JP2017170768A - Liquid discharge device, head unit, and large-sized printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device capable of effectively reducing overshoot generated in a drive waveform.SOLUTION: A liquid discharge device includes: a head unit comprising a discharge section discharging liquid by being applied with a driving signal, and a drive control section controlling application of the driving signal to the discharge section; a control unit comprising a driving circuit generating the driving signal; and a driving signal supply line supplying the driving signal from the control unit to the head unit. In the head unit, an anode comprises a diode electrically connected to the driving signal supply line.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a liquid ejection device, a head unit, and a large format printer.

  As a liquid ejecting apparatus such as an ink jet printer that ejects ink and prints an image or a document, an apparatus using a piezoelectric element (for example, a piezoelectric element) is known. Piezoelectric elements are provided corresponding to each of a plurality of nozzles in a head unit (inkjet head), and each is driven according to a drive signal, whereby a predetermined amount of ink (liquid) is ejected from the nozzles at a predetermined timing. As a result, dots are formed. Since the piezoelectric element is a capacitive load such as a capacitor when viewed electrically, it is necessary to supply a sufficient current to operate the piezoelectric element of each nozzle. For this reason, in the above-described liquid ejection apparatus, the drive circuit supplies the drive signal amplified by the amplifier circuit to the head to drive the piezoelectric element.

  For example, in the printer (liquid ejecting apparatus) disclosed in Patent Document 1 and Patent Document 2, a drive signal is generated in a drive signal generation unit (drive circuit) provided in a control unit arranged on the main body side, and The drive signal is transmitted to a recording head (head unit) through a flexible flat cable (FFC) and applied to the piezoelectric element through a selection switch.

JP 2014-218019 A JP 2014-223726 A

  In the printers (liquid ejection devices) disclosed in Patent Document 1 and Patent Document 2, an overshoot occurs in the waveform (drive waveform) of the drive signal transmitted by the flexible flat cable due to the inductance component of the flexible flat cable. Occur. In general, the maximum voltage of the drive signal is set to a voltage (for example, 37 V) that is slightly lower than the rated voltage (for example, 42 V) of the IC that constitutes the switch for selection, so that a slight overshoot occurs in the drive waveform. However, the absolute maximum rated voltage of the IC is not exceeded. However, the larger the inductance component of the FFC, that is, the longer the flexible flat cable, the larger the overshoot. In particular, a large format printer (large format printer) capable of printing on large paper of A2 size (420 mm x 594 mm) or larger. Then, since the flexible flat cable becomes 2 mm or more, an overshoot exceeding the absolute maximum rated voltage of the IC may occur in the drive waveform, which causes the IC to break down. Therefore, measures against overshoot of the drive waveform are required.

  If the magnitude of the overshoot generated in the drive waveform is always constant, it may be possible to take measures such as lowering the rising voltage by the amount of overshoot in the drive signal before being transmitted by the flexible flat cable. However, in a liquid ejection device such as a printer, the flexible flat cable moves while deforming as the head unit moves, so the size of the overshoot changes from moment to moment, and various noises are superimposed on the drive waveform. Due to the influence, it is difficult to estimate the maximum amount of overshoot, and such measures cannot be taken.

  According to some aspects of the present invention, it is possible to provide a liquid ejection device, a head unit, and a large-format printer that can effectively reduce overshoot generated in a drive waveform.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
A liquid discharge apparatus according to this application example includes: a head unit including a discharge unit that discharges liquid when a drive signal is applied; and a drive control unit that controls application of the drive signal to the discharge unit; A control unit including a drive circuit for generating the drive signal; and a drive signal supply line for supplying the drive signal from the control unit to the head unit. The head unit supplies the drive signal with an anode. A diode electrically connected to the wire;

  According to the liquid ejection apparatus according to this application example, even if an overshoot occurs in the waveform of the drive signal (drive waveform) due to the inductance component of the drive signal supply line, the gap is between the anode and the cathode of the diode. When a potential difference greater than the forward voltage drop occurs, current flows through the diode and the voltage of the drive signal is clamped. Therefore, according to the liquid ejection apparatus according to this application example, the voltage of the drive signal supplied to the drive control unit is limited to a predetermined voltage or less, so that the possibility of failure of the drive control unit can be reduced. . Further, according to the liquid ejection apparatus according to this application example, distortion of the waveform of the drive signal is reduced, so that the liquid ejection accuracy from the ejection unit is improved.

  Furthermore, according to the liquid ejection apparatus according to this application example, it is possible to realize a countermeasure against overshoot of the drive waveform at a low cost with a simple configuration using a diode.

[Application Example 2]
The liquid ejection apparatus according to the application example may include a flexible flat cable that connects the control unit and the head unit and is provided with at least a part of the drive signal supply line.

  According to the liquid ejection apparatus according to this application example, the deformation of the flexible flat cable causes the inductance component of the drive signal supply line to change from moment to moment, and various noises are superimposed on the drive waveform. Even if a very large overshoot occurs, a current flows through the diode and the voltage of the drive signal is limited to a predetermined voltage or less. Therefore, according to the liquid ejection device according to this application example, even if a very long flexible flat cable is used, a simple configuration using a diode realizes a countermeasure for overshooting the drive waveform at a low cost, and the drive control unit fails. In addition to reducing the possibility of the liquid being discharged, it is possible to improve the liquid discharge accuracy from the discharge portion.

[Application Example 3]
In the liquid ejection device according to the application example, the liquid ejection device includes a power supply voltage supply line that supplies a power supply voltage of the drive control unit from the control unit to the head unit, and a cathode of the diode is electrically connected to the power supply voltage supply line. It may be connected.

  According to the liquid ejection device according to this application example, even if an overshoot occurs in the drive waveform, if a potential difference greater than the forward drop voltage of the diode occurs between the drive signal supply line and the power supply voltage supply line, the diode Current flows, and the voltage of the drive signal is limited to the sum of the power supply voltage of the drive control unit and the forward drop voltage of the diode. Therefore, according to the liquid ejection device according to this application example, it is possible to realize a countermeasure for overshooting the drive waveform at a low cost with a simple configuration using a diode, and to reduce the possibility of failure of the drive control unit. The discharge accuracy of the liquid from the part can be improved.

[Application Example 4]
In the liquid ejection device according to the application example, a first power supply voltage supply line that supplies a first power supply voltage that is a power supply voltage of the drive control unit from the control unit to the head unit, and the head from the control unit A second power supply voltage supply line for supplying a second power supply voltage to the unit, and the cathode of the diode may be electrically connected to the second power supply voltage supply line.

  According to the liquid ejection apparatus according to this application example, even if an overshoot occurs in the drive waveform, a potential difference equal to or greater than the forward voltage drop of the diode occurs between the drive signal supply line and the second power supply voltage supply line. Current flows through the diode, and the voltage of the drive signal is limited to the sum of the second power supply voltage and the forward voltage drop of the diode. Therefore, according to the liquid ejection device according to this application example, it is possible to realize a countermeasure for overshooting the drive waveform at a low cost with a simple configuration using a diode, and to reduce the possibility of failure of the drive control unit. The discharge accuracy of the liquid from the part can be improved.

  Furthermore, according to the liquid ejection device according to this application example, even if an overshoot occurs in the drive waveform, no current flows into the first power supply voltage supply line via the diode, so the first voltage (drive control) The power supply voltage of the drive part does not fluctuate, and the malfunction of the drive control part due to the fluctuation of the first power supply voltage can be prevented.

[Application Example 5]
In the liquid ejection apparatus according to the application example, the head unit may include a capacitor having one end electrically connected to the cathode of the diode.

  According to the liquid ejection apparatus according to this application example, the current flowing from the drive signal supply line to the power supply voltage supply line via the diode due to the overshoot generated in the drive waveform is smoothed by the capacitor, and the power supply voltage of the drive control unit is reduced. Can be stabilized. Further, according to the liquid ejection device according to this application example, the current flowing from the drive signal supply line to the power supply voltage supply line via the diode due to overshoot generated in the drive waveform is regenerated and reused in the capacitor. Power saving can be improved.

[Application Example 6]
In the liquid ejection device according to the application example, the capacitor may be a ceramic capacitor.

  According to the liquid ejection apparatus according to this application example, the size and weight of the head unit may be reduced by using a ceramic capacitor having a small size and weight, and the power of the motor for moving the carriage is reduced. Also, the load on the motor can be reduced and its life can be extended.

[Application Example 7]
The liquid ejection apparatus according to the application example includes a pseudo drive signal supply line that supplies a pseudo drive signal that is not applied to the ejection unit, the drive signal being duplicated, from the control unit to the head unit. The cathode may be electrically connected to the pseudo drive signal supply line.

  According to the liquid ejection apparatus according to this application example, even if an overshoot occurs in the drive waveform, the diode is generated when a potential difference equal to or higher than the forward drop voltage of the diode occurs between the drive signal supply line and the pseudo drive signal supply line. Thus, the voltage of the drive signal is limited to the sum of the voltage of the pseudo drive signal in which the drive signal is duplicated and the forward drop voltage of the diode. Therefore, according to the liquid ejection device according to this application example, it is possible to realize a countermeasure for overshooting the drive waveform at a low cost with a simple configuration using a diode, and to reduce the possibility of failure of the drive control unit. The discharge accuracy of the liquid from the part can be improved.

  Furthermore, according to the liquid ejection apparatus according to this application example, even if an overshoot occurs in the drive waveform, current does not flow into the power supply voltage supply line via the diode, so that the power supply voltage of the drive control unit varies. Therefore, it is possible to prevent malfunction of the drive control unit due to fluctuations in the power supply voltage.

[Application Example 8]
In the head unit according to this application example, a discharge unit that discharges liquid by applying a drive signal, a drive control unit that controls application of the drive signal to the discharge unit, and the drive signal are input. A drive signal input terminal; and a diode having an anode electrically connected to the drive signal input terminal.

  According to the head unit of this application example, even if an overshoot occurs in the drive waveform, if a potential difference equal to or higher than the forward drop voltage occurs between the anode and the cathode of the diode, a current flows through the diode and the drive signal Is clamped. Therefore, according to the head unit according to this application example, the voltage of the drive signal supplied to the drive control unit is limited to a predetermined voltage or less, so that the possibility that the drive control unit breaks down can be reduced. In addition, according to the head unit according to this application example, the distortion of the waveform of the drive signal is reduced, so that the liquid ejection accuracy from the ejection unit is improved.

  Furthermore, according to the head unit according to this application example, it is possible to implement a drive waveform overshoot countermeasure at a low cost with a simple configuration using a diode.

[Application Example 9]
A large-sized printer according to this application example includes a head unit including a discharge unit that discharges liquid when a drive signal is applied, and a drive control unit that controls application of the drive signal to the discharge unit; A control unit having a drive circuit for generating the drive signal; a drive signal supply line for supplying the drive signal from the control unit to the head unit; and the control unit and the head unit connected to each other, and the drive signal A flexible flat cable provided with at least a part of a supply line, and the head unit includes a diode whose anode is electrically connected to the drive signal supply line.

  According to the large-format printer according to this application example, the inductance component of the drive signal supply line changes from moment to moment due to the deformation of the very long flexible flat cable, and various noises are superimposed on the drive waveform. Even if an unexpectedly large overshoot occurs, if a potential difference greater than the forward drop voltage occurs between the anode and cathode of the diode, a current flows through the diode and the voltage of the drive signal is clamped. Therefore, according to the large format printer according to this application example, the voltage of the drive signal supplied to the drive control unit is limited to a predetermined voltage or less, so that the possibility that the drive control unit breaks down can be reduced. Further, according to the large format printer according to this application example, distortion of the waveform of the drive signal is reduced, so that the liquid ejection accuracy from the ejection unit is improved.

  Furthermore, according to the large-format printer according to this application example, it is possible to realize a countermeasure for overshooting the drive waveform at a low cost with a simple configuration using a diode.

It is a figure which shows schematic structure inside a liquid discharge apparatus. It is a block diagram which shows the electrical structure of a liquid discharge apparatus. It is a figure which shows the structure of the discharge part in a head. It is a figure which shows the nozzle arrangement | sequence in a head. FIG. 5 is a diagram for explaining a basic resolution of image formation by the nozzle arrangement shown in FIG. 4. It is a figure for demonstrating operation | movement of the selection control part in a head unit. It is a figure which shows the structure of the selection control part in a head unit. It is a figure which shows the decoding content of the decoder in a head unit. It is a figure which shows the structure of the selection part in a head unit. It is a figure which shows the drive signal selected by the selection part. It is a figure which shows a part of electrical structure of the liquid discharge apparatus which concerns on 1st Embodiment. It is a figure which shows an example of the waveform of the drive signal which a drive circuit produces | generates. It is a figure which shows an example of the waveform of the drive signal input into a drive control part in 1st Embodiment. It is a figure which shows a part of electrical structure of the liquid discharge apparatus which concerns on 2nd Embodiment. It is a figure which shows a part of electrical structure of the liquid discharge apparatus which concerns on 3rd Embodiment. It is a figure which shows an example of the waveform of the drive signal input into a drive control part in 3rd Embodiment. It is a figure which shows a part of electrical structure of the liquid discharge apparatus which concerns on 4th Embodiment. It is a figure which shows an example of the waveform of the drive signal input into a drive control part in 4th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The drawings used are for convenience of explanation. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. 1. First embodiment 1-1. Overview of Liquid Ejecting Apparatus A printing apparatus as an example of a liquid ejecting apparatus according to the present embodiment ejects ink in accordance with image data supplied from an external host computer, whereby ink dot groups are applied to a printing medium such as paper. This is an inkjet printer that prints an image (including characters, graphics, etc.) according to the image data.

  As the liquid ejection device, for example, a printing device such as a printer, a color material ejection device used for manufacturing a color filter such as a liquid crystal display, an electrode used for forming an electrode such as an organic EL display, FED (surface emitting display), etc. Examples thereof include a material discharge device, a bio-organic matter discharge device used for biochip manufacturing, a three-dimensional modeling device (so-called 3D printer), and a textile printing device.

  FIG. 1 is a schematic external view of the liquid ejection apparatus 1. As shown in FIG. 1, the liquid ejection device 1 is a serial scan type large format printer (large format printer), and includes a main body 5 and a support stand 6 that supports the main body 5. The large format printer is, for example, a printer in which the maximum size of a printable medium is A2 size paper size (420 mm × 594 mm) or more.

  The liquid ejection apparatus 1 includes a head unit 2 including a carriage 24 and a head 20 mounted on the carriage 24 so as to face a print medium (roll paper) P. The head 20 is a liquid ejecting head for ejecting ink droplets (droplets) from a large number of nozzles. The carriage 24 is supported by the carriage guide shaft 32 and moves (reciprocates) in the main scanning direction. The print medium P is conveyed in the sub scanning direction orthogonal to the main scanning direction.

  A predetermined number of ink cartridges 22 (for example, four ink cartridges 22 corresponding to four colors of C (cyan), M (magenta), Y (yellow), and B (black)) are attached to the main body 5. Each ink cartridge 22 is filled with ink of a corresponding color. The ink stored in each ink cartridge 22 is supplied to the head 20 via an ink tube (not shown).

  The head 20 ejects ink droplets onto the print medium P while the carriage 24 reciprocates in synchronization with the conveyance of the print medium P. A home position serving as a base point for scanning of the head unit 2 is set in an end region within the movement range of the head unit 2 (carriage 24). The liquid ejecting apparatus 1 includes a forward movement in which the head unit 2 moves from the home position toward the opposite end, and a backward movement in which the head unit 2 returns from the opposite end to the home position. An image is formed on the surface of the print medium P in both directions.

1-2. FIG. 2 is a block diagram showing an electrical configuration of the liquid ejection device 1. As shown in FIG. 2, in the liquid ejection device 1, the control unit 10 and the head unit 2 are connected via a flexible flat cable 190.

  The control unit 10 includes a control unit 100, a carriage motor driver 35, a transport motor driver 45, drive circuits 50-a and 50-b, and a power supply circuit 70, and is fixed to the main body 5. Among these, the control unit 100 outputs various control signals and the like for controlling each unit when image data is supplied from the host computer.

  Specifically, the control unit 100 supplies a control signal Ctr1 to the carriage motor driver 35, and the carriage motor driver 35 drives the carriage motor 31 according to the control signal Ctr1. Thereby, the movement of the carriage 24 in the main scanning direction is controlled.

  Further, the control unit 100 supplies a control signal Ctr2 to the transport motor driver 45, and the transport motor driver 45 drives the transport motor 41 according to the control signal Ctr2. Thereby, the conveyance of the print medium P in the sub-scanning direction is controlled.

  The control unit 100 supplies the head unit 2 with a clock signal Sck, a data signal Data, control signals LAT and CH, and digital data dA and dB.

  Further, the control unit 100 causes the maintenance unit 80 to perform a maintenance process for recovering the ink ejection state in the ejection unit 600 normally. The maintenance unit 80 may include a cleaning mechanism 81 for performing a cleaning process (pumping process) for sucking the thickened ink, bubbles, and the like in the discharge unit 600 by a tube pump (not shown) as a maintenance process. Good. Further, the maintenance unit 80 may include a wiping mechanism 82 for performing a wiping process for wiping off foreign matters such as paper dust attached to the vicinity of the nozzles of the discharge unit 600 as a maintenance process.

  The drive circuits 50-a and 50-b generate drive signals COM-A and COM-B that drive the ejection unit 600 included in the head 20 and eject ink (liquid), respectively. Specifically, the drive circuit 50-a converts the data dA into analog data, generates a D-class amplified drive signal COM-A, and supplies the generated signal to each selection unit 230. Similarly, the drive circuit 50-b converts the data dB into analog data, generates a D-class amplified drive signal COM-B, and supplies it to each of the selection units 230. Here, the data dA defines the waveform of the drive signal COM-A among the drive signals supplied to the selection unit 230, and the data dB defines the waveform of the drive signal COM-B. For example, the drive circuits 50-a and 50-b are different only in input data and output drive signals, and may have the same circuit configuration.

  The power supply circuit 70 generates a power supply voltage VH and supplies it to the drive control unit 200 of the head unit 2.

  The head unit 2 includes a drive control unit 200 and a clamp circuit 220. The clamp circuit 220 is a circuit that limits the voltages of the drive signals COM-A and COM-B. Details of the clamp circuit 220 will be described later.

  The drive control unit 200 includes a selection control unit 210 and a plurality of selection units 230, and controls application of drive signals COM-A and COM-B to the ejection unit 600 provided in the head 20. For example, the drive control unit 200 is configured as a one-chip IC (Integrated Circuit).

  The selection control unit 210 is supplied from the control unit 100 as to whether one of the drive signals COM-A and COM-B should be selected for each of the selection units 230 (or whether they should be unselected). This is indicated by the clock signal Sck, the data signal Data, and the control signals LAT and CH.

  Each of the selection units 230 selects the drive signals COM-A and COM-B in accordance with instructions from the selection control unit 210, and supplies the drive signals COM-A and COM-B to the respective one ends of the piezoelectric elements 60 included in the head 20 as drive signals. In FIG. 2, the voltage of the drive signal is denoted as Vout. A voltage VBS is commonly applied to the other end of each of the piezoelectric elements 60.

  The piezoelectric element 60 is displaced when a drive signal is applied. The piezoelectric element 60 is provided corresponding to each of the plurality of ejection units 600 in the head 20. The piezoelectric element 60 is displaced in accordance with the difference between the voltage Vout and the voltage VBS of the drive signal selected by the selection unit 230, and ejects ink. Next, a configuration for ejecting ink by driving the piezoelectric element 60 will be briefly described.

1-3. FIG. 3 is a diagram illustrating a schematic configuration corresponding to one ejection unit 600 in the head 20. As shown in FIG. 3, the head 20 includes a discharge unit 600 and a reservoir 641.

  The reservoir 641 is provided for each color of ink, and the ink stored in the ink cartridge 22 is introduced from the supply port 661 to the reservoir 641 through the ink tube.

  The discharge unit 600 includes a piezoelectric element 60, a vibration plate 621, a cavity (pressure chamber) 631, and a nozzle 651. Among these, the diaphragm 621 functions as a diaphragm that is displaced (bending vibration) by the piezoelectric element 60 provided on the upper surface in the drawing, and expands / reduces the internal volume of the cavity 631 filled with ink. The nozzle 651 is an opening provided in the nozzle plate 632 and communicating with the cavity 631. The cavity 631 is filled with a liquid (for example, ink), and the internal volume changes due to the displacement of the piezoelectric element 60. The nozzle 651 communicates with the cavity 631 and discharges the liquid in the cavity 631 as droplets according to the change in the internal volume of the cavity 631.

  A piezoelectric element 60 shown in FIG. 3 has a structure in which a piezoelectric body 601 is sandwiched between a pair of electrodes 611 and 612. In the piezoelectric body 601 having this structure, the central portion in FIG. 3 is bent vertically with respect to both end portions together with the electrodes 611 and 612 and the diaphragm 621 in accordance with the voltage applied by the electrodes 611 and 612. Specifically, the piezoelectric element 60 is configured to bend upward when the voltage Vout of the drive signal increases, and to bend downward when the voltage Vout decreases. In this configuration, if the ink is bent upward, the internal volume of the cavity 631 is expanded. Therefore, if the ink is drawn from the reservoir 641, if the ink is bent downward, the internal volume of the cavity 631 is reduced. Depending on the degree, the ink is ejected from the nozzle 651.

  The piezoelectric element 60 is not limited to the illustrated structure, and may be any type that can deform the piezoelectric element 60 and discharge a liquid such as ink. Further, the piezoelectric element 60 is not limited to bending vibration, and may be configured to use so-called longitudinal vibration.

  Further, the piezoelectric element 60 is provided corresponding to the cavity 631 and the nozzle 651 in the head 20, and the piezoelectric element 60 is also provided corresponding to the selection unit 230 in FIG. For this reason, a set of the piezoelectric element 60, the cavity 631, the nozzle 651, and the selection unit 230 is provided for each nozzle 651.

1-4. Configuration of Drive Signal FIG. 4 is a diagram illustrating an example of the arrangement of the nozzles 651. As shown in FIG. 4, the nozzles 651 are arranged in, for example, two rows as follows. Specifically, when viewed in one row, the plurality of nozzles 651 are arranged at a pitch Pv along the sub-scanning direction, while the two rows are separated from each other by the pitch Ph in the main scanning direction and are sub-scanned. The relationship is shifted in the direction by half the pitch Pv.

  The nozzle 651 is provided with a pattern corresponding to each color such as C (cyan), M (magenta), Y (yellow), and B (black), for example, along the main scanning direction. In order to achieve this, a case where gradation is expressed in a single color will be described.

  FIG. 5 is a diagram for explaining the basic resolution of image formation by the nozzle arrangement shown in FIG. This drawing is an example of a method (first method) in which an ink droplet is ejected once from the nozzle 651 to form a single dot for the sake of simplicity, and a black circle is an ink. A dot formed by landing of a droplet is shown.

  When the head unit 2 moves at a speed v in the main scanning direction, as shown in FIG. 5, the dot interval D (in the main scanning direction) of dots formed by the landing of ink droplets and the speed v are The relationship is as follows.

  That is, when one dot is formed by one ink droplet ejection, the dot interval D is a value obtained by dividing the velocity v by the ink ejection frequency f (= v / f), in other words, the ink droplets It is indicated by the distance that the head unit 2 moves in the cycle (1 / f) of repeated ejection.

  In the example of FIGS. 4 and 5, the ink droplets ejected from the two rows of nozzles 651 are aligned in the same row in the print medium P with the relationship that the pitch Ph is proportional to the dot interval D by the coefficient n. It ’s landed like this. For this reason, as shown in FIG. 5, the dot interval in the sub-scanning direction is half of the dot interval in the main scanning direction. Needless to say, the arrangement of dots is not limited to the example shown in the figure.

  Incidentally, in order to realize high-speed printing, simply, the speed v at which the head unit 2 moves in the main scanning direction may be increased. However, simply increasing the speed v increases the dot interval D. For this reason, in order to achieve high-speed printing while ensuring a certain level of resolution, it is necessary to increase the number of dots formed per unit time by increasing the ink ejection frequency f.

  In addition to the printing speed, in order to increase the resolution, the number of dots formed per unit area may be increased. However, when the number of dots is increased, if the amount of ink is not reduced, not only the adjacent dots are combined but also the printing speed is reduced unless the ink ejection frequency f is increased.

  As described above, in order to realize high-speed printing and high-resolution printing as described above, it is necessary to increase the ink ejection frequency f.

  On the other hand, as a method of forming dots on the print medium P, in addition to a method of ejecting ink droplets once to form one dot, ink droplets can be ejected twice or more in a unit period, A method of forming one dot (second method) by combining one or more ejected ink droplets and combining the landed one or more ink droplets, or combining these two or more ink droplets There is a method (third method) for forming two or more dots. In the following description, a case where dots are formed by the second method will be described.

  In the present embodiment, the second method will be described assuming the following example. That is, in the present embodiment, for one dot, the ink is ejected at most twice to express four gradations of large dot, medium dot, small dot, and non-printing. In order to express these four gradations, in this embodiment, two types of drive signals COM-A and COM-B are prepared, and each has a first half pattern and a second half pattern in one cycle. The drive signals COM-A and COM-B are selected (or not selected) in accordance with the gradation to be expressed in the first half and the second half of one cycle and supplied to the piezoelectric element 60.

  FIG. 6 is a diagram illustrating waveforms of the drive signals COM-A and COM-B. As shown in FIG. 6, the drive signal COM-A has a trapezoidal waveform arranged in a period T <b> 1 from when the control signal LAT is output (rises) to when the control signal CH is output in the printing cycle Ta. In the printing cycle Ta, the trapezoidal waveform Adp2 arranged in the period T2 from when the control signal CH is output until the next control signal LAT is output is a continuous waveform.

  In the present embodiment, the trapezoidal waveforms Adp1 and Adp2 are substantially the same as each other, and if each is supplied to one end of the piezoelectric element 60, a specific amount from the nozzle 651 corresponding to the piezoelectric element 60, specifically, Specifically, it is a waveform for ejecting a medium amount of ink.

  The drive signal COM-B has a waveform in which the trapezoidal waveform Bdp1 arranged in the period T1 and the trapezoidal waveform Bdp2 arranged in the period T2 are continuous. In the present embodiment, the trapezoidal waveforms Bdp1 and Bdp2 are different from each other. Among these, the trapezoidal waveform Bdp1 is a wave for finely vibrating the ink in the vicinity of the opening portion of the nozzle 651 to prevent the ink viscosity from increasing. For this reason, even if the trapezoidal waveform Bdp1 is supplied to one end of the piezoelectric element 60, ink droplets are not ejected from the nozzle 651 corresponding to the piezoelectric element 60. The trapezoidal waveform Bdp2 is different from the trapezoidal waveform Adp1 (Adp2). If the trapezoidal waveform Bdp2 is supplied to one end of the piezoelectric element 60, it is a waveform that causes an amount of ink smaller than the predetermined amount to be ejected from the nozzle 651 corresponding to the piezoelectric element 60.

  The voltage at the start timing and the voltage at the end timing of the trapezoidal waveforms Adp1, Adp2, Bdp1, and Bdp2 are all the same as the voltage Vc. That is, the trapezoidal waveforms Adp1, Adp2, Bdp1, and Bdp2 are waveforms that start at the voltage Vc and end at the voltage Vc, respectively.

1-5. Configuration of Selection Control Unit and Selection Unit FIG. 7 is a diagram illustrating a configuration of the selection control unit 210 in FIG. As shown in FIG. 7, the selection control unit 210 is supplied with the clock signal Sck, the data signal Data, and the control signals LAT and CH from the control unit 10. In the selection control unit 210, a set of a shift register (S / R) 212, a latch circuit 214, and a decoder 216 is provided corresponding to each of the piezoelectric elements 60 (nozzles 651).

  The data signal Data defines the size of the dot when forming one dot of the image. In this embodiment, in order to express four gradations of non-recording, small dots, medium dots, and large dots, the data signal Data is composed of two bits, an upper bit (MSB) and a lower bit (LSB).

  The data signal Data is serially supplied from the control unit 100 in synchronization with the main scanning of the head unit 2 for each nozzle in synchronization with the clock signal Sck. A shift register 212 is a configuration for temporarily holding the serially supplied data signal Data for 2 bits corresponding to the nozzle.

  Specifically, the shift registers 212 having the number of stages corresponding to the piezoelectric elements 60 (nozzles) are connected in cascade, and the serially supplied data signal Data is sequentially transferred to the subsequent stage according to the clock signal Sck. Yes.

  Note that when the number of piezoelectric elements 60 is m (m is a plurality), in order to distinguish the shift register 212, the first stage, the second stage,..., M stage in order from the upstream side to which the data signal Data is supplied. It is written.

  The latch circuit 214 latches the data signal Data held by the shift register 212 at the rising edge of the control signal LAT.

  The decoder 216 decodes the 2-bit data signal Data latched by the latch circuit 214 and outputs selection signals Sa and Sb for each of the periods T1 and T2 defined by the control signal LAT and the control signal CH. The selection by the selection unit 230 is defined.

  FIG. 8 is a diagram showing the decoding contents in the decoder 216. In FIG. 8, the latched 2-bit data signal Data is represented as (MSB, LSB). For example, if the latched data signal Data is (0, 1), the decoder 216 sets the logic levels of the selection signals Sa and Sb to H and L levels in the period T1, and to L and H levels in the period T2, respectively. , Which means output.

  Note that the logic levels of the selection signals Sa and Sb are shifted to higher amplitude logic by a level shifter (not shown) than the logic levels of the clock signal Sck, the data signal Data, and the control signals LAT and CH.

  FIG. 9 is a diagram illustrating a configuration of the selection unit 230 corresponding to one piezoelectric element 60 (nozzle 651) in FIG.

  As illustrated in FIG. 9, the selection unit 230 includes inverters (NOT circuits) 232a and 232b and transfer gates 234a and 234b.

  The selection signal Sa from the decoder 216 is supplied to the positive control terminal that is not circled in the transfer gate 234a, while being logically inverted by the inverter 232a and negative control that is circled in the transfer gate 234a. Supplied to the end. Similarly, the selection signal Sb is supplied to the positive control terminal of the transfer gate 234b, while logically inverted by the inverter 232b and supplied to the negative control terminal of the transfer gate 234b.

  The drive signal COM-A is supplied to the input terminal of the transfer gate 234a, and the drive signal COM-B is supplied to the input terminal of the transfer gate 234b. The output ends of the transfer gates 234a and 234b are connected in common and connected to one end of the corresponding piezoelectric element 60.

  When the selection signal Sa is at the H level, the transfer gate 234a conducts (turns on) between the input end and the output end, and when the selection signal Sa is at the L level, the transfer gate 234a does not conduct between the input end and the output end. (Off). Similarly, the transfer gate 234b is turned on / off between the input end and the output end according to the selection signal Sb.

  Next, operations of the selection control unit 210 and the selection unit 230 will be described with reference to FIG.

  The data signal Data is serially supplied from the control unit 100 for each nozzle in synchronization with the clock signal Sck, and sequentially transferred in the shift register 212 corresponding to the nozzle. When the control unit 100 stops the supply of the clock signal Sck, the data signal Data corresponding to the nozzle is held in each of the shift registers 212. The data signal Data is supplied in the order corresponding to the last m stages,..., Two stages, and one stage nozzles in the shift register 212.

  Here, when the control signal LAT rises, each of the latch circuits 214 simultaneously latches the data signal Data held in the shift register 212. In FIG. 6, LT1, LT2,..., LTm indicate data signals Data latched by the latch circuit 214 corresponding to the shift register 212 of the first stage, the second stage,.

  The decoder 216 outputs the logic levels of the selection signals Sa and Sb with the contents as shown in FIG. 8 in each of the periods T1 and T2 in accordance with the dot size defined by the latched data signal Data.

  That is, first, when the data signal Data is (1, 1) and the size of a large dot is specified, the decoder 216 sets the selection signals Sa and Sb to the H and L levels in the period T1, and the period At T2, the H and L levels are set. Second, when the data signal Data is (0, 1) and the size of the medium dot is defined, the decoder 216 sets the selection signals Sa and Sb to the H and L levels in the period T1, and in the period T2. L and H level. Third, when the data signal Data is (1, 0) and the size of the small dot is defined, the decoder 216 sets the selection signals Sa and Sb to the L and L levels in the period T1, and in the period T2. L and H level. Fourth, the decoder 216 sets the selection signals Sa and Sb to L and H levels in the period T1 and L and L in the period T2 when the data signal Data is (0, 0) and defines non-recording. Set to L level.

  FIG. 10 is a diagram illustrating a voltage waveform of a drive signal that is selected according to the data signal Data and is supplied to one end of the piezoelectric element 60.

  When the data signal Data is (1, 1), the selection signals Sa and Sb are at the H and L levels in the period T1, so that the transfer gate 234a is turned on and the transfer gate 234b is turned off. For this reason, the trapezoidal waveform Adp1 of the drive signal COM-A is selected in the period T1. Since the selection signals Sa and Sb are at the H and L levels also during the period T2, the selection unit 230 selects the trapezoidal waveform Adp2 of the drive signal COM-A.

  As described above, when the trapezoidal waveform Adp1 is selected in the period T1, and the trapezoidal waveform Adp2 is selected in the period T2, and supplied to one end of the piezoelectric element 60 as a drive signal, the nozzle 651 corresponding to the piezoelectric element 60 causes A certain amount of ink is ejected in two steps. For this reason, the respective inks land and merge on the print medium P, and as a result, large dots as defined by the data signal Data are formed.

  When the data signal Data is (0, 1), the selection signals Sa and Sb are at the H and L levels in the period T1, so that the transfer gate 234a is turned on and the transfer gate 234b is turned off. For this reason, the trapezoidal waveform Adp1 of the drive signal COM-A is selected in the period T1. Next, since the selection signals Sa and Sb are at the L and H levels in the period T2, the trapezoidal waveform Bdp2 of the drive signal COM-B is selected.

  Therefore, medium and small amounts of ink are ejected from the nozzle in two steps. For this reason, the respective inks land and merge on the printing medium P, and as a result, medium dots as defined by the data signal Data are formed.

  When the data signal Data is (1, 0), the selection signals Sa and Sb are both at the L level in the period T1, so that the transfer gates 234a and 234b are turned off. For this reason, none of the trapezoidal waveforms Adp1, Bdp1 is selected in the period T1. When both the transfer gates 234a and 234b are turned off, the path from the connection point between the output ends of the transfer gates 234a and 234b to one end of the piezoelectric element 60 is in a high impedance state that is not electrically connected to any part. . However, the piezoelectric element 60 holds the voltage (Vc−VBS) immediately before the transfer gates 234a and 234b are turned off due to the capacitance of the piezoelectric element 60.

  Next, since the selection signals Sa and Sb are at the L and H levels in the period T2, the trapezoidal waveform Bdp2 of the drive signal COM-B is selected. For this reason, since a small amount of ink is ejected from the nozzle 651 only in the period T2, small dots as defined by the data signal Data are formed on the print medium P.

  When the data signal Data is (0, 0), the selection signals Sa and Sb are at the L and H levels in the period T1, so the transfer gate 234a is turned off and the transfer gate 234b is turned on. For this reason, the trapezoidal waveform Bdp1 of the drive signal COM-B is selected in the period T1. Next, since the selection signals Sa and Sb are both at the L level in the period T2, neither of the trapezoidal waveforms Adp2 and Bdp2 is selected.

  For this reason, in the period T1, the ink in the vicinity of the opening portion of the nozzle 651 only vibrates slightly, and the ink is not ejected. As a result, no dots are formed, that is, non-defects as defined by the data signal Data. Become a record.

  As described above, the selection unit 230 selects (or does not select) the drive signals COM-A and COM-B in accordance with an instruction from the selection control unit 210, and supplies the drive signals COM-A and COM-B to one end of the piezoelectric element 60. Therefore, each piezoelectric element 60 is driven according to the dot size defined by the data signal Data.

  Note that the drive signals COM-A and COM-B illustrated in FIG. 6 are merely examples. Actually, various combinations of waveforms prepared in advance are used according to the moving speed of the head unit 2 and the properties of the print medium P.

  Further, here, the example in which the piezoelectric element 60 bends upward as the voltage increases has been described. However, when the voltage supplied to the electrodes 611 and 612 is reversed, the piezoelectric element 60 increases as the voltage increases. Will bend downward. For this reason, in the configuration in which the piezoelectric element 60 bends downward as the voltage increases, the drive signals COM-A and COM-B illustrated in FIG. 10 have waveforms that are inverted with respect to the voltage Vc.

  As described above, in the present embodiment, one dot is formed on the printing medium P in units of the printing cycle Ta that is a unit period. For this reason, in this embodiment in which one dot is formed by ejecting ink droplets twice (at most) in the printing cycle Ta, the ink ejection frequency f is 2 / Ta, and the dot interval D is moved by the head unit 2. Is a value obtained by dividing the speed v by the ink ejection frequency f (= 2 / Ta).

  In general, in the case where the ink droplets can be ejected Q (Q is an integer of 2 or more) times in the unit period T and one dot is formed by ejecting the ink droplets Q times, the ink ejection frequency f is Q / T can be expressed.

  As in this embodiment, the case where dots of different sizes are formed on the print medium P is required to form one dot as compared to the case where one dot is formed by ejecting one ink droplet. Even if the time (cycle) is the same, it is necessary to shorten the time because one ink droplet is ejected once.

  The third method for forming two or more dots without combining two or more ink droplets will not require any special explanation.

1-6. Configuration and Function of Clamp Circuit In the liquid ejection apparatus 1, the control unit 10 and the head unit 2 are connected by a flexible flat cable 190. Therefore, the waveforms (drive waveforms) of the drive signals COM-A and COM-B transmitted from the control unit 10 to the drive control unit 200 of the head unit 2 by the flexible flat cable 190 are caused by the inductance component of the flexible flat cable 190. Overshoot occurs.

  In particular, in the present embodiment, since the liquid ejection device 1 is a large format printer (large format printer), the maximum distance between the control unit 10 and the head unit 2 is long, and the flexible flat cable 190 is 2 mm or more. Therefore, the inductance component of the flexible flat cable 190 becomes very large, and the overshoot generated in the drive waveform also becomes large. When an overshoot exceeding the absolute maximum rated voltage of the IC that constitutes the drive control unit 200 occurs, an excessive voltage is instantaneously applied to the IC, causing a failure of the IC. Therefore, it is necessary to take measures against overshoot of the drive waveform.

  If the magnitude of the overshoot generated in the drive waveform is always constant, the drive circuits 50-a and 50-b may previously generate a drive signal in which the voltage at the rise is reduced by the amount of overshoot. May be possible. However, in the liquid ejecting apparatus 1 that is a large format printer (large format printer), the flexible flat cable 190 moves while being greatly deformed as the head unit 2 moves, so the size of the overshoot changes from moment to moment, and Since various noises are superimposed on the drive waveform, it is difficult to estimate the maximum amount of overshoot, and such measures cannot be taken.

  Therefore, in the present embodiment, as shown in FIG. 2, the maximum voltage of the drive waveform applied to the IC constituting the drive control unit 200 is equal to or less than the absolute maximum rated voltage of the IC regardless of the magnitude of the overshoot. A clamp circuit 220 is provided in the head unit 2 so that

  FIG. 11 is a diagram illustrating a part of the electrical configuration of the liquid ejection apparatus 1 according to the first embodiment. In FIG. 11, illustration of the same configuration as that in FIG. 2 is omitted. As shown in FIG. 11, the liquid ejection apparatus 1 includes a flexible flat cable 190 that connects the control unit 10 and the head unit 2.

  In addition, the liquid ejection apparatus 1 includes a power supply voltage supply line 91 that supplies the power supply voltage VH of the drive control unit 200 from the control unit 10 to the head unit 2. Specifically, the power supply voltage supply line 91 is supplied from the power supply circuit 70 provided in the control unit 10 to the drive control unit 200 provided in the head unit 2 (specifically, the selection control unit 210 illustrated in FIG. The power supply voltage VH is supplied to the selection unit 230). The power supply voltage supply line 91 is configured by electrically connecting the power supply voltage output terminal 101 of the control unit 10 and the power supply voltage input terminal 201 of the head unit 2 by the flexible flat cable 190. That is, at least a part of the power supply voltage supply line 91 is provided in the flexible flat cable 190.

  Further, the liquid ejection apparatus 1 includes drive signal supply lines 92 and 93 for supplying drive signals COM-A and COM-B to the head unit 2 from the control unit 10, respectively. Specifically, the drive signal supply line 92 is supplied from the drive circuit 50-a provided in the control unit 10 to the drive control unit 200 provided in the head unit 2 (specifically, a plurality of selection units illustrated in FIG. 2). 230) is supplied with the drive signal COM-A. Similarly, the drive signal supply line 93 is supplied from the drive circuit 50-b provided in the control unit 10 to the drive control unit 200 provided in the head unit 2 (specifically, a plurality of selection units 230 shown in FIG. 2). Is supplied with a drive signal COM-B. The drive signal supply lines 92 and 93 are configured by electrically connecting the drive signal output terminals 102 and 103 of the control unit 10 and the drive signal input terminals 202 and 203 of the head unit 2 with the flexible flat cable 190, respectively. Is done. That is, at least a part of the drive signal supply lines 92 and 93 is provided in the flexible flat cable 190.

  As shown in FIG. 11, in the liquid ejection device 1 according to the first embodiment, the clamp circuit 220 includes a diode 221 and a diode 222. The anode of the diode 221 is electrically connected to the drive signal supply line 92 and the drive signal input terminal 202, and the cathode of the diode 221 is electrically connected to the power supply voltage supply line 91 and the power supply voltage input terminal 201. The anode of the diode 222 is electrically connected to the drive signal supply line 93 and the drive signal input terminal 203, and the cathode of the diode 222 is electrically connected to the power supply voltage supply line 91 and the power supply voltage input terminal 201.

  12 shows a drive signal COM (any one of the drive signals COM-A and COM-B) generated by the drive circuit 50 (any one of the drive circuits 50-a and 50-b), that is, the drive signal supply line 92 or 7 is a diagram illustrating an example of a waveform of a drive signal COM before propagating through a drive signal supply line 93. FIG. FIG. 13 is a diagram illustrating an example of a waveform of the drive signal COM that propagates through the drive signal supply line 92 or the drive signal supply line 93 and is input to the drive control unit 200.

  As shown in FIG. 12, the voltage of the drive signal COM before propagating through the drive signal supply line 92 or the drive signal supply line 93 transits between Vmin and Vmax, and overshoot occurs in the waveform of the drive signal COM. Not.

  On the other hand, as shown in FIG. 13, since the flexible flat cable 190 is very long (inductance component is very large), the drive signal COM propagated through the drive signal supply line 92 or the drive signal supply line 93 A very large overshoot occurs in the waveform, and the maximum voltage Vos of this overshoot may exceed the absolute maximum rated voltage VHmax of the IC constituting the drive control unit 200. However, when this overshoot exceeds the sum of the power supply voltage VH and the forward drop voltage Vf1 of the diode 221 or the diode 222, a current flows through the diode 221 or the diode 222, and the voltage of the drive signal COM is limited to VH + Vf1 or less. Is done. That is, the diodes 221 and 222 function as clamp diodes that clamp the voltages of the drive signals COM-A and COM-B to VH + Vf1 or less, respectively.

  The clamp voltage (VH + vf1) is equal to or lower than the absolute maximum rated voltage VHmax of the IC constituting the drive control unit 200, and the voltage of the drive signal COM input to the IC exceeds the absolute maximum rated voltage VHmax. There is no.

  Further, the forward voltage drop Vf1 of the diodes 221 and 222 is a parasitic diode (silicon diode) parasitic between the drive signal supply lines 92 and 93 and the power supply voltage supply line 91 in the IC constituting the drive control unit 200. The forward voltage drop voltage Vf2 (approximately 0.6V to 0.7V) is reduced, and current is prevented from flowing through the parasitic diode. That is, IC failure due to current flowing through the parasitic diode is prevented. If, for example, Schottky diodes are used as the diodes 221 and 222, the forward voltage drop Vf1 can be set to about 0.4V.

  As described above, according to the liquid ejection apparatus 1 and the head unit 2 according to the first embodiment, the drive signal COM− is caused by the inductance component of the flexible flat cable 190 (drive signal supply lines 92 and 93). Even if a very large overshoot occurs in the waveforms of A and COM-B, the voltages of the drive signals COM-A and COM-B are clamped to VH + Vf1 or less by the functions of the diodes 221 and 222. Accordingly, since the drive signals COM-A and COM-B having a voltage exceeding the absolute maximum rated voltage VHmax of the IC are not supplied to the IC constituting the drive control unit 200, the possibility that the IC breaks down is reduced. Can be made. Further, even if a very large overshoot occurs in the waveforms of the drive signals COM-A and COM-B, the distortion of the drive waveform is reduced, so that the ink ejection accuracy is improved.

  Furthermore, according to the liquid ejection device 1 and the head unit 2 according to the first embodiment, even when the very long flexible flat cable 190 is used, the countermeasure for overshooting of the drive waveform is reduced by the clamp circuit 220 having a simple configuration. Can be realized at a cost.

  Even if the overshoot generated in the waveforms of the drive signals COM-A and COM-B is clamped by the diodes 221 and 222, of the drive signal supply lines 92 and 93, the anodes of the diodes 221 and 222 and the drive signal supply line If the signal line from the connection point to the drive control unit 200 is long, the waveforms of the drive signals COM-A and COM-B input to the drive control unit 200 may be distorted. Therefore, as shown in FIG. 11, the clamp circuit 220 (diodes 221 and 222) and the drive control unit 200 are preferably mounted on the same main board 250. However, when the main board 250 is provided inside the head 20 and the space for mounting the diodes 221 and 222 cannot be secured on the main board 250, the diodes 221 and 222 are mounted on a sub-board different from the main board 250. You may be made to do. This sub-board may be provided outside the head 20 in the head unit 2.

2. Second Embodiment The liquid ejection apparatus 1 according to the second embodiment has the same configuration as the liquid ejection apparatus 1 according to the first embodiment, but the configuration of the clamp circuit 220 is different. Below, the description which overlaps with 1st Embodiment is abbreviate | omitted or simplified, and the content different from 1st Embodiment is mainly demonstrated.

  FIG. 14 is a diagram showing a part of the electrical configuration of the liquid ejection apparatus 1 according to the second embodiment. In FIG. 14, the same configuration as that of the first embodiment (FIG. 2) is not shown. Yes.

  As shown in FIG. 14, in the liquid ejection device 1 according to the second embodiment, the clamp circuit 220 includes a diode 221, a diode 222, and a capacitor 223. As in the first embodiment, the anode of the diode 221 is electrically connected to the drive signal supply line 92 and the drive signal input terminal 202, and the cathode of the diode 221 is electrically connected to the power supply voltage supply line 91 and the power supply voltage input terminal 201. It is connected. The anode of the diode 222 is electrically connected to the drive signal supply line 93 and the drive signal input terminal 203, and the cathode of the diode 222 is electrically connected to the power supply voltage supply line 91 and the power supply voltage input terminal 201.

  One end of the capacitor 223 is electrically connected to the power supply voltage supply line 91 and the power supply voltage input terminal 201, and the other end is connected to the ground. That is, one end of the capacitor 223 is electrically connected to the cathode of the diode 221 and the cathode of the diode 222.

  The connection point between the cathode of the diode 221 and the power supply voltage supply line 91 and the connection point between the cathode of the diode 222 and the power supply voltage supply line 91 are all the power supply voltage input terminal 201, one end of the capacitor 223, and the power supply voltage supply line. 91 to the connection point. Therefore, the current flowing from the drive signal supply lines 92 and 93 to the power supply voltage supply line 91 via the diodes 221 and 222 due to overshoot occurring in the drive waveform is smoothed by the capacitor 223 and supplied to the drive control unit 200. The power supply voltage VH is stabilized. That is, the capacitor 223 functions as a smoothing capacitor that stabilizes the power supply voltage VH. Further, the current flowing into the power supply voltage supply line 91 is regenerated in the capacitor 223 and reused. That is, the capacitor 223 also functions as a regeneration capacitor.

  As described above, according to the liquid ejection device 1 and the head unit 2 according to the second embodiment, the same effect as that of the first embodiment can be obtained, and the power supply voltage VH can be stabilized by the capacitor 223. The possibility that the drive control unit 200 malfunctions can be reduced. Further, since the capacitor 223 functions as a regeneration capacitor, the power saving performance of the liquid ejection device 1 and the head unit 2 is improved.

  When the overshoot generated in the drive waveform is very large, the current flowing into the power supply voltage supply line 91 is also very large. Therefore, a capacitor having a large capacitance value, for example, an electrolytic capacitor is used as the capacitor 223. Since the electrolytic capacitor is large in size, when the main substrate 250 on which the drive control unit 200 is mounted is provided inside the head 20, the mounting space for the diodes 221 and 222 and the capacitor 223 cannot be secured on the main substrate 250. The diodes 221 and 222 and the capacitor 223 are mounted on the sub-board 260. The sub-board 260 may be provided outside the head 20 in the head unit 2.

  However, if the electrolytic capacitor is heavy and the sub-board 260 is also required, the size and weight of the head unit 2 increase, the power of the carriage motor 31 increases, the load on the carriage motor 31 also increases, and the life thereof is increased. Shorter. Therefore, the capacitor 223 is preferably a ceramic capacitor as long as the stabilization of the power supply voltage VH is achieved. Since the ceramic capacitor is small in size and weight, the diodes 221 and 222 and the capacitor 223 may be mounted on the main board 250 (the sub board 260 is unnecessary), and the size and weight of the head unit 2 are reduced. The power of the carriage motor 31 can be reduced, and the load of the carriage motor 31 can be reduced to extend its life.

3. Third Embodiment A liquid ejection apparatus 1 according to a third embodiment includes a clamp circuit 220 similar to that of the liquid ejection apparatus 1 according to the second embodiment, but the signal line to which the clamp circuit 220 is connected is the second embodiment. And different. Below, the description which overlaps with 2nd Embodiment is abbreviate | omitted or simplified, and the content different from 2nd Embodiment is mainly demonstrated.

  FIG. 15 is a diagram illustrating a part of the electrical configuration of the liquid ejection apparatus 1 according to the third embodiment. In FIG. 15, the same configuration as that of the first embodiment (FIG. 2) is not illustrated. Yes.

  As shown in FIG. 15, the liquid ejection apparatus 1 according to the third embodiment supplies a power supply voltage supply line for supplying the power supply voltage VH1 (first power supply voltage) of the drive control unit 200 from the control unit 10 to the head unit 2. 91 (first power supply voltage supply line) and drive signal supply lines 92 and 93 for supplying drive signals COM-A and COM-B from the control unit 10 to the head unit 2. Furthermore, the liquid ejection apparatus 1 according to the third embodiment includes a power supply voltage supply line 94 (second power supply voltage supply line) that supplies a power supply voltage VH2 (second power supply voltage) from the control unit 10 to the head unit 2. including. A power supply voltage supply line 94 is configured by electrically connecting the power supply voltage output terminal 104 of the control unit 10 and the power supply voltage input terminal 204 of the head unit 2 by the flexible flat cable 190. That is, at least a part of the power supply voltage supply line 94 is provided in the flexible flat cable 190.

  As shown in FIG. 15, in the liquid ejection apparatus 1 according to the third embodiment, the anode of the diode 221 is electrically connected to the drive signal supply line 92 and the drive signal input terminal 202, and the cathode of the diode 221 is The power supply voltage supply line 94 and the power supply voltage input terminal 204 are electrically connected. The anode of the diode 222 is electrically connected to the drive signal supply line 93 and the drive signal input terminal 203, and the cathode of the diode 222 is electrically connected to the power supply voltage supply line 94 and the power supply voltage input terminal 204. One end of the capacitor 223 is electrically connected to the power supply voltage supply line 94 and the power supply voltage input terminal 204, and the other end is connected to the ground.

  FIG. 16 shows an example of the waveform of the drive signal COM (any one of the drive signals COM-A and COM-B) that propagates through the drive signal supply line 92 or the drive signal supply line 93 and is input to the drive control unit 200. FIG. The drive signal COM generated by the drive circuit 50 (any one of the drive circuits 50-a and 50-b), that is, the waveform of the drive signal COM before propagating through the drive signal supply line 92 or the drive signal supply line 93 is as follows. This is the same as FIG.

  As shown in FIG. 16, the power supply voltage VH2 is higher than the maximum voltage Vmax of the drive signal COM and lower than the power supply voltage VH1. When the overshoot generated in the waveform of the drive signal COM propagated through the drive signal supply line 92 or the drive signal supply line 93 exceeds the sum of the power supply voltage VH2 and the forward drop voltage Vf1 of the diode 221 or the diode 222, A current flows through the diode 221 or the diode 222, and the voltages of the drive signals COM-A and COM-B are limited to VH2 + Vf1 or less. That is, the diodes 221 and 222 function as clamp diodes that clamp the voltages of the drive signals COM-A and COM-B to VH2 + Vf1 or less, respectively.

  The clamp voltage (VH2 + vf1) is lower than the absolute maximum rated voltage VHmax of the IC constituting the drive control unit 200, and the maximum voltage of the drive signal COM input to the IC is the absolute maximum rated voltage VHmax. Limited to: Further, if the power supply voltage VH2 is set so that the difference between the power supply voltage VH1 and the power supply voltage VH2 is equal to or greater than the forward drop voltage Vf1 of the diode 221 or the diode 222, the clamp voltage (VH2 + vf1) is equal to the drive signal COM. The voltage is higher than the maximum voltage Vmax and lower than or equal to the power supply voltage VH1, so that a voltage higher than the power supply voltage VH1 is not applied to the IC.

  As described above, according to the liquid ejection apparatus 1 and the head unit 2 according to the third embodiment, the drive signal COM− is caused by the inductance component of the flexible flat cable 190 (drive signal supply lines 92 and 93). Even if a very large overshoot occurs in the waveforms of A and COM-B, the voltages of the drive signals COM-A and COM-B are clamped to VH2 + Vf1 or less by the functions of the diodes 221 and 222. Accordingly, since the drive signals COM-A and COM-B having a voltage exceeding the absolute maximum rated voltage VHmax of the IC are not supplied to the IC constituting the drive control unit 200, the possibility that the IC breaks down is reduced. Can be made. Further, even if a very large overshoot occurs in the waveforms of the drive signals COM-A and COM-B, the distortion of the drive waveform is reduced, so that the ink ejection accuracy is improved.

  Further, according to the liquid ejection device 1 and the head unit 2 according to the third embodiment, even if a large overshoot occurs in the drive waveform, the power supply voltage is supplied from the drive signal supply lines 92 and 93 via the diodes 221 and 222. Since no current flows into the line 91, the power supply voltage VH1 of the drive control unit 200 does not vary. Therefore, it is possible to prevent the malfunction of the drive control unit 200 due to the fluctuation of the power supply voltage VH1.

  Further, according to the liquid ejection device 1 and the head unit 2 according to the third embodiment, the drive signal supply lines 92 and 93 flow into the power supply voltage supply line 94 via the diodes 221 and 222 due to overshoot generated in the drive waveform. The current is regenerated in the capacitor 223 and reused. That is, since the capacitor 223 functions as a regeneration capacitor, the power saving performance of the liquid ejection device 1 and the head unit 2 is improved.

  Furthermore, according to the liquid ejection device 1 and the head unit 2 according to the third embodiment, even when a very long flexible flat cable 190 is used, the overshooting of the drive waveform is reduced by the clamp circuit 220 having a simple configuration. Can be realized at a cost.

  As in the second embodiment, the liquid discharge apparatus 1 and the head unit 2 according to the third embodiment also use a large electrolytic capacitor as the capacitor 223, and the diodes 221 and 222 and the capacitor 223 are provided on the main substrate 250. When the mounting space cannot be secured, the diodes 221 and 222 and the capacitor 223 are mounted on the sub-board 260. The sub-board 260 may be provided outside the head 20 in the head unit 2. When a ceramic capacitor having a small size and weight is used as the capacitor 223, the diodes 221 and 222 and the capacitor 223 can be mounted on the main board 250 (the sub board 260 is not necessary), and the size and weight of the head unit 2 are reduced. As the power is reduced, the power of the carriage motor 31 is reduced, and the load on the carriage motor 31 is also reduced to extend its life.

4). Fourth Embodiment A liquid ejection apparatus 1 according to a fourth embodiment includes a clamp circuit 220 similar to that of the liquid ejection apparatus 1 according to the first embodiment, but a signal line to which the clamp circuit 220 is connected is the first embodiment. And different. Below, the description which overlaps with 1st Embodiment is abbreviate | omitted or simplified, and the content different from 1st Embodiment is mainly demonstrated.

  FIG. 17 is a diagram illustrating a part of the electrical configuration of the liquid ejection apparatus 1 according to the fourth embodiment. In FIG. 17, the same configuration as that of the first embodiment (FIG. 2) is not illustrated. Yes.

  As shown in FIG. 17, the liquid ejection apparatus 1 according to the fourth embodiment includes a power supply voltage supply line 91 that supplies the power supply voltage VH of the drive control unit 200 from the control unit 10 to the head unit 2, and a head from the control unit 10. Drive signal supply lines 92 and 93 for supplying drive signals COM-A and COM-B to the unit 2 are included. Further, in the liquid ejection apparatus 1 according to the fourth embodiment, a pseudo drive signal supply line that supplies a pseudo drive signal that is not applied to the ejection unit 600 and that the drive signal COM-A is duplicated from the control unit 10 to the head unit 2. 95 and a pseudo drive signal supply line 96 for supplying a pseudo drive signal that is not applied to the ejection unit 600 and in which the drive signal COM-B is copied from the control unit 10 to the head unit 2. The pseudo drive signal supply line 95 is configured by electrically connecting the pseudo drive signal output terminal 105 of the control unit 10 and the pseudo drive signal input terminal 205 of the head unit 2 by the flexible flat cable 190. That is, at least a part of the pseudo drive signal supply line 95 is provided in the flexible flat cable 190. Similarly, the pseudo drive signal supply line 96 is configured by electrically connecting the pseudo drive signal output terminal 106 of the control unit 10 and the pseudo drive signal input terminal 206 of the head unit 2 by the flexible flat cable 190. The That is, at least a part of the pseudo drive signal supply line 96 is provided in the flexible flat cable 190.

  As shown in FIG. 17, in the liquid ejection apparatus 1 according to the fourth embodiment, the anode of the diode 221 is electrically connected to the drive signal supply line 92 and the drive signal input terminal 202, and the cathode of the diode 221 is The pseudo drive signal supply line 95 and the pseudo drive signal input terminal 205 are electrically connected. The anode of the diode 222 is electrically connected to the drive signal supply line 93 and the drive signal input terminal 203, and the cathode of the diode 222 is electrically connected to the pseudo drive signal supply line 96 and the pseudo drive signal input terminal 206. Yes.

  FIG. 18 shows an example of the waveform of the drive signal COM (any of the drive signals COM-A and COM-B) that propagates through the drive signal supply line 92 or the drive signal supply line 93 and is input to the drive control unit 200. FIG. In FIG. 18, the solid line W1 is the waveform of the drive signal COM, and the broken line W2 is the waveform of the pseudo drive signal. The drive signal COM generated by the drive circuit 50 (any one of the drive circuits 50-a and 50-b), that is, the waveform of the drive signal COM before propagating through the drive signal supply line 92 or the drive signal supply line 93 is as follows. This is the same as FIG.

  As shown in FIG. 18, the waveform of the drive signal COM propagated through the drive signal supply line 92 or the drive signal supply line 93 and the waveform of the pseudo drive signal propagated through the pseudo drive signal supply line 95 or the pseudo drive signal supply line 96. Exceeds the forward drop voltage Vf1 of the diode 221 or the diode 222, a current flows through the diode 221 or the diode 222, and the voltage of the drive signal COM is limited to Vmax + Vf1 or less. That is, the diodes 221 and 222 function as clamp diodes that clamp the voltages of the drive signals COM-A and COM-B to Vmax + Vf1, respectively.

  The clamp voltage (Vmax + Vf1) is equal to or lower than the absolute maximum rated voltage VHmax of the IC constituting the drive control unit 200, and the maximum voltage of the drive signal COM input to the IC is equal to or lower than the absolute maximum rated voltage VHmax. Limited to Further, if the maximum voltage Vmax of the drive signal COM is set so that the difference between the power supply voltage VH and the maximum voltage Vmax of the drive signal COM is equal to or higher than the forward drop voltage Vf1 of the diode 221 or the diode 222, the clamp voltage (Vmax + Vf1) is limited to the power supply voltage VH or less.

  As described above, according to the liquid ejection apparatus 1 and the head unit 2 according to the fourth embodiment, the drive signal COM− is caused by the inductance component of the flexible flat cable 190 (drive signal supply lines 92 and 93). Even if a very large overshoot occurs in the waveforms of A and COM-B, the voltages of the drive signals COM-A and COM-B are clamped to Vmax + Vf1 or less by the functions of the diodes 221 and 222. Accordingly, since the drive signals COM-A and COM-B having a voltage exceeding the absolute maximum rated voltage VHmax of the IC are not supplied to the IC constituting the drive control unit 200, the possibility that the IC breaks down is reduced. Can be made. Further, even if a very large overshoot occurs in the waveforms of the drive signals COM-A and COM-B, the distortion of the drive waveform is reduced, so that the ink ejection accuracy is improved.

  Further, according to the liquid ejection device 1 and the head unit 2 according to the fourth embodiment, even if a large overshoot occurs in the drive waveform, the power supply voltage is supplied from the drive signal supply lines 92 and 93 via the diodes 221 and 222. Since no current flows into the line 91, the power supply voltage VH of the drive control unit 200 does not fluctuate. Therefore, it is possible to prevent malfunction of the drive control unit 200 due to fluctuations in the power supply voltage VH.

  Furthermore, according to the liquid ejection device 1 and the head unit 2 according to the fourth embodiment, even when a very long flexible flat cable 190 is used, the clamp circuit 220 having a simple configuration reduces the countermeasure against overshoot of the drive waveform. Can be realized at a cost.

  As in the first embodiment, the liquid ejection apparatus 1 and the head unit 2 according to the fourth embodiment also include the anodes of the diodes 221 and 222 and the drive signal supply lines 92 and 93 among the drive signal supply lines 92 and 93. If the signal line from the connection point to the drive control unit 200 is long, the waveforms of the drive signals COM-A and COM-B input to the drive control unit 200 may be distorted. Therefore, as shown in FIG. 17, it is preferable that the clamp circuit 220 (diodes 221 and 222) and the drive control unit 200 are mounted on the same main board 250. However, when the main board 250 is provided inside the head 20 and the space for mounting the diodes 221 and 222 cannot be secured on the main board 250, the diodes 221 and 222 are mounted on a sub-board different from the main board 250. You may be made to do. This sub-board may be provided outside the head 20 in the head unit 2.

5. In each of the above embodiments, ink is supplied from the ink cartridge 22 provided in the main body 5 of the liquid ejecting apparatus 1 to the head 20 via the ink tube, but the ink cartridge mounted on the carriage is supplied to the head 20. The configuration may be such that ink is supplied.

  In addition, the liquid ejecting apparatus 1 according to each of the above embodiments is a large format printer in which the maximum size of a printable medium is A2 size paper size (420 mm × 594 mm) or more, but the maximum size of a printable medium is The printer may be a B3 size paper size (364 mm × 515 mm) or less. If the liquid ejecting apparatus 1 is not a large format printer, the flexible flat cable 190 can be shorter and the inductance component is smaller than when the liquid ejecting apparatus 1 is a large format printer. For example, the drive signal COM-A, If the difference between the maximum voltage Vmax of COM-B and the power supply voltage VH (or power supply voltage VH1) is small, the overshoot generated in the drive waveform may exceed the absolute maximum rated voltage VHmax of the IC. Even if the overshoot does not exceed the absolute maximum rated voltage VHmax of the IC, it is conceivable that the ink ejection accuracy is reduced by distorting the drive waveform due to the overshoot. Therefore, the configuration in which the head unit 2 includes the clamp circuit 220 is effective even when the liquid ejection apparatus 1 according to each of the above embodiments is not a large format printer.

  In each of the above embodiments, the piezoelectric element that ejects ink is described as an example of the drive target of the drive circuit. However, the drive target is not limited to the piezoelectric element. For example, an ultrasonic motor, a touch panel, or a flat speaker is used. It may be a capacitive load such as a liquid crystal display. That is, the drive circuit may be any circuit that drives such a capacitive load.

  As mentioned above, although this embodiment or the modification was demonstrated, this invention is not limited to these this embodiment or a modification, It is possible to implement in a various aspect in the range which does not deviate from the summary. For example, the above embodiments and modifications can be appropriately combined.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

DESCRIPTION OF SYMBOLS 1 ... Liquid ejection apparatus, 2 ... Head unit, 5 ... Main body, 6 ... Support stand, 10 ... Control unit, 20 ... Head, 22 ... Ink cartridge, 24 ... Carriage, 31 ... Carriage motor, 32 ... Carriage guide shaft, 35 DESCRIPTION OF SYMBOLS ... Carriage motor driver, 41 ... Conveyance motor, 45 ... Conveyance motor driver, 50, 50-a, 50-b ... Drive circuit, 60 ... Piezoelectric element, 70 ... Power supply circuit, 80 ... Maintenance unit, 81 ... Cleaning mechanism, 82 DESCRIPTION OF SYMBOLS ... Wiping mechanism, 91 ... Power supply voltage supply line, 92 ... Drive signal supply line, 93 ... Drive signal supply line, 94 ... Power supply voltage supply line, 95 ... Pseudo drive signal supply line, 96 ... Pseudo drive signal supply line, 101 ... Power supply voltage output terminal, 102 ... Drive signal output terminal, 103 ... Drive signal output terminal, 104 ... Power supply voltage output terminal DESCRIPTION OF SYMBOLS 105 ... Pseudo drive signal output terminal, 106 ... Pseudo drive signal output terminal, piezoelectric element, 190 ... Flexible flat cable, 200 ... Drive control part, 201 ... Power supply voltage input terminal, 202 ... Drive signal input terminal, 203 ... Drive signal input Terminals 204, power supply voltage input terminals, 205, pseudo drive signal input terminals, 206, pseudo drive signal input terminals, 210, selection control unit, 212, shift register, 214, latch circuit, 216, decoder, 220, clamp circuit, 221 ... Diode, 222 ... Diode, 223 ... Condenser, 230 ... Selector, 232a, 232b ... Inverter, 234a, 234b ... Transfer gate, 250 ... Main board, 260 ... Sub-board, 600 ... Discharge part, 601 ... Piezoelectric body, 611, 612 ... electrode, 621 ... diaphragm, 6 1 ... cavity, 632 ... nozzle plate, 641 ... reservoir, 651 ... nozzle, 661 ... supply port

Claims (9)

A head unit comprising: a discharge unit that discharges liquid when a drive signal is applied; and a drive control unit that controls application of the drive signal to the discharge unit;
A control unit comprising a drive circuit for generating the drive signal;
A drive signal supply line for supplying the drive signal from the control unit to the head unit,
The head unit is
An anode comprising a diode electrically connected to the drive signal supply line;
A liquid discharge apparatus characterized by that. Including a flexible flat cable connecting the control unit and the head unit and provided with at least a part of the drive signal supply line;
The liquid ejection apparatus according to claim 1, wherein A power supply voltage supply line for supplying a power supply voltage of the drive control unit from the control unit to the head unit;
A cathode of the diode is electrically connected to the power supply voltage supply line;
The liquid discharge apparatus according to claim 1, wherein the liquid discharge apparatus is a liquid discharge apparatus. A first power supply voltage supply line for supplying a first power supply voltage which is a power supply voltage of the drive control unit from the control unit to the head unit;
A second power supply voltage supply line for supplying a second power supply voltage from the control unit to the head unit,
A cathode of the diode is electrically connected to the second power supply voltage supply line;
The liquid discharge apparatus according to claim 1, wherein the liquid discharge apparatus is a liquid discharge apparatus. The head unit is
One end includes a capacitor electrically connected to the cathode of the diode;
The liquid discharge apparatus according to claim 3 or 4, wherein The capacitor is a ceramic capacitor,
The liquid ejection apparatus according to claim 5, wherein Including a pseudo drive signal supply line for supplying a pseudo drive signal that is not applied to the ejection unit, in which the drive signal is copied from the control unit to the head unit;
A cathode of the diode is electrically connected to the pseudo drive signal supply line;
The liquid discharge apparatus according to claim 1, wherein the liquid discharge apparatus is a liquid discharge apparatus. An ejection unit that ejects liquid by applying a drive signal;
A drive control unit that controls application of the drive signal to the ejection unit;
A drive signal input terminal to which the drive signal is input;
A diode having an anode electrically connected to the drive signal input terminal;
A head unit characterized by that. A head unit comprising: a discharge unit that discharges liquid when a drive signal is applied; and a drive control unit that controls application of the drive signal to the discharge unit;
A control unit comprising a drive circuit for generating the drive signal;
A drive signal supply line for supplying the drive signal from the control unit to the head unit;
A flexible flat cable connecting the control unit and the head unit and provided with at least a part of the drive signal supply line;
The head unit is
An anode comprising a diode electrically connected to the drive signal supply line;
A large format printer.

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