JP4822664B2 - Multilayer piezoelectric element, manufacturing method thereof, and injection apparatus - Google Patents

Description

The present invention, multi-layer piezoelectric element and its manufacturing method, and relates to injection devices, for example, an automobile fuel injection valve, about the drive element or the like for precision positioning device or vibration preventing such optical device.

Conventionally, as a laminated piezoelectric element, for example, in order to obtain large displacement using the electrostrictive effect, a laminate of the piezoelectric layers and conductor layers alternately have been proposed. Such a laminated piezoelectric element generally forms a piezoelectric laminated body in which a green sheet containing piezoelectric powder and a conductor pattern containing metal powder are alternately laminated, and this is degreased and fired to obtain a laminated piezoelectric element. Then, an external electrode is formed on the side surface of the piezoelectric laminate. Thereafter, the multilayer piezoelectric element, the polarization treatment is performed by applying a 1kV voltage of approximately (e.g., Patent Document 1).
JP 2002-293625 A

  However, the polarization treatment conditions applied to the multilayer piezoelectric element disclosed in Patent Document 1 are: (1) immersing the multilayer piezoelectric element having external electrodes in a heated oil bath, and (2) applying a voltage. (3) The conditions for cooling after lowering the voltage are such that under such polarization treatment conditions, the crystal particles constituting the piezoelectric layer cannot be sufficiently saturated and polarized, for example, for a long period of time. In the driving test, there was a problem that the displacement amount was reduced particularly in the piezoelectric characteristics. This is based on the fact that the rate of change in the degree of orientation of the crystal particles constituting the piezoelectric layer before and after driving is large.

  Accordingly, the present invention provides a multilayer piezoelectric element in which the rate of change in the degree of orientation of crystal grains constituting a piezoelectric layer is small before and after driving, and the piezoelectric characteristics are less deteriorated even in a long-term driving test, and a method for producing the same It is another object of the present invention to provide an injection device using the same.

The multilayer piezoelectric element of the present invention is a multilayer piezoelectric element in which piezoelectric layers and internal electrode layers are alternately stacked. The driving frequency of the crystal particles constituting the piezoelectric layer is a load of 150 kgf and a temperature of 150 ° C. The rate of change of the lattice constant (c / a) before and after driving 10 ⁹ times or more under the condition of a frequency of 50 Hz is within 5%.

That is, according to the present invention, the crystal particles constituting the piezoelectric layer, the number of times of driving the load 150 kgf, temperature 0.99 ° C., frequency 50Hz conditions repeated at ¹⁰⁹ times or more drive before and after the lattice constant at the (c / a ) Is set to 5% or less, even in a long-term driving test, it is possible to reduce a decrease in piezoelectric characteristics, in particular, a displacement amount, and to obtain high reliability.

In the stacked piezoelectric device, wherein the average grain size of crystal grains is not more than 2.5 [mu] m. According to the present invention, the average particle size of the crystal particles constituting the piezoelectric layer is 2.5 μm or less, thereby increasing the degree of orientation of the crystal particles in the polarization treatment and thereby changing the polarizability of the piezoelectric characteristics. The rate can be further reduced.

In the multilayer piezoelectric element, the number of times of driving is 10 ⁹ times or more repeatedly under the conditions of a load of 150 kgf, a temperature of 150 ° C., and a frequency of 50 Hz. By setting the number of times of driving of the multilayer piezoelectric element of the present invention as described above, the present invention can be sufficiently applied to an apparatus such as an injection device that requires high reliability in continuous driving.

  The multilayer piezoelectric element is characterized in that the piezoelectric layer has a thickness of 200 μm or less. In the present invention, when the thickness of the piezoelectric layer to be polarized is 200 μm or less, an electric field is sufficiently applied in the thickness direction, so that more saturated polarization can be performed.

  The multilayer piezoelectric element is characterized in that the number of stacked layers is 200 or more. INDUSTRIAL APPLICABILITY According to the present invention, it can be used particularly effectively for a highly laminated product in which a large number of piezoelectric layers are laminated and the change rate of the polarizability is increased.

  The multilayer piezoelectric element is characterized in that the conductor layer has a thickness of 5 μm or less. By reducing the thickness of the conductor layer to 5 μm or less, the conductivity in the thickness direction of the conductor layer can be increased, and thereby the degree of orientation and the polarizability of crystal grains constituting the piezoelectric layer can be further increased.

In the stacked piezoelectric device, wherein the metal component in the internal electrode layer has a Group VIII metal, either or both of the Group VIII metal and the metal of group Ib, of the group Ib metal as the main component. That is, when the group VIII metal content is M1% by mass and the group Ib metal content is M2% by mass, 0.001 ≦ M1 ≦ 15, 85 ≦ M2 ≦ 99.999, M1 + M2 = 100% by mass In addition, the group VIII metal is at least one of Ni, Pt, Pd, Rh, Ir, Ru, and Os, and the group Ib metal is at least one of Cu, Ag, and Au. It is characterized by being.

  That is, in the present invention, by using a combination of the above-described metals as the metal component of the conductor layer, Ag or Cu, which has higher ductility and lower Young's modulus than the other metals, is used as the main component of the conductor layer. As a result, followability and adhesion to the surface of the piezoelectric layer are improved, and polarization can be performed by applying an electric field uniformly to almost the entire surface of the piezoelectric layer.

Further, in the present invention, the group VIII metal is at least one of Pt and Pd, the group Ib metal is at least one of Ag, and Au. In particular, the group VIII metal is Ni or the group Ib metal is Cu. It is desirable that

  In the multilayer piezoelectric element, the conductor layer contains an inorganic component, the inorganic component is the same component as the piezoelectric layer, and the average particle size of the inorganic component is the average of the piezoelectric layer. It is smaller than the particle size.

  As described above, in the present invention, the conductor layer contains the same common material component as that of the piezoelectric particles constituting the piezoelectric layer, and the particle diameter on the internal electrode layer side is made smaller than that on the piezoelectric layer side. The piezoelectric particles that come into contact with the conductor layer can be reduced, which can increase the effective area of the conductor layer, suppress the increase in rigidity of the conductor layer due to the addition of inorganic components, and improve the adhesion to the piezoelectric layer. And the application of the electric field can be improved.

  The method for producing a laminated piezoelectric element of the present invention includes a step of forming a conductor pattern on a green sheet containing piezoelectric powder, and then laminating a plurality of green sheets on which the conductor pattern is formed to form a piezoelectric laminate. Firing the piezoelectric laminate to form a laminated piezoelectric body; applying an external electrode paste to the end face of the laminated piezoelectric body and then heat-treating to form a laminated piezoelectric element having external electrodes; The voltage is applied to the external electrode to immerse the laminated piezoelectric element in (1) a heated oil bath, (2) voltage is applied, and (3) the voltage is applied while cooling. And a step of cooling the piezoelectric layer under a condition of t / 3 (° C./min) or less when the Curie temperature of the piezoelectric layer is t (° C.), and (4) performing a polarization treatment by lowering the voltage after cooling. It is characterized by doing.

  That is, in the manufacturing method of the present invention, the polarization process is performed through the above-described steps, whereby a sufficient polarization process can be performed on the piezoelectric layer, thereby suppressing the rate of decrease in piezoelectric characteristics before and after driving.

  In the method for manufacturing the laminated piezoelectric element, the average particle size of the piezoelectric powder is 0.8 μm or less. By using a piezoelectric powder having an average particle size as small as described above, the ceramics of the piezoelectric layer become dense, and crystal grains sensitive to the applied electric field can be easily formed.

  The method for producing the multilayer piezoelectric element is characterized in that the firing temperature is 1000 ° C. or lower. According to the production method of the present invention, the firing temperature is preferably 1000 ° C. or less in terms of enabling simultaneous firing with the above-described components and composition of the conductor layer, thereby suppressing abnormal crystal growth. Thus, a piezoelectric layer having a uniform polarizability with respect to the applied electric field can be easily formed.

The manufacturing method of the multilayer piezoelectric element is characterized in that the polarization treatment is performed so that the rate of change of c / a, which is the ratio of lattice constants of crystal grains, is 0.5% or less. In the polarization treatment step, the cooling rate from the highest temperature of the heat treatment is t / 3 (° C./min) or less when the Curie temperature of the piezoelectric layer is t (° C.). Furthermore, in the heat treatment step, when the Curie temperature of the piezoelectric layer is t (° C.) during cooling from the heat treatment, the cooling rate in the temperature range of 0.8 t to 1.2 t is t / 3 ( ° C / min) or less.

  In other words, in the present invention, in addition to the effect of improving the average particle diameter of the piezoelectric powder constituting the green sheet, the distortion generated electrically or thermally in the piezoelectric layer so that the crystal particles have an appropriate crystal structure. By suppressing this, it is possible to easily form a piezoelectric layer having a high polarizability of the piezoelectric layer.

  An injection device according to the present invention includes a storage container having an injection port, the laminated piezoelectric element stored in the storage container, and a valve that ejects liquid from the injection hole by driving the stacked piezoelectric element. It is characterized by becoming.

  In such an injection device, as described above, the multilayer piezoelectric element has a piezoelectric layer composed of crystal particles whose degree of change in the degree of orientation before and after driving is within 5%. As a result, it is possible to obtain excellent injection characteristics as an injection device and improve reliability.

  That is, in the multilayer piezoelectric element of the present invention, the change rate of the degree of orientation of the crystal particles constituting the piezoelectric layer before and after driving is set to 5% or less, so that even in a long-term driving test, In particular, the decrease in the amount of displacement can be reduced, and the injection apparatus incorporating the same can be provided with high reliability.

  FIG. 1 is a longitudinal sectional view showing an embodiment of a multilayer piezoelectric element composed of a multilayer piezoelectric actuator. FIG. 1 is a cross-sectional view of the multilayer piezoelectric element of the present invention.

  As shown in FIG. 1, the multilayer piezoelectric element of the present invention has a side surface on which one side of a conductor layer 2 is exposed in a piezoelectric laminate 3 in which a plurality of piezoelectric layers 1 and a plurality of conductor layers 2 are alternately laminated. External electrodes 4 are respectively formed on (opposing side surfaces). Here, the conductor layer 2 has a rectangular shape as shown in FIG. 2, and one side of the conductor layer 2 is exposed on every other side surface (external electrode forming surface) of the piezoelectric laminate 3, and the external electrode 4 is electrically connected. Are alternately connected. The external electrode 4 is connected to a lead wire 6 for taking power.

The piezoelectric layer 1 is made of, for example, a piezoelectric ceramic material mainly composed of lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT), but is not limited thereto. Any ceramic having piezoelectricity may be used. As this piezoelectric material, a material having a high piezoelectric strain constant d33 is desirable.

  Further, the thickness of the piezoelectric layer 1, that is, the distance between the conductor layers 2, is more preferably 200 μm or less, particularly 150 μm or less from the viewpoints of downsizing and applying a high electric field. On the other hand, 50 μm or more, particularly 70 μm or more is desirable in terms of shortening the saturation time of the electric energy applied to the piezoelectric layer 1 and improving drivability. The number of stacked layers is preferably 200 or more. A method of increasing the number of stacked layers in order to obtain a larger amount of displacement by applying a voltage to the stacked piezoelectric element is used, but when the number of stacked layers is increased, the thickness of the piezoelectric layer 1 in the piezoelectric stacked body 3 is increased. If the thickness is too thick, the actuator cannot be reduced in size and height. On the other hand, if the thickness of the piezoelectric layer 1 in the piezoelectric laminate 3 is too thin, dielectric breakdown tends to occur with the above reason.

In the crystal particles constituting the piezoelectric layer 1 of the present invention, the average particle size is particularly preferably 5 μm or less, particularly 3 μm or less.

On the other hand, the thickness of the conductor layer of the present invention is 5 μm or less, and more preferably 4 μm or less. In the conductive layer 2 described above, it is desirable that the metal component constituting it is mainly composed of either or both of the Group VIII metal and Group Ib metals, of Group VIII metals, Group Ib metals, in particular, the Group VIII Satisfying the relationship of 0.001 ≦ M1 ≦ 15, 85 ≦ M2 ≦ 99.999, M1 + M2 = 100% by mass when the metal content is M1% by mass and the group Ib metal content is M2% by mass. In particular, 3 ≦ M1 ≦ 8 and 92 ≦ M2 ≦ 97 are more preferable.

Here, VIII group metals Ni, Pt, Pd, Rh, Ir, Ru, at least one of Os, Ib group metals Cu, Ag, preferably at least one of Au, in particular, VIII group metals It is more desirable that at least one of Pt and Pd, the group Ib metal is at least one of Ag and Au, further, the group VIII metal is Ni, or the group Ib metal is Cu. .

  In addition, the internal electrode layer 2 of the present invention contains an inorganic component, and the component of the inorganic component is preferably the same component as that of the piezoelectric layer 1, and further, the average particle size of the inorganic component is The average particle diameter of the piezoelectric layer 1 is preferably smaller.

Then, in the multi-layer piezoelectric element of the present invention, the crystal grains 7 of the piezoelectric layer 1, it is important rate of change in orientation degree f of the front and rear driving is within 5%, in particular, continuous drive 10 ⁹ more preferably within 3% in terms of achieving more times, it in such a multilayer piezoelectric element, the driving frequency is, load 150 kgf, temperature 0.99 ° C., is repeated at ¹⁰⁹ times or more at a frequency of 50Hz Is desirable in order to obtain reliability of the injection device or the like.

  On the other hand, when the rate of change of the orientation degree f before and after driving of the crystal particles 7 constituting the piezoelectric layer 1 is greater than 5%, uniform piezoelectric characteristics can be obtained by continuous driving. Not only will it not be possible, but it will also shorten the durability time.

FIG. 2 is a process diagram for manufacturing the multilayer piezoelectric element of the present invention. A manufacturing method of a multilayer piezoelectric actuator, which is a representative example of the multilayer piezoelectric element of the present invention, will be described in detail. The multilayer piezoelectric element according to the present invention includes: (a) First, a calcined powder (ceramic powder) of a piezoelectric ceramic such as lead zirconate titanate Pb (Zr, Ti) O ₃ , and an organic material such as an acrylic resin or a butyral resin. A slurry in which an organic binder made of a polymer and a plasticizer are mixed is prepared, and a ceramic green sheet 21 having a thickness of 50 to 250 μm is prepared by, for example, a slip casting method.

  In the present invention, the average particle size of the piezoelectric powder that is the calcined powder forming the piezoelectric layer 1 is desirably 0.3 to 0.8 μm. By setting the average particle size of the piezoelectric powder to 0.3 μm or more, the organic binder necessary for preventing the generation of dry cracks during the production of the green sheet 21 can be reduced.

  On the other hand, by setting the average particle size of the piezoelectric powder to 0.8 μm or less, sintering during firing can be sufficiently performed, and the ceramic strength can be increased. For example, cracks due to stress generated by an electric field in a multilayer piezoelectric element Can be suppressed.

  Further, the thickness of the green sheet 21 is preferably 90 μm or more, particularly 100 μm or more for the purpose of improving the insulation strength.

  (B) Next, after the produced green sheet 21 is punched out to a predetermined size, a conductor paste containing, for example, Ag-Pd and a solvent, which becomes the conductor layer 2, is screen printed on one side of the green sheet 21. The conductor pattern 23 is formed by printing to a thickness of 1 to 10 μm and drying. In this case, in the present invention, it is desirable to mix ceramic powder as a co-material in the conductor paste.

  The conductor pattern 23 used in the manufacturing method of the present invention has a rectangular shape, has an area smaller than that of the rectangular green sheet 21, and has a portion where a conductor pattern is not formed.

  (C) Next, a predetermined number of the green sheets 21 on which the conductor pattern 23 is formed are laminated so that one side of the conductor pattern is alternately exposed on the opposite side surface of the laminated molded body 23 to activate the piezoelectric element. A laminated molded body 23a to be a part is prepared, and an inactive part molded body 23b that is inactive by laminating a plurality of green sheets 21 on which conductor paste is not printed is laminated on the upper and lower surfaces of the laminated molded body 23a. The piezoelectric laminated molded body 23 is produced. Next, pressure is applied while heating the piezoelectric laminate molded body 23 to integrate the piezoelectric laminate molded body 23.

  The integrated piezoelectric layered product is cut to a predetermined size, and then degreased at 400 to 800 ° C. for 5 to 40 hours in the atmosphere, and then at 900 to 1200 ° C. for 2 to 5 hours. Firing is performed to form a laminated piezoelectric body 3 as shown in FIG.

  In the present invention, the firing is more preferably performed at 1000 ° C. or less, particularly 980 ° C. or less, for example, in terms of increasing the Ag ratio in the conductor layer 2 and reducing the cost.

  Next, an external electrode paste containing Ag-glass is applied to the end face of the piezoelectric laminate 3 and heat-treated at a temperature of 500 to 900 [deg.] C. to form the external electrode 4 as shown in FIG. In this case, in the heat treatment step, the cooling rate from the maximum temperature of the heat treatment is such that delamination and cracks can be suppressed. In this case, when the Curie temperature of the piezoelectric layer is t (° C.), t / 3 (° C. / Min), and further, when cooling from the heat treatment, when the Curie temperature of the piezoelectric layer is t (° C.), the cooling rate in the temperature range of 0.8 t to 1.2 t is t / 3. It is more desirable that the temperature be (C / min) or less. The piezoelectric layer 1 is cubic at a temperature higher than the Curie temperature, and is rhombohedral or tetragonal at a temperature lower than the Curie temperature. This is because the polarized crystal changes due to the internal stress caused by this.

  Usually, for example, when the conductor layer 2 contains Ag, it diffuses to the piezoelectric layer side during firing. When Ag diffuses, oxygen defects are formed in the porcelain due to mutual diffusion of the piezoelectric layer with the porcelain. Oxygen vacancies become oxygen vacancies during continuous driving, affect the displacement direction of B site (Zr, Ti) ions constituting the piezoelectric layer, and the orientation of the porcelain changes over time. On the other hand, in the present invention, since sufficient polarization is performed under the following conditions, a change with time in the orientation of the porcelain is suppressed.

FIG. 3 is a schematic diagram showing the steps of the polarization treatment of the present invention. Next, as shown in FIG. 3, the element is polarized. It is important that the multilayer piezoelectric element of the present invention is polarized through the following steps. That is, it is immersed in an oil bath heated to a temperature of 100 to 400 ° C., a direct current voltage of 0.1 to 3 kV / mm is applied to the pair of external electrodes 4 of this element, and the crystal particles constituting the piezoelectric layer are formed. After sufficient polarization, the sample is cooled to the Curie point or lower and room temperature while maintaining the applied voltage. Thereafter, the electric field is dropped. By such a minute electrode process, the multilayer piezoelectric element as a product is completed.

  Here, it is desirable that the rate of change of c / a, which is the ratio of lattice constants, before and after polarization is 0.5% or less. This is because if the change rate of c / a is larger than 0.5%, peeling occurs between the conductor layer 2 and the piezoelectric layer 1 due to stress generated during polarization. In the present invention, in order to prevent peeling due to stress during polarization, the change rate of c / a is more preferably 0.2% or less. Here, the lattice constant ratio c / a is obtained from the peak of the plane index (200) from the XRD diffraction pattern, and similarly, the lattice constant c is obtained from the peak of the plane index (002). Find c / a.

  By using the manufacturing method as described above, the change rate of the degree of orientation of the crystal particles constituting the piezoelectric layer 1 before and after driving can be made within 5%.

The method for manufacturing a multilayer piezoelectric element of the present invention is suitably used for a method of manufacturing a multilayer electronic component such as a multilayer piezoelectric transformer, a multilayer capacitor, or a multilayer piezoelectric actuator. In particular, in a laminated piezoelectric actuator using piezoelectric ceramics that is continuously driven in a high electric field, the method for producing a laminated piezoelectric element of the present invention is preferably used. The drive test conditions are desirably 10 ⁹ times or more repeatedly under the conditions of a load of 150 kgf, a temperature of 150 ° C., and a frequency of 50 Hz.

  Next, an explanation will be given of an injection device constituted by the above-described multilayer piezoelectric element. FIG. 4 shows an injection apparatus 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.

  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.

  The upper end of the needle valve 35 has a large diameter, and has a cylinder 39 formed in the storage container 31 and a piston 41 that can slide. In the storage container 31, a stacked piezoelectric element 43 serving as a piezoelectric actuator in the ejection device is stored.

  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.

A slurry is prepared by mixing a piezoelectric powder made of lead zirconate titanate Pb (Zr, Ti) O _{3 with} a Curie temperature of 300 ° C. and a particle size of 0.7 μm, an organic binder made of butyral resin, and a plasticizer. A green sheet having a thickness of 150 μm was produced by a casting method.

  On one side of this green sheet, as shown in FIG. 2, a metal paste having a predetermined composition with an Ag—Pd component to be a conductor layer, and a conductor paste containing an organic resin and a solvent are formed to a thickness of 4 μm by screen printing. Printing was performed to form a conductor pattern. Next, 30 green sheets on which conductive patterns are formed are stacked, and 5 green sheets to which conductive paste is not applied are stacked on the upper and lower surfaces of the stacked body, and the structure as shown in FIG. A laminated molded body was produced.

  Next, this laminated molded body was placed in a mold and integrated by applying a pressure of 100 MPa by a hydrostatic press while heating at 90 ° C.

  This was cut into a size of 10 mm × 10 mm, then debindered at 800 ° C. for 10 hours, and then fired at 1130 ° C. for 2 hours to obtain a piezoelectric laminate. The piezoelectric layer constituting the piezoelectric laminated body thus fabricated had a thickness of 120 μm and the conductor layer had a thickness of 3 μm. The temperature drop during firing was performed at a rate of t / 3 (° C./min) from the maximum temperature, where the Curie temperature was t.

  Thereafter, an Ag glass paste mainly composed of silver is applied to the opposite side surfaces of the active part, heated at 750 ° C. for 1 hour, and then subjected to heat treatment at the cooling rates shown in Table 1 to form external electrodes. did.

Thereafter, it is immersed in a heated oil bath set at a temperature of 400 ° C., a DC voltage of 3 kV / mm is applied to the pair of external electrodes of this element for 1 hour, and the crystal grains constituting the piezoelectric layer are sufficiently After polarization, the laminated piezoelectric element was manufactured by cooling to room temperature below the Curie point while maintaining the applied voltage. Moreover, the degree of orientation of the crystal grains was determined by X-ray diffractometry after the driving test and 10 ⁹ times after polarization. The rate of change of the lattice constant ratio c / a at this time is shown in Table 1. The evaluation of the effective piezoelectric strain constant is performed by applying a voltage of 0 to 200 V to the laminated piezoelectric element sample fixed on the anti-seismic table with a preload of 150 kgf applied in the laminating direction, and the laminated piezoelectric element at that time. The amount of change in the total length of the element sample was measured, and the amount of change was calculated by dividing by the number of layers and the applied voltage. The Curie temperature was obtained by measuring the temperature characteristics of the capacitance of the piezoelectric ceramic. High-temperature durability test, using a high-temperature bath, while applying a load of 150 kgf, temperature 0.99 ° C., was repeated driving of up to 10 ⁹ times with a frequency of 50 Hz.

On the other hand, a laminated piezoelectric element produced through a conventional polarization process was used as a comparative example. The crystal particle diameter was determined by observation with an electron microscope.

  From Table 1, the sample No. 5 was subjected to the polarization treatment of the present invention, and the change rate of the orientation degree of the crystal particles constituting the piezoelectric layer before and after driving was within 5%. Nos. 2 to 6 were good results when the displacement after continuous driving was within 10% even under the driving test conditions of the present invention.

  On the other hand, the change in the degree of orientation before and after driving was greater than 5%. In No. 1, the displacement after continuous driving was more than 10% and 15%.

It is sectional drawing of the lamination type piezoelectric element of this invention. It is process drawing for manufacturing the laminated piezoelectric element of this invention. It is a schematic diagram which shows the process of the polarization process of this invention. It is a schematic sectional drawing which shows the injection apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric layer 2 ... Conductor layer 21 ... Green sheet 22 ... Conductor pattern 23 ... Piezoelectric laminated body

Claims (21)

In a stacked piezoelectric element in which piezoelectric layers and conductor layers are alternately stacked, the number of times that the crystal particles constituting the piezoelectric layer are driven is 150 kgf, a temperature is 150 ° C., and a frequency is 50 Hz. A multilayer piezoelectric element having a change rate of a lattice constant (c / a) before and after ^nine or more drivings within 5%. The multilayer piezoelectric element according to claim 1, wherein an average particle diameter of the crystal particles is 2.5 μm or less. The multi-layer piezoelectric element according to claim 1 or 2, wherein the thickness of the piezoelectric layer is not 200μm or less. Multi-layer piezoelectric element according to any one of claims 1 to 3, wherein the number of layers is 200 layers or more. Multi-layer piezoelectric element according to any one of claims 1 to 4, wherein the thickness of the conductor layer is 5μm or less. Multi-layer piezoelectric element according to any one of claims 1 to 5 metal component of the conductive layer is characterized in that any of a Group VIII metal, Ib group metal. 6. The multilayer piezoelectric element according to claim 1, wherein the metal component in the conductor layer is composed mainly of both a Group VIII metal and a Group Ib metal. The content of M1 mass% of the Group VIII metal, when the content of the Ib group metal and the M2 mass%, 0.001 ≦ M1 ≦ 15,85 ≦ M2 ≦ 99.999, M1 + M2 = 100 wt% of the relationship the multi-layer piezoelectric element according to claim 7, characterized by satisfying the. The Group VIII metal is Ni, Pt, Pd, Rh, Ir, Ru, at least one of Os, the group Ib metal is Cu, Ag, to claim 8, characterized in that at least one of a Au The laminated piezoelectric element described. The Group VIII metal is Pt, at least one of Pd, multilayer piezoelectric element according to claim 8, wherein the group Ib metal is Ag, and wherein the at least one kind of Au. The multilayer piezoelectric element according to claim 9, wherein the Group VIII metal is Ni. The multilayer piezoelectric element according to claim 9, wherein the group Ib metal is Cu. Multi-layer piezoelectric element according to any one of claims 1 to 12, characterized by containing an inorganic component to the conductor layer. The inorganic component, multi-layer piezoelectric element according to claim 13, characterized in that it contains the same components as the piezoelectric layer. The average particle diameter of the inorganic component, multi-layer piezoelectric element according to claim 13 or 14, wherein the smaller than the average grain size of crystal grains of the piezoelectric layer. A method of multi-layer piezoelectric element according to any one of claims 1 to 16, the green sheets containing a piezoelectric powder, a conductor pattern is formed, then the green sheets conductor patterns are formed forming a piezoelectric laminate by stacking a plurality, forming a piezoelectric said laminated piezoelectric body by firing the laminate, and heat-treated after application of the external electrode paste to the end face of the laminated piezoelectric body Forming a laminated piezoelectric element having an external electrode; applying a voltage to the external electrode to immerse the laminated piezoelectric element in (1) a heated oil bath; (2) applying a voltage; (3) in the state where a voltage is applied, the cooling rate, the Curie temperature of the piezoelectric layer when a t (° C.), cooled in t / 3 (° C. / minute) the following conditions, (4) Polarization treatment by lowering the voltage after cooling Preparation of the multilayer piezoelectric element characterized by comprising that the step. The method for producing a multilayer piezoelectric element according to claim 16, wherein an average particle diameter of the piezoelectric powder is 0.8 μm or less.   The method for producing a multilayer piezoelectric element according to claim 16 or 17, wherein the firing temperature is 1000 ° C or lower. The multilayer piezoelectric element according to any one of claims 16 to 18, wherein a polarization treatment is performed so that a change rate of c / a which is a ratio of lattice constants of crystal grains is 0.5% or less. Manufacturing method. In the step of the polarization treatment, when the Curie temperature before Symbol piezoelectric layer was t (° C.), that the cooling rate of the temperature range of 0.8t~1.2t is t / 3 (℃ / min) or less The method for producing a laminated piezoelectric element according to any one of claims 16 to 19.   A storage container having an injection port, the stacked piezoelectric element according to any one of claims 1 to 15 stored in the storage container, and a valve for ejecting liquid from the injection hole by driving the stacked piezoelectric element An injection device comprising:

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