JP7288494B2 - Inkjet head and inkjet printer - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to inkjet heads and inkjet printers.

Inkjet heads installed in ink jet printers include shear mode, shear wall, and side shooter type ink jet heads. A shear mode shear wall side shooter type ink jet head actuator includes, for example, a drive pressure chamber having a pair of side walls in which two piezoelectric members are laminated on a substrate so that the polarization directions thereof are opposite to each other. Then, a predetermined driving electric field is applied in a direction perpendicular to the polarization axis of the piezoelectric member to generate shear strain in the side wall, and the driving pressure chamber is pressurized or depressurized and then pressurized to eject ink.

A piezoelectric member usually has a hysteresis that does not return to its original state even when the application of the driving electric field is stopped. Therefore, practically, a linear region with little hysteresis is used, or a piezoelectric material with little hysteresis is selected. This is because due to the hysteresis, even if the application of the driving electric field is stopped, the piezoelectric member retains a history of distortion in the previous operation direction (pressurization or decompression).

On the other hand, a piezoelectric material with a large hysteresis has the advantage of being distorted more as it is driven with a larger electric field, and being distorted in both the plus and minus directions, allowing the drive pressure chamber to be greatly pressurized and decompressed. However, in the shear mode share wall side shooter type ink jet head, the adjacent driving pressure chambers share the sidewall of the piezoelectric member, so the history of the distortion of the piezoelectric member immediately before may be in the positive direction or in the negative direction. In some cases. Furthermore, for example, even if pressure is reduced once and then pressurized, the amount of pressure reduction differs depending on whether the history of strain in the previous operation direction is in the positive direction or in the negative direction. The problem of token remains.

For this reason, it has been practically avoided to use a piezoelectric material with large hysteresis for the piezoelectric member of the actuator of the inkjet head.

JP 2016-22645 A JP-A-2004-136634 Japanese Patent Application Laid-Open No. 2004-202706

SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet head and an inkjet printer having an actuator that can be driven with a large strain by using a piezoelectric material with a large hysteresis for a piezoelectric member.

In order to solve the above problems, an inkjet head of an embodiment has a pair of side walls formed of a piezoelectric member, and has a driving pressure chamber communicating with a nozzle, and a driving pressure chamber provided on both sides of the driving pressure chamber via the side walls. and a drive circuit for applying a drive electric field to the piezoelectric member. The drive pressure chamber includes a plurality of sidewalls formed of the piezoelectric members arranged at intervals on the substrate, a nozzle plate formed with the nozzles disposed in contact with the sidewalls in the first direction, and the sidewalls. The ink chambers are formed by openings communicating with ink chambers located on both end sides in a second direction different from the first direction. The air chamber is formed by a plurality of side walls formed of the piezoelectric member, a nozzle plate arranged in contact with the side walls in the first direction, and covers closing openings on both end sides of the side walls in the second direction. It is The piezoelectric member is made of a lead-containing piezoelectric material having a piezoelectric constant _d15 of 1000 pC/N or more at an electric field of 300 V/mm.

An inkjet head of another embodiment has a pair of side walls made of a piezoelectric member, and includes a driving pressure chamber communicating with a nozzle, air chambers provided on both sides of the driving pressure chamber via the side walls, and a driving circuit for applying a driving electric field to the piezoelectric member. The drive pressure chamber includes a plurality of sidewalls formed of the piezoelectric members arranged at intervals on the substrate, a nozzle plate formed with the nozzles disposed in contact with the sidewalls in the first direction, and the sidewalls. The ink chambers are formed by openings communicating with ink chambers located on both end sides in a second direction different from the first direction. The air chamber is formed by a plurality of side walls formed of the piezoelectric member, a nozzle plate arranged in contact with the side walls in the first direction, and covers closing openings on both end sides of the side walls in the second direction. It is The piezoelectric member is made of a lead-containing piezoelectric material having a piezoelectric constant _d15 of 400 pC/N or more when the electric field is 300 V/mm.

1 is a longitudinal sectional view showing a schematic configuration of an inkjet printer equipped with an inkjet head according to an embodiment; FIG. 1 is a perspective view showing a schematic configuration of an inkjet head according to an embodiment; FIG. 3 is a partial cross-sectional view showing the internal structure of the inkjet head of the embodiment; FIG. 1 is a cross-sectional view showing the configuration of an inkjet head according to an embodiment; FIG. 4 is a cross-sectional view showing another configuration of the inkjet head of the embodiment; FIG. 4 is a hysteresis curve of a piezoelectric member used in the inkjet head of the embodiment; 4 is a characteristic diagram showing the piezoelectric constant _d15 of the piezoelectric material used for the piezoelectric member of the inkjet head of the embodiment; FIG. FIG. 4 is an explanatory diagram illustrating a method for measuring the piezoelectric constant _d15 of a piezoelectric material; 4 is a waveform diagram of drive voltage applied to the inkjet head of the embodiment. FIG. 4A and 4B are explanatory diagrams for explaining the operation of the inkjet head of the embodiment; FIG.

Hereinafter, an inkjet head and an inkjet printer according to embodiments will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same structure is attached with the same code|symbol.

An inkjet printer 100 that prints an image on a recording medium such as a sheet S will be described as an example of an inkjet printer equipped with the inkjet head of the embodiment. FIG. 1 shows a schematic configuration of an inkjet printer 100 equipped with four inkjet heads 10A to 10D. The inkjet printer 100 includes, for example, a box-shaped housing 101 that is an exterior body. Inside the housing 101 are cassettes 102A and 102B that store sheets S, which are examples of recording media, an upstream transport path 106 for the sheets S, a transport belt 110 that freely transports the sheets S on which images are to be printed, and sheets. Inkjet heads 10A to 10D for ejecting ink droplets toward S, downstream transport path 120 for sheet S, and discharge tray 123 are arranged. The inkjet printer 100 further includes an operation unit 144 including a display screen as a user interface, and a control substrate 140 as a control unit.

Data of an image to be formed on the sheet S by the inkjet printer 100 is generated by the computer 150, for example. Image data generated by computer 150 is input to inkjet printer 100 through cable 143 and connectors 141A and 141B. The inkjet heads 10A to 10D eject predetermined amounts of ink droplets of, for example, cyan, magenta, yellow, and black onto predetermined positions of the sheet S on the transport belt 110 to print an image corresponding to the image data on the sheet S. .

The cassette 102A and the cassette 102B accommodate sheets S of different sizes, for example. The upstream conveying path 106 is composed of feed roller pairs 105a, 105b and 105c and sheet guide plates 106a and 106b that define the sheet conveying path. The pickup roller 104 supplies the sheets S one by one from the cassette 102A to the upstream conveyance path 106 . The sheet S is conveyed by the rotating pair of feed rollers 105a and 105b, and after passing the pair of feed rollers 105a, is conveyed to the upper surface of the conveying belt 110 by the sheet guide plate 106a. An arrow R1 in the drawing indicates the transport path of the sheet S from the cassette 102A. On the other hand, the pickup roller 109 supplies the sheets S one by one from the cassette 102B to the upstream conveyance path 106 . The sheet S is transported by rotating feed roller pairs 105a, 105b, and 105c, and after passing the feed roller pair 105c, is transported to the upper surface of the transport belt 110 by sheet guide plates 106a and 106b. An arrow R2 in the drawing indicates the conveying path of the sheet S from the cassette 102B.

The conveyor belt 110 is a net-like endless belt with a large number of through holes formed on its surface. The conveying belt 110 is rotatably supported by three rollers, a drive roller 112a and driven rollers 112b and 112c. The driving roller 112a is rotated by a motor 111, which is an example of a driving device. R3 in the drawing indicates the rotation direction of the conveyor belt 110 . A negative pressure container 113 is arranged on the back side of the conveying belt 110 . The upper surface of the negative pressure container 113 is in contact with the rear surface of the conveyor belt 110 . A large number of fine holes 114 are formed on the upper surface of the negative pressure container 113 . The negative pressure container 113 is connected to a decompression fan 115 , and the inside of the container is decompressed by the airflow generated by the fan 115 . R4 in the drawing indicates the flow of the air current. The sheet S is adsorbed and held on the upper surface of the conveying belt 110 by reducing the pressure in the negative pressure container 113 . The cassettes 102A and 102B, the upstream conveying path 106, and the conveying belt 110 constitute a recording medium conveying device that conveys the sheet S to a position facing the inkjet heads 10A to 10D. An image is formed on the sheet S sucked and held on the upper surface of the conveying belt 110 as it passes below the inkjet heads 10A to 10D.

The inkjet heads 10A to 10D are arranged so as to face the sheet S sucked and held on the conveying belt 110 with a gap of, for example, 1 mm. The inkjet heads 10A to 10D have the same structure except that the colors of the inks ejected are different. Detailed structures of the inkjet heads 10A to 10D will be described later.

Ink tanks 130A to 130D and ink supply pressure adjusting devices 131A to 131D are connected to the ink jet heads 10A to 10D through ink flow paths 135, respectively. When the ink is supplied in a circulating manner, the ink flow path 135 is provided with an outward path and a return path. The ink channel 135 is, for example, a resin tube. The same applies to the inkjet heads 10B to 10D. The ink tanks 130A to 130D are containers that store ink. Further, maintenance units 132A-132D are arranged near the respective inkjet heads 10A-10D. For example, the maintenance unit 132A of the inkjet head 10A includes a cap 133 that protects the surfaces of the nozzles 25 of the inkjet head 10A, and a blade 134 that removes deposits remaining on the surfaces of the nozzles 25. FIG. The maintenance units 132B-132D of the other inkjet heads 10B-10D also have the same configuration.

Each ink tank 130A-130D is arranged above each inkjet head 10A-10D. In order to prevent ink from leaking from the nozzles 25 of the inkjet heads 10A to 10D during standby, each of the ink supply pressure adjusting devices 131A to 131D maintains a negative pressure in each of the inkjet heads 10A to 10D with respect to the atmospheric pressure. I'm trying to be The negative pressure is set to -1 kPa, for example. During image formation, the ink in each of the ink tanks 130A-130D is circulated and supplied to each of the inkjet heads 10A-10D by the ink supply pressure adjusting devices 131A-131D.

The sheet S on which an image is formed is conveyed from the conveying belt 110 to the downstream conveying path 120 . The downstream conveying path 120 includes feed roller pairs 120a, 120b, 120c, and 120d and sheet guide plates 121a and 121b that define the conveying path of the sheet S. As shown in FIG. The sheet S is sent from the discharge port 122 to the discharge tray 123 by the feed roller pairs 120a, 120b, 120c, and 120d. An arrow R5 in the drawing indicates the transport path of the sheet S. FIG.

Next, configurations of the inkjet heads 10A to 10D will be described with reference to FIGS. 2 to 5. FIG. Although the inkjet head 10A is described below, the inkjet heads 10B to 10D have the same structure as the inkjet head 10A.

2 to 5 show a shear mode side shooter type inkjet head 10A. The inkjet head 10A includes an independently driven actuator. As shown in FIGS. 2 to 5, the inkjet head 10A includes a nozzle head section 2, a flexible printed wiring board 3, and a drive circuit board 4. FIG. Further, the nozzle head section 2 includes a nozzle plate 21, a substrate 22, a frame member 23 forming a common ink chamber, and an ink supply section 24 for supplying ink to the common ink chamber.

The nozzle plate 21 is a rectangular plate made of resin such as polyimide or metal such as stainless steel. A plurality of nozzles 25, which are ejection holes for ejecting ink droplets, are provided on the surface of the nozzle plate 21. As shown in FIG. The nozzle density of the nozzle plate 21 is set within a range of, for example, 150 to 1200 dpi. The substrate 22 is a rectangular substrate made of insulating ceramics, for example.

The frame member 23 is formed in a box shape surrounding the lower portion of the substrate 22, for example, symmetrically. An opening on the lower surface of the frame member 23 is sealed by the nozzle plate 21 . A space defined by the frame member 23, the substrate 22 and the nozzle plate 21 becomes a common ink chamber 26 (26A, 26B). The common ink chamber 26 forms two common ink chambers 26A and 26B with the substrate 22 interposed therebetween. The frame member 23 on the common ink chamber 26A side is formed with an ink supply port 27 that is, for example, a circular opening. A supply ink chamber 26A in which an ink supply port 27 is formed serves as an ink supply path for supplying ink to a plurality of drive pressure chambers 5, which will be described later. The ink supply port 27 communicates with an ink supply pipe 28 provided in the ink supply section 24 . The ink supply pipe 28 further communicates with an ink supply pressure adjusting device 131A. On the other hand, although not shown, the frame member 23 on the common ink chamber 26B side is formed with an ink discharge port, which is, for example, a circular opening like the ink supply port 27 . The ink discharge port communicates with an ink discharge pipe 29 provided in the ink supply section 24 . The ink discharge pipe 29 further communicates with an ink supply pressure adjusting device 131A for circulation supply. The frame member 23, the ink supply section 24, the ink supply pipe 28, and the ink discharge pipe 29 are made of resin, for example. A support member 24a having a symmetrical structure with respect to the ink supply portion 24 is arranged at a symmetrical position with the substrate 22 interposed therebetween, except that the ink supply pipe 28 and the ink discharge pipe 29 are not provided. The ink supply section 24 and the support member 24a are each provided with a fixing member 24b that is used when the inkjet head 10A is attached to the inkjet printer 100.

A plurality of driving pressure chambers 5 constituting ink ejection channels and air chambers 51 constituting dummy channels are arranged on the surface of the substrate 22 positioned within the common ink chamber 26 (26A, 26B). The drive pressure chamber 5 and the air chamber 51 are partitioned by the piezoelectric members 6 (6A, 6B), which are side walls formed at a height contacting the surface of the nozzle plate 21. As shown in FIG. The driving pressure chamber 5 and the air chamber 51 are formed by rectangular grooves formed by cutting two piezoelectric members 6A and 6B laminated on the surface of the substrate 22 in the width direction of the substrate. The two piezoelectric members 6A and 6B are laminated in opposite polarization directions (opposing directions as an example). A piezoelectric material having a large hysteresis, which will be described later, is used for the piezoelectric members 6 (6A, 6B). The driving pressure chamber 5 and the air chambers 51 are arranged so that the air chambers 51 are positioned on both sides of the driving pressure chamber 5 . Each drive pressure chamber 5 is arranged so as to communicate with each nozzle 25 on a one-to-one basis.

Further, two cover plates 7 forming short side walls of the air chamber 51 are arranged on both side surfaces of the substrate 22 . The lower end surface of the cover plate 7 is at the same height as the tip end surfaces of the piezoelectric members 6 (6A, 6B) forming the side walls, and the upper end surface of the cover plate 7 is at the same height as the common ink chamber 26 (26A, 26B). extends outside. The air chamber 51 forms a sealed space that is isolated from the common ink chamber 26 (26A, 26B) by the cover plate 7. As shown in FIG. The cover plate 7 is made of, for example, a zirconia plate having a thickness of about 50 μm. On the other hand, the cover plate 7 is formed with a groove-shaped opening 71 corresponding to the shape of the drive pressure chamber 5 so that the drive pressure chamber 5 and the left and right common ink chambers 26A and 26B communicate with each other. The opening 71 of the cover plate 7 on the side of the common ink chamber 26A is an ink supply port, and the opening 71 of the cover plate 7 on the side of the common ink chamber 26B is an ink discharge port. be.

When the ink used is, for example, an insulating ink, electrodes 61 are integrally formed on the upper surface and both side surfaces of the driving pressure chamber 5 as shown in FIG. An electrode 62 is subsequently formed. Wiring electrodes 63 and 64 are connected to the electrode 61 of the driving pressure chamber 5 and the electrode 62 of the air chamber 51, respectively. The electrodes 61 and 62 and the wiring electrodes 63 and 64 are made of nickel thin film, for example. In this case, the electrode 61 connected to the driving pressure chamber 5 is used as an individual electrode to apply a driving electric field, and the electrode 62 connected to the air chamber 51 is used as a common electrode and grounded, for example.

When the ink used is, for example, a conductive water-based ink, electrodes 61 are integrally formed on the upper surface and both side surfaces of the driving pressure chamber 5, and the side surfaces of the air chamber 51 are electrically connected, as shown in FIG. Separated electrodes 62 are formed respectively. Wiring electrodes 63 and 64 are connected to the electrode 61 of the driving pressure chamber 5 and the electrode 62 of the air chamber 51, respectively. The electrodes 61 and 62 and the wiring electrodes 63 and 64 are made of nickel thin film, for example. In this case, the electrode 61 connected to the driving pressure chamber 5 is used as a common electrode, for example grounded, and the electrode 62 connected to the air chamber 51 is used as an individual electrode to apply the driving electric field.

Returning to FIG. 2, the wiring electrode 63 from the driving pressure chamber 5 and the wiring electrode 64 from the air chamber 51 are connected to the flexible printed wiring board 3, and further connected to the driving circuit board 4 serving as a driving circuit for the ejection operation. electrically connected. A driving IC (Integrated Circuit) 31 is mounted on the flexible printed wiring board 3 . The drive circuit board 4 temporarily stores image data from the control board 140 of the inkjet printer 100 in a buffer, and outputs an electric signal so that ink droplets are ejected at a predetermined timing for forming an image. The electric signal is a pulse voltage, which is a drive voltage.

With the above configuration, a driving electric field is applied in a direction that intersects (preferably, perpendicularly) the polarization axis of the piezoelectric members 6 (6A, 6B) so that the piezoelectric members 6 (6A, 6B) undergo shear mode deformation, and ink droplets are ejected from the nozzles 25. is configured as an independently driven actuator that ejects the

Next, the piezoelectric material used for the piezoelectric members 6 (6A, 6B) will be described.
FIG. 6 shows the relationship between the drive electric field E (V/mm) and the amount of strain ε when the piezoelectric members 6 (6A, 6B) are made of high-hysteresis material, middle-hysteresis material, and low-hysteresis material. For example, looking at the relationship between the driving electric field E (V/mm) and the strain amount ε for the high hysteresis material indicated by the solid line, for example, the strain amount ε is zero (A0) in the initial state after the inkjet head 10A is manufactured. As the driving electric field E is applied in the plus direction (+) to pressurize the driving pressure chamber 5, the strain amount ε increases in the pushing direction and reaches the maximum value (strain A1). If there is no hysteresis, the strain amount ε returns to the original zero (A0) when the driving electric field E (V/mm) is made zero. A history of distortion in the pushing direction remains (distortion A2).

Conversely, when the driving electric field E is applied in the negative direction (-) to reduce the pressure in the driving pressure chamber 5, the strain amount ε increases in the pulling direction and reaches the maximum value (strain A3). Since the pull direction also has hysteresis, even if the driving electric field E (V/mm) is set to zero, the strain amount ε does not return to zero (A0) and the history of strain in the pull direction remains (distortion A4 ). The medium hysteresis material and the low hysteresis material also exhibit the same hysteresis characteristics as the high hysteresis material, although the amount of strain ε and strain history are relatively small.

As is clear from FIG. 6, if a material with high hysteresis is used, ink is ejected with a large strain amount _εT from the maximum value in the pulling direction (strain A3) to the maximum value in the pushing direction (strain A1). has the advantage of being able to On the other hand, the history of distortion (distortion A2, distortion A4) remaining when the driving electric field E (V/mm) is made zero is also large. In the conventional shear-mode share-wall side-shooter type inkjet head, adjacent drive pressure chambers share the side walls of the piezoelectric member, so even if the previous strain history of the piezoelectric member is in the positive direction (strain A2), If there is, it may be in the negative direction (distortion A4). Therefore, for example, even if the pressure is reduced once (distortion A3) and then driven, the amount of pressure reduction (distortion Since A2-A3 or distortion A4-A3) are different, the problem of crosstalk due to pressure propagation, for example, remains, although it is improved. Therefore, low hysteresis materials were selected, and large and medium hysteresis materials were avoided.

On the other hand, for the shear mode side shooter type ink jet head 10A shown in FIGS. 2 to 5, a material having a large hysteresis is selected from lead-containing piezoelectric materials and lead-free piezoelectric materials. Specifically, as shown in FIG. 7, a lead-containing piezoelectric material having a piezoelectric constant _d15 of 1000 pC/N or more at an electric field of 300 V/mm is used. Note that "p" is the prefix pico in the SI unit system. A lead-containing piezoelectric material is, for example, lead zirconate titanate (PZT). Lead zirconate titanate (PZT) is a mixed crystal of lead titanate and lead zirconate. The magnitude of hysteresis differs depending on the type, composition ratio, and the like. Among them, lead zirconate titanate having a piezoelectric constant _d15 of 1000 pC/N or more at an electric field of 300 V/mm is selected as a high hysteresis material and a medium hysteresis material. Of course, the lead-containing piezoelectric material is not limited to lead zirconate titanate.

For the piezoelectric constant _d15 , for example, in the case of a commercially available piezoelectric material, the value indicated by the manufacturer may be used. Alternatively, it may be actually measured. FIG. 7 shows an example of the piezoelectric constant _d15 actually measured and obtained for the high hysteresis material (A-1), medium hysteresis material (A-2), and low hysteresis material (A-3). . As a measuring method, as shown schematically in FIG. A driving electric field E is applied. A driving electric field E of 5 V/mm, 300 V/mm, and 750 V/mm is applied, and the inclination (shear strain) at that time is measured by the laser Doppler vibrometer sensor 82 . The piezoelectric constant _d15 , which indicates shear strain, can be obtained by dividing the amount of strain by the electric field. The formula and units are piezoelectric constant d ₁₅ (m/V)=[induced strain (m/m)/applied electric field (V/m)].

As another example of the piezoelectric material, as shown in FIG. 7, a lead-free piezoelectric material having a piezoelectric constant _d15 of 400 pC/N or more at an electric field of 300 V/mm is used. A lead-free piezoelectric material is, for example, potassium sodium niobate (KNN). Other niobate-based piezoelectric materials may be used. Alternatively, materials other than niobic acid, such as barium titanate (BaTiO ₃ ), may be used. Also in the case of lead-free piezoelectric materials, the piezoelectric constant _d15 may be the value indicated by the manufacturer, for example, in the case of commercially available piezoelectric materials. Alternatively, it may be actually measured. FIG. 7 shows an example of the piezoelectric constant _d15 actually measured and obtained for the high hysteresis material (B-1), medium hysteresis material (B-2), and low hysteresis material (B-3). . Among them, a lead-free piezoelectric material having a piezoelectric constant _d15 of 400 pC/N or more at an electric field of 300 V/mm is selected.

Next, the waveform of the pulse voltage applied as the drive voltage for ejecting ink will be described. FIG. 9 shows waveforms of pulse voltages of (a) pressing, (b) pressing with pre-waveform, (c) pulling, and (d) pulling with pre-waveform. Further, FIG. 9 shows the strain displacement of the piezoelectric member 6 (6A, 6B) corresponding to the voltage waveform. Reference numerals A1 to A4 in the figure correspond to distortions A1 to A4 in FIG.

(a) Pushing is to apply a voltage in the positive direction (+) and then return it to the ground potential. In this case, the piezoelectric member 6 ( 6 A, 6 B) deforms in the pushing direction from the strain A 2 to the strain A 1 to pressurize the driving pressure chamber 5 , and ink is ejected from the nozzle 25 . After that, when the voltage returns to the ground potential, the piezoelectric member 6 (6A, 6B) also returns from strain A1 to strain A2. Since the driving pressure chamber 5 is repeatedly pressurized in a linear range from strain A1 to strain A2, the driving frequency can be maximized.

(b) Pressing with a pre-waveform applies a voltage in the negative direction (-) with a waveform so small that ink is not ejected, then in the positive direction (+), and then returns the voltage to the ground potential. . In this case, the piezoelectric member 6 (6A, 6B) is first deformed in the strain A3 direction and then deformed in the pushing direction of the strain A1 to pressurize the driving pressure chamber 5. FIG. After that, when the voltage returns to the ground potential, the piezoelectric member 6 (6A, 6B) also returns from strain A1 to strain A2. The pre-wavy pressing can increase the amount of strain compared to the pressing because it is once deformed in the strain A3 direction.

(c) Pulling and striking involves first applying a voltage in the negative direction (-), then applying a voltage in the positive direction (+), and then returning the voltage to the ground potential. In this case, the piezoelectric members 6 ( 6 A, 6 B) are deformed sufficiently in the pulling direction of the strain A 3 and then deformed in the pushing direction of the strain A 1 to pressurize the drive pressure chamber 5 . After that, when the voltage returns to the ground potential, the piezoelectric member 6 (6A, 6B) also returns from strain A1 to strain A2. In the pulling stroke, ink can be ejected with a large strain amount ε _T from the maximum value in the pulling direction (distortion A3) to the maximum value in the pushing direction (distortion A1). Pull-hitting is a preferable driving method that can obtain a large amount of strain and can drive at a relatively high frequency.

(d) In pre-waveform pull-off, voltage is applied in the plus direction (+) with a waveform so small that ink is not ejected, then in the minus direction (-), and then again in the plus direction (+). After applying the voltage, the voltage is returned to ground potential. In this case, the piezoelectric member 6 ( 6 A, 6 B) is first deformed in the strain A 1 direction and then deformed in the strain A 3 pulling direction to reduce the pressure in the driving pressure chamber 5 . Then, the drive pressure chamber 5 is pressurized by being deformed in the pushing direction of the strain A1. After that, when the voltage returns to the ground potential, the piezoelectric member 6 (6A, 6B) also returns from strain A1 to strain A2.

Next, the movement of the actuator when performing a pull strike, which is a preferred driving method, will be described with reference to FIG. At the ground potential before applying the drive voltage, the piezoelectric member 6 (6A, 6B) retains the history of the previous ejection operation. In other words, when viewed from the driving pressure chamber 5, the history of distortion in the pushing direction remains. When a voltage is applied in the negative direction (-) from this state, the piezoelectric members 6 (6A, 6B) are deformed in the pulling direction, and the pressure in the driving pressure chamber 5 is reduced. Subsequently, when a voltage is applied in the positive direction (+), the piezoelectric members 6 ( 6 A, 6 B) are deformed in the pushing direction, the driving pressure chambers 5 are pressurized, and ink droplets are ejected from the nozzles 25 .

According to the embodiment described above, the ink jet head 10A is a shear mode side shooter type ink jet head 10A equipped with independently driven actuators in which the air chambers 51 having less pressure propagation than the ink are arranged on both sides of the driving pressure chambers 5. , a lead-containing piezoelectric material having a piezoelectric constant _d15 of 1000 pC/N or more at an electric field of 300 V/mm can be used. That is, even if a piezoelectric material having a large hysteresis is used and driven with a large strain, an ink ejection operation can be performed while suppressing crosstalk. For the same reason, a lead-free piezoelectric material having a piezoelectric constant _d15 of 400 pC/N or more at an electric field of 300 V/mm can be used.

Furthermore, according to the above-described embodiment, the state of the piezoelectric member 6 (6A, 6B) at the end of driving is always the same strain A2. No pre-driving required. As a result, not only crosstalk can be suppressed, but also the driving frequency can be increased.

Furthermore, according to the above-described embodiment, although it is an example, the drive voltage that satisfies the desired performance of the piezoelectric members 6 (6A, 6B) using the low hysteresis material was 30 V, whereas the high hysteresis material was used. It was confirmed that the piezoelectric member 6 (6A, 6B) used satisfies the same performance at a drive voltage of 21V.

In the above-described embodiment, the ink-circulating inkjet head 10A has been described as an example, but the ink-non-circulating inkjet head may also be used. Also, the inkjet head 10A may be installed in a 3D printer. In this case, the liquid modeling material and support material are discharged as ink.

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

10A inkjet head 2 nozzle head section 21 nozzle plate 25 nozzle 26 common ink chamber 3 flexible wiring board 4 drive circuit board 5 drive pressure chamber 51 air chamber 6 piezoelectric member 7 cover plate 100 inkjet printer

Claims (4)

A driving pressure chamber having a pair of side walls made of a piezoelectric member and communicating with the nozzle; air chambers provided on both sides of the driving pressure chamber via the side walls; and applying a driving electric field to the piezoelectric member. a drive circuit;
The drive pressure chamber includes a plurality of sidewalls formed of the piezoelectric members arranged at intervals on the substrate, a nozzle plate formed with the nozzles disposed in contact with the sidewalls in the first direction, and the sidewalls. formed by openings communicating with ink chambers positioned on both end sides in a second direction different from the first direction,
The air chamber is formed by a plurality of side walls formed of the piezoelectric member, a nozzle plate arranged in contact with the side walls in the first direction, and covers closing openings on both end sides of the side walls in the second direction. has been
An inkjet head, wherein the piezoelectric member is made of a lead-containing piezoelectric material having a piezoelectric constant _d15 of 1000 pC/N or more when an electric field of 300 V/mm is applied. A driving pressure chamber having a pair of side walls made of a piezoelectric member and communicating with the nozzle; air chambers provided on both sides of the driving pressure chamber via the side walls; and applying a driving electric field to the piezoelectric member. a drive circuit;
The drive pressure chamber includes a plurality of sidewalls formed of the piezoelectric members arranged at intervals on the substrate, a nozzle plate formed with the nozzles disposed in contact with the sidewalls in the first direction, and the sidewalls. formed by openings communicating with ink chambers positioned on both end sides in a second direction different from the first direction,
The air chamber is formed by a plurality of side walls formed of the piezoelectric member, a nozzle plate arranged in contact with the side walls in the first direction, and covers closing openings on both end sides of the side walls in the second direction. has been
An inkjet head, wherein the piezoelectric member is formed of a lead-free piezoelectric material having a piezoelectric constant _d15 of 400 pC/N or more when an electric field of 300 V/mm is applied. The driving circuit applies a driving electric field that decompresses the driving pressure chamber, and then applies a driving electric field having a polarity opposite to the driving electric field to pressurize the driving pressure chamber and apply a driving electric field that ejects ink . 3. The inkjet head according to claim 1 or 2, characterized by: The inkjet head according to any one of claims 1 to 3;
a recording medium conveying device that conveys a recording medium to a position facing the inkjet head;
and a controller for controlling the inkjet head to eject ink onto a predetermined position of the recording medium.

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