JP2023170460A - liquid discharge head - Google Patents

Abstract

To provide a liquid discharge head capable of securing stable discharge characteristics.SOLUTION: A liquid discharge head includes an actuator part, and a cover part. The actuator part has a plurality of pressure chambers and a plurality of air chambers which are composed of piezoelectric materials and are alternately aligned. The cover part has a plurality of wall members, and blocks the air chamber.SELECTED DRAWING: Figure 4

Description

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

In recent years, high productivity has been required for inkjet heads, and issues such as increased speed and increased droplet volume have become issues. For example, a share mode shared wall type inkjet head has a pressure chamber formed of a piezoelectric material and has high rigidity, so it has high power and is suitable for ejecting high viscosity ink and ejecting large droplets. Share mode Shared wall type inkjet head. A so-called 3-cycle drive is common in which two pressure chambers share the same drive column and one-third of the plurality of chambers are driven simultaneously as pressure chambers. Furthermore, an independent drive head has been developed in which air chambers are used on both sides of the pressure chamber to be driven, and one pressure chamber is driven by two independent drive columns. For example, a structure has been developed in which a large number of grooves are formed in a piezoelectric member, every other groove is closed with a resin wall to serve as an air chamber, and the grooves whose openings are not blocked are used as pressure chambers, which are driven independently.

In such an inkjet head, if the resin wall that closes the air chamber is insufficiently formed, ink will enter the air chamber, causing the AL (Acoustic Length) of adjacent pressure chambers to shift, causing in-plane AL Variability increases. AL is 1/2 of the acoustic resonance period of the pressure wave in the pressure chamber. Furthermore, when the air chamber is filled with ink, a so-called crosstalk phenomenon occurs in which vibrations are transmitted to adjacent pressure chambers.

Japanese Patent Application Publication No. 2015-189031

An object of the present invention is to provide a liquid ejection head that can ensure stable ejection characteristics.

A liquid ejection head according to one embodiment includes an actuator section and a cover section. The actuator section is made of a piezoelectric member and has a plurality of pressure chambers and a plurality of air chambers arranged alternately. The cover portion includes a plurality of wall members and closes the air chamber.

FIG. 1 is a perspective view showing an inkjet head according to an embodiment. FIG. 1 is an exploded perspective view showing a partial configuration of an inkjet head according to an embodiment. FIG. 3 is a perspective view showing a part of the inkjet head of FIG. 2; FIG. 3 is an enlarged cross-sectional view showing a part of the configuration of the inkjet head. FIG. 5 is a cross-sectional view of the inkjet head of FIG. 4 taken at a pressure chamber position. FIG. 5 is a cross-sectional view of the inkjet head of FIG. 4 taken at the position of the air chamber. FIG. 3 is a partially enlarged sectional view of a cross section taken along VII-VII of the inkjet head of FIG. 2; FIG. 3 is an explanatory diagram showing the relationship between AL and printing state of the inkjet head according to the embodiment. FIG. 3 is an explanatory diagram showing the relationship between the channel length and AL of the same inkjet head. FIG. 1 is a schematic diagram showing an inkjet printer according to an embodiment. FIG. 3 is a cross-sectional view showing a part of an inkjet head according to another embodiment.

The configuration of an inkjet head 10, which is a liquid ejection head according to a first embodiment, will be described below with reference to FIGS. 1 to 8. FIG. 1 is a perspective view showing an inkjet head according to a first embodiment, and FIG. 2 is an exploded perspective view of a part of the inkjet head. FIG. 3 is a perspective view showing an enlarged structure of a part of the inkjet head, and FIGS. 4 to 7 are sectional views showing an enlarged structure of a part of the inkjet head. FIG. 8 is an explanatory diagram showing the relationship between the AL of the inkjet head and the printing state, and FIG. 9 is an explanatory diagram showing the relationship between the flow path length and AL of the inkjet head. In the figure, X, Y, and Z indicate a first direction, a second direction, and three directions, respectively, which are orthogonal to each other. In addition, in this embodiment, the arrangement direction of the nozzle and the grooves constituting the pressure chamber 31 and the air chamber 32 is along the X axis, the extending direction of the pressure chamber 31 and the air chamber 32 is along the Y axis, and the liquid discharge direction is along the Z axis. Although directions will be described based on postures along the respective axes, the directions are not limited thereto.

The inkjet head 10 shown in FIGS. 1 to 7 is a so-called side shooter type share mode shared 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 air chambers 32 are alternately arranged. The air chamber 32 is an air chamber to which ink is not supplied, and does not include the nozzle 28.

The inkjet head 10 includes 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 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 a path between the inkjet head 10 and the ink tank.

As shown in FIG. 2, the actuator base 11 includes a substrate 21 and a pair of actuator parts 22.

The substrate 21 is made of ceramic such as alumina and has a rectangular plate shape. The substrate 21 has a flat mounting surface. A pair of actuator sections 22 are bonded to the mounting surface of the substrate 21. A plurality of supply holes 25 and discharge holes 26 are formed in the substrate 21 .

As shown in FIGS. 2 and 3, pattern wiring 211 is formed on the substrate 21 of the actuator base 11. As shown in FIGS. The pattern wiring 211 is formed of, for example, a nickel thin film. The pattern wiring 211 has a common pattern or individual patterns, and is configured in a predetermined pattern shape to be connected to the electrode layer 34 formed on the actuator section 22. For example, the pattern wiring 211 is formed at a position avoiding the supply hole 25 and the discharge hole 26.

The supply holes 25 are provided in the center of the substrate 21 and between the pair of actuator sections 22 in parallel in the longitudinal direction of the actuator sections 22 . The supply hole 25 communicates with the ink supply section of the manifold 18. The supply hole 25 is connected to an ink tank via an ink supply section. The supply hole 25 supplies ink from 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 parts 22 in between. The discharge hole 26 communicates with an ink discharge section of the manifold 18. The discharge hole 26 is connected to the ink tank via an ink discharge section. The discharge hole 26 discharges ink from the ink chamber 27 to an ink tank. In such a configuration, the inkjet head 10 is of a circulation type, and ink flows from one side of each pressure chamber 31 where the supply hole 25 is located to the other side where the discharge hole 26 is located. Alternatively, the ink discharge section may be opened only during maintenance, and communicated with the ink supply section during printing, for example. In such a configuration, the inkjet head 10 is of a non-circulating type, and ink flows into each pressure chamber 31 from both sides.

The pair of actuator sections 22 are bonded to the mounting surface of the substrate 21. The pair of actuator sections 22 are provided on the substrate 21 in two rows with the supply hole 25 in between. Each actuator section 22 is formed by two plate-shaped piezoelectric bodies 201 and 202 made of, for example, lead zirconate titanate (PZT). For example, the two piezoelectric bodies 201 and 202 are polarized such that their polarization directions are opposite to each other in the thickness direction. That is, in the actuator section 22, a pair of piezoelectric bodies 201 and 202 are stacked and polarized in opposite directions in the stacking direction. The actuator section 22 is bonded to the mounting surface of the substrate 21 using, for example, a thermosetting epoxy adhesive. As shown in FIG. 2, the actuator sections 22 are arranged in parallel in the ink chamber 27, corresponding to the nozzles 28 arranged in two rows. The actuator section 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 top of the actuator section 22 is glued to the nozzle plate 12.

The actuator section 22 is composed of a laminated piezoelectric member in which a plurality of piezoelectric bodies 201 and 202 are laminated, and includes a plurality of side walls 33 that serve as driving elements. The plurality of piezoelectric bodies 201 and 202 are laminated with the thickness direction along the third direction and are bonded to each other. Note that the laminated piezoelectric member is polarized during the manufacturing process.

In the actuator section 22, the plurality of grooves constituting the pressure chamber 31 and the air chamber 32 are arranged in parallel on one side surface in the third direction, which is the depth direction, that is, on one side surface facing the nozzle plate 12. They are formed in line in the first direction. The actuator section 22 has a comb-teeth shape in which a laminated piezoelectric member is divided into a plurality of parts on one side by a plurality of grooves, and the bottom sides of the plurality of grooves are connected together. The actuator section 22 is divided into a plurality of parts by forming a groove on one side by, for example, dicing, and the other end is connected, and side walls 33 sandwich the groove along the first direction indicated by X in the figure. Multiple units are arranged in parallel.

The actuator section 22 has a plurality of side walls 33 and, between the side walls 33, grooves forming a pressure chamber 31 and an air chamber 32. In other words, the side wall 33 is formed as a drive element between the grooves forming the pressure chamber 31 and the air chamber 32. The side wall 33 is formed between the pressure chamber 31 and the air chamber 32, and changes the volume of the pressure chamber 31 by deforming in response to a drive signal.

The width of the actuator section 22 in the lateral direction gradually increases from the top side toward the substrate side. The actuator section 22 has a trapezoidal cross-sectional shape along a direction (short side direction) perpendicular to the longitudinal direction. The side surface portion 221 of the actuator section 22 has an inclined surface inclined with respect to the second direction and the third direction.

FIG. 4 is a partially enlarged cross-sectional view of one of the actuator sections 22 of the inkjet head 10 shown in FIG. 2. As shown in FIG. FIG. 5 is a cross-sectional view of a groove forming the pressure chamber 31 of the inkjet head 10 shown in FIG. 4. As shown in FIG. FIG. 6 is a cross-sectional view of a groove forming the air chamber 32 of the inkjet head 10 shown in FIG. 4. As shown in FIG.

As shown in FIGS. 2, 5, and 6, the bottom surface of the groove and the main surface of the substrate 21 are connected by an inclined side surface 221. As shown in FIG. A plurality of pressure chambers 31 and air chambers 32 are arranged alternately. The pressure chambers 31 and the air chambers 32 each extend in a direction intersecting the longitudinal direction of the actuator section 22, and are arranged in parallel in a first direction (X-axis in the figure) that is the longitudinal direction of the actuator section 22. In this embodiment, for example, the plurality of grooves constituting the pressure chamber 31 and the air chamber 32 have a constant width in the X direction in the depth direction along the Z direction, and a constant width in the Y direction, which is the direction in which the grooves extend. The orthogonal cross sections are configured in a rectangular shape.

The bottom of the pressure chamber 31, the bottom of the air chamber 32, and the side wall 33 are made of laminated piezoelectric members. That is, the inner wall surfaces of the pressure chamber 31 and the air chamber 32 including the bottom are configured by piezoelectric members, and the nozzle plate 12 which is a non-piezoelectric member is arranged in the opening on one side, and the extending direction of the air chamber 32 is Openings at both ends are closed by cover portions 23 which are non-piezoelectric members.

Electrode layers 34 are provided on the inner wall surfaces of the pressure chamber 31 and the air chamber 32 of the actuator section 22, and on the side surface portion 221, respectively. The electrode layer 34 is formed of a conductive film such as a nickel thin film, for example. The electrode layer 34 passes from the inner surface of the groove, passes through the side surface 221 , reaches onto the substrate 21 , and is connected to the pattern wiring 211 . For example, the electrode layer 34 is formed on the inner surface of the groove including the bottom portion of the side wall 33. As an example, the electrode layer 34 formed in the pressure chamber 31 constitutes an individual electrode, and the electrode layer 34 formed in the air chamber 32 constitutes a common electrode. The electrode layer 34 constituting the individual electrode is formed on the inner surface including the bottom of the pressure chamber 31 , is led out from one side in the extending direction of the pressure chamber 31 to one side surface 221 , and is connected to the pattern wiring 211 . The electrode layer 34 constituting the common electrode is formed on the inner surface including the bottom of the air chamber 32 , is led out from the other side to the other side surface 221 , and is connected to the pattern wiring 211 .

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 into the first common chamber 271 of the ink chamber 27 , and the other end opens into the second common chamber 272 of the ink chamber 27 . Therefore, ink flows into the pressure chamber 31 from the communication section that is one end of the pressure chamber 31, and flows out from the communication section that is the other end. Further, ink may flow in from both ends of the pressure chamber 31.

As shown in FIGS. 3 and 6, the air chamber 32 is closed on one side in the third direction (Z direction) by the nozzle plate 12 joined to the top. Further, the plurality of air chambers 32 are closed at both ends in the second direction by the cover portion 23, for example. That is, the cover portions 23 are disposed at the communication portions between the first common chamber 271 and the air chamber 32 of the ink chamber 27 and between the air chamber 32 and the second common chamber 272, and both ends of the air chamber 32 are covered with ink. It is separated from room 27. Therefore, the air chamber 32 constitutes an air chamber into which ink does not flow.

For example, the cover portions 23 are provided at both ends of each air chamber 32 in the Y direction, which is the extending direction. The cover portion 23 connects the ends of the side walls 33 and separates the common chambers 271 and 272 from the air chamber 32.

The cover part 23 has a plurality of wall members 231, 232, and 233 lined up in the extending direction. In this embodiment, the cover part 23 is formed into a triple wall structure by three wall members 231, 232, and 233, and a gap 2311 is formed between the plurality of wall members 231, 232, and 233. The plurality of wall members 231, 232, and 233 connect the ends of a pair of side walls 33 forming both sides of the air chamber 32. The plurality of wall members 231, 232, and 233 are made of a photosensitive resin material, and are formed to have a constant thickness, which is a dimension in the extending direction, for example. For example, the plurality of wall members 231, 232, 233 are formed by applying a photosensitive resin to both ends of the air chamber 32 and then exposing it to light from the top side in a predetermined exposure pattern. Formed by curing the area. For example, a plurality of wall members 231 , 232 , 233 are arranged inside the air chamber 32 .

In each air chamber 32, the structure of the cover portion 23 on one end side and the other end side has symmetry with respect to the nozzle 28. That is, the wall members 231, 232, and 233 have symmetry in the extending direction, and specifically, the dimensions and number of the wall members 231, 232, and 233 at one end and the other end are equal. Moreover, the plurality of cover parts 23 respectively configured in the plurality of air chambers 32 in the actuator part 22 have uniformity. For example, the plurality of cover parts 23 formed in two rows of air chambers 32 lined up in the parallel direction are configured to have the same shape, position, and size.

The cover portion 23 is formed at a position where the AL change range is within 0.4 μs. That is, in the air chamber 32, the distance between the pair of inner wall members 233, which is the length in the extending direction of the movable range of the side wall 33, is AL The range of change is set to within 0.4 μs. Here, AL (Acoustic Length) is the duration of expanding or contracting the volume of the pressure chamber, and is 1/2 of the acoustic resonance period of the pressure wave in the pressure chamber 31. AL is the pulse width at which the flying speed of the liquid is maximized when the voltage value is constant and the pulse width is changed to the drive electrode. For example, the velocity of an ink droplet ejected when a rectangular wave driving pulse is applied can be measured, and the pulse width at which the velocity becomes maximum can be defined as AL.

AL changes depending on the movable range in which the side wall 33 deforms; for example, as the movable range becomes smaller, AL becomes smaller. For example, the standard state in which the length LB (flow path length) of the air chamber 32 in the extending direction of the movable range that is not blocked by the cover part 23 is the same as the flow path length LA of the pressure chamber 31, that is, the side wall 33 is In contrast to the state in which the range of motion is secured by the length of the flow path of the pressure chamber 31, the range of motion of the side wall 33 is reduced due to the presence of the cover portion 23, and the region in which deformation of the side wall 33 is suppressed is The closer it is to the side, the smaller the AL becomes.

For example, AL changes as the flow path length changes, and depending on the value of AL, there may be cases where ejection fails. FIG. 8 shows the printing state when the pulse width is changed with AL as a reference. As shown in FIG. 8, when the AL is -0.3 μs, ejection failure occurs. On the other hand, ejection failure also occurs when the time is longer than AL+0.3 μs. For example, it can be seen that good ejection performance can be obtained in the range of AL±0.2 μs (0.4 μs in the range).

FIG. 9 shows the calculation results of AL when the flow path length LB of the air chamber 32 is changed. As shown in FIG. 9, when the flow path length LB of the air chamber 32, which is the length in the extending direction (second direction) of the movable range of the side wall 33, is in the range of 1 mm to 1.5 mm, the amount of change in AL (range ) is 0.37 μs. That is, when the length of the side wall 33 in the extending direction that defines the flow path length LA of the pressure chamber 31 is 1.5 mm, when the end of the air chamber 32 is closed with the cover part 23, the unblocked air If the length of the area (range of movement) of the chamber 32, that is, the flow path length LB of the air chamber 32, is in the range of 1 to 1.5 mm, no matter which wall member 231, 232, 233 the liquid leaks from, it will all leak. If not, the change range of AL can be within 0.4 μs. Therefore, by providing the wall members 231, 232, and 233 of the cover portion 23 in the range of flow path length from 1 to 1.5 mm, the discharge performance can be ensured. Therefore, in this embodiment, the cover section 23 is configured under the condition that the AL change range is within 0.4 μs. For example, in the present embodiment, the wall members 231, 232, 233 of the cover part 23 are arranged within a range of 1/6 times or less of the total length from both ends of the air chamber 32 in the extending direction, and 2/3 or more of the total length. The range functions as the range of motion.

The nozzle plate 12 is a non-piezoelectric member, and is formed of a rectangular film made of polyimide, for example. 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, passing through 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 are arranged to face the pressure chambers 31, respectively. A plurality of nozzles 28 are lined up along the first direction (X direction) and arranged in two rows corresponding to the pair of actuator sections 22 . Each nozzle 28 has a cylindrical 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 decreases toward the center or tip. The nozzles 28 are disposed opposite to each other in the middle of the pressure chambers 31 formed in the pair of actuator sections 22 in the extending direction, and communicate with the pressure chambers 31, respectively. The plurality of nozzles 28 are arranged at corresponding positions between both ends of each pressure chamber 31, for example, one at a time at the center in the longitudinal direction.

The frame 13 is made of, for example, a nickel alloy and has a rectangular frame shape. The frame 13 is interposed between the mounting surface of the actuator base 11 and the nozzle plate 12. The frame 13 is bonded 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 actuator base 11 on the side opposite to the nozzle plate 12. An ink supply section that is a flow path that communicates with the supply hole 25 and an ink discharge section that is a flow path that communicates with the discharge hole 26 are formed inside the manifold 18 .

The circuit board 17 shown in FIG. 1 is a film carrier package (FCP). The circuit board 17 includes a flexible resin film 51 on which a plurality of wirings are formed, and a drive IC 52 connected to the plurality of wirings of the film 51. The drive IC 52 is electrically connected to the electrode layer 34 via the wiring of the film 51 and the pattern wiring 211.

Inside the inkjet head 10 configured as described above, an ink chamber 27 surrounded by the actuator base 11, the nozzle plate 12, and the frame 13 is formed. 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 (Y direction) by the two actuator sections 22, and includes two second common chambers 272 as common chambers in which the discharge hole 26 opens, and a second common chamber 272 in which the supply hole 25 opens. It has a first common room 271 as an open common room. The first common chamber 271 and the second common chamber 272 communicate with the plurality of 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 25, the pressure chamber 31, and the discharge hole 26. 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 the control unit of an inkjet printer, thereby causing the electrode layer 34 of the pressure chamber 31 and the air chamber By creating a potential difference between the side wall 33 and the electrode layer 34 of 32, the side wall 33 is selectively deformed in a shear mode. The side wall 33 is shear-deformed so that the cross-sectional shape of the laminated piezoelectric material is bent into a dogleg shape. By deforming the side wall 33 formed between the pressure chamber 31 and the air chamber 32 in accordance with the drive signal, the volume of the pressure chamber 31 is changed.

When the side wall 33 deforms in a shear mode, the volume of the pressure chamber 31 in which the electrode layer 34 is provided increases, and the pressure decreases. As a result, ink in the ink chamber 27 flows into the pressure chamber 31 .

When the drive IC 52 applies a drive voltage of a reverse potential to the electrode layer 34 of the pressure chamber 31 in a state where the volume of the pressure chamber 31 has increased, the side wall 33 deforms in a shear mode and the pressure chamber 31 provided with the electrode layer 34 is deformed. volume decreases and pressure increases. As a result, the ink in the pressure chamber 31 is pressurized and is ejected from the nozzle 28.

A method for manufacturing the inkjet head 10 will be explained. First, a piezoelectric member forming a plurality of grooves is attached to a plate-shaped substrate 21 using an adhesive or the like, and then machining is performed using a dicing saw, a slicer, etc. to form the actuator base 11 having a predetermined external shape. Note that, for example, a plurality of actuator bases 11 having a predetermined shape may be manufactured by forming a block-shaped base member with a thickness equivalent to a plurality of base members in advance and then dividing the base member.

Subsequently, the electrode layer 34 and pattern wiring 211 are formed on the inner surface of the groove constituting the pressure chamber 31 and the air chamber 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 surface of the actuator base 11, respectively.

Subsequently, the cover portions 23 are formed at the ends of the air chamber 32 to close both ends of the air chamber 32. For example, a groove constituting the air chamber 32 is filled with a photosensitive resin, a mask corresponding to the pattern of the plurality of wall members 231, 232, and 233 is overlapped, and exposure is performed from the top side to harden the target area and cover part 23. form.

Then, 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 using a thermoplastic resin adhesive sheet.

Then, the assembled frame 13 and the side wall 33 of the actuator section 22 are polished so that the top surfaces of the side walls 33 on the nozzle plate 12 side are flush with each other. Then, the nozzle plate 12 is attached to the top of the side wall 33 and the polished surface of the frame 13 by bonding. At this time, the nozzle 28 is positioned so as to face the pressure chamber 31. Furthermore, as shown in FIG. 1, the inkjet head 10 is completed by connecting the drive IC 52 and the circuit board 17 to the pattern wiring 211 formed on the main surface of the substrate 21 via a flexible printed circuit board.

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

The inkjet printer 100 ejects ink or the like while transporting, for example, paper P as a recording medium to be ejected, along a predetermined transport path A that extends from a medium supply unit 112 through an image forming unit 113 to a medium discharge unit 114. This is a liquid ejecting device that performs image forming processing on paper P by ejecting liquid.

The housing 111 constitutes the outer shell of the inkjet printer 100. A discharge port for discharging the paper P to the outside is provided at a predetermined location of the casing 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 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 that are disposed opposite to each other above the support section 117.

The support unit 117 includes a conveyor belt 118 provided in a loop shape in a predetermined area where image formation is performed, a support plate 119 that supports the conveyor belt 118 from the back side, and a plurality of belt rollers 120 provided on the back side of the conveyor belt 118. , is provided.

During image formation, the support section 117 supports the paper P on a holding surface that is the upper surface of the conveyor belt 118, and also transports the paper P downstream by feeding the conveyor belt 118 at a predetermined timing by rotation of the belt roller 120. Transfer to the side.

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

This embodiment includes inkjet heads 10 of four colors, cyan, magenta, yellow, and black, and ink tanks 132 that accommodate inks of these colors, respectively. 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 .

Further, a negative pressure control device such as a pump (not shown) is connected to the ink tank 132. Then, the negative pressure control device controls the negative pressure inside the ink tank 132 in accordance with the water head values 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 shaped into a predetermined shape. form a meniscus.

The circulation pump 134 is, for example, a liquid pump made up of a piezoelectric pump. Circulation pump 134 is provided in the supply channel. The circulation pump 134 is connected to the drive circuit of the control unit 116 by wiring, and is configured to be controllable by a CPU (Central Processing Unit). The circulation pump 134 circulates the liquid in a circulation path that includes the inkjet head 10 and the ink tank 132.

The conveyance device 115 conveys the paper P along a conveyance path A that extends from the medium supply section 112 through the image forming section 113 to the medium discharge section 114. The conveyance device 115 includes a plurality of guide plate pairs 121 arranged along the conveyance path A and a plurality of conveyance rollers 122.

Each of the plurality of guide plate pairs 121 includes a pair of plate members disposed opposite to each other with the paper P to be transported interposed therebetween, and guides the paper P along the transport path A.

The conveyance roller 122 is driven and rotated under the control of the control unit 116 to convey the paper P along the conveyance path A to the downstream side. Note that sensors for detecting the conveyance status of the paper are arranged at various locations on the conveyance path A.

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

In the inkjet printer 100 configured as described above, when the control unit 116 detects a print instruction by the user operating the operation input unit in the interface unit, for example, the control unit 116 drives the conveying device 115 to convey the paper P and The inkjet head 10 is driven by outputting a print signal to the head unit 130 at this timing. During the ejection operation, the inkjet head 10 sends a drive signal to the drive IC 52 using an image signal corresponding to the image data, and applies a drive voltage to the electrode layer 34 of the pressure chamber 31 via wiring to cause the side wall 33 of the actuator section 22 to move. It is selectively driven to eject ink droplets from the nozzles 28 to form an image on the paper P held on the conveyor belt 118. Further, as a liquid ejection operation, the control unit 116 drives the circulation pump 134 to circulate the liquid in a circulation channel passing through the ink tank 132 and the inkjet head 10 . Due to the circulation operation, the ink in the ink tank 132 is circulated through the ink supply section of the manifold 18 by the circulation pump 134 being driven, and the ink in the ink tank 132 is transferred from the supply hole 25 to the first common ink chamber 27. It is supplied to chamber 271. This ink is supplied to the plurality of pressure chambers 31 of the pair of actuator sections 22 . Ink flows into the second common chamber 272 of the ink chamber 27 through the pressure chamber 31 . This ink is discharged from the discharge hole 26 into the ink tank 132 through the ink discharge portion of the manifold 18 .

According to the inkjet head 10 according to the embodiment described above, so-called crosstalk can be suppressed and stable ejection performance can be easily ensured. For example, in general, if the cover portion that closes the air chamber is insufficiently formed, ink will enter the air chamber, the ALs of adjacent pressure chambers will shift, and the in-plane AL variation will increase. Furthermore, when the air chamber is filled with ink, a phenomenon occurs in which vibrations are transmitted to the adjacent pressure chamber (crosstalk). These may cause deterioration in landing accuracy or dropout. On the other hand, according to the inkjet head 10 of the above embodiment, the cover part 23 is configured to have a plurality of wall members 231, 232, and 233, so that, for example, any one of the plurality of wall members 231, 232, and 233 Even if it is damaged, the other wall members 231, 232, 233 can prevent ink from flowing in. Therefore, the possibility that the air chamber 32 is filled with ink can be reduced, and the vibration of the side wall 33 when the pressure chamber 31 is driven in the actuator section 22 is transmitted to the ink in another adjacent pressure chamber 31. It is possible to suppress so-called crosstalk that affects ink pressure, and it is easy to maintain ejection performance.

Further, by forming the gap 2311 between the plurality of wall members 231, 232, and 233, it becomes possible to release the adhesive into the gap 2311 when bonding the nozzle plate 12. Therefore, when the nozzle plate 12 is joined, the adhesive does not flow into the pressure chamber 31 side, and deterioration of printing quality can be suppressed.

Further, by making the cover part 23 symmetrical and having uniformity in the actuator part 22, uniformity of AL and uniformity of the adhesive escape groove can be ensured.

Furthermore, by configuring the cover portion 23 under conditions such that the change range of AL is within 0.4 μs, it is possible to ensure good ejection performance.

It should be noted that the present invention is not limited to the above-described embodiments as they are, but can be implemented by modifying the constituent elements within the scope of the invention at the implementation stage.

For example, the shape of the cover part 23 is not limited to the above embodiment, and can be changed as appropriate. For example, in the above embodiment, a three-layer wall structure having the same thickness is illustrated, but the present invention is not limited to this. For example, it may have two layers or four layers, and each layer may have a different thickness. As another embodiment, an inkjet head 1010 shown in FIG. 11 has double wall members 234 and 235, and one wall member 234 is thicker than the other wall member 235. Even in such a form, the same effects as in the above embodiment can be obtained.

In the above embodiment, the cover part 23 is arranged inside the air chamber 32, but the cover part 23 is not limited to this, and for example, part or all of it may be arranged outside the air chamber 32.

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

Further, in the embodiment described above, the actuator base 11 is exemplified in which the substrate 21 is provided with a laminated piezoelectric member made of a plurality of piezoelectric bodies, but the present invention is not limited to this. For example, the actuator base 11 may be formed only from a piezoelectric member without using a substrate. Further, the supply side and the discharge side may be reversed, or may be configured to be switchable.

Further, in the above embodiment, as an example, one side of the pressure chamber 31 is a supply side and the other side is a discharge side, and ink flows into the pressure chamber from one side and flows out from the other side. is shown as an example, but is not limited to this example. For example, it may be a non-circulating type. Alternatively, for example, a common chamber on both sides of the pressure chamber 31 may be the supply side, and ink may flow in from both sides. That is, the configuration may be such that ink flows in from both sides of the pressure chamber 31 and flows out from the nozzle 28 disposed in the center of the pressure chamber 31.

Further, in the above embodiment, a side shooter type inkjet head is illustrated in which the nozzles 28 are disposed facing each other in the middle of the pressure chamber 31 and both sides communicate with a common chamber, but the present invention is not limited to this. For example, the pressure chamber 31 and the air chamber 32 may be of an end shooter type in which one end side in the extending direction is closed, and only the other end side of the air chamber 32 is closed with the cover part 23. Even in this case, the same effects as in the above embodiment can be obtained by making the cover portion 23 of the air chamber 32 have a double wall structure or a multi-wall structure of three or more layers.

Further, for example, the liquid to be ejected is not limited to ink for printing, but may be an apparatus that ejects a liquid containing conductive particles for forming a wiring pattern of a printed wiring board, for example.

Further, in the above embodiments, an example is shown in which the inkjet head is used in a liquid ejection device such as an inkjet printer, but the inkjet head is not limited to this, and can also be used, for example, in 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 can ensure stable ejection characteristics.

Although several other embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 10, 1010... Inkjet head, 11... Actuator base, 12... Nozzle plate, 13... Frame, 17... Circuit board, 18... Manifold, 21... Board, 22... Actuator part, 23... Cover part, 231-235... Wall member , 2311... Gap, 25... Supply hole, 26... Discharge hole, 27... Ink chamber, 31... Pressure chamber, 32... Air chamber, 33... Side wall, 34... Electrode layer, 51... Film, 52... Drive IC, 100... Inkjet printer, 111... Housing, 112... Medium supply unit, 113... Image forming unit, 114... Medium discharge unit, 115... Conveyance device, 116... Control unit, 117... Support unit, 118... Conveyance 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 part, 271 ...First common room, 272...Second common room.

Claims (5)

an actuator section made of a piezoelectric member and having a plurality of pressure chambers and a plurality of air chambers that are arranged alternately;
a cover portion having a plurality of wall members and closing the air chamber;
Share mode shared wall type liquid ejection head. The pressure chambers and the air chambers are arranged alternately in a row direction,
The plurality of pressure chambers have ends in an extension direction intersecting the arrangement direction communicating with a common chamber,
The cover portion is disposed at an end of the air chamber in the extending direction, and closes a communication portion with the common chamber,
The plurality of wall members are arranged in the extending direction,
The liquid ejection head according to claim 1, further comprising a nozzle plate having nozzles that are arranged opposite to each other in a direction intersecting the arrangement direction and the extension direction of the actuator section and communicate with the pressure chamber. The liquid ejection head according to claim 2, wherein the cover portion is at least partially disposed inside the air chamber and formed in a region where the AL change range is within 0.4 μs. The common chamber is arranged on both sides of the air chamber in the extending direction,
The cover portion is provided at both ends of the air chamber in the extending direction,
The liquid ejection head according to claim 2, wherein the cover portions provided at both ends of the air chamber have symmetry. The liquid ejection head according to claim 2, wherein the cover portions provided in each of the plurality of air chambers have uniformity.