JP2006076260A - Inkjet head driving method and inkjet head recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the discharge volume of an ink without varying the width of a driving pulse and a driving frequency. <P>SOLUTION: The inkjet head driving method increases the discharge quantity of an ink discharged from a nozzle by the application of the driving pulse, when the meniscus of the nozzle of an ink chamber adjacent to an ink chamber 13 to which the driving pulse is applied are advancing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink-jet head driving method and an ink-jet head recording apparatus capable of changing a discharge volume by utilizing pressure fluctuations when driving adjacent nozzles.

  Recording apparatuses having an ink jet head are widely used. It is desired to improve the print quality printed by this inkjet head. For example, as a method for improving the printing quality, a method for controlling an ink discharge volume discharged from a nozzle of an inkjet head is known. For example, there is known a technique in which small ink droplets are ejected from an inkjet head nozzle a plurality of times to change the dot size (see, for example, Patent Documents 1 and 2). In the methods of Patent Documents 1 and 2, recording is performed by controlling the number of drive pulses applied to the ink jet head to eject a small droplet of ink a plurality of times from the nozzle and changing the number of ejected small droplets. The dot size of ink droplets to be projected on the medium is changed.

Also known are those that change the ejection volume of ink ejected from the nozzles of an inkjet head (see Patent Documents 3 to 5). In these methods, the volume of the ink droplet ejected from the nozzle is changed by changing the voltage, pulse width, etc. of the drive signal applied to the inkjet head.
U.S. Patent 4,513,299 JP2003-1821 U.S. Patent 5,461,493 Japanese Patent Laid-Open No. 4-250045 Patent No.327,795

  As described in Patent Documents 1 and 2, the method of ejecting a plurality of small droplets requires the ejection of a plurality of inks to form one pixel, and in order to increase the ink ejection volume. It is necessary to discharge a plurality of small droplets at a high driving frequency. Further, in Patent Documents 1 and 2, in order to increase the printing speed, when a driving pulse is continuously applied at a high frequency, a meniscus vibration generated by a driving pulse for discharging a small droplet immediately before is added. The meniscus vibration becomes large and disturbs. For this reason, it is difficult to increase the printing speed because the ink discharge speed is lowered or the ink is not discharged in some cases.

  Further, as shown in Patent Documents 3 to 5, in the method of changing the ejection volume, a plurality of drive pulses having different voltages must be prepared according to the volume to be changed. Further, in the method of controlling the ejection volume by changing the pulse width of the drive pulse, it is easily affected by the meniscus position, and the next ejection cannot be performed until the meniscus position becomes constant. Therefore, the drive frequency of the drive pulse cannot be increased. This is because when the drive frequency is increased, the meniscus position is not constant, and thus the ink ejection volume cannot be stably controlled.

  For this reason, in order to increase the printing speed, in an inkjet head in which the drive frequency of the drive pulse is increased, it is the mainstream not to control the ink ejection volume.

  The present invention has been made in view of the above points, and an object thereof is an ink jet head driving method and an ink jet head capable of controlling an ink ejection volume without changing a pulse width or a driving frequency of a driving pulse. It is to provide a recording apparatus.

  The inkjet head driving method according to claim 1, wherein in the inkjet head driving method, the driving pulse is applied when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the driving pulse is applied is advanced. The discharge amount of the ink discharged from the nozzle is increased.

  As described above, when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the drive pulse is applied is advanced, the drive pulse is applied, so the pulse width and the drive frequency of the drive pulse are changed. The ink ejection volume can be controlled without the need for this.

  The ink jet head driving method according to claim 2, wherein in the ink jet head driving method, a dummy pulse is applied to the ink chamber in advance to expand the volume of the ink chamber and advance the meniscus position of the adjacent ink chamber, It is characterized in that the ejection amount of ink ejected from the nozzle is increased by applying a drive pulse to the adjacent ink chamber.

  In this way, the volume of the adjacent ink chamber is expanded to advance the meniscus position, and the drive pulse is applied to increase the amount of ink ejected from the nozzle. The ink ejection volume can be controlled without changing the width and driving frequency.

  An inkjet head recording apparatus according to claim 3, comprising an ink chamber provided with a nozzle for ejecting ink, and ejecting ink by changing the volume of the ink chamber by an electromechanical conversion means; A drive pulse generator for outputting a drive pulse to the electromechanical conversion means; the drive pulse generator is configured to advance a meniscus position of a nozzle in an ink chamber adjacent to an ink chamber to which the drive pulse is applied; In this case, the ejection amount of ink ejected from the nozzle is increased by applying a driving pulse during the operation.

    As described above, when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the drive pulse is applied is advanced, the drive pulse is applied, so the pulse width and the drive frequency of the drive pulse are changed. The ink ejection volume can be controlled without the need for this.

  An ink jet head recording apparatus according to claim 4, comprising an ink chamber provided with a nozzle for ejecting ink, and ejecting ink by changing the volume of the ink chamber by an electromechanical conversion means; A drive pulse generator that outputs a drive pulse to the electromechanical conversion means, and the drive pulse generator expands the volume of the ink chamber by applying a dummy pulse to the ink chamber in advance, thereby adjacent ink; It is characterized in that the amount of ink ejected from the nozzles is increased by advancing the meniscus position of the chamber and applying a drive pulse to the adjacent ink chamber.

    In this way, the volume of the adjacent ink chamber is expanded to advance the meniscus position, and the drive pulse is applied to increase the amount of ink ejected from the nozzle. The ink ejection volume can be controlled without changing the width and driving frequency.

  According to a fifth aspect of the present invention, there is provided an ink jet head driving method, wherein the ink jet head according to the first or second aspect is driven by a three-division drive.

  An ink jet head recording apparatus according to a sixth aspect is characterized in that the drive pulse generator according to the third or fourth aspect outputs a drive pulse by three-division driving.

  According to the present invention, in the inkjet head driving method and the recording apparatus, when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the driving pulse is applied is advanced, or the volume of the adjacent ink chamber is increased. Since the meniscus position is expanded and the meniscus position is advanced and the ejection amount of ink ejected from the nozzle is increased by applying the drive pulse, the ink can be changed without changing the pulse width or drive frequency of the drive pulse. The discharge volume can be controlled.

  An inkjet head recording apparatus and an inkjet head driving method according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an ink jet head according to the present invention, and FIG. 2 is a cross-sectional view along a direction orthogonal to the direction of the groove 5.

  In the figure, an inkjet head 1 has a laminated piezoelectric member 4 in which two piezoelectric materials 2 and 3 formed of a piezoelectric material such as PZT are laminated as shown in FIG. Here, the polarization directions of the piezoelectric members 2 and 3 are opposite to each other along the thickness direction of the laminated piezoelectric member 4 as indicated by arrows.

  In the laminated piezoelectric member 4, a plurality of grooves 5 whose upper side and front side are open are formed in parallel to each other. These grooves 5 are ground by a die saw diamond wheel or the like. As a result, each groove 5 is partitioned by the side wall 6.

  A plurality of electrodes 7 formed by electroless nickel plating are provided on the inner surface of the groove 5 and the upper surface of the laminated piezoelectric member 4. Here, the electrode 7 is not particularly limited to nickel, and may be gold or copper, for example.

  In the groove 5, the front opening 8 that is open on the front side of the multilayer piezoelectric member 4 is closed by a nozzle plate 10 in which a plurality of nozzles 9 are formed.

  Further, the upper opening 11 that opens toward the upper side of the laminated piezoelectric member 4 in the groove 5 is closed by a lid member 12. The lid member 12 is formed with an ink supply path 15 as an ink flow path that communicates with an ink supply pipe 14 that supplies ink to each ink 13 (described later) that communicates with an ink tank (not shown).

  An ink chamber 13 is formed by closing the front opening 8 and the upper opening 11 of the groove 5 of the head substrate by the lid member 12 and the nozzle plate 10. The ink chambers 13 communicate with each other via an ink supply path 15.

  The inkjet head 1 configured as described above is connected as shown in FIG. 3 to configure an inkjet head recording apparatus.

  In FIG. 3, reference numeral 21 denotes a CPU (central processing unit) for controlling the inkjet head 1 in an integrated manner. Connected to the CPU 21 are a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, a head driver 24 and a motor driver 25 in which various control programs are stored.

  The head driver 24 outputs a driving pulse of three-division driving as shown in FIG. 4 and a dummy pulse shown in FIG.

 A conveyance motor 26 for conveying a recording medium (not shown) along the surface of the nozzle plate 10 is connected to the motor driver 25.

  By the way, the plurality of ink chambers 13 constitute one set of three continuous ink chambers 13A, 13B, and 13C, and the electrodes 7A, 7B, and 7C corresponding to the ink chambers 13A, 13B, and 13C of the respective sets are respectively provided. A drive pulse as shown in FIG. 4 is applied at the same timing. That is, the driving is divided into three. In this embodiment, the case where ink is ejected in the order of each ink chamber 13B → 13A → 13C will be described as an example.

  First, the basic principle for causing ink to protrude from the ink chamber 13 will be described. First, in a state where ink is supplied to the ink chamber 13, a voltage is applied to the electrodes 7 located on both sides of the ink chamber 13 from which the ink is projected. The pair of side walls 6 corresponding to the electrodes 7 to which this voltage is applied are curved in a direction to increase the volume of the ink chamber 13 due to the shear mode deformation of the piezoelectric members 2 and 3 having opposite polarization directions. Next, a reverse polarity voltage is applied to the electrodes 7 located on both sides of the ink chamber 13 through which the ink protrudes. Then, the side wall 6 suddenly returns to the initial position. When the side wall 6 returns to the initial position, the ink in the ink chamber 13 is pressurized, and a part of the ink in the ink chamber 13 becomes an ink droplet and is ejected from the nozzle 9.

  For example, a case where ink is ejected from the ink chamber 13B will be described. In this case, a drive pulse having a waveform as shown in FIG. 4 is applied between the electrode 7B of the ink chamber 13B and the electrodes 7A and 7C of the ink chambers 13A and 13C adjacent to the ink chamber 13B.

  This drive pulse changes from the standby voltage Vres that does not change the ink chamber 13 to the first voltage V1 that expands the volume of the ink chamber, and then changes to the second voltage V2 that contracts the ink chamber 13.

  More specifically, the drive pulse rises from the standby voltage Vres to the first voltage V1 at time t1. This voltage V1 is held for a certain time (Tc / 2). Tc is the ink Helmholtz period, that is, the ink meniscus resonance period. Then, at time t3, the voltage suddenly falls from the first voltage V1 to the second voltage V2 via the standby voltage Vres. The second voltage V2 is held for a certain time Tc from time t3 to t5. At time t5, the voltage rapidly rises from the second voltage V2 to the standby voltage Vres, and after holding the standby voltage Vres for a certain time, the voltage is suddenly lowered to the standby voltage Vres at time t8.

   The pulse from time t1 to t3 is referred to as pre-pulse P1, the pulse from time t4 to t5 is referred to as ejection pulse P2, and the pulse from time t6 to t8 is referred to as damping pulse P3.

  Here, the pulse width of the damping pulse P3 is set to a value that can effectively cancel the residual vibration of the ink pressure in the ink chamber 13. For example, the pulse width is determined by a head structure such as ink or an ink supply form. For example, the interval between the midpoint of the pulse width of the damping pulse P3 and the time t5 is set to Tc / 4.

  Next, how the meniscus position is changed by the drive pulse of FIG. 4 will be described with reference to FIG. For example, when the drive pulse of FIG. 4 is applied to the ink chamber 13B, both side walls 6 are deformed outward so as to expand the volume of the ink chamber 13B at the rising edge of the pre-pulse P1. As a result, the ink pressure in the ink chamber 13B decreases. If the first voltage V1 of the pre-pulse P1 is kept as it is, the ink pressure in the ink chamber 13B becomes negative from time t1 to time t2, so that the meniscus position moves backward as indicated by A. Next, since the ink pressure in the ink chamber 13B is reversed from the negative pressure to the positive pressure at the time t2, the meniscus position advances as indicated by B after the time t2.

  When the ejection pulse P2 is applied at time t3 immediately before time t4, the increase in ink pressure in the ink chamber 13B overlaps with the meniscus forward speed, and ink is ejected from the nozzle 9.

  Further, at time t4, the meniscus position generated by the pre-pulse P1 changes from forward to backward. If the ejection pulse P2 is continuously held as it is, the meniscus position continues to retreat from time t4 to time t4 ′ as indicated by C. Then, after the time t4 ′, the meniscus position moves forward as indicated by D.

  After that, by returning to the standby voltage Vres at time t5 and applying the damping pulse P3 at time t6, the meniscus vibration in the ink chamber 13B is canceled and converged as indicated by E.

  In this manner, the mace vibration is stabilized until the next ink ejection timing from the ink chamber 13B. Thereby, ink can be ejected continuously at a high driving frequency.

  6 is a diagram in which the driving pulse in FIG. 4 and the meniscus position in FIG. 5 are overlapped.

  In the above description, the manner in which the meniscus position is changed by the drive pulse in FIG. 4 has been described focusing on one ink chamber 13B.

  As described above, in the present embodiment, in each group, an operation of ejecting ink is performed in the order of the ink chambers 13B → 13A → 13C. That is, drive pulses are supplied as shown in FIGS. 9B to 9D in the order of the ink chambers 13B → 13A → 13C. Since the ink chamber 13B is adjacent to the ink chambers 13A and 13C with the side wall 6 therebetween, the ink chamber 13B is affected by the deformation of the side wall. That is, when the volume of the ink chamber 13A or the ink chamber 13C increases, the volume of the ink chamber 13B decreases. When the volume of the ink chamber 13A or the ink chamber 13C decreases, the volume of the ink chamber 13B increases. To work. That is, when a drive pulse is applied to the adjacent ink chamber 13A or 13B, the meniscus position of the ink chamber 13B has a waveform similar to the waveform obtained by inverting the waveform of FIG.

  When the drive pulse shown in FIG. 4 is applied to the ink chamber 13A at time t8 in FIG. 9C, the meniscus position in the ink chamber 13B varies as indicated by α from time t8 in FIG. 9A. .

  Further, when the drive pulse shown in FIG. 4 is applied to the ink chamber 13C at time t9 in FIG. 9D, the meniscus position of the ink chamber 13B is changed from β to time t9 in FIG. 9A. fluctuate.

  Then, the meniscus position of the ink chamber 13B in FIG. 9A comes to the advanced position as shown by the oblique lines. The position indicated by γ in this oblique line is the position where the meniscus position has advanced most.

  Accordingly, when the drive pulse is applied to the ink chamber 13B when the meniscus position of the ink chamber 13B in FIG. 9A is at the forward position indicated by the oblique lines, the amount of ink ejected from the nozzle 9 of the ink chamber 13B is reduced. Can be increased. Therefore, it is possible to increase the ink ejection amount without changing the pulse width and the driving frequency of the driving pulse. Thus, high speed printing is possible because the pulse width and drive frequency are not changed.

FIG. 10 is a diagram in which the meniscus volume position shown in FIG. For example, when the standby voltage Vres of the drive pulse is 0V, the first voltage V1 is 20V, and the second voltage is -20V, when the meniscus position is 5 × E-15m ³ as indicated by X, it is usually 20 pl. The ink discharge volume can be increased by about 8 pl.

  As described above, the volume of ink ejected from the nozzle 9 in the ink chamber 13B is increased when a drive pulse is applied to the ink chambers 13A and 13C adjacent to the ink chamber 13B.

  Therefore, the ejection volume of the ink ejected from the nozzle 9 in the ink chamber 13B does not increase by the drive pulse D1 in FIG. 9B.

  If it is desired to increase the volume of ink ejected from the nozzle 9 in the ink chamber 13B when the drive pulse D1 is first applied to the ink chamber 13B, a dummy pulse as shown in FIG. May be applied. This dummy pulse has the same voltage V1 as the drive pulse shown in FIG. 4, and the pulse width is Tc time. By applying such a dummy pulse to the ink chamber 13A, the volume of the ink chamber 13A is expanded. Since the ink chamber 13B is disposed across the ink chamber 13A and the side wall 6, the ink chamber 13B is reduced by the dummy pulse. Thereby, the meniscus position of the ink chamber 13B can be advanced. As described above, by moving the meniscus position of the ink chamber 13B forward, even when the drive pulse D1 is first applied, the ejection volume of the ink ejected from the nozzle 9 of the ink chamber 13 can be increased.

  As described above, according to an embodiment of the present invention, when a driving pulse is applied to an ink chamber after a driving pulse is applied to an ink chamber adjacent to a wall, ink ejected from the nozzle of the ink chamber The discharge amount can be increased. For example, in the case of three-division driving, printing is performed with a dot diameter as shown in FIG. For example, as shown in FIG. 11A, after a drive pulse is applied in the order of ink chambers 13A → 13B → 13C as shown in a as shown in a, the next three-division drive is performed as shown in b. Will be described. When the three-division driving is performed at the timing shown in a, the ink chamber 13A is not applied with a driving pulse in the adjacent ink chamber, and therefore printing is performed with the same dot as the normal dot diameter shown in FIG. Is done. Next, when the three-division driving is performed at the timing indicated by b, only the leftmost dot 30 in the ink chamber 13A has a normal size. This is because the drive pulse is not applied to the adjacent ink chamber. Also, the dots ejected from the ink chamber 13A at the timing a have a normal dot diameter, but when ejected from the ink chamber 13A at the next timing b, printing is performed with the dots 32 having an increased ejection volume. The

  In the above-described embodiment, the three-division driving method has been described. However, the present invention is not limited to the three-division driving unless the drive pulses are simultaneously applied to the ink chambers sharing the side wall.

  In addition, if the driving method of the present invention is applied to an inkjet head that can perform high-speed printing of only binary values, it is desired to increase the amount of ink discharged from the nozzles and perform light printing when performing dark printing. Sometimes, printing with gradation can be performed by reducing the amount of ink discharged from the nozzles.

1 is a perspective view of an ink jet head according to an embodiment of the present invention. Sectional drawing of the principal part of the inkjet head. 1 is a block diagram of an inkjet head recording apparatus. FIG. 3 is a diagram showing drive pulses supplied to the inkjet head. The figure which shows the meniscus position of the inkjet head. The figure which shows the relationship between the drive pulse supplied to the inkjet head, and a meniscus position. The figure which shows the fluctuation | variation of the meniscus position of the ink chamber 13B of the inkjet head. The figure which shows the dummy pulse supplied to the inkjet head. The figure which shows the relationship between the meniscus position of the ink chamber 13B of the inkjet head, and the drive pulse supplied to each ink chamber. The figure which shows the fluctuation | variation of the meniscus position of the ink chamber of the inkjet head. FIG. 11A is a diagram showing a printing state of normal printing printed by the inkjet head, and FIG. 11B is a diagram showing a printing state where the discharge volume printed by the inkjet head is increased.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Inject head, 4 ... Laminated piezoelectric member, 6 ... Side wall, 10 ... Nozzle plate, 13 ... Pressure chamber, 14 ... Ink supply pipe, 21 ... CPU, 22 ... ROM, 23 ... RAM, 24 ... Head driver, 25 ... motor driver.

Claims (6)

In the inkjet head driving method, by applying a driving pulse when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the driving pulse is applied is advanced, the amount of ink discharged from the nozzle is reduced. An ink-jet head driving method characterized in that it increases. In the inkjet head driving method, by applying a dummy pulse to the ink chamber in advance, the volume of the ink chamber is expanded to advance the meniscus position of the adjacent ink chamber, and the driving pulse is applied to the adjacent ink chamber. An inkjet head driving method characterized in that the ejection amount of ink ejected from the nozzles is increased by the above. An ink jet head having an ink chamber provided with a nozzle for ejecting ink, and ejecting ink by changing the volume of the ink chamber by an electromechanical converter;
A drive pulse generator for outputting a drive pulse to the electromechanical conversion means;
The drive pulse generation unit applies the drive pulse when the meniscus position of the nozzle of the ink chamber adjacent to the ink chamber to which the drive pulse is applied advances, thereby reducing the amount of ink discharged from the nozzle. An ink jet head recording apparatus characterized in that the number increases. An ink jet head having an ink chamber provided with a nozzle for ejecting ink, and ejecting ink by changing the volume of the ink chamber by an electromechanical converter;
A drive pulse generator for outputting a drive pulse to the electromechanical conversion means;
The drive pulse generator applies a dummy pulse to the ink chamber in advance to enlarge the volume of the ink chamber, advance the meniscus position of the adjacent ink chamber, and apply the drive pulse to the adjacent ink chamber. An ink jet head recording apparatus characterized in that the discharge amount of ink discharged from the nozzles is increased. The inkjet head driving method according to claim 1, wherein the inkjet head is driven by three-division driving. 5. The ink jet head recording apparatus according to claim 3, wherein the driving pulse generator outputs a driving pulse by three-division driving.

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