JP2008300430A - Multilayer piezoelectric element and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to provide a high-power multilayer piezoelectric element and to provide a production method that can stably obtain an extremely high-quality multilayer piezoelectric element with excellent productivity.
A stacked type in which unit unit layers 10a and 10b including internal electrode layers 120a and 120b and piezoelectric ceramic layers 100a and 100b are stacked in an n-layer so that the polarization P in the thickness direction is reversed for each layer. In the piezoelectric element 1, the piezoelectric ceramic layers 100a and 100b are divided into a plurality of regions, which are low resistance regions 110a, 110b, and 111a that have a relatively lower electric resistance than other regions in the same piezoelectric ceramic layer. , 111b are formed. In the low resistance region, since the electric field density is high, a region HR having a high electric field density and a region LR having a low electric field density are mixed in the piezoelectric ceramic layers 100a and 100b. Due to the difference, the piezoelectric ceramic layer is bent and deformed. A large output displacement can be obtained by superimposing the displacement dS due to this bending and the displacement dL due to the inherent inverse piezoelectric effect.
[Selection] Figure 2

Description

  The present invention relates to an improvement in output of a laminated piezoelectric element in which piezoelectric ceramic layers and internal electrode layers are alternately laminated.

2. Description of the Related Art Conventionally, as a drive source for a fuel injection valve or the like used in an internal combustion engine, application of a piezo actuator using the inverse piezoelectric effect has been proposed because of its quick response.
In particular, piezoelectric actuator for a vehicle, repeat the above operation ¹⁰⁸ times, which corresponds to a travel distance 30-500000 km is required, reliability is required and high durability to ensure this.

  As a piezoelectric element used in such a piezoelectric actuator, a piezoelectric ceramic thin plate is laminated with several dozen to several hundreds of piezoelectric ceramic layers and internal electrode layers alternately so that the polarization in the thickness direction is reversed for each layer. Such a laminated piezoelectric element is promising.

  As a manufacturing method for stably forming such a multilayer piezoelectric element having a very large number of layers, the present inventors have disclosed a multilayer piezoelectric element that is difficult to cause delamination and forms an integral sintered body as disclosed in Patent Document 1. A method of manufacturing a ceramic laminate suitable for mass production of devices was proposed.

  In addition, a fuel injection valve using such a piezoelectric actuator has a laminated piezoelectric element, a piston member that transmits the displacement, a piston member that is in close contact with the piezoelectric element, and a predetermined preset load applied to the laminated piezoelectric element. A spring member is provided, and the piston member slides as the piezoelectric element expands and contracts to drive a control valve that controls the opening and closing of the fuel injection valve.

For further miniaturization and higher accuracy of the fuel injection valve, higher conversion efficiency is desired for the piezoelectric actuator.
For example, Patent Literature 2 includes pre-compression means, and a partial compression in the piezoelectric ceramic layer is caused by a pre-compression force applied from the surface portions of a pair of electrode layers arranged along the stacking direction of the piezoelectric ceramic layers. A piezoelectric actuator is disclosed that obtains a large amount of displacement when the polarization direction of a region is changed in a direction transverse to the stacking direction, an electric field is applied between the electrode layers, and all polarization directions are converted parallel to the stacking direction. .
JP 2003-174210 A JP 2005-535136 A

However, in the structure in which the pre-compression means and the piezoelectric elements as alternately described in Patent Document 2 are alternately stacked, the physique of the element for obtaining a necessary output may be very large.
In addition, since the pre-compression means is disposed between the single-layer piezoelectric elements, the structure is complicated and the assembly cost may increase.
Furthermore, as disclosed in Patent Document 2, when a metal intermediate layer is disposed between the patterned electrode layers of the piezoelectric element as pre-compression means, even if the displacement per unit piezoelectric ceramic layer is large, the metal intermediate layer Due to the elastic deformation, the generated displacement and the generated force are absorbed, and there is a possibility that a sufficient amount of displacement as the actuator for driving the fuel injection valve cannot be obtained as a whole laminate.

  In view of such circumstances, the present invention has an object to provide a high-power multilayer piezoelectric element and a manufacturing method that is excellent in productivity, and can stably obtain an extremely high-quality and high-power multilayer piezoelectric element. And

  According to the first aspect of the present invention, in the multilayer piezoelectric element formed by repeatedly laminating the unit unit layer on which the internal electrode layer is printed on the surface of the piezoelectric ceramic layer, the boundary portion between the piezoelectric ceramic layer and the internal electrode layer In the piezoelectric ceramic layer, there are a plurality of divided regions, and low resistance regions having relatively lower electrical resistance than other regions in the same piezoelectric ceramic layer are distributed.

According to the first aspect of the present invention, when the electric field is applied to the piezoelectric ceramic layer, the piezoelectric ceramic layer has a low electric resistance region and a relatively high electric resistance region in the same piezoelectric ceramic layer. In this, a region having a high electric field density and a region having a low electric field density are mixed.
Since the displacement amount of the piezoelectric ceramic due to the inverse piezoelectric effect is proportional to the electric field strength, if there is a difference in the electric field density, a difference in the output displacement amount occurs, and the piezoelectric ceramic layer is bent and deformed.
The displacement due to this bending is added to the displacement of the piezoelectric ceramic layer due to the inverse piezoelectric effect.
Even if the deflection per unit piezoelectric ceramic layer is very small, in a laminated piezoelectric element in which several hundred layers are stacked, this deflection is superimposed and a larger output displacement than the conventional one can be obtained.

  According to a second aspect of the present invention, the low resistance region is disposed at a position where the low resistance regions in the piezoelectric ceramic layer facing each other across the one internal electrode layer are not opposed to each other.

According to the second aspect of the present invention, when an electric field is applied, regions having a high electric field density are distributed so as to cross obliquely with respect to the thickness direction of the piezoelectric ceramic layer.
Therefore, the piezoelectric ceramic layer can be easily bent and deformed, and a larger output displacement can be obtained.

  Further, as in a third aspect of the invention, the low resistance region may be formed in the piezoelectric ceramic layer on at least one of the upper and lower sides with respect to the internal electrode layer.

  Further, as in a fourth aspect of the invention, the low resistance region may be formed on both sides of the internal electrode layer.

  According to a fifth aspect of the present invention, in the method for manufacturing a multilayer piezoelectric element according to any one of the first to fourth aspects, the piezoelectric ceramic layer is formed on a surface of a piezoelectric ceramic layer formed in a sheet shape using a piezoelectric ceramic material. A low-resistance region layer printing forming process for printing a low-resistance region layer using a piezoelectric ceramic paste for a low-resistance region including a piezoelectric ceramic material whose electrical characteristics after firing are relatively low resistance than the layer; Low resistance region forming layer printing with the same thickness as the above low resistance region layer using a piezoelectric ceramic paste for low resistance region forming layer that has the same electrical characteristics after firing as the ceramic layer Forming step.

  According to the invention of claim 5, it is possible to manufacture a laminated piezoelectric element in which low resistance regions are distributed in the same piezoelectric ceramic layer very easily.

  According to a sixth aspect of the present invention, in the method for manufacturing a multilayer piezoelectric element according to any one of the first to fourth aspects, a piezoelectric ceramic layer is formed on a surface of a piezoelectric ceramic layer formed into a sheet shape using a piezoelectric ceramic material. Using the piezoelectric ceramic paste of the same material, a piezoelectric ceramic layer convex portion forming step for printing a convex portion from which a part of the surface of the piezoelectric ceramic layer protrudes, and pressing the convex portion into the piezoelectric ceramic layer and compressing, A high-density region compression forming step of forming a high-density region in the piezoelectric ceramic layer;

  According to the sixth aspect of the present invention, the high-density region is formed in the same piezoelectric ceramic layer, the electric resistance is relatively low in the high-density region, and the low-resistance region is distributed in the same piezoelectric ceramic layer. The laminated piezoelectric element can be manufactured very easily.

  According to a seventh aspect of the present invention, in the method for manufacturing a multilayer piezoelectric element according to any one of the first to fourth aspects, the low resistance region on the surface of the piezoelectric ceramic layer formed into a sheet shape using a piezoelectric ceramic material is used. Piezoelectric firing accelerators that contain metals or metal compounds in the partitioned areas by any of the methods of dripping, coating, transferring, and printing, diffuse in the piezoelectric ceramic layer during firing, and promote grain growth of the piezoelectric ceramic. A firing accelerator distribution step for distributing the surface of the ceramic layer is provided.

According to the seventh aspect of the present invention, densification of the region to which the firing accelerator is applied is promoted, and a laminated piezoelectric element having low resistance regions distributed in the same piezoelectric ceramic layer can be manufactured very easily.
In addition, in the conventional manufacturing method, since the sintering proceeds from the outer peripheral edge of the element, the sintering speed of the central portion is slower than that of the outer peripheral edge, and the sintered body is distorted. Since the sintering proceeds from the area where the sintering accelerator is distributed on the surface of the layer, a sintered body with very little distortion can be obtained.
Accordingly, it is possible to stably manufacture a high-quality multilayer piezoelectric element.

According to an eighth aspect of the present invention, in the method for manufacturing a multilayer piezoelectric element according to any one of the first to fourth aspects,
The internal electrode layer is printed on the surface of the piezoelectric ceramic layer in which the low-resistance region is formed, and the unit unit layer is formed by drying, and the adhesive layer is printed on the surface of the obtained unit unit layer. A step of performing the punching process using a Thomson mold at the same time as laminating another unit unit layer on the adhesive layer while the adhesive layer is in an undried state, and degreasing and firing the ceramic laminated molded body. Obtaining a multilayer piezoelectric element.

According to invention of Claim 8, lamination | stacking and adhesion | attachment can be performed simultaneously.
Furthermore, since the adhesive layer in an undried state flows and eliminates variations in film thickness, a multilayer piezoelectric element with high dimensional accuracy, complete integration, and low resistance areas distributed in the same piezoelectric ceramic layer can be manufactured at low cost. Can be produced.

An outline of the configuration of the multilayer piezoelectric element 1 according to the first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the multilayer piezoelectric element 1 includes unit unit layers 10 a and unit unit layers 10 b that are alternately layered from several tens to several hundreds so that the polarization P in the thickness direction is reversed every layer. The slit part 150 is formed every several to several tens of layers, and the protective layer 6 is formed at the upper and lower ends.

In the unit unit layers 10a and 10b, internal electrode layers 120a and 120b are formed on the surfaces of piezoelectric ceramic layers 100a and 100b formed in a thin plate shape.
The boundary portions between the piezoelectric ceramic layers 100a and 100b and the internal electrode layers 120a and 120b are divided into a plurality of regions, which are relatively low in electric resistance than other regions in the same piezoelectric ceramic layer. Resistance regions 110a, 110b, 111a, and 111b are distributed on both upper and lower sides with the internal electrode layers 120a and 120b interposed therebetween.
Further, the low resistance regions 110a and 110b are disposed at positions that do not face each other with the low resistance regions 111a and 111b facing each other with the piezoelectric ceramic layers 100a and 100b interposed therebetween.

The internal electrode layers 120a and 120b are provided with internal electrode terminal portions 123a and 123b for conducting to the outside so as to be alternately drawn from the side surface of the piezoelectric ceramic layer.
In addition, the insulating properties of the outer peripheral edges of the internal electrodes other than the internal electrode terminal portions 123a and 123b are secured by the spacer portions 130a and 130b.
The unit unit layers 10a and 10b are bonded and laminated by adhesive layers 140a and 140b having the same quality as the piezoelectric ceramic layers 100a and 100b, and are then fired to form a completely integrated multilayer piezoelectric element 1.

The effect of this embodiment will be described with reference to FIG.
FIG. 2A is an enlarged schematic view of the unit unit layers 10a and 10b showing the operation principle of the present invention, and FIG. 2B is a multilayer piezoelectric element 1X having a conventional structure as a comparative example 1 and the multilayer type in the present embodiment. FIG. 3 is a schematic diagram showing a difference in output displacement from the piezoelectric element 1.
As shown in FIG. 2A, the low resistance regions 110a and 110b and the low resistance regions 111a and 111b facing each other with the piezoelectric ceramic layer 100a interposed therebetween are formed at positions where they do not face each other.
When an electric field is applied parallel to the polarization direction P of the piezoelectric ceramic layers 100a and 100b, a high electric field density region HR having a high electric field density is formed in an oblique direction with respect to the plate thickness direction of the piezoelectric ceramic layer 100a. Becomes a low electric field density region LR having a relatively low electric field density.
Since the elongation due to the inverse piezoelectric effect of the high electric field density region HR is very small but larger than the elongation of the low electric field density region LR, the piezoelectric ceramic layers 100a and 100b are bent.
Accordingly, the piezoelectric ceramic layer 100a having a thickness of _{L 0,} when added in parallel to the electric field and the polarization direction P of the 100b, the piezoelectric ceramic layer 100a, the displacement dL according to the specific voltage d constant _{d 33} of 100b, deflection caused by the displacement dS will be added.
As shown in FIG. 2B, when a laminated piezoelectric element in which several hundreds of piezoelectric ceramic layers are laminated, the laminated piezoelectric element 1X having a conventional structure in which a low resistance region is not formed in the piezoelectric ceramic layer is manufactured. Although the displacement amount is about 10 to 15 μm, in the present embodiment, the displacement due to the bending is superimposed, and the entire device can be expected to increase the displacement amount of about 1 to 2 μm.

A second embodiment of the present invention will be described with reference to FIG.
Since the basic configuration and effects are the same as those of the first embodiment, description of substantially the same parts will be omitted, and only the parts that are different from the first embodiment will be described.
In the multilayer piezoelectric element 1 ′ in the present embodiment, the low resistance regions 110a ′ and 110b ′ are formed on the piezoelectric ceramic layers 100a ′ and 100b ′ on either one of the upper and lower sides with respect to the internal electrode layers 120a ′ and 120b ′. It is formed.
With such a configuration, the conductivity of the low resistance regions 110a ′ and 110b ′ in the piezoelectric ceramic layers 100a ′ and 100b ′ is slightly higher than the surrounding regions, and the electric field density is increased.
Accordingly, since the elongation due to the inverse piezoelectric effect in the region where the electric field density is high becomes longer than the surroundings, the piezoelectric ceramic layers 100a ′ and 100b ′ are curved in a waveform and the output displacement is increased.

Below, the manufacturing method of the lamination type piezoelectric element in each embodiment of the present invention is explained in full detail.
Piezoelectric ceramic layers 100a and 100b are made of sheet thin plates by a doctor blade method using a slurry in which a piezoelectric ceramic material powder such as PZT is dispersed in a dispersion medium, a binder such as PVB, and a plasticizer such as DBP. Is obtained.
The internal electrode layers 120a and 120b are made of a paste made by adding a piezoelectric ceramic slurry of the same material as the piezoelectric ceramic layers 100a and 100b to a conductive material containing Ag, Pd, etc. by screen printing or the like. It is obtained by printing on the surface of the piezoelectric ceramic layers 100a and 100b.

4 to 7 show the manufacturing method of the multilayer piezoelectric element 1 according to the first embodiment of the present invention in the order of (a) to (s).
In addition, the top view corresponding to sectional drawing of (a)-(q) in the figure was shown by (a ')-(q').
Also, in the following steps, a piezoelectric ceramic material whose electric characteristics after firing is lower than that of the piezoelectric ceramic layers 100a and 100b is dispersed in the formation of the low resistance regions 110a, 110b, 111a, and 111b described later. A paste is used, and for the formation of the low-resistance region forming layers 111a, 111b, 112a, 112b and the spacer layers 130a, 130b, a piezoelectric ceramic paste in which a piezoelectric ceramic of the same material as the piezoelectric ceramic layers 100a, 100b is dispersed is used. The adhesive layers 140, 140a, and 140b are formed using an adhesive layer paste that has an increased amount of binder of piezoelectric ceramic paste to improve adhesion.

As shown in (a) and (a ′) in the figure, a substantially oval annular slit layer 150 is printed on the surface of the piezoelectric ceramic layer 100 formed in a sheet shape and dried.
The slit layer 150 is made of a paste composed of a burnable material such as carbon, a binder for imparting viscosity, and a dispersion medium so that the slit layer 150 is burned off by firing.
The dummy layer 30 is formed by laminating and printing the adhesive layer 140 with substantially the same thickness as the slit layer 150 using the adhesive layer paste.
Next, a protective layer 6 in which an insulating ceramic such as alumina or a green sheet made of the same material as that of the piezoelectric ceramic layer 100 is punched out into a substantially oval shape using the Thomson mold 7 is housed in the Thomson mold 7. deep.
As shown in (c) and (c ′), using the Thomson mold 7 in which the protective layer 6 is housed, a dummy is interposed between the lower surface of the protective layer 6 and the adhesive layer 140 while the adhesive layer 140 is in an undried state. At the same time as bonding the layer 30, the outer periphery of the dummy layer 30 is punched into a substantially oval shape.
The dummy layer 30 may be formed by appropriately inserting several layers to several tens of layers in the following steps.

Next, as shown in (d) and (d ′), the low-resistance region 110a is dotted on the surface of the sheet-like piezoelectric ceramic layer 100a using the low-resistance region layer forming paste. Print formed and dried.
Next, as shown in (e) and (e ′), the low-resistance region forming layer 112a is printed in a substantially oval shape with the same thickness as the low-resistance region 110a, using the low-resistance region-forming layer forming paste. Form and dry.
Note that either the low resistance region 110a or the low resistance region formation layer 112a may be formed first (in the following steps, a plurality of printed layers having the same film thickness are formed in the same layer). Same when forming).
At this time, when printing is performed so that the boundary between the low resistance region 110a and the low resistance region forming layer 112a overlaps, a film thickness distribution is reduced, and a multilayer piezoelectric element with high dimensional accuracy can be obtained (also in the following steps, The same applies when multiple printing layers with the same film thickness are formed in the same layer.)

As shown in (f) and (f ′), the outer peripheral edge is substantially oval and the outer peripheral edge is kept behind the low resistance region forming layer 112a. In the state, the internal electrode layer 120 in which the terminal portion 123a is drawn out to one side is printed and dried.
Further, as shown in (g) and (g ′), the spacer layer 130a is printed so as to cover the outer periphery of the internal electrode layer 120a and dried.

As shown in (h) and (h ′), the low-resistance regions 111a are dotted in the form of dots, and the low-resistance regions 110a and the internal electrode layers 120a are sandwiched between the stacked layers. Printed out and dried.
Furthermore, as shown in (i) and (i ′), using the paste of the component which becomes the same material after firing with the piezoelectric ceramic layer 100a, or the paste which increases the binder component to this and strengthens the adhesiveness, The adhesive layer 140a is printed.
Thus, the unit unit layer 10a is formed.

Next, as shown in (j) and (j ′), using the Thomson mold 7 in which the protective layer 6 and the dummy layer 30 are stacked and housed, the adhesive layer 140a is left in an undried state, The unit unit layer 10a is bonded to the lower surface via the adhesive layer 140, and at the same time, the outer periphery of the unit unit layer 10a is punched into a substantially oval shape.
As described above, the protective layer 6, the dummy layer 30, and the unit unit layer a are stacked in the Thomson mold 7.

(K) to (p) and (k ′) to (p ′) show a method of forming the unit unit layer 10b. Since the unit unit layer 10b can be formed by basically the same process as the unit unit layer 10a described above, only the differences will be described.
As shown in (k) and (k ′), the low resistance region 110b is opposed to the low resistance region 110a formed on the lower side of the internal electrode layer 120a, and the low resistance region formed on the upper side of the internal electrode layer 120a. It arrange | positions so that it may become a position which does not oppose the area | region 111a, and is printed and formed in the shape of a dot on the surface of the piezoelectric ceramic layer 100b, and is dried.
Next, as shown in (l) and (l ′), the low-resistance region forming layer 112b is printed and dried.
Then, as shown in (m) and (m ′), the internal electrode layer 120b is formed by printing and dried.
At this time, the terminal portion 123b is formed so as to protrude from the side surface opposite to the terminal portion 123a formed in the unit unit layer 10a.
Further, as shown in (n) and (n ′), the spacer layer 130b is printed and dried.
Then, as shown in (o) and (o ′), the low resistance region 111b is formed by printing and dried.
Next, as shown in (p) and (p ′), the adhesive layer 140b is printed.
Thus, the unit unit layer 10b is formed.
As shown in (q) and (q ′), using the Thomson type 7 in which the protective layer 6, the dummy layer 30, and the unit unit layer 10 a are stored in a stacked state while the adhesive layer 140 b is in an undried state, The unit unit layer 10b is bonded to the lower surface of the unit unit layer 10a via the adhesive layer 140b, and at the same time, the outer periphery of the unit unit layer 10b is punched into a substantially oval shape. As described above, the protective layer 6, the dummy layer 30, the unit unit layer 10 a, and the unit unit layer 10 b are stacked in the Thomson mold 7.

As shown in FIG. 7 (r), after repeating the above steps until the predetermined number of layers is reached, the protective layer 6 is laminated on the lower end portion via the adhesive layer 140, whereby a laminated piezoelectric element molded body is obtained. 1G is possible.
This is degreased in a degreasing furnace, and then fired in a firing furnace, whereby a completely integrated multilayer piezoelectric element 1 shown in a partially cutaway perspective view in FIG. 7 (s) is completed.
The slit layer 150 is burned away by firing, and the spacer layers 130a, 130b and the adhesive layers 140, 140a, 140b are completely integrated with the piezoelectric ceramic layers 100, 100a, 100b.
By adopting the above-described manufacturing method in which the adhesion by the adhesive layers 140, 140a, and 140b and the lamination and punching using the Thomson mold 7 are simultaneously performed, it is possible to obtain a completely integrated multilayer piezoelectric element with extremely high dimensional accuracy. Therefore, it is possible to use the slight deflection of the piezoelectric ceramic layer of the present invention for increasing the output displacement.

  In the description of the present embodiment, the manufacturing method of one element has been described. However, if a printing layer that becomes a plurality of elements is simultaneously formed using a large green sheet, the productivity can be extremely increased.

A method for manufacturing a multilayer piezoelectric element according to the second embodiment of the present invention will be described with reference to FIG.
FIGS. 8A and 8B are cross-sectional views showing the print layers printed by dividing the unit unit layers 10a ′ and 10b ′ in a plurality of times, respectively, in the stacking order.
In this embodiment, the low resistance regions 110a ′ and 110b ′ and the low resistance region forming layers 112a ′ and 112b ′ are printed and formed on either one of the upper and lower sides of the internal electrode layers 210a ′ and 210b ′. Unit layers 10a ′ and 10b ′ are formed and laminated through adhesive layers 140a ′ and 140b ′.
Similar to the multilayer piezoelectric element 1 according to the first embodiment of the present invention, adhesive layers 140a ′ and 140b ′ are printed and formed on the obtained unit units 10a ′ and 10b ′, and the adhesive layers 140a ′ and 140b ′ are in an undried state. If the unit units 10a ′ and 10b ′ are alternately laminated, and degreased and fired, the laminated piezoelectric element 1a ′ according to the second embodiment of the present invention can be obtained.

The configuration of the multilayer piezoelectric element 1 '' according to the third embodiment of the present invention is the same as that of the first embodiment or the second embodiment, but the method of forming the low resistance region is different in this embodiment. .
The main points of the manufacturing method of the multilayer piezoelectric element 1 ″ in this embodiment are shown in FIG. 9 in order of (a) to (e).
Hereinafter, in the present embodiment, an example in which the low resistance regions 110a ″ and 110b ″ are formed on one side with respect to the internal electrodes 120a ″ and 120b ″ will be described.
First, as shown to (a), the convex part which a part of piezoelectric ceramic layer surface protrudes on the surface of the piezoelectric ceramic layer 100a '' using the piezoelectric ceramic paste which becomes the same material as the piezoelectric ceramic layer 100a '' 110a ″ is printed and dried.
Next, as shown in (b), the convex portion 110a ″ is pushed into the piezoelectric ceramic layer 100a ″ by using a uniaxial pressure press or the like so that the thickness is substantially the same as that of the piezoelectric ceramic layer 100a ″. Compressed under pressure.
As a result, the density of the region into which the convex portion 110a '' is pressed becomes relatively higher than that of the other regions, and becomes a low resistance region 110a '' after firing, and is distributed in the piezoelectric ceramic layer 100a ''. .
As shown in (c), the unit electrode layer 120a '' and the adhesive layer 140a '' are printed and laminated to form a unit unit layer 10a ''.
Further, by the same process, the unit unit layer 10b ″ is formed by printing the internal electrode layer 120b ″ and the adhesive layer 140b ″ on the piezoelectric ceramic layer 100b ″ in which the low resistance region 110b ″ is formed. , (D), similarly to the above embodiment, the unit unit layers 10a ″ and 10b ″ are repeatedly stacked to form the stacked piezoelectric element 1 ″.

The configuration of the multilayer piezoelectric element 1 ′ ″ according to the fourth embodiment of the present invention is the same as that of the first embodiment or the second embodiment, but in this embodiment, a method for forming a low resistance region is used. Different.
The main points of the manufacturing method of the multilayer piezoelectric element 1 ′ ″ in the present embodiment will be shown in the order of FIGS. 10 (a) to 10 (d).
First, as shown in (a), a metal or a metal compound is contained in a region defined as a low resistance region on the surface of the piezoelectric ceramic layer 100a ′ ″ by any one of dropping, coating, transferring, and printing. The firing accelerator 200 diffusing into the piezoelectric ceramic layer 100a ″ during firing and promoting the grain growth of the piezoelectric ceramic is distributed on the surface of the piezoelectric ceramic layer to form the firing accelerator attaching portion 201a.
Next, as shown in FIG. 5B, the internal electrode layer 120a ′ ″ and the adhesive layer 140a ′ ″ are printed and laminated to form the unit unit layer 10a ′ ″.
Further, by the same process, the unit unit layer 10b in which the internal electrode layer 120b ′ ″ and the adhesive layer 140b ′ ″ are printed on the piezoelectric ceramic layer 100b ′ ″ on which the firing accelerator attaching portion 201b is formed. As shown in (d), the unit unit layers 10a ′ ″ and 10b ′ ″ are repeatedly stacked as in the above embodiment.
When this is degreased and fired, as shown in (e), the firing accelerator diffuses from the firing accelerator adhering portions 201a and 201b to the neighboring piezoelectric ceramic layers 100a ′ ″ and 100b ′ ″, and Densification is promoted, the density of the low resistance regions 110a ′ ″ and 110b ′ ″ is higher than that of other regions, the grain growth of the piezoelectric ceramic proceeds, and the conductivity increases.
According to the tests by the present inventors, as the firing accelerator 200, for example, a metal material such as Ag, Pt, Pb, or SiC, Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , BN, Nb _It has been found that ceramic materials such as ₂ O ₃ , Ta ₂ O ₃ , and Si ₃ N ₄ are effective.

  In the description of the above embodiment, the case where the low resistance regions 110a, 110b, 111a, and 111b are formed in a dot shape has been described as a representative example. However, the present invention is not limited to the dot shape, and FIG. ) To (d), the low resistance regions 110a, 110b, 111a, 111b of the opposing piezoelectric ceramic layers 100a, 100b may be formed so as to be shifted to positions that do not face each other. The low resistance regions 110a, 110b, 111a and 111b may be formed with a plurality of circular dots as shown in (a), or may be formed with a plurality of polygonal dots as shown in (b). As shown in c), it may be formed in a strip shape, or may be formed in a staggered pattern as shown in (d).

  In the above embodiment, the case where PZT is used as the piezoelectric ceramic material and Ag, Pd or the like is used as the electrode material has been described as an example. However, the present invention is not limited to the above embodiment. For example, PLZT is used as the piezoelectric material. It can be used as appropriate without departing from the spirit of the present invention.

These are the cross-sectional schematic diagrams of the laminated piezoelectric element in the 1st Embodiment of this invention. (A) is a cross-sectional schematic diagram which shows the principle of operation in the 1st Embodiment of this invention, (b) is a conceptual diagram which shows the effect in the 1st Embodiment of this invention with a comparative example. These are the cross-sectional schematic diagrams of the lamination type piezoelectric element in the 2nd Embodiment of this invention. These are sectional drawings which show a part of manufacturing process of the laminated piezoelectric element in the 1st Embodiment of this invention later on in order of (a)-(f), (a ')-(f') is the top view. . These are sectional drawings which show a part of manufacturing process of the laminated piezoelectric element in the 1st Embodiment of this invention later on in order of (g)-(l), (g ')-(l') is the top view. . These are sectional drawings which show a part of manufacturing process of the lamination type piezoelectric element in a 1st embodiment of the present invention in order of (m)-(q), and (m ')-(q') is the top view . (R) is a cross-sectional view of the multilayer piezoelectric element molded body 1G in the first embodiment of the present invention, and (s) is a partially cutaway perspective view showing the multilayer piezoelectric element 1 that is completely integrated. . These show the principal part of the manufacturing process of the lamination type piezoelectric element in the 2nd Embodiment of this invention, (a) is an expanded sectional view of unit unit layer 10a ', (b) is unit unit layer 10b'. FIG. These are sectional drawings which show the principal part in the other manufacturing method of the lamination type piezoelectric element in the 3rd Embodiment of this invention later on in order of (a)-(d). These are sectional drawings which show the principal part in the other manufacturing method of the lamination type piezoelectric element in the 4th Embodiment of this invention later on in order of (a)-(d). (A)-(d) is a top view which shows the some example of a shape of a low resistance area | region which can be applied to the laminated piezoelectric element in the 1st-4th embodiment of this invention.

Explanation of symbols

1 Multilayer Piezoelectric Element 10a, 10b Unit Unit Layer 100, 100a, 100b Piezoelectric Ceramic Layer 110a, 110b, 111a, 111b Low Resistance Region 120a, 120b Internal Electrode Layer
P Polarization direction HR High electric field density region LR Low electric field density region dS Bending displacement dL Reverse piezoelectric effect displacement

Claims (8)

In a multilayer piezoelectric element formed by repeatedly laminating unit unit layers formed by printing an internal electrode layer on the surface of a piezoelectric ceramic layer,
In the boundary portion between the piezoelectric ceramic layer and the internal electrode layer, the piezoelectric ceramic layer is divided into a plurality of regions and has a relatively lower electric resistance than other regions in the same piezoelectric ceramic layer. A multilayer piezoelectric element characterized in that low resistance regions are distributed.   2. The multilayer piezoelectric element according to claim 1, wherein the low resistance region is disposed at a position where the low resistance regions in the piezoelectric ceramic layer facing each other across the one internal electrode layer are not opposed to each other. element.   3. The multilayer piezoelectric element according to claim 1, wherein the low resistance region is formed in the piezoelectric ceramic layer on at least one of upper and lower sides with respect to the internal electrode layer.   4. The multilayer piezoelectric element according to claim 1, wherein the low-resistance region is formed on both sides of the internal electrode layer. 5. In the manufacturing method of the lamination type piezoelectric element according to any one of claims 1 to 4,
A piezoelectric ceramic paste for a low resistance region containing a piezoelectric ceramic material having electrical resistance after firing relatively lower than that of the piezoelectric ceramic layer on the surface of the piezoelectric ceramic layer formed into a sheet shape using the piezoelectric ceramic material. Using, a low resistance region layer printing forming step of printing the low resistance region layer;
A low-resistance region forming layer having a thickness substantially the same as that of the low-resistance region layer printed using a piezoelectric ceramic paste for a low-resistance region-forming layer having the same electrical characteristics after firing. A method of manufacturing a laminated piezoelectric element, comprising: a printing formation step. In the manufacturing method of the lamination type piezoelectric element according to any one of claims 1 to 4,
Piezoelectric ceramics that are printed on the surface of a piezoelectric ceramic layer formed from a piezoelectric ceramic material using a piezoelectric ceramic paste of the same material as that of the piezoelectric ceramic layer. A layer protrusion forming step;
A method of manufacturing a multilayer piezoelectric element, comprising: a high density region compression forming step of pressing and compressing the convex portion into the piezoelectric ceramic layer to form a high density region in the piezoelectric ceramic layer. In the manufacturing method of the lamination type piezoelectric element according to any one of claims 1 to 4,
In the region divided as a low resistance region on the surface of the piezoelectric ceramic layer formed into a sheet shape using a piezoelectric ceramic material, it contains a metal or a metal compound by any one of dripping, coating, transferring, and printing, and at the time of firing A method of manufacturing a laminated piezoelectric element, comprising: a firing accelerator distribution step in which a firing accelerator that diffuses into the piezoelectric ceramic layer and promotes grain growth of the piezoelectric ceramic is distributed on the surface of the piezoelectric ceramic layer. In the manufacturing method of the lamination type piezoelectric element according to any one of claims 1 to 4,
Printing the internal electrode layer on the surface of the piezoelectric ceramic layer in which the low resistance region is formed, and drying to form the unit unit layer;
A step of printing and forming the adhesive layer on the surface of the obtained unit unit layer;
The step of punching using the Thomson mold at the same time as laminating another unit unit layer to the adhesive layer while the adhesive layer is in an undried state;
A method for producing a multilayer piezoelectric element according to any one of claims 5 to 7, further comprising: degreasing and firing the ceramic multilayer molded body to obtain the multilayer piezoelectric element.