JP4373643B2 - LAMINATED PIEZOELECTRIC ELEMENT, ITS MANUFACTURING METHOD, AND INJECTION DEVICE - Google Patents

Description

【００５４】
この表１から、破断面において内部電極層２に留まっているセラミック粒子７の存在割合が大きいほど、曲げ強度が強くなっていることが分かる。特に面積比率が４％より大きい実施例１〜３では、曲げ強度が７５ＭＰａ以上を示している。また、焼成温度が１１５０℃の実施例３に対して焼成温度が１１００℃以下である実施例１、２、４は、変位量が４１μｍ以上と大きくなっていることが分かる。これは、焼成温度が低いことにより焼成時に鉛成分の蒸発が抑制され、圧電磁器の変位特性が優れたものとなっているためである。
【００５５】
【発明の効果】
本発明の積層型圧電素子によれば、内部電極層に一部が埋設されたセラミック粒子が、内部電極層側の破断面に分散して存在しているとともに、内部電極層側の破断面に露出するセラミック粒子の割合が、内部電極層側の破断面中２．０〜６．１％であるため、このセラミック粒子が、圧電磁器層のセラミック粒子と焼結することで、強いアンカー効果を実現し、内部電極層と圧電磁器層との接合強度を向上できる。これにより、内部電極層と圧電磁器層との界面における破損を抑制できる耐久性に優れた積層型圧電素子を提供することができる。
【図面の簡単な説明】
【図１】本発明の積層型圧電素子を示すもので、（ａ）は斜視図、（ｂ）は（ａ）のＡ−Ａ’線に沿った縦断面図である。
【図２】本発明の積層型圧電素子の破断面における内部電極層表面を示すもので、（ａ）は反射電子像写真、（ｂ）はその模式図である。
【図３】本発明の噴射装置を示す説明図である。
【図４】本発明の製法に用いるセラミック粉末を示す顕微鏡写真である。
【符号の説明】
１・・・圧電磁器層
２・・・内部電極層
７・・・内部電極層に一部が埋設されたセラミック粒子
３１・・・収納容器
３３・・・噴射孔
３５・・・ニードルバルブ
４３・・・圧電アクチュエータ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer piezoelectric element, a method for manufacturing the same, and an injection device, for example, a multilayer piezoelectric element used for a precision positioning device such as an automobile fuel injection device and an optical device, a drive element for vibration prevention, and a method for manufacturing the same. The present invention relates to an injection device.
[0002]
[Prior art]
Conventionally, a multilayer piezoelectric actuator in which piezoelectric ceramic layers and internal electrode layers are alternately stacked is known as a multilayer piezoelectric element. The laminated piezoelectric actuators are classified into two types: a simultaneous 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 the piezoelectric ceramic layer. Piezoelectric ceramics are widely used. The co-fired multilayer piezoelectric element is formed by pressing 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 having a conductive paste printed on one side are pressed, debinder, It is obtained by firing and forming external electrodes alternately connected to the internal electrode layers on the two side surfaces of the sintered body.
[0003]
In the co-fired multilayer piezoelectric element, it is easy to break at the joint interface between the internal electrode layer and the piezoelectric ceramic layer due to an impact, so in order to improve the impact resistance, for example, in Japanese Patent Laid-Open No. 4-299588, the internal electrode By incorporating ceramic powder with controlled particle size in the layer as a co-material, and effectively forming a bridge that connects the two piezoelectric ceramic layers sandwiching the internal electrode layer, a highly reliable device for impact is obtained. It is described that it can.
[0004]
As the internal electrode layer, platinum, palladium, or an alloy of silver and palladium is used depending on the firing temperature of the PZT-based piezoelectric ceramic. However, from the viewpoint of cost reduction, a lower firing temperature is required. ing. In addition, lowering the firing temperature is very important from the standpoint of the characteristics of suppressing evaporation of the lead component contained in the piezoelectric ceramic layer and preventing the deterioration of the displacement characteristics. The lowering of the firing temperature is achieved by making the ceramic powder used for producing the green sheet finer.
[0005]
[Problems to be solved by the invention]
However, in the multilayer piezoelectric actuator, since the firing temperature is lowered to 1100 ° C. or lower, it is necessary to produce a green sheet using a ceramic powder having a specific surface area of about 3 to 4 m ² / g or more. Therefore, it has been necessary to contain 9 parts by mass or more of an organic binder with respect to 100 parts by mass of the ceramic powder according to the specific surface area of the raw material ceramic powder. This organic binder needs to be removed, but if it contains a large amount of organic binder in this way, a large amount of gas is released from between the weakest electrode coating film and green sheet as the bonding surface during binder removal processing. The interface between the electrode coating film and the green sheet weakens, and ceramic particles as a co-material in the electrode coating film are extruded from the electrode coating film (internal electrode layer) during firing, and the internal electrode layer and the piezoelectric ceramic layer There was a problem that the bonding strength was lowered.
[0006]
That is, as described above, the gap between the electrode coating film and the green sheet is weakened by a large amount of gas generated at the time of removing the binder. Ceramic powder as a material is extruded between the electrode coating film and the green sheet from the electrode coating film, a part of the internal electrode layer is embedded, and ceramic particles bonded and sintered with the ceramic particles of the piezoelectric ceramic layer are reduced. As a result, the anchor effect by the ceramic particles in the internal electrode layer is reduced, the bonding strength between the internal electrode layer and the piezoelectric ceramic layer is reduced, and the laminated piezoelectric actuator is easily broken.
[0007]
The present invention relates to a laminated piezoelectric element having excellent durability capable of improving the bonding strength between an internal electrode layer and a piezoelectric ceramic layer and suppressing damage at the interface between the internal electrode layer and the piezoelectric ceramic layer, a manufacturing method thereof, and an injection device The purpose is to provide.
[0008]
[Means for Solving the Problems]
The 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 fired simultaneously, wherein the internal electrode layer contains ceramic particles , when serial broken at the interface between the piezoelectric ceramic layers and the internal electrode layer, the fracture surface of the internal electrode layer side, together with the ceramic particles partially in the internal electrode layer is embedded is present dispersed, the The exposed area of the ceramic particles exposed on the fracture surface on the internal electrode layer side is 2.0 to 6.1% in the fracture surface on the internal electrode layer side .
[0009]
In the present invention, since the ceramic particles partially embedded in the internal electrode layer are dispersed on the fracture surface on the internal electrode layer side , the ceramic particles are sintered with the ceramic particles of the piezoelectric ceramic layer. Thus, a strong anchor effect can be realized, and the bonding strength between the internal electrode layer and the piezoelectric ceramic layer can be improved. Further, the multi-layer piezoelectric element of the present invention, said the exposed area of the ceramic particles exposed on the fracture surface of the internal electrode layer side is 2.0 to 6.1% in fracture surfaces of the internal electrode layer side To do. Thus, since the ratio of the ceramic particles exposed to the fracture surface on the internal electrode layer side is 2.0 to 6.1% in the fracture surface on the internal electrode layer side, the bonding force of the piezoelectric ceramic layer with the ceramic particles Is strengthened, and the bonding strength between the internal electrode layer and the piezoelectric ceramic layer can be improved.
[0010]
The production method of the multilayer piezoelectric element of the present invention is made of a ceramic powder having a specific surface area of 1.5 to 2.5 m ² / g made of PZT piezoelectric calcined powder in which a plurality of fine particles are aggregated, and 100 parts by mass of the ceramic powder. On the other hand, a step of forming an electrode coating film by applying a conductive paste containing a metal powder, a ceramic powder, and an organic solvent on a green sheet containing an organic binder of 9 parts by mass or less and an organic solvent And a step of laminating a plurality of the green sheets on which the electrode coating film is formed and pressurizing to form a laminate, and a step of removing the binder from the laminate and firing at 1100 ° C. or lower. Features.
[0011]
In such a method of manufacturing a laminated piezoelectric element, ceramic powder made of PZT-based piezoelectric calcined powder in which a plurality of fine particles are aggregated is used, so that ceramic powder in which fine particles are dispersed (non-aggregated ceramic powder) is used. The specific surface area can be reduced to 1.5 to 2.5 m ² / g, and the amount of the organic binder contained in the green sheet can be reduced to 9 parts by mass or less with respect to 100 parts by mass of the ceramic powder . As a result, gas emission at the time of binder removal is reduced, and weakening between the electrode coating film and the green sheet is suppressed, thereby suppressing the extrusion of ceramic particles of the electrode coating film into the green sheet, partly A large number of ceramic particles embedded in the internal electrode layer are formed, and the ceramic particles are bonded and sintered with the ceramic particles of the piezoelectric ceramic layer, thereby strengthening the bonding between the internal electrode layer and the piezoelectric ceramic layer.
[0012]
Moreover, since the ceramic powder in which a plurality of fine particles are aggregated is used for the green sheet for forming the piezoelectric ceramic layer, low temperature firing at 1100 ° C. or lower can be achieved.
[0013]
In particular, by using a PZT-based piezoelectric calcined powder (ceramic powder) obtained by calcining and agglomerating fine powder, and having a specific surface area of 1.5 to ^2.5 m ² / g, a green sheet is obtained. The amount of the organic binder in the ceramic powder can be 9 parts by mass or less with respect to 100 parts by mass of the ceramic powder, weakening between the electrode coating film and the green sheet can be suppressed, and the firing temperature can be 1100 ° C. or less. . As a result, the bonding strength between the internal electrode layer and the piezoelectric ceramic layer can be improved, the evaporation of the lead component contained in the piezoelectric ceramic layer can be suppressed, and a multilayer piezoelectric element with excellent displacement characteristics can be obtained. Obtainable.
[0014]
An injection device of the present invention includes a storage container having an injection hole, the stacked piezoelectric element stored in the storage container, and a valve for ejecting liquid from the injection hole by driving the stacked piezoelectric element. It is made.
[0015]
In such an injection device, as described above, the displacement characteristics of the multilayer piezoelectric element are excellent, and the damage at the interface between the internal electrode layer and the piezoelectric ceramic layer is suppressed, so that excellent injection characteristics and long-term reliability are achieved. Can be improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
1A and 1B show an embodiment of a laminated piezoelectric element comprising a laminated piezoelectric actuator of the present invention, wherein FIG. 1A is a perspective view and FIG. 1B is a longitudinal section taken along line AA ′ of FIG. FIG.
[0017]
As shown in FIG. 1, the co-fired multilayer piezoelectric element of the present invention has two opposing piezoelectric element bodies 1a formed by alternately laminating a plurality of piezoelectric ceramic layers 1 and a plurality of internal electrode layers 2. In the side surface, the insulator 3 is formed every other layer at the end of the internal electrode layer 2, and the end of the internal electrode layer 2 not formed with the insulator 3 is connected to the same external electrode 4. Yes.
[0018]
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 in the stacking direction of the piezoelectric element body 1a.
[0019]
In order to prevent creeping discharge between the internal electrode layers 2 and apply a large voltage, it is desirable to coat the outer peripheral surface of the co-fired multilayer piezoelectric element with an insulating material such as silicone rubber.
[0020]
In the multilayer piezoelectric element of the present invention, when the piezoelectric element body 1a is damaged by bending stress or the like, the piezoelectric element body 1a is broken at the interface between the piezoelectric ceramic layer 1 and the internal electrode layer 2. FIG. As shown, the ceramic particles 7 partially embedded in the internal electrode layer 2 are exposed on the surface of the internal electrode layer 2. The ceramic particles 7 are dispersed on the surface of the internal electrode layer 2 and are exposed on a part of the internal electrode layer 2.
[0021]
That is, in the laminated piezoelectric element, the weakest part is the interface between the internal electrode layer 2 and the piezoelectric layer 1, and most of the parts that are damaged when a bending stress is applied are between the piezoelectric ceramic layer 1 and the internal electrode layer 2. It is an interface, 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 with a reflection electron image of a scanning electron microscope, the fracture surface where the internal electrode layer 2 is exposed is contained in the conductive paste as shown in FIG. The presence of the ceramic particles 7 remaining on the internal electrode layer 2 can be confirmed among the ceramic particles as the common material. 2A is a reflected electron image photograph, and FIG. 2B is a schematic diagram thereof.
[0022]
The ceramic particles 7 were sintered and bonded to the ceramic particles on the fracture surface side of the piezoelectric ceramic layer 1 before breaking, but because the anchor effect with the internal electrode layer 2 was large, the internal electrode layer 2 remains on the surface side. That is, the greater the proportion of 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.
[0023]
Such an exposed area of the ceramic particles 7 can be measured by image processing (trade name: Luzex) of the ceramic particles 7 observed in the reflection electron image of the 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. In particular, it is desirable to be 4% or more.
[0024]
In order to expose the ceramic particles 7 on the surface of the internal electrode layer 2, as described later, it is necessary to use a PZT-based piezoelectric ceramic powder in which fine particles are aggregated. In order to set the exposed area of the ceramic particles 7 exposed on the surface of the internal electrode layer 2 to 2% or more in the entire surface of the internal electrode layer 2, agglomerated powder having a specific surface area of 1.5 to 2.5 m ² / g is green. It can be achieved by using it as a ceramic powder in the sheet and setting the amount of organic binder to 9 parts by mass or less with respect to 100 parts by mass of the ceramic powder. In order to produce a ceramic powder in which fine particles are agglomerated, it is necessary to calcinate a powder having a D ₉₀ of 1.0 μm or less in the particle size distribution of the primary material powder.
[0025]
A method for producing the multilayer piezoelectric actuator of the present invention will be described. First, a PZT piezoelectric ceramic calcined powder in which fine particles are aggregated is produced as a raw material used for producing a green sheet.
[0026]
This PZT-based piezoelectric ceramic calcined powder has a specific surface area of 1.5 to 2.5 m ² / g by calcining a primary raw material powder having a particle size distribution of D ₉₀ of 1.0 μm or less at a temperature of 900 ° C. or less. It is produced by wet pulverization or the like.
[0027]
The piezoelectric ceramic calcined powder (ceramic powder) thus obtained is mixed with a binder made of an organic polymer such as acrylic and a plasticizer such as DBP (diethyl phthalate) or DOP (dibutyl phthalate). Then, a slurry is prepared, and a ceramic green sheet to be the piezoelectric ceramic layer 1 is prepared from the slurry by a tape molding method such as a known doctor blade method or calendar roll method.
[0028]
The amount of the organic binder is 9 parts by mass or less with respect to 100 parts by mass of the ceramic powder.
[0029]
Here, the PZT-based piezoelectric ceramic calcined powder is a piezoelectric ceramic material mainly composed of lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT), and a piezoelectric strain constant indicating its piezoelectric characteristics. what d ₃₃ is high is desirable.
[0030]
Next, an internal electrode paste is prepared by adding and mixing ceramic powder, a binder, a plasticizer, and the like as a co-material to the metal powder composed of silver-palladium. Printing is performed to a thickness of 40 μm, and an internal electrode pattern is formed on the green sheet.
[0031]
Next, a plurality of ceramic green sheets on which no internal electrode pattern is formed are stacked, then a plurality of ceramic green sheets on which the internal electrode pattern is formed are stacked, and then the internal electrode pattern is formed. A plurality of non-ceramic green sheets are laminated to obtain a columnar laminate.
[0032]
Due to the influence of the internal electrode pattern, this columnar laminate has a larger firing shrinkage ratio in the active portion laminate in which the internal electrode pattern is not formed than in the inactive portion laminate in which the internal electrode pattern is not formed. It is easy to cause stacking faults such as delamination.
[0033]
In order to avoid this stacking fault, for example, the green sheet used in the inactive part is printed on the upper surface of a conductive paste containing ceramic powder as a co-material, or contains a glass component as a sintering aid. It is desirable to use a device that has a means for increasing the shrinkage rate, such as a device that performs the above.
[0034]
Next, pressure is applied while heating the columnar laminate at 50 to 200 ° C. to integrate the columnar laminate. After the integrated columnar laminate is cut to a predetermined size, binder removal is performed at 300 to 800 ° C. for 5 to 40 hours, and main baking is performed at 900 to 1100 ° C. for 2 to 5 hours. The piezoelectric element body 1a is obtained. The end of the internal electrode layer 2 is exposed on the side surface of the piezoelectric element body 1a.
[0035]
Thereafter, grooves are formed in every other layer on the two opposing side surfaces of the piezoelectric element main body 1a so as to alternate between the two side surfaces at the end portions of the piezoelectric ceramic layer 1 including the end portions of the internal electrode layer 2. By embedding the insulator 3, the internal electrode layers 2 can be alternately insulated every other layer.
[0036]
Thereafter, the internal electrode layer 2 and the external electrode 4 are connected so that each of the piezoelectric ceramic layers 1 constituting the active part layer is connected in parallel. The external electrode 4 is suitable to be easily expanded and contracted in order to make it difficult to break at the joint interface with the internal electrode layer 2 when the actuator expands and contracts. For example, the external electrode 4 has conductivity such as silver, nickel, and copper. The provided metal or alloy, or a thermosetting conductor is used.
[0037]
Further, the insulator 3 is preferably made of a material having a low elastic modulus that follows the displacement of the actuator, specifically, silicone rubber or the like. The groove may be embedded at any time before and after the formation of the electrode 4. Thereafter, the lead wire 6 is connected to the external electrode 4 to complete the multilayer piezoelectric actuator of the present invention.
[0038]
A direct current 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 multilayer piezoelectric element 1a, thereby completing a multilayer piezoelectric actuator as a product. When the lead wire 6 is connected to an external voltage supply unit and a voltage is applied to the internal electrode layer 2 via the lead wire 6 and the external electrode 4, each piezoelectric ceramic layer 1 is greatly displaced by the inverse piezoelectric effect, Thus, for example, it functions as an automobile fuel injection valve that injects and supplies fuel to the engine.
[0039]
In such a multilayer piezoelectric element manufacturing method, the amount of organic binder can be reduced by producing a ceramic green sheet using raw material powder with a small specific surface area in which fine particles are aggregated. The weakening of the adhesion strength between the films can be suppressed, whereby the piezoelectric ceramic layer 1 is bonded to the internal electrode layer 2 by a strong anchor effect, and a laminated piezoelectric element having excellent bonding strength can be obtained. In addition, 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, thereby reducing evaporation of the lead component during firing, and thus excellent displacement characteristics. A laminated piezoelectric element can be obtained.
[0040]
FIG. 3 shows an injection device according to the present invention. In the figure, reference numeral 31 denotes 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.
[0041]
A fuel passage 37 is provided in the injection hole 33 so as to be able to communicate. The fuel passage 37 is connected to an external fuel supply source, and 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 formed to be injected into a fuel chamber (not shown) of the internal combustion engine at a constant high pressure.
[0042]
Further, the upper end portion of the needle valve 35 has a large diameter, and serves as a piston 41 slidable with a cylinder 39 formed in the storage container 31. In the storage container 31, the piezoelectric actuator 43 described above is stored.
[0043]
In such an injection device, when the piezoelectric actuator 43 is extended by applying a voltage, the piston 41 is pressed, the needle valve 35 closes the injection hole 33, and the supply of fuel is stopped. When the application of voltage is stopped, the piezoelectric actuator 43 contracts, the disc spring 45 pushes back the piston 41, and the injection hole 33 communicates with the fuel passage 37 so that fuel is injected.
[0044]
【Example】
Example 1
A ceramic powder containing PZT as the main component and Yb, W, Sr as subcomponents is selected, wet mixed, dried, and mesh-passed. The primary powder with a particle size distribution of D ₉₀ of 0.8 μm Got. The obtained primary raw material powder was calcined under conditions of 870 ° C. × 3 Hr, and wet pulverized so that the specific surface area was 2.1 m ² / g.
[0045]
When the raw material obtained by wet pulverization was observed with a scanning electron microscope, it was a ceramic powder in which fine particles having an average particle diameter 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 ceramic green sheet having a thickness of 150 μm was prepared by a slip casting method. Here, the amount of the organic binder was a minimum necessary amount that did not cause dry cracks in the green sheet. In this case, the amount was 8 parts by mass with respect to 100 parts by mass of the ceramic powder.
[0046]
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 an internal electrode containing a solvent The paste was printed to form an internal electrode pattern.
[0047]
Thereafter, 15 layers of ceramic green sheets having a thickness of 150 μm were laminated, 300 layers of ceramic green sheets having an internal electrode pattern formed thereon were laminated, and 15 layers of ceramic green sheets having a thickness of 150 μm were laminated on the upper surface. However, in the ceramic green sheet on which the internal electrode pattern used as the inactive part is not formed, 1 part by mass of 100 parts by mass of the ceramic powder is used as a sintering aid so as to increase the shrinkage rate during firing. Si component was added.
[0048]
And it pressurized, heating at 100 degreeC, and the columnar laminated body was obtained by cut, a binder removal, and baking. Here, the debuy 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.
[0049]
Thereafter, grooves are formed on the two side surfaces of the piezoelectric element body at intervals of the dicing device so as to alternate between the two side surfaces at the end portions of the piezoelectric ceramic layer including the inner electrode layer end portions. Silicone rubber was filled as an insulator. Thereafter, a thermosetting conductor was formed in a strip shape as an external electrode on the other end face of the non-insulated internal electrode layer, and a heat treatment at 200 ° C. was performed. Thereafter, lead wires are connected, and the outer peripheral surface of the actuator is coated with silicon rubber by dipping, and then a 3 kV / mm DC electric field is applied to the external electrodes via the lead wires for 15 minutes to perform polarization treatment. A laminated piezoelectric actuator as shown in FIG.
[0050]
As a result of applying a DC voltage of 150 V to the obtained multilayer piezoelectric actuator, a displacement 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 a frequency of 60 Hz at room temperature, and a driving test of 5 × 10 ⁹ cycles was performed. As a result, no change in displacement was observed even after 5 × 10 ⁹ cycles.
[0051]
In addition, the bending strength of the multilayer piezoelectric element was evaluated as the strength evaluation of the bonding interface between the piezoelectric ceramic layer and the internal electrode layer. An evaluation sample was obtained by cutting out a JIS bending test piece (width 4 mm, thickness 3 mm, length 40 mm) from the sample subjected to the driving test based on JIS R 1601, and evaluated it by four-point bending. Further, the ratio of the ceramic particles remaining in the internal electrode layer 2 among the ceramic particles contained in the conductive paste was evaluated on the fracture surface of the multilayer piezoelectric element whose bending strength was evaluated. The results are shown in Table 1.
Example 2
A laminated piezoelectric element was produced in the same manner as in Example 1 using raw materials that were pulverized so that the calcining temperature was 850 ° C. and the specific surface area was 2.5 m ² / g. At this time, the necessary amount of the binder was 8.5 parts by mass, and the laminate was fired at 1000 ° C., which is a firing temperature at which the laminate density becomes 7.8 g / cm ³ . The obtained multilayer piezoelectric element was evaluated in the same manner as in Example 1 for the amount of displacement, the drive test (durability), the bending strength, and the exposure ratio of the ceramic particles 7 remaining on the internal electrodes on the fracture surface. The results are shown in Table 1. Example 3
A laminated piezoelectric element was produced in the same manner as in Example 1 using raw materials that were pulverized to a calcining temperature of 900 ° C. and a specific surface area of 1.5 m ² / g. At this time, the necessary binder amount was 6.5 parts by mass, and the laminate was fired at 1150 ° C., which is a firing temperature at which the laminate density becomes 7.8 g / cm ³ . About the obtained multilayer piezoelectric element, the displacement amount, the drive test, the bending strength, and the existence ratio of the ceramic particles 7 remaining on the internal electrode in the fracture surface were evaluated in the same manner as in Example 1. The results are shown in Table 1.
Example 4
A laminated piezoelectric element was produced in the same manner as in Example 1 using raw materials that were pulverized so that the calcining temperature was 830 ° C. and the specific surface area was 2.8 m ² / g. At this time, the necessary binder amount was 9.0 parts by mass, and the laminate was fired at 1000 ° C., which is a firing temperature at which the laminate density becomes 7.8 g / cm ³ . For the obtained multilayer piezoelectric element, the displacement amount, the driving test, the bending strength, and the existence ratio of the ceramic particles 7 remaining on the internal electrode layer 2 in the fracture surface were evaluated in the same manner as in Example 1. The results are shown in Table 1.
Comparative Example 1
The primary raw material powder having a particle size distribution of D ₉₀ of 1.3 μm was calcined under the condition of 900 ° C. × 3 Hr, and wet pulverized so that the specific surface area was 3.2 m ² / g.
[0052]
When observed with a scanning electron microscope, the raw material obtained by the wet pulverization was a ceramic powder having an average particle diameter of 0.9 μm and not agglomerated. Using this ceramic powder, a multilayer piezoelectric element was produced in the same manner as in Example 1. At this time, the necessary binder amount was 10.0 parts by mass, and the laminate was fired at 1000 ° C., which is the firing temperature at which the density of the laminate was 7.8 g / cm ³ . However, in the sample of Comparative Example 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 sectional surface of the sample after firing was observed, the entire surface of the internal electrode was covered with ceramic particles. This is because the common material in the internal electrode layer was extruded to the surface of the internal electrode layer in the divided section by firing. The results are shown in Table 1.
[0053]
[Table 1]

[0054]
From Table 1, it can be seen that the bending strength increases as the existence ratio of the ceramic particles 7 remaining on the internal electrode layer 2 in the fracture surface increases. Particularly in Examples 1 to 3, where the area ratio is larger than 4%, the bending strength is 75 MPa or more. Moreover, it turns out that the displacement amount is large with 41 micrometers or more in Example 1,2,4 whose baking temperature is 1100 degrees C or less with respect to Example 3 whose baking temperature is 1150 degreeC. This is because the low firing temperature suppresses evaporation of the lead component during firing, and the displacement characteristics of the piezoelectric ceramic are excellent.
[0055]
【The invention's effect】
According to the multilayer piezoelectric element of the present invention, the ceramic particles partially embedded in the internal electrode layer are dispersed on the internal electrode layer side fracture surface, and the internal electrode layer side fracture surface is present. Since the ratio of the exposed ceramic particles is 2.0 to 6.1% in the fracture surface on the internal electrode layer side, the ceramic particles sinter with the ceramic particles of the piezoelectric ceramic layer, thereby providing a strong anchor effect. It is possible to improve the bonding strength between the internal electrode layer and the piezoelectric ceramic layer. Thereby, it is possible to provide a laminated piezoelectric element with excellent durability capable of suppressing breakage at the interface between the internal electrode layer and the piezoelectric ceramic layer.
[Brief description of the drawings]
1A and 1B show a multilayer piezoelectric element according to the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a longitudinal sectional view taken along line AA ′ of FIG.
FIGS. 2A and 2B show a surface of an internal electrode layer at a fracture surface of the multilayer piezoelectric element of the present invention, wherein FIG. 2A is a reflected electron image photograph, and FIG.
FIG. 3 is an explanatory view showing an injection device of the present invention.
FIG. 4 is a photomicrograph showing ceramic powder used in the production method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric ceramic layer 2 ... Internal electrode layer 7 ... Ceramic particle 31 partially embedded in the internal electrode layer ... Storage container 33 ... Injection hole 35 ... Needle valve 43 ..Piezoelectric actuator

Claims (3)

A laminated piezoelectric element in which a plurality of piezoelectric ceramic layers and a plurality of internal electrode layers are alternately laminated and fired simultaneously, wherein the internal electrode layer includes ceramic particles, and the piezoelectric ceramic layer and the internal electrode layer when fractured at the interface, the fracture surface of the internal electrode layer side, together with the ceramic particles partially embedded in the inner electrode layer is present in a dispersed and exposed on the fracture surfaces of the internal electrode layer side An exposed area of the ceramic particles is 2.0 to 6.1% in the fracture surface on the internal electrode layer side . A ceramic powder comprising a PZT-based piezoelectric calcined powder in which a plurality of fine particles are aggregated and having a specific surface area of 1.5 to 2.5 m ² / g, an organic binder of 9 parts by mass or less with respect to 100 parts by mass of the ceramic powder , on the green sheet containing an organic solvent, a metal powder, a ceramic powder, a step of forming a conductive paste is applied electrode coating film containing an organic solvent, the electrode coating layer is formed the A method for producing a multilayer piezoelectric element comprising: a step of laminating a plurality of green sheets and applying pressure to form a laminate; and a step of removing the binder from the laminate and firing at 1100 ° C. or lower . A container having an injection hole, formed by and a valve for ejecting the multilayer piezoelectric element according to claim 1, wherein accommodated in the storage container, the liquid from the ejection hole by a drive of the laminated piezoelectric element An injection device characterized by that.

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