JP2013179786A - Piezoelectric element and piezoelectric actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact piezoelectric element having a configuration that is achieved by easy but precise processing, and to provide a piezoelectric actuator.SOLUTION: A piezoelectric element 1 has: a rod-shaped elastic body 3; long hole-shaped slits s1, s2, and s3; a piezoelectric member 9; and electrode members 7-1, 7-2, and 7-3. The slits s1, s2, and s3 are formed in a side circumferential surface of the rod-shaped elastic body 3, along a longitudinal direction of the rod-shaped elastic body 3 and within a range not reaching both longitudinal end surfaces of the rod-shaped elastic body 3. The piezoelectric member 9 is provided in a portion of the side circumferential surface other than portions where the respective slits s1, s2, and s3 are formed. The electrode members 7-1, 7-2, and 7-3 are provided on the piezoelectric member 9 on the side circumferential surface, within a range not reaching both longitudinal ends of the respective slits s1, s2, and s3, and electrically insulated from each other by the slits s1, s2, and s3. The slits s1, s2, and s3 are formed at respective positions that divide the rod-shaped elastic body 3 circumferentially into three equal sections.

Description

  The present invention relates to a piezoelectric element and a piezoelectric actuator using the piezoelectric element.

  Conventionally, downsizing of a cylindrical piezoelectric element has been desired. The downsizing of the cylindrical piezoelectric element involves manufacturing difficulties. Patent Document 1 discloses a method of manufacturing a small cylindrical piezoelectric element. That is, according to the manufacturing method disclosed in Patent Document 1, first, a piezoelectric element having a cylindrical shape, in which a convex portion having a radial direction and an axial direction as a longitudinal direction is provided on the outer peripheral surface. The piezoelectric element is extruded. Subsequently, a drive electrode is formed on the outer peripheral surface including the convex portion, and a reference electrode is formed on the inner peripheral surface. And after performing a polarization process to the said piezoelectric element using these electrodes, the said convex part is removed by machining. Through these series of steps, a cylindrical piezoelectric element having a drive electrode divided into a plurality of parts can be obtained.

JP 2009-212519 A

  By the way, when a piezoelectric element is miniaturized (for example, when it is miniaturized to an outer diameter of about 100 μm to 1 mm), the accuracy required for the component parts to maintain the performance is increased. In other words, in order to achieve downsizing while maintaining performance, the processing difficulty of the component parts becomes high.

  According to the manufacturing method disclosed in Patent Document 1, high-precision machining is required in the step of removing the convex portion on the outer peripheral surface described above. If the accuracy of this machining is not good, there may be various problems such as cracking of the cylindrical piezoelectric element and short circuit of the drive electrode. Specifically, for example, if the removal of the convex portion is incomplete, a sufficient displacement may not be obtained even when a voltage is applied to the drive electrode. Moreover, when the removal process of the said convex part is too deep and the groove | channel is formed, there exists a possibility that a crack may generate | occur | produce in the said cylindrical piezoelectric element by the deformation | transformation at the time of applying a voltage to a drive electrode. That is, it is difficult to reduce the size of the piezoelectric element while maintaining good processing accuracy by using the technique disclosed in Patent Document 1.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric element and a piezoelectric actuator that achieve good processing accuracy and downsizing with simple processing.

In order to achieve the above object, a piezoelectric element according to the first aspect of the present invention comprises:
A rod-like elastic body having a substantially cylindrical shape;
In the range that does not reach both end faces in the major axis direction of the rod-like elastic body along the major axis direction of the rod-like elastic body, an elongated hole-shaped slit formed on the side peripheral surface of the rod-like elastic body;
A piezoelectric member provided on a portion of the side peripheral surface other than the portion where the slit is formed;
The electrode provided on the piezoelectric member on the side peripheral surface in a range that does not reach both end portions of the slit in the major axis direction and that straddles the slit in the circumferential direction of the rod-shaped elastic body Members,
Comprising
The slits are respectively formed at three positions that divide the rod-like elastic body into three equal parts in the circumferential direction,
The electrode members are three electrode members that are electrically insulated from each other by the slits.

In order to achieve the above object, a piezoelectric actuator according to a second aspect of the present invention comprises:
A rod-like elastic body having a substantially cylindrical shape;
In the range that does not reach both end faces in the major axis direction of the rod-like elastic body along the major axis direction of the rod-like elastic body, an elongated hole-shaped slit formed on the side peripheral surface of the rod-like elastic body;
A piezoelectric member provided on a portion of the side peripheral surface other than the portion where the slit is formed;
The electrode provided on the piezoelectric member on the side peripheral surface in a range that does not reach both end portions of the slit in the major axis direction and that straddles the slit in the circumferential direction of the rod-shaped elastic body Members,
A drive circuit for applying a predetermined alternating signal to the electrode member;
Comprising
The slits are respectively formed at three positions that divide the rod-like elastic body into three equal parts in the circumferential direction,
The electrode members are three electrode members that are electrically insulated from each other by the slits.

  The present invention has been made in view of the above circumstances, and can provide a piezoelectric element and a piezoelectric actuator that achieves good processing accuracy and downsizing with simple processing.

FIG. 1 is a perspective view showing a configuration of a piezoelectric element according to an embodiment of the present invention. FIG. 2 is a perspective view showing an elastic body constituting the piezoelectric element shown in FIG. FIG. 3 is a perspective view showing the elastic body shown in FIG. 2 provided with a piezoelectric member. FIG. 4 is a perspective view showing the piezoelectric element shown in FIG. 1 during polarization processing. FIG. 5 is a diagram showing a cross-sectional arrow view taken along line AA ′ shown in FIG. 4. FIG. 6 is a diagram illustrating a phase difference between the alternating signals V1, V2, and V3. FIG. 7 is a diagram illustrating an example of alternating signals V1, V2, V3, and V4 applied to each electrode member included in a piezoelectric element having a four-electrode structure. FIG. 8 is a diagram illustrating a modification of the drive circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration of a piezoelectric element according to an embodiment of the present invention. FIG. 2 is a perspective view showing an elastic body included in the piezoelectric element shown in FIG. FIG. 3 is a perspective view showing the elastic body shown in FIG. 2 provided with a piezoelectric member. FIG. 4 is a perspective view showing a piezoelectric element according to an embodiment of the present invention during polarization processing. FIG. 5 is a diagram showing a cross-sectional arrow view taken along the line AA ′ shown in FIG. 4.
As shown in FIGS. 1 to 5, the piezoelectric element 1 according to this embodiment includes a substantially cylindrical rod-shaped elastic body 3, a piezoelectric member 9, electrode members 7-1, 7-2, and 7-3. Are provided. Here, as shown in FIG. 1, the Z axis is set in the major axis direction of the rod-shaped elastic body 3. As shown in FIG. 1, an X axis and a Y axis are set in directions orthogonal to each other in a plane perpendicular to the long axis direction of the rod-shaped elastic body 3.

  The rod-like elastic body 3 is a substantially cylindrical elastic body having a through hole 3H formed so as to penetrate through the central portions of both end faces in the long axis direction (Z-axis direction) as shown in FIG. It is a cylindrical shell-shaped elastic body made of stainless steel (SUS material), titanium or the like. A plurality of slits s 1, s 2, s 3 are formed along the long axis direction (Z-axis direction) on the side peripheral surface of the rod-shaped elastic body 3 at a portion excluding the vicinity of both ends of the rod-shaped elastic body 3. Is formed. In other words, the slits s1, s2, and s3 are formed along the major axis direction in a range that does not reach both end faces in the major axis direction of the rod-shaped elastic body 3.

  As shown in FIG. 5, the slits s1, s2, and s3 are formed at three positions that divide the rod-shaped elastic body 3 into three equal parts in the circumferential direction. In other words, the slits s1, s2, and s3 are formed such that straight lines that connect the adjacent slits at the shortest form approximately 120 degrees.

As a specific method for forming the slits s1, s2, and s3, for example, fine processing such as laser processing and etching can be exemplified. The slits s1, s2, s3 are formed so as to be aligned with the central axis of the rod-shaped elastic body 3 by these fine processing.
After forming the slits s1, s2, s3 in the rod-shaped elastic body 3 as described above (see FIG. 2), in a state where one end surface 3E of the rod-shaped elastic body is masked, for example, PVD method (sputtering, laser ablation, etc.) A piezoelectric member (for example, lead zirconate titanate (PZT), for example, is formed on the surface of the rod-shaped elastic body 3 by using a film forming technique such as CVD, chemical solution (CSD), hydrothermal synthesis, or aerosol deposition (AD). ) Etc.). As a result, the piezoelectric member is deposited on the surface of the rod-like elastic body 3 excluding the one end face 3E and the slits s1, s2, and s3.

  Here, as shown in FIG. 5, the piezoelectric member 9-1 is attached to the piezoelectric member deposited on the portion of the side peripheral surface of the rod-shaped elastic body 3 that overlaps the electrode member 7-1. The piezoelectric member deposited on the portion overlapping 2 is labeled with the piezoelectric member 9-2, and the piezoelectric member deposited on the portion overlapping the electrode member 7-3 is labeled with the piezoelectric member 9-3. The electrode members 7-1, 7-2 and 7-3 are electrodes formed in “predetermined regions (details will be described later)” on the piezoelectric member 9.

As described above, the piezoelectric members 9-1, 9-2, and 9-3 are provided at sites other than the site where the three slits s 1, s 2, and s 3 are formed on the side circumferential surface of the rod-shaped elastic body 3. Each of the rod-like elastic bodies 3 is polarized in the radial direction to become an active region.
The electrode members 7-1, 7-2 and 7-3 are formed in “predetermined areas” on the piezoelectric member 9 provided on the side peripheral surface of the rod-like elastic body 3. Specifically, the electrode members 7-1, 7-2, and 7-3 have a range that does not reach both ends of the slits s 1, s 2, and s 3 in the major axis direction (Z-axis direction) of the rod-shaped elastic body 3 And the circumferential direction of the rod-like elastic body 3 is provided over the entire circumference of the rod-like elastic body 3 in such a manner as to straddle the slits s1, s2, and s3.

As a specific method for forming the electrode members 7-1, 7-2, 7-3, for example, a method of sputtering or vapor deposition with gold, platinum, or the like, or an electrode material such as nickel, gold, or silver is formed by plating. A method can be mentioned.
These electrode members 7-1, 7-2 and 7-3 are used when a high voltage V is applied between the piezoelectric member 9 and the rod-shaped elastic body 3 in the polarization process shown in FIG. 4. That is, by applying a high voltage V between the electrode members 7-1, 7-2, 7-3 and the one end face 3 E where the rod-shaped elastic body 3 is exposed, A portion overlapping the member is polarized in the radial direction, and the piezoelectric members 9-1, 9-2, 9-3 are used as active regions. Thus, in the polarization process, one end face 3E of the rod-shaped elastic body 3 is utilized as a common electrode (one electrode of the electrode for polarization).

Hereinafter, a driving method when the piezoelectric element according to the present embodiment is used as a piezoelectric actuator will be described.
The piezoelectric members 9 are vibrated by applying predetermined charges to the piezoelectric members 9-1, 9-2, and 9-3 using the electrode members 7-1, 7-2, and 7-3. The element is displaced in the above-described X-axis direction, Y-axis direction, and Z-axis direction. That is, a bending operation is excited in the rod-shaped elastic body 3 by sequentially applying predetermined alternating signals to the electrode members 7-1, 7-2, and 7-3 by the drive circuit shown in FIG. Let

The predetermined alternating signal is, for example, the alternating signal V1 = sin θ for the electrode member 7-3, the alternating signal V2 = sin (θ + 2π / 3) for the electrode member 7-2, and the electrode member 7-1. Is the alternating signal V3 = sin (θ-2π / 3).
The phase difference between these alternating signals V1, V2, and V3 has a relationship as shown in detail in FIG. FIG. 6 is a diagram illustrating a phase difference between the alternating signals V1, V2, and V3. As shown in the figure, the phase difference between the alternating signal V1 = sin θ and the alternating signal V2 = sin (θ + 2π / 3), the alternating signal V2 = sin (θ + 2π / 3) and the alternating signal V3 = sin (θ-2π). / 3) and the phase difference between the alternating signal V3 = sin (θ−2π / 3) and the alternating signal V1 = sin θ are both approximately 120 degrees.

In other words, the phase difference between the alternating signals applied to the electrode members adjacent to each other among the electrode members 7-1, 7-2, and 7-3 is approximately 120 degrees.
As described above, the bar-shaped elastic body 3 swings and rotates by sequentially applying an alternating signal having a phase difference of approximately 120 degrees to each electrode member.

  Note that the direction of rotation of the rod-shaped elastic body 3 in the swinging rotational motion can be switched by the advance / delay of the phase of the alternating signal applied to the electrode member. Further, when an in-phase alternating signal is simultaneously applied to the electrode members 7-1, 7-2 and 7-3, the rod-shaped elastic body 3 expands and contracts in the Z-axis direction.

As described above, according to the present embodiment, it is possible to provide a piezoelectric element and a piezoelectric actuator that achieves good processing accuracy and downsizing with simple processing.
As specific application fields of the piezoelectric element and the piezoelectric actuator according to the present embodiment, for example, the following fields can be cited. That is, examples include a microactuator, a sensor, a rotating micromotor, a light source (for example, laser light source or LED light source), a fiber or image fiber drive source, and a scanning of a microsensor (for example, cantilever).

By the way, although the piezoelectric element 1 which concerns on this one embodiment is set as the structure provided with three electrode members, a slit is formed in the position which divides the rod-shaped elastic body 3 into 4 equally in the circumferential direction, etc. A configuration including four electrode members insulated from each other is also conceivable.
Hereinafter, the configuration in which the four electrode members are provided in the piezoelectric element 1 (hereinafter referred to as “four-electrode structure”) and the configuration in which the three electrode members are provided in the piezoelectric element 1 (hereinafter, “ Consider the difference in function and effect with the three-electrode structure.

Note that the alternating signals V1, V2, V3, V4 applied to the respective electrode members included in the piezoelectric element 1 having a four-electrode structure are, for example, as shown in FIG. Is an alternating signal of approximately 90 degrees.
Even if the outer diameters of the rod-shaped elastic bodies 3 are the same value, the three-electrode structure piezoelectric element can have a larger electrode width than the four-electrode structure piezoelectric element. Therefore, according to the piezoelectric element having the three-electrode structure, a larger output can be obtained even when the outer diameter is the same as compared with the piezoelectric element having the four-electrode structure. Can be reduced).
-According to the piezoelectric element having the three-electrode structure, the number of wirings can be reduced as compared with the piezoelectric element having the four-electrode structure.
-According to the three-electrode piezoelectric element, it is possible to manufacture a smaller piezoelectric actuator while maintaining accuracy with a simpler configuration than the four-electrode piezoelectric element.
Employing the three-electrode structure is superior to the four-electrode structure from the viewpoint of ease of miniaturization.

The present invention has been described based on one embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that modifications / applications are possible within the scope of the gist of the present invention.
<Modification>
For example, the drive circuit of the piezoelectric element is not limited to the configuration shown in FIG. 5 and may have the configuration shown in FIG. FIG. 8 is a diagram illustrating a modification of the drive circuit. The drive circuit shown in FIG. 8 is a circuit obtained by so-called star delta conversion of the drive circuit shown in FIG.

  Further, the above-described embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be extracted as an invention.

    DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element, s1, s2, s3 ... Slit, 3 ... Bar-shaped elastic body, 3H ... Through-hole, 3E ... One end surface, 7-1, 7-2, 7-3 ... Electrode member, 9 ... Piezoelectric member, 9 −1, 9-2, 9-3... Piezoelectric members overlapping the electrode members, V1, V2, V3.

Claims (4)

A rod-like elastic body having a substantially cylindrical shape;
In the range that does not reach both end faces in the major axis direction of the rod-like elastic body along the major axis direction of the rod-like elastic body, an elongated hole-shaped slit formed on the side peripheral surface of the rod-like elastic body;
A piezoelectric member provided on a portion of the side peripheral surface other than the portion where the slit is formed;
The electrode provided on the piezoelectric member on the side peripheral surface in a range that does not reach both end portions of the slit in the major axis direction and that straddles the slit in the circumferential direction of the rod-shaped elastic body Members,
Comprising
The slits are respectively formed at three positions that divide the rod-like elastic body into three equal parts in the circumferential direction,
The said electrode member is three electrode members electrically insulated from each other by the said slit. The piezoelectric element characterized by the above-mentioned. The length of the said electrode member in the said circumferential direction of the said rod-shaped elastic body is a length more than the length of the said slit in the said circumferential direction of the said rod-shaped elastic body. The piezoelectric element of Claim 1 characterized by the above-mentioned. A rod-like elastic body having a substantially cylindrical shape;
In the range that does not reach both end faces in the major axis direction of the rod-like elastic body along the major axis direction of the rod-like elastic body, an elongated hole-shaped slit formed on the side peripheral surface of the rod-like elastic body;
A piezoelectric member provided on a portion of the side peripheral surface other than the portion where the slit is formed;
The electrode provided on the piezoelectric member on the side peripheral surface in a range that does not reach both end portions of the slit in the major axis direction and that straddles the slit in the circumferential direction of the rod-shaped elastic body Members,
A drive circuit for applying a predetermined alternating signal to the electrode member;
Comprising
The slits are respectively formed at three positions that divide the rod-like elastic body into three equal parts in the circumferential direction,
The said electrode member is three electrode members electrically insulated from each other by the said slit. The piezoelectric actuator characterized by the above-mentioned. The phase difference between the predetermined alternating signals applied to the electrode members adjacent to each other among the three electrode members is approximately 120 degrees,
The piezoelectric actuator according to claim 3, wherein the driving circuit sequentially applies the predetermined alternating signal to the three electrode members.

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