JP4831104B2 - Liquid pressure generation mechanism - Google Patents

Description

  The present invention relates to a liquid pressure generating mechanism used to apply pressure to ink accommodated in an ink chamber, for example, in an ink jet printer.

  A piezo method is known as an example of a liquid pressure generating mechanism used for applying pressure to ink stored in a pressure chamber in an inkjet head (Patent Documents 1 and 2). FIG. 9 shows a cross-sectional view of an ink jet head having a piezoelectric liquid pressure generating mechanism as an actuator unit. The inkjet head 101 depicted in FIG. 9 includes an actuator unit 106 driven by a drive pulse signal (selectively taking either a ground potential or a positive predetermined potential) generated by a drive circuit (not shown), and an ink flow. A flow path unit 107 that forms a path is stacked. The actuator unit 106 and the flow path unit 107 are bonded together by an epoxy thermosetting adhesive. A flexible wiring board (not shown) or the like is joined to the upper surface of the actuator unit 106 in order to apply a drive pulse signal generated by a drive circuit (not shown).

  The flow path unit 107 includes three thin plate plates (cavity plate 107a, spacer plate 107b, manifold plate 107c) made of a metal material, and a nozzle plate made of a synthetic resin such as polyimide having a nozzle 109 for ejecting ink. 107d is laminated. The uppermost cavity plate 107 a is in contact with the actuator unit 106.

  On the surface of the cavity plate 107a, a plurality of pressure chambers 110 for storing ink selectively ejected by the operation of the actuator unit 106 are formed in two rows along the longitudinal direction. The plurality of pressure chambers 110 are separated from each other by a partition wall 110a, and are arranged with their longitudinal directions aligned in parallel. The spacer plate 107b is formed with a communication hole 111 for communicating one end of the pressure chamber 110 with the nozzle 109 and a communication hole (not shown) for communicating the other end of the pressure chamber 110 with a manifold channel (not shown). Has been.

  The manifold plate 107 c is formed with a communication hole 113 that allows one end of the pressure chamber 110 to communicate with the nozzle 109. Further, a manifold channel that supplies ink to each pressure chamber 110 is formed in the manifold plate 107 c so as to be long in the column direction below the column formed by the plurality of pressure chambers 110. One end of the manifold channel is connected to an ink supply source (not shown). In this way, an ink flow path is formed from the manifold flow path to the nozzle 109 through the communication hole (not shown), the pressure chamber 110, the communication hole 111, and the communication hole 113.

  In the actuator unit 106, six piezoelectric ceramic plates 106a to 106f made of a ceramic material of lead zirconate titanate (PZT) are laminated. The common electrodes 121 and 123 correspond to the pressure chamber 110 of the flow path unit 107 between the piezoelectric ceramic plate 106b and the piezoelectric ceramic plate 106c and between the piezoelectric ceramic plate 106d and the piezoelectric ceramic plate 106e, respectively. It is arranged only within the range. On the other hand, individual electrodes 122 and 124 correspond to the pressure chamber 110 of the flow path unit 107 between the piezoelectric ceramic plate 106c and the piezoelectric ceramic plate 106d and between the piezoelectric ceramic plate 106e and the piezoelectric ceramic plate 106f, respectively. It is placed only within the range.

  The common electrodes 121 and 123 are always held at the ground potential. On the other hand, a drive pulse signal is given to the individual electrodes 122 and 124. The sandwiched regions of the piezoelectric ceramic plates 106c to 106e sandwiched between the common electrodes 121 and 123 and the individual electrodes 122 and 124 become active portions 125 that are polarized in the stacking direction when an electric field is applied in advance by these electrodes. ing. Therefore, when the potentials of the individual electrodes 122 and 124 become a predetermined positive potential, the active portions 125 of the piezoelectric ceramic plates 106c to 106e are applied with an electric field and tend to extend in the stacking direction. However, since such a phenomenon does not appear in the piezoelectric ceramic plates 106a and 106b, the portion corresponding to the active portion 125 of the actuator unit 106 swells to extend toward the pressure chamber 110 as a whole. Then, since the volume of the pressure chamber 110 is reduced, an ejection pressure is applied to the ink filled in the pressure chamber 110 and the ink is ejected from the nozzle 109.

  The left side of the two pressure chambers 110 shown in FIG. 9 is such that the volume of the pressure chamber 110 is increased by the actuator unit 106 which is given a positive predetermined potential to the individual electrodes 122 and 124 and extends to the pressure chamber 110 side. A state in which ink is about to be ejected from the nozzle 109 communicating with the pressure chamber 110 by reduction is illustrated. Further, the right side shows a state in which ink is not ejected from the nozzle 109 communicating with the pressure chamber 110 because the drive pulse signal is held at the ground potential similarly to the potentials of the common electrodes 121 and 123.

Patent Document 3 describes a piezo-type actuator unit having a so-called unimorph structure as an actuator unit for an inkjet head. In the actuator unit having a unimorph structure described in Patent Document 3, a conductive film and a flexible plate are bonded so as to sandwich a thin layer made of a piezoelectric element polarized in the thickness direction. When an electric field is applied between the flexible plate and the piezoelectric element, the thin layer of the piezoelectric element tends to shrink in the plane direction by extending in the thickness direction. Then, the thin layer is curved so as to swell to the flexible plate side (that is, the pressure chamber side) together with the flexible plate. When the electric field is released, both the thin layer and the flexible plate return to a flat state due to their elasticity. Thereby, ink in the pressure chamber can be ejected.
Japanese Patent Laying-Open No. 2002-59547 (FIG. 11) Japanese Patent Laid-Open No. 2002-127420 (FIG. 6) Japanese Patent Laid-Open No. 6-316070 (FIGS. 1 and 2)

  The actuator units described in Patent Documents 1 to 3 all have a structure in which the piezoelectric element is sandwiched between electrodes because the piezoelectric element is deformed by applying an electric field in the thickness direction of the piezoelectric element. Need to be. However, in order to obtain the actuator unit having such a structure, a complicated manufacturing process is required, and the manufacturing cost of the actuator unit is increased.

  In addition, the actuator units described in Patent Documents 1 and 2 have a structure in which very thin piezoelectric element plate-like bodies are laminated. Failures such as short-circuiting between the electrodes are likely to occur, and there is a problem with durability.

  The present invention has been made in view of the above problems, and provides a highly durable liquid pressure generating mechanism that can be manufactured by a relatively simple process.

  The liquid pressure generating mechanism of the present invention includes a plate-like body made of a piezoelectric material, a first electrode disposed in the plate-like body so as to extend in the thickness direction from the surface without penetrating the plate-like body, A liquid pressure comprising: a second electrode disposed in the plate-like body so as to extend in the thickness direction from the surface of the plate-like body so as to face the first electrode in the plane direction of the plate-like body. It is a generation | occurrence | production mechanism, Comprising: Each of the said 1st electrode and the said 2nd electrode is provided with two or more, These each have a column shape, Furthermore, the said some 1st electrode and the said some The second electrodes are alternately arranged in concentric rings, and on the circle formed by arranging the plurality of first electrodes, the plurality of first electrodes are arranged at intervals from each other. On the circle formed by arranging the second electrodes, the plurality of second electrodes In which the plurality of first electrodes arranged on the same circle have the same diameter as the circle formed by arranging the plurality of first electrodes. The plurality of second electrodes connected via a ring-shaped first metal wiring and arranged on the same circle have the same diameter as a circle formed by arranging the plurality of second electrodes. The first metal wiring and the second metal wiring are connected via an annular second metal wiring, and are arranged in a concentric ring shape (Claim 1).

  According to this liquid pressure generating mechanism, since the first electrode does not penetrate the plate-like body made of the piezoelectric material, if a potential difference is applied between the first electrode and the second electrode, the first electrode of the plate-like body is used. A region sandwiched between the first electrode and the second electrode (hereinafter sometimes referred to as an “electrode region” in this specification) tends to be deformed by a piezoelectric action by applying an electric field in a plane direction. An electric field is applied to a region where the first electrode and the second electrode adjacent to the region in the thickness direction of the plate-like body are not disposed (hereinafter, referred to as “non-electrode region” in this specification). Resist the electrode region extending in the surface direction. As a result, the plate-like body is deformed so as to be concave or convex in the thickness direction. When the electric field is released, the plate-like body returns to its original shape due to elasticity. By operating in this way, it is possible to apply pressure to the liquid.

The liquid pressure generating mechanism of the present invention includes a first electrode and the second electrode on a line extending from a center of a circle formed by arranging the plurality of first electrodes and the plurality of second electrodes toward the circle. The second electrodes may be arranged so as to face each other (claim 2).
In the liquid pressure generating mechanism of the present invention, the first electrode or the second electrode is arranged at the center of a circle formed by arranging the plurality of first electrodes and the plurality of second electrodes. (Claim 3).
In the liquid pressure generating mechanism of the present invention, the first electrode is connected to a terminal to which a signal for selectively taking either a ground potential or a positive predetermined potential is applied via the first metal wiring. The second electrode is connected to a terminal held at a ground potential via the second metal wiring, and the first electrode includes the plurality of first electrodes and the plurality of second electrodes. It may be arranged at the center of a circle formed by arranging the electrodes.
In the liquid pressure generating mechanism of the present invention, the plate-like body has at least three circles formed by arranging the plurality of first electrodes and the plurality of second electrodes,
The distance between the first electrode and the second electrode may increase as the distance from the center increases (Claim 5).
In the liquid pressure generating mechanism of the present invention, a concave portion having the same shape as that of the first electrode and the second electrode may be formed in the plate-like body .

  As described above, according to the present invention, the liquid pressure generating device can be easily manufactured by a simple process of arranging the first electrode and the second electrode halfway through the thickness of the plate-like body. Therefore, the manufacturing cost can be kept low. In addition, since it does not have a structure in which a large number of plate-like bodies and electrodes are laminated, even if there are fine cracks in the plate-like body, there is a failure such as short-circuiting between adjacent electrodes due to ink leakage etc. It is less likely to occur and has high durability.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
An ink jet head including an actuator unit that is a liquid pressure generating mechanism according to a first embodiment of the present invention will be described. FIG. 1 is a partial cross-sectional view of an inkjet head including an actuator unit according to the present embodiment cut along the longitudinal direction. FIG. 2 is a partial cross-sectional view of the inkjet head cut along the width direction. The piezoelectric ink jet head 1 shown in FIG. 1 has an actuator unit 6 of substantially the same shape stacked on a substantially rectangular parallelepiped flow path unit 7, and a flexible flat cable for connection to an external circuit on the actuator unit 6. Alternatively, a flexible printed circuit (FPC) (not shown) is attached. The ink jet head 1 ejects ink downward from a nozzle 9 opened on the lower surface side of the flow path unit 7.

  A large number of pressure chambers (ink storage chambers) 10 opened upward are provided on the upper surface of the flow path unit 7. In addition, a pair of supply holes (not shown) communicating with a manifold channel 15 described later are formed in the vicinity of one end in the longitudinal direction of the channel unit 7. These supply holes are covered with a filter (not shown) for removing dust in the ink supplied from the ink cartridge (not shown).

  As shown in FIGS. 1 and 2, the inkjet head 1 is driven through an FPC by a drive pulse signal (selectively taking either a ground potential or a positive predetermined potential) generated by a drive circuit (not shown). The actuator unit 6 and the flow path unit 7 forming the ink flow path are stacked. The actuator unit 6 and the flow path unit 7 are bonded by an epoxy thermosetting adhesive. The terminals on the FPC side are connected to the corresponding terminals 21a, 22a, 21b and 22b on the actuator unit 6 side.

  The flow path unit 7 is a nozzle plate made of synthetic resin such as polyimide having three thin plate plates (cavity plate 7a, spacer plate 7b, manifold plate 7c) made of a metal material and a nozzle 9 for ejecting ink. 7d is laminated. The uppermost cavity plate 7 a is in contact with the actuator unit 6.

  On the surface of the cavity plate 7a, a plurality of pressure chambers 10 having a substantially disk shape for containing ink selectively ejected by the operation of the actuator unit 6 are formed in two rows along the longitudinal direction. The plurality of pressure chambers 10 are separated from each other by a partition wall 10a. The spacer plate 7b is formed with a communication hole 11 for communicating one end of the pressure chamber 10 with the nozzle 9 and a communication hole 12 for communicating the other end of the pressure chamber 10 with a manifold channel 15 described later. .

  The manifold plate 7 c is formed with a communication hole 13 that allows one end of the pressure chamber 10 to communicate with the nozzle 9. Further, a manifold channel 15 for supplying ink to the pressure chambers 10 is formed in the manifold plate 7 c so as to be long in the column direction below the column formed by the plurality of pressure chambers 10. One end of the manifold channel 15 is connected to an ink supply source (not shown) through one of the supply holes described above. In this way, an ink flow path from the manifold flow path 15 to the nozzle 9 through the communication hole 12, the pressure chamber 10, the communication hole 11, and the communication hole 13 is formed.

  FIG. 3 is a partially enlarged perspective view of the actuator unit 6. The actuator unit 6 has one piezoelectric ceramic plate 6a made of a ceramic material of lead zirconate titanate (PZT). As shown in FIGS. 1 and 3, a large number of electrodes 17a, 17b, 17c, and 17d having a cylindrical shape whose thickness direction is the axial direction are arranged in the piezoelectric ceramic plate 6a. These electrodes 17a, 17b, 17c, and 17d have a length slightly shorter than ½ of the thickness of the piezoelectric ceramic plate 6a in the axial direction. All the electrodes 17a, 17b, 17c, and 17d are exposed so that one end face in the longitudinal direction is exposed without protruding from the upper surface of the piezoelectric ceramic plate 6a (surface opposite to the flow path unit 7). In the plate 6a, it is unevenly distributed upward. Therefore, the electrodes 17a, 17b, 17c, and 17d extend in the thickness direction without penetrating the piezoelectric ceramic plate 6a.

  The electrodes 17b are arranged at equal intervals on one circle centered on the electrode 17a, and the electrodes 17c are equally spaced on one circle centered on the electrode 17a that is slightly larger than the circle formed by the electrode 17b. The electrodes 17d are arranged at equal intervals on a circle centered on the electrode 17a that is slightly larger than the circle formed by the electrode 17c. Thus, the electrodes 17b, 17c, and 17d are arranged in a triple concentric ring with the electrode 17a as a center point.

  As can be seen from FIG. 1, the circle formed by arranging the plurality of electrodes 17 d has substantially the same diameter as the pressure chamber 10. The plurality of electrodes 17d are arranged so as to be substantially contained in the pressure chamber 10. That is, the large number of electrodes 17 a, 17 b, 17 c, and 17 d are arranged substantially uniformly in a region corresponding to the pressure chamber 10 of the flow path unit 7. In addition, even if the space | interval is not uniform as mentioned above, the electrode should just be distributed over the whole area | region corresponding to the pressure chamber 10. FIG.

  The electrode region 6c of the piezoelectric ceramic plate 6a (in the circle formed by the electrode 17d is disposed on the electrode 17a, 17b, 17c, 17d from the upper surface (the surface opposite to the pressure chamber 10) of the piezoelectric ceramic plate 6a. The region up to the distance for the length) is alternately in the radial direction around the electrode 17a, such as the direction from the electrode 17a to the electrode 17b along the plane direction, and the direction from the electrode 17c to the electrodes 17b and 17d. It is a polarized active part.

  The electrode 17a is connected to a terminal 22a to which a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential is applied. All the electrodes 17b are connected to a terminal 21a that is always held at the ground potential via an annular metal wiring 24 having the same diameter as a circle formed by arranging a plurality of electrodes 17b. All the electrodes 17c are connected to a terminal 22b to which the same drive pulse signal as that applied to the terminal 22a is applied via an annular metal wiring 25 having the same diameter as a circle formed by arranging a plurality of electrodes 17c. It is connected. All the electrodes 17d are connected to a terminal 21b that is always held at the ground potential via an annular metal wiring 26 having the same diameter as a circle formed by arranging a plurality of electrodes 17d. That is, in this embodiment, the potentials of the electrode 17a and the electrode 17c are always the same, and the potentials of the electrode 17b and the electrode 17d are always the same. Therefore, the four types of electrodes 17a, 17b, 17c, and 17d can be classified into a first electrode composed of the electrode 17a and the electrode 17c and a second electrode composed of the electrode 17b and the electrode 17d.

  As can be seen from the above description, when the electrodes 17a and 17c are at the ground potential, the electrodes are adjacent to each other in the radial direction (that is, between the electrodes 17a and 17b, between the electrodes 17b and 17c, and between the electrodes 17c and 17d). No electric field is generated. However, when the electrodes 17a and 17c are at a predetermined positive potential, an electric field is generated between the radially adjacent electrodes.

  Of the two pressure chambers 10 shown in FIG. 1, the left side depicts the state when the electrodes 17a and 17c are at a predetermined positive potential, and the right side is where the electrodes 17a and 17c are at the ground potential. It is a picture of the situation when you are. As described above, when the electrodes 17a and 17c have a positive predetermined potential, an electric field in a direction (a surface direction of the piezoelectric ceramic plate 6a) as indicated by an arrow in FIG. 1 is generated between the radially adjacent electrodes. Since the direction of this electric field is the same as the polarization direction of the piezoelectric ceramic plate 6a, the electrode region sandwiched between the electrodes 17a, 17b, 17c and 17d of the piezoelectric ceramic plate 6a tends to extend in the plane direction by the piezoelectric action.

  On the other hand, in the non-electrode region 6d in which the electrodes 17a, 17b, 17c, and 17d adjacent to the electrode region in the thickness direction of the piezoelectric ceramic plate 6a are not disposed, an electric field is not applied, and the force tends to extend in the plane direction. Does not work. Accordingly, a difference in elongation in the surface direction occurs between the electrode region and the non-electrode region, and the non-electrode region resists the electrode region from extending in the surface direction. As a result, an action similar to that of the actuator unit having the unimorph structure described in Patent Document 3 occurs, and as shown on the left side of FIG. 1, the piezoelectric ceramic plate 6a is curved in the thickness direction so that the electrode region side is convex. To do. At this time, the lower surface (surface on the pressure chamber 10 side) of the piezoelectric ceramic plate 6a is curved in a direction in which the pressure chamber 10 is enlarged. Therefore, ink flows into the pressure chamber 10 from the manifold channel, and the pressure chamber 10 is filled with ink.

  Thereafter, when the electrodes 17a and 17c reach the ground potential, the electric field is released, and the piezoelectric ceramic plate 6a returns to the original flat plate shape due to its own elasticity as shown on the right side of FIG. Then, since the position of the lower surface of the piezoelectric ceramic plate 6a also returns to the original position, the volume of the pressure chamber 10 decreases from the state on the left side of FIG. As a result, pressure is applied to the ink in the pressure chamber 10, and ink droplets are ejected from the nozzle 9 communicating with the pressure chamber 10.

  As a method for ejecting ink from the ink jet head 1 shown in FIGS. 1 to 3, either so-called pushing or striking may be used. In the case of pushing, in an ordinary state, an electric field is applied to the electrode region by setting the electrodes 17a and 17c at a predetermined positive potential in a portion corresponding to the entire pressure chamber 10, and the piezoelectric ceramic plate 6a is shown on the left side of FIG. Keep it curved like this. Then, by setting only the electrodes 17a and 17c corresponding to the pressure chamber 10 to which ink is to be ejected to the ground potential, the electric field in the electrode region is released, and the pressure chamber 10 is reduced as shown on the right side of FIG. Pressure is applied to the ink inside.

  On the other hand, when pulling is performed, in the normal state, by setting the electrodes 17a and 17c to the ground potential in the portion corresponding to the entire pressure chamber 10, no electric field is applied to the electrode region, and the piezoelectric ceramic plate 6a is placed on the right side of FIG. Keep flat as shown. Then, only the electrodes 17a and 17c corresponding to the pressure chambers 10 to which ink is to be ejected are temporarily applied with an electric field to the electrode region as a positive predetermined potential, and the piezoelectric ceramic plate 6a is curved as shown on the left side of FIG. To enlarge the pressure chamber 10. At this time, a pressure wave is generated in the pressure chamber 10 and propagates in the pressure chamber 10 in the longitudinal direction. Thereafter, at the timing when the pressure wave becomes positive, the electrodes 17a and 17c are returned to the ground potential again to release the electric field in the electrode region, and the pressure chamber 10 is reduced as shown in the right side of FIG. Apply pressure. When striking is performed, the pressures can be superimposed, so that a large ejection pressure can be applied to the ink with relatively small energy.

  Next, a method for manufacturing the inkjet head 1 will be briefly described. In order to manufacture the ink jet head 1 as described with reference to FIGS. 1 to 3, components such as the flow path unit 7 and the actuator unit 6 are separately manufactured, and then the components are assembled.

  In order to fabricate the flow path unit 7, the four plates 7a to 7d depicted in FIGS. 1 and 2 are independently fabricated, and then the adhesive is used in a state where the plates are aligned and stacked. Glue them together. Etching is used to form the pressure chambers 10 and the communication holes 11 in the plates 7a to 7c, and laser processing is used to form the nozzles 9 in the plate 7d.

  On the other hand, in order to manufacture the actuator unit 6, first, a green sheet of piezoelectric ceramics is prepared, and a large number of cylindrical recesses for electrode arrangement are formed by pressing or laser processing in a portion corresponding to the pressure chamber of the green sheet. To do. The press working is advantageous in that it can be performed simultaneously when the green sheet is formed into a predetermined shape corresponding to the actuator unit 6.

  Thereafter, a paste-like conductive material is poured into the cylindrical recess, and then the piezoelectric ceramic green sheet is degreased in the same manner as known ceramics and further fired at a predetermined temperature. Thereby, the piezoelectric ceramic plate 6a in which the electrodes 17a, 17b, 17c, and 17d are disposed in the cylindrical recess is obtained. And the actuator unit 6 is obtained by giving the metal wiring 24-26 to the electrodes 17a, 17b, 17c, 17d by printing or vapor deposition. Note that the piezoelectric ceramic green sheet is designed in advance in consideration of the amount of shrinkage caused by firing.

  Thereafter, the flow path unit 7 and the actuator unit 6 are bonded together using a thermosetting adhesive with the position of the electrode region and the position of the pressure chamber 10 aligned, and between the adjacent electrode groups of the actuator unit 6. The lower surface, that is, the outer peripheral portion of each electrode region is fixed on the partition wall 10a. Then, the actuator unit 6 and a separately prepared FPC are bonded using solder so that corresponding terminals overlap each other.

  Thereafter, a high potential is applied to the electrodes 17a and 17c while the potentials of the electrodes 17b and 17d are held at the ground potential, so that the piezoelectric ceramic plate 6a in the electrode region is placed in the direction opposite to the electrode, that is, the surface 17a. Polarization is performed in the radial direction from the center, and this region is defined as an active portion. The inkjet head 1 is completed through the above steps.

  In the manufacturing process described above, a cylindrical recess may be formed by laser processing after the green sheet is fired. Moreover, you may make it arrange | position an electrode in a cylindrical recessed part after baking of a green sheet. Further, FPC may be bonded after the polarization step. In this case, it is necessary to apply a potential to the electrodes 17a, 17b, 17c, and 17d from other than the FPC.

  Thus, according to the actuator unit 6 which is the liquid pressure generating mechanism according to the present embodiment, the electrodes 17a and 17c and the electrodes 17b and 17d arranged so as not to penetrate the single piezoelectric ceramic plate 6a. By controlling the potential difference, the piezoelectric ceramic plate 6a can be switched between the curved state in the thickness direction and the uncurved state. Therefore, it is possible to apply pressure to the ink in the desired pressure chamber 10 to eject the ink.

  In addition, the actuator unit 6 of the present embodiment can be easily manufactured by a simple process in which the electrodes 17a, 17b, 17c, and 17d are arranged in the piezoelectric ceramic plate 6a halfway through its thickness. Therefore, it has the outstanding advantage that manufacturing cost can be suppressed low. Further, since the actuator unit 6 does not have a structure in which a large number of piezoelectric ceramic plates and thin layer electrodes are laminated as in Patent Document 1 and Patent Document 2, the electrode has a non-electrode region 6d having a sufficient thickness. Therefore, even if there are fine cracks in the piezoelectric ceramic plate 6a, there are few failures such as short-circuiting between adjacent electrodes due to ink leakage, and the durability is high.

  Further, since the polarization direction of the electrode region of the piezoelectric ceramic plate 6a is the opposite direction of the electrode as in the direction of the electric field, that is, the radial direction about the electrode 17a along the surface direction of the piezoelectric ceramic plate 6a, the piezoelectric ceramic plate 6a. Is curved in the thickness direction so that the electrode region side is convex based on the principle similar to the unimorph type, whereby pressure can be applied to the ink in the pressure chamber 10.

  Further, in the actuator unit 6, a large number of electrodes 17 a, 17 b, 17 c, and 17 d are arranged in the electrode region of the piezoelectric ceramic plate 6 a, so that the piezoelectric ceramic plates and electrodes described in Patent Document 1 and Patent Document 2 The distance between the electrodes and the electrode area can be reduced as compared with the case where a large electrode is used as in the actuator unit in which is stacked. Therefore, the potential applied to the electrodes 17a and 17c and the capacitance of the actuator unit 6 can be reduced. As a result, the cost of the driver IC and the electric circuit of the inkjet head 1 can be reduced, and the energy consumption and the heat generation amount can be reduced. It becomes possible to reduce.

  Moreover, in the actuator unit 6 according to the present embodiment, the electrodes 17a, 17b, 17c, and 17d are concentrically arranged so that the first electrode and the second electrode are alternately arranged in this order. As a result, the electric field strength is increased and the deformation amount of the piezoelectric ceramic plate 6a can be increased.

  Further, in the actuator unit 6 of the present embodiment, the pressure chamber 10 is disposed on the surface of the piezoelectric ceramic plate 6a on the non-electrode region 6d side. Therefore, when performing the above-described striking, the piezoelectric ceramic plate 6a is in a normal state. It is not necessary to apply an electric field to. Therefore, compared with the case where the pressure chamber 10 is arranged on the surface of the piezoelectric ceramic plate 6a on the electrode region side, the total electric field application time is remarkably shortened, and energy consumption can be reduced and safety is ensured. Increases nature.

  Further, in the actuator unit 6 according to the present embodiment, the plurality of pressure chambers 10 separated from each other by the partition wall 10a are arranged on the surface of the piezoelectric ceramic plate 6a on the non-electrode region side, and the electrodes 17a, 17b, 17c, 17d. Is disposed in each region corresponding to the pressure chamber 10, so that pressure can be efficiently applied to the ink in each pressure chamber 10.

  Next, a modification of the actuator unit according to the present embodiment will be described with reference to FIG. 4 which is a perspective view thereof. The actuator unit according to this modification is used together with the flow path unit and the FPC as one component of the ink jet head, as described with reference to FIGS.

  In FIG. 4, the actuator unit 36 has a single piezoelectric ceramic plate 36a made of a ceramic material of lead zirconate titanate (PZT). In the piezoelectric ceramic plate 36a, a large number of electrodes 47a, 47b, 47c, 47d, 47e, 47f, 47g having a cylindrical shape whose axial direction is the thickness direction are arranged. These electrodes 47a to 47g have a length slightly shorter than ½ of the thickness of the piezoelectric ceramic plate 36a in the axial direction. All the electrodes 47a to 47g are unevenly distributed upward in the piezoelectric ceramic plate 36a so that one end surface in the longitudinal direction is exposed without protruding from the surface of the piezoelectric ceramic plate 36a opposite to the flow path unit 7. Are arranged. Therefore, the electrodes 47a to 47g extend in the thickness direction without penetrating the piezoelectric ceramic plate 36a.

  A plurality of electrodes 47a to 47g are arranged at equal intervals on a straight line. The distance between the line formed by the electrode 47a and the line formed by the electrode 47b, the distance between the line formed by the electrode 47b and the line formed by the electrode 47c, the distance between the line formed by the electrode 47c and the line formed by the electrode 47d, and the electrode 47d The distance between the line formed by the electrode 47e, the line formed by the electrode 47e and the line formed by the electrode 47f, and the distance formed by the line formed by the electrode 47f and the line formed by the electrode 47g are the same. Thus, the electrodes 47a to 47g are arranged in a matrix. Then, it is assumed that the actuator unit 36 and the flow path unit are bonded together so that the range in which the electrodes 47a to 47g are disposed corresponds to the pressure chamber 10 of the flow path unit. Thereby, the large number of electrodes 47a to 47g are arranged substantially uniformly in a region corresponding to the pressure chamber 10 of the flow path unit.

  From the upper surface (surface opposite to the pressure chamber) of the piezoelectric ceramic plate 36a to the distance of the length of the electrodes 47a to 47g in the electrode region of the piezoelectric ceramic plate 36a (in the range where the electrodes 47a to 47g are arranged) Is a direction from the electrode 47b to the electrodes 47a and 47 along the surface direction of the piezoelectric ceramic plate 36a, a direction from the electrode 47d to the electrodes 47c and 47e, and a direction from the electrode 47f to the electrodes 47e and 47g. The active portions are alternately polarized in the direction orthogonal to the lines formed by the electrodes 47a to 47g.

  All the electrodes 47a are connected to a terminal 51a that is always held at the ground potential through a linear metal wiring 54 arranged along a line formed by the plurality of electrodes 47a. All the electrodes 47b are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential via a linear metal wiring 55 arranged along a line formed by the plurality of electrodes 47b. It is connected to the terminal 52a. All the electrodes 47c are connected to a terminal 51b that is always held at a ground potential via a linear metal wiring 56 arranged along a line formed by the plurality of electrodes 47c. All electrodes 47d are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential through a linear metal wiring 57 arranged along a line formed by a plurality of electrodes 47d. It is connected to the terminal 52b. All the electrodes 47e are connected to a terminal 51c that is always held at the ground potential via a linear metal wiring 58 disposed along a line formed by the plurality of electrodes 47e. All electrodes 47f are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential via a linear metal wiring 59 arranged along a line formed by a plurality of electrodes 47f. It is connected to the terminal 52c. All the electrodes 47g are connected to a terminal 51d that is always held at the ground potential through a linear metal wiring 60 arranged along a line formed by the plurality of electrodes 47g.

  The same drive pulse signal is given to the terminals 52a, 52b, and 52c. That is, in this embodiment, the potentials of the electrodes 47b, 47d, and 47f are always the same, and the potentials of the electrodes 47a, 47c, 47e, and 47g are always the same ground potential. Therefore, the seven types of electrodes 47a to 47g can be classified into a first electrode composed of electrodes 47b, 47d and 47f and a second electrode composed of electrodes 47a, 47c, 47e and 47g.

  As can be seen from the above description, when the electrodes 47b, 47d, and 47f are at the ground potential, the electrodes 47a to 47g are adjacent to each other in the direction perpendicular to the line (that is, between the electrodes 47a and 47b, No electric field is generated between the electrodes 47b and 47c, between the electrodes 47c and 47d, between the electrodes 47d and 47e, between the electrodes 47e and 47f, and between the electrodes 47f and 47g). However, when the electrodes 47b, 47d, 47f are at a predetermined positive potential, an electric field is generated between the electrodes adjacent to each other in the direction orthogonal to the line formed by the electrodes 47a-47g.

  Since the direction of the electric field is the same as the polarization direction of the piezoelectric ceramic plate 36a, the electrode region sandwiched between the electrodes 47a to 47g of the piezoelectric ceramic plate 36a tends to extend in the plane direction by the piezoelectric action. On the other hand, no force is applied to the non-electrode region where the electrodes 47a to 47g adjacent to the electrode region in the thickness direction of the piezoelectric ceramic plate 36a are not applied and no electric field is applied. Accordingly, a difference in elongation in the surface direction occurs between the electrode region and the non-electrode region, and the non-electrode region resists the electrode region from extending in the surface direction. As a result, an action similar to the actuator unit having the unimorph structure described in Patent Document 3 occurs, and the piezoelectric ceramic plate 36a is curved in the thickness direction so that the electrode region side is convex. At this time, the lower surface (surface on the pressure chamber side) of the piezoelectric ceramic plate 36a is curved in the direction of expanding the pressure chamber. Therefore, ink flows from the manifold channel into the pressure chamber, and the pressure chamber is filled with ink.

  Thereafter, when the electrodes 47b, 47d, 47f reach the ground potential, the electric field is released, and the piezoelectric ceramic plate 36a returns to its original flat plate shape due to its own elasticity. Then, since the position of the lower surface of the piezoelectric ceramic plate 36a also returns to the original position, the volume of the pressure chamber decreases. As a result, pressure is applied to the ink in the pressure chamber, and ink droplets are ejected from nozzles communicating with the pressure chamber.

Even when the actuator unit 36 of this modification is used, the same benefits as those of the first embodiment described above can be obtained.
[Second Embodiment]
Next, an ink jet head including an actuator unit that is a liquid pressure generating mechanism according to a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member similar to embodiment mentioned above, and the description is abbreviate | omitted. FIG. 5 is a partial cross-sectional view of the inkjet head including the actuator unit according to the present embodiment cut along the longitudinal direction. The piezoelectric ink jet head 61 shown in FIG. 5 has an actuator unit 66 of substantially the same shape laminated on a substantially rectangular flow path unit 7, and a flexible flat cable for connection to an external circuit on the actuator unit 66. Alternatively, a flexible printed circuit (FPC) (not shown) is attached. The ink jet head 61 ejects ink downward from the nozzle 9 opened on the lower surface side of the flow path unit 7. Since the flow path unit 7 is the same as that of the first embodiment, the detailed description thereof is omitted here.

  As shown in FIG. 5, in the inkjet head 61, an actuator unit driven via an FPC by a drive pulse signal (selectively taking either a ground potential or a positive predetermined potential) generated by a drive circuit (not shown). 66 and a flow path unit 7 forming an ink flow path are stacked. The actuator unit 66 and the flow path unit 7 are bonded by an epoxy thermosetting adhesive. The terminals on the FPC side are connected to the corresponding terminals 71a, 72a, 71b, 72b on the actuator unit 66 side.

  FIG. 6 is a partially enlarged perspective view of the actuator unit 66. In the actuator unit 66, two piezoelectric ceramic plates 66a and 66b made of a ceramic material of lead zirconate titanate (PZT) and having substantially the same thickness are laminated. As shown in FIGS. 5 and 6, a large number of electrodes 77a, 77b, 77c, and 77d having a cylindrical shape whose axial direction is the thickness direction are arranged in the piezoelectric ceramic plate 66a. These electrodes 77a, 77b, 77c, and 77d have substantially the same length as the thickness of the piezoelectric ceramic plate 66a in the axial direction. That is, the electrodes 77a, 77b, 77c, and 77d have the same length as the thickness of the piezoelectric ceramic plate 66a and extend in the thickness direction without protruding from the piezoelectric ceramic plate 66b.

  The electrodes 77b are arranged at equal intervals on one circle centered on the electrode 77a, and the electrodes 77c are equally spaced on one circle centered on the electrode 77a that is slightly larger than the circle formed by the electrode 77b. The electrodes 77d are arranged at equal intervals on a circle centered on the electrode 77a that is slightly larger than the circle formed by the electrode 77c. Thus, the electrodes 77b, 77c, and 77d are arranged in a triple concentric ring with the electrode 77a as the center point.

  As can be seen from FIG. 5, the circle formed by arranging the plurality of electrodes 77 d has substantially the same diameter as the pressure chamber 10. The plurality of electrodes 77d are disposed so as to be substantially contained in the pressure chamber 10. That is, the large number of electrodes 77 a, 77 b, 77 c, 77 d are arranged substantially uniformly in a region corresponding to the pressure chamber 10 of the flow path unit 7.

  The electrode region of the piezoelectric ceramic plate 66a (the region in the circle formed by the electrode 77d) is alternately polarized in the radial direction around the electrode 77a along the surface direction, as in FIG. It is an active part.

  The electrode 77a is connected to a terminal 72a to which a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential is applied. All the electrodes 77b are connected to a terminal 71a that is always held at the ground potential via an annular metal wiring 74 having the same diameter as a circle formed by arranging a plurality of electrodes 77b. All the electrodes 77c are connected to a terminal 72b to which the same drive pulse signal as that applied to the terminal 72a is applied via an annular metal wiring 75 having the same diameter as a circle formed by arranging a plurality of electrodes 77c. It is connected. All the electrodes 77d are connected to a terminal 71b that is always held at the ground potential via an annular metal wiring 76 having the same diameter as a circle formed by arranging a plurality of electrodes 77d. That is, in this embodiment, the potentials of the electrode 77a and the electrode 77c are always the same, and the potentials of the electrode 77b and the electrode 77d are always the same. Therefore, the four types of electrodes 77a, 77b, 77c, and 77d can be classified into a first electrode composed of the electrodes 77a and 77c and a second electrode composed of the electrodes 77b and 77d.

  As can be understood from the above description, when the electrodes 77a and 77c are at the ground potential, the electrodes adjacent to each other in the radial direction (that is, between the electrodes 77a and 77b, between the electrodes 77b and 77c, and between the electrodes 77c and 77d). No electric field is generated. However, when the electrodes 77a and 77c are at a predetermined positive potential, an electric field is generated between the radially adjacent electrodes.

  Of the two pressure chambers 10 shown in FIG. 5, the left side depicts the state when the electrodes 77a and 77c are at a predetermined positive potential, and the right side is where the electrodes 77a and 77c are at the ground potential. It is a picture of the situation when you are. Thus, when the electrodes 77a and 77c have a positive predetermined potential, an electric field is generated between the radially adjacent electrodes in the direction indicated by the arrow in FIG. 5 (the surface direction of the piezoelectric ceramic plate 66a). Since the direction of the electric field is the same as the polarization direction of the piezoelectric ceramic plate 66a, the electrode region sandwiched between the electrodes 77a, 77b, 77c, and 77d of the piezoelectric ceramic plate 66a tends to extend in the plane direction by the piezoelectric action.

  On the other hand, in the non-electrode region (the region within the piezoelectric ceramic plate 66b and below the electrode region) where the electrodes 77a, 77b, 77c, and 77d adjacent to the electrode region in the thickness direction of the piezoelectric ceramic plate 66a are not disposed. In this case, no force is applied to the surface without applying an electric field. Accordingly, a difference in elongation in the surface direction occurs between the electrode region and the non-electrode region, and the non-electrode region resists the electrode region from extending in the surface direction. As a result, an action similar to that of the actuator unit having the unimorph structure described in Patent Document 3 occurs. As shown on the left side of FIG. 5, the piezoelectric ceramic plates 66a and 66b are arranged in the thickness direction so that the electrode region side is convex. To curve. At this time, the lower surface (the surface on the pressure chamber 10 side) of the piezoelectric ceramic plate 66b is curved in a direction in which the pressure chamber 10 is enlarged. Therefore, ink flows into the pressure chamber 10 from the manifold channel, and the pressure chamber 10 is filled with ink.

  Thereafter, when the electrodes 77a and 77c reach the ground potential, the electric field is released, and the piezoelectric ceramic plates 66a and 66b return to the original flat plate shape due to their own elasticity as shown on the right side of FIG. Then, the position of the lower surface of the piezoelectric ceramic plate 66b also returns to the original position, so that the volume of the pressure chamber 10 decreases from the left side in FIG. As a result, pressure is applied to the ink in the pressure chamber 10, and ink droplets are ejected from the nozzle 9 communicating with the pressure chamber 10. Also in the case of the ink jet head 61 of the present embodiment, either pushing or striking may be used as a method for ejecting ink.

  Next, a method for manufacturing the inkjet head 61 will be briefly described. In order to manufacture the inkjet head 61, components such as the flow path unit 7 and the actuator unit 61 are separately manufactured, and then the components are assembled.

  Since the procedure for producing the flow path unit 7 is the same as that of the first embodiment described above, description thereof is omitted here. In order to manufacture the actuator unit 61, first, two green sheets of piezoelectric ceramics are prepared, and a number of cylindrical through holes for electrode arrangement are pressed into a portion corresponding to the pressure chamber of one of the green sheets. Alternatively, it is formed by laser processing. The press working is advantageous in that it can be performed simultaneously when the green sheet is formed into a predetermined shape corresponding to the actuator unit 6.

  Then, after the two green sheets are overlaid, a paste-like conductive material is poured into the cylindrical through-hole, and then the piezoelectric ceramic green sheet is degreased in the same manner as known ceramics, and further fired at a predetermined temperature. To do. Thereby, the piezoelectric ceramic plates 66a and 66b in which the electrodes 77a, 77b, 77c, and 77d are disposed in the cylindrical through holes are obtained. And the actuator unit 61 is obtained by giving the metal wiring 74-76 to the electrodes 77a, 77b, 77c, 77d by printing or vapor deposition. Note that the piezoelectric ceramic green sheet is designed in advance in consideration of the amount of shrinkage caused by firing.

  Thereafter, the flow path unit 7 and the actuator unit 61 are bonded using a thermosetting adhesive with the position of the electrode region and the position of the pressure chamber 10, and prepared separately from the actuator unit 61. Bonding is performed using solder so that terminals corresponding to the FPCs overlap each other.

  Thereafter, a high potential is applied to the electrodes 77a and 77c while the potentials of the electrodes 77b and 77d are held at the ground potential, so that the piezoelectric ceramic plate 66a in the electrode region is placed in the direction opposite to the electrode, that is, along the surface direction. Polarization is performed in the radial direction from the center, and this region is defined as an active portion. The inkjet head 1 is completed through the above steps.

  In the manufacturing process described above, a cylindrical recess may be formed by laser processing after the green sheet is fired. Moreover, you may make it arrange | position an electrode in a cylindrical recessed part after baking of a green sheet. Further, FPC may be bonded after the polarization step. In this case, it is necessary to apply a potential to the electrodes 77a, 77b, 77c, and 77d from other than the FPC.

  Thus, according to the actuator unit 61 which is the liquid pressure generating mechanism according to the present embodiment, the piezoelectric ceramic is controlled by controlling the potential difference between the electrodes 77a and 77c and the electrodes 77b and 77d arranged in the piezoelectric ceramic plate 66a. The plates 66a and 66b can be switched between a state in which the plates 66a and 66b are bent in the thickness direction and a state in which the plates 66a and 66b are not bent. Therefore, it is possible to apply pressure to the ink in the desired pressure chamber 10 to eject the ink.

  The actuator unit 61 according to the present embodiment is easily manufactured by a simple process in which the electrodes 77a, 77b, 77c, and 77d are arranged on the piezoelectric ceramic plate 66a and the piezoelectric ceramic plate 66a and the piezoelectric ceramic plate 66b are laminated. Is possible. Therefore, it has the outstanding advantage that manufacturing cost can be suppressed low. When this embodiment is compared with the first embodiment, although a step of laminating two piezoelectric ceramic plates 66a and 66b is added, the piezoelectric ceramic plate 66a has through holes instead of recesses (non-through holes). There is an advantage that the manufacturing process can be simplified in that it can be formed.

  Further, since the actuator unit 61 does not have a structure in which a large number of piezoelectric ceramic plates and thin layer electrodes are stacked as in Patent Document 1 and Patent Document 2, the electrodes are disposed through a non-electrode region having a sufficient thickness. Therefore, even if there are fine cracks in the piezoelectric ceramic plates 66a and 66b, there are few failures such as short-circuiting between adjacent electrodes due to ink leakage, and the durability is high. In addition, the same benefits as in the first embodiment can be obtained.

In the present embodiment, the axial length of the electrodes 77a to 77d is the same as the thickness of the piezoelectric ceramic plate 66a. However, the axial length of the electrodes 77a to 77d is larger than the thickness of the piezoelectric ceramic plate 66a. The same result can be obtained even if it is reduced.
[Third Embodiment]
Next, an ink jet head including an actuator unit which is a liquid pressure generating mechanism according to a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member similar to embodiment mentioned above, and the description is abbreviate | omitted. FIG. 7 is a partial cross-sectional view of the inkjet head including the actuator unit according to the present embodiment cut along the longitudinal direction. In the piezoelectric ink jet head 81 shown in FIG. 7, an actuator unit 86 having substantially the same shape is laminated on a substantially rectangular parallelepiped flow path unit 7, and a flexible flat cable for connection to an external circuit is formed on the actuator unit 86. Alternatively, a flexible printed circuit (FPC) (not shown) is attached. The ink jet head 81 ejects ink downward from the nozzle 9 opened on the lower surface side of the flow path unit 7. Since the flow path unit 7 is the same as that of the first embodiment, the detailed description thereof is omitted here.

  As shown in FIG. 7, in the ink jet head 81, an actuator unit driven via an FPC by a drive pulse signal (selectively taking either a ground potential or a positive predetermined potential) generated by a drive circuit (not shown). 86 and a flow path unit 7 forming an ink flow path are stacked. The actuator unit 86 and the flow path unit 7 are bonded with an epoxy thermosetting adhesive. The terminals on the FPC side are the corresponding terminals 91a, 92a, 91b, 92b, 91c, 92c, 91d on the actuator unit 86 side (only 92a is shown in FIG. 7; see FIG. 8 for the rest). Connected with.

  FIG. 8 is a partially enlarged perspective view of the actuator unit 86. In FIG. 8, the actuator unit 86 has one piezoelectric ceramic plate 86a made of a lead zirconate titanate (PZT) ceramic material. A large number of electrodes 87 a, 87 b, 87 c, 87 d, 87 e, 87 f, 87 g having a cylindrical shape whose thickness direction is the axial direction are arranged in the piezoelectric ceramic plate 86 a. These electrodes 87a to 87g have a length slightly shorter than ½ of the thickness of the piezoelectric ceramic plate 86a in the axial direction. Then, all the electrodes 87a to 87g are arranged upward in the piezoelectric ceramic plate 86a so that one end surface in the longitudinal direction is exposed without protruding from the upper surface of the piezoelectric ceramic plate 86a (surface opposite to the pressure chamber 10). Are unevenly distributed. Therefore, the electrodes 87a to 87g extend in the thickness direction without penetrating the piezoelectric ceramic plate 86a.

  A plurality of electrodes 87a to 87g are arranged at equal intervals on a straight line. The distance between the line formed by the electrode 87a and the line formed by the electrode 87b, the distance between the line formed by the electrode 87b and the line formed by the electrode 87c, the distance between the line formed by the electrode 87c and the line formed by the electrode 87d, and the electrode 87d The distance between the line formed by the electrode 87e and the line formed by the electrode 87e, the line formed by the electrode 87f, and the line formed by the electrode 87f and the line formed by the electrode 87g are the same. Thus, the electrodes 87a to 87g are arranged in a matrix. Then, it is assumed that the actuator unit 86 and the flow path unit 7 are bonded together so that the range in which the electrodes 87a to 87g are disposed corresponds to the pressure chamber 10 of the flow path unit. As a result, the multiple electrodes 87 a to 87 g are arranged substantially uniformly in a region corresponding to the pressure chamber 10 of the flow path unit 7.

  The electrode region of the piezoelectric ceramic plate 86a (the region within the range where the electrodes 87a to 87g are disposed and the distance from the upper surface of the piezoelectric ceramic plate 86a to the length of the electrodes 87a to 87g) is that of the piezoelectric ceramic plate 86a. The active portions are alternately polarized in the direction perpendicular to the lines formed by the electrodes 87a to 87g along the plane direction.

  All the electrodes 87a are connected to a terminal 91a that is always held at the ground potential through a linear metal wiring 94 arranged along a line formed by the plurality of electrodes 87a. All the electrodes 87b are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential via a linear metal wiring 95 arranged along a line formed by the plurality of electrodes 87b. It is connected to the terminal 92a. All the electrodes 87c are connected to a terminal 91b that is always held at the ground potential through a linear metal wiring 96 arranged along a line formed by the plurality of electrodes 87c. All electrodes 87d are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential via a linear metal wiring 97 arranged along a line formed by a plurality of electrodes 87d. It is connected to the terminal 92b. All the electrodes 87e are connected to a terminal 91c that is always held at the ground potential via a linear metal wiring 98 arranged along a line formed by the plurality of electrodes 87e. All the electrodes 87f are given a drive pulse signal that selectively takes either a ground potential or a positive predetermined potential via a linear metal wiring 99 arranged along a line formed by the plurality of electrodes 87f. It is connected to the terminal 92c. All the electrodes 87g are connected to a terminal 91d that is always held at the ground potential through a linear metal wiring 100 arranged along a line formed by the plurality of electrodes 87g.

  The same drive pulse signal is applied to the terminals 92a, 92b, and 92c. That is, in this embodiment, the potentials of the electrodes 87b, 87d, and 87f are always the same, and the potentials of the electrodes 87a, 87c, 87e, and 87g are always the same ground potential. Accordingly, the seven types of electrodes 87a to 87g can be classified into a first electrode composed of the electrodes 87b, 87d and 87f and a second electrode composed of the electrodes 87a, 87c, 87e and 87g.

  As can be seen from the above description, when the electrodes 87b, 87d, and 87f are at the ground potential, the electrodes 87a to 87g are adjacent to each other in the direction orthogonal to the line (that is, between the electrodes 87a and 87b, No electric field is generated between the electrode 87b and the electrode 87c, between the electrode 87c and the electrode 87d, between the electrode 87d and the electrode 87e, between the electrode 87e and the electrode 87f, and between the electrode 87f and the electrode 87g). However, when the electrodes 87b, 87d, 87f are at a predetermined positive potential, an electric field is generated between the electrodes adjacent to each other in the direction perpendicular to the line formed by the electrodes 87a-87g.

  Since the direction of the electric field is the same as the polarization direction of the piezoelectric ceramic plate 86a, the electrode region sandwiched between the electrodes 87a to 87g of the piezoelectric ceramic plate 86a tends to extend in the plane direction by the piezoelectric action. On the other hand, an electric field is not applied to the non-electrode region where the electrodes 87a to 87g adjacent to the electrode region in the thickness direction of the piezoelectric ceramic plate 86a are not applied, and no force is applied to the surface region. Accordingly, a difference in elongation in the surface direction occurs between the electrode region and the non-electrode region, and the non-electrode region resists the electrode region from extending in the surface direction. As a result, an action similar to that of the actuator unit having the unimorph structure described in Patent Document 3 occurs, and as shown on the left side of FIG. 8, the piezoelectric ceramic plate 86a is curved in the thickness direction so that the electrode region side is convex. To do. At this time, the lower surface (surface on the pressure chamber side) of the piezoelectric ceramic plate 86a is curved in the direction of expanding the pressure chamber. Therefore, ink flows from the manifold channel into the pressure chamber, and the pressure chamber is filled with ink.

  Thereafter, when the electrodes 87b, 87d, 87f reach the ground potential, the electric field is released, and the piezoelectric ceramic plate 86a returns to its original flat plate shape as shown on the right side of FIG. 8 due to its own elasticity. Then, the position of the lower surface of the piezoelectric ceramic plate 86a also returns to the original position, so that the volume of the pressure chamber decreases from the left side in FIG. As a result, pressure is applied to the ink in the pressure chamber, and ink droplets are ejected from nozzles communicating with the pressure chamber. Also in the case of the ink jet head 81 of the present embodiment, either pushing or striking may be used as a method for ejecting ink.

  Further, as illustrated in FIG. 7, concave portions 88 having the same shape as the electrode 87b are formed on both sides of a line formed by the plurality of electrodes 87b. Similarly, as illustrated in FIG. 8, recesses 88 having the same shape as the electrodes 87b to 87f are formed on both sides of each line formed by the plurality of electrodes 87b to 87f. The recess 88 is separated from the outermost electrodes 87b to 87f of each line by the same distance as the distance between the electrodes adjacent in the line direction. As described above, the electrode region of the piezoelectric ceramic plate 86 a is partially and discontinuously surrounded in the plane direction by the plurality of recesses 88.

  Next, a method for manufacturing the inkjet head 81 will be briefly described. In order to manufacture the inkjet head 81, components such as the flow path unit 7 and the actuator unit 81 are separately manufactured, and then the components are assembled.

  Since the procedure for producing the flow path unit 7 is the same as that of the first embodiment described above, description thereof is omitted here. In order to manufacture the actuator unit 81, first, one green sheet of piezoelectric ceramic is prepared, and a large number of cylindrical recesses and recesses 88 for electrode placement are pressed or laser-processed in a portion corresponding to the pressure chamber of the green sheet. Formed by processing. The press working is advantageous in that it can be performed simultaneously when the green sheet is formed into a predetermined shape corresponding to the actuator unit 6.

  Thereafter, a paste-like conductive material is poured into the cylindrical recess, and then the piezoelectric ceramic green sheet is degreased in the same manner as known ceramics and further fired at a predetermined temperature. Thereby, the piezoelectric ceramic plate 86a in which the electrodes 87a to 87g are arranged in the cylindrical recess and the recesses 88 are formed on both sides of each line formed by the plurality of electrodes 87b to 87f is obtained. And actuator unit 86 is obtained by giving metal wiring 94-100 to electrodes 87a-87g by printing or vapor deposition. Note that the piezoelectric ceramic green sheet is designed in advance in consideration of the amount of shrinkage caused by firing.

  Thereafter, the flow path unit 7 and the actuator unit 86 are bonded together using a thermosetting adhesive with the position of the electrode region and the position of the pressure chamber 10, and prepared separately from the actuator unit 86. Bonding is performed using solder so that terminals corresponding to the FPCs overlap each other.

  Thereafter, in a state where the potentials of the electrodes 87a, 87c, 87e, and 87g are held at the ground potential, a high potential is applied to the electrodes 87b, 87d, and 87f, so that the piezoelectric ceramic plate 86a in the electrode region is opposed to the electrodes, that is, in the plane direction. Are polarized in a direction perpendicular to the lines formed by the electrodes 87a to 87g, and this region is defined as an active portion. The ink jet head 81 is completed through the above steps.

  In the manufacturing process described above, the cylindrical recess and the recess 88 may be formed by laser processing after the green sheet is fired. Moreover, you may make it arrange | position an electrode in a cylindrical recessed part after baking of a green sheet. Further, FPC may be bonded after the polarization step. In this case, it is necessary to apply a potential to the electrodes 87a to 87g from other than the FPC.

  Thus, according to the actuator unit 81 which is the liquid pressure generating mechanism according to the present embodiment, the potential difference between the electrodes 87a, 87c, 87e, 87g and the electrodes 87b, 87d, 87f arranged in the piezoelectric ceramic plate 86a is controlled. By doing so, it is possible to switch the piezoelectric ceramic plate 86a to either a curved state in the thickness direction or a non-curved state. Therefore, it is possible to apply pressure to the ink in the desired pressure chamber 10 to eject the ink.

  In addition, the actuator unit 81 of the present embodiment can be easily manufactured by a simple process of disposing the electrodes 87a to 87g on the piezoelectric ceramic plate 86a. Therefore, it has the outstanding advantage that manufacturing cost can be suppressed low. In addition, since the recessed part 88 can be formed simultaneously with many cylindrical recessed parts for electrode arrangement | positioning, a manufacturing process does not become complicated compared with 1st Embodiment. Further, since the actuator unit 81 does not have a structure in which a large number of piezoelectric ceramic plates and thin layer electrodes are stacked as in Patent Document 1 and Patent Document 2, the electrodes are disposed through a non-electrode region having a sufficient thickness. Therefore, even if there are fine cracks in the piezoelectric ceramic plate 86a, there are few failures such as short-circuiting between adjacent electrodes due to ink leakage, and the durability is high.

  In the present embodiment, since the electrode region of the piezoelectric ceramic plate 86a is partially and discontinuously surrounded by the plurality of recesses 88 in the plane direction, one electrode region of the piezoelectric ceramic plate 86a is deformed. Can be prevented from propagating to adjacent electrode regions. Therefore, the ink ejection from the nozzle 9 adjacent to the nozzle 9 from which the ink is ejected is less likely to be adversely affected, and crosstalk is suppressed. In addition, the same benefits as in the first embodiment can be obtained.

  In the present embodiment, the axial length of the recess 88 is the same as the axial length of the electrodes 87a to 87g, but the axial length of the recess 88 is the axial length of the electrodes 87a to 87g. By making it longer than this, the crosstalk reduction effect can be enhanced. Further, the crosstalk reduction effect can be further enhanced by surrounding the electrode region continuously with a groove-like recess rather than discontinuously surrounding the electrode region with the cylindrical recess 88. The recess 88 can be provided on the outer periphery of a circular arrangement of electrodes as shown in FIG. 3, and can also be applied to the two-layer structure shown in FIG.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications are possible as long as they are described in the claims. . For example, the electrodes may be arranged not only in concentric rings or lines but also in concentric elliptical or concentric rectangular shapes in the piezoelectric ceramic plate, and may or may not be arranged in a ring. It may not be equally spaced. In the first and third embodiments, the piezoelectric ceramic plate has one layer, and in the second embodiment, the piezoelectric ceramic plate has two layers. However, three or more piezoelectric ceramic plates may be stacked. At this time, the electrode should just be arrange | positioned in the outermost layer so that it may not penetrate all the layers.

  Further, the shape and distribution of the electrodes arranged in the plate-like body made of the piezoelectric material are arbitrary. For example, in the above-described embodiment, relatively small electrodes are used and these are appropriately distributed. However, one set of large strip-shaped electrodes may be arranged so as to face each other. In the above-described embodiment, the electrode is unevenly distributed on the upper surface side of the actuator unit so that one end of the electrode is exposed. However, the electrode may be embedded in the actuator unit and the one end of the electrode may not be exposed. . The electrode may be unevenly distributed on the lower surface (surface on the pressure chamber side) side of the actuator unit. This reduces the volume of the pressure chamber when an electric field is applied.

  Moreover, in the above-described embodiment, the polarization direction of the piezoelectric ceramic plate is the same as the electric field direction, but the polarization direction may be a direction intersecting the electric field direction. For example, in FIG. 1, the electrodes 17a and 17b, the electrodes 17b and 17c, and the electrodes 17c and 17d are polarized in the thickness direction of the piezoelectric ceramic plate and alternately in opposite directions. Furthermore, it is polarized symmetrically about the electrode 17a. If it does in this way, between each electrode will carry out shear mode deformation | transformation, and it will deform | transform into the cone shape which made the electrode 17a the vertex as the whole electrode area | region. At this time, since the electrodes cannot be used to polarize the piezoelectric ceramic plate, it is necessary to polarize the piezoelectric ceramic plate by another means before attaching the FPC. In the above-described embodiment, the relationship between the positive potential and the ground potential applied to a large number of electrodes may be interchanged, and the positive potential and the negative potential or the negative potential and the ground potential may be applied.

  In addition, in the liquid droplet ejecting apparatus configured in the same manner as the ink jet printer described in the above-described embodiment, by using a conductive paste as the ejecting medium, an extremely fine electric circuit pattern can be printed or the ejecting medium can be used. A high-definition display device such as an organic electroluminescence display (OELD) can also be created by using an organic light emitter. In addition, the droplet ejecting apparatus configured in the same manner as the ink jet printer described in the above-described embodiment can be used in a wide range as long as it is used for forming minute dots on a print medium.

It is the fragmentary sectional view which cut | disconnected the inkjet head containing the actuator unit which is a liquid pressure generation mechanism which concerns on the 1st Embodiment of this invention along the longitudinal direction. It is the fragmentary sectional view which cut | disconnected the inkjet head shown in FIG. 1 along the width direction. FIG. 2 is a partially enlarged perspective view of the actuator unit shown in FIG. 1. It is a perspective view which shows the modification of the actuator unit shown by FIG. It is the fragmentary sectional view which cut | disconnected the inkjet head containing the actuator unit which is a liquid pressure generation mechanism which concerns on the 2nd Embodiment of this invention along the longitudinal direction. FIG. 6 is a partially enlarged perspective view of the actuator unit shown in FIG. 5. It is the fragmentary sectional view which cut | disconnected the inkjet head containing the actuator unit which is a liquid pressure generation mechanism which concerns on the 3rd Embodiment of this invention along the longitudinal direction. FIG. 8 is a partially enlarged perspective view of the actuator unit shown in FIG. 7. It is the fragmentary sectional view which cut | disconnected the conventional inkjet head along the longitudinal direction.

1 Inkjet head (fluid pressure generating mechanism)
6 Actuator unit 6a Piezoelectric ceramic plate (plate-shaped body)
7 Channel unit 9 Nozzle 10 Pressure chamber 10a Partition wall 17a, 17c Electrode (first electrode)
17b, 17d electrode (second electrode)
21a, 22a, 21b, 22b Terminal 24, 25, 26 Metal wiring

Claims (6)

A plate-like body made of a piezoelectric material;
A first electrode disposed in the plate-like body so as to extend in the thickness direction from the surface without penetrating the plate-like body;
A liquid pressure comprising: a second electrode disposed in the plate-like body so as to extend in the thickness direction from the surface of the plate-like body so as to face the first electrode in the plane direction of the plate-like body. Generation mechanism,
A plurality of the first electrode and the second electrode are provided, each of which has a cylindrical shape,
Further, the plurality of first electrodes and the plurality of second electrodes are alternately arranged in a concentric ring shape,
On the circle formed by arranging the plurality of first electrodes, the plurality of first electrodes are arranged at intervals from each other, and on the circle formed by arranging the plurality of second electrodes, The plurality of second electrodes are spaced apart from each other;
The plurality of first electrodes arranged on the same circle are connected to each other via a ring-shaped first metal wiring having the same diameter as a circle formed by arranging the plurality of first electrodes. The plurality of second electrodes arranged on the same circle are connected to each other via an annular second metal wiring having the same diameter as the circle formed by arranging the plurality of second electrodes. The liquid pressure generating mechanism is characterized in that the first metal wiring and the second metal wiring are arranged concentrically.   The first electrode and the second electrode are opposed to each other on a line extending from the center of the circle formed by arranging the plurality of first electrodes and the plurality of second electrodes toward the circle. The liquid pressure generating mechanism according to claim 1, wherein the liquid pressure generating mechanism is arranged.   The first electrode or the second electrode is arranged at the center of a circle formed by arranging the plurality of first electrodes and the plurality of second electrodes. The liquid pressure generation mechanism according to 1 or 2. The first electrode is connected to a terminal to which a signal for selectively taking either a ground potential or a positive predetermined potential is applied via the first metal wiring,
The second electrode is connected to a terminal held at a ground potential via the second metal wiring,
The first electrode is arranged at the center of a circle formed by arranging the plurality of first electrodes and the plurality of second electrodes. Liquid pressure generation mechanism. The plate-like body has at least three circles formed by arranging the plurality of first electrodes and the plurality of second electrodes,
5. The liquid pressure generating mechanism according to claim 3, wherein a portion where the first electrode and the second electrode face each other increases as the distance from the center increases. The liquid pressure generating mechanism according to claim 1, wherein a concave portion having the same shape as the first electrode and the second electrode is formed in the plate-like body .

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