JPH10144976A - Piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the amount of displacement without reducing a generation force in a piezoelectric actuator. SOLUTION: A plurality of disk-shaped piezoelectric bimorphs 1 are coaxially laminated, and are connected one another at a center part by a center connecting member 2 and at an outer edge part by a plurality of outer-periphery posts 3. Each piezoelectric bimorph 1 is pressed toward the center part at the periphery edge part with a compression force by an outer pipe 4, via the outer- periphery post 3 and is bent in projecting curved surface shape in one direction. When an application voltage is applied so that it projects in the other direction, the direction of buckling is inverted, and then the amount of displacement due to piezoelectric effect is added. Therefore, the amount of displacement due to bucking deformation is added to the amount of displacement due to the piezoelectric effect, thus increasing the amount of displacement by several tens of percentages without reducing a generation force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a micromachine,
It belongs to the technical field of piezoelectric actuators used for micromanipulators and various precision machines.

[0002]

2. Description of the Related Art As a conventional piezoelectric actuator, there is a laminated piezoelectric actuator disclosed in JP-A-7-193290. The actuator is configured such that a plurality of laminated piezoelectric unimorphs are alternately connected by a center connecting member connecting the center portions and an outer edge connecting member connecting the outer edge portions to each other.

[0003]

In the above-mentioned piezoelectric actuator according to the prior art, the displacement generated by the piezoelectric effect of the piezoelectric unimorph itself, which is a piezoelectric element itself, is the maximum displacement, and a larger displacement is obtained statically. It is not possible. However, in each application field such as a micromachine, a piezoelectric actuator that provides a larger displacement is desired, and the conventional technology cannot meet this demand.

Therefore, an object of the present invention is to provide a piezoelectric actuator capable of generating a displacement larger than a displacement (stroke) originally possessed by a piezoelectric element.

[0005]

Means for Solving the Problems and Their Functions and Effects In order to solve the above problems, the inventors have invented the following means. (First Means) A first means of the present invention is a piezoelectric actuator according to claim 1. According to this means, the planar deformation element, which is a piezoelectric element, is pressed by the sandwiching member from the peripheral edge toward the center and buckles to form a curved surface. here,
The amount of displacement of the plane deformation element due to buckling is set smaller than the original amount of displacement of the plane deformation element due to voltage application so that the direction of buckling can be reversed by the force generated by the plane deformation element.

If a voltage is applied to the planar deformation element in this state with a polarity displaced in the same direction as the buckling direction, a displacement amount resulting from the superposition of the displacement amount due to the buckling and the displacement amount due to the piezoelectric effect is generated. Can be. Conversely, if a voltage is applied with a polarity that displaces in the direction opposite to the direction of buckling, buckling deformation is reversed and the plane deformation element buckles to the opposite side, and as a result, displacement due to buckling also occurs in the opposite direction A displacement amount is generated in which the displacement amount and the displacement amount due to the piezoelectric effect are superimposed. Therefore, in the piezoelectric actuator of the present means, the displacement amount at the time of voltage application is larger than the displacement amount caused by the piezoelectric effect of the plane deformation element by the displacement amount due to buckling.

Therefore, according to this means, there is an effect that it is possible to provide a piezoelectric actuator capable of generating a larger displacement than the displacement originally possessed by the piezoelectric element. The amount of increase in the amount of displacement is at most about the same as the original amount of displacement of the planar deformation element caused by the piezoelectric effect. (Second Means) A second means of the present invention is a piezoelectric actuator according to claim 2.

According to this means, the displacement due to deformation of the plane deforming element due to buckling (displacement to one side) is the maximum displacement due to the piezoelectric effect of the plane deforming element when no compressive force is applied (displacement to both sides). Is 以上 or more and ／ or less. This is because, if the amount of displacement due to buckling is less than 1/8 of the amount of displacement due to the piezoelectric effect, the amount of increase in the amount of displacement due to buckling will not be so large, and it will be difficult to achieve an insufficient effect. . Further, if the ratio is less than 1/8, it is difficult to maintain the buckled state of the planar deformation element stably.

On the other hand, when the amount of displacement due to buckling exceeds ８ of the amount of displacement due to the piezoelectric effect and approaches １ ／, the force generated by the piezoelectric effect is sufficient to reverse the deformation of the planar deformation element due to buckling. It becomes difficult to obtain. Then, there is a possibility that the planar deformation element is buckled to one side and does not turn over, and the intended operation and effect are not exhibited. Therefore, the maximum value needs to be set to about 3/8 in consideration of a safety margin.

Therefore, according to this means, there is an effect that the displacement amount can be increased by a predetermined ratio or more, and
There is also an effect that there is no inconvenience that the direction of buckling does not reverse. (Fourth Means) A fourth means of the present invention is the piezoelectric actuator according to the fourth aspect.

In this means, the holding member includes a plurality of outer pillars that sandwich the disk-shaped planar deforming element at the outer periphery, and an outer peripheral pillar that circumscribes the outer pillar at the inner peripheral surface and has a pressing force. And the outer peripheral pipe sandwiching the outer peripheral pipe between the outer peripheral portion of the planar deforming element. Since the holding member is composed of the outer pipe and the plurality of outer pillars as described above,
The piezoelectric actuator of this means is assembled as follows.

That is, first, a plurality of peripheral struts are bonded to the peripheral edge of the disk-shaped planar deforming element, which is stacked and arranged, with an adhesive or the like, and the planar deforming elements are fixed in parallel with each other. At this time, it is assumed that each of the outer peripheral supports has a length such that one end thereof protrudes from the stacked planar deformation element, and the other end of the outer peripheral support has an end portion at the same position in the axial length direction. Shall be. Next, one end of each peripheral strut protruding from the stacked plane deforming element is inserted into the peripheral pipe, and a sub-assembly of the laminated plane deforming element and the plurality of peripheral struts is pressed into the inside of the peripheral pipe. . At this time, while maintaining the parallelism and coaxiality of each planar deformation element,
Care is taken to insert the sub-assembly into the outer pipe. When the insertion is completed, each planar deforming element receives a strong compressive force from the outer peripheral pipe toward the center via the peripheral peripheral struts, so that each planar deforming element buckles and deforms into a curved surface.

Therefore, according to this means, the assembling step of disposing the planar deforming element in the holding member is facilitated, and especially in the case of a laminated piezoelectric actuator having a plurality of planar deforming elements, the assembling step is dramatically performed. This has the effect of being easier. (Fifth Means) A fifth means of the present invention is the piezoelectric actuator according to the fifth aspect.

In this means, the central connecting member connecting the central portions of the plurality of stacked planar deforming elements to each other, and the outer edge connecting member connecting the outer edges of the planar deforming elements to each other are provided. is there. Therefore, one of the generated force and the displacement amount of the plane deforming element is superimposed and increased by the number of the plane deforming elements due to the connecting action of the center connecting member and the outer circumferential connecting member.

Therefore, according to this means, there is an effect that one of the generated force and the displacement amount of the plane deforming element is increased by being superposed by the number of the plane deforming elements.

[0016]

[Example 1]

(Structure of Embodiment 1) As shown in FIGS. 1A and 1B, a piezoelectric actuator according to Embodiment 1 of the present invention includes four coaxially stacked piezoelectric bimorphs 1 and a center connecting member 2. And four outer supporting columns 3 and one outer pipe 4 as clamping members.

The piezoelectric bimorph 1 is a disc-shaped planar deforming element, and an elastic plate 12 which is a thin plate made of stainless steel having spring elasticity, and a piezoelectric material PZT joined to both the front and back surfaces of the elastic plate 12. And two piezoelectric plates 11 which are thin plates made of On the surface of each piezoelectric plate 11, a surface electrode 13 made of a conductive film is formed. A through hole is formed in the center of each piezoelectric plate 11, and the center connecting member 2 is made to pass therethrough. In the center of the elastic plate 12, a through hole 120 slightly larger than the above through hole is formed.

The central connecting member 2 includes a central connecting rod 21 having the same length as the entire length of the central connecting member 2, and three central connecting rods 21 inserted between the piezoelectric bimorphs 1. It is composed of a spacer 22 and two bushes 23 into which both ends of the central connecting rod 21 are inserted and fixed. The center connecting rod 21, the spacer 22, and the bush 23 are all members made of stainless steel, and are electrically connected to the surface electrodes 13 on both surfaces of each piezoelectric bimorph 1. On the other hand, since the through-hole 120 of the elastic plate 12 is slightly larger than the through-hole of the piezoelectric plate 11, it does not conduct to the center connecting rod 21 and the like. The two bushes 23 are fixed to both ends of the center connecting rod 21 by silver brazing, respectively, and between each bush 23, each piezoelectric bimorph 1 and each spacer 22 are held with a pressing force. . The spacing between the adjacent piezoelectric bimorphs 1 is kept constant by each spacer 22.

The outer circumferential support 3 is a stainless steel round bar member as an outer circumferential connecting member. The outer circumferential support 3 is made of a conductive adhesive with a 90-degree space around the elastic plate 12 of the piezoelectric bimorph 1. Are joined. Each outer column 3 is joined to the inner surface of the outer pipe 4 with a conductive adhesive, and receives a strong compressive force from the outer pipe 4 in the centripetal direction. That is, in a state where each piezoelectric bimorph 1 is in a flat plate shape, the distance between the opposing ends of the outer peripheral surfaces of the two pairs of outer peripheral columns 3 facing each other is larger than the inner diameter of the outer peripheral pipe 4. Therefore, in a state where each piezoelectric bimorph 1 is buckled to form a curved surface, and the distance between the opposing outer peripheral columns 3 is slightly reduced,
The sub-assembly including the piezoelectric bimorph 1, the center connecting member 2, and the outer support 3 is inserted in the outer pipe 4.

The above can be summarized as follows. That is, four piezoelectric bimorphs 1 are coaxially stacked, the central portions of which are connected to each other by a central connecting member 2, and the outer edges of the piezoelectric bimorphs 1 are connected to each other by an outer peripheral support 3 as an outer edge connecting member. Are linked. The peripheral edge of each piezoelectric bimorph 1 is pressed with a compressive force toward the center by the tightening force of the outer peripheral pipe 4 containing these, and the piezoelectric force causes each piezoelectric bimorph 1 to buckle and form a curved surface. doing. One-sided displacement due to deformation of the piezoelectric bimorph 1 caused by this buckling is 1/4 of the maximum displacement on both sides due to the piezoelectric effect of the piezoelectric bimorph 1 in a state where the compressive force is not applied.
And within the range of 1/8 or more and 3/8 or less.

(Operation of the First Embodiment) The polarization directions of the piezoelectric materials forming the two piezoelectric plates 11 of each piezoelectric bimorph 1 are oriented in the same direction as shown in FIG. In addition, all of the stacked piezoelectric bimorphs 1 are arranged with the polarization direction facing the same direction. Therefore, when a predetermined voltage is applied between the common electrode which is the piezoelectric plate 11 of each piezoelectric bimorph 1 and both surface electrodes 13, each piezoelectric bimorph 1 generates a force which tends to be deformed to one of the front and back sides. I do.
In addition, when the polarity of the applied voltage is reversed, each piezoelectric bimorph 1 generates a force that tends to be convexly deformed to the other side.

As described above, the one-sided displacement due to the buckling deformation of the piezoelectric bimorph 1 is about ４ of the maximum displacement on both sides due to the piezoelectric effect. Therefore, when an applied voltage that generates a deforming force in the opposite direction is applied to the piezoelectric bimorph 1 that is convexly buckled on one side, the force generated by the piezoelectric effect reverses the stability of the buckling, and the piezoelectric bimorph 1 is convex on the other side. Deform to. The displacement at that time is approximately the sum of the displacement due to buckling and the displacement due to the piezoelectric effect. Therefore, in this embodiment, the piezoelectric bimorph 1 can be deformed convexly in both directions depending on the polarity of the applied voltage, and the displacement is about 50% of the displacement due to the piezoelectric effect alone.

That is, the piezoelectric actuator of this embodiment can selectively take any of the four states shown in FIG. 3 by the presence or absence of the applied voltage and the switching of the polarity. First, when there is no applied voltage (V = 0),
Either state a which is convex downward in the figure due to buckling deformation or state b which is upward convex in the figure is taken. When a negative applied voltage is applied from this state a (V = −V1), the displacement due to the buckling deformation and the displacement due to the piezoelectric effect are superimposed, and the state becomes a state c which is largely convex downward. On the other hand, when a negative applied voltage is applied from the state b (V = −
In V1), the buckling direction is instantaneously reversed and passes through state a.
The buckling displacement and the displacement due to the piezoelectric effect are superimposed on each other, and the state c is largely deformed downward and convex.

Similarly, a state b in which the buckling deformation is upwardly convex
When a positive applied voltage is applied from (V) (V = V1), the buckling displacement and the displacement due to the piezoelectric effect are superimposed, resulting in a state d in which the deformation is largely convex upward. On the other hand, when a positive applied voltage is applied from the above state a (V = V1), the buckling direction is instantaneously reversed, and through the state b, the buckling displacement and the displacement due to the piezoelectric effect are superimposed and upward. The state becomes the state d which is largely deformed to be convex.

Here, for comparison, the operation of the prior art laminated bimorph that is not buckled will be described.
As shown in FIG. 4, when there is no applied voltage (V = 0), the piezoelectric bimorph 1 is in a neutral position and has a flat plate shape. When a positive or negative applied voltage is applied from this state, displacement occurs due to the piezoelectric effect, and a displacement amount occurs upward (V = V1) or downward (V = -V1). However, in this prior art, since the buckling displacement is not added to the displacement due to the piezoelectric effect, only a displacement amount that is somewhat smaller than the displacement amount of the piezoelectric bimorph 1 of the piezoelectric actuator of the present embodiment can be obtained.

As shown in FIG. 5, the piezoelectric bimorph 1 in this embodiment takes four states a to d corresponding to the states shown in FIG. 3 depending on the presence or absence of an applied voltage and switching of its polarity. sell. In the symbols indicating the amount of displacement in FIG. 5, x represents one-sided amplitude of the amount of displacement due to buckling deformation, and y represents both-sided amplitude components of deformation due to the piezoelectric effect. Therefore, the amplitude on both sides of the piezoelectric bimorph 1 is (y + 2x) in this embodiment, whereas the amplitude on both sides of the piezoelectric bimorph 1 is y in the prior art, and the displacement (stroke) of the amplitude on both sides is increased by 2x.

When the above is expressed by a phase diagram in which the applied voltage is plotted on the horizontal axis and the displacement is plotted on the vertical axis, as shown in FIG. 6, a phase line having a hysteresis loop due to a jump j due to the inversion of buckling. The figure is obtained. However, since the hysteresis inherent to the material of the piezoelectric bimorph 1 itself is very small, it is not shown in FIG. Each of the above states a to d
Correspond to the parts indicated in the figure. From the figure, when the applied voltage is applied (V = V1 or V =
-V1), it can be seen that, with respect to the amplitude (one side) of the piezoelectric actuator of the present embodiment, a displacement amount larger than that of the conventional piezoelectric actuator is obtained by the displacement amount x due to buckling.

(Effects of Embodiment 1) Since the piezoelectric actuator of this embodiment is configured as described above, a plurality of effects are exhibited as follows. The first effect is an increase in the amount of displacement generated by the piezoelectric actuator. In the piezoelectric actuator of this embodiment, the piezoelectric bimorph 1 is pressed from the peripheral edge toward the center by the outer peripheral column 3 and the outer peripheral pipe 4 serving as the sandwiching members and buckles to form a curved surface. Here, the amount of displacement of the piezoelectric bimorph 1 due to buckling is set to about half of the original amount of displacement of the piezoelectric bimorph 1 due to voltage application so that the direction of buckling can be reversed by the force generated by the piezoelectric bimorph 1. ing.

This buckled piezoelectric bimorph 1
If a voltage is applied with a polarity displaced in the same direction as the buckling direction, a displacement amount in which the displacement amount due to the buckling and the displacement amount due to the piezoelectric effect are superimposed can be generated. Conversely, if a voltage is applied with a polarity displaced in the direction opposite to the buckling direction, the buckling deformation is reversed and the piezoelectric bimorph 1 buckles to the opposite side,
As a result, a displacement is generated in the reverse direction in which the displacement due to buckling and the displacement due to the piezoelectric effect are superimposed. Therefore, in the piezoelectric actuator according to the present embodiment, the amount of displacement at the time of applying a voltage is equal to the amount of displacement due to buckling.
Is larger than the displacement caused by the piezoelectric effect.

Therefore, according to the piezoelectric actuator of this embodiment, it is possible to generate a displacement amount which is about 50% larger than the displacement amount which the piezoelectric bimorph 1 originally has. The increase in the amount of displacement due to buckling deformation is:
It can be further increased by increasing the buckling deformation, but there is a limit naturally. That is, the amount of increase in the amount of displacement due to buckling deformation is at most about the same as the original amount of displacement of the piezoelectric bimorph 1 caused by the piezoelectric effect.

The second effect is an increase in the force generated by the piezoelectric actuator. The piezoelectric actuator according to the present embodiment includes a central connecting member 2 that connects the central portions of the four piezoelectric bimorphs 1 each having four layers, and a piezoelectric bimorph 1 that
And an outer peripheral support member 3 as an outer peripheral connecting member that connects the outer edges of the outer peripheral columns to each other. The connecting structures 1, 2, 3 are parallel with respect to the displacement, and the amount of displacement does not increase by stacking. Instead, the piezoelectric bimorph 1 is formed by the parallel connection action of the center connection member 2 and the outer support 3.
Are superimposed and increased by the number of piezoelectric bimorphs 1.

Therefore, according to the piezoelectric actuator of the present embodiment, there is an effect that the generated force of the piezoelectric bimorph 1 is increased by being superposed by the number of the piezoelectric bimorphs 1.
The third effect is cost reduction and improvement in reliability due to reduction in the number of parts and the number of assembly steps. That is, the conductive central connecting member 2 is connected to the surface electrodes 13 on both surfaces of all the piezoelectric bimorphs 1, and the conductive outer peripheral support 3 is connected to the elastic plates 12 of all the piezoelectric bimorphs 1. ing. Therefore, the piezoelectric actuator of this embodiment has no wiring such as a lead wire, and can be manufactured without wiring work.

Therefore, according to the piezoelectric actuator of this embodiment, since there is no lead wire, the number of defective parts is reduced, and since there is no wiring work, the number of assembling steps is reduced, and cost reduction and high reliability can be obtained. (Assembling method of the first embodiment) First, four peripheral columns 3 are joined to the peripheral portion of each of the disc-shaped piezoelectric bimorphs 1 stacked by a conductive adhesive or brazing. The two piezoelectric bimorphs 1 are fixed in parallel with each other. At this time, it is assumed that each outer peripheral column 3 has a length such that one end thereof protrudes from one end of the laminated piezoelectric bimorph 1, and the other end of the outer peripheral column 3 is located at the same position in the axial direction. Assume that there is an end.

Next, one end of each of the outer peripheral columns 3 protruding from the laminated piezoelectric bimorph 1 is inserted along the inner peripheral surface of the outer peripheral pipe 4, and the laminated piezoelectric bimorph 1 and four outer peripheral columns are inserted. 3 is pressed into the outer peripheral pipe 4. At this time, care is taken to insert the sub-assembly into the outer peripheral pipe 4 while maintaining the parallelism and coaxiality of each piezoelectric bimorph 1. When the insertion operation is completed, each piezoelectric bimorph 1 receives a strong compressive force from the outer peripheral pipe 4 toward the center via the outer peripheral column 3, and buckles in a convex manner on one of the front and back sides. Deforms into a curved shape.

Therefore, according to the present embodiment, the assembling process of disposing the piezoelectric bimorph 1 in the outer peripheral column 3 and the outer peripheral pipe 4 which are the holding members becomes easy. Therefore, in the laminated piezoelectric actuator having a plurality of piezoelectric bimorphs 1 as in this embodiment, there is an effect that the assembling process is dramatically simplified. (Variation 1 of Embodiment 1) In the piezoelectric actuator of Embodiment 1 described above, a rectangular plate-shaped piezoelectric bimorph is adopted in place of the disk-shaped piezoelectric bimorph 1, and a rectangular frame is used in place of the outer peripheral column 3 and the outer peripheral pipe 4. A variant with a pinch-like holding member is feasible. Also in this modified embodiment, it is possible to increase the displacement amount by using the buckling deformation as in the first embodiment.

(Modification 2 of Embodiment 1) FIGS.
As shown in (b), instead of the outer peripheral pipe 4 of FIG.
A modification is possible in which one end of the output end of the piezoelectric actuator is fixed by using a ring-shaped pedestal having a hole for inserting and fixing the outer circumferential support 3 of the piezoelectric actuator. In this modification, the ring-shaped pedestal acts as a holding member,
Each piezoelectric bimorph 1 is buckled and deformed. The pedestal may be provided at both ends of the piezoelectric actuator, or may be provided only at one end in some cases.

According to this modified embodiment, in addition to the effect of the first embodiment, the laminated piezoelectric actuator of the present invention can be constituted without using the outer peripheral pipe 4, so that the air flow is improved and the piezoelectric actuator is improved. There is an effect that the actuator hardly overheats. Embodiment 2 (Structure of Embodiment 2) As shown in FIG. 8, a piezoelectric actuator according to Embodiment 2 of the present invention includes a central connecting member 2 ′ connecting central portions of a piezoelectric bimorph 1 to each other. And outer peripheral connecting members 3 ′ and 4 ′ connecting the outer edges of the piezoelectric bimorph 1 to each other. As the outer peripheral connecting member, an outer peripheral column 3 'and an outer peripheral pipe 4' shorter than those of the first embodiment are arranged. The center connecting member 2 ′ is a cylindrical member made of stainless steel, and is adhered to the surface of the piezoelectric plate 11 of the piezoelectric bimorph 1.

Here, the center connecting member 2 'and the outer connecting members 3' and 4 'alternately connect the central portion and the outer edge of the piezoelectric bimorph 1 to each other, and the piezoelectric bimorph 1 is connected in series with respect to displacement. Are linked. (Effects of Embodiment 2) Therefore, the displacement amount of the piezoelectric bimorph 1 whose displacement amount is increased by 50% in the same manner as in the first embodiment as compared with the conventional piezoelectric bimorph is added in series, and the piezoelectric bimorph is added. The number increases by a factor of one.
According to this embodiment, there is an effect that a displacement amount of about 50% can be obtained as compared with the piezoelectric actuator in which the piezoelectric bimorphs according to the related art are joined in series.

(Modification of Embodiment 2) In the piezoelectric actuator of this embodiment, a modification employing a rectangular piezoelectric bimorph corresponding to the modification of Embodiment 1 can be implemented. According to this modification, the same operation and effect as those of the second embodiment can be obtained. Third Embodiment (Configuration of Third Embodiment) As shown in FIG. 9, a piezoelectric actuator according to a third embodiment of the present invention has a structure in which the piezoelectric bimorph 1 is replaced by the piezoelectric unimorph 1 'in the piezoelectric actuator of the first embodiment. It is. The outer peripheral support member 3 and the outer peripheral pipe 4 as the outer peripheral connecting member and the holding member are the same as those in the first embodiment.
It is the same as the one. The center connecting member 2 is substantially the same as that of the first embodiment, but an insulating ring (not shown) is inserted in a portion where the conductive spacer 22 contacts the elastic plate 12 of the piezoelectric unimorph 1 ′. The central connecting member 2 and the elastic plate 12 are insulated from each other.

Therefore, the piezoelectric actuator according to the present embodiment is also driven by applying a voltage between the central connecting member 2 and the outer peripheral support 3 as in the first embodiment. (Effects of Embodiment 3) Also in the piezoelectric actuator of this embodiment, as shown in FIG. 10, when no applied voltage is applied to each piezoelectric unimorph 1 '(states a and b), the piezoelectric unimorph 1' It is buckled and deformed convexly to one of the front and back. Therefore, according to the piezoelectric actuator of the present embodiment, the displacement amount due to the buckling deformation is added to the displacement amount due to the piezoelectric effect of the piezoelectric unimorph 1 ′, so that a larger displacement amount can be obtained as in the first embodiment. .

However, the piezoelectric unimorph 1 ′ differs from the piezoelectric bimorph 1 in that the amount of displacement due to the piezoelectric effect varies depending on the polarization direction of the piezoelectric plate 11. That is, it can be greatly deformed to one side but not so much to the other side. Therefore, as shown in FIG. 10, a large one-sided amplitude (x + y ₁ ) is obtained on one side in the state d, but a not so large one-sided amplitude is obtained on the one side in the state c, which is about (x + y ₂ ).

The two-sided amplitude of the piezoelectric actuator of this embodiment is (2x + y ₁ + y ₂ ). According to this embodiment, an effect of increasing the displacement amount due to buckling deformation equivalent to 2x can be obtained similarly to the first embodiment. There is. (Modification of Embodiment 3) In this embodiment, too, Embodiment 1
Similarly to the above-described modification, a modification employing a rectangular piezoelectric unimorph can be implemented, and the same operation and effect as those of the piezoelectric actuator of this embodiment can be obtained.

As in the second embodiment with respect to the first embodiment, another modification in which the connection of the piezoelectric unimorphs 1 'is connected in series with respect to the displacement is also possible. In the present modification, the adjacent piezoelectric unimorphs 1 ′ are disposed so as to face or face each other, and a displacement amount that is the number of piezoelectric unimorphs 1 ′ times that of the third embodiment is obtained. However, also in this modification, the displacement amount to one side and the displacement amount to the other are different as in the third embodiment.

[Brief description of the drawings]

FIG. 1 is a set diagram showing a configuration of a piezoelectric actuator as a first embodiment (a) Plan view (b) Side end view

FIG. 2 is a cross-sectional view schematically illustrating a configuration of a piezoelectric bimorph of Example 1.

FIG. 3 is a schematic view illustrating the operation of the piezoelectric actuator according to the first embodiment.

FIG. 4 is a schematic view illustrating the operation of a conventional piezoelectric actuator.

FIG. 5 is a schematic view showing a deformed state of the piezoelectric bimorph of Example 1.

FIG. 6 is a phase plan view showing the operation of the piezoelectric bimorph of the first embodiment.

FIG. 7 is a set diagram showing the shape of a pedestal according to a second modification of the first embodiment; (a) a plan view;

FIG. 8 is a side end view showing a configuration of a piezoelectric actuator according to a second embodiment.

FIG. 9 is a set diagram showing a configuration of a piezoelectric actuator as a third embodiment (a) Plan view (b) Side end view

FIG. 10 is a schematic view illustrating the operation of the piezoelectric actuator according to the third embodiment.

[Explanation of symbols]

1: Piezoelectric bimorph (disk shape) 1 ': Piezoelectric unimorph (disk shape) 11: Piezoelectric plate (PZT) 12: Elastic plate (stainless steel) 120: Through hole 13: Surface electrode 2, 2': Central connecting member (any 21: Central connecting rod 22: Spacer 23: Bush 3, 3 ': Peripheral support (stainless steel) 4, 4': Peripheral pipe (stainless steel)

Claims (5)

[Claims] 1. A planar deformation element comprising: an elastic plate which is a thin plate having spring elasticity; and a piezoelectric plate which is a thin plate made of a piezoelectric material which is joined to at least one surface of the elastic plate and expands and contracts by an applied voltage. A piezoelectric member comprising: a holding member that presses a peripheral portion of the plane deforming element toward a central portion with a compressive force to buckle the plane deforming element to a curved surface. 2. One-sided displacement due to buckling deformation of the plane deforming element is at least 1/8 and 3 or more of the maximum displacement which is the amplitude on both sides of the plane deforming element when the compressive force is not applied. The piezoelectric actuator according to claim 1, wherein the ratio is / 8 or less. 3. The piezoelectric actuator according to claim 1, wherein the planar deformation element is one of a disk-shaped or rectangular-plate-shaped piezoelectric bimorph and a piezoelectric unimorph. 4. The planar deforming element is one of a disk-shaped piezoelectric bimorph and a piezoelectric unimorph, and the holding member includes a plurality of outer peripheral posts that sandwich the planar deforming element at an outer peripheral portion, and an inner peripheral member. 2. The piezoelectric actuator according to claim 1, further comprising an outer peripheral pipe circumscribing the outer peripheral column by a surface, and holding the outer peripheral column with an outer peripheral portion of the planar deformation element with a pressing force. 5. A planar connecting element, wherein a plurality of the planar deformation elements are stacked, a central connecting member connecting the central portions of the planar deformation elements to each other, and an outer edge connecting the outer edges of the planar deformation elements to each other. The piezoelectric actuator according to claim 1, further comprising a connecting member.