JP2018007360A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator which makes an amount of displacement less likely to be reduced even when driven for a long time.SOLUTION: A piezoelectric actuator 10 of the disclosure includes: a lamination type piezoelectric element 1; and a metal case 2 which houses the lamination type piezoelectric element 1 so that an upper end and a lower end of the lamination type piezoelectric element 1 contact with an inner wall. The metal case 2 includes: a substrate 21 placed in contact with the lower end of the lamination type piezoelectric element 1; and a cylindrical body 22 joined to an upper surface of the substrate 21. The cylindrical body 22 has: a cylindrical part 221 extending vertically; and a flange part 222 connected to a lower end of the cylindrical part 221. Further, a positioning part 3 is provided on an upper surface of the substrate 21 so as to contact with an inner surface of the cylindrical part 221, and a contact part in the positioning part 3, which contacts with at least the cylindrical part 221, is formed by an insulator.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a piezoelectric actuator used in, for example, a mass flow controller, an XY table precision positioning device, and the like.

  The piezoelectric actuator includes a multilayer piezoelectric element and a metal case that houses the multilayer piezoelectric element so that the upper end and the lower end of the multilayer piezoelectric element are in contact with the inner wall, and the metal case contacts the lower end of the multilayer piezoelectric element. It includes a base that is in contact with and a cylinder that is bonded to the upper surface of the base (see, for example, Patent Document 1). Further, the cylindrical body has a structure in which a collar portion for maintaining sealing performance and bonding strength is connected to a lower end of a cylindrical portion extending vertically. Then, for example, it is produced by joining the base body and the collar portion by laser welding or resistance welding in a state where a compressive load is applied to the multilayer piezoelectric element.

Japanese Patent Laid-Open No. 11-22845

  Here, there is a case where a positioning portion is provided on the upper surface of the base body in order to align the base body and the cylindrical body (tubular portion) when the base body and the flange portion are welded.

  However, when such a positioning part is provided, when the base and the collar part are energized to be welded, the positioning part and the cylindrical body (cylindrical part) come into contact with each other, and the parts other than the collar part are welded. For this reason, there is a possibility that the current will be shunted and the welding strength may be reduced. As a result, the displacement amount of the piezoelectric actuator may decrease when driven for a long time.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a piezoelectric actuator capable of maintaining a stable displacement even when driven for a long period of time.

  The piezoelectric actuator of the present disclosure includes a multilayer piezoelectric element, and a metal case that houses the multilayer piezoelectric element so that an upper end and a lower end of the multilayer piezoelectric element are in contact with an inner wall, and the metal case includes the multilayer piezoelectric element. Including a base that is in contact with the lower end of the piezoelectric element and a cylindrical body joined to the upper surface of the base, the cylindrical body being connected to the cylindrical part extending vertically and the lower end of the cylindrical part A positioning portion is provided on the upper surface of the base body so as to contact the inner surface of the cylindrical portion, and at least a contact portion of the positioning portion with the cylindrical portion is made of an insulator. It is characterized by.

  According to the piezoelectric actuator of the present disclosure, stable displacement can be maintained even when driven for a long time.

It is a schematic perspective view which shows an example of embodiment of a piezoelectric actuator. It is the schematic sectional drawing cut | disconnected by the AA line of the piezoelectric actuator shown in FIG. (A) is an expanded sectional view of an example of the region B shown in FIG. 2, and (b) is a partially omitted plan view of the example of the region B shown in FIG. FIG. 3 is a partially omitted perspective view of an example of a region B shown in FIG. 2. FIG. 3 is a schematic perspective view of an example of the multilayer piezoelectric element shown in FIG. 2. FIG. 10 is a partially omitted plan view of another example of the region B shown in FIG. 2. FIG. 10 is a partially omitted plan view of another example of the region B shown in FIG. 2. (A) is an expanded sectional view of the other example of the area | region B shown in FIG. 2, (b) is a partially-omission top view of the other example of the area | region B shown in FIG. It is a partially-omission perspective view of the other example of the area | region B shown in FIG. (A) is an expanded sectional view of the other example of the area | region B shown in FIG. 2, (b) is a partially-omission perspective view of the other example of the area | region B shown in FIG. (A) is an expanded sectional view of the other example of the area | region B shown in FIG. 2, (b) is a partially-omission top view of the other example of the area | region B shown in FIG. It is. FIG. 10 is a partially omitted plan view of another example of the region B shown in FIG. 2. FIG. 10 is a partially omitted plan view of another example of the region B shown in FIG. 2. FIG. 10 is a partially omitted plan view of another example of the region B shown in FIG. 2. It is an expanded sectional view of the other example of the area | region B shown in FIG. It is an expanded sectional view of the other example of the area | region B shown in FIG.

  Hereinafter, embodiments of the piezoelectric actuator of the present disclosure will be described with reference to the drawings. In addition, this invention is not limited by embodiment shown below.

  1 is a schematic perspective view of an example of an embodiment of a piezoelectric actuator, FIG. 2 is a schematic cross-sectional view of the piezoelectric actuator shown in FIG. 1 cut along the line AA, and FIG. 3A is an example of a region B shown in FIG. 3B is a partially omitted plan view of an example of the region B shown in FIG. 2, FIG. 4 is a partially omitted perspective view of the example of the region B shown in FIG. 2, and FIG. It is a schematic perspective view of an example of the laminated piezoelectric element shown.

  The piezoelectric actuator 10 shown in FIGS. 1 to 4 includes a multilayer piezoelectric element 1 and a metal case 2 that houses the multilayer piezoelectric element 1 so that the upper end and the lower end of the multilayer piezoelectric element 1 are in contact with the inner wall. Yes. The metal case 2 includes a base 21 that is in contact with the lower end of the multilayer piezoelectric element 1 and a cylindrical body 22 that is joined to the upper surface of the base 21. The cylindrical body 22 is a cylindrical portion 221 that extends vertically. And a flange portion 222 connected to the lower end of the cylindrical portion 221. Further, the positioning portion 3 is provided on the upper surface of the base body 21 so as to be in contact with the inner surface of the tubular portion 221, and at least the contact portion with the tubular portion 221 in the positioning portion 3 is made of the insulator 31.

  As shown in FIG. 5, the stacked piezoelectric element 1 includes, for example, an active portion in which a plurality of piezoelectric layers 11 and internal electrode layers 12 are alternately stacked, and a piezoelectric layer that is stacked at both ends of the active portion in the stacking direction. 11 is a multilayer piezoelectric element including a multilayer body 13 having an inactive portion 11. Here, the active part is a part where the piezoelectric layer expands or contracts in the stacking direction during driving, and the inactive part is a part where the piezoelectric layer does not extend or contract in the stacking direction during driving.

  The multilayer body 13 constituting the multilayer piezoelectric element 1 is formed in a rectangular parallelepiped shape having, for example, a length of 4 to 7 mm, a width of 4 to 7 mm, and a height of about 20 to 50 mm. In addition, as the laminated body 13, a hexagonal column shape, an octagonal column shape, etc. may be sufficient, for example.

The plurality of piezoelectric layers 11 constituting the laminated body 13 are made of piezoelectric ceramics, and the piezoelectric ceramics have an average particle diameter of, for example, 1.6 to 2.8 μm. Examples of piezoelectric ceramics include perovskite oxides composed of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (L
iTaO ₃ ) or the like can be used.

  Further, the plurality of internal electrode layers 12 constituting the laminate 13 are mainly composed of a metal such as silver, silver-palladium, silver-platinum, or copper. For example, positive electrodes and negative electrodes are alternately arranged in the stacking direction. The positive electrode is drawn out on one side surface of the laminate 13 and the negative electrode is drawn out on the other side surface.

  The laminate 13 may include a metal layer that is a layer for relaxing stress and does not function as an internal electrode layer.

  The pair of side surfaces of the laminate 13 from which the positive electrode or the negative electrode (or the ground electrode) of the internal electrode layer 12 is drawn are provided with external electrodes 14 and are electrically connected to the drawn internal electrode layer 12. ing. The external electrode 14 is a metallized layer made of a sintered body of silver and glass, for example.

On the other hand, both the positive electrode and the negative electrode (or the ground electrode) of the internal electrode layer 12 are exposed on the other pair of side surfaces facing each other of the laminate 13, and the coating layer 15 made of oxide is necessary on this side surface. Is formed. Formation of the covering layer 15 can prevent creeping discharge between the two electrodes that occurs when a high voltage is applied during driving. Examples of the oxide forming the coating layer 15 include ceramic materials. In particular, the oxide can form a creeping discharge due to the coating layer 15 being peeled off due to the driving deformation (stretching) of the laminate 13 when the piezoelectric actuator 10 is driven. It is preferable that the material be deformable by stress so that it does not occur. Specifically, stress occurs when locally phase transformation to volume change to deformable partially stabilized _{zirconia, Ln 1-X Si X AlO} 3 + 0.5X (Ln is, Sn, Y, La, Ce, A ceramic material such as Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, at least one selected from x = 0.01 to 0.3), Alternatively, piezoelectric materials such as barium titanate and lead zirconate titanate, in which the distance between ions in the crystal lattice changes so as to relieve the generated stress, can be mentioned. The covering layer 15 is formed, for example, by forming it into an ink form, applying it to the side surface of the laminate 13 by dipping or screen printing, and sintering.

  The piezoelectric actuator 10 includes a metal case 2 that houses the multilayer piezoelectric element 1 so that the upper and lower ends of the multilayer piezoelectric element 1 are in contact with the inner wall. The metal case 2 includes a base body 21, a cylindrical body 22 having a lower end portion joined to the upper surface of the base body 21, and a lid body 23 joined to the upper end portion of the cylindrical body 22. The lower end surface of the multilayer piezoelectric element 1 is brought into contact with the upper surface of the base body 21, and the upper end surface of the multilayer piezoelectric element 1 is brought into contact with the lower surface of the lid body 23.

  The base body 21, the cylindrical body 22, and the lid body 23 are made of a metal body such as SUS304 or SUS316L.

  The cylindrical body 22 has a cylindrical portion 221 that extends vertically and a flange portion 222 that is connected to the lower end of the cylindrical portion 221. The cylindrical body 22 is formed, for example, in a bellows shape by producing a seamless tube with a predetermined shape and then rolling or hydrostatic pressing. The cylindrical body 22 has a predetermined spring constant so that it can follow the expansion and contraction of the multilayer piezoelectric element 1 when a voltage is applied to the multilayer piezoelectric element 1, and the spring 22 depends on the thickness, groove shape, and number of grooves. The constant is adjusted. For example, the thickness of the cylindrical body 22 is set to 0.1 to 0.5 mm, for example. The cylindrical portion 221 extending vertically from the cylindrical body 22 to the one end side opening (upper end side opening) is cylindrical, but the other end side opening (lower end side opening) of the cylindrical body 22 is directed radially outward. It has a so-called trumpet shape. As described above, the other end side opening of the cylindrical body 22 has a trumpet shape, so that the cylindrical body 22 has a structure having the flange portion 222.

  Moreover, the base | substrate 21 is a disk-shaped thing, and the peripheral part is thinner than another site | part in the example shown to a figure. The peripheral portion of the base body 21 and the flange portion 222 of the cylindrical body 22 are joined by, for example, welding so that a compressive load is applied to the multilayer piezoelectric element 1. The base 21 is formed with two through holes through which the lead pins 43 can be inserted, and the lead pins 43 are inserted through the through holes. And the clearance gap of a through-hole is filled with the soft glass 44, for example, and the lead pin 43 is being fixed. A lead wire 41 is connected to the tip of the lead pin 43, and the lead wire 41 is attached to the external electrode 14 with solder 422. A drive voltage is applied to the multilayer piezoelectric element 1 via the lead pin 43 and the lead wire 41. Is applied.

  The lid body 23 is formed to have the same outer diameter as the inner diameter of the opening on the one end side of the cylindrical body 22. A lid body 23 is fitted from one end side opening of the cylindrical body 22, and the side surface is joined to the inner wall near the one end side opening (near the upper end) of the cylindrical body 22 by welding, for example.

  At this time, the flange portion 222 of the cylindrical body 22 and the base body 21 are joined in a state where a compressive load is applied to the multilayer piezoelectric element 1.

  As shown in FIGS. 2 to 4, the positioning portion 3 is provided on the upper surface of the base 21 so as to be in contact with the inner surface of the cylindrical portion 221. The positioning portion 3 is provided to align the position of the base body 21 and the cylindrical body 22 (cylindrical part 221) when welding the base body 21 and the flange portion 222 (position in a direction parallel to the upper surface of the base body 21). It is what was done. The positioning unit 3 places the laminated piezoelectric element 1 in a region between the laminated piezoelectric element 1 and the cylindrical body 22 on the upper surface of the base 21 constituting the metal case 2 with a gap from the laminated piezoelectric element 1. It is provided so as to surround it.

  Further, the positioning part 3 is an insulator 31 at least in contact with the cylindrical part 221. With such a configuration, the current during resistance welding between the base body 21 and the flange portion 222 is not diverted toward the positioning portion 3. Therefore, it is possible to realize the piezoelectric actuator 10 that can maintain a stable displacement even when driven for a long period of time without reducing the welding strength.

  As shown in FIGS. 2 to 4, the positioning portion 3 can be configured by an annular wall in plan view surrounding the multilayer piezoelectric element 1 continuously around the circumference. Here, the thickness of the positioning portion 3 in the example shown in FIGS. 2 to 4 (width along the radial direction of the base body 21) is preferably 0.1 to 0.3 mm, for example, from the viewpoint of heat distribution and miniaturization. Is set. The height of the positioning portion 3 in the examples shown in FIGS. 2 to 4 is preferably from the viewpoint of suppressing the intrusion of particles generated during welding or improving the insertability of the cylindrical body 22. For example, the thickness is set to be 0.5 to 1.0 mm higher than the thickness.

  Moreover, as the positioning part 3, as shown in FIG. 6, the structure which consists of a circular arc-shaped wall by the planar view arrange | positioned around the lamination type piezoelectric element 1 may be sufficient, and it shows in FIG. Thus, the structure which consists of a some thin columnar body arrange | positioned around the lamination type piezoelectric element 1 in the circumferential direction may be sufficient.

  Here, as the insulator 31, a resin such as polyimide or PEEK (polyetheretherketone) can be used. By making the insulator 31 that is in contact with the cylindrical portion 221 from resin, it is difficult to inhibit the shrinkage of the metal case 2 during welding, and the stress applied during welding can be further reduced to increase the welding strength. it can. Therefore, a more stable displacement can be maintained even when driven for a long time.

In addition, the structure where the whole positioning part 3 consists of the insulator 31 may be sufficient as the contact part with the cylindrical part 221 in the positioning part 3 being the insulator 31. The cylindrical part in the positioning part 3 may be sufficient as it. This means that the contact portion with 221 may be an insulator 31 and the non-contact portion (an opposite side far from the contact portion) may be a metal body 32. 2 to 4, 6, and 7, a configuration in which the entire positioning portion 3 is formed of the insulator 31 is illustrated.

  On the other hand, as shown in FIGS. 8 to 16, the positioning portion 3 includes a metal body 32 erected on the upper surface of the base 21 and an insulator 31 provided on the outer surface of the metal body 32. You can also Since the positioning portion 3 is composed of the inner metal body 32 and the insulator 31 provided on the outer surface of the metal body 32, the lateral displacement during welding is reduced, and the base body 21 and the flange portion 222 are accurately connected. It can be welded, and more stable displacement can be maintained even when driven for a long time.

  Specifically, as shown in FIGS. 8 to 10, the positioning unit 3 is configured such that the upper surface of the base body 21 protrudes over almost the entire area between the multilayer piezoelectric element 1 and the cylindrical portion 221 of the cylindrical body 22. It can be. The configuration shown in FIGS. 8 to 10 includes a pair of penetrations having a recess for inserting the end of the multilayer piezoelectric element 1 at the center of the positioning unit 3 and the lead pin 43 inserted through the positioning unit 3. It is the structure which has a hole.

  Here, as shown in FIGS. 8 and 9, the insulator 31 can cover the outer surface of the metal body 32. Here, the insulator 31 covering the outer surface of the metal body 32 means that the entire outer peripheral surface (side surface) is covered. As shown in FIG. 10, the insulator 31 may cover a part of the outer peripheral surface of the metal body 32. However, as shown in FIGS. 8 and 9, the insulator 31 is formed of the metal body 32. By adopting a configuration that covers the entire outer peripheral surface, it is possible to reduce the possibility that a shunt path is formed by spark or the like.

  Further, as shown in FIG. 11, the positioning portion 3 is configured by an annular wall having a two-layer structure of an insulator 31 and a metal body 32 in a plan view surrounding the multilayer piezoelectric element 1 continuously around the circumference. be able to. In this case, the thickness of the metal body 32 in plan view is set to 0.3 to 1 mm, for example, and the thickness of the insulator 31 in plan view is set to 0.05 to 0.3 mm, for example.

  Further, as shown in FIG. 12, as the positioning portion 3, a metal body 32 composed of a plurality of arc-shaped walls arranged in the circumferential direction around the multilayer piezoelectric element 1 and an outer side of the metal body 32. The structure provided with the insulator 31 which consists of the cyclic | annular wall provided in one round continuously may be sufficient. Further, as shown in FIG. 13, as the positioning portion 3, a metal body 32 composed of a plurality of thin columnar bodies arranged in the circumferential direction around the multilayer piezoelectric element 1, and one round continuous to the outside of the metal body 32. The structure provided with the insulator 31 which consists of the cyclic | annular wall provided in this way may be sufficient.

  Further, as shown in FIG. 14, as the positioning portion 3, from a plurality of arc-shaped walls having a two-layer structure of an insulator 31 and a metal body 32 in a circumferential view around the multilayer piezoelectric element 1. In this configuration, the insulator 31 can be wider than the metal body 32 in the circumferential direction. Also with this configuration, it is possible to reduce the possibility that a shunt path is formed due to spark or the like.

  Further, as shown in FIG. 15, the height of the upper surface of the insulator 31 can be higher than the height of the upper surface of the metal body 32. By setting the insulator 31 arranged on the outer side to be taller than the inner metal body 31, the possibility that a shunt path is formed by spark or the like can be further reduced. The height of the upper surface of the insulator 31 is set to be, for example, 0.03 to 0.2 mm higher than the height of the upper surface of the metal body 32.

Further, as shown in FIG. 16, the insulator 31 may be covered up to the upper surface of the metal body 32. With this configuration, it is possible to further reduce the possibility that a shunt path is formed due to spark or the like.

  Further, as shown in FIGS. 14 to 16, the thickness of the insulator 31 (thickness along the radial direction of the base 21) can be made thinner than the thickness of the metal body 32 in the cross-sectional view. Thereby, the heat extraction from the insulator 31 at the time of welding becomes good, and it can be made small and excellent in reliability. For example, when the thickness of the metal body 32 is 0.5 mm, the thickness of the insulator 31 can be set to 0.1 to 0.6 times the thickness of the metal body 32.

  Moreover, as shown in FIGS. 2 to 4 and FIGS. 8 to 13, it is preferable that the positioning unit 3 continuously surrounds the multilayer piezoelectric element 1. With this configuration, the heat dissipation effect is most excellent, and it also has a role to reinforce the base body 21 from being twisted from driving vibration or external impact.

  Further, as shown in FIGS. 2 to 4, 6, 7, and 11 to 16, the metal body 32 is surrounded so as not to come into contact with the multilayer piezoelectric element 1. Since part of the heat generated when welding the flange portion 222 can be released to the positioning portion 3 and radiated from the positioning portion 3, the piezoelectric actuator 10 having higher reliability can be obtained.

  Next, a method for manufacturing the piezoelectric actuator 10 according to the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 11 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced from this ceramic slurry by using tape forming methods, such as a well-known doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of PbZrO ₃ —PbTiO ₃ may be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

  Next, a conductive paste to be the internal electrode layer 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is printed on the ceramic green sheet using a screen printing method, and then a plurality of ceramic green sheets on which the conductive paste is printed are stacked, and the conductive paste is formed at both ends in the stacking direction. A multilayer molded body is obtained by laminating a plurality of ceramic green sheets that are not printed. After debinding the laminated molded body at a predetermined temperature, the laminated body 13 is obtained by firing at 900 to 1200 ° C.

  Next, an oxide ink is printed by screen printing on a pair of side surfaces from which both internal electrode layers 12 (positive electrode and negative electrode) are led out of the side surfaces of the laminate 13, and then fired at 900 to 1200 ° C. Layer 15 is formed.

  The oxide ink disperses the powder of the oxide in a solution of a solvent, a dispersant, a plasticizer, and a binder, and then pulverizes the powder by passing three rolls several times. It is produced by dispersing powder.

Next, the external electrode 14 made of a metallized layer is formed. First, a silver glass-containing conductive paste is prepared by adding a binder to silver particles and glass powder, and printing is performed by screen printing on a pair of opposing side surfaces of the laminate 13 from which the positive electrode or negative electrode of the internal electrode layer 12 is derived. The baking process is performed at a temperature of about 500 to 800 ° C. As a result, the external electrode 14 made of a metallized layer is formed to complete the multilayer piezoelectric element 1.

  Next, the external electrode 14 and the lead wire 41 are soldered.

  Moreover, while forming the annular part (not shown) for resistance welding by cutting, the base | substrate 21 which forms a through-hole by drilling is prepared. Here, when the positioning portion 3 is made of the insulator 31, the insulator 31 is formed by a method of fixing a member made of the insulator 31 with an adhesive or by forming a groove in the base 21 during cutting and press-fitting into the groove. It can be produced using a method for fixing. On the other hand, when the positioning part 3 is composed of the insulator 31 and the metal body 32, the metal body 32 portion is formed by cutting, and at the same time, a groove is formed in the base 21, and the insulator 31 is fixed by press-fitting into the groove. Or a method of fixing the insulator 31 to the outer surface of the metal body 32 with an adhesive or the like.

  The metal body 32 constituting the positioning unit 3 may be formed by cutting the base body 21 or by fixing another member (for example, a ring-shaped member).

  Next, the lead pins 43 are inserted into the two through holes formed in the base body 21 and the gap is filled with the soft glass 44 and fixed, and the lower end portion of the multilayer piezoelectric element 1 is bonded to the upper surface of the base body 21. Glue with the agent. Then, the lead wire 41 soldered to the external electrode 14 of the multilayer piezoelectric element 1 with the solder 42 and the lead pin 43 attached to the base 21 are connected by solder.

  Next, a bellows shape is formed on the seamless cylindrical cylindrical body 22 made of SUS304 by rolling. By changing the die shape during rolling, the thickness of the groove and the radius of curvature can be changed. A lid body 23 made of SUS304 is welded by laser welding so as to close an opening on one end side (upper end side) of the cylindrical body 22. A flange 222 is formed on the other end side (lower end side) of the cylindrical body 22.

  Next, the cylindrical body 22 is placed on the laminated piezoelectric element 1 bonded to the base 21, the cylindrical body is pulled with a predetermined load, and a load is applied to the laminated piezoelectric element 1. In this state, the flange portion 222 of the cylindrical body 22 and the base body 21 are welded by resistance welding.

  Finally, the piezoelectric actuator of this embodiment is completed by applying a DC electric field of 0.1 to 3 kV / mm to the lead pins 43 attached to the base 21 to polarize the laminate 13. Then, by connecting the lead pin 43 and an external power source and applying a voltage to the piezoelectric layer 11, each piezoelectric layer 11 can be largely displaced by the inverse piezoelectric effect.

  The piezoelectric actuator 10 of this embodiment is obtained by the above manufacturing method.

  The piezoelectric actuator as an example was produced as follows.

First, a ceramic slurry is prepared by mixing a calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ) having an average particle size of 0.4 μm, a binder, and a plasticizer. A ceramic green sheet to be a piezoelectric layer having a thickness of 120 μm was prepared.

On one side of this ceramic green sheet, 260 ceramic green sheets obtained by printing a conductive paste to be an internal electrode prepared by adding a binder to a silver-palladium alloy (silver 95% by mass-palladium 5% by mass) by screen printing. A laminated molded body was prepared by laminating 20 sheets of ceramic green sheets without conductive paste on the top and bottom thereof.

  Next, after cutting the laminated molded body with a dicing saw machine so as to have a predetermined size, the laminated molded body was dried and fired to produce a laminated body. Firing was performed at 1000 ° C. for 200 minutes after holding a temperature of 800 ° C. for 90 minutes. The laminate had a rectangular parallelepiped shape, and the size thereof was 5 mm in length, 5 mm in width, and 35 mm in height.

  Next, an ink made of lead zirconate titanate is prepared, and each of the internal electrode layers is exposed on the side surface of the laminate by screen printing so that the coating layer has a thickness of 20 μm. After printing, it was baked at 1000 ° C. to form a coating layer on the side surface of the laminate.

  Next, a silver glass-containing conductive paste is prepared by adding a binder to silver particles and glass powder, and this is printed on the side surface of the laminate by a screen printing method and baked at a temperature of about 500 to 800 ° C. After forming the electrode, the lead wire was connected to the external electrode by soldering.

  In addition, a disk-shaped substrate was made of SUS304. Specifically, a metal body constituting the positioning portion by cutting and an annular portion to be welded were provided, and a base body having a shape shown in FIG. 2 in which through holes were formed at two locations was produced. And the lead pin was attached to the through-hole formed in the base | substrate with soft glass. In addition, the metal body which comprises a positioning part was made into the ring shape of height 1.0mm and thickness (width of the radial direction of a base | substrate) 0.3mm. The annular portion had a triangular cross section with a height of 0.2 mm and a width of 0.5 mm.

  And the insulator was provided in the outer side of the metal body. The insulator was made of a polyimide film having a thickness of 0.05 mm and a height of 1.5 mm, and was fixed to the outer surface of the metal body with an adhesive. In addition, the form of the positioning part produced here was made into the form shown in FIG.

  Next, the laminate was fixed to the upper surface of the base with an adhesive, and the lead wire soldered to the external electrode and the lead pin attached to the base were connected by soldering.

  Next, a disk-shaped lid was made of SUS304.

  Moreover, the cylindrical body which formed the bellows shape and the trumpet-shaped lower end part (ridge part) by rolling to the seamless cylinder made from SUS316L with a thickness of 0.15 mm was produced.

  The lid was inserted into the produced cylinder, and the cylinder and the lid were welded. Then, the welded material is placed on the laminated piezoelectric element bonded to the base, the cylinder is pulled with a predetermined load, the load is applied to the laminated piezoelectric element, and the cylindrical body and the annular portion of the base are brought into contact with each other. The parts were welded by resistance welding.

  Finally, a 3 kV / mm DC electric field was applied to the two lead pins for 15 minutes for polarization treatment, and the piezoelectric actuator of the example was manufactured.

  On the other hand, as a comparative example, the positioning portion has the same configuration as described above except that the positioning portion is made of a ring-shaped metal body having a height of 1.0 mm and a thickness (width in the radial direction of the substrate) of 0.3 mm. A piezoelectric actuator was fabricated.

  And about each piezoelectric actuator of an Example and a comparative example, the displacement amount before and behind an endurance test was measured with the displacement measuring device.

First, a 200 V DC voltage was applied to each piezoelectric actuator to determine the initial displacement. The displacement of the piezoelectric actuators of the example and the comparative example were both 55 μm.

  Further, an endurance test was performed on these piezoelectric actuators, which continued to be driven at room temperature at a voltage of 200 V for 1000 hours. As a result, the displacement amount of the piezoelectric actuator of the example hardly changed, whereas the displacement amount of the piezoelectric actuator of the comparative example decreased by about 10%.

  Thus, it was confirmed that the displacement amount of the piezoelectric actuator of the example can be obtained stably for a long period of time.

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric actuator 1 ... Laminated piezoelectric element 11 ... Piezoelectric layer 12 ... Internal electrode layer 13 ... Laminated body 14 ... External electrode 15 ... Covering layer 2 ... Metal case 21 ... Base 22 ... Cylinder 221 ... Cylindrical part 222 ... Bridge 23 ... Lid 3 ... Positioning part 31 ... Insulator 32 ... Metal 41 ... lead wire 42 ... solder 43 ... lead pin 44 ... soft glass

Claims (7)

  A multi-layer piezoelectric element; and a metal case that houses the multi-layer piezoelectric element so that an upper end and a lower end of the multi-layer piezoelectric element are in contact with an inner wall, and the metal case contacts the lower end of the multi-layer piezoelectric element. A cylindrical body joined to the upper surface of the base body, the cylindrical body extending vertically, and a flange portion connected to the lower end of the cylindrical part, A piezoelectric actuator, wherein a positioning portion is provided on an upper surface of the base so as to be in contact with an inner surface of the cylindrical portion, and at least a contact portion of the positioning portion with the cylindrical portion is made of an insulator.   The piezoelectric actuator according to claim 1, wherein the insulator is a resin.   3. The piezoelectric actuator according to claim 1, wherein the positioning portion includes a metal body erected on an upper surface of the base body and an insulator provided on an outer surface of the metal body.   The piezoelectric actuator according to claim 3, wherein the insulator covers an outer surface of the metal body.   The piezoelectric actuator according to claim 3 or 4, wherein a height of an upper surface of the insulator is higher than a height of an upper surface of the metal body.   6. The piezoelectric actuator according to claim 3, wherein a thickness of the insulator is thinner than a thickness of the metal body.   The piezoelectric actuator according to any one of claims 1 to 6, wherein the positioning portion continuously surrounds the multilayer piezoelectric element.

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