Vibration actuators, optical instruments, and electronic equipment

Abstract

To solve a problem in which there is a problem in which a vibration actuator malfunction due to poor polarization when a voltage is applied to a piezoelectric material through an elastic body to attempt polarization processing.SOLUTION: An elastic body and a piezoelectric material are joined by a conductive adhesive portion in which conductive particles are dispersed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a vibration-type actuator including an ultrasonic motor. [Background technology]

[0002] A vibration-type actuator has a vibrator configured such that vibrations are excited in an elastic body bonded to a piezoelectric element by applying an alternating voltage to the piezoelectric element. The vibration-type actuator is used as an ultrasonic motor that utilizes the driving force of the vibrations excited in the vibrator to move the vibrator relative to a contact body that is pressurized and in contact with the vibrator.

[0003] Patent Document 1 discloses a method for manufacturing a vibrator used in a vibratory actuator. In one of its embodiments, it discloses a step in which, after bonding a diaphragm and a power supply member to a piezoelectric element, the diaphragm is used as a ground and the piezoelectric ceramic is subjected to polarization treatment. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-184233 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the process described in Patent Document 1 had a problem in that insufficient electrical contact between the piezoelectric element and the elastic body resulted in polarization failure, causing the vibration-type actuator to malfunction. [Means for solving the problem]

[0006] To solve the above problems, the vibration-type actuator of the present invention comprises a vibrator in which an electrode, a rectangular piezoelectric material, and an elastic body are arranged in that order, In contact with the aforementioned elastic body, Due to the vibrations generated in the vibrator So that it can move relative to the vibrator Composition Equipped with a contact body, The elastic body and the piezoelectric material are joined together via a conductive adhesive portion. The electrodes are a first electrode and a second electrode that are adjacent to each other. The oscillator is configured such that the regions in the common piezoelectric material where the first electrode and the second electrode are provided are designated as the first region and the second region, A first bending vibration mode in which both the first region and the second region stretch or contract, When the first region stretches and contracts, the second region contracts and stretches, respectively, forming a second bending vibration mode. The average thickness of the conductive adhesive portion is 1.5 microns or more and 7 microns or less. the law of nature, The thickness of the elastic body is 0.2 mm to 1.0 mm. It is characterized by the following. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a vibration-type actuator that does not suffer from characteristic defects due to polarization defects. [Brief explanation of the drawing]

[0008] [Figure 1] This figure illustrates the schematic structure of the vibration-type actuator of the present invention, which uses an annular piezoelectric material or a rectangular piezoelectric material. (a)(d) Side view, (b)(e) Perspective view, (c)(f) Rear view [Figure 2] This diagram illustrates the two vibration modes emitted by the oscillator of the present invention, which is equipped with a rectangular piezoelectric material. (a) Mode A, (b) Mode B [Figure 3] This diagram illustrates the schematic structure of a rectangular piezoelectric material provided with the first, second, and third electrodes. [Figure 4] This diagram illustrates the schematic structure of a rectangular piezoelectric material equipped with the first, second, third, and fourth electrodes. [Figure 5] This is a diagram illustrating the schematic structure of the optical instrument of the present invention. [Modes for carrying out the invention]

[0009] The vibrating actuator of the present invention includes a vibrator in which an electrode, a piezoelectric material, and an elastic body are arranged in this order, and a contact body that contacts the elastic body and is provided so as to be relatively movable with respect to the vibrator, and the elastic body and the piezoelectric material are joined via a conductive adhesive portion.

[0010] The schematic structure of the vibrating actuator of the present invention is illustrated in FIGS. 1 and 2. In the vibrating actuators illustrated in FIGS. 1 and 2, an annular piezoelectric material and a rectangular piezoelectric material are used, respectively.

[0011] The vibrating actuator 100 of the present invention includes a vibrator 102 in which an electrode 101, a piezoelectric material 102, and an elastic body 103 are arranged in this order, and a contact body 104 that contacts the elastic body 103, and the elastic body 103 and the piezoelectric material 102 are joined via a conductive adhesive portion 105.

[0012] The elastic body 103 has a protrusion 106, and the protrusion 106 and the contact body 104 are configured to be in pressure contact.

[0013] The contact body 104 only needs to be a member that can move relative to the vibrator 110, and is not limited to a member that directly contacts the vibrator 110, and may be a member that indirectly contacts the vibrator 110 via another member.

[0014] (Electrode) When an annular piezoelectric material is used, the piezoelectric material is provided with an electrode 101 divided in the circumferential direction. The electrode 101 includes a driving-phase electrode 101e and a non-driving-phase electrode 101f. The circumferential length of the driving-phase electrode is 1 / 2 of the wavelength λ of the driving frequency. The circumferential length of the non-driving-phase electrode (ground electrode, monitoring electrode) is 1 / 4 of the wavelength λ of the driving frequency. The number of driving-phase electrodes and non-driving-phase electrodes changes according to the number of traveling waves excited in the annular piezoelectric material. The piezoelectric material corresponding to each driving-phase electrode is subjected to polarization treatment with voltages of different polarities in adjacent regions.

[0015] The driving phase electrode is separated by an odd number of non-driving phase electrodes. After polarization treatment, a first electrode 101a and a second electrode 101b are provided to short-circuit the two driving phase electrode groups separated by the non-driving phase electrodes, respectively. The first electrode 101a and the second electrode 101b are used to drive a vibratory actuator using an annular piezoelectric material.

[0016] When a rectangular piezoelectric material is used, 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 treatment of the rectangular piezoelectric material and for driving a vibratory actuator using the rectangular piezoelectric material.

[0017] The electrode consists of a metal film with a thickness of approximately 0.3 to 10 μm. While the material is not particularly limited, silver, gold, or platinum electrodes are generally used. The manufacturing method of the electrode is not limited and can be formed by screen printing, sputtering, vacuum deposition, etc. If lead is to be removed from the piezoelectric element, a paste or target with a lead content of less than 1000 ppm is used for electrode formation.

[0018] (Piezoelectric materials) The piezoelectric material 102 includes piezoelectric ceramics (sintered bodies) without crystal orientation, crystal-oriented ceramics, and piezoelectric single crystals. The piezoelectric material may be a laminate of inner layer electrodes and piezoelectric material, or a single sheet of piezoelectric material. From the standpoint of cost, a single sheet of piezoelectric material is superior. In order to drive the vibration wave actuator, the piezoelectric material is subjected to polarization treatment. When the AC electric field frequency applied to the polarized piezoelectric material approaches the resonance frequency of the piezoelectric material, the piezoelectric material vibrates greatly due to the resonance phenomenon.

[0019] (Elastic body) The elastic body 103 is preferably made of metal from the viewpoint of its elastic properties and workability. 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 preferred, and SUS420J2 is the most preferred. The elastic body has protrusions 106 that come into contact with the contact body. To improve the wear resistance of the protrusions, the elastic body may be subjected to quenching, plating, or nitriding.

[0020] (Conductive adhesive part) The elastic body 103 and the piezoelectric material 102 are joined via a conductive adhesive portion 105. The conductive adhesive portion of the present invention is a mixture of conductive particles and a non-conductive adhesive portion. The conductive particles are sandwiched between the objects to be bonded, thereby electrically connecting the objects to be bonded.

[0021] The conductive particles are made of resins (such as acrylic or styrene) coated with metals such as gold, nickel, or silver. The volume resistivity of the conductive particles is less than 0.01 Ωcm. The shape of the conductive particles is not limited, but they are typically spherical. Protrusions may be provided on the outermost metal coating layer to improve adhesion to the substrate.

[0022] Conductive particles not only electrically connect the materials to be bonded, but also function as gap fillers to maintain a constant adhesive layer thickness. Because the materials to be bonded (elastic bodies, piezoelectric materials, electrodes on piezoelectric materials, etc.) have surface roughness determined by their processing or formation methods, excessively small conductive particles will not function as gap fillers. Conversely, excessively large conductive particles will result in an excessively thick adhesive layer, dampening the vibrations emitted by the piezoelectric material and degrading the performance of the vibration-type actuator. Obtaining conductive particles with a diameter of less than 2 microns is extremely difficult; the diameter of commonly available conductive particles is typically around 2 to 30 microns. The diameter distribution of conductive particles is expressed by the CV value.

[0023] For conductive particles to function as a gap filler, there is an optimal range of elastic modulus. If the elastic modulus of the conductive particles is too low, the pressure pressing the adherends together will cause plastic deformation, rendering them ineffective as a gap filler. If the elastic modulus of the conductive particles is too high, the probability of plastic deformation due to the pressure pressing the adherends together decreases, but the contact area with the adherends is small, resulting in only moderate reliability of the electrical connection. It is preferable that the conductive particles are compressed within the range of elastic deformation between the adherends, increasing the contact area between the conductive particles and the adherends, thereby improving the reliability of the electrical connection.

[0024] Using an adhesive that does not contain conductive particles results in direct contact between the bonded materials. This means that the amount of adhesive remaining between the elastic body and the piezoelectric material is significantly reduced, leading to a decrease in adhesive strength. Low adhesive strength can cause the elastic body and piezoelectric material to separate during operation of a vibrating actuator, resulting in malfunction.

[0025] At the same time, because the amount of adhesive remaining between the elastic body and the piezoelectric material is uneven, if a voltage is applied to the piezoelectric material through the elastic body after bonding the elastic body and piezoelectric material to attempt polarization, polarization failure occurs. When polarization failure occurs, the piezoelectric performance of the piezoelectric material deteriorates, and the performance of the vibration-type actuator no longer meets the specifications. In other words, if a conductive adhesive is not used, a decrease in adhesive strength and polarization failure occur with a certain probability, resulting in a decrease in the yield rate.

[0026] When conductive particles simultaneously come into contact with both an elastic body and a piezoelectric material, the elastic body and the piezoelectric material are electrically connected and conduction occurs. In other words, by applying a voltage between an electrode provided on the piezoelectric material and the elastic body, the piezoelectric material can be stably polarized.

[0027] During the polarization process, for example, an elastic body is grounded, and a voltage is applied to the electrodes provided on the piezoelectric material. When bonding the power supply member to the electrodes, an exposed portion of the electrodes that is not covered by the power supply member is left. When performing the polarization process after the bonding process of the power supply member, an external electrode (for example, a metal pin) is brought into contact with the exposed portion, and a voltage is applied between the electrodes and the elastic body. Conversely, a voltage may be applied to the elastic body to ground the electrodes provided on the piezoelectric material. In any case, this voltage application method does not use a power supply member for the polarization process.

[0028] If the power supply components have sufficient electrical withstand voltage, it is possible to connect each power supply component to a power source and apply polarization treatment to the piezoelectric material, but this is inefficient. Furthermore, the shape of the power supply components is often changed according to the specifications (stroke, etc.) of the vibrating actuator. Therefore, automating the connection between the electrode terminals of the power supply components and the power source is also difficult. For this reason, a polarization treatment method that applies voltage to the piezoelectric material without using power supply components is preferred.

[0029] While the type of adhesive is not particularly limited, epoxy resins are preferred because they offer superior strength, curing time, and environmental resistance (temperature changes, high humidity, etc.).

[0030] When polarization treatment is performed after bonding an elastic body and a power supply member to a piezoelectric material, it is preferable that the glass transition temperature (Tg) of the adhesive be 20°C or more higher than the polarization treatment temperature so that the bonded members do not move or peel off at the polarization treatment temperature. Considering that the polarization treatment is generally performed at 80°C or higher, it is preferable that the Tg of the adhesive be 100°C or higher. A Tg of 120°C or higher is even preferable because it allows the polarization treatment temperature to be extended by another 20°C, the polarization treatment time to be shortened, or the voltage intensity to be set lower.

[0031] To transmit vibrations emitted by the piezoelectric material to the elastic body with minimal damping, the elastic modulus of the epoxy resin is preferably 1 GPa or higher. A modulus of 2 GPa or higher is preferable for further damping. Furthermore, during the cooling period from the curing temperature of the adhesive to room temperature, shear strain is applied to the adhesive due to the difference in thermal expansion coefficients between the elastic body and the piezoelectric material. To ensure that the elastic body and the piezoelectric material remain bonded without delamination even under shear strain, the shear strength of the adhesive is preferably 10 MPa or higher. A shear strength of 20 MPa or higher is even preferable because it allows for the selection of a higher curing temperature and a shorter curing time. The shear strength of the adhesive can be measured according to the JIS standard (JIS 6850).

[0032] (contact body) Stainless steel is preferred for the contact body 104 from the viewpoint of rigidity. Among stainless steels, martensitic stainless steel is preferred, and SUS420J2 is the most preferred. Since the contact body 104 is in frictional contact with the elastic body 103, it needs to have excellent wear resistance, and its surface is treated with nitriding or anodizing. A frictional force acts between the projection 106 and the contact body 104 due to pressurized contact. The tip of the projection 106 vibrates elliptically due to the vibrations emitted by the piezoelectric material 102, which can generate a driving force (thrust) to drive the contact body 104. The contact body is commonly called a slider or rotor.

[0033] (Vibration-type actuator using annular piezoelectric material) In an annular piezoelectric element, the piezoelectric material in contact with adjacent driving phase electrodes is polarized with different polarities. Therefore, when an electric field of the same polarity is applied to the driving phase electrode 101e, the expansion and contraction polarity of the piezoelectric material in that region alternately reverses at a pitch of λ / 2. When an alternating voltage is applied to the first electrode 101a, a first standing wave with wavelength λ is generated over the entire circumference of the oscillator. Similarly, when an alternating voltage is applied to the second electrode 101b, a second standing wave is generated, but the position of the wave is rotated by λ / 4 in the circumferential direction relative to the first standing wave. On the other hand, two types of alternating voltages with the same frequency and a temporal phase difference of π / 2 are applied to the first and second electrodes. As a result of the combination of the first and second standing waves, a traveling wave of bending vibration (vibration with amplitude perpendicular to the surface of the oscillator) (wavenumber n along the annulus, wavelength λ) is generated in the oscillator over the entire circumference in the circumferential direction.

[0034] When a bending vibration traveling wave (hereinafter sometimes simply referred to as a "bending vibration wave") is generated, each point on the surface of the diaphragm constituting the oscillator undergoes elliptical motion. As a result, a moving object in contact with this surface receives a circumferential frictional force (driving force) from the diaphragm and rotates. The direction of this rotation can be reversed by switching the positive or negative phase difference of the alternating voltage applied to the first and second electrodes. Furthermore, the rotation speed can be controlled by the frequency and amplitude of the alternating voltage applied to the first and second electrodes.

[0035] (Vibration mode) In the vibration-type actuator of the present invention, The piezoelectric material is rectangular, The electrodes are a first electrode and a second electrode that are adjacent to each other. The oscillator is configured such that when the regions in the piezoelectric material where the first electrode and the second electrode are provided are designated as the first region and the second region, A first bending vibration mode in which both the first region and the second region stretch or contract, It is preferable that a second bending vibration mode is formed in which the second region contracts and stretches when the first region stretches and contracts.

[0036] Figure 2 illustrates two vibration modes emitted by the oscillator of the present invention, which comprises a rectangular piezoelectric material. The rectangular piezoelectric material is provided with the first electrode 101a and the second electrode 101b, and their respective regions are designated as the first region and the second region.

[0037] Mode A When both the first region and the second region are stretched or contracted, a first bending vibration mode (mode A) is generated. Mode A is generated when an alternating voltage V is applied to the first electrode 101a and the second electrode 101b. A , V B The oscillator is most strongly excited when the phase difference is 0° and the frequency is near the resonant frequency of mode A. Mode A is a first-order out-of-plane vibration mode in which two nodes (where the amplitude is minimum) appear approximately parallel to the long side of the oscillator 110. The projection 106 of the elastic body is positioned near the antinode (where the amplitude is maximum) of mode A. Therefore, the tip surface of the projection 106 reciprocates in the Z direction due to vibration mode A.

[0038] Mode B When the first region stretches and contracts, and the second region also contracts and stretches, a second bending vibration mode (mode B) is generated. Mode B is generated when the alternating voltage V applied to the first electrode 101a and the second electrode 101b is applied. A , V B The oscillator is most strongly excited when the phase difference is 180° and the frequency is near the resonant frequency of mode B. Mode B is a second-order out-of-plane vibration mode in which three nodes appear approximately parallel to the short side of the oscillator 110. The projection 106 of the elastic body is positioned near the location of the nodes of mode B. Therefore, the tip surface of the projection 106 reciprocates in the X direction due to mode B.

[0039] In the vibration actuator 100, the alternating voltage V A , V B When the phase difference between the modes is 0 to ±180°, mode A and mode B are excited simultaneously, and elliptical vibration is excited in the projection 106 of the elastic body. A vibration-type actuator using a rectangular piezoelectric material and driven by modes A and B is preferable because it is easy to miniaturize.

[0040] (Structure of an elastic body 1) The elastic body 103 has a rectangular portion 108 to which the rectangular piezoelectric material is joined by a conductive adhesive portion, and it is preferable that the vibrator is held by the vibrator holding member at the four corners of the rectangular portion. Protrusions may be provided on the inside of the rectangular portion. In order for the piezoelectric element and the elastic body to be joined with sufficient adhesive strength for driving the vibratory actuator, the bonding area needs to be as large as possible. On the other hand, if there are unnecessary parts in the elastic body that are not joined to the piezoelectric element, these unnecessary parts may cause vibrations other than the aforementioned modes A and B, which may reduce the efficiency of the vibratory actuator. Taking into account the misalignment of the joining position, it is preferable that the rectangular portion 108 is 0.1 to 0.6 mm larger in dimension than one side of the rectangular piezoelectric material.

[0041] (Structure of elastic bodies 2) Preferably, the elastic body 103 has a support portion 107 that protrudes from the end of the rectangular portion 108. The vibrator 110 can be held by providing, for example, a fitting portion on the support portion. By devising the shape of the support portion extending from the rectangular portion and positioning the fitting portion within the support portion at a location close to the vibration node, it is possible to hold the vibrator with the support portion while preventing interference with the vibration of the vibrator.

[0042] (Electrode arrangement 1) The vibration-type actuator of the present invention preferably has a third electrode that sandwiches the piezoelectric material together with the first electrode and the second electrode.

[0043] The rectangular piezoelectric material in Figure 3 has a third electrode 101c that sandwiches the piezoelectric material 102 together with the first electrode 101a and the second electrode 101b. A projection 106 is formed on the elastic body as shown in Figure 1(e). Directly below the projection 106, there is a non-contact area where the elastic body and the piezoelectric material are not joined via a conductive adhesive portion. When attempting polarization treatment by applying a voltage to the piezoelectric material through the elastic body, if the third electrode is absent, the voltage will not be applied to the piezoelectric material below the non-contact area. As a result, the portion of the piezoelectric material that has not been polarized increases, and vibrations degrade the performance of the actuator. Therefore, the presence of the third electrode 101c is preferable because it makes it possible to apply polarization treatment to the piezoelectric material below the non-contact area as well.

[0044] (Electrode arrangement 2) The vibration actuator of the present invention preferably further has a fourth electrode adjacent to the first electrode and the second electrode, respectively, and which is electrically connected to the third electrode.

[0045] The rectangular piezoelectric material in Figure 4 has a first electrode 101a, a second electrode 101b, a third electrode 101c, and a fourth electrode 101d adjacent to the first and second electrodes, respectively, and electrically connected to the third electrode. Figure 6 illustrates a configuration in which the third electrode 101c and the fourth electrode 101d are connected via the side surface of the piezoelectric material 107. Alternatively, for example, the third and fourth electrodes may be connected without passing through the side surface of the piezoelectric material by forming a through-hole that penetrates the piezoelectric material 107 and wiring the electrode material within the through-hole. The diameter of the through-hole is preferably less than 200 microns so as not to interfere with the vibration of the piezoelectric material. When the fourth electrode is formed on the piezoelectric material, the first, second, and fourth electrodes are formed on the same surface of the piezoelectric material. That is, the shape of the power supply member can be made into a simple planar structure. Even if the third electrode is covered with an elastic material, it is still possible to apply a driving voltage to the third electrode via a fourth electrode that is electrically connected to the third electrode.

[0046] (Adhesive thickness) The thickness of the conductive adhesive portion of the vibration-type actuator of the present invention is preferably 1.5 microns or more and 7 microns or less.

[0047] If the thickness of the conductive adhesive portion is greater than 7 microns, the conductive adhesive portion will absorb the vibrations emitted by the piezoelectric material, resulting in poor performance of the vibration-type actuator.

[0048] If the thickness of the conductive adhesive portion is less than 1.5 microns, the amount of adhesive between the piezoelectric material and the elastic body will be insufficient, and there is a risk that the elastic body may detach during operation of the vibration-type actuator. Therefore, it is preferable that the average thickness of the conductive adhesive portion be between 1.5 microns and 7 microns.

[0049] The thickness of the conductive adhesive layer refers to the average thickness of the conductive adhesive layer determined by the evaluation method described below. The average thickness of the conductive adhesive layer can be determined by observing the cross-section of the surface containing the piezoelectric element, conductive adhesive layer, and elastic body. An electron microscope can be used for cross-sectional observation. For example, the cross-section of the conductive adhesive layer is observed from a direction perpendicular to the lamination direction of the piezoelectric material, conductive adhesive layer, and elastic body. An observation magnification of around 500x is appropriate. The cross-sectional area of ​​the conductive adhesive layer is calculated from the observed image. The average thickness of the conductive adhesive layer is calculated by dividing the obtained cross-sectional area by the width of the observation area = the horizontal length of the conductive adhesive layer.

[0050] (Dimensions and volume density of conductive particles) The conductive adhesive portion preferably contains conductive particles with an average particle diameter of 2 microns or more and 5 microns or less in volume fraction of 0.4% or more and 2% or less.

[0051] The distance between the piezoelectric element and the elastic body can be controlled by standardizing the size of the conductive particles contained in the conductive adhesive. The particle size distribution can be expressed by the CV value (Coefficient of Variation, CV (%) = standard deviation of particle diameter ÷ mean particle diameter × 100). A larger CV value increases the proportion of conductive particles larger than the average particle diameter, and the thickness of the conductive adhesive becomes greater than the average particle diameter. Standardized particle size refers to a CV value of less than 10%. A CV value of 6% or less is preferable because it increases the thickness uniformity of the conductive adhesive.

[0052] Conductive particles with an average particle size of less than 2 microns may become embedded in the surface irregularities of piezoelectric materials, elastic materials, and electrodes, and may not function as gap fillers. The surface irregularities of piezoelectric materials, elastic materials, and electrodes increase or decrease depending on scratches caused by lapping or the degree of grain growth during firing or firing of the piezoelectric material or electrode material.

[0053] If the average particle size of the conductive particles is larger than 5 microns, the thickness of the conductive adhesive layer will exceed 7 microns, which is undesirable because it reduces the efficiency of the vibratory actuator. The average particle size of the conductive particles is determined by observing the conductive adhesive layer between the elastic body and the piezoelectric material and averaging the diameters of at least three particles.

[0054] If the volume fraction of conductive particles in the conductive adhesive area is less than 0.4%, pressure will concentrate on the conductive particles during bonding between the elastic body and the piezoelectric material, causing them to collapse. When conductive particles collapse, the thickness of the conductive adhesive area cannot be controlled, resulting in insufficient adhesive strength. Alternatively, the low number of conductive particles will increase the resistance between the elastic body and the piezoelectric material, leading to poor polarization and thus poor performance of the vibration-type actuator.

[0055] If the volume fraction of conductive particles in the conductive adhesive area exceeds 2%, the reliability of the electrical connection between the elastic body and the piezoelectric element increases, but the adhesive area decreases, resulting in a decrease in the adhesive strength between the piezoelectric material and the elastic body.

[0056] Therefore, when the conductive adhesive portion contains conductive particles having an average particle diameter of 2 μm or more and 5 μm or less at a volume fraction of 0.4% or more and 2% or less, it is possible to achieve both the adhesive strength and conductivity between the elastic body and the piezoelectric material. When it is conductive, the electrical resistance between the fourth electrode and the elastic body is less than 10 Ω. The volume fraction can be calculated by substituting the cross-sectional areas of the adhesive portion and the conductive particle portion constituting the conductive adhesive portion using the cross-sectional observation result of the conductive adhesive portion.

[0057] (Density of conductive particles) The specific gravity of the conductive particles is 2.0 g / cm 3 or more and 4.0 g / cm 3 or less. The specific gravity of the conductive particles varies depending on the volume fraction of the metal layer with a large specific gravity and the resin ball with a small specific gravity.

[0058] If the specific gravity of the conductive particles is less than 2.0 g / cm 3 , the proportion of the metal component contained in the conductive particles is low, and good conductivity cannot be obtained between the elastic body and the electrode. Also, the conductive particles are likely to be crushed when the piezoelectric material and the elastic body are adhered.

[0059] If the specific gravity of the conductive particles is greater than 4.0 g / cm 3 , the specific gravity difference from the adhesive increases, and the conductive particles precipitate in the adhesive. When the conductive particles precipitate, the amount of conductive particles contained in the conductive adhesive portion does not become constant every time the adhesive is applied to the joint portion, and it cannot be used for manufacturing the vibration type actuator of the present invention.

[0060] Therefore, it is preferable that the specific gravity of the conductive particles is 2.0 g / cm 3 or more and 4.0 g / cm 3 or less. When the specific gravity of the conductive particles cannot be measured, it can be calculated using the structure of the conductive particles and the specific gravity of the constituent materials.

[0061] (Anisotropy of the conductive adhesive portion) The conductive adhesive portion is preferably an anisotropic conductive material.

[0062] The conductive adhesive portion may protrude from the bonding area during joining and adhere to the side surface of the piezoelectric material. If the conductive adhesive portion is made of an anisotropic conductive material, even if the protruding conductive adhesive portion touches the first or second electrode via the side surface of the piezoelectric material, it is possible to prevent the first or second electrode from electrically short-circuiting with the elastic body. When the conductive adhesive portion is made of an anisotropic conductive material, if the surface resistance is measured by applying a tester to the surface of the conductive adhesive portion protruding from the bonding area between the piezoelectric element and the elastic body at a distance of 2 mm or more, the resistance will be greater than 10 Ω.

[0063] (Composition of piezoelectric material 1) It is preferable that the lead content in the piezoelectric material is less than 1000 ppm. In particular, it is preferable that the main component of the piezoelectric material is barium titanate-based.

[0064] From the viewpoint of having a high piezoelectric constant and being relatively easy to manufacture, piezoelectric materials are preferably made of barium titanate-based materials. Here, barium titanate-based materials include barium titanate (BaTiO3), calcium barium titanate ((Ba,Ca)TiO3), and barium zirconate titanate (Ba(Ti,Zr)O3). Calcium barium zirconate titanate ((Ba,Ca)(Ti,Zr)O3) is another example. Compositions such as sodium niobate-barium titanate (NaNbO3-BaTiO3), sodium bismuth titanate-barium titanate, and potassium bismuth titanate-barium titanate are also examples. These materials refer to materials whose main components are these compositions. Among these, the following materials are preferred from the viewpoint of achieving both a high piezoelectric constant and a high mechanical quality coefficient for piezoelectric ceramics. Specifically, it is preferable that the main components be barium calcium zirconate titanate ((Ba,Ca)(Ti,Zr)O3) and sodium niobate-barium titanate (NaNbO3-BaTiO3). In addition to the main components, it is preferable that manganese and bismuth are included. The main component is defined as a material whose weight fraction is greater than 10%.

[0065] Furthermore, it is even more preferable if the lead content of the piezoelectric material is 1000 ppm or less, as this reduces the environmental impact. Generally, lead zirconate titanate (Pb(Zr,Ti)O3), which contains lead, is widely used in piezoelectric devices. Therefore, it has been pointed out that when piezoelectric elements are discarded and exposed to acid rain or left in harsh environments, the lead component in conventional piezoelectric ceramics may dissolve into the soil and harm the ecosystem. For this reason, it is preferable that the piezoelectric material of the present invention is a barium titanate-based piezoelectric material with a lead content of less than 1000 ppm. The lead content can be measured, for example, by ICP emission spectrometry.

[0066] (Composition of piezoelectric material 2) It is preferable that the main component of the piezoelectric material is barium calcium zirconate titanate (hereinafter referred to as BCTZ). When BCTZ is the main component, the piezoelectric properties of BCTZ can be adjusted according to the application by adjusting the amount of Ca and Zr. In addition, the amount of expensive niobium used can be reduced.

[0067] (Composition of piezoelectric material 3) The piezoelectric material is a piezoelectric material containing an oxide with a perovskite-type structure containing Ba, Ca, Ti, and Zr, and Mn, The molar ratio x of Ca to the sum of Ba and Ca is 0.02 ≤ x ≤ 0.30, and the molar ratio y of Zr to the sum of Ti and Zr is 0.020 ≤ y ≤ 0.095, and y ≤ x. Preferably, α, which is the ratio of the molar amounts of Ba and Ca to the molar amounts of Ti and Zr, is 0.9955 ≤ α ≤ 1.01, and the content of Mn per 100 parts by weight of the oxide is 0.02 parts by weight or more and 1.0 part by weight or less in terms of metal.

[0068] Such piezoelectric materials can be represented by the following general formula (1). (Ba 1-x Ca x ) α (Ti 1-y Zr y )O3(1)

[0069] however, 0.986≦α≦1.100, 0.02 ≤ x ≤ 0.30, 0.02 ≤ y ≤ 0.095 Preferably, the piezoelectric ceramic has a perovskite-type metal oxide represented by as the main component, and the content of metal components other than the main component in the piezoelectric ceramic is 1 part by weight or less in terms of metal per 100 parts by weight of the metal oxide.

[0070] In particular, it is preferable that the metal oxide contains Mn, and that the Mn content is between 0.02 parts by weight and 0.40 parts by weight in terms of metal per 100 parts by weight of the metal oxide. Containing Mn within this range improves insulation properties and the mechanical quality coefficient Qm. Here, the mechanical quality coefficient Qm is a coefficient that represents the elastic loss due to vibration when the piezoelectric material is evaluated as an oscillator, and the magnitude of the mechanical quality coefficient is observed as the sharpness of the resonance curve in impedance measurement. In other words, it is a constant that represents the sharpness of the oscillator's resonance. When the mechanical quality coefficient Qm is large, the amount of strain in the piezoelectric material becomes larger near the resonance frequency, and the piezoelectric material can be vibrated more effectively.

[0071] The metal oxide represented by the general formula (1) above means that the metal elements located at the A site of the perovskite structure are Ba and Ca, and the metal elements located at the B site are Ti and Zr. However, some Ba and Ca may be located at the B site. Similarly, some Ti and Zr may be located at the A site.

[0072] In general formula (1), the molar ratio of the element at the B site to the element O is 1:3, but even if the molar ratio deviates slightly, as long as the metal oxide has a perovskite structure as its main phase, it falls within the scope of the present invention.

[0073] The perovskite structure of a metal oxide can be determined, for example, from structural analysis using X-ray diffraction or electron diffraction.

[0074] 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. Substituting a portion of the Ba in perovskite-type barium titanate with Ca within this range shifts the phase transition temperature between orthorhombic and tetragonal crystals to a lower temperature, thus enabling stable piezoelectric vibration within the operating temperature range of the vibration actuator. However, if x is greater than 0.30, the piezoelectric constant of the piezoelectric material becomes insufficient, which may lead to inadequate performance of the vibration actuator. On the other hand, if x is less than 0.02, the dielectric loss (tanδ) may increase. Increased dielectric loss increases the heat generated when applying voltage to the piezoelectric material to drive the vibration actuator, which may reduce motor driving efficiency and increase power consumption.

[0075] In general formula (1), y, which represents the molar ratio of Zr at site B, is in the range of 0.02 ≤ y ≤ 0.1. If y is greater than 0.1, Td becomes low, below 80°C, which is undesirable as it limits the temperature range in which the vibration actuator can be used to below 80°C.

[0076] In this specification, Td refers to the lowest temperature at which the piezoelectric constant decreases by more than 10% compared to the piezoelectric constant before heating, after heating the piezoelectric material from room temperature to Td and then cooling it back to room temperature, one week after polarization treatment.

[0077] Furthermore, in general formula (1), α, which represents the ratio of the molar amounts of Ba and Ca at site A to the molar amounts of Ti and Zr at site B, is preferably in the range of 0.9955 ≤ α ≤ 1.010. If α is smaller than 0.9955, abnormal grain growth is more likely to occur in the crystal grains constituting the piezoelectric material, and the mechanical strength of the piezoelectric material decreases. On the other hand, if α is larger than 1.010, the piezoelectric material does not become dense enough and its insulating properties become extremely brittle.

[0078] The means for measuring the composition of piezoelectric materials are not particularly limited. Examples of such methods include X-ray fluorescence analysis, ICP emission spectrometry, and atomic absorption spectrometry. Regardless of the measurement method used, the weight ratio and composition ratio of each element contained in the piezoelectric material can be calculated.

[0079] The metal equivalent of Mn content is calculated by determining the content of each metal, Ba, Ca, Ti, Zr, and Mn, from piezoelectric materials using methods such as X-ray fluorescence analysis (XRF), ICP emission spectrometry, and atomic absorption spectrometry. From this content, the elements constituting the metal oxide represented by general formula (1) are converted to oxide equivalents, and the value is expressed as the ratio of the weight of Mn to the total weight of these elements, with the total weight set to 100.

[0080] If the Mn content is less than 0.02 parts by weight, the polarization treatment necessary for driving the vibratory actuator may not be sufficiently effective. On the other hand, if the Mn content is greater than 0.40 parts by weight, the piezoelectric properties of the piezoelectric material may not be sufficient, or hexagonal crystals without piezoelectric properties may appear. The Mn is not limited to metallic Mn; it is acceptable as long as it is included in the piezoelectric material as a Mn component, and the form of its inclusion is not important. For example, it may be solid-dissolved at the B site or contained within the grain boundaries. A more preferable form of inclusion is solid-dissolved at the B site from the viewpoint of insulation and ease of sintering.

[0081] (Composition of piezoelectric material 4) The piezoelectric material preferably contains 0.042 parts by weight or more and 0.850 parts by weight or less of Bi in terms of metal equivalent.

[0082] The piezoelectric material may contain 0.85 parts by weight or less of Bi (in terms of metal equivalent) per 100 parts by weight of the metal oxide shown in general formula (1). The Bi content relative to the metal oxide can be measured, for example, by ICP emission spectroscopy. Bi may be present at the grain boundaries of the ceramic piezoelectric material, or it may be in a solid solution within the perovskite-type structure of (Ba,Ca)(Ti,Zr)O3. When Bi is present at the grain boundaries, inter-particle friction is reduced and the mechanical quality coefficient increases. On the other hand, when Bi is incorporated into the solid solution forming the perovskite structure, the phase transition temperature is lowered, which reduces the temperature dependence of the piezoelectric constant and further improves the mechanical quality coefficient. It is preferable that the position of Bi when incorporated into the solid solution is at site A, as this improves the charge balance with Mn.

[0083] The piezoelectric material may contain elements other than those in the general formula (1) and Mn and Bi (hereinafter referred to as "sub-components"), as long as the properties do not change. Preferably, the total amount of sub-components is less than 1.2 parts by weight per 100 parts by weight of the metal oxide represented by the general formula (1). If the amount of sub-components exceeds 1.2 parts by weight, the piezoelectric properties and insulating properties of the piezoelectric material may deteriorate.

[0084] (Power supply component) The vibration-type actuator of the present invention preferably has a power supply member joined to a piezoelectric element comprising the piezoelectric material and the electrodes.

[0085] For the power supply component, it is preferable to use a flexible printed circuit board (hereinafter referred to as FPC) because it offers high dimensional accuracy and easy positioning. Polyimide is preferred as the material for the FPC. The method of joining the FPC and the piezoelectric element is not particularly limited, but it is preferable to use an anisotropic conductive paste (ACP) or anisotropic conductive film (ACF) which offers high reliability in terms of adhesive cycle and electrical connection. By supplying power with the FPC, power can be supplied without hindering 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 fourth electrode.

[0086] (Composition of an elastic body) The elastic body of the present invention is preferably JIS standard SUS402J2 stainless steel that has been pre-treated with vacuum hardening. JIS standard SUS420J2 has low electrical resistance (resistivity at room temperature is 55 μΩcm). When SUS420J2 is used as the elastic body, a piezoelectric material or piezoelectric element bonded to the elastic body by a conductive adhesive can be subjected to polarization treatment by applying a voltage through the elastic body. By hardening SUS420J2 in a vacuum, its strength can be increased while preventing the formation of an oxide film that increases electrical resistance. Vacuum hardened SUS420J2 has high hardness and is suitable for the vibration-type actuator of the present invention, which drives a contact body by friction with the elastic body.

[0087] The thickness of the elastic body bonded to the rectangular piezoelectric material is in the range of 0.2 to 1.0 mm, and a thickness in the range of 0.2 to 0.35 mm is preferable because it combines resilience and spring properties, and is easy to mold.

[0088] (electronic equipment) The electronic device of the present invention is characterized by comprising the above-described vibration actuator, a member connected to the contact body of the vibration actuator, and a means for detecting the position of the member (e.g., an encoder). This electronic device can precisely control the position of the member by detecting the position of the member and operating the vibration actuator until the member reaches a target position.

[0089] (optical equipment) The optical instrument of the present invention is equipped with the above-mentioned vibration-type actuator in the drive unit, and further comprises at least one of an optical element and an image sensor.

[0090] Figure 5 is a schematic diagram showing one embodiment of the optical instrument (focus lens section of the lens barrel device) of the present invention. In Figure 5, the transducer 110, which is equipped with a rectangular piezoelectric material, is in pressurized contact with the contact body (slider) 104, similar to Figure 1(d). The power supply member 507 is connected to the side having first and second regions. When a desired voltage is applied to the transducer 110 via the power supply member 507 by a voltage input means (not shown), elliptical motion occurs in the protrusion of the elastic body (not shown). The holding member 501 is joined to the transducer 110 and is configured to prevent the generation of unwanted vibrations. The movable housing 502 is fixed to the holding member 501 with screws 503 and is integral with the transducer 110. These components form the electronic device of the present invention. By attaching the movable housing 502 to the guide member 504, the electronic device of the present invention can move linearly in both directions (forward and reverse directions) along the guide member 504.

[0091] Next, the lens 506 (optical component) that serves as the focusing lens for the lens barrel device will be described. The lens 506 is fixed to the lens holding member 505 and has an optical axis (not shown) parallel to the direction of movement of the vibration actuator. The lens holding member 505, like the vibration actuator, performs focus adjustment (focusing operation) by moving in a straight line on two guide members 504, which will be described later. The two guide members 504 are components that engage the moving housing 502 and the lens holding member 505, enabling the moving housing 502 and the lens holding member 505 to move in a straight line. With this configuration, the moving housing 502 and the lens holding member 505 can move in a straight line on the guide members 504.

[0092] Furthermore, the connecting member 510 is a member that transmits the driving force generated by the vibrating actuator to the lens holding member 505, and is fitted and attached to the lens holding member 505. As a result, the lens holding member 505 can move smoothly in both directions along the two guide members 504 together with the movable housing 502.

[0093] Furthermore, the sensor 508 is provided to detect the position of the lens holding member 505 on the guide member 504 by reading the position information of the scale 509 attached to the side surface of the lens holding member 505. As described above, the focus lens section of the lens barrel device is formed by assembling each of the above-mentioned components.

[0094] In the above, we described a lens barrel device for a single-lens reflex camera as an optical instrument, but it can be applied to a variety of optical instruments equipped with a vibration actuator, regardless of the type of camera, such as compact cameras with integrated lenses and camera bodies, and electronic still cameras.

[0095] Furthermore, as another configuration for a vibratory actuator, multiple vibrators may be in contact with a single common contact body, and the contact body may be arranged so that it moves relative to the multiple vibrators due to the vibration of the multiple vibrators.

[0096] Furthermore, the vibration actuator of the present invention can be applied to medical or engineering fields. Specifically, it is also possible to configure a wire-driven actuator comprising an elongated member, a wire inserted through the elongated member and fixed to a part of the elongated member, and the vibration actuator described above that drives the wire, wherein the elongated member bends when the wire is driven.

[0097] (Manufacturing method of oscillators) The method for manufacturing the oscillator of the present invention is, A process of obtaining a piezoelectric element by attaching electrodes to an unpolarized piezoelectric material, A step of joining the piezoelectric element and the elastic body at a temperature T1 using a conductive adhesive portion, A step of joining the piezoelectric element and the power supply member at a temperature T2, A step of applying a voltage between the electrode and the elastic body and performing polarization treatment at a temperature T3, The process is carried out in order, and T1, T2, and T3 satisfy the relationship T1 > T3 and T2 > T3.

[0098] By using a conductive adhesive joint to bond a piezoelectric material and an elastic body, the adhesive strength can be increased by continuously interposing the adhesive between the piezoelectric element and the elastic body, while simultaneously applying a voltage for polarization treatment to the piezoelectric material via the elastic body. This method allows for the high-yield manufacturing of vibratory actuators, even for piezoelectric materials whose depolarization temperature is lower than the bonding temperature.

[0099] When a piezoelectric element and an elastic body are fixed together with a non-conductive adhesive in direct contact, a voltage for polarization can be applied to the piezoelectric material via the elastic body. However, when the piezoelectric element and the elastic body are in close contact, the amount of adhesive held between them is significantly reduced, resulting in insufficient adhesive strength between the piezoelectric element and the elastic body. If the adhesive strength between the elastic body and the piezoelectric element is insufficient, the elastic body may detach from the piezoelectric element during operation of the vibrating actuator, leading to a malfunction.

[0100] On the other hand, if the goal is to increase the adhesive strength by continuously interposing an adhesive between the piezoelectric element and the elastic body, rather than allowing them to come into direct contact, then if the adhesive is non-conductive, it becomes impossible to apply the voltage necessary for polarization to the piezoelectric material via the elastic body. This is because most of the applied voltage is then transferred to the non-conductive adhesive.

[0101] Therefore, in order to perform polarization treatment by applying a voltage to the piezoelectric material through the elastic material while maintaining the adhesive strength between the elastic material and the piezoelectric material, it is necessary to join the elastic material and the piezoelectric material at a conductive adhesive joint.

[0102] In the method for manufacturing the oscillator of the present invention, it is preferable that the polarization treatment is performed by bringing an external electrode other than the power supply member into contact with the electrode and applying a voltage between the external electrode and the elastic body.

[0103] An example of an external electrode is a contact pin in a polarization device for polarizing the oscillator of the present invention. By applying a voltage to the electrode using the external electrode and grounding the elastic body, a voltage can be applied to the piezoelectric element without using the power supply member. This method eliminates the need to connect a power supply for polarization processing to the power supply member.

[0104] In the method for manufacturing the vibrator of the present invention, the elastic body is preferably a martensitic stainless steel of JIS standard SUS420J2 that has been pre-treated with vacuum quenching. Vacuum quenching can increase the strength of the elastic body without forming a high-resistance oxide film on the surface of the elastic body.

[0105] The driving method of the vibration-type actuator of the present invention is A vibrator in which electrodes, piezoelectric material, and elastic body are arranged in that order. A vibrating actuator having a contact body in contact with the elastic body, The elastic body and the piezoelectric material are joined together via a conductive adhesive portion. The piezoelectric material comprises a first electrode provided in a first region, A second electrode is provided in a second region adjacent to the first region, A third electrode that sandwiches the piezoelectric material together with the first and second electrodes, The device has a third region adjacent to the first and second regions, and a fourth electrode that is electrically connected to the third electrode. The invention is characterized by applying a voltage between the first electrode and the fourth electrode, and between the second electrode and the fourth electrode.

[0106] In other words, when polarization treatment is applied to a piezoelectric material, a voltage is applied between the first electrode and the elastic body, and between the second electrode and the elastic body. However, when driving a vibratory actuator, a voltage is applied between the first electrode and the fourth electrode, and between the second electrode and the fourth electrode. By separating the electrodes used for polarization treatment and driving, vibratory actuators can be manufactured with a high yield, and the driving voltage can be easily applied to the piezoelectric material. [Examples]

[0107] The vibration-type actuator and vibrator of the present invention will now be described with reference to examples, but the present invention is not limited to the following examples.

[0108] Next, the present invention will be described with reference to examples of the method for manufacturing a piezoelectric vibrator, a vibration wave driving device, and an optical instrument. However, the present invention is not limited to the following examples. The examples will be described based on the drawings, using the reference numerals in the drawings.

[0109] (Example 1) The metal oxide powder was calcined at 1340°C to obtain the piezoelectric material described in Manufacturing Composition 1 of Table 2.

[0110] The obtained piezoelectric material was ground and polished to a thickness of 0.5 mm and then processed into an annular shape with an outer diameter of 62 mm and an inner diameter of 54 mm. On one side of the shaped piezoelectric material 102, the driving phase electrode 101e and non-driving phase electrode 101f shown in Figure 1(c) were formed. The electrodes were formed by applying silver paste to the piezoelectric material 102 by screen printing, drying, and baking.

[0111] Next, a conductive adhesive portion 105 was applied to an elastic body 103 made of SUS420J2, and it was pressed against a piezoelectric material 102 on which electrodes were formed. The annular piezoelectric material and the annular elastic body were positioned using a positioning jig so that the centers of their respective circles coincided. Next, a heat treatment was performed to cure the conductive adhesive portion. The piezoelectric material to which the elastic body was pressed 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 oscillator. Details of the conductive adhesive portion used are shown in Table 1.

[0112] Next, the FPC coated with ACP was thermocompressed onto electrodes provided on the piezoelectric material. The thermocompression conditions were a temperature T2 = 140°C and a holding time of 20 seconds. After that, the elastic material SUS420J2 was grounded, and polarization treatment was performed by alternately applying voltages of different polarities to adjacent driving phase electrodes 101e. In the polarization treatment, multiple external electrodes connected to a power supply were brought into contact with the electrodes used as sensors among the driving phase electrodes 101e and driven phase electrodes 101f. After heating to T3 = 100°C, an electric field equivalent to 2kV / mm was applied for 30 minutes, and then the electric field was applied while cooling to 40°C over 40 minutes before the voltage application was terminated. After that, the first electrode 101a and the second electrode 101b were printed and dried to obtain an oscillator. In the drying process, the temperature of the piezoelectric material was kept below 80°C to prevent depolarization of the piezoelectric material. The obtained vibrator was subjected to pressurized contact with a contact body (rotor) made of SUS420J2 to fabricate a vibrating actuator.

[0113] (Example 2) A piezoelectric material described in Manufacturing Composition 1 was obtained in the same manner as in Example 1. The obtained piezoelectric material was ground and polished to a thickness of 0.35 mm and then processed into a rectangle of 8.9 × 5.7 mm. The first to third electrodes shown in Figure 3 were formed on both sides of the shaped piezoelectric material using the same method as in Example 1.

[0114] Next, a conductive adhesive was applied to an elastic body made of SUS420J2, and it was pressed against a rectangular piezoelectric material on which electrodes had been formed. The elastic body used had a rectangular section measuring 9.1 × 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. The rectangular piezoelectric material and the elastic body were positioned using a positioning jig so that the centers of their respective rectangular sections coincided and the sides of the rectangular sections were parallel. While pressed together, 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 oscillator. Details of the conductive adhesive used are shown in Table 1.

[0115] Next, using a soldering iron with a temperature T2 = 140°C, the FPC coated with ACP and the piezoelectric material were pressed together for 20 seconds, thus thermocompressing the FPC to the electrodes provided on the piezoelectric material.

[0116] Next, the piezoelectric material was subjected to polarization treatment. In the polarization treatment, the elastic body was grounded, and external electrodes connected to the power supply were brought into contact with the first and second electrodes, respectively. Although the first and second electrodes already had FPCs connected to them, the entire structure was not covered by the FPCs, and the external electrodes for polarization treatment made contact with the exposed portions. After heating to T3 = 100°C, an electric field equivalent to 2 kV / mm was applied for 30 minutes, and then the material was cooled to 40°C over 40 minutes while the electric field was still applied, after which the voltage application was terminated. The vibrator obtained through the above process was then brought into pressurized contact with a contact body (slider) made of SUS420J2 to fabricate a vibrating actuator.

[0117] (Example 3) A green sheet of piezoelectric material was prepared using the sheet molding method with the raw material powder of manufacturing composition 1. A through-hole with a diameter of 0.2 mm was made in the green sheet within the area where the fourth electrode would be printed after firing and processing. When fired in the same manner as in Example 1, the diameter of the through-hole became 0.18 mm. The obtained piezoelectric material was ground and polished to a thickness of 0.35 mm to a nearly uniform extent, and then processed into a rectangle of 8.7 × 5.7 mm. The first to fourth electrodes shown in Figure 4 were formed on both sides of the shaped piezoelectric material. Silver electrodes were provided on the inner walls of the through-holes, and the third and fourth electrodes were electrically connected through the through-holes. A vibrating actuator was fabricated in the same manner as in Example 2 for the subsequent steps.

[0118] (Examples 4 to 9) A vibrating actuator was fabricated using the same method as in Example 3, with conductive particles added in a concentration ranging from 0.9 to 5 weight percent (corresponding to a volume fraction of 0.4 to 2.0% of conductive particles in the adhesive).

[0119] (Examples 10 to 12) A vibrating actuator was fabricated using the method described in Example 3, with a conductive adhesive containing conductive particles having a diameter in the range of 2 to 5 microns. The amount of conductive particles added (weight percentage concentration) was varied so that the volume fraction of conductive particles in the conductive adhesive was 0.8%.

[0120] (Examples 13 to 14) A vibrating actuator was fabricated using the method described in Example 3, with conductive particles having a metallic material portion (shell) on the surface of the conductive particles that is either a laminated film of Au / Ni or conductive adhesive portion containing conductive particles with a metallic material portion (shell) of Ag.

[0121] (Examples 15 to 18) A vibrating actuator was fabricated using a conductive adhesive containing epoxy adhesive B or epoxy adhesive C, which has a different glass transition point than epoxy adhesive A used in Examples 1-14. The conductive particles were the same as those used in Example 2, and the process temperatures T1-T3 were varied as shown in Table 1. In all cases, T1 > T3, T2 > T3, and T3 was more than 20°C lower than the glass transition point of the adhesive used. In Example 16, epoxy adhesive D was used instead of ACP for bonding the power supply member.

[0122] (Evaluation and manufacturing methods for vibratory actuators, evaluation) Ten vibration actuators were prepared for each example and comparative example, and driving tests were conducted by applying an alternating voltage with an amplitude of 130 Vpp to the first and second electrodes. At that time, the phase difference between the voltages of the first and second electrodes was set to -90° and 90°.

[0123] When the frequency of the alternating voltage is swept from a frequency higher than the resonant frequencies of vibration modes A and B towards the resonant frequencies, the contact body is driven in a direction according to the phase difference of the alternating 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 the forward direction, respectively. The maximum speed of the oscillator and the frequency at which it reached its maximum speed were measured with a sensor. The power at a certain rated speed lower than the maximum speed (rated power) was calculated from the current flowing through the drive circuit.

[0124] The maximum speed and rated power are specified according to the product specifications, and for vibratory actuators whose initial characteristics meet the standards, durability was evaluated by continuously performing reciprocating motion. Table 1 also shows the yield rate of the 10 vibratory actuators of each type that were manufactured, provided that they met the following conditions. (1) Both forward and reverse movement must be driven at a maximum speed equal to or greater than the specified minimum speed (lower limit). (2) Both forward and reverse movement shall be driven with rated power below the specified limit (upper limit). (3) The conditions in (1) and (2) must be met even after the durability test.

[0125] The main causes of defects in each item are as follows: (1) The piezoelectric material has poor polarization treatment and insufficient piezoelectric performance. (2) The conductive adhesive layer has a large vibration absorption capacity, and the vibrations of the piezoelectric material cannot be efficiently transmitted to the contacts. (3) Delamination occurs between the elastic material and the piezoelectric material during durability testing.

[0126] When the vibratory actuators manufactured in Examples 1 to 18 were evaluated from the perspectives of (1) to (3) above, all 10 out of 10 were deemed good products. Next, the evaluation results of the comparative example vibratory actuators are shown.

[0127] [Table 1]

[0128] [Table 2]

[0129] [Table 3]

[0130] (Comparative Example 1) The amount of conductive particles in the conductive adhesive portion was significantly reduced to 0.5% by weight (0.2% by volume), and an oscillator was fabricated using the same method as in Example 3. Due to the small amount of conductive particles, the conductive particles were crushed during bonding between the elastic body and the piezoelectric material. The thickness of the conductive adhesive portion became significantly thinner, and the maximum speed did not meet the specifications after the durability test.

[0131] (Comparative Example 2) The amount of conductive particles in the conductive adhesive portion was significantly increased to 10% by weight (4.4% by volume), and an oscillator was fabricated in the same manner as in Example 3. In the vibration-type actuator using this oscillator, the adhesive strength between the elastic body and the piezoelectric element was insufficient, and the elastic body sometimes peeled off during durability testing.

[0132] (Comparative Example 3) A vibrator was fabricated using a conductive adhesive layer containing conductive particles with a diameter of 10 microns. The thickness of the outermost conductive particle layer was the same as in Example 3. In this case, the thickness of the metal coating of the conductive particles was the same as that of the conductive particles used in Example 3, so the proportion of the resin portion of the core increased, and the specific gravity became 2 g / cm³. 3 It is less than [amount missing].

[0133] (Comparative Example 4) A vibrator was fabricated using a conductive adhesive layer containing conductive particles with a diameter of 10 microns. The thickness of the outermost conductive particle layer was the same as in Example 3. Compared to Comparative Example 3, the thickness of the surface Ni coating layer was increased, resulting in a specific gravity of 4 g / cm³. 3 The difference lies in the fact that the vibrating actuators using the vibrators in Comparative Example 3 and Comparative Example 4 had poor driving efficiency and their driving performance did not meet the specifications.

[0134] (Comparative Example 5) A vibrator was fabricated using a conductive adhesive section containing Ni spheres (without a resin core) with a diameter of 2.5 microns as conductive particles. Except for the material of the conductive particles, the design was the same as in Example 3. The conductive particles precipitated within the conductive adhesive section, resulting in an uneven concentration of conductive particles. In the vibration-type actuator using this vibrator, the adhesive strength between the elastic body and the piezoelectric element was insufficient, and the elastic body sometimes peeled off during durability testing.

[0135] (Comparative Example 6) A vibrator was fabricated using an adhesive that did not contain conductive particles instead of a conductive adhesive portion. Except for the absence of conductive particles, it was the same as in Example 3. In the vibration-type actuator using this vibrator, the adhesive strength between the elastic body and the piezoelectric element was insufficient, and the elastic body sometimes peeled off during durability testing.

[0136] (Comparative Example 7) In contrast to Example 17, the bonding time was extended and the conductive adhesive portion was cured at a temperature below T3 (T3 > T1). Furthermore, the power supply member was also bonded at a low temperature using the epoxy adhesive C used for elastic body bonding to produce the vibration-type actuator of the present invention (T3 > T2). Although the conductive adhesive portion cured, it remained soft, resulting in poor driving efficiency and performance that did not meet the specifications for the vibration-type actuator using the vibrator of Comparative Example 7.

[0137] (Example 19) The vibrating actuator and optical element fabricated in Example 3 were mechanically connected to create the optical device shown in Figure 5. By controlling the alternating voltage applied to the piezoelectric material based on the position information provided to an encoder consisting of a sensor and a scale, the vibrating actuator and the optical element connected to it could be precisely driven to the target position. In this optical device, an optical lens was connected to the vibrating actuator, and it was confirmed that it has an autofocus function.

[0138] The above description uses manufacturing composition 1 as an example, but it has been confirmed that the vibration actuator of the present invention can be manufactured with the same high yield as in Example 3 even with manufacturing compositions 2 to 101. The vibration actuator of the present invention, which comprises a vibrator in which electrodes, piezoelectric material, and elastic body are arranged in that order, and a contact body that contacts the elastic body, and in which the elastic body and the piezoelectric material are joined via a conductive adhesive portion, can be manufactured with good yield. [Industrial applicability]

[0139] The vibration actuator of the present invention can be used in a variety of applications, such as driving lenses and image sensors in imaging devices (optical instruments), rotating the photosensitive drum of a copier, and driving stages. Although this specification describes a single vibration actuator, multiple vibration actuators can be arranged in a ring shape to rotate a ring-shaped contact body. [Explanation of symbols]

[0140] 100 Vibration-type actuators 101 Electrode 101a 1st electrode 101b 2nd electrode 101c 3rd electrode 101d 4th electrode 101e drive phase electrode 101f Non-driving phase electrode 102 Piezoelectric materials 103 Elastic body 104 Contact body 105 Conductive adhesive part 106 Protrusion 107 Support part 108 Rectangular part 110 transducer 501 Retaining member 502 Mobile enclosure 503 Bis 504 Guide member 505 Lens holding member 506 Lens 507 Power supply component 508 Sensor 509 scale 510 Connecting member

Claims

1. A vibrator comprising an electrode, a rectangular piezoelectric material, and an elastic body arranged in that order, The elastic body is in contact with the contact body and is configured to be movable relative to the vibrator due to vibrations generated in the vibrator, The elastic body and the piezoelectric material are joined together via a conductive adhesive portion. The electrodes are a first electrode and a second electrode that are adjacent to each other. The oscillator is configured such that when the regions in the common piezoelectric material where the first electrode and the second electrode are provided are designated as the first region and the second region, A first bending vibration mode in which both the first region and the second region stretch or contract, When the first region stretches and contracts, the second region contracts and stretches, respectively, forming a second bending vibration mode. The average thickness of the conductive adhesive portion is 1.5 microns or more and 7 microns or less. A vibratory actuator having an elastic body with a thickness of 0.2 mm to 1.0 mm.

2. The vibration-type actuator according to claim 1, wherein the elastic body has a rectangular portion, and the vibrator is held by a vibrator holding member at the four corners of the rectangular portion.

3. The vibration actuator according to claim 2, wherein the elastic body has a support portion protruding from the end of the rectangular portion.

4. The device has a third electrode that sandwiches the piezoelectric material together with the first and second electrodes. A vibrating actuator according to any one of claims 1 to 3.

5. The first electrode and the second electrode are adjacent to each other, The vibration actuator according to claim 4, further comprising a fourth electrode that is electrically connected to the third electrode.

6. The vibrating actuator according to any one of claims 1 to 5, wherein the conductive adhesive portion contains conductive particles having an average particle size of 2 microns or more and 5 microns or less in a volume fraction of 0.4% or more and 2% or less.

7. The specific gravity of the conductive particles is 2.0 g / cm³. ３ 4.0g / cm or more ３ The following is The vibration-type actuator according to claim 6.

8. The vibrating actuator according to any one of claims 1 to 7, wherein the conductive adhesive portion is made of an anisotropic conductive material.

9. The vibrating actuator according to any one of claims 1 to 8, wherein the lead content in the piezoelectric material is less than 1,000 ppm.

10. The vibrating actuator according to any one of claims 9, wherein the piezoelectric material includes a barium titanate-based material.

11. The vibrating actuator according to claim 10, wherein the piezoelectric material comprises barium calcium zirconate titanate.

12. A vibrating actuator according to any one of claims 1 to 11, comprising a power supply member joined to a piezoelectric element comprising the piezoelectric material and the electrode.

13. The vibration actuator according to any one of claims 1 to 12, wherein the elastic body is made of martensitic stainless steel.

14. A vibration-type actuator according to any one of claims 1 to 13, wherein a plurality of vibrators are in contact with a common contact body, and the contact body moves relative to each other due to the vibration of the plurality of vibrators.

15. Components and An electronic device comprising a vibrating actuator according to any one of claims 1 to 14, provided on the aforementioned member.

16. The drive unit is equipped with a vibratory actuator according to any one of claims 1 to 15. An optical instrument further comprising at least one of an optical element and an image sensor.

17. A long, slender member, A wire is inserted through the elongated member and fixed to a part of the elongated member, A wire-driven actuator having a vibratory actuator according to any one of claims 1 to 16 for driving the wire, wherein the elongated member is bent by the driving of the wire.

18. A process of obtaining a piezoelectric element by attaching electrodes to an unpolarized piezoelectric material, A step of joining the piezoelectric element and the elastic body via a conductive adhesive portion at a temperature T1, A step of joining the piezoelectric element and the power supply member at a temperature T2, A step of applying a voltage between the electrode and the elastic body and performing polarization treatment at a temperature T3, A step to obtain the vibration-type actuator according to claim 1, by performing the steps in order, wherein the vibrator obtained by satisfying the relationship T1 > T3 and T2 > T3, and the contact body provided to be in contact with the elastic body and to be movable relative to the vibrator, A method for manufacturing a vibrating actuator equipped with [the specified feature].

19. The method for manufacturing a vibrating actuator according to claim 18, wherein the polarization treatment involves bringing an external electrode other than the power supply member into contact with the electrode and applying a voltage between the external electrode and the elastic body.

20. The method for manufacturing a vibrating actuator according to claim 18 or 19, wherein the elastic body is made of martensitic stainless steel.

21. A method for driving a vibratory actuator, A vibrator in which electrodes, piezoelectric material, and elastic body are arranged in that order. A vibratory actuator according to claim 1, having a contact body in contact with the elastic body, The elastic body and the piezoelectric material are joined together via a conductive adhesive portion. The piezoelectric material comprises a first electrode provided in a first region, A second electrode is provided in a second region adjacent to the first region, A third electrode that sandwiches the piezoelectric material together with the first electrode and the second electrode, The device has a third region adjacent to the first and second regions, and a fourth electrode that is electrically connected to the third electrode. A method for driving a vibratory actuator, characterized by applying a voltage between the first electrode and the fourth electrode, and between the second electrode and the fourth electrode.

Images