JPH0984367A - Vibration actuator - Google Patents

Abstract

In the vibration actuator proposed by Japanese Patent Application No. 6-275022, the number of parts of the vibrator 1 increases, the assembly process at the time of bonding becomes complicated, and the work man-hour increases. . In a vibration actuator using a so-called deformed mode degenerate oscillator 10, an electromechanical conversion element is composed of an electromechanical conversion element 13 for generating longitudinal vibration and an electromechanical conversion element 12 for generating torsional vibration. The electromechanical conversion element for generation 13 is arranged in a position including a node of longitudinal vibration, and the electromechanical conversion element 12 for generation of torsional vibration is arranged in a position including a node of torsional vibration so as to be located on substantially the same plane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called irregular mode degeneracy, which includes an oscillator to which an electromechanical conversion element is joined to generate a plurality of oscillation modes, and a relative motion member which is brought into pressure contact with the oscillator. Type vibration actuator.

[0002]

2. Description of the Related Art FIG. 6 is a perspective view showing an example of a conventional longitudinal-torsion vibration type vibration actuator.

Conventionally, in this type of vibration actuator,
The stator (stator) 101 includes two cylindrical vibrators 1.
A piezoelectric element 104 for torsional vibration is arranged between 02 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. Furthermore, the rotor (moving element) 10
6 is arranged above the piezoelectric element 105 for longitudinal vibration.

A vibrator 102 constituting a stator 101,
103 and the piezoelectric elements 104 and 105
The rotor 106 is rotatably provided on the shaft 107 via a ball bearing 108 by being screwed and fixed to the threaded portion of the. A nut 110 is screwed onto the tip of the shaft 107 via a spring 109 to bring the rotor 106 into pressure contact with the stator 101 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 piezoelectric element 104 for torsional vibration is the rotor 1
06 provides a mechanical displacement for rotation, while the piezoelectric element 105 for longitudinal vibration periodically synchronizes the frictional force acting between the stator 101 and the rotor 106 with the cycle of torsional vibration by the piezoelectric element 104. By virtue of this, it plays the role of a clutch that converts vibration into movement in one direction.

FIG. 7 is an exploded perspective view showing a stator of this conventional vibration actuator. Since the piezoelectric element 104 for torsional vibration needs to be polarized in the circumferential direction,
As shown in FIG. 7, the piezoelectric material was once divided into about 6 to 8 fan-shaped small pieces, and each small piece was polarized and then recombined into an annular shape. Reference numeral 104a is an electrode.

[0008]

However, in the conventional vibration actuator described above, 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 areas of the piezoelectric element 105 for longitudinal vibration and the piezoelectric element 104 for torsional vibration are both
It was substantially equal to or smaller than the cross-sectional area of the stator 106. Also, the shaft 10
It is also necessary to make a hole in the central portion of each of the piezoelectric element 105 for longitudinal vibration and the piezoelectric element 104 for torsional vibration in order to penetrate the piezoelectric element 7. Therefore, the piezoelectric element 10 for longitudinal vibration is provided.
5, 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 been able to drive with high torque and high rotation according to Japanese Patent Application No. 6-275022, and the structure and the manufacturing are easy. We proposed a vibration actuator that uses a so-called odd-mode degenerate oscillator that generates first-order longitudinal vibration and first-order torsional vibration.

FIG. 8 is a diagram for explaining the driving principle of a vibration actuator which combines this vibrator with longitudinal vibration and torsional vibration to generate an elliptical motion on the driving surface. FIG. 8 (A) is a top view and FIG. 8B is a side view, and FIG. 8C is an explanatory diagram showing waveforms of a longitudinal vibration mode and a torsional vibration mode generated in the vibrator.

The vibrator 1 includes two semi-cylindrical elastic bodies 2 obtained by vertically dividing a hollow cylindrical elastic body in a plane including the rotation axis.
a and 2b are combined. Between the two semi-cylindrical elastic bodies 2a and 2b, two piezoelectric elements 4 and 5, which are electromechanical conversion elements, are bonded in total, and a total of four piezoelectric elements 4, 4 and 5, 5 are connected by a drive signal. Is excited, a first-order torsional vibration and a first-order longitudinal vibration are generated in the vibrator 1, respectively, as shown in FIG. 8 (C).

When the resonance frequencies of the longitudinal vibration and the torsional vibration generated in the vibrator 1 substantially coincide with each other, the vibrator 1 simultaneously generates the longitudinal vibration and the torsional vibration (hereinafter, such a state is referred to as "degenerate"). ), An elliptic motion in which a fixed point oscillates in an elliptical shape is generated on the driving surface 6 which is one end surface of the vibrator 1.

The generated elliptical movement drives the moving element 7 by rotationally driving the moving element 7 which is a relative moving member that is brought into pressure contact with the driving surface 6. FIG. 9 is an explanatory view showing the structure of the vibrator 1 in detail. FIG. 9 (A) is a top view,
FIG. 9B is a side view.

The vibrator 1 is a combination of semi-cylindrical elastic bodies 2a and 2b obtained by vertically dividing a hollow cylindrical body into two parts, and the divided surfaces have piezoelectric elements 4 and 5, and an electrode plate 7. , 8 and 9 are sandwiched and held in a laminated state as shown in the drawing.

The piezoelectric element 4 and the piezoelectric element 5 are composed of two groups, and each group is composed of four layers. Of the four layers of piezoelectric elements, two layers (piezoelectric element 5 for torsional vibration) have a large piezoelectric constant d ₁₅ , and the remaining two layers (piezoelectric element 4 for longitudinal vibration) have a large piezoelectric constant d ₃₁ . Each is composed. Piezoelectric element 5 for torsional vibration having a large piezoelectric constant d _15.
Generates shear displacement in the longitudinal direction of the vibrator 1.

When a voltage is applied to the torsional vibration piezoelectric element 5 having a large piezoelectric constant d _15, a torsional displacement occurs in the vibrator 1, and a voltage is applied to the longitudinal vibration piezoelectric element 4 having a large piezoelectric constant d _31. Then, the vibrator 1 is vertically displaced.

As described above, by inputting the sinusoidal voltage to the piezoelectric element 5 for torsional vibration, a torsional motion is generated in the vibrator 1 accordingly, and the sinusoidal voltage is input to the piezoelectric body 4 for longitudinal vibration. As a result, a stretching motion (longitudinal motion) is generated in the vibrator 1 accordingly. FIG. 10 is an explanatory diagram showing the operation of a vibration actuator using such a variant mode degenerate oscillator over time.

As shown in FIG. 10, when the phase difference between the period of the torsional vibration T and the period of the longitudinal vibration L is shifted by (1/4) λ (λ: wavelength), the fixed point on the driving surface 6 is elliptical. Exercise occurs. At time t = (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 mover 7 is brought into pressure contact with the drive surface 6 of the vibrator 1 by a pressure member (not shown).

From this state, t = (7/4) π˜0
Up to (2/4) π, the torsional vibration T is displaced from the left maximum to the right maximum, while the longitudinal vibration L is displaced from zero to the upper maximum and returns to zero again. Therefore, the fixed point of the drive surface 6 of the vibrator 1 rotates to the right while pushing the mover 7, and the mover 7 is driven.

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 L is from zero to below. It shifts to the maximum on the side and returns to zero again. Therefore, the fixed point of the drive surface 6 of the moving element 7 rotates to the left while moving away from the moving element 7, so that the moving element 7 is not driven. At this time, the moving element 7 does not follow the contraction of the vibrator 1 even if it is pressed by a pressing member (not shown), because the natural frequency of the pressing member is smaller than the driving frequency.

By inputting a sine wave voltage to the piezoelectric element 4 for longitudinal vibration and the piezoelectric body 5 for torsional vibration, torsional vibration T is generated in the vibrator 1 in response to this, and at this time, the vibrator 1
By arranging the piezoelectric elements 4 and 5 at the nodes of the respective vibrations that occur, the vibrations are efficiently excited.

By the way, the above-mentioned Japanese Patent Application No. 6-27502.
The vibration actuator proposed by No. 2 generates an elliptic motion on the drive surface 6 by combining the primary longitudinal vibration and the primary torsional vibration. Therefore, in order to dispose the piezoelectric element so as to straddle the nodes of the respective vibrations that are close to each other, the piezoelectric element 4 for longitudinal vibration and the piezoelectric element 5 for torsional vibration are stacked in a stacked state, and the divided surface of the vibrator 1 is overlapped. Had to be placed in.

Therefore, the vibrator 1 includes two divided semi-cylindrical elastic bodies 2a and 2b and a two-layer piezoelectric body 4 for longitudinal vibration.
And two layers of piezoelectric element 5 for torsional vibration and three layers of electrodes 7, 8,
9 and 9 had to be assembled by laminating, for example, by adhesion. Therefore, there is a problem in that the number of parts of the vibrator 1 increases, the assembly process at the time of bonding becomes complicated, and the number of work steps increases.

Further, in the vibration actuator proposed in Japanese Patent Application No. 6-275022, the components of the vibrator 1 are bonded by adhesion, and since there are many bonding points, the reliability during continuous driving for a long time is improved. In addition, there is a problem that reliability such as humidity resistance and temperature resistance is lowered.

Further, when the vibrator 1 of the vibration actuator proposed in Japanese Patent Application No. 6-275022 generates longitudinal vibration and torsional vibration, the torsional vibration is more likely to be excited than the longitudinal vibration. Therefore, even if the size of the piezoelectric element 5 for torsional vibration is smaller than that of the piezoelectric element 4 for longitudinal vibration, it is possible to sufficiently excite the torsional vibration. That is, if the piezoelectric element 5 for torsional vibration is made smaller, the electrostatic capacity can be made smaller and the input energy can be made smaller, so that the driving efficiency can be improved.

However, in the vibration actuator proposed in Japanese Patent Application No. 6-275022, since the piezoelectric element for torsional vibration and the piezoelectric element for longitudinal vibration are laminated, the piezoelectric element for torsional vibration 5 is formed. There is a problem that it is difficult to change the size and the size of the piezoelectric element 4 for longitudinal vibration.

Furthermore, when the moving element 7 is brought into pressure contact with the vibrator 1 as shown in FIG. 8, it is necessary to press the moving element 7 in the same direction as the longitudinal vibration direction. Therefore, the vertical vibration of the vibrator 1 may be attenuated by the pressure applied to the moving element 7.

In order to reduce the attenuation of the longitudinal vibration due to the pressurization of the moving element 7 as much as possible, it is necessary to make the size of the piezoelectric element 5 for torsional vibration larger than that of the piezoelectric element 4 for longitudinal vibration. . However, Japanese Patent Application No. 6-275022
Of the vibration actuator proposed by No. 1
However, there is a problem that it is difficult to change the sizes of the torsional vibration piezoelectric element 5 and the longitudinal vibration piezoelectric element 4 for the same reason.

[0030]

According to a first aspect of the present invention, there is provided a vibrator having two elastic bodies and an electromechanical conversion element which is arranged between the two elastic bodies and which is excited by a drive signal. A relative movement member that is brought into pressure contact with the vibrator, and is displaced in the vibrator in a direction substantially parallel to a joint surface between the electromechanical conversion element and the elastic body by excitation of the electromechanical conversion element. Driving the driving surface formed in a direction substantially perpendicular to the rotation axis of the torsional vibration by generating a longitudinal vibration that causes the vibration and a torsional vibration having a rotation axis in a direction substantially the same as the displacement direction of the longitudinal vibration. A vibration actuator that generates force, wherein the electromechanical conversion element includes a longitudinal vibration generation electromechanical conversion element and a torsional vibration generation electromechanical conversion element, and the vertical vibration generation electromechanical conversion element is the longitudinal vibration generation electromechanical conversion element. Includes vibration node The location, the torsional vibration generating electromechanical transducer is a position including the section of the torsional vibration, a vibration actuator, characterized in that it is arranged so as to be positioned on substantially the same plane.

According to a second aspect of the present invention, in the vibration actuator according to the first aspect, the joint area between the electromechanical conversion element for generating torsional vibration and the elastic body is the same as the electromechanical conversion element for generating longitudinal vibration. It is characterized in that it is smaller than the joint area with the elastic body.

[0032]

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.

FIG. 1 is a sectional view for explaining the structure of a vibration actuator 10 according to the first embodiment of the present invention.
Piezoelectric elements 12 and 13, which are electromechanical conversion elements excited by a drive signal, and these piezoelectric elements 12 and 13 are joined to the vibrator 11.
The excitation of 13 generates a first-order longitudinal vibration and a second-order torsional vibration to generate a driving force on the driving surface 11c.

The vibrator 11 is made of a metal material such as steel, stainless steel or phosphor bronze, and has four large diameter portions 14A, 14B, 14C and 14D and three small diameter portions 14
a thick cylinder with a, 14b and 14c
It is configured by combining hollow semi-cylindrical elastic bodies 11a and 11b which are divided into two. Semi-cylindrical elastic bodies 11a, 11b
The two layers of the piezoelectric bodies 12 and 13 and the electrode 15 are sandwiched and held between them.

The small diameter portions 14a, 14b and 14c are formed at positions including the nodes of the secondary torsional vibration. The piezoelectric element 12 for torsional vibration is arranged at a position including a node portion of the torsional vibration to be generated, while the piezoelectric element 13 for longitudinal vibration is arranged at a position including a node portion of primary longitudinal vibration. The vibrator 11 includes four large diameter portions 14A to 14D and three small diameter portions 14a to 14D.
The shape having c is to cause degeneracy by causing the resonance frequency of the primary longitudinal vibration and the resonance frequency of the secondary torsional vibration to substantially match. The piezoelectric element for torsional vibration 1
Although not shown in FIG. 1, neither the piezoelectric element 2 for vertical vibration nor the piezoelectric element 13 for longitudinal vibration will be described in detail with reference to FIG. 2 described later.

The vibrator 11 has a substantially center in the longitudinal direction,
Through holes 16a and 16b are formed in a direction parallel to the stacking direction of each of the piezoelectric element 12 for torsional vibration and the piezoelectric element 13 for longitudinal vibration.

In the semi-cylindrical elastic bodies 11a and 11b, the bolts 17a and 17b are inserted into the formed through holes 16a and 16b and fixed by the nut 18, so that the torsional vibration piezoelectric element 12 and the longitudinal vibration piezoelectric element are formed. Insert 13

Further, the vibrator 11 is provided with an annular flange portion 19 directed toward the center side at a substantially central portion in the longitudinal direction, and the flange portion 19 has a columnar shape which is screwed with each other in the vertical direction. When the upper fixed shaft 20b and the lower fixed shaft 20a are sandwiched, the vibrator 11 is fixed by the cylindrical fixed shaft 20 into which the inside is inserted.

Thick annular mover 2 which is a relative motion member
Reference numeral 1 is composed of a moving element base material 21a made of stainless steel, aluminum alloy or the like, and a sliding material 21b mainly made of a polymer material or the like which comes into contact with the driving surface 11c of the vibrator 11, and has an inner peripheral portion. It is positioned with respect to the fixed shaft 20 by a positioning member 22 such as a fitted bearing. On the outer peripheral surface of the mover base material 21a, a gear 23 for extracting output is provided.
Is provided, and its output is transmitted to a gear of a driven body (not shown).

Further, the moving element 21 is provided with a vibrating element 1 by a pressing member 24 such as a disc spring, a spring spring, and a leaf spring.
The first driving surface 11a is brought into pressure contact. Cylindrical fixed shaft 2
Reference numeral 0 penetrates through a hollow portion formed in the longitudinal direction (axial direction) of the vibrator 11, sandwiches and fixes the flange portion 19 of the vibrator 11, and positions the mover 21 in the radial direction. .

The fixed shaft 20 has a screw portion 20c formed on the upper fixed shaft 20b side, and an adjusting member 25 such as a nut for adjusting the amount of pressure applied by the pressure member 24 is screwed onto the fixed shaft 20.

FIG. 2 is an explanatory view showing the arrangement of piezoelectric elements in the vibrator 11. The vibrator 11 has four large diameter parts 1
4A to 14D and three small-diameter portions 14a to 14c, which are members having a shape of a thick hollow cylinder vertically divided into two parts. The element 13 and the electrode 15 are sandwiched.

The small diameter portions 14a to 14c are arranged at the nodes of torsional vibration. That is, the piezoelectric element 12 for torsional vibration is arranged at the node of the torsional vibration that occurs, and the piezoelectric element 13 for longitudinal vibration is arranged so as to straddle the node of the longitudinal vibration that occurs.

The torsional vibration piezoelectric element 12 is composed of a piezoelectric material having a large piezoelectric constant d _15, and when a frequency voltage is applied, shear deformation occurs in accordance with the direction of the voltage, which causes torsional vibration.

The torsional vibration piezoelectric element group is composed of two torsional vibration piezoelectric elements 12a on the front side in the drawing and two torsional vibration piezoelectric elements 12b on the back side in the drawing, and the torsional vibration piezoelectric element 12a on the front side. , And the piezoelectric element 12 for torsional vibration on the back side
When the shear deformations of the respective b are arranged so as to be opposite to each other when a voltage in the same direction is applied, a torsional displacement in a certain direction is generated in the vibrator 11.

For example, as shown in FIG. 2, the torsional vibration piezoelectric element 12a on the front side and the torsional vibration piezoelectric element 1 on the back side are provided.
When 2b is sheared and deformed, the drive surface 11a is twisted in the direction indicated by the arrow in FIG. Further, when a voltage in the opposite direction is applied, shear deformation in the opposite direction occurs, so that the drive surface 11a is twisted in the direction opposite to that in FIG.

On the other hand, the longitudinal vibration piezoelectric element 13 is composed of a piezoelectric material having a large piezoelectric constant d ₃₁ , and when a frequency voltage is applied, expansion / contraction deformation occurs in accordance with the direction of the voltage, which causes longitudinal vibration.

The piezoelectric element 13 for longitudinal vibration is the front side 2 in the drawing.
It is composed of one piezoelectric element for vertical vibration 13a and two piezoelectric elements for vertical vibration 13b on the back side in the drawing, and they are arranged so that they are vertically deformed in the same direction when voltages in the same direction are applied.

In this way, the longitudinal vibration piezoelectric elements 13a, 13
By arranging b, when the same frequency voltage is applied to the piezoelectric element group for longitudinal vibration, the primary longitudinal vibration mode is easily excited.

In this embodiment, the size of the piezoelectric element 12 for torsional vibration is smaller than that of the piezoelectric element 13 for longitudinal vibration, and the surface area of the piezoelectric element 12 for torsional vibration is smaller than the surface area of the piezoelectric element 13 for longitudinal vibration. Make it smaller.

FIG. 3 shows semi-cylindrical elastic bodies 11a and 11b, piezoelectric elements 13a and 13b for longitudinal vibration, and piezoelectric elements 12a and 12 for torsional vibration, which constitute the vibrator 11 of this embodiment.
b, longitudinal vibration detecting piezoelectric elements 26a and 26b, torsional vibration detecting piezoelectric elements 27a and 27b, and electrodes 15-1, 1
It is an exploded view showing arrangement of 5-2, 15-3, and 15-4. Note that, in FIG. 3, reference numerals are given only to the illustrated portions, and hidden portions (denoted by reference numeral b) are given since the vibrator 1 is symmetric about the axis. Omitted.

Two divided semi-cylindrical elastic bodies 11a,
Piezoelectric elements 13a and 13b for longitudinal vibration, piezoelectric elements 12a and 12b for torsional vibration, piezoelectric elements 26a and 26b for longitudinal vibration detection, and a piezoelectric element 27 for torsional vibration detection between 11b.
a and 26b, and piezoelectric elements 12a and 12b for torsional vibration
15-1a and 15-1b, 15-2 for applying a driving voltage to the piezoelectric elements 13a and 13b for longitudinal vibration
a and 15-2b, electrodes 15-3a and 15-3b, 15-4a and 1 for applying a voltage to the piezoelectric element 26 for detecting longitudinal vibration and the piezoelectric element 27 for detecting torsional vibration, respectively.
5-4b is held in a sandwiched state. The semi-cylindrical elastic bodies 11a and 11b, the longitudinal vibration piezoelectric element 13, the torsional vibration piezoelectric element 12, and the electrode 15 are bonded by an adhesive.

Further, the piezoelectric elements for torsional vibration 12a, 12b
The piezoelectric elements 27a and 27b for detecting torsional vibration are arranged on the drive surface 11c side of the vibrator 11, and the longitudinal vibration detection piezoelectric elements 26a and 26b are located on the opposite drive surface side of the longitudinal vibration piezoelectric elements 13a and 13b. Are placed. Electrode 15-1
a and 15-1b, 15-2a and 15-2b are arranged so that a drive signal can be simultaneously applied to the two layers of the longitudinal vibration piezoelectric element 13 and the two layers of the torsion vibration piezoelectric element 12.

Vibration actuator 10 having such a configuration
When two drive signals having a 1 / 4λ phase difference are input to the longitudinal vibration piezoelectric element 13 and the torsional vibration piezoelectric element 12, respectively, the phases of the longitudinal vibration and the torsional vibration are 9
The elliptical motion, which is a combination of these vibrations, is shifted by 0 ° and the oscillator 1
No. 1 drive surface 11c.

FIG. 4 is an explanatory diagram showing that the longitudinal vibration and the torsional vibration generated in the vibrator 11 of the present embodiment are combined to generate an elliptic motion on the drive surface 11c. In this way, when the phase difference between the period of the torsional motion and the period of the expansion / contraction motion is shifted by ¼λ (wavelength), the driving surface 11c of the vibrator 11 is
An elliptic motion, which is a combined vibration of the twisting motion and the stretching motion, is generated above.

At the time of t = 6 / 4π, the displacement of the torsional motion is maximum on the left side, and the displacement of the longitudinal vibration is zero. In this state, the mover 21 is in contact with the drive surface 11c of the vibrator 11 by the pressing member 24.

From this state, t = 7 / 4π to 0 to 2/4
Up to π, the torsional movement is displaced from the maximum on the left side to the maximum on the right side, while the longitudinal vibration is displaced from zero to the maximum on the upper side and returns to zero again. Therefore, the driving surface 11c of the vibrator 11 rotates in the right direction while pushing the mover 21, and the mover 21 is driven.

Next, from t = 2 / 4π to 6 / 4π, the torsional movement is displaced from the maximum on the right side to the maximum on the left side, while
The longitudinal vibration is displaced from zero to the maximum on the lower side and returns to zero again. Therefore, the driving surface 11c of the vibrator 11 rotates to the left while moving away from the moving element 21, so that the moving element 21 is not driven. At this time, the moving element 21 cannot follow the contraction of the vibrator 11 even if it is pressed by the pressing member 24 because the natural frequency of the pressing member 24 is lower than the ultrasonic vibration range. .

In the present embodiment, if the order of the longitudinal vibration and the order of the torsional vibration are different so that the vibrator 11 generates the first-order longitudinal vibration and the second-order torsional vibration which is an order larger than the first-order. Therefore, the positions of the nodes of the longitudinal vibration and the torsional vibration can be positively changed.

Like the conventional vibration actuator, this embodiment has a structure in which the torsional vibration piezoelectric element 12 and the longitudinal vibration piezoelectric element 13 are sandwiched by two elastic bodies, but like the conventional vibration actuator. It is not necessary to stack the piezoelectric element 12 for torsional vibration and the piezoelectric element 13 for longitudinal vibration, and the number of piezoelectric element layers can be reduced from four layers to two layers and the number of electrodes can be reduced from three layers to one layer.

As described above, the vibration actuator 10 of the present embodiment can reduce the number of parts as compared with the conventional vibration actuator, and the assembly process can be simplified. In addition, the number of adhesive layers between the semi-cylindrical elastic bodies 11a and 11b, the piezoelectric element 13 for longitudinal vibration, the piezoelectric element 12 for torsional vibration, and the electrode 15 can be reduced from the conventional eight layers to four layers. .

For example, the semi-cylindrical elastic bodies 11a and 11b
When the piezoelectric element 13 for longitudinal vibration and the piezoelectric element 12 for torsional vibration are bonded to each other by adhesion, vibration with a large amplitude or the like is generated in the vibrator 1.
When it occurs in No. 1, the adhesive layer, which is the weakest part of mechanical strength, may peel off. Therefore, the smaller the number of bonded portions, the lower the possibility of peeling, and the higher the reliability during continuous driving over a long period of time.

Since some adhesive layers are easily affected by environmental factors such as temperature and humidity, the more adhesive layers are reduced as in the vibration actuator 10 of the present embodiment, the more the moisture resistance becomes. Actuator 10 with heat resistance and heat resistance
The reliability of can be improved.

In this embodiment, the vibrator 11 has
Since the following longitudinal vibration and the second-order torsional vibration, which is an order larger than the first-order, are generated, it is possible to reduce the arrangement range of the torsional vibration piezoelectric element 12 necessary for exciting the torsional vibration. it can. Therefore, the piezoelectric element for torsional vibration 1
The size of 2 can be made smaller. Thereby, the driving efficiency can be improved. The piezoelectric element for torsional vibration 1
If 2 is placed in the abdomen of the torsional vibration, only the inputs unrelated to the outputs increase.

The current input to the vibration actuator in the drive range (anti-resonance point) is given by the following approximate expression when the equivalent circuit of the vibration actuator is considered. Input current I = V ・ R ・ Cd ²・ ω ²

Where Cd is the capacitance of the piezoelectric element of the vibration actuator, V is the applied voltage, R is the resistance component of the vibration actuator, and ω is the angular velocity of the frequency voltage.

Therefore, the input current I can be reduced by reducing the capacitance of the piezoelectric element without installing the piezoelectric element in a portion that does not contribute much to vibration. Also,
In the present embodiment, since the vibrator 11 is caused to generate the first-order longitudinal vibration and the second-order torsional vibration that is an order larger than the first-order, the size of the torsional vibration piezoelectric element 12 is reduced. We were able to. In this way, the size of the longitudinal vibration piezoelectric element 13, which is less likely to be excited when compared with the torsional vibration, can be increased by the amount by which the size of the torsional vibration piezoelectric element 12 is reduced. The size of can also be improved.

Further, in the so-called modified mode degenerate type vibration actuator as in the present embodiment, among the motion components of the elliptic motion on the drive surface 11c of the vibrator 11, the motion components in the drive direction and the vertical direction are Transducer 11 and mover 21
Serves as a clutch (power transmission) between and. Therefore, if the motion component in the direction perpendicular to the driving direction becomes smaller among the motion components of the elliptical motion, the function of such a clutch becomes incomplete, and the driving force may decrease or the driving efficiency may deteriorate. is there.

However, like the vibration actuator of this embodiment, if the longitudinal vibration piezoelectric element 13 is enlarged to increase the longitudinal vibration displacement, the damping of the longitudinal vibration due to the pressurization of the moving element 21 can be reduced. . As a result, it is possible to reduce a decrease in driving force and driving efficiency.

(Second Embodiment) FIG. 5 is an explanatory view showing the configuration of a second embodiment of the vibration actuator according to the present invention.

In the following description of the second embodiment, only the parts different from the first embodiment will be described, and the same parts are designated by the same reference numerals in the drawings, and the description thereof will be omitted as appropriate.

In the first embodiment, the longitudinal vibration detecting piezoelectric elements 26a and 26b and the torsional vibration detecting piezoelectric elements 27a and 27b are arranged on the driving surface 11c side of the vibrator 11 or on the surface side opposite thereto. In this embodiment, the longitudinal vibration detecting piezoelectric elements 26 a and 26 b, and the torsional vibration detecting piezoelectric element 27.
a and 27b on the outer diameter side of the elastic body 11, the electrodes 15-1,
15-2, 15-3 and 15-4 were arranged on the inner diameter side.

The configuration other than the longitudinal vibration detection piezoelectric element 26 and the torsional vibration detection piezoelectric element 27, that is, the configuration and arrangement of the vibrator 11, the fixed shaft 20, the mover 21, etc., is exactly the same as that of the first embodiment. Therefore, further description is omitted.

Like the vibrator 11-1 used in the vibration actuator of the present embodiment, the longitudinal vibration detecting piezoelectric element 26, the torsional vibration detecting piezoelectric element 27, and the electrode 15 are combined in the longitudinal direction. Piezoelectric element for torsional vibration 1 by the amount that the piezoelectric element for longitudinal vibration detection 26 and the piezoelectric element for torsional vibration detection 27 can be extended in the longitudinal direction.
The length of 2 and the length of the piezoelectric element 13 for longitudinal vibration can be set to be greatly different from each other.

Further, in this embodiment, the same piezoelectric element 12a and 12b, 13a and 13b is used to perform both driving and detection. By making the vibration detection electrode and the drive signal application electrode separate, the detection action and the excitation action can be separated. By doing so, the four piezoelectric elements, that is, the piezoelectric element 12 for torsional vibration, the piezoelectric element 13 for longitudinal vibration, the piezoelectric element 27 for detecting torsional vibration, and the piezoelectric element 26 for longitudinal vibration detection are replaced by the piezoelectric element for torsional vibration 12 Also, the number of piezoelectric elements 13 for vertical vibration can be two, and the number of parts can be further reduced.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating a structure of a vibration actuator according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of piezoelectric elements in the vibrator 11 of the vibration actuator according to the first embodiment.

FIG. 3 shows an arrangement of a semi-cylindrical elastic body, a piezoelectric element for longitudinal vibration, a piezoelectric element for torsional vibration, a piezoelectric element for longitudinal vibration detection, a piezoelectric element for torsional vibration detection, and electrodes that constitute the vibrator of the first embodiment. It is an exploded view shown.

FIG. 4 is an explanatory diagram showing that the longitudinal vibration and the torsional vibration generated in the vibrator of the first embodiment are combined to generate an elliptic motion on the drive surface.

FIG. 5 shows an arrangement of a semi-cylindrical elastic body, a piezoelectric element for longitudinal vibration, a piezoelectric element for torsional vibration, a piezoelectric element for longitudinal vibration detection, a piezoelectric element for torsional vibration detection, and electrodes that constitute the vibrator of the second embodiment. It is an exploded view shown.

FIG. 6 is a perspective view showing a structure of an example of a conventional longitudinal vibration-torsional vibration type vibration actuator.

FIG. 7 is an exploded perspective view showing a stator of a conventional vibration actuator.

FIG. 8 is a diagram for explaining a driving principle of a vibration actuator that generates an elliptic motion on a driving surface by combining a vibrator of the vibration actuator proposed in Japanese Patent Application No. 6-275022 with longitudinal vibration and torsional vibration; 8 (A) is a top view,
8B is a side view, and FIG. 8C is an explanatory diagram showing a longitudinal vibration mode and a torsional vibration mode generated in the vibrator.

9A and 9B are explanatory views showing in detail the structure of the vibrator 1 of the vibration actuator proposed in Japanese Patent Application No. 6-275022, wherein FIG. 9A is a top view and FIG. 9B is a side view. is there.

FIG. 10 is an explanatory diagram showing the operation of the vibration actuator proposed in Japanese Patent Application No. 6-275022 over time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vibration actuator 11 Vibrator 11a Drive surface 12 Piezoelectric element for torsional vibration 13 Piezoelectric element for longitudinal vibration 14A to 14D Large diameter part 14a to 14c Small diameter part 15 Electrode 16 Through hole 17 Bolt 18 Nut 19 Flange 20 Fixed shaft 21 Mover ( Relative motion member) 22 Positioning member (bearing) 23 Gear 24 Pressing member 25 Nuts 26, 27 Vibration detecting piezoelectric element

Claims (2)

[Claims] 1. A vibrator having two elastic bodies and an electromechanical conversion element disposed between the two elastic bodies and excited by a drive signal, and a relative motion member which is brought into pressure contact with the vibrator. And a longitudinal vibration in which a displacement occurs in the vibrator in a direction substantially parallel to a joint surface between the electromechanical conversion element and the elastic body by excitation of the electromechanical conversion element, and A vibration actuator that generates a driving force on a driving surface formed in a direction substantially perpendicular to the rotation axis of the torsional vibration by generating a torsional vibration having a rotation axis substantially in the same direction as the displacement direction, The electromechanical conversion element includes an electromechanical conversion element for generating longitudinal vibration and an electromechanical conversion element for generating torsional vibration, and the electromechanical conversion element for generating longitudinal vibration is provided with the torsional vibration at a position including the node of the longitudinal vibration. Electric machine for generation The vibration actuator, wherein the mechanical conversion elements are arranged at positions including the nodes of the torsional vibration so as to be located on substantially the same plane with each other. 2. The vibration actuator according to claim 1, wherein the joint area between the electromechanical conversion element for generating torsional vibration and the elastic body is equal to that of the electromechanical conversion element for generating longitudinal vibration and the elastic body. A vibration actuator characterized by being smaller than the joint area.