JP2003111457A - Actuator applying driving force in a plurality of directions using single displacement element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a relatively inexpensive actuator for driving a driven body in a plurality of directions using a single displacement element. SOLUTION: The actuator 2 comprises a vibrator having a plurality of free vibration modes, and a piezoelectric element 4 for vibrating the vibrator upon power supply. The vibrator has a plurality of rods 22 (22A, 22B, 22C, 22D) and one of free vibration modes is excited by supplying power to the piezoelectric element 4 and vibrating it at a specified frequency thereby resonating any one rod 22. Vibration of the rod 22 is transmitted to the driven body through a chip part 24.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention generally relates to an actuator using a displacement element such as a piezoelectric element. The present invention particularly relates to an actuator that excites a plurality of natural vibration modes using a single displacement element and applies a driving force to a driven body in different directions.

[0002]

2. Description of the Related Art Many actuators using displacement elements such as piezoelectric elements have been known.

For example, as shown in FIG. 14, the actuator proposed in Japanese Patent Laid-Open No. 10-225151 discloses a pair of vibrating members 502 and 504 each having a piezoelectric element (not shown), and each of these vibrating members. And a tip portion 506 in which vibrating pieces provided at one end in the vibrating direction are connected so as to have a predetermined angle with each other, and the resonance frequencies of the two vibrating members 502 and 504 are different. The driven body 508 is pressed against the chip portion 506, and the driven body 508 is resonated by resonating the vibrating member 502.
By moving the vibrating member 504 to resonate, the driven body 508 is moved in the direction of arrow 512.

The actuator proposed in Japanese Unexamined Patent Publication No. 2000-188887, as shown in FIG. 15, has a primary natural vibration mode of a vibration member 520 having a piezoelectric element (not shown) [FIG. (A)]. And the secondary natural vibration mode [Fig. (B)] are used. Rotor 522 to the vibrating member 520 is pressed with the driven member, in primary natural vibration mode, rotates in the clockwise direction 524 under the force of F _1, while in the secondary natural vibration mode, the F ₂ It receives a force and rotates in a counterclockwise direction 526.

[0005]

In the actuator shown in FIG. 14, a piezoelectric element and a drive circuit for driving the piezoelectric element are required for each of the vibrating members 502 and 504, so the actuator is relatively expensive.

In the actuator shown in FIG. 15, only one piezoelectric element is provided for the vibrating member 520. However, since the vibration modes of the vibrating member 520 are different, the vibrating member 520 has different natural vibration modes. The difference between the frequencies and the amplitudes is large, so that an output difference occurs in the driving directions 524 and 526. Further, this actuator can be used only for switching the rotational direction of the driven body about one axis, and it is substantially difficult to rotate the driven body about two or more axes.

Therefore, the present invention is to provide a relatively inexpensive actuator that drives a driven body in a plurality of directions using a single displacement element and a drive circuit.

Another object of the present invention is to provide an actuator having a small difference in driving force in a plurality of driving directions.

[0009]

In order to achieve the above object, an actuator according to the present invention vibrates by vibrating with a vibrating body having first and second natural vibration modes, and thereby vibrating the vibrating body. An actuator having a displacement element (for example, a piezoelectric element) for vibrating the first element, wherein the displacement element is energized to vibrate at a first frequency.
By exciting the natural vibration mode of, the vibration of the vibrating body is transmitted to the driven body at this time, the driven body is driven in the first direction, and the displacement element is energized to vibrate at the second frequency. A feature of the present invention is that the driven body is driven in a second direction different from the first direction by exciting the second natural vibration mode and transmitting the vibration of the vibrating body to the driven body at this time.

The vibrating body has first and second vibrating members,
The first vibrating member resonates in the first natural vibration mode, and the second vibrating member resonates in the second natural vibration mode. By making the first and second vibrating members substantially the same in material, configuration, arrangement, etc., and using the same order as the natural vibration modes of the first and second vibrating members, The difference in driving force can be reduced in the two directions.

The actuator preferably further comprises a pressing member for pressing the vibrating body against the driven body. Thereby, the vibration of the vibrating body can be transmitted to the driven body with high efficiency and accuracy.

The actuator may be designed so that the displacement element resonates when exciting the first and / or second natural vibration modes in the vibrating body. Accordingly, the vibration of the displacement element as well as the vibration of the vibrating body can be used to drive the driven body.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view showing an embodiment of an actuator according to the present invention. The outer shape of the actuator, which is generally denoted by reference numeral 2, is formed in a substantially quadrangular pyramid shape. A piezoelectric element 4, which is a displacement element, is arranged on the central axis (between the apex of the quadrangular pyramid and the center of the bottom surface).

As shown in FIG. 2, the piezoelectric element 4 is a PZT.
It is a laminated piezoelectric element formed by alternately laminating a plate 6 formed by thinly extending a ceramic material having a piezoelectric effect such as (lead zirconate titanate) and electrodes 8 and 10. The ceramic plate 6 and the electrodes 8 and 10 are joined with an adhesive or the like. The electrode groups 8 and 10 arranged at intervals of two are connected to the drive circuit 16 via the wirings 12 and 14, respectively, and as a result, a predetermined voltage is applied to the electrodes 8 and 10 by the drive circuit 16. Then, the direction of polarization of the ceramic plate 6 sandwiched between the electrodes 8 and 10 is alternately repeated upward and downward along the stacking direction. With this configuration, when the driving circuit 16 applies an AC voltage of a predetermined frequency between the electrodes 8 and 10, the entire piezoelectric element 4 repeats expansion and contraction in the stacking direction. The members 18 and 20 provided at both ends in the longitudinal direction of the piezoelectric element 4 are protective layers, one of which is a chip portion (described later) and the other is a base portion (described later).
It is for connecting with.

Returning to FIG. 1, a square rod-shaped metal rod 22 (22A, 22B, 22C, 22D) is arranged as a vibrating member on the four hypotenuses extending from the top of the quadrangular pyramid to the bottom surface. These rods 22A, 22B, 22
C and 22D have a cross shape when viewed from the apex side. One end of the rod 22 in the longitudinal direction and one end of the piezoelectric element 4 in the longitudinal direction are bonded to the metal tip portion 24 located at the apex of the quadrangular pyramid with an adhesive. When a voltage of a predetermined frequency is applied to the piezoelectric element 4 as described later, the tip portion 24 reciprocates substantially in a predetermined direction, and a driven body (not shown) pressed by the tip portion 24 is thereby moved. It is driven in a predetermined direction. The tip portion 24 has a contact surface with the driven body. Tip part 2 of actuator 2
A pressing member such as a spring 25 is provided on the side opposite to the contact surface 4 so that the contact surface is pressed by the driven body. The other end of the rod 22 in the longitudinal direction and the other end of the piezoelectric element 4 in the longitudinal direction are joined by an adhesive to a metal base portion 26 located on the bottom surface of the quadrangular pyramid.

The rod 22 is preferably made of iron or the like because of its high strength and low damping rate. The material of the tip portion 24 is preferably tungsten carbide or the like, which can stably obtain a high friction coefficient and is excellent in wear resistance. As a material of the base portion 26, stainless steel or the like which is easy to manufacture and has excellent strength is preferable. Further, as the adhesive, an epoxy resin or the like having excellent adhesive strength and strength is preferable. The rod 22 and the tip portion 24 may be integrally formed from the same material.

Rods 22A, 22B, 22C, 22D
Have the same length in the hypotenuse direction of the quadrangular pyramid (longitudinal direction of the rod), but the thickness or width is slightly different (which is the length of each side of the rectangular prism cross section perpendicular to the longitudinal direction) for the reason described later. As a result, when a voltage of a predetermined frequency is applied from the drive circuit 16 to the piezoelectric element 4, only one of the four rods 22 is designed in accordance with the frequency. Are resonating. At this time, the tip portion 24 vibrates along the longitudinal direction of the resonating rod 22, and the driven body contacting the tip portion 24 receives a driving force in the extending direction of the resonating rod 22.

For example, when the driven body is a sphere 28 as shown in FIG. 3 (a), the resonance of the rod 22A is caused by the resonance of the rod 22A with respect to the circular cross section of the sphere 28 cut by the plane including the oblique sides of the opposing rods 22A and 22C. The driven body 28 is the rod 22.
Rotate in the counterclockwise direction 30A when viewed from the B side. Similarly, with respect to the circular cross section, the driven body 28 moves in the clockwise direction 3 when viewed from the rod 22B side due to the resonance of the rod 22C.
Rotate to 0C.

On the other hand, regarding the circular cross section of the sphere 28 cut by the plane including the oblique sides of the opposing rods 22B and 22D, the driven body 28 is moved to the rod 22 due to the resonance of the rod 22B.
Rotate clockwise 30B when viewed from the A side. Similarly,
With respect to the circular cross section, the driven body 28 moves in the counterclockwise direction 30 as viewed from the rod 22A side due to the resonance of the rod 22D.
Rotate to D.

As shown in FIG. 3B, when the driven body is a plane member (slider) 32, the slider 32 slides in the direction 34A from the rod 22A side toward the rod 22C side due to the resonance of the rod 22A. The slider 32 moves from the rod 22C side to the rod 22C due to the resonance of the rod 22C.
Slide in the direction 34C toward the A side. On the other hand, the resonance of the rod 22B causes the slider 32 to slide in the direction 34B from the rod 22B side toward the rod 22D (not shown in FIG. 3B) side, and the resonance of the rod 22D causes the slider 32 to move from the rod 22D side to the rod 22D side. It slides in the direction 34D toward the 22B side.

The relationship between the driving force of the rod 22 and the motion of the driven body will be described when the driven body is a sphere 28. When the rod of the actuator 2, for example, the rod 22A is resonated, as shown in FIG. 4A, when the rod 22A moves in a direction approaching the sphere 28 (extension direction), the tip portion 24 causes the sphere 28 to move. The tangential force applied, that is, the driving force transmitted to the sphere 28, increases. On the other hand, as shown in FIG. 4B, when the rod 22A moves in the direction away from the spherical body 28 (reduction direction), the driving force transmitted to the spherical body 28 decreases or the driving force does not transmit.
Therefore, in the former case, a large driving force is transmitted to the driven body 28, but in the latter case, the driving force transmitted is small or the driving force is not transmitted. Due to the difference in the driving force during the reciprocating movement of the rod 22A, the spherical body 28 rotates in the counterclockwise direction 36.

Next, in the actuator 2 constructed as shown in FIG. 1, a condition for resonating only one of the four rods 22 when a voltage of a predetermined frequency is applied to the piezoelectric element 4. This will be described with reference to FIGS.

FIG. 5 shows four rods 22A, 22B, 2
It is a figure which shows the mode of the natural vibration of the actuator 2 provided with 2C and 22D (it does not illustrate the base part 26). Mode 1 [Fig. (A)] in which four rods 22 vibrate in the same phase as the natural vibration, two adjacent rods vibrate in the same phase and the remaining two rods vibrate in a phase opposite to the above phase. Modes 2 and 3 [Figure (b),
(C)], the opposing rods vibrate in the same phase, and the remaining 2
Mode 4 in which two rods vibrate in the opposite phase to the above
There are four types as shown in FIG. In mode 2, the pair of rods 22A and 22D and the pair of rods 22B and 22C vibrate in the same phase, and in mode 3, the rod 22A and 22C vibrate in the same phase.
The pair of A and 22B and the pair of rods 22C and 22D vibrate in the same phase.

When these rods 22 are the same, assuming that the tip portion 24 is not deformed and the rod 22 is a curved beam with both ends fixed, the frequencies of the four natural vibration modes are in principle the same. However, in reality, due to the displacement and deformation of the tip portion 24 and the base portion 26, the frequency of the natural vibration mode takes different values except that the modes 2 and 3 match.

Therefore, the structure of the actuator 2 is devised so that the frequencies of the four natural vibration modes match. In general, the natural vibration mode can be represented by one vibration system including a spring element and a weight element. When the rigidity of the spring element of the vibration system is increased, the frequency increases, and when the rigidity is decreased, the frequency decreases. The frequency decreases as the mass of the weight element increases, and increases as the mass decreases. Therefore, in modes 1, 2 (3) and 4, attention is paid to the difference between the spring element and the weight element of the vibration system.

For example, in the mode 2 (3), the chip unit 2
Since 4 is a weight element (the tip portion 24 reciprocates substantially), increasing the mass lowers the frequency, but in modes 1 and 4, the tip portion 24 is not a weight element (the tip portion 24 Does not move much), so increasing the mass does not change the frequency.

On the contrary, in the modes 1 and 4, the tip portion 24
Is a spring element (the tip portion 24 receives the deforming force from the rod 22 in the same phase in mode 1 and in the opposite phase in mode 4), so increasing the stiffness increases the frequency, but In 3), since the tip portion 24 is not a spring element (the tip portion 24 does not receive a deforming force from the rod 22), the frequency does not change even if the rigidity is increased. When changing the rigidity, the deformation force that the tip portion 24 receives in mode 1 is compressed by the fixing portion with the rod 22 at the same time.
It is extended. On the other hand, in mode 4, the chip section 24
The deforming force received by the
Since it is extended, the amount of deformation of the tip portion 24 is larger than in mode 1. Therefore, when the rigidity is increased, the frequency of mode 4 is higher than that of mode 1.

Thus, the mass and rigidity of the tip portion 24 are
By adjusting and changing the shape, the density of the material, the elastic modulus, etc., the frequencies of the four natural vibration modes can be made substantially equal. In this case, since the four natural vibration modes are degenerated, the vibration system of the actuator 2 has four degrees of freedom. Therefore, the thickness and width of each rod 22 are slightly different from each other, and
By virtue of vibrating the piezoelectric element 4 at a predetermined driving frequency by making a slight difference in the natural frequency of 2, one of the four rods 22 is substantially independent corresponding to this driving frequency. It is possible to excite any of the four types of natural vibration modes that resonate. As described above, reducing the difference in the characteristics of the four rods 22 that are the vibrating members reduces the control range of the drive frequency of the piezoelectric element 4 and also minimizes the difference in the drive force depending on the drive direction. It is preferable in terms.

FIG. 6 shows the vibration of each natural vibration mode in which each rod 22 resonates substantially independently. Figures (a), (b), (c), and (d) show the rod 2 respectively.
The case where 2A, 22B, 22C, and 22D independently resonate is shown. Although these natural vibration modes have different frequencies, the damping characteristics of the four rods 22 are equal to each other, so that the tip portions 24 have substantially the same amplitude. Due to these natural vibrations, the tip portion 24 substantially reciprocates along the longitudinal direction of the resonating rod 22.

The difference in the natural frequency of each rod 22 is set according to the damping characteristic of the rod 22 (this is mainly determined by the material of the rod 22). That is, when the damping of the rod 22 is large, the resonance curve has a shape with a small peak value and a wide skirt, so that the difference in natural frequency must be relatively large (the degenerate frequency is, for example, 100 kHz).
(A difference of about 10 kHz with respect to the degree), an extra vibration is generated in another rod 22 when resonating a specific rod 22, and the tip portion 24 performs an elliptic movement instead of a reciprocating movement. Rod 2
When the attenuation of 2 is small, the resonance curve draws a steep curve, so that even if the natural frequencies between the modes are relatively close (for example, the degenerate frequency is about 1 kHz for 100 kHz).
Excessive vibration does not easily occur in the other rods 22 when the specific rod 22 resonates, so that the tip portion 24 reciprocates. However, in the latter case, when the vibration characteristic (eg, resonance curve) of the rod changes due to an assembly error of the actuator 2 or a change in operating environment (eg, temperature) of the actuator 2, the amplitude of the tip portion 24 changes, so The piezoelectric element 4 detects the magnitude of displacement of the portion 24 and detects the natural frequency that changes due to environmental changes.
It is desirable to provide a circuit for matching the drive frequency of the. As a method of detecting the displacement of the tip portion 24, 1) a distance sensor or the like is used, 2) a current flowing through the piezoelectric element 4 is detected, and 3) when the driven body is a sphere, the rotational speed of the sphere is detected. Can be exemplified.

In the present actuator 2, when the driving force varies depending on the driving direction, the rod 22 that resonates is used.
By adjusting the drive voltage value of the piezoelectric element 4 in accordance with, it is possible to eliminate the difference in drive force.

FIG. 7 is a block diagram showing an example of the drive circuit 16 for the piezoelectric element 4. The drive circuit 16 includes an oscillator 40 that outputs a sine wave signal, a power amplifier 42 that amplifies the output signal so as to drive the piezoelectric element 4, and an oscillator 40.
And a control unit 44 for controlling the frequency of the signal output by and the amplification factor of the power amplifier 42. According to this configuration, the control unit 44 controls the oscillator 40 to generate a drive signal having a frequency corresponding to any one of the above four natural vibration modes, thereby driving the piezoelectric element 4 to obtain a desired natural vibration. Excite the mode. The control unit 44 also controls the amplification factor in accordance with the switching of the natural vibration mode and adjusts the driving voltage value of the piezoelectric element 4 in order to exactly match the driving force in each direction.

The above description relates to one embodiment of the present invention, and the present invention can be variously modified. For example, the actuator according to the present invention is not limited to the configuration shown in FIG. 1 as long as it applies a driving force in a plurality of directions by utilizing the vibration of a single displacement element.

For example, the actuator 102 shown in FIG.
Is a rod 122 (122A, 122B, 122C, 1
22D) has one end that is not fixed to the base portion 126 and is a free end. The length of each rod 122 (in the longitudinal direction) is slightly different, so that each rod 122
Resonate at different frequencies. The natural frequency of each rod 122 is set to the resonance frequency of the piezoelectric element 104 or in the vicinity thereof.
It is possible to resonate 04 at the same time. Piezoelectric element 1
By utilizing the resonance phenomenon of 04, the actuator 10
2 is a chip portion 1 as compared with the actuator 2 shown in FIG.
The displacement of 24 can be made larger and the driving efficiency can be improved. Note that a mode of utilizing the resonance of the piezoelectric element will be described in detail in an embodiment described later.

FIG. 9 shows a schematic perspective view of another actuator according to the present invention. The actuator 202 includes four thin plate-shaped metal arms 250A and 2A as vibration members.
50B, 250C, and 250D are integrally formed in a cross shape, and the center thereof is located on the side opposite to the joint between the piezoelectric element 204 and the base portion 226. The free ends of the rods 250A, 250B, 250C and 250D are respectively provided with tip parts 224A, 224B, 224C for contacting with a spherical body 228 (FIG. 10) which is a driven body.
224D is provided. The lengths of the arms 250 are slightly different so that the arms 250 resonate at different frequencies. The natural frequency of each arm 250 is set to the resonance frequency of the piezoelectric element 204 or in the vicinity thereof, and any one of the arms 250 can resonate.

Referring to FIG. 10, when the arm 250A is resonated at its natural frequency as shown in FIG. 10A with the actuator 202 pressed against the sphere 228, the force F ₁ is applied to the sphere 228. And the sphere 228 rotates clockwise in the drawing. On the other hand, for example, when the arm 250C resonates at its natural frequency as shown in FIG. 7B, the force F ₂ acts on the sphere 228, and the sphere 228 rotates counterclockwise in the drawing.

FIG. 11 is a schematic perspective view showing still another actuator according to the present invention. The piezoelectric element 304 of the actuator 302 is a laminated piezoelectric element that is joined to a base portion 326 arranged on the XY plane and has a rectangular prism shape extending in the Z direction. A tip portion 324 having the same XY cross-sectional shape is attached to the side opposite to the joint portion with the base portion 326. A thin plate-shaped arm 350 serving as a vibrating member is provided from two facing surfaces of the tip portion 324.
A and 350C extend in the Y direction. Two arms 35
There is a slight difference between the lengths of 0A and 350C, and each arm resonates at a different natural frequency.
A rotor 352 as a driven body is pressed against the tip of the tip portion 324.

In the present embodiment, the piezoelectric element 304 is designed so that the natural frequencies of the stretching vibration and the bending vibration are substantially equal to each other, whereby the tip portion 324 is caused by the stretching vibration of the piezoelectric element 304 in the Z direction. With respect to, the bending vibration can vibrate in the Y direction. Arm 350
The natural frequencies of the bending vibrations of A and 350C are the piezoelectric element 30.
4 is set near the degenerate frequency, and the arms 350A and 350 extending in the Y direction are attached to the tip portion 324.
Since C is attached, when the piezoelectric element 304 is resonated at the degenerated natural frequency or in the vicinity thereof, the piezoelectric element 304
In the YZ plane, that is, the vibration of the tip portion 324 is restricted in the Y direction.

In such a structure, the piezoelectric element 304
When the driving frequency of the arm 350A is matched with the natural frequency of the arm 350A, the piezoelectric element 30 is synchronized with the vibration of the arm 350A.
4 performs stretching vibration and bending vibration at the same time. For more details,
When the piezoelectric element 304 contracts, it bends to the left [state of FIG. 12 (a)], and when it extends, it bends to the right. The actuator 302 is
In this natural vibration mode, the tip portion 324 is designed to vibrate in the first direction at approximately 45 degrees in the upper right of FIG. On the other hand, the drive frequency of the piezoelectric element 304 is set to the arm 350.
When the natural frequency of C is matched, the piezoelectric element 304 simultaneously performs stretching vibration and bending vibration in accordance with the vibration of the arm 350C. More specifically, when the piezoelectric element 304 contracts, it bends to the right [state of FIG. 12 (b)], and when it extends, it bends to the left.
The actuator 302 is designed so that the tip portion 324 vibrates in the second direction of about 45 degrees at the upper left of FIG. 12 in this natural vibration mode. In this embodiment, since two natural vibration modes (one stretching vibration and one bending vibration) are degenerated, the vibration system of the actuator 304 has two degrees of freedom, and the tip portion 424 is It can be independently displaced in the first and second directions.
Therefore, the rotor 352 pressed by the tip of the tip portion 324 can rotate forward and backward by switching the drive frequency of the piezoelectric element 304 and selectively vibrating the arms 350A and 350C. Arm 350A, 350C
Since the difference in the shape of is small, it is possible to make the outputs in the two natural vibration modes substantially equal.

When the piezoelectric element 304 contracts, it bends to the right, and when it expands, it bends to the left. When the piezoelectric element 304 contracts, it bends to the left, and when it expands, it bends to the right. The phase of the vibration in the Y direction is inverted with respect to the vibration. Arm 350A, 3
Which one of the natural vibration modes is excited when one of the vibrations of 50B vibrates is determined by the condition that the sum of the momentums of the vibration system including the arm and the piezoelectric element becomes zero.

FIG. 13 is a schematic perspective view showing still another actuator according to the present invention. The piezoelectric element 404 and the tip portion 424 of this actuator 402 are formed in a cylindrical shape having a central axis in the Z direction. Further, three thin plate-shaped arms 450A, 450B, and 450C as vibrating members extend from the tip portion 424 on the XY plane with an interval of 120 degrees therebetween. Three arms 4
There is a slight difference in the length of 50A, 450B, and 450C, and each arm resonates at a different natural frequency. At the tip of the tip portion 424, a spherical body 428 is pressed as a driven body. The base portion is not shown in FIG.

In this embodiment, the piezoelectric element 404 is designed so that the natural frequencies of the stretching vibration and the bending vibration are substantially the same. Also, the arms 450A, 450B, 450
The natural frequency of the bending vibration of C is set near the degenerated frequency of the piezoelectric element 404. Since the piezoelectric element 404 and the tip portion 424 have a circular cross-sectional shape, when the piezoelectric element 404 is resonated in the bending vibration mode with the arms 450A, 450B, and 450C not attached, the tip portion 424 has the XY plane. It can vibrate in any direction. In practice, the tip portion 424 has arms 450A, 450B, 45 extending in a predetermined direction of the XY plane.
Since 0C is attached, when the piezoelectric element 404 resonates at the degenerated natural frequency or in the vicinity thereof, the tip portion 42
The vibration of No. 4 is restricted in the above predetermined direction.

In such a structure, the piezoelectric element 404
When the drive frequency is matched with the natural frequency of any of the arms 450A, 450B, and 450C, the piezoelectric element 404 simultaneously performs stretching vibration and bending vibration in accordance with the resonance of the selected arm. FIG. 13 shows only the displacement direction of the tip portion 424 when the arm 450A is resonated. In this embodiment, since three natural vibration modes (one stretching vibration and two bending vibrations) are degenerated, the vibration system of the actuator 404 has three degrees of freedom, and the tip portion 424 is Arms 450A, 450B,
It can be independently displaced in three directions according to the vibration of any of 450C. Therefore, the actuator 402 can rotate the spherical body 428 that is a driven body around three axes.

[0045]

According to the present invention, it is possible to provide a relatively inexpensive actuator which can drive a driven body in a plurality of directions by using a single displacement element and a drive circuit.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of an actuator according to the present invention.

2 is a cross-sectional view of a laminated piezoelectric element used in the actuator of FIG.

FIG. 3A is a diagram showing a driving direction in the case of driving a sphere as a driven body. (B) The figure which shows the drive direction at the time of driving a slider as a driven body.

FIG. 4 is a diagram showing the principle of rotating a sphere by the actuator of FIG.

FIG. 5 is a diagram showing natural vibration modes in the actuator of FIG. 1 when the characteristics of four rods are designed to be the same.

FIG. 6 is a diagram showing natural vibration modes in the actuator of FIG. 1 when the characteristics of four rods are designed to be slightly different.

FIG. 7 is a block diagram showing an example of a drive circuit for the piezoelectric element shown in FIG.

FIG. 8 is a schematic perspective view showing another embodiment of the actuator according to the present invention.

FIG. 9 is a schematic perspective view showing another embodiment of the actuator according to the present invention.

10 is a diagram showing the principle of rotating a sphere by the actuator of FIG.

FIG. 11 is a schematic perspective view showing still another embodiment of the actuator according to the present invention.

12 is a diagram showing a natural vibration mode in the actuator of FIG.

FIG. 13 is a schematic perspective view showing still another embodiment of the actuator according to the present invention.

FIG. 14 is a schematic perspective view showing an example of a conventional actuator.

FIG. 15 is a schematic perspective view showing another example of a conventional actuator.

[Explanation of symbols]

2: Actuator, 4: Piezoelectric element (displacement element), 2
2: rod (vibration member), 24: tip portion, 25: pressing member, 26: base portion, 28: spherical body (driven body).

Claims (6)

[Claims] 1. An actuator comprising: a vibrating body having first and second natural vibration modes; and a displacement element for vibrating when energized to vibrate the vibrating body. The first natural vibration mode is excited by energizing and vibrating at the first frequency, and at this time, the driven body is driven in the first direction by transmitting the vibration of the vibrating body to the driven body, The displacement element is energized to vibrate at the second frequency to excite the second natural vibration mode, and at this time, the vibration of the vibrating body is transmitted to the driven body so that the driven body moves in the first direction. An actuator which drives in a different second direction. 2. The vibrating body has first and second vibrating members, wherein the first vibrating member resonates in a first natural vibration mode and the second vibrating member in a second natural vibration mode. The actuator according to claim 1, which resonates. 3. The actuator according to claim 1, further comprising a pressing member that presses the vibrating body against a driven body. 4. The actuator according to claim 1, wherein the displacement element resonates when the vibrating body excites the first and / or second natural vibration modes. . 5. The actuator according to claim 1, wherein the displacement element is a piezoelectric element. 6. An actuator having a vibrating body having first and second natural vibration modes, and a displacement element for vibrating when energized to vibrate the vibrating body, the actuator comprising: The first natural vibration mode is excited by energizing and vibrating at the first frequency, and at this time, the driven body is driven in the first direction by transmitting the vibration of the vibrating body to the driven body, The second element that is slightly different from the first frequency when the displacement element is energized
The second natural vibration mode is excited by vibrating at a frequency of, and the vibration of the vibrating body is transmitted to the driven body at this time, so that the driven body has a second direction different from the first direction.
An actuator characterized by being driven in the direction of.