JP3545930B2 - Manufacturing method of laminated piezoelectric actuator - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a laminated piezoelectric actuator, for example, a laminated piezoelectric actuator used for a precision positioning device such as an optical device, a driving element for preventing vibration, a driving element for fuel injection of an automobile engine, and the like. And a method for producing the same .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in order to obtain a large displacement amount by using an inverse piezoelectric effect, a large number of multilayer piezoelectric actuator structures in which a plurality of piezoelectric plates and electrodes are alternately stacked have been proposed. A high voltage is applied to the piezoelectric body to extend the piezoelectric body by several to several tens of [mu] m and use it as a driving force source for the actuator.
[0003]
As a method for manufacturing a laminated piezoelectric actuator, there is a method based on simultaneous firing. According to this simultaneous firing method, it is relatively easy to reduce the thickness of the piezoelectric plate, and the applied electric field can be increased, so that low voltage and high displacement are possible. However, it is necessary to use a noble metal such as Pd or Pt as a material for an internal electrode for co-firing with a piezoelectric plate material (for example, composed of ceramics such as Pb (Zr, Ti) O ₃ ). As the number increases, the amount of the internal electrode material used also increases, resulting in a problem that the cost increases.
[0004]
Therefore, conventionally, a laminated piezoelectric actuator in which piezoelectric plates and electrode plates are alternately laminated has been developed.
[0005]
For example, JP-A-59-218784 discloses that a plurality of piezoelectric plates each having a conductive adhesive layer formed on both surfaces are laminated, and a thin metal plate is arranged between the conductive adhesive layers. A laminated piezoelectric actuator is disclosed in which connection projections are bent in the axial direction so as to leave a predetermined gap with respect to the outer peripheral surface of the piezoelectric plate, and connection projections having the same polarity are overlapped and joined with solder or the like.
[0006]
Japanese Patent Publication No. 4-16029 discloses a plurality of piezoelectric plates, a first ribbon-shaped metal plate, and a second ribbon-shaped metal plate, wherein the first and second ribbon-shaped metal plates are provided. It is bent and inserted between predetermined piezoelectric plates, and a plurality of piezoelectric plates and the first and second ribbon-shaped metal plates are alternately stacked and laminated to form a laminate, and the laminate is housed in a case. A multilayer piezoelectric actuator in which bent portions of first and second ribbon-shaped metal plates are inserted into grooves along the longitudinal direction of the inner wall of the case is disclosed.
[0007]
[Problems to be solved by the invention]
However, in the multilayer piezoelectric actuator disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Sho 59-218784, it is necessary to overlap the connection protrusions of the same polarity and join them with solder or the like, so that it is difficult to connect the connection protrusions. However, there is a problem that the manufacturing process is complicated.
[0008]
In addition, there has been a problem that the joint is fatigued due to long-term use and is easily peeled. Further, a laminated body is formed by alternately laminating a plurality of piezoelectric plates on which the conductive adhesive layer is formed, and a metal thin plate, and heating is performed to join the metal thin plate to the piezoelectric plate via the conductive adhesive layer. For this reason, it is difficult to make the centers of the piezoelectric body and the metal thin plate coincide with each other due to the displacement of the metal thin plate during the laminating step, and to perform the lamination joining. As a result, there is a problem that the displacement amount is reduced.
[0009]
Further, in the laminated piezoelectric actuator disclosed in Japanese Patent Publication No. 4-16029, a laminated body in which a ribbon-shaped metal plate and a piezoelectric plate are laminated is accommodated in a cylindrical case, and a bent portion of the ribbon-shaped metal plate is bent. Was inserted in the groove along the longitudinal direction of the case, a gap was formed between the outer peripheral surface of the laminate and the inner peripheral surface of the case, and the bent portion of the ribbon-like metal plate was deformed, etc., The piezoelectric plate and the ribbon-shaped metal plate are displaced, and it is difficult to stack the piezoelectric body and the ribbon-shaped metal plate so that their centers are aligned. As a result, the amount of displacement is reduced, the amount of protrusion of the bent portion is reduced, and fatigue deformation occurs in the bent portion due to the displacement operation, so that long-term operation reliability cannot be obtained.
[0010]
The present invention provides a laminated type in which the centers of the piezoelectric body and the metal sheet can be easily aligned and laminated and joined, the displacement can be improved, and the electrical connection between the metal sheets can be maintained reliably and for a long time. An object of the present invention is to provide a method for manufacturing a piezoelectric actuator .
[0012]
[Means for Solving the Problems]
The manufacturing method of the laminated piezoelectric actuator of the present invention is a method for manufacturing a plurality of piezoelectric plates in which a conductive adhesive layer is formed on one surface and a thin metal plate having connection protrusions formed on the other surface is formed by the conductive adhesive layer. And a step of laminating the piezoelectric plate and the metal thin plate alternately on the metal thin plate of the piezoelectric plate so that the other piezoelectric plate abuts the conductive adhesive layer, and the metal thin plate is placed from below. A laminated body is formed alternately as the first metal sheet or the second metal sheet, and the tip of the connection projection formed on the first metal sheet and the second metal sheet is connected to the first metal sheet and the second metal sheet, respectively. Engaging the engaging recess formed in the second metal sheet to electrically connect the first metal sheets and the second metal sheets, and heating the laminate to remove the metal sheet; The piezoelectric plate via a conductive adhesive layer A method comprising the step of bonding.
[0015]
[Action]
In the manufacturing method of the laminated piezoelectric actuator of the present invention, in order to produce a piezoelectric plate in which a metal thin plate is joined by a conductive adhesive layer in advance, it is possible to stack the piezoelectric body and the metal thin plate so that their centers are aligned, The displacement amount can be increased.
[0016]
Specifically, by bonding a set of piezoelectric plates and a metal thin plate in advance and then laminating them, accurate positioning of the piezoelectric plate and the metal thin plate can be performed, and further, a positional deviation can be confirmed before lamination. Further, at the time of lamination, the positioning of the piezoelectric bodies may be performed, and the process is greatly simplified, and the yield can be improved. Further, in order to engage the tip of the connection projection with the engagement recess formed in the first metal thin plate and the second metal thin plate, the connection projection is folded in an arch shape keeping a sufficient distance from the outer peripheral surface of the piezoelectric plate. It becomes possible to tune. Since the connecting projections are formed in an arch shape as described above, stress generated in the connecting projections can be reduced, and fatigue breakage of the connecting projections during long-term continuous driving can be reduced.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show one embodiment of a laminated piezoelectric actuator according to the present invention, and reference numeral 1 denotes a disk-shaped piezoelectric plate. These piezoelectric plates 1 are made of a sintered body containing Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT) as a main component.
[0018]
As a piezoelectric material constituting the piezoelectric plate 1, for example, a piezoelectric ceramic material mainly containing lead zirconate titanate is used. However, the present invention is not limited to this, and any ceramic or crystal having piezoelectricity, or any ceramic or crystal having electrostriction may be used. The piezoelectric material constituting the piezoelectric plate 1, those piezoelectric strain constant d ₃₃ is greater is desirable.
[0019]
The thickness t of the piezoelectric plate 1 is desirably 0.2 to 0.6 mm from the viewpoint of miniaturization and application of a high electric field.
[0020]
A plurality of piezoelectric plates 1 are stacked to form a laminate 2, and a conductive adhesive layer 3 is formed on both main surfaces of the piezoelectric plate 1. A disk-shaped metal thin plate 6 is interposed between the piezoelectric plates 1 on which the conductive adhesive layer 3 is formed, and the metal thin plate 6 is joined to the piezoelectric plate 1 by the conductive adhesive layer 3. The metal sheets 6 are alternately referred to as a first metal sheet 6a or a second metal sheet 6b from below.
[0021]
The metal sheet 6 has conductivity, and is preferably, for example, a metal such as silver, brass, copper, or stainless steel. The thickness of the metal sheet 6 is preferably as thin as possible so as not to contribute to the amount of displacement, for example, 10 to 50 μm. Further, in order to prevent a short circuit and discharge with another metal thin plate 6, the metal thin plate 6 is desirably smaller than the piezoelectric plate 1 so as not to be exposed on the outer peripheral surface of the laminated body 2 of the piezoelectric plate 1.
[0022]
The conductive adhesive layer 3 preferably contains a conductive metal powder such as Ag and a glass component, and melts at about 400 to 600 ° C. This is because if the glass component contained in the conductive adhesive layer 3 is melted by applying pressure and heating during lamination, the piezoelectric plates 1 are strongly bonded to each other, and separation at the interface caused by repeated application of a high electric field is prevented. This is because the reliability of the multilayer piezoelectric actuator can be improved. The conductive adhesive layer 3, in particular, and 70 to 98 wt% of Ag powder, it is preferably made of a 2-30 wt% glass component consisting _{PbO-SiO 2 -B 2 O 3} .
[0023]
The thin metal plates 6 of the same polarity are connected by a connecting projection 7 formed in an arch shape, and the first thin metal plates 6a and the second thin metal plates 6b are electrically connected. As shown in FIG. 1 and FIG. 3, the arch-shaped connection projections 7 include connection projections 7 for connecting the first metal thin plates 6a and connection projections 7 for connecting the second metal thin plates 6b. It is formed so as to form an angle of 90 degrees alternately.
[0024]
As shown in FIG. 3, the connection projection 7 of the first metal thin plate 6a is bent in an arch shape at a position separated from the outer peripheral surface of the piezoelectric plate 1, and the distal end portion 8 of the connection projection 7 holds the second metal thin plate 6b therebetween. It is interposed between the piezoelectric plates 1 in a state of being engaged with the engaging concave portions 9 of the first thin metal plate 6 a on the separated piezoelectric plate 1. Similarly, the connection projection 7 of the second metal thin plate 6b is bent in an arch shape at a position separated from the outer peripheral surface of the piezoelectric plate 1, and the tip 8 of the connection projection 7 is separated by the first metal thin plate 6a. It is interposed between the piezoelectric plates 1 in a state where it is engaged with the engaging concave portion 9 of the second thin metal plate 6b on the first plate.
[0025]
As shown in FIG. 4, a connection projection 7 projecting from the piezoelectric plate 1 in the diameter direction is formed on the thin metal plate 6, and a tip 8 of the connection projection 7 is formed into a circular shape. On the other hand, an engagement recess 9 is formed in the same direction as the projecting direction of the connection projection 7, and the engagement recess 9 has a shape matching the tip 8 of the connection projection 7.
[0026]
Note that the metal thin plate 6 and the connection projections 7 formed on the metal thin plate 6 are not limited to the above-described example. For example, the metal thin plate 6 has a shape as shown in FIG. The engagement recess 12 is formed, and the tip 13 of the connection projection 7 is formed in a rectangular shape so as to match the engagement recess 12. The shape shown in FIG. May be formed in a triangular shape such that the tip 15 of the connection projection 7 matches the engagement recess 14. It is only necessary that the shapes match.
[0027]
The connecting projection 7 formed in an arch shape is separated from the outer peripheral surface of the piezoelectric plate 1 by a distance L as shown in FIG. This distance L is set to 0.5 mm or more.
[0028]
The arch-shaped connection protrusion 7 is formed in an arch shape protruding from the outer peripheral surface of the piezoelectric plate 1 by 0.5 mm or more when the distance L from the outer peripheral surface of the piezoelectric plate 1 is smaller than 0.5 mm. This is because, when the piezoelectric actuator is operated, stress acts on the connection projection 7 and there is a possibility that the connection projection 7 may be damaged. It is desirable that the connection projection 7 protrudes from the outer peripheral surface of the piezoelectric plate 1 by 0.5 to 3 mm, particularly 1 to 1.5 mm. This is because if the protrusion is 3 mm or more, the size of the laminated piezoelectric actuator increases. The width of the connection projection 7 is desirably 1 mm or more.
[0029]
And, although not shown, an inert body for transmitting the displacement amount is joined to the upper and lower sides of the laminate 2.
[0030]
It is desirable to fill the outer peripheral surface of the laminate 2 and the gap between the arch-shaped connecting projection 7 and the outer peripheral surface of the piezoelectric plate 1 with a water-resistant resin or the like so that there is no gap. The water-resistant resin used may be any organic resin that has high insulation properties and can be cured at a temperature from room temperature to 200 ° C. However, silicon-based resins are preferable because they have high insulation properties and are easy to fill. Alternatively, an epoxy resin is desirable.
[0031]
First, as shown in FIG. 2, a conductive adhesive layer 3 is formed on one side, and a thin metal plate 6 is formed on the other side of the conductive adhesive layer. A plurality of piezoelectric plates 1 joined by 3 are manufactured.
[0032]
Specifically, a conductive adhesive is applied to one main surface of the piezoelectric plate 1, and after drying the conductive adhesive, the metal thin plate 6 is placed on the surface of the piezoelectric plate 1 to which the conductive adhesive has been applied. They are arranged at concentric positions and are baked and joined. Further, a conductive adhesive is applied to the other main surface of the piezoelectric plate 1, dried and baked. In this way, a plurality of piezoelectric plates 1 to which the metal thin plates 6 as shown in FIG. 2 are joined are produced.
[0033]
In addition, two inactive bodies are made of the same material as the piezoelectric plate 1, and an insulating paste made of the same material as the conductive paste glass is applied to one surface of these inactive bodies, and dried. Then, a glass layer is formed.
[0034]
Thereafter, as shown in FIG. 3, the eight rod members 11 are arranged in a circular shape, and a cylindrical space is formed therein. This cylindrical hollow has substantially the same outer shape as the piezoelectric plate 1.
[0035]
Then, one inert body is first accommodated in the cylindrical space with the glass layer facing upward. The piezoelectric plate 1 is arranged on the upper surface of the inactive body such that the first thin metal plate 6a is on the upper side. At this time, the connection projections 7 formed on the first thin metal plate 6a are sandwiched between the two rod members 11. Thereafter, the piezoelectric plates 1 are stacked so that the second thin metal plate 6b faces upward. The connecting projections 7 formed on the second thin metal plate 6b are formed so as to project at an angle of 90 degrees with the lower connecting projections 7 and to be sandwiched by the two rod members 11. .
[0036]
Further, the piezoelectric plate 1 is arranged so that the first metal plate 6a is on the upper side. The connection projection 7 of the lowermost first metal sheet 6a is bent in an arch shape, and engages with the engagement recess 9 of the first metal sheet 6a of the piezoelectric plate 1 placed on the second metal sheet 6b. Then, in this state, the piezoelectric plate 1 to which the second thin metal plate 6b is bonded is further laminated. By repeating such a process and laminating a desired number of layers, an inert body having a glass layer formed on the lower surface is laminated.
[0037]
Thereafter, pressure is applied while heating, the plurality of piezoelectric plates 1 are joined to each other, and the laminate 2 is taken out of the accommodation space formed by the bar member 11.
[0038]
Next, the entire laminated body 2 produced as desired is coated with a water-resistant resin such as silicon rubber by a method such as dipping. Thereafter, a DC electric field is applied between the first metal thin plate 6a and the second metal thin plate 6b, and polarization processing is performed on the entire laminate 2 to produce a multilayer piezoelectric actuator.
[0039]
The multilayer piezoelectric actuator of the present invention may have any shape such as a columnar shape or a square pillar shape. The first metal sheet 6a and the second metal sheet 6b are electrically connected to each other by being engaged with the engagement concave portions 9 formed on the metal sheet 6a and the second metal sheet 6b. Although electrically connected by the connection projections 7, the connection portions are not exposed to the outside, and the distal end portions 8 of the connection projections 7 and the engagement recesses 9 of the thin metal plate 6 are securely connected. You. Therefore, even when used for a long time, fatigue destruction, peeling and the like hardly occur.
[0040]
Further, unlike the related art, there is no need to overlap the connection protrusions having the same polarity and join them with solder or the like, so that the first metal thin plates 6a and the second metal thin plates 6b can be easily connected to each other. .
[0041]
Further, according to the manufacturing method of the present invention, since the piezoelectric plate 1 in which the metal sheet 6 is bonded in advance by the conductive adhesive layer 3 is manufactured, the piezoelectric body 1 and the metal sheet 6 can be laminated with their centers aligned. And the amount of displacement can be increased. That is, by bonding one set of the piezoelectric plate 1 and the metal thin plate 6 in advance, and then laminating, the piezoelectric plate 1 and the metal thin plate 6 can be accurately positioned, and furthermore, a positional deviation can be confirmed before the lamination. . Further, at the time of lamination, positioning of the piezoelectric bodies 1 may be performed, so that the process is greatly simplified and the yield can be improved. Further, since the distal end portion 8 of the connection projection 7 is engaged with the engagement recess 9 formed in the first metal thin plate 6a and the second metal thin plate 6b, the connection projection 7 has a sufficient distance from the outer peripheral surface of the piezoelectric plate 1. Since the connection projection 7 is bent in an arch shape maintaining L, the stress generated in the connection projection 7 can be relaxed, and the fatigue failure of the connection projection 7 during long-term continuous driving can be reduced.
[0042]
【The invention's effect】
In the laminated piezoelectric actuator obtained by the manufacturing method of the present invention, although electrically connected by the connection protrusion, the connection portion is not exposed to the outside, and furthermore, the tip of the connection protrusion and the metal The engagement recesses of the thin plate are securely connected, and are unlikely to cause fatigue destruction or peeling even after long-term use.
[0043]
Further, unlike the related art, it is not necessary to overlap the connection protrusions having the same polarity and join them with solder or the like, so that the first metal thin plates and the second metal thin plates can be easily connected.
[0044]
Furthermore, in the manufacturing method of the present invention, since a piezoelectric plate in which a metal thin plate is joined in advance by a conductive adhesive layer is manufactured, it is possible to stack the piezoelectric body and the metal thin plate so that their centers are aligned, and the displacement amount is reduced. Increase can be achieved.
[Brief description of the drawings]
FIG. 1 is a side view of a laminated piezoelectric actuator of the present invention.
FIG. 2 is a perspective view showing a state in which a metal plate is joined to a piezoelectric plate.
FIG. 3 is a perspective view illustrating a manufacturing process of the multilayer piezoelectric actuator of the present invention.
FIG. 4 is a plan view showing a metal thin plate on which connection projections of FIG. 2 are formed.
FIG. 5 is a plan view showing another example of a thin metal plate on which connection projections are formed.
FIG. 6 is a plan view showing still another example of a metal sheet on which connection projections are formed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric plate 2 ... Laminated body 3 ... Conductive adhesive layer 6 ... Metal thin plate 6a ... 1st metal thin plate 6b ... 2nd metal thin plate 7 ... Connection projection 8, 13, 15: tip 9, 12, 14: engaging recess 11: rod member

Claims (1)

Forming a conductive adhesive layer on one side, and forming a plurality of piezoelectric plates joined to a thin metal plate having connection protrusions formed by the conductive adhesive layer on the other side,
On the metal plate of the piezoelectric plate, another piezoelectric plate is alternately laminated with the piezoelectric plate and the metal thin plate such that the conductive adhesive layer is in contact with the other piezoelectric plate, and the metal thin plates are alternately stacked from the bottom in the first direction. A laminated body made of a metal thin plate or a second metal thin plate is manufactured, and tips of connection projections formed on the first metal thin plate and the second metal thin plate are respectively replaced with the first metal thin plate and the second metal thin plate. A step of engaging the first metal sheet and the second metal sheet electrically with each other,
Heating the laminate and joining the thin metal plate to the piezoelectric plate via the conductive adhesive layer.

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