JP5342846B2 - Multilayer piezoelectric element, injection device including the same, and fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element capable of obtaining a stable displacement amount even in drive of a long period of time under the condition of a high voltage and a high pressure. <P>SOLUTION: The laminated piezoelectric element 1 includes an external electrode 11 electrically connected to an internal electrode layer 5 on the side face of a laminate 7 in which a piezoelectric layer 3 and the internal electrode layer 5 are alternatively laminated, and a groove 12 whose bottom does not reach the laminate 7 is formed on the external electrode 11. Since the groove 12 whose bottom does not reach the laminate 7 is formed on the external electrode 11, stress is mitigated, the peeling of the external electrode 11 and cracks in the laminate 7 are suppressed, and the laminated piezoelectric element 1 having excellent durability is provided. <P>COPYRIGHT: (C)2010,JPO&amp;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, multilayer piezoelectric elements have been required to be able 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 the multilayer piezoelectric element be used under severe conditions in which a higher voltage corresponding to a larger displacement amount is applied and continuous driving is performed for a long time.

When driving continuously for a long time under high voltage and high pressure conditions, as the stacked piezoelectric element is driven, the external electrode joined to the side surface of the stacked body composed of the internal electrode layer and the piezoelectric layer is greatly increased. As a result, stress is applied, and the external electrode may be peeled off from the side surface of the laminated body and broken. Therefore, for the purpose of relaxing the stress caused by the multilayer body so that the external electrode of the multilayer piezoelectric element does not break, for example, a slit-shaped stress relaxation portion is provided in the piezoelectric layer as disclosed in Patent Document 1. A multilayer piezoelectric element in which a porous layer as a target fracture layer is previously provided inside a piezoelectric layer, as disclosed in Japanese Patent Application Laid-Open No. 2004-133260, has been proposed. Furthermore, an external electrode having a structure in which a plurality of electrodes are combined has been proposed, for example, as disclosed in Patent Document 3, so that the external electrode can be driven even when it is broken by stress.
JP 2005-223013 A Special Table 2006-518934 JP 2006-128466 Gazette

  However, if it is attempted to relieve only the stress applied to the external electrode by the piezoelectric layer during driving of the multilayer piezoelectric element in order to prevent the external electrode from being broken, the piezoelectric body will be exposed when stress is applied to the multilayer piezoelectric element from the outside. Even if the layer is deformed by stress, the part restricted by the external electrode cannot be deformed, and the stress is concentrated on the piezoelectric layer at the boundary between the part without the external electrode and the part with the external electrode. The problem arises that the body cracks. In addition, during the driving of the multilayer piezoelectric element, the thermal expansion of the external electrode differs from the thermal expansion of the multilayer body due to self-heating due to the driving, so the boundary between the part without the external electrode and the part with the external electrode is also present. There is a problem that the stress concentrates on the external electrode, and the external electrode is peeled off from the laminated body, or the external electrode is cracked and the drive is lowered without supplying voltage to the internal electrode layer.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a multilayer piezoelectric element that can obtain a stable displacement even when driven for a long time under high voltage and high pressure conditions.

The multilayer piezoelectric element of the present invention is a multilayer piezoelectric element having an external electrode electrically connected to the internal electrode layer on the side surface of the multilayer body in which piezoelectric layers and internal electrode layers are alternately stacked. In the external electrode, a plurality of grooves whose bottoms do not reach the stacked body are formed in the stacking direction of the stacked body, and an interval between adjacent grooves is an end in the stacking direction of the stacked body It is characterized by becoming larger toward the side .

  The multilayer piezoelectric element according to the present invention is characterized in that, in the above configuration, the groove is formed in a layer on a surface side of a deepest layer located on the multilayer body side of the external electrode. is there.

  In the multilayer piezoelectric element of the present invention, the groove has one end reaching the edge of the external electrode in each of the above configurations.

  The multilayer piezoelectric element of the present invention is characterized in that, in each of the above-described configurations, the groove has a width of an opening on the surface of the external electrode larger than a width of a bottom surface.

  In the multilayer piezoelectric element of the present invention, the groove has an opening whose width is increased on the edge side of the external electrode.

  In the multilayer piezoelectric element of the present invention, the groove is formed from the edge of the external electrode to the edge facing the external electrode.

  In the multilayer piezoelectric element of the present invention, the groove is formed in parallel with the internal electrode layer in each of the above configurations.

  In the multilayer piezoelectric element of the present invention, in each of the above structures, the multilayer body includes a planned fracture layer that relaxes stress by breaking preferentially over the internal electrode layer during driving, and the groove Is formed in the vicinity of the expected fracture layer.

  In the multilayer piezoelectric element of the present invention, in each of the above-described configurations, a slit is further formed in the thickness direction of the external electrode so that the external electrode extends along a direction intersecting the stacking direction of the multilayer body. It is characterized by this.

  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 that stores high-pressure fuel, the 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 And an injection control unit for supplying a drive signal to the apparatus.

  According to the multilayer piezoelectric element of the present invention, since the groove whose bottom does not reach the multilayer body is formed in the external electrode, both ends in the direction perpendicular to the stacking direction of the multilayer body of the external electrode, that is, Since the groove formed in the external electrode can absorb the stress generated at the boundary between the part without the external electrode and the part with the external electrode on the side surface of the multilayer body, the external electrode can be peeled off from the multilayer body It is possible to suppress the occurrence of cracks. In particular, even when stress is suddenly applied to the laminated body, cracks are generated in the external electrode starting from the groove to relieve the stress, thereby suppressing the occurrence of cracks in the laminated body and external electrodes from the laminated body. It is possible to suppress the occurrence of peeling.

  Furthermore, since the surface area of the external electrode is increased by the formation of the groove, the self-heating generated in the multilayer body during driving of the multilayer piezoelectric element is effectively prevented from the surface of the external electrode through the external electrode from the multilayer body. Can be dissipated. As a result, even when the driving is performed for a long time under a high voltage and high pressure condition, it is possible to suppress the peeling of the external electrode and the cracking of the laminated body, so that the amount of displacement can be stabilized.

  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. Can be prevented from peeling off or cracking in the laminated body, and problems due to self-heating of the laminated body can be suppressed, so that desired discharge from the fluid injection holes can be performed over a long period of time. It can be performed stably.

  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 an example of an embodiment of a laminated piezoelectric element of the present invention. As shown in FIG. 1, the multilayer piezoelectric element 1 of this example is electrically connected to the internal electrode layer 5 on the side surface of the multilayer structure 7 in which the piezoelectric layers 3 and the internal electrode layers 5 are alternately stacked. 1 is a multilayer piezoelectric element 1 having an external electrode 11 connected to a groove in which the bottom does not reach the multilayer body 7 on the surface side of the external electrode 11 (the bottom is the multilayer body over the thickness direction of the external electrode 11). A slit 12) that does not reach the side surface 7 is formed.

  Thus, by forming the groove 12 whose bottom does not reach the laminate 7 in the external electrode 11, a region that is locally deformed in the external electrode 11 is formed around the groove 12. The stress applied to 11 can be absorbed. In particular, even when stress is suddenly applied to the laminate 7, cracks are generated in the external electrodes 11 starting from the grooves 12 to relieve the stress, thereby suppressing the occurrence of cracks in the laminate 7, and the laminate The occurrence of peeling of the external electrode 11 from 7 can be suppressed.

  Further, since the surface area of the external electrode 11 is increased by the formation of the groove 12 due to the formation of the groove 12 in the external electrode 11, the self-heating generated in the multilayer body 7 during the driving of the multilayer piezoelectric element 1 is prevented. The laminate 7 can be effectively diffused from the surface of the external electrode 11 through the external electrode 11. As a result, even when the driving is performed for a long time under a high voltage and high pressure condition, it is possible to suppress the peeling of the external electrode 11 and the cracking of the laminated body 7, and thus the amount of displacement can be stabilized.

  Such a groove 12 can relieve stress effectively by setting the groove 12 so that the external electrode 11 is easily deformed according to the expansion and contraction of the multilayer body 7 when the multilayer piezoelectric element 1 is driven. Providing grooves 12 in a direction perpendicular to the longitudinal direction of the external electrode 11 that is long in the laminating direction of the body 7 (a direction perpendicular to the laminating direction and along the piezoelectric layer 3 and the internal electrode layer 5) Is preferred. If the external electrode 11 is a rectangular shape that is long in the vertical direction of the laminate 7, it is preferable to provide the groove 12 in a direction perpendicular to the longitudinal direction of the external electrode 11 as shown in FIG. 1. Further, if the external electrode 11 is square, it is preferable to provide the groove 12 in a direction orthogonal to the side of the stacked body 7 in the stacking direction. Further, for the S-shaped or crank-shaped external electrode 11, the groove 12 is provided in a direction orthogonal to the longitudinal direction along the stacking direction of the multilayer body 7 when the entire external electrode 11 is viewed. Is preferred.

  The groove 12 whose bottom does not reach the multilayer body 7 is preferably formed along a direction orthogonal to the stacking direction of the multilayer body 7, that is, parallel to the internal electrode layer 5. This is because the width of the groove 12 provided in the external electrode 11 widens or narrows in the direction in which the multilayer piezoelectric element 1 is driven and the multilayer body 7 expands and contracts. This is because the external electrode 11 can be expanded and contracted together with the multilayer body 7, and a stress relaxation effect can be effectively obtained.

  Furthermore, as shown in FIGS. 2 (a) and 2 (b), respectively, in a side view and a cross-sectional view taken along the line AA of another embodiment of the multilayer piezoelectric element of the present invention, the external electrode 11 has a plurality of layers. It is preferable that the groove 12 is formed in a layer above the deepest layer of the external electrode 11. In this example, an external electrode 11 is shown in which a layer (deepest layer) 11A located on the laminate 7 side and a layer 11B located on the surface side are laminated. By providing the external electrode 11 having a laminated structure in which a plurality of layers are laminated in this manner, cracks are caused between the layers of the external electrode 11 with the groove 12 as a starting point, even when stress is suddenly applied to the laminated body 7. Since the stress can be relieved by being generated, it is possible to achieve both prevention of peeling of the external electrode 11 from the laminate 7 and prevention of cracks in the laminate 7. Further, in the case of the external electrode 11 having a laminated structure, the groove 12 can be formed relatively easily by forming and laminating various patterns of the groove 12 for the layer in which the groove 12 is formed, It is also preferable that the width of the groove 12 can be changed relatively easily.

  At this time, the component of the deepest layer (in this example, the layer 11A) located on the outermost electrode 7 side of the external electrode 11 is made of glass such as silicon oxide rather than the component of the other layer of the external electrode 11 (in this example, 11B). By containing a large amount of components, the adhesion strength between the external electrode 11 (layer 11A) and the laminate 7 is increased, so that the external electrode 11 is difficult to peel off from the laminate 7 and becomes more preferable.

  Furthermore, as shown in FIGS. 4 (a) and 4 (b), respectively, a side view and a cross-sectional view taken along line AA of the embodiment of the multilayer piezoelectric element of the present invention, an external electrode having a multilayer structure. 11 is composed of three or more external electrodes 11 such as the deepest layer 11A located closest to the laminate 7, the layer 11B located on the surface side, and the layer 11C located therebetween. In the case where the groove 12 is formed so that the bottom is located on the surface side of the deepest layer 11A, if the low rigidity metal layer made of isolated metal particles is provided on the layer 11C in contact with the deepest layer 11A, the laminate 7 is particularly Even when abrupt stress is applied, cracks can be generated in the layer 11C of the external electrode 11 starting from the groove 12 to relieve the stress, so that the peeling of the external electrode 11 from the laminate 7 can be prevented. It becomes easy to achieve both suppression of cracks in the laminate 7.

  2 (a) and 2 (b), and FIGS. 3 (a) and 3 (b), respectively, a side view and a cross-sectional view taken along line AA of another embodiment of the laminated piezoelectric element of the present invention. As shown in the drawing, it is preferable that one end of the groove 12 formed on the external electrode 11 whose bottom does not reach the multilayer body 7 reaches the edge of the external electrode 11. This is because when the multilayer piezoelectric element 1 is driven and the multilayer body 7 expands and contracts, the groove 12 whose bottom does not reach the multilayer body 7 is more easily deformed at the edge of the external electrode 11 where stress tends to concentrate. This is because the stress of the external electrode 11 can be effectively relieved. Further, regarding the stress caused by the difference in thermal expansion of the external electrode 11 with respect to the thermal expansion of the laminate 7 due to self-heating due to driving, the stress tends to concentrate on the edge of the external electrode 11. By increasing the outer peripheral distance (length along the outer periphery) of the edge of 11 by the groove 12, it can be effectively relaxed.

  FIG. 2 shows an example where so-called staggered grooves 12 each having one end reaching the opposite edge of the external electrode 11 are shown, and FIG. In the example, the grooves 12 each having one end reaching the edge are respectively arranged at positions corresponding to the opposite edges. When the groove 12 is arranged as in the example shown in FIG. 2, the surface layer of the external electrode 11 has a so-called S-shape, and it is deformed as if it were a spring-like movement in response to the expansion and contraction of the laminate 7. Therefore, the stress in the external electrode 11 can be relaxed. When the grooves 12 are arranged as in the example shown in FIG. 3, the external electrodes 11 having the grooves 12 formed symmetrically with respect to the driving direction of the multilayer piezoelectric element 1, that is, the direction of expansion and contraction of the multilayer body 7. Therefore, the multilayer body 7 and the external electrode 11 can be deformed with their axes aligned with respect to the expansion and contraction of the multilayer body 7, and the drive shaft of the multilayer piezoelectric element 1 is prevented from being shaken. Can do.

  Further, as in the example shown in FIG. 3, when the external electrodes 11 having different polarities are arranged opposite to each other on the opposite side surfaces of the multilayer body 7, the bottom of each external electrode 11 is the multilayer body. Preferably, the grooves 12 that do not reach 7 are also formed at opposite positions. As a result, when stress is applied to the multilayer body 7, the external electrodes 11 having different polarities are formed on the opposing side surfaces of the multilayer body 7 and face each other, so that the stress is evenly distributed to the respective external electrodes 11. Further, by disposing the grooves 12 at positions facing each other, the stress relaxation portions can be arranged symmetrically with respect to the laminated body 7, so that the stress applied to the laminated body 7 can be evenly distributed. An excellent stress relaxation effect can be obtained by being able to disperse and avoiding stress concentration in one place.

  When the external electrodes 11 having different polarities are arranged opposite to the opposite side surfaces of the stacked body 7, the groove 12 whose bottom does not reach the stacked body 7 extends in the stacking direction of the stacked body 7. Since the center of the drive shaft of the multilayer piezoelectric element 1 coincides with the center axis of the multilayer body 7, the drive shaft is not shaken and has high durability. The multilayer piezoelectric element 1 can be obtained. Further, the stress applied to the laminate 7 is evenly distributed by arranging the grooves 12 at positions facing each other across the laminate 7 and at rotationally symmetric positions with respect to the central axis extending in the lamination direction of the laminate 7. As a result, not only can the stress be relieved, but also the advantage that the drive shaft does not shake is provided, and self-heating can be suppressed when the multilayer piezoelectric element 1 is driven. The piezoelectric element 1 can be obtained.

  Further, as shown in FIGS. 4A and 4B, the groove 12 whose bottom does not reach the multilayer body 7 has a width at the bottom surface, that is, a width of the bottom on the joint surface side of the external electrode 11 with the multilayer body 7. It is preferable that the width of the opening on the surface of the external electrode 11 is larger than that. In the example shown in FIG. 4, the width of the groove 12 in the layer 11 </ b> B located on the surface side is larger than the width of the groove 12 in the layer 11 </ b> C of the external electrode 11. Thus, by making the groove 12 have a width of the opening on the surface of the external electrode 11 larger than the width of the bottom surface, the heat generated by the stress concentrated on the joint interface between the external electrode 11 and the laminate 7 is reduced. It can be efficiently propagated to the surface of the external electrode 11 through the opening 12 toward the opening having a large width and dissipated, and the stress can be relieved. Further, by efficiently dissipating heat toward the opening having a large width through the groove 12, the stress due to thermal expansion can be suppressed, so that the stress relaxation can be excellent.

  When the width of the opening is made larger than the width of the bottom surface of the groove 12 in this way, the width of the bottom surface is set to 0.05 to 0.5 mm, for example, and the width of the opening is set to 0.1 to 1.5, which is two to three times. What is necessary is just to set to mm.

  Further, as shown in FIGS. 5A and 5B, respectively, a side view and a cross-sectional view taken along line AA of the embodiment of the multilayer piezoelectric element of the present invention, the bottom is the multilayer body 7. The width of the opening of the groove 12 that has not reached is preferably increased on the edge side of the external electrode 11. According to this, stress concentrated on the edge of the external electrode 11 can be effectively relieved by the groove 12 formed with a large opening width toward the edge. Generation | occurrence | production can be suppressed effectively and durability of the lamination type piezoelectric element 1 can be made high. More preferably, the edge of the opening of the groove 12 whose bottom does not reach the laminate 7 is chamfered like a C surface or an R surface, thereby avoiding stress concentration at the opening edge of the groove 12. Can do.

When the width of the opening of the groove 12 is increased toward the edge of the external electrode 11 in this way, the width of the opening of the groove 12 is set at the edge of the external electrode 11 in the opening of the piezoelectric layer 3. The stress relaxation effect is enhanced by having 10 layers or more. This is because the stress concentrated in the groove 12 can be relaxed by the piezoelectric layer 3 in the opening of the groove 12 being deformed according to the pressure. In particular, since there are 10 or more piezoelectric layers 3, the stress between the piezoelectric layers 3 can be dispersed, so that stress can be prevented from concentrating on one layer of the piezoelectric layers 3, and the stress can be satisfactorily improved. This is because it can be relaxed.
In addition, a plurality of grooves 12 whose bottom portions do not reach the stacked body 7 are formed, and an interval between adjacent grooves 12 is on the end side in the stacking direction of the stacked body 7 (upper end side and lower end side). It is preferable that it becomes large toward. This is because the deformation mode at the time of driving the multilayer piezoelectric element 1 expands and contracts in the stacking direction on the end side in the stacking direction of the stacked body 7, but is orthogonal to the stacking direction in the central portion of the stacked body 7. Therefore, stress concentrated on the edge of the external electrode 11 can be relieved by disposing a large number of grooves 12 at the central portion in the stacking direction, so that the stack 7 is driven by driving the stack 7. The deformation can be increased and the external electrode 11 can be prevented from peeling off from the edge, and the durability of the multilayer piezoelectric element 1 can be enhanced.

When the plurality of grooves 12 are thus formed and the distance between adjacent grooves 12 is increased toward the end in the stacking direction of the stacked body 7, the distance between the grooves 12 is, for example, the ratio between the interval 1: 2: 4: 8 as 2 ⁿ as that, or 3 ⁿ by increasing exponentially as can be densely arranged with respect to both end portions of the grooves 12 of the central portion , The stress can be relaxed gradually.

  6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b) are a side view and a cross-sectional view taken along line AA of still another example of the embodiment of the multilayer piezoelectric element of the present invention, respectively. As shown, the groove 12 whose bottom does not reach the laminated body 7 is preferably formed from the edge of the external electrode 11 to the edge facing it. In the example shown in FIG. 6, as in the example shown in FIG. 3, grooves 12 having one end reaching the edge of the external electrode 11 are formed in the upper and lower portions of the external electrode 11 at the corresponding positions of the opposing edges, respectively. A groove 12 formed from one edge to the other opposite edge is disposed in the center of the electrode 11. In the example shown in FIG. 7, grooves 12 formed from one edge of the external electrode 11 to the other edge are arranged above and below the external electrode 11, respectively. According to this, as the stacked piezoelectric element 1 expands and contracts, the opening of the groove 12 formed from one edge to the other edge widens or narrows, thereby concentrating on the edge of the external electrode 11. Since the stress can be effectively relieved, peeling from the edge of the external electrode 11 and cracking can be prevented, and the durability of the multilayer piezoelectric element 1 can be increased.

  When the groove 12 is arranged as in the example shown in FIG. 6, the groove 12 formed from one edge of the external electrode 11 to the other edge is formed in the central portion of the laminate 7 where the stress is most concentrated. Thus, when an extremely large stress is applied to the external electrode 11 from any direction, the stress can be relaxed by causing a crack in the external electrode 11 starting from the groove 12. Further, when the groove 12 is arranged as in the example shown in FIG. 7, when the laminated piezoelectric element 1 is housed in a container and used as in an injection device or the like, the container is placed above and below the laminated body 7. By relieving the applied stress by the groove 12, the durability of the multilayer piezoelectric element 1 can be improved. In the case of this example as well, when extremely large stress is applied to the external electrode 11 by forming the groove 12 formed from one edge of the external electrode 11 to the other edge on the both ends of the laminate 7 respectively. In addition, starting from the groove 12, the external electrode 11 can be cracked to relieve the stress.

  In any of the above examples, it is preferable that the groove 12 formed in the external electrode 11 and whose bottom does not reach the multilayer body 7 is formed in parallel with the internal electrode layer 5. In this case, since the groove 12 can be formed in a direction orthogonal to the electric field applied to the multilayer body 7, the groove 12 is formed in a direction orthogonal to the direction in which the multilayer piezoelectric element 1 is driven and deformed. Since the external electrode 11 is easily expanded and contracted according to the deformation of the multilayer body 7, the stress applied to the external electrode 11 can be relaxed. Further, in order to prevent the internal electrode layer 5 from energizing the external electrode 11 and short-circuiting the internal electrode layers 5 having different polarities, the internal electrode layer 5 is not formed over the entire surface of the piezoelectric layer 3. In the case of a partial electrode structure in which an insulating region is provided between the external electrode 11 so as to maintain insulation with one external electrode 11 of the external electrodes 11 of different polarities, Since the active region sandwiched between the internal electrode layers 5 of different poles and the other inactive region are formed in the piezoelectric layer 3, the groove 12 corresponds to the inactive region in a direction parallel to the internal electrode layer 5. Since the stress applied to the groove 12 can be relieved by using the effect that the piezoelectric layer 3 expands and contracts due to pressure, the external electrode 11 having higher durability can be obtained. Making the laminated piezoelectric element 1 highly durable It can be.

  Further, the groove 12 whose bottom does not reach the laminated body 7 is preferably located between the adjacent internal electrode layers 5. In this case, the stress applied to the groove 12 induces deformation of the piezoelectric layer 3 in which the groove 12 is located, and the electromotive force generated by the piezoelectric effect of the piezoelectric layer 3 is transmitted to the adjacent internal electrode layer 5. As a result, an effect of correcting the voltage applied to the multilayer piezoelectric element 1 is generated and the driving voltage is lowered, so that a stress relaxation effect is generated in the multilayer piezoelectric element 1. Further, even if a crack or peeling occurs on the surface of the laminated body 7 due to a sudden stress applied to the groove 12, the groove 12 does not reach the internal electrode layer 5, so that a short circuit occurs between the internal electrode layers 5. There is nothing.

  Further, as shown in FIGS. 8A and 8B in a side view and a cross-sectional view taken along line AA of still another example of the embodiment of the multilayer piezoelectric element of the present invention, the multilayer body 7 is driven at the time of driving. A groove 12 in which the bottom of the external electrode 11 does not reach the multilayer body 7 is included, which includes a planned fracture layer 13 that relieves stress in the multilayer body 7 by breaking preferentially in the multilayer body 7 over the internal electrode layer 5. Is formed in the vicinity of the expected fracture layer 13, the stress is concentrated on the innermost part of the groove 12 (the other end of the groove 12 located in the external electrode 11). The stress applied to the electrode 11 can be transmitted to the planned fracture layer 13 through the groove 12, and by breaking the planned fracture layer 13, the stress in the laminate 7 can be relaxed. As a result, even when the multilayer piezoelectric element 1 is used in an environment in which a high load is applied for a long period of time, the piezoelectric body layer 3 is expected to break without causing stress and cracks due to the stress. Stress relaxation in which cracks are effectively generated only in the fault 13 becomes possible, and the multilayer piezoelectric element 1 can be made highly durable. Furthermore, since the fracture can be started with respect to the planned fracture layer 13 from the position where the groove 12 is provided, from where the fracture can be started when the planned fracture layer 13 is provided in the laminate 7 Thus, the layout design of the planned fracture layer 13 can be facilitated, and the multilayer piezoelectric element 1 excellent in mass productivity can be obtained. In particular, it is more preferable to form the groove 12 so as to be located in the portion of the planned fracture layer 13 because stress can be more effectively concentrated on the planned fracture layer 13.

  In addition, as shown in FIGS. 9A and 9B in a side view and a cross-sectional view taken along the line AA of another embodiment of the multilayer piezoelectric element of the present invention, a laminate is formed on the external electrode 11. 7 across the thickness direction of the external electrode 11 so as to extend in a direction intersecting with the stacking direction of the outer electrode 7, preferably along a direction orthogonal to the stacking direction It is preferable that a gap 14 is further formed. In the example shown in FIG. 9, a groove 12 formed from one edge to the other opposite edge is formed in the center of the external electrode 11, and the bottom reaches the laminate 7 at the top and bottom of the external electrode 11. The slits 14 having one end reaching the edge of the external electrode 11 are respectively formed at positions corresponding to the opposite edges. By forming such a slit 14, the length of the external electrode 11 along the surface of the laminated body 7, that is, the distance along the outer periphery of the external electrode 11 (length along the outer periphery) is increased. Therefore, the stress due to the difference in thermal expansion between the external electrode 11 and the piezoelectric layer 3 can be relaxed.

  In the case where the slits 14 are further formed in the external electrode 11, in particular, FIGS. 10 (a) and 10 (b) are side views and AA lines of still another example of the embodiment of the laminated piezoelectric element of the present invention. As shown in the sectional view, when the slit 14 is formed in the vicinity of the planned fracture layer 13 included in the laminate 7, the innermost part of the slit 14 (the other end of the slit 14 positioned in the external electrode 11) The stress applied to the external electrode 11 can be transmitted to the planned fracture layer 13 through the slit 14 by utilizing the fact that the stress is concentrated on the layer 7. Can be relaxed. As a result, even when the multilayer piezoelectric element 1 is used in an environment in which a high load is applied for a long period of time, the piezoelectric body layer 3 is expected to break without causing stress and cracks due to the stress. Stress relaxation in which cracks are effectively generated only in the fault 13 becomes possible, and the multilayer piezoelectric element 1 can be made highly durable. Furthermore, since the fracture can be started with respect to the planned fracture layer 13 from the position where the slit 14 is provided, when the planned fracture layer 13 is provided in the laminated body 7, from which position the fracture can be started Thus, the layout design of the planned fracture layer 13 can be facilitated, and the multilayer piezoelectric element 1 excellent in mass productivity can be obtained. In particular, it is more preferable to form the slit 14 so as to be located in the portion of the planned fracture layer 13 because stress can be more effectively concentrated on the planned fracture layer 13.

  When the slit 14 is set so that the external electrode 11 is easily deformed according to the expansion and contraction of the multilayer body 7 when the multilayer piezoelectric element 1 is driven, the stress of the external electrode 11 can be effectively relieved, Since stress can be concentrated on the innermost part of the slit 14, the planned fracture layer 13 can be effectively broken by disposing the planned fracture layer 13 in the vicinity of the slit 14. The slit 14 is preferably provided in a direction orthogonal to the longitudinal direction of the external electrode 11, that is, in a direction along the piezoelectric layer 3 and the internal electrode layer 5. In particular, it is preferably formed along the direction orthogonal to the stacking direction of the stacked body 7, which is the expansion / contraction direction of the stacked piezoelectric element 1, that is, parallel to the piezoelectric layer 3 and the internal electrode layer 5.

  The width of the slit 14 is set so that there are ten or more piezoelectric layers 3 in the slit 14, thereby increasing the stress relaxation effect. This is because the stress concentrated in the slit 14 can be relieved by the piezoelectric layer 3 in the slit 14 being deformed according to the pressure. In particular, since there are ten or more piezoelectric layers 3 in the slit 14, the stress between the piezoelectric layers 3 can be dispersed, so that stress can be prevented from concentrating on one layer of the piezoelectric layer 3. This is because the stress can be relieved well. The length of the slit 14 is preferably less than half the width of the external electrode 11 in terms of preventing breakage of the external electrode 11 starting from the end of the slit 14.

  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 3 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 5 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 7 provided with the piezoelectric material layer 3 and the internal electrode layer 5 which were laminated | stacked alternately can be formed by baking as mentioned later.

  At this time, for example, when forming a porous metal particle layer including a large number of independent metal particles as the expected fracture layer 13, carbon powder is included 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. In addition, if the porous metal particle layer containing a large number of independent metal particles is formed as the planned fracture layer 13, the conductive paste of the porous metal particle layer to be the planned fracture layer 13 and other By changing the metal component ratio of the internal electrode layer 5 to the conductive paste and utilizing the difference in concentration during firing, the metal is transferred from the expected fracture layer 13 to the adjacent internal electrode layer 5 via the piezoelectric layer 3. It can be made porous by diffusing. This method is preferable in terms of excellent mass productivity. In particular, when a conductive paste mainly made of silver-palladium is used and the silver concentration of the layer to be the expected fracture layer 13 is made higher than the silver concentration of the other internal electrode layers 5, the silver forms a liquid phase during firing. At the same time, since it can easily move between the piezoelectric particles of the piezoelectric layer 3, it is possible to form the expected fracture layer 13 made of a very uniform porous metal particle layer.

  After that, the external electrode 11 is formed on the outer surface of the multilayer body 7 of the multilayer piezoelectric element 1 so as to obtain conduction with the internal electrode layer 5 whose end is exposed. The external electrode 11 can be obtained by adding a binder to silver powder and glass powder to produce a silver glass conductive paste, printing this on the side surface of the laminate 7, drying adhesion, or baking.

  In order to provide the groove 12 whose bottom does not reach the laminated body 7 in the external electrode 11, a method of printing by forming a multi-layer pattern when printing a silver glass conductive paste is most mass-produced. First, after printing the deepest layer 11A as the external electrode 11 and drying it, the pattern of the external electrode 11 plus the shape of the groove 12 is used to screen the deepest layer 11A on the deepest layer 11A by screen printing. A layer 11C positioned between the surface 11B located on the surface side of the groove 12 and the pattern 11 in the shape of the groove 12 and a layer 11B positioned in the shape of the groove 12 on the surface side 11 did. At this time, the width of the opening can be made larger than the width of the bottom surface of the groove 12 by printing with the opening width of the groove 12 being increased in the pattern of the upper layer (layer 11C and layer 11B) to be laminated. .

  In addition to the method of forming the external electrode 11 by printing and laminating in the order of the laminated structure as described above, a groove whose bottom does not reach the laminated body 7 after the external electrode 11 is formed by a printing method, a vapor deposition method, or the like. A method of etching into a pattern of 12, similarly, a method of carrying out sand blasting or dry ice blasting by placing a metal mask provided with a pattern of the shape of the groove 12 whose bottom does not reach the laminated body 7 after forming the external electrode 11; Alternatively, similarly, after forming the external electrode 11, there is a method of cutting into a pattern of the groove 12 whose bottom does not reach the laminated body 7 using a cutting means such as a diamond disk.

  Next, a lead wire made of a metal wire, a conductive member made of a metal mesh or a mesh-like metal plate, etc. are joined and fixed to the surface of the external electrode 11 using a bonding material such as solder or conductive adhesive. To do. Here, the material of the conductive member is preferably a metal or alloy such as silver, nickel, copper, phosphor bronze, iron, and stainless steel. The surface of the conductive member may be plated with silver or nickel.

  It should be noted that the conductive member may be joined over the entire lamination direction of the external electrodes 11 or may be joined to a part of the external electrodes 11.

  Next, the laminate 7 on which the external electrode 11 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 7, and then the laminate 7 is pulled up from the silicone resin solution. Thereby, the silicone resin is coated on the side surface of the laminated body 7 on which the external electrode 11 having the groove 12 is formed.

  Thereafter, a direct current voltage of 0.1 to 3 kV / mm is applied from the pair of external electrodes 11 to the piezoelectric layer 3 through the conductive member connected to the external electrode 11 by the internal electrode layer 5. By polarizing, the laminated piezoelectric element 1 of this example is completed. Then, the conductive member is connected to an external voltage supply unit, and a voltage is applied to the piezoelectric layer 3 by the internal electrode layer 5 via the conductive member and the external electrode 11, whereby each piezoelectric layer 3 is subjected to the inverse piezoelectric effect. It can be displaced greatly. Thereby, for example, it is possible to function as an automobile fuel injection valve mechanism for injecting and supplying fuel to the engine.

  Next, an example of an embodiment of a fluid ejection device as the ejection device of the present invention will be described. FIG. 11 is a schematic cross-sectional view showing an example of an embodiment of an injection device of the present invention.

  As shown in FIG. 11, in the injection device 21 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 25 having an injection hole 23 at one end. Yes.

  A needle valve 27 that can open and close the injection hole 23 is disposed in the container 25. A fluid passage 29 is arranged in the injection hole 23 so that it can communicate with the movement of the needle valve 27. The fluid passage 29 is connected to an external fluid supply source, and is constantly supplied with, for example, a liquid that is a fluid at a high pressure. Therefore, when the needle valve 27 opens the injection hole 23 by driving the multilayer piezoelectric element 1, the fluid supplied to the fluid passage 29 is transferred to the outside of the injection hole 23 or a container adjacent to the injection hole 23, for example, an internal combustion engine. The fuel chamber (not shown) is configured to be discharged from the injection hole 23 and injected.

  The upper end of the needle valve 27 has a large inner diameter, and a cylinder 31 formed in the container 25 and a slidable piston 33 are disposed in that portion. In the container 25, the multilayer piezoelectric element 1 of the present invention is accommodated.

  In such an injection device 21, when the multilayer piezoelectric element 1 functioning as a piezoelectric actuator is applied with a voltage and extended, the piston 33 is pressed, the needle valve 27 closes the injection hole 23, and the supply of fluid is stopped. The When the application of voltage is stopped, the laminated piezoelectric element 1 contracts, the disc spring 35 pushes back the piston 33, the fluid passage 29 is opened, the injection hole 23 communicates with the fluid passage 29, and the injection hole The fluid is ejected from 23.

  The fluid ejection operation is to apply a voltage to the multilayer piezoelectric element 1 to open the fluid passage 29 and discharge the fluid from the ejection hole 23, and to stop applying the voltage to close the fluid passage 29. Thus, the discharge of the fluid may be stopped.

  The injection device 21 of the present invention includes a container 25 having an injection hole 23 and the multilayer piezoelectric element 1 of the present invention, and the fluid filled in the container 25 is ejected by driving the multilayer piezoelectric element 1. It may be configured to discharge from 23. That is, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 25, and the pressure for supplying and stopping the fluid to the injection hole 23 is applied to the inside of the container 25 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 23 through the fluid passage 29, but also provided in the container 25 with a portion for temporarily storing the fluid in an appropriate place in the container 25. The filled fluid may be discharged from the injection hole 23.

  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 21 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 21 of the present invention that employs the multilayer piezoelectric element 1 of the present invention is used in an internal combustion engine, fuel can be injected into a combustion chamber of an internal combustion engine such as an engine more accurately over a longer period than a conventional injection device. Can be made.

  Next, the example of embodiment of the fuel-injection system of this invention is demonstrated. FIG. 12 is a schematic diagram showing an example of an embodiment of a fuel injection system of the present invention.

  As shown in FIG. 12, the fuel injection system 41 of this example includes a common rail 43 that stores high-pressure fuel, a plurality of injection devices 21 of the present invention that inject the high-pressure fuel stored in the common rail 43, and a high pressure on the common rail 43. A pressure pump 45 for supplying fuel and an injection control unit 47 for supplying a drive signal to the injection device 21 are provided.

  The injection control unit 47 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 47 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 45 serves to supply fluid fuel from the fluid tank 49 to the common rail 43 at a high pressure. For example, in the case of an engine fuel injection system 41, fluid fuel is fed into the common rail 43 at a high pressure of about 1000 to 2000 atmospheres, preferably about 1500 to 1700 atmospheres.

  In the common rail 43, the high-pressure fuel sent from the pressure pump 45 is stored and appropriately sent to the injection device 21 in accordance with the driving of the multilayer piezoelectric element 1. As described above, the injection device 21 discharges (injects) high-pressure fuel, which is a predetermined amount of fluid, from the injection hole 23 to the outside of the injection hole 23 or a container adjacent to the injection hole 23 at high pressure. For example, when the target for injecting and supplying fuel is an engine, high-pressure fuel, which is a fluid, is injected from the injection hole 23 into the combustion chamber of the engine in a mist form.

  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.

  An example of the multilayer piezoelectric element of the present invention was produced as follows.

  First, a slurry is prepared by mixing a binder powder and a plasticizer with a raw material powder mainly composed of lead zirconate titanate (PZT) powder having an average particle diameter of 0.4 μm, and a ceramic green sheet having a thickness of 150 μm is prepared by a doctor blade method. Produced.

  Next, a conductive paste A 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 a raw material containing silver powder having a metal composition of Ag 100 mass% A conductive paste B was prepared by adding a binder to the powder.

  Then, the conductive paste A was printed on one side of the ceramic green sheet with a pattern of the internal electrode layer 5 so as to have a thickness of 30 μm by screen printing. And each green ceramic sheet on which conductive paste A was printed was laminated to produce a green laminate. As for the number of laminated layers, the number of internal electrode layers 5 is laminated to be 300, and only 20 ceramic green sheets on which no conductive paste is printed are provided at both ends in the lamination direction of the green laminate. It laminated | stacked and it was set as the sample numbers 1-3.

  Next, in order to provide a low-rigidity metal layer made of isolated metal particles as the expected fracture layer 13, in the sample number 4, the internal electrode layer 5 located at the 50th and 250th positions in the stacking direction is used as the conductive paste B. Was used for printing. Similarly, in Sample No. 5, the internal electrode layers 5 positioned at the 50th, 100th, 150th, 200th and 250th in the stacking direction were printed using the conductive paste B.

  Next, the raw laminate of each sample number was subjected to binder removal treatment at a predetermined temperature, and then fired at 800 to 1000 ° C. to obtain a laminate 7. Here, in Sample Nos. 4 and 5, since the silver of the electrode component of the layer using the conductive paste B diffuses into the adjacent metal layer having a low silver concentration during firing, the layer using the conductive paste B As a result, the expected fracture layer 13, which is a low-rigidity metal layer made of isolated metal particles, was formed.

  And after processing to the laminated body 7 of each sample number to a desired dimension, as shown in Table 1, the bottom becomes the laminated body 7 like the example shown in FIG.3, FIG.4, FIG.7 and FIG. The external electrodes 11 were formed so that the grooves 12 that did not reach could be formed. Here, first, a conductive paste C was prepared by adding and mixing a binder, a plasticizer, a glass powder and the like to a metal powder containing silver as a main component. Next, a conductive paste D was prepared by adding and mixing a binder and a plasticizer to metal powder containing silver as a main component. Furthermore, for the purpose of forming the external electrode 11 that is the expected fracture layer 13 of the low-rigidity metal layer made of isolated metal particles, acrylic beads that have the same weight as silver together with a binder and a plasticizer in a metal powder mainly composed of silver Were added and mixed to prepare a conductive paste E.

  Next, the conductive paste C was pattern printed by screen printing or the like on the side surface of the laminate 7 where the external electrodes 11 are to be formed. After drying, Sample No. 1 uses the same print pattern as when the conductive paste C was printed, and Sample Nos. 2 to 5 use a print pattern in which the shape of the groove 12 whose bottom does not reach the laminate 7 is added. The conductive paste D was printed. Sample No. 6 shows the shape of the groove 12 whose bottom does not reach the laminate 7 after the conductive paste E is printed and dried using the print pattern to which the shape of the groove 12 whose bottom does not reach the laminate 7 is added. The conductive paste D was printed using the printing pattern to which is added. And after drying all, it baked at 600-800 degreeC and the external electrode 11 was formed.

  In the external electrode 11 of each sample obtained, the shape of the groove 12 whose bottom did not reach the laminated body 7 was such that the opening width was about 10% larger than the width of the bottom surface. This is because the pattern edge portion of the conductive paste immediately after is rounded by the surface tension, so that the edge of the opening is chamfered. Since the shape of the bottom surface of the groove 12 whose bottom does not reach the laminated body 7 is a rectangular shape, the width and length of the bottom surface of the rectangular shape are shown in the dimension column of Table 1 as width × length. As shown.

  For sample numbers 4 and 5, the groove 12 was provided at the position of the expected fracture layer 13. This is indicated as “scheduled fracture layer” in the number column of Table 1.

  Driving evaluation was performed using each sample thus produced. As drive evaluation, high-speed response evaluation and durability evaluation were performed. First, a lead wire is connected to the external electrode 11, and a polarization treatment is performed by applying a direct voltage of 3 kV / mm for 15 minutes from the positive and negative external electrodes 11 to the piezoelectric layer 3 via the lead wire. A piezoelectric actuator using the element 1 was produced. A DC voltage of 170 V was applied to the obtained piezoelectric actuator, and the amount of displacement in the initial state was measured.

For high-speed response evaluation, an AC voltage of 0 to +170 V at room temperature was applied to each piezoelectric actuator with a frequency gradually increased from 150 Hz. For durability evaluation, an AC voltage of 0 to +170 V was applied to each piezoelectric actuator at a frequency of 150 Hz at room temperature, and a test was continuously performed up to 1 × 10 ⁹ times. The production conditions for each of these samples are shown in Table 1, and the test results are shown in Table 2.

  As shown in Tables 1 and 2, only the sample No. 1 of the comparative example in which the groove 12 whose bottom does not reach the laminated body 7 is not formed in the external electrode 11 is obtained when the frequency exceeds 1 kHz in the piezoelectric actuator. Generation of a roaring sound was observed. This is because, in the laminated piezoelectric element of sample number 1, since the laminated body 7 is constrained by the external electrode 11, when local heat is generated between the internal electrode layers 5 with driving, the piezoelectric layer 3 It is considered that a disturbance sound was generated in each displacement speed, and a beat sound was generated because the displacement could not follow the frequency of the applied AC voltage.

  In order to confirm the drive frequency, the pulse waveform of the drive signal of sample number 1 was confirmed using an oscilloscope DL1640L manufactured by Yokogawa Electric Corporation, and harmonic noise was confirmed at a location corresponding to an integer multiple of the drive frequency. It was done. Regarding this, in Table 1, “present” is shown in the column of noise generation of harmonic components.

As a result of the durability evaluation, in Sample No. 1, the displacement amount after the durability evaluation test (displacement amount after 1 × 10 ⁹ times) is 5 μm, which is nearly 90% compared with that before the durability evaluation test. ({(45-5) / 45} × 100 = 88.9 (%)). Further, in the piezoelectric actuator of sample number 1, peeling was observed on the external electrode 11 after continuous driving (1 × 10 ⁹ times), and peeling was observed on a part of the laminated portion in the laminated body 7.

On the other hand, in the piezoelectric actuators of Sample Nos. 2 to 6 which are the examples of the present invention, peeling of the external electrode 11 and peeling of the laminated portion in the laminated body 7 are observed after continuous driving (1 × 10 ⁹ times) There wasn't. In addition, the decrease in the displacement after the durability evaluation test is 3 μm or less, and the decrease in the displacement is 7% or less ({(48−45) / 48} × 100 = 6.25 (%)). As described above, the piezoelectric actuators of sample numbers 4 to 6 which are the embodiments of the present invention have very high durability because no decrease in the displacement amount is confirmed even after continuous driving of 1 × 10 ⁹ times. I understood that.

  In addition, after the durability evaluation test, in the laminated piezoelectric elements of sample numbers 4 and 5, the planned fracture layer 13 was cracked. Since it was confirmed that the position of the crack was a portion where the groove 12 where the bottom did not reach the laminated body 7 was provided, the expected fracture layer 13 was preferentially broken by using the groove 12, and the stress in the laminated body 7 was Was confirmed.

  In the laminated piezoelectric element of sample number 6, the layer 11C of the external electrode 11 is formed of a low-rigidity metal layer made of isolated metal particles. After the durability evaluation test, the external electrode that is the low-rigidity metal layer The 11 layer 11C had cracks. Since it was confirmed that the position of the crack was only in the layer 11C of the external electrode 11 starting from the portion where the groove 12 was provided, the layer 11C of the external electrode 11 formed of a low-rigidity metal layer by using the groove 12 was confirmed. Was preferentially broken, and it was confirmed that the stress in the laminate 7 was relaxed.

It is a perspective view which shows an example of embodiment of the lamination type piezoelectric element of this invention. (A) is a side view which shows the other example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. (A) is a side view which shows the further another example of embodiment of the lamination type piezoelectric element of this invention, (b) is the AA sectional view taken on the line. 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 3 ... Piezoelectric layer 5 ... Internal electrode layer 7 ... Laminated body
11 ... External electrode
11A: Deepest layer (layer located on the laminate side)
11B: Layer located on the surface side
11C: Layer located between the deepest layer and the layer located on the surface side
12 ... Groove
13 ... Scheduled fracture layer
14 ... Slit
21 ... Injection device
23 ・ ・ ・ Injection hole
25 ・ ・ ・ Container
27 ... Needle valve
29 ・ ・ ・ Fluid passage
31 ... Cylinder
33 ... Piston
35 ... Belleville spring
41 ... Fuel injection system
43 ... Common rail
45 ... Pressure pump
47 ・ ・ ・ Injection control unit
49 ... Fuel tank

Claims (11)

A laminated piezoelectric element comprising an external electrode electrically connected to the internal electrode layer on a side surface of a laminate in which piezoelectric layers and internal electrode layers are alternately laminated, wherein the external electrode has a bottom There are a plurality of grooves not reaching the laminate is formed in the stacking direction of the laminate, the interval of the grooves adjacent to each other are increased toward the end of the stacking direction of the laminate A laminated piezoelectric element characterized by the above.   The external electrode has a stacked structure in which a plurality of layers are stacked, and the groove is formed in a layer on the surface side of the deepest layer positioned on the stacked body side of the external electrode. The multilayer piezoelectric element according to claim 1.   3. The multilayer piezoelectric element according to claim 1, wherein one end of the groove reaches an edge of the external electrode.   4. The multilayer piezoelectric element according to claim 1, wherein the groove has a width of an opening on a surface of the external electrode larger than a width of a bottom surface. 5.   The multilayer piezoelectric element according to claim 3, wherein the groove has an opening whose width is increased on an edge side of the external electrode.   The multilayer piezoelectric element according to claim 1, wherein the groove is formed from an edge of the external electrode to an edge facing the external electrode.   The multilayer piezoelectric element according to claim 1, wherein the groove is formed in parallel with the internal electrode layer.   The laminate includes a planned fracture layer that relaxes stress by breaking preferentially over the internal electrode layer during driving, and the groove is formed in the vicinity of the planned fracture layer. The multilayer piezoelectric element according to any one of claims 1 to 7.   The slit is further formed in the thickness direction of the said external electrode so that the said external electrode may extend along the direction which cross | intersects the lamination direction of the said laminated body. The laminated piezoelectric element described.   A container having an injection hole and the multilayer piezoelectric element according to any one of claims 1 to 9, wherein fluid stored in the container is discharged from the injection hole by driving the multilayer piezoelectric element. An injection device.   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.

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