WO2013065709A1 - Multilayer piezoelectric element, and piezoelectric actuator, injection apparatus and fuel injection system provided with multilayer piezoelectric element - Google Patents

Multilayer piezoelectric element, and piezoelectric actuator, injection apparatus and fuel injection system provided with multilayer piezoelectric element Download PDF

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Publication number
WO2013065709A1
WO2013065709A1 PCT/JP2012/078105 JP2012078105W WO2013065709A1 WO 2013065709 A1 WO2013065709 A1 WO 2013065709A1 JP 2012078105 W JP2012078105 W JP 2012078105W WO 2013065709 A1 WO2013065709 A1 WO 2013065709A1
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Prior art keywords
piezoelectric element
external electrode
metal layer
multilayer
bonding material
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PCT/JP2012/078105
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French (fr)
Japanese (ja)
Inventor
隆晶 平
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京セラ株式会社
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Priority to JP2013541801A priority Critical patent/JP5701397B2/en
Publication of WO2013065709A1 publication Critical patent/WO2013065709A1/en

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
    • H10N30/872—Connection electrodes of multilayer piezoelectric or electrostrictive devices, e.g. external electrodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/06—Forming electrodes or interconnections, e.g. leads or terminals
    • H10N30/063—Forming interconnections, e.g. connection electrodes of multilayered piezoelectric or electrostrictive parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M2200/00—Details of fuel-injection apparatus, not otherwise provided for
    • F02M2200/21—Fuel-injection apparatus with piezoelectric or magnetostrictive elements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M51/00—Fuel-injection apparatus characterised by being operated electrically
    • F02M51/06—Injectors peculiar thereto with means directly operating the valve needle
    • F02M51/0603—Injectors peculiar thereto with means directly operating the valve needle using piezoelectric or magnetostrictive operating means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M63/00—Other fuel-injection apparatus having pertinent characteristics not provided for in groups F02M39/00 - F02M57/00 or F02M67/00; Details, component parts, or accessories of fuel-injection apparatus, not provided for in, or of interest apart from, the apparatus of groups F02M39/00 - F02M61/00 or F02M67/00; Combination of fuel pump with other devices, e.g. lubricating oil pump
    • F02M63/0012—Valves
    • F02M63/0014—Valves characterised by the valve actuating means
    • F02M63/0015—Valves characterised by the valve actuating means electrical, e.g. using solenoid
    • F02M63/0026—Valves characterised by the valve actuating means electrical, e.g. using solenoid using piezoelectric or magnetostrictive actuators

Definitions

  • the present invention relates to a laminated piezoelectric element used for, for example, a drive element (piezoelectric actuator), a sensor element, a circuit element, etc., and a piezoelectric actuator, an injection device, and a fuel injection system provided with the same.
  • the multilayer piezoelectric element includes, for example, a multilayer body in which piezoelectric layers and internal electrode layers are alternately stacked, and an external electrode provided on a side surface of the multilayer body so as to be electrically connected to the internal electrode layer. (For example, refer patent document 1).
  • the effect of reducing the resistance of the external electrode and preventing the surface oxidation can be obtained.
  • the interface between the external electrode and the conductive bonding material peels off due to the temperature cycle. There was a problem of disconnection due to local heat generation.
  • the present invention has been made in view of the above circumstances, and a multilayer piezoelectric element having a high bonding strength between an external electrode and a conductive bonding material without causing external electrodes to oxidize with low resistance and a piezoelectric device including the same.
  • An object is to provide an actuator, an injection device, and a fuel injection system.
  • the present invention provides a laminate in which a piezoelectric layer and an internal electrode layer are laminated, a conductive bonding material provided on a side surface of the laminate so as to be electrically connected to the internal electrode layer, and the conductive An external electrode provided so as to have a region in contact with the bonding material, the external electrode having a metal layer non-forming portion in at least a part of the region in contact with the conductive bonding material, and other regions
  • the multilayer piezoelectric element is characterized in that a metal layer is formed thereon.
  • the present invention also provides a piezoelectric actuator comprising the above multilayer piezoelectric element and a case for accommodating the multilayer piezoelectric element therein.
  • the present invention includes a container having an injection hole and the multilayer piezoelectric element described above, and fluid stored in the container is discharged from the injection hole by driving the multilayer piezoelectric element. It is the injection device which does.
  • the present invention also provides a common rail that stores high-pressure fuel, the above-described injection device that injects the high-pressure fuel stored in the common rail, a pressure pump that supplies the high-pressure fuel to the common rail, and a drive signal to the injection device.
  • a fuel injection system comprising: an injection control unit for supplying the fuel.
  • the functional group of the oxide film and the functional group of the conductive bonding material Reacts (chemical bond), and the bonding strength between the conductive bonding material and the external electrode is improved.
  • electricity flows preferentially over the low-resistance metal layer so that the temperature of the metal layer non-forming portion is unlikely to rise.
  • the metal layer in the metal layer forming portion expands or contracts or peels to relieve stress. Therefore, since the joining state of the metal layer non-forming portion is stabilized, the sudden stop of the multilayer piezoelectric element is suppressed.
  • FIG. 1 It is a perspective view which shows an example of embodiment of the lamination type piezoelectric element of this invention. It is a longitudinal cross-sectional view which shows an example of embodiment of the lamination type piezoelectric element of this invention. It is a longitudinal cross-sectional view which shows the other example of embodiment of the lamination type piezoelectric element of this invention.
  • (A) is a top view which shows an example of the external electrode which comprises the lamination type piezoelectric element of this invention
  • (b) is a cross-sectional view which shows an example of the principal part of the lamination type piezoelectric element of this invention. It is a cross-sectional view which shows the other example of the principal part of the lamination type piezoelectric element of this invention.
  • FIG. 1 is a perspective view showing an example of the embodiment of the multilayer piezoelectric element of the present invention
  • FIG. 2 is a longitudinal sectional view showing an example of the embodiment of the multilayer piezoelectric element of the present invention.
  • a laminated piezoelectric element 1 shown in FIGS. 1 and 2 includes a laminated body 4 in which a piezoelectric layer 2 and an internal electrode layer 3 are laminated, and a side surface of the laminated body 4 so as to be electrically connected to the internal electrode layer 3.
  • the external electrode 6 provided so as to have a region in contact with the conductive bonding material 5, and the external electrode 6 has a region in contact with the conductive bonding material 5.
  • the metal layer non-formation part 61 is at least partly formed, and the metal layer 62 is formed in other regions.
  • the multilayer body 4 constituting the multilayer piezoelectric element 1 includes, for example, an active portion in which a plurality of piezoelectric layers 2 and internal electrode layers 3 are alternately stacked, and piezoelectric layers 2 provided at both ends of the active portion in the stacking direction.
  • it is formed in a rectangular parallelepiped shape having a length of 0.5 to 10 mm, a width of 0.5 to 10 mm, and a height of 1 to 100 mm.
  • the piezoelectric layer 2 constituting the multilayer body 4 is formed of ceramics having piezoelectric characteristics.
  • ceramics for example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3 ), Lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), or the like can be used.
  • the thickness of the piezoelectric layer 3 is, for example, 3 to 250 ⁇ m.
  • the internal electrode layer 3 constituting the multilayer body 4 is formed by simultaneous firing with the ceramics forming the piezoelectric layer 2, and is alternately stacked with the piezoelectric layer 2 to sandwich the piezoelectric layer 2 from above and below.
  • a driving voltage is applied to the piezoelectric layer 2 sandwiched between them.
  • this forming material for example, a conductor mainly composed of a silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum, or the like can be used.
  • the positive electrode and the negative electrode (or the ground electrode) are alternately led out to a pair of opposing side surfaces of the laminate 4.
  • the internal electrode layer 3 has a thickness of 0.1 to 5 ⁇ m, for example.
  • a conductive bonding material 5 is provided on the side surface of the laminate 4 so as to be electrically connected to the internal electrode layer 2, and an external electrode 6 is provided so as to have a region in contact with the conductive bonding material 5. ing.
  • the conductive bonding material 5 is made of a conductive adhesive made of an epoxy resin or a polyimide resin containing a metal powder having good conductivity, such as Ag powder or Cu powder, and is formed to a thickness of, for example, 5 to 500 ⁇ m.
  • the conductive bonding material 5 may be provided directly on the side surface of the multilayer body 4 as shown in FIG. 2, but it is not directly provided on the side surface of the multilayer body 4 as shown in FIG.
  • the conductive layer 7 may be interposed between the conductive bonding material 5 and the conductive layer 5.
  • the conductor layer 7 is formed by applying and baking a paste made of silver and glass, for example. It is joined to the side surface and electrically connected to the internal electrode layers 3 that are alternately led to the opposite side surface of the laminate 4.
  • the thickness of the conductor layer 7 is, for example, 5 to 500 ⁇ m.
  • the external electrode 6 is made of metal such as copper, iron, stainless steel, phosphor bronze, etc., and is formed to have a width of 0.5 to 10 mm and a thickness of 0.01 to 1.0 mm, for example.
  • a shape having slits in the width direction, a shape having a corrugated longitudinal section, a metal plate processed into a mesh shape, or a linear metal is knitted as a shape having a high effect of relieving stress caused by expansion and contraction of the laminate 4 Wire mesh conductors can be used.
  • an electrode having a mesh structure such as a wire mesh conductor knitted with a linear metal.
  • a lead member 8 is joined to the external electrode 6 and electrically connected to an external circuit, so that the multilayer piezoelectric element 1 is driven.
  • the external electrode 6 has a metal layer non-forming portion 61 in at least a part of a region in contact with the conductive bonding material 5, and a metal layer 62 is formed in the other region.
  • the metal layer non-forming part 61 on the surface of the external electrode 6 is formed by moisture in the conductive bonding material 5.
  • the functional group of the oxide film and the functional group in the conductive bonding material 5 are chemically bonded, and the bonding strength between the conductive bonding material 5 and the external electrode 6 can be improved.
  • the metal layer 62 in the metal layer forming portion expands or contracts or peels to relieve stress. Therefore, since the joining state of the metal layer non-forming portion 61 is stabilized, the sudden stop of the multilayer piezoelectric element 1 is suppressed.
  • the other region including the exposed surface of the external electrode 6 is formed with a metal layer 62 made of, for example, tin or silver, thereby reducing the resistance of the external electrode 6 and preventing surface oxidation. An effect is also obtained.
  • the thickness of the metal layer 62 is preferably 1 to 10 ⁇ m.
  • the external electrode 6 has the surface of the metal layer non-forming portion 61 exposed from the surface of other regions.
  • the contact area can be increased and the bonding strength can be increased.
  • the surface of the metal layer non-forming portion 61 that is exposed from the surface of the other region may be a surface processed so as to show only the metal layer non-forming portion 61, A metal layer 62 may be formed in a portion other than the layer non-forming portion 61 to vary the surface roughness.
  • having the surface of the metal layer non-formation part 61 exposed from the surface of the other region may mean that part of the surface of the metal layer non-formation part 61 is exposed. It means that. It is effective that the surface roughness Ra on the surface of the exposed metal layer non-forming portion 61 is 5 to 20 ⁇ m.
  • the external electrode 6 when the conductive bonding material 5 reaches the side surface of the external electrode 6, the external electrode 6 is at least a part of the side surface adjacent to the side surface side surface of the multilayer body 4.
  • the metal layer non-forming portion 61 on the surface, it is possible to improve the bonding strength between the conductive bonding material 5 and the external electrode 6 on the side surface of the external electrode 6 where the conductive bonding material 5 is easily peeled off. it can.
  • the external electrode 6 has the metal layer non-shaped portion 61 on at least a part of the side surface of the multilayer body 4, so that the portion with the metal layer 62 and the metal layer non-shaped portion are formed.
  • a step is generated between the forming portion 61 (portion where the metal layer 62 is not provided), and the contact strength between the stepped structure and the metal layer non-shaped portion 61 and the conductive bonding material 5 is increased to increase the bonding strength. Can do.
  • the external electrode 6 has the metal layer non-forming portion 61 at least at a part corresponding to the central portion in the stacking direction of the stacked body 4.
  • the bonding strength at the central portion in the large stacking direction can be increased.
  • the center part here means the middle part when the laminated body 4 is equally divided into three in the lamination direction.
  • the external electrode 6 has a slit or a through hole, and the external electrode 6 has a metal layer non-forming portion 61 on at least a part of a side surface facing the slit or the through hole.
  • the conductive bonding material 5 is hardly peeled even on the above-mentioned side surface of the surface of the external electrode 6, and the bonding strength between the conductive bonding material 5 and the external electrode 6 can be further improved.
  • the metal-mesh conductor which braided the metal plate processed by mesh shape and a linear metal is also included.
  • the boundary between the metal layer 62 and the metal layer non-forming portion 61 is preferably located at the ridge between the main surface and the side surface of the external electrode 6.
  • a metal layer 62 is formed on the main surface of the external electrode 6, and a metal layer non-forming portion 61 is formed on the side surface of the external electrode 6.
  • the main surface of the external electrode 6 can be mainly contributed to energization, the bonding strength of the side surface of the external electrode 6 can be increased, and the energization can be stabilized.
  • the entire region of the side surface facing the slit or the through hole may be the metal layer non-formed portion 61, and this configuration can be easily manufactured by punching with a die press.
  • the side surfaces of the external electrodes 6 facing the slits or the through holes are all the metal layer non-formed portions 61, and the conductive bonding material enters the slits or the through holes. The bonding strength with the electrode 6 can be made stronger.
  • the multilayer piezoelectric element 1 is used for, for example, a piezoelectric drive element (piezoelectric actuator), a pressure sensor element, a piezoelectric circuit element, and the like.
  • the driving element include a fuel injection device for an automobile engine, a liquid injection device such as an inkjet, a precision positioning device such as an optical device, and a vibration prevention device.
  • the sensor element include a combustion pressure sensor, a knock sensor, an acceleration sensor, a load sensor, an ultrasonic sensor, a pressure sensor, and a yaw rate sensor.
  • Examples of the circuit element include a piezoelectric gyro, a piezoelectric switch, a piezoelectric transformer, and a piezoelectric breaker.
  • a ceramic green sheet to be the piezoelectric layer 2 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method.
  • the piezoelectric ceramic any material having piezoelectric characteristics may be used.
  • a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3 ) can be used.
  • the plasticizer dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.
  • a conductive paste to be the internal electrode layer 3 is produced.
  • a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrode layer 3 using a screen printing method. Further, a plurality of ceramic green sheets printed with this conductive paste are laminated, subjected to a binder removal treatment at a predetermined temperature, and then fired at a temperature of 900 to 1200 ° C. A laminate 4 including the layer 2 and the internal electrode layer 3 is produced.
  • the laminate 4 is not limited to the one produced by the above manufacturing method, and any laminate 4 can be produced as long as the laminate 4 formed by laminating a plurality of piezoelectric layers 2 and internal electrode layers 3 can be produced. It may be produced by a manufacturing method.
  • the laminated body 4 obtained by firing is subjected to a grinding process so as to have a predetermined shape using a surface grinder or the like.
  • a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly containing silver and glass is used to form a side surface of the laminate 4 in the pattern of the conductor layer 7.
  • a baking process is performed at a temperature of 650 to 750 ° C. to form the conductor layer 7.
  • this process is abbreviate
  • the external electrode 6 is bonded to the surface of the conductor layer 7 through the conductive bonding material 5. Specifically, the external electrode 6 is fixed to the laminated piezoelectric element 1 coated with the conductive bonding material 5 on the side surface, for example, at 150 to 250 ° C. for 0.5 to 1.5 hours.
  • the conductive bonding material 5 uses a conductive adhesive made of an epoxy resin or a polyimide resin containing a highly conductive metal powder such as Ag powder or Cu powder, solder, etc., and has a predetermined thickness by screen printing or dispensing method. It can be formed with a controlled width.
  • plating is performed by masking a target location, or plating is partially removed with a predetermined chemical.
  • the method of punching in a predetermined shape with a die press is also mentioned. Furthermore, methods such as blasting and polishing can be used to roughen the metal layer non-forming portion 61.
  • the lead member 8 is joined to the external electrode 6 by welding, solder, conductive joining material or the like.
  • the multilayer piezoelectric element 1 connects the internal electrode layer 2 and an external power source via the external electrode 6 and applies a voltage to the piezoelectric layer 3, thereby causing each piezoelectric layer 2 to have an inverse piezoelectric effect. It can be displaced greatly. This makes it possible to function as an automobile fuel injection valve that injects and supplies fuel to the engine, for example.
  • FIG. 7 is a schematic sectional view showing an example of the piezoelectric actuator of the present invention.
  • the piezoelectric actuator of the example shown in FIG. 7 is obtained by housing the multilayer piezoelectric element 1 in a case 10.
  • the case 10 is made of, for example, a metal material such as SUS304 or SUS316L. Since the multilayer piezoelectric element 1 is sealed in such a case 10, the case 10 is used in corrosive gas or in water. can do. Further, in order to prevent ion migration of the internal electrode layer 3, sealing may be performed using an inert gas. In this case, since oxygen is insufficient, oxygen vacancies in the piezoelectric layer 2 are likely to be generated. However, by using the multilayer piezoelectric element 1 of the present invention, the resin can be removed from the resin even in a sealed space in the case 10. Oxygen can be effectively supplied, and generation of oxygen vacancies in the piezoelectric layer 2 can be suppressed.
  • a metal material such as SUS304 or SUS316L.
  • FIG. 8 is a schematic cross-sectional view showing an example of an embodiment of the injection device of the present invention.
  • the multilayer piezoelectric element 1 according to the present embodiment is stored in a storage container (container) 23 having an injection hole 21 at one end. .
  • a needle valve 25 capable of opening and closing the injection hole 21 is disposed.
  • a fluid passage 27 is disposed in the injection hole 21 so as to be able to communicate with the movement of the needle valve 25.
  • the fluid passage 27 is connected to an external fluid supply source, and fluid is constantly supplied to the fluid passage 27 at a high pressure. Accordingly, when the needle valve 25 opens the injection hole 21, the fluid supplied to the fluid passage 27 is discharged from the injection hole 21 to an external or adjacent container, for example, a fuel chamber (not shown) of the internal combustion engine. It is configured.
  • the upper end portion of the needle valve 25 has a larger inner diameter to form a piston 31, which can slide with a cylinder 29 formed in the storage container 23.
  • the multilayer piezoelectric element 1 of the above-described example is stored in contact with the piston 31.
  • the fluid passage 27 may be opened by applying a voltage to the multilayer piezoelectric element 1 and the fluid passage 27 may be closed by stopping the application of the voltage.
  • the ejection device 19 includes a container 23 having ejection holes and the multilayer piezoelectric element 1 according to the present embodiment, and the fluid filled in the container 23 is driven to drive the multilayer piezoelectric element 1. May be configured to discharge from the injection hole 21. That is, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 23, as long as the multilayer piezoelectric element 1 is configured to apply pressure for controlling the ejection of fluid to the inside of the container 23 by driving the multilayer piezoelectric element 1. Good.
  • the fluid includes various liquids and gases such as a conductive paste in addition to fuel and ink.
  • the injection device 19 of the present embodiment that employs the multilayer piezoelectric element 1 of the present embodiment is used for an internal combustion engine, the fuel is supplied to the combustion chamber of the internal combustion engine such as an engine over a longer period than the conventional injection device. It is possible to inject with high accuracy.
  • FIG. 9 is a schematic view showing an example of an embodiment of the fuel injection system of the present invention.
  • the fuel injection system 35 of the present embodiment includes a common rail 37 that stores high-pressure fuel as high-pressure fluid, and a plurality of injections of the present embodiment that inject high-pressure fluid stored in the common rail 37.
  • a device 19 a pressure pump 39 that supplies a high-pressure fluid to the common rail 37, and an injection control unit 41 that supplies a drive signal to the injection device 19 are provided.
  • the injection control unit 41 controls the amount and timing of high-pressure fluid injection based on external information or an external signal. For example, if the injection control unit 41 is used for fuel injection of the engine, the amount and timing of fuel injection can be controlled while sensing the condition in the combustion chamber of the engine with a sensor or the like.
  • the pressure pump 39 serves to supply fluid fuel from the fuel tank 43 to the common rail 37 at a high pressure. For example, in the case of the fuel injection system 35 of the engine, the fluid fuel is fed into the common rail 37 at a high pressure of about 1000 to 2000 atmospheres (about 101 MPa to about 203 MPa), preferably about 1500 to 1700 atmospheres (about 152 MPa to about 172 MPa).
  • the high-pressure fuel sent from the pressure pump 39 is stored and sent to the injection device 19 as appropriate.
  • the ejection device 19 ejects a certain fluid from the ejection holes 21 to the outside or an adjacent container.
  • the target for injecting and supplying fuel is an engine
  • high-pressure fuel is injected from the injection hole 21 into the combustion chamber of the engine in the form of a mist.
  • the external electrodes 6 are formed one by one on the two opposite side surfaces of the multilayer body 4 in the above example, but the two external electrodes 6 may be formed on adjacent side surfaces of the multilayer body 4. It may be formed on the same side of the body 4.
  • the cross-sectional shape in the direction orthogonal to the stacking direction of the stacked body 4 is not limited to the quadrangular shape which is an example of the above embodiment, but a polygonal shape such as a hexagonal shape or an octagonal shape, a circular shape, or a straight line and an arc. You may be the shape which combined.
  • the multilayer piezoelectric element of the present invention was produced as follows. First, a ceramic slurry was prepared by mixing calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO 3 -PbTiO 3 ) having an average particle diameter of 0.4 ⁇ m, a binder, and a plasticizer. Using this ceramic slurry, a ceramic green sheet serving as a piezoelectric layer having a thickness of 50 ⁇ m was prepared by a doctor blade method. Further, a binder was added to the silver-palladium alloy to produce a conductive paste to be an internal electrode layer.
  • a ceramic slurry was prepared by mixing calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO 3 -PbTiO 3 ) having an average particle diameter of 0.4 ⁇ m, a binder, and a plasticizer.
  • a conductive paste serving as an internal electrode layer was printed on one side of the ceramic green sheet by a screen printing method, and 200 ceramic green sheets printed with the conductive paste were laminated. Further, a total of 15 ceramic green sheets not printed with the conductive paste serving as the internal electrode were laminated on the top and bottom of the 200 ceramic green sheets printed with the conductive paste serving as the internal electrode layer. Then, a laminate was obtained by firing at 980 to 1100 ° C. The obtained laminate was ground into a predetermined shape using a surface grinder.
  • a conductive paste in which a binder was mixed with silver and glass was printed by a screen printing method on the conductive layer forming portion on the side surface of the laminate, and baked at 700 ° C.
  • a conductive bonding material made of polyimide containing silver powder is applied to the conductor layer with a dispenser, and an external electrode with a mesh structure made of a wire mesh conductor knitted with a linear metal is connected in parallel with the surface of the laminate. And fixed.
  • a laminated piezoelectric element (sample 1) having the cross section shown in FIG. 6 was produced.
  • the external electrode employ
  • These laminated piezoelectric elements were subjected to polarization treatment by applying a DC electric field of 3 kV / mm to the external electrodes for 15 minutes through lead members welded to the external electrodes.
  • a DC voltage of 160 V was applied to these stacked piezoelectric elements, a displacement of 30 ⁇ m was obtained in the stacking direction of the stacked body.

Abstract

[Problem] To provide a multilayer piezoelectric element, wherein external electrodes thereof have low resistance and will not be oxidized, and connection strength between the external electrodes and conductive connection materials is high, and also provide a piezoelectric actuator, an injection apparatus, and a fuel injection system provided with same. [Solution] A multilayer piezoelectric element according to the present invention comprises: a multilayer body in which piezoelectric layers and inner-electrode layers are laminated; conductive connection materials (5) provided at the side faces of the multilayer body so as to be connected electrically with the inner-electrode layers; and external electrodes (6) that are provided so as to have sections contacting the conductive connection materials (5). These external electrodes (6) are characterized in comprising sections with no metal layers formed (61) at least at portions of the sections contacting the conductive connection materials (5), and having metal layers (62) formed at other sections.

Description

積層型圧電素子およびこれを備えた圧電アクチュエータ、噴射装置、燃料噴射システムMultilayer piezoelectric element, piezoelectric actuator including the same, injection device, and fuel injection system
　本発明は、例えば駆動素子（圧電アクチュエータ）、センサ素子、回路素子等に用いられる積層型圧電素子およびこれを備えた圧電アクチュエータ、噴射装置、燃料噴射システムに関するものである。 The present invention relates to a laminated piezoelectric element used for, for example, a drive element (piezoelectric actuator), a sensor element, a circuit element, etc., and a piezoelectric actuator, an injection device, and a fuel injection system provided with the same.
　積層型圧電素子は、例えば、圧電体層および内部電極層が交互に積層された積層体と、内部電極層と電気的に接続されるように積層体の側面に設けられた外部電極とを含む構成になっている（例えば、特許文献１を参照）。 The multilayer piezoelectric element includes, for example, a multilayer body in which piezoelectric layers and internal electrode layers are alternately stacked, and an external electrode provided on a side surface of the multilayer body so as to be electrically connected to the internal electrode layer. (For example, refer patent document 1).
特開２００８－６６５６０号公報JP 2008-66560 A
　ここで、外部電極の表面にメッキなどからなる金属層を設けることにより、外部電極の低抵抗化および表面酸化防止などの効果が得られる。しかし、このような構成とすると、積層体の側面にポリイミドやエポキシ樹脂を含む導電性接合材を介して外部電極を接合した際に、温度サイクルによって外部電極と導電性接合材との界面が剥がれ、局所発熱によって断線するという問題があった。 Here, by providing a metal layer made of plating or the like on the surface of the external electrode, the effect of reducing the resistance of the external electrode and preventing the surface oxidation can be obtained. However, with such a configuration, when the external electrode is bonded to the side surface of the laminate via a conductive bonding material containing polyimide or epoxy resin, the interface between the external electrode and the conductive bonding material peels off due to the temperature cycle. There was a problem of disconnection due to local heat generation.
　本発明は、上記の事情に鑑みてなされたもので、外部電極が低抵抗で酸化することなく、かつ外部電極と導電性接合材との接合強度の高い積層型圧電素子およびこれを備えた圧電アクチュエータ、噴射装置、燃料噴射システムを提供することを目的とする。 The present invention has been made in view of the above circumstances, and a multilayer piezoelectric element having a high bonding strength between an external electrode and a conductive bonding material without causing external electrodes to oxidize with low resistance and a piezoelectric device including the same. An object is to provide an actuator, an injection device, and a fuel injection system.
　本発明は、圧電体層および内部電極層が積層された積層体と、前記内部電極層と電気的に接続されるように前記積層体の側面に設けられた導電性接合材と、該導電性接合材に当接する領域を有するように設けられた外部電極とを含み、該外部電極は、前記導電性接合材に当接する領域の少なくとも一部に金属層非形成部を有し、その他の領域に金属層が形成されていることを特徴とする積層型圧電素子を特徴とする。 The present invention provides a laminate in which a piezoelectric layer and an internal electrode layer are laminated, a conductive bonding material provided on a side surface of the laminate so as to be electrically connected to the internal electrode layer, and the conductive An external electrode provided so as to have a region in contact with the bonding material, the external electrode having a metal layer non-forming portion in at least a part of the region in contact with the conductive bonding material, and other regions The multilayer piezoelectric element is characterized in that a metal layer is formed thereon.
　また本発明は、上記の積層型圧電素子と、該積層型圧電素子を内部に収容するケースとを備えていることを特徴とする圧電アクチュエータである。 The present invention also provides a piezoelectric actuator comprising the above multilayer piezoelectric element and a case for accommodating the multilayer piezoelectric element therein.
　また本発明は、噴射孔を有する容器と、上記の積層型圧電素子とを備え、前記容器内に蓄えられた流体が前記積層型圧電素子の駆動により前記噴射孔から吐出されることを特徴とする噴射装置である。 Further, the present invention includes a container having an injection hole and the multilayer piezoelectric element described above, and fluid stored in the container is discharged from the injection hole by driving the multilayer piezoelectric element. It is the injection device which does.
　また本発明は、高圧燃料を蓄えるコモンレールと、該コモンレールに蓄えられた前記高圧燃料を噴射する上記の噴射装置と、前記コモンレールに前記高圧燃料を供給する圧力ポンプと、前記噴射装置に駆動信号を与える噴射制御ユニットとを備えたことを特徴とする燃料噴射システムである。 The present invention also provides a common rail that stores high-pressure fuel, the above-described injection device that injects the high-pressure fuel stored in the common rail, a pressure pump that supplies the high-pressure fuel to the common rail, and a drive signal to the injection device. A fuel injection system comprising: an injection control unit for supplying the fuel.
　本発明によれば、導電性接合材中の水分で外部電極の表面のうちの金属層非形成部に酸化膜が生じやすいことから、この酸化膜の官能基と導電性接合材が有する官能基とが反応（化学結合）して、導電性接合材と外部電極との接合強度が向上する。また、急激な電流負荷がかかったとき、電気が低抵抗の金属層に優先して流れることから、金属層非形成部は温度上昇しにくい。一方、積層型圧電素子の駆動で外部電極が引っ張られても、金属層形成部における金属層が伸縮または剥がれて応力を緩和する。したがって、金属層非形成部の接合状態は安定するので、積層型圧電素子の急停止は抑制される。 According to the present invention, since an oxide film is likely to be formed on the metal layer non-formed portion of the surface of the external electrode due to moisture in the conductive bonding material, the functional group of the oxide film and the functional group of the conductive bonding material Reacts (chemical bond), and the bonding strength between the conductive bonding material and the external electrode is improved. In addition, when a sudden current load is applied, electricity flows preferentially over the low-resistance metal layer, so that the temperature of the metal layer non-forming portion is unlikely to rise. On the other hand, even when the external electrode is pulled by driving the multilayer piezoelectric element, the metal layer in the metal layer forming portion expands or contracts or peels to relieve stress. Therefore, since the joining state of the metal layer non-forming portion is stabilized, the sudden stop of the multilayer piezoelectric element is suppressed.
本発明の積層型圧電素子の実施の形態の一例を示す斜視図である。It is a perspective view which shows an example of embodiment of the lamination type piezoelectric element of this invention. 本発明の積層型圧電素子の実施の形態の一例を示す縦断面図である。It is a longitudinal cross-sectional view which shows an example of embodiment of the lamination type piezoelectric element of this invention. 本発明の積層型圧電素子の実施の形態の他の例を示す縦断面図である。It is a longitudinal cross-sectional view which shows the other example of embodiment of the lamination type piezoelectric element of this invention. （ａ）は本発明の積層型圧電素子を構成する外部電極の一例を示す平面図であり、（ｂ）は本発明の積層型圧電素子の要部の一例を示す横断面図である。(A) is a top view which shows an example of the external electrode which comprises the lamination type piezoelectric element of this invention, (b) is a cross-sectional view which shows an example of the principal part of the lamination type piezoelectric element of this invention. 本発明の積層型圧電素子の要部の他の例を示す横断面図である。It is a cross-sectional view which shows the other example of the principal part of the lamination type piezoelectric element of this invention. 本発明の積層型圧電素子の要部の他の例を示す横断面図である。It is a cross-sectional view which shows the other example of the principal part of the lamination type piezoelectric element of this invention. 本発明の圧電アクチュエータを示す概略断面図であるIt is a schematic sectional drawing which shows the piezoelectric actuator of this invention. 本発明の噴射装置の実施の形態の一例を示す概略的な断面図である。It is a rough sectional view showing an example of an embodiment of an injection device of the present invention. 本発明の燃料噴射システムの実施の形態の一例を示す概略的なブロック図である。It is a schematic block diagram which shows an example of embodiment of the fuel-injection system of this invention.
　以下、本発明の積層型圧電素子の実施の形態の一例について図面を参照して詳細に説明する。 Hereinafter, an example of an embodiment of the multilayer piezoelectric element of the present invention will be described in detail with reference to the drawings.
　図１は本発明の積層型圧電素子の実施の形態の一例を示す斜視図であり、図２は本発明の積層型圧電素子の実施の形態の一例を示す縦断面図である。 FIG. 1 is a perspective view showing an example of the embodiment of the multilayer piezoelectric element of the present invention, and FIG. 2 is a longitudinal sectional view showing an example of the embodiment of the multilayer piezoelectric element of the present invention.
　図１および図２に示す積層型圧電素子１は、圧電体層２および内部電極層３が積層された積層体４と、内部電極層３と電気的に接続されるように積層体４の側面に設けられた導電性接合材５と、導電性接合材５に当接する領域を有するように設けられた外部電極６とを含み、この外部電極６は、導電性接合材５に当接する領域の少なくとも一部に金属層非形成部６１を有し、その他の領域に金属層６２が形成されている。 A laminated piezoelectric element 1 shown in FIGS. 1 and 2 includes a laminated body 4 in which a piezoelectric layer 2 and an internal electrode layer 3 are laminated, and a side surface of the laminated body 4 so as to be electrically connected to the internal electrode layer 3. And the external electrode 6 provided so as to have a region in contact with the conductive bonding material 5, and the external electrode 6 has a region in contact with the conductive bonding material 5. The metal layer non-formation part 61 is at least partly formed, and the metal layer 62 is formed in other regions.
　積層型圧電素子１を構成する積層体４は、例えば圧電体層２および内部電極層３が交互に複数積層されてなる活性部と、活性部の積層方向両端に設けられた圧電体層２からなる不活性部とを有し、例えば縦０．５～１０ｍｍ、横０．５～１０ｍｍ、高さ１～１００ｍｍの直方体状に形成されている。 The multilayer body 4 constituting the multilayer piezoelectric element 1 includes, for example, an active portion in which a plurality of piezoelectric layers 2 and internal electrode layers 3 are alternately stacked, and piezoelectric layers 2 provided at both ends of the active portion in the stacking direction. For example, it is formed in a rectangular parallelepiped shape having a length of 0.5 to 10 mm, a width of 0.5 to 10 mm, and a height of 1 to 100 mm.
　積層体４を構成する圧電体層２は、圧電特性を有するセラミックスで形成されたもので、このようなセラミックスとして、例えばチタン酸ジルコン酸鉛（ＰｂＺｒＯ３－ＰｂＴｉＯ３）からなるペロブスカイト型酸化物、ニオブ酸リチウム（ＬｉＮｂＯ３）、タンタル酸リチウム（ＬｉＴａＯ３）などを用いることができる。この圧電体層３の厚みは、例えば３～２５０μｍとされる。 The piezoelectric layer 2 constituting the multilayer body 4 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3 ), Lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), or the like can be used. The thickness of the piezoelectric layer 3 is, for example, 3 to 250 μm.
　積層体４を構成する内部電極層３は、圧電体層２を形成するセラミックスと同時焼成により形成されたもので、圧電体層２と交互に積層されて圧電体層２を上下から挟んでおり、積層順に正極および負極が配置されることにより、それらの間に挟まれた圧電体層２に駆動電圧を印加するものである。この形成材料として、例えば圧電セラミックスとの反応性が低い銀－パラジウム合金を主成分とする導体、あるいは銅、白金などを含む導体を用いることができる。図１および図２に示す例では、正極および負極（もしくはグランド極）がそれぞれ積層体４の対向する一対の側面に互い違いに導出されている。この内部電極層３の厚みは、例えば０．１～５μｍとされる。 The internal electrode layer 3 constituting the multilayer body 4 is formed by simultaneous firing with the ceramics forming the piezoelectric layer 2, and is alternately stacked with the piezoelectric layer 2 to sandwich the piezoelectric layer 2 from above and below. By arranging the positive electrode and the negative electrode in the order of lamination, a driving voltage is applied to the piezoelectric layer 2 sandwiched between them. As this forming material, for example, a conductor mainly composed of a silver-palladium alloy having low reactivity with piezoelectric ceramics, or a conductor containing copper, platinum, or the like can be used. In the example shown in FIGS. 1 and 2, the positive electrode and the negative electrode (or the ground electrode) are alternately led out to a pair of opposing side surfaces of the laminate 4. The internal electrode layer 3 has a thickness of 0.1 to 5 μm, for example.
　積層体４の側面には、内部電極層２と電気的に接続されるように導電性接合材５が設けられるとともに、導電性接合材５に当接する領域を有するように外部電極６が設けられている。 A conductive bonding material 5 is provided on the side surface of the laminate 4 so as to be electrically connected to the internal electrode layer 2, and an external electrode 6 is provided so as to have a region in contact with the conductive bonding material 5. ing.
　導電性接合材５は、例えばＡｇ粉末やＣｕ粉末など導電性の良好な金属粉末を含んだエポキシ樹脂やポリイミド樹脂からなる導電性接着剤からなり、例えば５～５００μｍの厚さに形成される。この導電性接合材５は、図２に示すように積層体４の側面に直接設けられていてもよいが、図３に示すように積層体４の側面に直接設けられずに内部電極層３と導電性接合材５との間に導体層７が介在した構成であってもよい。 The conductive bonding material 5 is made of a conductive adhesive made of an epoxy resin or a polyimide resin containing a metal powder having good conductivity, such as Ag powder or Cu powder, and is formed to a thickness of, for example, 5 to 500 μm. The conductive bonding material 5 may be provided directly on the side surface of the multilayer body 4 as shown in FIG. 2, but it is not directly provided on the side surface of the multilayer body 4 as shown in FIG. The conductive layer 7 may be interposed between the conductive bonding material 5 and the conductive layer 5.
　内部電極層３と導電性接合材５との間に導体層７が介在した場合の導体層７は、例えば銀とガラスからなるペーストを塗布して焼き付けて形成されたもので、積層体４の側面に接合されて、積層体４の対向する側面に互い違いに導出された内部電極層３とそれぞれ電気的に接続されている。この導体層７の厚みは、例えば５～５００μｍとされる。 When the conductor layer 7 is interposed between the internal electrode layer 3 and the conductive bonding material 5, the conductor layer 7 is formed by applying and baking a paste made of silver and glass, for example. It is joined to the side surface and electrically connected to the internal electrode layers 3 that are alternately led to the opposite side surface of the laminate 4. The thickness of the conductor layer 7 is, for example, 5 to 500 μm.
　外部電極６は、銅、鉄、ステンレス、リン青銅等の金属からなり、例えば幅０．５～１０ｍｍ、厚み０．０１～１．０ｍｍに形成されたものである。積層体４の伸縮により生じる応力を緩和する効果の高い形状として、例えば幅方向にスリットの入った形状、縦断面波型の形状、網目状に加工された金属板、線状の金属を編み込んだ金網導体などを採用することができる。特に、図４（ａ）に示すように線状の金属を編み込んだ金網導体などの網目構造の電極とするのが好ましい。この外部電極６にリード部材８が接合され、外部回路と電気的に接続されて、積層型圧電素子１が駆動する。 The external electrode 6 is made of metal such as copper, iron, stainless steel, phosphor bronze, etc., and is formed to have a width of 0.5 to 10 mm and a thickness of 0.01 to 1.0 mm, for example. For example, a shape having slits in the width direction, a shape having a corrugated longitudinal section, a metal plate processed into a mesh shape, or a linear metal is knitted as a shape having a high effect of relieving stress caused by expansion and contraction of the laminate 4 Wire mesh conductors can be used. In particular, as shown in FIG. 4A, it is preferable to use an electrode having a mesh structure such as a wire mesh conductor knitted with a linear metal. A lead member 8 is joined to the external electrode 6 and electrically connected to an external circuit, so that the multilayer piezoelectric element 1 is driven.
　そして、外部電極６は、導電性接合材５と当接する領域の少なくとも一部に金属層非形成部６１を有し、その他の領域に金属層６２が形成されている。 The external electrode 6 has a metal layer non-forming portion 61 in at least a part of a region in contact with the conductive bonding material 5, and a metal layer 62 is formed in the other region.
　導電性接合材５と当接する領域の少なくとも一部に金属層非形成部６１を有することで、導電性接合材５中の水分によって外部電極６の表面のうちの金属層非形成部６１に形成される酸化膜の官能基と導電性接合材５中の官能基とが化学結合し、導電性接合材５と外部電極６との接合強度を向上させることができる。また、急激な電流負荷がかかったとき、電気が低抵抗の金属層６２に優先して流れることから、金属層非形成部６１は温度上昇しにくい。一方、積層型圧電素子１の駆動で外部電極６が引っ張られても、金属層形成部における金属層６２が伸縮または剥がれて応力を緩和する。したがって、金属層非形成部６１の接合状態は安定するので、積層型圧電素子１の急停止は抑制される。 By having the metal layer non-forming part 61 in at least a part of the region in contact with the conductive bonding material 5, the metal layer non-forming part 61 on the surface of the external electrode 6 is formed by moisture in the conductive bonding material 5. Thus, the functional group of the oxide film and the functional group in the conductive bonding material 5 are chemically bonded, and the bonding strength between the conductive bonding material 5 and the external electrode 6 can be improved. In addition, when a sudden current load is applied, electricity flows preferentially over the low-resistance metal layer 62, so that the temperature of the metal layer non-formation part 61 does not easily rise. On the other hand, even if the external electrode 6 is pulled by driving the multilayer piezoelectric element 1, the metal layer 62 in the metal layer forming portion expands or contracts or peels to relieve stress. Therefore, since the joining state of the metal layer non-forming portion 61 is stabilized, the sudden stop of the multilayer piezoelectric element 1 is suppressed.
　なお、外部電極６の露出する表面を含む上記のその他の領域は、例えばすず、銀などのメッキによる金属層６２が形成されていることで、外部電極６の低抵抗化および表面酸化防止などの効果も得られる。金属層６２の厚みとしては、１～１０μｍであるのがよい。 The other region including the exposed surface of the external electrode 6 is formed with a metal layer 62 made of, for example, tin or silver, thereby reducing the resistance of the external electrode 6 and preventing surface oxidation. An effect is also obtained. The thickness of the metal layer 62 is preferably 1 to 10 μm.
　ここで、外部電極６は金属層非形成部６１の面がその他の領域の面よりもあらされているのが好ましい。その他の領域の面よりもあらされている金属層非形成部６１の面を有していることで、接触面積が増えて接合強度を上げることができる。ここで、その他の領域の面よりもあらされている金属層非形成部６１の面とは、金属層非形成部６１のみをあらすように加工されたものでもよく、全域をあらしたうえで金属層非形成部６１以外の部位に金属層６２を形成して表面粗さを異ならせたものでもよい。また、その他の領域の面よりもあらされている金属層非形成部６１の面を有しているとは、金属層非形成部６１の面のうちの一部があらされているのでもよいことを意味している。なお、あらされている金属層非形成部６１の面における表面粗さＲａは５～２０μｍであるのが効果的である。 Here, it is preferable that the external electrode 6 has the surface of the metal layer non-forming portion 61 exposed from the surface of other regions. By having the surface of the metal layer non-forming portion 61 that is exposed from the surface of other regions, the contact area can be increased and the bonding strength can be increased. Here, the surface of the metal layer non-forming portion 61 that is exposed from the surface of the other region may be a surface processed so as to show only the metal layer non-forming portion 61, A metal layer 62 may be formed in a portion other than the layer non-forming portion 61 to vary the surface roughness. Moreover, having the surface of the metal layer non-formation part 61 exposed from the surface of the other region may mean that part of the surface of the metal layer non-formation part 61 is exposed. It means that. It is effective that the surface roughness Ra on the surface of the exposed metal layer non-forming portion 61 is 5 to 20 μm.
　また、図４（ｂ）に示すように、導電性接合材５が外部電極６の側面まで達している場合に、外部電極６が積層体４の側面側の面に隣接する側面の少なくとも一部に金属層非形成部６１を有していることで、外部電極６の表面のうち導電性接合材５が剥がれやすい側面における導電性接合材５と外部電極６との接合強度を向上させることができる。 In addition, as shown in FIG. 4B, when the conductive bonding material 5 reaches the side surface of the external electrode 6, the external electrode 6 is at least a part of the side surface adjacent to the side surface side surface of the multilayer body 4. By having the metal layer non-forming portion 61 on the surface, it is possible to improve the bonding strength between the conductive bonding material 5 and the external electrode 6 on the side surface of the external electrode 6 where the conductive bonding material 5 is easily peeled off. it can.
　また、図５に示すように、外部電極６が積層体４の側面側の面の少なくとも一部に金属層非形部６１を有していることで、金属層６２がある部分と金属層非形成部６１（金属層６２がない部分）との間で段差が生じ、このような段差構造および金属層非形部６１と導電性接合材５との接触面積が増えることにより接合強度を上げることができる。 Further, as shown in FIG. 5, the external electrode 6 has the metal layer non-shaped portion 61 on at least a part of the side surface of the multilayer body 4, so that the portion with the metal layer 62 and the metal layer non-shaped portion are formed. A step is generated between the forming portion 61 (portion where the metal layer 62 is not provided), and the contact strength between the stepped structure and the metal layer non-shaped portion 61 and the conductive bonding material 5 is increased to increase the bonding strength. Can do.
　また、外部電極６が積層体４の積層方向中央部に対応する位置の少なくとも一部に金属層非形成部６１を有しているのが好ましく、このような構成とすることで、変位量の大きな積層方向中央部の接合強度を上げることができる。なお、ここでいう中央部とは、積層体４を積層方向に３等分したときの真ん中の部分を意味する。 Moreover, it is preferable that the external electrode 6 has the metal layer non-forming portion 61 at least at a part corresponding to the central portion in the stacking direction of the stacked body 4. The bonding strength at the central portion in the large stacking direction can be increased. In addition, the center part here means the middle part when the laminated body 4 is equally divided into three in the lamination direction.
　また、外部電極６がスリットまたは貫通穴を有し、外部電極６はスリットまたは貫通穴に面した側面の少なくとも一部に金属層非形成部６１を有しているのが好ましい。外部電極６の表面のうちの上記側面においても導電性接合材５が剥がれにくく、導電性接合材５と外部電極６との接合強度をさらに向上させることができる。なお、ここでいうスリットまたは貫通穴を有する形状としては、網目状に加工された金属板、線状の金属を編み込んだ金網導体も含まれる。 Further, it is preferable that the external electrode 6 has a slit or a through hole, and the external electrode 6 has a metal layer non-forming portion 61 on at least a part of a side surface facing the slit or the through hole. The conductive bonding material 5 is hardly peeled even on the above-mentioned side surface of the surface of the external electrode 6, and the bonding strength between the conductive bonding material 5 and the external electrode 6 can be further improved. In addition, as a shape which has a slit or a through-hole here, the metal-mesh conductor which braided the metal plate processed by mesh shape and a linear metal is also included.
　さらに、図４（ａ）および図６に示すように、金属層６２と金属層非形成部６１との境界が外部電極６の主面と側面との間の稜部に位置するのが好ましい。ここで、外部電極６の主面には金属層６２が形成され、外部電極６の側面には金属層非形成部６１が形成される。この構成によれば、外部電極６の主面を主に通電に寄与させ、外部電極６の側面の接合強度を高くして、通電を安定させることができる。 Furthermore, as shown in FIGS. 4A and 6, the boundary between the metal layer 62 and the metal layer non-forming portion 61 is preferably located at the ridge between the main surface and the side surface of the external electrode 6. Here, a metal layer 62 is formed on the main surface of the external electrode 6, and a metal layer non-forming portion 61 is formed on the side surface of the external electrode 6. According to this configuration, the main surface of the external electrode 6 can be mainly contributed to energization, the bonding strength of the side surface of the external electrode 6 can be increased, and the energization can be stabilized.
　また、図６に示すように、スリットまたは貫通穴に面した側面の全域が金属層非形成部６１であってもよく、この構成は金型プレスで打ち抜くことによって容易に作製することができる。また、外部電極６がスリットまたは貫通穴に面した側面が全て金属層非形成部６１となっており、スリットまたは貫通穴に導電性接合材が入り込んでいることで、導電性接合材５と外部電極６との接合強度をより強固なものとすることができる。 Further, as shown in FIG. 6, the entire region of the side surface facing the slit or the through hole may be the metal layer non-formed portion 61, and this configuration can be easily manufactured by punching with a die press. Further, the side surfaces of the external electrodes 6 facing the slits or the through holes are all the metal layer non-formed portions 61, and the conductive bonding material enters the slits or the through holes. The bonding strength with the electrode 6 can be made stronger.
　本実施の形態の積層型圧電素子１は、例えば、圧電駆動素子（圧電アクチュエータ），圧力センサ素子および圧電回路素子等に用いられる。駆動素子としては、例えば、自動車エンジンの燃料噴射装置，インクジェットのような液体噴射装置，光学装置のような精密位置決め装置，振動防止装置が挙げられる。センサ素子としては、例えば、燃焼圧センサ，ノックセンサ，加速度センサ，荷重センサ，超音波センサ，感圧センサおよびヨーレートセンサが挙げられる。また、回路素子としては、例えば、圧電ジャイロ，圧電スイッチ，圧電トランスおよび圧電ブレーカーが挙げられる。 The multilayer piezoelectric element 1 according to the present embodiment is used for, for example, a piezoelectric drive element (piezoelectric actuator), a pressure sensor element, a piezoelectric circuit element, and the like. Examples of the driving element include a fuel injection device for an automobile engine, a liquid injection device such as an inkjet, a precision positioning device such as an optical device, and a vibration prevention device. Examples of the sensor element include a combustion pressure sensor, a knock sensor, an acceleration sensor, a load sensor, an ultrasonic sensor, a pressure sensor, and a yaw rate sensor. Examples of the circuit element include a piezoelectric gyro, a piezoelectric switch, a piezoelectric transformer, and a piezoelectric breaker.
　次に、本実施の形態の積層型圧電素子１の製造方法について説明する。 Next, a method for manufacturing the multilayer piezoelectric element 1 of the present embodiment will be described.
　まず、圧電体層２となるセラミックグリーンシートを作製する。具体的には、圧電セラミックスの仮焼粉末と、アクリル系，ブチラール系等の有機高分子からなるバインダーと、可塑剤とを混合してセラミックスラリーを作製する。そして、ドクターブレード法、カレンダーロール法等のテープ成型法を用いることにより、このセラミックスラリーを用いてセラミックグリーンシートを作製する。圧電セラミックスとしては圧電特性を有するものであればよく、例えば、チタン酸ジルコン酸鉛（ＰｂＺｒＯ３－ＰｂＴｉＯ３）からなるペロブスカイト型酸化物等を用いることができる。また、可塑剤としては、フタル酸ジブチル（ＤＢＰ），フタル酸ジオクチル（ＤＯＰ）等を用いることができる。 First, a ceramic green sheet to be the piezoelectric layer 2 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3 ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.
　次に、内部電極層３となる導電性ペーストを作製する。具体的には、銀－パラジウム合金の金属粉末にバインダーおよび可塑剤を添加混合することによって導電性ペーストを作製する。この導電性ペーストを上記のセラミックグリーンシート上に、スクリーン印刷法を用いて内部電極層３のパターンで塗布する。さらに、この導電性ペーストが印刷されたセラミックグリーンシートを複数枚積層し、所定の温度で脱バインダー処理を行なった後、９００～１２００℃の温度で焼成することによって、交互に積層された圧電体層２および内部電極層３を備えた積層体４を作製する。 Next, a conductive paste to be the internal electrode layer 3 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrode layer 3 using a screen printing method. Further, a plurality of ceramic green sheets printed with this conductive paste are laminated, subjected to a binder removal treatment at a predetermined temperature, and then fired at a temperature of 900 to 1200 ° C. A laminate 4 including the layer 2 and the internal electrode layer 3 is produced.
　なお、積層体４は、上記の製造方法によって作製されるものに限定されるものではなく、圧電体層２と内部電極層３とを複数積層してなる積層体４を作製できれば、どのような製造方法によって作製されてもよい。 The laminate 4 is not limited to the one produced by the above manufacturing method, and any laminate 4 can be produced as long as the laminate 4 formed by laminating a plurality of piezoelectric layers 2 and internal electrode layers 3 can be produced. It may be produced by a manufacturing method.
　次に、焼成して得られた積層体４に、平面研削盤等を用いて所定の形状になるよう研削処理を施す。 Next, the laminated body 4 obtained by firing is subjected to a grinding process so as to have a predetermined shape using a surface grinder or the like.
　その後、銀を主成分とする導電性粒子とガラスとを混合したものに、バインダー，可塑剤および溶剤を加えて作製した銀ガラス含有導電性ペーストを、導体層７のパターンで積層体４の側面にスクリーン印刷法等によって印刷後、乾燥させた後、６５０～７５０℃の温度で焼き付け処理を行ない、導体層７を形成する。なお、導電性接合材５を直接積層体４の側面に設ける場合は、この工程は省略される。 Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles mainly containing silver and glass is used to form a side surface of the laminate 4 in the pattern of the conductor layer 7. After being printed by a screen printing method or the like, and dried, a baking process is performed at a temperature of 650 to 750 ° C. to form the conductor layer 7. In addition, this process is abbreviate | omitted when providing the conductive joining material 5 in the side surface of the laminated body 4 directly.
　次に、導電性接合材５を介して外部電極６を導体層７の表面に接合する。具体的には、側面に導電性接合材５を塗布した積層型圧電素子１に、例えば１５０℃～２５０℃で、０．５～１．５時間かけて外部電極６を固着させる。 Next, the external electrode 6 is bonded to the surface of the conductor layer 7 through the conductive bonding material 5. Specifically, the external electrode 6 is fixed to the laminated piezoelectric element 1 coated with the conductive bonding material 5 on the side surface, for example, at 150 to 250 ° C. for 0.5 to 1.5 hours.
　導電性接合材５は、Ａｇ粉末やＣｕ粉末などの導電性の良好な金属粉末を含んだエポキシ樹脂やポリイミド樹脂からなる導電性接着剤、はんだなどを用い、スクリーン印刷やディスペンス方式により所定の厚みや幅に制御して形成することができる。 The conductive bonding material 5 uses a conductive adhesive made of an epoxy resin or a polyimide resin containing a highly conductive metal powder such as Ag powder or Cu powder, solder, etc., and has a predetermined thickness by screen printing or dispensing method. It can be formed with a controlled width.
　外部電極６の一部に金属層非形成部６１を設けるには、例えば狙った場所をマスクしてメッキしたり、所定の薬品により、部分的にメッキを剥がしたりするなどの方法が挙げられる。また、外部電極６の側面に金属層非形成部６１を設けるには、所定の形状に金型プレスで打ち抜く方法も挙げられる。さらに、金属層非形成部６１を荒らすには、ブラストや研磨などの方法が挙げられる。 In order to provide the metal electrode non-forming portion 61 on a part of the external electrode 6, for example, plating is performed by masking a target location, or plating is partially removed with a predetermined chemical. Moreover, in order to provide the metal layer non-formation part 61 in the side surface of the external electrode 6, the method of punching in a predetermined shape with a die press is also mentioned. Furthermore, methods such as blasting and polishing can be used to roughen the metal layer non-forming portion 61.
　そして、リード部材８を外部電極６に溶接またははんだ、導電性接合材などで接合する。 Then, the lead member 8 is joined to the external electrode 6 by welding, solder, conductive joining material or the like.
　その後、一対の導体層７にそれぞれ接合させた外部電極６に０．１～３ｋＶ／ｍｍの直流電界を印加し、積層体４を構成する圧電体層２を分極することによって、積層型圧電素子１が完成する。この積層型圧電素子１は、外部電極６を介して内部電極層２と外部の電源とを接続して、圧電体層３に電圧を印加することにより、各圧電体層２を逆圧電効果によって大きく変位させることができる。これにより、例えばエンジンに燃料を噴射供給する自動車用燃料噴射弁として機能させることが可能となる。 Thereafter, a direct current electric field of 0.1 to 3 kV / mm is applied to the external electrodes 6 respectively joined to the pair of conductor layers 7 to polarize the piezoelectric layer 2 constituting the multilayer body 4, so that the multilayer piezoelectric element is obtained. 1 is completed. The multilayer piezoelectric element 1 connects the internal electrode layer 2 and an external power source via the external electrode 6 and applies a voltage to the piezoelectric layer 3, thereby causing each piezoelectric layer 2 to have an inverse piezoelectric effect. It can be displaced greatly. This makes it possible to function as an automobile fuel injection valve that injects and supplies fuel to the engine, for example.
　次に、本発明の圧電アクチュエータの実施の形態の例について説明する。図７は、本発明の圧電アクチュエータの一例を示す概略断面図であり、図７に示す例の圧電アクチュエータは積層型圧電素子１をケース１０に収容してなるものである。 Next, an example of an embodiment of the piezoelectric actuator of the present invention will be described. FIG. 7 is a schematic sectional view showing an example of the piezoelectric actuator of the present invention. The piezoelectric actuator of the example shown in FIG. 7 is obtained by housing the multilayer piezoelectric element 1 in a case 10.
　ケース１０は、例えばＳＵＳ３０４やＳＵＳ３１６Ｌなどの金属材料で形成されたもので、このようなケース１０にて積層型圧電素子１が封止されているため、腐食性のガス中や、水中等で使用することができる。また、内部電極層３のイオンマイグレーションを防止するために、不活性ガスを用いて封止してもよい。この場合は、酸素が不足するため、圧電体層２の酸素空孔が発生しやすくなるが、本発明の積層型圧電素子１を用いることで、ケース１０内の密閉された空間においても樹脂から有効的に酸素を供給することができ、圧電体層２中に酸素空孔が発生するのを抑制することができる。 The case 10 is made of, for example, a metal material such as SUS304 or SUS316L. Since the multilayer piezoelectric element 1 is sealed in such a case 10, the case 10 is used in corrosive gas or in water. can do. Further, in order to prevent ion migration of the internal electrode layer 3, sealing may be performed using an inert gas. In this case, since oxygen is insufficient, oxygen vacancies in the piezoelectric layer 2 are likely to be generated. However, by using the multilayer piezoelectric element 1 of the present invention, the resin can be removed from the resin even in a sealed space in the case 10. Oxygen can be effectively supplied, and generation of oxygen vacancies in the piezoelectric layer 2 can be suppressed.
　次に、本発明の噴射装置の実施の形態の例について説明する。図８は、本発明の噴射装置の実施の形態の一例を示す概略断面図である。 Next, an example of an embodiment of the injection device of the present invention will be described. FIG. 8 is a schematic cross-sectional view showing an example of an embodiment of the injection device of the present invention.
　図８に示すように、本実施の形態の噴射装置１９は、一端に噴射孔２１を有する収納容器（容器）２３の内部に上記の本実施の形態の積層型圧電素子１が収納されている。 As shown in FIG. 8, in the injection device 19 according to the present embodiment, the multilayer piezoelectric element 1 according to the present embodiment is stored in a storage container (container) 23 having an injection hole 21 at one end. .
　収納容器２３内には、噴射孔２１を開閉することができるニードルバルブ２５が配設されている。噴射孔２１には流体通路２７がニードルバルブ２５の動きに応じて連通可能になるように配設されている。この流体通路２７は外部の流体供給源に連結され、流体通路２７に常時高圧で流体が供給されている。従って、ニードルバルブ２５が噴射孔２１を開放すると、流体通路２７に供給されていた流体が外部または隣接する容器、例えば内燃機関の燃料室（不図示）に、噴射孔２１から吐出されるように構成されている。 In the storage container 23, a needle valve 25 capable of opening and closing the injection hole 21 is disposed. A fluid passage 27 is disposed in the injection hole 21 so as to be able to communicate with the movement of the needle valve 25. The fluid passage 27 is connected to an external fluid supply source, and fluid is constantly supplied to the fluid passage 27 at a high pressure. Accordingly, when the needle valve 25 opens the injection hole 21, the fluid supplied to the fluid passage 27 is discharged from the injection hole 21 to an external or adjacent container, for example, a fuel chamber (not shown) of the internal combustion engine. It is configured.
　また、ニードルバルブ２５の上端部は内径が大きくなってピストン３１になっており、収納容器２３に形成されたシリンダ２９と摺動可能になっている。そして、収納容器２３内には、上述した例の積層型圧電素子１がピストン３１に接して収納されている。 Further, the upper end portion of the needle valve 25 has a larger inner diameter to form a piston 31, which can slide with a cylinder 29 formed in the storage container 23. In the storage container 23, the multilayer piezoelectric element 1 of the above-described example is stored in contact with the piston 31.
　このような噴射装置１９では、積層型圧電素子１が電圧を印加されて伸長すると、ピストン３１が押圧され、ニードルバルブ２５が噴射孔２１に通じる流体通路２７を閉塞し、流体の供給が停止される。また、電圧の印加が停止されると積層型圧電素子１が収縮し、皿バネ３３がピストン３１を押し返し、流体通路２７が開放され噴射孔２１が流体通路２７と連通して、噴射孔２１から流体の噴射が行なわれるようになっている。 In such an injection device 19, when the multilayer piezoelectric element 1 is extended by applying a voltage, the piston 31 is pressed, the needle valve 25 closes the fluid passage 27 leading to the injection hole 21, and the supply of fluid is stopped. The When the voltage application is stopped, the laminated piezoelectric element 1 contracts, the disc spring 33 pushes back the piston 31, the fluid passage 27 is opened, and the injection hole 21 communicates with the fluid passage 27. Fluid injection is performed.
　なお、積層型圧電素子１に電圧を印加することによって流体通路２７を開放し、電圧の印加を停止することによって流体通路２７を閉鎖するように構成してもよい。 Note that the fluid passage 27 may be opened by applying a voltage to the multilayer piezoelectric element 1 and the fluid passage 27 may be closed by stopping the application of the voltage.
　また、本実施の形態の噴射装置１９は、噴射孔を有する容器２３と、本実施の形態の積層型圧電素子１とを備え、容器２３内に充填された流体を積層型圧電素子１の駆動により噴射孔２１から吐出させるように構成されていてもよい。すなわち、積層型圧電素子１が必ずしも容器２３の内部にある必要はなく、積層型圧電素子１の駆動によって容器２３の内部に流体の噴射を制御するための圧力が加わるように構成されていればよい。なお、本実施の形態の噴射装置１９において、流体とは、燃料，インク等の他、導電性ペースト等の種々の液体および気体が含まれる。本実施の形態の噴射装置１９を用いることによって、流体の流量および噴出タイミングを長期にわたって安定して制御することができる。 In addition, the ejection device 19 according to the present embodiment includes a container 23 having ejection holes and the multilayer piezoelectric element 1 according to the present embodiment, and the fluid filled in the container 23 is driven to drive the multilayer piezoelectric element 1. May be configured to discharge from the injection hole 21. That is, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 23, as long as the multilayer piezoelectric element 1 is configured to apply pressure for controlling the ejection of fluid to the inside of the container 23 by driving the multilayer piezoelectric element 1. Good. In the ejection device 19 of the present embodiment, the fluid includes various liquids and gases such as a conductive paste in addition to fuel and ink. By using the ejection device 19 according to the present embodiment, the flow rate of fluid and the ejection timing can be stably controlled over a long period of time.
　本実施の形態の積層型圧電素子１を採用した本実施の形態の噴射装置１９を内燃機関に用いれば、従来の噴射装置に比べてエンジン等の内燃機関の燃焼室に燃料をより長い期間にわたって精度よく噴射させることができる。 If the injection device 19 of the present embodiment that employs the multilayer piezoelectric element 1 of the present embodiment is used for an internal combustion engine, the fuel is supplied to the combustion chamber of the internal combustion engine such as an engine over a longer period than the conventional injection device. It is possible to inject with high accuracy.
　次に、本発明の燃料噴射システムの実施の形態の例について説明する。図９は、本発明の燃料噴射システムの実施の形態の一例を示す概略図である。 Next, an example of an embodiment of the fuel injection system of the present invention will be described. FIG. 9 is a schematic view showing an example of an embodiment of the fuel injection system of the present invention.
　図９に示すように、本実施の形態の燃料噴射システム３５は、高圧流体としての高圧燃料を蓄えるコモンレール３７と、このコモンレール３７に蓄えられた高圧流体を噴射する複数の本実施の形態の噴射装置１９と、コモンレール３７に高圧流体を供給する圧力ポンプ３９と、噴射装置１９に駆動信号を与える噴射制御ユニット４１とを備えている。 As shown in FIG. 9, the fuel injection system 35 of the present embodiment includes a common rail 37 that stores high-pressure fuel as high-pressure fluid, and a plurality of injections of the present embodiment that inject high-pressure fluid stored in the common rail 37. A device 19, a pressure pump 39 that supplies a high-pressure fluid to the common rail 37, and an injection control unit 41 that supplies a drive signal to the injection device 19 are provided.
　噴射制御ユニット４１は、外部情報または外部からの信号に基づいて高圧流体の噴射の量およびタイミングを制御する。例えば、エンジンの燃料噴射に噴射制御ユニット４１を用いた場合であれば、エンジンの燃焼室内の状況をセンサ等で感知しながら燃料噴射の量およびタイミングを制御することができる。圧力ポンプ３９は、燃料タンク４３から流体燃料を高圧でコモンレール３７に供給する役割を果たす。例えばエンジンの燃料噴射システム３５の場合には１０００～２０００気圧（約１０１ＭＰａ～約２０３ＭＰａ）程度、好ましくは１５００～１７００気圧（約１５２ＭＰａ～約１７２ＭＰａ）程度の高圧にしてコモンレール３７に流体燃料を送り込む。コモンレール３７では、圧力ポンプ３９から送られてきた高圧燃料を蓄え、噴射装置１９に適宜送り込む。噴射装置１９は、前述したように噴射孔２１から一定の流体を外部または隣接する容器に噴射する。例えば、燃料を噴射供給する対象がエンジンの場合には、高圧燃料を噴射孔２１からエンジンの燃焼室内に霧状に噴射する。 The injection control unit 41 controls the amount and timing of high-pressure fluid injection based on external information or an external signal. For example, if the injection control unit 41 is used for fuel injection of the engine, the amount and timing of fuel injection can be controlled while sensing the condition in the combustion chamber of the engine with a sensor or the like. The pressure pump 39 serves to supply fluid fuel from the fuel tank 43 to the common rail 37 at a high pressure. For example, in the case of the fuel injection system 35 of the engine, the fluid fuel is fed into the common rail 37 at a high pressure of about 1000 to 2000 atmospheres (about 101 MPa to about 203 MPa), preferably about 1500 to 1700 atmospheres (about 152 MPa to about 172 MPa). In the common rail 37, the high-pressure fuel sent from the pressure pump 39 is stored and sent to the injection device 19 as appropriate. As described above, the ejection device 19 ejects a certain fluid from the ejection holes 21 to the outside or an adjacent container. For example, when the target for injecting and supplying fuel is an engine, high-pressure fuel is injected from the injection hole 21 into the combustion chamber of the engine in the form of a mist.
　なお、本発明は、上記の実施の形態の例に限定されるものではなく、本発明の要旨を逸脱しない範囲内で種々の変更を行なうことは何ら差し支えない。例えば、外部電極６は、上記の例では積層体４の対向する２つの側面に１つずつ形成したが、２つの外部電極６を積層体４の隣り合う側面に形成してもよいし、積層体４の同一の側面に形成してもよい。また、積層体４の積層方向に直交する方向における断面の形状は、上記の実施の形態の例である四角形状以外に、六角形状や八角形状等の多角形状、円形状、あるいは直線と円弧とを組み合わせた形状であっても構わない。 In addition, this invention is not limited to the example of said embodiment, A various change may be performed within the range which does not deviate from the summary of this invention. For example, the external electrodes 6 are formed one by one on the two opposite side surfaces of the multilayer body 4 in the above example, but the two external electrodes 6 may be formed on adjacent side surfaces of the multilayer body 4. It may be formed on the same side of the body 4. Moreover, the cross-sectional shape in the direction orthogonal to the stacking direction of the stacked body 4 is not limited to the quadrangular shape which is an example of the above embodiment, but a polygonal shape such as a hexagonal shape or an octagonal shape, a circular shape, or a straight line and an arc. You may be the shape which combined.
　本発明の積層型圧電素子の実施例について以下に説明する。 Examples of the multilayer piezoelectric element of the present invention will be described below.
　本発明の積層型圧電素子を以下のようにして作製した。まず、平均粒径が０．４μｍのチタン酸ジルコン酸鉛（ＰｂＺｒＯ３－ＰｂＴｉＯ３）を主成分とする圧電セラミックスの仮焼粉末、バインダーおよび可塑剤を混合したセラミックスラリーを作製した。このセラミックスラリーを用いてドクターブレード法により厚み５０μｍの圧電体層となるセラミックグリーンシートを作製した。また、銀－パラジウム合金にバインダーを加えて、内部電極層となる導電性ペーストを作製した。 The multilayer piezoelectric element of the present invention was produced as follows. First, a ceramic slurry was prepared by mixing calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO 3 -PbTiO 3 ) having an average particle diameter of 0.4 μm, a binder, and a plasticizer. Using this ceramic slurry, a ceramic green sheet serving as a piezoelectric layer having a thickness of 50 μm was prepared by a doctor blade method. Further, a binder was added to the silver-palladium alloy to produce a conductive paste to be an internal electrode layer.
　次に、セラミックグリーンシートの片面に、内部電極層となる導電性ペーストをスクリーン印刷法により印刷し、導電性ペーストが印刷されたセラミックグリーンシートを２００枚積層した。また、内部電極層となる導電性ペーストが印刷されたセラミックグリーンシート２００枚を中心にして、その上下に、内部電極となる導電性ペーストが印刷されていないセラミックグリーンシート合計１５枚を積層した。そして、９８０～１１００℃で焼成することにより積層体を得た。得られた積層体を、平面研削盤を用いて所定の形状に研削した。 Next, a conductive paste serving as an internal electrode layer was printed on one side of the ceramic green sheet by a screen printing method, and 200 ceramic green sheets printed with the conductive paste were laminated. Further, a total of 15 ceramic green sheets not printed with the conductive paste serving as the internal electrode were laminated on the top and bottom of the 200 ceramic green sheets printed with the conductive paste serving as the internal electrode layer. Then, a laminate was obtained by firing at 980 to 1100 ° C. The obtained laminate was ground into a predetermined shape using a surface grinder.
　次に、積層体の側面の導体層の形成部に、銀とガラスにバインダーを混合した導電性ペーストをスクリーン印刷法により印刷し、７００℃で焼き付け処理を行なった。 Next, a conductive paste in which a binder was mixed with silver and glass was printed by a screen printing method on the conductive layer forming portion on the side surface of the laminate, and baked at 700 ° C.
　次に、導体層に、銀粉末を含むポリイミドからなる導電性接合材をディスペンサーにて塗布し、線状の金属を編み込んだ金網導体からなる網目構造の外部電極を積層体の表面と平行に接続し固定した。図６に示す断面を有する積層型圧電素子（試料１）を作製した。 Next, a conductive bonding material made of polyimide containing silver powder is applied to the conductor layer with a dispenser, and an external electrode with a mesh structure made of a wire mesh conductor knitted with a linear metal is connected in parallel with the surface of the laminate. And fixed. A laminated piezoelectric element (sample 1) having the cross section shown in FIG. 6 was produced.
　なお、外部電極は板状体を金型プレスで打ち抜くことで金属層非形成部を形成したものを採用した。 In addition, the external electrode employ | adopted what formed the metal layer non-formation part by punching a plate-shaped object with the metal mold press.
　一方、比較例として、外部電極に金属層非形成部のない表面全体にめっきがほどこされたものを採用した。 On the other hand, as a comparative example, an external electrode with a metal layer not formed on the entire surface was used.
　これらの積層型圧電素子に、外部電極に溶接で接合されたリード部材を介して外部電極に３ｋＶ／ｍｍの直流電界を１５分間印加して、分極処理を行なった。これらの積層型圧電素子に１６０Ｖの直流電圧を印加したところ、積層体の積層方向に３０μｍの変位量が得られた。 These laminated piezoelectric elements were subjected to polarization treatment by applying a DC electric field of 3 kV / mm to the external electrodes for 15 minutes through lead members welded to the external electrodes. When a DC voltage of 160 V was applied to these stacked piezoelectric elements, a displacement of 30 μm was obtained in the stacking direction of the stacked body.
　さらに、室温で０Ｖ～＋１６０Ｖの交流電圧を１５０Ｈｚの周波数で印加して、連続駆動した耐久性試験を行なったところ、試料２（比較例）の積層型圧電素子は、１×１０４回の連続駆動でメタライズ層と導電性接合材層との境界に亀裂が入るのを確認した。 Furthermore, when a durability test was carried out by continuously applying an AC voltage of 0 V to +160 V at a frequency of 150 Hz at room temperature, the laminated piezoelectric element of Sample 2 (Comparative Example) was continuously 1 × 10 4 times. It was confirmed that a crack occurred at the boundary between the metallized layer and the conductive bonding material layer by driving.
　これに対し、試料１（本発明実施例）の積層型圧電素子は、連続駆動１×１０７回をすぎても亀裂が入ることなく駆動していた。 On the other hand, the laminated piezoelectric element of Sample 1 (invention example) was driven without cracking even after continuous driving 1 × 10 7 times.
　以上の結果から、本発明によれば、長期間の耐久性に優れた積層型圧電素子を実現することができることがわかる。 From the above results, it can be seen that according to the present invention, a multilayer piezoelectric element having excellent long-term durability can be realized.
　１・・・積層型圧電素子
　２・・・圧電体層
　３・・・内部電極層
　４・・・積層体
　５・・・導電性接合材
　６・・・外部電極
　６１・・・金属層非形成部
　６２・・・金属層
　７・・・導体層
　８・・・リード部材
　１０・・・ケース
　１９・・・噴射装置
　２１・・・噴射孔
　２３・・・収納容器（容器）
　２５・・・ニードルバルブ
　２７・・・流体通路
　２９・・・シリンダ
　３１・・・ピストン
　３３・・・皿バネ
　３５・・・燃料噴射システム
　３７・・・コモンレール
　３９・・・圧力ポンプ
　４１・・・噴射制御ユニット
　４３・・・燃料タンク DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element 2 ... Piezoelectric layer 3 ... Internal electrode layer 4 ... Laminated body 5 ... Conductive joining material 6 ... External electrode 61 ... Metal layer non-formation Portion 62 ... Metal layer 7 ... Conductor layer 8 ... Lead member 10 ... Case 19 ... Injection device 21 ... Injection hole 23 ... Storage container (container)
25 ... Needle valve 27 ... Fluid passage 29 ... Cylinder 31 ... Piston 33 ... Belleville spring 35 ... Fuel injection system 37 ... Common rail 39 ... Pressure pump 41 ... Injection control unit 43 ... Fuel tank

Claims (11)

  1. 　圧電体層および内部電極層が積層された積層体と、前記内部電極層と電気的に接続されるように前記積層体の側面に設けられた導電性接合材と、該導電性接合材に当接する領域を有するように設けられた外部電極とを含み、該外部電極は、前記導電性接合材に当接する領域の少なくとも一部に金属層非形成部を有し、その他の領域に金属層が形成されていることを特徴とする積層型圧電素子。 A laminate in which a piezoelectric layer and an internal electrode layer are laminated, a conductive bonding material provided on a side surface of the multilayer body so as to be electrically connected to the internal electrode layer, and a contact with the conductive bonding material An external electrode provided so as to have a region in contact therewith, the external electrode having a metal layer non-forming portion in at least a part of the region in contact with the conductive bonding material, and a metal layer in the other region A laminated piezoelectric element characterized by being formed.
  2. 　前記内部電極層と前記導電性接合材との間に導体層が介在していることを特徴とする請求項１に記載の積層型圧電素子。 The multilayer piezoelectric element according to claim 1, wherein a conductor layer is interposed between the internal electrode layer and the conductive bonding material.
  3. 　前記外部電極は前記金属層非形成部の面が前記その他の領域の面よりもあらされていることを特徴とする請求項１または請求項２に記載の積層型圧電素子。 3. The multilayer piezoelectric element according to claim 1, wherein the external electrode has a surface of the metal layer non-forming portion exposed from a surface of the other region.
  4. 　前記外部電極は前記積層体の側面側の面の少なくとも一部に前記金属層非形成部を有していることを特徴とする請求項１または請求項２に記載の積層型圧電素子。 The multilayer piezoelectric element according to claim 1 or 2, wherein the external electrode has the metal layer non-forming portion on at least a part of a side surface of the multilayer body.
  5. 　前記外部電極は前記積層体の側面側の面に隣接する側面の少なくとも一部に前記金属層非形成部を有していることを特徴とする請求項１または請求項２に記載の積層型圧電素子。 3. The stacked piezoelectric device according to claim 1, wherein the external electrode has the metal layer non-forming portion on at least a part of a side surface adjacent to a side surface of the stacked body. element.
  6. 　前記外部電極は前記積層体の積層方向中央部に対応する位置の少なくとも一部に前記金属層非形成部を有していることを特徴とする請求項１または請求項２に記載の積層型圧電素子。 3. The stacked piezoelectric device according to claim 1, wherein the external electrode has the metal layer non-forming portion at least at a part of a position corresponding to a central portion in the stacking direction of the stacked body. element.
  7. 　前記外部電極はスリットまたは貫通穴を有し、前記外部電極は前記スリットまたは前記貫通穴に面した側面の少なくとも一部に前記金属層非形成部を有していることを特徴とする請求項１または請求項２に記載の積層型圧電素子。 The said external electrode has a slit or a through-hole, and the said external electrode has the said metal layer non-formation part in at least one part of the side surface facing the said slit or the said through-hole. Alternatively, the multilayer piezoelectric element according to claim 2.
  8. 　前記外部電極は前記スリットまたは前記貫通穴に面した側面が全て前記金属層非形成部となっており、前記スリットまたは前記貫通穴に前記導電性接合材が入り込んでいることを特徴とする請求項７に記載の積層型圧電素子。 The side surface of the external electrode facing the slit or the through hole is the metal layer non-formed part, and the conductive bonding material enters the slit or the through hole. 8. The laminated piezoelectric element according to 7.
  9. 　請求項１に記載の積層型圧電素子と、該積層型圧電素子を内部に収容するケースとを備えていることを特徴とする圧電アクチュエータ。 A piezoelectric actuator comprising: the laminated piezoelectric element according to claim 1; and a case for housing the laminated piezoelectric element therein.
  10. 　噴射孔を有する容器と、請求項１に記載の積層型圧電素子とを備え、前記容器内に蓄えられた流体が前記積層型圧電素子の駆動により前記噴射孔から吐出されることを特徴とする噴射装置。 A container having an injection hole and the multilayer piezoelectric element according to claim 1, wherein fluid stored in the container is discharged from the injection hole by driving the multilayer piezoelectric element. Injection device.
  11. 　高圧燃料を蓄えるコモンレールと、該コモンレールに蓄えられた前記高圧燃料を噴射する請求項１０に記載の噴射装置と、前記コモンレールに前記高圧燃料を供給する圧力ポンプと、前記噴射装置に駆動信号を与える噴射制御ユニットとを備えたことを特徴とする燃料噴射システム。 A common rail for storing high-pressure fuel, the injection device according to claim 10 for injecting the high-pressure fuel stored in the common rail, a pressure pump for supplying the high-pressure fuel to the common rail, and a drive signal for the injection device A fuel injection system comprising an injection control unit.
PCT/JP2012/078105 2011-10-31 2012-10-31 Multilayer piezoelectric element, and piezoelectric actuator, injection apparatus and fuel injection system provided with multilayer piezoelectric element WO2013065709A1 (en)

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