JP7130416B2 - Vibrators, vibrating actuators and electronic devices - Google Patents

Description

The present invention relates to vibrators, vibrating actuators, and electronic devices.

Vibration actuators are known that include a vibrating body (hereinafter referred to as a “vibrator”) in which an elastic body and piezoelectric ceramics are bonded (joined). For example, Patent Document 1 discloses that a vibrator and a driven body are brought into contact with each other, and the vibrator and the driven body are relatively moved by a synthetic vibration generated by exciting two different modes of vibration in the vibrator. A vibration actuator is described.

Here, as piezoelectric ceramics, perovskite-type metal oxides represented by a general formula of ABO ₃ (A and B are metal elements) are widely used. Lead zirconate titanate-based materials (hereinafter referred to as “PZT-based materials”) having a large piezoelectric constant are widely used as representative piezoelectric ceramics. However, since the PZT-based material contains a large amount of lead, its influence on the environment is regarded as a problem.

To address this problem, the use of lead-free piezoelectric ceramics (hereinafter referred to as "lead-free piezoelectric ceramics") has been investigated. Barium titanate (BaTiO ₃ ) and its derivative (solid solution) are known as perovskite-type lead-free piezoelectric ceramics. For example, in Patent Document 2 and Non-Patent Document 1, piezoelectric properties are improved by replacing part of the A site of barium titanate with calcium (Ca) and part of the B site with zirconium (Zr). Piezoelectric ceramics are described.

Japanese Patent Application Laid-Open No. 2004-297910 JP 2009-215111 A

“Journal of Applied Physics”, 2011, Vol.109, 054110-1～054110-6

However, in general, the piezoelectric constant of lead-free piezoelectric ceramics is smaller than that of lead-based piezoelectric ceramics. Therefore, if an attempt is made to obtain vibration displacement equivalent to that of a vibrator using lead-based piezoelectric ceramics with a vibrator using lead-free piezoelectric ceramics, there arises a problem that power consumption increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vibrator capable of obtaining a desired vibration displacement while suppressing power consumption.

A vibrator according to the present invention is a vibrator in which a piezoelectric ceramic, a piezoelectric element having electrodes, and an elastic body are bonded via an adhesive layer, and the adhesive layer extends in the thickness direction of the adhesive layer. The piezoelectric element and the elastic body are projected in a region near the nodal line of the vibration when the first-order out-of-plane bending vibration mode vibration is excited in the vibrator in the region where the piezoelectric device and the elastic body overlap each other. It is characterized by having a non-adhesive region that does not adhere to the elastic body.

According to the present invention, it is possible to realize a vibrator capable of obtaining a desired vibration displacement while suppressing power consumption.

1 is a diagram showing a schematic configuration of a piezoelectric element and a vibrator according to an embodiment of the invention; FIG. FIG. 4 is a diagram illustrating an example of an out-of-plane vibration mode excited in a vibrator; FIG. 4 is a diagram illustrating the frequency dependency of admittance of a vibrator and the relationship between resonance frequency difference Δf and power consumption; FIG. 4 is a diagram for explaining nodal lines and antinodes of an out-of-plane vibration mode excited in a vibrator; FIG. 4 is a diagram for explaining the configuration of an adhesive layer in an oscillator according to an example; FIG. 10 is a diagram illustrating a configuration of a bonding layer in a vibrator according to a comparative example; It is a figure which shows the relationship between the non-bonded area ratio and the value of (DELTA)f in an Example and a comparative example. 2 is a plan view showing a modification of the piezoelectric element of FIG. 1; FIG. 1 is a diagram showing an embodiment of a vibration wave driving device using a piezoelectric element and a vibrator according to the present invention; FIG. 1 is a perspective view showing a schematic configuration of an optical device including a vibration actuator; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a piezoelectric element 101 and a vibrator 100 according to an embodiment of the invention. FIG. 1(a) is a side view of the piezoelectric element 101. FIG. 1B and 1C are plan views (top view and back view) of the piezoelectric element 101, respectively. A piezoelectric element 101 has a structure in which a first electrode 2 is formed on one surface of a piezoelectric ceramic 1 and second electrodes 3a and 3b are formed on the other surface. For convenience of explanation, the X direction, Y direction and Z direction which are orthogonal to each other are defined as shown in FIGS. 1(a) to 1(c). FIG. 1D is a side view of the vibrator 100. FIG. The vibrator 100 has a structure in which a piezoelectric element 101 and an elastic body 5 are adhered (also referred to as bonding or fixing) by an adhesive layer 4 . As shown in FIG. 2, which will be described later, the elastic body 5 is provided with a protrusion 51, but the illustration of the protrusion 51 is omitted in FIG. 1(d).

First, the configuration of the piezoelectric element 101 that constitutes the vibrator 100 will be described. The piezoelectric ceramic 1 has a substantially rectangular flat shape, and the longitudinal direction, the lateral direction and the thickness direction of the piezoelectric ceramic 1 are defined as the X direction, the Y direction and the Z direction, respectively. A substantially rectangular shape does not need to be a perfect rectangle, and includes, for example, a shape in which each side is chamfered. The piezoelectric ceramic 1 is a sintered body having a substantially uniform composition, and is subjected to polarization treatment so that, for example, the absolute value of the piezoelectric constant _d31 is 10 pm/V or more or the piezoelectric constant d33 is 30 pC/N at 20 _° C. The piezoelectric material exhibits the above.

The piezoelectric constant of the piezoelectric ceramic 1 is calculated based on the electronic information technology industry standard (JEITA EM-4501) using, for example, the density of the piezoelectric ceramic 1 and the resonance frequency and anti-resonance frequency (resonance-anti-resonance method). can be obtained by In that case, the density can be measured by the Archimedes method. The resonance frequency and anti-resonance frequency can be measured using an impedance analyzer. In addition to the resonance-antiresonance method, it is also possible to measure the piezoelectric constant of the piezoelectric ceramic 1 with a piezoelectric constant measuring apparatus using the Berlin coat method as the principle of measurement.

Piezoelectric ceramics constituting vibrators have been widely used for a long time, mainly composed of lead zirconate titanate (PZT), which has a large piezoelectric constant. However, if a piezoelectric element containing piezoelectric ceramics is discarded and exposed to acid rain or left in a harsh environment, the lead component contained in the piezoelectric ceramics will leach into the soil, harming the ecosystem. There is a risk. In view of such problems, in the present embodiment, lead-free piezoelectric ceramics are used for the piezoelectric ceramics 1, and lead-free piezoelectric ceramics is defined as piezoelectric ceramics having a lead content of less than 1000 ppm. This is because if the lead content is less than 1000 ppm, even if the piezoelectric element 101 is discarded and exposed to acid rain or left in a harsh environment, the lead component contained in the piezoelectric ceramic 1 does not cause substantial environmental pollution. because it does not occur The lead content of the piezoelectric ceramics 1 can be detected using a well-known quantitative analysis method. For example, it can be obtained from the ratio of the weight of lead to the total weight of the piezoelectric ceramics 1 quantified by X-ray fluorescence analysis (XRF) or by ICP emission spectrometry.

Among lead-free piezoelectric ceramics, it is desirable to use barium titanate or its derivative from the viewpoint that it has a large piezoelectric constant and is relatively easy to manufacture, and the Young's modulus of the sintered body is 100 GPa to 140 GPa. Anything in the range is desirable. Barium titanate or derivatives thereof include barium titanate (BaTiO ₃ ), barium calcium titanate ([Ba, Ca]TiO ₃ ), barium zirconate titanate (Ba[Ti, Zr]O ₃ ), titanic acid Barium calcium zirconate ([Ba, Ca] [Ti, Zr] O ₃ ), sodium niobate-barium titanate (NaNbO ₃ -BaTiO ₃ ), sodium bismuth titanate-barium titanate ([Bi, Na] TiO ₃ -BaTiO ₃ ), bismuth potassium titanate-barium titanate ([Bi, K]TiO ₃ -BaTiO ₃ ).

The lead-free piezoelectric ceramics may be one that substantially has each of these compositions, one that combines each composition, or one that contains other elements based on each composition. From the viewpoint of achieving both a piezoelectric constant and a mechanical quality factor (Q value), a material containing barium calcium titanate zirconate or sodium niobate-barium titanate as a main component is preferably used. From the viewpoint of improving the mechanical quality factor and insulating properties, it is preferable to use those containing manganese (Mn) and bismuth (Bi) as elements other than the above main components. The piezoelectric ceramics 1 can be manufactured by a well-known manufacturing method. For example, it can be produced by molding a raw material powder (generally a metal oxide) containing a metal element, firing it, and processing the resulting sintered body into a desired shape, but is not particularly limited. not a thing

The first electrode 2 and the second electrodes 3a and 3b are provided on the front and rear surfaces of the piezoelectric ceramics 1, respectively, in order to apply a voltage for causing the piezoelectric ceramics 1 to undergo a predetermined displacement. The second electrodes 3a and 3b are used as electrodes for applying an alternating voltage (driving voltage), and the first electrode 2 is used as a common electrode connected to the ground (earth). When a voltage is applied so as to generate a predetermined potential difference between the first electrode 2 and the second electrodes 3a and 3b, an electric field is applied to the piezoelectric ceramics 1 in the thickness direction, and the piezoelectric characteristics (piezoelectric constant ) can be generated.

The first electrode 2 and the second electrodes 3a and 3b are made of a conductive material and have a thickness of about 5 nm to 10 μm. Examples of conductive materials include metals such as titanium (Ti), platinum (Pt), gold (Au), nickel (Ni), palladium (Pd), silver (Ag), copper (Cu), and alloys thereof. It is desirable to use Silver is preferably used from the viewpoint of low cost and good conductivity. For example, a silver paste is printed (applied) on the front and rear surfaces of the piezoelectric ceramic 1 using a screen printing method or the like, dried, and then baked at a predetermined temperature to form the first electrode 2 and the second electrodes 3a and 3b. can be formed with As a method of forming the first electrode 2 and the second electrodes 3a and 3b with the metal or alloy described above, a sputtering method or the like can also be used.

In order to generate displacement in the piezoelectric element 101 based on the piezoelectric characteristics, the piezoelectric ceramics 1 must be polarized. The polarization treatment may be performed before or after bonding the piezoelectric element 101 to the elastic body 5 . When the polarization treatment is performed before the bonding step, the steps after the polarization treatment must be performed at a temperature lower than the Curie temperature of the piezoelectric ceramics 1 so that the piezoelectric ceramics 1 are not depolarized.

Next, the adhesive layer 4 and the elastic body 5 of the vibrator 100 will be described. The adhesive layer 4 is generally formed by applying a liquid resin adhesive to either one of the piezoelectric element 101 and the elastic body 5 and extending the thickness direction (Z direction) while applying a predetermined force. In FIG. 1D, the thickness of the adhesive layer 4 is shown in order to clearly show it, but the thickness of the adhesive layer 4 is generally about several microns. The elastic body 5 is made of, for example, a metal material such as stainless steel.

Here, a method of adhering the piezoelectric element 101 and the elastic body 5 will be described. First, a liquid resin adhesive is applied to the bonding surface of the piezoelectric element 101 or the bonding surface of the elastic body 5 . A resin adhesive is a resin material that has fluidity at the time of application (before curing treatment), but loses its fluidity after a predetermined curing treatment and hardens (solidifies) to become a solid resin material. It may be curable or two-component curable. Specific examples of resin adhesives include epoxy-based resins, acrylic-based resins, and silicone-based resins.

Subsequently, the bonding surface of the piezoelectric element 101 and the bonding surface of the elastic body 5 are bonded together via the applied resin adhesive, and the piezoelectric element 101 and the elastic body 5 are pressed in the thickness direction (Z direction). to cure the resin adhesive. The pressure applied to the piezoelectric element 101 and the elastic body ⁵ should be such that the piezoelectric element 101 and the elastic body 5 do not move and the piezoelectric ceramic ¹ does not crack. 10 kg/cm ² or less is more preferable. When the resin adhesive is thermosetting, the curing time is reduced by heating at least one of the piezoelectric element 101 and the elastic body 5 while the piezoelectric element 101 and the elastic body 5 are in pressure contact with each other. can be shortened. Thus, the vibrator 100 is obtained by forming the adhesive layer 4 in which the resin adhesive is cured.

When the piezoelectric element 101 that has undergone polarization treatment is used to bond the piezoelectric element 101 and the elastic body 5 with a thermosetting resin adhesive, the curing temperature of the resin adhesive is set to the Curie temperature of the piezoelectric ceramics 1 or lower. As such, it is desirable to prevent depolarization of the piezoelectric ceramics 1 . Also, the method of adhering the piezoelectric element 101 and the elastic body 5 is not limited to the above method. If necessary, the first electrode 2 and the second electrodes 3a, 3b are provided with a power supply member (see FIG. 8) for electrical connection with voltage input means (power source).

FIG. 2 is a diagram illustrating an example of two different out-of-plane vibration modes excited in the vibrator 100. FIG. In FIGS. 2A and 2B, the amount of deformation is enlarged to facilitate understanding of the vibration displacement occurring in the vibrator 100, and the illustration of the adhesive layer 4 is omitted. . Protrusions 51 are provided at predetermined intervals in the longitudinal direction (X direction) on the surface of the elastic body 5 opposite to the bonding surface with the piezoelectric element 101 . Note that the function of the projecting portion 51 will be described later.

2A and 2C are diagrams for explaining one of the two out-of-plane vibration modes (hereinafter referred to as "out-of-plane vibration mode A"). The out-of-plane vibration mode A is a primary out-of-plane bending vibration mode having two nodal lines substantially parallel to the long side (X direction) of the vibrator 100 and not intersecting each other. In FIG. 2(c), the position of the nodal line is indicated by a black circle, and the position of the abdominal line is indicated by a white circle, and the amplitude is maximum at the position of the abdominal line. 2B and 2D are diagrams for explaining the other out-of-plane vibration mode (hereinafter referred to as "out-of-plane vibration mode B") of the two out-of-plane vibration modes. The out-of-plane vibration mode B is a secondary out-of-plane bending vibration mode having three nodal lines substantially parallel to the short side (Y direction) of the vibrator 100 and not intersecting each other. In FIG. 2(d), the position of the nodal line is indicated by a black circle, and the position of the abdominal line is indicated by a white circle, and the amplitude is maximum at the position of the abdominal line.

The resonance frequencies of the out-of-plane vibration modes A and B, the number of nodal lines, and their positions can be determined, for example, by applying an alternating voltage to the vibrator 100 while changing the drive frequency, and determining the amount of displacement in the out-of-plane direction for each drive frequency. It can be known by measuring the in-plane distribution with a laser Doppler vibrometer. The projecting portion 51 is provided at a position where the antinode line of the out-of-plane vibration mode A and the nodal line of the out-of-plane vibration mode B intersect. Although the details will be described later, by simultaneously exciting the vibrations of the out-of-plane vibration modes A and B with a predetermined phase difference, the tip of the protrusion 51 can be caused to make an elliptical motion within the ZX plane. As will be described later with reference to FIG. 9, the tip of the protrusion 51 contacts the driven body, and the elliptical motion generated at the tip of the protrusion 51 causes the protrusion 51 to apply thrust to the driven body. Thereby, the vibrator 100 and the driven body can be relatively moved in the X direction.

With respect to the out-of-plane vibration mode A, the location where the displacement amount is zero in the short side direction (Y direction) of the vibrator 100 or the location where the positive/negative of the displacement amount is reversed is defined as a nodal line. At any place in the long side direction (X direction) of , two frequencies in the short side direction are obtained. The resonance frequency f _A of the out-of-plane vibration mode A is the frequency at which the amount of displacement at the position of the central portion (abdominal line) of the two nodal lines is maximum in the vicinity of the frequencies thus obtained. In the out-of-plane vibration mode B, a node line is a location where the displacement amount is zero in the long side direction (X direction) of the vibrator 100 or a boundary location where the displacement amount is reversed. Three frequencies in the long side direction are obtained at any place in the short side direction (Y direction). The resonance frequency f _B of the out-of-plane vibration mode B is the frequency at which the amount of displacement at the central portion (abdominal line) of two adjacent nodal lines out of the three is maximized in the vicinity of the frequencies obtained in this way. be.

FIG. 3A is a diagram showing the frequency dependence of the admittance of the vibrator 100. FIG. The admittance of the vibrator 100 becomes maximum at the resonance frequencies f _A and f _B of the out-of-plane vibration modes A and B, respectively, and the difference between the resonance frequencies f _A and f _B (f _B −f _A ) is the resonance frequency difference Δf defined as FIG. 3B is a diagram showing the results of measuring power consumption when vibrating actuators using vibrators 100 having different resonance frequency differences Δf are driven. The structure of the vibration type actuator conforms to the structure of the vibration type actuator shown in FIG. 9, which will be described later, and the difference in the resonance frequency difference Δf is caused by the difference in the shape of the vibrator 100. FIG. In FIG. 3(b), the power consumption when driven at a constant vibration speed is plotted on the vertical axis, and the resonance frequency difference Δf is plotted on the horizontal axis. Power consumption tends to decrease as the resonance frequency difference Δf increases. appears. Therefore, in the present embodiment, the bonding state between the piezoelectric element 101 and the elastic body 5 is characterized to increase the resonance frequency difference Δf, thereby realizing a vibration actuator that can be driven with low power consumption.

FIG. 4(a) shows the positions of antinodes (Cn−Cn′ (n=1, 2, 3)) and nodal lines (Dn−Dn′ (n=1, 2)) in out-of-plane vibration mode A. 2 is a plan view seen from the side of the piezoelectric ceramics 1 during driving; FIG. FIG. 4(b) shows antinode lines (En-En' (n=1, 2, 3, 4)) and nodal lines (Fn-Fn' (n=1, 2, 3)) in the out-of-plane vibration mode B. is a plan view of the position of , viewed from the side of the piezoelectric ceramics 1 when not driven. Note that the nodal lines and antinodes are not necessarily straight lines parallel to the short side or long side as shown in FIGS. 4(a) and 4(b). It may also be a curved curve. However, in this embodiment, it is assumed that the nodal line and the abdominal line are approximately straight.

In the vibrator 100, the change in the resonance frequency difference Δf when the state of bonding between the piezoelectric ceramics 1 and the elastic body 5 (form of the bonding layer 4) is changed is estimated using the finite element method package software ANSYS (ANSYS Inc.). rice field. In this simulation, the Young's modulus Ysb of the elastic body 5 at 20° C. was set to 200 GPa, and the Young's modulus Yce of the piezoelectric ceramics 1 was set to 120 GPa.

FIG. 5 is a diagram for explaining the structure of the adhesive layer 4 according to Examples 1 to 5. FIG. A dot-patterned region inside the piezoelectric element 101 indicates a region where the piezoelectric element 101 and the elastic body 5 are adhered to each other by the adhesive layer 4 . On the other hand, the plain area (white area) inside the piezoelectric element 101 is an area where no adhesive is present or where the piezoelectric element 101 and the elastic body 5 are not substantially adhered even if the adhesive is present (hereinafter referred to as (referred to as "non-bonded areas"). The non-adhesion region can be formed, for example, by providing a layer of fluorine-based resin or the like on the surface of the piezoelectric element 101 that is to be adhered to the elastic body 5 to prevent adhesion of the adhesive. In the non-adhesive region, a soluble material is prepared in the adhesive layer in advance and the soluble material is removed after the piezoelectric element 101 and the elastic body 5 are adhered. It is also possible to form by using a method of forming a void at the interface.

FIG. 6 is a diagram illustrating the configuration of the adhesive layer 4 according to Comparative Examples 1 to 6. FIG. FIG. 6(a) shows a conventional general form in which a substantially uniform adhesive layer 4 is provided without forming a non-adhesive region in the adhesive layer 4 between the piezoelectric element 101 and the elastic body 5. is referred to as Comparative Example 1. With the resonance frequency difference Δf in the configuration of Comparative Example 1 as the reference value Δf ₀ , the calculated values of the resonance frequency differences Δfex ₁ to Δfex ₅ of Examples 1 to 5 and the resonance frequency differences of Comparative Examples 2 to 6 are calculated. The calculated values Δfc ₁ to Δfc ₅ are compared with the reference value Δf ₀ .

FIG. 5(a) shows the configuration of the adhesive layer 4 of Example 1. FIG. In Example 1, two strip-shaped non-bonded regions are provided in the vicinity of each node line centering on the node lines D1-D1' and D2-D2' of the out-of-plane vibration mode A. FIG. In the present embodiment, the near-field region of the nodal line means that when the vibrator 100 is not driven and viewed from the side of the piezoelectric ceramics 1, the region of the out-of-plane vibration mode is closer to the anti-node of the predetermined out-of-plane vibration mode. A region near a nodal line is defined as a region containing the nodal line. Further, the ratio of the area Su of the non-bonded region to the total area Sce of the bonding surface of the piezoelectric ceramic 1 to the elastic body 5, that is, Su/Sce, is called the non-bonded area ratio. For example, in FIG. 5(a), one rectangular area consisting of the width between the antinodes C1-C1′ and C3-C3′ and the length of the adhesive area in the X direction covers the entire area Sce of the adhesive surface. Equivalent to. In Example 1, the width (length in the Y direction) of each of the two strip-shaped non-bonded regions was varied, and the non-bonded area ratio obtained from the sum of the two strip-shaped non-bonded regions was 4.9%. , 9.8% and 14.6%, the values of Δfex ₁ /Δf ₀ were 1.003, 1.010 and 1.025, respectively. Here, when the non-bonded area ratio is 14.6%, as shown in FIGS. A non-bonded region with a width of 0.073λ is defined for each of the two nodal lines at a position containing the nodal line in the Y direction, more preferably at a position where the nodal line is centered in the Y direction. be. In this embodiment, however, each of the two nodal lines is provided with a non-adhesive region having a width of 0.073λ or less, and the adhesive layer 4 is formed so that the piezoelectric element 101 and the elastic body 5 are not adhered to each other in this non-adhesive region. It is preferable to configure

FIG. 5(b) shows the configuration of Example 2 of the adhesive layer 4. As shown in FIG. In Example 2, four belt-shaped non-bonded strips are arranged on the longitudinal end side (X direction end side) of the piezoelectric ceramic 1 centering on the nodal lines D1-D1' and D2-D2' of the out-of-plane vibration mode A. A region is provided in a region near each nodal line. In Example 2, the ratios of Δfex ₂ /Δf ₀ when the widths of the four strip-shaped non-bonded regions are changed to set the non-bonded area ratios to 4.3%, 8.7%, and 14.6%, respectively The values were 1.003, 1.012 and 1.025 respectively.

FIG. 5(c) shows the configuration of Example 3 of the adhesive layer 4. As shown in FIG. In Example 3, two band-shaped non-adhesive regions are formed in the central portion in the longitudinal direction (the central portion in the X direction) of the piezoelectric ceramic 1 centering on the nodal lines D1-D1′ and D2-D2′ of the out-of-plane vibration mode A. are provided in the vicinity of each nodal line. The values of Δfex ₃ /Δf ₀ are 1.024 and 1.025 when the widths of the two belt-shaped non-bonded regions are changed to set the non-bonded area ratios to 8.8% and 14.6%, respectively. became.

FIG. 5(d) shows the configuration of Example 4 of the adhesive layer 4. As shown in FIG. In Example 4, one belt-shaped non-adhesive region is centered on the nodal line D1-D1′ of the out-of-plane vibration mode A, and the nodal line D1-D1- It is configured to be provided in a region near D1'. The value of Δfex ₄ /Δf ₀ was 1.012 when the non-bonded area ratio of one strip-shaped non-bonded region was 4.4%.

FIG. 5( e ) shows the configuration of Example 5 of the adhesive layer 4 . Example 5 has a configuration in which non-adhesive areas are scattered near the nodal lines D1-D1' and D2-D2' of the out-of-plane vibration mode A. FIG. The value of Δfex ₅ /Δf ₀ was 1.018 when the non-bonded area ratio obtained by adding the areas of the scattered non-bonded regions was 7.4%.

FIG. 6B shows the configuration of Comparative Example 2 of the adhesive layer 4 . Comparative Example 2 has a configuration in which one strip-shaped non-adhesive region is provided in the vicinity of the anti-ablation line C2-C2' of the out-of-plane vibration mode A as the center. The values of Δfc ₂ /Δf ₀ are 0.994, 0.968, and 0.994, 0.968, respectively, when the non-bonded area ratios of one band-shaped non-bonded region are 2.4%, 7.3%, and 12.2%. 0.915.

FIG. 6C shows the configuration of Comparative Example 3 of the adhesive layer 4 . Comparative Example 3 has a configuration in which two strip-shaped non-bonded regions are provided in the vicinity of antinodes C1-C1' and C3-C3' of the out-of-plane vibration mode A, respectively. The value of Δfc ₃ /Δf ₀ was 0.915 when the non-bonded area ratio of the two band-shaped non-bonded regions was 9.8%.

FIG. 6(d) shows the configuration of Comparative Example 4 of the adhesive layer 4. As shown in FIG. Comparative Example 4 has two strip-shaped non-bonded regions extending in the X direction at intermediate portions between antinodes C2-C2′ of out-of-plane vibration mode A and node lines D1-D1′ and D2-D2′. It has a set configuration. The value of Δfc ₄ /Δf ₀ was 0.991 when the non-bonded area ratio of the two band-shaped non-bonded regions was 9.8%.

FIG. 6E shows the configuration of Comparative Example 5 of the adhesive layer 4 . In Comparative Example 5, the piezoelectric ceramic 1 Two belt-shaped non-bonded regions extending in the longitudinal direction (X direction) are provided. The value of Δfc ₅ /Δf ₀ was 0.994 when the non-bonded area ratio of the two strip-shaped non-bonded regions was 9.8%.

FIG. 6( f ) shows the configuration of Comparative Example 6 of the adhesive layer 4 . In Comparative Example 6, one belt-like member extending in the transverse direction (Y direction) at the central portion in the longitudinal direction (X direction) of the piezoelectric ceramic 1 so as to intersect the nodal line and antinode line of the out-of-plane vibration mode A It has a configuration in which a non-bonded area is provided. The value of Δfc ₆ /Δf ₀ was 0.959 when the non-bonded area ratio of one band-shaped non-bonded region was 5.0%.

FIG. 7(a) is a diagram showing the relationship between the non-bonded area ratio and the value of Δfex/ _Δf0 in Examples 1 to 5. FIG. FIG. 7B is a diagram showing the relationship between the non-bonded area ratio and the value of Δfc/Δf ₀ in Comparative Examples 1-6. In Examples 1 to 3, the width (length in the Y direction) and length (length in the X direction) of the non-bonded region were changed, and when the non-bonded area ratio reached 14.6%, the non-bonded region adjusted to have the same shape.

In FIGS. 7A and 7B, the fact that the value of Δfex/ _Δf0 is greater than 1 means that the resonance frequency difference Δf between the out-of-plane vibration modes A and B is large, that is, the power consumption can be reduced. means big. On the other hand, the fact that the value of Δfc/ _Δf0 is smaller than 1 means that the resonance frequency difference Δf between the out-of-plane vibration modes A and B is small, that is, it can be seen that the effect of suppressing power consumption cannot be obtained. Therefore, as in Examples 1 to 5, power consumption can be suppressed by providing a non-bonded region in the region centered on the nodal line of the out-of-plane vibration mode A to increase the non-bonded area ratio. . On the other hand, as in Comparative Examples 2 to 6, when the non-adhesive region is provided in the region centered on the antinode of the out-of-plane vibration mode A, the effect of suppressing the power consumption is not obtained.

In the case where the vibrator 100 is provided with the protrusion 51 as shown in FIG. 2 and the inside of the protrusion 51 is hollow, the area inside the protrusion 51 is a non-bonded area where the piezoelectric element 101 is not bonded. becomes. In this case, in addition to the non-bonded areas in Examples 1 to 5, the non-bonded area ratio of the non-bonded area inside the protrusion 51 may be about 20%. That is, if the non-bonded regions of Examples 1 to 5 are formed, the resonance frequency difference Δf can be made larger than that of Comparative Example 1 even if the non-bonded region is further formed inside the protrusion 51. . However, if the total non-bonded area ratio becomes too large, there is a problem that the vibration excited by the piezoelectric element 101 is difficult to transmit to the elastic body 5, and the vibrator 100 is likely to be broken (the piezoelectric element 101 and the elastic body 5 are likely to break). It becomes easy to peel off) and other problems may occur. Therefore, it is desirable that the non-bonded area ratio, which is the ratio of the area of the non-bonded region to the area facing the elastic body 5 in the piezoelectric ceramics 1, is less than 40%.

Further, as described above, a metal member such as stainless steel is used for the elastic body 5 . Here, when the Young's modulus of the elastic body 5 is small, the neutral plane of bending vibration of the vibrator 100 shifts from the elastic body 5 side to the piezoelectric ceramics 1 side, and as a result, the vibration displacement amount of the vibrator 100 decreases. There is a risk. Therefore, it is desirable that the Young's modulus Yce of the piezoelectric ceramic at 20° C. and the Young's modulus Ysb of the elastic body 5 at 20° C. have a relationship of Yce<Ysb. Here, the reason why 20° C. is used as an example is to take into consideration the average value of the general operating temperature of the general vibrator 100 . If the Young's modulus of the elastic body 5 is small, it is possible to increase the thickness of the elastic body 5 and adjust the neutral plane toward the elastic body 5 side. become. Therefore, from the viewpoint of miniaturizing the vibrator 100 as well, it is desirable to use a material having a Young's modulus larger than that of the piezoelectric ceramics 1 for the elastic body 5 .

Furthermore, in the vibrator 100, the length ratio Nn (%) of the non-bonded region in the length direction of the two nodal lines in the out-of-plane vibration mode A is the length of the anti-node line located between the two nodal lines. It is preferably greater than the length ratio Na (%) of the non-bonded region in the longitudinal direction. This is because the apparent rigidity of the piezoelectric ceramic 1 located on the nodal line of the out-of-plane vibration mode A decreases, and the resonance frequency of the out-of-plane vibration mode A is more selective than the resonance frequency of the out-of-plane vibration mode B. , and the resonance frequency difference Δf can be increased. In Comparative Examples 1 to 6, Nn≦Na, but in Examples 1 to 5, the condition of Nn>Na is satisfied. In general, more vibration modes appear as the shape of the piezoelectric element 101 becomes more complicated and as the symmetry becomes lower. Therefore, from the viewpoint of suppressing the occurrence of vibrations other than the desired vibration mode, it is desirable to provide the non-bonded regions symmetrically with respect to the XZ plane or the YZ plane passing through the center of the piezoelectric element 101 .

By the way, the present invention has been made for the purpose of suppressing power consumption when obtaining a desired vibration displacement in a vibrator using lead-free piezoelectric ceramics. The morphology of the adhesive layer 4 is characteristic. Therefore, the adhesive layer 4 of Examples 1 to 5 described above can be applied not only to vibrators using lead-free piezoelectric ceramics, but also to vibrators using lead-based piezoelectric ceramics. In other words, by adopting the form of the adhesive layer 4 exemplified in Examples 1 to 5 in a vibrator using lead-based piezoelectric ceramics, power consumption can be made smaller than in the prior art.

Next, driving of the piezoelectric element 101 will be described. FIG. 8 shows an embodiment of a vibration wave driving device using the piezoelectric element 101 and vibrator 100 of the present invention. The aspect ratio (long side length/short side length) of the piezoelectric element 101A is different from the aspect ratio of the piezoelectric element 101A. The ratio is not limited. The shape of the elastic body 5 joined to the piezoelectric element 101A can be designed according to the shape of the piezoelectric element 101A.

In the piezoelectric element 101A, a common electrode 21 (first electrode) is provided on one surface of the piezoelectric ceramics 1, drive electrodes 31a and 31b (second electrodes) are provided on the other surface, and drive electrodes 31a and 31b are provided. The power supply member 7 is attached to the surface where the power supply member 7 is mounted. The surface of the piezoelectric element 101A on which the common electrode 21 is formed is adhered via an elastic body (not shown) and an adhesive layer (not shown), and the adhesive layer is formed to have the form of Examples 1 to 5 described above. be. The entire common electrode 21 is not shown in FIG. The common electrode 21 is provided on substantially the entire surface of the piezoelectric ceramics 1 opposite to the surface on which the drive electrodes 31a and 31b are formed, and extends from the center of the long side of the piezoelectric ceramics 1 along the side surfaces of the piezoelectric ceramics 1 to the drive electrodes. It is pulled out to the surface where 31a and 31b are formed. The drive electrodes 31a and 31b are formed with a predetermined gap in the X direction in order to provide the lead portion of the common electrode 21 on the surface on which the drive electrodes 31a and 31b are formed.

The power supply member 7 is, for example, a flexible printed circuit board and includes a power supply line 71 and a ground line 72 . The power supply member 7 has the drive electrodes 31a and 31b in the piezoelectric ceramics 1 so that the power supply line 71 is electrically connected to the drive electrodes 31a and 31b and the ground line 72 is electrically connected to the lead portion of the common electrode 21 . is attached to the surface on which the

An alternating voltage V1 is applied to the drive electrode 31b from the power source through the power supply line 71 of the power supply member 7, and at the same time, an alternating voltage V2 having the same absolute value of amplitude (voltage) as that of the alternating voltage V1 is applied to the drive electrode 31a. Here, when the alternating voltages V1 and V2 are made to have the same phase at a frequency near the resonance frequency fA of the out-of-plane vibration mode _A , the entire piezoelectric element 101A (drive electrodes 31a and 31b) expands and contracts. As a result, vibration of the out-of-plane vibration mode A occurs in the vibrator using the piezoelectric element 101A. Further, when the alternating voltages V1 and V2 are applied at a frequency near the resonance frequency fB of the out-of-plane vibration mode _B with a phase shift of 180°, in the regions of the piezoelectric element 101A where the driving electrodes 31a and 31b are respectively formed, one One shrinks and the other stretches. As a result, vibration of the out-of-plane vibration mode B occurs in the vibrator using the piezoelectric element 101A. In this way, by measuring the frequencies when the respective vibrations of the out-of-plane vibration modes A and B are independently excited using, for example, an impedance analyzer, the resonance frequencies f _A and f A of the out-of-plane vibration modes A and B _fB can be measured.

If the phase difference θ between the alternating voltages V1 and V2 is between 0° and 180° (0°<θ<180°), the vibrations of the out-of-plane vibration modes A and B have a phase difference of 90° ( The phase difference of the oscillations must be either 90° or −90°). Further, by changing the phase difference θ between the alternating voltages V1 and V2, the amplitudes of the out-of-plane vibration modes A and B can be adjusted.

Next, a specific example of a vibration type actuator using the vibrator 100 (100A) will be described. FIG. 9 is a perspective view showing a schematic configuration of a vibration type actuator. A vibrator 100 constituting a vibration type actuator has the structure shown in FIGS. It has a configuration. The two protrusions 51 are desirably provided symmetrically with respect to the XZ plane or the YZ plane passing through the center of the elastic body 5 . The bias is reduced and a stable contact state can be maintained.

As described with reference to FIG. 8, the vibrator 100 is excited to vibrate in the out-of-plane vibration modes A and B with a phase difference of 90°. As a result, the tip of the protrusion 51 can be caused to make an elliptical motion in the ZX plane. The driver 8 is relatively movable in the X direction. The two protrusions 51 are desirably provided on the antinode of the out-of-plane vibration mode A and on the nodal line of the out-of-plane vibration mode B, and the tips of the protrusions 51 and the driven body 8 are applied with a predetermined pressure. Pressure contact is desirable. As a result, it is possible to efficiently apply a thrust force to the driven body 8 by using the elliptical motion generated at the tip of the protrusion 51 by the vibration generated by the vibrator 100 .

Next, an optical device, which is an example of an electronic device using the vibrator 100, will be described. By dynamically connecting the moving body in the vibration type actuator shown in FIG. 9 to the optical member, the optical member can be moved in a predetermined direction. Note that mechanical connection refers to a state in which one member is in direct contact so that force generated by coordinate fluctuation, volume change, or shape change is transmitted to the other member, or contact is made through another member. It refers to the state where In the vibration type actuator, one of the vibrator 100 and the driven body 8 is fixed at a predetermined position and the other moves. Point.

FIG. 10 is a perspective view showing a schematic configuration of the optical device 200. As shown in FIG. Specifically, the optical device 200 is a mechanism for moving a focus lens arranged inside a lens barrel of an imaging device such as a digital camera or a digital video camera in the shooting optical axis direction. In the optical device 200, a rectangular driven body 8 is in pressure contact with the vibrator 100, and the driven body 8 is fixed at a predetermined position within the lens barrel in which the optical device 200 is arranged.

The vibrator 100 (the elastic body 5 thereof) is held by a holding member 211 by welding or the like so as not to generate unnecessary vibrations. A movable housing 212 is fixed to the holding member 211 using screws 213, whereby the holding member 211, the movable housing 212, and the vibrator 100 are integrated. The movable housing 212 is slidably fitted to two guide members 214 fixed at predetermined positions in the lens barrel, and is movable in the length direction of the guide members 214. .

The lens holding member 215 holds the focus lens 216 and is slidably fitted to the two guide members 214 so that the optical axis of the focus lens 216 is substantially parallel to the length direction of the guide members 214 . are in agreement. A connecting member 217 is attached to the holding member 211 , and the connecting member 217 connects the lens holding member 215 to the moving housing 212 so that the guide member 214 does not rattle in the longitudinal direction. As a result, the lens holding member 215 can smoothly move in the length direction of the two guide members 214 integrally with the moving housing 212 .

When a predetermined alternating voltage is supplied from a power source (not shown) to the vibrator 100 through the power supply member 7 connected to the vibrator 100, the protruding portion of the vibrator 100 is generated as described with reference to FIGS. Elliptical motion occurs at 51 (not shown in FIG. 10). As a result, the movable housing 212 , the lens holding member 215 , the holding member 211 and the vibrator 100 are integrally guided by the guide member 214 and moved in the longitudinal direction of the driven body 8 . That is, by moving the focus lens 216 held by the lens holding member 215 in the optical axis direction, it is possible to perform a focusing operation for focusing on the subject.

A scale 219 is attached to the side surface of the lens holding member 215, and when the vibrator 100 is driven, the position information of the scale 219 is received by the sensor 18 fixed at a predetermined position within the lens barrel. read. The position information read by the sensor 218 is sent to a control device (not shown) that controls the power supply, and the control device controls the voltage and phase of the alternating voltage supplied from the power supply to the vibrator 100 . Thereby, the focus lens 216 (lens holding member 215) can be moved to a predetermined position in the optical axis direction.

<Other embodiments>
Although the present invention has been described in detail based on its preferred embodiments, the present invention is not limited to these specific embodiments, and various forms without departing from the gist of the present invention can be applied to the present invention. included. For example, in the above-described embodiment, the piezoelectric element 101 in which the first electrode 2 and the second electrodes 3a and 3b are formed on the substantially rectangular plate-shaped piezoelectric ceramics 1 is taken up. , but not limited to. In other words, the shape of the piezoelectric ceramics is not limited to a substantially rectangular shape, nor is it limited to a flat plate shape, and can be designed in a shape that allows desired vibration to be obtained. Furthermore, a piezoelectric element capable of exciting a desired vibration is provided by forming electrodes in a configuration different from the configuration shown in FIGS. It can also be realized.

Further, in the above-described embodiments, as an electronic device using a vibration-type actuator, an imaging apparatus having a mechanism for moving the focus lens 216 in the photographing optical axis direction using a vibration-type actuator was taken up. However, vibration-type actuators are used in image pickup devices such as a mechanism for moving a zoom lens in the shooting optical axis direction, and an image blur correction lens arranged in a lens barrel for image blur correction on a plane orthogonal to the shooting optical axis. It can also be applied to a mechanism that drives inside. Furthermore, the vibration type actuator can be applied to a mechanism that corrects image blur by driving an imaging device mounted on the imaging apparatus main body in a plane parallel to the imaging surface. Application examples of vibration actuators are not limited to imaging devices, but can be used in drive mechanisms that drive members that require positioning in various electronic devices, thereby realizing electronic devices with low power consumption. be able to.

Reference Signs List 1 piezoelectric ceramics 2 first electrode 3a, 3b second electrode 4 adhesive layer 5 elastic body 8 driven body 100 vibrator 101, 101A piezoelectric element 200 optical device

Claims (9)

A vibrator in which a piezoelectric element having piezoelectric ceramics and electrodes and an elastic body are bonded via an adhesive layer,
The adhesive layer is configured to generate the vibration when the vibrator is excited to vibrate in a primary out-of-plane bending vibration mode in a region where the piezoelectric element and the elastic body overlap when projected in the thickness direction of the adhesive layer. A vibrator characterized by having a non-adhesive region in which the piezoelectric element and the elastic body are not adhered in a region near the nodal line of the vibrator. 2. The vibrator according to claim 1, wherein the ratio of the area of said non-bonded region to the total area of the bonding surface of said piezoelectric element to said elastic body is less than 40%. 2. The vibrator according to claim 1, wherein Young's modulus of said elastic body at 20.degree. C. is greater than Young's modulus of said piezoelectric ceramic at 20.degree. 4. A region near the nodal line is a region closer to the nodal line than an antinode of vibration of the primary out-of-plane bending mode and includes the nodal line. 1. The vibrator according to any one of . 2. The non-adhesive region is a region within 0.073λ with respect to each of the two nodal lines with respect to the primary out-of-plane bending vibration wavelength λ with respect to the direction intersecting the nodal lines. 5. The vibrator according to any one of 4. The length ratio Nn (%) of the non-bonded region in the length direction of the two nodal lines is the length ratio Na of the non-bonded region in the length direction of the abdominal line located between the two node lines. (%). each of the piezoelectric element and the elastic body has a substantially rectangular plate-like shape,
7. The vibrator according to any one of claims 1 to 6, wherein when the first-order out-of-plane bending vibration mode vibration is excited in the vibrator, a nodal line of the vibration appears substantially parallel to a long side of the piezoelectric element. or the vibrator according to item 1. a vibrator according to any one of claims 1 to 7;
and a driven body that contacts the vibrator. a vibration type actuator according to claim 8;
and a member in contact with the vibration type actuator.

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