JP2000294843A - Piezoelectric element and laminated piezoelectric actuator - Google Patents

Abstract

(57) [Summary] [PROBLEMS] An electric field applied to a portion around an internal electrode of a piezoelectric element is continuously reduced around the internal electrode without using a specially shaped internal electrode. An object of the present invention is to provide a highly reliable multilayer actuator that does not crack a piezoelectric element. SOLUTION: This is a piezoelectric element in which a piezoelectric element substrate 1 is sandwiched between internal electrode layers 4. A low dielectric constant layer 5 having a lower relative dielectric constant than the piezoelectric element substrate 1 is interposed between the piezoelectric element substrate 1 and a peripheral portion of the internal electrode layer 4. This piezoelectric element and metal plate 2
Are stacked to form a laminated piezoelectric actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element and a laminated piezoelectric actuator using the same, and more particularly, to a laminated piezoelectric actuator utilizing a longitudinal effect, for example, a fuel for an automobile engine. The present invention relates to a laminated piezoelectric actuator used as an actuator such as an injection valve, a precision positioning device such as an optical device, and an anti-vibration mount of an anti-vibration table.

[0002]

2. Description of the Related Art Hitherto, in order to obtain a large displacement by applying an electrostrictive effect, a structure of a laminated piezoelectric actuator in which piezoelectric ceramic plates and internal electrode layers are alternately laminated has been proposed. A conventional example of such a laminated piezoelectric actuator is disclosed in Japanese Patent Application Laid-Open No. 62-299093, and the configuration is shown in FIG.

In FIG. 5, this laminated piezoelectric actuator is a piezoelectric element substrate 101 (FIG. 5) in which a baked internal electrode layer 105 of Ag or the like is formed on both surfaces in advance and baked and processed.
(C)) and a metal plate 102 such as stainless steel (FIG. 5).
(B)) are alternately laminated. The metal plate 102 has three tongue-shaped pieces 103, and the metal plates 10 adjacent to each other with the piezoelectric element substrate 101 interposed therebetween.
The two are arranged out of phase by about 60 ° about the vertical axis. That is, three tongue-shaped pieces 103 of one metal plate 102 are located between each of the three tongue-shaped pieces 103 of another adjacent metal plate 102 (see FIG. 5C). . The metal plates 102 having the same phase among the metal plates 102, that is, the tongue-shaped pieces 103 of the metal plates 102 arranged alternately are electrically connected to each other by welding or soldering to the band-shaped metal plate 104 or the like. Connected (Fig. 5
(See (a)). In the laminated piezoelectric actuator having such a configuration, when a voltage is applied to the band-shaped metal plate 104, an electric field is applied to each of the piezoelectric element substrates 101, and each piezoelectric element generates strain, and functions as an actuator.

[0004]

In such a conventional multilayer piezoelectric actuator, the internal electrode layer 105 is printed and fired in order to apply an electric field to both surfaces of each piezoelectric element substrate constituting the multilayer body. The shape is shown in FIG. In this case, it is necessary to cover and form the internal electrode layer leaving a blank portion around the periphery of the piezoelectric element substrate 101 so as not to make electrical contact with the strip-shaped metal plate 104 provided on the side surface of the laminate. is there. When an electric field is applied to the internal electrode layer having such a shape, the piezoelectric element substrate 10
1, electrostriction occurs only in the portion covered with the internal electrode layer 105 (see FIG. 6B).

However, when the applied voltage increases in this state, the applied voltage drops sharply in the region from the periphery of the internal electrode layer of the piezoelectric element substrate to the margin, and as a result, the margin where electrostriction does not occur is reduced. Tensile stress is generated at the boundary between the portion and the lower portion of the internal electrode layer. Therefore, when such a multilayer piezoelectric actuator is driven for a long time, a stress is repeatedly applied to the periphery of the internal electrode layer, cracks 106 are generated from this portion, and the piezoelectric element is subject to fatigue failure (FIG. 6 (b)).

In order to address this problem, Japanese Patent Laid-Open No.
No. 35785 discloses a configuration around an internal electrode layer as shown in FIG.
It has been proposed to deform as shown in (a) and (b) so that the electric field applied to the piezoelectric element gradually disappears from the internal electrode layer to the periphery where no electric field is applied. However, when the periphery of the internal electrode layer 105 is formed in a saw-like shape as shown in FIG. 7A, the electric field directed toward the periphery of the piezoelectric element 101 is concentrated at the apex of the saw, and the metal contained in the internal electrode layer material is removed. There is a problem in that ions cause electromigration toward the periphery of the piezoelectric element substrate, and a short circuit easily occurs with the band-shaped metal plate 104 provided on the side surface of the multilayer body.

On the other hand, as shown in FIG. 7 (b), when an extremely narrow electrode pattern of two or three layers is formed around the internal electrode layer 105b which is usually only about 1 mm wide, There is a manufacturing problem that the area must be 0.5 mm or less, and the positions of the internal electrode layers formed on both surfaces of the piezoelectric element substrate 101 must be precisely adjusted. If the electrode pattern region is made wider, there is a problem that the internal electrode layer area is reduced accordingly and the effective utilization rate of the piezoelectric element substrate is reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and an electric field applied to a portion around an internal electrode of a piezoelectric element substrate without using an internal electrode having a peculiar shape is obtained. It is an object of the present invention to provide a highly reliable piezoelectric element in which the piezoelectric element is continuously reduced around an internal electrode and does not crack on the piezoelectric element substrate even when driven repeatedly, and a multilayer piezoelectric actuator using the same.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, a low dielectric constant layer having a lower dielectric constant than the piezoelectric element substrate has been formed. The present inventors have found that the above problem can be solved by interposing between the layer and the peripheral portion of the layer, and have completed the present invention.

That is, in the piezoelectric element according to the present invention, in a piezoelectric element having a piezoelectric element substrate sandwiched between internal electrode layers, a low dielectric constant layer having a lower relative dielectric constant than the piezoelectric element substrate is formed by the piezoelectric element substrate and the piezoelectric element substrate. It is characterized by being interposed between the internal electrode layer and the peripheral portion.

In a preferred embodiment of the piezoelectric element according to the present invention, the low dielectric constant layer has a relative dielectric constant in a range of 10 to 2,000.

Further, the laminated piezoelectric actuator according to the present invention comprises a plurality of piezoelectric elements as described above and a plurality of piezoelectric elements sandwiched between the piezoelectric elements and electrically connected to the piezoelectric elements, the plurality of piezoelectric elements having connection projections. A laminate having a metal plate laminated thereon, and a piezoelectric plate joined to upper and lower ends of the laminate and having mutually parallel end faces, wherein the connection protrusions of the metal plate are provided in two or more directions. The connection protrusions are alternately projected from between the elements, and the connection protrusions are bent along the stacking direction of the laminate, and are joined to other connection protrusions projected in the same direction. .

[0013]

According to the present invention, a low dielectric constant layer having a lower dielectric constant than the piezoelectric element substrate is interposed between the piezoelectric element substrate of the multilayer piezoelectric actuator and the peripheral portion of the internal electrode layer. Therefore, the voltage applied to the piezoelectric element in the peripheral portion of the internal electrode layer is suitably reduced.

That is, between the peripheral portion of the internal electrode layer and the surface of the piezoelectric element substrate therebelow, there is a low dielectric constant layer whose relative dielectric constant is sufficiently lower than that of the piezoelectric element. Even if the low dielectric layer is formed into a film having a thickness of about 10 μm that can be produced by a printing and firing method, it has a low relative dielectric constant such that the capacitance becomes equivalent to that of a piezoelectric element having a thickness of several hundred μm. Have Therefore, the electric field applied to this region is distributed to the low dielectric constant layer and the piezoelectric element, and only about 1/2 of the total voltage is applied to the piezoelectric element. As described above, by providing the region where the above-mentioned low dielectric constant layer is interposed at the boundary between the internal electrode layer and the margin around the electrode, the electric field applied to the piezoelectric element is once reduced to １ ／ around the internal electrode layer. After decreasing to the extent, it becomes 0 in the margin, so that the tensile stress in this region is alleviated, and the occurrence of fatigue fracture can be avoided even when the electric field is repeatedly applied.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piezoelectric element and a laminated piezoelectric actuator according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing an embodiment of the laminated piezoelectric actuator of the present invention, and FIG. 2 is a partial sectional view of the actuator. In this actuator, in this actuator, a plate-shaped piezoelectric element substrate 1 and a metal plate 2 are alternately laminated to form a laminate 3. An internal electrode layer 4 is provided between the piezoelectric element substrate 1 and the metal plate 2 to join the two and electrically connect the surface of the piezoelectric element substrate 1 to the metal plate 2. A low dielectric layer 5 is provided between the peripheral portion of the internal electrode layer 4 and the piezoelectric element substrate 1.
Are formed to constitute the piezoelectric element of the present invention, and the voltage applied to the piezoelectric element around the internal electrode layer is reduced.

FIG. 3 is a plan view showing the configuration of a metal plate and a piezoelectric element in the laminated piezoelectric actuator of the present invention. The metal plate 2 has a structure shown in FIG. 3A and includes a disk portion 6 and a connection projection 7. Also, the piezoelectric element substrate 1
As shown in FIG. 2B, arc-shaped low dielectric constant layers 5a and 5a 'are formed on one surface of the surface of the substrate at a portion corresponding to the peripheral portion of the internal electrode layer. (See FIG. 3C). On the other hand, on the other surface of the piezoelectric element substrate 1, low dielectric layers 5b and 5b 'are formed at positions rotated by 90 degrees with respect to the low dielectric layer formed on one surface. Further, the internal electrode layer is covered (see FIG. 3D). Further, in this actuator, as shown in FIG. 3 (e), the metal plate 2 and the piezoelectric element substrate 1 are arranged such that the connection projections 7 are located at positions where the low dielectric constant layer is not formed.

In the actuator of the present invention, the above-described metal plate or piezoelectric element is laminated to form a laminate. At this time, as shown in FIG. The projections 8a, 8a 'and 8b, 8b' are located at positions displaced by 90 degrees around the axis of the laminate. By arranging the metal plates 2 in this manner, the same voltage can be applied to the stacked metal plates 2 one by one. That is, in FIG. 2, the connection projections 7 of the metal plate 2 projecting from the outer periphery of the laminate 3 are bent along the lamination direction, and are electrically connected every other layer by welding, solder, or the like. Constitute. In this case,
The “stacking direction” refers to the vertical direction in FIG. 1A, particularly the vertical downward direction.

Further, in the actuator of the present invention, FIG.
As shown in (a), lead wires 9a and 9b are connected to the external electrodes 8a and 8b, and a voltage is applied to the individual piezoelectric elements of the multilayer body 3 by applying a voltage to the lead wires. It is configured as follows. In addition, an inert plate 10 is bonded to the upper and lower ends (the top and bottom in FIG. 1A) of the laminate 3 by an adhesive.

Next, the materials, dimensions and the like of the various components described above will be described. Examples of the piezoelectric element substrate 1 include a sintered body mainly composed of lead zirconate titanate Pb (ZrTi) O ₃ and (PZT), but are not limited thereto. sufficient if, it is preferable to use a large piezoelectric constant d _33. The shape of the piezoelectric element substrate 1 may be circular or rectangular.

Further, it is preferable that the thickness of the piezoelectric element substrate is 0.2 mm to 0.6 mm. In the actuator of the present invention, because of stacking the element substrates that have been sintered in advance, they are formed and sintered into a plate shape, or the block body is cut out into a plate shape after sintering. It is unrealistic, and if it exceeds 0.6 mm, a high driving voltage is required and the power supply becomes expensive, which is not preferable.

It is preferable that the metal plate has a low electric resistance and a melting point higher than a sintering temperature of a conductive adhesive described later. Specific examples of such metals include silver, brass,
Copper, phosphor bronze, stainless steel, etc. can be mentioned,
It is not limited to these. Further, the thickness of the metal plate is preferably as small as possible from the aspect of the efficiency of the multilayer piezoelectric actuator because the metal plate itself does not generate electrostriction. The thickness is preferably 20 μm or more so that a portion having a low dielectric constant layer under the internal electrode layer does not contact.

The diameter of the disk portion 6 (see FIG. 3A) of the metal plate is determined by the low dielectric layers 5a and 5a when the laminate is manufactured.
It is preferable to set the value as large as possible within a range not overlapping with a ′, and in this case, it is preferable to set the inner diameter of the arc-shaped low dielectric constant layer to be smaller by 0.6 mm or more.

When the low dielectric constant layer is covered with an arc, the outer diameter of the area is 0.3 mm around the piezoelectric element substrate 1.
It is preferable that the above margin is set in a range where the margin remains. This is because it is ensured that the ink does not reach the side surface of the piezoelectric element substrate due to a printing error due to convenience of manufacturing by printing and firing. Note that it is effective to set the width of the arc in the range of 0.5 to 2 mm in order to secure a voltage relaxation region.

The distance L between the low permittivity layers 5a and 5a 'provided at two places on the same surface of the piezoelectric element substrate (see FIG. 3).
(See (b)) is preferably 0.5 mm or more wider than the width of the connection projection so as not to overlap with the connection projection 7 of the metal plate 2. Further, since the upper internal electrode layer 4 is also manufactured by printing and firing, the low dielectric constant layer preferably has a thickness of about 5 to 20 μm.

Further, the low dielectric constant layer has a relative dielectric constant of 1
It is preferably in the range of 0 to 2000. The reason is as follows. In FIG. 2, the portion where the low dielectric constant layer 5 is provided below the internal electrode layer 4 generally has a configuration in which a piezoelectric element having a high dielectric constant is sandwiched between the low dielectric constant layers from both sides. Here, as shown in FIG. 4, different relative dielectric constants ε _p ,
When the application of the electric field of the dielectric with epsilon _x superimposed on three layers, because electric flux density D is equal in all the dielectric layers, the electric field E _x, the ratio of E _p in each dielectric follows ( As shown in equation (1), it is equal to the ratio of the reciprocal of each dielectric constant.

[0027]

(Equation 1)

Further, the applied voltage _{V T} is a respective thickness _d x, a value obtained by taking the sum is multiplied by _{d p} electric field _E x, the _{E p} in each dielectric ((2)).

[0029]

(Equation 2)

[0030] Therefore, when using a low dielectric constant layer made of the dielectric constant epsilon _x of K _epsilon times the relative dielectric constant epsilon _p of the piezoelectric element, when K _V times the voltage of the total voltage V _T is applied to the piezoelectric element It can be seen from the simple calculation that the two have the relationship of the following equation (3).

[0031]

(Equation 3)

Here, an object of the present invention is to suppress a steep drop of the voltage applied to the piezoelectric element in a region from the periphery of the internal electrode layer of the piezoelectric element to the margin in the multilayer piezoelectric actuator. It is. Therefore, the voltage applied to the piezoelectric element at the portion where the low dielectric layer 5 is provided below the internal electrode layer 4 is the total voltage V _T 0.25 to 0.75.
Is preferable.

The preferred thickness of the piezoelectric element is 0.2
~ 0.6mm and low dielectric constant layer thickness of 5-20μm
Then, when calculated by the above equation (3), the relative dielectric constant of the low dielectric constant layer is calculated.
Rate ε _xIs the relative permittivity ε of the piezoelectric element_p0.5-60% of
It is preferably within the range. Furthermore, PZ as a piezoelectric element
When using T ceramics, the relative permittivity is usually
Since it is in the range of 2000 to 5000, as described above,
Dielectric constant ε of dielectric layer_xIs in the range of 10 to 2000
Preferably.

The dielectric layer is made of TiO-based fine powder in the range of ε _x ≦ 100 and BaT in the range of ε _x ≦ 2000.
It can be produced by mixing iO ₃ -based fine powder with a glass frit at an appropriate mixing ratio and printing and firing. The glass frit mixed with the dielectric powder is made of PbO-
It is preferable that the main component be SiO ₂ —B ₂ O ₃ and the heat resistance such as softening point is 600 ° C. or higher. If the temperature is lower than 600 ° C., as described later, when the internal electrode layer is printed and fired on the upper layer, it is melted at the firing temperature (300 to 600 ° C.).

It is preferable that the diameter of the internal electrode layer is set smaller than the outer diameter of the arc formed by the low dielectric constant layer so that the peripheral portion is located on the low dielectric constant layer. The conductive adhesive layer paste used for the internal electrode layer contains a metal powder such as Ag and a glass powder, and the glass powder melts at a temperature (about 300 to 600 ° C.) at which the metal plate does not melt. And the glass powder is preferably Z
nO—SiO ₂ —B ₂ O ₃ or the like is used, but is not limited thereto.

Next, the laminated piezoelectric actuator of the present embodiment will be described.
An example of a method for manufacturing data will be described. First, the piezoelectric
Disc-shaped PZT system suitable as material for actuator
Lapping and polishing both sides of sintered body, diameter 14mm, thickness
0.3 mm thick piezoelectric ceramic plate (piezoelectric element substrate 1)
To manufacture. Next, BaTiO 3 having a particle size of 3 μm or less is used.₃Powder
PbO, ZnO, SiO₂And B ₂O₃The main component
Mix into glass powder so that the volume content is 40%
To make a paste by adding an appropriate resin binder solvent
Then, the shape shown in FIG.
Printed and baked at 50 ° C to obtain a low dielectric constant layer 5 having a thickness of 10 µm.
To form

The low dielectric constant layer has an arc shape, an outer diameter of 13 mm, an inner diameter of 11 mm, and an interval L between two arc patterns of 3 mm, on each surface (front and back) of the piezoelectric element substrate 1. A 90 ° rotational displacement arrangement (Fig. 3
(See (b), (c) and (d)). Further, on both surfaces of the piezoelectric element substrate 1, a paste containing a metal powder such as Ag and a glass powder is printed and dried to have a diameter of 12 mm and a thickness of 10 μm.
And fired at 520 ° C. to produce the internal electrode layer 4 (see FIG. 3E). At this time, a region having a peripheral portion width of 0.5 mm of the internal electrode layer 4 is overlapped with the low dielectric constant layer 5.

On the other hand, an Ag thin plate having a thickness of 30 μm is punched into a disk having a diameter of 9 mm having connection projections 7 having a width of 2 × 5.5 mm in length at two locations, as shown in FIG. The metal plate 2 is manufactured. The obtained metal plate 2 is placed on the low dielectric layer 5
It overlaps on the piezoelectric element substrate 1 so that the connection projection 7 is located at the interval L between a and 5b (see FIG. 3E).

Using 99 pieces of the combination of the piezoelectric element substrate 1 and the metal plate 2, the piezoelectric element substrate 1 and the metal plate 2 are alternately laminated as shown in FIGS. The stacked bodies 3 arranged at an angle of 90 ° are assembled so that the protrusions 7 are located at the same position (directly above or immediately below) every other layer (see FIGS. 1 and 2). At the upper and lower ends (top surface and bottom surface) of the laminate 3, an inert plate 10 in which the Ag paste used for forming the internal electrode layer 4 is printed and baked in advance is arranged (see FIG. 1A). . Next, the laminated body 3 assembled as described above is pressed with an appropriate load for 520 minutes.
The internal electrode layer is remelted and joined at 30 ° C. for 30 minutes.

Next, the connection projections 7 protruding from the outer peripheral side surface of the laminate 3 are bent in the axial direction (lamination direction) of the laminate, and are joined to the next adjacent connection projections 7 by soldering. An electrode 8 is formed (see FIG. 2). As described above, by forming the external electrodes 8 at four locations on the outer peripheral side surface of the laminate 3,
The 100 metal plates 2 constituting the laminate are connected to the external electrodes 8a.
Metal plates 2 electrically connected to each other by 8a '
Are electrically connected by external electrodes 8b and 8b ', and the above-mentioned 50 metal plates are divided into two sets of the other 50 metal plates 2 which are insulated with the piezoelectric element 1 therebetween (FIG. 1).
(A)).

Further, the lead wires 9a and 9b are joined to the external electrodes 8a and 8b by soldering, the outer peripheral side surface of the laminate 3 is covered with a silicone resin, and defoaming treatment is performed. After completely filling the gap with the resin, the resin is cured. Then, by grinding the upper and lower single plates (inactive plates 10) of the laminate 3, the parallelism of the upper and lower surfaces is adjusted.
Thereafter, the laminate 3 is immersed in silicone oil at 80 ° C., the lead wire 9a is connected to the positive electrode of the DC power supply, the negative electrode 9b is connected to the negative electrode, and an electric field of 3 kV / mm is applied to the piezoelectric element substrate 1 for 30 minutes. Then, the piezoelectric element substrate 1 is subjected to polarization processing to obtain the multilayer piezoelectric actuator of the present embodiment.

[0042]

(Embodiment) The laminated piezoelectric actuator obtained by the above-described manufacturing process was subjected to 5 directions in the same direction as the electric field at the time of polarization.
When a DC voltage of 00 V was applied, a displacement of 40 μm or more was obtained, and it was confirmed that the actuator normally functions. Further, an AC electric field of 0 V to 500 V was applied at a frequency of 50 Hz under the environment of 95% humidity and the 10 piezoelectric actuators of this example were driven 1 × 10 ⁸ times continuously. It did not occur and all worked normally.

(Comparative Example) Except that the low dielectric constant layer 5 was not provided and the internal electrode layer 4 was directly formed on the surface of the piezoelectric element substrate 1,
The laminated piezoelectric actuator of this example was manufactured by adopting the same configuration as that of the example. In the obtained actuator,
As a result of polarization by applying an electric field of 3 kV / mm for 30 minutes,
A displacement of 40 μm was obtained with a DC voltage of 500 V.
However, under the same conditions as in the example, an AC electric field of 0 V to 500 V was applied at a frequency of 50 Hz, and the device was continuously driven 1 × 10 ⁷ times. Was. In addition, as a result of observing the side surface of the laminated body of the short-circuited actuator, a cracked piezoelectric element was observed, and when this portion was cut and observed, a crack was generated around the internal electrode layer, and the fracture surface was observed. A short circuit had occurred.

Although the present invention has been described in detail with reference to preferred embodiments and examples, the present invention is not limited to these, and various modifications can be made within the scope of the present invention. For example, the connection protrusion 7 of the metal plate is 2
Not only the number but also the number of the layers can be three or more, and the number of the intervals L between the low dielectric constant layers may be adjusted accordingly. Further, the shape of the laminate 3 is not limited to a columnar shape, and may be a polygonal columnar shape, and the pattern shape of the low dielectric constant layer and the number of the intervals L may be adjusted according to the shape. .

[0045]

As described above, according to the present invention,
Because a low dielectric constant layer having a lower relative dielectric constant than the piezoelectric element substrate is interposed between the piezoelectric element substrate and the peripheral portion of the internal electrode layer, without using a specially shaped internal electrode,
The electric field applied around the internal electrodes of the piezoelectric element substrate is
It is possible to provide a highly reliable piezoelectric element and a laminated piezoelectric actuator using the piezoelectric element, which continuously become smaller around the internal electrode and do not crack the piezoelectric element substrate even when driven repeatedly.

In other words, the laminated piezoelectric actuator of the present invention is provided between the peripheral portion of the printed internal electrode layer and the piezoelectric element substrate.
By interposing a low dielectric constant layer having a lower relative dielectric constant than the piezoelectric element substrate, the electric field applied to the piezoelectric element below the low dielectric constant layer is reduced, and the margin from the peripheral portion of the internal electrode layer of the piezoelectric element to the surrounding area is reduced. Since the change of the applied electric field to the part becomes gentle, even if the piezoelectric element is driven for a long time at a driving voltage where cracks are generated in the conventional piezoelectric element without employing the internal electrode layer having a peculiar shape, A highly reliable laminated piezoelectric actuator that does not crack around the internal electrode layer of the piezoelectric element can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view and an upper end view showing one embodiment of a laminated piezoelectric actuator of the present invention.

FIG. 2 shows a portion A of the multilayer piezoelectric actuator shown in FIG.
FIG. 2 is a partial cross-sectional view taken along an axial direction.

FIG. 3 is a plan view showing the shape of a component used in the multilayer piezoelectric actuator shown in FIG.

In Figure 4 across the dielectric of relative permittivity epsilon _p in the dielectric constant epsilon _x becomes dielectric dielectric laminated structure is an explanatory diagram showing a distribution of an electric field applied to the dielectric.

FIG. 5 is a perspective view showing an example of a conventional laminated piezoelectric actuator.

FIGS. 6A and 6B are a cross-sectional view and a vertical cross-sectional view showing a state where a voltage is applied to a piezoelectric element constituting a conventional laminated piezoelectric actuator, in which electrostriction occurs due to the shape of an internal electrode layer and an applied voltage. Is shown.

FIG. 7 is a partial plan view showing a conventional example of a portion A of the internal electrode layer shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element board 2 Metal plate 3 Laminated body 4 Internal electrode layer 5 Low dielectric constant layer 6 Disk part 7 Connection projection part 8a, 8a ', 8b, 8b' External electrode 9a, 9b Lead wire 10 Inactive plate 101 Piezoelectric Element substrate 102 Metal plate 103 Tongue-shaped piece 104 Strip-shaped metal plate 105 Internal electrode layer 106 Crack A Site of laminated piezoelectric actuator

Continued on the front page (72) Inventor Yoshio Akimune 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. (72) Inventor Katsuhiko Onizuka 1-4-4 Yamashitacho, Kokubu-shi, Kagoshima Kyocera Corporation (72) Inventor Makoto Higashi Beppu 1-4-4 Yamashita-cho, Kokubu-shi, Kagoshima Pref.

Claims (3)

[Claims] 1. A piezoelectric element comprising a piezoelectric element substrate sandwiched between internal electrode layers, wherein a low dielectric constant layer having a lower relative dielectric constant than the piezoelectric element substrate is provided between the piezoelectric element substrate and a peripheral portion of the internal electrode layer. A piezoelectric element interposed therebetween. 2. The low dielectric constant layer has a relative dielectric constant of 10 to 20.
2. The piezoelectric element according to claim 1, wherein the value is in the range of 00. 3. A laminate of the plurality of piezoelectric elements according to claim 1 and a plurality of metal plates having connection projections sandwiched between the piezoelectric elements and electrically connected to the piezoelectric elements. And a piezoelectric plate joined to upper and lower ends of the laminate and having mutually parallel end faces, wherein the connection projections of the metal plate are alternately arranged in two or more directions between the piezoelectric elements. Wherein the connecting projection is bent along the laminating direction of the laminated body and joined to another connecting projection protruding in the same direction.