WO2010001800A1 - Multilayer piezoelectric element, and injection apparatus and fuel injection system comprising the same - Google Patents

Abstract

Multilayer piezoelectric elements are required to have higher durability.  However, conventionally, if a multilayer piezoelectric element is displaced greatly or driven at high speed, the element cannot absorb the stress to thereby increase self-heating due to the drive and cause cracks.  This causes a problem that the multilayer piezoelectric element cannot be stably driven. A multilayer piezoelectric element (1) has a multilayer structure wherein piezoelectric layers (3) and internal electrode layers (5) are formed alternately, and the piezoelectric layer (3) has voids (11) each containing metal bodies (13).  The voids (11) absorb the stress, and the metal bodies (13) inside the voids (11) can improve the heat conduction of the piezoelectric layer (3).  Therefore the multilayer piezoelectric element (1) has excellent durability.

Description

Multilayer piezoelectric element, injection device and fuel injection system including the same

The present invention relates to a laminated piezoelectric element used for, for example, a driving element (piezoelectric actuator) using a piezoelectric body, a sensor element, or a circuit element. Examples of the drive 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 while being reduced in size. For this reason, it is required that a higher voltage corresponding to a larger displacement amount is applied and that it can be used under harsh conditions in which continuous driving is performed for a long time.

When driving continuously for a long time under high voltage or high pressure conditions, stress is applied to the internal electrodes and the piezoelectric body. Therefore, the voids (voids) in the piezoelectric layer are reduced and reduced so as not to cause cracks in the piezoelectric body and short-circuiting of the internal electrodes in the multilayer piezoelectric element, as disclosed in Patent Document 1, for example. It has been proposed.
JP 2002-54526 A

However, if the voids in the piezoelectric layer are reduced and reduced, there is no deformable void in the piezoelectric layer even if the piezoelectric layer attempts to deform due to stress when external stress is applied to the multilayer piezoelectric element. For this reason, there is no local deformation region, and the entire piezoelectric element is deformed. Further, during driving of the piezoelectric element, there is a problem that self-heating due to driving increases due to the absence of a region that absorbs stress in the piezoelectric layer. In particular, since the heat conduction of the piezoelectric layer is poorer than that of the internal electrode, it is difficult to dissipate heat to the surface of the piezoelectric element. Therefore, once self-heating starts during driving of the piezoelectric element, the piezoelectric characteristics are increased by heating. Due to fluctuations, the drive deformation becomes larger, further overheating proceeds and the drive amount decreases, or local expansion due to local heating causes cracks in the piezoelectric element, resulting in a laminated type There was a problem that the piezoelectric element could not be driven stably.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a laminated piezoelectric element having a stable displacement even when driven for a long time.

The multilayer piezoelectric element of the present invention is a multilayer piezoelectric element having a multilayer structure in which piezoelectric layers and internal electrode layers are alternately stacked, and the piezoelectric layer has a gap including a metal body. It is characterized by being.

According to the multilayer piezoelectric element of the present invention, the voids of the piezoelectric layer form a locally deformed region in the piezoelectric layer to absorb the stress, and the metal contained in the voids The body can improve the heat conduction of the piezoelectric layer and dissipate the self-heating generated during the driving of the piezoelectric element to the surface of the piezoelectric element. As a result, the amount of displacement can be stabilized even when driven for a long time.

Hereinafter, the multilayer piezoelectric element of the present invention will be described in detail with reference to the drawings. Fig.1 (a) is a perspective view which shows the example of embodiment of the lamination type piezoelectric element of this invention. FIG. 1B is an exploded perspective view of the example shown in FIG. FIG. 2 is a cross-sectional view of the main part including internal electrodes that are adjacent to each other in the stacking direction, that is, opposite to each other in the direction perpendicular to the stacking direction of the piezoelectric elements in the example shown in FIG.

As shown in FIG. 2, the laminated piezoelectric element 1 of this example (hereinafter also simply referred to as the piezoelectric element 1) includes a laminated body 7 having a laminated structure in which piezoelectric layers 3 and internal electrode layers 5 are alternately laminated. A multilayer piezoelectric element 1 having a void 11 including a metal body 13 in a piezoelectric layer 3.

Since the piezoelectric layer 3 has the void 11 including the metal body 13 as described above, the void 11 forms a locally deformed region in the piezoelectric layer 3 to absorb stress, and further, the void 11, the heat conduction of the piezoelectric layer 3 can be improved and the self-heating generated during driving of the piezoelectric element 1 can be dissipated to the surface of the piezoelectric element 1. As a result, the amount of displacement can be stabilized even when driven for a long time.

The size of the gap 11 included in the piezoelectric layer 3 is preferably 50% or less with respect to the thickness of the piezoelectric layer 3. By making it within this range, the void 11 forms a locally deformed region in the piezoelectric layer 3 to effectively absorb the stress, and has an effect of having a high insulation resistance over the entire surface of the piezoelectric layer 3. Play. Moreover, it is preferable that the shape of the metal body 13 contained in the space | gap 11 is extended in the direction (direction parallel to the main surface of a piezoelectric material layer) orthogonal to the lamination direction. At this time, the metal body 13 in the gap 11 can preferentially improve the heat conduction of the piezoelectric layer 3 in the direction of the side surface of the element, and the self-heating generated during driving of the piezoelectric element 1 can be reduced. The effect of dissipating to the surface of is improved.

Further, it is preferable to have the gap 11 at a portion sandwiched between the internal electrode layers 5 facing each other such as being positioned one above the other. At this time, since the stress relaxation effect and the heat dissipation effect can be brought about by the air gap 11 in the drive region called the active layer in the multilayer piezoelectric element 1, the heat generated during the drive can be effectively dissipated. Furthermore, in the part pinched | interposed between the internal electrode layers 5 of different polarities, it is possible to suppress local thermal expansion by suppressing local heating, so that the piezoelectric element 1 can be prevented from cracking and laminated. The type piezoelectric element 1 can be driven stably.

In addition, the internal electrode layer 5 includes a porous internal electrode layer 5 (not shown separately) including a large number of independent metal particles, and voids 11 are formed in the piezoelectric layer 3 in contact with the porous internal electrode layer 5. It is preferable to have.

Since the porous internal electrode layer 5 including a large number of independent metal particles has an effect of relieving stress on itself, it is highly durable due to a synergistic effect with the piezoelectric layer 3 having the voids 11. The multilayer piezoelectric element 1 can be obtained. In addition, since the porous internal electrode layer 5 has lower heat conduction than the other dense internal electrode layers 5, heat can be effectively dissipated by bringing the gap 11 including the metal body 13 close thereto. As a result, a highly durable multilayer piezoelectric element 1 can be obtained.

Further, it is preferable that the metal body 13 contained in the gap 11 is attached to the wall surface of the gap 11. According to this, since the metal body 13 can be in direct contact with the heated piezoelectric layer 3, heat can be effectively dissipated, so that a highly durable multilayer piezoelectric element 1 is obtained. Can do.

Particularly, since the gap 11 is filled with the metal body 13, heat dissipation can be most effectively performed. This state can be said that the piezoelectric layer 3 has a metal body 13 in which the periphery is in contact with the piezoelectric layer 3 (the metal body 13 is included in the piezoelectric layer 3). is there.

Moreover, if the metal body 13 is porous (porous), it contributes effectively to the absorption of stress, and if it is dense, the heat conduction characteristics can be improved effectively. Therefore, the multi-layer piezoelectric element 1 having high durability can be obtained by disposing the gap 11 including the dense metal body 13 at the boundary between the active layer and the inactive layer where heat is easily generated and is easily trapped. It can be.

Further, since the metal body 13 is made of the same material as the main component of the internal electrode layer 5, the thermal expansion can be made equal to that of the internal electrode layer 5, so that the temperature of the multilayer piezoelectric element 1 changes rapidly. Even when used in a harsh environment, the generation of stress due to thermal expansion can be prevented, so that the multilayer piezoelectric element 1 can be used stably over a long period of time. Further, the thermal stress in the piezoelectric element 1 can be evenly dispersed.

Further, since the metal body 13 is silver, excellent heat conduction is realized, and at the same time, since the silver is a relatively soft metal, the metal body 13 can be deformed at the same time even when the gap 11 is deformed. Thus, since the stress can be effectively absorbed, a highly durable multilayer piezoelectric element 1 can be obtained.

The void 11 is closed in the piezoelectric layer 3, that is, is a so-called closed pore, and functions as a damper containing gas in the piezoelectric layer 3. The laminated piezoelectric element 1 that functions and has high durability can be obtained.

Next, a method for manufacturing the multilayer piezoelectric element 1 according to this embodiment 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 this slurry for tape forming methods, such as a known doctor blade method and a calender roll method. 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. Moreover, as a plasticizer, DBP (dibutyl phthalate), DOP (dioctyl phthalate), etc. can be used.

Next, a conductive paste to be the internal electrode layer 5 is produced. Specifically, a conductive paste can be prepared by adding and mixing a binder, a plasticizer, and the like with 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, in order to form the porous internal electrode layer 5 including a large number of independent metal particles as the internal electrode layer 5, for example, the carbon powder is contained in the conductive paste, and the carbon powder disappears during firing. Or a pattern printing so as to form a dot pattern when the conductive paste is printed, or a dry ice blasting is performed after the conductive paste is printed and dried to roughen the printed surface. Further, by changing the metal component ratio between the conductive paste of the internal electrode layer 5 to be the porous internal electrode layer 5 and the conductive paste of the other internal electrode layers 5, the concentration difference is used during firing to make the porous A method in which a metal is made porous by diffusing metal from the internal electrode layer 5 to be the internal electrode layer 5 is preferable. In particular, when a conductive paste mainly made of silver-palladium is used and the silver concentration of the internal electrode layer 5 to be the porous internal electrode layer 5 is higher than the silver concentration of the other internal electrode layers 5, Since a liquid phase is formed and a liquid phase containing silver can easily move between the piezoelectric particles of the piezoelectric layer 3, it is preferable because a very uniform porous internal electrode layer 5 is completed.

Here, in order to form the void 11 including the metal body 13 in the piezoelectric layer 3, a powder (which becomes the metal body 13 after firing) pulverized after printing silver or silver-palladium or the like on a carbon sheet is formed. The powder is prepared and contained in a slurry for producing a ceramic green sheet to produce a ceramic green sheet for voids. By using the ceramic green sheet for voids as a part or all of the ceramic green sheets constituting the laminate 7, the laminate 7 is formed and fired to have the voids 11 including the metal bodies 13. The multilayer piezoelectric element 1 including the piezoelectric layer 3 can be obtained.

Alternatively, a conductive paste having a different silver-palladium ratio is prepared as the conductive paste to be the internal electrode layer 5, and metal diffusion is actively generated between the internal electrode layers 5 using a concentration gradient. The ceramic green sheet, which is the piezoelectric layer 3 where the diffusion occurs, contains carbon or excessive binder so that voids 11 are easily formed, and the metal is diffused into the piezoelectric layer 3 during firing. On the other hand, by trapping the metal in the gap 11 formed in the piezoelectric layer 3, the multilayer piezoelectric element 1 including the piezoelectric layer 3 having the gap 11 including the metal body 13 can be obtained.

Thereafter, an external electrode 9 is formed on the outer surface of the multilayer body 7 of the multilayer piezoelectric element 1 so as to obtain electrical continuity with the internal electrode layer 5 whose end is exposed. The external electrode 9 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, and drying or bonding.

Next, the laminate 7 on which the external electrodes 9 are 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, a silicone resin (not shown) is coated on the side surface of the laminate 7. Then, a lead wire is connected to the external electrode 9 as a current-carrying portion with a conductive adhesive (not shown) or the like.

Next, a direct current electric field of 0.1 to 3 kV / mm is applied to the piezoelectric layer 3 from the pair of external electrodes 9 via the lead wires by the internal electrode layer 5 to polarize the piezoelectric layer 3 of the laminate 7. Thus, the laminated piezoelectric element 1 of this example is completed. Then, the lead wire is connected to an external voltage supply unit (not shown), and a voltage is applied to the piezoelectric layer 3 by the internal electrode layer 5 via the lead wire and the external electrode 9, whereby each piezoelectric layer 3 is It can be displaced greatly by the inverse piezoelectric effect. Thereby, for example, it is possible to function as an automobile fuel injection valve mechanism for injecting and supplying fuel to the engine.

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

As shown in FIG. 3, the injection device 21 of the present example includes a multilayer piezoelectric element 1 of the present invention represented by the example of the above embodiment inside a storage container (container) 25 having an injection gap 23 at one end. Is stored.

In the storage container 25, a needle valve 27 capable of opening and closing the injection gap 23 is disposed. A fluid passage 29 is arranged in the ejection gap 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 fluid is constantly supplied at a high pressure. Therefore, when the needle valve 27 opens the injection gap 23 by driving the multilayer piezoelectric element 1, the fluid supplied to the fluid passage 29 is outside the injection gap 23 or a container adjacent to the injection gap 23, for example, an internal combustion engine. It is configured to be ejected into a fuel chamber (not shown).

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

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

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

In addition, the ejection device 21 of the present invention includes a container (storage container) 25 having an ejection gap 23 and the multilayer piezoelectric element 1 of the present invention, and the fluid filled in the container 25 is used as the multilayer piezoelectric element 1. You may comprise so that it may make it discharge from the injection space | gap 23 by a drive. 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 ejection gap 23 is applied to the inside of the container 25 by driving the multilayer piezoelectric element 1. It suffices to be configured. The fluid is not only supplied to the ejection gap 23 through the fluid passage 29 but also provided with a portion for temporarily storing the fluid at an appropriate location in the container 25 so that the fluid filled in the container 25 can be stored. You may make it discharge from the ejection space | gap 23. FIG.

In the present invention, the fluid includes various liquid materials (such as conductive paste) and gas in addition to fuel or ink. By using the ejection device 21 for these fluids, the flow rate and ejection timing of the fluid can be controlled.

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 is more accurately injected into a combustion chamber of an internal combustion engine such as an engine for a longer period of time than a conventional injection device. Can be made.

Next, the fluid ejection system of the present invention will be described. FIG. 4 is a schematic diagram showing an example of an embodiment of the fuel injection system of the present invention.

As shown in FIG. 4, the fluid ejection system 41 of the present example includes a common rail 43 that stores high-pressure fluid, a plurality of injection devices 21 according to the present invention that inject the fluid stored in the common rail 43, and a high pressure applied to the common rail 43. A pressure pump 45 that supplies fluid and an injection control unit 47 that supplies a drive signal to the injection device 21 are provided.

The ejection control unit 47 controls the amount and timing of fluid ejection 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 plays a role of feeding 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, fluid is fed into the common rail 43 at a pressure of about 1000 to 2000 atmospheres, preferably about 1500 to 1700 atmospheres.

In the common rail 43, the fluid fuel sent from the pressure pump 45 is stored, and is appropriately sent to the injection device 21 according to the driving of the multilayer piezoelectric element 1. The injection device 21 discharges (injects) a predetermined amount of fluid from the injection gap 23 to the outside of the injection gap 23 or a container adjacent to the injection gap 23 as described above. For example, in the case of an engine, fuel, which is a fluid, is injected into the combustion chamber in a mist form.

In addition, this invention is not limited to the example of said embodiment, A various change may be performed within the range which does not deviate from the summary of this invention. Further, the present invention relates to a multilayer piezoelectric element, an injection device, and a fuel injection system, but is not limited to the example of the above embodiment, for example, a printing device of an inkjet printer, a pressure sensor, etc. A multilayer piezoelectric element utilizing piezoelectric characteristics can be implemented with the same configuration.

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

First, a slurry in which a binder and a plasticizer are mixed with a raw material powder mainly composed of lead zirconate titanate (PZT) powder having an average particle size of 0.4 μm is prepared, and a ceramic green sheet A having a thickness of 150 μm is obtained by a doctor blade method. Was made. And the slurry which increased the amount of binders 50 mass% rather than the ceramic green sheet A was produced, and the ceramic green sheet B with a thickness of 150 micrometers was produced by the doctor blade method.

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 95% by mass of Ag-Pd of 5% by mass, and a raw material containing silver powder having a metal composition of 100% by mass of Ag 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 A 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 A on which conductive paste A was printed was laminated to produce a green laminate. As the number of layers, the internal electrode layers 5 are stacked so that the number of layers is 300, and only the ceramic green sheets A on which the conductive paste A is not printed are provided at both ends in the stacking direction of the green laminate. Each sample was laminated to give sample number 1.

Next, in the sample number 2, the internal electrode layer 5 positioned at the 50th and 250th positions in the stacking direction is printed using the conductive paste B, and the sheet that becomes the piezoelectric layer 3 at the position where the conductive paste B is sandwiched. A ceramic green sheet B was used. Similarly, in the sample number 3, the internal electrode layers 5 positioned at the 100th and 200th positions in the stacking direction are printed using the conductive paste B, and in the sample number 4, the 50th, 100th, The internal electrode layers 5 located at the 150th, 200th and 250th positions were printed using the conductive paste B.

Furthermore, in sample number 5, the internal electrode layers 5 positioned at the 50th, 100th, 150th, 200th and 250th positions in the stacking direction are printed using the conductive paste B, and the conductive paste B is sandwiched between them. The ceramic green sheet B was used for the sheet to be the piezoelectric layer 3 and the sheet to be the adjacent (upper and lower) piezoelectric layers 3.

Next, the raw laminate of each sample number was subjected to a binder removal treatment at a predetermined temperature, and then fired at 800 to 1000 ° C. to obtain a laminate 7.

And after processing to the desired dimension in the laminated body 7 of each sample number, the external electrode 9 was formed, respectively. First, a conductive paste for the external electrode 9 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. This conductive paste was printed on the side surface of the laminate 7 where the external electrodes 9 are to be formed by screen printing or the like. Thereafter, the external electrode 9 was formed by baking at 600 to 800 ° C.

The drive evaluation was performed using each sample thus prepared. As drive evaluation, high-speed response evaluation and durability evaluation were performed. First, a lead wire is connected to the external electrode 9, a 3 kV / mm DC electric field is applied to the piezoelectric layer 3 from the positive electrode and the negative external electrode 9 via the lead wire for 15 minutes, and polarization treatment is performed. 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 results of these tests are shown in Table 1.

As shown in Table 1, as a result of the high-speed response evaluation, as shown in Table 1, as a result of the response evaluation, only the sample number 1 beats when the frequency exceeds 1 kHz in the piezoelectric actuator. It was making a sound. This is because, in the multilayered piezoelectric element of sample number 1, when local heat generation occurs between the internal electrode layers with driving, a part of the piezoelectric layer is locally heated without sufficient heat dissipation. This is because the displacement speed is delayed due to the increase of the dielectric loss accompanying the temperature rise, and as a result, the displacement speed of each piezoelectric layer is disturbed. Further, since local heating increases deformation of the piezoelectric layer, the high-speed response of the piezoelectric element is hindered by these, and it is considered that the frequency of the applied AC voltage could not be followed.

In order to check the drive frequency, the pulse waveform of the drive signal of sample number 1 was checked using a Yokogawa oscilloscope DL1640L. As a result, harmonic noise was found at a location corresponding to an integer multiple of the drive frequency. . 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 cycles) 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 in a part of the laminated portion of the piezoelectric element after continuous driving (1 × 10 ⁹ times).

On the other hand, in each of the piezoelectric actuators of sample numbers 2 to 5, no peeling of the laminated portion of the piezoelectric element was confirmed after continuous driving (1 × 10 ⁹ times). Further, the decrease in the displacement after the durability evaluation test is 3 μm or less, and the decrease in the displacement is 8% or less ({(40−37) / 40} × 100 = 7. 7) compared with that before the durability evaluation test. 5 (%)). In particular, it was found that the piezoelectric actuator of Sample No. 5 has very high durability since no decrease in displacement was confirmed even after 1 × 10 ⁹ cycles.

Further, after the durability evaluation test, the multilayer piezoelectric element was cut and observed with a microscope. As a result, in any of sample numbers 2 to 5, the voids and the metal bodies contained in the voids were included in the piezoelectric layer. And found. In Table 1, these are indicated as “Yes” in the column of voids (voids) containing a metal body.

In addition, in the porous internal electrode layer containing a large number of independent metal particles due to excessive absorption of stress by the voids, the metal particles are slightly peeled off from the adjacent piezoelectric layer in the region close to the voids. It was.

In Sample No. 5, the initial displacement was 38 μm, which was relatively small compared to Sample Nos. 2 to 4 of 40 μm. This is because, in the internal electrode layer, there were many voids in the porous internal electrode layer containing a large number of independent metal particles to improve durability, and the voids in this internal electrode layer absorbed the displacement of the laminate. As mentioned.

(A) is a perspective view which shows the example of embodiment of the lamination type piezoelectric element of this invention, (b) is a disassembled perspective view of the example shown to Fig.1 (a). FIG. 2 is a cross-sectional view of a main part including internal electrodes adjacent to each other in a direction perpendicular to the stacking direction of piezoelectric elements in the example illustrated in FIG. It is a schematic sectional drawing which shows the example of embodiment of the injection apparatus of this invention. It is the schematic which shows the example of embodiment of the fuel-injection system of this invention.

DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element 3 ... Piezoelectric layer 5 ... Internal electrode layer 7 ... Laminated body 9 ... External electrode 11 ... Gap 13 ... Metal body 21 ... Injection Device 23 ... Injection gap 25 ... Storage container (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 having a laminated structure in which piezoelectric layers and internal electrode layers are alternately laminated, wherein the piezoelectric layer has a void including a metal body. element. The multilayer piezoelectric element according to claim 1, wherein the gap is provided at a portion sandwiched between the internal electrode layers facing each other. 2. The internal electrode layer includes a porous internal electrode layer including a large number of independent metal particles, and the piezoelectric layer in contact with the porous internal electrode layer has the voids. Alternatively, the multilayer piezoelectric element according to claim 2. 4. The multilayer piezoelectric element according to claim 1, wherein the metal body contained in the gap is attached to a wall surface of the gap. The multilayer piezoelectric element according to any one of claims 1 to 4, wherein the void is filled with the metal body. The multilayer piezoelectric element according to any one of claims 1 to 5, wherein the metal body is dense. The multilayer piezoelectric element according to any one of claims 1 to 6, wherein the metal body is made of the same material as a main component of the internal electrode layer. The multilayer piezoelectric element according to any one of claims 1 to 7, wherein the metal body is made of silver. The multilayer piezoelectric element according to any one of claims 1 to 8, wherein the gap is closed in the piezoelectric layer. A container having an ejection gap and the multilayer piezoelectric element according to any one of claims 1 to 9, wherein the liquid supplied to the container is discharged from the ejection gap by driving the multilayer piezoelectric element. An injection device characterized by that. A common rail that stores high-pressure fuel, the injection device according to claim 10 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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