Liquid ejection head

Abstract

To provide a liquid ejection head that is able to prevent ejection of liquid from a channel from affecting the ejection characteristics of another channel.SOLUTION: A liquid ejection head according to an embodiment includes a pressure chamber, a common liquid chamber, an actuator, and a nozzle portion. A plurality of channels for ejecting liquid each include the pressure chamber. The common liquid chamber communicates with at least one end of each pressure chamber in a longitudinal direction thereof. The actuator changes the volume of the pressure chamber. The nozzle unit includes a liquid ejection nozzle and a nozzle that does not eject liquid. The liquid ejection nozzle is provided at a position where a longitudinal liquid column resonance in a pressure chamber, generated when the actuator is driven, increases a pressure change in the pressure chamber. The nozzle that does not eject liquid is provided on a communication path between another channel and the pressure chamber and at a position where a pressure change by liquid column resonance is small.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

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

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

[0004] When the volume of the pressure chamber changes, liquid flows in and out between the pressure chamber and the common liquid chamber, but it is desirable that the pressure change in the common liquid chamber when liquid flows in and out be as small as possible. If the pressure change is large, the effect of the pressure change when the actuator of the channel selected to eject liquid is driven will be propagated to the surroundings via the common liquid chamber, affecting the ejection characteristics of other channels. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP2015-080923A [Patent Document 2] JP2012-166462A [Patent Document 3] JP2010-23241A Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a liquid ejection head capable of suppressing the influence of ejection of liquid from one channel on the ejection characteristics of another channel. [Means for solving the problem]

[0007] A liquid ejection head according to an embodiment of the present invention includes a pressure chamber, a common liquid chamber, an actuator, and a nozzle portion. Each of a plurality of channels for ejecting liquid includes a pressure chamber. The common liquid chamber is disposed at least at one end in the longitudinal direction of each of the pressure chambers. Open end of The actuator changes the volume of the pressure chamber. The nozzle section includes a nozzle for discharging liquid and a nozzle that does not discharge liquid. The nozzle for discharging liquid is a nozzle for discharging liquid, which is generated when the actuator is driven. 1 / 4 or 1 / 2 wavelength The nozzle is provided at a position where the pressure change in the pressure chamber due to liquid column resonance becomes large. The nozzle that does not eject liquid is provided on a communication path between the pressure chamber of another channel and the pressure chamber and at a position where the pressure change due to liquid column resonance is small. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram of an inkjet printer equipped with an inkjet head according to an embodiment. [Diagram 2] FIG. 2 is a perspective view of the inkjet head. [Diagram 3] FIG. 2 is a partially enlarged perspective view of a nozzle head portion of the inkjet head. [Figure 4] FIG. 2 is a partially enlarged cross-sectional view of a nozzle head portion of the inkjet head. [Diagram 5] This is a driving waveform given to the actuator of the inkjet head. [Figure 6] 5A to 5C are diagrams illustrating the operation of an actuator driven by the above drive waveform. [Figure 7] FIG. 2 is a layout diagram of ejection nozzles and pressure relief nozzles of the inkjet head. [Figure 8] 4A to 4C are diagrams illustrating the arrangement of the ejection nozzles and pressure relief nozzles of the inkjet head, and liquid column resonance occurring within a pressure chamber. [Figure 9] FIG. 2 is a diagram showing cross-sectional shapes of the discharge nozzle and the pressure relief nozzle. [Figure 10] 3 is an explanatory diagram of the arrangement of ejection nozzles and pressure relief nozzles of the inkjet head and pressure propagation. FIG. [Figure 11] 3 is an explanatory diagram of the arrangement of ejection nozzles and pressure relief nozzles of the inkjet head and pressure propagation. FIG. [Figure 12] 3 is an explanatory diagram of the arrangement of ejection nozzles and pressure relief nozzles of the inkjet head and pressure propagation. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

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

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

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

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

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

[0015] The inkjet heads 100-103 are connected to ink tanks 315-318 and ink supply pressure adjusting devices 321-324 via ink flow paths 311-314, respectively. The ink tanks 315-318 are disposed above the inkjet heads 100-103. During standby, the ink supply pressure adjusting devices 321-324 adjust the pressure inside the inkjet heads 100-103 to a negative pressure, for example, -1.2 kPa, relative to atmospheric pressure so that ink does not leak from the ejection nozzles 3 and pressure relief nozzles 31 (see FIG. 2) of the inkjet heads 100-103. During image formation, the ink in the ink tanks 315-318 is supplied to the inkjet heads 100-103 by the ink supply pressure adjusting devices 321-324.

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

[0017] Next, a description will be given of the configuration of the inkjet heads 100 to 103. Below, the inkjet head 100 will be described with reference to Figures 2 to 4, but the inkjet heads 101 to 103 have the same structure as the inkjet head 100.

[0018] 2, the inkjet head 100 includes a nozzle head unit 2, which is an example of a liquid ejection unit. The nozzle head unit 2 is connected to a flexible printed wiring board 21. The nozzle head unit 2 includes a plurality of channels for ejecting ink. The nozzle head unit 2 includes a nozzle plate 22, an actuator substrate 23, and an ink supply unit 24, which is an example of a liquid supply unit. The ink supply unit 24 is connected to the ink supply pressure adjustment device 321 of FIG. 1 via an ink flow path 311.

[0019] The flexible printed wiring board 21 is equipped with a driver chip, a driving integrated circuit (IC) 25 (hereinafter referred to as a driving IC). The driving IC 25 temporarily stores print data sent from the control board 17 of the inkjet printer 10, and provides driving signals to each channel to eject ink at a predetermined timing.

[0020] The nozzle plate 22, which is an example of a nozzle section, is a rectangular plate formed of, for example, a resin such as polyimide or a metal such as stainless steel. The nozzles (ejection nozzles) 3 that eject ink are arranged on the surface of the nozzle plate 22 along the longitudinal direction (X direction) of the nozzle plate 22. The nozzle density is set, for example, within a range of 150 to 1200 dpi. The pressure relief nozzles 31 are nozzles that do not eject ink. The pressure relief nozzles 31 are arranged on both sides of the ejection nozzles 3 in the short-side direction (Y direction) of the nozzle plate 22. That is, each channel that ejects ink includes one ejection nozzle 3 and two pressure relief nozzles 31. Note that, in FIG. 2, the ejection nozzles 3 are arranged in two rows in the short-side direction (Y direction) of the nozzle plate 22, but this is not limited thereto. The ejection nozzles 3 may be arranged in one row, for example.

[0021] As shown in particular in Figures 3 and 4, the nozzle plate 22 is attached to the actuator substrate 23 via a frame member 26. The actuator substrate 23 is a rectangular substrate made of, for example, insulating ceramics. A plurality of pressure chambers 4 for ink of each channel are formed in a space surrounded by the nozzle plate 22, the frame member 26, and the actuator substrate 23. A plurality of pressure chambers 4 are arranged on the actuator substrate 23 along the longitudinal direction of the substrate. The pressure chamber 4 of each channel communicates with the ejection nozzle 3 and pressure relief nozzle 31 of each channel.

[0022] The pressure chambers 4 are formed, for example, by cutting out two piezoelectric members 41, which are laminated with their polarization directions in opposite directions (for example, facing directions), into a rectangular groove shape on the surface of the actuator substrate 23. That is, the piezoelectric members 41 are formed so that their longitudinal direction extends in the short-side direction of the actuator substrate 23. The piezoelectric members 41 are formed so that they are trapezoidal in side view, for example, but the shape in side view is not limited to a trapezoid.

[0023] Adjacent pressure chambers 4 are partitioned by the piezoelectric member 41 as a side wall. That is, each pressure chamber 4 has a side wall of the piezoelectric member 41 erected on both sides in the short side direction, and both ends in the long side direction are open. One opening at the end of the pressure chamber 4 communicates with a central common ink chamber 42, which is an example of a common liquid chamber, and the other opening communicates with an outer common ink chamber 43, which is an example of a common liquid chamber. The central common ink chamber 42 communicates with the ink supply groove 27 of the ink supply unit 24 through an ink supply hole 44 formed in the actuator substrate 23. The outer common ink chamber 43 communicates with the ink discharge path 28 of the ink supply unit 24 through an ink discharge hole 45 formed in the actuator substrate 23. With this configuration, ink is circulated and supplied to the pressure chambers 4 of each channel. However, the ink supply does not have to be by a circulation method.

[0024] The electrodes 46 are integrally formed on the bottom and both side surfaces of the pressure chamber 4. The electrodes 46 of each pressure chamber 4 are connected to wiring electrodes 47. The piezoelectric member 41 and the electrodes 46 constitute an actuator 5 that changes the volume of the pressure chamber 4. The wiring electrodes 47 are extended to the outside of the frame member 26. The surfaces of the electrodes 46 and the wiring electrodes 47 on the inside of the frame member 26 are covered with a protective film (not shown) so as not to come into contact with ink. The electrodes 46 and the wiring electrodes 47 are formed of, for example, a nickel thin film. The wiring electrodes 47 are connected to the flexible wiring board 21 at the end of the actuator substrate 23, and are connected to a driver (i.e., a drive circuit) of the drive IC 25. The driver of each channel provides, for example, a drive voltage as a drive signal to the actuator 5 of each channel. With this configuration, when a drive voltage is applied to the actuator 5, an electric field is applied in a direction intersecting (preferably perpendicular to) the polarization axis of the piezoelectric member 41, and the piezoelectric members 41 that form the side walls on both sides of the pressure chamber 4 deform in shear mode.

[0025] That is, the ink pressure chamber 4 is formed by being sandwiched between a pair of columnar actuators 5 using piezoelectric members 41. A potential difference is applied to both walls of the columnar actuator 5, i.e., the inner wall and the outer wall of the pressure chamber 4, and the actuator 5 is charged, thereby deforming the actuator 5. This changes the volume of the pressure chamber 4, and as a result, the ink pressure inside the pressure chamber 4 changes. Ink is ejected from the ejection nozzle 3 by adjusting the magnitude and timing of this change.

[0026] FIG. 5 shows a drive waveform (DRP waveform) as an example of a drive waveform for driving the actuator 5. FIG. 5 also shows changes in the ink pressure and ink flow velocity in the pressure chamber 4 during driving. The drive waveform sequentially applies a negative potential voltage (-V) to the actuator 5 during period t1, a ground potential (GND) during period t2, and a positive potential voltage (+V) during period t3. The period t1 is set to, for example, half the pressure vibration period of the nozzle head 2. When the pressure vibration period is, for example, 4.8 [μs], the period t1 is set to 2.4 [μs]. The period t2 is, for example, 3.25 [μs], and the period t3 is set to 0.9 [μs], which is shorter than the period t2.

[0027] The actuator 5 can be driven, for example, by dividing the pressure chambers 4 into three groups of two pressure chambers each, so-called three-division driving. FIG. 6(a) shows a state in which the potentials of the electrodes 46 of the groups of three adjacent pressure chambers 4 are all at ground potential (GND). In this state, the piezoelectric members 41, which are the partitions between the pressure chambers 4, are not distorted at all. FIG. 6(b) shows a state in which a negative voltage (-V) is applied to the electrode 46 of the central pressure chamber 4 during period t1 of the drive waveform in FIG. 5. In this state, an electric field acts on the piezoelectric members 41 on both sides of the central pressure chamber 4 to which the voltage (-V) is applied in a direction perpendicular to the polarization direction, and the piezoelectric members 41 are deformed outward, thereby expanding the volume of the central pressure chamber 4.

[0028] In the following period t2, the potential of the electrode 46 of the central pressure chamber 4 is set to ground potential (GND), thereby causing the expanded volume of the central pressure chamber 4 to contract to the state shown in Fig. 6(a). By contracting the volume of the pressure chamber 4 in this way at the end point of period t1, which is set to 1 / 2 the pressure oscillation period, the pressure of the ink in the pressure chamber 4 increases, as shown in Fig. 5, and ink droplets are ejected from the nozzle 3.

[0029] During the further following period t3, a positive voltage (+V) is applied to the electrode 46 of the central pressure chamber 4. In this state, as shown in Fig. 6(c), an electric field acts on the piezoelectric members 41 on both sides of the central pressure chamber 4 in the opposite direction to that in Fig. 6(b), causing the piezoelectric members 41 to deform inwards, contracting the volume of the central pressure chamber 4. After the period t3 has elapsed, the potential of the electrode 46 of the central pressure chamber 4 is set to ground potential (GND), causing the contracted volume of the central pressure chamber 4 to return to the state shown in Fig. 6(a). This contraction and recovery cancels the residual vibration.

[0030] Next, the arrangement of the discharge nozzle 3 and the pressure relief nozzle 31 will be described in detail with reference to FIG. 7 to FIG. 9. As described above, ink is discharged by driving the actuator 5 that changes the volume of the pressure chamber 4 and controlling the pressure in the pressure chamber 4. In the case of a pressure chamber 4 in which the longitudinal ends are open and communicate with the common ink chamber 42 (43), liquid column resonance in the longitudinal direction of the pressure chamber that occurs when the actuator 5 is driven is used for ink discharge. In the case of liquid column resonance, the value obtained by multiplying the above-mentioned pressure oscillation period by the sound speed of the ink in the pressure chamber 4 is the wavelength. Then, as shown in FIG. 7(a), in the case of a pressure chamber 4 in which both longitudinal ends are open, it becomes a 1 / 2 wavelength resonance tube. On the other hand, as shown in FIG. 7(b), in the case of a pressure chamber 4 in which one longitudinal end is open and the other end is closed, it becomes a 1 / 4 wavelength resonance tube. This is different from an inkjet head configured to utilize Helmholtz resonance.

[0031] In the case of a 1 / 2 wavelength resonance tube, the pressure amplitude is maximum and the flow velocity amplitude is minimum at the center of the pressure chamber in the longitudinal direction. In other words, when shown diagrammatically in Figure 8, the center of the pressure chamber in the longitudinal direction corresponds to the node of the 1 / 2 wavelength standing wave W. On the other hand, the pressure amplitude is minimum and the flow velocity amplitude is maximum at both ends of the pressure chamber in the longitudinal direction. In other words, both ends of the pressure chamber in the longitudinal direction correspond to the antinode of the 1 / 2 wavelength standing wave W. When considering the opening correction of the liquid column resonance, the pressure amplitude starts outside the boundary between the pressure chamber 4 and the common ink chambers 42, 43.

[0032] The discharge nozzle 3 is disposed at a position where the pressure change due to the liquid column resonance becomes large. In the example of the 1 / 2 wavelength resonance tube in FIG. 7(a), as a preferred example, the nozzle is disposed at the center in the longitudinal direction where the pressure amplitude is the largest. In the example of the 1 / 4 wavelength resonance tube in FIG. 7(b), as a preferred example, the nozzle is disposed at the back in the longitudinal direction where the pressure amplitude is the largest. Of course, the nozzle is not limited to the position where the pressure amplitude is strictly the largest, and may be disposed in the vicinity of the position. Although not particularly limited, the nozzle is disposed within a range of 1 / 10 wavelength, for example. The discharge nozzle 3 has a tapered shape in which the diameter becomes smaller toward the tip side. The diameter of the base end side of the discharge nozzle 3 is, for example, 40 to 55 μm. The diameter of the tip side of the discharge nozzle 3 is, for example, 20 to 30 μm.

[0033] In this way, the nozzle head unit 2 has the discharge nozzle 3 provided at a position where the pressure change due to the liquid column resonance becomes large, and forms the meniscus M of the ink near the opening (see FIG. 9). The pressure change due to the liquid column resonance that occurs when the actuator 5 is driven is introduced into the discharge nozzle 3 to discharge the ink. The tapered discharge nozzle 3 increases the ink flow rate by narrowing the tip side to a narrow opening, and applies a load to the pressure chamber 4 by the wide opening on the base end side. Note that both the discharge nozzle 3 and the pressure relief nozzle 31 apply negative pressure to the pressure chamber 4 when it is stationary and not discharging ink, thereby maintaining the meniscus M in a concave shape (see FIG. 9). That is, as described above, the ink supply pressure adjustment device 321 adjusts the pressure inside the inkjet head 100 to a negative pressure relative to the atmospheric pressure.

[0034] The pressure relief nozzle 31 is disposed at a position where the pressure change of the liquid column resonance is small. In the example of the 1 / 2 wavelength resonance tube in FIG. 7(a), as a preferred example, the nozzle is disposed at both ends in the longitudinal direction where the pressure amplitude is smallest. In the example of the 1 / 4 wavelength resonance tube in FIG. 7(b), as a preferred example, the nozzle is disposed at the end on the longitudinal opening side where the pressure amplitude is smallest. As described above, the position where the pressure amplitude of the liquid column resonance is smallest is outside the boundary between the pressure chamber 4 and the common ink chamber 42 (43), so the pressure relief nozzle 31 is disposed at that position. The position where the pressure amplitude of the liquid column resonance is smallest is confirmed, for example, by actually conducting a test or by simulation. Of course, the nozzle is not limited to the position where the pressure amplitude is smallest strictly, and may be in the vicinity of the boundary. In other words, the pressure relief nozzle 31 does not have to be outside the boundary between the pressure chamber 4 and the common ink chamber 42 (43), and may be disposed inside the boundary or straddling the boundary. As an example, as shown in FIG. 7C, it is disposed at a position 1 / 10 wavelength inward from the end of the pressure chamber 4 or at a position closer to the common ink chamber 42 (43) side.

[0035] The pressure relief nozzle 31 is disposed at a position where the pressure amplitude of the liquid column resonance is small, so that ink is not ejected even when the actuator 5 is driven. In other words, the pressure relief nozzle 31 is a nozzle that does not eject ink. It is desirable that the pressure relief nozzle 31 has a shape with a smaller taper angle than the ejection nozzle 3. This is because the pressure relief nozzle 31 does not need to have a tapered shape like the ejection nozzle 3, since the purpose of the pressure relief nozzle 31 is not to eject ink. A preferable shape of the pressure relief nozzle 31 is, for example, a cylindrical shape of 20 to 30 μm. The cylindrical shape makes it difficult for unnecessary erroneous ejection from the pressure relief nozzle 31 to occur, and also makes it possible to suppress the intrusion of air from the pressure relief nozzle 31.

[0036] The operating principle of the liquid column resonance tube is as follows: Open It is desirable that there is no pressure change at the open end position. As described above, the pressure chamber 4 and the common ink chambers 42, 43 communicate at the position where the pressure change due to the liquid column resonance is the smallest and the flow rate change is the largest, but in reality, when the actuator 5 is driven, pressure changes also occur at both ends of the pressure chamber 4 due to the flow of ink entering and exiting between the common ink chambers 42, 43 and the pressure chamber 4. This can have a negative effect on the ejection characteristics. This pressure change is also propagated to the pressure chamber 4 of another surrounding channel through the communication path. Therefore, a pressure relief nozzle 31 is provided. The pressure relief nozzle 31 changes the position and shape of the meniscus M (see FIG. 9) in the nozzle even if it does not eject ink, so that the pressure change can be suppressed. The pressure relief nozzle 31 is provided on the communication path 300 between the channel and the adjacent channel as shown in FIG. 10. If the position is too far from the end of the pressure chamber 4, a pressure difference will occur between that location and the end of the pressure chamber 4, so it is desirable to position it near the end of the pressure chamber 4.

[0037] The pressure relief nozzle 31 absorbs pressure changes at the site, and therefore reduces pressure propagation through the communication path 300. This action has the effect of preventing a drop in print quality due to so-called crosstalk, in which the operation of one channel affects the operation of the other channel. If the pressure relief nozzle 31 is located in a common ink chamber 42 (43) that is located on a communication path between a pressure chamber 4 and another pressure chamber 4 adjacent to that pressure chamber 4, the effect of reducing crosstalk can be obtained. For this purpose, the pressure relief nozzle 31 does not necessarily have to be provided for each channel as shown in FIG. 7. For example, as shown in FIG. 11, the effect of reducing crosstalk can be expected even if the pressure relief nozzle 31 is located near the end side of each piezoelectric member 41 in the common ink chamber 42 (43). Alternatively, as shown in FIG. 12, for example, the effect of reducing crosstalk can be obtained even if the pressure relief nozzle 31 is located on the end side of every other piezoelectric member 41. Note that the arrows 300 in the figure are schematic arrows showing pressure propagation along the communication path between the channels, as in FIG. 10.

[0038] According to the above-described embodiment, in the inkjet head 100 equipped with the pressure chamber 4 utilizing the longitudinal liquid column resonance, the ejection nozzle 31 is disposed in a position where the pressure change is large, and the pressure relief nozzle 31 is provided at a position on the end side of the pressure chamber where the pressure change due to the liquid column resonance is small, thereby suppressing the problem of crosstalk, which causes the ejection characteristics of another channel to become unstable due to pressure propagation via the common ink chambers 42, 43. As a result, the ejection characteristics of each channel are stabilized, and the print quality can be improved.

[0039] Furthermore, in the case of the above-mentioned configuration, the pressure relief nozzle 31 on the common ink chamber 43 side prevents the flow path from becoming a dead end, and an effect can be obtained that the common ink chamber 43 can be easily filled with ink.

[0040] It is desirable to provide the ejection nozzle 3 and the pressure relief nozzle 31 on the same surface of the nozzle plate 22. This makes it easier to purge the ink and to clean after purging. Also, the pressure relief nozzle 31 does not necessarily have to be circular in plan view.

[0041] In the above embodiment, the pressure relief nozzle 31 is provided on both the common ink chamber 42 side and the common ink chamber side, but the configuration is not limited to providing the nozzle on both sides. Also, the above embodiment is a side shooter type configuration, but an end shooter type configuration is also acceptable.

[0042] The inkjet head 100 is not limited to the shear mode type actuator 5 in which a plurality of pressure chambers 4 are arranged. It may be a drop-on-demand piezoelectric type actuator or the like.

[0043] In the above embodiment, the inkjet head 100 of the inkjet printer 10 has been described as an example of a liquid ejection head, but the liquid ejection head may be a modeling material ejection head of a 3D printer or a sample ejection head of a dispensing device.

[0044] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0045] 10. Inkjet Printer 100~103 Inkjet head 2 Nozzle head 22 Nozzle plate 23 Actuator board 3 Discharge nozzle 31 Pressure relief nozzle 4. Pressure Chamber 41 Piezoelectric components 42 Common ink chamber 43 Common ink chamber 5 Actuators

Claims

1. A pressure chamber for a plurality of channels for discharging liquid; a common liquid chamber communicating with at least one open end of the plurality of pressure chambers in the longitudinal direction; an actuator that changes the volume of the pressure chamber; a nozzle section including: a liquid ejection nozzle provided at a position where a pressure change within the pressure chamber becomes large due to liquid column resonance of 1 / 4 wavelength or 1 / 2 wavelength in the longitudinal direction within the pressure chamber that occurs when the actuator is driven; and a nozzle that does not eject liquid provided on a communication path between the pressure chamber of another channel and the pressure chamber and at a position where the pressure change due to the liquid column resonance is small.

2. A liquid ejection head as described in claim 1, characterized in that the nozzle that does not eject the liquid is located on a communicating passage with the pressure chamber of another channel and at a position 1 / 10 wavelength inside the open end of the pressure chamber or further inside the common liquid chamber side where the pressure change of the liquid column resonance is smaller.

3. 3. The liquid ejection head according to claim 1, wherein the liquid ejection nozzles and the nozzles not ejecting liquid are formed on the same surface of a nozzle plate.

4. 4. The liquid ejection head according to claim 1, wherein a taper angle of the nozzle that does not eject liquid is smaller than a taper angle of the nozzle for ejecting liquid.

5. 5. The liquid ejection head according to claim 1, wherein the nozzles that do not eject the liquid are provided for each channel that ejects the liquid.

6. the pressure chamber communicates with the common liquid chamber at both ends in a longitudinal direction; 6. The liquid ejection head according to claim 1, wherein the nozzles that do not eject liquid are provided on both ends in the longitudinal direction.

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