JPH0345174A - Ultrasonic oscillator and ultrasonic motor - Google Patents

Abstract

PURPOSE:To operate with a large output and a high efficiency by arranging a lamination type piezo-electric element in the pressing mechanism of an ultrasonic oscillator to change a pressing force. CONSTITUTION:The ultrasonic oscillator 11 of an ultrasonic motor is equipped with a driving piezo-electric element 20 having a circular hole at the center thereof while electrodes 21, 22 are attached to both surfaces of the driving piezo-electric element 20. An elastic body 23 is attached to the other surface of the electrode 21 and a controlling piezo-electric element 24, consisting of a lamination type piezo-electric elements, is attached to the other surface of the electrode 22 while these parts are clamped to a base table 26 through a bolt 25. As a result, when a DC power source 31 is impressed on the controlling piezo-electric element 24, the pressing force of the elastic body 23 may be changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic vibrator whose resonance frequency is adjustable, and an ultrasonic motor suitably utilizing the ultrasonic vibrator.

[Prior Art] Conventionally, electromechanical transducers using electrostrictive elements and magnetostrictive elements have been used to convert electrical signals into mechanical vibrations and generate ultrasonic vibrations. The ultrasonic vibrator is constructed by attaching a resonator to these electromechanical transducers to obtain ultrasonic vibration with a large amplitude.

In the above ultrasonic transducer, the shape and dimensions of the resonator and the resonator structure are adjusted in order to obtain desired resonance frequencies for various purposes.

Such an ultrasonic transducer is disclosed in Japanese Patent Application Laid-Open No. 63-125100.
It has been proposed in the Publication No. An example of the conventional example is shown in FIG.

In the figure, 2 is an ultrasonic vibrator, 4 is a drive piezoelectric element, 6 and 8 are thick elastic bodies, 10 is a bolt, 12 is a nut, 14 is a drive electrode plate, 16 is an insulating plate, and 18 is a A control electrode plate, 20 a control piezoelectric element, 30 a driving power source, 3
2 is a matching circuit, and 36 is a DC power supply. Ultrasonic transducer 2
A DC voltage is applied to the specific control piezoelectric element 20 from a variable voltage DC power source 36 connected to the control electrode plate 18. As is well known, piezoelectric elements have an expansion and contraction effect proportional to the applied voltage, and if a DC voltage is applied, the control piezoelectric element 20 will expand or contract in proportion to the applied voltage value, causing ultrasonic waves. When viewing the whole vibrator 2, the bolt tightening force can be changed arbitrarily.

This changes the resonance frequency of the ultrasonic transducer 2 from the DC power supply 36.
This means that the resonant frequency of the ultrasonic transducer 2 can be controlled by the voltage value of the DC power supply 36. Therefore, by controlling the DC voltage to match the mechanical resonance frequency of the ultrasonic vibrator 2 with the AC frequency, ie, the electrical frequency, of the driving power source 30, highly efficient excitation of ultrasonic vibration is achieved.

[Problems to be Solved by the Invention] However, when the compression force is adjusted only by expansion and contraction of the piezoelectric element as in the above-mentioned ultrasonic vibrator, the expansion and contraction displacement is very small, so the resonant frequency must be adjusted over a wide range. It was impossible.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to provide an excellent ultrasonic transducer that allows the resonance frequency of the ultrasonic transducer to be adjusted over a wide range. .

Another object of the present invention is to provide an excellent ultrasonic motor capable of high output and highly efficient operation by suitably utilizing the ultrasonic vibrator.

[Means for Solving the Problems] In order to achieve this object, in the ultrasonic transducer of the present invention, an electromechanical transducer that excites ultrasonic vibrations by applying an alternating current electric signal, In an ultrasonic vibrator that obtains large-amplitude ultrasonic vibration by crimping an elastic body using a crimping mechanism with a predetermined crimping force and utilizing the resonance effect of a resonator, the electromechanical transducer and the elastic body are bonded together. The structure is such that a laminated piezoelectric element for changing the crimping force is arranged in the crimping mechanism for crimping.

Further, in the ultrasonic motor of the present invention, in the above-mentioned ultrasonic vibrator, an electromechanical transducer for exciting vibration in a direction substantially orthogonal to the ultrasonic vibration is added to the elastic body, and the ultrasonic The structure is such that a movable element is brought into contact with a sound wave vibrator.

[Operation] When a DC voltage is applied to the laminated piezoelectric element disposed in the crimping mechanism of the ultrasonic transducer of the present invention having the above configuration,
The laminated piezoelectric element expands and the pressing force increases. Since the laminated piezoelectric element has a large range of variable expansion and contraction, the resonance frequency of the ultrasonic transducer can be controlled over a wide range.

Further, the ultrasonic motor of the present invention applies alternating current of the same frequency to a separately added electromechanical transducer to generate approximately elliptical vibration on the contact surface with the movable element. A driving force is obtained due to the frictional force accompanying this vibration.

[Example] Hereinafter, an example embodying the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the ultrasonic transducer of this embodiment. In the figure, electrodes 21 and 22 are attached to both sides of a driving piezoelectric element 20 having a circular hole in the center. A thick elastic body 23 is attached to the other surface of the electrode 21. Further, a control piezoelectric element 24 made of a laminated piezoelectric element is attached to the other surface of the electrode 22, and the bolt 25 passing through the central axis of these elements and the base 26 are tightened. The drive piezoelectric element 20, the elastic body 23, and the control piezoelectric element 24 are crimped together by force.

Lead wires 27 and 28 are connected to the electrodes 21 and 22, and the lead wire 28 is grounded.

Further, the control piezoelectric element 24 is connected to a DC power source 31 through a positive lead wire 29 and a negative lead wire 30.

Next, the operation of the control piezoelectric element 24 will be explained with reference to FIG.

The control piezoelectric element 24 has a structure in which a large number of piezoelectric elements 24a to 24h, which are polarized in the thickness direction, are stacked in a layered manner, and the polarization directions of adjacent piezoelectric elements are as shown by the arrows in FIG. They are facing oppositely to each other. Here, if the thickness of the piezoelectric element per layer is t, and the displacement amount is Δt, then the total displacement amount Δl when n layers are laminated is calculated as follows.

Δt=d33◆V x Δl m n−Δt−n◆d, 3·V ceramic〒·do◆vHere, d33 is a piezoelectric constant, and ■ is an applied voltage.

That is, in order to increase the amount of displacement of the control piezoelectric element 24, n, Z+ d3i, ■ may be increased and t may be decreased. According to this, a displacement of more than 10 pieces can be easily obtained.

The operation of the ultrasonic transducer 11 configured as above will be explained below.

A DC voltage is applied to the control piezoelectric element 24 provided in the ultrasonic transducer 11 of the embodiment from a variable voltage DC power source 31 connected to the lead wires 29 and 30. As is clear from the above equation, the control piezoelectric element 24 has an expansion and contraction effect proportional to the applied voltage, and the tightening force of the bolt can be arbitrarily changed when viewed from the entire ultrasonic vibrator 11. . The resonant frequency of the bolted type ultrasonic vibrator as described above depends on the pressure applied between the piezoelectric element 20, which is the excitation source, and the elastic body 23. This is the ultrasonic transducer 1
This means that the resonant frequency of 1 can be varied by the voltage applied from the DC power supply 31, and in the above configuration, the relationship shown in FIG. 3 was obtained.

Next, the configuration of an ultrasonic motor that suitably utilizes the above-mentioned ultrasonic transducer 11 will be explained based on FIG. 4. In the same figure, each member with the same reference numeral as in Figs. 1 and 2 is optimized for an ultrasonic motor, and therefore has a slightly different shape from each component detailed above, but has the same function. It means.

In the ultrasonic motor 41, the ultrasonic vibrator 11 is fixed to a yoke 50. At this time, the elastic body 23 has a flat plate shape.

A second piezoelectric element 51 that stretches and vibrates in the longitudinal direction is attached to the elastic body 23, and the stretching vibration excites the elastic body 23 with stretching vibration in the direction of arrow A in the figure.

Further, a rotor 52 is crimped to the end of the elastic body 23 by the elasticity of a leaf spring 53 provided between the rotor 52 and the yoke 50. An output shaft 54 is formed at the center of the rotor 52 and supported by a roller bearing 55.

Furthermore, the elastic body 23 is adjusted by its shape and dimensions so that the piezoelectric element 51 causes longitudinal vibration in the six directions of arrows in the figure at a frequency f1, and the piezoelectric element 20 causes bending vibration in the direction of the arrow B in the figure at a frequency f2. has been done.

As mentioned above, the resonance frequency f2 of the bending vibration can be controlled arbitrarily and over a wide range by adjusting the DC voltage applied to the control piezoelectric element 24.
It is possible to match the resonance frequencies of directional vibrations.

As a result, the rotor 52 receives a driving force of approximately elliptical vibration due to the combination of the two-directional vibrations, and rotates in a predetermined direction.

This driving force is generated by the frictional force between the elastic body 23 and the rotor 52.

Although the above embodiments have been explained using longitudinal vibration and bending vibration as examples, the present invention is not limited thereto, and various modes such as torsional vibration, shear vibration, and higher order modes may be applied without departing from the gist of the present invention. It is possible to realize this.

In addition, by adding a frequency control circuit for performing dynamic t'III+, it is possible to always match the vibration frequencies in the two directions.

Further, although the above embodiment uses a piezoelectric element as the driving element of the vibrator, the invention is not limited to this, and other elements capable of converting electrical energy into mechanical energy, such as an electrostrictive element or a magnetostrictive element, may also be used. It's okay.

In addition, in the embodiment, an example was explained in which the shape of the elastic body of the vibrator used in the ultrasonic motor is a flat plate shape, but the shape is not limited to this, and various shapes such as a cylindrical shape, a rod shape, a rectangular shape, etc. May be used. In addition, various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As is clear from the detailed description above, according to the present invention, it is possible to obtain an excellent ultrasonic transducer in which the resonance frequency of the ultrasonic transducer can be adjusted over a wide range.

Furthermore, by suitably utilizing the ultrasonic vibrator, an excellent ultrasonic motor capable of high output and highly efficient operation can be obtained.

[Brief explanation of drawings]

1 to 4 show embodiments embodying the present invention, FIG. 1 is a cross-sectional view of an ultrasonic transducer to which the present invention is applied, and FIG. 2 is a cross-sectional view of an ultrasonic transducer used in the above-mentioned ultrasonic transducer. FIG. 3 is a diagram showing the relationship between resonance frequency and applied voltage, and FIG. 4 is a sectional view of an ultrasonic motor to which the above ultrasonic vibrator is applied. FIG. 5 is a diagram illustrating an embodiment of a conventional ultrasonic transducer. In the figure, 11 is an ultrasonic transducer, 20 is a drive piezoelectric element, 2
3 is an elastic body, 24 is a control piezoelectric element, and 52 is a rotor. Figure 5 Figure 1 @ Figure 2 Figure 3 t117 Jofurin Figure 4

Claims (1)

[Claims] 1. An elastic body (
23) in an ultrasonic vibrator that obtains ultrasonic vibration by crimping using a crimping mechanism and resonantly vibrating a resonator, the electromechanical transducer (20) and the elastic body (23)
An ultrasonic transducer characterized in that a laminated piezoelectric element (24) for changing the crimping force is disposed in the crimping mechanism that crimps the two. 2. The ultrasonic transducer according to claim 1, wherein an electromechanical transducer (51) for exciting vibration in a direction substantially orthogonal to the ultrasonic vibration is attached to the elastic body, the ultrasonic transducer An ultrasonic motor characterized in that a movable element (52) is brought into contact with the.