Vibration type actuator, manufacturing method of vibration type actuator, electronic device, and optical device

Abstract

To provide a vibration type actuator whose speed reciprocating difference is much smaller, when a value obtained by dividing a maximum speed difference between a forward-moving direction and a backward-moving direction by the maximum speed in the forward-moving direction is set to the speed reciprocating difference.SOLUTION: A vibration type actuator is characterized in that a content of lead contained in a piezoelectric material is 1000 ppm or less; an elastic body comprises a protrusion provided with a head top part being in contact with a contact body, and a flat plate part; the protrusion in which a space part is provided comprises a face on an outer side and a face on an inner side; in plan view, the head top part is arranged at a position of crossing a nodal line of out-of-plane vibration of the elastic body; and a value obtained by dividing a total area of part surrounded by the face on the outer side, when cross-sectionally viewing a base part of the protrusion in a direction parallel to the flat plate part by a product obtained by multiplying a length of a short side of a main face of a piezoelectric element by a length of a long side thereof is smaller than 0.178.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vibration actuator, a method for manufacturing a vibration actuator, and electronic equipment and optical equipment that include a vibration actuator. [Background technology]

[0002] A vibration actuator has a vibrating body configured such that vibrations are excited in an elastic body joined to a piezoelectric element by applying an alternating voltage to the electromechanical energy conversion element such as a piezoelectric element. The vibration actuator is used as an ultrasonic motor that uses the driving force of the vibrations excited in the vibrating body to move the vibrating body relative to a contact body that is brought into pressure contact with the vibrating body.

[0003] Piezoelectric ceramics used in vibrators are generally made of lead zirconate titanate (PZT)-based materials. This material contains a large amount of lead in the A site of the ABO3-type perovskite metal oxide, which raises concerns about its impact on the environment. To address this issue, proposals have been made to develop piezoelectric ceramics that use lead-free perovskite metal oxides (with a lead content of less than 1000 ppm).

[0004] Patent Document 1 discloses a method for manufacturing a vibrator using lead-free piezoelectric ceramics. The manufacturing method discloses a step of bonding an elastic body (referred to as a diaphragm in the document) and a power supply member to a piezoelectric element, and then heating the piezoelectric ceramic to perform polarization processing.

[0005] Patent Document 2 discloses a vibration actuator using an elastic body having protrusions with spring properties, and a method for manufacturing the same. It also discloses that a space is formed between the protrusions of the elastic body and a piezoelectric element (referred to in the document as an electromechanical energy conversion element). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-184233 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-200051 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the polarization process described in Patent Document 1 is used in a vibration actuator using the elastic body described in Patent Document 2 and lead-free piezoelectric ceramics, a temperature distribution occurs within the surface of the piezoelectric element, resulting in an in-plane distribution of the piezoelectric characteristics. As a result, there is a problem in that the vibration characteristics of the vibration actuator in the forward and reverse directions are not equivalent. Therefore, an object of the present invention is to provide a vibration actuator in which the reciprocating speed difference is smaller when the difference in maximum speed between the forward and reverse directions is divided by the maximum speed in the forward direction. [Means for solving the problem]

[0008] The present invention provides a vibrating body including a rectangular elastic body and a piezoelectric element having a piezoelectric material; a contact body that contacts the elastic body, a vibration type actuator in which the vibrating body and the contact body move relatively to each other due to vibration of the vibrating body, The lead content of the piezoelectric material is 1000 ppm or less, the elastic body has a protrusion with a top portion that contacts the contact body, and a flat portion, the protrusion having a space therein and having an outer surface and an inner surface, In a plan view, the top portion is disposed at a position that crosses a nodal line of an out-of-plane vibration of the elastic body, This is a vibration actuator characterized in that, when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.178. The present invention also provides A method for manufacturing a vibration actuator having a vibrating body with high vibration symmetry, comprising: a step of providing electrodes on an unpolarized piezoelectric material to obtain a piezoelectric element; a step of bonding the piezoelectric element and the elastic body at a temperature T1; a step of bonding the piezoelectric element and the power supply member at a temperature T2; a step of subjecting the piezoelectric material to a polarization treatment at a temperature T3 to produce a vibrating body; a step of bringing the vibrating body into pressure contact with a contact body; in this order, The elastic body has a protrusion with a top and a flat plate, the protrusion has an inner space and an outer surface and an inner surface; when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is smaller than 0.178, The method for manufacturing a vibration type actuator is characterized in that T1, T2, and T3 satisfy the relationships T1>T3 and T2>T3. The present invention also provides an electronic device equipped with the vibration type actuator. The present invention also provides an optical device comprising at least one of an optical element and an imaging element, and the vibration-type actuator described above. [Effects of the Invention]

[0009] According to the present invention, it is possible to stably provide a vibration actuator having equivalent vibration characteristics in the forward and reverse directions, thereby further improving the yield of vibration actuators. [Brief explanation of the drawings]

[0010] [Figure 1A] FIG. 1A is a perspective view illustrating the schematic structure of a vibration actuator of the present invention using a rectangular piezoelectric material. [Figure 1B]FIG. 1B is a cross-sectional view taken along a center line (not shown) along the longitudinal direction of FIG. 1A when a contact body 104 is added to FIG. 1A. [Figure 1C] FIG. 1C is a rear view illustrating the schematic structure of a vibration type actuator of the present invention using a rectangular piezoelectric material. [Figure 2A] FIG. 2A is a diagram illustrating two vibration modes generated by a vibrating body of the present invention having a rectangular piezoelectric material, and is a diagram illustrating mode A. FIG. [Figure 2B] FIG. 2B is a diagram illustrating two vibration modes generated by a vibrating body of the present invention having a rectangular piezoelectric material, and is a diagram illustrating mode B. [Figure 3] FIG. 3 is a diagram illustrating a vibrating body in the polarization treatment of the present invention. [Figure 4A] FIG. 4A is an example of a diagram (plan view) for explaining the positions of nodes and antinodes of two vibration modes generated in the vibrating body of the present invention. [Figure 4B] FIG. 4B is another example of a diagram (plan view) for explaining the positions of the nodes and antinodes of two vibration modes generated in the vibrating body of the present invention. [Figure 5] FIG. 5 is a graph showing an example of the vibration of mode B generated by the vibrating body of the present invention measured with a laser Doppler vibrometer. [Figure 6A] FIG. 6A is a diagram illustrating the structure of the vibrating body of the present invention, and is an exploded perspective view showing the appearance of the vibrating body and the contact body. [Figure 6B] FIG. 6B is a cross-sectional view of the periphery of the protrusion when the vibrating body and the contact body are in contact with each other, taken along line AA in FIG. 6A. [Figure 6C] FIG. 6C is a cross-sectional view of the base of the protrusion in FIG. 6A cut in a direction parallel to the flat plate portion. [Figure 7] FIG. 7 is a diagram illustrating the schematic structure of the optical device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment The first embodiment relates to a vibration type actuator. The vibration actuator of the present invention comprises: a vibrating body including a rectangular elastic body and a piezoelectric element having a piezoelectric material; a contact body that contacts the elastic body, a vibration type actuator in which the vibrating body and the contact body move relatively to each other due to vibration of the vibrating body, The lead content of the piezoelectric material is 1000 ppm or less, The elastic body has a protrusion with a top portion that contacts the contact body, and a flat plate portion, the protrusion having a space therein and having an outer surface and an inner surface, In a plan view, the top portion is disposed at a position that crosses a nodal line of an out-of-plane vibration of the elastic body, When the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.178. Hereinafter, an embodiment of the present invention will be described.

[0012] (Vibration Actuator) The vibration actuator of the present invention comprises a vibrating body having a rectangular elastic body and a piezoelectric element having a piezoelectric material, and a contact body in contact with the elastic body, and the vibrating body and the contact body move relative to each other due to vibration of the vibrating body. Figures 1A to 1C show an example of the schematic structure of the vibration actuator of the present invention. The vibration actuators shown in Figures 1A to 1C use a rectangular piezoelectric material.

[0013] The vibration actuator 100 includes an electromechanical energy conversion element 120 made up of an electrode 101 and a piezoelectric material 102. Furthermore, in the vibration actuator of the present invention, the elastic body 103 has two protrusions 106 with tops that contact the contact body 104, and a flat plate portion 108.

[0014] The vibration actuator 100 includes an elastic body 103 having a flat plate portion 108 and protrusions 106 that protrude in the same direction outside the surface of the flat plate portion, and these are arranged in this order to form a vibrating body 110. The vibration actuator 100 further includes a contact body 104 that comes into contact with the protrusions 106.

[0015] In addition, the vibration actuator 100 is configured to include a pressure member 121 for bringing the vibrating body 110 into pressure contact with the contact body 104, and a foam member 122 provided between the vibrating body 110 and the pressure member 121. The contact body 104 may be any member that is movable relative to the vibrating body 110, and is not limited to being in direct contact with the vibrating body 110, but may also be in indirect contact with the vibrating body 110 via another member.

[0016] The surface of the electromechanical energy conversion element 120 is pressed by a pressurizing member 121 via a foam member 122. There are no particular restrictions on the means of pressing, but it is preferable to use a compression spring or a tension spring, as this makes it easy to adjust the pressure.

[0017] (Two out-of-plane bending vibration modes) 2A and 2B illustrate two vibration modes generated by the vibrating body of the present invention having a rectangular piezoelectric material. The regions where the first electrode and the second electrode are provided are referred to as the first region and the second region, respectively.

[0018] Mode A When both the first and second regions expand or contract, a first bending vibration mode (mode A) occurs. Mode A occurs when an alternating voltage V A , V B is most strongly excited when the phase difference is 0° and the frequency is near the resonant frequency of mode A.

[0019] Mode A is a primary out-of-plane vibration mode in which two nodes (where the amplitude is minimum) appear approximately parallel to the long sides of vibrating body 110. Protrusion 106 of the elastic body is positioned near the position that becomes the antinode (where the amplitude is maximum) of mode A. Therefore, the tip surface of protrusion 106 reciprocates in the Z direction due to vibration mode A.

[0020] Mode B When the first region expands / contracts, the second region contracts / expands, generating a second bending vibration mode (Mode B). Mode B is generated by the AC voltage V applied to the first electrode 101a and the second electrode 101b. A , V B is most strongly excited when the phase difference between them is 180° and the frequency is near the resonant frequency of mode B.

[0021] Mode B is a second-order out-of-plane vibration mode in which three nodes appear approximately parallel to the short sides of vibrating body 110. Protrusion 106 of the elastic body is positioned at a position that becomes a node of Mode B. Therefore, the tip surface of protrusion 106 reciprocates in the X direction due to Mode B.

[0022] In the vibration actuator 100 equipped with a rectangular piezoelectric element, the alternating voltage V A , V B When the phase difference is between 0 and ±180°, mode A and mode B are excited simultaneously, and elliptical vibration is excited in protrusion 106 of the elastic body.

[0023] (Vibration antinodes and nodes) In the vibration actuator of the present invention, the top portion is disposed at a position that crosses a nodal line of the out-of-plane vibration of the elastic body in a plan view. The vibrating piezoelectric element has vibration antinodes and vibration nodes depending on the vibration mode.

[0024] 4A and 4B show the positions of the nodal lines and antinodes of vibrations corresponding to Mode A and Mode B that occur in the vibrating body of the present invention. Figures 4A and 4B are plan views of vibrating body 110 as viewed from the piezoelectric material 102 side.

[0025] 4A shows two nodal lines of vibration in mode A with dashed lines 411 and three antinode lines of vibration with dashed-dotted lines 412. The nodal lines and antinode lines of mode A can be obtained by connecting the positions of the nodal lines and antinode lines of vibration in any YZ plane in the X direction.

[0026] 4B shows three nodal lines of vibration in mode B with dashed lines 421 and two antinode lines of vibration with dashed-dotted lines 422. The nodal lines and antinode lines of mode B are obtained by connecting the positions of the nodal lines and antinode lines of vibration in any XZ plane in the Y direction. When using the vibration actuator 100, both mode A and mode B of the vibrating body 110 are used.

[0027] The nodal positions and antinode positions of the vibration generated in the piezoelectric material 102 by excitation of the vibration body 110 in modes A and B are measured as follows. That is, vibration in mode A or mode B is generated in the vibration body 110. When vibration in mode A is generated, an alternating voltage V A and V B The phase difference between the two is 0°. When generating Mode B, the alternating voltage V A and V B The phase difference is 180°.

[0028] Then, for example, by using a laser Doppler vibrometer to measure the vibration velocity in the Z direction two-dimensionally on the XY plane and calculating the displacement in the Z direction at each point, the positions of the nodal lines and antinodes of Mode A and Mode B can be measured.

[0029] Figure 5 shows data obtained by exciting Mode B, scanning the center of the rectangular section in the short direction in the longitudinal direction, and measuring the amplitude in the Z direction. Three vibration nodes where the amplitude is minimal can be confirmed within the rectangular section.

[0030] (Elastic material) The elastic body 103 is preferably made of metal from the viewpoint of its properties as an elastic body and its workability. Examples of metals that can be used for the elastic body 103 include aluminum, brass, and stainless steel. In the vibration actuator of the present invention, the elastic body is preferably martensitic stainless steel. Furthermore, vacuum-quenched SUS420J2 has high hardness and is suitable for the vibration actuator of the present invention, which drives a contact body by friction with the elastic body.

[0031] The elastic body 103 has two protrusions 106 that come into contact with the contact body 104. To further improve the wear resistance of the protrusions, the elastic body is subjected to quenching, plating, or nitriding. The thickness of the elastic body that is bonded to the piezoelectric element is preferably in the range of 0.20 to 0.35 mm, as this provides both rigidity and springiness and is easy to mold.

[0032] (piezoelectric element) A piezoelectric element is composed of a piezoelectric material and electrodes. (Piezoelectric materials) The shape of the piezoelectric material 102 is preferably rectangular. The vibration actuator of the present invention has a rectangular elastic body, and a rectangular piezoelectric material is preferable because it allows the production of a vibrating body with good electrical-mechanical energy conversion efficiency.

[0033] The thickness of the piezoelectric element is processed to a design value within the range of approximately 0.20 to 0.50 mm. By reducing the thickness of the piezoelectric element, the neutral plane of strain shifts toward the elastic body side, making it possible to create a vibrating body with high electromechanical energy conversion efficiency. On the other hand, reducing the thickness of the piezoelectric element increases the stress during deformation in proportion to the negative square of the thickness, making the piezoelectric element more susceptible to cracking. Therefore, a more preferable thickness is 0.25 to 0.40 mm.

[0034] The structure of the piezoelectric material 102 is not limited, but may be, for example, a piezoelectric material (sintered body) without crystal orientation, crystal-oriented ceramics, a piezoelectric single crystal, etc. The form that the piezoelectric material can take is not limited, but for example, a layered piezoelectric material may be used to form a laminate of electrodes and piezoelectric material, or a single plate of piezoelectric material may be used.

[0035] From the viewpoint of cost, a single plate is superior to a piezoelectric material. In order to drive a vibration actuator, the piezoelectric material is subjected to a polarization process. When the AC electric field frequency applied to the polarization-processed piezoelectric material approaches the resonant frequency of the piezoelectric material, the piezoelectric material vibrates greatly due to the resonance phenomenon.

[0036] (Composition of piezoelectric material) In the actuator of the present invention, the lead content in the piezoelectric material is 1000 ppm or less, which means that the actuator of the present invention has a small environmental impact.

[0037] Generally, lead zirconate titanate (Pb(Zr,Ti)O3), which contains lead, is widely used in piezoelectric devices. For this reason, it has been pointed out that when discarded piezoelectric elements are exposed to acid rain or left in harsh environments, the lead content in conventional piezoelectric materials may leach into the soil and cause harm to ecosystems. The lead content can be measured, for example, by ICP atomic emission spectroscopy.

[0038] In the vibration actuator of the present invention, the piezoelectric material preferably contains a barium titanate-based material. The main component of the piezoelectric material is preferably barium titanate. From the viewpoints of a high piezoelectric constant and relative ease of manufacture, the piezoelectric material is preferably made of a barium titanate-based material.

[0039] Here, barium titanate-based materials include barium titanate (BaTiO3), barium calcium titanate ((Ba,Ca)TiO3), barium zirconate titanate (Ba(Ti,Zr)O3), and barium calcium zirconate titanate ((Ba,Ca)(Ti,Zr)O3).

[0040] Other examples include compositions such as sodium niobate-barium titanate (NaNbO3-BaTiO3), sodium bismuth titanate-barium titanate, and potassium bismuth titanate-barium titanate. The term "barium titanate" refers to materials that have these compositions as their main components.

[0041] Among these, the following materials are preferred from the viewpoint of achieving both a desired piezoelectric constant and mechanical quality factor of the piezoelectric material. Specifically, it is preferred that the main component be barium calcium zirconate titanate ((Ba, Ca)(Ti, Zr)O3) or sodium niobate-barium titanate ((1-x)NaNbO3-xBaTiO3, x = 0.1 to 0.15). It is preferred that the main component contain manganese or bismuth as an element other than the main component. A main component refers to a material whose mass fraction is greater than 10%.

[0042] In the vibration actuator of the present invention, the piezoelectric material preferably contains barium calcium titanate zirconate. The main component of the piezoelectric material is preferably barium calcium titanate zirconate (hereinafter also referred to as BCTZ). When BCTZ is the main component, the piezoelectricity of BCTZ can be adjusted according to the application by adjusting the amount of Ca and Zr. Furthermore, the amount of expensive niobium used can be reduced.

[0043] The vibration actuator of the present invention is characterized in that the piezoelectric material is a piezoelectric material containing an oxide having a perovskite structure containing Ba, Ca, Ti, and Zr, and Mn, x, which is a ratio of the molar amount of Ca to the sum of the molar amount of Ba and the molar amount of Ca, is 0.02≦x≦0.30; a ratio y of the molar amount of Zr to the sum of the molar amount of Ti and the molar amount of Zr is 0.020≦y≦0.095 and y≦x; a ratio of the sum of the molar amount of Ba and the molar amount of Ca to the sum of the molar amount of Ti and the molar amount of Zr is 0.9955≦α≦1.01; The content of the Mn relative to 100 parts by mass of the oxide is preferably 0.02 parts by mass or more and 1.0 parts by mass or less in terms of metal.

[0044] Such a piezoelectric material can be expressed by the following general formula (1): (Ba 1-x Ca x ) α (Ti 1-y Zr y )O3(1) however, 0.9955≦α≦1.01, 0.02≦x≦0.30, 0.020≦y≦0.095 and the content of metal components other than the main component contained in the piezoelectric material is preferably 1 part by mass or less in terms of metal per 100 parts by mass of the metal oxide.

[0045] In particular, it is preferable that the metal oxide contains Mn in an amount of 0.02 to 0.40 parts by mass (metal equivalent) per 100 parts by mass of the metal oxide, which improves the insulating properties and mechanical quality factor Qm.

[0046] Here, the mechanical quality factor Qm is a coefficient that represents the elastic loss due to vibration when evaluating a piezoelectric material as a vibrating body, and the magnitude of the mechanical quality factor is observed as the sharpness of the resonance curve in impedance measurements. In other words, it is a constant that represents the sharpness of the resonance of the vibrating body. If the mechanical quality factor Qm is large, the amount of strain in the piezoelectric material near the resonance frequency becomes greater, allowing the piezoelectric material to vibrate more effectively.

[0047] The metal oxide represented by the general formula (1) has a perovskite structure in which the metal elements located at the A site are Ba and Ca, and the metal elements located at the B site are Ti and Zr. However, some of the Ba and Ca may be located at the B site. Similarly, some of the Ti and Zr may be located at the A site.

[0048] In general formula (1), the molar ratio of the B-site element to the O element is 1:3, but even if the molar ratio is slightly different, it is still within the scope of the present invention as long as the metal oxide has a perovskite structure as the main phase.

[0049] Whether a metal oxide has a perovskite structure can be determined, for example, by structural analysis using X-ray diffraction or electron beam diffraction.

[0050] In general formula (1), x, which represents the molar ratio of Ca at the A site, is in the range of 0.02≦x≦0.30. When part of the Ba in perovskite-type barium titanate is substituted with Ca within this range, the phase transition temperature between orthorhombic and tetragonal crystals shifts to the lower temperature side, making it possible to obtain stable piezoelectric vibration within the operating temperature range of the vibration actuator.

[0051] However, if x is greater than 0.30, the piezoelectric constant of the piezoelectric material will be insufficient, and the performance of the vibration actuator may be insufficient. On the other hand, if x is less than 0.02, the dielectric loss (tan δ) may increase. If the dielectric loss increases, heat generation increases when applying voltage to the piezoelectric material to drive the vibration actuator, which may reduce the motor drive efficiency and increase power consumption.

[0052] In general formula (1), y, which represents the molar ratio of Zr in the B site, is in the range of 0.02≦y≦0.30. If y is greater than 0.30, Td becomes low, less than 80°C, and the temperature range in which the vibration actuator can be used becomes less than 80°C, which is undesirable.

[0053] In this specification, Td refers to the lowest temperature at which the piezoelectric constant of a piezoelectric material, when heated from room temperature to Td one week after polarization treatment and then cooled back to room temperature, decreases by more than 10% compared to the piezoelectric constant before heating.

[0054] In general formula (1), α, which represents the ratio of the molar amounts of Ba and Ca at the A site to the molar amounts of Ti and Zr at the B site, is preferably in the range of 0.9955≦α≦1.01. If α is less than 0.9955, abnormal grain growth is likely to occur in the crystal grains that make up the piezoelectric material, reducing the mechanical strength of the piezoelectric material. On the other hand, if α is greater than 1.01, the piezoelectric material will not be densified and its insulation will become significantly brittle.

[0055] The method for measuring the composition of a piezoelectric material is not particularly limited. Examples of the method include X-ray fluorescence analysis, ICP atomic emission spectroscopy, and atomic absorption spectroscopy. Any of the methods can be used to calculate the mass ratio and composition ratio of each element contained in the piezoelectric material.

[0056] The metal equivalent indicating the Mn content is calculated by calculating the content of each metal, Ba, Ca, Ti, Zr, and Mn, measured from the piezoelectric material by X-ray fluorescence analysis (XRF), ICP atomic emission spectroscopy, atomic absorption spectroscopy, etc. From these contents, the elements constituting the metal oxide represented by general formula (1) are converted into oxides, and the value is calculated as the ratio of the mass of Mn to the total mass of 100.

[0057] If the Mn content is less than 0.02 parts by mass, the polarization effect required to drive the vibration actuator may be insufficient, while if the Mn content is more than 0.40 parts by mass, the piezoelectric properties of the piezoelectric material may be insufficient or hexagonal crystals without piezoelectric properties may appear.

[0058] Mn is not limited to metallic Mn, and may be contained in the piezoelectric material as a Mn component, regardless of the form of inclusion. For example, Mn may be present in the B site as a solid solution or at grain boundaries. From the viewpoint of insulation properties and ease of sintering, a more preferable form of inclusion is a solid solution in the B site.

[0059] The piezoelectric material preferably contains 0.042 parts by mass or more and 0.850 parts by mass or less of Bi in terms of metal.

[0060] The piezoelectric material may contain 0.85 parts by mass or less of Bi, calculated as metal, per 100 parts by mass of the metal oxide represented by general formula (1). The content of Bi relative to the metal oxide can be measured, for example, by ICP emission spectroscopy.

[0061] Bi may be present at the grain boundaries of ceramic piezoelectric materials, or may be present as a solid solution in the perovskite structure of (Ba,Ca)(Ti,Zr)O3. When Bi is present at the grain boundaries, friction between particles is reduced and the mechanical quality factor is increased. On the other hand, when Bi is incorporated into a solid solution that forms a perovskite structure, the phase transition temperature is lowered, thereby reducing the temperature dependence of the piezoelectric constant and further improving the mechanical quality factor. When Bi is incorporated into a solid solution, it is preferably located in the A site, as this improves the charge balance with the Mn.

[0062] The piezoelectric material may contain components (hereinafter referred to as auxiliary components) other than the elements contained in the general formula (1) and Mn and Bi, to the extent that the properties are not affected. The total amount of auxiliary components is preferably less than 1.2 parts by mass per 100 parts by mass of the metal oxide expressed by the general formula (1).

[0063] If the amount of the accessory component exceeds 1.2 parts by mass, the piezoelectric properties and insulating properties of the piezoelectric material may be degraded. In the vibration actuator of the present invention, the depolarization temperature Td of the piezoelectric material is preferably 126°C or less. The Curie temperature of (Ba,Ca)(Ti,Zr)O3 is in the range of 85°C or more and 126°C or less.

[0064] (Structure of piezoelectric element) 6A to 6C are diagrams illustrating the structure of the vibrating body of the present invention. In the vibration actuator of the present invention, the protrusions 38 and 39 have a space 40 provided therein and have an outer surface 401 and an inner surface 402. The vibrating body 30 has the protrusions 38 and 39 and a flat plate portion 32, and has the space 40 surrounded by the wall portion 34 and the piezoelectric element 35. The protrusions 38 and 39 have the wall portion 34, a connecting portion 31, and a contact portion 36, and come into contact with the contact body 104 at the contact surface 37.

[0065] In the vibration actuator of the present invention, when the bases of the protrusions 38, 39 are viewed in cross section in a direction parallel to the flat plate portion 32, it is preferable that the value S2 / S1 obtained by dividing the total area S2 (sum of areas) of the portions surrounded by the outer surface 401 by the product S1 of the lengths of the short sides and the long sides of the main surfaces of the piezoelectric element is smaller than 0.178. This makes it possible to achieve a uniform temperature distribution and ensure uniform piezoelectric characteristics.

[0066] A more preferable ratio of S2 / S1 is 0.099 or more and 0.156 or less. This makes the temperature distribution more uniform, improving the uniformity of the piezoelectric characteristics. Regarding S2, if there is one protrusion, it is the area surrounded by the outer surface 401, and if there are two or more protrusions, it is the sum of the area surrounded by the outer surface 401.

[0067] Furthermore, in the vibration actuator of the present invention, when the bases of the protrusions 38, 39 are viewed in cross section in a direction parallel to the flat plate portion 32, it is preferable that the value S3 / S1 obtained by dividing the total area S3 (sum of areas) of the portions surrounded by the inner surface 402 by the product S1 of the lengths of the short sides and the long sides of the main surfaces of the piezoelectric element is smaller than 0.124. This makes it possible to achieve a uniform temperature distribution and ensure uniform piezoelectric characteristics.

[0068] A more preferable ratio of S3 / S1 is 0.069 or more and 0.093 or less. This makes the temperature distribution more uniform, improving the uniformity of the piezoelectric characteristics. Regarding S3, if there is one protrusion, it is the area surrounded by the inner surface 402, and if there are two or more protrusions, it is the sum of the areas surrounded by the inner surface 402.

[0069] FIG. 6A is an exploded perspective view showing the appearance of the vibrating body and the contact body, FIG. 6B is a cross-sectional view along line AA in FIG. 6A of the periphery of the protrusion when the vibrating body and the contact body are in contact, and FIG. 6C is a cross-sectional view of the base of the protrusion cut in a direction parallel to the flat plate portion.

[0070] As shown in Figures 6A, 6B, and 6C, S1, S2, and S3 can be calculated from W1, L1, R1, and R2 by assuming a perfect circle or rectangle. W1, L1, and R1 can be measured, for example, using an optical microscope. R2 can also be measured using an optical microscope by peeling the interface between the piezoelectric element and the elastic body. Ultrasonic flaw detection testing also allows for non-destructive shape measurement.

[0071] In the vibration actuator of the present invention, the vertex is disposed at a position crossing a nodal line of the out-of-plane vibration of the elastic body in a plan view. In the vibration actuator of the present invention, it is preferable that the vertex is disposed crossing a nodal line of the out-of-plane vibration of the elastic body and that the distance between the two protrusions is minimized.

[0072] Arranging the two protrusions so that the distance between them is shortest is preferable because it puts them near the antinode of out-of-plane vibration mode A, maximizing the amplitude in the Z direction. Whether the top of protrusion 106 crosses the nodal line of mode B or is near the antinode of mode A can be verified using a laser Doppler vibrometer. The vibration velocity in the Z direction of the top of protrusion 106 is measured two-dimensionally on the XY plane, and the position of the nodal line and antinode of mode A and mode B can be measured by calculating the displacement of each point in the Z direction.

[0073] In the vibration actuator of the present invention, the elastic body preferably has a support portion 107 that protrudes from the end of the flat plate portion 108. The vibrator is supported by a fitting hole provided in the support portion 107. By having the support portion 107, it is possible to hold the vibrator in a heating tool during polarization processing, and positional deviation is suppressed. This makes it possible to reduce individual differences in uneven heating, leading to improved yields.

[0074] Figure 5 shows data obtained by exciting mode B, scanning the center of the rectangular section in the short direction in the longitudinal direction, and measuring the amplitude in the Z direction. The graph shows the voltage value of the vibration velocity meter versus the distance from the edge of the flat section. Of the three vibration nodes where the amplitude is at a minimum, the top of the protrusion 106 is positioned so that it crosses the two outer nodal lines. It is more preferable to position the nodal lines 80% of the diameter of the top of the protrusion 106 from the center. This can further reduce the impact of piezoelectric property distribution on the vibration properties.

[0075] <Second embodiment> The second embodiment relates to a method for manufacturing a vibration type actuator. The method for manufacturing a vibration type actuator of the present invention includes the steps of: A method for manufacturing a vibration actuator having a vibrating body with high vibration symmetry, comprising: a step of providing electrodes on an unpolarized piezoelectric material to obtain a piezoelectric element; a step of bonding the piezoelectric element and the elastic body at a temperature T1; a step of bonding the piezoelectric element and the power supply member at a temperature T2; a step of subjecting the piezoelectric material to a polarization treatment at a temperature T3 to produce a vibrating body; a step of bringing the vibrating body into pressure contact with a contact body; in this order, The elastic body has a protrusion with a top and a flat plate, the protrusion has an inner space and an outer surface and an inner surface; when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is smaller than 0.178, The T1, T2, and T3 satisfy the relationships T1>T3 and T2>T3. The following description will be made with reference to Figures 1A to 1C, 2A, 2B, etc. The description of the matters described in the first embodiment may be omitted.

[0076] (Process for obtaining piezoelectric element) The method for manufacturing a vibration actuator of the present invention is a method for manufacturing a vibration actuator having a vibrating body with high vibration symmetry, and includes a step of providing electrodes on an unpolarized piezoelectric material to obtain a piezoelectric element. When a rectangular piezoelectric material is used as the piezoelectric material, a rectangular electrode 101 is provided. The electrode 101 consists of a first electrode 101a and a second electrode 101b. The first electrode 101a and the second electrode 101b are used for polarization of the rectangular piezoelectric material and for driving the vibration actuator using the rectangular piezoelectric material.

[0077] The electrode 101 is made of a metal film having a thickness of about 0.3 to 10 μm. There are no particular restrictions on the material, but silver, gold, or platinum electrodes are generally used. There are no restrictions on the method for manufacturing the electrode, and it can be formed by screen printing, sputtering, vacuum deposition, or the like. In order to manufacture an electromechanical energy conversion element with a lead content of 1000 ppm or less, it is necessary to use a paste or target with a lead content of less than 1000 ppm when forming the electrode.

[0078] (Bonding process at temperature T1) The method for manufacturing a vibration actuator of the present invention includes a step of bonding a piezoelectric element and an elastic body at a temperature T1. Fig. 3 shows a diagram illustrating the state of the vibrating body during polarization treatment of the present invention. The elastic body 103 is preferably made of metal from the viewpoint of its properties as an elastic body and its workability.

[0079] Examples of metals that can be used for the elastic body 103 include aluminum, brass, and stainless steel. Among stainless steels, martensitic stainless steel is preferable, and vacuum-hardened SUS420J2 has high hardness and is suitable for the vibration actuator of the present invention, which drives the contact body by friction with the elastic body. The elastic body 103 has two protrusions 106 that come into contact with the contact body 104. To further improve the wear resistance of the protrusions, the elastic body is hardened, plated, or nitrided.

[0080] The elastic body 103 is provided on the piezoelectric material 102 via a first adhesive layer. This is to integrate the piezoelectric material 102 and the elastic body 103 to form a traveling wave of bending vibration in the out-of-plane direction (hereinafter also referred to as out-of-plane vibration). The first adhesive layer is obtained by curing an adhesive, and an epoxy resin is preferably used as the adhesive. The temperature T1 is set to a temperature at which the adhesive cures in a short time and the first adhesive layer has sufficient adhesive strength. Specifically, the temperature is 20°C or higher, preferably 80°C or higher, and more preferably 120°C or higher.

[0081] Note that temperature T1 does not refer to the ambient temperature, but rather to the temperature of the piezoelectric material 102, and can be measured using a thermocouple or radiation thermometer. T2, which will be described later, also refers to the temperature of the piezoelectric material 102, just like T1. It is preferable to arrange the piezoelectric material 102 and the elastic body 103 so that the centers of their respective adhesive surfaces coincide with each other. This makes the vibration characteristics in the forward and reverse directions equivalent, and increases the yield of the piezoelectric vibrator.

[0082] (Bonding process at temperature T2) The method for manufacturing a vibration actuator of the present invention includes a step of bonding a piezoelectric element and a power supply member at a temperature T2. The vibration actuator of the present invention has a power supply member 109 bonded to a piezoelectric element including the piezoelectric material and the electrodes. The power supply member 109 is provided on the piezoelectric material 102 via a second adhesive layer.

[0083] It is preferable to use a flexible printed circuit board (hereinafter referred to as FPC) as the power supply member because it has high dimensional accuracy and is easy to position. Polyimide is a preferable material. There are no particular restrictions on the method of joining the FPC and the piezoelectric element, but it is preferable to use an anisotropic conductive paste (ACP) or anisotropic conductive film (ACF), which have high adhesive tact and electrical connection reliability. Supplying power via the FPC allows power to be supplied without interfering with the vibration of the piezoelectric element. The FPC is connected to at least the first and second electrodes, and may also be connected to the non-driving phase electrode.

[0084] The FPC and electrodes are bonded at temperature T2. It is preferable that temperature T2 satisfy the relationship T2 ≥ Td with the depolarization temperature Td of the piezoelectric material. By satisfying this relationship, the piezoelectric constant of the piezoelectric material can be made as close to 0 as possible.

[0085] Here, the depolarization temperature Td refers to the temperature at which the piezoelectric constant decreases compared to the piezoelectric constant before the temperature increase when the piezoelectric material is heated from room temperature (e.g., 20 to 30°C) to a certain temperature and then cooled back to room temperature after a sufficient time has passed since the piezoelectric material was subjected to polarization treatment. In the present invention, the temperature at which the piezoelectric constant becomes less than 90% of the piezoelectric constant before the temperature increase is referred to as the depolarization temperature Td.

[0086] The temperature T2 is a temperature at which the adhesive hardens in a short time and the second adhesive joint has sufficient adhesive strength. Specifically, it is 20°C or higher, preferably 100°C or higher, and more preferably 140°C or higher. At 140°C or higher, the second adhesive joint can achieve sufficient adhesive strength in about 10 to 30 seconds. Furthermore, the pressure used when forming the second adhesive joint by thermocompression bonding is preferably 1 MPa or higher. If it is less than 1 MPa, there is a risk of so-called lifting.

[0087] It is preferable that the power supply member 109 be bonded to the regions of the two drive phase electrodes with an equal area. If there is an extreme difference in area, when the vibrating body 110 vibrates, there will be a difference in the area where the power supply member 109 inhibits the vibration, and as a result, there is a risk that the vibration characteristics in the forward and reverse directions will no longer be equivalent.

[0088] (Process for producing the vibrating body) The manufacturing method of the vibration actuator of the present invention includes a step of producing a vibrating body by performing a polarization process on a piezoelectric material at a temperature T3. Ceramics are generally a collection of minute crystals (also called polycrystals), and each crystal is composed of positively charged atoms and negatively charged atoms. In most ceramics, the positive and negative charges are balanced.

[0089] However, some dielectric ceramics, known as ferroelectrics, have an imbalance of positive and negative charges in the crystal even in their natural state, resulting in a charge imbalance (spontaneous polarization). In ferroelectric ceramics that have not undergone polarization treatment, the direction of this spontaneous polarization is random, and the ceramic as a whole appears to have no charge imbalance.

[0090] However, when a high voltage is applied to a ferroelectric ceramic that has not been subjected to polarization treatment, the spontaneous polarization aligns in a uniform direction, and it does not return to its original state even when the voltage is removed. This process of aligning the direction of spontaneous polarization is called polarization treatment.

[0091] If the temperature at which the vibration body used in the present invention is polarized is T3, then the temperature T1 at which the piezoelectric element and the elastic body are bonded and the temperature T2 at which the piezoelectric element and the power supply member are bonded must satisfy the relationships T1>T3 and T2>T3. In other words, in the method for manufacturing a vibration actuator of the present invention, T1, T2, and T3 satisfy the relationships T1>T3 and T2>T3.

[0092] If temperature T3 is higher than temperature T1, the adhesive portion between piezoelectric material 102 and elastic body 103 softens, causing the center of the adhesive surface of piezoelectric material 102 to deviate from the center of the adhesive surface of elastic body 103, and the vibration characteristics in the forward and reverse directions are no longer equivalent. On the other hand, if temperature T3 is higher than temperature T2, the adhesive portion between piezoelectric material 102 and power supply member 109 softens, which may cause the center line of power supply member 109 to deviate from the center line of piezoelectric material 102 in the long side direction.

[0093] In this case, the power supply member 109 will not be attached to the areas of the two drive phase electrodes with an equal area, and when the vibrating body 110 vibrates, there will be a difference in the area where the power supply member 109 inhibits the vibration, which may result in the vibration characteristics in the forward and reverse directions no longer being equivalent.

[0094] Therefore, in the method for manufacturing a vibration actuator of the present invention, it is preferable that T1, T2, and T3 satisfy the relationship T1>T2>T3, which makes it possible to more reliably obtain equivalent vibration characteristics.

[0095] Furthermore, it is preferable that the temperature T3, the glass transition temperature Tg1 of the adhesive joint between the piezoelectric element and the elastic body, and the glass transition temperature Tg2 of the adhesive joint between the piezoelectric element and the power supply member satisfy the relationships Tg1>T3 and Tg2>T3.

[0096] When temperature T3 is equal to or higher than Tg1 or Tg2, the adhesive joints soften. Then, when the polarization process is terminated and the temperature drops below Tg1 or Tg2, the adhesive joints harden again. At this time, the center of the adhesive surface of piezoelectric material 102 may be misaligned with the center of the adhesive surface of elastic body 103. This is undesirable because it may result in the vibration characteristics in the forward and reverse directions no longer being equivalent.

[0097] The electric field strength applied to the vibrating body 110 during polarization treatment is not particularly limited, but from the viewpoint of performing the polarization treatment in a short time, it is preferably 0.5 kV / mm to 2.0 kV / mm. Furthermore, the temperature T3 is preferably 20°C or higher. If the temperature T3 is lower than 20°C, it may take a long time for the piezoelectric material to reach a state where it has a sufficient piezoelectric constant. From the viewpoint of completing the polarization treatment in a short time, it is preferably 100°C or higher, and more preferably 120°C or higher.

[0098] 3 is a diagram illustrating the vibrating body in the polarization treatment of the present invention. In the vibration type actuator of the present invention, the protrusion 106 has a space 303 provided therein, an outer surface, and an inner surface, and the space 303 is formed between the protrusion 106 and the piezoelectric material 102 to which it is joined. During polarization treatment, this space 303 hinders the heating of the piezoelectric element (by the heating tool 302), resulting in an in-plane heating distribution of the piezoelectric element. As a result, an in-plane distribution of the polarization treatment occurs, and an in-plane distribution of the piezoelectric properties also occurs.

[0099] (Pressure contact process) The method for manufacturing a vibration actuator of the present invention includes the steps of: polarizing a piezoelectric material at a temperature T3 to produce a vibrating body; and bringing the vibrating body into pressure contact with a contact body. Stainless steel is preferable for the contact body 104 in terms of rigidity. Among stainless steels, martensitic stainless steel is preferable, with SUS420J2 being the most preferable.

[0100] Since the contact body 104 is in frictional contact with the elastic body 103, it must have excellent wear resistance, and its surface is subjected to nitriding or alumite treatment. A frictional force is generated between the protrusion 106 and the contact body 104 due to pressure contact. There are no particular restrictions on the means of pressure contact, but using a compression spring or tension spring is preferable because it makes it easy to adjust the pressure. The vibration generated by the piezoelectric material 102 causes the tip of the protrusion 106 to vibrate elliptically, generating a driving force (thrust) that drives the contact body 104.

[0101] The contact body is generally called a slider or rotor. Note that the "contact body" refers to a member that comes into contact with the vibrating body and moves relative to the vibrating body due to vibrations generated in the vibrating body. The contact between the contact body and the vibrating body is not limited to direct contact with no other member interposed between the contact body and the vibrating body.

[0102] The contact between the contact body and the vibrating body may be indirect contact with another member interposed between them, provided that the contact body moves relative to the vibrating body due to vibrations generated in the vibrating body. The "other member" is not limited to a member independent of the contact body and the vibrating body (for example, a high-friction material made of a sintered body). The "other member" may also be a surface-treated portion formed on the contact body or the vibrating body by plating, nitriding, or the like.

[0103] <Application example> Examples of applications are in electronic and optical equipment. (electronic equipment) The electronic device of the present invention includes the vibration type actuator described above. The electronic device of the present invention is characterized by including the vibration type actuator described above, a member connected to the contact body of the vibration type actuator, and a member position detection means (e.g., an encoder). The electronic device detects the position of the member and operates the vibration type actuator until the member reaches a target position, thereby enabling precise control of the position of the member.

[0104] (optical equipment) The optical apparatus of the present invention includes at least one of an optical element and an imaging element, and the vibration actuator described above. Fig. 7 is a schematic diagram showing one embodiment of the optical apparatus of the present invention (focus lens portion of a lens barrel device).

[0105] 7, vibrating body 110 having a rectangular piezoelectric material is in pressure contact with contact body (slider) 104, as in FIG. 1B. Power supply member 507 is connected to the surface having the first and second regions. When a desired voltage is applied to vibrating body 110 via power supply member 507 by voltage input means (not shown), an elliptical motion occurs in the protrusion of the elastic body (not shown).

[0106] Holding member 501 is joined to vibrating body 110 and is configured not to generate unnecessary vibrations. Moving housing 502 is fixed to holding member 501 with screws 503 and is integrated with vibrating body 110. These members form the electronic device of the present invention. By attaching moving housing 502 to guide member 504, the electronic device of the present invention can move linearly in both directions (forward and reverse) along guide member 504.

[0107] Next, we will explain the lens 506 (optical member) that serves as the focus lens of the lens barrel device. The lens 506 is fixed to a lens holding member 505, and has an optical axis (not shown) parallel to the movement direction of the vibration actuator. Like the vibration actuator, the lens holding member 505 moves linearly on two guide members 504 (described later) to perform focal positioning (focusing operation).

[0108] Two guide members 504 are members that engage movable housing 502 and lens holding member 505, enabling movable housing 502 and lens holding member 505 to move in a straight line. With this configuration, movable housing 502 and lens holding member 505 can move in a straight line on guide members 504.

[0109] Furthermore, the connecting member 510 is a member that transmits the driving force generated by the vibration actuator to the lens holding member 505, and is fitted and attached to the lens holding member 505. This allows the lens holding member 505 to move smoothly in both directions along the two guide members 504 together with the movable housing 502.

[0110] Further, sensor 508 is provided to detect the position of lens holding member 505 on guide member 504 by reading position information from scale 509 attached to the side surface of lens holding member 505. As described above, the focus lens unit of the lens barrel device is configured by incorporating the above-mentioned components.

[0111] In the above, a lens barrel device for a single-lens reflex camera has been described as an example of an optical device, but the present invention can be applied to a variety of optical devices equipped with a vibration actuator, regardless of the type of camera, such as a compact camera in which the lens and camera body are integrated, or an electronic still camera.

[0112] Another configuration of the vibration type actuator may be one in which multiple vibrating bodies are in contact with one common contact body, and the contact body moves relative to the multiple vibrating bodies due to vibration of the multiple vibrating bodies.

[0113] The vibration actuator of the present invention can be applied to the vibrating body 110 and the contact body 104. Possible applications of the vibration actuator of the present invention include applications in the medical or engineering fields. Specifically, it is possible to configure a wire-driven actuator that includes an elongated member, a wire that is inserted through the elongated member and fixed to a part of the elongated member, and the above-mentioned vibration actuator that drives the wire, and in which the elongated member is bent by driving the wire. [Example]

[0114] Next, the vibration actuator and vibrator of the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

[0115] Example 1 The metal oxide powder was fired at 1340° C. to obtain a piezoelectric material shown in Production Composition 1 in Table 3. Production composition 1 is a composition represented by general formula (1), and the values ​​of x, y, and α shown in Table 3 correspond to the respective values ​​in general formula (1) described above.

[0116] The obtained piezoelectric material was ground and polished to approximately uniform thicknesses of 0.25, 0.30, 0.35, and 0.40 mm, and then processed into a rectangle measuring 8.7-9.1 x 5.5-5.7 mm. Electrodes 101, as shown in Figures 1A-1C, were formed on both sides of the shaped piezoelectric material. The electrodes were formed by applying silver paste to the piezoelectric material 102 by screen printing, followed by drying and baking.

[0117] Next, adhesive was applied to an elastic body made of SUS420J2 and pressure-bonded to a rectangular piezoelectric material with electrodes. The elastic body used had a rectangular portion measuring 9.3 x 5.8 mm, which was larger than the piezoelectric material, and the thickness of the elastic body was between 0.25 and 0.30 mm.

[0118] The rectangular piezoelectric material and the elastic body were positioned using a positioning jig so that the centers of their rectangular parts were aligned and the sides of the rectangular parts were parallel. In the pressed state, the piezoelectric material was heated to a temperature T1 = 160°C and held for 180 seconds, then cooled to room temperature, and the pressure was released to obtain the vibrating body.

[0119] Next, the FPC coated with ACP and the piezoelectric material were pressed together for 20 seconds using a soldering iron at a temperature T2 of 140°C, thereby thermocompression bonding the FPC to the electrodes provided on the piezoelectric material.

[0120] Next, the piezoelectric material was subjected to polarization processing. In the polarization processing, the elastic body was grounded, and power supply part 301 connected to a power source was brought into contact with the first electrode and the second electrode, respectively. Although the first electrode and the second electrode were already connected to an FPC, they were not entirely covered by the FPC, and power supply part 301 for polarization processing came into contact with the exposed parts.

[0121] After that, it was heated to T3 = 100°C, and an electric field equivalent to 2.0 kV / mm was applied for 30 minutes, and then it was cooled to 40°C over 40 minutes while the electric field was still applied, and then the voltage application was stopped. The vibrator obtained by the above process was brought into pressurized contact with a contact body (slider) made of SUS420J2 using a tension spring, and 10 vibration type actuators were produced.

[0122] (Examples 2 to 10) Ten vibration actuators each of Examples 2 to 10 were fabricated using the same method as in Example 1, except that the types of piezoelectric elements and the types of elastic bodies to be bonded were those shown in Table 1.

[0123] (Comparative Example 1) Ten vibration actuators as Comparative Example 1 were produced in the same manner as in Example 1, except that the types of piezoelectric elements and the types of elastic bodies to be bonded shown in Table 1 were used. S1, S2, and S3 are calculated values ​​obtained from W1, L1, R1, and R2. W1, L1, R1, and R2 are actual values ​​measured using an optical microscope.

[0124] [Table 1]

[0125] (Method for evaluating vibration type actuators) A drive test was performed on the vibration actuators of each example and comparative example by applying an alternating voltage with an amplitude of 130 Vpp to the first and second electrodes, with a phase difference of -90° and 90° between the voltages on the first and second electrodes.

[0126] When the frequency of the AC voltage is swept from a frequency higher than the resonance frequency of vibration mode A and vibration mode B toward the resonance frequency, the contact body is driven in a direction according to the phase difference of the AC voltage and stops after reaching its maximum speed. For convenience, the directions of travel when the phase difference is -90° and 90° are called the reverse direction and forward direction, respectively. The maximum speed of the vibrating body was measured with a sensor.

[0127] The difference between the maximum speeds in the forward and reverse directions was divided by the maximum speed in the forward direction to define the round-trip speed difference, and a product was defined as being good if it was within ±20%. The average absolute value of the round-trip speed difference was also calculated. The results are shown in Table 2.

[0128] [Table 2]

[0129] First, the yield rate of the vibration type actuators fabricated in Examples 1 to 4 and Examples 6 to 10 was 100%. The yield rate of the vibration type actuator fabricated in Example 5 was 90%. The yield rate of the vibration type actuator fabricated in Comparative Example 1 was 80%.

[0130] The vibration actuators fabricated in Examples 1 to 10 had S2 / S1 smaller than 0.178, and therefore had a yield rate of 90% or higher. On the other hand, the vibration actuator fabricated in Comparative Example 1 had S2 / S1 of 0.178, and therefore had a yield rate of 80%.

[0131] As in Examples 1 to 10, by making S2 / S1 smaller than 0.178, the in-plane distribution of the piezoelectric properties caused by the in-plane heating distribution of the piezoelectric element during polarization processing can be reduced, and it was confirmed that the yield rate was improved.

[0132] From the results of the average absolute value of the reciprocating velocity difference in Examples 1 to 10, it can be seen that a smaller S3 / S1 reduces the in-plane distribution of the piezoelectric properties, making it possible to manufacture a vibration actuator with a smaller average absolute value of the reciprocating velocity difference.

[0133] Example 11 The vibration actuator produced in Example 1 was mechanically connected to an optical element to produce the optical device shown in Figure 7. By controlling the AC voltage applied to the piezoelectric material based on position information provided to an encoder consisting of a sensor and a scale, it was possible to precisely drive the vibration actuator and the optical element connected to the vibration actuator to the target position. In this optical device, an optical lens was connected to the vibration actuator, and it was confirmed that it had an autofocus function.

[0134] The above has been described using manufacturing composition 1 as an example, but it has been confirmed that manufacturing compositions 2 to 46 also allow the manufacturing of vibration actuators with improved yield rates and driving characteristics similar to those of Example 1.

[0135] As described above, by using an elastic body having small protrusions S2 / S1 and S3 / S1, it is possible to reduce the difference in reciprocating speed, and it is possible to stably provide a vibration actuator in which the vibration characteristics in the forward and reverse directions are equivalent.

[0136] [Table 3] [Industrial Applicability]

[0137] The vibration actuator of the present invention can be suitably used as a drive unit for optical devices, and can also be widely used as a drive unit for electronic devices.

[0138] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) a vibrating body including a rectangular elastic body and a piezoelectric element having a piezoelectric material and an electrode; a contact body that contacts the elastic body, a vibration type actuator in which the vibrating body and the contact body move relatively to each other due to vibration of the vibrating body, The lead content of the piezoelectric material is 1000 ppm or less, the elastic body has a protrusion with a top portion that comes into contact with the contact body, and a flat portion, the protrusion having a space therein and having an outer surface and an inner surface, In a plan view, the top portion is disposed at a position that crosses a nodal line of an out-of-plane vibration of the elastic body, A vibration actuator characterized in that, when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.178. (Configuration 2) A vibration actuator as described in configuration 1, which has two protrusions, and when the bases of the two protrusions are viewed in cross section in a direction parallel to the flat plate portion, the sum of the areas surrounded by the outer surfaces divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.178. (Configuration 3) A vibration actuator as described in configuration 1, which has two protrusions, and when the bases of the two protrusions are viewed in cross section in a direction parallel to the flat plate portion, the sum of the areas surrounded by the inner surfaces divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.124. (Configuration 4) 2. The vibration actuator according to claim 1, wherein the top portion is disposed across a nodal line of the out-of-plane vibration of the elastic body, and the distance between the two protrusions is minimized. (Configuration 5) 2. The vibration actuator according to configuration 1, wherein the elastic body has a support portion protruding from an end of the rectangular portion. (Configuration 6) 2. The vibration actuator according to claim 1, wherein the piezoelectric element has a thickness of 0.25 to 0.40 mm. (Configuration 7) 2. The vibration actuator according to claim 1, wherein the piezoelectric material comprises a barium titanate-based material. (Configuration 8) 2. The vibration actuator of claim 1, wherein the piezoelectric material comprises barium calcium zirconate titanate. (Configuration 9) the piezoelectric material is a piezoelectric material containing an oxide having a perovskite structure containing Ba, Ca, Ti, and Zr, and Mn, x, which is a ratio of the molar amount of Ca to the sum of the molar amount of Ba and the molar amount of Ca, is 0.02≦x≦0.30; a ratio y of the molar amount of Zr to the sum of the molar amount of Ti and the molar amount of Zr is 0.020≦y≦0.095 and y≦x; a ratio of the sum of the molar amount of Ba and the molar amount of Ca to the sum of the molar amount of Ti and the molar amount of Zr is 0.9955≦α≦1.01; 2. The vibration actuator according to claim 1, wherein the content of the Mn is 0.02 parts by mass or more and 1.0 parts by mass or less in terms of metal relative to 100 parts by mass of the oxide. (Configuration 10) 2. The vibration actuator according to claim 1, wherein the depolarization temperature Td of the piezoelectric material is 126° C. or less. (Configuration 11) 2. The vibration actuator according to configuration 1, wherein the elastic body is made of martensitic stainless steel. (Method 1) A method for manufacturing a vibration actuator having a vibrating body with high vibration symmetry, comprising: a step of providing electrodes on an unpolarized piezoelectric material to obtain a piezoelectric element; a step of bonding the piezoelectric element and the elastic body at a temperature T1; a step of bonding the piezoelectric element and the power supply member at a temperature T2; a step of subjecting the piezoelectric material to a polarization treatment at a temperature T3 to produce a vibrating body; a step of bringing the vibrating body into pressure contact with a contact body; in this order, The elastic body has a protrusion with a top and a flat plate, the protrusion has an inner space and an outer surface and an inner surface; when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is smaller than 0.178, A method for manufacturing a vibration type actuator, wherein T1, T2, and T3 satisfy the relationships T1>T3 and T2>T3. (Method 2) The method for manufacturing a vibration actuator according to method 1, wherein T1, T2, and T3 satisfy the relationship T1>T2>T3. (Configuration 12) 12. An electronic device comprising the vibration actuator according to any one of configurations 1 to 11. (Configuration 13) 12. An optical device comprising at least one of an optical element and an imaging element, and the vibration actuator according to any one of configurations 1 to 11. [Explanation of symbols]

[0139] 100 Vibration Actuator 101 Electrode 101a 1st electrode 101b 2nd electrode 102 Piezoelectric Materials 103 Elastic Body 104 Contact body 106 Protrusion 107 Support part 108 Flat plate part 109 Power supply components 110 Vibration body 120 Electromechanical energy conversion element 121 Pressure member 122 Foam materials 301 Power Supply Unit 302 Heating appliances 303 Space section 411 Nodal lines of the first order out-of-plane bending vibration (mode A) 412 Antinode of the first out-of-plane bending vibration (mode A) 421 Nodal lines of second-order out-of-plane bending vibration (mode B) 422 Antinode of second-order out-of-plane bending vibration (mode B) 30 vibrating body 31 Connecting part 32 Flat plate part 34 Wall 35 Piezoelectric element 36 Contact area 37 Contact surface 38 Protrusion 39 Protrusion 40 Space section 401 outer surface 402 inner surface 501 Holding member 502 Mobile enclosure 503 Bis 504 Guide member 505 Lens holding member 506 Lens 507 Power supply components 508 Sensors 509 scale 510 Connecting member

Claims

1. a vibrating body including a rectangular elastic body and a piezoelectric element having a piezoelectric material and an electrode; a contact body that contacts the elastic body, a vibration type actuator in which the vibrating body and the contact body move relatively to each other due to vibration of the vibrating body, The content of lead contained in the piezoelectric material is 1000 ppm or less, the elastic body has a protrusion with a top portion that contacts the contact body, and a flat portion, the protrusion has an inner space and an outer surface and an inner surface; In a plan view, the top portion is disposed at a position that crosses a nodal line of an out-of-plane vibration of the elastic body, A vibration actuator characterized in that, when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.

178.

2. 2. The vibration actuator of claim 1, wherein the actuator has two protrusions, and when the bases of the two protrusions are viewed cross-sectionally in a direction parallel to the flat portion, the sum of the areas of the portions surrounded by the outer surfaces divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.

178.

3. 2. The vibration actuator of claim 1, wherein the vibration actuator has two protrusions, and when the bases of the two protrusions are viewed cross-sectionally in a direction parallel to the flat portion, the sum of the areas of the portions surrounded by the inner surfaces divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is less than 0.

124.

4. 2. The vibration actuator according to claim 1, wherein the top portion is disposed across a nodal line of out-of-plane vibration of the elastic body, and the distance between the two protrusions is minimized.

5. 2. The vibration type actuator according to claim 1, wherein the elastic body has a support portion protruding from an end of the flat plate portion.

6. 2. The vibration actuator according to claim 1, wherein the thickness of the piezoelectric element is 0.25 to 0.40 mm.

7. The vibration actuator according to claim 1 , wherein the piezoelectric material includes a barium titanate-based material.

8. The vibration actuator according to claim 1 , wherein the piezoelectric material comprises barium calcium zirconate titanate.

9. the piezoelectric material is a piezoelectric material containing an oxide having a perovskite structure containing Ba, Ca, Ti, and Zr, and Mn, x, which is a ratio of the molar amount of Ca to the sum of the molar amount of Ba and the molar amount of Ca, is 0.02≦x≦0.30; a ratio y of the molar amount of Zr to the sum of the molar amount of Ti and the molar amount of Zr is 0.020≦y≦0.095 and y≦x; a, which is a ratio of the sum of the molar amount of Ba and the molar amount of Ca to the sum of the molar amount of Ti and the molar amount of Zr, is 0.9955≦α≦1.01; 2. The vibration actuator according to claim 1, wherein the content of said Mn is 0.02 parts by mass or more and 1.0 parts by mass or less in terms of metal, relative to 100 parts by mass of said oxide.

10. 2. The vibration actuator according to claim 1, wherein the depolarization temperature Td of the piezoelectric material is 126° C. or lower.

11. 2. The vibration actuator according to claim 1, wherein the elastic body is made of martensitic stainless steel.

12. A method for manufacturing a vibration actuator having a vibrating body with high vibration symmetry, comprising: a step of providing electrodes on an unpolarized piezoelectric material to obtain a piezoelectric element; a step of bonding the piezoelectric element and the elastic body at a temperature T1; a step of bonding the piezoelectric element and the power supply member at a temperature T2; a step of subjecting the piezoelectric material to a polarization treatment at a temperature T3 to produce a vibrating body; a step of bringing the vibrating body into pressure contact with a contact body; in this order, The elastic body has a protrusion with a top and a flat plate, the protrusion has an inner space and an outer surface and an inner surface; when the base of the protrusion is viewed in cross section in a direction parallel to the flat plate portion, the total area of ​​the portion surrounded by the outer surface divided by the product of the length of the short side and the length of the long side of the main surface of the piezoelectric element is smaller than 0.178, A method for manufacturing a vibration type actuator, wherein T1, T2, and T3 satisfy the relationships T1>T3 and T2>T3.

13. The method for manufacturing a vibration actuator according to claim 12 , wherein T1, T2, and T3 satisfy the relationship T1>T2>T3.

14. An electronic device comprising the vibration type actuator according to any one of claims 1 to 11.

15. An optical device comprising at least one of an optical element and an imaging element, and the vibration type actuator according to any one of claims 1 to 11.

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