JP2725767B2 - Vibration wave drive - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a vibration wave driving device that generates mechanical power without using electromagnetic force, and is particularly suitable for being mounted on a small portable device such as a camera. The present invention relates to a small and light vibration wave driving device. [Background of the Invention] There are various types of rotary power generators, which are motors in a broad sense, according to the principle of power generation. The so-called electric motor, which generates a mechanical rotary force using electromagnetic force, is the smallest and practical. Therefore, the electric motor is known as a motor in a narrow sense. Recent advances in technology have made electric motors (i.e., motors) very small, so small motors have also been installed in various small portable devices, such as cameras, and the performance of the motors has been reduced. Contribute to the improvement of However, a small motor mounted on a camera or the like can rotate at a high speed, but cannot generate a large torque at a low speed, so a deceleration mechanism is necessary.
There is a disadvantage that the volume of the power generation mechanism including the motor and the reduction mechanism is considerably increased due to the reduction mechanism. Therefore, development of a small and lightweight motor that can generate a large torque at low speed without requiring a speed reduction mechanism has been desired. Under such circumstances, in recent years, attempts have been made to use a piezoelectric element as a power generation source, and as a result, a vibration wave motor as a vibration wave driving device that converts vibration generated by the piezoelectric element into rotary motion. Has recently been developed. This known vibration wave motor has an annular stator and an annular rotor, and generates a progressive elastic bending wave in the stator by a piezoelectric element that is annularly bonded to an end face of the stator. Thus, the rotor that is in contact with the end face of the stator is configured to rotate. Since this known vibration wave motor can generate a large torque at a low speed, it does not require a speed reduction mechanism. Therefore, it is suitable as a motor for mounting on a small device such as a camera, and because it has an annular shape. It is suitable as a motor for autofocus of a camera. FIG. 1 (a) is an example showing the technology of a vibration wave motor developed by the present inventors prior to the present invention (hereinafter referred to as a prior art).
FIG. 1 (b) is a left side view of FIG. 1 (a). In FIG. 1, reference numeral 1 denotes a rotor configured as a stepped annular body, and the rotor 1 is supported by a structural member (not shown) so as to be rotatable about its own axis. On the inner peripheral surface of the small diameter portion of the rotor 1, a flexible coating material 1a having a large friction coefficient is fixed by bonding or the like. A vibrating rod 2 as a vibrating body for causing the rotor 1 to perform a rotational movement is disposed parallel to the axis of the rotor 1, and a tip of the vibrating rod 2 is inserted into a small diameter portion of the rotor 1 and the tip Is positioned so that the upper surface of the substrate is close to the coating material 1a of the small diameter portion. The vibrating bar 2 is configured as a square bar having a rectangular cross-sectional shape in the prior art, and the outer peripheral surface of the vibrating bar 2 is configured by a pair of horizontal planes and a pair of vertical planes. Piezoelectric elements (electrical-mechanical energy conversion elements) 3 and 4 as vibration excitation means for generating a circular or elliptical orbital vibration displacement at the tip of the vibrating rod 2 are arranged on the vertical surface of the vibrating rod 2. It is adhered to the horizontal surface, respectively. The bonding position of the piezoelectric elements 3 and 4 is a central position in the longitudinal direction of the vibrating rod 2 and is bonded to a position that is an antinode of vibration generated in the vibrating rod 2. On the outer peripheral surface of the vibrating rod 2, a thin hole is formed at a position serving as a node of the vibration generated in the vibrating rod 2, and thin supporting rods 5 and 6 fitted into the narrow hole and fixed to the vibrating rod 2. Project from the vertical plane and the horizontal plane of the vibrating rod 2, respectively. The support rod 5
And 6 are steel wires, and both ends of the support rod 5 are provided with support rings 7.
, And both ends of the support rod 6 are fixed to a support ring 8. The support rings 7 and 8 are rings having the same inner diameter and the same outer diameter. The support rings 7 and 8 are fitted into the spigot portions at both ends of a cylindrical support base 10 and have a fixing ring 9. And is fixed to the support base 10. The support 10 is elastically supported on a stationary member (not shown) by a spring 11 and is urged vertically upward by the spring 11. Accordingly, the vibrating rod 2 is also urged toward the coating 1a of the rotor 1 by the force of the spring 11. Three adhesive terminals 12 to 14 are provided on the lower surface of the support base 10, and the adhesive terminals 12 to 14 are connected to a control circuit. The connection terminal 12 is connected to the piezoelectric element 3 via a lead, and the connection terminal 13 is connected to the piezoelectric element 4 via a lead. The connection terminal 14 is a ground terminal, and is connected to the vibrating rod 2 by a lead wire. The vibrating rod 2 is grounded via the connecting terminal 14, the support 10 and the spring 11. Next, vibrations generated in the vibrating rod 2, the principle of generating the vibration, and a method of supporting the vibrating rod 2 will be described with reference to FIG. As shown in FIG. 2 (b), when the piezoelectric element 4 is fixed on a horizontal plane in the middle part of the vibrating rod 2 and a positive voltage is applied to the piezoelectric element 4, for example, the piezoelectric element central axial force to Chijimimo in (longitudinal direction) acts, Therefore vibrating rod 2 is elastically deformed as indicated by a curve C _1. When a negative voltage is applied to the piezoelectric element 4, a force is applied to the piezoelectric element 4 to extend the piezoelectric element 4 in the longitudinal direction.
It is elastically deformed upwardly convex as indicated by a curve C _2. Therefore,
Vibrating rod 2 each time of changing the polarity of the voltage applied to the piezoelectric element 4 is vibrated in the vertical direction and elastically deformed as indicated by a curve C ₁ and C _2, the neutral line of the vibrating rod 2 is vibrating rod 2 elastically deformed there is S ₁ and S ₂ points not at all also displaced, S ₁ this point
And S ₂ is a section of the so-called vibration. Therefore, the vibration energy at this point S ₁ and S ₂ is zero, this point
Fixing the vibrating rod 2 in S ₁ and S ₂ (support) and not the vibration is attenuated even. Therefore, it is fixed to the vibrating rod 2 supporting rods 5 and 6 of the at points S ₁ and S _2. By applying an alternating voltage to the piezoelectric element 3 in the same manner as the piezoelectric element 4, the vibrating rod 2 also vibrates in the lateral direction.
When the longitudinal vibration (vibration in the y direction) generated by the piezoelectric element 4 and the lateral vibration (vibration in the x direction) generated by the piezoelectric element 3 are simultaneously applied to the vibrating rod 2, the end of the vibrating rod 2 is at the center of the vibrating rod 2. Vibrates so as to draw a circular orbit in the xy plane about the axis Z. By changing the level of the voltage applied to the piezoelectric element 3 and the piezoelectric element 4, the vibration trajectory drawn by the tip of the vibrating rod 2 can be freely changed from a perfect circle to an ellipse. Further, by shifting the phase, the ellipse can be tilted. However, both piezoelectric elements 3 and 4 are made to draw a horizontally long elliptical orbit (that is, an elliptical orbit whose diameter is parallel to the x-axis) at the tip of the vibrating rod 2. It is desirable to set the level and phase difference of the applied voltage with respect to. Figure 2 (c) is a diagram showing an alternating voltage V ₂ applied to the alternating voltage V ₁ and the piezoelectric element 4 to be applied to the piezoelectric element 3, FIG. 2 (d) shows the alternating voltage V to the piezoelectric element 3 ₁ shows the elliptical vibration generated at the end portion of the vibrating rod 2 when applying an alternating voltage V ₂ to the piezoelectric element 4 at the same time the application of a. Note that, as a property of the piezoelectric element, when the vibrator is in a resonance state, the alternating displacement has a phase delayed by 90 ° from the alternating voltage. displacement will correspond to each time the instantaneous voltage of ~ the alternating voltage V ₁ and V ₂ applied to the piezoelectric element 3 and 4 as shown in FIG. 2 (c). That is, the voltage V ₁ applied to the piezoelectric element 3 at the time of the time in FIG. 2 (c) is V ₁ = 0, since the voltage V ₂ applied to the piezoelectric element 4 is V ₂ = V _m vibration The tip of the rod 2 makes a maximum displacement in one direction along the + y axis, and at time V ₂ = 0 and V ₁ = V _n , the tip of the vibrating rod 2
Make the maximum displacement in the x direction. Between the times, the bending stress in the x direction and the bending stress in the y direction act on the vibrating rod 2 simultaneously and with mutually different magnitudes. Therefore, as shown in FIG. Moves in an elliptical orbit. The tip of the vibrating rod 2 moves along the path of →→ in the movement locus of FIG.
Contact with the coating material 1a on the inner peripheral surface of the rotor 1 to apply a rotational force to the rotor 1, and the rotor 1
Away from the covering material 1a. FIG. 3 is a diagram showing the relative positional relationship between the vibrating bar 2 and the rotor 1 and the movement of the vibrating bar 2. In FIG. 3, the vibrating bar 2 is at a position where it does not contact the inner peripheral surface of the rotor 1. However, when the vibrating bar 2 is vibrated by the piezoelectric elements 3 and 4, each point of the vibrating bar 2 Since the vibration of the circular orbit or the elliptical orbit occurs as shown by the arrow, the vibrating rod 2 contacts the inner peripheral surface of the rotor 1 in the upper half of the circular orbit or elliptical orbit, and the rotor 1 It is rotated under the force F in the direction. In order to increase the contact area between the vibrating rod 2 and the rotor 1, the outer surface of the vibrating rod 2 facing the inner peripheral surface of the rotor 1 may be formed in a convex curved surface instead of a horizontal plane. May be formed in a curved surface. The number of vibrating rods is not limited to one, and several vibrating rods may be arranged in parallel. FIG. 4 is a block diagram showing a configuration of the vibration excitation means including the piezoelectric elements 3 and 4. In FIG. 4, reference numeral 15 denotes a power supply circuit for generating a sine wave voltage of, for example, Asin ωt, 16 denotes a phase shifter for shifting the phase of the output voltage Asin ωt generated by the power supply circuit 15 by an arbitrary value φ, and 17 and 18 denote a phase shifter. amplifier amplification factor B ₁ and B _2, is. Since the piezoelectric element 3 is connected to the output terminal of the amplifier 17, a voltage of V ₁ = AB ₁ sin ωt is applied to the piezoelectric element 3, and the piezoelectric element 4 is connected to the output terminal of the amplifier 18. 4 is applied with a voltage of V ₂ = AB ₂ sin (ωt−φ). Therefore, voltages having phases shifted by φ from each other are applied to the piezoelectric element 3 and the piezoelectric element 4, so that the z-axis (the axis in the longitudinal direction of the vibrating rod 2) is applied to the tip of the vibrating rod 2 in the xy plane.
(In the case of B ₁ = B ₂ , φ = 90 × (2n−1) ° (n = 0, ± 1, ± 2, ± 3...)), Circular vibration, φ ≠ In the case of 90 × (2n−1) °, an inclined elliptical vibration occurs.) Although the case where the voltage applying means for the piezoelectric elements 3 and 4 is constituted by an analog circuit is shown, it is obvious that the voltage applying means may be constituted by a digital circuit. is there. Further, the waveform of the voltage applied to the piezoelectric element does not need to be limited to a sine wave, and various voltages can be used. In the above-described prior art of the present invention, since there is no annular stator such as a known vibration wave motor, there is no danger of vibration damping, so that high energy efficiency can be obtained and stable rotation can be achieved. can get. In addition, since there is no difficulty in supporting the stator for preventing vibration attenuation as in the case of the annular stator, it is practical and can be easily mounted on various devices. FIG. 5 shows that the vibrating rod for driving the rotor is provided on the outer peripheral side of the rotor and the inner peripheral side of the rotor, and the rotor is rotated while sandwiching the inner and outer peripheral surfaces of the cylindrical portion of the rotor with both vibrating rods. This is another prior example configured. In FIG. 5, 2A is a first vibrating rod arranged close to the outer peripheral surface of the small diameter portion of the rotor 1, 2B is a second vibrating rod arranged close to the inner peripheral surface of the small diameter portion of the rotor 1, and 3A is a vibrating rod. Rod 2A
In the figure, a first piezoelectric element for generating vibration in the front-rear direction in the figure, 3B is a second piezoelectric element for generating vibration in the front-rear direction on the vibration bar 2B in the figure, and 4A is vertical in the figure on the vibration rod 2A. The first piezoelectric element for generating vibration in the direction 1B, 4B is the second piezoelectric element for generating vibration in the vertical direction in the vibrating rod 2B in the figure, and 19 is the small diameter of the rotor 1 for both the vibrating rods 2A and 2B. A spring urges the inner and outer peripheral surfaces of the portion close to each other. Reference numeral 20 denotes a support that supports both vibrating rods 2A and 2B in substantially the same manner as in the prior example of FIG. (Note that
Naturally, two piezoelectric elements are adhered to both the vibrating rods 2A and 2B on the horizontal plane and the vertical plane of the vibrating rods, similarly to the previous example of FIG. In the other prior example of FIG. 5, the vibrating rod 2A is also provided close to the outer peripheral surface side of the cylindrical portion of the rotor 1, so that there is no possibility that the rotor 1 vibrates in the radial direction, and the rotation of the rotor 1 is prevented. , And a larger driving torque than that of the prior example shown in FIG. 1 can be obtained. In the case of the other prior art in FIG. 5, the vibrating rod 2A arranged on the outer peripheral side of the rotor 1 is vibrated in a direction opposite to the vibration direction of the other vibrating rod 2B. That is, as shown in FIG. 5 (b), counterclockwise vibration is excited in the vibrating rod 2A, and clockwise vibration is excited in the vibrating rod 2B. Further, as a vibrating rod provided in the vibration wave driving device of another prior art in FIG. 5, two vibrations which can be engaged with the inner peripheral surface and the outer peripheral surface of the rotor as shown in FIG. 6 (b). Rods 22A and 22B
May be used at one end side. In FIG. 6 (b), 22
a is a support rod corresponding to the support rod 5 of the prior example of FIG. 1, and the support rod 22a is provided at the position of the node of the vibration generated in the vibrating rod 22 as in the prior example of FIG. is there. Also,
In FIG. 6 (b), 3A, 4A and 3B indicate piezoelectric elements. FIG. 7 is a schematic sectional view of an interchangeable lens 23 incorporating the vibration wave driving device according to another prior art of FIG. In the interchangeable lens shown in FIG. 7, the vibrating rod assembly for rotating the rotor 1 is present only on a part of the circumference of the rotor 1. Therefore, when the vibration wave driving device is incorporated in the interchangeable lens, the helicoid ring 23a is used. A large empty space 23b is generated outside the space. Therefore, an electronic device such as a control circuit can be accommodated in the empty space 23b, and as a result,
The utilization rate of the space in the interchangeable lens can be increased. [Object of the Invention] An object of the present invention is to provide a vibration wave driving device that can be made smaller and lighter and can obtain a high torque, based on the technology of the above-mentioned prior art. [Summary of the Invention] A vibration wave driving device according to the present invention is a vibration wave driving device including a vibrating body and an electro-mechanical energy conversion element for vibrating the vibrating body, wherein the vibrating body is a non-driving unit. , And first and second portions provided so as to sandwich the intermediate portion. At least one of the first and second portions is a driving portion, and the intermediate portion is the first portion. ,
By making the cross-sectional area smaller than that of the second portion, the rigidity is lower than the rigidity of the first and second portions, and the conversion element is joined to the intermediate portion, and the vibrating body is formed by synthetic vibration. A plurality of vibrations in different directions are generated so that the driving unit vibrates so as to draw a circular or elliptical trajectory around a line connecting the first part and the second part. Embodiment of the Invention Hereinafter, an embodiment of the present invention will be described with reference to FIG. In the two prior examples shown in FIGS. 1 and 5, the shape and structure of the vibrating rod are not limited to those shown in the drawings, and it is obvious that various shapes and structures can be adopted. For example, if you want to increase the vibration amplitude or make the vibration stronger, you need to increase the length and mass of the vibrating rod.However, increasing the length of the vibrating rod increases the overall length of the motor. Therefore, in order to increase the vibration without increasing the length of the vibrating rod, as shown in FIG. 6A as an embodiment of the present invention, a large mass
It is preferable to use a vibrating rod 21 having 21a, that is, a vibrating rod 21 whose rigidity is reduced by making the cross-sectional area of an intermediate portion sandwiched between both ends smaller than that of both end portions. When a voltage is applied to the piezoelectric elements 3 and 4 in the same manner as in the previous example, the vibrating rod 21 shown in FIG. 6 (a) also has one of the large mass portions 21a centered on a line (axis) connecting both ends.
Make a circular or elliptical motion. In the illustrated vibration wave driving device, a piezoelectric element is used as a means for applying an alternating bending load to the vibration bar.
It is clear that an alternating bending load generating means other than the piezoelectric element may be used if the size is small. [Effects of the Invention] As described above, in the vibration wave driving device of the present invention,
Compact and lightweight, large vibration displacement and high torque can be achieved. For example, when mounted on an interchangeable lens of a camera, the space utilization rate in the interchangeable lens can be increased, and driving with large power Is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (a) is a longitudinal sectional view of a main part of one prior art of the present invention, and FIG.
FIG. 2 (b) is a left side view of FIG. 1 (a), and FIGS. 2 (a) and 2 (b) are views for explaining a vibrating rod provided in the apparatus of FIG. 1 and a supporting structure thereof. FIG. 2 (c) shows a waveform of a voltage applied to two piezoelectric elements attached to the vibrating rod, and FIG. 2 (d) shows a waveform of a vibration generated at the tip of the vibrating rod. FIG. 3 is a diagram showing a locus, FIG. 3 is a diagram showing a positional relationship between a tip portion of the vibrating body and a rotor, and FIG. 4 is a block diagram showing a vibration exciting means for generating vibration on the vibrating rod. FIG. 5 (a) is a longitudinal sectional view of a main part of another prior art of the present invention, FIG. 5 (b) is a partial side view of FIG. 5 (a) viewed from the left side, and FIG. 6 (a) is a perspective view showing one embodiment of the present invention, FIG. 6 (b) is a perspective view of another modification of the prior art relating to the vibrating rod shown in FIG. 5, and FIG. Other prior examples in the figure The is a longitudinal sectional view of the assembled in configured interchangeable lens. DESCRIPTION OF SYMBOLS 1 ... Rotor 2,2A, "B, 21,22 ... Vibrating rod 3,3A, 3B ... Piezoelectric element 4,4A, 4B ... Piezoelectric element 5,6,22a ... Support rod 7,8 ... Support ring 9 ... Fixing ring 10,20 ... Support 11 ... Spring 12-14 ... Connection terminal 15 ... Power supply circuit 16 ... Phase shifter 17,18 ... Amplifier 19 ... Spring 23 ... Interchangeable lens 23a ... Helicoid ring

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-61-229077 (JP, A)                 JP-A-62-259485 (JP, A)                 Shokai Sho 59-155892 (JP, U)

Claims (1)

(57) [Claims] A vibration wave driving device having a vibrating body and an electro-mechanical energy conversion element for vibrating the vibrating body, wherein the vibrating body is provided so as to sandwich the intermediate part as a non-driving part and the intermediate part. First and second parts, at least one of the first and second parts is a drive unit, and the intermediate part has a smaller cross-sectional area than the first and second parts. The stiffness is lower than the stiffness of the first and second parts, the conversion element is joined to the intermediate part, and the driving unit of the vibrating body is combined with the first part and the first part by synthetic vibration. A vibration wave driving device that generates a plurality of vibrations in different directions so as to vibrate in a circular or elliptical trajectory around a line connecting the second portions.