JP2023041524A - Liquid discharge head - Google Patents

Abstract

To provide a liquid discharge head which can suppress that discharge of liquid affects on discharge characteristics of another channel.SOLUTION: A liquid discharge head includes a nozzle part, pressure chambers, an actuator and a liquid standby chamber. The nozzle part forms a plurality of nozzles which discharge liquid. The plurality of pressure chambers are respectively communicated with each nozzle. The actuator changes a volume of each pressure chamber and causes a pressure change due to liquid column resonance of longitudinal direction in the pressure chamber. The plurality of liquid standby chambers are communicated with each open end of the longitudinal direction of the respective pressure chambers and, further, are separated from each other.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD Embodiments of the present invention relate to liquid ejection heads.

A liquid ejection head is known that supplies a predetermined amount of liquid to a predetermined position. A liquid ejection head is installed in, 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 hardens them to form a three-dimensional model. The pipetting device discharges droplets of a sample to supply a predetermined amount to a plurality of containers or the like.

A liquid ejection head has a plurality of channels for ejecting liquid. Each channel includes a nozzle for discharging liquid, a pressure chamber communicating with the nozzle, and an actuator for changing the volume of the pressure chamber. The pressure chamber of each channel communicates with a common liquid chamber. The liquid ejection head selects a channel for ejecting liquid from among a 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 the liquid is ejected from the nozzle. A liquid ejection head having such a configuration has a problem of crosstalk, in which the influence of pressure change when the actuator is driven propagates to the surroundings through the common liquid chamber and affects the ejection characteristics of another channel.

JP-A-4-156333 JP 2011-194675 A Japanese Patent Application Laid-Open No. 2003-89203 JP-A-11-147315 JP-A-2003-39665

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejection head capable of suppressing the ejection characteristics of other channels from being affected by the ejection of liquid.

A liquid ejection head according to an embodiment of the present invention includes a nozzle section, a pressure chamber, an actuator, and a liquid standby chamber. The nozzle section forms a plurality of nozzles for ejecting liquid. A plurality of pressure chambers communicate with each of the nozzles. The actuator changes the volume of each of the pressure chambers, causing pressure changes in each of the pressure chambers due to liquid column resonance in the longitudinal direction of the pressure chambers. A plurality of liquid waiting chambers communicate with the longitudinal open ends of the pressure chambers and are separated from each other.

1 is an overall configuration diagram of an inkjet printer provided with an inkjet head according to a first embodiment; FIG. It is a perspective view of the said inkjet head. FIG. 3 is a partially enlarged cross-sectional view of the head portion of the inkjet head; It is the top view which partially expanded the head part of the said inkjet head. 3 is an enlarged sectional view of pressure chambers and air chambers of the inkjet head; FIG. It is a drive waveform given to the actuator of the inkjet head. FIG. 4 is an operation explanatory diagram of an actuator driven by the drive waveform; FIG. 4 is an explanatory diagram of liquid column resonance occurring in pressure chambers of the inkjet head; It is sectional drawing which expanded the nozzle of the said inkjet head. FIG. 8 is a partially enlarged cross-sectional view of the head portion of the inkjet head according to the second embodiment; FIG. 8 is a partially enlarged plan view of the head portion of the inkjet head according to the second embodiment; FIG. 4 is an explanatory diagram of liquid column resonance occurring in pressure chambers of the inkjet head; FIG. 12 is a partially enlarged plan view of the head portion of the inkjet head according to the third embodiment; 4 is an enlarged cross-sectional view of a pressure relief nozzle of the inkjet head; FIG. FIG. 12 is a partially enlarged plan view of the head portion of the inkjet head according to the fourth embodiment;

Hereinafter, liquid ejection heads according to embodiments will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same structure is attached with the same code|symbol.

(First embodiment)
An 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 of the embodiment. FIG. 1 shows a schematic configuration of an inkjet printer 10. As shown in FIG. The inkjet printer 10 includes a housing 11 that includes 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 from the cassette 12, a transport A plurality of inkjet heads 100 to 103 for ejecting ink droplets toward the sheet S on the belt 14, a downstream transport path 15 for 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 .

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

The pickup roller 204 supplies the sheets S one by one from the cassette 12 to the upstream transport path 13 . The upstream conveying path 13 is composed of feed roller pairs 131 and 132 and sheet guide plates 133 and 134 . The sheet S is sent to the upper surface of the conveying belt 14 via the upstream conveying path 13 . An arrow 104 in the drawing indicates the conveying path of the sheet S from the cassette 12 to the conveying belt 14 .

The conveying belt 14 is a net-like endless belt with a large number of through holes formed on its surface. Three rollers, a driving roller 141 and driven rollers 142 and 143, support the conveying belt 14 so as to be rotatable. The motor 205 rotates the transport belt 14 by rotating the drive roller 141 . Motor 205 is an example of a drive device. Reference numeral 105 in the drawing indicates the direction of rotation of the conveyor belt 14 . A negative pressure container 206 is arranged on the back side of the conveying belt 14 . The negative pressure container 206 is connected to a decompression fan 207 . The fan 207 creates a negative pressure in the negative pressure container 206 by the generated air current, and causes the upper surface of the conveying belt 14 to adsorb and hold the sheet S. FIG. Reference numeral 106 in the figure indicates the air flow.

The inkjet heads 100 to 103, which are examples of liquid ejection heads, are arranged so as to face the sheet S sucked and held on the conveying belt 14 with a slight gap of, for example, 1 mm. The inkjet heads 100 to 103 eject ink droplets toward the sheet S, respectively. The inkjet heads 100-103 print an image when the sheet S passes below. Each of the inkjet heads 100 to 103 has the same structure except that the colors of ink ejected are different. Ink colors are, for example, cyan, magenta, yellow, and black.

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. Each ink tank 315-318 is arranged above each inkjet head 100-103. Each of the ink supply pressure adjusting devices 321 to 324 keeps the inside of each of the inkjet heads 100 to 103 negative with respect to the atmospheric pressure so that the ink does not leak from the nozzles 3 (see FIG. 2) of the inkjet heads 100 to 103 during standby. The pressure is adjusted to -1.2 kPa, for example. During image formation, the ink in each of the ink tanks 315-318 is supplied to each of the inkjet heads 100-103 by the ink supply pressure adjusting devices 321-324.

After image formation, the sheet S is fed from the conveying belt 14 to the downstream conveying path 15 . The downstream conveying path 15 is composed of feed roller pairs 151 , 152 , 153 and 154 and sheet guide plates 155 and 156 that define the conveying path of the sheet S. As shown in FIG. The sheet S is sent to the discharge tray 16 from the discharge port 157 via the downstream conveying path 15 . An arrow 107 in the drawing indicates the conveying path of the sheet S. FIG.

Next, configurations of the inkjet heads 100 to 103 will be described. Although the inkjet head 100 will be described below with reference to FIGS. 2 to 5, the inkjet heads 101 to 103 have the same structure as the inkjet head 100.

As shown in FIG. 2, the inkjet head 100 includes a head section 2, which is an example of a liquid ejection section. Head section 2 is connected to flexible printed wiring board 21 . The head section 2 includes a nozzle plate 22, an actuator substrate 23, and an ink supply section 24, which is an example of a liquid supply section. The ink supply unit 24 is connected to the ink supply pressure adjusting device 321 of FIG. 1 via the ink flow path 311 .

The flexible printed wiring board 21 is mounted with a driving IC (Integrated Circuit) 25 which is a driver chip (hereinafter referred to as a driving IC). The drive IC 25 temporarily stores print data sent from the control board 17 of the inkjet printer 10, and gives a drive signal to each channel to eject ink at a predetermined timing.

The nozzle plate 22, which is an example of the nozzle portion, is a rectangular plate made of resin such as polyimide or metal such as stainless steel. The nozzles 3 of each channel for ejecting ink are arranged along the longitudinal direction (X direction) of the nozzle plate 22 . The nozzle density is set within a range of 150 to 1200 dpi, for example. Although the nozzles 3 are arranged in one row in FIG. 2, they may be arranged in two or more rows.

Particularly, as shown in FIGS. 3 to 5, the nozzle plate 22 having the nozzles 3 formed thereon is attached to the actuator substrate 23 with, for example, a frame member 26 interposed therebetween. The actuator substrate 23 is a substrate made of insulating ceramics, for example. The frame member 26 is made of resin, for example. The ink pressure chambers 4 of each channel are arranged alternately with the air chambers 40 in the space surrounded by the nozzle plate 22, the frame member 26 and the actuator substrate 23, for example, in the longitudinal direction (X direction) of the nozzle plate 22. . The pressure chamber 4 of each channel for ejecting ink communicates with the nozzle 3 of each channel.

The pressure chamber 4 is formed on the surface of the actuator substrate 23 by, for example, cutting two piezoelectric members 41 laminated in opposite polarization directions (opposing directions as an example) into a rectangular groove shape (FIG. 5). That is, the piezoelectric member 41 is formed so that its longitudinal direction extends in the lateral direction (Y direction) of the actuator substrate 23 . The piezoelectric member 41 is formed at a height that contacts the surface of the nozzle plate 22 . Therefore, the pressure chamber 4 has side walls of the piezoelectric member 41 standing on both sides in the short direction thereof, and is, for example, an elongated space with both ends in the longitudinal direction opened. Although the piezoelectric member 41 is formed to have a trapezoidal shape when viewed from the side, the shape of the piezoelectric member 41 when viewed from the side is not limited to the trapezoidal shape.

The air chambers 40 are arranged on both sides of the pressure chamber 4 with the piezoelectric member 41 interposed therebetween. The air chamber 40 is formed by cutting the piezoelectric member 41 into, for example, a rectangular groove like the pressure chamber 4 , and closing the openings at both ends in the longitudinal direction with, for example, convex wall members 27 extending inward from the frame member 26 . A closed space where ink is not introduced. The wall member 27 is, for example, a resin wall.

Openings at both ends of the pressure chamber 4 in the longitudinal direction communicate with the ink standby chambers 42 respectively. The ink standby chamber 42 is an example of a liquid standby chamber. Each ink waiting chamber 42 is separated from the ink waiting chamber 42 of the adjacent channel by, for example, a convex wall member 27 extending from the frame member 26 . That is, the ink standby chamber 42 is separated for each channel for ejecting ink. When the pressure chamber 4 has openings at both ends, an ink standby chamber 42 is provided at each end. The ink standby chamber 42 is laterally wider than the width of the opening of the pressure chamber 4 by the width of the piezoelectric members 41 on both sides in plan view. Further, when viewed in a vertical section, the space is extended in the vertical direction along the extension of the inclined surface of the piezoelectric member 41, for example. By making the space of the ink standby chamber 42 larger than the opening at the end of the pressure chamber 4 in this manner, both ends of the pressure chamber 4 are made open ends where pressure changes due to liquid column resonance, which will be described later, are small. However, the space of the ink waiting chamber 42 need not necessarily be expanded in both the horizontal direction and the vertical direction, but may be in either direction. Further, although the wall member 27 that partitions the ink standby chamber 42 of the adjacent channel is shared with the wall member 27 that blocks the opening of the air chamber 40, it may be formed separately. Furthermore, the wall member 27 may be formed of other members such as plates.

The ink standby chambers 42 on both sides of the pressure chamber 4 communicate with the ink supply manifold 44 through the constricted portions 43 respectively. That is, the constricted portion 43 is provided for each ink standby chamber 42 of each channel. The narrowed portion 43 is, for example, a rectangular ink passage. As an example, the narrowed portion 43 is formed so as to penetrate the actuator substrate 23 in the height direction from the bottom surface of the outwardly convex portion of the ink waiting chamber 42 . As an example, the ink supply manifold 44 is formed in a groove shape on the surface of the ink supply section 24 along the arrangement direction (X direction) of the constriction sections 43 . By stacking the actuator substrate 23 and the ink supply section 24 , the constricted section 43 of each channel communicates with the ink supply manifold 44 . The opening area of the constricted portion 43 is at least smaller than the cross-sectional area of the ink standby chamber 42 . Further, the opening area of the pressure chamber 4 is normally further reduced. That is, it is preferable that the cross-sectional area through which the ink passes through the constricted portion 43 is smaller than the cross-sectional area through which the ink passes through the ink standby chamber 42 and the cross-sectional area through which the ink passes through the pressure chamber 4 . The length of the narrowed portion 43 is the thickness of the actuator substrate 23 . The resistance when the ink passes through the constricted portion 43 is determined by the opening area and length of the constricted portion 43. The smaller the opening area and the longer the length, the greater the resistance. In FIGS. 3 and 4, ink is supplied from both ink supply manifolds 44, but one of them may be used as an ink discharge manifold to circulate and supply ink to the pressure chambers 4. FIG. The ink supply manifold 44 and the ink discharge manifold are examples of manifolds that communicate with the narrowed portion 43 .

Although not shown in FIGS. 3 and 4, as shown in FIG. 5, the electrodes 45 are integrally formed on the bottom surface and both side surfaces of the pressure chamber 4, for example. The electrodes 45 of each pressure chamber 4 are connected to wiring electrodes 46 as individual electrodes. The electrodes 47 are integrally formed, for example, on the bottom surface and both side surfaces of the air chamber 40 . An electrode 47 of each air chamber 40 is connected to a wiring electrode 48 as a common electrode. The piezoelectric member 41 and the electrodes 45 and 47 sandwiching the piezoelectric member 41 constitute an actuator 5 that changes the volume of the pressure chamber 4 by shear mode deformation. The electrodes 45 and 47 and the wiring electrodes 46 and 48 are formed of a nickel thin film or the like by electroless plating, for example. In particular, the electrode 45 of the pressure chamber 4 may be covered with a protective film (not shown) so as not to come into contact with ink. The wiring electrode 46 from the pressure chamber 4 is connected to the flexible printed wiring board 21 at the end of the actuator substrate 23 , for example, and is connected to the drive driver (that is, drive circuit) of the drive IC 25 . A drive driver for each channel supplies, for example, a drive voltage as a drive signal to the actuator 5 for each channel. On the other hand, the wiring electrode 48 from the air chamber 40 is connected to the ground (GND), for example. With such a configuration, the actuator 5 to which the driving voltage is applied is applied with an electric field in a direction intersecting (preferably, perpendicularly) the polarization axis of the piezoelectric member 41, and the piezoelectric members 41 forming the side walls on both sides of the pressure chamber 4 are Transforms in shear mode.

FIG. 6 shows a drive waveform (DRP waveform) as an example of drive waveforms for driving the actuator 5 . FIG. 6 also shows changes in the pressure of the ink in the pressure chamber 4 and the flow velocity of the ink during driving. The driving waveforms are a negative potential voltage (-V) during the period t1, a ground potential (GND) during the period t2, and a positive potential voltage (+V) during the period t3. The period t1 is set to, for example, half the period of the pressure vibration of the head section 2 . When the pressure oscillation period is, for example, 4.8 [μs], the period t1 is set to 2.4 [μs]. For example, the period t2 is 3.25 [μs], and the period t3 is 0.7 [μs], which is shorter than the period t2. At this time, the center interval between period t1 and period t3 is t1/2+t2+t3/2=(pressure vibration period).

FIG. 7A shows a state in which the potentials of the electrodes 45 and 47 of the pressure chamber 4 and the air chamber 40 adjacent to each other are both ground potential (GND). In this state, the piezoelectric members 41 on both sides of the pressure chamber 4 are not distorted. FIG. 7B shows a state in which a negative potential voltage (-V) is applied to the electrode 45 of the pressure chamber 4 during the period t1 of the driving waveform of FIG. In this state, an electric field acts on the piezoelectric members 41 on both sides of the pressure chamber 4 in a direction orthogonal to the polarization direction, and the piezoelectric members 41 deform outward in a shear mode, thereby expanding the volume of the pressure chamber 4. do.

In the subsequent period t2, the potential of the electrode 45 of the pressure chamber 4 is set to the ground potential (GND), so that the expanded volume of the pressure chamber 4 returns to the state shown in FIG. 7(a). By restoring the volume of the pressure chamber 4 at the end point of the period t1 set to 1/2 of the pressure vibration cycle, the pressure of the ink in the pressure chamber 4 increases as shown in FIG. A droplet of ink is ejected from the nozzle 3 . This pressure change utilizes liquid column resonance in the longitudinal direction of the pressure chamber, which will be described later in detail.

A positive voltage (+V) is applied to the electrode 45 of the pressure chamber 4 in the subsequent period t3. In this state, as shown in FIG. 7(c), an electric field acts on the piezoelectric members 41 on both sides of the pressure chamber 4 in a direction opposite to that in FIG. The inward deformation causes the volume of the pressure chamber 4 to shrink. After the period t3 has passed, the potential of the electrode 45 of the pressure chamber 4 is set to the ground potential (GND), so that the contracted volume of the pressure chamber 4 returns to the state shown in FIG. 7(a). This contraction and return attenuate residual vibration.

In this manner, the ink is ejected by driving the actuator 5 and controlling the pressure in the pressure chamber 4 . When the longitudinal ends of the pressure chambers 4 are open ends, liquid column resonance in the longitudinal direction of the pressure chambers that occurs when the actuator 5 is driven is used for ejecting ink. In other words, it differs from an inkjet head that uses Helmholtz resonance. The wavelength of the liquid column resonance is the value obtained by multiplying the above-mentioned pressure vibration period by the speed of sound of the ink in the pressure chamber 4 . If both ends of the pressure chamber 4 in the longitudinal direction are open, it becomes a 1/2 wavelength resonance tube of this wavelength.

In the case of a half-wave resonance tube, if the pressure amplitude and the flow velocity amplitude are represented by standing waves as shown in FIG. 8, the pressure amplitude is maximum and the flow velocity amplitude is minimum at the central portion in the longitudinal direction of the pressure chamber. On the other hand, at the release end of the standing wave, the pressure amplitude is minimum and the flow velocity amplitude is maximum. Therefore, the nozzle 3 is arranged in the central portion in the longitudinal direction where the pressure amplitude is the largest. Strictly speaking, the position is not limited to the position where the pressure amplitude is the largest, and it may be in the vicinity thereof. An example of its vicinity is within 1/10 wavelength. The nozzle 3 preferably has a tapered shape in which the diameter becomes smaller toward the tip side. The diameter of the proximal end of the nozzle 3 is, for example, 40-55 μm. The diameter of the nozzle 3 on the tip side is, for example, 20 to 30 μm.

The nozzle 3 forms an ink meniscus M near its opening (see FIG. 9), introduces a pressure change due to liquid column resonance that occurs when the actuator 5 is driven into the nozzle 3, and ejects ink. The tapered nozzle 3 has a narrow opening on the tip end side to increase the ink flow rate, and a wide opening on the base end side applies a load to the pressure chamber 4 . When the ink is not ejected, the meniscus M is kept concave by applying a negative pressure to the pressure chamber 4 . That is, as described above, the ink supply pressure adjusting device 321 adjusts the inside of the inkjet head 100 to a negative pressure with respect to the atmospheric pressure.

From the operating principle of the liquid column resonance tube, it is desirable that the pressure does not change at the open end position of the pressure chamber 4 . For this reason, the ink standby chamber 42 is provided and both ends of the pressure chamber 4 are open ends. Pressure changes may also occur across the pressure chamber 4 . If the pressure vibration due to this pressure change propagates to the surrounding channels, a crosstalk problem may occur. ing. Furthermore, since the ink waiting chamber 42 of each channel communicates with each other through the ink supply manifold 44, a constricted portion 43 is provided between the ink waiting chamber 42 and the ink supply manifold 44 to prevent pressure vibration through the ink supply manifold 44. suppresses propagation.

Further, when ink is ejected continuously at high speed such as multi-drop, it is preferable to eject the next ink droplet after the state of the ink meniscus M in the nozzle 3 is stabilized after the ink droplet is ejected. preferable. This is for stabilizing the ejection state such as the ejection amount of the ink. If the constricted portion 43 were not provided, the meniscus would be formed by resonance other than the liquid column resonance described above, due to the restoring force that tends to return the meniscus M to its original state after ejection and the mass of the ink in the head that resists this force. An oscillation of M occurs and the state of the meniscus M becomes unstable. Since the meniscus M protrudes toward the outside of the nozzle 3 immediately after the ink is discharged, the speed of the next ink discharge becomes slow, which may cause a problem of degraded print quality when the drive frequency is high. A constriction 43 located between the ink waiting chamber 42 and the ink supply manifold 44 reduces pressure propagation that contributes to crosstalk between the channels discussed above. By adjusting the cross-sectional area and length of the constricted portion 43 to appropriately set the resistance when the ink passes, unnecessary vibration of the meniscus M is suppressed, swelling of the meniscus M is suppressed, and the meniscus M is quickly stabilized. to enable high-quality, high-speed printing. Therefore, even if high-speed continuous ejection is performed at a frequency of 50 kHz, for example, the ink ejection state is stabilized.

(Second embodiment)
Next, an inkjet head 100 according to the second embodiment will be described. The ink jet head 100 according to the second embodiment has the same configuration as the ink jet head 100 of the first embodiment, except that the open end of the pressure chamber 4 is only on one side to form a 1/4 wavelength resonator tube. Therefore, the same components as those of the inkjet head 100 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIGS. 10 and 11, the pressure chambers 4 of the inkjet head 100 are open at one end in the longitudinal direction and closed at the other end by a frame member 26, for example. The open end communicates with the ink standby chamber 42 . In the case of the pressure chamber 4 having an open end on only one side in the longitudinal direction, it becomes a 1/4 wavelength resonance tube. In the case of a 1/4 wavelength resonance tube, if the pressure amplitude and the flow velocity amplitude are represented by standing waves as shown in FIG. Maximum pressure amplitude and minimum flow velocity amplitude. On the other hand, at the release end of the standing wave, the pressure amplitude is minimum and the flow velocity amplitude is maximum. The nozzle 3 is arranged at the depth in the longitudinal direction where the pressure amplitude is large. Of course, it may be in the vicinity thereof. An example of its vicinity is within 1/10 wavelength.

In the inkjet head 100 of this embodiment, as in the first embodiment, the end of the pressure chamber 4 is an open end communicating with the ink waiting chamber 42, and the ink waiting chamber 42 is separated for each channel. It communicates with the ink supply manifold 44 via the constricted portion 43 . Therefore, by providing the ink standby chamber 42 separated for each channel, it is possible to suppress the propagation of pressure vibration between the channels. Furthermore, the constricted portion 43 can suppress propagation of pressure vibration through the ink supply manifold 44 .

Furthermore, by arranging the constricted portion 43 between the ink standby chamber 42 and the ink supply manifold 44, not only pressure propagation that causes crosstalk between channels but also the meniscus M in the nozzle 3 after ejection is suppressed. Pressure oscillations that contribute to instability can also be suppressed.

(Third embodiment)
Next, an inkjet head 100 according to the third embodiment will be described. The inkjet head 100 according to the third embodiment has the same configuration as the inkjet head 100 of the first embodiment, except that pressure relief nozzles are provided. Accordingly, the same components as those of the inkjet head 100 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 13 , the inkjet head 100 has pressure relief nozzles 31 in the nozzle plate 22 that communicate with the ink waiting chamber 42 . Since pressure changes caused by liquid column resonance are suppressed by opening the ends of the pressure chambers 4 , even if the actuator 5 is driven, ink is not ejected from the pressure relief nozzles 31 . That is, the pressure relaxation nozzles 31 are nozzles that do not eject ink. As shown in FIG. 14A, the nozzle 3 for ejecting ink must be tapered so that the cross-sectional area of the nozzle 3 decreases toward the outside. However, in the case of the tapered nozzle 3, when the negative pressure in the pressure chamber 4 increases and the meniscus M retreats toward the pressure chamber 4 as indicated by the dashed line in the figure, the meniscus force weakens, making it easier for air to enter from the nozzle 3. Mitigation capacity is low. Therefore, it is preferable that the pressure relief nozzle 31 has a cylindrical shape as shown in FIG. 14(b). In the case of the cylindrical shape, the meniscus force does not change even if the meniscus M retreats toward the ink standby chamber 42 as indicated by the dashed line in the figure. Furthermore, a plurality of pressure relief nozzles 31 may be provided. As another preferred shape, the pressure relieving nozzle 31 may have a reverse tapered shape as shown in FIG. 14(c).

Since the pressure relief nozzle 31 changes the position and shape of the meniscus M in the nozzle even when ink is not ejected, it is possible to suppress the pressure change. If the position of the pressure relief nozzle 31 is too far from the end of the pressure chamber 4, a pressure difference will occur between that position and the end of the pressure chamber 4. Therefore, it is desirable that the pressure relief nozzle 31 is located near the end of the pressure chamber 4. . Furthermore, the number of pressure relief nozzles 31 is not limited to one. In the example of FIG. 13, three pressure relief nozzles 31 are arranged in series toward, for example, the narrowed portion 43 side. In this way, when the nozzle plate 22 is provided with a hole corresponding to the ink standby chamber 42, the pressure change in the ink standby chamber 42 is suppressed by the meniscus M formed in the hole, and the pressure in the ink standby chamber 42 is further stabilized. be able to. The pressure relaxation nozzles 31 absorb pressure changes due to changes in the position of the meniscus M within the nozzles. The higher the capacity of pressure relaxation to absorb pressure changes. 14(c), the curvature of the meniscus M increases as the position of the meniscus M recedes, and the meniscus force becomes stronger. It has a difficult advantage.

(Fourth embodiment)
Next, an inkjet head 100 according to the fourth embodiment will be described. The inkjet head 100 according to the fourth embodiment has the same configuration as the inkjet head 100 of the second embodiment, except that the pressure relief nozzle is provided. Furthermore, the shape and the like of the pressure relief nozzle are the same as in the third embodiment. Accordingly, the same components as those of the inkjet heads 100 of the second and third embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 15, the pressure chambers of the inkjet head 100 are opened at one end in the longitudinal direction of the pressure chamber 4 and closed at the other end by a frame member 26, for example. That is, it becomes a 1/4 wavelength resonance tube as in the second embodiment. The pressure relief nozzles 31 are formed in the nozzle plate 22 so as to communicate with the ink standby chamber 42 . By providing holes similar to the nozzles in the nozzle plate 22 corresponding to the ink standby chamber 42 in this manner, the pressure in the ink standby chamber 42 can be further stabilized.

According to any of the above-described embodiments, it is possible to provide the inkjet head 100 that can suppress the influence of ink ejection on the ejection characteristics of another channel.

The inkjet head 100 is not limited to the shear mode type actuator 5 in which a plurality of pressure chambers 4 are arranged. A drop-on-demand piezo type actuator or the like may also be used.

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, 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.

According to the above-described embodiments, it is possible to provide the following liquid ejection head.
(1) a nozzle section having a plurality of nozzles for ejecting liquid;
a plurality of pressure chambers respectively communicating with the nozzles;
an actuator that changes the volume of each of the pressure chambers and causes pressure changes in each of the pressure chambers due to liquid column resonance in the longitudinal direction of the pressure chamber;
and a plurality of liquid standby chambers separated from each other and communicating with the longitudinal open ends of the pressure chambers.
(2) a plurality of constricted portions respectively communicating with the respective liquid waiting chambers;
a manifold that communicates with each of the liquid standby chambers through each of the constrictions.
(3) The cross-sectional area through which the liquid passes through the constricted portion is smaller than the cross-sectional area through which the liquid passes through each of the liquid standby chambers.
(4) The cross-sectional area through which the liquid passes through the constricted portion is smaller than the cross-sectional area through which the liquid passes through the pressure chambers.
(5) It has a wall member that separates each of the two adjacent liquid waiting chambers.
(6) Adjacent to said pressure chamber, there are a plurality of air chambers which do not introduce liquid, said wall members further separating each of said two adjacent liquid waiting chambers and air chambers.
(7) The liquid standby chamber communicates with nozzles that do not eject ink.
(8) The wall member that separates each of the two adjacent liquid standby chambers also serves as a wall member that closes the opening of the air chamber.

Embodiments of the invention are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and its equivalents.

REFERENCE SIGNS LIST 10 inkjet printer 100 to 103 inkjet head 2 head section 22 nozzle plate 23 actuator substrate 3 nozzle 31 pressure relief nozzle 4 pressure chamber 41 piezoelectric member 42 ink waiting chamber 43 constricted section 44 ink supply manifold 5 actuator

Claims (6)

a nozzle section having a plurality of nozzles for ejecting liquid;
a plurality of pressure chambers respectively communicating with the nozzles;
an actuator that changes the volume of each of the pressure chambers and causes pressure changes in each of the pressure chambers due to liquid column resonance in the longitudinal direction of the pressure chamber;
A liquid ejection head comprising a plurality of liquid waiting chambers separated from each other and communicating with the longitudinal open ends of the pressure chambers. a plurality of constricted portions respectively communicating with the respective liquid waiting chambers;
2. The liquid ejection head according to claim 1, further comprising a manifold that communicates with each of the liquid standby chambers through each of the constricted portions. 3. The liquid ejection head according to claim 1, wherein a cross-sectional area through which liquid passes through said constricted portion is smaller than a cross-sectional area through which liquid passes through each of said liquid standby chambers. 3. The liquid ejection head according to claim 1, wherein a cross-sectional area through which liquid passes through said constricted portion is smaller than a cross-sectional area through which liquid passes through each of said pressure chambers. 5. The liquid ejection head according to claim 1, further comprising a wall member separating each of the two adjacent liquid waiting chambers. 6. A liquid ejection head according to claim 5, wherein there are a plurality of air chambers adjacent to said pressure chambers to which no liquid is introduced, said wall member further separating each of said two adjacent liquid standby chambers from said air chambers.

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