JP5322431B2 - Vibration wave driving apparatus and apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillatory wave driving device wherein the production of unwanted oscillatory waves can be suppressed without great influence on the production of driving oscillatory waves regardless of the relation between the order of driving oscillatory waves and the order of unwanted oscillatory waves. <P>SOLUTION: Multiple grooves 1a radially extended from inside to outside are formed on one end face (upper face) of the vibrating body 1 of a vibration motor M. The portions of the vibrating body 1 between the grooves 1a form protrusions 1b brought into a rotor 3 under pressure. Each groove 1a is so formed that its depth ta varies along one sinusoidal curve. Each portion 1c with a groove 1a formed therein constitutes a portion where mainly bending vibration is caused. Since the depth ta of each groove 1a varies along one sinusoidal curve, the thickness tc of each portion 1c varies along one sinusoidal curve. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a vibration wave driving apparatus that excites a bending vibration wave of a predetermined order as a driving vibration wave in a vibrating body, and drives a moving element by the driving vibration wave excited by the vibrating body, and an apparatus using the same. .

  One of the vibration wave driving devices is a vibration wave motor. This vibration wave motor excites a bending vibration wave of a predetermined order m (m is an integer of 1 or more) as a drive vibration wave (progressive vibration wave), and is moved by the drive vibration wave excited by the vibration body. It drives the child. The m-th order bending vibration wave refers to a bending vibration wave having m waves. Here, due to factors such as inaccuracy of the contact surface where the vibrating body and the moving element contact each other, unevenness of mechanical vibration generated in the vibrating body, unevenness of the contact pressure distribution between the vibrating body and the moving element, Bending vibration waves other than the set order m bending vibration waves (drive vibration waves), so-called unnecessary vibration waves, may be generated. This unnecessary vibration wave causes generation of abnormal noise, reduction of output, and the like.

  Therefore, in order to reduce the generation of unnecessary vibration waves, a configuration has been proposed in which a part having bending rigidity different from other parts is provided on the vibrator (see, for example, Patent Document 1). In addition, a configuration has been proposed in which a difference is provided in the bending rigidity and a portion where the bending rigidity is lower than others is provided over a predetermined angle range (see, for example, Patent Document 2).

  A vibration wave motor in which a configuration in which a bending rigidity is different from that of other parts is used for the vibrator will be specifically described with reference to FIG. FIG. 18 is an exploded perspective view of a main part of a conventional vibration wave motor.

  As shown in FIG. 18, the vibration wave motor includes a vibrating body 101 made of a ring-shaped elastic member to which a ring-shaped piezoelectric element 102 (electromechanical energy conversion element) is bonded. The vibrating body 101 constitutes a vibrator in cooperation with the piezoelectric element 102. A plurality of grooves 101a having a depth h1 are formed in the vibrating body 101, and a portion 101c between the grooves 101a constitutes a protrusion for expanding vibration and amplitude. The part 101c, that is, the protrusion 101c is in pressure contact with a moving element (not shown).

  By applying a voltage to the piezoelectric element 102, a seventh-order bending vibration wave (a bending vibration wave having seven waves) is excited in the vibrating body 101 as a driving vibration wave. A mover (not shown) that is in pressure contact with each protrusion 101 c is rotationally driven by a driving vibration wave excited by the vibrating body 101.

In order to achieve the above object, a vibration wave driving device of the present invention includes a vibrator and an vibrator having an electromechanical energy conversion element that excites a bending vibration wave of a predetermined order in the vibration body as a driving vibration wave. A moving element that contacts the vibrating body of the vibrator and is driven by a driving vibration wave excited by the vibrating body, wherein the vibrating body includes a portion where bending vibration occurs and a portion where bending vibration occurs a projecting, a plurality of projections in contact with the moving element, from a plurality of grooves is provided between the plurality of protrusions, wherein the vibrating body, the site where the bending vibration occurs, the vibration The thickness in the axial direction of the vibrating body of the portions overlapping with the plurality of grooves in the axial direction of the body changes along a curve defined by at least one sine wave with respect to the traveling direction of the driving vibration wave Like Is, the plurality of protrusions, the plurality of such projections is contactable with the moving element in the axial direction of said vibrating body, and having a height corresponding to the curve.

  Here, each groove 101b is arranged at a position that is an integral multiple of the wavelength λ of the third-order bending vibration wave or an integral multiple of ½ thereof. That is, the grooves 101b are arranged at an angular pitch of θ = π / 3 (rad) in the circumferential direction of the vibrating body 101, and the number thereof is six. The depths h1 and h2 of the grooves 101a and 101b satisfy the relationship of h2> h1. Accordingly, the bending rigidity of the six portions where the grooves 101b are respectively formed is smaller than the bending rigidity of the portion where the grooves 101a are formed.

  When a third-order bending vibration wave is generated in the vibrating body 101, the antinodes and nodes of the vibration of the third-order bending vibration are approximately equally spaced at six locations along the circumferential direction of the ring-shaped elastic body 1, respectively. To position. That is, depending on the generation position of the third-order bending vibration wave, the positions of the six grooves 101b and the six vibration antinodes all coincide, or the positions of the six grooves 101b and the six vibration nodes. Happens to all match. The antinode of vibration is a position where the maximum value of the bending vibration displacement is taken and a position where the maximum value of the bending deformation is taken. For this reason, when the six grooves 101b and the positions of the six vibration antinodes all coincide, the natural frequency of the vibration wave is lowered. When the positions of the six grooves 101b and the six vibration nodes all coincide with each other, the vibration nodes are positions where the bending deformation becomes zero, and thus the natural frequency does not change much.

In order to excite the tertiary vibration wave as a progressive vibration wave, the standing wave vibration in which the positions of the antinodes of the six grooves 101b and the six vibrations all coincide, and the six grooves 101b and the six vibration waves are It is necessary that standing wave vibrations in which the positions of the vibration nodes all coincide are generated at the same frequency at the same time. Therefore, in the configuration of FIG. 18 in which the two natural frequencies are different, when the self-excited vibration of the third-order bending vibration is generated as a progressive vibration wave and propagates in the vibrator in one direction, the third-order bending vibration The wave is not excited as a progressive vibration wave, and generation of a third-order bending vibration wave that is an unnecessary vibration wave is suppressed.
JP-A-2-214477 JP-A-3-145974

  However, the conventional configuration for reducing the generation of the unnecessary vibration wave described above can excite the drive vibration wave when the order of the bending vibration wave that becomes the drive vibration wave is a multiple of the order of the unnecessary vibration wave. I found out that sometimes I can't. In other words, depending on the relationship between the order of the drive vibration wave and the order of the unnecessary vibration wave, the generation of the unnecessary vibration wave may not be suppressed.

  Accordingly, an object of the present invention is to provide a vibration that can suppress the generation of an unnecessary vibration wave without greatly affecting the generation of the drive vibration wave, regardless of the relationship between the order of the drive vibration wave and the order of the unnecessary vibration wave. The object is to provide a wave drive device and a device using the same.

  In order to achieve the above object, the present invention provides a vibrator having an oscillating body and an electromechanical energy conversion element that excites a bending vibration wave of a preset order in the oscillating body as a driving vibration wave, and the vibrator A movable body that is in contact with the vibration body and is driven by a driving vibration wave excited by the vibration body, and the vibration body has a thickness where a bending vibration deformation occurs in a traveling direction of the driving vibration wave. Thus, a vibration wave driving device is provided that is configured to change along a curve defined by at least one sine wave.

  In order to achieve the above object, the present invention provides an apparatus using the vibration wave driving device.

  According to the present invention, it is possible to suppress the generation of the unnecessary vibration wave without greatly affecting the generation of the drive vibration wave regardless of the relationship between the order of the drive vibration wave and the order of the unnecessary vibration wave.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the reason why the generation of the unnecessary vibration wave cannot be suppressed depending on the relationship between the order of the driving vibration wave and the order of the unnecessary vibration wave will be described.

  The natural frequency ν of the vibrating body 101 with respect to bending vibration waves of the same order is approximately proportional to the square root of the ratio of the cross-sectional secondary moment I to the linear density ρ. That is, the natural frequency ν is expressed by the following relational expression.

ν∝ (I / ρ) ^0.5
When the thickness of the portion where bending occurs in the vibrating body 101 is t ′, the cross-sectional secondary moment I is proportional to the third power of the thickness t ′, and the linear density ρ is proportional to the first power of the thickness t ′. To do. Therefore, the natural frequency ν is
ν∝t '
It is expressed.

  Even when the thickness of the vibrating body 101 is not uniform, the distribution of the natural frequency can be calculated by applying the thickness of the vibrating body 101 at each groove position to the above relationship. The natural frequency in this case is the thickness of the vibrating body 101 at the position of each groove and represents the natural frequency when the vibrating body 101 is manufactured. When bending vibration occurs as a standing wave, the position of the antinode where the vibration displacement becomes maximum and the stiffness and density in the vicinity greatly affect the natural frequency, and the position of the node and the vicinity of it Stiffness and density do not significantly affect the natural frequency.

  Therefore, by comparing the distribution of the natural frequency at each position of the vibrating body 101 with the distribution of the position where the vibration displacement is maximized according to the order of the bending vibration to be excited, according to the bending vibration of each order. The difference in natural frequency at the position of the distributed vibrating body 101 can be expressed.

  That is, if the distribution of the natural frequency of the bending vibration at each position of the vibrating body 101 is calculated and the comparison with the order is clearly expressed, it can be expressed as a spatial frequency distribution with one round of the vibrator 101 as a unit length. Good.

  FIG. 19 is a diagram showing changes in the natural frequency with respect to the angular position of the vibrating body 101 in FIG. FIG. 20 is a diagram showing the change in the natural frequency in FIG. 19 as a spatial frequency with the circumference of the vibrating body as a unit length.

  As can be seen from FIG. 20, the change of the natural frequency ν mainly occurs at 6 cycles / circumference. By looking at this spatial frequency component, it is possible to vary the natural frequency according to the generation position of the third-order bending vibration wave having six antinodes in one circle. For this reason, even when a plurality of third-order bending vibration waves are combined, the natural vibration frequency is different, so that it is not a progressive vibration wave that is an unnecessary vibration wave, and the generation thereof is suppressed.

  Similarly, from FIG. 20, the change in the natural frequency ν has a higher-order (6, 12, 18,...) Spatial frequency component that is an integral multiple of the number of portions of the vibrating body 101 where the bending rigidity is small. However, since it does not occur at 14 cycles / circumference, it does not affect the natural frequency of the 7th-order bending vibration wave that is the drive vibration wave.

  Here, in the above-described configuration for suppressing the generation of unnecessary vibration waves, the sixth-order bending vibration wave is a progressive vibration wave, and the progressive vibration is composed of a bending third-order bending vibration wave that becomes an unnecessary vibration wave. Consider the case of suppressing the generation of waves. In this case, as shown in FIG. 20, since the change of the natural frequency ν of the vibrating body 101 occurs at 6 cycles / circumference, the natural frequency differs depending on the generation position even for the 6th bending vibration wave, The sixth-order bending vibration wave is prevented from being a traveling vibration wave as a driving vibration wave. As a result, the amplitude of the generated vibration wave is uneven, and the driving efficiency is lowered. As a result, the sixth-order bending vibration wave that becomes the drive vibration wave may not be excited.

  Therefore, in each of the embodiments described below, a detailed description will be given of a configuration for suppressing unnecessary vibration waves without affecting the drive vibration waves.

(First embodiment)
FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a lens barrel in which the vibration wave driving device according to the first embodiment of the present invention is used as an autofocus drive motor. FIG. 2 is an exploded perspective view of a main part of the vibration wave driving device of FIG. FIG. 3 is a diagram showing electrodes formed on the front and back surfaces of the piezoelectric element 2 of FIG. FIG. 4 is a development view showing the arrangement of a plurality of grooves formed in the vibrating body 1 of FIG. FIG. 5 is a diagram showing changes in the natural frequency of the vibrator 1 shown in FIG. FIG. 6 is a diagram showing the magnitude of the change in the natural frequency ν with respect to the spatial frequency of the vibrating body 1 in FIG. In the present embodiment, a vibration wave motor for driving a focus lens of a lens barrel will be described as a vibration wave driving device.

  The lens barrel having an autofocus function includes an outer cylinder 12 fixed to a camera mount 19 as shown in FIG. In the outer cylinder 12, a fixed cylinder 11, a fixed inner cylinder 18, and a moving ring 17 are arranged. The moving ring 17 holds a focus lens 27. The moving ring 17 is provided with a key groove (not shown) that engages with the connecting roller 15. Further, the moving ring 17 is provided with a threaded portion 17a, and this threaded portion 17a is Helicoid-coupled with the threaded portion 18a of the fixed inner cylinder 18.

  The moving ring 17 is moved in a direction along the optical axis L while rotating about the optical axis L via an output transmission body 25 that is rotationally driven by the vibration wave motor M. Specifically, as shown in FIG. 1B, the vibration wave motor M includes a ring-shaped vibrating body 1, a piezoelectric element 2 bonded to one end face of the vibrating body 1, and an annular rotor (moving element). ) 3. The vibrating body 1 and the piezoelectric element 2 work together to form a vibrator. The rotor 3 is in pressure contact with the other end surface of the vibrating body 1. A drive signal having a predetermined phase is applied to the piezoelectric element 2, whereby a bending vibration wave of a predetermined order is excited in the vibrating body 1 as a drive vibration wave (progressive vibration wave). The rotor 3 is driven to rotate about the optical axis L by the driving vibration wave.

  As shown in FIG. 1 (a), the vibrator has a pair of disc springs 9 inserted between a base 8 for holding an insulator 4 and a fixed cylinder 18 so that the piezoelectric element 2 side is overlaid. It is pressed from.

  The rotor 3 is brought into contact with and held by an annular connecting plate 22 via the vibration absorber 5. The connecting plate 22 is fixed to the output transmission body 25, and the output transmission body 25 is supported rotatably around the optical axis L by ball races 13 and 14 fixed to the ball 10 and the outer cylinder 12. . The connecting roller 15 is attached to the tip of the output transmission body 25.

  The vibration wave motor M is driven based on an AF (focus adjustment) signal sent from the camera side or a signal generated in conjunction with the operation of the manual ring 16. 25 is driven to rotate about the optical axis L. In conjunction with the rotational drive of the output transmission body 25, the moving ring 17 is moved in the direction along the optical axis L while rotating about the optical axis L. That is, the focus lens 27 is moved in the direction along the optical axis L, and focusing is performed.

  Next, the vibrating body 1 and the piezoelectric element 2 constituting the vibrator of the vibration wave motor M will be described in detail.

  As shown in FIG. 2, the vibrating body 1 is made of a ring-shaped member made of a metal such as aluminum, brass, or stainless steel. A plurality of grooves 1a extending radially from the inside to the outside are formed on one end face (upper surface) of the vibrator 1. Each groove 1 a is arranged along the circumferential direction of the vibrating body 1. Here, assuming that the depth of each groove 1a is ta, each groove 1a is formed such that each depth ta changes along a sine wave curve, as will be described later.

A portion between the grooves 1 a in the vibrating body 1 constitutes a protrusion 1 b that is in pressure contact with the rotor 3. Moreover, the part 1c in which each groove 1a is formed mainly constitutes a part where bending deformation (bending vibration) occurs, and the part 1c expands the displacement in the circumferential direction due to the bending vibration wave generated in the vibrating body 1. Demonstrate the effect. Here, a straight line passing through the centers of the ring-shaped vibrating body 1, the piezoelectric element 2, and the rotor 3 is used as an axis. When the thickness of the part 1c (the length in the axial direction of the vibrating body 1) is tc and the thickness in the axial direction of the vibrating body 1 is t, the thickness tc is
tc = t−ta
Is satisfied (see FIG. 4).

  The piezoelectric element 2 has a ring shape, and is bonded to the vibrating body 1 so that one end face (back face) 2 b thereof faces the other end face (lower face) of the vibrating body 1. As shown in FIG. 3B, a common electrode 22 is formed on the back surface 2b of the piezoelectric element 2 so as to cover the entire surface. Further, as shown in FIG. 3A, a drive electrode 21 divided into a plurality of electrode regions is formed on the other end surface (surface) 2 a of the piezoelectric element 2. The drive electrode 21 is composed of two groups of A phase and B phase, and each electrode region is polarized to (+) and (−) polarities as shown in the figure. In each group of A-phase and B-phase, adjacent (+) and (-) electrodes are provided in a region of an angle range of π / 6 (rad) so as to perform excitation for one wavelength. ing. That is, the (+) and (-) electrodes are formed in a pattern for exciting a standing wave of sixth-order bending vibration (standing wave of bending vibration having six wavelengths) in each of the A phase and the B phase. Has been. An alternating voltage having a time phase difference of π / 2 (rad) is applied to each group of the A phase and the B phase. As a result, standing vibration waves of 6 o'clock bending vibrations of the A phase and the B phase are synthesized in the vibrating body 1, and driving vibrations that are progressive vibration waves composed of sixth-order bending vibrations for driving the rotor 3. Waves are excited.

  As shown in FIG. 4, each groove 1 a formed in the vibrating body 1 is formed so that the depth ta changes along a sinusoidal curve along the circumferential direction of the ring-shaped vibrating body 1. Has been. Since each thickness tc of the portion 1c where the groove 1a is formed is a thickness in a direction orthogonal to the traveling direction of the progressive vibration wave, it has a sinusoidal curve with respect to the traveling direction of the progressive vibration wave. Will change along. Specifically, the thickness tc of the part 1c of the vibrating body 1 is expressed by the following equation.

tc = t0 + Δt · sin (2nθ)
Here, t0 is the thickness that is the center of the maximum value and the minimum value of the thickness tc, Δt is the thickness fluctuation amplitude, n is the order of the bending vibration wave, and θ is the angle that represents the position on the outer periphery of the vibrating body 1. (Rad).

  Since the bending rigidity K of each part 1c is proportional to the cube of the thickness tc, it can be expressed as follows.

K∝ (t0 + Δt · sin (2nθ)) ³
Further, the linear density ρ can be expressed as follows.

ρ∝t0 + Δt · sin (2nθ)
Further, the natural frequency ν of the bending vibration at each part 1c can be expressed as follows.

ν∝ (K / ρ) ^0.5
ν∝t0 + Δt · sin (2nθ)
That is, the natural frequency ν with respect to the bending vibration wave of the vibrating body 1 is such that the thickness tc of each portion 1c is along one sinusoidal curve for six cycles per round of the vibrating body 1, as shown in FIG. Similarly to the change, it changes along one sinusoidal curve for six cycles per round of the vibrating body 1.

  When the change of the natural frequency ν is expressed by a Fourier transform as a function having a spatial frequency of one cycle of the vibrating body 1 as a variable, as shown in FIG. It can be seen that it occurs only at 6 cycles / lap. On the other hand, since the third-order bending vibration wave having three wavelengths shows the maximum value of vibration displacement at six positions on the outer periphery of the vibrating body 1, a difference in natural frequency occurs depending on the position where the vibration occurs. Not excited as a vibration wave. That is, a third-order bending vibration wave that is an unnecessary vibration wave is difficult to be generated.

  The sixth-order bending vibration wave, which is a driving vibration wave, has maximum vibration displacement at 12 positions on the outer periphery of the vibrating body 1. Further, as shown in FIG. 6, the change in the natural frequency ν of the vibrating body 1 occurs only in 6 cycles / circulation, and the change does not include a spatial frequency component of 12 cycles / circulation. Therefore, the sixth-order bending vibration wave is not affected by the change in the natural frequency at each angular position (position on the outer periphery) of the vibrating body 1. Therefore, even when the sixth-order bending vibration wave is used as the driving vibration wave, it is possible to reduce the generation of the third-order bending vibration wave that is an unnecessary vibration wave.

  As described above, since the thickness tc of the part 1c of the vibrating body 1 changes along one sinusoidal curve, the generation of the driving vibration wave is generated regardless of the relationship between the order of the driving vibration wave and the order of the unnecessary vibration wave. Generation of unnecessary vibration waves can be suppressed without significant influence. In addition, the design freedom of the vibration wave motor can be increased.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a development view of a vibrating body provided in a vibration wave driving device according to the second embodiment of the present invention. FIG. 8 is a diagram showing a change in the thickness tc of the portion 1c where the groove 1a of the vibrating body is formed in the second embodiment of the present invention. FIG. 9 is a diagram showing a change in the natural frequency with respect to the angular position of the vibrating body in the second embodiment of the present invention. FIG. 10 is a diagram illustrating the magnitude of the change in the natural frequency of the vibrating body according to the second embodiment of the present invention in terms of spatial frequency. FIG. 11 shows the thickness tc of the portion 1c where the groove 1a is formed when the sinusoidal curves for 6 cycles and 8 cycles are linearly added so that either the maximum value or the minimum value position overlap each other. It is a figure which shows a change. FIG. 12 shows the thickness of the portion 1c in which the groove 1a is formed when the sinusoidal curves for 6 cycles and 8 cycles are added so that the positions of the maximum value or the minimum value do not overlap with each other. It is a figure which shows the change of tc. In the present embodiment, description will be made using the same reference numerals as those in the first embodiment.

  In the present embodiment, in order to suppress the generation of third and fourth order bending vibration waves, which are unnecessary vibration waves, the thickness tc of the portion 1c in the vibrating body 1 where the groove 1a is formed is set to a different period (wavelength). ) Is changed along a linearly added curve. In this respect, the present embodiment is different from the first embodiment.

  Specifically, as shown in FIG. 7, the portion 1 c where the groove 1 a is formed has a thickness tc of 6 cycles of sine wave curve and 8 cycles of sine wave per round of the vibrating body 1. It is formed so as to change along a curve obtained by linearly adding the curves. Here, the sine wave curve for 6 cycles and the sine wave curve for 8 cycles are linearly added so that the positions indicating the maximum value or the minimum value do not overlap each other. That is, as shown in FIG. 8, the thickness tc of the portion 1c where the groove 1a is formed has a thickness defined by a sine wave curve for six cycles and a thickness defined by a sine wave curve for eight cycles. It becomes the addition.

  The natural frequency ν of the vibrator 1 in the case where the thickness tc of the part 1c is changed along a curve obtained by linearly adding sinusoidal curves having different periods is shown in FIG. As shown in FIG. As shown in FIG. 10, this change in the natural frequency ν can be expressed as a function of the spatial frequency with one cycle of the vibrating body 1 as one cycle by Fourier transform. From FIG. 10, it can be seen that the change in the natural frequency ν has a spatial frequency component corresponding to each of sinusoidal curves having different periods for defining the thickness tc of the part 1c.

  In this way, by forming a portion 1c that varies along a curve obtained by linearly adding sinusoidal curves with different periods of thickness tc, generation of bending vibration waves of the order of unnecessary vibration waves is simultaneously suppressed. be able to. Therefore, in order to simultaneously suppress the generation of bending vibration waves that become unnecessary vibration waves, a plurality of sine wave curves having different periods to be added may be selected, and the design of the vibrator 1 can be facilitated.

  Here, as shown in FIG. 11, two sine wave curves having different periods (6 periods and 8 periods) are linearly added so that either of the positions indicating the maximum value or the minimum value overlaps each other. Is assumed. Here, as shown in FIG. 12, two sinusoidal curves having different periods (6 periods and 8 periods) are linearly added so that the positions of the maximum value or the minimum value do not overlap (in the case of FIG. 8). ) In thickness tc is represented by curve P1. Further, a change in the thickness tc when the two sine wave curves are linearly added so that the positions of the maximum value or the minimum value overlap each other (in the case of FIG. 11) is represented by a curve P2. A curve P2 indicates that the change width of the thickness tc of the portion 1c where the groove 1a is formed is larger than the curve P1. This indicates that the range of change of the natural frequency ν is increased. The fact that the width of the change of the natural frequency ν is locally increased indicates that the influence on the propagation speed and wavelength of the bending vibration wave of the order m, which is the driving vibration wave, is increased.

  Therefore, it is more desirable to linearly add sinusoidal curves having different periods (6 periods and 8 periods) so that the positions of the maximum values or the minimum values do not overlap as in the present embodiment. With this configuration, it is possible to reduce an adverse effect on excitation of a bending vibration wave serving as a driving vibration wave.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 13 is a development view of a vibrating body provided in a vibration wave driving device according to the third embodiment of the present invention. FIG. 14 is a diagram showing a change in the natural frequency with respect to the angular position of the vibrating body in the third embodiment of the present invention. FIG. 15 is a diagram showing the magnitude of the change in the natural frequency in FIG. In the present embodiment, description will be made using the same reference numerals as those in the first embodiment.

  In the present embodiment, it is assumed that the vibrating body 1 excites a driving vibration wave composed of seventh-order bending vibration. In the present embodiment, the thickness tc of the portion 1c where the groove 1a is formed is changed so that the change of the natural frequency ν does not include only the spatial frequency component twice the order of the drive vibration. Different from the first and second embodiments.

  Specifically, as shown in FIG. 13, the vibrating body 1 linearly adds a plurality of sinusoidal curves in which the thickness tc of the portion 1 c where the groove 1 a is formed has a cycle that is double the corresponding order. Configured to change along the curved line. Here, the above curve shows that the change in the natural frequency ν per unit wavelength of the vibrating body 1 does not include a spatial frequency component twice the order of the driving vibration wave and is an even number less than half the number of the grooves 1a. It is defined to include a spatial frequency component.

  With this configuration, the change in the natural frequency per unit wavelength in the circumferential direction of the vibrator 1 is a change that does not include a spatial frequency component that is twice the drive order, as shown in FIG. As a result, it is possible to prevent self-excited oscillation of bending vibration waves of all orders other than the order of bending vibration waves that become drive vibration waves.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 16 is a longitudinal sectional view showing the configuration of the main part of a vibration wave driving device according to the fourth embodiment of the present invention. FIG. 17 is a side view of the vibrating body of FIG.

  In the first to third embodiments, a plurality of grooves 1a are formed in the vibrator 1, and the thickness ta of each groove 1a is changed along a curve defined by one or a plurality of sinusoidal curves. Thus, a configuration is adopted in which the thickness tc of the portion 1c where the groove 1a is formed is changed.

  On the other hand, as shown in FIG. 16, this embodiment uses a vibrating body 1 in which a base portion 31 made of an elastic member formed in a ring shape and a projection portion 32 formed in a ring shape are joined.

  As shown in FIG. 17, the base 31 has an end surface 31a and an end surface 31b. The end surface 31a is finished into a curved surface along a curve defined by one or a plurality of sinusoidal curves. Thereby, the axial thickness of the base portion 31 changes along a curve defined by one or more sinusoidal curves with respect to the circumferential direction of the base portion 31. The end surface 31b is finished to be a flat surface, and the piezoelectric element 2 is bonded to the end surface 31b.

  As a method of manufacturing the base 31 of the vibrating body 1, plasticity such as powder sintering, molding by MIM, or the like, one end surface of a ring-shaped member is processed into a corresponding curved surface by pressing, and then the back surface is surface ground. There is a method by processing.

  The protrusion 32 is formed into a ring shape having a U-shaped cross-sectional shape by drawing a thin plate. The protrusion 32 is provided with a plurality of grooves 32a, and the thickness (depth) of each groove 32a is the same thickness td. A plurality of protrusions 32b are formed between the grooves of the protrusions 32 so as to be in pressure contact with the mover (rotor). The opening of the protrusion 32 is fitted from the end surface 31 a side of the base 31 and is fixed to the base 31.

  Here, it is assumed that the thickness of the base portion 31 in the axial direction changes along one sine wave curve for six cycles with respect to the circumferential direction of the base portion 31, for example, as in the first embodiment. In this case, the change in the natural frequency ν of the base 31 (vibrating body 1) occurs only with the spatial frequency component of 6 cycles / circumference. Therefore, as in the first embodiment, the third-order bending vibration wave having three wavelengths shows the maximum value of the vibration displacement at the six positions on the outer periphery of the vibrating body 1. Due to the difference in natural frequency, it is not excited as a progressive vibration wave. That is, a third-order bending vibration wave that is an unnecessary vibration wave is difficult to be generated.

  Further, the change in the natural frequency ν occurs only at 6 cycles / circulation, and the change does not include a spatial frequency component of 12 cycles / circulation. Therefore, the sixth-order bending vibration wave is not affected by the change in the natural frequency at each angular position (position on the outer periphery) of the vibrating body 1. Therefore, even when the sixth-order bending vibration wave is used as the driving vibration wave, it is possible to suppress the generation of the third-order bending vibration wave that is an unnecessary vibration wave.

  Further, the axial thickness of the base 31 may be changed as in the second or third embodiment. Also in this case, the same effect as the second or third embodiment can be obtained.

  In the first to third embodiments, a ring-shaped vibrating body is used. However, instead of this, a disk-shaped vibrating body can be used. The vibrating body in this case is made of a disk-like member having a ring-shaped protrusion that is in contact with the moving element (rotor) on one surface. This protrusion is configured, for example, in the same manner as in the first embodiment (see FIG. 2). That is, the protrusion is formed with a plurality of grooves arranged along the circumferential direction, and the thicknesses of the portions where the grooves are formed are defined by one or more sinusoidal curves. Varies along.

  In the first to fourth embodiments, the vibration wave motor used in the lens barrel has been described as the vibration wave driving device. However, the vibration wave motor is not a lens barrel but is a device or device other than the lens barrel. Needless to say, the present invention can be applied as a drive source for the above.

It is a longitudinal cross-sectional view which shows the structure of the principal part of the lens barrel in which the vibration wave drive device which concerns on the 1st Embodiment of this invention is used as a drive motor for autofocus. It is a disassembled perspective view of the principal part of the vibration wave drive device of FIG. It is a figure which shows the electrode currently formed in each of the surface of the piezoelectric element 2 of FIG. 2, and a back surface. FIG. 3 is a development view showing an arrangement of a plurality of grooves formed in the vibrator 1 of FIG. 2. It is a figure which shows distribution of the natural frequency of the vibrating body 1 of FIG. It is a figure which shows the magnitude | size of the fluctuation | variation of the natural frequency (nu) with respect to the spatial frequency of the vibrating body 1 of FIG. It is an expanded view of the vibrating body provided in the vibration wave drive device which concerns on the 2nd Embodiment of this invention. It is a figure which shows the change of thickness tc of the site | part 1c in which the groove | channel 1a of the vibrating body in the 2nd Embodiment of this invention was formed. It is a figure which shows the change state of the natural frequency with respect to the angular position of the vibrating body in the 2nd Embodiment of this invention. It is a figure which shows the magnitude | size of a change of the natural frequency in the spatial frequency in the 2nd Embodiment of this invention. A change in the thickness tc of the portion 1c in which the groove 1a is formed when the sinusoidal curves for 6 cycles and 8 cycles are linearly added so that either the maximum value or the minimum value position overlap each other is shown. FIG. Changes in the thickness tc of the portion 1c where the groove 1a is formed when the sine wave curves for 6 cycles and 8 cycles are added so as to overlap with each other so that the positions of the maximum value or the minimum value do not overlap. FIG. It is an expanded view of the vibrating body provided in the vibration wave drive device which concerns on the 3rd Embodiment of this invention. It is a figure which shows the fluctuation state of the natural frequency with respect to the angular position of the vibrating body in the 3rd Embodiment of this invention. It is a figure which shows the magnitude | size of the fluctuation | variation of the natural frequency with respect to a spatial frequency. It is a longitudinal cross-sectional view which shows the principal part structure of the vibration wave drive device which concerns on the 4th Embodiment of this invention. It is a side view of the vibrating body of FIG. It is a disassembled perspective view of the principal part of the conventional vibration wave motor. It is a figure which shows the change of the natural frequency with respect to the angular position of the vibrating body of FIG. It is the figure which represented the change of the natural frequency of FIG. 19 with the spatial frequency which made the perimeter of the vibrating body the unit length.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrator 1a, 32a Groove 1b, 32b Protrusion 1c Part 2 Piezoelectric element 3 Rotor (moving element)
31 Base 31a, 31b End face M Vibration wave motor

Claims (11)

A vibrator including an oscillating body and an electromechanical energy conversion element that excites a bending oscillating wave of a predetermined order in the oscillating body as a driving oscillating wave;
A moving element that contacts the vibrating body of the vibrator and is driven by a driving vibration wave excited by the vibrating body;
The vibrator has a site where bending vibration occurs, protrudes from the site where the bending vibration occurs, and a plurality of projections in contact with the moving element, and
A plurality of grooves are provided between the plurality of protrusions,
In the vibrating body, the thickness of the portion where the bending vibration occurs in the axial direction of the portion of the vibrating body that overlaps the plurality of grooves in the axial direction of the vibrating body is relative to the traveling direction of the driving vibration wave. , Configured to vary along a curve defined by at least one sine wave;
The plurality of protrusions have a height corresponding to the curve in the axial direction of the vibrating body so that the plurality of protrusions can come into contact with the moving element. The vibrating body is made of a ring-shaped member, for each of the thickness before Symbol bending point which vibration occurs traveling direction of the driving vibration wave along a curve defined by the at least one sinusoidal variation The vibration wave driving device according to claim 1, wherein the depth of the plurality of grooves is changed. The vibrating body, to one made disc-shaped member having a plurality of protrusions are formed in a ring shape on the face, before Symbol bending the traveling direction of the thickness of each of the sites that vibration occurs the drive vibration wave The vibration wave driving device according to claim 1, wherein the depth of the plurality of grooves is changed so as to change along a curve defined by the at least one sine wave. A vibrator including an oscillating body and an electromechanical energy conversion element that excites a bending oscillating wave of a predetermined order in the oscillating body as a driving oscillating wave;
A moving element that contacts the vibrating body of the vibrator and is driven by a driving vibration wave excited by the vibrating body;
The vibrating body includes a base portion in which bending vibration of a predetermined order by the electromechanical energy conversion element is excited as a driving vibration wave, and a protrusion portion fixed to the base portion so as to contact the moving element. A vibration wave drive characterized in that the thickness of the base portion in the axial direction of the vibrating body changes along a curve defined by at least one sine wave with respect to the traveling direction of the drive vibration wave apparatus.   5. The vibration wave drive according to claim 1, wherein the curve defined by the at least one sine wave is a curve obtained by linearly adding a plurality of sine waves having different wavelengths. apparatus.   6. The vibration wave driving device according to claim 5, wherein the plurality of sine waves having different wavelengths are linearly added so that the maximum value and the minimum value do not coincide with each other. The change in the thickness in the axial direction of the vibrating body where the bending vibration occurs with respect to the traveling direction of the driving vibration wave does not include a spatial frequency component that is twice the preset order of the bending vibration wave. vibration wave driven apparatus according to any one of claims 1 to 3, characterized in that the change. Thickness in the axial direction of said vibrating body sites where the bending vibration occurs, in part not overlapping the overlap in the axial direction before Symbol plurality of projecting portions and the vibrating body, the traveling direction of the driving vibration wave continuously, the vibration wave driven apparatus according to any one of claims 1 to 3, characterized in that the changes along the curve defined by at least one sine wave. The change in the thickness of the base in the axial direction of the vibrating body with respect to the traveling direction of the driving vibration wave is a change that does not include a spatial frequency component that is twice the preset order of the bending vibration wave. The vibration wave driving device according to claim 4 . The thickness of the base in the axial direction of the vibrating body varies continuously along the curve defined by the at least one sine wave in the traveling direction of the drive vibration wave. The vibration wave drive device according to claim 4 .   11. A device using the vibration wave driving device according to claim 1 as a driving source.

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