JPH1080159A - Vibrating actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibrating actuator whose driving efficiency can be enhanced by increasing a driving force. SOLUTION: A vibrating actuator 20 is provided with a vibrator 21 in which piezoelectric bodies 24a, 24b in three groups are mounted and attached and by which a secondary torsional vibration to a relative motion direction and a primary longitudinal vibration to a direction at right angles to the relative motion direction are generated so as to generate a driving force on a driving face D and with a moving element 22 which is brought into press contact with the driving face D and which generates a relative motion between itself and the vibrator 21. In the vibrating actuator, the piezoelectric bodies 24a, for the torsional vibration, in two groups are mounted and attached, and the piezoelectric bodies 24b in one group are mounted and attached in an axial direction crossing the driving face D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vibration actuator.

[0002]

2. Description of the Related Art Traveling wave type vibration actuators are reported, for example, in "Nikkei Mechanical, February 28, 1983". In brief, the vibration actuator generates a traveling wave of ultrasonic waves on the drive surface of the stator made of an elastic body by applying a two-phase drive signal. Then, the moving element that comes into pressure contact with the driving surface is frictionally driven by the elliptical motion at the traveling wave wavefront.

FIG. 6 is a perspective view showing an example of the structure of a vertical-torsional vibration type vibration actuator. Conventionally, in a vibration actuator of this type, a stator 101 has an annular torsional vibration piezoelectric body 104 interposed between two cylindrical vibrators 102 and 103, and a vibrator 103. The ring-shaped piezoelectric body 105 for longitudinal vibration is arranged on the upper side. The piezoelectric body for torsional vibration 104 is polarized in the circumferential direction. Further, the piezoelectric body for longitudinal vibration 105 is polarized in the thickness direction. Further, the moving element 10
Numeral 6 is arranged on the upper end side of the piezoelectric body 105 for longitudinal vibration.

The vibrators 102, 1 constituting the stator 101
03 and the piezoelectric bodies 104 and 105
7 is fixed by being screwed to a threaded portion provided on the outer surface of 7. Further, the moving element 106 is rotatably attached to the fixed shaft 107 via a ball bearing 108 mounted at the center. At the tip of the fixed shaft 107,
The nut 110 is screwed via the spring 109. The moving element 106 is fixed to the stator 10 by the spring force F of the spring 109.
1 is brought into pressure contact with the end face.

The torsional vibration piezoelectric body 104 and the longitudinal vibration piezoelectric body 105 are both driven by appropriately controlling the phase of the drive voltage of the same frequency oscillated from the oscillator 111 by the phase shifter 112. You.

The piezoelectric body 104 for torsional vibration is
6 provide a mechanical displacement for rotation about the fixed axis 107. On the other hand, the piezoelectric body 105 for longitudinal vibration is
The vibration generated in the stator 101 is changed periodically by synchronizing the frictional force acting between the piezoelectric element 104 with the cycle of the torsional vibration caused by the piezoelectric body 104 to thereby reduce the vibration generated in the stator 101.
6 serves as a clutch that converts the movement into one direction.

FIG. 7 is an exploded perspective view showing the stator 101 constituting the vibration actuator shown in FIG. As described above, the torsional vibration piezoelectric body 104 needs to be polarized in the circumferential direction. Therefore, as shown in FIG.
It has been configured such that the small pieces are once divided into about fan-shaped small pieces, and each of the divided small pieces is polarized in the circumferential direction and then combined in a ring shape again. Reference numeral 104a in FIG. 7 denotes an electrode for applying a drive voltage to the torsional vibration piezoelectric body 104.

[0008]

However, in the conventional vibration actuator configured as described above, it is extremely difficult to secure desired dimensional accuracy when assembling the torsional vibration piezoelectric body 104 in a ring shape. .

On the other hand, in FIG.
5 and the cross-sectional area of each torsional vibration piezoelectric body 104 are:
The cross-sectional area of the stator 101 is substantially equal to or
It was a little smaller than the cross-sectional area of No. 1. In addition, the fixed shaft 107
Vibrating piezoelectric body 10 to penetrate
4. It was necessary to make a hole in the center of the piezoelectric body 105 for longitudinal vibration. Therefore, the cross-sectional areas of the torsional vibration piezoelectric body 104 and the longitudinal vibration piezoelectric body 105 are further reduced, and it is difficult to increase the torque and the rotation of the vibration actuator.

[0010] In order to solve such a problem, the present applicant has already developed a modified mode degeneration that can be driven by high torque and high rotation, has a simple structure, and is easy to manufacture. For example, Japanese Patent Application Nos. 6-180279 and 6-275022 propose a vibration actuator of the type.

FIG. 8 is a longitudinal sectional view showing an example of the structure of the vibration actuator 1 according to these proposals. FIG. 9 is a block diagram showing the control of the vibration actuator 1 shown in FIG. 10A is a view of the vibrator 2 held between the semi-cylindrical elastic bodies 2a and 2b shown in FIG. 8 when viewed from the bottom, and FIG. 10B is a vibrator shown in FIG. FIG. 2 is a view of the apparatus 2 viewed from the side. Further, FIG. 11 is an explanatory diagram showing a driving principle of the vibration actuator 1 that generates an elliptical motion on the driving surface 2c by combining the longitudinal vibration and the torsional vibration generated in the vibrator 2.

That is, in FIGS. 8 and 9, the vibrator 2 of the longitudinal-torsional vibration type vibration actuator 1 is an electromechanical transducer that is excited by a drive signal and converts electric energy into mechanical displacement. The piezoelectric bodies 3 and 4 are joined to the piezoelectric bodies 3 and 4, and these piezoelectric bodies 3 and 4 are joined.
The first and second longitudinal vibrations and the first torsional vibration are generated by the excitation of No. 4, and are constituted by hollow semi-cylindrical elastic members 2a and 2b which generate a driving force on the driving surface 2c which is an end surface. .

The elastic members 2a and 2b are elastic members having a shape in which a thick hollow cylinder is vertically divided into two. Elastic body 2a,
The piezoelectric bodies 3 and 4 are sandwiched between the divided surfaces 2b.
The piezoelectric bodies 3 and 4 are each composed of a total of four layers, two layers each. Two of the four layers of the piezoelectric body 3 are torsional vibration piezoelectric bodies using the piezoelectric constant d ₁₅ , and the remaining two layers of the piezoelectric body 4 are piezoelectric constants d ₃₁
Is a piezoelectric body for longitudinal vibration.

The elastic bodies 2a and 2b have through holes 2d and 2e at substantially the center in the height direction in parallel with the laminating direction of the piezoelectric bodies 3 and 4.
Is formed. The elastic bodies 2a and 2b are
By fixing the bolts 6a and 6b using d and 2e, the piezoelectric bodies 3 and 4 are sandwiched and screwed to the fixed shaft 5 inserted at the center in the axial direction.

The moving element 7 as a relative moving member is provided with a moving element base material 7-1 and a sliding member 7 which is attached to an end face of the moving element base material 7-1 and comes into contact with the driving surface 2c of the vibrator 2. And 2. The movable element 7 is rotatably positioned and fixed to the fixed shaft 5 via a bearing 8 which is a positioning member fitted to an inner peripheral portion thereof.

The moving element 7 is urged toward the vibrator 2 by a disc spring 9a as a pressing member,
It is brought into pressure contact with the drive surface 2c. The fixed shaft 5 includes the elastic body 2
a, 2b penetrates the hollow portion formed in the axial direction,
The vibrator 2 composed of the elastic bodies 2a, 2b and the like is fixed and held, and the moving element 7 is positioned in the radial direction.
The fixed shaft 5 has a threaded portion at the upper end, and a nut 9b, which is a pressing force adjusting member for adjusting the pressing force of the disc spring 9a, is screwed.

Piezoelectric body for torsional vibration 3, Piezoelectric body for longitudinal vibration 4
As shown in FIG. 9, an oscillating unit 1 for oscillating a drive signal is provided.
0, a phase shifter 11 that divides the output drive signal into a signal having a (1/4) λ phase difference, a T amplifier 13 that amplifies the drive signal input to the torsional vibration piezoelectric body 3, L amplifying unit 1 for amplifying a drive signal input to piezoelectric body 4 for longitudinal vibration
2 and so on.

The control circuit 16 includes a detecting unit 14 for detecting torsional vibration, a control unit 15 for controlling a frequency and a voltage output from the oscillating unit 10 in accordance with a detection amount of the detecting unit 14, and the like. Consists of The detection unit 14 includes a piezoelectric body 14a that is attached to a side surface of the vibrator 2 and converts mechanical displacement into electric energy. Thus, by detecting the amount of displacement generated in the vibrator 2 due to torsion, the torsional displacement generated in the vibrator 2 is indirectly detected.

As shown in FIGS. 10 (a) and 10 (b), the piezoelectric members 3 and 4 are composed of two groups sandwiched between two elastic members 2a and 2b. Each group of the piezoelectric bodies 3 and 4 has four layers. Among the piezoelectric four layers of piezoelectric material 2 layer is composed of a piezoelectric element 3 using a piezoelectric constant d _15, whereas, the piezoelectric body of the remaining two layers composed of a piezoelectric body 4 using a piezoelectric constant d _31.

The piezoelectric element 3 is a piezoelectric constant d _15, the elastic body 2a, the shear displacement is generated with respect to the longitudinal direction of 2b. In FIG. 10A, the piezoelectric bodies 3 are arranged on the two divided surfaces of the elastic bodies 2a and 2b such that the shear deformation alternates in the circumferential direction with respect to the front direction and the opposite direction.

By disposing the piezoelectric bodies 3 in this manner, when each of them is subjected to shear deformation, a torsional displacement is generated in the vibrator 2, and the end face of the vibrator 2 is twisted. On the other hand, the piezoelectric body 4 is using a piezoelectric constant d _31, the elastic body 2a, to generate the elastic displacement with respect to the longitudinal direction of 2b. The four longitudinal vibration piezoelectric members 4 are arranged such that when a certain potential is applied, displacement occurs in the same direction.

[0022] As described above, the vibration piezoelectric member 3 torsional using a piezoelectric constant d _15, with arranging the longitudinal vibration piezoelectric member 4 using a piezoelectric constant d _31, the torsional vibration piezoelectric member 3 , A torsional motion is generated in the vibrator 2 accordingly. On the other hand, when a sinusoidal voltage is applied to the piezoelectric body 4 for longitudinal vibration, the vibrator 2 expands and contracts accordingly.

In such a vibration actuator 1, in FIG. 9, the T amplifying unit 13 and the L amplifying unit 12 transmit the torsional vibration piezoelectric body 3 via the oscillation unit 10 and the phase shift unit 11.
When a drive signal is applied to the piezoelectric body 4 for longitudinal vibration, the piezoelectric body 3 for torsional vibration and the piezoelectric body 4 for longitudinal vibration are excited, respectively.
The vibrator 2 generates torsional vibration and longitudinal vibration.

That is, as shown in FIG. 11, if the phase difference between the period of the torsional vibration T and the period of the longitudinal vibration (expansion / contraction movement) L is set to be shifted by (1/4) λ (λ: wavelength), An elliptical motion occurs at a fixed point A on the driving surface 2c of the vibrator 2.

In FIG. 11, if the frequency of the drive signal is f and the angular frequency at this time is ω (= 2πf), t
= (6/4) · (π / ω), the displacement of the torsional vibration T is maximum on the left side. On the other hand, the displacement of the longitudinal vibration L is zero. In this state, the moving element is in a state of being pressed by the pressing member to the driving surface 2 c of the vibrator 2.

From this state, t = (7/4) · (π /
ω) to 0 to (2/4) · (π / ω), the torsional vibration T is displaced from the maximum on the left to the maximum on the right. On the other hand, the longitudinal vibration L is displaced from zero to the upper maximum and returns to zero again. Therefore, the driving surface 2c of the vibrator 2 contacts the end face of the moving element and rotates to the right while pushing the moving element, and the rotation drives the moving element to the right.

Next, t = (2/4) · (π / ω)-(6
/ 4) · (π / ω), the torsional vibration T is displaced from the maximum on the right to the maximum on the left. On the other hand, the longitudinal vibration L is displaced from zero to the maximum below and returns to zero again. Accordingly, the driving surface 2c of the vibrator 2 rotates leftward while moving away from the moving element, and the moving element is not driven. At this time, the moving element is pressed toward the driving surface 2c side of the vibrator 2 by the pressing member (not shown in FIG. 11) as described above. Cannot follow shrinkage.

When the resonance frequencies of the torsional vibration and the longitudinal vibration generated in this way are substantially matched, the torsional vibration and the longitudinal vibration are simultaneously generated (this state is referred to as "degeneration").
That. ) Elliptic motion, which is a combination of torsional vibration and longitudinal vibration, is generated on the driving surface 2c of the vibrator 2 to generate a driving force, and the movable element is driven to rotate.

In these deformed mode degenerate type vibration actuators, the vibration generating piezoelectric members 3 and 4 are joined to the entire divided surfaces of the elastic members 2a and 2b, and a group of piezoelectric members 3 is twisted. They were arranged at two node positions across the antinode of vibration. In order to generate vibration using such a piezoelectric body, it is possible to generate vibration most efficiently by disposing the piezoelectric body at a node of the vibration to be generated.
On the other hand, even if it is arranged on the antinode of the vibration that generates the piezoelectric body, it does not contribute to the generation of excessive vibration, and additional energy input to the torsional vibration piezoelectric body 3 and the longitudinal vibration piezoelectric body 4 is required. It just became. For this reason, there is a problem that extra energy input to the abdomen of the vibration is required, and the driving efficiency is not improved.

Further, in the conventional modified mode degenerate type vibration actuator, there are two torsional vibration nodes in a group of piezoelectric bodies. Therefore, when two vibration nodes exist in the piezoelectric body 3 as described above, the elastic body is excited by application of a certain frequency voltage to generate torsional vibration in the elastic body. In the portion, a torsional vibration displacement occurs in the same direction as the vibration in which the piezoelectric body excites the elastic body. However, torsional vibration displacement occurs in the other node in the opposite direction. Therefore, 1
When two different vibration displacements are to be generated by the group of piezoelectric bodies, there is a problem that the input energy cannot be sufficiently converted into the output at one node, and the vibration amplitude does not increase. .

In view of the above problems, an object of the present invention is to provide a vibration actuator capable of improving driving efficiency by increasing driving force.

[0032]

According to a first aspect of the present invention, a plurality of electromechanical transducers which are excited by a drive signal are mounted, and the vibration of the first order or more in the first direction is different from the first direction. And vibration of the first order or more in the second direction.
A vibration actuator comprising: an elastic body that generates a driving force on an end face; and a relative motion member that presses and contacts the end face of the elastic body to generate relative motion between the elastic body and an axial direction intersecting the end face. With respect to the electromechanical transducers that generate vibration in the first direction are mounted in the same number as the order of the vibrations, and the electromechanical transducers that generate vibration in the second direction are:
It is characterized in that it is mounted in the same number as the order of vibration.

According to a second aspect of the present invention, in the vibration actuator according to the first aspect, the electromechanical transducer for generating the vibration in the first direction has a center in the axial direction corresponding to a node position of the vibration. Is attached to the second
The electromechanical transducer that generates vibration in the direction is mounted such that the center in the axial direction coincides with the nodal position of the vibration.

[0034] The invention of claim 3 is claim 1 or claim 2.
In the vibration actuator described in (1), the elastic body has a columnar shape, the vibration in the first direction is a longitudinal vibration in the axial direction of the elastic body, and the vibration in the second direction is caused by a twist in the axis of the elastic body. It is characterized by torsional vibration.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION

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

FIG. 1 is a longitudinal sectional view showing the structure of the ultrasonic actuator according to the first embodiment. The ultrasonic actuator 20 according to the present embodiment includes a vibrator 21 that is a vibration generating member.
And a moving element 22 that is a relative motion member that makes a relative motion between the vibrator 21 and the driving face 21 a that is one end face of the vibrator 21 under pressure.

The vibrator 21 has piezoelectric members 23a and 23b, which are electromechanical transducers, which are excited by a drive signal, and these piezoelectric members 23a and 23b are joined to each other. The elastic bodies 24a, 24a, which generate a driving force on the driving surface D by the occurrence of the torsional vibration of
4b.

The elastic bodies 24a and 24b are formed by two small-diameter portions 21a and 21b formed in a ring shape on the side surface and three large-diameter portions 21A and 21B formed by being separated by the small-diameter portions 21a and 21b. , 21C is an elastic member obtained by vertically dividing a thick cylindrical body into two.

On the two divided surfaces of the elastic members 24a and 24b, two layers of piezoelectric members 23a and 23b and electrodes 25a and 25b
Is held in a state of being sandwiched. Small diameter portions 21a, 21
b is disposed at each of two nodes of torsional vibration generated in the elastic bodies 24a and 24b. The torsional vibration piezoelectric body 23a is disposed at two torsional vibration nodes, and the longitudinal vibration piezoelectric body 23b is disposed at the longitudinal vibration nodes.

The elastic members 24a and 24b have through holes 26a and 26b formed substantially at the center in the height direction in parallel with the laminating direction of the piezoelectric members 23a and 23b. Elastic bodies 24a, 24b
Are bolts 27a, 2b in these through holes 26a, 26b.
7b is inserted and screwed to a large-diameter portion 28a formed substantially at the center of a fixed shaft 28 described later, so that the piezoelectric members 23a and 23b are sandwiched and the elastic members 24a and 2b are sandwiched.
4b is fixed and held on a fixed shaft 28 that passes through a through hole formed at the center of 4b.

The moving element 22 is composed of a moving element base material 22a and a sliding member 22b which comes into pressure contact with the driving surface D of the vibrator 21. A bearing 29, which is a positioning member, is fitted to the center edge of the end face of the movable element base material 22a on the anti-vibrator side. The bearing 29 is rotatably mounted on the fixed shaft 28 so that the moving element 22
Is rotatably positioned with respect to.

A gear 22c for taking out output is formed on the outer peripheral surface of the moving element base material 22a. The output is transmitted to a gear of a driven body (not shown). In addition, the moving element 22
Is pressed against the drive surface D of the vibrator 21 via the force transmitting member 31 by a disc spring 30 (which may be a spring or a leaf spring) as a pressing member.

The fixed shaft 28 penetrates through hollow portions formed in the elastic members 24a and 24b in the axial direction, and fixes and holds the vibrator 21 and positions the movable member 22 in the radial direction. The fixed shaft 28 has a screw portion 28b formed at the tip, and a nut 32 which is a pressing force adjusting member for adjusting the pressing force of the disc spring 30 is screwed.

FIG. 2 shows the piezoelectric body 2 mounted on the vibrator 21.
FIG. 2A is a top view of the vibrator 21, and FIG. 2B is a diagram of the vibrator 21 showing an example of generated longitudinal vibration and torsional vibration. It is a side view.

The elastic members 24a and 24b are formed of two small diameter portions 2
1a, 21b and three large diameter portions 21A, 21B and 21C
This is an elastic member having a shape obtained by vertically dividing a thick-walled cylinder including the following into two. Two layers of piezoelectric bodies 23a, 23b and electrodes 25a, 25b are sandwiched between the divided surfaces of the elastic bodies 24a, 24b.

The small diameter portions 21a and 21b are arranged at two nodes X and Z of torsional vibration. Piezoelectric body 25 for torsional vibration
a is located at a position including these nodes X and Z,
The vertical vibration piezoelectric body 25b is arranged at a position including the node Y of the vertical vibration.

When a frequency voltage is applied, the torsional vibration piezoelectric body 25a generates a shearing deformation according to the direction of the applied voltage, and the shearing deformation generates a torsional vibration in the vibrator 21.

In FIG. 2 (b), the first
The group of torsional vibration piezoelectric members 23a includes two torsional vibration piezoelectric members 23a located on the near side in the drawing and two torsional vibration piezoelectric members located on the other side in the drawing. 23a. Piezoelectric body 2 for torsional vibration located on the near side
The group of torsional vibration piezoelectric members 23a is configured such that shear deformation between the piezoelectric member 3a and the torsional vibration piezoelectric member 23b located on the opposite side occurs in opposite directions when a voltage in the same direction is applied. Is arranged, torsional displacement occurs in the vibrator 21 in a certain direction. For example, as shown in FIG. 2, when the two torsional vibration piezoelectric members 23a on the front side and the two torsional vibration piezoelectric members 23a on the other side are sheared, respectively,
The drive surface D is twisted as shown in FIG. Also, when a voltage in the opposite direction is applied, shearing deformation in the opposite direction is generated, so that the driving surface D is twisted in the direction opposite to that in FIG.

In FIG. 2B, the second
The group of torsional vibration piezoelectric bodies 23a is composed of two torsional vibration piezoelectric bodies 23a located on the near side in the drawing and two torsional vibration piezoelectric bodies 23a located on the other side. Is done. The second group of torsional vibration piezoelectric bodies 23a has a voltage in the same direction in which the shear deformation of the torsional vibration piezoelectric body 23a located on the near side and the torsional vibration piezoelectric body 23b located on the other side are the same. If the oscillators 21 are arranged so as to be in opposite directions when applied, the oscillator 21 is twisted in a certain direction.

The two first torsional vibration piezoelectric bodies 23a located on the near side and the two second torsional vibration piezoelectric bodies 23a located on the front side have voltages in the same direction. The arrangement is such that when applied, it will shear in different directions. Further, a voltage in the same direction is applied to the two second torsional vibration piezoelectric bodies 23a located on the opposite side and the two second torsional vibration piezoelectric bodies 23a located on the opposite side. If so, they are arranged so that they are sheared in different directions. For example, as shown in FIG.
When the two second torsional vibration piezoelectric members 23a and the two second torsional vibration piezoelectric members 23a located on the other side are sheared, the anti-drive surface at the position opposed to the drive surface D becomes FIG.
Is twisted in the same direction as shown in FIG.

As described above, by arranging the torsional vibration piezoelectric bodies 23a, the same frequency voltage is applied to the first torsional vibration piezoelectric bodies 23a and the second torsional vibration piezoelectric bodies 23a. When the voltage is applied, the torsional vibration direction of the driving surface of the torsional vibration is the same as the torsional vibration direction of the anti-driving surface, and the secondary torsional vibration is easily excited.

The piezoelectric body 23b for vertical vibration expands and contracts when a frequency voltage is applied, and a longitudinal vibration is generated in the vibrator 21 by the expansion and contraction.

The group of longitudinal vibration piezoelectric members 23b is composed of two longitudinal vibration piezoelectric members 23b located on the near side in the drawing and two longitudinal vibration piezoelectric members 23b located on the other side. When voltages in the directions are applied, they are arranged so as to be vertically deformed in the same direction. As described above, by arranging the piezoelectric members for longitudinal vibration 23b, when the same frequency voltage is applied to the group of piezoelectric members for longitudinal vibration 23b, the primary longitudinal vibration is easily excited.

The driving signal having two (1/4) λ phase differences is applied to the ultrasonic actuator 20 of the present embodiment having the above-described configuration, respectively, by the piezoelectric body 23a for torsional vibration and the piezoelectric body 23b for longitudinal vibration. , The phases of the torsional vibration and the longitudinal vibration are shifted by 90 °, and an elliptic motion obtained by combining these vibrations is generated on the driving surface D of the vibrator 21.

FIG. 3 is an explanatory view showing the generation of an elliptical motion on the drive surface D of the vibrator 21 by combining the torsional vibration and the longitudinal vibration generated on the vibrator 21 with time. Note that, in FIG. 3, for convenience of description, a moving element that comes into pressure contact with the driving surface D of the vibrator 21 is omitted.

As described above, when the phase difference between the period of the torsional vibration and the period of the longitudinal vibration is set to be shifted by (１ ／) λ (λ: wavelength), the fixed point on the driving surface D of the vibrator 21 is Generates an elliptical motion in which torsional vibration and longitudinal vibration are combined.

Assuming that the angular velocity of the moving element is ω, t = (6 /
4) At the point of (π / ω), the displacement of the torsional vibration is the largest on the left side, and the displacement of the longitudinal vibration is zero. In this state, the moving element is pressed by the vibrator 21 by a pressing member (not shown).
Is brought into pressure contact with the drive surface D.

From this state, t = (7/4) · (π /
From ω) to 0 to (2/4) · (π / ω), the torsional vibration is displaced from the maximum on the left to the maximum on the right, and the longitudinal vibration is displaced from zero to the maximum on the upper side, and returns to zero again. Return. Therefore, the driving surface D of the vibrator 21 rotates rightward while pressing the moving element, and the moving element is driven.

Next, t = (2/4) · (π / ω)-(6
Up to / 4) · (π / ω), the torsional vibration is displaced from the maximum on the right to the maximum on the left, and the longitudinal vibration is displaced from zero to the maximum on the lower side and returns to zero again. Therefore, the driving surface D of the vibrator 21 rotates leftward while moving away from the moving element, and the moving element is not driven. At this time, the moving element is pressed by the pressing member, but cannot follow the contraction of the vibrator 21 because the natural frequency of the pressing member is lower than the ultrasonic vibration range.

In the present embodiment, two groups of torsional vibration piezoelectric bodies 23a are arranged for secondary torsional vibration, and one group of longitudinal vibration piezoelectric bodies for primary longitudinal vibration. 23b
The arrangement prevents the vibration piezoelectric member from being disposed at the antinode position of the torsional vibration.

Here, when the current input to the ultrasonic actuator 20 is obtained from an equivalent circuit of the vibrator (“Introduction to Ultrasonic Motor”, page 81, quoted by Sogo Denshi Publishing Co., Ltd.), the vicinity of the anti-resonance point is obtained. Is a driving point, the input current is represented by the following approximate expression. Here, the attenuation due to pressurization or the like is ignored. Input current ^{I = V · R · ω 2} · C 2 ·······

C: Capacitor component of vibrator (mainly capacitance of piezoelectric body) V: Applied voltage R: Resonance resistance of vibrator ω: Angular velocity of frequency voltage

Therefore, according to the ultrasonic actuator 20 of the present embodiment, the capacitance of the piezoelectric body is reduced by not arranging the piezoelectric body at the antinode position which does not significantly contribute to the generation of vibration. The input current can be reduced.

In this embodiment, two groups of torsional vibration piezoelectric bodies 23a are arranged for secondary torsional vibration, and one group of longitudinal vibrations for primary torsional vibration. Piezoelectric body 2
Since the 3b is disposed, the torsional vibration displacement to be excited by the piezoelectric body and the torsional vibration displacement of the elastic bodies 24a and 24b to be actually excited can be substantially matched. Therefore, the torsional vibration and the longitudinal vibration are easily excited, respectively, so that a large vibration amplitude generated in the vibrator 21 can be secured, and the driving force and the driving efficiency of the ultrasonic actuator 20 can be improved.

In the present embodiment, in the first group of torsional vibration piezoelectric bodies 23a, the center portion and the first node of torsional vibration are made to coincide with each other. Also, the second torsional vibration piezoelectric body 23
In the group b, the center part and the second node part of the torsional vibration are matched. By arranging the first torsional vibration piezoelectric body 23a group and the second torsional vibration piezoelectric body 23b group in this manner, natural torsional vibration is easily excited, and the torsional vibration amplitude is reduced. It is possible to secure a larger size.

Further, in the group of vertical vibration piezoelectric members 23b, the central portion and the node portion of the vertical vibration coincide with each other. By arranging the piezoelectric body 23b for longitudinal vibration in this way, natural torsional vibration is easily excited, and the longitudinal vibration amplitude can be further secured. As described above, the vibration piezoelectric body 23b
By matching the central portion of the group with the vibration node, a large longitudinal vibration amplitude and a large torsional vibration amplitude can be secured, thereby improving the driving efficiency and driving force of the ultrasonic actuator 20. it can. Further, loss of vibration energy can be prevented.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the following description of the embodiment, only parts different from the first embodiment will be described, and common parts will be denoted by the same reference numerals in the drawings.
A duplicate description will be omitted.

FIG. 4 is an explanatory view showing the structure of the vibrator 21-1 of the ultrasonic actuator 20-1 according to the second embodiment. FIG. 2A is a top view of the vibrator 21-1. (B)
Is a vibrator 2 showing the generated longitudinal vibration and torsional vibration together
It is a side view of 1-1.

The moving element 22 and the fixed shaft 28 have exactly the same configuration as in the first embodiment, and thus the description is omitted. The vibrator 21-1 includes piezoelectric bodies 23 a and 23 b which are electromechanical transducers excited by a drive signal, and these piezoelectric bodies 2
3a and 23b are joined, and these piezoelectric bodies 23
The first and second torsional vibrations are generated by the excitation of the a and b, so that the driving surface D of the vibrator 21-1 is generated.
And elastic bodies 24a and 24b that generate a driving force.

The elastic members 24a and 24b are formed by two small-diameter portions 21a and 21b formed in a ring shape on the side surface and three large-diameter portions 21A and 21B formed by being separated by the small-diameter portions 21a and 21b. And an elastic member having a shape obtained by vertically dividing a thick cylinder having 21C and 21C into two.

Two layers of piezoelectric members 23a and 23b and electrodes 25a and 25b are sandwiched between the divided surfaces of the elastic members 24a and 24b. The small diameter portions 21a and 21b are arranged at nodes of the torsional vibration.

Near the antinodes of the longitudinal vibration and the torsional vibration generated in the elastic bodies 24a and 24b,
Reinforcing members 40a, 40b, 40c, and 40d having the same width as a, 23b and electrodes 25a, 25b are arranged. The torsional vibration piezoelectric body 23a is disposed at a node of the torsional vibration,
The piezoelectric body for longitudinal vibration 23b is arranged at a node of longitudinal vibration.

The arrangement of the torsional vibration piezoelectric body 23a and the longitudinal vibration piezoelectric body 23b and the deformation direction generated when a frequency voltage is applied are the same as those in the first embodiment. Omitted.

Also in this embodiment, two groups of torsional vibration piezoelectric bodies 23a are arranged for secondary torsional vibration, and one group of longitudinal vibration piezoelectric bodies 23a for primary longitudinal vibration. Body 2
By arranging 3b, the vibration piezoelectric body is not arranged at the antinode position of the torsional vibration, whereby the capacitance of the entire piezoelectric body can be reduced.

Also in this embodiment, two groups of torsional vibration piezoelectric members 23a are arranged for secondary torsional vibration, and one group of longitudinal vibrations for primary longitudinal vibration. By arranging the piezoelectric body 23b for use, torsional vibration and longitudinal vibration are easily excited, respectively, so that a large vibration amplitude generated in the vibrator 21 can be ensured. Therefore, the driving force and driving efficiency of the ultrasonic actuator 20 can be improved.

Also in the present embodiment, the center of the first torsional vibration piezoelectric body 23a and the first node of the torsional vibration are made to coincide with each other. Also, the second torsional vibration piezoelectric body 23a
For the group, the center and the second node of the torsional vibration are matched. Thus, by disposing the first torsional vibration piezoelectric body 23a group and the second torsional vibration piezoelectric body 23a group, natural torsional vibration is easily excited in the vibrator 21-1. Thus, the torsional vibration amplitude can be further increased.

On the other hand, also for the group of longitudinal vibration piezoelectric bodies 23b, the central portion and the node of longitudinal vibration are made to coincide. As described above, by disposing the group of vertical vibration piezoelectric members 23b, natural torsional vibration is easily excited in the vibrator 21-1.
A larger longitudinal vibration amplitude can be ensured. As described above, the central portion of the vibration piezoelectric bodies 23a and 23b is
The longitudinal vibration amplitude and the torsional vibration amplitude can be kept large by matching the nodes of the vibrations generated in the vibrator 21-1.
0-1 driving efficiency and driving force can be improved.

(Modifications) In each of the embodiments described in detail above, an ultrasonic actuator using an ultrasonic vibration region is taken as an example of the vibration actuator. However, the vibration actuator according to the present invention has such an aspect. The present invention is not limited to this, and can be equally applied to a vibration actuator using another vibration region.

Further, in each of the embodiments, the piezoelectric body is used as the electromechanical conversion element. However, any other element may be used as long as it can convert electric energy into mechanical displacement. For example, an electrostrictive element other than the piezoelectric body can be exemplified.

In the description of each embodiment, the hollow cylindrical elastic body is divided into two by a vertical surface including the central axis, and the torsional vibration piezoelectric body and the longitudinal vibration piezoelectric body are formed on these divided surfaces. Although the ultrasonic actuator which holds it while sandwiching it is used, the vibration actuator according to the present invention is not limited to such an embodiment. A plurality of electromechanical transducers excited by the drive signal are mounted, and a first or more order vibration in a first direction and a first or more order vibration in a second direction different from the first direction are generated. The same applies to a vibration actuator using an elastic body that generates a driving force on its end face, regardless of the arrangement of the piezoelectric body for vibration.

FIG. 5 is an explanatory diagram showing such an ultrasonic actuator 50 together with examples of generated longitudinal vibration and torsional vibration. A cylindrical first torsional vibration piezoelectric body 51a, a second torsional vibration piezoelectric body 51b, a vertical vibration piezoelectric body 52, and four cylindrical elastic bodies 53a, 53b,
An ultrasonic actuator 50 constituted by 53c and 53d.

Also in this modification, the torsional vibration 2
The torsional vibration piezoelectric members 51a and 51b are arranged at the two nodes X and Z, and the longitudinal vibration piezoelectric member 52 is arranged at one longitudinal vibration node Y. This makes it possible to achieve the same effect (improvement in driving efficiency) as in each of the above-described embodiments.

The vibration actuator according to the present invention is not limited to such an embodiment, and generates m-th (m: natural number) torsional vibration and n-th (n: natural number) longitudinal vibration. In the case of an ultrasonic actuator using a vibrating element, a piezoelectric body for longitudinal vibration is arranged at each node of the n group, and a piezoelectric body for torsional vibration is arranged at each node of the m group. The same effects as in the embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of an ultrasonic actuator according to a first embodiment.

2A and 2B are explanatory diagrams showing an arrangement of a piezoelectric body mounted on a vibrator in the first embodiment. FIG. 2A is a top view of the vibrator, and FIG. It is a side view of a vibrator also showing an example of torsional vibration.

FIG. 3 is an explanatory diagram showing, over time, generation of an elliptical motion on a driving surface of a vibrator by combining torsional vibration and longitudinal vibration generated in the vibrator in the first embodiment.

FIG. 4 is an explanatory view showing a structure of a vibrator according to a second embodiment. FIG. 4A is a top view of the vibrator, and FIG.
FIG. 5 is a side view of the vibrator, showing both longitudinal vibration and torsional vibration.

FIG. 5 is an explanatory view showing a modified form of an ultrasonic actuator together with examples of generated longitudinal vibration and torsional vibration.

FIG. 6 is a perspective view showing a structural example of a vertical-torsion vibration type vibration actuator.

FIG. 7 is a perspective view showing a state where a stator constituting the vibration actuator shown in FIG. 6 is expanded.

FIG. 8 is a longitudinal sectional view showing a structural example of a modified mode degenerate type vibration actuator.

FIG. 9 is a block diagram illustrating control of the vibration actuator of FIG. 8;

10 (a) is a view of the vibrator held in a state of being sandwiched between the semi-cylindrical elastic bodies shown in FIG. 8, viewed from the bottom direction, and FIG. 10 (b) is a view of FIG. It is the figure which looked at the vibrator shown from the side.

FIG. 11 is an explanatory diagram showing a driving principle of a vibration actuator that generates elliptical motion on a driving surface by combining longitudinal vibration and torsional vibration generated in a vibrator.

[Explanation of symbols]

 Reference Signs List 20 ultrasonic actuator 21 vibrator 21a drive surface 21a, 21b small diameter portion 21A, 21B, 21C large diameter portion 22 mover 22a mover base material 22b sliding material 22c gear 23a piezoelectric body for torsional vibration 23b piezoelectric for longitudinal vibration Body 24a, 24b Elastic body 25a, 25b Electrode 26a, 26b Through hole 27a, 27b Bolt 28 Fixed shaft 28a Large diameter portion 28b Screw portion

Claims (3)

[Claims] 1. A plurality of electromechanical transducers, which are excited by a drive signal, are mounted, and a first or more order vibration in a first direction and a first or more order in a second direction different from the first direction. A vibration actuator comprising: an elastic body that generates a driving force on an end face of the elastic body by generating vibration; and a relative motion member that presses against the end face of the elastic body to generate relative motion between the elastic body and the elastic body. In the axial direction intersecting with the end face, the electromechanical transducers that generate the vibration in the first direction are mounted in the same number as the order of the vibration, and the vibration in the second direction is A vibration actuator, wherein the number of generated electromechanical transducers is the same as the order of the vibration. 2. The vibration actuator according to claim 1, wherein the electromechanical transducer that generates the vibration in the first direction has a center in the axial direction corresponding to a node position of the vibration. And the electromechanical transducer that generates the vibration in the second direction is mounted such that a center in the axial direction coincides with a node position of the vibration. Vibration actuator. 3. The vibration actuator according to claim 1, wherein the elastic body has a columnar shape, and the vibration in the first direction is a longitudinal vibration of the elastic body in the axial direction. In addition, the vibration in the second direction is a torsional vibration about an axis of the elastic body.