JPH08154385A - Ultrasonic vibrator and ultrasonic motor using this ultrasonic vibrator - Google Patents

Abstract

PURPOSE: To provide an ultrasonic vibrator which does not require two kinds of piezoelectric elements, which can be simplified in constitution and driven by a low voltage. CONSTITUTION: An ultrasonic vibrator 10 is provided with a square pillar-shaped elastic body 11 and with a drive element 15 in which a plurality of laminated piezoelectric elements installed at least on two faces out of faces parallel to the length direction of the elastic body 11 in such a way that their respective displacement directions form an acute angle with the length direction of the elastic body 11 are installed on edges in the length direction of the elastic body 11. The ultrasonic vibrator is constituted in such a way that alternating voltages having a phase difference from each other are applied to the plurality of laminated piezoelectric elements and that longitudinal resonance vibrations are generated along the length direction in the elastic body 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vibrator using an electromechanical transducer 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) Magnetic noise is not generated, and the influence of noise is not exerted.

As a conventional ultrasonic motor, there is an ultrasonic motor disclosed in Japanese Patent Laid-Open No. 62-203570 proposed by the present applicant. A conventional ultrasonic motor will be described below based on JP-A-62-203570.

The conventional ultrasonic motor disclosed in the publication is:
As shown in FIG. 11, the thickness sliding piezoelectric element 51 is sandwiched in the opening of the U-shaped member 52, and the U-shaped member 5 is formed.
2 has a pair of thickness longitudinal piezoelectric elements 53 on both shoulders on the outer surface of the coupling end.
Is attached. Then, the rotor 54 having the shaft 54a is arranged in a pressed state so that one side surface can come into contact with the thickness longitudinal piezoelectric element 53.

Next, the operation of this ultrasonic motor will be described. An alternating voltage having the same frequency as the natural frequency of the pendulum oscillation (torsional vibration) of the U-shaped member 52 is applied to the thickness sliding piezoelectric element 51 to excite the torsional vibration. At the same time, an alternating voltage having the same frequency as that described above is applied to the thickness longitudinal oscillator 53 to excite longitudinal vibration at the same time. When these torsional vibration and longitudinal vibration are excited, the rotor 54 can be rotated in a fixed direction. When the torsional vibration and the longitudinal vibration are excited in opposite phases, the rotor 54 can be rotated in the opposite direction.

[0006]

However, the above-mentioned conventional ultrasonic motor has the following problems. (1) A sliding piezoelectric element and a thickness longitudinal piezoelectric element Two types of piezoelectric elements are required. (2) Since one or two plate-shaped piezoelectric elements are used for both the slip piezoelectric element and the thickness longitudinal piezoelectric element, the driving voltage becomes as high as several hundred Vp-p.

Therefore, an object of claim 1 of the present invention is to provide an ultrasonic transducer which does not require two kinds of piezoelectric elements and which can be simplified in structure and which can be driven at a low voltage. A second object of the present invention is to provide an ultrasonic motor which can be driven at a low voltage and whose structure can be simplified by using the ultrasonic vibrator of the first embodiment.

[0008]

In order to achieve the above object, an ultrasonic transducer according to a first aspect of the invention is an ultrasonic transducer having a prismatic shape and at least two of the planes parallel to the longitudinal direction of the elastic body. A plurality of stacked piezoelectric devices provided on one or more surfaces so that their displacement directions form acute angles with the longitudinal direction of the elastic body, and a driver provided on the longitudinal end face of the elastic body. By applying an alternating voltage having a phase difference to the plurality of laminated piezoelectric elements, longitudinal resonance vibration along the longitudinal direction of the elastic body is excited at the same time as torsional resonance vibration, and the driving is performed. The ultrasonic elliptical vibration is generated on the end face provided with the child.

According to another aspect of the ultrasonic motor of the present invention, a prismatic elastic body and at least two or more of the planes parallel to the longitudinal direction of the elastic body have respective displacement directions of the elastic body. It is provided with a plurality of laminated piezoelectric elements provided so as to form an acute angle with respect to the longitudinal direction, a driver provided on an end face in the longitudinal direction of the elastic body, and a rotor pressed against the driver. That is, by applying an alternating voltage having a phase difference to the plurality of laminated piezoelectric elements, longitudinal resonance vibration along the longitudinal direction of the elastic body is simultaneously excited with torsional resonance vibration, and the driver element is Ultrasonic elliptical vibration is generated on the provided end surface to drive the rotor.

[0010]

The following actions are brought about by taking such means.

(Operation of Claim 1) In at least two or more surfaces of the prismatic elastic body of the ultrasonic transducer according to claim 1 which are parallel to the longitudinal direction, the respective displacement directions are elastic. By applying an alternating voltage having a phase difference to a plurality of laminated piezoelectric elements provided so as to form an acute angle with respect to the longitudinal direction of the body, longitudinal resonance vibration along the longitudinal direction is generated in the elastic body. The torsional resonance vibration is excited at the same time, and the longitudinal resonance vibration causes ultrasonic elliptical vibration on the end face where the driver is provided. According to such an ultrasonic transducer, it is not necessary to use different types of piezoelectric elements, the configuration can be simplified, and it is possible to drive at a low voltage.

(Operation of claim 2) The ultrasonic motor according to claim 2 holds the rotor in a pressed state by the driver of the ultrasonic oscillator according to claim 1, and the rotor is attached to the end face on which the driver is provided. Since the rotor is rotationally driven based on the generated ultrasonic elliptical vibration, it is not necessary to use different types of piezoelectric elements, the configuration can be simplified, and the rotor can be rotated by low voltage driving.

[0013]

【Example】

First Embodiment (Structure of Ultrasonic Transducer) FIG. 1 shows a plan view of the ultrasonic transducer 10 of the first embodiment, FIG. 2 shows a front view of the ultrasonic transducer 10, and FIG. The rear view of the ultrasonic transducer | vibrator 10 of 1st Example is shown. 2 is a view seen from the direction of arrow α shown in FIG. 1, and FIG. 3 is a view seen from the direction of arrow β shown in FIG.

The ultrasonic vibrator 10 has a prismatic elastic body 11 made of a stainless material and the elastic body 11.
It has two laminated piezoelectric elements 14a and 14b of the same structure which are respectively arranged on the front surface and the back surface, and an annular driving element 15 which is arranged on one end surface of the elastic body 11.

As shown in FIG.
As shown in FIG. 3, a protrusion 12a having a triangular shape and having an inclined surface to the right which is integrated with the elastic body 11 is formed, and as shown in FIG. A protruding portion 12b having a triangular shape and having an inclined surface that descends to the left and is integral with 11 is formed.

On the lower side of the front surface of the elastic body 11, there is provided a sandwiching elastic body 13a having a triangular shape and having a slanting surface facing downward to the right so as to face the projecting portion 12a.
It is fixed to the elastic body by means of 6, so that the protrusion 12a is provided on the front surface of the elastic body 11.
And the sandwiching elastic body 13 holds one of the laminated piezoelectric elements 14a in a compressed state.

Similarly, on the lower side of the back surface of the elastic body 11, there is provided a sandwiching elastic body 13b having a triangular shape and having a slanting surface facing leftward so as to face the projecting portion 12b.
It is fixed to the elastic body by means of 6, so that the protrusion 12b is formed on the back surface of the elastic body 11.
The sandwiching elastic body 13b holds the other laminated piezoelectric element 14b in a compressed state.

A through hole 17 is formed in the center of the elastic body 11, and a tap 18 is formed in the middle portion of the through hole 17 as shown in FIG. The laminated piezoelectric element 14
The dimensions of a and 14b are set to 2 mm × 3 mm × 9 mm.

The driver 15 is made of a grindstone in which abrasive grains of alumina ceramic are dispersed in a synthetic resin and is formed in an annular shape.

When the ultrasonic transducer 10 described above is produced, as shown in FIG. 4, the laminated piezoelectric element 14a is formed with the elastic body 11 and the protruding portion 12 having an inclined surface is formed integrally with the elastic body 11.
a, and an elastic body 13a for sandwiching which also has a similar inclined surface
The laminated piezoelectric element 14 is placed on the front side of the elastic body 11 in a state where it is sandwiched by applying a compressive force, and the sandwiching elastic body 13 a is screwed to the elastic body 11 with screws 16. The same applies to the laminated piezoelectric element 14b.

The laminated piezoelectric elements 14a and 14b are
All surfaces in contact with the elastic body 11 and the protruding portions 12a and 12b thereof and the sandwiching elastic bodies 13a and 13b are adhered and fixed using an epoxy adhesive.

The size and shape of the ultrasonic oscillator 10 are primary resonant longitudinal vibration (vertical vibration in FIG. 2) and primary resonant torsional vibration (vertical vibration direction is the axis of twist). Vibration can be excited at almost the same frequency Fr (50 kHz to 56 kHz).

Further, the shape is designed so that there is no natural vibration of bending resonance vibration in the vicinity of the above-mentioned frequency.

(Operation of Ultrasonic Transducer) Next, the operation of the ultrasonic transducer 10 will be described. First, the laminated piezoelectric element 1
Amplitude 10V at frequency Fr between A terminal and GND terminal of 4a
By applying an alternating voltage of pp, B of the laminated piezoelectric element 14b
When an alternating voltage of the same frequency and the same amplitude and the same phase is applied between the terminals and the GND terminal, primary resonant longitudinal vibration can be excited. Next, an alternating voltage having an amplitude of 10 Vp-p is applied between the A terminal and the GND terminal of the laminated piezoelectric element 14a at a frequency Fr, and the B terminal and the GND terminal of the laminated piezoelectric element 14b have the same frequency and the same amplitude and are reversed. When the alternating voltage of the phase is applied, the primary resonance torsional vibration can be excited.

Next, the A terminal and G of the laminated piezoelectric element 14a
When an alternating voltage having an amplitude of 10 Vp-p with a frequency Fr is applied between the ND terminals and an alternating voltage having the same frequency and the same amplitude but a phase difference of 90 degrees is applied between the B terminal and the GND terminal of the laminated piezoelectric element 14b, resonance occurs. The longitudinal vibration and the resonance torsional vibration are combined, and elliptical vibration (ultrasonic elliptical vibration) can be excited at the position of the driver 15.

(Structure and Operation of Ultrasonic Motor) Next, referring to FIG.
An ultrasonic motor 20 using the ultrasonic transducer 10 will be described with reference to FIGS. FIG. 5 shows an ultrasonic motor 2
0 is a plan view, FIG. 6 is a front view of the ultrasonic motor 20, and FIG. 7 is a sectional view of a part of the ultrasonic motor 20.

The through hole 17 of the ultrasonic transducer 10 is provided with a screw on the outer periphery and a shaft 21 coated with an adhesive.
Is inserted, and the screw of the shaft 21 is screwed into the tap 18 provided in the through hole 17, so that the shaft 21 is moved to the ultrasonic vibrator 1
It is designed to be bonded and fixed at the position of the center of 0. Further, by the driver 15 in the ultrasonic transducer 10,
A rotor 28 including an annular sliding member 25 made of zirconia ceramics and an annular rotating body 22 adhered to the sliding member 25 is held in a pressed state.

That is, by inserting the coil spring 23 from above the rotor 28 so as to surround the shaft 21 and screwing the nut 24 into the shaft 21, the rotor 28 is pressed against the driver 15 by the urging force of the coil spring 23. It has become. The rotational force of the rotor 28 is adjusted by adjusting the rotation of the nut 24, thereby adjusting the rotational torque of the rotor 28.
A bearing 26 is press-fitted inside the rotating body 22, and is connected to the shaft 21 via the bearing 26. In addition, this ultrasonic motor 2
When 0 is fixed at a fixed position, the shaft 21 protruding from the lower portion of the elastic body 11 may be screwed into a base (not shown).

An alternating voltage with an amplitude of 10 Vp-p at a frequency Fr is applied between the A terminal and the GND terminal of the laminated piezoelectric element 14a in the ultrasonic motor 20 to produce the laminated piezoelectric element 14a.
When an alternating voltage having the same frequency and the same amplitude but different phase by 90 degrees (+90 degrees or -90 degrees) is applied between the B terminal and the GND terminal of b, the resonance longitudinal vibration and the resonance torsional vibration are combined, and the driver element Elliptical vibration can be excited at the position of 15.
This elliptical vibration is transmitted to the rotor 28 and the rotor 2
8 can be driven to rotate clockwise or counterclockwise.

[Effect] According to the ultrasonic transducer 10 of the present embodiment, since two laminated piezoelectric elements 14a and 14b having the same structure are used, two types of piezoelectric elements as in the conventional example are used. It is not necessary to use it, and the drive voltage of this ultrasonic transducer 10 can be lowered. In addition, the laminated piezoelectric element 14
Since a and 14b are assembled in a state in which a compressive force is applied, breakage inside these is eliminated, and the life is greatly extended. Further, since it has a simple structure, there is an advantage that it is easy to reduce the cost.

Since the ultrasonic motor 20 is constructed by using the ultrasonic vibrator 10, it can be driven at a low voltage.
Moreover, the ultrasonic motor 20 with high efficiency can be provided.

Second Embodiment (Structure of Ultrasonic Transducer) FIG. 8 shows an ultrasonic transducer 30 according to a second embodiment. The ultrasonic oscillator 30 has basically the same configuration as the ultrasonic oscillator 10 of the first embodiment, but has four end faces of the elastic body 11 as compared with the ultrasonic oscillator 10 of the first embodiment. A feature is that four laminated piezoelectric elements 14a to 14d are arranged in the same arrangement as that described above.

FIG. 8 is a top view of the ultrasonic transducer 30 of this embodiment. 9 shows a state as viewed from the directions of arrows α and γ shown in FIG. 8, and FIG. 10 shows arrows β and δ shown in FIG.
It is the state seen from the direction. In addition, in FIG.
In FIG. 10, the reference numerals shown below are attached when viewed from the direction of the arrow γ, and in FIG. 10, the reference numerals shown below are attached when viewed in the direction of the arrow δ shown in FIG.

Multilayer piezoelectric element 14 of ultrasonic transducer 30
a and 14b are attached to the elastic body 11 in the same manner as shown in FIGS. 2 and 3, and the laminated piezoelectric elements 14c and 1c are also attached.
As shown in FIGS. 9 and 10, 4d is a protrusion 12c, 12d having an inclined surface integrally formed with the elastic body 11, and
The sandwiching elastic bodies 13c, 13 also having the similar inclined surface
The laminated piezoelectric elements 14c and 14d are attached to the elastic body 11 in a state of being sandwiched by applying a compressive force.

Regarding the electrical wiring, the A terminals of each of the laminated piezoelectric elements 14a to 14d are connected to form an A phase, and the B terminals are connected to form a B phase. This ultrasonic oscillator 30 can also be assembled in the same manner as the ultrasonic oscillator 10 of the first embodiment. In addition, this ultrasonic transducer 30
According to this, since the laminated piezoelectric elements 14c and 14d are added to the ultrasonic vibrator 10 of the first embodiment and the number is increased by two, the output of the longitudinal resonance vibration and the torsional resonance vibration is increased, The output of the elliptical vibration of the driver 15 can be increased.

Further, by arranging the rotor 28, the coil spring 23, and the nut 24 on the ultrasonic transducer 30 as in the case of the first embodiment, an ultrasonic motor is constructed.
It is possible to provide an ultrasonic motor that can be driven at a low voltage and that has high output and high efficiency.

[Effect] Compared to the first embodiment, since four laminated piezoelectric elements 14a to 14d are used, the vibration outputs thereof are increased, and two types of laminated piezoelectric elements as in the conventional example are used. Therefore, the drive voltage of the ultrasonic transducer 30 can be lowered. Moreover, since the laminated piezoelectric elements 14a to 14d are assembled in a state in which a compressive force is applied, destruction inside these is eliminated,
The life is greatly extended. Further, since it has a simple structure, there is an advantage that it is easy to reduce the cost. Further, when an ultrasonic motor is configured using this ultrasonic vibrator 30, it is possible to provide an ultrasonic motor that can be driven at a low voltage and that has high output and high efficiency.

[0038]

The effect of the invention according to claim 1 is that it is not necessary to use different types of piezoelectric elements, the structure can be simplified, and it is possible to drive at a low voltage. The effect of the invention according to claim 2 is that it is not necessary to use different types of piezoelectric elements, the structure can be simplified, and the rotor can be rotated by low voltage driving.

[Brief description of drawings]

FIG. 1 is a plan view showing an ultrasonic transducer according to a first embodiment of the present invention.

FIG. 2 is a front view showing an ultrasonic transducer according to the first embodiment of the present invention.

FIG. 3 is a front view showing the ultrasonic transducer according to the first embodiment of the present invention.

FIG. 4 is an exploded view showing a production state of the ultrasonic transducer of the first embodiment of the present invention.

FIG. 5 is a plan view showing an ultrasonic motor according to the first embodiment of the present invention.

FIG. 6 is a front view showing the ultrasonic motor according to the first embodiment of the present invention.

FIG. 7 is a cross-sectional view showing an ultrasonic motor according to the first embodiment of the present invention.

FIG. 8 is a plan view showing an ultrasonic transducer according to a second embodiment of the present invention.

FIG. 9 is a right side view showing the ultrasonic transducer according to the second embodiment of the present invention.

FIG. 10 is a left side view showing the ultrasonic transducer according to the second embodiment of the present invention.

FIG. 11 is a perspective view showing a conventional ultrasonic motor.

[Explanation of symbols]

 Reference Signs List 10 ultrasonic transducer 11 elastic body 12a protruding portion 12b protruding portion 13a sandwiching elastic body 13b sandwiching elastic body 14a laminated piezoelectric element 14b laminated piezoelectric element 15 driver 16 screw 17 through hole 18 tap 20 ultrasonic motor 21 shaft 22 Rotating body 23 Coil spring 24 Nut 25 Sliding material 26 Bearing 28 Rotor

Claims (2)

[Claims] 1. A prismatic elastic body and at least two or more of the planes parallel to the longitudinal direction of the elastic body so that the respective displacement directions form an acute angle with the longitudinal direction of the elastic body. And a driver element provided on the end face of the elastic body in the longitudinal direction, the alternating voltage having a phase difference between the plurality of laminated piezoelectric elements. Is applied to simultaneously excite longitudinal resonance vibration and torsion resonance vibration along the longitudinal direction in the elastic body, and generate ultrasonic elliptical vibration on the end face provided with the driver. Oscillator. 2. A prismatic elastic body and at least two or more of the planes parallel to the longitudinal direction of the elastic body so that the respective displacement directions form an acute angle with the longitudinal direction of the elastic body. A plurality of laminated piezoelectric elements, a driver element provided on an end face in the longitudinal direction of the elastic body, and a rotor pressed against the driver element. By applying an alternating voltage having a phase difference to each other, a longitudinal resonance vibration and a torsion resonance vibration along the longitudinal direction are simultaneously excited in the elastic body, and the end face provided with the driver is super-excited. An ultrasonic motor, characterized in that sonic elliptical vibration is generated to drive the rotor.