JPH09312981A - Vibrating actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the attenuation of vibration of a vibrator as much as possible by processing the rigidity of the part of a fixing shaft for fixing a vibrator so as to make the rigidity lower in the direction of displacement of at least one of vibrating modes used. SOLUTION: This actuator 10, as an ultrasonic actuator, is made up of a fixing shaft 15, a vibrator 11 fixed by the fixing shaft 15 and a mover 12 rotatably supported by the fixing shaft 15 and pressure-contacted onto the end surface of the vibrator 11. In this case, the fixing shaft 15 is brought into contact with the vibrator 11 via a large diameter part 15a and at positions close to the large diameter part 15a of the fixing shaft 15, extremely small diameter parts 15f, 15g are formed as grooves, where torsion rigidity lowers with regard to the same direction with at least one direction of displacement of vibration which occurs on the vibrator 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a fixing member, a vibrator fixed by the fixing member, and a relative motion member which is rotatably supported by the fixing member and is brought into pressure contact with the vibrator. The present invention relates to a vibration actuator, and in particular, is intended to reduce both the support loss of the vibration actuator and the vibration isolation to other parts in the mounted device.

[0002]

2. Description of the Related Art Vibration actuators characterized by small size, light weight, low speed, high torque, etc. are being put to practical use in various products such as cameras. It is becoming more active.

FIG. 16 is a perspective view showing the structure of a conventional example of a longitudinal-torsion vibration type vibration actuator. Conventionally,
In this type of vibration actuator, the stator
In 101, a piezoelectric element 104 for torsional vibration is arranged between two cylindrical vibrators 102 and 103, and a piezoelectric element 105 for longitudinal vibration is arranged above the vibrator 103. The piezoelectric element 104 for torsional vibration is polarized in the circumferential direction, while the piezoelectric element 105 for longitudinal vibration is polarized in the thickness direction. Further, the mover (rotor) 106 is arranged above the piezoelectric element 105 for longitudinal vibration.

The vibrators 102, 1 constituting the stator 101
03 and the piezoelectric elements 104 and 105 are screwed and fixed to the threaded portion of the shaft 107, and the mover 106 is rotatably provided on the shaft 107 via a ball bearing 108. A nut 110 is screwed onto the tip of the shaft 107 via a spring 109 to attach the moving element 106 to the stator 10.
1 is brought into pressure contact with a pressing force F.

The piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration are driven by phase-shifting a voltage of the same frequency oscillated from an oscillator 111 by a phase shifter 112.

The torsional vibration piezoelectric element 104 is
06 provides mechanical displacement for rotation, while the longitudinal vibration piezoelectric element 105 synchronizes the frictional force acting between the stator 101 and the moving element 106 with the cycle of torsional vibration by the piezoelectric element 104. By virtue of periodic fluctuations, it plays the role of a clutch that converts vibration into movement in one direction.

FIG. 17 is an exploded perspective view showing a stator 101 of this conventional vibration actuator. Since the piezoelectric element 104 for torsional vibration needs to be polarized in the circumferential direction, the piezoelectric material is once divided into about 6 to 8 fan-shaped small pieces as shown in FIG. 17, and after each small piece is polarized. It was combined again in a ring. Reference numeral 104a is an electrode.

[0008]

However, in the above-described conventional vibration actuator, the piezoelectric element 10 for torsional vibration is used.
When combining 4 in a ring shape, it was difficult to obtain shape accuracy.

On the other hand, the area of each of the longitudinal vibration piezoelectric element 105 and the torsional vibration piezoelectric element 104 is substantially equal to the cross-sectional area of the stator 106 or the stator 106.
Was smaller than the cross-sectional area. Further, in order to penetrate the shaft 107, it is necessary to make a through hole in the central portion of each of the piezoelectric element 105 for longitudinal vibration and the piezoelectric element 104 for torsional vibration. The area of each of the piezoelectric elements 104 for torsional vibration is further reduced, and it has been difficult to achieve both high torque and high rotation of the vibration actuator.

In order to solve such a problem, the applicant of the present invention has already proposed, in Japanese Patent Application No. 6-275022, a variant which can be driven with a high torque and a high rotation and is easy in structure and manufacturing. A mode degenerate vibration actuator is proposed.

FIG. 18 is a cross-sectional view showing the structure of an example of the variant mode degenerate vibration actuator.
FIG. 3 is a perspective view showing a vibrator 2 that constitutes this vibration actuator in an extracted manner.

In FIG. 18, a vibrator 2 which is a hollow cylindrical elastic body is attached to the outer peripheral surface of a cylindrical fixed shaft 1 by means of mounting bolts 3a and 3b which are screwed into a substantially central portion 1a of the fixed shaft 1. Be stuck.

As shown in FIG. 18, the vibrator 2 is constructed by combining two thick semi-cylindrical elastic bodies 2a and 2b, and the joint surface thereof is twisted using a piezoelectric constant d _15. A total of four piezoelectric elements 4 and 4 for vertical vibration and two piezoelectric elements 5 and 5 for vertical vibration using the piezoelectric constant d ₃₁ are sandwiched.

In FIG. 18, on the driving surface D which is the upper end surface of the vibrator 2, a moving element 7 which is a relative moving member rotatably arranged on the fixed shaft 1 by a bearing 6 arranged at the center is provided. Contact.

The moving element 7 has a thick annular moving element base material 7a.
And a sliding member 7b that comes into contact with the driving surface D of the vibrator 2 and is positioned with respect to the fixed shaft 1 by a bearing 6 fitted to the inner peripheral portion of the moving element base member 7a.

The mover 7 is pressed and brought into contact with the driving surface D of the elastic body 2 by an appropriate contact pressure by means of a disc spring 8 (which may be a spring spring or a leaf spring) which is a pressing member. To be done.

As described above, the fixed shaft 1 fixes and holds the vibrator 2 and positions the movable element 7 so as to be rotatable in the radial direction, and prevents the occurrence of shaft run-out when driving as a vibration actuator. The threaded portion 1 is attached to the tip of the fixed shaft 1.
b is formed, and a nut 9 which is a pressing force adjusting member for adjusting the pressing force of the disc spring 8 is screwed into the screw portion 1b.

The vibration actuator constructed as described above is excited by applying a drive voltage from a drive voltage generator (not shown) to each of the piezoelectric elements 4 and 5, and the vibrator 2 is twisted and longitudinally vibrated. Occur harmoniously. When the resonance frequencies of the torsional vibration and the longitudinal vibration are substantially the same, the torsional vibration and the longitudinal vibration simultaneously occur (degenerate), and an elliptic motion is generated on the driving surface D, and this elliptic motion serves as a driving force. The moving element 7 that is in pressure contact is driven to rotate around the fixed shaft 1.

The vibration actuator is composed of elastic bodies 2a and 2b.
And the electromechanical conversion element 4 and 5
Is configured. Then, the vibration actuator excites a resonance mode that is mainly determined by the size, shape, material constant, etc. of the vibrator 2 by using the inverse piezoelectric effect of the electromechanical conversion elements 4 and 5, and at that time, the vibrator 2 The moving element 7 is driven by utilizing the large amplitude generated in the.

As described above, the vibration actuator excites a plurality of vibrations on the vibrator 2 and takes out the excited plurality of vibrations as a driving force. Therefore, in order to obtain a highly efficient vibration actuator, it is necessary to transmit the vibration amplitude generated in the vibrator 2 to the moving element 7 as efficiently as possible. On the other hand, the vibrator 2 is fixed to the fixed shaft 1 which is a fixed member for positioning with the mover 7 and for mounting on a mounting target device or the like.
Need to be attached to. The fixed shaft 1 needs to be aligned to some extent in order to accurately position the vibrator 2, and to secure a fixed area necessary for holding the vibrator 2. Therefore, conventionally, the vibrator 2 has been firmly fixed to the fixed shaft 1 by the bolts 3a and 3b.

However, when the vibrator 2 is fixed to the fixed shaft 1 by the bolts 3a, 3b, etc., even if the fixed position is near a plurality of vibration nodes excited by the vibrator 2, a large fixed area is provided. Since the fixing method is used and has high rigidity, the energy dissipation (energy attenuation) of each vibration generated in the vibrator 2, that is, the support loss of the vibrator 2 cannot be avoided.

In order to reduce such a supporting loss as much as possible, the vibrator 2 and the fixed shaft 1 are conventionally arranged for the purpose of reducing the fixing area and the rigidity of the supporting member.
It has been considered to connect / fix the pins instead of the bolts 3a and 3b.

FIG. 20 is an enlarged cross-sectional view showing a mode in which the vibrator 2 and the fixed shaft 1 are fixed by using the pin 3c as a supporting member. By using the pin 3c, the fixing area of the vibrator 2 is reduced, and the rigidity of the support member is reduced to reduce the support loss in the vibrator 2.

As shown in FIG. 20, it is certainly possible to reduce the supporting loss by using the pin 3c as the supporting member. However, in this case, the fixed area between the vibrator 2 and the fixed shaft 1 is reduced, so that the vibrator 2 swings with respect to the fixed shaft 1 as the vibration actuator is driven. Therefore, in order to accurately position the vibrator 2 with respect to the fixed shaft 1, it is necessary to mount another member such as the annular collars A1 and A2 in the gap between the vibrator 2 and the fixed shaft 1. .

However, as shown in FIG. 20, even if the collars A1 and A2 are used in the gap between the vibrator 2 and the fixed shaft 1,
Between the collars A1 and A2 and the inner peripheral surface of the vibrator and the outer peripheral surface of the fixed shaft, a clearance is required for fitting. Therefore, there is a problem that accurate positioning of the vibrator 2 and the fixed shaft 1 is extremely difficult.

Further, conventionally, when the vibration actuator is incorporated in a part of the equipment to be mounted, the vibration generated in the vibrator 2 propagates through the fixed shaft 1 and is mounted near the periphery of the vibration actuator. There is a problem that it adversely affects other components (for example, sensors).

In such a case, the driving frequency of the vibration actuator is designed to be out of the frequency band which is not preferable for the other parts mentioned above. However, this significantly impairs the freedom of design of the vibration actuator.

As another measure, it may be considered to increase the distance between the vibration actuator and other parts as much as possible, or to provide a vibration isolator or the like near the vibration actuator for vibration insulation. However, this causes various constraint requirements in the design of the vibration actuator and the device to be mounted, and similarly, the degree of freedom in designing the device to be mounted is significantly impaired.

[0029]

DISCLOSURE OF THE INVENTION The present invention is directed to the above-mentioned vibration actuator of degenerate mode odd-shaped mode, in which the rigidity of a part of a fixed shaft for fixing the vibrator is utilized in the displacement direction of at least one vibration mode. By working so as to be lower than the above, vibration damping of the vibrator is suppressed as much as possible, and the above-mentioned problem is solved.

According to a first aspect of the present invention, the rod-shaped fixing member is fixed by the fixing member in a state where the fixing member penetrates the through portion directed in the axial direction, and a plurality of vibrations are generated so that the end surface is A vibration actuator including a hollow cylindrical vibrator that generates a driving force, and a thick-walled annular relative movement member that is rotatably supported by the above-mentioned fixing member and that is in pressure contact with the end surface of the vibrator. The fixing member is in contact with the vibrator via the large diameter portion formed in a part in the axial direction, and at least other portions of the fixing member other than the large diameter portion are generated in the vibrator. The rigidity lowering portion is formed in the same direction or substantially the same direction as the displacement direction of one vibration.

According to a second aspect of the invention, in the vibration actuator according to the first aspect, the rigidity lowering portion is one or both of a torsional rigidity lowering portion and a bending rigidity lowering portion.

According to a third aspect of the present invention, in the vibration actuator according to the second aspect, the torsional rigidity reduced portion is a very small diameter portion, and the bending rigidity reduced portion is a cross-sectional area reduced portion. To do.

According to a fourth aspect of the present invention, in the vibration actuator according to the third aspect, the extremely small diameter portion is formed by a groove or a recess provided in the fixing member, and the cross-sectional area reducing portion is formed in the fixing member. It is characterized in that it is formed by a hole portion provided.

The invention of claim 5 is from claim 1 to claim 4.
In the vibration actuator described in any one of the above items, the reduced rigidity portion is formed at a position near the large diameter portion.

The invention of claim 6 is from claim 1 to claim 5.
In the vibration actuator described in any one of the above items, the contact portion of the large diameter portion with the vibrator is part of the outer peripheral surface of the large diameter portion.

According to a seventh aspect of the invention, in the vibration actuator according to the sixth aspect, the contact portion is provided at a position in contact with the node portion of the vibration generated in the vibrator.

The invention of claim 8 is claim 6 or claim 7.
In the vibration actuator described in [1], a part of the contact part is further formed with a non-contact part that does not contact the vibrator.

According to a ninth aspect of the present invention, in the vibration actuator according to the eighth aspect, the non-contact portion is formed by a counterbore provided in the contact portion.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. In the following description of each embodiment, an ultrasonic actuator using an ultrasonic vibration region is used as an example of the vibration actuator.

FIG. 1 is a vertical sectional view for explaining an ultrasonic actuator 10 according to the first embodiment of the present invention. FIG.
It is a longitudinal cross-sectional view which expands and shows the fixing | fixed part of the oscillator 11 and the fixed shaft 15 in FIG. 3 is a cross-sectional view taken along the line AA in FIG. 4A and 4B are explanatory views showing the structure of the oscillator 11 used in the ultrasonic actuator 10, FIG. 4A is a top view, and FIG. 4B is a front view.

The ultrasonic actuator 10 of the first embodiment
Is provided with a vibrator 11 which is a columnar elastic body, and a mover 12 which is a columnar relative moving member that comes into pressure contact with a driving surface D which is an end face of the vibrator 11.

The vibrator 11 comprises two semi-cylindrical elastic bodies 11
a, a 11b, a piezoelectric element 13a for longitudinally torsional vibration generating generates the shear displacement of the vibrator 11 with a total of four piezoelectric constant d ₁₅ by two sandwiched these, one by two Piezoelectric element 13b for generating longitudinal vibration that causes expansion and contraction displacement in the longitudinal direction of the vibrator 11 using a total of four piezoelectric constants d _31.
And an electrode 14 connected to each piezoelectric element 13a, 13b.

In the present embodiment, the semi-cylindrical elastic bodies 11a and 11b are made of stainless steel (another metallic material such as iron-based alloy or copper alloy, or an elastic material such as plastic).
And is manufactured by vertically dividing the thick circular tubular body made of stainless steel into two in a plane including the rotation axis thereof.

Each of the piezoelectric elements 13a and 13b is an electromechanical conversion element that converts electric energy into mechanical displacement (mechanical energy), and is formed of PZT (lead zirconate titanate) or the like into a rectangular thin plate shape. . Also, electrode 1
Reference numeral 4 represents a thin plate having the same shape as the piezoelectric elements 13a and 13b, and a copper electrode is used in this embodiment.

In the vibrator 11, the piezoelectric elements 13a and 13b and the electrodes 14 are alternately laminated as shown in FIGS. 3 and 4, and these are sandwiched by the semi-cylindrical elastic bodies 11a and 11b, respectively. By adhering, it is assembled into a substantially cylindrical shape.

In the present embodiment, the mover 12 is mainly composed of a mover base material 12a made of an aluminum alloy (other light alloy, stainless steel or the like may be used). An annular sliding member 12b for reducing sliding resistance with the vibrator 11 is attached to an end surface of the two planes of the mover base material 12a that is in contact with the vibrator 11.

A fixed shaft 15, which is a rod-shaped fixing member, is inserted into a hollow portion provided at the center of the vibrator 11. In this embodiment, the fixed shaft 15 is made of stainless steel (copper alloy,
It may be an aluminum alloy or a resin material. )
It is manufactured by

A large-diameter portion 15a having a cross-sectional shape shown in FIG. 3 is provided at a substantially central portion of the fixed shaft 15, and the large-diameter portion 15a has two arcuate side surfaces 15b and 15c in the drawing. The arcuate side surface 15b located on the left side is pressed against and comes into contact with the circumferential mounting reference portion 11c having the same radius of curvature provided on the inner circumferential surface of the semi-cylindrical elastic body 11a. That is, the arcuate side surface 15b is a contact portion that abuts the attachment reference portion 11c.

Then, the bolt 16 which is a fastening member screwed to the semi-cylindrical elastic bodies 11a and 11b through the arcuate side surfaces 15b and the attachment reference portion 11c which are pressed against each other.
The elastic body 11 is fastened and fixed to the fixed shaft 15 by a and 16b.

The bolts 16a and 16b are fixed to the fixed shaft 15
It also functions as an abutting member for abutting the arc-shaped side surface 15b toward the attachment reference portion 11c of the elastic body 11. In the present embodiment, the other arcuate side surface 15c does not contact the inner peripheral surface 11d of the semi-cylindrical elastic body 11b, and the fixed shaft 15
Is arranged in an eccentric state with respect to the hollow portion of the vibrator 11 by contacting only the attachment reference portion 11c.

On the drive surface D, which is the upper end surface of the vibrator 11,
A bearing 17 arranged at the center of the movable shaft 12 is brought into contact with the fixed shaft 15 so as to be rotatable relative to the fixed shaft 15.

In the present embodiment, the mover 12 is applied to the driving surface D of the vibrator 11 with an appropriate contact pressure by a disc spring 18 (which may be a spring spring or a leaf spring, etc.) which is a pressing member. Pressure contact is made.

In this way, the fixed shaft 15 fixes the vibrator 11 and positions the movable element 12 so as to be rotatable in the radial direction, and prevents the occurrence of shaft run-out when driving as a vibration actuator. The fixed shaft 15 has a threaded portion 15d formed at its tip, and a nut 19 which is a pressing force adjusting member for adjusting the pressing force of the disc spring 18 is screwed into the fixed shaft 15. The pressing force of the disc spring 18 is adjusted by adjusting the screwing position of the nut 19 with respect to the threaded portion 15d.

A screw portion 15e is engraved on the other end of the fixed shaft 15 and is screwed into the screw portion 20a of the fixed body 20. As described above, only the attachment reference portion 11c of the vibrator 11 is in contact with the fixed shaft 15, and the other portions of the vibrator 11 are fixed to the fixed shaft 1.
5, the contact area (fixed area) between the vibrator 11 and the fixed shaft 15 is significantly reduced. Therefore, the vibration loss of the vibrator 11 is remarkably reduced as compared with the conventional case, and the driving efficiency and driving force of the mover 12 are improved.

Further, since the contact area between the vibrator 11 and the fixed shaft 15 is greatly reduced, the contact pressure at the contact portion is made uniform. Therefore, generation of abnormal noise such as chatter noise when the ultrasonic actuator is driven is suppressed.

When the radius of curvature of the arcuate side surface 15b of the large-diameter portion 15a is matched with the radius of curvature of the inner surface of the vibrator 11, and the fixed shaft 15 is eccentrically fixed to the vibrator 11, when the eccentricity is not provided. Compared with, the contact area can be further reduced and a greater effect can be obtained.

Further, in the structure shown in FIG.
After joining the vibrator 2 and the piezoelectric elements 4 and 5, the elastic body 2
So that the inner diameter of the fixed shaft 1 and the outer diameter of the fixed shaft 1 match.
It was necessary to perform machining (grinding, etc.) on the outer surface of the. However, in the present embodiment, since the fixed shaft 15 is eccentrically fixed to the hollow portion of the vibrator 2, and fixed, in other words, the fixed shaft 15 having an outer diameter smaller than the inner diameter of the hollow portion of the vibrator 2 is used, the fixed shaft 15 is fixed. It is not necessary to carry out such machining on the shaft 15.

Further, in this embodiment, a torsional rigidity lowering portion in the same direction as the displacement direction of the torsional vibration generated in the vibrator 11 is formed at a position near the large diameter portion. In the present embodiment, the torsional rigidity lowering portion is formed by the extremely small diameter portions 15f and 15g formed in a groove shape on the outer peripheral surface of the fixed shaft 15.

That is, in this embodiment, since the vibrator 11 is fixed to the fixed shaft 15 in the vicinity of the antinode position of the torsional vibration, the vibration damping of the torsional vibration may increase. is there. Therefore, in order to reduce the vibration damping of the torsional vibration as much as possible, the small diameter portions 15f and 15g are formed in the vicinity of both axial ends of the large diameter portion 15a.
It is intended to reduce the torsional rigidity with respect to the displacement direction of the torsional vibration that occurs in the.

The formation positions of the extremely small diameter portions 15f and 15g need not be near both axial ends of the large diameter portion 15a, but this position is desirable because the vibration damping becomes small.

According to the present embodiment, the large diameter portion 15a is brought into contact with the node position of the vibration for longitudinal vibration, while the small diameter portion 15f is attached to the fixed shaft 15 for torsional vibration. , 15g, it is possible to arrange the vibrator 11 at an accurate position with respect to the fixed shaft 15 while significantly reducing the support loss against any vibration.

Particularly, with respect to the drive frequency of the vibrator 11,
The frequency of the vibration mode determined by the "vibration system in which the entire vibrator 11 is one inertial body and the torsional rigidity at that time is the torsional rigidity of the minimum diameter portions 15f and 15g" is very low. From the viewpoints of reduction of support loss and vibration isolation to the outside, it is desirable. That is, under the above conditions, the frequency of the vibration generated in the vibrator 11 is
For the frequency of the vibration mode group determined by “the vibration system when the whole vibrator 11 is one inertial body and the torsional rigidity at that time is the torsional rigidity of the minimum diameter portions 15f and 15g” Since it is extremely high, the latter vibration system cannot follow its vibration speed. Therefore, so-called "vibration isolation" occurs, and the vibration of the vibrator 11 is reduced to the minimum diameter portion 1
The large-diameter portion 15 of the fixed shaft 15 is blocked by 5f and 15g.
It becomes difficult to propagate to parts other than a.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic actuator 10 of this embodiment. That is,
The drive circuit includes an oscillator 31 that oscillates a drive signal, a phase shifter 32 that divides the drive signal into signals having a phase difference of (1/4) λ (λ: wavelength), and a piezoelectric element 13a for torsional vibration. T amplifying section 33 for amplifying the drive signal input to the L type and L amplifying section 3 for amplifying the drive signal input to the longitudinal vibration piezoelectric element 13b.
And 4.

The control circuit is composed of a detector 35 for detecting torsional vibration and a controller 36 for controlling the frequency and voltage of the oscillator according to the amount detected by the detector 35. The detection unit 35 includes a mechanical-electrical conversion element (not shown) attached to the bottom surface of the vibrator 11 opposite to the drive surface D, and detects the voltage generated in the mechanical-electrical conversion element due to the generated twist. By detecting it, the torsional displacement can be indirectly detected. In this way, the detection unit 35 detects the torsional vibration of the vibrator 11 by the voltage. The drive speed and drive torque of the mover 12 are estimated based on the value of this voltage.

The control unit 36 controls the drive frequency and voltage of the vibrator 11 according to the detection result of the detection unit 35. For example,
When the detected amount is larger than a predetermined value, the drive frequency is increased or the voltage is decreased. On the other hand, if the detected amount is smaller than the predetermined value, lower the drive frequency,
Increase the voltage.

Next, referring to FIG. 6, in the ultrasonic actuator 10 according to the present embodiment, the longitudinal primary vibration and the torsional primary vibration generated in the vibrator 11 are combined to form an ellipse on the drive surface D. Explain the occurrence of movement over time.

As shown in FIG. 6, the period of torsional vibration and
When the phase difference from the period of longitudinal vibration is shifted by (1/4) λ (λ: wavelength), an elliptic motion occurs at a fixed point on the drive surface D. t =
At the time of (6/4) π, the displacement of the torsional vibration T is maximum on the left side, while the displacement of the longitudinal vibration T is zero. In this state, the moving element 12 moves the vibrator 1 by the pressing member 18.
1 is brought into contact with the driving surface D under pressure.

From this state, t = (7/4) π˜0
Up to (2/4) π, the torsional vibration T is displaced from the maximum on the left side to the maximum on the right side, while the longitudinal vibration T is displaced from zero to the maximum on the upper side and returns to zero again. Therefore, the oscillator 11
The fixed point of the drive surface D of is rotated to the right while pressing the mover 12, and the mover 12 is driven to the right.

Next, from t = (2/4) π to (6/4) π, the torsional vibration T is displaced from the maximum on the right side to the maximum on the left side, while the longitudinal vibration T is zero. Then, it moves to the lower maximum and returns to zero again. Therefore, the fixed point of the drive surface D of the vibrator 11 rotates to the left while moving away from the mover 12, so the mover 12 is not driven to the left. At this time, the moving element 12 does not follow the contraction of the vibrator 11 because the natural frequency is different even if it is pressed by the pressing member 18.

The frequency T ₁ of the torsional vibration T is made substantially equal to the resonance frequency ω _0T of the torsional vibration T, and the frequency L ₁ of the longitudinal vibration L is set to the resonance frequency ω _0L of the longitudinal vibration L. When they are made to substantially coincide with each other, they resonate and the elliptical motion expands.

[0071] torsional resonance frequency ω _0T of vibration T, and shows the longitudinal vibration L resonant frequency ω _0L approximate expression of the following and by. The resonance frequency _{ω 0T = Ls × (G /} ρ) 2/2 ······· resonance frequency _{ω 0L = Ls × (E /} ρ) 2/2 ······· However, Ls: vibrators In the longitudinal direction, E: longitudinal elastic modulus, G: lateral elastic modulus, ρ: density.

As described above, according to the formulas and the formulas, the resonance frequency ω _0T of the torsional vibration T and the resonance frequency ω _{0L of the} longitudinal vibration L are adjusted by adjusting the length of the vibrator 11 in the longitudinal direction.
And can be adjusted to be close or coincident.

(Second Embodiment) FIG. 7 is a sectional view showing the structure of an ultrasonic actuator according to the second embodiment of the present invention.

In the following description of each embodiment, only the parts different from the above-described first embodiment will be described, and the common parts will be denoted by the same reference numerals and redundant description will be omitted.

Ultrasonic actuator 10 of this embodiment
In No. 1, the small diameter portion 21 is formed in a groove shape near the lower end portion of the outer peripheral surface of the vibrator 11, and the first large diameter portion 22 and the second large diameter portion 23 are arranged by being divided by the small diameter portion 21. It

The small-diameter portion 21 is formed on the elastic base material before being divided into two by an appropriate means such as cutting. FIG. 8 shows the elastic body 11 of the ultrasonic actuator of the present embodiment.
FIG. 4 is an explanatory diagram showing that first-order longitudinal vibration and second-order torsional vibration occur.

The ultrasonic actuator 10 of this embodiment-
In FIG. 1, as shown in FIG. 8A, a small diameter portion 21 having low torsional rigidity is provided between the first large diameter portion 22 and the second large diameter portion 23, and the first large diameter portion 21 is provided. The length of the portion 22 is longer than that of the second large diameter portion 23. Therefore, as shown in FIG. 8B, the torsional vibration is a secondary mode in which two nodes of vibration occur in the small diameter portion 21 and the substantially central portion of the first large diameter portion 22 in the axial direction.

On the other hand, the longitudinal vibration is unlikely to be affected by the shape change of the elastic body 11 due to the provision of the small diameter portion 21, so the small diameter portion 2
The first-order mode in which one vibration node occurs in the middle of the entire length including the first large diameter portion 22 and the second large diameter portion 23. In this case, the drive surface D becomes an antinode of vibration having large amplitude in both torsional vibration and longitudinal vibration.

The natural frequency of the torsional vibration is as follows:
Although it is determined by the total length of the first large diameter portion 22 and the second large diameter portion 23, there is a characteristic that it is hardly affected by the length of the second large diameter portion 23 among them. On the other hand, the natural frequency of the longitudinal vibration is also small, the small diameter portion 21, the first large diameter portion 22 and the second large diameter portion 2
Although it is determined by the total length of 3, the natural frequency can be changed by changing the length of the second large diameter portion 23. Therefore, by changing the length of the second large-diameter portion 23 (changing the installation position of the small-diameter portion 21), the natural frequencies of the torsional vibration and the longitudinal vibration are adjusted to bring them closer to each other. Or they can be matched.

In this embodiment, the vibrator 11 is supported at the node position of the torsional vibration, but as described above, the torsional vibration has a great influence on the driving force of the ultrasonic actuator. Therefore, the vibration is not attenuated as much as possible. This can be similarly applied to the first embodiment.

(Third Embodiment) FIG. 9 is a vertical sectional view showing the structure of an ultrasonic actuator 40 according to a third embodiment of the present invention.

This embodiment is a further development of the first embodiment and the second embodiment. When the oscillator and the fixed shaft are accurately aligned, the energy dissipation of the oscillator is achieved. Is further reduced.

The vibrator 41 includes a plurality of piezoelectric elements (not shown in FIG. 9) which are electromechanical conversion elements excited by a drive signal. The arrangement of the piezoelectric elements and the like are shown in FIG. , And by connecting these piezoelectric elements to each other, excitation of the piezoelectric elements causes primary longitudinal vibration and secondary torsional vibration to generate a driving force on the driving surface 42c. It is composed of elastic bodies 42a and 42b which are generated.

As shown in FIG. 9, each of the elastic bodies 42a and 42b has three small diameter portions 43 formed in a groove shape on the outer peripheral surface thereof.
a, 43b, 43c and their small diameter portions 43a to 43c
Four large diameter portions 43A, 43 formed by being separated by
B, 43C, 43D.

The elastic bodies 42a, 42b are obtained by dividing a hollow cylindrical elastic member into two parts along a vertical surface including the central axis, and sandwich the above-mentioned piezoelectric element between the two divided surfaces.
10A and 10B are explanatory diagrams of the configuration of the vibrator 41 used in the present embodiment. FIG. 10A is a side view showing a half section from the center line in cross section, and FIG. 10B is A in FIG. 10A. It is explanatory drawing which shows -A cross section, BB cross section, and CC cross section with the application condition of drive voltage.

As shown in FIGS. 10 (a) and 10 (b), the piezoelectric bodies 44a and 44b are composed of three groups in the axial direction of the vibrator, and each group of the piezoelectric bodies 44a and 44b is composed of two layers. Become. The piezoelectric body of one of the three groups is a piezoelectric body 44b that uses the piezoelectric constant d ₃₁ near the node of the first-order longitudinal vibration.
In the remaining two groups of piezoelectric bodies, the piezoelectric body 44a uses the piezoelectric constant d ₁₅ at two places near the node of the secondary torsional vibration.
Has been arranged.

The piezoelectric body 44a using the piezoelectric constant d ₁₅ generates shear displacement in the longitudinal direction of the elastic bodies 42a and 42b. The piezoelectric body 44a is arranged so that the twisting directions of the AA cross section and the CC cross section in FIG. When the piezoelectric bodies 44 a are arranged in this way and are shear-deformed, the vibrator 41 undergoes a secondary torsional displacement.

The piezoelectric body 44b using the latter piezoelectric constant d ₃₁
Causes expansion and contraction displacement in the longitudinal direction of the elastic bodies 42a and 42b. The two sets of longitudinal vibration piezoelectric bodies 44b of the BB cross section in FIG. 10B are arranged so that displacement occurs in the same direction when a certain electric potential is generated.

As described above, when the torsional vibration piezoelectric body 44a using the piezoelectric constant d ₁₅ and the longitudinal vibration piezoelectric body 44b using the piezoelectric constant d ₃₁ are arranged, the torsional vibration piezoelectric body 4 is obtained.
By inputting a sine wave voltage to 4a, a torsional motion is generated in the vibrator 41 accordingly, while inputting a sine wave voltage to the longitudinal vibration piezoelectric body 44b causes the vibrator 41 to move.
Stretching motion occurs accordingly.

In the elastic bodies 42a, 42b, through holes 45a, 45b, 45c, 45d are formed in the central portions of the four large diameter portions 43A to 43D substantially in the elastic body length direction in parallel with the piezoelectric body stacking direction.
Is provided. Further, the through hole 4 is also formed in the fixed shaft 47 described later.
Through holes 47a to 47d are formed at the same pitch as 5a to 45d.

Then, in order to obtain the state shown in FIG. 10 described above, the piezoelectric body 44 is formed on the divided surfaces of the elastic bodies 42a and 42b.
The fixing shaft 47 is inserted into the hollow portions of the elastic bodies 42a and 42b by sandwiching the a and 44b, and the through holes 45a to 45d and 47.
By inserting the bolts 46a to 46d into the a to 47d and screwing the nuts 48a to 48 at both ends, the elastic body 4 is formed.
2a and 42b are fastened with the piezoelectric bodies 44a and 44b sandwiched therebetween.

In this embodiment, the elastic bodies 42a and 42b are used.
As shown in FIG. 9, is fixed to the fixed shaft 47 through the inner peripheral surface of the small diameter portion 43b including the vicinity of the node of the primary longitudinal vibration. The structure of this portion will be described in detail with reference to FIG. 11 described later.

In FIG. 9, a mover 49 is a hollow thick-walled annular mover base material 49a, and a slide body affixed to the vibrator-side end surface of the mover base material 49a and contacting the drive surface 42c of the vibrator 41. It is composed of moving material 49b. A bearing 50, which is a positioning means, is fitted to the inner peripheral portion of the end face of the mover base material 49a on the side opposite to the oscillator. The bearing 50 is fixed to the fixed shaft 47, and the mover 49 is rotatably positioned with respect to the fixed shaft 47.

A screw portion is provided on the upper end of the fixed shaft 47, and the nut 51, which is a pressing force adjusting member, is attached to the screw portion.
Is screwed. Further, between the bearing 50 and the nut 51, a disc spring 52 (which may be a spring spring, a leaf spring, or the like) which is a pressurizing unit, and an external member which transmits the pressing force of the disc spring 52 to the bearing 50. The pressing force transmission member 53, which is a tubular body with a facing flange, is held by the fixed shaft 47. As a result, by changing the screwing position of the nut 51 with respect to the fixed shaft 47, the spring force of the disc spring 52 is changed, and the pressing force between the moving element 49 and the vibrator 41 is adjusted.

As described above, the fixed shaft 47 penetrates the hollow portion of the vibrator 41 to fix the vibrator 41 and positions the mover 49 rotatably in the radial direction. 11 shows the elastic bodies 42a and 42b and the fixed shaft 4 in FIG.
7 is an enlarged cross-sectional view showing a fixed state with 7; FIG.

As shown in FIG. 9, also in this embodiment, the elastic member 4 is used as in the first and second embodiments.
A part of the inner peripheral surface in the vicinity of the node position of the vertical vibrations generated in 2a and 42b (in the vicinity of the antinode position of the torsional vibration) is the mounting reference surface 42c.

On the other hand, the mounting reference plane 4 in the axial direction of the fixed shaft
A large-diameter portion 54 having a curved surface with the same radius of curvature as the mounting reference surface 42c is formed in a part of the fixed shaft 47 that is in the same range as 2c. The large-diameter portion 54 contacts the mounting reference surface 42c via this curved surface. Fixed shaft 4
The small-diameter portion 55 other than the large-diameter portion 54 of 7 has elastic bodies 42a, 4
It does not contact the inner peripheral surface of 2b. That is, also in this embodiment, the large diameter portion 54 acts as a contact portion with the elastic bodies 42a and 42b, and the small diameter portion 55 acts as a non-contact portion.

Further, a counterbore 54a is formed on the contact surface of the large diameter portion 54 with the mounting reference surface 42c, and a non-contact portion with the mounting reference surface 42c is formed. That is, in the present embodiment, the large-diameter portion 54 contacts the elastic bodies 42a and 42b by the annular aspect of the large-diameter portion 54 that contacts the attachment reference surface 42c, excluding the counterbore hole 54a formation range.

With the contact surface of the large-diameter portion 54 formed on the fixed shaft 47 being in close contact with the mounting reference surface 42c of the elastic body 42a, the fixing bolts 56a and 56b are screw holes formed in the large-diameter portion 54. By being screwed onto the elastic bodies 42a, 4
2b is fixed and held by a fixed shaft 47. In addition, the fixing bolt 56a is provided with the large-diameter portion 5 while passing through the counterbore 54a.
4 is screwed.

As described above, in this embodiment, the elastic body 42 is
In order to minimize the contact area between the a and 42b and the fixed shaft 47, the large diameter portion 54 is provided with a counterbore 54a. By doing so, the contact area of the large-diameter portion 54 that comes into contact with the mounting reference surface 42c formed on the inner peripheral surface of the vibrator can be reduced, so that the vibrator 41 can be attached without degrading the positioning accuracy. The contact area can be minimized.

In other words, since the positioning of the two rigid bodies is basically determined by three-point contact, the contact area portion for positioning does not all contribute to the positioning, and depending on the part, It is considered that there are some parts that merely restrain the vibration. In this embodiment, a counterbore 54a is formed in such a portion.

Further, in the present embodiment, since the oscillator 41 is fixed to the fixed shaft 47 near the antinode position of the torsional vibration, the vibration damping of the torsional vibration may increase. is there. Therefore, in order to reduce the vibration damping of the torsional vibration as much as possible, the minimum diameter portions 57a and 57b are formed on both axial ends of the large diameter portion 54 to displace the torsional vibration generated in the vibrator 41. It is intended to reduce the torsional rigidity in the direction.

According to this embodiment, the large-diameter portion 54 with the counterbore 54a is brought into contact with the node position of the vibration for the longitudinal vibration, so that the fixed shaft 47 for the torsional vibration.
By forming the extremely small diameter portions 57a and 57b on the elastic bodies 42a and 42b at the correct positions with respect to the fixed shaft 47, the support loss is greatly reduced against any vibration.
Can be arranged.

In particular, with respect to the drive frequency of the vibrator, “vibration when the whole vibrator 41 is made to be one inertial body and the torsional rigidity at that time is made to be the torsional rigidity of the extremely small diameter portions 57a and 57b. It is desirable that the frequency of the vibration mode determined by the "system" be extremely low from the viewpoint of reduction of support loss and vibration isolation to the outside. That is, in the case of the above-mentioned conditions, the frequency of the vibration generated in the vibrator 41 is "the entire vibrator 41 is one inertial body, and the torsional rigidity at that time is the torsion of the extremely small diameter portions 57a and 57b. For the frequency of the vibration mode group that is determined by the "vibration system when assuming rigidity",
Since it is extremely high, the latter vibration system cannot follow its vibration speed. Therefore, so-called "vibration isolation" occurs, and the vibration of the vibrator 41 is caused by the extremely small diameter portion 57a,
It is blocked by 57b and becomes difficult to propagate to the large diameter portion 55.

In FIG. 10B, the drive circuit 60 is
An oscillator 61 for oscillating a drive signal (not shown), a phase shifter 62 for dividing the drive signal into signals having a phase difference of (1/4) λ (λ: wavelength), and a piezoelectric element 44a for torsional vibration are inputted. A T-amplifying section 63 for amplifying a drive signal, and a longitudinal vibration piezoelectric body 44.
The L amplification unit 64 amplifies the drive signal input to b.

According to the above-mentioned structure, the oscillating unit 61 oscillates the drive signal, and the drive signal is transmitted by the phase shift unit 62.
The signals are divided into two signals having a phase difference of (1/4) λ, and are amplified by the T amplification unit 63 and the L amplification unit 64, respectively. T
The drive signal amplified by the amplification unit 63 is input to the torsional vibration piezoelectric body 44a, and the drive signal amplified by the L amplification unit 64 is input to the vertical vibration piezoelectric body 44b.

Due to the excitation of the piezoelectric bodies 44a and 44b, the vibrator 41, to which the drive signal is input, generates a first-order longitudinal vibration having antinodes and nodes as shown in FIG. 12 and a second-order torsional vibration. appear. Here, the phase difference between the periodic voltages applied to the torsional vibration piezoelectric body 44a and the longitudinal vibration piezoelectric body 44b is expressed by (1
/ 4) By shifting and setting λ, an elliptic motion is generated on the drive surface 42c as shown in FIG. FIG.
The change of the elliptic motion on the drive surface 42c shown in FIG.
Since it is the same as the change shown in FIG.

At this time, in the torsional vibration, nodes are generated at two places of the small diameter portions 43a and 43c having a small torsional rigidity, and the driving surface becomes an antinode. On the other hand, in the vertical vibration, a node is generated in the vicinity of the small diameter portion 42b, and the driving surface becomes antinode. The mover 49 pressed against the drive surface is frictionally driven by the vibrator 41 to be driven.

Here, as shown in FIG. 13, when the phase difference between the period of the twisting motion and the period of the stretching motion is shifted by (1/4) λ, an elliptic motion occurs at a point on the driving surface. When the driving frequency of the torsional vibration is made to substantially match the resonance frequency of the torsional vibration and the driving frequency of the longitudinal vibration is made to substantially match the resonance frequency of the longitudinal frequency, resonance occurs and the elliptical motion expands.

In this embodiment, since the torsional resonance frequency and the longitudinal resonance frequency can be determined only by the oscillator 41, the shape of the moving element 49 can be set relatively freely. . For this purpose, it is necessary to reduce the vibration propagation from the oscillator 41 to the mover 49.
For example, a sliding member 49b (for example, polyflon or the like) having a large vibration damping is used, or a material having a large damping property (for example, an aluminum alloy) is used as the moving member base material 49a, and the moving member 49 is used.
It is sufficient to secure large vibration damping of itself.

(Fourth Embodiment) FIG. 14 is an enlarged sectional view showing a fixing state of the elastic bodies 42a, 42b and the fixed shaft 47 of the fourth embodiment.

The present embodiment differs from the third embodiment shown in FIGS. 9 to 13 in that the fixing positions of the elastic bodies 42a and 42b and the fixed shaft 47 are changed so that the vicinity of the antinode position of the torsional vibration ( It is fixed by the vicinity of the antinode position of longitudinal vibration). Therefore,
The description of the present embodiment will be given only for the different parts from the third embodiment, and the same parts will be denoted by the same reference numerals in the drawings, and redundant description will be appropriately omitted.

In the present embodiment, in order to reduce the bending rigidity in the direction substantially perpendicular to the vibration displacement direction of the longitudinal vibration generated in the vibrator 41, a plurality of rigidity reductions are made on both ends of the large diameter portion 54 in the fixed axis direction. Holes 58a, 58b, 58c, 58d are formed. The rigidity lowering holes 58a to 58d are formed parallel to each other in a direction orthogonal to the drawing.

By forming these rigidity lowering holes 58a to 58d in the fixed shaft 47, the longitudinal vibration is reduced in rigidity 58a and 58b and the rigidity lowering hole 58c provided in the fixed shaft 47.
And 58d, the bending rigidity reduced portions 59a and 59b, which have a reduced bending rigidity, can resonate in a natural state without restraining the longitudinal vibration displacement. This makes it possible to significantly reduce the support loss of the vibrator 41.

Particularly, for the drive frequency of the oscillator 41,
The frequency of the vibration mode determined by "the vibration system in which the entire vibrator 41 is one inertial body and the bending rigidity at that time is the torsional rigidity of the bending rigidity lowering portions 59a and 59b" becomes extremely low, and the support loss is reduced. It is desirable from the viewpoint of reduction and vibration isolation to the outside.

(Fifth Embodiment) FIG. 15 is an enlarged cross-sectional view showing a fixed state of the elastic bodies 42a and 42b and the fixed shaft 47 of the fifth embodiment.

In brief, this embodiment is a combination of the fixed shaft of the third embodiment shown in FIG. 11 and the fixed shaft of the fourth embodiment shown in FIG.

That is, this embodiment differs from the third embodiment shown in FIGS. 9 to 13 and the fourth embodiment shown in FIG. 14 in that the fixing positions of the elastic bodies 42a and 42b and the fixed shaft 47 are changed. And is fixed near the antinode position of the longitudinal vibration and near the antinode position of the torsional vibration (large diameter portion 43C).

The fixed position of this embodiment is out of both the node position of longitudinal vibration and the node position of torsional vibration, which is not preferable from the viewpoint of eliminating vibration damping. Therefore, the fixed shaft 47
The rigidity reducing holes 58a to 58d are formed in the vicinity of the large diameter portion 54 to suppress the damping of the longitudinal vibration, and the extremely small diameter portion 57 is formed.
A and 57b are formed to suppress the damping of torsional vibration. This is effective when it is necessary to support the fixed shaft 47 at this position.

(Variations) In each of the embodiments, a vibrator that produces a torsional first-longitudinal first or a torsion second-longitudinal first-order vibration mode is used, but the present invention is not limited to this. However, the present invention is equally applicable to vibrators that generate torsional mth-longitudinal nth-order (m, n: natural number) vibration modes.

Further, although the piezoelectric element is used as the electromechanical conversion element, the present invention is not limited to such an embodiment, and is equally applicable as long as it can convert electric energy into mechanical displacement (mechanical energy). it can. For example, a magnetostrictive element or an electrostrictive element can be used instead. Further, the shape of the elastic body forming the vibrator is not limited to the cylindrical shape, and may be, for example, a quadrangular prism.

Further, in each of the embodiments, the bolt is used to fix the vibrator to the fixed shaft, but the vibration actuator according to the present invention is not limited to such a mode, and it is possible to reduce the support loss. Alternatively, a pin as shown in FIG. 20 may be used.

Furthermore, in the description of each embodiment, an ultrasonic actuator utilizing the vibration range of ultrasonic waves is taken as an example of the vibration actuator, but the vibration actuator according to the present invention is not limited to such a mode. Without
The same can be applied to vibration actuators using other vibration regions.

[Brief description of drawings]

FIG. 1 is a vertical sectional view illustrating an ultrasonic actuator according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view showing a fixing portion between the vibrator and the fixed shaft in FIG.

3 is a cross-sectional view taken along the line AA in FIG.

4A and 4B are explanatory views showing a structure of a vibrator used in the ultrasonic actuator of the first embodiment, FIG. 4A is a top view, and FIG. 4B is a front view.

FIG. 5 is a block diagram showing a drive circuit of the ultrasonic actuator of the first embodiment.

FIG. 6 is an explanatory view showing over time that an elliptic motion is generated on the drive surface D by combining the longitudinal primary vibration and the torsional primary vibration generated in the vibrator in the ultrasonic actuator of the first embodiment. It is a figure.

FIG. 7 is a cross-sectional view showing the structure of the ultrasonic actuator of the second embodiment.

FIG. 8 is an explanatory diagram showing that primary longitudinal vibration and secondary torsional vibration occur in the elastic body of the ultrasonic actuator of the second embodiment.

FIG. 9 is a vertical sectional view showing a configuration of an ultrasonic actuator according to a third embodiment of the present invention.

10A and 10B are explanatory views of a configuration of a vibrator used in the third embodiment of the present invention, FIG. 10A is a side view showing a half section from a center line, and FIG. ) In A
It is explanatory drawing which shows -A cross section, BB cross section, and CC cross section with the application condition of drive voltage.

11 is an enlarged cross-sectional view showing a fixed state of the elastic body and the fixed shaft in FIG.

FIG. 12 is an explanatory diagram showing first-order longitudinal vibrations having antinodes and nodes and second-order torsional vibrations that are generated in a vibrator to which a drive signal is input.

FIG. 13 is an explanatory view showing that, in the ultrasonic actuator of the third embodiment, longitudinal primary vibration and torsional secondary vibration generated in the vibrator are combined to generate an elliptic motion on the drive surface D with time. It is a figure.

FIG. 14 is an enlarged cross-sectional view showing a fixed state of an elastic body and a fixed shaft according to a fourth embodiment.

FIG. 15 is an enlarged cross-sectional view showing a fixed state of the elastic body and the fixed shaft of the fifth embodiment.

FIG. 16 is a perspective view showing a conventional example of a vertical-torsion vibration type vibration actuator.

FIG. 17 is an exploded perspective view showing a stator of a vibration actuator of a vertical-torsion vibration type.

FIG. 18 is a cross-sectional view showing the structure of a variant mode degenerate vibration actuator.

FIG. 19 is a perspective view showing an extracted elastic body which constitutes a vibration actuator of a modified mode degenerate mode.

FIG. 20 is an explanatory diagram showing a conventional fixing method.

[Explanation of symbols]

 10, 10-1 Vibration actuator 11 Vibrator (elastic body) 11a, 11b Semi-cylindrical elastic body 11c Mounting reference part 11d Inner peripheral surface 12 Moving element (relative motion member) 12a Moving element base material 12b Sliding material 13a, 13b Piezoelectric element 14 Electrode 15 Fixed shaft (supporting member) 15a Large diameter part 15b, 15c Arc-shaped side surface 15d Screw part 15f, 15g Smallest diameter part 16a, 16b Bolt (fixing member, contact member) 17 Bearing 18 Pressurizing member 19 Addition Pressure adjusting member 21 Small diameter portion 22 First large diameter portion 23 Second large diameter portion

Claims (9)

[Claims] 1. A rod-shaped fixing member, and the fixing member is fixed by the fixing member in a state where the fixing member penetrates an axially extending through portion, and a driving force is generated at an end face by generating a plurality of vibrations. A vibrating actuator comprising: a hollow cylindrical vibrator, and a thick-walled annular relative movement member that is rotatably supported by the fixing member and that is in pressure contact with the end surface of the vibrator. The fixing member comes into contact with the vibrator through a large diameter portion formed in a part in the axial direction, and other portions of the fixing member other than the large diameter portion are generated in the vibrator. The vibration actuator is characterized in that a rigidity lowering portion is formed in the same direction or substantially the same direction as at least one of the displacement directions of the vibration. 2. The vibration actuator according to claim 1, wherein the rigidity lowering portion is a torsional rigidity lowering portion and / or a bending rigidity lowering portion. 3. The vibration actuator according to claim 2, wherein the torsional rigidity lowering portion is an extremely small diameter portion and the bending rigidity lowering portion is a cross-sectional area reducing portion. . 4. The vibration actuator according to claim 3, wherein the minimum diameter portion is formed by a groove portion or a concave portion provided in the fixing member, and the cross-sectional area reduction portion is provided in the fixing member. A vibration actuator, wherein the vibration actuator is formed by a hole formed therein. 5. The method according to claim 1, wherein:
In the vibration actuator described in the paragraph (1), the rigidity lowering portion is formed at a position near the large diameter portion. 6. Any one of claims 1 to 5
In the vibration actuator described in the paragraph 1, the contact portion of the large diameter portion with the vibrator is a part of an outer peripheral surface of the large diameter portion. 7. The vibration actuator according to claim 6, wherein the contact portion is provided at a position in contact with a node portion of the vibration generated in the vibrator. 8. The vibration actuator according to claim 6 or 7, wherein a part of the contact portion further includes a non-contact portion that does not come into contact with the vibrator. Actuator. 9. The vibration actuator according to claim 8, wherein the non-contact portion is formed by a counterbore provided in the contact portion.