CN101504966B

CN101504966B - Multilayer piezoelectric device and ejection apparatus

Info

Publication number: CN101504966B
Application number: CN200810190350.3A
Authority: CN
Inventors: 中村成信
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-09-24
Filing date: 2004-09-22
Publication date: 2014-02-12
Anticipated expiration: 2024-09-22
Also published as: JP2005101207A; CN1856887A; CN101504966A; JP4808915B2; CN1856886A

Abstract

A multi-layer piezoelectric element having excellent durability in which the amount of displacement does not change even after subjecting to continuous operation over a long period of time under a high voltage and a high pressure is provided. The multi-layer piezoelectric element comprises a stack formed by stacking piezoelectric layers and internal electrodes alternately one on another and external electrodes formed on a first side face and on a second side face of the stack, wherein one of the adjacent internal electrodes is connected to the external electrode formed on the first side face and the other internal electrode is connected to the external electrode formed on the second side face. The external electrode is composed of the porous electric conductor which comprises conductive material and glass and is configured to a three-dimensional network structure.

Description

Multi-layer piezoelectric element and injection apparatus

The application be based on application number be 200480027657.1, denomination of invention for " multi-layer piezoelectric element ", the applying date be the dividing an application of patent application on September 22nd, 2004.

Technical field

The present invention relates to multi-layer piezoelectric element and injection apparatus, such as the multi-layer piezoelectric element and the injection apparatus that relate to stack-up type piezo-activator of being used in the precision positioning device of piezoelectric transformer or automotive fuel injection apparatus, Optical devices etc. or driving element that vibration prevents use etc. etc.

Background technology

All the time, as multi-layer piezoelectric element, known have a stack-up type piezo-activator that alternately lamination piezoelectrics and internal electrode form.In stack-up type piezo-activator, be categorized as slug type simultaneously, with these 2 types, the accumulation type of alternately lamination piezoelectricity chinaware and internal electrical pole plate, if reduce from the viewpoint of lower voltage, manufacturing cost, the stack-up type piezo-activator of slug type is favourable for thin layer simultaneously, so shown its superiority.

Fig. 6 means the figure of existing stack-up type piezo-activator, and in this actuator, piezoelectrics 51 and internal electrode 52 be lamination and form laminate 53 alternately, and the both ends of the surface lamination in its lamination direction has inert layer 55.Internal electrode 52, the end face of one side alternately exposes in the left and right, side of laminate 53, and the side of the laminate 53 exposing in the end of this internal electrode 52 is formed with outer electrode 70.The opposing party's of internal electrode 52 end is coated by insulator 61, with outer electrode 70 insulation.

Again, the stack-up type piezo-activator of while slug type, after lamination formed body being carried out to degreasing with the temperature of regulation, by sintering, obtain laminate, on the ceramic green sheet that described lamination formed body consists of with organic bond the powders calcined by piezoelectrics the printing of lamination regulation sheet number in silver-palladium powder, add and to have mixed the sheet that internal electrode paste that adhesive forms forms and obtain.

Its sintering temperature of existing piezoelectrics must be the temperature of 1200～1300 ℃, so the high silver-palladium alloy of ratio of the palladium of high price is used as internal electrode.But, the technology of low-temperature sintering is in development recently, having developed can be at the piezoelectrics of the temperature sintering of 1100 ℃ of left and right, even if but consider in this case the fusing point of internal electrode, must be also the silver-palladium alloy of silver-colored ratio 70% weight, palladium ratio 30% weight.

Again, all the time, outer electrode is with by silver 83～99% weight (silver 71～95% quality) and remainder glass powder 1～17% weight (glass powder 5～29% quality), be coated on the side of laminate 53 with the conductive paste consisting of organic principle, and the mode of sintering forms (for example,, with reference to patent documentation 1) at 500～1000 ℃.

Patent documentation 1: JP 2000-40635 communique

Patent documentation 2: open in fact clear 60-99522 communique

Patent documentation 3: JP 61-133715 communique

Patent documentation 4: Beneficial 1-130568 communique

Summary of the invention

But, in existing stack-up type piezo-activator, the in the situation that under high electric field, high pressure, long-time continuous driving, there is following problem: outer electrode 70 can not be followed the flexible of laminate 53 and be broken, or externally between electrode 70 and internal electrode 52, cause that contact is bad, voltage can not be supplied in a part of piezoelectrics 51, thereby displacement properties changes in driving.

Again, in recent years, in small-sized stack-up type piezo-activator, in order to guarantee larger addendum modification under larger pressure, carried out applying higher electric field, the operation that its long-time continuous is driven, but only conductive paste is coated to behind the side of laminate 53 to sintering again, have following problem: outer electrode 70 is not flexible, can not follow flexible to the lamination direction of laminate 53, thereby internal electrode 52 was removed with being connected of outer electrode 70, produce and peel off, externally on electrode 70, crack and break again, voltage can not be supplied to a part of piezoelectrics 51, thereby displacement properties changes in driving.

And then, because include the palladium that the cost of 30% weight is high, so there is high this problem of the cost of goods.

Therefore, though the object of the present invention is to provide a kind of under high electric field, high pressure, long-time continuous drives in the situation that, outer electrode and internal electrode also and do not break, the multi-layer piezoelectric element of good endurance.

The multi-layer piezoelectric element of first aspect present invention, it comprise piezoelectric body layer and the internal electrode laminate that alternately lamination forms, be formed at respectively the first side of this laminate and the outer electrode on the second side, in the internal electrode of adjacency, a side internal electrode is connected in outer electrode in the first side, and the opposing party's internal electrode is connected in outer electrode in the second side;

Described outer electrode is by containing electric conducting material and glass, and the Porous electric conductor that is configured to three-dimensional network structure forms, network portion in described three-dimensional network structure is the space of hollow, described outer electrode local engagement is on described the first side and described the second side, between described piezoelectrics and described outer electrode, be formed with the space of hollow, the voidage of described outer electrode is 30～70% volumes.

In the first such multi-layer piezoelectric element, because outer electrode is by containing electric conducting material and glass, and the Porous electric conductor that is configured to three-dimensional network structure forms, so have flexibility.Even if be for example that actuator body is flexible in lamination direction while driving in the situation that at laminate, outer electrode also can followed the flexible of laminate, thereby can prevent the broken string of outer electrode or bad these problems of the contact of outer electrode and internal electrode.

Thereby, according to the multi-layer piezoelectric element of first aspect present invention, because outer electrode can absorb the flexible stress producing because of laminate fully, even so the in the situation that under high electric field, high pressure, high speed long-time continuous turning round, also can suppress the broken string of outer electrode and internal electrode, thereby the multi-layer piezoelectric element with high reliability can be provided.

In the multi-layer piezoelectric element of first aspect present invention, be preferably described outer electrode and be partly engaged on described the first side and described the second side again.Like this, by making outer electrode partly be engaged in laminate side, just can more can flexibly absorb with respect to the contraction of laminate and the stress producing than the situation with whole joint.

And then the electric conducting material that the multi-layer piezoelectric element of first aspect present invention is preferably outer electrode be take silver as principal component.Like this, by making to form the electric conducting material of outer electrode, be the silver that Young's modulus is low, just can more flexibly absorb the flexible stress producing because of laminate.Again, by making to form the electric conducting material of outer electrode, be silver, the diffusion bond of the silver-palladium alloy usually using with electric conducting material as internal electrode just becomes easily, thereby can connect more firmly outer electrode and internal electrode.

And then the multi-layer piezoelectric element of first aspect present invention is preferably the softening point of the glass that forms outer electrode below the fusing point of electric conducting material that forms described outer electrode.Like this, the sintering temperature of outer electrode can be made for to the temperature more than softening point of the following and glass ingredient of the fusing point of electric conducting material, can prevent the aggegation of electric conducting material, thereby can obtain the sufficient bond strength that produces because of glass ingredient.

Again, the multi-layer piezoelectric element of first aspect present invention is preferably the contained metal ingredient of internal electrode and take Ag as principal component, and more than containing Pd below 15% weight and at least one in Pt family metal.By making the amount of the contained Pd of internal electrode and Pt family metal, be below 15% weight, the composition that just can reduce internal electrode and outer electrode is poor, so the phase counterdiffusion of the metal between internal electrode and outer electrode is good, thereby can improve the reliability engaging between internal electrode and outer electrode, improve durability.

The multi-layer piezoelectric element of second aspect present invention, it comprise piezoelectric body layer and the internal electrode laminate that alternately lamination forms, be formed at respectively the first side of this laminate and the outer electrode on the second side, one side's of the internal electrode of adjacency internal electrode is connected in outer electrode in the first side, and the opposing party's internal electrode is connected in outer electrode in the second side;

Described internal electrode and described outer electrode include respectively silver,

In establishing described internal electrode, with respect to the silver-colored weight rate of electric conducting material integral body, be X (%),

If in described outer electrode, while being Y (%) with respect to the silver-colored weight rate of the total weight of electric conducting material and glass,

To meet the mode of X >=85 and 0.9≤X/Y≤1.1, set the silver-colored ratio of described internal electrode and described outer electrode, described outer electrode consists of the Porous electric conductor that contains electric conducting material and glass and form three-dimensional network structure, network portion in described three-dimensional network structure is the space of hollow, and the voidage of described outer electrode is 30～70% volumes.

If as described in setting as the multi-layer piezoelectric element of this second aspect internal electrode and as described in the silver-colored ratio of outer electrode, can suppress the use amount of the palladium of high price, so cheap multi-layer piezoelectric element can be provided.

Again, because form the silver-colored weight rate in the electric conducting material of described internal electrode, with silver-colored weight rate in described outer electrode about equally, so when described outer electrode is sintered on described laminate, promoted the silver-colored phase counterdiffusion in silver in described outer electrode and described internal electrode, thereby described internal electrode becomes possibility with firmly engaging of described outer electrode, even at high electric field, in the situation that under high pressure, long-time continuous drives, described outer electrode and described internal electrode are also and do not break, thereby the durability that can have.

Again, in the multi-layer piezoelectric element of second aspect present invention, be preferably described internal electrode and include piezoelectric, when the silver-colored weight rate with respect to including the total weight of described piezoelectric in establishing described internal electrode is Z (%), meet 0.7≤Z/Y≤1.0.

If contain piezoelectric like this in described internal electrode, during the burning till of the electric conducting material in described internal electrode, piezoelectrics are sintering side by side, just can improve the bond strength of described internal electrode and described piezoelectrics, thereby can improve the durability of described laminate.

Again, because by so that silver-colored weight rate in described internal electrode meets the mode of 0.7≤Z/Y≤1.0 sets, silver-colored weight rate in described internal electrode and the silver-colored weight rate in described outer electrode are just about equally, so described in sintering during outer electrode, promoted the silver-colored phase counterdiffusion in silver in described outer electrode and described internal electrode, thereby described internal electrode becomes possibility with firmly engaging of described outer electrode.With this, even the in the situation that of high-speed driving, also can prevent the broken string of the contact portion of described outer electrode and described internal electrode.

Again, in the multi-layer piezoelectric element of second aspect present invention, being preferably described outer electrode consists of the Porous electric conductor that is configured to three-dimensional network structure, with this, even the in the situation that of flexible to lamination direction when driving, because described outer electrode is flexible, so described outer electrode is followed this situation with respect to the flexible of described laminate, also become possibility, thereby can prevent the broken string of described outer electrode or the contact of described outer electrode and described internal electrode bad etc.

Again, in the multi-layer piezoelectric element of second aspect present invention, be preferred for the glass in described outer electrode softening point (℃) be the fusing point that forms the electric conducting material of described internal electrode (℃) below 4/5.

If set like this softening point for the glass of outer electrode, temperature that can be fully low at the fusing point of electric conducting material than forming described internal electrode and than the high temperature of the softening point of described glass under carry out the sintering of described outer electrode, so can prevent the aggegation of the electric conducting material of described internal electrode and described outer electrode, and make the sufficient diffusion bond of the electric conducting material of electric conducting material in described internal electrode and described outer electrode become possibility, thereby can there is the strong bond strength producing because of softening glass.

Again, in the multi-layer piezoelectric element in the present invention aspect first and second, in order effectively to absorb the flexible stress producing when driving, prevent the breakage of outer electrode, the voidage that is preferably described outer electrode is 30～70% volumes.

Again, in the multi-layer piezoelectric element in the present invention aspect first and second, being preferably the glass that forms described outer electrode is noncrystalline.If forming the glass of described outer electrode is noncrystalline, can more reduce Young's modulus than crystalloid, so can be suppressed at crackle producing on described outer electrode etc.

The multi-layer piezoelectric element of third aspect present invention, comprise piezoelectric body layer and the internal electrode laminate that alternately lamination forms and be formed at respectively the first side of this laminate and the outer electrode on the second side, one side's of the internal electrode of adjacency internal electrode is connected in outer electrode in the first side, and the opposing party's internal electrode is connected in outer electrode in the second side;

Described internal electrode is by take silver as principal component and including palladium or at least one electric conducting material of platinum forms, described outer electrode forms by take electric conducting material and the glass that silver is principal component again, larger than the silver-colored ratio of the internal electrode electric conducting material of laminate inside with near the silver-colored ratio of the internal electrode electric conducting material connecting portion of outer electrode.

In the above multi-layer piezoelectric element of the present invention forming, the electric conducting material of internal electrode becomes more firm with being connected of the electric conducting material of outer electrode, even the in the situation that of high electric field Continuous Drive, also can prevent that the connecting portion of outer electrode and internal electrode is peeled off this problem.

; in order to make with to take engaging of outer electrode that silver is principal component firm; near the connecting portion with outer electrode; make the silver-colored ratio of internal electrode electric conducting material larger than the silver-colored ratio of laminate inside; with this; the principal component that can make outer electrode electric conducting material is that silver approaches with the silver-colored concentration in internal electrode electric conducting material, so outer electrode becomes reliable with engaging by silver-colored phase counterdiffusion of internal electrode.

, because the silver-colored concentration near the electric conducting material of the internal electrode connecting portion of formation and outer electrode and the silver-colored concentration in outer electrode are about equally, so when described outer electrode is sintered on described laminate, promoted the silver-colored phase counterdiffusion in silver in described outer electrode and described internal electrode, thereby described internal electrode becomes possibility with firmly engaging of described outer electrode, even at high electric field, in the situation that under high pressure, long-time continuous drives, described outer electrode and described internal electrode are also and do not break, thereby the durability that can have.

Again, in the multi-layer piezoelectric element of third aspect present invention, be preferably along with approaching outer electrode, the silver-colored ratio in internal electrode electric conducting material increases gradually.If form so continuously silver-colored concentration gradient, can establish engaging of stable internal electrode and internal electrode and outer electrode.

In the multi-layer piezoelectric element of third aspect present invention, be preferably outer electrode and internal electrode to be formed with the mode diffusion bond of neck again.If make like this, even in the situation that flowing large electric current high-speed driving, also can prevent the spark of contact portion of described internal electrode and outer electrode or broken string etc.

Again, in the multi-layer piezoelectric element of third aspect present invention, the silver-colored ratio being preferably in internal electrode electric conducting material is more than 85% weight.If make like this, can improve the silver-colored concentration in internal electrode, thereby can make the reliable with being connected of outer electrode of diffusion bond based on silver-colored.In addition, the silver-colored ratio in so-called internal electrode electric conducting material refers to the silver-colored ratio in the laminate inside of the silver-colored constant rate of internal electrode.

In the multi-layer piezoelectric element of third aspect present invention, be preferably below 80% of laminate top layer side that glass ingredient in outer electrode is present in the thickness of outer electrode substantially again.

; if make glass ingredient in outer electrode be present in substantially below 80% of laminate top layer side of the thickness of outer electrode; externally the atmospheric side skin section of electrode in fact only exists and take the electric conducting material that silver is principal component; even if thereby in the situation that wire being fastened on to described outer electrode with scolding tin, also can provide the external electrode surface that scolding tin wetting quality is good.

In the multi-layer piezoelectric element of third aspect present invention, be preferably in the glass ingredient in electrode externally and include lead oxide or bismuth oxide again.As included lead oxide or bismuth oxide in the glass ingredient in electrode externally, can make outer electrode firm with engaging of piezoelectrics.

Again, in the present invention first, to the multi-layer piezoelectric element of the third aspect, be preferably: the end diffusion bond of described outer electrode and described internal electrode, the electric conducting material composition of internal electrode is spread in outer electrode, thereby forms neck.Like this, can engage securely electric conducting material and the internal electrode that forms outer electrode by diffusion bond.With this, even in the situation that flowing large electric current high-speed driving, also can prevent local pyrexia, spark, the broken string of the contact portion of described internal electrode and described outer electrode.

In the present invention first, to the multi-layer piezoelectric element of the third aspect, be preferably in the piezoelectricity side of described outer electrode skin section and be formed with glass enriched layer again.If be formed with glass enriched layer in the piezoelectricity side of described outer electrode skin section like this, can improve the bond strength of described outer electrode and described laminate.

Again, in the present invention first, to the multi-layer piezoelectric element of the third aspect, the Thickness Ratio that is preferably described outer electrode forms the thin thickness of the described piezoelectrics of described laminate.If set like this thickness of described outer electrode, the hardness of described outer electrode diminishes, when flexible when described laminate drives, can make the load on the junction surface of described outer electrode and described internal electrode little, so it is bad to suppress the contact at described junction surface.

Again, in the present invention first to the multi-layer piezoelectric element of the third aspect, be preferably: in described the first side, between the end of described the opposing party's internal electrode and described outer electrode, be formed with groove, in this groove, be provided with insulator, in described the second side, between the end of the internal electrode of one and described outer electrode, be formed with groove, in this groove, be provided with insulator, described insulator is lower than described piezoelectrics Young's modulus.

If form in this wise, can guarantee the insulation of described internal electrode and described outer electrode, and flexible can follow the driving of described laminate time of the described insulator in groove and being out of shape, so can prevent near the generation of crackle groove etc., can reduce the generation of stress again.

Again, in the present invention first to the multi-layer piezoelectric element of the third aspect, can be in the outer surface setting of described outer electrode by the conductivity accessory that is embedded with the net of metal or the conductive adhesive of cancellous metallic plate and forms, if make in this wise, even with described in large electric current high-speed driving laminate in the situation that, also can make described large current flowing to conductivity accessory, so can prevent the broken string that the local pyrexia because of described outer electrode causes, thereby can improve significantly durability.

Again, by be embedded with net or the cancellous metallic plate of metal in described conductive adhesive, the crackle of the flexible conductive adhesive producing in the time of just can preventing the driving because of described laminate etc.

And then, in above-mentioned multi-layer piezoelectric element, be preferably conductive adhesive and formed by the polyimides that is dispersed with electroconductive particle.By making the bonding composition of conductive adhesive, be the polyimides that thermal endurance is high, even described conductive adhesive also can maintain high-adhesive-strength when applied at elevated temperature.

And then the electroconductive particle that is preferably conductive adhesive is silver powder.As electroconductive particle, use the silver powder lower than resistance, with this, just can reduce the resistance value of this conductive adhesive, even in the situation that flowing large driven current density, also can prevent local pyrexia.And then, can make the degree of polymerization between electroconductive particle firm, thereby can further improve the intensity of this conductive adhesive, from this reason, to consider, described electroconductive particle is preferably the aspheric particle of laminar or needle-like etc.

Accompanying drawing explanation

Figure 1A is the stereogram of the multi-layer piezoelectric element of embodiments of the present invention one to three;

Figure 1B is the sectional arrangement drawing of the A-A ' line of Figure 1A;

Fig. 2 A is the profile that represents enlargedly a part of Figure 1B;

Fig. 2 B is the profile of a part of presentation graphs 2A enlargedly;

Fig. 2 C is the cross sectional photograph of the part identical with Fig. 2 B;

Fig. 3 A is in the manufacture method of multi-layer piezoelectric element of the present invention, the profile after side forms groove;

Fig. 3 B is in the manufacture method of multi-layer piezoelectric element of the present invention, the profile after side forms conductive paste 21;

Fig. 3 C is in the manufacture method of multi-layer piezoelectric element of the present invention, the profile after side forms outer electrode 4;

Fig. 4 A means that the outer surface of electrode is externally formed with the stereogram of the multi-layer piezoelectric element of the present invention of conductivity accessory;

Fig. 4 B is the profile of Fig. 4 A;

Fig. 4 C is the profile of a part of presentation graphs 4B enlargedly;

Fig. 5 means the profile of formation of the injection apparatus of embodiments of the present invention four;

Fig. 6 is the profile of existing stack-up type piezo-activator;

Fig. 7 means the curve chart of the silver-colored ratio in the internal electrode electric conducting material in embodiments of the invention four.

Symbol description

1 piezoelectrics

2 internal electrodes

3 insulators

4 outer electrodes

4b neck

6 wires

10 laminates

31 accommodating containers

33 spray-holes

35 valves

43 piezo-activators

Embodiment

Execution mode one

Figure 1A is the stereogram of the multi-layer piezoelectric element (stack-up type piezo-activator) of embodiments of the present invention one, and Figure 1B is the sectional arrangement drawing along the A-A ' line in Figure 1A.

The stack-up type piezo-activator of present embodiment one, as shown in Figure 1A, 1B, by the laminate 10 of the square column that alternately a plurality of piezoelectrics 1 of lamination form with a plurality of internal electrodes 2, the outer electrode 4 being formed on its side with the mode being connected with internal electrode 2 with every alternating floor, form.Particularly, form as follows: be formed with on the side of outer electrode 4, by end, the end of the internal electrode 2 not being coated by insulator 3 and outer electrode 4 conductings of the coated internal electrode 2 of the every alternating floor of insulator 3.Again, that outer electrode 4 adopts is that electric conducting material that silver is principal component forms with glass by take, have the Porous electric conductor that three-dimensional network is constructed, and on each outer electrode 4, is connected with wire 6.In addition, in laminate 10, having marked the part that symbol 9 represents is the inert layer that is not formed with internal electrode.

Between piezoelectrics 1, dispose internal electrode 2, this internal electrode 2 forms with metal materials such as silver-palladiums, for applying the electrode of the voltage of regulation on each piezoelectrics 1, cause the displacement producing because of the corresponding reciprocal piezoelectric effect of the voltage with applied on piezoelectrics 1.

Again, the every alternating floor in the side of laminate 10 form the groove of width 30～200 μ m of the degree of depth 30～500 μ m, lamination direction, in this groove, be filled with the glass lower than piezoelectrics 1 Young's modulus, epoxy resin, polyimide resin, polyamide-imide resin, silicon rubber etc., thereby form insulator 3.Firm with engaging of laminate 10 in order to make, this insulator 3 is preferably low material, the particularly silicon rubber etc. of modulus of elasticity of being followed by the displacement with respect to laminate 10 and forms.

Opposed 2 sides at laminate 10 have engaged respectively outer electrode 4, and on this outer electrode 4, every alternating floor is electrically connected to the internal electrode 2 of lamination.This outer electrode 4 functions as follows: by utilizing reciprocal piezoelectric effect that the necessary voltage common land of piezoelectrics 1 displacement is supplied on each connected internal electrode 2.

And then, externally on electrode 4, utilize scolding tin to be fixedly connected with wire 6.This wire 6 functions as follows: outer electrode 4 is connected to outside voltage supply unit.

And, in present embodiment one, it is characterized in that, outer electrode 4 is by containing electric conducting material and glass, and the Porous electric conductor that is configured to as shown in Figure 2 three-dimensional network structure forms.At this, three-dimensional network structure is not to mean externally to have so-called spherical this state of space on electrode 4, and refer to following state: for conducting material powder and the glass powder of the temperature sintering formation outer electrode 4 lower, and at sintering, carry out constantly, with connecting state to a certain degree, have space, the conducting material powder that forms outer electrode 4 dimensionally links, engages with glass powder.In addition, Fig. 2 A has amplified a part for section as shown in Figure 1B and the profile that obtains, and Fig. 2 B is the further profile of a part of presentation graphs 2A enlargedly.

Outer electrode 4 consists of electric conducting material 80～97% volumes and glass 3～20% volumes, and the glass of trace is scattered in electric conducting material.Glass is preferably and contains 5～15% volumes.This outer electrode 4 is partly engaged in the side of laminate 10.That is, with the end diffusion bond of the internal electrode 2 exposing in the side of laminate 10, with the lateral parts of the piezoelectrics 1 of laminate 10 engage.That is, in the side of piezoelectrics 1 local engagement, there is the mixture of electric conducting material and glass, between the side of piezoelectrics 1 and outer electrode 4, be formed with space 4a.Again, externally in electrode 4, be also formed with a plurality of spaces, with this outer electrode 4, by Porous electric conductor, formed.How much the shape of space 4a is the remaining complicated shape that has the shape before electric conducting material and glass sintering still.

In execution mode one, like this by forming with electric conducting material and glass and being configured to the outer electrode 4 and internal electrode 2 diffusion bond that the Porous electric conductor of three-dimensional network structure forms, again, because outer electrode 4 partly engages with laminate 10, even so under high electric field, high pressure long-time continuous drive actuator in the situation that, also can prevent following problem: externally between electrode 4 and internal electrode 2, cause spark, or outer electrode 4 is peeled off or breaks from laminate 10.In present embodiment one, by carrying out at lower temperature by forming the electric conducting material of outer electrode 4 and the sintering of the conductive paste that glass forms, just outer electrode 4 integrally can be made for to porous plastid, can partly be engaged in the side of laminate 10.

The electric conducting material of formation outer electrode 4 is the flexible stress this point producing because of actuator from abundant absorption, is preferably the alloy that the silver that Young's modulus is low or the silver of take are principal component.

Again, in present embodiment one, as shown in Figure 2 B, in internal electrode 2 ends that are connected with outer electrode 4, be formed with neck 4b, can realize being firmly connected of internal electrode 2 and outer electrode 4.Neck 4b forms by the electric conducting material of outer electrode 4 and the electric conducting material diffusion bond of internal electrode 2.

If be formed with neck in internal electrode end like this, this neck is embedded in outer electrode, even if flow in multi-layer piezoelectric element large electric current, with high-speed driving in the situation that, also can prevent the local pyrexia on the junction surface of internal electrode and outer electrode.

And then in present embodiment one, being preferably voidage in outer electrode 4 and being the ratio that space 4a externally occupies in electrode 4 is 30～70% volumes.With this, can flexibly bear the flexible stress producing because of actuator.That is, externally the voidage in electrode 4 is than in the little situation of 30% volume, and outer electrode 4 can not bear the flexible stress producing because of actuator, thereby has the possibility of outer electrode 4 broken strings.On the other hand, externally the voidage in electrode 4 is than in 70% bulky situation, and it is large that the resistance value of outer electrode 4 becomes, thereby thereby has outer electrode 4 when the large electric current that flows to cause the possibility that local pyrexia is broken.

Again, in present embodiment one, the softening point that forms the glass ingredient of outer electrode 4 is made for below the fusing point of the electric conducting material that forms outer electrode 4.This is for the sintering temperature of outer electrode 4 being made for to the temperature more than softening point of the following and glass ingredient of the fusing point of electric conducting material.With this, just can under the temperature more than the softening point of glass ingredient and below the fusing point of electric conducting material, carry out sintering, so prevented the aggegation of electric conducting material, can be made for porous plastid, can carry out sintering with sufficient bond strength.

Again, in present embodiment one, the glass ingredient that forms outer electrode 4 is noncrystalline.With this, outer electrode 4 can absorb the flexible stress producing because of actuator, thereby can prevent the generation of crackle etc.

Again, in present embodiment one, the thickness that is preferably outer electrode 4 is made for than the thin thickness that forms the piezoelectrics 1 of laminate 10.With this, outer electrode 4 has suitable intensity with respect to the lamination direction of laminate 10, thereby can prevent the increase of the load on the contact of outer electrode 4 and internal electrode 2 when actuator is flexible, can prevent that contact is bad.

The manufacture method of multi-layer piezoelectric element of the present invention then, is described.First, by the powders calcined of the piezoelectric ceramic such as PZT, the adhesive forming with organic polymer by propylene base system, butyral system etc., mix to make slurry with the plasticizer such as DBP (dibutyl phthalate), DOP (dioctyl phthalate), utilize well-known scrape the skill in using a kitchen knife in cookery or stack method etc. with the method for forming, this slurry is made as to the ceramic green sheet that forms piezoelectrics 1.

Then, add mixed adhesive, plasticizer etc. and make conductive paste in silver-palladium powder, the thickness with 1～40 μ m is printed in the upper surface of described each raw cook by it to utilize screen printing etc.

Then, at a plurality of raw cooks that are printed with conductive paste of upper surface lamination, with regard to this laminate, at the temperature of regulation, carry out after unsticking mixture, by sintering at 900～1200 ℃, just produce laminate 10.

In addition, laminate 10 is not limited to make with above-mentioned manufacture method, as long as can make the laminate 10 that alternately a plurality of piezoelectrics of lamination and a plurality of internal electrode form, can utilize manufacture method arbitrarily to form.

Afterwards, as shown in Figure 3A, utilize cutter sweep etc. to form groove at the every alternating floor in the side of laminate 10.

And then, by silver powder 80～97% volumes, particle diameter 0.1～10 μ m, with 3～20% volumes, remainder particle diameter 0.1～10 μ m, mixture that the glass powder that silicon is principal component, that softening point is 450～800 ℃ of take forms in add adhesive to make silver-colored glass conductive paste.This silver glass conductive paste is configured as to tabular and dry (solvent is dispersed).It is 6～9g/cm that the green density of plate 21 is controlled ³.As shown in Figure 3 B, the outer electrode that this plate 21 is needed on to the laminate 10 that is formed with groove forms face, than the high temperature of the softening point of glass and the temperature below silver point (965 ℃) and sintering temperature (℃) the temperature below 4/5 under carry out sintering.With this, as shown in Figure 3 C, the disappearance of dispersing of the adhesive ingredients in the plate 21 of making of silver-colored glass conductive paste, thus the outer electrode 4 being formed by the Porous electric conductor that is configured to three-dimensional network structure formed.

Again, if the sintering temperature of outer electrode (℃) be laminate sintering temperature (℃) the temperature below 4/5, the glass ingredient that can make to form outer electrode is appropriate to the diffusing capacity in laminate, thereby can prevent that the bond strength of laminate and outer electrode from reducing.

Particularly, in order to form the outer electrode 4 of three-dimensional network structure, it is 6～9g/cm that the green density of plate 21 is controlled ³very important.The green density of plate 21 utilizes Archimedes's method to measure.Particularly, in order to be 30～70% by the voidage of outer electrode 4, preferably making green density is 6.2～7.0g/cm ³.

When the sintering of this silver glass conductive paste, externally in electrode 4, form space 4a, and the silver in silver-colored glass conductive paste and the silver-palladium alloy diffusion bond in internal electrode 2, neck 4b formed, again, this outer electrode 4 is partly engaged in laminate side.In neck 4b, Pd, from internal electrode 2 diffusions, forms silver-palladium alloy.

In addition, the sintering temperature of described silver-colored glass conductive paste is preferably 550～700 ℃.If be set as this scope, form effective neck 4b, the silver in silver-colored glass conductive paste and internal electrode 2 diffusion bond, again, the space in outer electrode 4 is effectively remaining, and then, engage outer electrode 4 and laminate 10 lateral parts.Again, the softening point of the glass ingredient in silver-colored glass conductive paste is preferably 500～700 ℃.

In the situation that sintering temperature is higher than 700 ℃, the sintering of the silver powder of silver glass conductive paste exceedingly carries out, thereby can not form the Porous electric conductor that is configured to effective three-dimensional network structure, it is too fine and close that outer electrode 4 becomes, consequently the Young's modulus of outer electrode 4 becomes too high, can not absorb fully the stress while driving, thereby have the possibility of outer electrode 4 broken strings.Preferably, 1.2 times of the softening point of glass, carry out sintering at interior temperature.

On the other hand, in sintering temperature be lower than 550 ℃ in the situation that, between internal electrode 2 ends and outer electrode 4, can not carry out fully diffusion bond, thus neck 4b can not be formed, thus there is the possibility that causes spark when driving between internal electrode 2 and outer electrode 4.

In addition, the thickness of the plate 21 of silver-colored glass conductive paste is preferably than the thin thickness of piezoelectrics 1.From following the flexible this point of brake, consider, more preferably below 50 μ m.

Making the silver powder in silver-colored glass conductive paste 21 is 80～97% volumes, the glass powder of remainder be 3～20% volumes be because, in silver powder than 80% volume few in the situation that, it is many that glass ingredient relatively becomes, when carrying out sintering, just externally in electrode 4, effectively form space 4a or this outer electrode 4 partly can not be engaged in to laminate 10 sides, on the other hand, in silver powder than more than 97% in the situation that, glass ingredient relatively tails off, outer electrode 4 dies down with the bond strength of laminate 10, thereby likely in drive actuator, make outer electrode 4 peel off from laminate 10.

Again, the glass ingredient that forms outer electrode 4 is used silex glass, soda-lime glass, plumbous alkali silicate glasses, aluminium oxide borosilicate glass, borosilicate glass, alumina silicate glass, borate glass, phosphate glass etc.

For example, as borosilicate glass, can use and contain SiO ₂40～70% quality, B ₂o ₃2～30% quality, Al ₂o ₃such alkaline earth metal oxide aggregate 0～10% quality of 0～20% quality, MgO, CaO, SrO, BaO, the glass of alkali metal oxide 0～10% quality.Use that in above-mentioned borosilicate glass, to include the such glass of the ZnO of 5～30% quality also harmless again.ZnO has the effect of the processing temperature that reduces borosilicate glass.

As phosphate glass, can use and include P again, ₂o ₅40～80% quality, Al ₂o ₃0～30% quality, B ₂o ₃0～30% quality, ZnO0～30% quality, alkaline earth metal oxide 0～30% quality, the such glass of alkali metal oxide 0～10% quality.

As lead glass, can use and include PbO again, ₃0～80% quality, SiO ₂0～40% quality, Bi ₂o ₃0～30% quality, Al ₂o ₃0～20% quality, ZnO0～30% quality, alkaline earth metal oxide 0～30% quality, the such glass of alkali metal oxide 0～10% quality.

Then, the laminate 10 that is formed with outer electrode 4 be impregnated in to silicone rubber solution, and utilize silicone rubber solution is carried out to vacuum degassing, carry out the inner filled silicon rubber of groove at laminate 10, from silicone rubber solution pull out laminate 10, at the side of laminate 10 coating silicon rubber thereafter.The described silicon rubber of the side that be filled in groove inside and be coated on laminate 10 solidified thereafter.

By wire 6 be connected in outer electrode 4 on, complete of the present invention multi-layer piezoelectric element thereafter.

Then, utilize wire 6 to the direct voltage that applies 0.1～3kV/mm in pair of external electrodes 4, to laminate 10 processing that polarizes, using this stack-up type piezo-activator as goods just to complete.If the wire of this stack-up type piezo-activator 6 is connected in to outside voltage supply unit, utilize 4 pairs of internal electrodes 2 of wire 6 and outer electrode to apply voltage, each piezoelectrics 1 are because of reciprocal piezoelectric effect displacement significantly, using that this for example brings into play its function as the automotive fuel injection valve to engine spray feed fuels.

Because serving as reasons, contain the outer electrode 4 of take electric conducting material and glass that silver is principal component and being configured to the Porous electric conductor formation of three-dimensional network structure and be partly connected in laminate 10 sides, even if so the multi-layer piezoelectric element more than forming Continuous Drive actuator in the situation that, also can absorb fully the stress producing when outer electrode 4 drives under high electric field.Thereby, can prevent from externally between electrode 4 and internal electrode 2, causing spark, or outer electrode 4 these problems of broken string, thereby the brake of high reliability can be provided.

Again, in present embodiment one, the contained metal ingredient of internal electrode 2 be preferably take silver as principal component and contain Pd below 15% weight and Pt family metal in more than one.By making the amount of the contained Pd of internal electrode 2 and Pt family metal, be below 15% weight, just can reduce internal electrode 2 poor with the composition of outer electrode 4, so the phase counterdiffusion of the metal between internal electrode 2 and outer electrode 4 is good, thereby can improve the reliability engaging between internal electrode 2 and outer electrode 4, improve durability.By contain aptly the powder of the composition roughly the same with laminate 10 in internal electrode 2, just can improve the engaging force of the internal electrode 2 in laminate 10 again.

Multi-layer piezoelectric element of the present invention is not limited to above-mentioned multi-layer piezoelectric element, as long as just can carry out all changes in the scope that does not depart from main idea of the present invention.

In above-mentioned example, the example that is formed with outer electrode 4 in the opposed side of laminate 10 has been described again.The side of for example establishing neighbour but in the present invention, forms pair of external electrodes and also can.

Execution mode two

The multi-layer piezoelectric element of embodiment of the present invention two (stack-up type piezo-activator), is in the multi-layer piezoelectric element of execution mode one, and outer electrode 4 forms as follows with internal electrode 2.

In the stack-up type piezo-activator of present embodiment two, outer electrode 4 forms by take electric conducting material and the glass that silver is principal component, and described internal electrode 2 includes electric conducting material and piezoelectric.

And, silver-colored weight rate in the electric conducting material of establishing internal electrode 2 is X (%), the silver-colored weight rate including in the internal electrode 2 of electric conducting material and piezoelectric is Z (%), when the silver-colored weight rate in outer electrode 4 is Y (%), each ratio is set to meet the mode of X >=85 and 0.9≤X/Y≤1.1.This is because following reason.If less than 85%, forming the weight rate of the palladium of internal electrode 2, X must increase, so just can not be with low cost fabrication stack-up type piezo-activator.Again, if X/Y is less than 0.9, the silver-colored amount in internal electrode 2 relatively tails off with respect to the silver-colored amount in outer electrode 4, so when sintering outer electrode 4, being contained in respectively internal electrode 2 tails off with the silver-colored phase counterdiffusion in outer electrode 4, internal electrode 2 dies down with the bond strength of outer electrode 4, thereby the durability of stack-up type piezo-activator reduces.Again, if X/Y surpasses 1.1, the silver-colored amount in outer electrode 4 relatively tails off with respect to internal electrode 2, so when sintering outer electrode 4, being contained in respectively internal electrode 2 tails off with the silver-colored phase counterdiffusion in outer electrode 4, internal electrode 2 dies down with the bond strength of outer electrode 4, thereby the durability of stack-up type piezo-activator reduces.

With respect to this, silver-colored weight rate in the electric conducting material of establishing internal electrode 2 is X (%), by the silver-colored weight rate of take in the outer electrode 4 that electric conducting material that silver is principal component and glass forms during as Y (%), if set X >=85 and 0.9≤X/Y≤1.1, can suppress to form the use amount of palladium of the high price of internal electrode 2, so can be with low cost fabrication multi-layer piezoelectric element.Again, because the silver-colored weight rate in internal electrode 2 be X (%) with outer electrode 4 in silver-colored weight rate Y (%) about equally, so when sintering outer electrode 4, promoted to be contained in respectively the silver-colored phase counterdiffusion in internal electrode 2 and outer electrode 4, internal electrode 2 becomes possibility with the strong bonded of outer electrode 4, even the in the situation that under high electric field, high pressure, long-time continuous driving, internal electrode 2 and outer electrode 4 also and do not break, thereby the durability that can have.

And then internal electrode 2 consists of electric conducting material and piezoelectric, when the silver-colored weight rate in making internal electrode 2 is Z (%), is preferably and meets 0.7≤Z/Y≤1.0.This is because following reason.If Z/Y is less than 0.7, the silver-colored amount in internal electrode 2 relatively tails off with respect to the silver-colored amount in outer electrode 4, thus the resistance value of internal electrode 2 than outer electrode 4 height, thereby in internal electrode 2, produce local pyrexia.Again, if Z/Y surpasses 1.0, the piezoelectric in internal electrode 2 tails off, thus internal electrode 2 and piezoelectrics 1 adhering to of interface connect airtight weakened, thereby at internal electrode 2 and the generation of interfaces of piezoelectrics 1, peel off.Again, the silver-colored amount in outer electrode 4 relatively tails off with respect to internal electrode 2, thus internal electrode 2 tail off with the silver-colored phase counterdiffusion between outer electrode 4, thereby the situation that has the bond strength of internal electrode 2 and outer electrode 4 to die down.

In present embodiment two, as used Fig. 2 B, Fig. 2 C in execution mode one illustrating, be preferably: the end diffusion bond of outer electrode 4 and the internal electrode 2 exposing in laminate 10 sides, the electric conducting material composition of internal electrode 2 is diffused in outer electrode 4, forms neck 4b.If there is not neck 4b,, when the large electric current high-speed driving stack-up type piezo-activator that flows, externally electrode 4 causes local pyrexia with the contact portions of internal electrode 2 sometimes, or produces spark etc.

Again, being preferably outer electrode 4 consists of the Porous electric conductor that is configured to three-dimensional network structure.If outer electrode 4 does not form to be configured to the Porous electric conductor of three-dimensional network structure, outer electrode 4 does not have flexibility, so can not follow the flexible of stack-up type piezo-activator, so it is bad with the contact of internal electrode 2 to produce sometimes broken string or the outer electrode 4 of outer electrode 4.

And then as illustrated in execution mode one, in present embodiment two, the voidage being also preferably in outer electrode 4 is 30～70% volumes.

And then, be preferably the externally piezoelectrics 1 side skin section of electrode 4 and be formed with glass enriched layer.This be because: if there is not glass enriched layer, with engaging of glass ingredient in outer electrode 4 difficulty that becomes, so there is the firm engagement of outer electrode 4 and piezoelectrics 1 to become, be not easy this possibility.

Again, be preferably the glass that forms outer electrode 4 softening point (℃) be the fusing point that forms the electric conducting material of internal electrode 2 (℃) below 4/5.This be because: if form the softening point of the glass of outer electrode 4 surpass the electric conducting material that forms internal electrode 2 fusing point 4/5, form the temperature that the softening point of glass of outer electrode 4 and the fusing point of the electric conducting material of formation internal electrode 2 become same degree, so the temperature of sintering outer electrode 4 must approach the fusing point of the electric conducting material that forms internal electrode 2, thereby externally when the sintering of electrode 4, the electric conducting material aggegation of internal electrode 2 and outer electrode 4, hindered diffusion bond, or sintering temperature can not be set as being enough to make the softening temperature of glass ingredient of outer electrode 4, the sufficient bond strength producing so sometimes can not obtain the glass based on softening.

And then the glass that is preferably formation outer electrode 4 is noncrystalline.This be because: if the glass of crystalloid, outer electrode 4 can not absorb the flexible stress producing because of stack-up type piezo-activator, so crack sometimes etc.

Again and then, be preferably the thin thickness of the Thickness Ratio piezoelectrics 1 of outer electrode 4.This be because: if the thickness of the Thickness Ratio piezoelectrics 1 of outer electrode 4 is thick, the intensity of outer electrode 4 increases, so when laminate 10 is flexible, outer electrode 4 increases with the load at the junction surface of internal electrode 2, produces sometimes contact bad.

Again, as shown in FIG. 2 and 3, be preferably in the groove on the side that is formed at laminate 10 and be filled with the insulator 3 that Young's modulus is lower than piezoelectrics 1, internal electrode 2 insulate with the every alternating floor of outer electrode 4 ground.The piezoelectrics 1 that are sandwiched between internal electrode 2 utilize the voltage between the internal electrode 2 that puts on next-door neighbour to stretch, but with regard near the piezoelectrics 1 not being sandwiched in the side of laminate 10 of internal electrode 2, even if internal electrode 2 is applied to voltage, and it is not flexible yet, so internal electrode 2 is applied to voltage, all can produce compression stress or tensile stress at every turn.With respect to this, side at laminate 10 forms groove, in this groove, fill the insulator 3 that Young's modulus is lower than piezoelectrics 1, with this, just can utilize insulator 3 to stretch to be reduced in the stress producing in the side of laminate 10 in the flexible situation of laminate 10, with this, just can improve durability.

Now, if it is larger than piezoelectrics 1 to be filled in the Young's modulus of the insulator 3 in described groove, because can not relax the stress producing near the side of laminate 10 with the flexible of insulator 3 as described above, so there is the durability of multi-layer piezoelectric element to reduce this possibility.

Again, from the aspect of cost, consider, be preferably the silver-palladium alloy that uses low palladium ratio as internal electrode 2.Therefore, being preferably use can be at the piezoelectrics 1 of left and right sintering below 980 ℃, and the material that forms these piezoelectrics 1 is preferably with PbZrO ₃-PbTiO ₃for principal component, the Pb (Yb that contains 10～20%mol as accessory ingredient _1/2nb _1/2) O ₃, Pb (Co _1/3nb _2/3) O ₃and Pb (Zn _1/3nb _2/3) O ₃material.That is, from the state diagram of silver-palladium alloy, consider, when using palladium to be the silver-palladium alloy of 5% weight, as can, at the piezoelectrics 1 of 980 ℃ of following temperature sintering, using for example with PbZrO ₃-PbTiO ₃for principal component, the Pb (Yb that contains 10～20%mol as accessory ingredient _1/2nb _1/2) O ₃, Pb (Co _1/3nb _2/3) O ₃and Pb (Zn _1/3nb _2/3) O ₃material.

At this, in the situation that the silver-palladium alloy of 5% weight palladium is used as internal electrode 2, if sintering at the temperature of 1100 ℃, sintering temperature surpasses the fusing point of the electric conducting material (silver-palladium alloy) that forms internal electrode 2, the electric conducting material aggegation of internal electrode 2, thus there is producing this problem of delamination.That is,, in order to use the silver-palladium alloy of low palladium ratio in the electric conducting material at internal electrode 2, the sintering temperature of piezoelectrics 1 must be reduced to 980 ℃ of following degree.

Outer electrode 4 consists of electric conducting material 87～99.5% weight, glass powder 0.5～13% weight, and the glass of trace is scattered in electric conducting material.This outer electrode 4 is partly engaged in the side of laminate 10.; the end of the internal electrode 2 exposing with the side of laminate 10; electric conducting material diffusion bond in electric conducting material in internal electrode 2 and outer electrode 4, the side with the piezoelectrics 1 of laminate 10, mainly utilizes the glass ingredient in outer electrode 4 to engage.That is, with the side of piezoelectrics 1, the electric conducting material in outer electrode 4 partly engages with the mixture of glass, between the side of piezoelectrics 1 and outer electrode 4, is formed with space 4a.Again, externally in electrode 4, be also formed with a plurality of space 4a, with this, outer electrode 4 just consists of Porous electric conductor.How much the shape of space 4a is the remaining complicated shape that has the shape before electric conducting material and glass sintering still.

Again, outer electrode 4 is in order fully to absorb the flexible stress producing because of stack-up type piezo-activator, the alloy that it is principal component that the electric conducting material of outer electrode 4 is preferably by the low silver of Young's modulus or the silver of take forms, again, as outer electrode 4 integral body, be preferably with Porous electric conductor flexibility, that be configured to three-dimensional network structure and form.

The stack-up type piezoelectric actuator of embodiment of the present invention two can similarly be manufactured with the stack-up type piezo-activator of execution mode one.

First, similarly make laminate 10 with execution mode one.

At this, from the aspect of cost, consider, as the silver-palladium alloy that forms internal electrode 2 silver-palladium alloy of low palladium ratio preferably, particularly, being preferably palladium ratio is the silver-palladium alloy below 10% weight.For this reason, be preferably can be at the material of sintering below 980 ℃, as long as for example will be with PbZrO for piezoelectrics 1 ₃-PbTiO ₃for principal component, the Pb (Yb that contains 10～20%mol as accessory ingredient _1/2nb _1/2) O ₃, Pb (Co _1/3nb _2/3) O ₃and Pb (Zn _1/3nb _2/3) O ₃materials'use in piezoelectrics 1.Again, the silver-palladium alloy that forms internal electrode can be used the alloy powder of silver and palladium, also can use the mixture of silver powder and palladium powder.In addition, in the situation that use the mixture of silver powder and palladium powder, when sintering, also form the alloy of silver-palladium.

Again, with regard to making an addition to the ratio of the piezoelectric (powders calcined of piezoelectric ceramic) in the conductive paste that is used to form internal electrode 2, owing to making internal electrode 2 firm with the bond strength of piezoelectrics 1, reduce fully again the resistance value of internal electrode 2, therefore be preferably and include electric conducting material 75～93% weight, piezoelectrics material 7～25% weight of remainder in the internal electrode 2 after sintering.

In addition, laminate 10 is not limited to utilize said method to make, as long as can make the laminate 10 that alternately a plurality of piezoelectrics of lamination and a plurality of internal electrode form, utilizes arbitrarily manufacture method to form and all can.

After producing laminate 10, as shown in Figure 3A, utilize cutter sweep etc. in the every alternating floor landform grooving of the side of laminate 10.

And then, silver powder 87～99.5% weight by particle diameter 0.1～10 μ m, with mixture remainder particle diameter 0.1～10 μ m, that glass powder 0.5～13% weight that silicon is principal component, softening point is 450～800 ℃ of take forms in add adhesive to make silver-colored glass conductive paste, it is 6～9g/cm that the green density of the plate 21 that its shaping dry (solvent is dispersed) are obtained is controlled ³, as shown in Figure 3 B, the outer electrode that this plate 21 is needed on to the laminate 10 that is formed with groove forms face, at than the high temperature of the softening point of glass and the temperature below silver point, carries out sintering, with this, can form outer electrode 4.

Again, as shown in Figure 3 C, also can use the disappearance of dispersing of adhesive ingredients in the plate 21 that silver-colored glass conductive paste makes, the outer electrode 4 that formation consists of the Porous electric conductor that is configured to three-dimensional network structure, particularly, in order to form the outer electrode 4 of three-dimensional network structure, it is 6～9g/cm that the green density of plate 21 is controlled ³, and then, in order to make the voidage of outer electrode 4, be 30～70%, being preferably and making green density is 6.2～7.0g/cm ³.The green density of plate 21 can utilize Archimedes's method to measure.

Utilize the sintering of this silver glass paste to come externally in electrode 4, to form space 4a, and the silver in silver-colored glass paste and the silver-palladium alloy diffusion bond in internal electrode 2, form neck 4b also can, outer electrode 4 is partly engaged in the side of laminate 10.In neck 4b, because the silver-colored phase counterdiffusion of the silver-palladium alloy of internal electrode 2 and outer electrode 4, so can for example, detect with common analytical method (, EPMA, EDS etc.) from the palladium of internal electrode diffusion.

In addition, in order effectively to form neck 4b, the sintering temperature of described silver-colored glass paste is preferably set at scope illustrated in execution mode one.

Again, the thickness of the plate 21 of silver-colored glass paste is preferably than the thin thickness of piezoelectrics 1.In order to follow the flexible of stack-up type piezo-activator, more preferably below 50 μ m.

Making the silver powder in silver-colored glass conductive paste 21 is 87～99.5% weight, the glass powder of remainder be 0.5～13% weight be because: in silver powder than 87% weight few in the situation that, it is many that glass ingredient relatively becomes, when carrying out sintering, just externally in electrode 4, effectively form space 4a or can not partly engage this outer electrode 4 and laminate 10 sides, on the other hand, in silver powder than 97% volume 99.5% weight many in the situation that, glass ingredient relatively tails off, outer electrode 4 dies down with the bond strength of laminate 10, thereby there is the possibility of peeling off from laminate 10 at the driving peripheral electrode 4 of stack-up type piezo-activator.

Again, the glass ingredient that forms outer electrode 4 is used silex glass, soda-lime glass, plumbous alkali silicate glasses, aluminium oxide borosilicate glass, borosilicate glass, alumina silicate glass, borate glass, phosphate glass, lead glass etc.

For example, as borosilicate glass, can use and contain SiO ₂40～70% weight, B ₂o ₃2～30% weight, Al ₂o ₃such alkaline earth metal oxide aggregate 0～10% weight of 0～20% weight, MgO, CaO, SrO, BaO, the glass of alkali metal oxide 0～10% weight.Again, above-mentioned borosilicate glass also can adopt the such glass of ZnO that includes 5～30% weight.ZnO has the effect of the processing temperature that reduces borosilicate glass.

As phosphate glass, can use and include P again, ₂o ₅40～80% weight, Al ₂o ₃0～30% weight, B ₂o ₃0～30% weight, ZnO 0～30% weight, alkaline earth metal oxide 0～30% weight, the such glass of alkali metal oxide 0～10% weight.

As lead glass, can use and include PbO again, ₃0～80% weight, SiO ₂0～40% weight, Bi ₂o ₃0～30% weight, Al ₂o ₃0～20% weight, ZnO 0～30% weight, alkaline earth metal oxide 0～30% weight, the such glass of alkali metal oxide 0～10% weight.

Below, the stack-up type piezo-activator of execution mode two can similarly be manufactured with execution mode one.

That is, the laminate 10 that is formed with outer electrode 4 be impregnated in to silicone rubber solution, and carry out vacuum degassing, carry out the inner filled silicon rubber of groove at laminate 10, and silicon rubber is solidified.

Then, wire 6 is connected on outer electrode 4, utilizes wire 6 in pair of external electrodes 4, to apply the direct voltage of 0.1～3kV/mm, to laminate 10 processing that polarizes.With this, for example, as the stack-up type piezo-activator of the automotive fuel injection valve of engine spray feed fuels being brought into play to its function, just complete.

Execution mode three

The multi-layer piezoelectric element of embodiment of the present invention three (stack-up type piezo-activator) is characterised in that, in the element as shown in Figure 1A, Figure 1B etc., internal electrode 2 is by take silver as principal component and including palladium or at least one electric conducting material of platinum forms, again, outer electrode 4 forms by take electric conducting material and the glass ingredient that silver is principal component, larger than the silver-colored ratio of the electric conducting material in the internal electrode 2 of laminate 10 inside with near the silver-colored ratio of the electric conducting material of internal electrode 2 connecting portion of outer electrode 4.

By making so near the silver-colored ratio of electric conducting material of the internal electrode 2 connecting portion with outer electrode 4 larger than the silver-colored ratio of the electric conducting material in the internal electrode 2 of laminate 10 inside, the principal component that just can make outer electrode 4 electric conducting materials is that silver is close with the silver-colored concentration in internal electrode 2 electric conducting materials, so by silver-colored phase counterdiffusion, outer electrode 4 just becomes reliable with engaging of internal electrode 2.

, because the silver-colored concentration near the electric conducting material of the internal electrode 2 connecting portion of formation and outer electrode 4 and the silver-colored concentration in outer electrode 4 are about equally, so when described outer electrode 4 is sintered on described laminate 10, promoted the silver-colored phase counterdiffusion in silver in described outer electrode 4 and described internal electrode 2, thereby described internal electrode 2 becomes possibility with firmly engaging of described outer electrode 4, even at high electric field, in the situation that under high pressure, long-time continuous drives, described outer electrode 4 and described internal electrode 2 are also and do not break, thereby the durability that can have.

And then preferably the silver-colored ratio in internal electrode 2 electric conducting materials becomes large gradually along with approaching outer electrode 4.Like this in internal electrode 2 electric conducting materials, just formed continuously silver-colored concentration gradient, so can establish engaging of stable internal electrode 2 and internal electrode 2 and outer electrode 4.

And then preferably outer electrode 4 utilizes neck 4b to carry out diffusion bond with internal electrode 2.With this, even in the situation that flowing large electric current high-speed driving actuator, because be formed with the neck 4b that can bear large electric current in internal electrode 2 and the bonding part of outer electrode 4, so can prevent spark or broken string in this contact portion.Again, because internal electrode 2 utilizes this neck 4b to carry out diffusion bond with outer electrode 4, thus on the junction surface of internal electrode 2 and outer electrode 4, do not have clear and definite composition boundary, thus the junction surface that reliability is high can be formed.In addition, described neck 4b refers to the part that the electric conducting material of internal electrode 2 forms with the electric conducting material phase counterdiffusion of outer electrode 4.

And then, by making the silver-colored ratio in internal electrode 2 electric conducting materials, be more than 85% weight, just can increase the silver-colored concentration in internal electrode 2, thereby can make to form because of silver-colored diffusion bond reliable with being connected of outer electrode 4.Again, by making the silver-colored ratio in the electric conducting material of internal electrode 2, be more than 85% weight, just can suppress the use amount of the palladium of high price or platinum etc., so can manufacture cheap multi-layer piezoelectric element.On the other hand, in the situation that the silver-colored ratio in the electric conducting material of internal electrode 2 is less than 85% weight, the palladium of high price or the use amount of platinum must increase, so can not manufacture cheap multi-layer piezoelectric element, again, because the silver-colored concentration step-down in the electric conducting material of internal electrode 2, so become unreliable with engaging of outer electrode 4.In addition, the silver-colored ratio in internal electrode 2 electric conducting materials refers to the silver-colored ratio of the above part of junction surface 1mm of leaving outer electrode 4 in laminate 10 inside of the silver-colored constant rate in internal electrode 2 electric conducting materials.

And then preferably externally the piezoelectrics 1 side skin section of electrode 4 is provided with glass enriched layer.By making like this glass ingredient in outer electrode 4 more be present on the joint interface with piezoelectrics 1, just can improve the bond strength of outer electrode 4 and laminate 10 sides.

And then, be preferably below 80% of laminate 10 top layer sides that glass ingredient in outer electrode 4 is present in outer electrode 4 thickness substantially.With this, because undertaking the skin section that the glass ingredient that engages this effect with laminate 10 is present in piezoelectrics 1 side, so outer electrode 4 becomes possibility with strong the engaging of laminate 10, on the other hand, externally the atmospheric side skin section of electrode 4 in fact only exists and take the electric conducting material that silver is principal component, even if thereby when wire etc. being connected and fixed on described outer electrode 4 with scolding tin, also can provide the outer electrode that scolding tin wetting quality is good 4 surfaces.

And then, be preferably in the glass ingredient in electrode 4 externally and include lead oxide or bismuth oxide.That is,, by including lead oxide or the bismuth oxide high with the bond strength of piezoelectrics 1 in the glass ingredient in electrode 4 externally, just can make outer electrode 4 firm with engaging of piezoelectrics.On the other hand, externally in the glass ingredient in electrode 4, do not include in the situation of lead oxide or bismuth oxide, while having the driving of generation, outer electrode 4 is peeled off the possibility of this problem from laminate 10 sides.

Again, from the aspect of cost, consider, be preferably the silver-palladium alloy that uses low palladium ratio as internal electrode 2.Therefore, preferably use and can, at the piezoelectrics 1 of sintering below 980 ℃, form the material of these piezoelectrics 1 preferably with PbZrO ₃-PbTiO ₃for principal component, the Pb (Yb that contains 10～20%mol as accessory ingredient _1/2nb _1/2) O ₃, Pb (Co _1/3nb _2/3) O ₃and Pb (Zn _1/3nb _2/3) O ₃material.That is, from the state diagram of silver-palladium alloy, consider, when using the silver-palladium alloy of palladium 5% weight, as can be at the temperature below 980 ℃ the piezoelectrics 1 of sintering, can use with PbZrO ₃-PbTiO ₃for principal component, the Pb (Yb that contains 10～20%mol as accessory ingredient _1/2nb _1/2) O ₃, Pb (Co _1/3nb _2/3) O ₃and Pb (Zn _1/3nb _2/3) O ₃material.

At this, in the situation that the silver-palladium alloy of palladium 5% weight is used as internal electrode 2, if sintering at the temperature of 1100 ℃, sintering temperature surpasses the fusing point of the electric conducting material (silver-palladium alloy) that forms internal electrode 2, the electric conducting material aggegation of internal electrode 2, thus there is producing this problem of delamination.That is,, in order to use the silver-palladium alloy of low palladium ratio in the electric conducting material at internal electrode 2, the sintering temperature of piezoelectrics 1 must be reduced to 980 ℃ of following degree.

Outer electrode 4 by take electric conducting material 87～99.5% weight that silver is principal component, form with at least one glass ingredient 0.5～13% weight that includes lead oxide or bismuth oxide, this glass ingredient is in fact only present in below 80% of laminate 10 top layer sides of outer electrode 4 thickness.Again, the end of described outer electrode 4 and the internal electrode 2 that exposes in the side of laminate 10, electric conducting material diffusion bond in electric conducting material in internal electrode 2 and outer electrode 4, the side with the piezoelectrics 1 of laminate 10, mainly utilizes the glass ingredient in outer electrode 4 to engage.

The manufacture method of the stack-up type piezo-activator consisting of multi-layer piezoelectric element of the present invention then, is described.

In this manufacture method, similarly make laminate 10 with execution mode two, as shown in Figure 3A, utilize the every alternating floor of cutter sweep in the side of laminate 10 and form groove.

Then, form as follows outer electrode 4.

First, silver powder 87～99.5% weight by particle diameter 0.1～10 μ m, with remainder particle diameter 0.1～10 μ m and include lead oxide or mixture that more than at least one of bismuth oxide glass powder 0.5～13% weight forms in add adhesive to make silver-colored glass paste for lower floor.And then, in the silver powder of particle diameter 0.1～10 μ m, add adhesive to make the silver-colored paste in upper strata.

And, on the film of processing in the demoulding, with the thickness of 5～40 μ m, carry out silver-colored glass paste 21a screen printing lower floor for, after being dried, the thickness with 5～40 μ m carrys out silver-colored paste 21b for screen printing upper strata thereon.And then after dry, from mould release film, peel off paste plate 21, as shown in Fig. 3 (b), the mode that becomes laminate 10 sides with lower floor with silver-colored glass paste is needed on this paste plate 21 on the outer electrode 4 formation faces of the laminate 10 that is formed with groove, than being contained in lower floor with carrying out sintering at the high temperature of the softening point of the glass ingredient in silver-colored glass paste and the temperature below silver point, with this as shown in Fig. 3 (c), just can form outer electrode 4, described outer electrode 4 is formed with neck 4b.

In addition, in order to make the silver-colored ratio in internal electrode 2 electric conducting materials effectively become gradually large along with approaching outer electrode 4, be preferably in the situation that represent the Sintering mode of outer electrode 4 with the exponential function Y of the temperature shown in formula 1, take the time (unit minute) carry out integration Y and the value that obtains as more than 1000, more preferably 1800～4000.

(formula 1) Y=exp ((T+273)/273) [unit of T be ℃]

By making like this to take the time (dividing) to carry out the value that integration Y obtains, be 1800～4000, just can effectively make the silver-colored ratio in internal electrode 2 electric conducting materials along with approaching outer electrode 4, become gradually large, again, externally electrode 4 forms neck 4b with the junction surface of internal electrode 2, and then externally the laminate 10 top layer sides of electrode 4 form glass enriched layer.

Mode by becoming laminate 10 sides with silver-colored glass paste with lower floor is to carrying out sintering by the lower floor that includes glass ingredient with silver-colored glass paste and the paste plate 21 that the upper strata that does not include glass ingredient forms with silver-colored paste like this, and just externally the laminate 10 top layer sides of electrode 4 arrange glass enriched layer.By controlling with the thickness of silver-colored paste with silver-colored glass paste and upper strata forming the lower floor of described paste plate 21, just can make glass ingredient in outer electrode 4 be present in substantially below 80% of laminate 10 top layer sides of outer electrode 4 thickness again.And then, utilize described sintering to form neck 4b, in neck 4b, the silver-colored phase counterdiffusion of the silver-palladium alloy of internal electrode 2 and outer electrode 4, so can for example, detect with common analytical method (, EPMA, EDS) palladium spreading from internal electrode 2.

In addition, the formation method of outer electrode 4 is not limited to said method, is directly printed on the outer electrode 4 formation faces of laminate 10 sides and also can.And then, in said method, with 1 sintering, form outer electrode 4, but transfer printing or printing lower floor with silver-colored glass paste after, carry out sintering, then, after transfer printing or printing upper strata are with silver-colored paste, then carry out sintering, with 2 sintering, form outer electrode 4 and also can.

Again, the thickness of outer electrode 4 is preferably than the thin thickness of piezoelectrics 1.In order to follow actuator body, be the flexible of laminate, more preferably below 50 μ m.

Making lower floor is 80～99.5% weight by the silver powder in silver-colored glass paste, the glass powder of remainder be 0.5～13% weight be because: in silver powder than 80% weight few in the situation that, it is large that the ratio resistance of outer electrode 4 becomes, thereby likely in this outer electrode 4, cause local pyrexia in the situation that flowing large electric current high-speed driving, on the other hand, in silver powder than 99.5% weight many in the situation that, glass ingredient relatively tails off, outer electrode 4 dies down with the bond strength of laminate 10, thereby be likely created in, drive peripheral electrode 4 to peel off this problem from laminate 10.

Again, on upper strata with not including glass ingredient in silver-colored paste.This be because: in the situation that utilizing scolding tin that wire 6 is connected and fixed on outer electrode 4, if glass ingredient is present in the atmospheric side surface part of outer electrode 4, the wetting quality of scolding tin reduces significantly, wire 6 reduces to the bond strength of outer electrode 4, thereby this wire 6 likely comes off in driving.

By including at least one of lead oxide or bismuth oxide in the glass ingredient with silver-colored glass paste in lower floor, just can improve the bond strength with laminate 10 again.

Below, the stack-up type piezo-activator of execution mode two can similarly be manufactured with execution mode first-class.

That is, the laminate 10 that is formed with outer electrode 4 be impregnated in silicone rubber solution, and it is carried out to vacuum degassing, the groove that is just filled into laminate 10 with this silicon rubber is inner, and silicon rubber is solidified.

Then, wire 6 is connected to outer electrode 4, utilizes wire 6 pair of external electrodes 4 to be applied to the direct current of 0.1～3kV/mm, to laminate 10 processing that polarizes.With this, for example, as the stack-up type piezo-activator of the automotive fuel injection valve of engine spray feed fuels being brought into play to its function, just completed.

In execution mode one to three described above, piezoelectrics 1 are for example by with lead zirconate titanate Pb (Zr, Ti) O ₃(being slightly called below PZT) or barium titanate BaTiO ₃the formation such as piezoceramic material for principal component.This piezoelectric ceramic is preferably and represents that the piezoelectricity distortion constant d33 of its piezoelectric property is high.

Again, in execution mode one to three, the thickness of piezoelectrics 1 is that the distance of 2 of internal electrodes is preferably 0～250 μ m.With this, even if stack-up type piezo-activator increases lamination number in order to apply voltage to obtain larger addendum modification, also can realize miniaturization, the low level of actuator, and can prevent the insulation breakdown of piezoelectrics 1.

And then in present embodiment one to three, as shown in Figure 4, externally the outer surface of electrode 4 is formed with by being embedded with the conductivity accessory 7 that the net of metal or the conductive adhesive 7a of cancellous metallic plate 7b form and also can.In this situation, by the outer surface of electrode 4 externally, conductivity accessory 7 is set, even large electric current being put into actuator, with high-speed driving in the situation that, also can make large electric current flow into conductivity accessory 7, flow into the electric current in outer electrode 4 thereby reduce.With this, can prevent that outer electrode 4 from causing local pyrexia and breaking, thereby can improve significantly durability.And then, if bury net or the cancellous metallic plate 7b of metal underground in conductive adhesive 7a, can prevent from cracking on conductive adhesive 7a.

Again, externally the outer surface of electrode 4 is not used in the situation of net or cancellous metallic plate, with regard to the flexible stress producing because of laminate 10 likely, directly act on outer electrode 4, outer electrode 4 is easily because the fatigue in driving is easily peeled off from the side of laminate 10.

The net of metal refers to braided metal line and the net that obtains, and cancellous metallic plate refers to and on metallic plate, forms hole, makes cancellous metallic plate.

At this, preferably conductive adhesive consists of the polyimide resin that is dispersed with electroconductive particle.This be because: by using polyimide resin, even while at high temperature driving laminate 10, because use has higher stable on heating polyimide resin, conductive adhesive also easily maintains high-adhesive-strength.

Again, the conductive adhesive 7a that more preferably forms described conductivity accessory 7 consists of the polyimide resin that is dispersed with the silver powder lower than resistance.This be because: by use the silver powder that resistance value is lower in electroconductive particle, just easily suppress the local pyrexia in conductive adhesive.

And then to be preferably described electroconductive particle be laminar or the aspheric particle of needle-like etc.This be because: by making the aspheric particle of the laminar or needle-like of being shaped as of electroconductive particle etc., just can make the polymerization between this electroconductive particle firm, thereby can further improve the shear strength of this conductive adhesive 7a.

Execution mode four

Fig. 5 represents the injection apparatus of embodiment of the present invention four, uses piezo-activator of the present invention and forms.In Fig. 5, symbol 31 represents accommodating container.In one end of this accommodating container 31, be provided with spray-hole 33, in accommodating container 31, contain again the needle valve 35 that can open and close spray-hole 33.

The fuel passage 37 that can be communicated with spray-hole 33 is set, and this fuel passage 37 is linked to outside fuels sources, and fuel is supplied in fuel passage 37 under always constant high pressure.Thereby, be formed as follows: if the open spray-hole 33 of needle valve 35, the fuel being supplied in fuel passage 37 is ejected in the not shown fuel chambers of internal combustion engine under constant high pressure.

Again, the upper end diameter of needle valve 35 becomes large, becomes the piston 41 that can slide with the cylinder 39 being formed in accommodating container 31.And, in accommodating container 31, taken in above-mentioned piezo-activator 43.

At this, piezo-activator 43 is piezo-activators of the present invention.

In such injection apparatus, if piezo-activator is applied in voltage and extends, piston 41 is pressed, the inaccessible spray-hole 33 of needle valve 35, thus the supply of fuel stops.Again, if applying of voltage stops, piezo-activator 43 shrinks, and disk spring 45 pushes back piston 41, and spray-hole 33 is communicated with fuel passage 37, thereby carries out the injection of fuel.

In such device, as illustrated in execution mode one to three, can in multi-layer piezoelectric element, suppress the broken string of outer electrode and internal electrode, can improve significantly durability, so the durability of injection apparatus also can improve.

Embodiment mono-

As embodiment mono-, first make laminate.Piezoelectrics form with the PZT of thickness 150 μ m, and internal electrode forms with the silver-palladium alloy (containing Pd10% weight) of thickness 3 μ m, and piezoelectrics and internal electrode lamination number is separately 300 layers.In addition, sintering temperature is 1000 ℃.

As shown in Figure 3A, utilize cutter sweep on the end of the internal electrode of the side of laminate form to every alternating floor the groove of the degree of depth 50 μ ms, width 50 μ ms thereafter.

Then, laminar silver powder 90% volume of average grain diameter 2 μ m, with mixtures remainder average grain diameter 2 μ m, that take that silicon is principal component, softening point is 640 ℃ amorphous glass powder 10% volume in, total weight 100 mass parts with respect to silver powder and glass powder are added the adhesive of 8 mass parts, mix and make silver-colored glass conductive paste fully.Utilize screen printing that the silver-colored glass conductive paste of making like this and obtaining is formed on mould release film, from mould release film, peel off after dry, thereby obtain the plate of silver-colored glass conductive paste.The green density of utilizing Archimedes's method to measure this plate is 6.5g/cm ³.

Then, as shown in Figure 3 B, the plate of described silver-colored glass paste is needed on the outer electrode face of laminate, at 650 ℃, sintering is 30 minutes, as shown in Figure 3 C, forms the outer electrode consisting of the Porous electric conductor that is configured to three-dimensional network structure.In addition, known by measure the section photo of outer electrode with image analysis apparatus, the voidage of outer electrode is now 40%.Again, utilize analytical electron microscope (EPMA) to measure known, silver in silver glass conductive paste with the silver-palladium alloy phase counterdiffusion in internal electrode, engage, on the junction surface with internal electrode, be formed with palladium and spread and the neck that obtains from internal electrode.And then, utilize the section photo of outer electrode to measure known, the bonding part of outer electrode and laminate side is about 50%.

, connect the line to outer electrode, utilize wire outer electrode anodal and negative pole to be applied to the DC electric field of 15 minutes 3kV/mm thereafter, the processing that polarizes, thus produce stack-up type piezo-activator as shown in Figure 1.

The direct voltage of 170V is put on the stack-up type piezo-activator obtaining, consequently, in lamination direction, obtain the addendum modification of 45 μ m.And then the alternating voltage that at room temperature this actuator is applied to 0～+ 170V with the frequency of 150Hz, to drive test, consequently, drives and has circulated 2 * 10 ⁸after inferior, obtain the addendum modification of 45 μ m, do not found the abnormal of outer electrode.Again, except the green density of silver-colored glass conductive paste is changed, the voidage that forms outer electrode is beyond the outer electrode of 30% volume, 70% volume, with the above-mentioned stack-up type piezo-activator of similarly making, and it is evaluated known, drive and to have circulated 2 * 10 ⁸after inferior, obtain the addendum modification of 45 μ m, do not found the abnormal of outer electrode.

Comparative example 1

Except silver-colored glass conductive paste being coated on to side dry (the green density 9.1g/cm of laminate ³), sintering temperature is changed to beyond 820 ℃, make the stack-up type piezo-activator of the formation same with embodiment.Outer electrode now is not configured to three-dimensional network structure, but is block roughly, and voidage is 10%, has spherical space, engages by entire surface with laminate side.

With embodiment similarly, the alternating voltage that at room temperature the stack-up type piezo-activator obtaining is applied to 0～+ 170V with the frequency of 150Hz, to drive test, consequently, drives and has circulated 5 * 10 ⁶after inferior, outer electrode broken string, produces spark.

Embodiment bis-

As embodiment bis-, make as follows multi-layer piezoelectric element of the present invention.

First, make to be mixed with and take the slurry of powders calcined, adhesive and plasticizer of the piezoelectric ceramic that PZT is principal component, with scraper legal system, make to form the ceramic green sheet of the piezoelectrics 1 of thickness 150 μ m.

Utilize screen printing with the thickness of 3 μ m by by adding the conductive paste that adhesive obtains to be formed on the one side of this ceramic green sheet in being mixed with the silver-palladium alloy of palladium take mode that silver-colored weight rate X (%) is 85～95% weight, 300 described ceramic green sheets of lamination, and at 980～1100 ℃, carry out sintering, thereby obtain the laminate 10 of Fig. 1.

Then, as shown in Figure 3A, utilize cutter sweep on the end of the internal electrode 2 of laminate 10 sides, to form the groove of the degree of depth 50 μ m, width 50 μ m every alternating floor.

Then, take silver-colored weight rate Y (%) as the mode of 84～97% weight mix the laminar silver powder of average grain diameter 2 μ m and average grain diameter 2 μ m, take amorphous glass powder that silicon is principal component, that softening point is 640 ℃, and then, with respect to silver powder, add and mix the adhesive of 8 weight portions with total weight 100 weight portions of glass powder, thereby make silver-colored glass conductive paste.Utilize screen printing that the silver-colored glass paste of making is like this formed on mould release film, after dry, from mould release film, peel off, thereby obtain the plate of silver-colored glass conductive paste, afterwards the plate of described silver-colored glass conductive paste is needed on the opposed a pair of side of laminate 10, at 650 ℃, carry out the sintering of 30 minutes, thereby form outer electrode 4.

Again, on the junction surface of internal electrode 2 and outer electrode 4, be formed with the neck 4b obtaining by the silver-colored phase counterdiffusion in the silver-colored glass conductive paste in the silver-palladium alloy in internal electrode 2 and outer electrode 4, utilize EPMA that this neck 4b is analyzed and can be confirmed, palladium is from internal electrode 2 diffusions.

Again, with regard to the voidage of the outer electrode 4 of above-mentioned formation, utilize the section photo of outer electrode 4 to analyze known, voidage is 40%.And then, utilize the section photo of outer electrode 4 to measure known, outer electrode 4 is approximately 50% with the bonding part of laminate 10 sides.Externally in the piezoelectricity side skin section of electrode 4, be formed with the glass enriched layer that the glass ingredient institute segregation in silver-colored glass conductive paste forms again.

, wire be connected in outer electrode on, utilize wire the outer electrode of positive pole and negative pole to be applied to the DC electric field of 15 minutes 3kV/mm thereafter, the processing that polarizes, thus manufacture stack-up type piezo-activator as shown in Figure 1.

In the stack-up type piezo-activator of the present invention that the method for stating is in the use made, in the scope of X >=85, form the silver-colored weight rate Y (%) in silver-colored weight rate X (%) in internal electrode 2 electric conducting materials and outer electrode, and verify associated between the value of X/Y and the driving of stack-up type piezo-activator.

Again, as a comparative example, make to make the value of X/Y at X/Y < 0.9, or in the scope of X/Y > 1.1 and the sample forming.

To the above-mentioned stack-up type piezo-activator obtaining like that, while applying the direct voltage of 185V, in all stack-up type piezo-activators, all in lamination direction, obtain the addendum modification of 49 μ m.And then at room temperature the frequency with 150Hz applies the AC field of 0～+ 185V to these stack-up type piezo-activators, circulates 2 * 10 ⁸inferior driving test.Result is as shown in table 1.

[table 1]

Evaluation result (2 * 10 in outer electrode in internal electrode ⁸

After time circulation of sample number silver weight rate X silver weight rate Y X/Y value)

1 95 97 0.98 without abnormal

2 95 86.5 1.1 without abnormal

3 88 97.5 0.9 without abnormal

^*4 85 97 0.88 addendum modifications reduce

^*5 95 84 1.13 addendum modifications reduce

As known from Table 1, comparative example be sample number 4 because the value of its X/Y less than 0.9, so the silver-colored amount in internal electrode 2 relatively tails off with respect to outer electrode 4, again, silver-colored quantitative change in internal electrode 2 is few, fusing point with this internal electrode 2 uprises, so the phase counterdiffusion of silver tails off between internal electrode 2 and outer electrode 4, strength decreased with this neck 4b, so in the situation that high-speed and continuous drives stack-up type piezo-activator, neck 4b breaks because of the flexible stress producing of laminate 10, thereby voltage can not be supplied in a part of piezoelectrics 1, so along with driving circulation to increase, the addendum modification of laminate 10 reduces, so the durability as stack-up type piezo-activator reduces.

Again, comparative example is that sample number 5 is because the value of its X/Y surpasses 1.1, so the silver-colored amount in outer electrode 4 relatively tails off with respect to the silver-colored amount in internal electrode 2 electric conducting materials, between internal electrode 2 and outer electrode 4, the phase counterdiffusion of silver tails off, with this and similarly above-mentioned, neck 4b breaks because of the flexible stress producing of laminate 10, thereby voltage can not be supplied in a part of piezoelectrics 1, so along with driving circulation to increase, the addendum modification of laminate 10 reduces, so reduce as the durability of stack-up type piezo-activator.

With respect to this, at embodiments of the invention, be in sample number 1～3, it is the stack-up type piezo-activator forming in the scope of X>=85 and 0.9≤X/Y≤1.1, so promoted the phase counterdiffusion of silver between internal electrode 2 and outer electrode 4, thereby internal electrode 2 becomes firmly with engaging of outer electrode 4, so 2 * 10 ⁸after inferior circulation, also can obtain the addendum modification of 49 μ m, again, 2 * 10 ⁸after inferior circulation, externally in electrode 4, do not produce the abnormal of spark or broken string etc., thus the durability having had as stack-up type piezo-activator.

Embodiment tri-

In embodiment tri-, the internal electrode 2 forming at the conductive paste of using to add the powders calcined of piezoelectric ceramic to form in silver-palladium alloy and in the stack-up type piezo-activator made, the silver-colored weight rate that makes to have the internal electrode 2 of electric conducting material and piezoelectric is Z (%), with the silver-colored weight rate Y (%) in electrode 4 externally and the silver-colored weight rate Z (%) in internal electrode 2, form stack-up type piezo-activator, and verify associated between the value of Z/Y and the driving of stack-up type piezo-activator.Manufacture method is identical with embodiment bis-.

To the above-mentioned stack-up type piezo-activator obtaining like that, while applying the direct voltage of 185V, in all samples, all in lamination direction, obtain the addendum modification of 49 μ m.And then at room temperature the frequency with 150Hz applies the AC field of 0～+ 185V to these stack-up type piezo-activators, circulates 5 * 10 ⁸inferior driving test.Result is as shown in table 2.

[table 2]

Evaluation result (5 * 10 in outer electrode in internal electrode ⁸inferior following

Sample number Z/Y value

After silver weight rate Z silver weight rate Y ring)

6 80 97 0.82 without abnormal

7 86.5 868 1 without abnormal

8 68.5 97.5 0.7 without abnormal

9 90 84 1.07 addendum modifications reduce

10 63 96 0.66 addendum modifications reduced than initial stage

As known from Table 2, sample number 9 is because the value of its Z/Y is larger than 1.0, so the piezoelectric in internal electrode 2 tails off, thereby internal electrode 2 adhering to of interface connects airtight weakened with piezoelectrics 1, so produce and peel off in a part for internal electrode 2 and piezoelectrics 1 in driving, voltage can not be supplied on a part of piezoelectrics 1, thereby addendum modification reduces.

Again, sample number 10 is because the value of its Z/Y is less than 0.7, so the silver-colored quantitative change in internal electrode 2 is few, thereby compare with outer electrode 4, the resistance value of internal electrode 2 uprises, so the in the situation that of high-frequency Continuous Drive, the voltage drop causing because of this high resistance just can not be supplied to sufficient voltage in piezoelectrics 1, thereby addendum modification reduces.

With respect to this, in sample number 6～8,5 * 10 ⁸also can access the addendum modification of 49 μ m after inferior circulation, not produce broken string etc. abnormal of internal electrode 2 and the contact portion of outer electrode 4.

Embodiment tetra-

The following stack-up type piezo-activator being formed by multi-layer piezoelectric element of the present invention of making.

First, with embodiment bis-laminate 10 of construction drawing 1 similarly, as shown in Figure 3A, utilize cutter sweep on the end of the internal electrode 2 of laminate 10 sides, to form the groove of the degree of depth 50 μ m, width 50 μ m every alternating floor.

Then, mix average grain diameter 2 μ m silver powder 80～99.5% weight, with include lead oxide or bismuth oxide at least one, the glass powder of average grain diameter 2 μ m, and then, add adhesive, make silver-colored glass paste for lower floor.Similarly, in the silver powder of average grain diameter 2 μ m, add adhesive, make silver-colored glass paste for upper strata.

Then, utilize screen printing with the thickness of 5～40 μ m, lower floor to be printed onto on mould release film with silver-colored glass paste, after being dried, utilize screen printing with the thickness of 5～40 μ m, upper strata to be printed onto on it with silver-colored glass paste.After being dried described paste, from mould release film, peeling off, thereby obtain paste plate.Thereafter the mode that ，Yi lower floor becomes laminate 10 top layer sides with silver-colored glass paste is transferred to described paste plate on the opposed a pair of side of laminate 10 sides, carries out the sintering of 30 minutes at 800 ℃, thereby forms outer electrode 4.In addition, now, the value of coming the Y of integration type 1 to obtain with the time (dividing) is 3240.

The quantitative analysis that utilizes EPMA to carry out element to internal electrode 2 along the line X shown in Fig. 2 B is known, as shown in Figure 5, the silver-colored ratio in internal electrode 2 electric conducting materials from increasing gradually towards the connecting portion being connected in outer electrode 4 near being connected in the connecting portion 50 μ m of outer electrode 4.

Again, on the junction surface of internal electrode 2 and outer electrode 4, be formed with the silver-colored phase counterdiffusion in silver-palladium alloy in internal electrode 2 and outer electrode 4 and the neck 4b that obtains, utilize EPMA that this neck 4b is analyzed and can be confirmed, palladium spreads from internal electrode 2.

Again, externally the piezoelectricity side skin section of electrode 4 is formed with glass ingredient segregation and the glass enriched layer that obtains.And then the glass ingredient being contained in outer electrode 4 is present in below 60% of laminate 10 top layer sides substantially.

, wire be connected in to outer electrode thereafter, the processing that polarizes of the DC electric field of utilizing wire to apply 15 minutes 3kV/mm to the outer electrode of positive pole and negative pole, thus make stack-up type piezo-activator as shown in Figure 1.

Embodiment five

In embodiment five, except changing the kind and sintering temperature thereof of the conductive paste that forms outer electrode 4, use the manufacture method identical with embodiment tetra-to make multiple stack-up type piezo-activator.To the stack-up type piezo-activator obtaining, near silver-colored ratio internal electrode 2 electric conducting materials and connecting portion outer electrode 4, with respect to the ratio of the silver-colored ratio of laminate 10 inside, analyze.To the above-mentioned stack-up type piezo-activator obtaining like that, apply the direct voltage of 185V, in all stack-up type piezo-activators, all in lamination direction, obtained the displacement of 49 μ m.And then at room temperature the frequency with 150Hz applies the AC field of 0～+ 185V to these stack-up type piezo-activators, circulates 2 * 10 ⁸inferior driving test.Result is as shown in table 3.

[table 3]

Silver-colored ratio in internal electrode electric conducting material

The ratio evaluation result of silver ratio

Sample number laminate internal-external electrode connects (E/I) 2 * 10 ⁸after inferior circulation

(I%) near portion (E%)

11 95 98 1.03 without abnormal

12 85 95 1.12 without abnormal

^*13 95 95 1.00 addendum modifications reduce

From this table 3, comparative example is sample number 13 because near silver-colored ratio its internal electrode 2 electric conducting materials and connecting portion outer electrode 4, ratio with respect to the silver-colored ratio of laminate 10 inside is large unlike 1, with the connecting portion of outer electrode 4 near internal electrode 2 electric conducting materials in silver-colored ratio large unlike the silver-colored ratio in internal electrode 2 electric conducting materials of laminate 10 inside, so a little less than the bond strength of the contact portions of internal electrode 2 and outer electrode 4, so the internal electrode 2 of a part is peeled off with the contact portions of outer electrode 4 in driving, voltage can not be supplied in a part of piezoelectrics 1, thereby displacement properties reduces.

With respect to this, embodiments of the invention be sample number 11 and 12 its with the connecting portion of outer electrode 4 near internal electrode 2 electric conducting materials in silver-colored ratio larger than the silver-colored ratio in internal electrode 2 electric conducting materials of laminate 10 inside, so internal electrode 2 is high with the bond strength of

outer electrode

4,2 * 10 ⁸after circulation, also can access the addendum modification of 49 μ m, again, 2 * 10 ⁸after circulation, externally on electrode 4, do not produce the abnormal of spark or broken string etc. yet, thus the durability having had as stack-up type piezo-activator.

Embodiment six

In embodiment six, change kind and the sintering temperature thereof of the conductive paste that forms outer electrode 4, make multiple stack-up type piezo-activator.Sample number 16 does not externally have glass enriched layer in laminate 10 skin section of electrode 4, sample number 17 externally the thickness of electrode 4 laminate top layer side 95% on there is glass ingredient.To the stack-up type piezo-activator obtaining, the direct voltage that applies 185V is known, and all samples can both obtain the addendum modification of 49 μ m in lamination direction.And then, to these stack-up type piezo-activators, at room temperature with the frequency of 150Hz, apply the AC field of 0～+ 185V, circulate 5 * 10 ⁸inferior driving test.Result is as shown in table 4.

[table 4]

Evaluation result

The distribution 5 * 10 of sample number glass enriched layer glass ingredient ⁸after inferior circulation

14 have below 60% without abnormal

15 have below 80% without abnormal

^*16 reduce without 60% following addendum modification

^*17 have 95% following wire dropping

As known from Table 4, sample number 16 is because there is not glass enriched layer in laminate 10 skin section of electrode 4 externally, so a little less than the bond strength of outer electrode 4 with respect to laminate 10, drive peripheral electrode 4 to peel off from laminate 10, voltage can not be supplied on a part of piezoelectrics 1, thereby displacement properties reduces.Again, sample number 17 externally electrode 4 thickness laminate 10 top layer sides 95% on there is glass ingredient, so a little less than the bond strength of the scolding tin that is connected and fixed wire 6 with respect to outer electrode 4, thereby in driving, wire 6 comes off.

With respect to this, in sample number 14 and 15,5 * 10 ⁸also can access the addendum modification of 49 μ m after inferior circulation, broken string etc. abnormal of internal electrode 2 and the contact portion of outer electrode 4 do not occur.

Industrial applicibility

Multi-layer piezoelectric element of the present invention can be used in piezoelectric transformer.Again, multi-layer piezoelectric element of the present invention can be used in the stack-up type piezo-activator being used in the precision positioning device of automotive fuel injection apparatus, Optical devices etc. or driving element that vibration prevents use etc.And then the multi-layer piezoelectric element of the application of the invention, can be used in the injection apparatus of ink etc. of automotive fuel or ink-jet printer.

Claims

1. a multi-layer piezoelectric element; it comprises piezoelectrics and the internal electrode laminate that alternately lamination forms and is formed at respectively the first side of this laminate and the outer electrode on the second side; in the internal electrode of adjacency; one side's internal electrode is connected with described outer electrode in described the first side, and the opposing party's internal electrode is connected with described outer electrode in described the second side; It is characterized in that,

Described outer electrode consists of the Porous electric conductor that contains electric conducting material and glass and form three-dimensional network structure,

Network portion in described three-dimensional network structure is the space of hollow,

Described outer electrode local engagement, on described the first side and described the second side, is formed with the space of hollow between described piezoelectrics and described outer electrode,

The voidage of described outer electrode is 30～70% volumes,

In the end being connected with described outer electrode of described internal electrode, be formed with the neck consisting of diffusion bond the metal ingredient of described internal electrode and the described electric conducting material of described outer electrode, this neck is embedded in described outer electrode.

2. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, the principal component of the electric conducting material of described outer electrode is silver.

3. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, is contained in the softening point of the glass in described outer electrode below the fusing point of electric conducting material that forms described outer electrode.

4. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, the metal ingredient of described internal electrode be take Ag as principal component, and contains Pd below 15% weight and more than one in Pt family metal.

5. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, the glass that forms described outer electrode is noncrystalline.

6. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, on the piezoelectricity side of said external electrode, skin section is provided with glass enriched layer.

7. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, the Thickness Ratio of described outer electrode forms the thin thickness of the piezoelectrics of described laminate.

8. multi-layer piezoelectric element as claimed in claim 1, it is characterized in that, in described the first side, between the end of described the opposing party's internal electrode and described outer electrode, be formed with groove, in this groove, be provided with insulator, in described the second side, between the end of the internal electrode of one and described outer electrode, be formed with groove, in this groove, be provided with insulator, described insulator is lower than described piezoelectrics Young's modulus.

9. multi-layer piezoelectric element as claimed in claim 1, is characterized in that, in the arranged outside of described outer electrode, has the conductivity accessory forming by being embedded with the net of metal or the conductive adhesive of cancellous metallic plate.

10. multi-layer piezoelectric element as claimed in claim 9, is characterized in that, described conductive adhesive consists of the polyimide resin that is dispersed with electroconductive particle.

11. multi-layer piezoelectric elements as claimed in claim 10, is characterized in that, described electroconductive particle is silver powder.

12. 1 kinds of multi-layer piezoelectric elements, it comprises piezoelectric body layer and the internal electrode laminate that alternately lamination forms and is formed at respectively the first side of this laminate and the outer electrode on the second side, in the internal electrode of adjacency, one side's internal electrode is connected with outer electrode in described the first side, and the opposing party's internal electrode is connected with outer electrode in the second side; It is characterized in that,

In establishing described internal electrode, with respect to the silver-colored weight rate of electric conducting material integral body, be X%,

If in described outer electrode, while being Y% with respect to the silver-colored weight rate of the total weight of electric conducting material and glass,

To meet the mode of X >=85 and 0.9≤X/Y≤1.1, set the silver-colored ratio of described internal electrode and described outer electrode,

The voidage of described outer electrode is 30～70% volumes,

13. multi-layer piezoelectric elements as claimed in claim 12, it is characterized in that, described internal electrode includes piezoelectric, when the silver-colored weight rate with respect to including the total weight of described piezoelectric in establishing described internal electrode is Z%, meets 0.7≤Z/Y≤1.0.

14. multi-layer piezoelectric elements as claimed in claim 13, is characterized in that, for the softening point of the glass of described outer electrode, are below 4/5 of fusing point that forms the electric conducting material of described internal electrode.

15. 1 kinds of injection apparatus, it is characterized in that possessing: have the accommodating container of spray-hole, the driving that is housed in the multi-layer piezoelectric element as described in claim 1～14 any one in this accommodating container and utilizes this multi-layer piezoelectric element from as described in the needle valve of spray-hole ejection liquid.