JP2006205620A - Liquid transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid transfer device which enables an improvement in the driving efficiency of a piezoelectric actuator and suppressing of cross talk, and moreover which can more surely discharge bubbles that stay in a pressure chamber. <P>SOLUTION: An ink inlet 14a and an ink outlet 14b of the pressure chamber 14 are arranged near an edge of the pressure chamber 14. A groove 40 extending along the edge of the pressure chamber 14 is formed inside the edge of each pressure chamber 14 of a face at the pressure chamber 14 side of a diaphragm 30, and outside a region which overlaps with a discrete electrode 32 (outside a driving part 31a). Moreover, a parting part 41 which parts the groove 40 is set at each of a region that overlaps with the ink inlet 14a and a region that overlaps with the ink outlet 14b of the face at the pressure chamber 14 side of the diaphragm 30. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquid transfer device that transfers liquid by applying pressure thereto.

  Some liquid transfer devices such as inkjet heads that discharge ink from nozzles include a flow path unit in which a liquid flow path is formed and a piezoelectric actuator that applies transfer energy to the liquid in the flow path unit. . For example, in the ink jet head described in Patent Document 1, the flow path unit (substrate) is formed with a plurality of pressure chambers each communicating with a nozzle and a manifold (common passage). The piezoelectric actuator includes a metal diaphragm arranged to cover a plurality of pressure chambers (pressure chambers) of the flow path unit, and lead zirconate titanate (PZT) formed on the surface of the diaphragm. This is a so-called unimorph type piezoelectric actuator including a piezoelectric layer composed of the like and a plurality of upper electrodes (individual electrodes) formed on the surface of the piezoelectric layer so as to correspond to a plurality of pressure chambers.

  When a drive voltage is selectively supplied to the plurality of upper electrodes of the piezoelectric actuator, the piezoelectric layer portion (drive unit) sandwiched between the upper electrode and the metal diaphragm is connected to the drive electrode. An electric field acts in the thickness direction to expand and contract the drive unit. Along with the expansion and contraction of the drive unit, the vibration plate in a region facing the pressure chamber bends, and pressure is applied to the ink in the pressure chamber.

Japanese Patent Laid-Open No. 11-334087 (FIG. 3)

  However, in the piezoelectric actuator as described in Patent Document 1 described above, when the rigidity of the diaphragm in the region facing the pressure chamber (particularly the region around the drive unit) is high, the region facing the pressure chamber. As a whole, the diaphragm is difficult to deform, and the deformation efficiency of the piezoelectric actuator is lowered. In that case, in order to apply a predetermined pressure to the ink in the pressure chamber, it is necessary to apply a high voltage to the individual electrodes, which increases the power consumption of the piezoelectric actuator. Further, when the vibration plate has a high rigidity around the drive unit, when the piezoelectric layer facing a certain pressure chamber and a portion of the vibration plate are deformed, this deformation is caused by the piezoelectric layer facing another adjacent pressure chamber and A phenomenon of propagation to the diaphragm portion, so-called crosstalk occurs. In this case, the deformation amount of the portion of the diaphragm covering each pressure chamber varies depending on the drive patterns of the plurality of pressure chambers (voltage application patterns to the plurality of individual electrodes). In this case, since the ink ejection characteristics such as the droplet velocity and the droplet volume are fluctuated, the print quality is deteriorated.

  In addition, when the ink cartridge is replaced, bubbles may enter the flow path unit, and the bubbles may stay in the pressure chamber. In this state, since a part of the pressure applied to the ink in the pressure chamber by the piezoelectric actuator is absorbed by the bubbles, the ink droplet is not ejected from the nozzle at a normal speed. Will not be injected at all. In such a case, a so-called purge operation is generally performed in which bubbles staying in the pressure chamber are forcibly discharged from the nozzle together with the ink. However, near the inlet where ink flows from the manifold into the pressure chamber, or near the outlet where ink flows out from the pressure chamber to the nozzle, the ink flow changes, so the ink tends to stagnate and the ink flow rate is locally low. Therefore, it is difficult to completely discharge the bubbles remaining in the vicinity of the inlet and the outlet.

  An object of the present invention is to provide a liquid transfer device capable of improving the driving efficiency of a piezoelectric actuator and suppressing crosstalk, and more reliably discharging bubbles staying in a pressure chamber.

Means for Solving the Problems and Effects of the Invention

  According to a first aspect of the present invention, there is provided the liquid transfer device, wherein a plurality of pressure chambers each having a liquid inlet and a liquid outlet are formed along a plane and disposed on one surface of the flow path unit. A piezoelectric actuator that changes the volume of the pressure chamber and applies pressure to the liquid inside the pressure chamber, and the piezoelectric actuator is disposed on the opposite side of the diaphragm from the diaphragm that covers the plurality of pressure chambers. A plurality of individual electrodes respectively disposed in regions overlapping with central portions of the plurality of pressure chambers when viewed from a direction orthogonal to the plane, and the piezoelectric layer between the plurality of individual electrodes. The liquid inlet and the liquid outlet are arranged in the vicinity of the edge of the pressure chamber when viewed from a direction orthogonal to the plane, and are arranged on the pressure chamber side surface of the diaphragm. , A direction perpendicular to the plane As seen, a groove extending along the edge of the pressure chamber is formed in a region inside the edge of each pressure chamber and outside the region overlapping with both the individual electrode and the common electrode, Further, as viewed from a direction orthogonal to the plane of the surface on the pressure chamber side of the diaphragm, the dividing is performed to divide the groove into at least one of a region overlapping with the liquid inlet and a region overlapping with the liquid outlet. A part is provided.

  In this liquid transfer device, when a driving voltage is applied to a certain individual electrode, a portion of the piezoelectric layer (driving unit) located between the individual electrode and the common electrode has a polarization direction in the thickness direction. A parallel electric field is generated. Then, the drive unit extends in the thickness direction and contracts in a direction parallel to the surface, and the diaphragm is deformed along with the deformation of the drive unit, so that the volume of the pressure chamber changes and pressure is applied to the liquid inside the drive chamber. Is granted.

  Here, a groove extending along the edge of the pressure chamber is formed in a region outside the region overlapping the both of the individual electrode and the common electrode (region outside the driving unit) on the pressure chamber side surface of the diaphragm. Has been. Accordingly, in the region where the groove around the drive unit is formed, the rigidity of the diaphragm is lower than that of other portions. Therefore, the diaphragm is more easily deformed when the drive unit is deformed, and the drive efficiency of the piezoelectric actuator is improved. Further, since the rigidity of the diaphragm is reduced in the region outside the drive unit, when a portion of the piezoelectric layer facing a certain pressure chamber is deformed, this deformation is opposed to another adjacent pressure chamber. Propagation hardly occurs in the piezoelectric layer and the diaphragm, and crosstalk is suppressed. In addition, the groove | channel may be extended not only to the area | region outside a drive part but to the area | region which overlaps with a drive part.

  By the way, since the liquid inlet and the liquid outlet are arranged in the vicinity of the edge of the pressure chamber, the liquid tends to stagnate at the liquid inlet and the liquid outlet, and bubbles that have entered the pressure chamber are retained. Cheap. However, in the liquid transfer device according to the first aspect of the present invention, the dividing portion that divides the groove is formed in a region overlapping the liquid inlet or a region overlapping the liquid outlet on the pressure chamber side surface of the diaphragm. Is formed. That is, a groove is not partially formed in a region overlapping with the liquid inflow port or a region overlapping with the liquid outflow port. For this reason, the flow passage area near the liquid inlet or the liquid outlet is narrowed and the flow velocity of the liquid is locally increased, so that bubbles staying near the liquid inlet or the liquid outlet are easily discharged. Become.

  In the liquid transfer device according to a second aspect of the present invention, in the first aspect of the invention, the dividing portion includes a region overlapping the liquid inlet and a region overlapping the liquid outlet on the pressure chamber side surface of the diaphragm. It is provided in both. Accordingly, the flow velocity of the liquid increases at both the liquid inlet and the liquid outlet, and bubbles that have entered the pressure chamber are less likely to stay near the liquid inlet and the liquid outlet, and are easily discharged downstream from the pressure chamber. In addition, since the two divided portions (locations where no groove is formed) are formed, the rigidity of the entire diaphragm is relatively high, and the diaphragm can be easily handled during manufacturing.

  According to a third aspect of the present invention, there is provided the liquid transfer device according to the first or second aspect, wherein a thickness of the dividing portion of the diaphragm is equal to a thickness of a portion where the groove is not formed. It is. Therefore, the dividing portion can be formed at the same time by forming the groove except for the portion that overlaps at least one of the liquid inlet and the liquid outlet in the portion along the edge of the pressure chamber of the diaphragm. The process of forming the dividing portion separately from the groove is not necessary, and the manufacturing process can be simplified.

  According to a fourth aspect of the present invention, there is provided the liquid transfer device according to any one of the first to third aspects, wherein the dividing portion is formed in a tapered shape that becomes narrower toward the pressure chamber side. . Therefore, since the angle of the corner between the dividing portion and the groove is larger than 90 degrees, the bubbles are less likely to stay in the corner, and the bubbles can be discharged more reliably.

  In a liquid transfer device according to a fifth aspect of the present invention, in any one of the first to fourth aspects, the plurality of pressure chambers are each formed in a shape that is long in a predetermined direction, and the length of each pressure chamber is The liquid inflow port and the liquid outflow port are provided at both ends in the direction. If the propagation time of the pressure wave generated in the pressure chamber is too short, it may not be possible to transfer a desired amount of liquid, so if the pressure chamber is formed in a long shape in one direction, In order to increase the propagation time of the pressure wave inside to some extent, it is preferable that a liquid inlet and a liquid outlet are formed at both longitudinal ends of the pressure chamber. In this case, the dividing portion is provided in a region overlapping with the longitudinal end portion of the pressure chamber. Therefore, the rigidity of the diaphragm in the region overlapping with the end portion in the longitudinal direction is higher than that in the region overlapping with the end portion in the short direction of the pressure chamber in which a groove extending along the edge of the pressure chamber is formed. However, the rigidity of the diaphragm in the region overlapping with the end portion in the longitudinal direction of the pressure chamber does not affect the driving efficiency (deformation efficiency of the diaphragm) of the piezoelectric actuator in the region overlapping with the end portion in the short direction. In other words, by arranging the dividing portion in a region overlapping the longitudinal direction end portion of the pressure chamber that does not significantly affect the driving efficiency, it is possible to suppress a decrease in the driving efficiency of the piezoelectric actuator due to the dividing portion as much as possible.

  The liquid transfer device according to a sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the groove has a tapered cross-sectional shape that expands toward the pressure chamber side. Therefore, since the angle of the corner of the groove is larger than 90 degrees, it is difficult for bubbles to accumulate in the corner, and the bubbles can be discharged more reliably.

  According to a seventh aspect of the present invention, in the liquid transfer device according to any one of the first to sixth aspects, the flow path unit has a common liquid chamber communicating with the plurality of pressure chambers. When viewed from the direction orthogonal to the region extending to the outside of the region overlapping the pressure chamber, a portion extending to the outside of the region overlapping the pressure chamber of the groove, and one surface of the flow path unit Between the common liquid chamber and each pressure chamber, a throttle channel having a partially narrowed channel area is formed. The throttle channel provided between the common liquid chamber and each pressure chamber is used to throttle the channel so that the pressure wave generated in each pressure chamber is difficult to propagate to the common liquid chamber. The flow path area of the flow path has a great influence on the propagation of the pressure wave in the pressure chamber, and hence the liquid transfer amount, etc. Therefore, the throttle flow path needs to be formed with high accuracy. Here, since the throttle channel is formed between a part of the groove and one surface of the channel unit, the throttle channel can be formed simultaneously by forming the groove in the diaphragm. become. Therefore, the manufacturing process can be simplified and the yield can be reduced as compared with the case where the narrowing channel that needs to be formed with high accuracy is formed by half etching or the like separately from the groove.

  The liquid transfer device according to an eighth aspect of the present invention is the fluid transfer device according to any one of the first to seventh aspects, wherein the region outside the pressure chamber corresponds to the individual electrode from each individual electrode when viewed from the direction orthogonal to the plane. And each terminal portion is arranged in a region overlapping with the dividing portion when viewed from a direction orthogonal to the plane. That is, since the groove is not formed, the terminal portion is provided in a region overlapping with the dividing portion having higher strength than other portions. Therefore, for example, when connecting a wiring member such as a flexible printed circuit (FPC) for supplying a driving voltage to the individual electrode to each terminal portion, the wiring member is sufficiently pressed against the terminal portion. Thus, the terminal portion and the wiring member can be reliably bonded.

A first embodiment of the present invention will be described. This first embodiment is an example in which the present invention is applied to an inkjet head that ejects ink from nozzles onto recording paper as a liquid transfer device.
First, the ink jet printer 100 including the ink jet head 1 will be briefly described. As shown in FIG. 1, an inkjet printer 100 includes a carriage 101 that can move in the left-right direction in FIG. 1, a serial inkjet head 1 that is provided on the carriage 101 and that ejects ink onto a recording paper P, A conveyance roller 102 that conveys the recording paper P forward in FIG. 1 is provided. The ink-jet head 1 moves in the left-right direction (scanning direction) integrally with the carriage 101, and is applied to the recording paper P from the emission port of the nozzle 20 (see FIGS. 6 to 8) formed on the lower surface of the ink ejection surface. On the other hand, ink is ejected. Then, the recording paper P recorded by the inkjet head 1 is discharged forward (paper feeding direction) by the transport roller 102.

Next, the inkjet head 1 will be described in detail with reference to FIGS.
As shown in FIGS. 2 to 8, the inkjet head 1 is disposed on a flow path unit 2 in which an individual ink flow path 21 (see FIG. 6) including a pressure chamber 14 is formed, and on the upper surface of the flow path unit 2. And a piezoelectric actuator 3.

  First, the flow path unit 2 will be described. As shown in FIGS. 3, 4, and 6 to 8, the flow path unit 2 includes a cavity plate 10, a base plate 11, a manifold plate 12, and a nozzle plate 13. Bonded in a stacked state. Among these, the cavity plate 10, the base plate 11 and the manifold plate 12 are stainless steel plates, and ink flow paths such as a manifold 17 and a pressure chamber 14 described later can be easily etched in these three plates 10-12. It can be formed. The nozzle plate 13 is formed of, for example, a polymer synthetic resin material such as polyimide, and is bonded to the lower surface of the manifold plate 12. Or this nozzle plate 13 may be formed with metal materials, such as stainless steel, similarly to the three plates 10-12.

  As shown in FIG. 2 to FIG. 4 and FIG. 6 to FIG. 8, the cavity plate 10 is formed with a plurality of pressure chambers 14 arranged along a plane. It opens to the diaphragm 30 side (upward in FIG. 4). The plurality of pressure chambers 14 are arranged in two rows in the paper feeding direction (up and down direction in FIG. 2). Each pressure chamber 14 is formed in a substantially elliptical shape that is long in the scanning direction (left-right direction in FIG. 2) in plan view.

  The pressure chamber 14 has an ink inlet 14a (liquid inlet) and an ink outlet 14b (liquid outlet) both having a circular planar shape. Here, when pressure is applied to the ink in the pressure chamber 14 by the piezoelectric actuator 3 described later, if the propagation time of the pressure wave generated in the pressure chamber 14 is too short, a desired amount of ink is ejected from the nozzle 20. You may not be able to. Therefore, in order to increase the propagation time of the pressure wave in the pressure chamber 14 to some extent, the separation distance between the ink inlet 14a and the ink outlet 14b is preferably as large as possible. Therefore, in the ink jet head 1 of the first embodiment, the ink inlet 14a and the ink outlet 14b are disposed in the vicinity of the edge of the pressure chamber 14 and at both ends in the longitudinal direction of the pressure chamber 14, respectively. . That is, in the pressure chambers 14 arranged on the left side of FIG. 2, the ink inlet 14a is disposed at the left end portion, and the ink outlet 14b is disposed at the right end portion. On the other hand, in the pressure chambers 14 arranged on the right side of FIG. 2, an ink inflow port 14a is disposed at the right end, and an ink outflow port 14b is disposed at the left end.

  As shown in FIGS. 3 and 4, communication holes 15 and 16 are formed at positions where the base plate 11 overlaps the ink inlet 14 a and the ink outlet 14 b of the pressure chamber 14 in plan view, respectively. The manifold plate 12 is formed with a manifold 17 extending in the paper feeding direction (vertical direction in FIG. 2). 2 to 4, the manifold 17 overlaps the left half of the pressure chambers 14 arranged on the left side and the right half of the pressure chambers 14 arranged on the right side in plan view. Is arranged. The manifold 17 is connected to an ink supply port 18 formed in a vibration plate 30 described later, and ink is supplied from an ink tank (not shown) through the ink supply port 18. A plurality of communication holes 19 that are continuous with the plurality of communication holes 16 are also formed at positions where the manifold plate 12 overlaps the ends of the pressure chambers 14 opposite to the manifolds 17 in plan view. Further, a plurality of nozzles 20 are respectively formed at positions where the nozzle plate 13 overlaps the plurality of communication holes 19 in a plan view. These nozzles 20 are formed by, for example, excimer laser processing on a polymer synthetic resin substrate such as polyimide. In addition, the communication hole 16, the communication hole 19, and the nozzle 20 are each arrange | positioned in the position which becomes concentric with the ink outflow port 14b by planar view.

  As shown in FIG. 6, the manifold 17 communicates with the ink inlet 14 a of the pressure chamber 14 through the communication hole 15, and the ink outlet 14 b of the pressure chamber 14 passes through the communication holes 16 and 19. It communicates with the nozzle 20. In this way, the individual ink flow path 21 extending from the manifold 17 to the nozzle 20 through the pressure chamber 14 is formed in the flow path unit 2.

  Next, the piezoelectric actuator 3 will be described. As shown in FIGS. 2, 3, 5 to 8, the piezoelectric actuator 3 includes a vibration plate 30 disposed on the upper surface of the flow path unit 2, and an upper surface of the vibration plate 30 (on the side opposite to the pressure chamber 14). And a plurality of individual electrodes 32 formed on the upper surface of the piezoelectric layer 31 so as to correspond to the plurality of pressure chambers 14, respectively.

  The diaphragm 30 is a plate made of a substantially rectangular metal material in plan view, and is made of, for example, an iron-based alloy such as stainless steel, a copper-based alloy, a nickel-based alloy, or a titanium-based alloy. The diaphragm 30 is disposed on the upper surface of the cavity plate 10 so as to cover the plurality of pressure chambers 14, and is joined to the upper surface of the cavity plate 10. The metal diaphragm 30 has conductivity, and also serves as a common electrode for applying an electric field to the piezoelectric layer 31 sandwiched between the diaphragm 30 and the individual electrode 32.

  As shown in FIGS. 3 and 7, the pressure chamber 14 is formed on the lower surface (the surface on the pressure chamber 14 side) of the diaphragm 30 in a plan view (viewed from a direction orthogonal to the plane on which the pressure chamber 14 is disposed). A groove 40 extending substantially the same width along the edge of the pressure chamber 14 is formed in an annular shape inside the edge of the pressure chamber 14 and outside the region overlapping the individual electrode 32. And in the part in which this groove | channel 40 was formed, since the thickness of the diaphragm 30 is thinner than the other part, the rigidity of the diaphragm 30 partially falls. The groove 40 can be formed using various processing methods such as half etching and press processing.

  Further, as shown in FIGS. 3 and 8, an area overlapping the ink inlet 14 a (communication hole 15) and an area overlapping the ink outlet 14 b (communication hole 16) in plan view on the lower surface of the vibration plate 30 are Two dividing portions 41 that extend in the longitudinal direction of the pressure chamber 14 (left and right direction in FIGS. 2 and 3) and divide the groove 40 are provided. The width of the dividing portion 41 is smaller than the diameters of the ink inlet 14a and the ink outlet 14b having a circular planar shape, and is formed so as to cross the centers of the ink inlet 14a and the ink outlet 14b to the left and right. ing. That is, the groove 40 is not formed in a region overlapping with the central portion of the ink inlet 14a and a region overlapping with the central portion of the ink outlet 14b. The grooves 40 and the dividing portions 41 will be described in more detail later together with the actions and effects thereof.

  On the upper surface of the diaphragm 30, a piezoelectric layer 31 mainly composed of lead zirconate titanate (PZT), which is a solid solution and is a ferroelectric substance, is formed of lead titanate and lead zirconate. As shown in FIGS. 2, 3, 7, and 8, the piezoelectric layer 31 is continuously formed across the plurality of pressure chambers 14 on the upper surface of the vibration plate 30. Here, the piezoelectric layer 31 can be formed using, for example, an aerosol deposition method (AD method) in which particles of very small piezoelectric material are sprayed onto a substrate to collide at high speed and deposited on the substrate. Alternatively, it can be formed by a sputtering method, a chemical vapor deposition method (CVD method), a sol-gel method, a hydrothermal synthesis method, or the like.

  A plurality of individual electrodes 32 having an elliptical planar shape that is slightly smaller than the pressure chamber 14 are formed on the upper surface of the piezoelectric layer 31. Each of the plurality of individual electrodes 32 is formed at a position overlapping the central portion of the corresponding pressure chamber 14 in plan view. The individual electrode 32 is made of a conductive material such as gold, copper, silver, palladium, platinum, or titanium. Further, on the upper surface of the piezoelectric layer 31, the region outside the corresponding pressure chamber 14 is parallel to the longitudinal direction (left and right direction in FIG. 2) of the individual electrode 32 from the end of the plurality of individual electrodes 32 on the manifold 17 side. A plurality of terminal portions 35 are also formed extending respectively. Here, the plurality of individual electrodes 32 and the plurality of terminal portions 35 can be formed by, for example, screen printing, sputtering, vapor deposition, or the like. A flexible wiring member (not shown) such as a flexible printed circuit (FPC) is joined to the plurality of terminal portions 35, and as shown in FIG. 6, the driver IC 37 is interposed via the wiring member. And are electrically connected. Then, a drive voltage is selectively supplied from the driver IC 37 to the plurality of individual electrodes 32 via the terminal portion 35.

  As shown in FIGS. 2 and 3, the terminal portion 35 extends to a region outside the pressure chamber 14 through a region overlapping with the dividing portion 41 located above the ink inlet 14 a in a plan view. . Here, as described above, since the dividing portion 41 is a portion where the groove 40 is not partially formed, the strength of the diaphragm 30 in the dividing portion 41 is higher than the portion where the groove 40 is formed. ing. Therefore, when connecting a wiring member such as an FPC to the terminal part 35, the wiring member is sufficiently pressed against the terminal part 35, so that the terminal part 35 and the wiring member can be reliably joined, and the electrical Connection reliability is improved.

  Next, the operation of the piezoelectric actuator 3 will be described. When a driving voltage is selectively applied to the plurality of individual electrodes 32 from the driver IC 37, the individual electrodes 32 on the upper side of the piezoelectric layer 31 to which the driving voltage is supplied and the lower side of the piezoelectric layer 31 held at the ground potential. The potentials of the diaphragm 30 as the common electrode are in different states, and an electric field in the vertical direction is generated in the portion of the piezoelectric layer 31 (drive unit 31a) sandwiched between the individual electrode 32 and the diaphragm 30. Then, the piezoelectric layer 31 of the drive unit 31a contracts in a horizontal direction perpendicular to the vertical direction that is the polarization direction. At this time, as the piezoelectric layer 31 contracts, the vibration plate 30 is deformed so that the surface to be bonded to the piezoelectric layer 31 contracts and protrudes toward the pressure chamber 14. Decreases, pressure is applied to the ink in the pressure chamber 14, and ink droplets are ejected from the nozzle 20 communicating with the pressure chamber 14.

  By the way, as described above, a region overlapping the individual electrode 32 (and the diaphragm 30 as the common electrode) on the lower surface (the surface on the pressure chamber 14 side) of the diaphragm 30, that is, a piezoelectric layer that deforms the diaphragm 30. A groove 40 extending along the edge of the pressure chamber 14 is formed in a region outside the drive unit 31 a of 31. That is, in the area around the drive unit 31a, the thickness of the diaphragm 30 is thinner than other parts. Here, since the bending rigidity of the plate material is proportional to the cube of the plate thickness, the rigidity of the diaphragm 30 in the portion where the groove 40 is formed is lower than the other portion where the groove 40 is not formed. Become. Therefore, when the driving voltage is applied to the individual electrode 32 and the driving unit 31a is deformed, the surrounding diaphragm 30 is more easily deformed, so that the driving voltage applied to the individual electrode 32 can be lowered. The driving efficiency of the piezoelectric actuator 3 is improved.

  Further, in the piezoelectric actuator 3 according to the first embodiment, since the piezoelectric layer 31 is continuously formed over the plurality of pressure chambers 14, the drive unit 31 a of the piezoelectric layer 31 facing the certain pressure chamber 14. In particular, a phenomenon (so-called crosstalk) in which the deformation of the drive unit 31a propagates to the piezoelectric layer 31 and the diaphragm 30 facing another adjacent pressure chamber 14 easily occurs. However, as described above, since the rigidity of the diaphragm 30 is reduced in the region outside the drive unit 31a where the groove 40 is formed, the deformation of the drive unit 31a propagates to the surrounding pressure chamber 14. Since it becomes difficult, crosstalk is suppressed.

  By the way, when the ink cartridge is replaced, air may enter the flow path unit 2 and air bubbles may remain in the pressure chamber 14. In this state, since a part of the pressure applied to the ink in the pressure chamber 14 by the piezoelectric actuator 3 is absorbed by the bubbles, the bubbles staying in the pressure chamber 14 are forcibly discharged from the nozzle 20 together with the ink. It is necessary to perform a so-called purge operation. This purge operation is performed, for example, by forcibly sucking ink from the nozzle 20 side with a purge pump.

  Here, as shown in FIGS. 2 to 4 and 6, the ink inlet 14 a and the ink outlet 14 b are disposed in the vicinity of the edge of the pressure chamber 14, and further, the ink inlet 14 a and the ink outlet 14 b are arranged. At the outlet 14b, the ink flow direction changes substantially at right angles, so that the ink is stagnated and a point where the ink flow velocity is locally low occurs. For this reason, bubbles that have entered the pressure chamber 14 tend to stay near the ink inlet 14a and the ink outlet 14b. Further, the ink inflow port 14a and the ink outflow port 14b are respectively disposed at both ends in the longitudinal direction of the substantially elliptical pressure chamber 14 in plan view. Therefore, as shown by the arrow in FIG. 4, the ink that has flowed into the pressure chamber 14 from the ink inlet 14 a located at one end (the right end in FIG. 4) of the pressure chamber 14 extends in the longitudinal direction of the pressure chamber 14. A flow symmetric with respect to the center line C (see FIG. 4) is formed and flows out from the ink outlet 14b located at the other end of the pressure chamber 14 (left end in FIG. 4). For this reason, the ink flow outlet 14b has a point where the line-symmetric flow in the pressure chamber 14 collides and the velocity becomes almost zero, so that bubbles are particularly likely to remain.

  However, in the inkjet head 1 according to the first embodiment, the pressure chamber 14 is located in a region of the lower surface of the vibration plate 30 that overlaps the central portion of the ink inlet 14a and a region that overlaps the central portion of the ink outlet 14b. A dividing portion 41 that extends in the longitudinal direction and divides the groove 40 is formed. That is, the groove 40 is not formed in the region of the lower surface of the diaphragm 30 that overlaps the ink inlet 14a and the ink outlet 14b, and the dividing portion 41 has the groove 40 as shown in FIG. Projects downward from the surrounding area. For this reason, the flow path area in the vicinity of the ink inlet 14a and the ink outlet 14b is locally narrowed, and the ink flow velocity is increased. Accordingly, the bubbles staying in the vicinity of the ink inlet 14a and the ink outlet 14b can be reliably discharged together with the ink from the nozzle 20 during the purge operation.

  The dividing portion 41 is provided in both the area overlapping the ink inlet 14a and the area overlapping the ink outlet 14b on the lower surface of the vibration plate 30, and therefore, in both the ink inlet 14a and the ink outlet 14b. The flow rate of the ink is increased, and the bubbles staying in the pressure chamber 14 are more reliably discharged. Further, even if the rigidity of the diaphragm 30 is locally reduced in the portion where the groove 40 is formed, the dividing portion 41 (the portion where the groove 40 is not formed) is formed in two places. The rigidity of the entire diaphragm 30 is relatively high, and handling of the diaphragm 30 (for example, carrying of the diaphragm 30 and adhesion to the cavity plate 10) during manufacture and the like becomes easy. In particular, when the piezoelectric layer 31 is formed on the upper surface of the vibration plate 30 by the AD method, particles of the piezoelectric material collide with the vibration plate 30 at a high speed, which is sufficient to withstand the impact at that time. Strength can be secured.

  Further, as shown in FIG. 8, the thickness of the dividing portion 41 of the diaphragm 30 is equal to the thickness of the portion other than the dividing portion 41 where the groove 40 is not formed. Therefore, the ink 40 can be formed simply by forming the groove 40 by etching, pressing, or the like on the portion of the metallic diaphragm 30 along the edge of the pressure chamber 14 except for the portion overlapping the ink inlet 14a and the ink outlet 14b. Since the dividing portion 41 can be simultaneously formed in the region overlapping with the inflow port 14a and the ink outflow port 14b, a step of forming the dividing portion 41 separately from the groove 40 is not required, and the manufacturing process of the inkjet head 1 can be simplified.

  Further, as shown in FIGS. 7 and 8, the groove 40 has a tapered cross-sectional shape that expands toward the pressure chamber 14 side (lower side), and the angle of the corner of the groove 40 is larger than 90 degrees. . Further, as shown in FIG. 8, the dividing portion 41 is formed in a tapered shape that becomes thinner toward the pressure chamber 14 side (lower side), and the angle of the corner between the dividing portion 41 and the groove 40 is 90 degrees. It is getting bigger. Therefore, bubbles are less likely to stay in the corners of the grooves 40 or in the corners between the dividing portions 41 and the grooves 40, and the bubbles in the pressure chamber 14 can be discharged more reliably. Here, the groove 40 and the dividing portion 41 can be formed so that the angle of the corner becomes a desired angle by adjusting the processing conditions such as the etching rate, for example.

  In addition, when the dividing part 41 is arrange | positioned in the vicinity of the edge of the pressure chamber 14 (the groove | channel 40 is not partially formed), when there is no dividing part 41 (an undivided annular groove is formed). As compared with the case), the vibration efficiency of the piezoelectric actuator 3 is slightly lowered because the diaphragm 30 is somewhat difficult to deform. However, the rigidity of the diaphragm 30 in the region overlapping with both ends in the longitudinal direction of the pressure chamber 14 does not affect the driving efficiency of the piezoelectric actuator 3 in the region overlapping with both ends in the width direction (short direction). In other words, by disposing the dividing portion 41 in a region that overlaps both longitudinal ends of the pressure chamber 14 that does not significantly affect the driving efficiency of the piezoelectric actuator 3, the driving efficiency of the piezoelectric actuator 3 caused by the dividing portion 41 is reduced. It can be suppressed as much as possible.

  Next, modified embodiments in which various modifications are made to the first embodiment will be described. However, components having the same configuration as in the first embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

  1] In the first embodiment, the width of the dividing portion 41 is smaller than the diameters of the circular ink inlet port 14a and the ink outlet port 14b. However, as shown in FIG. It may be formed in a larger width that overlaps the entire area of the inlet 14a (communication hole 15) and the ink outlet 14b (communication hole 16) (Modification 1).

  2] Further, as shown in FIG. 10, the region where the groove 40B extending along the edge of the pressure chamber 14 overlaps the individual electrode 32 (and the diaphragm 30 as the common electrode), that is, the driving portion of the piezoelectric layer 31. May extend to a region overlapping with (Modification 2).

  3] On the upper surface of the vibration plate 30, it is not always necessary that the piezoelectric layer be continuously formed across the plurality of pressure chambers 14, and as shown in FIG. Thus, a plurality of piezoelectric layers 31C may be arranged (Modification 3).

  4] Unlike the piezoelectric actuator 3 of the first embodiment, the diaphragm 30 does not necessarily have to serve as a common electrode, and the common electrode 34 is provided separately from the diaphragm 30 as shown in FIG. (Modification 4). However, when the diaphragm 30 is a metal plate, the diaphragm 30 and the common electrode 34 need to be insulated by an insulating material layer made of a ceramic material, a synthetic resin material, or the like. On the other hand, when the diaphragm 30 is made of an insulating material, the common electrode 34 is directly formed on the upper surface of the diaphragm 30.

  5] It is not always necessary that the dividing portion is provided in both the region overlapping with the ink inlet 14a and the region overlapping with the ink outlet 14b. An effect is obtained.

  6] The shape of the pressure chamber is not limited to that having a planar shape that is long in one direction, like the pressure chamber 14 of the first embodiment. For example, the present invention can be applied to an ink jet head having a pressure chamber formed in a circular shape or a square shape.

  Next, a second embodiment of the present invention will be described. This second embodiment is also an example in which the present invention is applied to an inkjet head. However, components having the same configuration as in the first embodiment are denoted by the same reference numerals and description thereof is omitted as appropriate.

  As shown in FIGS. 13 to 16, the inkjet head 51 according to the second embodiment is disposed on a flow path unit 52 in which an ink flow path including a plurality of pressure chambers 64 is formed, and on the upper surface of the flow path unit 52. And a piezoelectric actuator.

  As shown in FIGS. 14 and 16, the flow path unit 52 includes a cavity plate 60, a base plate 11, a manifold plate 12, and a nozzle plate 13, and these four plates 60, 11, 12, and 13 are laminated. It is joined in a state. Of these four plates 60, 11, 12, 13, the three plates of the base plate 11, the manifold plate 12, and the nozzle plate 13 are the same as those in the first embodiment, and the description thereof is omitted. .

  In the cavity plate 60, a plurality of pressure chambers 64 arranged along a plane are formed. Each pressure chamber 64 is formed in a shape obtained by removing one end in the longitudinal direction (the right end in FIG. 14) from a substantially elliptical shape (the shape of the pressure chamber 14 of the first embodiment) in plan view. . A circular communication hole 65 that overlaps with the communication hole 15 of the base plate 11 in plan view is formed on the right side of the pressure chamber 64 in FIGS. 13 and 14. The pressure chamber 64 and the communication hole 65 are separated from each other by a partition wall 66 positioned therebetween. Further, as shown in FIG. 16, an ink inflow port 64 a is formed between the right end edge of the pressure chamber 64 and a vibration plate 70 which will be described later, and further, a pressure is applied between the partition wall 66 and the vibration plate 70. A throttle channel 67 that connects the chamber 64 and the communication hole 65 is formed. On the other hand, a circular ink outlet 64 b that overlaps the communication hole 16 of the base plate 11 in a plan view is formed at the left end of the pressure chamber 64. That is, as shown in FIG. 16, the manifold 17 communicates with the pressure chamber 64 via the communication holes 15 and 65, the throttle channel 67, and the ink inlet 64a, and the pressure chamber 64 further includes an ink outlet. The nozzle 20 communicates with the nozzle 64 through the communication holes 16 and 19.

  As shown in FIGS. 13, 15, and 16, the piezoelectric actuator 53 is provided on the vibration plate 70 disposed on the upper surface of the flow path unit 52 and on the upper surface of the vibration plate 70 (the surface opposite to the pressure chamber 64). The formed piezoelectric layer 31 and a plurality of individual electrodes 32 formed on the upper surface of the piezoelectric layer 31 respectively corresponding to the plurality of pressure chambers 64 are provided. The piezoelectric layer 31 and the individual electrode 32 are the same as those in the first embodiment, and a description thereof will be omitted.

  The diaphragm 70 is joined to the cavity plate 60 so as to cover the plurality of pressure chambers 64. Here, on the lower surface of the diaphragm 70 (the surface opposite to the pressure chamber 64), the pressure chamber 64 is located inside the edge of the pressure chamber 64 and outside the region overlapping the individual electrode 32 in plan view. A groove 80 extending along the edge is formed in a substantially annular shape. Therefore, the diaphragm 70 is easily deformed in the portion where the groove 80 is formed, and the driving efficiency of the piezoelectric actuator 53 is improved. Moreover, crosstalk is also suppressed.

  In addition, a dividing portion 81 that extends in the longitudinal direction of the pressure chamber 64 (left and right direction in FIG. 13) and divides the groove 80 is provided in a region of the lower surface of the vibration plate 70 that overlaps the ink outlet 64b in plan view. It has been. That is, the groove 80 is not formed in a region of the vibration plate 70 that overlaps the central portion of the ink outlet 64 b, and the flow path area near the ink outlet 64 b is narrowed by the dividing portion 81. For this reason, since the ink flow rate is locally increased at the ink outlet 64b, it is easy to discharge bubbles remaining in the pressure chamber 64 during the purge operation.

  Further, the groove 80 formed on the lower surface of the diaphragm 70 extends in a substantially semicircular shape to the right in FIG. 13 so as to cover even the communication hole 65 outside the pressure chamber 64. As shown in FIG. 16, an ink inlet 64 a is formed between the portion of the diaphragm 70 where the groove 80 is formed and the end of the pressure chamber 64, and further, between the upper surface of the partition wall 66. A throttle channel 67 is formed. Here, the flow path height of the throttle flow path 67 is equal to the depth of the groove 80. Therefore, the flow passage area of the throttle channel 67 is sufficiently narrow between the pressure chamber 64 and the manifold 17 as compared with the ink inlet 64 a and the communication holes 65 and 15. The pressure wave generated in the pressure chamber 64 is difficult to propagate to the manifold 17.

  By the way, the flow passage area of the throttle flow passage 67 affects the propagation of the pressure wave in the pressure chamber 64, and as a result, the ink discharge characteristics such as the droplet velocity and the droplet volume of the ink discharged from the nozzle 20 are large. Therefore, the throttle channel 67 needs to be formed with considerably high accuracy. However, in the ink jet head 51 of the second embodiment, the throttle channel 67 is formed between a part of the groove 80 formed on the lower surface of the vibration plate 70 and the upper surface of the cavity plate 60 (channel unit 52). Therefore, only by forming the groove 80 in the diaphragm 70 with high accuracy, the throttle channel 67 is also formed at the same time. Therefore, the manufacturing process of the inkjet head 51 can be simplified and the yield can be reduced as compared with the case where the throttle channel 67 is formed by half etching or the like separately from the groove 80.

  As mentioned above, although the form which applied this invention to the inkjet head was described taking the 1st Embodiment and 2nd Embodiment as an example, the form which can apply this invention is these 1st Embodiment and 2nd Embodiment. It is not limited. For example, the present invention can be applied to various liquid transfer devices that transfer liquids other than ink.

1 is a schematic configuration diagram of an inkjet printer according to a first embodiment of the present invention. It is a top view of an inkjet head. FIG. 3 is a partially enlarged view of FIG. 2. It is a partially expanded plan view of a flow path unit. FIG. 4 is a partially enlarged plan view of a diaphragm. It is the VI-VI sectional view taken on the line of FIG. It is the VII-VII sectional view taken on the line of FIG. It is the VIII-VIII sectional view taken on the line of FIG. It is FIG. 3 equivalent view of the modification 1 of 1st Embodiment. FIG. 6 is a diagram corresponding to FIG. FIG. 8 is a diagram corresponding to FIG. FIG. 7 is a diagram corresponding to FIG. FIG. 5 is a partially enlarged plan view of an inkjet head according to a second embodiment of the present invention. It is a partially expanded plan view of a flow path unit. FIG. 4 is a partially enlarged plan view of a diaphragm. It is the XVI-XVI sectional view taken on the line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Flow path unit 3 Piezoelectric actuator 14 Pressure chamber 14a Ink inlet 14b Ink outlet 17 Manifold 30 Diaphragm 31, 31C Piezoelectric layer 32 Individual electrode 34 Common electrode 35 Terminal part 40, 40B Groove 41, 41A Dividing part 51 Inkjet head 52 Channel unit 53 Piezoelectric actuator 64 Pressure chamber 64a Ink inlet 64b Ink outlet 67 Restriction channel 70 Diaphragm 80 Groove 81 Dividing part

Claims (8)

A plurality of pressure chambers each having a liquid inlet and a liquid outlet are formed along a plane, and are arranged on one surface of the channel unit, and the volume of the pressure chamber is changed to change the inside of the channel. A piezoelectric actuator that applies pressure to the liquid of
The piezoelectric actuator includes a diaphragm that covers the plurality of pressure chambers, a piezoelectric layer that is disposed on the opposite side of the diaphragm from the pressure chamber, a central portion of the plurality of pressure chambers as viewed from a direction orthogonal to the plane, A plurality of individual electrodes respectively disposed in the overlapping region, and a common electrode sandwiching the piezoelectric layer between the plurality of individual electrodes,
The liquid inflow port and the liquid outflow port are disposed in the vicinity of the edge of the pressure chamber when viewed from a direction orthogonal to the plane,
As seen from the direction perpendicular to the plane of the surface on the pressure chamber side of the diaphragm, in the region inside the edge of each pressure chamber and outside the region overlapping both the individual electrode and the common electrode Is formed with a groove extending along the edge of the pressure chamber,
Further, as viewed from a direction orthogonal to the plane of the surface on the pressure chamber side of the diaphragm, the dividing is performed to divide the groove into at least one of a region overlapping with the liquid inlet and a region overlapping with the liquid outlet. A liquid transfer device characterized in that a part is provided.   The said parting part is provided in both the area | region which overlaps with the said liquid inflow port, and the area | region which overlaps with the said liquid outflow port of the surface at the side of the said pressure chamber of the said diaphragm. Liquid transfer device.   3. The liquid transfer device according to claim 1, wherein a thickness of the dividing portion of the diaphragm is equal to a thickness of a portion where the groove is not formed.   The liquid transfer device according to claim 1, wherein the dividing portion is formed in a tapered shape that becomes thinner toward the pressure chamber side. Each of the plurality of pressure chambers is formed in a long shape in one predetermined direction,
The liquid transfer device according to claim 1, wherein the liquid inflow port and the liquid outflow port are provided at both ends in the longitudinal direction of each pressure chamber.   The liquid transfer device according to claim 1, wherein the groove has a tapered cross-sectional shape that widens toward the pressure chamber side. The flow path unit has a common liquid chamber communicating with the plurality of pressure chambers,
The groove extends to a region outside the region overlapping the pressure chamber when viewed from a direction orthogonal to the plane,
The channel area is partially narrow between the common liquid chamber and each pressure chamber between the portion of the groove extending outside the region overlapping the pressure chamber and one surface of the channel unit. The liquid transfer device according to claim 1, wherein a throttle channel is formed. A terminal portion extending from each individual electrode to a region outside the pressure chamber corresponding to the individual electrode when viewed from a direction orthogonal to the plane;
8. The liquid transfer device according to claim 1, wherein each terminal portion is disposed in a region overlapping with the dividing portion when viewed from a direction orthogonal to the plane.

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