Vibration wave motor, optical apparatus, and electronic apparatus

Abstract

To provide a vibration wave motor provided with an electric-machinery energy conversion element in which circuit loss is small and the number of layers is less relative to outputted machinery energy.SOLUTION: A vibration wave motor for solving the above problem rotates a contact body about a center axis of a first elastic body by exciting a vibration body in two bending vibration modes of displacing the vibration body in a direction orthogonal to the center axis. The electric-machinery energy conversion element is formed by alternately layering active layers which are polarized piezoelectric bodies, and electrode layers. The number of the active layers is at least two. The number of the electrode layers is at least three. When the thickness of the active layers is t1, 0.26 mm≤t1≤1.00 mm is satisfied.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] There are various known configurations of vibration wave motors using electromechanical energy conversion elements such as piezoelectric elements. For example, there is a vibration wave motor that is driven by pressurizing a rotor, which is a contact body, against a Langevin type vibration body that is configured by sandwiching a piezoelectric element between an elastic body such as stainless steel. The driving principle of this type is that by applying a predetermined AC voltage (hereinafter also referred to as "driving voltage") to the piezoelectric element, two bending vibrations perpendicular to the vibration body are generated, causing elliptical or circular motion on the surface of the elastic body, and the rotor is rotated by frictional force.

[0003] Piezoelectric elements are made from piezoelectric material, a representative material that has the electro-mechanical energy conversion function of converting electrical energy into mechanical energy, and are used in a wide variety of piezoelectric actuators, including oscillatory wave motors and piezoelectric actuators.

[0004] Recently, in addition to single plate-shaped piezoelectric elements, multi-layer piezoelectric elements in which multiple piezoelectric layers and electrode layers are alternately stacked and sintered together, and elements in which single plate-shaped sintered piezoelectric elements are stacked and bonded together, are being used. This is because stacking allows for large displacement and force to be obtained at a low voltage compared to single plate-shaped piezoelectric elements. In particular, multi-layer piezoelectric elements sintered together are suitable for miniaturization and thin layering.

[0005] Incidentally, the electrode layers of this integrally fired multilayer piezoelectric element must be made of platinum or an alloy of silver and palladium in order to withstand the firing temperature of the piezoelectric body. However, because palladium and platinum are precious metals, this increases the cost of the multilayer piezoelectric element.

[0006] In response to this, Patent Document 1 proposes a method of lowering the palladium ratio by adding a sintering aid to the piezoelectric body and lowering the firing temperature. However, because the sintering aid does not contribute to the piezoelectric properties, this method has the problem of lowering the piezoelectric constant of the piezoelectric body by about 10%.

[0007] To address this issue, if the number of layers is reduced without changing the sintering temperature, it is possible to reduce the amount of silver and palladium used while maintaining the piezoelectric constant. However, simply reducing the number of layers and applying a voltage to compensate for it would result in an increase in current and larger circuit losses. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2012-191733 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides a vibration wave motor including an electromechanical energy conversion element having small circuit loss and a small number of laminations relative to the output mechanical energy. [Means for solving the problem]

[0010] The oscillatory wave motor that solves the above problems is as follows: a vibrator having a first elastic body, a second elastic body, and an electromechanical energy conversion element sandwiched between the first elastic body and the second elastic body; a contact body that contacts the first elastic body, a vibration wave motor for rotating the contact body around a central axis by exciting the vibrator in two bending vibration modes having different spatial phases that are displaced in a direction perpendicular to a central axis of the first elastic body by applying a voltage to the electromechanical energy conversion element, The electromechanical energy conversion element is formed by alternately stacking active layers, which are polarized piezoelectric bodies, and electrode layers, The active layer has two or more layers, and the electrode layer has three or more layers, When the thickness of the active layer is taken as t1, the thickness satisfies 0.26 mm≦t1 ≦1.00 mm. Effect of the Invention

[0011] According to the present invention, it is possible to provide a vibration wave motor including an electromechanical energy conversion element which has small circuit loss and a small number of laminations relative to the output mechanical energy. [Brief description of the drawings]

[0012] [Figure 1] 1 is an exploded view of a vibration wave motor according to a first embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a vibration wave motor according to a first embodiment of the present invention; [Diagram 3] Vibration mode shape of a vibration wave motor according to a first embodiment of the present invention [Figure 4] FIG. 1 is an enlarged cross-sectional view of the vicinity of a laminated piezoelectric element of a vibration wave motor according to a first embodiment of the present invention; [Diagram 5] FIG. 1A is a multilayer piezoelectric element according to a first embodiment of the present invention, and FIG. [Figure 6] Graph showing the relationship between the number of active layers and the required applied voltage according to the first embodiment of the present invention. [Figure 7] Graph showing the relationship between the number of active layers and the capacitance according to the first embodiment of the present invention. [Figure 8] Graph showing the relationship between the number of active layers and heat loss of a circuit according to the first embodiment of the present invention. [Figure 9] Graph showing the relationship between the appropriate number of active layers and the active layer thickness according to the first embodiment of the present invention. [Figure 10] FIG. 1A is a multilayer piezoelectric element having two active layers according to a first embodiment of the present invention, and FIG. 1B is an exploded view of the same. [Figure 11] Graph showing the relationship between the appropriate number of active layers and capacitance according to the second embodiment of the present invention. [Figure 12]13A and 13B are a top view and a block diagram showing a schematic configuration of an imaging device using a vibration wave driven device according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An example of a vibration wave motor for implementing the present invention is as follows.

[0014] The vibration wave motor includes a vibrator having a first elastic body, a second elastic body, and an electro-mechanical energy conversion element sandwiched between the first elastic body and the second elastic body, and a contact body in contact with the first elastic body. This vibration wave motor is a vibration wave motor that rotates the contact body around the central axis by applying a voltage to the electro-mechanical energy conversion element to excite the vibrator in two bending vibration modes that are displaced in a direction perpendicular to the central axis of the first elastic body.

[0015] The electromechanical energy conversion element has a structure in which an active layer, which is a polarized piezoelectric body, and an electrode layer are alternately laminated, the active layer has two or more layers, and the electrode layer has three or more layers. When the thickness of the active layer is t1, the relationship of 0.26 mm≦t1 ≦1.00 mm is satisfied.

[0016] Hereinafter, examples of the embodiments of the invention will be described in detail with reference to the drawings. The term "contact body" as used below 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. EXAMPLES

[0017] [Embodiment of the invention] Fig. 1 is an exploded view of a vibration wave motor according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view of the vibration wave motor according to the first embodiment of the present invention. The basic principle of the vibration wave motor of this embodiment will be described with reference to Figs. 1 and 2.

[0018] Reference numeral 1 denotes a first elastic body, 2 denotes a second elastic body, 3 denotes a laminated piezoelectric element (electrical-mechanical energy conversion element), 4 denotes a flexible printed circuit board, 5 denotes a shaft, and 6 denotes a nut. The first elastic body 1, the second elastic body 2, the laminated piezoelectric element 3, and the flexible printed circuit board 4 are fastened by the shaft 5 and the nut 6 so as to apply a predetermined clamping force, forming a rod-shaped vibrating body 15 whose central axis is in the direction in which the shaft 5 extends.

[0019] The laminated piezoelectric element 3 includes electrode groups (phase A and phase B) each consisting of two electrodes. AC voltages of different phases are applied to each electrode group from a power source (not shown) via a flexible printed circuit board 4. As a result, two bending vibrations with different spatial phases that displace the vibrator 15 in a direction perpendicular to the central axis of the first elastic body are excited. FIG. 3 shows the vibration modes. FIG. 3(a) shows a state where no voltage is applied, FIG. 3(b) shows a vibration mode in which the vibrator bends in the X direction (left-right direction on the paper), and FIG. 3(c) shows a vibration mode in which the vibrator bends in the Y direction (vertical direction on the paper).

[0020] Furthermore, by adjusting the phase of the applied AC electric field, a time phase difference of 90 degrees can be given to these two vibration modes, which have a spatial phase difference of 90 degrees around the central axis of the vibrating body described above. As a result, the bending vibration of the vibrating body 15 rotates around the central axis, and an elliptical motion is generated on the first elastic body 1. Then, by pressing the contact portion 7 of a contact body described later into contact with the first elastic body 1, the frictional force causes the contact portion 7 to rotate around the Z axis (central axis).

[0021] The contact body includes a contact portion 7 and a rotor ring 8. The contact portion 7 has a small contact area with the first elastic body 1 and is structured to have moderate springiness. The material of the contact portion 7 is preferably stainless steel, which has abrasion resistance, strength, and corrosion resistance, and is more preferably SUS420J2. It can be processed by lathe processing or 3D printer, but press processing is preferable in terms of processing accuracy and cost. The contact portion 7 can be bonded with a resin adhesive, brazed with metal such as solder, or It is fixed to the rotor ring 8 by welding such as laser welding or resistance welding, or by mechanical joining such as press fitting or crimping.

[0022] The rotor ring 8 is pressurized by a pressure spring 10 via rubber 9. This pressure creates friction between the contact portion 7 of the contact body and the first elastic body 1, allowing the contact body to be driven by the elliptical motion described above. The rubber 9 works to equalize the pressure and reduce unnecessary vibration of the spring 9 and the rotor ring 8.

[0023] A gear 11 that transmits output to the outside is provided on the upper surface of the rotor ring 8 in the Z direction in the figure, and a recess is formed on the upper surface of the rotor ring 8, which engages with a protrusion formed on the gear 11. As described above, the contact part 7 rotates around the Z axis (central axis) due to the elliptical motion and frictional force on the first elastic body 1. Therefore, the rotor ring 8 fixed to the contact part 7, the gear 11 engaged with the rotor ring 8, and the pressure spring 10 and rubber 9 sandwiched between them rotate together around the Z axis (central axis), and the gear 11 transmits output to the outside. Since the gear 11 slides against the flange cap 12 while being subjected to pressure, a material that satisfies strength and wear resistance is preferable, and in consideration of cost and quietness, a resin containing reinforced fibers is most preferable.

[0024] The vibrating body 15 is fixed to the flange 13, which is a fixed member, by the shaft 5 and the nut 14. Between the gear 11 and the flange 13, a flange cap 12, which is a pressure receiving member, is provided. The flange cap 12 may be fixed to the flange 13 with an adhesive or the like. A material that is wear-resistant is preferable for the flange cap 12. Stainless steel press processing is more preferable because it has good dimensional accuracy and good productivity. In addition, since the flange 13 has a complex shape, it is made by resin molding, zinc die casting, aluminum die casting, or metal sintering. In this embodiment, zinc die casting is used, which has a good balance between dimensional accuracy and cost. The gear 11 and the flange cap 12 slide in the axial direction, and the gear 11 and the flange 13 slide in the radial direction, acting as a sliding bearing.

[0025] FIG. 4 is an enlarged view of (DT B) in FIG. 2. The laminated piezoelectric element 3 is formed by alternately laminating active layers 3-1 and electrode layers 3-3, which are polarized piezoelectric bodies, and the bottom and top layers are provided with inactive layers 3-2, which are unpolarized piezoelectric bodies. The active layer 3-1 is polarized by applying a DC voltage to the electrode layer 3-3 during manufacturing, and expands and contracts in the Z direction due to the inverse piezoelectric effect by applying an AC voltage to the electrode layer 3-3, exciting the above-mentioned vibration. The inactive layer 3-2, which is also a piezoelectric body, plays a role as a lapping margin in double-sided lapping during manufacturing and as an insulating layer between the first elastic body 1. The electrode layer 3-3 polarizes the active layer 3-1 during manufacturing, and applies a voltage to the active layer 3-1 during operation.

[0026] FIG. 5(a) is a perspective view of the multilayer piezoelectric element 3, and FIG. 5(b) is a view showing it disassembled into each layer. The active layer 3-1 is composed of an electrode part 3-4 on which an electrode layer 3-3 is formed, and a non-electrode layer 3-5 on which no electrode layer 3-3 is formed, and the non-electrode layer 3-5 is naturally not polarized. The electrodes of each layer are divided into four parts at 90 degrees intervals, and in the figure, A+, A-, B+, and B- are formed on the same layer, and AG+, AG-, BG+, and BG- are also formed on another adjacent same layer, and these are laminated alternately. The electrode layers formed on the same layer are not conductive with each other, but the electrode layers are conductive with each other by through-hole electrodes 3-6 extending in the Z direction. For example, the A+ electrode on the first layer and the A+ electrode on the third layer are conductive. The through-hole electrodes 3-6 are exposed on the surface of the multilayer piezoelectric element 3, and a voltage is applied to each electrode by pressing the flexible printed circuit board 5 into contact with it.

[0027] The polarization process is performed by applying DC voltages (+) to A+, (-) to A-, (+) to B+, and (-) to B- to A+, A-, B+, and B- of each electrode layer 3 and to the grounds AG+, AG-, BG+, and BG- via the through-hole electrodes 3-6. In other words, with respect to the grounds AG+, AG-, BG+, and BG-, A+ has polarity (+), A- has polarity (-), B+ has polarity (+), and B- has polarity (-).

[0028] The laminated piezoelectric element 3 is manufactured by first making a green sheet that will become the piezoelectric layer from the piezoelectric material and organic binder by the doctor blade method, and then forming the electrode layer 3-3 and the connection electrode 3-6 made of electrode material paste at predetermined positions on the green sheet by screen printing. A predetermined number of these green sheets are then stacked on a flat surface and laminated under pressure, and the piezoelectric layer and electrode layer are integrated and fired, after which a polarization process is performed and the product is finished by double-sided lapping.

[0029] In order to integrally fire the piezoelectric layer and the electrode layer in this way, the electrode material needs to be an expensive precious metal with a high heat resistance, such as platinum or a palladium-silver alloy, so that it can withstand the firing temperature. In other words, the more layers there are, the more electrode layers 3-3 are used, and the higher the manufacturing cost of the multilayer piezoelectric element 3 becomes.

[0030] Taking this into consideration, the present embodiment sets the number of layers in the active layer 3-1 to five. However, as the number of layers is reduced, the force generated decreases proportionately, so it is necessary to compensate for the decrease in force by increasing the voltage. Figure 6 shows the relationship between the number of active layers and the required applied voltage when generating the same force. It can be seen that the number of active layers and the applied voltage are inversely proportional to each other.

[0031] Meanwhile, the relationship between the number of active layers and capacitance is shown in Figure 7. In Figure 7, ◯ (white circle) is a plot when the number of active layers is changed while the thickness of the active layers is kept constant, and ◇ (white diamond) is a plot when the number of active layers is changed while changing the thickness of the active layers so that the overall length of the multilayer piezoelectric element 3 is constant. When the active layer thickness is constant, the number of active layers is proportional to the capacitance, whereas when the overall length is constant, in addition to the effect of the number of layers, the thickness of the active layers is also proportional to the capacitance, so the square of the number of active layers is proportional to the capacitance.

[0032] Figure 8 is a graph showing the relationship between the number of active layers and the heat loss of the circuit. Here, the heat loss on the primary side of the transformer circuit is proportional to the square of the current on the primary side and can be expressed by the following formula. P ∝ (I1) 2

[0033] Here, when the active layer thickness is constant, if the applied voltage required when there is one active layer is V, the capacitance is C, and the winding ratio of the transformer is N, then when the number of active layers is n, the voltage is V / n, the capacitance is C×n, and the winding ratio is N / n times. From the above, the primary side current and heat loss P are calculated as follows: I1 ∝(C × n × V / n × N / n) P ∝ (C × n × V / n × N / n) 2 P ∝ (C V N / n) 2

[0034] In other words, when the active layer thickness is constant, the fewer the number of active layers, the greater the heat loss, as shown in Figure 8. The heat loss on the secondary side is also inversely proportional to the square of the number of active layers, and the graph plots the sum of the heat losses on the primary and secondary sides.

[0035] On the other hand, when the total length is constant, the voltage is V / n and the capacitance is C×n when the number of active layers is n. 2 , the winding ratio is N / n times. From the above, the heat loss P is calculated as follows: I1 ∝(C×n 2 ×V / n×N / n) P ∝ (C × n 2 ×V / n×N / n) 2 P ∝ (C V N) 2

[0036] In other words, if the overall length is constant, the heat loss will be a constant value regardless of the number of active layers. The same applies to the heat loss on the secondary side. Therefore, by keeping the overall length of the multilayer piezoelectric element 3 constant, it is possible to reduce the number of layers while maintaining the efficiency of the oscillatory wave motor, and by reducing the amount of internal electrodes used, it is possible to reduce manufacturing costs.

[0037] FIG. 9 shows the relationship between the number of active layers and the thickness suitable for achieving the effect of the present invention. If the thickness of the active layer 3-1 is thin, the capacitance increases and the circuit loss increases as described above, so it is preferable that the thickness is 0.26 mm or more (broken line A in FIG. 9). On the other hand, if it is too thick, polarization becomes difficult, so it is preferable that the thickness is 1.00 mm or less (broken line B in FIG. 9). In addition, when the thickness of the active layer 3-1 of the laminated piezoelectric element 3 is t1 and the number of layers is n, n×t1 is preferably 1.07 mm or more (broken line C in FIG. 9) and 3.03 mm or less (broken line D in FIG. 9). This is because the total length of the laminated piezoelectric element 3 is too small or too large, and the vibration shape of the vibrating body deviates from the desired one, and the driving efficiency of the motor decreases. In addition, if the number of active layers is less than two layers, it exceeds the limit of the applied voltage that can be increased, so it is preferable that the number is 2 or more (broken line E in FIG. 9). In this way, by setting the relationship between the number of active layers and the capacitance in the area surrounded by dashed lines A to E (shaded area in Figure 9), it is possible to achieve both reduced manufacturing costs and good motor efficiency by reducing the amount of internal electrodes used.

[0038] From the viewpoint of the amount of electrodes used, it is preferable that the number of active layers is two or more and four or less, and the configuration of a multilayer piezoelectric element 3 with two layers is shown in Fig. 10. Here, the number of active layers is two and the thickness is 0.9 mm. This makes it possible to minimize the amount of electrodes used.

[0039] In any example, it is preferable to satisfy T ≥ 30 × t2 and t1 ≥ 2 × t2, where t2 is the thickness of the inactive layer 3-2 and T is the overall length (total thickness) of the laminated piezoelectric element 3. This is because if the inactive layer 3-2 is thick, it will increase the axial size of the vibration wave motor and cause vibration inhibition. EXAMPLES

[0040] The appropriate range of capacitance in this embodiment will be described with reference to FIG. 11. The configuration of the vibration wave motor is the same as that in the first embodiment, so the description will be omitted. If the capacitance is C and the unit of C is nF, and the number of layers of the active layer is n, then the appropriate range of capacitance is 0.05n 2 nF (Dotted line G in Figure 11) ≦ C ≦ 0.14n 2 nF (dotted line F in FIG. 11).

[0041] This is because if the capacity is too small compared to the number of active layers, the generated force will be small, and if it is too large, the circuit loss will be large as described above. The number of active layers is preferably 2 or more (Dotted line E in Fig. 11) as in Example 2, and 14 layers or less from the viewpoint of reducing the amount of electrodes used (Dotted line H in Fig. 11).

[0042] In this way, by setting the relationship between the number of active layers and the capacitance within the shaded area surrounded by dashed lines E to H, it is possible to achieve both reduced manufacturing costs and good motor efficiency by reducing the amount of internal electrodes used. EXAMPLES

[0043] The vibration wave driving device can be used, for example, for driving lenses in imaging devices (optical devices, electronic devices), etc. As an example, an imaging device that uses a vibration wave driving device to drive a lens arranged in a lens barrel will be described.

[0044] 12(a) is a top view showing a schematic configuration of an imaging device 700. The imaging device 700 includes a camera body 730 equipped with an imaging element 710 and a power button 720. The imaging device 700 also includes a lens barrel 740 having a first lens group (not shown), a second lens group 320, a third lens group (not shown), a fourth lens group 340, and vibration type driving devices 620 and 640. The lens barrel 740 is replaceable as an interchangeable lens, and a lens barrel 740 suitable for a subject to be photographed can be attached to the camera body 730. In the imaging device 700, the second lens group 320 and the fourth lens group 340 are driven by the two vibration type driving devices 620 and 640, respectively.

[0045] Although the detailed configuration of the vibration type driving device 620 is not shown, the vibration type driving device 620 has a vibration wave driving device and a driving circuit of the vibration wave driving device. The rotor 211, which is composed of the contact portion 7 and the rotor main ring 8, is arranged in the lens barrel 740 so that the radial direction is approximately perpendicular to the optical axis. In the vibration type driving device 620, the rotor 211 is rotated around the optical axis, and the rotation output of the contact body is converted into linear motion in the optical axis direction via gears (not shown), thereby moving the second lens group 320 in the optical axis direction. The vibration type driving device 640 has a configuration similar to that of the vibration type driving device 620, and moves the fourth lens group 340 in the optical axis direction.

[0046] 12(b) is a block diagram showing a schematic configuration of the imaging device 700. The first lens group 3a0, the second lens group 320, the third lens group 330, the fourth lens group 340, and the light amount adjustment unit 350 are disposed at predetermined positions on the optical axis inside the lens barrel 740. Light passing through the first lens group 3a0 to the fourth lens group 340 and the light amount adjustment unit 350 forms an image on the imaging element 710. The imaging element 710 converts the optical image into an electrical signal and outputs it, and the output is sent to the camera processing circuit 750.

[0047] The camera processing circuit 750 performs amplification, gamma correction, and the like on the output signal from the image sensor 710. The camera processing circuit 750 is connected to the CPU 790 via an AE gate 755, and is also connected to the CPU 790 via an AF gate 760 and an AF signal processing circuit 765. The video signal that has been subjected to a predetermined process in the camera processing circuit 750 is sent to the CPU 790 via the AE gate 755, the AF gate 760, and the AF signal processing circuit 765. The AF signal processing circuit 765 extracts high frequency components from the video signal to generate an evaluation value signal for autofocus (AF), and supplies the generated evaluation value to the CPU 790.

[0048] The CPU 790 is a control circuit that controls the overall operation of the imaging device 700, and generates control signals for determining exposure and adjusting focus from the acquired video signal. The CPU 790 adjusts the optical axis positions of the second lens group 320, the fourth lens group 340, and the light amount adjustment unit 350 by controlling the driving of the vibration type driving devices 620, 640 and the meter 630 so as to obtain the determined exposure and an appropriate focus state. Under the control of the CPU 790, the vibration type driving device 620 moves the second lens group 320 in the optical axis direction, the vibration type driving device 640 moves the fourth lens group 340 in the optical axis direction, and the light amount adjustment unit 350 is driven and controlled by the meter 630.

[0049] The optical axis direction position of the second lens group 320 driven by the vibration type driving device 620 is detected by a first linear encoder 770, and the detection result is notified to the CPU 790, thereby being fed back to the driving of the vibration type driving device 620. Similarly, the optical axis direction position of the fourth lens group 340 driven by the vibration type driving device 640 is detected by a second linear encoder 775, and the detection result is notified to the CPU 790, thereby being fed back to the driving of the vibration type driving device 640. The optical axis direction position of the light amount adjustment unit 350 is detected by an aperture encoder 780, and the detection result is notified to the CPU 790, thereby being fed back to the driving of the meter 630. [Explanation of symbols]

[0050] 1 First Elastic Body 2 Second Elastic Body 3. Multilayer Piezoelectric Element 3-1 Active layer 3-2 Inactive layer 3-3 Electrode layer 4. Flexible Printed Circuit Boards 5 Shaft 6 Nuts 7 Contact Part 8 Rotor ring 9. Rubber 10 Pressure spring 11 Gear 12 Flange cap 13 Flange 14 Upper nut 15 Vibration body

Claims

1. a vibrating body having a first elastic body, a second elastic body, and an electromechanical energy conversion element sandwiched between the first elastic body and the second elastic body; a contact body that contacts the first elastic body, a vibration wave motor that rotates the contact body around the central axis by exciting two bending vibration modes in which the vibrator is displaced in a direction perpendicular to the central axis of the first elastic body by applying a voltage to the electromechanical energy conversion element, The electromechanical energy conversion element is formed by alternately stacking active layers, which are polarized piezoelectric bodies, and electrode layers, the active layer is two or more layers, and the electrode layer is three or more layers, A vibration wave motor characterized in that, when the thickness of the active layer is t1 [mm], 0.26≦t1≦1.00 is satisfied.

2. 2. The oscillatory wave motor according to claim 1, wherein, when the number of layers of the active layer is n, 1.07≦n×t1≦3.03 is satisfied.

3. The vibration wave motor according to claim 1 or 2, characterized in that an inactive layer, which is a non-polarized piezoelectric material, is arranged on the top and bottom layers of the electromechanical energy conversion element, and when the thickness of the inactive layer is t2 [mm], t1 ≧ 2 × t2 is satisfied.

4. 3. The oscillatory wave motor according to claim 1, wherein when the total thickness of the electromechanical energy conversion element is T, T≧30×t2 is satisfied.

5. 3. The oscillatory wave motor according to claim 1, wherein the number of layers of the active layer is two or more and four or less.

6. a vibrating body having a first elastic body, a second elastic body, and an electromechanical energy conversion element sandwiched between the first elastic body and the second elastic body; a contact body that contacts the first elastic body, In a vibration wave motor, a voltage is applied to the electromechanical energy conversion element to excite two bending vibration modes in the vibrating body, which are displaced in a direction perpendicular to the central axis of the first elastic body, thereby rotating the contact body around the central axis, The electromechanical energy conversion element is formed by alternately stacking active layers, which are polarized piezoelectric bodies, and electrode layers, the active layer is two or more layers, and the electrode layer is three or more layers, When the capacitance of the electromechanical energy conversion element is C [nF] and the number of layers of the active layer is n, 0.05n ２ ≦ C ≦ 0.14n ２ A vibration wave motor characterized by satisfying the above.

7. an optical element; An optical device comprising the oscillatory wave motor according to any one of claims 1 to 6.

8. The components and An electronic device comprising the oscillatory wave motor according to any one of claims 1 to 6 for driving the member.

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