JP6978160B2 - Inkjet heads and inkjet printers - Google Patents

Description

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

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

The piezoelectric member usually has a hysteresis that does not return to the original state even if the application of the driving electric field is stopped. Therefore, practically, a linear region having a small hysteresis is used, or a piezoelectric material having a small hysteresis is selected. This is because, due to hysteresis, even if the application of the driving electric field is stopped, the history of distortion in the operating direction (pressurization or depressurization) in advance remains in the piezoelectric member.

On the other hand, the piezoelectric material having a large hysteresis has an advantage that the driving pressure chamber can be greatly pressurized and depressurized if it is distorted so much that it is driven by a large electric field and is distorted in both positive and negative directions. However, in the shear mode share wall side shooter type inkjet head, since the adjacent drive pressure chambers share the side wall of the piezoelectric member, the history of distortion of the immediately preceding piezoelectric member may be in the positive direction or in the negative direction. In some cases. Furthermore, for example, even if the pressure is reduced once and then the pressure is applied, the amount of pressure reduction differs depending on whether the history of distortion in the immediately preceding operating direction is in the positive direction or in the negative direction. The problem of talk remains.

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

Japanese Unexamined Patent Publication No. 2016-22645 Japanese Unexamined Patent Publication No. 2004-136634 Japanese Unexamined Patent Publication No. 2004-202706

An object to be solved by the present invention is to provide an inkjet head and an inkjet printer provided with an actuator capable of driving a piezoelectric member with a piezoelectric material having a large hysteresis with a large strain.

In order to solve the above problems, the inkjet head of the embodiment has a pair of side walls formed of a piezoelectric member, a drive pressure chamber communicating with an ink supply path and a nozzle, and the side walls on both sides of the drive pressure chamber. It is provided with an independently drive type actuator including an air chamber provided via the above and a drive circuit for applying a drive electric field to the piezoelectric member. The drive pressure chamber and the air chamber are arranged on a plurality of side walls formed of the piezoelectric members arranged at intervals on one surface of the substrate, a nozzle plate arranged in contact with the side wall, and both ends of the side wall. It is formed by a pair of cover plates having an ink supply port and an ink discharge port at a location corresponding to the drive pressure chamber. The piezoelectric member, the piezoelectric constant _{d 15} when the electric field 300 V / mm is formed in the lead-containing piezoelectric material as a 1000pC / N or more.

The inkjet head of another embodiment has a pair of side walls formed of a piezoelectric member, and is provided with a drive pressure chamber communicating with an ink supply path and a nozzle, and both sides of the drive pressure chamber via the side walls. It includes an independently drive type actuator including an air chamber and a drive circuit for applying a drive electric field to the piezoelectric member. The drive pressure chamber and the air chamber are arranged on a plurality of side walls formed of the piezoelectric members arranged at intervals on one surface of the substrate, a nozzle plate arranged in contact with the side wall, and both ends of the side wall. It is formed by a pair of cover plates having an ink supply port and an ink discharge port at a location corresponding to the drive pressure chamber. The piezoelectric member, the piezoelectric constant _{d 15} when the electric field 300 V / mm is formed in the lead-free piezoelectric material which is a 400 pC / N or more.

It is a vertical sectional view which shows the schematic structure of the inkjet printer equipped with the inkjet head of an embodiment. It is a perspective view which shows the schematic structure of the inkjet head of an embodiment. It is a partial cross-sectional view which shows the internal structure of the inkjet head of an embodiment. It is sectional drawing which shows the structure of the inkjet head of an embodiment. It is sectional drawing which shows the other structure of the inkjet head of an embodiment. It is a hysteresis curve of the piezoelectric member used for the inkjet head of an embodiment. It is a characteristic diagram showing the piezoelectric constant d ₁₅ of the piezoelectric material used for the piezoelectric member of the ink jet head of the embodiment. It is an explanatory view for explaining a method of measuring the piezoelectric constant d ₁₅ of the piezoelectric material. It is a waveform diagram of the drive voltage applied to the inkjet head of an embodiment. It is explanatory drawing explaining the operation of the inkjet head of an embodiment.

Hereinafter, the inkjet head and the inkjet printer according to the embodiment will be described in detail with reference to the attached drawings. In each figure, the same configurations are designated by the same reference numerals.

As an inkjet printer equipped with the inkjet head of the embodiment, an inkjet printer 100 that prints an image on a recording medium such as a sheet S will be described as an example. 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 which is an exterior body. Inside the housing 101, cassettes 102A and 102B for storing the sheet S, which is an example of a recording medium, an upstream transport path 106 for the sheet S, a transport belt 110 for freely transporting the sheet S for printing an image, and a sheet. Inkjet heads 10A to 10D for ejecting ink droplets toward S, a downstream transport path 120 for the sheet S, and an ejection tray 123 are arranged. The inkjet printer 100 further includes an operation unit 144 including a display screen and the like as a user interface, and a control board 140 as a control unit.

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

The cassette 102A and the cassette 102B accommodate, for example, different sized sheets S. The upstream transport path 106 is composed of a feed roller pair 105a, 105b, 105c and a seat guide plate 106a, 106b that defines a seat transport path. The pickup roller 104 supplies the sheets S one by one from the cassette 102A to the upstream transport path 106. The sheet S is conveyed by the rotating feed roller pairs 105a and 105b, and after passing through the feed roller pair 105a, is conveyed to the upper surface of the transfer belt 110 by the sheet guide plate 106a. The arrow R1 in the figure indicates a 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 transport path 106. The sheet S is conveyed by the rotating feed roller pairs 105a, 105b, 105c, and after passing through the feed roller pair 105c, is conveyed to the upper surface of the transfer belt 110 by the sheet guide plates 106a, 106b. An arrow R2 in the figure indicates a transport path of the sheet S from the cassette 102B.

The conveyor belt 110 is a net-like endless belt having a large number of through holes formed on its surface. The transport belt 110 is rotatably supported by three rollers, a drive roller 112a, a driven roller 112b, and 112c. The drive roller 112a is rotated by a motor 111, which is an example of a drive device. In the figure, R3 indicates the rotation direction of the transport belt 110. A negative pressure container 113 is arranged on the back surface side of the transport belt 110. The upper surface of the negative pressure container 113 is in contact with the back surface of the transport belt 110. A large number of micropores 114 are formed on the upper surface of the negative pressure container 113. The negative pressure container 113 is connected to the decompression fan 115, and the inside of the container is depressurized by the air flow formed by the fan 115. In the figure, R4 indicates the flow of airflow. The sheet S is adsorbed and held on the upper surface of the transport belt 110 by depressurizing the negative pressure container 113. The cassettes 102A and 102B, the upstream transport path 106, and the transport belt 110 constitute a recording medium transport device that transports the sheet S to a position facing the inkjet heads 10A to 10D. When the sheet S attracted and held on the upper surface of the transport belt 110 passes below the inkjet heads 10A to 10D, an image is formed.

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

The ink tanks 130A to 130D and the ink supply pressure adjusting devices 131A to 131D are connected to the inkjet heads 10A to 10D via the ink flow path 135, respectively. When the ink is supplied in a circulating manner, an outward path and a return path are provided in the ink flow path 135. The ink flow path 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 for storing ink. Further, maintenance units 132A to 132D are arranged in the vicinity of the inkjet heads 10A to 10D. For example, the maintenance unit 132A of the inkjet head 10A includes a cap 133 that protects the surface of the nozzle 25 of the inkjet head 10A, and a blade 134 that removes deposits remaining on the surface of the nozzle 25. The maintenance units 132B to 132D of the other inkjet heads 10B to 10D have the same configuration.

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

The sheet S on which the image is formed is sent from the transport belt 110 to the downstream transport path 120. The downstream transport path 120 is composed of feed roller pairs 120a, 120b, 120c, 120d and seat guide plates 121a, 121b that define the transport path of the sheet S. The sheet S is fed from the discharge port 122 to the discharge tray 123 by the feed roller pairs 120a, 120b, 120c, 120d. In the figure, the arrow R5 indicates the transport path of the sheet S.

Subsequently, the configuration of the inkjet heads 10A to 10D will be described with reference to FIGS. 2 to 5. 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 portion 2, a flexible printed wiring board 3, and a drive circuit board 4. Further, the nozzle head unit 2 includes a nozzle plate 21, a substrate 22, a frame member 23 forming a common ink chamber, and an ink supply unit 24 for supplying ink to the common ink chamber.

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

The frame member 23 is formed in a box shape that surrounds the lower portion of the substrate 22 symmetrically, for example. The opening on the lower surface of the frame member 23 is sealed by the nozzle plate 21. The space partitioned 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, for example, an ink supply port 27 which is a circular opening. The supply ink chamber 26A in which the 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 the ink supply pipe 28 provided in the ink supply unit 24. The ink supply pipe 28 further communicates with the 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, for example, an ink discharge port which is 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 unit 24. The ink discharge pipe 29 further communicates with the ink supply pressure adjusting device 131A for circulation supply. The frame member 23, the ink supply unit 24, the ink supply pipe 28, and the ink discharge pipe 29 are made of, for example, resin. Further, except that the ink supply pipe 28 and the ink discharge pipe 29 are not provided, the ink supply unit 24 and the support member 24a having a symmetrical structure are arranged at symmetrical positions with the substrate 22 interposed therebetween. The ink supply unit 24 and the support member 24a are each provided with a fixing member 24b used when the inkjet head 10A is attached to the inkjet printer 100.

A plurality of drive pressure chambers 5 constituting the ink ejection channel and air chambers 51 constituting the dummy channel are arranged on the surface of the substrate 22 located in the common ink chambers 26 (26A, 26B). The drive pressure chamber 5 and the air chamber 51 are partitioned by a piezoelectric member 6 (6A, 6B) which is a side wall formed at a height in contact with the surface of the nozzle plate 21. The drive pressure chamber 5 and the air chamber 51 are formed by two piezoelectric members 6A and 6B laminated on the surface of the substrate 22 formed by grooves notched in a rectangular shape in the width direction of the substrate. The two piezoelectric members 6A and 6B are laminated in directions in which the polarization directions are opposite to each other (for example, in opposite directions). For the piezoelectric member 6 (6A, 6B), a piezoelectric material having a large hysteresis, which will be described later, is used. The drive pressure chamber 5 and the air chamber 51 are arranged so that the air chambers 51 are located on both sides of the drive 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 the side wall on the short side of the air chamber 51 are arranged on both side surfaces of the substrate 22, respectively. The lower end surface of the cover plate 7 is at the same height as the tip surface of the piezoelectric member 6 (6A, 6B) forming the side wall, and the upper end surface of the cover plate 7 is the common ink chamber 26 (26A, 26B). It extends to the outside. The air chamber 51 forms a closed space that is shielded from the common ink chambers 26 (26A, 26B) by the cover plate 7. The cover plate 7 is formed 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 common ink chamber 26A side is an ink supply port, the opening 71 of the cover plate 7 on the common ink chamber 26B side is an ink discharge port, and ink is supplied to the drive pressure chamber 5 in a circulating manner. Ink.

When the ink used is, for example, an insulating ink, as shown in FIG. 4, electrodes 61 are integrally formed on the upper surface and both side surfaces of the drive pressure chamber 5, and are similarly integrated on the upper surface and both side surfaces of the air chamber 51. The electrode 62 is formed. Wiring electrodes 63 and 64 extending along the side surface of the substrate 22 to the outside of the common ink chambers 26 (26A and 26B) are connected to the electrodes 61 of the drive pressure chamber 5 and the electrodes 62 of the air chamber 51, respectively. The electrodes 61 and 62 and the wiring electrodes 63 and 64 are formed of, for example, a nickel thin film. In this case, a driving electric field is applied using the electrode 61 connected to the driving pressure chamber 5 as an individual electrode, and the electrode 62 connected to the air chamber 51 is used as a common electrode, for example, to be grounded.

When the ink used is, for example, a conductive water-based ink, as shown in FIG. 5, electrodes 61 are integrally formed on the upper surface and both side surfaces of the drive pressure chamber 5, and the side surfaces of the air chamber 51 are electrically formed. The separated electrodes 62 are formed respectively. Wiring electrodes 63 and 64 extending along the side surface of the substrate 22 to the outside of the common ink chambers 26 (26A and 26B) are connected to the electrodes 61 of the drive pressure chamber 5 and the electrodes 62 of the air chamber 51, respectively. The electrodes 61 and 62 and the wiring electrodes 63 and 64 are formed of, for example, a nickel thin film. In this case, for example, the electrode 61 connected to the drive pressure chamber 5 is grounded as a common electrode, and the drive electric field is applied using the electrode 62 connected to the air chamber 51 as an individual electrode.

Returning to FIG. 2, the wiring electrode 63 from the drive pressure chamber 5 and the wiring electrode 64 from the air chamber 51 are connected to the flexible printed wiring board 3 and are further connected to the drive circuit board 4 which is a drive circuit for the discharge operation. It is electrically connected. An IC (Integrated Circuit) 31 for driving 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 driving voltage.

With the above configuration, a driving electric field is applied in a direction intersecting (preferably orthogonal to) the polarization axis of the piezoelectric member 6 (6A, 6B), the piezoelectric member 6 (6A, 6B) is deformed in shear mode, and ink droplets are dropped from the nozzle 25. An independently driven actuator is configured to discharge.

Subsequently, the piezoelectric material used for the piezoelectric member 6 (6A, 6B) will be described.
FIG. 6 shows the relationship between the driving electric field E (V / mm) and the strain amount ε when the piezoelectric member 6 (6A, 6B) is formed of the high hysteresis material, the medium hysteresis material, and the 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 shown by the solid line, for example, the strain amount ε is zero (A0) in the initial state after the manufacture of the inkjet head 10A. When the driving electric field E is applied in the positive 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 the drive electric field E (V / mm) is set to zero without hysteresis, the strain amount ε returns to the original zero (A0), but since it has hysteresis, it does not return to the original zero (A0). The history of distortion in the pushing direction remains (distortion A2).

On the contrary, 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). Even in the pulling direction, since it 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 pulling direction remains (strain A4). ). The medium hysteresis material and the low hysteresis material also exhibit the same hysteresis characteristics as the high hysteresis material, although the strain amount ε and the strain history are relatively small.

As is clear from FIG. 6, when a high hysteresis material is used, ink _{is ejected with a large strain amount ε T} from the maximum value in the pulling direction (strain A3) to the maximum value in the pushing direction (strain A1). There is an advantage that can be done. On the other hand, the history of distortion (distortion A2, distortion A4) remaining when the driving electric field E (V / mm) is set to zero is also large. In the conventional shear mode share wall side shooter type inkjet head, since the adjacent drive pressure chambers share the side wall of the piezoelectric member, the history of distortion of the immediately preceding piezoelectric member may be in the positive direction (distortion 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 the drive is performed, the amount of pressure reduction (distortion) differs depending on whether the history of distortion in the immediately preceding operating direction is in the plus direction (distortion A2) or in the minus direction (distortion A4). Since A2-A3 or strain A4-A3) is different, although improvement is made, the problem of crosstalk due to, for example, pressure propagation still remains. Therefore, low hysteresis materials were selected, and large hysteresis materials and medium hysteresis materials were avoided.

On the other hand, for the shear mode side shooter type inkjet head 10A shown in FIGS. 2 to 5, a material having a large hysteresis is selected from the lead-containing piezoelectric material and the lead-free piezoelectric material. Specifically, as shown in FIG. 7, the piezoelectric constant _{d 15} when the electric field 300 V / mm is used lead-containing piezoelectric material as a 1000pC / N or more. Note that "p" is the prefix pico of the SI unit system. The lead-containing piezoelectric material is, for example, lead zirconate titanate (PZT). Lead zirconate titanate (PZT) is a mixed crystal of lead zirconate and lead zirconate. Lead zirconate titanate is a composition ratio of zirconium (Zr) and titanium (Ti) to lead (Pb) and a dope metal. The magnitude of hysteresis varies depending on the type and composition ratio. Among them, a lead zirconate titanate piezoelectric constant _{d 15} is equal to or higher than 1000pC / N when the electric field 300 V / mm, is selected as the high hysteresis material and medium hysteresis material. Of course, the lead-containing piezoelectric material is not limited to lead zirconate titanate.

For the piezoelectric constant d ₁₅ , for example, in the case of a commercially available piezoelectric material, a value indicated by the manufacturer may be used. Alternatively, it may actually be measured. Figure 7 is a high hysteresis material (A-1), the middle hysteresis material (A-2) and low hysteresis material (A-3), shows actual examples of the measured piezoelectric constant d ₁₅ was determined .. As a measuring method, as outlined in FIG. 8, for example, an electrode 80 is formed on a test piece 8 having a length of 1.5 mm, a width of 1 mm, and a height of 0.2 mm, and the electrode 80 is fixed to the fixing base 81 and attached to the electrode 80. A driving electric field E is applied. The drive electric field E is applied so as to be 5 V / mm, 300 V / mm, and 750 V / mm, and the inclination (shear strain) at that time is measured by the laser Doppler vibrometer sensor 82. The piezoelectric constant d ₁₅ indicating the shear strain can be obtained by dividing the strain amount by an electric field. The calculation formula and unit are the piezoelectric constant d ₁₅ (m / V) = [generated strain (m / m) / given electric field (V / m)].

Further, as another example of the piezoelectric material, as shown in FIG. 7, a _{lead-free piezoelectric material having a piezoelectric constant d 15} at an electric field of 300 V / mm of 400 pC / N or more is used. The lead-free piezoelectric material is, for example, sodium potassium niobate (KNN). Other niobate-based piezoelectric materials may be used. Further, it may be other than the niobic acid type such as barium titanate (BaTIO _3). Also in the case of the lead-free piezoelectric material, the piezoelectric constant d ₁₅ may be a value indicated by the manufacturer in the case of a commercially available piezoelectric material, for example. Alternatively, it may actually be measured. Figure 7 is a high hysteresis material (B-1), the middle hysteresis material (B-2) and low hysteresis material (B-3), shows actual examples of the measured piezoelectric constant d ₁₅ was determined .. Among them, the piezoelectric constant _{d 15} when the electric field 300 V / mm to select the 400 pC / N or more lead-free piezoelectric material.

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

(A) Pushing is performed by applying a voltage in the positive direction (+) and then returning to the ground potential. In this case, the piezoelectric members 6 (6A, 6B) are deformed from the strain A2 in the pushing direction of the strain A1 to pressurize the drive 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 the strain A1 to the strain A2. Since the push-pushing repeatedly pressurizes the drive pressure chamber 5 in a linear range from the strain A1 to the strain A2, the drive frequency can be made the fastest.

(B) Pushing with a pre-waveform is a small waveform that does not eject ink once, and after applying a voltage in the negative direction (-) and then in the positive direction (+), the voltage is returned to the ground potential. .. In this case, the piezoelectric member 6 (6A, 6B) is once deformed in the strain A3 direction and then deformed in the pushing direction of the strain A1 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 the strain A1 to the strain A2. In the push-strike with pre-waveform, the amount of strain can be increased as compared with the push-strike by the amount of once deforming in the strain A3 direction.

(C) In the pulling, a voltage is first applied in the negative direction (−), then a voltage is applied in the positive direction (+), and then the voltage is returned to the ground potential. In this case, the piezoelectric member 6 (6A, 6B) is sufficiently deformed in the pulling direction of the strain A3 and then deformed in the pushing direction of the strain A1 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 the strain A1 to the strain A2. Ink can be ejected with a _{large strain amount ε T} from the maximum value in the pulling direction (strain A3) to the maximum value in the pushing direction (strain A1). Pulling is a preferable driving method in which a large amount of distortion can be obtained and the driving frequency can be relatively fast.

(D) With pre-waveform pulling, a voltage is applied in the positive direction (+) with a small waveform that does not eject ink once, then a voltage is applied in the negative direction (-), and then in the positive direction (+) again. After applying the voltage, the voltage is returned to the ground potential. In this case, the piezoelectric member 6 (6A, 6B) is once deformed in the strain A1 direction and then deformed in the pulling direction of the strain A3 to reduce the pressure in the drive pressure chamber 5. Then, the strain A1 is deformed in the pushing direction 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 the strain A1 to the strain A2.

Next, the movement of the actuator when pulling, which is a preferable driving method, will be described with reference to FIG. At the ground potential before applying the drive voltage, the piezoelectric member 6 (6A, 6B) has a history of the immediately preceding ejection operation. That is, when viewed from the drive 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 member 6 (6A, 6B) is deformed in the pulling direction, and the drive pressure chamber 5 is depressurized. Subsequently, when a voltage is applied in the positive direction (+), the piezoelectric member 6 (6A, 6B) is deformed in the pushing direction, the drive pressure chamber 5 is pressurized, and ink droplets are ejected from the nozzle 25.

According to the embodiment described above, the shear mode side shooter type inkjet head 10A is provided with an independently driven actuator in which an air chamber 51 having a smaller pressure propagation than ink is arranged on both sides of the driving pressure chamber 5. _{A lead-containing piezoelectric material having a piezoelectric constant d 15} of 1000 pC / N or more when the electric field is 300 V / mm can be used. That is, even if a piezoelectric material having a large hysteresis is used and the ink is driven with a large strain, the ink ejection operation with suppressed crosstalk can be performed. For the same reason, the piezoelectric constant _{d 15} when the electric field 300 V / mm can be used lead-free piezoelectric material which is a 400 pC / N or more.

Further, according to the above-described embodiment, the state at the end of driving of the piezoelectric member 6 (6A, 6B) is always the same strain A2, so that the variation in the history of the immediately preceding strain as in the share wall type can be eliminated. No pre-drive required. As a result, not only crosstalk can be suppressed, but also the drive frequency can be increased.

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

Although the above-described embodiment has been described by taking the ink circulation type inkjet head 10A as an example, the ink non-circulation type inkjet head may be used. Further, the inkjet head 10A may be mounted on a 3D printer. In this case, a liquid modeling material or support material is discharged as ink.

The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

10A Inkjet head 2 Nozzle head 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 drive pressure chamber having a pair of side walls formed of a piezoelectric member and communicating with an ink supply path and a nozzle, an air chamber provided on both sides of the drive pressure chamber via the side wall, and a drive to the piezoelectric member. Equipped with an independent drive type actuator including a drive circuit that applies an electric field,
The drive pressure chamber and the air chamber are arranged on a plurality of side walls formed of the piezoelectric members arranged at intervals on one surface of the substrate, a nozzle plate arranged in contact with the side wall, and both ends of the side wall. It is formed by a pair of cover plates having an ink supply port and an ink discharge port at a location corresponding to the drive pressure chamber.
The piezoelectric member, ink jet head, characterized in that the piezoelectric constant _{d 15} when the electric field 300 V / mm is formed in the lead-containing piezoelectric material to be 1000pC / N or more. A drive pressure chamber having a pair of side walls formed of a piezoelectric member and communicating with an ink supply path and a nozzle, an air chamber provided on both sides of the drive pressure chamber via the side wall, and a drive to the piezoelectric member. Equipped with an independent drive type actuator including a drive circuit that applies an electric field,
The drive pressure chamber and the air chamber are arranged on a plurality of side walls formed of the piezoelectric members arranged at intervals on one surface of the substrate, a nozzle plate arranged in contact with the side wall, and both ends of the side wall. It is formed by a pair of cover plates having an ink supply port and an ink discharge port at a location corresponding to the drive pressure chamber.
The piezoelectric member, ink jet head, characterized in that the piezoelectric constant d ₁₅ when the electric field 300 V / mm is formed in the lead-free piezoelectric material which is a 400 pC / N or more. The inkjet head according to claim 1 or 2 , wherein the drive circuit applies a drive electric field that pressurizes the drive pressure chamber after applying a drive electric field that depressurizes the drive pressure chamber. The inkjet head according to any one of claims 1 to 3 and the inkjet head.
A recording medium transport device that transports a recording medium to a position facing the inkjet head,
An inkjet printer including a control unit that controls the inkjet head so as to eject ink to a predetermined position on the recording medium.

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