JPH08163879A - Ultrasonic oscillator and ultrasonic motor - Google Patents

Abstract

PURPOSE: To obtain highly durable ultrasonic oscillator and ultrasonic motor which can be driven with low voltage through a simple structure. CONSTITUTION: The ultrasonic oscillator 10 comprises a basic resilient body 11, a multilayer piezoelectric element 15, a clamping resilient body 16 and a driver 17. The basic resilient body 11 is bonded, to four side faces thereof, with the multilayer piezoelectric elements 15. A rotor is pressed against the upper end of the ultrasonic oscillator 10 and secured in place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vibrator having an electromechanical conversion element as a drive source and an ultrasonic motor using the ultrasonic vibrator.

[0002]

2. Description of the Related Art In recent years, ultrasonic motors have attracted attention as new motors to replace electromagnetic motors. This ultrasonic motor has the following advantages over conventional electromagnetic motors. (1) Low rotation and high torque can be obtained without gears. (2) Large holding power. (3) High resolution. (4) It is extremely quiet. (5) It does not generate magnetic noise and is not affected by noise.

As an invention of an ultrasonic motor having the above advantages, Japanese Patent Application Laid-Open No. 5-32 previously proposed by the present applicant was proposed.
There is an invention described in Japanese Patent No. 8755. The above invention is shown in FIG.
As shown in FIG. 1, the ultrasonic motor is composed of an ultrasonic vibrator 1 having a prism shape, a rotor 2, a fastening member 3, and a pressing means 4. The ultrasonic vibrator 1 includes piezoelectric element groups 5 and 6 and resonators 7 and 8.
And a plurality of electrode plates.

In the ultrasonic motor having the above-mentioned structure, when sinusoidal voltages having a phase difference of 90 ° are applied to the piezoelectric element groups 5 and 6, first-order bending vibrations of which vibration planes are orthogonal to each other are excited. The ultrasonic elliptical vibration is excited on the end face. Then, the rotor 2 rotates clockwise or counterclockwise according to the direction of the ellipse.

[0005]

However, the ultrasonic motor disclosed in Japanese Patent Laid-Open No. 5-328755 has the following problems. That is, the piezoelectric element and the resonator are fastened by the fastening member, but the resonance frequency changes significantly due to variations in the fastening pressure. Moreover, since a piezoelectric element having a thickness of 0.3 to 0.5 mm is used, the driving voltage becomes as high as several hundreds Vp-p.

It is an object of the present invention to provide an ultrasonic vibrator in which the resonance frequency does not vary and at the same time provide an ultrasonic vibrator that can be driven at a low voltage. An object of claim 2 is to provide an ultrasonic motor in which the resonance frequency does not vary, and to provide an ultrasonic motor that can be driven at a low voltage.

[0007]

According to a first aspect of the present invention, there is provided a prismatic elastic body and at least two of the four side surfaces parallel to the longitudinal direction of the prismatic elastic body whose displacement direction is the prismatic elastic body. Of a plurality of laminated piezoelectric elements sandwiched so as to be in the longitudinal direction, and an annular driving element joined to an end surface perpendicular to the longitudinal direction of the prismatic elastic body. By applying an alternating voltage with a phase difference to each, it is possible to simultaneously excite degenerate bending resonance vibrations in which vibration mode planes are orthogonal to each other, and to excite ultrasonic elliptical vibrations at the position of the annular driver. It is a characteristic ultrasonic transducer.

It is an object of the present invention to provide a prismatic elastic body and at least two of the four side surfaces parallel to the longitudinal direction of the prismatic elastic body whose displacement direction is the longitudinal direction of the prismatic elastic body. A plurality of laminated piezoelectric elements sandwiched between the two, an annular drive element joined to the end face of the prismatic elastic body at a right angle to the longitudinal direction, and a rotor pressed against the annular drive element. By applying an alternating voltage having a phase difference to each of the plurality of laminated piezoelectric elements, degenerate bending resonance vibrations in which vibration mode planes are orthogonal to each other are simultaneously excited, and at the position of the annular driver. It is an ultrasonic motor characterized in that ultrasonic elliptical vibration is excited to drive the rotor to rotate.

[0009]

According to the operation of claim 1, when a voltage is applied to a first pair of laminated piezoelectric elements among a plurality of laminated piezoelectric elements, a first bending resonance vibration can be excited. When a voltage is applied to the second pair of laminated piezoelectric elements, a second bending resonance vibration orthogonal to the vibration surface of the first bending vibration can be excited. When voltages having a phase difference of π / 2 are applied to the first pair of laminated piezoelectric elements and the second pair of laminated piezoelectric elements, the first bending resonance vibration and the second bending resonance vibration are simultaneously excited. , Ultrasonic elliptical vibration can be formed at the position of the annular driver.

According to the second aspect of the invention, when the rotor is pressed against the annular driving element in which the ultrasonic elliptical vibration is excited by the action of the first aspect, the rotor rotates clockwise or counterclockwise depending on the direction of the ultrasonic elliptical vibration. It is driven to rotate clockwise.

[0011]

Embodiment 1 FIGS. 1 to 7 show the present embodiment, FIG. 1 is a front view of an ultrasonic transducer, FIG. 2 is a front view of a basic elastic body, and FIG. 3 is a plan view of an ultrasonic transducer. 4 is an explanatory view showing a stationary state and a resonance state, FIG. 5 is a front view of the ultrasonic motor, FIG. 6 is a plan view of the same, and FIG. 7 is an exploded sectional view showing a part of the member.

As shown in FIG. 1, the ultrasonic transducer 10 includes a basic elastic body 11, a laminated piezoelectric element 15, and a sandwiching elastic body 16.
And a driver element 17. As shown in FIG. 2, the basic elastic body 11 is made of a stainless steel material and has a prismatic shape with a square cross section. The upper half has a large cross section (8 mm × 8 mm) and the remaining lower half has a small size. (4 mm x 4 mm), and the step 14
Is provided. And φ3m in the longitudinal center
A hole 12 of m is drilled and a tap 13 of φ2 mm is cut at the center.

The method of producing the ultrasonic transducer 10 will be described below. As shown in FIG. 1, the laminated piezoelectric element 15 is fixed to the four side surfaces of the basic elastic body 11 with screws by the sandwiching elastic body 16 so that the laminated piezoelectric element 15 contacts the step 14 as shown in the figure. At this time, it is fixed using an epoxy adhesive while applying a compressive force of about 50N to 200N. The surfaces to be bonded are all surfaces where the laminated piezoelectric element 15 contacts the basic elastic body 11 and the sandwiching elastic body 16. The surface viewed from the directions of β, γ, and δ shown in FIG. 3 is also created by the same method.

The electric terminals coming out of the laminated piezoelectric element 15 are provided on opposite surfaces of the laminated piezoelectric element 1.
5 Connect the wires so that they expand and contract in the opposite direction. Specifically, for example, B (+) and B '(-), B (-) shown in FIG.
And B '(+). The connected A and A ′ terminals are hereinafter referred to as electric terminals A (A ′ terminal is a laminated piezoelectric element 15 disposed on a surface facing the laminated piezoelectric element 15 of the A terminal).
The electrical terminals are shown in the figure and are not shown), and the B and B'terminals are hereinafter referred to as electrical terminals B. A driver element 17 made of a grindstone in which abrasive grains of alumina ceramic are dispersed in an annular resin is joined to the tip of the vibrator.

Next, the operation of the ultrasonic transducer 10 will be described. When an alternating voltage of 50 kHz is applied to the electric terminal A of the laminated piezoelectric element 15, the ultrasonic vibrator 10 can excite a secondary bending vibration in the α (β) direction as shown in FIG.
When an alternating voltage of 50 kHz is applied to the electric terminal B of the laminated piezoelectric element, secondary bending vibration in the γ (δ) direction as shown in FIG. 4 can be excited. Therefore, an alternating voltage having an amplitude of 10 Vp-p at the resonance frequency is applied to the electric terminal A, and the electric terminal B is applied.
When an alternating voltage having the same frequency and the same amplitude with a phase difference of 90 degrees is applied to each of them, as shown in FIG. 1, ultrasonic elliptical vibration (C.W. or C.W. .C.W.) Could be excited.

Next, an ultrasonic motor 20 using the ultrasonic vibrator 10 will be described. As shown in FIG. 5, the ultrasonic motor 20 is composed of the ultrasonic vibrator 10, a threaded shaft 21, a rotor 24, a coil spring 22, and an adjusting screw 23. Hereinafter, a method for producing the ultrasonic motor 20 will be described with reference to FIG. 7. Ultrasonic transducer 1
The shaft 21 is inserted into the hole 12 of 0 and adhered at the cut portion of the tap 13. As shown in the sectional view of FIG. 7, the rotor 24 has a bearing 26 press-fitted in the center thereof, and an annular sliding member 25 made of zirconia ceramics at a portion in contact with the driver 17 of the ultrasonic transducer 10. Are joined. The rotor 24 uses the spring 22 for the ultrasonic transducer 1.
It is pressed and fixed at 0. The pressing force is adjusted by the adjusting screw 23. When the ultrasonic motor 20 is fixed, the shaft 21 protruding below the screw motor 21 is screwed and fixed to a base (not shown).

As described above, the ultrasonic motor 20 having the above-described structure has a frequency of 50 kHz, an amplitude of 10 Vp-p, and a phase difference of +90 between the electric terminals A and B of the ultrasonic vibrator 10.
Or an alternating voltage of -90 degrees is applied. Then, the rotor 24 rotates clockwise or counterclockwise.

According to this embodiment, since the laminated piezoelectric element is used as the vibration source, the driving voltage can be lowered. Further, since the piezoelectric element and the resonator are not structured to be fastened by the fastening member, variations in resonance frequency can be suppressed. Furthermore, since the laminated piezoelectric element is assembled under the condition that a compressive force is applied, the piezoelectric element is not broken and the life is greatly extended. Further, since the bending secondary vibration is used, a node is formed at the center of the vibrator, and the vibrator can be fixed there.
Further, the simple structure facilitates cost reduction. Moreover, when an ultrasonic motor is configured using this vibrator, a highly efficient ultrasonic motor can be provided.

[0019]

Second Embodiment FIGS. 8 to 10 show the present embodiment, FIG. 8 is a front view of an ultrasonic transducer, FIG. 9 is a plan view of the same, and FIG. 10 is an explanatory view showing a stationary state and a resonance state. .

The ultrasonic vibrator 30 of the present embodiment is different from the ultrasonic vibrator 10 of the first embodiment mainly in that four side surfaces of the basic elastic body 11 are formed into flat surfaces, and the four side surfaces are substantially longitudinal. The point is that the laminated piezoelectric element 15 is provided over the entire length in the direction. The electrical wiring is the same as in the first embodiment. The method of manufacturing the ultrasonic transducer 30 is the same as that in the first embodiment, and therefore the description thereof is omitted.

The operation of the ultrasonic oscillator 30 is different from that of the first embodiment, as shown in FIG. 10, in that the ultrasonic oscillator 30 excites a primary bending vibration in two directions whose vibration planes are orthogonal to each other. Is. As a result, ultrasonic elliptical vibration similar to that shown in the first embodiment can be generated in each part of the driver element 17.

Although the configuration of the ultrasonic motor using the ultrasonic transducer 30 of this embodiment is different from that of the first embodiment, the illustration is omitted, but the same axis as that of the first embodiment is used for the ultrasonic transducer 30.
It is a point to be inserted into the hole 12 and fixed at the node position of the primary bending vibration. The operation of the ultrasonic motor is the same as that in the first embodiment, and the explanation is omitted.

According to this embodiment, the adhesion area of the laminated piezoelectric element is made larger than that of the first embodiment, so that the vibration output can be increased. Moreover, the motor output can be increased accordingly.

In each of the above-mentioned embodiments, the ultrasonic oscillator or ultrasonic motor utilizing orthogonal primary or secondary bending vibrations has been described, but the present invention is not limited to this, and higher The following bending vibration may be used.

[0025]

According to the effect of the present invention, since the laminated piezoelectric element is used as the vibration source, the driving voltage can be lowered.
Further, since the piezoelectric element and the resonator are not structured to be fastened by the fastening member, variations in resonance frequency can be suppressed. Furthermore, since the laminated piezoelectric element is assembled under the condition that a compressive force is applied, there is no destruction inside the piezoelectric element,
The life is greatly extended. In addition, the simple structure facilitates cost reduction.

According to the effect of claim 2, by using the ultrasonic vibrator obtained according to claim 1, it is possible to realize a highly durable rotary motor which can be driven at a low voltage with a simple structure.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment.

FIG. 2 is a front view showing the first embodiment.

FIG. 3 is a plan view showing the first embodiment.

FIG. 4 is an explanatory view showing the first embodiment.

FIG. 5 is a front view showing the first embodiment.

FIG. 6 is a plan view showing the first embodiment.

FIG. 7 is an exploded cross-sectional view showing the first embodiment.

FIG. 8 is a front view showing a second embodiment.

FIG. 9 is a plan view showing a second embodiment.

FIG. 10 is an explanatory diagram showing a second embodiment.

FIG. 11 is a perspective view showing a conventional example.

[Explanation of symbols]

 10 Ultrasonic Transducer 11 Basic Elastic Body 15 Laminated Piezoelectric Element 16 Elastic Body for Holding 17 Driver 20 Ultrasonic Motor 21 Shaft 22 Coil Spring 23 Adjusting Screw 24 Rotor 25 Sliding Material 26 Bearing

Claims (2)

[Claims] 1. A prismatic elastic body, and a plurality of prismatic elastic bodies sandwiched by at least two of the four side surfaces parallel to the longitudinal direction of the prismatic elastic body such that the displacement direction is the longitudinal direction of the prismatic elastic body. Of the laminated piezoelectric element and an annular driving element joined to an end surface perpendicular to the longitudinal direction of the prismatic elastic body, and an alternating voltage with a phase difference is applied to each of the plurality of laminated piezoelectric elements. An ultrasonic vibrator characterized in that when applied, it simultaneously excites degenerate bending resonance vibrations in which vibration mode planes are orthogonal to each other, and excites ultrasonic elliptical vibrations at the position of the annular driver. 2. A prismatic elastic body and a plurality of prismatic elastic bodies sandwiched by at least two of the four side surfaces parallel to the longitudinal direction of the prismatic elastic body such that the displacement direction is the longitudinal direction of the prismatic elastic body. Of the multilayer piezoelectric element, an annular drive element joined to an end surface of the prismatic elastic body at a right angle to the longitudinal direction, and a rotor pressed against the annular drive element. By applying an alternating voltage with a phase difference to each of the piezoelectric elements, the degenerate bending resonance vibrations in which the vibration mode planes are orthogonal to each other are simultaneously excited, and the ultrasonic elliptical vibration is generated at the position of the annular driver. An ultrasonic motor which is excited to rotate the rotor.