JP2023046015A - liquid ejection head - Google Patents

Abstract

To provide a liquid ejection head which can secure stable ejection characteristics.SOLUTION: A liquid ejection head according to an embodiment comprises; an actuator member which has a plurality of grooves constituting a plurality of pressure chambers and a plurality of dummy chambers arranged between the plurality of pressure chambers, side walls formed between the plurality of grooves and wall portions blocking both end parts of the grooves; and nozzle plates which are, oppositely arranged at one sides of the plurality of grooves of the actuator member and covering one sides of the dummy chambers and of the pressure chambers, and which have a plurality of nozzles ejecting liquid to positions corresponding to the pressure chambers, and communicate common chambers formed outside the wall portions at both end parts of the pressure chambers with the pressure chambers to thereby form clearances which are larger in fluid resistance than the insides of the pressure chambers.SELECTED DRAWING: Figure 4

Description

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

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 shared mode shared wall type inkjet head, the same drive column is shared by two pressure chambers, and one-third of the plurality of arranged chambers are used as pressure chambers and driven 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 capable of ensuring stable ejection characteristics.

A liquid ejection head according to an embodiment is of a side shooter type, and includes a plurality of grooves forming a plurality of pressure chambers, a plurality of dummy chambers arranged between the plurality of pressure chambers, and a plurality of grooves forming the plurality of pressure chambers. an actuator member having side walls formed therebetween and wall portions closing both ends of the groove; a plurality of nozzles for ejecting liquid at positions facing the pressure chambers, and communicating the pressure chambers with common chambers formed outside the wall portions at both ends of the pressure chambers; a nozzle plate that forms a gap having a greater fluid resistance than the interior of 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. The top view which expands and shows a structure of one part of the same inkjet head. FIG. 2 is a perspective view showing the configuration of part of the nozzle plate of the 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. 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. Sectional drawing which expands and shows a one part structure of the inkjet head concerning other 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 7. 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. FIG. 3 is an enlarged cross-sectional view showing a partial configuration of the inkjet head, and FIG. 4 is an enlarged plan view showing a partial configuration of the inkjet head. Note that the nozzle plate 12 is omitted in FIG. FIG. 5 is a perspective view showing the configuration of part of the nozzle plate. 6 and 7 are enlarged cross-sectional views showing the configuration of a part of the ink jet head, FIG. 6 showing a cross section of the pressure chamber, and FIG. 7 showing a cross section of the dummy chamber. In the drawing, X, Y, and Z indicate the first direction, the second direction, and the third direction, which are orthogonal to each other. In this embodiment, the parallel direction of the nozzles 28 and the pressure chambers 31 of the inkjet head 10 is the X axis, the extending direction of the pressure chambers 31 is the Y axis, and the liquid ejection direction of the nozzles 28 is the Z axis. Although the description of the direction is described based on the posture along the line, it is not limited to this.

As shown in FIGS. 1 to 7, the inkjet head 10 is a so-called side shooter type share mode shared wall 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 15 .

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. An ink chamber 27 is formed inside the inkjet head 10 to which ink, which is an example of a liquid, is supplied.

As shown in FIG. 2, the actuator base 11 includes a substrate 21, a pair of actuator members 22, and a cover portion 23 as a wall portion.

The substrate 21 is an example of a base material. 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 actuator members 22 are joined to the mounting surface of the substrate. Further, the substrate 21 is formed with a plurality of supply holes 25 and discharge holes 26 .

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 member 22 .

The supply holes 25 are arranged in the longitudinal direction of the actuator members 22 between the pair of actuator members 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 actuator members 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 actuator members 22 are adhered to the mounting surface of the substrate 21 . A pair of actuator members 22 are arranged in two rows on the substrate 21 with the supply hole 25 interposed therebetween. Each actuator member 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 member 22 is adhered to the mounting surface of the substrate 21 with, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuator members 22 are arranged in parallel in the ink chamber 27 corresponding to the nozzles 28 arranged in two rows. The actuator member 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 pair of actuator members 22 are provided with their longitudinal directions along the first direction, and have a trapezoidal cross section perpendicular to the first direction. The side surface portion 221 of the actuator member 22 has inclined surfaces that are inclined with respect to the second direction and the third direction. That is, the actuator member 22 is configured to have a trapezoidal cross-sectional view orthogonal to the second direction. The top of actuator member 22 is glued to nozzle plate 12 . The actuator member 22 includes multiple pressure chambers 31 and multiple dummy chambers 32 . The actuator member 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 . The plurality of pressure chambers 31 and the dummy chambers 32 are composed of grooves that open to both ends in the second direction and to one side in the third direction.

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 side walls 33 , the pressure chambers 31 , and the dummy chambers 32 each extend in a direction crossing the longitudinal direction of the actuator member 22 , and are arranged in parallel in a first direction (the X axis in the figure), which is the longitudinal direction of the actuator member 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 are arranged to face the nozzle plate 12 and communicate with the plurality of nozzles 28 of the nozzle plate 12 . One side of the plurality of pressure chambers 31 in the third direction is covered by the nozzle plate 12 and both ends in the second direction are covered by the cover portion 23 . It communicates with the ink chamber 27 via a communication port 123 which is a gap formed between the ink chambers 23 . That is, one end of the pressure chamber 31 communicates with the first common chamber 271 of the ink chamber 27 , and the other end communicates with 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 communicating ports 123 formed by the concave portions 122 at both ends of the pressure chamber 31 form throttle portions 240 having a higher fluid resistance than the inside of the pressure chamber 31 .

One side of the dummy chamber 32 in the third direction is blocked by the nozzle plate 12 . Further, both ends of the plurality of dummy chambers 32 in the second direction are closed by the cover portions 23, for example. That is, the covers 23 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.

The cover portion 23 is made of, for example, photosensitive resin. The cover portion 23 closes the openings at both ends in the second direction of the grooves forming the plurality of pressure chambers 31 and the dummy chambers 32 . The cover portion 23 is molded into a predetermined shape by exposing and developing after film formation of the photosensitive resin, or by exposing, developing and machining after film formation of the photosensitive resin. For example, the cover portion 23 has a predetermined shape that closes both ends of the groove by applying a photosensitive resin to the entrances on both sides of the pressure chamber 31, curing the target portion by exposure, and washing away unnecessary unexposed resin with a developing solution. configured to

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 inner surface of the groove to the substrate 21 and is connected to the pattern wiring 211 . An electrode layer 34 is formed on the inner wall of the groove. For example, the electrode layer 34 is formed on the side surface portion and the bottom surface portion of the side wall portion 33 .

The nozzle plate 12 is formed of, for example, a rectangular polyimide film. The nozzle plate 12 extends in the first direction and the second direction and faces the mounting surface of the actuator base 11 . The nozzle plate 12 is joined to the top 222 of the actuator member 22 and the frame 15 . The nozzle plate 12 covers one side in the third direction of the area including the actuator member 22 and the common chamber formed at the side of the actuator member 22 . A plurality of nozzles 28 are formed in the nozzle plate 12 so as to penetrate the nozzle plate 12 in the thickness direction. In addition, a concave portion 122 forming a gap between the nozzle plate 12 and the cover portion 23 is formed on the facing surface of the nozzle plate 12 on the side of the actuator member 22 .

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. As an example, the nozzle 28 is provided at a position facing the center of the pressure chamber 31 in the second direction. Further, the nozzle 28 is provided at a position facing the center of the pressure chamber 31 in the first direction.
A plurality of nozzles 28 are arranged along the first direction in two rows corresponding to the pair of actuator members 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 actuator members 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 concave portion 122 is configured by a step or groove. For example, the recessed portion 122 is a portion of the nozzle plate 12 configured to have a small thickness dimension. The concave portion 122 forms a gap or opening that serves as a communication port 123 between the side wall portion 33 and the cover portion 23 . For example, the recess 122 may be formed in the entire area facing the pressure chamber 31 or may be formed in part. Further, the recess 122 may be formed in a region between the end surface of the side wall portion 33 and the nozzle plate 12 . Further, for example, the concave portion 122 is formed in a portion avoiding the portion between the dummy chamber 32 and the common chambers 271 and 272 . The recess 122 may have the same width as the pressure chamber 31 or may be configured with a narrower width than the pressure chamber 31 . In the present embodiment, the concave portions 122 are arranged at positions facing one side of the cover portion 23 in the third direction at both end portions of the pressure chamber 31 in the second direction. Further, in this embodiment, the recess 122 is configured to be smaller than the width dimension of the pressure chamber 31 . Further, in the present embodiment, the opening area perpendicular to the second direction, which is the channel cross-sectional area of the recess 122 , is larger than the opening area perpendicular to the third direction, which is the channel cross-sectional area of the ejection surface of the nozzle 28 .

The nozzle plate 12 covers at least a region facing one side in the third direction of the groove forming the dummy chamber 32 and at least a region facing a portion of the side wall portion 33 . The nozzle plate 12 forms a gap having a larger fluid resistance than the inside of the pressure chamber 31 between the recessed portion 122 and the end surface of the cover portion 23 at both ends of the pressure chamber 31 . The formed common chambers 271 and 272 and the pressure chamber 31 are communicated with each other. The nozzle plate 12 closes the dummy chamber 32 with respect to the first common chamber 271 and the second common chamber 272 , and communicates the pressure chamber 31 with the first common chamber 271 , the second common chamber 272 and the nozzle 28 .

That is, the nozzle plate 12 forms communication ports 123 that communicate the pressure chambers 31 with the first common chamber 271 and the second common chamber 272 . The communication ports 123 are arranged at both ends of the pressure chamber 31 in the second direction. The communication port 123 is a gap having a predetermined dimension in the third direction, which is the depth direction, and the width in the third direction is smaller than the width in the third direction inside the pressure chamber 31. , is smaller than the flow passage cross-sectional area of the pressure chamber 31 . In other words, the communication ports 123 at both ends in the second direction constitute the narrowed portion 240 having a higher flow resistance than the inside of the pressure chamber 31 .

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 dimension of the recess 122 in the third direction, the width dimension along the first direction, and the position where the recess 122 is formed are determined by the throttle section 240 according to the ink replenishment conditions and the meniscus swelling characteristics. It is set so that the flow path resistance is the same. The shape and dimensions of the narrowed portion 240 formed by the communication ports 123 formed on both sides may be configured under the same conditions, or may be set under different conditions.

The frame 15 is made of, for example, a nickel alloy and has a rectangular shape. The frame 15 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12 . The frame 15 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 15 .

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 15 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 actuator members 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 as 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 for forming a plurality of grooves is attached to a plate-shaped substrate 21 with an adhesive or the like, and then machined using a dicing saw, a slicer, or the like to form a plurality of grooves and have a predetermined outer shape. The actuator member 22 is molded. 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 described above, the electrode layer 34 and the pattern wiring 211 are formed at predetermined locations on the actuator base 11 . Subsequently, the cover portion 23 is formed with a photosensitive resin. For example, the cover part 23 is filled with a photosensitive resin material in the communication openings, which are entrances and exits on both sides of the grooves that constitute the dummy chamber 32 and the pressure chamber 31, and the openings at both ends of the grooves in the second direction are filled with the photosensitive resin. and a molding process for molding the photosensitive resin into a predetermined shape. As described above, both ends of the pressure chamber 31 and the dummy chamber 32 in the second direction are closed with the photosensitive resin material.

At this time, the fluid resistance can be set by setting the dimensions of the concave portion 122 and the cover portion 23 constituting the narrowed portion 240 in the second direction and the third direction along the flow path direction according to the fluid resistance.

Further, the actuator base 11 is assembled to the manifold 18, and the frame 15 is attached to one surface of the substrate 21 of the actuator base 11 with an adhesive sheet of thermoplastic resin.

Then, the faces of the assembled frame 15, the top portion 222 of the side wall portion 33 of the actuator member 22, and the frame 15 facing the nozzle plate 12 are polished so as to be flush with each other. Then, the nozzle plate 12 in which the concave portions 122 and the nozzles 28 are formed in advance is adhered to the polished top portion 222 of the side wall portion 33 and the facing surface of the frame 15 . At this time, positioning is performed so that the nozzle 28 faces the pressure chamber 31 .

For example, the nozzle plate 12 has a nozzle 28 which is a through hole formed at a predetermined position communicating with the pressure chamber 31, and a concave portion 122 having a predetermined depth formed at a predetermined position on the surface facing the actuator member 22. be done. For example, the recesses 122 are formed by mechanical processing using a diamond cutter or the like, laser processing, or half-etching using chemicals, depending on the material of the nozzle plate 12 . At this time, by adjusting the width, depth, or position of the recess 122, it is possible to form an appropriate fluid resistance.

When the nozzle plate 12 is joined to the actuator member 22 and the frame 15, an adhesive is transferred and applied to the top portion 222 of the actuator member 22 and the end surface of the frame 15, which are rigid bodies. It is possible to make the adhesive portion thinner than when the adhesive is applied to the surface, and to set the accuracy of the application position with high accuracy. Here, by making the width dimension of the recess in the first direction smaller than the width dimension of the pressure chamber 31, the adhesive does not flow into the recess and the value of the fluid resistance can be stabilized.

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 transport device 115 includes a plurality of guide plate pairs 121 arranged along the transport path A and a plurality of transport rollers 124 .

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 roller 124 is 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, the control unit 116 drives the transport device 115 to transport the paper P when, for example, an interface detects a print instruction by the user operating the operation input unit, and a predetermined The inkjet head 10 is driven by outputting a print signal to the head unit 130 at the timing. As an ejection operation, the inkjet head 10 sends a driving signal to the IC according to an image signal corresponding to image data, and applies a driving voltage to the electrode layer 34 of the pressure chamber 31 via the wiring to push the side wall portion 33 of the actuator member 22 . It is selectively driven to eject ink from the nozzles 28 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 actuator members 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 above-described embodiments, it is possible to provide a liquid ejection head and a method for manufacturing the liquid ejection head that can ensure stable ejection characteristics. That is, in the ink jet head 10 according to the above-described embodiment, the entrance and exit of the pressure chamber 31 are covered with the cover portion 23 and the concave portion 122 is formed on the nozzle plate 12 side, so that the entrance and exit of the pressure chamber 31 are located inside the pressure chamber 31 and at the second end. The channel resistance is greater than that of the first common chamber 271 and the second common chamber 272 . 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.

The inkjet head 110 according to Test Example 1 is a side shooter in which both sides in 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. is a 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.

Generally, 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. Although difficult, according to the above-described embodiment, the constricted portion 240 can be formed by processing the opposing surface side of the nozzle plate 12, and the constriction can be formed easily and inexpensively with fewer steps. Furthermore, since the hole shape of the concave portion 122 can be selected relatively freely, it is also easy to freely design the fluid resistance of the throttle. That is, it is easy to ensure the accuracy of the depth of the concave portion 122 and the accuracy of the position of the concave portion 122, and it is easy to set the flow path resistance.

In addition, in the inkjet head 10 according to the above-described embodiment, the length of the concave portion 122 and the cover portion 23 constituting the throttle portion 240 in the second direction along the flow path direction is set in accordance with the fluid resistance. The channel length of the portion 240 can be set, and the fluid resistance can be easily adjusted. For example, as another embodiment, as shown in FIG. 18, by increasing the dimensions of the cover portion 23 and the recessed portion 122 in the second direction, the channel length of the constricted portion 240 is increased and the channel resistance is increased. can be done.

Further, in the above embodiment, by making the width dimension of the recess 122 in the first direction smaller than the width dimension of the pressure chamber 31, the adhesive does not flow into the recess 122, and the fluid resistance value can be stabilized. .

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 the above embodiment, as an example, the first common chamber 271 is arranged on one side of the pressure chamber 31, the second common chamber 272 is arranged on the other side, and the fluid flows from one side of the pressure chamber to the other side. Although an example of flowing out from is shown, 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 throttles at the inlet portions on both sides of the pressure chamber 31, the fluid resistance increases and the ejection efficiency can be improved. In addition, the shape, position, and size of the narrowed portions 240 provided on both sides can be set according to the flow path resistance, and both sides may be configured under the same conditions. may be configured under different conditions.

Further, in the above embodiment, the shape of the constricted portion 240 that increases the flow path resistance is not limited to this. In the above embodiment, the cover portion 23 is formed inside the grooves forming the pressure chambers 31 and the dummy chambers 32 and has a shape that fills the grooves, but the shape is not limited to this. For example, on the side surface of the actuator member 22 , a photosensitive resin may be placed outside the grooves forming the pressure chambers 31 and the dummy chambers 32 to block the ends of the dummy chambers 32 and the pressure chambers 31 .

In the above-described embodiment, an example in which the actuator member 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 made of the piezoelectric member on the substrate 21 was 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, it may be non-circulating. Further, 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 communicating ports serving as inlets on both sides of the pressure chamber 31, the fluid resistance increases and the ejection efficiency can be improved. For example, a non-circulating configuration may be employed by not providing a discharge-side flow path or by closing the discharge-side flow path. For example, a supply hole 25 may be provided instead of the discharge hole 26, or the discharge side flow path may be configured to be open only during ink replenishment or maintenance and closed during printing, thereby forming a non-circulating system.

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 and a method for manufacturing the liquid ejection head that can ensure stable ejection characteristics.

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 15... Frame 17... Circuit board 18... Manifold 21... Substrate 22... Actuator member (actuator) 23... Cover part (wall part) 25 Supply hole 26 Discharge hole 27 Ink chamber 31 Pressure chamber 32 Dummy chamber 33 Side wall 34 Electrode layer 51 Film 52 Drive IC chip 100 Inkjet printer 111 Housing 112 Medium supply unit 113 Image forming unit 114 Medium discharge unit 115 Conveying device 116 Control unit 117 Supporting unit 118 Conveying belt 119 Supporting plate 120 Belt Rollers 121 Guide plate pair 122 Concave portion 123 Communication port 124 Carrying roller 130 Head unit 132 Ink tank 133 Connection channel 134 Circulation pump 122 Concave portion 123 Communicating port 211 Pattern wiring 221 Side portion 222 Top portion 240 Constricted portion 271 First common chamber 27 Ink chamber 272 Second common chamber.

Claims (5)

a plurality of grooves forming a plurality of pressure chambers and a plurality of dummy chambers disposed between the plurality of pressure chambers; side walls formed between the plurality of grooves; and closing both ends of the grooves. an actuator member having a wall;
a plurality of nozzles arranged opposite one side of the plurality of grooves of the actuator member, covering one side of the dummy chamber and the pressure chamber, and ejecting liquid at a position facing the pressure chamber; a nozzle plate that communicates a common chamber formed outside the wall portions at both ends of the chamber with the pressure chamber to form a gap having a greater fluid resistance than the inside of the pressure chamber;
A side shooter type liquid ejection head. 2. The liquid ejection head according to claim 1, wherein said nozzle plate is formed on a surface facing said pressure chambers and has recesses forming said gaps with said wall portions. The plurality of nozzles and the plurality of pressure chambers are arranged side by side in a first direction,
the width of the recess in the first direction is smaller than the width of the pressure chamber in the first direction;
3. The liquid ejection head according to claim 2, wherein said nozzle plate is adhered to one surface of said side wall with an adhesive. a substrate to which the actuator member is bonded;
a frame provided on one side of the substrate and surrounding the actuator member and the common chamber formed on the side of the actuator member;
with
4. The liquid ejection head according to any one of claims 1 to 3, wherein the nozzle plate is joined to the side wall, the wall portion, and the frame of the actuator member. The plurality of nozzles and the plurality of pressure chambers are arranged side by side in a first direction,
each of the plurality of pressure chambers and the dummy chambers extends in a second direction crossing the first direction;
the nozzle is arranged at a position corresponding to an intermediate portion of the pressure chamber in the second direction;
The nozzle extends along a third direction intersecting the first direction and the second direction,
2. The gap is configured such that the dimension in the third direction is smaller than the dimension in the third direction of the interior of the pressure chamber, and forms a throttle opening having a greater fluid resistance than the interior of the pressure chamber. 5. The liquid ejection head according to any one of 1 to 4.

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