JPH0355890A - Piezoelectric driver and case for containing the driver - Google Patents

Abstract

PURPOSE:To stabilize characteristics of a rodlike piezoelectric element and to prevent the element from damaging by incorporating the element elongating or contracting in an axial direction depending upon an applied voltage when the voltage is applied, applying a predetermined prepressure thereto, and providing elasticity for allowing the elongation and contraction of the element. CONSTITUTION:A case 2 is connected to an object 8 to be driven through an elastic link 7. The other end of an elastic holder 10 has an opening, which receives a prepressure structure 3. The holder 10 has a hollow bottomed cylindrical structure, and a piezoelectric element 1 is contained therein. A flange 9 is provided at the opening side end of the case 2. A bolt 5 is adjusting to apply suitable prepressure to the element 1. When a stress is operated to elongate the element 1, a connecting member 12a tends to move upward, while a connecting member 12b tends to move downward. An elastic member 11 is elastically deformed (bent) upward near the member 12a and downward near the member 12b to obtain axial flexibility at the case 2.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a piezoelectric drive device and a storage case for the piezoelectric drive device, and more particularly, to a piezoelectric drive device and a storage case for the piezoelectric drive device that can reduce load rigidity. ．． ; Traditional technology 1 Piezoelectric materials have the property of expanding and contracting in shape by applying a voltage. It is possible to utilize this property of expansion and contraction to form a precision drive device. Applying voltage to a piezoelectric device The displacement obtained by applying L, is quite small and is 1. Therefore, when trying to obtain a somewhat large displacement, it has been proposed to use a stack of multiple piezoelectric elements.Laminated piezoelectric elements is a drive device that laminates multiple layers of 5 piezoelectric elements and applies a voltage to each layer to cause displacement. If a voltage of V is applied to one layer of piezoelectric elements and a displacement of ΔX can be obtained, then If piezoelectric elements are stacked and a voltage V is applied to each, a displacement of n·ΔX can be obtained. Figure 6 is a cross-sectional view showing an example of a stacked piezoelectric element.nN
piezoelectric element"; O-1.
．． ' et2.-2,...51-n52-n is formed9. : One electrode 51- of the piezoelectric element of each layer. ，
51-2. ...51-n is commonly connected and connected to the positive electrode 11, the other $452 1.52-2
...52-n are connected in common and connected to a negative electrode. In this way, 2. As soon as the voltage of each Mk''.power supply voltage is applied, the displacement obtained is n times the displacement ΔX of one layer, n ΔX. Insulating layer 54
1 is provided to provide insulation between each piezoelectric element. In such a laminated piezoelectric device, a certain amount of play may occur between the layers when laminated. Therefore, when a voltage is applied, the initial displacement may be consumed to fill up the play, and after a certain amount of applied voltage, the applied voltage and displacement will have a regular proportional relationship. In order to obtain a correct proportional relationship, some kind of countermeasure is required.

When a certain amount of preload is applied to a laminated piezoelectric element, the play between the layers is consumed. Therefore, the displacement obtained when voltage is applied L7 to the laminated piezoelectric element can be made directly proportional to the applied voltage. However, when a preload is applied to a piezoelectric element, the displacement obtained by applying voltage changes depending on the rigidity of the member applying the preload to the piezoelectric element. Although the piezoelectric element is made of ceramic, it is itself an elastic body, so the amount of elongation is determined by the balance with the rigidity of the load. In other words, if the load stiffness is large, even if the piezoelectric element tries to displace, the load stiffness will prevent that displacement, so the resulting displacement will be small. If the load rigidity becomes smaller, the force that prevents the displacement of the piezoelectric element from being applied to fIJ+- is smaller, so the resulting displacement becomes larger Z. In this way, the characteristic of the variable atl voltage of the piezoelectric element changes as shown in Fig. 7 depending on the load stiffness. As mentioned above, it is preferable to give a predetermined preload to the piezoelectric element from the viewpoint of stabilizing the characteristics. However, if a storage container or the like is used to give the piezoelectric element, the rigidity becomes too high.
Although the explanation has been given for the case of a two-layer piezoelectric element in which i becomes small, the above problem cannot be applied to the entire piezoelectric element. [Problems to be Solved by the Invention] As explained above, it is preferable to apply an appropriate preload to the piezoelectric element in order to make the characteristics of the piezoelectric element safe, and to prevent damage to the piezoelectric element, It is preferable that the piezoelectric element is housed in a case for.

However, if the piezoelectric element is housed in a case that serves the purpose of providing preload or medical protection, there is a problem in that the displacement of the piezoelectric element becomes small due to the rigidity of the Coos. An object of the present invention is to provide a piezoelectric drive device that includes a case that can sufficiently secure displacement of the piezoelectric element and ε that applies an appropriate preload to the piezoelectric element. Another object of the invention is to house a piezoelectric element. Still another feature of the present invention is to provide a piezoelectric drive device with a storage case that can protect the piezoelectric element. By providing a storage case for the piezoelectric drive device that can be protected.
P）Ru, L T・Measures to solve the problems] When the storage goose is constructed of a metal plate, etc., the rigidity tends to be high even if the plate thickness is small. According to the present invention, for example, referring to FIG. The notch 41 is formed along the circumferential direction to weaken the axial rigidity of the storage case 2 and give it flexibility.Looking at it from a different perspective, as shown in Fig. 1(C), this The storage case 2 has a plurality of stages arranged along the axial direction, each stage having a loop shape surrounding the shaft, and a flexible case that elastically deforms in response to stresses applied at different positions in opposite directions in the axial direction. . . , and a plurality of connection members 12a, 12b. . [Function] To explain with reference to FIG. A plurality of notches 41 are provided in the storage coove 2 that provides preload, and a side wall portion thereof is provided with a plurality of elastic members if and a plurality of connection members 1.
2i is formed as shown in FIG. Ensure displacement.

[Embodiment 1] Figures 1(A) and 1(C) schematically show a piezoelectric drive stage device according to an embodiment of the present invention. Figure 1 (A) is a partially cutaway view schematically showing the overall structure. Figure 1 (B) is a sectional view taken along line IB-IB in Figure 1 (A). Fig. 1(C) is a conceptual diagram for explaining the operation of the elastic holder portion.Referring to Fig. 1(A>.iB), the storage case 2 has an elastic holder 10 and
and is connected to a driven object 8 via an elastic link 7. The @ end of the elastic holder 10 has an opening to receive the preloaded elliptical body 3. The elastic holder 10 has a hollow bottomed ellipse, and the piezoelectric cord 1 is housed inside the elastic holder 10. A 7-lunge 9 is provided at the end of the release gauge of the storage gauge 2.
For example, the flange 9 has four holes 6a, 6b, 6.
c, 6d are provided, and bolts 5a, 5b. 5c,
5d to pull the preload structure 3 and fix it. ,B
When the bolt 5 is tightened, the preload structure 3 is compressed by the elastic polder 10.
It is drawn to the side and presses on the piezoelectric element l. By adjusting the bolts 5 in this way, an appropriate preload can be applied to the piezoelectric element 1.As schematically shown in FIG. 1(C), the elastic holder 10 has a plurality of elastic members 11a
, i-1b. 11. c, . . . and connecting members 12a, 12b, 12c, --- for connecting these elastic members. Adjacent connecting members 12a and 12b are arranged to be rotated around the axial direction by 90 degrees with respect to each other, and each is connected to an elastic member at two opposing positions. Elastic member 1
Taking 1a as an example, when the piezoelectric element 1 exerts stress in an attempt to lengthen, the connecting member 12a tends to move upward and the connecting member 12b tends to move downward. Due to these opposing forces, the elastic member 11a causes elastic deformation (bending) upward in the vicinity of the connection member 12a and downward in the vicinity of the connection member 12b. In this way, the storage cage 2 acquires axial flexibility. Figures 2 (A) to (E) show the storage game in more detail. FIG. 2 (A> is a plan view of the storage case 2. The elastic link 7 is made of, for example, solid metal, and the elastic holder 10 is formed of, for example, a metal hollow cylindrical structure with a bottom. Furthermore, a plurality of notches or grooves 41 are provided in the side wall portion of the elastic holder 10, the positions of which are alternately changed.The grooves 41 are elongated in the direction perpendicular to the axis, and In Fig. 2 (A>), the left end notch 4a. The groove 4b leaves two connecting parts 12lb. In order to explain the pattern of the connection part, cut along the IfB-IIB line and the IIC-11C line.
>, the connection part L2f is located above and below 4.
In FIG. 2(C), the connecting portions 12J are arranged on the left and right. The force applied to the elastic member 11i arranged in the in-plane direction in the figure is from these connecting parts 121 and 12J)
Since the applied force is applied in the vertical direction, the elastic member 11i is elastically deformed by 1−·l &j. Figure 2 (D), (E
> shows 62 embodiments in which the piezoelectric element 1 is housed in the elastic holder 10. In FIG. 2(D), the piezoelectric element 1 has a square cross-sectional shape, and is arranged so that its edge abuts the connection point ]2.

FIG. 2(F) shows a case where the cross section of the piezoelectric cord -f1 is circular, and a connecting part 13 made of Teflon or the like is arranged between the piezoelectric element 1 and the elastic holder 10. An appropriate number of joint holes 13 are arranged between the inner wall of the connecting member 12 and the outer periphery of the piezoelectric element 1 to stabilize the position of the piezoelectric element 1. FIGS. 3(A) and 3(B) are diagrams for explaining the elastic link 7. In FIG. 3(A), the elastic link 7 includes a rigid portion 16 and hinge portions 17a and 17b. The connecting portion between the elastic boulder lυ and the elastic link 7 is a hinge portion Y7a whose cross section is cut into a spherical (circular arc) shape. Similarly, a hinge portion 1 with a spherical cutout is provided at the connection portion between the elastic link 7 and the driven body 8. 7b. These hinge parts 17a and 17b have a diameter that decreases toward the center, so that they are easily elastically deformed by a force in a direction perpendicular to the axial direction. That is, when a force is applied to the elastic link 7 in the vertical or longitudinal direction in the figure, the hinge portion 17a bends and changes the coupling angle between the rigid portion 16 and the elastic holder 10. The hinge portion 17b between the driven body 8 and the rigid portion 16 similarly deforms elastically, changing the coupling angle of the rigid portion 16 to the driven body 8. Therefore, the elastic holder 10 and the driven body 8 are When changing its position in parallel, the hinge parts 1''/a, 1'7b allow the displacement by changing their coupling angle. On the other hand, the elastic holder 10 forces S7 in the horizontal direction. , the hinge portions 17a and 17b have sufficient rigidity and transmit the displacement to the driven body 8.In addition, if both ends of the rigid portion 16;
A case will be described in which the portions 17a and 17b are provided, but such a structure may be provided in multiple stages. FIG. 3(B) shows an elastic link made of a shaft-shaped member with a small diameter instead of the elastic link shown in FIG. The shaft 18 is selected to have a small diameter, so that it easily deforms elastically against stress in the direction perpendicular to the axis, but is rigid against stress in the axial direction.
Similar to the case of the elastic link shown in A>, stress in the axial direction is transmitted to the driven body 8, while relative displacement between the elastic holder 10 and the driven body 8 in the direction perpendicular to the axis is allowed.

Although the embodiments have been described above, the present invention is not limited thereto. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Effects of the Invention] As explained above, according to the present invention, by storing the piezoelectric element in a storage case having a plurality of notches in the circumferential direction, an appropriate preload can be applied to the piezoelectric element. , which allows sufficient displacement of the piezoelectric element. Therefore, a piezoelectric drive device with excellent characteristics can be obtained.

[Brief explanation of drawings]

1(A) to 1(C) show a piezoelectric drive device according to an embodiment of the present invention, FIG. 1(A) is a partially cutaway plan view of the schematic structure, and FIG. A) is a sectional view taken along line IB-IB, and FIG. 1 (C) is a conceptual diagram explaining the operation of the elastic holder. Figure 2 (A) is a plan view showing the external appearance, Figure 2 (B), (
C) is a sectional view taken along the nB-nB line and nc-nc@ in FIG. 2(A); FIGS. 2(D) and (E) are sectional views showing the engagement between the elastic holder and the piezoelectric element; Figures 3 (A>, (B) are perspective views showing two forms of elastic links, Figure 4 is a sectional view showing one example of a laminated piezoelectric element, and Figure 5 is a graph showing the characteristics of the piezoelectric element. In, 1 piezoelectric element 2 storage case 3 preload structure 41 notch 5 bolt 6 hole 7 elastic link 8 driven object 9 1 0 11i 12i 16 17 1 8 flange elastic holder elastic member connecting member rigid part hinge part shaft

Claims (6)

[Claims] (1). a rod-shaped piezoelectric element that expands and contracts in the axial direction depending on the applied voltage when a voltage is applied; housing the piezoelectric element and applying a predetermined preload;
It is a cylindrical storage case having elasticity that allows the piezoelectric element to expand and contract, and is arranged in multiple stages along the axial direction of the piezoelectric element, each stage having a loop shape surrounding the piezoelectric element, and applying voltage to different positions. a plurality of elastic members that cause elastic deformation in response to a stress in an opposite axial direction; and a plurality of connecting members that connect adjacent ones of the plurality of elastic members, wherein the adjacent connecting members a storage case comprising: a plurality of connecting members disposed at different angular positions with respect to an azimuthal angle around an axis; first and second end members defining the axial ends; Piezoelectric drive device. (2). Furthermore, a link member is connected to the first and second end members of the storage case and has high rigidity against axial force and flexibility against force in a direction perpendicular to the axial direction. The piezoelectric drive device according to claim 1, comprising: (3). The piezoelectric drive device according to claim 2, wherein the link member includes an axially elongated elastic member. (4). 2. The link member has a rigid portion having a large diameter in a radial direction perpendicular to the axial direction and a pair of hinge portions having a small diameter in the radial direction before and after the rigid portion.
The piezoelectric drive device described. (5). A cylindrical side wall portion having a plurality of annular portions arranged at intervals in the axial direction and a plurality of connecting portions connecting adjacent annular portions at two opposing positions; and at one end of the side wall portion. It has a fixed bottom part, and the annular part of the side wall part has flexibility against stress in the axial direction, and the connection part of the side wall part is rotated approximately 90 degrees about the axis in each stage alternately. A storage case for the piezoelectric drive device located at the location. (6). 6. The storage case for a piezoelectric drive device according to claim 5, wherein a link portion of the laminated piezoelectric element has a large rigidity in an axial direction and a small rigidity in a direction perpendicular to the axial direction and is connected to the bottom portion.