Liquid ejecting head

Abstract

The invention provides a liquid ejection head capable of suppressing in-row linearity reduction of landing positions of liquid ejected from a plurality of nozzles and suppressing current concentration during driving. The liquid ejection head according to an embodiment is configured such that adjacent nozzles belong to a first group and a second group, respectively, and the driving timings of the nozzles in each group are different from each other by a primary offset time, and the driving timings of the nozzles in each group are different from each other by a secondary offset time. The main offset time is set to 1AL. With respect to the secondary offset time, M settings of A + K (M-1) + / -i are assigned to the first group, N settings of B + K (N-1) + / -j are assigned to the second group, M is an integer of 1, 2,..., and N is an integer of 1, 2,.... In addition, the difference between the driving timings of adjacent pressure chambers is set to be within the range of 1AL + / -(A + K-B + i) and 1AL + / -(A + K-B + j).

Description

Technical Field

[0001] Embodiments of the present invention relate to a liquid ejection head. Background Art

[0002] There is known a liquid ejection head that supplies a predetermined amount of liquid to a predetermined position. The liquid ejection head is mounted, for example, on an inkjet printer, a 3D printer, a dispensing device, or the like. The inkjet printer ejects ink droplets from an inkjet head to form an image or the like on the surface of a recording medium. The 3D printer ejects droplets of a modeling material from a modeling material ejection head and cures them to form a three-dimensional object. The dispensing device ejects droplets of a sample to supply a predetermined amount to a plurality of containers or the like.

[0003] The liquid ejection head has a plurality of channels for ejecting liquid. Each channel includes a nozzle for ejecting liquid, a pressure chamber communicating with the nozzle, and an actuator for changing the volume of the pressure chamber. The control unit of the liquid ejection head selects a channel for ejecting liquid from the plurality of channels and applies a drive signal to the actuator to drive it. When the actuator is driven, the volume of the pressure chamber filled with liquid changes, and liquid is ejected from the nozzle.

[0004] In a multi-nozzle liquid ejection head that ejects liquid from a plurality of nozzles, adjacent nozzles among the plurality of nozzles are set to belong to different groups. When ejecting liquid, the control unit is set so that the stagger amount of the timing of applying a drive signal to the actuator reaches an integer multiple of the conduction pulse peak (AP) or half of the natural vibration period (AL) in the pressure chamber between groups, and the drive timings between groups are different from each other. However, if the number of groups reaches three or more, the stagger amount of the drive timings between groups becomes large. For example, there is a case where the in-column linearity of the landing position (drop position) when ejecting liquid at a high frequency decreases. On the other hand, when the number of groups is two, the number of actuators driven simultaneously increases, resulting in current concentration.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-107860

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2000-238248

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-32715

[0010] Patent Document 4: Japanese Patent Application Laid-Open No. 2019-98721 Summary of the Invention

[0011] Technical Problem to be Solved by the Invention

[0012] The technical problem to be solved by the present invention is to provide a liquid ejection head that can suppress a decrease in the in-column linearity of the landing positions of liquids ejected from a plurality of nozzles and can suppress current concentration during driving.

[0013] Solution for Solving the Technical Problem

[0014] The liquid ejection head according to an embodiment of the present invention includes a nozzle portion, a plurality of pressure chambers, a plurality of piezoelectric actuators, and a control unit. The nozzle portion has a plurality of nozzles for ejecting a liquid arranged therein. The plurality of pressure chambers are individually connected to the plurality of nozzles, and the liquid is filled in the plurality of pressure chambers, respectively. The plurality of piezoelectric actuators change the volume in the plurality of pressure chambers, respectively. The control unit causes the volume in the pressure chamber to expand and contract by applying a drive signal to the piezoelectric actuator, thereby ejecting the liquid from the nozzle. In the liquid ejection head, the drive timings for applying the drive signal are different between the first group and the second group mainly by staggering the time, and the drive timings for applying the drive signal to the nozzles within each group are different from each other mainly by staggering the time. The main stagger time is set to be one time (1AL) of half of the natural vibration period in the pressure chamber. Regarding the secondary stagger time, when represented by a time A and a time B shorter than the 1AL, a certain time interval K shorter than the 1AL, and a fine adjustment time i and a fine adjustment time j shorter than the time A or the time B, the first group is assigned M settings of A + K(M - 1) ± i, and the second group is assigned N settings of B + K(N - 1) ± j, where M is an integer of 1, 2,..., and N is an integer of 1, 2,.... In addition, the drive timings are arranged such that the difference in drive timings between adjacent nozzles is within an allowable range of 1AL ± (A + K - B + i) and within an allowable range of 1AL ± (A + K - B + j). Description of the Drawings

[0015] Figure 1 It is an overall configuration diagram of an inkjet printer including an inkjet head according with the first embodiment.

[0016] Figure 2 It is a perspective view of the above inkjet head.

[0017] Figure 3 It is an internal configuration diagram of the above inkjet head.

[0018] Figure 4 It is a cross-sectional view of the actuator of the above inkjet head.

[0019] Figure 5 It is a circuit diagram of the control system of the above inkjet head.

[0020] Figure 6 It is a drive waveform applied to the above actuator.

[0021] Figure 7 Actuator operation explanatory diagram for the above-described driving waveform.

[0022] Figure 8 Diagram for explaining the grouping of nozzles of the above-described inkjet head.

[0023] Figure 9 Chart showing the results of crosstalk between two groups.

[0024] Figure 10 Diagram showing the arrangement of driving timing stagger times of the first embodiment and the comparative example.

[0025] Figure 11 Chart plotting the total stagger times of the first embodiment and the comparative example.

[0026] Figure 12 Chart showing the results of crosstalk of the first embodiment and the comparative example.

[0027] Figure 13 Chart showing the landing positions of the liquid of the first embodiment and the comparative example.

[0028] Figure 14 Diagram showing the arrangement of driving timing stagger times of the second embodiment.

[0029] Figure 15 Diagram showing the arrangement of driving timing stagger times of the third embodiment.

[0030] Explanation of reference numerals

[0031] 10: Inkjet printer; 100 - 103: Inkjet head; 2: Head; 20: Nozzle; 5: Pressure chamber; 51: Air chamber; 8: Actuator. Detailed description of the specific embodiment

[0032] The liquid ejection head according to the embodiment will be described in detail below with reference to the accompanying drawings. It should be noted that in each figure, the same reference numerals are assigned to the same components.

[0033] (First embodiment)

[0034] The inkjet printer 10 that prints an image on a recording medium will be described as an example of an image forming apparatus equipped with the liquid ejection head according to the embodiment. Figure 1Shows a schematic configuration of an inkjet printer 10. Inside the housing 11 of the inkjet printer 10, a cassette 12 for accommodating a sheet S as an example of a recording medium, an upstream conveyance path 13 of the sheet S, a conveyor belt 14 for conveying the sheet S taken out from the cassette 12, a plurality of inkjet heads 100 to 103 for ejecting ink droplets toward the sheet S on the conveyor belt 14, a downstream conveyance path 15 of the sheet S, a discharge tray 16, and a control board 17 are arranged. An operation unit 18 as a user interface is arranged on the upper side of the housing 11.

[0035] Image data printed on the sheet S is generated, for example, by a computer 200 as an external connection device. The image data generated by the computer 200 is transported to the control board 17 of the inkjet printer 10 through a cable 201, connectors 202, 203.

[0036] A pickup roller 204 supplies the sheet S one by one from the cassette 12 to the upstream conveyance path 13. The upstream conveyance path 13 is composed of conveyance roller pairs 131, 132 and sheet guide plates 133, 134. The sheet S is conveyed to the upper surface of the conveyor belt 14 via the upstream conveyance path 13. The arrow 104 in the figure indicates the conveyance path of the sheet S from the cassette 12 to the conveyor belt 14.

[0037] The conveyor belt 14 is a net-like endless belt having a relatively large number of through holes formed on its surface. Three rollers, a driving roller 141, driven rollers 142, 143, rotatably support the conveyor belt 14. A motor 205 rotates the conveyor belt 14 by rotating the driving roller 141. The motor 205 is an example of a driving device. The number 105 in the figure indicates the rotation direction of the conveyor belt 14. A negative pressure container 206 is arranged on the back side of the conveyor belt 14. The negative pressure container 206 is connected to a fan 207 for decompression. The fan 207 makes the inside of the negative pressure container 206 negative pressure by forming an air flow, so as to adsorb and hold the sheet S on the upper surface of the conveyor belt 14. The number 106 in the figure indicates the flow of the air flow.

[0038] Inkjet heads 100 to 103 as an example of liquid ejection heads are arranged to face the sheet S adsorbed and held on the conveyor belt 14 with a minute gap of, for example, 1 mm therebetween. The inkjet heads 100 to 103 eject ink droplets toward the sheet S respectively. The inkjet heads 100 to 103 print an image when the sheet S passes below them. Each of the inkjet heads 100 to 103 has the same structure except for the color of the ejected ink. The colors of the ink are, for example, cyan, magenta, yellow, and black.

[0039] The inkjet heads 100 to 103 are respectively connected to the ink tanks 315 to 318 and the ink supply pressure adjustment devices 321 to 324. Each of the ink tanks 315 to 318 is arranged above each of the inkjet heads 100 to 103. In standby, each of the ink supply pressure adjustment devices 321 to 324 adjusts the pressure inside each of the inkjet heads 100 to 103 to a negative pressure relative to the atmospheric pressure, for example, -1.2 kPa, so that ink does not leak from the nozzles 20 (refer to Figure 2 ). When forming an image, the ink from each of the ink tanks 315 to 318 is supplied to each of the inkjet heads 100 to 103 through the ink supply pressure adjustment devices 321 to 324.

[0040] After image formation, the sheet S is conveyed from the conveyor belt 14 to the downstream conveyance path 15. The downstream conveyance path 15 is constituted by conveyance roller pairs 151, 152, 153, 154 and sheet guide plates 155, 156 that define the conveyance path of the sheet S. The sheet S is conveyed from the discharge port 157 to the discharge tray 16 via the downstream conveyance path 15. The arrow 107 in the figure indicates the conveyance path of the sheet S.

[0041] Next, the configuration of the inkjet heads 100 to 103 will be described. Hereinafter, the inkjet head 100 will be described, but the inkjet heads 101 to 103 have the same structure as the inkjet head 100. Figures 2 - 4

[0042] As Figures 2 - 4 shown, the inkjet head 100 includes a head 2 as an example of a liquid ejection unit. The head 2 is connected to a flexible printed wiring board 3 as an example of a thin film wiring board. The flexible printed wiring board 3 is connected to a printed circuit board 4 as an example of a relay board.

[0043] The multi-nozzle head 2 includes a nozzle plate 21 as an example of a nozzle unit in which a plurality of nozzles 20 are arranged, an actuator substrate 22 that forms actuators corresponding to the respective nozzles 20, a frame member 23 that forms a common ink chamber 26, and an ink supply unit 24 that supplies ink to the common ink chamber 26.

[0044] The nozzle plate 21 is, for example, a rectangular plate formed of a resin such as polyimide or a metal such as stainless steel. The nozzles 20 for ejecting ink are arranged in a row in the X direction of the first direction on the surface of the nozzle plate 21. It should be noted that arranging in a row does not necessarily mean that the centers of the nozzles 20 are on a straight line. For example, they can also be offset in the Y direction of the second direction. The nozzle density is, for example, set within the range of 150 to 1200 dpi. The actuator substrate 22 is, for example, a rectangular substrate formed of insulating ceramic.

[0045] ​The frame member 23 surrounds the periphery of the lower portion of the actuator substrate 22. The opening on the lower surface of the frame member 23 is sealed by the nozzle plate 21. The space defined by the frame member 23, the actuator substrate 22, and the nozzle plate 21 forms a common ink chamber 26 (261, 262). The common ink chamber 26 has two common ink chambers 261 and 262 sandwiching the actuator substrate 22. One common ink chamber 261 communicates with the ink supply port 27 and serves as an ink supply path for supplying ink to the plurality of pressure chambers 5. The ink supply port 27 is connected to Figure 1 the ink supply pressure adjusting device 321. The other common ink chamber 262 communicates with an opening portion (not shown) that is the same as the ink supply port 27, namely, an ink discharge port, and serves as an ink discharge path for discharging ink from the plurality of pressure chambers 5. When ink is circulated and supplied, the ink discharge port is connected to the ink supply pressure adjusting device 321 through the ink discharge pipe 29.

[0046] As Figure 3 and Figure 4 shown, the plurality of pressure chambers 5 and the air chambers 51 are formed to be alternately arranged on the surface of the actuator substrate 22 located within the common ink chamber 26 (261, 262). The pressure chambers 5 and the air chambers 51 are separated by piezoelectric members 6 (61, 62) serving as side walls. The piezoelectric members 6 (61, 62) are piezoelectric bodies such as piezoelectric elements, for example. The pressure chambers 5 and the air chambers 51 are formed on the surface of the actuator substrate 22 by grooves cut out in two piezoelectric members 61 and 62 laminated in the Z direction along the third direction and along the Y direction. The two piezoelectric members 61 and 62 are laminated in opposite directions of the polarization direction (taking the relative direction as an example). Each pressure chamber 5 communicates with each nozzle 20 one-to-one. The air chambers 51 are located on both sides of the pressure chambers 5.

[0047] Furthermore, on both side surfaces of the actuator substrate 22, a pair of cover members 67 forming the side walls on both sides in the Y direction of the air chambers 51 are respectively provided. The air chambers 51 are separated from the common ink chamber 26 (261, 262) by the cover members 67. Groove-shaped openings 68 corresponding to the shape of the pressure chambers 5 are formed in the cover members 67 so that the pressure chambers 5 communicate with the left and right common ink chambers 261 and 262. The opening 68 of the cover member 67 on the side of the common ink chamber 261 is the ink supply port, and the opening 68 of the cover member 67 on the side of the common ink chamber 262 is the ink discharge port. Ink is supplied or discharged to the pressure chambers 5 through the ink supply port and the ink discharge port. As an example, Figure 3 the cover member 67 formed of a plate material is illustrated, but the cover member 67 can be formed of resin, a plate material, etc., for example. Moreover, it can be set that the cover member 67 only fills the portions of the side walls on both sides in the Y direction of the air chambers 51.

[0048] As Figure 4As shown, the individual electrode 63 is integrally formed on the bottom surface in the Z direction and both side surfaces in the X direction of the pressure chamber 5. The common electrode 64 is integrally formed on the bottom surface in the Z direction and both side surfaces in the Y direction of the air chamber 51. The individual electrodes 63 of the respective pressure chambers 5 are respectively connected to the individual wirings 65. The common electrodes 64 of the respective air chambers 51 are commonly connected to the common wiring 66. The individual electrode 63, the common electrode 64, the individual wiring 65, and the common wiring 66 are formed of, for example, a nickel thin film and are covered with, for example, an insulating layer (not shown) or the like for insulation.

[0049] The connection point of the individual electrode 63 and the individual wiring 65 is the individual terminal of the actuator 8. The individual terminals of the actuator 8 are respectively connected to the drive driver D (i.e., the drive circuit) of the drive IC 31 through the individual wirings 65. The power sources of the drive voltages V1, V2, and ground (GND) are connected to the drive driver D. On the other hand, the connection point of the common electrode 64 and the common wiring 66 is the common terminal of the actuator 8. The common terminals of the respective actuators 8 are commonly connected to, for example, ground (GND) or a common potential of a predetermined constant voltage. The drive drivers D of the respective drive channels (1ch, 2ch,... nch) respectively apply drive voltages to the individual terminals of the respective actuators 8 and enable independent driving. With this configuration, in the actuator 8 to which the drive voltage is applied, an electric field is applied in a direction crossing (preferably orthogonal to) the polarization axis of the piezoelectric members 6 (61, 62), and the piezoelectric members 6 (61, 62) that form the side walls in the X direction of the pressure chamber 5 are symmetrically deformed in the X direction in a shear mode. The actuator 8 is an example of a piezoelectric actuator.

[0050] That is, the pressure chamber 5 is formed to be sandwiched by a pair of columnar actuators 8 using the piezoelectric members 6 (61, 62). By applying a potential difference to both walls of the columnar actuator 8, that is, the inner wall and the outer wall of the pressure chamber 5, and charging the actuator 8, the actuator 8 is deformed. As a result, the volume of the pressure chamber 5 changes, and the ink pressure in the pressure chamber 5 changes. By adjusting the magnitude and timing of this change, ink is ejected from the nozzle 20.

[0051] Figure 5This is a block diagram of the control system of the inkjet printer 10. The control substrate 17, which serves as the control unit of the inkjet printer 10, is equipped with a CPU 9, a ROM 91, a RAM 92, an I / O port 93 serving as an input / output port, and an image memory 94. The CPU 9 controls the motor 205, the ink supply pressure adjustment devices 321 to 324, the operation unit 18, and various sensors through the I / O port 93. The image data from the computer 200, which is an external connection device, is sent to the control substrate 17 through the I / O port 93 and stored in the image memory 94. The CPU 9 sequentially sends the image data stored in the image memory 94 to the drive circuits 95 of the inkjet heads 100 to 103 according to the printing order. The data sent may include grayscale data based on the grayscale of the specified points in the image data.

[0052] The drive circuit 95 includes a data buffer 96, a decoder 97, and a drive driver 98. The drive driver 98 is provided by the drive IC 31 serving as the control unit of the inkjet head 100. The data buffer 96 stores the image data for the actuators 8 in time series. The decoder 97 controls the drive driver 98 according to the actuators 8 based on the image data stored in the data buffer 96. Based on the control of the decoder 97, the drive driver 98 outputs a drive signal that causes each actuator 8 to operate. The drive signal is a voltage applied to the actuator 8 according to the drive waveform.

[0053] In Figure 6 An example of the drive waveform is shown. Figure 6 The drive waveform of Figure 4 is a multi-drop drive waveform that ejects three drops of ink in one drive cycle. Before the ink ejection operation, this drive waveform applies a voltage Vb to the individual terminals of the actuator 8 in advance. Then, various potentials are applied to the individual terminals of the actuator 8 as the drive signal, that is, voltage Va is applied from time t1 to time t2, voltage Vc is applied from time t2 to time t3, voltage Va is applied from time t3 to time t4, voltage Vb is applied from time t4 to time t5, voltage Va is applied from time t5 to time t6, voltage Vb is applied from time t6 to time t7, voltage Vc is applied from time t7 to time t8, and voltage Vb is applied at time t8. The voltage Va is, for example, 0V and is supplied by Figure 4 the GND of Figure 4 The voltages Vb and Vc are positive-potential voltages and are supplied by the power supplies V2 and V1 of Figure 4 respectively. Va < Vb < Vc. The common terminals of the respective actuators 8 are commonly connected to the ground (GND) of 0V, for example.

[0054] The periods from time t1 to time t2, from time t2 to time t3, from time t3 to time t4, from time t4 to time t5, from time t5 to time t6, from time t6 to time t7, and from time t7 to time t8 are each set to 1AL. 1AL is the time that is half of the natural vibration period in the pressure chamber 5 filled with ink. When the natural vibration period is, for example, 4 μs, 1AL is 2 μs.

[0055] As Figure 7 shown in (b) of, the piezoelectric members 6 (61, 62) on both sides of the pressure chamber 5 of the actuator 8 to which the voltage Vb is applied to the individual terminals before the ink ejection operation each deform inward in a shear mode, and the volume in the pressure chamber 5 contracts. Then, as Figure 7 shown in (a) of, the piezoelectric members 6 (61, 62) of the actuator 8 to which the voltage Va is applied to the individual terminals at time t1 and which have deformed in a shear mode return to their original state, and the volume in the pressure chamber 5 expands relatively from the Figure 7 state of (b) of, thereby supplying ink into the pressure chamber 5. As Figure 7 shown in (c) of, at the next time t2, the piezoelectric members 6 (61, 62) of the actuator 8 to which the voltage Vc is applied to the individual terminals each deform inward in a shear mode, whereby the volume in the pressure chamber 5 contracts. The pressure of the ink increases due to this series of volume changes in the pressure chamber 5, and the first drop of ink is ejected from the nozzle 20.

[0056] Next, at time t3, the volume in the pressure chamber 5 of the actuator 8 to which the voltage Va is applied to the individual terminals expands from the Figure 7 state of (c) of to the Figure 7 state of (a) of, and by applying the voltage Vb at time t4, the volume in the pressure chamber 5 contracts to the Figure 7 state of (b) of, thereby ejecting the second drop of ink. Next, at time t5, the volume in the pressure chamber 5 of the actuator 8 to which the voltage Va is applied to the individual terminals expands from the Figure 7 state of (b) of to the Figure 7 state of (a) of, and by applying the voltage Vb at time t6, the volume in the pressure chamber 5 contracts to the Figure 7 state of (b) of, thereby ejecting the third drop of ink.

[0057] Then, at time t7, the volume in the pressure chamber 5 of the actuator 8 to which the voltage Vc is applied to the individual terminals contracts to the Figure 7 state of (c) of, and by applying the voltage Vb at time t8, the contracted volume in the pressure chamber 5 returns to the Figure 7 state of (b) of. By this contraction and restoration, the residual vibration is attenuated.

[0058] As Figure 8As shown, in this embodiment, for example, a plurality of nozzles 20 arranged in a column are alternately grouped into a first group and a second group. The nozzles 20 of the first group and the nozzles 20 of the second group are set such that the timings of applying drive signals to the actuator 8 are staggered from each other between the groups. Further, both the first group and the second group are set such that even the timings of applying drive signals to the nozzles 20 belonging to the same group are staggered from each other. The staggering time of the drive timings is set to two types: a main staggering time and a secondary staggering time. The main staggering time is used to stagger the drive timings between the first group and the second group. The secondary staggering time is used to stagger the drive timings between the nozzles 20 belonging to the same group.

[0059] The main staggering time is set to be around one time (1AL) of half of the natural vibration period within the pressure chamber 5 filled with ink. Preferably, it is 1AL. When the secondary staggering time is expressed by a time A and a time B shorter than 1AL, a certain time interval K shorter than 1AL, a fine adjustment time i shorter than time A or time B, and a fine adjustment time j, the nozzles 20 of the first group are assigned M types of staggering times of A + K(M - 1) ± i (M is an integer such as 1, 2,...). The nozzles 20 of the second group are assigned N types of staggering times of B + K(N - 1) ± j (N is an integer such as 1, 2,...).

[0060] The drive timing staggering times (total staggering times) set by the main staggering time and the secondary staggering time are assigned to each nozzle 20 in such a way that the absolute value of the difference in drive timings between adjacent nozzles 20 is within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). That is, they are arranged in such a way that they are within the range of the larger value of 1AL ± (A + K - B + i) or 1AL ± (A + K - B + j).

[0061] An explanation will be given for the reason of setting the main staggering time around 1AL. Figure 9 It shows the difference in the starting positions of the ink droplets when all nozzles are driven and when a single nozzle is driven when the staggering times of the drive timings between the two groups are variously set at intervals of 0.2AL within the range of 0.8AL to 1.2AL. The drive waveform used is Figure 7 a multi-drop drive waveform. In order to confirm the effect of setting the main staggering time, the secondary staggering time is not set. All-nozzle drive is a drive method in which ink is ejected from all the nozzles 20 within the same drive cycle. Single-nozzle drive is a drive method in which ink is ejected from one nozzle 20. The difference in the starting positions of the ink droplets when all nozzles are driven and when a single nozzle is driven means the difference in the flight distances of the first ink droplet at a predetermined timing (for example, 100 μs from the start of ejection). The closer the difference in the starting positions is to zero, the smaller the deviation in the ejection speed caused by crosstalk.

[0062] According toFigure 9 As a result, the driving timing crosstalk of the first group is minimized when it is staggered by 1.1AL from the second group. The driving timing crosstalk of the second group is minimized when it starts driving 0.9AL after the start of driving of the first group. Thus, for two-part driving, if the stagger time of the driving timing that is optimal for one of the groups is set, the crosstalk of the other group deteriorates. As can be seen from Figure 2 , the stagger time of the driving timing suitable for the two groups is around 1AL. That is, it is good to set the main stagger time around 1AL. As an example, it is 0.96AL to 1.04AL. Preferably it is 1AL. The main stagger time can be set within the range of 0.8AL to 1.2AL which is the evaluation range as Figure 9 .

[0063] However, in two-part driving with only the main stagger time, since multiple actuators 8 in each group are driven simultaneously, current concentration sometimes occurs particularly in the common wiring 66. In order to suppress the occurrence of this current concentration, a secondary stagger time with a certain time interval K is provided so as to perform segmented driving also within the group. However, if the secondary stagger time is set to a large value, it becomes impossible to maintain the crosstalk between the two groups in an appropriate state. Therefore, the value of the secondary stagger time is set to be small, and the difference in driving timing between the groups does not deviate from around 1AL.

[0064] Next, the secondary stagger time will be described. As described above, the nozzles 20 of the first group are assigned M kinds of secondary stagger times of A + K(M - 1) ± i (M is an integer such as 1, 2...). The nozzles 20 of the second group are assigned N kinds of secondary stagger times of B + K(N - 1) ± j (N is an integer such as 1, 2...). The times A and B are arbitrary driving start timings. The times i and j are arbitrary variable fine adjustment times. As an example, the times A and B are set to 0.02 μs. However, it is not limited to the times A and B being the same. In order to prevent current concentration, it is preferable to set the certain interval K to at least 0.04 μs or more. On the other hand, since if the certain time interval K is too large, the difference in driving timing will deviate from around 1AL, it is preferable to set the certain time interval K to 0.2AL or less. As an example, when 1AL is 2 μs, the certain time interval K is set to 0.1 μs. However, the time interval K is not limited to 0.1 μs.

[0065] In the present embodiment, an example will be described in which different driving timing stagger times are set for a group of eight nozzles 20 for eight-part driving. Regarding the nozzles 20 arranged on the nozzle plate 21, by repeating the model of the driving timing stagger times for a group of eight along the arrangement direction, all the nozzles 20 can perform eight-part driving.

[0066] Four different driving timing offset times are set for the four nozzles 20 belonging to the first group among the eight nozzles 20 in a set. The main offset time of the first group is set to 0 μs. As an example, regarding the secondary offset time, let M = 4, A = 0.02 μs, K = 0.1 μs, i = 0, and set the following four (M kinds).

[0067] 0.02 μs = A + K(M - 1) ± i = 0.02 + 0.1×(1 - 1) ± 0

[0068] 0.12 μs = A + K(M - 1) ± i = 0.02 + 0.1×(2 - 1) ± 0

[0069] 0.22 μs = A + K(M - 1) ± i = 0.02 + 0.1×(3 - 1) ± 0

[0070] 0.32 μs = A + K(M - 1) ± i = 0.02 + 0.1×(4 - 1) ± 0

[0071] The total offset time (driving timing offset time) obtained by adding the main offset time to each secondary offset time becomes as follows.

[0072] 0.02 μs = main offset time 0 μs + secondary offset time 0.02 μs

[0073] 0.12 μs = main offset time 0 μs + secondary offset time 0.12 μs

[0074] 0.22 μs = main offset time 0 μs + secondary offset time 0.22 μs

[0075] 0.32 μs = main offset time 0 μs + secondary offset time 0.32 μs

[0076] Four different driving timing offset times are set for the four nozzles 20 belonging to the second group among the eight nozzles 20 in a set. The main offset time of the second group is set to 2 μs. As an example, regarding the secondary offset time, let N = 4, B = 0.02 μs, K = 0.1 μs, j = 0, and set the following four (N kinds).

[0077] 0.02 μs = B + K(N - 1) ± j = 0.02 + 0.1×(1 - 1) ± 0

[0078] 0.12 μs = B + K(N - 1) ± j = 0.02 + 0.1×(2 - 1) ± 0

[0079] 0.22 μs = B + K(N - 1) ± j = 0.02 + 0.1×(3 - 1) ± 0

[0080] 0.32 μs = B + K(N - 1) ± j = 0.02 + 0.1×(4 - 1) ± 0

[0081] The total stagger time (drive timing stagger time) obtained by adding the main stagger time to each secondary stagger time is as follows.

[0082] 2.02 μs = main stagger time 2 μs + secondary stagger time 0.02 μs

[0083] 2.12 μs = main stagger time 2 μs + secondary stagger time 0.12 μs

[0084] 2.22 μs = main stagger time 2 μs + secondary stagger time 0.22 μs

[0085] 2.32 μs = main stagger time 2 μs + secondary stagger time 0.32 μs

[0086] The stagger times of the above-mentioned total eight drive timings are arranged such that the absolute value of the difference in drive timings between adjacent nozzles 20 is within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). In the above example, both 1AL ± (A + K - B + i) and 1AL ± (A + K - B + j) are 2 μs ± 0.1 μs. In Figure 10 (a) shows an example of the arrangement of the present embodiment. In Figure 10 (a), the difference in drive timings between adjacent nozzles 20, that is, the time difference from the previous one and the time difference from the next one, is shown together. The time difference from the previous one is the difference in drive timing of the nozzle number relative to the previous nozzle 20. The time difference from the next one is the difference in drive timing of the nozzle number relative to the next nozzle 20. According to Figure 10 (a), it is clear that for any nozzle 20, the absolute value of the difference in drive timings between adjacent nozzles 20 is within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). By arranging in this way, as shown in Figures 11 - 13 described later, good linearity within the column of the ink landing position (drop position) can be achieved.

[0087] Figure 10 (b) is a comparative example, showing an example of arranging the stagger times of the above-mentioned total eight drive timings differently from Figure 10 (a). In this arrangement, although the same Figure 10The (a) same eight driving timing stagger times, but the time difference between the (n + 6)th nozzle 20 and the adjacent one behind, and the time difference between the (n + 7)th nozzle 20 and the adjacent one in front have become 2.3 μs. That is, it has deviated from the range of 2 μs ± 0.1 μs of 1AL ± (A + K - B + i) and 1AL ± (A + K - B + j). Refer to Figures 11 - 13 How the ejection state of the ink is different in Figure 10 the arrangement of the present embodiment in (a) and Figure 10 the arrangement of the comparative example in (b).

[0088] Figure 11 Figure (a) is a chart that separately plots the total stagger times of the nozzles 20 from the 149th to the 164th of the present embodiment. Repeated twice Figure 10 The eight - nozzle - in - a - group arrangement in (a) is used to assign driving timing stagger times to the sixteen nozzles 20 from the 149th to the 164th. Similarly, Figure 11 Figure (b) is a chart that separately plots the total stagger times of the nozzles 20 from the 149th to the 164th of the comparative example. Repeated twice Figure 10 The eight - nozzle - in - a - group arrangement in (b) is used to assign driving timing stagger times to the sixteen nozzles 20 from the 149th to the 164th. Comparing Figure 11 Figure (a) with Figure 11 the shape of the dashed line in Figure (b), it can be seen that the driving timing stagger times can be set more evenly in the present embodiment compared to the comparative example. That is, in the present embodiment, the difference in the total stagger times between adjacent nozzles 20 is all within 2 μs ± 0.1 μs. In contrast, in the comparative example, the difference in the total stagger times between the 155th and 156th nozzles 20 exceeds 2 μs ± 0.1 μs, which is the main reason for being strongly affected by crosstalk.

[0089] Figure 12 Figure (a) shows the measurement results of crosstalk when the arrangement of the driving timing stagger times of the present embodiment is applied. In the measurement of crosstalk, the differences in the starting positions of the ejected ink droplets between when all nozzles are driven and when a single nozzle is driven, the differences in the starting positions of the ejected ink droplets between when all nozzles are driven and when on - off driving is performed, and the differences in the starting positions of the ejected ink droplets between when on - off driving is performed and when a single nozzle is driven are measured. The conveying speed of the sheet S for ejecting the ink is set to 1990 mm / s. The on - off driving is a driving method for measuring the starting position of the ink droplets when only the first group or the second group ejects ink. Figure 12 Figure (b) shows the measurement results of crosstalk when the arrangement of the driving timing stagger times of the comparative example is applied.

[0090] In Figure 12 Figure (a) andFigure 12 The value of 3σ for evaluating the deviation is also shown in (b) below. By comparing Figure 12 in (a) below and Figure 12 in (b) below, it can be seen that the deviation of the difference in the starting positions is small in any driving method in the present embodiment. As described above, the closer the difference in the starting positions is to zero, the smaller the deviation of the ejection speed caused by crosstalk.

[0091] Figure 13 In (a) below, the droplet positions (landing positions) of the ink ejected from all the nozzles 20 using the arrangement of the driving timing stagger times of the present embodiment are shown. Figure 13 In (b) below, the droplet positions of the ink ejected from all the nozzles 20 using the arrangement of the driving timing stagger times of the comparative example are shown. In Figure 13 in (a) below and Figure 13 in (b) below, the results of the two-part driving are also shown together as a reference. The reference two-part driving is a driving method in which only the main stagger time is set to 2 μs. The present embodiment is an eight-part driving based on the main stagger time and the secondary stagger time. However, even compared with the two-part driving, the difference in the droplet positions is small. That is, even with the eight-part driving, it is possible to achieve the same level of in-column linearity as the two-part driving. In contrast, it can be seen that the difference in the droplet positions of the comparative example is large and the in-column linearity is worse than that of the present embodiment compared with the two-part driving.

[0092] As described above, the reference two-part driving that sets only the main stagger time can suppress crosstalk and has good in-column linearity. However, since the number of actuators 8 that are driven simultaneously is large, current concentration is likely to occur. Current concentration is also a main cause of electrical crosstalk. On the other hand, although the eight-part driving based on the main stagger time and the secondary stagger time of the present embodiment can avoid current concentration, there is a concern that the in-column linearity may decrease on the contrary. In fact, the in-column linearity of the comparative example has decreased. In contrast, the present embodiment is effective in suppressing the decrease in the in-column linearity of the landing positions of the ink ejected from the plurality of nozzles 20 and in suppressing current concentration during driving.

[0093] (Second Embodiment)

[0094] Next, the inkjet head 100 of the second embodiment will be described. As described above, in the first embodiment, the same number of four secondary stagger times are set in the first group and the second group, but it is not limited thereto. In the first group and the second group, the number of secondary stagger times may also be different. That is, the values of M and N may be different. Figure 14 As an example, the number of secondary stagger times in the first group is three and the number of secondary stagger times in the second group is two. In each group, the number of nozzles 20 is larger than the number of types of secondary stagger times.

[0095] Set the main stagger time of the first group to 0 μs. As an example, regarding the secondary stagger time, set M = 3, A = 0.02 μs, K = 0.2 μs, i = 0, and set the following three cases.

[0096] 0.02 μs = A + K(M - 1) ± i = 0.02 + 0.2×(1 - 1) ± 0

[0097] 0.22 μs = A + K(M - 1) ± i = 0.02 + 0.2×(2 - 1) ± 0

[0098] 0.42 μs = A + K(M - 1) ± i = 0.02 + 0.2×(3 - 1) ± 0

[0099] The total stagger time (drive timing stagger time) obtained by adding the main stagger time to each secondary stagger time becomes as follows.

[0100] 0.02 μs = main stagger time 0 μs + secondary stagger time 0.02 μs

[0101] 0.22 μs = main stagger time 0 μs + secondary stagger time 0.22 μs

[0102] 0.42 μs = main stagger time 0 μs + secondary stagger time 0.42 μs

[0103] Set the main stagger time of the second group to 2 μs. As an example, regarding the secondary stagger time, set N = 2, B = 0.12 μs, K = 0.2 μs, j = 0, and set the following two cases.

[0104] 0.12 μs = B + K(N - 1) ± j = 0.12 + 0.2×(1 - 1) ± 0

[0105] 0.32 μs = B + K(N - 1) ± j = 0.12 + 0.2×(2 - 1) ± 0

[0106] The total stagger time (drive timing stagger time) obtained by adding the main stagger time to each secondary stagger time becomes as follows.

[0107] 2.12 μs = main stagger time 2 μs + secondary stagger time 0.12 μs

[0108] 2.32 μs = main stagger time 2 μs + secondary stagger time 0.32 μs

[0109] The absolute value of the difference in driving timings between adjacent nozzles 20 among the above-mentioned total five driving timings is within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). In the above example, both 1AL ± (A + K - B + i) and 1AL ± (A + K - B + j) are 2 μs ± 0.1 μs, which are the same as those in the first embodiment. In Figure 14 An example of the arrangement of the present embodiment is shown. In Figure 14 The difference in driving timings between adjacent nozzles 20, that is, the time difference from the previous adjacent nozzle and the time difference from the subsequent adjacent nozzle, is shown together. It can be clarified from Figure 14 that for any nozzle 20, the absolute value of the difference in driving timings between its adjacent nozzles 20 is within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). Thus, even if the time interval K of the secondary stagger time is increased, it is possible to achieve the same degree of ejection linearity as in the first embodiment and suppress current concentration during driving.

[0110] (Third Embodiment)

[0111] Next, the inkjet head 100 of the third embodiment will be described. The third embodiment is an example in which while setting five first-group secondary stagger times and four second-group secondary stagger times for nine nozzles 20 in a group, fine adjustments are further made using the fine adjustment times i and j. For the first group, the secondary stagger time is set by A = 0 μs, K = 0.1 μs, M = 5, and i = 0.02 μs, and for the second group, the secondary stagger time is set by B = 0.06 μs, K = 0.1 μs, N = 4, and j = 0.02 μs.

[0112] Five different driving timing stagger times are set for the five nozzles 20 belonging to the first group among the nine nozzles 20 in a group. The main stagger time of the first group is set to 0 μs. As an example, for the secondary stagger time, let M = 5, A = 0 μs, K = 0.1 μs, i = (0.02, ±0, -0.02 variable), and the following five (M types) are set.

[0113] 0.02 μs = A + K(M - 1) ± i = 0 + 0.1×(1 - 1) + 0.02

[0114] 0.10 μs = A + K(M - 1) ± i = 0 + 0.1×(2 - 1) ± 0

[0115] 0.20 μs = A + K(M - 1) ± i = 0 + 0.1×(3 - 1) ± 0

[0116] 0.30 μs = A + K(M - 1) ± i = 0 + 0.1×(4 - 1) ± 0

[0117] 0.38 μs = A + K(M - 1) ± i = 0 + 0.1×(5 - 1) - 0.02

[0118] The total staggering time (drive timing staggering time) obtained by adding the main staggering time to each secondary staggering time becomes as follows.

[0119] 0.02 μs = main staggering time 0 μs + secondary staggering time 0.02 μs

[0120] 0.10 μs = main staggering time 0 μs + secondary staggering time 0.10 μs

[0121] 0.20 μs = main staggering time 0 μs + secondary staggering time 0.20 μs

[0122] 0.30 μs = main staggering time 0 μs + secondary staggering time 0.30 μs

[0123] 0.38 μs = main staggering time 0 μs + secondary staggering time 0.38 μs

[0124] For the four nozzles 20 of the second group among the nine nozzles 20 in a set, four different drive timing staggering times are set. The main staggering time of the second group is set to 2 μs. As an example, for the secondary staggering time, let N = 4, B = 0.06 μs, K = 0.1 μs, j = (±0, -0.02 variable), and the following four (N kinds) are set.

[0125] 0.04 μs = B + K(N - 1) ± j = 0.06 + 0.1×(1 - 1) - 0.02

[0126] 0.16 μs = B + K(N - 1) ± j = 0.06 + 0.1×(2 - 1) ± 0

[0127] 0.26 μs = B + K(N - 1) ± j = 0.06 + 0.1×(3 - 1) ± 0

[0128] 0.36 μs = B + K(N - 1) ± j = 0.06 + 0.1×(4 - 1) ± 0

[0129] The total staggering time (drive timing staggering time) obtained by adding the main staggering time to each secondary staggering time becomes as follows.

[0130] 2.04 μs = main staggering time 2 μs + secondary staggering time 0.02 μs

[0131] 2.16 μs = main staggering time 2 μs + secondary staggering time 0.16 μs

[0132] 2.26μs = main stagger time 2μs + secondary stagger time 0.26μs

[0133] 2.36μs = main stagger time 2μs + secondary stagger time 0.36μs

[0134] The above-mentioned nine types of drive timing staggered time arrangement is such that the absolute value of the difference between the drive timings of adjacent nozzles 20 is within the range of 1AL±(A+K-B+i) and 1AL±(A+K-B+j). In the above example, 1AL±(A+K-B+i) and 1AL±(A+K-B+j) are both 2μs±0.06μs (where i and j are variable to 0.02, ±0, and -0.02). Figure 15 An example of the arrangement of this embodiment is shown in FIG. Figure 15 The time difference with the preceding neighbor and the time difference with the following neighbor are shown together, which indicates the difference in driving timing between the adjacent nozzles 20. The third embodiment does not repeat the arrangement of eight groups directly along the arrangement direction of the nozzles 20 as in the first and second embodiments. Instead, after the arrangement of nine groups is assigned to the (n+1)th to (n+8)th nozzles 20, the arrangement direction is reversed to assign them to the (n+9)th to (n+15)th nozzles 20. The same is repeated for the (n+16)th and subsequent nozzles. Figure 15 It is clear that, for any nozzle 20, the absolute value of the difference in drive timing between adjacent nozzles 20 is within the range of 1AL±(A+K-B+i) and 1AL±(A+K-B+j), that is, 2μs±0.06μs. In this embodiment, the nozzles 20 arranged on the nozzle plate 21 are repeatedly assigned a model of staggered drive timings of nine groups as described above, so that all nozzles 20 can be driven in nine divisions.

[0135] According to the above embodiment, the influence of crosstalk received from the surrounding driving channels can be suppressed, and stable ink discharge can be performed.

[0136] It should be noted that the inkjet head 100 is not limited to the shear mode type actuator 8 in which the pressure chamber 5 and the air chamber 51 are alternately arranged. For example, a configuration in which both a plurality of nozzles 20 and a plurality of actuators 8 are arranged on the surface of the nozzle plate 21 may be adopted. Other drop-on-demand / piezoelectric actuators 8 may also be adopted. In addition, the actuator 8 may also be a stacked piezoelectric actuator formed by alternately stacking piezoelectric components and internal electrodes in layers.

[0137] In the above-described embodiment, the inkjet head 100 of the inkjet printer 10 is described as an example of a liquid ejection head. However, the liquid ejection head may be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0138] The embodiments of the present invention are presented only by way of example and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments or their modifications are included in the scope or gist of the invention and are included in the invention described in the claims and its equivalents.

Claims

1. A liquid ejection head, characterized in that: have: A nozzle portion, in which a plurality of nozzles for spraying liquid are arranged; a plurality of pressure chambers, which are individually connected to the plurality of nozzles, and the liquids are respectively filled in the plurality of pressure chambers; a plurality of piezoelectric actuators, respectively causing the volumes in the plurality of pressure chambers to change; as well as The control unit applies a driving signal to the piezoelectric actuator to expand and contract the volume in the pressure chamber, thereby causing the liquid to be ejected from the nozzle. The adjacent nozzles among the plurality of nozzles are set to belong to a first group and a second group different from each other. The driving timing of applying the driving signal is different between the first group and the second group by the main staggered time, and the driving timing of applying the driving signal to the nozzles in each group is different from each other by the secondary staggered time. The main offset time is set to 1AL, which is one time of half the natural vibration period in the pressure chamber, and When the secondary staggered time is represented by a time A and a time B shorter than the 1AL, a certain time interval K shorter than the 1AL, and a fine adjustment time i and a fine adjustment time j shorter than the time A or the time B, the first group is assigned M settings of A+K(M-1)±i, and the second group is assigned N settings of B+K(N-1)±j, where M is an integer of 1, 2, ..., and N is an integer of 1, 2, ..., and The drive timings of the adjacent nozzles are arranged so that the difference between the drive timings is within the allowable range of 1AL±(A+K−B+i) and the allowable range of 1AL±(A+K−B+j).

2. The liquid ejection head according to claim 1, wherein: The certain time interval K is set within a range of 0.04 μs to 0.2 μs.

3. The liquid ejection head according to claim 1, wherein: The allowable range is 1AL±0.1 μs.

4. The liquid ejection head according to claim 1, wherein: There are eight or nine kinds of shifted times of drive timing based on the major shifted time and the minor shifted time in total, and the eight or nine kinds of shifted times of drive timing are allocated to the plurality of nozzles to perform eight-division drive or nine-division drive.

5. The liquid ejection head according to claim 1, wherein: The piezoelectric actuator is alternately provided with the pressure chambers and the air chambers.

6. The liquid ejection head according to claim 1, wherein: The plurality of nozzles and the plurality of piezoelectric actuators are arranged on a surface of the nozzle portion.

7. The liquid ejection head according to claim 1, wherein: The piezoelectric actuator is a stacked piezoelectric actuator formed by alternately stacking piezoelectric members and internal electrodes in a layered form.

8. A liquid ejection head, characterized in that: have: A nozzle portion, in which a plurality of nozzles for spraying liquid are arranged; a plurality of pressure chambers, which are individually connected to the plurality of nozzles, and the liquids are respectively filled in the plurality of pressure chambers; a plurality of piezoelectric actuators, respectively causing the volumes in the plurality of pressure chambers to change; as well as The control unit applies a driving signal to the piezoelectric actuator to expand and contract the volume in the pressure chamber, thereby causing the liquid to be ejected from the nozzle. The adjacent nozzles among the plurality of nozzles are set to belong to a first group and a second group different from each other. The driving timing of applying the driving signal is different between the first group and the second group by the main staggered time, and the driving timing of applying the driving signal to the nozzles in each group is different from each other by the secondary staggered time. The main staggered time is set to 0.8 to 1.2 times the time of half the natural vibration period in the pressure chamber, that is, 0.8AL to 1.2AL, and When the secondary staggered time is represented by a time A and a time B shorter than the 0.8AL~1.2AL, a certain time interval K shorter than the 0.8AL~1.2AL, and a fine adjustment time i and a fine adjustment time j shorter than the time A or the time B, the first group is assigned M settings of A+K(M-1)±i, and the second group is assigned N settings of B+K(N-1)±j, where M is an integer of 1, 2, ..., and N is an integer of 1, 2, ..., and The drive timings of the adjacent nozzles are arranged so that the difference between the drive timings is within the range of (0.8AL to 1.2AL) ± (A + K - B + i) and within the range of (0.8AL to 1.2AL) ± (A + K - B + j).

9. The liquid ejection head according to claim 8, wherein: The piezoelectric actuator is alternately provided with the pressure chambers and the air chambers.

10. The liquid ejection head according to claim 8, wherein: The plurality of nozzles and the plurality of piezoelectric actuators are arranged on a surface of the nozzle portion.

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