JP2007189092A - Laminated piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for increasing the displacement of a laminated piezoelectric element. <P>SOLUTION: The laminated piezoelectric element comprises a laminate 1 having a plurality of piezoelectric layers 2 laminated in the direction of a prescribed axis A, and internal electrode layers 4, 5 formed between the adjacent piezoelectric layers 2; an underlayer 3 that is provided on the surface of the laminate 1 and is connected to the internal electrode layer 4 electrically; and a conductive reinforcement layer 10 joined to the underlayer 3. A resin layer 15 is provided at a non-coated section 30 on the surface of the laminate not coated with the underlayer 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer piezoelectric element.

  A diesel engine is an engine that injects fuel into a cylinder, compresses it to a high pressure and self-ignites, and controls the engine output by the amount of fuel injection. In a diesel engine, fuel injection that sends fuel into the cylinder The role of the device is important. In recent years, the use of diesel engines has increased largely due to the development of so-called common rail type fuel injection devices. This is expected to boost the use of diesel engines. This is because the piezoelectric element can open and close the injection nozzle faster and more accurately than the solenoid element, which makes it possible to send a more appropriate amount of fuel to the cylinder at a more appropriate timing, and to optimize the fuel. As a result, reduction of harmful substances such as particulates, nitrogen oxides, carbon monoxide, hydrocarbons, etc. contained in exhaust gas, improvement of fuel consumption, reduction of engine sound This is because the engine output is improved.

  A piezoelectric element applied to a fuel injection device is used as a drive source of an injection nozzle opening / closing mechanism that generates displacement and stress, and is often used in a state of being housed in a case of metal or the like. Usually, a laminated type is applied as the piezoelectric element.

  In a multilayer piezoelectric actuator in which internal electrodes are alternately offset, an active region (a region that expands and contracts) and an inactive region (a region that does not expand and contract) are included in the element, so that the boundary between the active region and the inactive region is large. There is a possibility that stress is generated and the external electrode is also divided by a crack caused by the stress, and it is required to improve the durability of the external electrode. For this purpose, it is conceivable to prevent the external electrode from being divided by simply increasing the strength of the external electrode. However, when the strength of the external electrode is large, the driving of the element may be hindered, and as a result, the displacement efficiency may be lowered.

Patent Document 1 describes securing conduction by bridging an external electrode base layer.
Japanese Patent Laid-Open No. 7-226541 describes that a single-layer external electrode reinforcing layer is bonded to an offset type element. JP-A-10-229227

The following documents also describe examples in which an external electrode reinforcing layer is joined in an offset type element.
Special table 2003-502869 Special table 2003-502870 Special table 2003-503859

Furthermore, Patent Document 6 describes that the base layer under the conductive reinforcing layer is formed in a stripe shape or a net shape, thereby attempting to prevent the occurrence of cracks and the progress in the ceramic. .
JP 2002-171004 A

  Due to recent demands for miniaturization of elements, it is necessary to further improve the displacement efficiency of the elements when a voltage is applied. For this purpose, it is necessary to reduce the restraining force of the piezoelectric layer by external electrodes. For this purpose, it should be useful to provide regular gaps by forming the underlayer into a net or stripe rather than covering the entire surface of the actuator body with the underlayer of the conductive reinforcing layer without any gaps. It is. However, when actually examined, the solder flows into the uncovered part that is not covered by the underlayer, and the underlayer tends to be fixed to the rigid to suppress deformation. There was a case that it was not so big. Further, when used repeatedly for a long period of time, there is moisture absorption in the gap between the solder and the actuator body surface, which may cause deterioration of the actuator internal electrode and the conductive reinforcing layer.

  The subject of this invention is providing the structure which can enlarge the displacement of a lamination type piezoelectric element.

  The present invention provides a laminate including a plurality of piezoelectric layers laminated in a predetermined axial direction and an internal electrode layer formed between adjacent piezoelectric layers, and is provided on the surface of the laminate. A laminated piezoelectric element comprising a base layer electrically connected to the internal electrode layer, and a conductive reinforcing layer joined to the base layer, the base layer being covered with the base layer The resin layer is provided in the non-coating part of the surface of the laminated body which is not.

Further, the present invention is a method of manufacturing the multilayer piezoelectric element,
Forming the base layer on a side surface of the laminate,
Next, the method includes a step of providing the resin layer on an uncovered portion of the surface of the laminate that is not covered with the base layer, and a step of bonding the conductive reinforcing layer to the base layer.

  According to the present invention, an uncoated portion that does not cover the surface of the laminate is provided in the underlayer pattern. At the same time, by providing the resin layer on the uncoated portion, it is possible to prevent the conductive bonding agent such as solder from flowing into the uncoated portion. Thus, it is possible to increase the displacement by preventing the influence of the conductive bonding agent accumulated in the uncoated portion. Furthermore, by providing a resin layer in the non-covered portion, the insulation in the non-covered portion can be further enhanced to eliminate unnecessary conduction, and the durability can be prevented from being lowered due to moisture absorption.

  Moreover, according to the manufacturing method of this invention, the following effects are obtained further. That is, when the reinforcing layer is bonded to the underlayer with a conductive bonding agent such as solder, a small amount of flux is used to remove the oxide on the underlayer and the solder surface. By using the flux, a stable bonding strength is obtained, and the reliability of the bonded portion is improved. However, it is difficult to completely clean the flux components that have entered the gaps or meshes of the reinforcing layer such as a metal mesh after joining.

  The residual flux component has such a reducibility that it will corrode piezoelectric ceramics when exposed to a high temperature and high humidity environment. Furthermore, when a rapid temperature change is applied in a high temperature / high humidity environment, cracks may develop from a slightly corroded portion. At the same time, when stress is applied when the element is driven, there is a possibility that destruction occurs inside the element. In addition, the bonding strength of the external electrode is reduced due to corrosion, and the external electrode is peeled off, so that the function of the element may be stopped. In the method of the present invention, since the element surface other than the base layer is filled with the resin layer before using the flux, the remaining flux component can be prevented from coming into contact with the ceramic, and ceramic corrosion can be prevented.

  In the present invention, a laminated body is manufactured by laminating a plurality of piezoelectric layers in a predetermined axial direction and forming an internal electrode layer between adjacent piezoelectric layers. Here, preferably, the internal electrode layers are alternately provided with internal electrode layers that function as positive electrodes and internal electrode layers that function as negative electrodes.

  The displacement of the laminate used in the element of the present invention is all of the displacement based on the strain induced in the piezoelectric body by the electric field. That is, the element of the present invention uses a piezoelectric effect that generates a strain amount approximately proportional to the applied electric field in a narrow sense and an electrostrictive effect that generates a strain amount approximately proportional to the square of the applied electric field. However, the present invention is not limited to this, and includes those utilizing phenomena such as polarization reversal observed in all ferroelectric materials and antiferroelectric phase-ferroelectric phase transition found in antiferroelectric materials.

  Although the laminated body which comprises the element of this invention is not limited, It can produce using the green sheet | seat lamination method and the punching simultaneous lamination method. An electrode pattern made of a conductive material is formed on a green sheet mainly composed of a piezoelectric material, and the punching machine is used to form the electrode pattern on the green sheet. Punching is performed while stacking to obtain a green laminate, and the green laminate is fired to obtain a columnar laminate, which is fired and integrated.

  For example, FIG. 1A is a perspective view schematically showing a laminate 1 that can be used in the element of the present invention, and FIG. 1B is a perspective view showing a pattern of internal electrode layers in each piezoelectric layer. is there. FIG. 2A is a longitudinal sectional view schematically showing the laminate, and FIG. 2B is a transverse sectional view of the laminate shown in FIG.

  In this example, a large number of piezoelectric layers 2 are laminated toward a predetermined axis A, and internal electrode layers 4 and 5 are formed between adjacent piezoelectric layers 2. A positive polarity voltage is applied to the internal electrode layer 4, and a negative polarity voltage is applied to the internal electrode layer 5. Since the internal electrode layers 4 and 5 are alternately formed and the planar patterns of the internal electrode layers 4 and 5 are different from each other as shown in FIG. Called. However, the present invention is not limited to the offset laminated piezoelectric element. Each internal electrode layer 4 is electrically connected to the electrode structure 23, and the internal electrode layer 5 is electrically connected to another electrode structure 27. Details of each electrode structure will be described later.

  In producing the laminate, it is preferable to use a green sheet lamination method and a punching simultaneous lamination method. First, a predetermined number of ceramic green sheets mainly comprising a piezoelectric / electrostrictive material are prepared. This ceramic green sheet constitutes the piezoelectric layer after firing. The ceramic green sheet can be produced by a conventionally known ceramic manufacturing method. For example, a piezoelectric / electrostrictive material powder is prepared, and an organic resin (binder), a solvent, a dispersant, a plasticizer, and the like are mixed into a desired composition to prepare a slurry. It is possible to form a sheet by a tape forming method such as a method, a reverse roll coater method, or a reverse doctor roll coater method and cut it to produce a sheet.

  Any piezoelectric (electrostrictive) material may be used as long as the material causes electric field induced strain. It may be crystalline or amorphous, and it is also possible to use a semiconductor ceramic material, a ferroelectric ceramic material, or an antiferroelectric ceramic material. What is necessary is just to select suitably according to a use and to employ | adopt. Moreover, even if it is a material which requires a polarization process, the material which is not required may be sufficient.

  Specifically, lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate, lead nickel tantalate, lead zinc niobate, lead manganese niobate, lead antimony stannate, lead manganese tungstate, cobalt niobium Lead oxide, lead magnesium tungstate, lead magnesium tantalate, barium titanate, sodium bismuth titanate, bismuth neodymium titanate (BNT), sodium niobate, potassium sodium niobate, strontium bismuth tantalate, barium copper tungsten, iron acid Bismuth or a composite oxide composed of two or more of these can be given. These materials include lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth, tin, An oxide such as copper may be dissolved. Above all, materials containing nickel oxide with a composite oxide of lead zirconate, lead titanate and lead magnesium niobate as the main component, composite of lead zirconate, lead titanate, lead magnesium niobate and lead nickel niobate A material containing an oxide as a main component is preferable because a large electric field induced strain can be used. In this case, what contains 0.05-3 mass% in conversion of an oxide as a nickel component is especially preferable. In addition, a material obtained by adding lithium bismutate, lead germanate, or the like to the above materials is preferable because it can exhibit high material properties while realizing low-temperature firing of the piezoelectric / electrostrictive layer, and in particular, the above-described lead zirconate. Lead oxide, lead titanate, magnesium niobate composite oxide as the main component, material containing nickel oxide, lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate composite oxide A material containing 0.05 to 3% by mass in terms of oxide and adding 0.3 to 4% by mass of lead germanate as the nickel component is desirable.

  Next, when a predetermined number of sheets are produced, a conductive film having a predetermined pattern (electrode pattern) is formed on the surface of the sheet using a conductive material. This conductor film is a film that later becomes an internal electrode layer.

  As the means for forming the conductor film, a screen printing method is preferably used, but it may be performed by means such as photolithography, transfer, stamping and the like. As the conductive material to be used, a metal that is solid at room temperature is employed. For example, simple metals such as aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, or lead, or these It is preferable to use an alloy composed of two or more types, for example, one of silver-platinum, platinum-palladium, silver-palladium, etc., alone or in combination of two or more. Further, a mixture or cermet of these materials and aluminum oxide, zirconium oxide, titanium oxide, silicon oxide, cerium oxide, glass, piezoelectric / electrostrictive material, or the like may be used. These materials are selected depending on whether they are fired simultaneously with the piezoelectric / electrostrictive layer. In the case of the internal electrode layer, since it is fired at the same time as the piezoelectric / electrostrictive layer, it does not dissolve even at the firing temperature of the piezoelectric / electrostrictive layer, such as platinum, palladium, platinum-palladium alloy, silver-palladium alloy, etc. Need to use. On the other hand, in the case of a conductor film to be a base film later, since the laminate is formed after firing, it can be fired at a temperature lower than the firing temperature of the piezoelectric body, so aluminum, gold, silver, silver-palladium alloy, silver -Platinum, copper, nickel etc. can be used.

  Next, for a predetermined number of sheets on which a conductor film to be an internal electrode layer is formed later, using a punching machine in which the clearance between the punch and the die is appropriately adjusted as described above, using the punch as a lamination axis, Punching is performed while laminating the processed sheet on the punch, and these are laminated and pressure-bonded to obtain a green laminate. The green laminate is fired to obtain an integrated laminate (fired) body.

  In a preferred embodiment, a conductive base layer is provided on the side surface 31 (see FIG. 1) of the laminate, and the base layer is electrically connected to the corresponding internal electrode. The side surface 31 of the laminated body means a direction substantially parallel to the expansion / contraction direction A of the piezoelectric body. Then, the base layer and the conductive reinforcing layer are joined, the upper conductive reinforcing material is joined to the conductive reinforcing layer, and the base layer and the conductive reinforcing layer are joined by the conductive adhesive. Here, the upper conductive reinforcing material is prevented from being bonded by the conductive bonding agent.

  FIG. 3 is a cross-sectional view showing a main part of an element according to an embodiment of the present invention. As described above, in the laminate 1, a large number of piezoelectric layers 2 are laminated in the direction of arrow A, and internal electrode layers 4 or 5 are formed between adjacent piezoelectric layers. Each internal electrode layer 4 is electrically connected to the base layer 3 through the terminal portion 20. The underlayer 3 does not continuously cover the surface of the laminate 1, and is provided with a regular uncovered portion 30. Each uncovered portion 30 is filled with a resin layer 15. The surface of the laminate is covered with the resin layer 15 and the base layer 3 without any gaps.

  The foundation layer 3 is bonded to the conductive reinforcing layer 10 via the conductive bonding agent 9, and the conductive reinforcing layer 10 is bonded to the upper conductive reinforcing material 11. A composite conductive reinforcing layer 12 is formed by the conductive reinforcing layer and the upper conductive reinforcing material. The upper conductive reinforcement 11 is not wetted by the conductive bonding agent 9 and is therefore not bonded to the underlying layer.

  Also in the example shown in FIG. 4, each internal electrode layer 4 is electrically connected to the base layer 3 through the terminal portion 20. The underlayer 3 does not continuously cover the surface of the laminate 1, and is provided with a regular uncovered portion 30. Each uncovered portion 30 is filled with a resin layer 15. The surface of the laminate is covered with the resin layer 15 and the base layer 3 without any gaps. The foundation layer 3 is bonded to the conductive reinforcing layer 10A via the conductive bonding agent 9, and the conductive reinforcing layer 10A is bonded to the upper conductive reinforcing material 11A. A composite conductive reinforcing layer 12A is formed by the conductive reinforcing layer 10A and the upper conductive reinforcing material 11A. The upper conductive reinforcing material 11 </ b> A is not wetted by the conductive bonding agent 9 and is therefore not bonded to the underlayer 3.

  In the present invention, the underlying layer may be provided with an uncovered portion, and the planar pattern of the underlying layer and the planar pattern of the uncovered portion are not particularly limited. Preferably, the underlayer is made up of regularly arranged island portions. The form of each island portion is not particularly limited, and may be a circle, an ellipse, a polygon, an elongated quadrilateral, or the like. Alternatively, the underlayer may have a net shape.

  As shown in FIG. 5A, the conductive portion 20 of the internal electrode is exposed on the surface of the multilayer body 1. Each conductive portion 30 has an elongated quadrilateral shape in this example. Next, as shown in FIG. 5B, a large number of elongated quadrilateral base layers 3 </ b> A are regularly formed and arranged on the conductive portion 20. Here, the resin layer described above is formed on the uncovered portion 30 of the adjacent base layer 3A.

  Further, as shown in FIG. 6A, a circular island portion 3B can be formed on the conductive portion 20 as a base layer. The shape of each island-like portion does not have to be a circle, and can be any shape such as an ellipse, a racetrack, a polygon, or a star.

  In the example shown in FIG. 6B, a net-like base layer 3 </ b> C is formed on the conductive portion 20. Each mesh 30 is an uncovered portion. A resin layer is formed in each uncoated portion 30.

  A screen printing method is preferably used as the base layer forming means, but it may be performed by means such as photolithography, transfer, stamping and the like. As the conductive material to be used, a metal that is solid at room temperature is employed. For example, simple metals such as aluminum, titanium, chromium, iron, cobalt, nickel, copper, zinc, niobium, molybdenum, ruthenium, palladium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, or lead, or these It is preferable to use an alloy composed of two or more types, for example, one of silver-platinum, platinum-palladium, silver-palladium, etc., alone or in combination of two or more. Further, a mixture or cermet of these materials and aluminum oxide, zirconium oxide, titanium oxide, silicon oxide, cerium oxide, glass, piezoelectric / electrostrictive material, or the like may be used.

  Further, in order to provide an uncoated portion on the underlayer, the uncoated portion can be patterned during the above-described screen printing, photolithography, transfer, and stamping. Alternatively, the non-covered portion can be formed by covering a predetermined portion of the surface of the laminate without gaps by the above-described method and then peeling off a part of the base layer by sawing, polishing, blasting, or the like.

In the present invention, the specific material of the resin layer formed on the uncoated portion of the base layer is not particularly limited, but the following can be exemplified. Fluorine resin, polyamideimide resin, fluorine-polyamideimide mixed resin, epoxy resin, polyester resin, silicone resin, polyimide resin are candidates.
A hybrid resin obtained by mixing these organic resins and silica particles is also useful in terms of heat resistance. Specifically, a material in which an epoxy resin, a polyimide resin, and a silica resin are mixed can be applied.

  In a preferred embodiment, the conductive reinforcing layer is connected to the base layer of the multilayer piezoelectric element, and the upper conductive reinforcing material is bonded onto the conductive reinforcing layer, and the conductive bonding agent is placed on the upper layer. The upper conductive reinforcement was not joined. With such a structure, the functions of the conductive reinforcing layer and the upper conductive reinforcing material were clearly separated, and the contradictory effects of improving displacement efficiency and improving durability were successfully achieved.

  That is, a desired restraining force can be generated on the element body by bonding the conductive reinforcing layer to the base layer with the conductive bonding agent. At this time, since the upper conductive reinforcing material is not directly bonded by the conductive bonding agent, the binding force can be set to the optimum value by designing the conductive reinforcing layer. At the same time, by providing a sufficiently high strength to the upper conductive reinforcing material, it is possible to ensure desired conduction even in a situation where the base layer and the conductive reinforcing layer are disconnected or the resistance value is increased. .

  The joining method of the conductive reinforcing layer and the upper conductive reinforcing material is not particularly limited. Preferably, the two are integrated by welding, diffusion bonding, brazing or a conductive adhesive. Such a joining method is well known in the metal working field.

  In a preferred embodiment, the conductive reinforcing layer is made of a metal plate. As a result, the thickness of the conductive reinforcing layer can be kept relatively small, and the restraining force can be reduced, so that the displacement of the laminate can be increased. In order to increase the displacement of the element, the thickness of the conductive reinforcing layer is preferably 500 μm or less, and more preferably 250 μm or less. However, if the conductive reinforcing layer is too thin, disconnection is likely to occur, so that it is preferably 10 μm or more, and more preferably 30 μm or more.

  The conductive reinforcing layer may be a plate-like material that does not substantially stretch. In this case, the displacement of the laminate can be increased by making the plate-like object thinner.

  Moreover, in suitable embodiment, the plate-shaped object which comprises an electroconductive reinforcement layer is an expanded metal, a punching metal, or an etching metal.

  The material of the conductive reinforcing layer is not particularly limited as long as it has a desired Young's modulus, strength, and conductivity. Preferably, the conductive reinforcing layer is made of one or more metals selected from the group consisting of Ni, Cu, Fe, Cr, Ti, Mg, Al, Ag, Pd, Pt, Au, and alloys thereof. Among these, the following are particularly preferable. From the viewpoint of cost, Ni, Cu, and Ti are desirable, and it can be said that Cu having a low Young's modulus and a low resistance material is an excellent material.

  The form of the upper conductive reinforcing material is not particularly limited, but is preferably a net-like material from the viewpoint of increasing the displacement of the laminate. The material of the upper conductive reinforcing material is not particularly limited as long as the desired Young's modulus, strength, and conductivity can be realized, but Ni, Cu, Fe, Cr, Ti, Mg, Al, Ag, Pd, Pt, Au And one or more metals selected from the group consisting of these alloys.

  The opening ratio of the conductive reinforcing layer is preferably larger than the opening ratio of the upper conductive reinforcing material. As a result, the displacement of the laminate can be increased by weakening the restraint of the laminate by the conductive reinforcing layer, and it is easy to ensure conduction by the conductive reinforcing layer when the conductive reinforcing layer is disconnected or the resistance value is increased. From this viewpoint, the difference between the opening ratio of the conductive reinforcing layer and the opening ratio of the upper conductive reinforcing material is preferably 5% or more, and more preferably 10% or more.

  From the viewpoint of increasing the displacement of the laminate, the aperture ratio of the conductive reinforcing layer is preferably 40% or more, and more preferably 50% or more. Moreover, it is preferable that the aperture ratio of an upper side conductive reinforcement is 75% or less from a viewpoint of ensuring conduction | electrical_connection.

  From the viewpoint of increasing the displacement of the laminate, the aperture ratio of the upper conductive reinforcing material is preferably 10% or more, and more preferably 25% or more. Moreover, it is preferable that the aperture ratio of an upper side conductive reinforcing material is 60% or less from a viewpoint of ensuring conduction | electrical_connection.

  In a preferred embodiment, the area of the conductive bonding agent is made larger than the area of the conductive reinforcing layer.

  The material of the conductive bonding agent is not particularly limited as long as it is a material capable of bonding the conductive reinforcing layer. Preferably, the material of the conductive reinforcing layer is one or more metals selected from the group consisting of Sn, Pb, Cu, Ag, Au, In, Ga, and Al, or alloys thereof. Particularly preferred are the following materials. Examples of the solder alloy in which Ag is doped in Sn-Pb eutectic solder and Pb-free solder include Sn-3Ag-0.5Cu, Sn-8Zn-3Bi, and Sn-7Zn-0.003Al alloy. In particular, an Sn-3Ag-0.5Cu alloy is desirable in terms of high connection reliability. Specifically, M705 (product number) material of Senju Metal Industry Co., Ltd. is preferable.

In this embodiment, the upper conductive reinforcement is not substantially bonded by the conductive bonding agent. This has the following two forms.
(1) By providing a gap between the upper conductive reinforcing material and the conductive bonding agent, the upper conductive reinforcing material and the conductive bonding agent are prevented from coming into direct contact with each other. In this case, the size of the gap is not particularly limited, but is preferably 30 um or more. In addition, due to manufacturing errors, it is allowed that the upper conductive reinforcing material and the conductive bonding agent partially contact each other. In this case, the upper conductive reinforcing material may be made of a material that is not easily wetted by the conductive bonding agent, and the upper conductive reinforcing material may be made of a material that is wetted by the conductive bonding agent.

(2) The upper conductive reinforcing material is made of a material that is not wetted by the conductive bonding agent or a material that is difficult to wet. Such combinations are exemplified below.
(Upper conductive reinforcement: conductive bonding agent)
(Stainless steel mesh (SUS304): Sn-3Ag-0.5Cu alloy solder)

  In a preferred embodiment, 10% or more and 70% or less of the surface area of the conductive reinforcing layer is in contact with the conductive bonding agent. By bringing 10% or more of the surface area of the conductive bonding agent into contact with the conductive bonding agent, adhesion can be strengthened and peeling of the conductive reinforcing layer can be prevented. Moreover, the displacement of the laminated body can be increased by bringing 50% or less of the surface area of the conductive bonding agent into contact with the conductive bonding agent.

  In a preferred embodiment, the upper conductive reinforcement is joined to the conductive reinforcement layer at the intersection of the upper conductive reinforcement. As a result, the upper conductive reinforcing material can be firmly joined to the conductive reinforcing layer, and can be prevented from falling off or peeling off, and conduction at the time of disconnection can be ensured.

  For example, FIG. 7A is a plan view showing a net 11 that is an upper conductive reinforcing material, and FIG. 7B is a plan view showing an expanded metal (or punching metal) 10 that is a conductive reinforcing layer. FIG. As shown in FIG. 7C, the upper conductive reinforcing material 11 is placed on the conductive reinforcing layer 10, and both are joined to produce the composite conductive reinforcing layer 12. At this time, each intersection of the upper conductive reinforcing material 11 is joined to the conductive reinforcing layer 10.

  As shown in FIG. 5A, the conductive lead portion 20 connected to the internal electrode layer 4 is exposed on the side surface of the multilayer body 1, and the conductive lead portion 20 is connected to the base layer. Then, the composite conductive reinforcing layer 12 is placed on and bonded to the base layer.

  The element according to the present invention is applicable as a multilayer capacitor, a multilayer piezoelectric element, or the like. The multilayer capacitor is the most used capacitor at present, and is used in almost all electric and electronic circuits and used in all products. For example, it is suitable for a computer, a communication device, or a portable terminal such as a cellular phone that is required to be reduced in size and weight. The laminated piezoelectric element is used as a piezoelectric device such as a sensor or an actuator. For example, an image display device such as a measuring instrument, an optical modulator, an optical switch, an electric switch, a micro relay, a micro valve, a transport device, a display, or a projector. , An image drawing device, a micro pump, a droplet discharge device, a micro mixing device, a micro stirring device, a micro reaction device, and the like.

  The element of the present invention is used as a drive source suitable for an injection nozzle opening / closing mechanism in a fuel injection device. Further, it is applied as a drive source for devices that require precise positioning, such as optical devices, and vibration prevention devices.

(Comparative Example 1)
The element shown in FIGS. 1 to 3 was produced. However, in FIG. 3, the base layer is continuously formed on the side surface of the element without a break, and the base layer gap and the resin layer in the gap are not provided. Specifically, 300 to 350 layers as active portions and 50 layers as upper and lower inactive portions are laminated and integrated. On the piezoelectric tape, an internal electrode layer (for example, 3 μm thick) is printed, and an adhesive layer (for example, 5 μm thick) with an increased amount of binder as compared to the tape is printed, thereby heating at 80 ° C. and 2 MPa. And integrated by weight.

  The laminated body thus integrated was degreased at 600 ° C. and fired at 900-1100 ° C. to obtain a piezoelectric ceramic laminate. This laminate was cut and ground to obtain a laminate having a desired shape. The cross-sectional shape of the laminate was 7 mm × 7 mm and the length was 35 mm. A base layer 3 of an external electrode was formed on the two side surfaces of the element from which the offset electrode layer was drawn. In this example, the AgPd fired film was baked at 800 ° C. to a thickness of 20 μm. The underlayer 3 is provided so as to cover the side surface of the element without a gap.

  As a member for reinforcing the external electrode, a multilayer mesh was bonded on the base layer. That is, the expanded metal 10 made of Cu and the SUS mesh 11 were integrated by diffusion bonding, and the integrated multilayer mesh 12 was bonded to the bonding base layer 3 using the solder 9. As solder, Sn-Ag-Cu alloy Pb-free solder was used and bonded under the conditions of 240 ° C. and 5 min.

Next, the entire element was coated with an insulating resin. Specifically, it was selectively coated by painting an epoxy resin or a fluorine resin. The resin thickness is 20-100 um.
Next, the element was polarized. Specifically, in the state heated to 170 ° C., DC 150 V was applied for 10 minutes and DC 240 V was applied for 10 minutes to complete the polarization. The electric field strengths at this time correspond to 1.9 kV / mm and 3.0 kV / mm, respectively.

  The element was driven by applying a voltage of 200 V under preload 750N. The applied waveform has a rise of 0.12 msc, a keep of 1 msec, and a fall of 0.12 msec. An element displacement of 50 μm was obtained.

Example 1
The element shown in FIGS. 1 to 3 was produced. Specifically, 300 to 350 layers as active portions and 50 layers as upper and lower inactive portions are laminated and integrated. On the piezoelectric tape, an internal electrode layer (for example, 3 μm thick) is printed, and an adhesive layer (for example, 5 μm thick) with an increased amount of binder as compared to the tape is printed, thereby heating at 80 ° C. and 2 MPa. And integrated by weight.

  The laminated body thus integrated was degreased at 600 ° C. and fired at 900-1100 ° C. to obtain a piezoelectric ceramic laminate. This laminate was cut and ground to obtain a laminate having a desired shape. The cross-sectional shape of the laminate was 7 mm × 7 mm and the length was 35 mm. A base layer 3 of an external electrode was formed on the two side surfaces of the element from which the offset electrode layer was drawn. In this example, the AgPd fired film was baked at 800 ° C. to a thickness of 20 μm. The planar pattern of the underlayer 3A was a stripe pattern as shown in FIG.

Next, the entire element was coated with an insulating resin. Specifically, the entire element was coated by painting an epoxy resin or a fluorine resin. The resin thickness is 20-100 um. Thereafter, the resin on the base layer 3 of the external electrode was removed, and the resin was filled in the uncovered portion of the base layer 3A without removing the resin, thereby filling the resin and forming a resin layer.
As a member that reinforces the external electrode, a multilayer mesh was joined on the base layer 3A. That is, the expanded metal 10 made of Cu and the SUS mesh 11 were integrated by diffusion bonding, and the integrated multilayer mesh 12 was bonded to the bonding base layer 3 </ b> A using the solder 9. As solder, Sn-Ag-Cu alloy Pb-free solder was used and bonded under the conditions of 240 ° C. and 5 min.

  Next, the element was polarized. Specifically, in the state heated to 170 ° C., DC 150 V was applied for 10 minutes and DC 240 V was applied for 10 minutes to complete the polarization. The electric field strengths at this time correspond to 1.9 kV / mm and 3.0 kV / mm, respectively.

  The element was driven by applying a voltage of 200 V under preload 750N. The applied waveform has a rise of 0.12 msc, a keep of 1 msec, and a fall of 0.12 msec. The displacement of the element was improved by about 10 to 15% as compared with Comparative Example 1, that is, about 55 to 58 μm.

(Example 2)
A device was fabricated in the same manner as in Example 1. However, the planar pattern of the base layer 3C was a net shape as shown in FIG. The mesh pitch was 500 μm, and the mesh diameter was 150 μm. The displacement of the element was improved by about 10 to 15% as compared with Comparative Example 1, that is, about 55 to 58 μm.

FIG. 8 is a graph showing the displacement of the actuator of each example of Example 1 and Comparative Example 1. Table 1 shows data corresponding to this.

(A) is a perspective view which shows the laminated body 1 typically, (b) is a disassembled perspective view of each piezoelectric layer and an internal electrode layer. (A) is a schematic longitudinal cross-sectional view of the laminated body 1, (b) is a schematic cross-sectional view of the laminated body 1. FIG. It is principal part sectional drawing of the element which concerns on one Embodiment of this invention. It is principal part sectional drawing of the element which concerns on other embodiment of this invention. (A) is a top view which shows the drawer | drawing-out conduction | electrical_connection part 20 of an internal electrode layer, (b) is a top view which shows 3 A of base layers provided on the conduction | electrical_connection part. (A) is a top view which shows base layer 3B provided on the conduction | electrical_connection part, (b) is a top view which shows base layer 3B provided on the conduction | electrical_connection part. (A) is a schematic plan view showing the upper conductive reinforcing material 11, (b) is a schematic plan view showing the conductive reinforcing layer 10, and (c) is a composite conductive property. 3 is a schematic plan view showing a reinforcing layer 12. FIG. 3 is a graph showing displacement of actuators in each example of Example 1 and Comparative Example 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Laminated body 2 Piezoelectric layer 3, 3A, 3B, 3C Internal electrode layer 9 Conductive bonding agent 10, 10A Conductive reinforcement layer 11, 11A Upper conductive reinforcement material 12 Composite conductive reinforcement layer 15 Resin layer 30 Non- Covering part A Predetermined axis

Claims (12)

  A laminated body comprising a plurality of piezoelectric layers laminated toward a predetermined axial direction and an internal electrode layer formed between adjacent piezoelectric layers, provided on a side surface of the laminated body; A laminated piezoelectric element comprising a base layer electrically connected to the internal electrode layer, and a conductive reinforcing layer joined to the base layer, and is not covered with the base layer A multilayer piezoelectric element, wherein a resin layer is provided on an uncoated portion of the surface of the multilayer body.   The multilayer piezoelectric element according to claim 1, wherein the base layer is composed of a plurality of island-shaped portions regularly arranged.   The multilayer piezoelectric element according to claim 1, wherein the underlayer is made of a net-like material.   The multilayer piezoelectric element according to any one of claims 1 to 3, wherein the resin layer covers the uncoated portion substantially without a gap.   An upper conductive reinforcing material bonded to the conductive reinforcing layer, and a conductive bonding agent for bonding the base layer and the conductive reinforcing layer, wherein the upper conductive reinforcing material is the conductive conductive material. The multilayer piezoelectric element according to any one of claims 1 to 4, wherein the multilayer piezoelectric element is not bonded by a bonding agent.   6. The multilayer piezoelectric element according to claim 5, wherein the conductive reinforcing layer and the upper conductive reinforcing material are integrated by welding, diffusion bonding, brazing, or a conductive adhesive.   The laminated piezoelectric element according to claim 1, wherein the conductive reinforcing layer is made of a metal plate.   The multilayer piezoelectric element according to claim 7, wherein the plate is a flat plate.   The multilayer piezoelectric element according to claim 7, wherein the plate-like material is expanded metal, punching metal, or etching metal.   The multilayer piezoelectric element according to any one of claims 5 to 9, wherein the upper conductive reinforcing material is made of a net-like material.   The multilayer piezoelectric element according to claim 1, wherein the multilayer piezoelectric element is used as a drive source of an injection nozzle opening / closing mechanism in a fuel injection device of an internal combustion engine. A method for manufacturing the multilayer piezoelectric element according to any one of claims 1 to 11,
Forming the base layer on a side surface of the laminate,
Next, a step of providing the resin layer on an uncovered portion of the surface of the laminate not covered with the underlayer, and then joining the conductive reinforcing layer to the underlayer Method for manufacturing a piezoelectric element.

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