JP5135674B2 - Multilayer piezoelectric element - Google Patents

Description

  The present invention relates to a laminated piezoelectric element, and more specifically, a plurality of piezoelectric elements each having an internal electrode formed on the surface of a piezoelectric body are laminated, and an internal electrode of an odd-numbered piezoelectric element and an internal electrode of an even-numbered piezoelectric element And a laminated piezoelectric element having an electrode lead portion for connecting these internal electrodes to external electrodes.

  As shown in FIG. 15, the laminated piezoelectric element is formed by laminating a plurality of piezoelectric elements each having an internal electrode 2 formed on the surface of the piezoelectric body 1, and the internal electrodes of the odd-numbered piezoelectric elements and the even-numbered piezoelectric elements. By applying a voltage between the electrodes, distortion due to the inverse piezoelectric effect of the piezoelectric body is generated.

  FIG. 16A is a schematic perspective view of a multilayer piezoelectric bimorph 3 using multilayer piezoelectric elements. The laminated piezoelectric bimorph element 3 is configured by adhering a laminated piezoelectric element 5a and a laminated piezoelectric element 5b to the front surface and the back surface of an intermediate material 4, respectively. The laminated piezoelectric elements 5a and 5b are polarized in advance so that when an arbitrary voltage is applied, one of them extends and the other contracts. Then, as shown in FIG. 16B, bending displacement can be generated at the tip of the element by fixing one end of the multilayered piezoelectric bimorph element 3 to the fixing portion 6 and applying an arbitrary voltage.

  As described above, the laminated piezoelectric element has a structure in which piezoelectric layers and electrode layers are alternately laminated. As shown in FIG. 17, a general method for manufacturing such a laminated piezoelectric element is as follows. First, a slurry 7 in which piezoelectric powder, an organic binder, an organic solvent and the like are mixed is used on a support 8 such as PET using a sheet molding machine 9. And thinly mold. Next, as shown in FIG. 18, an electrode paste material 11 is formed on the surface of the formed piezoelectric sheet 10 by screen printing or the like. Subsequently, as shown in FIG. 19, a plurality of piezoelectric sheets 10 on which an electrode paste material 11 serving as an internal electrode is formed are stacked, and a laminated body 12 is produced by thermocompression bonding. Then, the laminated body 12 is cut into an arbitrary size as shown in FIG. 20, the binder is thermally decomposed by degreasing, and then fired to produce a laminated piezoelectric element 13 having a predetermined shape.

  On the other hand, the internal electrodes 11 of the laminated piezoelectric element 13 need to be electrically connected alternately as shown in FIG. 21 in order to generate a potential difference between the opposing electrodes. For example, in the case of a strip-shaped bimorph element and when it is necessary to pull out an electrode from one end face of the element, an electrode lead-out portion 14 for pulling out each electrode is formed at the end of the element as shown in FIG. It becomes a structure (see Patent Document 1 below). The formation width of the electrode lead-out portion 14 is smaller than the formation width of the internal electrode 11 as viewed from the end face of the element and is formed uniformly.

  In this case, as shown in FIG. 23, the inner electrode 11A of the odd-numbered piezoelectric element and the inner electrode 11B of the even-numbered piezoelectric element are formed by offsetting the electrode lead portions 14A and 14B in the opposite directions. Are stacked alternately. After firing, a common external electrode is formed on each of the electrode lead-out portion 14A and the electrode lead-out portion 14B on the end face on the electrode lead-out side of the element.

JP 2002-305331 A

  In the piezoelectric element firing step, the amount of contraction of the piezoelectric layer on which the electrode is formed tends to be larger than the amount of contraction of the piezoelectric layer on which no electrode is formed. FIG. 24 is a view of the stacked electrode pattern as viewed from above. The hatched region P1 is an electrode forming portion, and the region P2 located between the electrode leading portion 14A of the lower layer side internal electrode and the electrode leading portion 14B of the upper layer side internal electrode 11B is an electrode non-forming portion.

  In FIG. 24, the shrinkage during firing is P1> P2. This is considered to be due to the influence of the contraction of the electrode layer and the influence that the piezoelectric sinterability is promoted by the dissolution of the electrode layer and the contraction becomes easier. Incidentally, the shrinkage in the firing process of the piezoelectric element is about 70% to 85% of the dimension before firing as a dimensional ratio, and the shrinkage difference between the electrode forming part P1 and the electrode non-forming part P2 is close to several% to 10%. There is a case.

  Thus, when there is a difference in the shrinkage of the piezoelectric layer between the electrode forming part P1 and the electrode non-forming part P2, the element is deformed due to internal stress due to the difference in shrinkage during the firing process and the cooling process after firing, When the difference in the amount of shrinkage is significant, there is a risk that the element will be cracked or cracked, or the interlayer short circuit of the electrode part may occur.

  The present invention has been made in view of the above-described problems, and has an electrode shape that can relieve internal stress generated due to a shrinkage difference during firing between an electrode forming portion and an electrode non-forming portion on a piezoelectric layer. It is an object of the present invention to provide a laminated piezoelectric element.

  In solving the above problems, the present inventors changed the shape of the electrode lead-out portion for connecting the external electrode formed on the internal electrode of each layer to a predetermined shape, thereby forming the electrode of the piezoelectric layer during firing. It was found that the generation of internal stress due to the difference in shrinkage between the part and the electrode non-formed part can be suppressed.

  That is, the present invention comprises a plurality of piezoelectric elements each having an internal electrode formed on the surface of the piezoelectric body, and is formed on the internal electrode of each layer of the piezoelectric element and is connected to the external electrode. In the laminated piezoelectric element having a portion on one end face of the element, the electrode lead-out portion located in the odd-numbered layer and the electrode lead-out portion located in the even-numbered layer are arranged on different sides with respect to the width direction of the element end face. At the same time, the inner dimension between the base end portions of the electrode lead portions of each layer is formed smaller than the inner dimension between the tip portions of the electrode lead portions of the respective layers.

  With this configuration, the internal stress generated due to the shrinkage difference during firing between the electrode forming portion and the electrode non-forming portion on the surface of the piezoelectric body can be reduced, and element cracks, cracks, interlayer shorts, etc. Occurrence can be suppressed.

  In particular, in the present invention, the electrode lead-out portion of each layer of the piezoelectric element is formed such that the formation width of the base end portion is larger than the formation width of the tip end portion. The base end portion of the electrode lead-out portion can be formed so that the formation width gradually increases toward the internal electrode side.

  Specifically, the base end portion of the electrode lead portion is connected to the internal electrode via the inclined portion, or the base end portion of the electrode lead portion is connected to the internal electrode via the step portion. be able to.

  The laminated body of the piezoelectric body and the internal electrode can be used as a bimorph element or a monomorph element in which one end is a fixed end and the other end is a free end. In this case, it is preferable that the electrode lead-out portion of each layer is provided on the fixed end side of the element.

  The application example of the laminated piezoelectric element according to the present invention is not limited to the above-described example, but can be applied to an ultrasonic wave generating element, a piezoelectric transformer, and the like.

  As described above, according to the multilayered piezoelectric element of the present invention, the internal stress generated due to the shrinkage difference during firing between the electrode forming portion and the electrode non-forming portion on the surface of the piezoelectric body is effectively reduced. Since it can be alleviated, it is possible to suppress the occurrence of element cracks, cracks, interlayer shorts, and the like.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
1 and 2 show the configuration of the laminated piezoelectric element 23 according to the embodiment of the present invention. The laminated piezoelectric element 23 is configured by laminating a plurality of piezoelectric elements in which internal electrodes 21 (21A, 21B) are formed on the surface of a sheet-like piezoelectric body 20. The internal electrodes 21 of each layer are connected to external electrodes 25 (25A, 25B) formed on the element surface via electrode lead portions 24 (24A, 24B), respectively.

  The electrode lead-out portion 24 is for electrically connecting the internal electrode 21 and the external electrode 25, and its formation width is smaller than the formation width of the internal electrode 21, and as will be described later, the internal electrode 21 It is formed simultaneously with the forming step. The electrode lead portion 24 is drawn out to the one end face 23F side of the multilayer piezoelectric element 23, and the external electrode 25 is also formed so as to straddle the one end face 23F side of the piezoelectric element 23. The laminated piezoelectric element 23 of the present embodiment is configured as a bimorph element that vibrates with one end face 23F as a fixed end and the other end face 23V as a free end when a predetermined voltage is applied to the external electrode 25. Has been.

  Therefore, in the laminated piezoelectric element 23 of the present embodiment, the electrode lead portions 24 connected to the internal electrodes 21 of the piezoelectric elements of each layer are formed so as to be biased toward different sides with respect to the width direction of the fixed end 23F of the element. Has been. That is, as shown in FIG. 2, the electrode lead portion 24A connected to the internal electrode 21A of the odd-numbered piezoelectric element and the electrode lead portion 24B connected to the internal electrode 21B of the even-numbered piezoelectric element are mutually connected. It is formed to be offset in the opposite direction.

  Accordingly, when viewed from the fixed end 23F side of the laminated piezoelectric element 23, the odd-numbered electrode lead portions 24A are concentrated on one side (left side in FIG. 1), and the even-numbered electrode lead portions 24B are on the other side (see FIG. 1 on the right side). The external electrode 25 is configured by an electrode portion 25A commonly connected to the electrode lead portion 24A and an electrode portion 25B commonly connected to the electrode lead portion 24B.

  Next, the electrode lead-out portions 24A and 24B of the piezoelectric elements of each layer of the laminated piezoelectric element 23 have a formation width of the base end portion on the internal electrodes 21A and 21B side rather than the formation width of the distal end portion on the external electrodes 25A and 25B side. It is formed larger (FIG. 2). In particular, in the present embodiment, the base end portions of the electrode lead portions 24A and 24B are connected to the internal electrodes 21A and 21B via the inclined portions 24S and 24S, so that the formation width is increased toward the internal electrodes 21A and 21B. It is formed to gradually increase.

  The inclined portions 24S, 24S of the electrode lead portions 24A, 24B in each layer are formed so as to face each other on the odd layer side and the even layer side as shown in FIG. As a result, the electrode lead portions 24A and 24B of each layer of the laminated piezoelectric element 23 have a relationship as shown in FIG. In the figure, a hatched region P1 is an electrode formation region, and a region P2 between the electrode lead portion 24A and the electrode lead portion 24B is an electrode non-formation region.

  In FIG. 3A, the inclined surface 24S of one electrode lead portion 24A and the inclined surface 24S of the other electrode lead portion 24B cross each other at the base end side of each electrode lead portion, and a substantially V-shaped boundary portion The example which formed the electrode non-formation part P2 which has is shown. Further, as shown in FIG. 3B, the inclined surface 24S of one electrode lead portion 24 and the inclined surface 24S of the other electrode lead portion 24B are separated from each other on the base end side of each electrode lead portion, It is good also as the electrode non-formation part P2 which has a shape boundary part. The shape of the boundary portion of the electrode non-forming portion P2 with respect to the electrode forming region P1 can be adjusted by the inclination angles of the inclined surfaces 24S and 24S.

  As shown in FIGS. 3A and 3B, the multilayer piezoelectric element 23 according to the present embodiment has an inner dimension S2 between the tip portions of the electrode lead portions 24A and 24B of each layer facing the fixed end 23F. It is larger than the inner dimension (S1) between the base ends of 24B. As will be described later, S1 is formed smaller than S2 in order to avoid cracking or cracking of the element due to a difference in thermal shrinkage between the electrode forming part P1 and the electrode non-forming part P2 during firing. FIG. 3A shows an example in which S1 = 0.

  The laminated piezoelectric element 23 of the present embodiment configured as described above is fixed to both surfaces of an intermediate material (not shown), and the polarization direction is such that one element expands and the other element contracts with respect to an arbitrary voltage. Thus, by applying a predetermined voltage between the external electrodes 25A and 25B, an actuator that generates a bending displacement at the free end of each element as shown in FIG. 16B can be configured.

  Then, the manufacturing method of the laminated piezoelectric element 23 comprised as mentioned above is demonstrated. FIG. 4 is a process diagram showing the manufacturing process.

(Mixing process)
Before the mixing process, there are processes peculiar to piezoelectric materials such as weighing, mixing, and calcining raw materials such as Ti (titanium), Zr (zirconium), and Pb (lead). These piezoelectric materials are in a powder state and are generally finely powdered to have a median diameter of 1 μm or less. This fine powder and an organic solvent are mixed to make a solution. For example, an organic solvent such as ethanol or MEK (methyl ethyl ketone), an acrylic binder resin, an antifoaming agent, etc. are mixed at a predetermined mixing ratio. Match. In this example, lead zirconate titanate piezoelectric material is used, but other piezoelectric materials such as barium titanate may be used.

(Sheet forming process)
The piezoelectric powder is dispersed in the solution by mixing, and this is called slurry. When this slurry is made into a thin coating film using a sheet molding machine as shown in FIG. 17 and dried in this state, a sheet (green sheet) having a certain degree of flexibility is completed.

(Electrode printing process)
The internal electrode 21 and the electrode lead-out portion 24 are printed and formed on the produced green sheet by screen printing or the like. At this time, the sheet may be in the form of a roll, or may be punched into a predetermined size before printing. In the present embodiment, an alloy paste of Ag (silver) and Pd (palladium) is used as the internal electrode material in consideration of the firing temperature of the piezoelectric element. In the alloy of Ag and Pd, if the Pd ratio increases, the firing temperature can be increased. For example, the Pd ratio is set to about 10 to 40%. It should be noted that attention must be paid to the reaction between the organic solvent used in the electrode paste and the resin component of the green sheet.

(Lamination crimping process)
Next, the green sheets on which the electrode paste is printed are stacked in a desired number of layers. At this time, the positions of the electrodes on the respective sheets are not shifted from each other. Specifically, a plurality of positioning holes are formed in predetermined corners of each sheet, and positioning sheets are fitted into these positioning holes to stack all sheets. The laminated green sheets are integrated by thermocompression bonding. Thereafter, the sheet laminate is cut into a predetermined size as necessary.

(Degreasing process)
The thermocompression-bonded laminated sheet is divided into a predetermined size by a cleaving machine or the like as necessary, and this is put in a degreasing furnace to thermally decompose organic materials (organic solvent or binder resin) contained in the laminated sheet. The degreasing temperature is determined by the thermal decomposition characteristics of the resin used, but in this example, the degreasing temperature is about 400 ° C to 600 ° C. Moreover, the temperature increase rate at the time of degreasing is appropriately determined in consideration of the decomposition rate of the resin. If the decomposition rate is too high, the element after degreasing will swell and crack, so care must be taken.

(Baking process)
The degreased element is basically only the remaining piezoelectric powder and electrode material, which is further fired at a high temperature to form a ceramic body. The firing temperature is about 1200 ° C. to 1300 ° C. for a general piezoelectric element, but is determined in consideration of the melting temperature of the internal electrode. As described above, the melting temperature of the electrode varies depending on the Pd ratio of the internal electrode material.

(Outline processing process)
The element after firing is subjected to external processing as necessary. The purpose of the outer shape processing is to stabilize the shape of the element and to expose the tip end portion of the electrode lead portion 24 formed on the internal electrode to the element end face. FIG. 5 shows the form of the element before and after the outer shape processing.

(External electrode formation)
Next, a surface electrode to be the external electrode 25 is printed on the surface of the element that has been subjected to external processing. For example, Ag paste is used as the electrode material. As shown in FIG. 1, the surface electrode (external electrode) 25 is connected to the electrode lead portion 24 exposed on the end face 23 </ b> F of the element 23. Accordingly, the external electrode 25A and the internal electrode 21A and the external electrode 25B and the internal electrode 21B are electrically connected to each other via the electrode lead portion 24A and the electrode lead portion 24B, respectively.

(Polarization process)
Finally, a polarization process is performed on the manufactured laminated piezoelectric element 23. 6A and 6B show the element polarization process. In the illustrated example, the positive electrode of the DC power source 26 is connected to the external electrode 25A, and the negative electrode of the DC power source 26 is connected to the external electrode 25B. As a result, a power supply voltage is applied in parallel between a plurality of adjacent electrodes, and the polarization of the piezoelectric body 20 sandwiched between these electrodes is performed.

  As described above, the laminated piezoelectric element 23 of the present embodiment is manufactured.

  By the way, in the manufacturing process of the laminated piezoelectric element 23 described above, particularly in the firing process, the cracking of the element due to the internal stress generated due to the difference in contraction rate between the electrode forming portion and the electrode non-forming portion in the firing process of the piezoelectric body. It is necessary to suppress cracks.

  Therefore, in the present embodiment, the shape of the electrode lead portion 24 of the internal electrode 21 is provided with the inclined portion 24S as shown in FIGS. 3A and 3B, and the inner dimension S1 between the base end portions of the electrode lead portion 24 is set to the tip portion. By making it smaller than the inner dimension S2, the internal stress at the time of firing is relieved and the occurrence of element cracks and cracks is suppressed. The inclined portion 24S can be formed only by changing the pattern shape of the screen printing plate on which the electrode paste material is printed.

  Regarding the relaxation of internal stress, the effect by the shape change of the electrode lead-out part has been confirmed by analysis by simulation. Hereinafter, the effect of the present invention will be described focusing on the simulation analysis of the stress distribution by the shape of the conventional electrode lead portion and the shape of the electrode lead portion of the present invention.

  FIG. 7 is a stress analysis model of an electrode lead portion of a conventional multilayer piezoelectric element. As shown in FIG. 7, the electrode non-forming portion P2 is sandwiched between two adjacent electrode lead portions 14A and 14B, the formation width is uniform, and the boundary with the electrode forming portion P1 is a square. It has a shape. Then, the simulation analysis of the in-plane stress distribution was performed assuming that the dimension of the electrode forming part P1 by firing was 70% of the dimension before firing and the dimension of the electrode non-formed part P2 was 85% of the dimension before firing. The formation length of the electrode forming portion P1 was 10 mm, the formation length of the electrode non-forming portion P2 was 3 mm, and the formation widths of the electrode lead portions 14A and 14B were each 1 mm.

  8A and 8B show simulation results of the stress analysis model shown in FIG. FIG. 8A is a scalar quantity distribution of in-plane stress, and FIG. 8B is a vector diagram of in-plane stress. In FIG. 8B, the arrows at both ends indicate the outward component as tensile stress, the inward component as compressive stress, and the length of the arrow indicates the magnitude of the force. The same applies to FIGS. 9 to 11 and 14.

As shown in FIG. 8B, it can be seen that compressive stress is applied to the electrode non-forming portion (P2) and tensile stress is applied to the electrode forming portion (P1). The maximum value of the tensile stress is 0.753e10 (0.753 × 10 ¹⁰ ) [N / m ² ], and the generation positions thereof are the electrode forming portion and the non-forming portion corresponding to the base end portions of the electrode lead portions 14A and 14B. And at the border. When tensile stress is applied during firing, voids and cracks are generated in the sintering process of the piezoelectric body, and the melted electrode material penetrates into the voids and cracks to induce a short circuit between layers. Cause malfunctions.

On the other hand, FIGS. 9A and 9B show simulation results when the inclined portion 24S is formed at the base end portion of the electrode lead-out portion 24 as in the laminated piezoelectric element of the present embodiment. As shown in FIGS. 9A and 9B, by forming the inclined portion 24S at the base end portion of the electrode lead portion 24, the concentration of tensile stress and compressive stress is alleviated, and the maximum tensile stress is 0.668e10 [N / m ^2]. It was able to be reduced to].

Further, as shown in FIGS. 10A and 10B, the maximum tensile stress is set to 0.574e10 [N / m ² ] by further increasing the inclination angle of the inclined portion 24S formed at the base end portion of the electrode lead-out portion 24. Could be reduced. Embodiment in which the inclination angle of the inclined portion 24S is increased to the extent that the inclined portions 24S of the respective layers intersect each other at the base end portion of the electrode lead-out portion 24, and the boundary portion between the electrode forming portion and the non-forming portion is V-shaped ( In FIG. 3A), the maximum tensile stress was further reduced as shown in FIGS. 11A and 11B, and the magnitude was 0.447e10 [N / m ² ].

  As described above, the inclination angle of the inclined portion 24S is increased, and as the internal dimension S1 between the base end portions of the electrode lead portions 24A and 24B of each layer is made smaller than the internal dimension S2 between the distal end portions, the internal stress ( It can be seen that the effect of reducing the tensile stress is significant.

  Therefore, according to the laminated piezoelectric element 23 of the present embodiment, the internal stress generated due to the shrinkage difference between the electrode forming portion and the non-forming portion at the time of firing can be relieved. Various problems such as cracks and interlayer shorts can be effectively suppressed.

  Next, the amount of inclination of the inclined part 24S of the electrode lead-out part 24 will be described with reference to FIG. The dimension of the electrode lead portion 24 is restricted by the width dimension of the element. FIG. 12 is a schematic diagram showing this relationship.

  First, with respect to the element width W, a margin G in the width outer shape direction of the internal electrode 21 and a margin S2 with respect to a short circuit between the internal electrodes 21 (inner dimensions between the tip portions of the electrode lead portions 24) are required. It becomes. The formation widths D1 and D2 of the tip end portions of the electrode lead portions 24 are D1 = D2 = (W−2G−S2) / 2. For example, when W = 3 mm, the margin G with respect to the outer shape is about G = 0.1 to 0.3 mm in consideration of the positional accuracy of internal electrode printing, the shrinkage variation during firing, the processing position variation during outer shape processing, and the like. . Further, the margin S2 for the short circuit between the internal electrodes is required to be 0.6 mm or more in consideration of securing insulation and migration in a high temperature and high humidity state. Therefore, D1 = D2 is about 0.9 to 1.1 mm in the case of an element having a width of 3 mm.

  The distance (internal dimension) S1 between the base end portions of the electrode lead-out portion 24 may be 0, but in consideration of variations in electrode printing position and stacking, 0.2 mm or more is necessary. In this case, the inclined portion 24S The dimension Ky in the width direction is a minimum of 0.2 mm.

  Next, regarding the length direction of the element, it is desirable that the formation length L of the electrode lead portion 24 is as short as possible. However, the printing position accuracy of the internal electrode 21, shrinkage variation during firing, and processing position variation during external processing. Considering the above, 1 mm or more is necessary. When the inclined portion 24S is actually provided in the electrode lead-out portion 24, if the inclined portion 24S is exposed from the element end face by external processing, a margin S2 for a short circuit between the internal electrodes 21 is reduced, which is not preferable. Therefore, it is necessary to set the inclined portion 24S not to be exposed from the element end face during the outer shape processing. Considering the variation, when the element length direction dimension of the inclined portion 24S is Kx, L-Kx is required to be 0.5 mm at the minimum. It becomes.

  From the above, Ky is a minimum of 0.2 mm and Kx is a minimum of 0.5 mm. Here, if the inclination ratio is defined as Ky / Kx, the inclination ratio is 0.2 mm / 0.5 mm = 0.4 under the minimum condition. In the simulation results shown in FIGS. 9A and 9B, the slope ratio is 0.25, in the simulation results shown in FIGS. 10A and 10B, the slope ratio is 0.35, and in the simulation results shown in FIGS. .6. When actual prototypes were made based on the analysis models shown in FIGS. 9 to 11, element cracks and inter-layer shorts were scattered in the conventional electrode structure (FIG. 8). According to this embodiment, it was possible to substantially eliminate element cracks and interlayer short-circuit defects. In particular, it has been confirmed that the electrode structure shown in FIG.

(Second Embodiment)
13 and 14 show a second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, by providing the stepped portion 24T on the base end side of the electrode lead portion 24 (24A, 24B) of the piezoelectric element of each layer, the base end portion is formed more than the formation width of the tip portion of the electrode lead portion 24. The difference from the first embodiment described above is that the formation width is increased. As shown in FIG. 13A, the step portion 24T of the electrode lead portion 24 is formed to face each other on the odd layer side and the even layer side.

  As a result, the electrode lead portions 24A and 24B of each layer of the multilayer piezoelectric element have a relationship as shown in FIG. 13B in plan view, and the inner dimension S1 between the base end portions of the electrode lead portion 24 is the electrode lead portion. It is formed smaller than the inner dimension S <b> 2 between the front end portions of the portion 24. In the figure, a hatched region P1 is an electrode formation region, and a region P2 between the electrode lead portion 24A and the electrode lead portion 24B is an electrode non-formation region.

14A and 14B show simulation results of the stress analysis model having the electrode lead portion structure described above. Also in the present embodiment, the maximum tensile stress is reduced as compared with the conventional electrode lead portion structure, and the magnitude thereof is 0.642e10 [N / m ² ].

  Therefore, also in the present embodiment, as in the first embodiment described above, the internal stress generated due to the shrinkage difference between the electrode forming portion and the non-forming portion at the time of firing can be relaxed. Therefore, it is possible to effectively suppress various problems such as element cracks, cracks, and interlayer shorts. When the prototype was actually tested and verified, it was confirmed that the device cracking and the interlayer short-circuit failure could be substantially eliminated by this embodiment.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the above embodiment, the inner dimension S1 between the base ends of the electrode lead portions of each layer is smaller than the inner dimension S2 between the tip portions of the electrode lead portions of the respective layers. Although the inclined portion 24S or the step portion 24T is provided, the inclined portion 24S is not limited to a linear shape, and may be formed in a curved shape, and the step portion 24T is not limited to a single step, and may be a multi-step of two or more steps. Good.

  In the above-described embodiments, examples in which the laminated piezoelectric element according to the present invention is applied to a piezoelectric bimorph element have been described. However, the present invention is not limited thereto, and an ultrasonic generator, a piezoelectric transformer, a piezoelectric speaker, an oscillation circuit / filter circuit The present invention can also be applied to piezoelectric vibration gyro sensors, multilayer ceramic capacitors, and the like.

1 is an overall perspective view of a multilayer piezoelectric element 23 according to a first embodiment of the present invention. 3 is an exploded perspective view showing an internal structure of a laminated piezoelectric element 23. FIG. 3 is a schematic plan view of a main part showing an electrode lead-out portion 24 of a laminated piezoelectric element 23. FIG. FIG. 5 is a process flow diagram illustrating a method for manufacturing a laminated piezoelectric element 23. FIG. 5 is an element plan view before and after processing for explaining an outer shape processing step in the method for manufacturing a laminated piezoelectric element 23. FIG. 5 is a diagram for explaining an element polarization process in the method for manufacturing a laminated piezoelectric element 23. It is a stress analysis model figure of the electrode extraction part in the conventional multilayer piezoelectric element. It is a simulation result which shows the stress distribution around the electrode extraction part in the conventional laminated piezoelectric element. It is a simulation result which shows the stress distribution around the electrode extraction part in one structural example of the multilayer piezoelectric element 23 which concerns on this invention. It is a simulation result which shows the stress distribution around the electrode extraction part in the other structural example of the multilayer piezoelectric element 23 which concerns on this invention. It is a simulation result which shows the stress distribution around the electrode extraction part in the further another structural example of the laminated piezoelectric element 23 which concerns on this invention. It is a schematic diagram explaining one specific example of a structure of the electrode extraction part of the multilayer piezoelectric element 23 which concerns on this invention. The internal structure of the laminated piezoelectric element by the 2nd Embodiment of this invention is shown, A is an exploded perspective view, B is a top view of an electrode extraction part periphery. It is a simulation result which shows the stress distribution around the electrode extraction part of the laminated piezoelectric element shown in FIG. It is a schematic diagram which shows schematic structure of a laminated piezoelectric element. It is a figure which shows a piezoelectric bimorph element using a laminated piezoelectric element, A is a schematic perspective view, B is a side view explaining 1 effect | action. It is a figure explaining the sheet forming process which is one manufacturing process of a lamination piezoelectric element. It is a figure explaining the printing process of the electrode paste material which is one manufacturing process of a laminated piezoelectric element. It is a figure explaining the sheet | seat lamination process which is one manufacturing process of a lamination piezoelectric element. It is a figure explaining the element cutting process which is one manufacturing process of a laminated piezoelectric element. It is a figure explaining the electrode connection structure of a laminated piezoelectric element. It is a perspective view which shows the electrode connection structure of the conventional piezoelectric bimorph element. It is a disassembled perspective view which shows the internal structure of the conventional piezoelectric bimorph element. It is a principal part top view explaining the structure of the electrode extraction part of the conventional piezoelectric bimorph element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Piezoelectric body, 21, 21A, 21B ... Internal electrode, 23 ... Multilayer piezoelectric element, 23F ... Fixed end of element, 23V ... Free end of element, 24, 24A, 24B ... Electrode extraction part, 24S ... Inclination part, 24T ... Step part, 25, 25A, 25B ... External electrode, P1 ... Electrode forming part, P2 ... No electrode forming part, S1 ... Inner dimension between base end parts of electrode lead part, S2 ... Between tip part of electrode lead part Inside dimension

Claims (2)

A first piezoelectric element in which an internal electrode connected to the first electrode lead portion is formed on the surface of the sheet-like piezoelectric member, and an internal portion connected to the second electrode lead portion on the surface of the sheet-like piezoelectric member. A second piezoelectric element having electrodes formed thereon, and a plurality of the first and second piezoelectric elements are alternately stacked, and each tip part of each of the first and second electrode lead parts A laminate having an element end face exposed to the outside;
An external electrode formed on each of the element end faces and having a first electrode part connected to the first electrode lead part and a second electrode part connected to the second electrode lead part; Prepared,
The first and second electrode lead portions include a base end portion connected to the internal electrode, a tip end portion exposed from the element end face, and an inclination formed between the base end portion and the tip end portion. Each of which is disposed on different sides with respect to the width direction of the element end face,
The inclined portion of the first and second electrode lead portions so that the inner dimension between the base end portions of the first and second electrode lead portions is smaller than the inner dimension between the tip portions. However, when viewed from the stacking direction, the piezoelectric elements cross each other in a V shape on the base end side . The laminated piezoelectric element according to claim 1,
The laminated piezoelectric element, a laminated piezoelectric element wherein the element end face constitutes the vibratable bimorph element end face of the other is a fixed end and a free end.