JP4225326B2 - Inkjet head - Google Patents

Description

  The present invention relates to an inkjet head that performs recording by ejecting ink onto a recording medium.

  As an inkjet head, an actuator unit in which a flow path unit having a large number of pressure chambers connected to a large number of nozzles arranged in one or two rows and a piezoelectric sheet provided facing each pressure chamber are laminated Are known. At least one piezoelectric sheet in the actuator unit is provided with an active portion sandwiched between a common electrode held at a ground potential and an individual electrode arranged at a position corresponding to each pressure chamber. Then, by setting the individual electrode corresponding to the pressure chamber to which ink is to be ejected to a potential different from that of the common electrode, the active portion is displaced in the stacking direction due to the piezoelectric effect, and the volume in the pressure chamber is changed to change the volume of the ink nozzle. It is possible to discharge from.

  In an ink jet head using an actuator unit composed of a piezoelectric sheet as described above, in principle, the volume change amount of the pressure chamber depends on the area of the active portion facing the pressure chamber and the drive voltage applied to the individual electrodes. It is determined. Therefore, if it is intended to secure the minimum ink discharge amount, it is difficult to realize a high-density arrangement by lowering the driving voltage and / or reducing the pressure chamber.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head that can achieve a low drive voltage and / or a high density arrangement of pressure chambers while ensuring a minimum ink discharge amount.

In order to achieve the above object, an ink jet head according to claim 1 is provided outside a side wall of each of the pressure chambers, a plurality of pressure chambers having one end connected to the discharge nozzle and the other end connected to an ink supply source. A flow path unit in which a plurality of thin plates including a first thin plate provided with a formed gap and a partition provided between the adjacent pressure chambers via the side wall and the gap are stacked; and the flow path An actuator that is stacked on the unit and that discharges ink from the discharge nozzle, and is configured so that opposite side walls of the pressure chamber can be bent in opposite directions, and the stacking direction of the flow path unit and the actuator on one side of the side edge of the side walls, wherein the actuator for applying a force to bend the side walls are connected, the actuator, the magnitude over the plurality of pressure chambers of A, and having a first piezoelectric sheet having a plurality of individual electrodes are provided on the upper surface corresponding to the plurality of pressure chambers, the same size as the first piezoelectric sheet, and, from the stacking direction in a plan view as seen, the plurality common electrodes a pressure chamber one body to cover of be one in which a second piezoelectric sheet formed on the upper surface are laminated, the each individual electrode by said common electrode Each of the sandwiched areas is defined as an active part, the active part is disposed corresponding to the pressure chamber, and an inactive part between the active parts is fixed to the partition wall. The both side walls are curved to change the volume of the pressure chamber, and ink droplets are ejected from the ejection nozzles.

  According to the first aspect, since both side walls of the pressure chamber can be deformed simultaneously and largely by deformation of the actuator, it is possible to reduce the drive voltage applied to the actuator while ensuring a sufficient ink discharge amount, Alternatively, high density can be realized by downsizing the pressure chamber. Further, by optimizing the deformation amount of the both side walls of the pressure chamber accompanying the deformation of the actuator, it is also possible to simultaneously realize a low drive voltage and a high density pressure chamber.

  In addition, since the deformation of the active portion is less likely to affect the adjacent pressure chambers, the occurrence of so-called crosstalk can be suppressed and the print quality is improved.

3. The ink jet head according to claim 2, wherein the two side walls at the intermediate portion of the pressure chamber in the longitudinal direction of the pressure chamber when no voltage is applied to the individual electrodes in a plan view as viewed from the stacking direction. Is formed narrower than the distance between the both side walls at both ends of the pressure chamber, and when the voltage is applied to the individual electrode and the actuator is deformed in a direction to reduce the volume of the pressure chamber, The both side walls are deformed in a direction to reduce the volume of the pressure chamber.

  According to the second aspect, since the volume change amount of the pressure chamber is obtained as the sum of the deformation due to the deformation of the actuator and the deformation due to the deformation of both side walls of the pressure chamber, the volume change amount of the pressure chamber due to the deformation of the actuator becomes large. Therefore, the drive voltage can be further lowered and the pressure chamber can be further densified.

  Further, in plan view, the distance between the side walls at the middle part of the pressure chamber in the longitudinal direction of the pressure chamber is formed narrower than the distance between the side walls at both ends of the pressure chamber. Even if it is provided, both side walls are curved to the inside of the pressure chamber when both side walls are buckled and deformed as the actuator is deformed.

  Note that “the two side walls of the pressure chamber are deformed in a direction that reduces the volume of the pressure chamber” means that not only the both side walls of the pressure chamber are deformed inward of the pressure chamber, but also the two side walls of the pressure chamber. It is assumed that one is deformed in the inner direction of the pressure chamber and the other is deformed in the outer direction, but the volume decrease amount due to deformation of one side wall is larger than the volume increase amount due to deformation of the other side wall.

According to a third aspect of the present invention, in the cross section perpendicular to the longitudinal direction of the pressure chamber, the both side walls are formed thinner than the partition wall.

According to the third aspect , the both side walls can be easily elastically deformed in the bending direction.
The inkjet head according to claim 4 has the second thin plate that sandwiches the pressure chamber with the actuator, and when the voltage is not applied to the individual electrode, the both side walls are formed of the pressure chamber. A cross section perpendicular to the longitudinal direction has a linear shape perpendicular to the second thin plate.

Inkjet head according to claim 5, when the voltage to the individual electrode is applied, as the two side walls buckles inward direction before Symbol pressure chamber, when the voltage is not applied to the individual electrodes, wherein Both side walls are formed to be curved inside the pressure chamber .

The inkjet head according to claim 6, wherein the pressure chamber is a flat surface of the second thin plate that is a concave wall body that forms the side walls and a top wall that connects the tip portions of the both side walls, and a thin metal plate. And the top wall is sandwiched between the pressure chamber and the actuator.

The inkjet head according to claim 7, wherein the actuator has a plurality of active layers each having the active part and made of a plurality of the piezoelectric sheets polarized in the stacking direction, and not sandwiched between the individual electrode and the common electrode. The piezoelectric sheet is composed of an inactive layer opposite to the pressure chamber with respect to the active layer, and when an electric field is generated in the polarization direction of the piezoelectric sheet constituting the active layer, It extends in the polarization direction.
9. The ink jet head according to claim 8, wherein the actuator has a resin adhesive layer that is at least impermeable to ink and has electrical insulation properties on the entire lower surface facing the pressure chamber. It is characterized by.
According to the eighth aspect, the adhesive layer serves as a film that does not allow ink to permeate, and firmly fixes the actuator and the flow path unit.

  A preferred embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is an exploded perspective view of an ink jet head according to the present embodiment. As shown in FIG. 1, the piezoelectric inkjet head 1 according to the present embodiment has an actuator unit 20 of substantially the same shape stacked on a substantially rectangular parallelepiped flow path unit 10, and an external device and an actuator unit 20 are connected to the actuator unit 20. A flexible flat cable 40 for connection is attached. The inkjet head 1 ejects ink downward from a nozzle 54 (see FIG. 2) opened on the lower surface side of the flow path unit 10.

  FIG. 2 is an exploded perspective view of the flow path unit. As shown in FIG. 2, the flow path unit 10 is formed by laminating and bonding five conductive thin plates of the nozzle plate 43, the manifold plates 11 and 12, the spacer plate 13, and the cavity plate 14 by bonding. Is. In the present embodiment, the manifold plates 11 and 12 and the spacer 13 are made of 42% nickel alloy steel plate and have a thickness of about 50 μm to 150 μm. The cavity plate 14 is made of silicon and has a thickness of about 150 μm to 500 μm. The nozzle plate 43 is provided with nozzles 54 for ejecting ink with a small diameter along a first direction (long-side direction) of the nozzle plate 43 in a two-row staggered arrangement. That is, a large number of nozzles 54 are drilled in the nozzle plate 43 in a staggered arrangement at fine pitch intervals along two reference lines parallel to the long side direction of the nozzle plate 43.

  In the manifold plate 12, a pair of manifold chambers 12a and 12a serving as ink passages are formed so as to extend along the outside of two reference lines in which the nozzles 54 are arranged. Each manifold chamber 12a overlaps with the row of pressure chambers 16 formed in the cavity plate 14 in plan view and extends across the row of pressure chambers 16 in the long side direction.

  A manifold chamber 11a is recessed on the upper surface of the manifold plate 11 below the manifold plate 12 so as to open upward in substantially the same shape in plan view at substantially the same position as each manifold chamber 12a. 11a and 12a are united to form one manifold chamber.

  The cavity plate 14 is provided with a large number of narrow pressure chambers 16 extending in a second direction (short side direction) orthogonal to the center line along the long side. The detailed structure of the pressure chamber 16 and the vicinity thereof will be described later. The pressure chambers 16 are arranged in two rows so as to sandwich the center line in the longitudinal direction of the cavity plate 14. The vicinity of the tip of each pressure chamber 16 extends beyond the center line. Therefore, the region in the vicinity of the tip of each pressure chamber 16 overlaps with each other in the longitudinal direction of the cavity plate 14, and the tips of the pressure chambers 16 are arranged in a staggered manner in two rows.

  The front ends of the pressure chambers 16 are formed in the staggered arrangement of nozzles 54 in the nozzle plate 43 through the small-diameter through-holes 17 and 17 formed in the spacer plate 13 and the manifold plates 11 and 12 in the same staggered arrangement. It communicates through. On the other hand, the other end of each pressure chamber 16 communicates with the manifold chambers 11a and 12a in the manifold plates 11 and 12 through through holes 18 drilled in the left and right side portions of the spacer plate 13. A pair of supply holes 19a and 19b communicating with the left and right manifold chambers 12a and 12a are formed at one end in the longitudinal direction of the cavity plate 14 and the spacer plate 13, respectively. As shown in FIG. 2, on the upper surface of the supply holes 19a, 19a formed at one end of the uppermost cavity plate 14, dust is removed from the ink supplied from an ink cartridge (not shown) thereabove. The filter 29 is stretched.

  The ink that has flowed from the ink cartridge into the left and right manifold chambers 11a, 11a, 12a, and 12a through the supply holes 19a and 19b is distributed to the pressure chambers 16 through the through holes 18 and then to the respective pressure chambers. The inside of the chamber 16 passes through the through hole 17 and reaches the nozzle 54 corresponding to the pressure chamber 16 (see FIG. 6).

  FIG. 3 is a partial exploded perspective view of the actuator unit 20. As shown in FIG. 3, the actuator unit 20 has a structure in which eight piezoelectric ceramic sheets (hereinafter simply referred to as “piezoelectric sheets”) 21a, 21b, 21c, 21d, 21e, 21f, 21g, and 23 are stacked. The sheet is sized across the entire pressure chamber 16. A large number of individual electrodes 24 are provided on the top surfaces of the second and fourth piezoelectric sheets 21b and 21d from the bottom (see FIG. 6). Each individual electrode 24 has a narrow shape extending in the short side direction of the actuator unit 20. A large number of individual electrodes 24 are arranged in two rows along the long side direction corresponding to the position of each pressure chamber 16 in the flow path unit 10. The potential of each individual electrode 24 can be controlled independently. In addition, a common electrode 25 is formed in a region excluding the vicinity of the end portion in the short side direction on the top surfaces of the first, third, and fifth piezoelectric sheets 21a, 21c, and 21e from the bottom (see FIG. 6). . Thereby, most of each individual electrode 24 except for the vicinity of the end in the longitudinal direction overlaps the common electrode 25 in plan view. The common electrode 25 is always kept at a constant potential (ground potential). The individual electrodes or common electrodes are not provided on the upper surfaces of the other piezoelectric sheets 21f, 21g, and 23. The uppermost piezoelectric sheet 23 may be an insulating material instead of a piezoelectric ceramic material. The thickness of each sheet is approximately 30 μm.

  The common electrode 25 has a long side at the center in the short side direction of the piezoelectric sheets 21a, 21c, 21e so as to integrally cover the pressure chambers 16, 16 arranged in two rows along the long side direction in a plan view. It is formed in a substantially rectangular shape in plan view extending along. Further, the common electrode 25 is integrally provided with a lead portion 25a extending substantially over the entire length of the edge portion in the vicinity of the edge portions along both short sides of the piezoelectric sheets 21a, 21c, and 21e.

  A dummy individual electrode having a short width and substantially the same width as the individual electrode 24 is provided on the surface of the piezoelectric sheet 21a, 21c, 21e near the end in the short side direction, where the common electrode 25 is not formed. 26 is formed. The dummy individual electrodes 26 are provided at positions corresponding to the individual electrodes 24 in plan view.

  In addition, dummy common electrodes 27 are formed on the upper surfaces of the piezoelectric sheets 21b and 21d at positions corresponding to the lead portions 25a (positions overlapping in plan view, that is, near both ends in the long side direction of the piezoelectric sheets).

  As shown in FIGS. 1 and 3, the upper surface of the uppermost piezoelectric sheet 23 has a surface electrode 30 for each individual electrode 24 and a lead-out portion for the common electrode 25 along the edge of the long side. A surface electrode 31 for 25a is provided.

  Further, the piezoelectric sheets 21b, 21c, 21d, 21e, 21f, 21g, and 23, excluding the lowermost piezoelectric sheet 21a, have respective surface electrodes 30, individual electrodes 24 at the corresponding positions (same vertical positions) and dummy. One through hole 32 for connecting the individual electrodes 26 to each other is formed for each individual electrode 24. Similarly, on the piezoelectric sheets 21b, 21c, 21d, 21e, 21f, 21g, 23 excluding the lowermost piezoelectric sheet 21a, the surface electrode 31, the lead portion 25a of the common electrode 25, and the dummy common electrode 27 are mutually connected. Several through holes 33 for connection are formed. The through holes 32 and 33 are filled with a conductive material. The individual electrode 24, the dummy individual electrode 26, and the surface electrode 30 that are overlapped in the stacking direction are electrically connected to each other through the conductive material in each through hole 32. Similarly, the common electrode 25, the dummy common electrode 27, and the surface electrode 31 that are overlapped in the stacking direction are electrically connected via the conductive material in each through-hole 33.

  When the through hole 33 is not formed, the lead portions of all the common electrodes 25 are exposed on one side surface of the actuator unit 20, and the connection electrodes connected to all the lead portions 25 a are arranged in the thickness direction of the actuator unit 20. It may be applied so as to extend, and this connection electrode may be electrically connected to the surface electrode 31 on the piezoelectric sheet 23. When the through holes 32 are not formed, the end portions of all the individual electrodes 24 are exposed on the other side surface of the actuator unit 20, and the connection electrodes connected to the individual electrodes 24 at the same position in the vertical direction are connected to the actuator unit 20. You may make it apply | coat to a side surface and connect a connection electrode to each corresponding surface electrode 30 on the piezoelectric sheet 23 electrically.

  An adhesive sheet (not shown) made of a non-ink-permeable synthetic resin material as an adhesive layer is formed on the entire lower surface (the surface facing the pressure chamber 16) of the plate-type actuator unit 20 having such a configuration. It is stuck. The actuator unit 20 is bonded and fixed to the flow path unit 10 so that each individual electrode 24 is arranged at a position corresponding to each pressure chamber 16 in plan view (see FIGS. 5 and 6). . Furthermore, the flexible flat cable 40 is overlaid on the upper surface of the actuator unit 20, whereby various wiring patterns formed on the flexible flat cable 40 are electrically connected to the surface electrodes 30 and 31.

  The material of the adhesive layer such as an adhesive sheet is at least an ink impermeable and electrically insulating material, and is a polyamide mainly composed of a nylon or dimer acid based polyamide resin. A film-type hot melt adhesive or polyester hot melt adhesive may be used, but the polyolefin hot melt adhesive is applied to the actuator unit 20 and then adhered to the flow path unit 10. You may make it do.

  FIG. 4 is a schematic diagram depicting a planar structure around the pressure chamber in the inkjet head 1 when no voltage is applied to the individual electrode 24 according to the present embodiment. FIG. 5 is a partial cross-sectional view of the inkjet head 1 taken along the line VV in FIG. FIG. 6 is a partial cross-sectional view of the inkjet head 1 taken along line VI-VI in FIG.

  As shown in these drawings, the elongate pressure chamber 16 provided in the cavity plate 14 so as to extend in the width direction of the cavity plate 14 has an elongate reverse concave shape that constitutes the left and right side walls 36a, 36b and the top wall 36c. It is surrounded by the wall 36 and the upper surface of the spacer plate 13. Both side walls 36 a and 36 b are formed to be perpendicular to the surface of the spacer plate 13 in a steady state where no voltage is applied to the individual electrode 24. The top wall 36c connects the tip portions of both side walls 36a, 36b so as to be parallel to the surface of the spacer plate 13.

  Gaps 37 a and 37 b are provided on both outer sides of the wall body 36. The pressure chamber structure in which the gaps 37a and 37b, the wall body 36, and the pressure chamber 16 form one set has the same height as the wall body 36 and extends in the same direction as the pressure chamber 16 and the gaps 37a and 37b. , 37b are separated from each other by a partition wall 39 disposed on the outer side. The cavity plate 14 may have a structure as described above by performing anisotropic etching.

  Further, the side walls 36a and 36b and the top wall 36c of the wall body 36 are formed thinner than the partition wall 39, and can be easily elastically deformed in the respective bending directions.

  As shown in FIGS. 5 and 6, in the present embodiment, the flow path unit 10 and the actuator unit 20 are arranged so that each individual electrode 24 is disposed at a position corresponding to each of the pressure chambers 16 in plan view. Assembly is fixed. A region sandwiched between the common electrode 25 of the four piezoelectric sheets 21b, 21c, 21d, and 21e in the actuator unit 20 and a large number of individual electrodes 24 is polarized in a direction in which both electrodes 24 and 25 face each other as is well known. When an electric field is generated between the electrodes and parallel to the polarization direction, the electrode is bent so as to swell or retract in the thickness direction, that is, the sheet stacking direction due to the piezoelectric effect. That is, this region is an active portion that is displaced by applying a voltage to the individual electrode 24. The active part is formed in an island shape in each piezoelectric sheet. The active portions respectively formed on the four piezoelectric sheets are formed at positions where the corresponding ones are vertically continuous with each other in plan view. Therefore, the four active parts that are continuous in the vertical direction form a group of active parts. The actuator unit 20 is fixed on the partition wall 39 in the inactive part between the active part groups.

  In order to manufacture the inkjet head 1 of the present embodiment, the actuator unit 20 and the flow path unit 10 are separately formed, and then both are fixed with an adhesive sheet. Thereafter, a voltage higher than that during normal discharge operation is applied between all the individual electrodes 24 and the common electrode 25 via the flexible flat cable 40. Then, the portions of the piezoelectric sheets 21b, 21c, 21d, and 21e sandwiched between the individual electrode 24 and the common electrode 25 are subjected to polarization processing to become active portions.

  Next, the ink ejection operation in the inkjet head 1 of the present embodiment will be described with further reference to FIGS. FIG. 7 is a schematic diagram illustrating a planar structure around the pressure chamber in the inkjet head 1 when a voltage is applied to the individual electrode 24 corresponding to FIG. 4. FIG. 8 is a partial cross-sectional view of the inkjet head 1 taken along line VIII-VIII in FIG. When a voltage for ejection operation is applied to the individual electrode 24 belonging to the selected active part group, an electric field in the same direction as the polarization direction is generated between the individual electrode 24 and the common electrode 25, as shown in FIG. Furthermore, the active part belonging to the active part group extends so as to protrude in the direction of the cavity plate 14 (downward) due to the piezoelectric effect, and the piezoelectric sheet 21a in the lowermost layer also curves downward at a position corresponding to the active part. Then, both side walls 36a and 36b receive a force in a direction along the surface via the top wall 36c of the wall body 36, and both are buckled and curved in the inner direction of the pressure chamber 16. In addition, as shown in FIG. 9, it is preferable to manufacture both the side walls 36a and 36b in the shape deform | transformed previously so that it might buckle inward. In this manner, the volume of the pressure chamber 16 corresponding to each individual electrode 24 is reduced, so that the ink in the pressure chamber 16 is ejected from the nozzle 54 in the form of droplets, and printing is performed. Thereafter, when the application of voltage to the individual electrode 24 is stopped, the elastically deformed wall body 36 also returns to the original shape as the active portions of the four piezoelectric sheets 21b to 21e return to the flat plate shape. Note that the curved displacements of the side walls 36a, 36b and the top wall 36c in FIGS. 7 and 8 are exaggerated for the sake of explanation.

  As described above, according to the inkjet head 1 of the present embodiment, the active portions of the four piezoelectric sheets 21b to 21e extend downward, so that three of the four walls on the top, bottom, left, and right surrounding the pressure chamber 16 are inside. Transforms into Accordingly, the volume reduction rate in the pressure chamber 16 is significantly larger than when only the active portion or the top wall 36c is deformed downward, or when only the top wall 36c and one of the side walls 36a and 36b are deformed. .

  Therefore, even if the voltage applied to the individual electrode 24 is lowered to reduce the displacement amount of the active portion, a sufficient ink discharge amount can be ensured. Therefore, power consumption can be reduced, and the driver IC for the individual electrode 24 can be reduced in size and cost. Even if the pressure chamber 16 is downsized and its volume is reduced, a sufficient ink discharge amount can be ensured. Therefore, by arranging the pressure chambers 16 at a higher density, it is possible to print an image with a higher resolution, and it is possible to reduce costs by reducing the amount of use of relatively expensive piezoelectric sheets and electrodes. The advantage is obtained.

  Furthermore, by optimizing the selection and shape of the material, the amount of deformation of the side walls 36a and 36b of the pressure chamber 16 accompanying the deformation of the active portion is optimized, thereby reducing the drive voltage of the individual electrode 24. It is also possible to realize the high density of the pressure chambers 16 at the same time, in which case both of the above-mentioned benefits can be obtained.

  The presence of the top wall 36c hardly contributes to the volume reduction rate of the pressure chamber 16, but in this embodiment, the top wall 36c is provided, so that ink leaks from the pressure chamber 16 to the gaps 37a and 37b. This can be prevented and the piezoelectric sheet 21a can be prevented from coming into contact with ink, so that there is an advantage that the degree of freedom in ink selection can be improved.

  Further, in the present embodiment, when the active portion is deformed downward, that is, in the direction of decreasing the volume of the pressure chamber 16, both side walls 36 a and 36 b of the pressure chamber 16 are both inward of the pressure chamber 16, that is, the pressure chamber 16. Therefore, the volume change amount of the pressure chamber 16 is obtained as the sum of the deformation due to the deformation of the active portion and the deformation due to the deformation of the side walls 36a and 36b of the pressure chamber 16. Therefore, when the active portion is deformed in the direction of decreasing the volume of the pressure chamber 16, the side walls 36a and 36b of the pressure chamber 16 are deformed in a direction of increasing the volume of the pressure chamber 16, compared with the case where the active portion is deformed. As a result, the volume change amount of the pressure chamber 16 increases. Therefore, the drive voltage of the individual electrode 24 can be further lowered and the pressure chamber 16 can be further densified.

  Here, as an example in which both side walls 36a, 36b of the pressure chamber 16 are deformed in a direction to reduce the volume of the pressure chamber 16, both side walls 36a, 36b are deformed in opposite directions, that is, both inward of the pressure chamber 16. However, both side walls 36a and 36b of the pressure chamber 16 are deformed in the same direction, that is, one of the side walls 36a and 36b is deformed inward of the pressure chamber 16 and the other is deformed outward. The same effect can be obtained when the volume reduction amount due to deformation is larger than the volume increase amount due to deformation of the other side wall. However, it is most preferable that the side walls 36a and 36b are deformed in directions opposite to each other (both inside the pressure chamber 16 or both outside the pressure chamber 16).

  In the present embodiment, since the gaps 37a and 37b are provided outside the both side walls 36a and 36b of the pressure chamber 16, the side walls 36a and 36b can be curved without affecting the adjacent pressure chambers 16, and both the side walls 36a and 36b are easy to bend and the displacement amount is relatively large. Therefore, compared with the case where the gaps 37a and 37b are not provided, the volume change amount of the pressure chamber 16 due to the deformation of the active portion is increased, and the drive voltage of the individual electrode 24 is further reduced and the pressure chamber 16 is reduced. Can be further increased in density. Note that the widths of the gaps 37a and 37b are preferably made as small as possible within a range that does not hinder the appropriate bending of the side walls 36a and 36b, from the viewpoint of realizing high density of the pressure chambers 16.

  Further, in the present embodiment, since the actuator unit 20 including eight piezoelectric sheets is fixed on the partition wall 39, the deformation of the active portion hardly affects the adjacent pressure chambers 16. Therefore, the occurrence of so-called crosstalk can be suppressed, and the print quality is improved.

  Further, in the inkjet head 1 according to the present embodiment, as described above, an adhesive sheet is interposed between the actuator unit 20 and the flow path unit 10 so as to cover all the pressure chambers 16. The sheet serves as a film that does not allow ink to permeate, and the actuator unit 20 and the flow path unit 10 are firmly fixed. Further, since the actuator unit 20 is configured by stacking the eight piezoelectric sheets 21a,... So as to straddle the plurality of pressure chambers 16, the amount of displacement with respect to the pressure chambers 16 can be easily changed depending on the number of stacked piezoelectric sheets. In addition, the actuator unit 20 can be easily manufactured by forming and stacking electrodes on each piezoelectric sheet by printing or the like. Furthermore, the length of the active portion can be easily changed by changing the size of the region where the individual electrode 24 and the common electrode 25 overlap.

  In order to ensure that the side walls 46a, 46b are curved and deformed in the direction toward the pressure chamber when the top wall 36c is bent downward, the side walls 46a, 46b are not necessarily formed into a drum shape, as shown in FIG. Even if it does not make a shape, it is sufficient if the side walls 46a and 46b are curved slightly inward.

  Next, a modified example of the present embodiment will be described with further reference to FIGS. FIG. 10 is a schematic view of one modified example depicting a planar structure around the pressure chamber when no voltage is applied to the individual electrode 24 as in FIG. 4. FIG. 11 is a cross-sectional view corresponding to FIG. 5 showing still another modification. In these modified examples, the same members as those in the above embodiment are given the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 10, both side walls 36 a and 36 b of the wall body 36 are manufactured so as to be curved in a drum shape in plan view so that the interval between the intermediate portions in the longitudinal direction of the pressure chamber 16 becomes narrow. In this way, even if the side walls 36a and 36b are linear shapes perpendicular to the base plate 13 as shown in FIG.

  In each of the above embodiments, when an ink ejection operation is to be performed, the active portion corresponding to the pressure chamber 16 is deformed. However, by applying a voltage to all the individual electrodes 24 in advance, The volume of all the pressure chambers 16 is reduced, the voltage of the individual electrode 24 corresponding to the pressure chamber 16 that is going to perform the ink ejection operation is released, and the volume of the pressure chamber 16 is expanded. It is also possible to perform so-called “strike” in which the voltage is applied to the electrode 24 to reduce the volume of the pressure chamber 16 and the ejection pressure is applied to the ink.

  Moreover, as shown in FIG. 11, when the top wall 36c of the wall body 36 is pushed by the active part of the actuator, the side walls 36a and 36b can be configured to be bent and deformed in directions away from each other. In this case, it is preferable that the side walls 36a and 36b are slightly deformed in advance so as to be deformed in that direction. At this time, the amount of bending of the side walls 36a, 36b is larger than the amount of lowering of the top wall 36c, so the volume of the pressure chamber 16 is expanded. Thereafter, by returning the active portion of the actuator, both side walls 36a and 36b can also be returned to apply ejection pressure to the ink. In other words, in a normal state, it is possible to “strike” by simply applying and stopping the voltage to the pressure chamber that performs the discharge operation without continuously applying the voltage as in the above embodiment.

  The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as they are described in the claims. . For example, in the above-described embodiment, the actuator unit is a laminate of piezoelectric sheets on which electrodes are printed. However, the actuator unit is not limited to this, and the volume of the pressure chamber is changed. Any type other than the piezoelectric type may be used as long as it has an active portion that deforms. Further, in the above-described embodiment, the active part is provided only on a part of the piezoelectric sheets in the actuator unit. However, the active part may be provided on all of the laminated piezoelectric sheets.

  Further, the length of the active part may be longer than that of the pressure chamber. Further, the shape of the pressure chamber and the active portion, the number of stacked piezoelectric sheets, the arrangement direction of the pressure chambers, and the like may be appropriately changed.

1 is an exploded perspective view of an inkjet head according to an embodiment of the present invention. It is a disassembled perspective view of the flow path unit which comprises the inkjet head shown in FIG. FIG. 2 is a partial exploded perspective view of an actuator unit constituting the ink jet head shown in FIG. 1. FIG. 2 is a schematic diagram illustrating a planar structure around a pressure chamber when no voltage is applied to an individual electrode of the inkjet head shown in FIG. 1. It is sectional drawing along the VV line of FIG. It is sectional drawing along the VI-VI line of FIG. FIG. 5 is a schematic diagram illustrating a planar structure around a pressure chamber when a voltage is applied to an individual electrode corresponding to FIG. 4. It is a fragmentary sectional view in alignment with the VIII-VIII line of FIG. It is sectional drawing equivalent to FIG. 5 in a modification. FIG. 6 is a schematic view corresponding to FIG. 4 in an ink jet head of still another modified example. Furthermore, it is sectional drawing equivalent to FIG. 5 in another modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 10 Flow path unit 16 Pressure chamber 20 Actuator unit 21a-21g, 23 Piezoelectric sheet 24 Individual electrode 25 Common electrode 36 Wall body 36a, 36b Side wall 36c Top wall 37a, 37b Space | gap 39 Bulkhead 40 Flexible flat cable 54 Nozzle

Claims (8)

A plurality of pressure chambers each having one end connected to the discharge nozzle and the other end connected to an ink supply source, gaps provided on the outer sides of both side walls of each pressure chamber, and the side wall A flow path unit in which a plurality of thin plates including a first thin plate provided with a partition provided through a gap are stacked, and an actuator that is stacked on the flow path unit and discharges ink from the discharge nozzle. Have
The opposing side walls of the pressure chamber are configured to be able to bend in directions opposite to each other, and the side walls are curved at one side edge of the both side walls with respect to the stacking direction of the flow path unit and the actuator . The actuator for applying force is coupled,
The actuator is
A first piezoelectric sheet having a size extending over the plurality of pressure chambers and provided with a plurality of individual electrodes respectively corresponding to the plurality of pressure chambers; and the same size as the first piezoelectric sheet the a, and, in a plan view as viewed from the stacking direction, be one and the second piezoelectric sheet common electrode covering the plurality of pressure chambers in one body manner is formed on the upper surface is laminated, The regions sandwiched between the individual electrodes and the common electrode are respectively active portions, the active portions are disposed corresponding to the pressure chambers, and the inactive portions between the active portions are the partition walls. Is fixed to
An ink jet head that discharges ink droplets from the discharge nozzle by bending the both side walls by the operation of the actuator to change the volume of the pressure chamber. When a voltage is not applied to the individual electrodes in a plan view as viewed from the stacking direction, the distance between the side walls at the intermediate portion of the pressure chamber in the longitudinal direction of the pressure chamber is the both ends of the pressure chamber. Is formed narrower than the interval between the side walls at the part,
The side walls are deformed in a direction to decrease the volume of the pressure chamber when the actuator is deformed in a direction to decrease the volume of the pressure chamber when a voltage is applied to the individual electrode. The inkjet head described in 1. 3. The ink jet head according to claim 1 , wherein the both side walls are formed thinner than the partition wall in a cross section perpendicular to the longitudinal direction of the pressure chamber . Having the second thin plate sandwiching the pressure chamber with the actuator;
When no voltage is applied to the individual electrodes, the side walls have a linear shape perpendicular to the second thin plate in a cross section perpendicular to the longitudinal direction of the pressure chamber. The inkjet head according to any one of claims 1 to 3 . When a voltage is applied to the individual electrodes, so that the both side walls buckles inward direction before Symbol pressure chamber, wherein when the voltage to the individual electrode is not applied, the inner said side walls of said pressure chamber The inkjet head according to claim 1, wherein the inkjet head is curved . The pressure chamber is defined by a concave wall body that forms the side walls and a top wall that connects the tips of the both side walls, and one plane of the second thin plate that is a metal thin plate,
The inkjet head according to claim 1, wherein the top wall is sandwiched between the pressure chamber and the actuator. The actuator is
An active layer comprising the plurality of piezoelectric sheets having the active portion and polarized in the stacking direction, and a plurality of the piezoelectric sheets not sandwiched between the individual electrodes and the common electrode, with respect to the active layer A non-active layer on the opposite side of the pressure chamber,
The inkjet head according to claim 1, wherein when an electric field is generated in a polarization direction of the piezoelectric sheet constituting the active layer, the piezoelectric sheet extends in the polarization direction. The actuator is characterized in that a resin adhesive layer that is at least impermeable to ink and has electrical insulation is disposed on the entire lower surface facing the pressure chamber. Item 8. The inkjet head according to any one of Items 1 to 7.

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