Liquid ejection head drive circuit, liquid ejection head

Abstract

To provide a liquid discharge head drive circuit capable of achieving delay of drive timing between channels, and to provide a liquid discharge head.SOLUTION: A liquid discharge head drive circuit includes a common waveform generation part, a selection part and an output part. The common waveform generation part generates, in a drive action section of a channel for discharging a liquid from a nozzle, a repeating waveform having a cycle shorter than the drive action section. The selection part selects the section in which part of the repeating waveform is allowed to pass. The output part allows part of the repeating waveform to pass in the selected section, and imparts it to a capacitance type actuator which drives the channel as a drive waveform.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] An embodiment of the present invention relates to a liquid ejection head drive circuit and a liquid ejection head. [Background technology]

[0002] Liquid ejection heads that supply a predetermined amount of liquid to a predetermined position are known. Liquid ejection heads are mounted on, for example, inkjet printers, 3D printers, and dispensing devices. Inkjet printers eject droplets of ink from an inkjet head to form an image or the like on the surface of a recording medium. 3D printers eject droplets of modeling material from a modeling material ejection head, harden the droplets, and form a three-dimensional object. Dispensing devices eject droplets of a sample and supply a predetermined amount to a plurality of containers, etc.

[0003] A liquid ejection head has multiple channels that eject liquid. Each channel has a nozzle that ejects liquid, a pressure chamber that communicates with the nozzle, and an actuator. The liquid ejection head selects a channel from the multiple channels that ejects liquid, and drives the actuator by providing a drive signal. When the actuator is driven, the volume of the pressure chamber filled with liquid changes, and liquid is ejected from the nozzle.

[0004] Liquid ejection heads with multiple channels have problems such as crosstalk between channels caused by pressure vibrations and voltage drops caused by current concentration when driving multiple channels. One solution to these problems is to shift the drive timing between surrounding channels. However, to achieve a delay in the drive timing between channels, a drive waveform and its wiring pattern must be prepared for each delay amount. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3264422 [Patent Document 2] Patent No. 3618733 [Patent Document 3] JP 2015-174401 A [Patent Document 4] JP 2011-62821 A [Patent Document 5] JP 2008-221793 A [Patent Document 6] JP 2002-154207 A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a liquid ejection head drive circuit and a liquid ejection head that are capable of realizing a delay in drive timing between channels. [Means for solving the problem]

[0007] The liquid ejection head drive circuit according to the embodiment of the present invention includes a common waveform generating section, a selection section, and an output section. The common waveform generating section selects a channel for ejecting liquid from a nozzle. Dispensing a single drop of liquid Within a drive operation section, a period shorter than that drive operation section Changes to charging and discharging waveforms A repeating waveform is generated. The selection unit selects the repeating waveform. The charging waveform and the discharging waveform The output section is selected to pass through the selected section. The charging waveform and the discharging waveform The driving waveform is applied to the capacitive actuator that drives the channel. Charge and discharge do. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram of an inkjet printer equipped with an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the inkjet head. [Diagram 3] FIG. 2 is a cross-sectional view of an actuator of the inkjet head. [Figure 4]FIG. 2 is a block diagram of an inkjet head drive circuit according to an embodiment. [Diagram 5] FIG. 4 is a detailed diagram of a selection drive circuit in the inkjet head drive circuit. [Figure 6] FIG. 4 is a detailed diagram of a selection circuit in the selection drive circuit. [Figure 7] 4 is a timing chart of the operation of the inkjet head driving circuit. [Figure 8] 4 is a timing chart of the operation of the inkjet head driving circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a liquid ejection head according to an embodiment will be described in detail with reference to the accompanying drawings, in which the same components are denoted by the same reference numerals.

[0010] As an example of an image forming apparatus equipped with a liquid ejection head according to an embodiment, an inkjet printer 10 that prints an image on a recording medium will be described. Fig. 1 shows a schematic configuration of the inkjet printer 10. Inside a housing 11, the inkjet printer 10 has a cassette 12 that stores a sheet S, which is an example of a recording medium, an upstream transport path 13 for the sheet S, a transport belt 14 that transports the sheet S taken out of the cassette 12, a plurality of inkjet heads 100-103 that eject ink droplets toward the sheet S on the transport belt 14, a downstream transport path 15 for the sheet S, an ejection tray 16, and a control board 17. An operation unit 18 that is a user interface is disposed on the upper side of the housing 11.

[0011] Image data to be printed on the sheet S is generated, for example, by a computer 200, which is an externally connected device. The image data generated by the computer 200 is sent to a control board 17 of the inkjet printer 10 via a cable 201 and connectors 202 and 203.

[0012] The pickup roller 204 supplies the sheets S one by one from the cassette 12 to the upstream conveying path 13. The upstream conveying path 13 is composed of a pair of feed rollers 131 and 132 and sheet guide plates 133 and 134. The sheet S is fed to the upper surface of the conveying belt 14 via the upstream conveying path 13. An arrow 104 in the figure indicates the conveying path of the sheet S from the cassette 12 to the conveying belt 14.

[0013] The conveyor belt 14 is a mesh-like endless belt with many through holes formed on its surface. Three rollers, a drive roller 141 and driven rollers 142 and 143, support the conveyor belt 14 so that it can rotate freely. A motor 205 rotates the conveyor belt 14 by rotating the drive roller 141. The motor 205 is an example of a drive device. In the figure, 105 indicates the rotation direction of the conveyor belt 14. A negative pressure container 206 is disposed on the back side of the conveyor belt 14. The negative pressure container 206 is connected to a fan 207 for reducing pressure. The fan 207 creates a negative pressure inside the negative pressure container 206 by forming an airflow, and adsorbs and holds the sheet S on the upper surface of the conveyor belt 14. In the figure, 106 indicates the flow of the airflow.

[0014] Inkjet heads 100-103, which are an example of liquid ejection heads, are arranged to face sheet S, which is attracted to and held on conveyor belt 14, with a small gap of, for example, 1 mm between them. Each of inkjet heads 100-103 ejects ink droplets toward sheet S. When sheet S passes below inkjet heads 100-103, the inkjet heads print images. Each of inkjet heads 100-103 has the same structure, except that they eject different colors of ink. The ink colors are, for example, cyan, magenta, yellow, and black.

[0015] The inkjet heads 100-103 are connected to ink tanks 315-318 and ink supply pressure adjusting devices 321-324 via ink flow paths 311-314, respectively. The ink tanks 315-318 are disposed above the inkjet heads 100-103. During standby, the ink supply pressure adjusting devices 321-324 adjust the pressure inside the inkjet heads 100-103 to a negative pressure, for example, -1.2 kPa, relative to atmospheric pressure so that ink does not leak from the nozzles 25 (see FIG. 2) of the inkjet heads 100-103. During image formation, the ink in the ink tanks 315-318 is supplied to the inkjet heads 100-103 by the ink supply pressure adjusting devices 321-324.

[0016] After the image is formed, the sheet S is sent from the conveyor belt 14 to a downstream conveying path 15. The downstream conveying path 15 is composed of pairs of feed rollers 151, 152, 153, and 154, and sheet guide plates 155 and 156 that define the conveying path of the sheet S. The sheet S passes through the downstream conveying path 15 and is sent from a discharge port 157 to a discharge tray 16. An arrow 107 in the figure indicates the conveying path of the sheet S.

[0017] Next, a description will be given of the configuration of the inkjet heads 100 to 103. The inkjet head 100 will be described below with reference to Figures 2 and 3, but the inkjet heads 101 to 103 have the same structure as the inkjet head 100.

[0018] 2, the inkjet head 100 includes a nozzle head section 2 which is an example of a liquid ejection section, and a flexible printed wiring board 3 which is an example of a printed wiring board. The nozzle head section 2 includes a nozzle plate 21, an actuator substrate 22, a sealing member 23 which seals the openings of a pressure chamber 51 and an air chamber 52 formed in the actuator substrate 22, and an ink supply port 24 formed in the sealing member 23. The ink supply port 24 is connected to an ink supply pressure adjustment device 321 shown in FIG. 1 via an ink flow path 311.

[0019] The flexible printed wiring board 3 is connected to the actuator board 22 of the nozzle head unit 2 and to a printed circuit board 4 that serves as a relay board. The flexible printed wiring board 3 is equipped with a driving IC (Integrated Circuit) 31 that is a driver chip (hereinafter referred to as a driving IC). The driving IC 31 temporarily stores print data sent from the control board 17 of the inkjet printer 10 via the printed circuit board 4, and provides driving signals to each channel so as to eject ink at a predetermined timing.

[0020] The nozzle plate 21 is a rectangular plate made of, for example, a resin such as polyimide or a metal such as stainless steel. A plurality of nozzles 25 for ejecting ink are formed on the surface of the nozzle plate 21. The nozzle density is set within the range of, for example, 150 to 1200 dpi.

[0021] The actuator substrate 22 is a rectangular substrate made of, for example, insulating ceramics. As shown in FIG. 3, a plurality of ink pressure chambers 51 and air chambers 52 are alternately formed in the actuator substrate 22 along a first direction, for example, the X direction. The pressure chambers 51 communicate with the nozzles 25. The pressure chambers 51 communicate with the ink supply ports 24 via a common ink chamber (not shown) formed in, for example, the actuator substrate 22 or the sealing member 23. That is, the nozzle head section 2 supplies ink to the pressure chambers 51 of each channel through the ink supply ports 24. That is, the nozzle head section 2 serves both as a liquid ejection section and a liquid supply section. On the other hand, the air chambers 52 arranged adjacent to the pressure chambers 51 are closed spaces that do not communicate with the nozzles 25 and the common ink chamber (not shown). The pressure chamber 51 and the air chamber 52 are formed by cutting out, for example, a rectangular groove shape in a second direction, for example, the Z direction, two piezoelectric members 26, 27 that are stacked in directions with opposite polarization directions (for example, facing directions) on the actuator substrate 22. That is, the pressure chamber 51 and the air chamber 52 are partitioned by the side walls of the piezoelectric members 26, 27 that are stacked in a third direction, for example, the Y direction.

[0022] The electrode 53 is integrally formed on the bottom and both side surfaces of the pressure chamber 51. The electrode 53 of the pressure chamber 51 is connected to an individual wiring 54, which is a wiring member. The electrode 55 is integrally formed on the bottom and both side surfaces of the air chamber 52. The electrode 55 of the air chamber 52 is connected to a common wiring 56, which is a wiring member. That is, the connection point of the electrode 53 of the pressure chamber 51 and the individual wiring 54 is one terminal of the actuator 5. The connection point of the electrode 55 of the air chamber 52 and the common wiring 56 is the other terminal of the actuator 5. The electrodes 53, 55, the individual wiring 54 and the common wiring 56 are formed of, for example, a nickel thin film. The individual wiring 54 is connected to the driving IC 31 (i.e., the driving circuit of each channel). The driving IC 31 provides a driving voltage as a driving signal to the actuator 5 of each channel. The voltages V1 and V2 are provided to the driving IC 31 as a power source for the driving voltage. The common wiring 56 is connected to, for example, ground (GND). With this configuration, when a drive voltage is applied to the actuator 5, an electric field is applied in a direction intersecting (preferably perpendicular to) the polarization axes of the piezoelectric members 26 and 27, and the piezoelectric members 26 and 27 forming the side walls of the actuator 5 in the X direction deform symmetrically in the X direction in shear mode.

[0023] That is, the ink pressure chamber 51 is formed by being sandwiched between a pair of columnar actuators 5 using piezoelectric members 26, 27. A potential difference is applied to both walls of the columnar actuator 5, i.e., the inner wall and the outer wall of the pressure chamber 51, and the capacitive actuator 5 using the piezoelectric members 26, 27 is charged / discharged, thereby deforming the actuator 5. This changes the volume of the pressure chamber 51, and as a result, the ink pressure inside the pressure chamber 51 changes. Ink is ejected from the nozzle 25 by adjusting the magnitude and timing of this change.

[0024] 4 is a block diagram of the inkjet head drive circuit 6 in the drive IC 31. The inkjet head drive circuit 6 includes a common waveform generation section 61, a timing generation section 62, an image generation section 63, and a selection drive circuit 64.

[0025] The common waveform generating unit 61 generates a repeating waveform, which will be described in detail later, as a common waveform. The common waveform is sent to a selection drive circuit 64. The timing generating unit 62 sends a waveform passing pulse and a group selection signal to the selection drive circuit 64, and synchronizes the operation timing of the common waveform generating unit 61 and the image generating unit 63. The image generating unit 63 generates image data for each channel and sends it to the selection drive circuit 64. The image data generated for each channel includes information on whether or not to eject ink from that channel, and gradation information of the dots to be formed when ink is ejected.

[0026] As shown in FIG. 5, the selective drive circuit 64 includes a selection unit 7 and an output unit for each channel (ch1 to chN). The selection unit 7 is, for example, a selection circuit such as a selector. An example of the selection circuit is an 8to1 selection circuit. The output unit is, for example, a switch 71. An example of the switch 71 is a CMOS analog switch. Image data (ch1 image to chN image) from the image generation unit 63 is input to the selection unit 7 of the corresponding channel. Also, the waveform passing pulse and the group selection signal from the timing generation unit 62 are input to the selection unit 7 of each channel. The selection unit 7 selects one of a plurality of prepared waveform passing pulses based on the image data and the group selection signal. Then, the selection unit 7 outputs a passing signal based on the selected waveform passing pulse. The passing signal controls the ON / OFF of the switch 71. While the switch 71 is ON, the common waveform passes through the switch 71 and applies a driving voltage to the actuator 5. That is, a part of the common waveform passes through the switch 71 and becomes a driving waveform and is applied to the actuator 5.

[0027] The selection unit 7 uses an 8to1 selection circuit shown in FIG. 6 as an example. For example, a 2-bit signal is provided to each of the inputs b0 and b1 for inputting image data. For example, when ink is not ejected, a signal of "0,0" is provided to the inputs b0 and b1, a signal of "1,0" is provided to the inputs b0 and b1, and a signal of "1,1" is provided to the inputs b2 for assigning the channel to either group A or group B. For example, a 1-bit signal of "1" is provided for group A and "0" is provided for group B. A waveform passing pulse, which will be described later in detail, is provided to each of the inputs A0 to A3 and inputs B0 to B3 of the 8to1 selection circuit. The 8to1 selection circuit, which is the selection unit 7, selects one of these multiple waveform passing pulses based on the signals provided to the inputs b0 to b2. Then, a passing signal based on the selected waveform passing pulse is output and provided to the switch 71.

[0028] The common waveform includes a first drive waveform element constituting a cancel pulse portion and a second drive waveform element constituting a cancel pulse portion, as shown in the time chart of Fig. 7. The first drive waveform element and the second drive waveform element are respectively a charge and discharge waveform (Charge and discharge waveforms) The change part of the pulse is a repetition of a triangular wave. As an example, when the voltage V1 is a positive voltage, the voltage V2 is a negative voltage, and the voltage V3 is 0V (=GND), the first drive waveform element constituting the back-firing pulse part is a triangular wave that oscillates between the negative voltage V2 and the voltage V3 (=0V), and the second drive waveform element constituting the cancel pulse part is a triangular wave that oscillates between the voltage V3 (=0V) and the positive voltage V1. The repetition period of the triangular wave is shorter than the drive operation section of the channel that ejects ink. Preferably, the period is shorter than the drive operation section that ejects one drop of ink. More preferably, the period is shorter than the drive operation section of the back-firing pulse part that does not include the cancel pulse part. Therefore, in the case of a multi-drop method in which one dot is formed by a total of multiple drops, the period is shorter than the drive operation section that ejects one drop of ink. A preferable example of the repetition period of the triangular wave is 1 MHz. That is, it is a triangular wave that rises in 500 ns and falls in 500 ns.

[0029] A plurality of types of pulse trains are prepared for each of the groups A and B as the waveform passing pulses. The group A pulse train is a waveform A3 passing pulse and a waveform A1 passing pulse shown in FIG. 7. Each passing pulse is provided to, for example, the inputs A1 and A3 of the 8to1 selection circuit shown in FIG. 6, respectively, and the selection unit 7 selects one of them as described above. Similarly, the group B pulse train is a waveform B3 passing pulse and a waveform B1 passing pulse shown in FIG. 7. Each passing pulse is provided to, for example, the inputs B1 and B3 of the 8to1 selection circuit shown in FIG. 6, respectively, and the selection unit 7 selects one of them as described above. The 8to1 selection circuit can select four types of pulse trains for each of the groups A and B. The timing chart in FIG. 7 illustrates two types of passing pulses, namely, passing pulses (waveforms A3 and B3) that form high-gradation dots and passing pulses (waveforms A1 and B1) that form low-gradation dots. The waveform passing pulses in the same group have different pulse widths and intervals. The waveform A3 passing pulse and waveform B3 passing pulse that form dots with high gradation have the same pulse width and interval, but since they are in different groups, there is a delay in the drive timing between them. The same is true for the waveform A1 passing pulse and waveform B1 passing pulse that form dots with low gradation. On the other hand, the waveform A3 passing pulse and waveform A1 passing pulse of the same group have no delay in the drive timing, but have different pulse widths. By changing the pulse width in this way, the drive voltage can be adjusted. The same is true for the waveform B3 passing pulse and waveform B1 passing pulse of group B.

[0030] Next, the operation of the inkjet head drive circuit 6 will be described with particular reference to Figures 5 and 7. Note that the following description will be given, as an example, of an operation in which odd-numbered channels (ch1, 3...n-1) are assigned to group A and even-numbered channels (ch2, 4...n) are assigned to group B and driven accordingly. Furthermore, as an example, it is assumed that channel 1 (ch1) and channel 2 (ch2) print high-tone dots, channel 3 (ch3) and channel 4 (ch4) print low-tone dots, and channel 5 (ch5) does not print.

[0031] The common waveform generating unit 61 generates a triangular wave as a repeating waveform and sends it to the selection driving circuit 64. The image generating unit 63 generates image data for each channel based on data sent from the control board 17 of the inkjet printer 10 and sends it to the selection driving circuit 64. The timing generating unit 62 synchronizes the operation timing of the common waveform generating unit 61 and the image generating unit 63, and sends a waveform passing pulse and a group selection signal to the selection driving circuit 64.

[0032] The selection unit 7 of each channel selects a waveform passing pulse based on the image data and the group selection signal. For example, for channel 1 (ch1), a signal to select group A is applied to input b2, and signals to form high gradation dots are applied to inputs b0 and b1. This causes the selection unit 7 of channel 1 (ch1) to select a waveform A3 passing pulse that forms high gradation dots at the drive timing of group A.

[0033] The selection unit 7 provides a passing signal according to the selected waveform A3 passing pulse to the switch 71, which is an output unit. In the case of the waveform A3 passing pulse, in the section of the first driving waveform element constituting the back-pulse pulse section, the pulse turns ON at the falling part of the triangular wave, turning the switch 71 ON. While the pulse is ON, the switch 71 maintains the ON state and negatively charges the actuator 5 toward the voltage V2. As a result, both side walls of the pressure chamber 51 deform outward, and the volume of the pressure chamber 51 expands. After that, the pulse turns OFF and the switch 71 turns OFF, but the capacitive actuator 5 retains the voltage of the driving waveform at the moment the switch 71 turns OFF, even if the switch 71 turns OFF. Next, the pulse turns ON at the rising part of the triangular wave, turning the switch 71 ON. While the pulse is ON, the switch 71 maintains the ON state and discharges the actuator 5. Due to this discharge, the actuator 5, which had been deformed outward, returns to its original state, and the expanded pressure chamber 51 contracts to its original volume, and ink is ejected from the nozzle 25.

[0034] Next, in the section of the second drive waveform element constituting the cancel pulse portion, the pulse turns ON at the rising portion of the triangular wave, turning the switch 71 ON. While the pulse is ON, the switch 71 maintains the ON state, and the actuator 5 is positively charged toward the voltage V1. This charging causes both side walls of the pressure chamber 51 to deform inward, and the volume of the pressure chamber 51 contracts. This contraction attenuates the residual vibration. Next, the pulse turns ON at the falling portion of the triangular wave, turning the switch 71 ON. While the pulse is ON, the switch 71 maintains ON, and the actuator 5 is discharged. Note that, when the actuator 5 is repeatedly driven, for example, a flat portion at voltage V3 (=0V) may be formed after the second drive waveform element, and the pulse may be turned ON here to reset (discharge) the actuator 5 to 0V. In this way, the channel 1 (ch1) is driven by the waveform A3, which is a drive waveform obtained by passing a part of the repetitive waveform, which is a common waveform.

[0035] Similarly, channel 2 (ch2) is driven by waveform B3. However, channel 2 (ch2) belonging to group B is driven with a delay relative to channel 1 (ch1) belonging to group A. For example, if the period of the triangular wave is 1 MHz, group B is driven with a delay of 1000 ns in the time chart of FIG. 7. That is, in this embodiment, multiple channels are divided into groups, and simultaneous driving is allowed in the same group, while simultaneous driving is avoided in different groups. By delaying between channels in this way, crosstalk due to pressure vibration can be suppressed. The reason for grouping by odd numbers and even numbers is that crosstalk between adjacent channels is the largest. Crosstalk between channels includes crosstalk through the ink flow path, crosstalk due to mechanical coupling, and electrical coupling (such as that due to common impedance), and all of these are effective. In addition, it is possible to suppress voltage drop due to current concentration when multiple channels are driven simultaneously. However, although grouping by odd numbers and even numbers is a preferred example, this is not limiting. Which channels are divided into which groups can be freely set by the group selection signal from the timing generation unit 62. Of course, the number of groups is not limited to two, group A and group B, and may be three or more.

[0036] Similarly, channel 3 (ch3) is driven by waveform A1. The waveform A1 passing pulse has a shorter pulse width than the waveform A3 passing pulse, so the actuator charging / discharging time is shorter and there is less change in the volume of the pressure chamber 51. In other words, the amount of ink ejected from the nozzle 25 is reduced to print low gradation dots. Similarly, channel 4 (ch4) is driven by waveform B1 at the drive timing of group B to print low gradation dots.

[0037] For example, a waveform A0 passing pulse without a pulse (not shown) is applied to the channel 5 (ch) that does not eject ink. Similarly, for group B, for example, a waveform B0 passing pulse without a pulse (not shown) is applied to the channel that does not eject ink. As a modified example, when a precursor is performed, that is, when it is necessary to apply a slight vibration to the actuator 5 of the channel that does not eject ink, as shown in FIG. 8, a waveform A0 passing pulse / waveform B0 passing pulse with a short pulse width that drives with a low voltage that does not eject ink may be applied only in the section of the second driving waveform element. In other words, it is possible to generate both a driving waveform that ejects ink and a waveform that applies a slight vibration without ejecting ink from a repeating waveform such as a triangular wave.

[0038] According to the above-described embodiment, a common waveform of a repeating waveform is used, and each channel that ejects ink passes a portion of the common waveform to create a drive waveform. This makes it possible to realize a delay in drive timing between channels, for example, without having to prepare a drive waveform and its wiring pattern for each delay amount.

[0039] As a modification of the triangular wave, the period of the triangular wave may be different between the sections of the first drive waveform element and the second drive waveform element. Also, the amplitude of the triangular wave of the first drive waveform element and the second drive waveform element may be the same. Although a triangular wave has been given as an example of a preferred common waveform, it is not limited to a triangular wave. For example, a repeating waveform in the form of an exponential function may be used. Also, although a back-and-forth drive waveform has been given as an example, a drive waveform other than back-and-forth drive waveform may be used. Furthermore, a multi-drop drive waveform may be used.

[0040] The inkjet head 100 is not limited to the actuator 5 of a shear mode type in which the pressure chambers 51 and the air chambers 52 are arranged alternately. For example, both the nozzles 25 and the actuators 5 may be arranged in multiples on the surface of the nozzle plate 21. Other drop-on-demand piezoelectric actuators 5 may also be used.

[0041] In the above embodiment, the inkjet head 100 of the inkjet printer 10 has been described as an example of a liquid ejection device, but the liquid ejection device may also be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0042] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0043] 10. Inkjet Printer 100~103 Inkjet head 2 Nozzle head 25 Nozzles 31 Driver IC 5 Actuators 51 Pressure Chamber 52 Air chamber 6 Inkjet head drive circuit 61 Common waveform generator 62 Timing Generation Unit 63 Image Generation Unit 64 Selective drive circuit 7 Selection section 71 Switch

Claims

1. a common waveform generating unit that generates a repeating waveform that changes between a charging waveform and a discharging waveform in a period shorter than a driving operation section in which one drop of liquid is discharged from a channel that discharges liquid from a nozzle; a selection unit that selects a section through which the charging waveform and the discharging waveform are passed in the repetitive waveform; A liquid ejection head driving circuit characterized by comprising: an output section that passes the charging waveform and the discharging waveform through the section selected by the selection section and applies them as a driving waveform to the capacitive actuator of the channel to charge and discharge it.

2. A liquid ejection head driving circuit as described in claim 1, characterized in that a plurality of waveform passing pulses are prepared in which the sections through which the charging waveform and the discharging waveform in the repetitive waveform are passed are different from each other, and the selection unit selects one of them to select the section through which the charging waveform and the discharging waveform in the repetitive waveform are passed.

3. 3. The liquid ejection head drive circuit according to claim 2, wherein the selection section selects the waveform passing pulse in accordance with image data.

4. The channels are classified into one of a plurality of groups; 3. The liquid ejection head drive circuit according to claim 2, wherein the selection section selects the waveform passing pulse in accordance with which group the channel is assigned to.

5. A plurality of channels each having a nozzle and an actuator for ejecting liquid; A liquid supply unit that supplies a liquid to the channel; A liquid ejection head comprising the liquid ejection head drive circuit according to any one of claims 1 to 4.

Images