JP2003318458A - Laminated piezoelectric element, method for producing the same, and injection device - Google Patents

Abstract

(57) Abstract: A laminated piezoelectric element excellent in durability capable of improving the bonding strength between an internal electrode layer and a piezoelectric ceramic layer and suppressing breakage at the interface between the internal electrode layer and the piezoelectric ceramic layer, and The manufacturing method and the injection device are provided. A plurality of piezoelectric ceramic layers and a plurality of internal electrode layers are provided.
Are laminated alternately and co-fired, wherein the piezoelectric ceramic layer 1 includes ceramic particles 7, and at a fracture surface at the interface between the piezoelectric ceramic layer 1 and the internal electrode layer 2,
The ceramic particles 7 partially embedded in the internal electrode layer 2 are exposed on the surface of the internal electrode layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element, a method of manufacturing the laminated piezoelectric element, and an injection device, for example, a laminated device used for a precision positioning device such as a fuel injection device for an automobile or an optical device, a drive element for preventing vibration, and the like. TECHNICAL FIELD The present invention relates to a piezoelectric element, a manufacturing method thereof, and an injection device.

[0002]

2. Description of the Related Art Conventionally, as a laminated piezoelectric element, a laminated piezoelectric actuator in which piezoelectric ceramic layers and internal electrode layers are alternately laminated is known. Laminated piezoelectric actuators are classified into two types, a co-firing type and a stack type in which piezoelectric ceramic layers and internal electrode plates are alternately laminated. PZT, which is a typical piezoelectric body, is used as a piezoelectric ceramic layer. System piezoelectric ceramics are widely used. A co-firing type multilayer piezoelectric element is a molded body in which a plurality of ceramic green sheets are laminated on the upper and lower end surfaces of a laminated body in which a plurality of ceramic green sheets each having a conductive paste printed on one side are laminated, by pressing, debinding, It is obtained by firing and forming external electrodes alternately connected to the internal electrode layers on the two side surfaces of this sintered body.

In the co-firing type laminated piezoelectric element, the joint interface between the internal electrode layer and the piezoelectric ceramic layer is easily damaged by an impact. Therefore, in order to improve the impact resistance, for example, in Japanese Unexamined Patent Publication No. 4-299588. , The inner electrode layer contains a ceramic powder having a controlled particle size as a co-material,
It is described that an element having high reliability against impact can be obtained by effectively forming a bridge connecting two piezoelectric ceramic layers sandwiching an internal electrode layer.

As the internal electrode layer, platinum or palladium or an alloy of silver and palladium is used depending on the firing temperature of the PZT type piezoelectric ceramics.
From the viewpoint of cost reduction, it is required to lower the firing temperature. Further, lowering the firing temperature is very important from the viewpoint of suppressing the evaporation of lead components contained in the piezoelectric ceramic layer and preventing the deterioration of displacement characteristics. The firing temperature has been lowered by making the ceramic powder used for producing the green sheet finer.

[0005]

However, in the above-mentioned laminated piezoelectric actuator, since the firing temperature is lowered to 1100 ° C. or lower, the specific surface area of the ceramic powder is 3
It was necessary to prepare a green sheet using a material of about 4 m ² / g or more. Therefore, the organic binder is added to the ceramic powder 1 according to the specific surface area of the raw material ceramic powder.
It was necessary to contain 9 parts by mass or more with respect to 00 parts by mass. This organic binder needs to be removed, but if such a large amount of organic binder is contained, a large amount of gas is released from between the electrode coating film, which is the weakest bonding surface, and the green sheet during binder removal processing. The interface between the electrode coating film and the green sheet is weakened, and ceramic particles as a co-material in the electrode coating film are extruded from the electrode coating film (internal electrode layer) during firing, so that the internal electrode layer and the piezoelectric ceramic layer are separated. There is a problem that the bonding strength becomes low.

That is, as described above, a large amount of gas generated during binder removal weakens the gap between the electrode coating film and the green sheet, and the metal of the electrode coating film tends to sinter during the subsequent firing. The ceramic powder as a co-material is extruded from the electrode coating film between the electrode coating film and the green sheet, and is partially embedded in the internal electrode layer,
The ceramic particles that are bonded and sintered with the ceramic particles of the piezoelectric ceramic layer are reduced, which reduces the anchoring effect of the ceramic particles in the internal electrode layers, and the bonding strength between the internal electrode layers and the piezoelectric ceramic layers is reduced, resulting in a laminated type There is a problem that the piezoelectric actuator is easily broken.

The present invention provides a laminated piezoelectric element having excellent durability that improves the bonding strength between the internal electrode layer and the piezoelectric ceramic layer and suppresses damage at the interface between the internal electrode layer and the piezoelectric ceramic layer, and a method of manufacturing the same. Another object is to provide an injection device.

[0008]

A laminated piezoelectric element of the present invention is a laminated piezoelectric element in which a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers are alternately laminated and co-fired. The electrode layer contains ceramic particles, and in the fracture surface at the interface between the piezoelectric ceramic layer and the internal electrode layer, the ceramic particles partially embedded in the internal electrode layer are exposed on the internal electrode layer surface. It is characterized by being

In the present invention, since the ceramic particles are exposed on a part of the surface of the internal electrode layer, the ceramic particles are sintered with the ceramic particles of the piezoelectric ceramic layer to realize a strong anchoring effect and The bonding strength between the electrode layer and the piezoelectric ceramic layer can be improved. Further, the laminated piezoelectric element of the present invention is characterized in that the exposed area of the ceramic particles exposed on the surface of the internal electrode layer is 2% or more on the surface of the internal electrode layer. Thus, the larger the proportion of the ceramic particles exposed on the surface of the internal electrode layer, the stronger the bonding force between the ceramic particles of the piezoelectric ceramic layer and the bonding strength between the internal electrode layer and the piezoelectric ceramic layer.

The method of manufacturing the laminated piezoelectric element of the present invention comprises: a ceramic powder in which a plurality of fine particles are aggregated; an organic binder;
A step of applying a conductive paste containing a metal powder, a ceramic powder, and an organic solvent to form an electrode coating film on a green sheet containing an organic solvent, and a green on which the electrode coating film is formed. The method is characterized by including a step of stacking a plurality of sheets and applying pressure to form a laminated body, and a step of subjecting the laminated body to binder removal processing and firing.

In the method for manufacturing such a laminated piezoelectric element, since the ceramic powder in which a plurality of fine particles are aggregated is used, the specific surface area is lowered as compared with the case where the ceramic powder in which fine particles are dispersed (ceramic powder which is not agglomerated) is used. It is possible to reduce the amount of organic binder contained in the green sheet. This reduces gas release during binder removal and suppresses weakening between the electrode coating film and the green sheet, which suppresses extrusion of ceramic particles of the electrode coating film into the green sheet,
A large number of ceramic particles, some of which are embedded in the internal electrode layer, are formed, and the ceramic particles can be bonded and sintered with the ceramic particles of the piezoelectric ceramic layer to strengthen the bonding between the internal electrode layer and the piezoelectric ceramic layer.

Further, since the ceramic powder formed by aggregating a plurality of fine particles is used for the green sheet for forming the piezoelectric ceramic layer, low temperature firing at 1100 ° C. or lower can be achieved.

Particularly, PZT obtained by calcining fine powder and agglomerating it.
-Based piezoelectric calcined powder (ceramic powder) having a specific surface area of 1.5 to ^2.5 m ² / g is used, so that the amount of the organic binder in the green sheet is 100 parts by mass of the ceramic powder. It is possible to suppress the weakening between the electrode coating film and the green sheet, and the firing temperature can be set to 1100 ° C. or less. This makes it possible to improve the bonding strength between the internal electrode layer and the piezoelectric ceramic layer, suppress evaporation of lead components contained in the piezoelectric ceramic layer, and provide a laminated piezoelectric element having excellent displacement characteristics in terms of characteristics. Obtainable.

The ejection device of the present invention comprises a container having an ejection hole, the above-mentioned laminated piezoelectric element accommodated in the container, and a valve for ejecting a liquid from the ejection hole by driving the laminated piezoelectric element. And is provided.

In such an injection device, as described above, the displacement characteristics of the laminated piezoelectric element are excellent and, in addition, the damage at the interface between the internal electrode layer and the piezoelectric ceramic layer is suppressed. The long-term reliability can be improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a laminated piezoelectric element comprising a laminated piezoelectric actuator of the present invention. (A) is a perspective view and (b) is AA of (a). It is a longitudinal cross-sectional view along the line.

As shown in FIG. 1, the simultaneous firing type laminated piezoelectric element of the present invention has a piezoelectric element body 1a formed by alternately laminating a plurality of piezoelectric ceramic layers 1 and a plurality of internal electrode layers 2. In each of the two side surfaces of the internal electrode layer 2, the insulators 3 are formed on the end portions of the internal electrode layers 2 every other layer, and the end portions of the internal electrode layers 2 on which the insulator 3 is not formed are connected to the same external electrode 4. It is configured.

Further, inactive portions 5 for transmitting the displacement generated by the expansion and contraction of the piezoelectric ceramic layer 1 of the active portion to the outside are arranged on both end faces of the piezoelectric element body 1a in the stacking direction.

In order to prevent creeping discharge between the internal electrode layers 2 and to apply a large voltage, it is desirable to coat the outer peripheral surface of the co-firing type laminated piezoelectric element with a stretchable insulator such as silicone rubber.

In the laminated piezoelectric element of the present invention, when the piezoelectric element body 1a is damaged by bending stress or the like, it breaks at the interface between the piezoelectric ceramic layer 1 and the internal electrode layer 2. As shown in FIG. 2, the ceramic particles 7 partially embedded in the internal electrode layer 2 are exposed on the surface of the internal electrode layer 2. Ceramic particles 7
Exist dispersedly on the surface of the internal electrode layer 2 and are exposed at a part of the internal electrode layer 2.

That is, in the laminated piezoelectric element, the weakest point in strength is the interface between the internal electrode layer 2 and the piezoelectric layer 1, and most of the portions that are damaged when bending stress is applied are the piezoelectric ceramic layer 1 and the internal electrode. This is the interface of the layer 2, and its fracture surface is divided into one in which the surface of the internal electrode layer 2 is exposed and one in which the surface of the piezoelectric ceramic layer 1 is exposed. When the fracture surface where the internal electrode layer 2 is exposed is observed by a backscattered electron image of a scanning electron microscope, the fracture surface where the internal electrode layer 2 is exposed contains the conductive paste as shown in FIG. The presence of the ceramic particles 7 remaining in the internal electrode layer 2 can be confirmed among the ceramic particles serving as the common material. 2A is a backscattered electron image photograph, and FIG. 2B is a schematic diagram thereof.

The ceramic particles 7 were sinter-bonded with the ceramic particles on the fracture surface side of the piezoelectric ceramic layer 1 before the fracture, but because the anchor effect with the internal electrode layer 2 was great. It remains on the surface side of the internal electrode layer 2. That is, the greater the proportion of the ceramic particles 7 having a large anchoring effect with the internal electrode layer 2, the greater the bonding strength between the piezoelectric ceramic layer 1 and the internal electrode layer 2.

The exposed area of such ceramic particles 7 can be measured by image processing (trade name: Luzex) of the ceramic particles 7 observed in a backscattered electron image of a scanning electron microscope. The exposed area of the ceramic particles present on the fracture surface is preferably 2% or more from the viewpoint of improving the interface strength between the piezoelectric ceramic layer 1 and the internal electrode layer 2. It is particularly desirable that the content be 4% or more.

The ceramic particles 7 are exposed on the surface of the internal electrode layer 2.
As described later, the PZT system piezoelectric ceramic
It is necessary to use powder that aggregates fine particles
is there. Of the ceramic particles 7 exposed on the surface of the internal electrode layer 2.
The exposed area is 2% or more on the entire surface of the internal electrode layer 2.
To have a specific surface area of 1.5 to 2.5 m²/ G of agglomerated powder
As a ceramic powder in the green sheet
Binder amount is 9 per 100 parts by mass of ceramic powder
This can be achieved by adjusting the amount to be less than or equal to the amount. Fine particles aggregate
To make the ceramic powder, the particle size of the primary raw material powder
In distribution D ₉₀Of 1.0 μm or less must be calcined
There is a point.

A method of manufacturing the laminated piezoelectric actuator of the present invention will be described. First, a PZT-based piezoelectric ceramic calcined powder in which fine particles are aggregated is manufactured as a raw material used for manufacturing the green sheet.

This PZT-based piezoelectric ceramic calcined powder is
In the particle size distribution, the primary raw material powder having D ₉₀ of 1.0 μm or less is calcined at a temperature of 900 ° C. or less, and the specific surface area is 1.5 to
It is prepared by wet pulverization or the like so that the weight becomes 2.5 m ² / g.

The piezoelectric ceramic calcined powder (ceramic powder) thus obtained is mixed with a binder made of an organic polymer such as acrylic resin, DBP (diotyl phthalate),
A slurry is prepared by mixing with a plasticizer such as DOP (dibutyl phthalate), and the slurry is prepared by a known tape molding method such as a doctor blade method or a calendar roll method to prepare a ceramic green sheet to be the piezoelectric ceramic layer 1. .

The amount of organic binder is 100 ceramic powder.
It is 9 parts by mass or less with respect to parts by mass.

Here, the PZT-based piezoelectric ceramic calcination powder is a piezoelectric ceramic material containing lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT) as a main component, and exhibits its piezoelectric characteristics. It is desirable that the piezoelectric strain constant d ₃₃ is high.

Next, a ceramic powder, a binder, a plasticizer, etc. are added as a co-material to the metal powder of silver-palladium to prepare an internal electrode paste, which is screen-printed on the upper surface of each ceramic green sheet. Then, the internal electrode pattern is formed on the green sheet by printing with a thickness of 1 to 40 μm.

Next, a plurality of ceramic green sheets on which internal electrode patterns are not formed are laminated, and thereafter,
A plurality of ceramic green sheets on which internal electrode patterns are formed are laminated, and thereafter, a plurality of ceramic green sheets on which internal electrode patterns are not formed are laminated to obtain a columnar laminated body.

Due to the influence of the internal electrode pattern, this columnar laminated body has a firing shrinkage rate in the active portion laminated body in which the internal electrode pattern is formed, as compared with the inactive portion laminated body in which the internal electrode pattern is not formed. Is likely to be large, and stacking faults such as delamination are likely to occur.

In order to avoid this stacking fault, for example, the green sheet used for the inactive portion has a conductive paste containing ceramic powder as an additive printed on its upper surface, or glass as a sintering aid. It is desirable to use those which are provided with a means for increasing the shrinkage rate, such as those containing the components.

Next, while heating the columnar laminate at 50 to 200 ° C., pressure is applied to integrate the columnar laminate. After the integrated columnar laminate is cut into a predetermined size,
The binder is removed at 300 to 800 ° C. for 5 to 40 hours, and the main firing is performed at 900 to 1100 ° C. for 2 to 5 hours to obtain the piezoelectric element body 1a. An end of the internal electrode layer 2 is exposed on the side surface of the piezoelectric element body 1a.

Thereafter, the piezoelectric ceramic layer 1 including the ends of the internal electrode layers 2 is provided on the two opposing side surfaces of the piezoelectric element body 1a.
Grooves are formed at every other layer at the end portions of the two side surfaces so that they alternate with each other, and an insulator 3 is embedded in the groove portions so that the internal electrode layers 2 can be alternately insulated every other layer.

After that, the piezoelectric ceramic layer 1 constituting the active portion layer
The inner electrode layer 2 and the outer electrode 4 are connected so that they are connected in parallel. The external electrode 4 is preferably one that easily expands and contracts in order to prevent the external electrode 4 from being damaged at the joint interface with the internal electrode layer 2 when the actuator expands and contracts,
For example, a metal or alloy having conductivity such as silver, nickel or copper, or a thermosetting conductor is used.

It is preferable that the insulator 3 is made of a material having a low elastic modulus that follows the displacement of the actuator, specifically, silicone rubber or the like, so that the insulating function is finally satisfied. For example, it may be embedded in the groove at any time before and after the formation of the external electrode 4. After that, the lead wire 6 is connected to the external electrode 4 to complete the laminated piezoelectric actuator of the present invention.

Then, a DC voltage of 0.1 to 3 kV / mm is applied to the pair of external electrodes 4 via the lead wires 6 to polarize the laminated piezoelectric element 1a, whereby a laminated piezoelectric actuator as a product is produced. Is completed, the lead wire 6 is connected to an external voltage supply unit, and the lead wire 6 and the external electrode 4 are connected.
When a voltage is applied to the internal electrode layer 2 via the, the respective piezoelectric ceramic layers 1 are largely displaced by the inverse piezoelectric effect, and thereby function as a fuel injection valve for an automobile, for example, to inject fuel and supply the fuel to the engine.

In the method for producing such a laminated piezoelectric element, the amount of organic binder can be reduced by producing a ceramic green sheet by using raw material powder having a small specific surface area in which fine particles are aggregated, and the green sheet at the time of binder removal processing can be reduced. It is possible to suppress the weakening of the adhesion strength between the electrode coating film and the electrode coating film, whereby the piezoelectric ceramic layer 1 is bonded to the internal electrode layer 2 with a strong anchor effect, and a laminated piezoelectric element having excellent bonding strength is obtained. You can Further, by producing a green sheet using ceramic powder in which fine particles are aggregated, the firing temperature can be lowered to 1100 ° C. or lower, which can reduce the evaporation of the lead component during firing, resulting in excellent displacement characteristics. A laminated piezoelectric element can be obtained.

FIG. 3 shows the injection device of the present invention.
In the figure, reference numeral 31 indicates a storage container. An injection hole 33 is provided at one end of the storage container 31, and a needle valve 35 that can open and close the injection hole 33 is stored in the storage container 31.

A fuel passage 37 is provided so as to be able to communicate with the injection hole 33. The fuel passage 37 is connected to an external fuel supply source so that fuel is always supplied to the fuel passage 37 at a constant high pressure. Therefore, when the needle valve 35 opens the injection hole 33, the fuel supplied to the fuel passage 37 is ejected at a constant high pressure into a fuel chamber (not shown) of the internal combustion engine.

The upper end of the needle valve 35 has a large diameter, and serves as a piston 41 slidable with a cylinder 39 formed in the container 31. The piezoelectric actuator 43 described above is stored in the storage container 31.

In such an injection device, when the piezoelectric actuator 43 is expanded by being applied with a voltage, the piston 41 is expanded.
Is pressed, the needle valve 35 closes the injection hole 33, and the supply of fuel is stopped. Further, when the voltage application is stopped, the piezoelectric actuator 43 contracts, and the disc spring 45
Pushes back the piston 41, and the injection hole 33 moves into the fuel passage 37.
Fuel injection is performed in communication with the.

[0044]

Example 1 A ceramic powder containing PZT as a main component and Yb, W, and Sr as sub-components was used. The mixture was wet-mixed, dried, and mesh-passed to obtain a particle size distribution of D ₉₀ A 0.8 μm primary raw material powder was obtained. The obtained primary raw material powder was calcined under the condition of 870 ° C. × 3 Hr and wet-ground so that the specific surface area was 2.1 m ² / g.

The raw material obtained by the wet pulverization, when observed with a scanning electron microscope, was a ceramic powder in which fine particles having an average particle size of 0.4 μm were aggregated as shown in FIG. An acrylic binder, a solvent, and a plasticizer were added to the ceramic powder thus obtained to prepare a slurry, and a thickness of 150 μm was obtained by a slip casting method.
m ceramic green sheets were produced. Here, the amount of the organic binder was the minimum necessary amount that does not cause dry cracks in the green sheet, and in this case, it was 8 parts by mass with respect to 100 parts by mass of the ceramic powder.

On the upper surface of the ceramic green sheet thus obtained, a silver-palladium alloy, an organic binder, a ceramic powder as a co-material having the same composition as the ceramic powder used for the ceramic green sheet, and a solvent were placed. The internal electrode paste containing the above was printed to form an internal electrode pattern.

Thereafter, 15 layers of ceramic green sheets having a thickness of 150 μm are laminated, 300 layers of ceramic green sheets having internal electrode patterns are laminated on the upper surface thereof, and 15 layers of ceramic green sheets having a thickness of 150 μm are formed on the upper surface. Laminated. However, for the ceramic green sheet on which the internal electrode pattern used as the inactive portion is not formed, the shrinkage rate during firing becomes large,
As a sintering aid, 1 part by mass of Si component was added to 100 parts by mass of the ceramic powder.

Then, pressure was applied while heating at 100 ° C., cutting, binder removal and firing were performed to obtain a columnar laminate. Here, the debye temperature was 400 ° C., and the firing temperature was a temperature at which the laminate density could satisfy 7.8 g / cm ³ or more, and in Example 1, it was 1050 ° C.

After that, on the two side surfaces of the piezoelectric element body, grooves are formed at every other layer from the dicing device so that the end portions of the piezoelectric ceramic layer including the inner electrode layer end portions are staggered on the two side surfaces, The groove was filled with silicone rubber as an insulator. Then, a thermosetting conductor was formed in a strip shape as an external electrode on the other end surface of the non-insulated internal electrode layer, and heat treatment was performed at 200 ° C. After that, a lead wire is connected and silicon rubber is coated on the outer peripheral surface of the actuator by dipping, and then a DC electric field of 3 kV / mm is applied to the external electrode through the lead wire for 15 minutes for polarization treatment. A laminated piezoelectric actuator as shown in 1 was manufactured.

The laminated piezoelectric actuator thus obtained has 15
As a result of applying a DC voltage of 0 V, a displacement amount of 43 μm was obtained in the stacking direction. Further, a sine wave voltage of 0 to +150 V was applied to this actuator at room temperature at a frequency of 60 Hz, and a drive test of 5 × 10 ⁹ cycles was conducted. As a result, no change in displacement was observed even after 5 × 10 ⁹ cycles.

Further, as the strength evaluation of the bonding interface between the piezoelectric ceramic layer and the internal electrode layer, the bending strength of the laminated piezoelectric element was evaluated. As the evaluation sample, a JIS bending test piece (width 4 mm, thickness 3 mm, length 40 mm) was cut out from the sample subjected to the drive test, based on JIS R 1601.
It was evaluated by 4-point bending. In addition, in the fracture surface of the laminated piezoelectric element whose bending strength was evaluated, the existence ratio of the ceramic particles remaining in the internal electrode layer 2 among the ceramic particles contained in the conductive paste was evaluated. The results are shown in Table 1.
It was shown to. Example 2 A multilayer piezoelectric element was produced in the same manner as in Example 1 using a raw material that was calcinated at a temperature of 850 ° C. and pulverized to have a specific surface area of 2.5 m ² / g. At this time, the amount of binder required was 8.5 parts by mass, and the laminate density was 7.8 g / cm ^3.
The firing temperature was 1000 ° C. With respect to the obtained laminated piezoelectric element, the displacement amount, the drive test (durability), the bending strength, and the exposure ratio of the ceramic particles 7 remaining on the internal electrode on the fracture surface were evaluated in the same manner as in Example 1. The results are shown in Table 1. Example 3 A multilayer piezoelectric element was produced in the same manner as in Example 1 except that the calcination temperature was set to 900 ° C. and the raw material was pulverized to have a specific surface area of 1.5 m ² / g. At this time, the required amount of binder was 6.5 parts by mass, and the laminate density was 7.8 g / cm ^3.
The firing temperature was 1150 ° C. With respect to the obtained laminated piezoelectric element, the displacement amount, the driving test, the bending strength, and the existence ratio of the ceramic particles 7 remaining in the internal electrode on the fracture surface were evaluated in the same manner as in Example 1.
The results are shown in Table 1. Example 4 A multilayer piezoelectric element was produced in the same manner as in Example 1 by using the raw material that was pulverized so that the calcination temperature was 830 ° C. and the specific surface area was 2.8 m ² / g. At this time, the amount of binder required was 9.0 parts by mass, and the density of the laminate was 7.8 g / cm ^3.
The firing temperature was 1000 ° C. With respect to the obtained laminated piezoelectric element, the displacement amount, the driving test, the bending strength, and the existence ratio of the ceramic particles 7 remaining in the internal electrode layer 2 on the fracture surface were evaluated in the same manner as in Example 1. The results are shown in Table 1. Comparative Example 1 A primary raw material powder having a D ₉₀ of 1.3 μm in a particle size distribution was 900 ° C.
Calcination was performed under the condition of × 3Hr, and the specific surface area was 3.2 m ² /
Wet pulverization was performed so as to obtain g.

The raw material obtained by the wet pulverization has a non-agglomerated average particle size of 0.
It was a 9 μm ceramic powder. Using this ceramic powder, a laminated piezoelectric element was manufactured in the same manner as in Example 1. At this time, the required amount of the binder was 10.0 parts by mass, and firing was performed at 1000 ° C., which is a firing temperature at which the laminated body has a density of 7.8 g / cm ³ . However, Comparative Example 1
In the sample No. 1, delamination occurred after the binder removal treatment, and the sample was divided during the firing set. Therefore, the bending strength and the like could not be evaluated. When the cross section of the sample after firing was observed, the entire surface of the internal electrode was covered with ceramic particles. This is because the co-material in the internal electrode layer was extruded to the surface of the internal electrode layer having a divided cross section by firing. The results are shown in Table 1.

[0053]

[Table 1]

From this Table 1, it can be seen that the bending strength increases as the proportion of the ceramic particles 7 remaining in the internal electrode layer 2 on the fracture surface increases. Particularly, in Examples 1 to 3 in which the area ratio is larger than 4%, the bending strength is 75 MPa or more. In addition, the firing temperature is 115
It can be seen that in Examples 1, 2 and 4 in which the firing temperature is 1100 ° C. or less, the displacement amount is as large as 41 μm or more as compared with Example 3 at 0 ° C. This is because the low firing temperature suppresses the evaporation of the lead component during firing, resulting in excellent displacement characteristics of the piezoelectric ceramic.

[0055]

According to the laminated piezoelectric element of the present invention, since the ceramic particles are exposed on a part of the surface of the internal electrode,
By sintering the ceramic particles with the ceramic particles of the piezoelectric ceramic layer, a strong anchor effect can be realized, and the bonding strength between the internal electrode layer and the piezoelectric ceramic layer can be improved. As a result, it is possible to provide a laminated piezoelectric element having excellent durability capable of suppressing damage at the interface between the internal electrode layer and the piezoelectric ceramic layer.

[Brief description of drawings]

FIG. 1 is a view showing a laminated piezoelectric element of the present invention, (a)
Is a perspective view and (b) is a vertical cross-sectional view taken along the line AA ′ of (a).

FIG. 2 is a view showing a surface of an internal electrode layer in a fracture surface of a multilayer piezoelectric element of the present invention, (a) is a backscattered electron image photograph,
(B) is the schematic diagram.

FIG. 3 is an explanatory view showing an injection device of the present invention.

FIG. 4 is a micrograph showing a ceramic powder used in the production method of the present invention.

[Explanation of symbols]

1 ... Piezoelectric layer 2 Internal electrode layer 7 ... Ceramic particles partially embedded in the internal electrode layer 31 ... Storage container 33 ... Injection hole 35 ... Needle valve 43 ... Piezoelectric actuator

Claims (6)

[Claims] 1. A laminated piezoelectric element in which a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers are alternately laminated and cofired, the piezoelectric ceramic layers containing ceramic particles, and the piezoelectric ceramic layers In the fracture surface at the interface with the internal electrode layer,
A laminated piezoelectric element, wherein ceramic particles partially embedded in the internal electrode layer are exposed on the surface of the internal electrode layer. 2. The laminated piezoelectric element according to claim 1, wherein the exposed area of the ceramic particles exposed on the surface of the internal electrode layer is 2% or more on the surface of the internal electrode layer. 3. A conductive paste containing a metal powder, a ceramic powder and an organic solvent is applied on a green sheet containing a ceramic powder in which a plurality of fine particles are aggregated, an organic binder and an organic solvent. A step of forming an electrode coating film with a plurality of layers, a step of laminating a plurality of green sheets having the electrode coating film formed thereon to form a layered body by pressurizing, and a step of debinding the layered body and firing the layered body. A method of manufacturing a laminated piezoelectric element, comprising: 4. The ceramic powder constituting the green sheet is composed of PZT-based piezoelectric calcination powder, and the specific surface area of the ceramic powder is 1.5 to 2.5 m ² / g. Manufacturing method of laminated piezoelectric element. 5. The organic binder in the green sheet is 9 parts by mass or less based on 100 parts by mass of the ceramic powder in the green sheet.
A method for producing the described laminated piezoelectric element. 6. A storage container having an injection hole, and the laminated piezoelectric element according to claim 1 or 2 housed in the storage container.
An ejection device comprising: a valve for ejecting a liquid from the ejection hole by driving the laminated piezoelectric element.