JP2023032319A - Liquid discharge head and method for manufacturing liquid discharge head - Google Patents

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics, and a method for manufacturing the liquid discharge head.SOLUTION: A liquid discharge head is of a side shooter type, and includes an actuator, a common chamber, and a cover plate. The actuator has a plurality of pressure chambers which communicate with nozzles for discharging a liquid, and a plurality of dummy chambers arranged among the plurality of pressure chambers. The common chamber is arranged on both ends of the actuator and communicates with the plurality of pressure chambers. The cover plate is joined to the side face of the actuator, is constituted in a plate shape, and has an opening which communicates the common chamber and the pressure chambers and has a fluid resistance larger than the inside of the pressure chamber at a position partitioning the pressure chambers, the dummy chambers and the common chamber and facing the plurality of pressure chambers.SELECTED DRAWING: Figure 6

Description

Embodiments of the present invention relate to a liquid ejection head and a method for manufacturing the liquid ejection head.

In recent years, there has been a demand for high productivity in inkjet heads, and increasing speed and increasing the amount of droplets have become issues. For example, a shared mode shared wall inkjet head has high power and is suitable for ejecting high-viscosity ink and ejecting large droplets. In the share mode share wall type ink jet head, the same driving column is shared by two pressure chambers, and 1/3 of the plurality of arranged chambers are commonly driven as pressure chambers at the same time, so-called three-cycle drive. . Also, an independent drive head has been developed in which both sides of the pressure chamber to be driven are used as dummy pressure chambers and two independent drive columns are used to drive one pressure chamber. For example, a structure has been developed in which a large number of grooves are formed in a piezoelectric body, the entrances and exits are closed every other one, the grooves in which the entrances and exits are not blocked are used as pressure chambers, and the closed grooves are used as air chambers, and are independently driven. ing.

In such an inkjet head, ink is replenished from the common liquid chamber to the pressure chamber after ink droplets are ejected. At this time, a phenomenon occurs in which the nozzle overshoots and the meniscus rises. The smaller the fluid resistance in the flow path from the common liquid chamber to the nozzles, the greater the overshoot. If the overshoot is not suppressed, the meniscus cannot be discharged in a stable state. Therefore, in order to increase the speed of an inkjet head, it is required to quickly converge the swelling of the meniscus and ensure stable ejection characteristics.

JP-A-2008-94036

A problem to be solved by the present invention is to provide a liquid ejection head and a method for manufacturing the liquid ejection head that can ensure stable ejection characteristics.

A liquid ejection head according to one embodiment is of a side shooter type and includes an actuator, a common chamber, and a cover plate. The actuator has a plurality of pressure chambers communicating with nozzles that eject liquid, and a plurality of dummy chambers arranged between the plurality of pressure chambers. Common chambers are arranged at both ends of the actuator and communicate with the plurality of pressure chambers. A cover plate is joined to a side surface of the actuator and has a plate-like shape. and an opening having a higher fluid resistance than the inside of the pressure chamber communicating with the pressure chamber.

1 is a perspective view showing an inkjet head according to an embodiment; FIG. 1 is an exploded perspective view showing a configuration of part of an inkjet head according to an embodiment; FIG. Sectional drawing which expands and shows a structure of one part of the same inkjet head. Sectional drawing which expands and shows a structure of one part of the same inkjet head. Sectional drawing which expands and shows a structure of one part of the same inkjet head. FIG. 2 is an enlarged perspective view showing the configuration of a part of the inkjet head; Explanatory drawing of the manufacturing method of the same inkjet head. FIG. 4 is an explanatory diagram of an inkjet head according to Test Example 1 and Test Example 2; 4 is a graph showing the ejection speed of the inkjet head according to Test Example 1. FIG. 9 is a graph showing the ejection speed of the inkjet head according to Test Example 2; 5 is a graph showing meniscus recovery characteristics of inkjet heads according to Test Examples 1 and 2; FIG. 4 is an explanatory diagram of an inkjet head of an end shooter according to Test Examples 1 and 3; 5 is a graph showing driving waveforms of inkjet heads according to Test Examples 1 and 3; 5 is a graph showing nozzle flow velocity vibrations of inkjet heads according to Test Examples 1 and 3. FIG. 5 is a graph showing ejection volumes of inkjet heads according to Test Examples 1 and 3. FIG. 5 is a graph showing meniscus recovery characteristics of inkjet heads according to Test Examples 1 and 3; 1 is a schematic diagram showing an inkjet printer according to an embodiment; FIG. FIG. 10 is an enlarged perspective view showing a partial configuration of an inkjet head according to a second embodiment;

The configuration of an inkjet head 10, which is a liquid ejection head according to the first embodiment, will be described below with reference to FIGS. 1 to 6. FIG. FIG. 1 is a perspective view showing an inkjet head according to the first embodiment, and FIG. 2 is an exploded perspective view of part of the inkjet head. 3, 4, and 5 are cross-sectional views enlarging a part of the structure of the inkjet head, and FIG. 6 is a perspective view showing a part of the structure of the inkjet head in an enlarged manner. FIG. 7 is an explanatory view of the manufacturing process of the inkjet head, omitting the cover member 24 to show the internal structure. In the drawing, X, Y, and Z indicate the first direction, the second direction, and the three directions orthogonal to each other, respectively. In the present embodiment, the orientation is such that the parallel direction of the nozzles 28 and the pressure chambers 31 of the inkjet head 10 is along the X axis, the extending direction of the pressure chambers 31 is along the Y axis, and the liquid ejection direction is along the Z axis. Although the description of the direction is described as a reference, it is not limited to this.

As shown in FIGS. 1 to 6, the inkjet head 10 is a so-called side shooter type share mode share wall type inkjet head. The inkjet head 10 is a device for ejecting ink, and is mounted inside an inkjet printer, for example. For example, the inkjet head 10 is an independently driven inkjet head in which pressure chambers 31 and dummy chambers 32 are alternately arranged. The dummy chamber 32 is an air chamber to which ink is not supplied and does not have the nozzles 28 .

The inkjet head 10 has an actuator base 11 , a nozzle plate 12 and a frame 13 . The actuator base 11 is an example of a base material. An ink chamber 27 is formed inside the inkjet head 10 to which ink, which is an example of a liquid, is supplied.

Furthermore, the inkjet head 10 includes components such as a circuit board 17 that controls the inkjet head 10 and a manifold 18 that forms part of the path between the inkjet head 10 and the ink tank.

As shown in FIG. 2, the actuator base 11 includes a substrate 21, a pair of actuators 22, and a cover member 24. As shown in FIG.

The substrate 21 is formed in a rectangular plate shape from ceramics such as alumina. The substrate 21 has a flat mounting surface. A pair of actuators 22 are joined to the mounting surface of the substrate. A plurality of supply holes 25 and discharge holes 26 are formed in the substrate 21 .

As shown in FIG. 2, pattern wiring 211 is formed on the substrate 21 of the actuator base 11 . The pattern wiring 211 is formed of, for example, a nickel thin film. The pattern wiring 211 has a common pattern or an individual pattern, and is configured in a predetermined pattern shape to be connected to the electrode layer 34 formed on the actuator 22 .

The supply holes 25 are arranged in the longitudinal direction of the actuators 22 between the pair of actuators 22 in the central portion of the substrate 21 . The supply hole 25 communicates with the ink supply portion of the manifold 18 . The supply hole 25 is connected to an ink tank via an ink supply section. The supply hole 25 supplies the ink in the ink tank to the ink chamber 27 .

The discharge holes 26 are arranged in two rows with the supply hole 25 and the pair of actuators 22 interposed therebetween. The discharge hole 26 communicates with the ink discharge portion of the manifold 18 . The discharge hole 26 is connected to the ink tank through the ink discharge portion. The discharge hole 26 discharges the ink in the ink chamber 27 to the ink tank.

A pair of actuators 22 are adhered to the mounting surface of the substrate 21 . A pair of actuators 22 are arranged in two rows on the substrate 21 with the supply hole 25 interposed therebetween. Each actuator 22 is formed of two plate-like piezoelectric bodies made of lead zirconate titanate (PZT), for example. The two piezoelectric bodies are bonded together so that their polarization directions are opposite to each other in the thickness direction. The actuator 22 is adhered to the mounting surface of the substrate 21 with, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuators 22 are arranged in parallel in the ink chamber 27 corresponding to the nozzles 28 arranged in two rows. The actuator 22 divides the ink chamber 27 into a first common chamber 271 in which the supply hole 25 opens and two second common chambers 272 in which the discharge hole 26 opens.

The actuator 22 is formed to have a trapezoidal cross section. The side portion 221 of the actuator 22 has inclined surfaces that are inclined with respect to the second direction and the third direction. That is, the actuator 22 is configured to have a trapezoidal cross-sectional view perpendicular to the second direction. The top of actuator 22 is glued to nozzle plate 12 . The actuator 22 includes multiple pressure chambers 31 and multiple dummy chambers 32 . The actuator 22 has a plurality of side wall portions 33 and has grooves forming the pressure chambers 31 and the dummy chambers 32 between the side wall portions 33 . In other words, the side wall portion 33 is formed as a driving element between the grooves forming the pressure chamber 31 and the dummy chamber 32 .

As shown in FIGS. 1 to 6 , the bottom surface of the groove and the main surface of the substrate 21 are connected by inclined side surfaces 221 . The pressure chambers 31 and the dummy chambers 32 are arranged alternately. The pressure chambers 31 and the dummy chambers 32 each extend in a direction intersecting the longitudinal direction of the actuator 22 and are arranged in parallel in a first direction (the X axis in the figure) which is the longitudinal direction of the actuator 22 .

The shape of the pressure chamber 31 and the shape of the dummy chamber 32 may be different. The side wall portion 33 is formed between the pressure chamber 31 and the dummy chamber 32 and deforms according to the drive signal to change the volume of the pressure chamber 31 .

The plurality of pressure chambers 31 communicate with the plurality of nozzles 28 of the nozzle plate 12 joined to the top. Both ends of the pressure chamber 31 in the second direction communicate with the ink chamber 27 . That is, one end opens to the first common chamber 271 of the ink chamber 27 and the other end opens to the second common chamber 272 of the ink chamber 27 . Therefore, the ink flows in from one end of the pressure chamber 31 and the ink flows out from the other end. The pressure chamber 31 has a constricted portion 240 whose openings at both ends in the second direction are partially closed by the cover member 24 to increase the flow path resistance. The narrowed portion 240 increases the fluid resistance by, for example, reducing the cross-sectional area of the flow path perpendicular to the second direction of the pressure chamber 31 as compared to the inside of the pressure chamber 31 . The narrowed portion 240 is configured, for example, at the entrances and exits at both ends of the pressure chamber 31 so that the width dimension in the direction intersecting the second direction, which is the extension direction of the pressure chamber 31, for example, the first direction or the third direction is narrowed. there is For example, the throttle portion 240 is provided with a cover member 24 that closes the flow path of the pressure chamber 31 so that a portion of the flow path between the pressure chamber 31 and the ink chamber 27 is blocked.

One side of the dummy chamber 32 in the third direction is closed by the nozzle plate 12 joined to the top, and both sides in the second direction are closed by the cover member 24 .

The cover member 24 has a cover plate 241 with a predetermined thickness. The cover plate 241 is configured in a shape corresponding to the inclined side portion 221 of the actuator, for example, in a rectangular shape extending in the first direction. A cover plate 241 is formed with aperture holes 242 as a plurality of aperture openings penetrating in the thickness direction. The cover members 24 are provided on both ends of the actuator 22 in the second direction, respectively, to block the opening of the dummy chamber 32 and partially block the opening of the pressure chamber. For example, the cover member 24 is made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate). The grooves forming the pressure chambers 31 communicate with the first common chamber 271 and the second common chamber 272 through throttle holes 242 formed in the cover member 24 . The throttle hole 242 is, for example, an opening smaller than the cross-sectional area of the pressure chamber, and is, for example, a circular through hole.

The cover member 24 closes a part of the opening communicating with the first common chamber 271 and the second common chamber 272 which are common chambers at both ends of the pressure chamber 31 , so that the narrowed portion 240 having a higher fluid resistance than the pressure chamber 31 is formed. to form

The cover member 24 is joined to the inclined side portion 221 of the actuator 22 . Also, one edge of the cover member 24 may be joined to the substrate 21 .

Note that if the fluid resistance of the throttle portion 240 is too large, the ink replenishment to the pressure chamber 31 after the ejection of the ink droplets will be delayed, which will hinder the speeding up. Also, the bulge of the meniscus varies depending on the ink viscosity, ejection volume, drive frequency, and the like. Therefore, the thickness of the cover member 24 and the size and position of the throttle hole 242 of the throttle portion 240 are set so as to provide flow path resistance according to the ink replenishment conditions and the meniscus swelling characteristics.

Both ends of the plurality of dummy chambers 32 are closed by cover members 24, for example. That is, cover members 24 are arranged between the first common chamber 271 of the ink chamber 27 and the entrance of the dummy chamber 32 and between the exit of the dummy chamber 32 and the second common chamber 272, respectively. is separated from the ink chamber 27 . Therefore, the dummy chamber 32 constitutes an air chamber into which ink does not flow.

An electrode layer 34 is provided in each of the pressure chambers 31 and the dummy chambers 32 of the actuator base 11 . The electrode layer 34 is formed of, for example, a nickel thin film. The electrode layer 34 extends from the bottom of the groove to the substrate 21 and is connected to the pattern wiring 211 .

The nozzle plate 12 is formed of, for example, a rectangular polyimide film. The nozzle plate 12 faces the mounting surface of the actuator base 11 . A plurality of nozzles 28 are formed in the nozzle plate 12 so as to penetrate the nozzle plate 12 in the thickness direction.

The plurality of nozzles 28 are provided in the same number as the pressure chambers 31 and arranged to face the pressure chambers 31 respectively. A plurality of nozzles 28 are arranged along the first direction and arranged in two rows corresponding to the pair of actuators 22 . Each nozzle 28 is configured in a tubular shape with an axis extending in the third direction. For example, the nozzle 28 may have a constant diameter, or may have a shape that tapers toward the center or tip. The nozzles 28 are disposed in the middle of the extending direction of the pressure chambers 31 formed in the pair of actuators 22 and communicate with the pressure chambers 31 respectively. One nozzle 28 is arranged in each pressure chamber 31 in the central portion in the longitudinal direction.

The frame 13 is made of, for example, a nickel alloy and has a rectangular shape. The frame 13 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12 . The frame 13 is adhered to the mounting surface of the actuator base 11 and the nozzle plate 12 respectively. That is, the nozzle plate 12 is attached to the actuator base 11 via the frame 13 .

The manifold 18 is joined to the opposite side of the actuator base 11 from the nozzle plate 12 . Inside the manifold 18, an ink supply section, which is a flow path communicating with the supply hole 25, and an ink discharge section, which is a flow path which communicates with the discharge hole 26, are formed.

Circuit board 17 is a film carrier package (FCP). The circuit board 17 has a flexible resin film 51 on which a plurality of wirings are formed, and an IC 52 connected to the plurality of wirings of the film 51 . The IC 52 is electrically connected to the electrode layer 34 via the wiring of the film 51 and the pattern wiring 211 .

An ink chamber 27 surrounded by the actuator base 11, the nozzle plate 12, and the frame 13 is formed inside the inkjet head 10 configured as described above. That is, the ink chamber 27 is formed between the actuator base 11 and the nozzle plate 12 . For example, the ink chamber 27 is partitioned into three sections in the second direction by the two actuators 22, and includes two second common chambers 272 as common chambers in which the discharge holes 26 open, and a common chamber in which the supply holes 25 open. and a first common chamber 271 of . The first common chamber 271 and the second common chamber 272 communicate with the multiple pressure chambers 31 .

In the inkjet head 10 configured as described above, ink circulates between the ink tank and the ink chamber 27 through the supply hole, the pressure chamber, and the discharge hole. For example, the drive IC 52 applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via the wiring of the film 51 in response to a signal input from a control unit of an inkjet printer, thereby causing the electrode layer 34 of the pressure chamber 31 and the dummy chamber to 32 and the electrode layer 34, the side wall portion 33 is selectively subjected to shear mode deformation. By deforming the side wall portion 33 formed between the pressure chamber 31 and the dummy chamber 32 according to the drive signal, the volume of the pressure chamber 31 is changed.

Due to the shear mode deformation of the side wall portion 33, the volume of the pressure chamber 31 provided with the electrode layer 34 increases and the pressure decreases. As a result, the ink in the ink chamber 27 flows into the pressure chamber 31 .

With the volume of the pressure chamber 31 increased, the IC 52 applies a drive voltage of opposite potential to the electrode layer 34 of the pressure chamber 31 . As a result, the side wall portion 33 undergoes shear mode deformation, the volume of the pressure chamber 31 provided with the electrode layer 34 decreases, and the pressure increases. As a result, the ink in the pressure chamber 31 is pressurized and ejected from the nozzle 28 .

A method for manufacturing the inkjet head 10 will be described. First, a piezoelectric member forming a plurality of grooves is attached to a plate-shaped substrate 21 with an adhesive or the like, and mechanical processing is performed using a dicing saw, a slicer, or the like to form the actuator base 11 having a predetermined outer shape. For example, a block-shaped base member having a thickness corresponding to a plurality of sheets may be formed in advance and then divided to manufacture a plurality of actuator bases 11 having a predetermined shape.

Subsequently, the electrode layer 34 and the pattern wiring 211 are formed on the inner surfaces of the grooves forming the pressure chambers 31 and the dummy chambers 32 and on the surface of the substrate 21 . As a result, as shown in FIG. 7, the electrode layer 34 and the pattern wiring 211 are formed at predetermined locations, and the actuators 22 forming the pressure chambers 31 and the dummy chambers 32 are formed. Then, a cover member 24 having a thin flat plate shape and having a plurality of throttle holes 242 formed therein is adhered to the side face portions 221 on both sides of the actuator 22 where the pressure chamber 31 and the dummy chamber 32 are opened. do. For example, the cover member 24 is obtained by forming a plurality of throttle holes 242 narrower than the inside of the pressure chamber 31 in a cover plate 241 made of an insulating material and having a plate shape. The cover plate is a plate-shaped mold part made of a film material made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate), or a ceramic material such as zirconia or alumina.

For example, when a resin film such as PI or PET is used as the cover plate 241, a plurality of throttle holes 242 are formed by forming openings narrower than the inside of the pressure chamber by laser processing. Alternatively, when a ceramic plate is used as the cover plate 241 , the throttle hole 242 is formed by forming an opening narrower than the inside of the pressure chamber by laser processing or machining. Alternatively, it may be created by cutting machinable ceramics. As described above, the opening of the dummy chamber 32 is covered and the opening of the pressure chamber 31 is partially covered by attaching the plate-shaped cover member 24 having the throttle hole 242 in advance. The common chambers 271 and 272 are communicated with through a throttle hole 242 having a channel cross-sectional area smaller than that inside the chamber 31 .

Further, the actuator base 11 is assembled to the manifold 18, and the frame 13 is attached to one surface of the substrate 21 of the actuator base 11 with an adhesive sheet of thermoplastic resin.

Then, the assembled frame 13, top portion 222 of the side wall portion 33 of the actuator 22, and surface of the cover member 24 on the nozzle plate 12 side are polished so as to be flush with each other. Then, the nozzle plate 12 is attached to the polished surfaces of the top portion 222 of the side wall portion 33, the frame 13, and the cover member 24 by bonding. At this time, positioning is performed so that the nozzle 28 faces the pressure chamber 31 . Further, as shown in FIG. 1, the inkjet head 10 is completed by connecting the driving IC chip 52 and the circuit board 17 to the pattern wiring 211 formed on the main surface of the substrate 21 via the flexible printed circuit board.

An example of an inkjet printer 100 including the inkjet head 10 will be described below with reference to FIG. The inkjet printer 100 includes a housing 111 , a medium supply section 112 , an image forming section 113 , a medium discharge section 114 , a conveying device 115 and a control section 116 .

The inkjet printer 100 conveys a recording medium, such as paper P, which is an object to be ejected, along a predetermined conveyance path A from a medium supply unit 112 through an image formation unit 113 to a medium discharge unit 114, while feeding ink or the like. It is a liquid ejection device that performs an image forming process on a sheet of paper P by ejecting liquid.

A housing 111 constitutes an outer shell of the inkjet printer 100 . A discharge port for discharging the paper P to the outside is provided at a predetermined position of the housing 111 .

The medium supply unit 112 includes a plurality of paper feed cassettes, and is configured to be able to stack and hold a plurality of sheets of paper P of various sizes.

The medium ejection unit 114 includes a paper ejection tray configured to hold the paper P ejected from the ejection port.

The image forming section 113 includes a support section 117 that supports the paper P, and a plurality of head units 130 arranged above the support section 117 so as to face each other.

The support portion 117 includes a conveying belt 118 provided in a loop shape in a predetermined area for image formation, a support plate 119 supporting the conveying belt 118 from the back side, and a plurality of belt rollers 120 provided on the back side of the conveying belt 118 . , provided.

During image formation, the support unit 117 supports the paper P on the holding surface, which is the upper surface of the transport belt 118, and feeds the transport belt 118 at a predetermined timing by the rotation of the belt roller 120, thereby moving the paper P downstream. carry to the side.

The head unit 130 includes a plurality of (four colors) inkjet heads 10, ink tanks 132 as liquid tanks mounted on each inkjet head 10, and a connection channel 133 connecting the inkjet heads 10 and the ink tanks 132. and a circulation pump 134 that is a circulation unit. The head unit 130 is a circulation type head unit that constantly circulates the liquid in the ink tank 132 , the pressure chamber 31 built inside the inkjet head 10 , the dummy chamber 32 , and the ink chamber 27 .

In this embodiment, there are four ink jet heads 10 of cyan, magenta, yellow, and black, and ink tanks 132 that respectively contain the inks of these colors. The ink tank 132 is connected to the inkjet head 10 by a connection channel 133 . The connection channel 133 includes a supply channel connected to the supply port of the inkjet head 10 and a recovery channel connected to the discharge port of the inkjet head 10 .

The ink tank 132 is also connected to a negative pressure control device such as a pump (not shown). The negative pressure control device controls the pressure inside the ink tank 132 according to the head value of the ink jet head 10 and the ink tank 132, so that the ink supplied to each nozzle 28 of the ink jet head 10 is formed into a predetermined shape. form a meniscus of .

The circulation pump 134 is, for example, a liquid feed pump configured by a piezoelectric pump. A circulation pump 134 is provided in the supply channel. The circulation pump 134 is connected to the drive circuit of the controller 116 by wiring, and is configured to be controllable under the control of a CPU (Central Processing Unit). A circulation pump 134 circulates the liquid in a circulation channel including the inkjet head 10 and the ink tank 132 .

The transport device 115 transports the paper P along the transport path A from the medium supply unit 112 through the image forming unit 113 to the medium discharge unit 114 . The conveying device 115 includes a plurality of guide plate pairs 121 arranged along the conveying path A and a plurality of conveying rollers 122 .

The plurality of guide plate pairs 121 each include a pair of plate members arranged opposite to each other with the paper P being transported therebetween, and guide the paper P along the transport path A. As shown in FIG.

The transport rollers 122 are driven and rotated under the control of the control unit 116 to transport the paper P along the transport path A to the downstream side. Sensors for detecting the state of transport of the paper are arranged at various locations along the transport path A. FIG.

The control unit 116 includes a control circuit such as a CPU as a controller, a ROM (Read Only Memory) for storing various programs, and a RAM (Random Access Memory) for temporarily storing various variable data and image data. and an interface unit for inputting data from the outside and outputting data to the outside.

In the inkjet printer 100 configured as described above, when the user detects a print instruction by operating the operation input unit at the interface, for example, the control unit 116 drives the transport device 115 to transport the paper P, and a predetermined By outputting a print signal to the head unit 130 at the timing of , the inkjet head 10 is driven. As an ejection operation, the inkjet head 10 sends a drive signal to the IC according to an image signal corresponding to image data, applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via wiring, and selects the side wall portion 33 of the actuator 22 . Ink is ejected from the nozzles 28 by being driven statically to form an image on the paper P held on the conveying belt 118 . Further, as the liquid ejection operation, the control unit 116 drives the circulation pump 134 to circulate the liquid in the circulation channel passing through the ink tank 132 and the inkjet head 10 . By driving the circulation pump 134 , the ink in the ink tank 132 passes through the ink supply portion of the manifold 18 and flows from the supply hole 25 to the first common ink chamber 27 . chamber 271 is supplied. This ink is supplied to the plurality of pressure chambers 31 and the plurality of dummy chambers 32 of the pair of actuators 22 . Ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chamber 31 and the dummy chamber 32 . This ink is discharged from the discharge hole 26 to the ink tank 132 through the ink discharge portion of the manifold 18 .

According to the embodiment described above, an inkjet head with high frequency characteristics can be provided. That is, in the inkjet head 10 according to the above-described embodiment, the pressure chambers 31 are provided with the cover members 24 so that the entrances and exits of the pressure chambers 31 are located closer to the inside of the pressure chambers 31 and than the first common chamber 271 and the second common chamber 272 . High flow resistance. As a specific example, the openings that open to the first common chamber 271 and the second common chamber 272 that are common chambers of the pressure chambers 31 are smaller than the flow channel cross-sectional area of the pressure chambers 31 . Therefore, the rise of the meniscus is reduced when the ink jet head 10 ejects the liquid. Therefore, the meniscus recovers quickly, the influence on the next bullet can be reduced, and the ejection stability can be improved.

FIG. 8 shows Test Example 1 of the inkjet head 110 with the aperture (the diaphragm portion 240) and Test Example 2 of the inkjet head 1010 without the aperture. FIG. 9 shows frequency characteristics of the inkjet head 110 having an aperture according to Test Example 1, and FIG. 10 shows frequency characteristics of an inkjet head 1010 having no aperture as Comparative Example 2. In FIG. 9 and 10 show the relationship between the nozzle ejection speed and the frequency for 1 drop and 3 drop, respectively.

Here, in the inkjet head 110 according to Test Example 1, both sides of the second direction, which is the extending direction of the pressure chambers 31, communicate with the common chamber, and the nozzles 28 are opened in the middle part of the extending direction of the pressure chambers 31. It is a side shooter type.

As shown in FIG. 10, in the inkjet head 1010 according to Test Example 2, the ejection speed is flat in the low frequency region, but the ejection speed tends to decrease as the frequency increases. There is a difference in ejection speed. At 1 drop of the inkjet head 1010 according to Test Example 2, the ejection speed is flat up to 25 kHz, but the ejection speed tends to decrease as the frequency increases above 25 kHz. In addition, in the 3 drop of the inkjet head 1010 according to Test Example 2, the ejection speed is flat up to 15 kHz, but the ejection speed tends to decrease as the frequency increases above 15 kHz. Therefore, the landing position is deviated depending on the printing pattern. If there is such a large difference in the ejection speed, it takes a long time for the meniscus to subside, which causes deterioration in print quality, so high-speed driving is not possible.

On the other hand, as shown in FIG. 9, in the ink jet head 110 having the constricted portion, the ejection speed tends to be flat for both 1 drop and 3 drops. This is because the fluid resistance between the nozzles increases from the common liquid, and the rise of the meniscus decreases.

FIG. 11 shows simulation results of meniscus restoration in Test Example 1 in which a throttle is provided in the pressure chamber and Test Example 2 in which no throttle is provided. According to FIG. 11, when the meniscus state of the nozzle is at a low frequency, there is sufficient time from the ejection of an ink droplet to the ejection of the next ink droplet. Ejection is possible in this state. On the other hand, in the case of high frequency, the time from ejection of a dot (ink droplet) to ejection of the next bullet is short, so ejection of the next bullet starts before the meniscus returns. For this reason, in the case of the inkjet head 1010 having no aperture, the meniscus swells up after ejection, and the meniscus cannot be restored before the next ejection, resulting in a decrease in ejection speed. On the other hand, if the aperture is provided, the rise of the meniscus is reduced, so the meniscus recovers quickly and the influence on the next shot can be reduced. Therefore, from these simulation results, it can be said that providing a diaphragm between the pressure chamber 31 and the common chamber leads to an improvement in ejection stability of the inkjet head 110 .

FIG. 12 illustrates a side shooter type inkjet head 110 as Test Example 1 and a share mode shared wall type end shooter type inkjet head 2010 as Test Example 3 in which an ink inlet/outlet is formed at one end and nozzles are formed at the other end. It is a diagram.

13 to 16 are diagrams comparing the simulation characteristics of the end shooter type ink jet head 2010 as Test Example 3 and the side shooter type ink jet head 110 of Test Example 1 when each aperture is provided. 13 shows the driving waveform, FIG. 14 shows the nozzle flow velocity vibration, FIG. 15 shows the discharge volume, and FIG. 16 shows the meniscus recovery characteristic.

In addition, in the inkjet head 2010 according to Test Example 3, one end side of the second direction, which is the extending direction of the pressure chambers 31, communicates with the common chamber, the other end portion is closed, and the nozzle is opened at the end portion of the flow path. Shooter type. That is, the inkjet head 2010 constitutes a flow path that flows toward the nozzle 28 from one side in the second direction.

The end shooter type ink jet head 2010 supplying from one side as Test Example 3 and the side shooter type ink jet head 110 as Test Example 1 supplying from both sides have the same ejection volume, nozzle flow velocity vibration, and meniscus recovery characteristics. Since the drive voltage is the lowest in the configuration of the side shooter type with both-side supply, it can be said that the two-side supply is superior to the one-side supply from the viewpoint of drive efficiency. That is, the so-called side-shooter type inkjet head 110, which has a nozzle in the center of the pressure chamber and ink inlet/outlets at both ends, is superior in ejection efficiency to the end-shooter type inkjet head 2010. FIG.

In the above-described embodiment, the actuator 22 is attached with the thin plate-like cover member 24 in which the throttle port is formed in advance. This reduces the number of assembling steps, and the grooves are formed in advance, so the precision is good and the assembly is easy. Aperture can be formed at

Moreover, the cover member 24 has a simple shape, can be manufactured at a low cost, and requires less manufacturing steps, which facilitates joining and positioning. PI, which is the material of the cover member 24, has good laser processability and excellent chemical resistance, so it is suitable for use as a part that comes into contact with ink.

It should be noted that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the present invention at the implementation stage.

For example, in the above embodiment, the cover member 24 in which the cover plate 241 is formed with the plurality of throttle holes 242 is illustrated, but the present invention is not limited to this. For example, the cover member 24 may form the narrowed portion 240 having a higher fluid resistance than the pressure chamber 31 . For example, as shown in FIG. 18 as another embodiment, the aperture may be formed by a plurality of grooves.

Ink jet heads according to other embodiments will be described below. As shown in FIG. 18, the cover member 24 has a cover plate 241 with a predetermined thickness. The cover plate 241 is configured in a shape corresponding to the inclined side portion 221 of the actuator, for example, in a rectangular shape extending in the first direction. The cover plate 241 is formed with throttle grooves 2242 as a plurality of throttle openings penetrating in the thickness direction. The cover members 24 are provided on both ends of the actuator 22 in the second direction, respectively, to block the opening of the dummy chamber 32 and partially block the opening of the pressure chamber. For example, the cover member 24 is made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate). The grooves forming the pressure chambers 31 communicate with the first common chamber 271 and the second common chamber 272 through throttle grooves 2242 formed in the cover member 24 . The throttle groove 2242 is formed on the nozzle plate 12 side of the cover plate 241 and is a slit extending over both main surfaces of the cover plate 241. The opening area of the throttle groove 2242 is smaller than the cross-sectional area of the pressure chamber. For example, the throttle groove 2242 is configured such that the depth dimension along the third direction is smaller than the depth dimension of the pressure chamber 31 . By closing the region of the pressure chamber 31 on the bottom side in the third direction with the cover member 24, a narrowed portion 240 having a narrow opening area is formed. The width dimension along the first direction of the throttle groove 2242 is appropriately set, for example, so as to provide a predetermined fluid resistance.

That is, the cover member 24 closes a part of the opening communicating with the first common chamber 271 and the second common chamber 272, which are common chambers at both ends of the pressure chamber 31, so that the pressure chamber 31 is perpendicular to the second direction. A narrowed portion 240 is formed to reduce the cross-sectional area of the flow path and increase the fluid resistance.

The cover member 24 is joined to the inclined side portion 221 of the actuator 22 . Also, one edge of the cover member 24 may be joined to the substrate 21 .

Note that if the fluid resistance of the throttle portion 240 is too large, the ink replenishment to the pressure chamber 31 after the ejection of the ink droplets will be delayed, which will hinder the speeding up. Also, the bulge of the meniscus varies depending on the ink viscosity, ejection volume, drive frequency, and the like. Therefore, the thickness of the cover member 24 and the size and position of the throttle groove 2242 of the throttle portion 240 are set so as to provide flow path resistance according to the ink replenishment conditions and the meniscus swelling characteristics.

Both ends of the plurality of dummy chambers 32 are closed by cover members 24, for example. That is, cover members 24 are arranged between the first common chamber 271 of the ink chamber 27 and the entrance of the dummy chamber 32 and between the exit of the dummy chamber 32 and the second common chamber 272, respectively. is separated from the ink chamber 27 . Therefore, the dummy chamber 32 constitutes an air chamber into which ink does not flow.

In the method of manufacturing the inkjet head 2010 according to the present embodiment, the side portions 221 at both ends of the actuator 22 where the pressure chambers 31 and the dummy chambers 32 are opened are formed in a thin flat plate shape and formed with a plurality of throttle grooves 2242 . A cover member 24 is adhered to. The cover member 24 is manufactured by forming a plurality of throttle grooves 2242, which are slits narrower than the inside of the pressure chamber, in a cover plate 241 made of an insulating material. The cover plate 241 uses a film material made of a resin material such as PI (polyimide) or PET (polyethylene terephthalate), or a plate-shaped mold part made of a ceramic material such as zirconia or alumina. For example, when a resin film such as PI or PET is used as the cover plate 241, a plurality of throttle grooves 2242 are formed by forming openings narrower than the inside of the pressure chamber by laser processing. Alternatively, when a ceramic plate is used as the cover plate 241 , an opening narrower than the inside of the pressure chamber is formed by laser processing or machining to form the throttle groove 2242 . Alternatively, it may be created by cutting machinable ceramics. As described above, the opening of the dummy chamber 32 is covered and the opening of the pressure chamber 31 is partially covered by attaching the plate-shaped cover member 24 having the throttle groove 2242 in advance. It communicates with the first common chamber 271 and the second common chamber 272, which are common chambers, by means of a throttle groove 2242 having a channel cross-sectional area smaller than that inside the chamber 31 .

In the inkjet head 2010 according to the present embodiment as well, stable ejection performance can be achieved by arranging cover members 24 having throttle grooves 2242 on both sides of the pressure chambers 31 to increase the fluid resistance at the entrance and exit of the pressure chambers 31. . That is, when the state of the meniscus at the nozzle portion becomes high frequency, the time from the ejection of the ink droplet to the ejection of the next droplet is short. Therefore, the frequency characteristic is deteriorated. However, by providing the throttle at the entrance of the pressure chamber 31, the time until the meniscus is restored is shortened, so that the frequency characteristic can be improved.

In general, in a shared-mode shared-wall type ink jet head, for example, pressure chambers are composed of fine grooves formed in a piezoelectric body by a diamond cutter, so the cross section of a part of the pressure chambers can be reduced. Although it is difficult, according to the above-described embodiment, by attaching the thin plate-like cover member 24 in which the throttle groove 2242 is formed in advance to the actuator 22, the assembly process is reduced. Further, since the groove 2242 is formed in the cover member 24, the aperture can be easily formed with good accuracy.

Moreover, the cover member 24 has a simple shape, can be manufactured at a low cost, and requires less manufacturing steps, which facilitates joining and alignment. PI, which is the material of the cover member 24, has good laser processability and excellent chemical resistance, so it is suitable for use as a part that comes into contact with ink.

It should be noted that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements without departing from the scope of the present invention at the implementation stage.

In addition, in the above-described embodiment, an example in which the actuator 22 having a plurality of grooves is arranged on the main surface portion of the substrate 21 is shown, but the present invention is not limited to this. For example, an actuator may be provided on the end face of the substrate 21 . Also, the number of nozzle rows is not limited to that of the above embodiment, and may be configured to have one row or three or more rows.

Further, in the above-described embodiment, the actuator base 11 having the laminated piezoelectric member including the piezoelectric member 131 on the substrate 21 is illustrated, but the present invention is not limited to this. For example, the actuator base 11 may be formed only by a piezoelectric member without using a substrate. Also, instead of using two piezoelectric members, one piezoelectric member may be used. The dummy room 32 may communicate with the first common room 271 and the second common room 272, which are common rooms. Also, the supply side and the discharge side may be reversed, or may be configured to be switchable.

In the above embodiment, as an example, one side of the pressure chamber 31 is the supply side, the other side is the discharge side, and the fluid flows in from one side of the pressure chamber and flows out from the other side. is exemplified, but it is not limited to this. For example, the common chambers on both sides of the pressure chamber 31 may be the supply side, and the configuration may be such that the fluid flows in from both sides. That is, the fluid may flow in from both sides of the pressure chamber 31 and flow out from the nozzle 28 arranged in the center of the pressure chamber 31 . Even in this case, by providing the throttle portions 240 at the inlet portions on both sides of the pressure chamber 31, the fluid resistance is increased and the discharge efficiency can be improved.

For example, the liquid to be ejected is not limited to ink for printing, and may be a device that ejects liquid containing conductive particles for forming a wiring pattern of a printed wiring board.

In the above embodiments, the inkjet head is used in a liquid ejection device such as an inkjet printer. However, it is not limited to this, and can also be used in, for example, 3D printers, industrial manufacturing machines, and medical applications. It is possible to reduce the size, weight, and cost.

According to at least one embodiment described above, it is possible to provide a liquid ejection head that is easy to manufacture.

Additionally, while several embodiments of the invention have been described, these embodiments have been presented by way of example 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 modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Inkjet head 11... Actuator base 12... Nozzle plate 13... Frame 17... Circuit board 18... Manifold 21... Substrate 22... Actuator 24... Cover member (wall part) 25... Supply hole, 26 discharge hole 27 ink chamber 31 pressure chamber 32 dummy chamber 33 side wall portion 34 electrode layer 51 film 52 drive IC chip 100 inkjet printer 111 casing DESCRIPTION OF SYMBOLS 112... Medium supply part 113... Image formation part 114... Medium discharge part 115... Conveyance apparatus 116... Control part 117... Support part 118... Conveyor belt 119... Support plate 120... Belt roller 121... Guide plate pair 122 Conveyance roller 130 Head unit 132 Ink tank 133 Connection channel 134 Circulation pump 211 Pattern wiring 221 Side portion 222 Top portion 240 Constriction portion 241... Cover plate, 242... Throttle hole (throttle mouth), 271... First common chamber, 272... Second common chamber, 2242... Throttle groove (throttle mouth).

Claims (5)

an actuator having a plurality of pressure chambers communicating with nozzles for ejecting liquid, and a plurality of dummy chambers disposed between the plurality of pressure chambers;
a common chamber arranged at both ends of the actuator and communicating with the plurality of pressure chambers;
It is joined to the side surface of the actuator and has a plate-like shape, and separates the pressure chamber and the dummy chamber from the common chamber, and communicates the common chamber with the pressure chamber at a position facing the plurality of pressure chambers. A side shooter type liquid ejection head comprising: a cover plate having an opening with a higher fluid resistance than the inside of the pressure chamber. The cover plate is a ceramic plate or a resin film,
said openings are grooves or holes;
the actuator includes a plurality of side walls arranged in parallel along a first direction and forming grooves forming the pressure chamber and the dummy chamber therebetween;
each of the pressure chambers extends in a second direction that intersects with the first direction;
the nozzle is arranged at a position corresponding to the middle portion of the pressure chamber in the second direction;
a liquid ejection direction of the nozzle intersects with the first direction and the second direction, and
The common chambers are arranged on both sides of the pressure chambers in the second direction,
2. The side shooter type liquid discharge head according to claim 1, wherein said cover plates are arranged between said common chambers at both ends of said pressure chambers and joined to said side walls. a plurality of pressure chambers communicating with nozzles for ejecting liquid; a plurality of dummy chambers arranged between the plurality of pressure chambers; and a common chamber communicating with both sides of the plurality of pressure chambers and the dummy chambers. a cover plate having a plate-like shape and having openings with higher fluid resistance than the pressure chambers at positions facing the plurality of pressure chambers. A method for manufacturing a liquid ejection head of a mold. 4. The method of manufacturing a side shooter type liquid ejection head according to claim 3, wherein said cover plate is a resin film, and said opening is formed by laser processing. 4. The method of manufacturing a side shooter type liquid ejection head according to claim 3, wherein said cover plate is a ceramic plate, and grooves or holes are formed by machining.

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