Vibration actuator, electronic device and optical device

Abstract

To provide a vibration actuator whose driving performance is unlikely to deteriorate even when an unexpectedly large input voltage is applied to a piezoelectric element.SOLUTION: A vibration actuator according to the present invention includes a piezoelectric material, an electrode disposed on a first surface of the piezoelectric material, a vibrator having an elastic body disposed on a side of the second surface of the piezoelectric material opposite the first surface, and a contact body that is in contact with the elastic body and is provided so as to be relatively movable with respect to the vibrator, and the vibrator vibrates by setting the contact body to a ground potential and applying a voltage between the contact body and the electrode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vibration actuator including a vibration actuator such as an ultrasonic motor. [Background technology]

[0002] Patent Document 1 discloses a vibration type actuator that is driven by utilizing elliptical vibrations formed by a vibrator made of an elastic body and a piezoelectric material bonded together.

[0003] The piezoelectric material is sandwiched between a pair of electrodes, one of which is at GND (ground) potential and the other is supplied with a drive voltage. Patent Document 1 discloses a vibration actuator that suppresses grounding failure by configuring the vibration plate, one of the piezoelectric element and vibration plate that make up the vibrator, to be grounded to GND potential.

[0004] However, in the vibration actuator described in Patent Document 1, if an unexpectedly large input voltage is applied to the piezoelectric element, unexpectedly large vibrations may occur, which could result in a decrease in the driving performance of the vibration actuator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2012-191765 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above, a vibration actuator is provided in which the driving performance is unlikely to deteriorate even when an unexpectedly large input voltage is applied to the piezoelectric element. [Means for solving the problem]

[0007] A vibration type actuator for solving the above problems includes: a vibrator having a piezoelectric material, an electrode disposed on a first surface of the piezoelectric material, and an elastic body disposed on a second surface of the piezoelectric material opposite to the first surface; a contact body that is in contact with the elastic body and is provided so as to be movable relative to the vibrator; The elastic body is configured to be able to separate from the contact body, The contact body is set to a ground potential, and a voltage is applied between the contact body and the electrode, causing the vibrator to vibrate. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vibration actuator whose driving performance is less likely to deteriorate. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating a schematic structure of a vibration actuator in which the piezoelectric material is annular, according to the present invention; (a) a side view, (b) a perspective view, and (c) a rear view. [Figure 2] 1A and 1B are diagrams illustrating the schematic structure of a vibration actuator in which the piezoelectric material is rectangular in the present invention; (a) a side view, (b) a perspective view, and (c) a rear view. [Figure 3] 1A and 1B are diagrams illustrating a schematic structure of a vibration actuator in which an elastic body and a piezoelectric material are bonded via a conductive adhesive in the present invention. [Figure 4] 10 is a diagram illustrating a schematic structure in which a piezoelectric material is sandwiched between the electrode and a third electrode in the present invention. FIG. [Figure 5] 1A and 1B are diagrams illustrating two vibration modes generated by a vibrator having a rectangular piezoelectric material according to the present invention. [Figure 6] 10A and 10B are diagrams illustrating a piezoelectric material provided with a non-driving phase electrode together with a conventional electrode and a third electrode. [Figure 7] 1A and 1B are diagrams illustrating a schematic structure of an optical device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of a vibration actuator, an optical device, and an electronic device for carrying out the present invention will be described. The vibration actuator has the following configuration. The vibrator includes a piezoelectric material, an electrode disposed on a first surface of the piezoelectric material, and an elastic body disposed on a second surface of the piezoelectric material opposite to the first surface. A contact body is provided in contact with the elastic body and is movable relative to the vibrator. The contact body is at ground potential, and a voltage is applied between the contact body and the electrode, causing the vibrator to vibrate.

[0011] The schematic structures of the vibration actuator of the present invention are shown in Figures 1 and 2. The vibration actuators shown in Figures 1 and 2 use a circular piezoelectric material and a rectangular piezoelectric material, respectively.

[0012] The vibration actuator 100 of the present invention comprises a vibrator 102 having an electrode 101, a piezoelectric material 102, and an elastic body 103 arranged in that order, and a contact body 104 in contact with the elastic body 103, and is driven by applying a voltage between the contact body 104 and the electrode 101.

[0013] The elements that make up the vibration actuator are explained below: The vibrator is made up of a piezoelectric material, electrodes, and an elastic body.

[0014] (electrode) The piezoelectric material is provided with divided electrodes 101 to induce elliptical vibrations in protrusions 105 formed on elastic body 103. When a circular piezoelectric material is used, the electrodes 101 are divided in the circumferential direction. When a rectangular piezoelectric material is used, a predetermined voltage is applied to each of the electrodes 101 to excite vibrations in Mode A and Mode B, which will be described later. Multiple electrodes 101 are formed depending on the shape of the piezoelectric material and the required performance. The piezoelectric material in contact with the electrodes 101 has been subjected to polarization treatment.

[0015] The electrodes are made of metal films with a thickness of approximately 0.3 to 10 μm. The material is not particularly limited, and examples include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, as well as compounds thereof. The multiple electrodes may each be made of a different material. To remove lead from a piezoelectric element, lead is removed not only from the piezoelectric ceramic but also from the electrodes. In other words, an electrode material with a lead content of less than 1000 ppm is used. The method for manufacturing the multiple electrodes is not limited, and they may be formed by screen printing of a metal paste, or by a vacuum film-forming process such as sputtering or vapor deposition.

[0016] (Piezoelectric materials) The piezoelectric material 102 can be made of piezoelectric ceramics (sintered body) with substantially no crystal orientation, crystal-oriented ceramics, piezoelectric single crystals, etc. In particular, piezoelectric materials that have been subjected to polarization treatment resonate at their natural vibration frequency and vibrate greatly. Piezoelectric materials that have been subjected to polarization treatment are suitable for use in vibration-type actuators. The piezoelectric material may be a laminate of layered electrodes and layered piezoelectric material, or a single plate of piezoelectric material. A single plate is superior in terms of the cost of the piezoelectric material.

[0017] (elastic body) The elastic body 103 in the vibration actuator of the present invention is preferably made of metal from the viewpoints of elastic properties, workability, and electrical conductivity. Examples of metals that can be used for the elastic body 103 include stainless steel and invar. Here, stainless steel refers to an alloy containing 50% by mass or more of steel and 10.5% by mass or more of chromium. Among stainless steels, martensitic stainless steel is preferable, and SUS420J2 is most preferable. The elastic body has a protrusion 105 that comes into contact with the contact body, and the protrusion 105 and the contact body 104 are configured to be in pressurized contact with each other by magnetic force from a pressure spring or magnet (not shown). The pressure is, for example, approximately 100 gf to 1500 gf. To improve the wear resistance of the protrusion, quenching, plating, or nitriding may be performed.

[0018] (contact body) The contact member is in contact with the elastic member that constitutes the vibrator, and is provided so as to be movable relative to the vibrator.

[0019] From the viewpoint of rigidity and workability, the contact body 104 is preferably made of stainless steel (especially SUS420J2) or aluminum. Since the contact body 104 is in frictional contact with the elastic body 103, it is preferable to use a material with excellent wear resistance. When stainless steel is used as the contact body, it is preferable to form nitride by nitriding treatment. When aluminum is used, it is preferable to form aluminum oxide by anodizing treatment. At least one of the surface of the contact body and the surface of the elastic body may be coated with nitride.

[0020] A frictional force due to pressure contact acts between the protrusion 105 and the contact body 104. The vibration generated by the piezoelectric material 102 causes the tip of the protrusion 105 to move elliptically, generating a driving force for relative movement with the contact body 104. The contact body is also called a slider or rotor, but in this application it will be referred to as a contact body.

[0021] It is more preferable that the elastic body and the contact body are coated with a highly wear-resistant conductor by surface treatment.

[0022] (Power supply components) The vibration actuator of the present invention may further include a power supply member that supplies power to the electrode 101. From the viewpoints of high dimensional accuracy and ease of positioning, it is preferable to use a flexible printed circuit (hereinafter referred to as FPC) as the power supply member. Polyimide is a preferable material for the power supply member. There are no particular restrictions on the method for joining the FPC and the piezoelectric element, but considering the takt time for bonding and the reliability of the electrical connection, it is preferable to use an anisotropic conductive paste (ACP) or anisotropic conductive film (ACF). Supplying power through the FPC allows power to be supplied without impeding the vibration of the piezoelectric element.

[0023] In the vibration actuator of the present invention, it is preferable that the elastic body and the piezoelectric material are bonded via a conductive adhesive. Figure 3 shows a conductive adhesive 301 formed by a conductive adhesive provided between the piezoelectric material 102 and the elastic body 103.

[0024] (Conductive adhesive) The elastic body 103 and the piezoelectric material 102 are bonded via a conductive adhesive 301. That is, a vibrator is formed that has the piezoelectric material, an electrode disposed on a first surface of the piezoelectric material, and an elastic body disposed on a second surface of the piezoelectric material opposite to the first surface.

[0025] The conductive adhesive of the present invention is an adhesive in which conductive particles are dispersed. The conductive particles contained in the adhesive are sandwiched between the adherends, thereby electrically connecting the adherends to each other.

[0026] The conductive particles are resin balls (acrylic, styrene, etc.) coated with a conductive metal such as Au, Ni, or Ag. 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. However, depending on the process used to coat the resin ball core with metal material, protrusions may appear on the outermost metal coating layer. The shape and dimensions of the conductive particles are optimized to maintain a consistent adhesive thickness. It is extremely difficult to obtain conductive particles with a diameter below 2 μm, and the diameter of commonly available conductive particles is around 2 to 30 μm. The diameter distribution of conductive particles is expressed as a CV value.

[0027] When an elastic body and a piezoelectric material are pressure-bonded using an adhesive that does not contain conductive particles, it is extremely difficult to control the distance between the elastic body and the piezoelectric material. If a very small amount of adhesive remains between the elastic body and the piezoelectric material, the adhesive strength decreases. If the adhesive strength is low, the elastic body and the piezoelectric material may peel off while the vibration actuator is operating, causing malfunction.

[0028] On the other hand, if too much adhesive remains between the elastic body and the piezoelectric material, it may not be possible to apply the drive voltage required to drive the vibration actuator to the piezoelectric material via the elastic body.Conductive particles come into contact with the elastic body and the piezoelectric material, or between the elastic body and the third electrode (described below), thereby electrically connecting the elastic body and the piezoelectric material and establishing conductivity.

[0029] The type of adhesive is not particularly limited, but epoxy resin is typically used because of its excellent strength, curing time, and environmental resistance (temperature changes, high humidity, etc.). Epoxy resins generally cure between 80°C and 140°C. When performing polarization treatment after bonding the elastic body and the power supply member to the piezoelectric material, it is preferable that the glass transition temperature (Tg) of the adhesive be 20°C or higher than the polarization treatment temperature so that the already-bonded components do not move at the polarization treatment temperature. Considering that polarization treatment is generally performed at 80°C or higher, it is preferable that the Tg of the adhesive be 100°C or higher.

[0030] (Thickness of conductive adhesive part) When the conductive adhesive portion of the vibration actuator of the present invention is configured in a layered form, there is no limitation on the average thickness, but it is particularly preferably 1.5 μm or more and 7 μm or less.

[0031] When the thickness of the conductive adhesive portion is 7 μm or less, the conductive adhesive portion does not absorb much of the vibrations generated by the piezoelectric material, and the vibration-type actuator tends to exhibit good performance.

[0032] When the thickness of the conductive adhesive portion is 1.5 μm or more, the amount of adhesive between the piezoelectric material and the elastic body is sufficient, and peeling of the elastic body is suppressed during operation of the vibration actuator. Therefore, it is preferable that the average thickness of the conductive adhesive portion is 1.5 μm or more and 7 μm or less.

[0033] The thickness of the layered conductive adhesive refers to the average thickness of the conductive adhesive, determined using the method described below. The average thickness of the conductive adhesive can be determined by observing a cross section of the vibrator, including the electrodes, the piezoelectric element having the piezoelectric material, the conductive adhesive, and the elastic body. An electron microscope can be used to observe the cross section. For example, the conductive adhesive is observed by stacking the piezoelectric material, conductive adhesive, and elastic body in a vertically upward direction. An observation magnification of around 500x is appropriate. The cross-sectional area of ​​the conductive adhesive is calculated from the observed image. The average thickness of the conductive adhesive can be calculated by dividing the obtained cross-sectional area by the width of the observation area = the horizontal length of the conductive adhesive.

[0034] (Conductive particle size) The conductive adhesive portion preferably contains conductive particles having an average particle size of 1 μm or more and 5 μm or less at a volume fraction of 0.4% or more and 2% or less.

[0035] The distance between the piezoelectric element and the elastic body can be controlled by making the size of the conductive particles contained in the uncured conductive adhesive uniform. The particle size distribution can be expressed as the CV value (Coefficient of Variation, CV (%) = standard deviation of particle size ÷ average particle size × 100). A uniform particle size refers to a CV value of less than 10%, and a CV value of 6% or less is preferable because it increases the uniformity of the thickness of the conductive adhesive after curing.

[0036] If the average particle size of the conductive particles is 5 μm or less, the driving efficiency of the vibration type actuator is good, which is preferable.

[0037] The average particle diameter of the conductive particles is determined by observing the conductive adhesive portion between the elastic body and the piezoelectric material and averaging the diameters of at least three particles.

[0038] If the volume fraction of conductive particles in the conductive adhesive is 0.4% or more, pressure is prevented from concentrating on the conductive particles when bonding the elastic body and piezoelectric material, making the conductive particles less likely to be crushed. If the conductive particles are crushed, it becomes difficult to adjust the thickness of the conductive adhesive with good yield, and there is a risk of insufficient adhesive strength.

[0039] If the volume fraction of the conductive particles in the conductive adhesive portion is 2% or less, the adhesive area is sufficient and the adhesive strength between the piezoelectric material and the elastic body is maintained, which is preferable.

[0040] Therefore, it is preferable for the conductive adhesive to contain conductive particles with an average particle size of 1 μm to 5 μm at a volume fraction of 0.4% to 2%, as this will ensure both adhesive strength and electrical continuity between the elastic body and the piezoelectric material. When electrical continuity is achieved, the electrical resistance between the fourth electrode and the elastic body will be less than 10 Ω. The volume fraction can be calculated using the area ratio of the adhesive layer to the particles, based on the results of the cross-sectional observation of the adhesive layer.

[0041] (Conductive particle density) The specific gravity of the conductive particles is 2.0 g / cm 3 More than 4.0g / cm 3 The specific gravity of the conductive particles varies depending on the volume fraction of the metal layer, which has a large specific gravity, and the resin balls, which have a small specific gravity.

[0042] The specific gravity of the conductive particles is 2.0 g / cm 3 If the ratio of metal contained in the conductive particles is high, good conductivity can be obtained between the elastic body and the electrode, and the conductive particles are less likely to be crushed when the piezoelectric material and the elastic body are bonded together.

[0043] The specific gravity of the conductive particles is 4.0 g / cm 3 If the specific gravity is less than this, the difference in specific gravity with the adhesive becomes large, preventing the conductive particles from settling in the adhesive. If the conductive particles settle, it becomes difficult to maintain a constant amount of conductive particles in the conductive adhesive each time the adhesive is applied to the joining location, which is undesirable.

[0044] Therefore, the specific gravity of the conductive particles is 2.0 g / cm3 More than 4.0g / cm 3 If 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.

[0045] (anisotropy) The conductive adhesive preferably uses an anisotropic conductive material.

[0046] For example, even if the conductive adhesive overflows from the joining point and adheres to the side of the piezoelectric material during joining, if the conductive adhesive is an anisotropic conductive material, an electrical short circuit between the electrode and the elastic body can be prevented.

[0047] In the case of an anisotropic conductive material, for example, if a tester is placed at a distance of 2 mm or more on the surface of the conductive adhesive that has protruded from the non-adhesive area and the surface resistance is measured, the resistance will be greater than 10 Ω.

[0048] The following describes the structural features of the vibration actuator of the present invention, such as the shape of each element. The piezoelectric material is rectangular, and although there is no limit to the number of electrodes, it is preferable to use first and second electrodes that are adjacent to each other.

[0049] FIG. 2(c) is a diagram illustrating the schematic structure of a vibrator 110 of the present invention, and the vibrator 110 has a first electrode 101a, a second electrode 101b, and a rectangular piezoelectric material .

[0050] By independently applying alternating voltages Va and Vb of different phases to the first electrode 101a and the second electrode 101b, two types of vibrations can be excited in the protrusion 105 of the contact body 104. By simultaneously exciting the two types of vibrations, an elliptical vibration can be generated in the protrusion 105. This elliptical vibration can relatively drive the contact body 104, which is in pressure contact with the protrusion 105. A vibration-type actuator using a rectangular piezoelectric material is preferable to a vibration-type actuator using a circular piezoelectric material because the piezoelectric material is easier to process, making it less expensive and easier to miniaturize.

[0051] The vibration actuator of the present invention preferably has a third electrode that sandwiches the piezoelectric material together with the electrode.

[0052] 4 illustrates a schematic structure in which a rectangular or annular piezoelectric material is sandwiched between the electrode 101 and the third electrode 401. The electrode 101 and the third electrode 401 sandwich the piezoelectric material 102.

[0053] 2(b), when protrusions 105 are formed on the elastic body 103, non-contact areas are generated where the elastic body and the piezoelectric material are not in contact. By providing a third electrode, it becomes possible to supply power from the elastic body to the piezoelectric material even when non-contact areas exist.

[0054] In the vibration actuator of the present invention, it is more preferable to use both the first bending vibration mode and the second bending vibration mode in combination. Specifically, the piezoelectric material is rectangular, and the vibrator defines the first and second regions as regions where the first and second electrodes are provided on the piezoelectric material, respectively.

[0055] The first bending vibration mode is a bending vibration mode in which both the first region and the second region expand or contract, and the second bending vibration mode is a bending vibration mode in which the second region contracts or expands when the first region expands or contracts, respectively.

[0056] 5 illustrates two vibration modes generated by a vibrator of the present invention having a rectangular piezoelectric material. The regions of the rectangular piezoelectric material 102 where the first electrode 101a and the second electrode 101b are provided are referred to as a first region and a second region.

[0057] When both the first and second regions expand or contract, a first bending vibration mode (Mode A) occurs. Mode A is generated by applying an AC voltage V A , V Bis excited most strongly when the phase difference between them is 0° and the frequency is near the resonance 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 sides of vibrator 110.

[0058] On the other hand, if the second region contracts and expands when the first region expands and contracts, respectively, a second bending vibration mode (mode B) occurs.

[0059] Mode B is an alternating voltage V applied to the first and second electrodes. A , V B is excited most strongly when the phase difference between them is 180° and the frequency is near the resonance 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 sides of vibrator 110.

[0060] The protrusion 105 provided on the elastic body 103 is located near the antinode (where the amplitude is maximum) of mode A. Therefore, the tip surface of the protrusion 105 reciprocates in the Z direction due to the thrust vibration.

[0061] The protrusion 105 of the elastic body 103 is disposed in the vicinity of a position that becomes a node of Mode B. Therefore, the tip surface of the protrusion 105 reciprocates in the X direction by Mode B.

[0062] In the vibration actuator 100, the alternating voltage V A , V B When the phase difference is 0 to ±180°, Mode A and Mode B are excited simultaneously, and elliptical vibration is excited in protrusion 105 of elastic body 103. A vibration type actuator that uses a rectangular piezoelectric material and is driven by Mode A and Mode B is preferred because it can be easily miniaturized.

[0063] (Another example of the vibration actuator configuration) A configuration may be adopted in which multiple vibrators are in contact with one common contact body, and the vibration of the multiple vibrators causes relative movement between the contact body and the multiple vibrators. By adopting such a configuration, vibrations of the multiple vibrators are transmitted to one contact body, making it possible to provide a vibration-type actuator with stronger driving force.

[0064] (Advantages of obtaining ground potential from the contact) In this configuration, if the amplitude of the vibration generated by the vibrator becomes significantly large, for example, due to an unexpectedly large voltage being applied to the vibrator, the elastic body separates from the contact body. As a result, the power supply to the vibrator is cut off, and the amplitude of the vibrator naturally decreases. Once the amplitude decreases, the elastic body and the contact body come into contact again, and the power supply is restored. Therefore, even if an unexpectedly large input voltage is applied to the piezoelectric element, it is possible to provide a vibration-type actuator that is less likely to generate excessive vibration, i.e., whose driving performance is less likely to decrease.

[0065] (Ground potential electrode) In the vibration actuator of the present invention, it is preferable that no electrode at ground potential is provided on the first surface of the piezoelectric material. As described in the cited document, in order to drive the vibration actuator, the third electrode is grounded and a ground electrode that is electrically connected to the third electrode is provided on the same surface as the electrode 101. This is because a drive voltage can be applied to the piezoelectric material by crimping an FPC with a simple two-dimensional structure onto the surface where the electrode 101 is provided.

[0066] On the other hand, if a ground electrode is provided on the surface on which the electrode 101 is provided, the area of ​​the electrode 101 will be reduced by the area occupied by the ground electrode. The piezoelectric material below the ground electrode is a piezoelectric inactive portion to which no driving voltage is applied. Providing a piezoelectric inactive portion reduces the volume of the piezoelectric active portion below the electrode 101 that contributes to the performance of the vibration actuator, thereby reducing the performance of the vibration actuator. Therefore, in order to avoid reducing the performance of the vibration actuator, it is preferable that a ground electrode not be provided on the surface on which the electrode 101 is provided.

[0067] (driving electrode) In the vibration actuator of the present invention, the electrode 101 preferably consists of only the first and second electrodes adjacent to each other, which is preferable because the electrodes can be further expanded to maximize the area of ​​the piezoelectric active portion.

[0068] (Rectangular elastic body) In the vibration actuator of the present invention, it is preferable that the elastic body 103 has a rectangular portion 106 as shown in Figure 2(c). A rectangular piezoelectric material 102 is bonded to the rectangular portion 106. Taking into consideration misalignment of the bond, the rectangular portion 106 is slightly larger than the rectangular piezoelectric material 102. It is preferable that the elastic body has a rectangular portion, because this allows the vibrations generated by the rectangular piezoelectric material to be efficiently transmitted to the contact body.

[0069] (Rectangular elastic support part) In the vibration actuator of the present invention, the elastic body 103 preferably has a support portion 107 that protrudes from the end of the rectangular portion 106. By providing the support portion with, for example, a fitting portion, it is possible to hold the vibrator 110. By providing the fitting portion at a position in the support portion close to the node of vibration, it is possible to hold the vibrator without interfering with its vibration.

[0070] (Piezoelectric material composition 1) In the vibration type actuator of the present invention, it is preferable that the main component of the piezoelectric material is lead zirconate titanate (Pb(Zr,Ti)O3) system. Although it is difficult to grow a single crystal of lead zirconate titanate, ceramics are widely available. The piezoelectric constant d of the ceramic is 31 There are compositions with a depolarization temperature T d It is possible to adjust the temperature to 250°C or higher. When joining an elastic body or a power supply member to the polarized lead zirconate titanate, it is preferable to keep the joining temperature at 200°C or lower, as this will prevent the lead zirconate titanate from becoming depolarized. Additives may be included to adjust the properties of the lead zirconate titanate.

[0071] (Piezoelectric material composition 2) In the vibration type actuator of the present invention, it is preferable that the main component of the piezoelectric material is a barium titanate-based material.

[0072] The piezoelectric material is preferably a barium titanate-based material because of its high piezoelectric constant and relative ease of manufacture. Examples of 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). Other examples include compositions such as sodium niobate-barium titanate (NaNbO3-BaTiO3), sodium bismuth titanate-barium titanate ((Bi,Na)TiO3-BaTiO3), and potassium bismuth titanate-barium titanate ((Bi,K)TiO3-BaTiO3), as well as materials based on these compositions. Among these, the following materials may be selected from the viewpoint of achieving both a high piezoelectric constant and a high mechanical quality factor for piezoelectric ceramics: That is, it is preferable that the main components are barium calcium zirconate titanate ((Ba,Ca)(Ti,Zr)O3) and sodium niobate-barium titanate (NaNbO3-BaTiO3). Elements other than the main components preferably include manganese and bismuth. The term "main component" refers to a material whose weight fraction is greater than 10%. Furthermore, it is even more preferable that the lead content of the piezoelectric material is 1000 ppm or less, as this reduces the environmental impact.

[0073] (Lead content in piezoelectric materials) Generally, lead zirconate titanate, which contains lead, is widely used in piezoelectric devices. Although lead zirconate titanate has excellent piezoelectric properties, it contains lead. Therefore, it has been pointed out that, for example, when piezoelectric elements are discarded and exposed to acid rain or left in harsh environments, the lead components in conventional piezoelectric ceramics may leach into the soil and cause harm to the ecosystem. However, it is desirable for the lead content in piezoelectric materials to be less than 1000 ppm, as this greatly reduces the impact on the environment. The lead content in piezoelectric materials can be measured, for example, using ICP atomic emission spectroscopy.

[0074] (Piezoelectric material composition 3) In the vibration actuator of the present invention, it is preferable that the main component of the piezoelectric material is barium calcium zirconate titanate (hereinafter referred to as BCTZ).

[0075] Specifically, it is a piezoelectric material containing Mn and an oxide with a perovskite structure containing Ba, Ca, Ti, and Zr. 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. In addition to this composition, the content of Mn per 100 parts by weight of the oxide is 0.02 parts by weight or more and 0.40 parts by weight or less, calculated as metal. Furthermore, the relative density of the piezoelectric material is 91.8% or more and 100% or less, and the piezoelectric constant d 33 It is advisable to use a piezoelectric material with a resistance of 110 pC / N or more.

[0076] When BCTZ is the main component, the piezoelectric properties of BCTZ can be adjusted depending on the application by adjusting the amount of Ca and Zr. In addition, it is acceptable to include a secondary component such as Bi to adjust the piezoelectric properties.

[0077] It is preferable that 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 relative to 100 parts by weight of the oxide is 0.02 parts by weight or more and 1.0 parts by weight or less in terms of metal.

[0078] Such a piezoelectric material can be expressed by the following general formula (1): (Ba1-xCax)α(Ti1-yZry)O3 (1)

[0079] however, 0.986≦α≦1.100, 0.02≦x≦0.30, 0.02≦y≦0.095 The content of metal components other than the main component contained in the piezoelectric material is preferably 1 part by weight or less in terms of metal relative to 100 parts by weight of the metal oxide.

[0080] In particular, when Mn is contained within the above-mentioned range, the insulating properties and the mechanical quality factor Qm are improved.

[0081] The metal oxide represented by general formula (1) 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 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.

[0082] 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.

[0083] Whether a metal oxide has a perovskite structure can be determined, for example, by structural analysis using X-ray diffraction or electron beam diffraction.

[0084] The value of x is in the range of 0.02≦x≦0.30. Replacing 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, thereby 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 may be insufficient, potentially resulting in insufficient performance of the vibration actuator. On the other hand, if x is less than 0.02, the dielectric loss (tan δ) may increase. Increased dielectric loss may increase heat generation when applying voltage to the piezoelectric material to drive the vibration actuator, reducing motor drive efficiency and increasing power consumption.

[0085] The value of y is in the range of 0.02≦y≦0.1 If y is greater than 0.1, 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.

[0086] In this specification, Td refers to the lowest temperature at which the piezoelectric constant after heating a piezoelectric material from room temperature to Td and then cooling it back to room temperature after a sufficient amount of time has passed since polarization treatment is performed, is reduced by more than 10% compared to the piezoelectric constant before heating.

[0087] Furthermore, the value of α is preferably in the range of 0.9955≦α≦1.010. When α is 0.9955 or more, abnormal grain growth is less likely to occur in the crystal grains that make up the piezoelectric material, and the mechanical strength of the piezoelectric material is sufficiently maintained. On the other hand, when α is 1.010 or less, the piezoelectric material is densified and its insulating properties are maintained well.

[0088] 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 weight of Mn to the total weight of 100.

[0089] When the Mn content is 0.02 parts by weight or more, the polarization effect required for driving the vibration actuator is sufficient, while when the Mn content is 0.40 parts by weight or less, the piezoelectric properties of the piezoelectric material are sufficient and there is little risk of hexagonal crystals that do not have piezoelectric properties appearing.

[0090] 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 solid-solved in the B site or contained in the grain boundaries. Alternatively, the Mn component may be contained in the piezoelectric ceramic 1 in the form of metal, ions, oxide, metal salt, complex, or the like. From the viewpoints of insulation properties and ease of sintering, a more preferable form of inclusion is solid-solubilization in the B site.

[0091] The piezoelectric material may contain 0.042 parts by weight or more and 0.850 parts by weight or less of Bi in terms of metal.

[0092] The piezoelectric material may contain 0.85 parts by weight or less of Bi, calculated as metal, per 100 parts by weight of the metal oxide represented by general formula (1). The Bi content relative to the metal oxide can be measured, for example, by ICP atomic emission spectroscopy. Bi may be present at the grain boundaries of the ceramic piezoelectric material or may be solid-solved in the perovskite structure of (Ba,Ca)(Ti,Zr)O3. The presence of Bi at the grain boundaries reduces interparticle friction and increases the mechanical quality factor. 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. It is preferable for Bi to be located in the A site when incorporated into the solid solution, as this improves the charge balance with the Mn.

[0093] The piezoelectric material may contain components (hereinafter referred to as "subcomponents") other than the elements contained in the general formula (1) and Mn and Bi, as long as the properties are not affected. There are no limitations on the amount of the subcomponents, but it is preferable that the total amount is less than 1.2 parts by weight per 100 parts by weight of the metal oxide expressed by the general formula (1). If the amount of the subcomponents is 1.2 parts by weight or less, the piezoelectric properties and insulating properties of the piezoelectric material are sufficiently maintained.

[0094] The method for measuring the composition of a piezoelectric material is not particularly limited. Examples of methods include X-ray fluorescence analysis, ICP atomic emission spectroscopy, and atomic absorption spectroscopy. Any of these methods can be used to calculate the weight ratio and composition ratio of each element contained in the piezoelectric material.

[0095] (Contacting body material) In the vibration actuator of the present invention, the material of the contact body is preferably SUS420J2.

[0096] JIS standard SUS420J2 has low electrical resistance (resistivity at room temperature is 55 μΩcm). Furthermore, by quenching SUS420J2 in a vacuum, it is possible to increase its strength while preventing the formation of an oxide film that increases electrical resistance. Vacuum-quenched SUS420J2 has high hardness, making it an ideal material for elastic bodies that come into frictional contact with contact bodies.

[0097] (stator and slider) In the vibration type actuator of the present invention, it is preferable that the contact body is a stator and the vibrator is a moving element.

[0098] This is because it becomes possible to select a desirable moving part by adjusting the weight ratio and volume ratio of the vibrator and the contact body, thereby increasing the degree of freedom in design.

[0099] (electronic equipment) The electronic device of the present invention is characterized by comprising a member and a vibration actuator provided on the member. When the member is driven in conjunction with a contact body, the member can be moved precisely by the vibration actuator of the present invention.

[0100] (optical equipment) The optical device of the present invention is characterized in that a drive unit includes the vibration type actuator described above, and at least one of an optical element and an imaging element.

[0101] 7 is a schematic diagram showing one embodiment of the optical device (focus lens unit of a lens barrel device) of the present invention. In FIG. 7, a contact body (slider) 101 is in pressure contact with a vibrator 102. A power supply member 707 is provided on the surface of the vibrator 102 that has the first and second regions. When a desired voltage is applied to the vibrator 102 via the power supply member 707 by a voltage input means (not shown), an elliptical motion is generated in the protrusion of the elastic body (not shown).

[0102] The holding member 701 supports the piezoelectric vibrator 102 and is configured to suppress unnecessary vibrations. If the elastic body is rectangular, the vibrator may be held by the vibrator holding member at the four corners of the rectangular portion of the elastic body. Furthermore, if the elastic body is configured to further have support portions protruding from the ends of the rectangular portion, the vibrator may be held by the vibrator holding member via the support portions.

[0103] The movable housing 702 is fixed to the holding member 701 with screws 703 and is integrated with the piezoelectric vibrator 102. These members form the electronic device of the present invention. By attaching the movable housing 702 to the two guide members 704, the electronic device of the present invention can move linearly in both directions (forward and reverse) on the guide members 704.

[0104] Next, we will explain the lens 706 (optical member) that serves as the focus lens of the lens barrel device. The lens 706 is fixed to a lens holding member 705 and has an optical axis (not shown) parallel to the movement direction of the vibration wave motor. Like the vibration wave motor, the lens holding member 705 moves linearly on two guide members 704 (described later) to perform focal positioning (focusing operation). The two guide members 704 are members that engage the movable housing 702 and the lens holding member 705, enabling the movable housing 702 and the lens holding member 705 to move linearly. With this configuration, the movable housing 702 and the lens holding member 705 can move linearly on the guide members 704.

[0105] Furthermore, the connecting member 711 is a member that transmits the driving force generated by the vibration actuator to the lens holding member 705, and is fitted and attached to the lens holding member 705. This allows the lens holding member 705 to move smoothly in both directions along the two guide members 704 together with the movable housing 702.

[0106] Further, a sensor 708 is provided to detect the position of the lens holding member 705 on the guide member 704 by reading position information from a scale 709 attached to the side surface of the lens holding member 705 .

[0107] As described above, the focus lens section of the lens barrel device is constructed by incorporating the above-mentioned components.

[0108] 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. [Example]

[0109] 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.

[0110] Example 1 Electrodes 101 shown in Figure 1(c) were formed, and a circular, polarized piezoelectric material 102 was created from lead zirconate titanate ceramic with a thickness of 0.5 mm, an outer diameter of 62 mm, and an inner diameter of 54 mm. Figure 1(c) shows an example in which seven traveling waves are generated in the circumferential direction. The circumferential length of one electrode 101 is equal to λ / 4, and 28 electrodes 101 are arranged in the circumferential direction. The piezoelectric material in contact with the electrodes 101 is polarized with a voltage of the same polarity. Traveling waves are generated by changing the phase difference of the AC voltage applied to the electrodes 101 in 90-degree increments in the circumferential direction.

[0111] Next, an adhesive listed in Table 2 below was applied to the elastic body 103 made of SUS420J2, and the piezoelectric material 102 and elastic body 103 were thermocompression bonded at 160°C. The annular piezoelectric material and the annular elastic body were positioned using a positioning jig so that the centers of their circles were aligned. The adhesive was a conductive adhesive with dispersed conductive particles, and formed a conductive adhesive part 301 shown in Figure 3(a) between the elastic body and the piezoelectric material.

[0112] Next, a flexible printed circuit board (FPC) coated with anisotropic conductive paste (ACP) was held at 140°C for 20 seconds and thermocompression bonded to the electrodes on the piezoelectric material to obtain a vibrator 110. The obtained vibrator was brought into pressure contact with an aluminum contactor (rotor) 104 to produce a vibration actuator of the present invention. The surface of the aluminum contactor was anodized to improve wear resistance, and screw holes were drilled to secure wiring and supply power.

[0113] Example 2 A vibration type actuator was produced in the same manner as in Example 1, except that the material of the elastic body 103 was Invar.

[0114] Example 3 A vibration type actuator was fabricated using the same procedure as in Example 1, except for the portion where the electrode 101 and the third electrode 401 shown in FIGS. 4(a) and 4(b) are formed on the front and back of the annular piezoelectric material 102.

[0115] Example 4 A vibration type actuator was fabricated in the same manner as in Example 3, except that the material of the contact body 104 was Invar.

[0116] Example 5 A circular piezoelectric material 102 made of BCTZ ceramic as shown in Table 3 was prepared, with a thickness of 0.5 mm, an outer diameter of 62 mm, and an inner diameter of 54 mm, and on which electrodes 101 as shown in Figure 1(c) were formed. Next, an adhesive as shown in Table 1 was applied to an elastic body 103 made of SUS420J2, and the piezoelectric material 102 and elastic body 103 were thermocompression bonded at 160°C. The circular piezoelectric material and the circular elastic body were positioned using a positioning jig so that the centers of their circles were aligned. Part of the adhesive was a conductive adhesive with conductive particles dispersed therein, forming a conductive adhesive part 301 as shown in Figure 3(a) between the elastic body and the piezoelectric material.

[0117] Next, the FPC coated with ACP was held at 140° C. for 20 seconds and thermocompressed to the electrodes 101 provided on the piezoelectric material, thereby obtaining the vibrator 110.

[0118] Because the bonding temperature of the elastic body and FPC exceeds the depolarization temperature of the piezoelectric material, the piezoelectric material was subjected to polarization treatment after the bonding process. In the polarization treatment, the elastic body was grounded, and an external electrode was brought into contact with electrode 101, and a voltage equivalent to 2 kV / mm was applied to the piezoelectric material.

[0119] The vibrator thus obtained was then brought into pressure contact with an aluminum contactor (rotor) 104 to produce a vibration actuator of the present invention. The surface of the aluminum contactor was anodized to improve wear resistance, and had screw holes drilled in it to secure wiring and supply power.

[0120] Example 6 A vibration type actuator was produced in the same manner as in Example 5, except that the material of the elastic body 103 was Invar.

[0121] Examples 1 to 6 are vibration actuators using an annular piezoelectric material, as shown in FIG. 1. As shown in FIG. 1(a), the contactor was grounded, and an AC voltage was applied to the electrode 101 to drive the vibration actuator. While FIG. 1(a) shows only one power supply for simplification, AC power supplies were connected to the electrodes 101 (shown in FIG. 1(c)), which were divided around the circumference of the annular piezoelectric material. Elliptical vibrations were excited in the protrusions 105 on the surface of the elastic body 103 by applying AC voltages with a phase difference of 90 degrees between them. The elliptical vibration of the protrusions 105 caused the contactor 104, which was in pressure contact with the protrusions 105, to rotate relative to it. When the AC voltage was swept from a starting frequency set higher than the resonant frequency of the bending vibration of the vibrator toward the resonant frequency, the rotation speed of the contactor gradually increased and stopped. Both the maximum speed and the power at the rated speed (rated power) were satisfactory. For comparison, the maximum speed and rated power of the vibration actuator of Example 3 are set to 100%.

[0122] Example 7 Electrode 101 and third electrode shown in Figures 4(c) and 4(d) were formed, and a rectangular piezoelectric material 102 made of lead zirconate titanate ceramic, measuring 0.4 mm thick and 8.9 x 5.7 mm, was fabricated after polarization treatment. Next, an adhesive listed in Table 2 was applied to elastic body 103 shown in Figure 2(b) made of SUS420J2, and piezoelectric material 102 and elastic body 103 were thermocompression bonded at 160°C. Rectangular piezoelectric material 102 and elastic body 103 having rectangular portion 106 were positioned using a positioning jig so that the centers of gravity of the rectangular portions were aligned. Part of the adhesive was a conductive adhesive with conductive particles dispersed therein, forming conductive adhesive portion 301 shown in Figure 3(b) between the elastic body and piezoelectric material.

[0123] Next, the FPC coated with ACP was held at 140°C for 20 seconds and thermocompression bonded to the electrodes provided on the piezoelectric material to obtain a vibrator 110. The obtained vibrator was brought into pressure contact with a contact body 104 made of SUS420J2 to produce a vibration type actuator of the present invention.

[0124] Example 8 A rectangular piezoelectric material 102 made of BCTZ ceramic (see Table 3) with a thickness of 0.35 mm and dimensions of 8.9 x 5.7 mm was prepared, with the electrode 101 and third electrode shown in Figures 4(c) and 4(d) formed on it. Next, an adhesive listed in Table 2 was applied to the elastic body 103 (see Figure 2(b)) made of SUS420J2, and the piezoelectric material 102 and elastic body 103 were thermocompression bonded at 160°C. The rectangular piezoelectric material 102 and the elastic body 103 with the rectangular portion 106 were positioned using a positioning jig so that the centers of gravity of the rectangular portions were aligned. A portion of the adhesive was a conductive adhesive with conductive particles dispersed therein, forming the conductive adhesive portion 301 shown in Figure 3(b) between the elastic body and the piezoelectric material.

[0125] Next, the ACP-coated FPC was held at 140°C for 20 seconds and thermocompressed to the electrodes on the piezoelectric material to obtain vibrator 110. Because the bonding temperature of the elastic body and FPC exceeds the depolarization temperature of the piezoelectric material, the piezoelectric material was subjected to a polarization process after the bonding process. In the polarization process, the elastic body was grounded, and external electrodes were brought into contact with first electrode 101a and second electrode 101b on rectangular piezoelectric material 102, and a voltage equivalent to 2 kV / mm was applied to the piezoelectric material.

[0126] The obtained vibrator was brought into pressure contact with a contact body 104 made of SUS420J2 to produce a vibration type actuator of the present invention.

[0127] Examples 7 and 8 are vibration actuators using the rectangular piezoelectric material shown in FIG. 2. As shown in FIG. 2(a), the contactor was grounded, and AC voltages with a 90-degree phase difference were applied to the first electrode 101a and the second electrode 101b to simultaneously generate vibrations in Mode A and Mode B. The elliptical vibration of the protrusion 105 caused the contactor 104, which was in pressure contact with the protrusion 105, to move relative to it. It was also possible to drive the contactor using the vibrator as a stator, or to drive the vibrator using the contactor as a stator. When the AC voltage was swept from a starting frequency set higher than the resonance frequencies of Mode A and Mode B toward the resonance frequency, the movement speed of the contactor gradually increased and then stopped. Both the maximum speed and the power at the rated speed (rated power) of each vibration actuator were good. For comparison, the maximum speed and rated power of the vibration actuator of Example 7 are set to 100%.

[0128] In all of the vibration type actuators of Examples 1 to 8, when the applied voltage was increased, the vibration amplitude of the vibrator did not exceed a certain level.

[0129] (Comparative Example 1) 6(a) and 6(b), first, the electrodes 101a and 1010b, the third electrode 401, and the non-driving phase electrode 601 are formed. Then, a polarization treatment is performed to produce a circular piezoelectric material 102 made of lead zirconate titanate ceramic with a thickness of 0.5 mm, an outer diameter of 62 mm, and an inner diameter of 54 mm.

[0130] The electrode 101 in contact with the electrodes 101a and 101b has a length equivalent to half the wavelength λ of the traveling wave generated in the circumferential direction by the annular piezoelectric material 102, and the piezoelectric material in contact with the electrode 101 is polarized in the circumferential direction with voltages of opposite polarities.

[0131] A standing wave can be generated by applying an AC electric field only to electrode 101a or only to electrode 101b. When two standing waves are spatially spaced λ / 4 apart and the voltages applied to electrodes 101a and 101b have a 90-degree phase difference, a traveling wave is generated in the annular piezoelectric material. Electrode 601a in Figure 6(a) is a non-driven phase electrode measuring λ / 4 in the circumferential direction. Since the non-driven phase electrode must be an integer multiple of λ, a non-driven phase electrode 601b measuring 3λ / 4 is provided opposite electrode 601a across the center of the annulus. The circumference of Figure 6(a) corresponds to 7λ, but the non-driven phase occupies λ, which corresponds to 1 / 7 of the circumference.

[0132] Next, the non-conductive adhesive listed in Table 2 was applied to the elastic body 103 made of SUS420J2, and the piezoelectric material 102 and the elastic body 103 were thermocompression bonded at 160° C. The annular piezoelectric material and the annular elastic body were positioned using a positioning jig so that the centers of their circles were aligned.

[0133] Next, the FPC coated with ACP was held at 140°C for 20 seconds to be thermocompressed to the electrodes 101a, 101b and the non-driving phase electrode 601 provided on the piezoelectric material, thereby obtaining a vibrator 110. The obtained vibrator was brought into pressure contact with an aluminum contact body (rotor) 104 to produce a vibration type actuator.

[0134] An AC voltage with a phase difference of 90 degrees was applied to electrodes 101a and 101b, exciting elliptical vibration in protrusion 105 on the surface of elastic body 103. The elliptical vibration of protrusion 105 caused contact body 104, which was in pressure contact with protrusion 105, to perform a relative rotational motion. When the AC voltage was swept from a starting frequency set higher than the resonance frequency of the bending vibration of the vibrator toward the resonance frequency, the number of rotations of the contact body gradually increased and then stopped. The maximum speed was similar to that of Example 3, but compared to Example 3, the maximum speed was 90% and the rated power was 120%.

[0135] (Comparative Example 2) 6(c) and (d), electrode 101, third electrode 401, and non-driven phase electrode 601 were formed, and a rectangular piezoelectric material 102 made of lead zirconate titanate ceramic, measuring 0.4 mm thick and 8.9 mm x 5.7 mm, was fabricated after polarization treatment. The non-driven phase electrode 601 is connected to the third electrode 401 by a side electrode that passes through the side of the piezoelectric material. The piezoelectric material sandwiched between the non-driven phase electrode 601 and third electrode 401 was not subjected to polarization treatment.

[0136] Next, the non-conductive adhesive shown in Table 2 was applied to the elastic body 103 made of SUS420J2, and the piezoelectric material 102 and the elastic body 103 were thermocompression bonded at 160° C. The rectangular piezoelectric material 102 and the elastic body 103 having the rectangular portion 106 were positioned using a positioning jig so that the centers of gravity of the respective rectangular portions were aligned.

[0137] Next, the FPC coated with ACP was held at 140°C for 20 seconds to be thermocompressed to the electrodes 101a, 101b and the non-driving phase electrode 601 provided on the piezoelectric material, thereby obtaining a vibrator 110. The obtained vibrator was brought into pressure contact with a contact body 104 made of SUS420J2, thereby producing a vibration type actuator of the present invention.

[0138] An AC voltage with a phase difference of 90 degrees was applied between electrode 101a and non-driven phase electrode 601, and between electrode 101b and non-driven phase electrode, and vibrations of modes A and B were generated simultaneously, exciting elliptical vibration in protrusion 105. The elliptical vibration of protrusion 105 caused relative movement of contact body 104, which was in pressure contact with protrusion 105. When the AC voltage was swept from a starting frequency set higher than the resonance frequencies of modes A and B toward the resonance frequency, the movement speed of the contact body gradually increased and stopped. Compared to Example 7, the maximum speed was 90% and the rated power was 110%.

[0139] In both of the vibration type actuators of Comparative Examples 1 and 2, when the applied voltage was increased, the amplitude of the vibrator generated large vibrations exceeding a certain vibration amplitude.

[0140] [Table 1]

[0141] [Table 2]

[0142] [Table 3]

[0143] [Table 4]

[0144] Example 9 The vibration actuator produced in Example 8 was mechanically connected to an optical member to produce the optical device shown in Figure 7. It was confirmed that the optical device also exhibited autofocus operation in response to the application of an AC voltage. While Example 8 has been described above as an example, optical members with low rated power could also be produced using the vibration actuator of the present invention in Examples 1 to 8.

[0145] By providing a vibrator in which an electrode, a piezoelectric material, and an elastic body are arranged in that order, and a contact body that contacts the elastic body, and by applying a voltage between the contact body and the electrode, it is possible to provide a vibration type actuator that has superior driving characteristics compared to when a piezoelectric material having a non-driving phase electrode is used. [Industrial Applicability]

[0146] The vibration actuator of the present invention can be used in a variety of applications, such as driving lenses and image pickup elements in imaging devices (optical instruments), rotating photosensitive drums in copiers, and driving stages. Furthermore, taking advantage of its large output per unit packaging volume, it can be suitably used in medical or industrial endoscopes, etc. Specifically, it can be applied to a wire-driven actuator that has an elongated member and a wire that passes through the elongated member and is fixed to a portion of the elongated member, and that bends a predetermined section of the elongated member by driving the wire.

[0147] In this specification, a vibration type actuator using a rectangular piezoelectric material has been described as an example in which a contact body is driven by a single vibration type actuator, but it is also possible to drive a heavier contact body by using multiple vibration type actuators. [Explanation of symbols]

[0148] 100 Vibration Actuator 101 Electrode 101a 1st electrode 101b 2nd electrode 102 Piezoelectric Materials 103 Elastic Body 104 Contact body 105 Protrusion 106 Rectangular part 107 Support part 110 Transducer 201 Conductive adhesive 401 3rd electrode 601 Non-driven phase electrode 601a Non-driven phase electrode a 601b Non-driven phase electrode b 701 Holding member 702 Mobile enclosure 703 Bis 704 Guide member 705 Lens holding member 706 Lens 707 Power Supply Materials 708 Sensors 709 scale 710 Guide member 711 Connecting members

Claims

1. a vibrator having a piezoelectric material, an electrode disposed on a first surface of the piezoelectric material, and an elastic body disposed on a second surface of the piezoelectric material opposite to the first surface; a contact body that is in contact with the elastic body and is provided so as to be movable relative to the vibrator; The elastic body is configured to be able to separate from the contact body, The contact body is set to a ground potential, and a voltage is applied between the contact body and the electrode, causing the vibrator to vibrate.

2. 2. The vibration actuator according to claim 1, wherein the elastic body and the piezoelectric material are bonded via a conductive adhesive.

3. 3. The vibration actuator according to claim 2, wherein the conductive adhesive portion is configured in a layered form, and the conductive adhesive portion has an average thickness of 1.5 μm or more and 7 μm or less.

4. 4. The vibration actuator according to claim 2, wherein the conductive adhesive portion contains conductive particles.

5. 5. The vibration actuator according to claim 4, wherein the conductive particles have an average particle size of 1 [mu]m or more and 5 [mu]m or less.

6. 6. The vibration actuator according to claim 4, wherein the conductive particles have a volume fraction of 0.4% to 2% of the conductive adhesive portion.

7. 7. The vibration actuator according to claim 1, wherein the contact body includes stainless steel.

8. 8. The vibration actuator according to claim 7, wherein at least one of the surface of the contact body and the surface of the elastic body is coated with a nitride.

9. 7. The vibration actuator according to claim 1, wherein the contact body includes aluminum.

10. 10. The vibration actuator according to claim 9, wherein the surface of the contact body is coated with an oxide of aluminum.

11. 7. The vibration actuator according to claim 1, wherein the elastic body is covered with a conductor.

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

13. 13. The vibration actuator according to claim 12, wherein the elastic body has support portions that protrude from the ends of the rectangular portion, and the vibrator is held by a vibrator holding member via the support portions.

14. 12. The vibration actuator according to claim 1, wherein the elastic body has an annular shape.

15. 15. The vibration type actuator according to claim 1, wherein the contact body is a stator, and the vibrator is a slider.

16. 16. The vibration actuator according to claim 1, wherein the electrodes are a first electrode and a second electrode adjacent to each other.

17. When regions of the piezoelectric material where the first electrode and the second electrode are provided are defined as a first region and a second region, the vibrator has: a first bending vibration mode in which the first region and the second region both expand or contract; 14. The vibration actuator according to claim 12, wherein a second bending vibration mode is formed in which the second region contracts and expands when the first region expands and contracts, respectively.

18. 18. The vibration actuator according to claim 1, wherein the first surface of the piezoelectric material is not provided with an electrode at ground potential.

19. 19. A vibration actuator according to claim 1, wherein a plurality of the vibrators are in contact with a common contact body, and vibration of the plurality of vibrators causes relative movement between the contact body and the plurality of vibrators.

20. 20. The vibration actuator according to claim 1, wherein the piezoelectric material includes a lead zirconate titanate-based material.

21. 20. The vibration actuator according to claim 1, wherein the piezoelectric material contains less than 1000 ppm of lead.

22. 22. The vibration actuator according to claim 21, wherein the piezoelectric material includes a barium titanate-based material.

23. 23. The vibration actuator according to claim 22, wherein the piezoelectric material includes a barium calcium zirconate titanate material.

24. a first member; a vibration type actuator according to any one of claims 1 to 23 provided on the first member; a second member connected to the contact body and at ground potential; Electronic equipment equipped with

25. a vibration type actuator according to any one of claims 1 to 23 provided in a drive section; The optical device further includes at least one of an optical element and an imaging element.

26. an elongated member; a wire passing through the elongated member and fixed to a portion of the elongated member; A wire-driven actuator comprising the vibration actuator according to claim 1 for driving the wire, wherein the elongated member is bent by driving the wire.

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