JP2022008140A - Vibration type actuator, optical device, and electronic device - Google Patents

Abstract

To provide a vibration type actuator having excellent vibration characteristics, which suppresses deterioration of the vibration characteristics due to a penetrating portion.SOLUTION: A vibration type actuator that solves the above problems is characterized in that a rectangular piezoelectric material, an oscillator having a piezoelectric element having a penetrating portion penetrating the piezoelectric material, and a contact body in contact with the oscillator are included, and the penetrating portion is formed outside a region surrounded by connecting an intersection between a node of a primary out-of-plane bending vibration and a node of a secondary out-of-plane bending vibration mode.SELECTED DRAWING: Figure 2

Description

The present invention relates to a vibrating actuator including an ultrasonic motor.

A vibrating actuator driven by two vibration modes excited by a vibrator in which an elastic diaphragm (elastic body) and a piezoelectric element are bonded is widely used. As an example, there is a vibration type actuator in which a voltage is applied to a piezoelectric element constituting the vibrator to generate two vibrations of mode A and mode B, and the vibrator is caused to elliptically vibrate. In such a vibration type actuator, the vibrator and the contact body move relatively due to the elliptical vibration generated in the vibrator due to the application of voltage and the frictional force generated on the contact surface of the contact body in contact with the vibrator.

Patent Document 1 discloses a vibration type actuator driven by two vibration modes. It is disclosed that the piezoelectric element used in the vibration type actuator is provided with a through hole at the intersection of the node lines of the vibration modes of mode A and mode B so as not to hinder the generated vibration.

However, the piezoelectric material constituting the piezoelectric element is partially lost in the penetrating portion penetrating the piezoelectric element. Therefore, there is a problem that the vibration characteristics of the vibration type actuator are deteriorated.

JP-A-2017-158429

The present invention provides a vibration type actuator in which deterioration of vibration characteristics due to a penetration portion is suppressed.

The vibration type actuator that solves the above problems is
A rectangular piezoelectric material, a pair of electrodes provided on the piezoelectric material, and
A piezoelectric element having a penetration portion that energizes one of the electrodes and penetrates the piezoelectric material, and a vibrator having an elastic body.
A contact body that is in contact with the vibrator and moves relative to the vibrator is provided.
The penetration is a primary out-of-plane bending vibration mode node where two vibration nodes occur along the long side of the piezoelectric material and three vibration nodes along the short side of the piezoelectric material. It is characterized in that it is formed outside the region surrounded by connecting the intersections with the nodes of the secondary out-of-plane bending vibration mode in which the above occurs.

According to the present invention, it is possible to provide a vibration type actuator having excellent vibration characteristics, in which deterioration of vibration characteristics due to a penetrating portion is suppressed.

It is a figure explaining the schematic structure of the vibration type actuator of this invention. It is a figure explaining the structure of the piezoelectric element which constitutes the vibration type actuator of this invention. It is a figure explaining two vibration modes which the oscillator of this invention generates. It is a figure explaining the node and the antinode position of two vibration modes generated in the oscillator of this invention. It is a figure explaining the node of distortion and the antinode position in two vibration modes generated in the oscillator of this invention. It is a figure explaining the structure of the penetration part corresponding to the Example of this invention. It is a figure explaining the arrangement of the penetration part of the vibration type actuator of this invention. It is a figure which shows the piezoelectric ceramics 114P and the penetration part 114E which concerns on this invention. It is a figure explaining the vibration type actuator which concerns on Example and comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The vibration type actuator of this embodiment includes the following elements.

That is, a rectangular piezoelectric material, a pair of electrodes provided on the piezoelectric material, a piezoelectric element having a penetrating portion that energizes one of the electrodes and penetrates the piezoelectric material, a vibrator having an elastic body, and a vibrator are in contact with each other. It is a contact body that moves relatively with the oscillator.

Two nodes of vibration are generated along the long side of the rectangular piezoelectric material, and three nodes of vibration are generated along the short side of the first-order out-of-plane bending vibration mode. Pay attention to the node line of the next out-of-plane bending vibration mode. A penetration is formed outside the area surrounded by connecting the intersections of these nodes.

FIG. 1 is a perspective view illustrating a schematic structure of the vibration type actuator 100.

The vibration type actuator 100 includes an oscillator 115 and a contact body 111 that is in contact with the oscillator and is arranged so as to be relatively movable with respect to the oscillator. The vibrator 115 is provided on a plate-shaped and elastic vibrating plate 113 (elastic body), a substantially rectangular and plate-shaped piezoelectric element 114 joined to one surface of the vibrating plate 113, and the other surface of the vibrating plate 113. It is composed of two protrusions 112.

The contact body 111 and the vibrator 115 are configured to be in pressure contact with each other by a pressure portion (not shown) composed of a spring member, a magnet, or the like.

The "contact body" refers to a member that comes into contact with the oscillator and moves relative to the oscillator due to the vibration generated in the oscillator. The contact between the contact body and the vibrator is not limited to the direct contact in which no other member intervenes between the contact body and the vibrator. The contact between the contact body and the vibrator is an indirect contact in which another member intervenes between the contact body and the vibrator if the contact body moves relative to the vibrator due to the vibration generated in the vibrator. May be good. The "other member" is not limited to a member independent of the contact body and the vibrator (for example, a high friction material made of a sintered body). The "other member" may be a surface-treated portion formed on the contact body or the vibrator by plating, nitriding treatment, or the like.

Therefore, the contact body 111 may be a member that is pressurized from the oscillator 115 and can move relatively with the oscillator 115, and is not limited to a member that is in direct contact with the oscillator 115, but vibrates via another member. It may be indirect contact with the child 115.

In the vibration type actuator 100, a predetermined vibration mode is excited to the vibrator 115 by applying a voltage of a specific frequency to the piezoelectric element 114. By using a plurality of vibrations in these vibration modes, elliptical vibration is generated at the tips of the two protrusions. As a result, the contact body 111 can be driven in a predetermined drive direction by the frictional force generated at the contact point between the vibrator and the contact body. This elliptical vibration is generated, for example, by exciting the oscillator 115 in two vibration modes.

In the following description, the "decrease in the performance of the vibrating actuator" may be described as an increase in power consumption (rated power) at a certain moving speed, that is, a decrease in efficiency.

FIG. 2 is a diagram illustrating the structure of the piezoelectric element 114 constituting the vibration type actuator 100 of the present invention. The piezoelectric element 114 is composed of a rectangular piezoelectric material and an electrode portion. The piezoelectric material may be any material that exhibits piezoelectricity, such as polycrystalline piezoelectric ceramics or piezoelectric single crystals, but the following will be described by taking polycrystalline piezoelectric ceramics as an example.

FIG. 2A shows the main surface of the piezoelectric element 114, and FIG. 2B shows the surface facing the main surface of the piezoelectric element 114. The rectangular piezoelectric ceramic 114P has a first region divided into two in the longitudinal direction and a second region adjacent to the first region. A first electrode 114A and a second electrode 114B are formed in the first and second regions, respectively. Further, it has a third electrode 114D that sandwiches the piezoelectric ceramics 114P together with the first electrode 114A and the second electrode 114B. Further, it has a penetrating portion 114E penetrating the piezoelectric ceramics in order to energize the third electrode from the surface (main surface) provided with the first electrode 114A and the second electrode 114B.

The surface of the piezoelectric element 114 facing the main surface is adhered to the surface of the diaphragm 113 not provided with the protrusion 112.

The polarization directions of the piezoelectric ceramics 114P in the region where the first electrode 114A and the second electrode 114B are provided are the same, and the polarization treatment may be performed in advance by a known polarization treatment method.

In order to generate vibrations in mode A and mode B, the third electrode 114D of the piezoelectric element 114 is grounded, an alternating voltage VA is applied to the first electrode 114A, and an alternating voltage _VA is applied to the second electrode 114B. The voltage V _B is applied independently.

Unless otherwise specified, the magnitudes of the amplitudes of the alternating voltages _VA and _BB will be described below.

As a means for supplying power to the first electrode 114A and the second electrode 114B, for example, a flexible printed substrate (not shown) is adhered to the surface of the piezoelectric element 114 as a feeding member. The flexible printed substrate is provided with at least an electrode connected to the first electrode 114A and the second electrode 114B to supply an alternating voltage, and an electrode having a ground potential connected to the electrode 114E. A fourth electrode electrically connected to the flexible printed circuit board and the penetration portion 114E on the main surface as shown in FIG. 2 (c) in order to suppress electrical disconnection and improve the reliability of conduction. 114F may be formed.

As depicted in FIG. 2 (c), the through portion 114E may have a structure in which the through hole and the inner wall of the through hole are provided with a conductive material. In that case, it is more preferable that the conductive material fills the through hole because it prevents the adhesive from diffusing and conducts conduction at a sufficiently low resistance value. Further, as shown in FIG. 2D, the penetrating portion 114E is provided on the end surface of the piezoelectric ceramics (rectangular piezoelectric material), and has a groove connecting the main surface of the piezoelectric element 114 and the surface facing the main surface. The inner wall of the groove may be provided with a conductive material. The conductive material may be the same conductive material as any one of the first, second, and third electrodes, or may be another conductive material as long as sufficient conduction is ensured.

The cross-sectional shape of the penetrating portion 114E is not particularly limited, but a circular shape is preferable. The circular shape also includes an elliptical shape having an ellipticity of 0.9 or more. When the penetrating portion is formed in the molded body of the piezoelectric ceramic before firing of the piezoelectric ceramics, if the cross-sectional shape of the penetrating portion is circular, isotropic shrinkage proceeds during sintering and cracks are unlikely to occur. Through holes can be formed by using a punch or a drill in the state of the green sheet before firing the piezoelectric ceramics.

When the electrode material is filled in the through holes provided in the molded body containing the raw material of piezoelectric ceramics and the electrode material and the molded body are fired together, the higher the firing temperature, the higher the heat resistance required for the electrode material. It gets higher. In the case of a silver-palladium electrode, it is necessary to increase the expensive palladium ratio, and when higher heat resistance than the silver-palladium electrode is required, it is necessary to use expensive platinum.

On the other hand, in order to reduce the production cost, it is preferable to employ a step of firing a molded body having a through hole formed in advance to obtain a piezoelectric ceramic, and then filling the through hole of the ceramic with an electrode material. When this step is adopted, an inexpensive electrode material such as silver paste can be used for the electrode to be filled in the through hole.

Further, as shown in FIG. 2D, when the penetrating portion 114E is exposed on the side surface of the piezoelectric ceramics 114P, the cross-sectional shape may be a semicircular arc shape, or the cross-sectional shape may be a semicircular groove shape. The shape may be adopted.

In manufacturing the penetration portion 114E having such a shape, a through hole formed in advance may be cut, or a rotating blade may be applied to the side surface for processing.

<Two out-of-plane bending vibration modes>
FIG. 3 is a diagram illustrating two vibration modes generated by the oscillator used to drive the vibration type actuator 100 of the present invention.

FIG. 3A is a perspective view illustrating a primary out-of-plane bending vibration mode (hereinafter referred to as “mode A”) excited by the vibrator 115 constituting the vibration type actuator 100. FIG. 3B is a perspective view illustrating a secondary out-of-plane bending vibration mode (hereinafter referred to as “mode B”) excited by the vibrator 115 constituting the vibration type actuator 100. When the temporal phase difference between the alternating voltages V _A and V _B is 0 ° and the frequencies of the alternating voltages V _A and V _B are close to the resonance frequency of the mode A, respectively, the oscillator 115 has FIG. 3 (a). The vibration of mode A shown in is generated. In mode A vibration, two nodes of vibration occur along the long sides of the rectangular piezoelectric material. Mode A is a vibration mode in which both the first region and the second region expand or contract.

On the other hand, when the temporal phase difference between the alternating voltages _VA and VA is 180 ° and their frequencies are near the resonance frequency of mode _B , the oscillator 115 has mode B shown in FIG. 3 (b). Vibration occurs. In mode B vibration, three nodes of vibration occur along the short sides of the piezoelectric material. Mode B is a mode in which the second region contracts when the first region expands, and conversely, the second region expands when the first region contracts.

The protrusion 112 of the diaphragm is in the vicinity of the position where the vibration of the mode A is the antinode (where the amplitude is maximum) and in the vicinity of the position where the vibration node of the mode B is (where the amplitude is the minimum). It is placed in a certain position. Due to the vibration of mode A, the tip surface of the protrusion 112 of the oscillator 115 reciprocates in the Z direction. Further, the tip surface of the protrusion 112 reciprocates in the X direction due to the vibration of mode B.

In the vibration type actuator 100, modes A and B are superimposed, and elliptical vibration is excited to the protrusion 112 of the diaphragm.

The Z direction in FIG. 3 is a direction in which the vibrator is pressed against the contact body (a direction in which the protrusion moves up and down in the vibration of mode A). The X direction is the direction in which the vibrator and the contact body move relatively (the direction in which the protrusion reciprocates in the vibration of mode B). The Y direction is a direction perpendicular to the XZ plane.

When the phase difference between the alternating voltages V _A and V _B is 0 to ± 180 °, the modes A and B are superimposed and an elliptical motion in the XZ plane can be generated on the tip surface of the protrusion 112.

Since a frictional force due to pressure contact acts between the protrusion 112 and the contact body 111, it is possible to generate a driving force (thrust) that drives the contact body 111 in the X direction by the elliptical movement of the protrusion 112. can.

The resonance frequencies of modes A and B can be adjusted by the dimensions of the long side and the short side of the rectangular piezoelectric material. It is preferable that the long side of the rectangular piezoelectric material is 1 mm or more and 20 mm or less, and the short side is 0.5 mm or more and 10 mm or less. It is more preferable that the long side is 6 mm or more and 20 mm or less and the short side is 3 mm or more and 10 mm or less because the variation in resonance frequency due to the processing accuracy is small.

The vibrating piezoelectric element has a vibration antinode, a vibration node, a strain antinode, and a strain node depending on the vibration mode.

<Vibration node / belly>
FIG. 4 shows the positions of the nodal lines and the abdominal lines of the vibrations corresponding to the modes A and B generated in the oscillator of the present invention. FIG. 4 is a plan view of the oscillator 115 as viewed from the piezoelectric element 114 side.

In FIG. 4A, the two nodal lines of the vibration of the mode A are shown by the broken line 411, and the three antinode lines of the vibration are shown by the alternate long and short dash line 412. The node line and the belly line of the mode A are obtained by connecting the vibration node and the belly position in an arbitrary YZ plane in the X direction, respectively.

Further, FIG. 4B shows the three node lines of the vibration of the mode B by the broken line 421 and the two abdominal lines of the vibration by the alternate long and short dash line 422. Mode B node lines and abdominal lines are obtained by connecting the vibration nodes and abdominal positions in any XZ plane in the Y direction, respectively.

When using the vibration type actuator 100, both mode A and mode B of the oscillator 115 are used. FIG. 4C shows the node of mode A and the node of mode B superimposed, and illustrates the position of the preferable penetration portion 114E (denoted as E in the figure). The intersection 423 of the node of mode A and the node of mode B is shown by a quadrangle. It can be seen that there are six intersections of the node lines generated by the vibrations of each of mode A and mode B. As will be described later, the region 431 surrounded by these six intersections is shown in the shaded area.

<Vibration node and belly line positions>
The node line position and the abdominal line position of the vibration generated in the piezoelectric ceramics 114P due to the excitation of the mode A and the mode B in the vibrator 115 are measured as follows. That is, the oscillator 115 is made to vibrate in mode A or mode B. When the mode A is generated, the phase difference between the alternating voltages _VA and _BB is set to 0 °. When the mode _B is generated, the phase difference between the alternating voltages _VA and VA is 180 °. Then, for example, the vibration velocity in the Z direction is measured two-dimensionally on the XY plane with a laser Doppler vibrometer, and the displacement of each point in the Z direction is calculated to obtain the node lines and abdominal lines of Mode A and Mode B. The position can be measured.

Since the flexible printed substrate is attached to the piezoelectric element 114, it may be difficult to directly measure the vibration of the piezoelectric element 114 or the piezoelectric ceramics 114P. In such a case, the vibration state of the surface of the diaphragm 113 is observed, the positions of the observed node lines and abdominal lines are projected onto the piezoelectric element 114, and the positions of the nodal lines and abdominal lines of the vibration generated in the piezoelectric ceramics 114P are projected. May be treated as. Further, since the electrode material provided on the surface of the piezoelectric ceramic 114P is sufficiently smaller in thickness and rigidity than the piezoelectric ceramic 114P, the vibration generated on the piezoelectric element 114 may be regarded as the vibration generated in the piezoelectric ceramic 114P. Alternatively, the positions of the nodes and antinodes of each vibration can be obtained from the modal analysis by the finite element method.

At the time of vibration measurement, the oscillator does not have to be pressurized to the contact body.

<Distorted node / belly>
When the oscillator 115 vibrates, distortion occurs inside the piezoelectric ceramics 114P. The strain knots and abdominal lines in modes A and B are obtained by the same procedure as the vibration knots and abdominal lines described above. The position of the strain node and belly line may differ from the position of the vibration node and belly line.

FIG. 5 shows the positions of the strain nodes and antinodes of the piezoelectric ceramics 114P in modes A and B generated in the oscillator of the present invention.

FIG. 5A shows the strain node of the piezoelectric ceramic 114P in the mode A by the broken line 511 and the antinode of the strain by the alternate long and short dash line 512. FIG. 5B shows the strain node position of the piezoelectric ceramic 114P in mode B by the broken line 521 and the antinode position of the strain by the alternate long and short dash line 522.

The strain node of mode A exists near the end of the piezoelectric ceramic in parallel with the long side.

The distortion node of mode B exists near the end of the piezoelectric ceramic and in the center of the piezoelectric ceramic in parallel with the short side. The belly is located between the nodes.

FIG. 5C shows the strain node of mode A and the strain node of mode B superimposed, and the strain node positions are mainly the outer peripheral portion of the piezoelectric ceramic 114P and the rectangular piezoelectric material. It exists on a line that intersects the two long sides and divides the two long sides into two equal parts.

As shown in FIGS. 4 and 5, the vicinity of the two long sides of the piezoelectric ceramic 114P corresponds to the antinode of the vibration of the mode A and corresponds to the strain node of the mode A. On the other hand, the vicinity of the two short sides of the rectangular piezoelectric ceramic 114P corresponds to the antinode of the vibration of the mode B and corresponds to the strain node of the mode B. Unlike the vibration node / antinode, it is difficult to directly observe, so the position of the strain node / antinode is obtained by analysis by the finite element method.

<Suitable penetration position 1>
The strain node position is a position where the work performed by the piezoelectric ceramics 114P to generate vibration is the minimum, and is suitable as a place where the through portion 114E is provided in the piezoelectric ceramics 114P.

On the contrary, the antinode position of strain is the position where the work performed by the piezoelectric ceramics 114P to generate vibration is the maximum, and it is not preferable as a place where the penetration portion 114E is provided in the piezoelectric ceramics 114P.

FIG. 5D is a diagram showing both the area 431 and the abdominal lines of the strains of the mode A and the mode B. The region 431 includes a region where the abdominal line 512 of the strain of the mode A and the abdominal line 522 of the strain of the mode B intersect, and is a region in which the strain of the piezoelectric ceramics due to vibration is large. Assuming that the amount of strain at the intersection of the abdominal line 512 of mode A and the abdominal line 522 of the strain of mode B and the point with the largest strain is 100%, the amount of strain in the region 431 is 30% or more. That is, the region 431 is a region where the work done by the piezoelectric ceramics 114P to generate vibration is large. Therefore, if the contour of the region 431 (the line connecting the intersections of the vibration nodes) and the penetrating portion inside the contour, the vibration is reduced and the efficiency of the vibration type actuator is lowered.

Since the vibration amount is small, the vibration node position is a suitable place for adhering a member such as a flexible printed substrate while suppressing vibration inhibition. On the other hand, since the vibration node position may have a large amount of strain generated in response to the vibration, the vibration node position is not always optimal as the position where the penetration portion is provided.

Therefore, the penetration portion 114E in the piezoelectric ceramics 114P is formed outside the region 431 surrounded by the intersection of the vibration node 411 of the mode A and the vibration node 421 of the mode B.

"The penetration portion 114E is formed outside the region 431" means that the penetration portion 114E is not formed in the region inside the region 431 and the penetration portion 114E is formed in the region outside the region 431. Point to.

It is preferable to provide at least one penetrating portion 114E in the region outside the contour of the region 431 surrounded by the intersections of the vibration nodes shown in FIG. 4 (c). As a result, it is possible to suppress a decrease in vibration characteristics due to a defect in the piezoelectric element, and it is possible to provide a vibration type actuator having excellent vibration characteristics.

<Suitable penetration position 2>
FIG. 7 is a diagram illustrating an arrangement of a penetrating portion of the vibration type actuator of the present invention.

It is more preferable that the penetrating portion 114E (denoted as E in the drawing) is formed in a region extending from the node line 411 of the mode A to the long end side of the rectangular piezoelectric ceramic 114P (FIG. 7A). , FIG. 7 (b), FIG. 7 (c)). Such an arrangement of the penetrating portion 114E is more preferable in the region outside the region 431 surrounded by the intersections of the vibration nodes. This is because there is no region in which the strain or amplitude of both mode A and mode B becomes antinodes in the region, and further, it is generally far from the antinode 512 (FIG. 5A) of the strain of mode A, so that the vibration of mode A is affected. This is because the vibration inhibition by the penetrating portion 114E is smaller.

<Suitable penetration position 3>
FIG. 8 is a diagram showing the piezoelectric ceramics 114P and the penetrating portion 114E (denoted as E in the figure) according to the present invention.

In the region outside the region 431 surrounded by the intersections of the vibration nodes (white squares in the figure), attention is paid to the line that bisects the two long sides of the rectangular piezoelectric ceramic 114P. It is preferable that at least one penetration portion 114E is formed in a region within 300 microns (= 0.3 mm) from this bisector. It is even more preferable that this region has the center of gravity of the XY plane cross section of the penetrating portion 114E.

This is because the region within 300 microns from the bisector includes both the strain node of mode B and the vibration node of mode B, so that the efficiency decrease of the vibration type actuator 100 due to the provision of the penetration portion 114E is further suppressed. Because it is possible. Since the distortion node 521 in mode B and the vibration node 421 in mode B overlap, they are drawn with one broken line for convenience in FIG. 8, and some of the other nodes are omitted. I'm drawing.

<Diameter of through hole>
It is preferable that the diameter of the through hole is larger than 140 microns and smaller than 400 microns. This is because if the diameter is 140 microns or less, the electric resistance inside the through hole becomes high and the efficiency of the vibrating actuator 100 may decrease. Further, when the diameter is 400 microns or more, the loss of the piezoelectric material due to the penetrating portion 114E may be large and the vibration characteristics may be deteriorated. It is more preferable that the diameter is larger than 140 microns and 300 microns or less because sufficient conductivity is maintained and the through holes are further filled with a conductive material to facilitate closing. If the diameter of the through hole is not constant, the diameter of the through hole as used herein is defined by the diameter of the largest through hole.

FIG. 6 is a diagram showing an example of the cross-sectional shape of the through hole and the through portion 114E provided with the conductive material on the inner wall of the through hole.

FIG. 6A is a schematic view of the case where the through hole is not filled (closed) with the conductive material, and FIG. 6B is a schematic view of the case where the through hole is filled with the conductive material. When the through hole is closed by the conductive material, the adhesive used for joining the diaphragm 113 and the piezoelectric element 114 can be prevented from diffusing through the through portion 114E, or the electric resistance of the through hole can be lowered. It is more preferable because it has the effect of

If the through hole is not closed, the light of the light source placed on the opposite surface of the piezoelectric element can be seen through the through hole.

<Number of penetrations>
Although the number of penetrating portions 114E is not limited, it is preferable that an even number of penetrating portions 114E are arranged line-symmetrically with respect to a line that bisects the short side of the rectangular piezoelectric ceramics 114P. By adopting such a configuration, the symmetry of the mode A is not impaired, and the efficiency decrease of the vibration type actuator 100 can be suppressed. Further, when attaching a flexible printed substrate or the like, it is not necessary to align the directions of the piezoelectric elements, which is suitable.

On the other hand, it is more preferable that the number of the penetrating portions 114E is one from the viewpoint of reducing the production cost. In particular, it is more preferable that the diameter of the through hole is larger than 140 microns and smaller than 300 microns because even one through portion does not disturb the symmetry of vibration. That is, it is preferable that the penetrating portion is substantially line-symmetrical with respect to the bisector of the two short sides of the rectangular piezoelectric material.

<Amount of lead contained in piezoelectric material>
Lead zirconate titanate (PZT), which has excellent piezoelectric properties, can be used for the piezoelectric ceramics 114P included in the piezoelectric element 114, but if the amount of lead contained in the piezoelectric material is less than 1000 ppm, the environmental load is small. More preferred. The content of lead contained in the piezoelectric material can be evaluated by the content of lead with respect to the total weight of the piezoelectric material quantified by, for example, fluorescent X-ray analysis (XRF) or ICP emission spectroscopy.

An example of a piezoelectric material having a low lead content is a piezoelectric material in which the piezoelectric material contains a perovskite-type oxide containing Ba, Ca, Ti, and Zr, and Mn. Then, x, which is the molar ratio of the Ca to the sum of the Ba and the Ca, is 0.02 ≦ x ≦ 0.30. The molar ratio y of Zr to the sum of Ti and Zr is 0.020 ≦ y ≦ 0.095 and y ≦ x. In addition, a, which is the molar ratio of the sum of Ba and Ca to the sum of Ti and Zr, is 1.00 ≦ a ≦ 1.01. Further, the content of Mn with respect to 100 parts by weight of the oxide is preferably 0.02 parts by weight or more and 0.40 parts by weight or less in terms of metal. This composition is hereinafter referred to as BCTZ.

Further, as a second example of the piezoelectric material having a low lead content, a piezoelectric material containing an oxide containing Na, Ba, Nb and Ti and at least one element selected from Mn and Ni can be used. The x, which is the mol ratio of the Na to 1 mol of the oxide, is 0.80 ≦ x <0.92. Then, y, which is the mol ratio of the Nb to the sum of the Nb and the Ti, is 0.83 ≦ y <0.92. In addition, the mol ratio of Ba to the sum of Nb and Ti is greater than 0.08 and 0.20 or less. The Ni content is 0.05 mol or less with respect to 1 mol of the oxide (that is, the molar ratio is 0.05 or less), and the Mn content is 0.005 mol or less with respect to 1 mol of the oxide (that is, the molar ratio is 0 or less). .005 or less). The piezoelectric material is more preferably a perovskite type piezoelectric material. This composition is hereinafter referred to as NNBT.

<Thickness of piezoelectric ceramics>
It is preferable that the piezoelectric ceramic 114P is a single layer having a thickness of 0.3 mm or more.

This is because if the thickness of the piezoelectric ceramics is 0.3 mm or more, it is difficult to break due to pressure applied when the diaphragm 113 or the like is bonded, and the yield increases. Further, the single-layer piezoelectric element is preferable because it is cheaper and more robust than the laminated piezoelectric element having an interpolated electrode.

On the other hand, if the thickness of the piezoelectric ceramic is thicker than 0.5 mm, it becomes difficult to form an electrode on the inner wall of the through hole, and the electrode may be broken inside the through hole. Therefore, the thickness of the piezoelectric ceramic is preferably 0.3 mm or more and 0.5 mm or less.

Next, the vibration type actuator and the oscillator of the present invention will be described with reference to examples, but the present invention is not limited to the following examples. Table 1 summarizes examples and comparative examples of the present invention.

First, prior to the description of the embodiment, the vibration type actuator of the comparative example to be compared with the embodiment will be described. The shape of the electrode formed on the main surface is appropriately changed according to the position and number of the penetrating portions.

<Comparative Example 1>
As shown in FIG. 9A, a piezoelectric element having a total of two penetration portions 114E provided inside the region 431 surrounded by the intersection of the vibration node of mode A and the vibration node of mode B was manufactured. A PZT having a thickness of 0.35 mm was used as the piezoelectric material. The two penetration portions 114E are provided at the intersection of the strain abdomen of mode A and the strain abdomen of mode B, and the diameter of the through hole is 600 microns. The rated power of the vibration type actuator manufactured by using this piezoelectric element was W _ref1 .

<Comparative Example 2>
As shown in FIG. 9B, a piezoelectric element having a penetrating portion inside a region 431 surrounded by the intersection of the vibration node of mode A and the vibration node of mode B was manufactured. That is, the piezoelectric element is the same as in Comparative Example 1 except that a total of two penetration portions 114E are provided at the intersections of the vibration node of mode A and the vibration node of mode B. The rated power of the vibrating actuator manufactured by using this piezoelectric element was W _ref2 , and the value of W _ref2 was lower than that of Comparative Example 1, and the relationship was W _ref2 <W _ref1 . The values of W _ref2 and W _ref1 were both large, and the efficiency of the vibrating actuator was not sufficient.

<Example 1>
As shown in FIG. 9 (c), a piezoelectric element having a penetrating portion provided outside the region 431 surrounded by the intersection of the vibration node of mode A and the vibration node of mode B was manufactured. That is, a comparative example except that a total of two penetration portions 114E are provided at the intersection of the straight line that bisects the two short sides of the piezoelectric ceramic and the node line of mode B, and the midpoint of the short side of the piezoelectric ceramic. It is a piezoelectric element similar to 1.

The position where the penetration portion 114E is provided is outside the region 431 but within the region sandwiched by the vibration node of the mode A.

Assuming that the rated power W _ex1 of the vibration type actuator manufactured by using this piezoelectric element, it was We _x1 <W _ref2 <W _ref1 . That is, the efficiency of the vibration type actuator was improved as compared with the configurations of Comparative Example 1 and Comparative Example 2.

<Example 2>
As shown in FIG. 9D, a penetration portion 114E having two through holes having a diameter of 600 microns is provided outside the region 431 surrounded by the intersection of the vibration node of mode A and the vibration node of mode B. A piezoelectric element was manufactured. Specifically, the position of the penetration portion 114E is the piezoelectric element from the midpoint between the intersection of the straight line that divides the two long sides of the piezoelectric ceramic into two equal parts and the node line of the vibration of mode A and the long side of the piezoelectric ceramic. It is located at a position where the center of gravity of the is shifted by 400 microns in a point-symmetrical manner. Assuming that the rated power of the vibration type actuator manufactured by using this piezoelectric element is W _ex2 , the measurement result was W _ex2 <W _ex1 <W _ref2 <W _ref1 . That is, the efficiency of the vibration type actuator was improved as compared with the configurations of Comparative Example 1 and Comparative Example 2. Furthermore, the efficiency of the vibration type actuator was improved as compared with the configuration of the first embodiment.

<Example 3>
As shown in FIG. 9 (e), the positions of the two penetrating portions 114E are outside the region 431, and the amount of deviation in the X direction is within 300 microns with respect to the straight line that bisects the two long sides of the piezoelectric ceramics. A piezoelectric element was manufactured. Assuming that the rated power of the vibration type actuator manufactured by using this piezoelectric element is W _ex3 , the measurement result was W _ex3 <W _ex2 <W _ex1 <W _ref2 <W _ref1 .

<Example 4>
The same piezoelectric element as in Example 3 was manufactured except that the diameter of the through hole was 140 microns. The rated power W _ex4 of the vibrating actuator using the same element was W _ex4 <We _x 3, and the efficiency of the vibrating actuator was further improved.

<Example 5>
The same piezoelectric element as in Example 3 was manufactured except that the diameter of the through hole was 400 microns, and the rated power _Wex5 of the vibration type actuator using the element was almost the same as _Wex4 .

<Comparative Example 3>
The same piezoelectric element as in Example 3 was manufactured except that the diameter of the through hole was 900 microns, and the rated power W _{ref 3} of the vibration type actuator using the same element was W _ex3 <Wr _{ef 3} . Summarizing the results of Example 3-5 and Comparative Example 3,
There was a relationship of W _ex5 ≈ W _ex4 <W _ex3 <W _ref3 .

From the above results, it is more preferable that the width of the penetrating portion is 140 microns or more and 400 microns or less.

<Example 6>
The same piezoelectric element as in Example 5 was manufactured except that the number of penetrating portions was one, and the rated power _Wex6 of the vibration type actuator using the same element was almost the same as _Wex5 .

<Example 7>
A piezoelectric element using BCTZ as a piezoelectric material was created. A piezoelectric element was produced in the same manner as in Example 6 except that the composition of the piezoelectric material was different. It was confirmed that the effect of the present invention can be obtained even with a vibration type actuator using the same element.

<Example 8>
A piezoelectric element using NNBT as a piezoelectric material was produced. A piezoelectric element was produced in the same manner as in Example 6 except that the composition of the piezoelectric material was different.

It was confirmed that the effect of the present invention can be obtained even with a vibration type actuator using the same element.

<Example 9>
The same piezoelectric element as in Example 7 was produced except that the diameter of the through hole was 200 microns. The efficiency of the vibrating actuator using the same element was equivalent to that of the vibrating actuator described in Example 7. The cross section of the piezoelectric element including the through hole was observed, and the average thickness of the electrode formed on the surface of the element and the electrode on the inner wall of the through hole were obtained. The average thickness was obtained by determining the cross-sectional area of the electrode formed on the surface of the device or in the through hole from image processing, and dividing the obtained cross-sectional area by the length of the electrode forming portion. The average thickness of the electrodes inside the through hole is obtained by dividing the cross-sectional area of the electrodes inside the through hole by a value obtained by doubling the thickness of the piezoelectric material. As a result, the ratio of the average thickness between the surface electrode and the electrode inside the through hole was 2.5 to 10 times, and the average thickness of the electrode inside the through hole was larger.

<Example 10>
The same piezoelectric element as in Example 7 was produced except that the diameter of the through hole was 140 microns. It was confirmed that the effect of the present invention can be obtained even with a vibration type actuator using the same element.

<Comparative Example 4>
The same piezoelectric element as in Example 9 was manufactured except that the thickness of the piezoelectric ceramic was 0.25 mm. However, when the piezoelectric element was pressure-bonded to the diaphragm, 10% of the piezoelectric element cracked, and it was found that the robustness of the piezoelectric element was not sufficient.

<Example 11>
The same piezoelectric element as in Example 9 was manufactured except that the thickness of the piezoelectric ceramic was 0.3 mm, and a vibration type actuator using the same element was manufactured. When the thickness of the piezoelectric ceramics was 0.3 mm, the frequency with which the piezoelectric element cracked when the diaphragm was adhered to the piezoelectric element was 1% or less. By increasing the thickness of the piezoelectric ceramics to 0.3 mm or more, the probability that the piezoelectric element will crack in the process of bonding the diaphragm and the piezoelectric element has become 1% or less. That is, when the thickness of the piezoelectric material is 0.3 mm or more, it is robust and more preferable.

<Example 12>
A vibration type actuator was produced in the same manner as in Example 9 except that the thickness of the piezoelectric ceramics was 0.5 mm. No cracking occurred in the piezoelectric element.

<Comparative Example 5>
A vibration type actuator was produced in the same manner as in Example 9 except that the thickness of the piezoelectric ceramics was 0.7 mm. Although the piezoelectric element did not crack, the electrode on the inner wall of the through hole was broken and the vibrating actuator did not operate. When the ratio of the average thickness of the surface electrode and the electrode in the through hole was measured by the same method as in Example 9, the ratio was as small as less than 2.5 times. Part of the inner wall was not covered with electrodes.

As described above, the vibration type actuator of the present invention using the piezoelectric element provided with the through portion outside the region 431 surrounded by connecting the intersections of the amplitude nodes of mode A and the amplitude nodes of mode B will be described. did. The vibration type actuator can be driven more efficiently than the vibration type actuator using the piezoelectric element provided with the penetration portion inside the region 431.

The vibration type actuator of the present invention can also be suitably used as a drive unit of an optical device. Further, the vibration type actuator of the present invention can be widely used as a drive unit of an electronic device.

Specifically, the vibrating actuator of the present invention can be used for various purposes such as driving a lens or an image sensor of an image pickup device (optical device), rotating a photosensitive drum of a copying machine, driving a stage, and the like. can. Although one vibration type actuator has been described in the present specification, it is also possible to arrange a plurality of vibration type actuators in an annular shape and rotationally drive a ring-shaped contact body.

100 Vibration type actuator 111 Contact body 112 Protrusion part 113 Vibration plate 114 Pietrical element 114A 1st electrode 114B 2nd electrode 114D 3rd electrode 114E Penetration part 114F 4th electrode 114P Pietrical ceramics 115 Transducer 411 Primary out-of-plane Bending vibration (mode A) node 412 Primary out-of-plane bending vibration (mode A) line 421 Secondary out-of-plane bending vibration (mode B) node 422 Secondary out-of-plane bending vibration (mode B) Abdominal line 423 Intersection of mode A node and mode B node 431 Area surrounded by the intersection of mode A vibration node and mode B vibration node 511 Distortion node of piezoelectric ceramics in mode A vibration Wire 512 Strain of piezoelectric ceramics in mode A vibration Nodal line of strain of piezoelectric ceramics in vibration of mode B 522 Abdomen of strain of piezoelectric ceramics in vibration of mode B 522

Claims (18)

A rectangular piezoelectric material, a pair of electrodes provided on the piezoelectric material, and
A piezoelectric element having a penetration portion that energizes one of the electrodes and penetrates the piezoelectric material, and a vibrator having an elastic body.
A contact body that is in contact with the vibrator and moves relative to the vibrator is provided.
The penetration is a primary out-of-plane bending vibration mode node where two vibration nodes occur along the long side of the piezoelectric material and three vibration nodes along the short side of the piezoelectric material. A vibration type actuator formed outside the area surrounded by connecting the intersections with the nodes of the secondary out-of-plane bending vibration mode. The electrodes include a first electrode provided in the first region of the piezoelectric material, a second electrode provided in a second region adjacent to the first region, the first electrode, and the first electrode. It is a third electrode that sandwiches the piezoelectric material with the second electrode, and the primary out-of-plane bending vibration mode is a vibration mode in which both the first region and the second region expand or contract. The secondary out-of-plane bending vibration mode is a mode in which the second region contracts when the first region expands and the second region expands when the first region contracts. The vibration type actuator according to claim 1. The vibration type according to claim 1 or 2, wherein the penetration portion is formed in a region extending from the node of the primary out-of-plane bending vibration mode to the long end side of the piezoelectric material. Actuator. The vibration type actuator according to any one of claims 1 to 3, wherein the piezoelectric material is provided with a through hole having a conductive material on the inner wall as the penetration portion. The vibrating actuator according to claim 4, wherein the conductive material fills the through hole. The vibrating actuator according to any one of claims 1 to 3, wherein a groove having a conductive material on the inner wall is provided on the end face of the piezoelectric material as the penetrating portion. The vibrating actuator according to any one of claims 1 to 6, wherein the long side of the rectangular piezoelectric material is 1 mm or more and 20 mm or less, and the short side is 0.5 mm or more and 10 mm or less. The vibration type actuator according to any one of claims 1 to 7, wherein the piezoelectric material has a thickness of 0.3 mm or more. Any of claims 1 to 8, wherein the penetrating portion is formed within 300 microns from a line that intersects the two long sides of the rectangular piezoelectric material and bisects the two long sides. The vibration type actuator according to item 1. The vibration type actuator according to any one of claims 1 to 9, wherein the width of the penetrating portion is 140 microns or more and 400 microns or less. The vibration type actuator according to any one of claims 1 to 10, wherein the penetration portion is one. One of claims 1 to 10, wherein the penetrating portion intersects two short sides of the rectangular piezoelectric material and is arranged line-symmetrically with respect to a line that bisects the two short sides. The vibration type actuator according to item 1. The vibration type actuator according to any one of claims 1 to 12, wherein the amount of lead contained in the piezoelectric material is less than 1000 ppm. The piezoelectric material is
Perovskite-type structural oxides containing Ba, Ca, Ti, and Zr,
A piezoelectric material containing Mn and
X, which is the molar ratio of Ca to the sum of Ba and Ca, is 0.02 ≦ x ≦ 0.30, and y, which is the molar ratio of Zr to the sum of Ti and Zr, is 0.020. In a piezoelectric material in which ≦ y ≦ 0.095 and y ≦ x, the content of Mn with respect to 100 parts by weight of the oxide is 0.02 parts by weight or more and 0.40 parts by weight or less in terms of metal. The vibration type actuator according to any one of claims 1 to 13, wherein the vibration type actuator is provided. The piezoelectric material is
Oxides containing Na, Ba, Nb and Ti,
Contains at least one element selected from Mn and Ni,
X, which is the mol ratio of Na to the sum of Nb and Ti, is 0.80 ≦ x <0.92, and y, which is the mol ratio of Nb to the sum of Nb and Ti, is 0. 80 ≦ y <0.92, the mol ratio of Ba to the sum of Nb and Ti is greater than 0.08 and 0.20 or less, and the mol ratio of Ni to the sum of Nb and Ti is One of claims 1 to 13, wherein the perovskite-type piezoelectric material has a mol ratio of Mn to the sum of Nb and Ti of 0.05 or less and 0.005 or less. The vibrating actuator described. The vibrating actuator according to any one of claims 1 to 15, wherein the electrode that energizes the penetrating portion is an electrode provided between the piezoelectric material and the elastic body. An optical device provided with a vibration type actuator according to any one of claims 1 to 16 in a drive unit. An electronic device having the vibration type actuator according to any one of claims 1 to 16 and a member attached to the vibration type actuator.

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