JPH09219982A - Vibration actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a vibration actuator by mounting electromechanical transducer elements at positions, which are not the looped positions of stretching vibration or twisting vibration with regard to the axial direction. SOLUTION: For semi-elastic bodies 13 and 14 of a vibrator 10, a thick hollow-shaped cylinder body, which has a first large-diameter part 11A, a second large-diameter part 11B and a small-diameter part 11b between the large- diameter parts in sequence, is vertically divided into two parts by a plane including a central axis, and the semi-cylinder parts are formed. Piezoelectric bodies 12a and 12b, which are the electromechanical transducer elements, are held at the divided surfaces of the semi-elastic bodies 13 and 14 formed in the semi- cylinder bodies. The primary stretching vibration and the secondary twisting vibration are generated by the excitation of the piezoelectric bodies 12a and 12b. The piezoelectric bodies 12a and 12b are mounted at the positions, which are not the loop positions generating the drive force at a drive plane D. Thus, the efficiency of the vibration actuator can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator using composite vibration of stretching vibration and torsional vibration.

[0002]

2. Description of the Related Art FIG. 9 is a perspective view showing a conventional example of a longitudinal-torsional 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 sandwiched between 02 and 103. A piezoelectric element 10 for longitudinal vibration is provided above the vibrator 103.
5 are arranged. The piezoelectric element 104 for torsional vibration is polarized in the circumferential direction, and the piezoelectric element 105 for longitudinal vibration is polarized in the thickness direction. Further, the relative motion member (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 screw portion formed on the shaft 107. Rotor 10
6 is rotatably provided on the shaft 107 via a ball bearing 108 arranged at the center. A nut 110 is screwed onto the tip of the shaft 107, and a spring 109 is mounted between the ball bearing 108 and the nut 110. The rotor 109 is fixed to the stator 1 by the spring 109.
01 is brought into pressure contact with the end surface.

The piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration are the oscillator 1 schematically shown in FIG.
The drive voltage of the same frequency oscillated from 11 is applied to phase shifter 1
It is phase-controlled by 12 and driven.

The piezoelectric element 104 for torsional vibration gives a mechanical displacement for rotating the rotor 106. On the other hand, the piezoelectric element 105 for longitudinal vibration includes the stator 101 and the rotor 10.
The frictional force acting between the vibrations 6 and 6 is synchronized by periodically changing in accordance with the cycle of the torsional vibration by the piezoelectric element 104, and plays a role of a clutch for converting the vibration into a movement in one direction.

FIG. 10 is an exploded perspective view showing the stator 101 of the vibration actuator shown in FIG. The piezoelectric element 104 for torsional vibration needs to be polarized in the circumferential direction. Therefore, in the piezoelectric element 104 for torsional vibration, the piezoelectric material is once divided into about 6 to 8 fan-shaped small pieces as shown in FIG. It was assembled by combining them in a ring. Reference numeral 104a is an electrode.

[0008]

However, in the conventional vibration actuator shown in FIGS. 9 and 10, when the piezoelectric element 104 for torsional vibration is assembled in an annular shape,
It was difficult to achieve shape accuracy. Therefore, the adhesion between the piezoelectric element 104 and the vibrator 103 or between the piezoelectric elements 104 decreases, and the vibration of the piezoelectric elements 104 and 105 causes the vibration of the vibrator 1.
02 and 103 are not sufficiently transmitted, and there is a problem that the driving efficiency of the vibration actuator is reduced.

Further, the piezoelectric element 104 for torsional vibration is
In order to obtain a sufficient adhesive strength when the fan-shaped small pieces are adhered and assembled, a thickness of at least several mm is required.
Therefore, the distance between the electrodes of the piezoelectric element 104 becomes large, and it is necessary to apply a high voltage between the electrodes in order to apply an electric field required for driving to the piezoelectric element 104.

On the other hand, the areas of the piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration are the same as those of the vibrators 102, 1.
03 is substantially equal to the cross-sectional area, or the oscillators 102, 10
It was smaller than the cross-sectional area of 3. Moreover, in order to penetrate the shaft 107, it is necessary to form a hole in the central portion of the piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration. Therefore, the area of each of the piezoelectric element 104 for torsional vibration and the piezoelectric element 105 for longitudinal vibration is further reduced, and it is difficult to achieve high torque and high rotation of the motor.

Therefore, the present applicant previously filed Japanese Patent Application No. 6-18.
No. 0279, Japanese Patent Application No. 6-275022, etc., a vibration actuator using a deformed mode degenerate oscillator that utilizes primary stretching vibration (longitudinal vibration) and primary (or secondary) torsional vibration. Proposed. FIG. 11 is a top view of a variant mode degenerate oscillator 50 used in this vibration actuator, and FIG. 12 is a side view of the oscillator 50.

The vibrator 50 is a piezoelectric element 52a which is an electromechanical conversion element for converting electric energy into mechanical displacement.
52b, and a hollow cylindrical elastic body 51 that generates stretching vibration and torsional vibration by the excitation of these piezoelectric elements 52a and 52b.

The elastic body 51 is obtained by combining the semi-elastic bodies 53 and 54 obtained by vertically dividing the hollow cylindrical body 51 in a plane including the central axis. A small diameter portion 51a is formed in a groove shape on the outer peripheral surface of the elastic body 51,
A first large-diameter portion 51A and a second large-diameter portion 51B are formed in the two parts separated by the small-diameter portion 51a. Therefore, the outer peripheral surface of the elastic body 51 has a central axis direction (see FIG. 12).
In the vertical direction), the first large diameter portion 51A, the small diameter portion 51a, and the second large diameter portion 51B are sequentially formed.

On the two dividing surfaces of the semi-elastic members 53, 54,
A total of four layers of piezoelectric elements 52a and 52b, two layers each, and an electrode plate 5 that applies a drive voltage to these piezoelectric elements 52a and 52b.
5a, 55b, and 55c are attached in a sandwiched state.

The piezoelectric elements 52a and 52b mounted on each of the two divided surfaces are made up of two layers, each having a total of four layers. The piezoelectric element 52a of two layers among the piezoelectric elements of four layers has a piezoelectric constant d
By using ₁₅ , shear displacement is generated in the longitudinal direction of the semi-elastic bodies 53 and 54. The remaining two layers of piezoelectric elements 52b use the piezoelectric constant d ₃₁ to cause expansion / contraction displacement in the longitudinal direction of the semi-elastic bodies 53, 54.

When a driving voltage is applied to the piezoelectric element 52a,
Torsional displacement occurs in the semi-elastic bodies 53 and 54. When a driving voltage is applied to the piezoelectric element 52b, the semi-elastic bodies 53 and 54 are
Vertical displacement occurs in the. Therefore, when a sinusoidal voltage is input to the piezoelectric element 52a for torsional vibration, torsional vibration is generated in the elastic body 51 accordingly, and the sinusoidal voltage is input to the piezoelectric element 52b for longitudinal vibration. As a result, elastic vibration is generated in the elastic body 51 accordingly.

Further, a cylindrical moving element (not shown), which is a rotatably supported relative movement member, comes into contact with a driving surface D, which is one end surface of the vibrator 51, with an appropriate pressing force. .

FIG. 13 shows the vibration actuator shown in FIGS. 11 and 12, in which the torsional vibration (T mode) and the stretching vibration (L mode) generated in the vibrator 51 are combined to generate an elliptic motion on the drive surface D. It is explanatory drawing which shows doing over time.

In FIG. 13, at time t = (6/4) π, the displacement of the torsional vibration T is maximum on the left side, while
The displacement of the stretching vibration L is zero. In this state, the mover (not shown) is brought into pressure contact with the drive surface D of the vibrator 51 by a pressure mechanism (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 stretching vibration L is displaced from zero to the upper maximum and returns to zero again. Therefore, the oscillator 5
The fixed point of the driving surface D of No. 1 rotates to the right while pushing the mover, and the mover 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 stretching vibration L is zero. Then, it moves to the lower maximum and returns to zero again. Therefore, the fixed point of the driving surface D of the vibrator 51 rotates leftward while separating from the moving element,
The mover is not driven. At this time, the moving element does not follow the contraction of the vibrator because the natural frequency is different even if it is pressed by the pressing member.

Here, when the resonance frequency of the torsional vibration and the resonance frequency of the stretching vibration are substantially equal to each other, the torsional vibration and the stretching vibration are simultaneously generated (degenerate) in the vibrator 51, and the driving surface D is generated. An elliptical motion occurs in the, and a driving force is generated.

When the frequency of the torsional vibration is made to substantially match the resonance frequency of the torsional vibration and the frequency of the stretching vibration is made to substantially match the resonance frequency of the stretching vibration when the elliptical motion is occurring. , And resonate, and the elliptical motion on the drive surface D expands.

By the way, in these variant mode degenerate type vibration actuators, the piezoelectric elements 52a and 52b are arranged on the entire dividing surface of each of the semi-elastic bodies 53 and 54 in the elastic body axial direction. Therefore, the piezoelectric element 52
The a and 52b were arranged at two node positions across the antinode position of the torsional vibration.

Generally, when a piezoelectric element is mounted on an elastic body and torsional vibration and stretching vibration are generated, the piezoelectric element is arranged at a position including a node position of each vibration. This is because the node position of each vibration is the position where the strain displacement is the largest, so by placing a piezoelectric element at the node part of each vibration, it is possible to extremely efficiently generate torsional vibration and stretching vibration. It is because

By the way, in the variant mode degenerate vibration actuator shown in FIGS. 11 to 13, piezoelectric elements are also arranged at the antinode positions of each of the torsional vibration and the stretching vibration. The position where the displacement is small. Therefore, the piezoelectric element arranged at the antinode position does not contribute much to the generation of vibration, and the energy input to the piezoelectric element attached at the antinode position is not effectively used. Therefore, there is a problem that the driving efficiency of the vibration actuator is not improved accordingly.

[0027]

According to a first aspect of the present invention, there is provided an elastic body and an electromechanical conversion element mounted on the elastic body, and a drive voltage is applied to the electromechanical conversion element.
In a vibration actuator that generates a driving force by generating a stretching vibration and a torsional vibration in the axial direction of the elastic body, the electromechanical conversion element is configured so that the stretching vibration or the torsional vibration is generated in the axial direction. At a position that is not the belly position,
It is characterized by being installed.

According to a second aspect of the invention, in the vibration actuator according to the first aspect, the antinode position is near both ends of the elastic body in the axial direction.

The invention of claim 3 is the invention of claim 1 or claim 2.
In the vibration actuator described in (1), a mechanical-electrical conversion element or a reinforcing member that converts mechanical displacement into electric energy is attached to the antinode position.

The invention of claim 4 is from claim 1 to claim 3.
In the vibration actuator described in any one of the above items, the extensional vibration has an order of 1 or more and the torsional vibration has an order of 1 or more.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a vertical sectional view for explaining a vibration actuator 1 according to a first embodiment of the present invention. Note that the following description of each embodiment will be given by taking an ultrasonic actuator that uses the frequency of an ultrasonic region as an example of the vibration actuator.

The vibrator 10 constituting the ultrasonic actuator 1 shown in FIG. 1 is formed by connecting piezoelectric bodies 12a and 12b, which are electromechanical conversion elements excited by a drive signal, with these piezoelectric bodies 12a and 12b. It is composed of semi-elastic bodies 13 and 14 which generate a driving force on the drive surface D by generating a primary stretching vibration and a secondary torsional vibration by the excitation of the bodies 12a and 12b.

The semi-elastic bodies 13, 14 are thick-walled hollow cylindrical bodies having a first large diameter portion 11A, a second large diameter portion 11B, and a small diameter portion 11a between them in this order in the axial direction of the outer peripheral surface. Is a semi-cylindrical body obtained by vertically dividing into two in a plane including the central axis. Piezoelectric bodies 12a and 12b are attached to the two divided surfaces of the semi-elastic bodies 13 and 14 in a state of being sandwiched therebetween.

The length of the first large diameter portion 11A in the vibrator axial direction is
It is set longer than the axial length of the second large diameter portion 11B.
In the present embodiment, the vibration generating piezoelectric bodies 12a and 12b for converting electric energy into mechanical displacement are arranged in the range in which the first large diameter portions 11A and 11B are formed in the vibrator axial direction.

Further, as shown in FIGS. 2 and 3 which will be described later, the piezoelectric bodies 12 and 12b are formed with a total of four layers, two layers on each of the two divided surfaces. Two layers of the four layers of the piezoelectric body 12a generate shear displacement in the elastic body longitudinal direction by using the piezoelectric constant d ₁₅ . The remaining two layers of the piezoelectric body 12b use the piezoelectric constant d ₃₁ to generate expansion / contraction displacement in the elastic body longitudinal direction.

Through holes 16 and 17 are formed in the semi-elastic bodies 13 and 14 in a direction parallel to the stacking direction of the piezoelectric bodies 12a and 12b (left-right direction in FIG. 1) substantially in the center of the elastic body axial direction.

Bolts 18 are formed in the formed through holes 16 and 17.
Insert a and 18b, and attach the tips of bolts 18a and 18b to
A screw hole 19 provided in a large diameter portion 19a of a fixed shaft 19 described later.
By being screwed into b, the semi-elastic bodies 13 and 14 hold the piezoelectric bodies 12a and 12b in a sandwiched state, and the vibrator 10 is held by the fixed shaft 19 penetrating the center in the axial direction.

The fixed shaft 19 penetrates through the hollow portions formed in the axial direction of the semi-elastic bodies 13 and 14, fixes the elastic body 11 as described above, and rotatably moves the mover 20 described later. Position and hold in the direction.

A cylindrical mover 20 which is a relative motion member.
Is a thick-walled annular mover base material 20a and mover base material 20
The sliding member 20b is attached to the end face of the elastic body 11 side of a and contacts the drive surface D.

An annular groove portion 20c is formed on the inner peripheral portion of the end surface of the mover base material 20a on the anti-vibrator 11 side, and a bearing 21 which is a positioning member is fitted in the groove portion 20c. 21 is attached to the fixed shaft 19.

An output take-out gear (not shown) is formed in an annular shape on the outer peripheral surface of the mover base material 20a. The output extracting gear meshes with a gear (not shown) formed in an annular shape on a driven body (not shown). In this way,
The output (rotational power) of the mover 20 is transmitted to the driven body, and the driven body is driven.

The bearing 21 is a disc spring which is a pressing member mounted between a bearing 22 and a nut 22 which is a pressing force adjusting member screwed to a screw portion 19c formed at the end of the fixed shaft 19. 23 (which may be a spring spring, a leaf spring, or the like) is pressed toward the vibrator 10. As a result, the end surface of the moving element 20 on the oscillator side is pressed against the driving surface D of the oscillator 10 with appropriate pressure. By adjusting the screwing position of the nut 22, the pressing force of the disc spring 23 is adjusted.

FIG. 2 is an explanatory view of the vibrator 10 used in the ultrasonic actuator according to the present embodiment as seen from the driving surface direction, and FIG. 3 shows the vibrator 10 used in the ultrasonic actuator according to the present embodiment. It is explanatory drawing seen from the side surface direction.

The elastic body 11 is obtained by combining the semi-elastic bodies 13 and 14 obtained by vertically dividing the hollow cylindrical elastic body in a plane including the central axis.
A small diameter portion 11a is formed in a groove shape on the side surface of the hollow cylindrical elastic body.

The small diameter portion 11 is formed on the outer peripheral surface of the elastic body 11.
The first large diameter portion 11A and the second large diameter portion 11B are separated by a. Therefore, on the outer peripheral surface of the elastic body 11, the first large diameter portion 11A and the small diameter portion 11 are arranged in this order in the oscillator axial direction.
a and the second large diameter portion 11B are formed.

Of the two divided surfaces between the elastic bodies 13 and 14, the piezoelectric elements 12a and 12b and the piezoelectric elements 12a and 12b are located in the area where the first large diameter portion 11A is formed in the elastic body axial direction. The electrode plates 15a, 15b, and 15c for applying a driving voltage are mounted in a state of being sandwiched therebetween.

The piezoelectric elements 12a and 12b mounted on each of the two divided surfaces are made up of two layers, that is, a total of four layers. Four
The two-layer piezoelectric element 12a of the layer piezoelectric elements generates shear displacement in the axial direction of the elastic body 11 by using the piezoelectric constant d ₁₅ . The remaining two layers of piezoelectric elements 12b generate expansion / contraction displacement in the axial direction of the elastic body 11 by using the piezoelectric constant d ₃₁ .

When a driving voltage is applied to the piezoelectric element 12a,
Torsional displacement occurs in the elastic body 11. Further, when a drive voltage is applied to the piezoelectric element 12b, the elastic body 11 is expanded and contracted.

When a certain positive voltage is applied, for example, the piezoelectric element 12a is arranged so that the shear deformation alternates between the front direction and the opposite direction along the circumferential direction, as shown in FIG. It is preferable that the position of shearing deformation on the front side is point-symmetrical and the position of shearing deformation on the opposite side is point-symmetrical. Further, when a certain negative voltage is applied, shear deformation occurs in the direction opposite to that in FIG.

As described above, the piezoelectric element 12a for torsional vibration and the piezoelectric element 12b for longitudinal vibration are arranged, and a sinusoidal voltage is input to the piezoelectric element 12a for torsional vibration. As a result, a torsional vibration is generated in the elastic body 11 accordingly, and a stretching vibration is generated in the elastic body 11 in response to the sinusoidal voltage input to the piezoelectric element 12b for longitudinal vibration.

Drive signals having two (1/4) λ phase differences are input to the piezoelectric element 12a for torsional vibration and the piezoelectric element 12b for expansion / contraction vibration in the vibration actuator 1 configured as described above. Then, the stretching vibration is directly generated by the piezoelectric element 12b for stretching vibration, while the torsional vibration is generated by the shear deformation generated in the elastic body 11.

In the elastic body 11 to which the driving signal is input, the torsional vibration and the stretching vibration are simultaneously generated by the excitation of the piezoelectric element 12a for the torsional vibration and the piezoelectric element 12b for the stretching vibration. An elliptic motion that combines vibrations is generated on the drive surface D.

FIG. 4 is an explanatory diagram showing over time that an elliptic motion is generated on the driving surface D by combining the torsional vibration and the stretching vibration generated in the vibrator 11 as described above. Note that, in FIG. 4, for convenience of description, the mover, which is a relative movement member, is not shown.

As shown in FIG. 4, when the phase difference between the period of the torsional vibration and the period of the stretching vibration is set to be shifted by (1/4) λ (λ: wavelength), the drive surface D of the vibrator 11 is set. Elliptic motion occurs in the.

In FIG. 4, at time t = (6/4) π, the displacement of the torsional vibration T is maximum on the left side, and the displacement of the stretching vibration L is zero. In this state, the mover is brought into pressure contact with the drive surface D of the vibrator 11 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 maximum on the left side to the maximum on the right side. On the other hand, the stretching vibration L is displaced from zero to the upper maximum and returns to zero again. Therefore, the driving surface D of the vibrator 11 rotates rightward while pressing the moving element, and the moving element is rotationally 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. On the other hand, the stretching vibration L is displaced from zero to the maximum on the lower side and returns to zero again. Therefore, the drive surface D of the elastic body 11
Rotates left while moving away from the mover, so the mover is not driven. At this time, even if the mover is pressed by the pressing member, the contracting displacement of the vibrator 11 cannot be followed because the natural frequency of the pressing member is lower than the ultrasonic vibration range.

FIG. 5 is an explanatory view showing that the vibrator 10 is caused to generate a first-order longitudinal vibration and a second-order torsional vibration by exciting the piezoelectric bodies 12a and 12b. ) Is a top view, FIG. 5 (b) is a side view, and FIG. 5 (c) is a graph showing an example of a situation in which torsional vibration and stretching vibration are generated.

The elastic bodies 13 and 14 used in the ultrasonic actuator of this embodiment are the first large diameter portion 11A and the second large diameter portion 11A.
It has a large diameter portion 11B and a small diameter portion 11a having low torsional rigidity between them.

Further, in the ultrasonic actuator of this embodiment, the length of the first large diameter portion 11A in the vibrator axial direction is set to be larger than the length of the second large diameter portion 11B in the vibrator axial direction. Therefore, as shown in FIG. 5C, in the torsional vibration, a node is generated at each of the small diameter portion 11a forming position and the first large diameter portion 11A at substantially the center of the axial length of the transducer. It becomes the secondary mode. On the other hand, since the stretching vibration is hardly affected by the shape surface due to the formation of the small diameter portion 11a, the substantially middle portion of the entire length of the vibrator including the first large diameter portion 11A, the second large diameter portion 11B and the small diameter portion 11a. Then, it becomes the primary mode in which one node is generated.

Therefore, as shown in FIG. 5 (c), the second large diameter portion 11B is in the antinode position of each of the torsional vibration and the stretching vibration. In the present embodiment, FIG.
As shown in (c), the piezoelectric bodies 12a and 12b are not arranged on the drive surface D side of the second large diameter portion 11B and the first large diameter portion 11A corresponding to the abdominal portions of the torsional vibration and the longitudinal vibration, respectively. Leave as a void. In other words, the piezoelectric bodies 12a and 12b are arranged at the nodes of the torsional vibration and the longitudinal vibration, and the piezoelectric bodies 12a and 12b are mounted at the mounting position which is not the antinode position of the torsional vibration or the stretching vibration in the axial direction of the elastic body.

Therefore, according to the ultrasonic actuator of the present embodiment, the mounting area of the piezoelectric bodies 12a and 12b, that is, the voltage application area is reduced, so that the piezoelectric bodies 12a and 1b are reduced.
The capacitance of 2b can be reduced.

Here, the current input to the ultrasonic actuator 1 is converted into the equivalent circuit of the vibrator ("Introduction to ultrasonic motor").
81 pages, quoted from Sogo Denshi Publisher)
The input current at the driving point (near the anti-resonance point) is expressed by the following approximate expression. Input current I = V ・ R ・ ω ²・ Cd ²

However, C: capacitor component of the vibrator 11 (mainly the capacitance of the piezoelectric bodies 12a and 12b) V: applied voltage R: resonance resistance of the vibrator 11 ω: angular velocity of frequency voltage

Therefore, by eliminating the piezoelectric bodies 12a and 12b arranged at the antinode positions of the torsional vibration and the stretching vibration, which do not contribute much to the vibration formation, the piezoelectric body 12 is eliminated.
Both the electrostatic capacitances of a and 12b and the input current can be reduced.

On the other hand, the piezoelectric body 12 is placed at the node position of the stretching vibration.
Since a and 12b are arranged, the output of the ultrasonic actuator 1 hardly decreases. As a result, the driving efficiency of the ultrasonic actuator 1 determined by the output and the input power amount can be improved.

That is, according to the ultrasonic actuator 1 of the present embodiment, since the piezoelectric bodies 12a and 12b are arranged at the mounting positions other than the antinode position of the primary stretching vibration and the secondary torsional vibration, almost no output is produced. The input energy can be reduced without lowering, and the driving efficiency of the vibration actuator 1 can be improved.

Further, according to the ultrasonic actuator 1 of this embodiment, the piezoelectric bodies 12a, 1 are provided at the ends of the elastic bodies 13, 14 which are the antinodes of the primary stretching vibration and the secondary torsional vibration.
Since 2b is not placed, elliptical motion at the end face (output)
It is possible to reduce the input energy with almost no reduction in the constraint amount for the, and it is possible to improve the drive efficiency of the ultrasonic actuator 1.

(Second Embodiment) FIG. 6 is a longitudinal sectional view showing a second embodiment of the ultrasonic actuator 31 according to the present invention. The ultrasonic actuator 31 of the present embodiment is different from the ultrasonic actuator 1 of the first embodiment in that
The vibrator 32 has two small-diameter portions, the piezoelectric elements are arranged, and the electromechanical transducers are arranged at the antinodes of the stretching vibration and the torsional vibration.

The vibrator 32 includes piezoelectric bodies 33a and 33b, which are electromechanical transducers excited by a drive signal, and piezoelectric bodies 33a and 33b, which are joined to each other.
The hollow cylindrical elastic body 34 generates a driving force on the driving surface E due to the generation of the primary stretching vibration and the secondary torsional vibration due to the excitation of 3b.

FIG. 7 is an explanatory view showing in detail the structure of the vibrator 32 used in the ultrasonic actuator 31 of this embodiment. FIG. 7A is a top view of the vibrator 32, and FIG.
FIG. 7B is a side view of the vibrator 32 showing how the piezoelectric bodies 33a and 33b are attached, and FIG. .

The elastic body 34 is made of a metal material such as steel, phosphor bronze, and stainless steel, and has three large diameter portions 34A, 34.
Two semi-elastic bodies 35, 36 obtained by vertically dividing a hollow cylindrical elastic body having B and 34C and two small diameter portions 34a, 34b on its outer peripheral surface in a plane including the central axis. It is configured by combining. On each of the two split surfaces of the two semi-elastic bodies 35, 36,
The piezoelectric bodies 33a, 33b composed of two layers and three groups and the electrodes 37a, 37b, 37c for inputting and outputting electrical energy are held between the piezoelectric bodies 33a, 33b. .

The small diameter portions 34a, 34b are arranged at the node positions of the torsional vibration generated in the elastic body 34. The piezoelectric body 33a for torsional vibration is arranged at a position including two nodes of torsional vibration. On the other hand, the piezoelectric body 33b for stretching (longitudinal) vibration
Are arranged at positions including one node of longitudinal vibration.

Through holes 38a and 38b are formed substantially in the center of each of the two semi-elastic members 35 and 36 in the longitudinal direction of the vibrator, parallel to the stacking direction of the piezoelectric members 33a and 33b. The two semi-elastic bodies 35 and 36 are formed by inserting bolts 39a and 39b into the through holes 38a and 38b and forming a screw hole 40b formed in a large diameter portion 40a provided at a substantially central portion of a fixed shaft 40 described later.
The piezoelectric bodies 33a and 33b are sandwiched by being screwed into and are held by the fixed shaft 40 inserted at the center in the axial direction.

The mover 41, which is a relative motion member, is mounted on the end face of the mover base material 41a on the vibrator side of the mover base material 41a having a thick annular shape, and is in contact with the drive surface E of the vibrator 32. It is composed of a moving material 41b. The sliding material is preferably a hard polymer material, for example, a composite material such as PEEK (70% by weight) -carbon fiber (20% by weight) -PTFE (10% by weight). A groove portion 41c is formed in an annular shape on the inner peripheral portion of the end surface of the mover base material 41a on the vibrator side, and a bearing 42, which is a positioning member, is fitted and mounted in the groove portion 41c. This bearing 42 is fixed shaft 4
By mounting the moving element 41 on the fixed shaft 40, the moving element 41 is rotatably positioned and held on the fixed shaft 40.

An output take-out gear 41d is formed in an annular shape on the outer peripheral surface of the mover base material 41a on the side opposite to the oscillator.
It meshes with a gear of a driven body (not shown). As a result, the power of the mover 41 is transmitted to the driven body, and the driven body is driven.

Further, a screw portion 40b is provided at the end of the fixed shaft 40.
Is formed, and the nut 43, which is a pressurizing force adjusting member, is screwed onto the screw portion 40b. Between the nut 43 and the bearing 42, a disc spring 44 (which may be a spring spring, a leaf spring, or the like) that is a pressing member is held by the fixed shaft 40. By the spring force of the disc spring 44,
The mover 41 is brought into pressure contact with the drive surface E of the vibrator 32.

As described above, the fixed shaft 40 has the semi-elastic body 3
A vibrator 32 formed of semi-elastic bodies 35, 36, etc., which penetrates a hollow portion formed in a direction parallel to the axial directions of 5, 5, 36.
Is fixed, and the mover 41 is positioned and fixed rotatably in the radial direction.

The semi-elastic members 35 and 36 have three large diameter portions 34.
A, 34B and 34C and two small diameter portions 34a, 34b
Is a member obtained by vertically dividing a hollow thick-walled cylindrical body having a vertical axis in a plane including the central axis into two layers and three groups of piezoelectric bodies 33a and 33b and an electrode 37.
a, 37b, 37c are sandwiched.

The small diameter portions 34a and 34b are located at the nodes of torsional vibration. Piezoelectric bodies 33a, 33a for torsional vibration
Are arranged at the nodes of the torsional vibration, which causes torsional vibration in the oscillator 32.

The piezoelectric element 33a for torsional vibration generates shear deformation in accordance with the direction of voltage when a frequency voltage is applied,
This shear deformation causes torsional vibration. The first group of piezoelectric elements 33a for torsional vibration comprises two piezoelectric elements 33a for torsional vibration on the front side and two piezoelectric elements 33a for torsional vibration on the other side in the drawing. To be done. The shear deformation between the two torsion-vibration piezoelectric bodies 33a on the front side and the two torsion-vibration piezoelectric bodies 33a on the other side is sheared in opposite directions when a voltage in the same direction is applied. When the vibrator 32 is arranged so as to be deformed, a torsional displacement in a certain direction is generated in the vibrator 32.

For example, as shown in FIG. 7A, the two piezoelectric bodies 33a for torsional vibration on the front side and the two piezoelectric bodies 33a on the other side.
When each of the piezoelectric bodies 33a for torsional vibration is sheared and deformed, the driving surface E is twisted as shown by an arrow in FIG. 7A. In addition, when a voltage in the opposite direction is applied, shear deformation in the opposite direction occurs, so that the drive surface E is shown in FIG.
It is twisted in the direction opposite to the state shown by the arrow in (a).

The second group of piezoelectric elements 33a for torsional vibration is
It is composed of two piezoelectric bodies 33a for torsional vibration on the front side and two piezoelectric bodies 33a for torsional vibration on the other side. The shear deformation of the two torsion-vibration piezoelectric bodies 33a on the front side and the two torsion-vibration piezoelectric bodies 33a on the other side are shear-deformed in opposite directions when a voltage in the same direction is applied. With this arrangement, torsional vibration in a certain direction is generated in the vibrator 32.

Two front side piezoelectric bodies 33a for torsional vibration and two front side piezoelectric bodies 33a for torsional vibration are provided.
And are arranged so that shearing deformation occurs in different directions when a voltage in the same direction is applied.

Further, a voltage of the same direction is applied to the two first piezoelectric bodies 33a for torsional vibration and the second group of second piezoelectric bodies 33 for torsional vibration. Then, they are arranged so that shear deformation occurs in different directions.

For example, as shown in FIG. 7 (a), two piezoelectric bodies 33a for the second torsional vibration on the front side and two piezoelectric bodies 33a for the second torsional vibration on the other side. When shear deformation occurs, the end face F (opposite drive face) facing the drive face E is
It is twisted in the same direction as the direction indicated by the arrow in (a).

As described above, the piezoelectric body 33a for torsional vibration is used.
By arranging the piezoelectric elements 3 for the first torsional vibration.
If the same frequency voltage is applied to the 3a group and the second piezoelectric body 33a for torsional vibration, the portion between the first node G and the second node H of the torsional vibration is applied. The direction of the torsional vibration is the same, and the torsional secondary mode is easily excited.

Next, in FIG. 7, the stretching vibration piezoelectric body 33b undergoes stretching deformation when a frequency voltage is applied, and this stretching deformation causes stretching vibration (longitudinal vibration). The stretching vibration piezoelectric body 33b is composed of two stretching vibration piezoelectric bodies 33b on the front side and two stretching vibration piezoelectric bodies 33b on the other side. These piezoelectric bodies 33b are
When the voltages in the same direction are applied, they are arranged so as to be vertically deformed in the same direction.

As described above, by arranging the piezoelectric body 33b for stretching vibration, the piezoelectric body 33 for stretching vibration is arranged.
When the same frequency voltage is applied to b, the expansion / contraction primary vibration mode is easily excited.

In the ultrasonic actuator 31 thus constructed, two drive signals having a (1/4) λ phase difference are supplied to the piezoelectric body 33b for stretching vibration and the piezoelectric body 33a for torsional vibration, respectively. When input, the phase difference between the stretching vibration and the torsional vibration deviates by 90 degrees, and an elliptic motion that combines these vibrations occurs on the drive surface E of the vibrator 32.

In the present embodiment, as shown in FIG. 7B, both ends of the two piezoelectric bodies 33a, 33a for torsional vibration, that is, the stretching vibration and the torsional vibration of the vibrator 32, respectively, are detected. A piezoelectric body for vibration detection, which is a mechanical-electrical conversion element that converts mechanical displacement into electric energy, is not a piezoelectric body for vibration, which is an electromechanical conversion element that converts electrical energy into mechanical displacement, in the vicinity of the antinode position. 45a, 45
b is arranged. No drive voltage is applied to the vibration detecting piezoelectric bodies 45a and 45b, and electric energy is generated and output according to the mechanical displacement generated in the vibrator 32.

Therefore, also in this embodiment, the first
Similarly to the embodiment, by not mounting the vibration piezoelectric bodies 33a and 33b at the antinode position of the vibration that does not contribute much to the vibration formation, the piezoelectric bodies 33a and 33 for generating the torsional vibration are formed.
It is possible to reduce the capacitance of b to reduce the amount of input power.

Since the position between the piezoelectric bodies 45a and 45b for vibration detection is near the antinode position of the stretching (longitudinal) vibration and the torsional vibration, the mechanical strain due to the stretching vibration and the torsional vibration is not so great. not big. Therefore, the loss of vibration energy due to the vibration detecting piezoelectric bodies 45a and 45b provided at this position is extremely smaller than that at the vibration node position. Therefore, the vibration generated in the elastic bodies 35 and 36 can be detected, and the drive efficiency of the ultrasonic actuator is hardly reduced.

(Third Embodiment) FIG. 8 is an explanatory view showing a third embodiment of an ultrasonic actuator 31-1 according to the present invention, and FIG. 8 (a) is a top view of a transducer 32-1. ，
FIG. 8B is a side view of the vibrator 32-1 showing a mounting state of the piezoelectric bodies 33a and 33b, and FIG. 8C is an example of a situation where stretching vibration and torsional vibration are generated in the vibrator 32-1. FIG.

The ultrasonic actuator 31- of this embodiment
1 is different from the ultrasonic actuator 31 of the second embodiment in that two piezoelectric bodies 33a, 33a for torsional vibration are used.
A piezoelectric body 45 for vibration detection, which is a mechanical-electrical conversion element for converting mechanical displacement into electric energy, on both ends of each of the
Instead of arranging a and 45b, reinforcing members 46a and 4b
This is the point where 6b is arranged. Therefore, the description of the present embodiment will be given only for the reinforcing members 46a and 46b, and the other points will be omitted by giving the same reference numerals to FIG. 8 as in FIG.

Two piezoelectric bodies 33a, 33 are provided near the antinode positions of the longitudinal vibration and the torsional vibration generated in the elastic bodies 35, 36.
Reinforcing members 46a, 46 made of a polymer material having the same width as b
b is arranged. The reinforcing members 46a and 46b do not have conductivity, and like the ultrasonic actuator 31 of the second embodiment, the mechanical displacement is converted into electric energy and output to the outside to output the vibration occurrence status. You cannot do it.

However, also in the ultrasonic actuator 31-1 of the present embodiment, since the reinforcing members 46a and 46b are formed between the piezoelectric bodies 33a and 33b, as shown in FIGS.
The voltage application area of the vibrating piezoelectric bodies 33a and 33b can be made smaller than that of the ultrasonic actuator shown in FIG. Therefore, in addition to the piezoelectric bodies 33a and 33b,
The capacitance can be reduced, and the amount of input power can be further reduced.

Since the portions where the reinforcing members 46a and 46b are arranged are the antinode positions of the vibration that do not contribute much to the vibration formation, the amount of input electric power can be increased without reducing the output of the ultrasonic actuator 31-1. Can be reduced and the drive efficiency of the vibration actuator 31-1 can be improved.

Furthermore, in the ultrasonic actuator 31-1 of this embodiment, the reinforcing members 46a and 46b are connected to the elastic body 3.
Since the two elastic bodies 35 and 36 are arranged so as to be sandwiched between the elastic bodies 35 and 36, the bonding strength between the two elastic bodies 35 and 36 is increased as compared with the case where nothing is arranged at this position to form a void. The durability of 1 is improved.

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

In each of the embodiments, the description has been given by taking the ultrasonic actuator as an example, which obtains the driving force by generating the secondary torsional vibration and the primary stretching vibration in the elastic bodies 35 and 36. However, the vibration actuator according to the present invention is not limited to such an aspect, and has a plurality of elastic bodies and electromechanical conversion elements mounted on the plurality of elastic bodies, and When a driving voltage is applied, stretching vibrations of 1st order or more in the axial direction of the elastic body and
A vibrating actuator that generates a driving force by generating a torsional vibration of the following degree or more has the effect of the present invention such as improved efficiency based on a reduction in the amount of input electric power.

In this embodiment, the elastic body is made of steel, phosphor bronze, or stainless steel. However, if a material having a large resonance sharpness such as Elinvar material is used, the amplitude is increased and the driving characteristics are improved, which is preferable. is there. Also, the Erin Bar material is
Since the transition of the resonance frequency is small depending on the temperature, when this is used as the elastic body, the change in the performance of the ultrasonic actuator with respect to the change in temperature becomes small, and the controllability is improved.

In the vibration actuator according to the present invention, the piezoelectric element is used as the electromechanical conversion element or the electromechanical conversion element. However, the ultrasonic actuator according to the present invention is not limited to such an aspect,
Any element that can perform mutual conversion between electrical energy and mechanical displacement can be equally applied. For example, other than the piezoelectric element, an electrostrictive element, a magnetostrictive element or the like can be exemplified.

Further, in the present embodiment, the case where the elastic body is composed of two semi-elastic bodies is taken as an example, but the present invention is not limited to such an aspect, and three or more elastic bodies are used. The same can be applied to the case where a plurality of elastic members are used.

[Brief description of drawings]

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

FIG. 2 is a top view of a variant mode degenerate oscillator used in the vibration actuator according to the first embodiment of the present invention.

FIG. 3 is a side view of a variant mode degenerate oscillator used in the vibration actuator according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing over time that an elliptic motion is generated on the drive surface D by combining the torsional vibration and the stretching vibration generated in the vibrator in the vibration actuator according to the first embodiment of the present invention. Is.

5 (a) and 5 (b) are explanatory views showing that a primary longitudinal vibration and a secondary torsional vibration are generated in the vibrator due to the excitation of the piezoelectric body, and FIG. 5 (a) is a top view and FIG. (B) is a side view, FIG.
(C) is a graph showing an example of a situation in which torsional vibrations and stretching vibrations are generated.

FIG. 6 is a vertical sectional view showing a second embodiment of an ultrasonic actuator according to the present invention.

FIG. 7 is an explanatory diagram showing in detail the structure of a vibrator used in the ultrasonic actuator of the second embodiment.
7A is a top view of the vibrator, FIG. 7B is a side view of the vibrator showing how the piezoelectric body is mounted, and FIG. 7C is a situation of stretching vibration and torsional vibration occurring in the vibrator. It is explanatory drawing which shows an example.

8A and 8B are explanatory views showing a third embodiment of an ultrasonic actuator according to the present invention, FIG. 8A is a top view of a vibrator, and FIG. 8B is a vibration showing a mounting state of a piezoelectric body. 8C is a side view of the child, and FIG. 8C is an explanatory diagram showing an example of a situation in which stretching vibration and torsional vibration are generated in the vibrator.

FIG. 9 is a perspective view showing a conventional example of a vertical-torsion vibration type vibration actuator.

FIG. 10 is a perspective view showing the stator of the vibration actuator shown in FIG. 9 in a developed state.

FIG. 11 is a top view of a variant mode degenerate oscillator used in the vibration actuator proposed in Japanese Patent Application No. 6-180279.

FIG. 12 is a side view of a variant mode degenerate oscillator used in the vibration actuator proposed in Japanese Patent Application No. 6-180279.

FIG. 13 is a graph showing the combination of torsional vibration (T mode) and stretching vibration (L mode) generated in a vibrator in the vibration actuator shown in FIGS. FIG.

[Explanation of symbols]

1, 31, 31-1 Ultrasonic actuator (vibration actuator) 10, 32, 32-1 Transducer 11, 34 Elastic body 11A, 11B, 34A to 34C Large diameter portion 11a, 34a, 34b Small diameter portion 12a, 12b, 33a , 33b Piezoelectric body 13, 14, 35, 36 Semi-elastic body 11 ', 34 Elastic body 16, 17, 38a, 38b Through hole 18a, 18b, 39a, 39b Bolt 19, 40 Fixed shaft 19a, 40a Large diameter portion 19b, 40b Screw hole 19b, 40b Screw part 20,41 Moving element 20a, 41a Moving element base material 20b, 41b Sliding material 20c, 41c Groove part 21,42 Bearing 22,43 Nut 23,44 Disc spring 37a-37b Electrode 45a, 45b Piezoelectric bodies for vibration detection 46a, 46b Reinforcing member

Claims (4)

[Claims] 1. An elastic body and an electromechanical conversion element mounted on the elastic body, and by applying a drive voltage to the electromechanical conversion element, stretching vibration and torsion in the axial direction of the elastic body are generated. In a vibration actuator that generates a torsional vibration and a driving force, the electromechanical conversion element is mounted in a position other than an antinode position of the stretching vibration or the torsional vibration in the axial direction. And a vibration actuator. 2. The vibration actuator according to claim 1, wherein the antinode position is near both ends of the elastic body in the axial direction. 3. The vibration actuator according to claim 1, wherein a mechanical-electrical conversion element or a reinforcing member for converting mechanical displacement into electric energy is attached to the antinode position. Vibration actuator. 4. One of claims 1 to 3
The vibration actuator according to the item 1, wherein the order of the stretching vibration is one or more and the order of the torsional vibration is one or more.