JP2009286134A - Liquid jet device and printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain printing of high image quality and high gradation by avoiding waveform distortion of driving pulses, restraining or preventing the weight fluctuation of liquid and avoiding a lag of liquid jet timing. <P>SOLUTION: A liquid jet device is provided with only one actuator 22 that is connected to a driving circuit to avoid the waveform distortion of driving pulses by providing transistor pairs for power amplification of drive waveform signals WCOM in the same number as the number of actuators, and interposing a smoothing filter 26 between the transistor pair and the actuator 22. In addition, modulating circuits 24 for the drive waveform signals WCOM and gate drive circuits 34 for driving the transistor pairs are provided in the same number as the number of transistor pairs. The drive waveform signals WCOM corresponding to the actuators 22 and nozzles can thereby be generated to restrain or prevent the weight fluctuation of liquid between the nozzles. Further, the drive waveform signals WCOM are simultaneously generated to the actuators 22 of the nozzles for jetting liquid. The lag of liquid jet timing is thereby avoided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a printing apparatus that prints predetermined characters, images, and the like by ejecting minute liquid from a plurality of nozzles and forming fine particles (dots) on a printing medium.

Inkjet printers, which are one of such printing devices, are generally inexpensive and can easily obtain high-quality color printed matter. Therefore, with the spread of personal computers and digital cameras, not only offices but also general users. It has become widespread.
Furthermore, recent ink jet printers require printing with high gradation. The gradation is the density state of each color contained in the pixel represented by the liquid dot. The dot size corresponding to the color density of each pixel is called the gradation, and the gradation that can be expressed by the liquid dot. The number is called the number of gradations. High gradation means that the number of gradations is large. In order to change the gradation, it is necessary to change the drive pulse to the actuator provided in the liquid ejecting head. When the actuator is a piezo element, the amount of displacement of the piezo element (more precisely, distortion of the diaphragm) increases as the voltage value applied to the piezo element increases. Can be changed.

  Therefore, in Patent Document 1 listed below, a plurality of drive pulses having different voltage peak values are connected in combination and output in common to the piezo elements of the same color nozzle provided in the liquid jet head, Among them, a drive pulse corresponding to the gradation of the liquid dot to be formed is selected for each nozzle, and the selected drive pulse is supplied to the piezo element of the corresponding nozzle so as to eject liquids having different weights. By doing so, the required gradation of liquid dots is achieved.

Japanese Patent Laid-Open No. 2003-1824

  However, in the conventional inkjet printer, there is a problem that the waveform of the drive pulse is distorted by the parasitic inductance and parasitic capacitance of the wiring of the drive circuit, the resistance, and the capacitance of the actuator such as a piezo element. It changes according to the number of actuators such as piezo elements. The waveform distortion of the drive pulse leads to a variation in the weight of the liquid, and the size of the liquid dot changes, leading to a deterioration in the print image quality. Note that the weight variation of the liquid also depends on individual differences between nozzles and actuators. In addition, a plurality of drive pulses are combined and connected in time series, and a drive pulse corresponding to the gradation of the liquid dot to be formed is selected for each nozzle, and the selected drive pulse is selected from the corresponding nozzles. When applied to the actuator, the liquid ejection timing shifts for each of the actuator nozzles for which different drive pulses are selected, causing the liquid dot formation (also called landing) position to change and the print image quality to deteriorate. Become.

  The present invention has been made paying attention to the above-described problems, and avoids waveform distortion of a drive pulse, suppresses and prevents fluctuations in the weight of liquid, and avoids deviation in liquid ejection timing. Accordingly, an object of the present invention is to provide a liquid ejecting apparatus and a printing apparatus that enable high-quality and high-gradation printing.

  In order to solve the above problems, a liquid ejecting apparatus according to the present invention includes a plurality of nozzles provided in a liquid ejecting head, an actuator provided corresponding to the nozzle, and a driving unit that applies a driving pulse to the actuator. The drive unit includes: a drive waveform signal generating unit that generates a drive waveform signal serving as a reference for a drive pulse to the actuator; and a drive generated by the drive waveform signal generating unit In order to amplify the waveform signal, the same number as the number of actuators is provided and a pair of transistors is formed by push-pull connection, and the transistor pair is disposed between the connection point of the transistor pair and the actuator. The number of smoothing filters is the same as the number of actuators.

According to the liquid ejecting apparatus of the above invention, since only one actuator is connected to the drive circuit composed of the transistor pair and the smoothing filter, the waveform distortion of the drive pulse can be avoided, and the ejection is thereby performed. In this way, it is possible to prevent high-quality and high-gradation printing by suppressing the fluctuation of the weight of the liquid.
Further, the modulation means for pulse-modulating the drive waveform signal generated by the drive waveform signal generation means, and the gate drive means for driving the transistor pair based on the modulation signal pulse-modulated by the modulation means are the transistor pair. Preferably, the transistor pairs are individually controlled based on the drive waveform signal.

Furthermore, a waveform data memory for storing waveform data corresponding to the actuator is provided, and the drive waveform signal generating means generates a drive waveform signal for each corresponding actuator based on the waveform data stored in the waveform data memory. It is desirable to generate.
According to the liquid ejecting apparatus of the above invention, it is possible to suppress and prevent the fluctuation in the weight of the liquid ejected between the nozzles by generating the drive waveform signal corresponding to the actuator or nozzle of the individual drive circuit. It is possible to print with high image quality and high gradation.

Further, it is desirable that the drive waveform signal generating means simultaneously generates drive waveform signals for all actuators corresponding to the nozzles that eject the liquid at the timing when the liquid is ejected from the nozzles.
According to the liquid ejecting apparatus of the invention described above, it is possible to avoid a shift in the liquid ejecting timing between the nozzles, thereby enabling high-quality and high-gradation printing.
Further, it is desirable that the modulation means, the gate drive means, the transistor pair, and the smoothing filter are arranged in the vicinity of the actuator as an integrated circuit.

Moreover, the printing apparatus of the present invention is preferably a printing apparatus including the above-described liquid ejecting apparatus.
According to the printing apparatus of the present invention, it is possible to suppress and prevent the fluctuation in the weight of the ejected liquid, thereby enabling high-quality and high-tone printing. Furthermore, by arranging the modulation means, the gate drive means, the transistor pair, and the smoothing filter as an integrated circuit in the vicinity of the actuator, it is possible to reduce power loss and save power, and to install a plurality of liquid jet heads. Therefore, the printing apparatus can be downsized.

FIG. 2 is a schematic configuration diagram illustrating an embodiment of a line head type printing apparatus to which the liquid ejecting apparatus of the invention is applied, where (a) is a plan view and (b) is a front view. It is a block block diagram of the control apparatus of the printing apparatus of FIG. It is explanatory drawing of drive waveform signal generation. It is explanatory drawing of the drive waveform signal of various forms. It is a block block diagram of a drive circuit alone. It is a block diagram which shows the whole structure of a drive circuit. FIG. 6 is a block diagram illustrating details of a modulation circuit, a digital power amplifier, and a smoothing filter of the drive circuit in FIG. 5. It is explanatory drawing of an effect | action of the modulation circuit of FIG. It is explanatory drawing of an effect | action of the digital power amplifier of FIG. It is a block diagram of a drive waveform signal generation circuit. It is explanatory drawing of a waveform data memory. It is a flowchart which shows the calculation process of the waveform data output performed with the memory controller of FIG. It is explanatory drawing of the drive waveform signal by the arithmetic processing of FIG.

Next, as an example of the present invention, an embodiment will be described with reference to the drawings using a printing apparatus that ejects liquid and prints characters, images, and the like on a print medium.
FIG. 1 is a schematic configuration diagram of a printing apparatus 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 printing apparatus that is transported in the direction of the arrow in the figure from the right to the left in the figure, and is printed in a print area in the middle of the conveyance. However, the liquid jet head according to the present embodiment is arranged not only at one place but also at two places.

  In the figure, reference numeral 2 denotes a first liquid ejecting head provided on the upstream side in the transport direction of the print medium 1, and reference numeral 3 denotes a second liquid ejecting head also provided on the downstream side, and the first liquid ejecting head 2. A first transport unit 4 for transporting the print medium 1 is provided below the second liquid ejecting head 3, and a second transport unit 5 is provided below the second liquid ejecting 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 liquid ejecting head 2 and the second liquid ejecting head 3 are arranged in a color unit of yellow (Y), magenta (M), cyan (C), and black (K) while being shifted in the transport direction of the print medium 1. Has been. The liquid jet heads 2 and 3 are supplied with liquid from liquid tanks of respective colors (not shown) via liquid supply tubes. Each of the liquid jet heads 2 and 3 is formed with a plurality of nozzles in a direction crossing the transport direction of the print medium 1 (that is, the nozzle row direction). By ejecting, fine liquid dots are formed on the print medium 1. By performing this for each color, it is possible to perform printing in one pass only 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 these liquid jet heads 2 and 3 are disposed corresponds to the print area.

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

  The liquid ejecting nozzles of the first liquid ejecting head 2 are formed only between the four first transport belts 6 of the first transporting unit 4, and the liquid ejecting nozzles of the second liquid ejecting head 3 are second transported. It is formed only between the four second conveyor belts 7 of the section 5. This is because the liquid ejecting heads 2 and 3 are cleaned by a cleaning unit, which will be described later. However, if one of the liquid ejecting heads is used in this way, the entire surface printing cannot be performed in one pass. Therefore, the first liquid ejecting head 2 and the second liquid ejecting 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.

  Disposed below the first liquid ejecting head 2 is the first cleaning cap 12 for cleaning the first liquid ejecting head 2 and disposed below the second liquid ejecting head 3. 2 is a second cleaning cap 13 for cleaning the liquid jet head 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 cover the nozzles formed on the lower surfaces of the liquid jet heads 2 and 3, that is, the nozzle surfaces, and are disposed at the bottoms of the rectangular bottomed cap bodies that can be in close contact with the nozzle surfaces. The liquid absorber, the 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 liquid jet heads 2 and 3. In this state, when a negative pressure is applied to the inside of the cap by the tube pump, liquid and bubbles are sucked out from the nozzles provided on the nozzle surfaces of the liquid jet heads 2 and 3, and the liquid jet heads 2 and 3 can be cleaned. it can. When the cleaning is completed, the cleaning caps 12 and 13 are lowered.

  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 19 is disposed below the drive rollers 8R and 8L. The belt charging device 19 includes a charging roller 20 that is in contact with the first conveying belt 6 and the second conveying belt 7 with the driving rollers 8R and 8L interposed therebetween, and the charging roller 20 is connected to the first conveying belt 6 and the second conveying belt 7. It comprises a spring 21 to be pressed and a power source 18 for applying a charge to the charging roller 20, and charges the first conveying belt 6 and the second conveying belt 7 from the charging roller 20 to charge them. In general, these belts are formed of a medium / high resistance body or an insulator, and when charged by the belt charging device 19, the charge applied to the surface thereof is also composed of a high resistance body or an insulator. The print medium 1 can be 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 corotron that drops the charge.

  Therefore, according to this printing apparatus, the belt charging device 19 charges the surfaces of the first conveyance belt 6 and the second conveyance belt 7, and in this state, the printing medium 1 is fed from the gate roller 14, and a spur (not shown) When the printing medium 1 is pressed against the first conveying belt 6 by a paper pressing roller composed of a roller, 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 manner, the first transport belt 6 is moved downstream in the transport direction while the print medium 1 is adsorbed, the print medium 1 is moved below the first liquid ejecting head 2, and the first liquid ejecting head 2 is moved to the first liquid ejecting head 2. Printing is performed by ejecting liquid from the nozzles formed. When printing by the first liquid ejecting head 2 is completed, the print medium 1 is moved downstream in the transport direction and transferred to the second transport belt 7 of the second transport unit 5. As described above, since the surface of the second transport belt 7 is also charged by the belt charging device 19, the print medium 1 is attracted to the surface of the second transport 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 liquid ejecting head 3, and the liquid is ejected from the nozzles formed in the second liquid ejecting head. To print. When the printing by the second liquid ejecting head is completed, the print medium 1 is further moved downstream in the transport direction, and 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). Make paper.

  When the first and second liquid jet heads 2 and 3 need to be cleaned, the first and second liquid jet heads 2 and 3 are lifted by raising the first and second cleaning caps 12 and 13 as described above. The cap body is brought into close contact with the nozzle surface, and in that state, the cap body is set to a negative pressure so that liquids and bubbles are sucked out from the nozzles of the first and second liquid ejecting heads 2 and 3 for cleaning. The second cleaning caps 12 and 13 are lowered.

  A control device for controlling itself is provided in the printing apparatus. As shown in FIG. 2, the control device performs printing processing 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. Is what you do. An input interface unit 61 that receives print data input from the host computer 60; a control unit 62 that includes 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 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 liquid ejecting 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 as external gate roller motors. 7, the pickup roller motor 51, the liquid jet 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 executes a predetermined process on the print data, and from which nozzle the liquid is ejected. Alternatively, print data (driving pulse selection data SI & SP) indicating how much liquid is to be ejected is output, and control signals are sent to the drivers 63 to 65, 66R, and 66L based on the print data and input data from various sensors. Output. When control signals are output from the drivers 63 to 65, 66R, and 66L, these are converted into drive signals by the interface unit 67, and actuators corresponding to a plurality of nozzles of the liquid ejecting head (in this embodiment, the previous stage). Drive circuit), the gate roller motor 17, the pickup roller motor 51, the right electric motor 11R, and the left electric motor 11L are operated to feed and convey the print medium 1, control the posture of the print medium 1, and to the print medium 1, respectively. The printing process is executed. Each component in the control unit 62 is electrically connected through a bus (not shown).

  The head driver 65 includes a drive waveform signal generation circuit 70 that forms a drive waveform signal WCOM, and an oscillation circuit 71 that outputs a clock signal SCK. As will be described in detail later, the drive waveform signal generation circuit 70 generates a drive waveform signal WCOM that serves as a reference for the drive pulse to the actuator 22, and as shown in FIG. 3, after the clear signal CLER is input. For each predetermined sampling period ΔT defined by the clock signal CLK, waveform data stored in a waveform data memory, which will be described later, is read, and a voltage value signal composed of the waveform data is output to be a drive waveform signal WCOM. This drive waveform signal WCOM is power amplified by a drive circuit including a digital power amplifier and a smoothing filter, which will be described later, and converted into a drive pulse for the actuator 22.

  The drive waveform signal WCOM generated in this way can be obtained by adjusting the waveform data to obtain voltage trapezoidal wave signals having various waveforms as shown in FIG. The power is amplified by the drive circuit shown in FIG. 5 and supplied as a drive pulse to the actuators 22 of the liquid jet heads 2 and 3, whereby the actuator can be driven and liquid is ejected from the nozzle corresponding to the actuator. can do. As will be described in detail later, this drive circuit includes, for each actuator, a modulation circuit 24 that performs pulse modulation on the drive waveform signal WCOM generated by the drive waveform signal generation circuit 70, and modulation (PWM) that is pulse-modulated by the modulation circuit 24. ) A digital power amplifier 25 that amplifies the signal and a smoothing filter 26 that smoothes the modulated (PWM) signal that has been power amplified by the digital power amplifier 25.

  The drive waveform signal WCOM or the rising portion of the drive pulse is a stage in which the volume of the cavity (pressure chamber) communicating with the nozzle is enlarged and the liquid is drawn (it can be said that the meniscus is drawn in view of the liquid ejection surface). The falling portion of COM is a stage in which the volume of the cavity is reduced to extrude the liquid (which can also be said to extrude the meniscus in view of the liquid ejection surface). As a result of extruding the liquid, the liquid is ejected from the nozzle. After drawing in this liquid, a series of waveform signals for extruding the liquid as needed are used as drive pulses.

  By variously changing the voltage increase / decrease slope and peak value of the drive pulse consisting of this voltage trapezoidal wave, it is possible to change the amount of liquid drawn in, the speed of drawing in, the amount of liquid pushed out and the speed of extrusion. By changing the amount, different liquid dot sizes can be obtained, and by forming ink dots of different sizes, it is possible to increase the gradation. In addition, the drive pulse at the left end in FIG. 4 only draws the liquid and does not push it out. This is called microvibration and is used to prevent or prevent drying of the nozzle without ejecting liquid.

  FIG. 6 shows the overall configuration of the drive circuits provided individually for all the actuators 22. As described above, in the present embodiment, the individual drive waveform signals WCOM for all the actuators 22 are set by the drive waveform signal generation circuit 70. Therefore, when the number of actuators 22 is N, N drives Waveform signals WCOM (1) to WCOM (N) are output and applied to N actuators 22 via individual drive circuits.

  FIG. 7 shows a specific configuration from the modulation circuit 24 to the smoothing filter 26 of the drive signal output circuit described above. A general pulse width modulation (PWM) circuit is used as the modulation circuit 24 that performs pulse modulation of the drive waveform signal WCOM. The modulation circuit 24 includes a known triangular wave oscillator 32 and a comparator 31 that compares the triangular wave output from the triangular wave oscillator 32 with the drive waveform signal WCOM. According to this modulation circuit 24, as shown in FIG. 8, a modulation (PWM) signal is output that is Hi when the drive waveform signal WCOM is greater than or equal to the triangular wave, and Lo when the drive waveform signal WCOM is less than the triangle wave. The In this embodiment, the pulse width modulation circuit is used as the pulse modulation circuit, but a pulse density modulation (PDM) circuit may be used instead.

  The digital power amplifier 25 substantially includes a half-bridge driver stage 33 composed of two MOSFETs TrP and TrN for amplifying power, and a gate of the MOSFETs TrP and TrN based on a modulation (PWM) signal from the modulation circuit 24. A gate drive circuit 34 for adjusting the inter-source signals GP and GN, and the half bridge driver stage 33 is a combination of a high-side MOSFET TrP and a low-side MOSFET TrN in a push-pull type. Among these, when the gate-source signal of the high-side MOSFET TrP is GP, the gate-source signal of the low-side MOSFET TrN is GN, and the output of the half-bridge driver stage 33 is Va, these correspond to the modulation (PWM) signal. FIG. 9 shows how these change. Note that the voltage value Vgs of the gate-source signals GP and GN of the MOSFETs TrP and TrN is set to a voltage value sufficient to turn on the MOSFETs TrP and TrN.

  When the modulation (PWM) signal is at the Hi level, the gate-source signal GP of the high-side MOSFET TrP is at the Hi level, and the gate-source signal GN of the low-side MOSFET TrN is at the Lo level. As a result, the low-side MOSFET TrN is turned off, and as a result, the output Va of the half-bridge driver stage 33 becomes the supply power VDD. On the other hand, when the modulation (PWM) signal is at the Lo level, the gate-source signal GP of the high-side MOSFET TrP is at the Lo level, and the gate-source signal GN of the low-side MOSFET TrN is at the Hi level. The MOSFET TrP is turned off, and the low-side MOSFET TrN is turned on. As a result, the output Va of the half bridge driver stage 33 becomes zero.

  The output Va of the half bridge driver stage 33 of the digital power amplifier circuit 25 is supplied as a drive signal COM to the selection switch 201 via the smoothing filter 26. The smoothing filter 26 is composed of a low-pass filter composed of a combination of two coils L1 and L2 and two capacitors C1 and C2. The smoothing filter 26 composed of the low-pass filter sufficiently attenuates the high-frequency component of the output Va of the half-bridge driver stage 33 of the digital power amplifier circuit 25, that is, the power amplification modulation (PWM) signal component and the drive signal component COM (or drive). The waveform component WCOM) is designed not to attenuate.

  As described above, when the MOSFETs TrP and TrN of the digital power amplifier 25 are digitally driven, a current flows through the MOSFET in the ON state because the MOSFET acts as a switching element, but the resistance value between the drain and the source is very high. And little power loss occurs. In addition, since no current flows through the MOSFET in the OFF state, no power loss occurs. Therefore, the power loss of the digital power amplifier 25 is extremely small, a small MOSFET can be used, and cooling means such as a cooling heat sink is unnecessary. Incidentally, the efficiency when the transistor is linearly driven is about 30%, whereas the efficiency of the digital power amplifier is 90% or more. In addition, since the cooling heat dissipation plate of the transistor needs to be about 60 mm square with respect to one transistor, if such a cooling heat dissipation plate is unnecessary, it is overwhelmingly advantageous in terms of actual layout.

  Next, the configuration and operation of the drive waveform signal generation circuit 70 will be described. The drive waveform signal generation circuit 70 is configured as shown in FIG. 10, and includes a shift register 111 that sequentially stores drive pulse selection data SI & SP for designating an actuator corresponding to a nozzle that ejects liquid, and a shift register 111. Of the latch circuit 112 based on the latch signal LAT, the decoder 113 for decoding the data of the latch circuit 112, and the waveform data memory 115 for storing the waveform data corresponding to the actuator 22 as described above. The cache memory 116 corresponding to the actuator 22 is read by reading the waveform data stored in the waveform data memory 115 based on the data decoded by the decoder 113 and the latch signal LAT by performing the arithmetic processing of FIG. Memory controller 1 stored in It comprises a 4, and a I / O port 117 to output to the modulation circuit 24 of the drive circuit waveform data stored in the cache memory 116 based on the decoded data by the latch signal LAT and the decoder 113.

  Here, the reason why the drive waveform signal generation circuit 70 outputs the drive waveform signal WCOM corresponding to the actuator 22 will be described. Since the actuator 22 composed of a piezo element has a capacitance, when all actuators that eject liquid to one drive pulse are connected in parallel, the parasitic inductance, parasitic capacitance, and resistance of the wiring of these actuators and drive circuit Depending on the minute, a low-pass filter is formed and the drive pulse is distorted. In addition, when the number of nozzles for ejecting liquid, that is, the number of actuators to be driven changes, the characteristics of the low-pass filter composed of the capacitance of the actuators change, so the distortion state of the drive pulse also changes. . Each time an actuator 22 such as a piezo element is connected to the smoothing filter 23, a low-pass filter is constructed in which electrostatic capacitances are connected in parallel one after another and are composed of the smoothing filter and the electrostatic capacitance of the actuator. The characteristics of this change. If the distortion state of the drive pulse changes, naturally, the weight of the liquid ejected from the nozzle also changes.

  Therefore, in the present embodiment, individual drive circuits are provided for all actuators 22, and individual drive waveform signals WCOM are output to all drive circuits and actuators 22. If individual drive circuits are provided for all the actuators 22, there is no drive pulse distortion variation due to the increase or decrease of the actuators 22, so even if the drive waveform signal WCOM is common, it is ejected from the nozzle. It becomes possible to suppress the weight fluctuation of the liquid. However, there are individual differences in the nozzles and the actuators 22 themselves, and even if the drive circuits of the actuators 22 are individualized, the liquids ejected from different nozzles may vary in weight if the drive waveform signal WCOM is common.

  In consideration of the individual difference between the nozzles and the actuators 22, in this embodiment, as shown in FIG. 11 a, the drive waveform signal optimal for the drive pulse when forming a small liquid dot is formed for N nozzles and actuators. Waveform data for small liquid dots (waveform data for small ink drops in the figure), medium waveform data for medium liquid dots (in the figure, waveform for medium ink drops) Data), the waveform data for large liquid dots (the waveform data for large ink droplets in the figure) of the drive waveform signal optimal for the drive pulse when forming a large liquid dot is measured and obtained, and this is obtained as the address of the waveform data memory 115 The numbers 1 to M are stored in the order of nozzle numbers 1 to N.

  In this case, based on the drive pulse selection data SI & SP, the memory controller 114 accesses the address number 2 of the waveform data memory 115 when the middle liquid dot is requested for the nozzle number 1 in FIG. When a small liquid dot is requested, the address number 4 of the waveform data memory 115 is accessed, and the waveform data stored at the address number is stored in the corresponding cache memory 116. The waveform data stored in all the cache memories 116 are simultaneously output from the I / O port 117 as the drive waveform signal WCOM every predetermined sampling period after the predetermined time t from the latch signal LAT.

  In order to reduce the storage capacity of the waveform data memory 115, similar waveform data to the actuators 22 of all the nozzles in FIG. 11a are collected, and as shown in FIG. Waveform data A for medium ink droplets, waveform data A for large ink droplets, waveform data B for small ink droplets, waveform data B for medium ink droplets, etc. are stored in addresses for each form. In this case, based on the drive pulse selection data SI & SP, the memory controller 114 accesses the address number 5 of the waveform data memory 115 when the middle liquid dot is requested for the nozzle number 1 in FIG. When a small liquid dot is requested, the address number 1 of the waveform data memory 115 is accessed, and the waveform data stored in the address number is stored in the corresponding cache memory 116. The waveform data stored in all the cache memories 116 are simultaneously output from the I / O port 117 as the drive waveform signal WCOM every predetermined sampling period after the predetermined time t from the latch signal LAT.

FIG. 12 shows a calculation process for reading and outputting waveform data performed by the memory controller 114 of FIG. In this calculation process, first, in step S1, drive pulse selection data (print data in the figure) SI & SP is received.
Next, the process proceeds to step S2, where it is determined whether or not the latch signal LAT is input. If the latch signal LAT is input, the process proceeds to step S3. Otherwise, the process proceeds to step S1.
In step S3, the received drive pulse selection data (print data) SI & SP is latched by the latch circuit 112 and further decoded (decoded in the figure) by the decoder 113.

Next, the process proceeds to step S4, and timer count Tc is started.
In step S5, data decoded by the decoder 113 (decoder signal in the figure) is acquired.
In step S6, the address of the waveform data memory 115 for acquiring the waveform data necessary for each actuator is designated.
In step S7, the waveform data memory 115 is accessed to acquire waveform data necessary for each actuator.

Next, the process proceeds to step S8, and the waveform data acquired in step S7 is stored in the corresponding cache memory 116.
Next, the process proceeds to step S9, where it is determined whether or not the timer count Tc has reached the predetermined time t. If the timer count Tc has reached the predetermined time t, the process proceeds to step S10. To do.
In step S 10, the waveform data is read from the cache memory 116 and output from the I / O port 117 for each sampling period.

Next, the process proceeds to step S11, where it is determined whether or not the transmission of all the waveform data has been completed. If the transmission of all the waveform data has been completed, the process returns to the main program. Otherwise, the process proceeds to step S10. Migrate to
According to this calculation process, as shown in FIG. 13, after the predetermined time t from the latch signal LAT, the waveform data is output at every predetermined sampling time, and thereby the actuators 22 of all the nozzles for ejecting the liquid simultaneously. A drive waveform signal WCOM is output, which is amplified in power by each drive circuit, converted into a drive pulse, and applied to each actuator 22. Since only one actuator 22 is connected to one drive pulse, the drive pulse is not distorted.

  As described above, according to the printing apparatus of the present embodiment, a half formed by push-pull connection of a pair of two transistors MOSFET TrP and TrN in order to amplify the power of the drive waveform signal WCOM serving as a reference for the drive pulse to the actuator 22. The number of bridge driver stages 33 (transistor pairs) is the same as the number of actuators, and a smoothing filter 26 is interposed between the connection point of the pair of transistor MOSFETs TrP and TrN of the half bridge driver stage 33 (transistor pair) and the actuator 22. As a result, only one actuator 22 is connected to the drive circuit composed of the half-bridge driver stage 33 (transistor pair) and the smoothing filter 26, so that waveform distortion of the drive pulse can be avoided. Prevents fluctuations in liquid weight It is possible to enable the printing of high image quality and high gradation Te.

  Further, the half-bridge driver stage 33 includes a modulation circuit 24 that performs pulse modulation on the drive waveform signal WCOM and a gate drive (drive) circuit 34 that drives the half-bridge driver stage 33 (transistor pair) based on the pulse-modulated modulation signal. The drive waveform signal WCOM corresponding to the actuator 22 and the nozzle of the drive circuit is generated by individually controlling the half bridge driver stage 33 (transistor pair) based on the drive waveform signal WCOM. Thus, it is possible to suppress and prevent the fluctuation of the liquid weight between the nozzles, thereby enabling printing with high image quality and high gradation.

Further, by generating the drive waveform signal WCOM for each corresponding actuator 22 based on the waveform data corresponding to the actuator 22 stored in the waveform data memory 115, the weight variation of the liquid between the nozzles can be suppressed and prevented. This makes it possible to print with high image quality and high gradation.
In addition, since the drive waveform signal WCOM is generated for all the actuators 22 corresponding to the nozzles that eject the liquid at the timing when the liquid is ejected from the nozzles, a deviation in the liquid ejection timing between the nozzles is avoided. Thus, printing with high image quality and high gradation can be made possible.

Further, the modulation circuit 24, the gate drive (drive) circuit 34, the half-bridge driver stage 33 (transistor pair), and the smoothing filter 26 are disposed in the vicinity of the actuator 22 as an integrated circuit, thereby reducing power loss and saving. Electricity can be achieved, and a plurality of liquid ejecting heads can be efficiently arranged, which makes it possible to reduce the size of the printing apparatus.
In addition, since the transistor pair is connected to each actuator 22, the current value flowing through the transistor pair is reduced, so that it is possible to configure the transistor pair using a transistor capable of higher speed operation, and increase the modulation frequency. The smoothing filter can be simplified. For example, it can be composed of a primary RC filter, or can be composed of only a resistor using the electrostatic capacity of the actuator, or the resistance component of the wiring or transistor and the electrostatic capacity of the actuator. A configuration in which a smoothing filter is substantially not provided separately by a capacitance component is also possible.

In this embodiment, only an example in which the present invention is applied to a line head type printing apparatus has been described in detail. However, the liquid ejecting apparatus and the printing apparatus according to the present invention eject liquid including a multi-pass type printing apparatus. Thus, the present invention can be applied to any type of printing apparatus that prints characters, images, and the like on a print medium. Moreover, each part which comprises the liquid ejecting apparatus or printing apparatus of this invention may be replaced with the thing of the arbitrary structures which can exhibit the same function, and the other arbitrary structures may be added. Moreover, it does not specifically limit as a liquid ejected from the liquid ejecting apparatus of this invention, For example, it can be set as the liquid (including dispersion liquids, such as a suspension and an emulsion) containing the following various materials. That is, an ink containing a filter material for a color filter, a light emitting material for forming an EL light emitting layer in an organic EL (Electro Luminescence) device, a fluorescent material for forming a phosphor on an electrode in an electron emitting device, PDP (Plasma Fluorescent material for forming phosphors in display panel devices, migrating material for forming electrophores in electrophoretic display devices, bank materials for forming banks on the surface of the substrate W, various coating materials, and electrodes Liquid electrode material to form, a particle material to form a spacer for forming a minute cell gap between two substrates, a liquid metal material to form a metal wiring, a lens material to form a microlens, A resist material, a light diffusion material for forming a light diffuser, and the like.
Further, in the present invention, the print medium that is the target of jetting the liquid is not limited to paper such as recording paper, but other media such as film, woven fabric, and non-woven fabric, and various substrates such as a glass substrate and a silicon substrate. Such work may be used.

  1 is a print medium, 2 is a first liquid ejecting head, 3 is a second liquid ejecting 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. , 8L are driving rollers, 9R and 9L are first driven rollers, 10R and 10L are second driven rollers, 11R and 11L are electric motors, 24 is a modulation circuit, 25 is a digital power amplifier, 26 is a smoothing filter, and 31 is a comparison. 32, a triangular wave oscillator, 33 a half bridge block stage, 34 a gate drive circuit, 70 a drive waveform signal generation circuit, 111 a shift register, 112 a latch circuit, 113 a decoder, 114 a memory controller, 115 a waveform Data memory, 116 is cache memory, 117 is I / O port

Claims (6)

A plurality of nozzles provided in the liquid jet head;
An actuator provided corresponding to the nozzle;
A liquid ejecting apparatus including a driving unit that applies a driving pulse to the actuator,
The driving means includes
Drive waveform signal generating means for generating a drive waveform signal serving as a reference of a drive pulse to the actuator;
A transistor pair that is provided in the same number as the number of the actuators and push-pull-connects a pair of transistors in order to amplify the power of the drive waveform signal generated by the drive waveform signal generator;
A liquid ejecting apparatus comprising the same number of smoothing filters as the number of actuators arranged between a connection point of the transistor pair and an actuator. Modulation means for pulse modulating the drive waveform signal generated by the drive waveform signal generating means;
Gate drive means for driving the transistor pairs based on the modulation signal pulse-modulated by the modulation means, and the same number as the transistor pairs,
The liquid ejecting apparatus according to claim 1, wherein the transistor pair is individually controlled based on the driving waveform signal. A waveform data memory for storing waveform data corresponding to the actuator;
The liquid ejecting apparatus according to claim 2, wherein the drive waveform signal generating unit generates a drive waveform signal for each corresponding actuator based on waveform data stored in the waveform data memory.   4. The liquid according to claim 3, wherein the drive waveform signal generation unit simultaneously generates drive waveform signals for all actuators corresponding to the nozzles that eject the liquid at a timing when the liquid is ejected from the nozzles. Injection device.   5. The liquid ejecting apparatus according to claim 2, wherein the modulation unit, the gate driving unit, the transistor pair, and the smoothing filter are disposed in the vicinity of the actuator as an integrated circuit. 6. .   A printing apparatus comprising the liquid ejecting apparatus according to claim 1.

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