Vibration type actuator, electronic apparatus, and optical apparatus

Abstract

To provide a vibration type actuator which maintains stable drive performance for a long time period and resists the deterioration of drive efficiency and the occurrence of abnormal sounds (noise).SOLUTION: A vibration type actuator according to the present invention includes a vibration body having an electricity-machine energy conversion element and an elastic body including a plate portion and a projection portion projected in the same direction to the outside of the plane of the plate portion, a contact body that is in contact with the projection portion of the vibration body and moves relatively to the vibration body, a foam member that is in contact with the vibration body, and an urging member that urges the vibration body to the contact body via the foam member. When measuring a loss factor tanδ of the foam member through viscoelasticity measurement by giving vibration to the foam member, the loss factor tanδ of the foam member measured at -20°C after vibration at a frequency of 1 Hz is greater than the loss factor tanδ of the foam member measured at 40°C after vibration at a frequency of 10 Hz.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vibration actuator, an electronic device, and an optical device. [Background technology]

[0002] A vibration actuator has a vibrating body made of an electromechanical energy conversion element such as a piezoelectric element and an elastic body, and a contact body that is in pressure contact with the vibrating body. The vibration actuator is used as a vibration wave motor that moves the contact body relatively by utilizing friction generated by the driving force of vibration excited in the vibrating body.

[0003] The structure and driving principle of a vibration wave motor, which is a type of vibration actuator, are shown in outline. A vibration wave motor has a vibrating body and a contact body that is in pressure contact with the vibrating body by a biasing member. In this case, in order for the biasing member to uniformly pressurize the vibrating body, it is desirable for the rigidity of the biasing member to be increased when it comes into contact with the vibrating body. However, when a highly rigid member comes into contact with the vibrating body, it inhibits the vibration of the vibrating body, causing a deterioration in the driving characteristics of the motor. Therefore, a structure is known in which a member that does not inhibit vibration is disposed between the biasing member and the vibrating body as a vibration damping member.

[0004] Patent Document 1 lists sponge, polystyrene foam, and felt as materials for supporting the vibrating body, and discloses that wool felt is particularly excellent among them. Note that the support for the vibrating body in Patent Document 2 uses a material that does not inhibit vibration, and is considered to have the same function as a vibration damping material.

[0005] Patent document 2 also describes a vibration actuator in which a foamed material is disposed between a vibrating body and a biasing member, and by selecting the average circular equivalent diameter of the cells of the foamed material, stable and sufficient output can be obtained over a long period of time. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 3-289371 [Patent Document 2] JP 2022-83146 A Summary of the Invention [Problem to be solved by the invention]

[0007] When driving a vibration actuator, unnecessary frequency components such as half the input drive frequency may be excited, resulting in problems such as reduced drive efficiency and abnormal noise (crying).

[0008] The present invention has been made to address the above-mentioned problems, and provides a vibration actuator that has stable driving characteristics over a long period of time and reduces the decrease in driving efficiency and the occurrence of abnormal sounds (crying).The present invention also provides electronic devices and optical devices that use a vibration actuator that has stable driving characteristics over a long period of time and reduces the decrease in driving efficiency and the occurrence of abnormal sounds (crying). [Means for solving the problem]

[0009] The vibration actuator of the present invention comprises an electro-mechanical energy conversion element, a vibrating body having an elastic body equipped with a plate portion and a protrusion portion protruding in the same direction outside the plane of the plate portion, a contact portion that contacts the protrusion portion of the vibrating body and moves relatively to the vibrating body, a foamed member in contact with the vibrating body, and a biasing member that biases the vibrating body against the contact portion via the foamed member, and is characterized in that when vibration is applied to the foamed member and the loss factor tan δ of the foamed member is measured by viscoelasticity measurement, the loss factor tan δ of the foamed member measured at -20°C when vibrations having a frequency of 1 Hz are applied is greater than the loss factor tan δ of the foamed member measured at 40°C when vibrations having a frequency of 10 Hz are applied. Effect of the Invention

[0010] According to the present invention, it is possible to provide a vibration actuator that has stable driving characteristics over a long period of time and reduces the decrease in driving efficiency and the occurrence of abnormal sounds (crying). Also, according to the present invention, it is possible to provide electronic devices and optical devices that use a vibration actuator that has stable driving characteristics over a long period of time and reduces the decrease in driving efficiency and the occurrence of abnormal sounds (crying). [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are diagrams illustrating a schematic structure of a vibration actuator of the present invention using a circular or rectangular piezoelectric material. [Diagram 2] 1A to 1C are diagrams illustrating two vibration modes generated by a vibrator of the present invention having a rectangular piezoelectric material. [Diagram 3] FIG. 2 is a schematic cross-sectional view illustrating a foam member according to the present invention. [Figure 4] FIG. 2 is a schematic side view of a foam member according to the present invention. [Diagram 5] 2 is an example of temperature dependence of viscoelastic properties in the foamed material of the present invention. [Figure 6] This is a composite curve obtained from the viscoelastic properties shown in FIG. [Figure 7] FIG. 1 is a diagram showing an FFT (Fast Fourier Transform) analysis of the current input to a vibration actuator. [Figure 8] 1 is a diagram illustrating a schematic structure of an optical device according to the present invention. [Figure 9] FIG. 4 is a diagram showing the driving characteristics of a vibration actuator according to an embodiment of the present invention. [Figure 10] FIG. 1 is a diagram showing a composite curve obtained by a time-temperature conversion rule. [Figure 11] FIG. 13 is a diagram showing an example of measurement results of speed and power versus frequency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described.

[0013] The present inventors have discovered that in a vibration actuator using a foamed material, a decrease in drive characteristics and generation of abnormal noise (crying) may occur. As a result of further investigation, the present inventors have found that by optimizing the viscoelastic characteristics of the foamed material, it is possible to obtain a vibration actuator that has stable drive characteristics over a long period of time and reduces the generation of abnormal noise.

[0014] The vibration actuator of the present invention has a vibrating body, a contact body, a foamed member, and a biasing member. The foamed member of the vibration actuator of the present invention is characterized in that, when vibration is applied by viscoelasticity measurement to measure the loss factor tan δ, tan δ at a vibration frequency of 1 Hz measured at -20°C is greater than tan δ at a frequency of 10 Hz measured at 40°C. Since the loss factor tan δ on the low frequency side of the foamed member is greater than the loss factor tan δ on the high frequency side at the same temperature, vibrations occurring on the low frequency side can be more effectively damped, reducing the generation of abnormal noise.

[0015] The schematic structure of the vibration actuator of the present invention is illustrated in Fig. 1 and Fig. 2. Fig. 1 (a) and (d) are side views of the vibration actuator, (b) and (e) are perspective views, and (c) and (f) are rear views. Fig. 2 (a) shows mode A of the vibration mode, and (b) shows mode B.

[0016] The vibration actuators illustrated in Figs. 1 and 2 use a vibrator with a circular plate portion and a vibrator with a rectangular plate portion, respectively. The vibration actuator 100 of the present invention includes an electromechanical energy conversion element 120 made of an electrode 101 and a piezoelectric material 102. The actuator further includes an elastic body 103 having a plate portion 108 and a protrusion portion 106 protruding in the same direction outside the surface of the plate portion, and these are arranged in order to form a vibrator 110. The vibration actuator 100 further includes a contact body 104 that contacts the protrusion portion 106. In addition, the actuator includes a biasing member 121 for bringing the vibrator 110 into pressure contact with (biasing) the contact body 104, and a foam member 122 provided between the vibrator 110 and the biasing member 121.

[0017] When the vibrating body 110 is driven, the vibrating body 110 and the contact body 104 move relatively. The contact body 104 may be any member that can move relatively to the vibrating body 110, and is not limited to being in direct contact with the vibrating body 110, but may be in indirect contact with the vibrating body 110 via another member. The surface of the electromechanical energy conversion element 120 is urged toward the contact body 104 by the urging member 121 via the foam member 122.

[0018] (Piezoelectric materials) The shape of the piezoelectric material 102 is not important, but if the plate portion is shaped like a ring, the piezoelectric material is preferably also shaped like a ring, and if the plate portion is shaped like a rectangle, the piezoelectric material is preferably also shaped like a rectangle.

[0019] The form of the piezoelectric material 102 is not limited, but may be, for example, a piezoelectric material (sintered body) without crystal orientation, crystal-oriented ceramics, piezoelectric single crystal, etc. The shape that the piezoelectric material can take is not limited, but for example, a layered piezoelectric material may be adopted to form a laminate of electrodes and piezoelectric material, or a single plate of piezoelectric material may be adopted. From the viewpoint of the cost of the piezoelectric material, a single plate is superior. In order to drive a vibration type actuator, a polarization process is performed on the piezoelectric material. When the AC electric field frequency applied to the polarization-processed piezoelectric material approaches the resonant frequency of the piezoelectric material, the piezoelectric material vibrates greatly due to the resonance phenomenon.

[0020] From the viewpoint of environmental load, the lead content of the piezoelectric material used in the electromechanical energy conversion element is preferably 1000 ppm or less.

[0021] (electrode) When a circular piezoelectric material is used, electrodes 101 divided in the circumferential direction are provided on the piezoelectric material to form a circular piezoelectric element. The electrodes 101 consist of a driving phase electrode 101e and a non-driving phase electrode 101f. The circumferential length of the driving phase electrode is 1 / 2 the wavelength λ of the vibration wave generated in the circumferential direction of the circular piezoelectric element when an alternating voltage is applied to the driving phase electrode. The circumferential length of the non-driving phase electrode (ground electrode, monitor electrode) is 1 / 4 of the wavelength λ. The number of driving phase electrodes and non-driving phase electrodes varies depending on the number of traveling waves excited in the circular piezoelectric material. The piezoelectric material corresponding to each driving phase electrode is polarized with a voltage of a different polarity from that of adjacent regions.

[0022] The driving phase electrodes are separated by an odd number of non-driving phase electrodes. After polarization processing, a first electrode 101a and a second electrode 101b are provided to short-circuit the two driving phase electrode groups separated by the non-driving phase electrodes. The first electrode 101a and the second electrode 101b are used to drive a vibration type actuator using a circular annular piezoelectric material.

[0023] When a rectangular piezoelectric material is used, a rectangular electrode 101 is provided. The electrode 101 is composed of a first electrode 101a and a second electrode 101b. The first electrode 101a and the second electrode 101b are used for polarization processing of the rectangular piezoelectric material and for driving a vibration type actuator using the rectangular piezoelectric material.

[0024] The electrodes are made of a metal film with a thickness of about 0.3 to 10 μm. The material is not particularly limited, but silver, gold, or platinum electrodes are generally used. The method for manufacturing the electrodes is not limited, and they can be formed by screen printing, sputtering, vacuum deposition, or the like. In order to manufacture an electromechanical energy conversion element with a lead content of 1000 ppm or less, it is necessary to use a paste or target with a lead content of less than 1000 ppm in forming the electrodes.

[0025] (Elastic body) From the viewpoint of the properties as an elastic body and workability, it is preferable that the elastic body 103 is made of a metal. Examples of metals that can be used for the elastic body 103 include aluminum, brass, and stainless steel. Among stainless steels, martensitic stainless steel is preferable, and SUS420J2 is most preferable. The elastic body has a protrusion 106 that contacts the contact body. To further improve the wear resistance of the protrusion, the elastic body is subjected to quenching, plating, or nitriding.

[0026] It is preferable that the plate portion of the elastic body is rectangular. By making the plate portion of the elastic body rectangular, the manufacturing process of the electromechanical energy conversion element becomes easier, and a small electromechanical energy conversion element can be produced. As a result, it becomes possible to produce a small vibration type actuator.

[0027] (Foam material) 1(a), the foam member 122 is provided on the surface of the electromechanical energy conversion element 120 opposite to the surface on which the elastic body 103 is provided. The foam member 122 uniformly presses the vibrating body 110 against the contact body 104 and is also required to function as a vibration damping member. The function of the foam member 122 as a vibration damping member is to dampen vibrations from adjacent members by absorbing or the like, and the foam member 122 may be provided separately as long as the driving characteristics are not deteriorated.

[0028] Fig. 3 shows a horizontal cross-sectional view (XY plane) of a foamed material of the present invention, and Fig. 4 shows a vertical side view (Z direction) of the foamed material of the present invention. Fig. 4(a) shows a side view of a foamed material without a skin layer on the surface, and Fig. 4(b) shows a side view of a foamed material with a skin layer on the surface.

[0029] When vibration is applied to the foamed material and the loss factor tan δ of the foamed material is measured by viscoelasticity measurement, the tan δ of the foamed material at a frequency of 1 Hz measured at -20° C. is greater than the tan δ at a frequency of 10 Hz measured at 40° C. Because this relationship holds, it is possible to reduce the generation of abnormal noise due to excitation at low frequencies while suppressing the deterioration of the drive characteristics of the vibration actuator.

[0030] The loss factor tanδ of a foamed material can be measured using a dynamic viscoelasticity measuring device. In the dynamic viscoelasticity measuring device, a sinusoidal vibration strain is applied to the foamed material, and the change in stress is observed to measure the frequency dependence of the storage modulus and loss modulus as viscoelastic properties. Tanδ is defined as the loss tangent obtained by dividing the loss modulus by the storage modulus, and can be used as an index of damping capacity.

[0031] There are several methods for applying a sinusoidal vibration strain to a foamed material, including a mode in which both ends of the material are held and pulled, a mode in which a torsion is applied, a mode in which a force is applied in the thickness direction of the material, and a mode in which a force is applied in the thickness direction to twist the material. The method can be selected according to the shape and size of the foamed material to be measured.

[0032] By applying a sinusoidal vibration strain to a foamed material while changing the temperature of the measurement environment and observing the stress change, the temperature change of the viscoelastic properties can be obtained. By evaluating the frequency dependence of the viscoelastic properties while changing the measurement temperature and applying the temperature-time conversion law, the frequency range of the frequency dependence measurement can be expanded. The temperature-time conversion law is a law that uses the fact that the stress relaxation behavior of a viscoelastic material changes depending on the temperature and converts the stress relaxation behavior at different relaxation times. By shifting the measured data to a reference temperature, a composite curve showing the relationship between time and stress is created. This composite curve is called a master curve, and can be plotted as, for example, the loss factor tan δ against the frequency. As a result, it is possible to obtain viscoelastic properties in the high frequency range, for example, from 1,000 Hz to 100 kHz, which is difficult to measure directly. The amount of shift against temperature can be approximated by the WLF law or the Arrhenius law.

[0033] Figure 5 shows some of the results of the viscoelastic properties obtained by applying vibrations with a frequency range of 0.1 Hz to 50 Hz and changing the measurement temperature from -20°C to 60°C, showing the temperature dependence results for 1.58 Hz, 12.6 Hz, and 25.1 Hz. Figure 6 shows the composite curve obtained from the above measurement results when the reference temperature was set to 23°C.

[0034] From the composite curve in Figure 6, for example, the loss factor tan δ is larger at 50 kHz compared to 100 kHz, and it can be seen that the damping performance is high in the low frequency range. A characteristic of a foamed material that has high damping performance in such a low frequency range is that the loss factor tan δ at a vibration frequency of 1 Hz measured at -20°C is larger than the loss factor tan δ at a frequency of 10 Hz measured at 40°C.

[0035] Here, -20°C is a temperature higher than the glass transition temperature at which viscoelastic properties can be obtained stably. 40°C is a temperature higher than the reference temperature for creating a synthetic curve, and is a temperature at which thermal deformation is small and viscoelastic properties can be obtained stably. In particular, since the viscoelastic properties change significantly near the glass transition temperature, it is not preferable to use measurement results including the glass transition temperature. When measuring the viscoelastic properties of the foamed material of the present invention, the foamed material was held under a pressure used in a vibration actuator, for example, a pressure of 600 to 700 g / cm2. It is considered that the viscoelastic properties of the foamed material are stabilized by holding the foamed material under the pressure conditions used once, and this is preferable.

[0036] In order to efficiently reduce the generation of abnormal noise, it is desirable that the loss factor tan δ at a frequency of 30 Hz is 0.2 or more in the composite curve obtained by the time-temperature conversion rule when the reference temperature is 23°C. Also, it is desirable that there is a frequency range in which the loss factor decreases as the frequency increases in the composite curve obtained by the time-temperature conversion rule when the reference temperature is 23°C, because this is expected to have the effect of reducing excitation on the low-frequency side.

[0037] Moreover, the loss factor tan δ of the foamed material when subjected to vibration with a frequency of 10 Hz and measured at −20° C. is desirably 0.1 or more for efficient vibration damping on the low frequency side.

[0038] The foam material preferably contains a siloxane bond (Si-O-Si) consisting of silicon and oxygen. When the foam material contains a siloxane bond (Si-O-Si) consisting of silicon and oxygen, the mobility of the molecules constituting the foam material increases, and it is possible to lower the glass transition temperature of the foam material below the operating temperature range of -30°C. This makes it possible to obtain stable viscoelastic properties over a wide temperature range from high to low, and it is expected that the physical properties of the foam material will be maintained at the same level as at room temperature.

[0039] In the process of producing the foamed material, the crosslinking density and the average circle equivalent diameter of the bubbles can be changed by controlling the heating temperature and time in the curing by heat curing or by the crosslinking reaction caused by mixing two liquid raw materials. 2 More than 700g / cm 2 A foamed material was obtained by heat treatment at a temperature of 60° C. to 80° C. under the following pressure. It is considered that the structure of the foamed material is stabilized by performing the pressurized heat treatment, and this is preferable.

[0040] The foamed material is preferably a sponge containing silicone rubber. Similar effects can also be obtained by substituting some of the methyl groups of the silicone rubber with vinyl groups or phenyl groups. Silicone sponges are preferred because they have smaller volumetric changes in the thickness direction under pressure than felt, and have excellent long-term stability. For example, felt with a pressure of 600 g / cm at room temperature 2 More than 700g / cm 2 When held under the following pressure for 500 hours, the thickness is compressed to about 50% and does not return to its original state even when the pressure is released. On the other hand, silicone sponge returns to almost its original thickness when the pressure is released, so the change in volume is small.

[0041] The foam material is characterized in that the average equivalent circular diameter of the bubbles contained therein is greater than 120 μm.

[0042] The average equivalent circle diameter of the bubbles contained in foamed material 122 is preferably greater than 120 μm. The presence of bubbles in the foamed material allows the foamed material to have spring properties, and the foamed material can uniformly pressurize vibrating body 110 against contact body 104 and function as a vibration damping member.

[0043] The average equivalent circular diameter is preferably calculated from the cross-sectional shape of the foamed material. When the average equivalent circular diameter of the bubbles in the cross section of the foamed material is greater than 120 μm, it is possible to uniformly pressurize the vibrating body while maintaining the driving characteristics of the motor without impeding the vibration of the vibrating body.

[0044] The average circular equivalent diameter of the foamed member 122 can be obtained by a method such as image processing of a cross-sectional image obtained by cross-sectional observation. In order to perform cross-sectional observation, a sample may be cut to expose the cross-section and observed with an optical microscope or a laser microscope. Another method is to obtain a non-destructive cross-sectional image by X-ray CT scanning. If it is possible to confirm the shape of the bubbles, the surface in contact with the electro-mechanical energy conversion element 120 may be treated as the cross-sectional shape. Image processing software may be optimized for a microscope or may be commercially available. Since bubbles of various sizes exist, it is preferable to observe many bubbles when calculating the average circular equivalent diameter. Specifically, it is preferable to calculate the average circular equivalent diameter from 50 or more bubbles.

[0045] The foamed material of the present invention may have columnar cells as shown in Fig. 4(b), or may have a skin layer on the surface of the foamed material. As shown in Fig. 4(b), when a skin layer is present on the surface, the bubbles cannot be accurately confirmed from the surface, so it is preferable to expose the cross section by cutting. The average equivalent circle diameter can be calculated from the obtained cross-sectional photograph by image processing.

[0046] It is preferable that the bubbles in the foamed material are mainly composed of closed bubbles. Closed bubbles refer to bubbles that are not connected to the front and back of the foamed material by bubbles. Closed bubbles are difficult to pass gas or liquid through. For this reason, closed bubbles are preferable for the foamed material to have spring properties. On the other hand, open bubbles have the characteristic that air is easily allowed to enter and exit because the bubbles are connected, and they are easily crushed when pressure is applied, and are undesirable because they have poor spring properties, so there is a risk that the vibrator cannot be pressurized uniformly and the vibration damping function is reduced. It is preferable that the number of closed bubbles is greater than the number of connected bubbles, that is, the number of closed bubbles accounts for 50% or more of the number of bubbles contained in the foamed material. In this case, the number can be counted from a cross-sectional photograph containing 50 or more bubbles.

[0047] It is more preferable that the average equivalent circular diameter of the bubbles of the foamed material is 200 μm or more. In order to realize stable operation within the operating temperature range of the vibration actuator (for example, -30°C to 60°C), it is effective to use a piezoelectric material with a phase transition temperature of -10°C or less for the vibration actuator. In other words, it is effective to use a piezoelectric material whose piezoelectric properties at -10°C are greater than those at room temperature for the vibration actuator. In this case, by making the average equivalent circular diameter of the bubbles 200 μm or more, it is possible to maintain the effect as a vibration damping member in the low temperature range and improve the driving efficiency. It is more preferable that the average equivalent circular diameter of the bubbles is 300 μm or more.

[0048] The average equivalent circular diameter of the foamed member is preferably smaller than 1 / 2 the thickness t of the foamed member. This allows the vibrator to be uniformly pressurized and the foamed member to function as a vibration damping member. More preferably, the foamed member has an average equivalent circular diameter smaller than 1 / 3 the thickness t of the foamed member.

[0049] (contact body) From the viewpoint of rigidity, the contact body 104 is preferably made of stainless steel. Among stainless steels, martensitic stainless steel is preferable, and SUS420J2 is most preferable. The contact body 104 must have excellent wear resistance because it is in frictional contact with the elastic body 103, and its surface is subjected to nitriding or anodizing. A frictional force is generated between the protrusion 106 and the contact body 104 due to the pressurized contact. The tip of the protrusion 106 vibrates elliptically due to the vibration generated by the electromechanical energy conversion element 120, and a driving force (thrust) for driving the contact body 104 can be generated. The contact body is generally called a slider or rotor.

[0050] The "contact body" refers to a member that comes into contact with the vibrating body and moves relative to the vibrating body due to vibrations generated in the vibrating body. The contact between the contact body and the vibrating body is not limited to direct contact with no other member interposed between the contact body and the vibrating body. The contact between the contact body and the vibrating body may be indirect contact with another member interposed between the contact body and the vibrating body, as long as the contact body moves relative to the vibrating body due to vibrations generated in the vibrating body. The "other member" is not limited to a member independent of the contact body and the vibrating body (e.g., a high-friction material made of a sintered body). The "other member" may be a surface-treated portion formed on the contact body or the vibrating body by plating, nitriding, or the like.

[0051] (Piezoelectric vibrator) In the annular piezoelectric element, the piezoelectric material in contact with the adjacent driving phase electrodes is polarized with different polarities, so when an electric field of the same polarity is applied to the driving phase electrode 101e, the expansion and contraction polarity in the corresponding region of the piezoelectric material is alternately reversed at a pitch of λ / 2. When an alternating voltage is applied to the first electrode 101a, a first standing wave with a wavelength λ is generated over the entire circumference of the vibrator. When an alternating voltage is applied to the second electrode 101b, a second standing wave is generated in the same manner, but the position of the wave is rotated by λ / 4 in the circumferential direction relative to the first standing wave. On the other hand, when two types of alternating voltages with the same frequency and a temporal phase difference of π / 2 are applied to the first and second electrodes, the following traveling wave is generated. That is, as a result of the synthesis of the first and second standing waves, a traveling wave (wave number n along the annulus, wavelength λ) of bending vibration (vibration whose amplitude is perpendicular to the surface of the vibrator) that travels in the circumferential direction over the entire circumference is generated in the vibrator.

[0052] When a traveling wave of bending vibration (hereinafter sometimes simply referred to as "bending vibration wave") is generated, each point on the surface of the diaphragm that constitutes the vibrating body moves elliptically, so that the moving body in contact with this surface receives a circumferential friction force (driving force) from the diaphragm and rotates. The direction of rotation can be reversed by switching the positive and negative phase difference of the alternating voltage applied to the first and second electrodes. The rotation speed can also be controlled by the frequency and amplitude of the alternating voltage applied to the first and second electrodes.

[0053] 2 illustrates two vibration modes generated by a vibrator of the present invention having a rectangular piezoelectric material. The rectangular piezoelectric material is provided with a first electrode 101a and a second electrode 101b, and the respective regions are referred to as a first region and a second region.

[0054] Mode A When both the first region and the second region expand or contract, a first bending vibration mode (mode A) is generated. Mode A is excited most strongly when the phase difference between the alternating voltages VA and VB applied to the first electrode 101a and the second electrode 101b is 0° and the frequency is near the resonance frequency of mode A. Mode A is a primary out-of-plane vibration mode in which two nodes (where the amplitude is minimum) appear approximately parallel to the long side of the vibrating body 110. Two protrusions 106 protruding in the same direction in the elastic body are disposed near positions that become antinodes (where the amplitude is maximum) of mode A. Therefore, the tip surfaces of the protrusions 106 reciprocate in the Z direction due to vibration mode A.

[0055] Mode B When the first region expands and contracts, the second region contracts and expands, respectively, and a second bending vibration mode (mode B) is generated. Mode B is excited most strongly when the phase difference between the alternating voltages VA and VB applied to the first electrode 101a and the second electrode 101b is 180° and the frequency is near the resonance frequency of mode B. Mode B is a secondary out-of-plane vibration mode in which three nodes appear approximately parallel to the short sides of the vibrating body 110. The protrusion 106 of the elastic body is disposed near the node position of mode B. Therefore, the tip surface of the protrusion 106 reciprocates in the X direction by mode B.

[0056] In the vibration actuator 100, when the phase difference between the alternating voltages VA and VB is 0 to ±180°, mode A and mode B are excited simultaneously, and elliptical vibration is excited in the protrusion 106 of the elastic body. A vibration actuator that uses a rectangular piezoelectric material and is driven by mode A and mode B is preferable because it can be easily miniaturized.

[0057] It is more preferable that there are two protrusions protruding in the same direction outside the plane of the plate. This is preferable because it is easy to miniaturize the vibration actuator that uses rectangular piezoelectric material and is driven by mode A and mode B as shown in Figure 2.

[0058] In order to prevent vibration inhibition due to deformation of the foam member caused by pressurization, it is preferable that the area of ​​the contact portion between the foam member and the electro-mechanical energy conversion element is smaller than the area of ​​the planar portion of the electro-mechanical energy conversion element including the above portion. In addition, it is preferable that the foam member is smaller than the electro-mechanical energy conversion element. It is expected that the foam member can be expected to suppress problems such as the foam member deforming and wrapping around the side of the foam member and the piezoelectric element, which is the electro-mechanical energy conversion element, inhibiting the vibration of the piezoelectric element, or interfering with surrounding members, inhibiting the vibration. In addition, it is preferable that the foam member is smaller than the elastic body. If the foam member is larger than the elastic body, it may deform and interfere with surrounding members, inhibiting the vibration, so it is expected that the foam member can be expected to suppress problems such as the foam member being smaller than the elastic body.

[0059] (unwanted frequency components) When driving a vibration actuator, unnecessary frequency components such as half the driving frequency may be excited with respect to the input driving frequency. FIG. 7 shows the result of FFT (Fast Fourier Transform) analysis of the current input to the vibration actuator when the input driving frequency is 104 kHz. In addition to the driving frequency of 104 kHz, a large peak is observed around 52 kHz, which is half the driving frequency. One of the factors that generates such a frequency component with a large intensity different from the driving frequency is thought to be unnecessary vibration of the components of the vibration actuator, which is transmitted to the piezoelectric vibrator. As a result, the unnecessary vibration reduces the driving efficiency and generates abnormal noise (crying). The vibration actuator using the foamed material of the present invention can reduce such unnecessary vibration, and can reduce the reduction in driving efficiency and abnormal noise (crying).

[0060] (Composition of piezoelectric material) The composition of the piezoelectric material 102 is not particularly limited as long as it can be used as a vibration type actuator.

[0061] Generally, lead zirconate titanate (PZT)-based materials are used for piezoelectric materials. However, in light of the recent concern over the impact of lead on the environment, it is more preferable to use a piezoelectric material that uses a perovskite-type metal oxide that does not contain lead (lead content is less than 1000 ppm). The lead content can be measured, for example, by ICP atomic emission spectrometry.

[0062] It is more preferable that the piezoelectric material does not contain lead, that is, is lead-free, and the main component is a barium titanate-based material.

[0063] The piezoelectric material is preferably made of a barium titanate-based material, from the viewpoint of high piezoelectric constant and relatively easy manufacturing. Here, 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, and potassium bismuth titanate-barium titanate. The term "main component" refers to a material whose main component is one of these compositions. The term "main component" refers to a material whose weight fraction is greater than 10%.

[0064] Furthermore, piezoelectric materials containing these compositions as main components or in combination can be used for the vibration actuator 100 of the present invention.

[0065] From the viewpoint of excellent temperature dependency of the piezoelectric characteristics within the operating temperature range and being able to balance the piezoelectric constant and mechanical quality factor of the piezoelectric material, the following materials are more preferable: namely, materials that are mainly composed of barium calcium zirconate titanate ((Ba,Ca)(Ti,Zr)O3) and sodium niobate-barium titanate (NaNbO3-BaTiO3).

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

[0067] The piezoelectric material is preferably a piezoelectric material containing an oxide having a perovskite structure containing Ba, Ca, Ti, and Zr, and Mn. It is preferable that x, which is the molar ratio of Ca to the sum of Ba and Ca, is 0.02≦x≦0.30. It is preferable that y, which is the molar ratio of Zr to the sum of Ti and Zr, is 0.020≦y≦0.095 and y≦x, and 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. It is preferable that the content of Mn per 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.

[0068] Such a piezoelectric material can be expressed by the following general formula (1). (Ba 1-x Ca x ) α (Ti 1-y Zr y )O3(1) however, 0.986≦α≦1.100, 0.02≦x≦0.30, 0.02≦y≦0.095 and 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 per 100 parts by weight of the metal oxide.

[0069] In particular, it is preferable that the metal oxide contains Mn, and the content of the Mn is 0.02 parts by weight or more and 0.40 parts by weight or less in terms of metal per 100 parts by weight of the metal oxide. When Mn is contained in this range, the insulating property and the mechanical quality factor Qm are improved. Here, the mechanical quality factor Qm is a coefficient that represents the elastic loss due to vibration when the piezoelectric material is evaluated as a vibrating body, and the magnitude of the mechanical quality factor is observed as the sharpness of the resonance curve in impedance measurement. In other words, it is a constant that represents the sharpness of the resonance of the vibrating body. When the mechanical quality factor Qm is large, the amount of distortion of the piezoelectric material becomes larger near the resonance frequency, and the piezoelectric material can be vibrated effectively.

[0070] The metal oxide represented by the 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.

[0071] In general formula (1), the molar ratio of the B site element to the O element is 1:3. However, even if the molar ratio is slightly different, it is within the scope of the present invention as long as the metal oxide has a perovskite structure as the main phase.

[0072] Whether a metal oxide has a perovskite structure can be determined, for example, by structural analysis using X-ray diffraction or electron beam diffraction.

[0073] In the general formula (1), x, which indicates the molar ratio of Ca in the A site, is in the range of 0.02≦x≦0.30. When a part of Ba in perovskite-type barium titanate is replaced with Ca within the range, the phase transition temperature between the orthorhombic and tetragonal crystals shifts to the lower temperature side, so that stable piezoelectric vibration can be obtained in the driving temperature range of the vibration actuator. However, if x is larger than 0.30, the piezoelectric constant of the piezoelectric material becomes insufficient, and the performance of the vibration actuator may be insufficient. On the other hand, if x is smaller than 0.02, the dielectric loss (tan δ) may increase. If the dielectric loss increases, the heat generated when applying a voltage to the piezoelectric material to drive the vibration actuator may increase, the motor driving efficiency may decrease, and the power consumption may increase.

[0074] In the general formula (1), y, which indicates the molar ratio of Zr in the B site, 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.

[0075] In this specification, Td refers to the lowest temperature at which the piezoelectric constant after heating a piezoelectric material from room temperature to Td one week after polarization treatment and then cooling it back to room temperature decreases by more than 10% compared to the piezoelectric constant before heating.

[0076] In general formula (1), α, which indicates the ratio of the molar amount of Ba and Ca at the A site to the molar amount of Ti and Zr at the B site, is preferably in the range of 0.9955≦α≦1.010. If α is smaller than 0.9955, abnormal grain growth is likely to occur in the crystal grains constituting the piezoelectric material, and the mechanical strength of the piezoelectric material is reduced. On the other hand, if α is larger than 1.010, the piezoelectric material does not become highly densified and the insulation becomes extremely brittle.

[0077] The method for measuring the composition of the piezoelectric material is not particularly limited. Examples of the method include X-ray fluorescence analysis, ICP emission spectrometry, and atomic absorption spectrometry. Regardless of the measurement method used, the weight ratio and composition ratio of each element contained in the piezoelectric material can be calculated.

[0078] The metal equivalent showing 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 spectrometry, atomic absorption spectrometry, etc. From the content, 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.

[0079] If the Mn content is less than 0.02 parts by weight, the effect of the polarization process required for driving the vibration actuator may be insufficient. On the other hand, if the Mn content is more than 0.40 parts by weight, the piezoelectric properties of the piezoelectric material may be insufficient, or crystals with a hexagonal structure that do not have piezoelectric properties may appear. Mn is not limited to metallic Mn, and it is sufficient that it is contained in the piezoelectric material as a Mn component, and the form of its inclusion does not matter. For example, it may be solid-dissolved in the B site or contained in the grain boundary. A more preferable form of inclusion is solid-dissolved in the B site from the viewpoint of insulation and sintering ease.

[0080] The piezoelectric material preferably contains 0.042 parts by weight or more and 0.850 parts by weight or less of Bi calculated as metal.

[0081] The piezoelectric material may contain 0.85 parts by weight or less of Bi in terms of metal, based on 100 parts by weight of the metal oxide represented by the general formula (1). The content of Bi relative to the metal oxide can be measured, for example, by ICP emission spectroscopy. Bi may be present at the grain boundaries of the ceramic piezoelectric material, or may be dissolved in the perovskite structure of (Ba,Ca)(Ti,Zr)O3. When Bi is present at the grain boundaries, friction between particles is reduced and the mechanical quality factor is increased. On the other hand, when Bi is incorporated into a solid solution that forms a perovskite structure, the phase transition temperature is lowered, so that the temperature dependence of the piezoelectric constant is reduced and the mechanical quality factor is further improved. It is preferable that Bi is incorporated into the solid solution at the A site, because this improves the charge balance with Mn.

[0082] The piezoelectric material may contain components (hereinafter, "auxiliary components") other than the elements contained in the general formula (1) and Mn and Bi, to the extent that the characteristics do not change. The total amount of the auxiliary components is preferably 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 auxiliary components exceeds 1.2 parts by weight, the piezoelectric characteristics and insulating characteristics of the piezoelectric material may be degraded. Since non-lead-based piezoelectric materials have a high Young's modulus, they tend to have a higher resonance frequency than lead-based piezoelectric materials. If the resonance frequency is high, the number of vibrations of the vibrating body increases, so that the material becomes sensitive to changes in the vibration damping member arranged between the biasing member and the vibrating body. Therefore, in a vibration type actuator using a non-lead-based piezoelectric material, it is preferable to use a foamed material that has excellent long-term stability and high damping performance.

[0083] It is further preferable that the phase transition temperature is −10° C. or lower, since this provides excellent temperature dependency of the piezoelectric characteristics within the operating temperature range of the vibration actuator (for example, −30° C. to 60° C.).

[0084] The piezoelectric material of the present invention undergoes a successive phase transition from tetragonal to orthorhombic as the temperature is lowered from room temperature. The phase transition temperature referred to in this specification refers to this phase transition. The phase transition temperature is calculated as the temperature at which the dielectric constant is maximized when the dielectric constant is differentiated with respect to the sample temperature by measuring the dielectric constant while changing the temperature. The crystal system can be evaluated by X-ray diffraction, electron beam diffraction, Raman scattering, or the like. The dielectric constant and electromechanical coupling coefficient are maximized and the Young's modulus is minimized near the phase transition temperature. The piezoelectric constant is a function of these three parameters, and shows a maximum value or an inflection point near the phase transition temperature.

[0085] (electronic equipment) The electronic device of the present invention is characterized by comprising the vibration actuator of the present invention, a member connected to the contact body of the vibration actuator, and a member position detection means (e.g., an encoder). The electronic device detects the position of the member and operates the vibration actuator until the member reaches a target position, thereby enabling precise control of the position of the member.

[0086] (optical equipment) The optical device of the present invention is characterized by comprising the electronic device of the present invention and at least one of an optical element and an imaging element. Fig. 8 is a schematic diagram showing one embodiment of the optical device of the present invention (focus lens part of the lens barrel device). In Fig. 8, a vibrating body 110 having a rectangular piezoelectric material is in pressure contact with a contact body (slider) 104 in the same manner as Fig. 1(d).

[0087] The power supply member 507 is connected to the surface side having the first and second regions. When a desired voltage is applied to the vibrating body 110 via the power supply member 507 by a voltage input means (not shown), an elliptical motion occurs in the protrusion of the elastic body (not shown). The holding member 501 is joined to the vibrating body 110 and is configured not to generate unnecessary vibrations. The moving housing 502 is fixed to the holding member 501 with a screw 503 and is integrated with the vibrating body 110. These members form the electronic device of the present invention. By attaching the moving housing 502 to the guide member 504, the electronic device of the present invention can move linearly in both directions (forward and reverse) along the guide member 504.

[0088] Next, a lens 506 (optical member) that plays the role of a focus lens of the lens barrel device will be described. The lens 506 is fixed to a lens holding member 505, and has an optical axis (not shown) parallel to the moving direction of the vibration actuator. The lens holding member 505, like the vibration actuator, moves linearly on two guide members 504 described later to perform focal position adjustment (focusing operation). The two guide members 504 are members that engage the movable housing 502 and the lens holding member 505, enabling the movable housing 502 and the lens holding member 505 to move linearly. With this configuration, the movable housing 502 and the lens holding member 505 can move linearly on the guide members 504.

[0089] Furthermore, the connecting member 510 is a member that transmits the driving force generated by the vibration actuator to the lens holding member 505, and is fitted and attached to the lens holding member 505. This allows the lens holding member 505 to move smoothly in both directions along the two guide members 504 together with the movable housing 502.

[0090] Further, sensor 508 is provided to detect the position of lens holding member 505 on guide member 504 by reading position information from scale 509 affixed to the side surface of lens holding member 505. As described above, the focus lens unit of the lens barrel device is configured by incorporating the above-mentioned respective members.

[0091] 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.

[0092] As another configuration of the vibration type actuator, multiple vibrating bodies may be in contact with one common contact body, and the contact body may be arranged so that the vibration of the multiple vibrating bodies causes relative movement of the multiple vibrating bodies with respect to the multiple vibrating bodies.

[0093] Furthermore, the vibration actuator of the present invention can be applied to medical or engineering fields. Specifically, a wire-driven actuator can be configured that includes a thin member, a wire that is inserted through the thin member and fixed to a part of the thin member, and the vibration actuator described above that drives the wire, and that bends the thin member by driving the wire.

[0094] [Example] 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.

[0095] Example 1 The metal oxide powder was sintered at 1340°C to obtain a piezoelectric material shown in manufacturing composition 1 in Table 2. Manufacturing composition 1 is a composition represented by general formula (1), and the values ​​of x, y, and α shown in Table 2 correspond to the respective values ​​in the above-mentioned general formula (1).

[0096] The obtained piezoelectric material was ground and polished to a thickness of 0.5 mm, and then processed into a circular ring shape with an outer diameter of 62 mm and an inner diameter of 54 mm. The driving phase electrode 101e and the non-driving phase electrode 101f shown in Fig. 1(c) were formed on one side of the shaped piezoelectric material 102. The electrodes were formed by applying silver paste to the piezoelectric material 102 by screen printing, drying, and baking.

[0097] Next, adhesive was applied to elastic body 103 made of SUS420J2, and it was pressed against piezoelectric material 102 on which electrodes were formed. The circular piezoelectric material and the circular elastic body were positioned using a positioning jig so that the centers of their circles were aligned. Next, heat treatment was performed to harden the adhesive. The piezoelectric material with the elastic body pressed against it was heated to a temperature T1 = 160°C and held for 180 seconds, then cooled to room temperature, and the pressure was released to obtain a vibrating body. Next, an FPC coated with ACP was thermocompression-bonded to the electrodes on the piezoelectric material. The thermocompression conditions were temperature T2 = 140°C and holding time of 20 seconds.

[0098] After that, the elastic body SUS420J2 was grounded, and voltages of different polarities were alternately applied to the adjacent driving phase electrodes 101e to perform polarization processing. In the polarization processing, multiple external electrodes connected to a power source were brought into contact with the electrodes used as sensors among the driving phase electrodes 101e and the driven phase electrodes 101f. After that, the electrodes were heated to T3=100°C, and an electric field equivalent to 2 kV / mm was applied for 30 minutes. After that, the electrodes were cooled to 40°C over 40 minutes while the electric field was still applied, and the voltage application was terminated.

[0099] After that, the first electrode 101a and the second electrode 101b were printed and dried to obtain a vibrating body. In the drying process, the temperature of the piezoelectric material was kept below 80°C to prevent depolarization of the piezoelectric material. The obtained vibrating body was pressed into contact with a contact body (rotor) made of SUS420J2 to produce a vibration type actuator. At this time, a foam member was placed between the vibrating body and the biasing member.

[0100] The measurement results of the viscoelastic properties of the foamed material are shown in Figure 9(b), and the composite curve is shown in Figure 10. The properties of the piezoelectric material and the foamed material are shown in Table 1. The foamed material A used in Example 1 was made of silicone rubber, and the proportion of closed cells among the cells was 50% or more. In addition, the tan δ of the foamed material at a frequency of 1 Hz measured at -20°C was greater than the tan δ at a frequency of 10 Hz measured at 40°C.

[0101] [Table 1]

[0102] Example 2 A vibration type actuator was produced in the same manner as in Example 1, except that the shape of the piezoelectric material was different from that in Example 1.

[0103] A piezoelectric material according to manufacturing composition 1 was obtained in the same manner as in Example 1. The obtained piezoelectric material was ground and polished to a thickness of 0.35 mm, and then processed into a rectangle of 8.9 mm x 5.7 mm. The first to third electrodes shown in FIG. 3 were formed on both sides of the shaped piezoelectric material in the same manner as in Example 1.

[0104] Next, adhesive was applied to an elastic body made of SUS420J2, and it was pressed against the rectangular piezoelectric material on which the electrodes were formed. The elastic body used had a rectangular section of 9.1 x 5.8 mm, which was larger than the piezoelectric material, and the thickness of the elastic body was between 0.25 and 0.30 mm. The rectangular piezoelectric material and the elastic body were positioned using a positioning jig so that the centers of the rectangular sections were aligned and the sides of the rectangular sections were parallel. In the pressed state, the piezoelectric material was heated to a temperature of T1 = 160°C and held for 180 seconds, then cooled to room temperature, and the pressure was released to obtain a vibrating body.

[0105] Next, the FPC coated with ACP and the piezoelectric material were pressed together for 20 seconds using a soldering iron at a temperature T2 of 140° C., and the FPC was thermally pressed onto the electrodes provided on the piezoelectric material.

[0106] Next, the piezoelectric material was subjected to a polarization process. In the polarization process, the elastic body was grounded, and external electrodes connected to a power source were brought into contact with the first and second electrodes, respectively. Although the first and second electrodes were already connected to an FPC, they were not entirely covered by the FPC, and the external electrodes used for polarization process were brought into contact with the exposed parts.

[0107] After that, it was heated to T3=100℃, and an electric field equivalent to 2kV / mm was applied for 30 minutes, and then it was cooled to 40℃ for 40 minutes while the electric field was still applied, and then the voltage application was stopped. The vibrator obtained by the above process was pressed into contact with a contact body (slider) made of SUS420J2 to produce a vibration type actuator. At this time, a foam member was placed between the vibrator and the biasing member.

[0108] The properties of the piezoelectric material and the foam material are shown in Table 1. In Example 2, the same foam material A as that used in Example 1 was used.

[0109] Comparative Example 1 A vibration actuator was produced in the same manner as in Example 1, except that foam material E shown in Table 1 was placed between the vibrator and the biasing member. Measurement results of the viscoelastic properties of foam material E of Comparative Example 1 are shown in FIG. 9(a). A composite curve of foam material E of Comparative Example 1 is shown in FIG. 10. Foam material E was made of silicone rubber, and the proportion of closed cells among the cells was 50% or more. In addition, the tan δ of the foam material at a frequency of 1 Hz measured at -20°C was smaller than the tan δ at a frequency of 10 Hz measured at 40°C.

[0110] Comparative Example 2 A vibration actuator was produced in the same manner as in Example 2, except that a foam member E was placed between the vibrating body and the biasing member.

[0111] (Method of evaluating vibration type actuators) A drive test was performed on the vibration actuators of each of the examples and comparative examples by applying an alternating voltage with an amplitude of 130 Vpp to the first and second electrodes, with the phase difference between the voltages of the first and second electrodes being -90° and 90°.

[0112] When the frequency of the AC voltage is swept from a frequency higher than the resonant frequency of vibration mode A and vibration mode B toward the resonant frequency, the contact body is driven in a direction according to the phase difference of the AC voltage and stops after reaching maximum speed. For convenience, the directions of movement when the phase difference is -90° and 90° are called the reverse direction and forward direction, respectively. The maximum speed of the vibration actuator and the frequency at which the maximum speed was reached were measured with a sensor. The power (rated power) at a rated speed lower than the maximum speed was calculated from the current flowing through the drive circuit.

[0113] FIG. 11 shows an example of the measurement results of speed and power versus frequency. The maximum speed and rated power were measured in an environmental atmosphere of 20°C, and the average values ​​in the reverse and forward directions were calculated. The maximum speed and rated power, which are driving performance, were equivalent in Example 1 and Comparative Example 1. In addition, in order to confirm the damping performance of unwanted vibrations, FFT analysis was performed on the current value when a frequency of 30 kHz was input as the driving frequency in Example 1 and Comparative Example 1. In Example 1, the unwanted vibration components, which are 1 / 2 of 30 kHz, were reduced, whereas in Comparative Example 1, no change was observed in the unwanted vibration components.

[0114] The maximum speed and rated power, which are driving performance, were equivalent in Example 2 and Comparative Example 2. In addition, in order to confirm the damping performance of unwanted vibrations, FFT analysis was performed on the current value when a frequency of 104 kHz was input as the driving frequency in Example 2 and Comparative Example 2. In Example 2, the unwanted vibration components, which are 1 / 2 of 104 kHz, were reduced, whereas in Comparative Example 2, no change was observed in the unwanted vibration components.

[0115] (Examples 3 to 5) Vibration actuators Examples 3 to 5 were produced in the same manner as Example 2, except that the type of foam member placed between the vibrator and the biasing member was as shown in Table 1. Each foam member was made of silicone rubber, and the ratio of the number of closed cells among the bubbles was 50% or more. In addition, the viscoelastic properties of each foam member were the same as in Example 1, and tan δ at a frequency of 1 Hz measured at -20°C was greater than tan δ at a frequency of 10 Hz measured at 40°C. In Examples 3 to 5, the current value when a frequency of 104 kHz was input as the driving frequency was analyzed by FFT in order to confirm the damping performance of unnecessary vibration. It was confirmed that the unnecessary vibration component, which is 1 / 2 of 104 kHz, was reduced in all of Examples 3 to 5.

[0116] Example 6 The vibration actuator produced in Example 2 was mechanically connected to an optical member to produce the optical device shown in Figure 8. By controlling the alternating voltage applied to the piezoelectric material based on the position information given to the encoder consisting of a sensor and a scale, it was possible to precisely drive the vibration actuator and the optical member connected to the vibration actuator to the target position. In this optical device, an optical lens was connected to the vibration actuator, and it was confirmed that it had an autofocus function.

[0117] The above has been described using manufacturing composition 1 as an example, but it has been confirmed that even with manufacturing compositions 2 to 46 and lead zirconate titanate (PZT), the driving characteristics of the vibration actuator of the present invention show reduced unwanted vibration components at 1 / 2 the driving frequency, similar to Example 2.

[0118] As described above, it has been found that there is an effect of reducing unnecessary vibrations by making the tan δ of the foamed material at a frequency of 1 Hz measured at -20° C. larger than the tan δ at a frequency of 10 Hz measured at 40° C. By adopting such a configuration, it is possible to provide a vibration actuator that has stable drive characteristics over a long period of time and reduces the decrease in drive efficiency and the occurrence of abnormal noise (crying).

[0119] [Table 2]

[0120] The disclosure of this embodiment includes the following configurations and methods.

[0121] (Configuration 1) a vibrating body having an electromechanical energy conversion element and an elastic body including a plate portion and a protrusion portion protruding in the same direction outside the surface of the plate portion; a contact body that comes into contact with the protrusion of the vibrating body and moves relatively to the vibrating body; A foam member in contact with the vibrator; a biasing member that biases the vibrator to the contact member via the foam member, A vibration actuator characterized in that, when vibration is applied to the foamed material and the loss factor tan δ of the foamed material is measured by viscoelasticity measurement, the loss factor tan δ of the foamed material measured at -20°C when vibration with a frequency of 1 Hz is applied is greater than the loss factor tan δ of the foamed material measured at 40°C when vibration with a frequency of 10 Hz is applied.

[0122] (Configuration 2) 2. The vibration actuator according to claim 1, wherein the foam member contains a siloxane bond (Si—O—Si) consisting of silicon and oxygen.

[0123] (Configuration 3) 3. The vibration actuator according to claim 1, wherein the foam member is a sponge containing silicone rubber.

[0124] (Configuration 4) 4. The vibration actuator according to any one of configurations 1 to 3, wherein the foamed material has bubbles having an average equivalent circle diameter of more than 120 μm.

[0125] (Configuration 5) 5. The vibration actuator according to any one of configurations 1 to 4, wherein the loss factor tan δ of the foamed material measured at −20° C. while being subjected to vibration at a frequency of 10 Hz is 0.1 or more.

[0126] (Configuration 6) The vibration actuator according to any one of configurations 1 to 5, wherein the foamed material has a loss factor tan δ of 0.2 or more when subjected to vibration with a frequency of 30 Hz in a composite curve obtained by a time-temperature conversion rule with a reference temperature of 23°C.

[0127] (Configuration 7) The vibration actuator according to any one of configurations 1 to 6, wherein the foamed material has a frequency range in which the loss factor decreases as the frequency increases in a composite curve obtained by a time-temperature conversion rule.

[0128] (Configuration 8) The electromechanical energy conversion element includes a piezoelectric material and an electrode. 8. The vibration actuator according to any one of claims 1 to 7, wherein the piezoelectric material has a lead content of 1000 ppm or less.

[0129] (Configuration 9) 9. The vibration actuator according to any one of configurations 1 to 8, wherein the plate portion is rectangular.

[0130] (Configuration 10) 10. The vibration actuator according to any one of configurations 1 to 9, wherein the elastic body has two protrusions.

[0131] (Configuration 11) 11. The vibration actuator according to any one of configurations 1 to 10, wherein the foam member is smaller than the electromechanical energy conversion element.

[0132] (Configuration 12) 12. The vibration actuator according to any one of configurations 1 to 11, wherein the foam member is smaller than the elastic body.

[0133] (Configuration 13) 13. The vibration actuator according to any one of configurations 1 to 12, wherein the main component of the electromechanical energy conversion element is a barium titanate system.

[0134] (Configuration 14) 14. The vibration actuator according to any one of configurations 1 to 13, wherein a main component of the electromechanical energy conversion element is barium calcium titanate zirconate.

[0135] (Configuration 15) The material, 15. An electronic device comprising the vibration actuator according to any one of configurations 1 to 14 provided on the member.

[0136] (Configuration 16) At least one of an optical element and an imaging element; 16. An optical device comprising the vibration actuator according to any one of configurations 1 to 15 provided on at least one of the optical devices. [Explanation of symbols]

[0137] 100 Vibration Actuator 101 Electrode 101a 1st electrode 101b 2nd electrode 101c 3rd electrode 101d 4th electrode 101e Driving phase electrode 101f Non-driven phase electrode 102 Piezoelectric Materials 103 Elastic Body 104 Contact body 106 Protrusion 107 Support part 108 Board part 110 Vibration Body 120 Electromechanical Energy Conversion Devices 121 Pressing member 122 Foam materials 133 Bubbles 134 Skin Layer 501 Retaining member 502 Mobile enclosure 503 Bis 504 Guide member 505 Lens holding member 506 Lens 507 Power Supply Materials 508 Sensors 509 Scale 510 Connecting members

Claims

1. a vibrating body having an electromechanical energy conversion element and an elastic body including a plate portion and a protrusion portion protruding in the same direction outside the surface of the plate portion; a contact body that comes into contact with the protrusion of the vibrating body and moves relatively to the vibrating body; A foam member in contact with the vibrator; a biasing member that biases the vibrator to the contact member via the foam member, A vibration actuator characterized in that, when vibration is applied to the foamed material and the loss factor tan δ of the foamed material is measured by viscoelasticity measurement, the loss factor tan δ of the foamed material measured at -20°C when vibration with a frequency of 1 Hz is applied is larger than the loss factor tan δ of the foamed material measured at 40°C when vibration with a frequency of 10 Hz is applied.

2. 2. The vibration actuator according to claim 1, wherein the foamed material contains a siloxane bond (Si--O--Si) consisting of silicon and oxygen.

3. 2. The vibration actuator according to claim 1, wherein the foam member is a sponge containing silicone rubber.

4. 2. The vibration actuator according to claim 1, wherein the foamed material has bubbles having an average equivalent circle diameter of more than 120 [mu]m.

5. 2. The vibration actuator according to claim 1, wherein the foamed member has a loss factor tan δ of 0.1 or more when vibrations having a frequency of 10 Hz are applied and measured at −20° C.

6. 2. The vibration actuator according to claim 1, wherein the foamed material has a loss factor tan δ of 0.2 or more when subjected to vibration with a frequency of 30 Hz in a composite curve obtained by a time-temperature conversion rule with a reference temperature of 23° C.

7. 2. The vibration actuator according to claim 1, wherein the foamed member has a frequency range in which the loss factor decreases as the frequency increases in a composite curve determined by a time-temperature conversion rule.

8. The electromechanical energy conversion element includes a piezoelectric material and an electrode.

2. The vibration actuator according to claim 1, wherein the piezoelectric material has a lead content of 1000 ppm or less.

9. 2. The vibration actuator according to claim 1, wherein the plate portion is rectangular.

10. 2. The vibration actuator according to claim 1, wherein the elastic body has two protrusions.

11. 2. The vibration actuator according to claim 1, wherein the foam member is smaller than the electromechanical energy conversion element.

12. 2. The vibration actuator according to claim 1, wherein the foam member is smaller than the elastic body.

13. 2. The vibration actuator according to claim 1, wherein the main component of the electromechanical energy conversion element is a barium titanate system.

14. 2. The vibration actuator according to claim 1, wherein a main component of said electromechanical energy conversion element is barium calcium zirconate titanate.

15. The material, An electronic device comprising the vibration actuator according to claim 1 provided on the member.

16. At least one of an optical element and an imaging element; An optical device comprising the vibration actuator according to claim 1 provided on at least one of the first and second surfaces.

Images