JP2010098026A - Laminated piezoelectric element, injection apparatus using the same and fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element capable of excellently coping with the displacement of a laminate, preventing peeling from an external electrode or the fracture of a feed electrode, and improving durability. <P>SOLUTION: The laminated piezoelectric element 1 includes: a laminate S in which a piezoelectric body layer 2 and an internal electrode layer 3 are alternatively laminated; the external electrode 4 bonded to the side face of the laminate S and electrically connected to the internal electrode layer 3; and the feed electrode 7 comprising a plurality of conductor wires 6 connected to a feed line 5 at one end side, disposed in a direction crossing a lamination direction on the side face of the laminate S, arranged in the lamination direction, and connected to the external electrode 4 in the middle. For the feed electrode 7, the other end side of at least a part of conductor wires 6 is connected at a connection part 8. The peeling from the external electrode 4 of the feed electrode 7 or the fracture of the feed electrode 7 is prevented, and the laminated piezoelectric element 1 excellent in durability is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laminated piezoelectric element used for a drive element (piezoelectric actuator), a sensor element or a circuit element using a piezoelectric body, for example. Examples of the driving element include a fuel injection device for an automobile engine, a liquid injection device such as a printing device for an ink jet printer, a precision positioning device such as a positioning device for 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.

  Conventionally, as a laminated piezoelectric element, a laminated body in which a large number of piezoelectric layers and internal electrode layers are alternately laminated, and an external electrode joined to a side surface of the laminated body and electrically connected to the internal electrode layer are provided. What you have is known. And in order to electrically connect an external drive power supply and an external electrode, a lead wire is connected to the external electrode as a power supply line from the drive power supply.

  Here, since the laminated body is displaced during driving, if the lead wire is directly connected to the external electrode, the joint portion of the lead wire may be peeled off. Therefore, a plurality of vertical lines and a plurality of metal wires are used as the feeding electrode. It has been proposed to connect a strip-shaped mesh formed by combining horizontal wires to an external electrode with silver paste or solder and to connect a lead wire to this mesh (see, for example, Patent Document 1).

Such a multilayered piezoelectric element is required to ensure a large amount of displacement under a large pressure at the same time as miniaturization proceeds. For this reason, it is required that a higher electric field is applied and that the device can be used under severe conditions in which continuous driving is performed for a long time.
Japanese Utility Model Publication No.3-116058

  Since the multilayer piezoelectric element is required to have a large amount of displacement and high durability, the specific piezoelectric layer or internal electrode layer breaks due to stress during driving in the multilayer body. Insertion of the planned fracture layer to be secured is performed.

  On the other hand, when a metal wire knitted into a mesh is used as the feeding electrode, the mesh itself expands and contracts according to the displacement of the laminate, but the stitch portion (the portion where the vertical and horizontal lines intersect) ) Has a problem that sparks may occur. In addition, when a mesh with stitches is used, there is a problem that stress cannot be absorbed and peeled off from the external electrode because the mesh cannot be sufficiently expanded or contracted according to the displacement of the laminate.

  The present invention has been made in view of the above problems, and even when used under severe conditions such as a high electric field, high pressure, or continuous driving for a long time, the power supply responds well to the displacement of the laminate. It is an object of the present invention to provide a multilayer piezoelectric element that can prevent the electrode from peeling or breaking from an external electrode and improve the durability.

  The laminated piezoelectric element of the present invention includes a laminated body in which piezoelectric layers and internal electrode layers are alternately laminated, an external electrode joined to a side surface of the laminated body and electrically connected to the internal electrode layer, One end side is connected to a power supply line, arranged on the side surface of the multilayer body in a direction crossing the stacking direction, aligned in the stacking direction, and a power supply electrode composed of a plurality of conductor wires connected to the external electrode in the middle In the multilayer piezoelectric element, the power supply electrode is characterized in that at least a part of the other end side of the conductor wire is connected by a connecting portion.

  In the multilayer piezoelectric element of the present invention, the connecting portion is a conductor in the above configuration.

  Moreover, the multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, the connecting portion is the same conductor as the conductor wire.

  Moreover, the multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, the connecting portion extends in the stacking direction of the multilayer body and connects all the conductor wires.

  Moreover, the multilayer piezoelectric element of the present invention is characterized in that, in the above-described configuration, the connecting portion connects the other ends of the plurality of conductor wires.

  In the multilayer piezoelectric element of the present invention, in the above configuration, the connecting portion is a conductor, and both ends thereof match the outer sides of the conductor wires arranged at both ends of the array of the plurality of conductor wires. It is characterized by that.

  In the multilayer piezoelectric element of the present invention, in the above configuration, the connecting portion is the same conductor as the conductor wire, and both ends of each of the conductor wires arranged at both ends of a plurality of the conductor wires are arranged. It is characterized by being fitted to the outer side.

  Moreover, the multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, the multilayer body has a predetermined fracture layer located between the conductor wires.

  The multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, a plurality of the conductor wires are arranged between the expected fracture layers.

  The multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, the plurality of conductor wires are spaced apart from the side surface of the multilayer body on the other end side from the external electrode. It is.

  The multilayer piezoelectric element of the present invention is characterized in that, in the above configuration, the connecting portion is integral with the conductor wire.

  The multilayer piezoelectric element according to the present invention is characterized in that, in the above configuration, the connecting portion between the connecting portion and the conductor wire has a smooth curved shape from the connecting portion to the conductor wire. .

  An ejection device according to the present invention includes a container having an ejection hole and any one of the multilayer piezoelectric elements according to the present invention, and fluid stored in the container is driven from the ejection hole by driving the multilayer piezoelectric element. It is characterized by being discharged.

  The fuel injection system of the present invention includes a common rail having a high-pressure fuel, an injection device of the present invention 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 the injection device And an injection control system for supplying a drive signal to the vehicle.

  According to the multilayer piezoelectric element of the present invention, one end side is connected to a power supply line, arranged on the side surface of the multilayer body in a direction intersecting with the stacking direction, aligned in the stacking direction, and a plurality of wires connected to the external electrode in the middle Since the power supply electrode composed of a plurality of conductor wires is connected at least to the other end side of the conductor wires by the connecting portion, it can be sufficiently expanded and contracted in accordance with the displacement of the multilayer body when the multilayer piezoelectric element is driven. In addition, since it has a conductor structure that does not hinder the expansion and contraction of the laminate, it is possible to prevent the feeding electrode from peeling off from the external electrode or the feeding electrode from being broken. In addition, even if the laminated body generates heat with driving and heat is transferred from the laminated body to the power feeding electrode through the external electrode, heat and stress can be dispersed through the connecting portion between the conductor wires connected by the connecting portion. The load may not be concentrated on a specific conductor wire. As a result, durability can be improved.

  Further, according to the ejection device of the present invention, the multilayer piezoelectric element of the present invention is provided as the multilayer piezoelectric element for discharging the fluid stored in the container from the ejection hole. It is possible to prevent the power supply electrode connected to the electrode from being peeled off or the power supply electrode from being broken, and to suppress the occurrence of problems by dispersing heat and stress from the laminate in the power supply electrode. Therefore, desired ejection from the fluid ejection holes can be stably performed over a long period of time.

  Furthermore, according to the fuel injection system of the present invention, since the injection device of the present invention is provided as a device for injecting the high-pressure fuel stored in the common rail, the desired injection of high-pressure fuel can be stably performed over a long period of time. Can do.

  Hereinafter, an example of an embodiment of a multilayer piezoelectric element of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of an example of an embodiment of a multilayer piezoelectric element of the present invention.
As shown in FIG. 1, a laminated piezoelectric element 1 of this example includes a laminated body S in which piezoelectric layers 2 and internal electrode layers 3 are alternately laminated, and an internal electrode layer bonded to a side surface of the laminated body S. 3 is electrically connected to the external electrode 4, one end side is connected to the feeder line 5, arranged on the side surface of the multilayer body S in the direction crossing the lamination direction of the multilayer body S, and arranged in the lamination direction. The multilayer piezoelectric element 1 includes a power feeding electrode 7 composed of a plurality of conductor wires 6 connected to an external electrode 4, and the power feeding electrode 7 has a connecting portion 8 at least on the other end side of the conductor wires 6. It is connected.

  As described above, a plurality of conductor wires 6 arranged in the direction crossing the stacking direction of the stack S on the side surface of the stack S, that is, in the direction parallel to the internal electrode layer 3 and arranged in the stacking direction are supplied to one end side. It is a laminate that is connected to the external electrode 4 as the feeding electrode 7 by being connected to the electric wire 5, being connected to the external electrode 4 in the middle, and at least a part of the other end being connected by the connecting portion 8. The feeder wire 5 and the connecting portion 8 that are a plurality of conductor wires 6 that can sufficiently follow the displacement of the body S and are arranged in the stacking direction of the multilayer body S and may suppress the displacement of the multilayer body S are laminated bodies. Since the power supply electrode 7 is not in contact with S, the power supply electrode 7 can sufficiently expand and contract in accordance with the displacement of the multilayer body S, and does not hinder the expansion and contraction of the multilayer body S. Prevents peeling from power supply or breakage of feeding electrode 7 It is possible. In addition, even when the multilayer body S generates heat as the multilayer piezoelectric element 1 is driven and heat is transmitted from the multilayer body S to the conductor wire 6 of the power feeding electrode 7 through the external electrode 4, the conductors connected by the connecting portion 8. Since heat can be dispersed between the wires 6 via the connecting portion 8 and stress can be dispersed, the load can be prevented from being concentrated on the specific conductor wire 6. As a result, the durability of the multilayer piezoelectric element 1 can be improved and the life can be extended.

  The power supply line 5 and the conductor line 6 constituting the power supply electrode 7 are made of metal wires having good conductivity, and these materials are preferably metals or alloys such as silver, nickel, copper, phosphor bronze, iron, and stainless steel. Further, the surfaces of the feeder line 5 and the conductor line 6 may be plated with silver, nickel, gold or the like. One end side of each of the plurality of conductor wires 6 is firmly connected to the power supply line 5 by soldering or welding. Further, the plurality of conductor wires 6 are connected to the external electrodes 4 whose intermediate portions are formed on the side surfaces of the multilayer body S by being fixed with a conductive adhesive or solder or the like.

The plurality of conductor wires 6 constituting the power supply electrode 7 are connected at the other end side of at least some of the conductor wires 6 by a connecting portion 8. The laminated piezoelectric element 1 shown in FIG. 1 is an example in which all of the plurality of conductor wires 6 are connected by the connecting portion 8. For example, of the plurality of conductor wires 6, the active region of the laminate S It is preferable that what is located in a center part is connected. The active region, which is a region in which the piezoelectric material layer 2 is sandwiched between the internal electrode layers 3 of different polarities in the multilayer body S, is a region that expands and contracts when the multilayer piezoelectric element 1 is driven. Therefore, this is a region where the degree of deformation of expansion and contraction is the largest and the degree of heat generation is large. Therefore, when the conductor wire 6 located in the central portion of the active region is connected by the connecting portion 8, the effect of heat dispersion is increased, and the peeling of the external electrode 4 can be suppressed. Further, since the heat generation region exists around the center of the active region in the stacked body S, a half region including the central portion of the active region, preferably the length of the active region 1 from the center of the active region to both end sides. It is preferable that the conductor wire 6 located in the area | region of the range of / 4 is connected with the connection part 8. FIG. Further, when the active region is divided into a plurality of layers in the stacked body S, it is preferable to connect the conductor wires 6 positioned in the respective active regions because the effect of heat dispersion through the connecting portion 8 is increased. .
In this way, one end side of the plurality of conductor wires 6 is connected to the feeder line 5, and the conductor wires 6 are arranged on the side surfaces of the multilayer body S in the direction of crossing in the stacking direction, and are arranged in the stacking direction. Is connected to the external electrode 4 so that the conductor wire 6 does not cross and a spark does not occur like a metal wire knitted in a mesh, and it is sufficiently good according to the displacement of the laminate S. The power supply electrode 7 expands and contracts following the above. Further, since the other end side of at least some of the plurality of conductor wires 6 is connected by the connecting portion 8, heat and stress applied to the conductor wire 6 are dispersed and relaxed through the connecting portion 8. Therefore, the load of heat and stress can be prevented from being concentrated on the specific conductor wire 6, so that the durability of the power supply electrode 7 is excellent.

  Such a connecting portion 8 may be a conductor or not a conductor. As the connecting portion 8 that is not a conductor, for example, a heat-resistant material such as polyimide resin, an elongated rectangular shape or a linear shape is used, and a heat-resistant adhesive having a strong adhesive force such as an epoxy resin is used as a conductor. Connect to line 6. Further, the connecting portion 8 which is a conductor is made of a material having high strength and good conductivity such as phosphor bronze C5191, for example, an elongated rectangular shape or a linear shape, for example, by a method such as resistance welding or soldering. Connect to line 6.

  In the multilayer piezoelectric element 1 of the present invention, the connecting portion 8 of the feeding electrode 7 is preferably a conductor. As a result, even if a part of the plurality of conductor lines 6 is disconnected at the connection part with the feeder line 5 or a part between the feeder line 5 and the external electrode 4 is generated, Since it is possible to energize driving power from the other conductor wire 6 via the connecting portion 8 to the connection portion with the external electrode 4, the multilayer piezoelectric element 1 can be stably operated for a long time.

  Furthermore, the connecting portion 8 is preferably the same conductor as the conductor wire 6. Since the connecting portion 8 is the same conductor as the conductor wire 6, the thermal expansions of both coincide with each other. Therefore, even if the laminated body S is overheated, the connecting portion between the connecting portion 8 and the conductor wire 6 is not easily peeled off, resulting in durability. It will be excellent.

  Moreover, it is preferable that the connection part 8 is extended in the lamination direction of the laminated body S, and has connected all the conductor wires 6. FIG. That is, it is preferable that all the conductor wires 6 are connected by a continuous connecting portion 8 extending in the stacking direction of the stacked body S. As a result, even if the laminated body S generates heat locally, heat can be transferred from the conductor wire 6 corresponding to the heat generation location to any of the other conductor wires 6 via the connecting portion 8. Can be performed almost uniformly on the power supply electrode 7.

  Moreover, it is preferable that the connection part 8 has connected the other end of the several conductor wire 6. FIG. That is, the connecting portion 8 is preferably provided at the other end side of the conductor wire 6. Thereby, generation | occurrence | production of the discharge in the edge part of the other end side of the conductor wire 6 protruded from the connection part 8 and generation | occurrence | production of the short circuit by discharge can be prevented.

  Furthermore, it is preferable that the connection part 8 is a conductor, and both ends are suitable for the outer sides of the conductor lines 6 arranged at both ends of the array of the plurality of conductor lines 6. As a result, it is possible to prevent the end of the connecting portion 8 from coming into contact with surrounding members other than the multilayer piezoelectric element 1 to cause a short circuit. Further, the drive power current is surrounded only by a necessary portion in the power supply electrode 7, for example, by the conductor wire 6 disposed at both ends of the conductor wire 6, the connecting portion 8, and the power supply wire 5, and the external electrode 4. Can be supplied to a portion where all the conductor wires 6 are in contact with each other. In this case, the connecting portion 8 is more preferably the same conductor as the conductor wire 6. Thereby, current can be efficiently supplied from the plurality of conductor wires 6 to the external electrode 4.

  Further, in the multilayer piezoelectric element 1 of the present invention, it is preferable that the multilayer body S has the planned fracture layer 9 located between the conductor wires 6. That is, the laminate S is formed by reducing the strength so that a part of the internal electrode layer 3 is broken between the piezoelectric layers 2 when a large stress is applied in advance. It is preferable to have a fractured layer 9, and this planned fractured layer 9 is located between the conductor wires 6 connected to the external electrode 4. As a result, when a large stress is generated in the multilayer body S as the multilayer piezoelectric element 1 is driven, the planned fracture layer 9 is fractured, thereby generating a crack in the piezoelectric layer 2 due to the stress and the stress. Therefore, it is possible to relieve stress by effectively generating cracks only in the expected fracture layer 9 of the multilayer body S, and the connection of the power supply electrode 7 to the external electrode 4 is maintained and the multilayer piezoelectric element 1 is maintained. Can be made highly durable. Furthermore, by arranging the conductor wire 6 and the planned fracture layer 9 so as to be suitable for relaxation of the stress in the multilayer body S, the multilayer piezoelectric element 1 can be excellent in durability.

  Thus, when the laminated body S has the planned fracture layer 9 positioned between the conductor wires 6, two or more of the conductor wires 6 are arranged between the planned fracture layers 9. It is preferable. Thereby, even if one conductor wire 6 breaks between the planned fracture layers 9, power can be supplied to the external electrode 4 by another conductor wire 6 between the same planned fracture layers 9. A laminated piezoelectric element 1 having excellent properties can be obtained.

  Moreover, it is preferable that the space | interval with the side surface of the laminated body S is wide at the other end side from the external electrode 4 in the multiple conductor wire 6. When the other end side opposite to the one end side connected to the feeder line 5 of the conductor wire 6 is close to the side surface of the multilayer body S, the conductor wire 6 vibrates with the displacement of the multilayer body S and the side surface of the multilayer body S. In order to avoid contact, the other end side of the conductor wire 6 is separated from the side surface of the multilayer body S in order to avoid contact. It is preferable that the other end side of the external electrode 4 be bent away from the laminate S. Thereby, even if the conductor wire 6 vibrates with the displacement of the multilayer body S, it is difficult to contact the side surface of the multilayer body S. Therefore, even if the internal electrode layer 3 is exposed on the side surface of the multilayer body S, the conductor wire 6 and the internal electrode layer 3 can be prevented from being short-circuited.

  In the multilayer piezoelectric element 1 of the present invention, when the connecting portion 8 is the same conductor as the conductor wire 6, the connecting portion 8 is preferably integral with the conductor wire 6. Since the connecting portion 8 is integral with the conductor wire 6, the connecting portion does not come off, so that the connecting portion 8 and the conductor wire 6 are not easily broken, and the laminated type having the feeding electrode 7 having excellent durability. The piezoelectric element 1 is obtained.

Here, FIG. 2 is a side view of a principal part of a connection portion between the conductor line of the power feeding electrode and the connecting portion in another example of the embodiment of the multilayer piezoelectric element of the present invention. As shown in FIG. 2, when the connecting portion 8 is integral with the conductor wire 6, the connecting portion between the connecting portion 8 and the conductor wire 6 has a smooth curved shape from the connecting portion 8 to the conductor wire 6. preferable. As described above, the connecting portion between the connecting portion 8 and the conductor wire 6 has a smooth curved portion 10 from the connecting portion 8 to the conductor wire 6, so that stress is applied to the connecting portion between the connecting portion 8 and the conductor wire 6. However, since the connecting portion is not easily torn and the connecting portion 8 and the conductor wire 6 are not easily broken, the multilayer piezoelectric element 1 having the power supply electrode 7 having higher durability is obtained.
Next, a method for manufacturing the multilayer piezoelectric element 1 of the present invention will be described.

First, a ceramic green sheet to be the piezoelectric layer 2 is produced. Specifically, a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer are mixed to prepare a slurry. And a ceramic green sheet is produced by using tape molding methods, such as a doctor blade method and a calender roll method, for this slurry. The piezoelectric ceramic may be any piezoelectric ceramic, and for example, a perovskite oxide made of PbZrO ₃ —PbTiO ₃ or the like can be used. As the plasticizer, DBP (dibutyl phthalate), DOP (dioctyl phthalate), or the like can be used.

  Next, a conductive paste to be the internal electrode layer 3 is produced. Specifically, a conductive paste is produced by adding and mixing a binder, a plasticizer, and the like to a metal powder such as silver-palladium. This conductive paste is printed on the ceramic green sheet in a predetermined pattern using a screen printing method. Further, a plurality of ceramic green sheets on which the conductive paste is screen-printed are stacked. And the laminated body S provided with the piezoelectric body layer 2 and the internal electrode layer 3 which were laminated | stacked alternately can be formed by baking as mentioned later.

  At this time, for example, in the case of forming a porous metal particle layer including a large number of independent metal particles as the expected fracture layer 9, carbon powder is contained in the conductive paste, and the carbon powder is baked during firing. There is a method of eliminating the ink, pattern printing so as to form a dot pattern when the conductive paste is printed, or performing dry ice blasting after the conductive paste is printed and dried to roughen the printed surface. Moreover, if the porous metal particle layer containing a large number of independent metal particles is mass-produced and formed as the planned fracture layer 9, the conductive paste of the porous metal particle layer to be the planned fracture layer 9 and other By changing the metal component ratio of the internal electrode layer 3 to the conductive paste and utilizing the difference in concentration during firing, the metal is transferred from the planned fracture layer 9 to the adjacent internal electrode layer 3 via the piezoelectric layer 2. It can be made porous by diffusing. This method is preferable in terms of excellent mass productivity. In particular, when a conductive paste mainly composed of silver-palladium is used and the silver concentration of the layer that becomes the expected fracture layer 9 is higher than the silver concentration of the other internal electrode layers 3, silver forms a liquid phase during firing. At the same time, since it can easily move between the piezoelectric particles of the piezoelectric layer 2, the expected fracture layer 9 made of a very uniform porous metal particle layer can be formed.

Thereafter, the external electrode 4 is formed on the outer surface of the multilayer body S of the multilayer piezoelectric element 1 so as to obtain electrical continuity with the internal electrode layer 3 whose end is exposed. The external electrode 4 is obtained by adding a binder to silver powder and glass powder to produce a silver glass conductive paste, printing it on the side surface of the laminate S by screen printing or the like, and performing dry adhesion or baking. be able to.
The plurality of conductor wires 6 constituting the power supply electrode 7 are made of a metal wire having good conductivity as described above, and one end side is connected to the power supply wire 5 by soldering or welding, and the middle is on the external electrode 4 And fixed with solder or conductive adhesive. Then, at least a part of the plurality of conductor wires 6 is connected by the connecting portion 8, or formed integrally with the connecting portion 8 and connected.

  At this time, the external electrode 4 has a length of, for example, 30 mm and a width of 2 mm, whereas, for example, 60 conductor wires 6 having a thickness of 0.2 mmφ and a length of 10 mm, for example, a spacing of 0.1 is 0.1 mm. In the middle of the conductor wires 6, for example, the central portion is connected to the external electrode 4.

  Next, the laminate S on which the external electrode 4 is formed is immersed in a resin solution containing an exterior resin made of silicone rubber. Then, the silicone resin solution is vacuum degassed to bring the silicone resin into close contact with the concavo-convex portions on the outer peripheral side surface of the laminate S, and then the laminate S is pulled up from the silicone resin solution. Thereby, a silicone resin is coated on the side surface of the laminate S on which the external electrode 4 is formed. Then, the plurality of conductor wires 6 of the power supply electrode 7 are connected to the external electrode 4 as a power supply unit with solder or conductive adhesive.

  Thereafter, a DC voltage of 0.1 to 3 kV / mm is applied to the piezoelectric layer 2 from the pair of external electrodes 4 through the internal electrode layer 3 via the feeding electrode 7 connected to the external electrode 4, and the piezoelectric layer 2 of the multilayer S Is completed, the laminated piezoelectric element 1 of this example is completed. Each power supply electrode 7 is connected to a power supply that supplies external driving power, and a voltage is applied to the piezoelectric layer 2 by the internal electrode layer 3 via the power supply electrode 7 and the external electrode 4. The layer 2 can be greatly displaced by the inverse piezoelectric effect. This makes it possible to function as an automobile fuel injection valve that injects and supplies fuel to the engine, for example.

  Next, an example of an embodiment of a fluid ejection device as the ejection device of the present invention will be described. FIG. 3 is a schematic cross-sectional view showing an example of an embodiment of the injection device of the present invention.

  As shown in FIG. 3, in the injection device 19 of this example, the multilayer piezoelectric element 1 of the present invention represented by the example of the above embodiment is housed in a container 23 having an injection hole 21 at one end. Yes.

  A needle valve 25 that can open and close the injection hole 21 is disposed in the container 23. A fluid passage 27 is disposed in the injection hole 21 so that it can communicate with the movement of the needle valve 25. The fluid passage 27 is connected to an external fluid supply source, and the fluid passage 27 is always supplied with a high-pressure fluid such as a liquid. Therefore, when the needle valve 25 opens the injection hole 21 by driving the multilayer piezoelectric element 1, the fluid supplied to the fluid passage 27 is transferred to the outside of the injection hole 21 or a container adjacent to the injection hole 21, such as an internal combustion engine. The fuel chamber (not shown) is configured to be discharged from the injection hole 21 and injected.

  The upper end portion of the needle valve 25 has a large inner diameter, and a cylinder 31 formed in the storage device 23 and a slidable piston 31 are disposed. In the storage device 23, the element 1 described above is stored.

  The upper end portion of the needle valve 25 has a large inner diameter, and a cylinder 29 formed in the container 23 and a slidable piston 31 are disposed in that portion. In the container 23, the multilayer piezoelectric element 1 of the present invention is accommodated.

  In such an injection device 19, when the multilayer piezoelectric element 1 that functions as a piezoelectric actuator is extended by applying a voltage, the piston 31 is pressed, the needle valve 25 closes the injection hole 21, and the supply of fluid is stopped. The When the application of voltage is stopped, the multilayer piezoelectric element 1 contracts, and the disc spring 33 pushes back the piston 31 to open the fluid passage 27, so that the injection hole 21 communicates with the fluid passage 27 and the injection hole. The fluid is ejected from 21.

  The fluid ejection operation is performed by applying a voltage to the multilayer piezoelectric element 1 to open the fluid flow path 27 to discharge the fluid from the ejection holes 21 and stopping the application of the voltage. May be closed to stop the discharge of fluid.

  The injection device 19 of the present invention includes a container 23 having an injection hole 21 and the multilayer piezoelectric element 1 of the present invention, and the fluid filled in the container 23 is ejected by driving the multilayer piezoelectric element 1. 21 may be configured to discharge from 21. That is, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 23, and the pressure for supplying and stopping the fluid to the injection hole 21 is applied to the inside of the container 23 by driving the multilayer piezoelectric element 1. It suffices to be configured. In addition, the fluid including the liquid is not only supplied to the injection hole 21 through the fluid passage 27, but also provided in the container 23 with a portion for temporarily storing the fluid in an appropriate place in the container 23. The filled fluid may be discharged from the ejection hole 21.

  In the present invention, the fluid includes various liquid materials (such as conductive paste) and gas, as well as liquid such as fuel or ink. By using the ejection device 19 of the present invention for these fluids, the fluid flow rate and ejection timing can be stably controlled over a long period of time.

  When the injection device 19 of the present invention that employs the multilayer piezoelectric element 1 of the present invention is used in an internal combustion engine, fuel is injected more accurately into a fuel chamber of an internal combustion engine such as an engine over a longer period of time than a conventional injection device. Can be made.

  Next, the example of embodiment of the fuel-injection system of this invention is demonstrated. FIG. 4 is a schematic view showing an example of an embodiment of the fuel injection system of the present invention.

  As shown in FIG. 4, the fuel injection system 35 of this example includes a common rail 37 that stores high-pressure fuel, a plurality of injection devices 19 of the present invention that inject high-pressure fuel stored in the common rail 37, and a high-pressure to the common rail 37. A pressure pump 39 for supplying fuel and an injection control unit 41 for supplying a drive signal to the injection device 19 are provided.

  The injection control unit 41 controls the amount and timing of high-pressure fuel injection based on external information or an external signal. For example, in the case of the injection control unit 35 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 engine fuel injection system 35, fluid fuel is fed into the common rail 37 at a high pressure of about 1000 to 2000 atmospheres, preferably about 1500 to 1700 atmospheres.

  In the common rail 37, the high-pressure fuel sent from the pressure pump 39 is stored and appropriately sent to the injection device 19 in accordance with the driving of the multilayer piezoelectric element 1. As described above, the injection device 19 discharges and injects high-pressure fuel, which is a predetermined amount of fluid, from the injection hole 21 to the outside or a container adjacent to the injection hole 21 from the injection hole 21 of the injection device 19 at high pressure. For example, when the target for injecting and supplying high-pressure fuel is an engine, high-pressure fuel that is a fluid is injected into the combustion chamber of the engine in a mist form from the injection hole 21.

  Note that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the scope of the present invention. In addition, the present invention relates to a multilayer piezoelectric element, an injection device, and a fuel injection system, but is not limited to the above-described embodiment, for example, a printing device of an ink jet printer, a pressure sensor, or the like Even if it is what is used for, if it is a laminated type piezoelectric element using a piezoelectric characteristic, it can implement by the same structure.

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

First, a slurry in which an organic binder and a plasticizer are mixed with a calcined powder of piezoelectric ceramic, which is a raw material powder mainly composed of lead zirconate titanate (PbZrO ₃ -PbTiO ₃ ) powder having an average particle diameter of 0.4 μm, is prepared. did. Using this slurry, a ceramic green sheet to be the piezoelectric layer 3 having a thickness of 150 μm was produced by the doctor blade method.

  Next, conductive paste A serving as an internal electrode obtained by adding a binder to a raw material powder containing silver-palladium alloy powder having a metal composition of Ag 95 mass% -Pd 5 mass%, and silver powder having a metal composition of Ag 100 mass% The electroconductive paste B which added the binder to the raw material powder containing this was produced.

  Then, the conductive paste A was printed on one side of the ceramic green sheet with a pattern of the internal electrode layer 3 so as to have a thickness of 30 μm by screen printing. Next, 300 ceramic green sheets on which these conductive pastes A were printed were laminated to produce a green laminate. Note that only 20 ceramic green sheets on which no conductive paste was printed were laminated at both ends in the lamination direction of the green laminate.

  Next, the internal electrode layer 3 located at the 50th and 250th positions in the stacking direction was printed using the conductive paste B in order to provide a low-rigidity metal layer made of isolated metal particles as the expected fracture layer 9. Thereby, in order that the silver of the electrode component of the layer using the conductive paste B may diffuse into the adjacent metal layer having a low silver concentration during firing, the layer using the conductive paste B is made of isolated metal particles. The planned fracture layer 9 that is a low-rigidity metal layer is formed.

  And after performing the binder removal process to each raw laminated body at predetermined | prescribed temperature, the laminated body S was obtained by baking at 980-1100 degreeC.

  After the obtained laminated body S is ground into a predetermined shape using a surface grinder, a silver-glass conductive paste to be the external electrode 4 is printed on the side surface of the laminated body S forming the external electrode 4, 700 Baking was performed at 0 ° C. At this time, the softening point of the glass contained in the silver glass conductive paste was 730 ° C.

  Next, a plurality of metal wires having a width of 0.2 mm and a thickness of 0.05 mm, which are conductor wires 6, are arranged on the external electrode 4 in a direction perpendicular to the lamination direction and arranged in the lamination direction, and Ag is a conductive component. And fixed with a conductive adhesive. As the conductor wire 6, a metal wire made of phosphor bronze C5191 was used as a base material, and the surface thereof was plated with silver. In addition, the feeder line 5 was fixed to one end side of the conductor line 6 with solder. The feeder line 5 is made of the same material as that of the conductor wire 6 and is plated with silver on the surface of a metal wire having a shape protruding at one end from the outer side of the conductor wire 6 in order to secure a connecting portion when taking out electricity. The one that has been applied. The other end side of the conductor wire 6 from the external electrode 4 is bent so that the gap with the side surface of the multilayer body S is wide so as not to contact the internal electrode layer 3 exposed on the side surface of the multilayer body S. Oita.

The connecting portion 8 is made of phosphor bronze C5191 having a width of 0.2 mm and a thickness of 0.05 mm as a base material, and the surface thereof is plated with silver, and is welded to the conductor wire 6. Connected.
Thereafter, a lead wire from the power source of the driving power is connected to the power supply line 5 of the power supply electrode 7, and a DC electric field of 3 kV / mm is applied to the positive and negative power supply lines 5 through the lead wire for 15 minutes, so that the piezoelectric body Layer 3 was polarized. In this way, a piezoelectric actuator using the multilayer piezoelectric element 1 of the present invention was produced.

When a DC voltage of 160 V was applied as driving power to the obtained piezoelectric actuator, a displacement of 40 μm was obtained in the stacking direction of the stack S. This was a displacement amount equal to or greater than that in the case of using a mesh formed by braiding metal wires instead of the conductor wires 6. Thereafter, a test was carried out by applying an AC voltage of 0 to +160 V to the piezoelectric actuator at room temperature via the feeding electrode 7 at a frequency of 150 kHz and continuously driving up to 1 × 10 ⁸ times. Although it entered and was broken, the feeding electrode 7 and the connecting portion between the feeding electrode 7 and the external electrode 4 did not break and continued to drive normally.

  Thus, it was confirmed that the multilayer piezoelectric element 1 of the present invention was a multilayer piezoelectric element 1 having excellent durability in which the connection of the power supply electrode 7 to the external electrode was stable for a long time.

It is a perspective view which shows schematic structure of an example of embodiment of the laminated piezoelectric element of this invention. It is a principal part side view which shows a part of connection part of the conductor wire of a feed electrode and a connection part in the other example of embodiment of the lamination type piezoelectric element of this invention. It is a schematic sectional drawing which shows an example of embodiment of the injection apparatus of this invention. It is the schematic which shows an example of embodiment of the fuel-injection system of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element 2 ... Piezoelectric layer 3 ... Internal electrode layer 4 ... External electrode 5 ... Feed line 6 ... Conductor line 7 ... Feed electrode 8 ... Connecting part 9 ... scheduled fracture layer
19 ... Injection device
21 ... Injection hole
23 ・ ・ ・ 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 (14)

  A laminated body in which piezoelectric layers and internal electrode layers are alternately laminated; an external electrode joined to a side surface of the laminated body and electrically connected to the internal electrode layer; and one end side is connected to a power supply line; A laminated piezoelectric element including a feeding electrode composed of a plurality of conductor wires arranged on the side surface of the laminated body in a direction intersecting in the laminating direction and arranged in the laminating direction, and halfway connected to the external electrode, The power supply electrode is a multilayer piezoelectric element characterized in that at least a part of the other end side of the conductor wire is connected by a connecting portion.   The multilayer piezoelectric element according to claim 1, wherein the connecting portion is a conductor.   The multilayer piezoelectric element according to claim 2, wherein the connecting portion is the same conductor as the conductor wire.   2. The multilayer piezoelectric element according to claim 1, wherein the connecting portion extends in the stacking direction of the multilayer body and connects all the conductor wires.   The multilayer piezoelectric element according to claim 1, wherein the connecting portion connects the other ends of the plurality of conductor wires.   6. The connecting portion according to claim 4, wherein the connecting portion is a conductor, and both ends of the connecting portion are aligned with outer sides of the conductor wires arranged at both ends of the plurality of conductor wires. The laminated piezoelectric element described.   5. The connecting portion is the same conductor as the conductor wire, and both ends thereof are respectively aligned with outer sides of the conductor wires arranged at both ends of the plurality of conductor wires. Alternatively, the multilayer piezoelectric element according to claim 5.   The multilayer piezoelectric element according to claim 1, wherein the multilayer body has a predetermined fracture layer located between the conductor wires.   The multilayer piezoelectric element according to claim 8, wherein a plurality of the conductor wires are disposed between the expected fracture layers.   2. The multilayer piezoelectric element according to claim 1, wherein a plurality of the conductor wires are spaced apart from a side surface of the multilayer body on the other end side from the external electrode.   The multilayer piezoelectric element according to claim 3 or 7, wherein the connecting portion is integral with the conductor wire.   The multilayer piezoelectric element according to claim 11, wherein a connecting portion between the connecting portion and the conductor wire has a smooth curved shape from the connecting portion to the conductor wire.   A container having an injection hole and the multilayer piezoelectric element according to any one of claims 1 to 12, wherein fluid stored in the container is discharged from the injection hole by driving the multilayer piezoelectric element. An injection device.   14. A common rail that stores high-pressure fuel, an injection device according to claim 13 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.

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