JPH07337042A - Ultrasonic actuator - Google Patents

Abstract

PURPOSE:To protect a laminate against damage due to tensile stress at the time of excitation by coupling a piezoelectric element, at the end part in the direction perpendicular to the field applying direction, with a resilient body on which a traveling oscillatory wave is generated. CONSTITUTION:Piezoelectric elements 121, 122 are coupled, at the end parts in the direction perpendicular to the field applying direction, with a resilient body 111. The piezoelectric elements 121, 122 are excited by a drive (signal to generate a traveling wave on the resilient body 111. Consequently, elliptical movement takes place on both drive faces 111a, 111b of the resilient body 111. Since the piezoelectric elements 121, 122 utilizes the reverse piezoelectric effect in the direction of d31 for excitation, a sufficient amplitude can be ensured without laminating the piezoelectric in the direction of amplitude of oscillation. This structure can protect the laminate against damage due to tensile stress at the time of oscillation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic actuator which generates a progressive vibration wave by exciting an electromechanical conversion element.

[0002]

2. Description of the Related Art Conventionally, among the ultrasonic actuators of this type, a linear type actuator, for example, generates a progressive vibration wave (hereinafter, abbreviated as a traveling wave) in a linear elastic body to drive the elastic body drive surface. Structure in which the moving element is driven under pressure contact with the
Annual Lecture Meeting on Structural Strength (July 6, 1993-
8th) p280-283 "Prototype of traveling wave type linear ultrasonic motor" (Ken Higuchi) etc.] is known.

FIG. 5 is a perspective view showing a conventional example of an ultrasonic actuator. The conventional ultrasonic actuator is composed of a stator 1 and a mover 2. The stator 1 is
An elastic body 11 having a shape extending in the driving direction and generating a driving force on the driving surface 11a, and a left end portion 11 of the elastic body 11.
It is composed of a piezoelectric element 21 for generating a traveling wave and a piezoelectric element 23 for absorbing a traveling wave, which are joined in the vicinity of L and the right end portion 11R. The moving element 2 has a driving surface 11 a of the elastic body 11.
Is pressed and contacted by a pressure means (not shown), and the elastic body 11
It moves due to the traveling wave generated in.

This ultrasonic actuator has an elastic body 11.
The elastic body 11 is attached by the piezoelectric element 21 mounted near one end of the
Is excited and the vibration of the elastic body is absorbed by the piezoelectric element 23 mounted near the other end of the elastic body 11, a traveling wave in only one direction can be generated in the elastic body 11.
The ultrasonic actuator of this type has an elastic body 11
Since it can be made longer, there is an advantage that a relatively long distance can be driven.

On the other hand, according to Mr. Higuchi mentioned above, it is also proposed to generate a traveling wave by exciting both ends of the elastic body. FIG. 6 is a diagram for explaining the structure and operating principle of a conventional example of a double-sided vibration type ultrasonic actuator.
In the both-end vibration type ultrasonic actuator, piezoelectric elements 21 and 22 are provided on the left end portion 11L and the right end portion 11R of the elastic body 11. First, as shown in FIG. 6A, a standing wave A is generated in the elastic body 11 by vibrating the left end portion 11L of the elastic body 11 by the piezoelectric element 21 [FIG.
(C-1)]. In this case, since the non-excitation side (11R) can be regarded as the support end, the standing wave has a node on the support end side and an antinode on the excitation end side.

Further, as shown in FIG. 6 (b), by vibrating the right end portion 11R of the elastic body 11 by the piezoelectric element 22, a standing wave B in which one is a node and the other is an antinode is similarly generated. Occurs (FIG. 6 (c-2)). The standing wave A and the standing wave B have a spatial phase difference of λ / 4. Therefore, if the temporal phase difference between the standing wave A and the standing wave B is shifted by λ / 4, the composite wave becomes a traveling wave [Fig. 6 (c-
3)].

[0007] Such a method of generating a traveling wave has the advantage that energy efficiency can be improved because it does not absorb the traveling wave of the elastic body 11 as compared with the method shown in the above-mentioned lecture collection. There is.

[0008]

In the above-mentioned conventional ultrasonic actuator, the laminated piezoelectric element has a structure in which several tens of piezoelectric plates having electrodes on both sides are stacked. In this laminated piezoelectric element, when an electric field is applied to each electrode, an electric field induced strain is generated on the plate of each piezoelectric body due to the piezoelectric inverse effect, and a large displacement is obtained by stacking the electric field induced strain. Was there.

In this case, the piezoelectric inverse effect to be used is the piezoelectric inverse effect in the d ₃₃ direction which is the strain in the direction of electric field application [the suffix on the front side of FIG. The subscript of indicates the direction of strain]. Since the electric field induced strain due to the piezoelectric inverse effect is proportional to the electric field strength of the applied electric field,
In order to drive at a low voltage, it is necessary to make the space between the electrodes as narrow as possible, and as a result, the piezoelectric plate must be thin.

However, in the case where the piezoelectric element utilizes the piezoelectric inverse effect in the d ₃₃ direction, which is the strain in the direction of applying an electric field, in the case of a thin plate-shaped piezoelectric body, even if the strain amount of the piezoelectric body itself is large, the displacement amount is Becomes smaller. For this reason, as a laminated piezoelectric element, a necessary displacement amount is obtained by laminating several tens of thin piezoelectric plates. d ₃₃
In the case of PZT, which is a typical piezoelectric material, even if a voltage of 1 kV is applied per mm, the amount of strain generated is in the order of 10 ⁻⁴ , and therefore the piezoelectric effect of Considering that the driving is performed by, the amount of displacement obtained by one piezoelectric plate is very small.

For the above reasons, when the piezoelectric element is directly excited by utilizing the piezoelectric inverse effect in the d ₃₃ direction, the piezoelectric element has to have a laminated structure. This results in a similar result when an electrostrictive material is used instead of the piezoelectric material. As described above, in the above-described conventional ultrasonic actuator, since the piezoelectric inverse effect in the d ₃₃ direction of the laminated piezoelectric element is used to excite the elastic body,
Particularly, when the piezoelectric element is excited at a high frequency, a strong tensile stress is applied in the laminating direction of the piezoelectric plates when the piezoelectric element is pulled. Such a laminated type piezoelectric element is weak against tensile stress in this direction because each piezoelectric body is laminated or adhered via electrodes, and in particular, it is vibrated at a high frequency. In this case, there is a problem that a force corresponding to the mass of the elastic body is also applied and the laminated portion of the laminated body is easily damaged.

An object of the present invention is to solve the above-mentioned problems and to provide an ultrasonic actuator capable of preventing the laminated layers from being damaged by the tensile stress at the time of excitation.

[0013]

In order to solve the above-mentioned problems, a first solution of the ultrasonic actuator of the present invention comprises a piezoelectric material or an electrostrictive material, and applies a drive signal in the electric field applying direction. Excited first and second electromechanical conversion elements and a shape elongated in one direction are formed, and the first and second electromechanical conversion elements are respectively coupled near both ends thereof. In an ultrasonic actuator including an elastic body in which a progressive vibration wave is generated by excitation of an electromechanical conversion element, and a mover brought into pressure contact with the elastic body, each electromechanical conversion element has a direction in which the electric field is applied. It is characterized in that an end extending in the vertical direction is connected to the elastic body.

The second means for solving the problems is an electromechanical conversion element which is made of a piezoelectric material or an electrostrictive material and is excited by applying a drive signal in the direction of electric field application, and has a shape elongated in one direction. The electromechanical conversion element is coupled in the vicinity of the portion, an elastic body that generates a progressive vibration wave by the excitation of the electromechanical conversion element, and is coupled in the vicinity of the other end of the elastic body, In an ultrasonic actuator including an absorbing portion that absorbs an oscillating wave and a moving element that is brought into pressure contact with the elastic body, the electromechanical conversion element has an end portion that extends in a direction perpendicular to the electric field application direction and is elastic. Characterized by being connected to the body.

A third solving means is characterized in that, in the ultrasonic actuator of the first or second solving means, the electromechanical conversion elements are laminated in the electric field applying direction.

According to a fourth solving means, in the ultrasonic actuator according to any one of the first to third solving means, a guide member is provided in the vicinity of the electromechanical conversion element and in parallel with the electromechanical conversion element. It is characterized by having and.

[0017]

In the present invention, the electromechanical conversion element utilizes the displacement of the element made of the piezoelectric material or the electrostrictive material in the direction perpendicular to the electric field application direction. The displacement can be obtained. That is, since the piezoelectric inverse effect in the d ₃₁ direction, which is the strain in the direction perpendicular to the electric field application direction, is used, the thickness of the piezoelectric body in the electric field application direction can be reduced, while the length in the strain direction can be increased. It is possible to obtain a high electric field at a low voltage and a large displacement at the same time. Therefore, it is possible to bring about a large displacement at a low voltage without stacking in the vibration direction. This makes it possible to avoid damage to the stack due to excitation during excitation. This is
The same effect can be obtained by using an electrostrictive material instead of the piezoelectric material.

[0018]

1 is a perspective view showing a first embodiment of an ultrasonic actuator according to the present invention, and FIG. 2 is a sectional view showing a moving body of the ultrasonic actuator of the first embodiment. The ultrasonic actuator of the first embodiment is composed of a stator 101 and a mover 102. The stator 101 has electromechanical conversion elements (hereinafter, simply referred to as piezoelectric elements) 121 and 122 that convert electric energy into mechanical energy, and a shape that extends in the driving direction, and is provided near the left end portion 111L and the right end portion 111R. The piezoelectric elements 121 and 122 are bonded to each other, and two driving surfaces 111 are formed by a traveling wave (see FIG. 6) generated by overlapping two types of standing waves.
a, an elastic body 111 that generates a driving force on the driving surface 111b
And supporting bodies 131 and 132 that support the elastic body 111 itself by fixing and supporting the piezoelectric elements 121 and 122.

In this embodiment, the piezoelectric element 121 (12
2) has a structure in which the conventional laminated piezoelectric element 21 (22) is laid down, and d is used for exciting the elastic body 111.
_{The 31-} direction piezoelectric inverse effect (see FIG. 1B) is used.
The piezoelectric element 121 includes an elastic body 111 and a support body 131,
It is fixed by a fixing member 133. Piezoelectric element 12
1 is joined to the fixing member 133 with an adhesive agent 134, and is fixed to the elastic body 111 and the support body 131 with bolts 135.

FIG. 2 is a sectional view showing in detail the moving element of the ultrasonic actuator according to the first embodiment. Mover 10
Reference numeral 2 is in pressure contact with each of the driving surfaces 111a and 111b of the elastic body 111, and the sliding portions 151 and 152 that frictionally receive the driving force of the driving surfaces 111a and 111b and the sliding portion 15 are provided.
1, 152 are drive surfaces 111a and 111b of the elastic body 111.
The pressurizing means 160 (which is hidden by the connecting means in FIG. 1) for making pressure contact with the respective sliding parts 151, 1
Sliding parts 151 and 152 so that 52 is integrally driven.
And a connecting means 170 that engages with and is connected to.

The connecting means 171 and 172 are the moving elements 102.
The moving direction of the sliding parts 151, 152, for example.
An uneven groove or the like is provided in each of the connection part 171 and the connection part 172 so that the connection part 171 and 172 can move together with the slide parts 151 and 152. The sliding parts 151 and 152 are movable independently of each other. The pressurizing means 160 has elastic members 161 and 162 such as rubber or spring.
61 and 162 are adjusting means 163 such as screws and nuts,
The amount of pressurization can be adjusted by 164.

According to the above configuration, the piezoelectric element 12
1, 122 are excited by the drive signal, and the elastic body 111
A traveling wave is generated. At this time, the two drive surfaces 111a,
An elliptic motion associated with the traveling wave occurs in both 111b. The sliding portions 151 and 152 are driven by being pressed into contact with the driving surfaces 111a and 111b by the pressing means 160, respectively, by obtaining driving force from the driving surfaces 111a and 111b of the elastic body 111, respectively. The connecting means 170 is for each sliding part 1
51, 152, so that the sliding portions 151, 1
Move with 52. The mover 102 has a plurality of drive surfaces 1.
Since the driving force is obtained from 11a and 111b, a large driving force can be obtained.

At this time, the piezoelectric elements 121 and 122 are
Since the piezoelectric inverse effect in the d ₃₁ direction is used for the excitation, a sufficient amplitude can be obtained without laminating the piezoelectric body in the vibration amplitude direction, so that the lamination damage due to the tensile stress at the time of excitation is prevented. It can be avoided.

In the present invention, the elastic body 1 described with reference to FIG. 5 is used.
The same can be applied to a method in which one end side of 1 is vibrated and a traveling wave is absorbed from the other end side of the elastic body 11. But first
In the method in which both ends of the elastic body 111 are vibrated to generate a traveling wave as in the above embodiment, the amplitude of the traveling wave is large and a large tensile stress acts, so that the effect of the present invention is greater.

FIG. 3A is a diagram showing a second embodiment of the ultrasonic actuator according to the present invention. In each of the embodiments described below, parts having the same functions as those of the first embodiment described above are designated by the same reference numerals, and a duplicate description will be omitted. In the second embodiment, the elastic body 111 and the support 1
31, the guide members 136 and 137 are fixed by bolts 135, and the guide members 136 and 137 and the piezoelectric element 12 are fixed.
There is no adhesion between 1 and 1. In addition, the guide member 13
Between 6 and 137, a gap δ equal to or larger than the amplitude of the piezoelectric element 121 is provided. In this embodiment, the guide member 13
Since 6, 6 and 137 are provided, the piezoelectric element 121 can be stably supported without buckling.

FIG. 3B is a diagram showing a third embodiment of the ultrasonic actuator according to the present invention. In the third embodiment, the piezoelectric element 121A is composed of two piezoelectric bodies, and the piezoelectric element 121A is also fixed to the fixing member 133 with bolts 138. At this time, the bolt 138 does not penetrate the piezoelectric body that constitutes the piezoelectric element 121A and is not electrically connected. According to the third embodiment, since the bolts 138 are used for fixing, the fixing can be performed easily and reliably.

FIG. 4 is a diagram showing a fourth embodiment of the ultrasonic actuator according to the present invention. In the fourth embodiment, the piezoelectric element 221 is formed by forming electrodes 222 and 223 on the outer wall and inner wall of a cylindrical piezoelectric body. According to the fourth embodiment, since the piezoelectric element 221 has a cylindrical shape, it can be stably supported without buckling or the like without providing a guide member or the like.

The present invention is not limited to the embodiments described above, and various modifications and changes are possible, which are also included in the present invention. For example, as a method of generating a traveling wave in the elastic body, a method of vibrating both ends of the elastic body to generate a traveling wave has been described with respect to the above-described respective embodiments. The method can be similarly applied to a system in which one end side of the elastic body is vibrated and the traveling wave is absorbed from the other end side of the elastic body.

Further, in each of the above embodiments, the electro-mechanical conversion element is described as a piezoelectric element, but it may be an electrostrictive element. Further, the piezoelectric element has been described as an example in which the piezoelectric elements are laminated, but one piezoelectric element may be used as long as the supporting strength is sufficient.

[0030]

As described above, according to the present invention,
Since the displacement of the electromechanical conversion element in the direction perpendicular to the electric field is utilized, a large displacement can be obtained at a low voltage without stacking in the vibration direction. Therefore, it is possible to cause a large displacement at a low voltage without stacking in the vibration direction, and it is possible to avoid damage to the stack due to excitation during excitation.

[Brief description of drawings]

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

FIG. 2 is a sectional view illustrating a moving element of the ultrasonic actuator according to the first embodiment.

FIG. 3 (A) is a diagram for explaining a second embodiment of the ultrasonic actuator according to the present invention, and FIG. 3 (B) is a diagram for explaining a third embodiment of the ultrasonic actuator according to the present invention. is there.

FIG. 4 is a diagram illustrating a fourth embodiment of the ultrasonic actuator according to the present invention.

FIG. 5 is an external view illustrating an example of a conventional ultrasonic actuator.

FIG. 6 is a diagram for explaining the configuration of an example of a conventional ultrasonic actuator of both-end excitation type together with the operation principle.

[Explanation of sign]

 Reference Signs List 101 stator 102 mover 111 elastic body 121, 122 piezoelectric element 131, 132 160 pressurizing means 170 connecting means

Claims (4)

[Claims] 1. A first and a second electromechanical conversion element, which is made of a piezoelectric material or an electrostrictive material and is excited by applying a drive signal in an electric field application direction, and has a shape elongated in one direction. The first and second electromechanical conversion elements are respectively coupled near both ends, and an elastic body that generates a progressive vibration wave by excitation of these electromechanical conversion elements is brought into pressure contact with the elastic body. An ultrasonic actuator including a movable element, wherein each electromechanical conversion element has an end extending in a direction perpendicular to the electric field application direction coupled to the elastic body. 2. An electromechanical conversion element, which is made of a piezoelectric material or an electrostrictive material and is excited by applying a drive signal in the electric field application direction, and a shape elongated in one direction. A mechanical conversion element is coupled, and an elastic body that generates a progressive vibration wave by excitation of the electromechanical conversion element is coupled to the elastic body near the other end of the elastic body to absorb the progressive vibration wave. In an ultrasonic actuator including an absorber and a moving element that is brought into pressure contact with the elastic body, the electromechanical conversion element has an end extending in a direction perpendicular to the electric field application direction coupled to the elastic body. An ultrasonic actuator characterized in that 3. The ultrasonic actuator according to claim 1, wherein the electromechanical conversion element is laminated in the electric field applying direction. 4. The ultrasonic actuator according to claim 1, further comprising: a guide member provided in the vicinity of the electromechanical conversion element in parallel with the electromechanical conversion element. An ultrasonic actuator characterized in that