JP4258238B2 - Multilayer piezoelectric element and method for manufacturing the same - Google Patents

Description

[0001]
【Technical field】
The present invention relates to a multilayer piezoelectric element formed by laminating a plurality of unit laminated bodies in which ceramic layers and electrode arrangement layers are alternately laminated with a bonding material interposed therebetween, and a method for manufacturing the same.
[0002]
[Prior art]
In order to obtain a large amount of displacement in the axial direction due to the piezoelectric effect of a laminated piezoelectric element in which ceramic layers and electrode arrangement layers are alternately laminated, it is necessary to increase the number of laminated ceramic layers.
However, it is not easy to accurately manufacture a stacked piezoelectric element having a large number of stacked layers, and it is difficult to maintain manufacturing efficiency.
[0003]
Therefore, first, a plurality of element units as sub-units with a small number of layers are prepared, and these element units are stacked on each other with a bonding material interposed therebetween, so that a stack having a desired number of layers as a whole is obtained. Type piezoelectric elements may be produced.
[0004]
[Patent Document 1]
JP-A-4-167580 (page 3-5, FIG. 1)
[0005]
[Problems to be solved]
However, the conventional multilayer piezoelectric element has the following problems. That is, when the hardness of the bonding material is not appropriate, there is a problem that the piezoelectric efficiency of the multilayer piezoelectric element is reduced or the fatigue life of the bonding material itself is shortened.
If the bonding material is too soft, the piezoelectric effect of each element unit constituting the laminated piezoelectric element may be absorbed as compressive deformation of the bonding material layer, which may reduce the piezoelectric efficiency.
On the other hand, if the bonding material is too hard, the bonding material itself is liable to cause fatigue failure due to stress distortion caused by the displacement of each element unit, and there is a risk of peeling between the element units.
[0006]
The present invention has been made in view of such conventional problems, and provides a multilayer piezoelectric element that is formed by laminating a plurality of element units and can maintain excellent performance over a long period of time, and a method for manufacturing the same. It is what.
[0007]
[Means for solving problems]
The first invention comprises a plurality of unit laminates in which ceramic layers and electrode arrangement layers including electrode portions constituting internal electrodes are alternately laminated, with a bonding material layer interposed therebetween, And in the laminated piezoelectric element in which both end portions in the laminating direction are constituted by the unit laminated body,
In the multilayer piezoelectric element, the thickness L2 of the bonding material layer and the cross-sectional area S2 orthogonal to the stacking direction are set so as to satisfy the following formulas 1 and 2. (Claim 1) .
[0008]
(N₁× L₁) / (S₁× Y₁) ≧ (N₂× L₂) / (S₂× ((2000-10800 × L₂) × Y₂)) ... Formula 1
S₂≦ S₁                                              ... Formula 2
L₁: Height in the stacking direction of the unit stack (mm)
S₁: Cross-sectional area perpendicular to the stacking direction of the unit stack (square mm)
Y₁: Young's modulus (MPa) in the stacking direction of the unit stack
N₁: Number of stacked units
L₂: Height of the bonding material layer in the stacking direction (mm)
S₂: Cross-sectional area perpendicular to the lamination direction of the bonding material layer (square mm)
Y₂: Young's modulus (MPa) of the material constituting the bonding material layer
N₂: Number of bonding material layers
[0009]
The multilayer piezoelectric element according to the first invention is obtained by laminating a plurality of the unit laminated bodies with a bonding material layer satisfying the relational expressions of Equation 1 and Equation 2 interposed therebetween.
The bonding material layer whose shape is defined by the above mathematical formulas 1 and 2 has a Young's modulus Y₂And cross-sectional area S₂And height L in the stacking direction₂Therefore, the bonding material layer as a whole exhibits appropriate hardness.
[0010]
That is, in the laminated piezoelectric element formed by laminating a plurality of the element units with the bonding material layer interposed therebetween, the bonding material layer has an appropriate hardness. Therefore, the displacement due to the piezoelectric effect produced by each element unit is less likely to be absorbed by the deformation of the bonding material layer.
Therefore, the laminated piezoelectric element has excellent performance with high piezoelectric effect that can generate a large displacement due to the piezoelectric effect.
[0011]
In the multilayer piezoelectric element, the bonding material layer has appropriate flexibility. Therefore, the bonding material layer is less likely to be fatigued due to stress strain or the like that may be caused by the piezoelectric effect of each element unit.
Therefore, the laminated piezoelectric element can maintain its excellent performance over a long period of use.
[0012]
The second invention comprises a plurality of unit laminates obtained by alternately laminating ceramic layers and electrode arrangement layers including electrode portions constituting internal electrodes, with a bonding material layer interposed therebetween, And in the laminated piezoelectric element comprising a holding member forming an inactive layer in at least one of both ends in the laminating direction and an intermediate part in the laminating direction,
In the multilayer piezoelectric element, the thickness L2 of the bonding material layer and the cross-sectional area S2 orthogonal to the stacking direction are set so as to satisfy the following formulas 3 and 4. (Claim 2) .
(N₁× L₁) / (S₁× Y₁) + (N₃× L₃) / (S₃× Y₃) ≧ (N₂× L₂) / (S₂× ((2000-10800 × L₂) × Y₂)) ... Formula 3
S₂≦ S₁                                              ... Formula 4
L₁: Height in the stacking direction of the unit stack (mm)
S₁: Cross-sectional area perpendicular to the stacking direction of the unit stack (square mm)
Y₁: Young's modulus (MPa) in the stacking direction of the unit stack
N₁: Number of stacked units
L₂: Height of the bonding material layer in the stacking direction (mm)
S₂: Cross-sectional area perpendicular to the lamination direction of the bonding material layer (square mm)
Y₂: Young's modulus (MPa) of the material constituting the bonding material layer
N₂: Number of bonding material layers
L₃: Height of holding member in the stacking direction (mm)
S₃: Cross-sectional area perpendicular to the stacking direction of the holding member (square mm)
Y₃: Young's modulus (MPa) in the stacking direction of the holding member
N₃: Number of holding members stacked
[0013]
The multilayer piezoelectric element according to the second invention is obtained by laminating a plurality of the unit laminate bodies and the holding members with a bonding material layer satisfying the relational expressions of Equation 3 and Equation 4 interposed therebetween.
The bonding material layer whose shape is defined by Equation 3 and Equation 4 has a Young's modulus Y₂And cross-sectional area S₂And height L in the stacking direction₂Therefore, the bonding material layer as a whole exhibits appropriate hardness.
That is, in the laminated piezoelectric element formed by laminating a plurality of the element units with the bonding material layer interposed therebetween, the bonding material layer has an appropriate hardness. Therefore, the displacement due to the piezoelectric effect produced by each element unit is less likely to be absorbed by the deformation of the bonding material layer.
Therefore, the multilayer piezoelectric element has excellent performance with high piezoelectric effect that can generate a large displacement due to the piezoelectric effect.
[0014]
In the multilayer piezoelectric element, the bonding material layer has appropriate flexibility. Therefore, the bonding material layer is less likely to be fatigued due to stress strain or the like that may be caused by the piezoelectric effect of each element unit.
Therefore, the above-described multilayer piezoelectric element can maintain its excellent performance over a long period of use.
Further, the above mathematical formula 3 indicates whether the holding member is bonded to both ends of the multilayer piezoelectric element or whether the holding member is bonded to only one end.₃It is configured to be able to respond flexibly by changing the above.
[0015]
According to a third aspect of the present invention, there is provided a multi-layer piezoelectric element according to the seventh aspect of the present invention, in which a plurality of unit laminated bodies in which ceramic layers and electrode arrangement layers are alternately laminated are laminated via a bonding material layer. In the manufacturing method for manufacturing
A unit production process for producing a unit laminate formed by alternately laminating the ceramic layers and the electrode arrangement layers;
A laminating step of laminating the unit laminated body via a bonding material disposed on an end surface of the unit laminated body;
A curing material is disposed in a gap between adjacent unit laminates and a unit gap formed by the outer peripheral surface of the bonding material to form the bonding material layer formed of the curing material and the bonding material. And a disposing step. The method of manufacturing a laminated piezoelectric element according to claim 9.
[0016]
In the method for manufacturing a multilayer piezoelectric element according to the third aspect of the present invention, the unit laminate is joined to each other by the lamination step, and then the curing material disposing step is performed.
In the curing material disposing step, a curing material is disposed in a gap formed by a gap between adjacent unit laminated bodies and an outer peripheral surface of the bonding material disposed in the laminating step, and the curing material and The bonding material layer made of the bonding material is formed.
[0017]
According to the manufacturing method, even if the bonding material is not sufficiently hard among the bonding material layers, the bonding material is disposed in the gap in the curing material disposing step, thereby providing the bonding material. Appropriate hardness can be maintained for the entire layer.
That is, the multilayer piezoelectric element manufactured by the above manufacturing method has an appropriate hardness of the bonding material layer formed by a combination of the bonding material and the curing material, and has excellent piezoelectric performance and a product over a long period of time. Both lifespan can be achieved.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The bonding material layer in the first or second invention can be formed of a bonding material such as a bonding material such as a silicone resin, an epoxy resin, a urethane resin, a polyimide resin, or a polyamideimide resin.
In the first aspect of the invention, it is preferable that the multilayer piezoelectric element satisfies Formula 1 and Formula 2 in an operating temperature range of 80 ° C. to 200 ° C. (Claim 3).
In this case, there is little possibility of causing troubles in the bonding material layer that may occur when the operating temperature of the multilayer piezoelectric element becomes 80 ° C. or higher and 200 ° C. or lower.
[0019]
In the second aspect of the invention, it is preferable that the multilayer piezoelectric element satisfies Formula 3 and Formula 4 in an operating temperature range of 80 ° C. to 200 ° C. (Claim 4).
In this case, there is little possibility of causing troubles in the bonding material layer that may occur when the operating temperature of the multilayer piezoelectric element becomes 80 ° C. or higher and 200 ° C. or lower.
[0020]
In the first invention or the second invention, the electrode arrangement layer is a conductive electrode portion and a region in which the electrode portion recedes inwardly from an end portion of the electrode arrangement layer. The region formed of the holding portion and formed with the bonding material layer on the end surface in the stacking direction of the unit laminate is included in the region where the electrode portion is overlapped in the stacking direction in each electrode arrangement layer. It is preferable that it is a region (Claim 5).
In this case, in the laminated piezoelectric element having a partial electrode structure, the bonding material layer can be disposed avoiding an inactive region where the electrode portion is not polymerized in the laminating direction and does not produce a piezoelectric effect. .
[0021]
Therefore, the stress due to the piezoelectric effect of the unit laminate can be applied to the end surface of the bonding material layer in the stacking direction substantially evenly, and there is little possibility of causing distortion or the like inside the bonding material layer.
Therefore, the bonding material layer is less likely to cause troubles such as fatigue failure and peeling of the bonding surface due to expansion and contraction of the multilayer piezoelectric element.
[0022]
In addition, the bonding material layer is preferably configured by combining a region made of the bonding material and a region made of a hardening material.
In this case, desired characteristics of the entire bonding material layer can be obtained by a combination of the bonding material and the curing material.
[0023]
Therefore, according to the combination with the curing material, the selection range of materials that can be applied as the bonding material can be expanded.
As the curing material, silicone resin, epoxy resin, urethane resin, polyimide resin, polyamideimide resin, or the like can be used.
[0024]
The bonding material forming the bonding material layer is preferably a material made of an epoxy resin, a silicone resin, a urethane resin, or a polyamideimide resin.
In this case, the above-mentioned bonding material layer having an appropriate hardness and excellent durability due to a bonding material made of epoxy resin, silicone resin, urethane resin or polyamide-imide resin having a good balance between bonding force and hardness. Can be formed.
[0025]
The thickness of the bonding material layer is preferably 0.0001 mm or more and 0.01 mm or less.
In this case, since the thickness of the bonding material layer is thin, the effects of the first invention and the second invention are particularly effective.
[0026]
On the other hand, if the thickness of the bonding material layer is less than 0.0001 mm, the unit laminate body may not be bonded sufficiently firmly.
If the thickness of the bonding material layer exceeds 0.01 mm, the piezoelectric efficiency of the multilayer piezoelectric element as a whole may not be maintained sufficiently high.
[0027]
In the third invention, the curing material disposing step is a step of filling the unit gap with the curing material using a vacuum method, a method utilizing a capillary phenomenon, or a liquid injection molding method. Preferred (claim 10).
In this case, the hardening material can be efficiently filled and arranged in the gap by the above-described methods.
[0028]
【Example】
Example 1
The laminated piezoelectric element 10 of this example will be described with reference to FIGS.
As shown in FIG. 3, the multilayer piezoelectric element 10 of the present example includes a plurality of unit laminates 11 in which ceramic layers 111 and electrode arrangement layers 112 including electrode portions 503 constituting internal electrodes are alternately laminated. It is an element formed by stacking. Here, the multilayer piezoelectric element 10 is an element in which both end portions in the stacking direction are configured by the unit stacked body 11. In this multilayer piezoelectric element 10, the thickness L of the bonding material layer 19₂And the cross-sectional area S substantially perpendicular to the stacking direction₂Is set so as to satisfy Equation 1 and Equation 2.
(N₁× L₁) / (S₁× Y₁) ≧ (N₂× L₂) / (S₂× ((2000-10800 × L₂) × Y₂)) ... Formula 1
S₂≦ S₁                                            ... Formula 2
L₁: Height in the stacking direction of the unit stack (mm)
S₁: Cross-sectional area perpendicular to the stacking direction of the unit stack (square mm)
Y₁: Young's modulus (MPa) in the stacking direction of the unit stack
N₁: Number of stacked units
L₂: Height of the bonding material layer in the stacking direction (mm)
S₂: Cross-sectional area perpendicular to the lamination direction of the bonding material layer (square mm)
Y₂: Young's modulus (MPa) of the material constituting the bonding material layer
N₂: Number of bonding material layers
This will be described in detail below.
[0029]
First, the structure of the multilayer piezoelectric element 10 of this example will be described.
As shown in FIG. 3, this multilayer piezoelectric element 10 is an element comprising 25 unit laminated bodies 11 with a bonding material layer 19 interposed therebetween, and comprising 500 active ceramic layers as a whole. is there.
The multilayer piezoelectric element 10 of this example has a cross-sectional shape that is substantially square and orthogonal to the stacking direction, and a pair of side electrodes 116 are bonded to the opposite side surfaces 115.
[0030]
As shown in FIG. 3, the unit laminated body 11 of this example is formed by alternately laminating a ceramic layer 111 having a thickness of 0.08 mm and an electrode arrangement layer 112 having a thickness of 0.003 mm. And a layered structure of partial electrodes composed of 21 electrode arrangement layers 112.
The unit laminate 11 has a height in the stacking direction of 1.8 mm and a cross-sectional area perpendicular to the stacking direction of 46 square mm. The measured Young's modulus of the unit laminate 11 is 57000 MPa.
[0031]
As shown in FIG. 2, the electrode arrangement layer 112 includes an electrode portion 503 made of a conductive material having conductivity, and a holding portion 504 not formed with a conductive material.
In each electrode arrangement layer 112, a holding portion 504 is formed facing one of the two side surfaces 115 to which the side electrode 116 (FIG. 3) is bonded, and the surface is formed on one side surface. In the electrode arrangement layer 112 exposing the holding portion 504, the electrode portion 503 is exposed on the other side surface. And in each side surface 115, it is comprised so that the reserve part 504 and the electrode part 503 may appear alternately in the lamination direction as the electrode arrangement | positioning layer 112. FIG.
[0032]
As shown in FIG. 3, the laminated piezoelectric element 10 of this example is formed by bonding the unit laminates 11 to each other and laminating them with a bonding material layer 19 formed by curing a bonding material made of silicone resin. is there.
In particular, in the multilayer piezoelectric element 10 of this example, the Young's modulus Y of the bonding material forming the bonding material layer 19 is used.₂And the height L in the stacking direction₂And the cross-sectional area S perpendicular to the stacking direction₂Are set so as to satisfy Equation 1 and Equation 2 above.
[0033]
It should be noted that the Young's modulus Y of the above bonding material of this example₂Is 1.2 MPa. Where Young's modulus Y₂Is a Young's modulus measured for a sample piece formed by molding the bonding material constituting the bonding material layer 10 into a block shape and drying and curing it.
In the multilayer piezoelectric element 10 of this example, the Young's modulus Y₂= 1.2 MPa so that the above formula 1 is satisfied, the height L of the bonding material layer₂Is 0.001 mm, and the cross-sectional area S perpendicular to the axial direction is as shown in FIG.₂Is set to 7 square mm.
[0034]
Here, the reason why the bonding material layer 19 can be optimally designed by applying Equations 1 and 2 will be described.
When a load is applied in the direction in which the laminated piezoelectric element 10 (see FIG. 3) of this example is compressed in the laminating direction, the unit laminated body 11 itself and the bonding material layer 19 that joins the unit laminated body 11 are compressed and deformed. .
If the sum of the amount of compressive deformation of all the bonding material layers 19 becomes larger than the sum of the amount of compressive deformation of all the unit laminates 11, the piezoelectric efficiency of the entire laminated piezoelectric element 10 may be significantly reduced. .
[0035]
In general, in order to realize a laminated piezoelectric element with good piezoelectric performance, it is necessary to suppress the amount of compressive deformation of the bonding material layer to be equal to or less than the amount of compressive deformation of the unit laminate as shown in Reference Formula 1. .
(N₁× L₁) / (S₁× Y₁) ≧ (N₂× L₂) / (S₂× Y₂) ... Reference formula 1
[0036]
Here, the inventors have said that the reference formula 1 may not be appropriate for an actual stacked piezoelectric element through research and demonstration experiments conducted on a stacked piezoelectric element formed by stacking unit stacks. Finding knowledge.
The inventors further conducted various experiments, and the Young's modulus (effective Young's modulus) actually measured for the bonding material layer of the multilayer piezoelectric element was as shown in FIG. 5 and FIG. We found the tendency to depend on the thickness of the direction, and paid attention to this fact.
5 and 6, the vertical axis represents the effective Young's modulus / Young's modulus Y.₂The ratio is shown on the horizontal axis, and the thickness of the bonding material layer 19 is shown on the horizontal axis.
[0037]
Further, as shown in FIG. 5, the inventors have revealed the above dependence tendency in a thin region of the bonding material layer 19, and in particular, the effective Young's modulus measured for the bonding material layer 19 in the region of the layer thickness of 500 μm or less. It has been demonstrated through various studies that the rate of increase is rapidly increasing.
On the other hand, the effective Young's modulus is stable in the region where the layer thickness is 1000 μm or more, and the value is Young's modulus Y₂It was confirmed that they almost match.
[0038]
Furthermore, the inventors have found the following knowledge through various additional tests conducted by changing the material of the bonding material, the arrangement shape of the bonding material layer 19, and the like.
(1) Effective Young's modulus / Young's modulus Y in the region where the layer thickness is 500 μm or less₂The ratio has a high correlation with the layer thickness.
(2) Effective Young's modulus / Young's modulus Y in the region where the layer thickness is 500 μm or less₂The ratio is not related to the arrangement shape of the bonding material layer 19 and depends exclusively on the thickness and the cross-sectional area of the bonding material layer 19.
(3) Effective Young's modulus / Young's modulus Y in the region of the layer thickness of 500 μm or less₂The ratio is low in relevance with the type of bonding material forming the bonding material layer 19.
[0039]
Furthermore, the inventors have determined that the effective Young's modulus / Young's modulus Y of (1) above.₂It has been found that the relationship between the ratio and the thickness of the bonding material layer 19 can be linearly approximated with high accuracy. That is, the effective Young's modulus is expressed as Young's modulus Y₂Can be approximated with high accuracy.
(Effective Young's modulus) = (2000-10800 × L₂) × Y₂  ... Formula 5
[0040]
And, the above mathematical formula 1 is the Y of the above reference formula 1.₂The effective Young's modulus based on Formula 5 is substituted.
That is, the above-mentioned general reference equation 1 is an equation that does not consider the dependency between the layer thickness of the bonding material layer and the Young's modulus at all, whereas the above-described equation 1 represents the thickness of the bonding material layer. The thin case is taken into consideration.
Therefore, if Formula 1 and Formula 1 are applied, it is possible to optimally design the bonding material layer 19 until the bonding material layer is thin.
[0041]
In the multilayer piezoelectric element 10 of this example, as shown in FIG. 3, a side electrode 116 is bonded to a side surface 115 of each unit multilayer body 11 with a conductive adhesive.
Here, on each side surface 115 of each unit laminate body 11, the electrode portion 503 is exposed as every other electrode arrangement layer 112 in the lamination direction. Therefore, one of the pair of side electrodes 116 bonded to the side surface 115 of the multilayer piezoelectric element 10 is electrically connected to the electrode portion 503 of the alternate electrode arrangement layer 112, and the other side electrode 116 is It is electrically connected to the electrode portion 503 of every other electrode arrangement layer 112 that is electrically insulated from the one side electrode 116.
The laminated piezoelectric element 10 is configured to generate a piezoelectric effect in each ceramic layer 111 of each unit laminated body 11 by applying a voltage between the pair of side surface electrodes 116.
[0042]
Next, a method for manufacturing the multilayer piezoelectric element 1 of this example will be described.
Here, first, a method for producing the unit laminate will be described.
In manufacturing the unit laminate 11, a green sheet (not shown) is prepared in advance from a slurry for a green sheet, which is a piezoelectric element material.
[0043]
This slurry is obtained by adding a binder, a small amount of a plasticizer, and an antifoaming agent to a ceramic raw material that becomes a piezoelectric ceramic such as lead zirconate titanate (PZT) and then dispersing it in an organic solvent.
In this example, the slurry was applied onto a carrier film (not shown) by a doctor blade method to produce a green sheet having a predetermined thickness. In addition, as a method of producing | generating a green sheet from a slurry, the extrusion method other various methods other than a doctor blade method can be taken.
[0044]
Next, as shown in FIG. 1, an Ag—Pd paste, which is a conductive material, is applied to the laminated surface of the green sheet pieces 521 by screen printing. Here, by applying the Ag-Pd paste leaving one side corresponding to the outer peripheral portion of the laminated surface, the region to be the above-described reserve portion 504 can be formed on the laminated surface.
Thereafter, the slurry as an adhesive is applied to the entire laminated surface to which the conductive material has been applied.
[0045]
Next, as shown in FIG. 1, the green sheet pieces 521 are sequentially laminated. Here, as shown in the figure, an intermediate laminate (not shown) was produced by laminating the green sheet pieces 521 so that the arrangement of the holding portions 504 was alternately reversed.
[0046]
Next, as shown in FIG. 2, this intermediate laminate is fired to produce a unit laminate 11. In this example, the intermediate laminate was fired by holding in an atmosphere at 1200 ° C. for 2 hours, and then furnace cooling was performed.
Then, the conductive material applied on the laminated surface of the green sheet pieces 521 forms a layered electrode portion 503. In the unit laminated body 11, each electrode arrangement layer 112 exposes the electrode portions 503 every other layer on the opposite side surfaces 115, and the electrode that exposes the electrode portions 503 on one side surface 115. The arrangement layer 112 is configured not to expose the electrode portion 503 on the other side surface 115.
[0047]
Next, the 25 unit laminates 11 manufactured as described above are joined and laminated with the joining material layer 19 interposed therebetween.
Here, first, the cross-sectional area S calculated by Equation 1 above is used.₂= 7 square mm and stacking direction height L₂= Calculate the required capacity of the bonding material based on 0.001 mm. And the joining material of the calculated | required predetermined capacity was apply | coated to the joint surface of each unit laminated body 11. FIG.
[0048]
The cross-sectional shape orthogonal to the axial direction of the bonding material layer 19 formed in this example has a substantially circular shape as shown in FIG.
Therefore, in this example, when the bonding material is applied to the bonding surface of each unit laminate 11, a bonding material having a predetermined capacity is applied so as to exhibit a substantially circular shape at the center of the bonding surface.
[0049]
It should be noted that the arrangement and the cross-sectional shape of the bonding material forming the bonding material layer are not limited to a single substantially circular shape, but various arrangements, cross-sectional shapes, and shapes as shown in FIGS. 7 (a) and (b). can do. In this case, the bonding material may be applied in accordance with the arrangement and cross-sectional shape of the bonding material forming the bonding material layer.
[0050]
Next, when joining each unit laminated body 11, first, each unit laminated body 11 which apply | coated the bonding material is laminated | stacked, and the said multilayer piezoelectric element 10 is temporarily assembled.
Then, stacking direction height L₁= 25 unit laminates 11 exhibiting 1.8 mm, and stacking direction height L₂The temporarily assembled laminated piezoelectric element 10 is compressed in the laminating direction so as to obtain a designed laminated height obtained by combining 24 bonding material layers 19 exhibiting 0.001 mm. Furthermore, the laminated piezoelectric element 10 is held while maintaining the designed laminated height, and the bonding material is dried to form the bonding material layer 19 having a predetermined shape.
[0051]
As described above, if the unit laminated bodies 11 are laminated and joined so that the laminated piezoelectric element 10 has the designed laminated height, the cross-sectional area S is increased from the bonding material having the predetermined capacity.₂And stacking direction height L₂It is possible to form the bonding material layer 19 exhibiting the following.
The multilayer piezoelectric element 10 of this example is formed by bonding the pair of side electrodes 116 to the side surface 115 of the multilayer piezoelectric element 10 with a conductive adhesive.
The multilayer piezoelectric element 10 generates a piezoelectric effect in each ceramic layer 111 by applying a predetermined voltage between the pair of side electrodes 116, and realizes a large displacement amount as a whole of the multilayer piezoelectric element 10. It is configured to be able to.
[0052]
As described above, in the multilayer piezoelectric element 10 of the present example designed based on the formulas 1 and 2, the reference Young's modulus Y for the bonding material layer 19 is used.₂Cross section S for₂And height L in the stacking direction₂And the balance is good.
Therefore, in the laminated piezoelectric element 10 in which the plurality of element units 11 are laminated with the bonding material layer 19 interposed, the bonding material layer 19 has an appropriate hardness. Therefore, the displacement due to the piezoelectric effect produced by each element unit 11 is less likely to be absorbed by the deformation of the bonding material layer 19.
Therefore, the laminated piezoelectric element 10 described above has an excellent performance that exhibits a large displacement due to the piezoelectric effect.
[0053]
In the multilayer piezoelectric element 10, the bonding material layer 19 has appropriate flexibility. Therefore, the bonding material layer 19 is less likely to undergo fatigue failure due to stress strain or the like that may be caused by the piezoelectric effect of each element unit 11.
Therefore, the laminated piezoelectric element 10 can maintain its excellent performance over a long period of use.
[0054]
(Example 2)
In this example, holding members 18 are further laminated on both ends of the multilayer piezoelectric element of Example 1.
A laminated piezoelectric element 10 in which holding members 18 are joined to both ends of this example will be described with reference to FIG.
[0055]
In this laminated piezoelectric element 10, the end surface of the unit laminate 11 and the end surface of the holding member 18 disposed at both ends are joined via a joining material layer 19 similar to the joining material 19 layer between the unit laminates 11. It is.
The holding member 18 made of alumina has a height L in the stacking direction.₃Is 2 mm, the cross-sectional area perpendicular to the stacking direction is 46 square mm, and the measured Young's modulus Y₃As 380000MPa.
[0056]
Then, the bonding material layer 19 of this example has a reference Young's modulus Y of the bonding material.₂And the height L in the stacking direction₂And the cross-sectional area S perpendicular to the stacking direction₂Are set so as to satisfy the following equations 3 and 4.
(N₁× L₁) / (S₁× Y₁) + (N₃× L₃) / (S₃× Y₃) ≧ (N₂× L₂) / (S₂× ((2000-10800 × L₂) × Y₂)) ... Formula 3
S₂≦ S₁                                              ... Formula 4
L₁: Height in the stacking direction of the unit stack (mm)
S₁: Cross-sectional area perpendicular to the stacking direction of the unit stack (square mm)
Y₁: Young's modulus (MPa) in the stacking direction of the unit stack
N₁: Number of stacked units
L₂: Height of the bonding material layer in the stacking direction (mm)
S₂: Cross-sectional area perpendicular to the lamination direction of the bonding material layer (square mm)
Y₂: Young's modulus (MPa) of the material constituting the bonding material layer
N₂: Number of bonding material layers
L₃: Height of holding member in the stacking direction (mm)
S₃: Cross-sectional area perpendicular to the stacking direction of the holding member (square mm)
Y₃: Young's modulus (MPa) in the stacking direction of the holding member
N₃: Number of holding members stacked
[0057]
Here, in this example, since the holding members 18 are laminated on both ends of the laminated piezoelectric element, the number N of laminated holding members 18 in the same formula is used.₃Will be two.
In this way, in this example, since the holding member 18 is bonded to both ends of the multilayer piezoelectric element 10, Expression 3 and Expression 4 are applied instead of Expression 1 and Expression 2 in Example 1.
According to these equations, for the laminated piezoelectric element 10 in which the holding member 18 is joined to both ends of the laminated piezoelectric element 10, the appropriate height L of the bonding material layer 19 in the lamination direction is always obtained.₂And cross-sectional area S₂Can be calculated.
[0058]
In this example, holding members 18 are laminated on both ends of the laminated piezoelectric element 10. Alternatively, the holding member 18 can be laminated only on one end of the laminated piezoelectric element 10. In this case, the number N of holding members 18 in Equation 2 is stacked.₃You only need to change
Furthermore, the holding member 18 can be laminated not at the end portion but at at least one of the intermediate portions in the lamination direction. In this case, Formula 2 can also be applied.
Furthermore, other configurations and operational effects are the same as those in the first embodiment.
[0059]
(Example 3)
In this example, the configuration of the bonding material layer is changed based on the multilayer piezoelectric element of the first embodiment.
As shown in FIG. 9, the multilayer piezoelectric element 10 of this example includes a bonding material layer 19 including a region made of a bonding material 191 and a region made of a hardening material 192.
The entire bonding material layer 19 is configured to satisfy the above mathematical formula 1.
[0060]
Further, in manufacturing the multilayer piezoelectric element 10 described above, as in the first embodiment, after the adjacent unit laminated bodies 11 are joined by the joining material 191, the capillary phenomenon is used in the gaps between the unit laminated bodies 11. By a method, a curing material 192 made of an epoxy resin was filled.
In addition to the method using the capillary phenomenon used in this example, the curing material 192 can be filled by a vacuum method, a liquid injection molding method, or the like.
[0061]
In this example, the curing material 192 is filled using a dispenser device (not shown).
This dispenser device is configured so that a fixed amount of liquid insulating material can be discharged from a position-controlled dispense nozzle. In this example, the dispenser device was used to fill the gap between the adjacent unit laminates 11 with the hardening material 192 to form the bonding material layer 19 composed of the bonding material 191 and the hardening material 192.
[0062]
As described above, according to the multilayered piezoelectric element 10 of this example, the bonding material 191 is formed of a part of the bonding material layer 19 with the curing material 192 while adopting a flexible material, so that the bonding material 191 is formed. The layer 19 as a whole can achieve a sufficient hardness.
That is, by disposing the hardening material 192 on the outer peripheral side of the bonding material 191, the Young's modulus of the entire bonding material layer 19 can be appropriately ensured.
Therefore, in this multilayer piezoelectric element 10, the range of selection of the bonding material 191, the range that the shape of the bonding material layer 19 can take, and the like can be expanded to increase the degree of design freedom.
Other configurations and operational effects are the same as those in the first embodiment.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory diagram showing a lamination procedure of a ceramic laminate in Example 1.
2 is a cross-sectional view showing a laminated structure of ceramic laminates in Example 1. FIG.
3 is a cross-sectional view showing a cross-sectional structure of a multilayer piezoelectric element in Example 1. FIG.
4 is a cross-sectional view showing a cross-sectional shape of a bonding material layer in Example 1. FIG.
5 is a graph showing the relationship between the thickness of a bonding material layer (in the range of 0 to 5000 μm) and Young's modulus in Example 1. FIG.
6 is a graph obtained by enlarging a region of 0 to 100 μm in thickness of the bonding material layer in the graph of FIG. 6 in Example 1. FIG.
7 is a cross-sectional view showing a cross-sectional shape of another bonding material layer in Example 1. FIG.
8 is a cross-sectional view showing a cross-sectional structure of a multilayer piezoelectric element in Example 2. FIG.
9 is a cross-sectional view showing a cross-sectional structure of a multilayer piezoelectric element in Example 3. FIG.
[Explanation of symbols]
10. . . Laminated piezoelectric elements,
11. . . Unit laminate,
111. . . Ceramic layer,
112. . . Electrode arrangement layer,
115. . . side,
116. . . Side electrode,
18. . . Holding member,
19. . . Bonding material layer,
191. . . Bonding material,
192. . . Hardener,
503. . . Electrode part,
504. . . Memorandum,

Claims (10)

A unit laminate formed by alternately laminating ceramic layers and electrode arrangement layers including electrode parts constituting internal electrodes is laminated with a bonding material layer interposed therebetween, and both ends in the laminating direction. In a laminated piezoelectric element having a unit composed of the unit laminated body,
A multilayer piezoelectric element, wherein the thickness L ₂ of the bonding material layer and the cross-sectional area S ₂ orthogonal to the stacking direction are set so as to satisfy the following formulas 1 and 2.
(N ₁ × L ₁ ) / (S ₁ × Y ₁ ) ≧ (N ₂ × L ₂ ) / (S ₂ × ((2000-10800 × L ₂ ) × Y ₂ )).
S ₂ ≦ S ₁ ... Formula 2
L ₁ : height (mm) in the stacking direction of the unit stack
S ₁ : cross-sectional area (square mm) perpendicular to the stacking direction of the unit stack
Y ₁ : Young's modulus (MPa) in the stacking direction of the unit stack
N ₁ : Number of unit laminates L ₂ : Height of joining material layers in the lamination direction (mm)
S ₂ : Cross-sectional area (square mm) orthogonal to the lamination direction of the bonding material layer
Y ₂ : Young's modulus (MPa) of the material constituting the bonding material layer
N ₂ : number of bonding material layers A unit laminate formed by alternately laminating ceramic layers and electrode arrangement layers including electrode parts constituting internal electrodes is laminated with a bonding material layer interposed therebetween, and both ends in the laminating direction. A laminated piezoelectric element in which a holding member forming an inactive layer is disposed in at least one of the intermediate portion and the intermediate portion in the lamination direction.
A multilayer piezoelectric element, wherein the thickness L ₂ of the bonding material layer and the cross-sectional area S ₂ orthogonal to the stacking direction are set so as to satisfy the following formulas 3 and 4.
(N ₁ × L ₁ ) / (S ₁ × Y ₁ ) + (N ₃ × L ₃ ) / (S ₃ × Y ₃ ) ≧ (N ₂ × L ₂ ) / (S ₂ × ((2000-10800 × L ₂ ) × Y ₂ ))... Formula 3
S ₂ ≦ S ₁ ... Formula 4
L ₁ : height (mm) in the stacking direction of the unit stack
S ₁ : cross-sectional area (square mm) perpendicular to the stacking direction of the unit stack
Y ₁ : Young's modulus (MPa) in the stacking direction of the unit stack
N ₁ : Number of unit laminates L ₂ : Height of joining material layers in the lamination direction (mm)
S ₂ : Cross-sectional area (square mm) orthogonal to the lamination direction of the bonding material layer
Y ₂ : Young's modulus (MPa) of the material constituting the bonding material layer
N ₂ : Number of bonding material layers L ₃ : Height (mm) of the holding member in the stacking direction
S ₃ : cross-sectional area (square mm) perpendicular to the stacking direction of the holding members
Y ₃ : Young's modulus (MPa) in the stacking direction of the holding member
N ₃ : number of holding members stacked 2. The multilayer piezoelectric element according to claim 1, wherein the multilayer piezoelectric element satisfies Formula 1 and Formula 2 in an operating temperature range of 80 ° C. to 200 ° C. 3. 3. The multilayer piezoelectric element according to claim 2, wherein the multilayer piezoelectric element satisfies Formula 3 and Formula 4 in an operating temperature range of 80 ° C. or higher and 200 ° C. or lower. 5. The electrode arrangement layer according to claim 1, wherein the electrode arrangement layer includes a conductive electrode section and a holding section that is an area in which the electrode section is recessed inward from an end of the electrode arrangement layer. The region where the bonding material layer is formed on the end surface in the stacking direction of the unit laminate body is a region included in the region where the electrode portions overlap and exist in the stacking direction in each electrode arrangement layer. A laminated piezoelectric element, characterized in that there is. 6. The multilayer piezoelectric element according to claim 1, wherein the bonding material layer is configured by combining a region made of the bonding material and a region made of a hardened material. 7. The multilayer piezoelectric element according to claim 1, wherein the bonding material forming the bonding material layer is a material made of an epoxy resin, a silicone resin, a urethane resin, or a polyamideimide resin. The multilayer piezoelectric element according to claim 1, wherein the bonding material layer has a thickness of 0.0001 mm to 0.01 mm. In the manufacturing method which manufactures the multilayer piezoelectric element concerning the invention of Claim 7 formed by laminating | stacking the unit laminated body which laminates | stacks a ceramic layer and an electrode arrangement | positioning layer alternately via a bonding material layer. ,
A unit production process for producing a unit laminate formed by alternately laminating the ceramic layers and the electrode arrangement layers;
A laminating step of laminating the unit laminated body via a bonding material disposed on an end surface of the unit laminated body;
A curing material is disposed in a gap between adjacent unit laminates and a unit gap formed by the outer peripheral surface of the bonding material to form the bonding material layer formed of the curing material and the bonding material. A method of manufacturing a laminated piezoelectric element, comprising: an arranging step. 9. The curing material disposing step according to claim 8, wherein the curing material is disposed in the unit gap using a vacuum method, a capillary phenomenon method, or a liquid injection molding method. A method for manufacturing a laminated piezoelectric element.

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