JP6809822B2 - Piezoelectric actuator - Google Patents

Description

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

The piezoelectric actuator includes a laminated piezoelectric element and a metal case containing the laminated piezoelectric element so that the upper and lower ends of the laminated piezoelectric element abut on the inner wall, and the metal case hits the lower end of the laminated piezoelectric element. It includes a contacted substrate and a cylinder bonded to the upper surface of the substrate (see, for example, Patent Document 1). Further, the tubular body has a structure in which a flange portion for maintaining sealing property and joint strength is connected to the lower end of a tubular portion extending vertically. Then, for example, it is manufactured by joining the substrate and the flange portion by laser welding or resistance welding in a state where a compressive load is applied to the laminated piezoelectric element.

Japanese Unexamined Patent Publication No. 11-22845

Here, a positioning portion may be provided on the upper surface of the substrate in order to align the substrate and the tubular body (cylindrical portion) when welding the substrate and the flange portion.

However, when such a positioning portion is provided, when an electric current is applied to weld the substrate and the flange portion, the positioning portion and the tubular body (cylindrical portion) come into contact with each other, and welding is performed on a portion other than the flange portion. There is a risk that the current will be diverted and the welding strength will decrease. As a result, the displacement amount of the piezoelectric actuator may decrease when driven for a long period of time.

The present invention has been made in view of the above circumstances, and an object of the present invention 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 laminated piezoelectric element and a metal case accommodating the laminated piezoelectric element so that the upper and lower ends of the laminated piezoelectric element abut on an inner wall, and the metal case is the laminated. A substrate abutting on the lower end of the mold piezoelectric element and a tubular body joined to the upper surface of the substrate are included, and the tubular body is connected to a tubular portion extending vertically and a lower end of the tubular portion. It has a flange portion, and a positioning portion is provided on the upper surface of the substrate so as to be in contact with the inner surface of the tubular portion. The flange portion is welded to the substrate, and the positioning portion is the substrate. It has a metal body erected on the upper surface of the metal body and an insulator provided on the outer surface of the metal body, and the insulator is a contact portion between the positioning portion and the tubular portion. The metal body surrounds the laminated piezoelectric element at a distance from the laminated piezoelectric element, and the thickness of the insulator is thinner than the thickness of the metal body .

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

It is a schematic perspective view which shows an example of the Embodiment of a piezoelectric actuator. It is the schematic cross-sectional view cut along the line AA of the piezoelectric actuator shown in FIG. (A) is an enlarged cross-sectional view of an example of region B shown in FIG. 2, and (b) is a partially omitted plan view of an example of region B shown in FIG. It is a partially omitted perspective view of an example of the region B shown in FIG. It is a schematic perspective view of an example of the laminated piezoelectric element shown in FIG. It is a partially omitted plan view of another example of region B shown in FIG. It is a partially omitted plan view of another example of region B shown in FIG. (A) is an enlarged cross-sectional view of another example of region B shown in FIG. 2, and (b) is a partially omitted plan view of another example of region B shown in FIG. It is a partially omitted perspective view of another example of region B shown in FIG. (A) is an enlarged cross-sectional view of another example of region B shown in FIG. 2, and (b) is a partially omitted perspective view of another example of region B shown in FIG. (A) is an enlarged cross-sectional view of another example of region B shown in FIG. 2, and (b) is a partially omitted plan view of another example of region B shown in FIG. Is. It is a partially omitted plan view of another example of region B shown in FIG. It is a partially omitted plan view of another example of region B shown in FIG. It is a partially omitted plan view of another example of region B shown in FIG. FIG. 5 is an enlarged cross-sectional view of another example of region B shown in FIG. FIG. 5 is an enlarged cross-sectional view of another example of region B shown in FIG.

Hereinafter, embodiments of the piezoelectric actuator of the present disclosure will be described with reference to the drawings. The present invention is not limited to the embodiments shown below.

FIG. 1 is a schematic perspective view of an example of an embodiment of a piezoelectric actuator, FIG. 2 is a schematic cross-sectional view taken along the line AA of the piezoelectric actuator shown in FIG. 1, and FIG. 3A is an example of region B shown in FIG. 3 (b) is a partially omitted plan view of an example of region B shown in FIG. 2, FIG. 4 is a partially omitted perspective view of an example of region B shown in FIG. 2, and FIG. 5 is shown in FIG. It is the schematic perspective view of the example of the laminated type piezoelectric element shown.

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

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

The laminated body 13 constituting the laminated 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. The laminated body 13 may have, for example, a hexagonal column shape or an octagonal column shape.

The plurality of piezoelectric layers 11 constituting the laminated body 13 are made of piezoelectric ceramics, and the piezoelectric ceramics have an average particle size of, for example, 1.6 to 2.8 μm. Piezoelectric ceramics include, for example, a perovskite-type oxide composed of lead zirconate titanate (PbZrO _3- PbTIO ₃ ), lithium niobate (LiNbO ₃ ), and lithium tantalate (L).
iTaO ₃ ) and the like can be used.

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

The laminated body 13 may include a metal layer or the like that is a layer for relieving stress and does not function as an internal electrode layer.

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

On the other hand, both positive and negative electrodes (or ground electrodes) of the internal electrode layer 12 are exposed on the other pair of opposite side surfaces of the laminated body 13, and a coating layer 15 made of an oxide is required on these side surfaces. Is formed. By forming the coating layer 15, it is possible to prevent creepage discharge between both 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 follow the drive deformation (expansion and contraction) of the laminate 13 when the piezoelectric actuator 10 is driven, and the coating layer 15 is peeled off to cause creeping discharge. It is preferable that the material is deformable by stress so that it does not occur. Specifically, partially stabilized zirconia, Ln _1-X Si _X AlO _{3 + 0.5X} (Ln is Sn, Y, La, Ce, which can be deformed by locally undergoing phase transformation when stress is generated and changing in volume. A ceramic material such as Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and at least one selected from Yb. 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 coating layer 15 is formed by, for example, forming an ink, applying it to the side surface of the laminate 13 by dipping or screen printing, and sintering it.

Further, the piezoelectric actuator 10 includes a metal case 2 containing the laminated piezoelectric element 1 so that the upper and lower ends of the laminated piezoelectric element 1 abut on the inner wall. The metal case 2 includes a base 21, a cylinder 22 having a lower end bonded to the upper surface of the base 21, and a lid 23 joined to the upper end of the cylinder 22. Then, the lower end surface of the laminated piezoelectric element 1 is in contact with the upper surface of the substrate 21, and the upper end surface of the laminated piezoelectric element 1 is in contact with the lower surface of the lid 23.

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

The tubular body 22 has a tubular portion 221 extending vertically and a flange portion 222 connected to the lower end of the tubular portion 221. The tubular body 22 is formed into a bellows shape by, for example, a seamless pipe having a predetermined shape and then rolling or hydrostatic pressing. The tubular body 22 has a predetermined spring constant so that it can follow the expansion and contraction of the laminated piezoelectric element 1 when a voltage is applied to the laminated piezoelectric element 1, and the spring thereof depends on the thickness, groove shape, and number of grooves. The constant is being adjusted. For example, the thickness of the tubular body 22 is, for example, 0.1 to 0.5 mm. The tubular portion 221 extending vertically from the tubular 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 tubular body 22 is radially outward. It has a so-called trumpet shape that spreads out. As described above, the opening on the other end side of the tubular body 22 has a trumpet shape, so that the tubular body 22 has a flange portion 222.

Further, the substrate 21 has a disk shape, and in the example shown in the figure, the peripheral portion is thinner than the other portions. The peripheral edge of the substrate 21 and the flange 222 of the tubular body 22 are joined by welding, for example, so that a compressive load is applied to the laminated piezoelectric element 1. The substrate 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. Then, for example, soft glass 44 is filled in the gap between the through holes, and the lead pin 43 is 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, and a drive voltage is applied to the laminated piezoelectric element 1 via the lead pin 43 and the lead wire 41. Is to be applied.

The lid body 23 is formed so that the outer diameter is the same as the inner diameter of the one-end side opening of the tubular body 22. The lid 23 is fitted from the one end side opening of the tubular body 22, and its side surface is joined to the inner wall in the vicinity of the one end side opening of the tubular body 22 (near the upper end) by, for example, welding.

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

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

Further, the positioning portion 3 has an insulator 31 at least in contact with the tubular portion 221. With such a configuration, the current at the time of resistance welding between the substrate 21 and the flange portion 222 does not flow to the positioning portion 3. Therefore, it is possible to realize the piezoelectric actuator 10 which does not reduce the welding strength and can maintain a stable displacement even if it is driven for a long period of time.

As shown in FIGS. 2 to 4, the positioning unit 3 may be configured to have an annular wall in a plan view that continuously surrounds the laminated piezoelectric element 1 around it. Here, the thickness of the positioning portion 3 (width along the radial direction of the substrate 21) in the examples shown in FIGS. 2 to 4 is preferably 0.1 to 0.3 mm, for example, from the viewpoint of heat distribution and miniaturization. Set. Further, the height of the positioning portion 3 in the examples shown in FIGS. 2 to 4 is preferably the height of the flange portion 222 from the viewpoint of suppressing the intrusion of particles generated during welding and improving the insertability of the tubular body 22. It is set to be, for example, 0.5 to 1.0 mm higher than the thickness.

Further, the positioning unit 3 may have a configuration of a plurality of arcuate walls arranged in the circumferential direction around the laminated piezoelectric element 1 as shown in FIG. 6, and is shown in FIG. 7. As described above, the structure may be composed of a plurality of thin columnar bodies arranged in the circumferential direction around the laminated piezoelectric element 1.

Here, as the insulator 31, a resin such as polyimide or PEEK (polyetheretherketone) can be used. Since the insulator 31 that serves as the contact portion with the tubular portion 221 is made of resin, it is difficult to hinder 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, more stable displacement can be maintained even if it is driven for a long period of time.

The fact that at least the contact portion of the positioning portion 3 with the tubular portion 221 is the insulator 31 may mean that the entire positioning portion 3 is composed of the insulator 31, and the tubular portion of the positioning portion 3 This means that the contact portion with the 221 may be the insulator 31, and the non-contact portion (the portion on the opposite side far from the contact portion) may be the metal body 32. 2 to 4, 6 and 7 show a configuration in which the entire positioning portion 3 is made of an insulator 31.

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

Specifically, as the positioning portion 3, as shown in FIGS. 8 to 10, the upper surface of the substrate 21 projects over almost the entire area between the laminated piezoelectric element 1 and the tubular portion 221 of the tubular body 22. Can be. The configurations shown in FIGS. 8 to 10 have a recess in the central portion of the positioning portion 3 for inserting the end portion of the laminated piezoelectric element 1, and a pair of penetrations through which the lead pin 43 is inserted into the positioning portion 3. It is configured to have holes.

Here, as shown in FIGS. 8 and 9, the insulator 31 can be configured to cover the outer surface of the metal body 32. The fact that the insulator 31 covers the outer surface of the metal body 32 here means that it covers the entire outer peripheral surface (side surface). As shown in FIG. 10, the insulator 31 may cover a part of the outer peripheral surface of the metal body 32, but as shown in FIGS. 8 and 9, the insulator 31 is the metal body 32. By covering the entire outer peripheral surface, it is possible to reduce the possibility that a diversion path is formed due to sparks or the like.

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

Further, as shown in FIG. 12, as the positioning portion 3, a metal body 32 composed of a plurality of arcuate walls arranged in the circumferential direction around the laminated piezoelectric element 1 and an outer side of the metal body 32. It may be configured to include an insulator 31 made of an annular wall provided continuously around the surface. 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 laminated piezoelectric element 1 and a metal body 32 continuous around the outside of the metal body 32. It may be configured to include an insulator 31 made of an annular wall provided therein.

Further, as shown in FIG. 14, as the positioning portion 3, from a plurality of arcuate walls having a two-layer structure of the insulator 31 and the metal body 32 in a plan view arranged around the laminated piezoelectric element 1 in the circumferential direction. In this configuration, the insulator 31 may have a wider width in the circumferential direction than the metal body 32. This configuration also reduces the possibility that a diversion path is formed due to sparks 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 making the insulator 31 arranged on the outer side taller than the metal body 31 on the inner side, it is possible to further reduce the possibility that a diversion path is formed due to sparks or the like. 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 cover the upper surface of the metal body 32. With this configuration, the possibility of forming a diversion path due to sparks or the like can be further reduced.

Further, as shown in FIGS. 14 to 16, the thickness of the insulator 31 (thickness along the radial direction of the substrate 21) can be thinner than the thickness of the metal body 32 in cross-sectional view. As a result, heat is drawn from the insulator 31 at the time of welding, and the size and reliability can be improved. 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.

Further, as shown in FIGS. 2 to 4 and 8 to 13, it is preferable that the positioning portion 3 continuously surrounds the laminated piezoelectric element 1 once. With this configuration, the heat dissipation effect is the best, and it also has a role of reinforcing the substrate 21 so as not to be twisted from the vibration of the drive and the impact from the outside.

Further, as shown in FIGS. 2 to 4, 6, 7, and 11 to 16, the metal body 32 is arranged so as to surround the laminated piezoelectric element 1 so as not to come into contact with the substrate 21. Since a part of the heat generated when welding the flange portion 222 can be released to the positioning portion 3 and dissipated from the positioning portion 3, the piezoelectric actuator 10 having more excellent reliability can be obtained.

Next, a method of 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 ceramics, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. Then, a ceramic green sheet is produced from this ceramic slurry by using a tape molding method such as a well-known doctor blade method or a calender roll method. As the piezoelectric ceramic, any ceramic having piezoelectric characteristics may be used, and for example, a perovskite-type oxide composed of PbZrO _3- PbTiO ₃ or the like can be used. Further, as the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP) and 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 metal powder of a silver-palladium alloy. This conductive paste is printed on the above-mentioned ceramic green sheet by a screen printing method, and then a plurality of ceramic green sheets on which the conductive paste is printed are laminated and conductive pastes are formed on both ends in the lamination direction. A laminated molded body is obtained by laminating a plurality of unprinted ceramic green sheets. The laminated body 13 is obtained by debindering the laminated molded product at a predetermined temperature and then firing it 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 derived from the side surfaces of the laminated body 13, and then fired at 900 to 1200 ° C. for coating. The layer 15 is formed.

In the oxide ink, the oxide powder is dispersed in a solution of a solvent, a dispersant, a plasticizer, and a binder, and then three rolls are passed several times to crush the agglomeration of the powder and at the same time. It is made by dispersing powder.

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

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

Further, a substrate 21 is prepared in which an annular portion (not shown) for resistance welding is formed by cutting and a through hole is formed by hole machining. Here, when the positioning portion 3 is made of an insulator 31, a method of fixing a member made of the insulator 31 with an adhesive, or a groove is formed in the substrate 21 at the time of cutting, and the insulator 31 is press-fitted into the groove. Can be produced by a method of fixing the above. On the other hand, when the positioning portion 3 is composed of the insulator 31 and the metal body 32, the metal body 32 portion is formed by cutting and a groove is formed in the base 21 at the same time, and the insulator 31 is fixed by press fitting into the groove. It can be produced by 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 portion 3 may be formed by cutting the substrate 21 or by fixing another member (for example, a ring-shaped member).

Next, the lead pin 43 is inserted into each of the two through holes formed in the substrate 21, and the gap is filled with soft glass 44 to fix the substrate 21, and the lower end of the laminated piezoelectric element 1 is adhered to the upper surface of the substrate 21. Adhere with an agent. Then, the lead wire 41 soldered to the external electrode 14 of the laminated piezoelectric element 1 with solder 42 and the lead pin 43 attached to the substrate 21 are connected by soldering.

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

Next, the tubular body 22 is put on the laminated piezoelectric element 1 bonded to the substrate 21, the tubular 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 tubular body 22 and the base 21 are welded by resistance welding.

Finally, the piezoelectric actuator of the present embodiment is completed by applying a DC electric field of 0.1 to 3 kV / mm to the lead pin 43 attached to the substrate 21 to polarize the laminated body 13. Then, by connecting the lead pin 43 and the 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 the present embodiment can be obtained by the above manufacturing method.

A piezoelectric actuator as an example was manufactured as follows.

First, a ceramic slurry in which a calcined powder of piezoelectric ceramics containing lead zirconate titanate (PbZrO _3- PbTiO ₃ ) having an average particle size of 0.4 μm as a main component, a binder and a plasticizer is mixed is prepared, and a doctor blade method is performed. A ceramic green sheet to be a piezoelectric layer having a thickness of 120 μm was produced.

260 ceramic green sheets printed with a conductive paste as an internal electrode prepared by adding a binder to a silver-palladium alloy (95% by mass of silver-5% by mass of palladium) on one side of this ceramic green sheet by a screen printing method. A laminated molded body was prepared by laminating 20 sheets of ceramic green sheets without conductive paste on the upper and lower layers.

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 prepare a laminated body. The firing was carried out at 1000 ° C. for 200 minutes after maintaining the temperature at 800 ° C. for 90 minutes. The laminated body had a rectangular parallelepiped shape, and its size was 5 mm in length and 5 mm in width and 35 mm in height.

Next, inks made of lead zirconate titanate were prepared, and screen printing was performed on the side surfaces of the laminate in which both electrodes of the internal electrode layer were exposed so that the thickness of the coating layer was 20 μm. It was printed and then fired at 1000 ° C. to form a coating layer on the side surface of the laminate.

Next, a binder is added to silver particles and glass powder to prepare a silver glass-containing conductive paste, which 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. to the outside. After forming the electrode, the lead wire was connected to the external electrode by soldering.

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

Then, an insulator was provided on the outside 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. The form of the positioning portion produced here is the form shown in FIG.

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

Next, a disk-shaped lid was produced with SUS304.

Further, a SUS316L seamless cylinder having a thickness of 0.15 mm was rolled to produce a cylinder having a bellows shape and a trumpet-shaped lower end portion (flange portion).

The lid was inserted into the prepared cylinder, and the cylinder and lid were welded together. Then, this welded material is put on the laminated piezoelectric element adhered to the substrate, the tubular body is pulled with a predetermined load, a load is applied to the laminated piezoelectric element, and then the tubular body and the annular portion of the substrate are brought into contact with each other. The part was welded by resistance welding.

Finally, a DC electric field of 3 kV / mm was applied to the two lead pins for 15 minutes to perform 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 the above except that it 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 formed by cutting the substrate. A piezoelectric actuator was manufactured.

Then, the displacement amount before and after the durability test was measured by the displacement measuring device for each of the piezoelectric actuators of the examples and the comparative examples.

First, when a DC voltage of 200 V was applied to each piezoelectric actuator to obtain the initial displacement amount, the displacement amount of both the piezoelectric actuators of the examples and the comparative examples was 55 μm.

Further, these piezoelectric actuators were subjected to a durability test in which they were continuously 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%.

From this, it was confirmed that the piezoelectric actuator of the example can obtain the displacement amount more stably for a long period of time.

10 ... Piezoelectric actuator 1 ... Piezoelectric element 11 ... Piezoelectric layer 12 ... Internal electrode layer 13 ... Laminated body 14 ... External electrode 15 ... Coating layer 2 ... Metal case 21 ... Base 22 ... Cylindrical body 221 ... Cylindrical portion 222 ... Flange portion 23 ... Lid body 3 ... Positioning portion 31 ... Insulator 32 ... Metal body 41 ... Lead wire 42 ... Solder 43 ... Lead pin 44 ... Soft glass

Claims (6)

A laminated piezoelectric element and a metal case accommodating the laminated piezoelectric element so that the upper and lower ends of the laminated piezoelectric element abut against the inner wall are provided, and the metal case hits the lower end of the laminated piezoelectric element. The tubular body includes a contacted substrate and a tubular body joined to the upper surface of the substrate, and the tubular body has a tubular portion extending vertically and a flange portion connected to the lower end of the tubular portion. A positioning portion is provided on the upper surface of the substrate so as to be in contact with the inner surface of the tubular portion.
The collar is welded to the substrate and
The positioning portion has a metal body erected on the upper surface of the substrate and an insulator provided on the outer surface of the metal body.
The insulator is a contact portion between the positioning portion and the tubular portion, and is a contact portion.
The metal body surrounds the laminated piezoelectric element at a distance from the laminated piezoelectric element .
A piezoelectric actuator characterized in that the thickness of the insulator is thinner than the thickness of the metal body . The piezoelectric actuator according to claim 1, wherein the insulator is a resin. The piezoelectric actuator according to claim 1 or 2, wherein the height of the positioning portion is larger than the thickness of the collar portion. 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 the height of the upper surface of the insulator is higher than the height of the upper surface of the metal body. The piezoelectric actuator according to any one of claims 1 to 5 , wherein the positioning portion continuously surrounds the laminated piezoelectric element once.

Images