body, and a lifting device that lifts and lowers the cap body. Therefore, the cap body is raised by the lifting device and is brought into close contact with the nozzle surfaces of the inkjet heads 2 and 3. In this state, when the cap body is made negative pressure by the tube pump, ink droplets and bubbles are sucked out from the nozzles established on the nozzle surfaces of the ink jet heads 2 and 3, and the ink jet heads 2 and 3 can be cleaned. . When the cleaning is completed, the cleaning caps 12 and 13 are lowered. In some cases, the nozzle surface may be stroked with a wiper to adjust the meniscus of each nozzle.

  On the upstream side of the first driven rollers 9R and 9L, there are two pairs of gate rollers 14 that adjust the paper feed timing of the printing medium 1 supplied from the paper feeding unit 15 and correct the skew of the printing medium 1. Is provided. The skew is a twist of the print medium 1 with respect to the transport direction. A pickup roller 16 for supplying the print medium 1 is provided above the paper supply unit 15. Reference numeral 17 in the drawing denotes a gate roller motor that drives the gate roller 14.

  A belt charging device is disposed below the drive rollers 8R and 8L. The belt charging device is configured to press the charging roller 20 against the first conveying belt 6 and the second conveying belt 7 with the driving rollers 8R and 8L sandwiched between the charging roller 20 contacting the first conveying belt 6 and the second conveying belt 7. A spring 21 and a power source 22 for applying a charge to the charging roller 20 are configured to apply a charge from the charging roller 20 to the first conveying belt 6 and the second conveying belt 7 to charge them. In general, these belts are composed of a medium / high resistance body or an insulator. Therefore, when charged by a belt charging device, the charge applied to the surface is also composed of a high resistance body or an insulator. The print medium 1 is caused to generate dielectric polarization, and the print medium 1 can be adsorbed to the belt by electrostatic force generated between the charge generated by the dielectric polarization and the charge on the belt surface. The charging means may be a so-called corotron that drops the charge.

  Therefore, according to this ink jet printer, the surface of the first conveying belt 6 and the second conveying belt 7 is charged by the belt charging device, and the printing medium 1 is fed from the gate roller 14 in this state, and a spur and a roller (not shown) are provided. When the printing medium 1 is pressed against the first conveying belt 6 by the paper pressing roller configured as follows, the printing medium 1 is attracted to the surface of the first conveying belt 6 by the action of the dielectric polarization described above. In this state, when the driving rollers 8R and 8L are rotationally driven by the electric motors 11R and 11L, the rotational driving force is transmitted to the first driven rollers 9R and 9L via the first conveying belt 6.

  In this way, the first conveyance belt 6 is moved downstream in the conveyance direction while the print medium 1 is adsorbed, and the print medium 1 is moved below the first inkjet head 2 to be formed on the first inkjet head 2. Printing is performed by ejecting ink droplets from the nozzles. When printing by the first ink jet head 2 is completed, the print medium 1 is moved downstream in the transport direction and transferred onto the second transport belt 7 of the second transport unit 5. As described above, since the surface of the second conveyance belt 7 is also charged by the belt charging device, the print medium 1 is attracted to the surface of the second conveyance belt 7 by the action of the dielectric polarization described above.

  In this state, the second conveying belt 7 is moved downstream in the conveying direction, the printing medium 1 is moved below the second inkjet head 3, and ink droplets are ejected from nozzles formed on the second inkjet head. To print. When printing by the second ink jet head is completed, the print medium 1 is further moved downstream in the transport direction, and the print medium 1 is discharged to the paper discharge unit while being separated from the surface of the second transport belt 7 by a separation device (not shown). To do.

  When the first and second inkjet heads 2 and 3 need to be cleaned, the first and second cleaning caps 12 and 13 are raised as described above to raise the nozzle surfaces of the first and second inkjet heads 2 and 3. In this state, the cap body is brought into a negative pressure so that ink drops and bubbles are sucked out from the nozzles of the first and second ink jet heads 2 and 3 and cleaned. 2 Lower the cleaning caps 12 and 13.

  A control device for controlling itself is provided in the ink jet printer. For example, as shown in FIG. 2, the control device prints on a print medium by controlling a printing device, a paper feeding device, and the like based on print data input from a host computer 60 such as a personal computer or a digital camera. The processing is performed. An input interface unit 61 that receives print data input from the host computer 60, a control unit 62 configured by, for example, a microcomputer that executes print processing based on the print data input from the input interface unit 61, A gate roller motor driver 63 for driving and controlling the gate roller motor 17, a pickup roller motor driver 64 for driving and controlling the pickup roller motor 51 for driving the pickup roller 16, and a head driver 65 for driving and controlling the inkjet heads 2 and 3. The right electric motor driver 66R for driving and controlling the right electric motor 11R, the left electric motor driver 66L for driving and controlling the left electric motor 11L, and the output signals of the drivers 63 to 65, 66R and 66L are externally gated. Ramota 17, the pickup roller motor 51, the inkjet heads 2 and 3, the right electric motor 11R, configured to include an interface 67 for converting the control signal used in the left electric motor 11L.

  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, 66R, and 66L based on the print data and input data from various sensors. When control signals are output from the drivers 63 to 65, 66R, 66L, these are converted into drive signals by the interface unit 67, and actuators corresponding to the plurality of nozzles of the inkjet head 20, the gate roller motor 17, and the pickup roller motor. 51, the right electric motor 11R and the left electric motor 11L are operated, respectively, to feed and convey the print medium 1, control the posture of the print medium 1, and print processing on the print medium 1. Each component in the control unit 62 is electrically connected through a bus (not shown).

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

  The head driver 65 includes a drive signal generation circuit 70 that generates a drive signal COM and an oscillation circuit 71 that outputs a clock signal SCK. As shown in FIG. 3, the drive signal generation circuit 70 includes a waveform memory 701 that stores 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. 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. 4, 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.

  Next, the principle of drive signal generation by the drive signal generation circuit 70 will be described. First, waveform data that is 0 as a voltage change amount per unit time is written in the address A0. Similarly, waveform data of + ΔV1 is written in the address A1, −ΔV2 is written in the address A2, and + ΔV3 is written in the address A3. In addition, the data stored in the latch circuits 702 and 704 is cleared by the clear signal CLER. The drive signal COM is raised to an intermediate potential (offset) by the waveform data.

  From this state, for example, as shown in FIG. 5, 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.

  When the digital signal thus generated is converted into an analog signal by the D / A converter 705, a drive signal WCOM as shown in FIG. 9a is obtained. The rising portion of the drive signal COM is a stage in which the volume of the cavity (pressure chamber) communicating with the nozzle is enlarged and ink is drawn in (it can be said that the meniscus is drawn in view of the ink discharge surface), and the fall of the drive signal COM The portion is a stage where the cavity volume is reduced and the ink is pushed out (which can be said to push out the meniscus in view of the ink discharge surface). As a result of the ink being pushed out, ink droplets are ejected from the nozzles. Incidentally, the waveform of the drive signal COM is, as easily guessed from the above, 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. Can be adjusted by. Then, by variously changing the voltage increase / decrease slope and peak value of the drive signal COM consisting of this voltage trapezoidal wave, the ink drawing amount and drawing speed, the ink pushing amount and the pushing speed can be changed. Different ink dot sizes can be obtained by changing the ejection amount of the ink droplets.

  Next, a configuration for connecting the drive signal COM output from the drive signal output circuit and an actuator such as a piezoelectric element will be described. This connection configuration is constructed in each of the inkjet heads 2 and 3. The inkjet heads 2 and 3 select a drive signal COM generated by the drive signal output circuit and a drive pulse for selecting a nozzle to be ejected based on the print data and determining a connection timing to the drive signal COM of an actuator such as a piezo element. After the selection data signal SI and the nozzle selection data are input to all the nozzles, the latch signal LAT, the channel signal CH, and the driving pulse for connecting the driving signal COM and the actuators of the inkjet heads 2 and 3 based on the driving pulse selection data SI. A clock signal SCK for transmitting the selection data signal SI to the inkjet heads 2 and 3 as a serial signal is input. This drive pulse selection data corresponds to the print data of the present invention. The actuators 202 such as piezoelectric elements of the inkjet heads 2 and 3 are connected in parallel to the drive signal COM as shown in FIG. 6, for example, and a selection switch 201 is provided for each of them.

  FIG. 6 is a block diagram of a selection unit that connects the drive signal COM described above and an actuator 202 such as a piezo element. The selection unit includes a shift register 211 that stores drive pulse selection data SI for designating an actuator such as a piezo element corresponding to a nozzle that should eject ink droplets, and a latch that temporarily stores data of the shift register 211. A circuit 212; a decoder 214 that decodes data stored in the latch circuit 212; a level shifter 213 that converts the level of the output of the latch circuit 212 decoded by the decoder 214; and a drive signal COM in accordance with the output of the level shifter. It is comprised by the selection switch 201 connected to actuators, such as.

  The drive pulse 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 pulse selection data SI for the number of nozzles is stored in the shift register 211. The signal stored in the latch circuit 212 is decoded by the decoder 214 and then converted to a voltage level by which the selection switch 201 at the next stage can be turned on and off by the level shifter 213. 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. Therefore, the actuator 202 such as a piezo element whose selection switch 201 is closed by the level shifter 213 is connected to the drive signal COM at the connection timing of the drive pulse selection data SI. In addition, after the drive pulse selection data signal SI of the shift register 211 is stored in the latch circuit 212, the next print data is input to the shift register 211, and the stored data in the latch circuit 212 is sequentially transferred in accordance with the ink droplet ejection timing. Update. In addition, the code | symbol HGND in a figure is a ground end of actuators, such as a piezo element. Further, according to the selection switch 201, the input voltage of the actuator 22 is maintained at the voltage just before the disconnection even after the actuator such as the piezo element is disconnected from the drive signal COM.

  Next, details of the drive signal COM supplied to the selection switch 201 and the actuator 202 such as a piezo element in the present embodiment will be described. A trapezoidal wave drive signal COM as shown in FIG. 7a also has a trapezoidal corner as shown in FIG. 7b when a plurality of actuators 202 such as piezo elements are actually connected. This is because the actuator 202 such as a piezo element is connected in parallel by the selection unit described above. The actuator 202 such as a piezo element has a capacitance C. For example, in addition to the resistance R or parasitic inductance of the wiring itself shown in FIG. 8a, each time the actuator 202 such as a piezo element is connected, FIGS. As indicated by d, the capacitances C are connected in parallel one after another, and a low-pass (low-pass) filter is formed by the entire drive circuit. Naturally, the drive signal COM supplied to the drive circuit constituting this low-pass filter is free from high-frequency components, that is, has a corner. The gain of the low-pass filter decreases as the number of actuators 202 such as piezo elements connected increases, that is, as the capacitance C increases.

  Thus, in the present embodiment, for example, for a drive pulse having a basic shape as shown in FIG. 9A, a frequency characteristic opposite to the frequency characteristic of the low-pass filter of the drive circuit including the actuator 202 such as a piezo element, that is, a high pass (high frequency band). 9) A plurality of drive pulses as shown in FIG. 9b, including the filter pass component, are prepared for each number of actuators such as piezo elements to be connected, and these are connected in time series to form a series of drive signals COM. . In the present embodiment, for each of the first inkjet printer 2 and the second inkjet printer 3, four types of first drive pulse PCOM1 to fourth drive pulse PCOM4 are provided for each number of nozzles connected to the drive signal COM, that is, for each number of actuators. A drive pulse is set and connected in time series as shown in FIG.

  Specifically, as shown in Table 1 below, the first drive pulse PCOM1 corresponds to 1 to 360 nozzles (= actuator number) that should eject ink droplets, and the second drive pulse PCOM2 corresponds to the number of nozzles (= The number of actuators) corresponds to 361 to 720, the third drive pulse PCOM3 corresponds to the number of nozzles (= actuator number) 721 to 1440, and the fourth drive pulse PCOM4 corresponds to the number of nozzles (= actuator number) 1441 to 2880. Correspond. That is, when the number of nozzles to which ink droplets are to be ejected is 1 to 360, the first drive pulse PCOM1 is supplied (connected) to actuators such as piezo elements corresponding to these nozzles, and ink droplets are ejected. When the number of nozzles to be driven is 361 to 720, the second drive pulse PCOM2 is supplied (connected) to an actuator such as a piezo element corresponding to these nozzles, and the number of nozzles to which ink droplets are to be discharged is 721 to 1440. In the case of the number of nozzles, the third drive pulse PCOM3 is supplied (connected) to an actuator such as a piezo element corresponding to these nozzles, and when the number of nozzles that should eject ink droplets is 1441 to 2800, The fourth drive pulse PCOM4 is supplied (connected) to an actuator such as a piezo element corresponding to these nozzles. Since these first drive pulse PCOM1 to fourth drive pulse PCOM4 are added with components removed by a low-pass filter composed of a drive circuit and wiring corresponding to the number of connected actuators, the corresponding number of actuators If the first drive pulse PCOM1 to the fourth drive pulse PCOM4 are supplied to the actuator, the actuator is substantially applied with the original drive signal (= first drive pulse), and as a result, the ink droplet ejection characteristics of the nozzles. Can be stabilized.

  Further, when these first drive pulse PCOM1 to fourth drive pulse PCOM4 are used, as shown in Table 1, when the number of nozzles that should eject ink droplets is 721 to 1080, for example, the nozzles Supply the original drive signal to each actuator by supplying (connecting) the first drive pulse PCOM1 to 360 of the corresponding actuators such as piezoelectric elements and supplying (connect) the second drive pulse PCOM2 to the remaining actuators. can do. Similarly, if the number of nozzles that should eject ink droplets is 1441 to 1800, the first drive pulse PCOM1 is supplied (connected) to 360 of actuators such as piezoelectric elements corresponding to these nozzles, for example. Then, the third drive pulse PCOM3 is supplied (connected) to the rest. When the number of nozzles that should eject ink droplets is 1801 to 2160, for example, the second drive pulse PCOM2 is supplied (connected) to 720, and the third drive pulse PCOM3 is supplied (connected) to the rest. . Further, when the number of nozzles that should eject ink droplets is 2161 to 2520, for example, 360 first drive pulses PCOM1, 720 second drive pulses PCOM2, and the remaining third drive pulse PCOM3. Supply (connect). Further, when the number of nozzles that should eject ink droplets is 2881 to 2240, for example, the first drive pulse PCOM1 is supplied (connected) to 360, and the fourth drive pulse PCOM4 is supplied (connected) to the remaining. Further, when the number of nozzles that should eject ink droplets is 3241 to 3600, for example, the second drive pulse PCOM2 is supplied (connected) to 720, and the fourth drive pulse PCOM4 is supplied (connected). Further, when the number of nozzles that should eject ink droplets is 3601 to 3960, for example, 360 first drive pulses PCOM1, 720 second drive pulses PCOM2, and the remaining fourth drive pulses PCOM4. Supply (connect). Further, when the number of nozzles that should eject ink droplets is 3961 to 4320, the third drive pulse PCOM3 is supplied (connected) to 1440, for example, and the remaining fourth drive pulse PCOM4 is supplied (connected). In addition, when the number of nozzles that should eject ink droplets is 4321 to 4680, for example, 360 first drive pulses PCOM1, 3440 third drive pulses PCOM3, and the remaining 4th drive pulses PCOM4. Supply (connect). Further, when the number of nozzles that should eject ink droplets is 4681 to 5040, for example, the second drive pulse PCOM2 is set to 720, the third drive pulse PCOM3 is set to 1440, and the fourth drive pulse PCOM4 is set to the rest. Supply (connect). When the number of nozzles that should eject ink droplets is 5041 to 5400, for example, 360 first drive pulses PCOM1, 720 second drive pulses PCOM2, and 1440 third drive pulses PCOM3. And the remaining fourth drive pulse PCOM4 is supplied (connected). That is, in the present embodiment, the ink droplet ejection characteristics of all the 5400 nozzles of the inkjet heads 2 and 3 can be stabilized by the four types of drive pulses first drive pulse PCOM1 to fourth drive pulse PCOM4. .

  Next, calculation processing performed in the control unit 62 in order to perform printing by appropriately selecting four types of driving pulses from the first driving pulse to the fourth driving pulse and supplying them to the actuators of the nozzles that should eject ink droplets. This will be described with reference to the flowchart of FIG. This arithmetic processing is executed when a print command is issued from the host computer 60. First, in step S1, print data from the host computer is received.

In step S2, the number of nozzles to be ejected is calculated for each color from print data for one nozzle row (= print pixel).
Next, the process proceeds to step S3, and the combination of drive pulses for each color is determined from the number of ejection nozzles for each color calculated in step S2 according to the table in Table 1.
Next, the process proceeds to step S4, and the drive pulse selection ratio for each color is calculated from the combination of the drive pulses for each color determined in step S3. The drive pulse selection ratio is, for example, in Table 1. When the number of ink droplet ejection nozzles is 1000, the first drive pulse PCOM1 is used for 360 actuators of the corresponding nozzle, and the second drive is used for the remaining 280. Since the pulse PCOM2 is supplied, the drive pulse selection ratio between the first drive pulse PCOM1 and the second drive pulse PCOM2 is 360: 640 (9:16). Of course, the method of setting the drive pulse selection ratio is not limited to this. For example, in such a case, the second drive pulse PCOM2 is supplied to 720 actuators, and the first drive pulse PCOM1 is supplied to 280 actuators. In this case, the drive pulse selection ratio between the first drive pulse PCOM1 and the second drive pulse PCOM2 is 280: 720 (7:18).

  In step S5, the print data is developed into drive pulse selection data SI for each color according to the drive pulse selection ratio for each color calculated in step S4. As described above, the drive pulse selection data SI determines which drive pulse the first drive pulse PCOM1 to the fourth drive pulse PCOM4 are supplied to which nozzle. If the drive pulse selection data SI is in accordance with the drive pulse selection ratio, For example, the first drive pulse PCOM1 to the fourth drive pulse PCOM4 may be randomly assigned, or may be assigned in the order of the oldest nozzle numbers (the youngest) assigned in advance. Even in the latter case, since the ink droplet ejection nozzles are different for each print data or nozzle row, there is no tendency for the drive pulses to be allocated.

Next, the process proceeds to step S6, and the drive pulse selection data SI for each color set in step S5 is output to the inkjet heads 2 and 3 for each color.
Next, the process proceeds to step S7, where it is determined whether or not the next row data exists in the print data received in step S1, and the process proceeds to step S2 if the next row data exists, and otherwise. Return to the main program.

  According to this arithmetic processing, one or a plurality of first drive pulses PCOM1 to a combination of the fourth drive pulses PCOM4 is set according to the number of nozzles that should eject ink droplets, and drive pulse selection data is set according to the combination. (Print data) Since the configuration is such that SI is set, different first drive pulses PCOM1 to fourth drive pulses PCOM4 corresponding to the number of actuators can be combined in time series and supplied to the actuator, thereby increasing the number of nozzles The ink droplet ejection characteristics can be stabilized.

  A plurality of different first drive pulses PCOM1 to PCOM4 corresponding to the number of actuators of the nozzles that should eject ink droplets and taking into account the frequency characteristics opposite to the frequency characteristics of the drive circuit including the actuators are time-series. To which actuator pulse to be supplied is selected based on drive pulse selection data (print data) SI, and the selected drive pulse is selected for one or more selected actuators. Since the first drive pulse PCOM1 to the fourth drive pulse PCOM4 corresponding to the number of actuators are combined in time series and supplied to the actuator, the ink droplet ejection characteristics of more nozzles are stabilized. It is possible to prevent the enlargement of the device by avoiding the addition of the drive circuit. Rutotomoni suppresses their variation by limiting the number of nozzles to be driven by the driving pulses, an increase in the dynamic range of the drive signal generating circuit power supply voltage can be suppressed.

  12 and 13 show a second embodiment of the ink jet printer in which the head drive device of the ink jet printer of the present invention is developed. The schematic configuration of this ink jet printer is the same as that of the first embodiment. In this embodiment, the first drive pulse PCOM1 to the fourth drive pulse PCOM4 of the first embodiment are independently and simultaneously output to each of the four signal lines connected to the drive signal generation circuit 70. The four signal lines are connected to each actuator 202 such as a piezo element via a switch 201.

  In the present embodiment, the same calculation process as that of the printing process of the first embodiment is applied, but different drive pulses are supplied at the same time, so the drive pulse selection timings are the same timing. Therefore, in the present embodiment, different drive pulses corresponding to the number of actuators can be supplied to the actuators at the same time, whereby the ink droplet ejection characteristics of more nozzles can be stabilized. Further, the time required for printing can be shortened by simultaneously supplying the first driving pulse PCOM1 to the fourth driving pulse PCOM4 to the actuator.

  In addition, by supplying different drive pulses according to the number of actuators to the actuator at the same time, it is possible to stabilize the ink droplet ejection characteristics of more nozzles, thereby avoiding the addition of drive circuits and increasing the size of the device. In addition to being able to prevent this, by limiting the number of nozzles driven by the drive pulse, the amount of change thereof can be suppressed, and an increase in the dynamic range of the drive signal generation circuit power supply voltage can be suppressed.

  In the above embodiment, only an example in which the head driving device of the ink jet printer of the present invention is applied to a so-called line head type ink jet printer is described in detail. However, the head driving device of the ink jet printer of the present invention is a multipass printer. It can be applied to all types of inkjet printers.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic block diagram which shows one Embodiment of the line head type inkjet printer to which the head drive device of the inkjet printer of this invention is applied, (a) is a top view, (b) is a front view. It is a block block diagram of the control apparatus of the inkjet printer of FIG. FIG. 3 is a block configuration diagram of a drive signal generation circuit of FIG. 2. 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 an actuator. It is explanatory drawing of the state from which a drive signal changes with the number of actuators connected. It is explanatory drawing of the low-pass filter comprised by the actuator connected. It is explanatory drawing of a different drive pulse. It is explanatory drawing of the drive signal which connected the different drive pulse in time series. It is a flowchart of the arithmetic processing performed for a printing process. FIG. 5 is a block diagram of a selection unit that connects a drive signal to an actuator, showing a second embodiment of a head drive device for an inkjet printer of the present invention. It is explanatory drawing of the drive signal which outputs a different drive signal simultaneously.

Explanation of symbols

  1 is a print medium, 2 is a first inkjet head, 3 is a second inkjet head, 4 is a first transport unit, 5 is a second transport unit, 6 is a first transport belt, 7 is a second transport belt, and 8R and 8L. Is a driving roller, 9R and 9L are first driven rollers, 10R and 10L are second driven rollers, 11R and 11L are electric motors, 70 is a driving signal generation circuit, 201 is a selection switch, and 202 is an actuator.

Claims (3)

  Equipped with a plurality of nozzles provided in the inkjet head and actuators provided for each nozzle, from which nozzles or how much ink droplets are discharged based on print data The number of actuators of the nozzles that should eject the ink droplets when the ink pulses are ejected from the nozzles by applying the drive pulse to the actuators of the nozzles that should eject the ink droplets based on the print data And a plurality of different driving pulses that are combined with a frequency characteristic opposite to the frequency characteristic of the driving circuit including the actuator at the same time or connected in time series and output to any actuator based on the print data. Select whether to supply a drive pulse and be selected for one or more selected actuators Head drive method for an ink jet printer and supplying the drive pulse.   Multiple nozzles provided on the inkjet head, actuators provided for each nozzle, and printing indicating which ink droplets are to be ejected or how much ink droplets are to be ejected based on print data Print data output means for outputting data, and drive means for applying a drive pulse to an actuator of a nozzle to which ink droplets are to be ejected based on the print data from the print data output means and ejecting ink droplets from the nozzles The driving means includes a plurality of different driving pulses according to the number of actuators of the nozzles to which the ink droplets are to be ejected and a frequency characteristic opposite to the frequency characteristic of the driving circuit including the actuator, simultaneously or in time series. Drive pulse output means for connecting and outputting to any actuator based on the print data Select whether to supply a driving pulse les, the head drive apparatus of an ink jet printer, characterized in that a selection means for supplying a drive pulse selected for one or more actuators that are selected.   The print data output means sets one or a combination of a plurality of drive pulses according to the number of nozzles that should eject ink droplets, and sets the print data according to the combination. 3. A head driving device for an inkjet printer according to 2.

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