JP2007118294A - Driving device for inkjet head, and driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving method for an inkjet head which does not generate a variation in the discharging speed of ink droplets. <P>SOLUTION: This inkjet driving device is equipped with a driving control section for the inkjet head. The driving control section divides a plurality of pressure chambers of the inkjet head into (N+1) sets at every N(N≥2) piece interval, applies a discharging pulse by a time-sharing driving for each set unit to a driving electrode, and makes ink droplets discharged by deforming a bulkhead. In the inkjet driving device, regarding the pressure chamber which should be driven from among the plurality of the pressure chambers, whether the discharging pulse has been applied to the driving electrodes of the pressure chamber to be driven and the pressure chambers being adjacent to the pressure chamber to be driven since the driving one printing cycle before driving this time, is judged. The driving control section which applies a pre-pulse for compensating the discharging speed of ink droplets which is pre-set to the driving electrode of the pressure chamber to be driven, based on the judgement result is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet head having a plurality of pressure chambers, and more particularly, to an ink jet head driving apparatus and a driving method for correcting variations in ejection speed of ink droplets.

  There is an ink jet head called a “shared wall head” in which ink is ejected by changing the volume of a pressure chamber due to deformation in a shearing mode of a partition wall serving as an actuator for partitioning adjacent pressure chambers. In such an ink jet head, the pressure chambers adjacent to each other share the partition wall serving as an actuator as described above, and therefore cannot be simultaneously driven and controlled. Therefore, these pressure chambers are divided into (N + 1) blocks every N blocks, and ink ejection control is performed by time-division driving in units of blocks.

  Further, in this shared wall head, since the pressure chambers adjacent to each other share a partition wall serving as an actuator, when a certain pressure chamber is driven and ink droplets are ejected, the pressure chamber adjacent to the pressure chamber is Variation in ink pressure occurs. Therefore, when the ink pressure in the pressure chamber fluctuates, the meniscus in the nozzle that communicates with the pressure chamber rises. In other words, before the drive pulse is applied to the pressure chamber to be driven, whether or not the drive pulse is applied to the pressure chamber adjacent to the pressure chamber is determined in the nozzle communicating with the pressure chamber to be driven. Meniscus position is different. For this reason, if the meniscus position when ink is ejected is different, the ejection speed of the ink droplet varies, and as a result, the landing position of the ink droplet on the recording medium changes and the quality of the printed image decreases. Is disclosed.

In order to solve such a problem that variations in the ejection speed of ink droplets occur, Patent Document 1 discloses that an ink chamber is adjacent to the ink chamber before it is driven to eject the ink droplet. A driving method is disclosed in which it is determined whether or not both ink chambers to be driven are driven, and the drive pulse waveform is changed so as to correct the ejection speed of the ink droplets based on the determination result.
Japanese Patent Laid-Open No. 10-16212

  However, the inventor of the present application also determines whether or not a pressure chamber that attempts to eject an ink droplet has been driven to eject an ink droplet before driving a certain pressure chamber. It was found by simulation analysis that the meniscus position varies due to a similar meniscus swell phenomenon, and therefore the ink droplet ejection speed varies depending on the meniscus position at the timing of applying the drive pulse for ejecting the ink droplet. .

  In the present invention, when an ink droplet is ejected by driving a certain pressure chamber, whether or not a driving pulse for ejecting the ink droplet has been applied to the pressure chamber and the pressure chamber adjacent to the pressure chamber before that time. Regardless, it is an object of the present invention to provide an ink jet head driving device and a driving method thereof that do not cause fluctuations in the ejection speed of the ink droplets.

(1) An ink jet driving device of the present invention includes a plurality of pressure chambers provided with nozzles for ejecting ink droplets separated by a partition made of piezoelectric material, and provided with a drive electrode provided on the partition. The plurality of pressure chambers of the ink jet head are divided into (N + 1) groups every N (N ≧ 2), and ejection pulses by time-division driving of each group unit are applied to the drive electrodes to deform the partition walls. In the ink jet drive device having the inkjet head drive control unit that discharges ink droplets, one of the (N + 1) sets prints the time from the time to drive to the next drive time. Of the plurality of pressure chambers, the pressure chamber to be driven and the pressure chamber to be driven from this time before driving one printing cycle until the current driving is performed. Drive control for applying a pre-pulse for correcting a preset ink droplet discharge speed to the drive electrode of the pressure chamber to be driven based on the determination result of whether or not the discharge pulse is applied to the drive electrode of the pressure chamber in contact A part was provided.

(2) The ink jet head driving method of the present invention includes a plurality of pressure chambers provided with nozzles for ejecting ink droplets separated by a partition made of piezoelectric material, and provided with a drive electrode provided on the partition. The plurality of pressure chambers of the ink jet head is divided into (N + 1) groups every N (N ≧ 2), an ejection pulse by time-division driving for each group is applied to the drive electrode, In the inkjet head driving method of deforming and discharging ink droplets, when one set of the (N + 1) sets has a time from a drive time to a next drive time as one print cycle, the plurality of print heads Among the pressure chambers, the pressure chamber to be driven is discharged to the pressure chamber to be driven and the drive electrode of the pressure chamber adjacent to the pressure chamber to be driven from the time of driving during one printing cycle to the current driving. It determines whether a pulse is applied, and to apply a pre-pulse for correcting the discharge speed of the preset ink droplets to the drive electrodes of the pressure chamber to be the drive based on the determination result.

  According to the present invention, the ejection speed of ink droplets ejected from a certain pressure chamber is determined by whether or not the pressure chamber is driven before one printing cycle, and adjacent to the pressure chamber from one printing cycle to the present time. Regardless of whether the pressure chamber is driven or not, it is possible to reduce the variation in the ejection speed of the ink droplets and improve the printing quality.

  Embodiments of the present invention will be described below with reference to the drawings. First, the structure of the ink jet head used for carrying out the present invention will be described. 1, 2-a, and 2-b are cross-sectional views showing the configuration of the inkjet head 101. A piezoelectric member 3 bonded so that the polarization directions of the piezoelectric material 3a and the piezoelectric material 3b are opposite to each other inward with respect to the plate thickness direction is embedded in the tip portion of the substrate 1 having a low dielectric constant. ing. A plurality of long grooves 6 are formed in parallel to each other at regular intervals so that the ends of the piezoelectric member 3 are opened on the upper surface of the piezoelectric member 3 and the substrate 1 behind the piezoelectric member 3 by, for example, cutting with a diamond cutter. Yes. On the top surface of the substrate 1, a top plate cover 5 having a top plate frame 4 and an ink supply port 9 is bonded and fixed to form an ink supply path 14. A plurality of pressure chambers 7 are formed by the long grooves 6, the top plate frame 4 and the top plate lid 5, and the pressure chambers 7 are separated from each other by a partition wall 13.

  In addition, on the side surface and the bottom surface of each long groove 6 constituting the pressure chamber 7, individually electrically independent drive electrodes 8 are formed by electroless plating. The drive electrode 8 extends from the rear end of the pressure chamber 7 to the upper surface of the substrate 1 and is connected to a drive circuit described later. The formation of the drive electrode 8 is not limited to electroless plating, and may be formed by photoetching or the like after the electrode material is formed by sputtering or vacuum evaporation. When an electric field is applied to the drive electrodes 8 on both side surfaces of the partition wall 13 having such a structure, a shear stress is generated and deformed as shown in FIG. It has a so-called actuator function for changing the volume of the actuator. A nozzle plate 11 on which nozzles 10 for ejecting ink droplets are formed is bonded and fixed to the tip of each pressure chamber 7 with an adhesive.

  Next, the operation of the inkjet head will be described with reference to FIGS. 2A and 2B in the case where ink droplets are ejected from the pressure chamber 7b.

  FIG. 2A shows a cross-sectional structure in which a plurality of pressure chambers 7 of the ink jet head 101 are arranged. Reference numerals 13a to 13j denote partition walls for partitioning the pressure chambers, and reference numerals 8a to 8i denote drive electrodes formed on the side and bottom surfaces of the pressure chambers. Moreover, 10a-10i shows the nozzle provided in the edge part of each pressure chamber. The drive electrodes of the plurality of pressure chambers 7 of the ink jet head 101 are divided into (N + 1) sets every N. In FIG. 2B, the drive electrodes 8a to 8i of the plurality of pressure chambers 7 of the ink jet head 101 are divided into three groups every N = 2, and the circuit configuration in the case of time-division driving for each group unit. Is illustrated. The drive electrodes 8a to 8j provided on the partition walls 13a to 13j are connected to the common electrodes l, m, n and the ground electrode G for each divided group through the switching elements 16a to 16j, respectively. . The switching elements 16a to 16j are connected to the drive signal lines 15a to 15j.

  Here, in FIG. 2A, as an example, a set of pressure chambers 7b, 7e, and 7h connected to the common electrode m is selected, and ejection pulses for ejecting ink droplets are applied to the drive electrodes corresponding to the pressure chambers. The state currently performed is shown typically.

  Hereinafter, the ink droplet ejection operation will be described focusing on only the pressure chamber 7b. The ink 12 supplied from the ink supply port 9 into the inkjet head 101 is filled into the pressure chamber 7 b through the ink supply path 14. The respective switching elements 16a are formed so that deformation of the partition walls as shown in the figure is caused in the set of drive electrodes 8a and 8b and the set of drive electrodes 8b and 8c provided with the partition walls 13b and 13c on both sides of the pressure chamber 7b. .About.16c are controlled, and the potential difference between the common electrode 1 and the ground electrode G is applied. As a result, an electric field is applied to both side walls of the partition walls 13b and 13c, the volume of the ink chamber 7b changes due to shear deformation corresponding to the direction of each electric field, and ink droplets are ejected from the nozzle 10b. Although only the pressure chamber 7 has been described above, the same pair of pressure chambers 7a and 7h are similarly subjected to the ink ejection operation. Next, a set of pressure chambers 7c (7f, 7i,...) Is sequentially selected and a discharge pulse is applied. Thereafter, a set of pressure chambers 7a is selected, and time-division driving is sequentially performed.

  FIG. 3 is a block diagram of a control unit that controls driving of the inkjet head 101 used in the embodiment of the present invention. In the configuration of the control unit, the calculation device 24 to which the print data 23 is input, and the drive signal data corresponding to the history data relating to the pressure chamber selected in the calculation device 24 are read from the storage device 25 and the drive signal generating means 21. To be supplied. A drive signal is generated from the drive signal data supplied to the drive signal generating means 21, and ink droplet ejection control from the inkjet head 101 is performed by the inkjet drive circuit 22.

  Next, whether or not the adjacent pressure chambers 7c and 7a are driven from the previous printing cycle to the current driving of the pressure chamber 7b to be driven to eject ink droplets, and the pressure before one printing cycle. The following experiment (examination) was performed in order to evaluate the degree of variation in the ink droplet ejection speed when the chamber 7b is driven. Here, one printing cycle refers to the time from a time when a certain group should be driven to a time when it is driven next.

  4A to 4H show the drive signals of the total print pattern from one pressure cycle before the pressure chamber 7b driven this time to the current drive. Drive signals for driving the pressure chambers 7a, 7b and 7c applied to the common signal lines l, m and n in FIGS. 4 (a) to 4 (h) are shown. When the drive signals in FIGS. 4A to 4D drive the pressure chamber 7b before one printing cycle, and the drive signals in FIGS. 4E to 4H do not drive the pressure chamber 7b before one printing cycle. This is a drive signal for the print pattern. FIG. 5 is a table summarizing the printing patterns of the adjacent pressure chambers 7c and 7a from the time before the pressure chamber 7b is driven to the current driving period. The print patterns for driving the pressure chambers 7c and 7a are divided into the following 1-4. The drive signals for driving the pressure chambers 7c and 7a of the print patterns 1 to 4 are as follows. The print pattern 1 is (a) and (e) in FIG. 4, the print pattern 2 is (b) and (f) in FIG. 3 is (c) and (g) in FIG. 4, and the print pattern 4 is (d) and (h) in FIG. The print patterns 1 to 4 will be specifically described below. The print pattern 1 is a print pattern when both the pressure chambers 7c and 7a adjacent to the pressure chamber 7b to be driven this time are driven. The print pattern 2 is a print pattern in the case of driving only the adjacent pressure chamber 7a at the timing of driving immediately before the pressure chamber 7b to be driven this time is driven. The print pattern 3 is a print pattern in the case where only the adjacent pressure chamber 7c that is driven immediately after the drive timing of the pressure chamber 7b that is driven this time immediately before the print cycle is driven. The print pattern 4 is a case where the pressure chamber 7b to be driven this time does not drive both the adjacent pressure chambers 7c and 7a from the time before one print cycle until the current drive.

  Next, FIG. 6 shows a case where the horizontal axis is the above-described print pattern, and the vertical axis is not driven one print cycle before the ink droplet ejection speed (B) when the pressure chamber 7b is driven one print cycle. The ratio of A / B is shown for the discharge speed (A) of the current ink droplet. This evaluation was performed when the drive frequency was 30 kHz. The value of A / B tends to increase as the drive frequency increases. That is, the ratio of the printing pattern 1 is the ratio of the ejection speed of the ink droplets ejected in the current driving period when the driving signal of FIG. 4E is applied to the driving signal of FIG. is there. The same applies to the remaining print patterns 2 to 4. From FIG. 6, when the drive patterns of the adjacent pressure chambers 7 c and 7 a are the same, when the ink is not ejected before one printing cycle, the ejection of the ink droplets this time is more than when the ink is ejected before one printing cycle. The speed will increase.

  Thus, not only whether or not the adjacent pressure chambers 7c and 7a are driven from the time before the printing chamber 7b is driven this time until the current driving time, but also whether the pressure chamber 7b is driven before one printing cycle. It was confirmed from the simulation result of the present inventors that the ejection speed of the ink droplets ejected from the nozzle communicating with the pressure chamber 7b that is driven this time varies depending on whether or not it is present.

  A simulation performed to eliminate variations in the ink droplet ejection speed as described above will be described below.

  The drive signals stored in the storage device 25 of FIG. 3 are shown in FIGS. 7 (a) and 7 (b). The drive signal in FIG. 7A is composed of only the ejection pulse P1 for ejecting ink droplets. The drive signal in FIG. 7B is composed of a pre-pulse P2 and an ejection pulse P1 that do not eject ink.

  Here, the ejection pulse P1 and the prepulse P2 constituting the drive signal shown in FIGS. 7A and 7B will be described. First, the ejection pulse P1 will be described with reference to FIG. The ejection pulse P1 is an ejection pulse for ejecting ink droplets from the nozzle 10 by deforming the partition wall 13 in accordance with the drive signal to change the volume of the pressure chamber 7. The ejection pulse P1 includes an expansion pulse P1a that expands the volume of the pressure chamber 7 and a contraction pulse P1b that contracts the volume. In this manner, one ink droplet is ejected from the nozzle 10 by the pair of expansion pulse P1a and contraction pulse P1b. The pulse widths of the expansion pulse P1a and the contraction pulse P1b are 1AL. Here, this AL is ½ of the resonance period of the ink in the pressure chamber 7. Further, the expansion pulse P1a and the contraction pulse P1b have opposite polarities, and the distance between the centers of these pulses is 2AL. This is because the vibration generated by the expansion pulse P1a is canceled by the contraction pulse P1b, and the ejection of the next ink droplet is stabilized. Further, the drive voltage when ejecting ink droplets by the ejection pulse P1 is set to V1.

  Here, AL of 1/2 of the resonance period of the ink in the pressure chamber 7 is measured as follows. The AL is measured by measuring the impedance of the partition wall 13 of the ink jet head 101 filled with ink using a commercially available impedance analyzer, and obtaining the AL from the frequency at which the impedance of the partition wall 13 decreases due to the resonance of the ink in the pressure chamber 7. it can. It can also be obtained by measuring the voltage induced by the ink pressure vibration in the partition wall 13 by a synchroscope or the like and examining the vibration period of the voltage.

  Next, the prepulse P2 will be described with reference to FIG. The pre-pulse P2 is a pulse that is applied before the ejection pulse P1 and expands the volume of the pressure chamber 7 to such an extent that an ink droplet is not ejected from the nozzle 10. The drive voltage V2 of the prepulse P2 is such that no ink is ejected from the nozzle 10. At this time, the relationship between V1 and V2 is always V1> V2. Let Pw be the pulse width of the pre-pulse P2. In this embodiment, the pre-pulse P2 and the expansion pulse P1a of the ejection pulse P1 have the same polarity, and the distance between the centers of their pulse widths is 1AL. In this way, the prepulse P2 and the expansion pulse P1a of the discharge pulse P1 have the same polarity and the center thereof is set to 1AL, so that the phase of the pressure vibration generated in the prepulse P2 in the pressure chamber 7 and the expansion pulse P1a of the discharge pulse P1. The phases of the pressure oscillations generated in the above are reversed. By setting the phases of the pressure oscillations generated in the pressure chambers 7 to be reversed with each other, the pressure of the ink generated when the ink droplet is ejected by the expansion pulse P1a of the ejection pulse P1 is lowered. In other words, the pre-pulse P2 reduces the pressure generated when the ink droplet is ejected by the ejection pulse P1. When the pressure at which ink is ejected decreases, the ejection speed of the ink droplets decreases. Thus, by applying the pre-pulse P2 immediately before applying the ejection pulse P1, and adjusting the magnitude of the drive pulse, the ejection speed of the ink droplet can be corrected. The magnitude of the pre-pulse P2 is set using a preliminary experiment performed in advance or a fluid analysis described below.

  FIG. 8 shows a result of comparison of changes in ink droplet ejection speed when the pulse width PW of the pre-pulse P2 is made constant and the driving voltage V2 of the pre-pulse P2 is changed by using fluid numerical analysis. At this time, the pulse width PW of the pre-pulse P2 is 0.5AL. The numerical value on the horizontal axis in FIG. 8 is the ratio of the drive voltage V2 of the prepulse P2 to the drive voltage V1 of the ejection pulse P1. The drive voltage V2 was changed at 0.05, 0.10, 0.15, 0.20, 0.25, 0.50, and 0.75 times the drive voltage V1 of the ejection pulse P1, respectively. The vertical axis represents the ratio of the ink droplet ejection speed when the prepulse P2 is applied before the ejection pulse P1 with respect to when the prepulse P2 is not applied before the ejection pulse P1. From this graph, it can be said that the ink droplet ejection speed decreases as the drive voltage V2 of the prepulse P2 increases. This can be said that the greater the drive voltage V2 of the prepulse P2, the smaller the ink pressure when ejecting ink droplets. The drive voltage V2 of the pre-pulse P2 that corrects the ink droplet ejection speed can be set using a value obtained from such a relationship.

  Next, using fluid numerical analysis in the same way, the result of comparing the change in the ejection speed of the ink droplet when the driving voltage V2 of the prepulse P2 is made constant and the pulse width PW of the prepulse P2 is changed is compared. As shown in FIG. At this time, the pre-pulse voltage V2 is 0.15 times the driving voltage V1 of the ejection pulse P1. The numerical value on the horizontal axis in FIG. 9 is the ratio of the pulse width PW of the prepulse P2 to AL. The pulse width PW of the pre-pulse was changed at 0.25, 0.50, and 0.75 times AL. The vertical axis in FIG. 9 represents the ratio of the ink droplet ejection speed when the prepulse P2 is applied before the ejection pulse P1 when the prepulse P2 is not applied before the ejection pulse P1. . From this graph, it can be said that the ejection speed of ink droplets decreases as the pulse width PW of the pre-pulse P2 increases. This can be said that the longer the pulse width PW of the pre-pulse P2, the smaller the ink pressure when ejecting ink droplets. The drive voltage V2 of the pre-pulse P2 that corrects the ink droplet ejection speed can be set using a value obtained from such a relationship.

  Ink droplet ejection speed when one pressure chamber is driven as described above, ink droplet ejection speed when the pressure chamber is driven before one printing cycle, pressure adjacent to the pressure chamber The pre-pulse P2 so that the ink droplet ejection speed when the chamber is driven and the ink droplet ejection speed when both the pressure chamber and the ink chamber adjacent to the pressure chamber are driven are the same. Drive parameters (pulse voltage, pulse width, drive timing) are set and the pre-pulse P2 drive vane and other meters of the storage device shown in FIG. 3 are stored.

  Hereinafter, an embodiment of a driving method for correcting variations in the ejection speed of ink droplets using the pre-pulse P2 will be described below.

  The case where the pressure chamber 7 to be driven this time is the pressure chamber 7b and the pressure chambers 7b → 7c → 7a → 7b →. FIGS. 10A to 10H show total print patterns from one pressure cycle before the pressure chamber 7b to the current drive period. This is a drive signal for driving the pressure chambers 7a, 7b and 7c to the common electrodes l, m and n in FIGS. It is determined whether or not the pressure chamber 7b is driven even before one printing cycle and whether or not both adjacent pressure chambers 7c and 7a are driven from one pressure cycle before the printing cycle to the current driving period, It is determined whether the pre-pulse P2 is applied before the ejection pulse P1 in the current driving period of the chamber 7b. Of the drive signals shown in FIGS. 10A to 10H, only the drive signal shown in FIG. 10A has no pre-pulse P2 in the current drive period. That is, the pressure chamber 7b is driven only by the ejection pulse P1 during the current driving period only when the pressure chamber 7b is driven before one printing cycle and both the adjacent pressure chambers 7c and 7a are driven. In other print patterns, that is, print patterns represented by the drive signals in FIGS. 10B to 10H, a pre-pulse that is set in advance before the ejection pulse P1 when the pressure chamber 7b is driven in the current drive period. The drive parameter P2 is transferred from the storage device 25 to the drive signal generator 21 and applied to the drive electrode of the pressure chamber to drive the pressure chamber 7b.

  As described above, it is not only determined whether or not ink droplets are ejected from the adjacent pressure chamber from one printing cycle before this printing cycle, but also whether or not ink droplets are ejected one printing cycle before. By applying the pre-pulse P2 before the ejection pulse P1 using the preset voltage V2 and the pulse width Pw of the pre-pulse P2, the ejection speed of the ink droplet can be corrected. That is, in the present embodiment, the pre-pulse P2 reduces the ink pressure when ejecting ink with the ejection pulse P1 immediately after the pre-pulse P2, and decreases the ejection speed of the ink droplets. By doing so, when the pressure chamber 7c is driven this time, whether the pressure chamber 7c is driven before one printing cycle or whether the adjacent pressure chambers 7b and 7d are driven from one printing cycle to this time. Regardless of this, variation in the ejection speed of the ink droplets ejected from the pressure chamber 7c can be reduced, and the print quality can be improved.

  A specific embodiment for reducing the variation in the ejection speed of ink droplets as described above will be described below with reference to FIGS.

  When the print data 23 is input to the arithmetic device 24, based on the print data 23 in the arithmetic device 24, whether or not the pressure chamber to be driven this time is driven before one printing cycle, and the current driving from one printing cycle before. Whether the adjacent pressure chamber is driven or not is determined. Further, drive signal data corresponding to the determined print pattern result is read from the storage device 25 and supplied to the drive signal generating means 21. A drive signal is generated from the drive signal data supplied to the drive signal generating means 21, and ink droplet ejection control from the inkjet head 101 is performed by the inkjet drive circuit 22.

  Next, FIG. 11 shows a control flowchart specifically executed by the calculation unit 24 of the drive control unit. First, when a printing signal is applied to the drive electrode 8 of the selected pressure chamber 7 (step S1), ink is applied to the pressure chamber 7 and the pressure chamber adjacent to the pressure chamber before the printing chamber one printing cycle. It is determined whether an ejection pulse has been applied (step S2). Next, based on the determination result, when the pressure chamber 7 is not driven before one printing cycle and the pressure chamber adjacent to the pressure chamber is not driven, an ink droplet ejection pulse is applied (step S1). S5). Whether an ink discharge pulse was applied to the pressure chamber 7 adjacent to the pressure chamber 7 or one of the pressure chamber 7 and the pressure chamber adjacent to the pressure chamber before one printing cycle. Is selected from the storage device 25, and the prepulse data is read out (step S3). Next, the read pre-pulse is applied at a predetermined timing before the ejection pulse is applied (step S4). Drive control is performed according to the control flow as described above.

  The pre-pulse P2 used in this embodiment is only an example of a pulse for correcting the ink droplet ejection speed. For this reason, the pulse used as the pre-pulse P2 may be any other pulse as long as it corrects the pressure at the time of ink ejection of the ejection pulse P1. The same applies to the ink ejection pulse 1, and any other pulse can be applied as long as it is a pulse for ejecting ink. Further, in this embodiment, the discharge speed of the ink droplets this time is driven by the pressure chamber that is driven this time before one printing cycle, and both adjacent pressure chambers are driven from the time before one printing cycle to the current driving. In the example of adjusting the drive voltage V2 and pulse width PW of the pre-pulse P2 so as to match the ejection speed of the ink droplets in the pressure chamber that is currently driven at the time of the printing pattern, the ejection speed of other printing patterns is exemplified. The driving voltage V2 and the pulse width PW of the prepulse P2 may be adjusted so as to match.

  In this embodiment, an example has been given in which the number of time divisions in one printing cycle is three-division driving. However, other division numbers can be similarly applied.

It is sectional drawing of the inkjet head used for embodiment of this invention. It is the figure which showed typically the deformation | transformation of the partition of the inkjet head used for embodiment of this invention. FIG. 3 is an equivalent view of a circuit configuration for driving each pressure chamber of the ink jet head of FIG. It is a block diagram of a drive control part of an ink jet head used in an embodiment of the present invention. It is a figure of the conventional drive signal which shows the total printing pattern from one printing cycle before the pressure chamber driven this time to this driving cycle. It is the figure which put together the printing pattern of the adjacent pressure chamber from one pressure cycle before the pressure chamber driven this time to this drive cycle. It is a figure showing the conventional ratio of the discharge speed of the ink droplet this time when ink was not discharged before one printing cycle with respect to when ink was discharged before one printing cycle. It is a figure which shows the drive signal used by embodiment of this invention. It is a figure showing the ratio of the ejection speed of an ink drop when there is a pre-pulse with respect to when there is no pre-pulse when changing the drive voltage of the pre-pulse. It is a figure showing the ratio of the discharge speed of an ink drop when there is a prepulse with respect to when there is no prepulse when the pulse width of the prepulse is changed. It is a figure of the drive signal of a present Example which shows the total printing pattern from one printing cycle before the pressure chamber driven this time to this driving cycle. It is a control flowchart figure performed by the calculating part 24 of a drive control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 3 Piezoelectric member 4 Top plate frame 5 Top plate lid 6 Long groove 7 Pressure chamber 8 Drive electrode 9 Ink supply port 10 Nozzle 11 Nozzle plate 13 Partition 14 Ink supply path 21 Drive signal generation circuit 23 Print data 24 Arithmetic device 25 Storage device 101 Inkjet head

Claims (6)

A plurality of pressure chambers provided with nozzles for ejecting ink droplets, separated by partition walls of piezoelectric material, are arranged side by side, and the plurality of pressure chambers of an ink jet head provided with drive electrodes provided on the partition walls are defined as N ( Driving control of an inkjet head that divides every N ≧ 2) groups into (N + 1) groups, applies ejection pulses by time-division driving for each group to the drive electrodes, and deforms the partition walls to eject ink droplets. In the inkjet drive device comprising a section,
When one set of the (N + 1) sets has the time from the time to be driven to the time to be driven next as one printing cycle,
Among the plurality of pressure chambers, a pressure chamber to be driven and a drive electrode of the pressure chamber adjacent to the pressure chamber to be driven from the time before driving one printing cycle until the current driving is performed. And a drive control unit that applies a pre-pulse for correcting a preset ink droplet ejection speed to the drive electrode of the pressure chamber to be driven based on the determination result of whether or not the ejection pulse is applied to the pressure chamber. An ink jet head drive device.   The ink jet head drive device according to claim 1, wherein the pre-pulse adjusts a pulse voltage value so as to correct an ejection speed of the ink droplet.   The ink jet head drive device according to claim 1, wherein the pre-pulse adjusts a pulse width so as to correct an ejection speed of the ink droplet. A plurality of pressure chambers provided with nozzles for ejecting ink droplets, separated by partition walls of piezoelectric material, are arranged side by side, and the plurality of pressure chambers of an ink jet head provided with drive electrodes provided on the partition walls are defined as N ( In an inkjet head driving method in which every N ≧ 2) groups are divided into (N + 1) groups, and ejection pulses by time-division driving for each group unit are applied to the drive electrodes, and the partition is deformed to eject ink droplets. ,
When one set of the (N + 1) sets has the time from the time to be driven to the time to be driven next as one printing cycle,
Among the plurality of pressure chambers, a pressure chamber to be driven and a drive electrode of the pressure chamber adjacent to the pressure chamber to be driven from the time before driving one printing cycle until the current driving is performed. It is determined whether or not a discharge pulse is applied, and a pre-pulse for correcting a preset discharge speed of the ink droplet is applied to the drive electrode of the pressure chamber to be driven based on the determination result. Ink jet head driving method.   5. The ink jet head driving method according to claim 4, wherein the pre-pulse adjusts a pulse voltage value so as to correct an ejection speed of the ink droplet.   5. The ink jet head driving method according to claim 4, wherein the pre-pulse adjusts a pulse width so as to correct an ejection speed of the ink droplet.

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