JP2005268393A - Multilayer piezoelectric element and jetting apparatus using the same - Google Patents

Abstract

A highly reliable multi-layer piezoelectric element having excellent durability without malfunctioning of a device because a desired displacement amount does not change effectively even when continuously driven, and an injection device using the same I will provide a.
A pair of external electrodes having a laminate formed by alternately laminating at least one piezoelectric body and a plurality of internal electrodes, wherein the internal electrodes are alternately connected to every other side surface of the laminate. In the multilayer piezoelectric element driven by applying an electric field to the external electrode, the thermal expansion coefficient of the metal element constituting the internal electrode is α1, and the thermal expansion coefficient of the metal constituting the external electrode is α2. The ratio of thermal expansion coefficients (α1 / α2) is 0.9 or more and less than 1.
[Selection] Figure 1

Description

  The present invention relates to a laminated piezoelectric element and an injection device, for example, a fuel injection device for an automobile engine, a liquid injection device such as an inkjet, a drive element mounted on a precision positioning device such as an optical device, a vibration prevention device, and the like, and a combustion Sensor elements mounted on pressure sensors, knock sensors, acceleration sensors, load sensors, ultrasonic sensors, pressure sensitive sensors, yaw rate sensors, etc., and circuit elements mounted on piezoelectric gyros, piezoelectric switches, piezoelectric transformers, piezoelectric breakers, etc. The present invention relates to a stacked piezoelectric element and a jetting device used.

  Conventionally, as a multilayer piezoelectric element, a multilayer piezoelectric actuator in which piezoelectric bodies and electrodes are alternately stacked is known. Multi-layer piezoelectric actuators are classified into two types: simultaneous firing type and stack type in which piezoelectric ceramics and internal electrode plates are stacked alternately. Considering low voltage and low manufacturing cost, simultaneous firing type The multilayer piezoelectric actuator is advantageous for thinning and is advantageous for durability.

  FIG. 1 shows a conventional multilayer piezoelectric element, in which piezoelectric bodies 11 and internal electrodes 12 are alternately stacked. However, the internal electrodes 12 are not formed on the entire main surface of the piezoelectric body 11 and are so-called. It has a partial electrode structure. By laminating the internal electrodes 12 of this partial electrode structure alternately on the left and right, the internal electrodes 12 can be alternately connected to the external electrodes 15 formed on the side surface of the multilayer electronic component. By printing an internal electrode paste on a ceramic green sheet in a pattern that has a predetermined electrode structure, producing a laminated molded body obtained by laminating a plurality of green sheets coated with this internal electrode paste, and firing this The laminated body was produced (for example, refer patent document 1).

  In such a laminated piezoelectric element, piezoelectric bodies 11 and internal electrodes 12 are alternately laminated to form a columnar laminated body 13, and inactive layers 14 are laminated on both end faces in the laminating direction. The internal electrode 12 is formed so that one end thereof is electrically connected to the external electrode 15 alternately on the left and right sides. When used as a multilayer piezoelectric actuator, lead wires are further connected and fixed to the external electrodes 15 by soldering.

  Further, as the internal electrode, an alloy of silver and palladium is used. Further, in order to simultaneously fire the piezoelectric body and the internal electrode, the metal composition of the internal electrode is 70% by mass of silver and 30% by mass of palladium. (For example, see Patent Document 2).

  As described above, the internal electrode made of a metal composition containing silver / palladium alloy containing palladium is used instead of the internal electrode made of silver-only metal composition. This is because when a potential difference is applied between the electrodes, a so-called silver migration phenomenon occurs in which silver in the electrode moves along the element surface from the positive electrode to the negative electrode of the pair of electrodes. This phenomenon occurred remarkably in a high temperature and high humidity atmosphere.

In recent years, in order to ensure a large amount of displacement under a large pressure with a small piezoelectric actuator, a higher electric field is applied to continuously drive for a long time.
JP-A-61-133715 Japanese Utility Model Publication No. 1-130568

  However, unlike an ordinary multilayer electronic component, the actuator has a feature that the piezoelectric ceramic is deformed when energized. That is, the number of driving times and the number of piezoelectric ceramic deformations are the same. For this reason, the internal electrode and the external electrode are required to be firmly bonded even during driving, but the element temperature rises as the number of continuous driving increases, and the internal electrode and the external electrode are caused by the difference in thermal expansion coefficient. There is a problem that the effective displacement amount is reduced by peeling or disconnection during continuous driving due to an adhesion failure, and further, there is a problem that the peeled portion sparks and breaks.

  In addition, if the connection point between the external electrode and the internal electrode is disconnected during displacement, the amount of displacement will change during driving, causing load fluctuations for the voltage-controlled power supply, which places a burden on the power supply. It was happening. Furthermore, when the rate of change of the displacement amount is large, not only the displacement amount itself deteriorates but also there is a problem that when the device temperature rise exceeds the heat dissipation amount, a thermal runaway phenomenon occurs and the device is destroyed.

  In addition, in order to suppress an increase in element temperature, an internal electrode having a small specific resistance has been demanded. However, the specific resistance value of the silver-palladium alloy is significantly higher than the specific resistance of silver or palladium alone depending on the composition ratio. In the composition of the silver-palladium alloy of 70 mass% silver and 30 mass% palladium, palladium There was a problem that the resistance was 1.5 times that of a single substance. Moreover, when the sintered density of the internal electrode is lowered, the resistance is further increased.

  It is an object of the present invention to provide a multilayer piezoelectric element and a jetting device that are excellent in durability and do not change in displacement even when a piezoelectric actuator is continuously driven for a long time under high voltage and high pressure. And

  The multilayer piezoelectric element of the present invention has a multilayer body in which at least one piezoelectric body and a plurality of internal electrodes are alternately stacked, and the internal electrodes are alternately connected to the side surface of the multilayer body every other layer. In the laminated piezoelectric element having a pair of external electrodes and driven by applying an electric field to the external electrodes, the thermal expansion coefficient of the metal constituting the internal electrode is α1, and the thermal expansion coefficient of the metal constituting the external electrode is When α2, the ratio of thermal expansion coefficients (α1 / α2) is 0.9 or more and less than 1.

In addition, the multilayer piezoelectric element of the present invention includes a multilayer body in which at least one piezoelectric body and a plurality of internal electrodes are alternately stacked, and the internal electrodes are alternately disposed on the side surfaces of the multilayer body. In the laminated piezoelectric element that includes a pair of connected external electrodes and is driven by applying an electric field to the external electrodes, an intermediate layer is provided at a joint between the internal electrode and the external electrode. The metal composition constituting the electrode contains 80 to 100% by mass of the main component of the metal composition constituting the external electrode.

  Furthermore, the intermediate layer is composed of a metal composition constituting the internal electrode and a metal composition constituting the external electrode.

  Furthermore, when the thermal expansion coefficient of the intermediate layer is α3, α1 <α3 <α2.

  Furthermore, the composition of the intermediate layer is changed in a gradient from the metal composition in the internal electrode to the metal composition in the external electrode.

  Furthermore, the metal composition in the internal electrode and the external electrode is mainly composed of a Group VIII metal and / or a Group Ib metal.

  Further, when the content of the group VIII metal in the internal electrode is M1 (mass%) and the content of the group lb metal is M2 (mass%), 0 <M1 ≦ 15, 85 ≦ M2 <100, M1 + M2 = 100 is satisfied.

  Furthermore, the group VIII metal in the internal electrode 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 that.

  Further, the group VIII metal in the internal electrode is at least one of Pt and Pd, and the group Ib metal is at least one of Ag and Au.

  Further, the Group VIII metal in the internal electrode is Ni.

  Further, the group Ib metal in the internal electrode is Cu.

  Furthermore, an inorganic composition is added to the internal electrode together with the metal composition.

Further, the inorganic composition contains a perovskite oxide composed of PbZrO ₃ —PbTiO ₃ as a main component.

  Further, the piezoelectric body is mainly composed of a perovskite oxide.

Further, the piezoelectric body is mainly composed of a perovskite oxide made of PbZrO ₃ —PbTiO ₃ .

  Furthermore, the firing temperature of the laminate is 900 ° C. or higher and 1000 ° C. or lower.

  The injection device of the present invention includes a storage container having an injection hole, a stacked 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.

  Thus, according to the multilayer piezoelectric element of the present invention, the multilayer piezoelectric element has a multilayer body in which at least one piezoelectric body and a plurality of internal electrodes are alternately stacked, and the internal electrode is formed on one side of the multilayer body. In a laminated piezoelectric element having a pair of external electrodes connected alternately and driven by applying an electric field to the external electrodes, the thermal expansion coefficient of the metal constituting the internal electrodes is α1, and the external electrodes are configured. When the coefficient of thermal expansion of the metal is α2, the ratio of the coefficient of thermal expansion (α1 / α2) is 0.9 or more and less than 1, so that even if the laminated piezoelectric element is continuously driven, the internal electrode and the external electrode Because the difference in thermal expansion coefficient is small, even if the number of continuous driving of the element increases and the element temperature rises, adhesion failure occurs between the internal electrode and the external electrode, suppressing peeling and disconnection during continuous driving Problem that the effective displacement is reduced, and Portion can be also prevented the problem of destruction by a spark, there is no malfunction of the device, further, it may have no superior durability thermal runaway.

  In addition, the multilayer piezoelectric element of the present invention includes a multilayer body in which at least one piezoelectric body and a plurality of internal electrodes are alternately stacked, and the internal electrodes are alternately disposed on the side surfaces of the multilayer body. In a laminated piezoelectric element that includes a pair of connected external electrodes and is driven by applying an electric field to the external electrodes, by providing an intermediate layer at the junction between the internal electrodes and the external electrodes, The stress resulting from the difference in thermal expansion can be relieved, electrode peeling can be prevented, and durability during driving can be improved.

  Furthermore, in the multilayer piezoelectric element of the present invention, the metal composition that constitutes the internal electrode contains the main component of the metal composition that constitutes the external electrode at 80% by mass or more and less than 100% by mass. The metal portion in the electrode and the metal portion in the external electrode can be diffused to generate extremely strong adhesion strength between the internal electrode and the external electrode. Therefore, even if a difference in thermal expansion occurs between the internal electrode and the external electrode, it does not peel off. Furthermore, when the main component of the metal composition constituting the external electrode is contained in an amount of 80% by mass or more and less than 100% by mass, no new intermetallic compound is formed between the internal electrode and the external electrode. Therefore, it is possible to prevent formation of a non-uniform compositional point that becomes a starting point of stress breakdown when the multilayer piezoelectric element is driven. This eliminates the malfunction of the apparatus, and can have excellent durability without thermal runaway.

  Furthermore, the multilayer piezoelectric element of the present invention is a new intermetallic compound because the intermediate layer is composed of a component comprising a metal composition constituting the internal electrode and a metal composition constituting the external electrode. Alternatively, no vitreous material is formed, and formation of a hard and brittle portion that becomes a starting point of stress fracture can be prevented.

  Furthermore, in the multilayer piezoelectric element of the present invention, when the thermal expansion coefficient of the intermediate layer is α3, α1 <α3 <α2 so that the intermediate layer exhibits stress due to the difference in thermal expansion between the internal electrode and the external electrode. Since it can be mitigated, the electrode can be prevented from peeling off and the durability can be further improved.

  Furthermore, the multilayer piezoelectric element of the present invention has a thermal expansion of the internal electrode and the external electrode because the composition of the intermediate layer changes in a gradient from the metal composition in the internal electrode to the metal composition in the external electrode. Since stress caused by the difference can be relaxed without concentrating on one point of the intermediate layer, electrode peeling is prevented, adhesion strength between the internal electrode and external electrode is improved, and durability is further improved can do.

  Furthermore, the metal composition in the internal electrode and the external electrode is mainly composed of a Group VIII metal and / or a Group Ib metal, thereby preventing a silver migration phenomenon even when the multilayer piezoelectric element is driven continuously. Therefore, dielectric breakdown between the internal electrodes can be prevented.

  Further, when the content of the group VIII metal in the internal electrode is M1 (mass%) and the content of the group lb metal is M2 (mass%), 0 <M1 ≦ 15, 85 ≦ M2 <100, M1 + M2 = By satisfying 100, the specific resistance of the internal electrode can be reduced, so that heat generation of the internal electrode portion can be suppressed even when the multilayer piezoelectric element is continuously driven for a long time. In addition, since the temperature rise of the multilayer piezoelectric element can be suppressed, the element displacement can be stabilized.

  Furthermore, the group VIII metal is at least one or more of Ni, Pt, Pd, Rh, Ir, Ru, and Os, and the group Ib metal is at least one or more of Cu, Ag, and Au. As an internal electrode raw material, either an alloy raw material or a mixed powder raw material can be used.

  Furthermore, when the Group VIII metal is at least one of Pt and Pd and the Group Ib metal is at least one of Ag and Au, the internal electrode excellent in heat resistance and oxidation resistance can be obtained. Can be formed.

  Furthermore, when the Group VIII metal is Ni, it is possible to relieve stress caused by displacement during driving and to form the internal electrode with excellent heat resistance.

  In addition, since the group Ib metal is Cu, stress generated by displacement during driving can be relieved and the internal electrode excellent in thermal conductivity can be formed.

  Further, by adding an inorganic composition together with the metal composition to the internal electrode, the adhesion strength at the interface between the internal electrode and the piezoelectric body is increased, so that peeling at the interface between the internal electrode and the piezoelectric body is suppressed. can do.

Furthermore, since the piezoelectric body is mainly composed of a perovskite oxide made of PbZrO ₃ —PbTiO ₃ , the piezoelectric body and the internal electrode can be fired at the same time. The specific resistance of the internal electrode can be reduced.

  1A and 1B show an embodiment of a laminated piezoelectric element according to the present invention. FIG. 1A is a perspective view, and FIG. 1B is a perspective development view showing a laminated state of a piezoelectric layer and an internal electrode layer.

  As shown in FIG. 1, the multilayer piezoelectric element of the present invention includes a pair of opposing side surfaces of a laminate 13 in which piezoelectric bodies 11 and internal electrodes 12 are alternately laminated, and an end portion where the internal electrodes 12 are exposed. The external electrodes 15 that are electrically conductive are joined every other layer. In addition, an inactive layer formed of the piezoelectric body 11 is stacked on both ends of the stacked body 13 in the stacking direction. Here, when the multilayer piezoelectric element of the present invention is used as a multilayer piezoelectric actuator, a lead wire may be connected and fixed to the external electrode 15 with solder, and the lead wire may be connected to an external voltage supply unit.

  An internal electrode 12 is arranged between the piezoelectric bodies 11. Since the internal electrode 12 is formed of a metal material such as silver-palladium, a predetermined voltage is applied to each piezoelectric body 11 through the internal electrode 12. The piezoelectric body 11 has a function of causing displacement due to the reverse piezoelectric effect.

  On the other hand, since the inert layer 14 is a layer of a plurality of piezoelectric bodies 11 in which the internal electrode 12 is not disposed, no displacement occurs even when a voltage is applied.

  The laminated piezoelectric element of the present invention has a laminated body 13 in which at least one piezoelectric body 11 and a plurality of internal electrodes 12 are alternately laminated, and the internal electrodes 12 are arranged on one side of the laminated body. In the laminated piezoelectric element having a pair of external electrodes 15 alternately connected to each other and driven by applying an electric field to the external electrodes 15, the thermal expansion coefficient of the metal element constituting the internal electrode 12 is α1, the external electrodes The thermal expansion coefficient ratio (α1 / α2) is 0.9 or more and less than 1, where α2 is the coefficient of thermal expansion of the metal composing 15.

  This is because when the ratio of the thermal expansion coefficients (α1 / α2) is smaller than 0.9, the difference between the thermal expansion coefficient of the metal in the internal electrode 12 and the thermal expansion coefficient of the metal in the external electrode 15 becomes too large. When the number of continuous driving of the element increases and the element temperature rises, adhesion failure occurs at the joint between the internal electrode 12 and the external electrode 15, and the effective displacement amount of the multilayer piezoelectric element becomes small or during continuous driving. This is because each electrode is peeled off or a disconnection occurs at the joint between the internal electrode 12 and the external electrode 15. On the other hand, when the ratio of the thermal expansion coefficients (α1 / α2) is 1 or more, the piezoelectric ceramic itself changes in size in addition to the thermal expansion of the internal electrode 12 when the multilayer piezoelectric element is continuously driven. And the load concerning the junction part of the external electrode 15 becomes large. For this reason, the durability of the multilayer piezoelectric element is reduced, the effective displacement amount is reduced, and peeling or disconnection as described above occurs during continuous driving.

  That is, when the ratio of thermal expansion coefficients (α1 / α2) is 0.9 or more and less than 1, the problem that the effective displacement amount of the multilayer piezoelectric element is reduced and the problem that the peeled portion is sparked and broken are prevented. it can. In addition, the malfunction of the apparatus is eliminated, and excellent durability without thermal runaway can be achieved.

  In the multilayer piezoelectric element of the present invention as described above, the ratio of thermal expansion coefficients (α1 / α2) may be set as follows in order to set it to 0.9 or more and less than 1.

  Up to now, in order to produce a laminated thermoelectric element, the piezoelectric bodies 11 and the internal electrodes 12 are alternately laminated, and then simultaneously fired to sinter the piezoelectric ceramic and the internal electrodes 12. It was provided. At this time, in order to sinter the piezoelectric body 11 and the internal electrode 12 at the same time, as the internal electrode 12 material, silver having a feature that the sintering temperature is higher than that of silver alone and the sintering temperature is lower than that of palladium or platinum alone. An alloy metal of palladium was used for the internal electrode 11 material. On the other hand, in order to form the external electrode 15 at a temperature lower than the temperature at which the piezoelectric body 11 and the internal electrode 12 were simultaneously fired, a silver paste obtained by adding glass frit to silver was printed and fired. However, the mismatch between the metal materials of the internal electrode 12 and the external electrode 15 causes a difference in thermal expansion, resulting in a decrease in durability of the element. That is, it was smaller than 0.9 when expressed by the ratio of thermal expansion coefficients (α1 / α2).

  On the other hand, in the present invention, in order to set the ratio (α1 / α2) of the thermal expansion coefficient to 0.9 or more and less than 1, the internal electrode 12 and the external electrode 15 are configured with an electrode material having a similar thermal expansion coefficient, It is necessary to add an inorganic compound having a thermal expansion coefficient close to the internal electrode 12 and the external electrode 15. In particular, if the metal component is unevenly distributed at the location where the internal electrode 12 metal and the external electrode 15 metal are joined without uniformly dispersing the metal and the inorganic compound in these electrodes, the internal electrode resistance is reduced and the element temperature is reduced. It is effective in suppressing the rise of For this purpose, there is a method of slowing the rate of temperature decrease from the maximum firing temperature when firing the external electrode 15. Specifically, the temperature lowering rate may be 600 ° C./hour or less, preferably 300 ° C./hour or less. In order to increase the durability of the element, the ratio of thermal expansion coefficients (α1 / α2) is preferably 0.95 or more and less than 1, more preferably, the ratio of thermal expansion coefficients (α1 / α2) is 0. It can be achieved by setting it to 97 or more and less than 1.

  Further, as shown in FIG. 2, the multilayer piezoelectric element of the present invention has a multilayer body 13 in which at least one piezoelectric body 11 and a plurality of internal electrodes 12 are alternately stacked. In a laminated piezoelectric element that includes a pair of external electrodes 15 in which the internal electrodes 12 are alternately connected to every other side surface and is driven by applying an electric field to the external electrodes 15, the bonding of the internal electrodes 12 and the external electrodes 15 The intermediate layer 20 must be provided in the part.

  This is because, for example, if the external electrode 15 is formed by a thin film manufacturing technique such as sputtering, an intermediate layer cannot be formed, so that stress caused by a difference in thermal expansion between the internal electrode 12 and the external electrode 15 is caused by the internal electrode 12 and the external electrode 15. When the laminated piezoelectric element is driven to concentrate on the joint portion, it breaks at the joint portion between the internal electrode 12 and the external electrode 15 and sparks at the fracture surface, or the driving of the element is easily stopped.

  On the other hand, in order to form the intermediate layer 20, the external electrode 15 may be formed by baking, and the metal components contained in the internal electrode 12 and the external electrode 15 may be interdiffused.

  Specifically, this is a method of baking an external electrode paste to which a low melting point glass frit is added so that a liquid phase can be formed in the external electrode at a temperature lower than the internal electrode firing temperature. However, since the intermediate layer 20 cannot be formed only by the above method, a metal oxide constituting the external electrode 15 may be further added to the external electrode paste to promote dispersion of the external electrode metal in the liquid phase. As a result, the sintering of the external electrode 15 proceeds, and at the same time, the intermediate layer 20 can be formed in the internal electrode 12 in contact with the external electrode 15 at the junction between the internal electrode and the external electrode via the liquid phase. At this time, only the metal oxide constituting the external electrode 15 may be added to the external electrode paste. However, in order to form a liquid phase at a low temperature, it is mixed with other glass components or glass in advance. It is preferable to add an oxide of a metal constituting the external electrode as a frit component.

  Moreover, although the method of confirming formation of the intermediate | middle layer 20 may be with a microscope, Preferably it can confirm with SEM.

  When the thermal expansion coefficient of the metal element constituting the internal electrode 12 is α1, and the thermal expansion coefficient of the metal constituting the external electrode 15 is α2, the ratio of thermal expansion coefficients (α1 / α2) is 0.9 or more and 1 By providing the intermediate layer 20 at the joint between the internal electrode 12 and the external electrode 15, a laminated piezoelectric element having extremely excellent durability can be obtained.

  At this time, 80% by mass or more of the metal composition constituting the internal electrode 12 is the main component of the metal composition constituting the external electrode 15, so that the metal part in the internal electrode 12 and the metal part in the external electrode 15 Can be mutually diffused, and at the same time, no new intermetallic compound or alloy is formed, so that formation of a non-uniform compositional point that becomes a starting point of stress breakdown is prevented at the joint between the internal electrode 12 and the external electrode 15. be able to. As a result, malfunction of the apparatus can be eliminated, and excellent durability without thermal runaway can be achieved. On the other hand, when the metal composition of the internal electrode 12 is composed of less than 80% by mass of the main component of the metal composition of the external electrode 15, a new intermetallic compound or alloy is formed between the internal electrode 12 and the external electrode 15. In some cases, the formation portion may become hard and brittle. In particular, since the laminated piezoelectric element is an element whose dimensions change by driving, a stress is applied to the joint between the external electrode 15 and the internal electrode 12 as the dimension changes. When a hard and brittle intermetallic compound or alloy is formed at this joint, the above-described peeling or disconnection may occur during continuous driving accompanied by deformation of the element. On the other hand, if the internal electrode 12 is constituted only by the main component of the metal composition constituting the external electrode 15, the intermediate layer 20 cannot be formed by mutual diffusion. Therefore, since a stress relaxation layer is not formed at the joint between the internal electrode 12 and the external electrode 15, durability cannot be achieved when the stacked piezoelectric element is displaced during continuous driving.

  In order to increase the durability of the element, 85% by mass or more of the metal composition constituting the internal electrode 12 is preferably the main component of the metal composition constituting the external electrode 15, more preferably, 90 mass% or more, More preferably, it can achieve by setting it as 95 mass%.

  In the multilayer piezoelectric element of the present invention, the intermediate layer 20 is preferably composed of a component composed of a metal component constituting the internal electrode 12 and a metal component constituting the external electrode 15. Thereby, the internal electrode 12 and the external electrode 15 can mutually diffuse and can have very strong adhesion strength. Furthermore, since the atmosphere when firing the internal electrode 12 and the atmosphere when firing the external electrode 15 can be made the same, it prevents chemical reactions such as oxidation-reduction reactions of the electrode constituent metals accompanying the firing atmosphere change. I can do it. Therefore, adhesion failure occurs between the internal electrode 12 and the external electrode 15, and the above-described peeling and disconnection can be suppressed during continuous driving, the device does not malfunction, and excellent durability without thermal runaway Can have.

  Here, when an inorganic compound such as glassy is present in the intermediate layer 20, stress due to the difference in thermal expansion between the internal electrode 12 and the external electrode 15 concentrates on the intermediate layer 20, so that an inorganic compound that is harder than metal and brittle Since this is a starting point of destruction, the above-described peeling or disconnection may occur during continuous driving accompanied by element deformation.

  In order to form the intermediate layer 20 with a component composed of a metal component constituting the internal electrode 12 and a metal component constituting the external electrode 15, a liquid phase to which an external electrode oxide is added is formed during the formation of the external electrode. The metal component is selectively crystal-grown between the metal and the external electrode metal, and the liquid phase component is driven out of the intermediate layer 20 to form the intermediate layer 20. For this purpose, it is required to form a liquid phase when maintaining the external electrode firing temperature and not leave the inorganic compound in the intermediate layer 20 in the cooling stage, but by adding external electrode oxide to the glass frit, During firing and cooling, the metal component of the external electrode oxide is taken into the intermediate layer 20, and the liquid phase can be deposited as a glass layer around the intermediate layer 20. At this time, if the cooling rate is high, the metal component of the external electrode oxide is formed in the intermediate layer 20 as it is before the metal component of the external electrode oxide is taken into the intermediate layer 20. The cooling rate may be slower than 500 ° C./hour.

  In the multilayer piezoelectric element of the present invention, when the thermal expansion coefficient of the intermediate layer 20 is α3, stress during element driving is concentrated on the intermediate layer 20 regardless of whether α3 is larger or smaller than α1 and α2. Break. Further, when α2 <α3 <α1, when the laminated piezoelectric element is continuously driven, the piezoelectric ceramic itself changes in size in addition to the thermal expansion of the internal electrode 12, and therefore, the joint portion between the internal electrode 12 and the external electrode 15 As a result, the load applied to the surface becomes large, the durability is lowered, the effective displacement amount is reduced, and peeling or disconnection occurs during continuous driving. Therefore, by satisfying α1 <α3 <α2, the internal electrode 12 and the external electrode 15 can mutually diffuse to generate a very strong adhesion strength, and also due to a difference in thermal expansion between the internal electrode and the external electrode. Since stress is concentrated on the entire intermediate layer, it is possible to avoid concentration of stress at one point, and adhesion failure occurs between the internal electrode 12 and the external electrode 15 to suppress the peeling and disconnection as described above during continuous driving. In addition, the malfunction of the apparatus can be eliminated, and furthermore, excellent durability without thermal runaway can be achieved. The thermal expansion coefficient of the intermediate layer 20 can be measured by measuring the temperature and the dimension of the intermediate layer 20 by heating while measuring the temperature at the observation location during SEM observation. Alternatively, a sample having the same composition can be separately prepared to obtain the thermal expansion coefficient.

  In the multilayer piezoelectric element of the present invention, it is preferable that the composition of the intermediate layer 20 changes in a gradient manner from the metal composition in the internal electrode 12 to the metal composition in the external electrode 15. As a result, when the multilayer piezoelectric element is continuously driven, the internal electrode 12 and the intermediate layer 20, and the external electrode 15 and the intermediate layer 20, even if the piezoelectric ceramic itself changes in size in addition to the thermal expansion of the internal electrode 12. Since the stress concentration between the internal electrode 12 and the external electrode 15 can be absorbed, the peeling and disconnection during continuous driving due to poor adhesion between the internal electrode 12 and the external electrode 15 can be suppressed. There is no malfunction, and it can have excellent durability without thermal runaway. For this purpose, heat treatment is required when the external electrode is mounted on the element. In particular, in order to prevent the metal composition of the internal electrode and the metal composition of the external electrode from diffusing and becoming uniform, the melting point or the liquidus is lower than the metal composition of the internal electrode and the metal composition of the external electrode. It is necessary to heat-treat at the temperature. Preferably, heat treatment is performed at a temperature of 50% to 95%, more preferably 80% to 95% of the melting point or the absolute temperature of the liquidus, so that the composition of the intermediate layer 20 is a metal composition in the internal electrode 12. To the metal composition in the external electrode 15 can be changed in a gradient manner.

  Furthermore, it is desirable that the metal composition in the internal electrode 12 and in the external electrode is mainly composed of a Group VIII metal and / or a Group Ib metal. This is because the above-described metal composition has high heat resistance, so that the piezoelectric body 11 and the internal electrode 12 having a high firing temperature can be fired simultaneously.

  Further, when the metal composition in the internal electrode 12 has a group VIII metal content of M1 (mass%) and a group Ib metal content of M2 (mass%), 0 <M1 ≦ 15, 85 ≦ M2 < It is preferable that the main component is a metal composition satisfying 100 and M1 + M2 = 100. This is because when the Group VIII metal exceeds 15 mass%, the specific resistance of the internal electrode 12 increases, and the internal electrode 12 may generate heat when the stacked piezoelectric element is continuously driven. Further, in order to suppress migration of the group Ib metal in the internal electrode 2 to the piezoelectric body 11, the group VIII metal is preferably 0.001% by mass to 15% by mass. Moreover, 0.1 mass% or more and 10 mass% or less are preferable at the point of improving the durability of a laminated piezoelectric element. Moreover, when it is excellent in heat conduction and needs higher durability, 0.5 mass% or more and 9.5 mass% or less are more preferable. In addition, when higher durability is required, 2% by mass or more and 8% by mass are more preferable.

  Here, when the group Ib metal content is less than 85% by mass, the specific resistance of the internal electrode 12 increases, and the internal electrode 12 may generate heat when the laminated piezoelectric element is continuously driven. Further, in order to suppress migration of the group Ib metal in the internal metal 12 to the piezoelectric body 11, the group Ib metal is preferably set to 85 mass% or more and 99.999 mass% or less. Moreover, 90 mass% or more and 99.9 mass% are preferable in the point of improving the durability of a laminated piezoelectric element. Moreover, when higher durability is required, 90.5 mass% or more and 99.5 mass% are more preferable. Moreover, when the further high durability is calculated | required, 92 to 98 mass% is further more preferable.

  The Group VIII metal and the Group Ib metal showing the mass% of the metal component in the internal electrode 12 can be specified by an analysis method such as an EPMA (Electron Probe Micro Analysis) method.

  Furthermore, the metal component in the internal electrode 12 of the present invention is such that the group VIII metal is at least one of Ni, Pt, Pd, Rh, Ir, Ru, and Os, and the group Ib metal is Cu, Ag, or Au. Of these, at least one is preferable. This is because the metal composition has excellent mass productivity in recent alloy powder synthesis techniques.

  Furthermore, it is preferable that the metal component in the internal electrode 12 is a group VIII metal of at least one of Pt and Pd and a group Ib metal of at least one of Ag and Au. Thereby, there is a possibility that the internal electrode 12 having excellent heat resistance and small specific resistance can be formed.

  Further, the metal component in the internal electrode 12 is preferably a group VIII metal Ni. Thereby, the internal electrode 12 excellent in heat resistance may be formed.

  Further, the metal component in the internal electrode 12 is preferably a group Ib metal of Cu. Thereby, the internal electrode 12 excellent in heat resistance and thermal conductivity may be formed.

Furthermore, it is preferable to add an inorganic composition to the internal electrode 12 together with the metal composition. Accordingly, there is a possibility that the internal electrode 12 and the piezoelectric body 11 can be firmly bonded, and it is preferable that the inorganic composition contains a perovskite oxide composed of PbZrO ₃ —PbTiO ₃ as a main component.

Furthermore, it is preferable that the piezoelectric body 11 has a perovskite oxide as a main component. This is because, for example, when formed of a perovskite type piezoelectric ceramic material typified by barium titanate (BaTiO ₃ ) or the like, the piezoelectric strain constant d ₃₃ indicating the piezoelectric characteristics is high, so that the amount of displacement can be increased. Further, the piezoelectric body 11 and the internal electrode 12 can be fired simultaneously. The piezoelectric body 11 described above preferably contains a perovskite oxide composed of PbZrO ₃ —PbTiO ₃ having a relatively high piezoelectric strain constant d ₃₃ as a main component.

  Furthermore, it is preferable that a calcination temperature is 900 degreeC or more and 1000 degrees C or less. This is because when the firing temperature is 900 ° C. or lower, the firing temperature is low, and thus firing is insufficient, making it difficult to manufacture the dense piezoelectric body 11. Further, if the firing temperature exceeds 1000 ° C., the stress due to the difference between the shrinkage of the internal electrode 12 and the shrinkage of the piezoelectric body 11 during firing becomes large, and cracks may occur during continuous driving of the multilayer piezoelectric element. Because there is.

  Next, a method for producing the multilayer piezoelectric element of the present invention will be described.

The multilayer piezoelectric element of the present invention includes a calcined powder of a perovskite oxide piezoelectric ceramic made of PbZrO ₃ —PbTiO ₃ or the like, a binder made of an organic polymer such as acrylic or butyral, and DOP (phthalate). A ceramic green sheet that becomes a piezoelectric body 11 by mixing a slurry with a plasticizer such as dioctyl acid) or DBP (dibutyl phthalate), and then forming the slurry by a tape molding method such as a known doctor blade method or calendar roll method. Is made.

  Next, a conductive paste is prepared by adding and mixing a binder, a plasticizer, and the like to the metal powder constituting the internal electrode such as silver-palladium, and this is applied to the upper surface of each green sheet by 1-40 μm by screen printing or the like. Print on thickness.

  Then, a plurality of green sheets with conductive paste printed on the upper surface are laminated, the binder is debindered at a predetermined temperature, and then fired at 900 to 1200 ° C., whereby the laminate 13 is produced.

  At this time, when adding a metal powder constituting an internal electrode such as silver-palladium to the green sheet of the inert layer 14 or laminating the green sheet of the inert layer 14, silver-palladium or the like. Inert layer 14 is prepared by mixing the metal powder constituting the internal electrode and other sintering aids in a slurry comprising an inorganic compound, binder and plasticizer constituting the green sheet and printing on the green sheet. Since the shrinkage behavior and shrinkage rate of the other portions can be made to coincide with each other, a dense laminate can be formed.

  In addition, the laminated body 13 is not limited to what is produced by the said manufacturing method, If what can produce the laminated body 13 which laminates | stacks alternately the several piezoelectric body 11 and the some internal electrode 12 will be what? It may be formed by any manufacturing method.

  Thereafter, the internal electrodes 12 whose ends are exposed and the internal electrodes 12 whose ends are not exposed are alternately formed on the side surfaces of the multilayer piezoelectric element, and the internal electrodes 12 and the external electrodes 15 whose ends are not exposed are formed alternately. A groove is formed in the piezoelectric portion, and an insulator such as resin or rubber having a Young's modulus lower than that of the piezoelectric body 11 is formed in the groove. Here, the groove is formed on the side surface of the laminate 13 by an internal dicing device or the like.

  The external electrode 15 is preferably made of silver having a low Young's modulus or an alloy containing silver as a main component because the conductive material constituting the external electrode 15 sufficiently absorbs stress generated by expansion and contraction of the actuator.

A binder is added to the glass powder to produce a silver glass conductive paste, which is formed into a sheet and dried (the solvent is scattered), and the raw density of the sheet is controlled to 6 to 9 g / cm ^3. The sheet is transferred to the external electrode forming surface of the columnar laminate 13, and is at a temperature higher than the softening point of the glass, at a temperature not higher than the melting point of silver (965 ° C.), and not higher than 4/5 of the firing temperature (° C.). By baking at a temperature, the binder component in the sheet prepared using the silver glass conductive paste is scattered and lost, and the external electrode 15 made of a porous conductor having a three-dimensional network structure can be formed.

  The baking temperature of the silver glass conductive paste effectively forms a neck portion, diffuses and joins silver in the silver glass conductive paste and the internal electrode 12, and effectively creates voids in the external electrode 15. The temperature is preferably 550 to 700 ° C. from the viewpoint that the external electrode 15 and the side surface of the columnar laminate 13 are partially joined. The softening point of the glass component in the silver glass conductive paste is preferably 500 to 700 ° C.

  When the baking temperature is higher than 700 ° C., the sintering of the silver powder of the silver glass conductive paste proceeds too much, so that a porous conductor having an effective three-dimensional network structure cannot be formed, and the external electrode 15 May become too dense, and as a result, the Young's modulus of the external electrode 15 may become too high to absorb the stress during driving sufficiently and the external electrode 15 may be disconnected. Preferably, baking should be performed at a temperature within 1.2 times the softening point of the glass.

  On the other hand, when the baking temperature is lower than 550 ° C., since the diffusion bonding is not sufficiently performed between the end portion of the internal electrode 12 and the external electrode 15, the neck portion is not formed, and the internal electrode 12 and the external electrode are not driven. There is a possibility of causing a spark between the electrodes 15.

  Note that the thickness of the silver glass conductive paste sheet is preferably thinner than the thickness of the piezoelectric body 11. More preferably, it is 50 μm or less from the viewpoint of following the expansion and contraction of the actuator.

  Next, the laminated body 13 on which the external electrode 15 is formed is immersed in a silicone rubber solution, and the silicone rubber solution is vacuum degassed to fill the groove of the laminated body 13 with silicone rubber. The laminated body 13 is pulled up, and the side surface of the laminated body 13 is coated with silicone rubber. Thereafter, the silicone rubber coated inside the grooves and coated on the side surfaces of the columnar laminate 13 is cured to complete the multilayer piezoelectric element of the present invention.

  Then, a lead wire is connected to the external electrode 15, a direct current voltage of 0.1 to 3 kV / mm is applied to the pair of external electrodes 15 via the lead wire, and the laminate 13 is subjected to polarization treatment. When a multilayer piezoelectric actuator using the multilayer piezoelectric element is completed, a lead wire is connected to an external voltage supply unit, and a voltage is applied to the internal electrode 12 via the lead wire and the external electrode 15, each piezoelectric The body 11 is largely displaced by the inverse piezoelectric effect, and thereby functions as an automobile fuel injection valve that injects and supplies fuel to the engine, for example.

  Furthermore, a conductive auxiliary member made of a conductive adhesive in which a metal mesh or a mesh-like metal plate is embedded on the outer surface of the external electrode 15 may be formed. In this case, even when a large current is input to the actuator by providing a conductive auxiliary member on the outer surface of the external electrode 15 and the actuator is driven at a high speed, a large current can flow through the conductive auxiliary member. For the reason that the current flowing through 15 can be reduced, the external electrode 15 can be prevented from causing local heat generation and disconnection, and the durability can be greatly improved. Furthermore, since a metal mesh or a mesh-like metal plate is embedded in the conductive adhesive, it is possible to prevent the conductive adhesive from cracking.

  The metal mesh is a braided metal wire, and the mesh metal plate is a mesh formed by forming holes in a metal plate.

  Furthermore, the conductive adhesive constituting the conductive auxiliary member is preferably made of a polyimide resin in which silver powder is dispersed. That is, by dispersing silver powder having a low specific resistance in a polyimide resin having high heat resistance, a conductive auxiliary member having a low resistance value and maintaining a high adhesive strength can be formed even when used at high temperatures. . More preferably, the conductive particles are non-spherical particles such as flakes or needles. This is because by making the shape of the conductive particles non-spherical particles such as flakes and needles, the entanglement between the conductive particles can be strengthened, and the shear strength of the conductive adhesive can be further increased. This is because it can be increased.

  The multilayer piezoelectric element of the present invention is not limited to these, and various modifications can be made without departing from the gist of the present invention.

  Moreover, although the example which formed the external electrode 15 in the side surface which the laminated body 13 opposes above was demonstrated, in this invention, you may form a pair of external electrode in the side surface provided adjacently, for example.

  FIG. 3 shows an injection device according to the present invention. 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. Has been.

  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.

  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.

  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.

  Further, the present invention relates to a multilayer piezoelectric element and an injection device, but is not limited to the above-described embodiments. For example, a fuel injection device for an automobile engine, a liquid injection device such as an ink jet, an optical device, etc. Drive elements mounted on precision positioning devices, vibration prevention devices, etc., or sensor elements mounted on combustion pressure sensors, knock sensors, acceleration sensors, load sensors, ultrasonic sensors, pressure sensors, yaw rate sensors, and piezoelectric elements Needless to say, the present invention can be applied to elements other than circuit elements mounted on a gyroscope, a piezoelectric switch, a piezoelectric transformer, a piezoelectric breaker, or the like as long as the elements use piezoelectric characteristics.

  A multilayer piezoelectric actuator comprising the multilayer piezoelectric element of the present invention was produced as follows.

First, a slurry in which a calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ), a binder, and a plasticizer is mixed, and the piezoelectric body 11 having a thickness of 150 μm is formed by a doctor blade method. A ceramic green sheet was prepared.

  On one side of this ceramic green sheet, 300 sheets of a conductive paste in which a binder is added to a silver-palladium alloy formed at an arbitrary composition ratio are laminated by a screen printing method to a thickness of 3 μm, and 1000 ° C. Baked in.

  Next, a groove having a depth of 50 μm and a width of 50 μm was formed at every other end of the internal electrode on the side surface of the columnar laminate by a dicing apparatus.

Next, a mixture of 90% by volume of flaky silver powder having an average particle diameter of 2 μm and 10% by volume of amorphous glass powder having a remaining softening point of 640 ° C. mainly composed of silicon having an average particle diameter of 2 μm. In addition, 8 parts by mass of the binder was added to 100 parts by mass of the total mass of the silver powder and the glass powder, and mixed sufficiently to prepare a silver glass conductive paste. The silver glass conductive paste thus produced was formed on a release film by screen printing, dried and then peeled off from the release film to obtain a sheet of silver glass conductive paste. The raw density of this sheet was measured by the Archimedes method and found to be 6.5 g / cm ³ .

  Next, the sheet of silver glass paste was transferred to the surface of the external electrode 15 of the laminate 13 and baked at 650 ° C. for 30 minutes to form the external electrode 15 made of a porous conductor having a three-dimensional network structure. The porosity of the external electrode 15 at this time was 40% when a cross-sectional photograph of the external electrode 15 was measured using an image analyzer.

  Thereafter, a lead wire is connected to the external electrode 15, a 3 kV / mm direct current electric field is applied to the positive and negative external electrodes 15 through the lead wire for 15 minutes, and polarization is performed. As shown in FIG. A piezoelectric element was produced.

  (Example 1) In addition to the above manufacturing method, in the multilayer piezoelectric actuator of the present invention manufactured by controlling the metal composition of the internal electrode 12 and the external electrode 15, the element displacement before and after continuous driving of the multilayer piezoelectric actuator The rate of change of was measured.

When a DC voltage of 170 V was applied to the multilayer piezoelectric actuator obtained as described above, a displacement of 45 μm in the stacking direction was obtained in all multilayer piezoelectric actuators. Further, a test was performed in which the multilayer piezoelectric actuator was continuously driven up to 1 × 10 ⁹ times by applying an AC voltage of 0 to +170 V at a frequency of 150 Hz at room temperature.

Further, the thermal expansion coefficients of the internal electrode 12 and the external electrode 15 were measured by heating while measuring the temperature at the observation location by SEM, and measuring the temperature and the dimensions of the internal electrode 12 and the external electrode 15. The results are as shown in Table 1.

  From Table 1, Sample Nos. 1, 2, and 15 as comparative examples have a thermal expansion coefficient of α1 for the metal element constituting the internal electrode 12 and α2 for the thermal expansion coefficient of the metal constituting the external electrode 15, Since the ratio (α1 / α2) of the thermal expansion coefficient was 1 or more, when the laminated piezoelectric actuator was continuously driven, the piezoelectric ceramic itself changed dimensions in addition to the thermal expansion of the internal electrode 12, and the internal electrode 12 and the external electrode The load applied to the joint portion 15 increased, sparking between the internal electrode 12 and the external electrode 15, and disconnection occurred during continuous driving. In Sample No. 14, the effective displacement amount of the multilayer piezoelectric actuator was reduced by the load applied to the joint portion.

  On the other hand, Sample No. 13, which is a comparative example, had a thermal expansion coefficient ratio (α1 / α2) smaller than 0.9, so that the thermal expansion coefficient α1 of the metal constituting the internal electrode 12 and the thermal expansion constituting the external electrode 15 were. The difference from the coefficient α2 was increased, an adhesion failure occurred between the internal electrode 12 and the external electrode 15, and the effective displacement amount of the multilayer piezoelectric element was reduced.

On the other hand, in Sample Nos. 3 to 12, which are examples of the present invention, the laminate formed with the ratio (α1 / α2) of the thermal expansion coefficient between the internal electrode 12 and the external electrode 15 in the range of 0.9 or more and less than 1. Since it is a piezoelectric actuator, it has an effective displacement required for a stacked piezoelectric actuator without significant decrease in element displacement even after continuous driving of 1 × 10 ⁹ times. A multilayer piezoelectric actuator having excellent durability that does not cause operation could be produced.

(Example 2) In addition to the above manufacturing method, in the laminated piezoelectric actuator of the present invention manufactured by controlling the metal composition of the internal electrode 12 and the external electrode 15, the formation state of the intermediate layer 20 and the main of the external electrode 15 The ratio of the component constituting the internal electrode and the change rate of the element displacement before and after continuous driving of the multilayer piezoelectric actuator were measured.

  The external electrode 15 was formed by printing and baking a paste obtained by adding glass frit to the metal composition of the external electrode 15.

When a DC voltage of 170 V was applied to the multilayer piezoelectric actuator obtained as described above, a displacement of 45 μm in the stacking direction was obtained in all multilayer piezoelectric actuators. Furthermore, a driving test was performed in which the multilayer piezoelectric actuator was continuously driven up to 1 × 10 ⁹ times by applying an AC voltage of 0 to +170 V at a frequency of 150 Hz at room temperature. The results are as shown in Table 2.

  From Table 2, since Sample Nos. 12 and 13 as comparative examples did not form an intermediate layer, the metal composition constituting the internal electrode 12 and the metal composition constituting the external electrode 15 were not similar. The load applied to the joint portion between the internal electrode 12 and the external electrode 15 increased, and sparking occurred between the internal electrode and the external electrode, resulting in disconnection during continuous driving.

In contrast, Sample Nos. 1 to 11 which are examples of the present invention formed an intermediate layer, and the metal composition constituting the internal electrode 12 and the metal composition constituting the external electrode 15 were similar. Even after being driven 1 × 10 ⁹ times continuously, the element displacement does not decrease significantly, it has the effective displacement required as a laminated piezoelectric actuator, and thermal runaway and malfunction do not occur A multilayer piezoelectric actuator with excellent durability could be fabricated.

  (Example 3) In the above-described manufacturing method, in the multilayer piezoelectric actuator having the internal electrode 12 formed with various electrode material compositions, the maximum rate of change of the element displacement amount during continuous driving of the multilayer piezoelectric actuator was measured. The relationship between the electrode material composition of the electrode 12 and the degree of deterioration due to continuous driving of the multilayer piezoelectric actuator was verified.

  Here, the degree of deterioration is the measurement of the maximum element displacement during driving the multilayer piezoelectric actuator at an arbitrary number of times (maximum element displacement during continuous driving). The amount of element displacement after being driven by the number of times (the amount of element displacement after continuous driving) is measured, and the amount of element displacement after the continuous driving is indicated as a ratio of change with respect to the maximum amount of element displacement during the continuous driving. ing. Accordingly, it is possible to confirm the deterioration caused by continuously driving the laminated piezoelectric actuator being driven at an arbitrary number of times.

When a DC voltage of 170 V was applied to the multilayer piezoelectric actuator obtained as described above, a displacement of 45 μm in the stacking direction was obtained in all multilayer piezoelectric actuators. Furthermore, a driving test was performed in which an AC voltage of 0 to +170 V was applied to the multilayer piezoelectric actuator at room temperature at a frequency of 150 Hz and continuously driven up to 1 × 10 ⁹ times. The results are as shown in Table 2.

  From Table 3, since the internal electrode 12 is formed of 100% silver in the sample number 1, silver migration occurs, and the load applied to the joint portion between the internal electrode 12 and the external electrode 15 increases, and the internal electrode 12 and the external electrode 15 are increased. Sparking between them caused disconnection during continuous driving, making continuous driving difficult.

  Sample Nos. 18 and 19 had a group VIII metal content of more than 15% by mass in the metal composition in the internal electrode 12, and a group Ib metal content of less than 85% by mass. Deterioration increased by continuous driving, and durability of the multilayer piezoelectric actuator decreased.

  In contrast, in Sample Nos. 2 to 16, when the metal composition in the internal electrode 12 has a group VIII metal content of M1 (mass%) and a group Ib metal content of M2 (mass%), 0 <M1 ≦ 15, 85 ≦ M2 <100, and a metal composition satisfying M1 + M2 = 100 is used as a main component, so that the specific resistance of the internal electrode 12 can be reduced and the heat generated in the internal electrode 12 can be suppressed even when continuously driven. As a result, a multilayer actuator with a stable element displacement could be produced.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention.

1A and 1B show a laminated piezoelectric element of the present invention, in which FIG. 1A is a perspective view, and FIG. 1B is a perspective developed view showing a laminated state of a piezoelectric layer and an internal electrode layer. It is a principal part enlarged view of the longitudinal cross-sectional view along the A-A 'line of Fig.1 (a). It is a side view which shows the injection apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Piezoelectric body 12 ... Internal electrode 13 ... Laminated body 14 ... Inactive layer 15 ... External electrode 20 ... Intermediate | middle layer 31 ... Storage container 33 ... Injection hole 35 ... Valve 43 ... Piezoelectric actuator

Claims (18)

It has a laminate formed by alternately laminating at least one piezoelectric body and a plurality of internal electrodes, and has a pair of external electrodes in which the internal electrodes are alternately connected to every other side surface of the laminate, In the multilayer piezoelectric element driven by applying an electric field to the external electrode, the thermal expansion coefficient of the metal constituting the internal electrode is α1, and the thermal expansion coefficient of the metal constituting the external electrode is α2. A multilayer piezoelectric element having a ratio (α1 / α2) of 0.9 or more and less than 1. It has a laminate formed by alternately laminating at least one piezoelectric body and a plurality of internal electrodes, and has a pair of external electrodes in which the internal electrodes are alternately connected to every other side surface of the laminate, A multilayer piezoelectric element that is driven by applying an electric field to the external electrode, wherein an intermediate layer is provided at a joint between the internal electrode and the external electrode. 3. The multilayered piezoelectric according to claim 1, wherein the metal composition constituting the internal electrode contains 80 mass% or more and less than 100 mass% of a main component of the metal composition constituting the external electrode. element. 4. The multilayer piezoelectric element according to claim 2, wherein the intermediate layer comprises a metal composition constituting the internal electrode and a metal composition constituting the external electrode. The multilayer piezoelectric element according to any one of claims 2 to 4, wherein α1 <α3 <α2 when α3 is a thermal expansion coefficient of the intermediate layer. 6. The multilayer piezoelectric element according to claim 2, wherein the composition of the intermediate layer changes in a gradient manner from the metal composition in the internal electrode to the metal composition in the external electrode. The multilayer piezoelectric element according to any one of claims 1 to 6, wherein the metal composition in the internal electrode and the external electrode contains a Group VIII metal and / or a Group Ib metal as a main component. When the content of the group VIII metal in the internal electrode is M1 (mass%) and the content of the group lb metal is M2 (mass%), 0 <M1 ≦ 15, 85 ≦ M2 <100, M1 + M2 = 100 The multilayer piezoelectric element according to claim 7, wherein the multilayer piezoelectric element is satisfied. The group VIII metal in the internal electrode 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. The multilayer piezoelectric element according to claim 7 or 8, characterized in that The group VIII metal in the internal electrode is at least one of Pt and Pd, and the group Ib metal is at least one of Ag and Au. The laminated piezoelectric element described. The multilayer piezoelectric element according to claim 7, wherein the group VIII metal in the internal electrode is Ni. The multilayer piezoelectric element according to claim 7, wherein the group Ib metal in the internal electrode is Cu. The multilayer piezoelectric element according to claim 1, wherein an inorganic composition is added to the internal electrode together with a metal composition. 14. The multilayer piezoelectric element according to claim 13, wherein the inorganic composition contains a perovskite oxide composed of PbZrO ₃ —PbTiO ₃ as a main component. 15. The multilayer piezoelectric element according to claim 1, wherein the piezoelectric body contains a perovskite oxide as a main component. The multilayer piezoelectric element according to claim 15, wherein the piezoelectric body contains a perovskite oxide composed of PbZrO ₃ —PbTiO ₃ as a main component. The multilayer piezoelectric element according to any one of claims 1 to 16, wherein a firing temperature of the multilayer body is 900 ° C or higher and 1000 ° C or lower. A storage container having an injection hole, the stacked piezoelectric element stored in the storage container, and a valve that ejects liquid from the injection hole by driving the stacked piezoelectric element. An injection device comprising:

Images