JP2010034271A - Stacked piezoelectric device, injection device using this, and fuel injection system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a stacked piezoelectric element without displacement performance deterioration at the time of driving and capable of maintaining an electrical contact and a physical connection even though a scheduled-break-layer is broken to ensure a longer operating life. <P>SOLUTION: The stacked piezoelectric element 1 includes: a piezoelectric layer 2 and an internal electrode layer 6 alternately laminated; a laminated body 7 including a scheduled-break-layer 3 preferentially broken earlier than the internal electrode layer 6 at the time of driving to relax stress; and a pair of external electrode 4 junctioned to the side surface of the laminated body 7 and electrically connected to the internal electrode layer 6. A linear conductor 5 obliquely passing the area of the scheduled-break-layer 3 is formed on the surface of the external electrode 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laminated piezoelectric element used as, for example, a drive element (piezoelectric actuator) utilizing a piezoelectric effect, a sensor element, a circuit element, or the like.

  Conventionally, as a driving element (piezoelectric actuator) using a piezoelectric effect, for example, it is applied to an optical device such as a fuel injection device for an automobile engine, a liquid injection device such as an ink jet device, and an exposure device used for manufacturing a semiconductor element. Examples thereof include a precision positioning device and a vibration preventing device.

  Examples of the sensor element using the piezoelectric effect 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 using the piezoelectric effect include a piezoelectric gyro, a piezoelectric switch, a piezoelectric transformer, and a piezoelectric breaker.

  In Patent Document 1, a laminate in which three or more piezoelectric ceramic layers are sandwiched with an internal electrode layer interposed therebetween, and an internal electrode layer is formed on each side of each side of the laminate so as to be a counter electrode. A laminated piezoelectric ceramic formed by an insulating layer and a pair of external electrodes that cover the upper part of each of the insulating layers and electrically connect the internal electrode layers every other layer. A multilayer piezoelectric ceramic is described which is a multilayer piezoelectric ceramic simple substance provided with either one of an internal connection conductor and a whole-surface conductor for connecting the parts.

  The internal connection conductor that connects at least two locations on the external electrode in Patent Document 1 includes at least one of a metal conductor such as a lead wire and a metal rigid body.

With the above configuration, on the external electrode to which the internal connection conductor is connected, for example, when there are two places at the end of the external electrode, the cutting of the intermediate part of the external electrode does not affect the characteristics, In addition, when a large number of connection locations are provided by a large number of internal connection conductors, or when the entire surface of the external electrode is covered with a conductor, the external electrode is strengthened, and the effect of suppressing the occurrence of damage to the external electrode can be obtained. .
JP 2000-269562 A

  However, a multilayer piezoelectric element using a multilayer body in which piezoelectric layers and internal electrode layers are alternately stacked and includes a planned fracture layer that relaxes stress by being preferentially fractured over the internal electrode layer during driving. In this case, when the planned rupture layer breaks during the driving, the laminated piezoelectric element may be separated, so using an auxiliary member made of a metal conductor such as a lead wire as described in Patent Document 1, It is necessary to maintain the laminated structure of the laminated body. However, by using the auxiliary member, there is a possibility that desirable displacement behavior at the time of driving the multilayer piezoelectric element may be hindered.

  Therefore, the present invention has been completed in view of the above-mentioned conventional problems, and the object thereof is not to impair the displacement performance during driving of the multilayer piezoelectric element, and even if the planned fracture layer is fractured. However, electrical contact and physical connection are maintained, and as a result, a multilayer piezoelectric element having a long life is obtained.

  The multilayer piezoelectric element of the present invention includes a multilayer body including piezoelectric layers and internal electrode layers that are alternately stacked and a planned fracture layer that relaxes stress by being preferentially fractured over the internal electrode layer during driving. And a pair of external electrodes joined to the side surface of the multilayer body and electrically connected to the internal electrode layer, wherein the external electrode has a surface of the predetermined fracture layer on the surface. A linear conductor that obliquely passes through the portion is formed.

  In addition, the multilayer piezoelectric element of the present invention is preferably adjacent to the linear conductor and the first planned fracture layer, where θ is an inclination angle formed between the linear conductor and the first planned fracture layer. The inclination angle formed with the second planned fracture layer is 180 ° −θ.

  In the multilayer piezoelectric element of the present invention, it is preferable that the pair of external electrodes have a first linear conductor formed on one side and a second linear conductor formed on the other side, and the first linear conductor is formed. The inclination angle formed between the second linear conductor and the one predetermined fracture layer is 180 ° −θ, where θ is the inclination angle formed between the second linear conductor and the one predetermined fracture layer. It is.

  In the multilayer piezoelectric element of the present invention, it is preferable that the linear conductor has a plurality of bent portions at portions between adjacent planned fracture layers on the surface of the external electrode. It is what.

  An injection device according to the present invention includes a container having an ejection hole and the multilayered piezoelectric element according to any one of claims 1 to 4, and a liquid filled in the container is formed of the multilayered piezoelectric element. The ink is discharged from the injection hole by driving.

  A fuel injection system according to the present invention includes a common rail that stores high-pressure fuel, an injection device according to claim 5 that injects the high-pressure fuel stored in the common rail, a pressure pump that supplies the high-pressure fuel to the common rail, An injection control unit that provides a drive signal to the injection device is provided.

  The multilayer piezoelectric element of the present invention includes a laminate including piezoelectric layers and internal electrode layers that are alternately stacked and a planned fracture layer that relaxes stress by being preferentially fractured over the internal electrode layers during driving. A laminated piezoelectric element including a pair of external electrodes joined to the side surface of the multilayer body and electrically connected to the internal electrode layer, the external electrode passing obliquely through a portion of the predetermined fracture layer on the surface Therefore, the linear conductor acts like a spring against the expansion / contraction and compression of the laminate in the longitudinal direction, and the linear conductor breaks against the expected fracture layer. Therefore, it is possible to prevent the planned fracture layer from being broken all at once from the portion of the linear conductor during driving. Therefore, as a result of the linear conductor acting so that the fracture of the planned fracture layer proceeds gradually, the durability of the multilayer piezoelectric element is improved. In addition, the linear conductor acting like a spring makes it difficult for the displacement performance of the multilayer piezoelectric element to be impaired, and even if the expected fracture layer is broken, the electrical contact and the physical connection are maintained, so a long life It becomes.

  In the multilayer piezoelectric element of the present invention, it is preferable that the second angle adjacent to the linear conductor and the first predetermined fracture layer when the inclination angle between the linear conductor and the first predetermined fracture layer is θ. Since the inclination angle formed with the planned fracture layer is 180 ° −θ, the starting point of the fracture can be prevented from overlapping in the vertical direction in the adjacent planned fracture layer. As a result, the progress of the entire fracture of the planned fracture layer can be further delayed, and the durability of the multilayer piezoelectric element is further improved.

  In the multilayer piezoelectric element of the present invention, it is preferable that the pair of external electrodes have a first linear conductor formed on one side and a second linear conductor formed on the other side, and the first linear conductor is identical to the first linear conductor. When the inclination angle formed with the predetermined fracture layer is θ, the inclination angle formed between the second linear conductor and the one predetermined fracture layer is 180 ° −θ. The passage portion of the first linear conductor and the passage portion of the second linear conductor are prevented from overlapping when viewed from the side surface on the first linear conductor side or the side surface on the second linear conductor side. be able to. As a result, it is possible to prevent the starting points of breakage caused by the passage portions of the first and second linear conductors from overlapping each other when viewed from the side surface in one planned fracture layer. Therefore, the progress of the entire rupture of the planned rupture layer can be further delayed, and the durability of the multilayer piezoelectric element is further improved.

  In the multilayer piezoelectric element of the present invention, preferably, the linear conductor has a plurality of bent portions at portions between adjacent planned fracture layers on the surface of the external electrode. The spring property of the linear conductor acting on the is improved. As a result, the displacement performance of the multilayer piezoelectric element is less likely to be impaired.

  The ejection device of the present invention includes a container having ejection holes and the multilayer piezoelectric element of the present invention, and the liquid filled in the container is discharged from the ejection holes by driving the multilayer piezoelectric element. Since the multilayer piezoelectric element having excellent displacement characteristics and durability is used, the liquid piezoelectric device has high durability with excellent controllability of liquid ejection.

  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 high-pressure fuel stored in the common rail, a pressure pump that supplies high-pressure fuel to the common rail, and a drive signal to the injection device. Since it has an injection control unit that provides the liquid, it has high durability with excellent controllability of liquid injection.

  Hereinafter, an example of a laminated piezoelectric element (hereinafter also referred to as an element) of the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing the multilayer piezoelectric element of the present embodiment. In FIG. 1, 1 is a laminated piezoelectric element, 2 is a piezoelectric layer, 3 is a planned fracture layer, 4 is an external electrode, 5 is a linear conductor, 6 is an internal electrode layer, and 7 is a laminate.

  In the multilayer piezoelectric element 1 of the present embodiment, the piezoelectric layers 2 and the internal electrode layers 6 are alternately laminated, and the stress is relieved by breaking preferentially over the internal electrode layers 6 during driving. A laminated piezoelectric element 1 including a laminated body 7 including a fault 3 and a pair of external electrodes 4 joined to the side surface of the laminated body 7 and electrically connected to the internal electrode layer 6, the external electrode 4 Is formed with a linear conductor 5 obliquely passing through a portion of the planned fracture layer 3 on the surface.

  With the above configuration, the linear conductor 5 acts as if it is a spring with respect to the longitudinal expansion / contraction and compression of the multilayer body 7, and the linear conductor 5 serves as a starting point of destruction for the expected fracture layer 3. For this reason, it is possible to prevent the planned fracture layer 3 from being broken from the portion of the linear conductor 5 at a time during driving. Therefore, the linear conductor 5 acts so that the fracture of the planned fracture layer 3 gradually proceeds, and as a result, the durability of the multilayer piezoelectric element 1 is improved. Further, the linear conductor 5 acting like a spring makes it difficult for the displacement performance of the multilayer piezoelectric element 1 to be impaired, and even if the expected fracture layer 3 is broken, the electrical contact and physical connection are maintained. Long life.

  A plurality of planned fracture layers 3 are formed, and the adjacent planned fracture layers 3 are separated from each other so that a plurality of internal electrode layers 6 and piezoelectric layers 2 exist between the adjacent planned fracture layers 3. Is formed.

The piezoelectric layer 2 is made of piezoelectric ceramics or the like mainly composed of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ), and has a thickness of about 50 to 100 μm. The internal electrode layer 6 is made of a fired body of metal powder such as silver-palladium and has a thickness of about 1 to 10 μm.

  The planned rupture layer 3 is made of a material containing the same piezoelectric ceramics as the piezoelectric layer 2, or a metal, and has a thickness of about 50 to 100 μm. Moreover, the planned fracture | rupture layer 3 is formed with the following method, for example.

  That is, a porous layer including a large number of independent metal particles is formed as the planned fracture layer 3. For example, after carbon powder is contained in the conductive paste and the carbon powder disappears during firing, pattern printing is performed so as to form a dot pattern when printing the conductive paste, or after the conductive paste is printed and dried There is a method of roughening the printing surface by dry ice blasting.

  Further, by changing the metal component ratio between the conductive paste of the planned fracture layer 3 to be a porous layer and the conductive paste of the internal electrode layer 6, the concentration difference is used during firing to start from the planned fracture layer 3. A method in which the metal is made porous by diffusing is preferred. In particular, when a conductive paste mainly composed of silver-palladium is used and the silver concentration of the expected fracture layer 3 to be a porous layer is made higher than the silver concentration of the internal electrode layer 6, silver forms a liquid phase during firing. In addition, since it can easily move between the piezoelectric particles of the piezoelectric layer 2, it is preferable because an extremely uniform porous layer is formed.

  The external electrode 4 is made of a sintered body of silver powder and glass powder, and has a thickness of about 5 to 100 μm.

  The linear conductor 5 is made of a highly conductive metal such as copper, silver, gold, or an alloy containing one or more of them, and is fixed on the external electrode 4 with a conductive adhesive or the like. The thickness of the linear conductor 5 is preferably about 10 to 100 μm. By setting the thickness within this range, it is possible to prevent the linear conductor 5 from becoming too thin and increase in resistance, and the linear conductor 5 becomes too thick and strong. It becomes possible to prevent the spring property from being lowered.

  The width of the linear conductor 5 is preferably about 10 to 100 μm. By setting the width within this range, it is possible to suppress the resistance of the linear conductor 5 from being excessively thin and increase the resistance and to be easily disconnected. Can be prevented from becoming too wide to increase the strength and lowering the spring property.

  The linear conductor 5 may be a metal wire such as a lead wire having a circular longitudinal cross-sectional shape. Further, the linear conductor 5 may be a metal wire or a metal band having a vertical cross-sectional shape of a quadrangle, a pentagon or more polygonal wire.

  In addition, as shown in FIG. 1, the multilayer piezoelectric element 1 according to the present embodiment preferably has a linear conductor 5 when the inclination angle formed between the linear conductor 5 and the first planned fracture layer 3 is θ. And the second planned fracture layer 3 adjacent to the first planned fracture layer 3 is 180 ° −θ. That is, the inclination direction of the linear conductor 5 with respect to the first planned fracture layer 3 is alternately opposite in the adjacent second planned fracture layer 3. In this case, it is possible to prevent the rupture starting points from overlapping in the vertical direction in the adjacent planned rupture layer 3. As a result, the progress of the entire fracture of the planned fracture layer 3 can be further delayed, and the durability of the multilayer piezoelectric element 1 is further improved.

  The inclination angle θ formed between the linear conductor 5 and the planned fracture layer 3 is preferably about 20 ° to 80 °. By setting it within this range, it is possible to prevent the linear conductor 5 from becoming too long and increase the resistance, and to maintain a good spring property of the linear conductor 5.

  In the multilayer piezoelectric element 1 of the present embodiment, preferably, the pair of external electrodes 4 includes the first linear conductor 5 on one side and the second linear conductor 5 on the other side. When the inclination angle formed between the first linear conductor 5 and the one predetermined fracture layer 3 is θ, the inclination angle formed between the second linear conductor 5 and the first predetermined fracture layer 3 is 180 ° −θ. In this case, the passage portion of the first linear conductor 5 and the passage portion of the second linear conductor 5 with respect to the one predetermined fracture layer 3 are the side surface on the first linear conductor 5 side or the second side. It can be made not to overlap when seen from the side of the linear conductor 5 side. As a result, it is possible to prevent the starting points of breakage caused by the passage portions of the first and second linear conductors 5 from overlapping with each other when viewed from the side. Therefore, the progress of the entire rupture of the planned rupture layer 3 can be further delayed, and the durability of the multilayer piezoelectric element 1 is further improved.

  The pair of external electrodes 4 has a first linear conductor 5 formed on one side and a second linear conductor 5 formed on the other side, and the first linear conductor 5 obliquely crosses the portion of the expected fracture layer 3. The second linear conductor 5 may be formed in a straight line shape.

  Moreover, in the multilayer piezoelectric element 1 of the present embodiment, the linear conductor 5 preferably has a plurality of bent portions at a portion between adjacent planned fracture layers 3 on the surface of the external electrode 4. . In this case, the spring property of the linear conductor acting like a spring is improved. As a result, the displacement performance of the multilayer piezoelectric element 1 is less likely to be impaired.

  In the multilayer piezoelectric element 1 of the present embodiment, the linear conductor 5 may have a curved bent portion. In this case, breakage of the linear conductor 5 at the bent portion is suppressed, and the spring property of the linear conductor 5 is improved.

  Moreover, as for the linear conductor 5, the site | part which passes the planned fracture | rupture layer 3 may be formed wider than other parts. In this case, the passage portion of the planned fracture layer 3 in the linear conductor 5 can be further suppressed from becoming the starting point of the fracture of the planned fracture layer 3.

  In addition, the linear conductor 5 has a width and / or thickness of a portion corresponding to an active portion that is a displacement portion of the multilayer body 7, and a width and / or thickness of a portion corresponding to an inactive portion that is a non-displacement portion of the multilayer body 7. Or it is good that it is larger than thickness. In this case, the occurrence of breakage, disconnection, etc. of the linear conductor 5 can be effectively suppressed.

  Next, the manufacturing method of the multilayer piezoelectric element 1 according to the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 2 is produced. Specifically, a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer are mixed to prepare a slurry. Then, a ceramic green sheet is produced from the slurry by using a known tape forming method such as a doctor blade method or 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 6 is produced. Specifically, a conductive paste can be produced 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 body layer 2 and the internal electrode layer 6 which were laminated | stacked alternately can be formed by baking.

  The planned fracture layer 3 is formed by the method described above.

  Thereafter, the external electrode 4 is formed on the outer surface of the multilayer body 7 of the multilayer piezoelectric element 1 so as to be electrically connected to the internal electrode layer 6 whose end is exposed. The external electrode 4 can be obtained by adding a binder to the silver powder and the 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 electrode 4 is formed is immersed in a resin solution containing an exterior resin made of silicone rubber. Then, the silicone resin solution is vacuum degassed to bring the silicone resin into close contact with the concavo-convex portions on the outer peripheral side surface of the laminate 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. And the linear conductor 5 as an electricity supply part is connected to the external electrode 4 with a conductive adhesive (not shown).

  Next, a direct current electric field of 0.1 to 3 kV / mm is applied to the piezoelectric layer 2 by the internal electrode layer 6 from the pair of external electrodes 4 via the linear conductors 5 to polarize the piezoelectric layer 2 of the multilayer body 7. By doing so, the laminated piezoelectric element 1 is completed.

  Then, the linear conductor 5 is connected to an external voltage supply unit (not shown), and a voltage is applied to the piezoelectric layer 2 by the internal electrode layer 6 via the linear conductor 5 and the external electrode 4, thereby each piezoelectric element. The body layer 2 can be greatly displaced 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. 2 is a schematic cross-sectional view showing an example of an embodiment of the injection device of the present invention.

  As shown in FIG. 2, in the injection device 19 of this example, the multilayer piezoelectric element 1 represented by the example of the above embodiment is stored inside a storage container (container) 23 having an injection hole 21 at one end. ing.

  A needle valve 25 that can open and close the injection hole 21 is provided in the storage container 23. A fluid passage 27 is disposed in the injection hole 21 so as to be able to communicate with the movement of the needle valve 25. The fluid passage 27 is connected to an external fluid supply source, and fluid is constantly supplied at a high pressure. Accordingly, when the needle valve 25 opens the injection hole 21 by driving the laminated piezoelectric element 1, the fluid supplied to the fluid passage 27 is transferred to the outside of the injection hole 21 or a container adjacent to the injection hole 21, such as an internal combustion engine. It is ejected into a fuel chamber (not shown).

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

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

  The fluid ejection operation is as follows. By applying a voltage to the multilayer piezoelectric element 1, the fluid passage 27 is opened to discharge the fluid from the ejection hole 21, and the application of the voltage is stopped to close the fluid passage 27. Thus, the discharge of the fluid may be stopped.

  Further, the ejection device 19 of the present invention includes a container (storage container) 23 having an ejection hole 21 and the multilayer piezoelectric element 1 of the present embodiment, and the fluid filled in the container 23 is used as the multilayer piezoelectric element. 1 may be configured to be ejected from the injection hole 21 by driving 1. That is, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 23, and the pressure for supplying and stopping the fluid to the injection hole 21 is applied to the inside of the container 23 by driving the multilayer piezoelectric element 1. It suffices to be configured. The fluid is not only supplied to the injection hole 21 through the fluid passage 27 but also provided with a portion for temporarily storing the fluid at an appropriate location in the container 23 so that the fluid filled in the container 23 can be stored. You may make it discharge from the injection hole 21. FIG.

  In the present embodiment, the fluid includes various liquid materials (such as conductive paste) and gas in addition to fuel or ink. By using the ejection device 19 for these fluids, the flow rate and ejection timing of the fluid can be controlled.

  When the injection device 19 of the present embodiment that employs the multilayer piezoelectric element 1 of the present embodiment is used in an internal combustion engine, the fuel is supplied to the combustion chamber of the internal combustion engine such as an engine for a longer period of time compared to the conventional injection device. Can be sprayed with high accuracy.

  Next, the fuel injection system of the present embodiment will be described. FIG. 3 is a cross-sectional view showing an example of an embodiment of the fuel injection system of the present embodiment.

  As shown in FIG. 3, the fuel injection system 35 includes a common rail 37 that stores high-pressure fuel, a plurality of injection devices 19 that inject high-pressure fuel stored in the common rail 37, and a pressure pump that supplies high-pressure fuel to the common rail 37. 39 and an injection control unit 41 that gives a drive signal to the injection device 19.

  The ejection control unit 41 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 41 used for engine fuel injection, the amount and timing of fuel injection are controlled while sensing the state of the combustion chamber of the engine with a sensor or the like.

  The pressure pump 39 plays a role of feeding fluid fuel from the fuel tank 43 to the common rail 37 at a high pressure. For example, in the case of an engine fuel injection system, fluid is fed into the common rail 37 at a pressure of about 1000 to 2000 atmospheres, preferably about 1500 to 1700 atmospheres.

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

  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. 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.

A piezoelectric actuator provided with a multilayer piezoelectric element was produced as follows. First, the average particle diameter was prepared calcined powder of piezoelectric ceramic composed mainly of 0.4μm lead zirconate titanate _{(PbZrO 3} -PbTiO 3), a binder, and a slurry obtained by mixing a plasticizer. Using this slurry, a ceramic green sheet serving as the piezoelectric layer 2 having a thickness of 150 μm was prepared by a doctor blade method.

  In addition, a binder was added to the silver-palladium alloy to produce a conductive paste to be the internal electrode layer 6.

  The conductive paste was printed on one side of the ceramic green sheet by a screen printing method, and 100 sheets on which these conductive pastes were printed were laminated. And the laminated body 7 was obtained by baking at about 11100 degreeC.

  In addition, the expected fracture layer 3 is produced by preparing a conductive paste in which acrylic beads, which are components in which a binder or resin scatters, are mixed in the above conductive paste, and this conductive paste is screen-printed on a ceramic green sheet. It formed by the method of using and arrange | positioning.

  Next, after the obtained laminated body 7 is ground into a predetermined quadrangular prism shape using a surface grinder, the silver-glass conductive material that becomes the external electrode 4 is formed on the side surface of the laminated body 7 that forms the external electrode 4. The adhesive paste was printed and baked at 700 ° C. In addition, the softening point of the glass contained in the silver-glass paste at this time was 730 degreeC.

  Next, a metal wire having a diameter of 0.2 mm (diameter) as the linear conductor 5 was placed on the external electrode 4 and fixed with a conductive adhesive containing Ag as a conductive component. The metal wire was bent and disposed so that the bent portion had a dogleg shape so as to pass through the portion of the planned fracture layer 3 at an inclination angle of 45 °.

  Thereafter, a lead wire was connected to the linear conductor 5, and a 3 kV / mm direct current electric field was applied to the positive and negative external electrodes 4 via the lead wire for 15 minutes for polarization treatment. In this way, the multilayer piezoelectric element 1 was produced. When a DC voltage of 90 V was applied to the obtained multilayer piezoelectric element 1, a displacement of 10 μm was obtained in the stacking direction. This was equivalent to the amount of displacement without the linear conductor 5.

After that, as a result of conducting a test in which an AC voltage of 0 to +20 V was applied to the multilayer piezoelectric element 1 at a frequency of 30 kHz and continuously driven up to 1 × 10 ⁸ times, the planned fracture layer 3 was cracked and fractured. Although it was, it continued to drive normally. As a result of a test in which the linear conductor 5 is not provided on the external electrode 4 and continuously driven up to 1 × 10 ⁸ times, the piezoelectric layer 2 is separated as the planned fracture layer 3 breaks, and is unusable. became.

It is a perspective view which shows an example of the lamination type piezoelectric element of this Embodiment. It is sectional drawing which shows an example of the injection device of this Embodiment. It is a block diagram which shows an example of the fuel-injection system of this Embodiment.

Explanation of symbols

1: Laminated piezoelectric element 2: Piezoelectric layer 3: Planned fracture layer 4: External electrode 5: Linear conductor 6: Internal electrode layer 7: Laminated body

Claims (6)

  Piezoelectric layers and internal electrode layers are alternately laminated, and include a laminate including a planned fracture layer that relaxes stress by being preferentially fractured over the internal electrode layer during driving, and bonded to the side surface of the laminate And a pair of external electrodes electrically connected to the internal electrode layer, wherein the external electrode is a linear conductor that obliquely passes through the portion of the predetermined fracture layer on the surface A laminated piezoelectric element characterized in that is formed.   When the inclination angle formed between the linear conductor and the first planned fracture layer is θ, the inclination angle formed between the linear conductor and the second planned fracture layer adjacent to the first planned fracture layer is 180. The multilayer piezoelectric element according to claim 1, wherein the stacked piezoelectric element is at −−θ.   The pair of external electrodes has a first linear conductor formed on one side and a second linear conductor formed on the other side, and has an inclination angle formed between the first linear conductor and the one predetermined fracture layer. 3. The multilayer piezoelectric element according to claim 1, wherein an inclination angle between the second linear conductor and one predetermined fracture layer is 180 ° −θ, where θ is θ. .   The said linear conductor has a some bending part in the site | part between the said predetermined fracture | rupture layers adjacent on the surface of the said external electrode, The Claim 1 thru | or 3 characterized by the above-mentioned. The laminated piezoelectric element described.   A container having an ejection hole and the multilayer piezoelectric element according to any one of claims 1 to 4, wherein the liquid filled in the container is discharged from the ejection hole by driving the multilayer piezoelectric element. An injection device.   6. A common rail that stores high-pressure fuel, an injection device according to claim 5 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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