Liquid discharge head

Abstract

To provide a liquid discharge head which can suppress deterioration of intra-row linearity of a landing position of liquid discharged from a plurality of nozzles and can suppress current concentration during driving.SOLUTION: In a liquid discharge head, nozzles adjacent to each other are set to belong to a first group and a second group, respectively. Pieces of drive timing are made different in each of the groups by primary deviation time. Pieces of drive timing of nozzles in each group are made different from each other by secondary deviation time. The primary deviation time is set to 1AL. As for the secondary deviation time, M types of settings of A + K (M-1) ± i are allocated to the first group (M is an integer of 1, 2 ...), and N types of settings of B + K (N-1) ± j are allocated to the second group (N is an integer of 1, 2 ...). The pieces of drive timing are arrayed so that a difference between the pieces of drive timing of pressure chambers adjacent to each other falls within a range of 1AL ± (A + K - B + i) and 1AL ± (A + K - B + J).SELECTED DRAWING: Figure 10

Description

Technical Field

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

Background Art

[0002] A liquid ejection head that supplies a predetermined amount of liquid to a predetermined position is known. The liquid ejection head is mounted on, for example, an inkjet printer, a 3D printer, a dispensing device, or the like. An inkjet printer ejects ink droplets from an inkjet head to form an image or the like on the surface of a recording medium. A 3D printer ejects droplets of a modeling material from a modeling material ejection head and cures them to form a three-dimensional object. A dispensing device ejects droplets of a sample and supplies 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 among 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, among the plurality of nozzles, adjacent nozzles are set to belong to different groups. When ejecting liquid, the control unit sets the deviation amount of the timing for applying the drive signal to the actuator to be near an integer multiple of the on-pulse peak (AP) or half the time of the natural vibration period in the pressure chamber between groups, and makes the drive timings between groups different from each other. However, when the number of groups is three or more, the deviation amount of the drive timing between groups becomes large, and for example, the in-column linearity of the landing position (drop position) when ejecting liquid at a high frequency may decrease. On the other hand, when the number of groups is two, the number of actuators driven simultaneously increases, resulting in current concentration.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] The problem to be solved by the present invention is to provide a liquid ejection head that can suppress a decrease in in-line linearity of the landing positions of liquids ejected from a plurality of nozzles and suppress current concentration during driving.

Means for Solving the Problems

[0007] The liquid ejection head according to an embodiment of the present invention includes a nozzle section, a plurality of pressure chambers, a plurality of piezoelectric actuators, and a control section. The nozzle section arranges a plurality of nozzles that eject liquid. The plurality of pressure chambers communicate individually with the plurality of nozzles and are filled with the liquid respectively. The plurality of piezoelectric actuators change the volume in the plurality of pressure chambers respectively. The control section applies a drive signal to the piezoelectric actuators to expand and contract the volume in the pressure chambers, thereby ejecting the liquid from the nozzles. The liquid ejection head makes the drive timings for applying the drive signal different from each other between the first group and the second group according to the primary deviation time, and makes the drive timings for applying the drive signal different from each other between the nozzles within each group according to the secondary deviation time. The primary deviation time is set to 1 times (1AL) the time that is half of the natural vibration period in the pressure chamber. When the secondary deviation time is represented by time A and time B shorter than 1AL, a constant time interval K shorter than 1AL, and fine adjustment times i and j shorter than time A or time B, M types of settings of A + K(M - 1) ± i are assigned to the first group (M is an integer such as 1, 2...), and N types of settings of B + K(N - 1) ± j are assigned to the second group (N is an integer such as 1, 2...). And the drive timings are arranged such that the difference in drive timings between adjacent nozzles falls within the allowable range of 1AL ± (A + K - B + i) and within the allowable range of 1AL ± (A + K - B + j).

Brief Description of the Drawings

[0008]

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Mode for Carrying Out the Invention

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

[0010] (First Embodiment) As an example of an image forming apparatus equipped with the liquid ejection head of the 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. The inkjet printer 10 includes, inside a housing 11, a cassette 12 that stores a sheet S which is an example of a recording medium, an upstream conveyance path 13 of the sheet S, a conveyance belt 14 that conveys the sheet S taken out from the cassette 12, a plurality of inkjet heads 100 to 103 that eject ink droplets toward the sheet S on the conveyance belt 14, a downstream conveyance path 15 of the sheet S, a discharge tray 16, and a control board 17. An operation unit 18 which is a user interface is arranged 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 external connection device. The image data generated by the computer 200 is sent to the control board 17 of the inkjet printer 10 through a cable 201 and connectors 202, 203.

[0012] A pickup roller 204 supplies the sheets S one by one from the cassette 12 to the upstream conveyance path 13. The upstream conveyance path 13 is composed of a pair of feed rollers 131, 132 and sheet guide plates 133, 134. The sheet S is sent to the upper surface of the conveyance 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 conveyance belt 14.

[0013] The conveyance belt 14 is a net-like endless belt having a large number of through holes formed on its surface. Three rollers, a driving roller 141, and driven rollers 142, 143 rotatably support the conveyance belt 14. A motor 205 rotates the driving roller 141 to rotate the conveyance belt 14. The motor 205 is an example of a driving device. Reference numeral 105 in the figure indicates the rotation direction of the conveyance belt 14. A negative pressure container 206 is arranged on the back side of the conveyance belt 14. The negative pressure container 206 is connected to a decompression fan 207. The fan 207 creates a negative pressure inside the negative pressure container 206 by the formed air flow, and adsorbs and holds the sheet S on the upper surface of the conveyance belt 14. Reference numeral 106 in the figure indicates the flow of the air current.

[0014] Examples of liquid ejection heads, inkjet heads 100 to 103, are arranged to face a sheet S adsorbed and held on a conveyance belt 14 with a slight 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. Each of the inkjet heads 100 to 103 has the same structure except that the color of the ejected ink is different. The colors of the ink are, for example, cyan, magenta, yellow, and black.

[0015] The inkjet heads 100 to 103 are respectively connected to ink tanks 315 to 318 and ink supply pressure adjusting devices 321 to 324. Each of the ink tanks 315 to 318 is arranged above each of the inkjet heads 100 to 103. During standby, each of the ink supply pressure adjusting devices 321 to 324 adjusts the inside of each of the inkjet heads 100 to 103 to a negative pressure with respect to the atmospheric pressure, for example, -1.2 kPa, so that ink does not leak from nozzles 20 (see FIG. 2) of the inkjet heads 100 to 103. During image formation, the ink in each of the ink tanks 315 to 318 is supplied to each of the inkjet heads 100 to 103 by the ink supply pressure adjusting devices 321 to 324.

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

[0017] Subsequently, the configuration of the inkjet heads 100 to 103 will be described. The following describes the inkjet head 100 with reference to FIGS. 2 to 4, but the inkjet heads 101 to 103 also have the same structure as the inkjet head 100.

[0018] As shown in FIGS. 2 to 4, the inkjet head 100 includes a head unit 2 which is an example of a liquid ejection unit. The head unit 2 is connected to a flexible printed wiring board 3 which is an example of a film wiring board. The flexible printed wiring board 3 is connected to a printed circuit board 4 which is an example of a relay board.

[0019] The multi-nozzle head unit 2 includes a nozzle plate 21 which is an example of a nozzle unit in which a plurality of nozzles 20 are arranged, an actuator substrate 22 forming an actuator corresponding to each nozzle 20, a frame member 23 forming a common ink chamber 26, and an ink supply unit 24 supplying ink to the common ink chamber 26.

[0020] The nozzle plate 21 is 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. Note that the arrangement in a row does not necessarily require the centers of the nozzles 20 to be in a straight line, and for example, there may be a shift in the Y direction which is the second direction. The nozzle density is set, for example, within a range of 150 to 1200 dpi. The actuator substrate 22 is a rectangular substrate formed of, for example, insulating ceramics.

[0021] 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 partitioned 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 with the actuator substrate 22 interposed therebetween. 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 the ink supply pressure adjusting device 321 in FIG. 1 via the ink supply pipe 28. The other common ink chamber 262, although not shown in the figure, communicates with an ink discharge port which is an opening similar to the ink supply port 27 and serves as an ink discharge path for discharging ink from the plurality of pressure chambers 5. When the ink is circulated and supplied, the ink discharge port is connected to the ink supply pressure adjusting device 321 via the ink discharge pipe 29.

[0022] As shown in FIGS. 3 and 4, 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 in the common ink chamber 26 (261, 262). The pressure chambers 5 and the air chambers 51 are partitioned by piezoelectric members 6 (61, 62) serving as side walls. The piezoelectric members 6 (61, 62) are piezoelectric bodies such as piezo elements. The pressure chambers 5 and the air chambers 51 are formed on the surface of the actuator substrate 22 by grooves obtained by notching two stacked piezoelectric members 61 and 62 in a rectangular shape in the Y direction in the Z direction of the third direction. The two piezoelectric members 61 and 62 are stacked in directions where the polarization directions are opposite (as an example, the opposing directions). Each pressure chamber 5 communicates with each nozzle 20 on a one-to-one basis. The air chambers 51 are located on both sides of the pressure chambers 5.

[0023] Further, a pair of cover members 67 that form side walls on both sides in the Y direction of the air chamber 51 are respectively provided on both side surfaces of the actuator substrate 22. The air chamber 51 is separated from the common ink chambers 26 (261, 262) by the cover members 67. Groove-shaped openings 68 corresponding to the shape of the pressure chamber 5 are formed in the cover members 67 so that the pressure chamber 5 communicates with the left and right common ink chambers 261 and 262. The opening 68 of the cover member 67 on the common ink chamber 261 side is an ink supply port, and the opening 68 of the cover member 67 on the common ink chamber 262 side is an ink discharge port. Ink is supplied to and discharged from the pressure chamber 5 through the ink supply port and the ink discharge port. FIG. 3 shows a cover member 67 formed of a plate material as an example, but the cover member 67 may be formed of, for example, resin or a plate material. Further, the cover member 67 may be configured to fill only the portions of the side walls on both sides in the Y direction of the air chamber 51.

[0024] As shown in FIG. 4, the individual electrodes 63 are 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 each pressure chamber 5 are respectively connected to individual wirings 65. The common electrodes 64 of each air chamber 51 are commonly connected to a common wiring 66 respectively. The individual electrodes 63, the common electrode 64, the individual wirings 65, and the common wiring 66 are formed of, for example, a nickel thin film and are insulated by being covered with, for example, an insulating layer (not shown).

[0025] 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 via the individual wiring 65. To the drive driver D, V1, V2, and ground (GND) are connected as the power sources of the drive voltage. 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 each actuator 8 are commonly connected to, for example, ground (GND) or a common potential of a predetermined constant potential. The drive drivers D of each drive channel (1ch, 2ch, ··· nch) respectively apply a drive voltage to the individual terminals of each actuator 8 to drive them independently. With this configuration, in the actuator 8 to which the drive voltage is applied, an electric field is applied in a direction intersecting (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 deformed symmetrically in the X direction in a shear mode. The actuator 8 is an example of a piezoelectric actuator.

[0026] That is, the pressure chamber 5 is formed being 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 consequently, the ink pressure inside the pressure chamber 5 changes. By adjusting the magnitude and timing of this change, ink is ejected from the nozzle 20.

[0027] FIG. 5 is a block configuration diagram of the control system of the inkjet printer 10. The control board 17 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 which is 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 transmitted to the control board 17 through the I / O port 93 and stored in the image memory 94. The CPU 9 sequentially transmits the image data stored in the image memory 94 to the drive circuits 95 of the inkjet heads 100 to 103 in the drawing order. The data to be transmitted can include tone data specifying the tone of dots based on the image data.

[0028] The drive circuit 95 includes a data buffer 96, a decoder 97, and a drive driver 98. The drive driver 98 is provided in the drive IC 31 as the control unit of the inkjet head 100. The data buffer 96 stores the image data in time series for each actuator 8. The decoder 97 controls the drive driver 98 based on the image data stored in the data buffer 96 for each actuator 8. The drive driver 98 outputs a drive signal for operating each actuator 3 based on the control of the decoder 97. The drive signal is a voltage applied to the actuator 3 according to the drive waveform.

[0029] Fig. 6 shows an example of a drive waveform. The drive waveform in Fig. 6 is a multi-drop drive waveform that ejects ink three drops in one drive cycle. Prior to the ink ejection operation, a voltage Vb is applied to the individual terminals of the actuator 8. Then, from time t1 to time t2, voltage Va, from time t2 to time t3, voltage Vc, from time t3 to time t4, voltage Va, from time t4 to time t5, voltage Vb, from time t5 to time t6, voltage Va, from time t6 to time t7, voltage Vb, from time t7 to time t8, voltage Vc, and at time t8, voltage Vb are applied as drive signals to the individual terminals of the actuator 8. The voltage Va is, for example, 0V and is supplied from the GND in Fig. 4. The voltages Vb and Vc are positive voltages and are supplied from the power supplies V2 and V1 in Fig. 4, respectively. Va < Vb < Vc. The common terminals of each actuator 8 are commonly connected to, for example, a ground (GND) of 0V.

[0030] 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.

[0031] Prior to the ink ejection operation, the actuator 8 with voltage Vb applied to the individual terminals causes the piezoelectric members 6 (61, 62) on both sides of the pressure chamber 5 to deform in the shear mode inwardly as shown in Fig. 7(b), and the volume inside the pressure chamber 5 contracts. Then, the actuator 8 with voltage Va applied to the individual terminals at time t1 causes the piezoelectric members 6 (61, 62) that were deformed in the shear mode to return to their original state as shown in Fig. 7(a), and the volume inside the pressure chamber 5 expands relatively from the state in Fig. 7(b), thereby supplying ink into the pressure chamber 5. At the subsequent time t2, the actuator 8 with voltage Vc applied to the individual terminals causes the piezoelectric members 6 (61, 62) to deform in the shear mode inwardly respectively as shown in Fig. 7(c), and the volume inside the pressure chamber 5 contracts. Due to this series of volume changes inside the pressure chamber 5, the pressure of the ink increases, and the first drop of ink is ejected from the nozzle 20.

[0032] Subsequently, the actuator 8 with voltage Va applied to the individual terminals at time t3 causes the volume inside the pressure chamber 5 to expand from the state in Fig. 7(c) to the state in Fig. 7(a), and by applying voltage Vb at time t4, the volume inside the pressure chamber 5 contracts to the state in Fig. 7(b), ejecting the second drop of ink. Subsequently, the actuator 8 with voltage Va applied to the individual terminals at time t5 causes the volume inside the pressure chamber 5 to expand from the state in Fig. 7(b) to the state in Fig. 7(a), and by applying voltage Vb at time t6, the volume inside the pressure chamber 5 contracts to the state in Fig. 7(b), ejecting the third drop of ink.

[0033] Then, the actuator 8 with voltage Vc applied to the individual terminals at time t7 causes the volume inside the pressure chamber 5 to contract to the state in Fig. 7(c), and by applying voltage Vb at time t8, the contracted volume inside the pressure chamber 5 returns to the state in Fig. 7(b). This contraction and return attenuate the residual amount vibration.

[0034] As shown in FIG. 8, in this embodiment, for example, a plurality of nozzles 20 arranged in a row are grouped so as to alternately belong to a first group and a second group. The timing of applying a drive signal to the actuator 8 for the nozzles 20 in the first group and the nozzles 20 in the second group is set so as to be shifted from each other between the groups. Further, for both the first group and the second group, the timing of applying a drive signal to the actuator 8 is also set so as to be shifted from each other even between the nozzles 20 belonging to the same group. The shift time of this drive timing is set by two times, a primary shift time and a secondary shift time. The primary shift time is used to shift the drive timing between the first group and the second group. The secondary shift time is used to shift the drive timing between the nozzles 20 belonging to the same group.

[0035] The primary shift time is set in the vicinity of one time (1AL) of half of the natural vibration period in the pressure chamber 5 filled with ink. Preferably, it is 1AL. When the secondary shift time is represented by times A and B shorter than 1AL, a constant time interval K shorter than 1AL, and fine adjustment times i and j shorter than time A or time B, the nozzles 20 in the first group are allocated M types of shift times of A + K(M - 1) ± i (M is an integer such as 1, 2...). The nozzles 20 in the second group are allocated N types of shift times of B + K(N - 1) ± j (N is an integer such as 1, 2...).

[0036] The drive timing shift time (total shift time) set by the primary shift time and the secondary shift time is allocated to each nozzle 20 so that the absolute value of the difference in drive timing between adjacent nozzles 20 falls within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). That is, it is arranged so as to fall within the range of the larger value of 1AL ± (A + K - B + i) or 1AL ± (A + K - B + j).

[0037] The reason for setting the primary shift time near 1AL will be described. Fig. 9 shows the difference in the leading position of the ink droplets during full nozzle driving and single nozzle driving when the shift time of the driving timing between two groups is variously set at intervals of 0.2AL within the range of 0.8AL to 1.2AL. The driving waveform used was the multi-drop driving waveform of Fig. 7. In order to confirm the effect of setting the primary shift time, the secondary shift time was not set. Full nozzle driving is a driving mode in which ink is ejected from all nozzles 20 within the same driving period. Single nozzle driving is a driving mode in which ink is ejected from one nozzle 20. The difference in the leading position of the ink droplets during full nozzle driving and single nozzle driving means the difference in the flying distance of the first drop of ink at a predetermined timing (for example, 100 μs after ejection). The closer the difference in the leading position is to zero, the smaller the variation in the ejection speed due to crosstalk.

[0038] According to the results of Fig. 9, crosstalk is minimized for the first group at a driving timing that is shifted by 1.1AL from the second group. For the second group, crosstalk is minimized at a driving timing that is 0.9AL after the driving of the first group. Thus, in two-part driving, if the shift time of the driving timing optimal for one group is set, the crosstalk of the other group deteriorates. As can be seen from Fig. 2, the shift time of the driving timing suitable for both groups is near 1AL. That is, it is advisable to set the primary shift time near 1AL. As an example, it is 0.96AL to 1.04AL. Preferably it is 1AL. The primary shift time may be set within the range of 0.8AL to 1.2AL, which is the evaluation range of Fig. 9.

[0039] However, in the two-phase drive using only the primary deviation time, since a plurality of actuators 8 are simultaneously driven within each group, current concentration may occur particularly in the common wiring 66. To suppress the occurrence of this current concentration, a secondary deviation time having a fixed time interval K is provided to perform split drive even within the group. However, if the secondary deviation time is set to a large value, crosstalk between the two groups cannot be maintained in an appropriate state. Therefore, the value of the secondary deviation time is set small so that the difference in drive timing between the groups does not deviate from around 1 AL.

[0040] Next, the secondary deviation time will be described. As described above, the nozzles 20 of the first group are assigned M types of secondary deviation 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 secondary deviation times of B + K(N - 1) ± j (N is an integer such as 1, 2...). The times A and B are arbitrary drive start timings. The times i and j are variable arbitrary fine adjustment times. As an example, the times A and B are set to 0.02 μs. However, the times A and B are not limited to being the same. To prevent current concentration, it is preferable that the fixed interval K is at least 0.04 μs or more. On the other hand, if the fixed time interval K is too large, the difference in drive timing will deviate from around 1 AL, so it is preferable that the fixed time interval K is 0.2 AL or less. As an example, when 1 AL is 2 μs, the fixed time interval K is set to 0.1 μs. However, the time interval K is not limited to 0.1 μs.

[0041] In this embodiment, an example of eight-phase drive will be described in which different drive timing deviation times are set for a set of eight nozzles 20. The nozzles 20 arranged on the nozzle plate 21 are each assigned a pattern of drive timing deviation times for a set of eight in the arrangement direction in a repeated manner so that all the nozzles 20 can be eight-phase driven.

[0042] Among the eight nozzles 20 in a group, four nozzles 20 belonging to the first group are set with four different driving timing deviation times. The primary deviation time of the first group is set to 0 μs. The secondary deviation time is, for example, set with M = 4, A = 0.02 μs, K = 0.1 μs, i = 0, and is the following four types (M types). 0.02 μs = A + K(M - 1) ± i = 0.02 + 0.1×(1 - 1) ± 0 0.12 μs = A + K(M - 1) ± i = 0.02 + 0.1×(2 - 1) ± 0 0.22 μs = A + K(M - 1) ± i = 0.02 + 0.1×(3 - 1) ± 0 0.32 μs = A + K(M - 1) ± i = 0.02 + 0.1×(4 - 1) ± 0 The total deviation time (driving timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 0.02 μs = primary deviation time 0 μs + secondary deviation time 0.02 μs 0.12 μs = primary deviation time 0 μs + secondary deviation time 0.12 μs 0.22 μs = primary deviation time 0 μs + secondary deviation time 0.22 μs 0.32 μs = primary deviation time 0 μs + secondary deviation time 0.32 μs

[0043] Among the eight nozzles 20 in a group, four nozzles 20 of the second group are set with four different driving timing deviation times. The primary deviation time of the second group is set to 2 μs. The secondary deviation time is, for example, set with N = 4, B = 0.02 μs, K = 0.1 μs, j = 0, and is the following four types (N types). 0.02 μs = B + K(N - 1) ± j = 0.02 + 0.1×(1 - 1) ± 0 0.12 μs = B + K(N - 1) ± j = 0.02 + 0.1×(2 - 1) ± 0 0.22 μs = B + K(N - 1) ± j = 0.02 + 0.1×(3 - 1) ± 0 0.32 μs = B + K(N - 1) ± j = 0.02 + 0.1×(4 - 1) ± 0 The total deviation time (drive timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 2.02 μs = primary deviation time 2 μs + secondary deviation time 0.02 μs 2.12 μs = primary deviation time 2 μs + secondary deviation time 0.12 μs 2.22 μs = primary deviation time 2 μs + secondary deviation time 0.22 μs 2.32 μs = primary deviation time 2 μs + secondary deviation time 0.32 μs

[0044] The deviation times of the above eight types of drive timings are arranged so that the absolute value of the difference in drive timings between adjacent nozzles 20 falls 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. An example of the arrangement of this embodiment is shown in Fig. 10(a). Fig. 10(a) shows together the time difference with the previous adjacent nozzle and the time difference with the next adjacent nozzle, which are the differences in drive timings between adjacent nozzles 20. The time difference with the previous adjacent nozzle is the difference in drive timing with respect to the nozzle 20 with the nozzle number one less. The time difference with the next adjacent nozzle is the difference in drive timing with respect to the nozzle 20 with the nozzle number one more. As is clear from Fig. 10(a), for any nozzle 20, the absolute value of the difference in drive timings between adjacent nozzles 20 falls 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 Figs. 11 to 13 described later, the in-column linearity of the ink landing position (drop position) can be improved.

[0045] FIG. 10(b) is an example in which, as a comparative example, the deviation times of the above total eight types of driving timings are arranged in an array different from that of FIG. 10(a). Although this array uses the same eight types of driving timing deviation times as those in FIG. 10(a), the time difference from the nozzle 20 adjacent to the rear of the (n + 6)-th nozzle 20 and the time difference from the nozzle 20 adjacent to the front of the (n + 7)-th nozzle 20 are 2.3 μs. That is, they are outside the range of 2 μs ± 0.1 μs of 1AL ± (A + K - B + i) and 1AL ± (A + K - B + j). How different the ink ejection states are between the array of the present embodiment in FIG. 10(a) and the array of the comparative example in FIG. 10(b) will be described with reference to FIGS. 11 to 13.

[0046] FIG. 11(a) is a graph in which the total deviation times of the nozzles 20 numbered 149 to 164 in the present embodiment are plotted respectively. For the 16 nozzles 20 numbered 149 to 164, the array of eight in a set in FIG. 10(a) is repeated twice to allocate the driving timing deviation times. Similarly, FIG. 11(b) is a graph in which the total deviation times of the nozzles 20 numbered 149 to 164 in the comparative example are plotted respectively. For the 16 nozzles 20 numbered 149 to 164, the array of eight in a set in FIG. 10(b) is repeated twice to allocate the driving timing deviation times. As can be seen by comparing the shapes of the broken lines in FIGS. 11(a) and 11(b), in the present embodiment, the driving timing deviation times can be set more evenly compared to the comparative example. That is, in the present embodiment, the difference in the total deviation times between adjacent nozzles 20 is all within 2 μs ± 0.1 μs, while in the comparative example, the difference in the total deviation times of the nozzles 20 numbered 155 and 156 exceeds 2 μs ± 0.1 μs, which is a factor that strongly receives the influence of crosstalk.

[0047] Figure 12(a) shows the measurement results of crosstalk when the driving timing deviation time array of this embodiment is applied. The measurement of crosstalk measures three types of differences in the leading positions of the ink droplets ejected during full nozzle driving and single nozzle driving, the difference in the leading positions of the ink droplets ejected during full nozzle driving and 1ON1OFF driving, and the difference in the leading positions of the ink droplets ejected during 1ON1OFF driving and single nozzle driving. The conveyance speed of the sheet S onto which the ink is ejected is set to 1990 mm / s. The 1ON1OFF driving measures the leading position of the ink droplets when only the first group or the second group ejects ink. Figure 12(b) shows the measurement results of crosstalk when the driving timing deviation time array of the comparative example is applied.

[0048] Figures 12(a) and 12(b) also show the 3σ values for evaluating the variation. As can be seen by comparing Figures 12(a) and 12(b), in this embodiment, the variation in the difference in the leading positions is small in any driving mode. As described above, the closer the difference in the leading positions is to zero, the smaller the variation in the ejection speed due to crosstalk.

[0049] Figure 13(a) shows the drop positions (landing positions) of the ink when ink is ejected from all the nozzles 20 using the driving timing deviation time array of this embodiment. Figure 13(b) shows the drop positions of the ink when ink is ejected from all the nozzles 20 using the driving timing deviation time array of the comparative example. Figures 13(a) and 13(b) also show the results of the two-division driving as a benchmark. The two-division driving of the benchmark has the primary deviation time set only to 2 μs. This embodiment is an eight-division driving based on the primary deviation time and the secondary deviation time, but the difference in the drop positions is small even compared to the two-division driving. That is, even with the eight-division driving, column linearity at the same level as the two-division driving can be achieved. In contrast, it can be seen that the comparative example has a larger difference in the drop positions compared to the two-division driving and is inferior in column linearity to this embodiment.

[0050] As described above, the two - split drive of the benchmark that sets only the primary deviation time suppresses crosstalk and has good in - column linearity. However, since the number of actuators 8 driven simultaneously is large, current concentration is likely to occur. Current concentration also becomes a factor for generating electrical crosstalk. On the other hand, the eight - split drive of the present embodiment based on the primary deviation time and the secondary deviation time can avoid current concentration, but there is a concern that the in - column linearity may decrease. Actually, in the comparative example, the in - column linearity has decreased. In contrast, the present embodiment is effective in that it can suppress the decrease in the in - column linearity of the landing positions of the ink ejected from the plurality of nozzles 20 and can suppress current concentration during driving.

[0051] (Second Embodiment) Subsequently, the inkjet head 100 of the second embodiment will be described. In the first embodiment, as described above, the same number of four types of secondary deviation times are set for the first group and the second group, but it is not limited to this. The number of secondary deviation times may be different between the first group and the second group. That is, the values of M and N may be different. FIG. 14 shows an example in which the number of secondary deviation times in the first group is three types and the number of secondary deviation times in the second group is two types. In each group, the number of nozzles 20 is larger than the number of types of secondary deviation times.

[0052] The primary deviation time of the first group is set to 0 μs. As an example, for the secondary deviation time, M = 3, A = 0.02 μs, K = 0.2 μs, i = 0, and the following three types are obtained. 0.02 μs = A + K(M - 1) ± i = 0.02+0.2×(1 - 1) ± 0 0.22 μs = A + K(M - 1) ± i = 0.02+0.2×(2 - 1) ± 0 0.42 μs = A + K(M - 1) ± i = 0.02+0.2×(3 - 1) ± 0 The total deviation time (drive timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 0.02 μs = primary deviation time 0 μs+secondary deviation time 0.02 μs 0.22 μs = Primary deviation time 0 μs + Secondary deviation time 0.22 μs 0.42 μs = Primary deviation time 0 μs + Secondary deviation time 0.42 μs

[0053] The primary deviation time of the second group is set to 2 μs. The secondary deviation time, as an example, is set with N = 2, B = 0.12 μs, K = 0.2 μs, j = 0, and there are the following two types. 0.12 μs = B + K(N - 1) ± j = 0.12 + 0.2×(1 - 1) ± 0 0.32 μs = B + K(N - 1) ± j = 0.12 + 0.2×(2 - 1) ± 0 The total deviation time (drive timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 2.12 μs = Primary deviation time 2 μs + Secondary deviation time 0.12 μs 2.32 μs = Primary deviation time 2 μs + Secondary deviation time 0.32 μs

[0054] The deviation times of the above five types of drive timing are arranged such that the absolute value of the difference in drive timing between adjacent nozzles 20 falls 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 the same as 2 μs ± 0.1 μs in the first embodiment. An example of the arrangement in this embodiment is shown in FIG. 14. FIG. 14 shows together the time difference with the previous adjacent nozzle and the time difference with the next adjacent nozzle, which are the differences in drive timing between adjacent nozzles 20. As is clear from FIG. 14, for any nozzle 20, the absolute value of the difference in drive timing between adjacent nozzles 20 falls within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j). In this way, even if the time interval K of the secondary deviation time is increased, the same degree of ejection linearity as in the first embodiment can be achieved, and current concentration during driving can be suppressed.

[0055] (Third Embodiment) Next, the inkjet head 100 of the third embodiment will be described. In the third embodiment, for a set of nine nozzles 20, five types of secondary deviation times are set for the first group and four types of secondary deviation times are set for the second group, and further fine adjustment is performed with fine adjustment times i and j. For the first group, the secondary deviation time is set with A = 0 μs, K = 0.1 μs, M = 5, and i = 0.02 μs. For the second group, the secondary deviation time is set with B = 0.06 μs, K = 0.1 μs, N = 4, and j = 0.02 μs.

[0056] Among the nine nozzles 20 in a set, five nozzles 20 belonging to the first group are set with five different driving timing deviation times. The primary deviation time of the first group is set to 0 μs. As an example, the secondary deviation time is set with M = 5, A = 0 μs, K = 0.1 μs, and i = (variable of 0.02, ±0, -0.02), and the following five types (M types) are obtained. 0.02 μs = A + K(M - 1) ± i = 0 + 0.1×(1 - 1) + 0.02 0.10 μs = A + K(M - 1) ± i = 0 + 0.1×(2 - 1) ± 0 0.20 μs = A + K(M - 1) ± i = 0 + 0.1×(3 - 1) ± 0 0.30 μs = A + K(M - 1) ± i = 0 + 0.1×(4 - 1) ± 0 0.38 μs = A + K(M - 1) ± i = 0 + 0.1×(5 - 1) - 0.02 The total deviation time (driving timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 0.02 μs = primary deviation time 0 μs + secondary deviation time 0.02 μs 0.10 μs = primary deviation time 0 μs + secondary deviation time 0.10 μs 0.20 μs = primary deviation time 0 μs + secondary deviation time 0.20 μs 0.30 μs = primary deviation time 0 μs + secondary deviation time 0.30 μs 0.38 μs = primary deviation time 0 μs + secondary deviation time 0.38 μs

[0057] Among the nine sets of nozzles 20, for the four nozzles 20 in the second group, four different driving timing deviation times are set. The primary deviation time of the second group is set to 2 μs. The secondary deviation time is, as an example, set with N = 4, B = 0.06 μs, K = 0.1 μs, j = (variable of ±0, -0.02), and there are the following four types (N types). 0.04 μs = B + K(N - 1) ± j = 0.06 + 0.1×(1 - 1) - 0.02 0.16 μs = B + K(N - 1) ± j = 0.06 + 0.1×(2 - 1) ± 0 0.26 μs = B + K(N - 1) ± j = 0.06 + 0.1×(3 - 1) ± 0 0.36 μs = B + K(N - 1) ± j = 0.06 + 0.1×(4 - 1) ± 0 The total deviation time (driving timing deviation time) obtained by adding the primary deviation time to each secondary deviation time is as follows. 2.04 μs = primary deviation time 2 μs + secondary deviation time 0.02 μs 2.16 μs = primary deviation time 2 μs + secondary deviation time 0.16 μs 2.26 μs = primary deviation time 2 μs + secondary deviation time 0.26 μs 2.36 μs = primary deviation time 2 μs + secondary deviation time 0.36 μs

[0058] The deviation times of the above-mentioned total nine types of driving timings are arranged such that the absolute value of the difference in driving timings between adjacent nozzles 20 falls 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 ± 0.06 μs (where i, j = 0.02, ±0, -0.02 are variable). An example of the arrangement of this embodiment is shown in FIG. 15. FIG. 15 shows together the time difference with the previous adjacent nozzle and the time difference with the subsequent adjacent nozzle, which indicate the difference in driving timings between adjacent nozzles 20. The third embodiment does not simply repeat the arrangement of eight in a set as in the first and second embodiments in the arrangement direction of the nozzles 20. After allocating the arrangement of nine in a set to the nozzles 20 from the (n + 1)-th to the (n + 8)-th, the arrangement direction is reversed and allocated to the nozzles 20 from the (n + 9)-th to the (n + 15)-th. The same is repeated for the nozzles 20 after the (n + 16)-th. As is clear from FIG. 15, for any nozzle 20, the absolute value of the difference in driving timings between adjacent nozzles 20 falls within the range of 1AL ± (A + K - B + i) and within the range of 1AL ± (A + K - B + j), that is, within 2 μs ± 0.06 μs. In this embodiment, for the nozzles 20 arranged on the nozzle plate 21, by repeatedly allocating the pattern of the deviation times of nine in a set of driving timings as described above, all the nozzles 20 can be driven in nine divisions.

[0059] According to the above-described embodiment, the influence of crosstalk received from the surrounding drive channels can be suppressed, and stable ink ejection can be performed.

[0060] Note that the inkjet head 100 is not limited to the shear mode actuator 8 in which the pressure chambers 5 and the air chambers 51 are alternately arranged. For example, a configuration in which a plurality of both the nozzles 20 and the actuators 8 are arranged on the surface of the nozzle plate 21 may be used. Other drop-on-demand piezo type actuators 8 may also be used. Further, the actuator 8 may be a laminated piezoelectric actuator formed by alternately laminating piezoelectric members and internal electrodes in layers.

[0061] In the above-described embodiment, the inkjet head 100 of the inkjet printer 10 has been 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.

[0062] 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, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0063] 10 Inkjet printer 100 to 103 Inkjet heads 2 Head unit 20 Nozzles 5 Pressure chamber 51 Air chamber 8 Actuator

Claims

1. A nozzle section in which a plurality of nozzles for discharging a liquid are arranged, a plurality of pressure chambers that communicate individually with the plurality of nozzles and are filled with the liquid respectively, a plurality of piezoelectric actuators that change the volume in the plurality of pressure chambers respectively, a control unit that expands and contracts the volume in the pressure chamber by applying a drive signal to the piezoelectric actuator, thereby discharging the liquid from the nozzle, and adjacent nozzles among the plurality of nozzles are set to belong to different first and second groups, the drive timings for applying the drive signal are made different between the first and second groups by a primary deviation time, and the drive timings for applying the drive signal are made different between the nozzles within each group by a secondary deviation time, the primary deviation time is set to 1 times (1AL) the time that is half of the natural vibration period in the pressure chamber, and when the secondary deviation time is represented by times A and B shorter than 1AL, a constant time interval K shorter than 1AL, and fine adjustment times i and j shorter than time A or time B, M types of settings of A + K(M - 1) ± i are assigned to the first group (M is an integer of 1, 2,...), N types of settings of B + K(N - 1) ± j are assigned to the second group (N is an integer of 1, 2,...), and a liquid discharge head characterized in that the difference in drive timings between adjacent nozzles is arranged within an allowable range of 1AL ± (A + K - B + i) and within an allowable range of 1AL ± (A + K - B + j).

2. The liquid discharge head according to claim 1, characterized in that the constant time interval K is set within a range of 0.04 μs or more and 0.2AL or less.

3. The liquid discharge head according to claim 1, characterized in that the allowable range is 1AL ± 0.1 μs.

4. The liquid discharge head according to claim 1, characterized in that there are a total of 8 or 9 types of deviation times of drive timings due to the primary deviation time and the secondary deviation time, and these 8 or 9 types of deviation times of drive timings are assigned to the plurality of nozzles to perform 8 - division drive or 9 - division drive.

5. A nozzle section in which a plurality of nozzles for discharging a liquid are arranged, A plurality of pressure chambers that communicate individually with the plurality of nozzles and are filled with the liquid respectively, A plurality of piezoelectric actuators that change the volume in the plurality of pressure chambers respectively, A control unit that expands and contracts the volume in the pressure chamber by applying a drive signal to the piezoelectric actuator to discharge the liquid from the nozzle, and Adjacent ones of the plurality of nozzles are set to belong to different first and second groups, The drive timings for applying the drive signal between the first and second groups are made different from each other by a primary deviation time, and the drive timings for applying the drive signal between the nozzles within each group are made different from each other by a secondary deviation time, The primary deviation time is set to 0.8 to 1.2 times (0.8AL to 1.2AL) the time that is half of the natural vibration period in the pressure chamber, and When the secondary deviation time is represented by a time A and a time B shorter than (0.8AL to 1.2AL), a constant time interval K shorter than (0.8AL to 1.2AL), a fine adjustment time i shorter than the time A or the time B, and a fine adjustment time j, M types of settings of A + K(M - 1) ± i are assigned to the first group (M is an integer such as 1, 2...), N types of settings of B + K(N - 1) ± j are assigned to the second group (N is an integer such as 1, 2...), and A liquid discharge head characterized in that the difference in drive timings between adjacent nozzles is arranged within a range of (0.8AL to 1.2AL) ± (A + K - B + i) and within a range of (0.8AL to 1.2AL) ± (A + K - B + j).

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