JP4498299B2 - Manufacturing method of multilayer piezoelectric element - Google Patents

Description

The present invention relates to the production how the multilayer piezoelectric element, for example, an automobile fuel injection device, the manufacture how the laminated piezoelectric element used in the driving device or the like for precision positioning device or vibration preventing such optical device regarding that.

Conventionally, as the multilayer piezoelectric element, the laminated piezoelectric actuator is known by laminating a piezoelectric material and internal electrodes alternately.

A laminated piezoelectric actuator, a simultaneous sintering type, are classified into two types of stack type of alternately laminated piezoelectric ceramic and internal electrode plates, lower voltage, when considered from the viewpoint of production cost, simultaneously Since the fired type multilayer piezoelectric actuator is advantageous for thinning, it is showing its superiority.

Figure 6 shows a conventional laminated piezoelectric actuator, in this actuator, a piezoelectric body 51 and the internal electrodes 52 are laminated alternately formed columnar laminate 53, the both end surfaces in the stacking direction not An active layer 55 is laminated.

The internal electrode 52 is formed so that one end thereof is alternately covered with the insulator 61 on the left and right sides, and the strip-like external electrode 70 is electrically connected to the internal electrode 52 every two layers on the left and right.

On the strip-shaped external electrode 70, a lead wire 76 is further fixed with solder 77.

By the way, in recent years, in order to ensure a large amount of displacement under a large pressure with a small piezoelectric actuator, a higher electric field is applied to continuously drive for a long time.
JP-A-7-283451 JP-A-8-51240

  However, in the above-described piezoelectric actuator, when continuously driven for a long time under a high electric field and high pressure, peeling occurs between the internal electrode 52 formed between the piezoelectric bodies 51 and the external electrode 70 for the positive electrode and the negative electrode. There is a problem that the voltage is not supplied to some of the piezoelectric bodies 51 and the displacement characteristics change during driving.

In addition, Patent Document 1 and Patent Document 2 disclose that conductive convex portions are formed by plating at the ends of every other internal electrode, and the thickness of the internal electrode at the center of the columnar laminate is disclosed. since the thickness of the internal electrode edge which is comparable thickness, weak bonding strength between the internal electrode end and the conductive protrusions of a columnar stack, and conductive projection during drive and an internal electrode end portion There is a problem in that peeling occurs, voltage is not supplied to a part of the piezoelectric body, and displacement characteristics are deteriorated.

The present invention, high electric field, under high pressure even when allowed long-term continuous driving is, that the external electrodes and the internal electrodes without disconnected, to provide a manufacturing how the multilayer piezoelectric element having excellent durability With the goal.

The method for manufacturing a laminated piezoelectric element of the present invention has a columnar laminate in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and a pair of external electrodes are formed on two side surfaces of the columnar laminate, respectively. a process for the preparation of the laminated piezoelectric element, a step of an end of said plurality of internal electrodes to produce a columnar laminate exposed alternately to the two sides, the exposed on the side surface of the columnar laminate Conductive metal powder 50 to 80% by volume and glass powder 20 to 50 in the step of forming a concave groove between the end portions of the internal electrode and at least the end portion of the internal electrode on the side surface of the columnar laminate. a step of applying a conductive paste containing a volume percent, in a state in which the load is applied so as to press the plate-like conductive member coated conductive paste, the conductive coated on the side surface of the columnar laminate The paste is heated and the internal power To form a projection-like conductive terminals to the ends projecting from the side surface of the columnar laminate, a step of connecting said external electrodes made of the plate-like conductive member on the tip portion of the projecting Okoshijo conductive terminals, the It is characterized by having.

  According to the method for manufacturing a multilayer piezoelectric element of the present invention, after forming a concave groove between the end portions of the internal electrode exposed on the side surface of the columnar laminated body, the protruding conductive terminal is formed as described above. Therefore, when the component (for example, silver) in the conductive paste diffuses and moves to the end of the internal electrode to form the projecting conductive terminal, the concave groove is deformed to join the projecting conductive terminal. It is possible to increase the thickness of the end portion of the inner electrode. As a result, the bonding strength between the end portion of the internal electrode and the protruding conductive terminal can be increased, so that a multilayer piezoelectric element having high reliability can be provided.

Figure 1 shows one embodiment of a product layer piezoelectric element of the invention, (a) is a perspective view, (b) is a longitudinal sectional view taken along the line A-A 'in (a), (c) is The perspective view which expands and shows a part of (a), (d) is an enlarged view of the junction part vicinity of an internal electrode and an external electrode.

  As shown in FIG. 1, the multilayer piezoelectric actuator has an end portion of the internal electrode 2 on the side surface of a quadrangular columnar stacked body 1a in which a plurality of piezoelectric bodies 1 and a plurality of internal electrodes 2 are alternately stacked. Protruding conductive terminals 5 that can be deformed in the expansion and contraction direction of the laminated piezoelectric element are provided at the ends of the internal electrodes 2 that are covered with the insulator 3 every other layer and are not covered with the insulator 3, An external electrode 4 made of a plate-like conductive member 4a is joined to the tip of the conductive terminal 5, and a lead wire 6 is connected and fixed to each external electrode 4 by soldering.

The lead wire 6 serves to connect the external electrode 4 to an external voltage supply unit.

The piezoelectric body 1 is formed of, for example, lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT) or a piezoelectric ceramic material mainly composed of barium titanate BaTiO ₃ .

The piezoelectric ceramics are those piezoelectric strain constant d ₃₃ indicating the piezoelectric characteristic is high is preferable.

  The thickness of the piezoelectric body 1, that is, the distance between the internal electrodes 2 is preferably 50 to 250 μm.

In order to obtain a larger displacement amount by applying a voltage to the stacked piezoelectric actuator, a method of increasing the number of stacked layers is used. However, when the number of stacked layers is increased, the piezoelectric body 1 is too thick. This is because the actuator cannot be reduced in size and height, and on the other hand, if the thickness of the piezoelectric body 1 is too thin, dielectric breakdown tends to occur.

  An internal electrode 2 is disposed between the piezoelectric bodies 1, and the internal electrode 2 is formed of a metal material such as silver-palladium, and a predetermined voltage is applied to each piezoelectric body 1. It acts to cause displacement due to the reverse piezoelectric effect.

  Further, a concave groove 11 is formed on every side of the internal electrode 2 on the side surface of the columnar laminated body 1 a on which the protruding conductive terminals 5 are formed, and the end of the internal electrode 2 is exposed on the bottom surface of the concave groove 11. is doing.

The insulator 11 is formed by filling the concave groove 11 with glass, epoxy resin, polyimide resin, polyamideimide resin, silicone rubber or the like.

The insulator 3 is preferably made of a material having a low elastic modulus that follows the displacement of the columnar laminated body 1a, specifically, silicone rubber or the like.

  The protruding conductive terminals 5 and the insulators 3 in the concave grooves 11 are alternately formed on the end portions of the internal electrodes 2 exposed on the side surfaces of the columnar laminate 1a on which the external electrodes 4 are formed.

  That is, the end portions of the internal electrodes 2 are alternately insulated by the insulators 3 filled in the concave grooves 11, and the other uninsulated end portions of the internal electrodes 2 are connected to the protruding conductive terminals 5. It is joined to the external electrode 4 made of the plate-like conductive member 4a.

  External electrodes 4 each composed of a plate-like conductive member 4a are connected and fixed to the opposing side surfaces of the columnar laminate 1a via projecting conductive terminals 5, and each external electrode 4 has a laminated internal structure. The electrodes 2 are electrically connected every other layer.

The external electrode 4 made of a plate-like conductive member 4a is an action to supply the common voltage necessary for the piezoelectric body 1 in the internal electrode 2 connected to displace the reverse piezoelectric effect.

Thus, since the external electrode 4 made of the plate-like conductive member 4a is connected to the end of the internal electrode 2 via the protruding conductive terminal 5, the actuator is continuously driven for a long time under a high electric field and high pressure. even if, to absorb stress protruding conductive terminal 5 is caused by the expansion and contraction of the actuator, it is possible to suppress the disconnection of the external electrode 4 and the internal electrode 2, it is possible to provide excellent actuator durability .

  As shown in FIG. 1C, the thickness B in the same direction as the stacking direction of the projecting conductive terminals 5 lowers the resistance of the connecting portion between the external electrode 4 and the internal electrode 2 and occurs when the actuator is driven. From the viewpoint of sufficiently absorbing the stress, it is desirable that the thickness is 1 μm or more and ½ or less of the thickness of the piezoelectric body 1. In particular, the thickness B is desirably 5 to 25 μm.

  The protrusion height h of the protruding conductive terminal 5 is desirably 1/20 or more of the thickness of the piezoelectric body 1 from the viewpoint of sufficiently absorbing the stress generated by the expansion and contraction of the actuator.

In particular, the protrusion height h is desirably 15 to 50 μm.

Further, the thickness t of the plate-shaped conductive member 4a follows the expansion and contraction of the actuator, between the external electrode 4 and the protruding conductive terminal 5, or disconnection between the protruding conductive terminal 5 and the internal electrode 2 From the viewpoint that it does not occur, it is preferably 50 μm or less.

  In addition, the projecting conductive terminal 5 is made of a metal having conductivity such as silver, nickel, copper, gold, and aluminum, and an alloy thereof, and sufficiently absorbs stress caused by expansion and contraction of the actuator. Silver having a low Young's modulus or an alloy containing silver as a main component is desirable.

  Further, the plate-like conductive member 4a is made of a metal having conductivity such as silver, nickel, copper, gold, aluminum, and an alloy thereof, and among these, the bonding strength with the protruding conductive terminal 5 is strong, From the viewpoint of low Young's modulus, silver or an alloy containing silver as a main component is desirable.

And in this invention, the thickness of the edge part 2a of the internal electrode 2 connected with the protruding conductive terminal 5 is thicker than the thickness of the internal electrode 2 (central part 2b of the internal electrode 2) of the columnar laminated body 1a. Has been. The thickness of the end 2a of the internal electrode 2 connected to the protruding conductive terminal 5 is such that the connection between the internal electrode 2 and the protruding conductive terminal 5 is effectively strengthened. It is desirable that it is 1.3 times or more the thickness of the portion 2b.

  Although the groove 11 may not be formed, as described above, the protruding conductive terminal 5 is not formed on the side surface of the columnar laminated body 1a on which the protruding conductive terminal 5 is formed. It is desirable that the groove 11 is formed at the end of the internal electrode 2.

This is because the thickness of the end 2a of the internal electrode 2 connected to the protruding conductive terminal 5 can be effectively increased, that is, in the process of forming the protruding conductive terminal 5 described later, Since the groove 11 is deformed and the opening width of the concave groove 11 on the external electrode 4 side is narrowed in the stacking direction, the end 2a of the internal electrode 2 to which the protruding conductive terminal 5 is connected can be thickened. It is.

  Further, the concave groove 11 effectively deforms the concave groove 11 without impairing the strength of the piezoelectric body 1 and the internal electrode 2 portion that are convex between the concave grooves 11, thereby forming the projecting conductive terminal 5. From the viewpoint that the thickness of the end 2a of the internal electrode 2 to be connected can be increased, it is desirable that the depth is 50 to 500 μm and the width in the stacking direction is 1/3 to 2/3 of the thickness of the piezoelectric body 1. .

  A method for producing the multilayer piezoelectric element of the present invention will be described. First, the columnar laminate 1a is produced. A columnar laminate 1a formed by alternately laminating a plurality of piezoelectric bodies 1 and a plurality of internal electrodes 2 includes a calcined powder of piezoelectric ceramics such as PZT and a binder made of an organic polymer such as acrylic or butyral. , DBP (dibutyl phthalate), DOP (dioctyl phthalate) and the like are mixed with a plasticizer to produce a slurry, and the slurry is formed into a piezoelectric material 1 by a tape molding method such as a known doctor blade method or calendar roll method. A ceramic green sheet is produced.

  Next, a conductive paste is prepared by adding a binder, a plasticizer, and the like to silver-palladium powder, and this is printed on the upper surface of each green sheet to a thickness of 1 to 40 μm by screen printing or the like.

  Then, a green sheet having a conductive paste printed on the upper surface is laminated, the binder is debindered at a predetermined temperature, and then fired at 900 to 1200 ° C.

  Thereafter, as shown in FIG. 2A, the concave grooves 11 are formed on every other side surface of the columnar laminated body 1a by a dicing apparatus or the like.

Next, as shown in FIG. 2 (b), a particle size of 0.1 to 10 μm is formed on the exposed internal electrode 2 of the columnar laminate 1 a between the concave grooves 11 and on the surface of the piezoelectric body 1 in the vicinity of the internal electrode 2. and silver powder 5 0-80 vol%, the softening point and the balance mainly of silicon with a particle size 0.1~10μm is adding a binder to a mixture consisting of a glass powder 20 to 50 vol% of the 600 to 950 ° C. The produced silver glass conductive paste 21 is applied and dried.

  Furthermore, as shown in FIG.2 (c), it heat-processes at 700-950 degreeC in the state which added the load so that the plate-shaped electroconductive member 4a may be pressed to the apply | coated silver glass conductive paste 21, and silver glass electroconductivity is carried out. As shown in FIG. 2 (d), the silver component present in the molten glass gathers at the end of the internal electrode 2 and protrudes from the side surface of the columnar laminate 1a. The conductive terminal 5 is formed, and the tip of the protruding conductive terminal 5 can be joined to the plate-like conductive member 4a.

  At this time, the silver component in the silver glass conductive paste 21 diffuses into the end 2a of the internal electrode 2, and the thickness of the end 2a of the internal electrode 2 becomes thicker than the thickness of the central portion 2b of the internal electrode 2. .

Note that the glass 5 a in the silver glass conductive paste 21 gathers at the base of the protruding conductive terminal 5 and holds the protruding conductive terminal 5.

  That is, by dispersing the glass component in the paste, the glass is softened during the above-described heat treatment, and in this state, silver that does not easily diffuse into the piezoelectric body 1 diffuses and gathers at the end of the internal electrode 2. A protruding conductive terminal 5 as shown in FIG. 2D can be formed.

In particular, in the present invention, after forming the concave groove 11, the thickness of the end 2 a of the internal electrode 2 is made larger than the thickness of the internal electrode 2 at the center of the columnar laminate 1 a by applying and heat-treating the silver glass conductive paste 21. Can also be thickened.

  As described above, since the thickness of the end portion 2a of the internal electrode 2 is increased, the bonding strength with the protruding conductive terminal 5 formed at the tip thereof is increased. Incidentally, the thickness of the end 2a of the internal electrode 2 can be made thicker than the thickness of the internal electrode 2 in the central portion of the columnar laminate 1a by forming the concave groove 11 after the heat treatment of the silver glass conductive paste 21 and performing the heat treatment again. .

  The thickness ratio of the internal electrode 2 at the end 2a of the internal electrode 2 and the central portion of the columnar laminate 1a can be controlled by changing the heat treatment temperature and the silver content in the silver glass conductive paste 21.

  The protruding conductive terminal 5 is formed on a part of the side surface of the columnar laminate 1a, is formed in a rail shape, and its length is substantially the same as the width of the external electrode 4 made of the plate-like conductive member 4a. ing.

The length of the protruding conductive terminal 5 may be shorter than the width of the external electrode 4.

The silver component in the silver glass conductive paste 21 is 50 to 80% by volume, and the remaining glass powder is 20 to 50% by volume. Becomes an appropriate amount, and the protruding height h of the formed projecting conductive terminal 5 can be increased, and the glass component which is the remaining solid content in the silver glass conductive paste 21 becomes an appropriate amount. glass component melt during baking of 21 is also an appropriate amount, since the silver component is easily set in the internal electrode 2 ends, possible to increase the protrusion height h of the protruding conductive terminal 5.

Incidentally, the formation of the protruding conductive terminal 5 described above, the load applied during the heat treatment of the joint butt Okoshijo conductive terminal 5 and the plate-like conductive member 4a and the pressure, 2～500KPa is desirable.

By setting this range, it is possible to sufficiently perform diffusion bonding between the protruding conductive terminal 5 and the plate-like conductive member 4a, increase the strength of the bonded portion, and the pressure becomes appropriate. The deformation of the conductive electrode 5 can be prevented.

  Incidentally, the internal electrode 2 exposed to the columnar laminated body 1a other than the concave groove 11 of the columnar laminated body 1a and the portion of the plate-like conductive member 4a corresponding to the surface of the piezoelectric body 1 in the vicinity of the internal electrode 2, that is, the concave A state in which a silver glass conductive paste 21 is applied and dried on a portion of the plate-like conductive member 4a corresponding to the convex portion between the grooves 11, and a load is applied so as to press the plate-like conductive member 4a against the columnar laminate 1a. You may heat-process with.

  Moreover, the silver glass conductive paste 21 is applied and dried on the entire surface of the plate-like conductive member 4a, and the conductive paste application surface side of the plate-like conductive member 4a is pressed against the surface where the internal electrodes 2 of the columnar laminate 1a are exposed. The protrusion-like conductive terminal 5 can be formed by heat treatment, and the tip portion can be connected to the plate-like conductive member 4a.

In this case, the process can be further shortened.

  Then, the insulator 3 made of silicone rubber is filled in the concave groove 11 and the lead wire 6 is connected to complete the multilayer piezoelectric element of the present invention.

  Then, by applying a direct current voltage of 0.1 to 3 kV / mm to the pair of external electrodes 4 via the lead wires 6 to polarize the columnar laminated body 1a, a laminated piezoelectric actuator as a product is completed, When the lead wire 6 is connected to an external voltage supply unit and a voltage is applied to the internal electrode 2 via the lead wire 6 and the external electrode 4, each piezoelectric body 1 is greatly displaced by the reverse piezoelectric effect, and for example, It functions as an automobile fuel injection valve that supplies fuel to the engine.

  In the multilayer piezoelectric element configured as described above, since the external electrode 4 made of the plate-like conductive member 4a is connected to the internal electrode 2 via the protruding conductive terminal 5, the actuator is continuously operated under a high electric field. Even when driven by the above, the projecting conductive terminal 5 is deformed and the projecting conductive terminal 5 can sufficiently absorb the stress generated during driving, so that a spark is generated between the external electrode 4 and the internal electrode 2. Problems can be prevented and a highly reliable actuator can be provided.

  Furthermore, in this invention, as shown in FIG. 3, you may form the electroconductive auxiliary member 7 in the outer side of the external electrode 4 which consists of a plate-shaped conductive member 4a. In this case, by providing the conductive auxiliary member 7 on the outer surface of the plate-like conductive member 4a, a large current can be supplied to the conductive auxiliary member 7 even when a large current is supplied to the actuator and the actuator is driven at a high speed. For the reason that the current flowing through the external electrode 4 can be reduced, it is possible to prevent the external electrode 4 from causing local heat generation and disconnection, and the durability can be greatly improved.

  The conductive auxiliary member 7 is preferably formed of a flexible conductive adhesive 7a in order to follow the expansion and contraction of the actuator and prevent disconnection of the conductive auxiliary member 7 during driving. Further, from the viewpoint of preventing cracks in the conductive adhesive 7a, a mesh such as metal or a mesh-like metal plate may be embedded in the conductive adhesive 7a.

Furthermore , it is desirable that the conductive adhesive 7a is obtained by dispersing a conductive agent in a polyimide resin having high heat resistance because it does not deteriorate even when driven at a high temperature.

  Further, in the present invention, as shown in FIGS. 4A, 4B, and 4C, the conductive coil 7b, the conductive corrugated plate 7c, or the conductive fiber aggregate (wool shape) 7d conducts The auxiliary member 7 may be formed.

In this case, the conductive auxiliary member 7 can follow the expansion and contraction of the actuator , the conductive auxiliary member 7 is disconnected during driving, or stress is applied between the conductive auxiliary member 7 and the external electrode 4. the resulting conductive auxiliary member 7 can be prevented problem or peeling, it is possible to greatly improve the durability. Note that the connection between the conductive auxiliary member 7 and the external electrode 4 is preferably a bonding with a brazing material or a bonding with a conductive adhesive.

  As the conductive auxiliary member 7, a conductive corrugated plate 7 c made of silver is desirable because it has a low resistance value and Young's modulus, is highly stretchable, and can reduce the sectional area of the actuator.

  In the above example, the example in which the external electrode 4 is formed on the opposing side surface of the columnar laminate 1a has been described. However, in the present invention, for example, a pair of external electrodes may be formed on the adjacent side surface.

FIG. 5 shows an injection device using a multilayer piezoelectric element manufactured by the method for manufacturing a multilayer piezoelectric element of the present invention. In the figure, reference numeral 31 indicates a storage container.

An injection hole 33 is provided at one end of the storage container 31, and a needle valve 35 that can open and close the injection hole 33 is stored in the storage container 31.

  A fuel passage 37 is provided in the injection hole 33 so as to be able to communicate. The fuel passage 37 is connected to an external fuel supply source, and fuel is always supplied to the fuel passage 37 at a constant high pressure.

Therefore, when the needle valve 35 opens the injection hole 33, the fuel supplied to the fuel passage 37 is formed to be injected into a fuel chamber (not shown) of the internal combustion engine at a constant high pressure.

  Further, the upper end portion of the needle valve 35 has a large diameter, and serves as a piston 41 slidable with a cylinder 39 formed in the storage container 31.

In the storage container 31, the piezoelectric actuator 43 described above is stored.

  In such an injection device, when the piezoelectric actuator 43 is extended by applying a voltage, the piston 41 is pressed, the needle valve 35 closes the injection hole 33, and the supply of fuel is stopped. When the application of voltage is stopped, the piezoelectric actuator 43 contracts, the disc spring 45 pushes back the piston 41, and the injection hole 33 communicates with the fuel passage 37 so that fuel is injected.

  First, a columnar laminate was produced. The piezoelectric body was formed of PZT having a thickness of 150 μm, the internal electrode was formed of a silver-palladium alloy having a thickness of 3 μm, and the number of stacked piezoelectric bodies and internal electrodes was 300 layers.

  Next, a groove having a depth of 150 μm and a width of 75 μm was formed every other internal electrode near the end of the internal electrode exposed on the external electrode formation surface.

Thereafter, the internal electrode and the piezoelectric body surface in the vicinity of the inner electrode between the grooves, and the average particle silver powder 6 0% by volume diameter 5 [mu] m, a softening point and the balance mainly of silicon having an average particle size 5 [mu] m 750 the ℃ glass powder 40% by volume of silver glass conductive paste mixture by adding a binder to prepare to the consisting of coating, and dried.

Further, a heat treatment is performed at 900 ° C. for 2 hours in a state where a plate-like conductive member made of silver having a thickness of 25 μm is pressed at 30 kPa on this silver glass conductive paste to form protruding conductive terminals protruding from the columnar laminate. , it was ligated distal portion of the impact Okoshijo conductive terminals on the plate Joshirubeden member.

  After that, silicon rubber as an insulator is filled in the concave groove, and the outside of the plate-like conductive member is a conductive material in which a mesh-like plate made of nickel is embedded in a flexible conductive adhesive in which silver is dispersed in polyimide resin. An auxiliary member was formed.

Further , a lead wire is connected to the conductive auxiliary member, and a polarization process is performed by applying a DC electric field of 3 kV / mm for 15 minutes to the positive and negative external electrodes via the lead wire, and the lamination as shown in FIG. Type piezoelectric actuator was fabricated.

  Note that silver and palladium were dispersed in the protruding conductive terminals. At this time, the average height of the protruding conductive terminals is 20 μm, the thickness of the end portion of the internal electrode connected to the protruding conductive terminal is 5 μm, and the thickness of the internal electrode at the center of the columnar laminate is It was 2 μm. The ratio of the thickness of the internal electrode at the center of the columnar laminate to the thickness of the internal electrode end was 2.5 times.

As a result of applying a DC voltage of 150 V to the obtained multilayer piezoelectric actuator, a displacement of 40 μm was obtained in the stacking direction. Furthermore, as a result of applying a driving test by applying an AC voltage of 0 to +150 V at a frequency of 120 Hz to this actuator at a room temperature, a displacement of 40 μm was obtained when driving up to 1 × 10 ⁹ cycles, and abnormalities in the external electrodes were observed. I couldn't see it.

  A laminated piezoelectric actuator was produced in the same manner as described above except that the heat treatment time of the silver glass conductive paste was set to 1 hour. The thickness of the internal electrode end portion was 2.6 μm, and the inside of the central portion of the columnar laminate was The electrode thickness was 2 μm, and the ratio of the thickness of the internal electrode at the center of the columnar laminate to the thickness of the end portion of the internal electrode was 1.3 times.

As a result of performing a driving test on this actuator in the same manner as described above, when it was driven up to 1 × 10 ⁹ cycles, a displacement of 40 μm was obtained, and no abnormality of the external electrode was observed.

On the other hand, as a comparative example, one end portion of the internal electrode is alternately covered with an insulator made of glass, and the above-described silver glass conductive paste is applied thereon and heat-treated at 700 ° C. The actuator shown in FIG. 6 that is electrically connected to the internal electrode every other layer on the left and right sides was manufactured and tested in the same manner as described above. As a result, a spark occurred in the external electrode in 1 × 10 ⁵ cycles in the driving test.

The laminated piezoelectric element of this invention is shown, (a) is a perspective view, (b) is a longitudinal cross-sectional view along the AA 'line of (a), (c) is a part of (a). The perspective view which expands and is shown, (d) is sectional drawing which expands and shows a part of (b). It is process drawing for demonstrating the manufacturing method of the lamination type piezoelectric element of this invention. 1A and 1B show a laminated piezoelectric element in which a conductive auxiliary member is formed, in which FIG. 1A is a perspective view and FIG. 2B is a sectional view taken along line A-A ′ in FIG. (A) is a coiled conductive auxiliary member, (b) is a corrugated conductive auxiliary member, and (c) is a longitudinal section of the laminated piezoelectric element of the present invention when a woolen conductive auxiliary member is used. FIG. It is explanatory drawing which shows the injection apparatus of this invention. It is a longitudinal cross-sectional view of a conventional multilayer piezoelectric actuator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric body 1a ... Columnar laminated body 2 ... Internal electrode 2a ... End part 2b of internal electrode ... Central part 4 of internal electrode ... External electrode 4a ... Plate-like conduction Member 5 ... Protruding conductive terminal 5a ... Glass 11 ... Groove 31 ... Storage container 33 ... Injection hole 35 ... Valve 43 ... Piezoelectric actuator

Claims (1)

A method of manufacturing a laminated piezoelectric element having a columnar laminated body in which a plurality of piezoelectric bodies and a plurality of internal electrodes are alternately laminated, and having a pair of external electrodes formed on two side surfaces of the columnar laminated body. Producing a columnar laminate in which end portions of the plurality of internal electrodes are alternately exposed on the two side surfaces;
Forming a groove between the ends of the internal electrode exposed on the side surface of the columnar laminate,
Applying a conductive paste containing conductive metal powder 50 to 80% by volume and glass powder 20 to 50% by volume to at least a portion of the side surface of the columnar laminate where the end of the internal electrode is exposed;
While applying a load to press the plate-like conductive member coated conductive paste, and heating the conductive paste applied to the side surface of the columnar laminate, the columnar to an end of the inner electrode to form a projection-like conductive terminals projecting from the side surface of the laminate, a step of connecting said external electrodes made of the plate-like conductive member on the tip portion of the projecting Okoshijo conductive terminal, and further comprising a A method for manufacturing a laminated piezoelectric element.

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