JP6913515B2 - Laminated piezoelectric element, injection device equipped with it, and fuel injection system - Google Patents

Description

The present disclosure relates to a laminated piezoelectric element used as a piezoelectric drive element (piezoelectric actuator), a pressure sensor element, a piezoelectric circuit element, etc., an injection device including the same, and a fuel injection system.

As a laminated piezoelectric element, a piezoelectric layer and an internal electrode layer are alternately laminated, and a laminate having a planned breaking layer between at least a part of adjacent piezoelectric layer layers is electrically connected to the internal electrode layer. Those provided with an external electrode provided on the side surface of the laminated body are known (see Patent Document 1). Here, the planned fracture layer is a layer that is more easily fractured than the surrounding layer. Such a laminated piezoelectric element is intended to reduce stress and cracks applied to other parts by generating cracks in a planned breaking layer, and to maintain performance for a long period of time.

Special Table 2006-518934

In recent years, there has been a demand for driving at higher displacements and higher frequencies, and there is a demand for a laminated piezoelectric element that can be stably used for a long period of time even in such driving.

However, in the above-mentioned drive, when the Young's modulus of the piezoelectric layer in all the active regions is formed to be the same, when the crack grows in the planned fracture layer, the crack growth rate is fast and the crack grows at once. Therefore, there is a risk that the external electrode will be cut off and noise will be generated. In addition, the generation of this noise may cause the displacement amount of the laminated piezoelectric element to increase momentarily.

The present disclosure has been made in view of the above circumstances, and an object of the present invention is to provide a laminated piezoelectric element capable of slowing the growth rate of cracks in a planned fracture layer, an injection device provided with the same, and a fuel injection system. ..

In the laminated piezoelectric element of the present disclosure, a piezoelectric layer and an internal electrode layer are alternately laminated, and a laminate having a planned breaking layer between at least a part of adjacent piezoelectric layers, and the internal electrode layer and the electric Each piezoelectric layer, which is connected to and provided with an external electrode provided on the side surface of the laminated body and is adjacent to each other via the planned breaking layer, has a different Young ratio from other piezoelectric layers . Each piezoelectric layer adjacent to each other via the planned breaking layer has a composition of a piezoelectric component excluding the same metal component as the metal component contained in the internal electrode layer or the planned breaking layer of another piezoelectric layer. It is characterized in that it is different from the composition of the constituent piezoelectric components.
Further, in the laminated piezoelectric element of another example of the present disclosure, the piezoelectric layer and the internal electrode layer are alternately laminated, and at least a laminated body having a planned breaking layer between adjacent piezoelectric layer layers and the above-mentioned Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned breaking layer has a Young ratio of another piezoelectric layer. The piezoelectric layers adjacent to each other via the planned breaking layer have a higher Young ratio than the other piezoelectric layers.
Further, the laminated piezoelectric element of another example of the present disclosure includes a laminate in which piezoelectric layers and internal electrode layers are alternately laminated, and at least a part of adjacent piezoelectric layers has a planned breaking layer. Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned breaking layer has a Young ratio of another piezoelectric layer. The piezoelectric layers adjacent to each other via the planned breaking layer are characterized in that the average particle size is smaller than the average particle size of the other piezoelectric layers.
Further, the laminated piezoelectric element of another example of the present disclosure includes a laminate in which piezoelectric layers and internal electrode layers are alternately laminated, and at least a part of adjacent piezoelectric layers has a planned breaking layer. Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned breaking layer has a Young ratio of another piezoelectric layer. It is characterized in that each piezoelectric layer adjacent to each other via the planned breaking layer is thicker than the other piezoelectric layers.

Further, the injection device of the present disclosure includes a container having an injection hole and a laminated piezoelectric element having the above configuration, and the injection hole is opened and closed by driving the laminated piezoelectric element.

Further, the fuel injection system of the present disclosure includes a common rail for storing high-pressure fuel, an injection device having the above configuration 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 the injection. It is characterized by including an injection control unit that gives a drive signal to the device.

According to the laminated piezoelectric element of the present disclosure, cracks cannot grow at once in the planned break layer and gradually grow, so that the external electrodes are less likely to be cut and noise is less likely to be generated.

Further, according to the injection device and the fuel injection system of the present disclosure, since the laminated piezoelectric element that is less likely to generate noise is provided, accurate and stable driving can be realized.

It is a schematic perspective view which shows an example of embodiment of a laminated piezoelectric element. It is the schematic sectional drawing of the example of the laminated body shown in FIG. It is the schematic sectional drawing of another example of the laminated body shown in FIG. It is the schematic sectional drawing of another example of the laminated body shown in FIG. It is the schematic sectional drawing which shows an example of an injection device. It is the schematic which shows an example of a fuel injection system.

Hereinafter, an example of the embodiment of the laminated piezoelectric element will be described with reference to the drawings.

FIG. 1 is a schematic perspective view showing an example of an embodiment of a laminated piezoelectric element, and FIG. 2 is a schematic cross-sectional view of an example of the laminated body shown in FIG.

In the laminated piezoelectric element 10 shown in FIGS. 1 and 2, the piezoelectric layer 1 and the internal electrode layer 2 are alternately laminated, and at least a part of the laminated piezoelectric element 1 having a planned breaking layer 4 is provided between adjacent piezoelectric layers 1. The body 3 is electrically connected to the internal electrode layer 2, and includes an external electrode 5 provided on the side surface of the laminated body 3.

The laminated body 3 is formed by alternately laminating the internal electrode layers 2 (the first internal electrode layer 21 and the second internal electrode layer 22) via the piezoelectric layer 1. The laminated body 3 has an active region in which the first internal electrode layer 21 and the second internal electrode layer 22 overlap when viewed from the stacking direction, and the first internal electrode layer 21 and the second interior when viewed from the stacking direction. It has an inert region that does not overlap with the electrode layer 22. Here, the active region is a site that expands or contracts in the stacking direction during driving. In addition, the inert region is a portion that does not expand or contract in the stacking direction during driving, or is difficult to expand.

The laminated body 3 has a portion in which the internal electrode layers 2 (the first internal electrode layer 21 and the second internal electrode layer 22) are alternately laminated via the piezoelectric layer 1, and the laminated body 3 has a portion of this portion. It has portions in which only the piezoelectric layer 1 is laminated at both ends in the stacking direction. The portion where only the piezoelectric layer 1 located at both ends in the stacking direction is laminated is also an inert region that does not expand or contract in the stacking direction during driving or is difficult to shrink.

The laminated body 3 has, for example, a rectangular parallelepiped shape having a length of 0.5 to 10 mm, a width of 0.5 to 10 mm, and a height of 1 to 100 mm. The shape of the laminated body 3 may be a hexagonal column shape, an octagonal column shape, a columnar shape, or the like.

The piezoelectric layer 1 is made of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite-type oxide made of _{lead zirconate titanate (PbZrO 3-} PbTIO _{3 ), lithium niobate (LiNbO 3} ), lithium tantalate (LiTaO ₃ ), and the like can be used. The thickness of the piezoelectric layer 1 is, for example, 3 to 250 μm.

The internal electrode layer 2 is formed by simultaneous firing with the ceramics forming the piezoelectric layer 1. The internal electrode layer 2 is composed of a first internal electrode layer 21 and a second internal electrode layer 22, and is alternately laminated with the piezoelectric layer 1 to sandwich the piezoelectric layer 1 from above and below. For example, by alternately arranging the first internal electrode layer 21 as the positive electrode and the second internal electrode layer 22 as the negative electrode or the ground electrode, a driving voltage is applied to the piezoelectric layer 1 sandwiched between them. .. As such a material, for example, a conductor containing a silver-palladium alloy as a main component, which can be fired at a low temperature, or a conductor containing copper, platinum, or the like can be used. The thickness of the first internal electrode layer 21 and the second internal electrode layer 22 is, for example, 0.1 to 5 μm.

In the example shown in the figure, the first internal electrode layer 21 and the second internal electrode layer 22 are alternately drawn out to the pair of opposite side surfaces of the laminated body 3, and are provided on the side surfaces of the laminated body 3, which will be described later. It is electrically connected to a pair of external electrodes 5. The end faces of both the first internal electrode layer 21 and the second internal electrode layer 22 may be exposed on the other pair of opposite side surfaces of the laminated body 3, and the first internal electrode layer 21 and the first internal electrode layer 22 may be exposed. Both end faces of the internal electrode layer 22 of 2 may be located inside away from the side surface without being exposed.

Further, the laminated body 3 has a planned breaking layer 4 between at least a part of adjacent piezoelectric layer 1 (11). Here, the planned breaking layer 4 is a layer for relaxing the stress generated in the laminated body 3 by driving the laminated piezoelectric element 10. Examples of the planned breaking layer 4 include a porous metal layer that does not function as an internal electrode layer, a metal layer that has been cracked in advance, and the like.

Further, as described above, the outer electrode 5 is provided on each of the pair of side surfaces reached by the end faces of either the first internal electrode layer 21 and the second internal electrode layer 22, and the first one is pulled out. It is electrically connected to the internal electrode layer 21 or the second internal electrode layer 22. The external electrode 5 can be produced by baking a conductive paste containing a metal such as Ag or Cu. Here, when the external electrode 5 is viewed in a cross section perpendicular to the side surface of the laminated body 3, the thickness of the external electrode 5 is, for example, 5 to 70 μm. Further, although not shown, a lead member is joined to the end of the external electrode 5, and an electrical connection with an external circuit is made via the lead member.

If necessary, a covering material may be provided on the side surface where both end faces of the first internal electrode layer 21 and the second internal electrode layer 22 are exposed or both end faces are not exposed. The covering material is made of, for example, a silicone resin, an epoxy resin, a nylon resin, or the like, and may be composed of not only a single layer but also a plurality of layers. This coating material has the effect of suppressing migration and discharge.

The Young's modulus of each of the piezoelectric layers 1 (11) adjacent to each other via the planned breaking layer 4 is different from that of the other piezoelectric layers 1 (12).

As a result, the Young's modulus of each of the piezoelectric layers 11 adjacent to each other via the planned breaking layer 4 is made different from the Young's modulus of the other piezoelectric layers 12, so that the piezoelectric layer adjacent to the planned breaking layer 4 is used. 11 is not easily deformed, and it is possible to prevent a large force from being momentarily concentrated on the planned break layer 4. Therefore, since the crack cannot grow at once in the planned break layer 4 and grows little by little, the external electrode 5 is less likely to be cut and noise is less likely to be generated. The Young's modulus of the piezoelectric layer 1 can be measured by cutting the laminate 3 and polishing the cross section to expose the piezoelectric layer 1 to be measured, and then using a nanoindentation test.

Each piezoelectric layer 1 (11) adjacent to each other via the planned break layer 4 has a Young's modulus different from that of the other piezoelectric layer 1 (12), so that the piezoelectric layer 1 (11) has a structure that is different from that of the other piezoelectric layer 1 (12). In each of the piezoelectric layers 11 adjacent to each other, the composition of the piezoelectric component excluding the same metal component as the metal component contained in the internal electrode layer 2 or the planned breaking layer 4 constitutes the other piezoelectric layer 12. It may be different from the composition of.

When the internal electrode layers 2 having the same poles are arranged above and below the two piezoelectric layers 11 arranged with the planned breaking layer 4 in between and no electric field is applied to both piezoelectric layers 11, an active region in which an electric field is applied. The piezoelectric layer 11 also deforms following the deformation of the piezoelectric layer 12, but cannot be deformed like a mass of piezoelectric material, and it is difficult for a large force to be instantaneously concentrated on the planned breaking layer 4. Therefore, cracks cannot grow at once in the planned fracture layer 4, but gradually grow, and noise is less likely to occur.

On the other hand, there is a case where internal electrode layers 2 having different poles are arranged above and below the two piezoelectric layers 11 arranged with the planned breaking layer 4 interposed therebetween and an electric field is applied to both piezoelectric layers 11. However, even if the piezoelectric layer 11 having a different composition of the piezoelectric components has the same displacement amount as the other piezoelectric layers 12, the displacement velocity (sensitivity) is different, so that the planned breaking layer 4 is instantaneously large. It is difficult to concentrate the force. Therefore, cracks cannot grow at once in the planned fracture layer 4, but gradually grow, and noise is less likely to occur.

Here, in the manufacturing process of the laminated piezoelectric element 10, an acceptor such as iron, manganese, chromium, or cobalt is added to the green sheet forming the piezoelectric layer 11, and the green sheet forming the other piezoelectric layer 12 is formed. It is possible not to add the acceptor. By doing so, oxygen vacancies are generated and a positive charge is generated in the crystal lattice, which ^{repels the positive of Zr 4+} or Ti ^{4+ at} the B site, thereby limiting the movement of the crystal lattice. A pinning effect can be obtained. Utilizing this effect, the piezoelectric layer 11 adjacent to the planned break layer 4 can be made into a layer having a higher Young's modulus than the other piezoelectric layers 12. At this time, the piezoelectric layer 11 and the piezoelectric layer 12 have different configurations of the piezoelectric components.

Further, in the manufacturing process of the laminated piezoelectric element 10, donors such as niobium and tungsten are added to the green sheet forming the piezoelectric layer 11, and the donor is not added to the green sheet forming the other piezoelectric layer 12. Can be done. By doing so, it is possible to suppress the formation of oxygen vacancies and suppress the increase in Young's modulus. As a result, the piezoelectric layer 11 adjacent to the planned break layer 4 can be made into a layer having a Young's modulus lower than that of the other piezoelectric layers 12. At this time, the piezoelectric layer 11 and the piezoelectric layer 12 have different configurations of the piezoelectric components.

The difference in the composition of the piezoelectric component between the piezoelectric layer 11 and the piezoelectric layer 12 is that after polishing the cross section of each layer, an energy dispersive X-ray spectroscope (EDS) or a wavelength dispersive X-ray analyzer ( It can be discriminated by measuring using WDS).

When the Young's modulus of the piezoelectric layer 12 other than the piezoelectric layer 11 adjacent to the planned break layer 4 is, for example, 40 to 60 Gpa, the piezoelectric layer 12 and the piezoelectric layer 11 adjacent to the planned break layer 4 The difference is, for example, 10 to 40 Gpa.

Here, each of the piezoelectric layers 11 adjacent to each other via the planned breaking layer 4 may have a Young's modulus larger or smaller than that of the other piezoelectric layers 12, but the Young's modulus of the piezoelectric layer 11 is large. The more difficult it is to deform, the greater the effect of suppressing the growth of cracks.

Further, the average particle size of each of the piezoelectric layers 11 adjacent to each other via the planned breaking layer 4 may be smaller than the average particle size of the other piezoelectric layers 12. When the average particle size of the piezoelectric particles constituting the piezoelectric layer 11 is small, the particles are densely arranged and the gaps between the particles are reduced, so that the particles are less likely to be deformed. When the average particle size of the other piezoelectric layer 12 is, for example, 1 to 5 μm, the average particle size of the piezoelectric layer 11 can be 75 to 95% of the average particle size of the piezoelectric layer 12. note that. For this average particle size, the cross section is observed with a scanning electron microscope (SEM), the number of particles contained in an arbitrary line segment and the length of the line segment contained in the particles are measured, and the total distance of these lengths is calculated. It can be obtained by dividing by the number of particles.

Further, as shown in FIG. 3, the respective piezoelectric layers 11 adjacent to each other via the planned break layer 4 may be thicker than the other piezoelectric layers 12. As the thickness of the piezoelectric layer 11 increases, the rigidity increases and it becomes difficult to deform, and the deformation force of the piezoelectric layer 12 becomes difficult to be transmitted to the planned breaking layer 4. The thickness of each piezoelectric layer 11 adjacent to each other via the planned break layer 4 is set to, for example, 105% to 250% of the thickness of the other piezoelectric layer 12.

Further, as shown in FIG. 4, the piezoelectric layers 11 adjacent to each other via the planned break layer 4 may have different thicknesses. Due to the difference in the thickness of the upper and lower piezoelectric layers 11 adjacent to each other via the planned breaking layer 4, the force is applied non-uniformly to the planned breaking layer 4, and the degree of deformation of these piezoelectric layers 11 is different. Therefore, the crack growth rate can be slowed down. As a result, cracks do not grow at once. The thickness of the other of the upper and lower piezoelectric layers 11 adjacent to each other via the planned break layer 4 is set to, for example, 105 to 200%.

Next, a method for manufacturing the laminated piezoelectric element of the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 1 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramics, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. Then, a ceramic green sheet is produced using this ceramic slurry by using a tape molding method such as a doctor blade method or a calendar roll method. The piezoelectric ceramic may be any one having piezoelectric properties, and for example, _{a perovskite-type oxide made of lead titanate (PbZrO 3-} PbTIO ₃ ) or the like can be used. Further, as the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP) and the like can be used.

Here, the ceramic green sheet to be the piezoelectric layer 11 adjacent to the upper and lower sides of the planned breaking layer 4 is assumed to have an acceptor such as iron, manganese, chromium or cobalt or a donor such as niobium or tungsten added, and other piezoelectric materials. The ceramic green sheet to be the body layer 12 can be free of acceptors and donors. By adding acceptors such as iron, manganese, chromium, and cobalt, it is possible to intentionally prepare a layer having a higher Young's modulus than the piezoelectric layer 12 other than the piezoelectric layers 11 above and below the planned break layer 4. .. On the other hand, by adding donors such as niobium and tungsten, it is possible to intentionally prepare a layer having a Young's modulus lower than that of the piezoelectric layer 12 other than the piezoelectric layers 11 above and below the planned break layer 4.

Next, a conductive paste to be the internal electrode layer 2 is produced. Specifically, for example, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a metal powder of a silver-palladium alloy. This conductive paste is applied onto the above-mentioned ceramic green sheet in the pattern of the internal electrode layer 2 by using, for example, a screen printing method.

In addition, a metal paste for the planned break layer 4 is prepared. This metal paste may be, for example, a metal powder containing silver as a main component, to which a binder, a plasticizer, etc. are added and mixed, and is a metal powder made of silver palladium having a higher ratio of silver than the conductor paste for the internal electrode 2. A binder, a plasticizing agent, or the like may be added and mixed. This metal paste is applied to the above ceramic green sheet in the pattern of the planned break layer 4 by using, for example, a screen printing method.

Further, a plurality of ceramic green sheets printed with these conductive pastes and metal pastes are laminated, debindered at a predetermined temperature, and then fired at a temperature of 900 to 1200 ° C. to grind a surface grinding machine or the like. It is manufactured by subjecting it to a grinding process so that it has a predetermined shape.

The piezoelectric layer 11 and the piezoelectric layer 12 may have a structure in which the composition of the piezoelectric component is different from that of the above-mentioned acceptor or donor, but the lead zirconate and two lead zirconate titans having different titanium ratios may be added. Ceramic green sheets may be prepared using lead acid (PZT) powder.

Further, in order to make the average particle size of the piezoelectric layer 11 smaller than the average particle size of the other piezoelectric layers 12, the particle size is increased by lengthening the crushing time of the lead zirconate titanate (PZT) powder. A small powder of Should be used.

Further, in order to make the thickness of each piezoelectric layer 11 adjacent to each other via the planned breaking layer 4 thicker than that of the other piezoelectric layer 12, the thickness of the ceramic green sheet to be the piezoelectric layer 11 is made piezoelectric. It may be thicker than the thickness of the ceramic green sheet to be the body layer 12.

Further, in order to configure the piezoelectric layers 11 adjacent to each other via the planned break layer 4 to have different thicknesses, the thickness of the ceramic green sheet to be the respective piezoelectric layers 11 may be different.

The laminate 3 is not limited to the one produced by the above-mentioned production method, and any production can be performed as long as the laminate 3 formed by laminating a plurality of the piezoelectric layer 1 and the internal electrode layer 2 can be produced. It may be produced by a method.

Next, the external electrode 5 is formed. Specifically, a conductive paste containing a metal such as Ag or Cu is used. This is baked into the region where one end face of the first internal electrode layer 21 and the second internal electrode layer 22 on the side surface of the laminated body 3 is pulled out, and an external electrode 5 having a thickness of, for example, 5 to 70 μm is formed. Form. It can be formed by controlling it to a predetermined thickness and width by screen printing or a dispense method. For example, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer, and a solvent to a mixture of conductive particles containing silver as a main component and glass is used. Then, the pattern of the external electrode 5 is printed on the side surface of the laminated body 3 by a screen printing method, dried, and then baked at a temperature of 650 to 750 ° C.

Next, if necessary, a covering material is formed. Specifically, for example, a resin such as epoxy, silicone, or nylon is used, and the resin is controlled to a predetermined thickness by printing or a dispensing method.

After that, a DC electric field of 0.1 to 3 kV / mm is applied to the external electrode 5 to polarize the piezoelectric layer 1 constituting the laminated body 3, thereby completing the laminated piezoelectric element 10.

Next, an example of the injection device of the present embodiment will be described.

FIG. 5 is a schematic cross-sectional view showing an example of the injection device of the present embodiment. As shown in FIG. 5, in the injection device 19 of this example, the laminated piezoelectric element 10 of the above example is housed inside a storage container 23 as a container having an injection hole 21 at one end.

A needle valve 25 capable of opening and closing the injection hole 21 is provided in the storage container 23. A fluid passage 27 is provided in the injection hole 21 so as to be able to communicate with the needle valve 25 in accordance with the movement of the needle valve 25. The fluid passage 27 is connected to an external fluid supply source, and the fluid is constantly supplied to the fluid passage 27 at a high pressure. Therefore, when the needle valve 25 opens the injection hole 21, the fluid supplied to the fluid passage 27 is discharged from the injection hole 21 to an external or adjacent container, for example, a fuel chamber (not shown) of an internal combustion engine. It is configured in.

The upper end of the needle valve 25 has a large inner diameter, and is a piston 31 that can slide with the cylinder 29 formed in the storage container 23. Then, in the storage container 23, the laminated piezoelectric element 10 of the above-described example is stored in contact with the piston 31.

In such an injection device 19, the injection hole 21 is opened and closed by driving the laminated piezoelectric element 10. Specifically, when the laminated piezoelectric element 10 is expanded by applying a voltage, the piston 31 is pressed, the needle valve 25 closes the fluid passage 27 leading to the injection hole 21, and the fluid supply is stopped. Further, when the application of the voltage is stopped, the laminated piezoelectric element 10 contracts, the disc spring 33 pushes back the piston 31, the fluid passage 27 is opened, the injection hole 21 communicates with the fluid passage 27, and the injection hole 21 communicates with the injection hole 21. The fluid is injected.

The fluid passage 27 may be opened by applying a voltage to the laminated piezoelectric element 10, and the fluid passage 27 may be closed by stopping the application of the voltage.

Further, the laminated piezoelectric element 10 does not necessarily have to be inside the storage container 23, and the pressure for controlling the injection of the fluid is applied to the inside of the storage container 23 by driving the laminated piezoelectric element 10. Just do it. In the injection device 19 of this example, the fluid includes various liquids and gases such as conductive paste in addition to fuel and ink. By using the injection device 19 of this example, the flow rate of the fluid and the injection timing can be stably controlled for a long period of time.

Further, if the injection device 19 of this example adopting the laminated piezoelectric element 10 of the above example is used for the internal combustion engine, fuel is injected more accurately into the combustion chamber of the internal combustion engine such as an engine as compared with the conventional injection device. be able to.

Next, an example of the fuel injection system of the present embodiment will be described.

FIG. 6 is a schematic view showing an example of the fuel injection system of the present embodiment. As shown in FIG. 6, the fuel injection system 35 of this example includes a common rail 37 that stores high-pressure fuel as a high-pressure fluid, and a plurality of injection devices 19 of the above-mentioned example that inject the high-pressure fluid stored in the common rail 37. A pressure pump 39 for supplying a high-pressure fluid to the common rail 37 and an injection control unit 41 for giving a drive signal to the injection device 19 are provided.

The injection control unit 41 controls the amount and timing of injection of the high-pressure fluid based on external information or an external signal. For example, when the fuel injection system 35 of this example is used for fuel injection of an engine, the amount and timing of fuel injection can be controlled while detecting the state of the combustion chamber of the engine with a sensor or the like. The pressure pump 39 serves to supply fluid fuel from the fuel tank 43 to the common rail 37 at high pressure. For example, in the case of the fuel injection system 35 of an engine, the fluid fuel is sent to the common rail 37 at a high pressure of 1000 to 2000 atm (about 101 MPa to about 203 MPa), preferably 1500 to 1700 atm (about 152 MPa to about 172 MPa). The common rail 37 stores the high-pressure fuel sent from the pressure pump 39 and appropriately sends it to the injection device 19. As described above, the injection device 19 injects a constant fluid from the injection hole 21 into an external or adjacent container. For example, when the target for injecting and supplying fuel is an engine, high-pressure fuel is injected into the combustion chamber of the engine in the form of mist from the injection holes 21.

According to the fuel injection system 35 of this example, the desired injection of high-pressure fuel can be stably performed.

The laminated piezoelectric element of this embodiment was manufactured as follows.

First, a slurry in which a piezoelectric ceramic calcined powder containing lead titanate (PbZrO3-PbTiO3) having an average particle size of 0.4 μm as a main component, a binder, and a plasticizer was mixed was prepared, and the thickness was prepared by a doctor blade method. A ceramic green sheet to be an 85 μm piezoelectric layer was produced.

On one side of this ceramic green sheet, a conductive paste obtained by adding a binder to a silver-palladium alloy (95% by mass of silver-5% by weight of palladium) was applied, and a ceramic green sheet formed by a screen printing method on a portion to be an internal electrode layer. Made. Further, a ceramic green sheet was prepared in which a metal paste of a silver-palladium alloy (99% by mass of silver-1% by weight of palladium) was formed on one side of the ceramic green sheet by a screen printing method on a portion to be a planned breaking layer. Here, the number of layers was 300, and the planned break layers were arranged in the 30th, 100th, and 200th layers.

Here, a ceramic green sheet to be a piezoelectric layer adjacent to the planned break layer to which an acceptor was added (Sample Nos. 2 to 5) and a sample to which an acceptor was not added (Sample No. 1) were prepared.

Further, the crushing time of the calcined powder of the piezoelectric ceramic used for the ceramic green sheet which is the piezoelectric layer adjacent to the planned breaking layer is lengthened so that the average particle size is 0.3 μm, and the average particle size of the other piezoelectric layers is increased. A material having a size of 0.4 μm (Sample No. 3) was prepared.

Further, a piezoelectric layer having a thickness of 170 μm adjacent to the planned break layer and another piezoelectric layer having a thickness of 85 μm (Sample No. 4) was prepared.

Further, among the piezoelectric layers adjacent to the planned breaking layer, those having a thickness of the upper piezoelectric layer of 85 μm and a thickness of the lower piezoelectric layer of 170 μm were prepared (Sample No. 5).

Then, this laminated body was fired. The firing was carried out by holding at 800 ° C., sintering at 950 ° C., further heating and holding at 900 ° C. for 1 hour, and then cooling.

Next, the silver glass paste was printed on the side surface of the laminate to be the external electrode forming surface, dried, and then baked at 700 ° C. for 30 minutes to form the external electrode 15.

After that, a lead wire is connected to the external electrode, and a DC electric field of 3 kV / mm is applied to the external electrodes of the positive electrode and the negative electrode via the lead wire for 15 minutes to perform polarization treatment. A piezoelectric element was manufactured.

When a DC voltage of 170 V was applied to the obtained laminated piezoelectric element, a displacement amount was obtained in the laminated direction in all the piezoelectric actuators.

^{Further, the piezoelectric actuator was continuously driven up to 1 × 10 9} times by applying an AC voltage of 0 to + 170 V at a frequency of 150 Hz at room temperature, and the number of times noise was generated was measured. The number of times noise was generated was counted by monitoring the drive waveform by connecting an oscilloscope in parallel with the drive circuit via a measurement probe. The results are shown in Table 1.

From the results shown in Table 1, it can be seen that according to the laminated piezoelectric element of the present embodiment, the number of times of noise generation is small and the crack growth rate of the planned break layer can be slowed down.

10 ... Laminated piezoelectric element 1 ... Piezoelectric layer 11 ... First piezoelectric layer 12 ... Second piezoelectric layer 2 ... Internal electrode layer 21 ... First internal Electrode layer 22 ... Second internal electrode layer 3 ... Laminated body 4 ... Scheduled breaking layer 5 ... External electrode 19 ... Injection device 21 ... Injection hole 23 ... Storage container 25・ ・ ・ Needle valve 27 ・ ・ ・ Fluid passage 29 ・ ・ ・ Cylinder 31 ・ ・ ・ Piston 33 ・ ・ ・ Counter spring 35 ・ ・ ・ Fuel injection system 37 ・ ・ ・ Common rail 39 ・ ・ ・ Pressure pump 41 ・ ・ ・ Injection Control unit 43 ・ ・ ・ Fuel tank

Claims (7)

A laminate in which the piezoelectric layer and the internal electrode layer are alternately laminated, and at least a part of the laminate having a planned break layer between adjacent piezoelectric layers,
Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned break layer has a Young's modulus of another piezoelectric material. Different from the layer ,
Each piezoelectric layer adjacent to each other via the planned breaking layer has a composition of a piezoelectric component excluding the same metal component as the metal component contained in the internal electrode layer or the planned breaking layer of another piezoelectric layer. A laminated piezoelectric element characterized in that the composition of the constituent piezoelectric components is different. A laminate in which the piezoelectric layer and the internal electrode layer are alternately laminated, and at least a part of the laminate having a planned break layer between adjacent piezoelectric layers,
Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned break layer has a Young's modulus of another piezoelectric material. Different from the layer,
Said predetermined breaking layer each piezoelectric layers adjacent to each other via shall be the wherein the Young's modulus is larger than the other piezoelectric layer product layer piezoelectric element. A laminate in which the piezoelectric layer and the internal electrode layer are alternately laminated, and at least a part of the laminate having a planned break layer between adjacent piezoelectric layers,
Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned break layer has a Young's modulus of another piezoelectric material. Different from the layer,
Said predetermined breaking layer each piezoelectric layers adjacent to each other via shall be the wherein the average particle diameter is smaller than the average particle diameter of the other piezoelectric layer product layer piezoelectric element. A laminate in which the piezoelectric layer and the internal electrode layer are alternately laminated, and at least a part of the laminate having a planned break layer between adjacent piezoelectric layers,
Each piezoelectric layer electrically connected to the internal electrode layer and provided with an external electrode provided on the side surface of the laminated body and adjacent to each other via the planned break layer has a Young's modulus of another piezoelectric material. Different from the layer,
It said predetermined breaking layer each piezoelectric layers adjacent to each other through the you wherein it is thicker than the other piezoelectric layer thickness product layer piezoelectric element. The laminated piezoelectric element according to any one of claims 1 to 4 , wherein the piezoelectric layers adjacent to each other via the planned breaking layer have different thicknesses. A container having an injection hole and the laminated piezoelectric element according to any one of claims 1 to 5 are provided, and the injection hole is opened and closed by driving the laminated piezoelectric element. Injection device. Providing a common rail for storing high pressure fuel, an ejection apparatus according to claim 6 which injects the high-pressure fuel stored in the common rail, a pressure pump for supplying serial high-pressure fuel to the common rail, a drive signal to the injection device A fuel injection system characterized by including an injection control unit.

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